Ion thermal confinement in the TFTR enhanced confinement regime
Energy Technology Data Exchange (ETDEWEB)
Fonck, R.J.; Howell, R.; Jaehnig, K.; Roquemore, L.; Schilling, G.; Scott, S.; Zarnstorff, M.C.; Bitter, M.; Bush, C.; Goldston, R.
1988-12-01
Measurements of the plasma ion temperature and toroidal rotation speed profiles have allowed the study of ion thermal transport in the TFTR hot ion enhanced confinement regime. Central ion temperatures up to 30 keV and rotation speeds up to 8 x 10/sup 5/ m/sec have been confirmed with new diagnostic measurements, and the ion thermal diffusivity is found to be non-neoclassical and comparable to the anomalous electron thermal diffusivity. The dominant effects of strong rotation are the down-shifting of the neutral beam energies in the plasma frame, which results in reduced ion and electron heating on axis, and the presence of off-axis ion heating from viscous damping of the plasma rotation. 14 refs., 3 figs.
Nanorheology of strongly confined oligomeric lubricants
Manias, E.; Brinke, G. ten; Hadziioannou, G.
1996-01-01
Lubricant films confined in nanometric slit pores and subjected to shear flow are studied by non-equilibrium molecular dynamics in a planar Couette flow geometry. An inhomogeneous, layered density profile is developed near the confining surfaces and the shape of the velocity profile across the pore
Spectral confinement and current for atoms in strong magnetic fields
DEFF Research Database (Denmark)
Fournais, Søren
2007-01-01
e study confinement of the ground state of atoms in strong magnetic fields to different subspaces related to the lowest Landau band. Using the results on confinement we can calculate the quantum current in the entire semiclassical region B<3......e study confinement of the ground state of atoms in strong magnetic fields to different subspaces related to the lowest Landau band. Using the results on confinement we can calculate the quantum current in the entire semiclassical region B
Thermalization and confinement in strongly coupled gauge theories
Directory of Open Access Journals (Sweden)
Ishii Takaaki
2016-01-01
Full Text Available Quantum field theories of strongly interacting matter sometimes have a useful holographic description in terms of the variables of a gravitational theory in higher dimensions. This duality maps time dependent physics in the gauge theory to time dependent solutions of the Einstein equations in the gravity theory. In order to better understand the process by which “real world” theories such as QCD behave out of thermodynamic equilibrium, we study time dependent perturbations to states in a model of a confining, strongly coupled gauge theory via holography. Operationally, this involves solving a set of non-linear Einstein equations supplemented with specific time dependent boundary conditions. The resulting solutions allow one to comment on the timescale by which the perturbed states thermalize, as well as to quantify the properties of the final state as a function of the perturbation parameters. We comment on the influence of the dual gauge theory’s confinement scale on these results, as well as the appearance of a previously anticipated universal scaling regime in the “abrupt quench” limit.
Nanorheology of strongly confined molecular fluids : a compter simulation study
Manias, Evangelos D.
1995-01-01
The method of Molecular Dynamics (MD) computer simulations is employed to study ultra thin films of oligomer fluids, confined in spaces comparable to their molecular dimensions and subjected to (very) strong flows. ... Zie: Summary
Rheology of Confined Polymer Melts under Shear Flow : Strong Adsorption Limit
Subbotin, A.; Manias, E.; Hadziioannou, G.; Brinke, G. ten
1995-01-01
The dynamics of a confined polymer melt between strong adsorbing surfaces is considered theoretically. In particular the influence of bridging on the theological behavior is investigated. It is shown that the bridges are very important for small enough shear velocities. Several regimes of
Gârlea, Ioana C; Mulder, Pieter; Alvarado, José; Dammone, Oliver; Aarts, Dirk G A L; Lettinga, M Pavlik; Koenderink, Gijsje H; Mulder, Bela M
2016-06-29
When liquid crystals are confined to finite volumes, the competition between the surface anchoring imposed by the boundaries and the intrinsic orientational symmetry-breaking of these materials gives rise to a host of intriguing phenomena involving topological defect structures. For synthetic molecular mesogens, like the ones used in liquid-crystal displays, these defect structures are independent of the size of the molecules and well described by continuum theories. In contrast, colloidal systems such as carbon nanotubes and biopolymers have micron-sized lengths, so continuum descriptions are expected to break down under strong confinement conditions. Here, we show, by a combination of computer simulations and experiments with virus particles in tailor-made disk- and annulus-shaped microchambers, that strong confinement of colloidal liquid crystals leads to novel defect-stabilized symmetrical domain structures. These finite-size effects point to a potential for designing optically active microstructures, exploiting the as yet unexplored regime of highly confined liquid crystals.
Confinement and αs in a strong magnetic field
Directory of Open Access Journals (Sweden)
Yu.A. Simonov
2015-07-01
Full Text Available Hadron decay widths are shown to increase in strong magnetic fields as Γ(eB∼eBκΓ(0. The same mechanism is shown to be present in the production of the sea quark pair inside the confining string, which decreases the string tension with the growing eB parallel to the string. On the other hand, the average energy of the qq¯ holes in the string world sheet increases, when the direction of B is perpendicular to the sheet. These two effects stipulate the spectacular picture of the B dependent confinement and αs, discovered on the lattice.
Kamanzi, Albert; Leith, Jason S.; Sean, David; Berard, Daniel; Guthrie, Andrew C.; McFaul, Christopher M. J.; Slater, Gary W.; de Haan, Hendrick W.; Leslie, Sabrina R.; McGill University Team; University of Ottawa, University of Ontario Collaboration
We directly measure the free energy of confinement for semi-flexible polymers from the nanoscale to bulk regimes in slit-like confinement. We use Convex Lens-induced Confinement (CLiC) microscopy of DNA to load and directly count molecules at equilibrium in a single chamber of smoothly increasing height. CLiC microscopy allows for direct visualization of polymers in free solution over long periods, as a function of tunable vertical confinement - from the millimeter to the nanometer scale, and within a single device. Our direct characterization of the free energy of confinement, across several orders of magnitude of applied confinement, agree with new simulations established in this work. We compare experimental results to the ``de Gennes blob model'', to theory published by Casassa, as well as to simulations by Chen and Sullivan, in appropriate regimes. This work establishes a robust platform for understanding and manipulating polymers at the nanoscale, with a wide range of applications to biomedical technologies.
Continuum strong QCD: Confinement and dynamical chiral symmetry breaking
International Nuclear Information System (INIS)
Continuum strong QCD is the application of models and continuum quantum field theory to the study of phenomena in hadronic physics, which includes; e.g., the spectrum of QCD bound states and their interactions. Herein the author provides a Dyson-Schwinger equation perspective, focusing on qualitative aspects of confinement and dynamical chiral symmetry breaking in cold, sparse QCD, and also elucidating consequences of the axial-vector Ward-Takahashi identity and features of the heavy-quark limit
Flow regime analysis for fluid injection into a confined aquifer: implications for CO2 sequestration
Guo, B.; Zheng, Z.; Celia, M. A.; Stone, H.
2015-12-01
Carbon dioxide injection into a confined saline aquifer may be modeled as an axisymmetric two-phase flow problem. Assuming the two fluids segregate in the vertical direction due to strong buoyancy, and neglecting capillary pressure and miscibility, the lubrication approximation leads to a nonlinear advection-diffusion equation that describes the evolution of the sharp fluid-fluid interface. The flow behaviors in the system are controlled by two dimensionless groups: M, the viscosity ratio of the displaced fluid relative to injected fluid, and Γ , the gravity number, which represents the relative importance of buoyancy and fluid injection. Four different analytical solutions can be derived as the asymptotic approximations, representing specific values of the parameter pairs. The four solutions correspond to: (1) Γ 1; and (4) Γ >> 1, any M values. The first two of these solutions are new, while the third corresponds to the solution of Nordbotten and Celia (2006) for confined injections and the fourth corresponds to the solution of (Lyle et al., 2005) for gravity currents in an unconfined aquifer. Overall, the various axisymmetric flows can be summarized in a Γ-M regime diagram with five distinct dynamic behaviors including the four asymptotic regimes and an intermediate regime (Fig. 1). Data from a number of CO2 injection sites around the world can be used to compute the two dimensionless groups Γ and M associated with each injection. When plotted on the regime diagram, these values show the flow behavior for each injection and how the values vary from site to site. For all the CO2 injections, M is always larger than 1, while Γ can range from 0.01 up to 100. The pairs of (Γ, M) with lower Γ values correspond to solution (3), while the ones with higher Γ values can move up to the intermediate regime and the flow regime for solution (4). The higher values of Γ correspond to pilot-scale injections with low injection rates; most industrial-scale injection
Dispersion of strongly confined channel plasmon polariton modes
DEFF Research Database (Denmark)
Zenin, Vladimir; Volkov, Valentyn S.; Han, Zhanghua
2011-01-01
We report on experimental (by use of scanning near-field optical microscopy) and theoretical investigations of strongly confined (∼λ/5) channel plasmon polariton (CPP) modes propagating at telecom wavelengths (1425–1630 nm) along V-grooves cut in a gold film. The main CPP characteristics (mode...... index, width, and propagation length) are determined directly from the experimental near-field images and compared to theoretical results obtained using an analytic description of CPP modes supported by (infinitely deep) V-grooves and finite-element simulations implemented in COMSOL....
Improved confinement regimes induced by limiter biasing in the TJ-II stellarator
International Nuclear Information System (INIS)
Hidalgo, C; Pedrosa, M A; Dreval, N; McCarthy, K J; Eliseev, L; Ochando, M A; Estrada, T; Pastor, I; AscasIbar, E; Calderon, E; Cappa, A; Chmyga, A A; Fernandez, A; Goncalves, B; Herranz, J; Jimenez, J A; Khrebtov, S M; Komarov, A D; Kozachok, A S; Krupnik, L; Lopez-Fraguas, A; Lopez-Sanchez, A; Melnikov, A V; Medina, F; Milligen, B van; Silva, C; Tabares, F; Tafalla, D
2004-01-01
The influence of limiter biasing on plasma confinement, turbulence and plasma flows is investigated in the TJ-II stellarator. Experimental results show that it is possible to modify global confinement and edge plasma parameters with both positive and negative biasing. Significant and minor modifications in the structure of plasma fluctuations have been observed during the transition to improved confinement regimes induced by limiter biasing. These results show evidence of electric field induced improved confinement via multiple mechanisms. The investigation of the relaxation of plasma potential and electric fields shows evidence of two different characteristic decay times
Membrane cholesterol strongly influences confined diffusion of prestin.
Kamar, R I; Organ-Darling, L E; Raphael, R M
2012-10-17
Prestin is the membrane motor protein that drives outer hair cell (OHC) electromotility, a process that is essential for mammalian hearing. Prestin function is sensitive to membrane cholesterol levels, and numerous studies have suggested that prestin localizes in cholesterol-rich membrane microdomains. Previously, fluorescence recovery after photobleaching experiments were performed in HEK cells expressing prestin-GFP after cholesterol manipulations, and revealed evidence of transient confinement. To further characterize this apparent confined diffusion of prestin, we conjugated prestin to a photostable fluorophore (tetramethylrhodamine) and performed single-molecule fluorescence microscopy. Using single-particle tracking, we determined the microscopic diffusion coefficient from the full time course of the mean-squared deviation. Our results indicate that prestin undergoes diffusion in confinement regions, and that depletion of membrane cholesterol increases confinement size and decreases confinement strength. By interpreting the data in terms of a mathematical model of hop-diffusion, we quantified these cholesterol-induced changes in membrane organization. A complementary analysis of the distribution of squared displacements confirmed that cholesterol depletion reduces prestin confinement. These findings support the hypothesis that prestin function is intimately linked to membrane organization, and further promote a regulatory role for cholesterol in OHC and auditory function. Copyright © 2012 Biophysical Society. Published by Elsevier Inc. All rights reserved.
Negative mobility of a Brownian particle: Strong damping regime
Słapik, A.; Łuczka, J.; Spiechowicz, J.
2018-02-01
We study impact of inertia on directed transport of a Brownian particle under non-equilibrium conditions: the particle moves in a one-dimensional periodic and symmetric potential, is driven by both an unbiased time-periodic force and a constant force, and is coupled to a thermostat of temperature T. Within selected parameter regimes this system exhibits negative mobility, which means that the particle moves in the direction opposite to the direction of the constant force. It is known that in such a setup the inertial term is essential for the emergence of negative mobility and it cannot be detected in the limiting case of overdamped dynamics. We analyse inertial effects and show that negative mobility can be observed even in the strong damping regime. We determine the optimal dimensionless mass for the presence of negative mobility and reveal three mechanisms standing behind this anomaly: deterministic chaotic, thermal noise induced and deterministic non-chaotic. The last origin has never been reported. It may provide guidance to the possibility of observation of negative mobility for strongly damped dynamics which is of fundamental importance from the point of view of biological systems, all of which in situ operate in fluctuating environments.
Extension of improved particle and energy confinement regime in the core of LHD plasma
International Nuclear Information System (INIS)
Kaneko, Osamu; Yokoyama, Masayuki; Yoshinuma, Mikiro
2009-01-01
Recent two major topics of Large Helical Device (LHD) towards fusion relevant conditions, high-density operation and high-ion-temperature operation, are reported. Super dense core plasma was obtained by the combination of repetitive hydrogen ice pellet injection and high power neutral beam injection (NBI) heating. A very peaked density profile with the highest central density of 1.1x10 21 m -3 was produced showing that the particle transport was suppressed very well in the plasma core. The spatial density varies as the position of magnetic axis (R ax ), and the steepest profile is obtained at R ax =3.95 m. The highest central ion temperature of 5.6 keV was obtained in hydrogen plasma at electron density of 1.6 x 10 19 m -3 by NBI, where a peaked ion-temperature profile with internal ion energy transport barrier was observed. The profile of electron temperature did not change much and was broad even when the ion temperature had a peaked profile. The central ion temperature is higher than the electron temperature, which is a new operation regime of LHD. High central ion temperature accompanied strong toroidal rotation and an extreme hollow profile of carbon ions (impurity hole). These steep temperature profiles were obtained so far at around R ax =3.6 m. The compatibility between particle and energy confinement is a new issue of LHD to explore a new operation regime for attractive fusion reactor. (author)
Mathematical structure of Rabi oscillations in the strong coupling regime
International Nuclear Information System (INIS)
Fujii, Kazuyuki
2003-01-01
In this paper, we generalize the Jaynes-Cummings Hamiltonian by making use of some operators based on Lie algebras su(1, 1) and su(2), and study a mathematical structure of Rabi floppings of these models in the strong coupling regime. We show that Rabi frequencies are given by matrix elements of generalized coherent operators (Fujii K 2002 Preprint quant-ph/0202081) under the rotating-wave approximation. In the first half, we make a general review of coherent operators and generalized coherent ones based on Lie algebras su(1, 1) and su(2). In the latter half, we carry out a detailed examination of Frasca (Frasca M 2001 Preprint quant-ph/0111134) and generalize his method, and moreover present some related problems. We also apply our results to the construction of controlled unitary gates in quantum computation. Lastly, we make a brief comment on application to holonomic quantum computation
The laser proton acceleration in the strong charge separation regime
Energy Technology Data Exchange (ETDEWEB)
Nishiuchi, M. [Advanced Photon Research Center, Japan Atomic Energy Agency, 8-1 Umemi-dai, Kizu, Kyoto 619-0215 (Japan)]. E-mail: nishiuchi.mamiko@jaea.go.jp; Fukumi, A. [Advanced Photon Research Center, Japan Atomic Energy Agency, 8-1 Umemi-dai, Kizu, Kyoto 619-0215 (Japan)]|[National Institute of Radiological Sciences, 4-9-1, Anagawa, Inage, Chiba 263-8555 (Japan); Daido, H. [Advanced Photon Research Center, Japan Atomic Energy Agency, 8-1 Umemi-dai, Kizu, Kyoto 619-0215 (Japan); Li, Z. [Advanced Photon Research Center, Japan Atomic Energy Agency, 8-1 Umemi-dai, Kizu, Kyoto 619-0215 (Japan)]|[National Institute of Radiological Sciences, 4-9-1, Anagawa, Inage, Chiba 263-8555 (Japan); Sagisaka, A.; Ogura, K.; Orimo, S.; Kado, M.; Hayashi, Y.; Mori, M. [Advanced Photon Research Center, Japan Atomic Energy Agency, 8-1 Umemi-dai, Kizu, Kyoto 619-0215 (Japan); Bulanov, S.V. [Advanced Photon Research Center, Japan Atomic Energy Agency, 8-1 Umemi-dai, Kizu, Kyoto 619-0215 (Japan)]|[A.M. Prokhorov General Physics Institute of Russian Academy of the Sciences, Vavilov St. 38, Moscow 119991 (Russian Federation); Esirkepov, T. [Advanced Photon Research Center, Japan Atomic Energy Agency, 8-1 Umemi-dai, Kizu, Kyoto 619-0215 (Japan); Nemoto, K.; Oishi, Y.; Nayuki, T.; Fujii, T. [Central Research Institute of Electric Power Industry, 2-6-1 Nagasaka, Yokosuka, Kanagawa 240-0196 (Japan); Noda, A.; Iwashita, Y.; Shirai, T. [Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan); Nakamura, S. [Advanced Photon Research Center, Japan Atomic Energy Agency, 8-1 Umemi-dai, Kizu, Kyoto 619-0215 (Japan)]|[Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan)
2006-09-18
We report the experimental results of proton acceleration as well as the simple one-dimensional model which explains our experimental data. The proton acceleration experiment is carried out with a TW short pulse laser irradiated on a tantalum thin-foil target (3 {mu}m thickness) with an intensity of {approx}3x10{sup 18} Wcm{sup -2}. Accelerated protons exhibit a typical energy spectrum with two quasi-Maxwellian components with a high energy cut-off. We can successfully explain the higher energy part as well as the cut off energy of the proton spectrum with the simple-one-dimensional model based on the strong charge separation regime, which is the extension of the model proposed originally by [M. Passoni et al., Phys. Rev. E 69 (2004) 026411].
International Nuclear Information System (INIS)
Goldston, R.J.
1984-02-01
Recent results from confinement scaling experiments on tokamaks with ohmic and strong auxiliary heating are reviewed. An attempt is made to draw these results together into a low-density ohmic confinement scaling law, and a scaling law for confinement with auxiliary heating. The auxiliary heating confinement law may also serve to explain the saturation in tau/sub E/ vs anti n/sub e/ observed in some ohmic heating density scaling experiments
Spindle-cusp confinement properties of laser-produced plasma in a low-beta regime
Energy Technology Data Exchange (ETDEWEB)
Yoshino, R.; Sekiguchi, T. (Tokyo Univ. (Japan). Faculty of Engineering); Sato, K.
1981-06-01
Behavior of a spindle-cusp plasma produced at its central null-field point from a thin wire target by laser pulse is experimentally studied, mainly in a low plasma-beta regime, by means of many different plasma diagnostics. As the results, somewhat queer confinement properties have been found, and some considerations are given for the observed results.
Peptide-microgel interactions in the strong coupling regime.
Hansson, Per; Bysell, Helena; Månsson, Ronja; Malmsten, Martin
2012-09-06
The interaction between lightly cross-linked poly(acrylic acid) microgels and oppositely charged peptides was investigated as a function of peptide length, charge density, pH, and salt concentration, with emphasis on the strong coupling regime at high charge contrast. By micromanipulator-assisted light microscopy, the equilibrium volume response of single microgel particles upon oligolysine and oligo(lysine/alanine) absorption could be monitored in a controlled fashion. Results show that microgel deswelling, caused by peptide binding and network neutralization, increases with peptide length (3 attraction between the network chains is described using an exponential force law, and the network elasticity by the inverse Langevin theory. The model was used to calculate the composition of microgels in contact with reservoir solutions of peptides and simple electrolytes. At high electrostatic coupling, the calculated swelling curves were found to display first-order phase transition behavior. The model was demonstrated to capture pH- and electrolyte-dependent microgel swelling, as well as effects of peptide length and charge density on microgel deswelling. The analysis demonstrated that the peptide charge (length), rather than the peptide charge density, determines microgel deswelling. Furthermore, a transition between continuous and discrete network collapse was identified, consistent with experimental results in the present investigations, as well as with results from the literature on microgel deswelling caused by multivalent cations.
Can confinement ensure natural CP-invariance of strong interactions
International Nuclear Information System (INIS)
Shifman, M.A.; Vainshtein, A.I.; Zakharov, V.I.
1979-01-01
P- and T-invariance violation in quantum chromodynamics (QCD) due to the so called THETA term Δα=THETAxgsub(s)sup(2)/32πsup(2)xGsub(μν)sup(a)xGsub(μν)sup(a) tilde, where Gsub(μν)sup(a) is the gluon field strength tensor, and gsub(s) is the quark-gluon coupling constant is discussed. It is shown that irrespectively of how the confinement works there emerge observable P- and T-odd effects. The proof is based on the assumption that QCD resolves the upsilon(1) problem, i.e. the mass of the singlet pseudoscalar meson does not vanish in the chiral limit. A modification of the axion scheme which restores the natural P and T invariance of the theory is suggested and cannot be ruled out experimentally
Static and kinetic friction of strongly confined polymer films under shear
Hirz, S; Subbotin, A; Frank, C; Hadziioannou, G
1996-01-01
In the present work, we investigate the dependence of relaxational processes in strongly confined polymer liquids as a function of the molecular mass and of the confining film thickness, both theoretically and experimentally. A qualitative agreement is observed between the theoretical predictions
Banana fluxes in the plateau regime for a nonaxisymmetrically confined plasma
International Nuclear Information System (INIS)
Balescu, R.; Fantechi, S.
1990-01-01
The banana (or banana-plateau) fluxes, related to the generalized stresses left-angle B·∇·π α(n) right-angle, left-angle B T ·∇·π α(n) right-angle have been determined in the plateau regime, for a plasma confined by a toroidal magnetic field of arbitrary geometry. The complete set of transport coefficients for both the ''parallel'' (ambipolar) and ''toroidal'' (nonambipolar) banana fluxes was obtained in the 13-moment (13M) approximation, going beyond the previously known expressions in the nonaxisymmetric case. The main emphasis is laid on the structure of the transport matrix and of its coefficients. It is shown that the Onsager symmetry of this matrix partly breaks down (for the mixed electron--ion coefficients) in a nonaxisymmetrically confined plasma
Robustness of predator-prey models for confinement regime transitions in fusion plasmas
Energy Technology Data Exchange (ETDEWEB)
Zhu, H. [Department of Physics, Centre for Fusion, Space and Astrophysics, University of Warwick, Coventry CV4 7AL (United Kingdom); Chapman, S. C. [Department of Physics, Centre for Fusion, Space and Astrophysics, University of Warwick, Coventry CV4 7AL (United Kingdom); Department of Mathematics and Statistics, University of Tromso (Norway); Dendy, R. O. [Euratom/CCFE Fusion Association, Culham Science Centre, Abingdon, Oxfordshire OX14 3DB (United Kingdom); Department of Physics, Centre for Fusion, Space and Astrophysics, University of Warwick, Coventry CV4 7AL (United Kingdom)
2013-04-15
Energy transport and confinement in tokamak fusion plasmas is usually determined by the coupled nonlinear interactions of small-scale drift turbulence and larger scale coherent nonlinear structures, such as zonal flows, together with free energy sources such as temperature gradients. Zero-dimensional models, designed to embody plausible physical narratives for these interactions, can help to identify the origin of enhanced energy confinement and of transitions between confinement regimes. A prime zero-dimensional paradigm is predator-prey or Lotka-Volterra. Here, we extend a successful three-variable (temperature gradient; microturbulence level; one class of coherent structure) model in this genre [M. A. Malkov and P. H. Diamond, Phys. Plasmas 16, 012504 (2009)], by adding a fourth variable representing a second class of coherent structure. This requires a fourth coupled nonlinear ordinary differential equation. We investigate the degree of invariance of the phenomenology generated by the model of Malkov and Diamond, given this additional physics. We study and compare the long-time behaviour of the three-equation and four-equation systems, their evolution towards the final state, and their attractive fixed points and limit cycles. We explore the sensitivity of paths to attractors. It is found that, for example, an attractive fixed point of the three-equation system can become a limit cycle of the four-equation system. Addressing these questions which we together refer to as 'robustness' for convenience is particularly important for models which, as here, generate sharp transitions in the values of system variables which may replicate some key features of confinement transitions. Our results help to establish the robustness of the zero-dimensional model approach to capturing observed confinement phenomenology in tokamak fusion plasmas.
Heating, current drive and confinement regimes with the JET ICRH and LHCD systems
DEFF Research Database (Denmark)
Jacquinot, J.; Adams, J.M.; Altmann, H.
1991-01-01
During its 1990 operation, 2 large RF systems were available on JET. The Ion Cyclotron Resonance Heating (ICRH) system was equipped with new beryllium screens and with feedback matching systems. Specific impurities generated by ICRH were reduced to negligible levels even in the most stringent H......-mode conditions. A maximum power of 22 MW was coupled to L-mode plasmas. High quality H-modes (tau-E greater-than-or-equal-to 2.5 tau-EG) were achieved using dipole phasing. A new high confinement mode was discovered. It combines the properties of the H-mode regime to the low central diffusivities obtained...... by pellet injection. A value of n(d) tau-E T(i) = 7.8 x 10(20) m-3 s keV was obtained in this mode with T(e) approximately T(i) approximately 11 keV. In the L-mode regime, a regime, a record (140 kW) D-He-3 fusion power was generated with 10 - 14 MW of ICRH at the He-3 cyclotron frequency. Experiments were...
Strong nucleon and Δ-isobar form factors in the quark-confinement model
International Nuclear Information System (INIS)
Efimov, G.V.; Ivanov, M.A.; Lubovitskij, V.E.
1989-01-01
The nucleon and the Δ-isobar are investigated as three-quark systems in the quark-confinement model (QCM). This model is based on two hypotheses. First, quark confinement is accomplished through averaging over some vacuum gluon fields which are assumed to provide the confinement of any colour states. Second, hadrons are treated as collective colourless excitations of quark-gluon interactions. The QCM is applied to low-energy baryon physics. The nucleon magnetic moments and electromagnetic radii, the ratio G A /G V , and the decay width for Δ→pπ are calculated. The behaviour of the electromagnetic and strong meson-nucleon (meson-isobar) form factors is determined for space-like momentum transfers. The results are compared with experimental data for the electromagnetic form factors and phenomenological strong form factors as used in the Bonn potential. 32 refs.; 10 figs.; 4 tabs
Energy Technology Data Exchange (ETDEWEB)
White, A. E., E-mail: whitea@mit.edu; Howard, N. T.; Creely, A. J.; Chilenski, M. A.; Greenwald, M.; Hubbard, A. E.; Hughes, J. W.; Marmar, E.; Rice, J. E.; Sierchio, J. M.; Sung, C.; Walk, J. R.; Whyte, D. G. [MIT Plasma Science and Fusion Center, Cambridge, Massachusetts 02139 (United States); Mikkelsen, D. R.; Edlund, E. M.; Kung, C. [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08540 (United States); Holland, C. [University of California, San Diego (UCSD) San Diego, California 92093 (United States); Candy, J.; Petty, C. C. [General Atomics, P.O. Box 85608, San Diego, California 92186 (United States); Reinke, M. L. [York University, Heslington, York YO10 5DD (United Kingdom); and others
2015-05-15
For the first time, nonlinear gyrokinetic simulations of I-mode plasmas are performed and compared with experiment. I-mode is a high confinement regime, featuring energy confinement similar to H-mode, but without enhanced particle and impurity particle confinement [D. G. Whyte et al., Nucl. Fusion 50, 105005 (2010)]. As a consequence of the separation between heat and particle transport, I-mode exhibits several favorable characteristics compared to H-mode. The nonlinear gyrokinetic code GYRO [J. Candy and R. E. Waltz, J Comput. Phys. 186, 545 (2003)] is used to explore the effects of E × B shear and profile stiffness in I-mode and compare with L-mode. The nonlinear GYRO simulations show that I-mode core ion temperature and electron temperature profiles are more stiff than L-mode core plasmas. Scans of the input E × B shear in GYRO simulations show that E × B shearing of turbulence is a stronger effect in the core of I-mode than L-mode. The nonlinear simulations match the observed reductions in long wavelength density fluctuation levels across the L-I transition but underestimate the reduction of long wavelength electron temperature fluctuation levels. The comparisons between experiment and gyrokinetic simulations for I-mode suggest that increased E × B shearing of turbulence combined with increased profile stiffness are responsible for the reductions in core turbulence observed in the experiment, and that I-mode resembles H-mode plasmas more than L-mode plasmas with regards to marginal stability and temperature profile stiffness.
Role of density modulation in the spatially resolved dynamics of strongly confined liquids.
Saw, Shibu; Dasgupta, Chandan
2016-08-07
Confinement by walls usually produces a strong modulation in the density of dense liquids near the walls. Using molecular dynamics simulations, we examine the effects of the density modulation on the spatially resolved dynamics of a liquid confined between two parallel walls, using a resolution of a fraction of the interparticle distance in the liquid. The local dynamics is quantified by the relaxation time associated with the temporal autocorrelation function of the local density. We find that this local relaxation time varies in phase with the density modulation. The amplitude of the spatial modulation of the relaxation time can be quite large, depending on the characteristics of the wall and thermodynamic parameters of the liquid. To disentangle the effects of confinement and density modulation on the spatially resolved dynamics, we compare the dynamics of a confined liquid with that of an unconfined one in which a similar density modulation is induced by an external potential. We find several differences indicating that density modulation alone cannot account for all the features seen in the spatially resolved dynamics of confined liquids. We also examine how the dynamics near a wall depends on the separation between the two walls and show that the features seen in our simulations persist in the limit of large wall separation.
International Nuclear Information System (INIS)
Alladio, F.; Micozzi, P.
1995-12-01
A correlation has been established between the improvement of the energy confinement time observed in some plasma regimes on the DIII-D tokamak (VH modes and shear reversed discharges) and a geometrical characteristic of the plasma column: the Pfirsch-Schluter-like factor, which multiplies the moment of inertia of the magnetic configuration. Such a quantity is generated by the compression that the flux tubes suffer going from the external to the internal part of the torus. Therefore the configurations in which the module of the total magnetic field is more constant upon the magnetic surfaces (near omnigeneous configurations) show a lower value of the moment of inertia. The geometric parameter of Pfirsch-Schluter determines the transient and steady state behaviour of the plasma rotation under the assumption that the anomalous parallel viscosity is greater that the neoclassical one. In this way, also the profile of the part of the radial electric field (and his absolute value) is influenced by the magnetic configuration. The radial electric field, or, at least, his radial derivative, is invoked by many authors as a principal factor in reducing the turbulence (and so the anomalous transport) in magnetically confined plasmas. In particular, DIII-D machine, the highly elongated and triangular plasma discharges that evolve toward the VH-mode show a lower value of the Pfirsch-Schluter quantity and a higher level of the radial electric field; also the shear reversed profiles tend to lower 1+2q 2 in the central region of the plasma column, driving towards very high values of the electric field within the reversal region
Electrically tunable single-dot nanocavities in the weak and strong coupling regimes
DEFF Research Database (Denmark)
Laucht, Arne; Hofbauer, Felix; Angele, Jacob
2008-01-01
We report the design, fabrication and optical investigation of electrically tunable single quantum dot - photonic crystal defect nanocavities [1] operating in both the weak and strong coupling regimes of the light matter interaction. Unlike previous studies, where the dot-cavity spectral detuning...... of the emitted photons from a single-dot nanocavity in the weak and strong coupling regimes. New information is obtained on the nature of the dot-cavity coupling in the weak coupling regime and electrical control of zero dimensional polaritons is demonstrated for the first time. Vacuum Rabi splittings up to 2g...... electrical readout of the strongly coupled dot-cavity system using photocurrent methods will be discussed. This work is financially supported by the DFG via SFB 631 and by the German Excellence Initiative via the “Nanosystems Initiative Munich (NIM)”....
BGK-type models in strong reaction and kinetic chemical equilibrium regimes
International Nuclear Information System (INIS)
Monaco, R; Bianchi, M Pandolfi; Soares, A J
2005-01-01
A BGK-type procedure is applied to multi-component gases undergoing chemical reactions of bimolecular type. The relaxation process towards local Maxwellians, depending on mass and numerical densities of each species as well as common velocity and temperature, is investigated in two different cases with respect to chemical regimes. These cases are related to the strong reaction regime characterized by slow reactions, and to the kinetic chemical equilibrium regime where fast reactions take place. The consistency properties of both models are stated in detail. The trend to equilibrium is numerically tested and comparisons for the two regimes are performed within the hydrogen-air and carbon-oxygen reaction mechanism. In the spatial homogeneous case, it is also shown that the thermodynamical equilibrium of the models recovers satisfactorily the asymptotic equilibrium solutions to the reactive Euler equations
International Nuclear Information System (INIS)
Verdoolaege, Geert; Van Oost, Guido
2012-01-01
Pattern recognition is becoming an important tool in fusion data analysis. However, fusion diagnostic measurements are often affected by considerable statistical uncertainties, rendering the extraction of useful patterns a significant challenge. Therefore, we assume a probabilistic model for the data and perform pattern recognition in the space of probability distributions. We show the considerable advantage of our method for identifying confinement regimes and edge localized mode behavior, and we discuss the potential for scaling laws.
Study of the Higgs-Yukawa theory in the strong-Yukawa coupling regime
Bulava, John; Hou, George W.S.; Jansen, Karl; Knippschild, Bastian; Lin, C.J.David; Nagai, Kei-Ichi; Nagy, Attila; Ogawa, Kenji; Smigielski, Brian
2011-01-01
In this article, we present an ongoing lattice study of the Higgs-Yukawa model, in the regime of strong-Yukawa coupling, using overlap fermions. We investigated the phase structure in this regime by computing the Higgs vacuum expectation value, and by exploring the finite-size scaling behaviour of the susceptibility corresponding to the magnetisation. Our preliminary results indicate the existence of a second-order phase transition when the Yukawa coupling becomes large enough, at which the Higgs vacuum expectation value vanishes and the susceptibility diverges.
Non-Newtonian flow of an ultralow-melting chalcogenide liquid in strongly confined geometry
Energy Technology Data Exchange (ETDEWEB)
Wang, Siyuan; Jain, Chhavi; Wondraczek, Katrin; Kobelke, Jens [Leibniz Institute of Photonic Technology, Albert-Einstein-Str. 9, 07745 Jena (Germany); Wondraczek, Lothar [Otto Schott Institute of Material Research (OSIM), Friedrich Schiller University Jena, Fraunhoferstr. 6, 07743 Jena (Germany); Troles, Johann; Caillaud, Celine [Université de Rennes I, Equipe Verres et Céramiques, UMR 6226 Sciences Chimiques de Rennes, Campus de Beaulieu, 35042 Rennes (France); Schmidt, Markus A., E-mail: markus.schmidt@ipht-jena.de [Leibniz Institute of Photonic Technology, Albert-Einstein-Str. 9, 07745 Jena (Germany); Otto Schott Institute of Material Research (OSIM), Friedrich Schiller University Jena, Fraunhoferstr. 6, 07743 Jena (Germany)
2015-05-18
The flow of high-viscosity liquids inside micrometer-size holes can be substantially different from the flow in the bulk, non-confined state of the same liquid. Such non-Newtonian behavior can be employed to generate structural anisotropy in the frozen-in liquid, i.e., in the glassy state. Here, we report on the observation of non-Newtonian flow of an ultralow melting chalcogenide glass inside a silica microcapillary, leading to a strong deviation of the shear viscosity from its value in the bulk material. In particular, we experimentally show that the viscosity is radius-dependent, which is a clear indication that the microscopic rearrangement of the glass network needs to be considered if the lateral confinement falls below a certain limit. The experiments have been conducted using pressure-assisted melt filling, which provides access to the rheological properties of high-viscosity melt flow under previously inaccessible experimental conditions. The resulting flow-induced structural anisotropy can pave the way towards integration of anisotropic glasses inside hybrid photonic waveguides.
Analog quantum simulation of the Rabi model in the ultra-strong coupling regime.
Braumüller, Jochen; Marthaler, Michael; Schneider, Andre; Stehli, Alexander; Rotzinger, Hannes; Weides, Martin; Ustinov, Alexey V
2017-10-03
The quantum Rabi model describes the fundamental mechanism of light-matter interaction. It consists of a two-level atom or qubit coupled to a quantized harmonic mode via a transversal interaction. In the weak coupling regime, it reduces to the well-known Jaynes-Cummings model by applying a rotating wave approximation. The rotating wave approximation breaks down in the ultra-strong coupling regime, where the effective coupling strength g is comparable to the energy ω of the bosonic mode, and remarkable features in the system dynamics are revealed. Here we demonstrate an analog quantum simulation of an effective quantum Rabi model in the ultra-strong coupling regime, achieving a relative coupling ratio of g/ω ~ 0.6. The quantum hardware of the simulator is a superconducting circuit embedded in a cQED setup. We observe fast and periodic quantum state collapses and revivals of the initial qubit state, being the most distinct signature of the synthesized model.An analog quantum simulation scheme has been explored with a quantum hardware based on a superconducting circuit. Here the authors investigate the time evolution of the quantum Rabi model at ultra-strong coupling conditions, which is synthesized by slowing down the system dynamics in an effective frame.
Cooling in the single-photon strong-coupling regime of cavity optomechanics
Nunnenkamp, A.; Børkje, K.; Girvin, S. M.
2012-05-01
In this Rapid Communication we discuss how red-sideband cooling is modified in the single-photon strong-coupling regime of cavity optomechanics where the radiation pressure of a single photon displaces the mechanical oscillator by more than its zero-point uncertainty. Using Fermi's golden rule we calculate the transition rates induced by the optical drive without linearizing the optomechanical interaction. In the resolved-sideband limit we find multiple-phonon cooling resonances for strong single-photon coupling that lead to nonthermal steady states including the possibility of phonon antibunching. Our study generalizes the standard linear cooling theory.
International Nuclear Information System (INIS)
Chang, C.S.; Miller, R.L.
1983-01-01
It has long been recognized that if an EBT-confined plasma could be maintained in the collisionless-ion regime, characterized by positive ambipolar potential and positive radial electric field, the particle loss rates could be reduced by a large factor. The extent to which the loss rate of energy could be reduced has not been as clearly determined, and has been investigated recently using a one-dimensional, time-dependent transport code developed for this purpose. We find that the energy confinement can be improved by roughly an order of magnitude by maintaining a positive radial electric field that increases monotonically with radius, giving a large ExB drift near the outer edge of the core plasma. The radial profiles of heat deposition required to sustain these equilibria will be presented, and scenarios for obtaining dynamical access to the equilibria will be discussed
Strong Optical Shock excitation in the mismatched regime of bubble plasma-wave based LWFA
Sahai, Aakash
2017-10-01
We present investigations into the excitation of a strong optical shock through slicing of a high intensity laser pulse driving a bubble plasma wave in a regime of mis-match between the incident laser waist-size and the bubble size ( = 2√{a0} c /ωpe). In the matched regime, it is well-known that over long timescales, the laser continuously undergoes differential frequency-shifts in different bubble phases, forming an optical shock. In the mis-matched regime, rapid laser waist and resulting bubble oscillations change the location of the peak laser ponderomotive force. This changes the location and the magnitude of the peak electron density interacting with the laser pulse. A sudden increase in the electron density during a laser radial squeeze event, slices the laser envelope longitudinally near its peak amplitude, exciting a strong optical shock state. This is shown to occur much earlier in laser evolution only over a narrow range of plasma densities where the imbalance between the longitudinal & radial ponderomotive forces excites elongated bubbles, injects ultra-low emittance electron beams and sustains ultra-high peak plasma fields. We acknowledge STFC Grants ST/J002062/1 and ST/P000835/1 for the John Adams Institute of Accelerator Science.
Characteristics of various confinement regimes obtained with EC and LH heating on the TdeV tokamak
International Nuclear Information System (INIS)
Pacher, G.W.; Decoste, R.; Demers, Y.
1999-01-01
Steady-state H-modes in type III ELM regime on TdeV with electron cyclotron and lower hybrid heating are investigated with respect to lower hybrid wave coupling, threshold power, helium pumping and separation between separatrix and surrounding structures. Energy confinement is found to improve as the distance between separatrix and divertor baffle is reduced. With off-axis EC heating, reduced particle transport is observed inside the deposition zone, but no energy transport barrier is obtained. New measurements on compact toroid fuelling are reported which indicate that further optimization of the injector is required. (author)
Characteristics of various confinement regimes obtained with EC and LH heating on the TdeV tokamak
International Nuclear Information System (INIS)
Pacher, G.W.; Decoste, R.; Demers, Y.
2001-01-01
Steady-state H-modes in type III ELM regime on TdeV with electron cyclotron and lower hybrid heating are investigated with respect to lower hybrid wave coupling, threshold power, helium pumping and separation between separatrix and surrounding structures. Energy confinement is found to improve as the distance between separatrix and divertor baffle is reduced. With off-axis EC heating, reduced particle transport is observed inside the deposition zone, but no energy transport barrier is obtained. New measurements on compact toroid fuelling are reported which indicate that further optimization of the injector is required. (author)
International Nuclear Information System (INIS)
Ernst, D.R.; Beer, M.; Batha, S.
2001-01-01
Turbulence suppression by radial electric field shear (E r ) is shown to be important in the enhanced confinement of TFTR supershot plasmas. Simulations of supershot ion temperature profiles are performed using an existing parameterization of transport due to toroidal ion temperature gradient modes, extended to include suppression by E r shear. New spectroscopic measurements of E r differ significantly from prior neoclassical estimates. Supershot temperature profiles appear to be consistent with a criterion describing near-complete turbulence suppression by intrinsically generated E r shear. Helium spoiling and xenon puffing experiments are simulated to illustrate the role of E r shear in the confinement changes observed. (author)
International Nuclear Information System (INIS)
Ernst, D.R.; Beer, M.; Batha, S.
1999-01-01
Turbulence suppression by radial electric field shear (E r ) is shown to be important in the enhanced confinement of TFTR supershot plasmas. Simulations of supershot ion temperature profiles are performed using an existing parameterization of transport due to toroidal ion temperature gradient modes, extended to include suppression by E r shear. New spectroscopic measurements of E r differ significantly from prior neoclassical estimates. Supershot temperature profiles appear to be consistent with a criterion describing near-complete turbulence suppression by intrinsically generated E r shear. Helium spoiling and xenon puffing experiments are simulated to illustrate the role of E r shear in the confinement changes observed. (author)
Quantum simulation of the general semi-classical Rabi model in regimes of arbitrarily strong driving
Dai, Kunzhe; Wu, Haiteng; Zhao, Peng; Li, Mengmeng; Liu, Qiang; Xue, Guangming; Tan, Xinsheng; Yu, Haifeng; Yu, Yang
2017-12-01
We propose and experimentally demonstrate a scheme to simulate the interaction between a two-level system and a classical light field. Under the transversal driving of two microwave tones, the effective Hamiltonian in an appropriate rotating frame is identical to that of the general semi-classical Rabi model. We experimentally realize this Hamiltonian with a superconducting transmon qubit. By tuning the strength, phase, and frequency of the two microwave driving fields, we simulate the quantum dynamics from the weak to extremely strong driving regime. Under these conditions, we observe that, as a function of increased Rabi drive strength, the qubit evolution gradually deviates from the normal sinusoidal Rabi oscillation, in accordance with the predictions of the general semi-classical Rabi model far beyond the weak driving limit. Our scheme provides an effective approach to investigate the extremely strong interaction between a two-level system and a classical light field. Such strong interactions are usually inaccessible in experiments.
A theoretical model of strong and moderate El Niño regimes
Takahashi, Ken; Karamperidou, Christina; Dewitte, Boris
2018-02-01
The existence of two regimes for El Niño (EN) events, moderate and strong, has been previously shown in the GFDL CM2.1 climate model and also suggested in observations. The two regimes have been proposed to originate from the nonlinearity in the Bjerknes feedback, associated with a threshold in sea surface temperature (T_c ) that needs to be exceeded for deep atmospheric convection to occur in the eastern Pacific. However, although the recent 2015-16 EN event provides a new data point consistent with the sparse strong EN regime, it is not enough to statistically reject the null hypothesis of a unimodal distribution based on observations alone. Nevertheless, we consider the possibility suggestive enough to explore it with a simple theoretical model based on the nonlinear Bjerknes feedback. In this study, we implemented this nonlinear mechanism in the recharge-discharge (RD) ENSO model and show that it is sufficient to produce the two EN regimes, i.e. a bimodal distribution in peak surface temperature (T) during EN events. The only modification introduced to the original RD model is that the net damping is suppressed when T exceeds T_c , resulting in a weak nonlinearity in the system. Due to the damping, the model is globally stable and it requires stochastic forcing to maintain the variability. The sustained low-frequency component of the stochastic forcing plays a key role for the onset of strong EN events (i.e. for T>T_c ), at least as important as the precursor positive heat content anomaly (h). High-frequency forcing helps some EN events to exceed T_c , increasing the number of strong events, but the rectification effect is small and the overall number of EN events is little affected by this forcing. Using the Fokker-Planck equation, we show how the bimodal probability distribution of EN events arises from the nonlinear Bjerknes feedback and also propose that the increase in the net feedback with increasing T is a necessary condition for bimodality in the RD
Confined surface plasmon sensors based on strongly coupled disk-in-volcano arrays.
Ai, Bin; Wang, Limin; Möhwald, Helmuth; Yu, Ye; Zhang, Gang
2015-02-14
Disk-in-volcano arrays are reported to greatly enhance the sensing performance due to strong coupling in the nanogaps between the nanovolcanos and nanodisks. The designed structure, which is composed of a nanovolcano array film and a disk in each cavity, is fabricated by a simple and efficient colloidal lithography method. By tuning structural parameters, the disk-in-volcano arrays show greatly enhanced resonances in the nanogaps formed by the disks and the inner wall of the volcanos. Therefore they respond to the surrounding environment with a sensitivity as high as 977 nm per RIU and with excellent linear dependence on the refraction index. Moreover, through mastering the fabrication process, biological sensing can be easily confined to the cavities of the nanovolcanos. The local responsivity has the advantages of maximum surface plasmon energy density in the nanogaps, reducing the sensing background and saving expensive reagents. The disk-in-volcano arrays also possess great potential in applications of optical and electrical trapping and single-molecule analysis, because they enable establishment of electric fields across the gaps.
Strong quantum-confined stark effect in germanium quantum-well structures on silicon
International Nuclear Information System (INIS)
Kuo, Y.; Lee, Y. K.; Gei, Y.; Ren, S; Roth, J. E.; Miller, D. A.; Harris, J. S.
2006-01-01
Silicon is the dominant semiconductor for electronics, but there is now a growing need to integrate such component with optoelectronics for telecommunications and computer interconnections. Silicon-based optical modulators have recently been successfully demonstrated but because the light modulation mechanisms in silicon are relatively weak, long (for example, several millimeters) devices or sophisticated high-quality-factor resonators have been necessary. Thin quantum-well structures made from III-V semiconductors such as GaAs, InP and their alloys exhibit the much stronger Quantum-Confined Stark Effect (QCSE) mechanism, which allows modulator structures with only micrometers of optical path length. Such III-V materials are unfortunately difficult to integrate with silicon electronic devices. Germanium is routinely integrated with silicon in electronics, but previous silicon-germanium structures have also not shown strong modulation effects. Here we report the discovery of the QCSE, at room temperature, in thin germanium quantum-well structures grown on silicon. The QCSE here has strengths comparable to that in III-V materials. Its clarity and strength are particularly surprising because germanium is an indirect gap semiconductor, such semiconductors often display much weak optical effects than direct gap materials (such as the III-V materials typically used for optoelectronics). This discovery is very promising for small, high-speed, low-power optical output devices fully compatible with silicon electronics manufacture. (author)
Energy Technology Data Exchange (ETDEWEB)
Takamoto, Makoto [Department of Earth and Planetary Science, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo, 113-0033 (Japan); Lazarian, Alexandre, E-mail: mtakamoto@eps.s.u-tokyo.ac.jp, E-mail: alazarian@facstaff.wisc.edu [Department of Astronomy, University of Wisconsin, 475 North Charter Street, Madison, WI 53706 (United States)
2016-11-10
In this Letter, we report compressible mode effects on relativistic magnetohydrodynamic (RMHD) turbulence in Poynting-dominated plasmas using three-dimensional numerical simulations. We decomposed fluctuations in the turbulence into 3 MHD modes (fast, slow, and Alfvén) following the procedure of mode decomposition in Cho and Lazarian, and analyzed their energy spectra and structure functions separately. We also analyzed the ratio of compressible mode to Alfvén mode energy with respect to its Mach number. We found the ratio of compressible mode increases not only with the Alfvén Mach number, but also with the background magnetization, which indicates a strong coupling between the fast and Alfvén modes. It also signifies the appearance of a new regime of RMHD turbulence in Poynting-dominated plasmas where the fast and Alfvén modes are strongly coupled and, unlike the non-relativistic MHD regime, cannot be treated separately. This finding will affect particle acceleration efficiency obtained by assuming Alfvénic critical-balance turbulence and can change the resulting photon spectra emitted by non-thermal electrons.
Electronic structure and superconductivity in strongly correlated systems in the pseudogap regime
Energy Technology Data Exchange (ETDEWEB)
Puig-Puig, L.; Lopez-Aguilar, F. [Grup d`Electromagnetisme, Departament de Fisica, Edifici Cn, Universitat Autonoma de Barcelona, E-08193 Ballaterra (Barcelona) (Spain)
1995-12-15
We propose effective potentials from a screened Coulomb interaction which arises from spin-fluctuation effects within a three-dimensional Hubbard single-band model for systems with strongly correlated electrons within the pseudogap regime. This regime is characterized by the existence in the normal state of at least two structures located at both sides of the Fermi level and split by a gap or pseudogap. This is the most crucial assumption in the analysis performed in this work. We consider the proposed effective interactions between fermions, analyzing the possibility of obtaining superconductivity by means of the formulation of the corresponding Dyson-like equations for the normal and anomalous one-body propagators in the state with bosonic condensation. We also include vertex effects within these effective fermion-fermion interactions and discuss their influence in this formalism in order to consider a Migdal-like theory appropriate to Hubbard systems. In cases where superconductivity is found, the critical temperature is obtained and the influence of the band and potential parameters is analyzed.
Turbulence and transport in enhanced confinement regimes of tokamaks: Simulation and theory
International Nuclear Information System (INIS)
Hahm, T.S.; Artun, M.; Beer, M.A.
1996-01-01
An integrated program of theory and computation has been developed to understand the physics responsible for the favorable confinement trends exhibited by, for example, enhanced reversed shear (ERS) plasmas in TFTR and DIII-D. This paper reports on (1) the quantitative assessment of ExB shear suppression of turbulence by comparison of the linear growth rate calculated from the gyrofluid/comprehensive kinetic codes and the experimentally measured shearing rate in TFTR ERS plasmas; (2) the first self-consistent nonlinear demonstration of ion temperature gradient turbulence reduction due to angle P i driven ExB shear by the global gyrokinetic simulation; (3) a revised neoclassical analysis and gyrokinetic particle simulation results in agreement with trends in ERS plasmas; (4) Shafranov shift induced stabilization of trapped electron mode in ERS plasmas calculated by the gyrofluid code; and (5) new nonlinear gyrokinetic equations for turbulence in core transport barriers
Evidence of different confinement regimes in site-controlled pyramidal InGaN structures
International Nuclear Information System (INIS)
Perez-Solorzano, V.; Groening, A.; Schweizer, H.; Jetter, M.
2005-01-01
We deposited InGaN on GaN micropyramids, which were grown by selective metal-organic vapor phase epitaxy on sapphire. We expected the formation of a quantum well on the side-walls of the pyramids, a quantum wire on the edges, and a quantum dot on its apex. We studied the emission properties of these structures using low-temperature time-resolved photoluminescence. Our measurements showed three regions of different confinement within the emission in the wavelength range between 2.12 eV and 2.40 eV. By analyzing the decay behavior, the characteristics of the luminescence was determined to originate from localized states. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)
Evidence of different confinement regimes in site-controlled pyramidal InGaN structures
Energy Technology Data Exchange (ETDEWEB)
Perez-Solorzano, V.; Groening, A.; Schweizer, H.; Jetter, M. [4. Physical Institute, University of Stuttgart, Pfaffenwaldring 57, 70569 Stuttgart (Germany)
2005-10-01
We deposited InGaN on GaN micropyramids, which were grown by selective metal-organic vapor phase epitaxy on sapphire. We expected the formation of a quantum well on the side-walls of the pyramids, a quantum wire on the edges, and a quantum dot on its apex. We studied the emission properties of these structures using low-temperature time-resolved photoluminescence. Our measurements showed three regions of different confinement within the emission in the wavelength range between 2.12 eV and 2.40 eV. By analyzing the decay behavior, the characteristics of the luminescence was determined to originate from localized states. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)
Gor'kov, L P; Teitel'baum, G B
2014-01-29
We address recent experiments shedding light on the energy spectrum of under and optimally doped cuprates at temperatures above the superconducting transition. Angle resolved photoemission reveals coherent excitation only near nodal points on parts of the 'bare' Fermi surface known as the Fermi arcs. The question debated in the literature is whether the small normal pocket, seen via quantum oscillations, exists at higher temperatures or forms below a charge order transition in strong magnetic fields. Assuming the former case as a possibility, expressions are derived for the resistivity and the Hall coefficient (in weak and strong magnetic fields) with both types of carriers participating in the transport. There are two regimes. At higher temperatures (at a fixed field) electrons are dragged by the Fermi arcs' holes. The pocket being small, its contribution to conductivity and the Hall coefficient is negligible. At lower temperatures electrons decouple from holes behaving as a Fermi gas in the magnetic field. As the mobility of holes on the arcs decreases in strong fields with a decrease of temperature, below a crossover point the pocket electrons prevail, changing the sign of the Hall coefficient in the low temperature limit. Such behavior finds its confirmation in recent high-field experiments.
Density-dependent electron scattering in photoexcited GaAs in strongly diffusive regime
DEFF Research Database (Denmark)
Mics, Zoltán; D’Angio, Andrea; Jensen, Søren A.
2013-01-01
In a series of systematic optical pump–terahertz probe experiments, we study the density-dependent electron scattering rate in photoexcited GaAs in the regime of strong carrier diffusion. The terahertz frequency-resolved transient sheet conductivity spectra are perfectly described by the Drude...... model, directly yielding the electron scattering rates. A diffusion model is applied to determine the spatial extent of the photoexcited electron-hole gas at each moment after photoexcitation, yielding the time-dependent electron density, and hence the density-dependent electron scattering time. We find...... that the electron scattering time decreases from 320 to 60 fs, as the electron density changes from 1015 to 1019 cm−3....
Modeling cavities exhibiting strong lateral confinement using open geometry Fourier modal method
Häyrynen, Teppo; Gregersen, Niels
2016-04-01
We have developed a computationally efficient Fourier-Bessel expansion based open geometry formalism for modeling the optical properties of rotationally symmetric photonic nanostructures. The lateral computation domain is assumed infinite so that no artificial boundary conditions are needed. Instead, the leakage of the modes due to an imperfect field confinement is taken into account by using a basis functions that expand the whole infinite space. The computational efficiency is obtained by using a non-uniform discretization in the frequency space in which the lateral expansion modes are more densely sampled around a geometry specific dominant transverse wavenumber region. We will use the developed approach to investigate the Q factor and mode confinement in cavities where top DBR mirror has small rectangular defect confining the modes laterally on the defect region.
Directory of Open Access Journals (Sweden)
Sawrab Chowdhury
2017-04-01
Full Text Available In this article, porous core porous cladding photonic crystal fiber (P-PCF has been proposed for aqueous analytes sensing applications. Guiding properties of the proposed P-PCF has been numerically investigated by utilizing the full vectorial finite element method (FEM. The relative sensitivity and confinement loss are obtained by varying distinct geometrical parameters like the diameter of air holes, a pitch of the core and cladding region over a wider range of wavelength. The proposed P-PCF is organized with five rings air hole in the cladding and two rings air hole in a core territory which maximizes the relative sensitivity expressively and minimizes confinement loss depressively compare with the prior-PCF structures. After completing all investigations, it is also visualized that the relative sensitivity is increasing with the increment of the wavelength of communication band (O + E + S + C + L + U. Higher sensitivity is gained by using higher band for all applied liquids. Finally the investigating effects of different structural parameters of the proposed P-PCF are optimized which shows the sensitivity of 60.57%, 61.45% and 61.82%; the confinement loss of 8.71 × 10−08 dB/m, 1.41 × 10−10 dB/m and 6.51 × 10−10 dB/m for Water (n = 1.33, Ethanol (n = 1.354 and Benzene (n = 1.366 respectively at 1.33 μm wavelength. The optimized P-PCF with higher sensitivity and lower confinement loss has high impact in the area of the chemical as well as gas sensing purposes. Keywords: Porous shaped PCF, Sensitivity, Optical sensing, Liquid sensor, Confinement loss
Energy Technology Data Exchange (ETDEWEB)
Kilkenny, J.D.
1994-08-04
As shown elsewhere an ablatively imploded shell is hydrodynamically unstable, the dominant instability being the well known Rayleigh-Taylor instability with growth rate {gamma} = {radical}Akg where k = 2{pi}/{lambda} is the wave number, g is the acceleration and A the Attwood number ({rho}{sub hi} {minus} {rho}{sub lo})/({rho}{sub hi} + {rho}{sub lo}) where {rho}{sub hi} is the density of the heavier fluid and {rho}{sub lo} is the density of the lighter fluid. A theoretical understanding of ablative stabilization has gradually evolved, confirmed over the last five years by experiments. The linear growth is very well understood with excellent agreement between experiment and simulation for planar geometry with wavelengths in the region of 30--100{mu}m. There is an accurate, albeit phenomenological dispersion relation. The non-linear growth has been measured and agrees with calculations. In this lecture, the authors go into the fundamentals of the Rayleigh-Taylor instability and the experimental measurements that show it is stabilized sufficiently by ablation in regimes relevant to ICF.
Engineering light emission of two-dimensional materials in both the weak and strong coupling regimes
Brotons-Gisbert, Mauro; Martínez-Pastor, Juan P.; Ballesteros, Guillem C.; Gerardot, Brian D.; Sánchez-Royo, Juan F.
2018-01-01
Two-dimensional (2D) materials have promising applications in optoelectronics, photonics, and quantum technologies. However, their intrinsically low light absorption limits their performance, and potential devices must be accurately engineered for optimal operation. Here, we apply a transfer matrix-based source-term method to optimize light absorption and emission in 2D materials and related devices in weak and strong coupling regimes. The implemented analytical model accurately accounts for experimental results reported for representative 2D materials such as graphene and MoS2. The model has been extended to propose structures to optimize light emission by exciton recombination in MoS2 single layers, light extraction from arbitrarily oriented dipole monolayers, and single-photon emission in 2D materials. Also, it has been successfully applied to retrieve exciton-cavity interaction parameters from MoS2 microcavity experiments. The present model appears as a powerful and versatile tool for the design of new optoelectronic devices based on 2D semiconductors such as quantum light sources and polariton lasers.
Lasing by driven atoms-cavity system in collective strong coupling regime.
Sawant, Rahul; Rangwala, S A
2017-09-12
The interaction of laser cooled atoms with resonant light is determined by the natural linewidth of the excited state. An optical cavity is another optically resonant system where the loss from the cavity determines the resonant optical response of the system. The near resonant combination of an optical Fabry-Pérot cavity with laser cooled and trapped atoms couples two distinct optical resonators via light and has great potential for precision measurements and the creation of versatile quantum optics systems. Here we show how driven magneto-optically trapped atoms in collective strong coupling regime with the cavity leads to lasing at a frequency red detuned from the atomic transition. Lasing is demonstrated experimentally by the observation of a lasing threshold accompanied by polarization and spatial mode purity, and line-narrowing in the outcoupled light. Spontaneous emission into the cavity mode by the driven atoms stimulates lasing action, which is capable of operating as a continuous wave laser in steady state, without a seed laser. The system is modeled theoretically, and qualitative agreement with experimentally observed lasing is seen. Our result opens up a range of new measurement possibilities with this system.
