On time scale invariance of random walks in confined space.
Bearup, Daniel; Petrovskii, Sergei
2015-02-21
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
Modeling the Relaxation Time of DNA Confined in a Nanochannel
NASA Astrophysics Data System (ADS)
Wang, Yanwei; Tree, Douglas R.; Dorfman, Kevin D.
2014-03-01
Using a mapping between a 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 (Tree et al., Biomicrofluidics 2013, 7, 054118). The relaxation time thus obtained agrees quantitatively with experimental data (Reisner et al., PRL 2005, 94, 196101) 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., PRL 2012, 108, 228105), which have been difficult to validate due to the lack of direct experimental data. Furthermore, our calculation shows that as the channel size passes below ~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. This work was supported by the NIH (R01-HG005216 and R01-HG006851) and the NSFC (21204061) and was carried out in part using computing resources at the University of Minnesota Supercomputing Institute.
Simulations of time-dependent fluorescence in nano-confined solvents
Thompson, Ward H.
2004-04-13
The time-dependent fluorescence of a model diatomic molecule with a charge-transfer electronic transition in confined solvents has been simulated. The effect of confining the solvent is examined by comparing results for solutions contained within...
Full-f gyrokinetic simulation over a confinement time
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
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.
Subdiffusion in time-averaged, confined random walks
Thomas Neusius; Igor M. Sokolov; Jeremy C. Smith
2009-01-01
Certain techniques characterizing diffusive processes, such as single-particle tracking or molecular dynamics simulation, provide time averages rather than ensemble averages. Whereas the ensemble-averaged mean-squared displacement (MSD) of an unbounded continuous time random walk (CTRW) with a broad distribution of waiting times exhibits subdiffusion, the time-averaged MSD, delta2¯ , does not. We demonstrate that, in contrast to the unbounded CTRW, in
Lao, L.L.; La Haye, R.J.; Burrell, K.H.; Chan, V.S.; Ferron, J.R.; Rettig, C.L.; Rewoldt, G.; Scoville, J.T.; Staebler, G.M.; Strait, E.J.; Tang, W.M.; Taylor, T.S.; Wroblewski, D. [General Atomics, P.O. Box 85608, San Diego, California92186-5608 (United States)] [General Atomics, P.O. Box 85608, San Diego, California92186-5608 (United States)
1998-04-01
The role of E{times}B flow shear on confinement enhancement in the DIII-D tokamak [{ital Plasma Physics and Controlled Nuclear Fusion Research}, 1986 (International Atomic Energy Agency, Vienna, 1987), Vol. 1, p. 159] high internal inductance discharges with high-confinement edge is investigated experimentally using a nonaxisymmetric poloidal magnetic-field perturbation from an external coil to drag down the plasma toroidal rotation. At similar values of internal inductance, discharges which rotate faster and have a stronger E{times}B flow shear have better confinement. These results indicate that E{times}B flow shear likely plays an important role in the confinement enhancement of these discharges. {copyright} {ital 1998 American Institute of Physics.}
Derivation of energy confinement time and ICRF absorption in LHD by power modulation
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
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
Transit time scattering of energetic electrons due to equatorially confined magnetosonic waves
J. Bortnik; R. M. Thorne
2010-01-01
Recent analysis using quasilinear theory (QLT) has shown that magnetosonic (MS) waves are able to accelerate electrons to relativistic energies on fast time scales (?1 day). However, the large obliquity of the wave and typical equatorial confinement of the MS wave power create conditions that bring into question the fundamental applicability of QLT to this problem. In this paper, a
Can inertial electrostatic confinement work beyond the ion--ion collisional time scale?
Nevins, W.M. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)] [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)
1995-10-01
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}.
Can inertial electrostatic confinement work beyond the ion-ion collisional time scale?
Nevins, W.M.
1995-01-01
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.
Fast gas injection as a diagnostic technique for particle confinement time measurements
Gray, T.; Kaita, R.; Majeski, R.; Spaleta, J.; Timberlake, J. [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States)
2006-10-15
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}*.
Triton confinement and energy-loss studies with a time-resolved neutron detector (abstract)
NASA Astrophysics Data System (ADS)
Newman, D. E.; Fisher, R. K.; Thomas, D. M.
1985-05-01
The expected results are presented for a fast, selective 14-MeV neutron detector which should be capable of separately measuring the confinement and energy loss of fast tritons for the first time. The tritons, from D-D reactions in a deuterium plasma, are observed when they collide with deuterons while slowing down, producing a characteristic 14-MeV neutron. Triton experiments are an excellent test for the confinement of fusion-produced alphas in a self-sustained reactor, which is critically dependent on plasma heating by the alphas. The triton production rate is pulsed by injecting a burst of deuterium using a neutral-beam heating source. The temporal distribution of the 14-MeV neutron flux is determined by the confinement and slowdown rate of the tritons. The expected flux is calculated as a function of time for the predicted triton transport, anomalous particle losses, and anomalous energy-loss rates, thus demonstrating how the various effects can be separately determined.
NASA Astrophysics Data System (ADS)
Peluso, E.; Gelfusa, M.; Murari, A.; Lupelli, I.; Gaudio, P.
The H mode of confinement in Tokamaks is characterized by a thin region of high gradients, located at the edge of the plasma and called the Edge Transport Barrier. Even if various theoretical models have been proposed for the interpretation of the edge physics, the main empirical scaling laws of the plasma confinement time are expressed in terms of global plasma parameters and they do not discriminate between the edge and core regions. Moreover all the scaling laws are assumed to be power law monomials. In the present paper, a new methodology is proposed to investigate the validity of both assumptions. The approach is based on Symbolic Regression via Genetic Programming and allows first the extraction of the most statistically reliable models from the available experimental data in the ITPA database. Non linear fitting is then applied to the mathematical expressions found by Symbolic regression. The obtained scaling laws are compared with the traditional scalings in power law form.
Mean first-passage times in confined media: from Markovian to non-Markovian processes
NASA Astrophysics Data System (ADS)
Bénichou, O.; Guérin, T.; Voituriez, R.
2015-04-01
We review recent theoretical works that enable the accurate evaluation of the mean first passage time (MFPT) of a random walker to a target in confinement for Markovian (memory-less) and non-Markovian walkers. For the Markovian problem, we present a general theory which allows one to accurately evaluate the MFPT and its extensions to related first-passage observables such as splitting probabilities and occupation times. We show that this analytical approach provides a universal scaling dependence of the MFPT on both the volume of the confining domain and the source–target distance in the case of general scale-invariant processes. This analysis is applicable to a broad range of stochastic processes characterized by length scale-invariant properties, and reveals the key role that can be played by the starting position of the random walker. We then present an extension to non-Markovian walks by taking the specific example of a tagged monomer of a polymer chain looking for a target in confinement. We show that the MFPT can be calculated accurately by computing the distribution of the positions of all the monomers in the chain at the instant of reaction. Such a theory can be used to derive asymptotic relations that generalize the scaling dependence with the volume and the initial distance to the target derived for Markovian walks. Finally, we present an application of this theory to the problem of the first contact time between the two ends of a polymer chain, and review the various theoretical approaches of this non- Markovian problem.
NASA Astrophysics Data System (ADS)
Cherstvy, Andrey G.; Metzler, Ralf
2015-05-01
We study generalized anomalous diffusion processes whose diffusion coefficient D(x, t) ? D0|x|?t? depends on both the position x of the test particle and the process time t. This process thus combines the features of scaled Brownian motion and heterogeneous diffusion parent processes. We compute the ensemble and time averaged mean squared displacements of this generalized diffusion process. The scaling exponent of the ensemble averaged mean squared displacement is shown to be the product of the critical exponents of the parent processes, and describes both subdiffusive and superdiffusive systems. We quantify the amplitude fluctuations of the time averaged mean squared displacement as function of the length of the time series and the lag time. In particular, we observe a weak ergodicity breaking of this generalized diffusion process: even in the long time limit the ensemble and time averaged mean squared displacements are strictly disparate. When we start to observe this process some time after its initiation we observe distinct features of ageing. We derive a universal ageing factor for the time averaged mean squared displacement containing all information on the ageing time and the measurement time. External confinement is shown to alter the magnitudes and statistics of the ensemble and time averaged mean squared displacements.
Real-Time Reciprocal Space Mapping of Nano-Islands Induced by Quantum Confinement
NASA Astrophysics Data System (ADS)
Hong, Hawoong; Gray, Aaron; Chiang, T.-C.
2011-01-01
The effects of quantum confinement have been observed pronouncedly in the island morphology of Pb thin films. The evolution of these nano-islands on Si (111)-(7 × 7) and sapphire (001) surfaces has been studied with a new X-ray diffraction method. A charge-coupled device (CCD) camera was used to collect two- and three-dimensional (2-D and 3-D, respectively) maps of the surface X-ray diffraction in real time. Large ranges of the reflectivity curves, with rocking curves at every point on the reflectivity curves, could be measured continuously in a relatively short amount of time. The abundance of information from 2-D k-space maps reveals clear changes in the growth modes of these thin Pb films. With the 3-D extension of this method, it was possible to observe the ordering of the islands. The islands maintain a nearly uniform interisland distance but lack any angular correlation. The interisland ordering is correlated well with the development of "magic" island heights caused by quantum confinement.
Real time reciprocal space mapping of nano-islands induced by quantum confinment.
Hong, H.; Gray, A.; Chiang, T. C. (X-Ray Science Division); ( PSC-USR); (Univ. of Illinois)
2011-01-01
The effects of quantum confinement have been observed pronouncedly in the island morphology of Pb thin films. The evolution of these nano-islands on Si (111)-(7 x 7) and sapphire (001) surfaces has been studied with a new X-ray diffraction method. A charge-coupled device (CCD) camera was used to collect two- and three-dimensional (2-D and 3-D, respectively) maps of the surface X-ray diffraction in real time. Large ranges of the reflectivity curves, with rocking curves at every point on the reflectivity curves, could be measured continuously in a relatively short amount of time. The abundance of information from 2-D k-space maps reveals clear changes in the growth modes of these thin Pb films. With the 3-D extension of this method, it was possible to observe the ordering of the islands. The islands maintain a nearly uniform interisland distance but lack any angular correlation. The interisland ordering is correlated well with the development of 'magic' island heights caused by quantum confinement.
Jeffrey M. Harbold; Hui Du; Todd D. Krauss; Kyung-Sang Cho; Chris B. Murray; Frank W. Wise
2005-01-01
The relaxation of strongly confined electrons and holes from higher excited states to their lowest excited states in colloidal PbSe nanocrystals has been time resolved using femtosecond transient absorption spectroscopy. In contrast to II-VI and III-V semiconductor nanocrystals, both electrons and holes are strongly confined in PbSe nanocrystals. Despite the large electron and hole energy level spacings (at least 12
Ruprecht, Verena; Wieser, Stefan; Marguet, Didier; Schütz, Gerhard J.
2011-01-01
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
NASA Astrophysics Data System (ADS)
Deshmukh, P. C.; Mandal, A.; Saha, S.; Kheifets, A. S.; Dolmatov, V. K.; Manson, S. T.
2014-05-01
The effects of confinement resonances on photoelectron group delay (Wigner time delay) following ionization of an atom encapsulated inside a C60 cage have been studied theoretically using both relativistic and nonrelativistic random phase approximations. The results indicate clearly the resonant character of the confinement oscillations in time delay of the 4d shell of Xe@C60 and present a most direct manifestation of Wigner time delay. These oscillations were missed in a previous theoretical investigation of Ar@C60 [Phys. Rev. Lett. 111, 203003 (2013), 10.1103/PhysRevLett.111.203003].
From the cover: temperature, ordering, and equilibrium with time-dependent confining forces.
Schiffer, J P; Drewsen, M; Hangst, J S; Hornekar, L
2000-09-26
The concepts of temperature and equilibrium are not well defined in systems of particles with time-varying external forces. An example is a radio frequency ion trap, with the ions laser cooled into an ordered solid, characteristic of sub-mK temperatures, whereas the kinetic energies associated with the fast coherent motion in the trap are up to 7 orders of magnitude higher. Simulations with 1,000 ions reach equilibrium between the degrees of freedom when only aperiodic displacements (secular motion) are considered. The coupling of the periodic driven motion associated with the confinement to the nonperiodic random motion of the ions is very small at low temperatures and increases quadratically with temperature. PMID:10995471
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
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.}
Jeffrey M. Harbold; Hui Du; Todd D. Krauss; Kyung-Sang Cho; Chris B. Murray; Frank W. Wise
2005-01-01
The relaxation of strongly-confined electrons and holes between 1P and 1S\\u000alevels in colloidal PbSe nanocrystals has been time-resolved using femtosecond\\u000atransient absorption spectroscopy. In contrast to II-VI and III-V semiconductor\\u000ananocrystals, both electrons and holes are strongly confined in PbSe\\u000ananocrystals. Despite the large electron and hole energy level spacings (at\\u000aleast 12 times the optical phonon energy), we
NASA Astrophysics Data System (ADS)
Jing, Longfei; Jiang, Shaoen; Yang, Dong; Li, Hang; Zhang, Lu; Lin, Zhiwei; Li, Liling; Kuang, Longyu; Huang, Yunbao; Ding, Yongkun
2015-02-01
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.
One-Dimensional, Time-Dependent, Integral Neutron Transport For Inertial Confinement Fusion
NASA Astrophysics Data System (ADS)
Aplin, Carol S.
Neutron transport is of great importance to inertial confinement fusion (ICF) for several reasons. An accurate neutron energy spectrum is necessary for tritium breeding purposes, and the deposition of energy in the ICF target by energetic neutrons born from fusion may have detrimental effects on the fusion burn. The goal of this research was to develop an accurate neutron transport method that can be incorporated into an existing radiation-hydrodynamics code for modeling ICF implosions. A novel time-dependent neutron transport method, based on the integral form of the neutron transport equation, was developed. This method utilizes a dimensionless integration space and the Neumann series method to obtain the integral form of the reduced collisions equations. This neutron transport method was implemented for infinite slab and sphere geometries. Using a pulsed source in space and time, the method was used to reproduce benchmark solutions previously published in the literature, and was found to have excellent agreement with these benchmarks. The method was expanded to incorporate finite slab and sphere geometries. The method was implemented for a finite slab, and benchmarked against PARTISN, a finite difference, discrete-ordinates code. The method was found to agree with PARTISN at intermediate mean free times, while diverging from PARTISN at late mean free times. The method was used to obtain analytic expression for the first two collided fluxes in a finite sphere geometry. A collision study was performed for both geometries to determine how many collisions were necessary to approximate the total flux at early mean free times. This study showed that only a few collisions were necessary to approximate the total flux at times of interest to ICF applications.
Demouchy, Sylvie
Real-Time Observation of a Non-Equilibrium Liquid Condensate Confined at Tensile Crack Tips. Condensate formation and changes in the extent and the shape are demonstrated for a wide range of macroscopic at the crack tip.3 Water is known to be the crucial reactant in this reaction.4,5 More recently, Davis
Axel Arnold; Suckjoon Jun
2007-09-07
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.
J. M. Roper; D. S. Cherry; J. W. Simmers; H. E. Tatem
1996-01-01
This study consisted of a site characterization followed by biomonitoring the zebra mussel, Dreissena polymorpha, at the Times Beach Confined Disposal Facility (CDF), located in Buffalo, New York. Concentrations of selected contaminants, polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and metals —arsenic (As), chromium (Cr), barium (Ba), mercury (Hg), cadmium (Cd), lead (Pb), selenium (Se) and silver (Ag)—were at or
Confined Vortices in Topologically Massive U(1)$\\times$U(1) Theory
Mohamed M. Anber; Yannis Burnier; Eray Sabancilar; Mikhail Shaposhnikov
2015-07-09
We report on a new topological vortex solution in U(1)$\\times$U(1) Maxwell-Chern-Simons theory. The existence of the vortex is envisaged by analytical means, and a numerical solution is obtained by integrating the equations of motion. These vortices have a long-range force because one of the U(1)s remains unbroken in the infrared, which is guarded by the Coleman-Hill theorem. The sum of the winding numbers of an ensemble of vortices has to vanish; otherwise the system would have a logarithmically divergent energy. In turn, these vortices exhibit classical confinement. We investigate the rich parameter space of the solutions, and show that one recovers the Abrikosov-Nielsen-Olesen, U(1) Maxwell-Chern-Simons, U(1) pure Chern-Simons and global vortices as various limiting cases. Unlike these limiting cases, the higher winding solutions of our vortices carry non-integer charges under the broken U(1). This is the first vortex solution exhibiting such behavior.
Euán-Díaz, Edith C; Herrera-Velarde, Salvador; Misko, Vyacheslav R; Peeters, François M; Castañeda-Priego, Ramón
2015-01-14
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
Saving the world from bad beans: deployment-time confinement checking
David Clarke; Michael Richmond; James Noble
2003-01-01
The Enterprise JavaBeans (EJB) framework requires developers to preserve architectural integrity constraints when writing EJB components. Breaking these constraints allows components to violate the transaction protocol, bypass security mechanisms, disable object persistence, and be susceptible to malicious attacks from other EJBs. We present an object confinement discipline that allows static verification of components' integrity as they are deployed into an
NASA Astrophysics Data System (ADS)
Parrish, K. E.; Zhang, J.; Teasdale, E.
2007-12-01
An exact analytical solution to the ordinary one-dimensional partial differential equation is derived for transient groundwater flow in a homogeneous, confined, horizontal aquifer using Laplace transformation. The theoretical analysis is based on the assumption that the aquifer is homogeneous and one-dimensional (horizontal); confined between impermeable formations on top and bottom; and of infinite horizontal extent and constant thickness. It is also assumed that there is only a single pumping well penetrating the entire aquifer; flow is everywhere horizontal within the aquifer to the well; the well is pumping with a constant discharge rate; the well diameter is infinitesimally small; and the hydraulic head is uniform throughout the aquifer before pumping. Similar to the Theis solution, this solution is suited to determine transmissivity and storativity for a two- dimensional, vertically confined aquifer, such as a long vertically fractured zone of high permeability within low permeable rocks or a long, high-permeability trench inside a low-permeability porous media. In addition, it can be used to analyze time-drawdown responses to pumping and injection in similar settings. The solution can also be used to approximate the groundwater flow for unconfined conditions if (1) the variation of transmissivity is negligible (groundwater table variation is small in comparison to the saturated thickness); and (2) the unsaturated flow is negligible. The errors associated with the use of the solution to unconfined conditions depend on the accuracies of the above two assumptions. The solution can also be used to assess the impacts of recharge from a seasonal river or irrigation canal on the groundwater system by assuming uniform, time- constant recharge along the river or canal. This paper presents the details for derivation of the analytical solution. The analytical solution is compared to numerical simulation results with example cases. Its accuracy is also assessed and discussed for confined and unconfined conditions.
Magali Rossi; Olivier Vidal; Bernd Wunder; François Renard
2007-01-01
Theoretical models of compaction processes, such as for example intergranular pressure-solution (IPS), focus on deformation occurring at the contacts between spherical grains that constitute an aggregate. In order to investigate the applicability of such models, and to quantify the deformation of particles within an aggregate, isostatic experiments were performed in cold-sealed vessels on glass sphere aggregates at 200 MPa confining pressure
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
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.
Time-Dependent Nuclear Measurements of Mix in Inertial Confinement Fusion J. R. Rygg, J. A. Frenje (Received 19 January 2007; published 24 May 2007) The first time-dependent nuclear measurements of turbulent reaction to proceed. The time necessary for Rayleigh-Taylor (RT) growth to induce mix delays peak nuclear
Donovan, D C; Boris, D R; Kulcinski, G L; Santarius, J F; Piefer, G R
2013-03-01
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
Extended gyrokinetic field theory for time-dependent magnetic confinement fields
Sugama, H.; Watanabe, T.-H.; Nunami, M. [National Institute for Fusion Science, Toki 509-5292 (Japan)] [National Institute for Fusion Science, Toki 509-5292 (Japan)
2014-01-15
A gyrokinetic system of equations for turbulent toroidal plasmas in time-dependent axisymmetric background magnetic fields is derived from the variational principle. Besides governing equations for gyrocenter distribution functions and turbulent electromagnetic fields, the conditions which self-consistently determine the background magnetic fields varying on a transport time scale are obtained by using the Lagrangian, which includes the constraint on the background fields. Conservation laws for energy and toroidal angular momentum of the whole system in the time-dependent background magnetic fields are naturally derived by applying Noether's theorem. It is shown that the ensemble-averaged transport equations of particles, energy, and toroidal momentum given in the present work agree with the results from the conventional recursive formulation with the WKB representation except that collisional effects are disregarded here.
Real-time approach to quark confined systems at finite temperatures
A. V. Nefediev; J. E. F. T. Ribeiro
2009-08-21
Generalised Nambu-Jona-Lasinio model for QCD is considered at finite temperatures in the framework of a real-time formalism. The proposed approach allows one to study various properties of the model at T>0, such as chiral symmetry breaking and restoration, properties of the bound-state spectrum, and so on.
NASA Astrophysics Data System (ADS)
Ribeiro, M. S.; Nobre, F. D.; Curado, E. M. F.
2012-12-01
By comparing numerical and analytical results, it is shown that a system of interacting particles under overdamped motion is very well described by a nonlinear Fokker-Planck equation, which can be associated with nonextensive statistical mechanics. The particle-particle interactions considered are repulsive, motivated by three different physical situations: (i) modified Bessel function, commonly used in vortex-vortex interactions, relevant for the flux-front penetration in disordered type-II superconductors; (ii) Yukawa-like forces, useful for charged particles in plasma, or colloidal suspensions; (iii) derived from a Gaussian potential, common in complex fluids, like polymer chains dispersed in a solvent. Moreover, the system is subjected to a general confining potential, ?( x) = ( ?| x| z )/ z ( ? > 0 , z > 1), so that a stationary state is reached after a sufficiently long time. Recent numerical and analytical investigations, considering interactions of type (i) and a harmonic confining potential ( z = 2), have shown strong evidence that a q-Gaussian distribution, P( x,t), with q = 0, describes appropriately the particle positions during their time evolution, as well as in their stationary state. Herein we reinforce further the connection with nonextensive statistical mechanics, by presenting numerical evidence showing that: (a) in the case z = 2, different particle-particle interactions only modify the diffusion parameter D of the nonlinear Fokker-Planck equation; (b) for z ? 2, all cases investigated fit well the analytical stationary solution P st( x), given in terms of a q-exponential (with the same index q = 0) of the general external potential ?( x). In this later case, we propose an approximate time-dependent P( x,t) (not known analytically for z ? 2), which is in very good agreement with the simulations for a large range of times, including the approach to the stationary state. The present work suggests that a wide variety of physical phenomena, characterized by repulsive interacting particles under overdamped motion, present a universal behavior, in the sense that all of them are associated with the same entropic form and nonlinear Fokker-Planck equation.
