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1

Confinement  

SciTech Connect

The problem of projecting the energy confinement properties of future devices is a lonf standing one in toroidal confinement research. While substantial progress has been made in characterizing the transport properties of tokamaks and stellarators, no definitive understanding of the mechanism(s) of cross-field transport has been achieved. The BPX physics groups, in collaboration with the Transport Task Force and the Doublet III-D (DIII-D) and the Tokamak Fusion Test Reactor (TFTR) experimental teams, has recently begun to explore another avenue of approach, in which dimensionally scaled confinement (eg. confinement time normalized by gyrofrequency [omega][sub c][tau][sub E]) is expressed in terms of key dimensionless variables such a [beta], collisionality [nu], and gyroradius divided by plasma half width [rho]/a. This paper presents the full range of different approaches to projecting the confinement performance of BPX.

Goldston, R.J.; Stotler, D.P.; Bateman, G. (PPPL (United States)); Waltz, R.E. (GA (United States)); Singer, C.E.; Kinsey, J. (Univ. of Illinois (United States))

1992-05-01

2

Progress toward the long time confinement of large positron numbers  

NASA Astrophysics Data System (ADS)

The requirements for, and recent progress toward, the long time confinement of large positron number using a novel microtrap array will be discussed, with reviews of previously published data highlighted in support of the current proposal.

Baker, C. J.; Jennings, J.; Verma, A.; Xu, J.; Weber, M. H.; Lynn, K. G.

2012-04-01

3

Plasma Flow Damping and Confinement Times on MCX  

Microsoft Academic Search

The Maryland Centrifugal eXperiment uses a sixteen-chord Halpha measurement system to measure absolute intensity levels of the Hydrogen Balmer- alpha line in a rotating plasma with mirror magnetic geometry. This newly enhanced multi-chord system has allowed us to characterize neutral Hydrogen behavior at the mid-plane and determine its affect on plasma flow and confinement times. We compare these results with

R. Clary; R. Ellis; A. Hassam; S. H. Choi; R. Elton; C. Teodorescu; I. Uzun-Kaymak; W. Young

2008-01-01

4

Short Lyapunov time: a method for identifying confined chaos  

NASA Astrophysics Data System (ADS)

Context. The orbital instability of minor solar system bodies (asteroids, small satellites, moonlets, and particles) is frequently studied in terms of the Lyapunov characteristic exponent (LCE). Asteroids interior to Jupiter often exihibit very short Lyapunov times, TL, and very large radial variations, becoming Jupiter's crossers and escapers. However, a few cases of asteroids with very short TL and no significant radial variation have been found. These orbits were called “confined chaos” or even “stable chaos”. This feature also appeared in the case of moonlets embedded in Saturn's F ring and disturbed by the nearby satellites Prometheus and Pandora. Aims: We present a simple approach to estimating the contribution of the radial component of the LCE to identify trajectories in the “confined chaos” regime. Methods: To estimate the radial contribution to the maximum LCE, we considered a rotating reference system in which one of the axis was aligned with the radial direction of the reference trajectory. Measuring the distance in the phase space between the two nearby orbits then allowed us to separate the contribution of the radial component from the others. We applied the method to two different dynamical systems: (a) an asteroid around the Sun disturbed by Jupiter; (b) a moonlet of Saturn's F-ring disturbed by the satellites Prometheus and Pandora. Results: In all cases, we found that the method of comparing the radial contribution of the LCE to the entire contribution allows us to correctly distinguish between confined chaos and escapers.

Winter, O. C.; Mourão, D. C.; Giuliatti Winter, S. M.

2010-11-01

5

Confined quantum time of arrival for the vanishing potential  

SciTech Connect

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

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

2005-12-15

6

Modeling the relaxation time of DNA confined in a nanochannel.  

PubMed

Using a mapping between a Rouse dumbbell model and fine-grained Monte Carlo simulations, we have computed the relaxation time of ?-DNA in a high ionic strength buffer confined in a nanochannel. The relaxation time thus obtained agrees quantitatively with experimental data [Reisner et al., Phys. Rev. Lett. 94, 196101 (2005)] using only a single O(1) fitting parameter to account for the uncertainty in model parameters. In addition to validating our mapping, this agreement supports our previous estimates of the friction coefficient of DNA confined in a nanochannel [Tree et al., Phys. Rev. Lett. 108, 228105 (2012)], which have been difficult to validate due to the lack of direct experimental data. Furthermore, the model calculation shows that as the channel size passes below approximately 100?nm (or roughly the Kuhn length of DNA) there is a dramatic drop in the relaxation time. Inasmuch as the chain friction rises with decreasing channel size, the reduction in the relaxation time can be solely attributed to the sharp decline in the fluctuations of the chain extension. Practically, the low variance in the observed DNA extension in such small channels has important implications for genome mapping. PMID:24309551

Tree, Douglas R; Wang, Yanwei; Dorfman, Kevin D

2013-01-01

7

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

8

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 reducin...

Ogilvie, Michael C

2014-01-01

9

Stability and control of a 1D quantum system with confining time dependent delta potentials  

E-print Network

The evolution problem for a quantum particle confined in a 1D box and interacting with one fixed point through a time dependent point interaction is considered. Under suitable assumptions of regularity for the time profile of the Hamiltonian, we prove the existence of strict solutions to the corresponding Schr\\"odinger equation. The result is used to discuss the stability and the steady-state local controllability of the wavefunction when the strenght of the interaction is used as a control parameter.

Andrea Mantile

2010-06-16

10

Sonic Time Reversal Imaging optimization in reverberating, confined or noisy environments  

E-print Network

: Outside views of the car trunk mock-up with AudaxR HM130Z12 loudspeakers mounted on 5 of the 6 sides on the recording of the pressure field and its normal spatial deriva- tive on a time-reversal mirror (TRM in a confined car-trunk mock-up and in a reverberation room. 1 Introduction Sonic time-reversal (TR

Boyer, Edmond

11

Fivefold Confinement Time Increase in MST using Inductive Poloidal Current Drive  

NASA Astrophysics Data System (ADS)

Current profile control is employed in the MST reversed field pinch to reduce the magnetic fluctuation amplitude. Global energy confinement is observed to improve by as much as five times. The dominant transport mechanism in the RFP is magnetic flutter transport. Large amplitude magnetic fluctuations arise due to resistive tearing instabilities and lead to a stochastic magnetic field topology; parallel particle and heat transport along the stochastic field result in rapid radial losses. On MST our strategy for improving confinement is to reduce or eliminate the free energy source for the tearing modes, i.e. the gradient in the parallel current density. The current profile is flattened by application of an inductive poloidal electric field. This method of current profile control, although transient, demonstrates the expected reduction in fluctuation amplitude (as much as 40%), and improvement in global confinement; a MST record low fluctuation amplitude and record high electron temperature (600 eV) were observed simultaneously during current drive experiments. The energy confinement time improves by as much as five times with application of the poloidal current drive pulse. Plasma beta increases by as much as 50% and the Ohmic input power drops by a factor of three or more. Particle confinement improves and plasma impurity contamination is reduced. The results of the transient current drive experiments provide motivation for development of steady-state current drive schemes. Experiments are underway on MST to drive parallel current with electrostatic sources (plasma source electron guns), and experiments using RF current drive in the lower hybrid frequency range are in the development stage. Work supported by USDOE grant No. DE-FG02-96ER54345. In collaboration with J.S. Sarff, S.C. Prager, N.E. Lanier, and the MST Group.

Stoneking, Matthew R.

1996-11-01

12

Heavy ion beam probe operation in time varying equilibria of improved confinement reversed field pinch discharges  

SciTech Connect

Operation of a heavy ion beam probe (HIBP) on a reversed field pinch is unique from other toroidal applications because the magnetic field is more temporal and largely produced by plasma current. Improved confinement, produced through the transient application of a poloidal electric field which leads to a reduction of dynamo activity, exhibits gradual changes in equilibrium plasma quantities. A consequence of this is sweeping of the HIBP trajectories by the dynamic magnetic field, resulting in motion of the sample volume. In addition, the plasma potential evolves with the magnetic equilibrium. Measurement of the potential as a function of time is thus a combination of temporal changes of the equilibrium and motion of the sample volume. A frequent additional complication is a nonideal balance of ion current on the detectors resulting from changes in the beam trajectory (magnetic field) and energy (plasma potential). This necessitates use of data selection criteria. Nevertheless, the HIBP on the Madison Symmetric Torus has acquired measurements as a function of time throughout improved confinement. A technique developed to infer the potential in the improved confinement reversed field pinch from HIBP data in light of the time varying plasma equilibrium will be discussed.

Demers, D. R.; Chen, X.; Schoch, P. M. [Rensselaer Polytechnic Institute, Troy, New York 12180 (United States); Fimognari, P. J. [University of Wisconsin, Madison, Wisconsin 53706 (United States)

2010-10-15

13

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

14

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

15

Fast gas injection as a diagnostic technique for particle confinement time measurements  

NASA Astrophysics Data System (ADS)

The determination of the effective particle confinement time (?p*), i.e., the particle confinement time normalized to recycling coefficient, is difficult when its value is long compared to the discharge duration in magnetically confined plasmas. Recent experiments on the current drive experiment upgrade (CDX-U) spherical torus have successfully achieved a significant reduction in recycling with large-area liquid lithium plasma-facing surfaces. The low recycling walls result in an increase in particle pumping and make it possible to measure ?p* in short duration plasmas. Measurements of ?p* are made using a supersonic gas injector which is closely coupled to plasma. A fast gas pulse is emitted from the supersonic gas injector, after which the density decay is measured using a microwave interferometer. The design of the supersonic gas injector and its configuration on CDX-U will be presented. The results of this technique will be shown as applied to the study of the effects of a liquid lithium toroidal limiter and evaporative lithium coatings on overall plasma density and ?p*.

Gray, T.; Kaita, R.; Majeski, R.; Spaleta, J.; Timberlake, J.

2006-10-01

16

Fast gas injection as a diagnostic technique for particle confinement time measurements  

SciTech Connect

The determination of the effective particle confinement time ({tau}{sub p}*), i.e., the particle confinement time normalized to recycling coefficient, is difficult when its value is long compared to the discharge duration in magnetically confined plasmas. Recent experiments on the current drive experiment upgrade (CDX-U) spherical torus have successfully achieved a significant reduction in recycling with large-area liquid lithium plasma-facing surfaces. The low recycling walls result in an increase in particle pumping and make it possible to measure {tau}{sub p}* in short duration plasmas. Measurements of {tau}{sub p}* are made using a supersonic gas injector which is closely coupled to plasma. A fast gas pulse is emitted from the supersonic gas injector, after which the density decay is measured using a microwave interferometer. The design of the supersonic gas injector and its configuration on CDX-U will be presented. The results of this technique will be shown as applied to the study of the effects of a liquid lithium toroidal limiter and evaporative lithium coatings on overall plasma density and {tau}{sub p}*.

Gray, T.; Kaita, R.; Majeski, R.; Spaleta, J.; Timberlake, J. [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States)

2006-10-15

17

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

18

Influence of ZnO nanorod morphology on optical confinement--finite-difference time-domain numerical simulation study.  

PubMed

We studied the influence of nanorod (NR) morphology on the optical confinement. In order to understand the optical field confinement by the ZnO NR, we obtained the spatial intensity distribution inside/outside the NR by solving Maxwell equations using the finite-difference time-domain numerical simulation. The hexagonal cylinder-shaped NR exhibits a strong confinement and the circular cylinder-shaped NR shows also similar confinement effect. Meanwhile, the rectangular cylinder-shaped NR, the tapered NR, and the NR with sharp cone show a weak confinement of optical field as compared to that of the hexagonal cylinder-shaped NR. Next, as the rod length and/or the rod diameter increase, the high intensity region increases. This suggests that longer nanorod will exhibit more efficient lasing action. PMID:22103166

Kim, Jihye; Lee, Geon Joon; Park, Inkyu; Lee, YoungPak

2011-08-01

19

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

20

Fragile-strong fluid crossover and universal relaxation times in a confined hard-disk fluid.  

PubMed

We show that a system of hard disks confined to a narrow channel exhibits a fragile-strong fluid crossover located at the maximum of the isobaric heat capacity and that the relaxation times for different channel widths fall onto a single master curve when rescaled by the relaxation times and temperatures of the crossover. Calculations of the configurational entropy and the inherent structure equation of state find that the crossover is related to properties of the jamming landscape for the model but that the Adam-Gibbs relation does not predict the relaxation behavior. We also show that a facilitated dynamics description of the system, where kinetically excited regions are identified with local packing arrangements of the disks, successfully describes the fragile-strong crossover. PMID:23368134

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

2012-11-30

21

Particle Confinement Times for Discharges with Lithium Plasma-facing Surfaces in CDX-U  

NASA Astrophysics Data System (ADS)

Recent experiments on the CDX-U spherical torus have successfully achieved a significant reduction in recycling with large-area liquid lithium plasma-facing surfaces. Modeling of low recycling discharges with DEGAS2, a neutral particle transport code, has been performed. Utilizing available spectroscopic data, this modeling allows a calculation of a global particle confinement time (?p) for the low recycling discharges. The ?p values deduced with the modeling were used with ?p^* to obtain the recycling coefficient R. Measurements of ?p^* were performed by using transient gas puffing and observing the time dependence of the plasma density with microwave interferometry. The effects of a liquid lithium toroidal limiter and evaporative lithium coatings on the recycling coefficient R will be presented.

Gray, Tim; Kaita, Robert; Majeski, Richard; Kugel, Henry; Spaleta, Jef; Stotler, Daren; Timberlake, John; Zakharov, Leonid; Soukhanovskii, Vlad; Maingi, Rajesh

2006-10-01

22

Relaxation and short time dynamics of bulk liquids and fluids confined in spherical cavities and slit pores.  

PubMed

The density of states for bulk and confined fluids have been modeled using a recently proposed gamma distribution (Krishnan, S. H.; Ayappa, K. G. J. Chem. Phys. 2004, 121, 3197). The gamma distribution results in a closed form analytical expression for the velocity autocorrelation function and the relaxation time of the fluid. The two parameters of the gamma distribution are related analytically to the second and fourth frequency moments of the fluid using short time expansions. The predictions by the proposed gamma model are compared with the velocity autocorrelation functions obtained using the theory of instantaneous normal modes (INMs) and from molecular dynamics simulations. The model is applied to a bulk soft sphere liquid and fluids confined in a spherical cavity and slit-shaped pores. The gamma model is able to capture the resulting changes in relaxation time due to changes in density and temperature extremely well for both the bulk liquid and confined inhomogeneous fluid situations. In all cases, the predictions by the gamma model are superior to those obtained from the INM theory. In the case of the fluid confined in a slit pore, the loadings were obtained from a grand canonical Monte Carlo simulation where the pore is equilibrated with a bulk fluid. This is similar to a confinement situation in a surface force apparatus. The predicted relaxation times vs pore widths from the gamma model are seen to accurately capture the oscillations due to formation and disruption of layers within the slit pore. PMID:16375288

Krishnan, S H; Ayappa, K G

2005-12-15

23

Measurement of Plasma Energy Confinement Time in Presence of Resonant Helical Field in IR-T1 Tokamak  

NASA Astrophysics Data System (ADS)

Plasma energy confinement time is one of the main parameters of tokamak plasma and Lawson criterion. In this paper we present an experimental method especially based on diamagnetic loop (toroidal flux loop) for measurement of this parameter in presence of resonance helical field (RHF) in IR-T1 tokamak. For this purpose a diamagnetic loop with its compensation coil constructed and installed on outer surface of the IR-T1. Also in this work we measured the plasma current and plasma voltage from the Rogowski coil and poloidal flux loop measurements. Measurement results of plasma energy confinement time with and without RHF ( L = 2, L = 3, L = 2 & 3) show that the addition of a relatively small amount of RHF could be effective for improving the quality of tokamak plasma discharge by flatting the plasma current and increasing the energy confinement time.

Salar Elahi, A.; Ghoranneviss, M.

2009-12-01

24

Short and long time behavior of the Fokker-Planck equation in a confining potential and applications  

E-print Network

Short and long time behavior of the Fokker-Planck equation in a confining potential Introduction and results In this article, we consider the linear Fokker-Planck equation in R2d x,v for d 3 the following result about the (short and) long time behavior of the solution of the Fokker- Planck equation: 2

Hérau, Frédéric

25

One-Dimensional, Time-Dependent, Integral Neutron Transport For Inertial Confinement Fusion  

NASA Astrophysics Data System (ADS)

Neutron transport is of great importance to inertial confinement fusion (ICF) for several reasons. An accurate neutron energy spectrum is necessary for tritium breeding purposes, and the deposition of energy in the ICF target by energetic neutrons born from fusion may have detrimental effects on the fusion burn. The goal of this research was to develop an accurate neutron transport method that can be incorporated into an existing radiation-hydrodynamics code for modeling ICF implosions. A novel time-dependent neutron transport method, based on the integral form of the neutron transport equation, was developed. This method utilizes a dimensionless integration space and the Neumann series method to obtain the integral form of the reduced collisions equations. This neutron transport method was implemented for infinite slab and sphere geometries. Using a pulsed source in space and time, the method was used to reproduce benchmark solutions previously published in the literature, and was found to have excellent agreement with these benchmarks. The method was expanded to incorporate finite slab and sphere geometries. The method was implemented for a finite slab, and benchmarked against PARTISN, a finite difference, discrete-ordinates code. The method was found to agree with PARTISN at intermediate mean free times, while diverging from PARTISN at late mean free times. The method was used to obtain analytic expression for the first two collided fluxes in a finite sphere geometry. A collision study was performed for both geometries to determine how many collisions were necessary to approximate the total flux at early mean free times. This study showed that only a few collisions were necessary to approximate the total flux at times of interest to ICF applications.

Aplin, Carol S.

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

Real-time monitoring of surface-confined platelet activation on TiO?.  

PubMed

For the development of advanced hemocompatible biomaterial functions, there is an unmet demand for in vitro evaluation techniques addressing platelet-surface interactions. We show that the quartz crystal microbalance with dissipation (QCM-D) monitoring technique, here combined with light microscopy, provides a surface sensitive technique that allows for real-time monitoring of the activation and aggregation of the surface-confined platelets on TiO2. The QCM-D signal monitored during adhesion and activation of platelets on TiO2 coated surfaces was found to be different in platelet-poor and platelet-rich environment although light microscopy images taken for each of the two cases looked essentially the same. Interestingly, aggregation of activated platelets was only observed in a protein-rich environment. Our results show that a layer of plasma proteins between the TiO2 surface and the platelets strongly influences the coupling between the platelets and the underlying substrate, explaining both the observed QCM-D signals and the ability of the platelets to aggregate. PMID:24549046

Kunze, Angelika; Hesse, Camilla; Svedhem, Sofia

2014-04-01

28

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

2007-04-24

29

Some Interesting Properties of Metals Confined in Time and Nanometer Space of Different Shapes  

Microsoft Academic Search

The properties of a material depend on the type of motion its electrons can execute, which depends on the space available for them (i.e., on the degree of their spatial confinement). Thus, the properties of each material are characterized by a specific length scale, usually on the nanometer dimension. If the physical size of the material is reduced below this

Mostafa A. El-Sayed

2001-01-01

30

Influence of time, temperature, confining pressure and fluid content on the experimental compaction of spherical grains  

Microsoft Academic Search

Theoretical models of compaction processes, such as for example intergranular pressure-solution (IPS), focus on deformation occurring at the contacts between spherical grains that constitute an aggregate. In order to investigate the applicability of such models, and to quantify the deformation of particles within an aggregate, isostatic experiments were performed in cold-sealed vessels on glass sphere aggregates at 200 MPa confining pressure

Magali Rossi; Olivier Vidal; Bernd Wunder; François Renard

2007-01-01

31

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

32

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

NASA Astrophysics Data System (ADS)

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.

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

2013-03-01

33

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)

The first ever measurements of energy confinement time for spherical tokamak plasmas in the presence of lithium coated plasma facing components (PFC's) have been made in the CDX-U device. The energy confinement time, as derived from power balance considerations using parameters calculated from plasma equilibria, was as large as 6 milliseconds for Ohmic 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 ITER98(y,1) confinement scaling. The improvement in confinement over this scaling correlates with the observed increase in density ``pump-out'', which is indicative of low wall-recycling. Plasma 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 in-situ magnetic field diagnostic calibration that is insensitive to toroidal asymmetries and vessel wall currents.

Spaleta, Jeffrey; Zakharov, Leonid; Majeski, Richard; Kaita, Robert; Gray, Timothy

2006-10-01

34

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

PubMed

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

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

2013-03-01

35

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

36

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

37

Bacteria in Confined Spaces  

NASA Astrophysics Data System (ADS)

Bacterial cells can display differentiation between several developmental pathways, from planktonic to matrix-producing, depending upon the colony conditions. We study the confinement of bacteria in hydrogels as well as in liquid-liquid double emulsion droplets and observe the growth and morphology of these colonies as a function of time and environment. Our results can give insight into the behavior of bacterial colonies in confined spaces that can have applications in the areas of food science, cosmetics, and medicine.

Wilking, Connie; Weitz, David

2010-03-01

38

Effect of time-of-flight bunching on efficiency of light-ion-beam inertial-confinement-fusion transport schemes  

Microsoft Academic Search

The Laboratory Microfusion Facility (LMF) has been proposed for the study of high-gain, high-yield inertial-confinement-fusion targets. The light-ion LMF approach uses a multimodular system with applied-[ital B] extraction diodes as ion sources. A number of ion-beam transport and focusing schemes are being considered to deliver the beams from the diodes to the target. These include ballistic transport with solenoidal lens

P. F. Ottinger; D. V. Rose; C. L. Olson

1994-01-01

39

Effect of time-of-flight bunching on efficiency of light-ion-beam inertial-confinement-fusion transport schemes  

Microsoft Academic Search

The Laboratory Microfusion Facility (LMF) has been proposed for the study of high-gain, high-yield inertial-confinement-fusion targets. The light-ion LMF approach uses a multimodular system with applied-B extraction diodes as ion sources. A number of ion-beam transport and focusing schemes are being considered to deliver the beams from the diodes to the target. These include ballistic transport with solenoidal lens focusing,

P. F. Ottinger; D. V. Rose; C. L. Olson

1994-01-01

40

Isothermal Confinement  

NASA Astrophysics Data System (ADS)

The concept of isothermal confinement is presented. The idea is a revival of the early magnetic fusion concepts with new insight. The plasma core is confined magnetically and is surrounded by a quasi-vacuum region. The temperature of the core is uniform and the turbulence associated with the temperature gradient is absent. The quasi-vacuum region is unstable against the pressure gradient and the turbulent transport rate is much larger than that of the core. Two modes of operation, pulsed and steady state, are considered. Recent experimental results in LHD and CDX-U appear to support the concept.

Ohkawa, Tihiro

41

Estimates of confinement time and energy gain for plasma liner driven magnetoinertial fusion using an analytic self-similar converging shock model  

SciTech Connect

Plasma liner driven magnetoinertial fusion (PLMIF) is a fusion energy concept that utilizes an imploding plasma liner to shock heat and compress a magnetized target plasma to fusion conditions. The fusion burn fraction is linearly proportional to the confinement (or ''dwell'') time of the liner-target system at peak compression, and therefore it is important to estimate the dwell time accurately in order to assess the fusion energy yield and gain. In this work, the dwell time has been estimated using the exact solution to a self-similar converging shock model. The dwell time was found to be determined by the sum of the outgoing shock and rarefaction times through the plasma liner at peak compression, and for chosen PLMIF conditions the dwell time was on the order of 1 {mu}s. In addition, we show that the engineering gain, i.e., the total energy extracted as electricity (from fusion plus expanded liner energy) divided by the electrical energy required to implode the liner, exceeds unity for a wide range of liner thicknesses and specific heat ratios.

Cassibry, J. T.; Cortez, R. J. [Propulsion Research Center, Technology Hall S-226, The University of Alabama in Huntsville, Huntsville, Alabama 35899 (United States); Hsu, S. C. [Physics Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Witherspoon, F. D. [HyperV Technologies Corp., Chantilly, Virginia 20151 (United States)

2009-11-15

42

Thermal noise in confined fluids.  

PubMed

In this work, we discuss a combined memory function equation (MFE) and generalized Langevin equation (GLE) approach (referred to as MFE/GLE formulation) to characterize thermal noise in confined fluids. Our study reveals that for fluids confined inside nanoscale geometries, the correlation time and the time decay of the autocorrelation function of the thermal noise are not significantly different across the confinement. We show that it is the strong cross-correlation of the mean force with the molecular velocity that gives rise to the spatial anisotropy in the velocity-autocorrelation function of the confined fluids. Further, we use the MFE/GLE formulation to extract the thermal force a fluid molecule experiences in a MD simulation. Noise extraction from MD simulation suggests that the frequency distribution of the thermal force is non-Gaussian. Also, the frequency distribution of the thermal force near the confining surface is found to be different in the direction parallel and perpendicular to the confinement. We also use the formulation to compute the noise correlation time of water confined inside a (6,6) carbon-nanotube (CNT). It is observed that inside the (6,6) CNT, in which water arranges itself in a highly concerted single-file arrangement, the correlation time of thermal noise is about an order of magnitude higher than that of bulk water. PMID:25381537

Sanghi, T; Aluru, N R

2014-11-01

43

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

44

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

SciTech Connect

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

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

1991-06-01

45

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

46

Effect of confinement during cookoff of TATB  

NASA Astrophysics Data System (ADS)

In practical scenarios, cookoff of explosives is a three-dimensional transient phenomenon where the rate limiting reactions may occur either in the condensed or gas phase. The effects of confinement are more dramatic when the rate-limiting reactions occur in the gas phase. Explosives can be self-confined, where the decomposing gases are contained within non-permeable regions of the explosive, or confined by a metal or composite container. In triaminotrinitrobenzene (TATB) based explosives, self-confinement is prevalent in plastic bonded explosives at full density. The time-to-ignition can be delayed by orders of magnitude if the reactive gases leave the confining apparatus. Delays in ignition can also occur when the confining apparatus has excess gas volume or ullage. Understanding the effects of confinement is required to accurately model explosive cookoff at various scales ranging from small laboratory experiments to large real systems.

Hobbs, M. L.; Kaneshige, M. J.

2014-05-01

47

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

48

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

49

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

50

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 ...

51

Deriving confinement via RG decimations  

E-print Network

We present the general framework and building blocks of a recent derivation of the fact that the SU(2) LGT is in a confining phase for all values of the coupling $0 < \\beta < \\infty$, for space-time dimension $d \\leq 4$. The method employs approximate but explicitly computable RG decimations that are shown to constrain the exact partition function and order parameters from above and below, and flow from the weak to the strong coupling regime without encountering a fixed point.

E. T. Tomboulis

2007-10-10

52

Hydrodynamics of confined membranes.  

PubMed

We calculate the hydrodynamic interaction Lambdak (Oseen interaction kernel) and relaxation frequency omegak for the fluctuations of a membrane that is harmonically bounded to a permeable or impermeable wall. We show that due to the confining wall there is an increase in the effective viscosity of the fluid surrounding the membrane. This has been observed in experiments on confined membranes, such as lamellar phases and the red-blood cell membrane. Our results allow a quantitative analysis of these experiments, in terms of the strength of the membrane confining potential and dislocations. PMID:15324039

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

2004-07-01

53

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

54

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

55

The Physics Basis of ITER Confinement  

SciTech Connect

ITER will be the first fusion reactor and the 50 year old dream of fusion scientists will become reality. The quality of magnetic confinement will decide about the success of ITER, directly in the form of the confinement time and indirectly because it decides about the plasma parameters and the fluxes, which cross the separatrix and have to be handled externally by technical means. This lecture portrays some of the basic principles which govern plasma confinement, uses dimensionless scaling to set the limits for the predictions for ITER, an approach which also shows the limitations of the predictions, and describes briefly the major characteristics and physics behind the H-mode--the preferred confinement regime of ITER.

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

2009-02-19

56

Fluids in Extreme Confinement  

E-print Network

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

Thomas Franosch; Simon Lang; Rolf Schilling

2012-11-08

57

Dynamics of polymer translocation into an anisotropic confinement  

E-print Network

Using Langevin dynamics simulations, we investigate the dynamics of a flexible polymer translocation into a confined area under a driving force through a nanopore. We choose an ellipsoidal shape for the confinement and consider the dependence of the asymmetry of the ellipsoid measured by the aspect ratio on the translocation time. Compared with an isotropic confinement (sphere), an anisotropic confinement (ellipsoid) with the same volume slows down the translocation, and the translocation time increases with increasing the aspect ratio of the ellipsoid. We further find that it takes different time for polymer translocation into the same ellipsoid through major-axis and minor-axis directions, depending on the average density of the whole chain in the ellipsoid, $\\phi$. For $\\phi$ lower than a critical value $\\phi_c$, the translocation through minor axis is faster, and vice versa. These complicated behaviors are interpreted by the degree of the confinement and anisotropic confinement induced folding of the tran...

