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1

Confinement: a real-time visualization  

E-print Network

Due to the mechanism of confinement, as known from quantum chromodynamics, it is difficult to observe individual particles carrying fractional quantum number (e.g. quark with fractional electric charge). A condensed matter example of fractionalized particles is spinons in quasi-one-dimensional spin systems, which are domain walls in the background of Neel configurations carrying spin-1/2. Using the time-evolving block decimation algorithm, we visualize the nontrivial domain wall dynamics induced by the confine mechanism in a two-leg spin-1/2 ladder. It can be illustrated by a simple single-particle picture of Bloch oscillation, not only qualitatively but also quantitatively. We propose the experimental realization and the real time detection of the domain wall dynamics in the ultra-cold boson systems of $^{87}$Rb.

Zi Cai; Congjun Wu; U. Schollwöck

2012-02-09

2

Confinement from gluodynamics in curved space-time  

SciTech Connect

We determine the static potential for a heavy quark-antiquark pair from gluodynamics in curved space-time. Our calculation is done within the framework of the gauge-invariant, path-dependent, variables formalism. The potential energy is the sum of a Yukawa and a linear potential, leading to the confinement of static charges.

Gaete, Patricio; Spallucci, Euro [Departamento de Fisica, Universidad Tecnica Federico Santa Maria, Valparaiso (Chile); Dipartimento di Fisica Teorica, Universita di Trieste and INFN, Sezione di Trieste (Italy)

2008-01-15

3

Confinement time of dust particles in a Kingdon trap  

NASA Astrophysics Data System (ADS)

The electrostatic orrery is a device in which negatively-charged dust particles orbit a wire in vacuum (Kingdon trap). The particles are glass microballoons about 50 microns in diameter charged negatively with 5× 10^5 electrons. The central elect rode is a 6 mm diameter rod at a potential of +8 kV. The particles are confined axially by grounded end plates. The orbits decay gradually until the particles strike the rod. Experiments with gas pressures from 2× 10-4 to 2× 10-6 To rr indicate that the confinement is limited by molecular drag. The longest confinement times are about 6 hours. At lower pressure, there may be additional mechanisms which prevent the confinement time from being further increased. For example, there is additional dissipation caused by the motion of image charges in the walls of the trap. This is being investigated by varying the placement of the walls and by resistively loading the walls. Resistive dissipation may account for elliptical orbits becomi ng circular at a rate more rapid than predicted from molecular drag alone.

Mahr, C.; Walch, R.; Robertson, S.

1996-11-01

4

On time scale invariance of random walks in confined space.  

PubMed

Animal movement is often modelled on an individual level using simulated random walks. In such applications it is preferable that the properties of these random walks remain consistent when the choice of time is changed (time scale invariance). While this property is well understood in unbounded space, it has not been studied in detail for random walks in a confined domain. In this work we undertake an investigation of time scale invariance of the drift and diffusion rates of Brownian random walks subject to one of four simple boundary conditions. We find that time scale invariance is lost when the boundary condition is non-conservative, that is when movement (or individuals) is discarded due to boundary encounters. Where possible analytical results are used to describe the limits of the time scaling process, numerical results are then used to characterise the intermediate behaviour. PMID:25481837

Bearup, Daniel; Petrovskii, Sergei

2015-02-21

5

Time spectral method for rotorcraft flow with vorticity confinement  

NASA Astrophysics Data System (ADS)

This thesis shows that simulation of helicopter flows can adhere to engineering accuracy without the need of massive computing resources or long turnaround time by choosing an alternative framework for rotorcraft simulation. The method works in both hovering and forward flight regimes. The new method has shown to be more computationally efficient and sufficiently accurate. By utilizing the periodic nature of the rotorcraft flow field, the Fourier based Time Spectral method lends itself to the problem and significantly increases the rate of convergence compared to traditional implicit time integration schemes such as the second order backward difference formula (BDF). A Vorticity Confinement method has been explored and has been shown to work well in subsonic and transonic simulations. Vortical structure can be maintained after long distances without resorting to the traditional mesh refinement technique.

Butsuntorn, Nawee

2008-10-01

6

Confinement on $R^{3}\\times S^{1}$: continuum and lattice  

E-print Network

There has been substantial progress in understanding confinement in a class of four-dimensional SU(N) gauge theories using semiclassical methods. These models have one or more compact directions, and much of the analysis is based on the physics of finite-temperature gauge theories. The topology $R^{3}\\times S^{1}$ has been most often studied, using a small compactification circumference $L$ such that the running coupling $g^{2}\\left(L\\right)$ is small. The gauge action is modified by a double-trace Polyakov loop deformation term, or by the addition of periodic adjoint fermions. The additional terms act to preserve $Z(N)$ symmetry and thus confinement. An area law for Wilson loops is induced by a monopole condensate. In the continuum, the string tension can be computed analytically from topological effects. Lattice models display similar behavior, but the theoretical analysis of topological effects is based on Abelian lattice duality rather than on semiclassical arguments. In both cases the key step is reducing the low-energy symmetry group from $SU(N)$ to the maximal Abelian subgroup $U(1)^{N-1}$ while maintaining $Z(N)$ symmetry.

Michael C. Ogilvie

2014-10-07

7

Full-f gyrokinetic simulation over a confinement time  

SciTech Connect

A long time ion temperature gradient driven turbulence simulation over a confinement time is performed using the full-f gyrokinetic Eulerian code GT5D. The convergence of steady temperature and rotation profiles is examined, and it is shown that the profile relaxation can be significantly accelerated when the simulation is initialized with linearly unstable temperature profiles. In the steady state, the temperature profile and the ion heat diffusivity are self-consistently determined by the power balance condition, while the intrinsic rotation profile is sustained by complicated momentum transport processes without momentum input. The steady turbulent momentum transport is characterized by bursty non-diffusive fluxes, and the resulting turbulent residual stress is consistent with the profile shear stress theory [Y. Camenen et al., “Consequences of profile shearing on toroidal momentum transport,” Nucl. Fusion 51, 073039 (2011)] in which the residual stress depends not only on the profile shear and the radial electric field shear but also on the radial electric field itself. Based on the toroidal angular momentum conservation, it is found that in the steady null momentum transport state, the turbulent residual stress is cancelled by the neoclassical counterpart, which is greatly enhanced in the presence of turbulent fluctuations.

Idomura, Yasuhiro, E-mail: idomura.yasuhiro@jaea.go.jp [Japan Atomic Energy Agency, Kashiwanoha 5-1-5, Kashiwa, Chiba 277-8587 (Japan)] [Japan Atomic Energy Agency, Kashiwanoha 5-1-5, Kashiwa, Chiba 277-8587 (Japan)

2014-02-15

8

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

9

Time-dependent model for diluted magnetic semiconductors including band structure and confinement effects  

E-print Network

Time-dependent model for diluted magnetic semiconductors including band structure and confinement dynamics in confined diluted magnetic semiconductors induced by laser. The hole-spin relaxation process light-induced magnetization dynamics in ferro- magnetic films and in diluted magnetic semiconductors DMS

Boyer, Edmond

10

Diffraction in time of a confined particle and its Bohmian paths  

E-print Network

Diffraction in time of a particle confined in a box which its walls are removed suddenly at $t=0$ is studied. The solution of the time-dependent Schr\\"{o}dinger 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.

S. V. Mousavi

2011-12-27

11

Singularity confinement in the discrete time Toda lattice and the Q-D algorithm  

NASA Astrophysics Data System (ADS)

An integrability criterion for discrete systems based on singularity confinement has been defined recently as an analogue of the Painlevé test for continuous systems. It will be demonstrated that the discrete time Toda lattice, equivalent to the Q-D algorithm for finding poles of a holomorphic function, satisfies the criterion.

Common, A. K.

1994-01-01

12

A transition state theory for calculating hopping times and diffusion in highly confined fluids.  

PubMed

Monte Carlo simulation is used to study the dynamical crossover from single file diffusion to normal diffusion in fluids confined to narrow channels. We show that the long time diffusion coefficients for a series of systems involving hard and soft interaction potentials can be described in terms of a hopping time that measures the time it takes for a particle to escape the cage formed by its neighbors in the pore. Free energy barriers for the particle hopping process are calculated and used to show that transition state theory effectively describes the hopping time for all the systems studied over a range of pore radii. Our work suggests that the combination of hopping times and transition state theory offers a useful and general framework to describe the dynamics of highly confined, single file fluids. PMID:24437894

Wanasundara, Surajith N; Spiteri, Raymond J; Bowles, Richard K

2014-01-14

13

A transition state theory for calculating hopping times and diffusion in highly confined fluids  

NASA Astrophysics Data System (ADS)

Monte Carlo simulation is used to study the dynamical crossover from single file diffusion to normal diffusion in fluids confined to narrow channels. We show that the long time diffusion coefficients for a series of systems involving hard and soft interaction potentials can be described in terms of a hopping time that measures the time it takes for a particle to escape the cage formed by its neighbors in the pore. Free energy barriers for the particle hopping process are calculated and used to show that transition state theory effectively describes the hopping time for all the systems studied over a range of pore radii. Our work suggests that the combination of hopping times and transition state theory offers a useful and general framework to describe the dynamics of highly confined, single file fluids.

Wanasundara, Surajith N.; Spiteri, Raymond J.; Bowles, Richard K.

2014-01-01

14

Strong and weak confinement of parity-time-symmetric acoustic surface wave  

NASA Astrophysics Data System (ADS)

A strongly confined acoustic surface wave is an acoustic eigenstate localized on an interface between an ordinary acoustic medium and an acoustic metamaterial with negative effective dynamical mass density. Here we show that there is a new unconventional acoustic surface wave sustained by a parity-time ({\\cal{PT}}) -symmetric acoustic interface system, in which the negative effective dynamical mass density is not required (but the effective mass densities of the two adjacent acoustic media should fulfill the parity-time symmetry). Such an acoustic parity-time symmetry in the effective mass density can be used to manipulate acoustic wave propagation, e.g., it can exhibit both weak and strong confinement of the unusual {\\cal{PT}} -symmetric acoustic surface wave, and can offer mechanisms for designing acoustic metamaterial devices that would have specific functions in controlling and guiding acoustic wave, including acoustic field enhancement and extraordinary acoustic transmission.

Shen, Jian Qi

2014-01-01

15

Occupation times of random walks in confined geometries: From random trap model to diffusion limited reactions  

E-print Network

We consider a random walk in confined geometry, starting from a site and eventually reaching a target site. We calculate analytically the distribution of the occupation time on a third site, before reaching the target site. The obtained distribution is exact, and completely explicit in the case or parallepipedic confining domains. We discuss implications of these results in two different fields: The mean first passage time for the random trap model is computed in dimensions greater than 1, and is shown to display a non-trivial dependence with the source and target positions ; The probability of reaction with a given imperfect center before being trapped by another one is also explicitly calculated, revealing a complex dependence both in geometrical and chemical parameters.

S. Condamin; V. Tejedor; O. Benichou

2008-06-03

16

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

17

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)] [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)

1995-10-01

18

Wave function for harmonically confined electrons in time-dependent electric and magnetostatic fields  

SciTech Connect

We derive via the interaction “representation” the many-body wave function for harmonically confined electrons in the presence of a magnetostatic field and perturbed by a spatially homogeneous time-dependent electric field—the Generalized Kohn Theorem (GKT) wave function. In the absence of the harmonic confinement – the uniform electron gas – the GKT wave function reduces to the Kohn Theorem wave function. Without the magnetostatic field, the GKT wave function is the Harmonic Potential Theorem wave function. We further prove the validity of the connection between the GKT wave function derived and the system in an accelerated frame of reference. Finally, we provide examples of the application of the GKT wave function.

Zhu, Hong-Ming; Chen, Jin-Wang; Pan, Xiao-Yin, E-mail: panxiaoyin@nbu.edu.cn [Department of Physics, Ningbo University, Ningbo 315211 (China)] [Department of Physics, Ningbo University, Ningbo 315211 (China); Sahni, Viraht [Department of Physics, Brooklyn College and The Graduate School of the City University of New York, New York, New York 10016 (United States)] [Department of Physics, Brooklyn College and The Graduate School of the City University of New York, New York, New York 10016 (United States)

2014-01-14

19

Wave function for harmonically confined electrons in time-dependent electric and magnetostatic fields  

NASA Astrophysics Data System (ADS)

We derive via the interaction "representation" the many-body wave function for harmonically confined electrons in the presence of a magnetostatic field and perturbed by a spatially homogeneous time-dependent electric field—the Generalized Kohn Theorem (GKT) wave function. In the absence of the harmonic confinement - the uniform electron gas - the GKT wave function reduces to the Kohn Theorem wave function. Without the magnetostatic field, the GKT wave function is the Harmonic Potential Theorem wave function. We further prove the validity of the connection between the GKT wave function derived and the system in an accelerated frame of reference. Finally, we provide examples of the application of the GKT wave function.

Zhu, Hong-Ming; Chen, Jin-Wang; Pan, Xiao-Yin; Sahni, Viraht

2014-01-01

20

Analysis of Molecular Diffusion by First-Passage Time Variance Identifies the Size of Confinement Zones  

PubMed Central

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.

2011-01-01

21

Waves, Currents, Drifts and Plasma Confinement Time in a Low Temperature, Pulsed, Toroidal, ECR Plasma  

NASA Astrophysics Data System (ADS)

Typically the plasma in purely toroidal field experimental systems is created by a filament source or, in some cases, a helicon plasma source. Here we present measurements of plasma density, electron temperature, flow and confinement time for an electron cyclotron resonance (ECR) created plasma in a purely toroidal field at the Institute of Plasma Research (IPR) in India. A linear array of Langmuir probes was used to measure the density and temperature in a horizontal plane of the torus and a pair or probes is used to measure the vertical electric field arising from charge separation. Mach probes were used to measure bulk plasma flows in the same plane. Through measurements of the decay rate of the plasma density after the 2.45 GHz ECR microwave source turns off, the plasma confinement time as a function of initial toroidal magnetic field strength and fill pressure was investigated. This work was supported by the American Physical Society and the Indo-U.S. Science and Technology Forum (IUSSTF) through the India-U.S. Physics Visitation Program.

Lindon, Michael; Thakur, Arvind; Sharma, P. K.; Satyanarayan, K.; Parmar, P. R.; Virani, Chetan; Scime, Earl; Houshmyandar, Saied

2009-11-01

22

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. PMID:21641330

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

2011-01-01

23

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

E-print Network

We show that a system of hard discs 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 Adams-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 discs, successfully describes the fragile-strong crossover.

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

2012-10-22

24

Time scale of entropic segregation of flexible polymers in confinement: Implications for chromosome segregation in filamentous bacteria  

E-print Network

We report molecular dynamics simulations of the segregation of two overlapping chains in cylindrical confinement. We find that the entropic repulsion between the chains can be sufficiently strong to cause segregation on a time scale that is short compared to the one for diffusion. This result implies that entropic driving forces are sufficiently strong to cause rapid bacterial chromosome segregation.

Axel Arnold; Suckjoon Jun

2007-09-07

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

Time-resolved 14-MeV neutron detector for triton confinement studies  

NASA Astrophysics Data System (ADS)

Previous measurements of triton burnup in deuterium tokamak plasmas show an anomalously small burnup for low-q discharges with significant magnetohydrodynamic activity. This may have important implications for alpha particle burnup in a fusion reactor. By developing a detector capable of time-resolved 14-MeV neutron measurements, it should be possible to separate triton confinement and slowdown anomalies. We are testing lithium-free glass scintillators which would observe 14-MeV neutrons through prompt 28Si(n, p) 28Al reactions. These detectors are not sensitive to the much larger 2.5-MeV neutron background and should also have less sensitivity to the large thermal neutron background when compared to conventional 6Li-depleted glasses. Measurements of detector sensitivity to signal and potential background sources are being performed using a 14-MeV neutron source and radioactive sources. The expected signal behavior under various DIII-D plasma and beam conditions will also be presented.

Smith, J. R.; Fisher, R. K.; Leffler, J. S.; Newman, D. E.

1986-08-01

27

Time of Flight Diagnosis of Fusion Profiles in Spherical Inertial Electrostatic Confinement Devices  

NASA Astrophysics Data System (ADS)

The Time of Flight (TOF) diagnostic produces 1-D fusion spatial profiles across the inertial electrostatic confinement (IEC) fusion device by coincidentally capturing protons and tritons from individual deuterium-deuterium (D-D) fusion events. Several experimental upgrades were implemented and a new TOF data set was recorded. The resulting fusion profile was peaked at the center of the cathode and did not show evidence for significant fusion occurring outside the anode. Previous TOF measurements indicated that a significant number of fusion events were occurring in the region between the anode and the chamber wall. Detailed analysis of the previous data indicated that the measurement suffered intermittent timing errors and confirmed that fusion is primarily occurring within the cathode. The current TOF results compared well with additional previous experiments conducted at UW-Madison that observed a peak in the fusion rate near the center of the cathode. Previous measurements indicated that fusion in spherical IEC devices is concentrated in beams that extend from the center of the cathode, through holes in the cathode grid, out to the chamber wall. The current TOF data and all previous UW-Madison experimental results appear to be consistent with fusion being concentrated along beams. A new capability of the TOF system was developed, in which the energy distribution function (EDF) is determined for deuterons that initiated fusion reactions. For an applied cathode voltage of -60 kV and background gas pressure of 1.5 mTorr, the fusion deuteron EDF peaked between 15-20 keV. The peak between 15-20 keV indicates that the primary fast deuterium ion species in the system may be D3+. Scattering, ionization and charge exchange also play a significant role in IEC physics at this pressure.

McEvoy, Aaron

28

A time-resolved x-ray ring coded-aperture microscope for inertial confinement fusion applications  

Microsoft Academic Search

For energetic x rays ([ital hv][ge]3 keV), ring coded-aperture imaging gives better signal-to-noise ratio than equivalent-resolution pinhole cameras for inertial confinement fusion (ICF) targets. We have created a time-resolved ring coded-aperture microscope by combining a 4[times]3 array of annular apertures with a gated microchannel-plate x-ray imager. The new instrument can produce 500-ps duration sequences of images with a temporal resolution

D. Ress; P. M. Bell; D. K. Bradley

1993-01-01

29

Structural transitions and long-time self-diffusion of interacting colloids confined by a parabolic potential.  

PubMed

We report on the ordering and dynamics of interacting colloidal particles confined by a parabolic potential. By means of Brownian dynamics simulations, we find that by varying the magnitude of the trap stiffness, it is possible to control the dimension of the system and, thus, explore both the structural transitions and the long-time self-diffusion coefficient as a function of the degree of confinement. We particularly study the structural ordering in the directions perpendicular and parallel to the confinement. Further analysis of the local distribution of the first-neighbors layer allows us to identify the different structural phases induced by the parabolic potential. These results are summarized in a structural state diagram that describes the way in which the colloidal suspension undergoes a structural re-ordering while increasing the confinement. To fully understand the particle dynamics, we take into account hydrodynamic interactions between colloids; the parabolic potential constricts the available space for the colloids, but it does not act on the solvent. Our findings show a non-linear behavior of the long-time self-diffusion coefficient that is associated to the structural transitions induced by the external field. PMID:25591382

Euán-Díaz, Edith C; Herrera-Velarde, Salvador; Misko, Vyacheslav R; Peeters, François M; Castañeda-Priego, Ramón

2015-01-14

30

Structural transitions and long-time self-diffusion of interacting colloids confined by a parabolic potential  

NASA Astrophysics Data System (ADS)

We report on the ordering and dynamics of interacting colloidal particles confined by a parabolic potential. By means of Brownian dynamics simulations, we find that by varying the magnitude of the trap stiffness, it is possible to control the dimension of the system and, thus, explore both the structural transitions and the long-time self-diffusion coefficient as a function of the degree of confinement. We particularly study the structural ordering in the directions perpendicular and parallel to the confinement. Further analysis of the local distribution of the first-neighbors layer allows us to identify the different structural phases induced by the parabolic potential. These results are summarized in a structural state diagram that describes the way in which the colloidal suspension undergoes a structural re-ordering while increasing the confinement. To fully understand the particle dynamics, we take into account hydrodynamic interactions between colloids; the parabolic potential constricts the available space for the colloids, but it does not act on the solvent. Our findings show a non-linear behavior of the long-time self-diffusion coefficient that is associated to the structural transitions induced by the external field.

Euán-Díaz, Edith C.; Herrera-Velarde, Salvador; Misko, Vyacheslav R.; Peeters, François M.; Castañeda-Priego, Ramón

2015-01-01

31

Patterned time-orbiting potentials for the confinement and assembly of magnetic dipoles  

PubMed Central

We present an all-magnetic scheme for the assembly and study of magnetic dipoles within designed confinement profiles that are activated on micro-patterned permalloy films through a precessing magnetic field. Independent control over the confinement and dipolar interactions is achieved by tuning the strength and orientation of the revolving field. The technique is demonstrated with superparamagnetic microspheres field-driven to assemble into closely packed lattice sheets, quasi-1D and other planar structures expandable into dipolar arrays that mirror the patterned surface motifs. PMID:24185093

Chen, A.; Sooryakumar, R.

2013-01-01

32

A time-resolved x-ray ring coded-aperture microscope for inertial confinement fusion applications  

Microsoft Academic Search

For energetic x rays (hv?3 keV), ring coded-aperture imaging gives better signal-to-noise ratio than equivalent-resolution pinhole cameras for inertial confinement fusion (ICF) targets. We have created a time-resolved ring coded-aperture microscope by combining a 4×3 array of annular apertures with a gated microchannel-plate x-ray imager. The new instrument can produce 500-ps duration sequences of images with a temporal resolution of

D. Ress; P. M. Bell; D. K. Bradley

1993-01-01

33

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

SciTech Connect

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 ({approx}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.

Donovan, D. C. [Sandia National Laboratories, 7011 East Avenue, Livermore, California 94550 (United States); Boris, D. R. [Naval Research Laboratory, 4555 Overlook Avenue, South West, Washington, DC 20375 (United States); Kulcinski, G. L.; Santarius, J. F. [Fusion Technology Institute, University of Wisconsin-Madison, 1500 Engineering Drive, Madison, Wisconsin 53706 (United States); Piefer, G. R. [Phoenix Nuclear Labs, 2555 Industrial Drive, Madison, Wisconsin 53713 (United States)

2013-03-15

34

A time-resolved x-ray ring coded-aperture microscope for inertial confinement fusion applications  

SciTech Connect

For energetic x rays ([ital hv][ge]3 keV), ring coded-aperture imaging gives better signal-to-noise ratio than equivalent-resolution pinhole cameras for inertial confinement fusion (ICF) targets. We have created a time-resolved ring coded-aperture microscope by combining a 4[times]3 array of annular apertures with a gated microchannel-plate x-ray imager. The new instrument can produce 500-ps duration sequences of images with a temporal resolution of 80 ps and a spatial resolution of 5 to 6 [mu]m. In demonstration experiments, coded images of imploded targets directly driven by the Omega laser at the Laboratory for Laser Energetics showed the formation and dissolution of the target cores with improved detail. Contour plots of the images indicate that the laser illumination pattern is imprinted in the imploded core region. The gated ring-aperture microscope will be useful in detailed studies of ICF target hydrodynamics.

Ress, D.; Bell, P.M. (Lawrence Livermore National Laboratory, P.O. Box 5508, Livermore, California 94551 (United States)); Bradley, D.K. (Laboratory for Laser Energetics, 250 East River Road, Rochester, New York 14623 (United States))

1993-06-01

35

Time-Dependent Nuclear Measurements of Mix in Inertial Confinement Fusion J. R. Rygg, J. A. Frenje, C. K. Li, F. H. Seguin, and R. D. Petrasso*  

E-print Network

Time-Dependent Nuclear Measurements of Mix in Inertial Confinement Fusion J. R. Rygg, J. A. Frenje (Received 19 January 2007; published 24 May 2007) The first time-dependent nuclear measurements of turbulent reaction to proceed. The time necessary for Rayleigh-Taylor (RT) growth to induce mix delays peak nuclear

36

A time-resolved x-ray ring coded-aperture microscope for inertial confinement fusion applications  

NASA Astrophysics Data System (ADS)

For energetic x rays (hv?3 keV), ring coded-aperture imaging gives better signal-to-noise ratio than equivalent-resolution pinhole cameras for inertial confinement fusion (ICF) targets. We have created a time-resolved ring coded-aperture microscope by combining a 4×3 array of annular apertures with a gated microchannel-plate x-ray imager. The new instrument can produce 500-ps duration sequences of images with a temporal resolution of 80 ps and a spatial resolution of 5 to 6 ?m. In demonstration experiments, coded images of imploded targets directly driven by the Omega laser at the Laboratory for Laser Energetics showed the formation and dissolution of the target cores with improved detail. Contour plots of the images indicate that the laser illumination pattern is imprinted in the imploded core region. The gated ring-aperture microscope will be useful in detailed studies of ICF target hydrodynamics.

Ress, D.; Bell, P. M.; Bradley, D. K.

1993-06-01

37

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

38

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

39

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.

40

Extended gyrokinetic field theory for time-dependent magnetic confinement fields  

SciTech Connect

A gyrokinetic system of equations for turbulent toroidal plasmas in time-dependent axisymmetric background magnetic fields is derived from the variational principle. Besides governing equations for gyrocenter distribution functions and turbulent electromagnetic fields, the conditions which self-consistently determine the background magnetic fields varying on a transport time scale are obtained by using the Lagrangian, which includes the constraint on the background fields. Conservation laws for energy and toroidal angular momentum of the whole system in the time-dependent background magnetic fields are naturally derived by applying Noether's theorem. It is shown that the ensemble-averaged transport equations of particles, energy, and toroidal momentum given in the present work agree with the results from the conventional recursive formulation with the WKB representation except that collisional effects are disregarded here.

Sugama, H.; Watanabe, T.-H.; Nunami, M. [National Institute for Fusion Science, Toki 509-5292 (Japan)] [National Institute for Fusion Science, Toki 509-5292 (Japan)

2014-01-15

41

Confined Phase In The Real Time Formalism And The Fate Of The World Behind The Horizon  

Microsoft Academic Search

In the real time formulation of finite temperature field theories, one introduces an additional set of fields (type-2 fields) associated to each field in the original theory (type-1 field). In (1), in the context of the AdS-CFT correspondence, Maldacena interpreted type-2 fields as living on a boundary behind the black hole horizon. However, below the Hawking-Page transition temperature, the thermodynamically

FURUUCHI Kazuyuki

42

Simulations of time-dependent fluorescence in nano-confined solvents  

E-print Network

carried out by Levinger and co-workers in a wide variety of reverse micelles,9–15 Bhatta- charyya and co-workers in reverse micelles, vesicles, sol- gels, and zeolites,4–8 Baumann et al. in sol-gels,16,17 and a number of other groups.18–25 In paper I we... to obtain a total of 1200 nonequilibrium trajectories for each cavity and density. The TDF result can be plotted as the time-dependent Stokes shift, ^ DEfl(t)2DEfl(0)&, or normalized in the usual way as S ~ t !5 ^ DEfl~ t !2DEfl~‘!& ^ DEfl~0 !2DEfl~‘!& . ~3...

Thompson, Ward H.

2004-04-13

43

Five-hole pitot probe time-mean velocity measurements in confined swirling flows  

NASA Technical Reports Server (NTRS)

Nonswirling and swirling nonreacting flows in an axisymmetric test section with an expansion ratio D/d = 2, which may be equipped with contraction nozzles of area ratios 2 and 4, are investigated. The effects of a number of geometric parameters on the flow-field are investigated, among them side-wall expansion angles of 90 and 45 deg, swirl vane angles of 0, 38, 45, 60, and 70 deg, and contraction nozzle locations L/D = 1 and 2 (if present). Data are acquired by means of a five-hole pitot probe enabling three time-mean velocity components in the axial, radial, and azimuthal directions to be measured. The velocities are extensively plotted and artistic impressions of recirculation zones are set forth. The presence of a swirler is found to shorten the corner recirculation zone and to generate a central recirculation zone followed by a precessing vortex core. A gradual inlet expansion has the effect of encouraging the flow to remain close to the sidewall and shortening the extent of the corner recirculation zone in all cases investigated.

Yoon, H. K.; Lilley, D. G.

1983-01-01

44

Early-time dynamics of actomyosin polarization in cells of confined shape in elastic matrices.  

PubMed

The cell shape and the rigidity of the extracellular matrix have been shown to play an important role in the regulation of cytoskeleton structure and force generation. Elastic stresses that develop by actomyosin contraction feedback on myosin activity and govern the anisotropic polarization of stress fibers in the cell. We theoretically study the consequences that the cell shape and matrix rigidity may have on the dynamics and steady state polarization of actomyosin forces in the cell. Actomyosin forces are assumed to polarize in accordance with the stresses that develop in the cytoskeleton. The theory examines this self-polarization process as a relaxation response determined by two distinct susceptibility factors and two characteristic times. These reveal two canonical polarization responses to local variations in the elastic stress: an isotropic response, in which actomyosin dipolar stress isotropically changes in magnitude, and an orientational response, in which actomyosin forces orient with no net change in magnitude. Actual polarization may show up as a superimposition of the two mechanisms yielding different phases in the polarization response as observed experimentally. The cell shape and elastic moduli of the surroundings are shown to govern both the dynamics of the process as well as the steady-state. We predict that in the steady-state, beyond a critical matrix rigidity, spherical cells exert maximal force, and below that rigidity, elongated or flattened cells exert more force. Similar behaviors are reflected in the rate of the polarization process. The theory is also applicable to study the elastic response of whole cell aggregates in a gel. PMID:24623163

Nisenholz, Noam; Botton, Mordechai; Zemel, Assaf

2014-04-14

45

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

46

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

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

X-Ray Imaging Spectrometer for Recording Calibrated Time-Resolved K-Shell Spectra from Magnetically Confined Fusion Plasmas  

SciTech Connect

Based on transmission crystal spectrometers recently optimized for recording high-resolution K-shell spectra from laser generated plasmas, an imaging spectrometer has been designed to record Mo and W K-shell spectra from magnetically confined plasmas. The spectrometer can be used to diagnose the electron energy distribution and transport of metal ions from the wall and divertor to the core plasma.

Seely, John F. [Naval Research Laboratory, Washington DC 20375 (United States); Feldman, Uri [Artep Inc., 2922 Excelsior Spring Circle, Columbia Md 21042 (United States); Suckewer, Szymon [Princeton University, Princeton NJ 08544 (United States); Hudson, Lawrence T. [National Institute of Standards and Technology, Gaithersburg MD 20899 (United States)

2008-03-12

49

Confined direct analysis in real time ion source and its applications in analysis of volatile organic compounds of Citrus limon (lemon) and Allium cepa (onion).  

PubMed

The DART (direct analysis in real time) ion source is a novel atmospheric pressure ionization technique that enables efficient ionization of gases, liquids and solids with high throughput. A major limit to its wider application in the analysis of gases is its poor detection sensitivity caused by open-air sampling. In this study, a confined interface between the DART ion source outlet and mass spectrometer sampling orifice was developed, where the plasma generated by the atmospheric pressure glow discharge collides and ionizes gas-phase molecules in a Tee-shaped flow tube instead of in open air. It leads to significant increase of collision reaction probability between high energy metastable molecules and analytes. The experimental results show that the ionization efficiency was increased at least by two orders of magnitude. This technique was then applied in the real time analysis of volatile organic compounds (VOCs) of Citrus Limon (lemon) and wounded Allium Cepa (onion). The confined DART ion source was proved to be a powerful tool for the studies of plant metabolomics. PMID:22499194

Li, Yue

2012-05-30

50

Alterations in streaming potential in presence of time periodic pressure-driven flow of a power law fluid in narrow confinements with nonelectrostatic ion-ion interactions.  

PubMed

We study the coupled effect of electrokinetic phenomena and fluid rheology in altering the induced streaming potential in narrow fluidic confinements, which is manifested by establishing a time periodic pressure-driven flow in presence of electrical double layer phenomenon. However, in sharp contrast with reported literature, we take into account nonelectrostatic ion-ion interactions toward estimating the same in addition to electrostatic interactions and steric effects. We employ power law based rheological model for estimating the induced streaming potential. We bring out an intricate interaction between nonelectrostatic interactions and fluid rheology on the concerned electrokinetic phenomena, bearing immense consequences toward designing of integrated lab-on-a-chip-based microdevices and nanodevices. PMID:24132646

Dhar, Jayabrata; Ghosh, Uddipta; Chakraborty, Suman

2014-03-01

51

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. PMID:20307314

2010-01-01

52

Proper orthogonal and dynamic mode decompositions of time-resolved PIV of confined backward-facing step flow  

NASA Astrophysics Data System (ADS)

The unsteady flow field past a backward-facing step in a rectangular duct is investigated by adopting time-resolved particle image velocimetry (PIV) in the Reynolds number range of 2,640-9,880 based on step height and the inlet average velocity. The PIV realizations are subjected to post-processing techniques, namely, proper orthogonal decomposition (POD) and dynamic mode decomposition (DMD). At low Reynolds numbers, the second spatial POD modes indicate the presence of the shear layer mode, whereas this feature shifts to higher modes at higher Reynolds numbers. The corresponding temporal modes are Fourier-transformed to obtain the dominant frequency, whose Strouhal number corroborates the above observation. Short-time windows in the transverse velocity component along the shear layer are selected to investigate the temporal stability of the flow field by DMD to quantify the growth rate of the shear layer mode. The higher harmonics of this mode are also observed to grow, albeit at lesser rate. By relating to POD analysis, the most energetic structures were found to correspond to the unstable modes. The correlation between these unstable DMD modes and the Fourier-filtered flow fields for the same frequencies indicate better match for the lower operating Reynolds number case as compared to higher ones. The spatial stability analysis demonstrates the growth of the shear layer vortices, which is combined with the temporal stability analysis to evaluate the phase velocity of the identified shear layer structures. The calculated phase velocity magnitude of the shear layer is found to be reasonably below the local velocity as expected.

Sampath, Ramgopal; Chakravarthy, S. R.

2014-09-01

53

Study of the 3D 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)

Non-potentiality of the solar coronal magnetic field accounts for the solar explosion like flares and CMEs. We apply a data-driven CESE-MHD model to investigate the three-dimensional (3D) coronal magnetic field of NOAA active region (AR) 11117 around the time of a C-class confined flare occurred on 2010 October 25. The CESE-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 photoshpere 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 basing on a set of vector magnetograms for AR 11117 taken by the Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamic Observatory (SDO) around the time of 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 (AIA), which shows that the coronal field can indeed be well characterized by the MHD equilibrium in most time. The magnetic configuration changes very limited during the studied time interval of two hours. A topological analysis reveals that the small flare is correlated with a bald patch (BP, where the magnetic field is tangent to the photoshpere), 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 magnetic free energy drops during the flare with an amount of 1.7 × 1030 erg, which can be interpreted as the energy budget released by the minor C-class flare.

Jiang, C.; Feng, X.; Wu, S.; Hu, Q.

2012-12-01

54

Turbulence and Transport The Secrets of Magnetic Confinement  

E-print Network

Turbulence and Transport The Secrets of Magnetic Confinement Martin Greenwald - MIT Plasma Science "CONFINEMENT" ? A simple analogy: water leaking out of a bucket At steady-state, define confinement time as. · #12;CONFINEMENT REQUIREMENTS FOR FUSION THE LAWSON CRITERION In steady state, Fusion Power = Loss

Greenwald, Martin

55

Confined Hard Disk System Model  

NSDL National Science Digital Library

The Confined Hard Disk System is an idealized statistical mechanics model that simulates a two-dimensional system of hard disks confined to a box with a constant temperature thermal reservoir at one end and a movable piston at the other. Slow-moving particles are color-coded as blue and fast particles are color-coded as yellow. The model computes and plots the time evolution of the kinetic energy K per particle, the pressure P, and the volume V. The model also displays histograms and mean values of these quantities. The Confined Hard Disk System was created using the Easy Java Simulations (Ejs) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_stp_hd_ConfinedHardDiskSystem.jar file will run the program if Java is installed.

Christian, Wolfgang

2010-12-27

56

Viral antigen density and confinement time regulate the reactivity pattern of CD4 T-cell responses to vaccinia virus infection.  

PubMed

T-cell recognition of ligands is polyspecific. This translates into antiviral T-cell responses having a range of potency and specificity for viral ligands. How these ligand recognition patterns are established is not fully understood. Here, we show that an activation threshold regulates whether robust CD4 T-cell activation occurs following viral infection. The activation threshold was variable because of its dependence on the density of the viral peptide (p)MHC displayed on infected cells. Furthermore, the activation threshold was not observed to be a specific equilibrium affinity (K(D)) or half-life (t(1/2)) of the TCR-viral pMHC interaction, rather it correlated with the confinement time of TCR-pMHC interactions, i.e., the half-life (t(1/2)) of the interaction accounting for the effects of TCR-pMHC rebinding. One effect of a variable activation threshold is to allow high-density viral pMHC ligands to expand CD4 T cells with a variety of potency and peptide cross-reactivity patterns for the viral pMHC ligand, some of which are only poorly activated by infections that produce a lower density of the viral pMHC ligand. These results argue that antigen concentration is a key component in determining the pattern of K(D), t(1/2) and peptide cross-reactivity of the TCRs expressed on CD4 T cells responding to infection. PMID:23248307

Vanguri, Vijay; Govern, Christopher C; Smith, Rebecca; Huseby, Eric S

2013-01-01

57

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.

2011-12-01

58

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

59

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

60

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

61

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

62

Coaxial cable stripper for confined areas  

NASA Technical Reports Server (NTRS)

Manual coaxial cable stripper quickly and accurately prepares a coaxial cable in a confined area. With this tool, preparation time is greatly reduced, and a completely inexperienced technician can perform the operation.

Brown, J. D.; Lipscomb, W. G.

1968-01-01

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

Dirac equations with confining potentials  

NASA Astrophysics Data System (ADS)

This paper is devoted to a study of relativistic eigenstates of Dirac particles which are simultaneously bound by a static Coulomb potential and added linear confining potentials. Under certain conditions, despite the addition of radially symmetric, linear confining potentials, specific bound-state energies surprisingly preserve their exact Dirac-Coulomb values. The generality of the "preservation mechanism" is investigated. To this end, a Foldy-Wouthuysen transformation is used to calculate the corrections to the spin-orbit coupling induced by the linear confining potentials. We find that the matrix elements of the effective operators obtained from the scalar, and time-like confining potentials mutually cancel for specific ratios of the prefactors of the effective operators, which must be tailored to the preservation mechanism. The result of the Foldy-Wouthuysen transformation is used to verify that the preservation is restricted (for a given Hamiltonian) to only one reference state, rather than traceable to a more general relationship among the obtained effective low-energy operators. The results derived from the nonrelativistic effective operators are compared to the fully relativistic radial Dirac equations. Furthermore, we show that the preservation mechanism does not affect antiparticle (negative-energy) states.

Noble, J. H.; Jentschura, U. D.

2015-01-01

65

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

66

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, using…

Delaplaine School District, AR.

67

Hazard Alert: Confined Spaces  

MedlinePLUS

... NIOSH. www.cpwr.com What is a confined space? Ask questions It is the employer’s responsibility to ... union. Call OSHA 1-800-321-OSHA COnFIned SpACeS Get training Your employer must train you for ...

68

Fusion, magnetic confinement  

SciTech Connect

An overview is presented of the principles of magnetic confinement of plasmas for the purpose of achieving controlled fusion conditions. Sec. 1 discusses the different nuclear fusion reactions which can be exploited in prospective fusion reactors and explains why special technologies need to be developed for the supply of tritium or {sup 3}He, the probable fuels. In Sec. 2 the Lawson condition, a criterion that is a measure of the quality of confinement relative to achieving fusion conditions, is explained. In Sec. 3 fluid equations are used to describe plasma confinement. Specific confinement configurations are considered. In Sec. 4 the orbits of particle sin magneti and electric fields are discussed. In Sec. 5 stability considerations are discussed. It is noted that confinement systems usually need to satisfy stability constraints imposed by ideal magnetohydrodynamic (MHD) theory. The paper culminates with a summary of experimental progress in magnetic confinement. Present experiments in tokamaks have reached the point that the conditions necessary to achieve fusion are being satisfied.

Berk, H.L.

1992-08-06

69

Swirl, confinement and nozzle effects on confined turbulent flow  

NASA Technical Reports Server (NTRS)

Predictions of swirl, confinement and nozzle effects on confined turbulent flow are exhibited and compared with five-hole pitot-probe time-mean velocity measurements. Two sets of computations are given, one using the standard k-epsilon turbulence model and the other using a C sub mu formulation model deduced from recent six-orientation single-wire hot-wire measurements. Results confirm that the accuracy of the latter model is superior. To highlight the effects of confinement and exit nozzle area on this flow, three expansion ratios and two contraction ratios are used. Predictions are given for a full range of swirl strengths using measured inlet conditions for axial, radial and swirl velocity profiles. The predicted velocity profiles illustrate the large-scale effects of inlet swirl on flowfields. It appears that a strong contraction nozzle has a pronounced effect, on swirl flow cases, with discouragement of central recirculation zones, and forward flow in highly swirled vortex core regions. The expansion ratio value has large-scale effects on the size and location of the recirculation zones.