Presto, Jorge Michael M; Prieto, Elizabeth Ann P; Omambac, Karim M; Afalla, Jessica Pauline C; Lumantas, Deborah Anne O; Salvador, Arnel A; Somintac, Armando S; Estacio, Elmer S; Yamamoto, Kohji; Tani, Masahiko
2015-06-01
We present experimental demonstration of photocarrier dynamics in InAs quantum dots (QDs) via terahertz (THz) time-domain spectroscopy (TDS) using two excitation wavelengths and observing the magnetic field polarity characteristics of the THz signal. The InAs QDs was grown using standard Stranski-Krastanow technique on semi-insulating GaAs substrate. Excitation pump at 800 nm- and 910 nm-wavelength were used to distinguish THz emission from the InAs/GaAs matrix and InAs respectively. THz-TDS at 800 nm pump revealed intense THz emission comparable to a bulk p-InAs. For 910 nm pump, the THz emission generally weakened and upon applying external magnetic field of opposite polarities, the THz time-domain plot exhibited anomalous phase-shifting. This was attributed to the possible current-surge associated with the permanent dipole in the QD. PMID:26072813
Felderhof, B U
2012-06-01
Time-dependent Poiseuille flow of a viscous compressible fluid confined between two planar walls is studied for a partial slip boundary condition with frequency-dependent slip length. After an initial uniform impulse parallel to the walls, the flow pattern quickly becomes nearly parabolic. For a narrow gap, a dynamic slip length can lead to damped oscillations of total fluid momentum. PMID:23005201
Early-time dynamics of actomyosin polarization in cells of confined shape in elastic matrices.
Nisenholz, Noam; Botton, Mordechai; Zemel, Assaf
2014-04-14
The cell shape and the rigidity of the extracellular matrix have been shown to play an important role in the regulation of cytoskeleton structure and force generation. Elastic stresses that develop by actomyosin contraction feedback on myosin activity and govern the anisotropic polarization of stress fibers in the cell. We theoretically study the consequences that the cell shape and matrix rigidity may have on the dynamics and steady state polarization of actomyosin forces in the cell. Actomyosin forces are assumed to polarize in accordance with the stresses that develop in the cytoskeleton. The theory examines this self-polarization process as a relaxation response determined by two distinct susceptibility factors and two characteristic times. These reveal two canonical polarization responses to local variations in the elastic stress: an isotropic response, in which actomyosin dipolar stress isotropically changes in magnitude, and an orientational response, in which actomyosin forces orient with no net change in magnitude. Actual polarization may show up as a superimposition of the two mechanisms yielding different phases in the polarization response as observed experimentally. The cell shape and elastic moduli of the surroundings are shown to govern both the dynamics of the process as well as the steady-state. We predict that in the steady-state, beyond a critical matrix rigidity, spherical cells exert maximal force, and below that rigidity, elongated or flattened cells exert more force. Similar behaviors are reflected in the rate of the polarization process. The theory is also applicable to study the elastic response of whole cell aggregates in a gel. PMID:24623163
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
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.
Calderon, Christopher P
2013-07-01
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
NASA Astrophysics Data System (ADS)
Kollasch, Jeffrey; Sovinec, Carl; Santarius, John
2013-10-01
Collisionless electron confinement times in polyhedral magnetic cusp configurations are investigated numerically with a particle-in-cell technique designed for steady-state conditions of the Vlasov-Poisson system. This method is based on iteratively solving particle trajectories in the time-independent electrostatic field produced by trajectories from a previous iteration. A new code based on this technique, SSUBPIC (steady-state unstructured-boundary particle-in-cell), is presented. It is found to converge rapidly for the cases investigated. The implementation is verified on computations of space-charge limited current in 1D and 2D configurations. Here, it is applied to study the effects of an ejecting virtual cathode potential well on a single electron species injected by guns into a Polywell(TM). Adverse effects of non-magnetically shielded structural members on confinement time are also calculated. Collisionless electron confinement times in polyhedral magnetic cusp configurations are investigated numerically with a particle-in-cell technique designed for steady-state conditions of the Vlasov-Poisson system. This method is based on iteratively solving particle trajectories in the time-independent electrostatic field produced by trajectories from a previous iteration. A new code based on this technique, SSUBPIC (steady-state unstructured-boundary particle-in-cell), is presented. It is found to converge rapidly for the cases investigated. The implementation is verified on computations of space-charge limited current in 1D and 2D configurations. Here, it is applied to study the effects of an ejecting virtual cathode potential well on a single electron species injected by guns into a Polywell(TM). Adverse effects of non-magnetically shielded structural members on confinement time are also calculated. Work supported by the Department of Defense (DoD) through the National Defense Science and Engineering Graduate Fellowship (NDSEG) Program.
Roper, J M; Cherry, D S; Simmers, J W; Tatem, H E
1996-01-01
This study consisted of a site characterization followed by biomonitoring the zebra mussel, Dreissena polymorpha, at the Times Beach Confined Disposal Facility (CDF), located in Buffalo, New York. Concentrations of selected contaminants, polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and metals -arsenic (As), chromium (Cr), barium (Ba), mercury (Hg), cadmium (Cd), lead (Pb), selenium (Se) and silver (Ag)-were at or below detection limits in the water column. Sediment contaminant concentrations, recorded as dry weight, were as high as 549 mg/kg for total PAHs, 9 mg/kg for PCB Aroclor 1248 and 54, 99, 6, 355, 637 and 16 mg/kg for the metals As, Ba, Cd, Cr, Pb and Hg, respectively. To predict contaminant bioavailability, elutriate and whole sediment toxicity tests were performed utilizing the cladoceran, Daphnia magna. Whole sediment tests indicated significant impact. Control survival was 84%, while sediment treatment had survival ranging from 1 to 7%. Mean control reproduction was 86.8 neonates, whereas treatment reproduction ranged from 1.4 to 9.0. Zebra mussels placed both in the water column (Upper) and at the sediment level (Lower) survived the 34-day exposure. Contaminants that significantly accumulated in zebra mussel tissue (wet wt mg/kg) were total PAHs (6.58), fluoranthene (1.23), pyrene (1.08), chrysene (0.98), benzo(a)anthracene (0.60), PCB Aroclor 1248 (1.64), As (0.97), Cr (2.87) and Ba (7.00). Accumulation of these contaminants in zebra mussel tissue represent a potentially realistic hazard to organisms (i.e. fish and birds) that feed on them. PMID:15093498
NASA Astrophysics Data System (ADS)
Ottinger, P. F.; Rose, D. V.; Olson, C. L.
1994-05-01
The Laboratory Microfusion Facility (LMF) has been proposed for the study of high-gain, high-yield inertial-confinement-fusion targets. The light-ion LMF approach uses a multimodular system with applied-B extraction diodes as ion sources. A number of ion-beam transport and focusing schemes are being considered to deliver the beams from the diodes to the target. These include ballistic transport with solenoidal lens focusing, z-discharge channel transport, and wire-guided transport. The energy transport efficiency ?t has been defined and calculated as a function of various system parameters so that point designs can be developed for each scheme. The analysis takes into account target requirements and realistic constraints on diode operation, beam transport, and packing. The effect on ?t of voltage ramping for time-of-flight beam bunching during transport is considered here. Although only 5 mrad microdivergence calculations are presented here, results for bunching factors of ?3 show that transport efficiencies of ?50% can be obtained for all three systems within a range of system parameters which seem achievable (i.e., for diode microdivergence within 5-10 mrad, for diode radius within 10-15 cm, and for diode-ion-current density within 2-10 kA/cm2). In particular, the point design for the baseline LMF system using ballistic transport with solenoidal lens focusing and a bunching factor of 2 was calculated to have ?t=84%. Other factors affecting the overall system efficiency, but not included in the analysis, are also identified and estimated.
NASA Astrophysics Data System (ADS)
Wilking, Connie; Weitz, David
2010-03-01
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.
E. Kiritsis; L. Mazzanti; F. Nitti
2014-12-03
We extend the holographic trailing string picture of a heavy quark to the case of a bulk geometry dual to a confining gauge theory. We compute the classical trailing confining string solution for a static as well as a uniformly moving quark. The trailing string is infinitely extended and approaches a confining horizon, situated at a critical value of the radial coordinate, along one of the space-time directions, breaking boundary rotational invariance. We compute the equations for the fluctuations around the classical solutions, which are used to obtain boundary force correlators controlling the Langevin dynamics of the quark. The imaginary part of the correlators has a non-trivial low-frequency limit, which gives rise to a viscous friction coefficient induced by the confining vacuum. The vacuum correlators are used to define finite-temperature dressed Langevin correlators with an appropriate high-frequency behavior.
NASA Astrophysics Data System (ADS)
Estacio, E.; Alonzo, C.; Samson, A.; Garcia, A.; Somintac, A.; Salvador, A.
2004-10-01
This work compares the speed characteristics of a ˜135-?m-diam GaAs /AlGaAs resonant cavity-enhanced (RCE) detector-emitter device with its laterally oxidized ˜80-?m-diam counterpart. The full width at half-maximum of the photocurrent spectrum exhibited no degradation in wavelength selectivity. Moreover, oxide confinement caused no current bottleneck that was inferred to adversely affect the device speed. The measured pulse responses were 65 and 75ps for the unoxidized and oxidized devices, respectively. Oxide-confined RCE photodetectors show relevant application in concentric hybrid RCE vertical cavity laser devices, this work deals with the speed characteristics of laterally oxidized resonant cavity-enhanced devices.
Dirk Rollmann; David E. Miller
2015-05-26
We discuss the forces on the internal constituents of the hadrons based on the bag model. The ground state of the hadrons forms a color singlet so that the effects of the colored internal states are neutralized. From the breaking of the dilatation and conformal symmetries under the strong interactions the corresponding currents are not conserved. These currents give rise to the forces changing the motion of the internal particles which causes confinement.
Thermal noise in confined fluids.
Sanghi, T; Aluru, N R
2014-11-01
In this work, we discuss a combined memory function equation (MFE) and generalized Langevin equation (GLE) approach (referred to as MFE/GLE formulation) to characterize thermal noise in confined fluids. Our study reveals that for fluids confined inside nanoscale geometries, the correlation time and the time decay of the autocorrelation function of the thermal noise are not significantly different across the confinement. We show that it is the strong cross-correlation of the mean force with the molecular velocity that gives rise to the spatial anisotropy in the velocity-autocorrelation function of the confined fluids. Further, we use the MFE/GLE formulation to extract the thermal force a fluid molecule experiences in a MD simulation. Noise extraction from MD simulation suggests that the frequency distribution of the thermal force is non-Gaussian. Also, the frequency distribution of the thermal force near the confining surface is found to be different in the direction parallel and perpendicular to the confinement. We also use the formulation to compute the noise correlation time of water confined inside a (6,6) carbon-nanotube (CNT). It is observed that inside the (6,6) CNT, in which water arranges itself in a highly concerted single-file arrangement, the correlation time of thermal noise is about an order of magnitude higher than that of bulk water. PMID:25381537
Thermal noise in confined fluids
NASA Astrophysics Data System (ADS)
Sanghi, T.; Aluru, N. R.
2014-11-01
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.
Quark Confinement and the Renormalization Group
Michael C. Ogilvie
2010-10-10
Recent approaches to quark confinement are reviewed, with an emphasis on their connection to renormalization group methods. Basic concepts related to confinement are introduced: the string tension, Wilson loops and Polyakov lines, string breaking, string tension scaling laws, center symmetry breaking, and the deconfinement transition at non-zero temperature. Current topics discussed include confinement on $R^3\\times S^1$, the real-space renormalization group, the functional renormalization group, and the Schwinger-Dyson equation approach to confinement.
Confined helium on Lagrange meshes
Daniel Baye; Jérémy Dohet-Eraly
2015-06-01
The Lagrange-mesh method has the simplicity of a calculation on a mesh and can have the accuracy of a variational method. It is applied to the study of a confined helium atom. Two types of confinement are considered. Soft confinements by potentials are studied in perimetric coordinates. Hard confinement in impenetrable spherical cavities is studied in a system of rescaled perimetric coordinates varying in [0,1] intervals. Energies and mean values of the distances between electrons and between an electron and the helium nucleus are calculated. A high accuracy of 11 to 15 significant figures is obtained with small computing times. Pressures acting on the confined atom are also computed. For sphere radii smaller than 1, their relative accuracies are better than $10^{-10}$. For larger radii up to 10, they progressively decrease to $10^{-3}$, still improving the best literature results.
Confined helium on Lagrange meshes
Baye, Daniel
2015-01-01
The Lagrange-mesh method has the simplicity of a calculation on a mesh and can have the accuracy of a variational method. It is applied to the study of a confined helium atom. Two types of confinement are considered. Soft confinements by potentials are studied in perimetric coordinates. Hard confinement in impenetrable spherical cavities is studied in a system of rescaled perimetric coordinates varying in [0,1] intervals. Energies and mean values of the distances between electrons and between an electron and the helium nucleus are calculated. A high accuracy of 11 to 15 significant figures is obtained with small computing times. Pressures acting on the confined atom are also computed. For sphere radii smaller than 1, their relative accuracies are better than $10^{-10}$. For larger radii up to 10, they progressively decrease to $10^{-3}$, still improving the best literature results.
NASA Astrophysics Data System (ADS)
Cassibry, J. T.; Cortez, R. J.; Hsu, S. C.; Witherspoon, F. D.
2009-11-01
Plasma liner driven magnetoinertial fusion (PLMIF) is a fusion energy concept that utilizes an imploding plasma liner to shock heat and compress a magnetized target plasma to fusion conditions. The fusion burn fraction is linearly proportional to the confinement (or "dwell") time of the liner-target system at peak compression, and therefore it is important to estimate the dwell time accurately in order to assess the fusion energy yield and gain. In this work, the dwell time has been estimated using the exact solution to a self-similar converging shock model. The dwell time was found to be determined by the sum of the outgoing shock and rarefaction times through the plasma liner at peak compression, and for chosen PLMIF conditions the dwell time was on the order of 1 ?s. In addition, we show that the engineering gain, i.e., the total energy extracted as electricity (from fusion plus expanded liner energy) divided by the electrical energy required to implode the liner, exceeds unity for a wide range of liner thicknesses and specific heat ratios.
Polymers under Cylindrical Confinement
NASA Astrophysics Data System (ADS)
Russell, Thomas
2009-03-01
Anodized alumina oxide (AAO) membranes offer a unique platform to investigate polymers under confinement. AAO membranes have been prepared where the diameters of the nanopores in the membrane have been varied from 8 to 50 nm by varying the anodization conditions. Capillary force is sufficiently large to draw high molecular weight polymers into the membrane, producing either nanotubes or nanorods. Polymer solutions can also be used place a thin film on the walls of the nanopores, forming nanotubes. With pore diameters less than the radius of gyration, a quantitative understanding of perturbations to chain dynamics due to geometric constraints was examined. We found a weak molecular weight-dependent mobility of polymers confined within AAO nanopores having diameters smaller than the dimension of the chains in the bulk. The measured mobility of polymers in the confined geometry was much higher than the mobility of the unconfined chain. Rayleigh instabilities in thin polymer films confined within nanoporous alumina membranes were also found where periodic undulations on the film surface were found to increase with time, eventually bridging across the cylindrical nanopore, resulting in the formation of polymer nanorods with a periodic array of encapsulated holes. With microphase separated block copolymers, where the characteristic period of the BCP morphology is comparable to the pore diameter, significant deviations from the bulk morphology as revealed by electron tomography. Small angle neutron scattering was also used to investigate the influence of cylindrical confinement on the order-to-disordered transition. This work was done in collaboration with T. J. McCarthy (UMass), K. Shin (Seoul National University), H. Jinnai (Kyoto University), D. Chen, J. Chen, H. Xiang, T. Kim, and P. Dobriyal, and was supported by the DOE, NSF MRSEC, NSF CHM.
NASA Astrophysics Data System (ADS)
Sampath, Ramgopal; Chakravarthy, S. R.
2014-09-01
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.
Diffusion in confined geometries.
Burada, P Sekhar; Hänggi, Peter; Marchesoni, Fabio; Schmid, Gerhard; Talkner, Peter
2009-01-12
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
NASA Astrophysics Data System (ADS)
Bhargava, Rameshwar
2001-03-01
When the size of Tb3+ doped Y2O3 nanoparticles is decreased from about 10 nm to 3 nm, the luminescent efficiency of Tb3+ green-emission (f-f transition) is increased by an order of magnitude1. This enhancement of oscillator strength is interpreted due to modulation of excited-states of the Tb3+ ion, brought about by the confinement-boundary of the Y2O3 nanocrystal2. This high efficiency of 'caged' single Tb3+ or Eu3+ ion in Y2O3 has led to the first observation of an atomic blinking3. The Quantum Confined Atoms (QCA) provide a novel way to modulate the luminescent properties of a single activator atom via quantum confinement of higher excited states. This QCA-effect occurs when the size of the host is about 5 to 10 times the size of the radius of the excited-state atom. This discovery is expected to impact many applications in the area of nanotechnology. 1. R.N Bhargava, V. Chhabra, B. Kulkarni and J.V. Veliadis Phys. stat. sol. (b) 210, 621 (1998) 2. R.N. Bhargava Jour. of Crystal Growth 214, 926 (2000) 3. M. Barnes, A. Mehta, T. Thundant, R.N. Bhargava, V. Chhabra, B .Kulkarni Jour. Chem. Phys. B 104, 6099 (2000)
Waugh, C. (Caleb Joseph)
2014-01-01
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 ...
NASA Astrophysics Data System (ADS)
Donovan, David C.
2011-12-01
The Inertial Electrostatic Confinement (IEC) Fusion Research Group at the University of Wisconsin-Madison utilizes IEC devices as small-scale neutron generators using D-D fusion to create 2.45 MeV neutrons for the purpose of detecting clandestine material. Detection of explosives in particular can be accomplished using thermal neutron capture methods to identify characteristic nitrogen signatures in explosive material. Research has been conducted to increase reliability of detection, decrease interrogation time, and increase the steady-state operational time. Efforts have also been made to increase the neutron production rate of the device. Optimization studies have varied the configuration and design of the electrodes and have resulted in system configurations with up to 50 percent higher neutron production rates than have previously been utilized. A new feedthrough design has been constructed that is intended to increase the maximum operating voltage from 175 kV with the previous feedthrough to 300 kV. Neutron production rates scale almost linearly with both current and voltage, so the IEC device will be capable of operation at higher neutron producing regimes than have ever before been achieved. The optimization efforts involve the use of several new diagnostic tools developed at UW, which are the Fusion Ion Doppler (FIDO) Diagnostic and the Time of Flight (TOF) Diagnostic. FIDO provides the energy spectra of the charged fusion products and reactants created in the IEC device. The FIDO Diagnostic was originally only capable of studying D-D fusion, but with recent advancements is now able to study both D-D and D-3He fusion. The TOF Diagnostic provides spatial information along with the energy resolution of where the fusion reactions are occurring in the IEC device. Development of the diagnostics has involved the implementation of timing electronics, alignment systems, data acquisition software, computational post-processing, and upgrades to the experimental facility. A significant rise in the concentration of fusion events was found outside of the anode, believed to be due in part from negative ions. The FIDO and TOF Diagnostics have proven to be valuable additions to the study of IEC devices and have greatly advanced IEC operation and theory.
Murakami, M.; Arunasalam, V.; Bell, J.D.; Bell, M.G.; Bitter, M.; Blanchard, W.R.; Boody, F.; Boyd, D.; Bretz, N.; Bush, C.E.
1985-06-01
The paper describes the present (end of February 1985) status of the plasma confinement studies in the TFTR tokamak with emphasis on those with neutral beam injection (NBI). Recent improvements in the device capabilities have substantially extended operating parameters: B/sub T/ increased to 4.0 T, I/sub p/ to 2.0 MA, injection power (P/sub b/) to 5 MW with H/sup 0/ or D/sup 0/ beams anti n/sub e/ to 5 x 10/sup 19/ m/sup -3/, and Z/sub eff/ reduced to 1.4. With ohmic heating (OH) alone, the previously established scaling for gross energy confinement time (tau/sub E/ = anti n/sub e/q) has been confirmed at higher I/sub p/ and B/sub T/, and the maximum tau/sub E/ of 0.4 sec has been achieved. With NBI at P/sub b/ substantially (by factor >2) higher than P/sub OH/, excellent power and particle accountability have been established. This suggests that the less-than-expected increase in stored energy with NBI is not due to problems of power delivery, but due to problems of confinement deterioration. tau/sub E/ is observed to scale approximately as I/sub p/ P/sub b//sup -0.5/ (independent of anti n/sub e/), consistent with previous L-mode scalings. With NBI we have achieved the maximum tau/sub E/ of 0.2 sec and the maximum T/sub i/(o) of 4.4 keV in the normal operating regime, and even higher T/sub i/(o) in the energetic-ion regime with low-n/sub e/ and low-I/sub p/ operation.
Uckan, N.A.; Hogan, J.T.
1990-01-01
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.
Momentum Confinement at Low Torque
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
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.
J. Kipritidis; K. Masuda; T. Kajiwara; Y. Yamagaki; K. Nagasaki
2011-01-01
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
Confinement and the safety factor profile
Batha, S.H.; Levinton, F.M. [Fusion Physics and Technology, Torrance, CA (United States); Scott, S.D. [Princeton Univ., NJ (United States). Plasma Physics Lab.] [and others
1995-12-01
The conjecture that the safety factor profile, q(r), controls the improvement in tokamak plasmas from poor confinement in the Low (L-) mode regime to improved confinement in the supershot regime has been tested in two experiments on the Tokamak Fusion Test Reactor (TFTR). First, helium was puffed into the beam-heated phase of a supershot discharge which induced a degradation from supershot to L-mode confinement in about 100 msec, far less than the current relaxation time. The q and shear profiles measured by a motional Stark effect polarimeter showed little change during the confinement degradation. Second, rapid current ramps in supershot plasmas altered the q profile, but were observed not to change significantly the energy confinement. Thus, enhanced confinement in supershot plasmas is not due to a particular q profile which has enhanced stability or transport properties. The discharges making a continuous transition between supershot and L-mode confinement were also used to test the critical-electron-temperature-gradient transport model. It was found that this model could not reproduce the large changes in electron and ion temperature caused by the change in confinement.
