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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

Real-time dynamics of the confining string  

NASA Astrophysics Data System (ADS)

Quantum chromodynamics (QCD) describes the interaction of quarks and gluons, which are charged under the color group. Due to confinement of color charge, only colorless hadrons are observed in experiment. At very short distances (hard processes), perturbation theory is a valid tool for calculations and predictions can be made which agree well with experiment. Confinement, which is not yet understood from first principles, is important even for hard processes, because after the perturbative evolution is finished, the final colored particles combine to create the final state hadrons. There are many effective theories of confinement developed over the years. We will consider the Abelian projection; the gauge theory becomes Abelian-like and the theory contains magnetic monopoles. Confinement happens due to the dual Meissner effect, where dual in this case means the roles of the electric and magnetic fields are reversed. The field between charges resembles that of an Abrikosov-Nielsen-Olesen vortex or string. Based on the Abelian nature of the confining string, because fermion zero modes are localized along the vortex and by considering very energetic jets, we assume that the dynamics along this string is described by massless quantum electrodynamics in 1+1 dimensions. This theory shares with QCD many important properties: confinement, chiral symmetry breaking, theta-vacuum, and is exactly soluble. We use the model to compute the fragmentation functions of jets in electron-positron annihilation and after fixing two adjustable parameters, we study the modification of fragmentation functions of jets in the QCD medium. We address an important puzzle in hadron scattering: the soft photon yield in processes with hadrons in the final state is much larger than what is expected from the Low theorem. We find that soft photons produced from currents induced during the real-time dynamics of jet fragmentation can contribute in the enhancement of photons. We compare the result with the recent DELPHI measurements and a reasonable agreement is found. Finally, assuming the QCD string to be thin, we address the observed phenomenon in recent lattice studies of partial chiral symmetry restoration along the string. Our result agrees well with the data.

Loshaj, Frasher

3

On time scale invariance of random walks in confined space.  

PubMed

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

Bearup, Daniel; Petrovskii, Sergei

2015-02-21

4

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

5

Modeling the relaxation time of DNA confined in a nanochannel  

PubMed Central

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

6

Full-f gyrokinetic simulation over a confinement time  

SciTech Connect

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

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

2014-02-15

7

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

Microsoft Academic Search

The determination of the effective particle confinement time (taup*), 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

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

2006-01-01

8

Long Time Motion of NLS Solitary Waves in a Confining Potential  

E-print Network

Long Time Motion of NLS Solitary Waves in a Confining Potential B. L. G. Jonsson1,2, , J. Fr. March 7, 2005 Abstract We study the motion of solitary-wave solutions of a family of focusing gener- alized nonlinear Schr¨odinger equations with a confining, slowly varying external potential, V (x

9

Time averaging for the strongly confined nonlinear Schrodinger equation.  

E-print Network

gas of quantum particles, evolving in the three dimensional space (x, z) R3 (x R2 , z R), yet´ematiques de Toulouse - Universit´e Paul Sabatier - 118 rte de Narbonne - 31062 Toulouse Cedex 2 IRMAR, Universit´e de Rennes 1 - Campus de Beaulieu - 35042 Rennes Cedex, France 1 #12;in time. In other words

Castella, François

10

Diffraction in time of a confined particle and its Bohmian paths  

E-print Network

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

S. V. Mousavi

2011-12-27

11

Derivation of energy confinement time and ICRF absorption in LHD by power modulation  

Microsoft Academic Search

A power modulation experiment was conducted in the third campaign of the LHD. In a conventional analysis of the modulation experiments, the energy confinement time and heating efficiency are taken as constant, disregarding their dependence on the plasma parameters. In this paper, their dependence on the plasma temperature and heating power is taken into consideration to improve the analysis of

Y. Torii; T. Watari; R. Kumazawa; K. Saito; T. Mutoh; T. Seki; F. Shimpo; G. Nomura; T. Watanabe; N. Takeuchi; T. Yamamoto; Y. Zhao; D. A. Hartmann; H. Yamada; T. Ozaki; S. Masuzaki; K. Tanaka; M. Yokota; A. Katoh; K. Akaishi; N. Ashikawa; P. de Vries; M. Emoto; H. Funaba; M. Goto; K. Ida; H. Idei; K. Ikeda; S. Inagaki; N. Inoue; M. Isobe; K. Itoh; S. Kado; O. Kaneko; K. Kawahata; T. Kobuchi; A. Komori; A. V. Krasilnikov; S. Kubo; T. Minami; J. Miyazawa; T. Morisaki; S. Morita; S. Murakami; S. Muto; Y. Nagayama; Y. Nakamura; H. Nakanishi; K. Narihara; K. Nishimura; N. Noda; S. Ohdachi; K. Ohkubo; N. Ohyabu; Y. Oka; M. Osakabe; B. J. Peterson; A. Sagara; S. Sakakibara; R. Sakamoto; H. Sasao; M. Sasao; K. Sato; M. Sato; T. Shimozuma; M. Shoji; S. Sudo; Y. Takeiri; K. Toi; T. Tokuzawa; K. Tsumori; K. Y. Watanabe; H. Suzuki; I. Yamada; Y. Hamada; S. Yamaguchi; S. Yamamoto; K. Yamazaki; M. Yokoyama; Y. Yoshimura; O. Motojima; M. Fujiwara

2001-01-01

12

Calculating the hopping times of confined fluids: two hard disks in a box.  

PubMed

The dynamical transition between the anomalous single file diffusion of highly confined fluids and bulk normal diffusion can be described by a phenomenological model involving a particle hopping time tau(hop). We suggest a theoretical formalism that will be useful for the calculation of tau(hop) for a variety of systems and test it using a simple model consisting of two hard disks confined to a rectangular box with hard walls. In the case where the particles are moving diffusively, we find the hopping time diverges as a power law in the threshold region with an exponent of -(3/2). Under conditions where the particles move inertially, transition state theory predicts a power law behavior with an exponent of -2. Molecular dynamics simulations confirm the transition state theory result for inertial dynamics, while Brownian dynamics simulations suggest the scaling exponent is highly sensitive to the details of the algorithm. PMID:15549951

Bowles, R K; Mon, K K; Percus, J K

2004-12-01

13

Calculating the hopping times of confined fluids: Two hard disks in a box  

NASA Astrophysics Data System (ADS)

The dynamical transition between the anomalous single file diffusion of highly confined fluids and bulk normal diffusion can be described by a phenomenological model involving a particle hopping time ?hop. We suggest a theoretical formalism that will be useful for the calculation of ?hop for a variety of systems and test it using a simple model consisting of two hard disks confined to a rectangular box with hard walls. In the case where the particles are moving diffusively, we find the hopping time diverges as a power law in the threshold region with an exponent of -(3/2). Under conditions where the particles move inertially, transition state theory predicts a power law behavior with an exponent of -2. Molecular dynamics simulations confirm the transition state theory result for inertial dynamics, while Brownian dynamics simulations suggest the scaling exponent is highly sensitive to the details of the algorithm.

Bowles, R. K.; Mon, K. K.; Percus, J. K.

2004-12-01

14

Long Time Motion of NLS Solitary Waves in a Confining Potential  

Microsoft Academic Search

We study the motion of solitary-wave solutions of a family of focusing generalized nonlinear Schroedinger equations with a confining, slowly varying external potential, $V(x)$. A Lyapunov-Schmidt decomposition of the solution combined with energy estimates allows us to control the motion of the solitary wave over a long, but finite, time interval. We show that the center of mass of the

B. Lars G. Jonsson; Jürg Fröhlich; Stephen Gustafson; Israel Michael Sigal

2006-01-01

15

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

PubMed

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. PMID:21033974

Demers, D R; Chen, X; Schoch, P M; Fimognari, P J

2010-10-01

16

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

SciTech Connect

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

Nevins, W.M.

1995-01-01

17

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

SciTech Connect

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

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

1995-10-01

18

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

19

Long time motion of NLS solitary waves in a confining potential  

E-print Network

We study the motion of solitary-wave solutions of a family of focusing generalized nonlinear Schroedinger equations with a confining, slowly varying external potential, $V(x)$. A Lyapunov-Schmidt decomposition of the solution combined with energy estimates allows us to control the motion of the solitary wave over a long, but finite, time interval. We show that the center of mass of the solitary wave follows a trajectory close to that of a Newtonian point particle in the external potential $V(x)$ over a long time interval.

B. L. G. Jonsson; J. Froehlich; S. Gustafson; I. M. Sigal

2005-03-07

20

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

PubMed

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

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

2011-03-16

21

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

22

Long Time Motion of NLS Solitary Waves in a Confining Potential  

Microsoft Academic Search

.  We study the motion of solitary-wave solutions of a family of focusing generalized nonlinear Schrdinger equations with a\\u000a confining, slowly varying external potential, V(x).\\u000a \\u000a A Lyapunov-Schmidt decomposition of the solution combined with energy estimates allows us to control the motion of the solitary\\u000a wave over a long, but finite, time interval.\\u000a \\u000a \\u000a \\u000a We show that the center of mass of the

B. Lars G. Jonsson; Jürg Fröhlich; Stephen Gustafson; Israel Michael Sigal

2006-01-01

23

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

PubMed Central

Resolving the dynamical interplay of proteins and lipids in the live-cell plasma membrane represents a central goal in current cell biology. Superresolution concepts have introduced a means of capturing spatial heterogeneity at a nanoscopic length scale. Similar concepts for detecting dynamical transitions (superresolution chronoscopy) are still lacking. Here, we show that recently introduced spot-variation fluorescence correlation spectroscopy allows for sensing transient confinement times of membrane constituents at dramatically improved resolution. Using standard diffraction-limited optics, spot-variation fluorescence correlation spectroscopy captures signatures of single retardation events far below the transit time of the tracer through the focal spot. We provide an analytical description of special cases of transient binding of a tracer to pointlike traps, or association of a tracer with nanodomains. The influence of trap mobility and the underlying binding kinetics are quantified. Experimental approaches are suggested that allow for gaining quantitative mechanistic insights into the interaction processes of membrane constituents. PMID:21641330

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

2011-01-01

24

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

E-print Network

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

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

2012-10-22

25

Fivefold confinement time increase in the Madison Symmetric Torus using inductive poloidal current drive  

SciTech Connect

Current profile control is employed in the Madison Symmetric Torus [R. N. Dexter {ital et al.}, Fusion Technol. {bold 19}, 131 (1991)] reversed field pinch to reduce the magnetic fluctuations responsible for anomalous transport. An inductive poloidal electric-field pulse is applied in the sense to flatten the parallel current profile, reducing the dynamo fluctuation amplitude required to sustain the equilibrium. This technique demonstrates a substantial reduction in fluctuation amplitude (as much as 50{percent}), and improvement in energy confinement (from 1 to 5 ms); a record low fluctuation (0.8{percent}) and record high temperature (615 eV) for this device were observed simultaneously during current drive experiments. Plasma beta increases by 50{percent} and the Ohmic input power is three times lower. Particle confinement improves and plasma impurity contamination is reduced. The results of the transient current drive experiments provide motivation for continuing development of steady-state current profile control strategies for the reversed field pinch. {copyright} {ital 1997 American Institute of Physics.}

Stoneking, M.R.; Lanier, N.E.; Prager, S.C.; Sarff, J.S.; Sinitsyn, D. [Department of Physics, University of Wisconsin---Madison, Madison, Wisconsin 53706 (United States)] [Department of Physics, University of Wisconsin---Madison, Madison, Wisconsin 53706 (United States)

1997-05-01

26

{bold E{times}B} flow shear and enhanced confinement in the Madison Symmetric Torus reversed-field pinch  

SciTech Connect

Strong {bold E{times}B} flow shear occurs in the edge of three types of enhanced confinement discharge in the Madison Symmetric Torus [Dexter {ital et al.}, Fusion Technol. {bold 19}, 131 (1991)] reversed-field pinch. Measurements in standard (low confinement) discharges indicate that global magnetic fluctuations drive particle and energy transport in the plasma core, while electrostatic fluctuations drive particle transport in the plasma edge. This paper explores possible contributions of {bold E{times}B} flow shear to the reduction of both the magnetic and electrostatic fluctuations and, thus, the improved confinement. In one case, shear in the {bold E{times}B} flow occurs when the edge plasma is biased. Biased discharges exhibit changes in the edge electrostatic fluctuations and improved particle confinement. In two other cases, the flow shear emerges (1) when auxiliary current is driven in the edge and (2) spontaneously, following sawtooth crashes. Both edge electrostatic and global magnetic fluctuations are reduced in these discharges, and both particle and energy confinement improve. {copyright} {ital 1998 American Institute of Physics.}

Chapman, B.E.; Almagri, A.F.; Anderson, J.K.; Chiang, C.; Craig, D.; Fiksel, G.; Lanier, N.E.; Prager, S.C.; Sarff, J.S.; Stoneking, M.R.; Terry, P.W. [Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin53706 (United States)] [Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin53706 (United States)

1998-05-01

27

Angular radiation temperature simulation for time-dependent capsule drive prediction in inertial confinement fusion  

NASA Astrophysics Data System (ADS)

The x-ray drive on a capsule in an inertial confinement fusion setup is crucial for ignition. Unfortunately, a direct measurement has not been possible so far. We propose an angular radiation temperature simulation to predict the time-dependent drive on the capsule. A simple model, based on the view-factor method for the simulation of the radiation temperature, is presented and compared with the experimental data obtained using the OMEGA laser facility and the simulation results acquired with VISRAD code. We found a good agreement between the time-dependent measurements and the simulation results obtained using this model. The validated model was then used to analyze the experimental results from the Shenguang-III prototype laser facility. More specifically, the variations of the peak radiation temperatures at different view angles with the albedo of the hohlraum, the motion of the laser spots, the closure of the laser entrance holes, and the deviation of the laser power were investigated. Furthermore, the time-dependent radiation temperature at different orientations and the drive history on the capsule were calculated. The results indicate that the radiation temperature from "U20W112" (named according to the diagnostic hole ID on the target chamber) can be used to approximately predict the drive temperature on the capsule. In addition, the influence of the capsule on the peak radiation temperature is also presented.

Jing, Longfei; Jiang, Shaoen; Yang, Dong; Li, Hang; Zhang, Lu; Lin, Zhiwei; Li, Liling; Kuang, Longyu; Huang, Yunbao; Ding, Yongkun

2015-02-01

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

2007-09-07

29

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

PubMed

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

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

2015-01-14

30

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

PubMed Central

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

Chen, A.; Sooryakumar, R.

2013-01-01

31

Selective measurement of hole tunneling times through AlGaAs barriers based on the quantum confined Stark effect  

NASA Astrophysics Data System (ADS)

We demonstrate a method able to measure selectively and over a wide dynamic range the tunneling time of electrons or holes through a given potential barrier in a semiconductor heterostructure. The method relies on appropriate band gap engineering of the intrinsic region of a p-i-n diode, and on the quantum confined Stark effect. As an example, the hole tunneling time through thick AlxGa1-xAs potential barriers has been measured over six orders of magnitude in InGaAs/AlGaAs structures. For x=0.6 , ultralong hole tunneling times are demonstrated in fair agreement with a semiclassical tunneling model. This model however turns out to be inapplicable for x?0.4 , overestimating the tunneling times by several orders of magnitude. This suggests the formation of intrinsic leakage current paths through the AlGaAs barriers at these concentrations.

Le Thomas, N.; Pelekanos, N. T.; Hatzopoulos, Z.

2005-12-01

32

Groundwater residence time and paleorecharge conditions in the deep confined aquifers of the coastal watershed, South-East Tanzania  

NASA Astrophysics Data System (ADS)

SummaryAnalysis of radiocarbon and stable isotopes of C, H and O in groundwater samples from the coastal watershed of Southeastern Tanzania is used to decipher the age of groundwater and the climatic conditions at the time of recharge. Radiocarbon dating was corrected on the basis of stable carbon isotope ratios and hydrochemical data. Two main recharge periods are recognised: (1) a recent recharge period with residence times dated to younger than 1.3 ka BP, for the shallow aquifer and some deep groundwater aquifers; and (2) a paleorecharge occurring during the Late Pleistocene to Holocene transition (between 6 and 13 ka BP), for the lower confined aquifer. The climatic excursions (arid and humid phases) identified in this study match well with those identified from studies of paleo-climatic records in Tanzania and East Africa. The oxygen-18 and radiocarbon results show that there is a potential mixing of groundwater of varying ages along flow paths in the coastal aquifer system. This has also been shown by redox parameters in some of the deeper aquifer samples. The data also revealed that there is relatively simple pattern of lateral groundwater flow in the deeper confined aquifer. Isotopic evidence from this study and related studies in paleolimnology improves our knowledge of the past climates. The data suggests that the paleorecharge to the confined aquifer was from inland under wetter climatic conditions than present. Therefore, paleorecharge from the adjacent mountain regions to coastal area like Ifakara, Morogoro and Udzungwa mountains could be important parts of recharge area of the Kimbiji aquifer. However, the hinterland mountains of Dar es Salaam (mainly Pugu, Mkuranga, Ruvu and Kisarawe) could also play an important role in replenishing the Kimbiji coastal aquifers. In contrast, recharge in the shallow unconfined aquifer is characterized by local rainfall and river water infiltration. This study is the first of its kind, assessing fingerprinting of paleoclimates in Southeastern coastal Tanzania using the isotopic composition of deep groundwater aquifers. The freshwater resources in the Neogene aquifer contain paleo-groundwater aquifers that have been mixed with recently-recharged flow systems. Hence, the resources may be sustainable. This study also provides information that may be useful for designing optimum strategies for a sustainable management of groundwater resources in the coastal aquifer, and it testifies to the importance of groundwater as a paleoclimatic archive. Such information is also essential for consideration by modellers in their attempts to simulate the hydrogeological processes in confined aquifers over very long time spans.

Bakari, Said S.; Aagaard, Per; Vogt, Rolf D.; Ruden, Fridtjov; Brennwald, Matthias S.; Johansen, Ingar; Gulliksen, Steinar

2012-10-01

33

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

SciTech Connect

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

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

2013-03-15

34

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

35

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

36

Two definitions of the hopping time in a confined fluid of finite particles  

NASA Astrophysics Data System (ADS)

We consider a fluid of hard disks diffusing in a flat long narrow channel of width approaching from above the doubled diameter of the disks. In this limit, the disks can pass their neighbors only rarely, in a mean hopping time growing to infinity, so the disks start by diffusing anomalously. We study the hopping time, which is the crucial parameter of the theory describing the subsequent transition to normal diffusion. We show that two different definitions of this quantity, based either on the mean first passage time calculated from solution of the Fick-Jacobs equation, or coming from transition state theory, are incompatible. They have different physical interpretation and also, they give different dependencies of the hopping time on the width of the channel.

Kalinay, Pavol; Percus, Jerome K.

2008-10-01

37

Two definitions of the hopping time in a confined fluid of finite particles.  

PubMed

We consider a fluid of hard disks diffusing in a flat long narrow channel of width approaching from above the doubled diameter of the disks. In this limit, the disks can pass their neighbors only rarely, in a mean hopping time growing to infinity, so the disks start by diffusing anomalously. We study the hopping time, which is the crucial parameter of the theory describing the subsequent transition to normal diffusion. We show that two different definitions of this quantity, based either on the mean first passage time calculated from solution of the Fick-Jacobs equation, or coming from transition state theory, are incompatible. They have different physical interpretation and also, they give different dependencies of the hopping time on the width of the channel. PMID:19045186

Kalinay, Pavol; Percus, Jerome K

2008-10-21

38

Time resolved laser-induced fluorescence of electrosprayed ions confined in a linear quadrupole trap  

SciTech Connect

We have designed and constructed a linear quadrupole ion trap for the measurement of laser-induced fluorescence (LIF) of mass selected gas-phase ions produced by electrospray ionization. The instrument consists of a simple electrospray source, radiofrequency octopole guide, a dc quadrupole bender, a quadrupole mass filter, the linear quadrupole trap (which is equipped with optics for LIF collection and a channeltron ion detector), and several multielement focusing lenses. With this instrument, the LIF decay lifetime of gas-phase Rhodamine 640 radical cations is determined for the first time.

Friedrich, Jochen; Fu Jinmei; Hendrickson, Christopher L.; Marshall, Alan G.; Wang Yisheng [Ion Cyclotron Resonance Program, National High Magnetic Field Laboratory, Florida State University, 1800 East Paul Dirac Drive, Tallahassee, Florida 32310-4005 (United States); Institute of Atomic and Molecular Sciences, Academia Sinica, P. O. Box 23-166, Taipei, Taiwan (China)

2004-11-01

39

Time-dependent filamentation and stimulated Brillouin forward scattering in inertial confinement fusion plasmas  

NASA Astrophysics Data System (ADS)

Numerical simulations of the temporal evolution of laser light filamentation and stimulated Brillouin forward scattering (SBFS) in plasmas, under conditions that are relevant to laser fusion, are presented and analyzed. Long term unsteady behavior of filaments is observed to be the norm. Temporal and spatial incoherence due to filamentation and SBFS are impressed upon time-independent incident laser beams. The bandwidth and angular divergence imposed upon the beam increase with the strength of the interaction. In addition, the spectrum of the transmitted light is redshifted by an amount that increases with the interaction strength. Spectral analysis of the transmitted light reveals that SBFS plays a role in the generation of the observed temporal incoherence. Incident beams with some spatial incoherence but no temporal smoothing are compared to those with ab initio temporal beam smoothing (TBS). Under typical conditions, TBS beams will undergo far less angular and spectral spreading and far less SBFS than unsmoothed beams.

Schmitt, Andrew J.; Afeyan, Bedros B.

1998-02-01

40

Time Evolution of In-plane Order in Confined Smectic C* Films  

NASA Astrophysics Data System (ADS)

We have studied recently the structural evolution as a function of film thickness of films of the smC* mix mx5112, which is a room temperature smectic C* liquid crystal, deposited on 10?m period gratings. There is a homogenously aligned layer for films as small as 1?m thick(L. J. Martinez-Miranda, in preparation). This layer, which is close to the LC-glass interface, shows a time dependence in azimuthal ordering, with the molecules rotating in the direction of the gratings over a 5-hour period. The azimuthal, and out of plane \\chi scans indicate the molecular layers are tilted between 6 and 10 degrees with respect to the plane of the substrate. Films thinner than 10?m exhibit an evolution of molecular layer spacing as a function of position within the sample. For a 5?m thick film, the layer spacing, once stabilized, varies approximately 3% from the air-LC interface (out-of-plane direction) to the LC-glass interface (in-plane direction). This work supported by NSF Grants Nos. ECS-92-01986 and GER-94-50118.

Martinez-Miranda, Luz J.

1996-03-01

41

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

SciTech Connect

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

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

2012-01-15

42

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

SciTech Connect

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

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

2004-12-09

43

Solitary Confinement  

Microsoft Academic Search

If short-term solitary confinement were reintroduced on a large scale, it is suggested that the possible victimization and corruption of inexperienced inmates by career criminals might be partially eliminated. Moreover, it has the possibility of saving taxpayers' money. Currently staff salaries account for about three-fourths of all prison expenditures. A solitary confinement system would initially have construction costs. This would

Robert Rogers

1993-01-01

44

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

PubMed

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

Calderon, Christopher P

2013-07-01

45

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

46

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

47

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

SciTech Connect

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

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

2008-03-12

48

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

SciTech Connect

A novel method for modeling the neutron time of flight (nTOF) detector response in current mode for inertial confinement fusion experiments has been applied to the on-axis nTOF detectors located in the basement of the Z-Facility. It will be shown that this method can identify sources of neutron scattering, and is useful for predicting detector responses in future experimental configurations, and for identifying potential sources of neutron scattering when experimental set-ups change. This method can also provide insight on how much broadening neutron scattering contributes to the primary signals, which is then subtracted from them. Detector time responses are deconvolved from the signals, allowing a transformation from dN/dt to dN/dE, extracting neutron spectra at each detector location; these spectra are proportional to the absolute yield.

Nelson, A. J.; Cooper, G. W. [Department of Chemical and Nuclear Engineering, University of New Mexico, Albuquerque, New Mexico 87131 (United States); Ruiz, C. L.; Chandler, G. A.; Fehl, D. L.; Hahn, K. D.; Leeper, R. J.; Smelser, R.; Torres, J. A. [Sandia National Laboratories, Albuquerque, New Mexico 87185-1196 (United States)

2012-10-15

49

Thermal noise in confined fluids  

NASA Astrophysics Data System (ADS)

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.

Sanghi, T.; Aluru, N. R.

2014-11-01

50

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

PubMed

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

Dhar, Jayabrata; Ghosh, Uddipta; Chakraborty, Suman

2014-03-01

51

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

52

Diffusion in confined geometries.  