Abujelala, M. T.; Lilley, D. G.

1984-01-01

70

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

71

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

72

Turbulence in Magnetically Confined Plasmas  

NASA Astrophysics Data System (ADS)

Experimental characterization of plasma fluctuations has lead to significant insights into the dynamics of turbulent transport processes in magnetically confined fusion plasmas. Fluctuations on the scale of the ion gyroradius result in cross-field transport of particles, energy and momentum at rates that significantly exceed collisional (neoclassical) transport. The energy confinement time and, ultimately, fusion power are thus strongly dependent on this turbulent-driven transport. Turbulent eddy structures are found to be highly anisotropic (k||k), with the magnetic field defining a symmetry direction: parallel wavelengths scale with machine size, while perpendicular wavelengths scale with gyroradius. Measurement techniques using optical, microwave, beam, and laser-based methods have been developed to remotely probe relevant fluctuations in density, temperature, potential and velocity, including density imaging. Measured fluctuation characteristics are generally consistent with gyrokinetic simulations of drift wave turbulence: correlation lengths scale with ion gyroradius (?I); amplitudes scale with &*circ;(=?I/a); decorrelation rates scale with the acoustic timescale, ?c˜a/cs; and wavenumber spectra peak near k??I˜0.25 and kr?I˜0. Measurements of potential fluctuations and poloidal turbulence flows show evidence for n=0, m=0 zonal flows, including the coherent geodesic acoustic mode. These nonlinearly driven flows saturate turbulence via flow shearing. Such flows appear crucial to L-H confinement transitions and core barrier formation. Dependencies of turbulence on critical transport parameters will be reviewed in tokamak, stellarator and spherical torus geometries. Understanding these dependencies, as well as challenging and validating simulations, will be crucial to confidently predicting transport and confinement in burning plasmas.

McKee, G. R.

2012-10-01

73

Confined Brownian ratchets  

E-print Network

We analyze the dynamics of Brownian ratchets in a confined environment. The motion of the particles is described by a Fick-Jakobs kinetic equation in which the presence of boundaries is modeled by means of an entropic potential. The cases of a flashing ratchet, a two-state model and a ratchet under the influence of a temperature gradient are analyzed in detail. We show the emergence of a strong cooperativity between the inherent rectification of the ratchet mechanism and the entropic bias of the fluctuations caused by spatial confinement. Net particle transport may take place in situations where none of those mechanisms leads to rectification when acting individually. The combined rectification mechanisms may lead to bidirectional transport and to new routes to segregation phenomena. Confined Brownian ratchets (CBR) could be used to control transport in mesostructures and to engineer new and more efficient devices for transport at the nanoscale.

Malgaretti, Paolo; Rubi, J Miguel

2013-01-01

74

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

75

Confinement of quarks  

Microsoft Academic Search

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

Gerard't Hooft

2003-01-01

76

Hazard Alert: Confined Spaces  

MedlinePLUS

... on your worksite. Do not enter without proper training. Never enter alone. A self-employed handyman died in this water service manhole. He had been called to fix a water leak in an adjacent rental house and was working alone. Know the basics… ... SpACeS Get training Your employer must train you for confined space ...

77

Polymer translocation into a confined space: Influence of the chain stiffness and the shape of the confinement  

NASA Astrophysics Data System (ADS)

Using two-dimensional Langevin dynamics simulations, we investigate the dynamics of polymer translocation into a confined space under a driving force through a nanopore, with particular emphasis on the chain stiffness and the shape of the confinement. We observe that with increasing the chain stiffness ?, the translocation time ? always increases for different shapes of confinements. For an ellipse, ? is different for the translocation through its minor and major axis directions. Under the weak confinement, the translocation through the minor axis direction is faster than that through the major axis direction for different ?, while this is true only for high ? under strong confinement. Particularly, for both weak and strong confinements we find that packaging into an ellipse through its minor axis direction is faster than that for a circle of the same area for high ?. These results are interpreted by the chain conformation during the translocation process and the time of an individual segment passing through the pore.

Zhang, Kehong; Luo, Kaifu

2014-03-01

78

Time-dependent resonant UHF CI approach for the photo-induced dynamics of the multi-electron system confined in 2D QD  

SciTech Connect

We extend the static multi-reference description (resonant UHF) to the dynamic system in order to include the correlation effect over time, and simplify the TD Schrödinger equation (TD-CI) into a time-developed rate equation where the TD external field ??(t) is then incorporated directly in the Hamiltonian without any approximations. We apply this TD-CI method to the two-electron ground state of a 2D quantum dot (QD) under photon injection and study the resulting two-electron Rabi oscillation.

Okunishi, Takuma; Clark, Richard; Takeda, Kyozaburo [Waseda University, Tokyo 169-8555 (Japan); Kusakabe, Kouichi [Osaka University, Osaka 560-8531 (Japan); Tomita, Norikazu [Yamagata University, Yamagata 960-8560 (Japan)

2013-12-04

79

Time-dependent resonant UHF CI approach for the photo-induced dynamics of the multi-electron system confined in 2D QD  

NASA Astrophysics Data System (ADS)

We extend the static multi-reference description (resonant UHF) to the dynamic system in order to include the correlation effect over time, and simplify the TD Schrödinger equation (TD-CI) into a time-developed rate equation where the TD external field ?'(t) is then incorporated directly in the Hamiltonian without any approximations. We apply this TD-CI method to the two-electron ground state of a 2D quantum dot (QD) under photon injection and study the resulting two-electron Rabi oscillation.

Okunishi, Takuma; Clark, Richard; Takeda, Kyozaburo; Kusakabe, Kouichi; Tomita, Norikazu

2013-12-01

80

Vortex Ring Dynamics in Radially Confined Domains  

NASA Astrophysics Data System (ADS)

Vortex ring dynamics have been studied extensively in semi-infinite quiescent volumes. However, very little is known about vortex-ring formation in wall-bounded domains where vortex wall interaction will affect both the vortex ring pinch-off and propagation velocity. This study addresses this limitation and studies vortex formation in radially confined domains to analyze the affect of vortex-ring wall interaction on the formation and propagation of the vortex ring. Vortex rings were produced using a pneumatically driven piston cylinder arrangement and were ejected into a long cylindrical tube which defined the confined downstream domain. A range of confinement domains were studied with varying confinement diameters Velocity field measurements were performed using planar Time Resolved Digital Particle Image Velocimetry (TRDPIV) and were processed using an in-house developed cross-correlation PIV algorithm. The experimental analysis was used to facilitate the development of a theoretical model to predict the variations in vortex ring circulation over time within confined domains.

Stewart, Kelley; Niebel, Casandra; Jung, Sunghwan; Vlachos, Pavlos

2010-11-01

81

Confined Hard Disk Two Piston System Model  

NSDL National Science Digital Library

The Confined Hard Disk Two Piston System simulates a constant-energy two-dimensional system of unit mass particles confined by two frictionless pistons of equal mass M. This computer model complements theoretical work describing the adiabatic expansion of an ideal gas using the quasi-static approximation. Users can set the number of particles N, their diameter and their initial particle kinetic energy. Slow-moving particles are color-coded as blue and fast particles are color-coded as yellow. The time evolution of temperature, pressure, and piston speed are shown in a second window.   Particles in this model have unit mass and interact through contact forces. Collision times are computed analytically because particles and pistons move with constant velocity between collisions. The time evolution algorithm advances the particle position from collision to collision until the requested time step is achieved. The time evolution is then paused, data is accumulated, and the screen is redrawn. The Confined Hard Disk Two Piston System was developed using the Easy Java Simulations (Ejs) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_stp_hd_ConfinedHardDiskTwoPistonSystem.jar file will run the program if Java is installed.

Christian, Wolfgang

2011-03-09

82

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

83

Properties of radio-frequency heated argon confined uranium plasmas  

NASA Technical Reports Server (NTRS)

Pure uranium hexafluoride (UF6) was injected into an argon confined, steady state, rf-heated plasma within a fused silica peripheral wall test chamber. Exploratory tests conducted using an 80 kW rf facility and different test chamber flow configurations permitted selection of the configuration demonstrating the best confinement characteristics and minimum uranium compound wall coating. The overall test results demonstrated applicable flow schemes and associated diagnostic techniques were developed for the fluid mechanical confinement and characterization of uranium within an rf plasma discharge when pure UF6 is injected for long test times into an argon-confined, high-temperature, high-pressure, rf-heated plasma.

1976-01-01

84

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

85

Freezing in confined geometries  

NASA Technical Reports Server (NTRS)

Results of detailed structural studies, using elastic neutron scattering, of the freezing of liquid O2 and D2 in porous vycor glass, are presented. The experimental studies have been complemented by computer simulations of the dynamics of freezing of a Lennard-Jones liquid in narrow channels bounded by molecular walls. Results point to a new simple physical interpretation of freezing in confined geometries.

Sokol, P. E.; Ma, W. J.; Herwig, K. W.; Snow, W. M.; Wang, Y.; Koplik, Joel; Banavar, Jayanth R.

1992-01-01

86

Inertial Confinement fusion targets  

NASA Technical Reports Server (NTRS)

Inertial confinement fusion (ICF) targets are made as simple flat discs, as hollow shells or as complicated multilayer structures. Many techniques were devised for producing the targets. Glass and metal shells are made by using drop and bubble techniques. Solid hydrogen shells are also produced by adapting old methods to the solution of modern problems. Some of these techniques, problems, and solutions are discussed. In addition, the applications of many of the techniques to fabrication of ICF targets is presented.

Hendricks, C. D.

1982-01-01

87

Shear Relaxations of Confined Liquids.  

NASA Astrophysics Data System (ADS)

Ultrathin (<40 A) 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^{-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 Celsius 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 (~80 nm ^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 (7nm^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 (>10^4 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, George Amos, Jr.

88

Confinement of test particles in warped spacetimes  

Microsoft Academic Search

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

Suman Ghoshand; Sayan Kar; Hemwati Nandan

2010-01-01

89

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

90

Preface: Special Topic on Interfacial and Confined Water  

SciTech Connect

This Special Topic on the Chemical Physics of Interfacial and Confined Water contains a collection of original research papers that showcase recent theoretical and experimental advances in the field. These papers provide a timely discussion of fundamental aspects of interfacial and confined water that are important in both natural environments and engineered applications.

Molinero, Valeria; Kay, Bruce D.

2014-11-14

91

Holographic collisions in confining theories  

NASA Astrophysics Data System (ADS)

We study the gravitational dual of a high-energy collision in a confining gauge theory. We consider a linearized approach in which two point particles traveling in an AdS-soliton background suddenly collide to form an object at rest (presumably a black hole for large enough center-of-mass energies). The resulting radiation exhibits the features expected in a theory with a mass gap: late-time power law tails of the form t -3/2, the failure of Huygens' principle and distortion of the wave pattern as it propagates. The energy spectrum is exponentially suppressed for frequencies smaller than the gauge theory mass gap. Consequently, we observe no memory effect in the gravitational waveforms. At larger frequencies the spectrum has an upward-stairway structure, which corresponds to the excitation of the tower of massive states in the confining gauge theory. We discuss the importance of phenomenological cutoffs to regularize the divergent spectrum, and the aspects of the full non-linear collision that are expected to be captured by our approach.

Cardoso, Vitor; Emparan, Roberto; Mateos, David; Pani, Paolo; Rocha, Jorge V.

2014-01-01

92

A novel method for modeling the neutron time of flight (nTOF) detector response in current mode to inertial confinement fusion experiments.  

SciTech Connect

There are several machines in this country that produce short bursts of neutrons for various applications. A few examples are the Zmachine, operated by Sandia National Laboratories in Albuquerque, NM; the OMEGA Laser Facility at the University of Rochester in Rochester, NY; and the National Ignition Facility (NIF) operated by the Department of Energy at Lawrence Livermore National Laboratory in Livermore, California. They all incorporate neutron time of flight (nTOF) detectors which measure neutron yield, and the shapes of the waveforms from these detectors contain germane information about the plasma conditions that produce the neutrons. However, the signals can also be %E2%80%9Cclouded%E2%80%9D by a certain fraction of neutrons that scatter off structural components and also arrive at the detectors, thereby making analysis of the plasma conditions more difficult. These detectors operate in current mode - i.e., they have no discrimination, and all the photomultiplier anode charges are integrated rather than counted individually as they are in single event counting. Up to now, there has not been a method for modeling an nTOF detector operating in current mode. MCNPPoliMiwas developed in 2002 to simulate neutron and gammaray detection in a plastic scintillator, which produces a collision data output table about each neutron and photon interaction occurring within the scintillator; however, the postprocessing code which accompanies MCNPPoliMi assumes a detector operating in singleevent counting mode and not current mode. Therefore, the idea for this work had been born: could a new postprocessing code be written to simulate an nTOF detector operating in current mode? And if so, could this process be used to address such issues as the impact of neutron scattering on the primary signal? Also, could it possibly even identify sources of scattering (i.e., structural materials) that could be removed or modified to produce %E2%80%9Ccleaner%E2%80%9D neutron signals? This process was first developed and then applied to the axial neutron time of flight detectors at the ZFacility mentioned above. First, MCNPPoliMi was used to model relevant portions of the facility between the source and the detector locations. To obtain useful statistics, variance reduction was utilized. Then, the resulting collision output table produced by MCNPPoliMi was further analyzed by a MATLAB postprocessing code. This converted the energy deposited by neutron and photon interactions in the plastic scintillator (i.e., nTOF detector) into light output, in units of MeVee%D1%84 (electron equivalent) vs time. The time response of the detector was then folded into the signal via another MATLAB code. The simulated response was then compared with experimental data and shown to be in good agreement. To address the issue of neutron scattering, an %E2%80%9CIdeal Case,%E2%80%9D (i.e., a plastic scintillator was placed at the same distance from the source for each detector location) with no structural components in the problem. This was done to produce as %E2%80%9Cpure%E2%80%9D a neutron signal as possible. The simulated waveform from this %E2%80%9CIdeal Case%E2%80%9D was then compared with the simulated data from the %E2%80%9CFull Scale%E2%80%9D geometry (i.e., the detector at the same location, but with all the structural materials now included). The %E2%80%9CIdeal Case%E2%80%9D was subtracted from the %E2%80%9CFull Scale%E2%80%9D geometry case, and this was determined to be the contribution due to scattering. The time response was deconvolved out of the empirical data, and the contribution due to scattering was then subtracted out of it. A transformation was then made from dN/dt to dN/dE to obtain neutron spectra at two different detector locations.

Nelson, Alan J. [University of New Mexico, Albuquerque, NM; Cooper, Gary Wayne [University of New Mexico, Albuquerque, NM; Ruiz, Carlos L.; Chandler, Gordon Andrew; Fehl, David Lee; Hahn, Kelly Denise; Leeper, Ramon Joe; Smelser, Ruth Marie; Torres, Jose A.

2013-09-01

93

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

94

Forecasting Confined Spatiotemporal Chaos with Genetic Algorithms  

NASA Astrophysics Data System (ADS)

A technique to forecast spatiotemporal time series is presented. It uses a proper orthogonal or Karhunen-Loève decomposition to encode large spatiotemporal data sets in a few time series, and genetic algorithms to efficiently extract dynamical rules from the data. The method works very well for confined systems displaying spatiotemporal chaos, as exemplified here by forecasting the evolution of the one-dimensional complex Ginzburg-Landau equation in a finite domain.

López, Cristóbal; Álvarez, Alberto; Hernández-García, Emilio

2000-09-01

95

Forecasting confined spatiotemporal chaos with genetic algorithms.  

PubMed

A technique to forecast spatiotemporal time series is presented. It uses a proper orthogonal or Karhunen-Loève decomposition to encode large spatiotemporal data sets in a few time series, and genetic algorithms to efficiently extract dynamical rules from the data. The method works very well for confined systems displaying spatiotemporal chaos, as exemplified here by forecasting the evolution of the one-dimensional complex Ginzburg-Landau equation in a finite domain. PMID:10977996

López, C; Alvarez, A; Hernández-García, E

2000-09-11

96

Understanding Confinement From Deconfinement  

E-print Network

We use effective magnetic SU(N) pure gauge theory with cutoff M and fixed gauge coupling g_m to calculate non-perturbative magnetic properties of the deconfined phase of SU(N) Yang-Mills theory. We obtain the response to an external closed loop of electric current by reinterpreting and regulating the calculation of the one loop effective potential in Yang-Mills theory. This effective potential gives rise to a color magnetic charge density, the counterpart in the deconfined phase of color magnetic currents introduced in effective dual superconductor theories of the confined phase via magnetically charged Higgs fields. The resulting spatial Wilson loop has area law behavior. Using values of M and g_m determined in the confined phase, we find SU(3) spatial string tensions compatible with lattice simulations in the temperature interval 1.5T_c < T < 2.5T_c. Use of the effective theory to analyze experiments on heavy ion collisions will provide applications and further tests of these ideas.

M. Baker

2007-12-03

97

Crystallization under nanoscale confinement.  

PubMed

Classical crystal growth models posit that crystallization outcomes are determined by nuclei that resemble mature crystal phases, but at a critical size where the volume free energy of nuclei begins to offset the unfavorable surface free energy arising from the interface with the growth medium. Crystallization under nanoscale confinement offers an opportunity to examine nucleation and phase transformations at length scales corresponding to the critical size, at which kinetics and thermodynamics of nucleation and growth intersect and dramatic departures in stability compared to bulk crystals can appear. This tutorial review focuses on recent investigations of the crystallization of organic compounds in nanoporous matrices that effectively provide millions of nanoscale reactors in a single sample, ranging from controlled porous glass (CPG) beads to nanoporous block-copolymer monoliths to anodic aluminum oxide (AAO) membranes. Confinement of crystal growth in this manner provides a snapshot of the earliest stages of crystal growth, with insights into nucleation, size-dependent polymorphism, and thermotropic behavior of nanoscale crystals. Moreover, these matrices can be used to screen for crystal polymorphs and assess their stability as nanocrystals. The well-aligned cylindrical nanoscale pores of polymer monoliths or AAO also allow determination of preferred orientation of embedded nanocrystals, affording insight into the competitive nature of nucleation, critical sizes, and phase transition mechanisms. Collectively, these investigations have increased our understanding of crystallization at length scales that are deterministic while suggesting strategies for controlling crystallization outcomes. PMID:24081010

Jiang, Qi; Ward, Michael D

2014-04-01

98

Confined diffusion in periodic porous nanostructures.  

PubMed

We performed fluorescence correlation spectroscopy measurements to assess the long-time self-diffusion of a variety of spherical tracer particles in periodic porous nanostructures. Inverse opal structures with variable cavity sizes and openings in the nanometer domain were employed as the model system. We obtained both the exponent of the scaling relation between mean-square displacement and time and the slow-down factors due to the periodic confinement for a number of particle sizes and confining characteristics. In addition, we carried out Brownian dynamics simulations to model the experimental conditions. Good agreement between experimental and simulation results has been obtained regarding the slow-down factor. Fickian diffusion is predicted and seen in almost all experimental systems, while apparent non-Fickian exponents that show up for two strongly confined systems are attributed to polydispersity of the cavity openings. The utility of confining periodic porous nanostructures holds promise toward understanding of constrained diffusion with a wide range of applications ranging from water purification and drug delivery to tissue engineering. PMID:21548605

Raccis, Riccardo; Nikoubashman, Arash; Retsch, Markus; Jonas, Ulrich; Koynov, Kaloian; Butt, Hans-Jürgen; Likos, Christos N; Fytas, George

2011-06-28

99

Amoeboid motion in confined geometry  

E-print Network

Cells of the immune system, as well as cancer cells, migrating in confined environment of tissues undergo frequent shape changes (described as amoeboid motion) that enable them to move forward through these porous media without the assistance of adhesion sites. In other words, they perform amoeboid swimming (AS) while using extracellular matrices and cells of tissues as support. We introduce a simple model of AS in a confined geometry solved by means of 2D numerical simulations. We find that confinement promotes AS, unless being so strong that it restricts shape change amplitude. A straight AS trajectory in the channel is found to be unstable, and ample lateral excursions of the swimmer prevail. For weak confinement, these excursions are symmetric, while they become asymmetric at stronger confinement, whereby the swimmer is located closer to one of the two walls. This is a spontaneous symmetry-breaking bifurcation. We find that there exists an optimal confinement for migration. We provide numerical results as...

Wu, Hao; Hu, Wei-Fan; Farutin, Alexander; Rafaï, Salima; Lai, Ming-Chih; Peyla, Philippe; Misbah, Chaouqi

2015-01-01

100

Confinement vessel analysis final report  

SciTech Connect

The overall purpose of the confinement vessel analysis program was to aid Los Alamos in validation of a new confinement vessel configuration. This was done in two steps: First, we developed a finite element analysis model of the benchmark confinement vessel and compared the results against test results to verify the accuracy of the model and analysis technique. We then changed the finite element model to represent the new confinement vessel configuration and predicted the response of the new vessel for specified loading conditions. This report describes the work done to achieve the objective.

Lewis, B.B. [APTEK, Inc., Colorado Springs, CO (United States)

1992-05-06

101

Dirac Equations with Linear Confining Potentials  

E-print Network

This paper is devoted to a study of relativistic eigenstates of Dirac particles which are simultaneously bound by a static Coulomb potential and added linear confining potentials. It has recently been shown that, despite the addition of radially symmetric, linear confining potentials, some specific bound-state energies surprisingly retain their exact Dirac-Coulomb values (in the sense of an "exact symmetry"). This observation raises pertinent questions as to the generality of the cancellation mechanism. A Foldy-Wouthuysen transformation is used to find the relevant nonrelativistic physical degrees of freedom, which include additional spin-orbit couplings induced by the linear confining potentials. The matrix elements of the effective operators obtained from the scalar, and time-like confining potentials mutually cancel for specific ratios of the prefactors of the effective operators, which must be tailored to the cancellation mechanism. The result of the Foldy-Wouthuysen transformation is used to explicitly show that the cancellation is accidental and restricted (for a given Hamiltonian) to only one reference state, rather than traceable to a more general relationship among the obtained effective low-energy operators. Furthermore, we show that the cancellation mechanism does not affect anti-particle (negative-energy) states.

J. H. Noble; U. D. Jentschura

2014-10-03

102

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

103

Structure and dynamics of a Gay-Berne liquid crystal confined in cylindrical nanopores  

NASA Astrophysics Data System (ADS)

Gay-Berne liquid crystals confined in two cylindrical nanopores with different pore sizes were studied by molecular dynamics simulation. Their structure and dynamics properties were obtained and compared with those of the bulk. Our data show that confinement changes the bulk isotropic-to-nematic transition to a continuous ordering from a paranematic to a nematic phase. Moreover, confinement strongly hinders the smectic translational order. The molecular dynamics is characterized by the translational diffusion coefficients and the first-rank reorientational correlation times. Very different characteristic times and temperature variations in the dynamics are observed in confinement. Spatially resolved quantities illustrate that confinement induces predominant structural and dynamical heterogeneities.

Ji, Qing; Lefort, Ronan; Busselez, Rémi; Morineau, Denis

2009-06-01

104

UNIVERSITY OF WASHINGTON CONFINED SPACE EVALUATION FORM  

E-print Network

UNIVERSITY OF WASHINGTON CONFINED SPACE EVALUATION FORM ENVIRONMENTAL HEALTH & SAFETY DateYour Name. Building/Area Room # Location Key # CONFINED SPACE AND PERMIT REQUIRED CONFINED SPACE This section must be filled out for both CS (Confined Space) and PRCS (Permit Required Confined Space). SIZE: Can a person get

Wilcock, William

105

Confinement scaling and ignition in tokamaks  

SciTech Connect

A drift wave turbulence model is used to compute the scaling and magnitude of central electron temperature and confinement time of tokamak plasmas. The results are in accord with experiment. Application to ignition experiments shows that high density (1 to 2) . 10/sup 15/ cm/sup -3/, high field, B/sub T/ > 10 T, but low temperature T approx. 6 keV constitute the optimum path to ignition.

Perkins, F.W.; Sun, Y.C.

1985-10-01

106

Confinement of semiflexible polymers  

NASA Astrophysics Data System (ADS)

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, R0, 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?2R0 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.

Guven, Jemal; Vázquez-Montejo, Pablo

2012-02-01

107

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

108

Dissipation-Driven Behavior of Nonpropagating Hydrodynamic Solitons Under Confinement  

NASA Astrophysics Data System (ADS)

We have identified a physical mechanism that rules the confinement of nonpropagating hydrodynamic solitons. We show that thin boundary layers arising on walls are responsible for a jump in the local damping. The outcome is a weak dissipation-driven repulsion that determines decisively the solitons' long-time behavior. Numerical simulations of our model are consistent with experiments. Our results uncover how confinement can generate a localized distribution of dissipation in out-of-equilibrium systems. Moreover, they show the preponderance of such a subtle effect in the behavior of localized structures. The reported results should explain the dynamic behavior of other confined dissipative systems.

Gordillo, Leonardo; García-Áustes, Mónica A.

2014-04-01

109

Dissipation-driven behavior of nonpropagating hydrodynamic solitons under confinement.  

PubMed

We have identified a physical mechanism that rules the confinement of nonpropagating hydrodynamic solitons. We show that thin boundary layers arising on walls are responsible for a jump in the local damping. The outcome is a weak dissipation-driven repulsion that determines decisively the solitons' long-time behavior. Numerical simulations of our model are consistent with experiments. Our results uncover how confinement can generate a localized distribution of dissipation in out-of-equilibrium systems. Moreover, they show the preponderance of such a subtle effect in the behavior of localized structures. The reported results should explain the dynamic behavior of other confined dissipative systems. PMID:24815651

Gordillo, Leonardo; García-Ñustes, Mónica A

2014-04-25

110

Dust confinement in anodic plasmas  

SciTech Connect

Experiments on dust confinement in a magnetized plasma region in front of a small positively biased electrode are analyzed. The axial confinement of d = 1{mu}m particles can be quantitatively described by a balance of ion drag and electric field force. Radial confinement is due to strong electric fields. It is demonstrated that this anodic plasma has a distinctly different discharge mechanism from fireballs with ionizing double layers. The plasma is stable against potential relaxations but shows a strong ion cyclotron mode in the shear layer at the anode edge.

Piel, A.; Trottenberg, T.; Block, D. [IEAP, Christian-Albrechts-University, D-24098 Kiel (Germany)

2005-10-31

111

Partial confinement photonic crystal waveguides  

SciTech Connect

One-dimensional photonic crystal waveguides with an incomplete photonic band gap are modeled and proposed for an integration application that exploits their property of partial angular confinement. Planar apodized photonic crystal structures are deposited by plasma enhanced chemical vapor deposition and characterized by reflectivity as a function of angle and polarization, validating a partial confinement design for light at 850 nm wavelength. Partial confinement identifies an approach for tailoring waveguide properties by the exploitation of conformal film deposition over a substrate with angularly dependent topology. An application for an optoelectronic transceiver is demonstrated.

Saini, S.; Hong, C.-Y.; Pfaff, N.; Kimerling, L. C.; Michel, J. [Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

2008-12-29

112

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

113

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

114

Single-molecule mobility in confined and crowded femtolitre chambers.  

PubMed

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 femtolitre-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. PMID:23303284

Fowlkes, Jason D; Collier, C Patrick

2013-03-01

115

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 {times} 10{sup 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.

Nebel, R.A.; Barnes, D.C.; Caramana, E.J.; Janssen, R.D.; Nystrom, W.D.; Tiouririne, T.N.; Trent, B.C. [Los Alamos National Lab., NM (United States); Miley, G.H.; Javedani, J. [Univ. of Illinois, Urbana, IL (United States)

1995-12-31

116

Ionic liquids in confined geometries.  

PubMed

Over recent years the Surface Force Apparatus (SFA) has been used to carry out model experiments revealing structural and dynamic properties of ionic liquids confined to thin films. Understanding characteristics such as confinement induced ion layering and lubrication is of primary importance to many applications of ionic liquids, from energy devices to nanoparticle dispersion. This Perspective surveys and compares SFA results from several laboratories as well as simulations and other model experiments. A coherent picture is beginning to emerge of ionic liquids as nano-structured in pores and thin films, and possessing complex dynamic properties. The article covers structure, dynamics, and colloidal forces in confined ionic liquids; ionic liquids are revealed as a class of liquids with unique and useful confinement properties and pertinent future directions of research are highlighted. PMID:22301770

Perkin, Susan

2012-04-21

117

Alternative approaches to plasma confinement  

NASA Technical Reports Server (NTRS)

The potential applications of fusion reactors, the desirable properties of reactors intended for various applications, and the limitations of the Tokamak concept are discussed. The principles and characteristics of 20 distinct alternative confinement concepts are described, each of which may be an alternative to the Tokamak. The devices are classed as Tokamak-like, stellarator-like, mirror machines, bumpy tori, electrostatically assisted, migma concept, and wall-confined plasma.

Roth, J. R.

1977-01-01

118

Quark confinement and metric fluctuations  

E-print Network

We analyse, by doing very simple calculations, the internal degree of freedom leading to the de Broglie frequency associated to a material particle, as well, the confinement of quarks provided both by the Cornell potential and by the MIT bag model.We propose that the driving forces behind these confining models could be originated in the fluctuations of the metric, namely the particle interacting self-gravitationally, when its mass fluctuates in position throught of a distance equal to the Planck length.

P. R. Silva

2009-08-23

119

Amoeboid motion in confined geometry  

E-print Network

Cells of the immune system, as well as cancer cells, migrating in confined environment of tissues undergo frequent shape changes (described as amoeboid motion) that enable them to move forward through these porous media without the assistance of adhesion sites. In other words, they perform amoeboid swimming (AS) while using extracellular matrices and cells of tissues as support. We introduce a simple model of AS in a confined geometry solved by means of 2D numerical simulations. We find that confinement promotes AS, unless being so strong that it restricts shape change amplitude. A straight AS trajectory in the channel is found to be unstable, and ample lateral excursions of the swimmer prevail. For weak confinement, these excursions are symmetric, while they become asymmetric at stronger confinement, whereby the swimmer is located closer to one of the two walls. This is a spontaneous symmetry-breaking bifurcation. We find that there exists an optimal confinement for migration. We provide numerical results as well as scaling laws. This study raises the question of the relevance of these scenarios to complex situations encountered in vivo.

Hao Wu; Marine Thiébaut; Wei-Fan Hu; Alexander Farutin; Salima Rafaï; Ming-Chih Lai; Philippe Peyla; Chaouqi Misbah

2015-02-13

120

Confined PBX 9501 gap reinitiation studies  

SciTech Connect

For explosive systems that exhibit gaps or cracks between their internal components (either by design or mechanical failure), measurable time delays exist for detonation waves crossing them. Reinitiation across such gaps is dependent on the type of explosive, gap width, gap morphology, confinement, and temperature effects. To examine this reinitiation effect, a series of tests has been conducted to measure the time delay across a prescribed gap within an 'infinitely' confined PBX 9501 system. Detonation breakout along the explosive surface is measured with a streak camera, and flow features are examined during reinitiation near the gap. Such tests allow for quantitative determination of the time delay corresponding to the time of initiation across a given gap oriented normal to the direction of the detonation wave. Measured time delays can be compared with numerical calculations, making it possible to validate initiation models as well as estimate detonation run-up distances. Understanding this reinitiation behavior is beneficial for the design and evaluation of explosive systems that require precision timing and performance.

Salyer, Terry R [Los Alamos National Laboratory; Hill, Larry G [Los Alamos National Laboratory; Lam, Kin [Los Alamos National Laboratory

2009-01-01

121

DNA Confined in Nanochannels and Nanoslits  

NASA Astrophysics Data System (ADS)

It has become increasingly apparent in recent years that next-generation sequencing (NGS) has a blind spot for large scale genomic variation, which is crucial for understanding the genotype-phenotype relationship. Genomic mapping methods attempt to overcome the weakesses of NGS by providing a coarse-grained map of the distances between restriction sites to aid in sequence assembly. From such methods, one hopes to realize fast and inexpensive de novo sequencing of human and plant genomes. One of the most promising methods for genomic mapping involves placing DNA inside a device only a few dozen nanometers wide called a nanochannel. A nanochannel stretches the DNA so that the distance between fluorescently labeled restriction sites can be measured en route to obtaining an accurate genome map. Unfortunately for those who wish to design devices, the physics of how DNA stretches when confined in a nanochannel is still an active area of research. Indeed, despite decades old theories from polymer physics regarding weakly and strongly stretched polymers, seminal experiments in the mid-2000s have gone unexplained until very recently. With a goal of creating a realistic engineering model of DNA in nanochannels, this dissertation addresses a number of important outstanding research topics in this area. We first discuss the physics of dilute solutions of DNA in free solution, which show distinctive behavior due to the stiff nature of the polymer. We then turn our attention to the equilibrium regimes of confined DNA and explore the effects of stiff chains and weak excluded volume on the confinement free energy and polymer extension. We also examine dynamic properties such as the diffusion coefficient and the characteristic relaxation time. Finally, we discuss a sister problem related to DNA confined in nanoslits, which shares much of the same physics as DNA confined in channels. Having done this, we find ourselves with a well-parameterized wormlike chain model that is remarkably accurate in describing the behavior of DNA in confinement. As such, it appears that researchers may proceed with the rational design of nanochannel mapping devices using this model.

Tree, Douglas R.

122

PREFACE: Water in confined geometries  

NASA Astrophysics Data System (ADS)

The study of water confined in complex systems in solid or gel phases and/or in contact with macromolecules is relevant to many important processes ranging from industrial applications such as catalysis and soil chemistry, to biological processes such as protein folding or ionic transport in membranes. Thermodynamics, phase behaviour and the molecular mobility of water have been observed to change upon confinement depending on the properties of the substrate. In particular, polar substrates perturb the hydrogen bond network of water, inducing large changes in the properties upon freezing. Understanding how the connected random hydrogen bond network of bulk water is modified when water is confined in small cavities inside a substrate material is very important for studies of stability and the enzymatic activity of proteins, oil recovery or heterogeneous catalysis, where water-substrate interactions play a fundamental role. The modifications of the short-range order in the liquid depend on the nature of the water-substrate interaction, hydrophilic or hydrophobic, as well as on its spatial range and on the geometry of the substrate. Despite extensive study, both experimentally and by computer simulation, there remain a number of open problems. In the many experimental studies of confined water, those performed on water in Vycor are of particular interest for computer simulation and theoretical studies since Vycor is a porous silica glass characterized by a quite sharp distribution of pore sizes and a strong capability to absorb water. It can be considered as a good candidate for studying the general behaviour of water in hydrophilic nanopores. But there there have been a number of studies of water confined in more complex substrates, where the interpretation of experiments and computer simulation is more difficult, such as in zeolites or in aerogels or in contact with membranes. Of the many problems to consider we can mention the study of supercooled water. It is particularly important to understand whether the glass transition temperature could be experimentally accessible for confined water. In this respect the modifications induced by the confinement on the dynamics of water on supercooling are of extreme interest and a number of experimental and computer simulation studies have been devoted in recent years to this topic. This special section contains papers from different groups which have contributed with various experimental and computer simulation techniques to the progress made in the study of water in confined geometry. I thank all of the authors for their stimulating contributions. I am very pleased in particular that Sow-Hsin Chen agreed to contribute since he has done pioneering experimental work on the dynamical properties of confined water upon supercooling, and he is still very active in the field. The work presented by the group of J Swenson concerns also the glass transition of confined water. The Messina group (Crupi et al) is very active in the study of dynamical properties of confined water and they present their results on water in zeolites. From the experimental side there is also a contribution from J Dore's group, one of the first to perform neutron scattering studies on confined water. The work of J Klein looks at the mobility of water molecules confined in subnanometre films. Important contributions on the computer simulation side come from the Geiger group (Brovchenko et al). They performed very accurate simulations of water in nanopores, exploring a large portion of the phase space. Puibasset et al were able to build a very realistic model to simulate water inside Vycor. Zangi et al review the extensive work performed on confined water. Jedlovszky is an expert on the model potential for water and studied how the hydrogen bond network of water can be modified by the presence of an interface. The special issue is intended to stimulate interest and future work on this important subject.

Rovere, Mauro

2004-11-01

123

Velocity alignment leads to high persistence in confined cells  

NASA Astrophysics Data System (ADS)

Many cell types display random motility on two-dimensional substrates but crawl persistently in a single direction when confined in a microchannel or on an adhesive micropattern. Does this imply that the motility mechanism of confined cells is fundamentally different from that of unconfined cells? We argue that both free- and confined-cell migration may be described by a generic model of cells as "velocity-aligning" active Brownian particles previously proposed to solve a completely separate problem in collective cell migration. Our model can be mapped to a diffusive escape over a barrier and analytically solved to determine the cell's orientation distribution and repolarization rate. In quasi-one-dimensional confinement, velocity-aligning cells maintain their direction for times that can be exponentially larger than their persistence time in the absence of confinement. Our results suggest an important connection between single- and collective-cell migration: high persistence in confined cells corresponds with fast alignment of velocity to cell-cell forces.

Camley, Brian A.; Rappel, Wouter-Jan

2014-06-01

124

Nanotribology of confined thin films  

NASA Astrophysics Data System (ADS)

In this dissertation I present the results of the study of the friction behavior of molecularly smooth mica surfaces confining thin films of different materials. The main objective was to improve the basic understanding of the mechanism underlying frictional processes, to assist the development of new techniques of control and reduction of frictional waste and wear. The behavior of thin films of branched hydrocarbon lubricants under shear is described in detail. The evolution of the systems to steady-state sliding from rest or after a change in sliding velocity was thoroughly studied, and the presence of different length and time scales was observed. Using a new 'extended bimorph slider' which allows continuous shearing for distances well beyond the contact diameter (asperity size) I show that the evolution to steady-state sliding in these films is governed by the distance the surfaces are sheared rather than the time. From these results it is clear that both time and distance of sliding have to be considered in order to fully describe the dynamic response of lubricants and complex fluids under shear. The behavior of linear and branched hydrocarbon films under shear is compared, and the physical reasons for the different types of transitions and friction traces observed in the two systems are discussed. Two approaches to friction reduction were investigated. First, a new method for friction control and reduction is proposed. Using a Surface Forces Apparatus modified for measuring friction forces while simultaneously inducing normal (out-of-plane) vibrations between two sliding surfaces, load- and frequency-dependent transitions between a number of "dynamic friction" states are observed. In particular, regimes of vanishingly small friction at small interfacial oscillation amplitudes are found. Despite its complexity, the phenomenon is shown to have a molecular origin. Second, a novel lubricant material was studied in detail. The tribological behavior of colloidal particles of tungsten disulfide of different structures was studied using different techniques. Shear induced material transfer (via third body processes) from the colloidal particles to the surfaces was shown to be a dominant factor in the tribological behavior observed. Both platelet and nested spherical structures were investigated. An ultrathin, ordered layer with promising lubricative properties was observed when nested particles were sheared, while WS2 platelets produced a rough and disordered transfer layer, with substantially inferior lubricating properties.

Drummond, Carlos Alberto

125

Quantum Confinement in Hydrogen Bond  

E-print Network

In this work, the quantum confinement effect is proposed as the cause of the displacement of the vibrational spectrum of molecular groups that involve hydrogen bonds. In this approach the hydrogen bond imposes a space barrier to hydrogen and constrains its oscillatory motion. We studied the vibrational transitions through the Morse potential, for the NH and OH molecular groups inside macromolecules in situation of confinement (when hydrogen bonding is formed) and non-confinement (when there is no hydrogen bonding). The energies were obtained through the variational method with the trial wave functions obtained from Supersymmetric Quantum Mechanics (SQM) formalism. The results indicate that it is possible to distinguish the emission peaks related to the existence of the hydrogen bonds. These analytical results were satisfactorily compared with experimental results obtained from infrared spectroscopy.

Santos, Carlos da Silva dos; Ricotta, Regina Maria

2015-01-01

126

Reactive collisions in confined geometries  

E-print Network

We consider low energy threshold reactive collisions of particles interacting via a van der Waals potential at long range in the presence of external confinement and give analytic formulas for the confinement modified scattering in such circumstances. The reaction process is described in terms of the short range reaction probability. Quantum defect theory is used to express elastic and inelastic or reaction collision rates analytically in terms of two dimensionless parameters representing phase and reactivity. We discuss the modifications to Wigner threshold laws for quasi-one-dimensional and quasi-two-dimensional geometries. Confinement-induced resonances are suppressed due to reactions and are completely absent in the universal limit where the short-range loss probability approaches unity.