Confinement Aquaculture. Final Report.
ERIC Educational Resources Information Center
Delaplaine School District, AR.
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…
Dynamics of confined water molecules
Gilijamse, J. J.; Lock, A. J.; Bakker, H. J.
2005-01-01
We present femtosecond midinfrared pump–probe measurements of the molecular motion and energy-transfer dynamics of a water molecule that is enclosed by acetone molecules. These confined water molecules show hydrogen-bond and orientational dynamics that are much slower than in bulk liquid water. This behavior is surprising because the hydrogen bonds to the C=O groups of the acetone molecules are weaker than the hydrogen bonds in bulk water. The energy transfer between the O—H groups of the confined water molecules has a time constant of 1.3 ± 0.2 ps, which is >20 times slower than in bulk water. We find that this energy transfer is governed completely by the rate at which hydrogen bonds are broken and reformed, and we identify the short-lived molecular complex that forms the transition state of this process. PMID:15722413
Kenichi Konishi; Yutaka Ookouchi
2009-09-21
The smallest integer t for which the Wilson loop W^{t} fails to exhibit area law is known as the confinement index of a given field theory. The confinement index provides us with subtle information on the vacuum properties of the system. We study the behavior of the Wilson and 't Hooft loops and compute the confinement index in a wide class of N=1 supersymmetric gauge theories. All possible electric and magnetic screenings are taken into account. The results found are consistent with the theta periodicity, and whenever such a check is available, with the factorization property of Seiberg-Witten curves.
Influence of confinement on thermodiffusion
NASA Astrophysics Data System (ADS)
Hannaoui, Rachid; Galliero, Guillaume; Hoang, Hai; Boned, Christian
2013-09-01
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.
F. V. Gubarev
2008-12-24
We critically reconsider our recent observation of confining string shrinkage in pure glue SU(2) lattice gauge theory near the continuum limit. Using the advanced numerical techniques we argue that imperfect overlap with the string ground state and corresponding ambiguities in T->\\infty extrapolation are likely to be the cause of the observed scaling violations. In particular, even in the limit of large Euclidean times the string shrinkage is apparent in torelon correlation function, however, in this case the best relevant overlap we could attain is of order 50%. To the contrary, when the ground state is selected properly the string width scales in physical units being ~0.3 fm for 1 fm long confining string.
Confinement Scaling and Transport Physics in NSTX
NASA Astrophysics Data System (ADS)
Kaye, S.; Bell, R.; Budny, R.; Horton, W.; Levinton, F.; Kim, J.; Menard, J.; Mueller, D.; Leblanc, B.; Mazzucato, E.; Mikkelsen, D.; Park, H.; Rewoldt, G.; Smith, D.; Wang, W.; Yuh, H.
2006-10-01
The confinement time trends in high power NSTX neutral beam heated discharges exhibit significant differences from those at conventional aspect ratio; the scaling with toroidal magnetic field is stronger while that with plasma current is weaker. The improvement of confinement with increasing field is due primarily to a reduction of the electron transport. The electron transport is the dominant anomalous loss mechanism in NSTX, with the ion transport can be close to neoclassical levels. Predictions from linear GS2 gyrokinetic calculations and from analytic theory indicate that ETG modes may play a role at low field. Details of the parametric trends of confinement and transport, along with the relation to changes in the high-k fluctuations and methods for improving the electron confinement, will be discussed.
Velocity alignment leads to high persistence in confined cells
Camley, Brian A
2014-01-01
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 new connection between single- and collective- cell migration: high persistence in confined cells correspo...
Dynamics and energetics of hydrophobically confined water
NASA Astrophysics Data System (ADS)
Bauer, Brad A.; Ou, Shuching; Patel, Sandeep; Siva, Karthik
2012-05-01
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).
Dynamics and energetics of hydrophobically confined water.
Bauer, Brad A; Ou, Shuching; Patel, Sandeep; Siva, Karthik
2012-05-01
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
Asymmetric confinement in a noisy bistable device
NASA Astrophysics Data System (ADS)
Borromeo, M.; Marchesoni, F.
2004-12-01
A Brownian particle hopping in a symmetric double-well potential can be statistically confined to a single well by the simultaneous action of a) two periodic input signals, one tilting the minima, the other one modulating the barrier height; b) an additive and a purely multiplicative random signal, generated by a unique source and thus preserving a certain degree of statistical correlation. In view of technological implementation, such a basic mechanism for asymmetric confinement can be conveniently maximized by tuning the input signal parameters (correlation time, phase/time lag, amplitudes), thus revealing a resonant localization mechanism of wide applicability.
Neutral Beam Heating and Fast Ion Confinement in the RFP
Ben Hudson; Gennady Fiksel; Stewart Prager
2003-01-01
The RFP provides a test-bed to study the confinement of energetic ions in a stochastic magnetic field; the degree of stochasticity can be varied by current profile control. Past work has measured the confinement of energetic ions injected by a low-power (20 KW, 3 ms) neutral beam. In standard plasmas with strong stochasticity, the fast ion (20 KeV) confinement time
Spatial Confinement of Laser Light in Active Random Media
NASA Astrophysics Data System (ADS)
Cao, H.; Xu, J. Y.; Zhang, D. Z.; Chang, S.-H.; Ho, S. T.; Seelig, E. W.; Liu, X.; Chang, R. P. H.
2000-06-01
We have observed spatial confinement of laser light in micrometer-sized random media. The optical confinement is attributed to the disorder-induced scattering and interference. Our experimental data suggest that coherent amplification of the scattered light enhances the interference effect and helps the spatial confinement. Using the finite-difference time-domain method, we simulate lasing with coherent feedback in the active random medium.
Gerard't Hooft
2003-01-01
A general introduction to the topological mechanism responsible for the absolute confinement of quarks inside hadronic bound states is given, including the effects of a finite instanton angle. We then propose a calculational technique for computing these states and their properties, where instead of topology we rely on a perturbative mechanism. It assumes that already before the topological mechanism can
Vortex Ring Dynamics in Radially Confined Domains
NASA Astrophysics Data System (ADS)
Stewart, Kelley; Niebel, Casandra; Jung, Sunghwan; Vlachos, Pavlos
2010-11-01
Vortex ring dynamics have been studied extensively in semi-infinite quiescent volumes. However, very little is known about vortex-ring formation in wall-bounded domains where vortex wall interaction will affect both the vortex ring pinch-off and propagation velocity. This study addresses this limitation and studies vortex formation in radially confined domains to analyze the affect of vortex-ring wall interaction on the formation and propagation of the vortex ring. Vortex rings were produced using a pneumatically driven piston cylinder arrangement and were ejected into a long cylindrical tube which defined the confined downstream domain. A range of confinement domains were studied with varying confinement diameters Velocity field measurements were performed using planar Time Resolved Digital Particle Image Velocimetry (TRDPIV) and were processed using an in-house developed cross-correlation PIV algorithm. The experimental analysis was used to facilitate the development of a theoretical model to predict the variations in vortex ring circulation over time within confined domains.
Properties of radio-frequency heated argon confined uranium plasmas
NASA Technical Reports Server (NTRS)
1976-01-01
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.
Cylindrical confinement of semiflexible polymers
NASA Astrophysics Data System (ADS)
Vázquez-Montejo, Pablo; McDargh, Zachary; Deserno, Markus; Guven, Jemal
2015-06-01
Equilibrium states of a closed semiflexible polymer binding to a cylinder are described. This may be either by confinement or by constriction. Closed completely bound states are labeled by two integers: the number of oscillations, n , and the number of times it winds the cylinder, p , the latter being a topological invariant. We examine the behavior of these states as the length of the loop is increased by evaluating the energy, the conserved axial torque, and the contact force. The ground state for a given p is the state with n =1 ; a short loop with p =1 is an elliptic deformation of a parallel circle; as its length increases it elongates along the cylinder axis with two hairpin ends. Excited states with n ?2 and p =1 possess n -fold axial symmetry. Short (long) loops possess energies ?p E0 (n E0 ), with E0 the energy of a circular loop with same radius as the cylinder; in long loops the axial torque vanishes. Confined bound excited states are initially unstable; however, above a critical length each n -fold state becomes stable: The folded hairpin cannot be unfolded. The ground state for each p is also initially unstable with respect to deformations rotating the loop off the surface into the interior. A closed planar elastic curve aligned along the cylinder axis making contact with the cylinder on its two sides is identified as the ground state of a confined loop. Exterior bound states behave very differently, if free to unbind, as signaled by the reversal in the sign of the contact force. If p =1 , all such states are unstable. If p ?2 , however, a topological obstruction to complete unbinding exists. If the loop is short, the bound state with p =2 and n =1 provides a stable constriction of the cylinder, partially unbinding as the length is increased. This motif could be relevant to an understanding of the process of membrane fission mediated by dynamin rings.
Preface: Special Topic on Interfacial and Confined Water
Molinero, Valeria; Kay, Bruce D.
2014-11-14
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.
Freezing in confined geometries
NASA Technical Reports Server (NTRS)
Sokol, P. E.; Ma, W. J.; Herwig, K. W.; Snow, W. M.; Wang, Y.; Koplik, Joel; Banavar, Jayanth R.
1992-01-01
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.
Topological confinement and superconductivity
Al-hassanieh, Dhaled A [Los Alamos National Laboratory; Batista, Cristian D [Los Alamos National Laboratory
2008-01-01
We derive a Kondo Lattice model with a correlated conduction band from a two-band Hubbard Hamiltonian. This mapping allows us to describe the emergence of a robust pairing mechanism in a model that only contains repulsive interactions. The mechanism is due to topological confinement and results from the interplay between antiferromagnetism and delocalization. By using Density-Matrix-Renormalization-Group (DMRG) we demonstrate that this mechanism leads to dominant superconducting correlations in aID-system.
Energy confinement in tokamaks
Sugihara, M.; Singer, C.
1986-08-01
A straightforward generalization is made of the ohmic heating energy confinement scalings of Pfeiffer and Waltz and Blackwell et. al. The resulting model is systematically calibrated to published data from limiter tokamaks with ohmic, electron cyclotron, and neutral beam heating. With considerably fewer explicitly adjustable free parameters, this model appears to give a better fit to the available data for limiter discharges than the combined ohmic/auxiliary heating model of Goldston.
F. Lenz
2009-09-17
By superposition of regular gauge instantons or merons, ensembles of gauge fields are constructed which describe the confining phase of SU(2) Yang-Mills theory. Various properties of the Wilson loops, the gluon condensate and the topological susceptibility are found to be in qualitative agreement with phenomenology or results of lattice calculations. Limitations in the application to the glueball spectrum and small size Wilson loops are discussed.
NASA Astrophysics Data System (ADS)
Shimaoka, T.; Kaneko, J. H.; Arikawa, Y.; Isobe, M.; Sato, Y.; Tsubota, M.; Nagai, T.; Kojima, S.; Abe, Y.; Sakata, S.; Fujioka, S.; Nakai, M.; Shiraga, H.; Azechi, H.; Chayahara, A.; Umezawa, H.; Shikata, S.
2015-05-01
A neutron bang time and burn history monitor in inertial confinement fusion with fast ignition are necessary for plasma diagnostics. In the FIREX project, however, no detector attained those capabilities because high-intensity X-rays accompanied fast electrons used for plasma heating. To solve this problem, single-crystal CVD diamond was grown and fabricated into a radiation detector. The detector, which had excellent charge transportation property, was tested to obtain a response function for intense X-rays. The applicability for neutron bang time and burn history monitor was verified experimentally. Charge collection efficiency of 99.5% ± 0.8% and 97.1% ± 1.4% for holes and electrons were obtained using 5.486 MeV alpha particles. The drift velocity at electric field which saturates charge collection efficiency was 1.1 ± 0.4 × 107 cm/s and 1.0 ± 0.3 × 107 cm/s for holes and electrons. Fast response of several ns pulse width for intense X-ray was obtained at the GEKKO XII experiment, which is sufficiently fast for ToF measurements to obtain a neutron signal separately from X-rays. Based on these results, we confirmed that the single-crystal CVD diamond detector obtained neutron signal with good S/N under ion temperature 0.5-1 keV and neutron yield of more than 109 neutrons/shot.
Shimaoka, T; Kaneko, J H; Arikawa, Y; Isobe, M; Sato, Y; Tsubota, M; Nagai, T; Kojima, S; Abe, Y; Sakata, S; Fujioka, S; Nakai, M; Shiraga, H; Azechi, H; Chayahara, A; Umezawa, H; Shikata, S
2015-05-01
A neutron bang time and burn history monitor in inertial confinement fusion with fast ignition are necessary for plasma diagnostics. In the FIREX project, however, no detector attained those capabilities because high-intensity X-rays accompanied fast electrons used for plasma heating. To solve this problem, single-crystal CVD diamond was grown and fabricated into a radiation detector. The detector, which had excellent charge transportation property, was tested to obtain a response function for intense X-rays. The applicability for neutron bang time and burn history monitor was verified experimentally. Charge collection efficiency of 99.5% ± 0.8% and 97.1% ± 1.4% for holes and electrons were obtained using 5.486 MeV alpha particles. The drift velocity at electric field which saturates charge collection efficiency was 1.1 ± 0.4 × 10(7) cm/s and 1.0 ± 0.3 × 10(7) cm/s for holes and electrons. Fast response of several ns pulse width for intense X-ray was obtained at the GEKKO XII experiment, which is sufficiently fast for ToF measurements to obtain a neutron signal separately from X-rays. Based on these results, we confirmed that the single-crystal CVD diamond detector obtained neutron signal with good S/N under ion temperature 0.5-1 keV and neutron yield of more than 10(9) neutrons/shot. PMID:26026521
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
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.
Predictions of Confinement from ITER Databases
B. Hu; W. Horton; R. Weigel
2000-01-01
The tokamak confinement times are related to the tokamak parameters via power laws and linear off-set scaling. We sort the tokamaks in the ITER database in a number of different ways. The sortings are performed according to machine size parameters, i.e. I_p, aB_T, Vol, and their performance parameters Lawson product and fusion triple product. Each time we perform a linear
Not Available
1990-07-01
The program objective is to demonstrate efficient removal of fine particulates to sufficiently low levels to meet proposed small scale coal combustor emission standards using a cleanup technology appropriate to small scale coal combustors. This to be accomplished using a novel particulate removal device, the Confined Vortex Scrubber (CVS), which consists of a cylindrical vortex chamber with tangential flue gas inlets. The clean gas exit is via vortex finder outlets, one at either end of the tube. Liquid is introduced into the chamber and is confined within the vortex chamber by the centrifugal force generated by the gas flow itself. This confined liquid forms a layer through which the flue gas is then forced to bubble, producing a strong gas/liquid interaction, high inertial separation forces and efficient particulate cleanup. During this quarter a comprehensive series of cleanup experiments have been made for three CVS configurations. The first CVS configuration tested gave very efficient fine particulate removal at the design air mass flow rate (1 MM BUT/hr combustor exhaust flow), but had over 20{double prime}WC pressure drop. The first CVS configuration was then re-designed to produce the same very efficient particulate collection performance at a lower pressure drop. The current CVS configuration produces 99.4 percent cleanup of ultra-fine fly ash at the design air mass flow at a pressure drop of 12 {double prime}WC with a liquid/air flow ratio of 0.31/m{sup 3}. Unlike venturi scrubbers, the collection performance of the CVS is insensitive to dust loading and to liquid/air flow ratio.
Quantum confined nanocrystalline silicon
NASA Astrophysics Data System (ADS)
Guan, Tianyuan; Kendrick, Chito; Theingi, San; Bagolini, Luigi; Riskey, Kory; Vitti, Lauren; Klafehn, Grant; Taylor, Craig; Lusk, Mark; Gorman, Brain; Collins, Reuben; Fields, Jeremy; Stradins, Pauls
2014-03-01
Quantum confined (QC) semiconductors have drawn much attention in photovoltaics due to their tunable optoelectronic properties and potential for efficiency improvements. Here, we report a study of nanocrystalline silicon (nc-Si:H), consisting of silicon nano-particles (SiNPs) embedded in hydrogenated amorphous silicon (a-Si:H) matrix. Films were grown by depositing the SiNPs and a-Si:H sequentially from separate plasma reactors in a common deposition chamber. Several characterizations were used to ensure the material had low defect density and that the SiNPs were highly crystalline and well within the QC regime. Optical properties of hybrid SiNP/a-Si:H films were explored using visible to near infrared photoluminescence (PL). At low temperature, PL revealed two primary emission features, one from conventional a-Si:H ~ 1.3 eV and a second peak which can be attributed to recombination in SiNPs. The energy of this peak is higher than the bulk c-Si bandgap (~ 1.2 eV), and with decreasing SiNP size, it increases to ~ 1.7 eV. This quantum confinement effect agrees with Density Functional Theory predictions. In addition, we also see that the PL peak for SiNPs surrounded by a-Si:H shifts to lower energy relative to the isolated SiNPs. This shift is also consistent with the modeling results which show that surrounding SiNPs with a-Si:H leads to a softening of the confinement barrier and a redshift in the optical gap.
Confinement Vessel Dynamic Analysis
R. Robert Stevens; Stephen P. Rojas
1999-08-01
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.
Confinement Contains Condensates
Brodsky, Stanley J.; Roberts, Craig D.; Shrock, Robert; Tandy, Peter C.
2012-03-12
Dynamical chiral symmetry breaking and its connection to the generation of hadron masses has historically been viewed as a vacuum phenomenon. We argue that confinement makes such a position untenable. If quark-hadron duality is a reality in QCD, then condensates, those quantities that have commonly been viewed as constant empirical mass-scales that fill all spacetime, are instead wholly contained within hadrons; i.e., they are a property of hadrons themselves and expressed, e.g., in their Bethe-Salpeter or light-front wave functions. We explain that this paradigm is consistent with empirical evidence, and incidentally expose misconceptions in a recent Comment.
Amoeboid motion in confined geometry
Wu, Hao; Hu, Wei-Fan; Farutin, Alexander; Rafaï, Salima; Lai, Ming-Chih; Peyla, Philippe; Misbah, Chaouqi
2015-01-01
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...
Crystallization under nanoscale confinement.
Jiang, Qi; Ward, Michael D
2014-04-01
Classical crystal growth models posit that crystallization outcomes are determined by nuclei that resemble mature crystal phases, but at a critical size where the volume free energy of nuclei begins to offset the unfavorable surface free energy arising from the interface with the growth medium. Crystallization under nanoscale confinement offers an opportunity to examine nucleation and phase transformations at length scales corresponding to the critical size, at which kinetics and thermodynamics of nucleation and growth intersect and dramatic departures in stability compared to bulk crystals can appear. This tutorial review focuses on recent investigations of the crystallization of organic compounds in nanoporous matrices that effectively provide millions of nanoscale reactors in a single sample, ranging from controlled porous glass (CPG) beads to nanoporous block-copolymer monoliths to anodic aluminum oxide (AAO) membranes. Confinement of crystal growth in this manner provides a snapshot of the earliest stages of crystal growth, with insights into nucleation, size-dependent polymorphism, and thermotropic behavior of nanoscale crystals. Moreover, these matrices can be used to screen for crystal polymorphs and assess their stability as nanocrystals. The well-aligned cylindrical nanoscale pores of polymer monoliths or AAO also allow determination of preferred orientation of embedded nanocrystals, affording insight into the competitive nature of nucleation, critical sizes, and phase transition mechanisms. Collectively, these investigations have increased our understanding of crystallization at length scales that are deterministic while suggesting strategies for controlling crystallization outcomes. PMID:24081010
Physisorption in confined geometry
NASA Astrophysics Data System (ADS)
Derycke, I.; Vigneron, J. P.; Lambin, Ph.; Lucas, A. A.; Derouane, E. G.
1991-03-01
The physisorption of molecules in confined geometry, i.e., in pores of atomic size such as found in zeolites, has been investigated using a simple pairwise-additive Lennard-Jones potential and an effective-medium model. In a spherical geometry, it is found that the equilibrium distance D corresponding to the lowest equilibrium energy is reduced to about 90% of the pair equilibrium distance ?e. This originates from the increased dominance of long-range forces in the condensed state. The enhancement of the physisorption energy due to surface curvature and confinement effects reaches its maximum value of 5.05, relative to the flat surface, when D=0.899?e. This value must be compared to the factor of 8 which was derived previously [D. H. Everett and P. C. Powl, J. Chem. Soc. Faraday Trans. 1 72, 619 (1976); E. G. Derouane, J.-M. André, and A. A. Lucas, Chem. Phys. Lett. 137, 336 (1987)] using a simple van der Waals model neglecting repulsion forces. It is also concluded that molecules can be strongly trapped in pores which are substantially narrower than their free (gaseous phase) sizes, the situation of lowest energy corresponding to R=D=0.899?e and the sorption energy remaining negative down to R=D=0.749?e (R denotes the pore radius).
Modeling the Effects of Confinement during Cookoff of Explosives
NASA Astrophysics Data System (ADS)
Hobbs, Michael
2013-06-01
In practical scenarios, cookoff of explosives is a three-dimensional transient phenomenon where the rate limiting reactions may occur either in the condensed or gas phase. The effects of confinement are more dramatic when the rate-limiting reactions occur in the gas phase. Explosives can be self-confined, where the decomposing gases are contained within non-permeable regions of the explosive, or confined by a metal or composite container. Self-confinement is prevalent in plastic bonded explosives at full density. The time-to-ignition can be delayed by orders of magnitude if the reactive gases leave the confining apparatus. Delays in ignition can also occur when the confining apparatus has excess gas volume or ullage. Explosives with low melting points, such as trinitrotoluene (TNT) or cyclotrimethylenetrinitramine (RDX) are complex since melting and flow need to be considered when simulating cookoff. Cookoff of composite explosives such as Comp-B (mixture of TNT and RDX) are even more complex since dissolution of one component increases the reactivity of the other component. Understanding the effects of confinement is required to accurately model cookoff at various scales ranging from small laboratory experiments to large real systems that contain explosives. In practical scenarios, cookoff of explosives is a three-dimensional transient phenomenon where the rate limiting reactions may occur either in the condensed or gas phase. The effects of confinement are more dramatic when the rate-limiting reactions occur in the gas phase. Explosives can be self-confined, where the decomposing gases are contained within non-permeable regions of the explosive, or confined by a metal or composite container. Self-confinement is prevalent in plastic bonded explosives at full density. The time-to-ignition can be delayed by orders of magnitude if the reactive gases leave the confining apparatus. Delays in ignition can also occur when the confining apparatus has excess gas volume or ullage. Explosives with low melting points, such as trinitrotoluene (TNT) or cyclotrimethylenetrinitramine (RDX) are complex since melting and flow need to be considered when simulating cookoff. Cookoff of composite explosives such as Comp-B (mixture of TNT and RDX) are even more complex since dissolution of one component increases the reactivity of the other component. Understanding the effects of confinement is required to accurately model cookoff at various scales ranging from small laboratory experiments to large real systems that contain explosives. Sandia National Laboratories is managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.