PubMed

Diffusive transport of particles or, more generally, small objects, is a ubiquitous feature of physical and chemical reaction systems. In configurations containing confining walls or constrictions, transport is controlled both by the fluctuation statistics of the jittering objects and the phase space available to their dynamics. Consequently, the study of transport at the macro- and nanoscales must address both Brownian motion and entropic effects. Herein we report on recent advances in the theoretical and numerical investigation of stochastic transport occurring either in microsized geometries of varying cross sections or in narrow channels wherein the diffusing particles are hindered from passing each other (single-file diffusion). For particles undergoing biased diffusion in static suspension media enclosed by confining geometries, transport exhibits intriguing features such as 1) a decrease in nonlinear mobility with increasing temperature or also 2) a broad excess peak of the effective diffusion above the free diffusion limit. These paradoxical aspects can be understood in terms of entropic contributions resulting from the restricted dynamics in phase space. If, in addition, the suspension medium is subjected to external, time-dependent forcing, rectification or segregation of the diffusing Brownian particles becomes possible. Likewise, the diffusion in very narrow, spatially modulated channels is modified via contact particle-particle interactions, which induce anomalous sub-diffusion. The effective sub-diffusion constant for a driven single file also develops a resonance-like structure as a function of the confining coupling constant. PMID:19025741

Burada, P Sekhar; Hänggi, Peter; Marchesoni, Fabio; Schmid, Gerhard; Talkner, Peter

2009-01-12

53

An improved method for measuring the absolute DD neutron yield and calibrating neutron time-of-flight detectors in inertial confinement fusion experiments  

E-print Network

Since the establishment of nuclear physics in the early 1900's and the development of the hydrogen bomb in the 1950's, inertial confinement fusion (ICF) has been an important field in physics. Funded largely though the ...

Waugh, C. (Caleb Joseph)

2014-01-01

54

Hydrodynamic description of the long-time tails of the linear and rotational velocity autocorrelation functions of a particle in a confined geometry.  

PubMed

We report a hydrodynamic analysis of the long-time behavior of the linear and angular velocity autocorrelation functions of an isolated colloid particle constrained to have quasi-two-dimensional motion, and compare the predicted behavior with the results of lattice-Boltzmann simulations. Our analysis uses the singularity method to characterize unsteady linear motion of an incompressible fluid. For bounded fluids we construct an image system with a discrete set of fundamental solutions of the Stokes equation from which we extract the long-time decay of the velocity. For the case that there are free slip boundary conditions at walls separated by H particle diameters, the time evolution of the parallel linear velocity and the perpendicular rotational velocity following impulsive excitation both correspond to the time evolution of a two-dimensional (2D) fluid with effective density rho_(2D)=rhoH. For the case that there are no slip boundary conditions at the walls, the same types of motion correspond to 2D fluid motions with a coefficient of friction xi=pi(2)nu/H(2) modulo a prefactor of order 1, with nu the kinematic viscosity. The linear particle motion perpendicular to the walls also experiences an effective frictional force, but the time dependence is proportional to t(-2) , which cannot be related to either pure 3D or pure 2D fluid motion. Our incompressible fluid model predicts correct self-diffusion constants but it does not capture all of the effects of the fluid confinement on the particle motion. In particular, the linear motion of a particle perpendicular to the walls is influenced by coupling between the density flux and the velocity field, which leads to damped velocity oscillations whose frequency is proportional to c_(s)/H , with c_(s) the velocity of sound. For particle motion parallel to no slip walls there is a slowing down of a density flux that spreads diffusively, which generates a long-time decay proportional to t(-1) . PMID:18233847

Frydel, Derek; Rice, Stuart A

2007-12-01

55

A Review of Quantum Confinement  

SciTech Connect

A succinct history of the Confined Atom problem is presented. The hydrogen atom confined to the centre of an impenetrable sphere counts amongst the exactly soluble problems of physics, alongside much more noted exact solutions such as Black Body Radiation and the free Hydrogen atom in absence of any radiation field. It shares with them the disadvantage of being an idealisation, while at the same time encapsulating in a simple way particular aspects of physical reality. The problem was first formulated by Sommerfeld and Welker - henceforth cited as SW - in connection with the behaviour of atoms at very high pressures, and the solution was published on the occasion of Pauli's 60th birthday celebration. At the time, it seemed that there was not much other connection with physical reality beyond a few simple aspects connected to the properties of atoms in solids, for which more appropriate models were soon developed. Thus, confined atoms attracted little attention until the advent of the metallofullerene, which provided the first example of a confined atom with properties quite closely related to those originally considered by SW. Since then, the problem has received much more attention, and many more new features of quantum confinement, quantum compression, the quantum Faraday cage, electronic reorganisation, cavity resonances, etc have been described, which are relevant to real systems. Also, a number of other situations have been uncovered experimentally to which quantum confinement is relevant. Thus, studies of the confined atom are now more numerous, and have been extended both in terms of the models used and the systems to which they can be applied. Connections to thermodynamics are explored through the properties of a confined two-level atom adapted from Einstein's celebrated model, and issues of dynamical screening of electromagnetic radiation by the confining shell are discussed in connection with the Faraday cage produced by a confining conducting shell. The conclusions are shown to be relevant to a proposed 'quantum computer'. The description of the actual geometry of C{sub 60}, as opposed to a purely spherical approximation, leads to some qualification of the computed results.

Connerade, Jean-Patrick [Quantum Optics and Laser Science Group, Physics Department, Imperial College, London (United Kingdom)

2009-12-03

56

ITER confinement capability  

SciTech Connect

The confinement capability of ITER was examined for a number of operational scenarios. The reference ITER physics baseline scenario (I = 22 MA) allows ignited burn under H-mode conditions ({tau}{sub E}(H-mode) {approximately} 2 {times} {tau}{sub E}(L-mode)). At higher currents (I = 25--28 MA) at which ITER can operate for limited pulse duration, there is an increased ignition margin if low-q operation proves acceptable. About a factor of 2 reduction in helium ash concentration (from the baseline value of 10% to 5%) in the reference ITER scenario has about the same impact on ignition capability as increasing the plasma current by about 15% (from the baseline value of 22 MA to {ge}25 MA). It might be possible to further optimize the ignition capability of ITER if some of the limits on operational boundaries can be relaxed by tailoring plasma profiles. 9 refs., 4 figs.

Uckan, N.A.; Hogan, J.T.

1990-01-01

57

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

58

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

59

High Coupling Efficiency Generation in Water Confined Laser Plasma Propulsion  

Microsoft Academic Search

High coupling efficiency generation in water confined laser plasma propulsion is investigated. It is found that the coupling efficiency is enhanced over thirty times in water confined ablation compared to that of direct ablation. From calculation of the ablation pressure induced by the plasma on the target surface, it is realized that high coupling efficiency is attributed to the confinement

Zhi-Yuan Zheng; Yi Zhang; Wei-Gong Zhou; Xin Lu; Yu-Tong Li; Jie Zhang

2007-01-01

60

Absence of reptation in highly confined polymers.  

PubMed

We present results of mechanical stress relaxation measurements on polymers confined at the air-water interface in the form of a monolayer. Systematic measurements allow, to our knowledge, for the first time, observation of the scaling of the stress relaxation time of the highly confined polymers as a function of both surface concentration and molecular weight. The observed scaling is found to be very close to that expected for motion of unentangled polymer solutions with hydrodynamic interactions. Our experimental observations thus clearly rule out the possibility of entanglement and hence reptation as a mode of relaxation in such highly confined polymeric systems. PMID:19530789

Srivastava, S; Basu, J K

2009-06-14

61

Dirac equations with confining potentials  

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

62

Confinement and the safety factor profile  

SciTech Connect

The conjecture that the safety factor profile, q(r), controls the improvement in tokamak plasmas from poor confinement in the Low (L-) mode regime to improved confinement in the supershot regime has been tested in two experiments on the Tokamak Fusion Test Reactor (TFTR). First, helium was puffed into the beam-heated phase of a supershot discharge which induced a degradation from supershot to L-mode confinement in about 100 msec, far less than the current relaxation time. The q and shear profiles measured by a motional Stark effect polarimeter showed little change during the confinement degradation. Second, rapid current ramps in supershot plasmas altered the q profile, but were observed not to change significantly the energy confinement. Thus, enhanced confinement in supershot plasmas is not due to a particular q profile which has enhanced stability or transport properties. The discharges making a continuous transition between supershot and L-mode confinement were also used to test the critical-electron-temperature-gradient transport model. It was found that this model could not reproduce the large changes in electron and ion temperature caused by the change in confinement.

Batha, S.H.; Levinton, F.M. [Fusion Physics and Technology, Torrance, CA (United States); Scott, S.D. [Princeton Univ., NJ (United States). Plasma Physics Lab.] [and others

1995-12-01

63

Confinement Aquaculture. Final Report.  

ERIC Educational Resources Information Center

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

Delaplaine School District, AR.

64

Supersymmetric strings and colour confinement  

Microsoft Academic Search

The (infinite-dimensional) supersymmetry algebra in 1 + 1 space-time dimension is extended in order to incorporate, in a non-trivial way, an internal symmetry. It turns out that this requirement implies that the internal symmetry is realized as a local gauge symmetry. Moreover, it is possible to construct string-like models with this underlying symmetry, where colour confinement is exactly realized as

M. Ademollo; L. Brink; A. D'Adda; R. D'Auria; E. Napolitano; S. Sciuto; E. del Giudice; P. di Vecchia; S. Ferrara; F. Gliozzi; R. Musto; R. Pettorino

1976-01-01

65

Influence of confinement on thermodiffusion  

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

66

Generating equilateral random polygons in confinement  

NASA Astrophysics Data System (ADS)

One challenging problem in biology is to understand the mechanism of DNA packing in a confined volume such as a cell. It is known that confined circular DNA is often knotted and hence the topology of the extracted (and relaxed) circular DNA can be used as a probe of the DNA packing mechanism. However, in order to properly estimate the topological properties of the confined circular DNA structures using mathematical models, it is necessary to generate large ensembles of simulated closed chains (i.e. polygons) of equal edge lengths that are confined in a volume such as a sphere of certain fixed radius. Finding efficient algorithms that properly sample the space of such confined equilateral random polygons is a difficult problem. In this paper, we propose a method that generates confined equilateral random polygons based on their probability distribution. This method requires the creation of a large database initially. However, once the database has been created, a confined equilateral random polygon of length n can be generated in linear time in terms of n. The errors introduced by the method can be controlled and reduced by the refinement of the database. Furthermore, our numerical simulations indicate that these errors are unbiased and tend to cancel each other in a long polygon.

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

2011-10-01

67

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

68

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

69

Longitudinal response of confined semiflexible polymers  

NASA Astrophysics Data System (ADS)

The longitudinal response of single semiflexible polymers to sudden changes in externally applied forces is known to be controlled by the propagation and relaxation of backbone tension. Under many experimental circumstances, realized, for example, in nanofluidic devices or in polymeric networks or solutions, these polymers are effectively confined in a channel- or tubelike geometry. By means of heuristic scaling laws and rigorous analytical theory, we analyze the tension dynamics of confined semiflexible polymers for various generic experimental setups. It turns out that in contrast to the well-known linear response, the influence of confinement on the nonlinear dynamics can largely be described as that of an effective prestress. We also study the free relaxation of an initially confined chain, finding a surprising superlinear ~t9/8 growth law for the change in end-to-end distance at short times.

Thüroff, Florian; Obermayer, Benedikt; Frey, Erwin

2011-02-01

70

Longitudinal Response of Confined Semiflexible Polymers  

E-print Network

The longitudinal response of single semiflexible polymers to sudden changes in externally applied forces is known to be controlled by the propagation and relaxation of backbone tension. Under many experimental circumstances, realized, e.g., in nano-fluidic devices or in polymeric networks or solutions, these polymers are effectively confined in a channel- or tube-like geometry. By means of heuristic scaling laws and rigorous analytical theory, we analyze the tension dynamics of confined semiflexible polymers for various generic experimental setups. It turns out that in contrast to the well-known linear response, the influence of confinement on the non-linear dynamics can largely be described as that of an effective prestress. We also study the free relaxation of an initially confined chain, finding a surprising superlinear t^(9/8) growth law for the change in end-to-end distance at short times.

Florian Thüroff; Benedikt Obermayer; Erwin Frey

2010-09-12

71

Confined subdiffusion in three dimensions  

NASA Astrophysics Data System (ADS)

Three-dimensional (3D) Fick's diffusion equation and fractional diffusion equation are solved for different reflecting boundaries. We use the continuous time random walk model (CTRW) to investigate the time-averaged mean square displacement (MSD) of a 3D single particle trajectory. Theoretical results show that the ensemble average of the time-averaged MSD can be expressed analytically by a Mittag—Leffler function. Our new expression is in agreement with previous formulas in two limiting cases: in short lag time and in long lag time. We also simulate the experimental data of mRNA diffusion in living E. coli using a 3D CTRW model under confined and crowded conditions. The simulation results are well consistent with experimental results. The calculations of power spectral density (PSD) further indicate the subdiffsive behavior of an individual trajectory.

Qin, Shan-Lin; He, Yong

2014-11-01

72

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

73

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

74

Confinement Vessel Dynamic Analysis  

Microsoft Academic Search

A series of hydrodynamic and structural analyses of a spherical confinement vessel has been performed. The analyses used a hydrodynamic code to estimate the dynamic blast pressures at the vessel's internal surfaces caused by the detonation of a mass of high explosive, then used those blast pressures as applied loads in an explicit finite element model to simulate the vessel's

R. Robert Stevens; Stephen P. Rojas

1999-01-01

75

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

PubMed

The self-assembly of diblock copolymers confined in channels of various shaped cross sections is studied using a simulated annealing technique with the "single-site bond fluctuation" model. In the bulk, the asymmetric diblock copolymers used in this study form hexagonally packed cylinders with period L0. The cross sections of the confining channels are of different shapes including regular triangles, rectangles, squares, regular hexagons, regular octagons, and ellipses. For a given geometry, the channel size (characterized by one or two lengths) is varied from very small to several times of L0. It is found that the geometry and size of the confining channels have a large effect on the structure and symmetry of the self-assembled morphologies. Multiple packed cylinders with the symmetry of the confining channels are the major morphologies for low-symmetry cross sections such as triangle, rectangle, and square. More complex structures such as helices or stacked toroids spontaneously form when the confining channels are shaped such as a regular hexagon, a regular octagon, or an ellipse. The domain spacing of the self-assembled structures can be altered by the shape and size of the confining channels. Our results are consistent with available experiments. These results indicate that the self-assembled structures of block copolymers can be manipulated by the shape of the confining channels. PMID:17552796

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

2007-05-28

76

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

77

Cylindrical confinement of semiflexible polymers  

E-print Network

Equilibrium states of a closed semiflexible polymer binding to a cylinder are described. This may be either by confinement or by constriction. Closed completely bound states are labeled by two integers, the number of oscillations, $n$, and the number of times it winds the cylinder, $p$, the latter a topological invariant. We examine the behavior of these states as the length of the loop is increased by evaluating the energy, the conserved axial torque and the contact force. The ground state for a given $p$ is the state with $n=1$; a short loop with $p=1$ is an elliptic deformation of a parallel circle; as its length increases it elongates along the cylinder axis, with two hairpin ends. Excited states with $n \\geq 2$ and $p=1$ posses $n$-fold axial symmetry. Short (long) loops possess energies $\\approx p E_0$ ($n E_0$), with $E_0$ the energy of a circular loop with same radius as the cylinder; in long loops the axial torque vanishes. Confined bound excited states are initially unstable; however, above a critical length they becomes stable: the folded hairpin cannot be unfolded. The ground state for each $p$ is also initially unstable with respect to deformations rotating the loop off the surface into the interior. A closed planar elastic curve aligned along the cylinder axis making contact with the cylinder on its two sides is identified as the ground state of a confined loop. Exterior bound states behave very differently, if free to unbind, as signaled by the reversal in the sign of the contact force. If $p=1$, all such states are unstable. If $p\\ge 2$, however, a topological obstruction to complete unbinding exists. If the loop is short, the bound state with $p=2$ and $n=1$ provides a stable constriction of the cylinder, partially unbinding as the length is increased. This motif could be relevant to an understanding of the process of membrane fission mediated by dynamin rings.

Pablo Vázquez-Montejo; Zachary McDargh; Markus Deserno; Jemal Guven

2015-03-03

78

Threshold power and energy confinement for ITER  

SciTech Connect

In order to predict the threshold power for L-H transition and the energy confinement performance in ITER, assembling of database and analyses of them have been progressed. The ITER Threshold Database includes data from 10 divertor tokamaks. Investigation of the database gives a scaling of the threshold power of the form P{sub thr} {proportional_to} B{sub t} n{sub e}{sup 0.75} R{sup 2} {times} (n{sub e} R{sup 2}){sup +-0.25}, which predicts P{sub thr} = 100 {times} 2{sup 0{+-}1} MW for ITER at n{sub e} = 5 {times} 10{sup 19} m{sup {minus}3}. The ITER L-mode Confinement Database has also been expanded by data from 14 tokamaks. A scaling of the thermal energy confinement time in L-mode and ohmic phases is obtained; {tau}{sub th} {approximately} I{sub p} R{sup 1.8} n{sub e}{sup 0.4{sub P{sup {minus}0.73}}}. At the ITER parameter, it becomes about 2.2 sec. For the ignition in ITER, more than 2.5 times of improvement will be required from the L-mode. The ITER H-mode Confinement Database is expanded from data of 6 tokamaks to data of 11 tokamaks. A {tau}{sub th} scaling for ELMy H-mode obtained by a standard regression analysis predicts the ITER confinement time of {tau}{sub th} = 6 {times} (1 {+-} 0.3) sec. The degradation of {tau}{sub th} with increasing n{sub e} R{sup 2} (or decreasing {rho}{sub *}) is not found for ELMy H-mode. An offset linear law scaling with a dimensionally correct form also predicts nearly the same {tau}{sub th} value.

Takizuka, T.

1996-12-31

79

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

80

Confinement of Equilibrium Polymers  

NASA Astrophysics Data System (ADS)

We consider supramolecular polymer systems in which reversible intermolecular bonding affects the thermodynamics of the system. While we have formulated models for a number of such systems, this presentation focuses on equilibrium polymers in which monomers can reversibly link together to form linear polymers. This serves as a model for giant micelles of surfactant molecules that can break and recombine at any point along the cylindrical micelle. While equilibrium polymers in bulk environments have been studied, we investigate their behavior in confined environments such as between two parallel plates. Our model features a continuous distribution of polymer lengths and assumes a favorable energy decrease when two monomers form a bond. We are interested in how confinement affects the density profile and the polymer length distribution, and we calculate these properties analytically using the ground state dominance approximation and computationally employing self-consistent field theory.

Feng, Edward

2005-03-01

81

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

82

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

83

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

84

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

85

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

86

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

87

Shear Relaxations of Confined Liquids.  

NASA Astrophysics Data System (ADS)

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

Carson, George Amos, Jr.

88

RANDOM COEFFICIENT H MODE CONFINEMENT SCALINGS  

E-print Network

confinement time by n.2 . We assume that the isotope enhancement factor is M1/2 . Unfortunately, 3 #12;no discharges have isotope equal 1.5. The within tokamak isotope scaling for D3D is roughly M.56 and we correct the hydrogen D3D discharges by this amou

89

Preface: Special Topic on Interfacial and Confined Water  

SciTech Connect

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

Molinero, Valeria; Kay, Bruce D.

2014-11-14

90

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

91

Holographic collisions in confining theories  

NASA Astrophysics Data System (ADS)

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

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

2014-01-01

92

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

SciTech Connect

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

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

2013-09-01

93

Confinement Vessel Dynamic Analysis  

SciTech Connect

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

R. Robert Stevens; Stephen P. Rojas

1999-08-01

94

Hadrosynthesis and Quark Confinement  

NASA Astrophysics Data System (ADS)

Multihadron production in high energy collisions, from e+e- annihilation to heavy ion interactions, shows remarkable thermal behaviour, specified by a universal "Hagedorn" temperature. We argue that this hadronic radiation is formed by tunnelling through the event horizon of colour confinement, i.e., that it is the QCD counterpart of Hawking-Unruh radiation from black holes. It is shown to be emitted at a universal temperature TH ? (?/2?)1/2, where ? denotes the string tension. Since the event horizon does not allow information transfer, the radiation is thermal "at birth".

Satz, Helmut

2014-04-01

95

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

96

Amoeboid motion in confined geometry  

E-print Network

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

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

2015-01-01

97

Color Confinement and Massive Gluons  

E-print Network

Color confinement is one of the central issues in QCD so that there are various interpretations of this feature. In this paper we have adopted the interpretation that colored particles are not subject to observation just because colored states are unphysical in the sense of Eq. (2.16). It is shown that there are two phases in QCD distinguished by different choices of the gauge parameter. In one phase, called the "confinement phase", color confinement is realized and gluons turn out to be massive. In the other phase, called the "deconfinement phase", color confinement is not realized, but the gluons remain massless.

M. Chaichian; K. Nishijima

2005-11-15

98

Deforming baryons into confining strings  

SciTech Connect

We find explicit probe D3-brane solutions in the infrared of the Maldacena-Nunez background. The solutions describe deformed baryon vertices: q external quarks are separated in spacetime from the remaining N-q. As the separation is taken to infinity we recover known solutions describing infinite confining strings in N=1 gauge theory. We present results for the mass of finite confining strings as a function of length. We also find probe D2-brane solutions in a confining type IIA geometry, the reduction of a G{sub 2} holonomy M theory background. The relation between these deformed baryons and confining strings is not as straightforward.

Hartnoll, Sean A. [DAMTP, Centre for Mathematical Sciences, Cambridge University, Wilberforce Road, Cambridge CB3 OWA (United Kingdom); Portugues, Ruben [Centro de Estudios Cientificos (CECS), Avenida Arturo Prat 514, Casilla 1469, Valdivia (Chile)

2004-09-15

99

PPPL-3155 -Preprint Date: December 1995, UC-420 Confinement and the Safety Factor Profile  

E-print Network

temperature, and reactivity triple product neETi (electron density, en- ergy confinement time and ion Stark effect polarimeter showed little change during the confinement degradation. Second, rapid current between supershot and L-mode confinement were also used to test the critical-electron-tem- perature

100

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

101

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

102

Inertial Electrostatic Confinement (IEC) devices  

Microsoft Academic Search

Inertial Electrostatic Confinement (IEC) is one of the earliest plasma confinement concepts, having first been suggested by P. T. Farnsworth in the 1950's. The concept involves a simple apparatus of concentric spherical electrostatic grids or a combination of grids and magnetic fields. An electrostatic structure is formed from the confluence of electron or ion beams. Gridded IEC systems have demonstrated

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

1994-01-01

103

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

NASA Astrophysics Data System (ADS)

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

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

2009-06-01

104

ITER L-Mode Confinement Database  

SciTech Connect

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

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

1997-10-01

105

Multishell inertial-confinement-fusion target  

SciTech Connect

This disclosure relates to fusion targets. It deals particularly with the production of multishell inertial confinement fusion targets. The fuel pellet within such targets is designed to compress isentropically under laser or particle irradiation. When a short pulse at extremely high power density strikes the target containing deuterium-tritium fuel, the resulting plasma is confined briefly by its own inertia. Thermonuclear energy can be released in less time than it takes the fuel pellet to blow apart. However, efficient thermonuclear burn requires that the plasma must remain intact at extremely high temperatures and densities for a time sufficient to allow a large fraction of the nuclei to react. Development of multishell targets has been directed at this problem.

Holland, J.R.; Del Vecchio, R.M.

1981-06-01

106

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

107

Inertial confinement fusion  

SciTech Connect

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

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

1992-01-01

108

Transversally confined, noncausal gluons  

NASA Astrophysics Data System (ADS)

A nonperturbative approach to the gluonic sector of four-dimensional QCD is defined, in which a gap equation is used to generate a mass scale M via dimensional transmutation in an arbitrary axial gauge, using a modification of Halpern's method of replacing conventional functional integration over gauge potentials by integration over equivalent field strengths. A consistency condition is used to show that, without further radiative corrections, the gluonic QCD system is apparently diaelectromagnetic against the insertion of color-electromagnetic fields when the spatial shape of the nonperturbative vacuum state is associated with tubes of color-electric or -magnetic flux. A final Gaussian approximation to the relevant functional integral over field strength leads to an extremely simple result of ``effective gluons'' propagating as ``free particles'' with a matrix-valued mass term, by means of a noncausal ``propagator'' that is effectively confined to the interior of a spatial tube, and that falls off with a large momentum k as [k2]-2. A non-Gaussian extension of this result for the effective gluon propagator (EGP) can be guessed. Either form of EGP may be used to compute a finite, gauge-invariant condensate which corresponds to color-electric flux inside and color-magnetic flux outside the tube, or vice versa. The introduction of quarks leads to a ``modified QED'' in an external, tadpole-generated field, where the EGP replaces the bare photon propagator.

Fried, H. M.