Idziaszek, Zbigniew; Julienne, Paul S

2014-01-01

127

Reactive collisions in confined geometries  

E-print Network

We consider low energy threshold reactive collisions of particles interacting via a van der Waals potential at long range in the presence of external confinement and give analytic formulas for the confinement modified scattering in such circumstances. The reaction process is described in terms of the short range reaction probability. Quantum defect theory is used to express elastic and inelastic or reaction collision rates analytically in terms of two dimensionless parameters representing phase and reactivity. We discuss the modifications to Wigner threshold laws for quasi-one-dimensional and quasi-two-dimensional geometries. Confinement-induced resonances are suppressed due to reactions and are completely absent in the universal limit where the short-range loss probability approaches unity.

Zbigniew Idziaszek; Krzysztof Jachymski; Paul S. Julienne

2015-02-06

128

Reactive collisions in confined geometries  

E-print Network

We consider low energy threshold reactive collisions of particles interacting via a van der Waals potential at long range in the presence of external confinement and give analytic formulas for the confinement modified scattering in such circumstances. The reaction process is described in terms of the short range reaction probability. Quantum defect theory is used to express elastic and inelastic or reaction collision rates analytically in terms of two dimensionless parameters representing phase and reactivity. We discuss the modifications to Wigner threshold laws for quasi-one-dimensional and quasi-two-dimensional geometries. Confinement-induced resonances are suppressed due to reactions and are completely absent in the universal limit where the short-range loss probability approaches unity.

Zbigniew Idziaszek; Krzysztof Jachymski; Paul S. Julienne

2014-12-08

129

Active control of MHD modes in magnetic confinement systems  

E-print Network

Active control of MHD modes in magnetic confinement systems A. Bondeson, Y. Q. Liu, D. Gregoratto Göteborg, Sweden C.M. Fransson, B. Lennartson, C. Breitholtz Department of Signals and Systems, Control controller works well, and the time constant of the feedback system can be several resistive wall times

130

Inertial Confinement Fusion: progress through close coupling of theory and experiment  

Microsoft Academic Search

It has been nearly 50 years since the first approach to Inertial Confinement Fusion (ICF) was discussed and 36 years since the first publication appeared. For DT plasmas, the ignition (Lawson) criterion can be simply stated as (pressure * time) > 10 atmosphere-seconds. In ICF, plasma confinement times are set by the plasma inertia to a few 10's of picoseconds.

Keith Matzen

2008-01-01

131

Traveling wave multiple mirror field for confinement of high temperature plasmas  

Microsoft Academic Search

Traveling wave multiple mirror confinement of high temperature plasma for fusion application was examined by theoretical discussion using a diffusion equation. It was shown that confinement time and plasma density in the traveling wave multiple mirror field were several hundred times longer and higher than those in the static multiple mirror field.

S. Aihara

1975-01-01

132

Glass Transition in Confined Geometry  

NASA Astrophysics Data System (ADS)

Extending mode-coupling theory, we elaborate a microscopic theory for the glass transition of liquids confined between two parallel flat hard walls. The theory contains the standard mode-coupling theory equations in bulk and in two dimensions as limiting cases and requires as input solely the equilibrium density profile and the structure factors of the fluid in confinement. We evaluate the phase diagram as a function of the distance of the plates for the case of a hard sphere fluid and obtain an oscillatory behavior of the glass transition line as a result of the structural changes related to layering.

Lang, Simon; Bo?an, Vitalie; Oettel, Martin; Hajnal, David; Franosch, Thomas; Schilling, Rolf

2010-09-01

133

Computation of confined turbulent coaxial jet flows  

NASA Technical Reports Server (NTRS)

The characteristics of the recirculation zones in confined coaxial turbulent jets are investigated numerically employing the k-epsilon turbulent model. The geometrical arrangement corresponds to the experimental study of Owen (1976) and the investigation is undertaken to provide information for isothermal flow relevant to combustor flows. For the first time, the shape, size, and location of the recirculation zones for the above experimental configuration are correctly predicted. The processes leading to the observed results are explained. Detailed comparisons of the prediction with measurements are made. It is shown that the recirculation zones are very sensitive to the central jet exit configuration and the velocity ratio of the jets.

Nallasamy, M.

1986-01-01

134

Dynamics of Confined Water Molecules in Aqueous Salt Hydrates  

SciTech Connect

The unusual properties of water are largely dictated by the dynamics of the H bond network. A single water molecule has more H bonding sites than atoms, hence new experimental and theoretical investigations about this peculiar liquid have not ceased to appear. Confinement of water to nanodroplets or small molecular clusters drastically changes many of the liquid’s properties. Such confined water plays a major role in the solvation of macro molecules such as proteins and can even be essential to their properties. Despite the vast results available on bulk and confined water, discussions about the correlation between spectral and structural properties continue to this day. The fast relaxation of the OH stretching vibration in bulk water, and the variance of sample geometries in the experiments on confined water obfuscate definite interpretation of the spectroscopic results in terms of structural parameters. We present first time-resolved investigations on a new model system that is ideally suited to overcome many of the problems faced in spectroscopical investigation of the H bond network of water. Aqueous hydrates of inorganic salts provide water molecules in a crystal grid, that enables unambiguous correlations of spectroscopic and structural features. Furthermore, the confined water clusters are well isolated from each other in the crystal matrix, so different degrees of confinement can be achieved by selection of the appropriate salt.

Werhahn, Jasper C.; Pandelov, S.; Yoo, Soohaeng; Xantheas, Sotiris S.; Iglev, H.

2011-04-01

135

Scattering for Nonlinear Schrödinger Equation Under Partial Harmonic Confinement  

NASA Astrophysics Data System (ADS)

We consider the nonlinear Schrödinger equation under a partial quadratic confinement. We show that the global dispersion corresponding to the direction(s) with no potential is enough to prove global in time Strichartz estimates, from which we infer the existence of wave operators, thanks to suitable vector-fields. Conversely, given an initial Cauchy datum, the solution is global in time and asymptotically free, provided that confinement affects one spatial direction only. This stems from anisotropic Morawetz estimates, involving a marginal of the position density.

Antonelli, Paolo; Carles, Rémi; Silva, Jorge Drumond

2014-09-01

136

Limiting Spectra from Confining Potentials.  

ERIC Educational Resources Information Center

The author explains that, for confining potentials and large quantum numbers, the bound-state energies rise more rapidly as a function of n the more rapidly the potential rises with distance. However, the spectrum can rise no faster than n squared in the nonrelativistic case, or n in the relativistic case. (Author/GA)

Nieto, Michael Martin; Simmons, L. M., Jr.

1979-01-01

137

Confined Fluids as Strain Meters  

Microsoft Academic Search

Earth dilatations due to earth tides and seismic waves cause periodic fluctuations of the fluid pressure within saturated porous formations. Pressures and water levels in wells that are connected with sufficiently confined subsurface fluids are also affected and provide a means of obtaining quantitative data on the earth strain. A theory is given of strain-induced pressure fluctuations in a well-aquifer

Gunnar Bodvarsson

1970-01-01

138

String Theory and Quark Confinement  

E-print Network

This article is based on a talk given at the ``Strings'97'' conference. It discusses the search for the universality class of confining strings. The key ingredients include the loop equations, the zigzag symmetry, the non-linear renormalization group. Some new tests for the equivalence between gauge fields and strings are proposed.

A. Polyakov

1997-11-01

139

Confinement regime transitions in ASDEX  

Microsoft Academic Search

The authors give an overview of the different confinement regimes observed on ASDEX and compare the changes during the transition phases with qualitative tendencies suggested by theoretical models. The transitions discussed are those between purely Ohmic heating and additional heating in the L-regime between the L- and the H-regime and between discharges with flat and peaked electron density profiles.

K. Lackner; O. Gruber; F. Wagner; G. Becker; M. Bessenrodt-Weberpals; B. Bomba; H.-S. Bosch; H. Bruhns; R. Buchse; A. Carlson; G. Dodel; A. Eberhagen; H.-U. Fahrbach; G. Fussmann; O. Gehre; J. Gernhardt; L. Giannone; S. von Goeler; K. Grassie; G. Haas; H. Herrmann; J. Hofmann; E. Holzhauer; K. Hubner; G. Janeschitz; A. Kallenbach; F. Karger; M. Kaufmann; O. Kluber; M. Kornherr; K. Krieger; J. Kucinski; R. Lang; G. Lisitano; H. M. Mayer; K. McCormick; D. Meisel; V. Mertens; E. R. Muller; H. D. Murmann; J. Neuhauser; H. Niedermeyer; R. Nolte; J. M. Noterdaeme; W. Poschenrieder; L. B. Ran; D. E. Roberts; H. Rohr; J. Roth; A. Rudyj; F. Ryter; W. Sandmann; F. Schneider; U. Schneider; W. Schneider; G. Siller; E. Speth; F. X. Soldner; A. Stabler; K. H. Steuer; U. Stroth; J. Szigeti; E. Taglauer; N. Tsois; H. Verbeek; O. Vollmer; R. Wunderlich; H. Wurz; H. R. Yang; H. Zohm

1989-01-01

140

Encapsulating Objects with Confined Types  

E-print Network

Encapsulating Objects with Confined Types Kevin O'Neill CS 711 September 15, 2003 A Security Breach Identity[] getSigners() { Identity[] pub; pub = new Identity[signers.length]; for (int i=0; ipub[i] = signers[i]; return pub; } } An Ad-hoc Fix: Is this fix good enough? · The better get

Myers, Andrew C.

141

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

142

String theory and quark confinement  

Microsoft Academic Search

This article is based on a talk given at the “Strings '97” conference. It discusses the search for the universality class of confining strings. The key ingredients include the loop equations, the zigzag symmetry, the non-linear renormalization group. Some new tests for the equivalence between gauge fields and strings are proposed.

Alexandre M. Polyakov

1998-01-01

143

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

144

Flex Circuitry for Confined Spaces  

NASA Technical Reports Server (NTRS)

To facilitate installation of electronic equipment in confined spaces, circuitry preassembled on flexible wiring. Mother boards, large bypass capacitors, and interface connectors mounted on flexible wiring and tested before installation. Flexible circuits eliminate need for in-place hardwiring and allow smaller enclosures to be used.

Fitzpatrick, J. B.; Maier, L. C.

1986-01-01

145

Time  

ERIC Educational Resources Information Center

When a teacher gives their time to a student, it is more significant to that student than anything else one could do for him or her. Music teachers deal with time all the time. Someone once said that "time is like money: we never have enough." This may seem true; however, time is not like money. One can make more money, but one cannot "make time."…

Circle, David

2005-01-01

146

Effects of confinement on protein folding and protein stability  

NASA Astrophysics Data System (ADS)

In a cell, proteins exist in crowded environments; these environments influence their stability and dynamics. Similarly, for an enzyme molecule encapsulated in an inorganic cavity as in biosensors or biocatalysts, confinement and even surface effects play important roles in its stability and dynamics. Using a minimalist model (two-dimensional HP lattice model), we have carried out Monte Carlo simulations to study confinement effects on protein stability. We have calculated heat capacity as a function of temperature using the histogram method and results obtained show that confinement tends to stabilize the folded conformations, consistent with experimental results (some reported here) and previous theoretical analyses. Furthermore, for a protein molecule tethered to a solid surface the stabilization effect can be even greater. We have also investigated the effects of confinement on the kinetics of the refolding and unfolding processes as functions of temperature and box size. As expected, unfolding time increases as box size decreases, however, confinement affects folding times in a more complicated way. Our theoretical results agree with our experimentally observed trends that thermal stability of horseradish peroxidase and acid phosphatase, encapsulated in mesoporous silica, increases as the pore size of the silica matrix decreases.

Ping, G.; Yuan, J. M.; Vallieres, M.; Dong, H.; Sun, Z.; Wei, Y.; Li, F. Y.; Lin, S. H.

2003-05-01

147

NUMERICAL SIMULATION OF MULTIPOLE CONFINEMENT (Examples)  

E-print Network

NUMERICAL SIMULATION OF MULTIPOLE CONFINEMENT (Examples) by J. R. Patau and J. C. Sprott April 1974 in a zero-dimensional calculation. l "Numerical Simulation of r..1ultipole Confinement, " J. R. Patau and J

Sprott, Julien Clinton

148

Quark confinement and the renormalization group.  

PubMed

Recent approaches to quark confinement are reviewed, with an emphasis on their connection to renormalization group (RG) methods. Basic concepts related to confinement are introduced: the string tension, Wilson loops and Polyakov lines, string breaking, string tension scaling laws, centre symmetry breaking and the deconfinement transition at non-zero temperature. Current topics discussed include confinement on R(3)×S(1), the real-space RG, the functional RG and the Schwinger-Dyson equation approach to confinement. PMID:21646275

Ogilvie, Michael C

2011-07-13

149

Static use-based object confinement  

Microsoft Academic Search

The confinement of object references is a significant se- curity concern for modern programming languages. We define a language that serves as a uniform model for a va- riety of confined object reference systems. A use-based approach to confinement is adopted, which we argue is more expressive than previous communication-based ap- proaches. We then develop a readable, expressive type system

Christian Skalka; Scott F. Smith

2005-01-01

150

Soft Confinement for Polymer Solutions  

E-print Network

As a model of soft confinement for polymers, we investigated equilibrium shapes of a flexible vesicle that contains a phase-separating polymer solution. To simulate such a system, we combined the phase field theory (PFT) for the vesicle and the self-consistent field theory (SCFT) for the polymer solution. We observed a transition from a symmetric prolate shape of the vesicle to an asymmetric pear shape induced by the domain structure of the enclosed polymer solution. Moreover, when a non-zero spontaneous curvature of the vesicle is introduced, a re-entrant transition between the prolate and the dumbbell shapes of the vesicle is observed. This re-entrant transition is explained by considering the competition between the loss of conformational entropy and that of translational entropy of polymer chains due to the confinement by the deformable vesicle. This finding is in accordance with the recent experimental result reported by Terasawa, et al.

Oya, Yutaka

2014-01-01

151

Ion beam inertial confinement target  

DOEpatents

A target for implosion by ion beams composed of a spherical shell of frozen DT surrounded by a low-density, low-Z pusher shell seeded with high-Z material, and a high-density tamper shell. The target has various applications in the inertial confinement technology. For certain applications, if desired, a low-density absorber shell may be positioned intermediate the pusher and tamper shells.

Bangerter, Roger O. (Danville, CA); Meeker, Donald J. (Livermore, CA)

1985-01-01

152

Viscoelastic transient of confined Red Blood Cells  

E-print Network

The unique ability of a red blood cell to flow through extremely small microcapillaries depends on the viscoelastic properties of its membrane. Here, we study in vitro the response time upon flow startup exhibited by red blood cells confined into microchannels. We show that the characteristic transient time depends on the imposed flow strength, and that such a dependence gives access to both the effective viscosity and the elastic modulus controlling the temporal response of red cells. A simple theoretical analysis of our experimental data, validated by numerical simulations, further allows us to compute an estimate for the two-dimensional membrane viscosity of red blood cells, $\\eta_{mem}^{2D}\\sim 10^{-7}$ N$\\cdot$s$\\cdot$m$^{-1}$. By comparing our results with those from previous studies, we discuss and clarify the origin of the discrepancies found in the literature regarding the determination of $\\eta_{mem}^{2D}$, and reconcile seemingly conflicting conclusions from previous works.

Gaël Prado; Alexander Farutin; Chaouqi Misbah; Lionel Bureau

2014-09-17

153

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

154

Model of a confined spherical cell in uniform and heterogeneous applied electric fields  

Microsoft Academic Search

Cells exposed to electric fields are often confined to a small volume within a solid tissue or within or near a device. Here we report on an approach to describing the frequency and time domain electrical responses of a spatially confined spherical cell by using a transport lattice system model. Two cases are considered: (1) a uniform applied field created

T. R. Gowrishankar; Donald A. Stewart; James C. Weaver

2006-01-01

155

Production and study of high-beta plasma confined by a superconducting dipole magneta...  

E-print Network

, and the absence of magnetic shear allows particle and energy confinement to decouple. In initial experiments, long, plasma dynamics and instability, and the roles of gas fueling, microwave power deposition profiles when the plasma fueling rate and confinement time become sufficiently large. © 2006 American Institute

Mauel, Michael E.

156

Production and study of high-beta plasma confined by a superconducting dipole magnet  

E-print Network

), and the absence of magnetic shear allows particle and energy confinement to decouple. In initial experiments, long evolution, plasma dynamics and instability, and the roles of gas fueling, microwave power deposition is observed when the plasma fueling rate and confinement time become sufficiently large. PACS numbers: 52

157

1.3 micron multiquantum well decoupled confinement heterostructure (MQW-DCH) laser diodes  

Microsoft Academic Search

A 1.3 micron multiquantum well decoupled confinement heterostructure (MQW-DCH) laser diode has been developed. This novel laser structure introduces internal barriers between the active quantum wells and the optical waveguide. It is thus possible to have, at the same time, deep quantum wells to prevent carrier leakage and a strong optical waveguide with a high confinement factor. The barrier parameters

S. Hausser; H. P. Meier; R. Germann; Ch. S. Harder

1993-01-01

158

Confined fission track lengths in apatite: a diagnostic tool for thermal history analysis  

Microsoft Academic Search

Fission-track ages in apatite are generally accepted as giving a measure of the time over which a sample has been exposed to temperatures below approximately 100° C. A compilation of the lengths of confined fission tracks in a wide variety of apatites from different geological environments has shown that the distribution of confined track lengths can provide unique thermal history

A. J. W. Gleadow; I. R. Duddy; P. F. Green; J. F. Lovering

1986-01-01

159

Confinement of injected silicon in the Alcator-A tokamak  

SciTech Connect

Results of injected-impurity transport studies on the Alcator-A tokamak are presented. It is found that injected silicon diffuses throughout the plasma and is then observed, contrary to the predictions of neoclassical theory, to leave the discharge, having confinement times much shorter than the discharge length. There is no observed buildup of silicon on the axis of the device. The impurity confinement is found to increase with plasma current and background-ion mass. Scalings with electron density and toroidal field are also discussed.

Marmar, E.S.; Rice, J.E.; Allen, S.L.

1980-12-22

160

Coronal Electron Confinement by Double Layers  

E-print Network

In observations of flare-heated electrons in the solar corona, a longstanding problem is the unexplained prolonged lifetime of the electrons compared to their transit time across the source. This suggests confinement. Recent particle-in-cell (PIC) simulations, which explored the transport of pre-accelerated hot electrons through ambient cold plasma, showed that the formation of a highly localized electrostatic potential drop, in the form of a double layer (DL), significantly inhibited the transport of hot electrons (T.C. Li, J.F. Drake, and M. Swisdak, 2012, ApJ, 757, 20). The effectiveness of confinement by a DL is linked to the strength of the DL as defined by its potential drop. In this work, we investigate the scaling of the DL strength with the hot electron temperature by PIC simulations, and find a linear scaling. We demonstrate that the strength is limited by the formation of parallel shocks. Based on this, we analytically determine the maximum DL strength, and find also a linear scaling with the hot e...

Li, T C; Swisdak, M

2014-01-01

161

Experimental and Theoretical Studies of Electrostatic Confinement  

NASA Astrophysics Data System (ADS)

Experimental and Theoretical Studies of Electrostatic Confinement J. Park, R. A. Nebel, C. P. Munson, W. G. Rellergert, M. D. Sekora Los Alamos National Laboratory Previous theoretical work [R. A. Nebel, D. C. Barnes, Fusion Technology (1998) and D. C. Barnes, R. A. Nebel, Phys. Plasmas (1998)] suggested that an ion cloud confined by a stable oscillating virtual cathode may undergo a self=similar collapse producing periodic and simultaneous attainment of high densities and temperatures. We are currently conducting experiments to test the stability of these virtual cathodes. Emissive probes have been used to measure time and space resolved potential and electron density profiles. Fluctuations in the plasma have been measured by a passive receiver and a combination of an external driver and a receiver. The observed virtual cathode exhibits a bifurcation between states where the well depth is 60potential. The transition is a function of the injected electron flux, grid biases, and the gas pressure. Experimental results on fluctuation and stability of a driven virtual cathode will be presented and compared with theoretical predictions [R. A. Nebel, J. M. Finn, Phys. Plasmas (2001)].

Park, Jaeyoung; Nebel, Richard

2002-11-01

162

Issues in tokamak/stellarator transport and confinement enhancement mechanisms  

SciTech Connect

At present, the mechanism for anomalous energy transport in low-{beta} toroidal plasmas -- tokamaks and stellarators -- remains unclear, although transport by turbulent E {times} B velocities associated with nonlinear, fine-scale microinstabilities is a leading candidate. This article discusses basic theoretical concepts of various transport and confinement enhancement mechanisms as well as experimental ramifications which would enable one to distinguish among them and hence identify a dominant transport mechanism. While many of the predictions of fine-scale turbulence are born out by experiment, notable contradictions exist. Projections of ignition margin rest both on the scaling properties of the confinement mechanism and on the criteria for entering enhanced confinement regimes. At present, the greatest uncertainties lie with the basis for scaling confinement enhancement criteria. A series of questions, to be answered by new experimental/theoretical work, is posed to resolve these outstanding contradictions (or refute the fine-scale turbulence model) and to establish confinement enhancement criteria. 73 refs., 4 figs., 5 tabs.

Perkins, F.W.

1990-08-01

163

Ingestive Behavior of Lambs Confined in Individual and Group Stalls  

PubMed Central

The experiment was conducted to evaluate the ingestive behavior of lambs confined in individual and group stalls. We used thirty-four lambs in their growing phase, aged an average of three months, with mean initial live weight of 17.8±5.2 kg. They were allotted in a completely randomized design with 24 animals kept in individual stalls and 10 animals confined as a group. The experiment lasted for a total of 74 days, and the first 14 days were dedicated to the animals’ adaption to the management, facilities and diets. The data collection period lasted 60 days, divided into three 20-d periods for the behavior evaluation. The animals were subjected to five days of visual observation during the experiment period, by the quantification of 24 h a day, with evaluations on the 15th day of each period and an interim evaluation consisting of two consecutive days on the 30th and 31st day of the experiment. The animals confined as a group consumed less (p<0.05) fiber. However, the animals confined individually spent less (p<0.05) time on feeding, rumination and chewing activities and longer in idleness. Therefore, the lower capacity of lambs confined in groups to select their food negatively affects their feeding behavior. PMID:25049953

Filho, A. Eustáquio; Carvalho, G. G. P.; Pires, A. J. V.; Silva, R. R.; Santos, P. E. F.; Murta, R. M.; Pereira, F. M.

2014-01-01

164

Quasielastic neutron scattering study of water confined in carbon nanopores  

SciTech Connect

Microscopic dynamics of water confined in nanometer and sub-nanometer pores of carbide-derived carbon (CDC) were investigated using quasielastic neutron scattering (QENS). The temperature dependence of the average relaxation time, {tau}, exhibits super-Arrhenius behavior that could be described by Vogel-Fulcher-Tammann (VFT) law in the range from 250 K to 190 K; below this temperature, {tau} follows Arrhenius temperature dependence. The temperature of the dynamic crossover between the two regimes in water confined in the CDC pores is similar to that observed for water in hydrophobic confinement of the larger size, such as 14 {angstrom} ordered mesoporous carbon (CMK) and 16 {angstrom} double-wall carbon nanotubes. Thus, the dynamical behavior of water remains qualitatively unchanged even in the very small hydrophobic pores.

Mavila Chathoth, Suresh [ORNL; Mamontov, Eugene [ORNL; Kolesnikov, Alexander I [ORNL; Gogotsi, Yury G. [Drexel University; Wesolowski, David J [ORNL

2011-01-01

165

Hot Electron Confinement in High Intensity Laser-Matter Interactions  

NASA Astrophysics Data System (ADS)

High-intensity (>10^18 W/cm^2) lasers can produce relativistic electrons (˜MeV) when focused onto solid density targets. We present measurements of escaped relativistic electron lifetimes in short pulse laser-irradiated solid experiments. Electron durations measured were significantly longer than the laser pulse length, suggesting the presence of phenomena which confine high energy electrons within the target-plasma volume. Investigating the confinement time of high energy electrons exceeds the limits of any simple plasma expansion models. Utilizing the implicit hybrid particle-in-cell code LSP [D. R. Welch et al., Phys. Plasmas 13, 063105 (2006)], experimental conditions were simulated to explore the physics of hot electron confinement in laser-irradiated materials. *This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

Elberson, Lee; Ping, Yuan; Wilks, Scott; Shepherd, Ronnie; MacKinnon, Andrew; Patel, Prav; Hill, Wendell

2009-11-01

166

Hot Electron Confinement in High Intensity Laser-Matter Interactions  

NASA Astrophysics Data System (ADS)

High-intensity (>10^18 W/cm^2) lasers can produce relativistic electrons (˜MeV) when focused onto solid density targets. We present measurements of escaped relativistic electron lifetimes in short pulse laser-irradiated solid experiments. Electron durations measured were significantly longer than the laser pulse length, suggesting the presence of phenomena which confine high energy electrons within the target-plasma volume. Investigating the confinement time of high energy electrons exceeds the limits of any simple plasma expansion models. Utilizing the implicit hybrid particle-in-cell code LSP [D. R. Welch et al., Phys. Plasmas 13, 063105 (2006)], experimental conditions were simulated to explore the physics of hot electron confinement in laser-irradiated materials. *This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

Elberson, Lee; Ping, Yuan; Shepherd, Ronnie; Wilks, Scott; MacKinnon, Andrew; Patel, Prav; Hill, Wendell

2010-11-01

167

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

168

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

169

Theory of rheology in confinement  

E-print Network

The viscosity of fluids is generally understood in terms of kinetic mechanisms, i.e., particle collisions, or thermodynamic ones as imposed through structural distortions upon e.g. applying shear. Often the former is less relevant, and (damped) Brownian particles are considered good fluid model systems. We formulate a general theoretical approach for rheology in confinement, based on the many particle diffusion equation, evaluated via classical density functional theory. We discuss the viscosity for the situation of two parallel walls in relative motion as a function of wall-to-wall distance.

Artem A. Aerov; Matthias Krüger

2014-12-12

170

Soft confinement for polymer solutions  

NASA Astrophysics Data System (ADS)

As a model of soft confinement for polymers, we investigated equilibrium shapes of a flexible vesicle that contains a phase-separating polymer solution. To simulate such a system, we combined the phase field theory (PFT) for the vesicle and the self-consistent field theory (SCFT) for the polymer solution. We observed a transition from a symmetric prolate shape of the vesicle to an asymmetric pear shape induced by the domain structure of the enclosed polymer solution. Moreover, when a non-zero spontaneous curvature of the vesicle is introduced, a re-entrant transition between the prolate and the dumbbell shapes of the vesicle is observed. This re-entrant transition is explained by considering the competition between the loss of conformational entropy and that of translational entropy of polymer chains due to the confinement by the deformable vesicle. This finding is in accordance with the recent experimental result reported by Terasawa et al. (Proc. Natl. Acad. Sci. U.S.A., 108 (2011) 5249).

Oya, Yutaka; Kawakatsu, Toshihiro

2014-07-01

171

Confined Lennard-Jones Two Piston System Model  

NSDL National Science Digital Library

The Confined Lennard-Jones Two Piston System simulates a constant-energy two-dimensional system of particles confined by two frictionless pistons of equal mass M. This computer model complements theoretical work describing the adiabatic expansion of an ideal gas using the quasi-static approximation. Users can set the initial particle kinetic energy, Lennard Jones parameters, and the initial particle separation. Slow-moving particles are color-coded as blue and fast particles are color-coded as yellow. The time evolution of temperature, pressure, and piston speed are shown in a second window. Particles in this model have unit mass and interact through pairwise Lennard-Jones forces and hard-wall contact forces. The instantaneous temperature is computed using the average particle kinetic energy and the pressure is computed using the virial expansion. The Confined Lennard-Jones Two Piston System is a supplemental simulation for the article "Evolution of ideal gas mixtures confined in an insulated container by two identical pistons" by Joaquim Anacleto, Joaquim Alberto C. Anacleto, and J. M. Ferreira in the American Journal of Physics 79(10), 1009-1014 (2011) and has been approved by the authors and the American Journal of Physics (AJP) editor. The Confined Lennard-Jones Two Piston System was created using the Easy Java Simulations (Ejs) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_stp_md_ConfinedLennardJonesTwoPistonSystem.jar file will run the program if Java is installed.

Christian, Wolfgang

2011-03-09

172

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

173

Composite mesostructures by nano-confinement  

Microsoft Academic Search

In a physically confined environment, interfacial interactions, symmetry breaking, structural frustration and confinement-induced entropy loss can play dominant roles in determining molecular organization. Here we present a systematic study of the confined assembly of silica-surfactant composite mesostructures within cylindrical nanochannels of varying diameters. Using exactly the same precursors and reaction conditions that form the two-dimensional hexagonal SBA-15 mesostructured thin film,

Yiying Wu; Guosheng Cheng; Kirill Katsov; Scott W. Sides; Jianfang Wang; Jing Tang; Glenn H. Fredrickson; Martin Moskovits; Galen D. Stucky

2004-01-01

174

Field-induced confined states in graphene  

SciTech Connect

We report an approach to confine the carriers in single-layer graphene, which leads to quantum devices with field-induced quantum confinement. We demonstrated that the Coulomb-blockade effect evolves under a uniform magnetic field perpendicular to the graphene device. Our experimental results show that field-induced quantum dots are realized in graphene, and a quantum confinement-deconfinement transition is switched by the magnetic field.

Moriyama, Satoshi, E-mail: MORIYAMA.Satoshi@nims.go.jp [International Center for Materials Nanoarchitectonics (WPI-MANA), National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan); Morita, Yoshifumi [Faculty of Engineering, Gunma University, Kiryu, Gunma 376-8515 (Japan); Watanabe, Eiichiro; Tsuya, Daiju [Nanotechnology Innovation Station, NIMS, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan)

2014-02-03

175

The identity of Thalictrum confine (Ranunculaceae)  

Microsoft Academic Search

A history of the collecting and naming ofThalictrum confine Fern, is detailed in an attempt to clear up long-standing nomenclatural and taxonomic confusions.Thalictrum confine has traditionally been distinguished fromT. venulosum Trel. on the basis of its larger, falcate fruits; however the lectotype ofT. confine consists only of a packet of terete, subcylindric fruits, even smaller than those of the type

Richard S. Mitchell

1988-01-01

176

Guiding and confining light in void nanostructure  

Microsoft Academic Search

We present a novel waveguide geometry for enhancing and confining light in a nanometer-wide low-index material. Light enhancement and confinement is caused by large discontinuity of the electric field at high- index-contrast interfaces. We show that by use of such a structure the field can be confined in a 50-nm-wide low-index region with a normalized intensity of 20 mm 22

Vilson R. Almeida; Qianfan Xu; Carlos A. Barrios; Michal Lipson

2004-01-01

177

Confined one- and two-center systems  

NASA Astrophysics Data System (ADS)

It is shown that the usual model for confined one-center systems can be extended to two-center systems and the theory is used to treat H2 and HeH2+. It is convenient to use spheroidal coordinates for the two-center problems and we use this formalism to compare hydrogenlike systems confined spheroidally with the more standard spherical confinement. A discussion of confinement by both penetrable and impenetrable barriers is given together with a technique for describing the effect of the external region.

Burrows, B. L.; Cohen, M.

2013-11-01

178

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

179

Spatially confined assembly of nanoparticles.  

PubMed

The ability to assemble NPs into ordered structures that are expected to yield collective physical or chemical properties has afforded new and exciting opportunities in the field of nanotechnology. Among the various configurations of nanoparticle assemblies, two-dimensional (2D) NP patterns and one-dimensional (1D) NP arrays on surfaces are regarded as the ideal assembly configurations for many technological devices, for example, solar cells, magnetic memory, switching devices, and sensing devices, due to their unique transport phenomena and the cooperative properties of NPs in assemblies. To realize the potential applications of NP assemblies, especially in nanodevice-related applications, certain key issues must still be resolved, for example, ordering and alignment, manipulating and positioning in nanodevices, and multicomponent or hierarchical structures of NP assemblies for device integration. Additionally, the assembly of NPs with high precision and high levels of integration and uniformity for devices with scaled-down dimensions has become a key and challenging issue. Two-dimensional NP patterns and 1D NP arrays are obtained using traditional lithography techniques (top-down strategies) or interfacial assembly techniques (bottom-up strategies). However, a formidable challenge that persists is the controllable assembly of NPs in desired locations over large areas with high precision and high levels of integration. The difficulty of this assembly is due to the low efficiency of small features over large areas in lithography techniques or the inevitable structural defects that occur during the assembly process. The combination of self-assembly strategies with existing nanofabrication techniques could potentially provide effective and distinctive solutions for fabricating NPs with precise position control and high resolution. Furthermore, the synergistic combination of spatially mediated interactions between nanoparticles and prestructures on surfaces may play an increasingly important role in the controllable assembly of NPs. In this Account, we summarize our approaches and progress in fabricating spatially confined assemblies of NPs that allow for the positioning of NPs with high resolution and considerable throughput. The spatially selective assembly of NPs at the desired location can be achieved by various mechanisms, such as, a controlled dewetting process, electrostatically mediated assembly of particles, and confined deposition and growth of NPs. Three nanofabrication techniques used to produce prepatterns on a substrate are summarized: the Langmuir-Blodgett (LB) patterning technique, e-beam lithography (EBL), and nanoimprint lithography (NPL). The particle density, particle size, or interparticle distance in NP assemblies strongly depends on the geometric parameters of the template structure due to spatial confinement. In addition, with smart design template structures, multiplexed NPs can be assembled into a defined structure, thus demonstrating the structural and functional complexity required for highly integrated and multifunction applications. PMID:25244100

Jiang, Lin; Chen, Xiaodong; Lu, Nan; Chi, Lifeng

2014-10-21

180

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

181

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

182

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

183

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

184

Multishell inertial confinement fusion target  

DOEpatents

A method of fabricating multishell fuel targets for inertial confinement fusion usage. Sacrificial hemispherical molds encapsulate a concentric fuel pellet which is positioned by fiber nets stretched tautly across each hemispherical mold section. The fiber ends of the net protrude outwardly beyond the mold surfaces. The joint between the sacrificial hemispheres is smoothed. A ceramic or glass cover is then deposited about the finished mold surfaces to produce an inner spherical surface having continuously smooth surface configuration. The sacrificial mold is removed by gaseous reaction accomplished through the porous ceramic cover prior to enclosing of the outer sphere by addition of an outer coating. The multishell target comprises the inner fuel pellet concentrically arranged within a surrounding coated cover or shell by fiber nets imbedded within the cover material.

Holland, James R. (Butler, PA); Del Vecchio, Robert M. (Vandergrift, PA)

1984-01-01

185

Multishell inertial confinement fusion target  

DOEpatents

A method of fabricating multishell fuel targets for inertial confinement fusion usage. Sacrificial hemispherical molds encapsulate a concentric fuel pellet which is positioned by fiber nets stretched tautly across each hemispherical mold section. The fiber ends of the net protrude outwardly beyond the mold surfaces. The joint between the sacrificial hemispheres is smoothed. A ceramic or glass cover is then deposited about the finished mold surfaces to produce an inner spherical surface having continuously smooth surface configuration. The sacrificial mold is removed by gaseous reactions accomplished through the porous ceramic cover prior to enclosing of the outer sphere by addition of an outer coating. The multishell target comprises the inner fuel pellet concentrically arranged within a surrounding coated cover or shell by fiber nets imbedded within the cover material.

Holland, James R. (Butler, PA); Del Vecchio, Robert M. (Vandergrift, PA)

1987-01-01

186

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

187

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

188

A study of an advanced confined linear energy source  

NASA Technical Reports Server (NTRS)

A literature survey and a test program to develop and evaluate an advanced confined linear energy source were conducted. The advanced confined linear energy source is an explosive or pyrotechnic X-Cord (mild detonating fuse) supported inside a confining tube capable of being hermetically sealed and retaining all products of combustion. The energy released by initiation of the X-Cord is transmitted through the support material to the walls of the confining tube causing an appreciable change in cross sectional configuration and expansion of the tube. When located in an assembly that can accept and use the energy of the tube expansion, useful work is accomplished through fracture of a structure, movement of a load, reposition of a pin, release of a restraint, or similar action. The tube assembly imparts that energy without release of debris or gases from the device itself. This facet of the function is important to the protection of men or equipment located in close proximity to the system during the time of function.

Anderson, M. C.; Heidemann, W. B.

1971-01-01

189

Hydrodynamic behavior of tumor cells in a confined model microvessel  

NASA Astrophysics Data System (ADS)

An important step in cancer metastasis is the hydrodynamic transport of circulating tumor cells (CTCs) through microvasculature. In vivo imaging studies in mice models show episodes of confined motion and trapping of tumor cells at microvessel bifurcations, suggesting that hydrodynamic phenomena are important processes regulating CTC dissemination. Our goal is to use microfluidics to understand the interplay between tumor cell rheology, confinement and fluid forces that may help to identify physical factors determining CTC transport. We use leukemia cells as model CTCs and mimic the in vivo setting by investigating their motion in a confined microchannel with an integrated microfluidic manometer to measure time variations in the excess pressure drop during cell motion. Using image analysis, variations in excess pressure drop, cell shape and cell velocity are simultaneously quantified. We find that the throughput of the technique is high enough ( 100 cells/min) to assess tumor cell heterogeneity. Therefore, in addition to measuring the hydrodynamic response of tumor cells in confined channels, our results indicate that the microfluidic manometer device could be used for rapid mechanical phenotyping of tumor cells.

Khan, Zeina S.; Vanapalli, Siva A.

2012-02-01

190

Hydrodynamics of DNA confined in nanoslits and nanochannels  

NASA Astrophysics Data System (ADS)

Modeling the dynamics of a confined, semiflexible polymer is a challenging problem, owing to the complicated interplay between the configurations of the chain, which are strongly affected by the length scale for the confinement relative to the persistence length of the chain, and the polymer-wall hydrodynamic interactions. At the same time, understanding these dynamics are crucial to the advancement of emerging genomic technologies that use confinement to stretch out DNA and "read" a genomic signature. In this mini-review, we begin by considering what is known experimentally and theoretically about the friction of a wormlike chain such as DNA confined in a slit or a channel. We then discuss how to estimate the friction coefficient of such a chain, either with dynamic simulations or via Monte Carlo sampling and the Kirkwood pre-averaging approximation. We then review our recent work on computing the diffusivity of DNA in nanoslits and nanochannels, and conclude with some promising avenues for future work and caveats about our approach.

Dorfman, K. D.; Gupta, D.; Jain, A.; Muralidhar, A.; Tree, D. R.

2014-12-01

191

Human enteric viruses in groundwater from a confined bedrock aquifer  

USGS Publications Warehouse

Confined aquifers are overlain by low-permeability aquitards that are commonly assumed to protect underlying aquifers from microbial contaminants. However, empirical data on microbial contamination beneath aquitards is limited. This study determined the occurrence of human pathogenic viruses in well water from a deep sandstone aquifer confined by a regionally extensive shale aquitard. Three public water-supply wells were each sampled 10 times over 15 months. Samples were analyzed by reverse transcription-polymerase chain reaction (RT-PCR) for several virus groups and by cell culture for infectious enteroviruses. Seven of 30 samples were positive by RT-PCR for enteroviruses; one of these was positive for infectious echovirus 18. The virus-positive samples were collected from two wells cased through the aquitard, indicating the viruses were present in the confined aquifer. Samples from the same wells showed atmospheric tritium, indicating water recharged within the past few decades. Hydrogeologic conditions support rapid porous media transport of viruses through the upper sandstone aquifer to the top of the aquitard 61 m below ground surface. Natural fractures in the shale aquitard are one possible virus transport pathway through the aquitard; however, windows, cross-connecting well bores, or imperfect grout seals along well casings also may be involved. Deep confined aquifers can be more vulnerable to contamination by human viruses than commonly believed. ?? 2007 American Chemical Society.

Borchardt, M.A.; Bradbury, K.R.; Gotkowitz, M.B.; Cherry, J.A.; Parker, B.L.

2007-01-01

192

Rotational diffusion of colloidal particles near confining walls.  