Zhang, Kehong

2012-01-01

58

Dynamics of polymer translocation into an anisotropic confinement  

E-print Network

Using Langevin dynamics simulations, we investigate the dynamics of a flexible polymer translocation into a confined area under a driving force through a nanopore. We choose an ellipsoidal shape for the confinement and consider the dependence of the asymmetry of the ellipsoid measured by the aspect ratio on the translocation time. Compared with an isotropic confinement (sphere), an anisotropic confinement (ellipsoid) with the same volume slows down the translocation, and the translocation time increases with increasing the aspect ratio of the ellipsoid. We further find that it takes different time for polymer translocation into the same ellipsoid through major-axis and minor-axis directions, depending on the average density of the whole chain in the ellipsoid, $\\phi$. For $\\phi$ lower than a critical value $\\phi_c$, the translocation through minor axis is faster, and vice versa. These complicated behaviors are interpreted by the degree of the confinement and anisotropic confinement induced folding of the translocated chain.

Kehong Zhang; Kaifu Luo

2012-12-05

59

Water in confined geometries  

Microsoft Academic Search

The dynamics of water molecules in the vicinity of a hydrophilic interface is modified as compared to that of bulk water. Recent experiments performed in porous silica show that water dynamics is well described by a stretched-exponential intermediate-scattering function. The behaviour of confined water is similar to that of supercooled water at lower (≈ 30 K) temperature. This temperature shift

J. Teixeira; J.-M. Zanotti; M.-C. Bellissent-Funel; S.-H. Chen

1997-01-01

60

Water in confined geometries  

Microsoft Academic Search

The dynamics of water molecules in the vicinity of a hydrophilic interface is modified as compared to that of bulk water. Recent experiments performed in porous silica show that water dynamics is well described by a stretched-exponential intermediate-scattering function. The behaviour of confined water is similar to that of supercooled water at lower (? 30 K) temperature. This temperature shift

J. Teixeira; J.-M. Zanotti; M.-C. Bellissent-Funel; S.-H. Chen

1997-01-01

61

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

62

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

63

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

64

Dynamics and energetics of hydrophobically confined water  

NASA Astrophysics Data System (ADS)

The effects of water confined in regions between self-assembling entities is relevant to numerous contexts such as macromolecular association, protein folding, protein-ligand association, and nanomaterials self-assembly. Thus assessing the impact of confined water, and the ability of current modeling techniques to capture the salient features of confined water is important and timely. We present molecular dynamics simulation results investigating the effect of confined water on qualitative features of potentials of mean force describing the free energetics of self-assembly of large planar hydrophobic plates. We consider several common explicit water models including the TIP3P, TIP4P, SPC/E, TIP4P-FQ, and SWM4-NDP, the latter two being polarizable models. Examination of the free energies for filling and unfilling the volume confined between the two plates (both in the context of average number of confined water molecules and “depth” of occupancy) suggests TIP4P-FQ water molecules generally occupy the confined volume at separation distances larger than observed for other models under the same conditions. The connection between this tendency of TIP4P-FQ water and the lack of a pronounced barrier in the potential of mean force for plate-plate association in TIP4P-FQ water is explored by artificially, but systematically, populating the confined volume with TIP4P-FQ water at low plate-plate separation distances. When the critical separation distance [denoting the crossover from an unoccupied (dry) confined interior to a filled (wet) interior] for TIP4P-FQ is reduced by 0.5 Å using this approach, a barrier is observed; we rationalize this effect based on increased resistant forces introduced by confined water molecules at these low separations. We also consider the dynamics of water molecules in the confined region between the hydrophobes. We find that the TIP4P-FQ water model exhibits nonbulklike dynamics, with enhanced lateral diffusion relative to bulk. This is consistent with the reduced intermolecular water-water interaction indicated by a decreased molecular dipole moment in the interplate region. Analysis of velocity autocorrelation functions and associated power spectra indicate that the interplate region for TIP4P-FQ at a plate separation of 14.4 Å approaches characteristics of the pure water liquid-vapor interface. This is in stark contrast to the other water models (including the polarizable SWM4-NDP model).

Bauer, Brad A.; Ou, Shuching; Patel, Sandeep; Siva, Karthik

2012-05-01

65

Dynamics and energetics of hydrophobically confined water.  

PubMed

The effects of water confined in regions between self-assembling entities is relevant to numerous contexts such as macromolecular association, protein folding, protein-ligand association, and nanomaterials self-assembly. Thus assessing the impact of confined water, and the ability of current modeling techniques to capture the salient features of confined water is important and timely. We present molecular dynamics simulation results investigating the effect of confined water on qualitative features of potentials of mean force describing the free energetics of self-assembly of large planar hydrophobic plates. We consider several common explicit water models including the TIP3P, TIP4P, SPC/E, TIP4P-FQ, and SWM4-NDP, the latter two being polarizable models. Examination of the free energies for filling and unfilling the volume confined between the two plates (both in the context of average number of confined water molecules and "depth" of occupancy) suggests TIP4P-FQ water molecules generally occupy the confined volume at separation distances larger than observed for other models under the same conditions. The connection between this tendency of TIP4P-FQ water and the lack of a pronounced barrier in the potential of mean force for plate-plate association in TIP4P-FQ water is explored by artificially, but systematically, populating the confined volume with TIP4P-FQ water at low plate-plate separation distances. When the critical separation distance [denoting the crossover from an unoccupied (dry) confined interior to a filled (wet) interior] for TIP4P-FQ is reduced by 0.5 Å using this approach, a barrier is observed; we rationalize this effect based on increased resistant forces introduced by confined water molecules at these low separations. We also consider the dynamics of water molecules in the confined region between the hydrophobes. We find that the TIP4P-FQ water model exhibits nonbulklike dynamics, with enhanced lateral diffusion relative to bulk. This is consistent with the reduced intermolecular water-water interaction indicated by a decreased molecular dipole moment in the interplate region. Analysis of velocity autocorrelation functions and associated power spectra indicate that the interplate region for TIP4P-FQ at a plate separation of 14.4 Å approaches characteristics of the pure water liquid-vapor interface. This is in stark contrast to the other water models (including the polarizable SWM4-NDP model). PMID:23004766

Bauer, Brad A; Ou, Shuching; Patel, Sandeep; Siva, Karthik

2012-05-01

66

Totally confined explosive welding  

NASA Technical Reports Server (NTRS)

The undesirable by-products of explosive welding are confined and the association noise is reduced by the use of a simple enclosure into which the explosive is placed and in which the explosion occurs. An infrangible enclosure is removably attached to one of the members to be bonded at the point directly opposite the bond area. An explosive is completely confined within the enclosure at a point in close proximity to the member to be bonded and a detonating means is attached to the explosive. The balance of the enclosure, not occupied by explosive, is filled with a shaped material which directs the explosive pressure toward the bond area. A detonator adaptor controls the expansion of the enclosure by the explosive force so that the enclosure at no point experiences a discontinuity in expansion which causes rupture. The use of the technique is practical in the restricted area of a space station.

Bement, L. J. (inventor)

1978-01-01

67

Energy confinement in tokamaks  

SciTech Connect

A straightforward generalization is made of the ohmic heating energy confinement scalings of Pfeiffer and Waltz and Blackwell et. al. The resulting model is systematically calibrated to published data from limiter tokamaks with ohmic, electron cyclotron, and neutral beam heating. With considerably fewer explicitly adjustable free parameters, this model appears to give a better fit to the available data for limiter discharges than the combined ohmic/auxiliary heating model of Goldston.

Sugihara, M.; Singer, C.

1986-08-01

68

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

69

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

70

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

71

Innovative confinement concepts workshop  

SciTech Connect

The Innovative Confinement Concepts Workshop occurred in California during the week preceding the Second Symposium on Current Trends in International Fusion Research. An informal report was made to the Second Symposium. A summary of the Workshop concluded that some very promising ideas were presented, that innovative concept development is a central element of the restructured US DOE. Fusion Energy Sciences program, and that the Workshop should promote real scientific progress in fusion.

Kirkpatrick, R.C.

1998-06-01

72

Classical confined particles  

NASA Technical Reports Server (NTRS)

An alternative picture of classical many body mechanics is proposed. In this picture particles possess individual kinematics but are deprived from individual dynamics. Dynamics exists only for the many particle system as a whole. The theory is complete and allows to determine the trajectories of each particle. It is proposed to use our picture as a classical prototype for a realistic theory of confined particles.

Horzela, Andrzej; Kapuscik, Edward

1993-01-01

73

Theories of quark confinement  

Microsoft Academic Search

It is conjectured that a non-Abelian gauge theory based on the color SU(3) group will confine quarks. Various techniques that have been applied to this question are reviewed. These include approximate methods based on strong coupling expansions of Hamiltonian and Euclidian lattice theories, instanton improvements on perturbation theory, and solutions of truncated Dyson-Schwinger equations for the gauge field propagator. Formal

Myron Bander

1981-01-01

74

Confined vortex scrubber  

SciTech Connect

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

Not Available

1990-05-01

75

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

76

Dynamics of small-molecule glass formers confined in nanopores.  

PubMed

We report a comparative neutron scattering study of the molecular mobility and nonexponential relaxation of three structurally similar glass-forming liquids, isopropanol, propylene glycol, and glycerol, both in bulk and confined in porous Vycor glass. Confinement reduces molecular mobility in all three liquids, and suppresses crystallization in isopropanol. High-resolution quasielastic neutron scattering spectra were fit to Fourier transformed Kohlrausch functions exp[-(t??)(?)], describing the ?-relaxation processes in these liquids. The stretching parameter ? is roughly constant with wavevector Q and over the temperature range explored in bulk glycerol and propylene glycol, but varies both with Q and temperature in confinement. Average relaxation times are longer at lower temperatures and in confinement. They obey a power law ? Q(-?), where the exponent ? is modified by confinement. Comparison of the bulk and confined liquids lends support to the idea that structural and?or dynamical heterogeneity underlies the nonexponential relaxation of glass formers, as widely hypothesized in the literature. PMID:21428631

Prisk, T R; Tyagi, M; Sokol, P E

2011-03-21

77

Dynamics of small-molecule glass formers confined in nanopores  

NASA Astrophysics Data System (ADS)

We report a comparative neutron scattering study of the molecular mobility and nonexponential relaxation of three structurally similar glass-forming liquids, isopropanol, propylene glycol, and glycerol, both in bulk and confined in porous Vycor glass. Confinement reduces molecular mobility in all three liquids, and suppresses crystallization in isopropanol. High-resolution quasielastic neutron scattering spectra were fit to Fourier transformed Kohlrausch functions exp[-(t/?)?], describing the ?-relaxation processes in these liquids. The stretching parameter ? is roughly constant with wavevector Q and over the temperature range explored in bulk glycerol and propylene glycol, but varies both with Q and temperature in confinement. Average relaxation times are longer at lower temperatures and in confinement. They obey a power law ~ Q-?, where the exponent ? is modified by confinement. Comparison of the bulk and confined liquids lends support to the idea that structural and/or dynamical heterogeneity underlies the nonexponential relaxation of glass formers, as widely hypothesized in the literature.

Prisk, T. R.; Tyagi, M.; Sokol, P. E.

2011-03-01

78

Dynamics of ultracold molecules in confined geometry and electric field  

SciTech Connect

We present a time-independent quantum formalism to describe the dynamics of molecules with permanent electric dipole moments in a two-dimensional confined geometry such as a one-dimensional optical lattice, in the presence of an electric field. Bose versus Fermi statistics and selection rules play a crucial role in the dynamics. As examples, we compare the dynamics of confined fermionic and bosonic polar KRb molecules under different confinements and electric fields. We show how chemical reactions can be suppressed, either by a 'statistical suppression' which applies for fermions at small electric fields and confinements, or by a 'potential energy suppression', which applies for both fermions and bosons at high electric fields and confinements. We also explore collisions that transfer molecules from one state of the confining potential to another. Although these collisions can be significant, we show that they do not play a role in the loss of the total number of molecules in the gas.

Quemener, Goulven; Bohn, John L. [JILA, University of Colorado, Boulder, Colorado 80309-0440 (United States)

2011-01-15

79

Magnetic properties of confined bosonic vacuum at finite temperature  

E-print Network

We compute the combined effect of confinement, an external magnetic field and temperature on the vacuum of the charged scalar field using Schwinger's formula for the effective action in the imaginary time formalism. The final result reproduces an effective Lagrangian similar to the Heisenberg-Euler one in the limit of no confinement, in the case of confinement it provides the necessary corrections to this Lagrangian at each order of magnitude of the magnetic field. The results show a finite temperature contribution to the vacum permeability constant apart from the one due to confinement alone.

M. V. Cougo-Pinto; C. Farina; M. R. Negrao

1998-11-10

80

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

81

Magnetic Confinement Fusion Science Status and Challenges  

E-print Network

in fundamental plasma physics and technology · Challenges and opportunities remain #12;Scientific issues the plasma to 100 million degrees · Confining the plasma energy replacement time ~ 1 second for density ~ 1015 cm-3 · Extracting energy from the plasma co-existence of hot plasma and material surface #12

82

Order in very cold confined plasmas  

Microsoft Academic Search

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

Schiffer

1995-01-01

83

Confined vortex scrubber  

SciTech Connect

The program objective is to demonstrate efficient removal of fine particulates to sufficiently low levels to meet proposed small scale coal combustor emission standards using a cleanup technology appropriate to small scale coal combustors. This to be accomplished using a novel particulate removal device, the Confined Vortex Scrubber (CVS), which consists of a cylindrical vortex chamber with tangential flue gas inlets. The clean gas exit is via vortex finder outlets, one at either end of the tube. Liquid is introduced into the chamber and is confined within the vortex chamber by the centrifugal force generated by the gas flow itself. This confined liquid forms a layer through which the flue gas is then forced to bubble, producing a strong gas/liquid interaction, high inertial separation forces and efficient particulate cleanup. During this quarter a comprehensive series of cleanup experiments have been made for three CVS configurations. The first CVS configuration tested gave very efficient fine particulate removal at the design air mass flow rate (1 MM BUT/hr combustor exhaust flow), but had over 20{double prime}WC pressure drop. The first CVS configuration was then re-designed to produce the same very efficient particulate collection performance at a lower pressure drop. The current CVS configuration produces 99.4 percent cleanup of ultra-fine fly ash at the design air mass flow at a pressure drop of 12 {double prime}WC with a liquid/air flow ratio of 0.31/m{sup 3}. Unlike venturi scrubbers, the collection performance of the CVS is insensitive to dust loading and to liquid/air flow ratio.

Not Available

1990-07-01

84

Holographic repulsion and confinement in gauge theory  

E-print Network

We show that for asymptotically anti-deSitter backgrounds with negative energy, such as the AdS soliton and regulated negative mass AdS-Schwarzshild metrics, the Wilson loop expectation value in the AdS/CFT conjecture exhibits a Coulomb to confinement transition. We also show that the quark-antiquark ($q \\bar q$) potential can be interpreted as affine time along null geodesics on the minimal string world sheet,and that its intrinsic curvature provides a signature of transition to confinement phase. The result demonstrates a UV/IR relation in that the boundary separation of the $q \\bar{q}$ pair exhibits an inverse relationship with the radial descent of the world sheet into the bulk. Our results suggest a generic (holographic) relationship between confinement in gauge theory and repulsive gravity, which in turn is connected with singularity avoidance in quantum gravity.

Viqar Husain; Dawood Kothawala

2012-01-27

85

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

86

Preface: Special Topic on Interfacial and Confined Water  

NASA Astrophysics Data System (ADS)

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.

2014-11-01

87

Preface: special topic on interfacial and confined water.  

PubMed

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. PMID:25399165

Molinero, Valeria; Kay, Bruce D

2014-11-14

88

Confinement from correlation functions  

NASA Astrophysics Data System (ADS)

We compute the Polyakov loop potential in Yang-Mills theory from the fully dressed primitively divergent correlation functions only. This is done in a variety of functional approaches ranging from functional renormalization group equations over Dyson-Schwinger equations to two-particle irreducible functionals. We present a confinement criterion that links the infrared behavior of propagators and vertices to the Polyakov loop expectation value. The present work extends the works of [J. Braun , Phys. Lett. B 684, 262 (2010)PYLBAJ0370-2693; F. Marhauser and J. M. Pawlowski, arXiv:0812.1144; J. Braun , Eur. Phys. J. C 70, 689 (2010)EPCFFB1434-6044] to general functional methods and sharpens the confinement criterion presented there. The computations are based on the thermal correlation functions in the Landau gauge calculated in [L. Fister and J. M. Pawlowski, arXiv:1112.5440; L. Fister and J. M. Pawlowski, arXiv:1112.5429; L. Fister, Ph.D. thesis, Heidelberg University, 2012].

Fister, Leonard; Pawlowski, Jan M.

2013-08-01

89

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

90

MHTGR confinement radiation releases  

SciTech Connect

Investigations of the chemical form and transport of two fission products released during selected modular high-temperature gas-cooled reactor (MHTGR) postulated accidents have resulted in the conclusion that estimated doses are reduced by as much as 30% when aerosol deposition and chemical species effects are included. Applying chemical equilibrium principles and collision theory, aerosol removal rates were calculated with MHTGR-NAUA, a modified version of the NAUA Mod-4 light water reactor aerosol analysis computer program. The effect of input assumptions on fission product release and off-site dose was then evaluated with the SCIMCA computer program. Preliminary estimates of radiation releases from an MHTGR during credible accidents are well below existing limits. These low estimated releases provide both a safety and an economic incentive for MHTGR development. For example, it is calculated that a non-pressure-retaining building, such as the confinement design shown could adequately protect the public from radiological releases.

Maneke, J.L.; Lanning, D.D.; Lidsky, L.M.; Oddo, J.M.; Baron, J.S.; Drozd, A.

1986-01-01

91

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

92

Classical impurity ion confinement in a toroidal magnetized fusion plasma.  

PubMed

High-resolution measurements of impurity ion dynamics provide first-time evidence of classical ion confinement in a toroidal, magnetically confined plasma. The density profile evolution of fully stripped carbon is measured in MST reversed-field pinch plasmas with reduced magnetic turbulence to assess Coulomb-collisional transport without the neoclassical enhancement from particle drift effects. The impurity density profile evolves to a hollow shape, consistent with the temperature screening mechanism of classical transport. Corroborating methane pellet injection experiments expose the sensitivity of the impurity particle confinement time to the residual magnetic fluctuation amplitude. PMID:22540593

Kumar, S T A; Den Hartog, D J; Caspary, K J; Magee, R M; Mirnov, V V; Chapman, B E; Craig, D; Fiksel, G; Sarff, J S

2012-03-23

93

Classical Impurity Ion Confinement in a Toroidal Magnetized Fusion Plasma  

NASA Astrophysics Data System (ADS)

High-resolution measurements of impurity ion dynamics provide first-time evidence of classical ion confinement in a toroidal, magnetically confined plasma. The density profile evolution of fully stripped carbon is measured in MST reversed-field pinch plasmas with reduced magnetic turbulence to assess Coulomb-collisional transport without the neoclassical enhancement from particle drift effects. The impurity density profile evolves to a hollow shape, consistent with the temperature screening mechanism of classical transport. Corroborating methane pellet injection experiments expose the sensitivity of the impurity particle confinement time to the residual magnetic fluctuation amplitude.

Kumar, S. T. A.; den Hartog, D. J.; Caspary, K. J.; Magee, R. M.; Mirnov, V. V.; Chapman, B. E.; Craig, D.; Fiksel, G.; Sarff, J. S.

2012-03-01

94

Dynamics of Small-Molecule Glass Formers Confined in Nanopores  

NASA Astrophysics Data System (ADS)

We report a comparative neutron scattering study of the molecular mobility and non-exponential relaxation of three structurally similar glass-forming liquids (isopropanol, propylene glycol, and glycerol) in bulk and confined in porous Vycor glass. Confinement reduces molecular mobility in all three liquids, and suppresses crystallization in isopropanol. High-resolution quasi-elastic neutron scattering spectra were fit to Fourier transformed Kohlrausch functions [-(t/?) ^?], describing ?-relaxation. The stretching parameter ? is roughly constant with wavevector Q and temperature. Average relaxation times are longer at lower temperatures and in confinement. They obey a power law Q^-?, where the exponent ? is modified by both temperature and confinement. Comparison of the bulk and confined liquids lends support to the idea that structural and/or dynamical heterogeneity underlies the non-exponential relaxation of glass- formers, as widely hypothesized in the literature.

Prisk, Timothy; Tyagi, Madhusudan; Sokol, Paul

2011-03-01

95

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

96

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

97

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

98

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

99

Toolbox Safety Talk Confined Spaces  

E-print Network

Toolbox Safety Talk Confined Spaces Environmental Health & Safety Facilities Safety & Health to Environmental Health & Safety for recordkeeping. Many Cornell University facilities and utilities Hazards Other hazards may include electrical hazards, mechanical hazards, chemical hazards, steam hazards

Pawlowski, Wojtek

100

Confined separated-swirling flows in diffusing ducts  

NASA Technical Reports Server (NTRS)

The objective is to establish a detailed experimental data base for evaluation of Navier-Stokes codes for confined separated flows in diffusing s-ducts. The computational thrusts include the following: (1) extension and validation of the LeRC parabolized Navier-Stokes solver, PEPSIG, into the separated flow regime using 'flare' type approximations; (2) evaluation and extensions of state-of-the-art turbulence models for confined separated flow with and without swirl; and (3) evaluation and validation of LeRC time marching 3-D Navier-Stokes code, PROTEUS, into confined separate flow regime. Various aspects of the study are presented in viewgraph form.

Anderson, Bernhard H.

1987-01-01

101

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

102

Effective confining potentials for QCD  

NASA Astrophysics Data System (ADS)

We observe that the linear potential used as a leading approximation for describing color confinement in the instant form of dynamics corresponds to a quadratic confining potential in the front form of dynamics. In particular, the instant-form potentials obtained from lattice gauge theory and string models of hadrons agree with the potentials determined from models using front-form dynamics and light-front holography, not only in their shape, but also in their numerical strength.

Trawi?ski, Arkadiusz P.; G?azek, Stanis?aw D.; Brodsky, Stanley J.; de Téramond, Guy F.; Dosch, Hans Günter

2014-10-01

103

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

104

An Index for Confined Monopoles  

NASA Astrophysics Data System (ADS)

We compute the index and associated spectral density for fluctuation operators which are defined via the Lagrangian of SQCD in the background of non-abelian confined multimonopoles. To this end we generalize the standard index calculations of Callias and Weinberg to the case of asymptotically nontrivial backgrounds. The resulting index is determined by topological charges. We conjecture that this index counts one quarter of the dimension of the moduli space of confined multimonopoles.

Wimmer, Robert

2014-04-01

105

Confined flow of polymer blends.  

PubMed

The influence of confinement on the steady-state morphology of two different emulsions is investigated. The blends, made from polybutene (PB) in polydimethylsiloxane (PDMS) and polybutadiene (PBD) in PDMS, are sheared between two parallel plates, mostly with a standard gap spacing of 40 microm, in the range of shear rates at which the transition from "bulk" behavior toward "confined" behavior is observed. For both cases, the influence of the concentration was systematically investigated, as well as the shear rate effects on the final steady-state morphology. By decreasing the shear rate, for each blend, the increasing droplets, i.e., increasing confinement for a fixed gap spacing, arrange themselves first into two layers, and when the degree of confinement reaches an even higher value, a single layer of droplets is formed. The ratio between the drop diameters and the gap spacing at which this transition occurs is always lower than 0.5. While decreasing the shear rate, the degree of confinement increases due to drop coalescence. Droplets arrange themselves in superstructures like ordered pearl necklaces and, at the lower shear rates, strings. The aspect ratio and the width of the droplet obtained from optical micrographs are compared to predictions of the single droplet Maffettone-Minale model (MM model(1)). It is found that the theory, meant for unconfined shear flow, is not able to predict the drop deformation when the degree of confinement is above a critical value that depends on the blends considered and the shear rate applied. A recently developed extension of the MM model is reported by Minale (M model(2)) where the effect of the confinement is included by using the Shapira-Haber correction.3 Further extending this M model, by incorporating an effective viscosity as originally proposed by Choi and Showalter,4 we arrive at the mM model that accurately describes the experiments of blends in confined flow. PMID:18348582

Tufano, C; Peters, G W M; Meijer, H E H

2008-05-01

106

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

107

Thermonuclear ignition in inertial confinement fusion and comparison with magnetic confinement  

SciTech Connect

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

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

2010-05-15

108

MRT Lattice Boltzmann schemes for confined suspension flows  

NASA Astrophysics Data System (ADS)

We introduce a novel multiple-relaxation time ( modified MRT) Lattice Boltzmann scheme for simulation of confined suspension flow. Via careful tuning of the free eigenvalues of the collision operator we can substantially reduce the error in the so-called hydrodynamic radius. Its performance has been compared to that of the TRT scheme for several benchmark problems. We have found that the optimal value of the free eigenvalue depends on the curvature of the solid-fluid interfaces. Hence, we have investigated suspension flow problems, with confining boundaries of different curvatures. We have found that the modified MRT scheme is better suited for suspension flow in curved confining walls, while the TRT scheme is better for suspension flow confined between planar walls. With both schemes we have investigated problems for confined suspension flows, namely 1) drag forces experienced by spheres flowing in confining flow channels of different cross sections, and 2) the lubrication force between a sedimenting sphere and the end cap of a confining cylindrical capillary.

van der Sman, R. G. M.

2010-09-01

109

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

110

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.

111

Plasma confinement studies in open systems  

NASA Astrophysics Data System (ADS)

Studies in open systems in the world are reviewed from viewpoints of the potential confinement and magnetohydrodynamic (MHD) stability. The tandem mirror GAMMA 10 has shown the potential confinement of a high-ion-temperature plasma from an analysis of the time evolution of end-loss ion current and end-loss ion energy distributions. The central cell density was increased by 50% by the potential confinement. In the HIEI tandem mirror H-mode-like phenomena were observed with an increase in density and diamagnetic signal in a limiter biasing experiment. Potential formation phenomena in plasmas are studied by 0741-3335/41/3A/024/img1-like Upgrade under different magnetic field configurations and plasma conditions. The fully axisymmetric tandem mirror AMBAL-M is under construction and its end mirror system has been assembled. Heating experiments of a plasma gun produced plasma by neutral beam injection and ICRF heating are in progress. The gas dynamic trap (GDT) experiment has successfully produced an MHD-stable high-temperature, high-density plasma. In GOL-3-II, a high-density plasma with several 100 eV temperature is created by powerful relativistic electron beam injection. Construction of HANBIT has been completed and experiments on plasma production and ICRF heating have begun.

Yatsu, Kiyoshi

1999-03-01

112

Status of global energy confinement studies  

SciTech Connect

Empirical scaling expressions, reflecting the parametric dependence of the L-mode energy confinement time, have been used not only as benchmarks for tokamak operation and theories of energy transport, but for predicting the performance of proposed tokamak devices. Several scaling expressions based on data from small-and medium-sized devices have done well in predicting performance in larger devices, although great uncertainty exists in extrapolating yet farther, into the ignition regime. Several approaches exist for developing higher confidence scaling expressions. These include reducing the statistical uncertainty by identifying and filling in gaps in the present database, making use of more sophisticated statistical techniques, and developing scalings for confinement regimes within which future devices will operate. Confidence in the scaling expressions will be increased still if the expressions can be more directly tied to transport physics theory. This can be done through the use of dimensionless parameters, better describing the edge and core confinement regimes separately, and by incorporating transport models directly into the scaling expressions. 50 refs., 5 figs., 3 tabs.