1992-12-01

109

Transversally confined, noncausal gluons  

SciTech Connect

A nonperturbative approach to the gluonic sector of four-dimensional QCD is defined, in which a gap equation is used to generate a mass scale [ital M] [ital via] dimensional transmutation in an arbitrary axial gauge, using a modification of Halpern's method of replacing conventional functional integration over gauge potentials by integration over equivalent field strengths. A consistency condition is used to show that, without further radiative corrections, the gluonic QCD system is apparently diaelectromagnetic against the insertion of color-electromagnetic fields when the spatial shape of the nonperturbative vacuum state is associated with tubes of color-electric or -magnetic flux. A final Gaussian approximation to the relevant functional integral over field strength leads to an extremely simple result of effective gluons'' propagating as free particles'' with a matrix-valued mass term, by means of a noncausal propagator'' that is effectively confined to the interior of a spatial tube, and that falls off with a large momentum [ital k] as [[ital k][sup 2

Fried, H.M. (Physique Theorique, Institut Nonlineaire de Nice, Universite de Nice, 06108 Nice CEDEX 2 (France))

1992-12-15

110

Weapons Activities/ Inertial Confinement Fusion Ignition  

E-print Network

Weapons Activities/ Inertial Confinement Fusion Ignition and High Yield Campaign FY 2012 Congressional Budget Inertial Confinement Fusion Ignition and High Yield Campaign Funding Profile by Subprogram FY 2010 Actual Appropriation FY 2011 Request FY 2012 Request Inertial Confinement Fusion Ignition

111

Dissipation-Driven Behavior of Nonpropagating Hydrodynamic Solitons Under Confinement  

NASA Astrophysics Data System (ADS)

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

Gordillo, Leonardo; García-Áustes, Mónica A.

2014-04-01

112

Drift and diffusion of a confined semiflexible chain.  

PubMed

We study the transverse and longitudinal linear response function of rigid chains subjected to an external force. Our main concern are stiff polymers confined in narrow pores with diameter less than their persistence length. We explicitly consider confinement in a transverse harmonic potential and generalize results by scaling arguments. Our results describe the drift of the filament under an external force, time evolution of the filament shape, and filament diffusion. Diffusion of a confined filament resembles the celebrated reptation process for flexible chains, albeit with distinct kinetic exponents. The limiting case of stiff free filaments is also mentioned. PMID:20577775

Nam, G; Johner, A; Lee, N-K

2010-06-01

113

Enhanced Energy Confinement and Performance in a Low-Recycling Tokamak  

Microsoft Academic Search

Extensive lithium wall coatings and liquid lithium plasma-limiting surfaces reduce recycling, with dramatic improvements in Ohmic plasma discharges in the Current Drive Experiment-Upgrade. Global energy confinement times increase by up to 6 times. These results exceed confinement scalings such as ITER98P(y,1) by 2-3 times, and represent the largest increase in energy confinement ever observed for an Ohmic tokamak plasma. Measurements

R. Majeski; T. Gray; R. Kaita; D. Mansfield; J. Spaleta; J. Timberlake; L. Zakharov; R. Doerner; R. Maingi; V. Soukhanovskii

2006-01-01

114

Enhanced Energy Confinement and Performance in a Low-Recycling Tokamak  

Microsoft Academic Search

Extensive lithium wall coatings and liquid lithium plasma-limiting surfaces reduce recycling, with dramatic improvements in Ohmic plasma discharges in the Current Drive Experiment-Upgrade. Global energy confinement times increase by up to 6 times. These results exceed confinement scalings such as ITER98P(y,1) by 2 3 times, and represent the largest increase in energy confinement ever observed for an Ohmic tokamak plasma.

R. Majeski; R. Doerner; T. Gray; R. Kaita; R. Maingi; D. Mansfield; J. Spaleta; V. Soukhanovskii; J. Timberlake; L. Zakharov

2006-01-01

115

Psychopathological effects of solitary confinement.  

PubMed

Psychopathological reactions to solitary confinement were extensively described by nineteenth-century German clinicians. In the United States there have been several legal challenges to the use of solitary confinement, based on allegations that it may have serious psychiatric consequences. The recent medical literature on this subject has been scarce. The author describes psychiatric symptoms that appeared in 14 inmates exposed to periods of increased social isolation and sensory restriction in solitary confinement and asserts that these symptoms form a major, clinically distinguishable psychiatric syndrome. PMID:6624990

Grassian, S

1983-11-01

116

Single-molecule mobility in confined and crowded femtoliter chambers  

SciTech Connect

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

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

2013-01-01

117

Improvement of energy confinement of neutral beam heated plasma by lower hybrid current drive in JT-60  

Microsoft Academic Search

Energy and particle confinements in a high power neutral beam heated plasma are improved by a lower hybrid current drive (LHCD) in JT-60. A clear correlation between the improvement of the energy confinement time and the decrease of the plasma internal inductance caused by LHCD is observed. The energy confinement time of the profile-controlled plasma by LHCD is close to

Kenkichi Ushigusa; Takeshi Imai; Ryuji Yoshino

1987-01-01

118

Singular diffusion in a confined sandpile  

NASA Astrophysics Data System (ADS)

We investigate the behavior of a two-state sandpile model subjected to a confining potential in one and two dimensions. From the microdynamical description of this simple model with its intrinsic exclusion mechanism, it is possible to derive a continuum nonlinear diffusion equation that displays singularities in both the diffusion and drift terms. The stationary-state solutions of this equation, which maximizes the Fermi-Dirac entropy, are in perfect agreement with the spatial profiles of time-averaged occupancy obtained from model numerical simulations in one as well as in two dimensions. Surprisingly, our results also show that, regardless of dimensionality, the presence of a confining potential can lead to the emergence of a power-law tail in the distribution of avalanche sizes.

Pires, R. S.; Moreira, A. A.; Carmona, H. A.; Andrade, J. S., Jr.

2015-01-01

119

Confinement made simple in the Coulomb gauge  

NASA Astrophysics Data System (ADS)

In Gribov's scenario in Coulomb gauge, confinement of color charge is due to a long-range instantaneous color-Coulomb potential V( R). This may be determined numerically from the instantaneous part of the gluon propagator D44,inst = V( R)?( t). Confinement of gluons is reflected in the vanishing at k = 0 of the equal-time three-dimensionally transverse would-be physical gluon propagator Dtr( k). We present exact analytic results on D44 and Dtr (which have also been investigated numerically, A. Cucchieri, T. Mendes, and D. Zwanziger, this conference), in particular the vanishing of Dtr( k) at k = 0, and the determination of the running coupling constant from x0g2( k) = k2D44,inst, where x0 = 12 N/(11 N - 2 N f).

Cucchieri, Attilio; Zwanziger, Daniel

2002-03-01

120

Confinement made simple in the Coulomb gauge  

NASA Astrophysics Data System (ADS)

In Gribov's scenario in Coulomb gauge, confinement of color charge is due to a long-range instantaneous color-Coulomb potential V(R). This may be determined numerically from the instantaneous part of the gluon propagator D44,inst = V(R)?(t). Confinement of gluons is reflected in the vanishing at k = 0 of the equal-time three-dimensionally transverse would-be physical gluon propagator Dtr(k). We present exact analytic results on D44 and Dtr (which have also been investigated numerically, A. Cucchieri, T. Mendes, and D. Zwanziger, this conference), in particular the vanishing of Dtr(k) at k = 0, and the determination of the running coupling constant from x0g2(k) = k2 D44,inst, where x0 = 12N/(11N - 2Nf).

Cucchieri, Attilio; Zwanziger, Daniel

121

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

122

Perturbation theory for confined systems  

E-print Network

We discuss the application of perturbation theory to a system of particles confined in a spherical box. A simple argument shows that the particles behave almost independently in sufficiently strong confinement. We choose the helium atom with a moving nucleus as a particular example and compare results of first order with those for the nucleus clamped at the center of the box. We provide a suitable explanation for some numerical results obtained recently by other authors.

Francisco M. Fernández

2010-04-14

123

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

124

Confined structures: basic crystallographic aspects.  

PubMed

The concept of a confined structure is introduced. The statistical properties of the structure factors for such structures are derived and the main features of the Patterson function are described. It is shown that the structure-factor distributions for the confined structures coincide with those derived for the rational index reflections of ordinary structures. Algorithms potentially useful for protein crystal structure solution are identified and checked via experimental applications. PMID:12192112

De Caro, Liberato; Giacovazzo, Carmelo; Siliqi, Dritan

2002-09-01

125

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

126

Amoeboid motion in confined geometry  

E-print Network

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

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

2015-02-13

127

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.

128

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

129

Enhanced energy confinement and performance in a low-recycling tokamak.  

PubMed

Extensive lithium wall coatings and liquid lithium plasma-limiting surfaces reduce recycling, with dramatic improvements in Ohmic plasma discharges in the Current Drive Experiment-Upgrade. Global energy confinement times increase by up to 6 times. These results exceed confinement scalings such as ITER98P(y,1) by 2-3 times, and represent the largest increase in energy confinement ever observed for an Ohmic tokamak plasma. Measurements of Dalpha emission indicate that global recycling coefficients decrease to approximately 0.3, the lowest documented for a magnetically confined hydrogen plasma. PMID:17026238

Majeski, R; Doerner, R; Gray, T; Kaita, R; Maingi, R; Mansfield, D; Spaleta, J; Soukhanovskii, V; Timberlake, J; Zakharov, L

2006-08-18

130

Enhanced Energy Confinement and Performance in a Low-Recycling Tokamak  

SciTech Connect

Extensive lithium wall coatings and liquid lithium plasma-limiting surfaces reduce recycling, with dramatic improvements in Ohmic plasma discharges in the Current Drive Experiment-Upgrade. Global energy confinement times increase by up to 6 times. These results exceed confinement scalings such as ITER98P(y,1) by 2-3 times, and represent the largest increase in energy confinement ever observed for an Ohmic tokamak plasma. Measurements of D{sub {alpha}} emission indicate that global recycling coefficients decrease to approximately 0.3, the lowest documented for a magnetically confined hydrogen plasma.

Majeski, R.; Gray, T.; Kaita, R.; Mansfield, D.; Spaleta, J.; Timberlake, J.; Zakharov, L. [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States); Doerner, R. [University of California at San Diego, La Jolla, California 92093 (United States); Maingi, R. [Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States); Soukhanovskii, V. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)

2006-08-18

131

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

132

Velocity alignment leads to high persistence in confined cells  

NASA Astrophysics Data System (ADS)

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

Camley, Brian A.; Rappel, Wouter-Jan

2014-06-01

133

Efimov Trimers under Strong Confinement  

NASA Astrophysics Data System (ADS)

The dimensionality of a system can fundamentally impact the behavior of interacting quantum particles. Classic examples range from the fractional quantum Hall effect to high-temperature superconductivity. As a general rule, one expects confinement to favor the binding of particles. However, attractively interacting bosons apparently defy this expectation: While three identical bosons in three dimensions can support an infinite tower of Efimov trimers, only two universal trimers exist in the two-dimensional case. Here, we reveal how these two limits are connected by investigating the problem of three identical bosons confined by a harmonic potential along one direction. We show that the confinement breaks the discrete Efimov scaling symmetry and successively destroys the weakest bound trimers. However, the deepest bound trimers persist even under strong confinement. In particular, the ground-state Efimov trimer hybridizes with the two-dimensional trimers, yielding a superposition of trimer configurations that effectively involves tunneling through a short-range repulsive barrier. Our results suggest a way to use strong confinement to engineer more stable Efimov-like trimers, which have so far proved elusive.

Levinsen, Jesper; Massignan, Pietro; Parish, Meera M.

2014-07-01

134

Semiflexible chains in confined spaces  

NASA Astrophysics Data System (ADS)

We develop an analytical method for studying the properties of a noninteracting wormlike chain (WLC) in confined geometries. The mean-field-like theory replaces the rigid constraints of confinement with average constraints, thus allowing us to develop a tractable method for treating a WLC wrapped on the surface of a sphere, and fully encapsulated within it. The efficacy of the theory is established by reproducing the exact correlation functions for a WLC confined to the surface of a sphere. In addition, the coefficients in the free energy are exactly calculated. We also describe the behavior of a surface-confined chain under external tension that is relevant for single molecule experiments on histone-DNA complexes. The force-extension curves display spatial oscillations, and the extension of the chain, whose maximum value is bounded by the sphere diameter, scales as f-1 at large forces, in contrast to the unconfined chain that approaches the contour length as f-1/2 . A WLC encapsulated in a sphere, that is relevant for the study of the viral encapsulation of DNA, can also be treated using the mean-field approach. The predictions of the theory for various correlation functions are in excellent agreement with Langevin simulations. We find that strongly confined chains are highly structured by examining the correlations using a local winding axis. The predicted pressure of the system is in excellent agreement with simulations but, as is known, is significantly lower than the pressures seen for DNA packaged in viral capsids.

Morrison, Greg; Thirumalai, D.

2009-01-01

135

Nanotribology of confined thin films  

NASA Astrophysics Data System (ADS)

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

Drummond, Carlos Alberto

136

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

137

Reactive collisions in confined geometries  

E-print Network

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

Zbigniew Idziaszek; Krzysztof Jachymski; Paul S. Julienne

2015-02-06

138

Hydrodynamics of Confined Active Fluids  

NASA Astrophysics Data System (ADS)

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

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

2013-01-01

139

Reactive collisions in confined geometries  

NASA Astrophysics Data System (ADS)

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

Idziaszek, Zbigniew; Jachymski, Krzysztof; Julienne, Paul S.

2015-03-01

140

Quantum Confinement in Hydrogen Bond  

E-print Network

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

Carlos da Silva dos Santos; Elso Drigo Filho; Regina Maria Ricotta

2015-02-09

141

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

142

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

2006-04-18

143

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

144

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

145

Capillary Condensation in Confined Media  

Microsoft Academic Search

We review here the physics of capillary condensation of liquids in confined media, with a special regard to the application in nanotechnologies. The thermodynamics of capillary condensation and thin film adsorption are first exposed along with all the relevant notions. The focus is then shifted to the modelling of capillary forces, to their measurements techniques (including SFA, AFM and crack

Elisabeth Charlaix; Matteo Ciccotti

2009-01-01

146

Confined Fluids as Strain Meters  

Microsoft Academic Search

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

Gunnar Bodvarsson

1970-01-01

147

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

148

Psychiatric Effects of Solitary Confinement  

Microsoft Academic Search

The author, Dr. Grassian, is a Board Certified Psychiatrist who was on the faculty of the Harvard Medical School for over twenty-five years. He has had extensive experience in evaluating the psychiatric effects of solitary confinement, and in the course of his professional involvement, has been involved as an expert regarding the psychiatric impact of federal and state segregation and

Stuart Grassian

2006-01-01

149

String Theory and Quark Confinement  

E-print Network

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

A. Polyakov

1997-11-01

150

Flex Circuitry for Confined Spaces  

NASA Technical Reports Server (NTRS)

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

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

1986-01-01

151

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 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

152

Time  

ERIC Educational Resources Information Center

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

Circle, David

2005-01-01

153

Improved Confinement During Magnetic Levitation in LDX  

NASA Astrophysics Data System (ADS)

We report improved particle confinement in the Levitated Dipole Experiment (LDXhttp://www.psfc.mit.edu/ldx/) when the high-field superconducting dipole is magnetically levitated. Magnet levitation eliminates power and particle losses to mechanical supports and causes radial transport processes to determine the profiles of the confined plasma. Initial LDX experiments used multiple-frequency electron cyclotron resonance heating (ECRH) to produce quasi-stationary discharges with stable high-beta energetic trapped electrons when the superconducting dipole was mechanically supported. When the mechanical supports are fully retracted and the dipole is magnetically levitated, the pressure increases and becomes more isotropic, and the plasma density is seen to increase by 2 to 5 as compared with supported operation. Variations of the microwave heating power, power deposition locations, and neutral fueling rates are used to investigate plasma confinement and profile evolution. Density profile measurements were obtained with a multi-chord interferometer, and under certain circumstances these show a rearrangement of the density profile that results in a highly peaked profile with equal number of particles per flux tube. Such a density profile is the expected stationary state that accompanies the strongly peaked pressure profiles of active magnetospheres and is also the very favorable, centrally peaked profile required for fusion applications. Low frequency fluctuations are seen during rapid profile evolution, but the fluctuations are reduced during this stationary state. Finally, we report excellent technical operation as evidenced by (1) accurate position control of the levitated dipole magnet, and (2) the enhanced float time and reduced cryostat warming during magnetic levitation. D. T. Garnier, et al., Phys. Plasmas 13, 056111 (2006).. D. T. Garnier, et al., Fusion Eng and Design 81, 2371 (2006).

Mauel, M. E.

2008-11-01

154

TOPICAL REVIEW: Biopolymer organization upon confinement  

Microsoft Academic Search

Biopolymers in vivo are typically subject to spatial restraints, either as a result of molecular crowding in the cellular medium or of direct spatial confinement. DNA in living organisms provides a prototypical example of a confined biopolymer. Confinement prompts a number of biophysics questions. For instance, how can the high level of packing be compatible with the necessity to access

D. Marenduzzo; C. Micheletti; E. Orlandini

2010-01-01

155

Two-electron atoms under spherical confinement  

NASA Astrophysics Data System (ADS)

The effect of spherical confinement on the ground state of helium-like have been calculated by using correlated Hylleraas basis sets within the variational framework. The thermodynamic pressure on the ions in the ground state due to confinement and the critical values of the confining radii close to fragmentation limit are also estimated.

Bhattacharyya, S.; Saha, J. K.; Mukhopadhyay, T. K.

2014-04-01

156

MHD Stability of Centrifugally Confined Plasmas  

Microsoft Academic Search

Centrifugally confined plasmas utilize centrifugal forces from plasma rotation to augment magnetic confinement, as an alternative approach to fusion. One magnetic geometry is mirror-type, with rotation about the axis induced from a central, biased core conductor. The outward centrifugal forces from the rotation have a component along the field lines, thus confining ions to the center. The immediate concern, of

Yi-Min Huang

2003-01-01

157

Soft Confinement for Polymer Solutions  

E-print Network

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

Yutaka Oya; Toshihiro Kawakatsu

2014-05-09

158

Physics of magnetic confinement fusion  

NASA Astrophysics Data System (ADS)

Fusion is the energy source of the universe. The local conditions in the core of the Sun allow the transfer of mass into energy, which is finally released in the form of radiation. Technical fusion melts deuterons and tritons to helium releasing large amounts of energy per fusion process. Because of the conditions for fusion, which will be deduced, the fusion fuel is in the plasma state. Here we report on the confinement of fusion plasmas by magnetic fields. Different confinement concepts — tokamaks and stellarators — will be introduced and described. The first fusion reactor, ITER, and the most modern stellarator, Wendelstein 7-X, are under construction. Their basic features and objectives will be presented.

Wagner, F.

2013-06-01

159

The redemption of singularity confinement  

NASA Astrophysics Data System (ADS)

We present a novel way to apply the singularity confinement property as a discrete integrability criterion. We shall use what we call a full deautonomization approach, which consists in treating the free parameters in the mapping as functions of the independent variable, applied to a mapping complemented with terms that are absent in the original mapping but which do not change the singularity structure. We shall show, on a host of examples including the well-known mapping of Hietarinta–Viallet, that our approach offers a way to compute the algebraic entropy for these mappings exactly, thereby allowing one to distinguish between the integrable and non-integrable cases even when both have confined singularities.

Ramani, A.; Grammaticos, B.; Willox, R.; Mase, T.; Kanki, M.

2015-03-01

160

Gluon confinement and quantum censorship  

E-print Network

The dynamical Maxwell-cut, a degeneracy is shown to be a precursor of condensate in the phi4 and the sine-Gordon models. The difference of the way the Maxwell-cut is obtained is pointed out and quantum censorship, the generation of semiclassically looking phenomenon by loop-corrections is conjectured in the sine-Gordon model. It is argued that quantum censorship and gluon confinement exclude each other.

Janos Polonyi

2010-09-19

161

Feynman amplitudes with confinement included  

SciTech Connect

Amplitudes for any multipoint Feynman diagram are written taking into account vacuum background confining field. Higher order gluon exchanges are treated within background perturbation theory. For amplitudes with hadrons in initial or final states vertices are shown to be expressed by the corresponding wave function with the renormalized z factors. Examples of two-point functions, three-point functions (form factors), and decay amplitudes are explicitly considered.

Simonov, Yu. A. [Institute of Theoretical and Experimental Physics (Russian Federation)

2009-07-15

162

Confinement of color and geometry  

E-print Network

A natural explanation of confinement can be given in terms of symmetry. Since color symmetry is exact, the candidate symmetry is dual and related to homotopy,i.e., in (3+1)d, to magnetic charge conservation. A set of r abelian 'tHooft-like tensors (r = rank of the gauge group) can be defined and the dual charge is a violation of the corresponding Bianchi identities. It is shown that this is equivalently described by non-abelian Bianchi identities.

A. Di Giacomo

2009-10-27

163

Inertial-confinement-fusion targets  

SciTech Connect

Inertial confinement fusion (ICF) targets are made as simple flat discs, as hollow shells or as complicated multilayer structures. Many techniques have been 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.

1981-11-16

164

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

165

Direct-Drive Inertial Confinement Fusion: Status and Future  

E-print Network

Direct-Drive Inertial Confinement Fusion: Status and Future P. B. Radha University of Rochester 8 10 Time (ns) Power(TW) #12;A number of key physics issues associated with capsule implosions 5002500 With single beam smoothing Z (m) ­500 ­250 5002500 Spherically symmetric implosion The NIF direct

166

Pellet fuelling into radiative improved confinement discharges in TEXTOR-94  

Microsoft Academic Search

Normally pellet injection in strongly heated discharges leads at most to a relatively short improvement of the energy and particle confinement times. In contrast to this finding, the radiative improved (RI) mode plasma of TEXTOR-94 is a very well suited target for pellet injection: the interaction of a pellet with the high density plasma together with the radiatively cooled edge

J. Hobirk; A. M. Messiaen; K. H. Finken; J. Ongena; M. Brix; R. Jaspers; H. R. Koslowski; A. Krämer-Flecken; G. Mank; J. Rapp; G. Telesca; B. Unterberg

2000-01-01

167

Highly Confined Tunable Mid-Infrared Plasmonics in Graphene Nanoresonators  

E-print Network

Highly Confined Tunable Mid-Infrared Plasmonics in Graphene Nanoresonators Victor W. Brar,, Min as a plasmonic material, as modes having plasmon wavelengths 20 times smaller than free space (p 0/20) have been observed in the 2-6 THz range, and active graphene plasmonic devices operating in that regime have been

168

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

169

Drift-diffusion kinetics of a confined colloid Yves Leroyer and Alois Wrger  

E-print Network

Drift-diffusion kinetics of a confined colloid Yves Leroyer and Alois Würger CPMOH, Université. As a possible application, we discuss confined colloidal suspensions subject to an external field. I coef- ficient or drift velocity affect the mean first-passage time [5--7]. In colloid science

Paris-Sud XI, Université de

170

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

Microsoft Academic Search

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

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

1986-01-01

171

Nonneutral Electron Plasmas Confined in a Compact Magnetic Mirror Trap  

NASA Astrophysics Data System (ADS)

With a new compact magnetic mirror trap, it was demonstrated that the confinement time of 2×107 electrons in a simple magnetic mirror can be longer than 40 ms and that electrostatic oscillations of the plasma can be detected with a multiring electrode configuration. Also, a solitary wave was excited and detected for a mirror-confined nonneutral electron plasma. Obtained results suggest that the new compact magnetic mirror trap will make it possible to investigate electron-positron plasmas experimentally, which have never been conducted so far.

Higaki, Hiroyuki; Sakurai, Shota; Ito, Kiyokazu; Okamoto, Hiromi

2012-10-01

172

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

173

Experimental and Theoretical Studies of Electrostatic Confinement  

NASA Astrophysics Data System (ADS)

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

Park, Jaeyoung; Nebel, Richard

2002-11-01

174

Ingestive behavior of lambs confined in individual and group stalls.  

PubMed

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

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

2014-02-01

175

Issues in tokamak/stellarator transport and confinement enhancement mechanisms  

SciTech Connect

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

Perkins, F.W.

1990-08-01

176

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

177

Jamming and dynamics in Confined Quasi-One Dimensional Systems  

NASA Astrophysics Data System (ADS)

Geometrically confining particles to a quasi-one dimensional arrangement so that they can only interact with their nearest neighbours simplifies the way the particles can pack to the extent that we can calculate the distribution of jammed packings exactly, making them ideal systems for exploring the connection between jamming and dynamics. We study the mean squared displacement (MSD) of a system of two dimensional hard discs subject to inertial motion and confined to a single file by two hard lines. At low densities the MSD of the discs increases linearly with time, consistent with the Einstein relation for normal diffusion. However, at high densities the system exhibits anomalous diffusion, where the MSD is proportional to t^1/2. We show how this dynamic transition is related to the nature and distribution of jammed structures. We also use this simple system to examine the role of dynamic heterogeneity in the motion of dense confined fluids.

Bowles, R. K.; Mon, K. K.; Percus, J. K.

2005-03-01

178

Structure and dynamics of supercooled water in neutral confinements.  

