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1

Confined quantum time of arrival for the vanishing potential  

SciTech Connect

We give full account of our recent report in E. A. Galapon, R. Caballar, and R. Bahague, Phys. Rev. Lett. 93, 180406 (2004), where it is shown that formulating the free quantum time of arrival problem in a segment of the real line suggests rephrasing the quantum time of arrival problem to finding a complete set of states that evolve to unitarily arrive at a given point at a definite time. For a spatially confined particle, here it is shown explicitly that the problem admits a solution in the form of an eigenvalue problem of a class of compact and self-adjoint time of arrival operators derived by a quantization of the classical time of arrival. The eigenfunctions of these operators are numerically demonstrated to unitarily arrive at the origin at their respective eigenvalues.

Galapon, Eric A. [Theoretical Physics Group, National Institute of Physics, University of the Philippines, Diliman, Quezon City, 1101 (Philippines); Theoretical Physics, University of the Basque Country, Apdo. 644, 48080 Bilbao (Spain); Chemical Physics, University of the Basque Country, Apdo. 644, 48080 Bilbao (Spain); Caballar, Roland F.; Bahague, Ricardo [Theoretical Physics Group, National Institute of Physics, University of the Philippines, Diliman, Quezon City, 1101 (Philippines)

2005-12-15

2

Soliton dynamics in confining time-dependent potentials  

NASA Astrophysics Data System (ADS)

The dynamics of nonlinear solitary waves is studied in the framework of the nonlinear Schrodinger equation model with time-dependent confining harmonic oscillator potential. The model allows one to analyse on the general basis a variety of nonlinear phenomena appearing both in Bose-Einstein condensate, condensed matter physics and in nonlinear optics and biophysics. The nonlinear effect of the soliton parametric resonance is investigated by using two complementary methods: the adiabatic perturbation theory and direct numerical experiments. Conditions for reversible and irreversible denaturation of soliton bound states are also considered.

Belyaeva, T. L.; Serkin, V. N.; Hernandez-Tenorio, C.; Kovachev, L. M.

2008-12-01

3

Wave function for time-dependent harmonically confined electrons in a time-dependent electric field.  

PubMed

The many-body wave function of a system of interacting particles confined by a time-dependent harmonic potential and perturbed by a time-dependent spatially homogeneous electric field is derived via the Feynman path-integral method. The wave function is comprised of a phase factor times the solution to the unperturbed time-dependent Schro?dinger equation with the latter being translated by a time-dependent value that satisfies the classical driven equation of motion. The wave function reduces to that of the Harmonic Potential Theorem wave function for the case of the time-independent harmonic confining potential. PMID:24070284

Li, Yu-Qi; Pan, Xiao-Yin; Sahni, Viraht

2013-09-21

4

Wave function for time-dependent harmonically confined electrons in a time-dependent electric field  

NASA Astrophysics Data System (ADS)

The many-body wave function of a system of interacting particles confined by a time-dependent harmonic potential and perturbed by a time-dependent spatially homogeneous electric field is derived via the Feynman path-integral method. The wave function is comprised of a phase factor times the solution to the unperturbed time-dependent Schrödinger equation with the latter being translated by a time-dependent value that satisfies the classical driven equation of motion. The wave function reduces to that of the Harmonic Potential Theorem wave function for the case of the time-independent harmonic confining potential.

Li, Yu-Qi; Pan, Xiao-Yin; Sahni, Viraht

2013-09-01

5

Confinement time and energy balance in the CTX spheromak  

SciTech Connect

The multipoint Thomson scattering diagnostic on CTX allows measurement of electron plasma pressure. The pressure correlates well with the poloidal flux function. Analysis using equilibrium models allows the (..beta..)/sub vol/ to be calculated from over 100 Thomson scattering profiles taken under standard conditions of spheromak operation where the plasma parameters vary widely within the discharge. The calculated tau/sub E/ increases with central core temperature and with density. The global magnetic energy decay time tau/sub B/2 is consistent with Spitzer-Harm resistivity, but with an anomaly factor of 2 to 4 which may decrease at small ratios of B/n. The n tau/sub E/ product reaches 4 x 10/sup 9/ s cm/sup -3/ during the hottest part of the discharge. A zero-dimensional energy balance code, which accurately includes all the major atomic physics processes and whose parameters have been constrained by comparision to experimental data, is used to identify the causes of energy loss that contribute to the observed confinement time. The most important power loss is that needed to replace the particles being lost and to maintain the constant density of the plateau.

Barnes, C.W.; Henins, I.; Hoida, H.W.; Jarboe, T.R.

1984-01-01

6

Parametric scaling studies of the energy confinement time for neutral beam heated Heliotron E plasmas  

Microsoft Academic Search

A kinetic analysis of the global energy confinement time for neutral beam heated Heliotron E plasmas has been performed with a 1-D, time independent transport analysis code, PROCTR-Mod. From a regression analysis of a representative sample selection of the presented data sets, the global energy confinement time, , is found to scale as , where ? = 0.53 0.10, ?

F. Sano; Y. Takeiri; K. Hanatani; H. Zushi; M. Sato; S. Sudo; T. Mutoh; K. Kondo; H. Kaneko; T. Mizuuchi; H. Okada; S. Morimoto; K. Itoh; S. Besshou; M. Nakasuga; Y. Nakamura; N. Noda; K. Akaishi; O. Motojima; M. Wakatani; T. Obiki; A. Iiyoshi; M. Murakami; H. C. Howe

1990-01-01

7

Can inertial electrostatic confinement work beyond the ion-ion collisional time scale.  

National Technical Information Service (NTIS)

Inertial electrostatic confinement systems are predicated on a non-equilibrium ion distribution function. Coulomb collisions between ions cause this distribution to relax to a Maxwellian on the ion-ion collisional time-scale. The power required to prevent...

W. M. Nevins

1995-01-01

8

Role of E{times}B flow shear on confinement enhancement in DIII-D high internal inductance discharges with high-confinement edge  

SciTech Connect

The role of E{times}B flow shear on confinement enhancement in the DIII-D tokamak [{ital Plasma Physics and Controlled Nuclear Fusion Research}, 1986 (International Atomic Energy Agency, Vienna, 1987), Vol. 1, p. 159] high internal inductance discharges with high-confinement edge is investigated experimentally using a nonaxisymmetric poloidal magnetic-field perturbation from an external coil to drag down the plasma toroidal rotation. At similar values of internal inductance, discharges which rotate faster and have a stronger E{times}B flow shear have better confinement. These results indicate that E{times}B flow shear likely plays an important role in the confinement enhancement of these discharges. {copyright} {ital 1998 American Institute of Physics.}

Lao, L.L.; La Haye, R.J.; Burrell, K.H.; Chan, V.S.; Ferron, J.R.; Rettig, C.L.; Rewoldt, G.; Scoville, J.T.; Staebler, G.M.; Strait, E.J.; Tang, W.M.; Taylor, T.S.; Wroblewski, D. [General Atomics, P.O. Box 85608, San Diego, California92186-5608 (United States)

1998-04-01

9

Measurements of the particle confinement time in the L-2M stellarator  

SciTech Connect

A novel method for measuring the particle confinement time by using spectroscopic data has been developed. The electron influx into plasma is estimated from the intensity of the H{sub {alpha}} line. The first results obtained by this method in the L-2M stellarator are discussed.

Voronov, G. S.; Grishina, I. A. [Russian Academy of Sciences, Prokhorov Institute of General Physics (Russian Federation); Nalivaiko, V. P. [Moscow Technical University of Communications and Informatics (Russian Federation)

2010-05-15

10

Measurements of the particle confinement time in the L-2M stellarator  

NASA Astrophysics Data System (ADS)

A novel method for measuring the particle confinement time by using spectroscopic data has been developed. The electron influx into plasma is estimated from the intensity of the H? line. The first results obtained by this method in the L-2M stellarator are discussed.

Voronov, G. S.; Grishina, I. A.; Nalivaiko, V. P.

2010-05-01

11

Diffraction in the time of a confined particle and its Bohmian paths  

NASA Astrophysics Data System (ADS)

Diffraction in the time of a particle confined in a box with its walls removed suddenly at t = 0 is studied. The solution of the time-dependent Schrödinger equation is discussed analytically and numerically for various initial wavefunctions. In each case Bohmian trajectories of the particles are computed and also the mean arrival time at a given location is studied as a function of the initial state.

Mousavi, S. V.

2010-01-01

12

Short-time dynamics of colloidal particles confined between two walls  

Microsoft Academic Search

The short-time dynamics of colloidal particles in a quasi-two-dimensional geometry is studied by digital video microscopy. The particles (polystyrene spheres) are suspended in water and confined between two parallel glass plates, forming an effective two-dimensional system. The (effective) two-dimensional van Hove function G(r,t) and its self and distinct part are measured with a time resolution of 1\\/30 s. We found

Jesús Santana-Solano; José Luis Arauz-Lara

2002-01-01

13

Time-Dependent Ballistic Phenomena of Electron Injected into Half-Ellipse Confined Room  

Microsoft Academic Search

We theoretically studied the time-developing ballistic phenomena of a single-electron confined in a half-ellipse infinite-potential wall by solving the time-dependent Schrödinger equation numerically. We also solved the corresponding Newton equation in order to compare the classical results with the quantum ones, and extracted the quantum features. The ellipse-shaped potential wall completely reflects an electron and causes the focusing ratio of

Takuji Koiso; Masakazu Muraguchi; Kyozaburo Takeda; Naoki Watanabe

2005-01-01

14

Application of Clenshaw-Curtis Method in Confined Time of Arrival Operator Eigenvalue Problem  

NASA Astrophysics Data System (ADS)

The Clenshaw-Curtis method in discretizing a Fredholm integral operator is applied to solving the confined time of arrival operator eigenvalue problem. The accuracy of the method is measured against the known analytic solutions for the noninteracting case, and its performance compared against the well-known Nystrom method. It is found that Clenshaw-Curtis's is superior to Nystrom's. In particular, Nystrom method yields at most five correct decimal places for the eigenvalues and eigenfunctions, while Clenshaw-Curtis yields eigenvalues correct to 16 decimal places and eigenfunctions up to 15 decimal places for the same number of quadrature points. Moreover, Clenshaw-Curtis's accuracy in the eigenvalues is uniform over a determinable range of the computed eigenvalues for a given number of quadrature abscissas. Clenshaw-Curtis is then applied to the harmonic oscillator confined time of arrival operator eigenvalue problem.

Vitancol, Roberto S.; Galapon, Eric A.

15

Can inertial electrostatic confinement work beyond the ion-ion collisional time scale?  

SciTech Connect

Inertial electrostatic confinement systems are predicated on a non-equilibrium ion distribution function. Coulomb collisions between ions cause this distribution to relax to a Maxwellian on the ion-ion collisional time-scale. The power required to prevent this relaxation and maintain the IEC configuration for times beyond the ion-ion collisional time scale is shown to be at least an order of magnitude greater than the fusion power produced. It is concluded that IEC systems show little promise as a basis for the development of commercial electric power plants.

Nevins, W.M.

1995-01-01

16

Can inertial electrostatic confinement work beyond the ion--ion collisional time scale?  

SciTech Connect

Inertial electrostatic confinement (IEC) systems are predicated on a nonequilibrium ion distribution function. Coulomb collisions between ions cause this distribution to relax to a Maxwellian on the ion--ion collisional time scale. The power required to prevent this relaxation and maintain the IEC configuration for times beyond the ion--ion collisional time scale is shown to be greater than the fusion power produced. It is concluded that IEC systems show little promise as a basis for the development of commercial electric power plants. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

Nevins, W.M. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)

1995-10-01

17

Analysis of molecular diffusion by first-passage time variance identifies the size of confinement zones.  

PubMed

The diffusion of receptors within the two-dimensional environment of the plasma membrane is a complex process. Although certain components diffuse according to a random walk model (Brownian diffusion), an overwhelming body of work has found that membrane diffusion is nonideal (anomalous diffusion). One of the most powerful methods for studying membrane diffusion is single particle tracking (SPT), which records the trajectory of a label attached to a membrane component of interest. One of the outstanding problems in SPT is the analysis of data to identify the presence of heterogeneity. We have adapted a first-passage time (FPT) algorithm, originally developed for the interpretation of animal movement, for the analysis of SPT data. We discuss the general application of the FPT analysis to molecular diffusion, and use simulations to test the method against data containing known regions of confinement. We conclude that FPT can be used to identify the presence and size of confinement within trajectories of the receptor LFA-1, and these results are consistent with previous reports on the size of LFA-1 clusters. The analysis of trajectory data for cell surface receptors by FPT provides a robust method to determine the presence and size of confined regions of diffusion. PMID:21402028

Rajani, Vishaal; Carrero, Gustavo; Golan, David E; de Vries, Gerda; Cairo, Christopher W

2011-03-16

18

Energy confinement time and electron density profile shape in TFTR (Tokamak Fusion Test Reactor)  

SciTech Connect

The electron density profiles of intense deuterium neutral-beam- heated plasmas (P{sub tot}/P{sub ohm} {gt} 10) are characterized as a peakedness parameter (F{sub ne} = n{sub eo}/{l angle}n{sub e}{r angle}) in the Tokamak Fusion Test Reactor (TFTR). The gross energy confinement time ({tau}{sub E} = E{sub tot}/P{sub tot}) at the time of maximum stored energy is found to be a weak function of the plasma current and total heating power but depends strongly on the peakedness parameter. A regression study showed {tau}{sub E} = 2.4 {times} 10{sup {minus}3}F{sub ne}{sup 0.76}I{sub P}{sup 0.18}P{sub tot}{sup {minus}0.12} for a data set of 561 discharges in the TFTR. Also {tau}{sub E} can be represented as {tau}{sub E} = {tau}{sub E}{sup L}f(F{sub ne}), where {tau}{sub E}{sup L} is the empirical L-mode scaling result. A similar scaling applies to an appropriately defined incremental energy confinement time ({tau}{sub inc} = dE{sub tot}/dP{sub tot}{vert bar}{sub F{sub ne} = constant}). 14 refs., 4 figs.

Park, H.K.; Bell, M.G.; Goldston, R.J.; Hawryluk, R.J.; Johnson, D.W.; Scott, S.D.; Wieland, R.M.; Zarnstorff, M.C.; Bitter, M.; Bretz, N.; Budny, R.; Dylla, H.F.; Grek, B.; Howell, R.B.; Hsuan , H.; Johnson, L.C.; Mansfield, D.K.; Ramsey, A.T.; Schivell, J.; Taylor, G.; Ulrickson, M.

1989-11-01

19

Transport in a confined compressible fluid under time-dependent volumetric heat sources  

NASA Astrophysics Data System (ADS)

The response of a confined compressible perfect gas to an uneven time-dependent volumetric heat source is investigated using an algorithm based on a splitting technique of Issa (1986) and called PISO (for pressure implicity with splitting of operators), to solve the low-Mach number compressible Navier-Stokes equations numerically. The numerical results obtained are compared with the first-order analytical solution in the bulk and boundary layers. Then, the second-order asymptotic solution in the bulk is obtained to improve the linkage between the numerical and the analytical results. Results obtained are interpreted in terms of the so-called long-time-scale boundary layer piston effect.

Zappoli, B.; Bailly, D.

1990-10-01

20

Fragile-Strong Fluid Crossover and Universal Relaxation Times in a Confined Hard-Disk Fluid  

NASA Astrophysics Data System (ADS)

We show that a system of hard disks confined to a narrow channel exhibits a fragile-strong fluid crossover located at the maximum of the isobaric heat capacity and that the relaxation times for different channel widths fall onto a single master curve when rescaled by the relaxation times and temperatures of the crossover. Calculations of the configurational entropy and the inherent structure equation of state find that the crossover is related to properties of the jamming landscape for the model but that the Adam-Gibbs relation does not predict the relaxation behavior. We also show that a facilitated dynamics description of the system, where kinetically excited regions are identified with local packing arrangements of the disks, successfully describes the fragile-strong crossover.

Yamchi, Mahdi Zaeifi; Ashwin, S. S.; Bowles, Richard K.

2012-11-01

21

Spot Variation Fluorescence Correlation Spectroscopy Allows for Superresolution Chronoscopy of Confinement Times in Membranes  

PubMed Central

Resolving the dynamical interplay of proteins and lipids in the live-cell plasma membrane represents a central goal in current cell biology. Superresolution concepts have introduced a means of capturing spatial heterogeneity at a nanoscopic length scale. Similar concepts for detecting dynamical transitions (superresolution chronoscopy) are still lacking. Here, we show that recently introduced spot-variation fluorescence correlation spectroscopy allows for sensing transient confinement times of membrane constituents at dramatically improved resolution. Using standard diffraction-limited optics, spot-variation fluorescence correlation spectroscopy captures signatures of single retardation events far below the transit time of the tracer through the focal spot. We provide an analytical description of special cases of transient binding of a tracer to pointlike traps, or association of a tracer with nanodomains. The influence of trap mobility and the underlying binding kinetics are quantified. Experimental approaches are suggested that allow for gaining quantitative mechanistic insights into the interaction processes of membrane constituents.

Ruprecht, Verena; Wieser, Stefan; Marguet, Didier; Schutz, Gerhard J.

2011-01-01

22

Effects of confinement on the statistics of encounter times: exact analytical results for random walks in a partitioned lattice  

NASA Astrophysics Data System (ADS)

We study the effects of temporarily and permanently confining domains on the statistics of first-passage times in finite lattices in one and two dimensions. We present exact results for the mean and variance of the first-passage time between arbitrary sites in the following: (1) a finite one-dimensional lattice partitioned into temporarily confining domains and (2) a finite two-dimensional lattice with reflecting boundaries for a single random walker and an immobile target. In the one-dimensional case, we also present the full first-passage time distribution via numerical inversion of Laplace transforms.

Kalay, Ziya

2012-06-01

23

Time-Dependent Ballistic Phenomena of Electron Injected into Half-Ellipse Confined Room  

NASA Astrophysics Data System (ADS)

We theoretically studied the time-developing ballistic phenomena of a single-electron confined in a half-ellipse infinite-potential wall by solving the time-dependent Schrödinger equation numerically. We also solved the corresponding Newton equation in order to compare the classical results with the quantum ones, and extracted the quantum features. The ellipse-shaped potential wall completely reflects an electron and causes the focusing ratio of unity in the classical limit. The dispersion of the wave packet of an electron, however, weakens this characteristic nature, and reduces the focusing ratio from unity. Because the dispersion also lets an electron arrive at the collector indistinctly, we define the effective arrival time by finding inflections in the time-dependent profile of the probability density at the collector. Based on the second-derivation technique, we further determine the quantum arrival time (QAT) at which the intrusion of the wave packet occurs dominantly. The comparison of this QAT with the classical arrival time (CAT) determines whether the corresponding ballistic propagation can be discussed on the basis of the quantum consideration or the classical prediction. We further studied how the change in the half-ellipse potential wall shape affects the ballistic phenomena through the change in the ellipticity ?, the system size L and the dispersion degree ? of the wave packet. Using the ellipse-shaped infinite-potential wall, the application of the magnetic field causes irrational cyclotron motion assisted by the ellipse potential, in addition to the rational cyclotron motions. The numerical solution of the time-dependent Schr\\"{o}dinger equation determines the unique cyclotron motion whose peculiarity is caused by the dispersion of the wave packet and is rarely predicted by the classical limit.

Koiso, Takuji; Muraguchi, Masakazu; Takeda, Kyozaburo; Watanabe, Naoki

2005-06-01

24

Long time dynamics of single linear and circular ds-DNA confined in sub-100nm nanoslits  

NASA Astrophysics Data System (ADS)

We investigate the role of topological constraints on DNA dynamics in very strong confinement to study the dynamics of nuclear chromosome and DNA viral packaging. Experiments and simulations were carried out to investigate the equilibrium shape and dynamics of the single linear and circular ?-DNA confined in a silicon/glass nanoslit. We measured the chain extension r, shape asphericity A, extensional (?||) and rotational relaxation time ?r, and examined the dependence on chain topology as functions of the slit height h (20 ˜ 780 nm) and the solvent ionic strength I (0.8 ˜250 mM). We observed that the shape asphericity increases as h and I decrease as the chain shape becomes anisotropic. Moreover, in sub-Kuhn length confinement, the DNA relaxation time increases with decreasing h in a smooth and broad transition.

Lin, Po-Keng; Chang, Jen-Fang; Stachiv, I.; Chou, Chia-Fu; Chen, Y.-L.

2011-03-01

25

Dynamics of confined cavity modes in a phononic crystal slab investigated by in situ time-resolved experiments  

NASA Astrophysics Data System (ADS)

The confinement of elastic waves within a single defect in a phononic crystal slab is investigated both experimentally and theoretically. The structure is formed by a honeycomb lattice of air holes in a silicon plate with one hole missing in its center. The frequencies and polarizations of the localized modes in the first band gap are computed with a finite element method. A noncontact laser ultrasonic technique is used both to excite flexural Lamb waves and to monitor in situ the displacement field within the cavity. We report on the time evolution of confinement, which is distinct according to the symmetry of the eigenmode.

Marchal, R.; Boyko, O.; Bonello, B.; Zhao, J.; Belliard, L.; Oudich, M.; Pennec, Y.; Djafari-Rouhani, B.

2012-12-01

26

{gamma}-ray 'bang-time' measurements with a gas-Cherenkov detector for inertial-confinement fusion experiments  

SciTech Connect

In a laser driven inertial-confinement fusion experiment, bang time is defined as the time between the laser light impinging the target and the peak of the fusion reactions. Bang time is often used to compare computed predictions to experiment. Large laser facilities, such as NIF and LMJ, which are currently under construction, will produce yields far in excess of any previous inertial-confinement fusion experiment. One of the implications of such high yields is that fusion {gamma} rays, which have branching ratios four orders of magnitude less than that of fusion neutrons, may be used to diagnose bang time. This article describes the first of such {gamma}-ray bang-time measurement made using the OMEGA laser facility at the Laboratory for Laser Energetics, University of Rochester. The diagnostic used for this was a gas Cherenkov detector. The experimental setup, data and error analyses, and suggested improvements are presented.

Horsfield, C. J.; Caldwell, S. E.; Christensen, C. R.; Evans, S. C.; Mack, J. M.; Sedillo, T.; Young, C. S.; Glebov, V. Yu. [Atomic Weapons Establishment, Aldermaston, Reading, Berkshire RG7 4PR (United Kingdom); Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Laboratory for Laser Energetics, University of Rochester, Rochester, New York 14623-1299 (United States)

2006-10-15

27

Electron relaxation times due to the deformation-potential interaction of electrons with confined acoustic phonons in a free-standing quantum well  

Microsoft Academic Search

The confined acoustic phonons in free-standing quantum wells are considered in detail. The Hamiltonian describing interactions of the confined acoustic phonons with electrons in the approximation of the deformation potential and the corresponding electron transition probability density are derived. They are used to analyze the electron scattering times (inverse scattering rate, momentum relaxation time, and the energy relaxation time) in

N. Bannov; V. Aristov; V. Mitin; M. A. Stroscio

1995-01-01

28

Long-time impurity confinement as a precursor to disruptions in ohmically heated tokamaks  

NASA Astrophysics Data System (ADS)

It has been observed in several tokamaks that the confinement of test impurities increases dramatically when operating near density limits. The characteristics of the working gas transport coefficients also change character under these conditions. These changes appear to be caused by a suppression of the anomalous transport mechanisms. This series of vugraphs investigates the role of these changes in initiating disruptions.

Isler, R. C.; Rowan, W. L.

29

Time-Resolved Nonlinear Optical Spectroscopy of Magnetically Confined Quantum Well Excitons.  

NASA Astrophysics Data System (ADS)

The electronic states in a semiconductor quantum well undergo a transition from quasi-two-dimensional (2D) excitons to quasi-zero-dimensional (0D) magneto-excitons when subjected to a strong perpendicular magnetic field. In this transition, the band of free carrier states in the 2D quantum well breaks up into a series of isolated resonance peaks characteristic of systems in 0D. Using high intensity femtosecond broad-band continuum laser pulses, the time resolved nonlinear optical response of magneto-excitons is measured at fields as high as 12 Tesla. The results of these experiments demonstrate that at zero field, excitons interact with each other through a molecular potential similar to that in a hydrogen molecule. Magneto-excitons are strongly compressed by the high magnetic field, resulting in the quenching of their molecular interactions. At high fields, a gas of magneto-excitons in a semiconductor quantum well behaves as an ensemble of noninteracting two-level atoms. Coherent nonresonant excitation of quantum well magneto-excitons demonstrates that their nonlinear optical response is that of a Coulomb-enhanced two-level system. Excitation below the lowest magneto-exciton resonance results in a Rabi blue shift, while excitation above it results in a Rabi red shift, as expected for two-level atomic systems. Relaxation dynamics are also affected by the 0D confinement produced by a perpendicular magnetic field. At zero field, a distribution of carriers excited into the above-bandgap states of the semiconductor exhibit rapid scattering to achieve thermalization of the initially nonthermal distribution. At high field, however, the resonance peaks are widely separated, all low-energy scattering channels are eliminated, and relaxation of the initial distribution slows by orders of magnitude. Semiconductor quantum well magneto-excitons provide a unique laboratory in which to investigate the physics of excitonic systems during the transition from 2D to 0D. The experimental results demonstrate that this transition is accompanied by the elimination of Coulomb interactions, so that in the limit, the 0D system behaves as a noninteracting gas of two-level atoms. (Copies available exclusively from MIT Libraries, Rm. 14-0551, Cambridge, MA 02139-4307. Ph. 617 -253-5668; Fax 617-253-1690.).

Stark, Jason Blain

30

Effects of E{times}B velocity shear and magnetic shear on turbulence and transport in magnetic confinement devices  

SciTech Connect

One of the scientific success stories of fusion research over the past decade is the development of the E{times}B shear stabilization model to explain the formation of transport barriers in magnetic confinement devices. This model was originally developed to explain the transport barrier formed at the plasma edge in tokamaks after the L (low) to H (high) transition. This concept has the universality needed to explain the edge transport barriers seen in limiter and divertor tokamaks, stellarators, and mirror machines. More recently, this model has been applied to explain the further confinement improvement from H (high) mode to VH (very high) mode seen in some tokamaks, where the edge transport barrier becomes wider. Most recently, this paradigm has been applied to the core transport barriers formed in plasmas with negative or low magnetic shear in the plasma core. These examples of confinement improvement are of considerable physical interest; it is not often that a system self-organizes to a higher energy state with reduced turbulence and transport when an additional source of free energy is applied to it. The transport decrease that is associated with E{times}B velocity shear effects also has significant practical consequences for fusion research. The fundamental physics involved in transport reduction is the effect of E{times}B shear on the growth, radial extent, and phase correlation of turbulent eddies in the plasma. The same fundamental transport reduction process can be operational in various portions of the plasma because there are a number of ways to change the radial electric field E{sub r}. An important theme in this area is the synergistic effect of E{times}B velocity shear and magnetic shear. Although the E{times}B velocity shear appears to have an effect on broader classes of microturbulence, magnetic shear can mitigate some potentially harmful effects of E{times}B velocity shear and facilitate turbulence stabilization. (Abstract Truncated)

Burrell, K.H. [General Atomics, P.O. Box 85608, San Diego, California 92186-5608 (United States)

1997-05-01

31

Carborane confined nanoparticles for boron neutron capture therapy: Improved stability, blood circulation time and tumor accumulation  

Microsoft Academic Search

Carborane confined nanoparticles based on the core cross-linked and boron-containing micelles (CL micelles) were prepared using the radical polymerization of poly(ethylene glycol)-block-poly(lactide) copolymer (PEG-b-PLA), which contained an acetal group at the PEG end and a methacryloyl group at the PLA end (acetal-PEG-b-PLA-MA), with polymerizable carborane (VB-carborane) as a cross-linker. No leakage of VB-carborane from the CL micelles was observed in

Shogo Sumitani; Motoi Oishi; Yukio Nagasaki

2011-01-01

32

Entanglement and confinement effects constraining polymer chain dynamics on different length and time scales  

Microsoft Academic Search

With the time constants usually considered to be characteristic for polymer dynamics, namely ?s (the segment fluctuation time), ?e (the entanglement time), and ?R (the longest Rouse relaxation time), the time scales of particular interest: (i) t?s; (ii) ?st?e; and (iii) ?et?R will be discussed and compared with experimental data. These ranges correspond to the chain-mode length scales: (i) ?b;

Rainer Kimmich

2010-01-01

33

Relationships between corticosterone concentration and season, time of day and confinement in a wild reptile (tuatara, Sphenodon punctatus).  

PubMed

Seasonal and daily variation in basal plasma concentrations of corticosterone and the effect of short-term confinement on plasma corticosterone concentration were examined in wild adult male and female tuatara (Sphenodon punctatus) on Stephens Island, New Zealand. Males and females sampled immediately upon capture at night (active period) showed significant variation in basal plasma corticosterone among four seasons of the year, and females also showed variation in concentration between reproductive states sampled at the same time. Highest basal concentrations in females were seen in November, when the level in gravid females about to nest (4.45 +/- 0.66 ng/ml; mean +/- SE) was almost twice that in nonnesting females at the same time (2.48 +/- 0.30 ng/ml). Plasma samples collected from tuatara at dusk, middle of the night, dawn, and middle of the day showed no significant daily variation in corticosterone concentration in either summer or winter. In these samples, significant positive correlations between body temperature and log plasma corticosterone were observed in males in summer and winter, but not in females in either season. Mean corticosterone concentrations in tuatara held in cloth bags for 3 h were significantly higher than in free-roaming controls (P < 0.01), with mean concentrations in males about 23 times, and vitellogenic females 9 times, those of their respective controls. Plasma corticosterone concentrations measured in this stress study were compared with previously published concentrations for plasma sex steroids in the same individuals. Corticosterone was positively correlated with progesterone (both sexes), but not with testosterone (both sexes) or estradiol (measured in females only). In summary, wild adult tuatara have low basal levels of plasma corticosterone that vary seasonally, but not diurnally. As in other reptiles, corticosterone concentration shows a significant elevation in response to short-term confinement. PMID:9570930

Tyrrell, C L; Cree, A

1998-05-01

34

Measuring time of flight of fusion products in an inertial electrostatic confinement fusion device for spatial profiling of fusion reactions.  

PubMed

A new diagnostic has been developed that uses the time of flight (TOF) of the products from a nuclear fusion reaction to determine the location where the fusion reaction occurred. The TOF diagnostic uses charged particle detectors on opposing sides of the inertial electrostatic confinement (IEC) device that are coupled to high resolution timing electronics to measure the spatial profile of fusion reactions occurring between the two charged particle detectors. This diagnostic was constructed and tested by the University of Wisconsin-Madison Inertial Electrostatic Confinement Fusion Group in the IEC device, HOMER, which accelerates deuterium ions to fusion relevant energies in a high voltage (?100 kV), spherically symmetric, electrostatic potential well [J. F. Santarius, G. L. Kulcinski, R. P. Ashley, D. R. Boris, B. B. Cipiti, S. K. Murali, G. R. Piefer, R. F. Radel, T. E. Radel, and A. L. Wehmeyer, Fusion Sci. Technol. 47, 1238 (2005)]. The TOF diagnostic detects the products of D(d,p)T reactions and determines where along a chord through the device the fusion event occurred. The diagnostic is also capable of using charged particle spectroscopy to determine the Doppler shift imparted to the fusion products by the center of mass energy of the fusion reactants. The TOF diagnostic is thus able to collect spatial profiles of the fusion reaction density along a chord through the device, coupled with the center of mass energy of the reactions occurring at each location. This provides levels of diagnostic detail never before achieved on an IEC device. PMID:23556815

Donovan, D C; Boris, D R; Kulcinski, G L; Santarius, J F; Piefer, G R

2013-03-01

35

Neutron time-of-flight ion temperature diagnostic for inertial confinement fusion experiments  

NASA Astrophysics Data System (ADS)

We are constructing a T(sub i) diagnostic for low neutron yield (5 x 10(exp 7) to above 10(exp 9)) d-d and d-t targets in the Nova facility at Livermore. The diagnostic measures the neutron energy spread with 960 scintillator-photomultiplier detectors located 28 m from the target and operates in the single-hit mode. Each detector can measure a single neutron arrival with time resolution of 1 nano-s or better. The arrival time distribution is constructed from the results of typically 200-500 detector measurements. The ion temperature is determined from the spread in neutron energy (Delta)E(sub n) proportional to T(sub i)(sup (1/2)), which is related to the arrival time spread by (Delta)t/t = -(1/2)(Delta)E(sub n)/E(sub n). Each neutron arrival is detected by using a photomultiplier tube to observe the recoil proton from elastic scattering in a fast plastic scintillator. The timing electronics for each channel consist of a novel constant fraction-like discriminator and a multiple hit time-to-digital converter (TDC). The overall system design, together with single channel performance data, is presented.

Chrien, R. E.; Simmons, D. F.; Holmberg, D. L.

36

A diamond detector for inertial confinement fusion X-ray bang-time measurements at the National Ignition Facility  

SciTech Connect

An instrument has been developed to measure X-ray bang-time for inertial confinement fusion capsules; the time interval between the start of the laser pulse and peak X-ray emission from the fuel core. The instrument comprises chemical vapor deposited polycrystalline diamond photoconductive X-ray detectors with highly ordered pyrolytic graphite X-ray monochromator crystals at the input. Capsule bang-time can be measured in the presence of relatively high thermal and hard X-ray background components due to the selective band pass of the crystals combined with direct and indirect X-ray shielding of the detector elements. A five channel system is being commissioned at the National Ignition Facility at Lawrence Livermore National Laboratory for implosion optimization measurements as part of the National Ignition Campaign. Characteristics of the instrument have been measured demonstrating that X-ray bang-time can be measured with {+-} 30ps precision, characterizing the soft X-ray drive to +/- 1eV or 1.5%.

MacPhee, A G; Brown, C; Burns, S; Celeste, J; Glenzer, S H; Hey, D; Jones, O S; Landen, O; Mackinnon, A J; Meezan, N; Parker, J; Edgell, D; Glebov, V Y; Kilkenny, J; Kimbrough, J

2010-11-09

37

Doping-profile effects on the tunneling times of electrons confined in double-barrier heterostructures  

Microsoft Academic Search

We study and compare the behavior of the left- and right-tunneling times of electrons quasiconfined in asymmetric double-barrier structures as a function of the bias for two different doping configurations in the electrodes: uniform doping and gradual doping. The potential experienced by the electrons is calculated self-consistently for each case by simultaneously solving the Schrödinger and Poisson equations. Afterwards, the

N. Mingo; J. A. Porto; J. Sánchez-Dehesa

1994-01-01

38

Time-resolved study of Raman gain in highly confined silicon-on-insulator waveguides  

NASA Astrophysics Data System (ADS)

We show time-resolved measurement of Raman gain in Silicon submicron-size planar waveguide using picosecond pump and probe pulses. A net nonlinear gain of 6 dB is obtained in a 7-mm long waveguide with 20.7-W peak pump power. We demonstrate an ultrafast all-optical switch based on the free-carrier dispersion effect in the silicon waveguide, whose transmission is enhanced by more than 13 dB due to the Raman effect.

Xu, Qianfan; Almeida, Vilson R.; Lipson, Michal

2004-09-01

39

Real-time plasma control in a dual-frequency, confined plasma etcher  

Microsoft Academic Search

The physics issues of developing model-based control of plasma etching are presented. A novel methodology for incorporating real-time model-based control of plasma processing systems is developed. The methodology is developed for control of two dependent variables (ion flux and chemical densities) by two independent controls (27 MHz power and O2 flow). A phenomenological physics model of the nonlinear coupling between

V. Milosavljevic; A. R. Ellingboe; C. Gaman; J. V. Ringwood

2008-01-01

40

The long time tail of molecular velocity correlation in a confined fluid: observation by modulated gradient spin-echo NMR  

NASA Astrophysics Data System (ADS)

In addition to the fast correlation for local stochastic motion the molecular velocity correlation function in a fluid enclosed within the pore boundaries features a slow long time tail decay [1,2]. This article presents a study by the NMR modulated gradient spin-echo method (MGSE) [3] on a system of water trapped in the space between the closely packed polystyrene beads. The results prove that the obtained dependence of spin-echo attenuation on time, gradient strength and modulation frequency nicely corresponds to the recently developed NMR approach, which is able to describe the effects of arbitrarily shaped gradient pulse sequence on the spin-echo attenuation [4,5]. With an MGSE pulse sequence, a repetitive train of RF pulses with interspersed gradient pulses periodically modulates the spin-phase, giving the spin-echo attenuation proportional to a value of the velocity correlation spectrum at the modulation frequency. It enables to extract the low-frequency correlation spectrum of confined water molecules. The function exhibits a negative long time tail characteristic (a low-frequency decay of the spectrum), that can be well fitted with the spectrum calculated from the solution of the Langevin equation for restricted diffusion (which exhibits an exponential decay) as well as with the spectrum obtained when simulating the hydrodynamics of molecular motion constrained by capillary walls (which gives an algebraic decay).

Stepišnik, J.; Callaghan, P. T.

2000-11-01

41

Using time-lapse electrical resistivity tomography to visualize conduit-matrix exchange a sink-rise system of a semi-confined karst aquifer  

NASA Astrophysics Data System (ADS)

The Santa Fe River Basin is a complex watershed containing hydrologic regions of confined, semi-confined and unconfined karst aquifer. Each region has unique characteristics that lead to difficulty in describing how groundwater and surface water interact. In the semi-confined region, the Santa Fe River is entirely captured by a sinkhole then flows through various karst windows and emerges as a spring 6 kilometers to the south. Recent work has developed a working hypothesis to describe how groundwater and surface water interact in the karst aquifer during high and low flow. In this study, we are interested in the semi-confined region and visualizing how groundwater and surface interactions control overall flow. Using electrical resistivity tomography, a time lapse study was conducted at two locations to study changes in conductivity during groundwater and rain flow driven events over a six-week time period. Our results reflect the locations of known karst conduits. Changes in resistivity during rainfall infiltration and in karst and matrix flow over time provide insight into exchange dynamics. These observations provide details about the surface water-groundwater exchange in a complicated, semi-confined, sink-rise system.

Meyerhoff, S. B.; Fiebig, F.; Maxwell, R. M.; Revil, A.; Karaoulis, M.; Martin, J. B.; Graham, W. D.

2011-12-01

42

Time evolution of filamentation and self-generated fields in the coronae of directly driven inertial-confinement fusion capsules  

SciTech Connect

Time-gated radiography with monoenergetic 15-MeV protons, 3-MeV protons, and 4-MeV alpha particles has revealed a rich and complex evolution of electromagnetic field structures in and around imploding, directly driven inertial-confinement fusion (ICF) targets at the OMEGA laser facility. Plastic-shell capsules and solid plastic spheres were imaged during and after irradiation with ICF-relevant laser drive (up to 6 x 10{sup 14} W/cm{sup 2}). Radial filaments appeared while the laser was on; they filled, and were frozen into, the out-flowing corona, persisting until well after the end of the laser drive. Data from specially designed experiments indicate that the filaments were not generated by two-plasmon-decay instabilities or by Rayleigh-Taylor instabilities associated with shell acceleration. Before the onset of visible filamentation, quasi-spherical field structures appeared outside the capsule in the images in a form that suggests outgoing shells of net positive charge. We conjecture that these discrete shells are related to multiple peaks seen previously in the spectra of protons ablated from the targets.

Seguin, F. H.; Li, C. K.; Manuel, M. J.-E.; Rinderknecht, H. G.; Sinenian, N.; Frenje, J. A.; Rygg, J. R.; Hicks, D. G.; Petrasso, R. D. [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Delettrez, J.; Betti, R.; Marshall, F. J.; Smalyuk, V. A. [Laboratory for Laser Energetics, University of Rochester, Rochester, New York 14623 (United States)

2012-01-15

43

Time-dependent Poiseuille flow of a viscous compressible fluid confined between two planar walls with dynamic partial slip boundary condition  

NASA Astrophysics Data System (ADS)

Time-dependent Poiseuille flow of a viscous compressible fluid confined between two planar walls is studied for a partial slip boundary condition with frequency-dependent slip length. After an initial uniform impulse parallel to the walls, the flow pattern quickly becomes nearly parabolic. For a narrow gap, a dynamic slip length can lead to damped oscillations of total fluid momentum.

Felderhof, B. U.

2012-06-01

44

Experimental study of the effects of lithium coated plasma facing components on energy confinement time in the CDX-U device  

NASA Astrophysics Data System (ADS)

Experimentally constrained equilibrium reconstructions are an important analysis tool used to understand the physics of magnetically confined plasmas. This thesis describes the first ever calculations of equilibrium reconstructions for spherical tokamak plasmas in the presence of lithium coated plasma facing components (PFC's) in the Current Drive eXperiment - Upgrade (CDX-U) device. Equilibria were calculated using a modified version of the Equilibrium and Stability Code (ESC), and were constrained by measurements made from a collection of magnetic field diagnostics. The ESC was modified to incorporate the first ever implementation of a novel response function technique for magnetic field diagnostic calibration. The technique is well suited for situations where the assumption of toroidal symmetry of the magnetic field is invalid, or when wall eddy currents are too large to neglect. Also included is a detailed discussion of the calculation of energy confinement time from power balance arguments, using parameters obtained from equilibrium reconstructions. The energy confinement time, as derived from plasma equilibria, was as large as 6 milliseconds for plasmas in the presence of both solid and liquid lithium PFC's. This represents a significant improvement over baseline plasmas, which typically had energy confinement times of 1 millisecond or less. The energy confinement for plasmas with lithium PFC's also showed an improvement over that expected from the ITER98y1 confinement scaling, which is derived from a database of earlier tokamak results. The improvement in confinement over this scaling correlates with the observed increase in density "pump-out", which is indicative of low wall-recycling. Traditionally, plasma fueling has been dominated by wall-recycling, with 90% or more of the fuel coming from recycling sources instead of externally controlled means, such as gas puffing or pellet injection. Previous lithium wall coating experiments on the Tokamak Fusion Test Reactor (TFTR) resulted in a reduction of recycling at the wall and the highest ever energy confinement on TFTR. However, the TFTR experiments were complicated by the surface chemistry of solid lithium on carbon, leaving unanswered questions concerning the achievable plasma performance in a fully lithium coated environment.

Spaleta, Jeffrey Dario

45

Dynamic response of materials on sub-nanosecond time scales, and beryllium properties for inertial confinement fusion  

SciTech Connect

During the past few years, substantial progress has been made in developing experimental techniques capable of investigating the response of materials to dynamic loading on nanosecond time scales and shorter, with multiple diagnostics probing different aspects of the behavior. these relatively short time scales are scientifically interesting because plastic flow and phase changes in common materials with simple crystal structures--such as iron--may be suppressed, allowing unusual states to be induced and the dynamics of plasticity and polymorphism to be explored. Loading by laser ablation can be particularly convenient. The TRIDENT laser has been used to impart shocks and isentropic compression waves from {approx}1 to 200GPa in a range of elements and alloys, with diagnostics including surface velocimetry (line-imaging VISAR), surface displacement (framed area imaging), x-ray diffraction (single crystal and polycrystal), ellipsometry, and Raman spectroscopy. A major motivation has been the study of the properties of beryllium under conditions relevant to the fuel capsule in inertial confinement fusion: magnetically-driven shock and isentropic compression shots at Z were used to investigate the equation of state and shock melting characteristics, complemented by laser ablation experiments to investigate plasticity and heterogeneous response. These results will help to constrain acceptable tolerances on manufacturing, and possible loading paths, for inertial fusion ignition experiments at the National Ignition Facility. Laser-based techniques are being developed further for future material dynamics experiments, where it should be possible to obtain high quality data on strength and phase changes up to at least 1TPa.

Swift, D C; Tierney, T E; Luo, S N; Paisley, D L; Kyrala, G A; Hauer, A; Greenfield, S R; Koskelo, A C; McClellan, K J; Lorenzana, H E; Knudson, M D; Peralta, P P; Loomis, E

2004-12-09

46

Correcting for bias of molecular confinement parameters induced by small-time-series sample sizes in single-molecule trajectories containing measurement noise.  

PubMed

Several single-molecule studies aim to reliably extract parameters characterizing molecular confinement or transient kinetic trapping from experimental observations. Pioneering works from single-particle tracking (SPT) in membrane diffusion studies [Kusumi et al., Biophys. J. 65, 2021 (1993)] appealed to mean square displacement (MSD) tools for extracting diffusivity and other parameters quantifying the degree of confinement. More recently, the practical utility of systematically treating multiple noise sources (including noise induced by random photon counts) through likelihood techniques has been more broadly realized in the SPT community. However, bias induced by finite-time-series sample sizes (unavoidable in practice) has not received great attention. Mitigating parameter bias induced by finite sampling is important to any scientific endeavor aiming for high accuracy, but correcting for bias is also often an important step in the construction of optimal parameter estimates. In this article, it is demonstrated how a popular model of confinement can be corrected for finite-sample bias in situations where the underlying data exhibit Brownian diffusion and observations are measured with non-negligible experimental noise (e.g., noise induced by finite photon counts). The work of Tang and Chen [J. Econometrics 149, 65 (2009)] is extended to correct for bias in the estimated "corral radius" (a parameter commonly used to quantify confinement in SPT studies) in the presence of measurement noise. It is shown that the approach presented is capable of reliably extracting the corral radius using only hundreds of discretely sampled observations in situations where other methods (including MSD and Bayesian techniques) would encounter serious difficulties. The ability to accurately statistically characterize transient confinement suggests additional techniques for quantifying confined and/or hop diffusion in complex environments. PMID:23944492

Calderon, Christopher P

2013-07-09

47

Correcting for bias of molecular confinement parameters induced by small-time-series sample sizes in single-molecule trajectories containing measurement noise  

NASA Astrophysics Data System (ADS)

Several single-molecule studies aim to reliably extract parameters characterizing molecular confinement or transient kinetic trapping from experimental observations. Pioneering works from single-particle tracking (SPT) in membrane diffusion studies [Kusumi , Biophys. J.BIOJAU0006-349510.1016/S0006-3495(93)81253-0 65, 2021 (1993)] appealed to mean square displacement (MSD) tools for extracting diffusivity and other parameters quantifying the degree of confinement. More recently, the practical utility of systematically treating multiple noise sources (including noise induced by random photon counts) through likelihood techniques has been more broadly realized in the SPT community. However, bias induced by finite-time-series sample sizes (unavoidable in practice) has not received great attention. Mitigating parameter bias induced by finite sampling is important to any scientific endeavor aiming for high accuracy, but correcting for bias is also often an important step in the construction of optimal parameter estimates. In this article, it is demonstrated how a popular model of confinement can be corrected for finite-sample bias in situations where the underlying data exhibit Brownian diffusion and observations are measured with non-negligible experimental noise (e.g., noise induced by finite photon counts). The work of Tang and Chen [J. Econometrics0304-407610.1016/j.jeconom.2008.11.001 149, 65 (2009)] is extended to correct for bias in the estimated “corral radius” (a parameter commonly used to quantify confinement in SPT studies) in the presence of measurement noise. It is shown that the approach presented is capable of reliably extracting the corral radius using only hundreds of discretely sampled observations in situations where other methods (including MSD and Bayesian techniques) would encounter serious difficulties. The ability to accurately statistically characterize transient confinement suggests additional techniques for quantifying confined and/or hop diffusion in complex environments.

Calderon, Christopher P.

2013-07-01

48

Microviscosity of supercooled water confined within aminopropyl-modified mesoporous silica as studied by time-resolved fluorescence spectroscopy.  

PubMed

The fluorescence dynamics of rhodamine B (RhB) immobilized on the pore surface of aminopropyl (AP)-modified mesoporous silica (diameter of the silica framework, 3.1 nm) was examined at temperatures between 293 and 193 K to study the microviscosity of supercooled water confined inside the pores. The mesoporous silica specimen with a dense AP layer (2.1 molecules nm(-2)) was prepared, and RhB isothiocyanate was covalently bound to part of the surface AP groups. The fluorescence lifetime of the surface RhB increased with decreasing temperature from 293 to 223 K, indicating that freezing of the confined water did not occur in this temperature range. The microviscosity of the supercooled confined water was evaluated from an analysis of the lifetime data based on a frequency-dependent friction model. PMID:23149606

Yamaguchi, Akira; Namekawa, Manato; Itoh, Tetsuji; Teramae, Norio

2012-01-01

49

Relationships between Corticosterone Concentration and Season, Time of Day and Confinement in a Wild Reptile (Tuatara, Sphenodon punctatus)  

Microsoft Academic Search

Seasonal and daily variation in basal plasma concentrations of corticosterone and the effect of short-term confinement on plasma corticosterone concentration were examined in wild adult male and female tuatara (Sphenodon punctatus) on Stephens Island, New Zealand. Males and females sampled immediately upon capture at night (active period) showed significant variation in basal plasma corticosterone among four seasons of the year,

C. L. Tyrrell; A. Cree

1998-01-01

50

Behavior of Plastic Sand Confinement Grids.  