Kaye, S.M.; Bell, M.G. (Princeton Univ., NJ (USA). Plasma Physics Lab.); Barnes, C.W. (Los Alamos National Lab., NM (USA)); DeBoo, J.C.; Waltz, R. (General Atomics Co., San Diego, CA (USA)); Greenwald, M.; Sigmar, D. (Massachusetts Inst. of Tech., Cambridge, MA (USA). Plasma Fusion Center); Riedel, K. (New York Univ., NY (USA). Courant Inst. of Mathematical Sciences); Uckan, N. (Oak Ridge National L

1990-02-01

113

Cosmic ray confinement in fossil cluster bubbles  

E-print Network

Most cool core clusters of galaxies possess active galactic nuclei (AGN) in their centers. These AGN inflate buoyant bubbles containing non-thermal radio emitting particles. If such bubbles efficiently confine cosmic rays (CR) then this could explain ``radio ghosts'' seen far from cluster centers. We simulate the diffusion of cosmic rays from buoyant bubbles inflated by AGN. Our simulations include the effects of the anisotropic particle diffusion introduced by magnetic fields. Our models are consistent with the X-ray morphology of AGN bubbles, with disruption being suppressed by the magnetic draping effect. We conclude that for such magnetic field topologies, a substantial fraction of cosmic rays can be confined inside the bubbles on buoyant rise timescales even when the parallel diffusivity coefficient is very large. For isotropic diffusion at a comparable level, cosmic rays would leak out of the bubbles too rapidly to be consistent with radio observations. Thus, the long confinement times associated with the magnetic suppression of CR diffusion can explain the presence of radio ghosts. We show that the partial escape of cosmic rays is mostly confined to the wake of the rising bubbles, and speculate that this effect could: (1) account for the excitation of the H$\\alpha$ filaments trailing behind the bubbles in the Perseus cluster, (2) inject entropy into the metal enriched material being lifted by the bubbles and, thus, help to displace it permanently from the cluster center and (3) produce observable $\\gamma$-rays via the interaction of the diffusing cosmic rays with the thermal intracluster medium (ICM).

M. Ruszkowski; T. A. Ensslin; M. Bruggen; M. C. Begelman; E. Churazov

2007-05-22

114

CORRELATIONS IN CONFINED QUANTUM PLASMAS  

SciTech Connect

This is the final report for the project 'Correlations in Confined Quantum Plasmas', NSF-DOE Partnership Grant DE FG02 07ER54946, 8/1/2007 - 7/30/2010. The research was performed in collaboration with a group at Christian Albrechts University (CAU), Kiel, Germany. That collaboration, almost 15 years old, was formalized during the past four years under this NSF-DOE Partnership Grant to support graduate students at the two institutions and to facilitate frequent exchange visits. The research was focused on exploring the frontiers of charged particle physics evolving from new experimental access to unusual states associated with confinement. Particular attention was paid to combined effects of quantum mechanics and confinement. A suite of analytical and numerical tools tailored to the specific inquiry has been developed and employed

DUFTY J W

2012-01-11

115

Glass Transition in Confined Geometry  

E-print Network

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 MCT 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 transtion line as a result of the structural changes related to layering.

Simon Lang; Vitalie Botan; Martin Oettel; David Hajnal; Thomas Franosch; Rolf Schilling

2010-08-23

116

Polyelectrolyte stars in planar confinement  

E-print Network

We employ monomer-resolved Molecular Dynamics simulations and theoretical considerations to analyze the conformations of multiarm polyelectrolyte stars close to planar, uncharged walls. We identify three mechanisms that contribute to the emergence of a repulsive star-wall force, namely: the confinement of the counterions that are trapped in the star interior, the increase in electrostatic energy due to confinement as well as a novel mechanism arising from the compression of the stiff polyelectrolyte rods approaching the wall. The latter is not present in the case of interaction between two polyelectrolyte stars and is a direct consequence of the impenetrable character of the planar wall.

Martin Konieczny; Christos N. Likos

2006-03-28

117

Confined Cubic Blue Phases under Shear  

E-print Network

We study the behaviour of confined cubic blue phases under shear flow via lattice Boltzmann simulations. We focus on the two experimentally observed phases, blue phase I and blue phase II. The disinclination network of blue phase II continuously breaks and reforms under shear, leading to an oscillatory stress response in time. The oscillations are only regular for very thin samples. For thicker samples, the shear leads to a "stick-slip" motion of part of the network along the vorticity direction. Blue phase I responds very differently: its defect network undergoes seemingly chaotic rearrangements under shear, irrespective of system size.

O. Henrich; K. Stratford; D. Marenduzzo; P. V. Coveney; M. E. Cates

2011-11-23

118

Confined cubic blue phases under shear.  

PubMed

We study the behaviour of confined cubic blue phases under shear flow via lattice Boltzmann simulations. We focus on the two experimentally observed phases, blue phase I and blue phase II. The disclination network of blue phase II continuously breaks and reforms under shear, leading to an oscillatory stress response in time. The oscillations are only regular for very thin samples. For thicker samples, the shear leads to a 'stick-slip' motion of part of the network along the vorticity direction. Blue phase I responds very differently: its defect network undergoes seemingly chaotic rearrangements under shear, irrespective of system size. PMID:22738991

Henrich, O; Stratford, K; Marenduzzo, D; Coveney, P V; Cates, M E

2012-07-18

119

Inertial Confinement Fusion Experiments & Modeling  

E-print Network

Spectroscopy Ablator Characterization #12;What is Fusion? Fusion is the joining together of small, light nuclei-drive ICF delivers the energy of a laser (or ion beam) not directly to the fuel capsule, but ratherInertial Confinement Fusion Experiments & Modeling Using X-ray Absorption Spectroscopy of Thin

Cohen, David

120

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

121

Biased Diffusion in Confined Media  

Microsoft Academic Search

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

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

2007-01-01

122

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

123

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

124

Predictions of Confinement from ITER Databases  

NASA Astrophysics Data System (ADS)

The tokamak confinement times are related to the tokamak parameters via power laws and linear off-set scaling. We sort the tokamaks in the ITER database in a number of different ways. The sortings are performed according to machine size parameters, i.e. I_p, aB_T, Vol, and their performance parameters Lawson product and fusion triple product. Each time we perform a linear regression fit on the whole data set except for one particular machine. In this way, we can observe the influence of the data set of a particular machine on the empirical formula and extrapolations made for future machines. The influence of one particular machine due to the number of shots is considered, and a new current-weighted database is introduced. In this way, we estimate the ranges of confinement time for the proposed ITER-FEAT and IGNITOR/FIRE tokamak machines. Numerous empirical scaling laws are presently used by scientists and engineers. A model validation method known as the bootstrap test(B. Efron and R. Tibshirani, An Introduction to the Bootstrap) (Chapman & Hall, 1993) is used to ask if there is a statistically significant difference between the predictions between the various empirical formulas.

Hu, B.; Horton, W.; Weigel, R.

2000-10-01

125

Nonlinear viscoelastic dynamics of nano-confined water  

E-print Network

The viscoelastic dynamics of nano-confined water is studied by means of atomic force microscopy (AFM). We observe a nonlinear viscoelastic behavior remarkably similar to that widely observed in metastable complex fluids. We show that the origin of the measured nonlinear viscoelasticity in nano-confined water is a strain rate dependent relaxation time and slow dynamics. By measuring the viscoelastic modulus at different frequencies and strains, we find that the intrinsic relaxation time of nano-confined water is in the range 0.1-0.0001 s, orders of magnitude longer than that of bulk water, and comparable to the dielectric relaxation time measured in supercooled water at 170-210 K.

Tai-De Li; Elisa Riedo

2007-07-17

126

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

127

H-mode confinement of Heliotron J  

NASA Astrophysics Data System (ADS)

The L-H transition in a helical-axis heliotron, Heliotron J, is investigated. For electron cyclotron heating (ECH), neutral beam injection (NBI) heating and ECH + NBI combination heating plasmas, the confinement quality of the H-mode is examined with an emphasis on its magnetic configuration dependence. The vacuum edge rotational transform, ?(a)/2?, is chosen as a label for the magnetic configuration where ?/2? is the rotational transform and a is the average plasma minor radius in metres. The experimental ?(a)/2? dependence of the enhancement factor H_ISS95(=\\tau_{E}^exp/ \\tau_{E}^ISS95) over the L-mode confinement reveals that specific configurations exist where high-quality H-modes (1.3 < HISS95 < 1.8) are attained. \\tau_{E}^exp(s) is the experimental global energy confinement time and \\tau_{E}^ISS95(s) is the confinement time scaling from the international stellarator database given as \\tau_{E}^ISS95=0.079 {a}^{2.21}{ R}^{0.65}{P}_L^{-0.59}\\bar{n}_e^{0.51}{B}_t^{0.83}({\\iota(2a/3)/2\\pi})^{0.4} . R is the plasma major radius in metres, \\bar{n}_e is the line-averaged plasma density in 1019 m-3, PL is the power loss in megawatts that accounts for the time derivative of the total plasma energy content and Bt is the toroidal magnetic field strength in tesla (Stroth U. et al 1996 Nucl. Fusion 36 1063). The ? (a)/2? ranges for these configurations are near values that are slightly less than those of the major natural resonances of Heliotron J, i.e. n/m = 4/8, 4/7 and 12/22. To better understand this configuration dependence, the geometrical poloidal viscous damping rate coefficient, Cp, is calculated for different values of ?(a)/2? and compared with the experimental results. The threshold line-averaged density of the H-mode, which depends on the configuration, is in the region of 0.7-2.0 × 1019 m-3 in ECH (0.29 MW) + NBI (0.57 MW) operation. As for the edge plasma characteristics, Langmuir probe measurements have shown a reduced fluctuation-induced transport in the region that begins inside the last closed flux surface (LCFS) and extends into the scrape-off layer. In addition, a negative radial electric field Er (or Er-shear) is simultaneously formed near the LCFS at the transition.

Sano, F.; Mizuuchi, T.; Kondo, K.; Nagasaki, K.; Okada, H.; Kobayashi, S.; Hanatani, K.; Nakamura, Y.; Yamamoto, S.; Torii, Y.; Suzuki, Y.; Shidara, H.; Kaneko, M.; Arimoto, H.; Azuma, T.; Arakawa, J.; Ohashi, K.; Kikutake, M.; Shimazaki, N.; Hamagami, T.; Motojima, G.; Yamazaki, H.; Yamada, M.; Kitagawa, H.; Tsuji, T.; Nakamura, H.; Watanabe, S.; Murakami, S.; Nishino, N.; Yokoyama, M.; Ijiri, Y.; Senju, T.; Yaguchi, K.; Sakamoto, K.; Tohshi, K.; Shibano, M.

2005-12-01

128

Detonation Diffraction into a Confined Volume  

E-print Network

little attention. Experimental work needs to be conducted on detonation diffraction into a confined volume to better understand how the interaction of the diffracted shock wave with a confining wall impacts the detonation diffraction process. Therefore, a...

Polley, Nolan Lee

2012-02-14

129

Confinement of high temperature plasmas  

US Patent & Trademark Office Database

A high temperature plasma is magnetically confined without leaks or cusps in a smooth toroidal configuration by tangential magnetic field lines on its surface which have a zero rotation number, and include a selected finite even non-zero number of closed toroidal magnetic field lines, which are limit cycles in the sense that all other surface field lines are asympototic to neighboring pairs of these closed field lines, and the poloidal cross-section of the plasma is non-convex. The resulting unique structure makes the confined plasma relatively insensitive to approximations, tolerances, and variations in the parameters of design, construction and operation. Furthermore, use of the sense of averaging appropriate to evaluation of interchange instabilities shows that the resulting magnetic bottle is an optimal toroidal magnetic well.

1980-12-02

130

Characteristic feature of 2p - 2s transition in spherically confined hydrogen atom  

NASA Astrophysics Data System (ADS)

The electronic transition 2p - 2s absent in the free hydrogen atom due to the Coulomb degeneracy becomes feasible when the atom is embedded inside a spherical cavity with impenetrable walls. We show, for the first time, that the oscillator strength corresponding to this transition in the confined state attains its maximum value at the characteristic confinement radius of 2 a.u. at which simultaneous degeneracy also takes place between the confined [ns,(n+1)d] levels with n >= 2.

Stevanovic, Lj.; Sen, K. D.

2008-07-01

131

Quark confinement mechanism for baryons  

E-print Network

The confinement mechanism proposed earlier and then successfully applied to meson spectroscopy by the author is extended over baryons. For this aim the wave functions of baryons are built as tensorial products of those corresponding to the 2-body problem underlying the confinement mechanism of two quarks. This allows one to obtain the Hamiltonian of the quark interactions in a baryon and, accordingly, the possible energy spectrum of the latter. Also one may construct the electric and magnetic form factors of baryon in a natural way which entails the expressions for the root-mean-square radius and anomalous magnetic moment. To ullustrate the formalism in the given Chapter for the sake of simplicity only symmetrical baryons (i.e., composed from three quarks of the same flavours) $\\Delta^{++}$, $\\Delta^{-}$, $\\Omega^-$ are considered. For them the masses, the root-mean-square radii and anomalous magnetic moments are expressed in an explicit analytical form through the parameters of the confining SU(3)-gluonic field among quarks and that enables one to get a number of numerical estimates for the mentioned parameters from experimental data. We also discuss chiral limit for the baryons under consideration and estimate the purely gluonic contribution to their masses. Further the problem of masses in particle physics is shortly discussed within the framework of the given approach. Finally, a few remarks are made about the so-called Yang-Mills Millennium problem and a possible way for proving it is outlined.

Yu. P. Goncharov

2013-12-14

132

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

133

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

134

KrF LASERS FOR INERTiAL CONFINEMENT FUSION  

Microsoft Academic Search

The KrF laser has been proposed for inertial confinement fusion (ICF) since its discovery in 1975. Since that time, the laser has seen significant development and has beer increased in energy many orders of magnitude to the several kilojoule energy level. The suitability of the KrF laser as a driver for ICF energy applications has been continually reviewed. The latest

David B. Harris; David C. CartWright; Joseph F. Figueira; Thomas E. McDonald; Michael E. Sorem

135

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

136

Tritium confinement, retention, and releases at the tritium laboratory Karlsruhe  

SciTech Connect

This paper describes the tritium confinement concept and the tritium retention systems at TLK. A description of the AMOR facility for the regeneration of the HTO loaded molecular sieve beds and the operational experience gained from the regeneration of molecular sieve beds (up to 20 times each) is also presented. Finally tritium releases over this period to the environment will also be given. (authors)

Besserer, U.; Doerr, L.; Glugla, M. [Forschungszentrum Karlsruhe GmbH, Inst. for Technical Physics, Tritium Laboratory Karlsruhe, P.O. Box 3640, D-76021 Karlsruhe (Germany)

2008-07-15

137

The cellular nature of confined spherical propane-air flames  

Microsoft Academic Search

Cellular structures of hydrodynamic origin are observed in laminar propane-air flames confined in a constant volume vessel. The flame structure is observed and the flame speed measured by high speed Schlieren photography. Measured pressure and time data are also used to compute the flame speeds, utilizing a two-zone thermodynamic combustion model. Results show that the onset of the observed cellular

E GROFF

1982-01-01

138

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

Microsoft Academic Search

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

Anwesha Banerjee; Kaushik Basu; Pradeep K. Sengupta

2007-01-01

139

Diffusion of single ellipsoids under quasi-2D confinements  

E-print Network

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 be larger than two, but wall confinement was found to substantially alter diffusion anisotropy and substantially slow particle diffusion along the short axis.

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

2009-03-07

140

Analysis of the ITER H-mode confinement database  

SciTech Connect

In order to predict the global energy confinement time in the next generation of large tokamaks it is essential to have data from machines of different sizes and operating parameter regimes. This data can also be used to construct dimensionless scalings and thereby attempt to differentiate between Bohm and gyro-Bohm based transport models. Previously, at the request of the ITER project, H-mode global confinement data was assembled from six machines ASDEX, DIII-D, JET, JFT-2M, PBX-M, and PDX into a single database. This collaboration has continued with the initial database being expanded by extending the plasma parameter space as well as by improving the precision of some of the relevant calculated plasma parameters. This paper summarizes work that has been performed on the newest version (ITERH.DB2) of the confinement database.

Schissel, D.P.; Kardaun, O.J.W.F.; Ryter, F.; Stroth, U.

1993-05-01

141

Dynamic, multiaxial impact response of confined and unconfined ceramic rods  

SciTech Connect

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

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

1993-09-01

142

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

143

Time?  

NASA Astrophysics Data System (ADS)

The concept of time in the `clockwork' Newtonian world was irrelevant; and has generally been ignored until recently by several generations of physicists since the implementation of quantum mechanics. We will set aside the utility of time as a property relating to physical calculations of events relating to a metrics line element or as an aspect of the transformation of a particles motion/interaction in a coordinate system or in relation to thermodynamics etc., i.e. we will discard all the usual uses of time as a concept used to circularly define physical parameters in terms of other physical parameters; concentrating instead on time as an aspect of the fundamental cosmic topology of our virtual reality especially as it inseparably relates to the nature and role of the observer in natural science.

Amoroso, Richard L.

2013-09-01

144

Electromelting of Confined Monolayer Ice  

NASA Astrophysics Data System (ADS)

In sharp contrast to the prevailing view that electric fields promote water freezing, here we show by molecular dynamics simulations that monolayer ice confined between two parallel plates can melt into liquid water under a perpendicularly applied electric field. The melting temperature of the monolayer ice decreases with the increasing strength of the external field due to the field-induced disruption of the water-wall interaction induced well-ordered network of the hydrogen bond. This electromelting process should add an important new ingredient to the physics of water.

Qiu, Hu; Guo, Wanlin

2013-05-01

145

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

Microsoft Academic Search

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

Anne M Sisto; Ted H Friend

2001-01-01

146

NRC survey on plasma physics and fluids fusion plasma confinement and heating. Chapter 8: Inertial confinement fusion  

NASA Astrophysics Data System (ADS)

A survey of inertial confinement fusion research is presented; current issues are emphasized. The inertial confinement approach to fusion is based on compressing thermonuclear fuel to extremely high density, and heating it to temperatures high enough that the fuel ignites and ''burns' before the compressed mass has time to disassemble. Inertial confinement research also has many other applications related to the physics of high energy density. The irradiation of plasmas by intense laser light allows the stud of many nonlinear processes with applications throughout plasma physics. The generation of pressures of tens to hundreds of megabars (1 megabar equals a million atmospheres) allows the investigation of matter under very high pressures. The generation of highly ionized matter and of intense short pulses of X-rays allows the study of atomic physics of importance in the development of X-ray lasers.

Ripin, B. H.; Kruer, W. L.

1984-06-01

147

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

148

Confinement and Mayer cluster expansions  

NASA Astrophysics Data System (ADS)

In this paper, we study a class of grand-canonical partition functions with a kernel depending on a small parameter ?. This class is directly relevant to Nekrasov partition functions of 𝒩 = 2 SUSY gauge theories on the 4d ?-background, for which ? is identified with one of the equivariant deformation parameter. In the Nekrasov-Shatashvili limit ??0, we show that the free energy is given by an on-shell effective action. The equations of motion take the form of a TBA equation. The free energy is identified with the Yang-Yang functional of the corresponding system of Bethe roots. We further study the associated canonical model that takes the form of a generalized matrix model. Confinement of the eigenvalues by the short-range potential is observed. In the limit where this confining potential becomes weak, the collective field theory formulation is recovered. Finally, we discuss the connection with the alternative expression of instanton partition functions as sums over Young tableaux.

Bourgine, Jean-Emile

2014-05-01

149

On the nonlinear instability of confined geometries  

E-print Network

The discovery of a "weakly-turbulent" instability of anti-de Sitter spacetime supports the idea that confined fluctuations eventually collapse to black holes and suggests that similar phenomena might be possible in asymptotically-flat spacetime, for example in the context of spherically symmetric oscillations of stars or nonradial pulsations of ultracompact objects. Here we present a detailed study of the evolution of the Einstein-Klein-Gordon system in a cavity, with different types of deformations of the spectrum, including a mass term for the scalar and Neumann conditions at the boundary. We provide numerical evidence that gravitational collapse always occurs, at least for amplitudes that are three orders of magnitude smaller than Choptuik's critical value and corresponding to more than $10^5$ reflections before collapse. The collapse time scales as the inverse square of the initial amplitude in the small-amplitude limit. In addition, we find that fields with nonresonant spectrum collapse earlier than in t...

Okawa, Hirotada; Pani, Paolo

2014-01-01

150

Confinement of test particles in warped spacetimes  

SciTech Connect

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

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

2010-07-15

151

Mixed confinement regimes during equilibrium confinement spectroscopy of DNA.  

PubMed

We have used a combination of fluorescence microscopy experiments and Pruned Enriched Rosenbluth Method simulations of a discrete wormlike chain model to measure the mean extension and the variance in the mean extension of ?-DNA in 100 nm deep nanochannels with widths ranging from 100 nm to 1000 nm in discrete 100 nm steps. The mean extension is only weakly affected by the channel aspect ratio. In contrast, the fluctuations of the chain extension qualitatively differ between rectangular channels and square channels with the same cross-sectional area, owing to the "mixing" of different confinement regimes in the rectangular channels. The agreement between experiment and simulation is very good, using the extension due to intercalation as the only adjustable parameter. PMID:24908035

Gupta, Damini; Sheats, Julian; Muralidhar, Abhiram; Miller, Jeremy J; Huang, Derek E; Mahshid, Sara; Dorfman, Kevin D; Reisner, Walter

2014-06-01

152

Optimized confinement of fermions in two dimensions  

NASA Astrophysics Data System (ADS)

One of the challenging features of studying model Hamiltonians with cold atoms in optical lattices is the presence of spatial inhomogeneities induced by the confining potential, which results in the coexistence of different phases.This paper presents quantum Monte Carlo results comparing methods for confining fermions in two dimensions, including conventional diagonal confinement, a recently proposed “off-diagonal confinement”, as well as a trap which produces uniform density in the lattice. At constant entropy and for currently accessible temperatures, we show that (1) diagonal confinement results in the strongest signature of magnetic order, primarily because of its judicious use of entropy sinks at the trap edge and that (2) for d-wave pairing, a trap with uniform density is optimal and can be effectively implemented via off-diagonal confinement. This feature is important to any prospective search for superconductivity in optical lattices.

Cone, J. D.; Chiesa, S.; Rousseau, V. R.; Batrouni, G. G.; Scalettar, R. T.

2012-02-01

153

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

154

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

155

Plasma confinement by a picket-fence  

NASA Technical Reports Server (NTRS)

It is shown that a current-produced line cusp field in a 'picket fence' configuration will confine both primary ionizing electrons and plasma. The 'picket fence' consists of a planar array of equally spaced water-cooled copper tubing with the current alternating in direction. The loss rates of both plasma and primary electrons are shown to be inversely proportional to the fence current. Plasma confinement is found to be much weaker than electron confinement.

Leung, K. N.; Romesser, T.; Hershkowitz, N.

1975-01-01

156

Spatially confined assembly of nanoparticles.  

PubMed

Conspectus 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

157

Colloidal glass transition observed in confinement  

E-print Network

We study a colloidal suspension confined between two quasi-parallel walls as a model system for glass transitions in confined geometries. The suspension is a mixture of two particle sizes to prevent wall-induced crystallization. We use confocal microscopy to directly observe the motion of colloidal particles. This motion is slower in confinement, thus producing glassy behavior in a sample which is a liquid in an unconfined geometry. For higher volume fraction samples (closer to the glass transition), the onset of confinement effects occurs at larger length scales.

Carolyn R. Nugent; Kazem V. Edmond; Hetal N. Patel; Eric R. Weeks

2006-01-28

158

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

159

Enzymatic reactivity of glucose oxidase confined in nanochannels.  

PubMed

The construction of nanodevices coupled with an integrated real-time detection system for evaluation of the function of biomolecules in biological processes, and enzymatic reaction kinetics occurring at the confined space or interface is a significant challenge. In this work, a nanochannel-enzyme system in which the enzymatic reaction could be investigated with an electrochemical method was constructed. The model system was established by covalently linking glucose oxidase (GOD) onto the inner wall of the nanochannels of the porous anodic alumina (PAA) membrane. An Au disc was attached at the end of the nanochannels of the PAA membrane as the working electrode for detection of H2O2 product of enzymatic reaction. The effects of ionic strength, amount of immobilized enzyme and pore diameter of the nanochannels on the enzymatic reaction kinetics were illustrated. The GOD confined in nanochannels showed high stability and reactivity. Upon addition of glucose to the nanochannel-enzyme system, the current response had a calibration range span from 0.005 to 2 mM of glucose concentration. The apparent Michaelis-Menten constant (K(m)(app)) of GOD confined in nanochannel was 0.4 mM. The presented work provided a platform for real-time monitoring of the enzyme reaction kinetics confined in nanospaces. Such a nanochannel-enzyme system could also help design future biosensors and enzyme reactors with high sensitivity and efficiency. PMID:24412427

Yu, Jiachao; Zhang, Yuanjian; Liu, Songqin

2014-05-15

160

Lévy flights in confining potentials.  

PubMed

We analyze confining mechanisms for Lévy flights. When they evolve in suitable external potentials their variance may exist and show signatures of a superdiffusive transport. Two classes of stochastic jump-type processes are considered: those driven by Langevin equation with Lévy noise and those, named topological Lévy processes (occurring in systems with topological complexity such as folded polymers or complex networks), whose Langevin representation is unknown and possibly nonexistent. Our major finding is that both above classes of processes stay in affinity and may share common stationary probability density, even if their detailed dynamical behavior look different. This near-equilibrium observation seems to be generic to a broad class of Lévy noise-driven processes, such as e.g., superdiffusion on folded polymers, geophysical flows, and even climatic changes. PMID:19905068

Garbaczewski, Piotr; Stephanovich, Vladimir

2009-09-01

161

TRANSPORT AND DYNAMICS IN SUPERCOOLED CONFINED WATER  

E-print Network

TRANSPORT AND DYNAMICS IN SUPERCOOLED CONFINED WATER FRANCESCO MALLAMACE,1,2 CARMELO CORSARO,2 SOW Water Dynamic Crossover IV. Recent Experiments on Confined Water A. Nuclear Magnetic Resonance B. Neutron Scattering V. The Breakdown of the Stokes­Einstein Relation VI. The LDL Phase and the Water

Stanley, H. Eugene

162

Plasma confinement. [Physics for magnetic geometries  

SciTech Connect

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

Boozer, A.H.

1985-03-01

163

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

164

MHD-Limits to Plasma Confinement  

Microsoft Academic Search

Ideal MHD restricts both the current and the pressure which can be stably confined in a Tokamak. A pressure profile optimisation is carried out for a variety of equilibria, which include JET and INTOR-like plasmas, in order to obtain the maximum ? which can be stably confined at constant current. The current is limited to a value corresponding to a

F. Troyon; R. Gruber; H. Saurenmann; S. Semenzato; S. Succi

1984-01-01

165

Quark confinement and surface critical phenomena  

SciTech Connect

Surface critical phenomena and the related onset of Goldstone modes probe the fundamental properties of the confining flux in Quantum Chromodynamics. New ideas on surface roughening and their implications for lattice studies of quark confinement are presented. Problems with the oversimplified string description of the Wilson flux sheet are discussed.

K.J. Juge, J. Kuti and C.J. Morningstar

1999-10-20

166

Weapons Activities/ Inertial Confinement Fusion Ignition  

E-print Network

Weapons Activities/ Inertial Confinement Fusion Ignition and High Yield Campaign FY 2012 a safe, secure, and reliable nuclear weapons stockpile without underground testing. Science-based weapons's Budget. Page 105 #12;Weapons Activities/ Inertial Confinement Fusion Ignition and High Yield Campaign FY

167

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

168

Boundaries Matter for Confined Colloidal Glasses  

NASA Astrophysics Data System (ADS)

We confine dense colloidal suspensions within emulsion droplets to examine how confinement and properties of the confining medium affect the colloidal glass transition. Samples are imaged via fast confocal microscopy. By observing a wide range of droplet sizes and varying the viscosity of the external continuous phase, we separate finite size and boundary effects on particle motions within the droplet. Suspensions are composed of binary PMMA spheres in organic solvents while the external phases are simple mixtures of water and glycerol. In analogy with molecular super-cooled liquids and thin-film polymers, we find that confinement effects in colloidal systems are not merely functions of the finite size of the system, but are strongly dependent on the viscosity of the confining medium and interactions between particles and the interface of the two phases.

Hunter, Gary; Edmond, Kazem V.; Weeks, Eric R.

2012-02-01

169

Confinement-induced resonances in anharmonic waveguides  

SciTech Connect

We develop the theory of anharmonic confinement-induced resonances (ACIRs). These are caused by anharmonic excitation of the transverse motion of the center of mass (c.m.) of two bound atoms in a waveguide. As the transverse confinement becomes anisotropic, we find that the c.m. resonant solutions split for a quasi-one-dimensional (1D) system, in agreement with recent experiments. This is not found in harmonic confinement theories. A new resonance appears for repulsive couplings (a{sub 3D}>0) for a quasi-two-dimensional (2D) system, which is also not seen with harmonic confinement. After inclusion of anharmonic energy corrections within perturbation theory, we find that these ACIRs agree extremely well with anomalous 1D and 2D confinement-induced resonance positions observed in recent experiments. Multiple even- and odd-order transverse ACIRs are identified in experimental data, including up to N=4 transverse c.m. quantum numbers.