PubMed

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

Klameth, F; Vogel, M

2013-04-01

179

Monte Carlo simulation of plasma confinement in mirror and cusp fields  

NASA Astrophysics Data System (ADS)

Plasma confinement times for mirror and cusp devices are investigated by using a newly developed Monte Carlo simulation model which can include the effects of binary collisions, arbitrary spatial change in the magnetic field, and external electric fields. For a mirror, the simulation results are in good agreement with theory. For a cusp (without an external electric field) the confinement time is found to be proportional to the plasma radius divided by the average velocity, which is approximately the same as the theoretical confinement time given by Kaye et al.

Ohsawa, Y.; Kamimura, T.

1980-07-01

180

Topological Confinement in Bilayer Graphene  

NASA Astrophysics Data System (ADS)

We study a new type of one-dimensional chiral states that can be created in bilayer graphene (BLG) by electrostatic lateral confinement. These states appear on the domain walls separating insulating regions experiencing the opposite gating polarity. While the states are similar to conventional solitonic zero modes, their properties are defined by the unusual chiral BLG quasiparticles, from which they derive. The number of zero mode branches is fixed by the topological vacuum charge of the insulating BLG state. We discuss how these chiral states can manifest experimentally and emphasize their relevance for valleytronics.

Martin, Ivar; Blanter, Ya. M.; Morpurgo, A. F.

2008-01-01

181

Theory of rheology in confinement  

E-print Network

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

Artem A. Aerov; Matthias Krüger

2014-12-12

182

Confinement effects in semimagnetic semiconductors  

NASA Astrophysics Data System (ADS)

An overview is given of selected novel effects observed recently by various groups in modulated structures of Cd 1- xMn xTe. Millikelvin studies of submicron wires doped with either indium or iodine have demonstrated the existence of a new mechanism, by which the universal conductance fluctuations can be generated in mesoscopic systems containing magnetic ions. Moreover, 1/ f conductance noise as well as thermal and magnetic irreversibilities have been observed, providing important information on spin-glass dynamics. Finite size effects in magnetic properties have been probed by direct static and dynamic SQUID measurements on superlattices consisting of few-monolayer spin-glass films separated by nonmagnetic barriers. The confined holes have been found to exert a strong influence upon the magnetic ions and to induce a ferromagnetic phase transition above 1 K in quantum wells modulation doped by nitrogen. Finally, it has been shown also that the giant spin-splitting of the bands offers a tool to tune the coupling between confined photon and exciton modes in photonic structures.

Dietl, Tomasz

1998-02-01

183

Vortex physics in confined geometries  

NASA Astrophysics Data System (ADS)

Patterned irradiation of cuprate superconductors with columnar defects allows a new generation of experiments which can probe the properties of vortex liquids by forcing them to flow in confined geometries. Such experiments can be used to distinguish experimentally between continuous disorder-driven glass transitions of vortex matter, such as the vortex glass or the Bose glass transition, and non-equilibrium polymer-like glass transitions driven by interaction and entanglement. For continuous glass transitions, an analysis of such experiments that combines an inhomogeneous scaling theory with the hydrodynamic description of viscous flow of vortex liquids can be used to infer the critical behavior. After generalizing vortex hydrodynamics to incorporate currents and field gradients both longitudinal and transverse to the applied field, the critical exponents for all six vortex liquid viscosities are obtained. In particular, the shear viscosity is predicted to diverge as | T- TBG| - ?z at the Bose glass transition, with ??1 and z?4.6 the dynamical critical exponent. The scaling behavior of the AC resistivity is also derived. As concrete examples of flux flow in confined geometries, flow in a channel and in the Corbino disk geometry are discussed in detail. Finally, the implications of scaling for the hydrodynamic description of transport in the DC flux transformer geometry are discussed.

Marchetti, M. Cristina; Nelson, David R.

2000-03-01

184

Functional Assembly of Protein Fragments Induced by Spatial Confinement  

PubMed Central

Natural proteins are often confined within their local microenvironments, such as three-dimensional confinement in organelles or two-dimensional confinement in lipid rafts on cytoplasmic membrane. Spatial confinement restricts proteins' entropic freedom, forces their lateral interaction, and induces new properties that the same proteins lack at the soluble state. So far, the phenomenon of environment-induced protein functional alteration still lacks a full illustration. We demonstrate here that engineered protein fragments, although being non-functional in solution, can be re-assembled within the nanometer space to give the full activity of the whole protein. Specific interaction between hexahistidine-tag (His-tag) and NiO surface immobilizes protein fragments on NiO nanoparticles to form a self-assembled protein "corona" on the particles inside the nanopores of mesoporous silica. Site-specific assembly forces a shoulder-by-shoulder orientation and promotes fragment?fragment interaction; this interaction together with spatial confinement of the mesopores results in functional re-assembly of the protein half fragments. To our surprise, a single half fragment of luciferase (non-catalytic in solution) exhibited luciferase activity when immobilized on NiO in the mesopores, in the absence of the complimentary half. This shows for the first time that spatial confinement can induce the folding of a half fragment, reconstitute the enzyme active site, and re-gain the catalytic capability of the whole protein. Our work thereby highlights the under-documented notion that aside from the chemical composition such as primary sequence, physical environment of a protein also determines its function. PMID:25875003

Yu, Yongsheng; Wang, Jianpeng; Liu, Jiahui; Ling, Daishun; Xia, Jiang

2015-01-01

185

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

186

Confinement studies of ohmically heated plasmas in TFTR  

SciTech Connect

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

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

1985-03-01

187

Mixed confinement regimes during equilibrium confinement spectroscopy of DNA  

NASA Astrophysics Data System (ADS)

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.

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

2014-06-01

188

Composite mesostructures by nano-confinement  

Microsoft Academic Search

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

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

2004-01-01

189

Improved confinement in JET hybrid discharges  

Microsoft Academic Search

A new technique has been developed to produce plasmas with improved confinement relative to the H98,y2 scaling law (ITER Physics Expert Groups on Confinement and Transport and Confinement Modelling and Database ITER Physics Basics Editors and ITER EDA 1999 Nucl. Fusion39 2175) on the JET tokamak. In the mid-size tokamaks ASDEX upgrade and DIII-D heating during the current formation is

J Hobirk; F Imbeaux; F Crisanti; P Buratti; C D Challis; E Joffrin; B Alper; Y Andrew; P Beaumont; M Beurskens; A Boboc; A Botrugno; M Brix; I Coffey; S Conroy; O Ford; D Frigione; J Garcia; C Giroud; N C Hawkes; D Howell; I Jenkins; D Keeling; M Kempenaars; H Leggate; P Lotte; E de la Luna; G P Maddison; P Mantica; C Mazzotta; D C McDonald; A Meigs; I Nunes; E Rachlew; F Rimini; M Schneider; A C C Sips; J K Stober; W Studholme; T Tala; M Tsalas; I Voitsekhovitch; P C de Vries

2012-01-01

190

DNA statics and dynamics in nanoscale confinement  

NASA Astrophysics Data System (ADS)

We present, along with theoretical scaling arguments, measurements of the equilibrium and dynamic properties of ? and T2 phage DNA molecules confined in quartz nanochannels. Such measurements serve a two-fold purpose: (1) we hope to assist in the design of future nanofluidic devices by quantifying the behavior of semiflexible polymers in confined environments and (2) we hope to test existing theories for confined semiflexible polymers.

Reisner, Walter W.; Morton, Keith; Riehn, Robert; Wang, Yan Mei; Chou, Stephen; Austin, Robert H.

2005-01-01

191

Spatially confined assembly of nanoparticles.  

PubMed

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

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

2014-10-21

192

Chiral symmetry breaking in confining theories and asymptotic limits of operator product expansion  

NASA Astrophysics Data System (ADS)

The pattern of spontaneous chiral symmetry breaking (CSB) in confining background fields is analyzed. It is explicitly demonstrated how to get the inverse square root large proper time asymptotic of the operator product expansion which is needed for CSB.

Shevchenko, Vladimir I.

2006-03-01

193

Millisecond burning of confined energetic materials during cookoff  

SciTech Connect

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

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

1997-11-01

194

Order in very cold confined plasmas  

SciTech Connect

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

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

1995-12-31

195

Multishell inertial confinement fusion target  

DOEpatents

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

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

1984-01-01

196

Multishell inertial confinement fusion target  

DOEpatents

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

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

1987-01-01

197

Planning for greater confinement disposal  

SciTech Connect

A report that provides guidance for planning for greater-confinement disposal (GCD) of low-level radioactive waste is being prepared. The report addresses procedures for selecting a GCD technology and provides information for implementing these procedures. The focus is on GCD; planning aspects common to GCD and shallow-land burial are covered by reference. Planning procedure topics covered include regulatory requirements, waste characterization, benefit-cost-risk assessment and pathway analysis methodologies, determination of need, waste-acceptance criteria, performance objectives, and comparative assessment of attributes that support these objectives. The major technologies covered include augered shafts, deep trenches, engineered structures, hydrofracture, improved waste forms, and high-integrity containers. Descriptive information is provided, and attributes that are relevant for risk assessment and operational requirements are given. 10 refs., 3 figs., 2 tabs.

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

1985-01-01

198

Magnetic confinement of cosmic clouds  

NASA Technical Reports Server (NTRS)

The role of the magnetic field in the confinement or compression of interstellar gas clouds is reconsidered. The virial theorem for an isolated magnetized cloud in the presence of distant magnetic sources is reformulated in terms of moments of the internal and external currents, and an equilibrium condition is derived. This condition is applied to the interaction between isolated clouds for the simple- and artificial-case in which the field of each cloud is a dipole. With the simplest of statistical assumptions, the probability of any given cloud being compressed is calculated as about 10 percent, the magnetic field acting as a medium which transmits the kinetic pressure between clouds. Even when compression occurs the magnetic pressure 1/2 B-squared may decrease on leaving the cloud surface.

Azar, Michel; Thompson, W. B.

1988-01-01

199

Carbon nanotubes in confined magneticCarbon nanotubes in confined magnetic fields: thefields: the  

E-print Network

Carbon nanotubes in confined magneticCarbon nanotubes in confined magnetic fields: thefieldsOutline Aharonov-Bohm oscillations in Carbon nanotubes Confined and extended magnetic fields & Curvature effects as a change in the interference pattern #12;The AB effect in carbon nano-tubes A. Bachtold et al., Nature 397

Marini, Andrea

200

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

201

Generating random walks and polygons with stiffness in confinement  

NASA Astrophysics Data System (ADS)

The purpose of this paper is to explore ways to generate random walks and polygons in confinement with a bias toward stiffness. Here the stiffness refers to the curvature angle between two consecutive edges along the random walk or polygon. The stiffer the walk (polygon), the smaller this angle on average. Thus random walks and polygons with an elevated stiffness have lower than expected curvatures. The authors introduced and studied several generation algorithms with a stiffness parameter s\\gt 0 that regulates the expected curvature angle at a given vertex in which the random walks and polygons are generated one edge at a time using conditional probability density functions. Our generating algorithms also allow the generation of unconfined random walks and polygons with any desired mean curvature angle. In the case of random walks and polygons confined in a sphere of fixed radius, we observe that, as expected, stiff random walks or polygons are more likely to be close to the confinement boundary. The methods developed here require that the random walks and random polygons be rooted at the center of the confinement sphere.

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

2015-03-01

202

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

203

Classical Coulomb fluids in a confined geometry  

Microsoft Academic Search

It has already been argued that a classical (three-dimensional) Coulomb fluid confined between two parallel walls exhibits ideal gas features when the distance between the walls becomes small; this is confirmed in the present paper. Two-dimensional models of Coulomb fluids (with a logarithmic interaction), confined in a strip, are also studied. These models do not become ideal gases in the

B. Jancovici; G. Manificat

1992-01-01

204

Weapons Activities/ Inertial Confinement Fusion Ignition  

E-print Network

Weapons Activities/ Inertial Confinement Fusion Ignition and High Yield Campaign FY 2011 Congressional Budget Inertial Confinement Fusion Ignition and High Yield Campaign Funding Profile by Subprogram Fusion Ignition and High Yield Campaign Ignition 100,535 106,734 109,506 NIF Diagnostics, Cryogenics

205

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

206

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

207

On the confinement of planetary arcs  

NASA Astrophysics Data System (ADS)

The necessary conditions for planetary arc confinement are investigated, concentrating on the limiting case where the arc is marginally confined. It is shown that periodic perturbations due to a discrete Lindblad resonance can induce a secular change of Jacobian energy as well as orbital eccentricity. If the particles are subject to the perturbation of only one inner (outer) Lindblad resonance, the Lindblad resonance's location must be exterior (interior) to that of the corotation resonance if the perturbations are to lead to confinement. The trajectories of particles that are subject to inelastic collisions and pertubations due to corotation and Lindblad resonances are computed, showing that the confinement mechanism can indeed operate provided the perturbation due to the Lindblad resonance is sufficiently strong to balance viscous effects. The possibility that internal nonradial oscillations of Neptune may provide the necessary perturbations for arc confinement is considered.

Lin, D. N. C.; Papaloizou, J. C. B.; Ruden, S. P.

1987-07-01

208

Confinement and screening in tachyonic matter  

E-print Network

In this paper we consider confinement and screening of the electric field. We study the behavior of a static electric field coupled to a dielectric function with the intent of obtaining an electrical confinement similar to what happens with the field of gluons that bind quarks in hadronic matter. For this we use the phenomenon of `anti-screening' in a medium with exotic dielectric. We show that tachyon matter behaves like an exotic way whose associated dielectric function modifies the Maxwell's equations and affects the fields which results in confining and Coulombian-like potentials in three spatial dimensions. We note that the confining regime coincides with the tachyon condensation, which resembles the effect of confinement due to condensation of magnetic monopoles. The Coulombian-like regime is developed at large distance which is associated with {a screening phase

F. A. Brito; M. L. F. Freire; W. Serafim

2014-11-20

209

Confinement and screening in tachyonic matter  

NASA Astrophysics Data System (ADS)

In this paper we consider confinement and screening of the electric field. We study the behavior of a static electric field coupled to a dielectric function with the intent of obtaining an electrical confinement similar to what happens with the field of gluons that bind quarks in hadronic matter. For this we use the phenomenon of `anti-screening' in a medium with exotic dielectric. We show that tachyon matter behaves like in an exotic way whose associated dielectric function modifies the Maxwell equations and affects the fields which results in confining and Coulombian-like potentials in three spatial dimensions. We note that the confining regime coincides with the tachyon condensation, which resembles the effect of confinement due to the condensation of magnetic monopoles. The Coulombian-like regime is developed at large distance, which is associated with a screening phase.

Brito, F. A.; Freire, M. L. F.; Serafim, W.

2014-12-01

210

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

211

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

212

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

213

Numerical Investigations On The Seismic Behaviour Of Confined Masonry Walls  

SciTech Connect

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

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

2008-07-08

214

Numerical Investigations On The Seismic Behaviour Of Confined Masonry Walls  

NASA Astrophysics Data System (ADS)

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

Calderini, Chiara; Cattari, Serena; Lagomarsino, Sergio

2008-07-01

215

Hydrodynamic fluctuations in confined emulsions  

E-print Network

When an ensemble of particles interact hydrodynamically, they generically display large-scale transient structures such as swirls in sedimenting particles [1], or colloidal strings in sheared suspensions [2]. Understanding these nonequilibrium fluctuations is a very difficult problem, yet they are of great importance for a wide range of processes including pigment deposition in cosmetic or paint films, the transport of microfluidic droplets, ... All these samples concern rigidly confined fluids, which we consider in this paper. We address the collective dynamics of non-Brownian droplets cruising in a shallow microchannel. We provide a comprehensive characterization of their spatiotemporal density fluctuations. We show that density excitations freely propagate at all scales, and in all directions even though the particles are neither affected by potential forces nor by inertia. We introduce a theory which quantitatively accounts for our experimental findings. By doing so we demonstrate that the fluctuation spectrum of this nonequilibrium system is shaped by the combination of truly long-range hydrodynamic interactions and local collisions.

Nicolas Desreumaux; Jean-Baptiste Caussin; Raphael Jeanneret; Eric Lauga; Denis Bartolo

2013-01-23

216

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

217

FRP confined smart concrete/mortar  

NASA Astrophysics Data System (ADS)

In this study, fiber reinforced polymer (FRP) confined smart concrete/mortar sensors were invented and validated for significantly improved measurement range. Several trial mixes were made using cement mortar and micron-phase graphite powders at different mix proportions. Compressive loading tests were conducted on smart mortar cylinder specimens with or without FRP confinement. Two-probe method was used to detect the electrical resistance of the smart cement mortar specimens. Strong correlation was recognized between the stress and electric resistance of the smart mortar. The test results indicated that the FRP wrapping could significantly enlarge the range of such self-sensing property as a consequence of confinement.

Xiao, Y.; Zhu, P. S.; Choi, K. G.; Wu, Y. T.; Huang, Z. Y.; Shan, B.

2006-03-01

218

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

219

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

220

Confinement studies of neutral beam heated discharges in TFTR  

SciTech Connect

The TFTR tokamak has reached its original machine design specifications (I/sub p/ = 2.5 MA and B/sub T/ = 5.2T). Recently, the D/sup 0/ neutral beam heating power has been increased to 6.3 MW. By operating at low plasma current (I/sub p/ approx. = 0.8 MA) and low density anti n/sub e/ approx. = 1 x 10/sup 19/m/sup -3/), high ion temperatures (9 +- keV) and rotation speeds (7 x 10/sup 5/ m/s) have been achieved during injection. At the opposite extreme, pellet injection into high current plasmas has been used to increase the line-average density to 8 x 10/sup 19/m/sup -3/ and the central density to 1.6 x 10/sup 20/m/sup -3// This wide range of operating conditions has enabled us to conduct scaling studies of the global energy confinement time in both ohmically and beam heated discharges as well as more detailed transport studies of the profile dependence. In ohmic discharges, the energy confinement time is observed to scale linearly with density only up to anti n/sub e/ approx. 4.5 x 10/sup 19/m/sup -3/ and then to increase more gradually, achieving a maximum value of approx. 0.45 s. In beam heated discharges, the energy confinement time is observed to decrease with beam power and to increase with plasma current. With P/sub b/ = 5.6 MW, anti n/sub e/ = 4.7 x 10/sup 19/m/sup -3/, I/sub p/ = 2.2 MA and B/sub T = 4.7T, the gross energy confinement time is 0.22 s and T/sub i/(0) = 4.8 keV. Despite shallow penetration of D/sup 0/ beams (at the beam energy less than or equal to 80 keV with low species yield), tau/sub E/(a) values are as large as those for H/sup 0/ injection, but central confinement times are substantially greater. This is a consequence of the insensitivity of the temperature and safety factor profile shapes to the heating profile. The radial variation of tau/sub E/ is even more pronounced with D/sup 0/ injection into high density pellet-injected plasmas. 25 refs.

Murakami, M.; Arunasalam, V.; Bell, J.D.; Stauffer, F.; Bell, M.G.; Bitte, M.; Blanchard, W.R.; Boody, F.; Britz, N.

1985-11-01

221

Confining boundary conditions from dynamical coupling constants  

NASA Astrophysics Data System (ADS)

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

Guendelman, E. I.; Steiner, R.

2014-06-01

222

Nutrient balance on Nebraska livestock confinement systems.  

PubMed

Managing the environmental risk associated with livestock production is a significant challenge. Nitrogen and phosphorus are commonly implicated as the sources of ground and surface water quality problems associated with livestock production. The degree of imbalance between these nutrient inputs and the managed nutrient outputs for a livestock operation defines the magnitude of potential environmental risk and provides insight as to the underlying causes of these challenges. A nitrogen and phosphorus balance was constructed for 33 Nebraska confinement livestock operations. Twenty-five and 17 of these operations experienced significant nitrogen and phosphorus imbalances, respectively (50% more nutrient inputs than outputs). Nutrient inputs on many livestock operations were observed to be two to four times greater than nutrient outputs as managed crop and livestock products. Size of the livestock operation and the degree of integration of livestock with a cropping operation provided only limited explanation of the variation in nutrient balance observed among the individual operations. Management options that contribute to a more favorable nutrient balance were also identified. Management decisions related to feeding program and exporting of manure nutrients to off-farm users were observed to have a substantial impact on the nutrient imbalance. For modern livestock production systems to successfully respond to nutrient-related environmental problems, management strategies must be implemented that address the commonly experienced imbalances of nitrogen and phosphorus. PMID:15526781

Koelsch, R; Lesoing, G

1999-01-01

223

Optical properties of matrix confined species  

NASA Astrophysics Data System (ADS)

A majority of optically functional materials can be perceived as a liaison between ionic or molecular guests and a more or less rigid host. The guests exhibit an optical function, whereas the host provides suitable space, both of them synergistically complementing each other. The embracement of guests and hosts is often very intimate, as e.g. in typical phosphors, where luminescent ions even become part of the host. While the host-guest terminology usually is not applied to such marriages, the term becomes appropriate, if the host grants some degrees of spatial freedom, yet giving order and structure to its guests. Zeolites, clays and inverse opals are porous materials naturally providing hospitable cavities, channels or other compartments, and at the same time the guests are often demanded to occupy preassigned positions within these, or to structurally adapt to the interior host topology. Whereas zeolites and clays are merely patient providers of guest space, inverse opals, can actively turn the light on and off. The present article summarises and highlights recent experimental evidence, ongoing research and some envisaged merits resulting from the interaction of matrix confined luminescent ions, complexes and molecules with a focus on the optical properties of rare earth based materials.

Lezhnina, M. M.; Kynast, U. H.

2010-11-01

224

Type Ia Supernova Explosion: Gravitationally Confined Detonation  

NASA Astrophysics Data System (ADS)

We present a new mechanism for Type Ia supernova explosions in massive white dwarfs. The scenario follows from relaxing assumptions of symmetry and involves a detonation born near the stellar surface. The explosion begins with an essentially central ignition of a deflagration that results in the formation of a buoyancy-driven bubble of hot material that reaches the stellar surface at supersonic speeds. The bubble breakout laterally accelerates fuel-rich outer stellar layers. This material, confined by gravity to the white dwarf, races along the stellar surface and is focused at the location opposite to the point of the bubble breakout. These streams of nuclear fuel carry enough mass and energy to trigger a detonation just above the stellar surface that will incinerate the white dwarf and result in an energetic explosion. The stellar expansion following the deflagration redistributes mass in a way that ensures production of intermediate-mass and iron group elements with ejecta having a strongly layered structure and a mild amount of asymmetry following from the early deflagration phase. This asymmetry, combined with the amount of stellar expansion determined by details of the evolution (principally the energetics of deflagration, timing of detonation, and structure of the progenitor), can be expected to create a family of mildly diverse Type Ia supernova explosions.

Plewa, T.; Calder, A. C.; Lamb, D. Q.

2004-09-01

225

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

226

Studies of high confinement plasma with lower hybrid current drive in the HT7 superconducting tokamak  

Microsoft Academic Search

A high confinement plasma (including core plasma and edge plasma) produced by using lower hybrid current drive (LHCD) has been obtained on the HT-7 superconducting tokamak. An internal transport barrier in the core plasma was formed. The energy confinement time increases from 14.6 ms (Ohmic (OH) phase) to 24.5 ms (LHCD phase), which is close to the value calculated using

Bojiang Ding; Guangli Kuang; Jiafang Shan; Guosheng Xu; Baonian Wan; Jiangang Li

2003-01-01

227

Confined electron model for single-bubble sonoluminescence  

SciTech Connect

The origin of sonoluminescence, the conversion of acoustic energy into ultraviolet/visible radiation in liquids, has remained elusive. We propose that the emission arises from electrons confined to voids in the hot, dense fluid formed during the final stages of bubble collapse. Such electrons are produced by high-temperature ionization of the bubble constituents. A hard-sphere-based model was developed for the fluid structure, thermodynamics, and confined electron emission. The model is consistent with the observed spectral distributions, powerout put, and time scale associated with emission from single cavitating rare gas bubbles. Effective temperatures during emission in the 200-700 nm spectral window are predicted to range from 20000 to 60000 K. 46 refs., 14 figs.

Bernstein, L.S.; Zakin, M.R. [Spectral Sciences, Inc., Burlington, MA (United States)

1995-10-05

228

The deflection of a jet by confining surfaces  

NASA Technical Reports Server (NTRS)

Thrust vectoring can be provided by the turning of a jet exhaust by the presence of confining surfaces. This approach is analogous to the upper surface blowing (USB) concept. Mean velocities, velocity autocorrelations, and pressure-velocity correlations are measured. From the autocorrelation curves, the Taylor microscales and the integral length scales are calculated. Convection velocities are calculated from the velocity space-time correlations. Two different confining surfaces (one flat, one with large curvature) are placed adjacent to the lip of a circular nozzle, and the resultant effects on the flow field are determined. In addition, two velocity ratios (exit plane velocity to ambient stream velocity) are examined. The velocity measurements were made with a laser Doppler velocimeter in conjunction with a phase locked-loop processor. Pressure measurements were made using a 1/8th inch condensor type microphone.