Frassinetti, L.; Yagi, Y.; Koguchi, H.; Shimada, T.; Hirano, Y.; Sakakita, H.
2006-04-01
The pulsed poloidal current drive technique reduces the magnetic chaos that characterizes reversed-field pinch configurations and produces a regime with an improved confinement. In this paper, we describe that, in TPE-RX [Y. Yagi et al., Fusion Eng. Des. 45, 409 (1999)], the termination phase of this regime is due to the increase of the slinky structure that creates a stochastic region and produces the expulsion of energy in a localized toroidal position. Before the plasma reaches the improved confinement regime, the slinky distorts the chain of m =0 islands on the reversal surface. During this regime, the magnetic activity and the phase locking decrease, the distortion in the island chain disappears, and the confinement increases. At the termination of this regime the magnetic activity markedly increases, as well as the phase locking, recreating the distortion in the m =0 magnetic island chain. As a consequence, at the position of the distortion the plasma region inside the reversal surface is characterized by a rapid energy loss, and outside the reversal surface a toroidally localized energy expulsion is induced.
International Nuclear Information System (INIS)
Frassinetti, L.; Yagi, Y.; Koguchi, H.; Shimada, T.; Hirano, Y.; Sakakita, H.
2006-01-01
The pulsed poloidal current drive technique reduces the magnetic chaos that characterizes reversed-field pinch configurations and produces a regime with an improved confinement. In this paper, we describe that, in TPE-RX [Y. Yagi et al., Fusion Eng. Des. 45, 409 (1999)], the termination phase of this regime is due to the increase of the slinky structure that creates a stochastic region and produces the expulsion of energy in a localized toroidal position. Before the plasma reaches the improved confinement regime, the slinky distorts the chain of m=0 islands on the reversal surface. During this regime, the magnetic activity and the phase locking decrease, the distortion in the island chain disappears, and the confinement increases. At the termination of this regime the magnetic activity markedly increases, as well as the phase locking, recreating the distortion in the m=0 magnetic island chain. As a consequence, at the position of the distortion the plasma region inside the reversal surface is characterized by a rapid energy loss, and outside the reversal surface a toroidally localized energy expulsion is induced
Optimization of confinement in a toroidal plasma subject to strong radial electric fields
International Nuclear Information System (INIS)
Roth, J.R.
1977-01-01
A preliminary report on the identification and optimization of independent variables which affect the ion density and confinement time in a bumpy torus plasma is presented. The independent variables include the polarity, position, and number of the midplane electrode rings, the method of gas injection, and the polarity and strength of a weak vertical magnetic field. Some characteristic data taken under condition when most of the independent variables were optimized are presented. The highest value of the electron number density on the plasma axis is 3.2 x 10 to the 12th power/cc, the highest ion heating efficiency is 47 percent, and the longest particle containment time is 2.0 milliseconds
Directory of Open Access Journals (Sweden)
Jingxuan Yang
2017-11-01
Full Text Available In extra-thick coal seams, mining operations can lead to large-scale disturbances, complex overburden structures, and frequent and strong strata behavior in the stope, which are serious threats to mine safety. This study analyzed the overburden structure and strata behavior and proposed the technique of confined blasting in water-filled deep holes as a measure to prevent strong rock pressure. It found that there are two primary reasons for the high effectiveness of the proposed technique in presplitting hard coal and rock. First, the fracture water enables much more efficient transfer of dynamic load due to its incompressibility. Second, the subsequent expansion of water can further split the rock by compression. A mechanical model was used to reveal how the process of confined blasting in water-filled deep holes presplit roof. Moreover, practical implementation of this technique was found to improve the structure of hard, thick roof and prevent strong rock pressure, demonstrating its effectiveness in roof control.
Self-assembly of a novel beta-In2S3 nanostructure exhibiting strong quantum confinement effects.
Zhang, Wu; Ma, Dekun; Huang, Zhen; Tang, Qun; Xie, Qin; Qian, Yitai
2005-05-01
The 3D beta-In2S3 flowerlike architecture assembled from nanoflakes was prepared via a novel complex-precursor assisted (CPA) solvothermal route. The as-prepared beta-In2S3 powder was characterized by X-ray diffraction pattern (XRD), X-ray photoelectron spectra (XPS), transition electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM), ultraviolet-visible light (UV-vis) spectra, and photoluminescence spectrum. The novel 3D beta-In2S3 nanostructure exhibit a strong quantum confinement effect. FT-IR spectra were used to investigate the coordinative chemical effect in the complex. A possible mechanism was discussed.
International Nuclear Information System (INIS)
Malik, M.A.
1988-01-01
There is a self-consistent theory of the effects of neutral beam injection on impurity transport in tokamak plasmas. The theory predicts that co-injection drives impurities outward and that counter-injection enhances the normally inward flow of impurities. The theory was applied to carry out a detailed analysis of the large experimental database from the PLT and the ISX-B tokamaks. The theory was found to generally model the experimental data quite well. It is, therefore, concluded that neutral beam co-injection can drive impurities outward to achieve clean central plasmas and a cool radiating edge. Theoretical predictions for future thermonuclear reactors such as INTOR, TIBER II, and ITER indicated that neutral beam driven flow reversal might be an effective impurity control method if the rate of beam momentum deposited per plasma ion is adequate. The external momentum drag, which is a pivotal concept in impurity flow reversal theory, is correctly predicted by the gyroviscous theory of momentum confinement. The theory was applied to analyze experimental data from the PLT and the PDX tokamaks with exact experimental conditions. The theory was found to be in excellent agreement with experiment over a wide range of parameters. It is, therefore, possible to formulate the impurity transport theory from first principles, without resort to empiricism
Wu, Ning; Feist, Johannes; Garcia-Vidal, Francisco J.
2016-11-01
We present a microscopic semianalytical theory for the description of organic molecules interacting strongly with a cavity mode. Exciton-vibration coupling within the molecule and exciton-cavity interaction are treated on an equal footing by employing a temperature-dependent variational approach. The interplay between strong exciton-vibration coupling and strong exciton-cavity coupling gives rise to a hybrid ground state, which we refer to as the lower polaron polariton. Explicit expressions for the ground-state wave function, the zero-temperature quasiparticle weight of the lower polaron polariton, the photoluminescence line strength, and the mean number of vibrational quanta are obtained in terms of the optimal variational parameters. The dependence of these quantities upon the exciton-cavity coupling strength reveals that strong cavity coupling leads to an enhanced vibrational dressing of the cavity mode, and at the same time a vibrational decoupling of the dark excitons, which in turn results in a lower polaron polariton resembling a single-mode dressed bare lower polariton in the strong-coupling regime. Thermal effects on several observables are briefly discussed.
High mobility of the strongly confined hole gas in AgTaO3/SrTiO3
Nazir, Safdar
2012-05-18
A theoretical study of the two-dimensional hole gas at the (AgO)−/(TiO2)0 p-type interface in the AgTaO3/SrTiO3 (001) heterostructure is presented. The Ag 4d states strongly hybridize with the O 2p states and contribute to the hole gas. It is demonstrated that the holes are confined to an ultra thin layer (∼4.9Å) with a considerable carrier density of ∼1014cm−2. We estimate a hole mobility of 18.6 cm2 V−1 s−1, which is high enough to enable device applications.
Directory of Open Access Journals (Sweden)
William J Platt
Full Text Available Fire seasonality, an important characteristic of fire regimes, commonly is delineated using seasons based on single weather variables (rainfall or temperature. We used nonparametric cluster analyses of a 17-year (1993-2009 data set of weather variables that influence likelihoods and spread of fires (relative humidity, air temperature, solar radiation, wind speed, soil moisture to explore seasonality of fire in pine savanna-grassland landscapes at the Avon Park Air Force Range in southern Florida. A four-variable, three-season model explained more variation within fire weather variables than models with more seasons. The three-season model also delineated intra-annual timing of fire more accurately than a conventional rainfall-based two-season model. Two seasons coincided roughly with dry and wet seasons based on rainfall. The third season, which we labeled the fire season, occurred between dry and wet seasons and was characterized by fire-promoting conditions present annually: drought, intense solar radiation, low humidity, and warm air temperatures. Fine fuels consisting of variable combinations of pyrogenic pine needles, abundant C4 grasses, and flammable shrubs, coupled with low soil moisture, and lightning ignitions early in the fire season facilitate natural landscape-scale wildfires that burn uplands and across wetlands. We related our three season model to fires with different ignition sources (lightning, military missions, and prescribed fires over a 13-year period with fire records (1997-2009. Largest wildfires originate from lightning and military ignitions that occur within the early fire season substantially prior to the peak of lightning strikes in the wet season. Prescribed ignitions, in contrast, largely occur outside the fire season. Our delineation of a pronounced fire season provides insight into the extent to which different human-derived fire regimes mimic lightning fire regimes. Delineation of a fire season associated with
Platt, William J.; Orzell, Steve L.; Slocum, Matthew G.
2015-01-01
Fire seasonality, an important characteristic of fire regimes, commonly is delineated using seasons based on single weather variables (rainfall or temperature). We used nonparametric cluster analyses of a 17-year (1993–2009) data set of weather variables that influence likelihoods and spread of fires (relative humidity, air temperature, solar radiation, wind speed, soil moisture) to explore seasonality of fire in pine savanna-grassland landscapes at the Avon Park Air Force Range in southern Florida. A four-variable, three-season model explained more variation within fire weather variables than models with more seasons. The three-season model also delineated intra-annual timing of fire more accurately than a conventional rainfall-based two-season model. Two seasons coincided roughly with dry and wet seasons based on rainfall. The third season, which we labeled the fire season, occurred between dry and wet seasons and was characterized by fire-promoting conditions present annually: drought, intense solar radiation, low humidity, and warm air temperatures. Fine fuels consisting of variable combinations of pyrogenic pine needles, abundant C4 grasses, and flammable shrubs, coupled with low soil moisture, and lightning ignitions early in the fire season facilitate natural landscape-scale wildfires that burn uplands and across wetlands. We related our three season model to fires with different ignition sources (lightning, military missions, and prescribed fires) over a 13-year period with fire records (1997–2009). Largest wildfires originate from lightning and military ignitions that occur within the early fire season substantially prior to the peak of lightning strikes in the wet season. Prescribed ignitions, in contrast, largely occur outside the fire season. Our delineation of a pronounced fire season provides insight into the extent to which different human-derived fire regimes mimic lightning fire regimes. Delineation of a fire season associated with timing of
Zhou, Ning; Yuan, Meng; Gao, Yuhan; Li, Dongsheng; Yang, Deren
2016-04-26
Strong coupling between semiconductor excitons and localized surface plasmons (LSPs) giving rise to hybridized plexciton states in which energy is coherently and reversibly exchanged between the components is vital, especially in the area of quantum information processing from fundamental and practical points of view. Here, in photoluminescence spectra, rather than from common extinction or reflection measurements, we report on the direct observation of Rabi splitting of approximately 160 meV as an indication of strong coupling between excited states of CdSe/ZnS quantum dots (QDs) and LSP modes of silver nanoshells under nonresonant nanosecond pulsed laser excitation at room temperature. The strong coupling manifests itself as an anticrossing-like behavior of the two newly formed polaritons when tuning the silver nanoshell plasmon energies across the exciton line of the QDs. Further analysis substantiates the essentiality of high pump energy and collective strong coupling of many QDs with the radiative dipole mode of the metallic nanoparticles for the realization of strong coupling. Our finding opens up interesting directions for the investigation of strong coupling between LSPs and excitons from the perspective of radiative recombination under easily accessible experimental conditions.
Energy deposition of heavy ions in the regime of strong beam-plasma correlations.
Gericke, D O; Schlanges, M
2003-03-01
The energy loss of highly charged ions in dense plasmas is investigated. The applied model includes strong beam-plasma correlation via a quantum T-matrix treatment of the cross sections. Dynamic screening effects are modeled by using a Debye-like potential with a velocity dependent screening length that guarantees the known low and high beam velocity limits. It is shown that this phenomenological model is in good agreement with simulation data up to very high beam-plasma coupling. An analysis of the stopping process shows considerably longer ranges and a less localized energy deposition if strong coupling is treated properly.
What occurs in the fragile-to-strong liquid transition regime?
DEFF Research Database (Denmark)
Yue, Yuanzheng; Hu, L.N.
The slow dynamics of glass-forming liquids is a complex subject of the condensed matter science. But the fragile-to-strong transition, which was observed not long ago [Ito, et al, Nature 1999], makes this subject even more complex since it is extremely challenging to directly probe the structural...
Zhang, Yu-Yu; Chen, Xiang-You
2017-12-01
An unexplored nonperturbative deep strong coupling (npDSC) achieved in superconducting circuits has been studied in the anisotropic Rabi model by the generalized squeezing rotating-wave approximation. Energy levels are evaluated analytically from the reformulated Hamiltonian and agree well with numerical ones in a wide range of coupling strength. Such improvement ascribes to deformation effects in the displaced-squeezed state presented by the squeezed momentum variance, which are omitted in previous displaced states. The atom population dynamics confirms the validity of our approach for the npDSC strength. Our approach offers the possibility to explore interesting phenomena analytically in the npDSC regime in qubit-oscillator experiments.
Strong-pinning regimes by spherical inclusions in anisotropic type-II superconductors
Willa, R.; Koshelev, A. E.; Sadovskyy, I. A.; Glatz, A.
2018-01-01
The current-carrying capacity of type-II superconductors is decisively determined by how well material defect structures can immobilize vortex lines. In order to gain deeper insights into the fundamental pinning mechanisms, we have explored the case of vortex trapping by randomly distributed spherical inclusions using large-scale simulations of the time-dependent Ginzburg–Landau equations. We find that for a small density of particles having diameters of two coherence lengths, the vortex lattice preserves its structure and the critical current j c decays with the magnetic field following a power-law {B}-α with α ≈ 0.66, which is consistent with predictions of strong-pinning theory. For a higher density of particles and/or larger inclusions, the lattice becomes progressively more disordered and the exponent smoothly decreases down to α ≈ 0.3. At high magnetic fields, all inclusions capture a vortex and the critical current decays faster than {B}-1 as would be expected by theory. In the case of larger inclusions with a diameter of four coherence lengths, the magnetic-field dependence of the critical current is strongly affected by the ability of inclusions to capture multiple vortex lines. We found that at small densities, the fraction of inclusions trapping two vortex lines rapidly grows within narrow field range leading to a peak in j c(B)-dependence within this range. With increasing inclusion density, this peak transforms into a plateau, which then smooths out. Using the insights gained from simulations, we determine the limits of applicability of strong-pinning theory and provide different routes to describe vortex pinning beyond those bounds.
Strong-pinning regimes by spherical inclusions in anisotropic type-II superconductors
Energy Technology Data Exchange (ETDEWEB)
Willa, R.; Koshelev, A. E.; Sadovskyy, I. A.; Glatz, A.
2017-11-27
The current-carrying capacity of type-II superconductors is decisively determined by how well material defect structures can immobilize vortex lines. In order to gain deeper insights into intrinsic pinning mechanisms, we have explored the case of vortex trapping by randomly distributed spherical inclusions using large-scale simulations of the time-dependent Ginzburg-Landau equations. We find that for a small density of particles having diameters of two coherence lengths, the vortex lattice preserves its structure and the critical current jc decays with the magnetic field following a power-law B-a with a ~ 0:66, which is consistent with predictions of strong pinning theory. For higher density of particles and/or larger inclusions, the lattice becomes progressively more disordered and the exponent smoothly decreases down to a ~ 0:3. At high magnetic fields, all inclusions capture a vortex and the critical current decays faster than B-1 as would be expected by theory. In the case of larger inclusions with diameter of four coherence length, the magnetic-field dependence of the critical current is strongly affected by the ability of inclusions to capture multiple vortex lines. We found that at small densities, the fraction of inclusions trapping two vortex lines rapidly grows within narrow field range leading to a shallow peak in jc(B)-dependence within this range. With increasing inclusion density, this peak transforms into a plateau, which then smooths out. Using the insights gained from simulations, we determine the limits of applicability of strong pinning theory and provide different routes to describe vortex pinning beyond those bounds.
Simple model of a Feshbach resonance in the strong-coupling regime
Wasak, T.; Krych, M.; Idziaszek, Z.; Trippenbach, M.; Avishai, Y.; Band, Y. B.
2014-11-01
We use the dressed potentials obtained in the adiabatic representation of two coupled channels to calculate s -wave Feshbach resonances in a three-dimensional spherically symmetric potential with an open channel interacting with a closed channel. Analytic expressions for the s -wave scattering length a and number of resonances are obtained for a piecewise constant model with a piecewise constant interaction of the open and closed channels near the origin. We show analytically and numerically that, for strong enough coupling strength, Feshbach resonances can exist even when the closed channel does not have a bound state.
Strong Quantum Confinement Effects and Chiral Excitons in Bio-Inspired ZnO–Amino Acid Cocrystals
Muhammed, Madathumpady Abubaker Habeeb
2018-02-20
Elucidating the underlying principles behind band gap engineering is paramount for the successful implementation of semiconductors in photonic and optoelectronic devices. Recently it has been shown that the band gap of a wide and direct band gap semiconductor, such as ZnO, can be modified upon cocrystallization with amino acids, with the role of the biomolecules remaining unclear. Here, by probing and modeling the light-emitting properties of ZnO-amino acid cocrystals, we identify the amino acids\\' role on this band gap modulation and demonstrate their effective chirality transfer to the interband excitations in ZnO. Our 3D quantum model suggests that the strong band edge emission blue-shift in the cocrystals can be explained by a quasi-periodic distribution of amino acid potential barriers within the ZnO crystal lattice. Overall, our findings indicate that biomolecule cocrystallization can be used as a truly bio-inspired means to induce chiral quantum confinement effects in quasi-bulk semiconductors.
Sokhoyan, R.; Azizbekyan, H.; Leroy, C.; Ishkhanyan, A.
2011-04-01
We discuss the strong-coupling regime of the nonlinear Landau-Zener problem occurring at coherent photo- and magneto-association of ultracold atoms. We apply a variational approach to an exact third-order nonlinear differential equation for the molecular state probability and construct an accurate approximation describing the time dynamics of the coupled atom-molecule system. The resultant solution improves the accuracy of the previous approximation [22]. The obtained results reveal a remarkable observation that in the strong-coupling limit, the resonance crossing is mostly governed by the nonlinearity, while the coherent atom-molecule oscillations occurring soon after crossing the resonance are principally of a linear nature. This observation is supposedly general for all nonlinear quantum systems having the same generic quadratic nonlinearity, due to the basic attributes of the resonance crossing processes in such systems. The constructed approximation turns out to have a larger applicability range than it was initially expected, covering the whole moderate-coupling regime for which the proposed solution accurately describes ail the main characteristics of the system evolution except the amplitude of the coherent atom-molecule oscillation, which is rather overestimated.
Second sound in a two-dimensional Bose gas: From the weakly to the strongly interacting regime
Ota, Miki; Stringari, Sandro
2018-03-01
Using Landau's theory of two-fluid hydrodynamics, we investigate first and second sounds propagating in a two-dimensional (2D) Bose gas. We study the temperature and interaction dependence of both sound modes and show that their behavior exhibits a deep qualitative change as the gas evolves from the weakly interacting to the strongly interacting regime. Special emphasis is placed on the jump of both sounds at the Berezinskii-Kosterlitz-Thouless transition, caused by the discontinuity of the superfluid density. We find that the excitation of second sound through a density perturbation becomes weaker and weaker as the interaction strength increases as a consequence of the decrease in the thermal expansion coefficient. Our results could be relevant for future experiments on the propagation of sound on the Bose-Einstein condensate (BEC) side of the BCS-BEC crossover of a 2D superfluid Fermi gas.
Kettmann, P.; Hannibal, S.; Croitoru, M. D.; Axt, V. M.; Kuhn, T.
2017-09-01
We present a numerical study of the dynamic response of a confined superfluid Fermi gas to a rapid change of the scattering length (i.e., an interaction quench). Based on a fully microscopic time-dependent density-matrix approach within the full Bogoliubov-de Gennes formalism that includes a 3D harmonic confinement we simulate and identify the emergence of a Goldstone mode of the BCS gap in a cigar-shaped 6Li gas. By analyzing this Goldstone mode over a wide range of parameters, we show that its excitation spectrum is gapless and that its main frequency is not fixed by the trapping potential but that it is determined by the details of the quench. Thus we report the emergence of a pure Goldstone mode of the BCS gap that—in contrast to situations in many previous studies—maintains its gapless excitation spectrum predicted by the Goldstone theorem. Furthermore, we observe that the size-dependent superfluid resonances resulting from the atypical BCS-BEC crossover have a direct impact on this Goldstone mode. Finally, we find that the interaction quench-induced Goldstone mode leads to a low-frequency in-phase oscillation of the single-particle occupations with complete inversion of the lowest-lying single-particle states which could provide a convenient experimental access to the pure gapless Goldstone mode.
Directory of Open Access Journals (Sweden)
Hamid Farrokh Ghatte
2016-09-01
Full Text Available Although many theoretical and experimental studies are available on external confinement of columns using fiber-reinforced polymer (FRP jackets, as well as numerous models proposed for the axial stress-axial strain relation of concrete confined with FRP jackets, they have not been validated with a sufficient amount and variety of experimental data obtained through full-scale tests of reinforced concrete (RC columns with different geometrical and mechanical characteristics. Particularly, no systematical experimental data have been presented on full-scale rectangular substandard RC columns subjected to reversed cyclic lateral loads along either their strong or weak axes. In this study, firstly, test results of five full-scale rectangular substandard RC columns with a cross-sectional aspect ratio of two (300 mm × 600 mm are briefly summarized. The columns were tested under constant axial load and reversed cyclic lateral loads along their strong or weak axes before and after retrofitting with external FRP jackets. In the second stage, inelastic lateral force-displacement relationships of the columns are obtained analytically, making use of the plastic hinge assumption and different FRP confinement models available in the literature. Finally, the analytical findings are compared with the test results for both strong and weak directions of the columns. Comparisons showed that use of different models for the stress-strain relationship of FRP-confined concrete can yield significantly non-conservative or too conservative retrofit designs, particularly in terms of deformation capacity.
Gangolf, Thomas; Blecher, Marius; Bolanos, Simon; Lancia, Livia; Marques, Jean-Raphael; Cerchez, Mirela; Prasad, Rajendra; Aurand, Bastian; Loiseau, Pascal; Fuchs, Julien; Willi, Oswald
2017-10-01
In the ongoing quest for novel techniques to obtain ever higher laser powers, plasma amplification has drawn much attention, benefiting from the fact that a plasma can sustain much higher energy densities than a solid state amplifier. As a plasma process, Stimulated Brillouin Backscattering in the strong coupling regime (sc-SBS) can be used to transfer energy from one laser pulse (pump) to another (seed), by a nonlinear ion oscillation forced by the pump laser. Here, we report on experimental results on amplification by sc-SBS using the ARCTURUS Ti:Sapphire multi-beam laser system at the University of Duesseldorf, Germany. Counter-propagating in a supersonic Hydrogen gas jet target, an ultrashort seed pulse with a pulse duration between 30 and 160 fs and an energy between 1 and 12 mJ was amplified by a high-energy pump pulse (1.7 ps, 700 mJ). For some of the measurements, the gas was pre-ionized with a separate laser pulse (780 fs, 460 mJ). Preliminary analysis shows that the amplification was larger for the longer seed pulses, consistent with theoretical predictions.
Maurer, J.; Willenberg, B.; Daněk, J.; Mayer, B. W.; Phillips, C. R.; Gallmann, L.; Klaiber, M.; Hatsagortsyan, K. Z.; Keitel, C. H.; Keller, U.
2018-01-01
We explore ionization and rescattering in strong mid-infrared laser fields in the nondipole regime over the full range of polarization ellipticity. In three-dimensional photoelectron momentum distributions (3D PMDs) measured with velocity map imaging spectroscopy, we observe the appearance of a sharp ridge structure along the major polarization axis. Within a certain range of ellipticity, the electrons in this ridge are clearly separated from the two lobes that commonly appear in the PMD with elliptically polarized laser fields. In contrast to the well-known lobes of direct electrons, the sharp ridge is created by Coulomb focusing of the softly recolliding electrons. These ridge electrons are directly related to a counterintuitive shift of the PMD peak opposite to the laser beam propagation direction when the dipole approximation breaks down. The ellipticity-dependent 3D PMDs give access to different ionization and recollision dynamics with appropriate filters in the momentum space. For example, we can extract information about the spread of the initial wave packet and the Coulomb momentum transfer of the rescattering electrons.
Effect of excluded volume on the force-extension of wormlike chains in slit confinement
Li, Xiaolan; Dorfman, Kevin
We will present a quantitative phase diagram for the stretching of a wormlike chain confined in a slit with excluded volume interactions. Using pruned-enriched Rosenbluth method (PERM) simulations, we demonstrate the existence of a ``confined Pincus'' regime in slit confinement. This regime is similar to the Pincus regime in free solution, where excluded volume effects are sensible. The lower bound for the confined Pincus regime in the force-contour length plane and the dependence of the extension with force and slit size are in agreement with scaling theory. The upper bound of the confined Pincus regime depends on the confinement strength; it ends in strong confinement when the Pincus blobs do not have excluded volume, while it ends in weak confinement when the Pincus blobs do not fit in the slit. We also show the existence of a free-solution Pincus regime in weak confinement that exists before ideal chain behavior sets in under strong forces. We will discuss the implication of our results on the analysis of experiments on the ``tug-of-war'' stretching of DNA partially confined to a slit.
Ryvkin, Boris S.; Avrutin, Eugene A.; Kostamovaara, Juha T.
2017-12-01
An analytical model for internal optical losses at high power in a 1.5 μm laser diode with strong n-doping in the n-side of the optical confinement layer is created. The model includes intervalence band absorption by holes supplied by both current flow and two-photon absorption (TPA), as well as the direct TPA effect. The resulting losses are compared with those in an identical structure with a weakly doped waveguide, and shown to be substantially lower, resulting in a significant improvement in the output power and efficiency in the structure with a strongly doped waveguide.
Continuum strong-coupling expansion of Yang-Mills theory: quark confinement and infra-red slavery
Energy Technology Data Exchange (ETDEWEB)
Mansfield, P. (Dept. of Mathematical Sciences, Univ. of Durham (United Kingdom))
1994-04-25
We solve Schroedinger's equation for the ground-state of four-dimensional Yang-Mills theory as an expansion in inverse powers of the coupling. Expectation values computed with the leading-order approximation are reduced to a calculation in two-dimensional Yang-Mills theory which is known to confine. Consequently the Wilson loop in the four-dimensional theory obeys an area law to leading order and the coupling becomes infinite as the mass scale goes to zero. (orig.)
Continuum strong-coupling expansion of Yang-Mills theory: quark confinement and infra-red slavery
Mansfield, Paul
1994-04-01
We solve Schrödinger's equation for the ground-state of four-dimensional Yang-Mills theory as an expansion in inverse powers of the coupling. Expectation values computed with the leading-order approximation are reduced to a calculation in two-dimensional Yang-Mills theory which is known to confine. Consequently the Wilson loop in the four-dimensional theory obeys an area law to leading order and the coupling becomes infinite as the mass scale goes to zero.
Ding, S.; Garofalo, A. M.; Qian, J.; Cui, L.; McClenaghan, J. T.; Pan, C.; Chen, J.; Zhai, X.; McKee, G.; Ren, Q.; Gong, X.; Holcomb, C. T.; Guo, W.; Lao, L.; Ferron, J.; Hyatt, A.; Staebler, G.; Solomon, W.; Du, H.; Zang, Q.; Huang, J.; Wan, B.
2017-05-01
Systematic experimental and modeling investigations on DIII-D show attractive transport properties of fully non-inductive high βp plasmas. Experiments on DIII-D show that the large-radius internal transport barrier (ITB), a key feature providing excellent confinement in the high βp regime, is maintained when the scenario is extended from q95 ˜ 12 to 7 and from rapid to near-zero toroidal rotation. The robustness of confinement versus rotation was predicted by gyrofluid modeling showing dominant neoclassical ion energy transport even without the E × B shear effect. The physics mechanism of turbulence suppression, we found, is the Shafranov shift, which is essential and sets a βp threshold for large-radius ITB formation in the high βp scenario on DIII-D. This is confirmed by two different parameter-scan experiments, one for a βN scan and the other for a q95 scan. They both give the same βp threshold at 1.9 in the experiment. The experimental trend of increasing thermal transport with decreasing βp is consistent with transport modeling. The progress toward the high βp scenario on Experimental Advanced Superconducting Tokamak (EAST) is reported. The very first step of extending the high βp scenario on DIII-D to long pulse on EAST is to establish a long pulse H-mode with ITB on EAST. This paper shows the first 61 s fully non-inductive H-mode with stationary ITB feature and actively cooled ITER-like tungsten divertor in the very recent EAST experiment. The successful use of lower hybrid wave as a key tool to optimize the current profile in the EAST experiment is also introduced. Results show that as the electron density is increased, the fully non-inductive current profile broadens on EAST. The improved understanding and modeling capability are also used to develop advanced scenarios for the China Fusion Engineering Test Reactor. Overall, these results provide encouragement that the high βp regime can be extended to a lower safety factor and very low rotation
Directory of Open Access Journals (Sweden)
Sharma Bishwaram
2012-01-01
Full Text Available Effects of a transverse magnetic field on separation of a binary mixture of incompressible viscous thermally and electrically conducting fluids confined between two stationary parallel plates are examined. Both the plates are maintained at constant temperatures. It is assumed that one of the components, which is rarer and lighter, is present in the mixture in a very small quantity. The equations governing the motion, temperature and concentration in Cartesian coordinate are solved analytically. The solution obtained for concentration distribution is plotted against the width of the channel for various values of non-dimensional parameters. It is found that the effect of transverse magnetic field is to separate the species of rarer and lighter component by contributing its effect directly to the temperature gradient and the pressure gradient. The effects of increase in the values of Hartmann number, magnetic Reynolds number, barodiffusion number, thermal diffusion number, electric field parameter and the product of Prandtl number and Eckert number are to collect the rarer and lighter component near the upper plate and throw away the heavier component towards the lower plate. The problem discussed here derives its application in the basic fluid dynamics separation processes to separate the rare component of the different isotopes of heavier molecules where electromagnetic method of separation does not work.
DEFF Research Database (Denmark)
Ou, Haiyan; Rottwitt, Karsten
2008-01-01
Standard silica-on-silicon waveguides with a core doped by Ge nanocrystals were fabricated using PECVD and RIE. Transmission of the waveguide was measured, and strong absorption peaks at 1056.8 nm, 1406 nm and 1263.2 nm were observed.......Standard silica-on-silicon waveguides with a core doped by Ge nanocrystals were fabricated using PECVD and RIE. Transmission of the waveguide was measured, and strong absorption peaks at 1056.8 nm, 1406 nm and 1263.2 nm were observed....
Weck, Philippe F.; Cochrane, Kyle R.; Root, Seth; Lane, J. Matthew D.; Shulenburger, Luke; Carpenter, John H.; Sjostrom, Travis; Mattsson, Thomas R.; Vogler, Tracy J.
2018-03-01
The shock Hugoniot for full-density and porous CeO2 was investigated in the liquid regime using ab initio molecular dynamics (AIMD) simulations with Erpenbeck's approach based on the Rankine-Hugoniot jump conditions. The phase space was sampled by carrying out NVT simulations for isotherms between 6000 and 100 000 K and densities ranging from ρ =2.5 to 20 g /cm3 . The impact of on-site Coulomb interaction corrections +U on the equation of state (EOS) obtained from AIMD simulations was assessed by direct comparison with results from standard density functional theory simulations. Classical molecular dynamics (CMD) simulations were also performed to model atomic-scale shock compression of larger porous CeO2 models. Results from AIMD and CMD compression simulations compare favorably with Z-machine shock data to 525 GPa and gas-gun data to 109 GPa for porous CeO2 samples. Using results from AIMD simulations, an accurate liquid-regime Mie-Grüneisen EOS was built for CeO2. In addition, a revised multiphase SESAME-type EOS was constrained using AIMD results and experimental data generated in this work. This study demonstrates the necessity of acquiring data in the porous regime to increase the reliability of existing analytical EOS models.
Energy Technology Data Exchange (ETDEWEB)
Batistoni, Paola; De Marco, Francesco; Pieroni, Leonardo (ed.)
2005-07-01
The Frascati Tokamak Upgrade (FTU) is a compact, high-magnetic-field tokamak capable of operating at density and magnetic field values similar to, or even encompassing, those of International Thermonuclear Experimental Reactor (ITER) and therefore provides a unique opportunity to explore physics issues that are directly relevant to ITER. During 2004 the experimental activities were focussed on fully exploiting the lower hybrid system (for generating and controlling the plasma current) and the electron cyclotron heating system (joint experiment with the Institute of Plasma Physics of the National Research Council, Milan). With all four gyrotrons in operation, full electron cyclotron power was achieved up to a record level of 1.5 MW. By simultaneously injecting lower hybrid waves, to tailor the plasma current radial profile, and electron cyclotron waves, to heat the plasma centre, good confinement regimes with internal transport barriers were obtained at the highest plasma density values ever achieved for this operation regime (n {approx}1.5X10{sup 20}m{sup -3}). Specific studies were devoted to optimising the coupling of lower hybrid waves to the plasma (by real-time control of the plasma position) and to generating current by electron cyclotron current drive. The new scanning CO{sub 2} interferometer (developed by the Reversed Field Experiment Consortium) for high spatial and time resolution (1 cm/50 {mu}s) density profile measurements was extensively used. The Thomson scattering diagnostic was upgraded and enabled observation of scattered signals associated with the Confinement background plasma dynamics. As for theoretical studies on the dynamics of turbulence in plasmas, the transition from Bohm-like scaling to gyro-Bohm scaling of the local plasma diffusivity was demonstrated on the basis of a generalised four wave model (joint collaboration with Princeton Plasma Physics Laboratory and the University of California at Irvine). The transition from weak to strong
International Nuclear Information System (INIS)
Batistoni, Paola; De Marco, Francesco; Pieroni, Leonardo
2005-01-01
The Frascati Tokamak Upgrade (FTU) is a compact, high-magnetic-field tokamak capable of operating at density and magnetic field values similar to, or even encompassing, those of International Thermonuclear Experimental Reactor (ITER) and therefore provides a unique opportunity to explore physics issues that are directly relevant to ITER. During 2004 the experimental activities were focussed on fully exploiting the lower hybrid system (for generating and controlling the plasma current) and the electron cyclotron heating system (joint experiment with the Institute of Plasma Physics of the National Research Council, Milan). With all four gyrotrons in operation, full electron cyclotron power was achieved up to a record level of 1.5 MW. By simultaneously injecting lower hybrid waves, to tailor the plasma current radial profile, and electron cyclotron waves, to heat the plasma centre, good confinement regimes with internal transport barriers were obtained at the highest plasma density values ever achieved for this operation regime (n ∼1.5X10 20 m -3 ). Specific studies were devoted to optimising the coupling of lower hybrid waves to the plasma (by real-time control of the plasma position) and to generating current by electron cyclotron current drive. The new scanning CO 2 interferometer (developed by the Reversed Field Experiment Consortium) for high spatial and time resolution (1 cm/50 μs) density profile measurements was extensively used. The Thomson scattering diagnostic was upgraded and enabled observation of scattered signals associated with the Confinement background plasma dynamics. As for theoretical studies on the dynamics of turbulence in plasmas, the transition from Bohm-like scaling to gyro-Bohm scaling of the local plasma diffusivity was demonstrated on the basis of a generalised four wave model (joint collaboration with Princeton Plasma Physics Laboratory and the University of California at Irvine). The transition from weak to strong energetic particle
International Nuclear Information System (INIS)
Knighton, Talbot; Tarquini, Vinicio; Wu, Zhe; Huang, Jian; Pfeiffer, Loren; West, Ken
2014-01-01
Quantum Hall measurements are performed for a two-dimensional hole system (2DHS) confined to a 20 nm quantum well in 〈100〉 GaAs. Quantum oscillations reveal a density of 4 - 5×10 10 cm −2 with mobility μ = 1 × 10 6 cm 2 /V s. For temperatures less than ∼350 mK, anomalous insulating peaks are observed between integer fillings 1-2, 2-3, and 3-4. A large out-of-phase signal appears at these peaks, which indicates a substantial inductance inherent to the charge carriers
Chu, Peng-Cheng; Li, Xiao-Hua; Ma, Hong-Yang; Wang, Bin; Dong, Yu-Min; Zhang, Xiao-Min
2018-03-01
We study the properties of strange quark matter (SQM) and quark stars (QSs) in strong magnetic fields within the extended confined isospin-density-dependent mass (CIDDM) model including the temperature dependence of the equivalent mass for quarks. The quark symmetry energy, quark symmetry free energy, and the equation of state (EOS) of SQM in constant magnetic fields at finite temperature are investigated, and it is found that including the temperature dependence in CIDDM model and considering strong magnetic fields can both significantly influence the properties of the SQM and the maximum mass of quark stars. Using the density-dependent magnetic field and assuming two extreme cases for the magnetic field orientation in QSs (the radial orientation in which the local magnetic fields are along the radial direction and the transverse orientation in which the local magnetic fields are randomly oriented but perpendicular to the radial orientation), we analyze the mass-radius relations for different stages of the protoquark stars (PQSs) along the star evolution. Our results indicate that the maximum mass of magnetized PQSs may depend on not only the strength distribution and the orientation of the magnetic fields inside the PQSs, but also the heating process and the cooling process in the star evolution.
Random nanolasing in the Anderson localized regime
DEFF Research Database (Denmark)
Liu, Jin; Garcia, P. D.; Ek, Sara
2014-01-01
multiple scattering. The applicability of random lasers has been limited due to multidirectional emission, lack of tunability, and strong mode competition with chaotic fluctuations due to a weak mode confinement. The regime of Anderson localization of light has been proposed for obtaining stable multimode...... random lasing, and initial work concerned macroscopic one-dimensional layered media. Here, we demonstrate on-chip random nanolasers where the cavity feedback is provided by the intrinsic disorder. The strong confinement achieved by Anderson localization reduces the spatial overlap between lasing modes...
International Nuclear Information System (INIS)
Konorov, S. O.; Hepburn, J. W.; Milner, V.
2011-01-01
Understanding the effect of strong laser pulses on the evolution of an atomic or molecular wave function is important in the context of coherent control in the strong-field regime, when power broadening and dynamic Stark shifts become comparable with or bigger than the bandwidth of the control field. We experimentally demonstrate the method of complete characterization of a complex-valued amplitude of a quantum state driven by a strong two-photon field. The method is based on coherent scattering of a weak probe pulse from the strong-field-induced atomic coherence, followed by the detection of the time- and frequency-resolved parametric four-wave-mixing signal. We show that the proposed technique corresponds to a cross-correlation frequency-resolved optical gating (XFROG) of the highly perturbed evolution of an atomic quantum state. Utilizing the XFROG retrieval algorithm, we determine both the amplitude and phase of an atomic wave function at any time moment throughout the interaction with the driving field. The direct retrieval of the time-dependent phase of the wave function, rather than the population dynamics only, enables us to observe the strong-field effects with arbitrary time and frequency resolution.
Salvesen, Greg; Simon, Jacob B.; Armitage, Philip J.; Begelman, Mitchell C.
2016-03-01
Strongly magnetized accretion discs around black holes have attractive features that may explain enigmatic aspects of X-ray binary behaviour. The structure and evolution of these discs are governed by a dynamo-like mechanism, which channels part of the accretion power liberated by the magnetorotational instability (MRI) into an ordered toroidal magnetic field. To study dynamo activity, we performed three-dimensional, stratified, isothermal, ideal magnetohydrodynamic shearing box simulations. The strength of the self-sustained toroidal magnetic field depends on the net vertical magnetic flux, which we vary across almost the entire range over which the MRI is linearly unstable. We quantify disc structure and dynamo properties as a function of the initial ratio of mid-plane gas pressure to vertical magnetic field pressure, β _0^mid = p_gas / p_B. For 10^5 ≥ β _0^mid ≥ 10 the effective α-viscosity parameter scales as a power law. Dynamo activity persists up to and including β _0^mid = 10^2, at which point the entire vertical column of the disc is magnetic pressure dominated. Still stronger fields result in a highly inhomogeneous disc structure, with large density fluctuations. We show that the turbulent steady state βmid in our simulations is well matched by the analytic model of Begelman et al. describing the creation and buoyant escape of toroidal field, while the vertical structure of the disc can be broadly reproduced using this model. Finally, we discuss the implications of our results for observed properties of X-ray binaries.
Dudin, G. N.; Ledovskiy, A. V.
2013-06-01
The flow in a spatial hypersonic laminar boundary layer on a planar wing with a point of inflection in the leading edge is considered in the regime of strong viscous-inviscid interaction. The boundary problems are formulated for two cases: self-similar flow near the point of inflection of the leading edge and full three-dimensional (3D) boundary layer on a wing with variable sweep angle. The numerical solution is obtained using the finite-difference method. The results of parametric calculations of influence of a wing shape and the temperature factor on flow characteristics in the boundary layer are presented. The possibility of formation of local regions with high shear stress and heat flux is shown.
Calculating hadronic properties in strong QCD
International Nuclear Information System (INIS)
Pennington, M.R.
1996-01-01
This talk gives a brief review of the progress that has been made in calculating the properties of hadrons in strong QCD. In keeping with this meeting I will concentrate on those properties that can be studied with electromagnetic probes. Though perturbative QCD is highly successful, it only applies in a limited kinematic regime, where hard scattering occur, and the quarks move in the interaction region as if they are free, pointlike objects. However, the bulk of strong interactions are governed by the long distance regime, where the strong interaction is strong. It is this regime of length scales of the order of a Fermi, that determines the spectrum of light hadrons and their properties. The calculation of these properties requires an understanding of non-perturbative QCD, of confinement and chiral symmetry breaking. (author)
International Nuclear Information System (INIS)
Seiler, E.
1985-01-01
Confinement of quarks is sometimes taken as some kind of dogma in the contemporary theory of strong interactions - quantum chromo-dynamics (QCD). Scientists should not be content with that. What is meant by ''permanent confinement'' should be formulated more precisely to see whether the theory has this property or not. The author looks at some possible interpretations of ''confinement'' and their shortcomings and then turns to the most widely used rather pragmatic definition based on the somewhat unphysical notion of infinitely heavy external sources. He describes what is known about the problem and tries to bring into focus some aspects that are insufficiently understood in his opinion
Topology of polymer chains under nanoscale confinement.
Satarifard, Vahid; Heidari, Maziar; Mashaghi, Samaneh; Tans, Sander J; Ejtehadi, Mohammad Reza; Mashaghi, Alireza
2017-08-24
Spatial confinement limits the conformational space accessible to biomolecules but the implications for bimolecular topology are not yet known. Folded linear biopolymers can be seen as molecular circuits formed by intramolecular contacts. The pairwise arrangement of intra-chain contacts can be categorized as parallel, series or cross, and has been identified as a topological property. Using molecular dynamics simulations, we determine the contact order distributions and topological circuits of short semi-flexible linear and ring polymer chains with a persistence length of l p under a spherical confinement of radius R c . At low values of l p /R c , the entropy of the linear chain leads to the formation of independent contacts along the chain and accordingly, increases the fraction of series topology with respect to other topologies. However, at high l p /R c , the fraction of cross and parallel topologies are enhanced in the chain topological circuits with cross becoming predominant. At an intermediate confining regime, we identify a critical value of l p /R c , at which all topological states have equal probability. Confinement thus equalizes the probability of more complex cross and parallel topologies to the level of the more simple, non-cooperative series topology. Moreover, our topology analysis reveals distinct behaviours for ring- and linear polymers under weak confinement; however, we find no difference between ring- and linear polymers under strong confinement. Under weak confinement, ring polymers adopt parallel and series topologies with equal likelihood, while linear polymers show a higher tendency for series arrangement. The radial distribution analysis of the topology reveals a non-uniform effect of confinement on the topology of polymer chains, thereby imposing more pronounced effects on the core region than on the confinement surface. Additionally, our results reveal that over a wide range of confining radii, loops arranged in parallel and cross
International Nuclear Information System (INIS)
Joos, H.
1976-07-01
The main topics of these lectures are: phenomenological approach to quark confinement, standard Lagrangian of hadrondynamics, Lagrangian field theory and quark confinement, classical soliton solutions in a simple model, quantization of extended systems, colour charge screening and quantization on a lattice and remarks on applications. A survey of the scientific publications listed according to the topics until 26 March 1976 is supplemented. (BJ) [de
Hazeltine, R D
2003-01-01
Detailed and authoritative, this volume examines the essential physics underlying international research in magnetic confinement fusion. It offers readable, thorough accounts of the fundamental concepts behind methods of confining plasma at or near thermonuclear conditions. Designed for a one- or two-semester graduate-level course in plasma physics, it also represents a valuable reference for professional physicists in controlled fusion and related disciplines.
Malkin, Vladimir; Fisch, Nathaniel
2009-11-01
Currently built powerful soft x-ray sources may be able to access intensities needed for backward Raman amplification (BRA) of x-ray pulses in plasmas. However, high plasma densities, needed to provide enough coupling between the pump and seed x-ray pulsed, cause strong damping of the Langmuir wave that mediates energy transfer from the pump to the seed pulse. Such damping could reduce the coupling, thus making efficient BRA impossible. This work shows that efficient BRA can survive despite the Langmuir wave damping significantly exceeding the linear BRA growth rate. Moreover, the strong Langmuir wave damping can suppress deleterious instabilities of BRA seeded by the thermal noise. This shows that it may be feasible to observe x-ray BRA for the first time soon.
Multichannel atomic scattering and confinement-induced resonances in waveguides
International Nuclear Information System (INIS)
Melezhik, V.S.; Saeidian, S.; Schmelcher, P. . Author
2008-01-01
Full text: Pair atomic collisions in restricted geometry principally differ from the conventional two- body free-space scattering. The restricted geometry leads to quantization of the atomic motion in the direction of confinement. Another nontrivial effect for two distinguishable quantum particles in a transverse harmonic trap is the confinement induced nonseparability of the center-of-mass (CM) and the relative motions. These effects can have experimental mesoscopic developments for ultracold atoms in optical traps and atomic chips. However, only simple analytical estimates were performed for the special case when identical atoms occupy lowest quantum states of a confining trap. In this zero-energy limit the total atom-atom reflection has been predicted for the case of confinement-induced resonance (CIR). The origin of the CIR is a virtual transition from the ground transverse state of the confining potential to the closed excited state during the collision. We have investigated what happens if the energy range of colliding atoms encompasses several quantum states of the confining potential. The developed method permits to analyze the transverse excitations/deexcitains and optimal conditions for avoiding decoherence-inducing mechanisms at atomic collisions in waveguides. Special attention was paid to the analysis of the CIRs for non-zero collision energies in the multimode regimes. We have suggested a nontrivial extension of the CIRs theory developed so far only for the single-mode regime at zero-energy limit. We have also fully taken into account the coupling between the CM and the relative motions in case of distinguishable atoms. Specifically we explore in detail the recently discovered dual CIR which is based on a destructive interference mechanism leading to complete transmission in the waveguide although the corresponding scattering in free space-exhibits strong s and p wave scattering. Possible applications include, e.g., cold and ultracold atom
Impurities confined in quantum structures
Holtz, Per Olof
2004-01-01
The introduction of impurities, even in very small concentrations, in a semiconductor can change its optical and electrical properties entirely. This attribute of the semiconductor is utilized in the manifoldness of their applications. In this book, the progress on elucidating the physical properties of impurities confined in quantum structures are reviewed with an emphasis on the experimental aspects. The major results of various kinds of characterization, such as infrared spectroscopy, Raman measurements, luminescence characterization, perturbation spectroscopy and dynamical studies of the confined impurities are reviewed, but also the theoretical basis to calculate the electronic structure of the confined donors and acceptors are presented. This monograph also describes more specific aspects of the confined impurities such as the properties in the high doping regime and the effects of hydrogen passivation.
Pellet injection with improved confinement in ASDEX
International Nuclear Information System (INIS)
Kaufmann, M.; Buechl, K.; Fussmann, G.; Gehre, O.; Grassie, K.; Gruber, O.; Haas, G.; Janeschitz, G.; Kornherr, M.; Lackner, K.; Lang, R.S.; Mast, K.F.; McCormick, K.; Mertens, V.; Neuhauser, J.; Niedermeyer, H.; Sandmann, W.; Zasche, D.; Zehrfeld, H.P.; Pietrzyk, Z.A.
1987-07-01
Tokamak discharges with repetitive pellet fueling were investigated in the ASDEX divertor device. The importance of sufficiently high divertor recycling for successful density build-up in the bulk plasma was demonstrated. In OH-heated discharges with high recycling an energy confinement time of 160 ms was reached, the normal values being 80 ms in the roll-over region. The peaked density profiles in this cases were accompanied by reduced or suppressed sawtooth activity and finally ended in a phase of strong central impurity accumulation. The particle transport was characterized by strong, non-classical inward drift, while the improved energy transport can be explained by two alternatives: (1) a local model which assumes neo-Alcator χ e for the electrons and an χ i = 3χ neocl for the ions in the gas puff cases reduced to χ i = χ neocl for the optimum pellet cases; (2) a profile consistency picture were T e (a) determines the energy confinement. Low-power, NI-heated discharges with pellet fueling behave like ohmic discharges, while for high power in the L-mode no successful density build-up was possible, and τ E was not improved. The H-regime was extended to anti n e = 1.2x10 20 m -3 by the injection of pellets. In this case a density build-up takes place, but a further density profile peaking could not be observed. (orig.)
Confinement and the safety factor profile
Energy Technology Data Exchange (ETDEWEB)
Batha, S.H.; Levinton, F.M. [Fusion Physics and Technology, Torrance, CA (United States); Scott, S.D. [Princeton Univ., NJ (United States). Plasma Physics Lab.] [and others
1995-12-01
The conjecture that the safety factor profile, q(r), controls the improvement in tokamak plasmas from poor confinement in the Low (L-) mode regime to improved confinement in the supershot regime has been tested in two experiments on the Tokamak Fusion Test Reactor (TFTR). First, helium was puffed into the beam-heated phase of a supershot discharge which induced a degradation from supershot to L-mode confinement in about 100 msec, far less than the current relaxation time. The q and shear profiles measured by a motional Stark effect polarimeter showed little change during the confinement degradation. Second, rapid current ramps in supershot plasmas altered the q profile, but were observed not to change significantly the energy confinement. Thus, enhanced confinement in supershot plasmas is not due to a particular q profile which has enhanced stability or transport properties. The discharges making a continuous transition between supershot and L-mode confinement were also used to test the critical-electron-temperature-gradient transport model. It was found that this model could not reproduce the large changes in electron and ion temperature caused by the change in confinement.
International Nuclear Information System (INIS)
Liles, D.R.
1982-01-01
Internal boundaries in multiphase flow greatly complicate fluid-dynamic and heat-transfer descriptions. Different flow regimes or topological configurations can have radically dissimilar interfacial and wall mass, momentum, and energy exchanges. To model the flow dynamics properly requires estimates of these rates. In this paper the common flow regimes for gas-liquid systems are defined and the techniques used to estimate the extent of a particular regime are described. Also, the current computer-code procedures are delineated and introduce a potentially better method is introduced
Confinement dynamics in the reversed field pinch
International Nuclear Information System (INIS)
Schoenberg, K.F.
1988-01-01
The study of basic transport and confinement dynamics is central to the development of the reversed field pinch (RFP) as a confinement concept. Thus, the goal of RFP research is to understand the connection between processes that sustain the RFP configuration and related transport/confinement properties. Recently, new insights into confinement have emerged from a detailed investigation of RFP electron and ion physics. These insights derive from the recognition that both magnetohydrodynamic (MHD) and electron kinetic effects play an important and strongly coupled role in RFP sustainment and confinement dynamics. In this paper, we summarize the results of these studies on the ZT-40M experiment. 8 refs
The confinement effect in spherical inhomogeneous quantum dots and stability of excitons
Directory of Open Access Journals (Sweden)
F. Benhaddou
2017-06-01
Full Text Available We investigate in this work the quantum confinement effect of exciton in spherical inhomogeneous quantum dots IQDs. The spherical core is enveloped by two shells. The inner shell is a semiconductor characterized by a small band-gap. The core and the outer shell are the same semiconductor characterized by a large band-gap. So there is a significant gap-offset creating a deep potential well where the excitons are localized and strongly confined. We have adopted the Ritz variational method to calculate numerically the excitonic ground state energy and its binding energy in the strong, moderate and low confinement regimes. The results show that the Ritz variational method is in good agreement with the perturbation method in strong confinement. There is a double confinement effect and dual control. The calculation checks the effective Rydberg R* at the asymptotic limit of bulk semiconductor when the thickness takes very large values. The excitonic binding energy increases, Thus giving the excitons a high stability even at ambient temperature. These nanosystems are promising in several applications: lighting, detection, biological labeling and quantum computing.
International Nuclear Information System (INIS)
Bordin, José Rafael; Krott, Leandro B.; Barbosa, Marcia C.
2014-01-01
The behavior of a confined spherical symmetric anomalous fluid under high external pressure was studied with Molecular Dynamics simulations. The fluid is modeled by a core-softened potential with two characteristic length scales, which in bulk reproduces the dynamical, thermodynamical, and structural anomalous behavior observed for water and other anomalous fluids. Our findings show that this system has a superdiffusion regime for sufficient high pressure and low temperature. As well, our results indicate that this superdiffusive regime is strongly related with the fluid structural properties and the superdiffusion to diffusion transition is a first order phase transition. We show how the simulation time and statistics are important to obtain the correct dynamical behavior of the confined fluid. Our results are discussed on the basis of the two length scales
Magnetic confinement in plasmas in nuclear devices
International Nuclear Information System (INIS)
Tull, C.G.
1979-01-01
The main emphasis of the magnetic fusion energy research program today lies in the development of two types of confinement schemes: magnetic mirrors and tokamaks. Experimental programs for both of these confinement schemes have shown steady progress toward achieving fusion power breakeven. The scaling of the current machines to a reactor operating regime and newly developed methods for plasma heating will very likely produce power breakeven within the next decade. Predictions are that the efficiency in a fusion power plant should exceed 32%
Methyl group dynamics in a confined glass
Moreno, A. J.; Colmenero, J.; Alegría, A.; Alba-Simionesco, C.; Dosseh, G.; Morineau, D.; Frick, B.
2002-01-01
We present a neutron scattering investigation on methyl group dynamics in glassy toluene confined in mesoporous silicates of different pore sizes. The experimental results have been analysed in terms of a barrier distribution model, such a distribution following from the structural disorder in the glassy state. Confinement results in a strong decreasing of the average rotational barrier in comparison to the bulk state. We have roughly separated the distribution for the confined state in a bul...
International Nuclear Information System (INIS)
Pilat, Joseph F.; Budlong-Sylvester, K.W.
2004-01-01
Following the 1998 nuclear tests in South Asia and later reinforced by revelations about North Korean and Iraqi nuclear activities, there has been growing concern about increasing proliferation dangers. At the same time, the prospects of radiological/nuclear terrorism are seen to be rising - since 9/11, concern over a proliferation/terrorism nexus has never been higher. In the face of this growing danger, there are urgent calls for stronger measures to strengthen the current international nuclear nonproliferation regime, including recommendations to place civilian processing of weapon-useable material under multinational control. As well, there are calls for entirely new tools, including military options. As proliferation and terrorism concerns grow, the regime is under pressure and there is a temptation to consider fundamental changes to the regime. In this context, this paper will address the following: Do we need to change the regime centered on the Treaty on the Nonproliferation of Nuclear Weapons (NPT) and the International Atomic Energy Agency (IAEA)? What improvements could ensure it will be the foundation for the proliferation resistance and physical protection needed if nuclear power grows? What will make it a viable centerpiece of future nonproliferation and counterterrorism approaches?
Comments on confinement criteria
International Nuclear Information System (INIS)
Kurak, V.; Schroer, B.; Swieca, J.A.
1977-01-01
For a QED 2 model with SU(n) flavour, the nature of the physical states space is more subtle than one expects on the basis of the loop criterion for confinement. One may have colour confinement without confinement of the fundamental flavour representation. Attempts to formulate confinement criteria in which the quark fields play a more fundamental role are discussed [pt
Energy confinement scaling from the international stellarator database
Energy Technology Data Exchange (ETDEWEB)
Stroth, U. [Max-Planck-Institut fuer Plasmaphysik, Garching (Germany); Murakami, M.; Dory, R.A.; Yamada, H.; Okamura, S.; Sano, F.; Obiki, T.
1995-09-01
An international stellarator database on global energy confinement is presented comprising data from the ATF, CHS and Heliotron E heliotron/torsatrons and the W7-A and W7-AS shearless stellarators. Regression expressions for the energy confinement time are given for the individual devices and the combined dataset. A comparison with tokamak L mode confinement is discussed on the basis of various scaling expressions. In order to make this database available to interested colleagues, the structure of the database and the parameter list are explained in detail. More recent confinement results incorporating data from enhanced confinement regimes such as H mode are reported elsewhere. (author).
Structure of polymer chains under confinement
Indian Academy of Sciences (India)
cluded volume interactions (so-called regime of “semi-dilute cigars”). For confined charged polymers, a peak is observed whose intensity increases with molecular weight and the asymptotic 1/q scattering region is extended compared to the bulk. We infer that the chains are sufficiently extended, under the influence of ...
't Hooft, Gerardus
QCD was proposed as a theory for the strong interactions long before we had any idea as to how it could be that its fundamental constituents, the quarks, are never seen as physical particles. Massless gluons also do not exist as free particles. How can this be explained? The first indication that this question had to be considered in connection with the topological structure of a gauge theory came when Nielsen and Olesen observed the occurrence of stable magnetic vortex structures [1] in the Abelian Higgs model. Expanding on such ideas, the magnetic monopole solution was found [2]. Other roundabout attempts to understand confinement involve instantons. Today, we have better interpretations of these topological structures, including a general picture of the way they do lead to unbound potentials confining quarks. It is clear that these unbound potentials can be ascribed to a string-like structure of the vortices formed by the QCD field lines. Can string theory be used to analyze QCD? Many researchers think so. The leading expert on this is Sacha Polyakov. In his instructive account he adds how he experienced the course of events in Gauge Theory, emphasizing the fact that quite a few discoveries often ascribed to researchers from the West, actually were made independently by scientists from the Soviet Union…
Confinement effects in sesquioxydes
Energy Technology Data Exchange (ETDEWEB)
Mercier, B. [Laboratoire de Physico-Chimie des Materiaux Luminescents, UMR 5620 du CNRS, Universite Claude Bernard Lyon I, 10 rue A.M. Ampere 69622 Villeurbanne Cedex (France); Dujardin, C. [Laboratoire de Physico-Chimie des Materiaux Luminescents, UMR 5620 du CNRS, Universite Claude Bernard Lyon I, 10 rue A.M. Ampere 69622 Villeurbanne Cedex (France); Ledoux, G. [Laboratoire de Physico-Chimie des Materiaux Luminescents, UMR 5620 du CNRS, Universite Claude Bernard Lyon I, 10 rue A.M. Ampere 69622 Villeurbanne Cedex (France)]. E-mail: ledoux@pcml.univ-lyon1.fr; Louis, C. [Laboratoire de Physico-Chimie des Materiaux Luminescents, UMR 5620 du CNRS, Universite Claude Bernard Lyon I, 10 rue A.M. Ampere 69622 Villeurbanne Cedex (France); Tillement, O. [Laboratoire de Physico-Chimie des Materiaux Luminescents, UMR 5620 du CNRS, Universite Claude Bernard Lyon I, 10 rue A.M. Ampere 69622 Villeurbanne Cedex (France); Perriat, P. [Groupe d' Etude de Metallurgie Physique et de Physique des Materiaux, UMR 5510 du CNRS, INSA de Lyon, 69622 Villeurbanne Cedex (France)
2006-07-15
When the size of a particle is decreased to nano-scales, confinement effects induce strong changes. The luminescence of Eu{sup 3+}-doped Gd{sub 2}O{sub 3} nanoparticles has been studied as a function of both the temperature and the size of the nanoparticles. Two consequences of the small sizes in Eu{sup 3+}-doped Gd{sub 2}O{sub 3} are observed. First the linewidth of the Eu{sup 3+} transitions are inhomogeneously broadened at low temperature, and second the population of the ground and the first excited state of Eu{sup 3+} as a function of temperature differs depending on the size: at low temperatures, the smaller the particles, the less populated the first excited state is. The explanation of this second phenomenon could be the absence of very low-energy phonons in small particles.