Fry, D.J.; Adams, E.
1983-09-01
A submerged, negatively buoyant radial jet, discharging horizontally beneath a free surface into water of initially uniform density, was studied experimentally and theoretically. The situation relates to the operation of an ocean thermal energy conversion plant and is an example of buoyancy and confinement offering opposing influences on jet trajectory. For shallow submergence, the jet is attached to the free surface while for large submergence or greater (negative) buoyancy, the jet is detached. An experimental program yielded data on jet trajectory, temperature, velocity and discharge conditions associated with transition between attached and detached regimes. A hysteresis effect was noted as the conditions for attachment and detachment were different. Dimensional analysis yielded a single parameter of primary importance and two parameters of secondary importance in describing jet behavior. An integral jet analysis based on a spreading assumption was successfully adapted to include induced velocity and pressure effects on jet behavior.
Inertial Electrostatic Confinement (IEC) devices
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
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
Dimensionless scaling of confinement in ATF
Murakami, M.; Bigelow, T.S.; Wilgen, J.B.; Dory, R.A.; Carreras, B.A.; Batchelor, D.B.; Baylor, L.R.; Bell, G.L.; Bell, J.D.; Colchin, R.J.; Crume, E.C.; Dominguez, N.; Dunlap, J.L.; Dyer, G.R.; England, A.C.; Glowienka, J.C.; Goldfinger, R.C.; Goulding, R.H.; Harris, J.H.; Hiroe, S.; Hirshman, S.P.; Howe, H.C.; Hutchinson, D.P.; Isler, R.C.; Jernigan, T.C.; Langley, R.A.; Lee, D.K.; Lyon, J.F.; Ma, C.H.; Menon, M.M.; Rasmusse
1992-01-01
The results of dimensionless-parameter modulation and configuration control experiments in the Advanced Toroidal Facility (ATF) are presented. The global energy confinement time fits gyro-Bohm scaling better than Bohm-like scaling. An additional dependence was detected by modulation of single dimensionless parameters (collisionality [nu]* and beta [beta]), yielding [tau][sub E]/[tau][sub gB][proportional to][nu]* [sup [alpha]v][beta][sup [alpha][beta
Confinement scaling and ignition in tokamaks
Perkins, F.W.; Sun, Y.C.
1985-10-01
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.
NASA Astrophysics Data System (ADS)
Grierson, B. A.; Burrell, K. H.; Nazikian, R. M.; Solomon, W. M.; Garofalo, A. M.; Belli, E. A.; Staebler, G. M.; Fenstermacher, M. E.; McKee, G. R.; Evans, T. E.; Orlov, D. M.; Smith, S. P.; Chrobak, C.; Chrystal, C.
2015-05-01
Impurity transport in the DIII-D tokamak [J. L. Luxon, Nucl. Fusion 42, 614 (2002)] is investigated in stationary high confinement (H-mode) regimes without edge localized modes (ELMs). In plasmas maintained by resonant magnetic perturbation (RMP), ELM-suppression, and QH-mode, the confinement time of fluorine (Z = 9) is equivalent to that in ELMing discharges with 40 Hz ELMs. For selected discharges with impurity injection, the impurity particle confinement time compared to the energy confinement time is in the range of ? p / ? e ? 2 - 3 . In QH-mode operation, the impurity confinement time is shown to be smaller for intense, coherent magnetic, and density fluctuations of the edge harmonic oscillation than weaker fluctuations. Transport coefficients are derived from the time evolution of the impurity density profile and compared to neoclassical and turbulent transport models NEO and TGLF. Neoclassical transport of fluorine is found to be small compared to the experimental values. In the ELMing and RMP ELM-suppressed plasma, the impurity transport is affected by the presence of tearing modes. For radii larger than the mode radius, the TGLF diffusion coefficient is smaller than the experimental value by a factor of 2-3, while the convective velocity is within error estimates. Low levels of diffusion are observed for radii smaller than the tearing mode radius. In the QH-mode plasma investigated, the TGLF diffusion coefficient is higher inside of ? = 0.4 and lower outside of 0.4 than the experiment, and the TGLF convective velocity is more negative by a factor of approximately 1.7.
NASA Astrophysics Data System (ADS)
Powers, L.; Condouris, R.; Kotowski, M.; Murphy, P. W.
This issue of the ICF Quarterly contains seven articles that describe recent progress in Lawrence Livermore National Laboratory's ICF program. The Department of Energy recently initiated an effort to design a 1-2 MJ glass laser, the proposed National Ignition Facility (NIF). These articles span various aspects of a program which is aimed at moving forward toward such a facility by continuing to use the Nova laser to gain understanding of NIF-relevant target physics, by developing concepts for an NIF laser driver and by envisioning a variety of applications for larger ICF facilities. This report discusses research on the following topics: Stimulated Rotational Raman Scattering in Nitrogen; A Maxwell Equation Solver in LASNEX for the Simulation of Moderately Intense Ultrashort Pulse Experiments; Measurements of Radial Heat-Wave Propagation in Laser-Produced Plasmas; Laser-Seeded Modulation Growth on Directly Driven Foils; Stimulated Raman Scattering in Large-Aperture, High-Fluence Frequency-Conversion Crystals; Fission Product Hazard Reduction Using Inertial Fusion Energy; and the Use of Inertial Confinement Fusion for Nuclear Weapons Effects Simulations.
Powers, L.; Condouris, R.; Kotowski, M.; Murphy, P.W. (eds.)
1992-01-01
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.
Enhanced charge collection in confined bulk heterojunction organic solar cells
Jonathan E. Allen; Kevin G. Yager; Htay Hlaing; Chang-Yong Nam; Benjamin M. Ocko; Charles T. Black
2011-01-01
Confining blended poly(3-hexylthiophene) and [6,6]-phenyl-C61-butyric acid methyl ester organic solar cell active layers within nanometer-scale cylindrical pores nearly double the supported short-circuit photocurrent density compared to equivalent unconfined volumes of the same blend and increases the poly(3-hexylthiophene) hole mobility in the blend by nearly 500 times. Grazing incidence x-ray diffraction measurements show that the confinement changes the polymer orientation distribution,
Quantum Confined Semiconductors for High Efficiency Photovoltaics
NASA Astrophysics Data System (ADS)
Beard, Matthew
2014-03-01
Semiconductor nanostructures, where at least one dimension is small enough to produce quantum confinement effects, provide new pathways for controlling energy flow and therefore have the potential to increase the efficiency of the primary photon-to-free energy conversion step. In this discussion, I will present the current status of research efforts towards utilizing the unique properties of colloidal quantum dots (NCs confined in three dimensions) in prototype solar cells and demonstrate that these unique systems have the potential to bypass the Shockley-Queisser single-junction limit for solar photon conversion. The solar cells are constructed using a low temperature solution based deposition of PbS or PbSe QDs as the absorber layer. Different chemical treatments of the QD layer are employed in order to obtain good electrical communication while maintaining the quantum-confined properties of the QDs. We have characterized the transport and carrier dynamics using a transient absorption, time-resolved THz, and temperature-dependent photoluminescence. I will discuss the interplay between carrier generation, recombination, and mobility within the QD layers. A unique aspect of our devices is that the QDs exhibit multiple exciton generation with an efficiency that is ~ 2 to 3 times greater than the parental bulk semiconductor.
Inertial electrostatic confinement (IEC) neutron sources
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
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.
Properties of Confinement in Holography
Giataganas, Dimitrios
2015-01-01
We review certain properties of confinement with added focus on the ones we study with holography. Then we discuss observables whose unique behavior can indicate the presence of confinement. Using mainly the Wilson loop in the gauge/gravity formalism, we study two main features of the QCD string: the string tension dependence on the temperature while in the confining phase, and the logarithmic broadening of the flux tube between the heavy static charges that turns out to be a generic property of all confining theories. Finally, we review the k-string bound state and we show that for a wide class of generic theories the k-string observables can be expressed in terms of the single meson bound state observables.
Response of nonrelativistic confined systems
NASA Astrophysics Data System (ADS)
Gurvitz, S. A.; Rinat, A. S.
1993-06-01
We study the nonrelativistic response of a ``diquark'' bound by confining forces, for which perturbation theory in the interaction fails. As nonperturbative alternatives we consider the Gersch-Rodriguez-Smith (GRS) theory and a summation method. We show that, contrary to the case of singular repulsive forces, the GRS theory can generally be applied to confined systems. When expressed in the GRS-West kinematic variable y, the response has a standard asymptotic limit and calculable dominant corrections of orders 1/q, 1/q2. That theory therefore clearly demonstrates how constituents, confined before and after the absorption of the transferred momentum and energy, behave as asymptotically free particles. We compare the GRS results with those of a summation method for harmonic and square-well confinement and also discuss the convergence of the GRS series for the response in powers of 1/q.
Ionic liquids in confined geometries.
Perkin, Susan
2012-04-21
Over recent years the Surface Force Apparatus (SFA) has been used to carry out model experiments revealing structural and dynamic properties of ionic liquids confined to thin films. Understanding characteristics such as confinement induced ion layering and lubrication is of primary importance to many applications of ionic liquids, from energy devices to nanoparticle dispersion. This Perspective surveys and compares SFA results from several laboratories as well as simulations and other model experiments. A coherent picture is beginning to emerge of ionic liquids as nano-structured in pores and thin films, and possessing complex dynamic properties. The article covers structure, dynamics, and colloidal forces in confined ionic liquids; ionic liquids are revealed as a class of liquids with unique and useful confinement properties and pertinent future directions of research are highlighted. PMID:22301770
Properties of Confinement in Holography
Dimitrios Giataganas
2015-05-26
We review certain properties of confinement with added focus on the ones we study with holography. Then we discuss observables whose unique behavior can indicate the presence of confinement. Using mainly the Wilson loop in the gauge/gravity formalism, we study two main features of the QCD string: the string tension dependence on the temperature while in the confining phase, and the logarithmic broadening of the flux tube between the heavy static charges that turns out to be a generic property of all confining theories. Finally, we review the k-string bound state and we show that for a wide class of generic theories the k-string observables can be expressed in terms of the single meson bound state observables.
Alternative approaches to plasma confinement
NASA Technical Reports Server (NTRS)
Roth, J. R.
1978-01-01
The paper discusses 20 plasma confinement schemes each representing an alternative to the tokamak fusion reactor. Attention is given to: (1) tokamak-like devices (TORMAC, Topolotron, and the Extrap concept), (2) stellarator-like devices (Torsatron and twisted-coil stellarators), (3) mirror machines (Astron and reversed-field devices, the 2XII B experiment, laser-heated solenoids, the LITE experiment, the Kaktus-Surmac concept), (4) bumpy tori (hot electron bumpy torus, toroidal minimum-B configurations), (5) electrostatically assisted confinement (electrostatically stuffed cusps and mirrors, electrostatically assisted toroidal confinement), (6) the Migma concept, and (7) wall-confined plasmas. The plasma parameters of the devices are presented and the advantages and disadvantages of each are listed.
Quark confinement and metric fluctuations
P. R. Silva
2009-08-23
We analyse, by doing very simple calculations, the internal degree of freedom leading to the de Broglie frequency associated to a material particle, as well, the confinement of quarks provided both by the Cornell potential and by the MIT bag model.We propose that the driving forces behind these confining models could be originated in the fluctuations of the metric, namely the particle interacting self-gravitationally, when its mass fluctuates in position throught of a distance equal to the Planck length.
An index for confined monopoles
Robert Wimmer
2012-06-08
We compute the index and associated spectral density for fluctuation operators which are defined via the Lagrangian of N=2 SQCD in the background of non-abelian confined multimonopoles. To this end we generalize the standard index calculations of Callias and Weinberg to the case of asymptotically nontrivial backgrounds. The resulting index is determined by topological charges. We conjecture that this index counts one quarter of the dimension of the moduli space of confined multimonopoles.
Alternative approaches to plasma confinement
NASA Technical Reports Server (NTRS)
Roth, J. R.
1977-01-01
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.
Confined PBX 9501 gap reinitiation studies
Salyer, Terry R [Los Alamos National Laboratory; Hill, Larry G [Los Alamos National Laboratory; Lam, Kin [Los Alamos National Laboratory
2009-01-01
For explosive systems that exhibit gaps or cracks between their internal components (either by design or mechanical failure), measurable time delays exist for detonation waves crossing them. Reinitiation across such gaps is dependent on the type of explosive, gap width, gap morphology, confinement, and temperature effects. To examine this reinitiation effect, a series of tests has been conducted to measure the time delay across a prescribed gap within an 'infinitely' confined PBX 9501 system. Detonation breakout along the explosive surface is measured with a streak camera, and flow features are examined during reinitiation near the gap. Such tests allow for quantitative determination of the time delay corresponding to the time of initiation across a given gap oriented normal to the direction of the detonation wave. Measured time delays can be compared with numerical calculations, making it possible to validate initiation models as well as estimate detonation run-up distances. Understanding this reinitiation behavior is beneficial for the design and evaluation of explosive systems that require precision timing and performance.
Amoeboid motion in confined geometry
Hao Wu; Marine Thiébaut; Wei-Fan Hu; Alexander Farutin; Salima Rafaï; Ming-Chih Lai; Philippe Peyla; Chaouqi Misbah
2015-02-13
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.
DNA Confined in Nanochannels and Nanoslits
NASA Astrophysics Data System (ADS)
Tree, Douglas R.
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.
Velocity alignment leads to high persistence in confined cells
Brian A. Camley; Wouter-Jan Rappel
2014-05-27
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 new connection between single- and collective- cell migration: high persistence in confined cells corresponds with fast alignment of velocity to cell-cell forces.
Viscous fluid injection into a confined channel
NASA Astrophysics Data System (ADS)
Zheng, Zhong; Rongy, Laurence; Stone, Howard A.
2015-06-01
We analyze the injection of a viscous fluid into a two-dimensional horizontal confined channel initially filled with another viscous fluid of different density and viscosity. We study the flow using the lubrication approximation and assume that the mixing between the fluids and their interfacial tension are negligible. When the injection rate is maintained constant, the evolution of the fluid-fluid interface can be described by a nonlinear advection-diffusion equation dependent only on the viscosity ratio between the two fluids. In the early time period, the advection-diffusion equation reduces to a well-known nonlinear diffusion equation, and a self-similar solution is obtained. In the late time period, the advection-diffusion equation is approximated by a nonlinear hyperbolic equation, and a compound wave solution is constructed to describe the time evolution of the fluid-fluid interface. Numerical solutions of the full equation show good agreement with the analytical solutions in both the early and late time periods. Finally, a regime diagram is obtained to summarize the flow behaviours with regard to two dimensionless groups: the viscosity ratio of the two fluids and the dimensionless time; three different dynamical behaviours are identified in the regime diagram: a nonlinear diffusion regime, a hyperbolic regime, and a transition regime. This problem is analogous to the corresponding injection flow problem into a confined porous medium.
Semiflexible chains in confined spaces
NASA Astrophysics Data System (ADS)
Morrison, Greg; Thirumalai, D.
2009-01-01
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.
On the study of quark confinement and the relativistic flux tube model
Y. H. Yuan
2005-09-15
The scalar potential, time component vector potential and flux tube quark confinements are studied in this paper. We find that the predictions of scalar confinement and time component vector confinement are in considerable conflict with measured values while the flux-tube confinement works well to explain the experimental data. We also study the relativistic flux tube model. From the comparison of the exact numerical solution with the analytic approximation solution for heavy-light mesons, we find that the solutions are much more in agreement with each other for higher excited states since the deep radial limit is better satisfied.
Reactive collisions in confined geometries
Zbigniew Idziaszek; Krzysztof Jachymski; Paul S. Julienne
2015-02-06
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.
Dynamics of Confined Water Molecules in Aqueous Salt Hydrates
Werhahn, Jasper C.; Pandelov, S.; Yoo, Soohaeng; Xantheas, Sotiris S.; Iglev, H.
2011-04-01
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.
Confined space manure storage and facilities safety assessment.
Murphy, D J; Manbeck, H B
2014-07-01
A mail survey of 1,200 farms across 16 states was conducted to identify the number, type, and size of manure storages per farm, as well as safety-related behaviors or actions related to entry into confined-space manure storage and handling facilities. Respondents provided data on 297 storage units and facilities, with approximately 75% reporting up to three storages per farm operation. Dimensions were provided for 254 manure pits: nearly 66% were less than or equal to 100 feet long, 75% were less than or equal to 40 feet wide, and 75% were less than or equal to 10 feet deep. Almost 14% of the reported storages were over 300 feet long, seven were wider than 100 feet, and 17 were more than 20 feet deep. Survey results suggest that most farm operations with confined-space manure storages do not follow best safety practices regarding their manure storages, including using gas detection equipment before entering a manure pit, using rescue lines when entering storages, or developing a written confined-space safety policy or plan. Survey results also suggest that few farmers post warning signs around their storages, post recommended ventilation times before entry, or conduct training for workers who enter confined-space manure storages. This article provides a benchmark against which the effectiveness of educational programs and design tools for confined-space manure pit ventilation systems and other confined-space manure pit safety interventions can be measured. PMID:25174151
Confined Cubic Blue Phases under Shear
O. Henrich; K. Stratford; D. Marenduzzo; P. V. Coveney; M. E. Cates
2012-03-14
We study the behaviour of confined cubic blue phases under shear flow via lattice Boltzmann simulations. We focus on the two experimentally observed phases, blue phase I and blue phase II. The disinclination network of blue phase II continuously breaks and reforms under shear, leading to an oscillatory stress response in time. The oscillations are only regular for very thin samples. For thicker samples, the shear leads to a "stick-slip" motion of part of the network along the vorticity direction. Blue phase I responds very differently: its defect network undergoes seemingly chaotic rearrangements under shear, irrespective of system size.
Aerofractures in Confined Granular Media
NASA Astrophysics Data System (ADS)
Eriksen, Fredrik K.; Turkaya, Semih; Toussaint, Renaud; Måløy, Knut J.; Flekkøy, Eirik G.
2015-04-01
We will present the optical analysis of experimental aerofractures in confined granular media. The study of this generic process may have applications in industries involving hydraulic fracturing of tight rocks, safe construction of dams, tunnels and mines, and in earth science where phenomena such as mud volcanoes and sand injectites are results of subsurface sediment displacements driven by fluid overpressure. It is also interesting to increase the understanding the flow instability itself, and how the fluid flow impacts the solid surrounding fractures and in the rest of the sample. Such processes where previously studied numerically [Niebling 2012a, Niebling 2012b] or in circular geometries. We will here explore experimentally linear geometries. We study the fracturing patterns that form when air flows into a dense, non-cohesive porous medium confined in a Hele-Shaw cell - i.e. into a packing of dry 80 micron beads placed between two glass plates separated by ~1mm. The cell is rectangular and fitted with a semi-permeable boundary to the atmosphere - blocking beads but not air - on one short edge, while the other three edges are impermeable. The porous medium is packed inside the cell between the semi-permeable boundary and an empty volume at the sealed side where the air pressure can be set and kept at a constant overpressure (1-2bar). Thus, for the air trapped inside the cell to release the overpressure it has to move through the solid. At high enough overpressures the air flow deforms the solid and increase permeability in some regions along the air-solid interface, which results in unstable flow and aerofracturing. Aerofractures are thought to be an analogue to hydrofractures, and an advantage of performing aerofracturing experiments in a Hele-Shaw cell is that the fracturing process can easily be observed in the lab. Our experiments are recorded with a high speed camera with a framerate of 1000 frames per second. In the analysis, by using various image processing techniques, we segment out and study the aerofractures over time looking at growth dynamics, fractal dimension and characteristics such as average finger thickness as function of depth into the solid. Also, by performing image correlation on two subsequent frames we estimate displacement fields and investigate the surrounding stress and strain fields in the solid around the fractures. Several experiments are performed with various overpressures and packing densities, and we compare the results. In a directly related project, acoustic emissions are recorded on a cell plate during experiments, and one of our goals is to correlate acoustic events and observations. We will also compare the dependence of the patterns on the saturation of the initial deformable porous material, by comparing experiments performed by air injection in air saturated granular media, to some in liquid saturated granular media. References: MJ Niebling, R Toussaint, EG Flekkøy, KJ Måløy, 2012, Dynamic aerofracture of dense granular packings, 2012, Physical Review E 86 (6), 061315 M Niebling, R Toussaint, EG Flekkøy, KJ Måløy, 2012, Numerical studies of aerofractures in porous media, Revista Cubana de Fisica 29 (1E), pp. 1E66-1E70
Scattering for Nonlinear Schrödinger Equation Under Partial Harmonic Confinement
NASA Astrophysics Data System (ADS)
Antonelli, Paolo; Carles, Rémi; Silva, Jorge Drumond
2015-02-01
We consider the nonlinear Schrödinger equation under a partial quadratic confinement. We show that the global dispersion corresponding to the direction(s) with no potential is enough to prove global in time Strichartz estimates, from which we infer the existence of wave operators, thanks to suitable vector-fields. Conversely, given an initial Cauchy datum, the solution is global in time and asymptotically free, provided that confinement affects one spatial direction only. This stems from anisotropic Morawetz estimates, involving a marginal of the position density.
NASA Astrophysics Data System (ADS)
M, Haritha; P, Durganandini
2015-06-01
We study the scattering and confinement of Dirac particles in external electrostatic and Lorentz scalar potentials. We use a numerical finite difference time -domain method to solve the equation and obtain the particle dynamics. We find qualitatively different dynamical behavior for electrostatic and Lorentz scalar potentials. Electrostatic potentials lead to Klein tunneling and do not exhibit confinement, while Lorentz scalar potentials inhibit Klein tunneling and exhibit confinement.
String theory and quark confinement
Alexandre M. Polyakov
1998-01-01
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.