Peng Shiguo [Department of Physics, Tsinghua University, Beijing 100084 (China); Centre for Atom Optics and Ultrafast Spectroscopy, Swinburne University of Technology, Melbourne 3122 (Australia); Hu Hui; Liu Xiaji; Drummond, Peter D. [Centre for Atom Optics and Ultrafast Spectroscopy, Swinburne University of Technology, Melbourne 3122 (Australia)

2011-10-15

170

29 CFR 1915.76 - Access to cargo spaces and confined spaces.  

Code of Federal Regulations, 2013 CFR

...when fixed ladders in cargo spaces do not meet the requirements...provided for access to cargo spaces shall not be used at the same time that cargo drafts, equipment...intention. (b) Confined spaces. (1) More than one...

2013-07-01

171

29 CFR 1915.76 - Access to cargo spaces and confined spaces.  

Code of Federal Regulations, 2011 CFR

...when fixed ladders in cargo spaces do not meet the requirements...provided for access to cargo spaces shall not be used at the same time that cargo drafts, equipment...intention. (b) Confined spaces. (1) More than one...

2011-07-01

172

29 CFR 1915.76 - Access to cargo spaces and confined spaces.  

Code of Federal Regulations, 2010 CFR

...when fixed ladders in cargo spaces do not meet the requirements...provided for access to cargo spaces shall not be used at the same time that cargo drafts, equipment...intention. (b) Confined spaces. (1) More than one...

2010-07-01

173

29 CFR 1915.76 - Access to cargo spaces and confined spaces.  

Code of Federal Regulations, 2012 CFR

...when fixed ladders in cargo spaces do not meet the requirements...provided for access to cargo spaces shall not be used at the same time that cargo drafts, equipment...intention. (b) Confined spaces. (1) More than one...

2012-07-01

174

Inertial Confinement Fusion Materials Science  

SciTech Connect

Demonstration of thermonuclear ignition and gain on a laboratory scale is one of science's grand challenges. The National Ignition Facility (NIF) is committed to achieving inertial confinement fusion (ICF) by 2010. Success in this endeavor depends on four elements: the laser driver performance, target design, experimental diagnostics performance, and target fabrication and target materials performance. This article discusses the current state of target fabrication and target materials performance. The first three elements will only be discussed insofar as they relate to target fabrication specifications and target materials performance. Excellent reviews of the physics of ICF are given by Lindl [Lindl 1998] and Lindl et al. [Lindl 2004]. To achieve conditions under which inertial confinement is sufficient to achieve thermonuclear burn, an imploded fuel capsule is compressed to conditions of high density and temperature. In the laboratory a driver is required to impart energy to the capsule to effect an implosion. There are three drivers currently being considered for ICF in the laboratory: high-powered lasers, accelerated heavy ions, and x rays resulting from pulsed power machines. Of these, high-powered lasers are the most developed, provide the most symmetric drive, and provide the most energy. Laser drive operates in two configurations. The first is direct drive where the laser energy impinges directly on the ICF capsule and drives the implosion. The second is indirect drive, where the energy from the laser is first absorbed in a high-Z enclosure or hohlraum surrounding the capsule, and the resulting x-rays emitted by the hohlraum material drives the implosion. Using direct drive the laser beam energy is absorbed by the electrons in the outer corona of the target. The electrons transport the energy to the denser shell region to provide the ablation and the resulting implosion. Laser direct drive is generally less efficient and more hydrodynamically unstable than the x-ray driven ablation of indirect drive. The symmetry of the implosion depends sensitively on the balance of the intensity of the individual beams driving the target. Variations in intensity imprint perturbations on the target that are amplified by hydrodynamic instabilities. Indirect drive is less efficient at coupling energy to a capsule than direct drive because of the conversion to x-rays in the hohlraum. However, indirect drive is less sensitive to variations in beam intensity and hydrodynamic instabilities. The ignition threshold for directly-driven and indirectly-driven targets is about the same. However, the gain is calculated to be about a factor of 2 greater in directly driven targets.

Hamza, A V

2004-06-01

175

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

176

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

177

Fast ion confinement in the three-dimensional helical reversed-field pinch  

NASA Astrophysics Data System (ADS)

Fast ions are well confined in the stochastic magnetic field of the multiple-helicity (MH) reversed-field pinch (RFP), with fast ion confinement times routinely a factor of 5 to 10 higher than thermal confinement time. Recent experiments have examined the behavior and confinement of beam-born fast ions in the three-dimensional (3D) helical RFP state. In lower current discharges, where the onset of the helical state is uncertain, high power neutral beam injection (NBI) tends to suppress the transition to the single helicity mode. In high current discharges (Ip ? 0.5 MA), where the onset of n = 5 single helicity is quite robust, a short blip of NBI is used to probe the confinement of fast ions with minimal perturbation to the 3D equilibrium. The fast ion confinement time is measured to be substantially lower than fast ions in comparable MH RFP states, and there is a strong dependence on the strength of the helical perturbation. The established helical equilibrium is stationary in the laboratory frame but the locking occurs over the entire range of possible phase with respect to the Madison Symmetric Torus vessel. This effectively scans both the location of the NBI with respect to the helical structure and the pitch of the NBI-born fast ions. Fast ion confinement is observed to be insensitive to this angle, and in fact counter-NB injection into quasi-single helicity discharges shows fast ion confinement times similar to co-injection cases, in contrast to the MH RFP, where counter-injected fast ion confinement time is substantially lower.

Anderson, J. K.; Capecchi, W.; Eilerman, S.; Koliner, J. J.; Nornberg, M. D.; Reusch, J. A.; Sarff, J. S.; Lin, L.

2014-09-01

178

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

NASA Astrophysics Data System (ADS)

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

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

2013-08-01

179

Investigation of the Influence of Confinement Effect on Regioselectivity as Probed by the Fukui Function  

NASA Astrophysics Data System (ADS)

Spatial confinement is known to influence the electronic structure, the energy spectra and the chemical properties of atoms and molecules. The influence of confinement effects on chemical properties has recently been confirmed via the calculation of global DFT reactivity descriptors (hardness and softness) of atoms and molecules under confined conditions. In this work we investigate for the first time the influence of confinement on the Fukui function—a local reactivity index which can serve as an indicator of regioselectivity. A case study of two molecules (H2CO and C2H4) is presented, by employing a simple potential barrier approach involving a single parameter. The results show an important influence of confinement on the topology of the Fukui function.

Borgoo, A.; De Proft, F.; Geerlings, P.; Tozer, D. J.

2009-08-01

180

Cell migration in confined environments.  

PubMed

We describe a protocol for measuring the speed of human neutrophils migrating through small channels, in conditions of mechanical confinement comparable to those experienced by neutrophils migrating through tissues. In such conditions, we find that neutrophils move persistently, at constant speed for tens of minutes, enabling precise measurements at single cells resolution, for large number of cells. The protocol relies on microfluidic devices with small channels in which a solution of chemoattractant and a suspension of isolated neutrophils are loaded in sequence. The migration of neutrophils can be observed for several hours, starting within minutes after loading the neutrophils in the devices. The protocol is divided into four main steps: the fabrication of the microfluidic devices, the separation of neutrophils from whole blood, the preparation of the assay and cell loading, and the analysis of data. We discuss the practical steps for the implementation of the migration assays in biology labs, the adaptation of the protocols to various cell types, including cancer cells, and the supplementary device features required for precise measurements of directionality and persistence during migration. PMID:24560508

Irimia, Daniel

2014-01-01

181

Human adaptation to isolated and confined environments  

NASA Technical Reports Server (NTRS)

A study was conducted over seven months in a winter Antarctic isolated and confined environment (ICE). Physiological and psychological data was collected several times a week. Information was collected on a monthly basis on behavior and the use of physical facilities. Adaptation and information indicated that there was a significant decrease in epinephrine and norepinephrine during the middle trimester of the winter. No vital changes were found for blood pressure. Self reports of hostility and anxiety show a linear increase. There were no significant changes in depression during ICE. The physiological and psychological data do not move in a synchronous fashion over time. The data also suggest that both ambient qualities of an ICE and discrete social environmental events, such as the arrival of the summer crew, have an impact on the outcome measures used. It may be most appropiate to develop a model for ICE's that incorporates not only global chronic stressors common to all ICE's but also the role of discrete environmental effects which can minimize or enhance the influence of more chronic stressors. Behavioral adjustment information highlight the importance of developing schedules which balance work and recreational activities.

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

1987-01-01

182

Nucleation on active centers in confined volumes.  

PubMed

Kinetic equations describing nucleation on active centers are solved numerically to determine the number of supercritical nuclei, nucleation rate, and the number density of nuclei for formation both of droplets from vapor and also crystalline phase from vapor, solution, and melt. Our approach follows standard nucleation model, when the exhaustion of active centers is taken into account via the boundary condition, and thus no additional equation (expressing exhaustion of active centers) is needed. Moreover, we have included into our model lowering of supersaturation of a mother phase as a consequence of the phase transition process within a confined volume. It is shown that the standard model of nucleation on active centers (Avrami approach) gives faster exhaustion of active centers as compared with our model in all systems under consideration. Nucleation rate (in difference to standard approach based on Avrami model) is equal to the time derivative of the total number of nuclei and reaches some maximum with time. At lower nucleation barrier (corresponding to higher initial supersaturation or lower wetting angle of nucleus on the surface of active center) the exhaustion of active centers is faster. Decrease in supersaturation of the mother phase is faster at higher number of active centers. PMID:22559495

Kožíšek, Zden?k; Hikosaka, Masamichi; Okada, Kiyoka; Demo, Pavel

2012-04-28

183

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

184

Mechanical collapse of confined fluid membrane vesicles.  

PubMed

Compact cylindrical and spherical invaginations are common structural motifs found in cellular and developmental biology. To understand the basic physical mechanisms that produce and maintain such structures, we present here a simple model of vesicles in confinement, in which mechanical equilibrium configurations are computed by energy minimization, balancing the effects of curvature elasticity, contact of the membrane with itself and the confining geometry, and adhesion. For cylindrical confinement, the shape equations are solved both analytically and numerically by finite element analysis. For spherical confinement, axisymmetric configurations are obtained numerically. We find that the geometry of invaginations is controlled by a dimensionless ratio of the adhesion strength to the bending energy of an equal area spherical vesicle. Larger adhesion produces more concentrated curvatures, which are mainly localized to the "neck" region where the invagination breaks away from its confining container. Under spherical confinement, axisymmetric invaginations are approximately spherical. For extreme confinement, multiple invaginations may form, bifurcating along multiple equilibrium branches. The results of the model are useful for understanding the physical mechanisms controlling the structure of lipid membranes of cells and their organelles, and developing tissue membranes. PMID:24700234

Rim, Jee E; Purohit, Prashant K; Klug, William S

2014-11-01

185

NMR investigation of gaseous SF6 confinement into EPDM rubber.  

PubMed

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

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

2005-02-01

186

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

187

Energy confinement studies in the tandem mirror experiment (TMX): Power balance  

SciTech Connect

The power balance in the Tandem Mirror Experiment (TMX) is studied for several days of operation. Between them, these days typified the operating range of TMX. Examining the power balance on axis, it is found that 60% to 100% of the power is carried to the end walls by escaping central-cell ions. Globally, these calculations account for 70% to 100% of the input power on each of the days studied. Based upon the power balance, the energy confinement times of the particle species are calculated. The end-cell ion energy confinement time is similar to that achieved in the 2XIIB single-cell magnetic mirror experiment, whereas the electron energy confinement in TMX was 10 to 100 times better. The central-cell ion energy confinement in the central flux tube was determined by axial particle loss. At the central-cell plasma-edge radial particle transport and charge exchange with the fueling gas are important processes.

Grubb, D.P.; Allen, S.L.; Casper, T.A.

1983-07-01

188

Influence of confinement on polymer-electrolyte relaxational dynamics.  

SciTech Connect

Conception and industrial production of viable high specific energy/power batteries is a central issue for the development of non-polluting vehicles. In terms of stored energy and safety, solid-state devices using polymer electrolytes are highly desirable. One of the most studied systems is PEO (polyethylene oxide) complexed by Li salts. Polymer segmental motions and ionic conductivity are closely related. Bulk PEO is actually a biphasic system where an amorphous and a crystalline state (Tm 335 K) coexist. To improve ionic conduction in those systems requires a significant increase of the amorphous phase fraction where lithium conduction is known to mainly take place. Confinement strongly affects properties of condensed matter and in particular the collective phenomena inducing crystallization. Confinement of the polymer matrix is therefore a possible alternative route to the unpractical use of high temperature. Results of a quasi-elastic incoherent neutron scattering study of the influence of confinement on polyethylene oxide (PEO) and (PEO)8Li+[(CF3SO2)2N]- (or (POE)8LiTFSI) dynamics are presented. The nano-confining media is Vycor, a silica based hydrophilic porous glass (characteristic size of the 3D pore network 50 {angstrom}). As expected, the presence of Li salt slows down the bulk polymer dynamics. The confinement also affects dramatically the apparent mean-square displacement of the polymer. Local relaxational PEO dynamics is described KWW model. We also present an alternate model and show how the detailed polymer dynamics (correlation times and local geometry of the motions) can be described without the use of such stretched exponentials so as to access a rheology-related meaningful physical quantity: the monomeric friction coefficient.

Zanotti, J.-M.; Smith, L. J.; Price, D. L.; Saboungi, M.-L.; Intense Pulsed Neutron Source; Lab. Leon Brillouin (CEA-CRNS); Clark Univ.; CRMHT (CNRS); CRMD (CNRS)

2004-01-01

189

Slow dynamics in cylindrically confined colloidal suspensions  

E-print Network

We study bidisperse colloidal suspensions confined within glass microcapillary tubes to model the glass transition in confined cylindrical geometries. We use high speed three-dimensional confocal microscopy to observe particle motions for a wide range of volume fractions and tube radii. Holding volume fraction constant, we find that particles move slower in thinner tubes. The tube walls induce a gradient in particle mobility: particles move substantially slower near the walls. This suggests that the confinement-induced glassiness may be due to an interfacial effect.

Nabiha Saklayen; Gary L. Hunter; Kazem V. Edmond; Eric R. Weeks

2012-09-05

190

Mechanism of diffusion slowdown in confined liquids.  

PubMed

With the aid of molecular dynamics simulation, we consider why the diffusivity of liquid becomes slower as the liquid is confined to a narrower space. The diffusion coefficient of octamethylcyclotetrasiloxane liquid confined between two mica surfaces was calculated for a range of surface separations from 64 to 23 Å. The resulting separation dependence of the diffusion coefficient can be explained by considering that the molecular diffusion is an activated process. In particular, we find that the increase in the activation energy is closely correlated with the decrease of the potential energy per molecule, from which we propose a molecular-level mechanism of this confined-induced diffusion slowdown. PMID:23215427

Matsubara, Hiroki; Pichierri, Fabio; Kurihara, Kazue

2012-11-01

191

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

192

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

SciTech Connect

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

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

1992-10-01

193

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

SciTech Connect

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

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

1992-10-01

194

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

195

Drift wave models of tokamak confinement  

SciTech Connect

Drift wave models are used to explain the observed tokamak confinement scaling with density, power, size, and magnetic field. Some additional edge mechanism is required to obtain the observed scaling with safety factor and account for H-mode transitions.

Waltz, R.E.; Dominguez, R.R.; Wong, S.K.; Diamond, P.H.; Lee, G.S.; Hahm, T.S.; Mattor, N.

1986-09-01

196

Random walks and polygons in tight confinement  

NASA Astrophysics Data System (ADS)

We discuss the effect of confinement on the topology and geometry of tightly confined random walks and polygons. Here the walks and polygons are confined in a sphere of radius R >= 1/2 and the polygons are equilateral with n edges of unit length. We illustrate numerically that for a fixed length of random polygons the knotting probability increases to one as the radius decreases to 1/2. We also demonstrate that for random polygons (walks) the curvature increases to ?n (?(n – 1)) as the radius approaches 1/2 and that the torsion decreases to ? ?n/3 (? ?(n – 1)/3). In addition we show the effect of length and confinement on the average crossing number of a random polygon.

Diao, Y.; Ernst, C.; Ziegler, U.

2014-10-01

197

A Localization Computation in Confining Phase  

E-print Network

In this note we show that the gaugino condensation of 4d N=1 supersymmetric gauge theories in the confining phase can be computed by the localization technique with an appropriate choice of a supersymmetry generator.

Seiji Terashima

2014-10-14

198

Inertial confinement fusion reactor cavity analysis  

SciTech Connect

This report discusses the following research topics on inertial confinement target chamber design: x-ray vaporization of first wall materials; liquid metal condensation experiment; droplet formation in ICF target chambers; and laboratory microfusion facility calculations.

MacFarlane, J.J.; Peterson, R.R.; Corradini, M.L.; Moses, G.A.; Bang, K.H.; Barry, J.J.

1989-07-01

199

Weapons Activities/ Inertial Confinement Fusion Ignition  

E-print Network

Weapons Activities/ Inertial Confinement Fusion Ignition and High Yield Campaign FY 2011, and reliability of the Nation's nuclear weapons without nuclear testing. The program provides this capability and pulsed power facilities. Science- based weapons assessments and certification requires

200

Entropic force on granular chains self-extracting from one-dimensional confinement.  

PubMed

The entropic forces on the self-retracting granular chains, which are confined in channels with different widths, are determined. The time dependence of the length of chain remaining in the channel Lin(t) is measured. The entropic force is treated as the only parameter in fitting the solution of the nonlinear equation of motion of Lin(t) to the experimental data. The dependence of the entropic force on the width of the confining channel can be expressed as a power-law with an exponent of 1.3, which is consistent with the previous theoretical predictions for the entropy loss due to confinement. PMID:24437916

Jeng, Pei-Ren; Chen, KuanHua; Hwang, Gwo-jen; Cho, Ethan Y; Lien, Chenhsin; To, Kiwing; Chou, Y C

2014-01-14

201

Vorticity confinement technique for drag prediction  

NASA Astrophysics Data System (ADS)

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

Povitsky, Alex; Snyder, Troy

2011-11-01

202

Simulation of Spheromak Confinement Physics Using NIMROD*  

NASA Astrophysics Data System (ADS)

Three-dimensional, time-dependent, nonlinear resistive MHD equations are solved in the NIMROD code[1] addressing spheromak formation, evolution, and stability. We are using NIMROD to assess the quality of spheromak magnetic surfaces with pulsed electrostatic drive and making comparisons to the SSPX experiment. Many features in the simulations are quite similar to experimental observations. NIMROD shows that pulsing the driving electrostatic field can allow the field lines to close in between pulses, and larger closed flux volumes can be created on successive pulses. The results of a series of simulations exploring scaling with respect to decreasing resistivity and increasing Lundquist number, and the sensitivity to thermal conduction rates and kinematic viscosity are presented. Geometry is another important influence on MHD activity that is being explored. Of particular interest is the morphology of modes that break toroidal symmetry, which play a vital role in spheromak formation and affect confinement, but whose relaxation/suppression is required for closed flux surfaces to form. This work was performed at the Univ. Calif. LLNL under US DOE contract W-7405-ENG-48 and at U. Wisconsin under contract DE-FC02ER54668. [1] C.R. Sovinec, J.M. Finn, and D. Del-Castillo-Negrete, Phys. Plasmas 8, 475 (2001).

Cohen, B. I.; Cohen, R. H.; Fowler, T. K.; Ryutov, D. D.; Woodruff, S.; Sovinec, C. R.; Cone, G. A.

2003-10-01

203

Combining confinement and conventional beef production  

E-print Network

COMBINING CONFINEMENT AND CONVENTIONAL BEEF PRODUCTION A PROFESSIONAL PAPER by Michael Ronald Gregg Submitted to the College of Agriculture of Texas A&M University in partial fulfillment of the requirements for the degree of MASTER... OF AGRICULTURE December, 1985 Major Subject: Animal Science Department of Animal Science COMBINING CONFINEMENT AND CONVENTIONAL BEEF PRODUCTION A PROFESSIONAL PAPER by Michael Ronald Gregg Approved as to style and content by: Chairman, Advzso ommit ee...

Gregg, Michael Ronald

2012-06-07

204

Confined Bilayers Passively Regulate Shape and Stress  

NASA Astrophysics Data System (ADS)

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

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

2013-01-01

205

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

206

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

207

Symmetry-Adapted Rotator Functions for Molecules in Cylindrical Confinement  

PubMed Central

We present a general description of the formalism of symmetry-adapted rotator functions (SARFs) for molecules in cylindrical confinement. Molecules are considered as clusters of interaction centers (ICs), can have any symmetry, and can display different types of ICs. Cylindrical confinement can be realized by encapsulation in a carbon nanotube (CNT). The potential energy of a molecule surrounded by a CNT can be calculated by evaluating a limited number of terms of an expansion into SARFs, which offers a significant reduction of the computation time. Optimal molecular orientations can be deduced from the resulting potential energy landscape. Examples, including the case of a molecule with cubic symmetry inside a CNT, are discussed. PMID:21339988

Verberck, Bart

2011-01-01

208

Study of eliminating fire dampers to maintain process confinement  

SciTech Connect

Fire dampers are required by NFPA 90A to maintain the integrity of fire areas. However, several fire dampers in the Defense Waste Processing Facility (DWPF) Vitrification Building at the Savannah River site are proposed to be eliminated in order to maintain the integrity of the process confinement system. In accordance with NFPA (1989), the closing operation of each fire damper should be tested biannually. Fire damper testing must consider the situation where there is a damper hangup in tripping or resetting taking several minutes or more. A fire will also close these dampers. Bechtel performed a fire damper simulation study of the heating, ventilation, and air conditioning (HVAC) system with a computer model. The study showed that 39 of 103 fire dampers, closed one at a time, causes ventilation system backflow, which upsets the integrity of the process confinement system. Elimination of the fire dampers will prevent a backflow upset.

Davis, P.L. (Westinghouse Savannah River Co., Aiken, SC (United States)); Walling, R.C.; Patel, J.B.; Strunk, A.J.

1991-01-01

209

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

210

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

211

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

212

Photon-assisted confinement-induced resonances for ultracold atoms  

E-print Network

We solve the two-particle s-wave scattering for an ultracold atom gas confined in a quasi-one-dimensional trapping potential which is periodically modulated. The interaction between the atoms is included in terms of Fermi's pseudopotential. For a modulated isotropic transverse harmonic confinement, the atomic center of mass and relative degrees of freedom decouple and an exact solution is possible. We use the Floquet approach to show that additional photon-assisted resonant scattering channels open up due to the harmonic modulation. Applying the Bethe-Peierls boundary condition, we obtain the general scattering solution of the time-dependent Schr\\"odinger equation which is universal at low energies. The binding energies and the effective one-dimensional scattering length can be controlled by the external driving.

Leyton, Vicente; Peano, Vittorio; Thorwart, Michael

2014-01-01

213

Photon-assisted confinement-induced resonances for ultracold atoms.  

PubMed

We solve the two-particle s-wave scattering for an ultracold-atom gas confined in a quasi-one-dimensional trapping potential which is periodically modulated. The interaction between the atoms is included via Fermi's pseudopotential. For a modulated isotropic transverse harmonic confinement, the atomic center of mass and relative degrees of freedom decouple and an exact solution is possible. The modulation opens additional photon-assisted resonant scattering channels. Applying the Bethe-Peierls boundary condition, we obtain the general scattering solution of the time-dependent Floquet-Schrödinger equation which is universal at low energies. The effective one-dimensional scattering length can be controlled by the external driving. PMID:24972205

Leyton, Vicente; Roghani, Maryam; Peano, Vittorio; Thorwart, Michael

2014-06-13

214

Photon-Assisted Confinement-Induced Resonances for Ultracold Atoms  

NASA Astrophysics Data System (ADS)

We solve the two-particle s-wave scattering for an ultracold-atom gas confined in a quasi-one-dimensional trapping potential which is periodically modulated. The interaction between the atoms is included via Fermi's pseudopotential. For a modulated isotropic transverse harmonic confinement, the atomic center of mass and relative degrees of freedom decouple and an exact solution is possible. The modulation opens additional photon-assisted resonant scattering channels. Applying the Bethe-Peierls boundary condition, we obtain the general scattering solution of the time-dependent Floquet-Schrödinger equation which is universal at low energies. The effective one-dimensional scattering length can be controlled by the external driving.

Leyton, Vicente; Roghani, Maryam; Peano, Vittorio; Thorwart, Michael

2014-06-01

215

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

NASA Astrophysics Data System (ADS)

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

Amitai, A.; Holcman, D.

2013-06-01

216

Quasistationary high confinement discharges with trans-greenwald density on TEXTOR-94  

PubMed

Confinement quality as good as ELM-free H-mode at densities substantially above the Greenwald density limit ( &nmacr;(e,0)/n(GW) = 1.4) has been obtained in discharges with a radiative boundary under quasistationary conditions for 20 times the energy confinement time. This is achieved by optimizing the gas-fueling rate of RI-mode discharges which tailors their favorable energy confinement and leads to discharges with beta values just below the operational limit beta(n) = 2 of TEXTOR-94, thereby effectively avoiding confinement back transitions or disruptions. In addition, this high-density regime is favorable for helium removal and results in figures of merit tau(*)(p,He)/tau(E) approximately 10-15, relevant for a future fusion power reactor. PMID:10978069

Mank; Messiaen; Ongena; Unterberg; Dumortier; Finken; Jaspers; Koslowski; Kramer-Flecken; Rapp; Samm; van Wassenhove G; Weynants

2000-09-11

217

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

Microsoft Academic Search

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

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

2007-01-01

218

Fragility of an Isochorically Confined Polymer Glass  

NASA Astrophysics Data System (ADS)

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

Zhang, Chuan; Guo, Yunlong; Priestley, Rodney

2013-03-01

219

Packing frustration in dense confined fluids.  

PubMed

Packing frustration for confined fluids, i.e., the incompatibility between the preferred packing of the fluid particles and the packing constraints imposed by the confining surfaces, is studied for a dense hard-sphere fluid confined between planar hard surfaces at short separations. The detailed mechanism for the frustration is investigated via an analysis of the anisotropic pair distributions of the confined fluid, as obtained from integral equation theory for inhomogeneous fluids at pair correlation level within the anisotropic Percus-Yevick approximation. By examining the mean forces that arise from interparticle collisions around the periphery of each particle in the slit, we calculate the principal components of the mean force for the density profile - each component being the sum of collisional forces on a particle's hemisphere facing either surface. The variations of these components with the slit width give rise to rather intricate changes in the layer structure between the surfaces, but, as shown in this paper, the basis of these variations can be easily understood qualitatively and often also semi-quantitatively. It is found that the ordering of the fluid is in essence governed locally by the packing constraints at each single solid-fluid interface. A simple superposition of forces due to the presence of each surface gives surprisingly good estimates of the density profiles, but there remain nontrivial confinement effects that cannot be explained by superposition, most notably the magnitude of the excess adsorption of particles in the slit relative to bulk. PMID:25194375

Nygård, Kim; Sarman, Sten; Kjellander, Roland

2014-09-01

220

Nonlocal effects in a hybrid plasmonic waveguide for nanoscale confinement.  

PubMed

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

Huang, Qiangsheng; Bao, Fanglin; He, Sailing

2013-01-28

221

Deformation and breakup of viscoelastic droplets in confined shear flow.  

PubMed

The deformation and breakup of Newtonian and viscoelastic droplets are studied in confined shear flow. Our numerical approach is based on a combination of lattice-Boltzmann models and finite difference schemes, the former used to model two immiscible fluids with variable viscosity ratio and the latter used to model the polymer dynamics. The kinetics of the polymers is introduced using constitutive equations for viscoelastic fluids with finitely extensible nonlinear elastic dumbbells with Peterlin's closure. We quantify the droplet response by changing the polymer relaxation time ?_{P}, the maximum extensibility L of the polymers, and the degree of confinement, i.e., the ratio of the droplet diameter to wall separation. In unconfined shear flow, the effects of droplet viscoelasticity on the critical capillary number Ca_{cr} for breakup are moderate in all cases studied. However, in confined conditions a different behavior is observed: The critical capillary number of a viscoelastic droplet increases or decreases, depending on the maximum elongation of the polymers, the latter affecting the extensional viscosity of the polymeric solution. Force balance is monitored in the numerical simulations to validate the physical picture. PMID:25215849

Gupta, A; Sbragaglia, M

2014-08-01

222

Deformation and breakup of viscoelastic droplets in confined shear flow  

NASA Astrophysics Data System (ADS)

The deformation and breakup of Newtonian and viscoelastic droplets are studied in confined shear flow. Our numerical approach is based on a combination of lattice-Boltzmann models and finite difference schemes, the former used to model two immiscible fluids with variable viscosity ratio and the latter used to model the polymer dynamics. The kinetics of the polymers is introduced using constitutive equations for viscoelastic fluids with finitely extensible nonlinear elastic dumbbells with Peterlin's closure. We quantify the droplet response by changing the polymer relaxation time ?P, the maximum extensibility L of the polymers, and the degree of confinement, i.e., the ratio of the droplet diameter to wall separation. In unconfined shear flow, the effects of droplet viscoelasticity on the critical capillary number Cacr for breakup are moderate in all cases studied. However, in confined conditions a different behavior is observed: The critical capillary number of a viscoelastic droplet increases or decreases, depending on the maximum elongation of the polymers, the latter affecting the extensional viscosity of the polymeric solution. Force balance is monitored in the numerical simulations to validate the physical picture.