Catalano, G. D.; Morton, J. B.; Humphris, R. R.

1981-01-01

229

Confinement and power balance in the S-1 spheromak  

SciTech Connect

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

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

1989-07-01

230

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

231

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

232

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

233

A model for melting of confined DNA  

E-print Network

When DNA molecules are heated they denature. This occurs locally so that loops of molten single DNA strands form, connected by intact double-stranded DNA pieces. The properties of this "melting" transition have been intensively investigated. Recently there has been a surge of interest in this question, caused by experiments determining the properties of partially bound DNA confined to nanochannels. But how does such confinement affect the melting transition? To answer this question we introduce, and solve a model predicting how confinement affects the melting transition for a simple model system by first disregarding the effect of self-avoidance. We find that the transition is smoother for narrower channels. By means of Monte-Carlo simulations we then show that a model incorporating self-avoidance shows qualitatively the same behaviour and that the effect of confinement is stronger than in the ideal case.

Werner, E; Ambjörnsson, T; Mehlig, B

2015-01-01

234

Communication: Folding of glycosylated proteins under confinement  

NASA Astrophysics Data System (ADS)

Conjugating flexible polymers (such as oligosaccharides) to proteins or confining a protein in a restricted volume often increases protein thermal stability. In this communication, we investigate the interplay between conjugation and confinement which is not trivial as the magnitude and the mechanism of stabilization are different in each instance. Using coarse-grained computational approach the folding biophysics is studied when the protein is placed in a sphere of variable radius and is conjugated to 0-6 mono- or penta-saccharides. We observe a synergistic effect on thermal stability when short oligosaccharides are attached and the modified protein is confined in a small cage. However, when large oligosaccharides are added, a conflict between confinement and glycosylation arises as the stabilizing effect of the cage is dramatically reduced and it is almost impossible to further stabilize the protein beyond the mild stabilization induced by the sugars.

Shental-Bechor, Dalit; Levy, Yaakov

2011-10-01

235

Steiner-tree confinement and tetraquarks  

E-print Network

The linear confinement in quarkonium is generalised as a minimal tree, with interesting geometrical properties. This model binds tetraquarks more easily than the additive model used in earlier investigations.

Jean-Marc Richard

2009-05-14

236

Quantum Electrodynamics of Confined Nonrelativistic Particles  

E-print Network

Quantum Electrodynamics of Confined Nonrelativistic Particles Volker Bach \\Lambda FB Mathematik MA directly on the space of Hamiltonians. Keywords: Quantum Electrodynamics, Nonrelativistic Particles, Ground field theory see [17]. I.1 The Standard Model of Nonrelativistic Quantum Electrodynamics The starting

237

Phonon confinement in stressed silicon nanocluster.  

PubMed

Confined acoustic and optical phonons in Si nanoclusters embedded in sapphire, synthesized using ion-beam implantation are investigated using Raman spectroscopy. The l=0 and l=2 confined acoustic phonons, found at low Raman shift, are analyzed using complex frequency model and the size of the nanoparticles are estimated as 4 and 6 nm. For the confined optical phonon, in contrast to expected red shift, the Raman line shape shows a substantial blue shift, which is attributed to size dependent compressive stress in the nanoparticles. The calculated Raman line shape for the stressed nanoparticles fits well to data. The sizes of Si nanoparticles obtained using complex frequency model are consistent with the size estimated from the fitting of confined optical phonon line shapes and those found from X-ray diffraction and TEM. PMID:19928273

Sahoo, Satyaprakash; Dhara, S; Mahadevan, S; Arora, A K

2009-09-01

238

Human Adaptation To Isolated And Confined Environments  

NASA Technical Reports Server (NTRS)

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

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

1992-01-01

239

Entropy, confinement, and chiral symmetry breaking  

NASA Astrophysics Data System (ADS)

This paper studies the way in which confinement leads to chiral symmetry breaking (CSB) through a gap equation. We argue that a combination of entropic effects, related to fluctuations of Wilson loops with massless constituents, and an Abelian gauge invariance of the confinement action as expressed in terms of the usual confining effective propagator 8?KF???/k4, in effect removes infrared singularities coming from use of this propagator in a standard gap equation (KF is the string tension). Beginning from an Abelian gauge-invariant description of CSB that differs from this standard gap equation, we show how to extract a corresponding gap equation that incorporates both entropic effects and Abelian gauge invariance by replacement of the confining propagator with 8?KF???/(k2+m2)2. Here the finite mass m turns out to be ?M(0) [M(p2) is the running quark mass], based on an extension of an old calculation of the author. This massive propagator gives semiquantitatively two critical properties of confinement: (1) a negative contribution to the confining potential coming from entropy; (2) an infrared cutoff required by Abelian gauge invariance. Entropic effects lead to a q¯q condensate and contribute a negative term ˜-KF/M(0), essential for a massless pion, to the pion Hamiltonian. The resulting gap equation leads to M2(0)?KF/?. We argue that one-gluon exchange is not strong enough in the IR to drive quark CSB, but in any case is necessary to get the correct renormalization-group ultraviolet behavior. We find the standard renormalization-group result with the improvement that the prefactor (related to ?q¯q?) can be calculated from the confining solution. Finally, we briefly point out the Minkowski-space virtues of using a principal-part propagator to describe confinement.

Cornwall, John M.

2011-04-01

240

Environmental Study of Poultry Confinement Buildings  

Microsoft Academic Search

Environmental measurements were made in three poultry confinement buildings in order to characterize gas and particulate contaminants. Levels of total and respirable dust averaged 4.4 and 0.24?mg\\/m, respectively. Particle size distribution as measured by cascade impactors was similar in the three confinement houses with a mass median aerodynamic diameter of about 15?µm and a geometric standard deviation of about 2.2.

WILLIAM JONES; KATHY MORRING; STEPHEN A. OLENCHOCK; TED WILLIAMS; JOHN HICKEY

1984-01-01

241

Programmed environment management of confined microsocieties  

NASA Technical Reports Server (NTRS)

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

Emurian, Henry H.

1988-01-01

242

Freezing of mixtures confined in silica nanopores: Experiment and molecular simulation  

NASA Astrophysics Data System (ADS)

Freezing of mixtures confined in silica nanopores is investigated by means of experiment and molecular simulation. The experiments consist of differential scanning calorimetry and dielectric relaxation spectroscopy measurements for CCl4/C6H5Br mixtures confined in Vycor having pores with a mean diameter of about D =4.2 nm. Molecular simulations consist of grand canonical Monte Carlo simulations combined with the parallel tempering technique for Lennard-Jones Ar/Kr mixtures confined in a silica cylindrical nanopore with a diameter of D =3.2 nm. The experimental and molecular simulation data provide a consistent picture of freezing of mixtures in cylindrical silica nanopores having a size smaller than ten times the size of the confined molecules. No sharp change in the properties of the confined mixture occurs upon melting, which suggests that the confined system does not crystallize. In the case of the molecular simulations, this result is confirmed by the fact that except for the contact layer, the percentage of crystal-like atoms is less than 6% (whatever the temperature). The molecular simulations also show that the composition of the mixture is shifted, upon confinement, toward the component having the strongest wall/fluid attraction.

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

2010-08-01

243

Ignition and burn in inertially confined magnetized fuel  

SciTech Connect

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

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

1991-01-01

244

Dynamic flow and failure of confined polymethylmethacrylate  

NASA Astrophysics Data System (ADS)

The static and dynamic mechanical behavior of confined commercial polymethylmethacrylate (PMMA) is investigated. Cylindrical specimens are confined by means of a tightly fit metal sleeve and subjected to compression tests. The rate and pressure sensitivity of PMMA are characterized over a range of strain rates of ??=10-104 s. In the quasi-static regime, the material is quite ductile, exhibiting noticeable barreling. The dynamic failure mode consists of axial splitting and fragmentation at the lower strain rates ( ??<2000 s) and confining pressures. But, at the higher strain rates and confining pressures, the failure mode changes to adiabatic shear formation of a conical plug. This failure mode transition, identified by SEM fractographic analysis, can be explained by the fact that the confinement delays the operation of damage micromechanisms, as evidenced from the post-peak slope. The response of this polymer is described using a fitted rate-dependent Drucker-Prager pressure-sensitive model, according to ?=66.78?+0.223p, for 10????104 s. This work shows that confining PMMA turns this brittle material into a ductile one, exactly like other brittle materials such as ceramics. The present results thus fit into a general description of the pressure induced brittle-ductile transition, including rate sensitivity effects for this material.

Rittel, D.; Brill, A.

245

The decay of confined vortex rings  

NASA Astrophysics Data System (ADS)

Vortex rings are produced during the ejection of fluid through a nozzle or orifice, which occurs in a wide range of biological conditions such as blood flow through the valves of the heart or through arterial constrictions. Confined vortex ring dynamics, such as these, have not been previously studied despite their occurrence within the biological flow conditions mentioned. In this work, we investigate laminar vortex rings using particle image velocimetry and develop a new semi-empirical model for the evolution of vortex ring circulation subject to confinement. Here we introduce a decay parameter ? which exponentially grows with increasing vortex ring confinement ratio, the ratio of the vortex ring diameter ( D VR) to the confinement diameter ( D), with the relationship ?=4.38 exp(9.5D_VR/D), resulting in a corresponding increase in the rate of vortex ring circulation decay. This work enables the prediction of circulation decay rate based on confinement, which is important to understanding naturally occurring confined vortex ring dynamics.

Stewart, K. C.; Niebel, C. L.; Jung, S.; Vlachos, P. P.

2012-07-01

246

Quasi-static impact damage in confined ceramic tiles  

Microsoft Academic Search

The effect of confinement on the failure mechanisms in dense alumina tiles during the penetration of a projectile was investigated and the role played by lateral mechanical confinement in inhibiting some failure modes was examined.Alumina tiles were placed in a confinement frame which simply and accurately allows high biaxial compressive pre-stresses. The confinement frame is a modular system which enables

Dov Sherman; Tamir Ben-Shushan

1998-01-01

247

Confinement jumps in a non-neutral plasma  

NASA Astrophysics Data System (ADS)

Measurements of confinement jumps in pure electron plasmas confined on magnetic surfaces are presented and discussed. The experiments were performed in the Columbia non-neutral torus stellarator [T. S. Pedersen, J. P. Kremer, R. G. Lefrancois, Q. Marksteiner, N. Pomphrey, W. Reiersen, F. Dahlgren, and X. Sarasola, Fusion Sci. Technol. 50, 372 (2006)]. The jumps exhibit hysteresis and are associated with a negative differential resistance. The jumps occur at particular emission currents of the biased emissive filaments that create and sustain the electron plasmas independent of the methods used to affect the emission current. This observation, as well as other experimental evidence, supports that the jumps are caused by a cathode instability. The jumps can also be triggered by the application of a bias potential on a nearby mesh. In most circumstances, the jumps occur between two stable but measurably different equilibrium states. These different equilibrium states have substantially different confinement times. The cathode physics is important for the jumps because the cathode instability provides the perturbation that triggers the jump of the whole plasma into the other equilibrium state, but as mentioned, an external electrostatic perturbation is also capable of triggering such a jump.

Hahn, Michael; Pedersen, Thomas Sunn; Brenner, Paul W.; Marksteiner, Quinn

2009-02-01

248

Confinement of supernova explosions in a collapsing cloud  

E-print Network

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

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

2005-05-13

249

COLLIMATION AND CONFINEMENT OF MAGNETIC JETS BY EXTERNAL MEDIA  

SciTech Connect

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

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

2013-02-20

250

Single-molecule microscopy using tunable nanoscale confinement  

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

251

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

252

Confinement and water quality-induced stress in largemouth bass  

SciTech Connect

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

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

1984-11-01

253

Statistics of confined self-avoiding walks. II. Entropy and pressure of confinement  

Microsoft Academic Search

For pt. 1, see ibid., vol. 27, p. 2653, (1994). Self-avoiding walks (SAWs) up to 198 steps and random-flight walks (RFWs) up to 598 steps were computer generated. The entropy change upon confinement of the walks, as well as the pressure exercised by corresponding chains obeying Hamiltonian mechanics on the surface of the confining spheres, was derived from the Monte

A. Jaeckel; J. Dayantis

1994-01-01

254

Stiffness and Confinement Ratios of SMA Wire Jackets for Confining Concrete  

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

255

Thermal-mechanical fluctuations of fluid membranes in confined geometries: The case of soft confinement  

Microsoft Academic Search

By definition, membrane or macromolecular assembly is an event of molecular confinement against the configurational entropy of a disordered state. Bilayer membranes under progressive confinement experience a continual damping of undulatory fluctuations, first interpreted as a steric force (Helfrich. Z. Naturforsch. 1978). This paper uses a new, diffusion-equation formalism based on the Feynman-type variational principle to describe how direct interbilayer

Rudi Podgornik; V. Adrian Parsegian

1992-01-01

256

Electrostatic Interactions between Nanoparticles in Confined Spaces: Influence of Confining Wall Roughness  

Microsoft Academic Search

Nanoparticles confined in capillaries is a commonly encountered system in a variety of micro and nano electromechanical devices. In this paper we study the influence of the confining geometry on the electrostatic-interaction forces between two nanoparticles. Predictions of electrostatic double layer interaction forces between two similarly charged smooth spherical colloidal particles inside a long \\

Prodip K. Das; Subir Bhattacharjee

2003-01-01

257

On the AlGaInP-bulk and AlGaInP/GaAs-superlattice confinement effects for heterostructure-emitter bipolar transistors  

NASA Astrophysics Data System (ADS)

The confinement effect and electrical characteristics of heterostructure-emitter bipolar transistors with an AlGaInP bulk-confinement layer and an AlGaInP/GaAs superlattice-confinement layer are first demonstrated and compared by experimentally results. In the two devices, the relatively large valence band discontinuity at AlGaInP/GaAs heterojunction provides excellent confinement effect for holes to enhance current gain. As to the AlGaInP/GaAs superlattice-confinement device, part of thermionic-emission electrons will be trapped in the GaAs quantum wells of the superlattice. This will result in lower collector current and current gain as compared with the bulk-confinement device. Nevertheless, the superlattice-confinement device exhibits a larger current-gain cutoff frequency, which can be attributed that the tunneling behavior is included in the carrier transportation and transporting time across the emitter region could be substantially reduced.

Tsai, Jung-Hui

2015-02-01

258

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

259

Neuroendocrine system and immune responses after confinement.  

PubMed

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

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

1996-01-01

260

Packing frustration in dense confined fluids  

E-print Network

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.

Kim Nygård; Sten Sarman; Roland Kjellander

2014-09-04

261

Neutron Assay System for Confinement Vessel Disposition  

SciTech Connect

Los Alamos National Laboratory has a number of spherical confinement vessels (CVs) remaining from tests involving nuclear materials. These vessels have an inner diameter of 6 feet with 1-inch thick steel walls. The goal of the Confinement Vessel Disposition (CVD) project is to remove debris and reduce contamination inside the CVs. The Confinement Vessel Assay System (CVAS) was developed to measure the amount of special nuclear material (SNM) in CVs before and after cleanout. Prior to cleanout, the system will be used to perform a verification measurement of each vessel. After cleanout, the system will be used to perform safeguards-quality assays of {le}100-g {sup 239}Pu equivalent in a vessel for safeguards termination. The CVAS has been tested and calibrated in preparation for verification and safeguards measurements.

Frame, Katherine C. [Los Alamos National Laboratory; Bourne, Mark M. [Los Alamos National Laboratory; Crooks, William J. [Los Alamos National Laboratory; Evans, Louise [Los Alamos National Laboratory; Mayo, Douglas R. [Los Alamos National Laboratory; Miko, David K. [Los Alamos National Laboratory; Salazar, William R. [Los Alamos National Laboratory; Stange, Sy [Los Alamos National Laboratory; Valdez, Jose I. [Los Alamos National Laboratory; Vigil, Georgiana M. [Los Alamos National Laboratory

2012-07-13

262

Plasma confinement with an RF trap  

SciTech Connect

A fusion device based on an RF trap is described. An RF trap combines the axial field of a Penning Trap with the pondermotive confinement of a Paul Trap. The pondermotive confinement is provided by standing electromagnetic waves in a resonant cavity, although driven electrostatic fields may also be employed if one wishes to operate at lower frequencies. The major advantage of this device is that the electrostatic breakdown problem for high energy Penning traps can be alleviated allowing one to utilize larger sizes and potentially higher fusion power densities than a standard Penning Trap. Also, multiple species can be confined and focused in this device permitting the utilization of advanced fuels in pure ion plasmas. The major disadvantage is that the device requires large standing wave energies which may lead to unacceptable wall dissipation. The equations describing the trap, spatial and temporal focusing criteria, and reactor embodiments of the device will be presented.

Nebel, R.A.; Finn, J.M.; Glasser, A.H. [Los Alamos National Lab., NM (United States)

1996-12-31

263

Electronic confinement in modulation doped quantum dots  

SciTech Connect

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

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

2014-04-14

264

The physics of spherical confinement systems  

NASA Astrophysics Data System (ADS)

Spherical torus magnetic confinement systems, covering spheromaks and spherical tokamaks (STs), are reviewed. As well as being potentially very important for fusion, spherical tori research is enhancing our understanding of magnetic confinement systems with wider applications than fusion research. The studies contribute to the conventional tokamak, for example, ITER via a range of scalings, as well as to our understanding of `quiescent' plasmas and those subject to `turbulent magnetohydrodynamic (MHD) relaxation'. The theoretical and experimental properties are described, showing how these vary with configuration and contrasting them with the conventional aspect ratio tokamak. Topics covered include equilibrium, refuelling, helicity injection, influence of trapped particle fraction, plasma heating, confinement, stability (including pressure limits and energetic particle instabilities) and disruption resilience.

Robinson, D. C.

1999-03-01

265

Cylindrical fabric-confined soil structures  

NASA Astrophysics Data System (ADS)

A cylindrical fabric-soil structural concept for implementation on the moon and Mars which provides many advantages is proposed. The most efficient use of fabric is to fashion it into cylindrical tubes, creating cylindrical fabric-confined soil structures. The length, diameter, and curvature of the tubes will depend on the intended application. The cylindrical hoop forces provide radial confinement while end caps provide axial confinement. One of the ends is designed to allow passage of the soil into the fabric tube before sealing. Transportation requirements are reduced due to the low mass and volume of the fabric. Construction requirements are reduced due to the self-erection capability via the pneumatic exoskeleton. Maintenance requirements are reduced due to the passive nature of the concept. The structure's natural ductility is well suited for any seismic activity.

Harrison, Richard A.

266

Monopoles and Confinement in Lattice Gauge Theory.  

NASA Astrophysics Data System (ADS)

The mechanism by which quarks, believed to be the fundamental constituents of matter, are prevented from existing in the free state is still unknown. The phenomenon of quark confinement is one of the fundamental problems in physics. One of the most viable candidates for a hypothesis of confinement is the dual superconductor mechanism that likens quark confinement to the Meissner effect in superconductors. The peculiarities of quark interactions make a numerical approach to the subject a necessity, and therefore, much of the work in this area has been done through the methods of lattice gauge theory, with the simplicities afforded by putting spacetime on a four-dimensional grid. Over the years a large amount of indirect evidence has accumulated that the dual superconductor hypothesis does indeed lead to quark confinement but unambiguous evidence has eluded research efforts until recently. This work presents the first direct proof of a Meissner-like effect that leads to confinement, using the numerical techniques of lattice gauge theory. It is shown that for a U(1) lattice gauge theory, that serves as a toy model for the real world of quarks, a dual London relation and an electric fluxoid quantization condition is satisfied, allowing us to conclude that the vacuum in this case acts like an extreme type -II superconductor, and that quarks are confined. We also show that SU(2) lattice gauge theory, which is qualitatively different and another step closer to reality, shows a Meissner -like effect. In contrast to the U(1) case, our results are found consistent with a dual version of the Ginsburg -Landau theory of superconductivity. We find reason to believe that the SU(2) vacuum behaves like a superconductor on the borderline between type-I and type-II. Our approach paves the way for a study of the more complicated theory, quantum chromodynamics, that is believed to describe quarks.

Singh, Vandana

267

Optimal confinement for internal polymer binding  

NASA Astrophysics Data System (ADS)

Internal binding between specific groups dilute along a polymer chain plays a paramount role in many technological and biological systems. Against common intuition, we show that the interplay between excluded-volume correlations and hydrodynamic interactions can produce an optimal confinement where the binding is fastest. Similarly, there is an optimal osmotic pressure for the binding rate of a chain immersed in a solution of (non-binding) spectator chains. When internal binding leads to higher-order vertices as in self-assembly, confinement can set the same kinetic rate for the formation of several low-order vertices.

Lee, N. K.; Abrams, C. F.; Johner, A.

2005-12-01

268

Tension of confining strings at low temperature  

NASA Astrophysics Data System (ADS)

In the low temperature confining phase of QCD or QCD-like theories it is challenging to capture the temperature dependence of observables through AdS/CFT. Using the blackfold approach we compute the quark-anti-quark linear static potential in the low temperature confining phase, taking into account the thermal excitations of the string. We find the explicit temperature dependence of the string tension and notice that, as naturally expected, tension decreases as temperature increases. We have also generalized the blackfold approach for the computation of the Wilson loops, making it directly applicable to a large class of backgrounds.

Giataganas, Dimitrios; Goldstein, Kevin

2015-02-01

269

Shearless transport barriers in magnetically confined plasmas  

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

270

Mean field and the confined single homopolymer  

NASA Astrophysics Data System (ADS)

We develop a statistical model for a confined chain molecule based on a monomer grand canonical ensemble. The molecule is subject to an external chemical potential, a backbone interaction, and an attractive interaction between all monomers. Using a Gaussian variable formalism and a mean field approximation, we analytically derive a minimum principle from which we can obtain relevant physical quantities, such as the monomer density, and we explore the limit in which the chain is subject to a tight confinement. Through a numerical implementation of the minimization process we show how we can obtain density profiles in three dimensions for arbitraty potentials, and we test the limits of validity of the theory.

Pasquali, S.; Percus, J. K.

2009-10-01

271

Flux-Confinement in Dilatonic Cosmic Strings  

E-print Network

We study dilaton-electrodynamics in flat spacetime and exhibit a set of global cosmic string like solutions in which the magnetic flux is confined. These solutions continue to exist for a small enough dilaton mass but cease to do so above a critcal value depending on the magnetic flux. There also exist domain wall and Dirac monopole solutions. We discuss a mechanism whereby magnetic monopolesmight have been confined by dilaton cosmic strings during an epoch in the early universe during which the dilaton was massless.

G. W. Gibbons; C. G. Wells

1993-12-02

272

Neutral Beam Ion Confinement in NSTX  

SciTech Connect

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

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

2001-07-24

273

Molecular transport under tight confinement  

NASA Astrophysics Data System (ADS)

We consider the transport of particles and fluids through channels so narrow that particle ordering is rarely broken. Starting with a fluid of hard point particles in one-dimensional space, but with known isolated particle kinetics, we find the space-time auto correlation of a tugged particle and discover its universal character. We then return to particles, in only quasi-one dimension and to the effect of pair interaction, concluding with an introduction to network flow.

Percus, J. K.

2014-01-01

274

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

275

High-performance inertial confinement fusion target implosions on OMEGA  

SciTech Connect

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

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

2011-04-18

276

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

277

KrF lasers for inertial confinement fusion  

SciTech Connect

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

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

1989-01-01

278

Magnetospheric vortex formation: self-organized confinement of charged particles.  

PubMed

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. PMID:20867249

Yoshida, Z; Saitoh, H; Morikawa, J; Yano, Y; Watanabe, S; Ogawa, Y

2010-06-11

279

All-optical confinement of ultracold plasma with resonant ions  

NASA Astrophysics Data System (ADS)

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

Krasnov, I. V.

2009-06-01

280

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

281

A COMPARATIVE STUDY OF CONFINED AND ERUPTIVE FLARES IN NOAA AR 10720  

SciTech Connect

We investigate the distinct properties of two types of flares: eruptive flares associated with coronal mass ejections (CMEs) and confined flares without CMEs. Our study sample includes nine M- and X-class flares, all from the same active region (AR), six of which are confined and three others which are eruptive. The confined flares tend to be more impulsive in the soft X-ray time profiles and show slenderer shapes in the Extreme-ultraviolet Imaging Telescope 195 A images, while the eruptive ones are long-duration events and show much more extended brightening regions. The location of the confined flares is closer to the center of the AR, while the eruptive flares are at the outskirts. This difference is quantified by the displacement parameter, which is the distance between the AR center and the flare location; the average displacement of the six confined flares is 16 Mm, while that of the eruptive ones is as large as 39 Mm. Further, through nonlinear force-free field extrapolation, we find that the decay index of the transverse magnetic field in the low corona ({approx}10 Mm) is larger for eruptive flares than for confined ones. In addition, the strength of the transverse magnetic field over the eruptive flare sites is weaker than it is over the confined ones. These results demonstrate that the strength and the decay index of the background magnetic field may determine whether or not a flare is eruptive or confined. The implication of these results on CME models is discussed in the context of torus instability of the flux rope.