Selenium Confined in Porous Membranes
Steve Ehrlich; David Narehood; Paul Sokol; Thomas Mallouk; Achim Amma
2001-01-01
Selenium posses many interesting and peculiar properties that are not entirely understood and that require further study. The bulk structure of selenium is a hexagonal structure with a small c\\/a ratio; while, under vaporization or high-pressure two monoclinic phases. In the two monoclinic phases (alpha and beta), the selenium forms long chains. No study of the effects of confinement on
Flex Circuitry for Confined Spaces
NASA Technical Reports Server (NTRS)
Fitzpatrick, J. B.; Maier, L. C.
1986-01-01
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.
Toolbox Safety Talk Confined Spaces
Pawlowski, Wojtek
and maintenance. Examples of confined spaces include manholes, storage tanks, boilers, vaults and pipelines material to drown, capture or asphyxiate an entrant. Examples include water, grains and soils. Other/Tag/Verify procedures when required. · Complete and record pre-entry air quality measurements. Continuously monitor
Confinement studies of auxiliary heated NSTX plasmas
NASA Astrophysics Data System (ADS)
LeBlanc, B. P.; Bell, R. E.; Kaye, S. M.; Stutman, D.; Bell, M. G.; Bitter, M. L.; Bourdelle, C.; Gates, D. A.; Maingi, R.; Medley, S. S.; Menard, J. E.; Mueller, D.; Paul, S. F.; Roquemore, A. L.; Rosenberg, A.; Sabbagh, S. A.; Soukhanovskii, V. A.; Synakowski, E. J.; Wilson, J. R.; NSTX Research Team
2004-04-01
The confinement of auxiliary heated national spherical torus experiment discharges is discussed. From a database analysis, it is found that the energy confinement time in NBI heated plasmas with either L- or H-modes edge is up to 2.5 times the values predicted by the ITER97L scaling. A high power NBI heated H-mode discharge is discussed in detail. TRANSP calculations based on the kinetic profile measurements reproduce well the magnetically determined stored energy, but overestimate the measured neutron rate by 30%. Power balance calculations reveal that the ion thermal transport is above or near neoclassical levels, and significantly below the electron thermal transport, which constitutes the main power loss channel. Perturbative impurity injection techniques indicate the particle diffusivity is slightly above the neoclassical level in discharges with L-mode edge. High-harmonic fast-wave (HHFW) bulk electron heating is described and thermal transport is discussed. Thermal ion transport is found to be above the neoclassical level, and thermal electron transport remains the main loss mechanism. Evidence of an electron thermal internal transport barrier obtained with HHFW heating is presented. A description of H-mode discharges obtained during HHFW heating is made.
Particle swarms in confining geometries
NASA Astrophysics Data System (ADS)
Boomsma, Eric Robert
The transport of micro- and nano-particles in subsurface fluid deposits is an area of increasing interest due to the rising use of these particles for consumer and industrial purposes. Subsurface particle transport is complicated by the presence of fractures and fracture networks which govern the paths that particles will be able to take. In this thesis, subsurface particle transport will be investigated using particle swarms; collections of hydro-dynamically interacting particles which exhibit group behavior. The effects of fluid viscosity, particle properties, fracture geometry, and fracture aperture on swarm behavior were experimentally investigated. Swarm parameters were examined in time with an emphasis on geometry (height, width) and speed. Fracture geometry and aperture strongly affected these parameters. As a result, swarms in artificial fluid filled fractures displayed behavior that was not obvious or expected based on current theory. The most significant of these is what we have termed the "Enhanced Transport Regime." In uniform aperture fractures (two finite parallel plates), a range of apertures exists in which swarms travel more quickly than swarms in larger apertures. This behavior was observed in 3 separate experimental sets using different combinations of bulk fluid and particles. In fractures with variable apertures, swarms changed shape and speed in response to fracture features: accelerating/elongating when apertures increased and decelerating/expanding when apertures decreased. Experiments and numerical models were also undertaken to investigate the importance of finite fractures on particle swarms. Closing the open boundaries on the sides and bottom of the uniform aperture fracture had a dramatic effect on the behavior of particle swarms, either eliminating or enhancing the enhanced transport regime. This was investigated with a numerical model which determined that a finite fracture allows fluid to exit the confined space and requires that fluid re-enter at a different location. This creates global scale fluid flow that interacts with particle swarms in ways that are impossible if the fracture has infinite length. The experimental results demonstrate the critical importance of the collective nature of particle swarms. As collections of particles that are free to move relative to each other, swarms are able to respond to fractures in ways that a single spherical object cannot (i.e. expanding, contracting, elongating, etc.). Additionally, the finite sizes of the fractures used in these experiments play a significant role in governing the behavior of particle swarms.
Properties of non-neutral electron plasmas confined with a magnetic mirror field
Higaki, H.; Ito, K.; Saiki, W.; Omori, Y.; Okamoto, H. [Advanced Sciences of Matter, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima, 739-8530 (Japan)
2007-06-15
A low energy non-neutral electron plasma was confined with a magnetic mirror field and an electrostatic potential to investigate the basic confinement properties of a simple magnetic mirror trap. The mirror ratio of the magnetic field was increased up to 5. As expected the confinement time became longer as a function of the mirror ratio. The axially integrated radial density profiles in equilibrium were measured and compared with a theoretical model. The axial electrostatic oscillations of a confined electron plasma were also observed.
Spectra of Confined Atoms and Molecules
D. Bielinska-Waz
2003-01-01
The properties of spectra of atoms and molecules confined by an external potential are analyzed. The effects of spatial confinement are studied using quantum-chemical models. The confinement of the system is described by an external one-particle potential. Two-electron atoms confined in a spherically symmetric harmonic oscillator potential are investigated in detail [1]. In this case the interplay between the effects
Random Matrices in Non-confining Potentials
NASA Astrophysics Data System (ADS)
Allez, Romain; Dumaz, Laure
2015-05-01
We consider invariant matrix processes diffusing in non-confining cubic potentials of the form V_a(x)= x^3/3 - a x, ain {R} . We construct the trajectories of such processes for all time by restarting them whenever an explosion occurs, from a new (well chosen) initial condition, insuring continuity of the eigenvectors and of the non exploding eigenvalues. We characterize the dynamics of the spectrum in the limit of large dimension and analyze the stationary state of this evolution explicitly. We exhibit a sharp phase transition for the limiting spectral density ? _a at a critical value a=a^* . If a? a^* , then the potential V_a presents a well near x=?{a} deep enough to confine all the particles inside, and the spectral density ? _a is supported on a compact interval. If aconfining potentials and we further investigate a family of quartic potentials, which were already studied in (Brezin et al. in Commun Math Phys 59:35-51, 1978) to count planar diagrams.
Lessons Learned in Confined Space Training
Denis E. Zeimet; John Van Ast
1996-01-01
A concern presently exists in industry regarding weak and inconsistent implementation of confined space programs which do not meet Occupational Safety and Health Administration requirements. To assist those personnel who are required to develop, implement, and evaluate a confined space program to achieve compliance with the regulation, an 8-hour Confined Space Program Management training session was held to present the
Drift-diffusion kinetics of a confined colloid Yves Leroyer and Alois Wrger
Paris-Sud XI, Université de
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
Modeling of ESD-induced confined ignition of solid rocket propellants
R. L. Raun
2000-01-01
Solid rocket propellants can be ignited by electrostatic discharge (ESD) events delivering energies orders of magnitude below those typically required to cause ignition. Confinement effects have been proposed as the cause of increased sensitivity to ignition. To better understand the factors influential in ESD ignition, a model for confined ignition of propellants was developed. This model integrates time-dependent, one-dimensional energy
PPPL-3155 -Preprint Date: December 1995, UC-420 Confinement and the Safety Factor Profile
1 PPPL-3155 - Preprint Date: December 1995, UC-420 Confinement and the Safety Factor Profile S. H, Columbia University, New York, New York 10027 (Received The conjecture that the safety factor profile, q temperature, and reactivity triple product neETi (electron density, en- ergy confinement time and ion
A parametric interpolator with confined chord errors, acceleration and deceleration for NC machining
Tsehaw Yong; Ranga Narayanaswami
2003-01-01
Parametric interpolation has many advantages over linear interpolation in machining curves. Real time parametric interpolation research so far has addressed achieving a uniform feed rate, confined chord errors and jerk limited trajectory planning. However, simultaneous consideration of confined chord errors that respect the acceleration and deceleration capabilities of the machine has not been attempted. In this paper, the offline detection
Measured dependence of nuclear burn region size on implosion parameters in inertial confinement-confinement-fusion implosions have been systematically studied for the first time using a proton emission imaging system-shell mix for the more unstable 3.6 atm implosions rather than to increased convergence, because total areal
Viscoelastic transient of confined red blood cells.
Prado, Gaël; Farutin, Alexander; Misbah, Chaouqi; Bureau, Lionel
2015-05-01
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, ?mem(2D) ? 10(-7) N?s?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 ?mem(2D), and reconcile seemingly conflicting conclusions from previous works. PMID:25954871
Viscoelastic transient of confined Red Blood Cells
Gaël Prado; Alexander Farutin; Chaouqi Misbah; Lionel Bureau
2014-09-17
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.
Phase transitions and universal dynamics in confined films
Peter A. Thompson; Gary S. Grest; Mark O. Robbins
1992-01-01
We describe molecular dynamics simulations of fluid films confined between two solid walls. The films consist of spherical molecules, or flexible linear chains with up to twenty monomers. When the wall separation is only a few molecular diameters, crystalline or glassy order is induced across the film. The onset of the glassy phase is characterized by rapidly increasing relaxation times.
SUMMER SCHOOL -KINETIC EQUATIONS LECTURE II: CONFINED CLASSICAL
Ringhofer, Christian
DYNAMICS HARMONIC APPROXIMATION RESULTS OVERVIEW Quantum and classical description of many particle systems;INTRODUCTION CONFINEMENT AND SCALING LARGE TIME DYNAMICS HARMONIC APPROXIMATION RESULTS CLASSICAL TRANSPORT WITH BGK OPERATOR tf + [E, f]c = Q[f] f = f(X, P, t): X: position P: momentum [E, f]c: classical commutator
Chain confinement in electrospun nanofibers of PET with carbon nanotubes
Huipeng Chen; Zhen Liu; Peggy Cebe
2009-01-01
Composite nanofibers of poly(ethylene terephthalate), PET, with multiwalled carbon nanotubes (PET\\/MWCNT) were prepared by the electrospinning method. Confinement, chain conformation, and crystallization of PET electrospun (ES) fibers were analyzed as a function of the weight fraction of MWCNTs. For the first time, we have characterized the rigid amorphous fraction (RAF) in polymer electrospun fibers, with and without MWCNTs. The addition
Preliminary studies of inertial-electrostatic confinement fusion experiments
Yasushi Yamamoto; Masami Ohnishi; Kiyoshi Yoshikawa; Hisayuki Toku; Mitsunori Hasegawa; Takashi Matsuo
1996-01-01
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
Tritium confinement, retention, and releases at the tritium laboratory Karlsruhe
Besserer, U.; Doerr, L.; Glugla, M. [Forschungszentrum Karlsruhe GmbH, Inst. for Technical Physics, Tritium Laboratory Karlsruhe, P.O. Box 3640, D-76021 Karlsruhe (Germany)
2008-07-15
This paper describes the tritium confinement concept and the tritium retention systems at TLK. A description of the AMOR facility for the regeneration of the HTO loaded molecular sieve beds and the operational experience gained from the regeneration of molecular sieve beds (up to 20 times each) is also presented. Finally tritium releases over this period to the environment will also be given. (authors)
Diffusion of single ellipsoids under quasi-2D confinements
Y. Han; A. Alsayed; M. Nobili; A. G. Yodh
2009-03-07
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.
Confinement scaling laws for the conventional reversed-field pinch
Scheffel; Schnack
2000-07-10
A series of high resolution, 3D, resistive MHD numerical simulations of the reversed-field pinch are performed to obtain scaling laws for poloidal beta and energy confinement at Lundquist numbers approaching 10(6). Optimum plasma conditions are attained by taking the transport coefficients to be classical, and ignoring radiation losses and resistive wall effects. We find that poloidal beta scales as beta(straight theta) approximately I-0.40 and that the energy confinement time scales as tau(E) approximately I0.34 for fixed I/N, with aspect ratio R/a = 1.25. PMID:10991273
Entanglement in helium atom confined in an impenetrable cavity
Przemyslaw Koscik; Jayanta K. Saha
2015-05-24
We explore ground-state entanglement properties of helium atom confined at the center of an impenetrable spherical cavity of varying radius by using explicitly correlated Hylleraas-type basis set. Results for the dependencies of the von Neumann and linear entanglement entropic measures on the cavity radius are discussed in details. Some highly accurate numerical results for the von Neumann and linear entropy are reported for the first time. It is found that the transition to the strong confinement regime is manifested by the entropies as an appearance of the inflection points on their variations.
Ion beam inertial confinement target
Bangerter, Roger O. (Danville, CA); Meeker, Donald J. (Livermore, CA)
1985-01-01
A target for implosion by ion beams composed of a spherical shell of frozen DT surrounded by a low-density, low-Z pusher shell seeded with high-Z material, and a high-density tamper shell. The target has various applications in the inertial confinement technology. For certain applications, if desired, a low-density absorber shell may be positioned intermediate the pusher and tamper shells.
High-Energy Electron Confinement in a Magnetic Cusp Configuration
NASA Astrophysics Data System (ADS)
Park, Jaeyoung; Krall, Nicholas A.; Sieck, Paul E.; Offermann, Dustin T.; Skillicorn, Michael; Sanchez, Andrew; Davis, Kevin; Alderson, Eric; Lapenta, Giovanni
2015-04-01
We report experimental results validating the concept that plasma confinement is enhanced in a magnetic cusp configuration when ? (plasma pressure/magnetic field pressure) is of order 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 ? a sharp boundary would form between the plasma and the magnetic field, leading to substantially smaller loss rates. While not able to confirm the details of Grad's work, the current experiment does validate, for the first time, the conjecture that confinement is substantially improved at high ? . This represents critical progress toward an understanding of the plasma dynamics in a high-? cusp system. We hope that these results will stimulate a renewed interest in the cusp configuration as a fusion confinement candidate. In addition, the enhanced high-energy electron confinement resolves a key impediment to progress of the Polywell fusion concept, which combines a high-? cusp configuration with electrostatic fusion for a compact, power-producing nuclear fusion reactor.
Issues in tokamak/stellarator transport and confinement enhancement mechanisms
Perkins, F.W.
1990-08-01
At present, the mechanism for anomalous energy transport in low-{beta} toroidal plasmas -- tokamaks and stellarators -- remains unclear, although transport by turbulent E {times} B velocities associated with nonlinear, fine-scale microinstabilities is a leading candidate. This article discusses basic theoretical concepts of various transport and confinement enhancement mechanisms as well as experimental ramifications which would enable one to distinguish among them and hence identify a dominant transport mechanism. While many of the predictions of fine-scale turbulence are born out by experiment, notable contradictions exist. Projections of ignition margin rest both on the scaling properties of the confinement mechanism and on the criteria for entering enhanced confinement regimes. At present, the greatest uncertainties lie with the basis for scaling confinement enhancement criteria. A series of questions, to be answered by new experimental/theoretical work, is posed to resolve these outstanding contradictions (or refute the fine-scale turbulence model) and to establish confinement enhancement criteria. 73 refs., 4 figs., 5 tabs.
Confinement dynamics in the reversed field pinch
Schoenberg, K.F.
1988-01-01
The study of basic transport and confinement dynamics is central to the development of the reversed field pinch (RFP) as a confinement concept. Thus, the goal of RFP research is to understand the connection between processes that sustain the RFP configuration and related transport/confinement properties. Recently, new insights into confinement have emerged from a detailed investigation of RFP electron and ion physics. These insights derive from the recognition that both magnetohydrodynamic (MHD) and electron kinetic effects play an important and strongly coupled role in RFP sustainment and confinement dynamics. In this paper, we summarize the results of these studies on the ZT-40M experiment. 8 refs.
Hydrodynamic modes in a confined granular fluid
Ricardo Brito; Dino Risso; Rodrigo Soto
2013-02-14
Confined granular fluids, placed in a shallow box that is vibrated vertically, can achieve homogeneous stationary states thanks to energy injection mechanisms that take place throughout the system. These states can be stable even at high densities and inelasticities allowing for a detailed analysis of the hydrodynamic modes that govern the dynamics of granular fluids. Analyzing the decay of the time correlation functions it is shown that there is a crossover between a quasielastic regime in which energy evolves as a slow mode, to a inelastic regime, with energy slaved to the other conserved fields. The two regimes have well differentiated transport properties and, in the inelastic regime, the dynamics can be described by a reduced hydrodynamics with modified longitudinal viscosity and sound speed. The crossover between the two regimes takes place at a wavevector that is proportional to the inelasticity. A two dimensional granular model, with collisions that mimic the energy transfers that take place in a confined system is studied by means of microscopic simulations. The results show excellent agreement with the theoretical framework and allows the validation of hydrodynamic-like models.
Congestion and communication in confined ant traffic
NASA Astrophysics Data System (ADS)
Gravish, Nick; Gold, Gregory; Zangwill, Andrew; Goodisman, Michael A. D.; Goldman, Daniel I.
2014-03-01
Many social animals move and communicate within confined spaces. In subterranean fire ants Solenopsis invicta, mobility within crowded nest tunnels is important for resource and information transport. Within confined tunnels, communication and traffic flow are at odds: trafficking ants communicate through tactile interactions while stopped, yet ants that stop to communicate impose physical obstacles on the traffic. We monitor the bi-directional flow of fire ant workers in laboratory tunnels of varied diameter D. The persistence time of communicating ant aggregations, ?, increases approximately linearly with the number of participating ants, n. The sensitivity of traffic flow increases as D decreases and diverges at a minimum diameter, Dc. A cellular automata model incorporating minimal traffic features--excluded volume and communication duration--reproduces features of the experiment. From the model we identify a competition between information transfer and the need to maintain jam-free traffic flow. We show that by balancing information transfer and traffic flow demands, an optimum group strategy exists which maximizes information throughput. We acknowledge funding from NSF PoLS #0957659 and #PHY-1205878.
Quasielastic neutron scattering study of water confined in carbon nanopores
NASA Astrophysics Data System (ADS)
Chathoth, S. M.; Mamontov, E.; Kolesnikov, A. I.; Gogotsi, Y.; Wesolowski, D. J.
2011-09-01
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, lang?rang, 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, lang?rang 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 Å ordered mesoporous carbon (CMK) and 16 Å double-wall carbon nanotubes. Thus, the dynamical behavior of water remains qualitatively unchanged even in the very small hydrophobic pores.
Quasielastic neutron scattering study of water confined in carbon nanopores
Mavila Chathoth, Suresh [ORNL; Mamontov, Eugene [ORNL; Kolesnikov, Alexander I [ORNL; Gogotsi, Yury G. [Drexel University; Wesolowski, David J [ORNL
2011-01-01
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.
Velocity alignment leads to high persistence in confined cells
Camley, Brian A.; Rappel, Wouter-Jan
2015-01-01
We study a simple model of a crawling cell as an active Brownian particle that aligns its polarity direction to its velocity, a mechanism that has been previously proposed to describe collective cell migration. We show that under quasi-one-dimensional confinement, velocity-aligning cells transition from a random-walk motility to a highly persistent crawling motion. This problem can be mapped to a classical diffusive escape over a barrier and analytically solved to determine the cell’s orientation distribution and repolarization rate. The cell’s repolarization time increases exponentially as the strength of the velocity alignment is increased. We relate this behavior to experiments showing that cells confined in microchannels and on adhesive micropatterns develop strong directional migration, and describe collective motion of quasi-one-dimensionally confined cells. PMID:25019812
Hermitesche Relativitätstheorie, Chromodynamik und Confinement
NASA Astrophysics Data System (ADS)
Treder, H.-J.
Die Ausdehnung der Riemannschen Metrik der Allgemeinen Relativitätstheorie ins Komplexe bedeutet die Ersetzung der Symmetrie-Bedingungenfür den metrischen Tensor, Affinität und Ricci-Tensor durch die Hermiteschen BedingungenMit diesen Bedingungen führt das Einstein-Hilbert-Hamilton-Prinzipzu einer erweiterten Gravitationstheorie (Einstein), die im Sinne der EIH-Approximation neben der Newton-Einsteinschen Gravodynamik, auch die Chromodynamik der Elementarteilchenphysik enthält.Die von den Einstein-Schrödingerschen Feldgleichungen der Hermiteschen Relativitätstheorie implizierte Wechselwirkung zwischen Gravo- und Chromodynamik erzwingt das Confinement. Ohne dieses Confinement würde das Gravitationspotential divergieren, d.h., es könnte keine - nach Maßgabe der Einstein-Schrödingerschen Feldgleichungen - Riemannsche Raum-Zeit-Metrik gik = aik geben.
Thermalization in a Holographic Confining Gauge Theory
Takaaki Ishii; Elias Kiritsis; Christopher Rosen
2015-03-26
Time dependent perturbations of states in a 3+1 dimensional confining gauge theory are considered in the context of holography. The perturbations are induced by varying the gauge theory's coupling to a dimension three scalar operator in time. The dual gravitational theory belongs to a class of Einstein-dilaton theories which exhibit a mass gap at zero temperature and a first order deconfining phase transition at finite temperature. The perturbation is realized in various thermal bulk solutions by specifying time dependent boundary conditions on the scalar, and we solve the fully backreacted Einstein-dilaton equations of motion subject to these boundary conditions. We compute the characteristic time scale of many thermalization processes, noting that in every case we examine, this time scale is determined by the imaginary part of the lowest lying quasi-normal mode of the final state black brane. We quantify the dependence of this final state on parameters of the quench, and construct a dynamical phase diagram. Further support for a universal scaling regime in the abrupt quench limit is provided.
Molecular modeling of confined polymers
NASA Astrophysics Data System (ADS)
Hehmeyer, Owen J.