Gupta, A.; Sbragaglia, M.

2014-08-01

223

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

224

Confinement induced binding of noble gas atoms  

NASA Astrophysics Data System (ADS)

The stability of Ngn@B12N12 and Ngn@B16N16 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 Ne2@B12N12 they are kinetically stable to retain their structures intact throughout the simulation time (500 fs) at 298 K. The Ne2@B12N12 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 B12N12 and B16N16 cages. Electron density analysis shows that the He-He interaction in He2@B16N16 is of closed-shell type whereas for the same in He2@B12N12 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 ?Eorb term contributes 40.9% and 37.3% towards the total attraction in the He2 dimers having the same distances as in He2@B12N12 and He2@B16N16, 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.

2014-04-01

225

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

PubMed

We investigate the photoresistance of a magnetically confined quantum wire in which microwave-coupled edge channels interfere at two pinning sites in the fashion of a Mach-Zehnder interferometer. The conductance is strongly enhanced by microwave power at B = 0 and develops a complex series of oscillations when the magnetic confinement increases. Both results are quantitatively explained by the activation of forward scattering in a multimode magnetically confined quantum wire. By varying the strength of the magnetic confinement we are able to tune the phase of electrons in the arms of the interferometer. Quantum interferences which develop between pinning sites explain the oscillations of the conductance as a function of the magnetic field. A fit of the data gives the distance between pinning sites as 11 µm. This result suggests that quantum coherence is conserved over a distance three times longer than the electron mean free path. PMID:21813973

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

2009-01-14

226

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

PubMed

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. PMID:25171499

Yang, C; Zhou, M; Xu, Q

2014-10-21

227

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

PubMed Central

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

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

2013-01-01

228

Layering instability in a confined suspension flow.  

PubMed

We show [J. Fluid Mech. 592, 447 (2007)] that swapping (reversing) trajectories in confined suspension flows prevent collisions between particles approaching each other in adjacent streamlines. Here we demonstrate that by inducing layering this hydrodynamic mechanism changes the microstructure of suspensions in a confined Couette flow. Layers occur either in the near-wall regions or span the whole channel width, depending on the strength of the swapping-trajectory effect. While our theory focuses on dilute suspensions, we postulate that this new hydrodynamic mechanism controls the formation of a layered microstructure in a wide range of densities. PMID:22401126

Zurita-Gotor, M; B?awzdziewicz, J; Wajnryb, E

2012-02-10

229

New confinement phases from singular SCFT  

NASA Astrophysics Data System (ADS)

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

Giacomelli, Simone; Konishi, Kenichi

2013-03-01

230

Excitation of confined modes on particle arrays  

E-print Network

We describe both theoretically and experimentally the existence and excitation of confined modes in planar arrays of gold nanodisks. Ordered 2D lattices of monodispersive nanoparticles are manufactured, embedded in a silica matrix, and exposed to evanescent prism-coupling illumination, leading to dark features in the reflectivity, which signal the presence of confined modes guided along the arrays. We find remarkable agreement between theory and experiment in the frequency-momentum dispersion of the resonances. Direct excitation of these modes reveals long propagation distances and deep extinction features. This characterization of guided modes shows the great potential of metallic particle arrays for optical signal processing and distant sensing applications.

Bendaña, Xesús Manoel; Pirruccio, Giuseppe; Rivas, Jaime Gómez; de Abajo, F Javier García

2012-01-01

231

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

232

Coulomb Energy, Vortices, and Confinement  

SciTech Connect

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

Greensite, J.; Olejnik, S.

2003-02-25

233

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

234

Quantum confinement in CdSe nanocrystallites  

Microsoft Academic Search

Quantum confinement increases the spacing between energy levels as the nanocrystallite size is decreased. Its qualitative features hold both for states localized near the center of a nanocrystallite and those near the surface, such as states due primarily to dangling bonds. However, different quantitative features are expected because of the different size constraints on each of these states. Since the

K. E. Andersen; C. Y. Fong; W. E. Pickett

2002-01-01

235

Confinement property in SU(3) gauge theory  

SciTech Connect

We study the confinement property of the pure SU(3) gauge theory, combining in this effort the nonperturbative gluon and ghost propagators obtained as solutions of Dyson-Schwinger equations with solutions of an integral ladder diagram summation type equation for the Wilson loop. We obtain the string potential and effective UV coupling.

Zayakin, A. V. [Department fuer Physik der Ludwig-Maximillians-Universitaet Muenchen, Maier-Leibniz-Laboratory, Am Coulombwall 1, 85748 Garching (Germany); ITEP, B. Cheremushkinskaya, 25, 117218, Moscow (Russian Federation); Rafelski, J. [Department fuer Physik der Ludwig-Maximillians-Universitaet Muenchen, Maier-Leibniz-Laboratory, Am Coulombwall 1, 85748 Garching (Germany); Department of Physics, University of Arizona, Tucson, Arizona, 85721 (United States)

2009-08-01

236

Soliton Stars as Holographic Confined Fermi Liquids  

E-print Network

In this paper, we study a holographic dual of a confined fermi liquid state by putting a charged fluid of fermions in the AdS soliton geometry. This can be regarded as a confined analogue of electron stars. Depending on the parameters such as the mass and charge of the bulk fermion field, we found three different phase structures when we change the values of total charge density at zero temperature. In one of the three cases, our confined solution (called soliton star) is always stable and this solution approaches to the electron star away from the tip. In both the second and third case, we find a confinement/deconfinement phase transition. Moreover, in the third one, there is a strong indication that the soliton star decays into an inhomogeneous solution. We also analyze the probe fermion equations (in the WKB approximation) in the background of this soliton star geometry to confirm the presence of many fermi-surfaces in the system.

Jyotirmoy Bhattacharya; Noriaki Ogawa; Tadashi Takayanagi; Tomonori Ugajin

2012-01-03

237

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

238

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

239

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

240

COVER IMAGE Magnetic vortices confined to thin  

E-print Network

COVER IMAGE Magnetic vortices confined to thin films gyrate with dynamics that are determined Gretchen K. Campbell LETTERS 645 Superfluid behaviour of a two-dimensional Bose gas Rémi Desbuquois, proving superfluid behaviour, has now been observed in an ultracold two- dimensional Bose gas

Loss, Daniel

241

Inertial Confinement Fusion with Light Ion Beams  

Microsoft Academic Search

The Particle Beam Fusion Accelerator II (PBFA II) is presently under construction and is the only existing facility with the potential of igniting thermonuclear fuel in the laboratory. The accelerator will generate up to 5 megamperes of lithium ions at 30 million electron volts and will focus them onto an inertial confinement fusion (ICF) target after beam production and focusing

J. Pace Vandevender; Donald L. Cook

1986-01-01

242

Inertial confinement fusion with light ion beams  

Microsoft Academic Search

The Particle Beam Fusion Accelerator II (PBFA II) is presently under construction and is the only existing facility with the potential of igniting thermonuclear fuel in the laboratory. The accelerator will generate up to 5 megamperes of lithium ions at 30 million electron volts and will focus them onto an inertial confinement fusion (ICF) target after beam production and focusing

J. P. VanDevender; D. L. Cook

1986-01-01

243

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

244

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

245

MFE Burning Plasmas Innovative Confinement Concepts (ICCs)  

E-print Network

Best Path to Energy Fusion Energy Development DEMO Advance burning plasma physics, technology university plasma science and technology programs ­ Engaging faculty by providing opportunities to contribute concepts share common science and technology: · The physics of confined plasmas · The dynamics of burning

246

Symmetries in confined classical Coulomb systems  

SciTech Connect

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

Schiffer, J.P.

1991-01-01

247

Study of Superfluid He Under Nanoscale Confinement  

NASA Astrophysics Data System (ADS)

We review recent experiments in which superfluid He has been studied under highly controlled confinement in nanofluidic sample chambers. We discuss the experimental challenges and their resolution. These methods open the way to a systematic investigation of the superfluidity of He films, and the surface and edge excitations of topological superfluids.

Levitin, L. V.; Bennett, R. G.; Casey, A.; Cowan, B.; Saunders, J.; Drung, D.; Schurig, Th.; Parpia, J. M.; Ilic, B.; Zhelev, N.

2014-06-01

248

Electroweak Symmetry Breaking due to Confinement  

E-print Network

Within the framework of gauge mediated supersymmetry breaking, we consider an electroweak symmetry breaking pattern in which there is no conventional $\\mu$ term. The pattern is made appealing through realizing it as low energy effective description of a supersymmetric Yang-Mills theory which is of confinement. Phenomenological implications are discussed.

Chun Liu

1999-03-18

249

Degenerate crystals from colloidal dimers under confinement.  

PubMed

Colloidal aperiodic phases (i.e., entropy stabilized degenerate crystals, DCs) are realized via self-assembly of hollow fluorescent silica dimers under wedge-cell confinement. The dimer building blocks approximate two tangent spheres and their arrangements are studied via laser scanning confocal microscopy. In the DCs, the individual lobes tile a lattice and five distinct DC arrangements with square, triangular or rectangular layer symmetry are determined as a function of confinement height. Moreover, Monte Carlo simulations are used to construct the phase diagram for DCs up to two layer confinements and to analyze structural order in detail. Just as for spheres, the DC structural transitions under confinement are attributed to the ability or frustration to accommodate an integral number of particle layers between hard walls. Unlike spheres, dimers can also experience transitions involving changes in orientation. DCs are among the unconventional structures (e.g., semi-regular tilings, quasicrystals, plastic crystals) expected to enhance the properties of photonic solids. PMID:25366128

Muangnapoh, Kullachate; Avendaño, Carlos; Escobedo, Fernando A; Liddell Watson, Chekesha M

2014-11-19

250

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

251

Kinetics of Polymer Ejection from Capsid Confinement: Scaling Considerations and Computer Experiment  

NASA Astrophysics Data System (ADS)

We investigate the ejection dynamics of a flexible polymer chain out of confined environment by means of scaling considerations and Monte Carlo simulations. Situations of this kind arise in different physical contexts, including a flexible synthetic polymer partially confined in a nanopore and a viral genome partially ejected from its capsid. In the case of cylindric confinement the entropic driving force which pulls the chain out of the pore is argued to be constant once a few persistent lengths are out of the pore. We demonstrate that in this case the ejection dynamics follows a ? {t}-law with elapsed time t. The mean ejection time ? depends nonmonotonically on chain length N. However, if the geometric constraints comprise a wider capsid chamber attached to a narrow exit tube, the mechanism of ejection changes and involves the surmounting of an activation barrier. The driving force then varies in time. One finds good agreement of theory and computer simulation with recent experiments with DNA.

Milchev, A.; Binder, K.

2012-08-01

252

Confined Phase Diagram of Binary n-Alkane Mixtures within Three-Dimensional Microcapsules.  

PubMed

The confined phase behaviors of microencapsulated normal hexadecane/octadecane mixtures (abbreviated as m-C16/C18) have been investigated by combination of differential scanning calorimetry and in situ wide-angle X-ray scattering. The binary alkane mixtures confined in three-dimensional geometrical space demonstrate two novel crystallization features. The surface freezing is significantly enhanced after C16/C18 mixtures being encapsulated, and the surface monolayer formed is proved to be an ideal solid solution composed by C16 and C18. Furthermore, m-C16/C18 mixtures are trapped into a stabilized rotator phase below the crystallization temperatures, whereas C16/C18 mixtures with certain compositions form the low-temperature crystalline structure directly. These confined crystallization features originate from the jointed effects of spatial confinement and chain mixing of the components. Moreover, the phase diagram of the confined binary alkane mixtures (m-C16/C18) is successfully established for the first time, which enlightens the crystallization features of other spatially confined soft-matter binary systems. PMID:25280012

Gao, Xia; Fu, Dongsheng; Xie, Baoquan; Su, Yunlan; Wang, Dujin

2014-10-30

253

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

254

Ultrasonic interferometer for first-sound measurements of confined liquid He4  

NASA Astrophysics Data System (ADS)

We present a new technique for probing the properties of quantum fluids in restricted geometries. We have confined liquid He4 within microfluidic devices formed from glass wafers, in which one dimension is on the micrometer scale. Using an ultrasonic analog to Fabry-Pérot interferometry, we have measured the first sound of the confined liquid He4, which can be a probe of critical behavior near the lambda point (T?). All thermodynamic properties of liquid He4 can be derived from first-sound and heat capacity measurements, and although quite a bit of experimental work has been done on the latter, no measurement of first sound has been reported for a precisely confined geometry smaller than a few tens of micrometers. In this work, we report measurements of isobaric first sound in liquid He4 confined in cavities as small as ˜5 ?m. Our experimental setup allows us to pressurize the liquid up to ˜25 bar without causing deformation of the confined geometry, a pressure which is about four times larger than previously reported with similar microfluidic devices. Our preliminary results indicate that one can possibly observe finite-size effects and verify scaling laws, by using similar devices with smaller confinement.

Rojas, X.; Hauer, B. D.; MacDonald, A. J. R.; Saberi, P.; Yang, Y.; Davis, J. P.

2014-05-01

255

Effect of Short-Circuit Pathways on Water Quality in Selected Confined Aquifers (Invited)  

NASA Astrophysics Data System (ADS)

Confined aquifers in the United States generally contain fewer anthropogenic contaminants than unconfined aquifers because confined aquifers often contain water recharged prior to substantial human development and redox conditions are more reducing, which favors degradation of common contaminants like nitrate and chlorinated solvents. Groundwater in a confined part of the High Plains aquifer near York, Nebraska had an adjusted radiocarbon age of about 2,000 years, and groundwater in a confined part of the Floridan aquifer near Tampa, Florida had apparent ages greater than 60 years on the basis of tritium measurements. Yet compounds introduced more recently into the environment (anthropogenic nitrate and volatile organic compounds) were detected in selected public-supply wells completed in both aquifers. Depth-dependent measurements of flow and chemistry in the pumping supply wells, groundwater age dating, numerical modeling of groundwater flow, and other monitoring data indicated that the confined aquifers sampled by the supply wells were connected to contaminated unconfined aquifers by short-circuit pathways. In the High Plains aquifer, the primary pathways appeared to be inactive irrigation wells screened in both the unconfined and confined aquifers. In the Floridan aquifer, the primary pathways were karst sinkholes and conduits. Heavy pumping in both confined systems exacerbated the problem by reducing the potentiometric surface and increasing groundwater velocities, thus enhancing downward gradients and reducing reaction times for processes like denitrification. From a broader perspective, several confined aquifers in the U.S. have experienced large declines in their potentiometric surfaces because of groundwater pumping and this could increase the potential for contamination in those aquifers, particularly where short-circuit pathways connect them to shallower, contaminated sources of water, such as was observed in York and Tampa.

McMahon, P. B.

2010-12-01

256

Chapter 2: Plasma confinement and transport ITER Physics Expert Groups on Confinement and  

E-print Network

-machi, Naka-gun, Ibaraki-ken, Japan Abstract. Physics knowledge in plasma confinement and transport relevant of ITER. Three approaches are being pursued: (i) derivation of empirical global scaling laws; (ii) non

Vlad, Gregorio

257

A brief report of gram-negative bacterial endotoxin levels in airborne and settled dusts in animal confinement buildings  

SciTech Connect

Gram-negative bacterial endotoxins, implicated in adverse worker health responses, were found in settled and airborne dust samples obtained from poultry and swine confinement units. Results of the Limulus amebocyte lysate gel test found endotoxin levels in dust samples ranged from 4.5 to 47.7 micrograms of FDA Klebsiella endotoxin equivalents/gm. Differences in endotoxin levels between dust samples may have been due to variables in time, geographic locations, confined animals, confinement buildings and equipment, and methods of sample collection. Animal confinement workers are potentially exposed to large amounts of gram-negative bacterial endotoxins; however, the respiratory health effects of such exposures to animal confinement workers have yet to be determined.

Thedell, T.D.; Mull, J.C.; Olenchock, S.A.

1980-01-01

258

High Confinement and High Density with Stationary Plasma Energy and Strong Edge Radiation in the TEXTOR-94 Tokamak  

Microsoft Academic Search

Stationary high energy confinement is observed on TEXTOR-94 for times limited only by the flux swing of the transformer using strong edge radiation cooling. Necessary tools are the feedback control of the radiated power and of the plasma energy content. At the highest densities obtained (up to 1.2 times the Greenwald limit), energy confinement exceeds the edge-localized-mode-free H-mode scaling ITERH93-P

A. M. Messiaen; J. Ongena; U. Samm; B. Unterberg; G. van Wassenhove; F. Durodie; R. Jaspers; M. Z. Tokar; P. E. Vandenplas; G. van Oost; J. Winter; G. H. Wolf; G. Bertschinger; G. Bonheure; P. Dumortier; H. Euringer; K. H. Finken; G. Fuchs; B. Giesen; R. Koch; L. Koenen; C. Koenigs; H. R. Koslowski; A. Kraemer-Flecken; A. Lyssoivan; G. Mank; J. Rapp; N. Schoon; G. Telesca; R. Uhlemann; M. Vervier; G. Waidmann; R. R. Weynants

1996-01-01

259

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

260

Yang-Mills streamlines and semi-classical confinement  

SciTech Connect

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

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

2011-05-23

261

The Entropic Cost of Polymer Confinement  

PubMed Central

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?4kT to ~30kT 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 ~5kT 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.

2012-01-01

262

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

263

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

264

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

265

www.nycaic.org BINGHAMTON WORKSHOP ON SOLITARY CONFINEMENT  

E-print Network

www.nycaic.org BINGHAMTON WORKSHOP ON SOLITARY CONFINEMENT The Campaign for Alternatives: Graduate student, Silberman School of Social Work, Hunter College; social justice advocate and community cause deep and permanent psychological damage. Campaign for Alternatives to Isolated Confinement: CAIC

Suzuki, Masatsugu

266

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 va, and run time ?. Our simulation results show that (D-D0)/va (2)? 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?. PMID:25399157

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

2014-11-14

267

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

268

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.

Vetter, Roman; Herrmann, Hans J

2014-01-01

269

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 (TL ? 225 K). The second, T(*) ? 315 ± 5 K, is a special locus of the isothermal compressibility KT(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 (TL) 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

270

Electromagnetic response of confined Dirac particles  

NASA Astrophysics Data System (ADS)

The eigenstates of a single massless Dirac particle confined in a linear potential are calculated exactly by direct solution of the Dirac equation. The electromagnetic structure functions are calculated from the Dirac wave functions of the ground and excited states of the particle by coupling to its conserved vector current. We obtain the longitudinal and transverse structure functions as a function of y˜=?-|q|, where ? and |q| are the energy and momentum transferred to the target in its rest frame. At values of |q|?2.5 GeV, much larger than the characteristic energy scale ˜440 MeV of the confining potential, the response exhibits y˜ scaling, a generalization of Bjorken scaling. We compare the exact structure functions with those obtained from the ground state wave functions in the plane wave impulse approximation. The deviation from the Callan-Gross relation is compared with the parton model prediction.

Paris, Mark W.

2003-08-01

271

Thermodynamic properties of bulk and confined water  

NASA Astrophysics Data System (ADS)

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 (TL ? 225 K). The second, T* ˜ 315 ± 5 K, is a special locus of the isothermal compressibility KT(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 (TL) and the onset of the unfolding process (T*).

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

2014-11-01

272

Pressure-confined Lyman-alpha clouds  

NASA Technical Reports Server (NTRS)

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

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

1989-01-01

273

Micelle fragmentation and wetting in confined flow  

E-print Network

We use coarse-grained molecular-dynamics (MD) simulations to investigate the structural and dynamical properties of micelles under non-equilibrium Poiseuille flow in a nano-confined geometry. The effects of flow, confinement, and the wetting properties of die-channel walls on spherical sodium dodecyl sulfate (SDS) micelles are explored when the micelle is forced through a die-channel slightly smaller than its equilibrium size. Inside the channel, the micelle may fragment into smaller micelles. In addition to the flow rate, the wettability of the channel surfaces dictates whether the micelle fragments and determines the size of the daughter micelles: The overall behavior is determined by the subtle balance between hydrodynamic forces, micelle-wall interactions and self-assembly forces.

Mona Habibi; Colin Denniston; Mikko Karttunen

2014-09-30

274

Optimal management of a confined groundwater system  

SciTech Connect

Dynamic programming is applied to a relatively simple economic and hydrologic model of a confined aquifer system in Southwest Montana to determine an optimal interseasonal allocation schedule. The derived decision rule demonstrates the economic advantage of maintaining a confined groundwater system. While localized intraseasonal loss of the artesian pressure may occur, it is important to maintain this pressure from year to year because of its role in reducing extraction costs. The welfare gap, as measured by differences in the net present value of economic returns to the basin under an optimal use policy versus an uncontrolled, common pool situation, is not trivial. Sensitivity analysis indicates that assumptions about uniformity of land productivity, vis-a-vis their impact on the shape of the returns function, the discount rate, and the level of electric power rates are particularly critical with respect to the magnitude of the commonality problem. 16 references, 7 figures, 3 tables.

Worthington, V.E.; Burt, O.R.; Brustkern, R.L.

1985-09-01

275

Micelle fragmentation and wetting in confined flow  

NASA Astrophysics Data System (ADS)

We use coarse-grained molecular-dynamics (MD) simulations to investigate the structural and dynamical properties of micelles under non-equilibrium Poiseuille flow in a nano-confined geometry. The effects of flow, confinement, and the wetting properties of die-channel walls on spherical sodium dodecyl sulfate (SDS) micelles are explored when the micelle is forced through a die-channel slightly smaller than its equilibrium size. Inside the channel, the micelle may fragment into smaller micelles. In addition to the flow rate, the wettability of the channel surfaces dictates whether the micelle fragments and determines the size of the daughter micelles: The overall behavior is determined by the subtle balance between hydrodynamic forces, micelle-wall interactions and self-assembly forces.

Habibi, Mona; Denniston, Colin; Karttunen, Mikko

2014-10-01

276

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

277

Morphogenesis of filaments growing in flexible confinements.  

PubMed

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. PMID:25026967

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

2014-01-01

278

Liquefaction of sand under low confining pressure  

NASA Astrophysics Data System (ADS)

Undrained behaviour of sand under low cell pressure was studied in static and cyclic triaxial tests. It was found that very loose sand liquefies under static loading with the relative density being a key parameter for the undrained behaviour of sand. In cyclic triaxial tests, pore water pressures built up during the cyclic loading and exceeded the confining cell pressure. this process was accompanied by a large sudden increase in axial deformation. The necessary number of cycles to obtain liquefaction was related to the confining cell pressure, the amplitude of cyclic loading and the relative density of sand. In addition, the patterns of pore water pressure response are different from those of sand samples with different relative densities. The test results are very useful for expounding scour mechanism around coastal structures since they relate to the low stress behaviour of the sand.

Shaoli, Yang; Sandven, Rolf; Grande, Lars

2003-10-01

279

Designing the Cascade inertial confinement fusion reactor  

SciTech Connect

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

Pitts, J.H.

1987-02-09

280

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

281

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

282

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

283

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

284

One dimensional analysis of inertially confined plasmas  

NASA Astrophysics Data System (ADS)

Energy transfer processes in a thermonuclear plasma including Coulombic phenomena, bremsstrahlung, and Compton scatter are critically reviewed. These processes are incorporated in a three temperature, inertially confined fusion computer simulation which uses a one dimensional, spherical, Lagrangian hydrodynamics scheme. The computer code, still in the validation phase, uses separate subroutines to model hydrodynamics, thermonuclear burn, neutron heating, alpha particle heating, and energy transfer processes in CGS units.

Debruyne, D. A.

1982-03-01

285

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

286

Status of 2XIIB plasma confinement experiments  

Microsoft Academic Search

The status of 2XIIB neutral beam injection experiments with stabilizing plasma is described. The stream suppresses ion-cyclotron fluctuations and permits denisty to 5 x ten to the 13th power \\/cu cm. The ion energy is 13 keV, and electron temperature reaches 140 eV. Plasma confinement increases with ion energy and n tau reaches 7 x ten to the 13th power\\/cu

F. J. Coensgen; J. F. Clauser; D. L. Correll; W. F. Cummins; C. Gormezano; B. G. Logan; A. W. Molvik; W. E. Nexsen; T. C. Simonen; B. W. Stallard

1976-01-01

287

[Ethics and solitary confinement in psychiatry].  

PubMed

The decision to treat a patient in solitary confinement in psychiatry does not follow any protocol and is not made on a case-by-case basis. Team deliberation opens discussion and enables the group as a whole to take responsibility for clarifying what is to be supported by the team and implemented by the carer during treatment. When presented with complex situations, uncertainty can be a force when it calls upon an ethical dilemma. PMID:25335218

Andrieu, Jean-Pierre

2014-01-01

288

Theoretical aspects of energy confinement in spheromaks  

SciTech Connect

It is shown that, despite the poor global energy confinement observed in spheromak experiments to date, the long-term prospects may be favorable as spheromaks are scaled to larger size and higher temperatures. The present performance is traced to excessive magnetic energy loss at the edge compared to tokamaks and heat transport due to magnetic fluctuations, both of which should scale away as the temperature increases.

Fowler, T.K.

1994-11-16

289

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

290

Helium in confinement: the filling A Neutron Scattering investigation.  

E-print Network

Helium in confinement: the filling parameter. A Neutron Scattering investigation. Francesco Albergamo Institut Laue-Langevin, France Helium in confinement: the filling parameter. ­ p.1/13 #12;outline introduction and motivation Helium in confinement: the filling parameter. ­ p.2/13 #12;outline introduction

Glyde, Henry R.

291

Numerical study of a confined slot impinging jet with nanofluids  

PubMed Central

Background Heat transfer enhancement technology concerns with the aim of developing more efficient systems to satisfy the increasing demands of many applications in the fields of automotive, aerospace, electronic and process industry. A solution for obtaining efficient cooling systems is represented by the use of confined or unconfined impinging jets. Moreover, the possibility of increasing the thermal performances of the working fluids can be taken into account, and the introduction of nanoparticles in a base fluid can be considered. Results In this article, a numerical investigation on confined impinging slot jet working with a mixture of water and Al2O3 nanoparticles is described. The flow is turbulent and a constant temperature is applied on the impinging. A single-phase model approach has been adopted. Different geometric ratios, particle volume concentrations and Reynolds number have been considered to study the behavior of the system in terms of average and local Nusselt number, convective heat transfer coefficient and required pumping power profiles, temperature fields and stream function contours. Conclusions The dimensionless stream function contours show that the intensity and size of the vortex structures depend on the confining effects, given by H/W ratio, Reynolds number and particle concentrations. Furthermore, for increasing concentrations, nanofluids realize increasing fluid bulk temperature, as a result of the elevated thermal conductivity of mixtures. The local Nusselt number profiles show the highest values at the stagnation point, and the lowest at the end of the heated plate. The average Nusselt number increases for increasing particle concentrations and Reynolds numbers; moreover, the highest values are observed for H/W = 10, and a maximum increase of 18% is detected at a concentration equal to 6%. The required pumping power as well as Reynolds number increases and particle concentrations grow, which is almost 4.8 times greater than the values calculated in the case of base fluid. List of symbols PMID:21711743

2011-01-01

292

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

293

Free-volume anomaly in confined glycerol.  

NASA Astrophysics Data System (ADS)

Glycerol is a small molecule glass-former which exhibits relatively high viscosity due to its extensive hydrogen bonding. Here we report the first measurements of local free volume and local mobility of glycerol confined in Vycor: a mesoporous silica glass with pores 70 Angstroms in diameter. We find that the lower molecular mobility in confinement (measured here using quasi-elastic neutron scattering) is accompanied by a higher mean free-volume size between molecules (as measured using positron annihilation lifetime spectroscopy). The strong wetting between glycerol and the glass surface appears to perturb the glycerol to such an extent that the normally observed free-volume/mobility relationship is reversed. Previous studies have come to similar conclusions (high glass transition temperature, low density) but this is the first to show that these effects originate locally. This is expected to have significant ramifications for the study of hydrogen-bonding liquids in confinement, for example water -- a topic of much current interest due to its application in hydration water in biological material.