Cheng, X.; Ding, M. D.; Guo, Y. [Department of Astronomy, Nanjing University, Nanjing 210093 (China); Zhang, J. [School of Physics, Astronomy, and Computational Sciences, George Mason University, 4400 University Drive, MSN 6A2, Fairfax, VA 22030 (United States); Su, J. T., E-mail: dmd@nju.edu.cn [National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China)

2011-05-10

282

Confinement matrices for low- and intermediate-level radioactive waste  

NASA Astrophysics Data System (ADS)

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

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

2012-02-01

283

Singularity confinement for matrix discrete Painlevé equations  

NASA Astrophysics Data System (ADS)

We study the analytic properties of a matrix discrete system introduced by Cassatella and Mañas (2012 Stud. Appl. Math. 128 252-74). The singularity confinement for this system is shown to hold generically, i.e. in the whole space of parameters except possibly for algebraic subvarieties. This paves the way to a generalization of Painlevé analysis to discrete matrix models.

Cassatella-Contra, Giovanni A.; Mañas, Manuel; Tempesta, Piergiulio

2014-09-01

284

Energy confinement and profile consistency in TFTR  

SciTech Connect

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

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

1987-04-01

285

Neutron imaging for inertial confinement fusion experiments  

Microsoft Academic Search

Neutron imaging of Inertial Confinement Fusion (ICF) targets provides a powerful tool for understanding the implosion conditions of deuterium and tritium filled targets at Mega-Joule\\/Tera-Watt scale laser facilities. The primary purpose of imaging ICF targets at that National Ignition Facility (NIF), sited at Lawrence Livermore National Laboratory, Livermore, California, is to determine the asymmetry of the fuel in an imploded

G. P. Grim; R. D. Day; D. D. Clark; V. E. Fatherley; F. P. Garcia; S. A. Jaramillo; A. J. Montoya; G. L. Morgan; J. A. Oertel; T. A. Ortiz; J. R. Payton; P. D. Pazuchanics; D. W. Schmidt; A. C. Valdez; C. H. Wilde; M. D. Wilke

2007-01-01

286

Monosymptomatic hypochondriacal psychosis and prolonged solitary confinement.  

PubMed

A man previously imprisoned for 11 years developed unremitting and treatment-resistant monosymptomatic hypochondriacal psychosis following a period in excess of 12 months in solitary confinement. We are unaware of any other reported incidences of this disorder arising in such circumstances. PMID:7830522

Humphreys, M; Burnett, F

1994-10-01

287

CONFINED SPACE ENTRY Table Of Contents  

E-print Network

are not required to be labeled. c. If activities, such as welding, in a NPRCS create or has a potential to create all CSs and determine any specific installation requirements for entry. 33.A.05 Confined Space Entry (CSE) Procedures. a. PRCS Entry Procedures. Entry into PRCSs shall comply with the requirements of 29

US Army Corps of Engineers

288

Hohlraum manufacture for inertial confinement fusion  

SciTech Connect

Hohlraums are an integral part of indirect drive targets for Inertial Confinement Fusion (ICF) research. Hohlraums are made by an electroforming process that combines elements of micromachining and coating technology. The authors describe how these target element are made and extension of the method that allow fabrication of other, more complex target components.

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

1994-07-01

289

UNIVERSTIY OF ROCHESTER CONFINED SPACE ENTRY PERMIT  

E-print Network

__ No Carbon Monoxide CO) ppm __Yes __ No . Location Fire Alarm 16. Location Emergency Shower AtmosphereTest Requirements Element (any change in task be informed of the nearest telephone, fire alarm, emergency shower and eyewash. 4. Do not enter the confined

Portman, Douglas

290

Neoclassical Transport in Enhanced Confinement Toroidal Plasmas  

Microsoft Academic Search

It has recently been reported that ion thermal transport levels in enhanced confinement tokamak plasmas have been observed^1 to fall below the ``irreducible minimum level'' predicted by standard neoclassical theory. This apparent contradiction is resolved 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

Zhihong Lin; W. M. Tang; W. W. Lee

1996-01-01

291

Chemical confinement systems for waste disposal  

Microsoft Academic Search

The overall objective of waste disposal systems is for long-term isolation of the waste. A waste confinement system can be developed as a three-step management strategy: (1) waste processing and packaging prior to disposal with the objective of immobilizing the contaminant, (2) selection and construction of engineered barriers to prevent or control the migration of the contaminant from the disposal

A. L. Rivera; R. L. Jolley

1990-01-01

292

M-Theory, Torons and Confinement  

E-print Network

We study the decompactification limit of M-theory superpotentials for N=1 four dimensional supersymmetric gauge theories. These superpotentials can be interpreted as generated by toron configurations. The connection with the confinement picture in the maximal abelian gauge is discussed.

Cesar Gomez; Rafael Hernandez

1997-04-29

293

SIGNIFICANCE OF MHD EFFECTS IN STELLARATOR CONFINEMENT  

E-print Network

of high-beta operation is closely linked with configuration effects on the con- finement optimization. In particular, a large Shafranov shift is accompanied by formation of islands and stochas- tic milestone in future fusion re- search based on magnetic confinement. The considerable progress achieved

Hudson, Stuart

294

CONFINED SPACE ENTRY PERMIT University of Maryland  

E-print Network

, winch, harness, life line) are in place. Space has been properly ventilated. Personal ProtectiveCONFINED SPACE ENTRY PERMIT University of Maryland Location: Type of Space: Reason for Entry: Ventilation Lockout/Tagout Combustible gas Toxic contaminants Chemical/Biological Noise Other Personal

Rubloff, Gary W.

295

Nuclear diagnostics for inertial confinement fusion implosions  

SciTech Connect

This abstract contains viewgraphs on nuclear diagnostic techniques for inertial confinement fusion implosions. The viewgraphs contain information on: reactions of interest in ICF; advantages and disadvantages of these methods; the properties nuclear techniques can measure; and some specifics on the detectors used.

Murphy, T.J.

1997-11-01

296

Microinstability of a Mirror-Confined Plasma  

Microsoft Academic Search

Infinite uniform magnetized plasmas with non-Maxwellian particle distributions are subject to electrostatic longitudinal instabilities of the type discussed by Harris. Mirror confinement leads to depletion of low energy ion populations and thus to the Rosenbluth-Post ``maser'' instability at frequencies ? » ?ci, the ion gyrofrequency, and to the flute-like instability of Dory, Guest, and Harris with ? ? ?ci and

G. E. Guest; R. A. Dory

1965-01-01

297

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

298

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

299

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

300

The Psychiatric Aspects of Solitary Confinement  

Microsoft Academic Search

Mental health workers who work in correctional facilities frequently have to assess and treat clients in solitary confinement (SC). SC is used as a procedure in correctional facilities for a variety of reasons including punishment, protection of the person, security of the institution, or for more intensive observation. In this article we have taken a fresh and critical view of

Graham D. Glancy; Erin L. Murray

2006-01-01

301

Confined laser ablation for single-shot nanoparticle deposition of silver  

NASA Astrophysics Data System (ADS)

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

Donnelly, T.; Lunney, J. G.

2013-10-01

302

Phase Transformations in Confined Nanosystems  

SciTech Connect

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

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

2014-04-29

303

Inertial-confinement-fusion targets  

SciTech Connect

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

Hendricks, C.D.

1982-08-10

304

Two-dimensional material confined water.  

PubMed

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

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

2015-01-20

305

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

306

Solvation dynamics of nile blue in ethanol confined in porous sol-gel glasses  

NASA Astrophysics Data System (ADS)

We report on solvation dynamics measurements of the chromophore nile blue in ethanol confined to sol-gel glasses with 50 Å and 75 Å average pore size and compare them with the dynamics of the respective bulk solution. Both the amplitude of the dynamic Stokes shift as well as the dynamics of the solvation process are drastically changed upon confinement. In both confined solutions the dynamic Stokes shift is reduced by a factor of about 2. As the large majority of the chromophores is adsorbed at the inner pore surfaces the solute molecules interact with only a "half-space" of solvent molecules. In a first approximation this decreases the stabilization energy by a factor of 2. The solvation dynamics in the confined solutions show nonexponential behavior comparable to the bulk. However, the whole solvation process slows down and the single decay time constants characterizing it increase with decreasing pore size of the sol-gel glass. We have introduced two phenomenological models to rationalize this behavior. The enhanced polarization field model takes into account the confinement and predicts a strengthening of the solvent's polarization field in an extended solvation cage induced by the electrical field of the chromophore. The steric hindrance model focuses on the interaction of the liquid with the surface reducing molecular mobility resulting in longer relaxation times. Probably both effects are of relevance in the confined solutions investigated. Confinement affects the steady-state spectra as well leading to a redshift of the absorption and a blueshift of the fluorescence. Additional data on the reorientational dynamics of the chromophore are consistent with the fact that the molecules are predominantly adsorbed at the pore surfaces.

Baumann, R.; Ferrante, C.; Deeg, F. W.; Bräuchle, C.

2001-04-01

307

Quantification of reaction violence and combustion enthalpy of plastic bonded explosive 9501 under strong confinement  

NASA Astrophysics Data System (ADS)

The confinement experienced by an explosive during thermal self-initiation can substantially affect performance in terms of deflagration-to-detonation characteristics and explosion/detonation violence. To this end, we have developed an experiment to quantitatively observe enthalpy change and reaction violence in thermally initiated plastic bonded explosive (PBX) 9501. Traditionally, researchers attempt to quantify violence using terminal observations of fragment size, fragment velocity, and through subjective observations. In the work presented here, the explosive was loaded into a heated gun assembly where we subjected a 300 mg charge to a cook-off schedule and a range of static and inertial confinements. Static confinement was controlled using rupture disks calibrated at 34.5 and 138 MPa. The use of 3.15 and 6.3 g projectile masses provided a variation in inertial confinement. This was a regime of strong confinement; a significant fraction of the explosive energy was required to rupture the disk, and the projectile mass was large compared to the charge mass. The state variables pressure and volume were measured in the breech. From these data, we quantified both the reaction enthalpy change and energy release rate of the explosive on a microsecond time scale using a thermodynamic analyisis. We used these values to unambiguously quantify explosion violence as a function of confinement at a fixed cook-off schedule of 190 C for 1 h. P2?, a measure of critical shock energy required for shock ignition of an adjacent explosive was also computed. We found variations in this confinement regime to have a weak effect on enthalpy change, power, violence and shock energy. Violence was approximately 100 times lower than detonating trinitrotoluene, but the measured shock energy approached the critical shock energy for initiating secondary high explosives.

Perry, W. Lee; Dickson, Peter M.; Parker, Gary R.; Asay, B. W.

2005-01-01

308

Incompatible Liquids in Confined Conditions  

E-print Network

In applications involving organic vapour, the performance of high surface area carbons is often challenged by water vapour in the atmosphere. Small angle neutron scattering (SANS), through its ability to distinguish between different components by means of contrast variation, is ideally suited to investigating the behaviour of adsorbed layers in simultaneous contact with a mixed vapour phase. Even at high relative humidity (RH), water alone forms a discontinuous film composed of clusters on the surface of the oxidized microporous carbon used for these studies. When toluene is also present, all the available carbon surface is wetted. Toluene and water adsorb as a single phase already at RH 11.5%, and the concentration of water present in the adsorbed phase is as high as 2.9 wt.%, far above its solubility in bulk toluene (0.033 wt.% at 25 deg C). At RH 87% the concentration of water in the adsorbed phase is four times higher, approximately 12 wt.%. The recently proposed mechanism of anchoring of the water by th...

László, Krisztina; Czakkel, Orsolya; Geissler, Erik

2015-01-01

309

Confinement induced binding of noble gas atoms  

SciTech Connect

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

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

2014-04-28

310

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

311

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

312

A new solution of transient confined-unconfined flow driven by a pumping well  

NASA Astrophysics Data System (ADS)

A new solution of transient confined-unconfined flow driven by a pumping well is developed and compared to previous approximate solutions of Moench and Prickett [Moench AF, Prickett TA. Radial flow in an infinite aquifer undergoing conversion from artesian to water table conditions. Water Resour Res 1972;8:494-9] and Hu and Chen [Hu L, Chen C. Analytical methods for transient flow to a well in a confined-unconfined aquifer. Ground Water 2008;46(4):642-6]. The problem is rewritten in dimensionless form with the Boltzmann transform. The nonlinear equation for flow in the unconfined zone is solved with the Runge-Kutta method. Position of the conversion interface is determined with an iteration scheme. This study shows that the confined-unconfined flow depends on three dimensionless parameters that represent the confined-unconfined storativity ratio ( aD), the ratio of the initial hydraulic head over the aquifer thickness ( fi), and the dimensionless pumping rate ( qD). The rate of expansion of the unconfined zone increases with qD, but decreases with aD and fi. Differences between the two previous approximate solutions and the new solution of this study are observable in the estimated position of the conversion interface and the drawdown-time curves. The new solution can be applied to estimate the time for confined-unconfined conversion to occur (critical conversion time), and the time when the pumping well becomes dry (critical drying time). The critical conversion time is found to be very sensitive to the initial hydraulic head. The critical drying time is often much larger than the critical conversion time and may never be observed during a finite pumping period.

Wang, Xu-Sheng; Zhan, Hongbin

2009-08-01

313

Interatomic collisions in a tightly confined Bose gas  

Microsoft Academic Search

We discuss binary atomic collisions in a Bose gas tightly confined in one (axial) direction and identify two regimes of scattering. In the quasi-two-dimensional (quasi-2D) regime, where the confinement frequency omega0 greatly exceeds the gas temperature T, the scattering rates exhibit 2D features of the particle motion. At temperatures T~homega0 one has a confinement-dominated 3D regime, where the confinement can

D. S. Petrov; G. V. Shlyapnikov

2001-01-01

314

Interpretation of Earth tide response of three deep, confined aquifers  

NASA Astrophysics Data System (ADS)

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

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

1984-03-01

315

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

316

Interpretation of earth tide response of three deep, confined aquifers  

SciTech Connect

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

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

1984-03-10

317

Spin probe dynamics of n-hexadecane in confined geometry  

NASA Astrophysics Data System (ADS)

A combined study of the rotational dynamics of the stable free radical 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) and the phase behavior of n-hexadecane (n-HXD) in the bulk and the confined states in a series of silica gels (SG) by means of ESR and DSC is presented. A slow to fast motion transition of the spin probe TEMPO in the bulk n-HXD occurs at T50 G,bulk ? Tm,bulk, i.e., well below the melting temperature due to its trapping and localized mobility in the interlamellar gap of the crystallites [J. Bartoš, H. Švajdlenková, M. Zaleski, M. Edelmann, M. Lukešová, Physica B 430, 99 (2013)]. On the other hand, the dynamics of the TEMPO in the confined systems is strongly slowing down with T50 G (Dpore) >Tm(Dpore) and slightly increases with the pore size Dpore = 60, 100 and 300 Å of the SG's. At the same time, both the corresponding melting temperature, Tm (Dpore), and melting enthalpy, ?Hm (Dpore), decrease with Dpore together with the mutual anti-correlation between T50 G and Tm as a function of the inverse of pore diameter, 1/Dpore. Moreover, the dynamic heterogeneity of the TEMPO in the confined state below T50 G (Dpore) is closely related to the phase transformation. The strong slowing down of the spin probe motion likely results from its preferential localization at the interface layer of the matrix pore due to specific interaction of TEMPO molecules with the polar silanol groups of the SG matrix. This is supported by special study on a series of the variously filled n-HXD/SG systems, other similar experimental findings as well as by theoretical spectral argument.

Lukešová, Miroslava; Švajdlenková, Helena; Sippel, Pit; Macová, Eva; Berek, Dušan; Loidl, Alois; Bartoš, Josef

2015-02-01

318

Confined Turbulent Swirling Recirculating Flow Predictions. Ph.D. Thesis  

NASA Technical Reports Server (NTRS)

Turbulent swirling flow, the STARPIC computer code, turbulence modeling of turbulent flows, the k-xi turbulence model and extensions, turbulence parameters deduction from swirling confined flow measurements, extension of the k-xi to confined swirling recirculating flows, and general predictions for confined turbulent swirling flow are discussed.

Abujelala, M. T.

1984-01-01

319

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

E-print Network

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

Weston, Ken

320

The Pennsylvania State University Confined Space Entry Program and Procedures  

E-print Network

only large enough for an employee's head or shoulders do not qualify as confined spaces. 2) The spaceThe Pennsylvania State University Confined Space Entry Program and Procedures Created: May 07, 2002 1 #12;2 The Pennsylvania State University Confined Space Entry Program Contents: · Purpose

Maroncelli, Mark

321

Impacts of confinement and research needs to underpin welfare standards  

Microsoft Academic Search

Confinement and its impacts The meaning of the term confinement requires some consideration, as like the term welfare, it is open to interpretation. Wild animals are generally considered to be free- roaming and in that sense are not usually considered to be confined. However, this may not be the case for wildlife living in isolated fragments of habitat or wildlife

John L. Barnett

322

Lasers and Inertial Confinement Fusion in the United States  

E-print Network

Lasers and Inertial Confinement Fusion in the United States R. L. McCrory Director and Vice Provost thermonuclear device began the Inertial Confinement Fusion Era I1860 · StanislawUlamandEdward Teller developed confinement fusion (ICF) has grown as successively larger lasers have been built I1859 · The

323

www.nycaic.org BINGHAMTON WORKSHOP ON SOLITARY CONFINEMENT  

E-print Network

www.nycaic.org BINGHAMTON WORKSHOP ON SOLITARY CONFINEMENT The Campaign for Alternatives the community about solitary confinement in NYS prisons/jails, to learn more about the work of people to Isolated Confinement (CAIC) is meeting with people and groups in the Binghamton area: to educate

Suzuki, Masatsugu

324

29 CFR 1910.146 - Permit-required confined spaces.  

Code of Federal Regulations, 2010 CFR

...2010-07-01 false Permit-required confined spaces. 1910.146 Section 1910.146 ...1910.146 Permit-required confined spaces. (a) Scope and application...of entry into permit-required confined spaces. This section does not apply to...

2010-07-01

325

29 CFR 1910.146 - Permit-required confined spaces.  

Code of Federal Regulations, 2011 CFR

...2011-07-01 false Permit-required confined spaces. 1910.146 Section 1910.146 ...1910.146 Permit-required confined spaces. (a) Scope and application...of entry into permit-required confined spaces. This section does not apply to...

2011-07-01

326

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

327

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

328

NEW APPROACHES TO CONFINED ALPHA DIAGNOSTICS  

SciTech Connect

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

FISHER,R.K

2004-04-01

329

Approaches to confined alpha diagnostics on ITER  

SciTech Connect

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

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

2004-10-01

330

On the Lorentz nature of confinement  

SciTech Connect

The Lorentz structure of the long-range confining force in the heavy quark approximation is studied within the model of QCD vacuum which is described by the bilocal gluonic correlators and assures the area law asymptotics for the isolated Wilson loop. The effective Dirac-type equation is written out for the quark propagating in such vacuum in the presence of static antiquark source. In the heavy quark limit the effective interaction is reduced to the potential one, with 5/6 Lorentz scalar and 1/6 Lorentz vector linear confinement. The next-to-leading in {radical}({sigma})/m corrections are calculated, and the sign and the coefficient at the spin-orbit term is found to be in agreement with both Eichten-Feinberg-Gromes results and demands of heavy quarkonia phenomenology.

Kalashnikova, Yulia S. [Institute of Theoretical and Experimental Physics, Moscow (Russian Federation)

1998-05-29

331

On the Lorentz nature of confinement  

NASA Astrophysics Data System (ADS)

The Lorentz structure of the long-range confining force in the heavy quark approximation is studied within the model of QCD vacuum which is described by the bilocal gluonic correlators and assures the area law asymptotics for the isolated Wilson loop. The effective Dirac-type equation is written out for the quark propagating in such vacuum in the presence of static antiquark source. In the heavy quark limit the effective interaction is reduced to the potential one, with 5/6 Lorentz scalar and 1/6 Lorentz vector linear confinement. The next-to-leading in ?? /m corrections are calculated, and the sign and the coefficient at the spin-orbit term is found to be in agreement with both Eichten-Feinberg-Gromes results and demands of heavy quarkonia phenomenology.

Kalashnikova, Yulia S.

1998-05-01

332

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

333

Morphogenesis of filaments growing in flexible confinements  

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

334

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

335

Inertial electrostatic confinement (IEC) neutron sources  

SciTech Connect

Inertial electrostatic confinement (IEC) is one of the earliest plasma confinement concepts, having first been suggested by P.T. Farnsworth in the 1950s. The concept involves a simple apparatus of concentric spherical electrostatic grids or a combination of grids and magnetic fields. An electrostatic structure is formed from the confluence of electron or ion beams. Gridded IEC systems have demonstrated neutron yields as high as 2 x 10(exp 10) neutrons/sec in steady state. These systems have considerable potential as small, inexpensive, portable neutron sources for assaying applications. Neutron tomography is also a potential application. This paper discusses the IEC concept and how it can be adapted to a steady-state assaying source and an intense pulsed neutron source. Theoretical modeling and experimental results are presented.

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

1995-01-01

336

Spiral precipitation patterns in confined chemical gardens.  

PubMed

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

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

2014-12-01

337

Spiral precipitation patterns in confined chemical gardens  

E-print Network

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

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

2014-12-15

338

Pressure-confined Lyman-alpha clouds  

SciTech Connect

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

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

1989-02-01

339

Light ion driven inertial confinement fusion  

Microsoft Academic Search

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(exp 2) proton beam

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

1992-01-01

340

Color-singlet confinement in chromostatics  

SciTech Connect

By constructing explicit projection operators for the SU(n) configurations of quark-antiquark (qq-bar) and quark-quark (qq) systems, we demonstrate that confinement occurs in the color-singlet state, while the (n/sup 2/-1)-plet of (qq-bar) and both the (1/2)n(n+1)-plet and the (1/2)n(n-1)-plet of qq have infinite energy and are hence decoupled from the spectrum.

Milton, K.A.; Wilcox, W.; Palmer, W.F.; Pinsky, S.S.

1983-03-15

341

[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

342

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

343

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

344

Comments supporting FIRE Confinement & Operating Space  

E-print Network

Comments supporting FIRE Confinement & Operating Space Greg Hammett, Dale Meade, Charles Kessel_cyl) suppresses influence of strong shaping? Note02/06/26 RMSE=? Fit to all tokamaks: H_Cs3 = 0.95 + 0.45 ln(q95/q Type-I ELMs H_Cs3 0.87 1.00 1.04 02/06/26 RMSE=? all tokamaks #12;#12;Comments added after presentation

Hammett, Greg

345

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

346

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

347

LDV Measurement of Confined Parallel Jet Mixing  

SciTech Connect

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

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

2001-01-31

348

Yukawa particles in a confining potential  

SciTech Connect

We study the density distribution of repulsive Yukawa particles confined by an external potential. In the weak coupling limit, we show that the mean-field theory is able to accurately account for the particle distribution. In the strong coupling limit, the correlations between the particles become important and the mean-field theory fails. For strongly correlated systems, we construct a density functional theory which provides an excellent description of the particle distribution, without any adjustable parameters.

Girotto, Matheus, E-mail: matheus.girotto@ufrgs.br; Levin, Yan, E-mail: levin@if.ufrgs.br [Instituto de Física, Universidade Federal do Rio Grande do Sul, Caixa Postal 15051, CEP 91501-970, Porto Alegre, RS (Brazil); Santos, Alexandre P. dos, E-mail: alexandreps@ufcspa.edu.br [Departamento de Educação e Informação em Saúde, Universidade Federal de Ciências da Saúde de Porto Alegre, 90050-170, Porto Alegre, RS (Brazil); Departamento de Física, Universidade Federal de Santa Catarina, 88040-900, Florianópolis, Santa Catarina (Brazil); Colla, Thiago, E-mail: thiago.colla@ufrgs.br [Faculty of Physics, University of Vienna, Boltzmanngasse 5, A-1090 Vienna (Austria)

2014-07-07

349

Combining confinement and conventional beef production  

E-print Network

AND METHODS Drylot Management Pasture Management Calving and Weaning Management Breeding Management RESULTS AND DISCUSSION Calving Performance Calf Performance Herd Health Activities of Cows and Calves Economics Management CONCLUSION LITERATURE... CITED VITA LIST OF TABLES Table 1. Live Calf Crop, Dystocia and Death Loss. . Page 2. Comparison of Live Calf Crop in Drylot and on Pasture 3. Average Weaning Weights of Calves. 4. Budget Analysis of Conventional, Total Confine- ment and Semi...

Gregg, Michael Ronald

1985-01-01

350

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

351

Gluon confinement and the two IR solutions  

E-print Network

We examine the two solutions (massive and scaling) for the covariant Yang-Mills Dyson-Schwinger equations within stochastic quantization, and find that the scaling solution does not survive outside Landau gauge. We also see that the (rainbow) massive solution has less Faddeev-Popov effective action. Finally, we argue that gluon confinement has only been marginally established in experiment and suggest further empirical work.