The Physics Basis of ITER Confinement
International Nuclear Information System (INIS)
Wagner, F.
2009-01-01
ITER will be the first fusion reactor and the 50 year old dream of fusion scientists will become reality. The quality of magnetic confinement will decide about the success of ITER, directly in the form of the confinement time and indirectly because it decides about the plasma parameters and the fluxes, which cross the separatrix and have to be handled externally by technical means. This lecture portrays some of the basic principles which govern plasma confinement, uses dimensionless scaling to set the limits for the predictions for ITER, an approach which also shows the limitations of the predictions, and describes briefly the major characteristics and physics behind the H-mode--the preferred confinement regime of ITER.
PREFACE: Water in confined geometries
Rovere, Mauro
2004-11-01
The study of water confined in complex systems in solid or gel phases and/or in contact with macromolecules is relevant to many important processes ranging from industrial applications such as catalysis and soil chemistry, to biological processes such as protein folding or ionic transport in membranes. Thermodynamics, phase behaviour and the molecular mobility of water have been observed to change upon confinement depending on the properties of the substrate. In particular, polar substrates perturb the hydrogen bond network of water, inducing large changes in the properties upon freezing. Understanding how the connected random hydrogen bond network of bulk water is modified when water is confined in small cavities inside a substrate material is very important for studies of stability and the enzymatic activity of proteins, oil recovery or heterogeneous catalysis, where water-substrate interactions play a fundamental role. The modifications of the short-range order in the liquid depend on the nature of the water-substrate interaction, hydrophilic or hydrophobic, as well as on its spatial range and on the geometry of the substrate. Despite extensive study, both experimentally and by computer simulation, there remain a number of open problems. In the many experimental studies of confined water, those performed on water in Vycor are of particular interest for computer simulation and theoretical studies since Vycor is a porous silica glass characterized by a quite sharp distribution of pore sizes and a strong capability to absorb water. It can be considered as a good candidate for studying the general behaviour of water in hydrophilic nanopores. But there there have been a number of studies of water confined in more complex substrates, where the interpretation of experiments and computer simulation is more difficult, such as in zeolites or in aerogels or in contact with membranes. Of the many problems to consider we can mention the study of supercooled water. It is
Confining strings in the Abelian-projected SU(3)-gluodynamics. Pt. 2. 4D case with θ-term
International Nuclear Information System (INIS)
Antonov, D.
2001-01-01
The generalization of 4D confining string theory to the SU(3)-inspired case is derived. It describes string representation of the Wilson loop in the SU(3) analogue of compact QED extended by the θ-term. It is shown that although the obtained theory of confining strings differs from that of compact QED, their low-energy limits have the same functional form. This fact leads to the appearance of the string θ-term in the low-energy limit of the SU(3)-inspired confining string theory. In particular, it is shown that in the extreme strong-coupling regime, the crumpling of string world sheets could disappear owing to the string θ-term at θ = π/12. Finally, some characteristic features of the SU(N) case are pointed out. (orig.)
International Nuclear Information System (INIS)
Floquet, N.; Coulomb, J.P.; Dufau, N.; Andre, G.; Kahn, R.
2004-01-01
Structural and dynamic properties of confined water have been investigated by 'in situ' neutron-scattering experiments. In the medium confinement regime (for MCM-41 host materials: 20 A≤diameter≤40 A) confined water has rather similar properties to bulk (3d) water. The major difference concerns the solidification phase transition. Strong triple-point depression ΔT 3t is observed and ΔT 3t increases when decreasing the pore diameter (213 K≤ΔT 3t ≤233 K). Such a confined water behaves as a supercooled liquid phase. The ultra-confinement (AlPO 4 -N zeolites: 8 A≤diameter≤12 A), is seen to induce the structuration of the confined water and its stability at room temperature T=300 K due to commensurability effect with the AlPO 4 -5 inner surface. No wetting phenomena are observed for both host materials, the silicic MCM-41 samples and the AlPO 4 -N zeolite family
Structural behavior of supercritical fluids under confinement
Ghosh, Kanka; Krishnamurthy, C. V.
2018-01-01
The existence of the Frenkel line in the supercritical regime of a Lennard-Jones (LJ) fluid shown through molecular dynamics (MD) simulations initially and later corroborated by experiments on argon opens up possibilities of understanding the structure and dynamics of supercritical fluids in general and of the Frenkel line in particular. The location of the Frenkel line, which demarcates two distinct physical states, liquidlike and gaslike within the supercritical regime, has been established through MD simulations of the velocity autocorrelation (VACF) and radial distribution function (RDF). We, in this article, explore the changes in the structural features of supercritical LJ fluid under partial confinement using atomistic walls. The study is carried out across the Frenkel line through a series of MD simulations considering a set of thermodynamics states in the supercritical regime (P =5000 bar, 240 K ≤T ≤1500 K ) of argon well above the critical point. Confinement is partial, with atomistic walls located normal to z and extending to "infinity" along the x and y directions. In the "liquidlike" regime of the supercritical phase, particles are found to be distributed in distinct layers along the z axis with layer spacing less than one atomic diameter and the lateral RDF showing amorphous-like structure for specific spacings (packing frustration) and non-amorphous-like structure for other spacings. Increasing the rigidity of the atomistic walls is found to lead to stronger layering and increased structural order. For confinement with reflective walls, layers are found to form with one atomic diameter spacing and the lateral RDF showing close-packed structure for the smaller confinements. Translational order parameter and excess entropy assessment confirms the ordering taking place for atomistic wall and reflective wall confinements. In the "gaslike" regime of the supercritical phase, particle distribution along the spacing and the lateral RDF exhibit features
Confinement and propagation characteristics of subwavelength plasmonic modes
International Nuclear Information System (INIS)
Oulton, R F; Bartal, G; Zhang, X; Pile, D F P
2008-01-01
We have studied subwavelength confinement of the surface plasmon polariton modes of various plasmonic waveguides and examined their relative merits using a graphical parametric representation of their confinement and propagation characteristics. While the same plasmonic phenomenon governs mode confinement in all these waveguides, the various architectures can exhibit distinctive behavior in terms of effective mode area and propagation distance. We found that the waveguides based on metal and one dielectric material show a similar trade-off between energy confinement and propagation distance. However, a hybrid plasmon waveguide, incorporating metal, low index and high index dielectric materials, exhibits longer propagation distances for the same degree of confinement. We also point out that plasmonic waveguides with sharp features can provide an extremely strong local field enhancement, which is not necessarily accompanied by strong confinement of the total electromagnetic energy. In these waveguides, a mode may couple strongly to nearby atoms, but suffer relatively low propagation losses due to weak confinement.
Confinement optimisation by plasma shaping on TCV
International Nuclear Information System (INIS)
Moret, J.M.; Behn, R.; Franke, S.; Hofmann, F.; Weisen, H.
1997-01-01
Any improvement in the energy confinement time of a tokamak reactor may facilitate its access to ignition. TCV has the unique capability of creating a wide variety of plasma shapes and can therefore investigate to which extent an appropriate choice of the plasma shape can improve the energy confinement time. For simple shapes defined only by their elongation and triangularity, it has already been observed on TCV that the confinement properties of the plasma depend strongly on the shape. This previous work has now been extended to include more complex shapes and higher elongations, in order firstly to test the applicability of the previously proposed explanation for the shape dependence of the confinement time and secondly to propose new shapes which offer a substantial gain on their confinement characteristics. (author) 4 figs., 1 tab., 2 refs
Confining membranes and dimensional reduction
Antonov, Dmitri
2001-11-01
The dual theory describing the 4D Coulomb gas of point-like magnetically charged objects, which confines closed electric strings, is considered. The respective generalization of the theory of confining strings to confining membranes is further constructed. The same is done for the analogous SU(3)-inspired model. We then consider a combined model which confines both electric charges and closed strings. Such a model is a mixture of the above-mentioned Coulomb gas with the condensate of the dual Higgs field, where the latter one is described by the dual abelian Higgs model. It is demonstrated that in a certain limit of this dual abelian Higgs model, the system under study undergoes naively the dimensional reduction and becomes described by the (completely integrable) 2D sine-Gordon theory. In particular, at finite temperature, this fact leads to the phase transition of the Berezinskii-Kosterlitz-Thouless type with the respective critical temperature expressed in terms of the parameters of the dual abelian Higgs model. However, it is finally discussed that the dimensional reduction is rigorously valid only in the strong coupling limit of the original 4D Coulomb gas. In such a limit, this reduction transforms the combined model into the 2D free bosonic theory.
A stationary long-pulse ELM-absent H-mode regime in EAST
Ye, Y.; Xu, G. S.; Wan, B. N.; Chen, R.; Yan, N.; Guo, H. Y.; Shao, L. M.; Yang, Q. Q.; Wang, H. Q.; Zhang, W.; Xia, T. Y.; Zhang, T.; Li, Y. Y.; Wang, T. F.; Zang, Q.; Hu, Y. J.; Wu, G. J.; Zhang, L.; Hao, B. L.; Wang, L.; Li, Y. L.; Wu, X. Q.; Chen, L.; Lan, H.; Wang, Y. F.; Xu, J. C.; Hu, G. H.; Ding, S. Y.; Zhang, H.; Zhao, N.; Li, J.; The EAST Team
2017-08-01
A stationary edge-localized mode (ELM)-absent H-mode regime, with an electrostatic edge coherent mode (ECM) which resides in the pedestal region, has been achieved in the EAST tokamak recently. This regime allows the operation of a nearly fully noninductive long pulse (>15 s), exhibiting a relatively high pedestal and good global energy confinement with {{H}98,y2} near 1.2, and excellent impurity control. Furthermore, this regime is mostly obtained with a 4.6 GHz lower hybrid current drive (LHCD) or counter-current neutral beam injection (NBI), plus electron cyclotron resonance heating, and an extensive lithium wall coating. This stationary ELM-absent H-mode regime transits to a stationary small ELM H-mode regime, and upon additional heating power from the 2.45 GHz LHCD, an ion cyclotron resonant frequency or co-current NBI is applied (under 4.6 GHz LHCD heating background). A slight change of the plasma configuration also makes the small ELMs reappear. The experimental observations suggest that a long-pulse ELM-absent regime can be induced by the ECM, which exhibits strong electrostatic fluctuations and may provide a channel for continuous particle (especially impurities) and heat exhaust across the pedestal. The ECM exists in the collisionality of ν e* = 2.5-4 and the pressure gradient |\
Tokamak confinement scaling laws
International Nuclear Information System (INIS)
Connor, J.
1998-01-01
The scaling of energy confinement with engineering parameters, such as plasma current and major radius, is important for establishing the size of an ignited fusion device. Tokamaks exhibit a variety of modes of operation with different confinement properties. At present there is no adequate first principles theory to predict tokamak energy confinement and the empirical scaling method is the preferred approach to designing next step tokamaks. This paper reviews a number of robust theoretical concepts, such as dimensional analysis and stability boundaries, which provide a framework for characterising and understanding tokamak confinement and, therefore, generate more confidence in using empirical laws for extrapolation to future devices. (author)
Plasma confinement in the TMX tandem mirror
International Nuclear Information System (INIS)
Hooper, E.B. Jr.; Allen, S.L.; Casper, T.A.
1981-01-01
Plasma confinement in the Tandem Mirror Experiment (TMX) is described. Axially confining potentials are shown to exist throughout the central 20-cm core of TMX. Axial electron-confinement time is up to 100 times that of single-cell mirror machines. Radial transport of ions is smaller than axial transport near the axis. It has two parts at large radii: nonambipolar, in rough agreement with predictions from resonant-neoclassical transport theory, and ambipolar, observed near the plasma edge under certain conditions, accompanied by a low-frequency, m = 1 instability or strong turbulence
FRP confined smart concrete/mortar
Xiao, Y.; Zhu, P. S.; Choi, K. G.; Wu, Y. T.; Huang, Z. Y.; Shan, B.
2006-03-01
In this study, fiber reinforced polymer (FRP) confined smart concrete/mortar sensors were invented and validated for significantly improved measurement range. Several trial mixes were made using cement mortar and micron-phase graphite powders at different mix proportions. Compressive loading tests were conducted on smart mortar cylinder specimens with or without FRP confinement. Two-probe method was used to detect the electrical resistance of the smart cement mortar specimens. Strong correlation was recognized between the stress and electric resistance of the smart mortar. The test results indicated that the FRP wrapping could significantly enlarge the range of such self-sensing property as a consequence of confinement.
DEFF Research Database (Denmark)
Wang, Yanwei; Peters, Günther H.J.; Hansen, Flemming Yssing
2008-01-01
structures (CABS), allows the computation of equilibrium partition coefficients as a function of confinement size solely based on a single sampling of the configuration space of a macromolecule in bulk. Superior in computational speed to previous computational methods, CABS is capable of handling slits...... parameter for characterization of spatial confinement effects on macromolecules. Results for the equilibrium partition coefficient in the weak confinement regime depend only on the ratio ofR-s to the confinement size regardless of molecular details....
International Nuclear Information System (INIS)
Nuckolls, J.H.; Wood, L.L.
1988-01-01
Edward Teller has been a strong proponent of harnessing nuclear explosions for peaceful purposes. There are two approaches: Plowshare, which utilizes macro- explosions, and inertial confinement fusion, which utilizes microexplosions. The development of practical fusion power plants is a principal goal of the inertial program. It is remarkable that Teller's original thermonuclear problem, how to make super high yield nuclear explosions, and the opposite problem, how to make ultra low yield nuclear explosions, may both be solved by Teller's radiation implosion scheme. This paper reports on the essential physics of these two thermonuclear domains, which are separated by nine orders of magnitude in yield, provided by Teller's similarity theorem and its exceptions. Higher density makes possible thermonuclear burn of smaller masses of fuel. The leverage is high: the scale of the explosion diminishes with the square of the increase in density. The extraordinary compressibility of matter, first noticed by Teller during the Los Alamos atomic bomb program, provides an almost incredible opportunity to harness fusion. The energy density of thermonuclear fuels isentropically compressed to super high-- -densities---even to ten thousand times solid density---is small compared to the energy density at thermonuclear ignition temperatures. In small masses of fuel imploded to these super high matter densities, the energy required to achieve ignition may be greatly reduced by exploiting thermonuclear propagation from a relatively small hot spot
Gravitationally confined relativistic neutrinos
Vayenas, C. G.; Fokas, A. S.; Grigoriou, D.
2017-09-01
Combining special relativity, the equivalence principle, and Newton’s universal gravitational law with gravitational rather than rest masses, one finds that gravitational interactions between relativistic neutrinos with kinetic energies above 50 MeV are very strong and can lead to the formation of gravitationally confined composite structures with the mass and other properties of hadrons. One may model such structures by considering three neutrinos moving symmetrically on a circular orbit under the influence of their gravitational attraction, and by assuming quantization of their angular momentum, as in the Bohr model of the H atom. The model contains no adjustable parameters and its solution, using a neutrino rest mass of 0.05 eV/c2, leads to composite state radii close to 1 fm and composite state masses close to 1 GeV/c2. Similar models of relativistic rotating electron - neutrino pairs give a mass of 81 GeV/c2, close to that of W bosons. This novel mechanism of generating mass suggests that the Higgs mass generation mechanism can be modeled as a latent gravitational field which gets activated by relativistic neutrinos.
Thermostating highly confined fluids.
Bernardi, Stefano; Todd, B D; Searles, Debra J
2010-06-28
In this work we show how different use of thermostating devices and modeling of walls influence the mechanical and dynamical properties of confined nanofluids. We consider a two dimensional fluid undergoing Couette flow using nonequilibrium molecular dynamics simulations. Because the system is highly inhomogeneous, the density shows strong fluctuations across the channel. We compare the dynamics produced by applying a thermostating device directly to the fluid with that obtained when the wall is thermostated, considering also the effects of using rigid walls. This comparison involves an analysis of the chaoticity of the fluid and evaluation of mechanical properties across the channel. We look at two thermostating devices with either rigid or vibrating atomic walls and compare them with a system only thermostated by conduction through vibrating atomic walls. Sensitive changes are observed in the xy component of the pressure tensor, streaming velocity, and density across the pore and the Lyapunov localization of the fluid. We also find that the fluid slip can be significantly reduced by rigid walls. Our results suggest caution in interpreting the results of systems in which fluid atoms are thermostated and/or wall atoms are constrained to be rigid, such as, for example, water inside carbon nanotubes.
Status of global energy confinement studies
International Nuclear Information System (INIS)
Kaye, S.M.; Bell, M.G.; DeBoo, J.C.; Waltz, R.; Greenwald, M.; Sigmar, D.
1990-02-01
Empirical scaling expressions, reflecting the parametric dependence of the L-mode energy confinement time, have been used not only as benchmarks for tokamak operation and theories of energy transport, but for predicting the performance of proposed tokamak devices. Several scaling expressions based on data from small-and medium-sized devices have done well in predicting performance in larger devices, although great uncertainty exists in extrapolating yet farther, into the ignition regime. Several approaches exist for developing higher confidence scaling expressions. These include reducing the statistical uncertainty by identifying and filling in gaps in the present database, making use of more sophisticated statistical techniques, and developing scalings for confinement regimes within which future devices will operate. Confidence in the scaling expressions will be increased still if the expressions can be more directly tied to transport physics theory. This can be done through the use of dimensionless parameters, better describing the edge and core confinement regimes separately, and by incorporating transport models directly into the scaling expressions. 50 refs., 5 figs., 3 tabs
Inertial Electrostatic Confinement (IEC) devices
International Nuclear Information System (INIS)
Nebel, R.A.; Turner, L.; Tiouririne, T.N.; Barnes, D.C.; Nystrom, W.D.; Bussard, R.W.; Miley, G.H.; Javedani, J.; Yamamoto, Y.
1994-01-01
Inertial Electrostatic Confinement (IEC) is one of the earliest plasma confinement concepts, having first been suggested by P. T. Farnsworth in the 1950s. The concept involves a simple apparatus of concentric spherical electrostatic grids or a combination of grids and magnetic fields. An electrostatic structure is formed from the confluence of electron or ion beams. Gridded IEC systems have demonstrated neutron yields as high as 2 * 10 10 neutrons/sec. These systems have considerable potential as small, inexpensive, portable neutron sources for assaying applications. Neutron tomography is also a potential application. Atomic physics effects strongly influence the performance of all of these systems. Important atomic effects include elastic scattering, ionization, excitation, and charge exchange. This paper discusses how an IEC system is influenced by these effects and how to design around them. Theoretical modeling and experimental results are presented
Plasma confinement using biased electrode in the TCABR tokamak
International Nuclear Information System (INIS)
Nascimento, I.C.; Kuznetsov, Y.K.; Severo, J.H.F.; Fonseca, A.M.M.; Elfimov, A.; Bellintani, V.; Machida, M.; Heller, M.V.A.P.; Galvao, R.M.O.; Sanada, E.K.; Elizondo, J.I.
2005-01-01
Experimental data obtained on the TCABR tokamak (R = 0.61 m, a = 0.18 m) with an electrically polarized electrode, placed at r = 0.16 m, is reported in this paper. The experiment was performed with plasma current of 90 kA (q 3.1) and hydrogen gas injection adjusted for keeping the electron density at 1.0 x 10 19 m -3 without bias. Time evolution and radial profiles of plasma parameters with and without bias were measured. The comparison of the profiles shows an increase of the central line-averaged density, up to a maximum factor of 2.6, while H α hydrogen spectral line intensity decreases and the C III impurity stays on the same level. The analysis of temporal behaviour and radial profiles of plasma parameters indicates that the confined plasma enters the H-mode regime. The data analysis shows a maximum enhanced energy confinement factor of 1.95, decaying to 1.5 at the maximum of the density, in comparison with predicted Neo-Alcator scaling law values. Indications of transient increase of the density gradient near the plasma edge were obtained with measurements of density profiles. Calculations of turbulence and transport at the Scrape-Off-Layer, using measured floating potentials and ion saturation currents, show a strong decrease in the power spectra and transport. Bifurcation was not observed and the decrease in the saturation current occurs in 50 μs
Sustainment of high confinement in JT-60U reversed shear plasmas
International Nuclear Information System (INIS)
Fujita, T.; Kamada, Y.; Ide, S.; Takeji, S.; Sakamoto, Y.; Isayama, A.; Suzuki, T.; Oikawa, T.; Fukuda, T.
2001-01-01
confinement is achieved owing to strong internal transport barriers (ITBs), are reported. In a high current plasma with an L-mode edge, deuterium-tritium-equivalent fusion power gain, Q DT eq =0.5 was sustained for 0.8 s (∼ energy confinement time) by adjusting plasma beta precisely using feedback control of stored energy. In a high triangularity plasma with an ELMy H-mode edge, the shrinkage of reversed shear region was suppressed and quasi steady sustainment of high confinement was achieved by raising the poloidal beta and enhancing the bootstrap current peaked at the ITB layer. High bootstrap current fraction (∼80%) was obtained in a high q regime (q 95 ∼9), which leaded to full non-inductive current drive condition. The normalized beta (β N ) of ∼ 2 and H-factor of H 89 ∼3.5 (HH 98y2 ∼2.2) were sustained for 2.7 s (∼ 6 times energy confinement time). (author)
Dynamics in geometrical confinement
Kremer, Friedrich
2014-01-01
This book describes the dynamics of low molecular weight and polymeric molecules when they are constrained under conditions of geometrical confinement. It covers geometrical confinement in different dimensionalities: (i) in nanometer thin layers or self supporting films (1-dimensional confinement) (ii) in pores or tubes with nanometric diameters (2-dimensional confinement) (iii) as micelles embedded in matrices (3-dimensional) or as nanodroplets.The dynamics under such conditions have been a much discussed and central topic in the focus of intense worldwide research activities within the last two decades. The present book discusses how the resulting molecular mobility is influenced by the subtle counterbalance between surface effects (typically slowing down molecular dynamics through attractive guest/host interactions) and confinement effects (typically increasing the mobility). It also explains how these influences can be modified and tuned, e.g. through appropriate surface coatings, film thicknesses or pore...
Elastic membranes in confinement.
Bostwick, J B; Miksis, M J; Davis, S H
2016-07-01
An elastic membrane stretched between two walls takes a shape defined by its length and the volume of fluid it encloses. Many biological structures, such as cells, mitochondria and coiled DNA, have fine internal structure in which a membrane (or elastic member) is geometrically 'confined' by another object. Here, the two-dimensional shape of an elastic membrane in a 'confining' box is studied by introducing a repulsive confinement pressure that prevents the membrane from intersecting the wall. The stage is set by contrasting confined and unconfined solutions. Continuation methods are then used to compute response diagrams, from which we identify the particular membrane mechanics that generate mitochondria-like shapes. Large confinement pressures yield complex response diagrams with secondary bifurcations and multiple turning points where modal identities may change. Regions in parameter space where such behaviour occurs are then mapped. © 2016 The Author(s).
Reorientational dynamics of water confined in zeolites.
Fogarty, Aoife C; Coudert, François-Xavier; Boutin, Anne; Laage, Damien
2014-02-24
We present a detailed molecular-dynamics study of water reorientation and hydrogen-bond dynamics in a strong confinement situation, within the narrow pores of an all-silica Linde type A (LTA) zeolite. Two water loadings of the zeolite are compared with the bulk case. Water dynamics are retarded in this extreme hydrophobic confinement and the slowdown is more pronounced at higher water loading. We show that water reorientation proceeds mainly by large-amplitude angular jumps, whose mechanism is similar to that determined in the bulk. The slowdown upon hydrophobic confinement arises predominantly from an excluded-volume effect on the large fraction of water molecules lying at the interface with the zeolite matrix, with an additional minor contribution coming from a structuring effect induced by the confinement. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Cosmic Ray Self-Confinement, Escape and Transport
Malkov, Mikhail
2014-10-01
Propagation of cosmic rays (CR) in a self-confinement regime is discussed. A self-similar solution for a CR-cloud expansion along the magnetic field strongly deviates from test-particle results. The normalized CR partial pressure is close to P (p , z , t) = 2 [ | z |5/3 +zdif5 / 3 (p , t) ]- 3 / 5 exp [ -z2 / 4DB (p) t ] , where p is the momentum of CR and z is directed along the field. The core of the cloud expands as zdif ~√{DNL p t } and decays in time as P ~ 2zdif- 1 (t) . The diffusion coefficient DNL is strongly suppressed compared to its background value DB: DNL ~DB exp - Π > 1 , the CRs drive Alfven waves efficiently enough to build a transport barrier (P ~ 2 / | z | -``pedestal'') that strongly reduces the leakage. The solution has a spectral break in momentum spectrum at p =pbr , where pbr satisfies the following equation DNLpbr ~=z2 / t . Magnetic focusing effects in CR transport are briefly discussed. Partially supported by NASA through ATP NNX14AH36G.
Kiritsis, E; Nitti, F
2014-01-01
We extend the holographic trailing string picture of a heavy quark to the case of a bulk geometry dual to a confining gauge theory. We compute the classical trailing confining string solution for a static as well as a uniformly moving quark. The trailing string is infinitely extended and approaches a confining horizon, situated at a critical value of the radial coordinate, along one of the space-time directions, breaking boundary rotational invariance. We compute the equations for the fluctuations around the classical solutions, which are used to obtain boundary force correlators controlling the Langevin dynamics of the quark. The imaginary part of the correlators has a non-trivial low-frequency limit, which gives rise to a viscous friction coefficient induced by the confining vacuum. The vacuum correlators are used to define finite-temperature dressed Langevin correlators with an appropriate high-frequency behavior.
Energy Technology Data Exchange (ETDEWEB)
Kiritsis, Elias [APC, Université Paris 7, CNRS/IN2P3, CEA/IRFU, Obs. de Paris, Sorbonne Paris Cité,Bâtiment Condorcet, F-75205, Paris Cedex 13 (UMR du CNRS 7164) (France); Theory Group, Physics Department, CERN,CH-1211, Geneva 23 (Switzerland); Crete Center for Theoretical Physics, Department of Physics, University of Crete,71003 Heraklion (Greece); Mazzanti, Liuba [Institute for Theoretical Physics and Spinoza Institute, Utrecht University,3508 TD Utrecht (Netherlands); Nitti, Francesco [APC, Université Paris 7, CNRS/IN2P3, CEA/IRFU, Obs. de Paris, Sorbonne Paris Cité,Bâtiment Condorcet, F-75205, Paris Cedex 13 (UMR du CNRS 7164) (France)
2014-02-19
We extend the holographic trailing string picture of a heavy quark to the case of a bulk geometry dual to a confining gauge theory. We compute the classical trailing confining string solution for a static as well as a uniformly moving quark. The trailing string is infinitely extended and approaches a confining horizon, situated at a critical value of the radial coordinate, along one of the space-time directions, breaking boundary rotational invariance. We compute the equations for the fluctuations around the classical solutions, which are used to obtain boundary force correlators controlling the Langevin dynamics of the quark. The imaginary part of the correlators has a non-trivial low-frequency limit, which gives rise to a viscous friction coefficient induced by the confining vacuum. The vacuum correlators are used to define finite-temperature dressed Langevin correlators with an appropriate high-frequency behavior.
International Nuclear Information System (INIS)
Swieca, J.A.
1976-01-01
Some aspects of two recent developments in quantum field theory are discussed. First, related with 'extended particles' such as soliton, kink and the 't Hooft monopole. Second, with confinement of particles which are realized in the Schwinger model [pt
Energy Technology Data Exchange (ETDEWEB)
Berk, H.L.
1992-08-06
An overview is presented of the principles of magnetic confinement of plasmas for the purpose of achieving controlled fusion conditions. Sec. 1 discusses the different nuclear fusion reactions which can be exploited in prospective fusion reactors and explains why special technologies need to be developed for the supply of tritium or {sup 3}He, the probable fuels. In Sec. 2 the Lawson condition, a criterion that is a measure of the quality of confinement relative to achieving fusion conditions, is explained. In Sec. 3 fluid equations are used to describe plasma confinement. Specific confinement configurations are considered. In Sec. 4 the orbits of particle sin magneti and electric fields are discussed. In Sec. 5 stability considerations are discussed. It is noted that confinement systems usually need to satisfy stability constraints imposed by ideal magnetohydrodynamic (MHD) theory. The paper culminates with a summary of experimental progress in magnetic confinement. Present experiments in tokamaks have reached the point that the conditions necessary to achieve fusion are being satisfied.
Holographic gauge mediation via strongly coupled messengers
International Nuclear Information System (INIS)
McGuirk, Paul; Shiu, Gary; Sumitomo, Yoske
2010-01-01
We consider a relative of semidirect gauge mediation where the hidden sector exists at large 't Hooft coupling. Such scenarios can be difficult to describe using perturbative field theory methods but may fall into the class of holographic gauge mediation scenarios, meaning that they are amenable to the techniques of gauge/gravity duality. We use a recently found gravity solution to examine one such case, where the hidden sector is a cascading gauge theory resulting in a confinement scale not much smaller than the messenger mass. In the original construction of holographic gauge mediation, as in other examples of semidirect gauge mediation at strong coupling, the primary contributions to visible sector soft terms come from weakly coupled messenger mesons. In contrast to these examples, we describe the dual of a gauge theory where there are significant contributions from scales in which the strongly coupled messenger quarks are the effective degrees of freedom. In this regime, the visible sector gaugino mass can be calculated entirely from holography.
Confinement and Local Transport in the National Spherical Torus Experiment NSTX
Energy Technology Data Exchange (ETDEWEB)
Kaye, S M; Stutman, D; Tritz, K; Yuh, H; Bell, M G; Bell, R E; Domier, C W; Gates, D; Horton, W; Kim, J; LeBlanc, B P; Luhmann Jr, N C; Maingi, R; Mazzucato, E; Menard, J E; Mikkelsen, D; Mueller, D; Park, H; Rewoldt, G; Sabbagh, S A; Smith, D R
2007-03-15
NSTX operates at low aspect ratio (R/a~1.3) and high beta (up to 40%), allowing tests of global confinement and local transport properties that have been established from higher aspect ratio devices. NSTX plasmas are heated by up to 7 MW of deuterium neutral beams with preferential electron heating as expected for ITER. Confinement scaling studies indicate a strong ΒΤ dependence, with a current dependence that is weaker than that observed at higher aspect ratio. Dimensionless scaling experiments indicate a strong increase of confinement with decreasing collisionality and a weak degradation with beta. The increase of confinement with ΒΤ is due to reduced transport in the electron channel, while the improvement with plasma current is due to reduced transport in the ion channel related to the decrease in the neoclassical transport level. Improved electron confinement has been observed in plasmas with strong reversed magnetic shear, showing the existence of an electron internal transport barrier (eITB). The development of the eITB may be associated with a reduction in the growth of microtearing modes in the plasma core. Perturbative studies show that while L-mode plasmas with reversed magnetic shear and an eITB exhibit slow changes of LΤe across the profile after the pellet injection, H-mode plasmas with a monotonic q-profile and no eITB show no change in this parameter after pellet injection, indicating the existence of a critical gradient that may be related to the q-profile. Both linear and non-linear simulations indicate the potential importance of ETG modes at the lowest ΒΤ. Localized measurements of high-κ fluctuations exhibit a sharp decrease in signal amplitude levels across the L-H transition, associated with a decrease in both ion and electron transport, and a decrease in calculated linear microinstability growth rates across a wide κ-range, from the ITG/TEM regime up to the ETG regime.
Energy Technology Data Exchange (ETDEWEB)
Pelaez, Jose R
1998-12-14
We present a brief pedagogical introduction to the Effective Electroweak Chiral Lagrangians, which provide a model independent description of the WW interactions in the strong regime. When it is complemented with some unitarization or a dispersive approach, this formalism allows the study of the general strong scenario expected at the LHC, including resonances.
Transient dynamics of confined liquid drops in a uniform electric field
Mandal, Shubhadeep; Chaudhury, Kaustav; Chakraborty, Suman
2014-05-01
We analyze the effect of confinement on the transient dynamics of liquid drops, suspended in another immiscible liquid medium, under the influence of an externally applied uniform dc electric field. For our analysis, we adhere to an analytical framework conforming to a Newtonian-leaky-dielectric liquid model in the Stokes flow regime, under the small deformation approximation. We characterize the transient relaxation of the drop shape towards its asymptotic configuration, attributed by the combined confluence of the charge-relaxation time scale and the intrinsic shape-relaxation time scale. While the former appears due to the charge accumulation process on the drop surface over a finite interval of time, the genesis of the latter is found to be intrinsic to the hydrodynamic situation under consideration. In an unbounded condition, the intrinsic shape-relaxation time scale is strongly governed by the viscosity ratio, defined as the ratio of dynamic viscosities of the droplet and the background liquid. However, when the wall effects are brought into consideration, the combined influence of the relative extent of the confinement and the intrinsic viscosity effects, acting in tandem, alter this time scale in a rather complicated and nontrivial manner. We reveal that the presence of confinement may dramatically increase the effective viscosity ratio that could have otherwise been required in an unconfined domain to realize identical time-relaxation characteristics. We also bring out the alterations in the streamline patterns because of the combinations of transient and confinement effects. Thus, our results reveal that the extent of fluidic confinement may provide an elegant alternative towards manipulating the transient dynamics of liquid drops in the presence of an externally applied electric field, bearing far-ranging consequences towards the design and functionalities of several modern-day microfluidic applications.
ATR confinement leakage determination
International Nuclear Information System (INIS)
Kuan, P.; Buescher, B.J.
1998-01-01
The air leakage rate from the Advanced Test Reactor (ATR) confinement is an important parameter in estimating hypothesized accidental releases of radiation to the environment. The leakage rate must be determined periodically to assure that the confinement has not degraded with time and such determination is one of the technical safety requirements of ATR operation. This paper reviews the methods of confinement leakage determination and presents an analysis of leakage determination under windy conditions, which can complicate the interpretation of the determined leakage rates. The paper also presents results of analyses of building air exchange under windy conditions. High wind can enhance air exchange and this could increase the release rates of radioisotopes following an accident
Yukawa particles in a confining potential
Energy Technology Data Exchange (ETDEWEB)
Girotto, Matheus, E-mail: matheus.girotto@ufrgs.br; Levin, Yan, E-mail: levin@if.ufrgs.br [Instituto de Física, Universidade Federal do Rio Grande do Sul, Caixa Postal 15051, CEP 91501-970, Porto Alegre, RS (Brazil); Santos, Alexandre P. dos, E-mail: alexandreps@ufcspa.edu.br [Departamento de Educação e Informação em Saúde, Universidade Federal de Ciências da Saúde de Porto Alegre, 90050-170, Porto Alegre, RS (Brazil); Departamento de Física, Universidade Federal de Santa Catarina, 88040-900, Florianópolis, Santa Catarina (Brazil); Colla, Thiago, E-mail: thiago.colla@ufrgs.br [Faculty of Physics, University of Vienna, Boltzmanngasse 5, A-1090 Vienna (Austria)
2014-07-07
We study the density distribution of repulsive Yukawa particles confined by an external potential. In the weak coupling limit, we show that the mean-field theory is able to accurately account for the particle distribution. In the strong coupling limit, the correlations between the particles become important and the mean-field theory fails. For strongly correlated systems, we construct a density functional theory which provides an excellent description of the particle distribution, without any adjustable parameters.
Three novel tokamak plasma regimes in TFTR
International Nuclear Information System (INIS)
Furth, H.P.
1985-10-01
Aside from extending ''standard'' ohmic and neutral beam heating studies to advanced plasma parameters, TFTR has encountered a number of special plasma regimes that have the potential to shed new light on the physics of tokamak confinement and the optimal design of future D-T facilities: (1) High-powered, neutral beam heating at low plasma densities can maintain a highly reactive hot-ion population (with quasi-steady-state beam fueling and current drive) in a tokamak configuration of modest bulk-plasma confinement requirements. (2) Plasma displacement away from limiter contact lends itself to clarification of the role of edge-plasma recycling and radiation cooling within the overall pattern of tokamak heat flow. (3) Noncentral auxiliary heating (with a ''hollow'' power-deposition profile) should serve to raise the central tokamak plasma temperature without deterioration of central region confinement, thus facilitating the study of alpha-heating effects in TFTR. The experimental results of regime (3) support the theory that tokamak profile consistency is related to resistive kink stability and that the global energy confinement time is determined by transport properties of the plasma edge region
Three novel tokamak plasma regimes in TFTR
Energy Technology Data Exchange (ETDEWEB)
Furth, H.P.
1985-10-01
Aside from extending ''standard'' ohmic and neutral beam heating studies to advanced plasma parameters, TFTR has encountered a number of special plasma regimes that have the potential to shed new light on the physics of tokamak confinement and the optimal design of future D-T facilities: (1) High-powered, neutral beam heating at low plasma densities can maintain a highly reactive hot-ion population (with quasi-steady-state beam fueling and current drive) in a tokamak configuration of modest bulk-plasma confinement requirements. (2) Plasma displacement away from limiter contact lends itself to clarification of the role of edge-plasma recycling and radiation cooling within the overall pattern of tokamak heat flow. (3) Noncentral auxiliary heating (with a ''hollow'' power-deposition profile) should serve to raise the central tokamak plasma temperature without deterioration of central region confinement, thus facilitating the study of alpha-heating effects in TFTR. The experimental results of regime (3) support the theory that tokamak profile consistency is related to resistive kink stability and that the global energy confinement time is determined by transport properties of the plasma edge region.
Quantum electrodynamics of strong fields
International Nuclear Information System (INIS)
Greiner, W.
1983-01-01
Quantum Electrodynamics of Strong Fields provides a broad survey of the theoretical and experimental work accomplished, presenting papers by a group of international researchers who have made significant contributions to this developing area. Exploring the quantum theory of strong fields, the volume focuses on the phase transition to a charged vacuum in strong electric fields. The contributors also discuss such related topics as QED at short distances, precision tests of QED, nonperturbative QCD and confinement, pion condensation, and strong gravitational fields In addition, the volume features a historical paper on the roots of quantum field theory in the history of quantum physics by noted researcher Friedrich Hund
Configurational effects on low collision plasma confinement in CHS Heliotron/Torsatron
Energy Technology Data Exchange (ETDEWEB)
Heyn, M.F.; Kernbichler, W. [Institut fuer Theoretische Physik, Technische Universitaet Graz, Graz (Austria); Kasilov, S.V.; Nemov, V.V.; Pavlichenko, O.S. [Institute of Plasma Physics, NSC KIPT, Kharkov (Ukraine); Matsuoka, K.; Okamura, S. [National Inst. for Fusion Science, Toki, Gifu (Japan)
2001-01-01
Multihelicity effects on low collisionality ({approx}1/v) regime of neoclassical transport has been analyzed for full range of magnetic field configurations of CHS Heliotron/Torsatron. Transport coefficients for this regime has been calculated according to an approach developed in the previous paper. It was shown that the drift-orbit-optimized configuration of CHS device investigated in the previous report has the best confinement properties for low collision plasma confinement. (author)
Magnetic properties of confined electron gas
International Nuclear Information System (INIS)
Felicio, J.R.D. de.
1977-04-01
The effects of confinement by a two or three-dimensional harmonic potential on the magnetic properties of a free electron gas are investigated using the grand-canonical ensemble framework. At high temperatures an extension of Darwin's, Felderhof and Raval's works is made taking into account spin effects at low temperature. A comprehensive description of the magnetic properties of a free electron gas is given. The system is regarded as finite, but the boundary condition psi=0 is not introduced. The limits of weak and strong confinement are also analysed [pt
Dyon condensation and colour confinement in dual QCD
Energy Technology Data Exchange (ETDEWEB)
Nandan, H.; Tulsi, Anna; Chandola, H.C. [Kumaun Univ., Nainital (India). Dept. of Physics
2004-09-01
A dynamical model based on the magnetic symmetry of QCD vacuum has been discussed to explore its magnetic response in dealing with the confinement mechanism. The flux tube formulation of the dyonically condensed dual QCD vacuum is presented by computing the asymptotic flux tube solutions of the field equations in the dynamically broken phase of the dual QCD vacuum which has been shown to be responsible for the confinement of the colour electric sources in the deep infrared regime. Deriving the generalised energy-momentum tensor, the energy and the quantized angular momentum of the flux tube system have been computed analytically, which provides a viable physical basis for the explanation of the colour confinement in the non-perturbative regime of QCD vacuum. (authors)
Modeling viscosity and diffusion of plasma mixtures across coupling regimes
Arnault, Philippe
2014-10-01
Viscosity and diffusion of plasma for pure elements and multicomponent mixtures are modeled from the high-temperature low-density weakly coupled regime to the low-temperature high-density strongly coupled regime. Thanks to an atom in jellium modeling, the effect of electron screening on the ion-ion interaction is incorporated through a self-consistent definition of the ionization. This defines an effective One Component Plasma, or an effective Binary Ionic Mixture, that is representative of the strength of the interaction. For the viscosity and the interdiffusion of mixtures, approximate kinetic expressions are supplemented by mixing laws applied to the excess viscosity and self-diffusion of pure elements. The comparisons with classical and quantum molecular dynamics results reveal deviations in the range 20--40% on average with almost no predictions further than a factor of 2 over many decades of variation. Applications in the inertial confinement fusion context could help in predicting the growth of hydrodynamic instabilities.
Confinement contains condensates
DEFF Research Database (Denmark)
Brodsky, S. J.; Roberts, C. D.; Shrock, R.
2012-01-01
Dynamical chiral symmetry breaking and its connection to the generation of hadron masses has historically been viewed as a vacuum phenomenon. We argue that confinement makes such a position untenable. If quark-hadron duality is a reality in QCD, then condensates, those quantities that have common...... evidence and incidentally expose misconceptions in a recent Comment....
DEFF Research Database (Denmark)
Kipnusu, Wycliffe K.; Elsayed, Mohamed; Kossack, Wilhelm
2015-01-01
Broadband dielectric spectroscopy and positron annihilation lifetime spectroscopy are employed to study the molecular dynamics and effective free volume of 2-ethyl-1-hexanol (2E1H) in the bulk state and when confined in unidirectional nanopores with average diameters of 4, 6, and 8 nm. Enhanced α...
Stirring Strongly Coupled Plasma
Fadafan, Kazem Bitaghsir; Rajagopal, Krishna; Wiedemann, Urs Achim
2009-01-01
We determine the energy it takes to move a test quark along a circle of radius L with angular frequency w through the strongly coupled plasma of N=4 supersymmetric Yang-Mills (SYM) theory. We find that for most values of L and w the energy deposited by stirring the plasma in this way is governed either by the drag force acting on a test quark moving through the plasma in a straight line with speed v=Lw or by the energy radiated by a quark in circular motion in the absence of any plasma, whichever is larger. There is a continuous crossover from the drag-dominated regime to the radiation-dominated regime. In the crossover regime we find evidence for significant destructive interference between energy loss due to drag and that due to radiation as if in vacuum. The rotating quark thus serves as a model system in which the relative strength of, and interplay between, two different mechanisms of parton energy loss is accessible via a controlled classical gravity calculation. We close by speculating on the implicati...
Static current profile control and RFP confinement
International Nuclear Information System (INIS)
Scheffel, Jan; Mirza, Ahmed A.; Schnack, Dalton D.
2013-01-01
Static current profile control (CPC) is shown numerically to substantially enhance plasma confinement in the reversed-field pinch (RFP). By suitable application of an auxiliary electric field and adjustment of its internal location, width and amplitude, strongly decreased levels of dynamo fluctuations are obtained. The simulations are performed using a fully non-linear, resistive magnetohydrodynamic model, including the effects of ohmic heating as well as parallel and perpendicular heat conduction along stochastic field lines. The importance of controlling the parallel current profile in the core plasma to minimize the effects of tearing modes on confinement is thus confirmed. A near three-fold increase in energy confinement is found and poloidal plasma beta increases by 30% from 0.20 to 0.27. The edge heat flux is reduced to a third of that of the conventional RFP. The high-confinement phase is interrupted here by a crash, characterized by a rapid decrease in confinement. A detailed study of the crash phase is carried out by the standard Δ′ theory and a fully resistive linearized time-spectral method; the generalized weighted residual method. The analysis suggests that the instability is caused by pressure-driven, resistive g-modes. Inclusion of anisotropic thermal conduction reduces the linear growth rates. As compared with our earlier numerical studies of CPC in the RFP, employing feedback control, the present static control scheme should be more easily implemented experimentally. (paper)
Energy confinement in Ohmic H-mode in TUMAN-3M
International Nuclear Information System (INIS)
Andrejko, M.V.; Askinazi, L.G.; Golant, V.E.; Kornev, V.A.; Lebedev, S.V.; Levin, L.S.; Tukachinsky, A.S.
1997-01-01
The spontaneous transition from Ohmically heated limiter discharges into the regime with improved confinement termed as ''Ohmic H-mode'' has been investigated in ''TUMAN-3''. The typical signatures of H-mode in tokamaks with powerful auxiliary heating have been observed: sharp drop of D α radiation with simultaneous increase in the electron density and stored energy, suppression of the density fluctuations and establishing the steep gradient near the periphery. In 1994 new vacuum vessel had been installed in TUMAN-3 tokamak. The vessel has the same sizes as old one (R 0 =0.55 m, a 1 =0.24 m). New vessel was designed to reduce mechanical stresses in the walls during B T ramp phase of a shot. Therefore modified device - TUMAN-3M is able to produce higher B T and I p , up to 2 T and 0.2 MA respectively. During first experimental run device was operated in Ohmic Regime. In these experiments the possibility to achieve Ohmic H-mode was studied. The study of the parametric dependencies of the energy confinement time in both OH and Ohmic H-mode was performed. In Ohmic H-mode strong dependencies of τ E on plasma current and on input power and weak dependence on density were found. Energy confinement time in TUMAN-3/TUMAN-3M Ohmic H-mode has revealed good agreement with JET/DIII-D/ASDEX scaling for ELM-free H-mode, resulting in very long τ E at the high plasma current discharges. (author)
Characteristics of radiated power for various TFTR [Tokamak Fusion Test Reactor] regimes
International Nuclear Information System (INIS)
Bush, C.E.; Schivell, J.; McNeill, D.H.
1988-04-01
Power loss studies were carried out to determine the impurity radiation and energy transport characteristics of various TFTR operation and confinement regimes including L-Mode, detached plasma, co-only neutral beam injection (energetic ion regime), and the enhanced confinement (''supershot'') regime. Combined bolometric, spectroscopic, and infrared photometry measurements provide a picture of impurity behavior and power accounting in TFTR. The purpose of this paper is to make a survey of the various regimes with the aim of determining the radiated power signatures of each. 10 refs., 6 figs., 1 tab
Topological confinement and superconductivity
Energy Technology Data Exchange (ETDEWEB)
Al-hassanieh, Dhaled A [Los Alamos National Laboratory; Batista, Cristian D [Los Alamos National Laboratory
2008-01-01
We derive a Kondo Lattice model with a correlated conduction band from a two-band Hubbard Hamiltonian. This mapping allows us to describe the emergence of a robust pairing mechanism in a model that only contains repulsive interactions. The mechanism is due to topological confinement and results from the interplay between antiferromagnetism and delocalization. By using Density-Matrix-Renormalization-Group (DMRG) we demonstrate that this mechanism leads to dominant superconducting correlations in aID-system.
Innovative confinement concepts workshop
International Nuclear Information System (INIS)
Kirkpatrick, R.C.
1998-01-01
The Innovative Confinement Concepts Workshop occurred in California during the week preceding the Second Symposium on Current Trends in International Fusion Research. An informal report was made to the Second Symposium. A summary of the Workshop concluded that some very promising ideas were presented, that innovative concept development is a central element of the restructured US DOE. Fusion Energy Sciences program, and that the Workshop should promote real scientific progress in fusion
Energy confinement in tokamaks
International Nuclear Information System (INIS)
Sugihara, M.; Singer, C.
1986-08-01
A straightforward generalization is made of the ohmic heating energy confinement scalings of Pfeiffer and Waltz and Blackwell et. al. The resulting model is systematically calibrated to published data from limiter tokamaks with ohmic, electron cyclotron, and neutral beam heating. With considerably fewer explicitly adjustable free parameters, this model appears to give a better fit to the available data for limiter discharges than the combined ohmic/auxiliary heating model of Goldston
International Nuclear Information System (INIS)
Torres, Clivia M.S.
1998-01-01
Full text: In this work, the exciton is considered as a sensor of the electronic and optical properties of materials such as semiconductors, which have size compared to the exciton De Broglie wavelength, approximately 20 nm, depending on the semiconductor. Examples of electron-phonon, electron-electron, photon-electron, exciton-polariton, phonon-plasmon, are presented, under different confinement conditions such as quantum wells, superlattices
Room temperature strong light-matter coupling in three dimensional terahertz meta-atoms
Energy Technology Data Exchange (ETDEWEB)
Paulillo, B., E-mail: bruno.paulillo@u-psud.fr; Manceau, J.-M., E-mail: jean-michel.manceau@u-psud.fr; Colombelli, R., E-mail: raffaele.colombelli@u-psud.fr [Institut d' Electronique Fondamentale, Univ. Paris Sud, UMR8622 CNRS, 91405 Orsay (France); Li, L. H.; Davies, A. G.; Linfield, E. H. [School of Electronic and Electrical Engineering, University of Leeds, Woodhouse Lane, Leeds LS2 9JT (United Kingdom)
2016-03-07
We demonstrate strong light-matter coupling in three dimensional terahertz meta-atoms at room temperature. The intersubband transition of semiconductor quantum wells with a parabolic energy potential is strongly coupled to the confined circuital mode of three-dimensional split-ring metal-semiconductor-metal resonators that have an extreme sub-wavelength volume (λ/10). The frequency of these lumped-element resonators is controlled by the size and shape of the external antenna, while the interaction volume remains constant. This allows the resonance frequency to be swept across the intersubband transition and the anti-crossing characteristic of the strong light-matter coupling regime to be observed. The Rabi splitting, which is twice the Rabi frequency (2Ω{sub Rabi}), amounts to 20% of the bare transition at room temperature, and it increases to 28% at low-temperature.
Weak and strong regime of a discharge in gases
International Nuclear Information System (INIS)
Podliasky, I.
1957-06-01
After having briefly recalled the content of a previous note in which he determined the electrodynamic action of the axial component of current density in a cylindrical tube of ionised gas submitted to an axial electric field, the author addresses the case of a column containing only electrons and in which Coulombian action prevails and, which, instead of being in contraction, will be in a status of axifugal expansion. He shows that the presence of a certain number of positive ions is absolutely necessary to provoke a pinch by partial compensation of Coulombian actions
International Nuclear Information System (INIS)
McCune, Matthew A; De, Ruma; Chakraborty, Himadri S; Madjet, Mohamed E
2010-01-01
We predict that the confined atom can qualitatively modify the energetic photoionization of some cage levels, even though these levels are of very dominant fullerene character. The effect imposes strong new oscillations in the cross sections which are forbidden to the ionization of empty fullerenes. Results are presented for the AratC 60 endofullerene compound. (fast track communication)
Z/sub N/ topology and charge confinement in SU(N) Higgs models
International Nuclear Information System (INIS)
Ezawa, Z.F.; Iwazaki, A.
1981-01-01
We analyze topological effects in frozen SU(N) Higgs models in continuous space-time, where topological excitations are Z/sub N/ vortices together with associated Z/sub N/ monopoles. The space dimension is either two or three. We show that vortex condensation generates magnetic gauge symmetry and that monopole condensation leads to a spontaneous breakdown of this symmetry. By summing up all possible excitation modes of Z/sub N/ vortices and Z/sub N/ monopoles, we derive an effective Lagrangian in the strong-coupling regime. We obtain the following conclusions: (i) if external charges are introduced in the fundamental representation, they are confined by electric vortex strings, and (ii) if external charges are introduced in the adjoint representation, they are screened completely
Inertial confinement fusion (ICF)
International Nuclear Information System (INIS)
Nuckolls, J.
1977-01-01
The principal goal of the inertial confinement fusion program is the development of a practical fusion power plant in this century. Rapid progress has been made in the four major areas of ICF--targets, drivers, fusion experiments, and reactors. High gain targets have been designed. Laser, electron beam, and heavy ion accelerator drivers appear to be feasible. Record-breaking thermonuclear conditions have been experimentally achieved. Detailed diagnostics of laser implosions have confirmed predictions of the LASNEX computer program. Experimental facilities are being planned and constructed capable of igniting high gain fusion microexplosions in the mid 1980's. A low cost long lifetime reactor design has been developed
Hadrosynthesis and Quark Confinement
Directory of Open Access Journals (Sweden)
Satz Helmut
2014-04-01
Full Text Available Multihadron production in high energy collisions, from e+e− annihilation to heavy ion interactions, shows remarkable thermal behaviour, specified by a universal “Hagedorn” temperature. We argue that this hadronic radiation is formed by tunnelling through the event horizon of colour confinement, i.e., that it is the QCD counterpart of Hawking-Unruh radiation from black holes. It is shown to be emitted at a universal temperature TH ≃ (σ/2π1/2, where σ denotes the string tension. Since the event horizon does not allow information transfer, the radiation is thermal “at birth”.
CERN. Geneva
2014-01-01
In this talk I will survey a connection between two very challenging problems, one in physics and one in math. The physics problem involves quantitative understanding of confinement in a system with least amount of supersymmetry that has been studied so far and that has a wide range of applications, from semi-realistic string models to qualitatively new examples of gauge-gravity duality. Surprisingly, the rich physics of this system translates into incredibly rich mathematics of the only remaining unsolved case of the Poincare conjecture.
Conductance quantization suppression in the quantum Hall regime
DEFF Research Database (Denmark)
Caridad, José M.; Power, Stephen R.; Lotz, Mikkel R.
2018-01-01
conduction channels. Despite being a universal effect, this regime has proven experimentally elusive because of difficulties in realizing one-dimensional systems with sufficiently hard-walled, disorder-free confinement. Here, we experimentally demonstrate the suppression of conductance quantization within...
Sustainable urban regime adjustments
DEFF Research Database (Denmark)
Quitzau, Maj-Britt; Jensen, Jens Stissing; Elle, Morten
2013-01-01
The endogenous agency that urban governments increasingly portray by making conscious and planned efforts to adjust the regimes they operate within is currently not well captured in transition studies. There is a need to acknowledge the ambiguity of regime enactment at the urban scale. This direc...
Yilmaz, Fatih; Coolidge, Jacqueline
2016-01-01
Simplified tax regimes for micro and small enterprises in developing countries are intended to facilitate voluntary tax compliance. However, survey evidence suggests that small business taxation based on simplified bookkeeping or turnover is sometimes perceived as too complex for microenterprises in countries with high illiteracy levels. Very simple fixed tax regimes not requiring any book...
Indian Academy of Sciences (India)
First page Back Continue Last page Overview Graphics. Flux scaling: Ultimate regime. With the Nusselt number and the mixing length scales, we get the Nusselt number and Reynolds number (w'd/ν) scalings: and or. and. scaling expected to occur at extremely high Ra Rayleigh-Benard convection. Get the ultimate regime ...
Confinement from correlation functions
Fister, Leonard; Pawlowski, Jan M.
2013-08-01
We compute the Polyakov loop potential in Yang-Mills theory from the fully dressed primitively divergent correlation functions only. This is done in a variety of functional approaches ranging from functional renormalization group equations over Dyson-Schwinger equations to two-particle irreducible functionals. We present a confinement criterion that links the infrared behavior of propagators and vertices to the Polyakov loop expectation value. The present work extends the works of [J. Braun , Phys. Lett. B 684, 262 (2010)PYLBAJ0370-2693; F. Marhauser and J. M. Pawlowski, arXiv:0812.1144; J. Braun , Eur. Phys. J. C 70, 689 (2010)EPCFFB1434-6044] to general functional methods and sharpens the confinement criterion presented there. The computations are based on the thermal correlation functions in the Landau gauge calculated in [L. Fister and J. M. Pawlowski, arXiv:1112.5440; L. Fister and J. M. Pawlowski, arXiv:1112.5429; L. Fister, Ph.D. thesis, Heidelberg University, 2012].
International Nuclear Information System (INIS)
Trevorrow, L.E.; Schubert, J.P.
1989-01-01
Greater-confinement disposal (GCD) is a general term for low-level waste (LLW) disposal technologies that employ natural and/or engineered barriers and provide a degree of confinement greater than that of shallow-land burial (SLB) but possibly less than that of a geologic repository. Thus GCD is associated with lower risk/hazard ratios than SLB. Although any number of disposal technologies might satisfy the definition of GCD, eight have been selected for consideration in this discussion. These technologies include: (1) earth-covered tumuli, (2) concrete structures, both above and below grade, (3) deep trenches, (4) augered shafts, (5) rock cavities, (6) abandoned mines, (7) high-integrity containers, and (8) hydrofracture. Each of these technologies employ several operations that are mature,however, some are at more advanced stages of development and demonstration than others. Each is defined and further described by information on design, advantages and disadvantages, special equipment requirements, and characteristic operations such as construction, waste emplacement, and closure
Regimes of operation in the Princeton Large Torus
Energy Technology Data Exchange (ETDEWEB)
Hosea, J.C.
1979-10-01
In the quest for optimum discharge conditions in the Princeton Large Torus (PLT), a variety of discharge regimes have been produced. These separate broadly into two main categories - those regimes with m greater than or equal to 2 oscillatory MHD instabilities and often hollow electron profiles for tungsten limiters, and those regimes for which the electron temperature is sufficiently peaked to support the internal sawtooth or near-sawtooth (m = 1) instability. The internal sawtooth regime is found to be optimum for confinement but to be more difficult to select when low-Z impurity concentrations have been reduced with low power discharge cleaning or gettering to permit extension of the high density operation limit. Gas programming is used to cool the plasma periphery, thereby reducing the high-Z impurity concentrations and causing the current channel to constrict into the sawtooth regime, and then to attain the desired plasma density. With discharges selected in this manner, gross energetic confinement times up to approx. 100 msec have been obtained at densities of approx. 10/sup 14/ cm/sup -3/, and very high ion and electron temperatures have been produced with neutral beam injection heating at lower densities with no observable deleterious effect on energy confinement.
Dynamics of water confined in clay minerals
International Nuclear Information System (INIS)
Le Caer, S.; Pommeret, S.; Renault, J.Ph.; Lima, M.; Righini, R.; Gosset, D.; Simeone, D.; Bergaya, F.
2012-01-01
Ultrafast infrared spectroscopy of the O-D stretching mode of dilute HOD in H 2 O probes the local environment and the hydrogen bond network of confined water. The dynamics of water molecules confined in the interlayer space of montmorillonites (Mt) and in interaction with two types of cations (Li + and Ca 2+ ) but also with the negatively charged siloxane surface are studied. The results evidence that the OD vibrational dynamics is significantly slowed down in confined media: it goes from 1.7 ps in neat water to 2.6 Ps in the case of Li + cations with two water pseudo-layers (2.2-2.3 ps in the case of Ca 2+ cations) and to 4.7 ps in the case of Li + cations with one water pseudo-layer. No significant difference between the two cations is noticed. In this 2D confined geometry (the interlayer space being about 0.6 nm for two water pseudo-layers), the relaxation time constants obtained are comparable to the ones measured in analogous concentrated salt solutions. Nevertheless, and in strong opposition to the observations performed in the liquid phase, anisotropy experiments evidence the absence of rotational motions on a 5 ps time scale, proving that the hydrogen bond network in the interlayer space of the clay mineral is locked at this time scale. (authors)
Atmospheric Water-Cycle Regimes and Cloud Regimes
Wong, S.; Fetzer, E. J.; L'Ecuyer, T. S.