Kilburn, Duncan; Garcia-Sakai, Victoria; Alam, Ashraf; Sokol, Paul

2007-03-01

294

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

295

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

2011-11-16

296

Ion confinement and transport in a toroidal plasma with externally imposed radial electric fields  

NASA Technical Reports Server (NTRS)

Strong electric fields were imposed along the minor radius of the toroidal plasma by biasing it with electrodes maintained at kilovolt potentials. Coherent, low-frequency disturbances characteristic of various magnetohydrodynamic instabilities were absent in the high-density, well-confined regime. High, direct-current radial electric fields with magnitudes up to 135 volts per centimeter penetrated inward to at least one-half the plasma radius. When the electric field pointed radially toward, the ion transport was inward against a strong local density gradient; and the plasma density and confinement time were significantly enhanced. The radial transport along the electric field appeared to be consistent with fluctuation-induced transport. With negative electrode polarity the particle confinement was consistent with a balance of two processes: a radial infusion of ions, in those sectors of the plasma not containing electrodes, that resulted from the radially inward fields; and ion losses to the electrodes, each of the which acted as a sink and drew ions out of the plasma. A simple model of particle confinement was proposed in which the particle confinement time is proportional to the plasma volume. The scaling predicted by this model was consistent with experimental measurements.

Roth, J. R.; Krawczonek, W. M.; Powers, E. J.; Kim, Y. C.; Hong, H. Y.

1979-01-01

297

Winter 2013 Time Time Time Time Time  

E-print Network

11/8/2012 Winter 2013 Time Time Time Time Time Ugrad Grad Section Lab 590 Ugrad Grad Section Lab/143 quiz sections offered multiple times Thurs. (142) and T/Th (143) Grad courses TBD: 599v1, 517 548 517

Borenstein, Elhanan

298

Monte Carlo simulations of supercoiled DNAs confined to a plane.  

PubMed Central

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

Fujimoto, Bryant S; Schurr, J Michael

2002-01-01

299

B activation enhancement in submicron confined implants in Si  

NASA Astrophysics Data System (ADS)

We implanted 3keV B ions into a crystalline Si film, grown by molecular-beam epitaxy and masked by SiO2 stripes with opening widths ranging from 3.2?m down to 0.38?m. Thermal anneals were performed at 800°C for several times. By quantitative high-resolution scanning capacitance microscopy, we demonstrated that the electrical reactivation of inactive B after postimplant annealing is obtained at faster rates as the window width decreases. Total electrical activation is gained first in the narrowest window, with times shorter by nearly a factor of 4 compared to the widest one. In addition, since inactive B seems to be caused by B clustering induced by implantation, our results put in evidence a strong effect of implantation confinement also on B clusters dissolution mechanism. These results have a strong impact on the modern silicon-based device engineering.

Bruno, E.; Mirabella, S.; Impellizzeri, G.; Priolo, F.; Giannazzo, F.; Raineri, V.; Napolitani, E.

2005-09-01

300

Fluid description of ion dynamics in a toroidally confined plasma  

SciTech Connect

Fluid equations describing ion dynamics in a toroidally confined plasma at low collision frequency are derived. The principle motivation is to present a framework for incorporating basic neoclassical effects into a fluid theory. The ions are assumed to be magnetized in the sense that relevant scale lengths are much longer than the ion gyroradius, and time scales of interest are assumed long compared to the ion bounce time. These assumptions are consistent with, for example, the evolution of unstable magnetic islands, as well as conventional transport. A special case of the present description is the quasistatic, axisymmetric state with nearly uniform pressure and density on flux surfaces. In that case the equations reproduce the radial ion heat transport predicted by neoclassical transport theory. The essential feature of our derivation is its emphasis on heat flow in the direction of the magnetic field.

Dieter, Abinadab; Hazeltine, R.D. [Institute for Fusion Studies, University of Texas, Austin, Texas 78712 (United States)

2005-05-15

301

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

SciTech Connect

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

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

2000-08-01

302

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

303

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

SciTech Connect

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

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

2010-03-15

304

Observations on the potential confinement of a light fermion  

SciTech Connect

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

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

1995-05-01

305

N reactor confinement system high-pressure test report  

SciTech Connect

This report presents the results of the High-Pressure Confiner Test (PT-N-605) performed at N Reactor in October 1987. This test pressurized the confiner building to a maximum design basis accident pressure of 3.9 psi. It utilized integrated leak rate tests before and after the pressurization to evaluate the damage done to the confiner by the pressure. The test demonstrated that the confiner structure and its penetration seals perform as designed when subjected to the maximum pressure postulated by a design basis accident. This report also reviews the N Reactor description, confinement concept, confinement system function, and safety analyses study done prior to the test. It describes and addresses some recommendations of the Accelerated Safety Enhancement program, and it reviews the development and performance of the High-Pressure Confiner Test. 36 refs., 12 figs., 6 tabs.

Galvin, M.R.; Holy, D.A.; Reed, R.W.

1987-10-01

306

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

SciTech Connect

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

NONE

1995-12-31

307

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

308

Generality of Deterministic Chaos, Exponential Spectra, and Lorentzian Pulses in Magnetically Confined Plasmas  

E-print Network

] is a fluctuation power spectrum with an exponential frequency depen- dence, i.e., Pð!� / expð�2!�, where is a time to the confining magnetic field. The phase space of such a system is two dimensional. The associationGenerality of Deterministic Chaos, Exponential Spectra, and Lorentzian Pulses in Magnetically

California at Los Angles, University of

309

On the horizontal-well pumping tests in anisotropic confined aquifers  

Microsoft Academic Search

A method that directly solves the boundary problem of flow to a horizontal-well in an anisotropic confined aquifer is provided. This method solves the point source problem first, and then integrates the point source solution along the horizontal well axis to obtain the horizontal well solution. The short and long time approximations of drawdowns are discussed and are utilized in

Hongbin Zhan; Lihong V. Wang

2001-01-01

310

Predicting Secure Detention Placement for African-American Juvenile Offenders: Addressing the Disproportionate Minority Confinement Problem  

Microsoft Academic Search

Disproportionate minority contact and confinement (DMC) are significant problems within the juvenile justice system in the United States. Minority youth are more often arrested, court referred, placed in locked facilities, and transferred to adult criminal courts. In fact, African American youth are 6 times more likely than White youth to experience a secure facility placement. Standardized risk assessments have been

Christopher A. Mallett; Patricia Stoddard-Dare

2010-01-01

311

Helical packing of nanoparticles confined in cylindrical domains of a self-assembled block copolymer structure.  

PubMed

Theoretical models predict that a variety of self-assembled structures of closely packed spherical particles may result when they are confined in a cylindrical domain. In the present work we demonstrate for the first time that the polymer-coated nanoparticles confined in the self-assembled cylindrical domains of a block copolymer pack in helical morphology, where we can isolate individual fibers filled with helically arranged nanoparticles. This finding provides unique possibilities for fundamental as well as application-oriented research in similar directions. PMID:24989683

Sanwaria, Sunita; Horechyy, Andriy; Wolf, Daniel; Chu, Che-Yi; Chen, Hsin-Lung; Formanek, Petr; Stamm, Manfred; Srivastava, Rajiv; Nandan, Bhanu

2014-08-18

312

Secondary cancer and relapse rates following radical prostatectomy for prostate-confined cancer.  

PubMed

In the SEER database, it is relatively easy to identify secondary cancers that follow an initial diagnosis of cancer. However, the SEER public-use data does not explicitly capture relapse of the initial cancer. One can assume that organ-confined prostate cancer treated by radical prostatectomy will show no evidence of disease after treatment. Death due to prostate cancer in such cases can be assumed to follow a relapse of previously occult metastatic disease. We devised an estimate of the timing of these relapses and tabulated rates for both new primaries and relapses following radical prostatectomy for organ-confined prostate cancer. PMID:18522141

Wesley, David; Cox, Hugh F

2007-01-01

313

Confinement of band-edge modes in a photonic crystal slab.  

PubMed

We study the confinement of low group velocity band-edge modes in a photonic crystal slab. We use a rigorous, three dimensional, finite-difference time-domain method to compute the electromagnetic properties of the modes of the photonic structures. We show that by combining a defect mode approach with the high-density of states associated with bandedge modes, one can design compact, fabrication-tolerant, high-Q photonic microcavities. The electromagnetic confinement properties of these cavities can foster enhanced radiation dynamics and should be well suited for ultralow-threshold microlasers and cavity quantum electrodynamics. PMID:19547446

Bordas, Frédéric; Steel, M J; Seassal, Christian; Rahmani, Adel

2007-08-20

314

Shear behavior of squalane and tetracosane under extreme confinement. III. Effect of confinement on viscosity  

SciTech Connect

This study uses nonequilibrium molecular dynamics simulation to explore the rheology of confined liquid alkanes. Two alkanes that differ in molecular structural complexity are examined: tetracosane (C{sub 24}H{sub 50}), which is a linear alkane, and squalane (C{sub 30}H{sub 62}), which has six symmetrically placed methyl branches along a 24 carbon backbone. These model lubricants are confined between model walls that have short chains tethered to them, thus screening the wall details. This paper, the third of a three part series, compares the viscosities of the confined fluids to those of the bulk fluids. The alkanes are described by a well-documented potential model that has been shown to reproduce bulk experimental viscosity and phase equilibria measurements. Details of the simulation method, and structural information can be found in the preceding two papers of this series. The measured strain rates in these simulations range between 10{sup 8} and 10{sup 11} s{sup {minus}1}, which is typical of a number of practical applications. The confined fluids undergo extensive shear thinning, showing a power-law behavior. Comparison of results for the confined fluid to those for the bulk fluid reveal that, for the conditions examined, there is no difference between the bulk and confined viscosities for these alkanes. This observation is in contrast to experimental results at much lower strain rates (10{endash}10{sup 5} s{sup {minus}1}), which indicate the viscosities of the confined fluid to be much larger than the bulk viscosities. In making the comparison, we have carefully accounted for slip at the wall and have performed simulations of the bulk fluid at the same conditions of strain rate, temperature, and pressure as for the corresponding confined fluid. The viscosity is found to be independent of the wall spacing. The calculated power-law exponents are similar to experimentally observed values. We also note that the exponent increases with increasing density of the fluid. {copyright} {ital 1997 American Institute of Physics.}

Gupta, S.A.; Cochran, H.D.; Cummings, P.T. [Department of Chemical Engineering, University of Tennessee, Knoxville, Tennessee 37996-2200 (United States)] [Department of Chemical Engineering, University of Tennessee, Knoxville, Tennessee 37996-2200 (United States); [Chemical Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6268 (United States)

1997-12-01

315

Dynamics of two-dimensional monolayer water confined in hydrophobic and charged environments  

NASA Astrophysics Data System (ADS)

We perform molecular dynamics simulations to study the effect of charged surfaces on the intermediate and long time dynamics of water in nanoconfinements. Here, we use the transferable interaction potential with five points (TIP5P) model of a water molecule confined in both hydrophobic and charged surfaces. For a single molecular layer of water between the surfaces, we find that the temperature dependence of the lateral diffusion constant of water up to very high temperatures remains Arrhenius with a high activation energy. In case of charged surfaces, however, the dynamics of water in the intermediate time regime is drastically modified presumably due to the transient coupling of dipoles of water molecules with electric field fluctuations induced by charges on the confining surfaces. Specifically, the lateral mean square displacements display a distinct super-diffusive behavior at intermediate time scale, defined as the time scale between ballistic and diffusive regimes. This change in the intermediate time-scale dynamics in the charged confinement leads to the enhancement of long-time dynamics as reflected in increasing diffusion constant. We introduce a simple model for a possible explanation of the super-diffusive behavior and find it to be in good agreement with our simulation results. Furthermore, we find that confinement and the surface polarity enhance the low frequency vibration in confinement compared to bulk water. By introducing a new effective length scale of coupling between translational and orientational motions, we find that the length scale increases with the increasing strength of the surface polarity. Further, we calculate the correlation between the diffusion constant and the excess entropy and find a disordering effect of polar surfaces on the structure of water. Finally, we find that the empirical relation between the diffusion constant and the excess entropy holds for a monolayer of water in nanoconfinement.

Kumar, Pradeep; Han, Sungho

2012-09-01

316

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

317

Confinement Scaling of Magnetically-Channeled SIEC Array (MCSA) Fusion Device  

NASA Astrophysics Data System (ADS)

A spherical inertia electrostatic confinement (SIEC) is one of the most attractive fusion concepts because of its simple structure. It requires only a spherical meshed grid in a vacuum chamber and yields 108 neutrons/s from deuterium plasma in small laboratory devices. However, detailed studies such as stability analysis and development of special ion beam sources are required for improving the performance of SIEC. After certain improvements to avoid instabilities and to integrate sharp-focusing ion sources, an improved SIEC might first be utilized for various ion beam or neutron beam applications. However, a proof of principle experiment to demonstrate the basic physics (recirculation type stable cusp confinement and end cone loss re-trapping in multiple units) of this concept is required to demonstrate the feasibility of this approach for development as a fusion power reactor. Such a POP experiment is the objective of this proposal. High-temperature plasma (SIEC in low-field region) is confined by stable magnetic configuration while radial losses are minimized by channeling flow is into neighboring IEC regions. Confinement time can be very long due to an extremely large effective mirror ratio resulting in higher efficiency than a single SIEC. Fusion-product heating and ignition is also possible using collimating properties of the confinement field. Predicted scaling is linear with radius of device, possibly allowing break-even machine at a few meter radius with a several Tesla field.

Miley, George; Stubbers, Robert; Webber, Jason; Momota, Hiromu

2003-10-01

318

Single particle dynamics of water confined in a hydrophobically modified MCM-41-S nanoporous matrix  

NASA Astrophysics Data System (ADS)

The single particle dynamics of water confined in a hydrophobically modified MCM-41-S sample has been studied using three high resolution quasielastic neutron scattering spectrometers in the temperature range from 300 to 210 K. A careful modeling of the dynamics allowed us to obtain good agreement among the results obtained with the three instruments, which have very different energy resolutions. The picture arising from the data is that, because of the heterogenous environment experienced by the water molecules, the dynamics show a broad distribution of relaxation times. However, the Fickian diffusive behavior is retained. In the investigated temperature range we found no evidence of the dynamic crossover, from a non-Arrhenius to an Arrhenius behavior, which was detected for water confined in hydrophilic MCM-41-S. This finding is in agreement with what was reported by Chu et al. [Phys. Rev. E 76, 021505 (2007)] for water confined in other hydrophobic confining media that the dynamic crossover takes place at a much lower temperature. The results reported in the paper help clarify the role that the chemical interaction between the water molecules and the walls of the confining host plays in determining the characteristics of the water dynamics, as compared to purely geometric constraints such as the size and shape of the pores.

Faraone, Antonio; Liu, Kao-Hsiang; Mou, Chung-Yuan; Zhang, Yang; Chen, Sow-Hsin

2009-04-01

319

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

320

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

321

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

322

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

Microsoft Academic Search

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

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

2004-01-01

323

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

324

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

325

Semiclassical dynamics for an ion confined within a nonlinear electromagnetic trap  

NASA Astrophysics Data System (ADS)

We investigate the spectral properties of the Hamiltonian function that describes an ion confined within a nonlinear trap. The Hamiltonian is then particularized for the case of dynamic traps and we introduce algebraic models with the aim to characterize the associated dynamics in such traps. The coherent states formalism for dynamic groups and the time-dependent variational principle are applied in order to study the semiclassical behaviour of the confined ion. We deal with the bosonic realization of the Lie algebra of the SU(1,1) group, which we particularize for the case of an ion confined in a combined (Paul and Penning) trap. We infer the equations of motion for the ion in a semiclassical approach. We suggest an algorithm by means of which we can associate a classical Hamiltonian with the quantum Hamiltonian that describes the ion. The classical Hamiltonian implicitly contains spectral information on the quantum system, which means we can dequantify the system.

Mihalcea, Bogdan M.

2011-02-01

326

Diagnostics of laser plasma plume dynamics within an electrically biased confining cavity  

NASA Astrophysics Data System (ADS)

The dynamics of laser generated plasma plumes expanding within confining surfaces display a two-phase nature. Early phase enhancement due to hydrodynamic containment results in higher temperatures, densities, and average charges states in comparison to freely expanding plasma plumes. Later phase dynamics result in rapid decay of the plasma plume due to lossy plasma—surface interactions. This paper examines laser plasma generation and expansion within rectangular aluminium cavities biased to high voltages (Vbias = ±9 kV). "Hydro-electro-dynamic" confinement of the laser plasma plumes and the expansion dynamics were studied via space and time resolved visible emission spectroscopy. The charged confining cavities displayed enhanced emission, higher electron densities (Ne) and longer emission durations compared to those of an unbiased cavity. This behavior is attributed to the influence of the electric fields in the cavity on the charged particle dynamics within the cavity volume. The degree of enhancement depended strongly on the applied polarity.

Yeates, P.; Kennedy, E. T.

2011-09-01

327

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

SciTech Connect

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

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

1984-06-01

328

The impact of confinement scaling on ITER (International Thermonuclear Experimental Reactor) parameters  

SciTech Connect

Energy confinement scaling is a major concern in the design of the International Thermonuclear Experimental Reactor (ITER). The existing database for tokamaks can be fitted with a number of different confinement scaling expressions that have similar degrees of approximation. These scaling laws predict confinement times for ITER that vary by over an order of magnitude. The uncertainties in the form and magnitude of these scaling laws must be substantially reduced before the plasma performance of ITER can be predicted with adequate reliability. The TETRA systems code is used to calculate the dependence of major ITER parameters on the scaling laws currently in use. Design constraints of interest in the present phase of ITER consideration are used, and the minimum-cost devices arising from these constraints are reviewed. 9 refs., 13 figs., 4 tabs.

Reid, R.L.; Galambos, J.D.; Peng, Y.K.M.

1988-09-01

329

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

330

Isolation and confinement - Considerations for colonization  

NASA Technical Reports Server (NTRS)

This paper discusses three types of isolation (sensory/perceptual, temporal, and social) that could adversely affect mankind in space. The literature dealing with laboratory and field experiments relevant to these areas is summarized and suggestions are given for dealing with these problems within the space colony community. Also, consideration is given to the potential effects of physical confinement and the need for usable space. Finally, a modification of Maslow's hierarchy of needs is proposed as a theoretical framework to understand and investigate mankind's psychological needs in space.

Akins, F. R.

1978-01-01

331

Perlite for permanent confinement of cesium  

NASA Astrophysics Data System (ADS)

We present the potential use of expanded perlite, a metastable amorphous hydrated aluminium silicate, as a permanent medium for the long-term confinement of cesium. The method requires simply a loading by mixing an aqueous cesium nitrate solution and expanded perlite at 300 K followed by densification by sintering. The formation of pollucite, CsAlSi 2O 6, a naturally occurring mineral phase, upon careful heat treatment is demonstrated by X-ray diffraction. Leaching tests on the resulting glass-ceramics reveal a very low Cs departure of 0.5 mg m -2 d -1.

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

2006-06-01

332

Alpha particle confinement in tandem mirrors  

SciTech Connect

Mechanisms leading to loss of alpha particles from non-axisymmetric tandem mirrors are considered. Stochastic diffusion due to bounce-drift resonances, which can cause rapid radial losses of high-energy alpha particles, can be suppressed by imposing a 20% rise in axisymmetric fields before the quadrupole transition sections. Alpha particles should then be well-confined until thermal energies when they enter the resonant plateau require. A fast code for computation of drift behavior in reactors is described. Sample calculations are presented for resonant particles in a proposed coil set for the Tandem Mirror Next Step.

Devoto, R.S.; Ohnishi, M.; Kerns, J.; Woo, J.T.

1980-10-10

333

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

334

Modified PRISM theory for confined polymers.  

PubMed

We propose a modified polymer reference interaction site model (PRISM) to describe the interfacial density profiles of polymers in contact with planar and curved solid surfaces. In the theoretical approach, a bridge function derived from density functional method is included. In description of hard-sphere polymer at planar and curved surfaces with an arbitrary external field, the effect of modification has been validated by the available simulation data, except for low density system. When extended to confined real systems, the modified theoretical model also shows an encouraging prospect in description of the interfacial structure and properties. PMID:23163388

Xu, Mengjin; Zhang, Chen; Du, Zhongjie; Mi, Jianguo

2012-11-14

335

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

336

Adjoint ``Quarks'' and the Physics of Confinement  

E-print Network

The quark-antiquark potential and the chromoelectric fields generated by ``quarks'' in the adjoint representation of SU(2) color are analyzed in the scaling region of the theory. New results with interesting implications for our understanding of the confinement mechanism are presented. In particular, the formation of color-electric flux-tubes between adjoint quarks is demonstrated in four-dimensional SU(2) color. The flux-tubes for fundamental and adjoint representation quarks are shown to have very similar cross-sections. This result could imply that the QCD vacuum is dual to a type I superconductor.

Howard D. Trottier

1995-11-04

337

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

338

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

NASA Astrophysics Data System (ADS)

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

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

2009-01-01

339

A GASFLOW analysis of a steam explosion accident in a typical light-water reactor confinement building  

SciTech Connect

Steam over-pressurization resulting from ex-vessel steam explosion (fuel-coolant interaction) may pose a serious challenge to the integrity of a typical light-water reactor confinement building. If the steam generation rate exceeds the removal capacity of the Airborne Activity Confinement System, confinement over pressurization occurs. Thus, there is a large potential for an uncontrolled and unfiltered release of fission products from the confinement atmosphere to the environment at the time of the steam explosion. The GASFLOW computer code was used to analyze the effects of a hypothetical steam explosion and the transport of steam and hydrogen throughout a typical light-water reactor confinement building. The effects of rapid pressurization and the resulting forces on the internal structures and the heat exchanger service bay hatch covers were calculated. Pressurization of the ventilation system and the potential damage to the ventilation fans and high-efficiency particulate air filters were assessed. Because of buoyancy forces and the calculated confinement velocity field, the hydrogen diffuses and mixes in the confinement atmosphere but tends to be transported to its upper region.

Travis, J.R. [ESSI Inc. (United States); Wilson, T.L.; Spore, J.W.; Lam, K.L. [Los Alamos National Lab., NM (United States); Rao, D.V. [SEA Inc. (United States)

1994-09-01

340

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

341

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

342

Fire Risk Analysis for Armenian NPP Confinement  

SciTech Connect

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

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

2006-07-01

343

Nematode locomotion in unconfined and confined fluids  

NASA Astrophysics Data System (ADS)

The millimeter-long soil-dwelling nematode Caenorhabditis elegans propels itself by producing undulations that propagate along its body and turns by assuming highly curved shapes. According to our recent study [V. Padmanabhan et al., PLoS ONE 7, e40121 (2012), 10.1371/journal.pone.0040121] all these postures can be accurately described by a piecewise-harmonic-curvature 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 of the body of the nematode on its locomotion. These effects are not accounted for by the classical resistive-force and slender-body theories.

Bilbao, Alejandro; Wajnryb, Eligiusz; Vanapalli, Siva A.; Blawzdziewicz, Jerzy

2013-08-01

344

Confinement and localization on domain walls  

SciTech Connect

We continue the studies of localization of the U(1) gauge fields on domain walls. Depending on dynamics of the bulk theory the gauge field localized on the domain wall can be either in the Coulomb phase or squeezed into flux tubes implying (Abelian) confinement of probe charges on the wall along the wall surface. First, we consider a simple toy model with one flavor in the bulk at weak coupling (a minimal model) realizing the latter scenario. We then suggest a model presenting an extension of the Seiberg-Witten theory which is at strong coupling, but all theoretical constructions are under full control if we base our analysis on a dual effective action. Finally, we compare our findings with the wall in a 'nonminimal' theory with two distinct quark flavors that had been studied previously. In this case the U(1) gauge field trapped on the wall is exactly massless because it is the Goldstone boson of a U(1) symmetry in the bulk spontaneously broken on the wall. The theory on the wall is in the Coulomb phase. We explain why the mechanism of confinement discussed in the first part of the paper does not work in this case, and strings are not formed on the walls.

Auzzi, R. [Department of Physics, Swansea University, Singleton Park, Swansea SA2 8PP (United Kingdom); Bolognesi, S. [William I. Fine Theoretical Physics Institute, University of Minnesota, 116 Church St. S.E., Minneapolis, Minnesota 55455 (United States); Shifman, M. [William I. Fine Theoretical Physics Institute, University of Minnesota, 116 Church St. S.E., Minneapolis, Minnesota 55455 (United States); Laboratoire de Physique Theorique Universite de Paris-Sud XI Batiment 210, F-91405 Orsay Cedex (France); Yung, A. [William I. Fine Theoretical Physics Institute, University of Minnesota, 116 Church St. S.E., Minneapolis, Minnesota 55455 (United States); Petersburg Nuclear Physics Institute, Gatchina, St. Petersburg 188300 (Russian Federation) and Institute of Theoretical and Experimental Physics, Moscow 117259 (Russian Federation)

2009-02-15

345

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

346

Hydrogen Confinement in Carbon Nanopores: Extreme Densification at Ambient Temperature  

SciTech Connect

In-situ small angle neutron scattering (SANS) studies of hydrogen confined in small pores of polyfurfuryl alcohol-derived activated carbon (PFAC) at room-temperature provided for the first time its phase behavior in equilibrium with external H2 at pressures up to 200 bar. The data was used to evaluate the density of the adsorbed fluid, which appears to be a function of both pore size and pressure, and approaches the liquid hydrogen density in narrow nanopores at 200 bar. The surface-molecule interactions responsible for densification of hydrogen within the pores create internal pressures which exceed by a factor of up to ~ 60 the external gas pressures, confirming the benefits of adsorptive over compressive storage. These results can be utilized to guide the development of new carbon adsorbents tailored for maximum hydrogen storage capacities at near ambient temperatures.

Gallego, Nidia C [ORNL; He, Lilin [ORNL; Saha, Dipendu [ORNL; Contescu, Cristian I [ORNL; Melnichenko, Yuri B [ORNL

2011-01-01

347

Integrated diagnostic analysis of inertial confinement fusion capsule performance  

SciTech Connect

A conceptual model is developed for typical inertial confinement fusion implosion conditions that integrates available diagnostic information to determine the stagnation properties of the interior fill and surrounding shell. Assuming pressure equilibrium at peak compression and invoking radiative and equation-of-state relations, the pressure, density, and electron temperature are obtained by optimized fitting of the experimental output to smooth, global functional forms. Typical observational data that may be used includes x-ray self-emission, directional neutron time-of-flight signals, neutron yield, high-resolution x-ray spectra, and radiographic images. This approach has been validated by comparison with radiation-hydrodynamic simulations, producing semi-quantitative agreement. Model results implicate poor kinetic energy coupling to the hot core as the primary cause of the observed low thermonuclear burn yields.

Cerjan, Charles; Springer, Paul T.; Sepke, Scott M. [Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550 (United States)] [Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550 (United States)

2013-05-15

348

Development of Compton Radiography Diagnostics for Inertial Confinement Fusion Implosions  

SciTech Connect

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

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

2010-11-16

349

Integrated diagnostic analysis of inertial confinement fusion capsule performancea)  

NASA Astrophysics Data System (ADS)

A conceptual model is developed for typical inertial confinement fusion implosion conditions that integrates available diagnostic information to determine the stagnation properties of the interior fill and surrounding shell. Assuming pressure equilibrium at peak compression and invoking radiative and equation-of-state relations, the pressure, density, and electron temperature are obtained by optimized fitting of the experimental output to smooth, global functional forms. Typical observational data that may be used includes x-ray self-emission, directional neutron time-of-flight signals, neutron yield, high-resolution x-ray spectra, and radiographic images. This approach has been validated by comparison with radiation-hydrodynamic simulations, producing semi-quantitative agreement. Model results implicate poor kinetic energy coupling to the hot core as the primary cause of the observed low thermonuclear burn yields.

Cerjan, Charles; Springer, Paul T.; Sepke, Scott M.

2013-05-01

350

Viscous nonpolar liquids in confinement studied by mechanical solvation.  