National Technical Information Service (NTIS)

The concept of improving the load carrying ability of unbound aggregates, particularly sand, by lateral confinement has been investigated for some time. Extensive full-scale testing of the trafficability of confined beach sand pavement layers has been car...

1986-01-01

51

The long time tail of molecular velocity correlation in a confined fluid: observation by modulated gradient spin-echo NMR  

Microsoft Academic Search

In addition to the fast correlation for local stochastic motion the molecular velocity correlation function in a fluid enclosed within the pore boundaries features a slow long time tail decay [1,2]. This article presents a study by the NMR modulated gradient spin-echo method (MGSE) [3] on a system of water trapped in the space between the closely packed polystyrene beads.

Janez Stepišnik; Paul T. Callaghan

2000-01-01

52

Use of microarray technology to assess the time course of liver stress response after confinement exposure in gilthead sea bream (Sparus aurata L.)  

PubMed Central

Background Selection programs for growth and stress traits in cultured fish are fundamental to the improvement of aquaculture production. The gilthead sea bream (Sparus aurata) is the main aquacultured species in the Mediterranean area and there is considerable interest in the genetic improvement of this species. With the aim of increasing the genomic resources in gilthead sea bream and identifying genes and mechanisms underlying the physiology of the stress response, we developed a cDNA microarray for gilthead sea bream that is enriched by suppression substractive hybridization with stress and immunorelevant genes. This microarray is used to analyze the dynamics of gilthead sea bream liver expression profile after confinement exposure. Results Groups of confined and control juvenile fish were sampled at 6, 24, 72 and 120 h post exposure. GeneSpring analyses identified 202 annotated genes that appeared differentially expressed at least at one sampling time (P < 0.05). Gene expression results were validated by quantitative PCR of 10 target genes, and K-means clustering of differently expressed genes identified four major temporal gene expression profiles. Set 1 encompassed a rapid metabolic readjustment with enhanced uptake and intracellular transport of fatty acids as metabolic fuels. Set 2 was associated with a wide variety of tissue repair and remodeling processes that were mostly mediated by the stress response of the endoplasmic reticulum (ER). Sets 3 and 4 encompassed the re-establishment of cellular homeostasis with increased intracellular trafficking and scavenging of reactive oxygen species (ROS), accompanied by a bidirectional regulation of the immune system and a general decline of ROS production. Conclusions Collectively, these findings show the complex nature of the adaptive stress response with a clear indication that the ER is an important control point for homeostatic adjustments. The study also identifies metabolic pathways which could be analyzed in greater detail to provide new insights regarding the transcriptional regulation of the stress response in fish.

2010-01-01

53

Long-term effects of dredging operations program. Collation and interpretation of data for Times Beach confined disposal facility, Buffalo, New York. Final report  

SciTech Connect

This interim report, collates all data gathered for the Times Beach confined disposal facility (CDF), Buffalo, New York. This purpose of the studies at the CDF was to determine the mobility and potential hazard of contaminants known to be in the dredged material placed at Times Beach by sampling and analyzing various components of the developing ecosystems. Upland, wetland, and aquatic areas are represented within the CDF and, for each area, inventories of colonizing biota were made and samples collected for measurement of heavy metals and organic compound contaminants. Samples of dredged material, vegetation, and soil-dwelling invertebrates, and vertebrates have been collected and heavy metal concentrations measured. Results suggest that the persistent contaminants, particularly cadmium, are concentrating in the leaf litter zone and moving into the detritivorous invertebrates. Highest concentrations of heavy metals were noted in earthworms. Earth worms, millipedes, woodlice, and spiders appeared to be target organisms for accumulation of heavy metals, and these groups contained higher concentrations of copper and cadmium than the other groups. Polychlorinated biphenyl (PCB) and polynuclear aromatic hydrocarbon contaminants in the dredged material were below machine detection limits in the vertebrate top-predators. Contaminant concentrations in water from ground water wells were below guidance limits.

Stafford, E.A.; Simmers, J.W.; Rhett, R.G.; Brown, C.P.

1991-06-01

54

Confinement contains condensates  

NASA Astrophysics Data System (ADS)

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 commonly been viewed as constant empirical mass scales that fill all space-time, are instead wholly contained within hadrons; i.e., they are a property of hadrons themselves and expressed, e.g., in their Bethe-Salpeter or light-front wave functions. We explain that this paradigm is consistent with empirical evidence and incidentally expose misconceptions in a recent Comment.

Brodsky, Stanley J.; Roberts, Craig D.; Shrock, Robert; Tandy, Peter C.

2012-06-01

55

Spatial profiling using a Time of Flight Diagnostic and applications of deuterim-deuterium fusion in Inertial Electrostatic Confinement fusion devices  

NASA Astrophysics Data System (ADS)

The Inertial Electrostatic Confinement (IEC) Fusion Research Group at the University of Wisconsin-Madison utilizes IEC devices as small-scale neutron generators using D-D fusion to create 2.45 MeV neutrons for the purpose of detecting clandestine material. Detection of explosives in particular can be accomplished using thermal neutron capture methods to identify characteristic nitrogen signatures in explosive material. Research has been conducted to increase reliability of detection, decrease interrogation time, and increase the steady-state operational time. Efforts have also been made to increase the neutron production rate of the device. Optimization studies have varied the configuration and design of the electrodes and have resulted in system configurations with up to 50 percent higher neutron production rates than have previously been utilized. A new feedthrough design has been constructed that is intended to increase the maximum operating voltage from 175 kV with the previous feedthrough to 300 kV. Neutron production rates scale almost linearly with both current and voltage, so the IEC device will be capable of operation at higher neutron producing regimes than have ever before been achieved. The optimization efforts involve the use of several new diagnostic tools developed at UW, which are the Fusion Ion Doppler (FIDO) Diagnostic and the Time of Flight (TOF) Diagnostic. FIDO provides the energy spectra of the charged fusion products and reactants created in the IEC device. The FIDO Diagnostic was originally only capable of studying D-D fusion, but with recent advancements is now able to study both D-D and D-3He fusion. The TOF Diagnostic provides spatial information along with the energy resolution of where the fusion reactions are occurring in the IEC device. Development of the diagnostics has involved the implementation of timing electronics, alignment systems, data acquisition software, computational post-processing, and upgrades to the experimental facility. A significant rise in the concentration of fusion events was found outside of the anode, believed to be due in part from negative ions. The FIDO and TOF Diagnostics have proven to be valuable additions to the study of IEC devices and have greatly advanced IEC operation and theory.

Donovan, David C.

56

A Review of Quantum Confinement  

NASA Astrophysics Data System (ADS)

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. The conclusions are shown to be relevant to a proposed `quantum computer'. The description of the actual geometry of C60, as opposed to a purely spherical approximation, leads to some qualification of the computed results.

Connerade, Jean-Patrick

2009-12-01

57

Confinement studies in TFTR  

SciTech Connect

The paper describes the present (end of February 1985) status of the plasma confinement studies in the TFTR tokamak with emphasis on those with neutral beam injection (NBI). Recent improvements in the device capabilities have substantially extended operating parameters: B/sub T/ increased to 4.0 T, I/sub p/ to 2.0 MA, injection power (P/sub b/) to 5 MW with H/sup 0/ or D/sup 0/ beams anti n/sub e/ to 5 x 10/sup 19/ m/sup -3/, and Z/sub eff/ reduced to 1.4. With ohmic heating (OH) alone, the previously established scaling for gross energy confinement time (tau/sub E/ = anti n/sub e/q) has been confirmed at higher I/sub p/ and B/sub T/, and the maximum tau/sub E/ of 0.4 sec has been achieved. With NBI at P/sub b/ substantially (by factor >2) higher than P/sub OH/, excellent power and particle accountability have been established. This suggests that the less-than-expected increase in stored energy with NBI is not due to problems of power delivery, but due to problems of confinement deterioration. tau/sub E/ is observed to scale approximately as I/sub p/ P/sub b//sup -0.5/ (independent of anti n/sub e/), consistent with previous L-mode scalings. With NBI we have achieved the maximum tau/sub E/ of 0.2 sec and the maximum T/sub i/(o) of 4.4 keV in the normal operating regime, and even higher T/sub i/(o) in the energetic-ion regime with low-n/sub e/ and low-I/sub p/ operation.

Murakami, M.; Arunasalam, V.; Bell, J.D.; Bell, M.G.; Bitter, M.; Blanchard, W.R.; Boody, F.; Boyd, D.; Bretz, N.; Bush, C.E.

1985-06-01

58

Fluctuations and confinement in ATF  

SciTech Connect

In the period immediately prior to the suspension of ATF operation in November, 1991, a great deal of emphasis was palced on investigations of the fundamental mechanisms controlling confinement in this device. At that time, measurements of the density fluctuations throughout the plasma volume indicated the existence of theoretically predicted dissipative trapped electron and resistive interchange instabilities. These identifications were supported by results of dynamic configuration scans of the magnetic fields during which the extent of the magnetic well, shear, and fraction of confined trapped particles were changed continuously. Interpretation of the data from these experiments has been an ongoing exercise. Most recently, analysis of discharges employing strong gas puffing to change density gradients and fluctuation levels have strengthened the view that dissipative trapped electron modes may be present but do not play a significant direct role in energy transport. The present paper summarizes the current understanding concerning the identification of instabilities and their relationship to confinement in ATF.

Isler, R.C.; Harris, J.H.; Murakami, M.

1993-10-01

59

Modeling the time variation of beam-grid fusion reaction rates in an Inertial Electrostatic Confinement device driven by a ring-shaped magnetron ion source  

Microsoft Academic Search

We use the two-dimensional analysis code KUAD2 to simulate D^{+_{2}} trajectories in an Inertial Electrostatic Confinement (IEC) device driven by a ring-shaped magnetron ion source (RS-MIS). This aims to maximize the path length lambdaCX for ion-gas charge exchange by operating at just units of mPa D2 gas pressures; however, under these conditions simulations reveal a surprisingly small path length for

J. Kipritidis; K. Masuda; T. Kajiwara; Y. Yamagaki; K. Nagasaki

2011-01-01

60

Momentum Confinement at Low Torque  

SciTech Connect

Momentum confinement was investigated on DIII-D as a function of applied neutral beam torque at constant normalized {beta}{sub N}, by varying the mix of co (parallel to the plasma current) and counter neutral beams. Under balanced neutral beam injection (i.e. zero total torque to the plasma), the plasma maintains a significant rotation in the co-direction. This 'intrinsic' rotation can be modeled as being due to an offset in the applied torque (i.e. an 'anomalous torque'). This anomalous torque appears to have a magnitude comparable to one co-neutral beam source. The presence of such an anomalous torque source must be taken into account to obtain meaningful quantities describing momentum transport, such as the global momentum confinement time and local diffusivities. Studies of the mechanical angular momentum in ELMing H-mode plasmas with elevated q{sub min} show that the momentum confinement time improves as the torque is reduced. In hybrid plasmas, the opposite effect is observed, namely that momentum confinement improves at high torque/rotation. The relative importance of E x B shearing between the two is modeled using GLF23 and may suggest a possible explanation.

Solomon, W M; Burrell, K H; deGrassie, J S; Budny, R; Groebner, R J; Heidbrink, W W; Kinsey, J E; Kramer, G J; Makowski, M A; Mikkelsen, D; Nazikian, R; Petty, C C; Politzer, P A; Scott, S D; Van Zeeland, M A; Zarnstorff, M C

2007-06-26

61

Confinement Aquaculture. Final Report.  

ERIC Educational Resources Information Center

|The Delaplaine Agriculture Department Confinement Project, begun in June 1988, conducted a confinement aquaculture program by comparing the growth of channel catfish raised in cages in a pond to channel catfish raised in cages in the Black River, Arkansas. The study developed technology that would decrease costs in the domestication of fish,…

Delaplaine School District, AR.

62

Computer Simulation of Electrostatic Inertial Confinement.  

National Technical Information Service (NTIS)

The technique of numerical plasma simulation is here used to study the behavior of the electrostatic-inertial confinement device. Particle type simulation models calculate the time evolution of the plasma contained within a spherical chamber into which hi...

C. Barnes

1973-01-01

63

Enhancement of confinement in tokamaks  

SciTech Connect

A plausible interpretation of the experimental evidence is that energy confinement in tokamaks is governed by two separate considerations: (1) the need for resistive MHD kink-stability, which limits the permissible range of current profiles - and therefore normally also the range of temperature profiles; and (2) the presence of strongly anomalous microscopic energy transport near the plasma edge, which calibrates the amplitude of the global temperature profile, thus determining the energy confinement time tau/sub E/. Correspondingly, there are two main paths towards the enhancement of tokamak confinement: (1) Configurational optimization, to increase the MHD-stable energy content of the plasma core, can evidently be pursued by varying the cross-sectional shape of the plasma and/or finding stable radial profiles with central q-values substantially below unity - but crossing from ''first'' to ''second'' stability within the peak-pressure region would have the greatest ultimate potential. (2) Suppression of edge turbulence, so as to improve the heat insulation in the outer plasma shell, can be pursued by various local stabilizing techniques, such as use of a poloidal divertor. The present confinement model and initial TFTR pellet-injection results suggest that the introduction of a super-high-density region within the plasma core should be particularly valuable for enhancing ntau/subE/. In D-T operation, a centrally peaked plasma pressure profile could possibly lend itself to alpha-particle-driven entry into the second-stability regime.

Furth, H.P.

1986-05-01

64

Spectral Properties of Confined Atoms  

Microsoft Academic Search

The changes in energy and photoionization spectra of atoms upon confinement by a spherical environment are explored theoretically. Two kinds of confinement are considered: an endohedral confinement, such as inside the bucky-ball C60, and an impenetrable spherical confinement of adjustable radius. We demonstrate modifications in the energy spectrum and electron correlation effects in confined atoms, the appearance, nature and origin

V. K. Dolmatov; J. P. Connerade; A. P. Lakshmi; S. T. Manson

2002-01-01

65

Placental Weight in Pregnancies With Trisomy Confined to the Placenta  

Microsoft Academic Search

Objective: Mosaicism with trisomy confined to the placenta is present in ~1% of ongoing pregnancies at the time of chorionic villus sampling. Some studies have found reduced fetal growth in confined placental trisomy. The objective of this study was to assess placental weight and feto-placental weight ratio in pregnancies with trisomy confined to the placenta, and to correlate them with

Paul J. Yong; Deborah E. McFadden; Irene J. Barrett; Dagmar K. Kalousek; Wendy P. Robinson

2009-01-01

66

Confinement and the safety factor profile  

SciTech Connect

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.

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

67

Reduced Swimming Performance of Striped Bass after Confinement Stress  

Microsoft Academic Search

Length of confinement in a dip net affected subsequent performance of 2–3-year-old striped bass Morone saxatilis in a swimming challenge. Fish that were not confined or were confined for only 5 min could consistently swim for 10 min at 100 cm\\/s, whereas fish confined for longer than 15 min often could not. Average swimming time was significantly less for striped

Richard J. Strange; Joseph J. Cech Jr

1992-01-01

68

On confinement index  

NASA Astrophysics Data System (ADS)

The smallest integer t for which the Wilson loop Wt fails to exhibit area law is known as the confinement index of a given field theory. The confinement index provides us with subtle information on the vacuum properties of the system. We study the behavior of the Wilson and 't Hooft loops and compute the confinement index in a wide class of N=1 supersymmetric gauge theories. All possible electric and magnetic screenings are taken into account. The results found are consistent with the ? periodicity, and whenever such a check is available, with the factorization property of Seiberg-Witten curves.

Konishi, Kenichi; Ookouchi, Yutaka

2010-03-01

69

Hydrodynamics of confined membranes  

NASA Astrophysics Data System (ADS)

We calculate the hydrodynamic interaction ?(k) (Oseen interaction kernel) and relaxation frequency ?(k) for the fluctuations of a membrane that is harmonically bounded to a permeable or impermeable wall. We show that due to the confining wall there is an increase in the effective viscosity of the fluid surrounding the membrane. This has been observed in experiments on confined membranes, such as lamellar phases and the red-blood cell membrane. Our results allow a quantitative analysis of these experiments, in terms of the strength of the membrane confining potential and dislocations.

Gov, N.; Zilman, A. G.; Safran, S.

2004-07-01

70

Influence of confinement on thermodiffusion  

NASA Astrophysics Data System (ADS)

This work focuses on a possible influence of a nanoporous medium on the thermodiffusion of a fluid ``isotopic'' mixture. To do so, we performed molecular dynamics simulations of confined Lennard-Jones binary equimolar mixtures using grand-canonical like and non-equilibrium approaches in sub- and super-critical conditions. The study was conducted in atomistic slit pore of three adsorbent natures for various widths (from 5 to 35 times the size of a molecule). The simulation results indicate that for all thermodynamic conditions and whatever the pore characteristics, the confinement has a negligible effect on the thermal diffusion factor/Soret coefficient. However, when considered separately, the mass diffusion and thermodiffusion coefficients have been found to be largely influenced by the pore characteristics. These two coefficients decrease noticeably when adsorption is stronger and pore width smaller, a behavior that is consistent with a simple hydrodynamic explanation.

Hannaoui, Rachid; Galliero, Guillaume; Hoang, Hai; Boned, Christian

2013-09-01

71

Influence of confinement on thermodiffusion.  

PubMed

This work focuses on a possible influence of a nanoporous medium on the thermodiffusion of a fluid "isotopic" mixture. To do so, we performed molecular dynamics simulations of confined Lennard-Jones binary equimolar mixtures using grand-canonical like and non-equilibrium approaches in sub- and super-critical conditions. The study was conducted in atomistic slit pore of three adsorbent natures for various widths (from 5 to 35 times the size of a molecule). The simulation results indicate that for all thermodynamic conditions and whatever the pore characteristics, the confinement has a negligible effect on the thermal diffusion factor?Soret coefficient. However, when considered separately, the mass diffusion and thermodiffusion coefficients have been found to be largely influenced by the pore characteristics. These two coefficients decrease noticeably when adsorption is stronger and pore width smaller, a behavior that is consistent with a simple hydrodynamic explanation. PMID:24070302

Hannaoui, Rachid; Galliero, Guillaume; Hoang, Hai; Boned, Christian

2013-09-21

72

Plasma confinement studies in LHD  

NASA Astrophysics Data System (ADS)

The initial experiments on the Large Helical Device (LHD) have extended confinement studies on currentless plasmas to a large scale (R = 3.9 m, a = 0.6 m). Heating by NBI of 3 MW produced plasmas with a fusion triple product of 8 × 1018m-3·keV·s at a magnetic field strength of 1.5 T. An electron temperature of 1.5 keV and an ion temperature of 1.1 keV were achieved simultaneously at a line averaged electron density of 1.5 × 1019 m-3. The maximum stored energy reached 0.22 MJ with neither unexpected confinement deterioration nor visible MHD instabilities, which corresponds to langle?rangle = 0.7%. Energy confinement times reached a maximum of 0.17 s. A favourable dependence of energy confinement time on density remains in the present power density (~40 kW/m3) and electron density (3 × 1019 m-3) regimes, unlike the L mode in tokamaks. Although power degradation and significant density dependence are similar to the conditions on existing medium sized helical devices, the absolute value is enhanced by up to about 50% from the International Stellarator Scaling 95. Temperatures of both electrons and ions as high as 200 eV were observed at the outermost flux surface, which indicates a qualitative jump in performance compared with that of helical devices to date. Spontaneously generated toroidal currents indicate agreement with the physical picture of neoclassical bootstrap currents. Change of magnetic configuration due to the finite ? effect was well described by 3-D MHD equilibrium analysis. A density pump-out phenomenon was observed in hydrogen discharges, which was mitigated in helium discharges with high recycling.

Fujiwara, M.; Yamada, H.; Ejiri, A.; Emoto, M.; Funaba, H.; Goto, M.; Ida, K.; Idei, H.; Inagaki, S.; Kado, S.; Kaneko, O.; Kawahata, K.; Kobuchi, T.; Komori, A.; Kubo, S.; Kumazawa, R.; Masuzaki, S.; Minami, T.; Miyazawa, J.; Morisaki, T.; Morita, S.; Murakami, S.; Muto, S.; Mutoh, T.; Nagayama, Y.; Nakamura, Y.; Nakanishi, H.; Narihara, K.; Nishimura, K.; Noda, N.; Ohdachi, S.; Ohyabu, N.; Oka, Y.; Osakabe, M.; Ozaki, T.; Peterson, B. J.; Sagara, A.; Sakakibara, S.; Sakamoto, R.; Sasao, H.; Sasao, M.; Sato, K.; Sato, M.; Seki, T.; Shimozuma, T.; Shoji, M.; Suzuki, H.; Takeiri, Y.; Tanaka, K.; Toi, K.; Tokuzawa, T.; Tsumori, K.; Tsuzuki, K.; Watanabe, K. Y.; Watari, T.; Yamada, I.; Yamaguchi, S.; Yokoyama, M.; Akiyama, R.; Chikaraishi, H.; Haba, K.; Hamaguchi, S.; Iima, M.; Imagawa, S.; Inoue, N.; Iwamoto, K.; Kitagawa, S.; Kodaira, J.; Kubota, Y.; Maekawa, R.; Mito, T.; Nagasaka, T.; Nishimura, A.; Takahashi, C.; Takahata, K.; Takita, Y.; Tamura, H.; Tsuzuki, T.; Yamada, S.; Yamauchi, K.; Yanagi, N.; Yonezu, H.; Hamada, Y.; Matsuoka, K.; Murai, K.; Ohkubo, K.; Ohtake, I.; Okamoto, M.; Satoh, S.; Satow, T.; Sudo, S.; Tanahashi, S.; Yamazaki, K.; Motojima, O.; Iiyoshi, A.

1999-11-01

73

New perspectives on FRC confinement  

NASA Astrophysics Data System (ADS)

Four factors relevant to FRC's motivate a rethinking the nature of confinement in FRCs. (1) Particle loss at the separatrix is regulated by drift turbulence with an oblique wave vector and perpendicular component comparable to the inverse of the ion gyroradius. The resulting transport scaling is better than gyroBohm, This mechanism gives a reasonable prediction of the particle confinement observed in FRC experiments. (2) The scrape-off layer can be modeled as a quasi-steady balance between radial particle diffusion and streaming endloss to the divertor region. (3) ``Tearing relaxation,'' i.e. tearing that maintains the internal profile at the marginal stability condition appears to explain the anomalous flux loss rate in FRCs. Application of the so-called nearby-equilibrium analysis led to this implication. If so, then the ``apparent'' resistivity at the O-point is only the manifestation of a completely different flux annihilation mechanism, namely tearing. (4) The transport of energy is convective, i.e. proportional to the particle diffusivity. Past extrapolations of FRC confinement were based on empirical scalings; these new advances allow, for the first time, a physics-based model of transport. This should foster more convincing extrapolations to next-generation experiments.

Steinhauer, Loren

2008-11-01

74

STUDY OF THE THREE-DIMENSIONAL CORONAL MAGNETIC FIELD OF ACTIVE REGION 11117 AROUND THE TIME OF A CONFINED FLARE USING A DATA-DRIVEN CESE-MHD MODEL  

SciTech Connect

We apply a data-driven magnetohydrodynamics (MHD) model to investigate the three-dimensional (3D) magnetic field of NOAA active region (AR) 11117 around the time of a C-class confined flare that occurred on 2010 October 25. The MHD model, based on the spacetime conservation-element and solution-element scheme, is designed to focus on the magnetic field evolution and to consider a simplified solar atomsphere with finite plasma {beta}. Magnetic vector-field data derived from the observations at the photosphere is inputted directly to constrain the model. Assuming that the dynamic evolution of the coronal magnetic field can be approximated by successive equilibria, we solve a time sequence of MHD equilibria based on a set of vector magnetograms for AR 11117 taken by the Helioseismic and Magnetic Imager on board the Solar Dynamic Observatory around the time of the flare. The model qualitatively reproduces the basic structures of the 3D magnetic field, as supported by the visual similarity between the field lines and the coronal loops observed by the Atmospheric Imaging Assembly, which shows that the coronal field can indeed be well characterized by the MHD equilibrium in most cases. The magnetic configuration changes very little during the studied time interval of 2 hr. A topological analysis reveals that the small flare is correlated with a bald patch (BP, where the magnetic field is tangent to the photosphere), suggesting that the energy release of the flare can be understood by magnetic reconnection associated with the BP separatrices. The total magnetic flux and energy keep increasing slightly in spite of the flare, while the computed magnetic free energy drops during the flare by {approx}10{sup 30} erg, which seems to be adequate in providing the energy budget of a minor C-class confined flare.

Jiang Chaowei; Feng Xueshang [SIGMA Weather Group, State Key Laboratory for Space Weather, Center for Space Science and Applied Research, Chinese Academy of Sciences, Beijing 100190 (China); Wu, S. T.; Hu Qiang, E-mail: cwjiang@spaceweather.ac.cn, E-mail: fengx@spaceweather.ac.cn, E-mail: wus@uah.edu, E-mail: qh0001@uah.edu [Center for Space Plasma and Aeronomic Research, University of Alabama in Huntsville, Huntsville, AL 35899 (United States)

2012-11-10

75

Study of the Three-dimensional Coronal Magnetic Field of Active Region 11117 around the Time of a Confined Flare Using a Data-Driven CESE-MHD Model  

NASA Astrophysics Data System (ADS)

We apply a data-driven magnetohydrodynamics (MHD) model to investigate the three-dimensional (3D) magnetic field of NOAA active region (AR) 11117 around the time of a C-class confined flare that occurred on 2010 October 25. The MHD model, based on the spacetime conservation-element and solution-element scheme, is designed to focus on the magnetic field evolution and to consider a simplified solar atomsphere with finite plasma ?. Magnetic vector-field data derived from the observations at the photosphere is inputted directly to constrain the model. Assuming that the dynamic evolution of the coronal magnetic field can be approximated by successive equilibria, we solve a time sequence of MHD equilibria based on a set of vector magnetograms for AR 11117 taken by the Helioseismic and Magnetic Imager on board the Solar Dynamic Observatory around the time of the flare. The model qualitatively reproduces the basic structures of the 3D magnetic field, as supported by the visual similarity between the field lines and the coronal loops observed by the Atmospheric Imaging Assembly, which shows that the coronal field can indeed be well characterized by the MHD equilibrium in most cases. The magnetic configuration changes very little during the studied time interval of 2 hr. A topological analysis reveals that the small flare is correlated with a bald patch (BP, where the magnetic field is tangent to the photosphere), suggesting that the energy release of the flare can be understood by magnetic reconnection associated with the BP separatrices. The total magnetic flux and energy keep increasing slightly in spite of the flare, while the computed magnetic free energy drops during the flare by ~1030 erg, which seems to be adequate in providing the energy budget of a minor C-class confined flare.

Jiang, Chaowei; Feng, Xueshang; Wu, S. T.; Hu, Qiang

2012-11-01

76

Fluids in extreme confinement.  

PubMed

For extremely confined fluids with a two-dimensional density n in slit geometry of an accessible width L, we prove that in the limit L ? 0, the lateral and transversal degrees of freedom decouple, and the latter become ideal-gas-like. For a small wall separation, the transverse degrees of freedom can be integrated out and renormalize the interaction potential. We identify nL(2) as the hidden smallness parameter of the confinement problem and evaluate the effective two-body potential analytically, which allows calculating the leading correction to the free energy exactly. Explicitly, we map a fluid of hard spheres in extreme confinement onto a 2D fluid of disks with an effective hard-core diameter and a soft boundary layer. Two-dimensional phase transitions are robust and the transition point experiences a shift O(nL(2)). PMID:23368297

Franosch, Thomas; Lang, Simon; Schilling, Rolf

2012-12-11

77

Confinement of quarks  

NASA Astrophysics Data System (ADS)

A general introduction to the topological mechanism responsible for the absolute confinement of quarks inside hadronic bound states is given, including the effects of a finite instanton angle. We then propose a calculational technique for computing these states and their properties, where instead of topology we rely on a perturbative mechanism. It assumes that already before the topological mechanism can come into effect there is already a strong inclination of quarks to be confined. In particular the planar limit of large N QCD should exhibit this mechanism. By renormalizing the infrared divergence of one-loop diagrams, one may already realize a confining potential. In practice, our procedure will require gauge-fixing in advance, but it would be more elegant if, at an intermediate level, the theory with infrared counter terms included could be written as a gauge-invariant effective model. Models of the desired kind are described. They are not renormalizable, but they are local, gauge- and lorentz invariant.

't Hooft, Gerard

2003-06-01

78

The Physics Basis of ITER Confinement  

SciTech Connect

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.

Wagner, F. [Max-Planck-Institut fuer Plasmaphysik EURATOM Association Wendelsteinstr. 1, 17491 Greifswald (Germany)

2009-02-19

79

Study of QCD Confinement  

NASA Astrophysics Data System (ADS)

Substantial numerical studies on pure lattice gauge theory have shown that the non-Abelian gauge theory is permanently confined at zero temperature and undergoes a deconfining phase transition at very high temperature. This thesis, however, is dedicated to the analytical study of the pure lattice gauge theory. Our focus is also on the confinement property of the gauge fields. This study is motivated by the effective spin model approach developed by Svetitsky and Yaffe. By using a variational principle, we have derived exactly the d dimensional effective spin model from the d + 1 dimensional SU(N) gauge theory for both zero and finite temperature cases. For both cases, the dynamics is rather simple: only nearest neighbor coupling exists. Therefore our effective spin model provides a competitive model for the study of the QCD vacuum properties. Based on our zero temperature effective spin model, our analysis shows that if the gauge field is confined, the quark anti-quark potential must be linear, which confirms the string picture of confinement. The 1 + 1 dimensional SU(2) gauge field theory has been solved exactly and its confinement is trivially confirmed. In particular, we have shown that in this case the Polyakov quark potential is equivalent to the Wilson potential. This strongly supports the conjecture that the definitions of the quark potential by Wilson and Polyakov are equivalent. We have also shown that our approach has the (tantalizing) potential to solve the confinement problem for 3 + 1 dimensional non-Abelian gauge fields. Finally, the 3 dimensional finite temperature effective spin model has also been investigated. We showed explicitly that the SU(2) gauge field undergoes second and SU(N) (N > 3) first order deconfining phase transitions. The deconfining phase transition temperature has also been studied for SU(2) gauge field by using the variational cumulant expansion method. The results are rather satisfactory.

Zhu, Zheng-Kun

1995-01-01

80

Comments on experimental results of energy confinement of tokamak plasmas  

SciTech Connect

The results of energy-confinement experiments on steady-state tokamak plasmas are examined. For plasmas with auxiliary heating, an analysis based on the heat diffusion equation is used to define heat confinement time (the incremental energy confinement time). For ohmically sustained plasmas, experiments show that the onset of the saturation regime of energy confinement, marfeing, detachment, and disruption are marked by distinct values of the parameter /bar n//sub e///bar j/. The confinement results of the two types of experiments can be described by a single surface in 3-dimensional space spanned by the plasma energy, the heating power, and the plasma density: the incremental energy confinement time /tau//sub inc/ = ..delta..W/..delta..P is the correct concept for describing results of heat confinement in a heating experiment; the commonly used energy confinement time defined by /tau//sub E/ = W/P is not. A further examination shows that the change of edge parameters, as characterized by the change of the effective collision frequency ..nu../sub e/*, governs the change of confinement properties. The totality of the results of tokamak experiments on energy confinement appears to support a hypothesis that energy transport is determined by the preservation of the pressure gradient scale length. 70 refs., 6 figs., 1 tab.

Chu, T.K.

1989-04-01

81

Studies in confined biopolymers  

Microsoft Academic Search

In this work we analyze the theoretical aspects of a single polymer confined inside a cavity. The problem is of biological relevance since it is known, for instance, that molecules like proteins need an isolated environment in order to quickly and correctly reach their folded native state. The polymer is considered in the Grand Canonical ensemble of its monomeric units,

Samuela Pasquali

2005-01-01

82

Totally Confined Explosive Welding.  

National Technical Information Service (NTIS)

A method and associated apparatus for confining the undesirable by-products and limiting noise of explosive welding are discussed. The apparatus consists fo a simple enclosure into which the explosive is placed and within which the explosion occurs. The s...

L. J. Bement

1974-01-01

83

Electrofreezing of confined water.  

PubMed

We report results from molecular dynamics simulations of the freezing transition of TIP5P water molecules confined between two parallel plates under the influence of a homogeneous external electric field, with magnitude of 5 V/nm, along the lateral direction. For water confined to a thickness of a trilayer we find two different phases of ice at a temperature of T=280 K. The transformation between the two, proton-ordered, ice phases is found to be a strong first-order transition. The low-density ice phase is built from hexagonal rings parallel to the confining walls and corresponds to the structure of cubic ice. The high-density ice phase has an in-plane rhombic symmetry of the oxygen atoms and larger distortion of hydrogen bond angles. The short-range order of the two ice phases is the same as the local structure of the two bilayer phases of liquid water found recently in the absence of an electric field [J. Chem. Phys. 119, 1694 (2003)]. These high- and low-density phases of water differ in local ordering at the level of the second shell of nearest neighbors. The results reported in this paper, show a close similarity between the local structure of the liquid phase and the short-range order of the corresponding solid phase. This similarity might be enhanced in water due to the deep attractive well characterizing hydrogen bond interactions. We also investigate the low-density ice phase confined to a thickness of 4, 5, and 8 molecular layers under the influence of an electric field at T=300 K. In general, we find that the degree of ordering decreases as the distance between the two confining walls increases. PMID:15267616

Zangi, Ronen; Mark, Alan E

2004-04-15

84

Spectral Properties of Confined Atoms  

NASA Astrophysics Data System (ADS)

The changes in energy and photoionization spectra of atoms upon confinement by a spherical environment are explored theoretically. Two kinds of confinement are considered: an endohedral confinement, such as inside the bucky-ball C60, and an impenetrable spherical confinement of adjustable radius. We demonstrate modifications in the energy spectrum and electron correlation effects in confined atoms, the appearance, nature and origin of ``confinement'' resonances in photoionization spectra of such atoms, as well as new regularities in the periodic table for ``compressed'' atoms. These findings are of importance for basic and applied physics and chemistry of atoms, molecules, surfaces, etc.

Dolmatov, V. K.; Connerade, J. P.; Lakshmi, A. P.; Manson, S. T.

85

Bifurcated equilibria in centrifugally confined plasma  

SciTech Connect

A bifurcation theory and associated computational model are developed to account for abrupt transitions observed recently on the Maryland Centrifugal eXperiment (MCX) [R. F. Ellis et al. Phys. Plasmas 8, 2057 (2001)], a supersonically rotating magnetized plasma that relies on centrifugal forces to prevent thermal expansion of plasma along the magnetic field. The observed transitions are from a well-confined, high-rotation state (HR-mode) to a lower-rotation, lesser-confined state (O-mode). A two-dimensional time-dependent magnetohydrodynamics code is used to simulate the dynamical equilibrium states of the MCX configuration. In addition to the expected viscous drag on the core plasma rotation, a momentum loss term is added that models the friction of plasma on the enhanced level of neutrals expected in the vicinity of the insulators at the throats of the magnetic mirror geometry. At small values of the external rotation drive, the plasma is not well-centrifugally confined and hence experiences the drag from near the insulators. Beyond a critical value of the external drive, the system makes an abrupt transition to a well-centrifugally confined state in which the plasma has pulled away from the end insulator plates; more effective centrifugal confinement lowers the plasma mass near the insulators allowing runaway increases in the rotation speed. The well-confined steady state is reached when the external drive is balanced by only the viscosity of the core plasma. A clear hysteresis phenomenon is shown.

Shamim, I.; Teodorescu, C.; Guzdar, P. N.; Hassam, A. B.; Clary, R.; Ellis, R.; Lunsford, R. [Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, Maryland 20742 (United States)

2008-12-15

86

Particle confinement scaling in field-reversed configurations  

SciTech Connect

The particle confinement time in field-reversed configurations has been experimentally investigated in the FRX-C device. The measured confinement times of 70 to 190 ..mu..s are consistent with R/sup 2//rho/sub i0/ scaling and are in good agreement with theoretical predictions of lower-hybrid-drift--induced particle transport.

McKenna, K.F.; Armstrong, W.T.; Bartsch, R.R.

1983-05-30

87

Anomalous thermal confinement in ohmically heated tokamaks  

SciTech Connect

A model is proposed to explain the behavior of the gross energy confinement time in ohmically heated tokamak plasmas. The analysis takes into account the effect of the anomalous thermal conductivity due to small scale turbulence and of the macroscopic MHD behavior, which provides some constraints on the temperature profile. Results indicate that the thermal conductivity associated with the dissipative trapped-electron mode and with the ion temperature gradient (eta/sub i/) mode can account, respectively, for the Neo-Alcator scaling and the saturation of the energy confinement time with density. Comparisons with experimental results show reasonable agreement. 32 refs., 12 figs.

Romanelli, F.; Tang, W.M.; White, R.B.

1986-02-01

88

Molecular reactivity dynamics in a confined environment.  

PubMed

Time evolution of various reactivity parameters viz. hardness, electrophilicity, chemical potential, polarizability, etc. in a confined environment has been studied through quantum fluid density functional theory formalism during time dependent processes such as proton-molecule collisions and molecule-field interaction. A Dirichlet type boundary condition has been incorporated to confine the systems. Responses in the reactivity parameters of the diatomic molecules, in the dynamical context, in ground state as well as in excited state, have been reported. Harmonic spectra are generated in the cases of the external laser field interacting with H2 and N2 molecules. PMID:23471169

Khatua, Munmun; Chattaraj, Pratim Kumar

2013-04-21

89

Phenomenology and Theory of Confinement.  

National Technical Information Service (NTIS)

Phenomenological and theoretical arguments of the separation of the hadronization dynamics from confinement and the idea of the ''kinematic'' confinement are discussed. The recent theory contains results which point out that the Wilson criterion and the c...

V. N. Pervushin

1987-01-01

90

Inertial Electrostatic Confinement (IEC) devices.  

National Technical Information Service (NTIS)

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...

R. A. Nebel L. Turner T. N. Tiouririne D. C. Barnes W. D. Nystrom

1994-01-01

91

Electrostatic-Inertial Plasma Confinement.  

National Technical Information Service (NTIS)

The work was directed towards an answer to the question: 'How dense a plasma can be confined by electrostatic-inertial means.' Electrostatic-inertial plasma confinement consists of trapping charged particles in potential wells (of the electric field), whi...

T. J. Dolan J. T. Verdeyen B. E. Cherrington D. J. Meeker

1970-01-01

92

Confined Vortex Scrubber  

SciTech Connect

The program objective is to demonstrate efficient removal of fine particulates to sufficiently low levels to meet proposed small scale coal combustor emission standards. This is to be accomplished using a novel particulate removal device, the Confined Vortex Scrubber. This is the first quarterly technical progress report under this contract. Accordingly, a summary of the cleanup concept and the structure of the program is given here.

Not Available

1990-02-01

93

Topological confinement and superconductivity  

SciTech Connect

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.

Al-hassanieh, Dhaled A [Los Alamos National Laboratory; Batista, Cristian D [Los Alamos National Laboratory

2008-01-01

94

Innovative confinement concepts workshop  

SciTech Connect

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.

Kirkpatrick, R.C.

1998-06-01

95

Working safely in confined spaces  

Microsoft Academic Search

Working in confined spaces is a delicate balance of the correct equipment, hazard knowledge, proper training, and common sense. Anything less has potentially deadly consequences. The dangerous atmospheric and physical hazards often encountered in confined spaces must be recognized and accounted for. In addition, procedures and practices must conform to Occupational Safety and health Administration (OSHA) confined space regulations. Last

C. Bush; J. Versweyveld

1992-01-01

96

Confinement effects on the dynamics of polymers  

NASA Astrophysics Data System (ADS)

Dewetting experiments of thin polystyrene films on a liquid substrate are performed in the vicinity of the glass transition. It is shown that this technique reveals the extensional creep compliance function of the polymer. The viscosity in the flow regime is very much reduced when the film thickness becomes comparable to the gyration radius of the polymer. This long time behaviour may be associated with the large length scales involved in the viscous flow which should be modified by confinement. On the contrary, the rubbery plateau remains unaffected by the confinement up to a fraction of the coil size. This can be related to the short length scales involved in the rubber elasticity. In the viscoelastic region, physical aging of the sample is clearly evidenced: Structural recovery complicates the short times dewetting response. Preliminary results are presented of the confinement effects on aging properties of ultra thin films as revealed in this original way.

Bodiguel, Hugues; Jing, Guang Yin; Fretigny, Christian

2008-03-01

97

Confined vortex scrubber  

SciTech Connect

The program objective is to demonstrate efficient removal of fine particulates to sufficiently low levels to meet proposed small scale coal combustor emission standards. This is to be accomplished using a novel particulate removal device, the Confined Vortex Scrubber (CVS). The CVS consists of a cylindrical vortex chamber with tangential flue gas inlets. The clean gas exit is via tangent slots in a central tube. Liquid is introduced into the chamber and is confined with the vortex chamber by the centrifugal force generated by the gas flow itself. This confined liquid forms a layer through which the flue gas is then forced to bubble, producing a strong gas/liquid interaction, high inertial separation forces and efficient particulate cleanup. In effect, each of the sub-millimeter diameter gas bubbles in the liquid layer acts as a micro-cyclone, inertially separating particles into the surrounding liquid. The CVS thus obtains efficient particle removal by forcing intimate and vigorous interaction between the particle laden flue gas and the liquid scrubbing medium.

Not Available

1990-05-01

98

Well responses to barometric-pressure fluctuations in confined and semi-confined aquifers  

NASA Astrophysics Data System (ADS)

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.

Mohammed, G. A.; Jin, W.; Butler, J. J., Jr.; Reboulet, E. C.

2009-04-01

99

Shear relaxations of confined liquids  

SciTech Connect

Ultrathin (<40 [angstrom]) films of octamethylcyclotetrasiloxane (OMCTS), hexadecane, and dodecane were subjected to linear and non-linear oscillatory shear between flat plates. Shearing frequencies of 0.1 to 800 s[sup [minus]1] were applied at pressures from zero to 0.8 MPa using a surface rheometer only recently developed. In most cases the plates were atomically smooth mica surfaces; the role of surface interactions was examined by replacing these with alkyl chain monolayers. OMCTS and hexadecane were examined at a temperature about 5 Celcius degrees above their melting points and tended to solidify. Newtonian plateaus having enormous viscosities were observed at low shear rates. The onset of shear thinning implied relaxation times of about 0.1 s in the linear structure of the confined liquids. Large activation volumes ([approximately]80 nm[sup 3]) suggested that shear involved large-scale collective motion. Dodecane was studied at a much higher temperature relative to its melting point and showed no signs of impending solidification though it exhibited well-defined regions of Newtonian response and power law shear thinning. When treated with molecular sieves before use, dodecane had relaxation times which were short (0.02 s) compared to hexadecane, but still exhibited large-scale collective motion. When treated with silica gel, an unexplained long-time relaxation (10 s) was seen in the Newtonian viscosity of dodecane. The relaxation time of the linear structure, 0.005 s was very small, and the storage modulus was unresolvable. The small activation volume (7 nm[sup 3]) indicated a much lower level of collective motion. The activation volume remained small when dodecane was confined between tightly bound, low energy, alkyl monolayers. At low strains the storage and loss moduli became very large (>10[sup 4] Pa), probably due to interactions with flaws in the monolayers. Dramatic signs of wall slip were observed at large strains even at low pressures.

Carson, G.A. Jr.

1992-01-01

100

FRC confinement studies in FRX-C  

SciTech Connect

The measured particle containment times of up to 190 ..mu..s in FRX-C correspond to R/sup 2/ scaling and agree with predictions based on lower-hybrid cross-field diffusion. Further improvement in confinement may be possible by translating a field-reversed configuration (FRC) in such a way as to increase x/sub s/.

McKenna, K.F.; Armstrong, W.T.; Bartsch, R.R.

1982-01-01

101

Wave propagation modelling in confined spaces  

Microsoft Academic Search

The wave propagation within small confined spaces is considered with an application to wireless access systems in cars. The field distributions are computed by time domain methods, and measured in selected areas inside a car with a special attention to a possible integration of a Bluetooth system. For the integration of the system, both standing wave patterns and polarization issues

Christian Waldschmidt; J. V. Hagen; H.-L. Blocher; K. Beilenhoff; J. Wenger; W. Wiesbeck

2002-01-01

102

Static current profile control and RFP confinement  

NASA Astrophysics Data System (ADS)

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 ?? 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.

Scheffel, Jan; Schnack, Dalton D.; Mirza, Ahmed A.

2013-11-01

103

Confinement Vessel Dynamic Analysis  

SciTech Connect

A series of hydrodynamic and structural analyses of a spherical confinement vessel has been performed. The analyses used a hydrodynamic code to estimate the dynamic blast pressures at the vessel's internal surfaces caused by the detonation of a mass of high explosive, then used those blast pressures as applied loads in an explicit finite element model to simulate the vessel's structural response. Numerous load cases were considered. Particular attention was paid to the bolted port connections and the O-ring pressure seals. The analysis methods and results are discussed, and comparisons to experimental results are made.

R. Robert Stevens; Stephen P. Rojas

1999-08-01

104

Confinement Contains Condensates  

SciTech Connect

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 commonly been viewed as constant empirical mass-scales that fill all spacetime, are instead wholly contained within hadrons; i.e., they are a property of hadrons themselves and expressed, e.g., in their Bethe-Salpeter or light-front wave functions. We explain that this paradigm is consistent with empirical evidence, and incidentally expose misconceptions in a recent Comment.

Brodsky, Stanley J.; Roberts, Craig D.; Shrock, Robert; Tandy, Peter C.

2012-03-12

105

Understanding Confinement From Deconfinement  

NASA Astrophysics Data System (ADS)

We show that a dual SU(N) effective theory of the confined phase of SU(N) Yang-Mills theory can be used in the temperature interval Tc < T < 4Tc to calculate non-perturbative magnetic properties of the deconfined phase, including the magnetic screening mass and the spatial string tension. We suggest that evidence for the quanta of the effective theory should be sought in analyses of both lattice simulations of Yang-Mills theory and experiments on heavy ion collisions.

Baker, M.

2007-02-01

106

Numerical Investigations On The Seismic Behaviour Of Confined Masonry Walls  

Microsoft Academic Search

In the last century, severe earthquakes highlighted the seismic vulnerability of unreinforced masonry buildings. Many technological innovations have been introduced in time in order to improve resistance, ductility, and dissipation properties of this type of constructions. The most widely diffused are reinforced masonry and confined masonry. Damage observation of recent earthquakes demonstrated the effectiveness of the response of confined masonry

Chiara Calderini; Serena Cattari; Sergio Lagomarsino

2008-01-01

107

Confinement from correlation functions  

NASA Astrophysics Data System (ADS)

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].

Fister, Leonard; Pawlowski, Jan M.

2013-08-01

108

Simulations of Knotting in Confined Circular DNA  

PubMed Central

The packing of DNA inside bacteriophages arguably yields the simplest example of genome organization in living organisms. As an assay of packing geometry, the DNA knot spectrum produced upon release of viral DNA from the P4 phage capsid has been analyzed, and compared to results of simulation of knots in confined volumes. We present new results from extensive stochastic sampling of confined self-avoiding and semiflexible circular chains with volume exclusion. The physical parameters of the chains (contour length, cross section, and bending rigidity) have been set to match those of P4 bacteriophage DNA. By using advanced sampling techniques, involving multiple Markov chain pressure-driven confinement combined with a thermodynamic reweighting technique, we establish the knot spectrum of the circular chains for increasing confinement up to the highest densities for which available algorithms can exactly classify the knots. Compactified configurations have an enclosing hull diameter ?2.5 times larger than the P4 caliper size. The results are discussed in relation to the recent experiments on DNA knotting inside the capsid of a P4 tailless mutant. Our investigation indicates that confinement favors chiral knots over achiral ones, as found in the experiments. However, no significant bias of torus over twist knots is found, contrary to the P4 results. The result poses a crucial question for future studies of DNA packaging in P4: is the discrepancy due to the insufficient confinement of the equilibrium simulation or does it indicate that out-of-equilibrium mechanisms (such as rotation by packaging motors) affect the genome organization, hence its knot spectrum in P4?

Micheletti, C.; Marenduzzo, D.; Orlandini, E.; Sumners, D. W.