Molecular Dynamics (MD) simulation, Monte Carlo (MC) simulation, and Mean Field (MF) theory were used to study the structure and thermodynamics of polymers in confined geometries. Molecular simulation is a valuable tool for accessing structural and thermodynamic information in systems where experiments are difficult to perform or where analytical theories are inadequate. End-tethered polyelectrolytes and polymers confined in a slit geometry are two such difficult systems. Analytical theories are limited because of the long-range nature of electrostatic interactions. Physical inaccessibility limits experiments. The effect of confinement on the phase behavior of lattice homopolymers was studied using grand canonical MC simulations in conjunction with multihistogram reweighting. The scaling of critical parameters and chain dimensions with chain length was determined for lattice homopolymers in strictly two dimensional and slab geometries, and compared to the bulk results. The influence of confinement on critical behavior persists even in a thick slab due to the diverging correlation length of density fluctuations. MD simulations were used to examine a model system that approximates a flexible polyelectrolyte, such as sodium polystyrene sulfonate, grafted to two apposing walls. The effect of the polymer grafting density, chain length, and gap width on the structure and pressure was examined. The apposing brushes seek to avoid interpenetration as the gap between the walls narrows. The avoidance of interpenetration may be the origin of lubrication in tethered polyelectrolyte systems. The structure of tethered polyelectrolytes on a single wall was studied using MC and single-chain MF theory. The monomer and counterion density profiles and the brush height were investigated as a function of grafting density, chain length, and charge strength. It was found that MF theory that incorporates counterion condensation agrees well with MC results. Grafting density is found to have only a mild effect on brush height. Grafted polymers carrying a single charge at the free-ends were studied with MC simulation. The brush height was found to change substantially with the surface charge density. The interaction of the same brush with adsorbing protein was examined with MC and MF. It was found that the brush hinders protein adsorption.
Lao, L.L.; Ferron, J.R.; Taylor, T.S.; Chan, V.S.; Osborne, T.H.; Burrell, K.H.; Chu, M.S.; DeBoo, J.C.; Greenfield, C.M.; Groebner, R.J.; Jackson, G.L.; St. John, H.; Strait, E.J.; Thompson, S.J.; Turnbull, A.D. (General Atomics, San Diego, CA (United States)); Doyle, E.J.; Rettig, C. (California Univ., Los Angeles, CA (United States)); James, R.; Wroblewski, D. (Lawrence Livermore National Lab., CA (United Sta
1992-09-01
Several regimes of improved confinement and stability have been obtained in recent experiments in the DIII-D tokamak by dynamically varying the toroidal current density profile to transiently produce a poloidal magnetic field profile with more favorable confinement and stability properties. A very peaked current density profile with high plasma internal inductance, [ell][sub i], is produced either by a rapid change in the plasma poloidal cross section or by a rapid change in the total plasma current. Values of thermal energy confinement times nearly 1.8 times the JET/DIII-D ELM-free H-mode thermal confinement scaling are obtained. The confinement enhancement factor over the ITER89-P L-mode confinement scaling, H, is as high as 3. Normalized toroidal beta, [beta][sub N], greater than 6%-m-T/MA and values of the product [beta][sub N]H greater than 15 have also been obtained. Both the confinement and the maximum achievable [beta] vary with [ell][sub i] and decrease as the current profile relaxes. For strongly shaped H-mode discharges, in addition to the current density profile peakedness, as measured by [ell][sub i] other current profile parameters, such as its distribution near the edge region, may also affect the confinement enhancement.
Lao, L.L.; Ferron, J.R.; Taylor, T.S.; Chan, V.S.; Osborne, T.H.; Burrell, K.H.; Chu, M.S.; DeBoo, J.C.; Greenfield, C.M.; Groebner, R.J.; Jackson, G.L.; St. John, H.; Strait, E.J.; Thompson, S.J.; Turnbull, A.D. [General Atomics, San Diego, CA (United States); Doyle, E.J.; Rettig, C. [California Univ., Los Angeles, CA (United States); James, R.; Wroblewski, D. [Lawrence Livermore National Lab., CA (United States); Lazarus, E.A. [Oak Ridge National Lab., TN (United States); Zohm, H. [Max-Planck-Institut fuer Plasmaphysik, Garching (Germany)
1992-09-01
Several regimes of improved confinement and stability have been obtained in recent experiments in the DIII-D tokamak by dynamically varying the toroidal current density profile to transiently produce a poloidal magnetic field profile with more favorable confinement and stability properties. A very peaked current density profile with high plasma internal inductance, {ell}{sub i}, is produced either by a rapid change in the plasma poloidal cross section or by a rapid change in the total plasma current. Values of thermal energy confinement times nearly 1.8 times the JET/DIII-D ELM-free H-mode thermal confinement scaling are obtained. The confinement enhancement factor over the ITER89-P L-mode confinement scaling, H, is as high as 3. Normalized toroidal beta, {beta}{sub N}, greater than 6%-m-T/MA and values of the product {beta}{sub N}H greater than 15 have also been obtained. Both the confinement and the maximum achievable {beta} vary with {ell}{sub i} and decrease as the current profile relaxes. For strongly shaped H-mode discharges, in addition to the current density profile peakedness, as measured by {ell}{sub i} other current profile parameters, such as its distribution near the edge region, may also affect the confinement enhancement.
Enzymatic reactivity of glucose oxidase confined in nanochannels.
Yu, Jiachao; Zhang, Yuanjian; Liu, Songqin
2014-05-15
The construction of nanodevices coupled with an integrated real-time detection system for evaluation of the function of biomolecules in biological processes, and enzymatic reaction kinetics occurring at the confined space or interface is a significant challenge. In this work, a nanochannel-enzyme system in which the enzymatic reaction could be investigated with an electrochemical method was constructed. The model system was established by covalently linking glucose oxidase (GOD) onto the inner wall of the nanochannels of the porous anodic alumina (PAA) membrane. An Au disc was attached at the end of the nanochannels of the PAA membrane as the working electrode for detection of H2O2 product of enzymatic reaction. The effects of ionic strength, amount of immobilized enzyme and pore diameter of the nanochannels on the enzymatic reaction kinetics were illustrated. The GOD confined in nanochannels showed high stability and reactivity. Upon addition of glucose to the nanochannel-enzyme system, the current response had a calibration range span from 0.005 to 2 mM of glucose concentration. The apparent Michaelis-Menten constant (K(m)(app)) of GOD confined in nanochannel was 0.4 mM. The presented work provided a platform for real-time monitoring of the enzyme reaction kinetics confined in nanospaces. Such a nanochannel-enzyme system could also help design future biosensors and enzyme reactors with high sensitivity and efficiency. PMID:24412427
NSDL National Science Digital Library
In this activity learners explore the connections of digital time displays with numeric and geometric properties. Students look for times that have bilateral or rotational symmetry, or have a certain digital sum, etc. Ideas for implementation, extension and support are included.
Elmo bumpy square plasma confinement device
Owen, L.W.
1985-01-01
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.
Water confinement in three different substances
NASA Astrophysics Data System (ADS)
Mirshamsi, Sahar; Cheng, Hai-Ping
2014-03-01
Confined water in nano-pores of different materials appears in geological, physical, industrial and biological systems. Confined water demonstrates significantly different behavior than bulk water, which has motivated researchers to study the effects of confinement on structural and dynamical properties of water. We study the confinement of water in silica, carbon nanotubes, and gold nano-pores and compare the effect of these different materials on the properties of water. Compared to bulk water viscosity, we find that the viscosity of water increases in silica nano-pores but decreases when confined in carbon nanotubes. Increasing water density inside the silica nano-pores further increases water viscosity. Finally, we discuss how the diffusion coefficient of water and its density profile changes due to confinement. This work is supported by NSF/PHY-1068138.
Confined compression of collagen hydrogels.
Busby, Grahame A; Grant, M Helen; Mackay, Simon P; Riches, Philip E
2013-02-22
Reconstituted collagen hydrogels are often used for in vitro studies of cell-matrix interaction and as scaffolds for tissue engineering. Understanding the mechanical and transport behaviours of collagen hydrogels is therefore extremely important, albeit difficult due to their very high water content (typically >99.5%). In the present study the mechanical behaviour of collagen hydrogels in confined compression was investigated using biphasic theory (J Biomechemical Engineering 102 (1980) 73), to ascertain whether the technique is sufficiently sensitive to determine differences in the characteristics of hydrogels of between 0.2% and 0.4% collagen. Peak stress, equilibrium stress, aggregate modulus and hydraulic permeability of the hydrogels exhibited sensitivity to collagen content, demonstrating that the technique is clearly able to discriminate between hydrogels with small differences in collagen content and may also be sensitive to factors that affect matrix remodelling. The results also offer additional insight into the deformation-dependent permeability of collagen hydrogels. This study suggests that confined compression, together with biphasic theory, is a suitable technique for assessing the mechanical properties of collagen hydrogels. PMID:23267779
Soft confinement for polymer solutions
NASA Astrophysics Data System (ADS)
Oya, Yutaka; Kawakatsu, Toshihiro
2014-07-01
As a model of soft confinement for polymers, we investigated equilibrium shapes of a flexible vesicle that contains a phase-separating polymer solution. To simulate such a system, we combined the phase field theory (PFT) for the vesicle and the self-consistent field theory (SCFT) for the polymer solution. We observed a transition from a symmetric prolate shape of the vesicle to an asymmetric pear shape induced by the domain structure of the enclosed polymer solution. Moreover, when a non-zero spontaneous curvature of the vesicle is introduced, a re-entrant transition between the prolate and the dumbbell shapes of the vesicle is observed. This re-entrant transition is explained by considering the competition between the loss of conformational entropy and that of translational entropy of polymer chains due to the confinement by the deformable vesicle. This finding is in accordance with the recent experimental result reported by Terasawa et al. (Proc. Natl. Acad. Sci. U.S.A., 108 (2011) 5249).
Confinement and Mayer cluster expansions
NASA Astrophysics Data System (ADS)
Bourgine, Jean-Emile
2014-05-01
In this paper, we study a class of grand-canonical partition functions with a kernel depending on a small parameter ?. This class is directly relevant to Nekrasov partition functions of 𝒩 = 2 SUSY gauge theories on the 4d ?-background, for which ? is identified with one of the equivariant deformation parameter. In the Nekrasov-Shatashvili limit ??0, we show that the free energy is given by an on-shell effective action. The equations of motion take the form of a TBA equation. The free energy is identified with the Yang-Yang functional of the corresponding system of Bethe roots. We further study the associated canonical model that takes the form of a generalized matrix model. Confinement of the eigenvalues by the short-range potential is observed. In the limit where this confining potential becomes weak, the collective field theory formulation is recovered. Finally, we discuss the connection with the alternative expression of instanton partition functions as sums over Young tableaux.
Field-induced confined states in graphene
Moriyama, Satoshi, E-mail: MORIYAMA.Satoshi@nims.go.jp [International Center for Materials Nanoarchitectonics (WPI-MANA), National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan); Morita, Yoshifumi [Faculty of Engineering, Gunma University, Kiryu, Gunma 376-8515 (Japan); Watanabe, Eiichiro; Tsuya, Daiju [Nanotechnology Innovation Station, NIMS, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan)
2014-02-03
We report an approach to confine the carriers in single-layer graphene, which leads to quantum devices with field-induced quantum confinement. We demonstrated that the Coulomb-blockade effect evolves under a uniform magnetic field perpendicular to the graphene device. Our experimental results show that field-induced quantum dots are realized in graphene, and a quantum confinement-deconfinement transition is switched by the magnetic field.
NASA Astrophysics Data System (ADS)
Verdoolaege, Geert; Karagounis, Giorgos; Van Oost, Guido
2013-08-01
Pattern recognition is becoming an increasingly important tool for making inferences from the massive amounts of data produced in fusion experiments. The purpose is to contribute to physics studies and plasma control. In this work, we address the visualization of plasma confinement data and their dynamics, the identification of confinement regimes and the establishment of a scaling law for the energy confinement time. We take an intrinsically probabilistic approach, modeling data from the International Global H-mode Confinement Database with Gaussian distributions. We show that pattern recognition operations working in the associated probability space are considerably more powerful than their counterparts in a Euclidean data space. This opens up new possibilities for analyzing confinement data and for fusion data processing in general.
Order in very cold confined plasmas
Schiffer, J.P. [Argonne National Lab., IL (United States)]|[Univ. of Chicago, Chicago, IL (United States)
1995-12-31
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.
Stacking structure of confined 1-butanol in SBA-15 investigated by solid-state NMR spectroscopy.
Lin, Yun-Chih; Chou, Hung-Lung; Sarma, Loka Subramanyam; Hwang, Bing-Joe
2009-10-12
Understanding the complex thermodynamic behavior of confined amphiphilic molecules in biological or mesoporous hosts requires detailed knowledge of the stacking structures. Here, we present detailed solid-state NMR spectroscopic investigations on 1-butanol molecules confined in the hydrophilic mesoporous SBA-15 host. A range of NMR spectroscopic measurements comprising of (1)H spin-lattice (T(1)), spin-spin (T(2)) relaxation, (13)C cross-polarization (CP), and (1)H,(1)H two-dimensional nuclear Overhauser enhancement spectroscopy ((1)H,(1)H 2D NOESY) with the magic angle spinning (MAS) technique as well as static wide-line (2)H NMR spectra have been used to investigate the dynamics and to observe the stacking structure of confined 1-butanol in SBA-15. The results suggest that not only the molecular reorientation but also the exchange motions of confined molecules of 1-butanol are extremely restricted in the confined space of the SBA-15 pores. The dynamics of the confined molecules of 1-butanol imply that the (1)H,(1)H 2D NOESY should be an appropriate technique to observe the stacking structure of confined amphiphilc molecules. This study is the first to observe that a significant part of confined 1-butanol molecules are orientated as tilted bilayered structures on the surface of the host SBA-15 pores in a time-average state by solid-state NMR spectroscopy with the (1)H,(1)H 2D NOESY technique. PMID:19746482
Farmers' exposure to airborne microorganisms in composting swine confinement buildings.
Rautiala, Sirpa; Kangas, Juhani; Louhelainen, Kyösti; Reiman, Marjut
2003-01-01
Farmers' exposure to airborne microorganisms was studied in 12 composting swine confinement buildings and in 7 buildings with traditional slatted-floor pit systems. Airborne cultivable mesophilic, xerophilic, and thermotolerant fungi, mesophilic bacteria, and thermophilic actinobacteria were determined with a six-stage impactor. Furthermore, the total concentrations of microorganisms were determined with filter sampling and direct count using a microscope. In swine confinement buildings where the composting system was functioning properly, the concentrations of microorganisms were 10-1000 times higher than in traditional swine buildings. High concentrations of thermotolerant fungi and thermophilic actinobacteria (up to 10(5) CFU/m(3)), which have been considered to be the main causative agents of farmer's lung, were found in the composting swine confinement buildings that were studied. The conclusion was reached that farmers are exposed to high concentrations of fungal and actinobacterial spores also in swineries, at least in composting confinement buildings. Therefore, personal protection is strongly recommended in composting swineries, especially during the turning of the compost bed. PMID:14521425
A study of an advanced confined linear energy source
NASA Technical Reports Server (NTRS)
Anderson, M. C.; Heidemann, W. B.
1971-01-01
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.
Human enteric viruses in groundwater from a confined bedrock aquifer
Borchardt, M. A.; Bradbury, K.R.; Gotkowitz, M.B.; Cherry, J.A.; Parker, B.L.
2007-01-01
Confined aquifers are overlain by low-permeability aquitards that are commonly assumed to protect underlying aquifers from microbial contaminants. However, empirical data on microbial contamination beneath aquitards is limited. This study determined the occurrence of human pathogenic viruses in well water from a deep sandstone aquifer confined by a regionally extensive shale aquitard. Three public water-supply wells were each sampled 10 times over 15 months. Samples were analyzed by reverse transcription-polymerase chain reaction (RT-PCR) for several virus groups and by cell culture for infectious enteroviruses. Seven of 30 samples were positive by RT-PCR for enteroviruses; one of these was positive for infectious echovirus 18. The virus-positive samples were collected from two wells cased through the aquitard, indicating the viruses were present in the confined aquifer. Samples from the same wells showed atmospheric tritium, indicating water recharged within the past few decades. Hydrogeologic conditions support rapid porous media transport of viruses through the upper sandstone aquifer to the top of the aquitard 61 m below ground surface. Natural fractures in the shale aquitard are one possible virus transport pathway through the aquitard; however, windows, cross-connecting well bores, or imperfect grout seals along well casings also may be involved. Deep confined aquifers can be more vulnerable to contamination by human viruses than commonly believed. ?? 2007 American Chemical Society.
Fingering in Confined Elastic Layers
NASA Astrophysics Data System (ADS)
Biggins, John; Mahadevan, L.; Wei, Z.; Saintyves, Baudouin; Bouchaud, Elizabeth
2015-03-01
Fingering has recently been observed in soft highly elastic layers that are confined between and bonded to two rigid bodies. In one case an injected fluid invades the layer in finger-like protrusions at the layer's perimeter, a solid analogue of Saffman-Taylor viscous fingering. In a second case, separation of the rigid bodies (with maintained adhesion to the layer) leads air to the formation of similar fingers at the layer's perimeter. In both cases the finger formation is reversible: if the fluid is removed or the separation reduced, the fingers vanish. In this talk I will discuss a theoretical model for such elastic fingers that shows that the origin of the fingers is large-strain geometric non-linearity in the elasticity of soft solids. Our simplified elastic model unifies the two types of fingering and accurately estimates the thresholds and wavelengths of the fingers.
Capillary Condensation in Confined Media
Charlaix, Elisabeth
2009-01-01
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 tips) and to their influence on AFM imaging techniques as well as on the static and dynamic friction properties of solids (including granular heaps and sliding nanocontacts). A great attention is spent in investigating the delicate role of the surface roughness and all the difficulties involved in the reduction of the probe size to nanometric dimensions. Another major consequence of capillary condensation in nanosystems is the activation of several chemical and corrosive processes that can significantly alter the surface properties, such as dissolution/redeposition of solid materials and stress-corrosion crack propagati...
Magnetic confinement of cosmic clouds
NASA Technical Reports Server (NTRS)
Azar, Michel; Thompson, W. B.
1988-01-01
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.
Multishell inertial confinement fusion target
Holland, James R. (Butler, PA); Del Vecchio, Robert M. (Vandergrift, PA)
1987-01-01
A method of fabricating multishell fuel targets for inertial confinement fusion usage. Sacrificial hemispherical molds encapsulate a concentric fuel pellet which is positioned by fiber nets stretched tautly across each hemispherical mold section. The fiber ends of the net protrude outwardly beyond the mold surfaces. The joint between the sacrificial hemispheres is smoothed. A ceramic or glass cover is then deposited about the finished mold surfaces to produce an inner spherical surface having continuously smooth surface configuration. The sacrificial mold is removed by gaseous 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.
CONFINED SPACE ENTRY PERMIT University of Maryland
Rubloff, Gary W.
: Ventilation Lockout/Tagout Combustible gas Toxic contaminants Chemical/Biological Noise Other Personal Confined Space." 1. Check the UM Confined Space Inventory at www.des.umd.edu/os/csp to verify that the space that will be entered is listed in the inventory. If it is, use the information found
Weapons Activities/ Inertial Confinement Fusion Ignition
Weapons Activities/ Inertial Confinement Fusion Ignition and High Yield Campaign FY 2012 a safe, secure, and reliable nuclear weapons stockpile without underground testing. Science-based weapons's Budget. Page 105 #12;Weapons Activities/ Inertial Confinement Fusion Ignition and High Yield Campaign FY
Inertial electrostatic confinement (IEC) neutron sources
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
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
Climate conditions in bedded confinement buildings
Technology Transfer Automated Retrieval System (TEKTRAN)
Confinement buildings are utilized for finishing cattle to allow more efficient collection of animal waste and to buffer animals against adverse climatic conditions. Environmental data were obtained from a 29 m wide x 318 m long bedded confinement building with the long axis oriented east to west. T...
Target Finding Mechanism of Microtubules in a Confined Geometry
NASA Astrophysics Data System (ADS)
Shojania Feizabadi, Mitra
2007-03-01
Discovery of a non-equilibrium dynamic of microtubules, called dynamic instability, raised this question: is stochastic polymerization dynamic of microtubules an advantage in the process of finding a chromosome as a target? Previous studies showed that compared to usual reversible polymerization, dynamic instability of microtubules with decreasing length distribution reduced the time required to find a target by several order of magnitude [1]. Dynamic Equations for growing and shrinking microtubules in a confined geometry is theoretically modeled by Govinden and Spillman [2]. This work calculates the target finding time for microtubules with exponentially increasing length distribution in a confined geometry. The efficiency of target finding mechanism based upon different dynamical parameters is discussed. [1] Holy TE, Leibler S. 1994, Proc. Natl. Acad. Sci. USA 91, 5682. [2] Govindan B, Spillman W. 2004, Phys. Rev. E 70, 032901.
Effect of confinement on the mode dynamics of dipole clusters.
Schella, André; Melzer, André; July, Christoph; Bechinger, Clemens
2015-02-14
Dynamical properties of colloidal clusters composed of paramagnetic beads are presented. The clusters were trapped either in a parabolic trough or in a hard-wall confinement. In order to access the dynamics of the ensembles, the instantaneous normal mode (INM) approach is utilized, which uses cluster configurations as an input. The peaks in the mode spectra weaken when the system size is increased and when the coupling strength is lowered. The short-time diffusive properties of the clusters are deduced using the INM technique. It is found that angular diffusion is always larger than radial diffusion regardless of the shape of the external trap. Further, short-time diffusion seems to be almost independent of the coupling strength in the solid regime, but decreases with increasing packing fraction and size of the ensembles. In general, it is found that diffusion is larger for parabolically confined than for hard-wall trapped clusters. PMID:25563898
Confinement and stability of VH-mode discharges in the DIII-D tokamak
Taylor, T.S.; Osborne, T.H.; Burrell, K.H.; Carlstrom, T.N.; Chan, V.S.; Chu, M.S.; DeBoo, J.C.; Doyle, E.J.; Greenfield, C.M.; Groebner, R.J.; Hsieh, C.L.; Jackson, G.L.; James, R.; Lao, L.L.; Lazarus, E.A.; Lippman, S.I.; Petrie, T.W.; Rettig, C.L.; St. John, H.; Schissel, D.P.; Stambaugh, R.D.; Strait, E.J.; Turnbull, A.D.; West, W.P.; Winter, J.; Wroblewski, D.