Felipe J. Llanes-Estrada; Carlos Hidalgo-Duque; Richard Williams

2012-10-31

352

Confined mobility in biomembranes modeled by early stage Brownian motion.  

PubMed

An equation of motion, derived from the fractal analysis of the Brownian particle trajectory, makes it possible to calculate the time dependence of the mean square displacement for early times, before the Einstein formula becomes valid. The diffusion coefficient increases with the distance travelled which can be restricted by the geometrical conditions. The corresponding diffusion coefficient cannot increase further to achieve a value characteristic for unrestricted environment. Explicit formula is derived for confined diffusivity related to the unrestricted one as dependent on the maximum particle mean square displacement possible normalized by the square of its mean free path. The model describes the lipid and protein diffusion in tubular membranes with different radii, originally fitted by the modified Saffman-Delbrück equation, and the lateral mobility of synthetic model peptides for which the diffusion coefficient is inversely proportional to the radius of the diffusing object and to the thickness of the membrane. PMID:24909813

Gmachowski, Lech

2014-08-01

353

Stationary shapes of confined rotating magnetic liquid droplets.  

PubMed

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

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

2010-09-01

354

Fluid description of ion dynamics in a toroidally confined plasma  

NASA Astrophysics Data System (ADS)

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.

2005-05-01

355

Fast ion JET diagnostics: confinement and losses  

NASA Astrophysics Data System (ADS)

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, 3He and 4He, 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 3He-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.; Borba, D.; Cecil, F. E.; Cecconello, M.; Darrow, D.; Goloborod'ko, V.; Hill, K.; Johnson, T.; Murari, A.; Nabais, F.; Pinches, S. D.; Reich, M.; Sharapov, S. E.; Yavorskij, V.; Chugunov, I. N.; Gin, D. B.; Gorini, G.; Shevelev, A. E.; Syme, D. B.; Zoita, V.

2008-03-01

356

"Soft" confinement of graphene in hydrogel matrixes.  

PubMed

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

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

2015-02-01

357

Reverse Monte Carlo modeling in confined systems  

SciTech Connect

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

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

2014-01-14

358

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

359

Evaporation rate of water in hydrophobic confinement  

PubMed Central

The drying of hydrophobic cavities is believed to play an important role in biophysical phenomena such as the folding of globular proteins, the opening and closing of ligand-gated ion channels, and ligand binding to hydrophobic pockets. We use forward flux sampling, a molecular simulation technique, to compute the rate of capillary evaporation of water confined between two hydrophobic surfaces separated by nanoscopic gaps, as a function of gap, surface size, and temperature. Over the range of conditions investigated (gaps between 9 and 14 ? and surface areas between 1 and 9 nm2), the free energy barrier to evaporation scales linearly with the gap between hydrophobic surfaces, suggesting that line tension makes the predominant contribution to the free energy barrier. The exponential dependence of the evaporation rate on the gap between confining surfaces causes a 10 order-of-magnitude decrease in the rate when the gap increases from 9 to 14 ?. The computed free energy barriers are of the order of 50kT and are predominantly enthalpic. Evaporation rates per unit area are found to be two orders of magnitude faster in confinement by the larger (9 nm2) than by the smaller (1 nm2) surfaces considered here, at otherwise identical conditions. We show that this rate enhancement is a consequence of the dependence of hydrophobic hydration on the size of solvated objects. For sufficiently large surfaces, the critical nucleus for the evaporation process is a gap-spanning vapor tube. PMID:22392972

Sharma, Sumit; Debenedetti, Pablo G.

2012-01-01

360

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

NASA Astrophysics Data System (ADS)

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

Rorrer, Nicholas A.; Dorgan, John R.

2014-12-01

361

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

362

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

363

Successional changes in the genetic diversity of a marine bacterial assemblage during confinement  

Microsoft Academic Search

The successional changes in the genetic diversity of Mediterranean bacterioplankton subjected to confinement were studied in an experimental 300 l seawater enclosure. Five samples were taken at different times and analyzed by polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) fingerprinting to rapidly monitor changes in the bacterial genetic diversity. DGGE analysis clearly showed variations between the samples. Three of the

Hendrik Schäfer; Pierre Servais; Gerard Muyzer

2000-01-01

364

Phase separation in confined geometries: Solving the Cahn–Hilliard equation with generic boundary conditions  

Microsoft Academic Search

We apply implicit numerical methods to solve the Cahn–Hilliard equation for confined systems. Generic boundary conditions for hard walls are considered, as they are derived from physical principles. Based on a detailed stability analysis an automatic time step control could be implemented, which makes it possible to explore the demixing kinetics of two thermodynamically stable phases over many orders in

R. Kenzler; F. Eurich; P. Maass; B. Rinn; J. Schropp; E. Bohl; W. Dieterich

2001-01-01

365

FREE ENERGY AND SOLUTIONS OF THE VLASOV-POISSON-FOKKER-PLANCK SYSTEM : EXTERNAL POTENTIAL AND CONFINEMENT  

E-print Network

FREE ENERGY AND SOLUTIONS OF THE VLASOV-POISSON-FOKKER-PLANCK SYSTEM : EXTERNAL POTENTIAL 1. Large time behavior in a confining potential 2. Vanishing when there is an external but non-Poisson-Fokker-Planck system is nonlin- ear since E(t, x) depends on f through equation (P). In the following, we shall assume

Dolbeault, Jean

366

Type II ELMy H modes on ASDEX Upgrade with good confinement at high density  

Microsoft Academic Search

H modes with good confinement and small ELMs with the characteristics of type II or grassy ELMs have been observed on ASDEX Upgrade. Such an ELM behaviour is essential to minimize erosion of the divertor tiles in any next step device. For the first time, operation with this favourable ELM type could be demonstrated close to the Greenwald density. Even

J. Stober; M. Maraschek; G. D. Conway; O. Gruber; A. Herrmann; A. C. C. Sips; W. Treutterer; H. Zohm

2001-01-01

367

Stability of a viscoelastic thread immersed in a confined region A.Y. Gunawan  

E-print Network

Stability of a viscoelastic thread immersed in a confined region A.Y. Gunawan Departemen Matematika an infinitely long viscoelastic thread in a tube filled with a Newtonian fluid. We apply Jeffreys model, the more time it takes to break up. A viscoelastic thread breaks up faster than a Newtonian one

Eindhoven, Technische Universiteit

368

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

Microsoft Academic Search

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

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

2003-01-01

369

Enhanced confinement regimes and control technology in the DIII-D tokamak  

SciTech Connect

Advanced tokamak performance has been demonstrated in the DIII-D tokamak in a series of experiments which brought together developments in technology and improved understanding of the physical principles underlying tokamak operation. The achievement of greatly improved confinement coupled with development of new systems for real time plasma control have permitted investigation of the heretofore hidden or poorly controlled variables which together determine global confinement. These experiments, which included work in transport and control of the plasma boundary, point toward development of operationally and economically attractive reactors based on the tokamak. Some of these experiments are described.

Lohr, J.; Burrell, K.H. [General Atomics, San Diego, CA (United States); Coda, S. [Massachusetts Inst. of Tech., Cambridge, MA (United States)] [and others

1993-07-01

370

Potential regime for heavy quarks dynamics and Lorentz nature of confinement  

NASA Astrophysics Data System (ADS)

Propagation of the heavy quark in the field of a static antiquark source is studied in the framework of effective Dirac equation. The model of QCD vacuum is described by bilocal gluonic correlators. In the heavy quark limit the effective interaction is reduced to the potential one with 5/6 Lorentz scalar and 1/6 Lorentz vector linear confinement, while spin-orbit term is in agreement with Eichten-Feinberg-Gromes results. New spin-independent corrections to the leading confining regime are identified, which arise due to the nonlocality of the interaction in time direction and quark Zitterbewegung.

Kalashnikova, Yu. S.; Nefediev, A. V.

1997-11-01

371

Generalized Bogoliubov transformation for confined fields: Applications for the Casimir effect  

SciTech Connect

The Bogoliubov transformation in thermofield dynamics, an operator formalism for the finite-temperature quantum field theory, is generalized to describe a field in arbitrary confined regions of space and time. Starting with the scalar field, the approach is extended to the electromagnetic field and the energy-momentum tensor is written via the Bogoliubov transformation. In this context, the Casimir effect is calculated for zero and nonzero temperature, and therefore it can be considered as a vacuum condensation effect of the electromagnetic field. This aspect opens an interesting perspective for using this procedure as an effective scheme for calculations in the studies of confined fields, including interacting fields.

Silva, J.C. da [Instituto de Fisica, Universidade Federal da Bahia, Campus de Ondina, 40210-340, Salvador, Bahia (Brazil); Centro Federal de Educacao Tecnologica da Bahia, Rua Emidio Santos, 40000-900, Salvador, Bahia (Brazil); Khanna, F.C. [Physics Department, Theoretical Physics Institute, University of Alberta, Edmonton, Alberta, T6G 2J1 (Canada); TRIUMF, 4004, Westbrook Mall, Vancouver, British Columbia, V6T 2A3 (Canada); Matos Neto, A. [Instituto de Fisica, Universidade Federal da Bahia, Campus de Ondina, 40210-340, Salvador, Bahia (Brazil); Santana, A.E. [Instituto de Fisica, Universidade Federal da Bahia, Campus de Ondina, 40210-340, Salvador, Bahia (Brazil); Physics Department, Theoretical Physics Institute, University of Alberta, Edmonton, Alberta, T6G 2J1 (Canada)

2002-11-01

372

Dynamics and statistics of wave-particle interactions in a confined geometry.  

PubMed

A walker is a droplet bouncing on a liquid surface and propelled by the waves that it generates. This macroscopic wave-particle association exhibits behaviors reminiscent of quantum particles. This article presents a toy model of the coupling between a particle and a confined standing wave. The resulting two-dimensional iterated map captures many features of the walker dynamics observed in different configurations of confinement. These features include the time decomposition of the chaotic trajectory in quantized eigenstates and the particle statistics being shaped by the wave. It shows that deterministic wave-particle coupling expressed in its simplest form can account for some quantumlike behaviors. PMID:25493868

Gilet, Tristan

2014-11-01

373

Dynamics and statistics of wave-particle interactions in a confined geometry  

NASA Astrophysics Data System (ADS)

A walker is a droplet bouncing on a liquid surface and propelled by the waves that it generates. This macroscopic wave-particle association exhibits behaviors reminiscent of quantum particles. This article presents a toy model of the coupling between a particle and a confined standing wave. The resulting two-dimensional iterated map captures many features of the walker dynamics observed in different configurations of confinement. These features include the time decomposition of the chaotic trajectory in quantized eigenstates and the particle statistics being shaped by the wave. It shows that deterministic wave-particle coupling expressed in its simplest form can account for some quantumlike behaviors.

Gilet, Tristan

2014-11-01

374

Confinement effects on glass forming liquids probed by DMA  

E-print Network

Many molecular glass forming liquids show a shift of the glass transition T-g to lower temperatures when the liquid is confined into mesoporous host matrices. Two contrary explanations for this effect are given in literature: First, confinement induced acceleration of the dynamics of the molecules leads to an effective downshift of T-g increasing with decreasing pore size. Second, due to thermal mismatch between the liquid and the surrounding host matrix, negative pressure develops inside the pores with decreasing temperature, which also shifts T-g to lower temperatures. Here we present dynamic mechanical analysis measurements of the glass forming liquid salol in Vycor and Gelsil with pore sizes of d=2.6, 5.0 and 7.5 nm. The dynamic complex elastic susceptibility data can be consistently described with the assumption of two relaxation processes inside the pores: A surface induced slowed down relaxation due to interaction with rough pore interfaces and a second relaxation within the core of the pores. This core relaxation time is reduced with decreasing pore size d, leading to a downshift of T-g proportional to 1/d in perfect agreement with recent differential scanning calorimetry (DSC) measurements. Thermal expansion measurements of empty and salol filled mesoporous samples revealed that the contribution of negative pressure to the downshift of T-g is small (<30%) and the main effect is due to the suppression of dynamically correlated regions of size xi when the pore size xi approaches.

J. Koppensteiner; W. Schranz; M. R. Puica

2010-01-21

375

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

376

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

377

Multicharged Ion Generation in Plasma Confined in a Cusp Magnetic Trap at Quasigasdynamic Regime  

SciTech Connect

Modern way of ECR multicharged ion sources development is connected with increasing of microwave frequency up to tens of GHz. Millimeter wave gyrotrons are used now in several laboratories. Traditional mirror magnetic traps with min B configuration for suppressing of MHD instabilities became too expensive because very strong magnetic fields are required. So prospection of axisymmetric plasma trap with MHD stabilization is quite relevant subject of modern plasma physics. The simplest trap of such kind is cusp one. The zero level of magnetic field in the center of the trap doesn't allow to achieve a good confinement in classical regime. A gasdynamic regime of plasma confinement was studied. The same regime may be realized in the cusp geometry trap if plasma density is high enough.In present work a theoretical model of quasi-gasdynamic plasma confinement in a cusp trap is developed. The possibilities of multicharged ion generation in a plasma confined in a cusp trap under the conditions of powerful ECR heating by pulsed radiation of a millimeter wavelength gyrotron were investigated numerically. Calculations were made. Confinement time was estimated with using of approach developed. The results of experiments with simplest kind of cusp trap have demonstrated good correspondence with theoretical calculations and therefore the adequacy of the developed approach and possibility to build more effective source on this base. Two ways of possible evolution of ECR ion sources based on a cusp magnetic trap are proposed.

Skalyga, V.; Zorin, V. [Institute of Applied Physics, Nizhny Novgorod (Russian Federation)

2005-03-15

378

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

379

Analysis of reflected blast wave pressure profiles in a confined room  

NASA Astrophysics Data System (ADS)

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

Sauvan, P. E.; Sochet, I.; Trélat, S.

2012-05-01

380

High-{beta}, improved confinement reversed-field pinch plasmas at high density  

SciTech Connect

In Madison Symmetric Torus [Dexter et al., Fusion Technol. 19, 131 (1991)] discharges where improved confinement is brought about by modification of the current profile, pellet injection has quadrupled the density, reaching n{sub e}=4x10{sup 19} m{sup -3}. Without pellet injection, the achievable density in improved confinement discharges had been limited by edge-resonant tearing instability. With pellet injection, the total beta has been increased to 26%, and the energy confinement time is comparable to that at low density. Pressure-driven local interchange and global tearing are predicted to be linearly unstable. Interchange has not yet been observed experimentally, but there is possible evidence of pressure-driven tearing, an instability usually driven by the current gradient in the reversed-field pinch.

Wyman, M. D.; Chapman, B. E.; Ahn, J. W.; Almagri, A. F.; Anderson, J. K.; Den Hartog, D. J.; Ebrahimi, F.; Ennis, D. A.; Fiksel, G.; Gangadhara, S.; Goetz, J. A.; O'Connell, R.; Oliva, S. P.; Prager, S. C.; Reusch, J. A.; Sarff, J. S.; Stephens, H. D. [Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States); Bonomo, F.; Franz, P. [Consorzio RFX, Corso Stati Uniti 4, 35127 Padova (Italy); Brower, D. L. [Department of Physics and Astronomy, University of California at Los Angeles, Los Angeles, California 90095-1594 (United States)] (and others)

2008-01-15

381

High-?, improved confinement reversed-field pinch plasmas at high density  

NASA Astrophysics Data System (ADS)

In Madison Symmetric Torus [Dexter et al., Fusion Technol. 19, 131 (1991)] discharges where improved confinement is brought about by modification of the current profile, pellet injection has quadrupled the density, reaching ne=4×1019m-3. Without pellet injection, the achievable density in improved confinement discharges had been limited by edge-resonant tearing instability. With pellet injection, the total beta has been increased to 26%, and the energy confinement time is comparable to that at low density. Pressure-driven local interchange and global tearing are predicted to be linearly unstable. Interchange has not yet been observed experimentally, but there is possible evidence of pressure-driven tearing, an instability usually driven by the current gradient in the reversed-field pinch.

Wyman, M. D.; Chapman, B. E.; Ahn, J. W.; Almagri, A. F.; Anderson, J. K.; Bonomo, F.; Brower, D. L.; Combs, S. K.; Craig, D.; Den Hartog, D. J.; Deng, B. H.; Ding, W. X.; Ebrahimi, F.; Ennis, D. A.; Fiksel, G.; Foust, C. R.; Franz, P.; Gangadhara, S.; Goetz, J. A.; O'Connell, R.; Oliva, S. P.; Prager, S. C.; Reusch, J. A.; Sarff, J. S.; Stephens, H. D.; Yates, T.

2008-01-01

382

High-Beta, Improved Confinement Reversed-Field Pinch Plasmas at High Density  

SciTech Connect

In Madison Symmetric Torus Dexter et al., Fusion Technol. 19, 131 1991 discharges where improved confinement is brought about by modification of the current profile, pellet injection has quadrupled the density, reaching ne=41019 m 3. Without pellet injection, the achievable density in improved confinement discharges had been limited by edge-resonant tearing instability. With pellet injection, the total beta has been increased to 26%, and the energy confinement time is comparable to that at low density. Pressure-driven local interchange and global tearing are predicted to be linearly unstable. Interchange has not yet been observed experimentally, but there is possible evidence of pressure-driven tearing, an instability usually driven by the current gradient in the reversed-field pinch.

Wyman, M. [University of Wisconsin, Madison; Chapman, B. E. [University of Wisconsin, Madison; Ahn, J. W. [University of Wisconsin, Madison; Almagri, A. [University of Wisconsin, Madison; Anderson, J. [University of Wisconsin, Madison; Bonomo, F. [Consorzio RFX, Italy; Brower, D. L. [University of California, Los Angeles; Combs, Stephen Kirk [ORNL; Craig, D. [University of Wisconsin, Madison; Hartog, D. J. Den [University of Wisconsin, Madison; Deng, B. [University of California, Los Angeles; Ding, W. X. [University of California, Los Angeles; Ebrahimi, F. [University of Wisconsin, Madison; Ennis, D. [University of Wisconsin, Madison; Fiksel, G. [University of Wisconsin, Madison; Foust, Charles R [ORNL; Franz, P. [EURATOM / ENEA, Italy; Gangadhara, S. [University of Wisconsin, Madison; Goetz, J. [University of Wisconsin, Madison; O'Connell, R, [University of Wisconsin, Madison; Oliva, S. [University of Wisconsin, Madison; Prager, S. C. [University of Wisconsin, Madison; Reusch, J. A. [University of Wisconsin, Madison; Sarff, J. S. [University of Wisconsin, Madison; Stephens, H. D. [University of Wisconsin, Madison; Yates, T. [University of California, Los Angeles

2008-01-01

383

Combined effect of confinement and affinity of crowded environment on conformation switching of adenylate kinase.  

PubMed

The actual conformation switching of proteins in the crowded cellular environment is completely different from that in vitro. Proteins in cytoplasm are continually subject to confinement and/or attraction to other molecules in their surroundings due to the existence of various biological species. To gain insight into the nature of crowded environments, we investigated the effects of confinement and affinity on the conformation switching of adenylate kinase (ADK) in a spherical cavity. It was found that even a small degree of confinement reduces the entropy of the open state and stabilizes the closed state, which leads to increased energy barriers for transition. Furthermore, the analysis of transition temperatures and mean first passage times indicates that the proper affinity can promote the transition of ADK from closed state to open state. This study reveals that the crowded cellular environment plays an important role in the thermodynamics and kinetics of proteins in vivo. PMID:25432855

Li, Min; Xu, Weixin; Zhang, John Z H; Xia, Fei

2014-12-01

384

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

385

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

386

Violation of the fluctuation-dissipation theorem in confined driven colloids  

NASA Astrophysics Data System (ADS)

Analytical models describing a colloidal particle confined in a harmonic well, e.g. provided by an optical trap, and driven by shear flows are presented. Violation of both static and dynamic fluctuation-dissipation theorem (FDT) is clearly seen, thus clarifying the connection between such FDT violation and the breakdown of the detailed balance. The simple shear and Taylor-Couette velocity fields are studied in detail, showing that loosening confinement enhances FDT violations. In addition, cases violating FDT but not energy equipartition are presented. For the cases under study, an effective temperature is defined via the static FDT, which appears to be more physically sound than the one defined via the time-dependent FDT. Confining sheared colloidal particles by optical tweezers yields considerable FDT violation.

Mauri, R.; Leporini, D.

2006-12-01

387

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

SciTech Connect

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

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

2011-12-23

388

Mechanical behavior of Anvil Points oil shale at elevated temperatures and confining pressures. [Compressive strength, ductility, fractures  

SciTech Connect

Twenty-one constant strain rate compression tests have been performed on 80 ml/kg (20 GPT) Anvil Points oil shale at elevated temperatures (50 to 200/sup 0/C) and confining pressures (0.5 to 40 MPa). The strength of oil shale increases with confining pressure and decreases with temperature. Ductility is greatly enhanced by addition of confining pressure. Elevated temperatures have little influence on ductility at low confining pressures; however, at greater confining pressures, temperature exerts a progressively stronger influence on ductility. A purely empirical failure law, incorporating the effects of temperature and confining pressure, has been fitted to the data. The failure law is in good agreement with the results of other studies on the compressive strength of oil shale. All specimens in this study exhibited some fracturing in post-test examination. However, with increasing temperature and confining pressure, plots of compressive differential stress versus axial strain tend to level off after an initial transient period of increasing stress. This indicates that (1) we are approaching the brittle-ductile transition, and (2) time-dependent effects may be important under physical conditions comparable to those of this study.

Zeuch, D.H.

1982-04-01

389

Studying the impurity charge and main ion mass dependence of impurity confinement in ECR-heated TJ-II stellarator  

NASA Astrophysics Data System (ADS)

The dependence of impurity confinement time on the charge and mass of the impurity ions injected from various samples (LiF, BN, W) by the laser blow-off method is reported for electron cyclotron heated discharges of the TJ-II heliac. Distinct impurity confinements are distinguished clearly for these injected ions in the plasma core as revealed by soft x-ray analysis and by tomographic reconstruction of bolometer array signals. A dependence of impurity confinement with charge seems to be the most probable explanation, as confirmed by the analysis of spectrally resolved data in the vacuum–ultraviolet range. This is discussed in terms of the dependence of impurity neoclassical transport on the background radial electric field. In addition, the impurity confinement of LiF is studied for a set of discharges in which the hydrogenic isotope mixture (H, D) is known (and evolves along the experiment), revealing a moderate isotope effect that is observed for the first time in particle confinement in a stellarator. This effect is consistent with a similar effect reported in global energy confinement time in the ATF stellarator.

Zurro, B.; Hollmann, E. M.; Baciero, A.; Ochando, M. A.; McCarthy, K. J.; Medina, F.; Velasco, J. L.; Pastor, I.; Baião, D.; de la Cal, E.; Rapisarda, D.; the TJ-II Team

2014-12-01

390

Thermal barrier confinement experiments in the TMX-U tandem mirror  

SciTech Connect

In our recent experiments on the TMX-U thermal-barrier device, we achieved the end plugging of axial ion losses up to a central cell density of n/sub c/ = 6 x 10/sup 12/ cm/sup -3/. During lower density experiments, we measured the axial potential profile characteristic of a thermal barrier and found an ion-confining potential greater than 1.5 kV and a potential depression of 0.45 kV in the barrier region. The average beta of hot end plug electrons has reached 15% and of hot central cell ions has reached 6%. In addition, we heated deuterium ions in the central cell with ICRF to an average perpendicular energy of 2 keV. During strong end plugging at low density (7 x 10/sup 11/ cm/sup -3/), the axial ion confinement time tau/sub parallel/ reached 50 to 100 ms while the nonambipolar radial ion confinement time tau/sub perpendicular/ was 14 ms - independent of end plugging. Electrically floating end walls increased the radial ion confinement time by a factor of 1.8. At higher densities and lower potentials, tau/sub parallel/ was 6 to 12 ms and tau/sub perpendicular/ exceeded 100 ms.

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

1984-07-26

391

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

SciTech Connect

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

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

1984-07-26

392

Nonequilibrium dynamics and ultraslow relaxation of confined DNA during viral packaging  

PubMed Central

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

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

2014-01-01

393

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

SciTech Connect

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

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

2005-05-03

394

Pathways to dewetting in hydrophobic confinement  

E-print Network

Liquid water can become metastable with respect to its vapor in hydrophobic confinement. The resulting dewetting transitions are often impeded by large kinetic barriers. According to macroscopic theory, such barriers arise from the free energy required to nucleate a critical vapor tube that spans the region between two hydrophobic surfaces - tubes with smaller radii collapse, whereas larger ones grow to dry the entire confined region. Using extensive molecular simulations of water between two nanoscopic hydrophobic surfaces, in conjunction with advanced sampling techniques, here we show that for inter-surface separations that thermodynamically favor dewetting, the barrier to dewetting does not correspond to the formation of a (classical) critical vapor tube. Instead, it corresponds to an abrupt transition from an isolated cavity adjacent to one of the confining surfaces to a gap-spanning vapor tube that is already larger than the critical vapor tube anticipated by macroscopic theory. Correspondingly, the barrier to dewetting is also smaller than the classical expectation. We show that the peculiar nature of water density fluctuations adjacent to extended hydrophobic surfaces - namely, the enhanced likelihood of observing low-density fluctuations relative to Gaussian statistics - facilitates this non-classical behavior. By stabilizing isolated cavities relative to vapor tubes, enhanced water density fluctuations thus stabilize novel pathways, which circumvent the classical barriers and offer diminished resistance to dewetting. Our results thus suggest a key role for fluctuations in speeding up the kinetics of numerous phenomena ranging from Cassie-Wenzel transitions on superhydrophobic surfaces, to hydrophobically-driven biomolecular folding and assembly.