2008-01-01

109

Home versus hospital confinement  

PubMed Central

The case for hospital rather than home delivery has been powerfully argued, especially in and since the Report of the Peel Committee. Nevertheless, evidence of comparison with other countries, notably the Netherlands, suggests the choice is not necessarily simple. Some general practitioner units are now reporting perinatal mortality rates which are consistently lower than those of specialist units, and recent statistical analyses suggest that the presence of more high risk cases in consultant units does not explain this. The only big controlled home-versus-hospital trial did not lead to a significantly lower perinatal mortality rate in the hospital group. The onus of proof now seems to lie with those who advocate 100 per cent hospital confinement.

Barry, C. N.

1980-01-01

110

Molecular mixing via jets in confined volumes  

NASA Astrophysics Data System (ADS)

A simple model is proposed to describe the molecular mixing characteristics of a two-dimensional turbulent jet that is discharged into a confined volume. The model, which is based on similarity and physical considerations of only the large-scale motions, derives the characteristic time for the problem and identifies the regime for which the mixing will be most rapid. Results are reported for experiments where helium and helium/argon mixtures were injected into a cylindrical volume initially containing air. Using an aspirating probe that measured transient helium concentrations in the volume, the mixing time was determined as a function of the size of the confining volume and the injection parameters. The experimental results are in general accord with the model, and validate the use of the model for the determination of the minimum mixing time.

Breidenthal, R. E.; Buonadonna, V. R.; Weisbach, M. F.

1990-10-01

111

QUANTUM CONFINEMENT IN NANOCRYSTALLINE SILICON  

Microsoft Academic Search

Quantum confinement effects in different kinds of nanocrystalline silicon systems are experimentally and theoretically investigated. Porous silicon structured as a nanowire network and silicon nanodots embedded in amorphous silicon dioxide are studied. The main quantum confinement effect in both cases is represented by the appearance of new energy levels in the silicon band gap. The corresponding energies can be experimentally

M. L. Ciurea

112

Working safely in confined spaces  

SciTech Connect

Working in confined spaces is a delicate balance of the correct equipment, hazard knowledge, proper training, and common sense. Anything less has potentially deadly consequences. The dangerous atmospheric and physical hazards often encountered in confined spaces must be recognized and accounted for. In addition, procedures and practices must conform to Occupational Safety and health Administration (OSHA) confined space regulations. Last year, three men were asphyxiated while surveying beneath a manhole in Boulder, CO. An area newspaper called the deaths the result of a freak accident. Whatever the cause, entering a manhole without first monitoring the air and posting an outside attendant is both extremely dangerous and a violation of safe entry procedures. The National Institute for Health and Occupational Safety (NIOSH) estimates that millions of workers from a wide range of occupations and industries are exposed to confined space hazards every year. Although confined space deaths are not a new phenomenon, only recently has the problem received serious study. Government regulatory agencies are becoming more involved OSHA recently proposed ruling 1910.146, Permit Required Confined Spaces, to mandate safe entry practices and procedures. The ruling requires all employers to develop a specific action plan for confined space entry, including entry procedures, worker training, safety equipment, and emergency action. This first article defines a confined space and examines some common hazards, including toxic, combustible, and oxygen-deficient atmospheres and combustible dusts. A subsequent article will review the use of test instruments, personal protective equipment, worker training, and emergency response.

Bush, C.; Versweyveld, J. (Lab Safety Supply, Janesville, WI (United States))

1992-08-13

113

Inertial Electrostatic Confinement (IEC) devices  

Microsoft Academic Search

Inertial Electrostatic Confinement (IEC) is one of the earliest plasma confinement concepts, having first been suggested by P. T. Farnsworth in the 1950's. 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

R. A. Nebel; L. Turner; T. N. Tiouririne; D. C. Barnes; W. D. Nystrom; R. W. Bussard; G. H. Miley; J. Javedani; Y. Yamamoto

1994-01-01

114

Single polymer systems under geometric confinement  

NASA Astrophysics Data System (ADS)

Confining a single polymer system leads to a competition between internal cooperativity length scales and external length scales arising from the confining geometry. This competition is relevant in the realm of polymer glasses and in the crowded environment inside cells. In this thesis, I present two different types of single polymer confinement, a single polymer confined to a tube and to a box. Both geometries lead to nontrivial changes in the static and dynamic properties of the polymer as is shown using Monte Carlo simulations. The simulations show confined polymers exhibit regimes of relaxation in their dynamics including non-monotonic time scales for dynamics in a box. In addition, equilibrium monomer-monomer correlations inside the box differ from that of the unconfined polymer. To understand the origin of these simulation results, a theory is developed using a set of Langevin equations. In general, this set of equations has no simple solution, but by assuming that non-interacting normal modes solve these equations, their Fourier transformed equivalents become linearized equations and I solve them self-consistently. The dynamical theory makes use of the equilibrium behavior of the polymer, specifically its monomer-monomer correlations functions which I extracted from blob picture arguments. I then compare the predictions of this linearized Rouse theory to the simulations results. I am not only able to extract the scaling relations, but also able to make predictions on the functional form of the dynamics and crossover time scales. The linearized Rouse theory agrees very well with the simulations of the polymer in a tube. For the polymer in a box, the theory makes good predictions for low volume fractions, but fails at high volume fractions. One approach introduced to solve this problem involves a renormalization of the friction coefficient.

Kalb, Joshua

115

Direct observation of confined single chain dynamics by neutron scattering.  

PubMed

Neutron spin echo has revealed the single chain dynamic structure factor of entangled polymer chains confined in cylindrical nanopores with chain dimensions either much larger or smaller than the lateral pore sizes. In both situations, a slowing down of the dynamics with respect to the bulk behavior is only observed at intermediate times. The results at long times provide a direct microscopic measurement of the entanglement distance under confinement. They constitute the first experimental microscopic evidence of the dilution of the total entanglement density in a polymer melt under strong confinement, a phenomenon that so far was hypothesized on the basis of various macroscopic observations. PMID:20866999

Martín, J; Krutyeva, M; Monkenbusch, M; Arbe, A; Allgaier, J; Radulescu, A; Falus, P; Maiz, J; Mijangos, C; Colmenero, J; Richter, D

2010-05-11

116

Molecule-Sized Gates Based on Surface-Confined Dendrimers.  

National Technical Information Service (NTIS)

In this report we demonstrate for the first time that surface confined-dendrimers embedded within self-assembled monolayers (SAMs) of alkylthiols can act as ion gates of molecular dimension. These composite organic thin films are conceptually, structurall...

M. Zhao H. Tokuhisa R. M. Crooks

1997-01-01

117

Correlation Between Low Frequency Turbulence and Energy Confinement in TFR.  

National Technical Information Service (NTIS)

An observed close correlation between density fluctuations detected with a coherent scattering experiment and the electron transport confinement time deduced from a OD code valid at the centre of the discharge, suggests that the observed turbulence could ...

A. Truc

1986-01-01

118

Mixed Confined-unconfined Flow In A Confined Aquifer  

NASA Astrophysics Data System (ADS)

Mixed confined and unconfined groundwater flow occurs in a bounded initially dry aquifer when the hydraulic head at the side boundary suddenly rises above the elevation of the aquifer's top boundary. The flow problem is modelled by the Boussinesq equation and involves two moving boundaries. Here, we present an approximate analytical solution for this flow problem. The approach is based on the transformed equation (a similarity transformation was used). This simple approximate analytical solution is compared with an "exact" numerical solution and is found to be a very accurate description of the mixed confined and unconfined flow in the confined aquifer.

Li, L.; Lockington, D. A.; Barry, D. A.; Parlange, J.-Y.

119

Inertial confinement fusion  

SciTech Connect

This issue of the ICF Quarterly contains seven articles that describe recent progress in Lawrence Livermore National Laboratory's ICF program. The Department of Energy recently initiated an effort to design a 1--2 MJ glass laser, the proposed National Ignition Facility (NIF). These articles span various aspects of a program which is aimed at moving forward toward such a facility by continuing to use the Nova laser to gain understanding of NIF-relevant target physics, by developing concepts for an NIF laser driver, and by envisioning a variety of applications for larger ICF facilities. This report discusses research on the following topics: Stimulated Rotational Raman Scattering in Nitrogen; A Maxwell Equation Solver in LASNEX for the Simulation of Moderately Intense Ultrashort Pulse Experiments; Measurements of Radial Heat-Wave Propagation in Laser-Produced Plasmas; Laser-Seeded Modulation Growth on Directly Driven Foils; Stimulated Raman Scattering in Large-Aperture, High-Fluence Frequency-Conversion Crystals; Fission Product Hazard Reduction Using Inertial Fusion Energy; Use of Inertial Confinement Fusion for Nuclear Weapons Effects Simulations.

Powers, L.; Condouris, R.; Kotowski, M.; Murphy, P.W. (eds.)

1992-01-01

120

Confinement of semiflexible polymers.  

PubMed

A variational framework is developed to examine the equilibrium states of a semiflexible polymer that is constrained to lie on a fixed surface. As an application the confinement of a closed polymer loop of fixed length 2? R within a spherical cavity of smaller radius, R(0), is considered. It is shown that an infinite number of distinct periodic completely attached equilibrium states exist, labeled by two integers: n = 2,3,4,... and p = 1,2,3,..., the number of periods of the polar and azimuthal angles, respectively. Small loops oscillate about a geodesic circle: n = 2, p = 1 is the stable ground state; states with higher n exhibit instabilities. If R ? 2R(0) new states appear as oscillations about a doubly covered geodesic circle; the state n = 3,p = 2 replaces the twofold as the ground state in a finite band of values of R. With increasing R, loop states make a transition from oscillatory and orbital behavior on crossing the poles, returning to oscillation upon collapse to a multiple cover of a geodesic circle (signaled, respectively, by an increase in p and an increase in n). The force transmitted to the surface does not increase monotonically with loop size, but does asymptotically. It behaves discontinuously where n changes. The contribution to energy from geodesic curvature is bounded. In large loops, the energy becomes dominated by a state independent contribution proportional to the loop size; the energy gap between the ground state and excited states disappears. PMID:22463345

Guven, Jemal; Vázquez-Montejo, Pablo

2012-02-16

121

Inertial Confinement Fusion  

NASA Astrophysics Data System (ADS)

This issue of the ICF Quarterly contains seven articles that describe recent progress in Lawrence Livermore National Laboratory's ICF program. The Department of Energy recently initiated an effort to design a 1-2 MJ glass laser, the proposed National Ignition Facility (NIF). These articles span various aspects of a program which is aimed at moving forward toward such a facility by continuing to use the Nova laser to gain understanding of NIF-relevant target physics, by developing concepts for an NIF laser driver and by envisioning a variety of applications for larger ICF facilities. This report discusses research on the following topics: Stimulated Rotational Raman Scattering in Nitrogen; A Maxwell Equation Solver in LASNEX for the Simulation of Moderately Intense Ultrashort Pulse Experiments; Measurements of Radial Heat-Wave Propagation in Laser-Produced Plasmas; Laser-Seeded Modulation Growth on Directly Driven Foils; Stimulated Raman Scattering in Large-Aperture, High-Fluence Frequency-Conversion Crystals; Fission Product Hazard Reduction Using Inertial Fusion Energy; and the Use of Inertial Confinement Fusion for Nuclear Weapons Effects Simulations.

Powers, L.; Condouris, R.; Kotowski, M.; Murphy, P. W.

122

Localization Dynamics of Fluids in Random Confinement  

NASA Astrophysics Data System (ADS)

The dynamics of two-dimensional fluids confined within a random matrix of obstacles is investigated using both colloidal model experiments and molecular dynamics simulations. By varying fluid and matrix area fractions in the experiment, we find delocalized tracer particle dynamics at small matrix area fractions and localized motion of the tracers at high matrix area fractions. In the delocalized region, the dynamics is subdiffusive at intermediate times, and diffusive at long times, while in the localized regime, trapping in finite pockets of the matrix is observed. These observations are found to agree with the simulation of an ideal gas confined in a weakly correlated matrix. Our results show that Lorentz gas systems with soft interactions are exhibiting a smoothening of the critical dynamics and consequently a rounded delocalization-to-localization transition.

Skinner, Thomas O. E.; Schnyder, Simon K.; Aarts, Dirk G. A. L.; Horbach, Jürgen; Dullens, Roel P. A.

2013-09-01

123

ITER L-Mode Confinement Database  

SciTech Connect

This paper describes the content of an L-mode database that has been compiled with data from Alcator C-Mod, ASDEX, DIII, DIII-D, FTU, JET, JFT-2M, JT-60, PBX-M, PDX, T-10, TEXTOR, TFTR, and Tore-Supra. The database consists of a total of 2938 entries, 1881 of which are in the L-phase while 922 are ohmically heated (OH) only. Each entry contains up to 95 descriptive parameters, including global and kinetic information, machine conditioning, and configuration. The paper presents a description of the database and the variables contained therein, and it also presents global and thermal scalings along with predictions for ITER. The L-mode thermal confinement time scaling was determined from a subset of 1312 entries for which the thermal confinement time scaling was provided.

S.M. Kaye and the ITER Confinement Database Working Group

1997-10-01

124

Alpha particle confinement in tokamaks  

SciTech Connect

An assessment of diffusive tokamak transport mechanisms of concern for alpha particles indicates that the ''stochastic regime'' is the only one which appears to pose a real danger for adequate alpha confinement. This fact, in conjunction with the threshold character of that mechanism, allows one to decide whether an alpha born at a given location will be lost or confined, according to a very simple criterion. Implementing this criterion numerically results in a new code for the assessment of alpha confinement, which is orders of magnitude faster than earlier codes used for this purpose. 13 refs., 3 figs., 1 tab.

White, R.B.; Mynick, H.E.

1988-11-01

125

Magnetic freezing of confined water  

NASA Astrophysics Data System (ADS)

We report results from molecular dynamic simulations of the freezing transition of liquid water in the nanoscale hydrophobic confinement under the influence of a homogeneous external magnetic field of 10 T along the direction perpendicular to the parallel plates. A new phase of bilayer crystalline ice is obtained at an anomalously high freezing temperature of 340 K. The water-to-ice translation is found to be first order. The bilayer ice is built from alternating rows of hexagonal rings and rhombic rings parallel to the confining plates, with a large distortion of the hydrogen bonds. We also investigate the temperature shifts of the freezing transition due to the magnetic field. The freezing temperature, below which the freezing of confined water occurs, shifts to a higher value as the magnetic field enhances. Furthermore, the temperature of the freezing transition of confined water is proportional to the denary logarithm of the external magnetic field.

Zhang, Guangyu; Zhang, Weiwei; Dong, Huijuan

2010-10-01

126

Magnetic freezing of confined water.  

PubMed

We report results from molecular dynamic simulations of the freezing transition of liquid water in the nanoscale hydrophobic confinement under the influence of a homogeneous external magnetic field of 10 T along the direction perpendicular to the parallel plates. A new phase of bilayer crystalline ice is obtained at an anomalously high freezing temperature of 340 K. The water-to-ice translation is found to be first order. The bilayer ice is built from alternating rows of hexagonal rings and rhombic rings parallel to the confining plates, with a large distortion of the hydrogen bonds. We also investigate the temperature shifts of the freezing transition due to the magnetic field. The freezing temperature, below which the freezing of confined water occurs, shifts to a higher value as the magnetic field enhances. Furthermore, the temperature of the freezing transition of confined water is proportional to the denary logarithm of the external magnetic field. PMID:20942551

Zhang, Guangyu; Zhang, Weiwei; Dong, Huijuan

2010-10-01

127

Polar confinement modulates solvation behavior of methane molecules  

NASA Astrophysics Data System (ADS)

Polar confinement induces an amorphous solidlike state of water characterized by an orientational correlation time longer than hundreds of picoseconds and significant structural disorder. Solvation behavior of methane molecules is dramatically modulated under polar confinement. Moreover our simulations indicate that the charges equivalent to those borne by atoms of amino acids could generate an electric field which is strong enough to stimulate the phase transition of water. In our results, polar confinement is found to be more capable of aggregating hydrophobic molecules. This study raises an interesting mechanism by which the cagelike structure of the Escherichia coli chaperonin GroEL and the cochaperonin GroES complex helps protein folding.

Xu, Weixin; Mu, Yuguang

2008-06-01

128

Solvent cavitation under solvophobic confinement.  

PubMed

The stability of liquids under solvophobic confinement can tip in favor of the vapor phase, nucleating a liquid-to-vapor phase transition that induces attractive forces between confining surfaces. In the case of water adjacent to hydrophobic surfaces, experimental and theoretical evidence support confinement-mediated evaporation stabilization of biomolecular and colloidal assemblies. The macroscopic thermodynamic theory of cavitation under confinement establishes the connection between the size of the confining surfaces, interfacial free energies, and bulk solvent pressure with the critical evaporation separation and interfacial forces. While molecular simulations have confirmed the broad theoretical trends, a quantitative comparison based on independent measurements of the interfacial free energies and liquid-vapor coexistence properties has, to the best of our knowledge, not yet been performed. To overcome the challenges of simulating a large number of systems to validate scaling predictions for a three-dimensional fluid, we simulate both the forces and liquid-vapor coexistence properties of a two-dimensional Lennard-Jones fluid confined between solvophobic plates over a range of plate sizes and reservoir pressures. Our simulations quantitatively agree with theoretical predictions for solvent-mediated forces and critical evaporation separations once the length dependence of the solvation free energy of an individual confining plate is taken into account. The effective solid-liquid line tension length dependence results from molecular scale correlations for solvating microscopic plates and asymptotically decays to the macroscopic value for plates longer than 150 solvent diameters. The success of the macroscopic thermodynamic theory at describing two-dimensional liquids suggests application to surfactant monolayers to experimentally confirm confinement-mediated cavitation. PMID:23947875

Ashbaugh, Henry S

2013-08-14

129

Hydration of ions under confinement  

Microsoft Academic Search

Molecular dynamics simulations are used to examine the changes in water density and hydration characteristics of NaCl solutions confined in slit-shaped graphitic pores. Using a structural signature, we define the hydration limit as the salt concentration at which a sharp drop in the hydration number is observed. At small pores (H = 8.0–10 Å), confined water does not possess bulk-like features and remains

Ateeque Malani; Sohail Murad; K. G. Ayappa

2010-01-01

130

Single-molecule mobility in confined and crowded femtoliter chambers  

SciTech Connect

The effects of increased crowding and confinement on the mobility of individual fluorescent molecules were studied using Fluorescence Correlation Spectroscopy (FCS) in a microfluidic device with sealable femtoliter-volume chambers, and compared to three dimensional stochastic Monte Carlo simulations. When crowding and the degree of confinement were increased simultaneously, extended correlation times of fluorescent intensity fluctuations were observed with FCS compared to varying either crowding or confinement alone. Both experimental data and simulation suggest these extended correlation times were due to increased fluorophore adsorption-desorption events at the chamber lid in the presence of crowders. The data in increasingly confined and crowded chambers described here captures some of the salient features of crowding in cell-like environments.

Collier, Pat [ORNL; Fowlkes, Jason Davidson [ORNL

2013-01-01

131

From Pauli's birthday to 'Confinement Resonances' – a potted history of Quantum Confinement  

NASA Astrophysics Data System (ADS)

Quantum Confinement is in some sense a new subject. International meetings dedicated to Quantum Confinement have occurred only recently in Mexico City (the first in 2010 and the second, in September 2011). However, at least in principle, the subject has existed since a very long time. Surprisingly perhaps, it lay dormant for many years, for want of suitable experimental examples. However, when one looks carefully at its origin, it turns out to have a long and distinguished history. In fact, the problem of quantum confinement raises a number of very interesting issues concerning boundary conditions in elementary quantum mechanics and how they should be applied to real problems. Some of these issues were missed in the earliest papers, but are implicit in the structure of quantum mechanics, and lead to the notion of Confinement Resonances, the existence of which was predicted theoretically more than ten years ago. Although, for several reasons, these resonances remained elusive for a very long time, they have now been observed experimentally, which puts the whole subject in much better shape and, together with the advent of metallofullerenes, has contributed to its revival.

Connerade, J. P.

2013-06-01

132

Thermonuclear ignition in inertial confinement fusion and comparison with magnetic confinement  

SciTech Connect

The physics of thermonuclear ignition in inertial confinement fusion (ICF) is presented in the familiar frame of a Lawson-type criterion. The product of the plasma pressure and confinement time Ptau for ICF is cast in terms of measurable parameters and its value is estimated for cryogenic implosions. An overall ignition parameter chi including pressure, confinement time, and temperature is derived to complement the product Ptau. A metric for performance assessment should include both chi and Ptau. The ignition parameter and the product Ptau are compared between inertial and magnetic-confinement fusion. It is found that cryogenic implosions on OMEGA[T. R. Boehly et al., Opt. Commun. 133, 495 (1997)] have achieved Ptauapprox1.5 atm s comparable to large tokamaks such as the Joint European Torus [P. H. Rebut and B. E. Keen, Fusion Technol. 11, 13 (1987)] where Ptauapprox1 atm s. Since OMEGA implosions are relatively cold (Tapprox2 keV), their overall ignition parameter chiapprox0.02-0.03 is approx5x lower than in JET (chiapprox0.13), where the average temperature is about 10 keV.

Betti, R.; Chang, P. Y.; Anderson, K. S.; Nora, R. [Laboratory for Laser Energetics, University of Rochester, Rochester, New York 14623 (United States); Fusion Science Center for Extreme States of Matter, University of Rochester, Rochester, New York 14623 (United States); Spears, B. K.; Edwards, J.; Lindl, J. D. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States); Fatenejad, M. [Department of Engineering Physics, University of Wisconsin, Madison, Wisconsin 53706 (United States); McCrory, R. L. [Laboratory for Laser Energetics, University of Rochester, Rochester, New York 14623 (United States); Shvarts, D. [NRCN, Negev and Ben Gurion University of the Negev, Beer-Sheva 84015 (Israel)

2010-05-15

133

Gas solubility in hydrophobic confinement.  

PubMed

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 apparent validity of Henry's law in the pores over a broad fugacity range. PMID:16853936

Luzar, Alenka; Bratko, Dusan

2005-12-01

134

CORRELATIONS IN CONFINED QUANTUM PLASMAS  

SciTech Connect

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

DUFTY J W

2012-01-11

135

Hydrodynamics of Confined Active Fluids  

NASA Astrophysics Data System (ADS)

We theoretically describe the dynamics of swimmer populations in rigidly confined thin liquid films. We first demonstrate that hydrodynamic interactions between confined swimmers depend solely on their shape and are independent of their specific swimming mechanism. We also show that, due to friction with the nearby rigid walls, confined swimmers do not just reorient in flow gradients but also in uniform flows. We then quantify the consequences of these microscopic interaction rules on the large-scale hydrodynamics of isotropic populations. We investigate in detail their stability and the resulting phase behavior, highlighting the differences with conventional active, three-dimensional suspensions. Two classes of polar swimmers are distinguished depending on their geometrical polarity. The first class gives rise to coherent directed motion at all scales, whereas for the second class we predict the spontaneous formation of coherent clusters (swarms).

Brotto, Tommaso; Caussin, Jean-Baptiste; Lauga, Eric; Bartolo, Denis

2013-01-01

136

Electrohydrodynamics of DNA in confinement  

NASA Astrophysics Data System (ADS)

New methods of DNA sequencing aim to exploit the direct reading of individual DNA molecules. Such methods require one be able to elongate DNA molecules so that individual base-pairs may be accessed. In turn, this requires a detailed understanding of the mechanical and thermodynamic behavior of DNA, so that external manipulation and confinement successfully stretch the molecule. We aim to study the interplay between electrostatic and hydrodynamic interactions on the conformations of coarse-grained DNA through use of computer simulations with the general geometry Ewald-like method (GGEM), both in bulk and under geometric confinement.

Whitmer, Jonathan K.; Hernandez-Ortiz, Juan P.; de Pablo, Juan J.

2012-02-01

137

Inertial confinement fusion (ICF) review  

SciTech Connect

During its 1996 winter study JASON reviewed the DOE Inertial Confinement Fusion (ICF) program. This included the National Ignition Facility (NIF) and proposed studies. The result of the review was to comment on the role of the ICF program in support of the DOE Science Based Stockpile Stewardship program.

Hammer, D.; Dyson, F.; Fortson, N.; Novick, B.; Panofsky, W.; Rosenbluth, M.; Treiman, S.; York, H.

1996-03-01

138

Biased Diffusion in Confined Media  

Microsoft Academic Search

We study biased, diffusive transport of Brownian particles through narrow, spatially periodic structures in which the motion is constrained in lateral directions. The problem is analyzed using the Fick-Jacobs equation in which the effect of the lateral confinement is replaced by an entropic barrier. The validity of this approximation, being based on the assumption of an instantaneous equilibration of the

P. S. Burada; G. Schmid; D. Reguera; J. M. Rubi´

2007-01-01

139

Prospects of inertial confinement fusion  

Microsoft Academic Search

The present status of inertial confinement fusion (ICF) is briefly reviewed, emphasizing the National Ignition Facility (NIF) project in the US and the Megajoule project in France. Critical aspects of target performance such as symmetry and stability of capsule implosions and interaction physics in hohlraum targets are discussed. The advantages of heavy-ion beam drivers and corresponding research programs are pointed

J. Meyer-ter-Vehn

1997-01-01

140

Confined drying of copolymer solutions  

NASA Astrophysics Data System (ADS)

We developed a simple tool for the rapid screening of phase diagrams of polymer and surfactant solutions. Our technique is based on the controlled drying of a droplet solution in a confined geometry. A ?L-sized droplet of an aqueous solution is confined between two wafers (diameter 3 cm), separated by a controlled thickness ( 150 ?m). The confinement casts a well-defined timescale to the drying kinetics, mainly governed by the wafer area. Indeed, water removal only occurs through a diffusive process from the edge of droplet to the edge of the wafer. Confinement also permits a simple 2D description, and allows simple observations of the drying. We studied the drying of an aqueous solution of a tribloc copolymer (Pluronics, P104) thanks to three different techniques: polarized microscopy, fluorescent microscopy, and Raman imaging. With our tool and techniques, we not only build an accurate phase diagram of the solution (with one microliter only) but also measure both the mutual diffusion coefficient and the activity of the solution as a function of its concentration, including the Flory-Huggins parameter.

Laure, Daubersies; Jacques, Leng; Jean-Baptiste, Salmon

2012-02-01

141

New confining N=1 supersymmetric gauge theories  

SciTech Connect

We examine N=1 supersymmetric gauge theories which confine in the presence of a tree-level superpotential. We show the confining spectra which satisfy the 't Hooft anomaly matching conditions and give a simple method to find the confining superpotential. Using this method we fix the confining superpotentials in the simplest cases, and show how these superpotentials are generated by multi-instanton effects in the dual theory. These new type of confining theories may be useful for model building, since the size of the matter content is not restricted by an index constraint. Therefore, one expects that a large variety of new confining spectra can be obtained using such models.

Csaki, C.; Murayama, H.

1998-10-01

142

Confinement Studies of Auxiliary Heated NSTX Plasmas  

SciTech Connect

The confinement of auxiliary heated NSTX discharges is discussed. The energy confinement time in plasmas with either L-mode or H-mode edges is enhanced over the values given by the ITER97L and ITER98Pby(2) scalings, being up to 2-3 times L-mode and 1.5 times H-mode. TRANSP calculations based on the kinetic profile measurements reproduce the magnetics-based determination of stored energy and the measured neutron production rate. Power balance calculations reveal that, in a high power neutral beam heated H-mode discharge, the ion thermal transport is near neoclassical levels, and well below the electron thermal transport, which is the main loss channel. Perturbative impurity injection techniques indicate the particle diffusivity to be slightly above the neoclassical level in discharges with L-mode edge. High-harmonic fast-wave (HHFW) bulk electron heating is described and thermal transport is discussed. Thermal ion transport is found to be above neoclassical level, but thermal electron transport remains the main loss mechanism. Evidences of an electron thermal internal transport barrier obtained with HHFW heating are presented. A description of H-mode discharges obtained during HHFW heating is presented.

B.P. LeBlanc; M.G. Bell; R.E. Bell; M.L. Bitter; C. Bourdelle; D.A. Gates; S.M. Kaye; R. Maingi; J.E. Menard; D. Mueller; S.F. Paul; A.L. Roquemore; A. Rosenberg1; S.A. Sabbagh; D. Stutman; E.J. Synakowski; V.A. Soukhanovskii; J.R.Wilson; the NSTX Research Team

2003-05-06

143

Membrane Cholesterol Strongly Influences Confined Diffusion of Prestin  

PubMed Central

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.

Kamar, R.I.; Organ-Darling, L.E.; Raphael, R.M.

2012-01-01

144

Membrane cholesterol strongly influences confined diffusion of prestin.  

PubMed

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. PMID:23083705

Kamar, R I; Organ-Darling, L E; Raphael, R M

2012-10-16

145

Conformation and Dynamics of DNA Confined in Slitlike Nanofluidic Channels  

NASA Astrophysics Data System (ADS)

Using laser fluorescence microscopy, we study the shape and dynamics of individual DNA molecules in slitlike nanochannels confined to a fraction of their bulk radius of gyration. With a confinement size spanning 2 orders of magnitude, we observe a transition from the de Gennes regime to the Odijk regime in the scaling of both the radius of gyration and the relaxation time. The radius of gyration and the relaxation time follow the predicted scaling in the de Gennes regime, while, unexpectedly, the relaxation time shows a sharp decrease in the Odijk regime. The radius of gyration remains constant in the Odijk regime. Additionally, we report the first measurements of the effect of confinement on the shape anisotropy.

Bonthuis, Douwe Jan; Meyer, Christine; Stein, Derek; Dekker, Cees

2008-09-01

146

Conformation and dynamics of DNA confined in slitlike nanofluidic channels.  

PubMed

Using laser fluorescence microscopy, we study the shape and dynamics of individual DNA molecules in slitlike nanochannels confined to a fraction of their bulk radius of gyration. With a confinement size spanning 2 orders of magnitude, we observe a transition from the de Gennes regime to the Odijk regime in the scaling of both the radius of gyration and the relaxation time. The radius of gyration and the relaxation time follow the predicted scaling in the de Gennes regime, while, unexpectedly, the relaxation time shows a sharp decrease in the Odijk regime. The radius of gyration remains constant in the Odijk regime. Additionally, we report the first measurements of the effect of confinement on the shape anisotropy. PMID:18851263

Bonthuis, Douwe Jan; Meyer, Christine; Stein, Derek; Dekker, Cees

2008-09-05

147

Effect of confinement on DNA dynamics in microfluidic devices  

NASA Astrophysics Data System (ADS)

The dynamics of dissolved long-chain macromolecules are different in highly confined environments than in bulk solution. A computational method is presented here for detailed prediction of these dynamics, and applied to the behavior of ~1-100 ?m DNA in micron-scale channels. The method is comprised of a self-consistent coarse-grained Langevin description of the polymer dynamics and a numerical solution of the flow generated by the motion of polymer segments. Diffusivity and longest relaxation time show a broad crossover from free-solution to confined behavior centered about the point H~10Sb, where H is the channel width and Sb is the free-solution chain radius of gyration. In large channels, the diffusivity is similar to that of a sphere diffusing along the centerline of a pore. For highly confined chains (H/Sb<<1), Rouse-type molecular weight scaling is observed for both translational diffusivity and longest relaxation time. In the highly confined region, the scaling of equilibrium length and relaxation time with H/Sb are in good agreement with scaling theories. In agreement with the results of Harden and Doi [J. Phys. Chem. 96, 4046 (1992)], we find that the diffusivity of highly confined chains does not follow the scaling relation predicted by Brochard and de Gennes [J. Chem. Phys. 67, 52 (1977)] that relationship does not account for the interaction between chain and wall.

Jendrejack, Richard M.; Schwartz, David C.; Graham, Michael D.; de Pablo, Juan J.

2003-07-01

148

Facilitated diffusion on confined DNA  

NASA Astrophysics Data System (ADS)

In living cells, proteins combine three-dimensional bulk diffusion and one-dimensional sliding along the DNA to reach a target faster. This process is known as facilitated diffusion and we investigate its dynamics in the physiologically relevant case of confined DNA. The confining geometry and DNA elasticity are key parameters: We find that facilitated diffusion is most efficient inside an isotropic volume and on a flexible polymer. By considering the typical copy numbers of proteins in vivo, we show that the speedup due to sliding becomes insensitive to fine tuning of parameters, rendering facilitated diffusion a robust mechanism to speed up intracellular diffusion-limited reactions. The parameter range we focus on is relevant for in vitro systems and for facilitated diffusion on yeast chromatin.

Foffano, G.; Marenduzzo, D.; Orlandini, E.

2012-02-01

149

Time.  

ERIC Educational Resources Information Center

Presents brief annotations of 41 children's books that explore the concept of time from varied perspectives to elucidate some of its meanings for children. Groups books to focus on milestones in children's lives; how they enjoy spending their time; visiting the past in suspending time; recognizing different ways to mark time; celebrating special…

Matthews, Susan; Reid, Rebecca; Sylvan, Anne; Woolard, Linda; Freeman, Evelyn B.

1999-01-01

150

Alternative approaches to plasma confinement  

Microsoft Academic Search

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

J. R. Roth

1978-01-01

151

Plasma confinement studies in LHD  

Microsoft Academic Search

The initial experiments on the Large Helical Device (LHD) have extended confinement studies on currentless plasmas to a large scale (R = 3.9 m, a = 0.6 m). Heating by NBI of 3 MW produced plasmas with a fusion triple product of 8 × 1018m-3·keV·s at a magnetic field strength of 1.5 T. An electron temperature of 1.5 keV and

M. Fujiwara; H. Yamada; A. Ejiri; M. Emoto; H. Funaba; M. Goto; K. Ida; H. Idei; S. Inagaki; S. Kado; O. Kaneko; K. Kawahata; T. Kobuchi; A. Komori; S. Kubo; R. Kumazawa; S. Masuzaki; T. Minami; J. Miyazawa; T. Morisaki; S. MURAKAMI; S. Murakami; S. Muto; T. Mutoh; Y. Nagayama; Y. Nakamura; H. Nakanishi; K. Narihara; K. Nishimura; N. Noda; S. Ohdachi; N. Ohyabu; Y. Oka; M. Osakabe; T. Ozaki; B. J. Peterson; A. Sagara; S. Sakakibara; R. Sakamoto; H. Sasao; M. Sasao; K. Sato; M. Sato; T. Seki; T. Shimozuma; M. Shoji; H. Suzuki; Y. Takeiri; K. Tanaka; K. Toi; T. Tokuzawa; K. Tsumori; K. Tsuzuki; K. Y. Watanabe; T. Watari; I. Yamada; S. Yamaguchi; M. Yokoyama; R. Akiyama; H. Chikaraishi; K. Haba; S. Hamaguchi; M. Iima; S. Imagawa; N. Inoue; K. Iwamoto; S. Kitagawa; J. Kodaira; Y. Kubota; R. Maekawa; T. Mito; T. Nagasaka; A. Nishimura; C. Takahashi; K. Takahata; Y. Takita; H. Tamura; T. Tsuzuki; S. Yamada; K. Yamauchi; N. Yanagi; H. Yonezu; Y. Hamada; K. Matsuoka; K. Murai; K. Ohkubo; I. Ohtake; M. Okamoto; S. Satoh; T. Satow; S. Sudo; S. Tanahashi; K. Yamazaki; O. Motojima; A. Iiyoshi

1999-01-01

152

Limits on rock strength under high confinement  

Microsoft Academic Search

Understanding of deep earthquake source mechanisms requires knowledge of failure processes active under high confinement. Under low confinement the compressive strength of rock is well known to be limited by frictional sliding along stress-concentrating flaws. Under higher confinement strength is usually assumed limited by power-law creep associated with the movement of dislocations. In a review of existing experimental data, we

Carl E. Renshaw; Erland M. Schulson

2007-01-01

153

Hermitesche Relativitätstheorie, Chromodynamik und Confinement  

NASA Astrophysics Data System (ADS)

Die Ausdehnung der Riemannschen Metrik der Allgemeinen Relativitätstheorie ins Komplexe bedeutet die Ersetzung der Symmetrie-Bedingungenfür den metrischen Tensor, Affinität und Ricci-Tensor durch die Hermiteschen BedingungenMit diesen Bedingungen führt das Einstein-Hilbert-Hamilton-Prinzipzu einer erweiterten Gravitationstheorie (Einstein), die im Sinne der EIH-Approximation neben der Newton-Einsteinschen Gravodynamik, auch die Chromodynamik der Elementarteilchenphysik enthält.Die von den Einstein-Schrödingerschen Feldgleichungen der Hermiteschen Relativitätstheorie implizierte Wechselwirkung zwischen Gravo- und Chromodynamik erzwingt das Confinement. Ohne dieses Confinement würde das Gravitationspotential divergieren, d.h., es könnte keine - nach Maßgabe der Einstein-Schrödingerschen Feldgleichungen - Riemannsche Raum-Zeit-Metrik gik = aik geben.Translated AbstractHermitian Relativity, Chromodynamics and ConfinementThe extension of the Riemannian metrics of General Relativity to the complex domain, i.e. the substitution of the symmetry conditions for the fundamental tensor gik, the affinity lik and the Ricci curvature Rik by the conditions of Hermiticity gives a Generalized Theory of Gravity (Einstein) which describes the Newton-Einstein gravodynamics combined with the chromodynamics of quarks.The Hermitian Theory of Relativity starts form the Einstein Lagrangian with and the Einstein-Schrödinger field equations result: > In the Einstein-Infeld-Hoffmann approximation (EIH) of General Relativity between point-like particles forces > are given by the conditions of integrability (generalized Bianchi-identics).Furthermore, solutions for the symmetrical part >

of the equations exist only if there is confinement for the charges QA = 0. Then the field masses MA are given by
>

with the distance L between the charges QA.The equations of motions with distance-independent forces QAQB and the confinement QA = 0 are a consequence of the Einstein-Schrödinger equations for Hermitian Relativity. The forte Einstein-Straus equations (with Rik = 0) do not give charges QA and therefore the Newtonian forces only.>

Treder, H.-J.

154

Strong light confinement in a photonic amorphous diamond structure  

NASA Astrophysics Data System (ADS)

Formation of cavity modes in a recently found unique photonic structure ``photonic amorphous diamond (PAD)'' has been investigated by finite-difference time domain calculations. A well-confined monopole mode has been found to form when a rod is removed from the structure. The quality (Q) factor and mode volume (Vm) of such a cavity mode in PAD have been evaluated and compared with those in a conventional photonic crystal with a crystalline diamond structure. The two structures have shown nealy the same Q-factor and Vm, leading to the conclusion that strong light confinement is realizable in PAD as well as conventional photonic crystals.

Imagawa, Shigeki; Edagawa, Keiichi; Notomi, Masaya

2012-04-01

155

A unified physical scaling law for tokamak energy confinement  

Microsoft Academic Search

From the equations which describe local transport in a turbulent plasma the scaling of the local diffusivity with the plasma parameters can be established. It is shown that, by appropriate choices of time and length scales for the turbulence, the scaling of the global energy confinement can be cast in two limiting forms: a short and a long wavelength scaling.

J. P. Christiansen; J. G. Cordey; K. Thomsen

1990-01-01

156

Effect of ?-cyclodextrin nanocavity confinement on the photophysics of robinetin  

Microsoft Academic Search

We have studied the confinement of robinetin, a therapeutically active plant flavonol, in cyclodextrin (CDx) nanocavities, using steady state and time resolved fluorescence spectroscopy. Enhanced tautomer emission (arising from excited state intramolecular proton transfer (ESIPT)) as well as dramatically blue shifted (?10nm in ?-CDx and ?33nm in SHP ?-CDx) normal fluorescence observed upon addition of the ?-CDxs indicate that robinetin

Anwesha Banerjee; Kaushik Basu; Pradeep K. Sengupta

2007-01-01

157

Preliminary studies of inertial-electrostatic confinement fusion experiments  

Microsoft Academic Search

Preliminary inertial-electrostatic confinement fusion experiments have been carried out using hydrogen gas, and measurements of the light from a plasma core were made. The life time of charged particles in gridded IECF configuration is found to be longer than in the conventional spherical electrode discharges. The light intensity is found to be proportional to about 2\\/3 power of the input

Yasushi Yamamoto; Masami Ohnishi; Kiyoshi Yoshikawa; Hisayuki Toku; Mitsunori Hasegawa; Takashi Matsuo

1996-01-01

158

A novel boundary-confined method for microlens arrays fabrication  

Microsoft Academic Search

We present a technique to improve microlens arrays (MLAs) uniformity after the thermal reflow process. Traditional photo resist thermal reflow processes cause micro lenses merge together easily due to an inexact reflow time and temperature distribution. This results in poor uniformity and low lens height. A new MLAs fabrication method, called the boundary-confined method, was proposed and demonstrated. By two

Hsin-Ta Hsieh; Vinna Lin; Guo-Dung J. Su

2011-01-01

159

Compact inertial confinement multireactor concepts  

SciTech Connect

Inertial confinement fusion (ICF) commercial-applications plant-optimum driver pulse repetition rates may exceed reactor pulse-repetition-rate capabilities. Thus, more than one reactor may be required for low-cost production of electric power, process heat, fissionable fuels, etc., in ICF plants. Substantial savings in expensive reactor containment cells and blankets can be realized by placing more than one reactor in a cell and by surrounding more than one reactor cavity with a single blanket system. There are also some potential disadvantages associated with close coupling in compact multicavity blankets and multireactor cells. Tradeoffs associated with several scenarios have been studied.

Pendergrass, J.H.

1985-01-01

160

Rheology of confined granular flows  

SciTech Connect

The properties of confined granular flows on a heap are studied through numerical simulations and experiments. We address how such system can be simulated with period boundaries in the flow direction. The packing fraction and velocity profiles are found to be described by one length scale. The dependence of the kinematic properties on the number of grains and on micromechanical parameters (coefficient of restitution and coefficient of friction) is described. Our results show that the friction at the sidewalls gradually decreases and that this decrease can be explained by the intermittent motion of the grains in the quasistatic part of the flow.

Richard, Patrick; Valance, Alexandre; Metayer, Jean-Francois; Crassous, Jerome; Delannay, Renaud [Universite Rennes 1, Institut de Physique de Rennes, UMR CNRS 6251, 263 av. General Leclerc, 35042 Rennes cedex FRANCE (France); Louge, Michel [Sibley School of Mechanical and Aerospace Engineering, Cornell University, Ithaca, NY 14853 (United States)

2010-05-05

161

Measurement of the orthopositronium confinement energy in mesoporous thin films  

SciTech Connect

In this paper, we present measurements of the ortho-positronium (ortho-Ps) emission energy in vacuum from mesoporous films using the time-of-flight technique. We show evidence of quantum mechanical confinement in the mesopores that defines the minimal energy of the emitted Ps. Two samples with different effective pore sizes, measured with positron annihilation lifetime spectroscopy, are compared for the data collected in the temperature range 50-400 K. The sample with smaller pore size exhibits a higher minimal energy (73{+-}5 meV), compared to the sample with bigger pores (48{+-}5 meV), due to the stronger confinement. The dependence of the emission energy with the temperature of the target is modeled as ortho-Ps being confined in rectangular boxes in thermodynamic equilibrium with the sample. We also measured that the yield of positronium emitted in vacuum is not affected by the temperature of the target.

Crivelli, Paolo; Gendotti, Ulisse; Rubbia, Andre; Liszkay, Laszlo; Perez, Patrice; Corbel, Catherine [Instituto de Fisica, Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro, 21941-972 (Brazil); Institut fuer Teilchenphysik, ETHZ, CH-8093 Zuerich (Switzerland); CEA, Saclay, IRFU, F-91191 Gif-sur-Yvette Cedex (France); LSI, Ecole Polytechnique, Route de Saclay, F-91128 Palaiseau Cedex (France)

2010-05-15

162

Dynamic, multiaxial impact response of confined and unconfined ceramic rods  

SciTech Connect

A new configuration for impact testing was implemented which yielded time-resolved measurements of the dynamic response of materials undergoing multiaxial strain. With this`-Method, one end of an initially stationary rod (ie., right circular cylinder) of test material was subjected to planar impact with a flat-faced projectile. The test rod was either free (unconfined) or mounted within a close-fitting sleeve which provided lateral confinement. Velocity interferometer diagnostics monitored the axial (longitudinal) velocity of the rod free end, and the transverse (radial) velocity for one or more points on the periphery of the rod or confinement sleeve. Analysis of the resultant velocity records allowed assessment of material properties, such as wave speeds and compressive yield strength, without the requirement of intact recovery of the rod. Data were obtained for alumina (Coors AD-99.5) rods in a series of tests involving variations in confinement and peak impact stress.

Wise, J.L.; Grady, D.E.

1993-09-01

163

Holographic confining gauge theory and response to the electric field  

SciTech Connect

We study the response of confining gauge theory to the external electric field by using holographic Yang-Mills theories in the large N{sub c} limit. Although the theories are in the confinement phase, we find a transition from the insulator to the conductor phase when the electric field exceeds its critical value. Then, the baryon number current is generated in the conductor phase. At the same time, in this phase, meson melting is observed through the quasinormal modes of the meson spectrum. Possible ideas are given for the string state corresponding to the melted mesons, and they lead to the idea that the source of this current may be identified with the quarks and antiquarks supplied by the melted mesons. We also discuss other possible carriers. Furthermore, from the analysis of the massless quark, chiral symmetry restoration is observed at the insulator-conductor transition point by studying a confining theory in which the chiral symmetry is broken.

Ghoroku, Kazuo [Fukuoka Institute of Technology, Wajiro, Higashi-ku Fukuoka 811-0295 (Japan); Ishihara, Masafumi; Taminato, Tomoki [Department of Physics, Kyushu University, Hakozaki, Higashi-ku Fukuoka 812-8581 (Japan)

2010-01-15

164

Staged heating of linear magnetically confined plasmas using laser irradiation and magnetic compression  

Microsoft Academic Search

It is demonstrated that staged laser heating of linear magnetically confined plasma lends flexibility to the laser solenoid fusion concept, by allowing laser absorption length to be matched to the plasma length, thereby enabling efficient use of beam energy. Hence the plasma length can be assigned on the basis of confinement time (considerations independent of the absorption process). An approximate

L. C. Steinhauer

1976-01-01

165

Effect of confinement on the collapsing mechanism of a flexible polymer chain  

Microsoft Academic Search

In this paper, Brownian dynamics simulation (BDS) studies are executed to demonstrate the distinctive influences of the extent of confinement on the collapsing mechanism and kinetics of a flexible hydrophobic polymer chain in a poor solvent. The collapsing behavior is quantified by the time of collapse, which below a critical dimension of the confinement (hc), encounters a drastic reduction with

Siddhartha Das; Suman Chakraborty

2010-01-01

166

Light-Cone Kaluza-Klein Geometry: Confined Propagation as a Particle Model  

Microsoft Academic Search

A modified Kaluza-Klein theory is proposed in which propagation takes place only at the speed of light. The propagation can be confined to a small volume, forming a particle with rest mass. The usual four space-time coordinates locate the confinement volume, and Kaluza's fifth coordinate is replaced by an internal degree of freedom. Electromagnetism corresponds to a gauge field on

Donald E. Jennings

2000-01-01

167

The effect of confinement on motivation to exercise in young dairy calves  

Microsoft Academic Search

The objective of this research was to determine if confinement of 8-day-old calves for varying lengths of time is associated with an increase in motivation to perform locomotor behaviors. Holstein heifer and bull calves (N=48) were used in a factorial arrangement with two crossed factors. Factor A was housing with two levels (individual confinement versus group pens) and factor B

Anne M Sisto; Ted H Friend

2001-01-01

168

Carrier and radiation confinement in a DFB Multiple Quantum Well Laser  

Microsoft Academic Search

Numerical results for carrier and radiation confinement in a Distributed Feedback (DFB) Multiple Quantum Well Laser (MQW) are presented. The energy eigenvalues for electrons and holes are calculated by solving the one dimensional time-independent Schrodinger equation and the TE confined modes are found by exploring the analogy between particle and electromagnetic wave equations. The optical gain is obtained for different

A. Cruz Serra; J. Torres Pereira; C. Ferreira Fernandes; A. Lopes Ribeiro

1994-01-01

169

Improved confinement in high li lower hybrid driven steady state plasmas in TORE SUPRA  

Microsoft Academic Search

The global energy confinement of combined ohmic and lower hybrid driven TORE SUPRA plasmas has been analysed at various densities. In contradiction to the L mode ITER scaling law, this analysis indicates that the global energy confinement time depends strongly on the plasma density. Furthermore, the thermal electron energy content of steady state discharges is found to be in good

G. T. Hoang; C. Gil; E. Joffrin; D. Moreau; A. Becoulet; P. Bibet; J. P. Bizarro; R. V. Budny; J. Carrasco; J. P. Coulon; C. DeMichelis; T. Dudok de Wit; P. Monier-Garbet; M. Goniche; R. Guirlet; T. Hutter; S. M. Kaye; J. Lasalle; L. Laurent; P. Lecoustey; X. Litaudon; M. Mattioli; Y. Peysson; A.-L. Pecquet; G. Rey; S. A. Sabbagh; B. Saoutic; G. Tonon; J. C. Vallet

1994-01-01

170

Modeling of ESD-induced confined ignition of solid rocket propellants  

Microsoft Academic Search

Solid rocket propellants can be ignited by electrostatic discharge (ESD) events delivering energies orders of magnitude below those typically required to cause ignition. Confinement effects have been proposed as the cause of increased sensitivity to ignition. To better understand the factors influential in ESD ignition, a model for confined ignition of propellants was developed. This model integrates time-dependent, one-dimensional energy

R. L. Raun

2000-01-01

171

Failure Diameter of Confined Explosive Rods  

NASA Astrophysics Data System (ADS)

It is known that the failure diameter (FD) of confined rods is smaller than that of unconfined rods, and that the heavier the confinement the smaller the FD. FD is usually determined for bare or very lightly confined rods, and standard explosives handbooks have unconfined FD data for many explosives and formulations. But there are very few FD data of confined explosive rods. In this work we use our hydroreactive code to explore the effect of confinement on rods of PBX-9502. First we calibrate our reaction model to match the standard pop-plot. Next we validate the calibration by reproducing the experimentally determined unconfined FD. Then we compute the FD as a function of confinement thickness for three confinement materials: light (PMMA), medium (aluminum) and heavy (copper). For the light material we find that it has no effect on the FD. For the medium and heavy materials we find, as expected, that the FD decreases when confinement thickness increases. But for each confinement material there is a lower limit to the FD, no matter how thick the confinement.