2013-12-01
The relationship between the atmospheric water vapor budget and cloud properties is investigated by collocated reanalysis fields from Modern Era Retrospective-analysis for Research and Applications (MERRA) and the observations from the Moderate Resolution Imaging Spectroradiometer (MODIS) satellite instrument. Intensities of surface water exchange (precipitation minus evaporation) are analyzed in the space of 'dynamical regimes', which are defined by combination of large-scale water vapor advection and convergence calculated from the MERRA. The atmospheric water vapor sinks associated with mid-latitude storm systems and precipitation in the west coast of United States are mainly driven by the large-scale dynamical advection, while those associated with tropical deep convection and summertime monsoons are mainly driven by water vapor convergence. Subtropical subsidence area over the eastern ocean basins is dominated by strong water vapor divergence. These dynamical regimes are then connected to the collocated MODIS cloud top pressure and cloud optical thickness. Probability density distributions of these MODIS cloud properties associated with each dynamical regime will be presented.
Section 1. Confinement systems
International Nuclear Information System (INIS)
Anon.
1975-01-01
Major experimental and theoretical results achieved by the Controlled Thermonuclear Research (CTR) program at Lawrence Livermore Laboratory during FY 1975 gave the greatest encouragement to date that the ultimate goal of a deuterium-tritium-fueled mirror reactor can be reached. In the experimental program, the year was characterized by unusually important physics results from the 2XIIB experiment and by significant steps in the plan to change the Baseball II mode of operation. The stabilization of ion-cyclotron instabilities in the 2XIIB experiment by the introduction of an auxiliary warm plasma permitted the buildup of a high-temperature, high-density plasma with an n tau parameter an order of magnitude larger than the 2XII experiment.I In the Baseball II experiment, preliminary tests and computer predictions indicated that a dense, transient, target plasma can be created by laser irradiation of a pellet in midflight through the center of the Baseball confinement zone
Measuring autocratic regime stability
Directory of Open Access Journals (Sweden)
Joseph Wright
2016-01-01
Full Text Available Researchers measure regime stability in autocratic contexts using a variety of data sources that capture distinct concepts. Often this research uses concepts developed for the study of democratic politics, such as leadership change or institutionalized authority, to construct measures of regime breakdown in non-democratic contexts. This article assesses whether the measure a researcher chooses influences the results they obtain by examining data on executive leadership, political authority, and autocratic regimes. We illustrate the conceptual differences between these variables by extending recent studies in the literature on the political consequences of non-tax revenue and unearned foreign income.
Review of strongly-coupled composite dark matter models and lattice simulations
Kribs, Graham D.; Neil, Ethan T.
2016-08-01
We review models of new physics in which dark matter arises as a composite bound state from a confining strongly-coupled non-Abelian gauge theory. We discuss several qualitatively distinct classes of composite candidates, including dark mesons, dark baryons, and dark glueballs. We highlight some of the promising strategies for direct detection, especially through dark moments, using the symmetries and properties of the composite description to identify the operators that dominate the interactions of dark matter with matter, as well as dark matter self-interactions. We briefly discuss the implications of these theories at colliders, especially the (potentially novel) phenomenology of dark mesons in various regimes of the models. Throughout the review, we highlight the use of lattice calculations in the study of these strongly-coupled theories, to obtain precise quantitative predictions and new insights into the dynamics.
Results from deuterium-tritium tokamak confinement experiments
Energy Technology Data Exchange (ETDEWEB)
Hawryluk, R.J.
1997-02-01
Recent scientific and technical progress in magnetic fusion experiments has resulted in the achievement of plasma parameters (density and temperature) which enabled the production of significant bursts of fusion power from deuterium-tritium fuels and the first studies of the physics of burning plasmas. The key scientific issues in the reacting plasma core are plasma confinement, magnetohydrodynamic (MHD) stability, and the confinement and loss of energetic fusion products from the reacting fuel ions. Progress in the development of regimes of operation which have both good confinement and are MHD stable have enabled a broad study of burning plasma physics issues. A review of the technical and scientific results from the deuterium-tritium experiments on the Joint European Torus (JET) and the Tokamak Fusion Test Reactor (TFTR) is given with particular emphasis on alpha-particle physics issues.
Results from deuterium-tritium tokamak confinement experiments
International Nuclear Information System (INIS)
Hawryluk, R.J.
1997-02-01
Recent scientific and technical progress in magnetic fusion experiments has resulted in the achievement of plasma parameters (density and temperature) which enabled the production of significant bursts of fusion power from deuterium-tritium fuels and the first studies of the physics of burning plasmas. The key scientific issues in the reacting plasma core are plasma confinement, magnetohydrodynamic (MHD) stability, and the confinement and loss of energetic fusion products from the reacting fuel ions. Progress in the development of regimes of operation which have both good confinement and are MHD stable have enabled a broad study of burning plasma physics issues. A review of the technical and scientific results from the deuterium-tritium experiments on the Joint European Torus (JET) and the Tokamak Fusion Test Reactor (TFTR) is given with particular emphasis on alpha-particle physics issues
Manipulating light with strongly modulated photonic crystals
International Nuclear Information System (INIS)
Notomi, Masaya
2010-01-01
Recently, strongly modulated photonic crystals, fabricated by the state-of-the-art semiconductor nanofabrication process, have realized various novel optical properties. This paper describes the way in which they differ from other optical media, and clarifies what they can do. In particular, three important issues are considered: light confinement, frequency dispersion and spatial dispersion. First, I describe the latest status and impact of ultra-strong light confinement in a wavelength-cubic volume achieved in photonic crystals. Second, the extreme reduction in the speed of light is reported, which was achieved as a result of frequency dispersion management. Third, strange negative refraction in photonic crystals is introduced, which results from their unique spatial dispersion, and it is clarified how this leads to perfect imaging. The last two sections are devoted to applications of these novel properties. First, I report the fact that strong light confinement and huge light-matter interaction enhancement make strongly modulated photonic crystals promising for on-chip all-optical processing, and present several examples including all-optical switches/memories and optical logics. As a second application, it is shown that the strong light confinement and slow light in strongly modulated photonic crystals enable the adiabatic tuning of light, which leads to various novel ways of controlling light, such as adiabatic frequency conversion, efficient optomechanics systems, photon memories and photons pinning.
From stripe to slab confinement for DNA linearization in nanochannels
Cifra, Peter; Benkova, Zuzana; Namer, Pavol
We investigate suggested advantageous analysis in the linearization experiments with macromolecules confined in a stripe-like channel using Monte Carlo simulations. The enhanced chain extension in a stripe that is due to significant excluded volume interactions between monomers in two dimensions weakens on transition to experimentally feasible slit-like channel. Based on the chain extension-confinement strength dependence and the structure factor behavior for the chain in stripe we infer the excluded volume regime typical for two-dimensional systems. On transition to the slab geometry, the advantageous chain extension decreases and the Gaussian regime is observed for not very long semiflexible chains. The evidence for pseudo-ideality in confined chains is based on indicators such as the extension curves, variation of the extension with the persistence length or the structure factor. The slab behavior is observed when the stripe (originally of monomer thickness) reaches the thickness larger than cca 10nm in the third dimension. This maximum height of the slab to retain the advantage of the stripe is very low and this have implication for DNA linearization experiments. The presented analysis, however, has a broader relevance for confined polymers. Support from Slovak R&D Agency (SRDA-0451-11) is acknowledged.
Semiclassical spinning strings and confining gauge theories
International Nuclear Information System (INIS)
Bigazzi, F.; Cotrone, A.L.; Martucci, L.
2004-03-01
We study multi-charged rotating string states on Type II B regular backgrounds dual to confining SU(N) gauge theories with (softly broken) N=1 supersymmetry, in the infra red regime. After exhibiting the classical energy/charge relations for the folded and circular two-charge strings, we compute in the latter case the one loop sigma-model quantum correction. The classical relation has an expansion in positive powers of the analogous of the BMN effective coupling, while the quantum corrections are non perturbative in nature and are not subleading in the limit of infinite charge. We comment about the dual field theory multi-charged hadrons and the implications of our computation for the AdS/N=4 duality. (author)
Spontaneous spherical symmetry breaking in atomic confinement
Sveshnikov, Konstantin; Tolokonnikov, Andrey
2017-07-01
The effect of spontaneous breaking of initial SO(3) symmetry is shown to be possible for an H-like atom in the ground state, when it is confined in a spherical box under general boundary conditions of "not going out" through the box surface (i.e. third kind or Robin's ones), for a wide range of physically reasonable values of system parameters. The most novel and nontrivial result, which has not been reported previously, is that such an effect takes place not only for attractive, but also for repulsive interactions of atomic electrons with the cavity environment. Moreover, in the limit of a large box size R ≫ aB the regime of an atom, soaring over a plane with boundary condition of "not going out", is reproduced, rather than a spherically symmetric configuration, which would be expected on the basis of the initial SO(3) symmetry of the problem.
Resolving Fast, Confined Diffusion in Bacteria with Image Correlation Spectroscopy.
Rowland, David J; Tuson, Hannah H; Biteen, Julie S
2016-05-24
By following single fluorescent molecules in a microscope, single-particle tracking (SPT) can measure diffusion and binding on the nanometer and millisecond scales. Still, although SPT can at its limits characterize the fastest biomolecules as they interact with subcellular environments, this measurement may require advanced illumination techniques such as stroboscopic illumination. Here, we address the challenge of measuring fast subcellular motion by instead analyzing single-molecule data with spatiotemporal image correlation spectroscopy (STICS) with a focus on measurements of confined motion. Our SPT and STICS analysis of simulations of the fast diffusion of confined molecules shows that image blur affects both STICS and SPT, and we find biased diffusion rate measurements for STICS analysis in the limits of fast diffusion and tight confinement due to fitting STICS correlation functions to a Gaussian approximation. However, we determine that with STICS, it is possible to correctly interpret the motion that blurs single-molecule images without advanced illumination techniques or fast cameras. In particular, we present a method to overcome the bias due to image blur by properly estimating the width of the correlation function by directly calculating the correlation function variance instead of using the typical Gaussian fitting procedure. Our simulation results are validated by applying the STICS method to experimental measurements of fast, confined motion: we measure the diffusion of cytosolic mMaple3 in living Escherichia coli cells at 25 frames/s under continuous illumination to illustrate the utility of STICS in an experimental parameter regime for which in-frame motion prevents SPT and tight confinement of fast diffusion precludes stroboscopic illumination. Overall, our application of STICS to freely diffusing cytosolic protein in small cells extends the utility of single-molecule experiments to the regime of fast confined diffusion without requiring advanced
Unitary Housing Regimes in Transition
DEFF Research Database (Denmark)
Bengtsson, Bo; Jensen, Lotte
2013-01-01
Path dependence is strong in housing institutions and policy. In both Denmark and Sweden, today’s universal and ‘unitary’ (Kemeny) housing regimes can be traced back to institutions that were introduced fifty years back in history or more. Recently, universal and unitary housing systems...... in Scandinavia, and elsewhere, are under challenge from strong political and economic forces. These challenges can be summarized as economic cutbacks, privatization and Europeanization. Although both the Danish and the Swedish housing system are universal and unitary in character, they differ considerably...... in institutional detail. Both systems have corporatist features, however in Denmark public housing is based on local tenant democracy and control, and in Sweden on companies owned and controlled by the municipalities, combined with a centralized system of rent negotiations. In the paper the present challenges...
High beta and confinement studies on TFTR
International Nuclear Information System (INIS)
Navratil, G.A.; Bhattacharjee, A.; Iacono, R.; Mauel, M.E.; Sabbagh, S.A.; Kesner, J.
1992-01-01
A new regime of high poloidal beta operation in TFTR was developed in the course of the first two years of this project (9/25/89 to 9/24/91). Our proposal to continue this successful collaboration between Columbia University and the Massachusetts Institute of Technology with the Princeton Plasma Physics Laboratory for a three year period (9/25/91 to 9/24/94) to continue to investigate improved confinement and tokamak performance in high poloidal beta plasmas in TFTR through the DT phase of operation was approved by the DOE and this is a report of our progress during the first 9 month budget period of the three year grant (9/25/91 to 6/24/92). During the approved three year project period we plan to (1) extend and apply the low current, high QDD discharges to the operation of TFTR using Deuterium and Tritium plasma; (2) continue the analysis and plan experiments on high poloidal beta phenomena in TFTR including: stability properties, enhanced global confinement, local transport, bootstrap current, and divertor formation; (3) plan and carry out experiments on TFTR which attempt to elevate the central q to values > 2 where entry to the second stability regime is predicted to occur; and (4) collaborate on high beta experiments using bean-shaped plasmas with a stabilizing conducting shell in PBX-M. In the seven month period covered by this report we have made progress in each of these four areas through the submission of 4 TFTR Experimental Proposals and the partial execution of 3 of these using a total of 4.5 run days during the August 1991 to February 1992 run
Directory of Open Access Journals (Sweden)
Maxim Goryachev
2018-04-01
Full Text Available A quartz Bulk Acoustic Wave resonator is designed to coherently trap phonons in such a way that they are well confined and immune to suspension losses so they exhibit extremely high acoustic Q-factors at low temperature, with Q × f products of order 10 18 Hz. In this work we couple such a resonator to a Superconducting Quantum Interference Device (SQUID amplifier and investigate effects in the strong signal regime. Both parallel and series connection topologies of the system are investigated. The study reveals significant non-Duffing response that is associated with the nonlinear characteristics of Josephson junctions. The nonlinearity provides quasi-periodic structure of the spectrum in both incident power and frequency. The result gives an insight into the open loop behaviour of a future Cryogenic Quartz Oscillator in the strong signal regime.
Burrell, Keith
2015-11-01
Experiments this summer in DIII-D have used edge turbulence control to achieve stationary, high confinement operation without Edge Localized Mode (ELM) instabilities and with no external torque input. Eliminating the ELM-induced heat bursts and controlling plasma stability at low rotation represent two of the great challenges for fusion energy. By exploiting edge turbulence in a novel manner, we achieved outstanding tokamak performance, well above the H98 international tokamak energy confinement scaling (H98 =1.25), thus meeting an additional confinement challenge that is usually difficult at low torque. The new regime is triggered in double null plasmas by ramping the injected torque to zero and then maintaining it there. This lowers ExB rotation shear in the plasma edge, allowing low-k, broadband, electromagnetic turbulence to increase. In the H-mode edge, a narrow transport barrier usually grows until MHD instability (a peeling ballooning mode) leads to the ELM heat burst. However, the increased turbulence reduces the pressure gradient, allowing the development of a broader and thus higher transport barrier. A 60% increase in pedestal pressure and 40% increase in energy confinement result. Strong double-null plasma shaping raises the threshold for the ELM instability, allowing the plasma to reach a transport-limited state near but below the explosive ELM stability boundary. The resulting plasmas have burning-plasma-relevant betan =1.6-1.8 and run without the need for extra torque from 3D magnetic fields. To date, stationary conditions have been produced for 2 s or 12 energy confinement times, limited only by external hardware constraints. Stationary operation with improved pedestal conditions is highly significant for future burning plasma devices, since operation without ELMs at low rotation and good confinement is key for fusion energy production. Supported by the US DOE under DE-FC02-04ER54698.
Experimental observations of pressure oscillations and flow regimes in an analogue volcanic system
Lane, S.J.; Chouet, B.A.; Phillips, J.C.; Dawson, P.; Ryan, G.A.; Hurst, E.
2001-01-01
Gas-liquid flows, designed to be analogous to those in volcanic conduits, are generated in the laboratory using organic gas-gum rosin mixtures expanding in a vertically mounted tube. The expanding fluid shows a range of both flow and pressure oscillation behaviors. Weakly supersaturated source liquids produce a low Reynolds number flow with foam expanding from the top surface of a liquid that exhibits zero fluid velocity at the tube wall; i.e., the conventional "no-slip" boundary condition. Pressure oscillations, often with strong long-period characteristics and consistent with longitudinal and radial resonant oscillation modes, are detected in these fluids. Strongly supersaturated source liquids generate more energetic flows that display a number of flow regimes. These regimes include a static liquid source, viscous flow, detached flow (comprising gas-pockets-at-wall and foam-in-gas annular flow, therefore demonstrating strong radial heterogeneity), and a fully turbulent transonic fragmented or mist flow. Each of these flow regimes displays characteristic pressure oscillations that can be related to resonance of flow features or wall impact phenomena. The pressure oscillations are produced by the degassing processes without the need of elastic coupling to the confining medium or flow restrictors and valvelike features. The oscillatory behavior of the experimental flows is compared to seismoacoustic data from a range of volcanoes where resonant oscillation of the fluid within the conduit is also often invoked as controlling the observed oscillation frequencies. On the basis of the experimental data we postulate on the nature of seismic signals that may be measured during large-scale explosive activity. Copyright 2001 by the American Geophysical Union.
Directory of Open Access Journals (Sweden)
Gavril PANDI
2011-03-01
Full Text Available The influenced flow regimes. The presence and activities ofhumanity influences the uniform environmental system, and in this context, therivers water resources. In concordance with this, the natural runoff regime suffersbigger and deeper changes. The nature of these changes depending on the type anddegree of water uses. The multitude of the use cause different types of influence,whit different quantitative aspects. In the same time, the influences havequalitative connotations, too, regarding to the modifications of the yearly watervolume runoff. So the natural runoff regime is modified. After analyzing thedistribution laws of the monthly runoff, there have been differenced four types ofinfluenced runoff regimes. In the excess type the influenced runoff is bigger thanthe natural, continuously in the whole year. The deficient type is characterized byinverse rapports like the first type, in the whole year. In the sinusoidal type, theinfluenced runoff is smaller than the natural in the period when the water isretained in the lake reservoirs, and in the depletion period the situation inverts. Atthe irregular type the ratio between influenced and natural runoff is changeable ina random meaner monthly. The recognition of the influenced regime and the gradeof influence are necessary in the evaluation and analysis of the usable hydrologicalriver resources, in the flood defence activities, in the complex scheme of thehydrographic basins, in the environment design and so on.
Proshutinsky, Andrey; Dukhovskoy, Dmitry; Timmermans, Mary-Louise; Krishfield, Richard; Bamber, Jonathan L
2015-10-13
Between 1948 and 1996, mean annual environmental parameters in the Arctic experienced a well-pronounced decadal variability with two basic circulation patterns: cyclonic and anticyclonic alternating at 5 to 7 year intervals. During cyclonic regimes, low sea-level atmospheric pressure (SLP) dominated over the Arctic Ocean driving sea ice and the upper ocean counterclockwise; the Arctic atmosphere was relatively warm and humid, and freshwater flux from the Arctic Ocean towards the subarctic seas was intensified. By contrast, during anticylonic circulation regimes, high SLP dominated driving sea ice and the upper ocean clockwise. Meanwhile, the atmosphere was cold and dry and the freshwater flux from the Arctic to the subarctic seas was reduced. Since 1997, however, the Arctic system has been under the influence of an anticyclonic circulation regime (17 years) with a set of environmental parameters that are atypical for this regime. We discuss a hypothesis explaining the causes and mechanisms regulating the intensity and duration of Arctic circulation regimes, and speculate how changes in freshwater fluxes from the Arctic Ocean and Greenland impact environmental conditions and interrupt their decadal variability. © 2015 The Authors.
Directory of Open Access Journals (Sweden)
Javad Khazaei
2016-09-01
Full Text Available Helical piles are environmentally friendly and economical deep foundations that, due to environmental considerations, are excellent additions to a variety of deep foundation alternatives available to the practitioner. Helical piles performance depends on soil properties, the pile geometry and soil-pile interaction. Helical piles can be a proper alternative in sensitive environmental sites if their bearing capacity is sufficient to support applied loads. The failure capacity of helical piles in this study was measured via an experimental research program that was carried out by Frustum Confining Vessel (FCV. FCV is a frustum chamber by approximately linear increase in vertical and lateral stresses along depth from top to bottom. Due to special geometry and applied bottom pressure, this apparatus is a proper choice to test small model piles which can simulate field stress conditions. Small scale helical piles are made with either single helix or more helixes and installed in fine grained sand with three various densities. Axial loading tests including compression and tension tests were performed to achieve pile ultimate capacity. The results indicate the helical piles behavior depends essentially on pile geometric characteristics, i.e. helix configuration and soil properties. According to the achievements, axial uplift capacity of helical model piles is about equal to usual steel model piles that have the helixes diameter. Helical pile compression bearing capacity is too sufficient to act as a medium pile, thus it can be substituted other piles in special geoenvironmental conditions. The bearing capacity also depends on spacing ratio, S/D, and helixes diameter.
Acoustic Focusing and Energy Confinement Based on Multilateral Metasurfaces
Qi, Shuibao; Li, Yong; Assouar, Badreddine
2017-05-01
Metamaterial-based acoustic wave manipulation shows great potential in effective acoustic energy confinement and low-frequency acoustic isolation. We numerically and theoretically propose here a concept based on multilateral metasurfaces for reflected acoustic focusing and energy confinement. The theoretical phase-shift profile required for reflected wave focusing and governed by the generalized Snell's law can be discretely realized by appropriately arraying the labyrinthine units in the right sequences. Based on this design, multilateral metasurfaces for acoustic wave focusing and energy confinement under point-source incidence are considered and sufficiently investigated. The coupling effects and multiple reflections between or among metasurfaces, which play a significant role in the energy confinement, are initially analyzed and discussed. We show that the acoustic focusing and confinement increase with the sides of the multilateral metasurfaces as anticipated. In addition to the contribution of the first reflection, multiple reflections also contribute to the acoustic focusing and energy confinement, especially when the metasurfaces are configured in parallel. The proposed multilateral metasurfaces should have excellent performance in acoustic energy confinement in various situations due to the variable designs and strong acoustic focusing capabilities.
Issues in tokamak/stellarator transport and confinement enhancement mechanisms
Energy Technology Data Exchange (ETDEWEB)
Perkins, F.W.
1990-08-01
At present, the mechanism for anomalous energy transport in low-{beta} toroidal plasmas -- tokamaks and stellarators -- remains unclear, although transport by turbulent E {times} B velocities associated with nonlinear, fine-scale microinstabilities is a leading candidate. This article discusses basic theoretical concepts of various transport and confinement enhancement mechanisms as well as experimental ramifications which would enable one to distinguish among them and hence identify a dominant transport mechanism. While many of the predictions of fine-scale turbulence are born out by experiment, notable contradictions exist. Projections of ignition margin rest both on the scaling properties of the confinement mechanism and on the criteria for entering enhanced confinement regimes. At present, the greatest uncertainties lie with the basis for scaling confinement enhancement criteria. A series of questions, to be answered by new experimental/theoretical work, is posed to resolve these outstanding contradictions (or refute the fine-scale turbulence model) and to establish confinement enhancement criteria. 73 refs., 4 figs., 5 tabs.
Strong Localization in Disordered Media: Analysis of the Backscattering Cone
Delgado, Edgar
2012-06-01
A very interesting effect in light propagation through a disordered system is Anderson localization of light, this phenomenon emerges as the result of multiple scattering of waves by electric inhomogeneities like spatial variations of index of refraction; as the amount of scattering is increased, light propagation is converted from quasi-diffusive to exponentially localized, with photons confined in a limited spatial region characterized by a fundamental quantity known as localization length. Light localization is strongly related to another interference phenomenon emerged from the multiple scattering effect: the coherent backscattering effect. In multiple scattering of waves, in fact, coherence is preserved in the backscattering direction and produces a reinforcement of the field flux originating an observable peak in the backscattered intensity, known as backscattering cone. The study of this peak provide quantitative information about the transport properties of light in the material. In this thesis we report a complete FDTD ab-initio study of light localization and coherent backscattering. In particular, we consider a supercontinuum pulse impinging on a sample composed of randomly positioned scatterers. We study coherent backscattering by averaging over several realizations of the sample properties. We study then the coherent backscattering cone properties as the relative permittivity of the sample is changed, relating the latter with the light localization inside the sample. We demonstrate important relationships between the width of the backscattering cone and the localization length, which shows a linear proportionality in the strong localization regime.
Feedback controlled, reactor relevant, high-density, high-confinement scenarios at ASDEX Upgrade
Lang, P. T.; Blanken, T. C.; Dunne, M.; McDermott, R. M.; Wolfrum, E.; Bobkov, V.; Felici, F.; Fischer, R.; Janky, F.; Kallenbach, A.; Kardaun, O.; Kudlacek, O.; Mertens, V.; Mlynek, A.; Ploeckl, B.; Stober, J. K.; Treutterer, W.; Zohm, H.; ASDEX Upgrade Team
2018-03-01
One main programme topic at the ASDEX Upgrade all-metal-wall tokamak is development of a high-density regime with central densities at reactor grade level while retaining high-confinement properties. This required development of appropriate control techniques capable of coping with the pellet tool, a powerful means of fuelling but one which presented challenges to the control system for handling of related perturbations. Real-time density profile control was demonstrated, raising the core density well above the Greenwald density while retaining the edge density in order to avoid confinement losses. Recently, a new model-based approach was implemented that allows direct control of the central density. Investigations focussed first on the N-seeding scenario owing to its proven potential to yield confinement enhancements. Combining pellets and N seeding was found to improve the divertor buffering further and enhance the operational range accessible. For core densities up to about the Greenwald density, a clear improvement with respect to the non-seeding reference was achieved; however, at higher densities this benefit is reduced. This behaviour is attributed to recurrence of an outward shift of the edge density profile, resulting in a reduced peeling-ballooning stability. This is similar to the shift seen during strong gas puffing, which is required to prevent impurity influx in ASDEX Upgrade. First tests indicate that highly-shaped plasma configurations like the ITER base-line scenario, respond very well to pellet injection, showing efficient fuelling with no measurable impact on the edge density profile.
Energy Technology Data Exchange (ETDEWEB)
Verdoolaege, Geert, E-mail: geert.verdoolaege@ugent.be [Department of Applied Physics, Ghent University, Sint-Pietersnieuwstraat 41, 9000 Gent (Belgium); Karagounis, Giorgos; Oost, Guido Van [Department of Applied Physics, Ghent University, Sint-Pietersnieuwstraat 41, 9000 Gent (Belgium)
2013-08-21
Pattern recognition for fusion data greatly contributes to a better understanding of the measurements and the physics of fusion plasmas. Through a geometric description of probability it is shown that consideration of the inherent uncertain nature of the data significantly improves the visualization of global confinement data and the identification of confinement regimes. The framework can be extended to the development of scaling laws for ITER.
Verdoolaege, Geert; Karagounis, Giorgos; Oost, Guido Van
2013-08-01
Pattern recognition for fusion data greatly contributes to a better understanding of the measurements and the physics of fusion plasmas. Through a geometric description of probability it is shown that consideration of the inherent uncertain nature of the data significantly improves the visualization of global confinement data and the identification of confinement regimes. The framework can be extended to the development of scaling laws for ITER.
Effect of shear in the radial electric field on confinement in JET
Energy Technology Data Exchange (ETDEWEB)
O`Brien, D.P.; Balet, B.; Deliyanakis, N.; Cordey, J.G.; Stubberfield, P.M. [Commission of the European Communities, Abingdon (United Kingdom). JET Joint Undertaking
1994-07-01
The role of the radial electric field during enhanced confinement of JET discharges is studied. Results from two series of experiments are presented: beam dominated with the addition of a small amount of ICRH, and ICRH dominated discharges, showing that for high performance ICRH heated discharges which obtain the high confinement regime, there is evidence against the E x B flow stabilisation. 4 refs., 4 figs.
Quantum chromodynamics near the confinement limit
Energy Technology Data Exchange (ETDEWEB)
Quigg, C.
1985-09-01
These nine lectures deal at an elementary level with the strong interaction between quarks and its implications for the structure of hadrons. Quarkonium systems are studied as a means for measuring the interquark interaction. This is presumably (part of) the answer a solution to QCD must yield, if it is indeed the correct theory of the strong interactions. Some elements of QCD are reviewed, and metaphors for QCD as a confining theory are introduced. The 1/N expansion is summarized as a way of guessing the consequences of QCD for hadron physics. Lattice gauge theory is developed as a means for going beyond perturbation theory in the solution of QCD. The correspondence between statistical mechanics, quantum mechanics, and field theory is made, and simple spin systems are formulated on the lattice. The lattice analog of local gauge invariance is developed, and analytic methods for solving lattice gauge theory are considered. The strong-coupling expansion indicates the existence of a confining phase, and the renormalization group provides a means for recovering the consequences of continuum field theory. Finally, Monte Carlo simulations of lattice theories give evidence for the phase structure of gauge theories, yield an estimate for the string tension characterizing the interquark force, and provide an approximate description of the quarkonium potential in encouraging good agreement with what is known from experiment.
Improved confinement in L-mode JET plasmas
International Nuclear Information System (INIS)
Jones, T.T.C.; Balet, B.; Bhatnagar, V.; Bures, M.; Campbell, D.J.; Christiansen, J.P.; Cordey, J.G.; Core, W.F.; Corti, S.; Costley, A.E.; Cottrell, G.A.; Edwards, A.; Ehrenberg, J.; Jacquinot, J.; Lallia, P.; Lomas, P.J.; Lowry, C.; Malacarne, M.; Muir, D.G.; Nave, M.F.; Nielsen, P.; Sack, C.; Sadler, G.; Start, D.F.H.; Taroni, A.; Thomas, P.R.; Thomsen, K.
1989-01-01
The JET confinement data show considerable variations of stored plasma energy W (thermal + fast ions) at fixed input power P, plasma current I, toroidal field B and plasma configuration C. The data on confinement properties, e.g. the confinement time τ E or its incremental value τ E (inc), derived from variations of P at fixed I, B, C thus exhibit scatter which makes the scaling of τ E with P, I, B, C difficult to establish. The effects from sawteeth, from variations in the power deposition profiles and from plasma edge physics on confinement do not depend on P, I, B, C in any simple way which would permit a deduced scaling law to be identified with a single (or more) physics loss mechanism(s). In this paper we examine the response of confinement to variations in plasma configuration at fixed I and B (3 MA and 3 T). Results from global and local transport analysis are discussed in sections 2 and 3; section 4 describes the role of fast ions produced by ICRF and NBI heating. High confinement in the L-mode regime at increased plasma currents up to 6 MA is also studied, in particular the effects from sawteeth on stored energy W. Such effects increase with current and presently only predictive transport studies (section 5) can estimate what may be achieved at high current without sawteeth effects. The predictive studies also assess the benefits which may arise from an increase of the neutral beam energy at high plasma currents (section 6). The conclusions are based on extensive study of data from JET pulses with up to 14 MW of ICRH, 21 MW of NBI and 6 MW of ohmic power. None of the pulses included in the study show the sudden reduction of D α emission characteristic of the L to H mode transition of confinement. 7 refs., 4 figs
Radiation control in fusion plasmas by magnetic confinement
International Nuclear Information System (INIS)
Dachicourt, R.
2012-10-01
The present work addresses two important issues for the industrial use of fusion: plasma radiation control, as a part of the more general power handling issue, and high density tokamak operation. These two issues will be most critical in the demonstration reactor, called DEMO, intermediate step between ITER and a future commercial reactor. For DEMO, the need to radiate a large fraction of the power so as to limit the peak power load on the divertor will be a key constraint. High confinement will have to be combined with high radiated power fraction, and the required level of plasma purity. The main achievement of this thesis is to have shown experimental evidence of the existence of a stable plasma regime meeting the most critical requirements of a DEMO scenario: an electron density up to 40% above the Greenwald value, together with a fraction of radiated power close to 80%, with a good energy confinement and limited dilution. The plasma is additionally heated with ion cyclotron waves in a central electron heating scenario, featuring alpha particle heating. The original observations reported in this work bring highly valuable new pieces of information both to the physics of the tokamak edge layer and to the construction of an 'integrated operational scenario' required to successfully operate fusion devices. In the way for getting high density plasmas, the new observations involve the following topics. First, the formation of a poloidal asymmetry in the edge electron density profile, with a maximum density located close to toroidal pumped limiter. This asymmetry occurs inside the separatrix, with a constant plasma pressure on magnetic surfaces. Secondly, a correlative decrease of the electron temperature in the same edge region. Thirdly, the excellent coupling capabilities of the ICRH waves, up to a central line averaged electron density of 1.4 times the Greenwald density. Fourthly, a poloidally asymmetric edge radiation region, providing the dissipation of 80% of
Alternative approaches to plasma confinement
Roth, J. R.
1978-01-01
The paper discusses 20 plasma confinement schemes each representing an alternative to the tokamak fusion reactor. Attention is given to: (1) tokamak-like devices (TORMAC, Topolotron, and the Extrap concept), (2) stellarator-like devices (Torsatron and twisted-coil stellarators), (3) mirror machines (Astron and reversed-field devices, the 2XII B experiment, laser-heated solenoids, the LITE experiment, the Kaktus-Surmac concept), (4) bumpy tori (hot electron bumpy torus, toroidal minimum-B configurations), (5) electrostatically assisted confinement (electrostatically stuffed cusps and mirrors, electrostatically assisted toroidal confinement), (6) the Migma concept, and (7) wall-confined plasmas. The plasma parameters of the devices are presented and the advantages and disadvantages of each are listed.
Assessing confinement in coastal lagoons.
Canu, Donata Melaku; Solidoro, Cosimo; Umgiesser, Georg; Cucco, Andrea; Ferrarin, Christian
2012-11-01
Measures of transport scale in aquatic systems can contribute to the formulation of definitions of indicators of the system's ecological properties. This paper addresses confinement, a specific transport scale proposed by biological scientists as a parameter that can capture and synthesize the principal properties that determine the spatial structure of biological communities in transitional environments. Currently, there is no direct experimental measure of confinement. In this study, a methodology based on the accumulation rate within a lagoon of a passive tracer of marine origin is proposed, the influences of different factors in the calculation of confinement are analyzed, and general recommendations are derived. In particular, we analyze the spatial and the temporal variability of confinement and its sensitivity to the seasonal variability of climatic forcing, the inputs from rivers and the parameterization of the tidal exchanges. The Lagoon of Venice is used as a case study. Copyright © 2012 Elsevier Ltd. All rights reserved.
DEFF Research Database (Denmark)
Abrahamson, Peter
2017-01-01
The paper asks if East Asian welfare regimes are still productivist and Confucian? And, have they developed public care policies? The literature is split on the first question but (mostly) confirmative on the second. Care has to a large, but insufficient extent, been rolled out in the region...
DEFF Research Database (Denmark)
Heymann, Matthias; Nielsen, Kristian Hvidtfelt
”. Danish wind power development is all the more surprising, as the innovation process in wind technology was carried to a large extent by non-academic craftsmen and political activists. Many features of this innovation story have been investigated and that research makes it possible to summarize...... the current understanding of the regime shift....
DEFF Research Database (Denmark)
Nielsen, Max
2006-01-01
Supply in fisheries is traditionally known for its backward bending nature, owing to externalities in production. Such a supply regime, however, exist only for pure open access fisheries. Since most fisheries worldwide are neither pure open access, nor optimally managed, rather between the extrem...
Infrared slavery and quark confinement
Alabiso, C
1976-01-01
The question is considered of whether the so-called infrared slavery mechanism as, e.g., being manifest in non-Abelian gauge theories, necessarily confines quarks. Making a specific ansatz for the long- range forces, the Schwinger-Dyson equation is solved for the quark Green function. Besides having a confining solution, it appears that quarks may by-pass the long-range forces and be produced. (20 refs).
International Nuclear Information System (INIS)
Weller, A.; Dinklage, A.; Geiger, J.; Preuss, R.; Werner, A.; Watanabe, K.Y.; Sakakibara, S.; Funaba, H.; Ohdachi, S.; Suzuki, Y.; Yamada, H.; Harris, J.H.; Zarnstorff, M.C.
2009-01-01
The International Stellarator/Heliotron Confinement Database was extended by high-β data compiled from the Large Helical System (LHD) and the W7-AS Stellarator. The main purpose is to enhance the basis for extrapolation of the global confinement properties to the reactor regime. The high-β configurations and experimental achievements in both devices are briefly described. The impact of beta on the configuration parameters and the global confinement is discussed. In particular, the confinement data in the high-β regime are compared with the ISS95 and ISS04 scaling laws which were derived from a database including relatively few high-β cases. In addition, a Bayesian model comparison approach is used to test scaling predictions derived from basic confinement models. Unlike in tokamaks, the operational boundaries in stellarators and helical systems are determined by the available heating power and confinement properties rather than by disruptive stability or density limits. The role of a pressure induced equilibrium limit is discussed in particular. An attempt is made to compare the high-β data with tokamak confinement and with operational boundaries observed in tokamaks. Further extensions of the database by parameters characterizing stability and local transport properties are proposed.
A Review of Quantum Confinement
Connerade, Jean-Patrick
2009-12-01
A succinct history of the Confined Atom problem is presented. The hydrogen atom confined to the centre of an impenetrable sphere counts amongst the exactly soluble problems of physics, alongside much more noted exact solutions such as Black Body Radiation and the free Hydrogen atom in absence of any radiation field. It shares with them the disadvantage of being an idealisation, while at the same time encapsulating in a simple way particular aspects of physical reality. The problem was first formulated by Sommerfeld and Welker [1]—henceforth cited as SW—in connection with the behaviour of atoms at very high pressures, and the solution was published on the occasion of Pauli's 60th birthday celebration. At the time, it seemed that there was not much other connection with physical reality beyond a few simple aspects connected to the properties of atoms in solids, for which more appropriate models were soon developed. Thus, confined atoms attracted little attention until the advent of the metallofullerene, which provided the first example of a confined atom with properties quite closely related to those originally considered by SW. Since then, the problem has received much more attention, and many more new features of quantum confinement, quantum compression, the quantum Faraday cage, electronic reorganisation, cavity resonances, etc have been described, which are relevant to real systems. Also, a number of other situations have been uncovered experimentally to which quantum confinement is relevant. Thus, studies of the confined atom are now more numerous, and have been extended both in terms of the models used and the systems to which they can be applied. Connections to thermodynamics are explored through the properties of a confined two-level atom adapted from Einstein's celebrated model, and issues of dynamical screening of electromagnetic radiation by the confining shell are discussed in connection with the Faraday cage produced by a confining conducting shell
Gas solubility in hydrophobic confinement.
Luzar, Alenka; Bratko, Dusan
2005-12-01
Measured forces between apolar surfaces in water have often been found to be sensitive to exposure to atmospheric gases despite low gas solubilities in bulk water. This raises questions as to how significant gas adsorption is in hydrophobic confinement, whether it is conducive to water depletion at such surfaces, and ultimately if it can facilitate the liquid-to-gas phase transition in the confinement. Open Ensemble molecular simulations have been used here to determine saturated concentrations of atmospheric gases in water-filled apolar confinements as a function of pore width at varied gas fugacities. For paraffin-like confinements of widths barely exceeding the mechanical instability threshold (spinodal) of the liquid-to-vapor transition of confined water (aqueous film thickness between three and four molecular diameters), mean gas concentrations in the pore were found to exceed the bulk values by a factor of approximately 30 or approximately 15 in cases of N2 and CO2, respectively. At ambient conditions, this does not result in visible changes in the water density profile next to the surfaces. Whereas the barrier to capillary evaporation has been found to decrease in the presence of dissolved gas (Leung, K.; Luzar, A.; and Bratko, D. Phys. Rev. Lett. 2003, 90, 065502), gas concentrations much higher than those observed at normal atmospheric conditions would be needed to produce noticeable changes in the kinetics of capillary evaporation. In simulations, dissolved gas concentrations corresponding to fugacities above approximately 40 bar for N2, or approximately 2 bar for CO2, were required to trigger expulsion of water from a hydrocarbon slit as narrow as 1.4 nm. For nanosized pore widths corresponding to the mechanical instability threshold or above, no significant coupling between adsorption layers at opposing confinement walls was observed. This finding explains the approximately linear increase in gas solubility with inverse confinement width and the
MODELING COMBINING TAX REGIMES
Directory of Open Access Journals (Sweden)
Prishchenko E. A.
2016-03-01
Full Text Available The article discusses the combination of tax regimes as a result of separation from the operating business of the revenues and costs for system of a united tax on imputed income (UTII with the analysis of the tax consequences of such allocation. Three models of taxation were built: both variants of the simplified system of taxation from UTII and common system of taxation with UTII. We propose a rapid method of the most preferred system of taxation for small businesses’ selection depending material to labor costs ratio. All these results could be implemented in the case when the company starts a new type of activity under the rules UTII, and solves the problem in the framework of the tax regime to conduct this activity - UTII applied or not, based on the criterion of tax savings. Using the relations describing the tax burden when combined tax regimes, we can determine what the yield should have a new business line and what cost structure should it have to reduce the tax burden. The main result is proposed approach that can be used as a tool of tax planning activities of small businesses.
Thermodynamics of confined gallium clusters.
Chandrachud, Prachi
2015-11-11
We report the results of ab initio molecular dynamics simulations of Ga13 and Ga17 clusters confined inside carbon nanotubes with different diameters. The cluster-tube interaction is simulated by the Lennard-Jones (LJ) potential. We discuss the geometries, the nature of the bonding and the thermodynamics under confinement. The geometries as well as the isomer spectra of both the clusters are significantly affected. The degree of confinement decides the dimensionality of the clusters. We observe that a number of low-energy isomers appear under moderate confinement while some isomers seen in the free space disappear. Our finite-temperature simulations bring out interesting aspects, namely that the heat capacity curve is flat, even though the ground state is symmetric. Such a flat nature indicates that the phase change is continuous. This effect is due to the restricted phase space available to the system. These observations are supported by the mean square displacement of individual atoms, which are significantly smaller than in free space. The nature of the bonding is found to be approximately jellium-like. Finally we note the relevance of the work to the problem of single file diffusion for the case of the highest confinement.
High Explosive Detonation–Confiner Interactions
Short, Mark; Quirk, James J.
2018-01-01
The primary purpose of a detonation in a high explosive (HE) is to provide the energy to drive a surrounding confiner, typically for mining or munitions applications. The details of the interaction between an HE detonation and its confinement are essential to achieving the objectives of the explosive device. For the high pressures induced by detonation loading, both the solid HE and confiner materials will flow. The structure and speed of a propagating detonation, and ultimately the pressures generated in the reaction zone to drive the confiner, depend on the induced flow both within the confiner and along the HE–confiner material interface. The detonation–confiner interactions are heavily influenced by the material properties and, in some cases, the thickness of the confiner. This review discusses the use of oblique shock polar analysis as a means of characterizing the possible range of detonation–confiner interactions. Computations that reveal the fluid mechanics of HE detonation–confiner interactions for finite reaction-zone length detonations are discussed and compared with the polar analysis. This includes cases of supersonic confiner flow; subsonic, shock-driven confiner flow; subsonic, but shockless confiner flow; and sonic flow at the intersection of the detonation shock and confiner material interface. We also summarize recent developments, including the effects of geometry and porous material confinement, on detonation–confiner interactions.
Inertial confinement fusion at the Los Alamos National Laboratory
International Nuclear Information System (INIS)
Lindman, E.; Baker, D.; Barnes, C.; Bauer, B.; Beck, J.B.
1997-01-01
The Los Alamos National Laboratory is contributing to the resolution of key issues in the US Inertial-Confinement-Fusion Program and plans to play a strong role in the experimental program at the National Ignition Facility when it is completed
Inertial confinement fusion at the Los Alamos National Laboratory
Energy Technology Data Exchange (ETDEWEB)
Lindman, E.; Baker, D.; Barnes, C.; Bauer, B.; Beck, J.B. [and others
1997-11-01
The Los Alamos National Laboratory is contributing to the resolution of key issues in the US Inertial-Confinement-Fusion Program and plans to play a strong role in the experimental program at the National Ignition Facility when it is completed.
International Nuclear Information System (INIS)
1992-09-01
The workshop of three large tokamak cooperation W22 on 'Energy confinement scaling under intensive auxiliary heating' was held 18-20 May, 1992, at Naka Fusion Research Establishment. This proceedings compiles 14 synopses of contributions (5 from JET, 4 from JT-60, 3 from TFTR, and 1 each from DIII-D JFT-2M) and the summary of the workshop. Topic sections are ; (i) L-mode confinement and scaling, (ii) Confinement at high β P regimes, Supershots, High poloidal beta enhanced confinement mode etc., (iii) Confinement at various H-mode regimes and scaling (including the VH-mode), (iv) Characteristic time scales for present tokamak regimes, and (v) Theoretical comparison with experimental data. (author)
Correlations In Confined Quantum Plasmas
International Nuclear Information System (INIS)
Dufty, J.W.
2012-01-01
This is the final report for the project 'Correlations in Confined Quantum Plasmas', NSF-DOE Partnership Grant DE FG02 07ER54946, 8/1/2007 - 7/30/2010. The research was performed in collaboration with a group at Christian Albrechts University (CAU), Kiel, Germany. That collaboration, almost 15 years old, was formalized during the past four years under this NSF-DOE Partnership Grant to support graduate students at the two institutions and to facilitate frequent exchange visits. The research was focused on exploring the frontiers of charged particle physics evolving from new experimental access to unusual states associated with confinement. Particular attention was paid to combined effects of quantum mechanics and confinement. A suite of analytical and numerical tools tailored to the specific inquiry has been developed and employed
Hermitian relativity, chromodynamics and confinement
International Nuclear Information System (INIS)
Treder, H.J.
1983-01-01
The extension of the Riemann metrics of General Relativity to the complex domain (substitution of the symmetry conditions for the fundamental tensor, the affinity and the Ricci curvature by the conditions of hermicity) leads to a 'Generalized Theory of Gravity' (Einstein) describing the Newton-Einstein gravodynamics combined with the chromodynamics of quarks. The interaction of gravodynamics and chromodynamics implied by the Einstein-Schroedinger field equations of the hermitian relativity theory enforces the 'confinement'. The 'confinement' prevents the gravitational potential from divergence which would result in the lack of a Riemann space-time metric
Hermitian relativity, chromodynamics and confinement
Energy Technology Data Exchange (ETDEWEB)
Treder, H.J. (Akademie der Wissenschaften der DDR, Potsdam-Babelsberg. Einstein-Laboratorium fuer Theoretische Physik)
1983-01-01
The extension of the Riemann metrics of General Relativity to the complex domain (substitution of the symmetry conditions for the fundamental tensor, the affinity and the Ricci curvature by the conditions of hermicity) leads to a 'Generalized Theory of Gravity' (Einstein) describing the Newton-Einstein gravodynamics combined with the chromodynamics of quarks. The interaction of gravodynamics and chromodynamics implied by the Einstein-Schroedinger field equations of the hermitian relativity theory enforces the 'confinement'. The 'confinement' prevents the gravitational potential from divergence which would result in the lack of a Riemann space-time metric.
Some aspects of geometrical confinement
Energy Technology Data Exchange (ETDEWEB)
Novello, M.; De Lorenci, V.A. [Centro Brasileiro de Pesquisas Fisicas (CBPF), Rio de Janeiro, RJ (Brazil); Elbaz, E. [Lyon-1 Univ., 69 - Villeurbanne (France)
1998-04-01
In this paper we present a toy model for the dynamics of a gauge field theory in such way that spin-one particles can be confined in a compact domain. We show that the property of confinement can be associated to the formation of a null surface identified to a horizon. This is due to the presence of an effective geometry generated by the self-interaction of the gauge field that guides the wave propagation of the field. This phenomenon has a striking analogy to the gravitational black hole in Einstein general theory of relativity, separating two domains of spacetime that can be trespassed only into one direction. (author) 4 refs.
Stick and Slip Behaviour of Confined Oligomer Melts under Shear. A Molecular-Dynamics Study.
Manias, E.; Hadziioannou, G.; Bitsanis, I.; Brinke, G. ten
1993-01-01
The flow behaviour of melts of short chains, confined in molecularly thin Couette flow geometries, is studied with molecular-dynamics simulations. The effect of wall attraction and confinement on the density and velocity profiles is analysed. In these highly inhomogeneous films, a strong correlation
STICK AND SLIP BEHAVIOR OF CONFINED OLIGOMER MELTS UNDER SHEAR - A MOLECULAR-DYNAMICS STUDY
MANIAS, E; HADZIIOANNOU, G; BITSANIS, [No Value; TENBRINKE, G
1993-01-01
The flow behaviour of melts of short chains, confined in molecularly thin Couette flow geometries, is studied with molecular-dynamics simulations. The effect of wall attraction and confinement on the density and velocity profiles is analysed. In these highly inhomogeneous films, a strong correlation
Dynamical nuclear polarization and confinement effects in ZnO quantum dots
Baranov, P.G.; Orlinskii, S.B.; Hofmann, D.M.; de Mello Donega, C.; Meijerink, A.; Schmidt, J.
2010-01-01
The spatial distribution of the electronic wave function of a shallow donor (SD) in a ZnO semiconductor quantum dots (QD's) has been determined in the regime of quantum confinement by using the nuclear spins as probes. Hyperfine (HF) interactions as monitored by electron nuclear double resonance
Virtual cathode in a spherical inertial electrostatic confinement
International Nuclear Information System (INIS)
Momota, Hiromu; Miley, G.H.
1999-01-01
Spherical inertial electrostatic confinement (SIEC) was proposed as a fusion device. Its best feature is that confinement scheme does not need any magnetic field. Ion orbits pass through the center of the device, and thus the resulting ion density profile shows strong peaking. On the other hand, electron orbits are sensitive to the electrostatic self-field. Complete solution of particle orbits and of self-field is difficult to obtain. In the present paper steady-state solutions are obtained for two extreme cases. The first case assumes no electron collision, and the second case frequent electron collisions, and thus electrons are described by the Boltzmann law. (M. Tanaka)
Confinement-deconfinement transition in dissipative gauge field
Nagaosa, Naoto
1993-12-01
The effect of dissipation on confinement is studied for compact QED. This model is relevant to the recently developed gauge theory of high-Tc superconductors. The global phase diagram of the gauge field is clarified in the parameter space of the coupling constant g, the strength of dissipation γ, and the temperature T. Confinement is drastically suppressed by dissipation, and the deconfining phase appears even in the strong-coupling and zero temperature limit when γ exceeds a critical value. This result supports the spin-charge separation in the resonating-valence-bond state.
Effective viscosity of confined hydrocarbons
DEFF Research Database (Denmark)
Sivebæk, Ion Marius; Samoilov, V.N.; Persson, B.N.J.
2012-01-01
We present molecular dynamics friction calculations for confined hydrocarbon films with molecular lengths from 20 to 1400 carbon atoms. We find that the logarithm of the effective viscosity ηeff for nanometer-thin films depends linearly on the logarithm of the shear rate: log ηeff=C-nlog γ̇, where...
On the implications of confinement
International Nuclear Information System (INIS)
Roberts, C.D.
1992-01-01
In this paper, the authors consider some implications of confinement starting from the basic observation that cross-sections for the production of colored asymptotic states, such as free quarks and gluons, from color singlet initial states must be zero if QCD is to be confining. The authors discuss two pictures of confinement: the failure of the cluster decomposition property and the absence of a pole at timelike momenta in the propagator of a confined particle. The authors use QCD-based models as a framework to relate the failure of the cluster decomposition property to other ideas, such as the role of a nonzero gluon condensate. The authors' primary interest is to address the question of the absence of a mass pole through a study of model Schwinger-Dyson equations. These equations contain some of the dynamical information that is present in the study of the cluster decomposition property. The authors discuss the problems within this idea and its study using the Schwinger-Dyson equations
Turbulent jet in confined counterflow
Indian Academy of Sciences (India)
Abstract. The mean flowfield of a turbulent jet issuing into a confined, uniform counterflow was investigated computationally. Based on dimensional analysis, the jet penetration length was shown to scale with jet-to-counterflow momentum flux ratio. This scaling and the computational results reproduce the well-known correct ...
Is confinement the ultimate truth
International Nuclear Information System (INIS)
Thirrring, W.
1980-01-01
This seminar discusses a field theory which leads to a r-potential and therefore to a confinement. By comparison to the instability due to a resonance phenomenon, the author concentrates on the theory's ghost problem and concludes that for some couplings this does not occur and the theory behaves reasonably
Turbulent jet in confined counterflow
Indian Academy of Sciences (India)
The mean flowfield of a turbulent jet issuing into a confined, uniform counterflow was investigated computationally. Based on dimensional analysis, the jet penetration length was shown to scale with jet-to-counterflow momentum flux ratio. This scaling and the computational results reproduce the well-known correct limit of ...
Transport in the quantum critical regime
Enss, Tilman
2014-05-01
In this talk I will explain the relevance of the quantum critical point for the phase diagram of the unitary Fermi gas, briefly review theoretical approaches, and present results for the shear viscosity and spin diffusion in strongly interacting Fermi gases. The unitary Fermi gas describes strongly interacting fermions ranging from ultracold atoms near a Feshbach resonance to dilute neutron matter, which share a common universal phase diagram. The behavior at finite temperature is governed by a quantum critical point (QCP) at zero temperature and zero density, and observables can be expressed by universal scaling functions of the distance from the critical point. In the quantum critical regime above the QCP, thermal and quantum fluctuations are equally important, and the absence of a small parameter makes the computation of critical properties demanding. I will mention two theoretical approaches to transport properties in this regime: the large-N expansion in the number of fermion flavors allows for a systematic and controlled expansion even at strong coupling and elucidates the importance of medium effects on scattering. Second, the Luttinger-Ward, or self-consistent T-matrix approach goes beyond the quasiparticle picture and also explains universal high-energy tails. I will present results on the shear viscosity, or internal friction, for mass transport and show that the strongly interacting Fermi gas is an almost perfect quantum fluid. On the other hand, if particles of different spin move in opposite directions, the dynamics are governed by spin diffusion. One can distinguish longitudinal diffusion, when atomic clouds of different spin collide, and transverse diffusion, when the magnetization is wound up in a helix in a spin-echo experiment. Medium scattering and spin rotation have a strong effect on spin diffusion, and I will discuss how spin transport becomes very slow at strong coupling in the quantum degenerate regime and reaches a quantum limit of
Thermodynamic properties of bulk and confined water
Energy Technology Data Exchange (ETDEWEB)
Mallamace, Francesco, E-mail: francesco.mallamace@unime.it [Dipartimento di Fisica e Scienza della Terra Università di Messina and CNISM, I-98168 Messina (Italy); Department of Nuclear Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Center for Polymer Studies and Department of Physics, Boston University, Boston, Massachusetts 02215 (United States); Corsaro, Carmelo [Dipartimento di Fisica e Scienza della Terra Università di Messina and CNISM, I-98168 Messina (Italy); Mallamace, Domenico [Dipartimento di Scienze dell' Ambiente, della Sicurezza, del Territorio, degli Alimenti e della Salute, Università di Messina, I-98166 Messina (Italy); Vasi, Sebastiano; Vasi, Cirino [IPCF-CNR, I-98166 Messina (Italy); Stanley, H. Eugene [Center for Polymer Studies and Department of Physics, Boston University, Boston, Massachusetts 02215 (United States)
2014-11-14
The thermodynamic response functions of water display anomalous behaviors. We study these anomalous behaviors in bulk and confined water. We use nuclear magnetic resonance (NMR) to examine the configurational specific heat and the transport parameters in both the thermal stable and the metastable supercooled phases. The data we obtain suggest that there is a behavior common to both phases: that the dynamics of water exhibit two singular temperatures belonging to the supercooled and the stable phase, respectively. One is the dynamic fragile-to-strong crossover temperature (T{sub L} ≃ 225 K). The second, T{sup *} ∼ 315 ± 5 K, is a special locus of the isothermal compressibility K{sub T}(T, P) and the thermal expansion coefficient α{sub P}(T, P) in the P–T plane. In the case of water confined inside a protein, we observe that these two temperatures mark, respectively, the onset of protein flexibility from its low temperature glass state (T{sub L}) and the onset of the unfolding process (T{sup *})
Confinement of helium tides by aerogel
Dolesi, R.; Bonaldi, M.; Vitale, S.
1999-12-01
In the context of scientific space missions that use liquid helium as a coolant, many methods have been proposed to solve the problem of helium confinement. This problem is particularly relevant for those missions which carry on board sensitive accelerometers, because the sub-millimetre motion of the liquid-vapour interface due to the varying gravitational field amplifies the gravitational disturbances beyond the affordable level. Within this framework it has been proposed to use the strong Van der Waals and capillary forces that rise in nanometer sized pores of aerogel to confine helium. Aerogel is a space qualified material and many of its properties have been already studied to a large extent. Its pores occupy a volume always larger than at least 90% of the total volume, with an overall density comparable to the density of the helium liquid itself. We report here on a preliminary experiment that has investigated, by means of the torsion pendulum method, the He II behaviour when only partially filling an aerogel sample. For pressure values below saturation, we observed in particular a high "tortuosity" of the liquid-vapour interface. This supports the idea that even a gravitational field of 1 g does not overcome capillary forces in shaping the superfluid configuration in aerogel.
Extremes of 2d Coulomb gas: universal intermediate deviation regime
Lacroix-A-Chez-Toine, Bertrand; Grabsch, Aurélien; Majumdar, Satya N.; Schehr, Grégory
2018-01-01
In this paper, we study the extreme statistics in the complex Ginibre ensemble of N × N random matrices with complex Gaussian entries, but with no other symmetries. All the N eigenvalues are complex random variables and their joint distribution can be interpreted as a 2d Coulomb gas with a logarithmic repulsion between any pair of particles and in presence of a confining harmonic potential v(r) \\propto r2 . We study the statistics of the eigenvalue with the largest modulus r\\max in the complex plane. The typical and large fluctuations of r\\max around its mean had been studied before, and they match smoothly to the right of the mean. However, it remained a puzzle to understand why the large and typical fluctuations to the left of the mean did not match. In this paper, we show that there is indeed an intermediate fluctuation regime that interpolates smoothly between the large and the typical fluctuations to the left of the mean. Moreover, we compute explicitly this ‘intermediate deviation function’ (IDF) and show that it is universal, i.e. independent of the confining potential v(r) as long as it is spherically symmetric and increases faster than \\ln r2 for large r with an unbounded support. If the confining potential v(r) has a finite support, i.e. becomes infinite beyond a finite radius, we show via explicit computation that the corresponding IDF is different. Interestingly, in the borderline case where the confining potential grows very slowly as v(r) ∼ \\ln r2 for r \\gg 1 with an unbounded support, the intermediate regime disappears and there is a smooth matching between the central part and the left large deviation regime.
Forms of cohesion in confinement institutions
Directory of Open Access Journals (Sweden)
Ekaterina D. Slobodenyuk
2015-12-01
Full Text Available Objective to identify the diversity of cohesion forms in confinement institutions. Methods qualitative analyses based on indepth semistructured interviews. Results the study included adaptation of Western methodologies of the cohesion phenomenon analysis to the Russian reality and operationalization of the moral bases of group cohesion. This served as the bases for designing a guide for indepth semistructured interviews 10 interviews were conducted with people recently released from general and strict regime colonies. Content analysis of the interviews revealed a number of structural sections that demonstrate the diversity of cohesion forms alongside with one that is most meaningful to the prisoners and therefore the most well perceived and articulated by respondents. Analysis of the latter allowed to identify a set of groups showing different degree and nature of cohesion. By the degree of cohesion one can identify the poorly cohesive groups quotloutsquot moderately cohesive quotredsquot quotthievesquot and highly cohesive quotfightersquot. By the nature of cohesion in the prisonersrsquo community there are both groups united on the basis of social morality quotredsquot quotthievesquot and groups demonstrating a high degree of cohesion based on the social justice morality quotfightersquot. A detailed analysis of the latter group also showed that the cohesion can have both traits of morality social justice and features of social order moral. Scientific novelty using the sociopsychological theory of the moral motives in determining the bases of cohesion. Practical significance the research results can be applied for the development of sociopsychological techniques for the penal system reform.