1992-10-01
A regime of very high confinement (VH-mode) has been observed in neutral beam-heated deuterium discharges in the DIII-D tokamak with thermal energy confinement times up to {approx}3.6 times that predicted by the ITER-89P L-mode scaling and 2 times that predicted by ELM-free H-mode thermal confinement scalings. This high confinement has led to increased plasma performance, n{sub D} (0)T{sub i}(0){tau}{sub E} = 2 {times} 10{sup 20} m{sup {minus}3} keV sec with I{sub p} = 1.6 MA, B{sub T} = 2.1 T, Z{sub eff} {le} 2. Detailed transport analysis shows a correspondence between the large decrease in thermal diffusivity in the region 0.75 {le} {rho} {le} 0.9 and the development of a strong shear in the radial electric field in the same region. This suggests that stabilization of turbulence by sheared E {times} B flow is responsible for the improved confinement in VH-mode. A substantial fraction of the edge plasma entering the second regime of stability may also contribute to the increase in confinement. The duration of the VH-mode phase has been lengthened by feedback controlling the input power to limit plasma beta.
Confinement and stability of VH-mode discharges in the DIII-D tokamak
Taylor, T.S.; Osborne, T.H.; Burrell, K.H.; Carlstrom, T.N.; Chan, V.S.; Chu, M.S.; DeBoo, J.C.; Doyle, E.J.; Greenfield, C.M.; Groebner, R.J.; Hsieh, C.L.; Jackson, G.L.; James, R.; Lao, L.L.; Lazarus, E.A.; Lippman, S.I.; Petrie, T.W.; Rettig, C.L.; St. John, H.; Schissel, D.P.; Stambaugh, R.D.; Strait, E.J.; Turnbull, A.D.; West, W.P.; Winter, J.; Wroblewski, D.
1992-10-01
A regime of very high confinement (VH-mode) has been observed in neutral beam-heated deuterium discharges in the DIII-D tokamak with thermal energy confinement times up to [approx]3.6 times that predicted by the ITER-89P L-mode scaling and 2 times that predicted by ELM-free H-mode thermal confinement scalings. This high confinement has led to increased plasma performance, n[sub D] (0)T[sub i](0)[tau][sub E] = 2 [times] 10[sup 20] m[sup [minus]3] keV sec with I[sub p] = 1.6 MA, B[sub T] = 2.1 T, Z[sub eff] [le] 2. Detailed transport analysis shows a correspondence between the large decrease in thermal diffusivity in the region 0.75 [le] [rho] [le] 0.9 and the development of a strong shear in the radial electric field in the same region. This suggests that stabilization of turbulence by sheared E [times] B flow is responsible for the improved confinement in VH-mode. A substantial fraction of the edge plasma entering the second regime of stability may also contribute to the increase in confinement. The duration of the VH-mode phase has been lengthened by feedback controlling the input power to limit plasma beta.
Confinement-induced resonances in anharmonic waveguides
Peng Shiguo [Department of Physics, Tsinghua University, Beijing 100084 (China); Centre for Atom Optics and Ultrafast Spectroscopy, Swinburne University of Technology, Melbourne 3122 (Australia); Hu Hui; Liu Xiaji; Drummond, Peter D. [Centre for Atom Optics and Ultrafast Spectroscopy, Swinburne University of Technology, Melbourne 3122 (Australia)
2011-10-15
We develop the theory of anharmonic confinement-induced resonances (ACIRs). These are caused by anharmonic excitation of the transverse motion of the center of mass (c.m.) of two bound atoms in a waveguide. As the transverse confinement becomes anisotropic, we find that the c.m. resonant solutions split for a quasi-one-dimensional (1D) system, in agreement with recent experiments. This is not found in harmonic confinement theories. A new resonance appears for repulsive couplings (a{sub 3D}>0) for a quasi-two-dimensional (2D) system, which is also not seen with harmonic confinement. After inclusion of anharmonic energy corrections within perturbation theory, we find that these ACIRs agree extremely well with anomalous 1D and 2D confinement-induced resonance positions observed in recent experiments. Multiple even- and odd-order transverse ACIRs are identified in experimental data, including up to N=4 transverse c.m. quantum numbers.
Preliminary studies of inertial-electrostatic confinement fusion experiments
Yamamoto, Yasushi; Ohnishi, Masami; Yoshikawa, Kiyoshi; Toku, Hisayuki; Hasegawa, Mitsunori; Matsuo, Takashi [Kyoto Univ. (Japan)
1996-12-31
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.
NASA Astrophysics Data System (ADS)
Yamagata, Yuji; Yamada, Yumi; Muto, Masanori; Sato, Syunta; Nogawa, Ryozaburo; Sakamoto, Akira; Yamaguchi, Masayuki
2015-03-01
915nm high-power and high-reliability single emitter laser diodes based on Asymmetric Decoupled Confinement Heterostructure (ADCH) are demonstrated. Advantage of ADCH is that it can optimize active layer confinement (?) and confinement ratio of p- to n-doped layer (?p/?n), independently, to manage large effective spot size and low internal loss without any penalty in carrier confinement. 4mm-cavity, 100?m wide stripe LDs with large effective spot size of 1.5?m demonstrates record high Catastrophic-optical-damage (COD) free operation over 42W output. Accelerated aging tests are conducted for 325 devices in total with 1.8 million device hours. Mean time to failure of random failure mode is estimated to be 1.1 million hours for 12W at room temperature.
Very high confinement discharges in DIII-D after boronization
Jackson, G.L.; Winter, J.; Taylor, T.S.; Greenfield, C.M.; Burrell, K.H.; Carlstrom, T.N.; DeBoo, J.C.; Doyle, E.J.; Groebner, R.J.; Lao, L.L.; Rettig, C.; Schissel, D.P.; Strait, E.J. (General Atomics, San Diego, California 92138 (United States)); the DIII-D Research Team
1992-07-01
A regime of very high confinement (VH mode) has recently been observed in DIII-D with global energy confinement times up to a factor of 3.5 above the ITER89-P L-mode scaling (Nucl. Fusion {bold 30}, 1999 (1990)) and 1.5 to 2 times greater than the DIII-D/JET edge-localized-mode-free H-mode scaling relation (Nucl. Fusion {bold 31}, 73 (1991)). These discharges were obtained after boronization in DIII-D and are characterized by low radiated power and {ital Z}{sub eff}, increasing confinement time during the VH phase of the discharge and low Ohmic target density. The low radiated power and {ital Z}{sub eff} are a consequence of the boronization. During the VH phase these discharges exhibit an inward shift in the region of highest electric field shear and a large calculated edge bootstrap current. The outer region ({rho}{approx gt}0.85) is calculated to be in the second stable regime to ideal ballooning modes.
Terahertz Wave Confinement in Pillar Photonic Crystal with a Tapered Waveguide and a Point Defect
NASA Astrophysics Data System (ADS)
Wang, Chang-Hui; Kuang, Deng-Feng; Chang, Sheng-Jiang; Lin, Lie
2012-12-01
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.
Tuszewski, M; Smirnov, A; Thompson, M C; Korepanov, S; Akhmetov, T; Ivanov, A; Voskoboynikov, R; Schmitz, L; Barnes, D; Binderbauer, M W; Brown, R; Bui, D Q; Clary, R; Conroy, K D; Deng, B H; Dettrick, S A; Douglass, J D; Garate, E; Glass, F J; Gota, H; Guo, H Y; Gupta, D; Gupta, S; Kinley, J S; Knapp, K; Longman, A; Hollins, M; Li, X L; Luo, Y; Mendoza, R; Mok, Y; Necas, A; Primavera, S; Ruskov, E; Schroeder, J H; Sevier, L; Sibley, A; Song, Y; Sun, X; Trask, E; Van Drie, A D; Walters, J K; Wyman, M D
2012-06-22
Field reversed configurations (FRCs) with high confinement are obtained in the C-2 device by combining plasma gun edge biasing and neutral beam injection. The plasma gun creates an inward radial electric field that counters the usual FRC spin-up. The n = 2 rotational instability is stabilized without applying quadrupole magnetic fields. The FRCs are nearly axisymmetric, which enables fast ion confinement. The plasma gun also produces E × B shear in the FRC edge layer, which may explain the observed improved particle transport. The FRC confinement times are improved by factors 2 to 4, and the plasma lifetimes are extended from 1 to up to 4 ms. PMID:23004613
Cambridge, University of
-27, 2008 Val-d'Or - Québec - Canada MODIFIED 2D FINITE-DIFFERENCE TIME-DOMAIN TECHNIQUE FOR TUNNEL PATH deploy wireless sensor networks (WSNs) for monitoring and assessing the condition of tunnels conducted in tunnels, the antennas have been positioned along the central axis of a tunnel. However
Enhanced D? confinement mode: a theoretical model
NASA Astrophysics Data System (ADS)
Rogister, André L.
2004-08-01
It has been shown in a previous paper that the neoclassical theory of plasma rotation explains well the large toroidal velocity that is measured in the core of edge localized mode (ELM)-free ALCATOR C-Mod H-mode discharges. It has also been noted that the gradient of the toroidal/parallel velocity estimated at the pedestal inflexion point approaches the value required for the onset of the parallel velocity shear Kelvin-Helmholtz (PVS K-H) instability when the discharge is about to undergo an ELM-free to enhanced Dagr (EDA) transition. The wavenumbers and frequencies of weakly unstable PVS K-H oscillations are consistent with those of the quasi-coherent mode that is observed in the EDA, but not in the ELM-free, regime—hence the suggestion, which is explored here further, that the transition is the consequence of PVS K-H instability onset. It is at first noted that the neoclassical expression for the toroidal velocity gradient warrants that large values of the safety factor, q, and of the triangularity parameter, dgr, favour the transition, as observed. It is also shown that outward convection of toroidal momentum reduces the toroidal velocity gradient and, therefore, the instability growth rate. The anomalous particle flow and the particle confinement time in EDA discharges are then estimated on the assumption that anomalous transport maintains the velocity gradient at the threshold value. The power balance consideration shows that heat transport across the H-mode pedestal is neoclassical, at most. A simple expression of the ratio of particle and energy fluxes is then obtained; the ratio tgrP/tgrE of the respective confinement times is in the range of reported values (although it must be noted that it is difficult to quantify tgrP as it varies rapidly across the edge layer). The scenario assumes that the H-mode pedestal of EDA discharges (the unstable layer where anomalous transport occurs) is impermeable for neutrals since charged particles issuing from ionization would otherwise accumulate in the core; experimental parameters justify this assumption. The possibility of matching simultaneously the requirements for PVS K-H instability onset and non-permeability to neutrals in large devices is discussed.
Subsystem functional for confinement physics
NASA Astrophysics Data System (ADS)
Hao, Feng; Mattsson, Ann; Armiento, Rickard
2010-03-01
Recent success of the AM05 [1,2] functional shows that the subsystem functional scheme is a practical framework to construct well-performing functionals in density functional theory (DFT). The idea is to divide the real material system into regions with different characteristic physics that can be described by model systems. In AM05, subsystem functionals based on a surface model system and a uniform electron gas model system are combined to include both the edge and interior physics. By studying a harmonic oscillator model system restricted in one dimension, we are aiming to build a subsystem functional that can include ``confinement physics'' into the scheme. The new model system may help in constructing a more generally accurate functional working for both solid-state and chemical systems. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000. [1] R. Armiento, A.E. Mattsson, PRB 72, 085108 (2005), [2] A.E. Mattsson et al. JCP 128, 084714 (2008).
Confinement-Induced Colloidal Attractions in Equilibrium
NASA Astrophysics Data System (ADS)
Han, Yilong; Grier, David G.
2003-07-01
The Poisson-Boltzmann theory for colloidal electrostatic interactions predicts that charged colloidal spheres dispersed in water should repel each other, even when confined by charged surfaces. Direct measurements on highly charged polystyrene spheres, however, reveal strong, long-ranged confinement-induced attractions that have yet to be explained. We demonstrate that anomalous attractions also characterize the equilibrium pair potential for more weakly charged colloidal silica spheres sedimented into a monolayer above a glass surface. This observation substantially expands the range of conditions for which mean-field theory incorrectly predicts the sign of macroions' interactions, and provides new insights into how confinement induces long-ranged like-charge attractions.
Confined packings of frictionless spheres and polyhedra
Jean-François Camenen; Yannick Descantes; Patrick Richard
2013-07-22
By means of numerical simulations, we study the influence of confinement on three-dimensional random close packed (RCP) granular materials subject to gravity. The effects of grain shape (spherical or polyhedral) and polydispersity on this dependence are investigated. In agreement with a simple geometrical model, the solid fraction is found to decrease linearly for increasing confinement no matter the grain shape. This decrease remains valid for bidisperse sphere packings although the gradient seems to reduce significantly when the proportion of small particles reaches 40% by volume. The aforementioned model is extended to capture the effect of the confinement on the coordination number.
Confinement studies of neutral beam heated discharges in TFTR
Murakami, M.; Arunasalam, V.; Bell, J.D.; Stauffer, F.; Bell, M.G.; Bitte, M.; Blanchard, W.R.; Boody, F.; Britz, N.
1985-11-01
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.
Defect topologies in chiral liquid crystals confined to mesoscopic channels
NASA Astrophysics Data System (ADS)
Schlotthauer, Sergej; Skutnik, Robert A.; Stieger, Tillmann; Schoen, Martin
2015-05-01
We present Monte Carlo simulations in the grand canonical and canonical ensembles of a chiral liquid crystal confined to mesochannels of variable sizes and geometries. The mesochannels are taken to be quasi-infinite in one dimension but finite in the two other directions. Under thermodynamic conditions chosen and for a selected value of the chirality coupling constant, the bulk liquid crystal exhibits structural characteristics of a blue phase II. This is established through the tetrahedral symmetry of disclination lines and the characteristic simple-cubic arrangement of double-twist helices formed by the liquid-crystal molecules along all three axes of a Cartesian coordinate system. If the blue phase II is then exposed to confinement, the interplay between its helical structure, various anchoring conditions at the walls of the mesochannels, and the shape of the mesochannels gives rise to a broad variety of novel, qualitative disclination-line structures that are reported here for the first time.
The inertial electrostatic confinement approach to fusion power
Miley, G.H. [Univ. of Illinois, Urbana, IL (United States). Fusion Studies Lab.
1995-12-31
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.
High Energy Electron Confinement in a Magnetic Cusp Configuration
Park, Jaeyoung; Sieck, Paul E; Offermann, Dustin T; Skillicorn, Michael; Sanchez, Andrew; Davis, Kevin; Alderson, Eric; Lapenta, Giovanni
2014-01-01
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.
Microscale Confinement features in microfluidic devices can affect biofilm
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
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.
Symmetry-Adapted Rotator Functions for Molecules in Cylindrical Confinement
Verberck, Bart
2011-01-01
We present a general description of the formalism of symmetry-adapted rotator functions (SARFs) for molecules in cylindrical confinement. Molecules are considered as clusters of interaction centers (ICs), can have any symmetry, and can display different types of ICs. Cylindrical confinement can be realized by encapsulation in a carbon nanotube (CNT). The potential energy of a molecule surrounded by a CNT can be calculated by evaluating a limited number of terms of an expansion into SARFs, which offers a significant reduction of the computation time. Optimal molecular orientations can be deduced from the resulting potential energy landscape. Examples, including the case of a molecule with cubic symmetry inside a CNT, are discussed. PMID:21339988
Thermal field theory: Algebraic aspects and applications to confined systems
NASA Astrophysics Data System (ADS)
Santana, A. E.; Malbouisson, J. M. C.; Malbouisson, A. P. C.; Khanna, F. C.
A resume of recent trends in thermal field theory is presented with emphasis on algebraic aspects. In this sense, some representations of Lie symmetries provide, in particular, a unified axiomatization, via the so-called thermofield dynamics (TFD) approach, of different methods treating thermal systems. First, a connection between imaginary and real time formalism is presented, with emphasis on physical paradigms of thermal physics. The study of Poincare Lie algebra leads us to a derivation of Liouville-like equations for the scalar and Dirac field, and as an application the Juttiner distribution for bosons is obtained. Exploring the fact that a finite temperature prescription results to be equivalent to a path-integral calculated on RD-1 × S1, where S1 is a circle of circumference ? = 1/T, a generalization of the thermal quantum field theory is presented in order to take into account the space confinement of fields. In other words, we consider the TFD and the Matsubara mechanism on a R^{D - N} × S^{1_1 } × S^{1_2 } ... × S^{1_N } topology, describing time (temperature) and space confinement. The resulting geometrical approach is then applied to analyse the 3 — D N — component Gross-Neveu model compactified in a square of side L, at a temperature T. The main result is a closed expression for the large-N effective coupling constant, g(L, T). For large values of the fixed coupling constant, we obtain simultaneously asymptotic freedom, spacial confinement and a decoupling transition at a temperature Td. Taking the Gross-Neveu model as describing the effective interaction between quarks, the confining length and the deconfining temperature obtained are of the order of the expected values for hadrons.
Human Adaptation To Isolated And Confined Environments
NASA Technical Reports Server (NTRS)
Evans, Gary W.; Stokols, Daniel; Carrere, Sna Sybil
1992-01-01
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.
Speeding up of Sedimentation under Confinement
NASA Astrophysics Data System (ADS)
Heitkam, S.; Yoshitake, Y.; Toquet, F.; Langevin, D.; Salonen, A.
2013-04-01
We show an increase of the sedimentation velocity as small particles are confined in circular capillaries. In general, confinement slows down sedimentation. But, we show that at low Reynolds numbers and in 1D confinement this is not the case. Particle sedimentation velocity is not homogeneous, which can lead to the formation of structures. These structures are enhanced and stabilized in the presence of walls and in the absence of other dissipative mechanisms. As a consequence, it is possible to achieve sedimentation velocities that even exceed the Stokes velocity. The segregation at critical capillary diameters has been directly observed using a large scale model. These simple experiments offer a new insight into the old problem of sedimentation under confinement.
A model for melting of confined DNA
Werner, E; Ambjörnsson, T; Mehlig, B
2015-01-01
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.
Steiner-tree confinement and tetraquarks
Jean-Marc Richard
2009-05-14
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.
Model for melting of confined DNA
NASA Astrophysics Data System (ADS)
Werner, E.; Reiter-Schad, M.; Ambjörnsson, T.; Mehlig, B.
2015-06-01
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, in part 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 behavior and that the effect of confinement is stronger than in the ideal case.
Confinement-Induced Colloidal Attractions in Equilibrium
Yilong Han; David G. Grier
2003-01-01
The Poisson-Boltzmann theory for colloidal electrostatic interactions predicts that charged colloidal spheres dispersed in water should repel each other, even when confined by charged surfaces. Direct measurements on highly charged polystyrene spheres, however, reveal strong, long-ranged confinement-induced attractions that have yet to be explained. We demonstrate that anomalous attractions also characterize the equilibrium pair potential for more weakly charged colloidal
Particle Segregation and Dynamics in Confined Flows
Di Carlo, Dino; Edd, Jon F.; Humphry, Katherine J.; Stone, Howard A.; Toner, Mehmet
2015-01-01
Nonlinearity in finite-Reynolds-number flow results in particle migration transverse to fluid streamlines, producing the well-known “tubular pinch effect” in cylindrical pipes. Here we investigate these nonlinear effects in highly confined systems where the particle size approaches the channel dimensions. Experimental and numerical results reveal distinctive dynamics, including complex scaling of lift forces with channel and particle geometry. The unique behavior described in this Letter has broad implications for confined particulate flows. PMID:19392526
Metallically confined microdisks with in-plane multiple guided emissions.
Che, Kai-Jun; Huang, Yong-Zhen; Chen, Lu-Jian; Cai, Zhi-Ping; Xu, Hui-Ying
2011-09-12
We theoretically present in-plane multiple guided emissions of metallically confined microdisk lasers which can be applied to drive multiple elements in compact photonic integration at the same time. Two to four-port microdisks with transverse magnetic and electric polarizations are investigated based on finite difference time domain simulation and padé approximation. Modes filtering of coupling ports are verified by the calculated mode quality factors (Q) which are decided by the matching of coupling ports with the energy density distribution of corresponding modes. Single mode lasing operation of semiconductor microdisk with guided emissions is possibly realized by selectively pumping. PMID:21935177
Propagation of confined excitonic polaritons at high densities
U. Neukirch; K. Wundke
1997-01-01
The propagation of excitonic polaritons is investigated in the nonlinear optical regime by real-time-resolved pump-and-probe measurements on a femtosecond time scale. High-quality ZnSxSe1-x\\/ZnSe\\/ZnSxSe1-x heterostructures are used which, in linear absorption, show clearly resolved Fabry-Pérot resonances of polaritons confined in the ZnSe layer. Without pumping, the transmitted probe pulses exhibit a complex temporal beating behavior caused by quantum beating between heavy-hole
Light-Cone Kaluza-Klein Geometry: Confined Propagation as a Particle Model
Donald E. Jennings
2000-04-24
A modified Kaluza-Klein theory is proposed in which propagation takes place only at the speed of light. The propagation can be confined to a small volume, forming a particle with rest mass. The usual four space-time coordinates locate the confinement volume, and Kaluza's fifth coordinate is replaced by an internal degree of freedom. Electromagnetism corresponds to a gauge field on the phase of the internal motion. Self-gravity might create the confinement, as in a geon, but the particle would have a Planck mass. This large mass could be made closer to the masses of observed particles if gravity were allowed to increase in strength within the confinement volume.
Nogaret, A; Portal, J-C; Beere, H E; Ritchie, D A; Phillips, C
2009-01-14
We investigate the photoresistance of a magnetically confined quantum wire in which microwave-coupled edge channels interfere at two pinning sites in the fashion of a Mach-Zehnder interferometer. The conductance is strongly enhanced by microwave power at B = 0 and develops a complex series of oscillations when the magnetic confinement increases. Both results are quantitatively explained by the activation of forward scattering in a multimode magnetically confined quantum wire. By varying the strength of the magnetic confinement we are able to tune the phase of electrons in the arms of the interferometer. Quantum interferences which develop between pinning sites explain the oscillations of the conductance as a function of the magnetic field. A fit of the data gives the distance between pinning sites as 11 µm. This result suggests that quantum coherence is conserved over a distance three times longer than the electron mean free path. PMID:21813973
Effect of confinement on failure in 95 TATB/5 KEL-F
Ramsay, J.B.
1985-01-01
A modification of the usual wedge test for measuring the failure thickness has been developed that eliminates the effect of the confinement provided by the witness plate. The new test uses a prism of the explosive with a line initiator to start a detonation along the trapezoidal face of the prism. Experiments using PBX 9502 have shown that the failure thickness measured using the prism test is 1/2 the failure diameter measured in long cyclindrical charges, provided the wave can propagate 15 to 25 times the failure width. No significant effects of confinement is observed for low impedance confinement, whereas high impedance materials reduce the failure thickness. Thin layers of confinement reduce the failure thickness significantly. Copper, 0.025 mm thick, and 0.25-mm aluminum each reduce the failure thickness of PBX 9502 by 35%. 6 refs., 7 figs.