Partom, Yehuda

1999-06-01

172

Structure and dynamics of supercooled water in neutral confinements.  

PubMed

We perform molecular dynamics simulations to study the structure and dynamics of liquid water in neutral nanopores, which are generated by pinning a suitable subset of water molecules in an equilibrium configuration of a bulk system. It is found that such neutral confinement does not disturb the structure of water, in particular, the local tetrahedral order, while it imposes a pronounced spatial inhomogeneity on the dynamics of water. Specifically, when the pore wall is approached, hopping motion sets in and water dynamics slows down. We show that the logarithm of the correlation time is an exponential function of the distance to the wall, indicating a tremendous gradient of water mobility across the confinement. Upon cooling, the length scale associated with this exponential distance dependence and, thus, the range of the wall effect increases, at least down to the critical temperature of mode coupling theory, T(c). Also, the temperature dependence of water dynamics varies across the pore, i.e., fragility is high in the pore center, while it is low near the pore wall. Due to all these effects, time-temperature superposition is violated. Our observations for a neutral confinement reveal that specific interactions at hydrophilic or hydrophobic walls are not the main cause of spatially inhomogeneous dynamics of confined water. In view of similarities with the behavior of Lennard-Jones liquids in neutral confinements, one may rather speculate that the effects observed for confined water are general and result from the existence of a static contribution to the energy landscape, which is imprinted by an immobile environment. PMID:23574240

Klameth, F; Vogel, M

2013-04-01

173

On Wilson's theory of confinement  

SciTech Connect

According to recent results, the Gell-Mann-Low function {beta}(g) of four-dimensional {phi}{sup 4} theory is nonalternating and has a linear asymptotics at infinity. According to the Bogoliubov and Shirkov classification, it means the possibility of constructing a continuous theory with finite interaction at large distances. This conclusion is in visible contradiction to the lattice results indicating triviality of {phi}{sup 4} theory. This contradiction is resolved by a special character of renormalizability in {phi}{sup 4} theory: to obtain the continuous renormalized theory, there is no need to eliminate a lattice from the bare theory. In fact, such kind of renormalizability is not accidental and can be understood in the framework of Wilson's many-parameter renormalization group. Application of these ideas to QCD shows that Wilson's theory of confinement is not purely illustrative, but has a direct relation to a real situation. As a result, the problem of analytical proof of confinement and a mass gap can be considered solved, at least on the physical level of rigor.

Suslov, I. M., E-mail: suslov@kapitza.ras.ru [Kapitza Institute for Physical Problems (Russian Federation)

2011-10-15

174

On Wilson's theory of confinement  

NASA Astrophysics Data System (ADS)

According to recent results, the Gell-Mann-Low function ?( g) of four-dimensional ?4 theory is nonalternating and has a linear asymptotics at infinity. According to the Bogoliubov and Shirkov classification, it means the possibility of constructing a continuous theory with finite interaction at large distances. This conclusion is in visible contradiction to the lattice results indicating triviality of ?4 theory. This contradiction is resolved by a special character of renormalizability in ?4 theory: to obtain the continuous renormalized theory, there is no need to eliminate a lattice from the bare theory. In fact, such kind of renormalizability is not accidental and can be understood in the framework of Wilson's many-parameter renormalization group. Application of these ideas to QCD shows that Wilson's theory of confinement is not purely illustrative, but has a direct relation to a real situation. As a result, the problem of analytical proof of confinement and a mass gap can be considered solved, at least on the physical level of rigor.

Suslov, I. M.

2011-10-01

175

Confinement of test particles in warped spacetimes  

SciTech Connect

We investigate test particle trajectories in warped spacetimes with a thick brane warp factor, a cosmological on-brane line element, and a time dependent extra dimension. The geodesic equations are reduced to a first order autonomous dynamical system. Using analytical methods, we arrive at some useful general conclusions regarding possible trajectories. Oscillatory motion, suggesting confinement about the location of the thick brane, arises for a growing warp factor. On the other hand, we find runaway trajectories (exponential-like) for a decaying warp factor. Variations of the extra dimensional scale factor yield certain quantitative differences. Results obtained from explicit numerical evaluations match well with the qualitative conclusions obtained from the dynamical systems analysis.

Ghosh, Suman; Kar, Sayan; Nandan, Hemwati [Department of Physics and Meteorology and Centre for Theoretical Studies, Indian Institute of Technology, Kharagpur 721 302 (India); Centre for Theoretical Studies, Indian Institute of Technology, Kharagpur 721 302 (India)

2010-07-15

176

Polymer translocation out of planar confinements  

NASA Astrophysics Data System (ADS)

Polymer translocation in three dimensions out of planar confinements is studied in this paper. Three membranes are located at z = -h, z = 0 and z = h1. These membranes are impenetrable, except for the middle one at z = 0, which has a narrow pore. A polymer with length N is initially sandwiched between the membranes placed at z = -h and z = 0 and translocates through this pore. We consider strong confinement (small h), where the polymer is essentially reduced to a two-dimensional polymer, with a radius of gyration scaling as Rg(2D)~N?2D here, ?2D = 0.75 is the Flory exponent in two dimensions. The polymer performs Rouse dynamics. On the basis of theoretical analysis and high-precision simulation data, we show that in the unbiased case h = h1, the dwell time ?d scales as N2+?2D, in perfect agreement with our previously published theoretical framework. For h_1=\\infty , the situation is equivalent to field-driven translocation in two dimensions. We show that in this case ?d scales as N2?2D, in agreement with several existing numerical results in the literature. This result violates the earlier reported lower bound N1+? for ?d for field-driven translocation. We argue, on the basis of energy conservation, that the actual lower bound for ?d is N2? and not N1+?. Polymer translocation in such theoretically motivated geometries thus resolves some of the most fundamental issues that have been the subject of much heated debate in recent times.

Panja, Debabrata; Barkema, Gerard T.; Ball, Robin C.

2008-02-01

177

Heating, Confinement, and Extrapolation to Reactors  

SciTech Connect

The total amount of heating power coupled to the plasma P{sub tot} and the energy confinement time are determining parameters for realizing the plasma conditions suitable for the reactor. We recall that the ignition condition can be expressed by the following condition on the triple fusion product:NT{tau} = P{sub tot}{tau}{sup 2}/(3 Vol) = 3N{sup 2}T{sup 2}Vol/P{sub tot} > (NT{tau}){sub ignition} (1)with T [approximately equal to] 15 keV where {tau} = E/P{sub tot} is the energy confinement time, E = 3NT Vol for an isothermal plasma with T{sub i} = T{sub e} = T and a plasma volume Vol; N is the plasma density. The value T [approximately equal to] 15 keV corresponds to the minimum value of (NT{tau}){sub ignition} as a function T (see Fig. 1). In the present discussion for the sake of simplicity, we neglect density and temperature profile factors. The heating power in most of the present experiments is given by P{sub tot} = P{sub OH} + P{sub add} where P{sub OH} is the ohmic power and P{sub add} is the additional heating due to neutral beam injection or R.F. heating. At ignition, the additional heating power must come completely from the energetic {alpha} particles produced by the fusion reactions and we must have P{sub tot} = P{sub {alpha}} if we neglect the residual P{sub OH} and the plasma losses by Bremsstrahlung (P{sub Br} [is proportional to] N{sup 2} T{sup 1/2})

Ongena, J.; Messiaen, A.M

2004-03-15

178

Elmo bumpy square plasma confinement device  

DOEpatents

The invention is an Elmo bumpy type plasma confinement device having a polygonal configuration of closed magnet field lines for improved plasma confinement. In the preferred embodiment, the device is of a square configuration which is referred to as an Elmo bumpy square (EBS). The EBS is formed by four linear magnetic mirror sections each comprising a plurality of axisymmetric assemblies connected in series and linked by 90/sup 0/ sections of a high magnetic field toroidal solenoid type field generating coils. These coils provide corner confinement with a minimum of radial dispersion of the confined plasma to minimize the detrimental effects of the toroidal curvature of the magnetic field. Each corner is formed by a plurality of circular or elliptical coils aligned about the corner radius to provide maximum continuity in the closing of the magnetic field lines about the square configuration confining the plasma within a vacuum vessel located within the various coils forming the square configuration confinement geometry.

Owen, L.W.

1985-01-01

179

Failure diameter of confined explosive rods  

NASA Astrophysics Data System (ADS)

We use our hydroreactive code to compute the failure diameter (FD) of confined PBX-9502 rods. First we calibrate our reaction model to match the standard pop-plot. Next we validate the calibration by reproducing the experimentally determined unconfined FD. Then we compute FD as a function of confinement thickness (CT) for three confinement materials: light (PMMA), medium (aluminum) and heavy (copper). We find that light confinement has no effect. For medium and heavy confinements we find, as expected, that FD decreases when CT increases. But for each material there is a lower limit to FD no matter how thick the confinement. We compare our results to data by Ramsay, obtained in slab symmetry, and agreement is reasonable. .

Partom, Yehuda

2000-04-01

180

New confining N=1 supersymmetric gauge theories  

SciTech Connect

We examine N=1 supersymmetric gauge theories which confine in the presence of a tree-level superpotential. We show the confining spectra which satisfy the {close_quote}t Hooft anomaly matching conditions and give a simple method to find the confining superpotential. Using this method, we fix the confining superpotentials in the simplest cases and show how these superpotentials are generated by multi-instanton effects in the dual theory. These new types of confining theories may be useful for model building, since the size of the matter content is not restricted by an index constraint. Therefore, one expects that a large variety of new confining spectra can be obtained using such models. {copyright} {ital 1999} {ital The American Physical Society}

Csaki, C.; Murayama, H. [Theoretical Physics Group, Ernest Orlando Lawrence Berkeley National Laboratory, University of California, Berkeley, California 94720 (United States)]|[Department of Physics, University of California, Berkeley, California 94720 (United States)

1999-03-01

181

Holographic Schwinger effect in confining phase  

NASA Astrophysics Data System (ADS)

We consider the Schwinger effect in confining phase by using a holographic setup. The potential analysis is performed for the confining D3-brane and D4-brane back-grounds. We find the critical electric field above which there is no potential barrier and the system becomes unstable catastrophically. An intriguing point is that no Schwinger effect occurs when the electric field is smaller than the confining string tension.

Sato, Yoshiki; Yoshida, Kentaroh

2013-09-01

182

Quark confinement in a constituent quark model  

SciTech Connect

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.

Langfeld, K.; Rho, M. [CEA Centre d`Etudes de Saclay, 91 - Gif-sur-Yvette (France). Service de Physique Theorique

1995-07-01

183

Spectra of confined two-electron atoms  

NASA Astrophysics Data System (ADS)

Spectra of two electrons confined in a spherically symmetric potential of mixed Coulomb and harmonic form are studied using the Hartree-Fock and configuration interaction methods. The model studied corresponds to a two-electron atom confined in a harmonic oscillator potential. The spectral consequences of the interplay between the effects of the confinement due to the Hooke's law and due to the nuclear attraction force are investigated in detail.

Bielinska-Waz, D.; Karwowski, J.; Diercksen, G. H. F.

2001-05-01

184

Spectra of Confined Atoms and Molecules  

NASA Astrophysics Data System (ADS)

The properties of spectra of atoms and molecules confined by an external potential are analyzed. The effects of spatial confinement are studied using quantum-chemical models. The confinement of the system is described by an external one-particle potential. Two-electron atoms confined in a spherically symmetric harmonic oscillator potential are investigated in detail [1]. In this case the interplay between the effects of the confinement due to the Hooke's law and due to the nuclear attraction forces are studied. The existence of a special case when the harmonic oscillator frequency ? and the nuclear charge Z are changed simultaneously so that the structure of the confined atom remains unchanged up to the second order of the perturbation theory, is demonstrated. Moreover, the structure and the spectral properties of the hydrogen molecule confined in a harmonic oscillator potential are studied [2]. The bond length and the vibronic transitions (the intensities and the number of lines) depend in a specific way on the strength of the confining potential. In particular, due to the confinement, the absorption and the emission vibronic bands are blue shifted.

Bieli?ska-Waz, D.

2003-04-01

185

A neutron spin-echo study of confined water  

Microsoft Academic Search

We have investigated the dynamics of confined water in a fully hydrated Na-vermiculite clay using the neutron spin-echo (NSE) technique. NSE measures the intermediate self-scattering function, i.e., the dynamics directly in the time domain. In the present experiments we performed measurements, in the time range 3-3000 ps and temperature ranging from 254 to 323 K, on the essentially two-dimensional water

J. Swenson; R. Bergman; S. Longeville

2001-01-01

186

Aspects of stellarator confinement scaling  

SciTech Connect

Extensive discussion has been made concerning stellarator experimental confinement scaling and the extrapolation to reactor systems. Two features are discussed here: (1) The role of hydrogen-impurity interactions. (2) The neoclassical (bootstrap) current has been invoked as an argument against the possibility of optimizing the stellarator magnetic configuration to reach high ..beta... It is felt that significant bootstrap current production under conditions of high ..beta.. will dominate the vacuum fields. In this regard, a brief summary is presented of a comparison made between ISX-B high-..beta.. data and the neoclassical predictions. The non-neoclassical rates of electron pitch-angle scattering serve to destroy this current, and are evidently responsible for a lack of evidence for the bootstrap current under conditions in tokamaks where a large effect is expected.

Hogan, J.

1981-01-01

187

Molecular Motion and Confined Polymers  

NASA Astrophysics Data System (ADS)

Microorganisms such as myxobacteria, cyanobacteria, and flexibacteria move by gliding. The gliding has been described by two quite different mechanisms: social (S) motility and adventurous (A) motility. Though retraction of type 4-pili provides the force for the S motility, extrusion of slime, which may be associated with the A motility, is not well known. Nozzle-like structures recently found in cyanobacteria can support the A motility. However, complete understaning A motility is still lacking. To describe the A motility, we use molecular dynamics simulations of a polymer growing inside a cylindrically shaped tube with one end capped. Confined polymers provide a driving force for a tube motion as if a rocket flew with emitting gas. It is seen from the mean-squared displacement of a tube that its motion is ballistic under constant applied force.

Dobrynin, Andrey V.; Jeon, Junhwan

2004-03-01

188

Prospects of inertial confinement fusion  

NASA Astrophysics Data System (ADS)

The present status of inertial confinement fusion (ICF) is briefly reviewed, emphasizing the National Ignition Facility (NIF) project in the US and the Megajoule project in France. Critical aspects of target performance such as symmetry and stability of capsule implosions and interaction physics in hohlraum targets are discussed. The advantages of heavy-ion beam drivers and corresponding research programs are pointed out with reference to the long-term prospects for ICF power production. The new concept of the fast ignition of precompressed fuel by petawatt, picosecond laser pulses is also covered. The laser plasma group at the Max-Planck-Institute for Quantum Optics (MPQ) is one of the European institutes funded by EURATOM for an ICF keep-in-touch activity, and we highlight results obtained at MPQ relevant to the recent progress of ICF.

Meyer-ter-Vehn, J.

1997-12-01

189

Confinement studies of ohmically heated plasmas in TFTR  

SciTech Connect

Systematic scans of density in large deuterium plasmas (a = 0.83 m) at several values of plasma current and toroidal magnetic field strength indicate that the total energy confinement time, tau/sub E/, is proportional to the line-average density anti n/sub e/ and the limiter q. Confinement times of approx. 0.3 s have been observed for anti n/sub e/ = 2.8 x 10/sup 19/ m/sup -3/. Plasma size scaling experiments with plasmas of minor radii a = 0.83, 0.69, 0.55, and 0.41 m at constant limiter q reveal a confinement dependence on minor radius. The major-radius dependence of tau/sub E/, based on a comparison between TFTR and PLT results, is consistent with R/sup 2/ scaling. From the power balance, the thermal diffusivity chi/sub e/ is found to be significantly less than the INTOR value. In the a = 0.41 m plasmas, saturation of confinement is due to neoclassical ion conduction (chi/sub i/ neoclassical >> chi/sub e/).

Efthimion, P.C.; Bretz, N.L.; Bell, M.G.; Bitter, M.; Blanchard, W.R.; Boody, F.; Boyd, D.; Bush, C.E.; Cecchi, J.L.; Coonrod, J.

1985-03-01

190

Regimes of improved confinement and stability in DIII-D obtained through current profile modifications  

SciTech Connect

Several regimes of improved confinement and stability have been obtained in recent experiments in the DIII-D tokamak by dynamically varying the toroidal current density profile to transiently produce a poloidal magnetic field profile with more favorable confinement and stability properties. A very peaked current density profile with high plasma internal inductance, [ell][sub i], is produced either by a rapid change in the plasma poloidal cross section or by a rapid change in the total plasma current. Values of thermal energy confinement times nearly 1.8 times the JET/DIII-D ELM-free H-mode thermal confinement scaling are obtained. The confinement enhancement factor over the ITER89-P L-mode confinement scaling, H, is as high as 3. Normalized toroidal beta, [beta][sub N], greater than 6%-m-T/MA and values of the product [beta][sub N]H greater than 15 have also been obtained. Both the confinement and the maximum achievable [beta] vary with [ell][sub i] and decrease as the current profile relaxes. For strongly shaped H-mode discharges, in addition to the current density profile peakedness, as measured by [ell][sub i] other current profile parameters, such as its distribution near the edge region, may also affect the confinement enhancement.

Lao, L.L.; Ferron, J.R.; Taylor, T.S.; Chan, V.S.; Osborne, T.H.; Burrell, K.H.; Chu, M.S.; DeBoo, J.C.; Greenfield, C.M.; Groebner, R.J.; Jackson, G.L.; St. John, H.; Strait, E.J.; Thompson, S.J.; Turnbull, A.D. (General Atomics, San Diego, CA (United States)); Doyle, E.J.; Rettig, C. (California Univ., Los Angeles, CA (United States)); James, R.; Wroblewski, D. (Lawrence Livermore National Lab., CA (United Sta

1992-09-01

191

Order in very cold confined plasmas  

SciTech Connect

The study of the structure and dynamic properties of classical systems of charged particles confined by external forces, and cooled to very low internal energies, is the subject of this talk. An infinite system of identical charged particles has been known for some time to form a body-centered cubic lattice and is a simple classical prototype for condensed matter. Recent technical developments in storage rings, ion traps, and laser cooling of ions, have made it possible to produce such systems in the laboratory, though somewhat modified because of their finite size. I would like to discuss what one may expect in such systems and also show some examples of experiments. If we approximate the potential of an ion trap with an isotropic harmonic force F = {minus}Kr then the Hamiltonian for this collection of ions is the same as that for J. J. Thomson`s ``plum pudding`` model of the atom, where electrons were thought of as discrete negative charges imbedded in a larger, positive, uniformly charged sphere. The harmonic force macroscopically is canceled by the average space-charge forces of the plasma-, and this fixes the overall radius of the distribution. What remains, are the residual two-body Coulomb interactions that keep the particles within the volume as nearly equidistant as possible in order to minimize the potential energy. The configurations obtained for the minimum energy of small ionic systems [2] in isotropic confinement are shown in figure 1. Indeed this is an `Exotic Atom` and fits well into the subject of this symposium honoring the 60th birthday of Professor Toshi Yamazaki.

Schiffer, J.P. [Argonne National Lab., IL (United States)]|[Univ. of Chicago, Chicago, IL (United States)

1995-12-31

192

Confined Zone Dispersion Project: A DOE assessment  

SciTech Connect

The goal of the US Department of Energy (DOE) Clean Coal Technology (CCT) program is to furnish the energy marketplace with a number of advanced, more efficient, and environmentally responsible coal utilization technologies through demonstration projects. These projects seek to establish the commercial feasibility of the most promising advanced coal technologies that have developed beyond the proof-of-concept (POC) stage. This document serves as a DOE post-project assessment of the Confined Zone Dispersion Project in CCT Round 3. In 1990, Bechtel Corporation entered into a cooperative agreement to conduct the demonstration project. The Seward Power Station of Pennsylvania Electric Company (now GPU Genco) was the host site. DOE funded 43 percent of the total project cost of $12,173,000. The project was started in June 1990 and was scheduled to be completed in June 1993. As a result of various operating problems, the schedule was extended into 1994 without additional cost to DOE. Bechtel provided the additional financing and GPU Genco provided electricity, steam, and water to operate the unit. The independent evaluation contained herein is based primarily on information from Bechtel's final technical report (1994) as well as other references cited. Confined Zone Dispersion (CZD) is a flue gas desulfurization (FGD) process that removes sulfur dioxide (SO{sub 2}). A finely atomized slurry of reactive lime, calcium hydroxide or Ca(OH){sub 2} is injected into the flue-gas duct work, between the air preheater and the second-stage ESP. The lime reacts with the SO{sub 2}, forming dry solid reaction products. The downstream ESP captures the 2 reaction products along with the fly ash entrained in the flue gas. The CZD process was demonstrated on Unit 5, a 147-MWe utility unit with two flue gas ducts. One of the ducts was extended to provide the requisite residence time and retrofitted with the CZD lime injection equipment.

NONE

1999-11-30

193

Studies of global energy confinement in TFTR supershots  

SciTech Connect

The global energy confinement time, {tau}{sub E}, from TFTR supershot plasmas has been correlated with the hydrogen recycling and the pressure anisotropy. An expression for the global confinement was obtained that describes its value at the time of peak neutron emission for all TFTR supershots obtained in the 1990 campaign, and simultaneously describes the time evolution of {tau}{sub E} for an extensive subset of the 1990 data. The obtained expression is probably not unique and it can be written with different variables. An analysis of the energy balance for many of these supershots indicates that the primary effect of larger {tau}{sub E} is that the central particle diffusivity is lower.

Strachan, J.D.

1993-08-01

194

Development of the turbulent confined jet  

Microsoft Academic Search

The mixing behavior of a confined jet is of great importance in connection with flow processes occurring in many devices, including ejector pumps, jet engine combustion chambers, and burners. The present study is concerned with a confined jet involving recirculation, taking into account a flow which is divided into four regions, each having different flow characteristics. It is pointed out

G. Ilic; I. G. Milojevic; S. Oka; D. Voronjec

1986-01-01

195

Positron confinement in embedded lithium nanoclusters  

Microsoft Academic Search

Quantum confinement of positrons in nanoclusters offers the opportunity to obtain detailed information on the electronic structure of nanoclusters by application of positron annihilation spectroscopy techniques. In this work, positron confinement is investigated in lithium nanoclusters embedded in monocrystalline MgO. These nanoclusters were created by means of ion implantation and subsequent annealing. It was found from the results of Doppler

M. A. van Huis; A. van Veen; H. Schut; C. V. Falub; S. W. H. Eijt; P. E. Mijnarends; J. Kuriplach

2002-01-01

196

Electrohydrodynamic Stretching of DNA in Confined Environments  

Microsoft Academic Search

The effect of confinement on the dynamics of polymers was studied by observing the transient extension and relaxation of single DNA molecules as they interacted with obstacles in a specially designed thing slit. Viscous drag was found to increase with the degree of confinement, which we interpret in terms of hydrodynamic screening by the planar surfaces of the slit. Since

O. Bakajin; T. A. J. Duke; C. F. Chou; S. S. Chan; Robert Austin; E. C. Cox

1998-01-01

197

Elastoplastic Confinement Model for Circular Concrete Columns  

Microsoft Academic Search

This paper presents relatively simple, analytically derived curves to model the axial and the lateral stress-strain relations of circular concrete columns. The analytical curves describe the full elastoplastic behavior of the confined concrete column. The solution to the partially confined reinforced concrete column in the elastoplastic range is derived by replacing the discrete lateral reinforcement with an equivalent tube and

R. Eid; A. N. Dancygier

2007-01-01

198

Polymer chain dynamics under nanoscopic confinements  

Microsoft Academic Search

It is shown that the confinement of polymer melts in nanopores leads to chain dynamics dramatically different from bulk behavior. This so-called corset effect occurs both above and below the critical molecular mass and induces the dynamic features predicted for reptation. A spinodal demixing technique was employed for the preparation of linear poly(ethylene oxide) (PEO) confined to nanoscopic strands that

Rainer Kimmich; Nail Fatkullin; Carlos Mattea; Elmar Fischer

2005-01-01

199

Confinement and Quark Structure of Light Hadrons.  

National Technical Information Service (NTIS)

We present a quark confinement model (QCM) for the description of the low-energy physics of light hadrons (mesons and baryons). The model is based on two hypotheses. First, the quark confinement is realized as averaging over vacuum gluon fields which are ...

G. V. Efimov M. A. Ivanov

1988-01-01

200

Inertial electrostatic confinement (IEC) neutron sources  

Microsoft Academic Search

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

R. A. Nebel; D. C. Barnes; E. J. Caramana; R. D. Janssen; W. D. Nystrom; T. N. Tiouririne; B. C. Trent; G. H. Miley; J. Javedani

1995-01-01

201

Evaluation of the confinement option for LMRs  

Microsoft Academic Search

The coolant in liquid metal cooled reactors operates at low pressures and therefore contains relatively little stored energy compared to LWR systems. This presents the possibility of using a more conventional building for containment coupled with a confinement system which vents the internal volume of the building through a filter\\/scrubber. The confinement system would be designed to keep the internal

D. A. Himes; D. D. Stepnewski; G. R. Franz

1985-01-01

202

Microstructural changes in confined submicrometer aluminum films  

Microsoft Academic Search

The stress effect on microstructure evolution in submicrometer Al dots in confinement has been studied by transmission electron microscopy. Direct observation of grain growth and void formation in the dots, unconfined as well as confined by sputtered quartz, was investigated. In the as-deposited state, most of the grains were larger than the film thickness of 300 A, indicating that the

M. L. Chou; S. A. Rishton; K. N. Tu; Haydn Chen

1993-01-01

203

Microstructural changes in confined submicrometer aluminum films  

Microsoft Academic Search

The stress effect on microstructure evolution in submicrometer Al dots in confinement has been studied by transmission electron microscopy. Direct observation of grain growth and void formation in the dots, unconfined as well as confined by sputtered quartz, was investigated. In the as-deposited state, most of the grains were larger than the film thickness of 300 A?, indicating that the

M. L. Chou; S. A. Rishton; K. N. Tu; Haydn Chen

1993-01-01

204

Plasma confinement. [Physics for magnetic geometries  

SciTech Connect

The physics of plasma confinement by a magnetic field is developed from the basic properties of plasmas through the theory of equilibrium, stability, and transport in toroidal and open-ended configurations. The close relationship between the theory of plasma confinement and Hamiltonian mechanics is emphasized, and the modern view of macroscopic instabilities as three-dimensional equilibria is given.

Boozer, A.H.

1985-03-01

205

Millisecond burning of confined energetic materials during cookoff  

SciTech Connect

The response of a system containing an energetic material (EM) to an abnormal thermal environment is termed cookoff. To predict the violence of reaction of confined energetic materials during cookoff requires a description of the relevant physical processes that occur on time scales Ranging from days to submicroseconds. The time-to-ignition can be characterized accurately using heat transfer with chemistry and quasistatic mechanics. After ignition the energetic material deflagrates on a millisecond time scale. During this time the mechanical processes become dynamic. If the confinement survives burning then accelerated deflagration can lead to shock formation and deflagration to detonation transition. The focus of this work is the dynamic combustion regime in the millisecond time domain. Due to the mathematical stiffness of the chemistry equations and the prohibitively fine spatial resolution requirements needed to resolve the structure of the flame, an interface tracking approach is used to propagate the burn front. Demonstrative calculations are presented that illustrate the dynamic interaction of the deflagrating energetic material with its confinement.

Schmitt, R.G.; Baer, T.A.

1997-11-01

206

Confined dynamics of a single DNA molecule.  

PubMed

The effect of a slit-like confinement on the relaxation dynamics of DNA is studied via a mesoscale model in which a bead and spring model for the polymer is coupled to a particle-based Navier-Stokes solver (multi-particle collision dynamics). The confinement is found to affect the equilibrium stretch of the chain when the bulk gyration radius is comparable to or smaller than the channel height and our data are in agreement with the (R(g,bulk)/h)(1/4) scaling of the polymer extension in the wall tangential direction. Relaxation simulation at different confinements indicates that, while the overall behaviour of the relaxation dynamics is similar for low and strong confinements, a small, but significant, slowing of the far-equilibrium relaxation is found as the confinement increases. PMID:21536580

Chinappi, M; De Angelis, E

2011-06-13

207

Dynamics of confined colloid-polymer mixtures  

NASA Astrophysics Data System (ADS)

We investigate the effect of confinement on particle dynamics in mixtures of colloidal particles and non-adsorbing depletant polymers that serve as models for attractive suspensions. Holding the volume fraction of particles and the polymer concentration constant, the dynamics of the particles become increasingly slow as the suspensions are confined in thin wedge-shaped cells. Confocal micrographs of the confined samples suggest that clustering and solidification contribute to changes in the dynamics of mixtures in which particles interact via a strong attraction. The dynamics of non-aggregating particles that do not undergo a phase transition also become slower in confinement, suggesting that additional mechanisms must contribute to slow dynamics in confined colloid-polymer mixtures.

Spannuth, Melissa; Conrad, Jacinta C.

2013-02-01

208

Ohmic Confinement Studies in the Pegasus Toroidal Experiment  

NASA Astrophysics Data System (ADS)

A key process in enhancing energy and effective particle confinement and plasma performance in tokamak discharges is particle recycling. Pegasus discharges indicate that a low-recycling regime is obtained through the use of titanium gettering and cryogenic pumping. The energy confinement and effective particle confinement times, ?e and ?p^*, respectively, are determined using: magnetic diagnostics to perform equilibrium reconstructions, a 32-channel AXUV bolometer diode array to measure PRAD, and a heterodyne Michelson microwave interferometer to measure ne. A fast wide-angle view D-? camera observes and measures recycling. Motivated by earlier results that indicate a decrease in ?p^* with decreased wall pumping, systematic studies of confinement and wall conditioning are in progress. Measurements of the instantaneous density decay rate after the termination of the external gas supply during an established Ohmic discharge with low-MHD activity indicate 2

Thome, K. E.; Barr, J. L.; Bongard, M. W.; Burke, M. G.; Dowd, A. S.; Fonck, R. J.; Redd, A. J.; Schlossberg, D. J.

2011-11-01

209

Geometry of nuclear fusion diagnostic data on information manifolds with an application to fusion plasma confinement  

NASA Astrophysics Data System (ADS)

Pattern recognition is becoming an increasingly important tool for making inferences from the massive amounts of data produced in fusion experiments. The purpose is to contribute to physics studies and plasma control. In this work, we address the visualization of plasma confinement data and their dynamics, the identification of confinement regimes and the establishment of a scaling law for the energy confinement time. We take an intrinsically probabilistic approach, modeling data from the International Global H-mode Confinement Database with Gaussian distributions. We show that pattern recognition operations working in the associated probability space are considerably more powerful than their counterparts in a Euclidean data space. This opens up new possibilities for analyzing confinement data and for fusion data processing in general.

Verdoolaege, Geert; Karagounis, Giorgos; Van Oost, Guido

2013-08-01

210

L-mode global energy confinement scaling for ion cyclotron heated tokamak plasmas  

Microsoft Academic Search

The paper presents a study of the parametric scaling of L-mode global energy confinement times in tokamaks with plasma heating by ion cyclotron resonance frequency (ICRF) waves. A total of 292 observations from PLT, JET, ASDEX, TEXTOR, JET-2M and JIPP T-IIU, have been analysed by the multiple linear regression method. The proposed scaling of the global energy confinement time is

Renchu Chin; Shihhai Li

1992-01-01

211

Wall-confined high beta spheromak  

SciTech Connect

The spheromak could be extended into the high beta regime by supporting the pressure on flux-conserving walls, allowing the plasma to be in a Taylor state with zero pressure gradient and thus stable to ideal and resistive MHD. The concept yields a potentially attractive, pulsed reactor which would require no external magnets. The flux conserver would be shaped to be stable to the tilt and shift instabilities. We envision a plasma which is ohmically ignited at low beta, with the kinetic pressure growing to beta > 1 by fueling from the edge. The flux conserver would be designed such that the magnetic decay time = the fusion burn time. The thermal capacity of the flux conserver and blanket would exceed the fusion yield per discharge, so that they can be cooled steadily. Ignition is estimated to require minimum technology: 30-100 MJ of pulsed power applied at a 0.5 GW rate generates an estimated bum yield > 1 GJ. The concept thus provides an alternate route to a fusion plasma that is MHD stable at high beta, yielding a reactor that is simple and cheap. The major confinement issue is transport due to grad(T), e.g. driven by high beta modes related to the ITG instability.

Fowler, T.K.; Hopper, E.B.; Moir, R.W.; Pearlstein, L.D.

1998-03-16

212

Enhanced D? confinement mode: a theoretical model  

NASA Astrophysics Data System (ADS)

It has been shown in a previous paper that the neoclassical theory of plasma rotation explains well the large toroidal velocity that is measured in the core of edge localized mode (ELM)-free ALCATOR C-Mod H-mode discharges. It has also been noted that the gradient of the toroidal/parallel velocity estimated at the pedestal inflexion point approaches the value required for the onset of the parallel velocity shear Kelvin-Helmholtz (PVS K-H) instability when the discharge is about to undergo an ELM-free to enhanced Dagr (EDA) transition. The wavenumbers and frequencies of weakly unstable PVS K-H oscillations are consistent with those of the quasi-coherent mode that is observed in the EDA, but not in the ELM-free, regime—hence the suggestion, which is explored here further, that the transition is the consequence of PVS K-H instability onset. It is at first noted that the neoclassical expression for the toroidal velocity gradient warrants that large values of the safety factor, q, and of the triangularity parameter, dgr, favour the transition, as observed. It is also shown that outward convection of toroidal momentum reduces the toroidal velocity gradient and, therefore, the instability growth rate. The anomalous particle flow and the particle confinement time in EDA discharges are then estimated on the assumption that anomalous transport maintains the velocity gradient at the threshold value. The power balance consideration shows that heat transport across the H-mode pedestal is neoclassical, at most. A simple expression of the ratio of particle and energy fluxes is then obtained; the ratio tgrP/tgrE of the respective confinement times is in the range of reported values (although it must be noted that it is difficult to quantify tgrP as it varies rapidly across the edge layer). The scenario assumes that the H-mode pedestal of EDA discharges (the unstable layer where anomalous transport occurs) is impermeable for neutrals since charged particles issuing from ionization would otherwise accumulate in the core; experimental parameters justify this assumption. The possibility of matching simultaneously the requirements for PVS K-H instability onset and non-permeability to neutrals in large devices is discussed.

Rogister, André L.

2004-08-01

213

Impact of confinement scaling laws on fusion power plant reactors  

Microsoft Academic Search

The best available theories of radial transport in tokamaks are based on various modifications of classical diffusion, and predict a confinement time scaling which varies, in part, as B²a²\\/n\\/sub e\\/. These dependencies are not observed. The experimental data from tokamaks are consistent with no magnetic field dependence and a direct proportionality to the electron number density. In the absence of

Roth

1986-01-01

214

Honey bee, Apis mellifera L., confinement behavior toward beetle invaders  

Microsoft Academic Search

We performed two experiments to study the hiding behavior of various beetles introduced into colonies of European honey bees,\\u000a Apis mellifera L. In the first experiment, we studied the spatial distribution within confinement sites of six beetle species at eight time\\u000a intervals following their introduction into honey bee observation hives. For each beetle species, we also determined whether\\u000a the beetle’s

E. B. Atkinson; J. D. Ellis

215

Global energy confinement scaling for neutral-beam-heated tokamaks  

Microsoft Academic Search

A total of 677 representative discharges from seven neutral-beam-heated tokamaks have been used to study the parametric scaling of global energy confinement time. Contributions to this data base were from Asdex, DITE, D-III, ISX-B, PDX, PLT and TFR, and were taken from results of gettered, L-mode type discharges. Assuming a power law dependence of ?E on the discharge parameters ?,

S. M. Kaye; R. J. Goldston

1985-01-01

216

Global energy confinement scaling for neutral-beam-heated tokamaks  

Microsoft Academic Search

A total of 677 representative discharges from seven neutral-beam-heated tokamaks has been used to study the parametric scaling of global energy confinement time. Contributions to this data base were from ASDEX, DITE, D-III, ISX-B, PDX, PLT, and TFR, and were taken from results of gettered, L-mode type discharges. Assuming a power law dependence of tau\\/sub E\\/ on discharge parameters kappa,

S. M. Kaye; R. J. Goldston

1984-01-01

217

NMR investigation of gaseous SF6 confinement into EPDM rubber.  

PubMed

The confinement process of gaseous sulphurhexafluoride (SF6) in ethylene-propylene-diene (EPDM) rubber was investigated by spectroscopic and spatially resolved NMR techniques. A strong elongation of T1 relaxation time of SF6 and a decrease of the diffusion coefficient were found. A possible explanation may be the strong restriction of molecular mobility due to interactions between SF6 and active centers of the EPDM. PMID:15833636

Neutzler, Sven; Terekhov, Maxim; Hoepfel, Dieter; Oellrich, Lothar Rainer

2005-02-01

218

NMR investigation of gaseous SF 6 confinement into EPDM rubber  

Microsoft Academic Search

The confinement process of gaseous sulphurhexafluoride (SF6) in ethylene-propylene-diene (EPDM) rubber was investigated by spectroscopic and spatially resolved NMR techniques. A strong elongation of T1 relaxation time of SF6 and a decrease of the diffusion coefficient were found. A possible explanation may be the strong restriction of molecular mobility due to interactions between SF6 and active centers of the EPDM.

Sven Neutzler; Maxim Terekhov; Dieter Hoepfel; Lothar Rainer Oellrich

2005-01-01

219

Preliminary studies of inertial-electrostatic confinement fusion experiments  

SciTech Connect

Preliminary inertial-electrostatic confinement fusion experiments have been carried out using hydrogen gas, and measurements of the light from a plasma core were made. The life time of charged particles in gridded IECF configuration is found to be longer than in the conventional spherical electrode discharges. The light intensity is found to be proportional to about 2/3 power of the input power. 9 refs., 6 figs.

Yamamoto, Yasushi; Ohnishi, Masami; Yoshikawa, Kiyoshi; Toku, Hisayuki; Hasegawa, Mitsunori; Matsuo, Takashi [Kyoto Univ. (Japan)

1996-12-31

220

Parallel processing numerical method for confined vortex dynamics and applications  

NASA Astrophysics Data System (ADS)

This paper explores a combined analytical and numerical technique to investigate the hydrodynamic instability of confined swirling flows, with application to vortex rope dynamics in a Francis turbine diffuser, in condition of sophisticated boundary constraints. We present a new approach based on the method of orthogonal decomposition in the Hilbert space, implemented with a spectral descriptor scheme in discrete space. A parallel implementation of the numerical scheme is conducted reducing the computational time compared to other techniques.

Bistrian, Diana Alina

2013-10-01

221

Numerical Investigations On The Seismic Behaviour Of Confined Masonry Walls  

NASA Astrophysics Data System (ADS)

In the last century, severe earthquakes highlighted the seismic vulnerability of unreinforced masonry buildings. Many technological innovations have been introduced in time in order to improve resistance, ductility, and dissipation properties of this type of constructions. The most widely diffused are reinforced masonry and confined masonry. Damage observation of recent earthquakes demonstrated the effectiveness of the response of confined masonry structures to seismic actions. In general, in this type of structures, reinforced concrete beams and columns are not main structural elements, however, they have the following functions: to confine masonry in order to increase its ductility; to bear tensile stresses derived from bending; to contrast the out-of-plane overturning of masonry panels. It is well evident that these functions are as much effectively performed as the connection between masonry and reinforced concrete elements is good (for example by mean of local interlocking or reinforcements). Confined masonry structures have been extensively studied in the last decades both from a theoretical point of view and by experimental tests Aims of this paper is to give a contribution to the understanding of the seismic behaviour of confined masonry walls by means of numerical parametrical analyses. There latter are performed by mean of the finite element method; a nonlinear anisotropic constitutive law recently developed for masonry is adopted. Comparison with available experimental results are carried out in order to validate the results. A comparison between the resistance obtained from the numerical analyses and the prevision provided by simplified resistance criteria proposed in literature and in codes is finally provided.

Calderini, Chiara; Cattari, Serena; Lagomarsino, Sergio

2008-07-01

222

Numerical Investigations On The Seismic Behaviour Of Confined Masonry Walls  

SciTech Connect

In the last century, severe earthquakes highlighted the seismic vulnerability of unreinforced masonry buildings. Many technological innovations have been introduced in time in order to improve resistance, ductility, and dissipation properties of this type of constructions. The most widely diffused are reinforced masonry and confined masonry. Damage observation of recent earthquakes demonstrated the effectiveness of the response of confined masonry structures to seismic actions. In general, in this type of structures, reinforced concrete beams and columns are not main structural elements, however, they have the following functions: to confine masonry in order to increase its ductility; to bear tensile stresses derived from bending; to contrast the out-of-plane overturning of masonry panels. It is well evident that these functions are as much effectively performed as the connection between masonry and reinforced concrete elements is good (for example by mean of local interlocking or reinforcements). Confined masonry structures have been extensively studied in the last decades both from a theoretical point of view and by experimental tests Aims of this paper is to give a contribution to the understanding of the seismic behaviour of confined masonry walls by means of numerical parametrical analyses. There latter are performed by mean of the finite element method; a nonlinear anisotropic constitutive law recently developed for masonry is adopted. Comparison with available experimental results are carried out in order to validate the results. A comparison between the resistance obtained from the numerical analyses and the prevision provided by simplified resistance criteria proposed in literature and in codes is finally provided.

Calderini, Chiara; Cattari, Serena; Lagomarsino, Sergio [University of Genoa, Department of Civil, Environmental and Architectural Engineering (Italy)

2008-07-08

223

Confined helium: Excited singlet and triplet states  

NASA Astrophysics Data System (ADS)

Energies for the first four singlet and triplet S states of a helium atom confined at the center of an impenetrable sphere are reported. All calculations used explicitly correlated Hylleraas basis sets. The first triplet state is shown to lie below the first excited singlet state only when the confinement radius is greater than 0.988a0. A simple configuration interaction calculation was performed in parallel with Hylleraas calculation. The one-electron atomic orbitals of the configuration treatment provide insight into the physical concepts behind the numerical results of the Hylleraas treatment. This was particularly helpful in understanding the level crossing and avoided crossings observed with changing confinement radius.

Montgomery, H. E.; Pupyshev, Vladimir I.

2013-11-01

224

Confined packings of frictionless spheres and polyhedra  

NASA Astrophysics Data System (ADS)

By means of numerical simulations, we study the influence of confinement on three-dimensional random close packed (RCP) granular materials subject to gravity. The effects of grain shape (spherical or polyhedral) and polydispersity on this dependence are investigated. In agreement with a simple geometrical model, the solid fraction is found to decrease linearly for increasing confinement no matter the grain shape. This decrease remains valid for bidisperse sphere packings although the gradient seems to reduce significantly when the proportion of small particles reaches 40% by volume. The aforementioned model is extended to capture the effect of the confinement on the coordination number.

Camenen, Jean-François; Descantes, Yannick; Richard, Patrick

2013-06-01

225

Review of Inertial Confinement Fusion  

NASA Astrophysics Data System (ADS)

The physics of inertial confinement fusion is reviewed. The trend to short-wavelength lasers is argued, and the distinction between direct and indirect (soft X-ray) drive is made. Key present issues include the non-linear growth of Rayleigh-Taylor (R-T) instabilities, the seeding of this instability by the initial laser imprint, the relevance of self-generated magnetic fields, and the importance of parametric instabilities (stimulated Brillouin and Raman scattering) in gas-filled hohlraums. Experiments are reviewed which explore the R-T instability in both planar and converging geometry. The employment of various optical smoothing techniques is contrasted with the overcoating of the capsule by gold coated plastic foams to reduce considerably the imprint problem. The role of spontaneously generated magnetic fields in non-symmetric plasmas is discussed. Recent hohlraum compression results are presented together with gas bag targets which replicate the long-scale-length low density plasmas expected in NIF gas filled hohlraums. The onset of first Brillouin and then Raman scattering is observed. The fast ignitor scheme is a proposal to use an intense short pulse laser to drill a hole through the coronal plasma and then, with laser excited fast electrons, create a propagating thermonuclear spark in a dense, relatively cold laser-compressed target. Some preliminary results of laser hole drilling and 2-D and 3-D PIC simulations of this and the > 10^8 Gauss self-generated magnetic fields are presented. The proposed National Ignition Facility (NIF) is described.

Haines, M. G.

226

Confinement and stability of VH-mode discharges in the DIII-D tokamak  

SciTech Connect

A regime of very high confinement (VH-mode) has been observed in neutral beam-heated deuterium discharges in the DIII-D tokamak with thermal energy confinement times up to {approx}3.6 times that predicted by the ITER-89P L-mode scaling and 2 times that predicted by ELM-free H-mode thermal confinement scalings. This high confinement has led to increased plasma performance, n{sub D} (0)T{sub i}(0){tau}{sub E} = 2 {times} 10{sup 20} m{sup {minus}3} keV sec with I{sub p} = 1.6 MA, B{sub T} = 2.1 T, Z{sub eff} {le} 2. Detailed transport analysis shows a correspondence between the large decrease in thermal diffusivity in the region 0.75 {le} {rho} {le} 0.9 and the development of a strong shear in the radial electric field in the same region. This suggests that stabilization of turbulence by sheared E {times} B flow is responsible for the improved confinement in VH-mode. A substantial fraction of the edge plasma entering the second regime of stability may also contribute to the increase in confinement. The duration of the VH-mode phase has been lengthened by feedback controlling the input power to limit plasma beta.

Taylor, T.S.; Osborne, T.H.; Burrell, K.H.; Carlstrom, T.N.; Chan, V.S.; Chu, M.S.; DeBoo, J.C.; Doyle, E.J.; Greenfield, C.M.; Groebner, R.J.; Hsieh, C.L.; Jackson, G.L.; James, R.; Lao, L.L.; Lazarus, E.A.; Lippman, S.I.; Petrie, T.W.; Rettig, C.L.; St. John, H.; Schissel, D.P.; Stambaugh, R.D.; Strait, E.J.; Turnbull, A.D.; West, W.P.; Winter, J.; Wroblewski, D.

1992-10-01

227

Confinement and stability of VH-mode discharges in the DIII-D tokamak  

SciTech Connect

A regime of very high confinement (VH-mode) has been observed in neutral beam-heated deuterium discharges in the DIII-D tokamak with thermal energy confinement times up to [approx]3.6 times that predicted by the ITER-89P L-mode scaling and 2 times that predicted by ELM-free H-mode thermal confinement scalings. This high confinement has led to increased plasma performance, n[sub D] (0)T[sub i](0)[tau][sub E] = 2 [times] 10[sup 20] m[sup [minus]3] keV sec with I[sub p] = 1.6 MA, B[sub T] = 2.1 T, Z[sub eff] [le] 2. Detailed transport analysis shows a correspondence between the large decrease in thermal diffusivity in the region 0.75 [le] [rho] [le] 0.9 and the development of a strong shear in the radial electric field in the same region. This suggests that stabilization of turbulence by sheared E [times] B flow is responsible for the improved confinement in VH-mode. A substantial fraction of the edge plasma entering the second regime of stability may also contribute to the increase in confinement. The duration of the VH-mode phase has been lengthened by feedback controlling the input power to limit plasma beta.