Thermalization in a holographic confining gauge theory
Ishii, Takaaki; Kiritsis, Elias; Rosen, Christopher
2015-08-01
Time dependent perturbations of states in the holographic dual of a 3+1 dimensional confining theory are considered. The perturbations are induced by varying the coupling to the theory's most relevant operator. The dual gravitational theory belongs to a class of Einstein-dilaton theories which exhibit a mass gap at zero temperature and a first order deconfining phase transition at finite temperature. The perturbation is realized in various thermal bulk solutions by specifying time dependent boundary conditions on the scalar, and we solve the fully backreacted Einstein-dilaton equations of motion subject to these boundary conditions. We compute the characteristic time scale of many thermalization processes, noting that in every case we examine, this time scale is determined by the imaginary part of the lowest lying quasi-normal mode of the final state black brane. We quantify the dependence of this final state on parameters of the quench, and construct a dynamical phase diagram. Further support for a universal scaling regime in the abrupt quench limit is provided.
Sorce, Barbara; Escobedo, Carlos; Toyoda, Yusuke; Stewart, Martin P.; Cattin, Cedric J.; Newton, Richard; Banerjee, Indranil; Stettler, Alexander; Roska, Botond; Eaton, Suzanne; Hyman, Anthony A.; Hierlemann, Andreas; Müller, Daniel J.
2015-01-01
Little is known about how mitotic cells round against epithelial confinement. Here, we engineer micropillar arrays that subject cells to lateral mechanical confinement similar to that experienced in epithelia. If generating sufficient force to deform the pillars, rounding epithelial (MDCK) cells can create space to divide. However, if mitotic cells cannot create sufficient space, their rounding force, which is generated by actomyosin contraction and hydrostatic pressure, pushes the cell out of confinement. After conducting mitosis in an unperturbed manner, both daughter cells return to the confinement of the pillars. Cells that cannot round against nor escape confinement cannot orient their mitotic spindles and more likely undergo apoptosis. The results highlight how spatially constrained epithelial cells prepare for mitosis: either they are strong enough to round up or they must escape. The ability to escape from confinement and reintegrate after mitosis appears to be a basic property of epithelial cells. PMID:26602832
Fire regimes during the last glacial
Daniau, A.; Harrison, S. P.; Bartlein, P. J.
2009-12-01
Fire regimes during the last glacial A.-L. Daniau (1), S.P. Harrison (1) and P.J. Bartlein (2) (1) School of Geographical Sciences, University of Bristol, Bristol, BS8 1SS, UK (2) Department of Geography, University of Oregon, Eugene, OR 97403, USA Sedimentary charcoal records document changes in fire regime. We have identified 67 sites which have records for some part of the last glacial and have used the 30 of these sites with better-than millennial-resolution to analyse changes in global fire regimes. Fire was consistently lower during the glacial than during the Eemian and Holocene. Within the glacial, Marine Isotope Stage (MIS) 3 is characterised globally by more fire than MIS 2. The signal for MIS 4 is less clear: there is more fire in the northern hemisphere and less fire in the southern hemisphere than during MIS 2 and 3. The records, most particularly records from the northern extratropics, show millennial-scale variability in fire regimes corresponding to the rapid climate changes associated with Dansgaard-Oeschger (D-O) cycles. Most of the D-O cycles during the last glacial and all of the Heinrich Stadials are apparent in the composite global record of the high-resolution sites: fire increases during D-O warming events and decreases during intervals of cooling. Our analyses show that fire regimes show a lagged response to rapid climate changes of ca 100-200 years in the case of D-O warming events, ca 0-100 years in the case of D-O cooling events and ca 200 years in the case of Heinrich Stadials. The strong climatic variability experienced during the glacial resulted in important changes in fire regimes even though the base level of biomass burning was less than today.
On the method of Fisher and Bekefi for measuring the confinement time of a tokamak plasma
International Nuclear Information System (INIS)
Simpson, S.W.; Drozak, R.M.P.; Galvao, R.M.O.
1980-01-01
The method of Fisher and Bekefi for measuring the electron energy confinement time is analysed using perturbation techniques. It is found that the accuracy of the method depends strongly on the experimental conditions. (orig.)
Surface motion and confinement potential for a microwave confined corona
International Nuclear Information System (INIS)
Ensley, D.L.
1979-07-01
Approximate time dependent solutions for surface velocities and potentials are given for a plane polarized microwave field confining a hot, over-dense plasma corona. Steady state solutions to Poissons' equation can be applied to the time dependent case, provided transit time effects are included. The product of ion pressure and potential wave (surface) velocity gives an average heating rate approx. 7/32 NKT 0 V/sub theta/ directly to the ions
The technology and science of steady-state operation in magnetically confined plasmas
International Nuclear Information System (INIS)
Becoulet, A; Hoang, G T
2008-01-01
The steady-state operation of magnetically confined fusion plasmas is considered as one of the 'grand challenges' of future decades, if not the ultimate goal of the research and development activities towards a new source of energy. Reaching such a goal requires the high-level integration of both science and technology aspects of magnetic fusion into self-consistent plasma regimes in fusion-grade devices. On the physics side, the first constraint addresses the magnetic confinement itself which must be made persistent. This means to either rely on intrinsically steady-state configurations, like the stellarator one, or turn the inductively driven tokamak configuration into a fully non-inductive one, through a mix of additional current sources. The low efficiency of the external current drive methods and the necessity to minimize the re-circulating power claim for a current mix strongly weighted by the internal 'pressure driven' bootstrap current, itself strongly sensitive to the heat and particle transport properties of the plasma. A virtuous circle may form as the heat and particle transport properties are themselves sensitive to the current profile conditions. Note that several other factors, e.g. plasma rotation profile, magneto-hydro-dynamics activity, also influence the equilibrium state. In the present tokamak devices, several examples of such 'advanced tokamak' physics research demonstrate the feasibility of steady-state regimes, though with a number of open questions still under investigation. The modelling activity also progresses quite fast in this domain and supports understanding and extrapolation. This high level of physics sophistication of the plasma scenario however needs to be combined with steady-state technological constraints. The technology constraints for steady-state operation are basically twofold: the specific technologies required to reach the steady-state plasma conditions and the generic technologies linked to the long pulse operation of a
General approach to polymer chains confined by interacting boundaries.
Freed, Karl F; Dudowicz, Jacek; Stukalin, Evgeny B; Douglas, Jack F
2010-09-07
Polymer chains, confined to cavities or polymer layers with dimensions less than the chain radius of gyration, appear in many phenomena, such as gel chromatography, rubber elasticity, viscolelasticity of high molar mass polymer melts, the translocation of polymers through nanopores and nanotubes, polymer adsorption, etc. Thus, the description of how the constraints alter polymer thermodynamic properties is a recurrent theoretical problem. A realistic treatment requires the incorporation of impenetrable interacting (attractive or repulsive) boundaries, a process that introduces significant mathematical complications. The standard approach involves developing the generalized diffusion equation description of the interaction of flexible polymers with impenetrable confining surfaces into a discrete eigenfunction expansion, where the solutions are normally truncated at the first mode (the "ground state dominance" approximation). This approximation is mathematically well justified under conditions of strong confinement, i.e., a confinement length scale much smaller than the chain radius of gyration, but becomes unreliable when the polymers are confined to dimensions comparable to their typically nanoscale size. We extend a general approach to describe polymers under conditions of weak to moderate confinement and apply this semianalytic method specifically to determine the thermodynamics and static structure factor for a flexible polymer confined between impenetrable interacting parallel plate boundaries. The method is first illustrated by analyzing chain partitioning between a pore and a large external reservoir, a model system with application to chromatography. Improved agreement is found for the partition coefficients of a polymer chain in the pore geometry. An expression is derived for the structure factor S(k) in a slit geometry to assist in more accurately estimating chain dimensions from scattering measurements for thin polymer films.
Impact of profile resilience on energy confinement
International Nuclear Information System (INIS)
Igitkhanov, Yu.; Janeschitz, G.; Sugihara, M.
2000-01-01
Multi-machine experimental observations indicate resilience in the temperature profiles at low pedestal temperatures,whereas at high pedestal temperatures the profile stiffness seems to disappear.The change of the profile behavior impacts the energy confinement,basically due to a strong non-linear dependence of the energy transport on the pedestal temperature together with different critical conditions for the onset of turbulence in the ions and electrons.This possible explanation for the different observations is based on the assumption that both ion and electron energy transport is governed by turbulence which sets in at a critical temperature gradient as well as on a significant energy equipartition between electrons and ions
Multiflavor QCD* on R_3 * S_1: Studying Transition From Abelian to Non-Abelian Confinement
Energy Technology Data Exchange (ETDEWEB)
Shifman, M.; /Minnesota U., Theor. Phys. Inst.; Unsal, M.; /SLAC /Stanford U., Phys. Dept.
2009-03-31
The center-stabilized multiflavor QCD* theories formulated on R{sub 3} x S{sub 1} exhibit both Abelian and non-Abelian confinement as a function of the S{sub 1} radius, similar to the Seiberg-Witten theory as a function of the mass deformation parameter. For sufficiently small number of flavors and small r(S{sub 1}), we show occurrence of a mass gap in gauge fluctuations, and linear confinement. This is a regime of confinement without continuous chiral symmetry breaking ({chi}SB). Unlike one-flavor theories where there is no phase transition in r(S{sub 1}), the multiflavor theories possess a single phase transition associated with breaking of the continuous {chi}S. We conjecture that the scale of the {chi}SB is parametrically tied up with the scale of Abelian to non-Abelian confinement transition.
Local order variations in confined hard-sphere fluids.
Nygård, Kim; Sarman, Sten; Kjellander, Roland
2013-10-28
Pair distributions of fluids confined between two surfaces at close distance are of fundamental importance for a variety of physical, chemical, and biological phenomena, such as interactions between macromolecules in solution, surface forces, and diffusion in narrow pores. However, in contrast to bulk fluids, properties of inhomogeneous fluids are seldom studied at the pair-distribution level. Motivated by recent experimental advances in determining anisotropic structure factors of confined fluids, we analyze theoretically the underlying anisotropic pair distributions of the archetypical hard-sphere fluid confined between two parallel hard surfaces using first-principles statistical mechanics of inhomogeneous fluids. For this purpose, we introduce an experimentally accessible ensemble-averaged local density correlation function and study its behavior as a function of confining slit width. Upon increasing the distance between the confining surfaces, we observe an alternating sequence of strongly anisotropic versus more isotropic local order. The latter is due to packing frustration of the spherical particles. This observation highlights the importance of studying inhomogeneous fluids at the pair-distribution level.
Liu, Peter Q.; Luxmoore, Isaac J.; Mikhailov, Sergey A.; Savostianova, Nadja A.; Valmorra, Federico; Faist, Jérôme; Nash, Geoffrey R.
2015-01-01
Metamaterials and plasmonics are powerful tools for unconventional manipulation and harnessing of light. Metamaterials can be engineered to possess intriguing properties lacking in natural materials, such as negative refractive index. Plasmonics offers capabilities of confining light in subwavelength dimensions and enhancing light–matter interactions. Recently, the technological potential of graphene-based plasmonics has been recognized as the latter features large tunability, higher field-confinement and lower loss compared with metal-based plasmonics. Here, we introduce hybrid structures comprising graphene plasmonic resonators coupled to conventional split-ring resonators, thus demonstrating a type of highly tunable metamaterial, where the interaction between the two resonances reaches the strong-coupling regime. Such hybrid metamaterials are employed as high-speed THz modulators, exhibiting ∼60% transmission modulation and operating speed in excess of 40 MHz. This device concept also provides a platform for exploring cavity-enhanced light–matter interactions and optical processes in graphene plasmonic structures for applications including sensing, photo-detection and nonlinear frequency generation. PMID:26584781
Liu, Peter Q.; Luxmoore, Isaac J.; Mikhailov, Sergey A.; Savostianova, Nadja A.; Valmorra, Federico; Faist, Jérôme; Nash, Geoffrey R.
2015-11-01
Metamaterials and plasmonics are powerful tools for unconventional manipulation and harnessing of light. Metamaterials can be engineered to possess intriguing properties lacking in natural materials, such as negative refractive index. Plasmonics offers capabilities of confining light in subwavelength dimensions and enhancing light-matter interactions. Recently, the technological potential of graphene-based plasmonics has been recognized as the latter features large tunability, higher field-confinement and lower loss compared with metal-based plasmonics. Here, we introduce hybrid structures comprising graphene plasmonic resonators coupled to conventional split-ring resonators, thus demonstrating a type of highly tunable metamaterial, where the interaction between the two resonances reaches the strong-coupling regime. Such hybrid metamaterials are employed as high-speed THz modulators, exhibiting ~60% transmission modulation and operating speed in excess of 40 MHz. This device concept also provides a platform for exploring cavity-enhanced light-matter interactions and optical processes in graphene plasmonic structures for applications including sensing, photo-detection and nonlinear frequency generation.
Mobility restrictions and glass transition behaviour of an epoxy resin under confinement.
Djemour, A; Sanctuary, R; Baller, J
2015-04-07
Confinement can have a big influence on the dynamics of glass formers in the vicinity of the glass transition. Already 40 to 50 K above the glass transition temperature, thermal equilibration of glass formers can be strongly influenced by the confining substrate. We investigate the linear thermal expansion and the specific heat capacity cp of an epoxy resin (diglycidyl ether of bisphenol A, DGEBA) in a temperature interval of 120 K around the glass transition temperature. The epoxy resin is filled into controlled pore glasses with pore diameters between 4 and 111 nm. Since DGEBA can form H-bonds with silica surfaces, we also investigate the influence of surface silanization of the porous substrates. In untreated substrates a core/shell structure of the epoxy resin can be identified. The glass transition behaviours of the bulk phase and that of the shell phase are different. In silanized substrates, the shell phase disappears. At a temperature well above the glass transition, a second transition is found for the bulk phase - both in the linear expansion data as well as in the specific heat capacity. The cp data do not allow excluding the glass transition of a third phase as being the cause for this transition, whereas the linear expansion data do so. The additional transition temperature is interpreted as a separation between two regimes: above this temperature, macroscopic flow of the bulk phase inside the porous structure is possible to balance the mismatch of thermal expansion coefficients between DGEBA and the substrate. Below the transition temperature, this degree of freedom is hindered by geometrical constraints of the porous substrates. Moreover, this second transition could also be found in the linear expansion data of the shell phase.
Directory of Open Access Journals (Sweden)
Meera Ramaswamy
2017-10-01
Full Text Available Confined systems ranging from the atomic to the granular are ubiquitous in nature. Experiments and simulations of such atomic and granular systems have shown a complex relationship between the microstructural arrangements under confinement, the short-ranged particle stresses, and flow fields. Understanding the same correlation between structure and rheology in the colloidal regime is important due to the significance of such suspensions in industrial applications. Moreover, colloidal suspensions exhibit a wide range of structures under confinement that could considerably modify such force balances and the resulting viscosity. Here, we use a combination of experiments and simulations to elucidate how confinement-induced structures alter the relative contributions of hydrodynamic and short-range repulsive forces to produce up to a tenfold change in the viscosity. In the experiments we use a custom-built confocal rheoscope to image the particle configurations of a colloidal suspension while simultaneously measuring its stress response. We find that as the gap decreases below 15 particle diameters, the viscosity first decreases from its bulk value, shows fluctuations with the gap, and then sharply increases for gaps below 3 particle diameters. These trends in the viscosity are shown to strongly correlate with the suspension microstructure. Further, we compare our experimental results to those from two different simulations techniques, which enables us to determine the relative contributions of hydrodynamic and short-range repulsive stresses to the suspension rheology. The first method uses the lubrication approximation to find the hydrodynamic stress and includes a short-range repulsive force between the particles while the second is a Stokesian dynamics simulation that calculates the full hydrodynamic stress in the suspension. We find that the decrease in the viscosity at moderate confinements has a significant contribution from both the
Quantum phases of the Rabi lattice in the dispersive regime
Zhu, Guanyu; Schmidt, Sebastian; Koch, Jens
2014-03-01
Photon-based strongly correlated lattice models like the Jaynes-Cummings and Rabi lattices differ from their more conventional relatives like the Bose-Hubbard model by the presence of an additional tunable parameter: the frequency detuning between the pseudo-spin degree of freedom and the harmonic mode frequency on each site. Whenever this detuning is large compared to relevant coupling strengths, the system is said to be in the dispersive regime. The physics of this regime is well-understood at the level of a single Jaynes-Cummings or Rabi site, and can be realized in circuit-QED architecture. Here, we extend the theoretical description of the dispersive regime to lattices with many sites, for both strong and ultra-strong coupling. We discuss the nature and spatial range of the resulting qubit-qubit and photon-photon coupling. In the ultra-strong coupling regime, we demonstrate the emergence of the paramagnetic-to-ferromagnetic phase transition of photon-dressed qubits in the negative detuning regime, and the photon-pairing and vacuum squeezing in the positive detuning regime. We illustrate our results by exact diagonalization of the Rabi dimer.
Theory of rheology in confinement.
Aerov, Artem A; Krüger, Matthias
2015-10-01
The viscosity of fluids is generally understood in terms of kinetic mechanisms, i.e., particle collisions, or thermodynamic ones as imposed through structural distortions upon, e.g., applying shear. Often the latter are more relevant, which allows a simpler theoretical description, and, e.g., (damped) Brownian particles can be considered good fluid model systems. We formulate a general theoretical approach for rheology in confinement, based on microscopic equations of motion and classical density functional theory. Specifically, we discuss the viscosity for the case of two parallel walls in relative motion as a function of the wall-to-wall distance, analyzing its relation to the slip length found for a single wall. The previously observed [A. A. Aerov and M. Krüger, J. Chem. Phys. 140, 094701 (2014).] deficiency of inhomogeneous (unphysical) stresses under naive application of shear in confinement is healed when hydrodynamic interactions are included.
Physics of magnetic confinement fusion
Wagner, F.
2013-06-01
Fusion is the energy source of the universe. The local conditions in the core of the Sun allow the transfer of mass into energy, which is finally released in the form of radiation. Technical fusion melts deuterons and tritons to helium releasing large amounts of energy per fusion process. Because of the conditions for fusion, which will be deduced, the fusion fuel is in the plasma state. Here we report on the confinement of fusion plasmas by magnetic fields. Different confinement concepts — tokamaks and stellarators — will be introduced and described. The first fusion reactor, ITER, and the most modern stellarator, Wendelstein 7-X, are under construction. Their basic features and objectives will be presented.
Physics of magnetic confinement fusion
Directory of Open Access Journals (Sweden)
Wagner F.
2013-06-01
Full Text Available Fusion is the energy source of the universe. The local conditions in the core of the Sun allow the transfer of mass into energy, which is finally released in the form of radiation. Technical fusion melts deuterons and tritons to helium releasing large amounts of energy per fusion process. Because of the conditions for fusion, which will be deduced, the fusion fuel is in the plasma state. Here we report on the confinement of fusion plasmas by magnetic fields. Different confinement concepts — tokamaks and stellarators — will be introduced and described. The first fusion reactor, ITER, and the most modern stellarator, Wendelstein 7-X, are under construction. Their basic features and objectives will be presented.
Confinement and diffusion in tokamaks
International Nuclear Information System (INIS)
McWilliams, R.
1988-01-01
The effect of electric field fluctuations on confinement and diffusion in tokamak is discussed. Based on the experimentally determined cross-field turbolent diffusion coefficient, D∼3.7*cT e /eB(δn i /n i ) rms which is also derived by a simple theory, the cross-field diffusion time, tp=a 2 /D, is calculated and compared to experimental results from 51 tokamak for standard Ohmic operation
Holographic confinement in inhomogeneous backgrounds
Energy Technology Data Exchange (ETDEWEB)
Marolf, Donald; Wien, Jason [Department of Physics, University of California,Santa Barbara, CA 93106 (United States)
2016-08-02
As noted by Witten, compactifying a d-dimensional holographic CFT on an S{sup 1} gives a class of (d−1)-dimensional confining theories with gravity duals. The prototypical bulk solution dual to the ground state is a double Wick rotation of the AdS{sub d+1} Schwarzschild black hole known as the AdS soliton. We generalize such examples by allowing slow variations in the size of the S{sup 1}, and thus in the confinement scale. Coefficients governing the second order response of the system are computed for 3≤d≤8 using a derivative expansion closely related to the fluid-gravity correspondence. The primary physical results are that i) gauge-theory flux tubes tend to align orthogonal to gradients and along the eigenvector of the Hessian with the lowest eigenvalue, ii) flux tubes aligned orthogonal to gradients are attracted to gradients for d≤6 but repelled by gradients for d≥7, iii) flux tubes are repelled by regions where the second derivative along the tube is large and positive but are attracted to regions where the eigenvalues of the Hessian are large and positive in directions orthogonal to the tube, and iv) for d>3, inhomogeneities act to raise the total energy of the confining vacuum above its zeroth order value.
Energy Technology Data Exchange (ETDEWEB)
Leon, V
2006-07-15
Physico-chemical properties of materials can be strongly modified by confinement because of the quantum effects that appear at such small length scales and also because of the effects of the confinement itself. The aim of this thesis is to show that both the nature of the confining material and the size of the pores and cavities have a strong impact on the confined material. We first show the effect of the pore size of the host meso-porous silica on the temperature of the solid-solid phase transition of silver selenide, a semiconducting material with enhanced magnetoresistive properties under non-stoichiometric conditions. Narrowing the pores from 20 nm to 2 nm raises the phase transition temperature from 139 C to 146 C. This result can be explained by considering the interaction between the confining and confined materials as a driving force. The effects of confinement are also studied in the case of hydrogen and deuterium inside cavities of organized carbon nano-structures. The effects that appear in the adsorption/desorption cycles are much stronger with carbon nano-horns as the host material than with C60 pea-pods and single-walled carbon nano-tubes. (author)
Analytic models of CMOS logic in various regimes
Directory of Open Access Journals (Sweden)
Dokić Branko
2014-01-01
Full Text Available In this paper, comparative analytic models of static and dynamic characteristics of CMOS digital circuits in strong, weak and mixed inversion regime have been described. Term mixed inversion is defined for the first time. The paper shows that there is an analogy in behavior and functional dependencies of parameters in all three CMOS regimes. Comparative characteristics of power consumption and speed in static regimes are given. Dependency of threshold voltage and logic delay time on temperature has been analyzed. Dynamic model with constant current is proposed. It is shown that digital circuits with dynamic threshold voltage of MOS transistor (DT-CMOS have better logic delay characteristics. The analysis is based on simplified current-voltage MOS transistor models in strong and weak inversion regimes, as well as PSPICE software using 180 nm technology parameters.
Axisymmetric magnetic mirrors for plasma confinement. Recent development and perspectives
International Nuclear Information System (INIS)
Kruglyakov, E.P.; Dimov, G.I.; Ivanov, A.A.; Koidan, V.S.
2003-01-01
Mirrors are the only one class of fusion systems which completely differs topologically from the systems with closed magnetic configurations. At present, three modern types of different mirror machines for plasma confinement and heating exist in Novosibirsk (Gas Dynamic Trap,- GDT, Multi-mirror,- GOL-3, and Tandem Mirror,- AMBAL-M). All these systems are attractive from the engineering point of view because of very simple axisymmetric geometry of magnetic configurations. In the present paper, the status of different confinement systems is presented. The experiments most crucial for the mirror concept are described such as a demonstration of different principles of suppression of electron heat conductivity (GDT, GOL-3), finding of MHD stable regimes of plasma confinement in axisymmetric geometry of magnetic field (GDT, AMBAL-M), an effective heating of a dense plasma by relativistic electron beam (GOL-3), observation of radial diffusion of quiescent plasma with practically classical diffusion coefficient (AMBAL-M), etc. It should be mentioned that on the basis of the GDT it is possible to make a very important intermediate step. Using 'warm' plasma and oblique injection of fast atoms of D and T one can create a powerful 14 MeV neutron source with a moderate irradiation area (about 1 square meter) and, accordingly, with low tritium consumption. The main plasma parameters achieved are presented and the future perspectives of different mirror machines are outlined. (author)
The scientific benefits of inertially confined fusion research
International Nuclear Information System (INIS)
Key, M
1999-01-01
A striking feature of 25 years of research into inertially confined fusion (ICF) and inertial fusion energy (IFE) has been its significant impact in other fields of science. Most ICF facilities worldwide are now being used in part to support a wider portfolio of research than simply ICF. Reasons for this trend include the high intrinsic interest of the new science coupled with the relative ease and low marginal cost of adapting the facilities particularly lasers, to carry out experiments with goals other than ICF. The availability at ICF laboratories of sophisticated theory and modeling capability and advanced diagnostics has given added impetus. The expertise of ICF specialists has also triggered more lateral scientific spin-offs leading for example to new types of lasers and to related developments in basic science. In a generic sense, the facilities developed for ICF have made possible study of new regimes of the properties of matter at extremely high-energy density and the interaction of ultraintense light with matter. This general opportunity has been exploited in numerous and diverse specific lines of research. Examples elaborated below include laboratory simulation of astrophysical phenomena; studies of the equation of state (EOS) of matter under conditions relevant to the interior of planets and stars; development of uniquely intense sources of extreme ultraviolet (EUV) to hard x-ray emission, notably the x-ray laser; understanding of the physics of strong field interaction of light and matter; and related new phenomena such as laser-induced nuclear processes and high-field-electron accelerators. Some of these developments have potential themselves for further scientific exploitation such as the scientific use of advanced light sources. There are also avenues for commercial exploitation, for example the use of laser plasma sources in EUV lithography. Past scientific progress is summarized here and projections are made for new science that may flow from the
Water confined in nanotubes and between graphene sheets: A first principle study
Energy Technology Data Exchange (ETDEWEB)
Cicero, G; Grossman, J C; Schwegler, E; Gygi, F; Galli, G
2008-10-17
Water confined at the nanoscale has been the focus of numerous experimental and theoretical investigations in recent years, y yet there is no consensus on such basic properties et as diffusion and the nature of hydrogen bonding (HB) under confinement. Unraveling these properties is important to understand fluid flow and transport at the nanoscale, and to shed light on the solvation of biomolecules. Here we report on a first principle, computational study focusing on water confined between prototypical non polar substrate, i.e. , single wall carbon nanotubes and graphene sheets, 1 to 2.5 nm apart. The results of our molecular dynamics simulations show the presence of a thin, interfacial liquid layer ({approx} 5 Angstroms) whose microscopic structure and thickness are independent of the distance between confining layers. The prop properties of the hydrogen bonded network are very similar to those of the bulk outside the interfacial region, even in the case of strong confinement , confinement. Our findings indicate that the perturbation induced by the presence of confining media is extremely local in liquid water, and we propose that many of the effects attributed to novel phases under confinement are determined by subtle electronic structure rearrangements occurring at the interface with the confining medium.
Origin of melting point depression for rare gas solids confined in carbon pores.
Morishige, Kunimitsu; Kataoka, Takaaki
2015-07-21
To obtain insights into the mechanism of the melting-point depression of rare gas solids confined in crystalline carbon pores, we examined the freezing and melting behavior of Xe and Ar confined to the crystalline pores of ordered mesoporous carbons as well as compressed exfoliated graphite compared to the amorphous pores of ordered mesoporous silicas, by means of X-ray diffraction. For the Xe and Ar confined to the crystalline carbon pores, there was no appreciable thermal hysteresis between freezing and melting. Furthermore, the position of the main diffraction peak did not change appreciably on freezing and melting. This strongly suggests that the liquids confined in the carbon pores form a multilayered structure parallel to the smooth walls. For the Xe and Ar confined to the amorphous silica pores, on the other hand, the position of the main diffraction peak shifted into higher scattering angle on freezing suggested that the density of the confined solid is distinctly larger than for the confined liquid. Using compressed exfoliated graphite with carbon walls of higher crystallinity, we observed that three-dimensional (3D) microcrystals of Xe confined in the slit-shaped pores melted to leave the unmelted bilayers on the pore walls below the bulk triple point. The lattice spacing of the 3D microcrystals confined is larger by ∼0.7% than that of the bilayer next to the pore walls in the vicinity of the melting point.
Origin of melting point depression for rare gas solids confined in carbon pores
International Nuclear Information System (INIS)
Morishige, Kunimitsu; Kataoka, Takaaki
2015-01-01
To obtain insights into the mechanism of the melting-point depression of rare gas solids confined in crystalline carbon pores, we examined the freezing and melting behavior of Xe and Ar confined to the crystalline pores of ordered mesoporous carbons as well as compressed exfoliated graphite compared to the amorphous pores of ordered mesoporous silicas, by means of X-ray diffraction. For the Xe and Ar confined to the crystalline carbon pores, there was no appreciable thermal hysteresis between freezing and melting. Furthermore, the position of the main diffraction peak did not change appreciably on freezing and melting. This strongly suggests that the liquids confined in the carbon pores form a multilayered structure parallel to the smooth walls. For the Xe and Ar confined to the amorphous silica pores, on the other hand, the position of the main diffraction peak shifted into higher scattering angle on freezing suggested that the density of the confined solid is distinctly larger than for the confined liquid. Using compressed exfoliated graphite with carbon walls of higher crystallinity, we observed that three-dimensional (3D) microcrystals of Xe confined in the slit-shaped pores melted to leave the unmelted bilayers on the pore walls below the bulk triple point. The lattice spacing of the 3D microcrystals confined is larger by ∼0.7% than that of the bilayer next to the pore walls in the vicinity of the melting point
Stripe to slab confinement for the linearization of macromolecules in nanochannels.
Benková, Zuzana; Námer, Pavol; Cifra, Peter
2015-03-21
We investigated the recently suggested advantageous analysis of chain linearization experiments with macromolecules confined in a stripe-like channel (Huang and Battacharya, EPL, 2014, 106, 18004) using Monte Carlo simulations. The enhanced chain extension in a stripe, which is due to the significant excluded volume interactions between the monomers in two dimensions, weakens considerably on transition to an experimentally feasible slit-like channel. Based on the chain extension-confinement strength dependence and the structure factor behavior for a chain in a stripe, we infer the excluded volume regime (de Gennes regime) typical for two-dimensional systems. On widening of the stripe in a direction perpendicular to the stripe plane, i.e. on the transition to the slab geometry, the advantageous chain extension decreases and a Gaussian regime is observed for not very long semiflexible chains. The evidence for pseudo-ideality in confined chains is based on four indicators: the extension curves, variation of the extension with the persistence length P, estimated limits for the regimes in the investigated systems, and the structure factor behavior. The slab behavior can be observed when the two-dimensional stripe (originally of a one-monomer thickness) reaches a reduced thickness D larger than approximately D/P ≈ 0.2 in the third dimension. This maximum height of a slab at which the advantage of a stripe is retained is very low and has implications for DNA linearization experiments.
Unitary Housing Regimes in Transition
DEFF Research Database (Denmark)
Bengtsson, Bo; Jensen, Lotte
2013-01-01
to the Danish and Swedish housing regimes are analysed and the responses and outcomes in terms of policy change and/or institutional continuity (path dependence) are compared. Overall, the more decentralized Danish housing regime seems to have resisted pressures for change and retrenchment better so far than...
Global regime shift dynamics of catastrophic sea urchin overgrazing
Ling, S. D.; Scheibling, R. E.; Rassweiler, A.; Johnson, C. R.; Shears, N.; Connell, S. D.; Salomon, A. K.; Norderhaug, K. M.; Pérez-Matus, A.; Hernández, J. C.; Clemente, S.; Blamey, L. K.; Hereu, B.; Ballesteros, E.; Sala, E.; Garrabou, J.; Cebrian, E.; Zabala, M.; Fujita, D.; Johnson, L. E.
2015-01-01
A pronounced, widespread and persistent regime shift among marine ecosystems is observable on temperate rocky reefs as a result of sea urchin overgrazing. Here, we empirically define regime-shift dynamics for this grazing system which transitions between productive macroalgal beds and impoverished urchin barrens. Catastrophic in nature, urchin overgrazing in a well-studied Australian system demonstrates a discontinuous regime shift, which is of particular management concern as recovery of desirable macroalgal beds requires reducing grazers to well below the initial threshold of overgrazing. Generality of this regime-shift dynamic is explored across 13 rocky reef systems (spanning 11 different regions from both hemispheres) by compiling available survey data (totalling 10 901 quadrats surveyed in situ) plus experimental regime-shift responses (observed during a total of 57 in situ manipulations). The emergent and globally coherent pattern shows urchin grazing to cause a discontinuous ‘catastrophic’ regime shift, with hysteresis effect of approximately one order of magnitude in urchin biomass between critical thresholds of overgrazing and recovery. Different life-history traits appear to create asymmetry in the pace of overgrazing versus recovery. Once shifted, strong feedback mechanisms provide resilience for each alternative state thus defining the catastrophic nature of this regime shift. Importantly, human-derived stressors can act to erode resilience of desirable macroalgal beds while strengthening resilience of urchin barrens, thus exacerbating the risk, spatial extent and irreversibility of an unwanted regime shift for marine ecosystems.
Pneumatic fractures in confined granular media.
Eriksen, Fredrik K; Toussaint, Renaud; Turquet, Antoine L; Måløy, Knut J; Flekkøy, Eirik G
2017-06-01
We perform experiments where air is injected at a constant overpressure P_{in}, ranging from 5 to 250 kPa, into a dry granular medium confined within a horizontal linear Hele-Shaw cell. The setup allows us to explore compacted configurations by preventing decompaction at the outer boundary, i.e., the cell outlet has a semipermeable filter such that beads are stopped while air can pass. We study the emerging patterns and dynamic growth of channels in the granular media due to fluid flow, by analyzing images captured with a high speed camera (1000 images/s). We identify four qualitatively different flow regimes, depending on the imposed overpressure, ranging from no channel formation for P_{in} below 10 kPa, to large thick channels formed by erosion and fingers merging for high P_{in} around 200 kPa. The flow regimes where channels form are characterized by typical finger thickness, final depth into the medium, and growth dynamics. The shape of the finger tips during growth is studied by looking at the finger width w as function of distance d from the tip. The tip profile is found to follow w(d)∝d^{β}, where β=0.68 is a typical value for all experiments, also over time. This indicates a singularity in the curvature d^{2}d/dw^{2}∼κ∼d^{1-2β}, but not of the slope dw/dd∼d^{β-1}, i.e., more rounded tips rather than pointy cusps, as they would be for the case β>1. For increasing P_{in}, the channels generally grow faster and deeper into the medium. We show that the channel length along the flow direction has a linear growth with time initially, followed by a power-law decay of growth velocity with time as the channel approaches its final length. A closer look reveals that the initial growth velocity v_{0} is found to scale with injection pressure as v_{0}∝P_{in}^{3/2}, while at a critical time t_{c} there is a cross-over to the behavior v(t)∝t^{-α}, where α is close to 2.5 for all experiments. Finally, we explore the fractal dimension of the fully
Shamsi, Javad; Dang, Zhiya; Bianchini, Paolo; Canale, Claudio; Stasio, Francesco Di; Brescia, Rosaria; Prato, Mirko; Manna, Liberato
2016-06-15
We report the nontemplated colloidal synthesis of single crystal CsPbBr3 perovskite nanosheets with lateral sizes up to a few micrometers and with thickness of just a few unit cells (i.e., below 5 nm), hence in the strong quantum confinement regime, by introducing short ligands (octanoic acid and octylamine) in the synthesis together with longer ones (oleic acid and oleylamine). The lateral size is tunable by varying the ratio of shorter ligands over longer ligands, while the thickness is mainly unaffected by this parameter and stays practically constant at 3 nm in all the syntheses conducted at short-to-long ligands volumetric ratio below 0.67. Beyond this ratio, control over the thickness is lost and a multimodal thickness distribution is observed.
Cylindrical confinement of semiflexible polymers.
Vázquez-Montejo, Pablo; McDargh, Zachary; Deserno, Markus; Guven, Jemal
2015-06-01
Equilibrium states of a closed semiflexible polymer binding to a cylinder are described. This may be either by confinement or by constriction. Closed completely bound states are labeled by two integers: the number of oscillations, n, and the number of times it winds the cylinder, p, the latter being a topological invariant. We examine the behavior of these states as the length of the loop is increased by evaluating the energy, the conserved axial torque, and the contact force. The ground state for a given p is the state with n=1; a short loop with p=1 is an elliptic deformation of a parallel circle; as its length increases it elongates along the cylinder axis with two hairpin ends. Excited states with n≥2 and p=1 possess n-fold axial symmetry. Short (long) loops possess energies ≈pE(0)(nE(0)), with E(0) the energy of a circular loop with same radius as the cylinder; in long loops the axial torque vanishes. Confined bound excited states are initially unstable; however, above a critical length each n-fold state becomes stable: The folded hairpin cannot be unfolded. The ground state for each p is also initially unstable with respect to deformations rotating the loop off the surface into the interior. A closed planar elastic curve aligned along the cylinder axis making contact with the cylinder on its two sides is identified as the ground state of a confined loop. Exterior bound states behave very differently, if free to unbind, as signaled by the reversal in the sign of the contact force. If p=1, all such states are unstable. If p≥2, however, a topological obstruction to complete unbinding exists. If the loop is short, the bound state with p=2 and n=1 provides a stable constriction of the cylinder, partially unbinding as the length is increased. This motif could be relevant to an understanding of the process of membrane fission mediated by dynamin rings.
International Nuclear Information System (INIS)
Choudhury, Niharendu
2013-01-01
Highlights: • We present atomistic MD simulation of water confined between two paraffin-like plates. • Effect of plate hydrophobicity on the confined water dynamics is investigated. • Diffusivity of confined water is calculated from mean squared displacements. • Rotational dynamics of the confined water has bimodal nature of relaxation. • Monotonic dependence of translational and rotational dynamics on hydrophobicity. - Abstract: We present detailed molecular dynamics simulations of water in and around a pair of plates immersed in water to investigate the effect of degree of hydrophobicity or hydrophilicity of the plates on dynamics of water confined between the two plates. The nature of the plate has been tuned from hydrophobic to hydrophilic and vice versa by varying plate-water dispersion interaction. Analyses of the translational dynamics as performed by calculating mean squared displacements of the confined water reveal a monotonically decreasing trend of the diffusivity with increasing hydrophilicity of the plates. Orientational dynamics of the confined water also follows the same monotonic trend. Although orientational time constant almost does not change with the increase of plate-water dispersion interaction in the hydrophobic regime corresponding to the smaller plate-water attraction, it changes considerably in the hydrophilic regime corresponding to larger plate-water dispersion interactions
Nonperturbative approach to quantum field theories: phase transitions and confinement
International Nuclear Information System (INIS)
Yankielowicz, S.
1976-08-01
Lectures are given on a nonperturbative approach to quantum field theories. Phenomena are discussed for which the usual weak coupling perturbative approach in terms of Feynman diagrams is of no assistance. Properties associated with large distance behavior, i.e., phase transitions, low lying spectra, coherent excitations which are presumably built out of the long wave structure of the theory are described. These methods are important for the study of strong coupling field theories and the question of quarks confinement. 25 references
Transport phenomena in a plasma of confining gluons
Directory of Open Access Journals (Sweden)
Ryblewski Radoslaw
2016-01-01
Full Text Available The plasma of confining gluons resulting from the Gribov quantization is considered. In the fluid dynamical framework the non-equilibrium properties of the system are studied. In the linear response approximation the formulas for the bulk, ζ, and shear, η, viscosities of the plasma are calculated analytically. Surprisingly, the approximate scaling of the ζ/η ratio reveals the strong-coupling properties of the system under consideration.
Transport phenomena in a plasma of confining gluons
Ryblewski, Radoslaw
2016-11-01
The plasma of confining gluons resulting from the Gribov quantization is considered. In the fluid dynamical framework the non-equilibrium properties of the system are studied. In the linear response approximation the formulas for the bulk, ζ, and shear, η, viscosities of the plasma are calculated analytically. Surprisingly, the approximate scaling of the ζ/η ratio reveals the strong-coupling properties of the system under consideration.
Phonon Scattering and Confinement in Crystalline Films
Parrish, Kevin D.
. Removing the isotropic assumption, leading to the formulation of modal ray-tracing, corrects the mean free path distribution. The effect of phonon line-of-sight is investigated in nanoporous silicon films using free path sampling. When the line-of-sight is cut off there is a distinct change in thermal conductivity versus porosity. By analyzing the free paths of an obstructed phonon mode, it is concluded that the trend change is due to a hard upper limit on the free paths that can exist due to the nanopore geometry in the material. The transient grating technique is an optical contact-less laser based experiment for measuring the in-plane thermal diffusivity of thin films and membranes. The theory of operation and physical setup of a transient grating experiment is detailed. The procedure for extracting the thermal diffusivity from the raw experimental signal is improved upon by removing arbitrary user choice in the fitting parameters used and constructing a parameterless error minimizing procedure. The thermal conductivity of ultra-thin argon films modeled with the Lennard-Jones potential is calculated from both the Monte Carlo free path sampling technique and from explicit reduced dimensionality lattice dynamics calculations. In these ultra-thin films, the phonon properties are altered in more than a perturbative manner, referred to as the confinement regime. The free path sampling technique, which is a perturbative method, is compared to a reduced dimensionality lattice dynamics calculation where the entire film thickness is taken as the unit cell. Divergence in thermal conductivity magnitude and trend is found at few unit cell thick argon films. Although the phonon group velocities and lifetimes are affected, it is found that alterations to the phonon density of states are the primary cause of the deviation in thermal conductivity in the confinement regime.
Confinement of high temperature plasmas
International Nuclear Information System (INIS)
Bass, R.W.; Ferguson, H.R.; Fletcher, H.J.; Gardner, J.H.; Harrison, B.K.; Larsen, K.M.
1980-01-01
A high temperature plasma is confined in the shape of a topological torus by a topologically stable magnetic field which is everywhere constant on and tangent to the surface of the torus. There are exactly an even finite number of closed magnetic field lines on the plasma surface and all other magnetic field lines on the surface are asymptotic to the closed field lines. This magnetic field configuration is achieved by a set of current carrying conductors appropriately arranged with respect to the plasma and carrying suitably selected currents
Frictional properties of confined polymers
DEFF Research Database (Denmark)
Sivebæk, Ion Marius; Samoilov, Vladimir N; Persson, Bo N J
2008-01-01
We present molecular dynamics friction calculations for confined hydrocarbon solids with molecular lengths from 20 to 1400 carbon atoms. Two cases are considered: a) polymer sliding against a hard substrate, and b) polymer sliding on polymer. In the first setup the shear stresses are relatively...... independent of molecular length. For polymer sliding on polymer the friction is significantly larger, and dependent on the molecular chain length. In both cases, the shear stresses are proportional to the squeezing pressure and finite at zero load, indicating an adhesional contribution to the friction force...
Runaway electrons and magnetic island confinement
Boozer, Allen H.
2016-08-01
The breakup of magnetic surfaces is a central feature of ITER planning for the avoidance of damage due to runaway electrons. Rapid thermal quenches, which lead to large accelerating voltages, are thought to be due to magnetic surface breakup. Impurity injection to avoid and to mitigate both halo and runaway electron currents utilizes massive gas injection or shattered pellets. The actual deposition is away from the plasma center, and the breakup of magnetic surfaces is thought to spread the effects of the impurities across the plasma cross section. The breakup of magnetic surfaces would prevent runaway electrons from reaching relativistic energies were it not for the persistence of non-intercepting flux tubes. These are tubes of magnetic field lines that do not intercept the walls. In simulations and in magnetic field models, non-intercepting flux tubes are found to persist near the magnetic axis and in the cores of magnetic islands even when a large scale magnetic surface breakup occurs. As long as a few magnetic surfaces reform before all of the non-intercepting flux tubes dissipate, energetic electrons confined and accelerated in these flux tubes can serve as the seed electrons for a transfer of the overall plasma current from thermal to relativistic carriers. The acceleration of electrons is particularly strong because of the sudden changes in the poloidal flux that naturally occur in a rapid magnetic relaxation. The physics of magnetic islands as non-intercepting flux tubes is studied. Expressions are derived for (1) the size of islands required to confine energetic runaway electrons, (2) the accelerating electric field in an island, (3) the increase or reduction in the size of an island by the runaway electron current, (4) the approximate magnitude of the runaway current in an island, and (5) the time scale for the evolution of an island.
Investigation of fluctuations in the HDH and H* regime of Wendelstein 7-AS
International Nuclear Information System (INIS)
Baeumel, S.; Werner, A.; McCormick, K.
2003-01-01
The High Density H-Mode Regime was discovered in Island Divertor operation of the Wendelstein 7-AS (W7-AS)stellerator. This regime is characterized by low impurity, high-energy confinement times - up to twice the value of the International Stellarator Scaling ISS95 - and edge radiated power fractions of up to 90% in detached state. Regarding the enhanced impurity transport at good energy confinement there are similarities to the enhanced D α H-mode found on the Alcator C-Mod tokamak. In W7-AS studies were performed in order to compare the HDH regime with the classical ELM-free discharges (H * ). Although both regimes are similar in collisionality and have almost the same n e (r)- and T e (r)-profile shapes, the H * regime suffers a radiation collapse due to impurity accumulation. The short impurity confinement times in HDH discharges requires enhanced transport at the plasma edge. The cause is not clear and this contribution looks for similarities to the enhanced D α H-mode of Alcator C-Mod, that is, whether quasicoherent modes exist in W7-AS causing enhanced edge transport. Discharges with a variation of magnetic configurations, densities (up to 4.10 20 m -3 ) and powers (up to 3.2 MW absorbed) will be discussed with respect to the different behaviour of fluctuations. (orig.)
Dispersive regime of the Jaynes-Cummings and Rabi lattice
Zhu, Guanyu; Schmidt, Sebastian; Koch, Jens
2013-11-01
Photon-based strongly correlated lattice models like the Jaynes-Cummings and Rabi lattices differ from their more conventional relatives like the Bose-Hubbard model by the presence of an additional tunable parameter: the frequency detuning between the pseudo-spin degree of freedom and the harmonic mode frequency on each site. Whenever this detuning is large compared to relevant coupling strengths, the system is said to be in the dispersive regime. The physics of this regime is well-understood at the level of a single Jaynes-Cummings or Rabi site. Here, we extend the theoretical description of the dispersive regime to lattices with many sites, for both strong and ultra-strong coupling. We discuss the nature and spatial range of the resulting qubit-qubit and photon-photon coupling, demonstrate the emergence of photon-pairing and squeezing and illustrate our results by exact diagonalization of the Rabi dimer.
Magnetic confinement fusion energy research
Energy Technology Data Exchange (ETDEWEB)
Grad, H
1977-03-01
Controlled Thermonuclear Fusion offers probably the only relatively clean energy solution with completely inexhaustible fuel and unlimited power capacity. The scientific and technological problem consists in magnetically confining a hot, dense plasma (pressure several to hundreds of atmospheres, temperature 10/sup 8/ degrees or more) for an appreciable fraction of a second. The scientific and mathematical problem is to describe the behavior, such as confinement, stability, flow, compression, heating, energy transfer and diffusion of this medium in the presence of electromagnetic fields just as we now can for air or steam. Some of the extant theory consists of applications, routine or ingenious, of known mathematical structures in the theory of differential equations and in traditional analysis. Other applications of known mathematical structures offer surprises and new insights: the coordination between sub-supersonic and elliptic-hyperbolic is fractured; supersonic propagation goes upstream; etc. Other completely nonstandard mathematical structures with significant theory are being rapidly uncovered (and somewhat less rapidly understood) such as non-elliptic variational equations and new types of weak solutions. It is these new mathematical structures which one should expect to supply the foundation for the next generation's pure mathematics, if history is a guide. Despite the substantial effort over a period of some twenty years, there are still basic and important scintific and mathematical discoveries to be made, lying just beneath the surface.
Japanese magnetic confinement fusion research
International Nuclear Information System (INIS)
McKenney, B.L.; McGrain, M.; Horton, C.W.; Rutherford, P.H.
1990-01-01
This report is the work of six US scientists who surveyed and assessed Japanese research and development in magnetic fusion. All of the panelists are very familiar with Japanese fusion research through their knowledge of the published scientific literature and through personal contacts with Japanese colleagues and with US colleagues who have visited Japanese research facilities. This report concentrates on the period from the early 1980s through June 1989. The technical accomplishments during this period are reviewed, and the Japanese capabilities and outlook for future contributions are assessed. Detailed evaluations are provided in the areas of basic and applied plasma physics, tokamak confinement, alternate confinement approaches, plasma technology, and fusion nuclear technology and materials. With a sustained national commitment, Japan will surpass US and West European capabilities in the early to middle 1990s in several important areas of fusion research and development. For example, it is expected that the planned upgrade of the Japanese JT-60 tokamak will surpass both the US Tokamak Fusion Test Reactor (TFTR) and the Joint European tours (JET) in the usual measures of plasma performance in the 1992 to 1993 timeframe, and will take a clear international lead in large-tokamak research by 1994 to 1995. The Japanese fusion program has the human and technological resources required to build and operate a fusion engineering test reactor without external participation. By the same measure, Japan would be a highly desirable partner in the bilateral undertaking of such a project
Edge energy transport barrier and turbulence in the I-mode regime on Alcator C-Moda)
Hubbard, A. E.; Whyte, D. G.; Churchill, R. M.; Cziegler, I.; Dominguez, A.; Golfinopoulos, T.; Hughes, J. W.; Rice, J. E.; Bespamyatnov, I.; Greenwald, M. J.; Howard, N.; Lipschultz, B.; Marmar, E. S.; Reinke, M. L.; Rowan, W. L.; Terry, J. L.
2011-05-01
We report extended studies of the I-mode regime [Whyte et al., Nucl. Fusion 50, 105005 (2010)] obtained in the Alcator C-Mod tokamak [Marmar et al., Fusion Sci. Technol. 51(3), 3261 (2007)]. This regime, usually accessed with unfavorable ion B × ∇B drift, features an edge thermal transport barrier without a strong particle transport barrier. Steady I-modes have now been obtained with favorable B × ∇B drift, by using specific plasma shapes, as well as with unfavorable drift over a wider range of shapes and plasma parameters. With favorable drift, power thresholds are close to the standard scaling for L-H transitions, while with unfavorable drift they are ˜ 1.5-3 times higher, increasing with Ip. Global energy confinement in both drift configurations is comparable to H-mode scalings, while density profiles and impurity confinement are close to those in L-mode. Transport analysis of the edge region shows a decrease in edge χeff, by typically a factor of 3, between L- and I-mode. The decrease correlates with a drop in mid-frequency fluctuations (f ˜ 50-150 kHz) observed on both density and magnetics diagnostics. Edge fluctuations at higher frequencies often increase above L-mode levels, peaking at f ˜ 250 kHz. This weakly coherent mode is clearest and has narrowest width (Δf/f ˜ 0.45) at low q95 and high Tped, up to 1 keV. The Er well in I-mode is intermediate between L- and H-mode and is dominated by the diamagnetic contribution in the impurity radial force balance, without the Vpol shear typical of H-modes.
Hydrological regimes in Balkan Area
International Nuclear Information System (INIS)
Stanescu, Viorel Alexandru
2004-01-01
Physical considerations of the deemed area are first considered in the paper. Then the regime types around the Balkan rivers are described in terms of the following characteristic features: -Types of the regimes defined by the timing of the high and low flow phases; -Regionalisation of the 'micro-types' -Stability of the river flow regimes. The available mean monthly discharge data of the representative rivers allows characterising the river regime of the Balkan area covered by WOISYDES and BALWOIS projects. The classification of the hydrological regimes (types of regimes) was done by assessing the discriminant periods (descriptors of the regime phases) defined by the first, the second and the third highest and lowest monthly values of flows. As sufficient data has been provided by countries involved in the Woisydes/Balwois Project a hydrological regionalisation is performed all around the considered space. The existence of different zones, which are quasi- homogeneous in terms of physiographical properties, the latter especially being expressed by their mean altitudes and the climatic features, allowed to carry out a hydrological regionalisation of the river flow regime types. The regionalisation of the river flow regimes is presented as hydrological maps both referring to each Balkan country and for the entire region as an overall map. The stability of a certain flow regime is an important descriptor of the ecological state of the river during the year. It may be quantitatively expressed by the stability coefficient determined by Corbus and Stanescu as the product between the frequency of the occurrence of any discriminant value in m subsequent month (m = 1,12) and a distribution coefficient along the period that depend on the length of the considered discriminant period. The advantage of this method stands in the fact that for several combinations of subsequent months, the maximisation of the stability coefficient leads to the assessment of the characteristic
International Nuclear Information System (INIS)
Shaikhislamov, I. F.; Prokopov, P. A.; Berezutsky, A. G.; Zakharov, Yu. P.; Posukh, V. G.; Khodachenko, M. L.; Lammer, H.; Kislyakova, K. G.; Fossati, L.; Johnstone, C. P.
2016-01-01
The interaction of escaping the upper atmosphere of a hydrogen-rich non-magnetized analog of HD 209458b with a stellar wind (SW) of its host G-type star at different orbital distances is simulated with a 2D axisymmetric multi-fluid hydrodynamic (HD) model. A realistic Sun-like spectrum of X-ray and ultraviolet radiation, which ionizes and heats the planetary atmosphere, together with hydrogen photochemistry, as well as stellar-planetary tidal interaction are taken into account to generate self-consistently an atmospheric HD outflow. Two different regimes of the planetary and SW interaction have been modeled. These are: (1) the “ captured by the star ” regime, when the tidal force and pressure gradient drive the planetary material beyond the Roche lobe toward the star, and (2) the “ blown by the wind ” regime, when sufficiently strong SW confines the escaping planetary atmosphere and channels it into the tail. The model simulates in detail the HD interaction between the planetary atoms, protons and the SW, as well as the production of energetic neutral atoms (ENAs) around the planet due to charge exchange between planetary atoms and stellar protons. The revealed location and shape of the ENA cloud, either as a paraboloid shell between the ionopause and bowshock (for the “ blown by the wind ” regime), or a turbulent layer at the contact boundary between the planetary stream and SW (for the “ captured by the star ” regime) are of importance for the interpretation of Ly α absorption features in exoplanetary transit spectra and characterization of the plasma environments.
Energy Technology Data Exchange (ETDEWEB)
Shaikhislamov, I. F.; Prokopov, P. A.; Berezutsky, A. G.; Zakharov, Yu. P.; Posukh, V. G. [Institute of Laser Physics SB RAS, Novosibirsk (Russian Federation); Khodachenko, M. L.; Lammer, H.; Kislyakova, K. G.; Fossati, L. [Space Research Institute, Austrian Acad. Sci., Graz (Austria); Johnstone, C. P., E-mail: maxim.khodachenko@oeaw.ac.at [Department of Astrophysics, University of Vienna, Vienna (Austria)
2016-12-01
The interaction of escaping the upper atmosphere of a hydrogen-rich non-magnetized analog of HD 209458b with a stellar wind (SW) of its host G-type star at different orbital distances is simulated with a 2D axisymmetric multi-fluid hydrodynamic (HD) model. A realistic Sun-like spectrum of X-ray and ultraviolet radiation, which ionizes and heats the planetary atmosphere, together with hydrogen photochemistry, as well as stellar-planetary tidal interaction are taken into account to generate self-consistently an atmospheric HD outflow. Two different regimes of the planetary and SW interaction have been modeled. These are: (1) the “ captured by the star ” regime, when the tidal force and pressure gradient drive the planetary material beyond the Roche lobe toward the star, and (2) the “ blown by the wind ” regime, when sufficiently strong SW confines the escaping planetary atmosphere and channels it into the tail. The model simulates in detail the HD interaction between the planetary atoms, protons and the SW, as well as the production of energetic neutral atoms (ENAs) around the planet due to charge exchange between planetary atoms and stellar protons. The revealed location and shape of the ENA cloud, either as a paraboloid shell between the ionopause and bowshock (for the “ blown by the wind ” regime), or a turbulent layer at the contact boundary between the planetary stream and SW (for the “ captured by the star ” regime) are of importance for the interpretation of Ly α absorption features in exoplanetary transit spectra and characterization of the plasma environments.
Testing strong interaction theories
International Nuclear Information System (INIS)
Ellis, J.
1979-01-01
The author discusses possible tests of the current theories of the strong interaction, in particular, quantum chromodynamics. High energy e + e - interactions should provide an excellent means of studying the strong force. (W.D.L.)
Liquefaction Mitigation Using Lateral Confinement Technique
Directory of Open Access Journals (Sweden)
W. R. Azzam
2012-01-01
Full Text Available The exploration of a series of shaking tests on circular model footing with and without cellular confinement constructed around the footing with variable depths and diameters under the effect of variable net bearing stress is studied. The effect of the confinement on the liquefaction time, final settlement, excess pore water pressure, and induced building acceleration were studied. The consequences showed that installing the cell with minimum diameter closer to footing and sufficient penetration depth significantly delayed the liquefaction time. It can be considered as an alternative technique to decrease both the lateral spreading and the final settlement below the foundation during the shaking. The results demonstrated that the cell reduced the excess pore water pressure within the confined zone and the pore water pressure migration outside the confined block where the liquefaction is induced. Moreover, the peak foundation acceleration of the confined footing soil system is reduced compared with the case of without cell confinement.
Quark confinement in a constituent quark model
International Nuclear Information System (INIS)
Langfeld, K.; Rho, M.
1995-01-01
On the level of an effective quark theory, we define confinement by the absence of quark anti-quark thresholds in correlation function. We then propose a confining Nambu-Jona-Lasinio-type model. The confinement is implemented in analogy to Anderson localization in condensed matter systems. We study the model's phase structure as well as its behavior under extreme conditions, i.e. high temperature and/or high density
Quark confinement in a constituent quark model
Energy Technology Data Exchange (ETDEWEB)
Langfeld, K.; Rho, M. [CEA Centre d`Etudes de Saclay, 91 - Gif-sur-Yvette (France). Service de Physique Theorique
1995-07-01
On the level of an effective quark theory, we define confinement by the absence of quark anti-quark thresholds in correlation function. We then propose a confining Nambu-Jona-Lasinio-type model. The confinement is implemented in analogy to Anderson localization in condensed matter systems. We study the model`s phase structure as well as its behavior under extreme conditions, i.e. high temperature and/or high density.
International Nuclear Information System (INIS)
Cui, S.T.; Cummings, P.T.; Cochran, H.D.
1999-01-01
We study the effect of wall endash fluid interactions on the state conditions and the effective properties of a model dodecane fluid confined between parallel solid walls. A significant increase in the effective density of the confined fluid is observed with increasing strength of the wall endash fluid interaction. The effect of the wall endash fluid interaction on the rotational relaxation and diffusional relaxation of the fluid is seen in the significant slowing down of the relaxation with increasing wall endash fluid interaction strength. The difference between the confined fluid and the three-dimensional bulk fluid is demonstrated by the strong anisotropy of the dynamical properties, the molecular rotation, and self-diffusion. The viscosity of the confined fluid shows a large difference between weak and strong wall endash fluid interactions, and a significant difference from bulk fluid at low shear rate. copyright 1999 American Institute of Physics
Confined subdiffusion in three dimensions
International Nuclear Information System (INIS)
Qin Shan-Lin; He Yong
2014-01-01
Three-dimensional (3D) Fick's diffusion equation and fractional diffusion equation are solved for different reflecting boundaries. We use the continuous time random walk model (CTRW) to investigate the time-averaged mean square displacement (MSD) of a 3D single particle trajectory. Theoretical results show that the ensemble average of the time-averaged MSD can be expressed analytically by a Mittag—Leffler function. Our new expression is in agreement with previous formulas in two limiting cases: <δ 2 -bar> ∼ Δ in short lag time and <δ 2 -bar> ∼ Δ 1-α in long lag time. We also simulate the experimental data of mRNA diffusion in living E. coli using a 3D CTRW model under confined and crowded conditions. The simulation results are well consistent with experimental results. The calculations of power spectral density (PSD) further indicate the subdiffsive behavior of an individual trajectory. (general)
Colour screening and quark confinement
International Nuclear Information System (INIS)
Mack, G.