PubMed

Using surface selective triplet state solvation techniques, we study the relaxation behavior of nonpolar liquids near their glass transition in confinement to porous glass with 4 nm pore diameter. As specific liquid-surface interactions are not expected for alkanes, we ask whether a substantial frustration of the dynamics is a general phenomenon for such liquids, and how the effects change with surface silanization. We find that interfacial dynamics display relaxation times that are increased by orders of magnitude for several nonpolar molecular liquids. Silanization removes this frustration effect almost entirely. Regarding the comparison of native versus silanized pore surfaces, it is concluded that the strong adhesive forces involved in alkanes wetting silica can explain the sluggish interfacial dynamics. The findings are not consistent with finite size effects. PMID:19725624

Wen, Wen; Richert, Ranko

2009-08-28

351

Viscous nonpolar liquids in confinement studied by mechanical solvation  

NASA Astrophysics Data System (ADS)

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

Wen, Wen; Richert, Ranko

2009-08-01

352

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

353

Quantum dynamics of a dissipative and confined cyclotron motion  

NASA Astrophysics Data System (ADS)

We study the dissipative dynamics of a charged oscillator in a magnetic field by coupling (a la Caldeira and Leggett) it to a heat bath consisting of non-interacting harmonic oscillators. We derive here the autocorrelation functions of the position and momentum and study its behavior at various limiting situations. The equilibrium (steady state) dispersions of position and momentum are obtained from their respective autocorrelation functions. We analyze the equilibrium position and momentum dispersions at low and high temperatures for both low and high magnetic field strengths. We obtain the classical diffusive behavior (at long times) as well as the equilibrium momentum dispersion of the free quantum charged particle in a magnetic field, in the limit of vanishing oscillator potential ?0. We establish the relations between the reduced partition function and the equilibrium dispersions of the dissipative and confined cyclotron problem.

Kumar, Jishad

2014-01-01

354

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

355

Antiproton powered propulsion with magnetically confined plasma engines  

NASA Technical Reports Server (NTRS)

The reaction of the matter-antimatter annihilation, with its specific energy being over 250 times the specific energy released in nuclear fusion, is considered as an energy source for spacecraft propulsion. A concept of a magnetically confined pulsed plasma engine is described. In this concept, antiproton beams are injected axially into a pulsed magnetic mirror system, where they annihilate with an initially neutral hydrogen gas; the resulting charge annihilation products transfer energy to the hydrogen propellant, which is then exhausted through one end of the pulsed mirror system to provide thrust. Numerical simulations were developed to calculate the annihilation rate of antiprotons in hydrogen and to follow the resulting ion, muon, and electron/positron number density evolutions.

Lapointe, Michael R.

1989-01-01

356

Nonvolatile semiconductor memory having three dimension charge confinement  

DOEpatents

A layered semiconductor device with a nonvolatile three dimensional memory comprises a storage channel which stores charge carriers. Charge carriers flow laterally through the storage channel from a source to a drain. Isolation material, either a Schottky barrier or a heterojunction, located in a trench of an upper layer controllably retains the charge within the a storage portion determined by the confining means. The charge is retained for a time determined by the isolation materials' nonvolatile characteristics or until a change of voltage on the isolation material and the source and drain permit a read operation. Flow of charge through an underlying sense channel is affected by the presence of charge within the storage channel, thus the presences of charge in the memory can be easily detected.

Dawson, L. Ralph (Albuquerque, NM); Osbourn, Gordon C. (Albuquerque, NM); Peercy, Paul S. (Albuquerque, NM); Weaver, Harry T. (Albuquerque, NM); Zipperian, Thomas E. (Albuquerque, NM)

1991-01-01

357

Investigation B: Laminar confined coaxial entrance flow with heat generation  

NASA Technical Reports Server (NTRS)

The results of a parametric study on the entrance flow region in a gas core nuclear reactor are presented. The physical system is modeled as laminar confined, coaxial flow with heat generation in the inner fluid. The governing equations include the boundary layer approximations and the assumptions of only radial radiative transport of energy represented as an energy diffusion term. The Von Mises transformation and a zeta transformation are used to transform the equations into nonlinear nonhomogeneous convective-diffusion equations. A unique combination of forward and backward difference equations which yields accurate results at moderate computational times, is used in the numerical method. Results show that the rapidly accelerating, heat generating inner stream actually shrinks in radius as it expands axially.

Bobba, G. K. M.; Weinstein, H.

1975-01-01

358

Development of Compton radiography of inertial confinement fusion implosionsa)  

NASA Astrophysics Data System (ADS)

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

Tommasini, R.; Hatchett, S. P.; Hey, D. S.; Iglesias, C.; Izumi, N.; Koch, J. A.; Landen, O. L.; MacKinnon, A. J.; Sorce, C.; Delettrez, J. A.; Glebov, V. Yu.; Sangster, T. C.; Stoeckl, C.

2011-05-01

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

Acid gas removal in a confined vortex scrubber  

SciTech Connect

This paper reports results of acid gas removal tests performed on a confined vortex scrubber. The confined vortex scrubber (CVS) was developed at the Energy Technology Office of Textron Defense Systems (ETO/TDS) under company as well as Pittsburgh Energy Technology Center (PETC) funding. Previous tests on the CVS have demonstrated > 98% capture for sub-micron fly ash particles, as well as high mercury vapor removal from gas streams. In the recent tests water, sodium hydroxide, and sodium sulfite and bisulfite solutions were used to scrub out hydrochloric, acid gas (HCl) and sulfur dioxide (SO{sub 2}) doped in air supplied to the CVS. The capture efficiency was determined as a function of acid gas concentration, liquor flow rate, and liquor type. When the liquor was supplied only inside the CVS squirrel cage the HCl removal efficiency varied from 85--100% while the SO{sub 2} removal efficiency varied from 60--80%. Significantly higher captures were obtained at 1/3 rd the liquor flow rate by spraying the liquor upstream of the CVS in the air inlet pipe, and increasing the liquor/gas contact time. Total HCl captures > 95% and SO{sub 2} captures > 85% were obtained at a liquid/gas ratio of only 2 gal/1,000 acf for acid gas concentrations of 200--1,800 ppmv. There were no significant differences in the SO{sub 2}, scrubbing ability of the three sodium solutions, and the HCl scrubbing ability of water and a sodium hydroxide solution. These results suggest that the acid gas capture in the CVS is mass transfer limited because of the extremely short gas residence times in the CVS.

Hura, H.S. [Energy Systems Associates, Pittsburgh, PA (United States); Diehl, R.C. [Textron Defense Systems, Everett, MA (United States). Energy Technology Office

1994-12-31

361

Confinement in Yang Mills: Elements of a Big Picture  

SciTech Connect

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

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

2008-10-22

362

Confinement and Tritium Stripping Systems for APT Tritium Processing  

SciTech Connect

This report identifies functions and requirements for the tritium process confinement and clean-up system (PCCS) and provides supporting technical information for the selection and design of tritium confinement, clean-up (stripping) and recovery technologies for new tritium processing facilities in the Accelerator for the Production of Tritium (APT). The results of a survey of tritium confinement and clean-up systems for large-scale tritium handling facilities and recommendations for the APT are also presented.

Hsu, R.H. [Westinghouse Savannah River Company, AIKEN, SC (United States); Heung, L.K.

1997-10-20

363

Soliton Staircases and Standing Strain Waves in Confined Colloidal Crystals  

E-print Network

We show by computer simulation of a two-dimensional crystal confined by corrugated walls that confinement can be used to impose a controllable mesoscopic superstructure of predominantly mechanical elastic character. Due to an interplay of the particle density of the system and the width D of the confining channel, "soliton staircases" can be created along both parallel confining boundaries, that give rise to standing strain waves in the entire crystal. The periodicity of these waves is of the same order as D. This mechanism should be useful for structure formation in the self-assembly of various nanoscopic materials.

Yu-Hang Chui; Surajit Sengupta; Kurt Binder

2009-12-07

364

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

365

The cruel and unusual phenomenology of solitary confinement.  

PubMed

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

366

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

367

Two dimensional beam smoothing by spectral dispersion for direct drive inertial confinement fusion  

SciTech Connect

Two dimensional smoothing by spectral dispersion is analyzed by using diffraction theory calculations. It is shown that by using standard frequency modulated light one can obtain bandwidth limited smoothing over integration times relevant to inertial confinement fusion (about 1 nsec) with modest induced beam divergence. At longer integration times one can obtain bandwidth limited smoothing by increasing the divergence and/or by using more advanced phase modulation methods.

Rothenberg, J.E.

1995-07-11

368

Modelling debris and shrapnel generation in inertial confinement fusion experiments  

NASA Astrophysics Data System (ADS)

Modelling and mitigation of damage are crucial for safe and economical operation of high-power laser facilities. Experiments at the National Ignition Facility use a variety of targets with a range of laser energies spanning more than two orders of magnitude (?14 kJ to ?1.9 MJ). Low-energy inertial confinement fusion experiments are used to study early-time x-ray load symmetry on the capsule, shock timing, and other physics issues. For these experiments, a significant portion of the target is not completely vaporized and late-time (hundreds of ns) simulations are required to study the generation of debris and shrapnel from these targets. Damage to optics and diagnostics from shrapnel is a major concern for low-energy experiments. We provide the first full-target simulations of entire cryogenic targets, including the Al thermal mechanical package and Si cooling rings. We use a 3D multi-physics multi-material hydrodynamics code, ALE-AMR, for these late-time simulations. The mass, velocity, and spatial distribution of shrapnel are calculated for three experiments with laser energies ranging from 14 to 250 kJ. We calculate damage risk to optics and diagnostics for these three experiments. For the lowest energy re-emit experiment, we provide a detailed analysis of the effects of shrapnel impacts on optics and diagnostics and compare with observations of damage sites.

Eder, D. C.; Fisher, A. C.; Koniges, A. E.; Masters, N. D.

2013-11-01

369

Confinement effects on strongly polar alkylcyanobiphenyl liquid crystals probed by dielectric spectroscopy  

NASA Astrophysics Data System (ADS)

Dielectric spectroscopy has often been used to study confinement effects in alkylcyanobiphenyl liquid crystals. In this paper, we highlight some of the effects that have been discovered previously and add new data and interpretation. Aerosil nanoparticles form a hydrogen bonded random porous network. In dispersions of alkylcyanobiphenyls with aerosils, an additional slow process arises, that we ascribe to the relaxation of liquid crystal molecules in close interaction with these nanoparticles. Their relaxation is retarded by a hydrogen bond interaction between the cyano group of the liquid crystals and an aerosil surface hydroxyl group. A similar surface process is also observed in Vycor porous glass, a random rigid structure with small pores. A comparison of the temperature dependence of the relaxation times of the surface processes in decylcyanobiphenyl and isopentylcyanobiphenyl is made, both for Vycor and aerosil confinement. In decylcyanobiphenyl, the temperature dependence for the bulk and surface processes is Arrhenius (in a limited temperature range above the melting point), except in Vycor, where it is a Vogel-Fulcher-Tamman dependence (over a much broader temperature range). In bulk and confined isopentylcyanobiphenyl, the molecular processes have a Vogel-Fulcher-Tamman dependence, whereas the surface processes have an Arrhenius one. Another effect is the acceleration of the rotation around the short molecular axis in confinement, and particularly in aerosil dispersions. This is a consequence of the disorder introduced in the liquid crystalline phase. The disorder drives the relaxation time towards a more isotropic value, resulting in an acceleration for the short axis rotation.

Leys, Jan; Glorieux, Christ; Thoen, Jan

2008-06-01

370

Helical Single Crystals Grown in Confined Space  

NASA Astrophysics Data System (ADS)

We report here the formation and growth process of the double-twist PET(R*-9) helical single crystals. It has been observed that the population of helical crystals increases with increasing the thickness of the thin films. In addition to the crystallization temperature effect, the pitch lengths along both the long and short twist axes also change with thin film thickness, which is attributed to the substrate confinement effect on the thin film samples. The early stage of the helical crystals has been studied using solvent washing experiments. It has been found that the morphology is a saddle-like shape. Nucleation starts at the center of the flat-on part, and growth directions include both along the long and short axes of the crystals. Coexistence of the flat-elongated and helical forms will also be discussed.

Li, Christopher; Cheng, Stephen; Zhang, John; Harris, Frank; Chien, Liang-Chy; Lotz, Bernard

2001-03-01

371

On Some Features of Color Confinement  

E-print Network

It is argued that a dual symmetry is needed to naturally explain experimental limits on color confinement. Since color is an exact symmetry the only possibility is that this symmetry be a dual symmetry, related to non trivial spatial homotopy. The sphere at infinity of 3-dimensional space being 2-dimensional, the relevant homotopy is $\\Pi_2$, the corresponding configurations monopoles, and the mechanism dual superconductivity. The consistency of the order-disorder nature of the deconfining transition is compared with lattice data . It is also shown that the only dual quantum number is magnetic charge and the key quantity is 't Hooft tensor, independent of the gauge group. The general form of the 't Hooft tensor is computed.

Di Giacomo, A

2008-01-01

372

On Some Features of Color Confinement  

E-print Network

It is argued that a dual symmetry is needed to naturally explain experimental limits on color confinement. Since color is an exact symmetry the only possibility is that this symmetry be a dual symmetry, related to non trivial spatial homotopy. The sphere at infinity of 3-dimensional space being 2-dimensional, the relevant homotopy is $\\Pi_2$, the corresponding configurations monopoles, and the mechanism dual superconductivity. The consistency of the order-disorder nature of the deconfining transition is compared with lattice data . It is also shown that the only dual quantum number is magnetic charge and the key quantity is 't Hooft tensor, independent of the gauge group. The general form of the 't Hooft tensor is computed.

A. Di Giacomo

2008-09-13

373

Chiral symmetry, Confinement and Nuclear Matter properties  

E-print Network

We discuss the possible influence of fundamental QCD properties such as spontaneous chiral symmetry breaking and nucleon substructure on nuclear matter properties. We propose a chiral version of the relativistic $\\sigma-\\omega$ model in which the attractive background scalar field is associated with the chiral invariant field governing the radial fluctuations of the quark condensate. Nuclear matter stability is ensured once the scalar response of the nucleon depending on the quark confinement mechanism is properly incorporated. The needed parameters are estimated from lattice results and a satisfactory description of bulk properties follows, the only really free parameter being the $\\omega NN$ coupling constant. Pion loops can be also incorporated to obtain in a consistent way the finite density chiral susceptibilities. A good description of the asymmetry energy is obtained once the full rho meson exchange and Fock terms are included.

G. Chanfray; M. Ericsson; E. Massot

2007-09-17

374

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 contribute to cell sorting in embryonic development.

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

2014-03-04

375

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

376

Light ion driven inertial confinement fusion  

SciTech Connect

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

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

1992-05-01

377

Fabrication issues of oxide-confined VCSELs  

SciTech Connect

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

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

1997-04-01

378

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

379

High beta and confinement studies on TFTR  

SciTech Connect

A new regime of high poloidal beta operation in TFTR was developed in the course of the first two years of this project (9/25/89 to 9/24/91). Our proposal to continue this successful collaboration between Columbia University and the Massachusetts Institute of Technology with the Princeton Plasma Physics Laboratory for a three year period (9/25/91 to 9/24/94) to continue to investigate improved confinement and tokamak performance in high poloidal beta plasmas in TFTR through the DT phase of operation was approved by the DOE and this is a report of our progress during the first 9 month budget period of the three year grant (9/25/91 to 6/24/92). During the approved three year project period we plan to (1) extend and apply the low current, high QDD discharges to the operation of TFTR using Deuterium and Tritium plasma; (2) continue the analysis and plan experiments on high poloidal beta phenomena in TFTR including: stability properties, enhanced global confinement, local transport, bootstrap current, and divertor formation; (3) plan and carry out experiments on TFTR which attempt to elevate the central q to values > 2 where entry to the second stability regime is predicted to occur; and (4) collaborate on high beta experiments using bean-shaped plasmas with a stabilizing conducting shell in PBX-M. In the seven month period covered by this report we have made progress in each of these four areas through the submission of 4 TFTR Experimental Proposals and the partial execution of 3 of these using a total of 4.5 run days during the August 1991 to February 1992 run.

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

1992-01-01

380

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

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

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

383

A SECURE JAILING SYSTEM FOR CONFINING UNTRUSTED APPLICATIONS  

E-print Network

A SECURE JAILING SYSTEM FOR CONFINING UNTRUSTED APPLICATIONS Guido van 't Noordende, ´Ad´am Balogh, Application Confinement, Jailing. Abstract: System call interception based jailing is a well-known method an overview of the most important threats to jailing systems, and presents novel mechanisms for implementing

Tanenbaum, Andrew S.

384

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

385

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

386

Respiratory symptoms and ventilatory capacity in swine confinement workers.  

PubMed Central

A group of 59 workers (41 men and 18 women) employed in swine confinement areas was studied to assess the presence of acute and chronic respiratory symptoms and the prevalence of abnormalities in ventilatory function. A control group of 46 (31 men and 15 women) unexposed workers was studied for the prevalence of chronic respiratory symptoms. For both male and female swine confinement workers complaints of chronic cough, dyspnoea, and chest tightness were significantly more frequent than among control workers. Male workers also complained more of chronic phlegm. Male swine confinement workers who were smokers had significantly higher prevalences of chronic cough, chronic phlegm, and chronic bronchitis than male non-smoking swine confinement workers. The frequency of acute symptoms associated with the workshift was high among the swine confinement workers with more than half of the workers complaining of cough and dyspnoea associated with work. Significant acute across shift reductions in lung function occurred in swine confinement workers, being largest for FEF25. All Monday preshift ventilatory capacity measurements in male confinement workers were significantly lower than predicted values; FVC and FEV1 were found to be lower than predicted values for women. The data indicate that exposure in swine confinement buildings is associated with the development of acute and chronic respiratory symptoms and impairment of lung function. Smoking appears to aggravate these changes. PMID:1606030

Zuskin, E; Zagar, Z; Schachter, E N; Mustajbegovic, J; Kern, J

1992-01-01

387

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

388

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

389

Recent results on heating and confinement in TEXTOR  

SciTech Connect

The experiments on plasma heating and confinement in a medium size tokamak are reported. A high neutron production is obtained due to reaching the I-mode of the confinement operation better energy storage and the efficient use of RF reactor systems. (AIP) {copyright} {ital 1996 American Institute of Physics.}

Vandenplas, P.E.; Koch, R.; Messiaen, A.M. [Laboratoire de Physique des Plasmas-Laboratorium voor Plasmafysica, Association Euratom-Etat belge-Associatie Euratom-Belgische Staat, Ecole Royale Militaire-B-1040 (Brussels) Koninklijke Militaire School; Finken, K.H. [Institut fuer Plasmaphysik, Forschungszentrum Juelich, GmbH, Association Euratom-KFA, D-52425 Juelich (Germany); Ongena, J. [Laboratoire de Physique des Plasmas-Laboratorium voor Plasmafysica, Association Euratom-Etat belge-Associatie Euratom-Belgische Staat, Ecole Royale Militaire-B-1040 (Brussels) Koninklijke Militaire School; Philipps, V.; Samm, U.; Unterberg, B. [Institut fuer Plasmaphysik, Forschungszentrum Juelich, GmbH Association Euratom-KFA, D-52425 Juelich (Germany); Van Oost, G.; Van Wassenhove, G. [Laboratoire de Physique des Plasmas-Laboratorium voor Plasmafysica, Association Euratom-Etat belge-Associatie Euratom-Belgische Staat, Ecole Royale Militaire-B-1040 (Brussels) Koninklijke Militaire School; Winter, J. [Institut fuer Plasmaphysik, Forschungszentrum Juelich, GmbH Association Euratom-KFA, D-52425 Juelich (Germany); Dumortier, P.; Durodie, F. [Laboratoire de Physique des Plasmas-Laboratorium voor Plasmafysica, Association Euratom-Etat belge-Associatie Euratom-Belgische Staat, Ecole Royale Militaire-B-1040 (Brussels) Koninklijke Militaire School; Esser, H.G.; Euringer, H.; Giesen, B.; Hintz, E.; Lochter, M.; Tokar, M.Z.; Wolf, G.H.; Bertschinger, G.; Fuchs, G. [Institut fuer Plasmaphysik, Forschungszentrum Juelich, GmbH Association Euratom-KFA, D-52425 Juelich, (Germany); Hillis, D.L. [Oak Ridge National Laboratory, P.O. Box X, Oak Ridge, Tennessee 37831 (United States); Hoenen, F.; Huettemann, P.; Koenen, L.; Koslowski, H.R.; Kraemer-Flecken, A.; Mank, G. [Institut fuer Plasmaphysik, Forschungszentrum Juelich, GmbH Association Euratom-KFA, D-52425 Juelich (Germany); Pettiaux, D.

1995-09-01

390

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.

391

Elastic wave propagation in confined granular systems Ellk Somfai,1,  

E-print Network

present numerical simulations of acoustic wave propagation in confined granular systems consisting as follows for an interplay between force chain type correlations and sound propagElastic wave propagation in confined granular systems Ellák Somfai,1, * Jean-Noël Roux,2 Jacco H

392

Helically forced MHD flows in confined cylindrical geometries  

E-print Network

Helically forced MHD flows in confined cylindrical geometries Malcolm Roberts1 , Matthieu Leroy1 the resistive magnetohydrodynamic (MHD) equations. A helical magnetic field is imposed via boundary conditions be used in complex geometries is also proposed. Keywords: MHD, self-organization, confined geometry

Boyer, Edmond

393

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

394

Checking Ownership and Confinement Properties Alex Potanin and James Noble  

E-print Network

to construct an ownership forest using the heap root set #12;2 objects as roots and makes the forestChecking Ownership and Confinement Properties Alex Potanin and James Noble alex- tures, including object ownership, confinement, and uniqueness. Understanding the kinds of aliasing

Potanin, Alex

395

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

396

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

397

Status and prospects for fusion energy from magnetically confined plasmas  

Microsoft Academic Search

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

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

1998-01-01

398

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

399

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

400

Psychological and Behavioral Changes during Confinement in a 520-Day Simulated Interplanetary Mission to Mars  

PubMed Central

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 m3 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

401

Theory of plasma confinement in non-axisymmetric magnetic fields.  

PubMed

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. PMID:25047050

Helander, Per

2014-08-01

402

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

403

Influence of Confinement on Dynamical Heterogeneities in Dense Colloidal Samples  

E-print Network

We study a dense colloidal suspension confined between two quasiparallel glass plates as a model system for a supercooled liquid in confined geometries. We directly observe the three-dimensional Brownian motion of the colloidal particles using laser scanning confocal microscopy. The particles form dense layers along the walls, but crystallization is avoided as we use a mixture of two particle sizes. A normally liquid-like sample, when confined, exhibits slower diffusive motion. Particle rearrangements are spatially heterogeneous, and the shapes of the rearranging regions are strongly influenced by the layering. These rearranging regions become more planar upon confinement. The wall-induced layers and changing character of the spatially heterogeneous dynamics appear strongly connected to the confinement induced glassiness.

Kazem V. Edmond; Carolyn R. Nugent; Eric R. Weeks

2010-03-03

404

Structural integrity of a confinement vessel for testing nuclear fuels for space propulsion  

SciTech Connect

Nuclear propulsion systems for rockets could significantly reduce the travel time to distant destinations in space. However, long before such a concept can become reality, a significant effort must be invested in analysis and ground testing to guide the development of nuclear fuels. Any testing in support of development of nuclear fuels for space propulsion must be safely contained to prevent the release of radioactive materials. This paper describes analyses performed to assess the structural integrity of a test confinement vessel. The confinement structure, a stainless steel pressure vessel with bolted flanges, was designed for operating static pressures in accordance with the ASME Boiler and Pressure Vessel Code. In addition to the static operating pressures, the confinement barrier must withstand static overpressures from off-normal conditions without releasing radioactive material. Results from axisymmetric finite element analyses are used to evaluate the response of the confinement structure under design and accident conditions. For the static design conditions, the stresses computed from the ASME code are compared with the stresses computed by the finite element method.

Bergmann, V.L.

1992-08-01

405

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

406

Room-temperature initialization, dynamics, and measurement of coherent electron spins in strongly confined quantum dots  

NASA Astrophysics Data System (ADS)

Semiconductor quantum dots provide a platform for studying and exploiting individual electron spins as they interact with a complex solid state environment. Colloidal nanocrystal quantum dots are of particular interest for potential applications, because they can achieve sufficient confinement to operate at room temperature with relatively robust electron spin coherence. The strong confinement in these nanostructures leads to significant effects caused by mixing of valence subbands and variation in particle size and shape. These effects influence the processes of carrier spin initialization and detection. We have performed ensemble time-resolved Faraday rotation experiments as well as single-dot photoluminescence excitation measurements to study how the strong quantum confinement affects the spin physics in these systems. Single dot PLE measurements reveal mechanisms of transition broadening that are relevant at room temperature, including thermal broadening and spectral diffusion due to mobile charges in the surrounding environment. We find that the mixing of valence subbands in the confined hole states largely determines the efficiency of optical spin pumping and Faraday-rotation-based spin detection. By studying these effects, we take a step towards controlling and exploiting spin coherence in this flexible room temperature platform.

Berezovsky, Jesse; Fumani, Ahmad K.; Wolf, Michael

2014-08-01

407

Atoms in boxes: From confined atoms to electron-atom scattering  

NASA Astrophysics Data System (ADS)

We show that both confined atoms and electron-atom scattering can be described by a unified basis set method. The central idea behind this method is to place the atom inside a hard potential sphere, enforced by a standard Slater type basis set multiplied by a cutoff factor. For confined atoms, where the wall is placed close to the atomic nucleus, we show how the energy of the highest occupied atomic orbital and the static polarizability of helium and neon atoms evolve with the confinement radius. To our knowledge, these are the first confined atom polarizability calculations that include correlation for many-electron atoms, through the use of time-dependent density-functional theory. By placing the atom in a large spherical box, with a wall outside the electron density, we obtain scattering phase shifts using a recently developed method [M. van Faassen, A. Wasserman, E. Engel, F. Zhang, and K. Burke, Phys. Rev. Lett. 99, 043005 (2007)]. We show that the basis set method gives identical results to previously obtained phase shifts for e-H and e-He+ scattering.

van Faassen, Meta

2009-09-01

408

Inertial Confinement Fusion: steady progressInertial Confinement Fusion: steady progress towards ignition and high gaintowards ignition and high gain  

E-print Network

for Theoretical and Experimental Physics, Moscow 20th IAEA Conference on Fusion Energy, November 1­6, 2004Inertial Confinement Fusion: steady progressInertial Confinement Fusion: steady progress towards cold main DT in pressure equilibrium with the hot spark · Laser light creates a "bath" of thermal X

409

Species separation in inertial confinement fusion fuels  

SciTech Connect

It is shown by means of multi-fluid particle-in-cell simulations that convergence of the spherical shock wave that propagates through the inner gas of inertial confinement fusion-relevant experiments is accompanied by a separation of deuterium (D) and tritium (T) ions across the shock front. Deuterons run ahead of the tritons due to their lower mass and higher charge-to-mass ratio and can reach the center several tens of picoseconds before the tritons. The rising edge of the DD and TT fusion rate is also temporally separated by the same amount, which should be an observable in experiments and would be a direct proof of the 'stratification conjecture' on the shock front [Amendt et al., Phys. Plasmas 18, 056308 (2011)]. Moreover, dephasing of the D and T shock components in terms of density and temperature leads to a degradation of the DT fusion yield as the converging shock first rebounds from the fuel center (shock yield). For the parameters of this study, the second peak in the fusion yield (compression yield) is strongly dependent on the choice of the flux limiter.

Bellei, C.; Amendt, P. A.; Wilks, S. C. [Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550 (United States); Haines, M. G. [Blackett Laboratory, Imperial College, London SW7 2AZ (United Kingdom); Casey, D. T. [Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550 (United States); Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Li, C. K.; Petrasso, R. [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Welch, D. R. [Voss Scientic, Albuquerque, New Mexico 87108 (United States)

2013-01-15

410

Ion concentration diffusion in inertially confined plasmas  

NASA Astrophysics Data System (ADS)

Optimizing fusion yield in inertial confinement fusion (ICF) experiments requires number densities of the reactants to be equal throughout the fuel assembly. This condition can be easily satisfied during target fabrication. However, dynamical process of implosion gives rise to the inter-ion-species transport, resulting in these species' concentrations being perturbed from their initial values. In particular, classical, baro-, electro- and thermo-diffusive mechanisms of such a transport should be distinguished. Baro- and electro-diffusion ratios are obtained from ion fluid equations without invoking a kinetic calculation. Interestingly, plasma baro-diffusion is found to be identical to its neutral counterpart. On the other hand, thermo-diffusion ratios appearing in front of the ion and electron temperature gradients, as well as the classical diffusion coefficient, are intrinsically non-thermodynamic quantities. Their evaluation therefore does require a kinetic approach. By employing such an approach explicit dependence of the diffusion coefficients on the species' concentrations is found numerically for selected pairs of ion species. Initial implications of these newly obtained results are discussed.