Taylor, T.S.; Osborne, T.H.; Burrell, K.H.; Carlstrom, T.N.; Chan, V.S.; Chu, M.S.; DeBoo, J.C.; Doyle, E.J.; Greenfield, C.M.; Groebner, R.J.; Hsieh, C.L.; Jackson, G.L.; James, R.; Lao, L.L.; Lazarus, E.A.; Lippman, S.I.; Petrie, T.W.; Rettig, C.L.; St. John, H.; Schissel, D.P.; Stambaugh, R.D.; Strait, E.J.; Turnbull, A.D.; West, W.P.; Winter, J.; Wroblewski, D.

1992-10-01

228

Dynamic Testing of Laterally Confined Concrete.  

National Technical Information Service (NTIS)

For investigating the effects of deformation rate in confined deformation of concrete, a hydraulic pressure cell has been designed and installed on the 3-inch diameter Split-Hopkinson Pressure Bar (SHPB) system at the University of Florida. Plain concrete...

D. A. Jenkins L. E. Malvern

1990-01-01

229

Evaluation of the Confinement Option for LMRs.  

National Technical Information Service (NTIS)

The coolant in liquid metal cooled reactors operates at low pressures and therefore contains relatively little stored energy compared to LWR systems. This presents the possibility of using a more conventional building for containment coupled with a confin...

D. A. Himes D. D. Stepnewski G. R. Franz

1985-01-01

230

Vorticity confinement technique for drag prediction  

NASA Astrophysics Data System (ADS)

This work couples wake-integral drag prediction and vorticity confinement technique (VC) for the improved prediction of drag from CFD simulations. Induced drag computations of a thin wing are shown to be more accurate than the more widespread method of surface pressure integration when compared to theoretical lifting-line value. Furthermore, the VC method improves trailing vortex preservation and counteracts the shift from induced drag to numerical entropy drag with increasing distance of Trefftz plane downstream of the wing. Accurate induced drag prediction via the surface integration of pressure barring a sufficiently refined surface grid and increased computation time. Furthermore, the alternative wake-integral technique for drag prediction suffers from numerical dissipation. VC is shown to control the numerical dissipation with very modest computational overhead. The 2-D research code is used to test specific formulations of the VC body force terms and illustrate the computational efficiency of the method compared to a ``brute force'' reduction in spatial step size. For the 3-D wing simulation, ANSYS FLUENT is employed with the VC body force terms added to the solver with user-defined functions (UDFs). VC is successfully implemented to highly unsteady flows typical for Micro Air Vehicles (MAV) producing oscillative drag force either by natural vortex shedding at high angles of attack or by flapping wing motion.

Povitsky, Alex; Snyder, Troy

2011-11-01

231

Vibrational dynamics of confined granular materials  

NASA Astrophysics Data System (ADS)

By means of two-dimensional contact dynamics simulations, we analyze the vibrational dynamics of a confined granular layer in response to harmonic forcing. We use irregular polygonal grains allowing for strong variability of solid fraction. The system involves a jammed state separating passive (loading) and active (unloading) states. We show that an approximate expression of the packing resistance force as a function of the displacement of the free retaining wall from the jamming position provides a good description of the dynamics. We study in detail the scaling of displacements and velocities with loading parameters. In particular, we find that, for a wide range of frequencies, the data collapse by scaling the displacements with the inverse square of frequency, the inverse of the force amplitude, and the square of gravity. Interestingly, compaction occurs during the extension of the packing, followed by decompaction in the contraction phase. We show that the mean compaction rate increases linearly with frequency up to a characteristic frequency and then it declines in inverse proportion to frequency. The characteristic frequency is interpreted in terms of the time required for the relaxation of the packing through collective grain rearrangements between two equilibrium states.

Azéma, Emilien; Radjaï, Farhang; Peyroux, Robert; Dubois, Frédéric; Saussine, Gilles

2006-09-01

232

Terahertz Wave Confinement in Pillar Photonic Crystal with a Tapered Waveguide and a Point Defect  

NASA Astrophysics Data System (ADS)

We demonstrate a photonic crystal cavity with a tapered waveguide and a point defect to highly confine terahertz waves. The terahertz wave is first guided into the tapered waveguide, gradually compressed to its end, and finally confined in the point defect cavity. Numerical simulations with the finite-difference time-domain method indicate that the narrow band terahertz wave is highly confined in the point defect cavity with a quality factor of 5323. The demonstrated device may be used as an antenna for enhancing light-matter interactions in the point defect cavity at terahertz frequencies and may improve the sensitivity of terahertz near-field microscopy.

Wang, Chang-Hui; Kuang, Deng-Feng; Chang, Sheng-Jiang; Lin, Lie

2012-12-01

233

Field reversed configuration confinement enhancement through edge biasing and neutral beam injection.  

PubMed

Field reversed configurations (FRCs) with high confinement are obtained in the C-2 device by combining plasma gun edge biasing and neutral beam injection. The plasma gun creates an inward radial electric field that counters the usual FRC spin-up. The n = 2 rotational instability is stabilized without applying quadrupole magnetic fields. The FRCs are nearly axisymmetric, which enables fast ion confinement. The plasma gun also produces E × B shear in the FRC edge layer, which may explain the observed improved particle transport. The FRC confinement times are improved by factors 2 to 4, and the plasma lifetimes are extended from 1 to up to 4 ms. PMID:23004613

Tuszewski, M; Smirnov, A; Thompson, M C; Korepanov, S; Akhmetov, T; Ivanov, A; Voskoboynikov, R; Schmitz, L; Barnes, D; Binderbauer, M W; Brown, R; Bui, D Q; Clary, R; Conroy, K D; Deng, B H; Dettrick, S A; Douglass, J D; Garate, E; Glass, F J; Gota, H; Guo, H Y; Gupta, D; Gupta, S; Kinley, J S; Knapp, K; Longman, A; Hollins, M; Li, X L; Luo, Y; Mendoza, R; Mok, Y; Necas, A; Primavera, S; Ruskov, E; Schroeder, J H; Sevier, L; Sibley, A; Song, Y; Sun, X; Trask, E; Van Drie, A D; Walters, J K; Wyman, M D

2012-06-21

234

Confinement and Light-Front QCD  

Microsoft Academic Search

Numerical results for the (rest-frame) $Q\\\\bar{Q}$ potential in light-front quantized $QCD_{2+1}$ on a $\\\\perp$ lattice are presented. Both in the longitudinal as well as the $\\\\perp$ spatial directions one obtains linear confinement. The confinement mechanism in light-front QCD depends on the orientation of the external charges: for longitudinally (with respect to the boost direction in the infinite momentum frame) separated

Matthias Burkardt

1996-01-01

235

Nonlinear Spectral Singularities for Confined Nonlinearities  

NASA Astrophysics Data System (ADS)

We introduce a notion of spectral singularity that applies for a general class of nonlinear Schrödinger operators involving a confined nonlinearity. The presence of the nonlinearity does not break the parity-reflection symmetry of spectral singularities but makes them amplitude dependent. Nonlinear spectral singularities are, therefore, associated with a resonance effect that produces amplified waves with a specific amplitude-wavelength profile. We explore the consequences of this phenomenon for a complex ?-function potential that is subject to a general confined nonlinearity.

Mostafazadeh, Ali

2013-06-01

236

Inertial confinement fusion reactor for space applications  

Microsoft Academic Search

One of the most exciting and promising approaches to fusion power that has emerged recently is the magnetically insulated inertial confinement fusion (MICF) concept proposed by Hasegawa et al. It is a scheme that combines the benefits of magnetic and inertial fusions in which a plasma with a density of approx.10²¹ cm⁻³ is confined by the inertia of a heavy

T. Kammash; D. L. Galbraith

1986-01-01

237

Microstructural changes in confined submicrometer aluminum films  

SciTech Connect

The stress effect on microstructure evolution in submicrometer Al dots in confinement has been studied by transmission electron microscopy. Direct observation of grain growth and void formation in the dots, unconfined as well as confined by sputtered quartz, was investigated. In the as-deposited state, most of the grains were larger than the film thickness of 300 A, indicating that the grains have grown during the Al deposition and/or the quartz deposition. Voids were only found in the confined samples. Grain growth was retarded in the confined samples upon a stepwise annealing from room temperature to 400 [degree]C, yet secondary grain growth occurred at temperatures above 500 [degree]C. For the unconfined samples, abnormal grain growth occurred at 200 [degree]C. The retardation of grain growth in the confined sample was attributed to the lack of stress gradient and vacancy sources and the hinderance of dislocation motion. The mechanism of secondary grain growth in the confined samples was observed to be the coalesence of adjacent grains.

Chou, M.L. (Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 (United States)); Rishton, S.A.; Tu, K.N. (IBM Research Division, T. J. Watson Research Center, Yorktown Heights, New York 10598 (United States)); Chen, H. (Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 (United States))

1993-03-01

238

Load-Induced Confinement Activates Diamond Lubrication by Water  

NASA Astrophysics Data System (ADS)

Tribochemical reactions are chemical processes, usually involving lubricant or environment molecules, activated at the interface between two solids in relative motion. They are difficult to be monitored in situ, which leaves a gap in the atomistic understanding required for their control. Here we report the real-time atomistic description of the tribochemical reactions occurring at the interface between two diamond films in relative motion, by means of large scale ab initio molecular dynamics. We show that the load-induced confinement is able to catalyze diamond passivation by water dissociative adsorption. Such passivation decreases the energy of the contacting surfaces and increases their electronic repulsion. At sufficiently high coverages, the latter prevents surface sealing, thus lowering friction. Our findings elucidate effects of the nanoscale confinement on reaction kinetics and surface thermodynamics, which are important for the design of new lubricants.

Zilibotti, G.; Corni, S.; Righi, M. C.

2013-10-01

239

Classical scattering of charged particles confined on an inhomogeneous helix  

NASA Astrophysics Data System (ADS)

We explore the effects arising due to the coupling of the center of mass and relative motion of two charged particles confined on an inhomogeneous helix with a locally modified radius. It is first proven that a separation of the center of mass and the relative motion is provided if and only if the confining manifold represents a homogeneous helix. In this case, bound states of repulsively Coulomb interacting particles occur. For an inhomogeneous helix, the coupling of the center of mass and relative motion induces an energy transfer between the collective and relative motion, leading to dissociation of initially bound states in a scattering process. Due to the time reversal symmetry, a binding of the particles out of the scattering continuum is thus equally possible. We identify the regimes of dissociation for different initial conditions and provide an analysis of the underlying phase space via Poincaré surfaces of section. Bound states inside the inhomogeneity as well as resonant states are identified.

Zampetaki, A. V.; Stockhofe, J.; Krönke, S.; Schmelcher, P.

2013-10-01

240

Structure and dynamics of water confined within reverse micelles  

NASA Astrophysics Data System (ADS)

The structure and dynamics of water confined within reverse micelles (RMs) of varying water content ([water]/[surfactant]) formed by the surfactant Aerosol-OT in iso-octane are studied using molecular dynamics simulations. The intrinsic density profile of water in the RM is constructed with respect to the surface formed by the surfactant sulfur atoms and reveals a high density shell at the surfactant interface, a core region which becomes more bulk-like as RM size increases and an intermediate region between the interface and core. Water diffusion in the presence of partially absorbing boundaries (compatible with the intrinsic profile) provides a simple picture for describing confined diffusion within the RM. Water reorientation is strongly perturbed with respect to bulk water due to the presence of surfactant head groups and counterions. Our results for water dynamics in RMs are compared with the results of time-resolved IR and quasielastic neutron scattering experiments.

Chowdhary, Janamejaya; Ladanyi, Branka

2010-03-01

241

Confinement and power balance in the S-1 spheromak  

SciTech Connect

The confinement and scaling features of the S-1 spheromak have been investigated using magnetic, spectroscopic, and Thomson scattering data in conjunction with numerical modeling. Results from the multipoint Thomson scattering diagnostic shows that the central beta remains constant (/beta//sub to/ /approximately/ 5%) as the plasma current density increases from 0.68--2.1 MA/m/sup 2/. The density is observed to increase slowly over this range, while the central electron temperature increases much more rapidly. Analysis of the global plasma parameters shows a decrease in the volume average beta and energy confinement as the total current is increased. The power balance has been modeled numerically with a 0-D non-equilibrium time-dependent coronal model and is consistent with the experimental observations. 20 refs., 12 figs., 2 tabs.

Levinton, F.M.; Meyerhofer, D.D.; Mayo, R.M.; Janos, A.C.; Ono, Y.; Ueda, Y.; Yamada, M.

1989-07-01

242

Load-induced confinement activates diamond lubrication by water.  

PubMed

Tribochemical reactions are chemical processes, usually involving lubricant or environment molecules, activated at the interface between two solids in relative motion. They are difficult to be monitored in situ, which leaves a gap in the atomistic understanding required for their control. Here we report the real-time atomistic description of the tribochemical reactions occurring at the interface between two diamond films in relative motion, by means of large scale ab initio molecular dynamics. We show that the load-induced confinement is able to catalyze diamond passivation by water dissociative adsorption. Such passivation decreases the energy of the contacting surfaces and increases their electronic repulsion. At sufficiently high coverages, the latter prevents surface sealing, thus lowering friction. Our findings elucidate effects of the nanoscale confinement on reaction kinetics and surface thermodynamics, which are important for the design of new lubricants. PMID:24138257

Zilibotti, G; Corni, S; Righi, M C

2013-10-02

243

Diffusing Polymers in Confined Microdomains and Estimation of Chromosomal Territory Sizes from Chromosome Capture Data  

NASA Astrophysics Data System (ADS)

Is it possible to extract the size and structure of chromosomal territories (confined domain) from the encounter frequencies of chromosomal loci? To answer this question, we estimate the mean time for two monomers located on the same polymer to encounter, which we call the mean first encounter time in a confined microdomain (MFETC). We approximate the confined domain geometry by a harmonic potential well and obtain an asymptotic expression that agrees with Brownian simulations for the MFETC as a function of the polymer length, the radius of the confined domain, and the activation distance radius ? at which the two searching monomers meet. We illustrate the present approach using chromosome capture data for the encounter rate distribution of two loci depending on their distances along the DNA. We estimate the domain size that restricts the motion of one of these loci for chromosome II in yeast.

Amitai, A.; Holcman, D.

2013-06-01

244

Ignition and burn in inertially confined magnetized fuel  

SciTech Connect

At the third International Conference on Emerging Nuclear Energy Systems, we presented computational results which suggested that breakeven'' experiments in inertial confinement fusion (ICF) may be possible with existing driver technology. We recently used the ICF simulation code LASNEX to calculate the performance of an idealized magnetized fuel target. The parameter space in which magnetized fuel operates is remote from that of both conventional'' ICF and magnetic confinement fusion devices. In particular, the plasma has a very high {beta} and is wall confined, not magnetically confined. The role of the field is to reduce the electron thermal conductivity and to partially trap the DT alphas. The plasma is contained in a pusher which is imploded to compress and adiabatically heat the plasma from an initial condition of preheat and pre-magnetization to the conditions necessary for fusion ignition. The initial density must be quite low by ICF standards in order to insure that the electron thermal conductivity is suppressed and to minimize the generation of radiation from the plasma. Because the energy loss terms are effectively suppressed, the implosion may proceed at a relatively slow rate of about 1 to 3 cm/{mu}s. Also, the need for low density fuel dictates a much larger target, so that magnetized fuel can use drivers with much lower power and power density. Therefore, magnetized fuel allows the use of efficient drivers that are not suitable for laser or particle beam fusion due to insufficient focus or too long pulse length. The ignition and burn of magnetized fuel involves very different dominant physical processes than does conventional'' ICF. The fusion time scale becomes comparable to the hydrodynamic time scale, but other processes that limit the burn in unmagnetized fuel are of no consequence. The idealized low gain magnetized fuel target presented here is large and requires a very low implosion velocity. 11 refs.

Kirkpatrick, R.C.; Lindemuth, I.R.

1991-01-01

245

Momentum Confinement on DIII-D with Low Net Neutral Beam Torque  

Microsoft Academic Search

Momentum confinement was investigated in ELMing H-mode plasmas with elevated qmin. Torque scans were performed at constant betaN, and the rotation profile was measured using charge exchange recombination (CER) spectroscopy. Studies of the mechanical angular momentum in the plasma show a non-uniform response to the applied neutral beam torque, resulting in a torque dependence of the momentum confinement time. Under

W. M. Solomon; R. V. Budny; D. Mikkelsen; R. Nazikian; S. D. Scott; M. C. Zarnstorff; K. H. Burrell; J. S. Degrassie; R. J. Groebner; J. E. Kinsey; C. C. Petty

2007-01-01

246

Light-Cone Kaluza-Klein Geometry: Confined Propagation as a Particle Model  

Microsoft Academic Search

A modified Kaluza-Klein theory is proposed in which propagation takes place\\u000aonly at the speed of light. The propagation can be confined to a small volume,\\u000aforming a particle with rest mass. The usual four space-time coordinates locate\\u000athe confinement volume, and Kaluza's fifth coordinate is replaced by an\\u000ainternal degree of freedom. Electromagnetism corresponds to a gauge field on

Donald E. Jennings

2000-01-01

247

Freezing of mixtures confined in silica nanopores: experiment and molecular simulation.  

PubMed

Freezing of mixtures confined in silica nanopores is investigated by means of experiment and molecular simulation. The experiments consist of differential scanning calorimetry and dielectric relaxation spectroscopy measurements for CCl(4)/C(6)H(5)Br mixtures confined in Vycor having pores with a mean diameter of about D=4.2 nm. Molecular simulations consist of grand canonical Monte Carlo simulations combined with the parallel tempering technique for Lennard-Jones Ar/Kr mixtures confined in a silica cylindrical nanopore with a diameter of D=3.2 nm. The experimental and molecular simulation data provide a consistent picture of freezing of mixtures in cylindrical silica nanopores having a size smaller than ten times the size of the confined molecules. No sharp change in the properties of the confined mixture occurs upon melting, which suggests that the confined system does not crystallize. In the case of the molecular simulations, this result is confirmed by the fact that except for the contact layer, the percentage of crystal-like atoms is less than 6% (whatever the temperature). The molecular simulations also show that the composition of the mixture is shifted, upon confinement, toward the component having the strongest wall/fluid attraction. PMID:20815584

Coasne, Benoit; Czwartos, Joanna; Sliwinska-Bartkowiak, Malgorzata; Gubbins, Keith E

2010-08-28

248

An experiment to test centrifugal confinement for fusion  

Microsoft Academic Search

The basic idea of centrifugal confinement is to use centrifugal forces from supersonic rotation to augment conventional magnetic confinement. Optimizing this “knob” results in a fusion device that features four advantages: steady state, no disruptions, superior cross-field confinement, and a simpler coil configuration. The idea rests on two prongs: first, centrifugal forces can confine plasmas to desired regions of shaped

R. F. Ellis; A. B. Hassam; S. Messer; B. R. Osborn

2001-01-01

249

An experiment to test centrifugal confinement for fusion  

Microsoft Academic Search

The basic idea of centrifugal confinement is to use centrifugal forces from supersonic rotation to augment conventional magnetic confinement. Optimizing this ``knob'' results in a fusion device that features four advantages: steady state, no disruptions, superior cross-field confinement, and a simpler coil configuration. The idea rests on two prongs: first, centrifugal forces can confine plasmas to desired regions of shaped

R. F. Ellis; A. B. Hassam; S. Messer; B. R. Osborn

2001-01-01

250

Ordering and disordering effects in confined liquid crystals  

Microsoft Academic Search

Confined liquid crystals exhibit significantly different physical properties from those of a bulk. The confinement could have either ordering or disordering effects on a liquid crystal (LC) phase depending on the topology of the confining surface and on the surface-LC interaction. This dissertation presents a deuteron nuclear magnetic resonance (DNMR) study of confined nCB liquid crystals, focusing on the surface

Tao Jin

2003-01-01

251

Fragility of an Isochorically Confined Polymer Glass  

NASA Astrophysics Data System (ADS)

When polymers are confined to the nanometer length-scale, the glass transition temperature (Tg) and its associated dynamics can deviate substantially from the bulk. As confined polymers continue to play an important role as enabling materials in technologies ranging from drug delivery to plastic electronics, a greater understanding of size effects on glass transition dynamics is warranted. Here, we present the effect of isochoric confinement on the dynamic fragility of a polymeric glass-former, i.e., polystyrene (PS). Utilizing silica-capped PS nanospheres as a model system, the fictive temperature (Tf) and the isochoric heat capacity (Cv) are measured as a function of diameter via differential scanning calorimetry (DSC). By examining Tf as a function of cooling rate for each sample, the isochoric fragility (mv) is obtained, which decreases significantly as the diameter of the nanospheres is reduced from 462 nm to 129 nm. Hence, the contribution of thermal effects on structural relaxation is reduced with isochoric confinement for PS geometrically restricted by silica. Furthermore, we explore the impact of chemical structure, via PS derivatives, on the observed confinement effect on the dynamic fragility.

Zhang, Chuan; Guo, Yunlong; Priestley, Rodney

2013-03-01

252

Neuroendocrine system and immune responses after confinement.  

PubMed

A confinement experiment in a normobaric diving chamber was undertaken to obtain more understanding of the effects of confinement and isolation on human psychology and physiology. Pre- and post-confinement blood samples were obtained from four test subjects and five control subjects for the analysis of plasma proteins, hormone levels and immune responses. The absence of significant changes in the immune responses correlates with the absence of major changes in neurohormones and other hormones such as cortisol, prolactin, growth hormone, insulin-like growth factor 1, triiodothyronin, thyrotrophin and 1,25-dihydroxyvitamin D. It is increasingly recognized that the immune system is not an independent physiological system, but a system that interacts multidirectionally with other organs and body functions. It seems that the conditions of this confinement experiment were not stressful from a psychological point of view. The presence of a female crew member had probably a positive effect on group behavior of the test subjects. In conclusion, the data suggest that confinement for 60 days in a small habitat without particularly stressful situations has no significant impact on a variety of neuroimmunological parameters. PMID:8814815

Husson, D; Abbal, M; Tafani, M; Schmitt, D A

1996-01-01

253

Quantum confinement in Si and Ge nanostructures  

NASA Astrophysics Data System (ADS)

We apply perturbative effective mass theory as a broadly applicable theoretical model for quantum confinement (QC) in all Si and Ge nanostructures including quantum wells (QWs), wires (Q-wires), and dots (QDs). Within the limits of strong, medium, and weak QC, valence and conduction band edge energy levels (VBM and CBM) were calculated as a function of QD diameters, QW thicknesses, and Q-wire diameters. Crystalline and amorphous quantum systems were considered separately. Calculated band edge levels with strong, medium, and weak QC models were compared with experimental VBM and CBM reported from X-ray photoemission spectroscopy (XPS), X-ray absorption spectroscopy (XAS), or photoluminescence (PL). Experimentally, the dimensions of the nanostructures were determined directly, by transmission electron microscopy (TEM), or indirectly, by x-ray diffraction (XRD) or by XPS. We found that crystalline materials are best described by a medium confinement model, while amorphous materials exhibit strong confinement regardless of the dimensionality of the system. Our results indicate that spatial delocalization of the hole in amorphous versus crystalline nanostructures is the important parameter determining the magnitude of the band gap expansion, or the strength of the quantum confinement. In addition, the effective masses of the electron and hole are discussed as a function of crystallinity and spatial confinement.

Barbagiovanni, E. G.; Lockwood, D. J.; Simpson, P. J.; Goncharova, L. V.

2012-02-01

254

Confinement and viscoelastic effects on chain closure dynamics  

NASA Astrophysics Data System (ADS)

Chemical reactions inside cells are typically subject to the effects both of the cell's confining surfaces and of the viscoelastic behavior of its contents. In this paper, we show how the outcome of one particular reaction of relevance to cellular biochemistry - the diffusion-limited cyclization of long chain polymers - is influenced by such confinement and crowding effects. More specifically, starting from the Rouse model of polymer dynamics, and invoking the Wilemski-Fixman approximation, we determine the scaling relationship between the mean closure time tc of a flexible chain (no excluded volume or hydrodynamic interactions) and the length N of its contour under the following separate conditions: (a) confinement of the chain to a sphere of radius d and (b) modulation of its dynamics by colored Gaussian noise. Among other results, we find that in case (a) when d is much smaller than the size of the chain, tc ~ Nd2, and that in case (b), tc ~ N2/(2 - 2H), H being a number between 1/2 and 1 that characterizes the decay of the noise correlations. H is not known a priori, but values of about 0.7 have been used in the successful characterization of protein conformational dynamics. At this value of H (selected for purposes of illustration), tc ~ N3.4, the high scaling exponent reflecting the slow relaxation of the chain in a viscoelastic medium.

Bhattacharyya, Pinaki; Sharma, Rati; Cherayil, Binny J.

2012-06-01

255

Nonlocal effects in a hybrid plasmonic waveguide for nanoscale confinement.  

PubMed

The effect of nonlocal optical response is studied for a novel silicon hybrid plasmonic waveguide (HPW). Finite element method is used to implement the hydrodynamic model and the propagation mode is analyzed for a hybrid plasmonic waveguide of arbitrary cross section. The waveguide has an inverted metal nano-rib over a silicon-on-insulator (SOI) structure. An extremely small mode area of~10???² is achieved together with several microns long propagation distance at the telecom wavelength of 1.55 ?m. The figure of merit (FoM) is also improved in the same time, compared to the pervious hybrid plasmonic waveguide. We demonstrate the validity of our method by comparing our simulating results with some analytical results for a metal cylindrical waveguide and a metal slab waveguide in a wide wavelength range. For the HPW, we find that the nonlocal effects can give less loss and better confinement. In particular, we explore the influence of the radius of the rib's tip on the loss and the confinement. We show that the nonlocal effects give some new fundamental limitation on the confinement, leaving the mode area finite even for geometries with infinitely sharp tips. PMID:23389124

Huang, Qiangsheng; Bao, Fanglin; He, Sailing

2013-01-28

256

Confinement and water quality-induced stress in largemouth bass  

SciTech Connect

Plasma values of corticosteroids, glucose, chloride, and osmolality were determined in largemouth bass Micropterus salmoides under various environmental conditions. No differences were observed in quiescent fish due to sex, size, time of day, or the types of holding facilities tested (tanks, raceways, ponds). Differences were observed in plasma glucose, chloride, and osmolality values among fish acclimated to 10, 16, and 23 C. Abrupt temperature changes caused elevations in plasma corticosteroid and glucose concentrations and reduced plasma chloride and osmolality. Confinement in a net, for up to 48 hours, caused elevated glucose and corticosteroids and reduced chloride and osmolality values. After 48 hours of confinement, fish required up to 14 days to recover normal plasma characters. Generally, short-term exposure to poor water quality (high concentrations of CO/sub 2/ and NH/sub 3/, and low concentrations of dissolved oxygen) altered plasma corticosteroids and glucose but had little effect on plasma chloride or osmolality. Net confinement plus poor water quality caused additional stress. Plasma glucose and corticosteroid values were good indicators of stress during application of acute stressors whereas chloride and osmolality were useful indicators of long-term stress and patterns of recovery after stressors were removed.

Carmichael, G.J.; Tomasso, J.R.; Simco, B.A.; Davis, K.B.

1984-11-01

257

Physics progress of Reversed Field Pinch magnetic confinement  

NASA Astrophysics Data System (ADS)

Over the last decade, the international RFP community has made large strides understanding key physics challenges for plasma confinement with weak external magnetization. This progress fundamentally changes the fusion outlook for the RFP. In several areas, resolving the RFP's fusion challenges is simultaneously advancing basic plasma physics, with potentially large impact in astrophysics. For example, the magnetic dynamo in the RFP reveals how large-scale instabilities can efficiently transport magnetic energy. An understanding of MHD tearing that supports dynamo action inspired current profile control. This produces a ten-fold improvement in confinement, comparable to a same-size, same-current tokamak. A recent push to higher plasma current reveals remarkable self-organization to a helical equilibrium, or quasi-single-helicity dynamo state, that also exhibits improved confinement. These controlled and spontaneous transitions from high to low levels of magnetic chaos probe transport in a stochastic magnetic field, the natural state of the field in astrophysical settings. High temperature ions >1 keV are observed, heated during magnetic reconnection events. This is reminiscent of non-collisonal heating in the solar atmosphere. Coupled with current profile control, improved confinement with multi-kilovolt temperature electrons and ions is demonstrated. Active control of the magnetic boundary is now routine to stabilize many resistive wall modes in pulse lengths >10 times their growth rate, an essential need for the RFP and likely other high beta configurations. Few options exist for steady-state current sustainment in fusion plasmas. One is Oscillating Field Current Drive, based on magnetic helicity conservation principles that underpin magnetic self-organization. Partial OFCD sustainment experiments so far agree with the self-organization physics basis. This work is supported by the US DOE and NSF.

Sarff, John S.

2009-11-01

258

Energy Confinement of both Ohmic and LHW Plasma on EAST  

NASA Astrophysics Data System (ADS)

Study on the characters of energy confinement in both Ohmic and lower hybrid wave (LHW) discharges on EAST is conducted and the linear Ohmic confinement (LOC), saturated ohmic confinement (SOC) and improved Ohmic confinement (IOC) regimes are investigated in this paper. It is observed that an improved confinement mode characterized by both a drop of D? line intensity and an increase in line average density can be triggered by a gas puffing pulse.

Yang, Yao; Gao, Xiang; EAST Team

2011-06-01

259

INERT Atmosphere confinement operability test procedure  

SciTech Connect

This Operability Test Procedure (OTP) provides instructions for testing operability of the Inert Atmosphere Confinement (IAC). The Inert Atmosphere Confinement was designed and built for opening cans of metal items that might have hydrided surfaces. Unreviewed Safety Question (USQ) PFP-97-005 addresses the discovery of suspected plutonium hydride forming on plutonium metal currently stored in the Plutonium Finishing Plant vaults. Plutonium hydride reacts quickly with air, liberating energy. The Inert Atmosphere Confinement was designed to prevent this sudden liberation of energy by opening the material in an inert argon atmosphere instead of the normal glovebox atmosphere. The IAC is located in glovebox HC-21A, room 230B of the 234-5Z Building at the Plutonium Finishing Plant (PFP) in the 200-West Area of the Hanford Site.

RISENMAY, H.R.

1999-02-22

260

Progress in toroidal confinement and fusion research  

SciTech Connect

During the past 30 years, the characteristic T/sub i/n tau/sub E/-value of toroidal-confinement experiments has advanced by more than seven orders of magnitude. Part of this advance has been due to an increase of gross machine parameters. Most of this advance has been due to an increase of gross machine parameters. Most of the advance is associated with improvements in the ''quality of plasma confinement.'' The combined evidence of spherator and tokamak research clarifies the role of magnetic-field geometry in determining confinement and points to the importance of shielding out plasma edge effects. A true physical understanding of anomalous transport remains to be achieved. 39 refs., 11 figs., 1 tab.

Furth, H.P.

1987-10-01

261

Magnetic field confinement for magnetically levitated vehicles  

SciTech Connect

A magnetically levitated vehicle adapted for movement along a guide way, comprising: a passenger compartment; first and second primary magnet means secured on the vehicle to produce a magnetic field having a magnetic flux density extending outward from the primary magnet means, to support the vehicle above and spaced from the guide way; and a plurality of confining magnets disposed on the vehicle to confine the magnetic flux extending outward from the primary magnet means and to reduce the strength of the primary magnetic field in the passenger compartment; wherein the primary magnet means has a capacity to produce a primary magnetic field having a maximum strength of at least 200 gauss in the passenger compartment, and the confining magnets maintain the strength of the primary magnetic field in the passenger compartment below 5 gauss.

Proise, M.

1993-05-25

262

Quantum interference of magnetic edge channels activated by intersubband optical transitions in magnetically confined quantum wires  

NASA Astrophysics Data System (ADS)

We investigate the photoresistance of a magnetically confined quantum wire in which microwave-coupled edge channels interfere at two pinning sites in the fashion of a Mach-Zehnder interferometer. The conductance is strongly enhanced by microwave power at B = 0 and develops a complex series of oscillations when the magnetic confinement increases. Both results are quantitatively explained by the activation of forward scattering in a multimode magnetically confined quantum wire. By varying the strength of the magnetic confinement we are able to tune the phase of electrons in the arms of the interferometer. Quantum interferences which develop between pinning sites explain the oscillations of the conductance as a function of the magnetic field. A fit of the data gives the distance between pinning sites as 11 µm. This result suggests that quantum coherence is conserved over a distance three times longer than the electron mean free path.

Nogaret, A.; Portal, J.-C.; Beere, H. E.; Ritchie, D. A.; Phillips, C.

2009-01-01

263

Subwavelength metallic waveguides as a tool for extreme confinement of THz surface waves.  

PubMed

Research on surface waves supported by metals at THz frequencies is experiencing a tremendous growth due to their potential for imaging, biological sensing and high-speed electronic circuits. Harnessing their properties is, however, challenging because these waves are typically poorly confined and weakly bound to the metal surface. Many design strategies have been introduced to overcome these limitations and achieve increased modal confinement, including patterned surfaces, coated waveguides and a variety of sub-wavelength geometries. Here we provide evidence, using a combination of numerical simulations and time-resolved experiments, that shrinking the transverse size of a generic metallic structure always leads to solutions with extreme field confinement. The existence of such a general behavior offers a new perspective on energy confinement and should benefit future developments in THz science and technology. PMID:23463351

Gacemi, D; Mangeney, J; Colombelli, R; Degiron, A

2013-01-01

264

Neutral Beam Ion Confinement in NSTX  

SciTech Connect

Neutral-beam (NB) heating in the National Spherical Torus Experiment (NSTX) began in September 2000 using up to 5 MW of 80 keV deuterium (D) beams. An initial assessment of beam ion confinement has been made using neutron detectors, a neutral particle analyzer (NPA), and a Faraday cup beam ion loss probe. Preliminary neutron results indicate that confinement may be roughly classical in quiescent discharges, but the probe measurements do not match a classical loss model. MHD activity, especially reconnection events (REs) causes substantial disturbance of the beam ion population.

D.S. Darrow; E.D. Fredrickson; S.M. Kaye; S.S. Medley; and A.L. Roquemore

2001-07-24

265

Thermal dark matter from a confining sector  

NASA Astrophysics Data System (ADS)

We study a class of dark matter models in which the dark matter is a baryon-like composite particle of a confining gauge group and also a pseudo-Nambu-Goldstone boson associated with the breaking of an enhanced chiral symmetry group. The approximate symmetry decouples the dark matter mass from the confinement scale of the new gauge group, leading to correct thermal relic abundances for dark matter masses far below the unitary bound, avoiding the typical conclusion of thermally produced composite dark matter. We explore the available parameter space in a minimal example model based on an SU(2) gauge group, and discuss prospects for experimental detection.

Buckley, Matthew R.; Neil, Ethan T.

2013-02-01

266

Shearless transport barriers in magnetically confined plasmas  

NASA Astrophysics Data System (ADS)

Shearless transport barriers appear in confined plasmas due to non-monotonic radial profiles and cause localized reduction of transport even after they have been broken. In this paper we summarize our recent theoretical and experimental research on shearless transport barriers in plasmas confined in toroidal devices. In particular, we discuss shearless barriers in Lagrangian magnetic field line transport caused by non-monotonic safety factor profiles. We also discuss evidence of particle transport barriers found in the TCABR Tokamak (University of São Paulo) and the Texas Helimak (University of Texas at Austin) in biased discharges with non-monotonic plasma flows.

Caldas, I. L.; Viana, R. L.; Abud, C. V.; Fonseca, J. C. D.; Guimarães Filho, Z. O.; Kroetz, T.; Marcus, F. A.; Schelin, A. B.; Szezech, J. D., Jr.; Toufen, D. L.; Benkadda, S.; Lopes, S. R.; Morrison, P. J.; Roberto, M.; Gentle, K.; Kuznetsov, Yu; Nascimento, I. C.

2012-12-01

267

New confinement phases from singular SCFT  

NASA Astrophysics Data System (ADS)

New types of confining phase emerge when some singular SCFT's appearing as infrared fixed points of {N}=2 supersymmetric QCD (SQCD) are deformed by an {N}=1 adjoint mass term. We make further checks on the Gaiotto-Seiberg-Tachikawa (GST) description of these vacua against the symmetry and vacuum counting argument, and show that the GST variables correctly describe these systems, brought into confinement phase by the {N}=1 perturbation. Several examples of such vacua, USp(2 N) and SU( N) theories with four flavors and SO( N) theories with one or two flavors, are discussed.

Giacomelli, Simone; Konishi, Kenichi

2013-03-01

268

Confinement effects on diffusiophoretic self-propellers.  

PubMed

We study theoretically the effects of spatial confinement on the phoretic motion of a dissolved particle driven by composition gradients generated by chemical reactions of their solvent, which are active only on certain parts of the particle surface. We show that the presence of confining walls increases in a similar way both the composition gradients and the viscous friction, and the overall result of these competing effects is an increase in the phoretic velocity of the particle. For the case of steric repulsion only between the particle and the product molecules of the chemical reactions, the absolute value of the velocity remains nonetheless rather small. PMID:19466850

Popescu, M N; Dietrich, S; Oshanin, G

2009-05-21

269

Confined bilayers passively regulate shape and stress.  

PubMed

Lipid membranes are commonly confined to adjacent subcellular structures or to artificial substrates and particles. We develop an experimental and theoretical framework to investigate the mechanics of confined membranes, including the influence of adhesion, strain, and osmotic pressure. We find that supported lipid bilayers respond to stress by nucleating and evolving spherical and tubular protrusions. In cells, such transformations are generally attributed to proteins. Our results offer insights into the mechanics of cell membranes and can further extend the applications of supported bilayers. PMID:23383939

Staykova, Margarita; Arroyo, Marino; Rahimi, Mohammad; Stone, Howard A

2013-01-09

270

Electron plasmas: Confinement and mode structure in a small aspect ratio toroidal experiment  

NASA Astrophysics Data System (ADS)

Toroidal electron plasmas have remained less explored due to their poor confinement properties. Their equilibrium, stability, and confinement properties are therefore not entirely understood and continue to remain a topic of intense ongoing research. Large aspect-ratio theory suggests poor confinement in toroidal devices can be overcome by the application of a radial electric field; this has been verified successfully in some of the recent experiments. In the present paper, we report the longest confinement time without these external forces. Increasing the toroidicity has helped us to generate these forces intrinsically. To this end, a trap to confine electron plasmas has been created in a small aspect-ratio (~1.6) torus. Electrons after being injected from a thermionic source are seen to remain confined with a purely toroidal magnetic field. The confinement time is far more than known single particle drift time scales. Importantly, it is in the absence of any external electric field, additional rotational transform, and/or magnetic fields, which, although not required, in principle, may appear essential particularly due to their role in improving confinement in some of the recent large aspect-ratio traps. The successful confinement in the small aspect-ratio limit has also led to several interesting observations: the evolution of the confined plasma is marked by an interesting nonlinear (large amplitude), electrostatic wave activity. Coherent, periodic, double peak oscillations result from a low-frequency E×B motion of a toroidal vortex in a plasma that closely leans against the inner wall. As many as 16 highly phase-coherent harmonics with dominant power in m=2 suggest that the mode is not merely a center-of-charge motion. Rather, a strong coupling of modes leads to a novel nonlinear state. The predominant energy is present in the shaping of the electron cloud (m=2) and not in the displacement of the center of charge (m=1) seen in large aspect-ratio traps. The absence of any power-law tail suggests absence of any turbulence, at least on time scales longer than the wall-probe resolution (40 ns). The frequency, (around 100 kHz at 200 G) shows an unusual shear in time: it reduces as the mode evolves, but later increases as the mode dies.

Pahari, S.; Ramachandran, H. S.; John, P. I.

2006-09-01

271

Mixing in confined stratified aquifers.  

PubMed

Spatial variability in a flow field leads to spreading of a tracer plume. The effect of microdispersion is to smooth concentration gradients that exist in the system. The combined effect of these two phenomena leads to an 'effective' enhanced mixing that can be asymptotically quantified by an effective dispersion coefficient (i.e. Taylor dispersion). Mixing plays a fundamental role in driving chemical reactions. However, at pre-asymptotic times it is considerably more difficult to accurately quantify these effects by an effective dispersion coefficient as spreading and mixing are not the same (but intricately related). In this work we use a volume averaging approach to calculate the concentration distribution of an inert solute release at pre-asymptotic times in a stratified formation. Mixing here is characterized by the scalar dissipation rate, which measures the destruction of concentration variance. As such it is an indicator for the degree of mixing of a system. We study pre-asymptotic solute mixing in terms of explicit analytical expressions for the scalar dissipation rate and numerical random walk simulations. In particular, we divide the concentration field into a mean and deviation component and use dominant balance arguments to write approximate governing equations for each, which we then solve analytically. This allows us to explicitly evaluate the separate contributions to mixing from the mean and the deviation behavior. We find an approximate, but accurate expression (when compared to numerical simulations) to evaluate mixing. Our results shed some new light on the mechanisms that lead to large scale mixing and allow for a distinction between solute spreading, represented by the mean concentration, and mixing, which comes from both the mean and deviation concentrations, at pre-asymptotic times. PMID:20207042

Bolster, Diogo; Valdés-Parada, Francisco J; LeBorgne, Tanguy; Dentz, Marco; Carrera, Jesus

2010-02-13

272

Inertial-confinement-fusion targets  

SciTech Connect

Much of the research in laser fusion has been done using simple ball on-stalk targets filled with a deuterium-tritium mixture. The targets operated in the exploding pusher mode in which the laser energy was delivered in a very short time (approx. 100 ps or less) and was absorbed by the glass wall of the target. The high energy density in the glass literally exploded the shell with the inward moving glass compressing the DT fuel to high temperatures and moderate densities. Temperatures achieved were high enough to produce DT reactions and accompanying thermonuclear neutrons and alpha particles. The primary criteria imposed on the target builders were: (1) wall thickness, (2) sphere diameter, and (3) fuel in the sphere.

Hendricks, C.D.

1982-08-10

273

Coulomb Energy, Vortices, and Confinement  

SciTech Connect

d on 25 Feb 2003 (v1), last revised 10 Apr 2003 (this version, v2))We estimate the Coulomb energy of static quarks from a Monte Carlo calculation of the correlator of timelike link variables in Coulomb gauge. We find, in agreement with Cucchieri and Zwanziger, that this energy grows linearly with distance at large quark separations. The corresponding string tension, however, is several times greater than the accepted asymptotic string tension, indicating that a state containing only static sources, with no constituent gluons, is not the lowest energy flux tube state. The Coulomb energy is also measured on thermalized lattices with center vortices removed by the de Forcrand-D'Elia procedure. We find that when vortices are removed, the Coulomb string tension vanishes.

Greensite, J.; Olejnik, S.

2003-02-25

274

Studies of energetic ion confinement during fishbone events in PDX  

SciTech Connect

The 2.5-MeV neutron emission from the beam-target d(d,n,)/sup 3/He fusion reaction has been examined for all PDX deuterium plasmas which were heated by deuterium neutral beams. The magnitude of the emission was found to scale classically and increase with T/sub e//sup 3/2/ as expected when electron drag is the primary energy degradation mechanism. The time evolution of the neutron emission through fishbone events was measured and used to determine the confinement properties of the energetic beam ions. Many of the experimental results are predicted by the Mode Particle Pumping theory.

Strachan, J.D.; Grek, B.; Heidbrink, W.; Johnson, D.; Kaye, S.; Kugel, H.; LeBlanc, B.; McGuire, K.

1984-11-01

275

High-performance inertial confinement fusion target implosions on OMEGA  

SciTech Connect

The Omega Laser Facility is used to study inertial confinement fusion (ICF) concepts. This paper describes progress in direct-drive central hot-spot (CHS) ICF, shock ignition (SI) and fast ignition (FI) since the 2008 IAEA FEC conference. CHS cryogenic deuterium-tritium (DT) target implosions on OMEGA have produced the highest DT areal densities yet measured in ICF implosions (~300 mg cm{sup -2}). Integrated FI experiments have shown a significant increase in neutron yield caused by an appropriately timed high-intensity, high-energy laser pulse.

Meyerhofer, D. D.; McCrory, R L; Betti, R; Boehly, T R; Casey, D T; Collins, T.J.B.; Craxton, R S; Delettrez, J A; Edgell, D H; Epstein, R; Fletcher, K A; Frenje, J A; Glebov, Y Yu; Goncharov, V N; Harding, D R; Hu, S X; Igumenshchev, I V; Knauer, J P; Li, C K; Marozas, J A; Marshall, F J; McKenty, P W; Nilson, P M; Padalino, S P; Petrasso, R D; Radha, P B; Regan, S P; Sangster, T C; Seguin, F H; Seka, W; Short, R W; Shvarts, D; Skupsky, S; Soures, J M; Stoeckl, C; Theobald, W; Yaakobi, B

2011-04-18

276

High-performance inertial confinement fusion target implosions on OMEGA  

NASA Astrophysics Data System (ADS)

The Omega Laser Facility is used to study inertial confinement fusion (ICF) concepts. This paper describes progress in direct-drive central hot-spot (CHS) ICF, shock ignition (SI) and fast ignition (FI) since the 2008 IAEA FEC conference. CHS cryogenic deuterium-tritium (DT) target implosions on OMEGA have produced the highest DT areal densities yet measured in ICF implosions (~300 mg cm-2). Integrated FI experiments have shown a significant increase in neutron yield caused by an appropriately timed high-intensity, high-energy laser pulse.

Meyerhofer, D. D.; McCrory, R. L.; Betti, R.; Boehly, T. R.; Casey, D. T.; Collins, T. J. B.; Craxton, R. S.; Delettrez, J. A.; Edgell, D. H.; Epstein, R.; Fletcher, K. A.; Frenje, J. A.; Glebov, Y. Yu.; Goncharov, V. N.; Harding, D. R.; Hu, S. X.; Igumenshchev, I. V.; Knauer, J. P.; Li, C. K.; Marozas, J. A.; Marshall, F. J.; McKenty, P. W.; Nilson, P. M.; Padalino, S. P.; Petrasso, R. D.; Radha, P. B.; Regan, S. P.; Sangster, T. C.; Séguin, F. H.; Seka, W.; Short, R. W.; Shvarts, D.; Skupsky, S.; Soures, J. M.; Stoeckl, C.; Theobald, W.; Yaakobi, B.

2011-05-01

277

Enhanced Motility of a Microswimmer in Rigid and Elastic Confinement  

NASA Astrophysics Data System (ADS)

We analyze the effect of confining rigid and elastic boundaries on the motility of a model dipolar microswimmer. Flexible boundaries are deformed by the velocity field of the swimmer in such a way that the motility of both extensile and contractile swimmers is enhanced. The magnitude of the increase in swimming velocity is controlled by the ratio of the swimmer-advection and elastic time scales, and the dipole moment of the swimmer. We explain our results by considering swimming between inclined rigid boundaries.

Ledesma-Aguilar, Rodrigo; Yeomans, Julia M.

2013-09-01

278

KrF lasers for inertial confinement fusion  

SciTech Connect

The KrF laser has been proposed for inertial confinement fusion (ICF) since its discovery in 1975. Since that time, the laser has seen significant development and has been increased in energy many orders of magnitude to the several kilojoule energy level. The suitability of the KrF laser as a driver for ICF energy applications has been continually reviewed. The latest assessments indicate that the KrF laser still appears to be the leading laser candidate. A worldwide effort exists to advance the KrF laser for ICF applications. 21 refs., 1 fig.

Harris, D.B.; Cartwright, D.C.; Figueira, J.F.; McDonald, T.E.; Sorem, M.E.

1989-01-01

279

All-optical confinement of ultracold plasma with resonant ions  

NASA Astrophysics Data System (ADS)

The solution of the problem of all-optical (nonmagnetic) confinement of ultracold electron-ion neutral plasma based on selective action on plasma ions with quantum transition J=1?J=0 of so-called rectified radiation forces in a strong nonmonochromatic light field is suggested. The presented scheme of the three-dimensional dissipative optical trap for plasma allows one to obtain long-lived ultracold plasma with controlled characteristics. The lifetime of the ultracold plasma in such a trap may exceed considerably (by orders of magnitude) the time of free plasma expansion and the lifetime in the (earlier proposed) optical molasses for the ultracold plasma.

Krasnov, I. V.