PubMed

We study the rotational diffusion of a spherical colloid confined in a narrow channel between parallel plane hard walls. The walls damp translational diffusion much more than rotational diffusion so that there is expected to be little translation-rotation coupling. Using a recent calculation of the nonisotropic rotational mobilities arising from the hydrodynamic interactions with the walls, we set up the rotational Smoluchowski equation for either a particle with a permanent dipole moment or a polarizable particle with axisymmetric polarizabilities subject to an external electric field. Using the Smoluchowski equation dynamics we calculate the time-correlation functions of orientation that are measured in depolarized light scattering for the cases of no external field, external field normal to the walls, and external field parallel to the walls. The decay of correlations is shown to be given by a weighted sum of decaying exponentials and can be characterized by an initial and a mean characteristic decay time. The weights and decay rates of each component and the characteristic decay times are studied numerically for a range of field strengths. The nonisotropic rotational mobilities make these decay times highly sensitive to the distance of the particle from the confining walls. This position dependence can be used as a method of measuring the rotational mobilities or, conversely, the rate of decay of correlations can be used as a probe of particle position between the confining walls. PMID:16268720

Jones, R B

2005-10-22

193

Climate conditions in bedded confinement buildings  

Technology Transfer Automated Retrieval System (TEKTRAN)

Confinement buildings are utilized for finishing cattle to allow more efficient collection of animal waste and to buffer animals against adverse climatic conditions. Environmental data were obtained from a 29 m wide x 318 m long bedded confinement building with the long axis oriented east to west. T...

194

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

195

Evaporation rate of water in hydrophobic confinement  

E-print Network

Evaporation rate of water in hydrophobic confinement Sumit Sharma and Pablo G. Debenedetti1, to compute the rate of capillary evaporation of water confined between two hydro- phobic surfaces separated to evaporation scales linearly with the gap between hydrophobic surfaces, suggesting that line tension makes

196

INERT Atmosphere confinement operability test procedure  

Microsoft Academic Search

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

1999-01-01

197

Tropical geometric interpretation of ultradiscrete singularity confinement  

NASA Astrophysics Data System (ADS)

Using the interpretation of the ultradiscretization procedure as a non-Archimedean valuation, we use results of tropical geometry to show how roots and poles manifest themselves in piece-wise linear systems as points of non-differentiability. This will allow us to demonstrate a correspondence between singularity confinement for discrete integrable systems and ultradiscrete singularity confinement for ultradiscrete integrable systems.

Ormerod, Christopher M.

2013-08-01

198

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

199

Laser compression and stability in inertial confinement fusion  

Microsoft Academic Search

Inertial confinement fusion (ICF) requires high compression of fusion fuel to densities approaching 1000 times liquid density of deuterium-tritium (DT), at central temperatures in excess of 5 keV. The direct-drive approach to ICF is more energy efficient than indirect drive if the stringent drive symmetry and hydrodynamic stability requirements can be met by a suitable laser irradiation and target design.

R. L. McCrory; J. M. Soures; C. P. Verdon; S. Skupsky; T. J. Kessler; S. A. Letzring; W. Seka; R. S. Craxton; R. Short; P. A. Jaanimagi; M. Skeldon; D. K. Bradley; J. Delettrez; R. L. Keck; H. Kim; J. P. Knauer; R. L. Kremens; F. J. Marshall

1989-01-01

200

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

201

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

202

Diffusion of single ellipsoids under quasi-2D confinements  

Microsoft Academic Search

We report video-microscopy measurements of the translational and rotational Brownian motions of isolated ellipsoidal particles in quasi-two-dimensional sample cells of increasing thickness. The long-time diffusion coefficients were measured along the long ($D_a$) and short ($D_b$) ellipsoid axes, respectively, and the ratio, $D_a\\/D_b$, was determined as a function of wall confinement and particle aspect ratio. In three-dimensions this ratio ($D_a\\/D_b$) cannot

Y. Han; A. Alsayed; M. Nobili; A. G. Yodh

2009-01-01

203

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

204

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

205

29 CFR 1910.146 - Permit-required confined spaces.  

Code of Federal Regulations, 2010 CFR

...hazard. Permit-required confined space program...spaces are permit- required confined spaces. ...Proper application of the decision flow chart in appendix...DANGER—PERMIT-REQUIRED CONFINED SPACE, DO NOT...A) Any conditions making it unsafe to...

2010-07-01

206

Fluid viscosity under confined conditions  

NASA Astrophysics Data System (ADS)

Closed equations of fluid transfer in confined conditions are constructed in this study using ab initio methods of nonequilibrium statistical mechanics. It is shown that the fluid viscosity is not determined by the fluid properties alone, but becomes a property of the "fluid-nanochannel walls" system as a whole. Relations for the tensor of stresses and the interphase force, which specifies the exchange by momentum of fluid molecules with the channel-wall molecules, are derived. It is shown that the coefficient of viscosity is now determined by the sum of three contributions. The first contribution coincides with the expression for the coefficient of the viscosity of fluid in the bulk being specified by the interaction of fluid molecules with each other. The second contribution has the same structure as the first one but is determined by the interaction of fluid molecules with the channel-wall molecules. Finally, the third contribution has no analog in the usual statistical mechanics of transport processes of a simple fluid. It is associated with the correlation of intermolecular forces of the fluid and the channel walls. Thus, it is established that the coefficient of viscosity of fluid in sufficiently small channels will substantially differ from its bulk value.

Rudyak, V. Ya.; Belkin, A. A.

2014-12-01

207

Direct evidence of the dielectric confinement effect in the infrared spectra of organic liquids  

NASA Astrophysics Data System (ADS)

In this study, the size (dielectric) confinement effect on the peak position of intra-molecular vibrations in the infrared spectra of liquid benzene, carbon disulphide and chloroform is described theoretically, and observed experimentally, for the first time. It is shown that the shift in the peak position due to the dielectric confinement effect can reach a few tenths of a wavenumber for strong vibrational bands. The results obtained confirm the applicability of the dispersive local-field approach for the description of the dielectric confinement effect for liquid media, as well as for crystalline and amorphous solids.

Perova, Tatiana S.; Shaganov, Igor I.; Melnikov, Vasily A.; Berwick, Kevin

2009-09-01

208

Non-classical diffusion of PDMS confined in a surface forces apparatus  

NASA Astrophysics Data System (ADS)

We present FRAP measurements inside a surface forces apparatus. Polydimethylsiloxane (PDMS), well above its glass transition, was confined into molecularly-thin films between atomically smooth mica sheets. Translational diffusion was measured using fluorescence recovery after photobleaching (FRAP) as the polymer film thickness was changed from tens of Rg to 3 Rg . The FRAP recovery curves of confined films are distinctly non-classical. Huge heterogeneity is suggested by stretched exponential behavior in which the power of time varies smoothly from ?=1 (thick films) to ?=0.3 (confined films) with a sharp transition between these limits.

Kumar, Subhalakshmi; Yu, Changqian; Bae, Sung Chul; Granick, Steve

2011-03-01

209

Example of an explicit function for confining classical Yang-Mills fields with quantum fluctuations in path integral scheme  

E-print Network

This article reports an explicit function of confining classical Yang-Mills vector potentials as well as quantum fluctuations around the classical field. The classical vector potential, which is composed of a confining localized function and an unlocalized function, satisfies the classical Yang-Mills equation. The confining localized function contributes to the Wilson loop, while the unlocalized function has no contribution to this loop. The confining linear potential between a pair of a heavy fermion particle and an antiparticle is due to the Lie algebra and the form of the confining localized function, which have opposite signs at positions of the particle and antiparticles along the Wilson loop in the time direction. Some classical confining parts of vector potentials also have the opposite sign for the inversion of coordinate of the axis perpendicular to the axis between two particles. The localized functions of vector potentials are squeezed around the axis connecting two particles, and the string tensio...

Fukushima, Kimichika

2014-01-01

210

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

211

Illness and injury in animal confinement workers.  

PubMed

Raising pigs and poultry indoors in large confinement facilities is increasingly common in U.S. agriculture. High endotoxin, ammonia, and dust levels contribute to acute and chronic respiratory symptoms in people who work in these settings. Respiratory conditions observed include the asthma-like syndrome, bronchitis, and asthma exacerbation. Organic dust toxic syndrome also has been described. Hypersensitivity pneumonitis is found in a small number of those who raise poultry. Hog confinement workers are at risk of hydrogen sulfide poisoning. These and other conditions seen in confinement workers are described, and health management procedures are outlined. PMID:10329909

Von Essen, S; Donham, K

1999-01-01

212

Confinement induced instability of thin elastic film  

E-print Network

A confined incompressible elastic film does not deform uniformly when subjected to adhesive interfacial stresses but with undulations which have a characteristic wavelength scaling linearly with the thickness of the film. In the classical peel geometry, undulations appear along the contact line below a critical film thickness or below a critical curvature of the plate. Perturbation analysis of the stress equilibrium equations shows that for a critically confined film the total excess energy indeed attains a minima for a finite amplitude of the perturbations which grow with further increase in the confinement.

Animangsu Ghatak

2005-05-02

213

Sensitivity of exciton spin relaxation in quantum dots to confining potential  

Microsoft Academic Search

We observe a strong dependence of the exciton spin relaxation in CdTe quantum dots on the average dot size and the depth of the confining potential. After rapid thermal annealing, which increases the average dot size and leads to weaker confinement, we measure the spin relaxation time of the quantum dot excitons to be 1.5 ns, as compared to 4.8

S. Mackowski; T. Gurung; H. E. Jackson; L. M. Smith; W. Heiss; J. Kossut; G. Karczewski

2005-01-01

214

The inertial electrostatic confinement approach to fusion power  

SciTech Connect

Inertial electrostatic confinement (IEC) of a non-Maxwellian beam-dominated plasma for fusion, originally proposed in the 1950s, has received little attention until recently. Experiments have shown that small IEC devices operating in a beam-background plasma mode are well-suited for a commercial portable low-level neutron source for activation analysis applications. However, the scaling to a high-power fusion reactor is uncertain, due to the lack of experimental data with the higher input currents necessary for beam-beam reactions. Three key issues need to be resolved: the stability of multiple potential well structures, the confinement time of energetic ions trapped in such wells, and the protection of grid structures during high-power operation. If these issues are positively resolved, conceptual design studies show that the resulting reactor would be economically and environmentally attractive and versatile.

Miley, G.H. [Univ. of Illinois, Urbana, IL (United States). Fusion Studies Lab.

1995-12-31

215

High Energy Electron Confinement in a Magnetic Cusp Configuration  

E-print Network

We report experimental results validating the concept that plasma confinement is enhanced in a magnetic cusp configuration when beta (plasma pressure/magnetic field pressure) is order of unity. This enhancement is required for a fusion power reactor based on cusp confinement to be feasible. The magnetic cusp configuration possesses a critical advantage: the plasma is stable to large scale perturbations. However, early work indicated that plasma loss rates in a reactor based on a cusp configuration were too large for net power production. Grad and others theorized that at high beta a sharp boundary would form between the plasma and the magnetic field, leading to substantially smaller loss rates. The current experiment validates this theoretical conjecture for the first time and represents critical progress toward the Polywell fusion concept which combines a high beta cusp configuration with an electrostatic fusion for a compact, economical, power-producing nuclear fusion reactor.

Park, Jaeyoung; Sieck, Paul E; Offermann, Dustin T; Skillicorn, Michael; Sanchez, Andrew; Davis, Kevin; Alderson, Eric; Lapenta, Giovanni

2014-01-01

216

Effects of limiters on reversed-field pinch confinement  

SciTech Connect

This paper documents the effects on confinement of introducing discrete limiters into the edge plasma of the ZT-40M reversed-field pinch (RFP) (Fusion Technol. {bold 8}, 1571 (1985)). RFP confinement is not significantly degraded by appropriately designed single limiters inserted to a sufficient depth for effective local vacuum vessel wall protection. Inserting limiters too deeply into the plasma results in excess limiter heating, and a consequent increase in the impurity content of the plasma. Under these conditions the plasma loop voltage increases. The heating of the limiters is observed to be asymmetric, with the majority of the heat flux in ZT-40M being attributable to suprathermal electrons ({ital T}{sub supra}{similar to}2--3{times}{ital T}{sub {ital e}}(0)) reaching the edge moving almost unidirectionally along magnetic-field lines.

Weber, P.G.; Ingraham, J.C.; Ellis, R.F.; Wurden, G.A.; Munson, C.P.; Downing, J.N. (Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (US))

1991-07-01

217

Physics of burning plasmas in toroidal magnetic confinement devices  

NASA Astrophysics Data System (ADS)

Some of the crucial physics aspects of burning plasmas magnetically confined in toroidal systems are presented from the viewpoint of nonlinear dynamics. Most of the discussions specifically refer to tokamaks, but they can be readily extended to other toroidal confinement devices. Particular emphasis is devoted to fluctuation induced transport processes of mega electron volts energetic ions and charged fusion products as well as to energy and particle transports of the thermal plasma. Long time scale behaviours due to the interplay of fast ion induced collective effects and plasma turbulence are addressed in the framework of burning plasmas as complex self-organized systems. The crucial roles of mutual positive feedbacks between theory, numerical simulation and experiment are shown to be the necessary premise for reliable extrapolations from present day laboratory to burning plasmas. Examples of the broader applications of fundamental problems to other fields of plasma physics and beyond are also given.

Zonca, F.; Briguglio, S.; Chen, L.; Fogaccia, G.; Hahm, T. S.; Milovanov, A. V.; Vlad, G.

2006-12-01

218

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

219

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

220

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

221

Microscale Confinement features in microfluidic devices can affect biofilm  

SciTech Connect

Biofilms are aggregations of microbes that are encased by extra-cellular polymeric substances (EPS) and adhere to surfaces and interfaces. Biofilm development on abiotic surfaces is a dynamic process, which typically proceeds through an initial phase of adhesion of plankntonic microbes to the substrate, followed by events such as growth, maturation and EPS secretion. However, the coupling of hydrodynamics, microbial adhesion and biofilm growth remain poorly understood. Here, we investigate the effect of semiconfined features on biofilm formation. Using a microfluidic device and fluorescent time-lapse microscopy, we establish that confinement features can significantly affect biofilm formation. Biofilm dynamics change not only as a function of confinement features, but also of the total fluid flow rate, and our combination of experimental results and numerical simulations reveal insights into the link between hydrodynamics and biofilm formation.

Kumar, Aloke [ORNL] [ORNL; Karig, David K [ORNL] [ORNL; Neethirajan, Suresh [University of Guelph] [University of Guelph; Acharya, Rajesh K [ORNL] [ORNL; Mukherjee, Partha P [ORNL] [ORNL; Retterer, Scott T [ORNL] [ORNL; Doktycz, Mitchel John [ORNL] [ORNL

2013-01-01

222

Confining boundary conditions from dynamical coupling constants  

NASA Astrophysics Data System (ADS)

It is shown that it is possible to consistently and gauge invariantly formulate models where the coupling constant is a non-trivial function of a scalar field. In the U(1) case, the coupling to the gauge field contains a term of the form g(?)j?(A?+??B) where B is an auxiliary field and j? is the Dirac current. The scalar field ? determines the local value of the coupling of the gauge field to the Dirac particle. The consistency of the equations determines the condition ???j?=0 which implies that the Dirac current cannot have a component in the direction of the gradient of the scalar field. As a consequence, if ? has a soliton behaviour, like defining a bubble that connects two vacua, we obtain that the Dirac current cannot have a flux through the wall of the bubble, defining a confinement mechanism where the fermions are kept inside those bags. Consistent models with time dependent fine structure constant can be also constructed

Guendelman, E. I.; Steiner, R.

2014-06-01

223

Thermonuclear burn in wall-confined plasmas  

NASA Astrophysics Data System (ADS)

The behavior of a hot, dense, thermonuclear reacting plasma which is contained between cold metal walls and thermally insulated by a strong magnetic field parallel to the wall is studied. The effects of thermal conduction and radiation energy losses from the plasma, convection, and a detailed treatment of alpha particle heating, as well as Ohmic heating and magnetic field diffusion, are included in the full set of one-fluid two-temperature equations. Losses parallel to the field lines are ignored since the plasma is assumed infinite in extent parallel to the walls in this one-dimensional study. The resulting initial value problem is solved numerically with a Lagrangian computer code employing finite difference methods. The dynamic behavior of the plasma is described by the time evolution of the temperature, number density, and magnetic field profiles. Cold alpha particles accumulate at the walls due to particle-wall collisions, but no atomic physics effects are considered at the plasma-wall interface. A sustained thermonuclear burn is demonstrated by the formation of an 'ignited' central region in which the alpha particles are sufficiently confined so that they heat and maintain a high plasma temperature.

Kmetyk, L. N.

1981-05-01

224

The confinement energy of quantum dots  

E-print Network

One of the most significant research interests in the field of electronics is that on quantum dot, because such materials have electronic properties intermediate between those of bulk semiconductors and those of discrete molecules. Confinement energy is a very important property of quantum dot. In this study, quantum confinement energy of a quantum dot is concluded to be h2/8md2 (d being the diameter of the confinement) and not h2/8ma2 (a being the radius of the confinement), as reported in the available literature. This is in the light of a recent study [1]. This finding should have a significant impact in the understanding of the physics of quantum dot and its technological application.

Dey, Samrat; Chakraborty, kishan; Dasgupta, Debasmita; Bordoloi, Darsana; Saikia, Rituja; Neog, Darsana; Shimray, Shishila; Paul, Supriyanka; Brahma, Kabita; Dey, Joydeep; Choudhury, Saurav

2012-01-01

225

Human Adaptation To Isolated And Confined Environments  

NASA Technical Reports Server (NTRS)

Data from Antarctic research station analyzed. Report describes study of physiology and psychology of humans in isolated and confined environment. Suggests ways in which such environments made more acceptable to human inhabitants.

Evans, Gary W.; Stokols, Daniel; Carrere, Sna Sybil

1992-01-01

226

Confinement studies for novel MCF reactor configurations  

NASA Astrophysics Data System (ADS)

Motivated by ideas from plasma theory, we use a suite of coupled plasma physics codes to explore the confinement performance of a range of tokamak configurations. The codes include GS2, Gryffin, Trinity and TOQ.

Dorland, William; Despain, Kate; Barnes, Michael; Parra, Felix; Highcock, Edmund; Schekochihin, Alex; Abel, Ian; Cowley, Steve

2010-11-01

227

Computer simulations of charged colloids in confinement.  

PubMed

We study by computer simulations the interaction between two similarly charged colloidal particles confined between parallel planes, in salt free conditions. Both the colloids and ions are simulated explicitly, in a fine-mesh lattice, and the electrostatic interaction is calculated using Ewald summation in two dimensions. The internal energy is measured by setting the colloidal particles at a given position and equilibrating the ions, whereas the free energy is obtained introducing a bias (attractive) potential between the colloids. Our results show that upon confining the system, the internal energy decreases, resulting in an attractive contribution to the interaction potential for large charges and strong confinement. However, the loss of entropy of the ions is the dominant mechanism in the interaction, irrespective of the confinement of the system. The interaction potential is therefore repulsive in all cases, and is well described by the DLVO functional form, but effective values have to be used for the interaction strength and Debye length. PMID:25460717

Puertas, Antonio M; de Las Nieves, F Javier; Cuetos, Alejandro

2015-02-15

228

A Review of Instanton Quarks and Confinement  

E-print Network

We review the recent progress made in understanding instantons at finite temperature (calorons) with non-trivial holonomy, and their monopole constituents as relevant degrees of freedom for the confined phase.

Pierre van Baal

2006-10-30

229

Detonation Diffraction into a Confined Volume  

E-print Network

Detonation diffraction has been, and remains, an active area of research. However, detonation diffraction into a confined volume, and specifically the transformation of a planar detonation into a cylindrical detonation, is an area which has received...

Polley, Nolan Lee

2012-02-14

230

Stellarator approach to toroidal plasma confinement  

SciTech Connect

An overview is presented of the development and current status of the stellarator approach to controlled thermonuclear confinement. Recent experimental, theoretical, and systems developments have made this concept a viable option for the evolution of the toroidal confinement program. Some experimental study of specific problems associated with departure from two-dimensional symmetry must be undertaken before the full advantages and opportunities of steady-state, net-current-free operation can be realized.

Johnson, J.L.

1981-12-01

231

Programmed environment management of confined microsocieties  

NASA Technical Reports Server (NTRS)

A programmed environment is described that assists the implementation and management of schedules governing access to all resources and information potentially available to members of a confined microsociety. Living and work schedules are presented that were designed to build individual and group performance repertoires in support of study objectives and sustained adaptation by participants. A variety of measurement requirements can be programmed and standardized to assure continuous assessment of the status and health of a confined microsociety.

Emurian, Henry H.

1988-01-01

232

Chiral symmetry, massive gluons and confinement  

SciTech Connect

It is quite difficult to obtain non-trivial chiral symmetry breaking solutions for the quark gap equation in the presence of dynamically generated gluon masses. An effective confining propagator has recently been proposed by Cornwall in order to solve this problem. We study phenomenological consequences of this approach, showing its compatibility with the experimental data. We argue that this confining propagator should be restricted to a small region of momenta, leading to effective four-fermion interactions at low energy.

Natale, A. A. [Instituto de Fisica Teorica - UNESP Rua Dr. Bento T. Ferraz, 271, Bl.II - 01140-070, Sao Paulo, SP (Brazil)

2013-03-25

233

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

234

Quantum confinement of nanocrystals within amorphous matrices  

NASA Astrophysics Data System (ADS)

Nanocrystals encapsulated within an amorphous matrix are computationally analyzed to quantify the degree to which the matrix modifies the nature of their quantum-confinement power—i.e., the relationship between nanocrystal size and the gap between valence- and conduction-band edges. A special geometry allows exactly the same amorphous matrix to be applied to nanocrystals of increasing size to precisely quantify changes in confinement without the noise typically associated with encapsulating structures that are different for each nanocrystal. The results both explain and quantify the degree to which amorphous matrices redshift the character of quantum confinement. The character of this confinement depends on both the type of encapsulating material and the separation distance between the nanocrystals within it. Surprisingly, the analysis also identifies a critical nanocrystal threshold below which quantum confinement is not possible—a feature unique to amorphous encapsulation. Although applied to silicon nanocrystals within an amorphous silicon matrix, the methodology can be used to accurately analyze the confinement softening of other amorphous systems as well.

Lusk, Mark T.; Collins, Reuben T.; Nourbakhsh, Zahra; Akbarzadeh, Hadi

2014-02-01

235

Effect of confinement on failure in 95 TATB/5 KEL-F  

SciTech Connect

A modification of the usual wedge test for measuring the failure thickness has been developed that eliminates the effect of the confinement provided by the witness plate. The new test uses a prism of the explosive with a line initiator to start a detonation along the trapezoidal face of the prism. Experiments using PBX 9502 have shown that the failure thickness measured using the prism test is 1/2 the failure diameter measured in long cyclindrical charges, provided the wave can propagate 15 to 25 times the failure width. No significant effects of confinement is observed for low impedance confinement, whereas high impedance materials reduce the failure thickness. Thin layers of confinement reduce the failure thickness significantly. Copper, 0.025 mm thick, and 0.25-mm aluminum each reduce the failure thickness of PBX 9502 by 35%. 6 refs., 7 figs.

Ramsay, J.B.

1985-01-01

236

COLLIMATION AND CONFINEMENT OF MAGNETIC JETS BY EXTERNAL MEDIA  

SciTech Connect

We study the collimation of a highly magnetized jet by a surrounding cocoon that forms as a result of the interaction of the jet with the external medium. We show that in regions where the jet is well confined by the cocoon, current-driven instabilities should develop over timescales shorter than the expansion time of the jet's head. We speculate that these instabilities would give rise to complete magnetic field destruction, whereby the jet undergoes a transition from high to low sigma above the collimation zone. Using this assumption, we construct a self-consistent model for the evolution of the jet-cocoon system in an ambient medium of arbitrary density profile. We apply the model to jet breakout in long gamma-ray bursts (GRBs) and show that the jet is highly collimated inside the envelope of the progenitor star and is likely to remain confined well after breakout. We speculate that this strong confinement may provide a channel for magnetic field conversion in GRB outflows, whereby the hot, low-sigma jet section thereby produced is the source of the photospheric emission observed in many bursts.

Levinson, Amir [School of Physics and Astronomy, Tel Aviv University, Tel Aviv 69978 (Israel)] [School of Physics and Astronomy, Tel Aviv University, Tel Aviv 69978 (Israel); Begelman, Mitchell C., E-mail: Levinson@wise.tau.ac.il, E-mail: mitch@jila.colorado.edu [JILA, University of Colorado and National Institute of Standards and Technology, 440 UCB, Boulder, CO 80309-0440 (United States)

2013-02-20

237

Molecular simulation of chevrons in confined smectic liquid crystals  

NASA Astrophysics Data System (ADS)

Chevron structures adopted by confined smectic liquid crystals are investigated via molecular dynamics simulations of the Gay-Berne model. The chevrons are formed by quenching nematic films confined between aligning planar substrates whose easy axes have opposing azimuthal components. When the substrates are perfectly smooth, the chevron formed migrates rapidly towards one of the confining walls to yield a tilted layer structure. However, when substrate roughness is included, by introducing a small-amplitude modulation to the particle-substrate interaction well depth, a symmetric chevron is formed which remains stable over sufficiently long run times for detailed structural information, such as the relevant order parameters and director orientation, to be determined. For both smooth and rough boundaries, the smectic order parameter remains nonzero across the entire chevron, implying that layer identity is maintained across the chevron tip. Also, when the surface-stabilized chevron does eventually revert to a tilted layer structure, it does so via surface slippage, such that layer integrity is maintained throughout the chevron to tilted layer relaxation process.

Webster, Richard E.; Mottram, Nigel J.; Cleaver, Douglas J.

2003-08-01

238

Single-molecule microscopy using tunable nanoscale confinement  

NASA Astrophysics Data System (ADS)

We present the design, construction and implementation of a modular microscopy device that transforms a basic inverted fluorescence microscope into a versatile single-molecule imaging system. The device uses Convex Lens- Induced Confinement (CLIC) to improve background rejection and extend diffusion-limited observation time. To facilitate its integration into a wide range of laboratories, this implementation of the CLIC device can use a standard flow-cell, into which the sample is loaded. By mechanically deforming the flow-cell, the device creates a tunable, wedge-shaped imaging chamber which we have modeled using finite element analysis simulations and characterized experimentally using interferometry. A powerful feature of CLIC imaging technology is the ability to examine single molecules under a continuum of applied confinement, from the nanometer to the micrometer scale. We demonstrate, using freely diffusing ?-phage DNA, that when the imposed confinement is on the scale of individual molecules their molecular conformations and diffusivity are altered significantly. To improve the flow-cell stiffness, seal, and re-usability, we have innovated the fabrication of thin PDMS-bonded flow-cells. The presented flow-cell CLIC technology can be combined with surface-lithography to provide an accessible and powerful approach to tune, trap, and image individual molecules under an extended range of imaging conditions. It is well-suited to tackling open problems in biophysics, biotechnology, nanotechnology, materials science, and chemistry.

McFaul, Christopher M. J.; Leith, Jason; Jia, Bojing; Michaud, François; Arsenault, Adriel; Martin, Andrew; Berard, Daniel; Leslie, Sabrina

2013-09-01

239

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

240

Confinement of supernova explosions in a collapsing cloud  

E-print Network

We analyze the confining effect of cloud collapse on an expanding supernova shockfront. We solve the differential equation for the forces on the shockfront due to ram pressure, supernova energy, and gravity. We find that the expansion of the shockfront is slowed and in fact reversed by the collapsing cloud. Including radiative losses and a potential time lag between supernova explosion and cloud collapse shows that the expansion is reversed at smaller distances as compared to the non-radiative case. We also consider the case of multiple supernova explosions at the center of a collapsing cloud. For instance, if we scale our self-similar solution to a single supernova of energy 10^51 ergs occurring when a cloud of initial density 10^2 H/cm^3 has collapsed by 50%, we find that the shockfront is confined to ~15 pc in ~1 Myrs. Our calculations are pertinent to the observed unusually compact non-thermal radio emission in blue compact dwarf galaxies (BCDs). More generally, we demonstrate the potential of a collapsing cloud to confine supernovae, thereby explaining how dwarf galaxies would exist beyond their first generation of star formation.

M. M. Kasliwal; R. V. E. Lovelace; J. R. Houck

2005-05-13

241

Emerging Functionality in Complex Oxides Driven by Spatial Confinement  

NASA Astrophysics Data System (ADS)

The exotic properties displayed by correlated electronic materials (CEMs) such as the cuprates, manganites, ruthenates, Fe-based pnictides, and heavy-fermion compounds are intimately related to the coexistence of competing nearly degenerate states which couple simultaneously active degrees of freedom--charge, lattice, orbital, and spin states. The striking phenomenon in these materials is due in large part to spatial electronic inhomogeneities, or nanoscale phase separation. The functionality in these CEMs is almost always associated with a phase transition, metal-to-insulator, magnetic-to-nonmagnetic, normal metal to superconductor, etc. Spatial confinement on the length scale of the inherent phase separation can probe the basic physics and reveal new emergent behavior. Several examples of the manifestation of spatial confinement will be discussed [1,2], focusing on the observed fluctuations between the competing phases [2]. Work done in collaboration with Jian Shen and Zac Ward at ORNL. [4pt] [1] T. Z. Ward, S. H. Liang, K. Fuchigami, L. F. Yin, E. Daggotto, E. W. Plummer, and J. Shen, ``Reemergent Metal-Insulator Transitions in Manganites Exposed with Spatial Confinement,'' Phys. Rev. Lett. 100, 247204 (2008)[0pt] [2] T. Z. Ward, X. G. Zhang, L. F. Yin, X. Q. Zhang, Ming Liu, P. C. Snijders, S. Jesse, E. W. Plummer, Z. H. Cheng, and J. Shen, ``Time-Resolved Electronic Phase Transitions in Manganites,'' Phys. Rev. Letters, 102, 087201 (2009).

Plummer, Ward

2010-03-01

242

Characteristics of high-confinement modes in Alcator C Mod  

SciTech Connect

The regime of high particle and energy confinement known as the H mode [Phys. Rev. Lett. {bold 49}, 1408 (1982)] has been extended to a unique range of operation for divertor tokamaks up to toroidal fields of nearly 8 T, line-averaged electron densities of 3{times}10{sup 20} m{sup {minus}3}, and surface power densities of nearly 0.6 MW/m{sup 2} in the compact high-field tokamak Alcator C Mod [Phys. Plasmas {bold 1}, 1511 (1994)]. H modes are achieved in Alcator C Mod with Ion Cyclotron Resonant Frequency (ICRF) heating and with Ohmic heating alone without boronization of the all molybdenum tiled first wall. Large increases in charge exchange flux are observed during the H mode over the entire range of energies from 2 to 10 keV. There appears to be an upper limit to the midplane neutral pressure, of about 0.08 Pa above which no H modes have been observed. The plasmas with the best energy confinement have the lowest midplane neutral pressures, below 0.01 Pa. There is an edge electron temperature threshold such that {ital T}{sub {ital e}}{ge}280 eV {plus_minus}40 eV for sustaining the H mode, which is equal at L{endash}H and H{endash}L transitions. The hysteresis in the threshold power between L{endash}H and H{endash}L transitions is less than 25{percent} on average. Both core and edge particle confinement improve by a factor of 2{endash}4 from L mode to H mode. Energy confinement also improves by up to a factor of 2 over L mode. {copyright} {ital 1996 American Institute of Physics.}

Snipes, J.A.; Boivin, R.L.; Christensen, C.; Fiore, C.; Garnier, D.; Goetz, J.; Golovato, S.N.; Graf, M.; Granetz, R.S.; Greenwald, M.; Hubbard, A.; Hutchinson, I.H.; Irby, J.; LaBombard, B.; Marmar, E.S.; Niemczewski, A.; OShea, P.; Porkolab, M.; Stek, P.; Takase, Y.; Terry, J.L.; Umansky, M.; Wolfe, S.M. [Plasma Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)] [Plasma Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

1996-05-01

243

Confining Pt nanoparticles in porous carbon structures for achieving durable electrochemical performance  

NASA Astrophysics Data System (ADS)

Carbon-supported Pt catalysts have been widely employed as electrocatalysts for energy storage/conversion applications, but have encountered challenging instability issues. In this work, we investigated the degradation behaviors of pore-confined and surface-located Pt nanocatalysts, employing hollow porous carbon spheres with precisely controlled structure as catalyst supports. It is found that by uniformly confining Pt nanoparticles in porous carbon structures, remarkably improved stability and long-term performance of Pt electrocatalysts can be achieved. The nanopore-confined Pt exhibits high retention ratios of both ECSA (54%) and electrocatalytic activity after accelerated degradation tests (ADTs), both of which are almost two times higher than those of the surface-located ones. TEM analysis of the degraded electrocatalysts further revealed that the pore-confinement effect can significantly suppress the Pt degradation processes, including particle migration/agglomeration and detachment from the carbon support.Carbon-supported Pt catalysts have been widely employed as electrocatalysts for energy storage/conversion applications, but have encountered challenging instability issues. In this work, we investigated the degradation behaviors of pore-confined and surface-located Pt nanocatalysts, employing hollow porous carbon spheres with precisely controlled structure as catalyst supports. It is found that by uniformly confining Pt nanoparticles in porous carbon structures, remarkably improved stability and long-term performance of Pt electrocatalysts can be achieved. The nanopore-confined Pt exhibits high retention ratios of both ECSA (54%) and electrocatalytic activity after accelerated degradation tests (ADTs), both of which are almost two times higher than those of the surface-located ones. TEM analysis of the degraded electrocatalysts further revealed that the pore-confinement effect can significantly suppress the Pt degradation processes, including particle migration/agglomeration and detachment from the carbon support. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr03555k

Yang, C.; Zhou, M.; Xu, Q.

2014-09-01

244

Stiffness and Confinement Ratios of SMA Wire Jackets for Confining Concrete  

NASA Astrophysics Data System (ADS)

This article discusses the effects of the stiffness and confinement ratios of shape memory alloy (SMA) wire jackets on the behavior of confined concrete. SMA wire jackets are an effective confining material to improve concrete behavior; for example, by increasing peak strength and failure strain. The stiffness and confinement ratios of fiber-reinforced polymer jackets have been extensively discussed and their effects are well known. However, assessment of the stiffness and confinement ratios of SMA wire jackets has not previously been conducted. In this study, we investigate the effects of the stiffness and confinement ratios of steel jackets, and then compare the results with those of SMA wire jackets. In general, the stiffness ratios of SMA wire jackets are relatively smaller than those of steel jackets, and most of them have lower stiffness ratios because the Young's moduli of the SMAs are relatively small. The active confining pressure of the SMA wires does not improve the lower stiffness-ratio effect since the amount of active confining pressure is not sufficiently large.

Choi, Eunsoo; Kim, Dong Joo; Youn, Heejung

2014-07-01

245

Study of Chiral Confining Model with Vector Mesons  

NASA Astrophysics Data System (ADS)

This dissertation consists of two parts, the study of the chiral confining model and the investigation of vacuum instability. In the first part we present a chiral confining model in which a bag is formed dynamically. The major topics addressed are: construction of the model, mean-field solution, anomalously large rho nucleon tensor coupling, and a projection method including the quantum effects of mesons. Two features of QCD, namely, chiral invariance and vacuum condensates, are crucial ingredients of our chiral confining model. The interaction of the valence quarks with the quark condensate is described via the sigma field. It generates the quark dynamical mass. The interaction of the quarks with the gluon condensate is described in our model through the color dielectric function, epsilon. This interaction generates the bag within which quarks are absolutely confined. The introduction of the color dielectric function epsilon modifies the quark-meson interaction by multiplying a factor epsilon ^{-1/2}. Thus the quark part of the rho meson source current is structurally different from the isovector part of the electromagnetic current. Thus the chiral confining model provides a natural explanation why the tensor coupling of the rho meson, kappa_rho, is larger than the isovector part of the anomalous magnetic moment of the nucleon, kappa_upsilon . We have improved a simple method of calculating expectation values of operators in states of good angular momentum projected from a hedgehog baryon state. We have included the contributions of quantum mesons. The symmetry of the hedgehog state under grand-reversal introduces remarkable simplification in the calculation of matrix elements of operators which do not contain time derivatives of meson fields. The quantum meson contributions turn out to be (3/2)/< B|{bf J }^2| B> times the classical meson fields contributions, with | B> being the hedgehog state. In the second part we show that the perturbative vacuum of model field theories in which fermions are coupled to scalar bosons and contain no derivative coupling are unstable at the one-loop level. The instability is due to fluctuations at a sufficiently short-distance scale and is caused by fermion loop contributions.

Ren, Ching-Yun

1991-02-01

246

Ordering of confined water between metallic surfaces  

NASA Astrophysics Data System (ADS)

It has been pointed out (PCCP 2010, Poissier et al.) that the hydrogen bonding type interaction occuring at water/metal interface makes the two type of interfacial water orderings (hydrophobic or hydrophilic overlayers) very close in energy. The most stable, hydrophobic, overlayer has very small net dipole moment perpendicular to the surface, while the least stable (in vacuum) hydrophilic interface has a large ( 1.8 D) net dipole moment. First principles molecular dynamics simulations of liquid water confined between two Pd surfaces have been performed and structural and electronic water properties have been studied in detail. We show that water confinement in this situation results in a spontaneous symmetry breaking of the system, inducing an electric field across the liquid water slab. We discuss the origin of this spontaneous polarization and show its dependence with the confinement distance along the direction perpendicular to the planes of the surfaces.

Poissier, Adrien; Fernandez-Serra, Maria V.

2011-03-01

247

Electronic confinement in modulation doped quantum dots  

SciTech Connect

Modulation doping, an effective way to dope quantum dots (QDs), modifies the confinement energy levels in the QDs. We present a self-consistent full multi-grid solver to analyze the effect of modulation doping on the confinement energy levels in large-area structures containing Si QDs in SiO{sub 2} and Si{sub 3}N{sub 4} dielectrics. The confinement energy was found to be significantly lower when QDs were in close proximity to dopant ions in the dielectric. This effect was found to be smaller in Si{sub 3}N{sub 4}, while smaller QDs in SiO{sub 2} were highly susceptible to energy reduction. The energy reduction was found to follow a power law relationship with the QD size.

Puthen Veettil, B., E-mail: b.puthen-veettil@unsw.edu.au; König, D.; Patterson, R.; Smyth, S.; Conibeer, G. [Australian Centre for Advanced Photovoltaics, UNSW, Sydney 2052 (Australia)

2014-04-14

248

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

249

Confinement models at finite temperature and density  

NASA Astrophysics Data System (ADS)

This work presents a non-perturbative study of dynamical chiral symmetry breaking in various confinement models at finite temperature and density. The tool of choice is the Schwinger-Dyson equations. We shall discuss (i) the inadequacy of static confinement models in explaining thermal properties of QCD (ii) dynamical chiral and parity symmetry breaking of three dimensional QED with two-component fermions (iii) endemic infrared divergences in QED3 at finite temperature and the attempt to solve the system self-consistently.

Lo, Pok Man

250

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

251

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

252

Inertial Confinement Fusion with Tetrahedral Hohlraums at OMEGA  

SciTech Connect

Indirect-drive inertial confinement fusion will require for ignition a highly symmetric x-ray flux around the capsule. To this end, the {open_quotes}tetrahedral hohlraum,{close_quotes} spherical in shape with four laser entrance holes located at the vertices of a tetrahedron, has been proposed. The first experimental test of this concept, using the OMEGA laser, is reported here. Drive symmetry was probed using capsule implosion symmetries, which varied qualitatively as expected with hohlraum dimensions. Modeling of the experiments gives time-averaged flux asymmetries as low as 1{percent} rms over a 2.2-ns laser pulse. {copyright} {ital 1999} {ital The American Physical Society}

Wallace, J.M.; Murphy, T.J.; Delamater, N.D.; Klare, K.A.; Oertel, J.A.; Magelssen, G.R.; Lindman, E.L.; Hauer, A.A.; Gobby, P. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)] [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Schnittman, J.D.; Craxton, R.S.; Seka, W.; Kremens, R.; Bradley, D. [Laboratory for Laser Energetics, University of Rochester, Rochester, New York 14623-1299 (United States)] [Laboratory for Laser Energetics, University of Rochester, Rochester, New York 14623-1299 (United States); Pollaine, S.M.; Turner, R.E.; Landen, O.L. [Lawrence Livermore National Laboratory, Livermore, California 94551 (United States)] [Lawrence Livermore National Laboratory, Livermore, California 94551 (United States); Drake, D. [InterScience, Germantown, Maryland 20875-0659 (United States)] [InterScience, Germantown, Maryland 20875-0659 (United States); MacFarlane, J.J. [University of Wisconsin, Madison, Wisconsin 53706 (United States)] [University of Wisconsin, Madison, Wisconsin 53706 (United States)

1999-05-01

253

Inertial Confinement Fusion with Tetrahedral Hohlraums at OMEGA  

NASA Astrophysics Data System (ADS)

Indirect-drive inertial confinement fusion will require for ignition a highly symmetric x-ray flux around the capsule. To this end, the ``tetrahedral hohlraum,'' spherical in shape with four laser entrance holes located at the vertices of a tetrahedron, has been proposed. The first experimental test of this concept, using the OMEGA laser, is reported here. Drive symmetry was probed using capsule implosion symmetries, which varied qualitatively as expected with hohlraum dimensions. Modeling of the experiments gives time-averaged flux asymmetries as low as 1% rms over a 2.2-ns laser pulse.