Richard C. Remsing; Erte Xi; Srivathsan Vembanur; Sumit Sharma; Pablo G. Debenedetti; Shekhar Garde; Amish J. Patel

2015-02-23

395

Inverted critical adsorption of polyelectrolytes in confinement  

E-print Network

What are the fundamental laws for the adsorption of charged polymers onto oppositely charged surfaces, for convex, planar, and concave geometries? This question is at the heart of surface coating applications, various complex formation phenomena, as well as in the context of cellular and viral biophysics. It has been a long-standing challenge in theoretical polymer physics; for realistic systems the quantitative understanding is however often achievable only by computer simulations. In this study, we present the findings of such extensive Monte-Carlo in silico experiments for polymer-surface adsorption in confined domains. We study the inverted critical adsorption of finite-length polyelectrolytes in three fundamental geometries: planar slit, cylindrical pore, and spherical cavity. The scaling relations extracted from simulations for the critical surface charge density $\\sigma_c$-defining the adsorption-desorption transition-are in excellent agreement with our analytical calculations based on the ground-state analysis of the Edwards equation. In particular, we confirm the magnitude and scaling of $\\sigma_c$ for the concave interfaces versus the Debye screening length $1/\\kappa$ and the extent of confinement $a$ for these three interfaces for small $\\kappa a$ values. For large $\\kappa a$ the critical adsorption condition approaches the planar limit. The transition between the two regimes takes place when the radius of surface curvature or half of the slit thickness $a$ is of the order of $1/\\kappa$. We also rationalize how $\\sigma_c(\\kappa)$ gets modified for semi-flexible versus flexible chains under external confinement. We examine the implications of the chain length onto critical adsorption-the effect often hard to tackle theoretically-putting an emphasis on polymers inside attractive spherical cavities.

Sidney J. de Carvalho; Ralf Metzler; Andrey G. Cherstvy

2015-03-06

396

Spherical microwave confinement and ball lightning  

NASA Astrophysics Data System (ADS)

This dissertation presents the results of research done on unconventional energy technologies from 1995 to 2009. The present civilization depends on an infrastructure that was constructed and is maintained almost entirely using concentrated fuels and ores, both of which will run out. Diffuse renewable energy sources rely on this same infrastructure, and hence face the same limitations. I first examined sonoluminescence directed toward fusion, but demonstrated theoretically that this is impossible. I next studied Low Energy Nuclear Reactions and developed methods for improving results, although these have not been implemented. In 2000, I began Spherical Microwave Confinement (SMC), which confines and heats plasma with microwaves in a spherical chamber. The reactor was designed and built to provide the data needed to investigate the possibility of achieving fusion conditions with microwave confinement. A second objective was to attempt to create ball lightning (BL). The reactor featured 20 magnetrons, which were driven by a capacitor bank and operated in a 0.2 s pulse mode at 2.45 GHz. These provided 20 kW to an icosahedral array of 20 antennas. Video of plasmas led to a redesign of the antennas to provide better coupling of the microwaves to the plasma. A second improvement was a grid at the base of the antennas, which provided corona electrons and an electric field to aid quick formation of plasmas. Although fusion conditions were never achieved and ball lightning not observed, experience gained from operating this basic, affordable system has been incorporated in a more sophisticated reactor design intended for future research. This would use magnets that were originally planned. The cusp geometry of the magnetic fields is suitable for electron cyclotron resonance in the same type of closed surface that in existing reactors has generated high-temperature plasmas. Should ball lightning be created, it could be a practical power source with nearly ideal characteristics that could solve many of our current energy-production problems.

Robinson, William Richard

397

Neutronic effects in inertial confinement fusion targets  

SciTech Connect

This paper analyzes the effects induced by fusion-born neutrons within inertial confinement fusion targets. Some of these effects, such as neutron energy deposition, are always present and play a significant role in propagating ignition. Other effects, such as the suprathermal fusion induced by knocked-on ions, are of marginal importance. The possibility of inducing internal tritium breeding and other interesting neutronic reactions is also studied, but it is found that they usually produce negligible or even negative consequences in the target performance.

Martinez-Val, J.M. (Madrid Polytechnic Univ., ETSI Industriales, Inst. of Nuclear Fusion, J. Gutierrez Abascal 2, 28006 Madrid (ES))

1990-05-01

398

Quantized magnetic confinement in quantum wires.  

PubMed

Ballistic quantum wires are exposed to longitudinal profiles of perpendicular magnetic fields composed of a spike and a homogeneous part. An asymmetric magnetoconductance peak as a function of the homogeneous magnetic field is found, comprising quantized conductance steps in the interval where the homogeneous magnetic field and the magnetic barrier have identical polarities, and a characteristic shoulder with several resonances in the interval of opposite polarities. The observations are interpreted in terms of inhomogeneous diamagnetic shifts of the quantum wire modes leading to magnetic confinement. PMID:20482195

Tarasov, A; Hugger, S; Xu, Hengyi; Cerchez, M; Heinzel, T; Zozoulenko, I V; Gasser-Szerer, U; Reuter, D; Wieck, A D

2010-05-01

399

Graviton confinement inside hypermonopoles of any dimension  

SciTech Connect

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

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

2010-09-01

400

Hydatid Cyst Confined to the Papillary Muscle  

PubMed Central

Cardiac involvement of hydatid cysts is rare. Hydatidosis of the valvular apparatus can be treated successfully by the careful application of valvular surgical procedures. To the best of our knowledge, cardiac hydatidosis confined to the anterolateral papillary muscle has not been reported. Herein, we present a case involving a hydatid cyst that was located in a cardiac papillary muscle and that caused mitral regurgitation in a 37-year-old woman. The cyst was removed by papillary muscle incision, and the mitral valve was repaired. The patient experienced an uneventful recovery. PMID:20069089

Apaydin, Anil Z.; Oguz, Emrah; Ayik, Fatih; Nalbantgil, Sanem; Ceylan, Naim

2009-01-01

401

Relaxation pathway confinement in glassy dynamics.  

PubMed

We compute for an archetypical glass-forming system the excess of particle mobility distributions over the corresponding distribution of dynamic propensity, a quantity that measures the tendency of the particles to be mobile and reflects the local structural constraints. This enables us to demonstrate that, on supercooling, the dynamical trajectory in search for a relaxation event must deal with an increasing confinement of relaxation pathways. This "entropic funnel" of relaxation pathways built upon a restricted set of mobile particles is also made evident from the decay and further collapse of the associated Shannon entropy. PMID:25240370

Rodriguez Fris, J A; Frechero, M A; Appignanesi, G A

2014-09-21

402

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

403

Density fluctuations in nanochannel-confined DNA  

NASA Astrophysics Data System (ADS)

The dynamic behavior of a polymer chain in dense solution is typically described within the framework of reptation, which assumes that polymers primarily move along tubes formed by other chains. We have studied the dynamic density fluctuations of single DNA molecules confined to nanofabricated channels that mimic reptation tubes, and found that the classical harmonic spring model yields a satisfactory description. In particular, we have recovered the expected dispersion relationship. By looking at fluctuation amplitudes, we have also found that the description demands a minimum spring length approximately equal to the size of self-avoiding DeGennes blobs.

Carpenter, Joshua; Karpusenko, Alena; Zhou, Chunda; Lim, Shuang Fang; Pan, Junhan; Riehn, Robert

2012-02-01

404

Critical Behavior of Magnetically Confined Plasma Regimes  

SciTech Connect

Plasmas confined in a toroidal magnetic configuration can be characterized by different operational regimes, i.e., distinctive features of the spatial distributions of pressure and current. The poloidal current density is identified as a critical quantity allowing us to discriminate the regimes and an analytical criterion to predict transitions between regimes is derived. The theory also yields a formula which defines current alignment requirements for steady state in a precise way. An analogy with the topological approach of phase transition theory is pointed out and discussed.

Garcia, J.; Giruzzi, G. [CEA, IRFM, F-13108 Saint-Paul-lez-Durance (France)

2010-05-21

405

Relaxation pathway confinement in glassy dynamics  

NASA Astrophysics Data System (ADS)

We compute for an archetypical glass-forming system the excess of particle mobility distributions over the corresponding distribution of dynamic propensity, a quantity that measures the tendency of the particles to be mobile and reflects the local structural constraints. This enables us to demonstrate that, on supercooling, the dynamical trajectory in search for a relaxation event must deal with an increasing confinement of relaxation pathways. This "entropic funnel" of relaxation pathways built upon a restricted set of mobile particles is also made evident from the decay and further collapse of the associated Shannon entropy.

Rodriguez Fris, J. A.; Frechero, M. A.; Appignanesi, G. A.

2014-09-01

406

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

407

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

408

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

409

Clustering of branching Brownian motions in confined geometries.  

PubMed

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

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

2014-10-01

410

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

411

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

412

Temperature measurements on a HSLA-100 steel confinement vessel  

SciTech Connect

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

Lohsen, R.A.

1998-05-07

413

Development of Compton radiography of inertial confinement fusion implosions  

SciTech Connect

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

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

2011-05-15

414

Electron temperature and density fluctuations during improved confinement plasmas  

NASA Astrophysics Data System (ADS)

We plan to present initial results of Thomson scattering measurements of Te and ne fluctuations associated with electrostatic transport during improved confinement plasmas (PPCD). Recent upgrades to the MST Thomson scattering diagnostic have allowed detailed measurements of electron temperature fluctuations in a variety of plasmas. For example, previous studies have mapped temperature fluctuations to magnetic perturbations, observing remnant island structures between sawteeth events in standard plasmas. Electron temperature fluctuations have also been shown to decrease significantly during PPCD plasmas and it is thought that electrostatic fluctuations may dominate transport. Further upgrades to the Thomson diagnostic may enable absolute density measurements, and the planned addition of a fast laser system will improve maximum time resolution from 25 kHz to 250 kHz. These capabilities will allow investigations into correlated Te and ne fluctuations associated with electrostatic transport. This work supported by the USDoE.

Parke, E.; Stephens, H. D.; den Hartog, D. J.; Reusch, J. A.; Yang, Y. M.; Harris, W. S.; Falkowski, A. F.; Kasten, C. P.

2010-11-01

415

Confinement of Nonneutral Plasmas in a Trap Composed of a Cusped Magnetic Field and an Electrostatic Octapole Field  

NASA Astrophysics Data System (ADS)

The field configuration formed by the superposition of a cuspedmagnetic field and an electrostatic octapole field provides a closedsystem of confinement for a charged particle. In a cusped magneticfield, the Störmer region which constrains a charged particle isopen, but it is closed by adding a potential barrier made by theoctapole field. One-component plasmas are thus expected to beconfined in this configuration, preserving superior characteristicsof the cusp field for plasma stability. A preliminary experiment was performed on the confinement of electrons in thisfield configuration. An electron plasma was confinedfor 3 s in a magnetic field as weak as B=50 G at thecircular line cusp. The confinement time was roughly proportionalto B2, suggesting that the confinement would be improved substantially ina higher magnetic field.

Mohri, Akihiro; Yuyama, Tetsumori; Kiwamoto, Yasuhito; Yamazawa, Yohei; Michishita, Toshinori

1998-12-01

416

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

NASA Astrophysics Data System (ADS)

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

Yamada, Shinji

2012-11-01

417

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

418

Thermodynamic properties of bulk and confined water  

SciTech Connect

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

Mallamace, Francesco, E-mail: francesco.mallamace@unime.it [Dipartimento di Fisica e Scienza della Terra Università di Messina and CNISM, I-98168 Messina (Italy); Department of Nuclear Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Center for Polymer Studies and Department of Physics, Boston University, Boston, Massachusetts 02215 (United States); Corsaro, Carmelo [Dipartimento di Fisica e Scienza della Terra Università di Messina and CNISM, I-98168 Messina (Italy); Mallamace, Domenico [Dipartimento di Scienze dell'Ambiente, della Sicurezza, del Territorio, degli Alimenti e della Salute, Università di Messina, I-98166 Messina (Italy); Vasi, Sebastiano; Vasi, Cirino [IPCF-CNR, I-98166 Messina (Italy); Stanley, H. Eugene [Center for Polymer Studies and Department of Physics, Boston University, Boston, Massachusetts 02215 (United States)

2014-11-14

419

Quantum chromodynamics near the confinement limit  

SciTech Connect

These nine lectures deal at an elementary level with the strong interaction between quarks and its implications for the structure of hadrons. Quarkonium systems are studied as a means for measuring the interquark interaction. This is presumably (part of) the answer a solution to QCD must yield, if it is indeed the correct theory of the strong interactions. Some elements of QCD are reviewed, and metaphors for QCD as a confining theory are introduced. The 1/N expansion is summarized as a way of guessing the consequences of QCD for hadron physics. Lattice gauge theory is developed as a means for going beyond perturbation theory in the solution of QCD. The correspondence between statistical mechanics, quantum mechanics, and field theory is made, and simple spin systems are formulated on the lattice. The lattice analog of local gauge invariance is developed, and analytic methods for solving lattice gauge theory are considered. The strong-coupling expansion indicates the existence of a confining phase, and the renormalization group provides a means for recovering the consequences of continuum field theory. Finally, Monte Carlo simulations of lattice theories give evidence for the phase structure of gauge theories, yield an estimate for the string tension characterizing the interquark force, and provide an approximate description of the quarkonium potential in encouraging good agreement with what is known from experiment.

Quigg, C.

1985-09-01

420

Neutron imaging for inertial confinement fusion experiments  

NASA Astrophysics Data System (ADS)

Neutron imaging of Inertial Confinement Fusion (ICF) targets provides a powerful tool for understanding the implosion conditions of deuterium and tritium filled targets at Mega-Joule/Tera-Watt scale laser facilities. The primary purpose of imaging ICF targets at that National Ignition Facility (NIF), sited at Lawrence Livermore National Laboratory, Livermore, California, is to determine the asymmetry of the fuel in an imploded ICF target. The image data are then combined with other nuclear information to gain insight into the laser and radiation conditions used to drive the target. This information is requisite to understanding the physics of Inertial Confinement Fusion targets and provides a failure mode diagnostic used to optimize the conditions of experiments aimed at obtaining ignition. We present an overview of neutron aperture imaging including a discussion of image formation and reconstruction, requirements for the future (NIF) neutron imaging systems, a description of current imaging system capabilities, and ongoing work to affect imaging systems capable of meeting future system requirements.

Grim, G. P.; Day, R. D.; Clark, D. D.; Fatherley, V. E.; Garcia, F. P.; Jaramillo, S. A.; Montoya, A. J.; Morgan, G. L.; Oertel, J. A.; Ortiz, T. A.; Payton, J. R.; Pazuchanics, P. D.; Schmidt, D. W.; Valdez, A. C.; Wilde, C. H.; Wilke, M. D.

2007-09-01

421

Deuterium anions in inertial electrostatic confinement devices  

NASA Astrophysics Data System (ADS)

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

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

2009-09-01

422

Confined superadiabatic premixed flame-flow interaction  

SciTech Connect

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

Najm, H.N.

1995-12-31

423

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

424

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

425

Polymer escape from a confining potential  

E-print Network

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

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

2015-03-26

426

Perspectives on water science: transport and application of confined water  

NASA Astrophysics Data System (ADS)

The confinements of water can be divided into two main categories, namely, the confinements on surface or interface and the confinements in bulk water. By adding ions or applying electric field, the intensity and distribution of the hydrogen bonds can be greatly affected. These are collectively known as confinement on water surface or interface, which has potential applications in life science and industries involving evaporation control. Confined bulk water could be found everywhere in nature, such as in granular and porous materials, macromolecules and gels, etc. The investigation of the physical properties and the transports of the confined bulk water will contribute to understanding certain types of life activities such as the water transport in plant and in new application of extracting the shale oil and water.

Zeng, XiPing; Wu, JinBo; Li, ShunBo; Chau, YeungYeung; He, GuangHong; Wen, WeiJia; Yang, GuoZhen

2014-05-01

427

Helical conformations of semiflexible polymers confined between two concentric cylinders.  

PubMed

An off-lattice Monte Carlo method was used to study the conformational properties of semiflexible chains confined between two concentric cylinders. The conformations of confined semiflexible chains depend on the bending energy as well as the size of confinement, and the semiflexible chains with particular rigidities confined in the appropriate spaces can form helical structures under entropically driven. The inner cylinder plays a key role in the formation of helical conformations, whereas the outer cylinder affects the size of confinement. Furthermore, the helical structures keep fluctuating like a harmonic oscillation, and the clockwise or counterclockwise helical conformations will appear with the same possibility in the processes of relaxation-helix transitions. This study can help us understand the conformational behaviors of biological macromolecules in confined space. PMID:22011331

Zhang, Dong; Yang, Zhiyong; Wen, Xiaohui; Xiang, Zhangheng; He, Linli; Ran, Shiyong; Zhang, Linxi

2011-12-15

428

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

429

Molecular simulation of zinc oxide nanostructures confined in carbon nanotubes  

Microsoft Academic Search

This paper reports on a molecular simulation study of ZnO nanostructures confined within carbon nanotubes. Both the effects of confinement (by varying the pore size) and degree of pore filling (by varying the number of confined ZnO monomers) on the structure of the nanomaterial are addressed. None of the nanostructures exhibits the ideal structure of one of the ZnO bulk

Denis Horlait; Benoit Coasne; Aude Mezy; Didier Ravot; Jean-Claude Tedenac

2010-01-01

430

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

431

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

432

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

433

Structure of charged polymer chains in confined geometry.  

SciTech Connect

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

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

2000-12-15

434

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

435

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

436

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

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

437

Simulation of Spheromak Evolution and Energy Confinement  

NASA Astrophysics Data System (ADS)

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

Cohen, Bruce I.

2004-11-01

438

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 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 wave functions describing the internal structure of hadronic bound states in physical space-time. The pion is massless in the chiral limit 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

2015-02-13

439

Inertial Confinement Fusion Target Component Fabrication and Technology Development Support  

SciTech Connect

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

Steinman, D. (ed.)

1993-03-01

440

On the confinement of a tokamak plasma  

E-print Network

The goal of this paper is to understand from a mathematical viewpoint the magnetic confinement of plasmas for fusion. Following Fr\\'enod and Sonnendr\\"ucker \\cite{FS2}, we first use 2-scale convergence tools to derive a gyrokinetic system for a plasma submitted to a large magnetic field with a slowly spatially varying intensity. We finally investigate the behaviour of the plasma in such a regime and we prove non-linear stability or instability depending on which side of the tokamak we are looking at. In our analysis we will also show that there exists a temperature gradient threshold beyond which one can expect stability, even in the "bad" side : this is the so-called H-mode.

Han-Kwan, Daniel

2009-01-01

441

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

442

Inverted critical adsorption of polyelectrolytes in confinement  

E-print Network

What are the fundamental laws for the adsorption of charged polymers onto oppositely charged surfaces, for convex, planar, and concave geometries? This question is at the heart of surface coating applications, various complex formation phenomena, as well as in the context of cellular and viral biophysics. It has been a long-standing challenge in theoretical polymer physics; for realistic systems the quantitative understanding is however often achievable only by computer simulations. In this study, we present the findings of such extensive Monte-Carlo in silico experiments for polymer-surface adsorption in confined domains. We study the inverted critical adsorption of finite-length polyelectrolytes in three fundamental geometries: planar slit, cylindrical pore, and spherical cavity. The scaling relations extracted from simulations for the critical surface charge density $\\sigma_c$-defining the adsorption-desorption transition-are in excellent agreement with our analytical calculations based on the ground-state...

de Carvalho, Sidney J; Cherstvy, Andrey G

2015-01-01

443

Confinement and elastic modulus in polymer nanofibers  

NASA Astrophysics Data System (ADS)

Size-dependant behavior is considered in electrospun polymer nanofibers. Experimental results unambiguously show that the abrupt increase in the elastic modulus of polymer nanofibers, below a cross-over diameter, relative to the bulk could not be attributed to surface energy effect. Polyamide (Nylon-6.6) nanofibers were tested by using either bending or tensile deformation modes (the surface energy affects the effective modulus only in the case of bending, and has no effect in the case of tensile deformation). It turns out that the obtained experimental data cannot be explained by the influence of surface energy upon the elastic modulus either qualitatively or quantitatively. This fact supports the explanation which is based on the geometrical confinement of the supermolecular structures of nano-objects.

Zussman, Eyal; Burman, Michael; Arinstein, Arkadii

2011-03-01

444

Engineering tube shapes to control confined transport  

NASA Astrophysics Data System (ADS)

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

Reguera, D.; Rubi, J. M.

2014-12-01

445

Relativistic constituent quark model with infrared confinement  

SciTech Connect

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

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

2010-02-01

446

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

447

Echoes and revival echoes in systems of anharmonically confined atoms  

E-print Network

We study echoes and what we call 'revival echoes' for a collection of atoms that are described by a single quantum wavefunction and are confined in a weakly anharmonic trap. The echoes and revival echoes are induced by applying two, successive temporally localized potential perturbations to the confining potential, one at time $t=0$, and a smaller one at time $t=\\tau$. Pulse-like responses in the expectation value of position $$ are predicted at $t \\approx n\\tau$ ($n=2,3,...$) and are particularly evident at $t \\approx 2\\tau$. A novel result of our study is the finding of 'revival echoes'. Revivals (but not echoes) occur even if the second perturbation is absent. In particular, in the absence of the second perturbation, the response to the first perturbation dies away, but then reassembles, producing a response at revival times $mT_x$ ($m=1,2,...$). Including the second perturbation at $t=\\tau$, we find temporally localized responses, revival echoes, both before and after $t\\approx mT_x$, e.g., at $t\\approx m T_x-n \\tau$ (pre-revival echoes) and at $t\\approx mT_x+n\\tau$, (post-revival echoes), where $m$ and $n$ are $1,2,...$ . Depending on the form of the perturbations, the 'principal' revival echoes at $t \\approx T_x \\pm \\tau$ can be much larger than the echo at $t \\approx 2\\tau$. We develop a perturbative model for these phenomena, and compare its predictions to the numerical solutions of the time-dependent Schr\\"odinger Equation. The scaling of the size of the various echoes and revival echoes as a function of the symmetry and size of the perturbations applied at $t=0$ and $t=\\tau$ is investigated. We also study the presence of revivals and revival echoes in higher moments of position, $$, $p>1$, and the effect of atom-atom interactions on these phenomena.

Mark Herrera; Thomas M. Antonsen; Edward Ott; Shmuel Fishman

2012-08-15

448

A Simplified Confinement Method (SCM) for Calculating Absolute Free Energies and Free Energy and Entropy Differences  

PubMed Central

A simple and robust formulation of the path-independent confinement method for the calculation of free energies is presented. The simplified confinement method (SCM) does not require matrix diagonalization or switching off the molecular force field, and has a simple convergence criterion. The method can be readily implemented in molecular dynamics programs with minimal or no code modifications. Because the confinement method is a special case of thermodynamic integration, it is trivially parallel over the integration variable. The accuracy of the method is demonstrated using a model diatomic molecule, for which exact results can be computed analytically. The method is then applied to the alanine dipeptide in vacuum, and to the ?-helix ? ?-sheet transition in a sixteen-residue peptide modeled in implicit solvent. The SCM requires less effort for the calculation of free energy differences than previous formulations because it does not require computing normal modes. The SCM has a diminished advantage for determining absolute free energy values, because it requires decreasing the MD integration step to obtain accurate results. An approximate confinement procedure is introduced, which can be used to estimate directly the configurational entropy difference between two macrostates, without the need for additional computation of the difference in the free energy or enthalpy. The approximation has similar convergence properties as the standard confinement method for the calculation of free energies. The use of the approximation requires about five times less wall-clock simulation time than that needed to compute enthalpy differences to similar precision from an MD trajectory. For the biomolecular systems considered in this study, the errors in the entropy approximation are under 10%. The approximation will therefore be most useful for cases in which the dominant source of error is insufficient sampling in the estimation of enthalpies, as arises in simulations of large biomolecules. Practical applications of the methods to proteins are currently limited to implicit solvent simulations. PMID:23268557

Ovchinnikov, Victor; Cecchini, Marco; Karplus, Martin

2013-01-01

449

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

450

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

451

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

PubMed

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