2009-06-01

280

Magnetospheric Vortex Formation: Self-Organized Confinement of Charged Particles  

SciTech Connect

A magnetospheric configuration gives rise to various peculiar plasma phenomena that pose conundrums to astrophysical studies; at the same time, innovative technologies may draw on the rich physics of magnetospheric plasmas. We have created a ''laboratory magnetosphere'' with a levitating superconducting ring magnet. Here we show that charged particles (electrons) self-organize a stable vortex, in which particles diffuse inward to steepen the density gradient. The rotating electron cloud is sustained for more than 300 s. Because of its simple geometry and self-organization, this system will have wide applications in confining single- and multispecies charged particles.

Yoshida, Z.; Saitoh, H.; Morikawa, J.; Yano, Y.; Watanabe, S.; Ogawa, Y. [Graduate School of Frontier Sciences, University of Tokyo, Kashiwa, Chiba 277-8561 (Japan)

2010-06-11

281

Optical signatures of a tightly confined Bose condensate  

NASA Astrophysics Data System (ADS)

Optical properties of a Bose condensate of Nc atoms tightly confined to a harmonic oscillator potential are studied. A resonantly illuminated condensate scatters as much light as x independent atoms, where x depends on the size of the condensate and on the wavelength of light but not on Nc; the linewidth of the resonance is Nc/x times larger than the linewidth of an individual constituent atom. If the condensate is bigger than a wavelength, light is predominantly scattered in the forward direction.

Javanainen, Juha

1994-04-01

282

Confinement of Skyrmion states in noncentrosymmetric magnets  

Microsoft Academic Search

Skyrmionic states in noncentrosymmetric magnets with Lifshitz invariants are investigated within the phenomenological Dzyaloshinskii model. The interaction between the chiral Skyrmions, being repulsive in a broad temperature range, changes into attraction at high temperatures. This leads to a remarkable confinement effect: near the ordering temperature Skyrmions exist only as bound states, and Skyrmion lattices are formed by an unusual instability-type

A. A. Leonov; A. N. Bogdanov; U. K. Roessler

2010-01-01

283

Plasma confinement in the ORMAK device  

Microsoft Academic Search

Experiments in two different operating regimes of the Oak Ridge Tokamak ; (ORMAK), with Ohmic heating, are discussed. The confinement characteristics of a ; broad-profile discharge in a low-density regime and a peaked-profile discharge at ; high density are described in detail. Through charge-exchange analysis, particle ; diffusion coefficients for these discharges are evaluated, and it is shown that ;

L. A. Berry; J. D. Callen; J. F. Clarke

1975-01-01

284

Disproportionate Minority Confinement (DMC). A Special Report.  

ERIC Educational Resources Information Center

|As far back as the 1960s, research and statistics began to demonstrate what appeared to be an inequality in the criminal justice system in that minorities, particularly black males, were being arrested and confined in numbers far greater than their proportion to the general population. The Coalition for Juvenile Justice, in conjunction with…

Bumbarger, Brian, Ed.

285

Polymer Statics and Dynamics in Confined Geometries  

NASA Astrophysics Data System (ADS)

Current work on biological systems and glass forming polymers (JCP 106, 6176 (1997)) has led to an interest in the study of single polymer systems. The main questions concern relaxation phenomena and the shape adopted by single polymers under hard and soft boundaries. Little is known about the possibility of inducing a glass transition through pure dimensional confinement. We are concerned with whether or not there is a critical value of the confining length scale. Both structure and relaxation can be described using scaling arguments and tested with Monte Carlo simulations using the bond-fluctuation algorithm (Macromolecules 21,2819 (1988)), which uses a lattice representation of the polymer chain with excluded volume effects. We look at the effects of confinement on a single polymer chain by measuring quantities such as the magnitude end-to-end vector, the radius of gyration, and single monomer motion (JACS 124, 20 (2004)). A primary question is whether the self-avoidance constraint manifests itself in a manner similar to kinetically constrained models of the glass transition. Understanding how these quantities change with various confining geometries will lead to a deeper understanding of biological structures and glass formation. Work supported by NSF-DMR 0403997.

Kalb, Joshua; Chakraborty, Bulbul

2006-03-01

286

Polymer Statics and Dynamics Under Box Confinement  

NASA Astrophysics Data System (ADS)

Current work on biological systems and glass forming polymers (JCP 106, 6176 (1997)) has led to an interest in the study of single polymer systems. The main questions concern relaxation phenomena and the shape adopted by single polymers under hard and soft boundaries. We are concerned with whether or not there is a critical length scale for a confined polymer system. Both structure and relaxation can be described using scaling arguments and tested with Monte Carlo simulations using the bond-fluctuation algorithm (Macromolecules 21,2819 (1988)), which uses a lattice representation of the polymer chain with excluded volume effects. We look at the effects of confinement on a single polymer chain confined to a box by measuring dynamical quantities such as the end-to-end vector and single monomer positions (JACS 124, 20 (2004)). A primary question is how spatial correlations between monomers, `blob's, influence the dynamics. Understanding how these quantities change with various confining geometries will lead to a deeper understanding of biological structures and glass formation. Work supported by NSF-DMR 0403997.

Kalb, Joshua; Chakraborty, Bulbul

2007-03-01

287

Probing cell traction forces in confined microenvironments.  

PubMed

Cells migrate in vivo within three-dimensional (3D) extracellular matrices. Cells also migrate through 3D longitudinal channels formed between the connective tissue and the basement membrane of muscle, nerve, and epithelium. Although traction forces have been measured during 2D cell migration, no assay has been developed to probe forces during migration through confined microenvironments. We thus fabricated a novel microfluidic device consisting of deflectable PDMS microposts incorporated within microchannels of varying cross-sectional areas. Using NIH-3T3 fibroblasts and human osteosarcoma (HOS) cells as models, we found that the average traction forces per post decreased upon increasing confinement. Inhibition of myosin-II function by blebbistatin in HOS cells decreased traction forces in unconfined (wide) channels but failed to alter them in confined spaces. Myosin activation by calyculin A also failed to affect traction forces in confining channels but increased them in wide channels. These observations underlie the importance of the physical microenvironment in the regulation of cell migration and cellular traction forces. PMID:24100608

Raman, Phrabha S; Paul, Colin D; Stroka, Kimberly M; Konstantopoulos, Konstantinos

2013-10-29

288

Lattice QCD Study for Confinement in Hadrons  

SciTech Connect

We study three subjects on quark confinement in hadrons in SU(3)c lattice QCD. From the accurate lattice calculation for more than 300 different patterns of three-quark (3Q) systems, we find that the static 3Q potential is well described by Y-Ansatz, i.e., the Coulomb plus Y-type linear potential. We also study the multi-quark (4Q, 5Q) potentials in lattice QCD, and find that they are well described by the one-gluon-exchange (OGE) Coulomb plus string-theoretical linear potential, which supports the infrared string picture even for the multi-quarks. The second subject is a lattice-QCD determination of the relevant gluonic momentum component for confinement. The string tension (confining force) is found to be almost unchanged even after cutting off the high-momentum gluon component above 1.5GeV in the Landau gauge. In fact, quark confinement originates from the low-momentum gluon below about 1.5GeV. Finally, we consider a possible gauge of QCD for the quark potential model, by investigating 'instantaneous inter-quark potential' in generalized Landau gauge, which describes a continuous change from the Landau gauge to the Coulomb gauge.

Suganuma, H.; Iritani, T.; Yamamoto, A. [Department of Physics, Kyoto University, Kitashirakawaoiwake, Sakyo, Kyoto 606-8502 (Japan); Okiharu, F. [Faculty of Education, Niigata University, Ikarashi 2-8050, Niigata 950-2181 (Japan); Takahashi, T. T. [Gunma National College of Technology, Maebashi, Gunma 371-8530 (Japan)

2011-10-21

289

Confinement and free-volume requirements  

Microsoft Academic Search

Enclosure of individuals within a limited space may give rise to problems devolving from the associated restriction or constriction, as modified by any accompanying elements of social isolation and perceptual deprivation. In this paper, the nature of the resulting problems is outlined on the basis of analysis of some 60 studies of operational and experimental human confinement in which the

T. M. Fraser

1968-01-01

290

A numerical study of confined turbulent jets  

Microsoft Academic Search

A numerical investigation is reported of turbulent incompressible jets confined in two ducts, one cylindrical and the other conical with a 5 degree divergence. In each case, three Craya-Curtet numbers are considered which correspond, respectively, to flow situations with no moderate and strong recirculation. Turbulence closure is achieved by using the k-epsilon model and a recently proposed realizable Reynolds stress

J. Zhu; T.-H. Shih

1993-01-01

291

Confined flows of a polymer microgel.  

PubMed

In this paper, we probe the influence of confinement on the flows of a polymer microgel, namely Carbopol. We compare its bulk rheological behavior, measured with a rheometer and well described by a Hershel-Bulkley law, to velocity profiles measured in rough microchannels, obtained with a particle tracking velocimetry technique. We show a strong disagreement between the bulk prediction for the velocity profiles and the measured ones in the microchannels. Velocity profiles in confined conditions are successfully analyzed within the framework of a non-local fluidity model introduced recently (J. Goyon et al. Nature, 454, 84 (2008)). This allows to determine a cooperativity length ?, whose order of magnitude compares with the structure size of the microgel. Moreover, we measure flow curves using a rheometer for different gap conditions and also show that this set of data exhibit a strong effect of the confinement on the measured rheological properties. This is again characterized by a typical length of the same order as the cooperativity length scale ?. We thus evidence confinement effects with two complementary experiments which both give the same typical length for the rearrangements in the flows. PMID:23546693

Geraud, Baudouin; Bocquet, Lyderic; Barentin, Catherine

2013-03-28

292

National Ignition Facility for Inertial Confinement Fusion  

SciTech Connect

The National Ignition Facility for inertial confinement fusion will contain a 1.8 MJ, 500 TW frequency-tripled neodymium glass laser system that will be used to explore fusion ignition and other problems in the physics of high temperature and density. We describe the facility briefly. The NIF is scheduled to be completed in 2003.

Paisner, J.A.; Murray, J.R.

1997-10-08

293

Lattice QCD Study for Confinement in Hadrons  

NASA Astrophysics Data System (ADS)

We study three subjects on quark confinement in hadrons in SU(3)c lattice QCD. From the accurate lattice calculation for more than 300 different patterns of three-quark (3Q) systems, we find that the static 3Q potential is well described by Y-Ansatz, i.e., the Coulomb plus Y-type linear potential. We also study the multi-quark (4Q, 5Q) potentials in lattice QCD, and find that they are well described by the one-gluon-exchange (OGE) Coulomb plus string-theoretical linear potential, which supports the infrared string picture even for the multi-quarks. The second subject is a lattice-QCD determination of the relevant gluonic momentum component for confinement. The string tension (confining force) is found to be almost unchanged even after cutting off the high-momentum gluon component above 1.5GeV in the Landau gauge. In fact, quark confinement originates from the low-momentum gluon below about 1.5GeV. Finally, we consider a possible gauge of QCD for the quark potential model, by investigating ``instantaneous inter-quark potential'' in generalized Landau gauge, which describes a continuous change from the Landau gauge to the Coulomb gauge.

Suganuma, H.; Iritani, T.; Okiharu, F.; Takahashi, T. T.; Yamamoto, A.

2011-10-01

294

Casimir Force in Confined Crosslinked Polymer Blends  

Microsoft Academic Search

The physical system we consider is a crosslinked polymer blend (or an interpenetrating polymer network), made of two chemically incompatible polymers, which are confined to two parallel plates that are a finite distance L apart, that is L

M. Benhamou; A. Agouzouk; H. Kaidi; S. El Fassi; A. Derouiche

2008-01-01

295

Phase separation in confined polymer blends  

Microsoft Academic Search

We consider a binary blend of two polymers of different chemical nature, confined between two adsorptive parallel surfaces separated by a distance L. We assume that the two surfaces adsorb strongly one or both species at high temperature. This implies quenched compositions on surfaces. We assume that phase separation takes place at lower temperature. Two independent effects are present and

R. Cherrabi; A. Saout-Elhak; M. Benhamou; M. Daoud

1999-01-01

296

Optical studies of quantum confined nanostructures  

Microsoft Academic Search

Recent advances in material growth techniques have led to the laboratory realization of quantum confined nanostructures. By engineering the geometry of these systems it is possible to tailor their optical, electrical and vibrational properties. We now envision integrated electronic and optical devices potentially harnessing quantum mechanical properties of photons, electrons or even phonons. The realization of these next generation devices

Anthony Nickolas Vamivakas

2008-01-01

297

Myoglobin unfolding in crowding and confinement.  

PubMed

Crowding and confinement have often been used synonymously with regard to their effect on the structure and dynamics of proteins. In this work, we have investigated the unfolding of the protein myoglobin (Mb) entrapped in the confinement of the water pool of AOT reverse micelles and in the presence of some commonly used macromolecular crowding agents (Ficoll 70, Dextran 70, and Dextran 40). Our results reveal that confinement effects can be quite destabilizing in nature for Mb with the extent of distortion depending on a host of factors apart from the size of the confining cage. Effects of the crowding agents on myoglobin also show a deviation from the general notion that synthetic macromolecular crowding agents are always stabilizing in nature. Ficoll 70 was observed to be particularly destabilizing in its influence on Mb unfolding. Moreover, tryptophan lifetime studies point to the fact that the Trp-heme distance in Mb might not always be a reliable probe of the secondary structural dissolution of the protein. PMID:23025527

Malik, Ashima; Kundu, Jayanta; Mukherjee, Sanjib K; Chowdhury, Pramit K

2012-10-23

298

Chirally symmetric but confining dense, cold matter  

SciTech Connect

The folklore tradition about the QCD phase diagram is that at the chiral restoration phase transition at finite density hadrons are deconfined and there appears the quark matter. We address this question within the only known exactly solvable confining and chirally symmetric model. It is postulated within this model that there exists linear Coulomb-like confining interaction. The chiral symmetry breaking and the quark Green function are obtained from the Schwinger-Dyson (gap) equation while the color-singlet meson spectrum results from the Bethe-Salpeter equation. We solve this model at T=0 and finite chemical potential {mu} and obtain a clear chiral restoration phase transition at the critical value {mu}{sub cr}. Below this value the spectrum is similar to the previously obtained one at {mu}=0. At {mu}>{mu}{sub cr} the quarks are still confined and the physical spectrum consists of bound states which are arranged into a complete set of exact chiral multiplets. This explicitly demonstrates that a chirally symmetric matter consisting of confined but chirally symmetric hadrons at finite chemical potential is also possible in QCD. If so, there must be nontrivial implications for astrophysics.

Glozman, L. Ya.; Wagenbrunn, R. F. [Institute for Physics, Theoretical Physics Branch, University of Graz, Universitaetsplatz 5, A-8010 Graz (Austria)

2008-03-01

299

Diagnostics for magnetic confinement fusion research  

Microsoft Academic Search

Significant progress towards the development of an attractive fusion energy source based on magnetic or inertial plasma confinement has been achieved within the international fusion energy program. High-level diagnostics capabilities are required to characterize fusion plasmas and to achieve a sound physics basis to design a fusion power plant. A large variety of different measuring techniques is used, most of

Arthur Weller

2010-01-01

300

Beam optics in inertial electrostatic confinement fusion  

Microsoft Academic Search

We study the transport of ions and electrons near the cathode of the inertial electrostatic confinement fusion that is expected to be a portable neutron source. We carry out a PIC particle simulation in order to obtain the self-consistent electrostatic potential and the transparency of the cathode for the accelerated ions. The transparency is shown to be much less than

Masami Ohnishi; Chikara Hoshino; Kiyoshi Yoshikawa; Kai Masuda; Yasushi Yamamoto

2000-01-01

301

Negative ions in inertial electrostatic confinement devices  

Microsoft Academic Search

The UW-Inertial Electrostatic Confinement (IEC) device is comprised of concentric, nearly transparent, spherical metallic grids within a cylindrical vacuum vessel. The central grid, which can be held at high negative potentials (~ -100 to -200 kV) is the device cathode, while the outer grid, held at ground potential, is the device anode. This configuration accelerates ions, created near the anode,

D. R. Boris; J. F. Santarius; G. L. Kulcinski

2009-01-01

302

Inertial electrostatic confinement for fusion applications  

Microsoft Academic Search

Inertial electrostatic confinement (IEC) devices have demonstrated significant neutron yields (as high as 2×1010 neutrons\\/second, steady state) in a compact and inexpensive scale. Recent technological progress in plasma sources, vacuum technology and high voltage materials indicates that an order of magnitude increase in neutron yield may be achievable within a few years.

R. A. Nebel; C. P. Munson; W. G. Rellergert; M. D. Sekora

2003-01-01

303

Radioactivity Confinement Studies Within the SEAL Program  

Microsoft Academic Search

In the framework of the European SEAL program, investigations have been performed with the aim of optimizing the second confinement function and plant layout with respect to normal operation as well as abnormal operation, including accident conditions. This has been done for two conceptual fusion reactor designs: one using water as the coolant and the other using helium. The starting

Jan Collén; Ron Matsugu; Antonio Natalizio; Kecheng Shen

1997-01-01

304

Evaluation of the confinement option for LMRs  

Microsoft Academic Search

The primary coolant in liquid-metal-cooled reactors (LMRs) operates at low pressures, typically 175 psig at the pump discharge and near atmospheric at the pump suction for a loop system. Thus, the coolant in contact with the core contains relatively little stored energy compared with light water reactor systems. This condition presents the opportunity for application of confinement systems surrounding the

D. A. Himes; D. D. Stepnewski; G. R. Franz

1986-01-01

305

Hohlraum manufacture for inertial confinement fusion  

SciTech Connect

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 elements are made and extensions of the method that allow fabrication of other, more complex target components.

Foreman, L.R.; Gobby, P.; Bartos, J.; Brooks, P.M.; Bush, H.; Gomez, V.; Elliott, N.; Moore, J.; Rivera, G.; Salazar, M. [Los Alamos National Lab., NM (United States)] [and others

1994-11-01

306

Symmetries in confined classical Coulomb systems  

NASA Astrophysics Data System (ADS)

The properties of charged particles confined in a harmonic oscillator potential have become of increased interest lately in view of the development of techniques in ion traps and storage rings. The symmetries in such systems intrigued the imagination of Ted Hecht in connection with the storage ring at Heidelberg, and so perhaps it is an appropriate subject for this symposium.

Schiffer, J. P.

307

Confining Potential when a Biopolymer Filament Reptates  

NASA Astrophysics Data System (ADS)

Using single-molecule fluorescence imaging, we track Brownian motion perpendicular to the contour of tightly entangled F-actin filaments and extract the confining potential. The chain localization presents a small-displacement Hookean regime followed by a large amplitude regime where the effective restoring force is independent of displacement. The implied heterogeneity characterized by a distribution of tube width is modeled.

Wang, Bo; Guan, Juan; Anthony, Stephen M.; Bae, Sung Chul; Schweizer, Kenneth S.; Granick, Steve

2010-03-01

308

Hohlraum manufacture for inertial confinement fusion  

SciTech Connect

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.

Foreman, L.R.; Gobby, P.; Bartos, J. [Los Alamos National Lab., NM (United States). Materials Science and Technology Div.] [and others

1994-07-01

309

Symmetries in confined classical Coulomb systems  

SciTech Connect

The properties of charged particles confined in a harmonic oscillator potential have become of increased interest lately in view of the development of techniques in ion traps and storage rings. The symmetries in such systems intrigued the imagination of Ted Hecht in connection with the storage ring at Heidelberg, and so perhaps it is an appropriate subject for this symposium.

Schiffer, J.P.

1991-01-01

310

Disproportionate Minority Confinement, 2002 Update. Summary.  

National Technical Information Service (NTIS)

Although minority youth account for about one-third of the U.S. juvenile population, they comprise two-thirds of the juvenile detention/corrections population. Disproportionate minority confinement (DMC) has far-reaching consequences not only for these yo...

H. M. Hsia G. S. Bridges R. McHale

2004-01-01

311

Chapter 2: Plasma confinement and transport  

Microsoft Academic Search

The understanding and predictive capability of transport physics and plasma confinement is reviewed from the perspective of achieving reactor-scale burning plasmas in the ITER tokamak, for both core and edge plasma regions. Very considerable progress has been made in understanding, controlling and predicting tokamak transport across a wide variety of plasma conditions and regimes since the publication of the ITER

E. J. Doyle; W. A. Houlberg; Y. Kamada; V. Mukhovatov; T. H. Osborne; A. Polevoi; G. Bateman; J. W. Connor; J. G. Cordey; T. Fujita; X. Garbet; T. S. Hahm; L. D. Horton; A. E. Hubbard; F. Imbeaux; F. Jenko; J. E. Kinsey; Y. Kishimoto; J. Li; T. C. Luce; Y. Martin; M. Ossipenko; V. Parail; A. Peeters; T. L. Rhodes; J. E. Rice; C. M. Roach; V. Rozhansky; F. Ryter; G. Saibene; R. Sartori; A. C. C. Sips; J. A. Snipes; M. Sugihara; E. J. Synakowski; H. Takenaga; T. Takizuka; K. Thomsen; M. R. Wade; H. R. Wilson; ITPA Pedestal

2007-01-01

312

Colored states in quasi-confinement models  

Microsoft Academic Search

It is assumed in this paper that the interquark (or gluon) forces are dominated by color octet exchange, which leads to the attractive forces to form colored bound states. The mass spectrum of colored states is discussed in two quasi-confinement models. A qualitative prediction of the experimental signature on the colored bound states is included.

Yibing Ding; Guangda Zhao; Danhua Qin

1987-01-01

313

Spontaneous abortion and confined chromosomal mosaicism  

Microsoft Academic Search

Confined placental chorionic mosaicism is reported in 2% of viable pregnancies cytogenetically analyzed on chorionic villi samplings (CVS) at 9–12 weeks of gestation. In follow-up studies this mosaicism has been shown to be associated with increased frequency of second and third trimester pregnancy loss or intrauterine fetal growth retardation. We have studied 54 spontaneous abortions (SA) for the detection of

Dagmar K. Kalousek; Irene J. Barrette; Antia B. Gärtner

1992-01-01

314

`Confined coherence' in strongly correlated anisotropic metals  

NASA Astrophysics Data System (ADS)

We present a detailed discussion of both theoretical and experimental evidence in favour of the existence of states of ‘confined coherence’ in metals of sufficiently high anisotropy and with sufficiently strong correlations. The defining property of such a state is that single electron coherence is confined to lower dimensional subspaces (planes or chains) so that it is impossible to observe interference effects between histories which involve electrons moving between these subspaces. The most dramatic experimental manifestation of such a state is the coexistence of incoherent non-metallic transport in one or two directions (transverse to the lower dimensional subspaces) with coherent transport in at least one other direction (within the subspaces). The magnitude of the Fermi surface warping due to transverse (intersubspace) momentum plays the role of an order parameter (in a state of confined coherence, this order parameter vanishes) and the effect can occur in a pure system at zero temperature. Our theoretical approach is to treat an anisotropic two (2D)- or three (3D)-dimensional electronic system as a collection of one (1D)- or two-dimensional electron liquids coupled by weak interliquid single-particle hopping. We find that a necessary condition for the destruction of coherent interliquid transport is that the intraliquid state be a non-Fermi liquid. We present a very detailed discussion of coupled 1D Luttinger liquids and the reasons for believing in the existence of a phase of confined coherence in that model. This provides a paradigm for incoherent transport between weakly coupled 2D non-Fermi liquids, the case relevant to the experiments of which we are aware. Specifically, anomalous transport data in the (normal state of the) cuprate superconductors and in the low temperature metallic state of the highly anisotropic organic conductor (TMTSF)2PF6 cannot be understood within a Fermi liquid framework, and, we argue, the only plausible way to understand that transport is in terms of a state of confined coherence.

Clarke, David G.; Strong, S. P.

1997-11-01

315

Computational Support for Alternative Confinement Concepts Basic Plasma Science  

SciTech Connect

This is the final report for contract DE-FG03-99ER54528, ''Computational Support for Alternative Confinement Concepts''. Progress was made in the following areas of investigation: (1) Extensive studies of the confinement properties of conventional Reversed-field Pinch (RFP) configurations (i.e., without current profile control) were performed in collaboration with the Royal Institute of Technology (KTH) in Stockholm, Sweden. These studies were carried out using the full 3-dimensional, finite-{beta}, resistive MHD model in the DEBS code, including ohmic heating and anisotropic heat conduction, and thus for the first time included the self-consistent effects of the dynamo magnetic fluctuations on the confinement properties of the RFP. By using multi-variant regression analysis of these results, scaling laws for various properties characterizing the conventional RFP were obtained. In particular, it was found that the, for constant ratio of I/N (where I is the current and N = na{sup 2} is the line density), and over a range of Lundquist numbers S that approaches 10{sup 6}, the fluctuations scale as {delta}B/B {approx} S{sup -0.14}, the temperature scales as T {approx} I{sup 0.56}, the poloidal beta scales as {beta}{sub {theta}} {approx} I{sup -0.4}, and the energy confinement time scales as {tau}{sub E} {approx} I{sup 0.34}. The degradation of poloidal beta with current is a result of the weak scaling of the fluctuation level with the Lundquist number, and leads to the unfavorable scaling laws for temperature and energy confinement time. These results compare reasonably well with experimental data, and emphasize the need for external control of the dynamo fluctuations in the RFP. (2) Studies of feedback stabilization of resistive wall modes in the RFP were performed with the DEBS code in collaboration with the CNR/RFX group in Padua, Italy. The ideal growth rates are ''passively'' reduced by the presence of a resistive wall 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.

Dalton D. Schnack

2002-12-09

316

Numerical studies of confinement scalings for the dynamo-free reversed-field pinch  

NASA Astrophysics Data System (ADS)

In the reversed-field pinch (RFP), tearing modes associated with the dynamo are responsible for reduced energy- and particle confinement. In this study, it is observed that by implementing current profile control (CPC) in the RFP, a dynamo-free state can be achieved. The effect of CPC in the RFP is examined by the use of numerical simulations, and scaling laws are presented for confinement parameters. The model is nonlinear MHD in 3D including finite resistivity and pressure. A linear regression analysis is performed on simulation data from a series of computer runs for a set of initial parameter values. Scaling laws are determined for radial magnetic field, energy confinement time, poloidal beta and temperature. Confinement is improved substantially as compared with the conventional RFP—the temperature reaches reactor relevant levels by ohmic heating alone. It is observed that the configuration spontaneously develops into a quasi single helicity state. The CPC scheme is designed to eliminate the fluctuating electric dynamo field Ef = -langv × Brang, using feedback of an externally imposed electric field. The focus of this study is on obtaining principal theoretical optimization of confinement in the RFP by implementing CPC and to formulate scaling laws for confinement parameters, thus investigating the reactor viability of the concept.

Dahlin, J.-E.; Scheffel, J.

2007-01-01

317

Size-selective assessment of airborne particles in swine confinement building with the UVAPS  

Microsoft Academic Search

The ultraviolet aerodynamic particle sizer (UVAPS) is a novel aerosol counter for real-time monitoring of viable bioaerosols. The previous validation studies on the UVAPS were either laboratory based or were conducted outdoor with the artificially generated aerosols. In this study, the spectrometer was applied to investigate particulate pollution inside a swine confinement building (SCB). Real-time capabilities of the instrument were

Victoria Agranovski; Zoran Ristovski; Patrick J. Blackall; Lidia Morawska

2004-01-01

318

THE EFFECTS OF CONFINING PRESSURE AND STRESS DIFFERENCE ON STATIC FATIGUE OF GRANITE  

Microsoft Academic Search

Samples of Barre granite were creep creasing depth. The transition depth, where creep tested at room temperature at confining pressures rupture is no longer possible owing to increasing up to 2 kbar. The time to fracture increased ductility, is unknown. It is significant that with decreasing stress difference at every dilatancy caused by microfracturing occurs in pressure. The time to

Robert L. Kranzl

1980-01-01

319

Thermal expansion as a function of confining pressure for welded tuff from Yucca Mountain  

SciTech Connect

Thermal expansion measurements were conducted as a function of confining pressure on welded specimens of Topopah Spring Member tuff recovered from borehole USW SD-12 at Yucca Mountain, NV. Each specimen was tested at confining pressures between 1 and 30 MPa over a nominal temperature range of 25 to 250{degrees}C. On several specimens, the higher confining pressure thermal cycles were performed first to inhibit thermal effects, such as cracking, that occur at lower confining pressures in other rock types. The coefficient of thermal expansion for welded tuff increases with temperature. At temperatures below 100 {times} C the mean coefficient of thermal expansion range from 7.7 to 10.8 {times} 10{sup {minus}6}{sup C {minus}1}. As temperatures approach 250{degrees}C, the thermal expansions increase markedly to values of 14.2 to 20.6 {times} 10{sup {minus}6}{degrees}{sup C{minus}1}. The effect of confining pressure on thermal expansion for tuff is small.

Martin, R.J.; Noel, J.S.; Boyd, P.J. [New England Research, Inc., White River Junction, VT (United States); Price, R.H. [Sandia National Labs., Albuquerque, NM (United States)

1996-02-01

320

The entropic cost of polymer confinement.  

PubMed

The confinement of a polymer into a small space is thermodynamically unfavorable because of the reduction in the number of conformational states. The entropic penalty affects a variety of biological processes, and it plays an important role in polymer transport properties and in microfluidic devices. We determine the entropic penalty for the confinement of elastic polymer of persistence length P in the long-chain limit. We examine three geometries: (1) parallel planes separated by a distance d (a slit); (2) a circular tube of diameter d; and (3) a sphere of diameter d. We first consider infinitely thin (ideal) chains. As d/P drops from 100 to 0.01, T?S rises from ?5 × 10(-4) kT to ?30 kT per persistence length for cases (1) and (2), with the entropic penalty for case (2) being consistently about twice that for case (1). T?S is ?5 kT per persistence length for confinement to a sphere when d = P, about twice the value predicted by mean field theory. For all three geometries, in the limit d/P ? 1, the asymptotic behavior of ?S vs d is consistent with the d(-2) behavior predicted by theory. In the limit d/P ? 1, the scaling of ?S for slits and tubes is also consistent with earlier predictions (d(-2/3)). Finally, we treat volume exclusion effects, examining chains of diameter D > 0. Confinement to a narrow slit or tube (d/P ? 1) has the same entropic penalty as that for an ideal chain in a slit or tube with d' = d - D; in the weak confinement regime (d/P ? 1), the entropic penalties are significantly larger than those for infinitely thin chains. When a chain of finite diameter is forced into a sphere or other closed cavity, the entropic confinement penalty rises without limit because there are no configurations available to the chain once its volume exceeds that of the cavity. PMID:22905742

Smyda, Mark R; Harvey, Stephen C

2012-08-27

321

Confined laser ablation for single-shot nanoparticle deposition of silver  

NASA Astrophysics Data System (ADS)

Spatially confined laser ablation of silver was used to form long-lived dense plasma for single-shot deposition of a nanoparticle film. The expansion of the ablation plume was restricted by placing a glass substrate at 50 ?m from the silver target surface. Time-resolved optical emission spectroscopy showed that the confined plasma is sustained for longer time than for free ablation. A single laser shot is sufficient to produce a layer of silver nanoparticles on the substrate. In absorption the nanoparticle layer displays a surface plasmon resonance which is comparable to films made by conventional pulsed laser deposition in vacuum.

Donnelly, T.; Lunney, J. G.

2013-10-01

322

Yang-Mills streamlines and semi-classical confinement  

SciTech Connect

Semi-classical configurations in Yang-Mills theory have been derived from lattice Monte Carlo configurations using a recently proposed constrained cooling technique which is designed to preserve every Polyakov line (at any point in space-time in any direction). Consequently, confinement was found sustained by the ensemble of semi-classical configurations. The existence of gluonic and fermionic near-to-zero modes was demonstrated as a precondition for a possible semi-classical expansion around the cooled configurations as well as providing the gapless spectrum of the Dirac operator necessary for chiral symmetry breaking. The cluster structure of topological charge of the semi-classical streamline configurations was analysed and shown to support the axial anomaly of the right size, although the structure differs from the instanton gas or liquid. Here, we present further details on the space-time structure and the time evolution of the streamline configurations.

Langfeld, Kurt [School of Computing and Mathematics, University of Plymouth, Plymouth Pl4 8AA (United Kingdom); Ilgenfritz, Ernst-Michael [Institut fuer Physik, Humboldt-Universitaet zu Berlin, D-12489 Berlin (Germany)

2011-05-23

323

Status report of confinement studies Douglas United Nuclear operated reactors.  

National Technical Information Service (NTIS)

Confinement studies on the Hanford Production reactors were started in March at the request of the Richland Operations Office. The confinement studies were then undertaken with the following objectives established: (1) review and reestablish if necessary,...

J. R. Spink N. F. Fifer

1965-01-01

324

Atomic processes in Inertial Electrostatic Confinement (IEC) devices.  

National Technical Information Service (NTIS)

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...

R. A. Nebel L. Turner T. N. Tiouririne D. C. Barnes W. D. Nystrom

1993-01-01

325

System and method of operating toroidal magnetic confinement devices  

DOEpatents

This invention pertains to methods and arrangements for attaining high beta values in plasma confinement devices. More specifically, this invention pertains to methods for accessing the second stability region of operation in toroidal magnetic confinement devices.

Chance, M.S.; Jardin, S.C.; Stix, T.H.; Grimm, R.C.; Manickam, J.; Okabayashi, M.

1984-08-30

326

Extra weak bosons in a confining gauge theory with complementarity  

SciTech Connect

In composite models of weak bosons based on a confining gauge theory, extra weak bosons introduced as composites of scalar constituents are shown to exhibit kinetic mixing interactions describing the vector-meson dominance of the photon and to disguise themselves as massive elementary gauge particles in accord with the notion of complementarity. Detailed discussions are presented for a U(1){sub em}{sup loc} model with a confined SU(2){sub {ital L}}{sup loc}{times}{ital G-script}{sup loc} gauge symmetry, where {ital G-script}{sup loc}={ital S-scriptU-script}(2){sub {ital L}}{sup loc}{times}{ital S-script} {ital U-script}(2){sub {ital R}}{sup loc}, which is responsible for compositeness of quarks and leptons as well. This phenomenon is also shown to arise in QCD with three flavors, utilizing the diquark degrees of freedom, where the octet baryons and vector mesons are viewed as massive quarks and gluons, respectively.

Yasue, M. (Institute for Nuclear Study, University of Tokyo, Midori-cho, Tanashi, Tokyo (Japan))

1990-11-01

327

Shear Wave Generation from Confined Explosions  

NASA Astrophysics Data System (ADS)

Although the ratio of S- to P-waves is believed to be the best criterion to discriminate underground explosions from earthquakes, the mechanism of S-wave generation from confined explosions is still poorly understood. In order to measure P- and S-waves generated from confined explosions in ~1 meter size rock samples, a method is developed based on the different characteristics of incident P- and S-wave reflections from free-surfaces of rocks and the properties of strain gauges. The relationship between particle displacements of incident P- and S-waves and strains measured by strain gauges are decided and given analytically. From the tamped and decoupled experiments conducted on Bedford limestone, P- and SV-waves were clearly recorded. Initial experimental results show that tamped explosions are more efficient for SV-wave generations than decoupled explosions. The P- and S-wave decay with distance from the center of explosions also is given.

Liu, C.

1997-07-01

328

Spontaneous circulation of confined active suspensions.  

PubMed

Many active fluid systems encountered in biology are set in total geometric confinement. Cytoplasmic streaming in plant cells is a prominent and ubiquitous example, in which cargo-carrying molecular motors move along polymer filaments and generate coherent cell-scale flow. When filaments are not fixed to the cell periphery, a situation found both in vivo and in vitro, we observe that the basic dynamics of streaming are closely related to those of a nonmotile stresslet suspension. Under this model, it is demonstrated that confinement makes possible a stable circulating state; a linear stability analysis reveals an activity threshold for spontaneous autocirculation. Numerical analysis of the longtime behavior reveals a phenomenon akin to defect separation in nematic liquid crystals and a high-activity bifurcation to an oscillatory regime. PMID:23215137

Woodhouse, Francis G; Goldstein, Raymond E

2012-10-19

329

Extreme Lagrangian acceleration in confined turbulent flow.  

PubMed

A Lagrangian study of two-dimensional turbulence for two different geometries, a periodic and a confined circular geometry, is presented to investigate the influence of solid boundaries on the Lagrangian dynamics. It is found that the Lagrangian acceleration is even more intermittent in the confined domain than in the periodic domain. The flatness of the Lagrangian acceleration as a function of the radius shows that the influence of the wall on the Lagrangian dynamics becomes negligible in the center of the domain, and it also reveals that the wall is responsible for the increased intermittency. The transition in the Lagrangian statistics between this region, not directly influenced by the walls, and a critical radius which defines a Lagrangian boundary layer is shown to be very sharp with a sudden increase of the acceleration flatness from about 5 to about 20. PMID:18518379

Kadoch, Benjamin; Bos, Wouter J T; Schneider, Kai

2008-05-08

330

Bulk dynamics in confining gauge theories  

NASA Astrophysics Data System (ADS)

We consider gauge/string duality (in the supergravity approximation) for confining gauge theories. The system under scrutiny is a 5-dimensional consistent truncation of type IIB supergravity obtained using the Papadopoulos Tseytlin ansatz with boundary momentum added. We develop a gauge-invariant and sigma-model-covariant approach to the dynamics of 5-dimensional bulk fluctuations. For the Maldacena Nuñez subsystem, we study glueball mass spectra. For the Klebanov Strassler subsystem, we compute the linearized equations of motion for the 7-scalar system, and show that a 3-scalar sector containing the scalar dual to the gluino bilinear decouples in the UV. We solve the fluctuation equations exactly in the “moderate UV” approximation and check this approximation numerically. Our results demonstrate the feasibility of analyzing the generally coupled equations for scalar bulk fluctuations, and constitute a step on the way towards computing correlators in confining gauge theories.

Berg, Marcus; Haack, Michael; Mück, Wolfgang

2006-02-01

331

Confinement of Fractional Quantum Hall States  

NASA Astrophysics Data System (ADS)

Confinement of small-gapped fractional quantum Hall states facilitates quasiparticle manipulation and is an important step towards quasiparticle interference measurements. Demonstrated here is conduction through top gate defined, narrow channels in high density, ultra-high mobility heterostructures. Transport evidence for the persistence of a correlated state at filling fraction 5/3 is shown in channels of 2?m length but gated to near 0.3?m in width. The methods employed to achieve this confinement hold promise for interference devices proposed for studying potential non-Abelian statistics at filling fraction 5/2. R.L. Willett, M.J. Manfra, L.N. Pfeiffer, K.W. West, Appl. Phys. Lett. 91, 052105 (2007).

Willett, Robert; Manfra, Michael; West, Ken; Pfeiffer, Loren

2008-03-01

332

Confinement effect on semiconductor nanowires properties  

NASA Astrophysics Data System (ADS)

We study the effect of confinement on various properties of semiconductor nanowires. First, we study the size and direction dependence of the band gap of germanium nanowires. We use the density functional theory in the local density approximation. Results shows that the band gap decreases with the diameter. The susceptibility of these nanowires is also computed. Second, we look at the confinement effect on the piezoelectric coefficients of ZnO and MN nanowires. The Berry phase method is used. It is found that depending on passivation, the piezoelectric effect can decrease or increase. Finally, we study the size and direction dependence of the melting temperature of silicon nanowires. We use the molecular dynamics with the Stillinger Weber potential. Results indicate that the melting temperature increases with the nanowire diameter and that it is direction dependent.

Nduwimana, Alexis

333

Semiflexible Polymer Confined to a Spherical Surface  

NASA Astrophysics Data System (ADS)

We develop a formalism for describing the kinematics of a wormlike chain confined to the surface of a sphere that simultaneously satisfies the spherical confinement and the inextensibility of the chain contour. We use this formalism to study the statistical behavior of the wormlike chain on a spherical surface. In particular, we provide an exact, closed-form expression for the mean square end-to-end dis­tance that is valid for any value of chain length L, persistence length lp, and sphere radius R. We predict two qualitatively different behaviors for a long polymer depending on the ratio R/lp. For R/lp>4, the mean square end-to-end distance increases monotonically with the chain length, whereas for R/lp<4, a damped oscillatory behavior is predicted.

Spakowitz, Andrew J.; Wang, Zhen-Gang

2003-10-01

334

Pressure-confined Lyman-alpha clouds  

SciTech Connect

Results are presented of numerical models of pressure-confined spherical gas clouds which produce absorption resembling the low to intermediate atomic column density lines found in high-redshift QSO spectra. One-dimensional hydrodynamical models including electron conduction are described, and the rate equations are solved to find ionization and excitation states. Results are presented for both static and adiabatically expanding confining media covering a range of initial pressures. It is found that Ly-alpha lines are very similar over a wide range of conditions and that the most promising diagnostic of pressure is to compare the column density in H I to that in He I and He II. No single-pressure model can explain the wide range of observed H I column densities. 18 references.

Baron, E.; Carswell, R.F.; Hogan, C.J.; Weymann, R.J.

1989-02-01

335

Inertial electrostatic confinement (IEC) neutron sources  

SciTech Connect

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 x 10(exp 10) neutrons/sec in steady state. These systems have considerable potential as small, inexpensive, portable neutron sources for assaying applications. Neutron tomography is also a potential application. This paper discusses the IEC concept and how it can be adapted to a steady-state assaying source and an intense pulsed neutron source. Theoretical modeling and experimental results are presented.

Barnes, D.C.; Caramana, E.J.; Janssen, R.D.; Nystrom, W.D.; Tiouririne, T.N.; Trent, B.C.; Miley, G.H.; Javedani, J.

1995-01-01

336

Approaches to confined alpha diagnostics on ITER  

SciTech Connect

Three approaches to obtain information on the confined fast alphas in the International Thermonuclear Experimental Reactor (ITER) are proposed. The first technique measures the energetic charge exchange (CX) neutrals that result from the alpha collision-induced knock-on fuel ion tails undergoing electron capture on the MeV D neutral beams planned for heating and current drive. The second technique measures the energetic knock-on neutron tail due to alphas using the lengths of the proton recoil tracks produced by neutron collisions in nuclear emulsions. The range of the 14 to 20 MeV recoil protons increases by {approx}140 {mu}m per MeV. The third approach would measure the CX helium neutrals resulting from confined alphas capturing two electrons in the ablation cloud surrounding a dense gas jet that has been proposed for disruption mitigation in ITER.

Fisher, R.K. [General Atomics, PO Box 85608, San Diego, California 92186-5608 (United States)

2004-10-01

337

NEW APPROACHES TO CONFINED ALPHA DIAGNOSTICS  

SciTech Connect

Three new approaches to obtain information on the confined fast alphas in International Thermonuclear Experimental Reactor (ITER) are proposed. The first technique measures the energetic charge exchange (CX) neutrals that result from the alpha collision-induced knock-on fuel ion tails undergoing electron capture on the MeV D neutral beams planned for heating and current drive. The second technique measures the energetic knock-on neutron tail due to alphas using the lengths of the proton recoil tracks produced by neutron collisions in nuclear emulsions. The range of the 14 to 20 MeV recoil protons increases by {approx}140 microns per MeV. The third approach would measure the CX helium neutrals resulting from confined alphas capturing two electrons in the ablation cloud surrounding a dense gas jet that has been proposed for disruption mitigation in ITER.

FISHER,R.K

2004-04-01

338

Freezing of colloidal suspensions in confined spaces  

SciTech Connect

Simulation and experimental techniques have been developed to study the phase properties of a fluid confined between two closely-spaced walls and applied to investigate systems of charge-stabilized colloidal suspensions between repulsive smooth walls in contact with a reservoir. The phase behavior of confined suspensions is studied as a function of bulk particle volume fraction, surface charge, and wall separation. Complete crystallization within a fixed-size gap at sufficiently small wall separation occurs at bulk volume fractions well below the bulk freezing volume fraction. The simulations show a strong dependence of the freezing transition on a preferred wall separation corresponding to an integral number of layers. The simulation predictions match experimental observations at wall separations from five to ten particle diameters. 42 refs., 10 figs., 1 tab.

Hug, J.E.; Swol, F. van; Zukoski, C.F. (Univ. of Illinois, Urbana, IL (United States))

1995-01-01

339

LDV Measurement of Confined Parallel Jet Mixing  

SciTech Connect

Laser Doppler Velocimetry (LDV) measurements were taken in a confinement, bounded by two parallel walls, into which issues a row of parallel jets. Two-component measurements were taken of two mean velocity components and three Reynolds stress components. As observed in isolated three dimensional wall bounded jets, the transverse diffusion of the jets is quite large. The data indicate that this rapid mixing process is due to strong secondary flows, transport of large inlet intensities and Reynolds stress anisotropy effects.

R.F. Kunz; S.W. D'Amico; P.F. Vassallo; M.A. Zaccaria

2001-01-31

340

Work Schedules and Performance During Confinement1  

Microsoft Academic Search

Thirteen investigations were carried out as a part of an 8-year program of research on the performance effects of various work\\/rest schedules during confinement to a simulated aeorspace vehicle crew compartment. A total of 139 subjects were tested using a standard battery of performance tasks. The synthetic work approach used provided a reliable, face-valid, and sensitive technique for assessing complex

W. Dean Chiles; Earl A. Alluisi; Oscar S. Adams

1968-01-01

341

Inertial confinement fusion reactor for space applications  

SciTech Connect

One of the most exciting and promising approaches to fusion power that has emerged recently is the magnetically insulated inertial confinement fusion (MICF) concept proposed by Hasegawa et al. It is a scheme that combines the benefits of magnetic and inertial fusions in which a plasma with a density of approx.10/sup 21/ cm/sup -3/ is confined by the inertia of a heavy metallic shell, while its heat is insulated by a self-generated magnetic field of approx.100 T. In contrast to the conventional inertial confinement approach in which a large rate of implosion and simultaneous achievement of ignition temperature must occur (a condition that lies at the heart of the major difficulty to this approach), the MICF concept relies on generating the fusion plasma by ablation of the solid deuterium-tritium (D-T) fuel through a hole in the pellet by means of a laser (or particle) beam. As a result, the input energy is put directly into the fuel plasma (rather than the imploding pusher), thereby giving rise to a better energy efficiency than the conventional inertial confinement schemes. Because of its relative simplicity and its ability to utilize the comparatively efficient CO/sub 2/ lasers (which can be driven chemically), the above scheme is particularly well suited for space power applications. When examined for possible utilization as a rocket propulsion scheme, the authors have shown that specific impulses of 1000 or more seconds are readily attainable from MICF. This range of specific impulse is highly desirable for many space missions, especially those that cannot be accommodated by chemical propulsion.

Kammash, T.; Galbraith, D.L.

1986-01-01

342

Indirectly driven targets for inertial confinement fusion  

Microsoft Academic Search

The physics of indirectly driven targets for inertial confinement fusion — so-called hohlraum targets — is investigated. Scaling relations for radiation heat waves in high-Z and low-Z materials are derived from one-dimensional multigroup simulation. A two-temperature model is developed for radiation cavities including fusion capsules. The efficiency of X-ray transfer to the capsule by multiple absorption and re-emission inside the

M. Murakami; J. Meyer-ter-Vehn

1991-01-01

343

Perlite for permanent confinement of cesium  

Microsoft Academic Search

We present the potential use of expanded perlite, a metastable amorphous hydrated aluminium silicate, as a permanent medium for the long-term confinement of cesium. The method requires simply a loading by mixing an aqueous cesium nitrate solution and expanded perlite at 300K followed by densification by sintering. The formation of pollucite, CsAlSi2O6, a naturally occurring mineral phase, upon careful heat

J. Balencie; D. Burger; J.-L. Rehspringer; C. Estournès; S. Vilminot; M. Richard-Plouet; A. Boos

2006-01-01

344

Designing the Cascade inertial confinement fusion reactor  

SciTech Connect

The primary goal in designing inertial confinement fusion (ICF) reactors is to produce electrical power as inexpensively as possible, with minimum activation and without compromising safety. This paper discusses a method for designing the Cascade rotating ceramic-granule-blanket reactor (Pitts, 1985) and its associated power plant (Pitts and Maya, 1985). Although focus is on the cascade reactor, the design method and issues presented are applicable to most other ICF reactors.

Pitts, J.H.

1987-02-09

345

Target support for inertial confinement fusion  

SciTech Connect

General Atomics (GA) plays an important industrial support role for the US Inertial Confinement Fusion (ICF) program in the area of target technology. This includes three major activities: target fabrication support, target handling systems development, and target chamber design. The work includes target fabrication for existing ICF experiments, target and target system development for future experiments, and target research and target chamber design for experiments on future machines, such as the National Ignition Facility (NIF).

Schultz, K.R.