Wallace, J. M.; Murphy, T. J.; Delamater, N. D.; Klare, K. A.; Oertel, J. A.; Magelssen, G. R.; Lindman, E. L.; Hauer, A. A.; Gobby, P.; Schnittman, J. D.; Craxton, R. S.; Seka, W.; Kremens, R.; Bradley, D.; Pollaine, S. M.; Turner, R. E.; Landen, O. L.; Drake, D.; Macfarlane, J. J.

1999-05-01

254

Characterization of energy confinement in net-current free plasmas using the extended International Stellarator Database  

NASA Astrophysics Data System (ADS)

International collaboration on development of a stellarator confinement database has progressed. More than 3000 data points from nine major stellarator experiments have been compiled. Robust dependences of the energy confinement time on the density and the heating power have been confirmed. Dependences on other operational parameters, i.e. the major and minor radii, magnetic field and the rotational transform \\iobar , have been evaluated using inter-machine analyses. In order to express the energy confinement in a unified scaling law, systematic differences in each subgroup are quantified. An a posteriori approach using a confinement enhancement factor on ISS95 as a renormalizing configuration-dependent parameter yields a new scaling expression ISS04; \\tau _E^ISS04 = 0.134a^{2.28}R^{0.64}P^{ - 0.61}\\bar {n}_{\\rme}^{0.54} B^{0.84}\\iobar_{2 / 3}^{0.41} . Gyro-Bohm characteristic similar to ISS95 has been confirmed for the extended database with a wider range of plasma parameters and magnetic configurations than in the study of ISS95. It has also been discovered that there is a systematic offset of energy confinement between magnetic configurations, and its measure correlates with the effective helical ripple of the external stellarator field. Full documentation of the International Stellarator Confinement Database is available at http://iscdb.nifs.ac.jp/ and http://www.ipp.mpg.de/ISS.

Yamada, H.; Harris, J. H.; Dinklage, A.; Ascasibar, E.; Sano, F.; Okamura, S.; Talmadge, J.; Stroth, U.; Kus, A.; Murakami, S.; Yokoyama, M.; Beidler, C. D.; Tribaldos, V.; Watanabe, K. Y.; Suzuki, Y.

2005-12-01

255

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

256

Confinement matrices for low- and intermediate-level radioactive waste  

NASA Astrophysics Data System (ADS)

Mining of uranium for nuclear fuel production inevitably leads to the exhaustion of natural uranium resources and an increase in market price of uranium. As an alternative, it is possible to provide nuclear power plants with reprocessed spent nuclear fuel (SNF), which retains 90% of its energy resource. The main obstacle to this solution is related to the formation in the course of the reprocessing of SNF of a large volume of liquid waste, and the necessity to concentrate, solidify, and dispose of this waste. Radioactive waste is classified into three categories: low-, intermediate-, and high-level (LLW, ILW, and HLW); 95, 4.4, and 0.6% of the total waste are LLW, ILW, and HLW, respectively. Despite its small relative volume, the radioactivity of HLW is approximately equal to the combined radioactivity of LLW + ILW (LILW). The main hazard of HLW is related to its extremely high radioactivity, the occurrence of long-living radionuclides, heat release, and the necessity to confine HLW for an effectively unlimited time period. The problems of handling LILW are caused by the enormous volume of such waste. The available technology for LILW confinement is considered, and conclusion is drawn that its concentration, vitrification, and disposal in shallow-seated repositories is a necessary condition of large-scale reprocessing of SNF derived from VVER-1000 reactors. The significantly reduced volume of the vitrified LILW and its very low dissolution rate at low temperatures makes borosilicate glass an ideal confinement matrix for immobilization of LILW. At the same time, the high corrosion rate of the glass matrix at elevated temperatures casts doubt on its efficient use for immobilization of heat-releasing HLW. The higher cost of LILW vitrification compared to cementation and bitumen impregnation is compensated for by reduced expenditure for construction of additional engineering barriers, as well as by substantial decrease in LLW and ILW volume, localization of shallow-seated repositories in various geological media, and the use of inexpensive borosilicate glass.

Laverov, N. P.; Omel'Yanenko, B. I.; Yudintsev, S. V.; Stefanovsky, S. V.

2012-02-01

257

Energy confinement and profile consistency in TFTR  

SciTech Connect

A new regime of enhanced energy confinement has been observed on TFTR with neutral beam injection at low plasma current. It is characterized by extremely peaked electron density profiles and broad electron temperature profiles. The electron temperature profile shapes violate the concept of profile consistency in which T/sub e/(O)//sub v/ is assumed to be a tightly constrained function of q/sub a/, but they are in good agreement with a form of profile consistency based on examining the temperature profile shape outside the plasma core. The enhanced confinement regime is only obtained with a highly degassed limiter; in discharges with gas-filled limiters convective losses are calculated to dominate the edge electron power balance. Consistent with the constraint of profile consistency, global confinement is degraded in these cases. The best heating results in the enhanced confinement regime are obtained with nearly balanced co- and counter-injection. Much of the difference between balanced and co-only injection can be explained on the basis of classically predicted effects associated with plasma rotation.

Goldston, R.J.; Arunasalan, V.; Bell, M.G.; Bitter, M.; Blanchard, W.R.; Bretz, N.L.; Budny, R.; bush, C.E.; Callen, J.D.; Cohen, S.A.

1987-04-01

258

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

259

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

260

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

261

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

262

Effective diffusion of confined active Brownian swimmers  

NASA Astrophysics Data System (ADS)

We theoretically find the effect of confinement and thermal fluctuations on the diffusivity of a spherical active swimmer moving inside a two-dimensional narrow cavity of general shape. The explicit formulas for the effective diffusion coefficient of a swimmer moving inside two particular cavities are presented. We also compare our analytical results with Brownian dynamics simulations and we obtain excellent agreement.

Sandoval, Mario; Dagdug, Leornardo

2014-12-01

263

Confined Lennard-Jones System Model  

NSDL National Science Digital Library

The Confined Lennard-Jones System is an idealized statistical mechanics model that simulates a two-dimensional system of particles confined to a box with a constant temperature thermal reservoir at one end and a movable piston at the other. Particles in this model have unit mass and interact through pairwise Lennard-Jones forces and hard-wall contact forces. Slow-moving particles are color-coded as blue and fast particles are color-coded as yellow. The model computes and plots the evolution of the total energy E, the kinetic energy per particle K, the pressure P, and the volume V. The model also displays histograms and mean values of these quantities. The Confined Lennard-Jones System was created using the Easy Java Simulations (Ejs) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_stp_md_ConfinedLennardJonesSystem.jar file will run the program if Java is installed.

Christian, Wolfgang

2010-12-27

264

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

2013-12-01

265

THE EFFECT OF TENPERATURE AND CONFINING PRESSURZ  

E-print Network

measure absolute permeability under conditions of elevated temperature and overburden pressure. Several fTHE EFFECT OF TENPERATURE AND CONFINING PRESSURZ ON FLUID FLOW PROPERTIES OF CONSOLIDATED ROCYS work on the e f f e c t of temperature on r e l a t i v e permeability suggested t h a t absolute

Stanford University

266

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.

267

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

268

Phase Transformations in Confined Nanosystems  

SciTech Connect

This project discovered that non-equilibrium structures, including chemically ordered structures not observed in bulk systems, form in isolated nanoscale systems. Further, a generalized model was developed that effectively explained the suppression of equilibrium phase transformations. This thermodynamic model considered the free energy decrease associated with the phase transformation was less than the increase in energy associated with the formation of an interphase interface, therefore inhibiting the phase transformation. A critical diameter exists where the system transitions to bulk behavior, and a generalized equation was formulated that successfully predicted this transition in the Fe-Au system. This provided and explains a new route to novel structures not possible in bulk systems. The structural characterization was accomplished using transmission electron microscopy in collaboration with Matthew Kramer of Ames Laboratory. The PI and graduate student visited Ames Laboratory several times a year to conduct the experiments.

Shield, Jeffrey E. [Department of Mechanical & Materials Engineering] [Department of Mechanical & Materials Engineering; Belashchenko, Kirill [Department of Physics & Astronomy] [Department of Physics & Astronomy

2014-04-29

269

Two-dimensional material confined water.  

PubMed

Conspectus The interface between water and other materials under ambient conditions is of fundamental importance due to its relevance in daily life and a broad range of scientific research. The structural and dynamic properties of water at an interface have been proven to be significantly difference than those of bulk water. However, the exact nature of these interfacial water adlayers at ambient conditions is still under debate. Recent scanning probe microscopy (SPM) experiments, where two-dimensional (2D) materials as ultrathin coatings are utilized to assist the visualization of interfacial water adlayers, have made remarkable progress on interfacial water and started to clarify some of these fundamental scientific questions. In this Account, we review the recently conducted research exploring the properties of confined water between 2D materials and various surfaces under ambient conditions. Initially, we review the earlier studies of water adsorbed on hydrophilic substrates under ambient conditions in the absence of 2D coating materials, which shows the direct microscopic results. Subsequently, we focus on the studies of water adlayer growth at both hydrophilic and hydrophobic substrates in the presence of 2D coating materials. Ice-like water adlayers confined between hydrophobic graphene and hydrophilic substrates can be directly observed in detail by SPM. It was found that the packing structure of the water adlayer was determined by the hydrophilic substrates, while the orientation of intercalation water domains was directed by the graphene coating. In contrast to hydrophilic substrates, liquid-like nanodroplets confined between hydrophobic graphene and hydrophobic substrates appear close to step edges and atomic-scale surface defects, indicating that atomic-scale surface defects play significant roles in determining the adsorption of water on hydrophobic substrates. In addition, we also review the phenomena of confined water between 2D hydrophilic MoS2 and the hydrophilic substrate. Finally, we further discuss researchers taking advantage of 2D graphene coatings to stabilize confined water nanodroplets to manipulate nanofluidics through applying an external force by using novel SPM techniques. Moreover, for future technology application purposes, the doping effect of confined water is also discussed. The use of 2D materials as ultrathin coatings to investigate the properties of confined water under ambient conditions is developing and recognized as a profound approach to gain fundamental knowledge of water. This ideal model system will provide new opportunities in various research fields. PMID:25539031

Li, Qiang; Song, Jie; Besenbacher, Flemming; Dong, Mingdong

2015-01-20

270

Neutron moderation in inertial confinement fusion pellets and effects on damage and radioactive inventory  

Microsoft Academic Search

A standard time-dependent neutron transport computer code, TDA, is modified to allow time-varying material density to calculate the neutron spectrum from exploding inertial confinement fusion pellets with rho R values of 0 to 6 g\\/cm². Softening of the spectra due to neutron-fuel interactions causes a time-of-flight broadening of the neutron arrival time distribution at the chamber wall. It is found

F. Beranek; R. W. Conn

1980-01-01

271

Measurements of uranium mass confined in high density plasmas  

NASA Technical Reports Server (NTRS)

An X-ray absorption method for measuring the amount of uranium confined in high density, rf-heated uranium plasmas is described. A comparison of measured absorption of 8 keV X-rays with absorption calculated using Beer Law indicated that the method could be used to measure uranium densities from 3 times 10 to the 16th power atoms/cu cm to 5 times 10 to the 18th power atoms/cu cm. Tests were conducted to measure the density of uranium in an rf-heated argon plasma with UF6 infection and with the power to maintain the discharge supplied by a 1.2 MW rf induction heater facility. The uranium density was measured as the flow rate through the test chamber was varied. A maximum uranium density of 3.85 times 10 to the 17th power atoms/cu cm was measured.

Stoeffler, R. C.

1976-01-01

272

Surface force confinement cell for neutron reflectometry studies of complex fluids under nano-confinement  

SciTech Connect

In this paper, we describe the construction of a new neutron surface force confinement cell (NSFCC). The NSFCC is equipped with hydraulically powered in-situ, temporally stable, force control system for simultaneous neutron reflectometry studies of nano-confined complex fluid systems. Test measurements with deuterated toluene confined between two opposing diblock copolymer (polystyrene + poly 2-vinylpyridine) coated quartz substrates demonstrate the capabilities of the NSFCC. With increasing hydraulically-applied force, a series of well-defined decreasing separations were observed from neutron reflectivity measurements. No noticeable changes in the hydraulic pressure used for controlling the surface separation were observed during the measurements, demonstrating the high stability of the apparatus. This newly designed NSFCC introduces a higher level of control for studies of confinement and consequent finite size effects on nano-scale structure in a variety of complex fluid and soft condensed matter systems.

Cho, Jae-Hie [ORNL; Smith, Gregory Scott [ORNL; Hamilton, William A. [ANSTO; Mulder, D. [University of California, Davis; Kuhl, T. L. [University of California, Davis; Mays, Jimmy [ORNL

2008-01-01

273

Inertial confinement fusion neutron images  

SciTech Connect

At the OMEGA laser facility [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)], 14-MeV neutron images are acquired with a 20-{mu}m resolution and a large signal-to-noise ratio (SNR) using penumbral and ring apertures. The two aperture types produce coded images of the source that are unfolded using a similar autocorrelation method. The techniques provide comparable images for various deuterium-tritium filled target implosions, with glass and plastic (CH) shells. SNR analysis reveals that the annular (ring) technique will achieve a good image quality at the 10-{mu}m resolution level with the planned upgrade of our novel detector. The detector is an array of 85-{mu}m-diam capillary tubes filled with a liquid scintillator. Its resolution is limited to 650 {mu}m by the track length of the elastically scattered recoil protons. Replacing the hydrogen in the scintillator with deuterium improves detector spatial resolution to 325 {mu}m, and makes high source resolution achievable. The readout design provides an efficient light collection of the scintillation photons by relaying the image through a fiber optic taper. Improved efficiency produces images with better SNR. Also, the increased detector sensitivity allows single event recording of 2.45-MeV neutron interactions. For the first time ever, we show neutron images of deuterium filled, warm, and cryogenic target implosions.

Disdier, L.; Rouyer, A.; Lantuejoul, I.; Landoas, O.; Bourgade, J.L.; Sangster, T.C.; Glebov, V.Yu.; Lerche, R.A. [CEA-DAM Ile de France, BP 12, 91680 Bruyeres Le Chatel (France); Laboratory for Laser Energetics, Rochester, New York 14623-1299 (United States); Lawrence Livermore National Laboratory, Livermore, California 94551 (United States)

2006-05-15

274

Self-assembled morphologies of diblock copolymers confined in nanochannels: Effects of confinement geometry  

Microsoft Academic Search

The self-assembly of diblock copolymers confined in channels of various shaped cross sections is studied using a simulated annealing technique with the ``single-site bond fluctuation'' model. In the bulk, the asymmetric diblock copolymers used in this study form hexagonally packed cylinders with period L0. The cross sections of the confining channels are of different shapes including regular triangles, rectangles, squares,

Bin Yu; Pingchuan Sun; Tiehong Chen; Qinghua Jin; Datong Ding; Baohui Li; An-Chang Shi

2007-01-01

275

Diffusion and surface excess of a confined nanoswimmer dispersion.  

PubMed

The diffusivity and surface excess of nanoswimmers which are confined in two plates with the separation H are explored by dissipative particle dynamics. Both mean squared displacement and velocity autocorrelation function methods are used to study the diffusive behavior of nanoswimmers with the Brownian diffusivity D0 and the results obtained from both methods are consistent. The active diffusivity of confined nanoswimmers (D - D0) depends on the wall separation, swimming speed v(a), and run time ?. Our simulation results show that (D-D0)/v(a)(2)? is a function of v(a)?/H. The reduction in the diffusivity of active colloids is more significant than that of passive particles. The distribution of nanoswimmers between two parallel walls is acquired and two regions can be identified. The accumulation of nanoswimmers near walls is quantitatively described by the surface excess ?. It is found that ? grows as the nanoswimmer concentration c(b), swimming speed v(a), and run time ? are increased. The coupling between the ballistic trajectory of nanoswimmers and the walls results in nanoswimmer accumulation. The simulation outcomes indicate that ?/Hc(b) is a function of H/v(a)?. PMID:25399157

Xiao, Song; Wang, Zhengjia; Chen, Hsuan-Yi; Sheng, Yu-Jane; Tsao, Heng-Kwong

2014-11-14

276

Diffusion and surface excess of a confined nanoswimmer dispersion  

NASA Astrophysics Data System (ADS)

The diffusivity and surface excess of nanoswimmers which are confined in two plates with the separation H are explored by dissipative particle dynamics. Both mean squared displacement and velocity autocorrelation function methods are used to study the diffusive behavior of nanoswimmers with the Brownian diffusivity D0 and the results obtained from both methods are consistent. The active diffusivity of confined nanoswimmers (D - D0) depends on the wall separation, swimming speed va, and run time ?. Our simulation results show that (D-D0)/va2? is a function of va?/H. The reduction in the diffusivity of active colloids is more significant than that of passive particles. The distribution of nanoswimmers between two parallel walls is acquired and two regions can be identified. The accumulation of nanoswimmers near walls is quantitatively described by the surface excess ?. It is found that ? grows as the nanoswimmer concentration cb, swimming speed va, and run time ? are increased. The coupling between the ballistic trajectory of nanoswimmers and the walls results in nanoswimmer accumulation. The simulation outcomes indicate that ?/Hcb is a function of H/va?.

Xiao, Song; Wang, Zhengjia; Chen, Hsuan-Yi; Sheng, Yu-Jane; Tsao, Heng-Kwong

2014-11-01

277

The Evaporation Regime in a Confined Flare  

NASA Astrophysics Data System (ADS)

We studied the evolution of a small eruptive flare (GOES class C1) from its onset phase using multi-wavelength observations that sample the flare atmosphere from the chromosphere to the corona. The main instruments involved were the Coronal Diagnostic Spectrometer (CDS) aboard SOHO and facilities at the Dunn Solar Tower of the National Solar Observatory/Sacramento Peak. Transition Region and Coronal Explorer (TRACE) together with Ramaty High-Energy Spectroscopic Imager (RHESSI) also provided images and spectra for this flare. H? and TRACE images display two loop systems that outline the pre-reconnection and post-reconnection magnetic field lines and their topological changes revealing that we are dealing with an eruptive confined flare. RHESSI data do not record any detectable emission at energies ?25 keV, and the observed count spectrum can be well fitted with a thermal plus a non-thermal model of the photon spectrum. A non-thermal electron flux F ? 5 × 1010 erg cm-2 s-1 is determined. The reconstructed images show a very compact source whose peak emission moves along the photospheric magnetic inversion line during the flare. This is probably related to the motion of the reconnection site, hinting at an arcade of small loops that brightens successively. The analysis of the chromospheric spectra (Ca II K, He I D3 and H?, acquired with a four-second temporal cadence) shows the presence of a downward velocity (between 10 and 20 km s-1) in a small region intersected by the spectrograph slit. The region is included in an area that, at the time of the maximum X-ray emission, shows upward motions at transition region (TR) and coronal levels. For the He I 58.4 and O v 62.97 lines, we determine a velocity of ?-40 km s-1 while for the Fe XIX 59.22 line a velocity of ?-80 km s-1 is determined with a two-component fitting. The observations are discussed in the framework of available hydrodynamic simulations and they are consistent with the scenario outlined by Fisher (1989). No explosive evaporation is expected for a non-thermal electron beam of the observed characteristics, and no gentle evaporation is allowed without upward chromospheric motion. It is suggested that the energy of non-thermal electrons can be dissipated to heat the high-density plasma, where possibly the reconnection occurs. The consequent conductive flux drives the evaporation process in a regime that we can call sub-explosive.

Falchi, A.; Teriaca, L.; Maltagliati, L.

2006-12-01

278

Confinement induced binding of noble gas atoms  

SciTech Connect

The stability of Ng{sub n}@B{sub 12}N{sub 12} and Ng{sub n}@B{sub 16}N{sub 16} systems is assessed through a density functional study and ab initio simulation. Although they are found to be thermodynamically unstable with respect to the dissociation of individual Ng atoms and parent cages, ab initio simulation reveals that except Ne{sub 2}@B{sub 12}N{sub 12} they are kinetically stable to retain their structures intact throughout the simulation time (500 fs) at 298 K. The Ne{sub 2}@B{sub 12}N{sub 12} cage dissociates and the Ne atoms get separated as the simulation proceeds at this temperature but at a lower temperature (77 K) it is also found to be kinetically stable. He-He unit undergoes translation, rotation and vibration inside the cavity of B{sub 12}N{sub 12} and B{sub 16}N{sub 16} cages. Electron density analysis shows that the He-He interaction in He{sub 2}@B{sub 16}N{sub 16} is of closed-shell type whereas for the same in He{sub 2}@B{sub 12}N{sub 12} there may have some degree of covalent character. In few cases, especially for the heavier Ng atoms, the Ng-N/B bonds are also found to have some degree of covalent character. But the Wiberg bond indices show zero bond order in He-He bond and very low bond order in cases of Ng-N/B bonds. The energy decomposition analysis further shows that the ?E{sub orb} term contributes 40.9% and 37.3% towards the total attraction in the He{sub 2} dimers having the same distances as in He{sub 2}@B{sub 12}N{sub 12} and He{sub 2}@B{sub 16}N{sub 16}, respectively. Therefore, confinement causes some type of orbital interaction between two He atoms, which akins to some degree of covalent character.

Khatua, Munmun; Pan, Sudip; Chattaraj, Pratim K., E-mail: pkc@chem.iitkgp.ernet.in [Department of Chemistry and Centre for Theoretical Studies, Indian Institute of Technology, Kharagpur 721302 (India)

2014-04-28

279

28 CFR 115.263 - Reporting to other confinement facilities.  

...confinement facilities. 115.263 Section 115.263 Judicial Administration DEPARTMENT OF JUSTICE (CONTINUED) PRISON RAPE ELIMINATION ACT NATIONAL STANDARDS Standards for Community Confinement Facilities Official Response Following A...

2014-07-01

280

28 CFR 115.263 - Reporting to other confinement facilities.  

Code of Federal Regulations, 2013 CFR

...confinement facilities. 115.263 Section 115.263 Judicial Administration DEPARTMENT OF JUSTICE (CONTINUED) PRISON RAPE ELIMINATION ACT NATIONAL STANDARDS Standards for Community Confinement Facilities Official Response Following A...

2013-07-01

281

Confining properties of 2-color QCD at finite density  

E-print Network

We study the confining properties of QCD with two colors across the finite density phase transition. A disorder parameter detecting dual superconductivity of the QCD vacuum is used as a probe for the confinement/deconfinement phase transition.

S. Conradi; A. D'Alessandro; M. D'Elia

2006-09-27

282

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

283

System Description for the Double Shell Tank (DST) Confinement System  

SciTech Connect

This document provides a description of the Double-Shell Tank (DST) Confinement System. This description will provide a basis for developing functional, performance and test requirements (i.e., subsystem specification), as necessary, for the DST Confinement System.

ROSSI, H.

2000-01-12

284

Microdomain Ordering in Laterally Confined Block Copolymer Thin Films  

Microsoft Academic Search

We examine the effects of small-scale, hexagonal, lateral confinement on microdomain ordering in AB diblock copolymer thin films using self-consistent field theory simulations. Specifically, we examine a hexagonal confinement well with side length L approximately equal to five cylindrical microdomain lattice spacings. The commensurability constraints of the small-scale, lateral confinement, coupled with surface- induced effects allow the confining well to

August W. Bosse; Carlos J. Garc ´ õa-Cervera; Glenn H. Fredrickson

2007-01-01

285

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

2012-09-01

286

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 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 d< d c we find a second, low-temperature phase onsetting at from the polar phase to a periodic "B-like" phase. The low temperature phase is inhomogeneous, anisotropic and preserves time-reversal symmetry, but unlike the bulk B-phase has only point symmetry.

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

2014-04-01

287

Interpretation of earth tide response of three deep, confined aquifers  

SciTech Connect

The response of a confined, areally infinite aquifer to external loads imposed by earth tides is examined. Because the gravitational influence of celestial objects occurs over large areas of the earth, the confined aquifer is assumed to respond in an undrained fashion. Since undrained response is controlled by water compressibility, earth tide response can be directly used only to evaluate porous medium compressibility if porosity is known. Moreover, since specific storage S/sub s/ quantifies a drained behavior of the porous medium, one cannot directly estimate S/sub s/from earth tide response. Except for the fact that barometric changes act both on the water surface in the well and on the aquifer as a whole while stress changes associated with earth tides act only in the aquifer, the two phenomena influence the confined aquifer in much the same way. In other words, barometric response contains only as much information on the elastic properties of the aquifer as the earth tide response does. Factors such as well bore storage, aquifer transmissivity, and storage coefficient contribute to time lag and damping of the aquifer response as observed in the well. Analysis shows that the observation of fluid pressure changes alone, without concurrent measurement of external stress changes, is sufficient to interpret uniquely earth tide response. In the present work, change in external stress is estimated from dilatation by assuming a reasonable value for bulk modulus. Earth tide response of geothermal aquifers from Marysville, Montana. East Mesa, California; and Raft River Valley, Idaho, were analyzed, and the ratio of S/sub 3/ to porosity was estimated. Comparison of these estimates with independent pumping tests show reasonable agreement.

Narasimhan, T.N.; Kanehiro, B.Y.; Witherspoon, P.A.

1984-03-10

288

Improved confinement and current drive of high temperature field reversed configurations in the new translation, confinement, and sustainment upgrade device  

SciTech Connect

Previous work in the translation, confinement, and sustainment (TCS) device [Hoffman, Guo, Slough et al., Fusion Sci. Technol. 41, 92 (2002)] demonstrated formation and steady-state sustainment of field reversed configurations (FRC) by rotating magnetic fields (RMF). However, in TCS the plasma temperature was limited to several 10 s of eV due to high impurity content. These impurities are greatly reduced in the new TCS upgrade device (TCSU), which was built with a bakable, ultrahigh vacuum chamber, and advanced wall conditioning capabilities. This led to dramatic improvements in TCSU with temperatures well over 200 eV, using simple even-parity RMF drive. The higher temperatures, coupled with reduced recycling, allowed plasma to enter into a collisionless, high-{zeta} (ratio of average electron rotation frequency to RMF frequency) regime. These new FRC states exhibit the following key features: (1) Dramatic improvement in current drive efficiency with {zeta} approaching 100%, for the first time in TCSU; (2) up to threefold increase in global energy confinement time; and (3) significant reduction in transport rates, accompanied by a striking transition from a Bohm-type transport to a lower hybrid driftlike transport that scales better than gyro-Bohm and is very favorable for the next step FRC development.

Guo, H. Y.; Hoffman, A. L.; Milroy, R. D.; Steinhauer, L. C.; Brooks, R. D.; Deards, C. L.; Grossnickle, J. A.; Melnik, P.; Miller, K. E.; Vlases, G. C. [University of Washington, Redmond Plasma Physics Laboratory, 14700 NE 95th Street, Suite 100, Redmond, Washington 98052 (United States)

2008-05-15

289

Improved confinement and current drive of high temperature field reversed configurations in the new translation, confinement, and sustainment upgrade devicea)  

NASA Astrophysics Data System (ADS)

Previous work in the translation, confinement, and sustainment (TCS) device [Hoffman, Guo, Slough et al., Fusion Sci. Technol. 41, 92 (2002)] demonstrated formation and steady-state sustainment of field reversed configurations (FRC) by rotating magnetic fields (RMF). However, in TCS the plasma temperature was limited to several 10s of eV due to high impurity content. These impurities are greatly reduced in the new TCS upgrade device (TCSU), which was built with a bakable, ultrahigh vacuum chamber, and advanced wall conditioning capabilities. This led to dramatic improvements in TCSU with temperatures well over 200eV, using simple even-parity RMF drive. The higher temperatures, coupled with reduced recycling, allowed plasma to enter into a collisionless, high-? (ratio of average electron rotation frequency to RMF frequency) regime. These new FRC states exhibit the following key features: (1) Dramatic improvement in current drive efficiency with ? approaching 100%, for the first time in TCSU; (2) up to threefold increase in global energy confinement time; and (3) significant reduction in transport rates, accompanied by a striking transition from a Bohm-type transport to a lower hybrid driftlike transport that scales better than gyro-Bohm and is very favorable for the next step FRC development.

Guo, H. Y.; Hoffman, A. L.; Milroy, R. D.; Steinhauer, L. C.; Brooks, R. D.; Deards, C. L.; Grossnickle, J. A.; Melnik, P.; Miller, K. E.; Vlases, G. C.

2008-05-01

290

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

291

Author's personal copy Protein folding in confined and crowded environments  

E-print Network

Author's personal copy Review Protein folding in confined and crowded environments Huan-Xiang Zhou protein folding in cellular environments. Theories based on considerations of excluded volumes predict disparate effects on protein folding stability for confinement and crowding: confinement can stabilize

Weston, Ken

292

Concrete Cylinders Confined with Basalt Fibre Reinforced Polymer Eythor Thorhallsson  

E-print Network

1 Concrete Cylinders Confined with Basalt Fibre Reinforced Polymer Eythor Thorhallsson M that was done on concrete cylinders confined with basalt fibre reinforced polymer (BFRP) and examination of its of more ductile behaviour. Key words: Concrete, confinement, basalt, BFRP and strengthening. 1

Karlsson, Brynjar

293

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

294

Influenza Outbreak Control in Confined Settings  

PubMed Central

Influenza may rapidly disseminate within populations living in confined settings, causing considerable morbidity and disrupting daily activities. We describe an influenza A outbreak on a military base where 3,000 young adults, most of whom were unvaccinated, lived in close daily contact. Visits to the base clinic by 48 persons with acute respiratory illness within 2 days allowed early identification of this outbreak and prompted immediate epidemiologic investigation. Overall, 85 personnel (2.83% of base population) met the case definition for influenzalike illness. On-site laboratory confirmation with field detection kits, rapid implementation of respiratory illness control protocols, and a mass vaccination campaign were applied to limit disease dissemination. The outbreak was halted 14 days after the mass vaccination campaign was completed. We review the control measures available for controlling influenza outbreaks in confined settings and discuss the role of rapid mass vaccination within this context. PMID:15829197

Huerta, Michael; Levy, Yuval; Davidovitch, Nadav; Grotto, Itamar

2005-01-01

295

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

296

Spiral precipitation patterns in confined chemical gardens  

E-print Network

Chemical gardens are mineral aggregates that grow in three dimensions with plant-like forms and share properties with self-assembled structures like nano-scale tubes, brinicles or chimneys at hydrothermal vents. The analysis of their shapes remains a challenge, as their growth is influenced by osmosis, buoyancy and reaction-diffusion processes. Here we show that chemical gardens grown by injection of one reactant into the other in confined conditions feature a wealth of new patterns including spirals, flowers, and filaments. The confinement decreases the influence of buoyancy, reduces the spatial degrees of freedom and allows analysis of the patterns by tools classically used to analyze two-dimensional patterns. Injection moreover allows the study in controlled conditions of the effects of variable concentrations on the selected morphology. We illustrate these innovative aspects by characterizing quantitatively, with a simple geometrical model, a new class of self-similar logarithmic spirals observed in a lar...

Haudin, Florence; Brau, Fabian; De Wit, A

2014-01-01

297

Spiral precipitation patterns in confined chemical gardens  

E-print Network

Chemical gardens are mineral aggregates that grow in three dimensions with plant-like forms and share properties with self-assembled structures like nano-scale tubes, brinicles or chimneys at hydrothermal vents. The analysis of their shapes remains a challenge, as their growth is influenced by osmosis, buoyancy and reaction-diffusion processes. Here we show that chemical gardens grown by injection of one reactant into the other in confined conditions feature a wealth of new patterns including spirals, flowers, and filaments. The confinement decreases the influence of buoyancy, reduces the spatial degrees of freedom and allows analysis of the patterns by tools classically used to analyze two-dimensional patterns. Injection moreover allows the study in controlled conditions of the effects of variable concentrations on the selected morphology. We illustrate these innovative aspects by characterizing quantitatively, with a simple geometrical model, a new class of self-similar logarithmic spirals observed in a large zone of the parameter space.

Florence Haudin; Julyan H. E. Cartwright; Fabian Brau; A. De Wit

2014-11-19

298

Spiral precipitation patterns in confined chemical gardens.  

PubMed

Chemical gardens are mineral aggregates that grow in three dimensions with plant-like forms and share properties with self-assembled structures like nanoscale tubes, brinicles, or chimneys at hydrothermal vents. The analysis of their shapes remains a challenge, as their growth is influenced by osmosis, buoyancy, and reaction-diffusion processes. Here we show that chemical gardens grown by injection of one reactant into the other in confined conditions feature a wealth of new patterns including spirals, flowers, and filaments. The confinement decreases the influence of buoyancy, reduces the spatial degrees of freedom, and allows analysis of the patterns by tools classically used to analyze 2D patterns. Injection moreover allows the study in controlled conditions of the effects of variable concentrations on the selected morphology. We illustrate these innovative aspects by characterizing quantitatively, with a simple geometrical model, a new class of self-similar logarithmic spirals observed in a large zone of the parameter space. PMID:25385581

Haudin, Florence; Cartwright, Julyan H E; Brau, Fabian; De Wit, A

2014-12-01

299

Confinement improvement by fluctuating input power  

SciTech Connect

An interesting effect of the fluctuating input power on plasma confinement is reported. Specifically, the addition of the sinusoidal perturbation, Asin(wt), to constant power q{sub 0} is shown to promote the confinement, leading to the L-H transition at a lower value of q{sub 0}, as compared to the case of constant q{sub 0} without the sinusoidal perturbation. In general, higher amplitude (A) and lower frequency (w) are found to be more favorable for the L-H transition while an interesting linear relation between A and w leading to the L-H transition is established for different values of q{sub 0}.

Douglas, Sarah; Mohamed, Mabruka; Kim, Eun-jin [School of Mathematics and Statistics, University of Sheffield, Sheffield S3 7RH (United Kingdom)] [School of Mathematics and Statistics, University of Sheffield, Sheffield S3 7RH (United Kingdom)

2013-11-15

300

Morphogenesis of filaments growing in flexible confinements  

NASA Astrophysics Data System (ADS)

Space-saving design is a requirement that is encountered in biological systems and the development of modern technological devices alike. Many living organisms dynamically pack their polymer chains, filaments or membranes inside deformable vesicles or soft tissue-like cell walls, chorions and buds. Surprisingly little is known about morphogenesis due to growth in flexible confinements—perhaps owing to the daunting complexity lying in the nonlinear feedback between packed material and expandable cavity. Here we show by experiments and simulations how geometric and material properties lead to a plethora of morphologies when elastic filaments are growing far beyond the equilibrium size of a flexible thin sheet they are confined in. Depending on friction, sheet flexibility and thickness, we identify four distinct morphological phases emerging from bifurcation and present the corresponding phase diagram. Four order parameters quantifying the transitions between these phases are proposed.

Vetter, R.; Wittel, F. K.; Herrmann, H. J.

2014-07-01

301

Morphogenesis of filaments growing in flexible confinements  

E-print Network

Space-saving design is a requirement that is encountered in biological systems and the development of modern technological devices alike. Many living organisms dynamically pack their polymer chains, filaments or membranes inside of deformable vesicles or soft tissue like cell walls, chorions, and buds. Surprisingly little is known about morphogenesis due to growth in flexible confinements - perhaps owing to the daunting complexity lying in the nonlinear feedback between packed material and expandable cavity. Here we show by experiments and simulations how geometric and material properties lead to a plethora of morphologies when elastic filaments are growing far beyond the equilibrium size of a flexible thin sheet they are confined in. Depending on friction, sheet flexibility and thickness, we identify four distinct morphological phases emerging from bifurcation and present the corresponding phase diagram. Four order parameters quantifying the transitions between these phases are proposed.

Roman Vetter; Falk K. Wittel; Hans J. Herrmann

2014-07-17

302

Greater confinement disposal of radioactive wastes  

Microsoft Academic Search

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

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

1985-01-01

303

Waveforms Measured in Confined Thermobaric Explosion  

SciTech Connect

Experiments with 1.5-g Shock-Dispersed-Fuel (SDF) charges have been conducted in six different chambers. Both flake Aluminum and TNT were used as the fuel. Static pressure gauges on the chamber wall were the main diagnostic. Waveforms for explosions in air were significantly larger than those in nitrogen - thereby demonstrating a strong thermobaric (combustion) effect. This effect increases as the confinement volume decreases and the mixture richness approaches 1.

Reichenbach, H; Neuwald, P; Kuhl, A L

2007-05-04

304

Waveforms Measured in Confined Thermobaric Explosion  

Microsoft Academic Search

Experiments with 1.5-g Shock-Dispersed-Fuel (SDF) charges have been conducted in six different chambers. Both flake Aluminum and TNT were used as the fuel. Static pressure gauges on the chamber wall were the main diagnostic. Waveforms for explosions in air were significantly larger than those in nitrogen - thereby demonstrating a strong thermobaric (combustion) effect. This effect increases as the confinement

H Reichenbach; P Neuwald; A L Kuhl

2007-01-01

305

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

306

Efficient Algorithms to Implement the Confinement Tree  

Microsoft Academic Search

The aim of this paper is to present a new algorithm to calculate the confinement tree of an image - also known as component\\u000a tree or dendrone - for which we can prove that its worst-case complexity is O(n log n) where n is the number of pixels. More precisely, in a first part, we present an algorithm which separates

Julian Mattes; Jacques Demongeot

2000-01-01

307

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

308

Magnetic Confinement Fusion at the Crossroads  

E-print Network

~ pressure2 100 10 1 10-1 10-2 10-3 102 101 103 102 10 1 103 104 105 Temperature (keV) Powerdensity(MWm-3 ) Pressure(atm) D-T D-D Bremsstrahlung Pressure nD = nT = 5 x 1019m-3 #12;MGB / UT / 070307 6 Three Fusion, proposed fusion-bomb concept to Beria, and gridded electrostatic confinement for fusion energy ­ Sent

Princeton Plasma Physics Laboratory

309

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

310

Statistical mechanics of confined quantum particles  

E-print Network

We develop statistical mechanics and thermodynamics of Bose and Fermi systems in relativistic harmonic oscillator (RHO) confining potential, which may be applicable in quark gluon plasma (QGP), astrophysics, Bose-Einstein condensation (BEC), condensed matter physics etc. Detailed study of QGP system is carried out and compared with lattice results. Further, as an application, our equation of state (EoS) of QGP is used to study compact stars like quark star.

Vishnu M. Bannur; K. M. Udayanandan

2006-02-02

311

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

312

Stationary shapes of confined rotating magnetic liquid droplets.  

PubMed

We study the family of steady shapes which arise when a magnetic liquid droplet is confined in a rotating Hele-Shaw cell and subjected to an azimuthal magnetic field. Two different scenarios are considered: first, the magnetic fluid is assumed to be a Newtonian ferrofluid, and then it is taken as a viscoelastic magnetorheological fluid. The influence of the distinct material properties of the fluids on the ultimate morphology of the emerging stationary patterns is investigated by using a vortex-sheet formalism. Some of these exact steady structures are similar to the advanced time patterns obtained by existing time-evolving numerical simulations of the problem. A weakly nonlinear approach is employed to examine this fact and to gain analytical insight about relevant aspects related to the stability of such exact stationary solutions. PMID:21230182

Lira, Sérgio A; Miranda, José A; Oliveira, Rafael M

2010-09-01

313

Thermometry based on phonon confinement effect in nanoparticles  

SciTech Connect

Raman spectra of TiO{sub 2} nanoparticles (NPs) have a very strong finite-size dependency due to the phonon confinement effect. This provides a convenient way to characterize NPs size by simply using Raman spectroscopy. Together with fast grain growth kinetics and high stability under high temperature and pressure, these NPs have the potential to forensically retain the complete thermal history (temperature and time) of an event that they went through. Here, we demonstrate that both temperature and time can be determined simultaneously by using these thermosensors in the range of 400-700 deg. C and 5-60 s, assuming that the temperature is constant (a step-function approximation to a thermal spike) during a thermal event.