1978-03-01
It is proposed that in Quantum Chromodynamics the colour charge of gluons and of anything with zero triality is screened by a dynamical Higgs mechanism with Higgs scalars made out of gluons. The center Z 3 of the gauge group SU(3) is left unbroken in this way, and single quarks, which have nonzero triality, cannot be screened. Long range forces between them persist therefore. Given that the Higgs mechanism produces a mass gap, the most favorable configuration of field lines between e.g. quark and antiquark will be in strings analogous to magnetic field lines in a superconductor. The strings confine the quarks. The screening mechanism, on the other hand, produces not only the mass gap (which leads to string formation) but is also responsible for saturation of forces, i.e. absence of bound states of six quarks etc. (orig.) [de
Multishell inertial confinement fusion target
International Nuclear Information System (INIS)
Holland, J.R.; Del Vecchio, R.M.
1984-01-01
A method of fabricating multishell fuel targets for inertial confinement fusion usage. Sacrificial hemispherical molds encapsulate a concentric fuel pellet which is positioned by fiber nets stretched tautly across each hemispherical mold section. The fiber ends of the net protrude outwardly beyond the mold surfaces. The joint between the sacrificial hemispheres is smoothed. A ceramic or glass cover is then deposited about the finished mold surfaces to produce an inner spherical surface having continuously smooth surface configuration. The sacrificial mold is removed by gaseous reaction accomplished through the porous ceramic cover prior to enclosing of the outer sphere by addition of an outer coating. The multishell target comprises the inner fuel pellet concentrically arranged within a surrounding coated cover or shell by fiber nets imbedded within the cover material
Confined subdiffusion in three dimensions
Qin, Shan-Lin; He, Yong
2014-11-01
Three-dimensional (3D) Fick's diffusion equation and fractional diffusion equation are solved for different reflecting boundaries. We use the continuous time random walk model (CTRW) to investigate the time-averaged mean square displacement (MSD) of a 3D single particle trajectory. Theoretical results show that the ensemble average of the time-averaged MSD can be expressed analytically by a Mittag—Leffler function. Our new expression is in agreement with previous formulas in two limiting cases: in short lag time and in long lag time. We also simulate the experimental data of mRNA diffusion in living E. coli using a 3D CTRW model under confined and crowded conditions. The simulation results are well consistent with experimental results. The calculations of power spectral density (PSD) further indicate the subdiffsive behavior of an individual trajectory.
Endogenous Monetary Policy Regime Change
Troy Davig; Eric M. Leeper
2006-01-01
This paper makes changes in monetary policy rules (or regimes) endogenous. Changes are triggered when certain endogenous variables cross specified thresholds. Rational expectations equilibria are examined in three models of threshold switching to illustrate that (i) expectations formation effects generated by the possibility of regime change can be quantitatively important; (ii) symmetric shocks can have asymmetric effects; (iii) endogenous switching is a natural way to formally model preempt...
Effects of confinement in meso-porous silica and carbon nano-structures
International Nuclear Information System (INIS)
Leon, V.
2006-07-01
Physico-chemical properties of materials can be strongly modified by confinement because of the quantum effects that appear at such small length scales and also because of the effects of the confinement itself. The aim of this thesis is to show that both the nature of the confining material and the size of the pores and cavities have a strong impact on the confined material. We first show the effect of the pore size of the host meso-porous silica on the temperature of the solid-solid phase transition of silver selenide, a semiconducting material with enhanced magnetoresistive properties under non-stoichiometric conditions. Narrowing the pores from 20 nm to 2 nm raises the phase transition temperature from 139 C to 146 C. This result can be explained by considering the interaction between the confining and confined materials as a driving force. The effects of confinement are also studied in the case of hydrogen and deuterium inside cavities of organized carbon nano-structures. The effects that appear in the adsorption/desorption cycles are much stronger with carbon nano-horns as the host material than with C60 pea-pods and single-walled carbon nano-tubes. (author)
2XIIB plasma confinement experiments
International Nuclear Information System (INIS)
Coensgen, F.H.; Clauser, J.F.; Correll, D.L.
1976-01-01
This paper reports results of 2XIIB neutral-beam injection experiments with plasma-stream stabilization. The plasma stream is provided either by a pulsed plasma generator located on the field lines outside the plasma region or by ionization of neutral gas introduced at the mirror throat. In the latter case, the gas is ionized by the normal particle flux through the magnetic mirror. A method of plasma startup and sustenance in a steady-state magnetic field is reported in which the plasma stream from the pulsed plasma generator serves as the initial target for the neutral beams. After an energetic plasma of sufficient density is established, the plasma generator stream is replaced by the gas-fed stream. Lifetimes of the stabilized plasma increase with plasma temperature in agreement with the plasma stabilization of the drift-cyclotron loss-cone mode. The following plasma parameters are attained using the pulsed plasma generator for stabilization: n approximately 5 x 10 13 cm -3 , anti W/sub i/ approximately 13 keV, T/sub e/ = 140 eV, and ntau/sub p/ approximately 7 x 10 10 cm -3 .s. With the gas feed, the mean deuterium ion energy is 9 keV and the peak density n approximately 10 14 cm -3 . In the latter case, the energy confinement parameter reaches ntau/sub E/ = 7 x 10 10 cm -3 .s, and the particle confinement parameter reaches ntau/sub p/ = 1 x 10 11 cm -3 .s
Dynamics and reactivity of confined water
International Nuclear Information System (INIS)
Musat, R.
2008-01-01
In the context of new sustainable energy sources quest, the nuclear energy remains a key solution. However, with the development of nuclear technology, problems relating to nuclear waste disposal arise; thus, the radiolysis of water in confined media is extremely important with respect to matters related to long time storage of nuclear waste. Studies in model porous media would allow the projection of a confined water radiolysis simulator. A first step in this direction was made by studying the radiolysis of water confined in Vycor and CPG glasses; this study continues the trend set and investigates the effects of confinement in metal materials upon the water radiolysis allowing the understanding of metal - water radiation induced corrosion. A further/complete understanding of the radiolytic process under confinement requires knowledge of the effect of confinement upon the dynamics of confined molecules and on the evolution of the species produced upon ionizing radiation. In this respect, we have used the OH vibrator as a probe of the hydrogen bond network properties and thus investigated the dynamics of confined water using IR time resolved spectroscopy. The evolution of the hydrated electron under confinement was studied on a nano and picosecond time scale using UV pump - visible probe technique and single shot spectroscopy. (author) [fr
Cayao, Jorge; Prada, Elsa; San-Jose, Pablo; Aguado, Ramón
2015-01-01
We study normal transport and the subgap spectrum of superconductor-normal-superconductor (SNS) junctions made of semiconducting nanowires with strong Rashba spin-orbit coupling. We focus, in particular, on the role of confinement effects in long ballistic junctions. In the normal regime, scattering at the two contacts gives rise to two distinct features in conductance: Fabry-Perot resonances and Fano dips. The latter arise in the presence of a strong Zeeman field B that removes a spin sector in the leads (helical leads), but not in the central region. Conversely, a helical central region between nonhelical leads exhibits helical gaps of half-quantum conductance, with superimposed helical Fabry-Perot oscillations. These normal features translate into distinct subgap states when the leads become superconducting. In particular, Fabry-Perot resonances within the helical gap become parity-protected zero-energy states (parity crossings), well below the critical field Bc at which the superconducting leads become topological. As a function of Zeeman field or Fermi energy, these zero modes oscillate around zero energy, forming characteristic loops, which evolve continuously into Majorana bound states as B exceeds Bc. The relation with the physics of parity crossings of Yu-Shiba-Rusinov bound states is discussed.
Cayao, Jorge; Prada, Elsa; San-Jose, Pablo; Aguado, Ramón
2015-03-01
We study normal transport and the sub-gap spectrum of superconductor-normal-superconductor (SNS) junctions made of semiconducting nanowires with strong Rashba spin-orbit coupling. We focus, in particular, on the role of confinement effects in long ballistic junctions. In the normal regime, scattering at the two contacts gives rise to two distinct features in conductance, Fabry-Perot resonances and Fano dips. The latter arise in the presence of a strong Zeeman field B that removes a spin sector in the leads (helical leads), but not in the central region. Conversely, a helical central region between non-helical leads exhibits helical gaps of half-quantum conductance, with superimposed helical Fabry-Perot oscillations. These normal features translate into distinct subgap states when the leads become superconducting. In particular, Fabry-Perot resonances within the helical gap become parity-protected zero-energy states (parity crossings, related to Yu-Shiba-Rusinov bound states), well below the critical field Bc at which the superconducting leads become topological. As a function of Zeeman field or Fermi energy, these zero-modes oscillate around zero energy, forming characteristic loops, which evolve continuously into Majorana bound states as B exceeds Bc.
Enhanced confinement with plasma biasing in the MST reversed field pinch
International Nuclear Information System (INIS)
Craig, D.; Almagri, A.F.; Anderson, J.K.
1997-06-01
We report an increase in particle confinement with plasma biasing in a reversed field pinch. Miniature plasma sources are used as electrodes to negatively bias the plasma at the edge (r/a ∼ 0.9). Particle content increases and H α radiation decreases upon application of bias and global particle confinement roughly doubles as a result. Measurements of plasma potential, impurity flow, and floating potential fluctuations indicate that strong flows are produced and that electrostatic fluctuations are reduced
Transition from weak wave turbulence regime to solitonic regime
Hassani, Roumaissa; Mordant, Nicolas
2017-11-01
The Weak Turbulence Theory (WTT) is a statistical theory describing the interaction of a large ensemble of random waves characterized by very different length scales. For both weak non-linearity and weak dispersion a different regime is predicted where solitons propagate while keeping their shape unchanged. The question under investigation here is which regime between weak turbulence or soliton gas does the system choose ? We report an experimental investigation of wave turbulence at the surface of finite depth water in the gravity-capillary range. We tune the wave dispersion and the level of nonlinearity by modifying the depth of water and the forcing respectively. We use space-time resolved profilometry to reconstruct the deformed surface of water. When decreasing the water depth, we observe a drastic transition between weak turbulence at the weakest forcing and a solitonic regime at stronger forcing. We characterize the transition between both states by studying their Fourier Spectra. We also study the efficiency of energy transfer in the weak turbulence regime. We report a loss of efficiency of angular transfer as the dispersion of the wave is reduced until the system bifurcates into the solitonic regime. This project has recieved funding from the European Research Council (ERC, Grant Agreement No. 647018-WATU).
Energy dissipation in non-isothermal molecular dynamics simulations of confined liquids under shear.
Berro, Hassan; Fillot, Nicolas; Vergne, Philippe; Tokumasu, Takashi; Ohara, Taku; Kikugawa, Gota
2011-10-07
Energy is commonly dissipated in molecular dynamics simulations by using a thermostat. In non-isothermal shear simulations of confined liquids, the choice of the thermostat is very delicate. We show in this paper that under certain conditions, the use of classical thermostats can lead to an erroneous description of the dynamics in the confined system. This occurs when a critical shear rate is surpassed as the thermo-viscous effects become prominent. In this high-shear-high-dissipation regime, advanced dissipation methods including a novel one are introduced and compared. The MD results show that the physical modeling of both the accommodation of the surface temperature to liquid heating and the heat conduction through the confining solids is essential. The novel method offers several advantages on existing ones including computational efficiency and easiness of application for complex systems. © 2011 American Institute of Physics
Inertial Confinement Fusion R and D and Nuclear Proliferation
International Nuclear Information System (INIS)
Goldston, Robert J.
2011-01-01
In a few months, or a few years, the National Ignition Facility (NIF) at the Lawrence Livermore National Laboratory may achieve fusion gain using 192 powerful lasers to generate x-rays that will compress and heat a small target containing isotopes of hydrogen. This event would mark a major milestone after decades of research on inertial confinement fusion (ICF). It might also mark the beginning of an accelerated global effort to harness fusion energy based on this science and technology. Unlike magnetic confinement fusion (ITER, 2011), in which hot fusion fuel is confined continuously by strong magnetic fields, inertial confinement fusion involves repetitive fusion explosions, taking advantage of some aspects of the science learned from the design and testing of hydrogen bombs. The NIF was built primarily because of the information it would provide on weapons physics, helping the United States to steward its stockpile of nuclear weapons without further underground testing. The U.S. National Academies' National Research Council is now hosting a study to assess the prospects for energy from inertial confinement fusion. While this study has a classified sub-panel on target physics, it has not been charged with examining the potential nuclear proliferation risks associated with ICF R and D. We argue here that this question urgently requires direct and transparent examination, so that means to mitigate risks can be assessed, and the potential residual risks can be balanced against the potential benefits, now being assessed by the NRC. This concern is not new (Holdren, 1978), but its urgency is now higher than ever before.
Overview of JT-60U results toward high integrated performance in reactor-relevant regime
International Nuclear Information System (INIS)
Fujita, T.
2003-01-01
Recent JT-60U results toward high integrated performance are reported with emphasis on the projection to the reactor-relevant regime. N-NB and EC power increased up to 6.2 MW and 3 MW, respectively. A high β p H-mode plasma with full non-inductive current drive has been obtained at 1.8 MA and the fusion triple product reached 3.1x10 20 m -3 keVs. High beta with β N =2.7 was maintained for 7.4 s. NTM suppression with EC was accomplished using a real-time feedback control system and improvement in β N was obtained. A stable existence of current hole was observed. High DT-equivalent fusion gain of 0.8 was maintained for 0.55 s in a plasma with a current hole. The current profile control in high bootstrap current reversed shear plasmas was demonstrated using N-NB and LH. A new operation scenario has been established in which a plasma with high bootstrap current fraction and ITBs is produced without the use of OH coil. ECCD study was undertaken in a reactor-relevant high T e regime. A new type of AE mode has been proposed and found to explain the observed frequency chirp quite well. High confinement reversed shear plasmas with T e >T i were obtained. Ar exhaust with EC heating was obtained in a high β p mode plasma. Impurity accumulation related to strong ITBs in a reversed shear plasma and degradation of ITB by ECH in a weak positive shear plasma have been found. Dedicated measurement of ELM dynamics and SOL plasma flow advanced the physics understanding. N-NB heating in an Ar-seed plasma extended the density region to 95% of Greenwald density with HH y2 =0.9. The enhancement of pedestal pressure was obtained with an increase of β p in a high triangularity configuration. (author)
Preheating ablation effects on the Rayleigh-Taylor instability in the weakly nonlinear regime
International Nuclear Information System (INIS)
Wang, L. F.; Ye, W. H.; He, X. T.; Sheng, Z. M.; Don, Wai-Sun; Li, Y. J.
2010-01-01
The two-dimensional Rayleigh-Taylor instability (RTI) with and without thermal conduction is investigated by numerical simulation in the weakly nonlinear regime. A preheat model κ(T)=κ SH [1+f(T)] is introduced for the thermal conduction [W. H. Ye, W. Y. Zhang, and X. T. He, Phys. Rev. E 65, 057401 (2002)], where κ SH is the Spitzer-Haerm electron thermal conductivity coefficient and f(T) models the preheating tongue effect in the cold plasma ahead of the ablation front. The preheating ablation effects on the RTI are studied by comparing the RTI with and without thermal conduction with identical density profile relevant to inertial confinement fusion experiments. It is found that the ablation effects strongly influence the mode coupling process, especially with short perturbation wavelength. Overall, the ablation effects stabilize the RTI. First, the linear growth rate is reduced, especially for short perturbation wavelengths and a cutoff wavelength is observed in simulations. Second, the second harmonic generation is reduced for short perturbation wavelengths. Third, the third-order negative feedback to the fundamental mode is strengthened, which plays a stabilization role. Finally, on the contrary, the ablation effects increase the generation of the third harmonic when the perturbation wavelengths are long. Our simulation results indicate that, in the weakly nonlinear regime, the ablation effects are weakened as the perturbation wavelength is increased. Numerical results obtained are in general agreement with the recent weakly nonlinear theories as proposed in [J. Sanz, J. Ramirez, R. Ramis et al., Phys. Rev. Lett. 89, 195002 (2002); J. Garnier, P.-A. Raviart, C. Cherfils-Clerouin et al., Phys. Rev. Lett. 90, 185003 (2003)].
A theory of the strong interactions
International Nuclear Information System (INIS)
Gross, D.J.
1979-01-01
The most promising candidate for a fundamental microscopic theory of the strong interactions is a gauge theory of colored quarks-Quantum Chromodynamics (QCD). There are many excellent reasons for believing in this theory. It embodies the broken symmetries, SU(3) and chiral SU(3)xSU(3), of the strong interactions and reflects the success of (albeit crude) quark models in explaining the spectrum of the observed hadrons. The hidden quantum number of color, necessary to account for the quantum numbers of the low lying hadrons, plays a fundamental role in this theory as the SU(3) color gauge vector 'gluons' are the mediators of the strong interactions. The absence of physical quark states can be 'explained' by the hypothesis of color confinement i.e. that hadrons are permanently bound in color singlet bound states. Finally this theory is unique in being asymptotically free, thus accounting for the almost free field theory behvior of quarks observed at short distances. (Auth.)
Generating equilateral random polygons in confinement III
International Nuclear Information System (INIS)
Diao, Y; Ernst, C; Montemayor, A; Ziegler, U
2012-01-01
In this paper we continue our earlier studies (Diao et al 2011 J. Phys. A: Math. Theor. 44 405202, Diao et al J. Phys. A: Math. Theor. 45 275203) on the generation methods of random equilateral polygons confined in a sphere. The first half of this paper is concerned with the generation of confined equilateral random walks. We show that if the selection of a vertex is uniform subject to the position of its previous vertex and the confining condition, then the distributions of the vertices are not uniform, although there exists a distribution such that if the initial vertex is selected following this distribution, then all vertices of the random walk follow this same distribution. Thus in order to generate a confined equilateral random walk, the selection of a vertex cannot be uniform subject to the position of its previous vertex and the confining condition. We provide a simple algorithm capable of generating confined equilateral random walks whose vertex distribution is almost uniform in the confinement sphere. In the second half of this paper we show that any process generating confined equilateral random walks can be turned into a process generating confined equilateral random polygons with the property that the vertex distribution of the polygons approaches the vertex distribution of the walks as the polygons get longer and longer. In our earlier studies, the starting point of the confined polygon is fixed at the center of the sphere. The new approach here allows us to move the starting point of the confined polygon off the center of the sphere. (paper)
Thermonuclear plasma physic: inertial confinement fusion
International Nuclear Information System (INIS)
Bayer, Ch.; Juraszek, D.
2001-01-01
Inertial Confinement Fusion (ICF) is an approach to thermonuclear fusion in which the fuel contained in a spherical capsule is strongly compressed and heated to achieve ignition and burn. The released thermonuclear energy can be much higher than the driver energy, making energetic applications attractive. Many complex physical phenomena are involved by the compression process, but it is possible to use simple analytical models to analyze the main critical points. We first determine the conditions to obtain fuel ignition. High thermonuclear gains are achieved if only a small fraction of the fuel called hot spot is used to trigger burn in the main fuel compressed on a low isentrope. A simple hot spot model will be described. The high pressure needed to drive the capsule compression are obtained by the ablation process. A simple Rocket model describe the main features of the implosion phase. Several parameters have to be controlled during the compression: irradiation symmetry, hydrodynamical stability and when the driver is a laser, the problems arising from interaction of the EM wave with the plasma. Two different schemes are examined: Indirect Drive which uses X-ray generated in a cavity to drive the implosion and the Fast Ignitor concept using a ultra intense laser beam to create the hot spot. At the end we present the Laser Megajoule (LMJ) project. LMJ is scaled to a thermonuclear gain of the order of ten. (authors)
Proton radiography for inertial confinement fusion
Energy Technology Data Exchange (ETDEWEB)
Volpe, L.; Batani, D. [University of Milano-Bicocca (Italy); Baton, S.; Perez, F.; Koenig, M. [LULI Ecole Polytechnique-CNRS-UPMC, Palaiseau Cedex (France); Nicolai, Ph.; Vauzour, B.; Santos, J. J. [CELIA, University de Bordeaux (France)
2011-11-15
Generation of high-intensity and well collimated multi-energetic proton beams from laser-matter interaction extend the possibility for using protons as a diagnostic to image imploding targets in inertial confinement fusion experiments in the framework of the experimental road map of the Hiper project (the European High Power laser Energy Research facility Project). Due to the very large mass densities reached during implosion processes, protons traveling through the target undergo a very large number of collisions which deviate the protons from their original trajectories reducing the proton radiography resolution below our expectations. Here we present a simple analytical model to study the performance of proton radiography as a function of the main experimental parameters, such as the proton beam energies and targets areal density. This approach leads to define two different criteria for proton radiography resolution (called the 'strong' and the 'weak' conditions) describing different experimental conditions. Finally, numerical simulations using both hydrodynamic and Monte Carlo codes are presented to validate the analytical predictions.
Fuzzy Dark Matter from Infrared Confining Dynamics
Davoudiasl, Hooman; Murphy, Christopher W.
2017-04-01
A very light boson of mass O (10-22) eV may potentially be a viable dark matter (DM) candidate, which can avoid phenomenological problems associated with cold DM. Such "fuzzy DM (FDM)" may naturally be an axion with a decay constant fa˜1 016- 1 018 GeV and a mass ma˜μ2/fa with μ ˜1 02 eV . Here, we propose a concrete model, where μ arises as a dynamical scale from infrared confining dynamics, analogous to QCD. Our model is an alternative to the usual approach of generating μ through string theoretic instanton effects. We outline the features of this scenario that result from various cosmological constraints. We find that those constraints are suggestive of a period of mild of inflation, perhaps from a strong first order phase transition, that reheats the standard model (SM) sector only. A typical prediction of our scenario, broadly speaking, is a larger effective number of neutrinos compared to the SM value Neff≈3 , as inferred from precision measurements of the cosmic microwave background. Some of the new degrees of freedom may be identified as "sterile neutrinos," which may be required to explain certain neutrino oscillation anomalies. Hence, aspects of our scenario could be testable in terrestrial experiments, which is a novelty of our FDM model.
Characteristics of global strong earthquakes and their implications ...
Indian Academy of Sciences (India)
11
the Global/Harvard centroid moment tensor (CMT) catalogue, the characteristics of global strong earthquakes and the. 18 present-day stress pattern were analyzed based on these data. The majority of global strong earthquakes are located around. 19 plate boundaries, shallow-focus, and thrust faulting (TF) regime.
Kinetic transport in a magnetically confined and flux-constrained fusion plasma
International Nuclear Information System (INIS)
Darmet, G.
2007-11-01
This work deals with the kinetic transport in a fusion plasma magnetically confined and flux-constrained. The author proposes a new interpretation of the dynamics of zonal flows. The model that has been studied is a gyrokinetic model reduced to the transport of trapped ions. The inter-change stability that is generated allows the study of the kinetic transport of trapped ions. This model has a threshold instability and can be simulated over a few tens confining time for either thermal bath constraint or flux constraint. For thermal baths constraint, the simulation shows a metastable state where zonal flows are prevailing while turbulence is non-existent. In the case of a flux-constraint, zonal flows appear and relax by exchanging energy with system's kinetic energy and turbulence energy. The competition between zonal flows and turbulence can be then simulated by a predator-prey model. 2 regimes can be featured out: an improved confining regime where zonal flows dominate transport and a turbulent regime where zonal flows and turbulent transport are of the same magnitude order. We show that flux as well as the Reynolds tensor play an important role in the dynamics of the zonal flows and that the gyrokinetic description is relevant for all plasma regions. (A.C.)
Confinement enhances dispersion in nanoparticle-polymer blend films.
Chandran, Sivasurender; Begam, Nafisa; Padmanabhan, Venkat; Basu, J K
2014-05-08
Polymer nanocomposites constitute an important class of materials whose properties depend on the state of dispersion of the nanoparticles in the polymer matrix. Here we report the first observations of confinement-induced enhancement of dispersion in nanoparticle-polymer blend films. Systematic variation in the dispersion of nanoparticles with confinement for various compositions and matrix polymer chain dimensions has been observed. For fixed composition, strong reduction in glass transition temperature, Tg, is observed with decreasing blend-film thickness. The enhanced dispersion occurs without altering the polymer-particle interactions and seems to be driven by enhanced matrix-chain orientation propensity and a tendency to minimize the density gradients within the matrix. This implies the existence of two different mechanisms in polymer nanocomposites, which determines their state of dispersion and glass transition.
Enhancing the hydrophobic effect in confined water nanodrops.
Rao, Palla Venkata Gopala; Gandhi, K S; Ayappa, K G
2007-12-18
The distribution of hydrophobic solutes, such as methane, enclosed in a nanosized water droplet contained in a reverse micelle of diameter 2.82 nm is investigated using Monte Carlo simulations. The effect of the hydrophobic solute's atomic diameter on the solute-solute potential of mean force is also studied. The study reveals that confinement has a strong influence on the solute's tendency to associate. The potential of mean force exhibits only a single minimum, indicating that the contact pair is the only stable configuration between solutes. The solvent-separated pair that is universally observed for small solutes in bulk water is conspicuously absent. This enhanced hydrophobic effect is attributed to the lack of sufficient water to completely hydrate and stabilize the solvent-separated configurations. The study is expected to be important in understanding the role of hydrophobic forces during protein folding and nucleation under confinement.
Experimental studies of stable confined electron clouds using Gabor lenses
Meusel, O.; Glaeser, B.; Schulte, K.
2013-04-22
Based on the idea of D. Gabor [1] space charge lenses are under investigation to be a powerful focussing device for intense ion beams. A stable confined electron column is used to provide strong radially symmetric electrostatic focussing, e.g. for positively charged ion beams. The advantages of Gabor lenses are a mass independent focussing strength, space charge compensation of the ion beam and reduced magnetic or electric fields compared to conventional focussing devices. Collective phenomena of the electron cloud result in aberrations and emittance growth of the ion beam. The knowledge of the behaviour of the electron cloud prevents a decrease of the beam brilliance. Numerical models developed to describe the electron confinement and dynamics within a Gabor lens help to understand the interaction of the ion beam with the electron column and show the causes of non-neutral plasma instabilities. The diagnosis of the electron cloud properties helps to evaluate the numerical models and to investigate the influen...
Domain wall network as QCD vacuum: confinement, chiral symmetry, hadronization
Directory of Open Access Journals (Sweden)
Nedelko Sergei N.
2017-01-01
Full Text Available An approach to QCD vacuum as a medium describable in terms of statistical ensemble of almost everywhere homogeneous Abelian (anti-self-dual gluon fields is reviewed. These fields play the role of the confining medium for color charged fields as well as underline the mechanism of realization of chiral SUL(Nf × SUR(Nf and UA(1 symmetries. Hadronization formalism based on this ensemble leads to manifestly defined quantum effective meson action. Strong, electromagnetic and weak interactions of mesons are represented in the action in terms of nonlocal n-point interaction vertices given by the quark-gluon loops averaged over the background ensemble. Systematic results for the mass spectrum and decay constants of radially excited light, heavy-light mesons and heavy quarkonia are presented. Relationship of this approach to the results of functional renormalization group and Dyson-Schwinger equations, and the picture of harmonic confinement is briefly outlined.
Confined States and Tunnelling in Gated Graphene Nanoribbons
Guilleminot, E.,; Meza-Montes, L.
Graphene Quantum Dots (GQDs) are promising candidates for the development of quantum information processors. We propose a scheme to determine electronic states of GQDs as defined by voltage gates applied to armchair graphene nanoribbons. Using transfer matrix method based on the set of solutions proposed by Burkard et al ., we study confined states of double wells and the transmission of electrons through double barrier systems. Comparison with previous results for systems on the graphene sheet shows good agreement. Confined states of a double well turn out to be very sensitive to deformation of the potential profile, showing strong localization of the electron for asymmetric systems, which also depends on the considered state. Spikes of high transmission appeared for periodic values of the incident angle of the electron travelling through a double barrier and disappear as the systems approaches to a single barrier as one barrier vanishes. We remark effects not shown in usual semiconductor heterostructures. Partially supported by VIEP-BUAP, Mexico,.
International Nuclear Information System (INIS)
Chandran, Benjamin D. G.
2000-01-01
Theoretical studies of magnetohydrodynamic (MHD) turbulence and observations of solar wind fluctuations suggest that MHD turbulence in the interstellar medium is anisotropic at small scales, with smooth variations along the background magnetic field and sharp variations perpendicular to the background field. Turbulence with this anisotropy is inefficient at scattering cosmic rays, and thus the scattering rate ν may be smaller than has been traditionally assumed in diffusion models of Galactic cosmic-ray propagation, at least for cosmic-ray energies E above 1011-1012 eV at which self-confinement is not possible. In this paper, it is shown that Galactic cosmic rays can be effectively confined through magnetic reflection by molecular clouds, even when turbulent scattering is weak. Elmegreen's quasi-fractal model of molecular-cloud structure is used to argue that a typical magnetic field line passes through a molecular cloud complex once every ∼300 pc. Once inside the complex, the field line will in most cases be focused into one or more dense clumps in which the magnetic field can be much stronger than the average field in the intercloud medium (ICM). Cosmic rays following field lines into cloud complexes are most often magnetically reflected back into the ICM, since strong-field regions act as magnetic mirrors. For a broad range of cosmic-ray energies, a cosmic ray initially following some particular field line separates from that field line sufficiently slowly that the cosmic ray can be trapped between neighboring cloud complexes for long periods of time. The suppression of cosmic-ray diffusion due to magnetic trapping is calculated in this paper with the use of phenomenological arguments, asymptotic analysis, and Monte Carlo particle simulations. Formulas for the coefficient of diffusion perpendicular to the Galactic disk are derived for several different parameter regimes within the E-ν plane. In one of these parameter regimes in which scattering is weak, it
Turbulent regimes in the tokamak scrape-off layer
International Nuclear Information System (INIS)
Mosetto, A.
2014-01-01
The tokamak scrape-off layer (SOL) is the plasma region characterized by open field lines that start and end on the vessel walls. The plasma dynamics in the SOL plays a crucial role in determining the overall performance of a tokamak, since it controls the plasma-wall interactions, being responsible of exhausting the tokamak power, it regulates the overall plasma confinement, and it governs the plasma refueling and the removal of fusion ashes. Scrape-off layer physics is intrinsically non-linear and characterized by phenomena that occur on a wide range of spatio-temporal scales. Free energy sources drive a number of unstable modes that develop into turbulence and lead to transport of particles and heat across the magnetic field lines. Depending on the driving instability, different SOL turbulent regimes can be identified. As the SOL turbulent regimes determine the plasma confinement properties and the SOL width (and, consequently, the power flux on the vessel wall, for example), it is of crucial importance to understand which turbulent regimes are active in the SOL, under which conditions they develop, and which are the main properties of the associated turbulent transport. In the present thesis we define the SOL turbulent regimes, and we provide a framework to identify them, given the operational SOL parameters. Our study is based on the drift-reduced Braginskii equations and it is focused on a limited tokamak SOL configuration. We first describe the main SOL linear instabilities, such as the inertial and resistive branches of the drift waves, the resistive, inertial and ideal branches of the ballooning modes, and the ion temperature gradient mode. Then, we find the SOL turbulent regimes depending on the instability driving turbulent transport, assuming that turbulence saturates when the radial gradient associated to the pressure fluctuations is comparable to the equilibrium one. Our methodology for the turbulent regime identification is supported by the analysis
Characterization of local turbulence in magnetic confinement devices
International Nuclear Information System (INIS)
Rajkovic, Milan; Skoric, Milos; Solna, Knut; Antar, Ghassan
2007-07-01
A multifractal analysis based on evaluation and interpretation of Large Deviation spectra is applied to plasma edge turbulence data from different devices (MAST and Tore Supra). It is demonstrated that in spite of some universal features there are unique characteristics for each device as well as for different confinement regimes. In the second part of the exposition the issue of estimating the variable power law behavior of spectral densities is addressed. The analysis of this issue is performed using fractional Brownian motion (fBm) as the underlying stochastic model whose parameters are estimated locally in time by wavelet scale spectra. In such a manner information about the inertial range as well as variability of the fBm parameters is obtained giving more information important for understanding edge turbulence and intermittency. (author)
Anomalous diffusion and diffusion anomaly in confined Janus dumbbells.
B Krott, Leandro; Gavazzoni, Cristina; Bordin, José Rafael
2016-12-28
Self-assembly and dynamical properties of Janus nanoparticles have been studied by molecular dynamic simulations. The nanoparticles are modeled as dimers and they are confined between two flat parallel plates to simulate a thin film. One monomer from the dumbbells interacts by a standard Lennard-Jones potential and the other by a two-length scales shoulder potential, typically used for anomalous fluids. Here, we study the effects of removing the Brownian effects, typical from colloidal systems immersed in aqueous solution, and consider a molecular system, without the drag force and the random collisions from the Brownian motion. Self-assembly and diffusion anomaly are preserved in relation to the Brownian system. Additionally, a superdiffusive regime associated to a collective reorientation in a highly structured phase is observed. Diffusion anomaly and anomalous diffusion are explained in the two length scale framework.
Anomalous diffusion and diffusion anomaly in confined Janus dumbbells
Krott, Leandro B.; Gavazzoni, Cristina; Bordin, José Rafael
2016-12-01
Self-assembly and dynamical properties of Janus nanoparticles have been studied by molecular dynamic simulations. The nanoparticles are modeled as dimers and they are confined between two flat parallel plates to simulate a thin film. One monomer from the dumbbells interacts by a standard Lennard-Jones potential and the other by a two-length scales shoulder potential, typically used for anomalous fluids. Here, we study the effects of removing the Brownian effects, typical from colloidal systems immersed in aqueous solution, and consider a molecular system, without the drag force and the random collisions from the Brownian motion. Self-assembly and diffusion anomaly are preserved in relation to the Brownian system. Additionally, a superdiffusive regime associated to a collective reorientation in a highly structured phase is observed. Diffusion anomaly and anomalous diffusion are explained in the two length scale framework.
Room temperature strong light-matter coupling in 3D THz meta-atoms (Conference Presentation)
Paulillo, Bruno; Manceau, Jean-Michel; Li, Lianhe; Linfield, Edmund; Colombelli, Raffaele
2016-04-01
) within our recently developed 3D meta-atoms. A GaAs/AlGaAs parabolic quantum well is used as semiconductor active core to observe the strong coupling regime up to room temperature, as the structure ensures by design a sufficiently large useful electron population irrespective of temperature. In contrast with the previous metamaterial paradigm, the electrical dipoles responsible for the light-matter excitation are now exactly confined in the capacitive region of each meta-atom. Remarkably, we will show that we can modulate the light-matter interaction solely via the external inductor/antenna element while keeping the interaction volume (i.e. the capacitor size) unvaried. Perspectives about the exploitation of this metamaterial peculiar features (reconfigurability, dynamic tuning, …) for polaritonic devices will be discussed.
Assessment of the LiWall plasma regime for DD fusion
Zakharov, Leonid E.; Azizov, Englen A.; Sheffield, John
2007-11-01
The lithium plasma facing components pump out the plasma particles and eliminate the cold particles, which enter it in the conventional wall situation. Together with core plasma fueling by neutral beam injection this provides flat plasma temperature, eliminates the turbulence associated with the temperature gradient, and leads to the best possible confinement regime. The Reference Transport Model (RTM), which assumes all transport coefficients equal to the ion thermo-conductivity χi=χe=D=neoi can describe the LiWall confinement quantitatively. Implementation of the LiWall regime would make the path to the DT fusion straightforward. It is only the inability of the current fusion program to move beyond the outdated concept, which prevents the progress in DT fusion with the LiWall regime. In this regime, at a given beta, the confinement τET^3/2 is very favorable for DD fusion as well. The question, studied here using the RTM, is if it is possible to maintain the plasma in the hot-ion mode by NBI, while expelling the fusion products and keeping the radiation from electrons limited. Realization of DD fusion could be of great interest because of its independence from tritium fuel and possible use for transmutation of radioactive waste.
PREFACE: Strongly correlated electron systems Strongly correlated electron systems
Saxena, Siddharth S.; Littlewood, P. B.
2012-07-01
make use of 'small' electrons packed to the highest possible density. These are by definition 'strongly correlated'. For example: good photovoltaics must be efficient optical absorbers, which means that photons will generate tightly bound electron-hole pairs (excitons) that must then be ionised at a heterointerface and transported to contacts; efficient solid state refrigeration depends on substantial entropy changes in a unit cell, with large local electrical or magnetic moments; efficient lighting is in a real sense the inverse of photovoltaics; the limit of an efficient battery is a supercapacitor employing mixed valent ions; fuel cells and solar to fuel conversion require us to understand electrochemistry on the scale of a single atom; and we already know that the only prospect for effective high temperature superconductivity involves strongly correlated materials. Even novel IT technologies are now seen to have value not just for novel function but also for efficiency. While strongly correlated electron systems continue to excite researchers and the public alike due to the fundamental science issues involved, it seems increasingly likely that support for the science will be leveraged by its impact on energy and sustainability. Strongly correlated electron systems contents Strongly correlated electron systemsSiddharth S Saxena and P B Littlewood Magnetism, f-electron localization and superconductivity in 122-type heavy-fermion metalsF Steglich, J Arndt, O Stockert, S Friedemann, M Brando, C Klingner, C Krellner, C Geibel, S Wirth, S Kirchner and Q Si High energy pseudogap and its evolution with doping in Fe-based superconductors as revealed by optical spectroscopyN L Wang, W Z Hu, Z G Chen, R H Yuan, G Li, G F Chen and T Xiang Structural investigations on YbRh2Si2: from the atomic to the macroscopic length scaleS Wirth, S Ernst, R Cardoso-Gil, H Borrmann, S Seiro, C Krellner, C Geibel, S Kirchner, U Burkhardt, Y Grin and F Steglich Confinement of chiral magnetic
Wind regimes and their relation to synoptic variables using self-organizing maps
Berkovic, Sigalit
2018-01-01
This study exemplifies the ability of the self-organizing maps (SOM) method to directly define well known wind regimes over Israel during the entire year, except summer period, at 12:00 UTC. This procedure may be applied at other hours and is highly relevant to future automatic climatological analysis and applications. The investigation is performed by analysing surface wind measurements from 53 Israel Meteorological Service stations. The relation between the synoptic variables and the wind regimes is revealed from the averages of ECMWF ERA-INTERIM reanalysis variables for each SOM wind regime. The inspection of wind regimes and their average geopotential anomalies has shown that wind regimes relate to the gradient of the pressure anomalies, rather than to the specific isobars pattern. Two main wind regimes - strong western and the strong eastern or northern - are well known over this region. The frequencies of the regimes according to seasons is verified. Strong eastern regimes are dominant during winter, while strong western regimes are frequent in all seasons.
QCD confinement and the meson spectrum
González, P; Valcarce, A; Vijande, J
2003-01-01
From QCD and lattice calculations two specific forms of quark confining potential, a strict linear and a screened linear confinement, come out. Both forms of the potential, implemented by the one gluon exchange interaction, are applied to the description of heavy quarkonia: cc and bb. Applications to light hadrons, mesons and baryons, are also commented. (11 refs).
Structure of polymer chains under confinement
Indian Academy of Sciences (India)
Single chain form factor was observed both for bulk and confined chains using the condition of zero average contrast. Our measurements on neutral polymer chains are in agreement with the theoretical predictions established by Daoud and de Gennes for chains confined in a cylindrical pore when the chains are entangled ...
Climate conditions in bedded confinement buildings
Confinement buildings are utilized for finishing cattle to allow more efficient collection of animal waste and to buffer animals against adverse climatic conditions. Environmental data were obtained from a 29 m wide x 318 m long bedded confinement building with the long axis oriented east to west. T...
BOOK REVIEW: Instabilities in a confined plasma
Glasser, A. H.
1999-05-01
, at least in the USA, to encounter this material first in a course on general relativity, which they might not have taken previously when specializing in plasma physics. While good efforts are made by the author to provide an intuitive understanding of the many analytical results, this is often done with such brevity that a substantial level of maturity is required to comprehend the ideas. Another quote from the preface is, ``The book is based on analytical approaches and should therefore be useful for everybody who is interested in the topic.'' In a field where complex geometry and dynamics and the importance of practical results have required much novel and creative computational work over the past 25 years, there is no mention, no acknowledgment, no hint of its importance. The analytical approach presented here certainly fills an important need, and there is no need for the same work to cover numerical work in depth, but some recognition of the importance of numerical work and its relationship with the analytical side of the theory might have been justified. Despite these shortcomings, this book is a major and welcome addition to the literature on plasma instabilities which I heartily recommend. Contents: 1. Equilibrium of a plasma in toroidal confinement systems; 2. Internal magnetohydrodynamic modes in the cylindrical approximation; 3. Small-scale magnetohydrodynamic instabilities in toroidal confinement systems; 4. Magnetohydrodynamic internal kink modes in toroidal geometry; 5. Magnetohydrodynamic modes in collisionless and neoclassical regimes; 6. Drift-magnetohydrodynamic modes; 7. External kink modes; 8. Alfvén eigenmodes and their interaction with high-energy particles; References; Index.
Quantum electrodynamics in strong external fields
International Nuclear Information System (INIS)
Mueller, B.; Rafelski, J.; Kirsch, J.
1981-05-01
We review the theoretical description of quantum electrodynamics in the presence of strong and supercritical fields. In particular, the process of the spontaneous vacuum decay accompanied by the observable positron emission in heavy ion collisions is described. Emphasis is put on the proper formulation of many-body aspects in the framework of quantum field theory. The extension of the theory to the description of Bose fields and many-body effects is presented, and the Klein paradox is resolved. Some implications of the theoretical methods developed here are presented concerning non-abelian gauge theories and the quark confinement puzzle. (orig.)
Strongly-correlated ultracold atoms in optical lattices
International Nuclear Information System (INIS)
Dao, Tung-Lam
2008-01-01
liquids, but also in unusual phases such as the normal state of high-temperature superconductivity with a pseudo gap (leading to a differentiation between nodes and anti-nodes) observed in condensed mater physics. In the second part of this thesis, we have performed theoretical studies of several phases of strongly correlated fermions in optical lattices in the framework of theoretical models such as the Hubbard model. We have implemented and developed analytical methods (Hartree-Fock mean field theory at weak coupling, mapping on a effective spin model at strong coupling) and numerical methods (the dynamic mean field theory approach). This work has led to two particular types of studies. The first one studies the competition between a superfluid phase and a density wave (or phase separation) for fermions with mass imbalance and attractive interaction. We have shown that the superfluid phase is unstable beyond a certain value of the mass ratio, which depends on the interaction. The second study treats a gas with imbalanced populations (polarized gas) with an attractive interaction in a three dimensional optical lattice. The main result is a phase diagram showing the stability of a uniform superfluid phase with polarization (Sarma phase or breached pair phase) in a certain parameter regime. Via an energetic argument, we concluded that the stability of the polarized superfluid phase is due to the reduction of the polarizability and the critical field of the non-polarized superfluid phase. In the strong coupling regime of the Hubbard model, within the DMFT method, we have shown that the formation of the preformed pair in the normal state reduces the polarizability and favors the stability of the breached pair phase. Although some aspects have been addressed in this thesis, many interesting questions still remain open for future work. In the first part, the framework of the novel spectroscopy method established in chapter 2 can allow for different concrete studies of the
Scattering resonances of ultracold atoms in confined geometries
Energy Technology Data Exchange (ETDEWEB)
Saeidian, Shahpoor
2008-06-18
Subject of this thesis is the investigation of the quantum dynamics of ultracold atoms in confined geometries. We discuss the behavior of ground state atoms inside a 3D magnetic quadrupole field. Such atoms in enough weak magnetic fields can be approximately treated as neutral point-like particles. Complementary to the well-known positive energy resonances, we point out the existence of short-lived negative energy resonances. The latter originate from a fundamental symmetry of the underlying Hamiltonian. We drive a mapping of the two branches of the spectrum. Moreover, we analyze atomic hyperfine resonances in a magnetic quadrupole field. This corresponds to the case for which both the hyperfine and Zeeman interaction, are comparable, and should be taken into account. Finally, we develop a general grid method for multichannel scattering of two atoms in a two-dimensional harmonic confinement. With our approach we analyze transverse excitations/deexcitations in the course of the collisional process (distinguishable or identical atoms) including all important partial waves and their couplings due to the broken spherical symmetry. Special attention is paid to suggest a non-trivial extension of the CIRs theory developed so far only for the single-mode regime and zero-energy limit. (orig.)
Strongly interacting mesoscopic systems of anyons in one dimension
DEFF Research Database (Denmark)
Zinner, N. T.
2015-01-01
Using the fractional statistical properties of so-called anyonic particles, we present exact solutions for up to six strongly interacting particles in one-dimensional confinement that interpolate the usual bosonic and fermionic limits. Specifically, we consider two-component mixtures of anyons...
A systematic study of the strong interaction with PANDA
Messchendorp, J. G.; Hosaka, A; Khemchandani, K; Nagahiro, H; Nawa, K
2011-01-01
The theory of Quantum Chromo Dynamics (QCD) reproduces the strong interaction at distances much shorter than the size of the nucleon. At larger distance scales, the generation of hadron masses and confinement cannot yet be derived from first principles on basis of QCD. The PANDA experiment at FAIR
Friction regimes in the lubricants solid-state regime
Schipper, Dirk J.; Maathuis, O.; Dowson, D.; Taylor, C.M.; Childs, T.H.C.; Dalmaz, G.
1995-01-01
Friction measurements were performed in the lubricant's solid-state regime to study the transition from full-film lubrication, in which the separation is maintained by a solidified lubricant, to mixed lubrication. Special attention is paid to the influence of temperature (inlet viscosity) and
Quark confinement and hadronic interactions
International Nuclear Information System (INIS)
Lenz, F.
1985-01-01
With the possibility for 'exact' calculations within the framework of a fundamental theory, QCD, the role of models in strong interaction physics is changing radically. The relevance of detailed numerical model studies is diminishing with the development of those exact, numerical approaches to QCD. On the other hand, the insight gained from such purely numerical studies is necessarily limited and must be complemented by the more qualitative but also more intuitive insight gained from model studies. In particular, the subject of hadron-hadron interactions requires model studies to relate the wide variety of strong interaction physics to the fundamental properties of strong interaction physics. The author reports on such model studies of the hadron-hadron interaction
Energy Technology Data Exchange (ETDEWEB)
Angelini, S.; Theofanous, T.G.; Yuen, W.W. [California Univ., Santa Barbara, CA (United States). Center for Risk Studies and Safety
1998-01-01
The conditions of the MAGICO-2000 experiment are extended to more broadly investigate the regimes of premixing, and the corresponding internal structures of mixing zones. With the help of the data and numerical simulations using the computer code PM-ALPHA, we can distinguish extremes of behavior dominated by inertia and thermal effects - we name these the inertia and thermal regimes, respectively. This is an important distinction that should guide future experiments aimed at code verification in this area. Interesting intermediate behaviors are also delineated and discussed. (author)
Strongly-Interacting Fermi Gases in Reduced Dimensions
2015-11-16
superconductivity), nuclear physics (nuclear matter), high - energy physics (effective theories of the strong interactions ), astrophysics (compact stellar objects...strongly- interacting Fermi gases confined in a standing- wave CO2 laser trap. This trap produces a periodic quasi-two-dimensional pancake geometry...predictions of the phase diagram and high temperature superfluidity. Our recent measurements reveal that pairing energy and cloud profiles can be
Physics of Strongly Coupled Plasma
Energy Technology Data Exchange (ETDEWEB)
Kraeft, Wolf-Dietrich [Universitat Rostock (Germany)
2007-07-15
Strongly coupled plasmas (or non-ideal plasmas) are multi-component charged many-particle systems, in which the mean value of the potential energy of the system is of the same order as or even higher than the mean value of the kinetic energy. The constituents are electrons, ions, atoms and molecules. Dusty (or complex) plasmas contain still mesoscopic (multiply charged) particles. In such systems, the effects of strong coupling (non-ideality) lead to considerable deviations of physical properties from the corresponding properties of ideal plasmas, i.e., of plasmas in which the mean kinetic energy is essentially larger than the mean potential energy. For instance, bound state energies become density dependent and vanish at higher densities (Mott effect) due to the interaction of the pair with the surrounding particles. Non-ideal plasmas are of interest both for general scientific reasons (including, for example, astrophysical questions), and for technical applications such as inertially confined fusion. In spite of great efforts both experimentally and theoretically, satisfactory information on the physical properties of strongly coupled plasmas is not at hand for any temperature and density. For example, the theoretical description of non-ideal plasmas is possible only at low densities/high temperatures and at extremely high densities (high degeneracy). For intermediate degeneracy, however, numerical experiments have to fill the gap. Experiments are difficult in the region of 'warm dense matter'. The monograph tries to present the state of the art concerning both theoretical and experimental attempts. It mainly includes results of the work performed in famous Russian laboratories in recent decades. After outlining basic concepts (chapter 1), the generation of plasmas is considered (chapter 2, chapter 3). Questions of partial (chapter 4) and full ionization (chapter 5) are discussed including Mott transition and Wigner crystallization. Electrical and
Regimes of the magnetized Rayleigh endash Taylor instability
International Nuclear Information System (INIS)
Winske, D.
1996-01-01
Hybrid simulations with kinetic ions and massless fluid electrons are used to investigate the linear and nonlinear behavior of the magnetized Rayleigh endash Taylor instability in slab geometry with the plasma subject to a constant gravity. Three regimes are found, which are determined by the magnitude of the complex frequency ω=ω r +iγ. For |ω| i (Ω i = ion gyrofrequency), one finds the typical behavior of the usual fluid regime, namely the development of open-quote open-quote mushroom-head close-quote close-quote spikes and bubbles in the density and a strongly convoluted boundary between the plasma and magnetic field, where the initial gradient is not relaxed much. A second regime, where |ω|∼0.1Ω i , is characterized by the importance of the Hall term. Linearly, the developing flute modes are more finger-like and tilted along the interface; nonlinearly, clump-like structures form, leading to a significant broadening of the interface. The third regime is characterized by unmagnetized ion behavior, with |ω|∼Ω i . Density clumps, rather than flutes, form in the linear stage, while nonlinearly, longer-wavelength modes that resemble those in fluid regime dominate. Finite Larmor radius stabilization of short-wavelength modes is observed in each regime. copyright 1996 American Institute of Physics
International regime formation: Ozone depletion and global climate change
International Nuclear Information System (INIS)
Busmann, N.E.
1994-03-01
Two theoretical perspectives, neorealism and neoliberal institutionalism, dominate in international relations. An assessment is made of whether these perspectives provide compelling explanations of why a regime with specific targets and timetables was formed for ozone depletion, while a regime with such specificity was not formed for global climate change. In so doing, the assumptions underlying neorealism and neoliberal institutionalism are examined. A preliminary assessment is offered of the policymaking and institutional bargaining process. Patterns of interstate behavior are evolving toward broader forms of cooperation, at least with regard to global environmental issues, although this process is both slow and cautious. State coalitions on specific issues are not yet powerful enough to create a strong community of states in which states are willing to devolve power to international institutions. It is shown that regime analysis is a useful analytic framework, but it should not be mistaken for theory. Regime analysis provides an organizational framework offering a set of questions regarding the principles and norms that govern cooperation and conflict in an issue area, and whether forces independent of states exist which affect the scope of state behavior. An examination of both neorealism and neoliberal institutionalism, embodied by four approaches to regime formation, demonstrates that neither has sufficient scope to account for contextual dynamics in either the ozone depletion or global climate change regime formation processes. 261 refs
Aerofractures in Confined Granular Media
Eriksen, Fredrik K.; Turkaya, Semih; Toussaint, Renaud; Måløy, Knut J.; Flekkøy, Eirik G.
2015-04-01
We will present the optical analysis of experimental aerofractures in confined granular media. The study of this generic process may have applications in industries involving hydraulic fracturing of tight rocks, safe construction of dams, tunnels and mines, and in earth science where phenomena such as mud volcanoes and sand injectites are results of subsurface sediment displacements driven by fluid overpressure. It is also interesting to increase the understanding the flow instability itself, and how the fluid flow impacts the solid surrounding fractures and in the rest of the sample. Such processes where previously studied numerically [Niebling 2012a, Niebling 2012b] or in circular geometries. We will here explore experimentally linear geometries. We study the fracturing patterns that form when air flows into a dense, non-cohesive porous medium confined in a Hele-Shaw cell - i.e. into a packing of dry 80 micron beads placed between two glass plates separated by ~1mm. The cell is rectangular and fitted with a semi-permeable boundary to the atmosphere - blocking beads but not air - on one short edge, while the other three edges are impermeable. The porous medium is packed inside the cell between the semi-permeable boundary and an empty volume at the sealed side where the air pressure can be set and kept at a constant overpressure (1-2bar). Thus, for the air trapped inside the cell to release the overpressure it has to move through the solid. At high enough overpressures the air flow deforms the solid and increase permeability in some regions along the air-solid interface, which results in unstable flow and aerofracturing. Aerofractures are thought to be an analogue to hydrofractures, and an advantage of performing aerofracturing experiments in a Hele-Shaw cell is that the fracturing process can easily be observed in the lab. Our experiments are recorded with a high speed camera with a framerate of 1000 frames per second. In the analysis, by using various image
Generating equilateral random polygons in confinement
International Nuclear Information System (INIS)
Diao, Y; Ernst, C; Montemayor, A; Ziegler, U
2011-01-01
One challenging problem in biology is to understand the mechanism of DNA packing in a confined volume such as a cell. It is known that confined circular DNA is often knotted and hence the topology of the extracted (and relaxed) circular DNA can be used as a probe of the DNA packing mechanism. However, in order to properly estimate the topological properties of the confined circular DNA structures using mathematical models, it is necessary to generate large ensembles of simulated closed chains (i.e. polygons) of equal edge lengths that are confined in a volume such as a sphere of certain fixed radius. Finding efficient algorithms that properly sample the space of such confined equilateral random polygons is a difficult problem. In this paper, we propose a method that generates confined equilateral random polygons based on their probability distribution. This method requires the creation of a large database initially. However, once the database has been created, a confined equilateral random polygon of length n can be generated in linear time in terms of n. The errors introduced by the method can be controlled and reduced by the refinement of the database. Furthermore, our numerical simulations indicate that these errors are unbiased and tend to cancel each other in a long polygon. (paper)
Bifurcation to chaos in the Benard-Marangoni instability in a confined geometry
Energy Technology Data Exchange (ETDEWEB)
Rahal, S [Department of Mechanical Engineering, University of Batna, Rue Boukhlouf Mohamed el Hadi, 05000 Batna (Algeria); Cerisier, P [IUSTI - CNRS UMR 6595, Polytech' Marseille, Technopole de Chateau-Gombert, 5 rue Enrico Fermi, 13453, Marseille Cedex 13 (France)
2007-04-15
An experimental study of dynamical regimes in Benard-Marangoni convection, for various Prandt and Marangoni numbers, has been carried out in a confined geometry. Indeed, a small hexagonal vessel allowing the formation of only one convective cell, for a large extent of the Marangoni number, has been used. Fourrier spectra and a correlation function have been used to recognize the various dynamical regimes. For fixed values of the Prantl number and aspect ratio, an oscillatory, a quasi-periodic and chaotic states, were successively observed, as the Marangoni number was increased. The correlation dimensions of strange attractors corresponding to the chaotic regimes were calculated. The dimensions were found to be larger then those calculated by other authors for the Rayleigh-Benard convection in small aspect ratio geometries. The transition from temporal chaos to spatio - temporal chaos has also been observed. Indeed for higher values of the Marangoni number, spatial dynamics are observed.
Upper Basalt-Confined Aquifer System in the Southern Hanford Site
International Nuclear Information System (INIS)
Thorne, P.
1999-01-01
The 1990 DOE Tiger Team Finding GW/CF-202 found that the hydrogeologic regime at the Hanford Site was inadequately characterized. This finding also identified the need for completing a study of the confined aquifer in the central and southern portions of the Hanford Site. The southern portion of the site is of particular interest because hydraulic-head patterns in the upper basalt-confined aquifer system indicate that groundwater from the Hanford central plateau area, where contaminants have been found in the aquifer, flows southeast toward the southern site boundary. This results in a potential for offsite migration of contaminants through the upper basalt-confined aquifer system. Based on the review presented in this report, available hydrogeologic characterization information for the upper basalt-confined aquifer system in this area is considered adequate to close the action item. Recently drilled offsite wells have provided additional information on the structure of the aquifer system in and near the southern part of the Hanford Site. Information on hydraulic properties, hydrochemistry, hydraulic heads and flow directions for the upper basalt-confined aquifer system has been re-examined and compiled in recent reports including Spane and Raymond (1993), Spane and Vermeul ( 1994), and Spane and Webber (1995)
Strongly Correlated Topological Insulators
2016-02-03
Strongly Correlated Topological Insulators In the past year, the grant was used for work in the field of topological phases, with emphasis on finding...surface of topological insulators. In the past 3 years, we have started a new direction, that of fractional topological insulators. These are materials...in which a topologically nontrivial quasi-flat band is fractionally filled and then subject to strong interactions. The views, opinions and/or
Isenberg, James
2017-01-01
The Hawking-Penrose theorems tell us that solutions of Einstein's equations are generally singular, in the sense of the incompleteness of causal geodesics (the paths of physical observers). These singularities might be marked by the blowup of curvature and therefore crushing tidal forces, or by the breakdown of physical determinism. Penrose has conjectured (in his `Strong Cosmic Censorship Conjecture`) that it is generically unbounded curvature that causes singularities, rather than causal breakdown. The verification that ``AVTD behavior'' (marked by the domination of time derivatives over space derivatives) is generically present in a family of solutions has proven to be a useful tool for studying model versions of Strong Cosmic Censorship in that family. I discuss some of the history of Strong Cosmic Censorship, and then discuss what is known about AVTD behavior and Strong Cosmic Censorship in families of solutions defined by varying degrees of isometry, and discuss recent results which we believe will extend this knowledge and provide new support for Strong Cosmic Censorship. I also comment on some of the recent work on ``Weak Null Singularities'', and how this relates to Strong Cosmic Censorship.
intensive and extensive feeding regimes
African Journals Online (AJOL)
production and reproduction parameters in ram lambs, under intensive and extensive feeding regimes. J.P.C. Greyling* and G.J. Taylor. Department of Animal Science, University of the Orange Free State, PO. Box 339, Bloemfontein,. 9300, South Africa. Received revised 1 July 1999; accepted 28 July 1999. Forty Dorper ...
Monetary regimes in open economies
Korpos, A.
2006-01-01
This thesis presents a two-country open economy framework for the analysis of strategic interactions among monetary authorities and wage bargaining institutions. From this perspective, the thesis investigates the economic consequences of replacing flexible and fixed exchange rate regimes with a
Three Potential LiWall regimes in the Lithium Tokamak eXperiment (LTX)
Yoo, Jongsoo; Zakharov, Leonid
2008-11-01
The incoming Lithium Tokamak eXperiment (LTX) is designed for a low recycling operation with the plasma inside a close fitting shell coated with a pumping layer of lithium. This creates a special situation for confinement when the thermo-conduction is suppressed due to elevated edge temperature and the energy confinement is determined by the particle diffusion. The so- called Reference Transport Model (RTM) in which the diffusion coefficient as well as the ion/electron thermo-conduction coefficients are equal to the ion neoclassical thermo- conductivity, seems to be relevant for the low recycling regime. The RTM has been implemented in the ASTRA-ESC code system of transport analysis for simulation of the LTX stationary plasma regimes. Three zero recycling reference regimes have been identified earlier for LTX. In the Ohmic regime with the gas puff the central electron temperature is expected to be at the level of 1 keV and Ti˜0.15 keV. The combination of Ohmic-NBI (10 keV neutral beam injection) heating can elevate the ion temperature to ˜0.6 keV. With an enhanced NBI current, the third, hot-ion regime can be achieved with plasma fueling by NBI and Ti> Te. The focus of the present studies is on the effects of residual finite recycling.
Plasma confinement in a magnetic dipole
International Nuclear Information System (INIS)
Kesner, J.; Bromberg, L.; Garnier, D.; Mauel, M.
2001-01-01
A dipole fusion confinement device is stable to MHD interchange and ballooning modes when the pressure profile is sufficiently gentle. The plasma can be confined at high beta, is steady state and disruption free. Theory indicates that when the pressure gradient is sufficiently gentle to satisfy MHD requirements drift waves will also be stable. The dipole approach is particularly applicable for advanced fuels. A new experimental facility is presently being built to test the stability and transport properties of a dipole-confined plasma. (author)
Plasma confinement in a magnetic dipole
International Nuclear Information System (INIS)
Kesner, J.; Bromberg, L.; Garnier, D.; Mauel, M.