1995-08-01

346

Deuterium anions in inertial electrostatic confinement devices  

Microsoft Academic Search

A magnetic deflection-energy analyzer and Faraday trap diagnostic have been used to make measurements of divergent deuterium anion flow in the inertial electrostatic confinement experiment at the University of Wisconsin-Madison (UW-IEC) [J. F. Santarius, G. L. Kulcinski, R. P. Ashley, D. R. Boris, B. B. Cipiti, S. K. Murali, G. R. Piefer, R. F. Radel, I. E. Radel, and A.

D. R. Boris; E. Alderson; G. Becerra; D. C. Donovan; B. Egle; G. A. Emmert; L. Garrison; G. L. Kulcinski; J. F. Santarius; C. Schuff; S. J. Zenobia

2009-01-01

347

Laser driven instabilities in inertial confinement fusion  

SciTech Connect

Parametric instabilities excited by an intense electromagnetic wave in a plasma is a fundamental topic relevant to many applications. These applications include laser fusion, heating of magnetically-confined plasmas, ionospheric modification, and even particle acceleration for high energy physics. In laser fusion, these instabilities have proven to play an essential role in the choice of laser wavelength. Characterization and control of the instabilities is an ongoing priority in laser plasma experiments. Recent progress and some important trends will be discussed. 8 figs.

Kruer, W.L.

1990-06-04

348

Inertial confinement fusion with light ion beams  

SciTech Connect

Advances are reported in the theory and experiments investigating Inertial Confinement Fusion with light ion beams on the Particle Beam Fusion Accelerator II (PBFA II). Impedance of the accelerating gap, electron-ion instabilities, proton beam generation and focusing at 300 kJ, proton driven target experiments to measure beam non-uniformity, lithium beam generation and focusing at 185 kJ, and plasma opening switch improvements for voltage and power gain are reported.

Vandevender, J.P.; Adams, R.G.; Allshouse, G.O.; Bailey, J.E.; Beig, K.W.; Bloomquist, D.D.; Coats, R.S.; Cook, D.L.; Chandler, G.E.; Cuneo, M.E.; Derzon, M.S.; Desjarlais, M.P.; Dreike, P.L.; Gerber, R.A.; Hanson, D.L.; Humphreys, D.R.; Hussey, T.W.; Johnson, D.J.; Johnson, D.L.; Johnson, W.A.; Kuswa, G.W.; Lee, J.R.; Leeper, R.J.; Lockner, T.R.; Maenchen, J.E.; Matzen, M.K.; McDaniel, D.H.; McKay, P.F.; Mehlhorn, T.A.; Mend

1990-01-01

349

Neoclassical transport in enhanced confinement toroidal plasmas  

SciTech Connect

It has recently been reported that ion thermal transport levels in enhanced confinement tokamak plasmas have been observed to fall below the irreducible minimum level predicted by standard neoclassical theory. This apparent contradiction is resolved in the present analysis by relaxing the basic neoclassical assumption that the ions orbital excursions are much smaller than the local toroidal minor radius and the equilibrium scale lengths of the system.

Lin, Z.; Tang, W.M.; Lee, W.W.

1996-11-01

350

46 CFR 148.86 - Confined space entry.  

Code of Federal Regulations, 2011 CFR

...2011-10-01 2011-10-01 false Confined space entry. 148.86 Section 148.86...Requirements § 148.86 Confined space entry. (a) Except in an emergency, no person may enter a confined space unless that space has been...

2011-10-01

351

46 CFR 148.86 - Confined space entry.  

Code of Federal Regulations, 2012 CFR

...2012-10-01 2012-10-01 false Confined space entry. 148.86 Section 148.86...Requirements § 148.86 Confined space entry. (a) Except in an emergency, no person may enter a confined space unless that space has been...

2012-10-01

352

Industrial Applications to the Inertial Electrostatic Confinement Configuration  

Microsoft Academic Search

Since Fransworth's observation of inertial electrostatic confinement in the 1930's several applications have been proposed and studied with fusion being the main focus. Inertial electrostatic confinement is a scheme in which ions are focused and confined by means of either an electrostatic field or a combination of electrostatic and magnetic fields to produce an effective spherical potential well. Due to

Elijah Martin; Steve Shannon; Mohamed Bourham

2009-01-01

353

Flux confinement for a class of effective Lagrangians  

NASA Astrophysics Data System (ADS)

Confinement properties recently proved in the leading logarithm model are shown to be generally truc for a wide class of effective Lagrangians. These include nonexistence of isolated quarks, confining static potential betweenqbar q pair and flux confinement within a characteristic acting as a free boundary. A new variational principle is formulated.

Yong-Shi, Wu; Zee, A.

1983-06-01

354

Studies Of Enhanced Confinement In The Columbia Non-Neutral Torus  

SciTech Connect

Recently the measured confinement time in the Columbia Non-neutral Torus (CNT) has been increased by nearly an order of magnitude to 190 ms. Previously, enhanced transport caused in part by the mismatch of constant potential and magnetic surfaces limited confinement times to 20 ms. A conducting boundary conforming to the last closed magnetic flux surface has been installed to minimize potential variation along magnetic surfaces, provide new methods to influence the plasma, and act as an external diagnostic. A summary of new results with the conducting boundary installed will be presented, including discussion of how confinement is influenced by neutral pressure, magnetic field strength, and the effect of biasing individual sectors of the mesh.

Brenner, P. W.; Pedersen, T. Sunn; Hahn, M.; Berkery, J. W.; Lefrancois, R. G. [Columbia University, New York, NY 10027 (United States); Marksteiner, Q. R. [Columbia University, New York, NY 10027 (United States); Los Alamos National Laboratory, Los Alamos, NM 87545 (United States)

2009-03-30

355

Superfluid Phases of 3He in a Periodic Confined Geometry  

NASA Astrophysics Data System (ADS)

Predictions and discoveries of new phases of superfluid 3He in confined geometries, as well as novel topological excitations confined to surfaces and edges of near a bounding surface of 3He, are driving the fields of superfluid 3He infused into porous media, as well as the fabrication of sub-micron to nano-scale devices for controlled studies of quantum fluids. In this report we consider superfluid 3He confined in a periodic geometry, specifically a two-dimensional lattice of square, sub-micron-scale boundaries ("posts") with translational invariance in the third dimension. The equilibrium phase(s) are inhomogeneous and depend on the microscopic boundary conditions imposed by a periodic array of posts. We present results for the order parameter and phase diagram based on strong pair breaking at the boundaries. The ordered phases are obtained by numerically minimizing the Ginzburg-Landau free energy functional. We report results for the weak-coupling limit, appropriate at ambient pressure, as a function of temperature T, lattice spacing L, and post edge dimension, d. For all d in which a superfluid transition occurs, we find a transition from the normal state to a periodic, inhomogeneous "polar" phase with T_{c1} < Tc for bulk superfluid 3He. For fixed lattice spacing, L, there is a critical post dimension, d c , above which only the periodic polar phase is stable. For dtime-reversal symmetry, but unlike the bulk B-phase has only {D}_{{4h}}^{{L}+{S}} point symmetry.

Wiman, J. J.; Sauls, J. A.

2013-10-01

356

Confinement of atoms under general boundary conditions  

NASA Astrophysics Data System (ADS)

The energy spectrum of a nonrelativistic quantum particle and hydrogen-like atom is considered under the most general conditions of confinement in a spatial box (vacuum cavity). It is shown that the rearrangement of the lowest energy levels occurring in this case turns out to be considerably more significant when compared with the case of confinement achieved by the impenetrable potential barrier. The role in the rearrangement of this level, played by the von Neumann-Wigner level repulsion effect, is emphasized. For an atom confined in a spherical cavity of radius R, it is also shown that, when the role of the cavity boundary is played by the surface layer of nonzero depth d, the atomic ground state possesses a deep and pronounced minimum for the physically reasonable width and depth of that surface layer, in which the binding energy turns out to be an order of magnitude larger than that of the lowest 1 s-level of a free atom E 1 s . Also, it becomes possible to achieve a mode when the binding energy of an atom is noticeably higher than E 1 s at R on the order of 10-100 nm.

Sveshnikov, K. A.; Roenko, A. A.

2013-09-01

357

Evaporation rate of water in hydrophobic confinement.  

PubMed

The drying of hydrophobic cavities is believed to play an important role in biophysical phenomena such as the folding of globular proteins, the opening and closing of ligand-gated ion channels, and ligand binding to hydrophobic pockets. We use forward flux sampling, a molecular simulation technique, to compute the rate of capillary evaporation of water confined between two hydrophobic surfaces separated by nanoscopic gaps, as a function of gap, surface size, and temperature. Over the range of conditions investigated (gaps between 9 and 14 ? and surface areas between 1 and 9 nm(2)), the free energy barrier to evaporation scales linearly with the gap between hydrophobic surfaces, suggesting that line tension makes the predominant contribution to the free energy barrier. The exponential dependence of the evaporation rate on the gap between confining surfaces causes a 10 order-of-magnitude decrease in the rate when the gap increases from 9 to 14 ?. The computed free energy barriers are of the order of 50 kT and are predominantly enthalpic. Evaporation rates per unit area are found to be two orders of magnitude faster in confinement by the larger (9 nm(2)) than by the smaller (1 nm(2)) surfaces considered here, at otherwise identical conditions. We show that this rate enhancement is a consequence of the dependence of hydrophobic hydration on the size of solvated objects. For sufficiently large surfaces, the critical nucleus for the evaporation process is a gap-spanning vapor tube. PMID:22392972

Sharma, Sumit; Debenedetti, Pablo G

2012-03-05

358

Simulating tumor growth in confined heterogeneous environments  

NASA Astrophysics Data System (ADS)

The holy grail of computational tumor modeling is to develop a simulation tool that can be utilized in the clinic to predict neoplastic progression and propose individualized optimal treatment strategies. In order to develop such a predictive model, one must account for many of the complex processes involved in tumor growth. One interaction that has not been incorporated into computational models of neoplastic progression is the impact that organ-imposed physical confinement and heterogeneity have on tumor growth. For this reason, we have taken a cellular automaton algorithm that was originally designed to simulate spherically symmetric tumor growth and generalized the algorithm to incorporate the effects of tissue shape and structure. We show that models that do not account for organ/tissue geometry and topology lead to false conclusions about tumor spread, shape and size. The impact that confinement has on tumor growth is more pronounced when a neoplasm is growing close to, versus far from, the confining boundary. Thus, any clinical simulation tool of cancer progression must not only consider the shape and structure of the organ in which a tumor is growing, but must also consider the location of the tumor within the organ if it is to accurately predict neoplastic growth dynamics.

Gevertz, Jana L.; Gillies, George T.; Torquato, Salvatore

2008-09-01

359

Quantum Confined Silicon Clathrate Quantum Dots  

NASA Astrophysics Data System (ADS)

Silicon (Si) allotropes can be synthesized in such a way that tetrahedrally bonded atoms form cage-like structures with bulk mechanical and opto-electronic properties distinct from those of diamond silicon (dSi). We use DFT, supplemented with many-body Green function analysis, to explore the structural stability of clathrate Si quantum dots (QDs) and to characterize their confinement as a function of crystal symmetry and size. Our results show that that there is a simple relationship between the confinement character of the QDs and the effective mass of the associated bulk crystals. Clathrate QDs and dSiQDs of the same size can exhibit differences of gap energies by as much as 2 eV. This offers the potential of synthesizing Si dots on the order of 1 nm that have optical gaps in the visible range but that do not rely on high-pressure routes such as those explored for the metastable BC8 and R8 phases. These results prompt the question as to how minimal quantum confinement can be in dots composed of Si. More broadly, clathrate QDs can in principle be synthesized for a wide range of semiconductors, and the design space can be further enriched via doping.

Lusk, Mark; Brawand, Nicholas

2013-03-01

360

Central cell confinement in MFTF-B  

NASA Astrophysics Data System (ADS)

The point model code TANDEM was used to survey the range of plasma parameters which can be attained in MFTF-B. The code solves for the electron and ion densities and temperatures in the central cell, yin-yang, barrier, and A-cell regions as well as the plasma potential in each region. In these studies, the A-cell sloshing ion beams were fixed while the neutral beams in the yin-yang and central cell, the gas feed in the central cell, and the applied ECRH power in the barrier region were varied. The variations of the central cell beta, central cell ion density and temperature, and the confining potential are discussed. The calculations indicate that large changes in the central cell beta cannot be achieved by varying the central cell gas or neutral beams or the yin-yang beams. Changes in these beam and gas feeds have the greatest effect on the central cell ion temperature and generally degrade the central cell confinement. Increasing the ECRH power applied to the barrier region causes an improvement in the central cell confinement and a linear increase (with applied power) of the central cell beta.

Jong, R. A.

1981-09-01

361

Radioactivity Confinement Studies Within the SEAL Program  

NASA Astrophysics Data System (ADS)

In the framework of the European SEAL program, investigations have been performed with the aim of optimizing the second confinement function and plant layout with respect to normal operation as well as abnormal operation, including accident conditions. This has been done for two conceptual fusion reactor designs: one using water as the coolant and the other using helium. The starting point of these investigations was the SEAFP project design. For the water-cooled reactor design the studies were focused on design options such as pressure suppression spray system, pressure suppression pool with closed containment or with venting to gravel bed filter and stack, and separate expansion volume optionally operated with a vacuum and equipped with spray system. Similar analyses were performed for the helium-cooled reactor design. The analyses were focused on design options comprising a single, large confinement volume or a vent duct connected to an expansion volume operated at vacuum in comparison with the SEAFP Model 1. The thermal-hydraulic analyses performed with the MELCOR code provide an integrated assessment of the cooling loop and confinement system dynamics.

Collén, Jan; Matsugu, Ron; Natalizio, Antonio; Shen, Kecheng

1997-09-01

362

Monte Carlo simulations of supercoiled DNAs confined to a plane.  

PubMed

Recent advances in atomic force microscopy (AFM) have enabled researchers to obtain images of supercoiled DNAs deposited on mica surfaces in buffered aqueous milieux. Confining a supercoiled DNA to a plane greatly restricts its configurational freedom, and could conceivably alter certain structural properties, such as its twist and writhe. A program that was originally written to perform Monte Carlo simulations of supercoiled DNAs in solution was modified to include a surface potential. This potential flattens the DNAs to simulate the effect of deposition on a surface. We have simulated transfers of a 3760-basepair supercoiled DNA from solution to a surface in both 161 and 10 mM ionic strength. In both cases, the geometric and thermodynamic properties of the supercoiled DNAs on the surface differ significantly from the corresponding quantities in solution. At 161 mM ionic strength, the writhe/twist ratio is 1.20-1.33 times larger for DNAs on the surface than for DNAs in solution and significant differences in the radii of gyration are also observed. Simulated surface structures in 161 mM ionic strength closely resemble those observed by AFM. Simulated surface structures in 10 mM ionic strength are similar to a minority of the structures observed by AFM, but differ from the majority of such structures for unknown reasons. In 161 mM ionic strength, the internal energy (excluding the surface potential) decreases substantially as the DNA is confined to the surface. Evidently, supercoiled DNAs in solution are typically deformed farther from the minimum energy configuration than are the corresponding surface-confined DNAs. Nevertheless, the work (Delta A(int)) done on the internal coordinates, which include uniform rotations at constant configuration, during the transfer is positive and 2.6-fold larger than the decrease in internal energy. The corresponding entropy change is negative, and its contribution to Delta A(int) is positive and exceeds the decrease in internal energy by 3.6 fold. The work done on the internal coordinates during the solution-to-surface transfer is directed primarily toward reducing their entropy. Evidently, the number of configurations available to the more deformed solution DNA is vastly greater than for the less deformed surface-confined DNA. PMID:11806935

Fujimoto, Bryant S; Schurr, J Michael

2002-02-01

363

Louis Riel: a case study in involuntary psychiatric confinement.  

PubMed

Louis Riel was confined against his will in insane asylums from March 6, 1876 to January 23, 1878. Psychiatrists and historians have generally interpreted his certification as an act of benevolence to Riel at a time when he was non compos mentis. However, detailed study of surviving records and manuscript sources shows that the commitment was legally suspect in a number of ways: proper signatures were lacking, pseudonyms were used, records were falsified, and so on. Moreover, while Riel was clearly a religious enthusiast with eccentric ideas, there was no proof that he was dangerous to himself or others at this time. We may thus wish to revise our interpretation of Riel's certification. It was not an act of benevolence but an illegal and unjustifiable deprivation of liberty. PMID:361197

Flanagan, T E

1978-11-01

364

Electrostatically Shielded Quantum Confined Stark Effect Inside Polar Nanostructures  

PubMed Central

The effect of electrostatic shielding of the polarization fields in nanostructures at high carrier densities is studied. A simplified analytical model, employing screened, exponentially decaying polarization potentials, localized at the edges of a QW, is introduced for the ES-shielded quantum confined Stark effect (QCSE). Wave function trapping within the Debye-length edge-potential causes blue shifting of energy levels and gradual elimination of the QCSE red-shifting with increasing carrier density. The increase in the e?h wave function overlap and the decrease of the radiative emission time are, however, delayed until the “edge-localization” energy exceeds the peak-voltage of the charged layer. Then the wave function center shifts to the middle of the QW, and behavior becomes similar to that of an unbiased square QW. Our theoretical estimates of the radiative emission time show a complete elimination of the QCSE at doping densities ?1020 cm?3, in quantitative agreement with experimental measurements.

2009-01-01

365

High Density H-Mode Discharges with Gas Fueling and Good Confinement on DIII-D  

SciTech Connect

H-mode operation at high density is an attractive regime for future reactor-grade tokamaks [1]. High density maximizes fusion power output while the high confinement of H-mode keeps the plasma energy loss below the alpha heating power. One concern though is the energy released due to individual ELMs must be kept small to protect the diverter target from excess ablation. We report on discharges in DIII-D with electron densities as high as 1.45 times the Greenwald density, n{sub GW}(10{sup 20}m{sup -3})=I{sub p}(MA)/[{pi}{sup 2}(m)], with good confinement, H{sub ITER89P}=1.9, and ELMs with energy amplitude small enough to protect the divertor. These results were achieved at low triangularity single-null divertor, {delta}{approx}0.0 with a plasma current of 1.2 MA, q{sub 95} {approx} 3-4, and moderate neutral beam heating power of 2-4 MW. The density was controlled by moderate gas puffing and private flux pumping. A typical discharge is shown in Fig. 1 where upon gas puffing the pedestal density, n{sub e,epd}, quickly rises to {approx}0.8 x n{sub GW}. The confinement initially drops with the gas puff, on a longer timescale the central density rises, peaking the profile and increasing the confinement until an MHD instability terminates the high density and high confinement phase of the discharge. In this report we describe in detail edge pedestal changes and its effect on confinement as the density is increased. We then describe peaking of the density profile that offsets degradation of the pedestal at high density and restores good confinement. Finally we describe the small benign ELMs that result at these high densities.

A.W. Leonard; T.H. Osborne; M.A. Mahdavi; M.E. Fenstermacher; C.J. Lasnier; T.W. Petrie; J.G.Watkins

2000-08-01

366

Microscopic Dynamics of Liquid Helium Confined in 1D Nanopores  

NASA Astrophysics Data System (ADS)

Recently, Toda et al. performed torsional oscillator and heat capacity measurements on liquid He^4 confined within FSM-16. This porous silica glass has 1D pores with a very narrow diameter of d = 2.8 nm. This system is an example of a 1D quantum fluid in the sense that the thermal wavelength ? is longer than the pore diameter d. Because neutron time-of-flight (ToF) spectroscopy probes elementary excitations, it can be used to study the microscopic dynamics underlying the thermodynamic properties of this 1D quantum liquid. Using the Cold Neutron Chopper Spectrometer (CNCS) at the Spallation Neutron Source (SNS), we performed the first direct measurements of the elementary excitation spectrum of liquid He^4 confined in FSM-16. Measurements were performed at full pore at temperatures T = 33, 80, 800, and 1500 mK with an elastic energy resolution of approximately 80 ?eV. We will discuss the temperature T dependence of the static structure factor S(Q), the energies ? and line widths ? of the phonon-roton spectrum, and the evidence for 2D layer modes in this system. This research was supported by NIST and employed facilities sponsored by the Scientific User Facilities Division of the US Department of Energy.

Prisk, Timothy; Sokol, Paul; Das, Narayan; Diallo, Souleymane; Wada, Nobuo; Inagaki, Shinji

2012-02-01

367

Particle and recycling control in translation, confinement, and sustainment upgrade  

SciTech Connect

Previous work in the translation, confinement, and sustainment upgrade (TCSU) device [H. Y. Guo et al., Phys. Plasmas 15, 056101 (2008)] demonstrated improved plasma parameters; higher temperature, higher poloidal magnetic field, increased current drive, and increased energy confinement, for rotating magnetic field (RMF) driven field reversed configurations (FRC) relative to the earlier TCS device. This was accomplished by improving vacuum conditions and using moderate wall heating (approx100 deg. C) and glow discharge cleaning for wall conditioning. Two new wall conditioning techniques, siliconization and titanium gettering, have been employed to further reduce impurities and control recycling. Both techniques reduced oxygen line radiation by an order of magnitude, and total radiated power by 50%, but led to little change in overall FRC performance, reinforcing the earlier conclusion that TCSU FRCs are not radiation dominated. Titanium gettering substantially reduced deuterium recycling, requiring a new method of fueling to be developed. This is the first time a FRC has been operated without using wall recycling as the primary method of fueling. The low-recycling FRCs, maintained by enhanced puff fueling, performed similarly to standard recycling fueled FRCs in terms of a key current drive parameter B{sub e}/B{sub o}mega, the ratio of maximum sustained poloidal field to applied RMF field, but better density control allowed for higher temperatures.

Grossnickle, J. A.; Vlases, G. C.; Hoffman, A. L.; Melnik, P. A.; Milroy, R. D.; Tankut, A.; Velas, K. M. [Redmond Plasma Physics Laboratory, University of Washington, 14700 NE 95th St., Suite 100, Redmond, Washington 98052 (United States)

2010-03-15

368

Bandpass Filtering of DNA Elastic Modes Using Confinement and Tension  

PubMed Central

During a variety of biological and technological processes, biopolymers are simultaneously subject to both confinement and external forces. Although significant efforts have gone into understanding the physics of polymers that are only confined, or only under tension, little work has been done to explore the effects of the interplay of force and confinement. Here, we study the combined effects of stretching and confinement on a polymer's configurational freedom. We measure the elastic response of long double-stranded DNA molecules that are partially confined to thin, nanofabricated slits. We account for the data through a model in which the DNA's short-wavelength transverse elastic modes are cut off by applied force and the DNA's bending stiffness, whereas long-wavelength modes are cut off by confinement. Thus, we show that confinement and stretching combine to permit tunable bandpass filtering of the elastic modes of long polymers.

Lin, Jun; Persson, Fredrik; Fritzsche, Joachim; Tegenfeldt, Jonas O.; Saleh, Omar A.

2012-01-01

369

Bandpass filtering of DNA elastic modes using confinement and tension.  

PubMed

During a variety of biological and technological processes, biopolymers are simultaneously subject to both confinement and external forces. Although significant efforts have gone into understanding the physics of polymers that are only confined, or only under tension, little work has been done to explore the effects of the interplay of force and confinement. Here, we study the combined effects of stretching and confinement on a polymer's configurational freedom. We measure the elastic response of long double-stranded DNA molecules that are partially confined to thin, nanofabricated slits. We account for the data through a model in which the DNA's short-wavelength transverse elastic modes are cut off by applied force and the DNA's bending stiffness, whereas long-wavelength modes are cut off by confinement. Thus, we show that confinement and stretching combine to permit tunable bandpass filtering of the elastic modes of long polymers. PMID:22225802

Lin, Jun; Persson, Fredrik; Fritzsche, Joachim; Tegenfeldt, Jonas O; Saleh, Omar A

2012-01-03

370

Observations on the potential confinement of a light fermion  

SciTech Connect

We consider possible dynamical models for a light fermion confined by a potential field. With the Dirac equation only Lorentz scalar confinement yields normalizable wave functions, while with the ``no pair`` variant of the Dirac equation only Lorentz vector confinement has normal Regge behavior. A systematic investigation of Regge properties and phenomenological properties is carried out, including calculations of the Isgur-Wise (IW) function. We point out that the Isgur-Wise function provides a sensitive test of confinement models. In particular, the slope of the IW function at the zero recoil point is found to be {xi}{prime}(1){congruent}{minus}0.90 for the Dirac equation with scalar confinement and {xi}{prime}(1){congruent}{minus}1.20 for the no pair equation with vector confinement. Using heavy-light meson data alone we argue against scalar confinement.

Olsson, M.G.; Veseli, S. [Department of Physics, University of Wisconsin, Madison, Wisconsin 53706 (United States); Williams, K. [Continuous Electron Beam Accelerator Facility, Newport News, Virginia 29606 (United States)]|[Physics Department, Hampton University, Hampton, Virginia 29668 (United States)

1995-05-01

371

Confinement-induced resonance in quasi-one-dimensional systems under transversely anisotropic confinement  

NASA Astrophysics Data System (ADS)

We theoretically investigate the confinement-induced resonance for quasi-one-dimensional quantum systems under transversely anisotropic confinement, using a two-body s-wave-scattering model in the zero-energy collision limit. We predict a single resonance for any transverse anisotropy, whose position shows a slight downshift with increasing anisotropy. We compare our prediction with the recent experimental result by Haller [Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.104.153203 104, 153203 (2010)], in which two resonances are observed in the presence of transverse anisotropy. The discrepancy between theory and experiment remains to be resolved.

Peng, Shi-Guo; Bohloul, Seyyed S.; Liu, Xia-Ji; Hu, Hui; Drummond, Peter D.

2010-12-01

372

Fabrication of large curvature microlens array using confined laser swelling method.  

PubMed

This Letter proposes a confined laser swelling method to fabricate large curvature microlens arrays. Unlike the polymers in conventional free laser swelling, the swelling polymer, which is methyl red-doped polymethyl methacrylate here, is confined between walls formed by a substrate and a flexible cover layer. Because swelling occurs in an enclosed space, decomposed segments remain in the matrix, resulting in a large hump at the side of the flexible cover layer. The results show that these humps are tens of times higher than those acquired by conventional methods and this method has potential for high efficiency large curvature microlens fabrication. PMID:24104643

Shao, Jinyou; Ding, Yucheng; Zhai, Haipeng; Hu, Bing; Li, Xiangming; Tian, Hongmiao

2013-08-15

373

Unusual ceria dispersion formed in confined space: a stable and reusable adsorbent for aromatic sulfur capture.  

PubMed

An unusual ceria dispersion was achieved by using the confined space between template and silica walls in as-prepared mesoporous silica, for the first time. The new adsorbents exhibit high adsorptive desulfurization activity and, more importantly, excellent stability and reusability, which is impossible to realize with conventional adsorbents. PMID:22895488

Yin, Yu; Xue, Ding-Ming; Liu, Xiao-Qin; Xu, Ge; Ye, Peng; Wu, Mei-Yan; Sun, Lin-Bing

2012-10-01

374

Inertial Confinement Fusion quarterly report, April--June 1995. Volume 5, No. 3  

SciTech Connect

The ICF Quarterly Reports is published four times each fiscal year by the Inertial Confinement Fusion Program at the Lawrence Livermore National Laboratory. The journal reports selected current research within the ICF Program. Major areas of investigation presented here include fusion target theory and design, target fabrication, target experiments, and laser and optical science and technology.

NONE

1995-12-31

375

Numerical computation of buoyant airflows confined to attic spaces under opposing hot and cold wall conditions  

Microsoft Academic Search

The present paper addresses laminar natural convection of air confined to an isosceles triangular cavity representative of conventional attic spaces in houses and buildings with pitched roofs and horizontal suspended ceilings. Detailed experimental data in terms of velocities, temperatures and wall heat fluxes has become available for attic spaces under summer and winter conditions some time ago. However, the comparison

El Hassan Ridouane; Antonio Campo; Matthew McGarry

2005-01-01

376

Observation of thickness quantization in liquid films confined to molecular dimension  

Microsoft Academic Search

Liquid octamethylcyclotetrasiloxane (OMCTS) films have been prepared between two flat silicon substrates with varying nanometer-sized gaps which correspond to two to three molecular diameters of OMCTS. These extremely confined liquid films have been investigated using X-ray scattering methods as a function of applied pressure, in particular by observing the specular reflectivity and the diffuse scattering. For the first time, scattering

O. H. Seeck; Hyunjung Kim; D. R. Lee; D. Shu; I. D. Kaendler; J. K. Basu; S. K. Sinha

2002-01-01

377

Technical risks and R and D requirements for inertial confinement fusion. Volume 2. Final report  

Microsoft Academic Search

If the technology breakthroughs and\\/or inventions identified in this preliminary analysis occur in a timely manner, an aggressive R and D program may allow commercial demonstration of confinement fusion within 30 years. Using an innovative interview methodology analysts have mapped out near-term and long-term R and D requirements for ICF to become a viable energy source.

T. J. McCarville; J. D. Gordon; S. L. Salem; J. A. Maniscalco; D. H. Berwald; A. Sicherman; R. B. Kulkarni; R. N. Cherdack; K. C. Lee

1985-01-01

378

Sufficient Condition for Confinement of Static Quarks by a Vortex Condensation Mechanism.  

National Technical Information Service (NTIS)

We derive a sufficient condition for confinement of static quarks by a vortex condensation mechanism. It admits vortices that are thick at all times at the cost of constraining them to a finite volume lambda i whose complement is not simply connected. The...

G. Mack V. B. Petkova

1978-01-01

379

Civilian Applications of Particle-Beam-Initiated Inertial Confinement Fusion Technology.  

National Technical Information Service (NTIS)

Electrical power generation by controlled fusion may provide a partial solution to the world's long-term energy supply problem. Achievement of a fusion reaction requires the confinement of an extremely hot plasma for a time long enough to allow fuel burnu...

S. G. Varnado J. L. Mitchiner

1977-01-01

380

Confinement of multiply charged ions in an electron cyclotron resonance heated mirror plasma  

Microsoft Academic Search

Multiply charged ions are studied in the Constance B quadrupole mirror experiment (Phys. Rev. Lett. {bold 59}, 1821 (1987)) in order to better understand the ion physics of electron cyclotron resonance (ECR) high charge-state ion sources. By measuring the ion densities and end loss fluxes, the parallel confinement times for the first five charge states of oxygen plasmas are determined.

C. C. Petty; D. L. Goodman; D. L. Smatlak; D. K. Smith

1991-01-01

381

Confinement of multiply charged ions in an electron cyclotron resonance heated mirror plasma  

Microsoft Academic Search

Multiply charged ions are studied in the Constance B quadrupole mirror experiment [Phys. Rev. Lett. 59, 1821 (1987)] in order to better understand the ion physics of electron cyclotron resonance (ECR) high charge-state ion sources. By measuring the ion densities and end loss fluxes, the parallel confinement times for the first five charge states of oxygen plasmas are determined. The

C. C. Petty; D. L. Goodman; D. L. Smatlak; D. K. Smith

1991-01-01

382

Device for plasma confinement and heating by high currents and nonclassical plasma transport properties  

DOEpatents

A toroidal plasma containment device having means for inducing high total plasma currents and current densities and at the same time emhanced plasma heating, strong magnetic confinement, high energy density containment, magnetic modulation, microwaveinduced heating, and diagnostic accessibility is described. (Official Gazette)

Coppi, B.; Montgomery, D.B.

1973-12-11

383

Thermodynamic Properties of Alkanes in Confined Geometries  

NASA Astrophysics Data System (ADS)

Reported are the results of two related investigations. The first is a theoretical study of the thermal response of a model differential scanning calorimeter (DSC) yielding insights into proper techniques for sample preparation, instrument calibration, and interpretation of phase transition data. This is followed by a calorimetric study of the melting and freezing behavior of cyclohexane ( rm C_6H_{12}), cyclooctane (rm C_8H_{16}), and n-octane (rm C_8H_{18 }), confined within the pore spaces of a series of porous silica glasses with mean pore radii r between 4.1 +/- 0.3 and 64 +/- 5 nm. The melting and freezing temperatures and latent heats of the pore alkanes were found to be increasingly depressed from the bulk values with decreasing pore size r. Unlike previous studies of phase transitions of confined organic substances, we have observed melting temperature depressions which are stronger than r^{ -1}. These temperature depressions can be expressed by the empirical cluster equation rm T_{m} = T_{o} - A/(r - r_{rm o}). The latent heats were found to vary approximately linearly with the inverse pore radius. The transition data from incompletely filled pores indicate that the alkanes are not layering the pore walls evenly, but are gathering as plugs at the pore necks. Studies using glasses in which the silica surface was modified using a standard derivatization technique suggest that the replacement ligands are not forming a complete monolayer. We have also observed cyclooctane supercools by 10-15 K below the expected freezing point, both in bulk and confined within the porous glass.

Sheehan, Joseph F., III

384

Long-Pulse Operation and High-Energy Particle Confinement Study in ICRF Heating of LHD  

SciTech Connect

Long-pulse operation and high-energy particle confinement properties were studied using ion cyclotron range of frequency (ICRF) heating for the Large Helical Device. For the minority-ion mode, ions with energies up to 500 keV were observed by concentrating the ICRF heating power near the plasma axis. The confinement of high-energy particles was studied using the power-modulation technique. This confirmed that the confinement of high-energy particles was better with the inward-shifted configuration than with the normal configuration. This behavior was the same for bulk plasma confinement. Long-pulse operation for more than 2 min was achieved during the experimental program in 2002. This was mainly due to better confinement of the helically trapped particles and accumulation of fewer impurities in the region of the plasma core, in conjunction with substantial hardware improvements. Currently, the plasma operation time is limited by an unexpected density rise due to outgassing from the chamber materials. The temperature of the local carbon plates of the divertor exceeded 400 deg, C, and a charge-coupled device camera observed the hot spots. The hot spot pattern was well explained by a calculation of the accelerated-particle orbits, and those accelerated particles came from outside the plasma near the ICRF antenna.

Mutoh, Takashi [National Institute for Fusion Science (Japan); Kumazawa, Ryuhei [National Institute for Fusion Science (Japan); Seki, Tetsuo [National Institute for Fusion Science (Japan)] (and others)

2004-07-15

385

Dynamics of laser-blow-off induced Li plume in confined geometry  

NASA Astrophysics Data System (ADS)

Dynamics of Li plasma plume created by laser-blow-off technique in air ambient is reported. Plasma plume dynamics and its optical emission are investigated in planar and confined geometries using time resolved shadowgraph imaging and optical emission spectroscopy. Significant differences in the plasma characteristics in confined geometry are quantitatively investigated by comparing the plasma parameters (temperature and density) in free expansion and confined geometry configurations. Dynamics and physical parameters of the primary as well as the reflected shock waves (in confined geometry) and their interactions with expanding plasma are briefly addressed. A large enhancement in the emission intensities of Li I 610.3 nm (2p 2P1/2, 3/2 <-- 3d 2P3/2, 5/2) and 670.8 nm (2s 2S1/2 <-- 2p 2P1/2, 3/2) is correlated with the shock wave dynamics in the two geometries. Strong self reversal in the neutral emission infers an increase in the population density of neutrals within the confined plasma plume.

Kumar, Bhupesh; Singh, R. K.; Kumar, Ajai

2013-08-01

386

Next generation laser for Inertial Confinement Fusion  

SciTech Connect

We are in the process of developing and building the ``Mercury`` laser system as the first in a series of a new generation of diode-pumped solid-state Inertial Confinement Fusion (ICF) lasers at LLNL. Mercury will be the first integrated demonstration of a scalable laser architecture compatible with advanced high energy density (HED) physics applications. Primary performance goals include 10% efficiencies at 10 Hz and a 1-10 ns pulse with 1{omega} energies of 100 J and with 2{omega}/3{omega} frequency conversion.

Marshall, C.D.; Beach, J.; Bibeau, C. [and others

1997-07-18

387

Nanofabricated cells for confined ^3He  

NASA Astrophysics Data System (ADS)

We describe methods for fabrication of Silicon-Glass and all-silicon cells with a height specified to be between 100nm and 1100nm, and with areas on the order of cm x cm. These cells need to meet different requirements, including pressure capability to 30 bar with minimal distortion, and surface roughness which can be characterized and modified as needed to alter the transport characteristics of the confined ^3He. The cells are suitable for NMR and Torsion Oscillator measurements on the superfluid phases of ^3He.

Zhelev, Nikolay; Bennett, Robert; Ilic, Rob; Parpia, Jeevak; Levitin, Lev; Casey, Andrew; Saunders, John

2013-03-01

388

Dynamics of Layering Transitions in Confined Liquids  

SciTech Connect

Multiple beam interferometry and video microscopy were used to investigate the layering transition of thin liquid films of 1-undecanol confined between atomically smooth mica surfaces. The expulsion of a molecularly thin lubricant layer was followed directly in two dimensions. Overall, the dynamics of the transition follows theoretical predictions based on two-dimensional hydrodynamics. Frequently, pockets of liquid remain trapped inside the contact area at the end of the transition. The trapped pockets undergo shape transformations to minimize elastic and interfacial energy. (c) 2000 The American Physical Society.

Mugele, F.; Salmeron, M.

2000-06-19

389

Diamond Ablators for Inertial Confinement Fusion  

SciTech Connect

Diamond has a unique combination of physical properties for the inertial confinement fusion ablator application, such as appropriate optical properties, high atomic density, high yield strength, and high thermal conductivity. Here, we present a feasible concept to fabricate diamond ablator shells. The fabrication of diamond capsules is a multi-step process, which involves diamond chemical vapor deposition on silicon mandrels followed by polishing, microfabrication of holes, and removing of the silicon mandrel by an etch process. We also discuss the pros and cons of coarse-grained optical quality and nanocrystalline chemical vapor deposition diamond films for the ablator application.

Biener, J; Mirkarimi, P B; Tringe, J W; Baker, S L; Wang, Y M; Kucheyev, S O; Teslich, N E; Wu, K J; Hamza, A V; Wild, C; Woerner, E; Koidl, P; Bruehne, K; Fecht, H

2005-06-21

390

Micromachining of inertial confinement fusion targets  

SciTech Connect

Many experiments conducted on today`s largest inertial confinement fusion drive lasers require target components with sub-millimeter dimensions, precisions of a micron or less and surface finishes measured in nanometers. For metal and plastic, techniques using direct machining with diamond tools have been developed that yield the desired parts. New techniques that will be discussed include the quick-flip locator, a magnetically held kinematic mount that has allowed the direct machining of millimeter-sized beryllium hemishells whose inside and outside surface are concentric to within 0.25 micron, and an electronic version of a tracer lathe which has produced precise azimuthal variations of less than a micron.

Gobby, P.L.; Salzer, L.J.; Day, R.D. [and others

1996-12-31

391

Confinement free energy of semiflexible polymers  

NASA Astrophysics Data System (ADS)

Using a novel scheme to compute the chemical potential of semiflexible polymers, we have measured the confinement free energy of a wormlike chain in a tube. We compare our result for the dependence of the free energy on the chain length, the persistence length and the diameter of the cylinder with the corresponding theoretical predictions based on the scaling theory of Odijk and the fluctuation theory of Helfrich. Our simulation data agree well with the exponents of the theoretically predicted power laws. We find evidence that, for long wavelengths, the mode damping assumption underlying Helfrich's theory is valid.

Dijkstra, Marjolein; Frenkel, Daan; Lekkerkerker, Henk N. W.

1993-04-01

392

Stable configurations of confined cold ionic systems.  

PubMed

The simple structures formed by charged particles confined in a harmonic potential have been investigated and the configurations of minimum potential energy were identified. For fewer than 12 particles these form polyhedrons centered on the origin. For structures with 13-22 particles one sits in the middle, for 23-26 particles two are in the interior, etc., until a third shell starts forming at 60. When the isotropy of the trap is changed, distortions and discrete phase changes are seen. These structures should correspond to ones formed in ion traps at very low temperatures PMID:11607146

Rafac, R; Schiffer, J P; Hangst, J S; Dubin, D H; Wales, D J

1991-01-15

393

Anomalous diffusion in confined turbulent convection.  

PubMed

Turbulent convection in quasi-one-dimensional geometry is studied by means of high-resolution direct numerical simulations within the framework of Rayleigh-Taylor turbulence. Geometrical confinement has dramatic effects on the dynamics of the turbulent flow, inducing a transition from superdiffusive to subdiffusive evolution of the mixing layer and arresting the growth of kinetic energy. A nonlinear diffusion model is shown to reproduce accurately the above phenomenology. The model is used to predict, without free parameters, the spatiotemporal evolution of the heat flux profile and the dependence of the Nusselt number on the Rayleigh number. PMID:23005221

Boffetta, G; De Lillo, F; Musacchio, S

2012-06-27

394

Perlite for permanent confinement of cesium  

NASA Astrophysics Data System (ADS)

We present the potential use of expanded perlite, a metastable amorphous hydrated aluminium silicate, as a permanent medium for the long-term confinement of cesium. The method requires simply a loading by mixing an aqueous cesium nitrate solution and expanded perlite at 300 K followed by densification by sintering. The formation of pollucite, CsAlSi2O6, a naturally occurring mineral phase, upon careful heat treatment is demonstrated by X-ray diffraction. Leaching tests on the resulting glass-ceramics reveal a very low Cs departure of 0.5 mg m-2 d-1.

Balencie, J.; Burger, D.; Rehspringer, J.-L.; Estournès, C.; Vilminot, S.; Richard-Plouet, M.; Boos, A.

2006-06-01

395

Effects of strength training, using a gravity-independent exercise system, performed during 110 days of simulated space station confinement  

Microsoft Academic Search

The efficacy of a resistance exercise paradigm, using a gravity-independent flywheel principle, was examined in four men subjected\\u000a to 110 days of confinement (simulation of flight of international crew on space station; SFINCSS-99). Subjects performed six\\u000a upper- and lower-body exercises (calf raise, squat, back extension, seated row, lateral shoulder raise, biceps curl) 2–3 times\\u000a weekly during the confinement. The exercise regimen

Björn A. Alkner; Hans E. Berg; Inessa Kozlovskaya; Dimitri Sayenko; Per A. Tesch

2003-01-01

396

Mechanisms for selective radial dispersion of microparticles in the transitional region of a confined turbulent round jet  

Microsoft Academic Search

The dispersion of particles of different diameters in a confined turbulent round jet is dominated by the local interactions between dispersed phase and large-scale, time dependent flow structures which populate the near-field of the jet. In this work, we address first the problem of identifying the flow structures which form in a three-dimensional, turbulent confined round jet, considering also the

Fabio Sbrizzai; Roberto Verzicco; Marco F. Pidria; Alfredo Soldati

2004-01-01

397

Initial confinement studies of ohmically heated plasmas in the Tokamak Fusion Test Reactor  

SciTech Connect

Initial operation of the Tokamak Fusion Test Reactor (TFTR) has concentrated upon confinement studies of ohmically heated hydrogen and deuterium plasmas. Total energy confinement times (tau/sub E/) are 0.1 to 0.2 s for a line-average density range (anti n/sub e/) of 1 to 2.5 x 10/sup 19/ m/sup -3/ with electron temperatures of T/sub e/(o) approx. 1.2 to 2.2 keV, ion temperatures of T/sub i/(o) approx. 0.9 to 1.5 keV, and Z/sub eff/ approx. 3. A comparison of PLT, PDX, and TFTR plasma confinement supports a dimension-cubed scaling law.

Efthimion, P.C.; Bell, M.; Blanchard, W.R.; Bretz, N.; Cecchi, J.L.; Coonrod, J.; Davis, S.; Dylla, H.F.; Fonck, R.; Furth, H.P.

1984-06-01

398

Self-Induced Oscillation for Electron-Hole Pair Confined in Quantum Dot  

SciTech Connect

We study the time-dependent (TD) phenomena of the electron-hole or electron-electron pair confined in the square quantum dot (SQD) system by computationally solving TD Schroedinger equation under the unrestricted Hartree-Fock (UHF) approach. A typical vacillation is found both in the electron and hole when the charged pair is strongly confined in the SQD while the charged particles have initially the same orbital symmetry. The FFT analysis elucidates that the transition matrix element due to the coulomb interaction involves the eigen frequency {omega} being equal to the excitation energy when the resonative vacillation appears. Thus, Coulomb potential has a potential to cause the self-induced ''Rabi'' oscillation when the charged-particle pair is confined only in the QD.

Tagawa, Tomoki; Tsubaki, Atsushi; Ishizuki, Masamu; Takeda, Kyozaburo [Department of Electrical Engineering and Bioscience, Waseda University, Tokyo 169-8555 (Japan)

2011-12-23

399

Low beta confinement in a Polywell modelled with conventional point cusp theories  

SciTech Connect

The magnetic field structure in a Polywell device is studied to understand both the physics underlying the electron confinement properties and its estimated performance compared to other cusped devices. Analytical expressions are presented for the magnetic field in addition to expressions for the point and line cusps as a function of device parameters. It is found that at small coil spacings, it is possible for the point cusp losses to dominate over the line cusp losses, leading to longer overall electron confinement. The types of single particle trajectories that can occur are analysed in the context of the magnetic field structure which results in the ability to define two general classes of trajectories, separated by a critical flux surface. Finally, an expression for the single particle confinement time is proposed and subsequently compared with simulation.

Carr, Matthew; Gummersall, David; Cornish, Scott; Khachan, Joe [Nuclear Fusion Physics Group, School of Physics A28, University of Sydney, NSW 2006 (Australia)

2011-11-15

400

Low beta confinement in a Polywell modelled with conventional point cusp theories  

NASA Astrophysics Data System (ADS)

The magnetic field structure in a Polywell device is studied to understand both the physics underlying the electron confinement properties and its estimated performance compared to other cusped devices. Analytical expressions are presented for the magnetic field in addition to expressions for the point and line cusps as a function of device parameters. It is found that at small coil spacings, it is possible for the point cusp losses to dominate over the line cusp losses, leading to longer overall electron confinement. The types of single particle trajectories that can occur are analysed in the context of the magnetic field structure which results in the ability to define two general classes of trajectories, separated by a critical flux surface. Finally, an expression for the single particle confinement time is proposed and subsequently compared with simulation.

Carr, Matthew; Gummersall, David; Cornish, Scott; Khachan, Joe

2011-11-01

401

Confinement factor and absorption loss of AlInGaN based laser diodes emitting from ultraviolet to green  

NASA Astrophysics Data System (ADS)

Confinement factor and absorption loss of AlInGaN based multiquantum well laser diodes (LDs) were investigated by numerical simulation based on a two-dimensional waveguide model. The simulation results indicate that an increased ridge height of the waveguide structure can enhance the lateral optical confinement and reduce the threshold current. For 405 nm violet LDs, the effects of p-AlGaN cladding layer composition and thickness on confinement factor and absorption loss were analyzed. The experimental results are in good agreement with the simulation analysis. Compared to violet LD, the confinement factors of 450 nm blue LD and 530 nm green LD were much lower. Using InGaN as waveguide layers that has higher refractive index than GaN will effectively enhance the optical confinement for blue and green LDs. The LDs based on nonpolar substrate allow for thick well layers and will increase the confinement factor several times. Furthermore, the confinement factor is less sensitive to alloys composition of waveguide and cladding layers, being an advantage especially important for ultraviolet and green LDs.

Zhang, L. Q.; Jiang, D. S.; Zhu, J. J.; Zhao, D. G.; Liu, Z. S.; Zhang, S. M.; Yang, H.

2009-01-01

402

Confined superadiabatic premixed flame-flow interaction  

SciTech Connect

Laminar premixed unity-Lewis number flames are studied numerically, to examine flow-flame interaction in a two-dimensional closed domain. Two opposed planar flame fronts are perturbed sinusoidally and allowed to develop by consuming premixed reactants. Combustion heat release leads to global pressure and temperature rise in the domain, due to confinement. A superadiabatic condition, with products temperature rising with distance behind the flame front, is observed due to stagnation pressure rise. Variations in tangential strain rate behind the perturbed flame fronts, due to flame curvature and heat release, result in a modified local superadiabatic temperature gradient in the products. These variations in temperature gradients are shown to determine the net local confinement-heating rate in the products, leading to corresponding deviations in products temperature, and the local reaction rate along the flame front. These observations, which are not consistent with one-dimensional superadiabatic stagnation flame behavior, are a direct result of the unrestrained unsteady nature of two-dimensional flame-flow interaction.

Najm, H.N.

1995-12-31

403

Quantum chromodynamics near the confinement limit  

SciTech Connect

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.

Quigg, C.