Wang Junwei; Huang Liping [Department of Materials Science and Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States)

2011-03-14

314

Barrier-confinement-controlled carrier transport into quantum wires  

NASA Astrophysics Data System (ADS)

By using subpicosecond laser light pulses with a polarization perpendicular to deep etched In0.53Ga0.47As/InP quantum wires, initial spatial electron-hole distributions have been prepared that are predominantly located in the unpatterned InP buffer layer. Under these excitation conditions the photoluminescence rise time increases significantly with decreasing wire width from about 25 ps for a two-dimensional unetched reference structure to about 150 ps for 34-nm-wide wires. Temperature-dependent studies of the rise times indicate the existence of an effective barrier in the InP regions of the quantum wires. From detailed calculations of the electronic states, which extend from the unpatterned InP buffer into the quantum wires, we show that confinement effects in the InP barriers control the carrier transport from the buffer into the In0.53Ga0.47As wire.

Kieseling, F.; Braun, W.; Wang, K. H.; Forchel, A.; Knipp, P. A.; Reinecke, T. L.; Pagnod-Rossiaux, Ph.; Goldstein, L.

1995-10-01

315

Effects of polydispersity on confined homopolymer melts: A Monte Carlo study  

NASA Astrophysics Data System (ADS)

New insight into the molecular scale details of polymer melts under confined conditions is obtained from the first dynamic Monte Carlo study incorporating polydispersity. While confinement effects on polymers have been widely explored, little work exists on the effects of polydispersity. This is surprising given the near universal presence of polydispersity in physical systems. To address this shortcoming, a new variation of on-lattice dynamic Monte Carlo simulation is used to provide an understanding of how polydispersity alters confinement effects on polymer melts. Polymer melts of varying polydispersity are simulated between two hard walls (surface interaction parameter, ?s = 0) of variable spacing. As plate spacing decreases, polymer chains adopt conformations in which the end-to-end vector is parallel to the hard walls. However, polydisperse melts with the same length average molecular weight, Nw (which is analogous to the weight average molecular weight, Mw) show reduced orientation effects. Polydispersity provides greater degrees of freedom; that is, there are more configurations for the system to adopt to accommodate confinement without ordering. At plate spacings of four radii of gyration and only modest polydispersity index values (polydispersity index, PDI = 1.42), the order parameters are reduced by 15% compared to the monodisperse case. The same PDI value corresponds to a 10% reduction in the perturbations of the end-to-end vector and Rouse time. Interestingly, length-based migration effects are observed. Longer chains reside away from the walls and the shorter chains are found nearer the walls; at equilibrium there is a molecular weight based fractionation across the gap. Confinement also leads to a "speeding up" of the polymer dynamics. Altered dynamic phenomena include a reduction of the Rouse time for the same average molecular weight and an altered scaling behavior with plate spacing. Reptation times are also reduced and polydispersity smoothes out the transitions between different scaling regimes. The overall picture that emerges is not unexpected - polydispersity profoundly affects the behavior of confined homopolymers.

Rorrer, Nicholas A.; Dorgan, John R.

2014-12-01

316

Fast ion JET diagnostics: confinement and losses  

SciTech Connect

A study of magnetically confined fast ions in tokamaks plays an important role in burning plasma research. To reach ignition and steady burning of a reactor plasma an adequate confinement of energetic ions produced by NBI heating, accelerated with ICRF and born in fusion reactions is essential to provide efficient heating of the bulk plasma. Thus, investigation of the fast ion behaviour is an immediate task for present-day large machines, such as JET, in order to understand the main mechanisms of slowing down, redistribution and losses, and to develop optimal plasma scenarios. Today's JET has an enhanced suite of fast ion diagnostics both of confined and lost ions that enable to significantly contribute to this important area of research. Fast ion populations of p, d, t, {sup 3}He and {sup 4}He, made with ICRF, NBI, and fusion reactions have been investigated in experiments on JET with sophisticated diagnostics in conventional and shear-reversed plasmas, exploring a wide range of effects. This paper will introduce to the JET fast-ion diagnostic techniques and will give an overview of recent observations. A synergy of the unique diagnostic set was utilised in JET, and studies of the response of fast ions to MHD modes (e.g. tornado modes, sawtooth crashes), fast {sup 3}He-ions behaviour in shear-reversed plasmas are impressive examples of that. Some results on fast ion losses in JET experiments with various levels of the toroidal field ripple will be demonstrated.

Kiptily, V. G.; Pinches, S. D.; Sharapov, S. E.; Syme, D. B. [Euratom/UKAEA Fusion Association, Culham Science Centre, Abingdon, Oxon (United Kingdom); Borba, D.; Nabais, F. [Euratom/IST Fusion Association, Centro de Fusao Nuclear, 1049-001 Lisboa (Portugal); Cecil, F. E. [Colorado School of Mines, Golden, CO (United States); Cecconello, M. [Association EURATOM-VR, Royal Institute of Technology KTH, Stockholm (Sweden); Darrow, D.; Hill, K. [Princeton Plasma Physics Lab, Princeton NJ (United States); Goloborod'ko, V.; Yavorskij, V. [Euratom/OEAW Association, Institute for Theoretical Physics, University of Innsbruck (Austria); Institute for Nuclear Research, Kiev (Ukraine); Johnson, T. [Euratom--VR Association, Alfven Laboratory, Royal Institute of Technology, 10044 Stockholm (Sweden); Murari, A. [Consorzio RFX--Associazione Euratom-Enea sulla Fusione, I-35127 Padova (Italy); Reich, M. [Euratom/MPI fuaer Plasmaphysik Association, Garching (Germany); Chugunov, I. N.; Gin, D. B.; Shevelev, A. E. [Ioffe Physico-Thechnical Institute, 194021 St. Petersburg (Russian Federation); Gorini, G. [Istituto di Fisica del Plasma, EURATOM-ENEA-CNR Association, Milan (Italy); Zoita, V. [Euratom-MedC Association, National Institute for Laser, Plasma and Radiation Physics, Bucharest (Romania)

2008-03-12

317

Evaporation rate of water in hydrophobic confinement  

PubMed Central

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 nm2), 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 50kT and are predominantly enthalpic. Evaporation rates per unit area are found to be two orders of magnitude faster in confinement by the larger (9 nm2) than by the smaller (1 nm2) 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.

2012-01-01

318

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

319

Reverse Monte Carlo modeling in confined systems  

SciTech Connect

An extension of the well established Reverse Monte Carlo (RMC) method for modeling systems under close confinement has been developed. The method overcomes limitations induced by close confinement in systems such as fluids adsorbed in microporous materials. As a test of the method, we investigate a model system of {sup 36}Ar adsorbed into two zeolites with significantly different pore sizes: Silicalite-I (a pure silica form of ZSM-5 zeolite, characterized by relatively narrow channels forming a 3D network) at partial and full loadings and siliceous Faujasite (which exhibits relatively wide channels and large cavities). The model systems are simulated using grand canonical Monte Carlo and, in each case, its structure factor is used as input for the proposed method, which shows a rapid convergence and yields an adsorbate microscopic structure in good agreement with that of the model system, even to the level of three body correlations, when these are induced by the confining media. The application to experimental systems is straightforward incorporating factors such as the experimental resolution and appropriate q-sampling, along the lines of previous experiences of RMC modeling of powder diffraction data including Bragg and diffuse scattering.

Sánchez-Gil, V.; Noya, E. G.; Lomba, E. [Instituto de Química Física Rocasolano, CSIC, Serrano 119, E-28006 Madrid (Spain)] [Instituto de Química Física Rocasolano, CSIC, Serrano 119, E-28006 Madrid (Spain)

2014-01-14

320

Counterpropagating Rossby waves in confined plane wakes  

PubMed Central

In the present work, we revisit the temporal and the spatio-temporal stability of confined plane wakes under the perspective of the counterpropagating Rossby waves (CRWs). Within the context of broken line velocity profiles, each vorticity discontinuity can be associated to a counterpropagating Rossby wave. In the case of a wake modeled by a broken line profile, the interaction of two CRWs is shown to originate in a shear instability. Following this description, we first recover the stability results obtained by Juniper [J. Fluid Mech. 590, 163–185 (2007)]10.1017/S0022112007007975 and Biancofiore and Gallaire [Phys. Fluids 23, 034103 (2011)]10.1063/1.3554764 by means of the classical normal mode analysis. In this manner, we propose an explanation of the stabilizing influence of the confinement on the temporal stability properties. The CRW description further allows us to propose a new interpretation of the counterintuitive spatio-temporal destabilization in wake flows at moderate confinement noticed by Juniper [J. Fluid Mech. 565, 171–195 (2006)]10.1017/S0022112006001558: it is well predicted by the mean group velocity of the uncoupled CRWs. PMID:22865998

Biancofiore, L.; Gallaire, F.

2012-01-01

321

Reverse Monte Carlo modeling in confined systems  

NASA Astrophysics Data System (ADS)

An extension of the well established Reverse Monte Carlo (RMC) method for modeling systems under close confinement has been developed. The method overcomes limitations induced by close confinement in systems such as fluids adsorbed in microporous materials. As a test of the method, we investigate a model system of 36Ar adsorbed into two zeolites with significantly different pore sizes: Silicalite-I (a pure silica form of ZSM-5 zeolite, characterized by relatively narrow channels forming a 3D network) at partial and full loadings and siliceous Faujasite (which exhibits relatively wide channels and large cavities). The model systems are simulated using grand canonical Monte Carlo and, in each case, its structure factor is used as input for the proposed method, which shows a rapid convergence and yields an adsorbate microscopic structure in good agreement with that of the model system, even to the level of three body correlations, when these are induced by the confining media. The application to experimental systems is straightforward incorporating factors such as the experimental resolution and appropriate q-sampling, along the lines of previous experiences of RMC modeling of powder diffraction data including Bragg and diffuse scattering.

Sánchez-Gil, V.; Noya, E. G.; Lomba, E.

2014-01-01

322

Evaporation Rate of Water in Hydrophobic Confinement  

E-print Network

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 {\\AA} 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 ten order-of-magnitude decrease in the rate when the gap increases from 9 to 14 {\\AA}. The computed free energy barriers are of the order of 50kT, 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 (1nm^2) surfaces considered here, at otherwise identical conditions. We show that this is a direct 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 cylindrical vapor tube.

Sumit Sharma; Pablo G. Debenedetti

2011-12-29

323

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

324

"Soft" confinement of graphene in hydrogel matrixes.  

PubMed

Graphene plays as protagonist among the newly discovered carbon nanomaterials on the laboratory bench. Confinement of graphene, combined with enhanced exchange properties within aqueous environment, is key for the development of biosensors, biomedicine devices, and water remediation applications. Such confinement is possible using hydrogels as soft matrixes. Many entrapment methods focused on the modification of the graphene structure. In this paper, however, we address a confinement method that leaves unchanged the graphene structure, although intimately participating in the buildup of a network of polyvinyl alcohol (PVA) chains. PVA is a polymer known as biomaterial for its hydrophilicity, biocompatibility, and chemical versatility. A robust hybrid PVA - graphene construct was obtained starting from a surfactant-assisted sonication of an aqueous dispersion of graphite. Stable graphene sheets suspension was photopolymerized in a methacryloyl-grafted PVA, using the vinyl moiety present on the surfactant scaffold. This method can allow the incorporation in the polymer network of oligomers of N-(isopropylacrylammide), p(NiPAAm). These chains display in aqueous solution a low critical solution temperature, LCST, around 33 °C and trigger a volume phase transition when incorporated in a hydrophilic network around the physiological temperature. Raman analysis was used to characterize the state of hydrogel embedded graphene single sheets. Evidence for an intimate interaction of graphene sheets and polymer matrix was collected. Release of the anticancer drug doxorubicin showed the active role of the graphene/PVA/p(NiPAAm) construct in the drug delivery. PMID:25574863

Toumia, Yosra; Orlanducci, Silvia; Basoli, Francesco; Licoccia, Silvia; Paradossi, Gaio

2015-02-01

325

Unsteady effects of a pair of opposed confined impinging air jets and application to microelectronics cooling  

Microsoft Academic Search

The unsteady laminar flow and heat transfer characteristics for a pair of opposed confined impinging air jets in a channel were studied numerically. The space and time-averaged heat transfer coefficients for a pair of heat sources arranged at different locations on opposite target walls was determined together with the oscillating jet frequency. The present study continues the authors' previous investigations,

Victor Adrian Chiriac; Jorge Luis Rosales

2006-01-01

326

Fragile-to-strong liquid transition in deeply supercooled confined water  

Microsoft Academic Search

Confining water in lab synthesized nanoporous silica matrices MCM-41-S with pore diameters of 18 and 14 Å, we have been able to study the molecular dynamics of water in deeply supercooled states, down to 200 K. Using quasielastic neutron scattering and analyzing the data with the relaxing cage model, we determined the temperature variation of the average translational relaxation time

A. Faraone; L. Liu; C.-Y. Mou; C.-W. Yen; S.-H. Chen

2004-01-01

327

NUMERICAL STUDIES OF FLUID FLOW IN MICROGRAVITY CONDITIONS FOR CONFINED CRYSTAL GROWTH  

E-print Network

NUMERICAL STUDIES OF FLUID FLOW IN MICROGRAVITY CONDITIONS FOR CONFINED CRYSTAL GROWTH XAVIER RUIZ the convective flow induced by residual accelerations in microgravity conditions for different geometric the microgravity environtment couples to the fluid flow through the presence of an effective, time

Ramírez-Piscina, Laureano

328

New energy carriers in vehicles and their impact on confined infrastructures  

E-print Network

New energy carriers in vehicles and their impact on confined infrastructures - Overview of previous up with new environmentally friendly solutions. In 10 years time, or even faster depending. This quick development and the diversity of new energy carriers can jeopardize the safety in underground

Paris-Sud XI, Université de

329

Charge Exchange Loss of High Temperature Plasma Confined by Mirror Magnetic Field  

Microsoft Academic Search

Relaxation of the distribution function of ions confined in a mirror field is in investigated theoretically taking both the charge exchange and scattering effects into account. The result is compared with experiment. If the particles are not thermalized sufficiently, the ion density decays exponentially due to the charge exchange, but only linearly due to the mirror loss. The life time,

Ichiro Mori; Tokuo Suita

1966-01-01

330

Dynamics of instantaneous frequency and amplitude of coherent wave mixing in quantum confined semiconductor structures  

Microsoft Academic Search

In the last fifteen years, quantum confined semiconductor structures (QCSS) have attracted much attention because of their novel properties and their potential for electronic and photonic applications. Electronic and optical properties of QCSS are dominated by the combined effects of quantum statistics and Coulomb interaction. Their response to electromagnetic excitations is determined by a polarization which possesses a time dependent

Daniel S. Chemla

1994-01-01

331

Transient dynamics of confined liquid drops in a uniform electric field  

NASA Astrophysics Data System (ADS)

We analyze the effect of confinement on the transient dynamics of liquid drops, suspended in another immiscible liquid medium, under the influence of an externally applied uniform dc electric field. For our analysis, we adhere to an analytical framework conforming to a Newtonian-leaky-dielectric liquid model in the Stokes flow regime, under the small deformation approximation. We characterize the transient relaxation of the drop shape towards its asymptotic configuration, attributed by the combined confluence of the charge-relaxation time scale and the intrinsic shape-relaxation time scale. While the former appears due to the charge accumulation process on the drop surface over a finite interval of time, the genesis of the latter is found to be intrinsic to the hydrodynamic situation under consideration. In an unbounded condition, the intrinsic shape-relaxation time scale is strongly governed by the viscosity ratio, defined as the ratio of dynamic viscosities of the droplet and the background liquid. However, when the wall effects are brought into consideration, the combined influence of the relative extent of the confinement and the intrinsic viscosity effects, acting in tandem, alter this time scale in a rather complicated and nontrivial manner. We reveal that the presence of confinement may dramatically increase the effective viscosity ratio that could have otherwise been required in an unconfined domain to realize identical time-relaxation characteristics. We also bring out the alterations in the streamline patterns because of the combinations of transient and confinement effects. Thus, our results reveal that the extent of fluidic confinement may provide an elegant alternative towards manipulating the transient dynamics of liquid drops in the presence of an externally applied electric field, bearing far-ranging consequences towards the design and functionalities of several modern-day microfluidic applications.

Mandal, Shubhadeep; Chaudhury, Kaustav; Chakraborty, Suman

2014-05-01

332

Distribution of transverse chain fluctuations in harmonically confined semiflexible polymers  

NASA Astrophysics Data System (ADS)

Two different experimental studies of polymer dynamics based on single-molecule fluorescence imaging have recently found evidence of heterogeneities in the widths of the putative tubes that surround filaments of F-actin during their motion in concentrated solution. In one [J. Glaser, D. Chakraborty, K. Kroy, I. Lauter, M. Degawa, N. Kirchesner, B. Hoffmann, R. Merkel, and M. Giesen, Phys. Rev. Lett. 105, 037801 (2010)], 10.1103/PhysRevLett.105.037801, the observations were explained in terms of the statistics of a worm-like chain confined to a potential determined self-consistently by a binary collision approximation, and in the other [B. Wang, J. Guan, S. M. Anthony, S. C. Bae, K. S. Schweizer, and S. Granick, Phys. Rev. Lett. 104, 118301 (2010)], 10.1103/PhysRevLett.104.118301, they were explained in terms of the scaling properties of a random fluid of thin rods. In this paper, we show, using an exact path integral calculation, that the distribution of the length-averaged transverse fluctuations of a harmonically confined weakly bendable rod (one possible realization of a semiflexible chain in a tube), is in good qualitative agreement with the experimental data, although it is qualitatively different in analytic structure from the earlier theoretical predictions. We also show that similar path integral techniques can be used to obtain an exact expression for the time correlation function of fluctuations in the tube cross section.

Sharma, Rati; Cherayil, Binny J.

2012-05-01

333

Classical scattering of charged particles confined on an inhomogeneous helix.  

PubMed

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. PMID:24229295

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

2013-10-01

334

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

SciTech Connect

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 {sup 2}P{sub 1/2,3/2}? 3d {sup 2}P{sub 3/2,5/2}) and 670.8 nm (2s {sup 2}S{sub 1/2}? 2p {sup 2}P{sub 1/2,3/2}) 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 [Institute for Plasma Research, Bhat, Gandhinagar-382 428 (India)] [Institute for Plasma Research, Bhat, Gandhinagar-382 428 (India)

2013-08-15

335

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

336

Example of an explicit function for confining classical Yang-Mills fields with quantum fluctuations in the path integral scheme  

E-print Network

This article reports an explicit function form for confining classical Yang-Mills vector potentials and quantum fluctuations around the classical field. The classical vector potential, which is composed of a confining localized function and an unlocalized function, satisfies the classical Yang-Mills equation. The confining localized function contributes to the Wilson loop, while the unlocalized function makes no contribution to this loop. The confining linear potential between a heavy fermion and antifermion is due to (1) the Lie algebra and (2) the form of the confining localized function which has opposite signs at the positions of the particle and antiparticle along the Wilson loop in the time direction. Some classical confining parts of vector potentials also change sign on inversion of the coordinates of the axis perpendicular to the axis joining the two particles. The localized parts of the vector potentials are squeezed around the axis connecting the two particles, and the string tension of the confining linear potential is derived. Quantum fluctuations are formulated using a field expression in terms of local basis functions in real spacetime. The quantum path integral gives the Coulomb potential between the two particles in addition to the linear potential due to the classical fields.

Kimichika Fukushima; Hikaru Sato

2014-02-03

337

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

338

Effect of a simple double-confined structure on nanosecond pulse ablative laser propulsion  

NASA Astrophysics Data System (ADS)

We succeeded in obtaining propulsion of an aluminum bullet by a gigawatt nanosecond pulse Nd:glass laser, in which we demonstrated the effectiveness of a simple double-confined structure that consists of a thin black-paint coat covered with a glass board as a transparent overlay. The black-paint coat not only serves as a substitute for the target to be ablated, but also improves the absorbency of the incident laser energy. Another main feature of this structure is that it can lead to the enhancement of the coupling coefficient due to plasma confinement and impedance mismatch. Adopting this simple double-confined structure, a coupling coefficient up to 160 dyne/W was achieved, which was enhanced by about 20 times with respect to direct ablation.

Shi, Lei; Zhao, Shang-Hong; Chu, Xing-Chun; Ma, Li-Hua; Wu, Ji-Li; Li, Xiao-Liang; Li, Yong-Jun

2009-03-01

339

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

340

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

341

Analysis of reflected blast wave pressure profiles in a confined room  

NASA Astrophysics Data System (ADS)

To understand the blast effects of confined explosions, it is necessary to study the characteristic parameters of the blast wave in terms of overpressure, impulse and arrival time. In a previous study, experiments were performed using two different scales of a pyrotechnic workshop. The main purpose of these experiments was to compare the TNT equivalent for solid and gaseous explosives in terms of mass to define a TNT equivalent in a reflection field and to validate the similitude between real and small scales. To study the interactions and propagations of the reflected shock waves, the present study was conducted by progressively building a confined volume around the charge. In this way, the influence of each wall and the origins of the reflected shock waves can be determined. The purpose of this paper is to report the blast wave interactions that resulted from the detonation of a stoichiometric propane-oxygen mixture in a confined room.

Sauvan, P. E.; Sochet, I.; Trélat, S.

2012-05-01

342

Topological superfluids confined in a nanoscale slab geometry  

NASA Astrophysics Data System (ADS)

Nanofluidic samples of superfluid ^3He provide a route to explore odd-parity topological superfluids and their surface, edge and defect-bound excitations under well controlled conditions. We have cooled superfluid ^3He confined in a precisely defined nano-fabricated cavity to well below 1 mK for the first time. We fingerprint the order parameter by nuclear magnetic resonance, exploiting a SQUID NMR spectrometer of exquisite sensitivity. We demonstrate that dimensional confinement, at length scales comparable to the superfluid Cooper-pair diameter, has a profound influence on the superfluid order of ^3He. The chiral A-phase is stabilized at low pressures, in a cavity of height 650 nm. At higher pressures we observe ^3He-B with a surface induced planar distortion. ^3He-B is a time-reversal invariant topological superfluid, supporting gapless Majorana surface states. In the presence of the small symmetry breaking NMR static magnetic field we observe two possible B-phase states of the order parameter manifold, which can coexist as domains. Non-linear NMR on these states enables a measurement of the surface induced planar distortion, which determines the spectral weight of the surface excitations. The expected structure of the domain walls is such that, at the cavity surface, the line separating the two domains is predicted to host fermion zero modes, protected by symmetry and topology. Increasing confinement should stabilize new p-wave superfluid states of matter, such as the quasi-2D gapped A phase, which breaks time reversal symmetry, has a protected chiral edge mode, and may host half-quantum vortices with a Majorana zero-mode at the core. We discuss experimental progress toward this phase, through measurements on a 100 nm cavity. On the other hand, a cavity height of 1000 nm may stabilize a novel ``striped'' superfluid with spatially modulated order parameter.[4pt] In collaboration with L.V. Levitin, R.G. Bennett, A.J. Casey, B. Cowan, J. Parpia, E.V. Surovtsev

Saunders, John

2013-03-01

343

Nonequilibrium dynamics and ultraslow relaxation of confined DNA during viral packaging  

PubMed Central

Many viruses use molecular motors that generate large forces to package DNA to near-crystalline densities inside preformed viral proheads. Besides being a key step in viral assembly, this process is of interest as a model for understanding the physics of charged polymers under tight 3D confinement. A large number of theoretical studies have modeled DNA packaging, and the nature of the molecular dynamics and the forces resisting the tight confinement is a subject of wide debate. Here, we directly measure the packaging of single DNA molecules in bacteriophage phi29 with optical tweezers. Using a new technique in which we stall the motor and restart it after increasing waiting periods, we show that the DNA undergoes nonequilibrium conformational dynamics during packaging. We show that the relaxation time of the confined DNA is >10 min, which is longer than the time to package the viral genome and 60,000 times longer than that of the unconfined DNA in solution. Thus, the confined DNA molecule becomes kinetically constrained on the timescale of packaging, exhibiting glassy dynamics, which slows the motor, causes significant heterogeneity in packaging rates of individual viruses, and explains the frequent pausing observed in DNA translocation. These results support several recent hypotheses proposed based on polymer dynamics simulations and show that packaging cannot be fully understood by quasistatic thermodynamic models. PMID:24912187

Berndsen, Zachary T.; Keller, Nicholas; Grimes, Shelley; Jardine, Paul J.; Smith, Douglas E.

2014-01-01

344

Nonequilibrium dynamics and ultraslow relaxation of confined DNA during viral packaging.  

PubMed

Many viruses use molecular motors that generate large forces to package DNA to near-crystalline densities inside preformed viral proheads. Besides being a key step in viral assembly, this process is of interest as a model for understanding the physics of charged polymers under tight 3D confinement. A large number of theoretical studies have modeled DNA packaging, and the nature of the molecular dynamics and the forces resisting the tight confinement is a subject of wide debate. Here, we directly measure the packaging of single DNA molecules in bacteriophage phi29 with optical tweezers. Using a new technique in which we stall the motor and restart it after increasing waiting periods, we show that the DNA undergoes nonequilibrium conformational dynamics during packaging. We show that the relaxation time of the confined DNA is >10 min, which is longer than the time to package the viral genome and 60,000 times longer than that of the unconfined DNA in solution. Thus, the confined DNA molecule becomes kinetically constrained on the timescale of packaging, exhibiting glassy dynamics, which slows the motor, causes significant heterogeneity in packaging rates of individual viruses, and explains the frequent pausing observed in DNA translocation. These results support several recent hypotheses proposed based on polymer dynamics simulations and show that packaging cannot be fully understood by quasistatic thermodynamic models. PMID:24912187

Berndsen, Zachary T; Keller, Nicholas; Grimes, Shelley; Jardine, Paul J; Smith, Douglas E

2014-06-10

345

Electron Energy Confinement for HHFW Heating and Current Drive Phasing on NSTX  

SciTech Connect

Thomson scattering laser pulses are synchronized relative to modulated HHFW power to permit evaluation of the electron energy confinement time during and following HHFW pulses for both heating and current drive antenna phasing. Profile changes resulting from instabilities require that the total electron stored energy, evaluated by integrating the midplane electron pressure P(sub)e(R) over the magnetic surfaces prescribed by EFIT analysis, be used to derive the electron energy confinement time. Core confinement is reduced during a sawtooth instability but, although the electron energy is distributed outward by the sawtooth, the bulk electron energy confinement time is essentially unaffected. The radial deposition of energy into the electrons is noticeably more peaked for current drive phasing (longer wavelength excitation) relative to that for heating phasing (shorter wavelength excitation) as is expected theoretically. However, the power delivered to the core plasma is reduced consider ably for the current drive phasing, indicating that surface/peripheral damping processes play a more important role for this case.

J.C. Hosea; S. Bernabei; T. Biewer; B. LeBlanc; C.K. Phillips; J.R. Wilson; D. Stutman; P. Ryan; D.W. Swain

2005-05-03

346

Viscous fingering and liquid crystals in confinement  

NASA Astrophysics Data System (ADS)

This thesis focuses on two problems lying within the field of soft condensed matter: the viscous fingering or Saffman-Taylor instability and nematic liquid crystals in confinement. Whenever a low viscosity fluid displaces a high viscosity fluid in a porous medium, for example water pushing oil out of oil reservoirs, the interface between the two fluids is rendered unstable. Viscous fingers develop, grow and compete until a single finger spans all the way from inlet to outlet. Here, using a free energy lattice Boltzmann algorithm, we examine the Saffman-Taylor instability for two different wetting situations: (a) when neither of the two fluids wet the walls of the channel and (b) when the displacing fluids completely wets the walls. We demonstrate that curvature effects in the third dimension, which arise because of the wetting boundary conditions, can lead to a novel suppression of the instability. Recent experiments in microchannels using colloid-polymer mixtures support our findings. In the second part of the thesis we examine nematic liquid crystals confined in wedge-structured geometries. In these systems the final stable configuration of the liquid crystal system is controlled by the complex interplay between confinement, elasticity and surface anchoring. Varying the wedge opening angle this competition leads to a splay to bend transition mediated by a defect in the bulk of the wedge. Using a hybrid lattice Boltzmann algorithm we study the splay-bend transition and compare to recent experiments on {em fd} virus particles in microchannels. Our numerical results, in quantitative agreement with the experiments, enable us to predict the position of the defect as a function of opening angle, and elucidate its role in the change of director structure. This has relevance to novel energy saving, liquid crystal devices which rely on defect motion and pinning to create bistable director configurations.

Zacharoudiou, Ioannis

347

Graviton confinement inside hypermonopoles of any dimension  

SciTech Connect

We show the generic existence of metastable massive gravitons in the four-dimensional core of self-gravitating hypermonopoles in any number of infinite-volume extra-dimensions. Confinement is observed for Higgs and gauge bosons couplings of the order unity. Provided these resonances are light enough, they may realise the Dvali-Gabadadze-Porrati mechanism by inducing a four-dimensional gravity law on some intermediate length scales. The effective four-dimensional Planck mass is shown to be proportional to a negative power of the graviton mass. As a result, requiring gravity to be four-dimensional on cosmological length scales may solve the mass hierarchy problem.

Murray, Seán; Ringeval, Christophe; Zonetti, Simone, E-mail: sean.murray@uclouvain.be, E-mail: christophe.ringeval@uclouvain.be, E-mail: simone.zonetti@uclouvain.be [Institute of Mathematics and Physics, Centre for Cosmology, Particle Physics and Phenomenology, Louvain University, 2 Chemin du Cyclotron, 1348 Louvain-la-Neuve (Belgium)

2010-09-01

348

Spatiotemporal instability of a confined capillary jet.  

PubMed

Recent experimental studies on the instability of capillary jets have revealed the suitability of a linear spatiotemporal instability analysis to ascertain the parametrical conditions for specific flow regimes such as steady jetting or dripping. In this work, an extensive analytical, numerical, and experimental description of confined capillary jets is provided, leading to an integrated picture both in terms of data and interpretation. We propose an extended, accurate analytic model in the low Reynolds number limit, and introduce a numerical scheme to predict the system response when the liquid inertia is not negligible. Theoretical predictions show remarkable accuracy when compared with the extensive experimental mapping. PMID:18999531

Herrada, M A; Gañán-Calvo, A M; Guillot, P

2008-10-01

349

Microwave Reflectometry for Magnetically Confined Plasmas  

SciTech Connect

This paper is about microwave reflectometry -- a radar technique for plasma density measurements using the reflection of electromagnetic waves by a plasma cutoff. Both the theoretical foundations of reflectometry and its practical application to the study of magnetically confined plasmas are reviewed in this paper. In particular, the role of short-scale density fluctuations is discussed at length, both as a unique diagnostic tool for turbulence studies in thermonuclear plasmas and for the deleterious effects that fluctuations may have on the measurement of the average plasma density with microwave reflectometry.

Mazzucato, E.

1998-02-01

350

Experimental wrench faulting at confining pressure  

E-print Network

, the oeometries, ori- gins, and sequence of development of structural elements comprising the fault zones. Specimens (2. 8 or 3. 4 x 3. 4 x 9. 4 cm) are loaded parallel to their longest dimension, at an average displacement rate -3 -1 of 7. 3 x 10 cm sec...) is sandwiched between two rec- tangular plates of Indiana limestone (0. 50 or 0. 25 x 3. 35 x 8. 35 or 9. 40 cm) which are intact prior to deformation (Figs. l, p. 2, and 2, p. 3). Specimens are loaded parallel to their longest dimension, at confining...

Bartlett, Wendy Louise

2012-06-07

351

Spin asymmetries for confined Dirac particles  

SciTech Connect

We study the Bjorken x (or equivalently Nachtmann {xi}) dependence of the virtual photon spin asymmetry in polarized deep inelastic scattering of electrons from hadrons. We use an exactly solved relativistic potential model of the hadron, treating the constituents as independent massless Dirac particles confined to an infinitely massive force center. The importance of including the p--wave components of the Dirac wave function is demonstrated. Comparisons are made to the observed data on the proton by taking into account the observed flavor dependence of the valence quark distribution functions.

Mark Paris; V.R. Pandharipande; Ingo Sick

2004-06-01

352

Fractional electric charge and quark confinement  

E-print Network

Owing to their fractional electric charges, quarks are blind to transformations that combine a color center phase with an appropriate electromagnetic one. Such transformations are part of a global $Z_6$-like center symmetry of the Standard Model that is lost when quantum chromodynamics (QCD) is treated as an isolated theory. This symmetry and the corresponding topological defects may be relevant to non-perturbative phenomena such as quark confinement, much like center symmetry and ordinary center vortices are in pure SU($N$) gauge theories. Here we report on our investigations of an analogous symmetry in a 2-color model with dynamical Wilson quarks carrying half-integer electric charge.

Sam R. Edwards; André Sternbeck; Lorenz von Smekal

2012-02-07

353

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

354

Confined Dirac Particles in Constant and Tilted Magnetic Field  

E-print Network

We study the confinement of charged Dirac particles in 3+1 space-time due to the presence of a constant and tilted magnetic field. We focus on the nature of the solutions of the Dirac equation and on how they depend on the choice of vector potential that gives rise to the magnetic field. In particular, we select a "Landau gauge" such that the momentum is conserved along the direction of the vector potential yielding spinor wavefunctions, which are localized in the plane containing the magnetic field and normal to the vector potential. These wave functions are expressed in terms of the Hermite polynomials. We point out the relevance of these findings to the relativistic quantum Hall effect and compare with the results obtained for a constant magnetic field normal to the plane in 2+1 dimensions.

Alhaidari, Abdulaziz D; Jellal, Ahmed

2012-01-01

355

Radiation pressure confinement - IV. Application to broad absorption line outflows  

E-print Network

A fraction of quasars present broad absorption lines, produced by outflowing gas with typical velocities of 3000 - 10,000 km/s. If the outflowing gas fills a significant fraction of the volume where it resides, then it will be highly ionized by the quasar due to its low density, and will not produce the observed UV absorption. The suggestion that the outflow is shielded from the ionizing radiation was excluded by recent observations. The remaining solution is a dense outflow with a filling factor $fradiation pressure confinement (RPC) inevitably leads to gas compression and the formation of dense thin gas sheets/filaments, with a large gradient in density and ionization along the line of sight. The total column of ionized dustless gas is a few times $10^{22}$ cm$^{-2}$, consistent with the observed X-ray absorption and detectable P V absorption. The predicted maximal columns of various ions show a small dependence on the system parameters, a...

Baskin, Alexei; Stern, Jonathan

2014-01-01

356

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)] [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)] [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

1998-11-01

357

Confinement and focusing of geodesics in warped spacetimes  

NASA Astrophysics Data System (ADS)

We have explored certain characteristic features of test particle trajectories in five dimensional, warped bulk geometries with a single thick brane. After a brief introduction on such spacetimes, we have first discussed timelike geodesic motion. The geodesic equations, which reduce to a first order autonomous dynamical system, have been solved using analytical and numerical methods. We have demonstrated how a growing (decaying) warp factor leads to oscillatory (runaway) trajectories, suggesting confinement (deconfinement). Further, we have pointed out differences that arise when we have a cosmological brane and/or a time-dependent extra dimension. Next, we have moved on to the kinematics of geodesic congruences. The evolution of the kinematical variables (expansion, rotation and shear) along geodesic flows have been obtained using analytical and numerical approaches, with particular emphasis on the required conditions and occurence of geodesic focusing.

Kar, S.; Das Gupta, A.; Ghosh, S.; Nandan, H.

2014-03-01

358

Probing confined and unconfined hemoglobin molecules with photoacoustics  

NASA Astrophysics Data System (ADS)

Photoacoustic (PA) measurements on confined and unconfined hemoglobin molecules are presented. In vitro experiments were performed with porcine red blood cells (RBCs) at 532 and 1064 nm at various laser fluences. Fluence was gradually changed from 8 to 21 mJ/cm2/pulse for 532 nm and 353 to 643 mJ/cm2/pulse for 1064 nm. PA signals from suspended RBCs (SRBCs) and hemolyzed RBCs (HRBCs) were measured using a needle hydrophone at hematocrits ranging from 10 to 60%. PA amplitude was found to be varied linearly with the laser fluence for each type of samples at the above two optical radiations. At 532 nm, PA signals from SRBCs and HRBCs were measured to be nearly equal, whereas, at 1064 nm, signal amplitude for SRBCs was approximately 2 times higher than that of HRBCs. The results suggest that it may be feasible to detect hemolysis with PAs.

Saha, Ratan K.; Karmakar, Subhajit; Roy, Madhusudan

2014-03-01

359

Cation exchange dynamics confined in a synthetic clay mineral  

NASA Astrophysics Data System (ADS)

In this work we report X-Ray Diffraction (XRD) and Energy Dispersive X-Ray Spectroscopy (EDS) measurements to investigate the confined cation exchange process in saline aqueous suspensions of a synthetic clay mineral from Lithium-Fluorohectorite to Nickel-Fluorohectorite, as well as the reverse process from Nickel-Fluorohectorite to Lithium-Fluorohectorite and also from Lithium-Fluorohectorite to Sodium-Fluorohectorite. The dynamics of these cation exchanges was followed and it was observed that these processes can be faster than 1 minute. The results are compared to the observations on samples prepared by cation exchange procedures for which the exchange process was performed on the time-scale of months.

Grassi, G.; Michels, L.; Rozynek, Z.; Altoé, M. A. S.; dos Santos, E. C.; da Fonseca, C. L. S.; Droppa, R.; Gholamipour-Shirazi, A.; Fossum, J. O.; da Silva, G. J.

2014-09-01

360

Multiple-scale turbulence closure modeling of confined recirculating flows  

NASA Technical Reports Server (NTRS)

A multiple-scale turbulence closure scheme is developed for the numerical predictions of confined recirculating flows. This model is based on the multiple-time-scale concepts of Hanjalic et al. (1980) and takes into account the non-equilibrium spectra energy transfer mechanism. Problems concerning new formulation of energy transfer rate equations and subsequent model coefficient redefinition and energy spectrum partition are discussed. Comparisons are made with several experiments of internal recirculating flows for the purpose of model validation. Numerical results using the present model show significant improvement of predictive capability over that obtained with the single-scale k-epsilon model and show promising potential for complex turbulent flow predictions.

Chen, C. P.

1985-01-01

361

Clustering of branching Brownian motions in confined geometries.  

PubMed

We study the evolution of a collection of individuals subject to Brownian diffusion, reproduction, and disappearance. In particular, we focus on the case where the individuals are initially prepared at equilibrium within a confined geometry. Such systems are widespread in physics and biology and apply for instance to the study of neutron populations in nuclear reactors and the dynamics of bacterial colonies, only to name a few. The fluctuations affecting the number of individuals in space and time may lead to a strong patchiness, with particles clustered together. We show that the analysis of this peculiar behavior can be rather easily carried out by resorting to a backward formalism based on the Green's function, which allows the key physical observables, namely, the particle concentration and the pair correlation function, to be explicitly derived. PMID:25375449

Zoia, A; Dumonteil, E; Mazzolo, A; de Mulatier, C; Rosso, A

2014-10-01

362

Clustering of branching Brownian motions in confined geometries  

NASA Astrophysics Data System (ADS)

We study the evolution of a collection of individuals subject to Brownian diffusion, reproduction, and disappearance. In particular, we focus on the case where the individuals are initially prepared at equilibrium within a confined geometry. Such systems are widespread in physics and biology and apply for instance to the study of neutron populations in nuclear reactors and the dynamics of bacterial colonies, only to name a few. The fluctuations affecting the number of individuals in space and time may lead to a strong patchiness, with particles clustered together. We show that the analysis of this peculiar behavior can be rather easily carried out by resorting to a backward formalism based on the Green's function, which allows the key physical observables, namely, the particle concentration and the pair correlation function, to be explicitly derived.

Zoia, A.; Dumonteil, E.; Mazzolo, A.; de Mulatier, C.; Rosso, A.

2014-10-01

363

Quark Confinement Physics from Quantum Chromodynamics  

NASA Astrophysics Data System (ADS)

We show the construction of the dual superconducting theory for the confinement mechanism from QCD in the maximally abelian (MA) gauge using the lattice QCD Monte Carlo simulation. We find that essence of infrared abelian dominance is naturally understood with the off-diagonal gluon mass moff ?- 1.2GeV induced by the MA gauge fixing. In the MA gauge, the off-diagonal gluon amplitude is forced to be small, and the off-diagonal gluon phase tends to be random. As the mathematical origin of abelian dominance for confinement, we demonstrate that the strong randomness of the off-diagonal gluon phase leads to abelian dominance for the string tension. In the MA gauge, there appears the macroscopic network of the monopole world-line covering the whole system. We investigate the monopole-current system in the MA gauge by analyzing the dual gluon field B?. We evaluate the dual gluon mas as mB = 0.4 ˜ 0.5GeV in the infrared region, which is the lattice-QCD evidence of the dual Higgs mechanism by monopole condensation. Owing to infrared abelian dominance and infrared monopole condensation, QCD in the MA gauge is describable with the dual Ginzburg-Landau theory.

Suganuma, H.; Amemiya, K.; Ichie, H.; Tanaka, A.