1999-01-01
A dipole fusion confinement device is stable to MHD interchange and ballooning modes when the pressure profile is sufficiently gentle. The plasma can be confined at high beta, is steady state and disruption free. Theory indicates that when the pressure gradient is sufficiently gentle to satisfy MHD requirements drift waves will also be stable. The dipole approach is particularly applicable for advanced fuels. A new experimental facility is presently being built to test the stability and transport properties of a dipole-confined plasma. (author)
Dust confinement and dust acoustic waves in a magnetized plasma
Piel, A.
2005-10-01
Systematic laboratory experiments on dust acoustic waves require the confinement of dust particles. Here we report on new experiments in a magnetized plasma region in front of an additional positively biased disk electrode in a background plasma which is generated in argon at 27MHz between a disk and grid electrode. The plasma diffuses through the grid along the magnetic field. The three-dimensional dust distribution is measured with a horizontal sheet of laser light and a CCD camera, which are mounted on a vertical translation stage. Depending on magnetic field and discharge current, cigar or donut-shaped dust clouds are generated, which tend to rotate about the magnetic field direction. Measurements with emissive probes show that the axial confinement of dust particles with diameters between 0.7-2 μm is achieved by a balance of ion-drag force and electric field force. Dust levitation and radial confinement is due to a strong radial electric field. Dust acoustic waves are destabilized by the ion flow or can be stimulated by a periodic bias on the disk electrode. The observed wave dispersion is compared with fluid and kinetic models of the dust acoustic wave.
Plasma confinement of Nagoya high beta toroidal pinch experiments
International Nuclear Information System (INIS)
Hirano, K.; Kitagawa, S.; Wakatani, M.; Kita, Y.; Yamada, S.; Yamaguchi, S.; Sato, K.; Aizawa, T.; Osanai, Y.; Noda, N.
1976-01-01
Two different types of high β toroidal pinch experiments, STP and CCT, have been done to study the confinement of the plasma produced by theta-pinch. The STP is an axisymmetric toroidal pinch of high β tokamak type, while the CCT is multiply connected periodic toroidal traps. Internal current carrying copper rings are essential to the CCT. Since both apparatuses use the same fast capacitor bank system, they produce not so different plasma temperatures and densities. The observed laser scattering temperature and density is about 50 eV and 4 x 10 15 /cm 3 , respectively, when the filling pressure is 5 m torr. In the experiment of STP, strong correlations are found between the βsub(p) value and the amplitude of m = 2 mode. It has a minimum around the value of βsub(p) of 0.8. The disruptive instability is observed to expand the pinched plasma column without lowering the plasma temperature. Just before the distruption begins, the q value around the magnetic axis becomes far less than 1 and an increase of the amplitude of m = 2 mode is seen. The CCT also shows rapid plasma expansion just before the magnetic field reaches its maximum. Then the trap is filled up with the plasma by this irreversible expansion and the stable plasma confinement is achieved. The energy confinement time of the CCT is found to be about 35 μsec. (orig.) [de
Effects of confinement on the dielectric response of water extends up to mesoscale dimensions
DEFF Research Database (Denmark)
De Luca, Sergio; Kannam, Sridhar Kumar; Todd, B.D.
2016-01-01
of confined water under the influence of external electric fields along with the dipolar fluctuations at equilibrium. The confinement induces a strong anisotropic effect which is evident up to 100 nm channel width, and may extend to macroscopic dimensions. The root-mean-square fluctuations of the total......The extent of confinement effects on water is not clear in the literature. While some properties are affected only within a few nanometers from the wall surface, others are affected over long length scales, but the range is not clear. In this work, we have examined the dielectric response...... dimensions. Consistent with dipole moment fluctuations, the effect of confinement on the dielectric response also persists up to channel widths considerably beyond 100 nm. When an electric field is applied in the perpendicular direction, the orientational relaxation is 3 orders of magnitude faster than...
Extremely confined gap surface-plasmon modes excited by electrons
DEFF Research Database (Denmark)
Raza, Søren; Stenger, Nicolas; Pors, Anders Lambertus
2014-01-01
EELS to ultra-sharp convex grooves in gold, we directly probe extremely confined gap surface-plasmon (GSP) modes excited by swift electrons in nanometre-wide gaps. We reveal the resonance behaviour associated with the excitation of the antisymmetric GSP mode for extremely small gap widths, down to ~5...... nm. We argue that excitation of this mode, featuring very strong absorption, has a crucial role in experimental realizations of non-resonant light absorption by ultra-sharp convex grooves with fabrication-induced asymmetry. The occurrence of the antisymmetric GSP mode along with the fundamental GSP...
Controlling Confinement and Topology to Study Collective Cell Behaviors.
Duclos, Guillaume; Deforet, Maxime; Yevick, Hannah G; Cochet-Escartin, Olivier; Ascione, Flora; Moitrier, Sarah; Sarkar, Trinish; Yashunsky, Victor; Bonnet, Isabelle; Buguin, Axel; Silberzan, Pascal
2018-01-01
Confinement and substrate topology strongly affect the behavior of cell populations and, in particular, their collective migration. In vitro experiments dealing with these aspects require strategies of surface patterning that remain effective over long times (typically several days) and ways to control the surface topology in three dimensions. Here, we describe protocols addressing these two aspects. High-resolution patterning of a robust cell-repellent coating is achieved by etching the coating through a photoresist mask patterned directly on the coated surface. Out-of-plane curvature can be controlled using glass wires or corrugated "wavy" surfaces.
Optimized profiles for improved confinement and stability in the DIII-D tokamak
International Nuclear Information System (INIS)
Taylor, T.S.; St. John, H.; Turnbull, A.D.
1995-02-01
Simultaneous achievement of high energy confinement, τ E , and high plasma beta, β, leads to an economically attractive compact tokamak fusion reactor. High confinement enhancement, H = τ E /τ E-ITER89P = 4, and high normalized beta β N = β/(I/aB) = 6%-m-T/MA, have been obtained in DIII-D experimental discharges. These improved confinement and/or improved stability limits are observed in several DIII-D high performance operational regimes: VH-mode, high ell i H-mode, second stable core, and high beta poloidal. The authors have identified several important features of the improved performance in these discharges: details of the plasma shape, toroidal rotation or ExB flow profile, q profile and current density profile, and pressure profile. From the improved physics understanding of these enhanced performance regimes, they have developed operational scenarios which maintain the essential features of the improved confinement and which increase the stability limits using localized current profile control. The stability limit is increased by modifying the interior safety factor profile to be nonmonotonic with high central q, while maintaining the edge current density consistent with the improved transport regimes and the high edge bootstrap current. They have calculated high beta equilibria with β N = 6.5, stable to ideal n = 1 kinks and stable to ideal ballooning modes. The safety factor at the 95% flux surface is 6, the central q value is 3.9 and the minimum in q is 2.6. The current density profile is maintained by the natural profile of the bootstrap current, and a modest amount of electron cyclotron current drive
Strong screening by lattice confinement and resultant fusion reaction rates in fcc metals
Prados-Estévez, F. M.; Subashiev, A. V.; Nee, H. H.
2017-09-01
The effects of electronic screening on the cross sections and reactivities for the nuclear reactions between light nuclei in Pd and Ni is studied. We consider the applicability of the theory of thermonuclear burning in stars to the D-D nuclear reaction in metals. The screening model based on the mean field potential of the electron cloud in the metal plasma is used. We discuss the specifics of the screening for the H (D) atoms embedded in vacancies and divacancies. High concentration of hydrogen isotopes segregated to monovacancies and divacancies in face-centered cubic (fcc) metals such as Ni and Pd with densities of ∼ 6 ×1023atom /cm3 , makes the hydrogen cluster a favorable active site for the fusion reaction. Still the observation of a nuclear reaction requires an accumulation of energy in D nuclei of at least several eV, which is far above what can be achieved in the thermal heating experiments.
Modeling cavities exhibiting strong lateral confinement using open geometry Fourier modal method
DEFF Research Database (Denmark)
Häyrynen, Teppo; Gregersen, Niels
2016-01-01
We have developed a computationally eﬃcient Fourier-Bessel expansion based open geometry formalism for modeling the optical properties of rotationally symmetric photonic nanostructures. The lateral computation domain is assumed inﬁnite so that no artiﬁcial boundary conditions are needed. Instead......, the leakage of the modes due to an imperfect ﬁeld conﬁnement is taken into account by using a basis functions that expand the whole inﬁnite space. The computational eﬃciency is obtained by using a non-uniform discretization in the frequency space in which the lateral expansion modes are more densely sampled...
Route to strong localization of light: The role of disorder
Molinari, Diego P.
2012-01-01
By employing Random Matrix Theory (RMT) and firstprinciple calculations, we investigated the behavior of Anderson localization in 1D, 2D and 3D systems characterized by a varying disorder. In particular, we considered random binary layer sequences in 1D and structurally disordered photonic crystals in two and three dimensions. We demonstrated the existence of a unique optimal degree of disorder that yields the strongest localization possible. In this regime, localized modes are constituted by defect states, which can show subwavelength confinement properties. These results suggest that disorder offers a new avenue for subwavelength light localization in purely dielectric media. © 2012 Optical Society of America.
Transport properties of supercooled confined water
International Nuclear Information System (INIS)
Mallamace, F.; Baglioni, P.; Corsaro, C.; Spooren, J.; Stanley, H.E.; Chen, S.-H.
2011-01-01
We present an overview of recent experiments performed on water in the deeply supercooled region, a temperature region of fundamental importance in the science of water. We examine data generated by nuclear magnetic resonance, quasi-elastic neutron scattering, Fourier-transform infrared spectroscopy, and Raman spectroscopy, and study water confined in nanometer-scale environments. When contained within small pores, water does not crystallize and can be supercooled well below its homogeneous nucleation temperature T H. On this basis, it is possible to carry out a careful analysis of the well-known thermodynamic anomalies of water. Studying the temperature and pressure dependencies of water dynamics, we show that the liquid-liquid phase transition (LLPT) hypothesis represents a reliable model for describing liquid water. In this model, liquid water is a mixture of two different local structures: a low density liquid (LDL) and a high-density liquid (HDL). The LLPT line terminates at a low-T liquid-liquid critical point. We discuss the following experimental findings: 1.) the crossover from non-Arrhenius behavior at high T to Arrhenius behavior at low T in transport parameters; 2.) the breakdown of the Stokes-Einstein relation; 3.) the existence of a Widom line, which is the locus of points corresponding to a maximum correlation length in the P-T phase diagram and which ends in the liquid-liquid critical point; 4.) the direct observation of the LDL phase; and 5.) the minimum in the density at approximately 70 K below the temperature of the density maximum. In our opinion these results strongly support the LLPT hypothesis. All of the basic science and technology community should be impressed by the fact that, although the few ideas (apparently elementary) developed concerning water approximately 27 centuries ago have changed very little up to now, because of the current expansion in our knowledge in this area, they can begin to change in the near future.
Friction regimes in the lubricants solid-state regime
Schipper, Dirk J.; Maathuis, O.; Dowson, D.; Taylor, C.M.; Childs, T.H.C.; Dalmaz, G.
1995-01-01
Friction measurements were performed in the lubricant's solid-state regime to study the transition from full-film lubrication, in which the separation is maintained by a solidified lubricant, to mixed lubrication. Special attention is paid to the influence of temperature (inlet viscosity) and roughness on this transition. The friction measurements showed that in the lubricants solid-state region three lubrication modes can be distinguished: A) full-film lubrication; separation is maintained b...
Propagating confined states in phase dynamics
International Nuclear Information System (INIS)
Brand, H.R.; Deissler, R.J.
1992-01-01
We show that the nonlinear phase equation that applies to propagating patterns allows for a large range of parameter values for propagating confined states for which a spatially localized region with wavelengths different from that of the background travels on this background. This phenomenon is the generalization of the stationary confined states predicted a few years ago by the authors, which have since been seen experimentally in various systems. We suggest that the propagating confined states found here could arise in spirals in Taylor vortex flow or in convective systems showing traveling waves far above onset. We find that the propagating confined states can be replaced by a pattern that is irregular in space and time as the control parameter in the nonlinear phase equation is varied
Eros-based Confined Capability Client
National Research Council Canada - National Science Library
Shapiro, Jonathan S
2006-01-01
Objective of EROS-Based Confined Capability Client Project is to demonstrate that systems constructed using capability-based protection can be organized in a way that makes it defensible from hostile internet content...
High-Energy-Density-Physics Studies for Inertial Confinement Fusion Applications
Hu, S. X.
2017-10-01
Accurate knowledge of the static, transport, and optical properties of high-energy-density (HED) plasmas is essential for reliably designing and understanding inertial confinement fusion (ICF) implosions. In the warm-dense-matter regime routinely accessed by low-adiabat ICF implosions, many-body strong-coupling and quantum electron degeneracy effects play an important role in determining plasma properties. The past several years have witnessed intense efforts to assess the importance of the microphysics of ICF targets, both theoretically and experimentally. On the theory side, first-principles methods based on quantum mechanics have been applied to investigate the properties of warm, dense plasmas. Specifically, self-consistent investigations have recently been performed on the equation of state, thermal conductivity, and opacity of a variety of ICF ablators such as polystyrene (CH), beryllium, carbon, and silicon over a wide range of densities and temperatures. In this talk, we will focus on the most-recent progress on these ab initio HED physics studies, which generally result in favorable comparisons with experiments. Upon incorporation into hydrocodes for ICF simulations, these first-principles ablator-plasma properties have produced significant differences over traditional models in predicting 1-D target performance of ICF implosions on OMEGA and direct-drive-ignition designs for the National Ignition Facility. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944. *In collaboration with L. A. Collins, T. R. Boehly, G. W. Collins, J. D. Kress, and V. N. Goncharov.
Predictions of a theory of quark confinement
International Nuclear Information System (INIS)
Mack, G.
1980-03-01
We propose a theory of quark confinement which uses only the simplest of approximations. It explains persistence of quark confinement in Yang Mills theories with gauge group SU(2) or SU(3) as a consequence of asymptotic freedom in perturbation theory and of the known phase structure of Z(2) resp. Z(3) lattice gauge theory. Predictions are derived which can in principle be tested by computer simulation. Some are already tested by results of Creutz. They are in good agreement. (orig.)
Stellarator approach to toroidal plasma confinement
International Nuclear Information System (INIS)
Johnson, J.L.
1981-12-01
An overview is presented of the development and current status of the stellarator approach to controlled thermonuclear confinement. Recent experimental, theoretical, and systems developments have made this concept a viable option for the evolution of the toroidal confinement program. Some experimental study of specific problems associated with departure from two-dimensional symmetry must be undertaken before the full advantages and opportunities of steady-state, net-current-free operation can be realized
Espinoza, Benjamin; Gartside, Paul; Kovan-Bakan, Merve; Mamatelashvili, Ana
2012-01-01
A space is `n-strong arc connected' (n-sac) if for any n points in the space there is an arc in the space visiting them in order. A space is omega-strong arc connected (omega-sac) if it is n-sac for all n. We study these properties in finite graphs, regular continua, and rational continua. There are no 4-sac graphs, but there are 3-sac graphs and graphs which are 2-sac but not 3-sac. For every n there is an n-sac regular continuum, but no regular continuum is omega-sac. There is an omega-sac ...
Abortion: Strong's counterexamples fail
DEFF Research Database (Denmark)
Di Nucci, Ezio
2009-01-01
This paper shows that the counterexamples proposed by Strong in 2008 in the Journal of Medical Ethics to Marquis's argument against abortion fail. Strong's basic idea is that there are cases--for example, terminally ill patients--where killing an adult human being is prima facie seriously morally......'s scenarios have some valuable future or admitted that killing them is not seriously morally wrong. Finally, if "valuable future" is interpreted as referring to objective standards, one ends up with implausible and unpalatable moral claims....
Hydrogen combustion in a flat semi-confined layer with respect to the Fukushima Daiichi accident
Energy Technology Data Exchange (ETDEWEB)
Kuznetsov, Mike, E-mail: kuznetsov@kit.edu [Karlsruhe Institute of Technology, 76131 Karlsruhe (Germany); Yanez, Jorge [Karlsruhe Institute of Technology, 76131 Karlsruhe (Germany); Grune, Joachim; Friedrich, Andreas [Pro-Science GmbH, 76275 Ettlingen (Germany); Jordan, Thomas [Karlsruhe Institute of Technology, 76131 Karlsruhe (Germany)
2015-05-15
Graphical abstract: - Highlights: • Critical conditions for flame propagation regimes in a layer geometry are analyzed. • Numerical simulation of hydrogen explosion reproduces real strength of shock waves. • From 80 to 200 kg of hydrogen were exploded during Fukushima (Unit I) accident. • A sonic deflagration with TNT equivalent of 800 kg was the most probable regime. - Abstract: Hydrogen accumulations at the top of a containment or reactor building may occur due to the interaction of molten corium and water followed by a severe accident of a nuclear reactor (TMI, Chernobyl, Fukushima Daiichi). The hydrogen that is released from the reactor accumulates usually as a stratified semi-confined layer of hydrogen–air mixture. A series of large scale experiments on hydrogen combustion and explosion in a semi-confined layer of uniform and non-uniform hydrogen–air mixtures in the presence of obstructions or without them was performed at the Karlsruhe Institute of Technology (KIT). Different flame propagation regimes from slow subsonic to relatively fast sonic flames and then to detonations were experimentally investigated in different geometries and then simulated with COM3D code with respect to evaluate the amount of hydrogen that was involved in the Fukushima Daiichi Accident (FDA). The experiments were performed in a horizontal semi-confined layer with the dimensions 9 × 3 × 0.6 m with/without obstacles opened from below. The hydrogen concentration in the mixtures with air was varied in the range of 10–34 vol.% without or with a gradient of 20–60 vol.%H{sub 2}/m. Effects of hydrogen concentration gradient, layer thickness, obstruction geometry, average and maximum hydrogen concentration on the flame propagation regimes were investigated with respect to evaluate the maximum pressure loads on internal structures. Blast wave strength and dynamics of propagation after the explosion of the hydrogen–air mixture layer were numerically simulated to reproduce
Deuterium-tritium plasmas in novel regimes in the Tokamak Fusion Test Reactor
International Nuclear Information System (INIS)
Bell, M.G.; Beer, M.
1997-02-01
Experiments in the Tokamak Fusion Test Reactor (TFTR) have explored several novel regimes of improved tokamak confinement in deuterium-tritium (D-T) plasmas, including plasmas with reduced or reversed magnetic shear in the core and high-current plasmas with increased shear in the outer region (high-l i ). New techniques have also been developed to enhance the confinement in these regimes by modifying the plasma-limiter interaction through in-situ deposition of lithium. In reversed-shear plasmas, transitions to enhanced confinement have been observed at plasma currents up to 2.2 MA (q a ∼ 4.3), accompanied by the formation of internal transport barriers, where large radial gradients develop in the temperature and density profiles. Experiments have been performed to elucidate the mechanism of the barrier formation and its relationship with the magnetic configuration and with the heating characteristics. The increased stability of high-current, high-l i plasmas produced by rapid expansion of the minor cross-section, coupled with improvement in the confinement by lithium deposition has enabled the achievement of high fusion power, up to 8.7 MW, with D-T neutral beam heating. The physics of fusion alpha-particle confinement has been investigated in these regimes, including the interactions of the alphas with endogenous plasma instabilities and externally applied waves in the ion cyclotron range of frequencies. In D-T plasmas with q 0 > 1 and weak magnetic shear in the central region, a toroidal Alfven eigenmode instability driven purely by the alpha particles has been observed for the first time. The interactions of energetic ions with ion Bernstein waves produced by mode-conversion from fast waves in mixed-species plasmas have been studied as a possible mechanism for transferring the energy of the alphas to fuel ions
Energy Technology Data Exchange (ETDEWEB)
Sakhel, Asaad R., E-mail: asaad.sakhel@fet.edu.jo [Department of Physics and Basic Sciences, Faculty of Engineering Technology, Balqa Applied University, Amman 11134 (Jordan); Abdus-Salam International Center for Theoretical Physics, Strada Costiera 11, 34151 Trieste (Italy)
2016-07-15
The dynamics of a Bose–Einstein condensate are examined numerically in the presence of a one-dimensional bichromatic optical lattice (BCOL) with external harmonic confinement in the strongly interacting regime. The condensate is excited by a focusing stirring red laser. Two realizations of the BCOL are considered, one with a rational and the other with an irrational ratio of the two constituting wave lengths. The system is simulated by the time-dependent Gross Pitaevskii equation that is solved using the Crank Nicolson method in real time. It is found that for a weak BCOL, the long-time averaged physical observables of the condensate respond only very weakly (or not at all) to changes in the secondary OL depth V{sub 1} showing that under these conditions the harmonic trap plays a dominant role in governing the dynamics. However, for a much larger strength of the BCOL, the response is stronger as it begins to compete with the external harmonic trap, such that the frequency of Bloch oscillations of the bosons rises with V{sub 1} yielding higher time-averages. Qualitatively there is no difference between the dynamics of the condensate resulting from the use of a rational or irrational ratio of the wavelengths since the external harmonic trap washes it out. It is further found that in the presence of an external harmonic trap, the BCOL acts in favor of superflow.
Transport of a multiple ion species plasma in the Pfirsch--Schluter regime
International Nuclear Information System (INIS)
Hirshman, S.P.
1976-10-01
The classical parallel friction coefficients, which relate the collisional friction forces to the flow of particles and heat along the magnetic field, are calculated for a multiple ion species plasma. In the short mean free path regime, the neoclassical Pfirsch--Schlueter transport coefficients for a toroidally confined multispecies plasma are computed in terms of the classical friction coefficients. The dependence of the neoclassical cross-field transport on the equilibration of the parallel ion temperature profiles is determined
Confined Space Evaluation Student Manual, #19613
Energy Technology Data Exchange (ETDEWEB)
Wilmot, David Ezekiel [Los Alamos National Laboratory
2016-08-29
Many workplaces contain spaces that are considered to be “confined” because their configuration hinders the activities of employees who must enter into, work in, and exit from them. In general, the permit-required confined spaces (PRCSs) Occupational Safety and Health Administration (OSHA) standard requires that Los Alamos National Laboratory (LANL) evaluate the workplace to determine if any spaces are PRCSs. The standard specifies strict procedures for the evaluation and atmospheric testing of a space before and during an entry by workers. The OSHA PRCS standard provides for alternative (less stringent than full-permit) entry procedures in cases where the only hazard in a space is atmospheric and the hazard can be controlled by forced air. At LANL, all confined spaces or potential confined spaces on LANL-owned or -operated property must be identified and evaluated by a confined space evaluator accompanied by a knowledgeable person. This course provides the information needed by confined space evaluators to make judgements about whether a space is a confined space, and if so, whether the space will require a permit for entry.
The decay of confined vortex rings
Stewart, K. C.; Niebel, C. L.; Jung, S.; Vlachos, P. P.
2012-07-01
Vortex rings are produced during the ejection of fluid through a nozzle or orifice, which occurs in a wide range of biological conditions such as blood flow through the valves of the heart or through arterial constrictions. Confined vortex ring dynamics, such as these, have not been previously studied despite their occurrence within the biological flow conditions mentioned. In this work, we investigate laminar vortex rings using particle image velocimetry and develop a new semi-empirical model for the evolution of vortex ring circulation subject to confinement. Here we introduce a decay parameter β which exponentially grows with increasing vortex ring confinement ratio, the ratio of the vortex ring diameter ( D VR) to the confinement diameter ( D), with the relationship β=4.38 exp(9.5D_VR/D), resulting in a corresponding increase in the rate of vortex ring circulation decay. This work enables the prediction of circulation decay rate based on confinement, which is important to understanding naturally occurring confined vortex ring dynamics.
International Nuclear Information System (INIS)
Ninomiya, H.
2005-01-01
This paper summarizes the results presented at the 20th IAEA Fusion Energy Conference 2004 in the sessions of confinement, plasma-wall interaction and innovative confinement concept. The highlights of the presentations are as follows. Long pulse operation with high beta and high bootstrap fraction much longer than the current diffusion time has been achieved. The discharge scenario optimization and its extrapolation towards ITER have progressed remarkably. Significant progress has been made in understanding of global confinement and transport physics. (author)
International Nuclear Information System (INIS)
Marier, D.
1992-01-01
This article presents the results of a financial rankings survey which show a strong economic activity in the independent energy industry. The topics of the article include advisor turnover, overseas banks, and the increase in public offerings. The article identifies the top project finance investors for new projects and restructurings and rankings for lenders
Theoretical study of the crossover into hydrodynamic regime in graphene
Ho, Derek; Yudhistira, Indra; Hu, Ben Yu-Kuang; Adam, Shaffique
Experiments on graphene have recently succeeded in entering the hydrodynamic regime, as demonstrated by successful observations of strong violation of Wiedemann-Franz law, the Gurzhi effect and electronic Poiseuille flow. It is known that electronic systems enter the hydrodynamic regime when electron-electron scattering dominates over electron-impurity and electron-phonon scattering. However, a quantitative study of this transition from the Fermi liquid to hydrodynamic regime is still lacking. In view of this, we quantitatively analyze the electron-electron, electron-impurity and electron-phonon scattering rates as a function of temperature, charge doping and disorder (charge puddle) strength. This yields a quantitative understanding of the onset of hydrodynamic electronic behavior in graphene samples. This work is supported by the National Research Foundation of Singapore under its Fellowship program (NRF-NRFF2012-01) and by the Singapore Ministry of Education and Yale-NUS College through Grant No. R-607-265-01312.
Application of neutral-oxygen water regime at NPP
International Nuclear Information System (INIS)
Kruzhilin, G.N.; Dubrovskij, I.S.; Anan'ev, E.P.; Matskevich, E.B.; Gashenko, V.A.; Abakumova, O.N.
1985-01-01
A problem of using neutral-oxyoen water regime at NPP is considered. Data on the successful application of such regime at a national NPP with the VK-50 reactor and at some foreign NPP are given. It is noted that oxygen dissolved in a saltless water flow becomes a steel passivating agent forming a strong oxide film on surfaces of stainless- and carbon steels. After the film formation almost complete inhibition of the oxidation and corrosion processes is observe. The conclusion is drawn on the expediency of using the neutral-oxygen water regime at all the NPP equipped with condensate cleaning devices as well as on a wider use of carbon steels
Cooling in the single-photon regime of optomechanics
Nunnenkamp, Andreas; Borkje, Kjetil; Girvin, Steven
2012-02-01
Optomechanics experiments are rapidly approaching the regime where the radiation pressure of a single photon displaces the mechanical oscillator by more than its zero-point uncertainty. We show that in this limit the power spectrum has multiple sidebands and that the cavity response has several resonances in the resolved-sideband limit [Phys. Rev. Lett. 107, 063602 (2011)]. We then discuss how red-sideband cooling is modified in this nonlinear regime. Using Fermi's Golden rule we calculate the transition rates induced by the optical drive. In the resolved-sideband limit we find multiple cooling resonances for strong single-photon coupling. They lead to non-thermal steady states and are accompanied by multiple mechanical sidebands in the optical output spectrum. Our study provides the tools to detect and take advantage of this novel regime of optomechanics.
Hydrodynamic interaction of swimming organisms in an inertial regime
Li, Gaojin; Ostace, Anca; Ardekani, Arezoo M.
2016-11-01
We numerically investigate the hydrodynamic interaction of swimming organisms at small to intermediate Reynolds number regimes, i.e., Re˜O (0.1 -100 ) , where inertial effects are important. The hydrodynamic interaction of swimming organisms in this regime is significantly different from the Stokes regime for microorganisms, as well as the high Reynolds number flows for fish and birds, which involves strong flow separation and detached vortex structures. Using an archetypal swimmer model, called a "squirmer," we find that the inertial effects change the contact time and dispersion dynamics of a pair of pusher swimmers, and trigger hydrodynamic attraction for two pullers. These results are potentially important in investigating predator-prey interactions, sexual reproduction, and the encounter rate of marine organisms such as copepods, ctenophora, and larvae.
Ductility of reinforced concrete columns confined with stapled strips
International Nuclear Information System (INIS)
Tahir, M.F.; Khan, Q.U.Z.; Shabbir, F.; Sharif, M.B.; Ijaz, N.
2015-01-01
Response of three 150x150x450mm short reinforced concrete (RC) columns confined with different types of confining steel was investigated. Standard stirrups, strips and stapled strips, each having same cross-sectional area, were employed as confining steel around four comer column bars. Experimental work was aimed at probing into the affect of stapled strip confinement on post elastic behavior and ductility level under cyclic axial load. Ductility ratios, strength enhancement factor and core concrete strengths were compared to study the affect of confinement. Results indicate that strength enhancement in RC columns due to strip and stapled strip confinement was not remarkable as compared to stirrup confined column. It was found that as compared to stirrup confined column, stapled strip confinement enhanced the ductility of RC column by 183% and observed axial capacity of stapled strip confined columns was 41 % higher than the strip confined columns. (author)
International Nuclear Information System (INIS)
Ferreira, J.L.; Ferreira, J.G.; Sandonato, G.M.; Damasio, W.C.; Montes, A.; Ludwig, G.O.
1989-08-01
The anomalous particle diffusion in regions near to magnetic confinement walls due to ion acoustic turbulence in superficially confined quiescent plasma is studied comparing the measured diffusion coefficient with the Bohm diffusion coefficient. The plasma diagnostics are carried out using Langmuir probe, electron and ion energy analyzers, emission probes for measuring plasma potential and, mass spectrometer, the purchase of data acquisition system composed by storage unit and signal register interfaced with IBM PC computer is proposed for simultaneous measurements with several diagnostics in the quiescent plasma machine of LAP-INPE operating in pulsed regime. (M.C.K.)
Strong Interaction Studies with PANDA at FAIR
International Nuclear Information System (INIS)
Schönning, Karin
2016-01-01
The Facility for Antiproton and Ion Research (FAIR) in Darmstadt, Germany, provides unique possibilities for a new generation of nuclear-, hadron- and atomic physics experiments. The future PANDA experiment at FAIR will offer a broad physics programme with emphasis on different aspects of hadron physics. Understanding the strong interaction in the perturbative regime remains one of the greatest challenges in contemporary physics and hadrons provide several important keys. In these proceedings, PANDA will be presented along with some high-lights of the planned physics programme
Strong Interaction Studies with PANDA at FAIR
Schönning, Karin
2016-10-01
The Facility for Antiproton and Ion Research (FAIR) in Darmstadt, Germany, provides unique possibilities for a new generation of nuclear-, hadron- and atomic physics experiments. The future PANDA experiment at FAIR will offer a broad physics programme with emphasis on different aspects of hadron physics. Understanding the strong interaction in the perturbative regime remains one of the greatest challenges in contemporary physics and hadrons provide several important keys. In these proceedings, PANDA will be presented along with some high-lights of the planned physics programme.
DEFF Research Database (Denmark)
Nielsen, Per; Nielsen, Henri; Mørk, Jesper
2006-01-01
The interaction of optical pulses in a quantum dot waveguide in the slow-light regime is investigated. Dipole oscillations lead to strong interactions between the two pulses, implying a minimum pulse separation for optical buffer applications.......The interaction of optical pulses in a quantum dot waveguide in the slow-light regime is investigated. Dipole oscillations lead to strong interactions between the two pulses, implying a minimum pulse separation for optical buffer applications....
Computational Support for Alternative Confinement Concepts Basic Plasma Science
Energy Technology Data Exchange (ETDEWEB)
Dalton D. Schnack
2002-12-09
within the radius for perfectly conducting wall stabilization of these modes. In this work we consider cases with up to two resistive walls. Moreover the feedback system is assumed to react to any given Fourier harmonic with an ideal response, in the sense that no spurious harmonics are generated. Successful feedback schemes are shown to be possible. However, a careful choice of the gains, along with the simultaneous feedback on at least 4 or 5 modes, is found to be necessary. (3) Studies of a stable rampdown operating regime for the RFP were performed in collaboration with Los Alamos National Laboratory and the University of Wisconsin. It was found that completely stable mean profiles can be obtained by properly tailoring the decaying time dependence of the toroidal current and magnetic flux. Deviations from optimal decay rates were shown to lead to single helicity (SH) and quasi-single helicity (QSH) states. In all cases the prospects for improved confinement properties were obtained. These results may account for the experimental observation of QSH states when the toroidal current is allowed to decay.
Transient response of Salix cuttings to changing water level regimes
Gorla, L.; Signarbieux, C.; Turberg, P.; Buttler, A.; Perona, P.
2015-03-01
Sustainable water management requires an understanding of the effects of flow regulation on riparian ecomorphological processes. We investigated the transient response of Salix viminalis by examining the effect of water-level regimes on its above-ground and below-ground biomass. Four sets of Salix cuttings, three juveniles (in the first growing season) and one mature (1 year old), were planted and initially grown under the same water-level regime for 1 month. We imposed three different water-level regime treatments representing natural variability, a seasonal trend with no peaks, and minimal flow (characteristic of hydropower) consisting of a constant water level and natural flood peaks. We measured sap flux, stem water potential, photosynthesis, growth parameters, and final root architecture. The mature cuttings were not affected by water table dynamics, but the juveniles displayed causal relationships between the changing water regime, plant growth, and root distribution during a 2 month transient period. For example, a 50% drop in mean sap flux corresponded with a -1.5 Mpa decrease in leaf water potential during the first day after the water regime was changed. In agreement with published field observations, the cuttings concentrated their roots close to the mean water table of the corresponding treatment, allowing survival under altered conditions and resilience to successive stress events. Juvenile development was strongly impacted by the minimum flow regime, leading to more than 60% reduction of both above-ground and below-ground biomass, with respect to the other treatments. Hence, we suggest avoiding minimum flow regimes where Salix restoration is prioritized.
Strong Electroweak Symmetry Breaking
Grinstein, Benjamin
2011-01-01
Models of spontaneous breaking of electroweak symmetry by a strong interaction do not have fine tuning/hierarchy problem. They are conceptually elegant and use the only mechanism of spontaneous breaking of a gauge symmetry that is known to occur in nature. The simplest model, minimal technicolor with extended technicolor interactions, is appealing because one can calculate by scaling up from QCD. But it is ruled out on many counts: inappropriately low quark and lepton masses (or excessive FCNC), bad electroweak data fits, light scalar and vector states, etc. However, nature may not choose the minimal model and then we are stuck: except possibly through lattice simulations, we are unable to compute and test the models. In the LHC era it therefore makes sense to abandon specific models (of strong EW breaking) and concentrate on generic features that may indicate discovery. The Technicolor Straw Man is not a model but a parametrized search strategy inspired by a remarkable generic feature of walking technicolor,...
Plasmons in strong superconductors
International Nuclear Information System (INIS)
Baldo, M.; Ducoin, C.
2011-01-01
We present a study of the possible plasmon excitations that can occur in systems where strong superconductivity is present. In these systems the plasmon energy is comparable to or smaller than the pairing gap. As a prototype of these systems we consider the proton component of Neutron Star matter just below the crust when electron screening is not taken into account. For the realistic case we consider in detail the different aspects of the elementary excitations when the proton, electron components are considered within the Random-Phase Approximation generalized to the superfluid case, while the influence of the neutron component is considered only at qualitative level. Electron screening plays a major role in modifying the proton spectrum and spectral function. At the same time the electron plasmon is strongly modified and damped by the indirect coupling with the superfluid proton component, even at moderately low values of the gap. The excitation spectrum shows the interplay of the different components and their relevance for each excitation modes. The results are relevant for neutrino physics and thermodynamical processes in neutron stars. If electron screening is neglected, the spectral properties of the proton component show some resemblance with the physical situation in high-T c superconductors, and we briefly discuss similarities and differences in this connection. In a general prospect, the results of the study emphasize the role of Coulomb interaction in strong superconductors.
Climate Change and Future Fire Regimes: Examples from California
Directory of Open Access Journals (Sweden)
Jon E. Keeley
2016-08-01
Full Text Available Climate and weather have long been noted as playing key roles in wildfire activity, and global warming is expected to exacerbate fire impacts on natural and urban ecosystems. Predicting future fire regimes requires an understanding of how temperature and precipitation interact to control fire activity. Inevitably this requires historical analyses that relate annual burning to climate variation. Fuel structure plays a critical role in determining which climatic parameters are most influential on fire activity, and here, by focusing on the diversity of ecosystems in California, we illustrate some principles that need to be recognized in predicting future fire regimes. Spatial scale of analysis is important in that large heterogeneous landscapes may not fully capture accurate relationships between climate and fires. Within climatically homogeneous subregions, montane forested landscapes show strong relationships between annual fluctuations in temperature and precipitation with area burned; however, this is strongly seasonal dependent; e.g., winter temperatures have very little or no effect but spring and summer temperatures are critical. Climate models that predict future seasonal temperature changes are needed to improve fire regime projections. Climate does not appear to be a major determinant of fire activity on all landscapes. Lower elevations and lower latitudes show little or no increase in fire activity with hotter and drier conditions. On these landscapes climate is not usually limiting to fires but these vegetation types are ignition-limited. Moreover, because they are closely juxtaposed with human habitations, fire regimes are more strongly controlled by other direct anthropogenic impacts. Predicting future fire regimes is not rocket science; it is far more complicated than that. Climate change is not relevant to some landscapes, but where climate is relevant, the relationship will change due to direct climate effects on vegetation
Climate change and future fire regimes: Examples from California
Keeley, Jon E.; Syphard, Alexandra D.
2016-01-01
Climate and weather have long been noted as playing key roles in wildfire activity, and global warming is expected to exacerbate fire impacts on natural and urban ecosystems. Predicting future fire regimes requires an understanding of how temperature and precipitation interact to control fire activity. Inevitably this requires historical analyses that relate annual burning to climate variation. Fuel structure plays a critical role in determining which climatic parameters are most influential on fire activity, and here, by focusing on the diversity of ecosystems in California, we illustrate some principles that need to be recognized in predicting future fire regimes. Spatial scale of analysis is important in that large heterogeneous landscapes may not fully capture accurate relationships between climate and fires. Within climatically homogeneous subregions, montane forested landscapes show strong relationships between annual fluctuations in temperature and precipitation with area burned; however, this is strongly seasonal dependent; e.g., winter temperatures have very little or no effect but spring and summer temperatures are critical. Climate models that predict future seasonal temperature changes are needed to improve fire regime projections. Climate does not appear to be a major determinant of fire activity on all landscapes. Lower elevations and lower latitudes show little or no increase in fire activity with hotter and drier conditions. On these landscapes climate is not usually limiting to fires but these vegetation types are ignition-limited. Moreover, because they are closely juxtaposed with human habitations, fire regimes are more strongly controlled by other direct anthropogenic impacts. Predicting future fire regimes is not rocket science; it is far more complicated than that. Climate change is not relevant to some landscapes, but where climate is relevant, the relationship will change due to direct climate effects on vegetation trajectories, as well as
Strongly interacting photons and atoms
International Nuclear Information System (INIS)
Alge, W.
1999-05-01
This thesis contains the main results of the research topics I have pursued during the my PhD studies at the University of Innsbruck and partly in collaboration with the Institut d' Optique in Orsay, France. It is divided into three parts. The first and largest part discusses the possibility of using strong standing waves as a tool to cool and trap neutral atoms in optical cavities. This is very important in the field of nonlinear optics where several successful experiments with cold atoms in cavities have been performed recently. A discussion of the optical parametric oscillator in a regime where the nonlinearity dominates the evolution is the topic of the second part. We investigated mainly the statistical properties of the cavity output of the three interactive cavity modes. Very recently a system has been proposed which promises fantastic properties. It should exhibit a giant Kerr nonlinearity with negligible absorption thus leading to a photonic turnstile device based on cold atoms in cavity. We have shown that this model suffers from overly simplistic assumptions and developed several more comprehensive approaches to study the behavior of this system. Apart from the division into three parts of different contents the thesis is divided into publications, supplements and invisible stuff. The intention of the supplements is to reach researchers which work in related areas and provide them with more detailed information about the concepts and the numerical tools we used. It is written especially for diploma and PhD students to give them a chance to use the third part of our work which is actually the largest one. They consist of a large number of computer programs we wrote to investigate the behavior of the systems in parameter regions where no hope exists to solve the equations analytically. (author)
Energy Technology Data Exchange (ETDEWEB)
Bayer, Ch.; Juraszek, D
2001-07-01
Inertial Confinement Fusion (ICF) is an approach to thermonuclear fusion in which the fuel contained in a spherical capsule is strongly compressed and heated to achieve ignition and burn. The released thermonuclear energy can be much higher than the driver energy, making energetic applications attractive. Many complex physical phenomena are involved by the compression process, but it is possible to use simple analytical models to analyze the main critical points. We first determine the conditions to obtain fuel ignition. High thermonuclear gains are achieved if only a small fraction of the fuel called hot spot is used to trigger burn in the main fuel compressed on a low isentrope. A simple hot spot model will be described. The high pressure needed to drive the capsule compression are obtained by the ablation process. A simple Rocket model describe the main features of the implosion phase. Several parameters have to be controlled during the compression: irradiation symmetry, hydrodynamical stability and when the driver is a laser, the problems arising from interaction of the EM wave with the plasma. Two different schemes are examined: Indirect Drive which uses X-ray generated in a cavity to drive the implosion and the Fast Ignitor concept using a ultra intense laser beam to create the hot spot. At the end we present the Laser Megajoule (LMJ) project. LMJ is scaled to a thermonuclear gain of the order of ten. (authors)
Regime Change and the Role of Airpower
National Research Council Canada - National Science Library
Fahrenkrug, David T
2006-01-01
Drawing from the vision of airpower theorists and building on insights gained from studies on various regime changes, this thesis advances a theory of regime change and outlines a strategy for the use of airpower...
Regime Change and the Role of Airpower
National Research Council Canada - National Science Library
Fahrenkrug, David
2003-01-01
Drawing from the vision of airpower theorists, and building on insights gained from studies on various regime changes, this thesis advances a theory of regime change and outlines a strategy for the use of airpower...
HTR confinement/containment and the protection against aircraft crash
International Nuclear Information System (INIS)
Brinkmann, G.
2005-01-01
Does an HTR need a containment-pressure resistant-or is it possible- licensable-to have only a so called confinement. The answer depends on both the results of the safety analysis of the accidents considered in the design and the acceptance by the licensing authorities and the public of a safety approach only based on severe core damage exclusion. The safety approach to be developed for modular HTRs must describe the application of the defence in depth principle for such reactors. Whatever the requirements on the last confinement barrier could be, a convincing demonstration of the exclusion of any severe core damage is needed, relying on exhaustive and bounding considerations of severe core damage initiators and the use of non questionable arguments. The paper presents the containment issues for HTRs based on German experience background and considerations for modern modular HTR safety approach including beyond design situations. For the German HTRs (designed in the 80s), it could be shown in the licensing procedures in Germany that there was no need for a pressure retaining and gas tight containment to enclose radioactive nuclides released from the nuclear heat source. Instead, the confinement envelope acted in conjunction with other barriers to minimize the release of radioactive nuclides and the radiological impact on the environment. The confinement envelope consisted of the reactor building, a sub-atmospheric pressure system, a building pressure relief system, an HVAC systems isolation and a filtration system. During a major depressurization accident, unfiltered releases were discharged to the environment. The analyses results show that the environmental impact was far below the dose limits according to the German Radiological Protection Ordinance, even when the effect of filters was not taken into account. The demonstration strongly relied on the assumptions made for the source term definition e. g. the fuel particles failure rates (under irradiation and
Transport scaling in the collisionless-detrapping regime in stellarators
International Nuclear Information System (INIS)
Crume, E.C. Jr.; Shaing, K.C.; Hirshman, S.P.; van Rij, W.I.
1987-09-01
Stellarator transport scalings with electric field, geometry, and collision frequency in the reactor-relevant collisionless-detrapping regime are determined from numerical solutions of the drift kinetic equation. A new geometrical scaling, proportional to ε/sub t/sup 3/2/ rather than ε/sub t/ε/sub h/sup 1/2/, is found, where ε/sub t/ is the inverse aspect ratio and ε/sub h/ is the helical ripple. With the new scaling, no reduction in energy confinement time is associated with large helical ripple, which provides design flexibility. Integral expressions for the particle and heat fluxes that are useful for transport simulations are given. 11 refs
Confined catalysis under two-dimensional materials
Li, Haobo; Xiao, Jianping; Bao, Xinhe
2017-01-01
Confined microenvironments formed in heterogeneous catalysts have recently been recognized as equally important as catalytically active sites. Understanding the fundamentals of confined catalysis has become an important topic in heterogeneous catalysis. Well-defined 2D space between a catalyst surface and a 2D material overlayer provides an ideal microenvironment to explore the confined catalysis experimentally and theoretically. Using density functional theory calculations, we reveal that adsorption of atoms and molecules on a Pt(111) surface always has been weakened under monolayer graphene, which is attributed to the geometric constraint and confinement field in the 2D space between the graphene overlayer and the Pt(111) surface. A similar result has been found on Pt(110) and Pt(100) surfaces covered with graphene. The microenvironment created by coating a catalyst surface with 2D material overlayer can be used to modulate surface reactivity, which has been illustrated by optimizing oxygen reduction reaction activity on Pt(111) covered by various 2D materials. We demonstrate a concept of confined catalysis under 2D cover based on a weak van der Waals interaction between 2D material overlayers and underlying catalyst surfaces. PMID:28533413
Reinforced confinement in a nuclear reactor
International Nuclear Information System (INIS)
Norman, H.
1988-01-01
The present invention concerns a nuclear reactor containing a reactor core, a swimming pool space that is filled and pressurized with a neutron-absorbing solution, a reactor tank, at least one heat exchanger, at least one inlet line, at least one return line and at least one circulation pump, where the said reactor tank is confined in the said swimming pool space and designed to be cooled with the aid of relatively pure water, which is fed by means of the said at least one circulating pump to the said reactor tank from the said heat exchanger via the said at least one inlet line and is returned to the heat exchanger via the said at least one return line. The problem that is to be solved by the invention is to design a reactor of the above type in such a way that a complete confinement of the primary circuit of the reactor is achieved at relatively low extra cost. This problem is solved by providing the reactor with a special confinement space that confines the heat exchanger, but not the reactor tank, with the confinement space and the swimming pool space being fashioned in the same concrete body
Packing frustration in dense confined fluids.
Nygård, Kim; Sarman, Sten; Kjellander, Roland
2014-09-07
Packing frustration for confined fluids, i.e., the incompatibility between the preferred packing of the fluid particles and the packing constraints imposed by the confining surfaces, is studied for a dense hard-sphere fluid confined between planar hard surfaces at short separations. The detailed mechanism for the frustration is investigated via an analysis of the anisotropic pair distributions of the confined fluid, as obtained from integral equation theory for inhomogeneous fluids at pair correlation level within the anisotropic Percus-Yevick approximation. By examining the mean forces that arise from interparticle collisions around the periphery of each particle in the slit, we calculate the principal components of the mean force for the density profile--each component being the sum of collisional forces on a particle's hemisphere facing either surface. The variations of these components with the slit width give rise to rather intricate changes in the layer structure between the surfaces, but, as shown in this paper, the basis of these variations can be easily understood qualitatively and often also semi-quantitatively. It is found that the ordering of the fluid is in essence governed locally by the packing constraints at each single solid-fluid interface. A simple superposition of forces due to the presence of each surface gives surprisingly good estimates of the density profiles, but there remain nontrivial confinement effects that cannot be explained by superposition, most notably the magnitude of the excess adsorption of particles in the slit relative to bulk.
EFFECT OF SHEAR ON THE DESORPTION OF OLIGOMERS IN NANOSCOPICALLY CONFINED FILMS
MANIAS, E; HADZIIOANNOU, G; TENBRINKE, G
1994-01-01
Bitsanis et al. J. Chem. Phys. 99, 5520 (1993) found that in nanoscopically confined films between strongly physisorbing surfaces chains with many contacts with the walls are irreversibly adsorbed. When shear is imposed to these systems molecular dynamics (MD) simulations show that the majority of
Can Old Regimes Handle New Wars?
DEFF Research Database (Denmark)
Henningsen, Troels
strengthen Islamist insurgents. Using a comparative case study of the regimes in Chad and Mali from 2003 to 2016 and applying a theoretical framework of regime survival in states with internal anarchy, this paper explains how regimes in the Sahel region defend themselves against insurgents. Surprisingly...
Implementation Regimes and Street-Level Bureaucrats
DEFF Research Database (Denmark)
Winter, Søren; T. Dinesen, Peter; J. May, Peter
-government regimes foster greater policy commitment, attention to rules, and adherence among frontline workers than is the case for a local-government implementation regime. These lead to actions of street-level bureaucrats in central-government regimes that are more in line with national policies than those...
Strong-coupling approximations
International Nuclear Information System (INIS)
Abbott, R.B.
1984-03-01
Standard path-integral techniques such as instanton calculations give good answers for weak-coupling problems, but become unreliable for strong-coupling. Here we consider a method of replacing the original potential by a suitably chosen harmonic oscillator potential. Physically this is motivated by the fact that potential barriers below the level of the ground-state energy of a quantum-mechanical system have little effect. Numerically, results are good, both for quantum-mechanical problems and for massive phi 4 field theory in 1 + 1 dimensions. 9 references, 6 figures
International Nuclear Information System (INIS)
Ebata, T.
1981-01-01
With an assumed weak multiplet structure for bosonic hadrons, which is consistent with the ΔI = 1/2 rule, it is shown that the strong interaction effective hamiltonian is compatible with the weak SU(2) x U(1) gauge transformation. Especially the rho-meson transforms as a triplet under SU(2)sub(w), and this is the origin of the rho-photon analogy. It is also shown that the existence of the non-vanishing Cabibbo angle is a necessary condition for the absence of the exotic hadrons. (orig.)
Quantum Transport in Strongly Correlated Systems
DEFF Research Database (Denmark)
Bohr, Dan
2007-01-01
the density matrix renormalization group (DMRG) method. We present two DMRG setups for calculating the linear conductance of strongly correlated nanostructures in the infinitesimal source-drain voltage regime. The first setup describes the leads by modified real-space tight-binding chains, whereas the second...... screening plays a much less significant role than in bulk systems due to the reduced size of the objects, therefore making it necessary to consider the importance of correlations between electrons. The work presented in this thesis deals with quantum transport through strongly correlated systems using....... Thus both coherence and correlation effects are important in this model, and the methods applied should be able to handle both these effects rigorously. We present the DMRG setup for this model and benchmark against existing Greens function results for the model. Then we present initial DMRG results...
Strong Josephson Coupling in Planar Graphene Junctions
Park, Jinho; Lee, Gil-Ho; Lee, Jae Hyeong; Takane, Yositake; Imura, Ken-Ichiro; Taniguchi, Takashi; Watanabe, Kenji; Lee, Hu-Jong
A recent breakthrough of processing graphene, employing encapsulation by hexagonal boron nitride layers (BGB structure), allows realizing the ballistic carrier transport in graphene. Thereafter, ballistic Josephson coupling has been studied by closely edge-contacted BGB structure with two superconducting electrodes. Here, we report on the strong Josephson coupling with planar graphene junction in truly short and ballistic regime. Our device showed high transmission probability and the junction critical current (IC) oscillating for sweeping the gate voltage along with the normal conductance oscillation (Fabry-Perot oscillations), providing a direct evidence for the ballistic nature of the junction pair current. We also observed the convex-upward shape of decreasing critical currents with increasing temperature, canonical properties of the short Josephson coupling. By fitting these curves into theoretical models, we demonstrate the strong Josephson coupling in our devices, which is also supported by the exceptionally large value of ICRN ( 2 Δ / e RNis the normal resistance).
Transition metal catalysis in confined spaces.
Leenders, Stefan H A M; Gramage-Doria, Rafael; de Bruin, Bas; Reek, Joost N H
2015-01-21
Transition metal catalysis plays an important role in both industry and in academia where selectivity, activity and stability are crucial parameters to control. Next to changing the structure of the ligand, introducing a confined space as a second coordination sphere around a metal catalyst has recently been shown to be a viable method to induce new selectivity and activity in transition metal catalysis. In this review we focus on supramolecular strategies to encapsulate transition metal complexes with the aim of controlling the selectivity via the second coordination sphere. As we will discuss, catalyst confinement can result in selective processes that are impossible or difficult to achieve by traditional methods. We will describe the template-ligand approach as well as the host-guest approach to arrive at such supramolecular systems and discuss how the performance of the catalyst is enhanced by confining it in a molecular container.
Dvali, Gia
2009-01-01
We show that whenever a 4-dimensional theory with N particle species emerges as a consistent low energy description of a 3-brane embedded in an asymptotically-flat (4+d)-dimensional space, the holographic scale of high-dimensional gravity sets the strong coupling scale of the 4D theory. This connection persists in the limit in which gravity can be consistently decoupled. We demonstrate this effect for orbifold planes, as well as for the solitonic branes and string theoretic D-branes. In all cases the emergence of a 4D strong coupling scale from bulk holography is a persistent phenomenon. The effect turns out to be insensitive even to such extreme deformations of the brane action that seemingly shield 4D theory from the bulk gravity effects. A well understood example of such deformation is given by large 4D Einstein term in the 3-brane action, which is known to suppress the strength of 5D gravity at short distances and change the 5D Newton's law into the four-dimensional one. Nevertheless, we observe that the ...
Higher representations: Confinement and large N
International Nuclear Information System (INIS)
Sannino, Francesco
2005-01-01
We investigate the confining phase transition as a function of temperature for theories with dynamical fermions in the two index symmetric and antisymmetric representation of the gauge group. By studying the properties of the center of the gauge group we predict for an even number of colors a confining phase transition, if second order, to be in the universality class of Ising in three dimensions. This is due to the fact that the center group symmetry does not break completely for an even number of colors. For an odd number of colors the center group symmetry breaks completely. This pattern remains unaltered at a large number of colors. The confining/deconfining phase transition in these theories at large and finite N is not mapped in the one of super Yang-Mills theory. We extend the Polyakov loop effective theory to describe the confining phase transition of the theories studied here for a generic number of colors. Our results are not modified when adding matter in the same higher dimensional representations of the gauge group. We comment on the interplay between confinement and chiral symmetry in these theories and suggest that they are ideal laboratories to shed light on this issue also for ordinary QCD. We compare the free energy as a function of temperature for different theories. We find that the conjectured thermal inequality between the infrared and ultraviolet degrees of freedom computed using the free energy does not lead to new constraints on asymptotically free theories with fermions in higher dimensional representations of the gauge group. Since the center of the gauge group is an important quantity for the confinement properties at zero temperature our results are relevant here as well
Characteristics of global strong earthquakes and their implications ...
Indian Academy of Sciences (India)
Home; Journals; Journal of Earth System Science; Volume 126; Issue 7. Characteristics of global strong earthquakes and their implications for ... We grouped 518 of them into 12 regions (Boxes) based on their geographical proximity and tectonic setting. For each box, the present-day stress field and regime were obtained ...
Electron dynamics in metals and semiconductors in strong THz fields
DEFF Research Database (Denmark)
Jepsen, Peter Uhd
2017-01-01
Semiconductors and metals respond to strong electric fields in a highly nonlinear fashion. Using single-cycle THz field transients it is possible to investigate this response in regimes not accessible by transport-based measurements. Extremely high fields can be applied without material damage...
Strong-field-ionization suppression by light-field control
DEFF Research Database (Denmark)
Räsänen, Esa; Madsen, Lars Bojer
2012-01-01
in the intensity and thus preventing tunneling. In contrast, at high frequencies in the extreme ultraviolet regime the optimized pulses strongly couple with the (de)-excitations of the system, which leads to different pulse characteristics. Finally, we show that the applied target functional works, to some extent...
Resonances of the helium atom in a strong magnetic field
DEFF Research Database (Denmark)
Lühr, Armin Christian; Al-Hujaj, Omar-Alexander; Schmelcher, Peter
2007-01-01
We present an investigation of the resonances of a doubly excited helium atom in a strong magnetic field covering the regime B=0–100 a.u. A full-interaction approach which is based on an anisotropic Gaussian basis set of one-particle functions being nonlinearly optimized for each field strength...
Characteristics of global strong earthquakes and their implications ...
Indian Academy of Sciences (India)
Ju Wei
2017-10-06
Oct 6, 2017 ... compiled in the Global/Harvard centroid moment tensor (CMT) catalogue, the characteristics of global strong earthquakes and the present-day stress pattern were analyzed based on these ...... the WSM standard were calculated for individual mechanism (figure 2). Generally, the most common stress regime ...
Nonadiabatic effects in the Quantum Hall regime
International Nuclear Information System (INIS)
Page, D.A.; Brown, E.
1993-01-01
The authors consider the effect of a finite electric field on the states of a Bloch electron in two dimensions, with a uniform magnetic field present. They make use of the concept of electric time translation symmetry and treat the electric and magnetic fields symmetrically in a time dependent formalism. In addition to a wave vector k, the states are characterized by a frequency specifying the behavior under electric time translations. An effective Hamiltonian is employed to obtain the splitting of an isolated Bloch band into open-quotes frequencyclose quotes subbands. The time-averaged velocity and energy of the states are expressed in terms of the frequency dispersion. The relationship to the Stark ladder eigenstates in a scalar potential representation of the electric field is examined. This is seen to justify the use of the averaged energy in determining occupation of the states. In the weak electric field (adiabatic) limit, an expression is recovered for the quantized Hall conductivity of a magnetic subband as a topological invariant. A numerical procedure is outlined and results obtained over a range of electric field strengths. A transition between strong and weak field regimes is seen, with level repulsions between the frequencies playing an important role. The numerical results show how the magnetic subband structure and quantized Hall conductivity emerge as the electric field becomes weaker. In this regime, the behavior can be understood by comparison to the predictions of the adiabatic approximation. The latter predicts crossings in the frequencies at certain locations in wave vector space. Nonadiabatic effects are seen to produce gaps in the frequency spectrum at these locations. 35 refs., 14 figs
Synchrotron radiation in strongly coupled conformal field theories
Athanasiou, Christiana; Chesler, Paul M.; Liu, Hong; Nickel, Dominik; Rajagopal, Krishna
2010-01-01
Using gauge/gravity duality, we compute the energy density and angular distribution of the power radiated by a quark undergoing circular motion in strongly coupled ${\\cal N}=4$ supersymmetric Yang-Mills (SYM) theory. We compare the strong coupling results to those at weak coupling, and find the same angular distribution of radiated power, up to an overall prefactor. In both regimes, the angular distribution is in fact similar to that of synchrotron radiation produced by an electron in circula...
High-field penning-malmberg trap: confinement properties and use in positron accumulation
Energy Technology Data Exchange (ETDEWEB)
Hartley, J.H.
1997-09-01
This dissertation reports on the development of the 60 kG cryogenic positron trap at Lawrence Livermore National Laboratory, and compares the trap`s confinement properties with other nonneutral plasma devices. The device is designed for the accumulation of up to 2{times}10{sup 9} positrons from a linear-accelerator source. This positron plasma could then be used in Bhabha scattering experiments. Initial efforts at time-of-flight accumulation of positrons from the accelerator show rapid ({approximately}100 ms) deconfinement, inconsistent with the long electron lifetimes. Several possible deconfinement mechanisms have been explored, including annihilation on residual gas, injection heating, rf noise from the accelerator, magnet field curvature, and stray fields. Detailed studies of electron confinement demonstrate that the empirical scaling law used to design the trap cannot be extrapolated into the parameter regime of this device. Several possible methods for overcoming these limitations are presented.
On the ionization and burnout processes of a magnetically confined plasma
International Nuclear Information System (INIS)
Lehnert, B.