1985-09-01

404

The QCD Confinement Transition: Hadron Formation  

NASA Astrophysics Data System (ADS)

This document is part of Volume 23 `Relativistic Heavy Ion Physics' of Landolt-Börnstein - Group I `Elementary Particles, Nuclei and Atoms'. It contains the Section `4.3 The QCD Confinement Transition: Hadron Formation' of the Chapter `4 The Hadron-Parton Phase Transition' with the content: 4.3 The QCD Confinement Transition: Hadron Formation 4.3.1 Introduction 4.3.2 The Statistical Hadronization Model 4.3.2.1 Localized States 4.3.2.2 The Formalism: Basics 4.3.2.3 Rates of Multiparticle Channels 4.3.2.4 Interactions 4.3.2.5 High Energy Collisions 4.3.2.6 Heavy Ion Collisions 4.3.2.7 Strangeness Production 4.3.2.8 Thermalization: How Is It Achieved? 4.3.3 Quark Recombination 4.3.3.1 Parton Fragmentation and Its Limitations 4.3.3.2 The Recombination Formalism 4.3.3.2.1 Basic Theory 4.3.3.2.2 Different Implementations of Instantaneous Recombination 4.3.3.2.3 Dynamical Recombination 4.3.3.3 Connection with other Hadronization Models 4.3.3.4 Experimental Evidence for Recombination 4.3.3.4.1 Hadron Spectra and Ratios 4.3.3.4.2 Elliptic Flow 4.3.4 Summary and conclusions

Becattini, Francesco; Fries, Rainer J.

405

Photopolymerization induced phase ordering in confined regions  

NASA Astrophysics Data System (ADS)

Phase ordering in confined spaces such as stratified layers or columnar domains is of interest for a variety of optical and electronic applications. We have investigated various possibilities of creating photonic crystal structures using an optical wave interference technique subjected to holographic photopolymerization of acrylate systems blended with nematic liquid crystals or conductive crystalline polymers. Melting point depression is known to occur between acrylate monomers and polyethylene oxide or succinonitrile. During the course of photopolymerization, the increase in molecular weight of acrylate and subsequent network formation have shifted the melt point upward above the reaction temperature, which in turn drives PEO to undergo crystallization; hereafter called polymerization-induced crystallization. A variety of conditions have been investigated in the framework of phase field theory for crystallization by coupling with the extended Flory-Huggins theory for polymer blend demixing. The phenomenon of polymerization-induced crystallization during photolithography has been investigated with emphasis on the effect of intensity gradient on the emerging morphology. Additionally, crystallization in confined regions has also been explored.

Kyu, Thein; Matkar, Rushikesh

2005-03-01

406

Fire Risk Analysis for Armenian NPP Confinement  

SciTech Connect

Major fire occurred at Armenian NPP (ANPP) in October 1982 showed that fire-induced initiating events (IE) can have dominant contribution in overall risk of core damage. Probabilistic Safety Assessment study for fire-induced initiating events for ANPP was initiated in 2002. Analysis was performed for compartments fires in which could result in failure of components which are necessary for reactor cold shutdown. Analysis shows that main risk from fire at ANPP is conditioned by fire in cable tunnels 61-64. Meanwhile fire in confinement compartments don't have significant contribution to overall risk of core damage. The exception is so called 'confinement valves compartment' (room no.A-013/2) fire (more than 7.5% of CDF) in which fire could result in the loss of coolant accident with unavailability of primary makeup system, which directly leads to core damage. Detailed analysis of this problem that is common for typical WWER-440/230 reactors with no hermetic MCPs and recommendations for solution are presented in this paper. (authors)

Poghosyan, Shahen; Malkhasyan, Albert; Bznuni, Surik; Amirjanyan, Armen [Armenian Nuclear Regulatory Authority - Armgosatomnadzor (Armenia)

2006-07-01

407

Deuterium anions in inertial electrostatic confinement devices  

NASA Astrophysics Data System (ADS)

A magnetic deflection-energy analyzer and Faraday trap diagnostic have been used to make measurements of divergent deuterium anion flow in the inertial electrostatic confinement experiment at the University of Wisconsin-Madison (UW-IEC) [J. F. Santarius, G. L. Kulcinski, R. P. Ashley, D. R. Boris, B. B. Cipiti, S. K. Murali, G. R. Piefer, R. F. Radel, I. E. Radel, and A. L. Wehmeyer, Fusion Sci. Technol. 47, 1238 (2005)], a device to confine high-energy light ions in a spherically symmetric electrostatic potential well. Deuterium anion current densities as high as 8.5?A/cm2 have been measured at the wall of the UW-IEC device, 40 cm from the surface of the device cathode with a detector assembly of admittance area 0.7cm2 . Energy spectra obtained using a magnetic deflection-energy analyzer diagnostic indicate the presence of D2- , and D- ions produced through thermal electron attachment near the device cathode, as well as D- ions produced via charge-transfer processes between the anode and cathode of the device.

Boris, D. R.; Alderson, E.; Becerra, G.; Donovan, D. C.; Egle, B.; Emmert, G. A.; Garrison, L.; Kulcinski, G. L.; Santarius, J. F.; Schuff, C.; Zenobia, S. J.

2009-09-01

408

Deuterium anions in inertial electrostatic confinement devices.  

PubMed

A magnetic deflection-energy analyzer and Faraday trap diagnostic have been used to make measurements of divergent deuterium anion flow in the inertial electrostatic confinement experiment at the University of Wisconsin-Madison (UW-IEC) [J. F. Santarius, G. L. Kulcinski, R. P. Ashley, D. R. Boris, B. B. Cipiti, S. K. Murali, G. R. Piefer, R. F. Radel, I. E. Radel, and A. L. Wehmeyer, Fusion Sci. Technol. 47, 1238 (2005)], a device to confine high-energy light ions in a spherically symmetric electrostatic potential well. Deuterium anion current densities as high as 8.5 microA/cm2 have been measured at the wall of the UW-IEC device, 40 cm from the surface of the device cathode with a detector assembly of admittance area 0.7 cm2. Energy spectra obtained using a magnetic deflection-energy analyzer diagnostic indicate the presence of D2(-), and D- ions produced through thermal electron attachment near the device cathode, as well as D- ions produced via charge-transfer processes between the anode and cathode of the device. PMID:19905231

Boris, D R; Alderson, E; Becerra, G; Donovan, D C; Egle, B; Emmert, G A; Garrison, L; Kulcinski, G L; Santarius, J F; Schuff, C; Zenobia, S J

2009-09-30

409

Confined magnetic monopoles in dense QCD  

SciTech Connect

Non-Abelian strings exist in the color-flavor locked phase of dense QCD. We show that kinks appearing in the world-sheet theory on these strings, in the form of the kink-antikink bound pairs, are the magnetic monopoles-descendants of the 't Hooft-Polyakov monopoles surviving in such a special form in dense QCD. Our consideration is heavily based on analogies and inspiration coming from certain supersymmetric non-Abelian theories. This is the first ever analytic demonstration that objects unambiguously identifiable as the magnetic monopoles are native to non-Abelian Yang-Mills theories (albeit our analysis extends only to the phase of the monopole confinement and has nothing to say about their condensation). Technically, our demonstration becomes possible due to the fact that low-energy dynamics of the non-Abelian strings in dense QCD is that of the orientational zero modes. It is described by an effective two-dimensional CP(2) model on the string world sheet. The kinks in this model representing confined magnetic monopoles are in a highly quantum regime.

Gorsky, A. [Theory Department, Institute for Theoretical and Experimental Physics, Moscow (Russian Federation); William I. Fine Theoretical Physics Institute, University of Minnesota, Minneapolis, Minnesota 55455 (United States); Shifman, M. [William I. Fine Theoretical Physics Institute, University of Minnesota, Minneapolis, Minnesota 55455 (United States); Center for Theoretical Physics, Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Yung, A. [William I. Fine Theoretical Physics Institute, University of Minnesota, Minneapolis, Minnesota 55455 (United States); Petersburg Nuclear Physics Institute, Gatchina, St. Petersburg 188300 (Russian Federation)

2011-04-15

410

Density of States Simulations of Confined Glasses  

NASA Astrophysics Data System (ADS)

Glassy systems under confinement have been studied with great enthusiasm and effort for the last decades. They are relevant both fundamentally and technically because there is still debate about the nature of glass transition in small geometries which is important for lithographic processes in the semiconductor and other industries. In this work we are using the Wang-Landau approach also known as Density of States Monte Carlo to study glassy systems in bulk and under confinement. We apply the technique to a model binary Lennard Jones glass as well as the small organic glass former Ortho-terphenyl (OTP). For Lennard Jones glasses we use a well tested model. For OTP we start from a united atom model and then derive systematically a coarse grained representation by replacing each phenyl ring with a bead and using the Iterative Boltzmann Inversion. The properties of bulk Lennard Jones model show very good agreement with literature values. The atomistic and coarse grained representations of ortho-terphenyl in the bulk are in good agreement with experiments. Unsupported freestanding films show a lower glass transition than the bulk value.

Faller, Roland; Ghosh, Jayeeta

2008-03-01

411

Rythmes Biologiques, Sommeil et Vigilance en Confinement Prolonge (Biological Rhythms, Sleep, and Wakefulness in Prolonged Confinement).  

National Technical Information Service (NTIS)

The dysynchronization of human circadian rhythms during 7 long-term (2 to 6 months) confinement experiments in temporal isolation in caves was studied. Five subjects abandon the circadian period of sleep and wakefulness (S-W) and spontaneously reach a cir...

M. Siffre

1988-01-01

412

Thermal barrier confinement experiments in TMX-U tandem mirror. Revision 1  

SciTech Connect

In our recent experiments on the TMX-U thermal-barrier device, we achieved the end plugging of axial ion losses up to a central cell density of n/sub c/ = 6 x 10/sup 12/ cm/sup -3/. During lower density experiments, we measured the axial potential profile characteristic of a thermal barrier and found an ion-confining potential greater than 1.5 kV and a potential depression of 0.45 kV in the barrier region. The average beta of hot end plug electrons has reached 15% and of hot central cell ions has reached 6%. In addition, we heated deuterium ions in the central cell with ICRF to an average perpendicular energy of 2 keV. During strong end plugging at low density (7 x 10/sup 11/ cm/sup -3/), the axial ion confinement time tau/sub parallel to/ reached 50 to 100 ms while the nonambiopolar radial ion confinement time tau/sub perpendicular to/ was 14 ms - independent of end plugging. Electrically floating end walls doubled the radial ion confinement time. At higher densities and lower potentials, tau/sub parallel to/ was 6 to 12 ms and tau/sub perpendicular to/ exceeded 100 ms.

Simonen, T.C.; Allen, S.L.; Baldwin, D.E.; Casper, T.A.; Clauser, J.F.; Coensgen, F.H.; Cohen, R.H.; Correll, D.L.; Cummins, W.F.; Damm, C.C.

1984-07-26

413

Viscous nonpolar liquids in confinement studied by mechanical solvation  

NASA Astrophysics Data System (ADS)

Using surface selective triplet state solvation techniques, we study the relaxation behavior of nonpolar liquids near their glass transition in confinement to porous glass with 4 nm pore diameter. As specific liquid-surface interactions are not expected for alkanes, we ask whether a substantial frustration of the dynamics is a general phenomenon for such liquids, and how the effects change with surface silanization. We find that interfacial dynamics display relaxation times that are increased by orders of magnitude for several nonpolar molecular liquids. Silanization removes this frustration effect almost entirely. Regarding the comparison of native versus silanized pore surfaces, it is concluded that the strong adhesive forces involved in alkanes wetting silica can explain the sluggish interfacial dynamics. The findings are not consistent with finite size effects.

Wen, Wen; Richert, Ranko

2009-08-01

414

Development of Compton radiography of inertial confinement fusion implosions  

SciTech Connect

An important diagnostic tool for inertial confinement fusion will be time-resolved radiographic imaging of the dense cold fuel surrounding the hot spot. The measurement technique is based on point-projection radiography at photon energies from 60 to 200 keV where the Compton effect is the dominant contributor to the opacity of the fuel or pusher. We have successfully applied this novel Compton radiography technique to the study of the final compression of directly driven plastic capsules at the OMEGA facility [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)]. The radiographs have a spatial and temporal resolution of {approx}10 {mu}m and {approx}10 ps, respectively. A statistical accuracy of {approx}0.5% in transmission per resolution element is achieved, allowing localized measurements of areal mass densities to 7% accuracy. The experimental results show 3D nonuniformities and lower than 1D expected areal densities attributed to drive asymmetries and hydroinstabilities.

Tommasini, R.; Hatchett, S. P.; Hey, D. S.; Iglesias, C.; Izumi, N.; Koch, J. A.; Landen, O. L.; MacKinnon, A. J.; Sorce, C. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States); Delettrez, J. A.; Glebov, V. Yu.; Sangster, T. C.; Stoeckl, C. [Laboratory of Laser Energetics, Rochester, New York 14623-1299 (United States)

2011-05-15

415

Temperature measurements on a HSLA-100 steel confinement vessel  

SciTech Connect

Temperature measurements have been made on HSLA-100 steel confinement vessel number 6-2-3-1. These measurements are intended to give a view of the vessel temperature response under conditions similar to operational conditions, starting from worst case. The vessel`s temperature must be above the minimum operating temperature when used to contain an explosive event to ensure that the vessel material has the desired crack arrest properties. Several series of temperature measurements have been conducted over 24 and 48 hour periods during February 1998. These tests were intended to demonstrate that after running the heaters in the environmental shelter for some time, (1) the vessel warms up to temperatures well above the minimum operating temperature, (2) that through-thickness temperature gradients are negligible, and (3) that the temperature differences from one part of the vessel to another are small.

Lohsen, R.A.

1998-05-07

416

Tertiary proton diagnostics in future inertial confinement fusion experiments  

SciTech Connect

Recently, it was proposed to use energetic (up to 31 MeV) tertiary protons produced during the final stage of inertial confinement fusion implosions to measure the fuel areal density of compressed deuterium{endash}tritium (DT). The method is based on seeding the fuel with {sup 3}He. The reaction of {sup 3}He ions with the energetic knock-on deuterons, produced via the elastic scattering of 14.1 MeV neutrons, is a source of very energetic protons capable of escaping from very large areal density targets. This work presents results of detailed time-dependent Monte Carlo simulations of the nuclear processes involved in producing and transporting these protons through imploding targets proposed for direct-drive experiments on OMEGA [D. K. Bradley {ital et al.}, Phys. Plasmas {bold 5}, 1870 (1998)] and the National Ignition Facility [S. W. Haan {ital et al.}, Phys. Plasmas {bold 2}, 2480 (1995)]. {copyright} {ital 1998 American Institute of Physics.}

Cremer, S.; Verdon, C.P. [Laboratory For Laser Energetics, University of Rochester, 250 East River Road, Rochester, New York 14623-1299 (United States); Petrasso, R.D. [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

1998-11-01

417

Tertiary proton diagnostics in future inertial confinement fusion experiments  

NASA Astrophysics Data System (ADS)

Recently, it was proposed to use energetic (up to 31 MeV) tertiary protons produced during the final stage of inertial confinement fusion implosions to measure the fuel areal density of compressed deuterium-tritium (DT). The method is based on seeding the fuel with 3He. The reaction of 3He ions with the energetic knock-on deuterons, produced via the elastic scattering of 14.1 MeV neutrons, is a source of very energetic protons capable of escaping from very large areal density targets. This work presents results of detailed time-dependent Monte Carlo simulations of the nuclear processes involved in producing and transporting these protons through imploding targets proposed for direct-drive experiments on OMEGA [D. K. Bradley et al., Phys. Plasmas 5, 1870 (1998)] and the National Ignition Facility [S. W. Haan et al., Phys. Plasmas 2, 2480 (1995)].

Cremer, S.; Verdon, C. P.; Petrasso, R. D.

1998-11-01

418

Studies of plasma confinement in linear and RACETRACK mirror configurations  

SciTech Connect

During the period from November 1988 through April 1989 the experimental plasma physics program at UCLA produced several new results. The experiments were conducted on the toroidal RACETRACK device. Generation of a steady-state high-beta field-reversed configuration in one of the straight sections by the rotating electromagnetic wave technique is now routine and because of understanding gained in the course of experiments we succeeded in extending the range of operation was extended. The pressure balance relation was verified by independent pressure and magnetic field measurements for this field reversed-configuration. Studies of the equilibrium have been extended to spatial and temporal decay of the confining diamagnetic current. It has been observed, that the current decays on the resistive time scale due to electron-ion coulomb collisions. Current injection was also used to study the effects of mirror fields on toroidal currents and to reduce the neutral gas pressure for a given plasma density.

Kuthi, A.; Wong, A.Y.

1989-05-28

419

Sequential detection of temporal communities by estrangement confinement  

NASA Astrophysics Data System (ADS)

Temporal communities are the result of a consistent partitioning of nodes across multiple snapshots of an evolving network, and they provide insights into how dense clusters in a network emerge, combine, split and decay over time. To reliably detect temporal communities we need to not only find a good community partition in a given snapshot but also ensure that it bears some similarity to the partition(s) found in the previous snapshot(s), a particularly difficult task given the extreme sensitivity of community structure yielded by current methods to changes in the network structure. Here, motivated by the inertia of inter-node relationships, we present a new measure of partition distance called estrangement, and show that constraining estrangement enables one to find meaningful temporal communities at various degrees of temporal smoothness in diverse real-world datasets. Estrangement confinement thus provides a principled approach to uncovering temporal communities in evolving networks.

Kawadia, Vikas; Sreenivasan, Sameet

2012-11-01

420

Development of Compton Radiography Diagnostics for Inertial Confinement Fusion Implosions  

SciTech Connect

An important diagnostic tool for inertial confinement fusion will be time-resolved radiographic imaging of the dense cold fuel surrounding the hot spot. The measurement technique is based on point-projection radiography at photon energies from 60-200 keV where the Compton effect is the dominant contributor to the opacity of the fuel or pusher. We have successfully applied this novel Compton Radiography technique to the study of the final compression of directly driven plastic capsules at the OMEGA facility. The radiographs have a spatial and temporal resolution of {approx}10 {micro}m and {approx}10ps, respectively. A statistical accuracy of {approx}0.5% in transmission per resolution element is achieved, allowing localized measurements of areal mass densities to 7% accuracy. The experimental results show 3D non-uniformities and lower than 1D expected areal densities attributed to drive asymmetries and hydroinstabilities.

Tommasini, R; Hatchett, S P; Hey, D S; Izumi, N; Koch, J A; Landen, O L; Mackinnon, A J; Delettrez, J; Glebov, V; Stoeckl, C

2010-11-16

421

Multichannel effects near confinement-induced resonances in harmonic waveguides  

SciTech Connect

We analyze the impact of multichannel scattering in harmonic waveguides on the positions and widths of confinement-induced resonances for both isotropic and anisotropic transversal confinement. Multichannel scattering amplitudes and transmission coefficients are calculated and used to characterize the resonant behavior of atomic collisions with varying anisotropy. A mechanism is established which leads to a splitting of the confinement-induced resonance in the presence of anisotropy.

Melezhik, Vladimir S. [Bogoliubov Laboratory of Theoretical Physics, Joint Institute for Nuclear Research, Dubna, 141980 Dubna (Russian Federation); Schmelcher, Peter [Zentrum fuer Optische Quantentechnologien,Universitaet Hamburg, Luruper Chaussee 149, D-22761 Hamburg (Germany)

2011-10-15

422

Pure Mott phases in confined ultra-cold atomic systems  

Microsoft Academic Search

We propose a novel scheme for confining atoms to optical lattices by engineering a spatially-inhomogeneous hopping matrix element in the Hubbard-model (HM) description, a situation we term off-diagonal confinement (ODC). We show, via an exact numerical solution of the boson HM with ODC, that this scheme possesses distinct advantages over the conventional method of confining atoms using an additional trapping

Valery Rousseau; George Batrouni; Daniel Sheehy; Juana Moreno; Mark Jarrell

2010-01-01

423

Confinement in Yang Mills: Elements of a Big Picture  

SciTech Connect

We present a nontechnical review of the current understanding of the phenomenon of color confinement. The emphasis is put on recent advances. This is a combined and slightly expanded version of talks delivered at 14th International QCD Conference 'QCD 08,' 7-12th July 2008, Montpellier, France, the International Conference 'Quark Confinement and the Hadron Spectrum,' Mainz, Germany, September 1-6, 2008 (Confinement 08), and the International Conference 'Approaches to Quantum Chromodynamics,' Oberwoelz, Austria, September 7-13, 2008.

Shifman, M.; /Minnesota U., Theor. Phys. Inst. /Saclay, SPhT; Unsal, Mithat; /SLAC /Stanford U., Phys. Dept.

2008-10-22

424

Simulation of Spheromak Evolution and Energy Confinement  

NASA Astrophysics Data System (ADS)

Electron temperatures near 400 eV were observed transiently in the Los Alamos CTX spheromak experiment.[1] Temperatures of 100-200 eV have been observed in the SSPX spheromak.[2] Understanding the energy confinement in these experiments is a challenging problem. Results from numerical simulations with the NIMROD nonlinear resistive MHD code (at zero or finite plasma pressure) have shown that closed flux surfaces with net current can arise only after electrostatic drive is reduced.[3,4] Computations in the last year have directly investigated the importance of inductive effects on energy confinement including the evolution of the temperature and number density using thermal transport coefficients, electrical resistivity, and Ohmic heating that are appropriate for collisional plasmas. In conditions with sustained coaxial electrostatic drive, the cold edge plasma impedes parallel thermal conduction to the wall, despite the chaotic magnetic topology, allowing the plasma core temperature to reach tens of eVs. When the drive is temporarily removed, relatively symmetric closed flux surfaces form. Magnetic reconnection occurs rapidly in the cold outer plasma, and core temperatures increase toward 100 eV or more. Applying a second current pulse, as in some SSPX discharges,[5] is shown to improve performance by delaying the onset of MHD modes that are resonant in the closed-flux region, and higher current, increased magnetic fields, and larger volumes of closed flux can be achieved. The simulations reveal the sensitivity with respect to symmetry-breaking magnetic fluctuations of the magnetic surfaces and the energy confinement. We present a detailed comparison of results from nonlinear simulations with laboratory measurements from SSPX[5,6] and assess transport mechanisms through computational diagnostics. The simulation results are yielding electron temperatures and other features agreeing well with SSPX observations. [1] T. R. Jarboe, Plasma Phys. Control. Fusion 36, 945 (1994). [2] H. S. McLean, et al., Phys. Rev. Lett. 88, 125004 (2002); H.S. McLean, S. Woodruff, D.N. Hill, et al., 30th EPS Conference on Controlled Fusion and Plasma Physics, Saint Petersburg, Russia, July 7-11 2003. Europhysics conference abstracts, 27A, p3/230. http://epsppd.epfl.ch/StPetersburg/PDF/P3-230. [3] C. R. Sovinec, J. M. Finn, D. del-Castillo-Negrete, Phys. Plasmas 8, 475 (2001). [4] R.H. Cohen, H.L. Berk, B.I. Cohen, et al., Nucl. Fusion 43, 1220 (2003). [5] S. Woodruff, et al., submitted to Phys. Rev. Lett. [6] S. Woodruff, D. N. Hill, et al., Phys. Rev. Lett. 90, 95001(2003).

Cohen, Bruce I.

2004-11-01

425

Confinement dynamics of a semiflexible chain inside nano-spheres  

NASA Astrophysics Data System (ADS)

We study the conformations of a semiflexible chain, confined in nano-scaled spherical cavities, under two distinct processes of confinement. Radial contraction and packaging are employed as two confining procedures. The former method is performed by gradually decreasing the diameter of a spherical shell which envelopes a confined chain. The latter procedure is carried out by injecting the chain inside a spherical shell through a hole on the shell surface. The chain is modeled with a rigid body molecular dynamics simulation and its parameters are adjusted to DNA base-pair elasticity. Directional order parameter is employed to analyze and compare the confined chain and the conformations of the chain for two different sizes of the spheres are studied in both procedures. It is shown that for the confined chains in the sphere sizes of our study, they appear in spiral or tennis-ball structures, and the tennis-ball structure is more likely to be observed in more compact confinements. Our results also show that the dynamical procedure of confinement and the rate of the confinement are influential parameters of the structure of the chain inside spherical cavities.

Fathizadeh, A.; Heidari, Maziar; Eslami-Mossallam, B.; Ejtehadi, M. R.

2013-07-01

426

Hydration structure of water confined between mica surfaces  

NASA Astrophysics Data System (ADS)

We report further molecular dynamics simulations on the structure of bound hydration layers under extreme confinement between mica surfaces. We find that the liquid phase of water is maintained down to 2 monolayer (ML) thick, whereas the structure of the K+ ion hydration shell is close to the bulk structure even under D=0.92 nm confinement. Unexpectedly, the density of confined water remains approximately the bulk value or less, whereas the diffusion of water molecules decreases dramatically. Further increase in confinement leads to a transition to a bilayer ice, whose density is much less than that of ice Ih due to the formation of a specific hydrogen-bonding network.

Leng, Yongsheng; Cummings, Peter T.

2006-02-01

427

Aging and stiction dynamics in confined films of a star polymer melt.  

PubMed

The stiction properties of a star polyisoprene (PIP) melt (having 22 arms and an arm molecular weight of around 5000, M(w) ? 110,000) confined between mica surfaces were investigated using the surface forces apparatus. Stop-start experiments were carried out and the stiction spike was measured as a function of surface stopping (aging) time t and applied pressure P; the time constants of the phase transitions in the stiction dynamics (freezing on stopping and melting on starting) were obtained from the force relaxation behaviors. The results were compared with those of a confined linear-PIP melt (M(w) ? 48,000) and other confined fluid systems; the effect of star architecture on the phase transitions in confinement during aging is discussed. Estimation of the molecular size gives that the confined star-PIP films consist of three molecular layers; a non-adsorbed layer sandwiched between two layers adsorbed on opposed mica surfaces. There are (at least) four time constants in the freezing transition of the confined star-PIP melt; fast (?(1)) and slow (?(2)) time constants for lateral force relaxation on stopping, critical aging time for freezing (?(f)), and the logarithmic increase of the spike height against t. The three time constants on stopping, ?(1), ?(2), and ?(f), increase with the increase of P (decrease of the thickness D). As regards the melting transition on starting, spike force decay was fitted by a single exponential function and one time constant was obtained, which is insensitive to P (D). Comparison of the time constants between freezing and melting, and also with the results of linear-PIP reveals that the stiction dynamics of the star-PIP system involves the relaxation and rearrangement of segmental-level and whole molecular motions. Lateral force relaxation on stopping is governed by the individual and cooperative rearrangements of local PIP segments and chain ends of the star, which do not directly lead to the freezing of the system. Instead, geometrical rearrangements of the soft star-PIP spheres into dense packing between surfaces (analogous to the concept of a colloidal glass transition) are the major mechanism of the freezing transition (stiction) after aging. Interdigitation of PIP segments/chain ends between neighboring star molecules also contributes to the spike growth along with aging, and the melting transition on starting. PMID:23181327

Yamada, Shinji

2012-11-21

428

Relation between growth procedure and confinement properties of CdSe\\/ZnSe quantum dots  

Microsoft Academic Search

The influence of the growth conditions of CdSe\\/ZnSe quantum structures on the confinement properties are systematically investigated by time integrated and time resolved photoluminescence. Three samples grown on GaAs (001) by molecular beam epitaxy consisting of three CdSe monolayers embedded between two 40nm ZnSe barriers are studied. We focus on the influence of the treatment performed after the growth of

Ivan-Christophe Robin; Régis André; Jean-Michel Gérard

2006-01-01

429

a Quark-Independent Description of Confinement  

NASA Astrophysics Data System (ADS)

Currently the quantitative description of confinement inside nuclear matter is exclusively limited to computer experiments, mainly on lattices, and concentrating upon calculating the static potential. There is no independent reference for comparison and support of the results, especially when it comes to the quark potential in the continuum limit. Yet, we are entitled to be optimistic, for the basic results of these calculations seem to be correct from an entirely different point of view, suggested by Manton's geometrization of Skyrme theory. The present work shows the reasons of this point of view, and offers a static potential that might serve as independent reference for comparison and endorsement of any lattice calculations, and in fact of any structural hypotheses of nuclear matter. A historical review of the pertinent key moments in the history of modeling of nuclear matter, as well as an outlook anticipating the necessary future work, close the argument.

Mazilu, Nicolae; Ioannou, Pavlos D.; Diakonos, Fotios K.; Maintas, Xantis N.; Agop, Maricel

2013-09-01

430

Nonideal magnetohydrodynamic instabilities and toroidal magnetic confinement  

SciTech Connect

The marked divergence of experimentally observed plasma instability phenomena from the predictions of ideal magnetohydrodynamics led in the early 1960s to the formulations of finite-resistivity stability theory. Beginning in the 1970s, advanced plasma diagnostics have served to establish a detailed correspondence between the predictions of the finite-resistivity theory and experimental plasma behavior - particularly in the case of the resistive kink mode and the tokamak plasma. Nonlinear resistive-kink phenomena have been found to govern the transport of magnetic flux and plasma energy in the reversed-field pinch. The other predicted finite-resistivity instability modes have been more difficult to identify directly and their implications for toroidal magnetic confinement are still unresolved.

Furth, H.P.

1985-05-01

431

Inertial confinement fusion - Review and perspective  

NASA Astrophysics Data System (ADS)

Inertial confinement fusion (ICF) research from 1972 through 1983 is reviewed. Three elements, constructed and operated economically, are necessary for an ICF power system: a driver that couples well to the target, a target design that works, and a reactor that efficiently contains and converts fusion energy and controls hazardous materials. Topics considered include light- and heavy-ion drivers, KrF lasers, particle-beam deposition, hohlraum targets, direct-drive, and direct-implosion. Heavy-ion beams have a favorable efficiency rating and are considered a more likely long-term prospect for ICF power. Attention is also given to short-wavelength lasers and their hydrodynamic efficiencies, transport inhibition, attainable target gain and Nova experiments, and the cost of ICF plants. A four-reactor site using one driver to produce 4 GW of electric power could be economically competitive.

Johnson, T. H.

1984-05-01

432

Lesions Confined to the Sphenoid Ridge  

PubMed Central

Tumors confined to the sphenoid ridge with little or no extradiploic extension are very rare; we describe here five patients with these lesions. Three were females and two males, with an average age of 33.4 years; the clinical presentation included proptosis and facial deformity. The diagnoses were three meningiomas (one “en plaque,” one globous, and one intraosseous) and two fibrous dysplasias (compact form). Although the radiological findings were similar, we could find some details to establish the differential diagnosis before the surgical procedure. All the lesions were totally removed without complications. In a follow-up period of 15 to 36 months none of the lesions has shown clinical or radiological evidence of recurrence. We discuss the pathophysiology of each case, and propose the pterional orbito-zygomatic approach as the best way to resect lesions in this location. ImagesFigure 1Figure 2Figure 3Figure 4Figure 5Figure 6Figure 7Figure 8Figure 9

Guinto, Gerardo; Abello, Jhon; Felix, Ignacio; Gonzalez, Jose; Oviedo, Alejandro

1997-01-01

433

Surface Relaxations in Quantum Confined Pb  

SciTech Connect

The relationship between electronic and atomic structure of quantum confined objects is a key issue in nanoscience. We performed low-energy electron diffraction to determine the surface relaxations of ultrathin Pb films on Si(111)7 x 7 with thicknesses ranging from four to nine atomic layers. The results indicate a contraction of the first interlayer spacing d{sub 12} for all films. The d{sub 12} contraction exhibits a small bilayer modulation as a function of thickness, indicative of a quantum size effect. The oscillatory relaxations furthermore suggest an interesting correlation with the work function oscillations predicted from density functional theory [Wei and Chou, Phys. Rev. B 66, 233408 (2002)] and can be understood qualitatively on the basis of the jellium model.

Mans, A. [Delft University of Technology, Delft, Netherlands; Dil, J. H. [Delft University of Technology, Delft, Netherlands; Ettema, A. R. [Delft University of Technology, Delft, Netherlands; Weitering, Harm H [ORNL

2005-01-01

434

Fabrication issues of oxide-confined VCSELs  

SciTech Connect

To insert high-performance oxide-confined vertical-cavity surface- emitting lasers (VCSELs) into the manufacturing arena, we have examined the critical parameters that must be controlled to establish a repeatable and uniform wet thermal oxidation process for AlGaAs. These parameters include the AlAs mole fraction, sample temperature, carrier gas flow, and bubbler water temperature. Knowledge of these parameters has enable the compilation of oxidation rate data for AlGaAs which exhibits an Arrhenius rate dependence. The compositionally dependent activation energies for Al{sub x}Ga{sub 1-x}As layers of x=1.00, 0.98, and 0.92 are found to be 1.24, 1.75, and 1.88 eV, respectively. 7 figs, 1 tab, 14 refs.

Geib, K.M.; Choquette, K.D.; Hou, H.Q.; Hammons, B.E.

1997-04-01

435

Thermodynamics of Combustion in a Confined Explosion  

SciTech Connect

Considered here are explosions from condensed TNT charges--where the expanded detonation products gases are rich in C and CO [1]. Mixing with air causes oxidation/combustion [2], which dramatically increases the pressure in confined systems (vid. Fig. 1). We treat this as an Inverse Problem: infer fuel consumption from the measured pressure P {triple_bond} {bar p}(t)/p{sub i}. The Model expounded here represents a valuable tool for extracting the evolution of combustion system from a readily measurable quantity (pressure). The Model establishes the fuel consumption history as well as the evolution of thermodynamic solution (specific volumes, energies and densities) of the components that will generate the observed pressure profile. This solution in Thermodynamic (State) Space provides extraordinarily clear insight into the combustion process, which is normally clouded by a myriad of transport processes that occur in physical space.

Kuhl, A.L.; Oppenheim, A.K.; Ferguson, R.E.

2000-02-05

436

Greater confinement disposal of radioactive wastes  

SciTech Connect

Low-level radioactive waste (LLW) includes a broad spectrum of different radionuclide concentrations, half-lives, and hazards. Standard shallow-land burial practice can provide adequate protection of public health and safety for most LLW. A small volume fraction (approx. 1%) containing most of the activity inventory (approx. 90%) requires specific measures known as greater-confinement disposal (GCD). Different site characteristics and different waste characteristics - such as high radionuclide concentrations, long radionuclide half-lives, high radionuclide mobility, and physical or chemical characteristics that present exceptional hazards - lead to different GCD facility design requirements. Facility design alternatives considered for GCD include the augered shaft, deep trench, engineered structure, hydrofracture, improved waste form, and high-integrity container. Selection of an appropriate design must also consider the interplay between basic risk limits for protection of public health and safety, performance characteristics and objectives, costs, waste-acceptance criteria, waste characteristics, and site characteristics.

Trevorrow, L.E.; Gilbert, T.L.; Luner, C.; Merry-Libby, P.A.; Meshkov, N.K.; Yu, C.

1985-01-01

437

Planning for greater-confinement disposal  

SciTech Connect

This contribution is a progress report for preparation of a document that will summarize procedures and technical information needed to plan for and implement greater-confinement disposal (GCD) of low-level radioactive waste. Selection of a site and a facility design (Phase I), and construction, operation, and extended care (Phase II) will be covered in the document. This progress report is limited to Phase I. Phase I includes determination of the need for GCD, design alternatives, and selection of a site and facility design. Alternative designs considered are augered shafts, deep trenches, engineered structures, high-integrity containers, hydrofracture, and improved waste form. Design considerations and specifications, performance elements, cost elements, and comparative advantages and disadvantages of the different designs are covered. Procedures are discussed for establishing overall performance objectives and waste-acceptance criteria, and for comparative assessment of the performance and cost of the different alternatives. 16 references.

Gilbert, T.L.; Luner, C.; Meshkov, N.K.; Trevorrow, L.E.; Yu, C.

1984-01-01

438

Light ion driven inertial confinement fusion  

SciTech Connect

Intense light ion beams are being developed to drive inertial confinement fusion (ICF) targets. Recently, intense proton beams have been used to drive two different types of targets in experiments on the Particle Beam Fusion Accelerator. The experiments focused separately on ion deposition physics and on implosion hydrodynamics. In the ion deposition physics experiments, a 3--4 TW/cm{sup 2} proton beam heated a low-density foam contained within a gold cylinder with a specific power deposition exceeding 100 TW/gm for investigating ion deposition, foam heating, and generation of x-rays. The significant results from these experiments included the following: the foam provided an optically thin radiating region, the uniformity of radiation across the foam was good, and the foam tamped the gold case, holding it in its original position for the 15 ns beam pulse width.

Cook, D.L.; Adams, R.G.; Aubert, J.H.; Bacon, L.D.; Bailey, J.E.; Bloomquist, D.D.; Boyes, J.D.; Chandler, G.A.; Coats, R.S.; Corley, J.P.; Crow, J.T.; Cuneo, M.E.; Derzon, D.K.; Derzon, M.S.; Desjarlais, M.P.; Dukart, R.J.; Fehl, D.L.; Filuk, A.B.; Gerber, R.A.; Haill, T.A.; Hanson, D.L.; Humphreys, D.R.; Hussey, T.W.; Ives, H.L.; Johnson, D.J.; Johnson, D.L.; Leeper, R.J.; Lemke, R.W.; Lockner, T.R.; Maenchen, J.E.; Matzen, M.K.; McDaniel, D.H.; McKay, P.F.; McGuire, E.J.; Mehlhorn, T.A.; Mendel, C.W.; Mix, L.P.; Nelson, W.E.; Olson, C.L.; Olson, R.E.; Pointon, T.D.; Poukey, J.W.; Quintenz, J.P.; Ramirez, J.J.; Renk, T.J.; Rochau, G.E.; Rockett, P.D.; Rosenthal, S.E.; Rovang, D.C.; Ruiz, C.L.; Schmitt, D.R.; Seidel, D.B.; Slutz, S.A.; Stinnett, R.W.; Stygar, W.A.; Sweeney, M.A.; Tisone, G.C.; VanDevender, J.P.

1992-05-01

439

Light ion driven inertial confinement fusion  

SciTech Connect

Intense light ion beams are being developed to drive inertial confinement fusion (ICF) targets. Recently, intense proton beams have been used to drive two different types of targets in experiments on the Particle Beam Fusion Accelerator. The experiments focused separately on ion deposition physics and on implosion hydrodynamics. In the ion deposition physics experiments, a 3--4 TW/cm{sup 2} proton beam heated a low-density foam contained within a gold cylinder with a specific power deposition exceeding 100 TW/gm for investigating ion deposition, foam heating, and generation of x-rays. The significant results from these experiments included the following: the foam provided an optically thin radiating region, the uniformity of radiation across the foam was good, and the foam tamped the gold case, holding it in its original position for the 15 ns beam pulse width.

Cook, D.L.; Adams, R.G.; Aubert, J.H.; Bacon, L.D.; Bailey, J.E.; Bloomquist, D.D.; Boyes, J.D.; Chandler, G.A.; Coats, R.S.; Corley, J.P.; Crow, J.T.; Cuneo, M.E.; Derzon, D.K.; Derzon, M.S.; Desjarlais, M.P.; Dukart, R.J.; Fehl, D.L.; Filuk, A.B.; Gerber, R.A.; Haill, T.A.; Hanson, D.L.; Humphreys, D.R.; Hussey, T.W.; Ives, H.L.; Johnson, D.J.; Johnson, D.L.; Leeper, R.J.; Lemke, R.W.; Lockner, T.R.; Maenchen, J.E.; Matzen,

1992-01-01

440

Hiding and Confining Charges via Tube-Like Wormholes  

NASA Astrophysics Data System (ADS)

We describe two interesting effects in wormhole physics. First, we find that a genuinely charged matter source of gravity and electromagnetism may appear electrically neutral to an external observer — a phenomenon opposite to the famous Misner-Wheeler "charge without charge" effect. We show that this phenomenon takes place when coupling a bulk gravity/nonlinear-gauge-field system self-consistently to a codimension-one charged lightlike brane as a matter source. The "charge-hiding" effect occurs in a self-consistent wormhole solution of the above coupled gravity/nonlinear-gauge-field/lightlike-brane system which connects a noncompact "universe," comprising the exterior region of Schwarzschild-(anti-)de Sitter (or purely Schwarzschild) black hole beyond the internal (Schwarzschild) horizon, to a Levi-Civita-Bertotti-Robinson-type ("tube-like") "universe" with two compactified dimensions via a wormhole "throat" occupied by the charged lightlike brane. In this solution the whole electric flux produced by the charged lightlike brane is expelled into the compactified Levi-Civita-Bertotti-Robinson-type "universe" and, consequently, the brane is detected as neutral by an observer in the Schwarzschild-(anti-)de Sitter "universe." Next, the above "charge-hiding" solution can be further generalized to a truly charge-confining wormhole solution when we couple the bulk gravity/nonlinear-gauge-field system self-consistently to two separate codimension-one charged lightlike branes with equal in magnitude but opposite charges. The latter system possesses a "two-throat" wormhole solution, where the "left-most" and the "right-most" "universes" are two identical copies of the exterior region of the neutral Schwarzschild-de Sitter black hole beyond the Schwarzschild horizon, whereas the "middle" "universe" is of generalized Levi-Civita-Bertotti-Robinson "tube-like" form with geometry dS2 ×S2 (dS2 being the two-dimensional de Sitter space). It comprises the finite-extent intermediate region of dS2 between its two horizons. Both "throats" are occupied by the two oppositely charged lightlike branes and the whole electric flux produced by the latter is confined entirely within the middle finite-extent "tube-like" "universe." A crucial ingredient is the special form of the nonlinear gauge field action, which contains both the standard Maxwell term as well as a square root of the latter. This theory was previously shown to produce a QCD-like confining dynamics in flat space-time.

Guendelman, Eduardo; Kaganovich, Alexander; Nissimov, Emil; Pacheva, Svetlana

441

High beta and confinement studies on TFTR  

SciTech Connect

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.

Navratil, G.A.; Bhattacharjee, A.; Iacono, R.; Mauel, M.E.; Sabbagh, S.A. (Columbia Univ., New York, NY (United States)); Kesner, J. (Massachusetts Inst. of Tech., Cambridge, MA (United States))

1992-01-01

442

Inertial Confinement Fusion Target Component Fabrication and Technology Development Support  

SciTech Connect

On December 31, 1990, the US Department of Energy entered into a contract with General Atomics (GA) to be the Inertial Confinement Fusion (ICF) Target Component Fabrication and Technology Development Support contractor. This report documents the technical activities of the period January 1, 1991 through September 30, 1992. During this period, GA was assigned 15 tasks in support of the Inertial Confinement Fusion program and its laboratories. These tasks included Facilities Activation, Staff Development, and Capabilities Validation to establish facilities and equipment, and demonstrate capability to perform ICF target fabrication research, development and production activities. The capabilities developed and demonstrated are those needed for fabrication and precise characterization of polymer shells and polymer coatings. We made progress toward production capability for glass shells, barrier layer coatings, and gas idling of shells. We fabricated over 1000 beam diagnostic foil targets for Sandia National Laboratory Albuquerque and provided full-time on-site engineering support for target fabrication and characterization. We initiated development of methods to fabricate polymer shells by a controlled mass microencapsulation technique, and performed chemical syntheses of several chlorine- and silicon-doped polymer materials for the University of Rochester's Laboratory for Laser Energetics (UR/LLE). We performed the conceptual design of a cryogenic target handling system for UR/LLE that will fill, transport, layer, and characterize targets filled with cryogenic deuterium or deuterium-tritium fuel, and insert these cryogenic targets into the OMEGA-Upgrade target chamber for laser implosion experiments. This report summarizes and documents the technical progress made on these tasks.

Steinman, D. (ed.)

1993-03-01

443

Deflagration to detonation in HMX under high confinement. [HMX confined in steel tubes  

Microsoft Academic Search

The deflagration-to-detonation behavior of HMX confined in steel tubes was studied by means of x radiography, light emission, and various pin techniques. Unlike most reported experiments, the HMX bed was ignited by driving a piston (initially at rest and in contact with the HMX) into the bed with the pressure generated from burning, low-density HMX on the opposite side of

J. M. McAfee; A. W. Campbell; B. W. Asay

1987-01-01

444

Echoes and revival echoes in systems of anharmonically confined atoms  

NASA Astrophysics Data System (ADS)

We study echoes and what we call “revival echoes” for a collection of atoms that are described by a single quantum wave function and are confined in a weakly anharmonic trap. The echoes and revival echoes are induced by applying two successive temporally localized potential perturbations to the confining potential, one at time t=0, and a smaller one at time t=?. Pulselike responses in the expectation value of position are predicted at t?n? (n=2,3,...) and are particularly evident at t?2?. While such echoes are familiar from previous work, a result of our study is the finding of revival echoes. Revivals (but not echoes) occur even if the second perturbation is absent. In particular, in the absence of the second perturbation, the response to the first perturbation dies away but then reassembles, producing a response at revival times mTx (m=1,2,...). The existence of such revivals is due to the discreteness of the quantum levels in a weakly anharmonic potential, and has been well studied previously. If we now include the second perturbation at t=?, we find temporally localized responses, revival echoes, both before and after t?mTx [e.g., at t?mTx-n? (prerevival echoes) and at t?mTx+n?, (postrevival echoes)] where m and n are 1,2,.... One notable point is that, depending on the form of the perturbations, the “principal” revival echoes at t?Tx±? can be much larger than the echo at t?2?. We develop a perturbative model for these phenomena, and compare its predictions to the numerical solutions of the time-dependent Schrödinger equation. The scaling of the size of the various echoes and revival echoes as a function of the symmetry of the perturbations applied at t=0 and t=?, and of the size of the external perturbations is investigated. The quantum recurrence and revival echoes are also present in higher moments of position, , p>1. Recurrences are present at t?mTx/j, and dominant prerevival and postrevival echoes occur at fractional shifts of ? [i.e. t?(mTx±?)/j] where the m=1,2,... and the integer values of j are determined by p. Additionally, we use the Gross-Pitaevskii equation to study the effect of atom-atom interactions on these phenomena. We find that echoes and revival echoes become more difficult to discern as the size of the second perturbation is increased and/or as the atom-atom interactions become stronger.

Herrera, M.; Antonsen, T. M.; Ott, E.; Fishman, S.

2012-08-01

445

Status and prospects for fusion energy from magnetically confined plasmas  

Microsoft Academic Search

A broad review is presented of the status and outlook of achieving fusion energy production by the confinement of high temperature plasmas with magnetic fields. The paper describes the basic features of the fusion process, plasma confinement principles and concepts with emphasis on the Tokamak, issues of materials development, descriptions of the major components and subsystems of fusion reactors, prospects

Charles C. Baker; Robert W. Conn; Farrokh Najmabadi; Mark S. Tillack

1998-01-01

446

Confinement at large-N. [N = number of colors  

SciTech Connect

Recent numerical results indicate that QCD in the limit of an infinite number (N) of colors also has confinement and moreover that it looks rather similar to normal QCD with N = 3 colors. This imposes severe restrictions on what the mechanism of confinement can be.

Klinkhamer, F.R.

1985-06-01

447

West's proof of confinement and two-dimensional models  

SciTech Connect

West's proof of confinement by contradiction is studied for the unconfined SU(N) Gross-Neveu model to leading order in 1/N and for the confining Schwinger model. In both cases, we find that the contradiction found by West for four-dimensional QCD is averted.

Clark, T.E.; Love, S.T.

1982-05-15

448

Plasmid profiling of bacterial isolates from confined environments  

Microsoft Academic Search

Plasmid profiling of bacterial isolates from confined environments R. Van Houdt, I. Coninx, A. Provoost, N. Leys, and M. Mergeay Expertise group for Molecular and Cellular Biology, Institute for Environment, Health and Safety, Belgian Nuclear Research Centre (SCK•CEN), Boeretang 200, B-2400 Mol, Belgium. Human exploration of extreme and isolated hostile environments such as space requires special confined small volume habitats

Rob van Houdt; Ann Provoost; Ilse Coninx; Natalie Leys; Max Mergeay

2008-01-01

449

Planar Liquid Confinement for Optical Centering of Dielectric Liquid Lenses  

Microsoft Academic Search

In this letter, planar liquid confinement structures along with concentric electrodes are proposed for the optical centering of dielectric liquid lenses at the rest state and during actuation. Both the liquid confinement structures and electrodes that are photolithographically fabricated on glass substrates share the same geometric center, thereby minimizing the deviation of the optical axis at all operation modes. Tilt

C. Gary Tsai; Chi-Nan Chen; Li-Shun Cheng; Chih-Cheng Cheng; Jing-Tang Yang; J. Andrew Yeh

2009-01-01

450

HEATING AND CONFINEMENT OF A PLASMA BY ALTERNATING MAGNETIC FIELDS  

Microsoft Academic Search

A method is proposed in which a plasma is confined by an alternating ; magnetic field. The plasma is field-free except in a thin boundary layer. No ;