364

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

2009-09-01

365

Polymer escape from a confining potential  

NASA Astrophysics Data System (ADS)

The rate of escape of polymers from a two-dimensionally confining potential well has been evaluated using self-avoiding as well as ideal chain representations of varying length, up to 80 beads. Long timescale Langevin trajectories were calculated using the path integral hyperdynamics method to evaluate the escape rate. A minimum is found in the rate for self-avoiding polymers of intermediate length while the escape rate decreases monotonically with polymer length for ideal polymers. The increase in the rate for long, self-avoiding polymers is ascribed to crowding in the potential well which reduces the free energy escape barrier. An effective potential curve obtained using the centroid as an independent variable was evaluated by thermodynamic averaging and Kramers rate theory then applied to estimate the escape rate. While the qualitative features are well reproduced by this approach, it significantly overestimates the rate, especially for the longer polymers. The reason for this is illustrated by constructing a two-dimensional effective energy surface using the radius of gyration as well as the centroid as controlled variables. This shows that the description of a transition state dividing surface using only the centroid fails to confine the system to the region corresponding to the free energy barrier and this problem becomes more pronounced the longer the polymer is. A proper definition of a transition state for polymer escape needs to take into account the shape as well as the location of the polymer.

Mökkönen, Harri; Ikonen, Timo; Jónsson, Hannes; Ala-Nissila, Tapio

2014-02-01

366

Thermodynamic properties of bulk and confined water.  

PubMed

The thermodynamic response functions of water display anomalous behaviors. We study these anomalous behaviors in bulk and confined water. We use nuclear magnetic resonance (NMR) to examine the configurational specific heat and the transport parameters in both the thermal stable and the metastable supercooled phases. The data we obtain suggest that there is a behavior common to both phases: that the dynamics of water exhibit two singular temperatures belonging to the supercooled and the stable phase, respectively. One is the dynamic fragile-to-strong crossover temperature (T(L) ? 225 K). The second, T* ? 315 ± 5 K, is a special locus of the isothermal compressibility K(T)(T, P) and the thermal expansion coefficient ?(P)(T, P) in the P-T plane. In the case of water confined inside a protein, we observe that these two temperatures mark, respectively, the onset of protein flexibility from its low temperature glass state (T(L)) and the onset of the unfolding process (T*). PMID:25399169

Mallamace, Francesco; Corsaro, Carmelo; Mallamace, Domenico; Vasi, Sebastiano; Vasi, Cirino; Stanley, H Eugene

2014-11-14

367

Polymer Dynamics in Nanocomposites and under Confinement  

NASA Astrophysics Data System (ADS)

In this talk I will present neutron spin echo investigations on polymers interacting attractively with nanoparticles or confining surfaces. Polyethylene-oxide (PEO) was filled with neat SiO2 nanoparticles up to 15 vol%. Investigating a short chain matrix we realised that a fraction of chains is adsorbed at the nanoparticle surface suppressing completely its translational diffusion. Nevertheless these adsorbed chains undergo an unchanged segmental dynamics seemingly forming a micelle like corona of chains connected with their OH-end groups. Changing to methylene terminated chains the picture changes drastically now showing a tightly adsorbed layer that however is not glassy as often assumed but undergoes pico second local dynamics. These results are corrobated and extended in studying the dynamics of Polydimethylsiloxane (PDMS) confined in nanoporous Alumina. There a partly anchored chain fraction is found that undergoes restricted Rouse motions with segmental mobilities as in the bulk phase. The size of this layer exceeds significantly the length scale of the directly adsorbed polymer, presenting a first direct microscopic evidence for the hypothetical interphase.

Richter, Dieter

2013-03-01

368

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

369

Nematode Locomotion in Unconfined and Confined Fluids  

E-print Network

The millimeter-long soil-dwelling nematode {\\it C. elegans} propels itself by producing undulations that propagate along its body and turns by assuming highly curved shapes. According to our recent study [PLoS ONE \\textbf{7}, e40121 (2012)] all these postures can be accurately described by a piecewise-harmonic-curvature (PHC) model. We combine this curvature-based description with highly accurate hydrodynamic bead models to evaluate the normalized velocity and turning angles for a worm swimming in an unconfined fluid and in a parallel-wall cell. We find that the worm moves twice as fast and navigates more effectively under a strong confinement, due to the large transverse-to-longitudinal resistance-coefficient ratio resulting from the wall-mediated far-field hydrodynamic coupling between body segments. We also note that the optimal swimming gait is similar to the gait observed for nematodes swimming in high-viscosity fluids. Our bead models allow us to determine the effects of confinement and finite thickness...

Bilbao, Alejandro; Vanapalli, Siva; Blawzdziewicz, Jerzy

2013-01-01

370

Polymer escape from a confining potential  

SciTech Connect

The rate of escape of polymers from a two-dimensionally confining potential well has been evaluated using self-avoiding as well as ideal chain representations of varying length, up to 80 beads. Long timescale Langevin trajectories were calculated using the path integral hyperdynamics method to evaluate the escape rate. A minimum is found in the rate for self-avoiding polymers of intermediate length while the escape rate decreases monotonically with polymer length for ideal polymers. The increase in the rate for long, self-avoiding polymers is ascribed to crowding in the potential well which reduces the free energy escape barrier. An effective potential curve obtained using the centroid as an independent variable was evaluated by thermodynamic averaging and Kramers rate theory then applied to estimate the escape rate. While the qualitative features are well reproduced by this approach, it significantly overestimates the rate, especially for the longer polymers. The reason for this is illustrated by constructing a two-dimensional effective energy surface using the radius of gyration as well as the centroid as controlled variables. This shows that the description of a transition state dividing surface using only the centroid fails to confine the system to the region corresponding to the free energy barrier and this problem becomes more pronounced the longer the polymer is. A proper definition of a transition state for polymer escape needs to take into account the shape as well as the location of the polymer.

Mökkönen, Harri, E-mail: harri.mokkonen@aalto.fi [Department of Applied Physics and COMP CoE, Aalto University School of Science, P.O. Box 11100, FIN-00076 Aalto, Espoo (Finland) [Department of Applied Physics and COMP CoE, Aalto University School of Science, P.O. Box 11100, FIN-00076 Aalto, Espoo (Finland); Faculty of Physical Sciences, University of Iceland, Reykjavík (Iceland); Ikonen, Timo [Department of Applied Physics and COMP CoE, Aalto University School of Science, P.O. Box 11100, FIN-00076 Aalto, Espoo (Finland) [Department of Applied Physics and COMP CoE, Aalto University School of Science, P.O. Box 11100, FIN-00076 Aalto, Espoo (Finland); VTT Technical Research Centre of Finland, P.O. Box 1000, FI-02044 VTT (Finland); Jónsson, Hannes [Department of Applied Physics and COMP CoE, Aalto University School of Science, P.O. Box 11100, FIN-00076 Aalto, Espoo (Finland) [Department of Applied Physics and COMP CoE, Aalto University School of Science, P.O. Box 11100, FIN-00076 Aalto, Espoo (Finland); Faculty of Physical Sciences, University of Iceland, Reykjavík (Iceland); Department of Physics, Brown University, Providence, Rhode Island 02912-1843 (United States); Ala-Nissila, Tapio [Department of Applied Physics and COMP CoE, Aalto University School of Science, P.O. Box 11100, FIN-00076 Aalto, Espoo (Finland) [Department of Applied Physics and COMP CoE, Aalto University School of Science, P.O. Box 11100, FIN-00076 Aalto, Espoo (Finland); Department of Physics, Brown University, Providence, Rhode Island 02912-1843 (United States)

2014-02-07

371

Confined magnetic monopoles in dense QCD  

NASA Astrophysics Data System (ADS)

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.; Shifman, M.; Yung, A.

2011-04-01

372

Confinement From The Gauge Invariant Abelian Decomposition  

E-print Network

A common approach while considering confinement is to study the dominance of an Abelian subgroup of the SU(3) gauge Links. A good way to find the Abelian component of the field is through the Cho-Guan-De gauge invariant Abelian Decomposition, which uses a carefully chosen direction vector $n$ to split the gauge field into an Abelian restricted field and a remnant coloured field. The restricted field can be further subdivided into topological and non-topological terms. We show that there is a choice of $n$ which allows us to exactly represent the Wilson Loop of full QCD as a function of only the restricted Abelian field without requiring any path ordering or additional path integrals. We present numerical evidence showing that the topological part of the restricted field dominates the string tension. We also show that $n$ contains certain topological objects, which, if they exist, will be at least partially responsible for confinement. These leave distinctive patterns in the restricted field strength, and we search for these structures in quenched lattice QCD.

Nigel Cundy; Yongmin Cho; Weonjong Lee

2013-11-13

373

NMR studies on the temperature-dependent dynamics of confined water.  

PubMed

We use (2)H NMR to study the rotational motion of supercooled water in silica pores of various diameters, specifically, in the MCM-41 materials C10, C12, and C14. Combination of spin-lattice relaxation, line-shape, and stimulated-echo analyses allows us to determine correlation times in very broad time and temperature ranges. For the studied pore diameters, 2.1-2.9 nm, we find two crossovers in the temperature-dependent correlation times of liquid water upon cooling. At 220-230 K, a first kink in the temperature dependence is accompanied by a solidification of a fraction of the confined water, implying that the observed crossover is due to a change from bulk-like to interface-dominated water dynamics, rather than to a liquid-liquid phase transition. Moreover, the results provide evidence that ? process-like dynamics is probed above the crossover temperature, whereas ? process-like dynamics is observed below. At 180-190 K, we find a second change of the temperature dependence, which resembles that reported for the ? process of supercooled liquids during the glass transition, suggesting a value of Tg ? 185 K for interface-affected liquid water. In the high-temperature range, T > 225 K, the temperature dependence of water reorientation is weaker in the smaller C10 pores than in the larger C12 and C14 pores, where it is more bulk-like, indicating a significant effect of the silica confinement on the ? process of water in the former 2.1 nm confinement. By contrast, the temperature dependence of water reorientation is largely independent of the confinement size and described by an Arrhenius law with an activation energy of Ea ? 0.5 eV in the low-temperature range, T < 180 K, revealing that the confinement size plays a minor role for the ? process of water. PMID:25096474

Sattig, Matthias; Reutter, Stefan; Fujara, Franz; Werner, Mayke; Buntkowsky, Gerd; Vogel, Michael

2014-09-28

374

Theory of confinement-induced interlayer molecular resonances  

E-print Network

We study theoretically the interaction between two species of bosons confined parabolically in one transverse direction but with a finite separation between the centers of the confining potentials. We demonstrate the existence of new types of confinement-induced Feshbach resonances that can be tuned by changing separation between the layers. They are much sharper than usual two-dimensional confinement-induced resonances, and can be observed in the shaking spectrum of the two-dimensional layers, as shown by detailed many-body calculations for a thermal Bose gas.

Márton Kanász-Nagy; Eugene A. Demler; Gergely Zaránd

2014-01-22

375

The cruel and unusual phenomenology of solitary confinement  

PubMed Central

What happens when subjects are deprived of intersubjective contact? This paper looks closely at the phenomenology and psychology of one example of that deprivation: solitary confinement. It also puts the phenomenology and psychology of solitary confinement to use in the legal context. Not only is there no consensus on whether solitary confinement is a “cruel and unusual punishment,” there is no consensus on the definition of the term “cruel” in the use of that legal phrase. I argue that we can find a moral consensus on the meaning of “cruelty” by looking specifically at the phenomenology and psychology of solitary confinement. PMID:24971072

Gallagher, Shaun

2014-01-01

376

Confinement dynamics of a semiflexible chain inside nano-spheres  

E-print Network

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.

Arman Fathizadeh; Maziar Heidari; Behrouz Eslami-Mossallam; Mohammad Reza Ejtehadi

2014-09-26

377

Structure of charged polymer chains in confined geometry.  

SciTech Connect

The intra- and interchain structure of sodium poly(styrenesulphonate) when free and when confined in contrast matched porous Vycor has been investigated by SANS. When confined, a peak is observed whose intensity increases with molecular weight and the 1/q scattering region is extended compared to the bulk. We infer that the chains are sufficiently extended, under the influence of confinement, to highlight the large scale disordered structure of Vycor. The asymptotic behavior of the observed interchain structure factor is = 1/q{sup 2} and = 1/q for free and confined chains respectively.

Gilbert, E. P.; Auvray, L.; Lal, J.

2000-12-15

378

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

379

QENS investigation of proton confined motions in hydrated perfluorinated sulfonic membranes and self-assembled surfactants  

NASA Astrophysics Data System (ADS)

We report on QuasiElastic Neutron Scattering (QENS) investigations of the dynamics of protons and water molecules confined in nanostructured perfluorinated sulfonic acid (PFSA) materials, namely a commercial Aquivion membrane and the perfluorooctane sulfonic acid (PFOS) surfactant. The former is used as electrolyte in low-temperature fuel cells, while the latter forms mesomorphous self-assembled phases in water. The dynamics was investigated as a function of the hydration level, in a wide time range by combining time-of-flight and backscattering incoherent QENS experiments. Analysis of the quasielastic broadening revealed for both systems the existence of localized translational diffusive motions, fast rotational motions and slow hopping of protons in the vicinity of the sulfonic charges. The characteristic times and diffusion coefficients have been found to exhibit a very similar behaviour in both membrane and surfactant structures. Our study provides a comprehensive picture of the proton motion mechanisms and the dynamics of confined water in model and real PFSA nanostructures.

Berrod, Quentin; Lyonnard, Sandrine; Guillermo, Armel; Ollivier, Jacques; Frick, Bernhard; Gébel, Gérard

2015-01-01

380

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

381

Light-Front Holographic QCD and Emerging Confinement  

E-print Network

In this Report we explore the remarkable connections between light-front dynamics, its holographic mapping to gravity in a higher-dimensional anti-de Sitter (AdS) space, and conformal quantum mechanics. This approach provides new insights into the origin of a fundamental mass scale and the physics underlying confinement dynamics in QCD in the limit of massless quarks. The result is a relativistic light-front wave equation for arbitrary spin with an effective confinement potential derived from a conformal action and its embedding in AdS space. This equation allows for the computation of essential features of hadron spectra in terms of a single scale. The light-front holographic methods described here gives a precise interpretation of holographic variables and quantities in AdS space in terms of light-front variables and quantum numbers. This leads to a relation between the AdS wave functions and the boost-invariant light-front wavefunctions describing the internal structure of hadronic bound-states in physical space-time. The pion is massless and the excitation spectra of relativistic light-quark meson and baryon bound states lie on linear Regge trajectories with identical slopes in the radial and orbital quantum numbers. In the light-front holographic approach described here currents are expressed as an infinite sum of poles, and form factors as a product of poles. At large $q^2$ the form factor incorporates the correct power-law fall-off for hard scattering independent of the specific dynamics and is dictated by the twist. At low $q^2$ the form factor leads to vector dominance. The approach is also extended to include small quark masses. We briefly review in this Report other holographic approaches to QCD, in particular top-down and bottom-up models based on chiral symmetry breaking. We also include a discussion of open problems and future applications.

Stanley J. Brodsky; Guy F. de Teramond; Hans Gunter Dosch; Joshua Erlich

2014-07-30

382

Stirring by swimmers in confined microenvironments  

E-print Network

We consider the tracer diffusion $D_{rr}$ that arises from the run-and-tumble motion of low Reynolds number swimmers, such as bacteria. In unbounded dilute suspensions, where the dipole swimmers move in uncorrelated runs of length $\\lambda$, an exact solution showed that $D_{rr}$ is independent of $\\lambda$. Here we verify this result in numerical simulations for a particular model swimmer, the spherical squirmer. We also note that in confined microenvironments, such as microscopic droplets, microfluidic devices and bacterial microzones in marine ecosystems, the size of the system can be comparable to $\\lambda$. We show that this effect alone reduces the value of $D_{rr}$ in comparison to its bulk value, and predict a scaling form for its relative decrease.

Dmitri O. Pushkin; Julia M. Yeomans

2014-03-11

383

Aggregation and Segregation of Confined Active Particles  

E-print Network

We simulate a model of self-propelled disks with soft repulsive interactions confined to a box in two dimensions. For small rotational diffusion rates, monodisperse disks spontaneously accumulate at the walls. At low densities, interaction forces between particles are strongly inhomogeneous, and a simple model predicts how these inhomogeneities alter the equation of state. At higher densities, collective effects become important. We observe signatures of a jamming transition at a packing fraction $\\phi \\sim 0.88$, which is also the jamming point for non-active athermal monodisperse disks. At this $\\phi$, the system develops a critical finite active speed necessary for wall aggregation. At packing fractions above $\\phi \\sim 0.6$, the pressure decreases with increasing density, suggesting that strong interactions between particles are affecting the equation of state well below the jamming transition. A mixture of bidisperse disks segregates in the absence of any adhesion, identifying a new mechanism that could ...

Yang, Xingbo; Marchetti, M Cristina

2014-01-01

384

Aggregation and segregation of confined active particles.  

PubMed

We simulate a model of self-propelled disks with soft repulsive interactions confined to a box in two dimensions. For small rotational diffusion rates, monodisperse disks spontaneously accumulate at the walls. At low densities, interaction forces between particles are strongly inhomogeneous, and a simple model predicts how these inhomogeneities alter the equation of state. At higher densities, collective effects become important. We observe signatures of a jamming transition at a packing fraction ? ? 0.88, which is also the jamming point for non-active athermal monodisperse disks. At this ?, the system develops a critical finite active speed necessary for wall aggregation. At packing fractions above ? ? 0.6, the pressure decreases with increasing density, suggesting that strong interactions between particles are affecting the equation of state well below the jamming transition. A mixture of bidisperse disks segregates in the absence of any adhesion, identifying a new mechanism that could contribute to cell sorting in embryonic development. PMID:25046587

Yang, Xingbo; Manning, M Lisa; Marchetti, M Cristina

2014-09-14

385

Engineering tube shapes to control confined transport  

NASA Astrophysics Data System (ADS)

Transport of particles in confined structures can be modeled by means of diffusion in a potential of entropic nature. The entropic transport model proposes a drift-diffusion kinetic equation for the evolution of the probability density in which the diffusion coefficient depends on position and the drift term contains an entropic force. The model has been applied to analyze transport in single cavities and through periodic structures of different shape, and to investigate the nature of non-equilibrium fluctuations as well. The transport characteristics depends strongly on the contour of the region through which particles move, which defines the entropic potential. We show that the form of the entropic potential can be properly designed to optimize and govern how molecules diffuse and get drifted in tortuous channels. The shape of a tube or channel can be smartly engineered to control transport for the desired application.

Reguera, D.; Rubi, J. M.

2014-12-01

386

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

387

Preliminary Results from the Confined Helium Experiment  

NASA Technical Reports Server (NTRS)

We describe the preliminary results from an experiment to measure the heat capacity of helium confined within a stack of evenly spaced silicon plates at temperatures very close to the superfluid transition. The resolution of the heat capacity measurements was generally about 5x10 (exp -9)K, allowing the finite size peak to be mapped in detail. In addition, wide range data containing information on the behavior of the surface specific heat was collected. The preliminary analysis shows fair agreement with theory, but some discrepancies. The results can also be combined with related ground measurements on smaller length scales to perform additional tests of scaling predictions for cross-over to lower dimensional behavior. Some results in this area are also presented.

Lipa, J. A.; Swanson, D. R.; Nissen, J. A.; Williamson, P. R.; Geng, K.; Stricker, D. A.; Chui, T. C. P.; Israelson, U. E.; Larson, M.

1999-01-01

388

Relativistic constituent quark model with infrared confinement  

SciTech Connect

We refine the relativistic constituent quark model developed in our previous papers to include the confinement of quarks. It is done, first, by introducing the scale integration in the space of {alpha} parameters, and, second, by cutting this scale integration on the upper limit which corresponds to an infrared cutoff. In this manner one removes all possible thresholds present in the initial quark diagram. The cutoff parameter is taken to be the same for all physical processes. We adjust other model parameters by fitting the calculated quantities of the basic physical processes to available experimental data. As an application, we calculate the electromagnetic form factors of the pion and the transition form factors of the {omega} and {eta} Dalitz decays.

Branz, Tanja; Faessler, Amand; Gutsche, Thomas; Lyubovitskij, Valery E. [Institut fuer Theoretische Physik, Universitaet Tuebingen, Kepler Center for Astro and Particle Physics, Auf der Morgenstelle 14, D-72076 Tuebingen (Germany); Ivanov, Mikhail A. [Bogoliubov Laboratory of Theoretical Physics, Joint Institute for Nuclear Research, 141980 Dubna (Russian Federation); Koerner, Juergen G. [Institut fuer Physik, Johannes Gutenberg-Universitaet, D-55099 Mainz (Germany)

2010-02-01

389

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

390

Large-Nc confinement and turbulence.  

PubMed

We suggest that the transition that occurs at large N_{c} in the eigenvalue distribution of a Wilson loop may have a turbulent origin. We arrived at this conclusion by studying the complex-valued inviscid Burgers-Hopf equation that corresponds to the Makeenko-Migdal loop equation, and we demonstrate the appearance of a shock in the spectral flow of the Wilson loop eigenvalues. This picture supplements that of the Durhuus-Olesen transition with a particular realization of disorder. The critical behavior at the formation of the shock allows us to infer exponents that have been measured recently in lattice simulations by Narayanan and Neuberger in d=2 and d=3. Our analysis leads us to speculate that the universal behavior observed in these lattice simulations might be a generic feature of confinement, also in d=4 Yang-Mills theory. PMID:18851206

Blaizot, Jean-Paul; Nowak, Maciej A

2008-09-01

391

Broadband sound generation by confined turbulent jets.  

PubMed

Sound generation by confined stationary jets is of interest to the study of voice and speech production, among other applications. The generation of sound by low Mach number, confined, stationary circular jets was investigated. Experiments were performed using a quiet flow supply, muffler-terminated rigid uniform tubes, and acrylic orifice plates. A spectral decomposition method based on a linear source-filter model was used to decompose radiated nondimensional sound pressure spectra measured for various gas mixtures and mean flow velocities into the product of (1) a source spectral distribution function; (2) a function accounting for near field effects and radiation efficiency; and (3) an acoustic frequency response function. The acoustic frequency response function agreed, as expected, with the transfer function between the radiated acoustic pressure at one fixed location and the strength of an equivalent velocity source located at the orifice. The radiation efficiency function indicated a radiation efficiency of the order (kD)2 over the planar wave frequency range and (kD)4 at higher frequencies, where k is the wavenumber and D is the tube cross sectional dimension. This is consistent with theoretical predictions for the planar wave radiation efficiency of quadrupole sources in uniform rigid anechoic tubes. The effects of the Reynolds number, Re, on the source spectral distribution function were found to be insignificant over the range 20002.5. The influence of a reflective open tube termination on the source function spectral distribution was found to be insignificant, confirming the absence of a feedback mechanism. PMID:12186047

Zhang, Zhaoyan; Mongeau, Luc; Frankel, Steven H

2002-08-01

392

Psychological and behavioral changes during confinement in a 520-day simulated interplanetary mission to mars.  

PubMed

Behavioral health risks are among the most serious and difficult to mitigate risks of confinement in space craft during long-duration space exploration missions. We report on behavioral and psychological reactions of a multinational crew of 6 healthy males confined in a 550 m(3) chamber for 520 days during the first Earth-based, high-fidelity simulated mission to Mars. Rest-activity of crewmembers was objectively measured throughout the mission with wrist-worn actigraphs. Once weekly throughout the mission crewmembers completed the Beck Depression Inventory-II (BDI-II), Profile of Moods State short form (POMS), conflict questionnaire, the Psychomotor Vigilance Test (PVT-B), and series of visual analogue scales on stress and fatigue. We observed substantial inter-individual differences in the behavioral responses of crewmembers to the prolonged mission confinement and isolation. The crewmember with the highest average POMS total mood disturbance score throughout the mission also reported symptoms of depression in 93% of mission weeks, which reached mild-to-moderate levels in >10% of mission weeks. Conflicts with mission control were reported five times more often than conflicts among crewmembers. Two crewmembers who had the highest ratings of stress and physical exhaustion accounted for 85% of the perceived conflicts. One of them developed a persistent sleep onset insomnia with ratings of poor sleep quality, which resulted in chronic partial sleep deprivation, elevated ratings of daytime tiredness, and frequent deficits in behavioral alertness. Sleep-wake timing was altered in two other crewmembers, beginning in the first few months of the mission and persisting throughout. Two crewmembers showed neither behavioral disturbances nor reports of psychological distress during the 17-month period of mission confinement. These results highlight the importance of identifying behavioral, psychological, and biological markers of characteristics that predispose prospective crewmembers to both effective and ineffective behavioral reactions during the confinement of prolonged spaceflight, to inform crew selection, training, and individualized countermeasures. PMID:24675720

Basner, Mathias; Dinges, David F; Mollicone, Daniel J; Savelev, Igor; Ecker, Adrian J; Di Antonio, Adrian; Jones, Christopher W; Hyder, Eric C; Kan, Kevin; Morukov, Boris V; Sutton, Jeffrey P

2014-01-01

393

Computational fluid dynamics modeling of ventilation of confined-space manure storage facilities: applications.  

PubMed

Fatalities associated with entry into on-farm confined-space manure storage tanks occur each year The fatalities are due to asphyxiation or poisoning by exposure to high concentrations of hydrogen sulfide, methane, and carbon dioxide. Forced ventilation has been shown to be an effective way to reduce concentrations of these noxious gases to levels that are safe for human entry into these storage tanks. Hydrogen sulfide (H2S) was used as an indicator gas to investigate the effectiveness of forced ventilation strategies for eliminating the toxic and oxygen-deficient atmospheres in confined-space manure tanks. Validated computational fluid dynamics (CFD) modeling protocols were used to simulate H2S evacuation from fan-ventilated manure tanks. The simulation studies were conducted for rectangular and circular manure tanks, and the effects of pollutant source, inter-contamination (process by which a portion of exhausted contaminant gas enters a ventilated confined airspace through the fresh air intake), storage size (i.e., length, diameter), and air exchange rate on H2S removalfrom fan-ventilated manure tanks were investigated. For the same air exchange rate, as the size (i.e., length, diameter) of the tank increased, the rate of evacuation of the H2S from the confined space decreased. For rectangular and circular manure tanks, the higher the air exchange rate, the higher the rate of evacuation of the H2S from the confined space. For the rectangular tank geometries and ventilation system layouts simulated, evacuation times decreased exponentially with air exchange rate. Evacuation times for the circular tanks simulated decreased linearly with air exchange rate. PMID:19044169

Zhao, J; Manbeck, H B; Murphy, D J

2008-10-01

394

Polar confinement of Saturn's magnetosphere revealed by in situ Cassini observations  

NASA Astrophysics Data System (ADS)

Plasma rotation plays a large role in determining the size and shape of Saturn's disk-like magnetosphere. A magnetosphere more confined to the equator in the polar regions is expected as a result of the interaction between this type of obstacle and the solar wind. In addition, at times away from equinox, a north-south asymmetry is expected where the magnetopause will be further confined in one hemisphere but less confined in the opposite hemisphere. Examining the extent of this confinement has been limited by a lack of high-latitude spacecraft observations. Here for the first time, direct evidence for polar confinement of Saturn's magnetopause has been observed using in situ data obtained by the Cassini spacecraft during a series of high-inclination orbits between 2007 and 2009. Following techniques established by previous authors, we assume an equilibrium between the solar wind dynamic pressure (which Cassini is generally unable to measure directly), and the magnetic plus plasma pressure inside the magnetosphere. This assumption thus allows us to estimate the upstream solar wind dynamic pressure (DP) for a series of magnetopause crossings, and hence to determine the expected location and global shape of the magnetopause as a function of DP. A clear divergence from the familiar axisymmetric models of the magnetosphere is observed, which may be characterized by an "apparent flattening parameter" of 0.81+0.03/-0.06 (representing a simple dilation of the nominal axisymmetric boundary along the ZKSM axis such that the extent is reduced by approximately 19% in this direction). This figure is insensitive to variations in DP.

Pilkington, N. M.; Achilleos, N.; Arridge, C. S.; Masters, A.; Sergis, N.; Coates, A. J.; Dougherty, M. K.

2014-04-01

395

Final report for confinement vessel analysis. Task 3, Analysis of confinement vessel doors  

SciTech Connect

The confinement vessel has five closure doors of two different sizes. The vessel must withstand an initial dynamic load and a quasi-static internal pressure with no leakage of gases through the port seals. Task 3 of the Confinement Vessel Analysis Program was to assess the doors for safety. Of primary concern is the integrity of the seal. This encompasses the structural integrity of the door and nozzle as separate structural elements and the relative motion between the door and nozzle which could cause leakage of gases around the seals. In addition, the authors would like to obtain a better understanding of the effect of the bolt preload, especially as it affects the dynamic response of the structure. The authors explain the objectives of the task in Section 1, describe the models used for the analyses in Section 2, and give results in Section 3. They list conclusions and recommendations in Section 4.

Lewis, B.B. [APTEK, Inc., Colorado Springs, CO (United States)

1993-12-31

396

Effect of confinement potential geometry on entanglement in quantum dot-based nanostructures  

E-print Network

We calculate the spatial entanglement between two electrons trapped in a nanostructure for a broad class of confinement potentials, including single and double quantum dots, and core-shell quantum dot structures. By using a parametrized confinement potential, we are able to switch from one structure to the others with continuity and to analyze how the entanglement is influenced by the changes in the confinement geometry. We calculate the many-body wave function by `exact' diagonalization of the time independent Schr\\"odinger equation. We discuss the relationship between the entanglement and specific cuts of the wave function, and show that the wave function at a single highly symmetric point could be a good indicator for the entanglement content of the system. We analyze the counterintuitive relationship between spatial entanglement and Coulomb interaction, which connects maxima (minima) of the first to minima (maxima) of the latter. We introduce a potential quantum phase transition which relates quantum states characterized by different spatial topology. Finally we show that by varying shape, range and strength of the confinement potential, it is possible to induce strong and rapid variations of the entanglement between the two electrons. This property may be used to tailor nanostructures according to the level of entanglement required by a specific application.

S. Abdullah; J. P. Coe; I. D'Amico

2009-08-19

397

Exercise as a countermeasure to psycho-physiological deconditioning during long-term confinement.  

PubMed

Confinement studies are performed to simulate the psychological effects that may be experienced on a long-term space flight. A general psycho-physiological model assumes that mood and cognitive functioning are impaired during confinement as a result of an absence of physical activity. The aim of the MARS500 study initiated by the Institute of Biomedical Problems (IBMP) and the European Space Agency (ESA) is to gather data, knowledge and experience to help prepare for a real mission to Mars. A test run with 105 days of isolation was performed prior to 520 days of isolation. Psycho-physiological data of this study are presented here. We hypothesized that exercise, as it has been shown in laboratory settings, would be able to prevent and counteract mood changes during isolation. Electrocortical data (EEG) and a self report on current psychological and physical state were recorded several times prior to and after exercise during the isolation period. Data revealed a clear effect of exercise on mood and electrocortical activity. Moreover, it was shown that mood and brain cortical activity decreased during the first 11 weeks of isolation and reached baseline again in the last week of isolation. A correlation analysis revealed a significant relation between mood data and electrocortical activity. We conclude (1) that confinement is accompanied by psycho-physiological changes and (2) that exercise is a suitable method to counteract psycho-physiological deconditioning during confinement. PMID:20346985

Schneider, Stefan; Brümmer, Vera; Carnahan, Heather; Kleinert, Jens; Piacentini, Maria Francesca; Meeusen, Romain; Strüder, Heiko K

2010-08-25

398

Light confinement and mode splitting in rolled-up semiconductor microtube bottle resonators  

NASA Astrophysics Data System (ADS)

We report on the controlled light confinement in microtube bottle resonators formed by rolled-up strained semiconductor bilayers. We experimentally and theoretically discuss two important properties of this novel kind of microcavities: the axial light confinement and the mode splitting by broken rotational symmetry. Our model bases on the adiabatic separation of circular and axial mode propagation. The circular problem is solved by a simple waveguide model for the specific geometry along the microtube axis. These solutions act as a quasipotential in a quasi-Schrödinger equation for the axial propagation. We experimentally investigated microtubes with two different axial confinement mechanisms: lobes of varying winding number in the rolling edge and etched rings of a varying wall thickness along the microtube axis. For the microtubes with lobes, we observe a very good quantitative agreement with our model and show that axial mode dispersion can even be tailored by the shape of the lobe. For the microtubes with etched rings, we observe only a qualitative agreement. These microtubes exhibit a well pronounced mode splitting by broken rotational symmetry that is analyzed by two-dimensional finite-difference time-domain simulations. We observe an oscillating behavior of the amplitude of the splitting as well as of the quality factors of the split modes under variation of the winding number. We show that the splitting is connected to the axial confinement.

Strelow, Ch.; Schultz, C. M.; Rehberg, H.; Sauer, M.; Welsch, H.; Stemmann, A.; Heyn, Ch.; Heitmann, D.; Kipp, T.

2012-04-01

399

Lateral confinement effects on the structural properties of surfactant aggregates: SDS on graphene.  

PubMed

The structure of aqueous sodium dodecyl sulfate (SDS) surfactant aggregates formed on small graphene sheets and graphene nanoribbons has been studied using all-atom molecular dynamics simulations. Because the edges of the carbonaceous supports confine laterally the surfactant aggregates, by changing the size of the support (diameter of graphene sheets and width of graphene nanoribbons) it is possible to investigate lateral confinement effects on the aggregate morphology. The results are compared to those available on graphite, with no lateral confinement. Aqueous SDS aggregates were studied on 2.0 nm, 5.0 nm, and 10.0 nm circular graphene sheets and on 2.0 and 5.0 nm wide graphene nanoribbons. For the first time our results show that, because of lateral confinement provided by the graphene edges, SDS yields multiple layers, hemispheres, hemicylinders or multiple hemispheres depending on the graphene size and shape. Results are quantified in terms of morphology of the surfactant aggregates, order parameter of the adsorbed surfactant aggregates, and number of water molecules at contact with the carbonaceous support. PMID:20835489

Tummala, Naga Rajesh; Grady, Brian P; Striolo, Alberto

2010-10-28

400

Influence of confined fluids on nanoparticle-to-surroundings energy transfer.  

PubMed

Energy transfer from photoexcited nanoparticles to their surroundings was studied for both hollow and solid gold nanospheres (HGNs and SGNs, respectively) using femtosecond time-resolved transient extinction spectroscopy. HGNs having outer diameters ranging from 17 to 78 nm and fluid-filled cavities were synthesized by a sacrificial galvanic replacement method. The HGNs exhibited energy transfer half times that ranged from 105 ± 10 ps to 1010 ± 80 ps as the total particle surface area increased from 1005 to 28,115 nm(2). These data showed behaviors that were categorized into two classes: energy transfer from HGNs to interior fluids that were confined to cavities with radii <15 nm and ?15 nm. Energy transfer times were also determined for solid gold nanospheres (SGNs) having radii spanning 9-30 nm, with a similar size dependence where the relaxation times increased from 140 ± 10 to 310 ± 15 ps with increasing nanoparticle size. Analysis of the size-dependent energy transfer half times revealed that the distinct relaxation rate constants observed for particle-to-surroundings energy transfer for HGNs with small cavities were the result of reduced thermal conductivity of confined fluids. These data indicate that the thermal conductivity of HGN cavity-confined fluids is approximately one-half as great as it is for bulk liquid water. For all HGNs and SGNs studied, energy dissipation through the solvent and transfer across the particle/surroundings interface both contributed to the energy relaxation process. The current data illustrated the potential of fluid-filled hollow nanostructures to gain insight into the properties of confined fluids. PMID:23110583

Dowgiallo, Anne-Marie; Knappenberger, Kenneth L

2012-11-28

401

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

402

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

1995-01-01

403

Atomic processes in 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

1993-01-01

404

Admissible release from the chernobyl new safe confinement  

SciTech Connect

Calculation of admissible releases at different exploitation stages of New Safe Confinement at the existing ChNPP ''Shelter'' object are given. Vain conclusions of calculations are given as well as recommendations for planning of activities connected with the New Safe Confinement construction.

Batiy, Valeriy; Paskevych, Sergei; Rudko, Vladimir; Sizov, Andrey; Shcherbin, Vladimir; Schmieman, Eric A.

2005-08-08

405

Vortices and quark confinement in non-abelian gauge theories  

Microsoft Academic Search

It is shown that finite-length vortices in an SU(n) Nielsen-Olesen model require explicit introduction of monopoles, which are confined in multiples of n by the Meissner effect. The model therefore possesses a natural explanation of quark confinement.

S. Mandelstam

1975-01-01

406

LAGOON WATER FROM CONFINED ANIMAL FEED OPERATIONS AND AMPHIBIAN DEVELOPMENT  

EPA Science Inventory

Lagoon Water from Confined Animal Feed Operations and Amphibian Development. Dumont, J. N.* and Slagle, S., Oklahoma State University, Stillwater, OK, and Hutchins, S. R., U.S. Environmental Protection Agency (NRMRL/SPRD), Ada, OK. There is some evidence that confined anima...

407

A method to estimate groundwater depletion from confining layers  

USGS Publications Warehouse

Although depletion of storage in low-permeability confining layers is the source of much of the groundwater produced from many confined aquifer systems, it is all too frequently overlooked or ignored. This makes effective management of groundwater resources difficult by masking how much water has been derived from storage and, in some cases, the total amount of water that has been extracted from an aquifer system. Analyzing confining layer storage is viewed as troublesome because of the additional computational burden and because the hydraulic properties of confining layers are poorly known. In this paper we propose a simplified method for computing estimates of confining layer depletion, as well as procedures for approximating confining layer hydraulic conductivity (K) and specific storage (Ss) using geologic information. The latter makes the technique useful in developing countries and other settings where minimal data are available or when scoping calculations are needed. As such, our approach may be helpful for estimating the global transfer of groundwater to surface water. A test of the method on a synthetic system suggests that the computational errors will generally be small. Larger errors will probably result from inaccuracy in confining layer property estimates, but these may be no greater than errors in more sophisticated analyses. The technique is demonstrated by application to two aquifer systems: the Dakota artesian aquifer system in South Dakota and the coastal plain aquifer system in Virginia. In both cases, depletion from confining layers was substantially larger than depletion from the aquifers.

Konikow, L.F.; Neuzil, C.E.

2007-01-01

408

Light confinement via periodic modulation of the refractive index  

E-print Network

Light confinement via periodic modulation of the refractive index A Alberucci1,4 , L Marrucci2 and numerically, light confine- ment in dielectric structures with a transverse refractive index distribution pe and managing light signals and beams. The periodic modulation of the refractive index in the propagation

Marrucci, Lorenzo

409

Gaussian Confinement of Phonons in CdS Nanoparticles  

NASA Astrophysics Data System (ADS)

The Raman spectrum of CdS nanoparticles prepared by precipitation technique was studies in the light of Gaussian confinement model. The values of FWHM, asymmetry ratio and peak position were calculated BOTH experimentally and theoretically. It was found that all these parameters corresponding to 1LO and 2LO optical phonons vary from their bulk counterparts due to the quantum confinement effect.

Chandran, Anoop; Samuel, M. Soosen; Koshy, Jiji; George, K. C.

2011-07-01

410

Protein Simulations in Confined Environments Murat Cetinkaya1  

E-print Network

Protein Simulations in Confined Environments Murat Cetinkaya1 , Jorge Sofo2 , Melik C. Demirel1 1 Calculations, Protein Simulations Abstract Materials surfaces mimic cell like architecture and proteins can of surface interactions, this confine environment could destroy the protein or help it maintain its

Demirel, Melik C.

411

Turbulence and Transport The Secrets of Magnetic Confinement  

E-print Network

Turbulence and Transport The Secrets of Magnetic Confinement Presented by Martin Greenwald MIT statement of the requirements for good confinement and high temperature. In steady state, Fusion Power. · We also need to go from pulses to steady state. PROGRESS HAS BEEN DRAMATIC #12;1 Gravitational

Greenwald, Martin

412

Apparatus for Demonstrating Confined and Unconfined Aquifer Characteristics.  

ERIC Educational Resources Information Center

Students in hydrogeology classes commonly have difficulty appreciating differences between the mechanisms of water release from confined and unconfined aquifers. Describes a simple and inexpensive laboratory model for demonstrating the hydraulic responses of confined and unconfined aquifers to pumping. Includes a worked example to demonstrate the…

Gillham, Robert W.; O'Hannesin, Stephanie F.

1984-01-01

413

Confinement-driven increase in ionomer thin-film modulus.  