Kagan, Grigory; Tang, Xian-Zhu

2012-10-01

411

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

412

Inertial confinement fusion with light ion beams.  

PubMed

The Particle Beam Fusion Accelerator II (PBFA II) is presently under construction and is the only existing facility with the potential of igniting thermonuclear fuel in the laboratory. The accelerator will generate up to 5 megamperes of lithium ions at 30 million electron volts and will focus them onto an inertial confinement fusion (ICF) target after beam production and focusing have been optimized. Since its inception, the light ion approach to ICF has been considered the one that combines low cost, high risk, and high payoff. The beams are of such high density that their self-generated electric and magnetic fields were thought to prohibit high focal intensities. Recent advances in beam production and focusing demonstrate that these self-forces can be controlled to the degree required for ignition, break-even, and high gain experiments. ICF has been pursued primarily for its potential military applications. However, the high efficiency and cost-effectiveness of the light ion approach enhance its potential for commercial energy application as well. PMID:17755963

Vandevender, J P; Cook, D L

1986-05-16

413

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

414

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

415

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

Erbas, Aykut; Netz, Roland R.

2013-01-01

416

Improved plasma confinement and evidence for a pressure-driven instability from reduced magnetic field errors in the CTX spheromak  

SciTech Connect

The 0.67 m radius mesh flux conserver (MFC) in CTX was replaced by a solid flux conserver (SFC), resulting in greatly reduced field errors. Decreased spheromak open flux led to vastly improved decaying discharges, including increased global energy confinement times /tau//sub E/ (from 20 to 180 ..mu..s) and corresponding magnetic energy decay times /tau//sub B/sup 2// (from 0.7 to 2 ms). Improved confinement allowed the observation of a pressure-driven instability which ejects plasma from the spheromak interior to the wall. 9 refs., 3 figs.

Fernandez, J.C.; Wysocki, F.J.; Jarboe, T.R.; Barnes, C.W.; Henins, I.; Knox, S.O.; Marklin, G.J.

1989-01-01

417

Oil-in-water emulsification using confined impinging jets.  

PubMed

A confined impinging jet mixing device has been used to investigate the continuous sunflower oil/water emulsification process under turbulent flow conditions with oil contents between 5% (v/v) and 10% (v/v). Various emulsifiers (Tween20, Span80, Whey Protein, Lecithin and Sodium Dodecylsulphate) varying in molecular weights have been studied. Mean droplet sizes varied with the emulsifiers used and smallest droplets were obtained under fully turbulent flow regime, i.e. at the highest jet flow rate and highest jet Reynolds Number conditions. Sodium Dodecylsulfate (SDS) produced droplets in the range of 3.8 ?m while 6 ?m droplets were obtained with Whey Protein. Similar droplet sizes were obtained under fully turbulent flow conditions (610 mL/min; Reynolds Number=13,000) for oil content varying between 5% (v/v) and 10% (v/v). To investigate the smallest droplet size possible in the device, the emulsion was passed through the geometry multiple times. Multi-pass emulsification resulted in reduction in droplet size indicating that longer residence in the flow field under high shear condition allowed for breakage of droplets as well as the time for the emulsifier to stabilize the newly formed droplets, decreasing the impact of coalescence. This was confirmed by timescale analysis of the involved process steps for the droplet data obtained via experiments. Dependence of mean droplet size on the o/w interfacial tension and peak energy dissipation was also investigated. PMID:22533995

Siddiqui, Shad W; Norton, Ian T

2012-07-01

418

An ICF (Inertial Confinement Fusion) power plant development program  

SciTech Connect

The development of Inertial Confinement Fusion (ICF) as a power source will require demonstrating four principal objectives: ignition and propagating burn, adequate gain ({eta}G {approx gt} 10) at low drive energy for the reactor driver, reactor pulse rates of a few Hz, and the long-term reliability and economics of a reactor. Additionally, the potential value and applicability of special-purpose ICF reactors, such as tritium breeding reactors and reactors for burning high level fission waste (actinide and fission products) should be investigated. To keep development time and costs to a minimum these should be accomplished with as few major facilities as possible, and subsystems should be developed only as they are needed. A viable scenario for Inertial Fusion Energy (IFE) would include establishing the first milestone in the National Academy of Sciences (NAS) and Fusion Policy Advisory Committee (FPAC) recommended Nova Upgrade, and the latter three in an Engineering Test Facility (ETF)/Demonstration Power Plant (DPP), i.e. two major facilities. To be successful in so short a time, operations at the major facilities would have to be supported by off-line reactor driver and other technology development. The program plan discussed here assumes that enhanced funding is available beginning in FY 1992. It is estimated that such a program could provide a prototype IFE power plant by the second decade of the 21st century and make commercial power available in mid to late 2020s.

Storm, E.; Hogan, W.J.; Lindl, J.D.

1990-06-05

419

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

420

Highly confined water: two-dimensional ice, amorphous ice, and clathrate hydrates.  

PubMed

Understanding phase behavior of highly confined water, ice, amorphous ice, and clathrate hydrates (or gas hydrates), not only enriches our view of phase transitions and structures of quasi-two-dimensional (Q2D) solids not seen in the bulk phases but also has important implications for diverse phenomena at the intersection between physical chemistry, cell biology, chemical engineering, and nanoscience. Relevant examples include, among others, boundary lubrication in nanofluidic and lab-on-a-chip devices, synthesis of antifreeze proteins for ice-growth inhibition, rapid cooling of biological suspensions or quenching emulsified water under high pressure, and storage of H2 and CO2 in gas hydrates. Classical molecular simulation (MD) is an indispensable tool to explore states and properties of highly confined water and ice. It also has the advantage of precisely monitoring the time and spatial domains in the sub-picosecond and sub-nanometer scales, which are difficult to control in laboratory experiments, and yet allows relatively long simulation at the 10(2) ns time scale that is impractical with ab initio molecular dynamics simulations. In this Account, we present an overview of our MD simulation studies of the structures and phase behaviors of highly confined water, ice, amorphous ice, and clathrate, in slit graphene nanopores. We survey six crystalline phases of monolayer (ML) ice revealed from MD simulations, including one low-density, one mid-density, and four high-density ML ices. We show additional supporting evidence on the structural stabilities of the four high-density ML ices in the vacuum (without the graphene confinement), for the first time, through quantum density-functional theory optimization of their free-standing structures at zero temperature. In addition, we summarize various low-density, high-density, and very-high-density Q2D bilayer (BL) ice and amorphous ice structures revealed from MD simulations. These simulations reinforce the notion that the nanoscale confinement not only can disrupt the hydrogen bonding network in bulk water but also can allow satisfaction of the ice rule for low-density and high-density Q2D crystalline structures. Highly confined water can serve as a generic model system for understanding a variety of Q2D materials science phenomena, for example, liquid-solid, solid-solid, solid-amorphous, and amorphous-amorphous transitions in real time, as well as the Ostwald staging during these transitions. Our simulations also bring new molecular insights into the formation of gas hydrate from a gas and water mixture at low temperature. PMID:25088018

Zhao, Wen-Hui; Wang, Lu; Bai, Jaeil; Yuan, Lan-Feng; Yang, Jinlong; Zeng, Xiao Cheng

2014-08-19

421

Chain dynamics in mesoscopically confined polymer melts. A field-cycling NMR relaxometry study  

NASA Astrophysics Data System (ADS)

Polymer chain dynamics were studied with the aid of field-cycling NMR relaxometry (time scale: 10-9s... 10-4s) supplemented by field gradient NMR diffusometry (time scale: 10-4s...100s). Three sorts of samples of mesoscopically confined polymer melts were examined. In the first sample series, linear poly(ethylene oxide) was incorporated in strands embedded in a quasi-solid and impenetrable methacrylate matrix. The strand diameters ranged from 10 to 60 nm. It was shown that chain dynamics becomes dramatically different from bulk behavior. This so-called “corset effect” occurs both above and below the critical molecular mass and reveals dynamic features predicted for reptation. On the time scale of spin-lattice relaxation, the frequency and molecular weight, signature of reptation, T1 ˜M0 ?3/4, that is limit II of the Doi/Edwards formalism corresponding to the mean squared segment displacement law ˜M0 t1/4, showed up. A “tube” diameter of only 0.6 nm was concluded to be effective on this time scale even when the strand diameter was larger than the radius of gyration of the PEO random coils. The corset effect is traced back to the lack of the local fluctuation capacity of the free volume under nanoscopic confinements. The confinement dimension at which the cross-over from confined to bulk chain dynamics is expected was estimated to be micrometers. Using the so-called roll-coating technique, micrometer thick polymer melt layers between Kapton foils were prepared. Perceptible differences from the bulk materials were found. The polymer species studied in this case was perfluoropolyether with Flory radii in the order of 7 nm. Remarkably, the confinement effect was shown to reach polymer-wall distances of the order 100 Flory radii. As a third confinement system, melts of perfluoropolyether were filled into a porous silica glass (Vycor; 4 nm nominal pore size). In this case, a crossover from Rouse dynamics in the bulk to reptation in the Doi/Edwards limit III (T1˜M-1/2 ?1/2 corresponding to ˜M-1/2 t1/2) was observed.

Kausik, R.; Mattea, C.; Kimmich, R.; Fatkullin, N.

2007-02-01

422

Physical confinement alters tumor cell adhesion and migration phenotypes.  

PubMed

Cell migration on planar surfaces is driven by cycles of actin protrusion, integrin-mediated adhesion, and myosin-mediated contraction; however, this mechanism may not accurately describe movement in 3-dimensional (3D) space. By subjecting cells to restrictive 3D environments, we demonstrate that physical confinement constitutes a biophysical stimulus that alters cell morphology and suppresses mesenchymal motility in human breast carcinoma (MDA-MB-231). Dorsoventral polarity, stress fibers, and focal adhesions are markedly attenuated by confinement. Inhibitors of myosin, Rho/ROCK, or ?1-integrins do not impair migration through 3-?m-wide channels (confinement), even though these treatments repress motility in 50-?m-wide channels (unconfined migration) by ?50%. Strikingly, confined migration persists even when F-actin is disrupted, but depends largely on microtubule (MT) dynamics. Interfering with MT polymerization/depolymerization causes confined cells to undergo frequent directional changes, thereby reducing the average net displacement by ?80% relative to vehicle controls. Live-cell EB1-GFP imaging reveals that confinement redirects MT polymerization toward the leading edge, where MTs continuously impact during advancement of the cell front. These results demonstrate that physical confinement can induce cytoskeletal alterations that reduce the dependence of migrating cells on adhesion-contraction force coupling. This mechanism may explain why integrins can exhibit reduced or altered function during migration in 3D environments. PMID:22707566

Balzer, Eric M; Tong, Ziqiu; Paul, Colin D; Hung, Wei-Chien; Stroka, Kimberly M; Boggs, Amanda E; Martin, Stuart S; Konstantopoulos, Konstantinos

2012-10-01

423

Investigation of the vorticity confinement method for flows with separation  

NASA Astrophysics Data System (ADS)

The development of the Vorticity Confinement Method has been driven by the need to compute large scale flow solutions with thin vortical regions. Currently used flow solvers artificially spread these vortical structures, or use Lagrangian markers to prevent their spreading. The problem arises when these vortices interact with the solid bodies. The artificially spread vortices give too weak an effect and Lagrangian solvers use special logic to simulate these interactions. This special logic, if it is to work under a variety of flow conditions is quite extensive, thus computationally inefficient. The Vorticity Confinement Method relies only upon the primitive variables of the flow field, thus providing a more general and much simpler approach to computing the flow field, while keeping the vortical regions thin. An investigation of the Vorticity Confinement Method for flows with separation will be conducted. This work will examine three aspects pertaining to the Vorticity Confinement Method and boundary layer separation. First will be a limitation, where confinement will be applied to an exact Blasius Layer profile subject to separation. The second, will involve an extension of the technique to accommodate the shape of the computational grids near the boundary layer. Finally, a new capability of the Vorticity Confinement Method will be explored, where a simple boundary layer model will be applied to flow undergoing dynamic stall. All these findings will combine to better define the applicability the Vorticity Confinement Method could be utilized.

Underhill, David Brian

424

An analytical solution for modeling thermal energy transfer in a confined aquifer system  

Microsoft Academic Search

A mathematical model is developed for simulating the thermal energy transfer in a confined aquifer with different geological\\u000a properties in the underlying and overlying rocks. The solutions for temperature distributions in the aquifer, underlying rock,\\u000a and overlying rock are derived by the Laplace transforms and their corresponding time-domain solutions are evaluated by the\\u000a modified Crump method. Field data adopted from

Yang Shaw-Yang; Yeh Hund-der

2008-01-01

425

Transport and confinement in the Mega Ampère Spherical Tokamak (MAST) plasma  

Microsoft Academic Search

A combination of recently installed state-of-the-art imaging and profile diagnostics, together with established plasma simulation codes, are providing for the first time on Mega Ampère Spherical Tokamak (MAST) the tools required for studying confinement and transport, from the core through to the plasma edge and scrape-off-layer (SOL). The H-mode edge transport barrier is now routinely turned on and off using

R. J. Akers; J. W. Ahn; G. Y. Antar; L. C. Appel; D. Applegate; C. Brickley; C. Bunting; P. G. Carolan; C. D. Challis; N. J. Conway; G. F. Counsell; R. O. Dendy; B. Dudson; A. R. Field; A. Kirk; B. Lloyd; H. F. Meyer; A. W. Morris; A. Patel; C. M. Roach; V. Rohzansky; A. Sykes; D. Taylor; M. R. Tournianski; H. R. Wilson; K. B. Axon; R. J. Buttery; D. Ciric; G. Cunningham; J. Dowling; M. R. Dunstan; S. J. Gee; M. P. Gryaznevich; P. Helander; D. L. Keeling; P. J. Knight; F. Lott; M. J. Loughlin; S. J. Manhood; R. Martin; G. J. McArdle; M. N. Price; K. Stammers; J. Storrs; M. J. Walsh

2003-01-01

426

Interplay of explosive thermal reaction dynamics and structural confinement  

NASA Astrophysics Data System (ADS)

Explosives play a significant role in human affairs; however, their behavior in circumstances other than intentional detonation is poorly understood. Accidents may have catastrophic consequences, especially if additional hazardous materials are involved. Abnormal ignition stimuli, such as impact, spark, friction, and heat may lead to a very violent outcome, potentially including detonation. An important factor influencing the behavior subsequent to abnormal ignition is the strength and inertia of the vessel confining the explosive, i.e., the near-field structural/mechanical environment, also known as confinement (inertial or mechanical). However, a comprehensive and quantified understanding of how confinement affects reaction violence does not yet exist. In the research discussed here, we have investigated a wide range of confinement conditions and related the explosive response to the fundamentals of the combustion process in the explosive. In our experiments, a charge of an octahydrotetranitrotetrazine-based plastic bonded explosive (PBX 9501) was loaded into a gun assembly having variable confinement conditions and subjected to a heating profile. The exploding charge breached the confinement and accelerated a projectile down the gun barrel. High bandwidth pressure and volume measurements were made and a first-law analysis was used to obtain enthalpy and power from the raw data. These results were then used to quantify reaction violence. Enthalpy change and power ranged from 0-1.8 kJ and 0-12 MW for 300 mg charges, respectively. Below a confinement strength of 20 MPa, violence was found to decline precipitously with decreasing confinement, while the violence for the heaviest confinement experiments was found to be relatively constant. Both pressure and pressurization rate were found to have critical values to induce and sustain violent reaction.

Perry, W. Lee; Zucker, Jonathan; Dickson, Peter M.; Parker, Gary R.; Asay, Blaine W.

2007-04-01

427

The dependence of H-mode energy confinement and transport on collisionality in NSTX  

NASA Astrophysics Data System (ADS)

Understanding the dependence of confinement on collisionality in tokamaks is important for the design of next-step devices, which will operate at collisionalities at least one order of magnitude lower than in the present generation. A wide range of collisionality has been obtained in the National Spherical Torus Experiment (NSTX) by employing two different wall conditioning techniques, one with boronization and between-shot helium glow discharge conditioning (HeGDC+B), and one using lithium evaporation (Li EVAP). Previous studies of HeGDC+B plasmas indicated a strong increase of normalized confinement with decreasing collisionality. Discharges with lithium conditioning discussed in the present study generally achieved lower collisionality, extending the accessible range of collisionality by a factor of two. While the confinement dependences on dimensional, engineering variables of the HeGDC+B and Li EVAP datasets differed, collisionality was found to unify the trends, with the lower collisionality lithium conditioned discharges extending the trend of increasing normalized confinement time, BT?E, with decreasing collisionality when other dimensionless variables were held as fixed as possible. This increase of confinement with decreasing collisionality was driven by a large reduction in electron transport in the outer region of the plasma. This result is consistent with gyrokinetic calculations that show microtearing and electron temperature gradient (ETG) modes to be more stable for the lower collisionality discharges. Ion transport, near neoclassical at high collisionality, became more anomalous at lower collisionality, possibly due to the growth of hybrid TEM/KBM modes in the outer regions of the plasma.

Kaye, S. M.; Gerhardt, S.; Guttenfelder, W.; Maingi, R.; Bell, R. E.; Diallo, A.; LeBlanc, B. P.; Podesta, M.

2013-06-01

428

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

429

High Confinement and High Density with Stationary Plasma Energy and Strong Edge Radiation in the TEXTOR-94 Tokamak  

SciTech Connect

Stationary high energy confinement is observed on TEXTOR-94 for times limited only by the flux swing of the transformer using strong edge radiation cooling. Necessary tools are the feedback control of the radiated power and of the plasma energy content. At the highest densities obtained (up to 1.2 times the Greenwald limit), energy confinement exceeds the edge-localized-mode-free {ital H}-mode scaling ITERH93-P by more than 20{percent}. {beta} limits of TEXTOR-94 are reached with {ital f}{sub H89}/{ital q}{sub {ital a}}{approx_equal}0.6. No detrimental effect of the seeded impurity is seen. These high confinement discharges meet many conditions necessary for a fusion reactor regime. {copyright} {ital 1996 The American Physical Society.}

Messiaen, A.M.; Ongena, J.; Samm, U.; Unterberg, B.; Van Wassenhove, G.; Durodie, F.; Jaspers, R.; Tokar, M.Z.; Vandenplas, P.E.; Van Oost, G.; Winter, J.; Wolf, G.H.; Bertschinger, G.; Bonheure, G.; Dumortier, P.; Euringer, H.; Finken, K.H.; Fuchs, G.; Giesen, B.; Koch, R.; Koenen, L.; Koenigs, C.; Koslowski, H.R.; Kraemer-Flecken, A.; Lyssoivan, A.; Mank, G.; Rapp, J.; Schoon, N.; Telesca, G.; Uhlemann, R.; Vervier, M.; Waidmann, G.; Weynants, R.R. [Laboratoire de Physique des Plasmas-Laboratorium voor Plasmafysica, Association ``EURATOM-Belgian State,`` Ecole Royale Militaire, B-1040 Brussels, Koninklijke Militaire School (Belgium)] [Laboratoire de Physique des Plasmas-Laboratorium voor Plasmafysica, Association ``EURATOM-Belgian State,`` Ecole Royale Militaire, B-1040 Brussels, Koninklijke Militaire School (Belgium); [Institut fuer Plasmaphysik, Forschungszentrum Juelich, GmbH Association ``Euratom-KFA,`` D-52425 Juelich (Federal Republic of Germany); [FOM Instituut voor Plasmafysica Rijnhuizen, Associatie ``FOM-EURATOM,`` Nieuwegein (The Netherlands)

1996-09-01

430

On demand fusion and triggering of confined chemical reactions in femtoliter volume aqueous droplets controlled by interfacial tension  

NASA Astrophysics Data System (ADS)

Droplet-based microfluidic platforms offer many opportunities to confine chemical and biochemical reactants in discrete ultrasmall reaction volumes, and investigate the effects of increased confinement on reaction dynamics. Current state-of-the-art microfluidic sampling strategies for creating ultrasmall reaction volumes are predominately steady-state approaches, which result in difficulty in trapping reacting species with a well-defined time-zero for initiation of biochemical reactions in the confined space. This talk describes stepwise, on-demand generation and fusion of femtoliter aqueous droplets based on interfacial tension. Sub-millisecond reaction times from droplet fusion were demonstrated, as well as a reversible chemical toggle switch based on alternating fusion of droplets containing acidic or basic solution, monitored with the pH-dependent emission of fluorescein.

Collier, Pat; Jung, Seung-Yong; Retterer, Scott

2011-03-01

431

76 FR 45620 - Agency Information Collection Activities; Submission for OMB Review; Comment Request; Confined...  

Federal Register 2010, 2011, 2012, 2013

...Comment Request; Confined and Enclosed Spaces and Other Dangerous Atmospheres in Shipyard...ICR) titled, ``Confined and Enclosed Spaces and Other Dangerous Atmospheres in Shipyard...INFORMATION: The Confined and Enclosed Spaces and Other Dangerous Atmospheres in...

2011-07-29

432

Slow dynamics of supercooled water confined in nanoporous silica materials  

NASA Astrophysics Data System (ADS)

We review our incoherent quasielastic neutron scattering (QENS) studies of the dynamics of supercooled water confined in nanoporous silica materials. QENS data were analysed by using the relaxing cage model (RCM) previously developed by us. We first use molecular dynamics (MD) simulation of the extended simple point charge model (SPC/E) for bulk supercooled water to establish the validity of the RCM, which applies to both the translational and rotational motion of water molecules. We then assume that the dynamics of water molecules in the vicinity of a hydrophilic surface is similar to a bulk water at an equivalent lower supercooled temperature. This analogy was experimentally demonstrated in previous investigations of water in Vycor glasses and near hydrophilic protein surfaces. Studies were made of supercooled water in MCM-41-S (pore sizes 25, 18, and 14 Å) and MCM-48-S (pore size 22 Å) using three QENS spectrometers of respective energy resolutions 1, 30, and 60 µeV, covering the temperature range from 325 to 200 K. Five quantities are extracted from the analysis: they are ?, the stretch exponent characterizing the ?-relaxation ??, the exponent determining the power-law dependence of the relaxation time on Q; \\langle \\tau_{0} \\rangle , the Q-independent pre-factor for the average translational relaxation time; \\langle \\tau _{{\\mathrm {R}}_{1}} \\rangle , the relaxation time for the first-order rotational correlation function; and \\langle \\tau _{{\\mathrm {R}}_{2}} \\rangle , the relaxation time for the second-order rotational correlation function. We discuss the temperature dependence of these parameters and note that, in particular, the dynamics is rapidly slowing down at temperature around 220 K, signalling the onset of a structural arrest transition of liquid water into an amorphous solid water.

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

2004-11-01

433

Ion-mediated RNA structural collapse: effect of spatial confinement  

E-print Network

RNAs are negatively charged molecules residing in macromolecular crowding cellular environments. Macromolecular confinement can influence the ion effects in RNA folding. In this work, using the recently developed tightly bound ion model for ion fluctuation and correlation, we investigate the confinement effect on the ion-mediated RNA structural collapse for a simple model system. We found that, for both Na$^+$ and Mg$^{2+}$, ion efficiencies in mediating structural collapse/folding are significantly enhanced by the structural confinement. Such an enhancement in the ion efficiency is attributed to the decreased electrostatic free energy difference between the compact conformation ensemble and the (restricted) extended conformation ensemble due to the spatial restriction.

Zhi-Jie Tan; Shi-Jie Chen

2013-05-06

434

Macromolecular crowding and confinement: biochemical, biophysical, and potential physiological consequences*  

PubMed Central

Expected and observed effects of volume exclusion on the free energy of rigid and flexible macromolecules in crowded and confined systems, and consequent effects of crowding and confinement on macromolecular reaction rates and equilibria are summarized. Findings from relevant theoretical/simulation and experimental literature published from 2004 onward are reviewed. Additional complexity arising from the heterogeneity of local environments in biological media, and the presence of nonspecific interactions between macromolecules over and above steric repulsion are discussed. Theoretical and experimental approaches to the characterization of crowding- and confinement-induced effects in systems approaching the complexity of living organisms are suggested. PMID:18573087

Zhou, Huan-Xiang; Rivas, German; Minton, Allen P.

2009-01-01

435

Ultimate limit of field confinement by surface plasmon polaritons  

E-print Network

We show that electric field confinement in surface plasmon polaritons propagating at the metal/dielectric interfaces enhances the loss due to Landau damping and which effectively limits the degree of confinement itself. We prove that Landau damping and associated with it surface collision damping follow directly from Lindhard formula for the dielectric constant of free electron gas Furthermore, we demonstrate that even if all the conventional loss mechanisms, caused by phonons, electron-electron, and interface roughness scattering, were eliminated, the maximum attainable degree of confinement and the loss accompanying it would not change significantly compared to the best existing plasmonic materials, such as silver.

Khurgin, Jacob B

2014-01-01

436

Diamagnetism of Confined Dirac Fermions in Disordered Graphene  

E-print Network

The diamagnetism of confined Dirac fermions submitted to a uniform magnetic field in disordered graphene is investigated. The solutions of the energy spectrum are used to discuss the orbital magnetism from a statistical mechanical point of view. More precisely, by the technique of Green functions the self-energy for short and long-ranged disorders is obtained. This allows us to determine the susceptibility for short and long-ranged disorders together with confinement. We compare our results with already published work and point out the relevance of these findings to a systematic formulation of the diamagnetism in a confining potential.

Ahmed Jellal; Malika Bellati; Michael Schreiber

2011-05-17

437

Role of center vortices in Gribov's confinement scenario  

SciTech Connect

The connection of Gribov's confinement scenario in the Coulomb gauge with the center vortex picture of confinement is investigated. For this purpose we assume a vacuum wave functional that models the infrared properties of the theory and, in particular, shows strict confinement, i.e. an area law of the Wilson loop. We isolate the center vortex content of this wave functional by standard lattice methods and investigate their contributions to various static propagators of the Hamilton approach to Yang-Mills theory in the Coulomb gauge. We find that the infrared properties of these quantities, in particular, the infrared divergence of the ghost form factor, are dominated by center vortices.

Quandt, M.; Reinhardt, H.; Burgio, G. [Institut fuer Theoretische Physik, Auf der Morgenstelle 14, D-72076 Tuebingen (Germany)

2010-03-15

438

Orientational orders of small anisotropic molecules confined in slit pores  

E-print Network

We have studied phase behavior of hard gaussian overlap molecules with small anisotropic parameter confined in two plane parallel structureless hard walls. Our investigation based on standard constant-NPT Monte Carlo molecular simulation led us to some interesting findings. For small anisotropic molecules the nematic phase is instable in bulk, while, if the distance between the walls is small enough, an orientation-ordered phase can form. This result indicates that the required molecular elongation forming liquid-crystal phases is smaller in confinement than that in bulk. Considering the value of the elongation of molecules, the computed result inplies that small molecule liquid crystals may exist in confinement.

Xin Zhou; Hu Chen; Mitsumasa Iwamoto

2003-05-12

439

Highly confined photon transport in subwavelength metallic slot waveguides.  

PubMed

We report experimental realization of subwavelength slot waveguides that exhibit both micrometer-range propagation and high spatial confinement of light. Attention is given to rectangular waveguides with a Si3N4 core and Ag cladding; core thicknesses of 50-100 nm and widths of 250 nm - 10 microm are explored. Propagation lengths of approximately 5lambda are achieved with light confined to lateral and transverse dimensions of approximately lambda/5 and approximately lambda/2, respectively. This unique combination of light localization and propagation is achieved via interacting surface plasmons, which produce short modal wavelengths and strong field confinement at each metal/dielectric interface. PMID:16968003

Dionne, J A; Lezec, H J; Atwater, Harry A

2006-09-01

440

Spectra generated by a confined softcore Coulomb potential  

NASA Astrophysics Data System (ADS)

Analytic and approximate solutions for the energy eigenvalues generated by a confined softcore Coulomb potentials of the form a/(r + ?) in d > 1 dimensions are constructed. The confinement is effected by linear and harmonic-oscillator potential terms, and also through "hard confinement" by means of an impenetrable spherical box. A byproduct of this work is the construction of polynomial solutions for a number of linear differential equations with polynomial coefficients, along with the necessary and sufficient conditions for the existence of such solutions. Very accurate approximate solutions for the general problem with arbitrary potential parameters are found by use of the asymptotic iteration method.

Hall, Richard L.; Saad, Nasser

2014-08-01