1977-10-01
The particle and heat balance during plasma start-up are investigates, to specify the conditions for reaching various ion density ranges and high plasma temperatures in cases of a limited heating power. Particular attention is paid to the permeable-impermeable transition regime of plasmas being subject to Ohmic heating and confined in closed or open bottles with a main poloidal field. The ionization and burnout conditions are found to depend critically on the confinement and the filling density. They become optimal in closed bottles under symmetric and stable conditions, where the transition into a fully ionized state should be reached even at moderately large ionization rates, burnout powers and currents. Start-up methods based on constant as well as on variable filling densities are discussed as means of ion density control.(author)
High-gain direct-drive inertial confinement fusion for the Laser Megajoule: recent progress
International Nuclear Information System (INIS)
Canaud, B; Garaude, F; Ballereau, P; Bourgade, J L; Clique, C; Dureau, D; Houry, M; Jaouen, S; Jourdren, H; Lecler, N; Masse, L; Masson, A; Quach, R; Piron, R; Riz, D; Vliet, J van der; Temporal, M; Delettrez, J A; McKenty, P W
2007-01-01
Recent progress in high-gain direct-drive inertial confinement fusion with the laser Megajoule is reviewed. A new baseline direct-drive target design is presented which implodes with a two-cones irradiation pattern of indirect-drive beam configuration and zooming. Perturbation amplitudes and correlated growth rates of hydrodynamic instabilities in the compressed core of a directly driven inertial confinement fusion capsule are analyzed in planar and spherical geometries, with and without heat conduction, in the unsteady state regime of the deceleration. Shock propagation in heterogeneous media is addressed in the context of first shock. The neutron and photon emissions of high-gain direct-drive target are characterized. Numerical interpretations of directly driven homothetic cryogenic D 2 target implosion experiments on the Omega facility are presented
High-gain direct-drive inertial confinement fusion for the Laser Megajoule: recent progress
Energy Technology Data Exchange (ETDEWEB)
Canaud, B [CEA/DAM Ile-de-France, BP12, F-91680 Bruyeres-le-Chatel, Cedex (France); Garaude, F [CEA/DAM Ile-de-France, BP12, F-91680 Bruyeres-le-Chatel, Cedex (France); Ballereau, P [CEA/DAM Ile-de-France, BP12, F-91680 Bruyeres-le-Chatel, Cedex (France); Bourgade, J L [CEA/DAM Ile-de-France, BP12, F-91680 Bruyeres-le-Chatel, Cedex (France); Clique, C [CEA/DAM Ile-de-France, BP12, F-91680 Bruyeres-le-Chatel, Cedex (France); Dureau, D [CEA/DAM Ile-de-France, BP12, F-91680 Bruyeres-le-Chatel, Cedex (France); Houry, M [CEA/DAM Ile-de-France, BP12, F-91680 Bruyeres-le-Chatel, Cedex (France); Jaouen, S [CEA/DAM Ile-de-France, BP12, F-91680 Bruyeres-le-Chatel, Cedex (France); Jourdren, H [CEA/DAM Ile-de-France, BP12, F-91680 Bruyeres-le-Chatel, Cedex (France); Lecler, N [CEA/DAM Ile-de-France, BP12, F-91680 Bruyeres-le-Chatel, Cedex (France); Masse, L [CEA/DAM Ile-de-France, BP12, F-91680 Bruyeres-le-Chatel, Cedex (France); Masson, A [CEA/DAM Ile-de-France, BP12, F-91680 Bruyeres-le-Chatel, Cedex (France); Quach, R [CEA/DAM Ile-de-France, BP12, F-91680 Bruyeres-le-Chatel, Cedex (France); Piron, R [CEA/DAM Ile-de-France, BP12, F-91680 Bruyeres-le-Chatel, Cedex (France); Riz, D [CEA/DAM Ile-de-France, BP12, F-91680 Bruyeres-le-Chatel, Cedex (France); Vliet, J van der [CEA/DAM Ile-de-France, BP12, F-91680 Bruyeres-le-Chatel, Cedex (France); Temporal, M [Calle Grau, 685, Sucre (Bolivia); Delettrez, J A [Laboratory of Laser Energetics, University of Rochester, 250 East River Road, Rochester, NY 14623 (United States); McKenty, P W [Laboratory of Laser Energetics, University of Rochester, 250 East River Road, Rochester, NY 14623 (United States)
2007-12-15
Recent progress in high-gain direct-drive inertial confinement fusion with the laser Megajoule is reviewed. A new baseline direct-drive target design is presented which implodes with a two-cones irradiation pattern of indirect-drive beam configuration and zooming. Perturbation amplitudes and correlated growth rates of hydrodynamic instabilities in the compressed core of a directly driven inertial confinement fusion capsule are analyzed in planar and spherical geometries, with and without heat conduction, in the unsteady state regime of the deceleration. Shock propagation in heterogeneous media is addressed in the context of first shock. The neutron and photon emissions of high-gain direct-drive target are characterized. Numerical interpretations of directly driven homothetic cryogenic D{sub 2} target implosion experiments on the Omega facility are presented.
Chong, Kai Leong; Yang, Yantao; Huang, Shi-Di; Zhong, Jin-Qiang; Stevens, Richard J A M; Verzicco, Roberto; Lohse, Detlef; Xia, Ke-Qing
2017-08-11
Many natural and engineering systems are simultaneously subjected to a driving force and a stabilizing force. The interplay between the two forces, especially for highly nonlinear systems such as fluid flow, often results in surprising features. Here we reveal such features in three different types of Rayleigh-Bénard (RB) convection, i.e., buoyancy-driven flow with the fluid density being affected by a scalar field. In the three cases different stabilizing forces are considered, namely (i) horizontal confinement, (ii) rotation around a vertical axis, and (iii) a second stabilizing scalar field. Despite the very different nature of the stabilizing forces and the corresponding equations of motion, at moderate strength we counterintuitively but consistently observe an enhancement in the flux, even though the flow motion is weaker than the original RB flow. The flux enhancement occurs in an intermediate regime in which the stabilizing force is strong enough to alter the flow structures in the bulk to a more organized morphology, yet not too strong to severely suppress the flow motions. Near the optimal transport enhancements all three systems exhibit a transition from a state in which the thermal boundary layer (BL) is nested inside the momentum BL to the one with the thermal BL being thicker than the momentum BL. The observed optimal transport enhancement is explained through an optimal coupling between the suction of hot or fresh fluid and the corresponding scalar fluctuations.
Measuring the effectiveness of international environmental regimes
Energy Technology Data Exchange (ETDEWEB)
Helm, C.; Sprinz, D.F.
1999-05-01
While past research has emphasized the importance of international regimes for international governance, systematic assessments of regime effects are missing. This article derives a standardized measurement concept for the effectiveness of international environmental regimes by developing an operational rational choice calculus to evaluate actual policy simultaneously against a non-regime counterfactual and a collective optimum. Subsequently, the empirical feasibility of the measurement instrument is demonstrated by way of two international treaties regulating transboundary air pollution in Europe. The results demonstrate that the regimes indeed show positive effects - but fall substantially short of the collective optima. (orig.)
Adaptation in Collaborative Governance Regimes
Emerson, Kirk; Gerlak, Andrea K.
2014-10-01
Adaptation and the adaptive capacity of human and environmental systems have been of central concern to natural and social science scholars, many of whom characterize and promote the need for collaborative cross-boundary systems that are seen as flexible and adaptive by definition. Researchers who study collaborative governance systems in the public administration, planning and policy literature have paid less attention to adaptive capacity specifically and institutional adaptation in general. This paper bridges the two literatures and finds four common dimensions of capacity, including structural arrangements, leadership, knowledge and learning, and resources. In this paper, we focus on institutional adaptation in the context of collaborative governance regimes and try to clarify and distinguish collaborative capacity from adaptive capacity and their contributions to adaptive action. We posit further that collaborative capacities generate associated adaptive capacities thereby enabling institutional adaptation within collaborative governance regimes. We develop these distinctions and linkages between collaborative and adaptive capacities with the help of an illustrative case study in watershed management within the National Estuary Program.
Equilibria, Stability, and Transport of AN Ion Ring Confined Plasma.
Sparks, Lawrence Craig
This thesis studies various aspects of a fusion plasma magnetically confined in an axisymmetric field reversed geometry with no toroidal field, where part of the total azimuthal current is carried by a ring of energetic large orbit ions: (1) Two new methods are presented for efficiently computing ion ring equilibria in parameter regimes of physical interest. (2) Ideal magnetodydrodynamic stability is analyzed in the high toroidal mode number limit, where the ion ring can be taken to be noninteracting. A numerical study of field reversed configurations both with and without ring currents shows that plasma compression can stabilize interchange perturbations. High (beta) interchange stability is found to favor a peaked ring current density profile rather than one which is hollowed out in the region of plasma confinement. Stability to perturbations which bend magnetic field lines (e.g., ballooning modes) is also found to improve as the ring current density profile becomes more peaked. (3) The equations of motion for incompressible mode perturbations in the vicinity of the vortex point are solved analytically to obtain the ballooning stability condition F > (1 + (VBAR)(epsilon)(VBAR))/2 where F is the fraction of the current density carried by the ring ions and (epsilon) is the flux surface ellipticity. Higher order corrections to the eigenfrequencies due to compressional effects are obtained in the limit of circular flux surfaces. (4) Modeling the ring as an exponential rigid rotor, an iterative procedure is used to obtain optimal values of E(,P)/E(,R), the ratio of the total energy of the confined plasma to the total ring energy. Magnetohydrodynamically stable equilibria are obtained with E(,P)/E(,R(, )) (where B(,o) is the magnitude of the applied field and brackets indicate a volume average) varies between 1 and 7. (5) Classical mass and heat transport on time scales short compared to the ring decay time are analyzed using simple, steady state models. Mass flow is
Strong Turbulence in Low-beta Plasmas
DEFF Research Database (Denmark)
Tchen, C. M.; Pécseli, Hans; Larsen, Søren Ejling
1980-01-01
An investigation of the spectral structure of turbulence in a plasma confined by a strong homogeneous magnetic field was made by means of a fluid description. The turbulent spectrum is divided into subranges. Mean gradients of velocity and density excite turbulent motions, and govern the production...... subrange. The spectra of velocity and potential fluctuations interact in the coupling subrange, and the energy is transferred along the spectrum in the inertia subrange. Applying the method of cascade decomposition, the spectral laws k-3, k-3, k-2 are obtained for the velocity fluctuations, and k-3, k-5, k......-3/2 for the potential fluctuations in the production, coupling and inertia subranges, respectively. The coefficient of Bohm diffusion is reproduced, and its role in electrostatic coupling is derived. Comparison is made with measured power laws reported in the literature, from Q-devices, hot...
Strongly Interacting Matter at High Energy Density
International Nuclear Information System (INIS)
McLerran, L.
2008-01-01
This lecture concerns the properties of strongly interacting matter (which is described by Quantum Chromodynamics) at very high energy density. I review the properties of matter at high temperature, discussing the deconfinement phase transition. At high baryon density and low temperature, large N c arguments are developed which suggest that high baryonic density matter is a third form of matter, Quarkyonic Matter, that is distinct from confined hadronic matter and deconfined matter. I finally discuss the Color Glass Condensate which controls the high energy limit of QCD, and forms the low x part of a hadron wavefunction. The Glasma is introduced as matter formed by the Color Glass Condensate which eventually thermalizes into a Quark Gluon Plasma
Strong curvature effects in Neumann wave problems
DEFF Research Database (Denmark)
Willatzen, Morten; Pors, A.; Gravesen, Jens
2012-01-01
Waveguide phenomena play a major role in basic sciences and engineering. The Helmholtz equation is the governing equation for the electric field in electromagnetic wave propagation and the acoustic pressure in the study of pressure dynamics. The Schro¨dinger equation simplifies to the Helmholtz...... equation for a quantum-mechanical particle confined by infinite barriers relevant in semiconductor physics. With this in mind and the interest to tailor waveguides towards a desired spectrum and modal pattern structure in classical structures and nanostructures, it becomes increasingly important...... to understand the influence of curvature effects in waveguides. In this work, we demonstrate analytically strong curvature effects for the eigenvalue spectrum of the Helmholtz equation with Neumann boundary conditions in cases where the waveguide cross section is a circular sector. It is found that the linear...
Antonella Del Rosso
2016-01-01
Twenty years of designing, building and testing a number of innovative technologies, with the strong belief that the endeavour would lead to a historic breakthrough. The Bulletin publishes an abstract of the Courier’s interview with Barry Barish, one of the founding fathers of LIGO. The plots show the signals of gravitational waves detected by the twin LIGO observatories at Livingston, Louisiana, and Hanford, Washington. (Image: Caltech/MIT/LIGO Lab) On 11 February, the Laser Interferometer Gravitational-Wave Observatory (LIGO) and Virgo collaborations published a historic paper in which they showed a gravitational signal emitted by the merger of two black holes. These results come after 20 years of hard work by a large collaboration of scientists operating the two LIGO observatories in the US. Barry Barish, Linde Professor of Physics, Emeritus at the California Institute of Technology and former Director of the Global Design Effort for the Internat...
Strong coupling of collection of emitters on hyperbolic meta-material
Biehs, Svend-Age; Xu, Chenran; Agarwal, Girish S.
2018-04-01
Recently, considerable effort has been devoted to the realization of a strong coupling regime of the radiation matter interaction in the context of an emitter at a meta surface. The strong interaction is well realized in cavity quantum electrodynamics, which also show that strong coupling is much easier to realize using a collection of emitters. Keeping this in mind, we study if emitters on a hyperbolic meta materials can yield a strong coupling regime. We show that strong coupling can be realized for densities of emitters exceeding a critical value. A way to detect strong coupling between emitters and hyperbolic metamaterials is to use the Kretschman-Raether configuration. The strong coupling appears as the splitting of the reflectivity dip. In the weak coupling regime, the dip position shifts. The shift and splitting can be used to sense active molecules at surfaces.
Bulk superconductivity at 84 K in the strongly overdoped regime of cuprates
Gauzzi, A.; Klein, Y.; Nisula, M.; Karppinen, M.; Biswas, P. K.; Saadaoui, H.; Morenzoni, E.; Manuel, P.; Khalyavin, D.; Marezio, M.; Geballe, T. H.
2016-11-01
By means of magnetization, specific heat, and muon-spin relaxation measurements, we investigate newly synthesized high-pressure oxidized Cu0.75Mo0.25Sr2YCu2O7.54 , in which overdoping is achieved up to p ˜0.46 hole/Cu, well beyond the Tc-p superconducting dome of cuprates, where Fermi-liquid behavior is expected. Surprisingly, we find bulk superconductivity with Tc=84 K and superfluid density similar to those of optimally doped YBa2Cu3O7 -δ . On the other hand, specific heat data display a large electronic contribution at low temperature, comparable to that of nonsuperconducting overdoped La2 -xSrxCuO4 . These results point at an unusual high-Tc phase with a large fraction of unpaired holes. Further experiments may assess the Fermi-liquid properties of the present phase, which would put into question the paradigm that the high Tc of cuprates originates from a non-Fermi-liquid ground state.
Czech Academy of Sciences Publication Activity Database
Cavalier, Jordan; Lemoine, N.; Bousselin, G.; Plihon, N.; Ledig, J.
2017-01-01
Roč. 24, č. 1 (2017), č. článku 013506. ISSN 1070-664X Institutional support: RVO:61389021 Keywords : plasma * tokamak * emissive probes Subject RIV: BL - Plasma and Gas Discharge Physics OBOR OECD: Fluids and plasma physics (including surface physics) Impact factor: 2.115, year: 2016 http://dx. doi . org /10.1063/1.4973557
Quantum Zeno Effect in the Strong Measurement Regime of Circuit Quantum Electrodynamics
2016-05-17
electrodynamics DHSlichter1,5, CMüller2,3, RVijay1,6, S JWeber1,7, ABlais3,4 and I Siddiqi1 1 QuantumNanoelectronics Laboratory, Department of Physics...where the act ofmeasurement slows the rate of quantum state transitions—in a superconducting qubit using linear circuit quantum electrodynamics readout...already known to vonNeumann in 1932 [4]. The slowing of state evolution due to theQZE disappears in the classical limit 0,making theQZE auseful test
Fast X-Ray Timing: A Window into the Strong-Field Regime
Strohmayer, Tod
2010-01-01
The dynamical time-scales in the vicinity of neutron star surfaces and black hole horizons are in the millisecond range. Over the past decade, timing signatures on such scales, either quasi-periodic oscillations (QPOs) and/or coherent pulsations, have been discovered and studied from both neutron stars and black holes with NASA's Rossi X-ray Timing Explorer, Although theoretical interpretations are still hotly debated, these timing properties almost certainly reflect the dynamics of matter in regions dominated by relativistic gravity. I will survey our current understanding of these timing properties, with a focus on how they might he used as probes of fundamental physics.
Strongly aligned molecules inside helium droplets in the near-adiabatic regime.
Shepperson, Benjamin; Chatterley, Adam S; Søndergaard, Anders A; Christiansen, Lars; Lemeshko, Mikhail; Stapelfeldt, Henrik
2017-07-07
Iodine (I 2 ) molecules embedded in He nanodroplets are aligned by a 160 ps long laser pulse. The highest degree of alignment, occurring at the peak of the pulse and quantified by ⟨cos 2 2D ⟩, is measured as a function of the laser intensity. The results are well described by ⟨cos 2 2D ⟩ calculated for a gas of isolated molecules each with an effective rotational constant of 0.6 times the gas-phase value and at a temperature of 0.4 K. Theoretical analysis using the angulon quasiparticle to describe rotating molecules in superfluid helium rationalizes why the alignment mechanism is similar to that of isolated molecules with an effective rotational constant. A major advantage of molecules in He droplets is that their 0.4 K temperature leads to stronger alignment than what can generally be achieved for gas phase molecules-here demonstrated by a direct comparison of the droplet results to measurements on a ∼1 K supersonic beam of isolated molecules. This point is further illustrated for a more complex system by measurements on 1,4-diiodobenzene and 1,4-dibromobenzene. For all three molecular species studied, the highest values of ⟨cos 2 2D ⟩ achieved in He droplets exceed 0.96.
Rigol, Marcos; Olshanii, Maxim; Muramatsu, Alejandro
2007-03-01
We study the nonequilibrium dynamics of hard-core bosons (HCB's) on one-dimensional lattices. The dynamics is analyzed after a sudden switch-on or switch-off of a superlattice potential, which can bring the system into insulating or superfluid phases, respectively. A collapse and revival of the zero-momentum peak can be seen in the first case. We study in detail the relaxation of these integrable systems towards equilibrium. We show that after relaxation time averages of physical observables, like the momentum distribution function, can be predicted by means of a generalization of the Gibbs distribution. [M. Rigol, A. Muramatsu, and M. Olshanii, Phys. Rev. A 74, 053616 (2006).
Evolution of the dynamic susceptibility of simple glass formers in the strongly supercooled regime
International Nuclear Information System (INIS)
Adichtchev, S; Blochowicz, T; Gainaru, C; Novikov, V N; Roessler, E A; Tschirwitz, C
2003-01-01
We discuss dielectric and light scattering susceptibility spectra of simple glass formers at temperatures above as well as below the critical temperature of the mode coupling theory (MCT). Close to T g the systems are characterized by the presence of a pronounced excess wing (type A glass formers). The data are analysed within a phenomenological approach, on the one hand, and within MCT, on the other. Among other work we present a complete interpolation of the dielectric data for glycerol (Lunkenheimer et al2000 Contemp. Phys. 41 15). The crossover temperature T x , defined by the emergence of the excess wing upon cooling, is extracted from the phenomenological analysis and found to agree well with the critical temperature T c , extracted from the MCT analysis at high temperatures. Below T x the evolution of the susceptibility is characterized by a universal appearance of the excess wing. No difference is observed for the non-fragile system with respect to fragile glass formers provided that the wing parameters are studied as a function of the correlation time τ α . Finally, a generalized scaling for the susceptibility minimum is proposed which is a phenomenological extension of that of MCT but now also includes the data below T c
How will climate change modify river flow regimes in Europe?
Directory of Open Access Journals (Sweden)
C. Schneider
2013-01-01
Full Text Available Worldwide, flow regimes are being modified by various anthropogenic impacts and climate change induces an additional risk. Rising temperatures, declining snow cover and changing precipitation patterns will interact differently at different locations. Consequently, in distinct climate zones, unequal consequences can be expected in matters of water stress, flood risk, water quality, and food security. In particular, river ecosystems and their vital ecosystem services will be compromised as their species richness and composition have evolved over long time under natural flow conditions. This study aims at evaluating the exclusive impacts of climate change on river flow regimes in Europe. Various flow characteristics are taken into consideration and diverse dynamics are identified for each distinct climate zone in Europe. In order to simulate present-day natural flow regimes and future flow regimes under climate change, the global hydrology model WaterGAP3 is applied. All calculations for current and future conditions (2050s are carried out on a 5' × 5' European grid. To address uncertainty, bias-corrected climate forcing data of three different global climate models are used to drive WaterGAP3. Finally, the hydrological alterations of different flow characteristics are quantified by the Indicators of Hydrological Alteration approach. Results of our analysis indicate that on the European scale, climate change can be expected to modify flow regimes remarkably. This is especially the case in the Mediterranean (due to drier conditions with reduced precipitation across the year and in the boreal climate zone (due to reduced snowmelt, increased precipitation, and strong temperature rises. In the temperate climate zone, impacts increase from oceanic to continental. Regarding single flow characteristics, strongest impacts on timing were found for the boreal climate zone. This applies for both high and low flows. Flow magnitudes, in turn, will be
Signals of confinement in Green functions of SU(2) Yang-Mills theory.
Gattnar, Jochen; Langfeld, Kurt; Reinhardt, Hugo
2004-08-06
It has been well established that the removal of center vortices from SU(2) lattice configurations results in the loss of confinement. The running coupling constant, gluon form factor, and ghost form factor are studied in the Landau gauge for the full and the vortex removed theory. In the latter case, a strong suppression of the running coupling constant and the gluon form factor at low momenta is observed, and the IR singularity of the ghost form factor disappears. Hence, the removal of the vortices generates a theory for which Zwanziger's horizon condition for confinement is no longer satisfied.
Ideal gas behavior of a strongly coupled complex (dusty) plasma.
Oxtoby, Neil P; Griffith, Elias J; Durniak, Céline; Ralph, Jason F; Samsonov, Dmitry
2013-07-05
In a laboratory, a two-dimensional complex (dusty) plasma consists of a low-density ionized gas containing a confined suspension of Yukawa-coupled plastic microspheres. For an initial crystal-like form, we report ideal gas behavior in this strongly coupled system during shock-wave experiments. This evidence supports the use of the ideal gas law as the equation of state for soft crystals such as those formed by dusty plasmas.
Well responses to barometric-pressure fluctuations in confined and semi-confined aquifers
Mohammed, G. A.; Jin, W.; Butler, J. J., Jr.; Reboulet, E. C.
2009-04-01
Modern data logger and sensor technology enable well responses to barometric pressure changes to be monitored at a high frequency and precision. In this presentation, we demonstrate that such monitoring data can be utilized not just for the conventional calculation of a well's barometric efficiency but also to provide valuable information for site characterization applications. We investigate the water-level responses of wells in confined and semi-confined aquifers to changes in barometric pressure and show how simple analytical solutions can be fit to experimentally determined barometric response functions to place bounds on the properties of the confining bed. We demonstrate our approach at the Larned Research Site, located along the Arkansas River in south-central Kansas in the Great Plains region of the United States. The site contains monitoring wells tapping an unconsolidated, semi-confined aquifer (High Plains Aquifer) overlain by a clay unit and a shallow, unconfined aquifer. Water levels and atmospheric pressure have been monitored in the wells at 15-minute intervals for up to seven years. The spatial and temporal changes in the barometric response functions provide important insights on the degree of confinement and its change in space and time. Short term (hour or less) response functions indicate a classical confined aquifer, whereas long term responses (day) show semi-confined behavior, an indication that the air pressure exerted on the water table is being transmitted downward through the confining bed. The barometric response functions vary little in space, indicating the homogeneity of the confining bed, but do vary temporally as a function of the water table elevation and the pneumatic diffusivity of the vadose zone.
Plasma heating and confinement in the gol-3 multiple mirror trap
International Nuclear Information System (INIS)
Burdakov, A.V.; Astrelin, V.T.; Ivanov, I.A.; Koidan, V.S.
2005-01-01
Experiments on plasma confinement in a multiple mirror configuration are carried out at GOL-3 facility in Novosibirsk. Feature of experiments at this facility is high plasma density (up to 5 centre dot 10 21 m -3 ). High ion temperature (up to 2 keV) essentially differs the regime with multimirror configuration from previously studied plasma heating by the E-beam in a uniform magnetic field. Physical mechanism of effective heating of plasma ions, substantially dependent on corrugation of the magnetic field is discussed. In this paper the new experimental data from the GOL-3 facility are presented and the main attention to a stage of ion heating is addressed
A study of runaway electron confinement and theory of neoclassical MHD turbulence
International Nuclear Information System (INIS)
Kwon, Oh Jin
1989-07-01
This thesis consists of two major studies: a study of runaway electron confinement and a theory of neoclassical MHD turbulence. The aim of the former is to study the structure of internal magnetic turbulence in tokamaks, which is thought by many to be responsible for the heat transport. The aim of the latter is to extend existing theories of MHD turbulence in tokamaks into experimentally relevant low-collisionality regimes. This section contains a theory of neoclassical pressure-gradient-driven turbulence and a theory of neoclassical resistivity-gradient-driven turbulence
Inertial Confinement Fusion at Los Alamos
International Nuclear Information System (INIS)
Cartwright, D.C.
1989-09-01
This report discusses the following topics on Inertial Confinement Fusion: ICF contributions to science and technology; target fabrication; laser-target interaction; KrF laser development; advanced KrF lasers; KrF laser technology; and plasma physics for light-ion program
Large hadronic structures and colour confinement
International Nuclear Information System (INIS)
Abbas, Afsar; Paria, Lina; Abbas, Samar
1999-01-01
Colour confinement is an experimentally well established property of QCD at temperature T = 0. Though it has not been conclusively demonstrated in QCD, it is universally believed to be true. Several model calculations indicate that indeed the 3-q and qq-bar colour-singlet states are more bound than for example the colour octet, decuplet representations
Confinement, hidden color and multibaryon states
International Nuclear Information System (INIS)
Nicolescu, B.
1979-01-01
Ideas and theoretical results on multiquark states are reviewed. The measuring of concepts such as 'quarks', 'color' and 'confinement' is analysed first then the possible existence of multiquark states is discussed. the example of dibaryons is used to study their properties in the bag model and in the Dual Topological Unitarization theory [fr
Ultrafast chemistry in complex and confined systems
Indian Academy of Sciences (India)
Home; Journals; Journal of Chemical Sciences; Volume 116; Issue 1. Ultrafast chemistry in complex and ... Recent applications of ultrafast laser spectroscopy and computer simulations revealed that chemistry in a confined environment is fundamentally different from that in ordinary solutions. Many recent examples of slow ...
Mesoscale simulations of confined Nafion thin films
Vanya, P.; Sharman, J.; Elliott, J. A.
2017-12-01
The morphology and transport properties of thin films of the ionomer Nafion, with thicknesses on the order of the bulk cluster size, have been investigated as a model system to explain the anomalous behaviour of catalyst/electrode-polymer interfaces in membrane electrode assemblies. We have employed dissipative particle dynamics (DPD) to investigate the interaction of water and fluorocarbon chains, with carbon and quartz as confining materials, for a wide range of operational water contents and film thicknesses. We found confinement-induced clustering of water perpendicular to the thin film. Hydrophobic carbon forms a water depletion zone near the film interface, whereas hydrophilic quartz results in a zone with excess water. There are, on average, oscillating water-rich and fluorocarbon-rich regions, in agreement with experimental results from neutron reflectometry. Water diffusivity shows increasing directional anisotropy of up to 30% with decreasing film thickness, depending on the hydrophilicity of the confining material. A percolation analysis revealed significant differences in water clustering and connectivity with the confining material. These findings indicate the fundamentally different nature of ionomer thin films, compared to membranes, and suggest explanations for increased ionic resistances observed in the catalyst layer.
Enhanced heat transfer in confined pool boiling
Rops, C.M.; Lindken, R.; Velthuis, J.F.M.; Westerweel, J.
2009-01-01
We report the results of an experimental investigation of the heat transfer during nucleate boiling on a spatially confined boiling surface. The heat flux as a function of the boiling surface temperature was measured in pool boiling pots with diameters ranging from 15 mm down to 4.5 mm. It was found
Perspectives on confinement in helical systems
International Nuclear Information System (INIS)
Itoh, Kimitaka; Itoh, Sanae
1989-01-01
A review on recent experimental results and theoretical models on anomalous transport and density limit in toroidal helical devices is presented. Importance of transport problems is discussed. Experiments on Heliotron-E, Wendelstein-VIIA and new devices, i.e., ATF, Wendelstein-VIIAS and CHS, are reviewed and an overview on confinement property is given. From recent experimental results one sees that there are anomalous transport, which increases with temperature, and density limit, and that they limit the energy confinement time as well as the attainable beta value. The confinement characteristics of the scrape off layer plasma and loss cone loss are discussed, and perspectives on the high temperature plasma are given. These anomalous transport and density limit will be difficult obstacles in realizing a reactor grade plasma in helical systems. It is an urgent task to draw a realistic picture of the confinement based on the present data base. The relevant knowledge now would be critically essential for the successful development of the research in 1990's. (author) 102 refs
Hohlraum manufacture for inertial confinement fusion
International Nuclear Information System (INIS)
Foreman, L.R.; Gobby, P.; Bartos, J.
1994-01-01
Hohlraums are an integral part of indirect drive targets for Inertial Confinement Fusion (ICF) research. Hohlraums are made by an electroforming process that combines elements of micromachining and coating technology. The authors describe how these target element are made and extension of the method that allow fabrication of other, more complex target components
Non-resonant Nanoscale Extreme Light Confinement
Energy Technology Data Exchange (ETDEWEB)
Subramania, Ganapathi Subramanian [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Huber, Dale L. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
2014-09-01
A wide spectrum of photonics activities Sandia is engaged in such as solid state lighting, photovoltaics, infrared imaging and sensing, quantum sources, rely on nanoscale or ultrasubwavelength light-matter interactions (LMI). The fundamental understanding in confining electromagnetic power and enhancing electric fields into ever smaller volumes is key to creating next generation devices for these programs. The prevailing view is that a resonant interaction (e.g. in microcavities or surface-plasmon polaritions) is necessary to achieve the necessary light confinement for absorption or emission enhancement. Here we propose new paradigm that is non-resonant and therefore broadband and can achieve light confinement and field enhancement in extremely small areas [~(λ/500)^2 ]. The proposal is based on a theoretical work[1] performed at Sandia. The paradigm structure consists of a periodic arrangement of connected small and large rectangular slits etched into a metal film named double-groove (DG) structure. The degree of electric field enhancement and power confinement can be controlled by the geometry of the structure. The key operational principle is attributed to quasistatic response of the metal electrons to the incoming electromagnetic field that enables non-resonant broadband behavior. For this exploratory LDRD we have fabricated some test double groove structures to enable verification of quasistatic electronic response in the mid IR through IR optical spectroscopy. We have addressed some processing challenges in DG structure fabrication to enable future design of complex sensor and detector geometries that can utilize its non-resonant field enhancement capabilities.].
Clusters of polyhedra in spherical confinement
Teich, Erin G.; van Anders, Greg; Klotsa, Daphne; Dshemuchadse, Julia; Glotzer, Sharon C.
2016-01-01
Dense particle packing in a confining volume remains a rich, largely unexplored problem, despite applications in blood clotting, plasmonics, industrial packaging and transport, colloidal molecule design, and information storage. Here, we report densest found clusters of the Platonic solids in spherical confinement, for up to N=60 constituent polyhedral particles. We examine the interplay between anisotropic particle shape and isotropic 3D confinement. Densest clusters exhibit a wide variety of symmetry point groups and form in up to three layers at higher N. For many N values, icosahedra and dodecahedra form clusters that resemble sphere clusters. These common structures are layers of optimal spherical codes in most cases, a surprising fact given the significant faceting of the icosahedron and dodecahedron. We also investigate cluster density as a function of N for each particle shape. We find that, in contrast to what happens in bulk, polyhedra often pack less densely than spheres. We also find especially dense clusters at so-called magic numbers of constituent particles. Our results showcase the structural diversity and experimental utility of families of solutions to the packing in confinement problem. PMID:26811458
Somersault of Paramecium in extremely confined environments
Jana, Saikat; Eddins, Aja; Spoon, Corrie; Jung, Sunghwan
2015-08-01
We investigate various swimming modes of Paramecium in geometric confinements and a non-swimming self-bending behavior like a somersault, which is quite different from the previously reported behaviors. We observe that Paramecia execute directional sinusoidal trajectories in thick fluid films, whereas Paramecia meander around a localized region and execute frequent turns due to collisions with adjacent walls in thin fluid films. When Paramecia are further constrained in rectangular channels narrower than the length of the cell body, a fraction of meandering Paramecia buckle their body by pushing on the channel walls. The bucking (self-bending) of the cell body allows the Paramecium to reorient its anterior end and explore a completely new direction in extremely confined spaces. Using force deflection method, we quantify the Young’s modulus of the cell and estimate the swimming and bending powers exerted by Paramecium. The analysis shows that Paramecia can utilize a fraction of its swimming power to execute the self-bending maneuver within the confined channel and no extra power may be required for this new kind of self-bending behavior. This investigation sheds light on how micro-organisms can use the flexibility of the body to actively navigate within confined spaces.
Dynamics of Colloids Confined in Microcylinders
Ghosh, Somnath; Wijnperle, Daniël; Mugele, Friedrich Gunther; Duits, Michael H.G.
2016-01-01
We studied both global and local effects of cylindrical confinement on the diffusive behavior of hard sphere (HS) colloids. Using confocal scanning laser microscopy (CSLM) and particle tracking, we measured the mean squared displacement (MSD) of 1 micron sized silica particles in water–glycerol.
Transition metal catalysis in confined spaces
Leenders, S.H.A.M.; Gramage-Doria, R.; de Bruin, B.; Reek, J.N.H.
2015-01-01
Transition metal catalysis plays an important role in both industry and in academia where selectivity, activity and stability are crucial parameters to control. Next to changing the structure of the ligand, introducing a confined space as a second coordination sphere around a metal catalyst has
Inertial Confinement Fusion at Los Alamos
International Nuclear Information System (INIS)
Cartwright, D.C.
1989-09-01
This report discusses the following topics on inertial confinement fusion: distribution of electron-beam energy in KrF laser media; electron collision processes in KrF laser media; Krf laser kinetics; and properties of the KrF laser medium
Confining strings revisited - a short comment
International Nuclear Information System (INIS)
Botelho, Luiz C.L.
2000-03-01
We show that Polyakov's confining string Nucl. Phys. B486, (1997) 23, is the author's previously proposed self-avoiding extrinsic strings (Luiz C.L. Botelho), Rev. Bras. Fis. 16, 279, (1986); CALTECH-preprint 68, 1444, (1987); J. Math. Phys. 30 (9), (1989), 2160). (author)
Confining strings revisited - a short comment
Energy Technology Data Exchange (ETDEWEB)
Botelho, Luiz C.L. [Universidade Federal Rural do Rio de Janeiro, RJ (Brazil). Dept. de Fisica
2000-03-01
We show that Polyakov's confining string Nucl. Phys. B486, (1997) 23, is the author's previously proposed self-avoiding extrinsic strings (Luiz C.L. Botelho), Rev. Bras. Fis. 16, 279, (1986); CALTECH-preprint 68, 1444, (1987); J. Math. Phys. 30 (9), (1989), 2160. (author)
International Nuclear Information System (INIS)
Sung, C.; White, A.E.; Howard, N.T.; Oi, C.Y.; Rice, J.E.; Gao, C.; Ennever, P.; Porkolab, M.; Parra, F.; Ernst, D.; Walk, J.; Hughes, J.W.; Irby, J.; Kasten, C.; Hubbard, A.E.; Greenwald, M.J.; Mikkelsen, D.
2013-01-01
The first measurements of long wavelength (k y ρ s < 0.3) electron temperature fluctuations in Alcator C-Mod made with a new correlation electron cyclotron emission diagnostic support a long-standing hypothesis regarding the confinement transition from linear ohmic confinement (LOC) to saturated ohmic confinement (SOC). Electron temperature fluctuations decrease significantly (∼40%) crossing from LOC to SOC, consistent with a change from trapped electron mode (TEM) turbulence domination to ion temperature gradient (ITG) turbulence as the density is increased. Linear stability analysis performed with the GYRO code (Candy and Waltz 2003 J. Comput. Phys. 186 545) shows that TEMs are dominant for long wavelength turbulence in the LOC regime and ITG modes are dominant in the SOC regime at the radial location (ρ ∼ 0.8) where the changes in electron temperature fluctuations are measured. In contrast, deeper in the core (ρ < 0.8), linear stability analysis indicates that ITG modes remain dominant across the LOC/SOC transition. This radial variation suggests that the robust global changes in confinement of energy and momentum occurring across the LOC/SOC transition are correlated to local changes in the dominant turbulent mode near the edge. (paper)
Wickens, F
Our friend and colleague John Strong was cruelly taken from us by a brain tumour on Monday 31st July, a few days before his 65th birthday John started his career working with a group from Westfield College, under the leadership of Ted Bellamy. He obtained his PhD and spent the early part of his career on experiments at Rutherford Appleton Laboratory (RAL), but after the early 1970s his research was focussed on experiments in CERN. Over the years he made a number of notable contributions to experiments in CERN: The Omega spectrometer adopted a system John had originally developed for experiments at RAL using vidicon cameras to record the sparks in the spark chambers; He contributed to the success of NA1 and NA7, where he became heavily involved in the electronic trigger systems; He was responsible for the second level trigger system for the ALEPH detector and spent five years leading a team that designed and built the system, which ran for twelve years with only minor interventions. Following ALEPH he tur...
Strong-interaction nonuniversality
International Nuclear Information System (INIS)
Volkas, R.R.; Foot, R.; He, X.; Joshi, G.C.
1989-01-01
The universal QCD color theory is extended to an SU(3) 1 direct product SU(3) 2 direct product SU(3) 3 gauge theory, where quarks of the ith generation transform as triplets under SU(3)/sub i/ and singlets under the other two factors. The usual color group is then identified with the diagonal subgroup, which remains exact after symmetry breaking. The gauge bosons associated with the 16 broken generators then form two massive octets under ordinary color. The interactions between quarks and these heavy gluonlike particles are explicitly nonuniversal and thus an exploration of their physical implications allows us to shed light on the fundamental issue of strong-interaction universality. Nonuniversality and weak flavor mixing are shown to generate heavy-gluon-induced flavor-changing neutral currents. The phenomenology of these processes is studied, as they provide the major experimental constraint on the extended theory. Three symmetry-breaking scenarios are presented. The first has color breaking occurring at the weak scale, while the second and third divorce the two scales. The third model has the interesting feature of radiatively induced off-diagonal Kobayashi-Maskawa matrix elements
Energy Technology Data Exchange (ETDEWEB)
Avdonin, A., E-mail: avdonin@ifpan.edu.pl [Institute of Physics, Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warszawa (Poland); Skupiński, P. [Institute of Physics, Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warszawa (Poland); Grasza, K. [Institute of Physics, Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warszawa (Poland); Institute of Electronic Materials Technology, ul. Wólczyńska 133, 01-919 Warszawa (Poland)
2016-02-15
A simple description of the Hall effect in the hopping regime of conductivity in semiconductors is presented. Expressions for the Hall coefficient and Hall mobility are derived by considering averaged equilibrium electron transport in a single triangle of localization sites in a magnetic field. Dependence of the Hall coefficient is analyzed in a wide range of temperature and magnetic field values. Our theoretical result is applied to our experimental data on temperature dependence of Hall effect and Hall mobility in ZnO. - Highlights: • Expressions for Hall coefficient and mobility for hopping conductivity are derived. • Theoretical result is compared with experimental curves measured on ZnO. • Simultaneous action of free and hopping conduction channels is considered. • Non-linearity of hopping Hall coefficient is predicted.
Reassessing the nuclear liability regime
International Nuclear Information System (INIS)
Havinh Phuong
1985-01-01
The nuclear liability regime was thoroughly reviewed by nuclear plant operators, officials of regulatory authorities, and legal and insurance experts at the Symposium on Nuclear Third Party Liability and Insurance, held in September 1984 in Munich, Federal Republic of Germany. The symposium highlighted specific areas where adjustments or improvements would be needed in order to cope with practical problems encountered or emerging issues. By focusing on questions of legitimate concern to the public, it also sought to promote confidence in a compensation system for public protection that is in many ways unique. Topics addressed included the following: greater harmonization of the compensation amounts for nuclear damage established in different countries and in territorial scope; the concept of unlimited liability; the time limitation for compensation claims; the problem of proving causation; the concept of nuclear damage; and insurance coverage
Cavitation in microscale confinement: new concept of mild brain injury.
Akhatov, Iskander; Wang, Cheng; Ziejewski, Mariusz
2007-11-01
The present effort is to understand the possible damages in brain caused by the cavitation bubbles generated when the impacting shock waves passing through human head. In order to build an adequate mathematical model of this phenomenon, one should be able to model inception and dynamics of cavitation in biological liquid confined in macroscale or microscale space between solids, elastic surfaces, or membranes -- biological tissues, in general. A more in-depth understanding of the outcomes from the dynamic response of brain tissue, including the location, size, and geometry of the damage site, will be of assistance to physicians in the properly interpreting the neurodiagnostic results. In the present study it is stated that in micro scale confinement bubble collapse can not cause any damage. This is due to the fact that collapse is damped by viscous dissipation in micro channels. Otherwise, the bubble inception itself may cause damage. It is shown that cavitation inception in micro scale may happen for much higher tensions than in infinite liquid. At such a strong tension substantial amount of elastic energy is stored in liquid. This energy being released during cavitation inception generates `recoil pressure' that may be high enough to damage biological tissue.
Dynamics of flexible fibers transported in confined viscous flows
Cappello, Jean; Duprat, Camille; Du Roure, Olivia; Nagel, Mathias; Gallaire, François; Lindner, Anke
2017-11-01
The dynamics of elongated objects has been extensively studied in unbounded media as for example the sedimentation of fibers at low Reynolds numbers. It has recently been shown that these transport dynamics are strongly modified by bounding walls. Here we focus on the dynamics of flexible fibers confined by the top and bottom walls of a microchannel and transported in pressure-driven flows. We combine well-controlled microfluidic experiments and simulations using modified Brinkmann equations. We control shape, orientation, and mechanical properties of our fibers using micro-fabrication techniques and in-situ characterization methods. These elastic fibers can be deformed by viscous and pressure forces leading to very rich transport dynamics coupling lateral drift with shape evolution. We show that the bending of a perpendicular fiber is proportional to an elasto-viscous number and we fully characterize the influence of the confinement on the deformation of the fiber. Experiments on parallel flexible fibers reveal the existence of a buckling threshold. The European Research Council is acknowledged for funding the work through a consolidator Grant (ERC PaDyFlow 682367).
Hollow Carbon Nanopolyhedra for Enhanced Electrocatalysis via Confined Hierarchical Porosity.
Song, Xiaokai; Guo, Linli; Liao, Xuemei; Liu, Jian; Sun, Jianhua; Li, Xiaopeng
2017-06-01
A novel strategy for the fabrication of hollow Co and N-codoped carbon nanopolyhedra (H-CoNC) from metal-organic framework (MOF) using in situ evaporation of ZnO nanosphere templates is proposed. The excess Zn supply during the pyrolysis process is found beneficial in terms of high nitrogen (≈9.75 at%), relatively homogenous CoN bonding, and the electrochemically accessible hierarchical porous system. Compared with other reported "solid" CoNC of identical surface areas, the newly developed H-CoNC shows enhanced kinetic current in 0.1 m KOH electrolyte and elevated oxygen reduction reaction (ORR) performance in 6 m KOH. The latter exceeds results obtained with the benchmark 20 wt% Pt/C, which is related to the strong confinement of O 2 molecules in the H-CoNC hierarchical porous system. Furthermore, the H-CoNC displays great tolerance toward the methanol crossover and KSCN poisoning. Finally, the assembled Zn-air batteries with H-CoNC yield a record open circuit potential (1.59 V vs Zn, stabilized at 1.52 V), high power density (331.0 mW cm -2 ), and promising rate performance. This work provides a new guideline for the design of MOF-derived carbon materials, as well as novel insights into spatial confinement effect toward the ORR activity. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Confined Floodplain Dynamics on Semi-Arid Systems
Entwistle, N. S.
2017-12-01
Many watercourses across southern Africa are characterised by a bedrock influenced `macro-channel' created as a result of geologically recent fluvial incision into ancient planation surfaces. The rivers of the Kruger National Park in Mpumalanga Province, South Africa are no exception, displaying a varied set of channel types within a bedrock template. Contemporary flows are largely contained within the confines of this `macro-channel' and a diverse valley bottom morphology and ecology has developed in response to this flow regime coupled with intermittent fine sediment delivery from the catchment. Aerial imagery and field monitoring of the impact of two cyclone driven extreme flows and subsequent recovery phases suggests that flood impact is spatially variable with bedrock exposure greatest along watercourses already severely impacted by previous events. Subsequent system development has been characterised by the redistribution and vegetative colonisation of unconsolidated sandy sediment over bedrock. On less impacted systems vegetative induced recovery has, in contrast, been rapid with many of the species present displaying significant resilience to extreme flows forming residual pockets which are subsequently developing alongside embryonic morphologic recovery. Using these observations a model of valley bottom recovery is presented.
Strongly correlated Fermi-Bose mixtures in disordered optical lattices
International Nuclear Information System (INIS)
Sanchez-Palencia, L; Ahufinger, V; Kantian, A; Zakrzewski, J; Sanpera, A; Lewenstein, M
2006-01-01
We investigate theoretically the low-temperature physics of a two-component ultracold mixture of bosons and fermions in disordered optical lattices. We focus on the strongly correlated regime. We show that, under specific conditions, composite fermions, made of one fermion plus one bosonic hole, form. The composite picture is used to derive an effective Hamiltonian whose parameters can be controlled via the boson-boson and the boson-fermion interactions, the tunnelling terms and the inhomogeneities. We finally investigate the quantum phase diagram of the composite fermions and show that it corresponds to the formation of Fermi glasses, spin glasses and quantum percolation regimes
Strongly correlated Fermi-Bose mixtures in disordered optical lattices
Energy Technology Data Exchange (ETDEWEB)
Sanchez-Palencia, L [Laboratoire Charles Fabry de l' Institut d' Optique, CNRS and Universite Paris-Sud XI, Bat 503, Centre scientifique, F-91403 Orsay Cedex (France); Ahufinger, V [ICREA and Grup d' optica, Departament de FIsica, Universitat Autonoma de Barcelona, E-08193 Belaterra (Barcelona) (Spain); Kantian, A [Institut fuer Theoretische Physik, Universitaet Innsbruck, A-6020 Innsbruck (Austria); Zakrzewski, J [Instytut Fizyki imienia Mariana Smoluchowskiego i Centrum Badan Ukladow Zlozonych imienia Marka Kaca, Uniwersytet Jagiellonski, ulica Reymonta 4, PL-30-059 Krakow (Poland); Sanpera, A [ICREA and Grup de FIsica Teorica, Departament de FIsica, Universitat Autonoma de Barcelona, E-08193 Belaterra (Barcelona) (Spain); Lewenstein, M [ICREA and ICFO-Institut de Ciencies Fotoniques, Parc Mediterrani de la TecnologIa, E-08860 Castelldefels (Barcelona) (Spain); Institut fuer Theoretische Physik, Universitaet Hannover, D-30167 Hannover (Germany)
2006-05-28
We investigate theoretically the low-temperature physics of a two-component ultracold mixture of bosons and fermions in disordered optical lattices. We focus on the strongly correlated regime. We show that, under specific conditions, composite fermions, made of one fermion plus one bosonic hole, form. The composite picture is used to derive an effective Hamiltonian whose parameters can be controlled via the boson-boson and the boson-fermion interactions, the tunnelling terms and the inhomogeneities. We finally investigate the quantum phase diagram of the composite fermions and show that it corresponds to the formation of Fermi glasses, spin glasses and quantum percolation regimes.
Small-angle neutron scattering studies of hemoglobin confined inside silica tubes of varying sizes.
Mandal, Soumit S; Cristiglio, Viviana; Lindner, Peter; Bhattacharyya, Aninda J
2014-02-03
In addition to the chemical nature of the surface, the dimensions of the confining host exert a significant influence on confined protein structures; this results in immense biological implications, especially those concerning the enzymatic activities of the protein. This study probes the structure of hemoglobin (Hb), a model protein, confined inside silica tubes with pore diameters that vary by one order of magnitude (≈20-200 nm). The effect of confinement on the protein structure is probed by comparison with the structure of the protein in solution. Small-angle neutron scattering (SANS), which provides information on protein tertiary and quaternary structures, is employed to study the influence of the tube pore diameter on the structure and configuration of the confined protein in detail. Confinement significantly influences the structural stability of Hb and the structure depends on the Si-tube pore diameter. The high radius of gyration (Rg) and polydispersity of Hb in the 20 nm diameter Si-tube indicates that Hb undergoes a significant amount of aggregation. However, for Si-tube diameters greater or equal to 100 nm, the Rg of Hb is found to be in very close proximity to that obtained from the protein data bank (PDB) reported structure (Rg of native Hb=23.8 Å). This strongly indicates that the protein has a preference for the more native-like non-aggregated state if confined inside tubes of diameter greater or equal to 100 nm. Further insight into the Hb structure is obtained from the distance distribution function, p(r), and ab initio models calculated from the SANS patterns. These also suggest that the Si-tube size is a key parameter for protein stability and structure. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Accommodating human values in the climate regime
Directory of Open Access Journals (Sweden)
Rosalind Cook
2008-12-01
Full Text Available The climate regime addresses one of the most important challenges facing humankind today. However, while the environmental and economic sides of the problem are well represented, it lacks the inclusion of social and human aspects. The human rights regime, in contrast, is a regime which has been established precisely to implement human values. This article ex-plains the problems of climate change in terms of human values and argues that some proce-dures from the human rights regime offer possibilities for improvement. It is submitted that through the inclusion of human rights instruments, such as individual communication, pro-gressive realisation and authoritative interpretation, the inclusion of human values into the climate regime will be facilitated. This article presents these instruments and discusses their potential for inclusion in the climate regime.
Quantum fields in the non-perturbative regime. Yang-Mills theory and gravity
Energy Technology Data Exchange (ETDEWEB)
Eichhorn, Astrid
2011-09-06
In this thesis we study candidates for fundamental quantum field theories, namely non-Abelian gauge theories and asymptotically safe quantum gravity. Whereas the first ones have a stronglyinteracting low-energy limit, the second one enters a non-perturbative regime at high energies. Thus, we apply a tool suited to the study of quantum field theories beyond the perturbative regime, namely the Functional Renormalisation Group. In a first part, we concentrate on the physical properties of non-Abelian gauge theories at low energies. Focussing on the vacuum properties of the theory, we present an evaluation of the full effective potential for the field strength invariant F{sub {mu}}{sub {nu}}F{sup {mu}}{sup {nu}} from non-perturbative gauge correlation functions and find a non-trivial minimum corresponding to the existence of a dimension four gluon condensate in the vacuum. We also relate the infrared asymptotic form of the {beta} function of the running background-gauge coupling to the asymptotic behavior of Landau-gauge gluon and ghost propagators and derive an upper bound on their scaling exponents. We then consider the theory at finite temperature and study the nature of the confinement phase transition in d = 3+1 dimensions in various non-Abelian gauge theories. For SU(N) with N= 3,..,12 and Sp(2) we find a first-order phase transition in agreement with general expectations. Moreover our study suggests that the phase transition in E(7) Yang-Mills theory also is of first order. Our studies shed light on the question which property of a gauge group determines the order of the phase transition. In a second part we consider asymptotically safe quantum gravity. Here, we focus on the Faddeev-Popov ghost sector of the theory, to study its properties in the context of an interacting UV regime. We investigate several truncations, which all lend support to the conjecture that gravity may be asymptotically safe. In a first truncation, we study the ghost anomalous dimension
State Structure and Political Regime Structure
Paul – Iulian Nedelcu
2012-01-01
The political regime is the concrete form of organization and functioning of political system andtherefore, the regime means the concrete way of organize, institutionalize and function a political systemand of the exercise of political power by a social-political force in a social community or global socialistem. The political regime is not limited to institutions and state bodies, but it covers the entire politicalsystem. Form of expression in social practice plan is the result of balance of...
De Facto Regimes in International Law
Essen, Jonte van
2012-01-01
The ambiguous position of de facto regimes in international law has long been the subject of scholarly debate and a source of political conflict. An assessment of the current standing of these regimes in international law and the consequences of actions by international actors on this status has, however, been long overdue. The manner in which de facto regimes are regarded internationally has serious consequences for the individuals under the influence of this legal grey area. Therefore, the ...
B decay anomalies and dark matter from vectorlike confinement
Cline, James M.
2018-01-01
Lepton flavor universality violating B →K ℓℓ and K*ℓℓ decays tentatively observed by LHCb can be explained by leptoquark exchange. We explore a simple model for the B anomalies with a composite leptoquark from new strong dynamics at the TeV scale, a confining SU(NH C) hypercolor interaction. The new matter fields, fundamentals under SU (NH C) , are heavy vectorlike fermions Ψ , S , and an inert scalar doublet ϕ . Ψ is colored under QCD while S is neutral, and the hyperbaryon SN is an asymmetric dark matter candidate. The model is tightly constrained by meson-antimeson oscillations, lepton flavor violation, and LHC searches for resonant production of the exotic bound states. The dark matter may be detectable through its magnetic dipole moment. If mS is sufficiently small, composite leptoquarks and heavy lepton partners can be pair-produced at an observable level at LHC.
Confined granular flow in silos experimental and numerical investigations
Tejchman, Jacek
2013-01-01
During confined flow of bulk solids in silos some characteristic phenomena can be created, such as: — sudden and significant increase of wall stresses, — different flow patterns, — formation and propagation of wall and interior shear zones, — fluctuation of pressures and, — strong autogenous dynamic effects. These phenomena have not been described or explained in detail yet. The main intention of the experimental and theoretical research presented in this book is to explain the above mentioned phenomena in granular bulk solids and to describe them with numerical FE models verified by experimental results.
Polarizability of π-mesons in the quark confinement model
International Nuclear Information System (INIS)
Avakyan, E.Z.; Avakyan, S.L.; Efimov, G.V.; Ivanov, M.A.
1988-01-01
The electric α π and magnetic β π polarizabilities are calculated in the Quark Confinement Model (QCM). The diagrams with vector, scalar and axial intermediate states are taken into account. It is found that intermediate scalar mesons give an essential contribution to electric and magnetic polarizabilities of pions. The following values for α π and β π are obtained: α π ± =4.06x10 -43 cm 3 ; β π ± =-3.84x10 -43 ; α π 0 =-0.18x10 -43 cm 3 ; β π 0 =1.92x10 -43 cm 3 . The widths of strong (α 0 (980) → πη, f 0 (975) → ππ, ε(730) → ππ) and radiative (α 0 (980), f 0 (980), ε(730) → γγ) decays are calculated. The results are obtained to be in satisfactory agreement with expermental data
Basse, N. P.; Zoletnik, S.; Michelsen, P. K.; W7-As Team
2005-01-01
Confinement transitions in the Wendelstein 7-AS stellarator [H. Renner et al., Plasma Phys. Controlled Fusion 31, 1579 (1989)] can be induced by varying either the internal plasma current or the external magnetic field. In this paper we report on experiments where closely matched confinement states (good and bad) were constructed using the latter method. Analysis using the former scheme has been reported upon previously [S. Zoletnik et al., Plasma Phys. Controlled Fusion 44, 1581 (2002)]. The electron temperature, along with the major spectral characteristics of magnetic and small-scale electron density fluctuations, changes dramatically at the transition from good to bad confinement. The fluctuation power is intermittent, and core bursts traveling in the electron diamagnetic drift (DD) direction are correlated between the bottom and top of the plasma, especially during degraded confinement. A corresponding top-bottom correlation for the edge ion DD direction turbulence feature was not found. Strong correlations are observed both between the two density fluctuation signals and between magnetic and density fluctuations in bad compared to good confinement. The correlation time of the bursts is of order 100μs, similar to the lifetime observed during edge localized modes.
International Nuclear Information System (INIS)
Kim, Jeong-Gyu; Kim, Woong-Tae; Seo, Young Min; Hong, Seung Soo
2012-01-01
We investigate the gravitational instability (GI) of rotating, vertically stratified, pressure-confined, polytropic gas disks using a linear stability analysis as well as analytic approximations. The disks are initially in vertical hydrostatic equilibrium and bounded by a constant external pressure. We find that the GI of a pressure-confined disk is in general a mixed mode of the conventional Jeans and distortional instabilities, and is thus an unstable version of acoustic-surface-gravity waves. The Jeans mode dominates in weakly confined disks or disks with rigid boundaries. On the other hand, when the disk has free boundaries and is strongly pressure confined, the mixed GI is dominated by the distortional mode that is surface-gravity waves driven unstable under their own gravity and thus incompressible. We demonstrate that the Jeans mode is gravity-modified acoustic waves rather than inertial waves and that inertial waves are almost unaffected by self-gravity. We derive an analytic expression for the effective sound speed c eff of acoustic-surface-gravity waves. We also find expressions for the gravity reduction factors relative to a razor-thin counterpart that are appropriate for the Jeans and distortional modes. The usual razor-thin dispersion relation, after correcting for c eff and the reduction factors, closely matches the numerical results obtained by solving a full set of linearized equations. The effective sound speed generalizes the Toomre stability parameter of the Jeans mode to allow for the mixed GI of vertically stratified, pressure-confined disks.
New Small-ELM H-mode Regimes for Steady-state High-performance Operations in EAST
Xu, G. S.; Yang, Q. Q.; Wang, Y. F.; Yan, N.; Hu, G. H.; Lin, X.; Xu, X. Q.; Garofalo, A. M.; Maingi, R.; EAST Team
2017-10-01
A stationary high-confinement (H98y2 1.1) fully non-inductive H-mode regime characterized by high-frequency (2kHz) small ELMs (divertor peak heat flux 2MW/m2) at relatively low pedestal collisionality (ν*e 1) and optimized high internal inductance (li 1.1) plasma has been recently achieved with high heating power (source power 9MW) in EAST. This regime was obtained at high triangularity δ (0.55), high q95 (6) and high βp (1.6), close to the parameter space of the grassy ELM regime in JT-60U. The relatively low plasma current, high q95, βp, and therefore high bootstrap current fraction (>30%) make it a suitable regime to achieve steady-state operation with low disruptivity, good reproducibility and robustness. The access to this regime is insensitive to the change of toroidal torque or plasma density in the explored parameter range. Benefiting from the optimized high li and high βp, good core energy confinement has been achieved even at low core toroidal rotation (Vt down to 10 km/s). Good density control has been achieved at a line-averaged density up to 76% Greenwald. Impurity concentration and core radiation were maintained at an acceptably low level, suggesting that sufficient particle exhaust can be driven by the high-frequency small ELMs.
Heat transport in the XXZ spin chain: from ballistic to diffusive regimes and dephasing enhancement
International Nuclear Information System (INIS)
Mendoza-Arenas, J J; Al-Assam, S; Clark, S R; Jaksch, D
2013-01-01
In this work we study the heat transport in an XXZ spin-1/2 Heisenberg chain with homogeneous magnetic field, incoherently driven out of equilibrium by reservoirs at the boundaries. We focus on the effect of bulk dephasing (energy-dissipative) processes in different parameter regimes of the system. The non-equilibrium steady state of the chain is obtained by simulating its evolution under the corresponding Lindblad master equation, using the time evolving block decimation method. In the absence of dephasing, the heat transport is ballistic for weak interactions, while being diffusive in the strongly interacting regime, as evidenced by the heat current scaling with the system size. When bulk dephasing takes place in the system, diffusive transport is induced in the weakly interacting regime, with the heat current monotonically decreasing with the dephasing rate. In contrast, in the strongly interacting regime, the heat current can be significantly enhanced by dephasing for systems of small size. (paper)