PubMed

Ion-conductive polymers, or ionomers, are critical materials for a wide range of electrochemical technologies. For optimizing the complex heterogeneous structures in which they occur, there is a need to elucidate the governing structure-property relationships, especially at nanoscale dimensions where interfacial interactions dominate the overall materials response due to confinement effects. It is widely acknowledged that polymer physical behavior can be drastically altered from the bulk when under confinement and the literature is replete with examples thereof. However, there is a deficit in the understanding of ionomers when confined to the nanoscale, although it is apparent from literature that confinement can influence ionomer properties. Herein we show that as one particular ionomer, Nafion, is confined to thin films, there is a drastic increase in the modulus over the bulk value, and we demonstrate that this stiffening can explain previously observed deviations in materials properties such as water transport and uptake upon confinement. Moreover, we provide insight into the underlying confinement-induced stiffening through the application of a simple theoretical framework based on self-consistent micromechanics. This framework can be applied to other polymer systems and assumes that as the polymer is confined the mechanical response becomes dominated by the modulus of individual polymer chains. PMID:24773397

Page, Kirt A; Kusoglu, Ahmet; Stafford, Christopher M; Kim, Sangcheol; Kline, R Joseph; Weber, Adam Z

2014-05-14

414

TOPICS IN CONFINEMENT ANALYSIS OF TOKAMAKS WITH AUXILIARY HEATING  

E-print Network

TOPICS IN CONFINEMENT ANALYSIS OF TOKAMAKS WITH AUXILIARY HEATING R.J. GOLDSTON Princeton a potpourri of topics in confinement analysis of tokamaks with auxiliary heating. First we discuss, and what are the allowable weaknesses? Next we examine the analysis of plasma rotation experiments, a topic

Princeton Plasma Physics Laboratory

415

Inhibited emission of electromagnetic modes confined in subwavelength cavities  

SciTech Connect

We experimentally demonstrate the active inhibition of subwavelength confined cavity modes emission and quality factor enhancement by controlling the cavity optical surrounding. The intrinsic radiation angular spectrum of modes confined in planar photonics crystal cavities as well as its modifications depending on the environment are inferred via a transfer matrix modeling and k-space imaging.

Le Thomas, N.; Houdre, R. [Institut de Physique de la Matiere Condensee, Ecole Polytechnique Federale de Lausanne (EPFL), Station 3, CH-1015 Lausanne (Switzerland)

2011-07-15

416

Confined space entry program for the Westinghouse Hanford Company  

SciTech Connect

To comply with anticipated OSHA regulatory requirements concerning Permit-Required Confined Spaces, Westinghouse Hanford Company (WHC) created a Confined Spaces Task Team. The primary focus of the task team was to prepare a formal Confined Space Entry (CSE) Program that would ensure full compliance with the anticipated OSHA requirements. A comprehensive training plan was also prepared and submitted for approval as soon as the new CSE Program was approved and released for implementation. On January 14, 1993, OSHA released their final ruling which contained several further changes, requiring the WHC Confined Space Entry Program and Training Plan to be revised. The revised training manual and lessons learned in establishing a Confined Space Entry Program are presented.

Cornell, T.M.

1993-11-01

417

Prediction of Anomalous Blood Viscosity in Confined Shear Flow  

NASA Astrophysics Data System (ADS)

Red blood cells play a major role in body metabolism by supplying oxygen from the microvasculature to different organs and tissues. Understanding blood flow properties in microcirculation is an essential step towards elucidating fundamental and practical issues. Numerical simulations of a blood model under a confined linear shear flow reveal that confinement markedly modifies the properties of blood flow. A nontrivial spatiotemporal organization of blood elements is shown to trigger hitherto unrevealed flow properties regarding the viscosity ?, namely ample oscillations of its normalized value [?]=(?-?0)/(?0?) as a function of hematocrit ? (?0=solvent viscosity). A scaling law for the viscosity as a function of hematocrit and confinement is proposed. This finding can contribute to the conception of new strategies to efficiently detect blood disorders, via in vitro diagnosis based on confined blood rheology. It also constitutes a contribution for a fundamental understanding of rheology of confined complex fluids.

Thiébaud, Marine; Shen, Zaiyi; Harting, Jens; Misbah, Chaouqi

2014-06-01

418

Theory of plasma confinement in non-axisymmetric magnetic fields  

NASA Astrophysics Data System (ADS)

The theory of plasma confinement by non-axisymmetric magnetic fields is reviewed. Such fields are used to confine fusion plasmas in stellarators, where in contrast to tokamaks and reversed-field pinches the magnetic field generally does not possess any continuous symmetry. The discussion is focussed on magnetohydrodynamic equilibrium conditions, collisionless particle orbits, and the kinetic theory of equilbrium and transport. Each of these topics is fundamentally affected by the absence of symmetry in the magnetic field: the field lines need not trace out nested flux surfaces, the particle orbits may not be confined, and the cross-field transport can be very large. Nevertheless, by tailoring the magnetic field appropriately, well-behaved equilibria with good confinement can be constructed, potentially offering an attractive route to magnetic fusion. In this article, the mathematical apparatus to describe stellarator plasmas is developed from first principles and basic elements underlying confinement optimization are introduced.

Helander, Per

2014-08-01

419

Effect of confining overlay in micro scale laser bulge forming  

NASA Astrophysics Data System (ADS)

Micro scale laser bulge forming (?LBF) shows great potential in fabricating high precision and high-aspect-ratio metallic micro components. The present paper investigated the effect of the confining overlay in ?LBF experimentally. The surface morphology of micro bulged parts of pure copper foils with and without confining overlay was explored through the scanning electron microscope. The surface features of quartz glasses with different thickness shocked by single and multiple laser pulses were observed using the optical microscope. The effect of thickness of the confining overlay on the maximum bulging height of micro parts was investigated. Experiments reveal that the application of the confining overlay in ?LBF has significant influence on both the surface morphology and plastic deformation of micro bulged parts. The change of laser ablation mode is responsible for forming results. In addition, there is a moderate thickness of the confining overlay to induce noticeable plastic deformation without failure.

Zheng, Chao; Sun, Sheng; Zhang, Guofang; Song, Libin; Ji, Zhong

2013-11-01

420

Rate effects on layering of a confined linear alkane  

E-print Network

We perform drainage experiments of a linear alkane fluid (n-hexadecane) down to molecular thicknesses, and focus on the role played by the confinement rate. We show that molecular layering is strongly influenced by the velocity at which the confining walls are approached: under high enough shear rates, the confined medium behaves as a structureless liquid of enhanced viscosity for film thickness below $\\sim$10 nm. Our results also lead us to conclude that a rapidly confined film can be quenched in a metastable disordered state, which might be related with recent intriguing results on the shear properties of confined films produced at different rates [Zhu and Granick, Phys. Rev. Lett. {\\bf 93}, 096101 (2004)].

Lionel Bureau

2007-06-19

421

High-field penning-malmberg trap: confinement properties and use in positron accumulation  

SciTech Connect

This dissertation reports on the development of the 60 kG cryogenic positron trap at Lawrence Livermore National Laboratory, and compares the trap`s confinement properties with other nonneutral plasma devices. The device is designed for the accumulation of up to 2{times}10{sup 9} positrons from a linear-accelerator source. This positron plasma could then be used in Bhabha scattering experiments. Initial efforts at time-of-flight accumulation of positrons from the accelerator show rapid ({approximately}100 ms) deconfinement, inconsistent with the long electron lifetimes. Several possible deconfinement mechanisms have been explored, including annihilation on residual gas, injection heating, rf noise from the accelerator, magnet field curvature, and stray fields. Detailed studies of electron confinement demonstrate that the empirical scaling law used to design the trap cannot be extrapolated into the parameter regime of this device. Several possible methods for overcoming these limitations are presented.

Hartley, J.H.

1997-09-01

422

Starlight, a stationary inertial-confinement-fusion reactor with nonvaporizing walls  

Microsoft Academic Search

The Starlight concept for an inertial-confinement-fusion (ICF) reactor utilizes a softball-sized solid-lithium X-ray and debris shield that surrounds each pellet as it is injected into the reactor. The shield is sacrificial and vaporizes as it absorbs X-ray and ion-debris energy emanating from the fusion reactions in the fuel pellet. However, the energy deposition time at the surface of the first

John H. Pitts

1989-01-01

423

Starlight: A stationary inertial-confinement-fusion reactor with nonvaporizing walls  

Microsoft Academic Search

The Starlight concept for an inertial-confinement-fusion (ICF) reactor utilizes a softball-sized solid-lithium x ray and debris shield that surrounds each fuel pellet as it is injected into the reactor. The shield is sacrificial and vaporizes as it absorbs x ray and ion-debris energy emanating from the fusion reactions in the fuel pellets. However, the energy deposition time at the surface

John H. Pitts

1989-01-01

424

Onset of flow in a confined colloidal glass under an imposed shear stress  

E-print Network

A confined colloidal glass, under the imposition of a uniform shear stress, is investigated using numerical simulations. Both at macro- and microscales, the consequent dynamics during the onset of flow is studied. When the imposed stress is gradually decreased, the time scale for the onset of steady flow diverges, associated with long-lived spatial heterogeneities. Near this yield-stress regime, persistent creep in the form of shear-banded structures is observed.

Pinaki Chaudhuri; Jürgen Horbach

2014-10-26

425

Convex lens-induced confinement for imaging single molecules.  

PubMed

Fluorescence imaging is used to study the dynamics of a wide variety of single molecules in solution or attached to a surface. Two key challenges in this pursuit are (1) to image immobilized single molecules in the presence of a high level of fluorescent background and (2) to image freely diffusing single molecules for long times. Strategies that perform well by one measure often perform poorly by the other. Here, we present a simple modification to a wide-field fluorescence microscope that addresses both challenges and dramatically improves single-molecule imaging. The technique of convex lens-induced confinement (CLIC) restricts molecules to a wedge-shaped gap of nanoscale depth, formed between a plano-convex lens and a planar coverslip. The shallow depth of the imaging volume leads to 20-fold greater rejection of background fluorescence than is achieved with total internal reflection fluorescence (TIRF) imaging. Elimination of out-of-plane diffusion leads to an approximately 10,000-fold longer diffusion-limited observation time per molecule than is achieved with confocal fluorescence correlation spectroscopy. The CLIC system also provides a new means to determine molecular size. The CLIC system does not require any nanofabrication, nor any custom optics, electronics, or computer control. PMID:20557026

Leslie, Sabrina R; Fields, Alexander P; Cohen, Adam E

2010-07-15

426

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. PMID:20596407

2009-01-01

427

EDITORIAL: Energetic particles in magnetic confinement systems  

NASA Astrophysics Data System (ADS)

Energetic alpha particle physics plays an obviously crucial role in burning fusion plasmas. Good confinement of them is required to sustain fusion burn and to avoid damage of the first wall. Because of this importance for nuclear fusion research, Y. Kolesnichenko and the late D. Sigmar initiated a series of IAEA technical (committee) meetings (TCM, since the 8th meeting TM) in order to exchange information on the behaviour of energetic particles in magnetic confinement devices. The role of the TMs has become increasingly important since burning plasma projects such as ITER are in preparation. After every TM, invited speakers are encouraged to publish an adapted and extended version of their contributions to the meeting as an article in a special issue of Nuclear Fusion. An exception was the 8th TM the articles of which were published in a special issue of Plasma Physics and Controlled Fusion (2004 46 S1-118). These special issues attract much interest in the subject. The 9th IAEA TM of this series was held in Takayama, Japan, 9-11 November 2005, and 53 papers including 16 invited talks were presented. A total of 11 papers based on these invited talks are included in this special issue of Nuclear Fusion and are preceded by a conference summary. Experimental results of energetic ion driven global instabilities such as Alfvén eigenmodes (AEs), energetic particle modes (EPMs) and fishbone instabilities were presented from several tokamaks (JET, JT-60U, DIII-D and ASDEX Upgrade), helical/stellarator devices (LHD and CHS) and spherical tori (NSTX and MAST). Experimental studies from JET and T-10 tokamaks on the interaction of ion cyclotron waves with energetic ions and runaway electrons were also presented. Theoretical works on AEs, EPMs and nonlinear phenomena induced by energetic particles were presented and compared with experimental data. Extensive numerical codes have been developed and applied to obtain predictions of energetic particle behaviour in future ITER plasmas as well as a tool for design study of future machines. The trend in theoretical code work is to become self-consistent and integrated with a suite of predictive codes. The development of various diagnostics for energetic particle measurements was the subject of many presentations, in particular for burning plasma experiments such as ITER.

Toi, K.

2006-10-01

428

Radiofrequency-heated enhanced confinement modes in the Alcator C-Mod tokamak  

SciTech Connect

Enhanced confinement modes up to a toroidal field of B{sub T}=8T have been studied with up to 3.5 MW of radiofrequency (rf) heating power in the ion cyclotron range of frequencies (ICRF) at 80 MHz. H-mode is observed when the edge temperature exceeds a threshold value. The high confinement mode (H-mode) with higher confinement enhancement factors (H) and longer duration became possible after boronization by reducing the radiated power from the main plasma. A quasi-steady state with high confinement (H=2.0), high normalized beta ({beta}{sub N}=1.5), low radiated power fraction (P{sub rad}{sup main}/P{sub loss}=0.3), and low effective charge (Z{sub eff}=1.5) has been obtained in Enhanced D{sub {alpha}} H-mode. This type of H-mode has enhanced levels of continuous D{sub {alpha}} emission and very little or no edge localized mode (ELM) activity, and reduced core particle confinement time relative to ELM-free H-mode. The pellet enhanced performance (PEP) mode is obtained by combining core fueling with pellet injection and core heating. A highly peaked pressure profile with a central value of 8 atmospheres was observed. The steep pressure gradient drives off-axis bootstrap current, resulting in a shear reversed safety factor (q) profile. Suppression of sawteeth appears to be important in maintaining the highly peaked pressure profile. Lithium pellets were found to be more effective than deuterium pellets in raising q{sub 0}. {copyright} {ital 1997 American Institute of Physics.}

Takase, Y.; Boivin, R.L.; Bombarda, F.; Bonoli, P.T.; Christensen, C.; Fiore, C.; Garnier, D.; Goetz, J.A.; Golovato, S.N.; Granetz, R.; Greenwald, M.; Horne, S.F.; Hubbard, A.; Hutchinson, I.H.; Irby, J.; LaBombard, B.; Lipschultz, B.; Marmar, E.; May, M.; Mazurenko, A.; McCracken, G.; OShea, P.; Porkolab, M.; Reardon, J.; Rice, J.; Rost, C.; Schachter, J.; Snipes, J.A.; Stek, P.; Terry, J.; Watterson, R.; Welch, B.; Wolfe, S. [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)] [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

1997-05-01

429

Liquid injection in confined co-flow: Application to portal vein embolization by glue injection  

NASA Astrophysics Data System (ADS)

Drop formation in liquid-liquid systems has received considerable attention over the last century owing to its many industrial applications. More recent applications may be found in the field of endovascular/percutaneous treatments. The present study focuses on portal vein embolization (PVE), which consists in the blockage of part of the portal trunk though the injection of surgical glue. The short-time injection is dominated by fluid dynamic effects: the influence of polymerization is secondary owing to the presence of ethiodized oil in the injected mixture. If the mechanism of liquid injection is well understood for injections in unconfined fluids at rest, fewer studies have so far considered the case of outer liquids flowing in confined environments. The objective is therefore to conduct a large range parametric study of liquid injections in confined co-flows. An experimental setup has been designed to simulate in vitro the injection in an immiscible liquid flowing in a cylindrical tube. The transition from the dripping to the jetting regimes is found to be independent of confinement, but to depend on the ratio of the inertial forces of the injected liquid to the surface tension, i.e., the Weber number of the inner flow Wei. The confinement, however, has an influence on the drop size in the dripping regime. Its influence diminishes in the first phase of the jetting regime, as the drop size largely decreases. In the fully established jetting regime, the drop size is finally only a function of the ejection tube diameter. To predict the size of the drops in the dripping regime, we have developed a semiempirical model that takes into account the effects of both the tube confinement and outer flow. It will help the interventional radiologists predict the drop size depending on the geometrical and velocimetric conditions at the site of embolization. All these results can then serve as a base to optimize the PVE technique during clinical practice.

Sandulache, M.-C.; Paullier, P.; Bouzerar, R.; Yzet, T.; Balédent, O.; Salsac, A.-V.

2012-08-01

430

Robustness of predator-prey models for confinement regime transitions in fusion plasmas  

NASA Astrophysics Data System (ADS)

Energy transport and confinement in tokamak fusion plasmas is usually determined by the coupled nonlinear interactions of small-scale drift turbulence and larger scale coherent nonlinear structures, such as zonal flows, together with free energy sources such as temperature gradients. Zero-dimensional models, designed to embody plausible physical narratives for these interactions, can help to identify the origin of enhanced energy confinement and of transitions between confinement regimes. A prime zero-dimensional paradigm is predator-prey or Lotka-Volterra. Here, we extend a successful three-variable (temperature gradient; microturbulence level; one class of coherent structure) model in this genre [M. A. Malkov and P. H. Diamond, Phys. Plasmas 16, 012504 (2009)], by adding a fourth variable representing a second class of coherent structure. This requires a fourth coupled nonlinear ordinary differential equation. We investigate the degree of invariance of the phenomenology generated by the model of Malkov and Diamond, given this additional physics. We study and compare the long-time behaviour of the three-equation and four-equation systems, their evolution towards the final state, and their attractive fixed points and limit cycles. We explore the sensitivity of paths to attractors. It is found that, for example, an attractive fixed point of the three-equation system can become a limit cycle of the four-equation system. Addressing these questions which we together refer to as "robustness" for convenience is particularly important for models which, as here, generate sharp transitions in the values of system variables which may replicate some key features of confinement transitions. Our results help to establish the robustness of the zero-dimensional model approach to capturing observed confinement phenomenology in tokamak fusion plasmas.

Zhu, H.; Chapman, S. C.; Dendy, R. O.

2013-04-01

431

Dynamical couplings, dynamical vacuum energy and confinement/deconfinement from R2-gravity  

NASA Astrophysics Data System (ADS)

We study within Palatini formalism an f(R)-gravity with f(R)=R+?R2 interacting with a dilaton and a special kind of nonlinear gauge field system containing a square-root of the standard Maxwell term, which is known to produce confinement in flat space-time. Reformulating the model in the physical Einstein frame we find scalar field effective potential with a flat region where the confinement dynamics disappears, while in other regions it remains intact. The effective gauge couplings as well as the induced cosmological constant become dynamical. In particular, a conventional Maxwell kinetic term for the gauge field is dynamically generated even if absent in the original theory. We find few interesting classes of explicit solutions: (i) asymptotically (anti-)de Sitter black holes of non-standard type with additional confining vacuum electric potential even for the electrically neutral ones; (ii) non-standard Reissner-Nordström black holes with additional constant vacuum electric field and having non-flat-space-time “hedgehog” asymptotics; (iii) generalized Levi-Civita-Bertotti-Robinson “tube-like” space-times.

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

2013-01-01

432

Pure electron plasmas confined for 90 ms in a stellarator without electron sources or internal objects  

SciTech Connect

We report on the creation and up to 90 ms sustainment of pure electron plasmas confined in a stellarator without internal objects. Injection of positrons into such plasmas is expected to lead to the creation of the first electron-positron plasma experiments. These newly created plasmas will also allow a study of pure electron plasmas without the perturbing presence of internal objects. The plasmas were created by thermionic emission of electrons from a heated, biased filament that was retracted in 20 ms. The confinement of these transient plasmas is different from that of steady state plasmas with internal objects and emissive filaments, and is generally shorter, limited by ion buildup. The decay time is increased by lowering the neutral pressure, lowering the electron plasma temperature, or operating with neutrals with high ionization energies (helium). These findings are all consistent with ion accumulation being the cause for the shorter than expected confinement times. The magnetic field strength also moderately increases the decay times. The deleterious effect of ions is not expected to imply a similar deleterious effect when introducing positrons, but it implies that ion accumulation must be avoided also in an electron-positron experiment.

Brenner, P. W.; Sunn Pedersen, T.

2012-05-15

433

Relaxation processes in 8CB confined in cylindrical pores: homeotropic boundary conditions  

NASA Astrophysics Data System (ADS)

Dielectric Spectroscopy (DS) and Dynamic Light Scattering (DLS) were applied to investigate relaxation processes in 8CB confined in 2000 Å cylindrical pores of Anopore membranes treated with lecithin. This treatment provides homeotropic boundary conditions for confined 8CB. The homeotropic alignment of molecules facilitates the investigation of the librational mode using DS. The behavior of this mode is totally different from the behavior observed in investigations of relaxation due to reorientation of molecules around their short axis. The temperature dependence of relaxation times of librational mode could not be described by the Arrhenius law. Instead the interpretation of the results obtained in nematic phase might need the involvement of temperature dependence of orientational order parameter. In the smectic-A phase and the supercooled state the temperature dependence of relaxation times is mainly determined by the variations of viscosity. Two well-defined relaxation processes were observed in DLS experiments for confined 8CB in the nematic phase. The first process is qualitatively associated with bulk-like nematic director fluctuations. The second relaxation process (with relaxation time slower than the first one) is most likely due to the fluctuations in layers nearest to the wall surface, which show the onset of smectic-A phase ordering even though the rest of liquid crystal could be in the nematic phase.

Aliev, Fouad; Basu Majumder, Sarmistha

2002-03-01

434

Deuterium--tritium high confinement (H-mode) studies in the Tokamak Fusion Test Reactor  

SciTech Connect

High or enhanced confinement (H-mode) plasmas have been obtained for the first time with nearly equal concentrations of deuterium and tritium in high-temperature, high poloidal beta plasmas in the Tokamak Fusion Test Reactor (TFTR) [McGuire, Phys. Plasmas {bold 2}, 2176 (1995)]. Tritium fueling was provided mainly through high-power neutral beam injection (NBI) with powers up to 31 MW and beam energies of 90--110 keV. A transition to a circular limiter H-mode configuration has been obtained, following a programmed rapid decrease of the plasma current. Isotope effects, due to the presence of tritium, led to different behavior for deuterium--deuterium (DD) and deuterium--tritium (DT) H-modes relative to confinement, edge localized magnetohydrodynamic modes (ELMs), and ELM effects on fusion products. However, the threshold power for the H-mode transition was the same in DD and DT. Some of the highest values of the global energy confinement time, {tau}{sub {ital E}}, have been achieved on TFTR during the ELM-free phase of DT H-mode plasmas. Enhancements of {tau}{sub {ital E}} greater than four times the L-mode have been attained.

Bush, C.E.; Sabbagh, S.A.; Zweben, S.J.; Bell, R.E.; Synakowski, E.J.; Taylor, G.; Batha, S.; Bell, M.; Bitter, M.; Bretz, N.L.; Budny, R.; Chang, Z.; Darrow, D.S.; Efthimion, P.C.; Ernst, D.; Fredrickson, E.; Hanson, G.R.; Johnson, L.C.; Kesner, J.; LeBlanc, B.; Levinton, F.M.; Mansfield, D.; Mauel, M.E.; Mazzucato, E.; McCune, D.; Murakami, M.; Nazikian, R.; Navratil, G.A.; Park, H.; Paul, S.F.; Phillips, C.K.; Redi, M.H.; Schivell, J.; Scott, S.D.; Skinner, C.H.; Towner, H.H.; Wilgen, J.B.; Zarnstorff, M.C. [Princeton University, Plasma Physics Laboratory, P.O. 451, Princeton, New Jersey 08543 (United States)] [Princeton University, Plasma Physics Laboratory, P.O. 451, Princeton, New Jersey 08543 (United States); the TFTR Group

1995-06-01

435

Effects of polydispersity on confined homopolymer melts: a Monte Carlo study.  

PubMed

New insight into the molecular scale details of polymer melts under confined conditions is obtained from the first dynamic Monte Carlo study incorporating polydispersity. While confinement effects on polymers have been widely explored, little work exists on the effects of polydispersity. This is surprising given the near universal presence of polydispersity in physical systems. To address this shortcoming, a new variation of on-lattice dynamic Monte Carlo simulation is used to provide an understanding of how polydispersity alters confinement effects on polymer melts. Polymer melts of varying polydispersity are simulated between two hard walls (surface interaction parameter, ?(s) = 0) of variable spacing. As plate spacing decreases, polymer chains adopt conformations in which the end-to-end vector is parallel to the hard walls. However, polydisperse melts with the same length average molecular weight, N(w) (which is analogous to the weight average molecular weight, M(w)) show reduced orientation effects. Polydispersity provides greater degrees of freedom; that is, there are more configurations for the system to adopt to accommodate confinement without ordering. At plate spacings of four radii of gyration and only modest polydispersity index values (polydispersity index, PDI = 1.42), the order parameters are reduced by 15% compared to the monodisperse case. The same PDI value corresponds to a 10% reduction in the perturbations of the end-to-end vector and Rouse time. Interestingly, length-based migration effects are observed. Longer chains reside away from the walls and the shorter chains are found nearer the walls; at equilibrium there is a molecular weight based fractionation across the gap. Confinement also leads to a "speeding up" of the polymer dynamics. Altered dynamic phenomena include a reduction of the Rouse time for the same average molecular weight and an altered scaling behavior with plate spacing. Reptation times are also reduced and polydispersity smoothes out the transitions between different scaling regimes. The overall picture that emerges is not unexpected—polydispersity profoundly affects the behavior of confined homopolymers. PMID:25481167

Rorrer, Nicholas A; Dorgan, John R

2014-12-01

436

Light-Front Holographic QCD and the Confinement Potential  

NASA Astrophysics Data System (ADS)

Light-Front Hamiltonian theory, derived from the quantization of the QCD Lagrangian at fixed light-front time ?=t+z/c, provides a rigorous frame-independent framework for solving nonperturbative QCD. The eigenvalues of the light-front QCD Hamiltonian predict the hadronic mass spectrum, and the corresponding eigensolutions provide the light-front wavefunctions which describe hadron structure. The valence Fock-state wavefunctions of the light-front QCD Hamiltonian satisfy a single-variable relativistic equation of motion, analogous to the nonrelativistic radial Schrödinger equation, with an effective confining potential U which systematically incorporates the effects of higher quark and gluon Fock states. In fact, the potential U has a unique form if one requires that the action for zero quark mass remains conformally invariant. We also show that the holographic mapping of gravity in AdS space to QCD with a specific soft-wall dilaton yields the same light-front Schrödinger equation. Light-front holography also leads to a precise relation between the bound-state amplitudes in the fifth dimension z of AdS space and the boost-invariant light-front wavefunctions describing the internal structure of hadrons in physical space-time. The elastic and transition form factors of the pion and the nucleons are found to be well described in this framework. The predictions of the LF equations of motion include a zero-mass pion in the chiral mq?0 limit, and linear Regge trajectories M2(n,L)?n+L with the same slope in the radial quantum number n and orbital angular momentum L. The light-front AdS/QCD holographic approach thus gives a frame-independent representation of color-confining dynamics, Regge spectroscopy, and the excitation spectra of relativistic light-quark meson and baryon bound states in QCD in terms of a single mass parameter. We also briefly discuss the implications of the underlying conformal template of QCD for renormalization scale-setting and the implications of light-front quantization for the value of the cosmological constant.

Brodsky, Stanley J.; de Téramond, Guy F.; Dosch, Hans Günter

2014-06-01

437

Numerical Studies of Properties of Confined Helium  

NASA Technical Reports Server (NTRS)

We carry out state of the art simulations of properties of confined liquid helium near the superfluid transition to a degree of accuracy which allows to make predictions for the outcome of fundamental physics experiments in microgravity. First we report our results for the finite-size scaling behavior of heat capacity of superfluids for cubic and parallel-plate geometry. This allows us to study the crossover from zero and two dimensions to three dimensions. Our calculated scaling functions are in good agreement with recently measured specific heat scaling functions for the above mentioned geometries. We also present our results of a quantum simulation of submonolayer of molecular hydrogen deposited on an ideal graphite substrate using path-integral quantum Monte Carlo simulation. We find that the monolayer phase diagram is rich and very similar to that of helium monolayer. We are able to uncover the main features of the complex monolayer phase diagram, such as the commensurate solid phases and the commensurate to incommensurate transition, in agreement with the experiments and to find some features which are missing from the experimental analysis.

Manousakis, Efstratios

2003-01-01

438

An extragalactic supernebula confined by gravity.  

PubMed

Little is known about the origins of globular clusters, which contain hundreds of thousands of stars in a volume only a few light years across. Radiation pressure and winds from luminous young stars should disperse the star-forming gas and disrupt the formation of the cluster. Globular clusters in our Galaxy cannot provide answers; they are billions of years old. Here we report the measurement of infrared hydrogen recombination lines from a young, forming super star cluster in the dwarf galaxy NGC5253. The lines arise in gas heated by a cluster of about one million stars, including 4,000-6,000 massive, hot 'O' stars. It is so young that it is still enshrouded in gas and dust, hidden from optical view. The gases within the cluster seem bound by gravity, which may explain why the windy and luminous O stars have not yet blown away those gases. Young clusters in 'starbursting' galaxies in the local and distant Universe may also be gravitationally confined and cloaked from view. PMID:12789332

Turner, J L; Beck, S C; Crosthwaite, L P; Larkin, J E; McLean, I S; Meier, D S

2003-06-01

439

Theoretical studies on plasma heating and confinement  

SciTech Connect

Three principal topics are covered in this final report: Stabilization of low frequency modes of an axisymmetric compact torus plasma confinement system, such as, spheromaks and FRC'S, by a population of large orbit axis encircling energetic ions. Employing an extension of the energy principle' which utilizes a Vlasov description for the energetic 'ion component, it has been demonstrated that short wavelength MHD type modes are stabilized while the long wavelength tilt and precessional modes are marginally stable. The deformation of the equilibrium configuration by the energetic ions results in the stabilization of the tilt mode for spheromaks. Formation of Ion Rings and their coalescence with spheromaks. A two dimensional electromagnetic PIC codes has been developed for the study of ion ring formation and its propagation, deformation and slowing down in a cold plasma. It has been shown that a ring moving at a speed less than the Alfven velocity can merge with a stationary spheromak. Anomalous transport from drift waves in a Tokomak. The Direct Interaction Approximation in used to obtain incremental transport coefficients for particles and heat for drift waves in a Tokomak. It is shown that the transport matrix does not obey Onsager's principle.

Sudan, R.N.

1993-01-01

440

Target plane imager for inertial confinement fusion  

SciTech Connect

The Nova laser, completed in December 1984 at Lawrence Livermore National Laboratory, is being used to conduct inertial confinement fusion experiments. It is capable of focusing more than 100 kJ of energy on small fusion targets. This paper discusses an optical system called the target plane imager that is used during the beam alignment phase of these experiments. The TPI includes a three meter long periscope with a wide field of view, F/3 objective. The telescope relays images of the target focal plane to viewing optics and a video sensor located outside the target chamber. Operation of the system is possible at three wavelengths: 1.05..mu.., 0.527..mu.., and 0.351..mu... These are the three wavelengths at which the ten Nova laser beams can irradiate targets. Both nearfield and farfield images of the ten beams can be viewed with the TPI. This instrument is used to properly align the laser to the target before each target irradiation.

Swift, C.D.; Bliss, E.S.; Jones, W.A.; Seppala, L.G.

1985-01-30

441

Confinement-Dependent Friction in Peptide Bundles  

PubMed Central

Friction within globular proteins or between adhering macromolecules crucially determines the kinetics of protein folding, the formation, and the relaxation of self-assembled molecular systems. One fundamental question is how these friction effects depend on the local environment and in particular on the presence of water. In this model study, we use fully atomistic MD simulations with explicit water to obtain friction forces as a single polyglycine peptide chain is pulled out of a bundle of k adhering parallel polyglycine peptide chains. The whole system is periodically replicated along the peptide axes, so a stationary state at prescribed mean sliding velocity V is achieved. The aggregation number is varied between k = 2 (two peptide chains adhering to each other with plenty of water present at the adhesion sites) and k = 7 (one peptide chain pulled out from a close-packed cylindrical array of six neighboring peptide chains with no water inside the bundle). The friction coefficient per hydrogen bond, extrapolated to the viscous limit of vanishing pulling velocity V ? 0, exhibits an increase by five orders of magnitude when going from k = 2 to k = 7. This dramatic confinement-induced friction enhancement we argue to be due to a combination of water depletion and increased hydrogen-bond cooperativity. PMID:23528088

Erba?, Aykut; Netz, Roland R.

2013-01-01

442

Confined placental mosaicisms and uniparental disomy  

SciTech Connect

Approximately 2% of pregnancies studied with chorionic villous sampling (CVS) show confined placental mosaicism (CPM) which persists to term in 50-70% of cases. An increased frequency of complications, such as intrauterine fetal growth restriction or intrauterine death, is observed in these pregnancies. As trisomic zygote rescue is a common mechanism responsible for CPM, fetal uniparental disomy (UPD), resulting from the loss of the extra trisomic chromosome in the embryonic stem cells, would be expected to occur in a proportion of pregnancies with CPM. We have studied 27 pregnancies with CPM involving trisomies for chromosomes 2, 7, 9, 10, 12, and 16 for involvement of specific cell lineage(s) and levels of mosaicism in term placentas. Also, DNA from the parents and infant was analyzed for UPD or biparental disomy (BPD). Five infants with UPD for chromosome 16 and one infant with UPD for chromosome 7 were detected. All other infants showed BPD for the chromosome involved in CPM. For trisomy 16 mosaic gestations, a close correlation between high levels of trisomic cells in placenta and intrauterine fetal growth restriction has been found irrespective of the type of disomy present in the infant. The effect of other trisomies (2, 7, 9, 10, 12) on placental function appears to be similar, but the low numbers of pregnancies studied and lack of detection of UPD for chromosomes 2, 9, 10 and 12 does not allow a definitive conclusion.

Kalousek, D.K.; Langlois, S.; Harrison, K.J. [Univ. of British Columbia, Vancouver (Canada)] [and others

1994-09-01

443

Hydrodynamic instabilities in inertial confinement fusion  

SciTech Connect

The focus of the paper is on buoyancy-driven instabilities of the Rayleigh-Taylor type, which are commonly regarded as the most important kind of hydrodynamic instability in inertial-confinement-fusion implosions. The paper is intended to be pedagogical rather than research-oriented, and so is by no means a comprehensive review of work in this field. Rather, it is hoped that the student will find here a foundation on which to build an understanding of current research, and the experienced researcher will find a compilation of useful results. The aim of the paper is to discuss the evolution of a single Rayleigh-Taylor-unstable mode, from its linear phase to its late-stage constant-velocity bubble growth, with a brief consideration of the saturation of linear growth. The influence of other modes in invoked only in the short-range sense (in wavenumber space) of the Haan saturation model. Owing to limitations of space, the treatment of other instabilities such as Richtmyer-Meshkov and Kelvin-Helmholtz is necessarily very brief, and entirely inadequate as an introductory discussion. Likewise, there is no reference to the effect of convergent geometry, to long-range mode coupling, or to shape effects in three-dimensional growth. Furthermore, there is no reference to the large body of experimental research related to hydrodynamic instabilities.

Hoffman, N.M.

1994-12-01

444

Confinement Studies in High Temperature Spheromak Plasmas  

SciTech Connect

Recent results from the SSPX spheromak experiment demonstrate the potential for obtaining good energy confinement (Te > 350eV and radial electron thermal diffusivity comparable to tokamak L-mode values) in a completely self-organized toroidal plasma. A strong decrease in thermal conductivity with temperature is observed and at the highest temperatures, transport is well below that expected from the Rechester-Rosenbluth model. Addition of a new capacitor bank has produced 60% higher magnetic fields and almost tripled the pulse length to 11ms. For plasmas with T{sub e} > 300eV, it becomes feasible to use modest (1.8MW) neutral beam injection (NBI) heating to significantly change the power balance in the core plasma, making it an effective tool for improving transport analysis. We are now developing detailed designs for adding NBI to SSPX and have developed a new module for the CORSICA transport code to compute the correct fast-ion orbits in SSPX so that we can simulate the effect of adding NBI; initial results predict that such heating can raise the electron temperature and total plasma pressure in the core by a factor of two.

Hill, D N; Mclean, H S; Wood, R D; Casper, T A; Cohen, B I; Hooper, E B; LoDestro, L L; Pearlstein, L D; Romero-Talamas, C

2006-10-23

445

A numerical study of confined turbulent jets  

NASA Technical Reports Server (NTRS)

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 algebraic equation model that relates the Reynolds stresses explicitly to the quadratic terms of the mean velocity gradients and ensures the positiveness of each component of the turbulent kinetic energy. Calculations are carried out with a finite-volume procedure using boundary-fitted curvilinear coordinates. A second-order accurate, bounded convection scheme and sufficiently fine grids are used to prevent the solutions from being contaminated by numerical diffusion. The calculated results are compared extensively with the available experimental data. It is shown that the numerical methods presented are capable of capturing the essential flow features observed in the experiments and that the realizable Reynolds stress algebraic equation model performs much better than the k-epsilon model for this class of flows of great practical importance.

Zhu, J.; Shih, T.-H.

1993-01-01

446

Introducing confinement effects into ultraweak chemiluminescence for an improved sensitivity.  

PubMed

So-called confinement effects at the interface of nanomaterials could spring up unique properties in catalytical activities and optical amplifiers. There is apparently no good reason to disregard confinement effect-amplified chemiluminescence (CL). In this work, confinement effects were first introduced into CL field using cetyltrimethylammonium bromide (CTAB) bilayer aggregates confined at the interface of the CTAB-carbon dots, which were prepared by one-step microwave irradiation using glycerol as carbon source in the presence of CTAB. Interestingly, it was found that the CTAB bilayer confined at the interface of carbon dots can amplify H2O2 induced ultraweak CL emissions, such as the Co(II)-triggered Fenton-like reaction, the peroxynitrous acid (ONOOH) system, and the peroxymonocarbonate (HCO4(-)) system. The study of fluorescent properties of the as-prepared CTAB-carbon dots and the comparison with the CL efficiency of their analogues indicated that the CTAB bilayer confined in carbon dots could act as a special micelle microenvironment, helping the access of reactive intermediates to the central carbon core. Our findings opened up new possibilities in confinement-enhanced CL emissions. PMID:25010336

Dong, Shichao; Zhong, Jinpan; Lu, Chao

2014-08-01

447

Probing cell migration in confined environments by plasma lithography  

PubMed Central

Cellular processes are regulated by various mechanical and physical factors in their local microenvironment such as geometric confinements, cell-substrate interactions, and cell-cell contact. Systematic elucidation of these regulatory mechanisms is crucial for fundamental understanding of cell biology and for rational design of biomedical devices and regenerative medicine. Here, we report a generally applicable plasma lithography technique, which performs selective surface functionalization on large substrate areas, for achieving long-term, stable confinements with length scales from 100 nm to 1 cm toward the investigation of cell-microenvironment interactions. In particular, we applied plasma lithography for cellular confinement of neuroblastomas, myoblasts, endothelial cells, and mammary gland epithelial cells, and examined the motion of mouse embryonic fibroblasts in directionality-confined environments for studying the effect of confinements on migratory behavior. In conjunction with live cell imaging, the distance traveled, velocity, and angular motion of individual cells and collective cell migration behaviors were measured in confined environments with dimensions comparable to a cell. A critical length scale that a cell could conceivably occupy and migrate to was also identified by investigating the behaviors of cells using confined environments with subcellular length scales. PMID:21134692

Junkin, Michael; Wong, Pak Kin

2010-01-01

448

Fusion radioactivity confinement and application to postulated ITER accidents  

SciTech Connect

An assessment of the ITER radioactivity confinement shows reduction of potential accidental releases to the environment by two orders of magnitude. Important credits are the 1% volume/day confinement leakage rate, radioactivity decay for short-lived isotopes, resumption of detritiation/negative pressure within seven days of the accident, and wind meander during the slow confinement leakage. Achieving this two order of magnitude credit in practice requires appropriate design details, especially the leakage rate and detritiation/negative pressure equipment, and research to validate some key assumptions. The confinement maximizes dependence on passive safety features, thereby working toward using fusion's potential safety advantages. The confinement includes several confinement zones with varying human access allowances. Some confinement areas are normally isolated from the environment, the closed ventilation zone. Some areas have an inert cover gas to inhibit combustion. If future assessments of accidental overpressure show the need, we propose a filter/vent system. This report documents our work for the ITER Conceptual Design Activity (CDA). The report is consistent with the final CDA design reports and descriptions, except that our analysis includes a filter/vent. For gaseous or vapor tritium and for most activated aerosols, the reference release fraction is about 2%. For short-lived tungsten-rhenium aerosols, the reference release fraction is somewhat lower, as low as 0.5% for some accident scenarios. Even without resumption of detritiation/decontamination or negative pressure within seven days of the accident, the release fraction for stays below 4%.

Piet, S.J.; Brereton, S.J.

1991-03-01

449