Subwavelength metallic waveguides as a tool for extreme confinement of THz surface waves
Gacemi, D.; Mangeney, J.; Colombelli, R.; Degiron, A.
2013-01-01
Research on surface waves supported by metals at THz frequencies is experiencing a tremendous growth due to their potential for imaging, biological sensing and high-speed electronic circuits. Harnessing their properties is, however, challenging because these waves are typically poorly confined and weakly bound to the metal surface. Many design strategies have been introduced to overcome these limitations and achieve increased modal confinement, including patterned surfaces, coated waveguides and a variety of sub-wavelength geometries. Here we provide evidence, using a combination of numerical simulations and time-resolved experiments, that shrinking the transverse size of a generic metallic structure always leads to solutions with extreme field confinement. The existence of such a general behavior offers a new perspective on energy confinement and should benefit future developments in THz science and technology. PMID:23463351
Confinement and viscoelastic effects on chain closure dynamics
NASA Astrophysics Data System (ADS)
Bhattacharyya, Pinaki; Sharma, Rati; Cherayil, Binny J.
2012-06-01
Chemical reactions inside cells are typically subject to the effects both of the cell's confining surfaces and of the viscoelastic behavior of its contents. In this paper, we show how the outcome of one particular reaction of relevance to cellular biochemistry - the diffusion-limited cyclization of long chain polymers - is influenced by such confinement and crowding effects. More specifically, starting from the Rouse model of polymer dynamics, and invoking the Wilemski-Fixman approximation, we determine the scaling relationship between the mean closure time tc of a flexible chain (no excluded volume or hydrodynamic interactions) and the length N of its contour under the following separate conditions: (a) confinement of the chain to a sphere of radius d and (b) modulation of its dynamics by colored Gaussian noise. Among other results, we find that in case (a) when d is much smaller than the size of the chain, tc ˜ Nd2, and that in case (b), tc ˜ N2/(2 - 2H), H being a number between 1/2 and 1 that characterizes the decay of the noise correlations. H is not known a priori, but values of about 0.7 have been used in the successful characterization of protein conformational dynamics. At this value of H (selected for purposes of illustration), tc ˜ N3.4, the high scaling exponent reflecting the slow relaxation of the chain in a viscoelastic medium.
Rapid Confined Mixing with Transverse Jets Part 1: Single Jet
NASA Astrophysics Data System (ADS)
Salazar, David; Forliti, David
2012-11-01
Transverse jets have been studied extensively due to their relevance and efficiency in fluid mixing applications. Gas turbine burners, film cooling, and chemical reactors are some examples of rapid transverse jet mixing. Motivated by a lack of universal scaling laws for confined and unconfined transverse jets, a newly developed momentum transfer parameter was found to improve correlation of literature data. Jet column drag and entrainment arguments for momentum transfer are made to derive the parameter. A liquid-phase mixing study was conducted to investigate confined mixing for a low number of jets. Planar laser induced fluorescence was implemented to measure mixture fraction for a single confined transverse jet. Time-averaged cross-sectional images were taken with a light sheet located three diameters downstream of transverse injection. A mixture of water and sodium fluorescein was used to distinguish jet fluid from main flow fluid for the test section images. Image data suggest regimes for under- and overpenetration of jet fluid into the main flow. The scaling parameter is found to correlate optimum unmixedness for multiple diameter ratios at a parameter value of 0.75. Distribution A: Public Release, Public Affairs Clearance Number: 12655.
Dynamics of Water Confined in Partially Hydrophobic Nanosized Cylindrical Sieves
NASA Astrophysics Data System (ADS)
Faraone, Antonio; Zhang, Yang; Liu, Kao-Hsiang; Mou, Chung-Yuan; Chen, Sow-Hsin
2009-03-01
Using three high resolution quasielastic neutron scattering spectrometers we have investigated the single particle dynamics of water confined in a hydrophobically modified MCM-41-S sample. This latter is a silica matrix containing cylindrical sieves with diameter < 20 å arranged in a hexagonal geometry. In the hydrophobically modified sample some of the sylanol groups in the pores' wall have been substituted with methanol groups resulting in a partially hydrophobic confining surface, which could be used as a model system. We have been able to analyze the data in the temperature range from 300 K to 210 K using a single consistent model, the Relaxing Cage Model (RCM) for the dynamics of supercooled water. Because of the heterogenous environment experienced by the water molecules in the pores, the relaxational dynamics show a broad distribution of relaxation times. However, the Fickian diffusive behaviour is retained. The obtained results help clarify the role that the chemical interaction between the water molecules and the walls of the confining host plays in determining the characteristics of the water dynamics, as compared to purely geometric constraints such as the size and shape of the pores.
Deformation and breakup of viscoelastic droplets in confined shear flow.
Gupta, A; Sbragaglia, M
2014-08-01
The deformation and breakup of Newtonian and viscoelastic droplets are studied in confined shear flow. Our numerical approach is based on a combination of lattice-Boltzmann models and finite difference schemes, the former used to model two immiscible fluids with variable viscosity ratio and the latter used to model the polymer dynamics. The kinetics of the polymers is introduced using constitutive equations for viscoelastic fluids with finitely extensible nonlinear elastic dumbbells with Peterlin's closure. We quantify the droplet response by changing the polymer relaxation time ?(P), the maximum extensibility L of the polymers, and the degree of confinement, i.e., the ratio of the droplet diameter to wall separation. In unconfined shear flow, the effects of droplet viscoelasticity on the critical capillary number Ca(cr) for breakup are moderate in all cases studied. However, in confined conditions a different behavior is observed: The critical capillary number of a viscoelastic droplet increases or decreases, depending on the maximum elongation of the polymers, the latter affecting the extensional viscosity of the polymeric solution. Force balance is monitored in the numerical simulations to validate the physical picture. PMID:25215849
Impact of production systems on swine confinement buildings bioaerosols.
Létourneau, Valérie; Nehmé, Benjamin; Mériaux, Anne; Massé, Daniel; Duchaine, Caroline
2010-02-01
Hog production has been substantially intensified in Eastern Canada. Hogs are now fattened in swine confinement buildings with controlled ventilation systems and high animal densities. Newly designed buildings are equipped with conventional manure handling and management systems, shallow or deep litter systems, or source separation systems to manage the large volumes of waste. However, the impacts of those alternative production systems on bioaerosol concentrations within the barns have never been evaluated. Bioaerosols were characterized in 18 modern swine confinement buildings, and the differences in bioaerosol composition in the three different production systems were evaluated. Total dust, endotoxins, culturable actinomycetes, fungi, and bacteria were collected with various apparatuses. The total DNA of the air samples was extracted, and quantitative polymerase chain reaction (PCR) was used to assess the total number of bacterial genomes, as a total (culturable and nonculturable) bacterial assessment. The measured total dust and endotoxin concentrations were not statistically different in the three studied production systems. In buildings with sawdust beds, actinomycetes and molds were found in higher concentrations than in the conventional barns. Aspergillus, Cladosporium, Penicillium, and Scopulariopsis species were identified in all the studied swine confinement buildings. A. flavus, A. terreus, and A. versicolor were abundantly present in the facilities with sawdust beds. Thermotolerant A. fumigatus and Mucor were usually found in all the buildings. The culturable bacteria concentrations were higher in the barns with litters than in the conventional buildings, while real-time PCR revealed nonstatistically different concentrations of total bacteria in all the studied swine confinement buildings. In terms of workers' respiratory health, barns equipped with a solid/liquid separation system may offer better air quality than conventional buildings or barns with sawdust beds. The impact of ventilation rates, air distribution, or building design still has to be explored. PMID:19953413
Carbon nanotubes in confined magneticCarbon nanotubes in confined magnetic fields: thefields: the
Marini, Andrea
as a change in the interference pattern #12;The AB effect in carbon nano-tubes A. Bachtold et al., Nature 397Zone-FoldingApproach J.C. Charlier et al, Rev. Mod. Phys. 79, 677 (2007) #12;The AB effect in carbon nano-tubes (CNTsCarbon nanotubes in confined magneticCarbon nanotubes in confined magnetic fields: thefields
Neuroendocrine system and immune responses after confinement.
Husson, D; Abbal, M; Tafani, M; Schmitt, D A
1996-01-01
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
Circularly confined microswimmers exhibit multiple global patterns
NASA Astrophysics Data System (ADS)
Tsang, Alan Cheng Hou; Kanso, Eva
2015-04-01
Geometric confinement plays an important role in the dynamics of natural and synthetic microswimmers from bacterial cells to self-propelled particles in high-throughput microfluidic devices. However, little is known about the effects of geometric confinement on the emergent global patterns in such self-propelled systems. Recent experiments on bacterial cells report that, depending on the cell concentration, cells either spontaneously organize into vortical motion in thin cylindrical and spherical droplets or aggregate at the inner boundary of the droplets. Our goal in this paper is to investigate, in the context of an idealized physical model, the interplay between geometric confinement and level of flagellar activity on the emergent collective patterns. We show that decreasing flagellar activity induces a hydrodynamically triggered transition in confined microswimmers from swirling to global circulation (vortex) to boundary aggregation and clustering. These results highlight that the complex interplay between confinement, flagellar activity, and hydrodynamic flows in concentrated suspensions of microswimmers could lead to a plethora of global patterns that are difficult to predict from geometric consideration alone.
Confinement induced binding of noble gas atoms.
Khatua, Munmun; Pan, Sudip; Chattaraj, Pratim K
2014-04-28
The stability of Ngn@B12N12 and Ngn@B16N16 systems is assessed through a density functional study and ab initio simulation. Although they are found to be thermodynamically unstable with respect to the dissociation of individual Ng atoms and parent cages, ab initio simulation reveals that except Ne2@B12N12 they are kinetically stable to retain their structures intact throughout the simulation time (500 fs) at 298 K. The Ne2@B12N12 cage dissociates and the Ne atoms get separated as the simulation proceeds at this temperature but at a lower temperature (77 K) it is also found to be kinetically stable. He-He unit undergoes translation, rotation and vibration inside the cavity of B12N12 and B16N16 cages. Electron density analysis shows that the He-He interaction in He2@B16N16 is of closed-shell type whereas for the same in He2@B12N12 there may have some degree of covalent character. In few cases, especially for the heavier Ng atoms, the Ng-N/B bonds are also found to have some degree of covalent character. But the Wiberg bond indices show zero bond order in He-He bond and very low bond order in cases of Ng-N/B bonds. The energy decomposition analysis further shows that the ?Eorb term contributes 40.9% and 37.3% towards the total attraction in the He2 dimers having the same distances as in He2@B12N12 and He2@B16N16, respectively. Therefore, confinement causes some type of orbital interaction between two He atoms, which akins to some degree of covalent character. PMID:24784269
Kinetics of Polymer Ejection from Capsid Confinement: Scaling Considerations and Computer Experiment
NASA Astrophysics Data System (ADS)
Milchev, A.; Binder, K.
2012-08-01
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.
Excitons confined by split-gate potentials
NASA Astrophysics Data System (ADS)
Cocoletzi, Gregorio H.; Ulloa, Sergio E.
1994-03-01
Quasi-one-dimensional excitons in a GaAs-AlxGa1-xAs quantum well are studied; they are produced by an applied twin-split-gate potential which confines the particles laterally and allows free motion in one dimension. A variational approach is used to calculate the binding energies Eex and oscillator strength fex of these excitonic transitions as functions of the applied voltage and width of the induced potential wells. In the limit of high electrostatic confinement the excitons are strongly polarized and the system resembles a type II structure where electron and hole are spatially separated. The resulting Eex and fex show a strong dependence on applied voltage and structure width. Strong oscillations are found, which should be observed experimentally, as a consequence of subtle competition between confinement and Coulomb attraction.
Progress in toroidal confinement and fusion research
Furth, H.P.
1987-10-01
During the past 30 years, the characteristic T/sub i/n tau/sub E/-value of toroidal-confinement experiments has advanced by more than seven orders of magnitude. Part of this advance has been due to an increase of gross machine parameters. Most of this advance has been due to an increase of gross machine parameters. Most of the advance is associated with improvements in the ''quality of plasma confinement.'' The combined evidence of spherator and tokamak research clarifies the role of magnetic-field geometry in determining confinement and points to the importance of shielding out plasma edge effects. A true physical understanding of anomalous transport remains to be achieved. 39 refs., 11 figs., 1 tab.
Properties of Water Confined in Ionic Liquids
Saihara, Koji; Yoshimura, Yukihiro; Ohta, Soichi; Shimizu, Akio
2015-01-01
The varying states of water confined in the nano-domain structures of typical room temperature ionic liquids (ILs) were investigated by 1H NMR and by measurements of self-diffusion coefficients while systematically varying the IL cations and anions. The NMR peaks for water in BF4-based ILs were clearly split, indicating the presence of two discrete states of confined water (H2O and HOD). Proton and/or deuterium exchange rate among the water molecules was very slowly in the water-pocket. Notably, no significant changes were observed in the chemical shifts of the ILs. Self-diffusion coefficient results showed that water molecules exhibit a similar degree of mobility, although their diffusion rate is one order of magnitude faster than that of the IL cations and anions. These findings provide information on a completely new type of confinement, that of liquid water in soft matter. PMID:26024339
Interacting Living Polymers Confined between Two Surfaces
NASA Astrophysics Data System (ADS)
Besseling, Nicolaas A. M.; Korobko, Alexander V.
2013-11-01
We present predictions on the equilibrium behavior of solutions of living polymers confined in a gap between surfaces, including the ensuing potential of mean force between those surfaces (the disjoining potential). We highlight the occurrence of a transition upon narrowing the gap, which arises from a cooperative simultaneous increase of the local density and degree of polymerization. At this transition, many properties of the confined solution, including the disjoining potential, change by orders of magnitude over a minute change of the surface separation. These results were obtained owing to two extensions to a previously introduced self-consistent field-propagator formalism. (i) We derive this formalism from a free-energy functional of the distribution of chain lengths and configurations. This enables evaluation of thermodynamic properties, including the disjoining potential. (ii) We solved for a system confined between two surfaces.
Confinement-induced colloidal attractions in equilibrium.
Han, Yilong; Grier, David G
2003-07-18
The Poisson-Boltzmann theory for colloidal electrostatic interactions predicts that charged colloidal spheres dispersed in water should repel each other, even when confined by charged surfaces. Direct measurements on highly charged polystyrene spheres, however, reveal strong, long-ranged confinement-induced attractions that have yet to be explained. We demonstrate that anomalous attractions also characterize the equilibrium pair potential for more weakly charged colloidal silica spheres sedimented into a monolayer above a glass surface. This observation substantially expands the range of conditions for which mean-field theory incorrectly predicts the sign of macroions' interactions, and provides new insights into how confinement induces long-ranged like-charge attractions. PMID:12906461
Scaling of confined and interacting comb polymers
NASA Astrophysics Data System (ADS)
Yeh, Catherine; Pincus, Philip
2011-03-01
We study the scaling of polymer chains grafted to a line, i.e. a 1-D brush or comb polymer, on a repulsive plane in good solvent using classical molecular dynamics. The grafting density is large enough to cause chain stretching. The confined comb geometry is motivated by intermediate filaments where the unstructured monomer c-termini form annular rings that can be modeled as a confined comb bent into a ring. We find that the scaling of brush size as a function of the number of monomers per chain is the same for a comb with and without confinement by a repulsive plane. We also consider the transition of a line of parallel interacting combs to the planar brush geometry as they are compressed from isolated combs; we present results for the dependence of brush height on the distance between combs.
Neutron Assay System for Confinement Vessel Disposition
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
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.
Properties of water confined in ionic liquids.
Saihara, Koji; Yoshimura, Yukihiro; Ohta, Soichi; Shimizu, Akio
2015-01-01
The varying states of water confined in the nano-domain structures of typical room temperature ionic liquids (ILs) were investigated by (1)H NMR and by measurements of self-diffusion coefficients while systematically varying the IL cations and anions. The NMR peaks for water in BF4-based ILs were clearly split, indicating the presence of two discrete states of confined water (H2O and HOD). Proton and/or deuterium exchange rate among the water molecules was very slowly in the water-pocket. Notably, no significant changes were observed in the chemical shifts of the ILs. Self-diffusion coefficient results showed that water molecules exhibit a similar degree of mobility, although their diffusion rate is one order of magnitude faster than that of the IL cations and anions. These findings provide information on a completely new type of confinement, that of liquid water in soft matter. PMID:26024339
Ultrasonic interferometer for first-sound measurements of confined liquid He4
NASA Astrophysics Data System (ADS)
Rojas, X.; Hauer, B. D.; MacDonald, A. J. R.; Saberi, P.; Yang, Y.; Davis, J. P.
2014-05-01
We present a new technique for probing the properties of quantum fluids in restricted geometries. We have confined liquid He4 within microfluidic devices formed from glass wafers, in which one dimension is on the micrometer scale. Using an ultrasonic analog to Fabry-Pérot interferometry, we have measured the first sound of the confined liquid He4, which can be a probe of critical behavior near the lambda point (T?). All thermodynamic properties of liquid He4 can be derived from first-sound and heat capacity measurements, and although quite a bit of experimental work has been done on the latter, no measurement of first sound has been reported for a precisely confined geometry smaller than a few tens of micrometers. In this work, we report measurements of isobaric first sound in liquid He4 confined in cavities as small as ˜5 ?m. Our experimental setup allows us to pressurize the liquid up to ˜25 bar without causing deformation of the confined geometry, a pressure which is about four times larger than previously reported with similar microfluidic devices. Our preliminary results indicate that one can possibly observe finite-size effects and verify scaling laws, by using similar devices with smaller confinement.
A molecular dynamics study of freezing in a confined geometry
NASA Technical Reports Server (NTRS)
Ma, Wen-Jong; Banavar, Jayanth R.; Koplik, Joel
1992-01-01
The dynamics of freezing of a Lennard-Jones liquid in narrow channels bounded by molecular walls is studied by computer simulation. The time development of ordering is quantified and a novel freezing mechanism is observed. The liquid forms layers and subsequent in-plane ordering within a layer is accompanied by a sharpening of the layer in the transverse direction. The effects of channel size, the methods of quench, the liquid-wall interaction and the roughness of walls on the freezing mechanism are elucidated. Comparison with recent experiments on freezing in confined geometries is presented.
Magnetospheric Vortex Formation: Self-Organized Confinement of 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
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.
Primary sinonasal tuberculosis confined to the unilateral maxillary sinus
Kim, Kyung Yeon; Bae, Jung Ho; Park, Jee Soo; Lee, Seung-Sin
2014-01-01
Extrapulmonary tuberculosis is not rare and occurs mainly in the head and neck region. Cervical tuberculous lymphadenopathy is the most common form of extrapulmonary tuberculosis. Sinonasal tuberculosis is known to occur very rarely due to the protective functions of sinonasal mucosa. Although some signs of sinonasal tuberculosis may be present, such as associated facial abscesses, the symptoms and signs are usually nonspecific. Clinical suspicion is important for timely diagnosis and proper management of sinonasal tuberculosis due to its rarity and nonspecific clinical presentation. We report a case of tuberculosis confined to the unilateral maxillary sinus that was first misdiagnosed as recurrent rhinosinusitis after endoscopic sinus surgery. PMID:24551309
Extreme optical confinement in a slotted photonic crystal waveguide
Caër, Charles; Le Roux, Xavier; Cassan, Eric, E-mail: eric.cassan@u-psud.fr [Institut d'Électronique Fondamentale, Université Paris-Sud CNRS UMR 8622 Bat. 220, Centre scientifique d'Orsay, 91405 Orsay (France); Combrié, Sylvain, E-mail: sylvain.combrie@thalesgroup.com; De Rossi, Alfredo [Thales Research and Technology, 1 Av. Augustin Fresnel, 91767 Palaiseau (France)
2014-09-22
Using Optical Coherence Tomography, we measure the attenuation of slow light modes in slotted photonic crystal waveguides. When the group index is close to 20, the attenuation is below 300?dB cm{sup ?1}. Here, the optical confinement in the empty slot is very strong, corresponding to an ultra-small effective cross section of 0.02??m{sup 2}. This is nearly 10 times below the diffraction limit at ??=?1.5??m, and it enables an effective interaction with a very small volume of functionalized matter.
New confinement phases from singular SCFT
NASA Astrophysics Data System (ADS)
Giacomelli, Simone; Konishi, Kenichi
2013-03-01
New types of confining phase emerge when some singular SCFT's appearing as infrared fixed points of {N}=2 supersymmetric QCD (SQCD) are deformed by an {N}=1 adjoint mass term. We make further checks on the Gaiotto-Seiberg-Tachikawa (GST) description of these vacua against the symmetry and vacuum counting argument, and show that the GST variables correctly describe these systems, brought into confinement phase by the {N}=1 perturbation. Several examples of such vacua, USp(2 N) and SU( N) theories with four flavors and SO( N) theories with one or two flavors, are discussed.
cap alpha. -Particle confinement in compact tori
Bozhokin, S.V.
1986-11-01
The motion of high-energy ..cap alpha.. particles in compact tori is studied. The classically accessible regions of motion of charged particles are found. The conditions are formulated under which the ..cap alpha.. particles produced in fusion reactions are absolutely confined. An ..cap alpha.. particle starting in a region enclosed by a ''critical'' surface will never, in the course of its motion, intersect the separatrix of a compact torus. These critical surfaces are constructed. The ratio of the volume of absolute ..cap alpha.. confinement to the total volume of a compact torus is calculated as a function of the magnetic field strength and the dimensions of the compact torus.
Neutral Beam Ion Confinement in NSTX
D.S. Darrow; E.D. Fredrickson; S.M. Kaye; S.S. Medley; and A.L. Roquemore
2001-07-24
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.
Gold nanobelts as high confinement plasmonic waveguides.
Anderson, Lindsey J E; Zhen, Yu-Rong; Payne, Courtney M; Nordlander, Peter; Hafner, Jason H
2013-01-01
Plasmon propagation in thin plasmonic waveguides is strongly damped, making it difficult to study with diffraction-limited optics. Here we directly characterize plasmon propagation in gold nanobelts with incoherent light. The data indicate a short average propagation length of 0.94 ?m but also reveal a weakly excited antisymmetric mode that has a propagation length greater than 10 ?m with strong confinement of 2400 nm(2). These results demonstrate that high confinement and long propagation length can be achieved with thin plasmonic structures. PMID:24205882
Polymer Translocation out of Planar Confinements
Debabrata Panja; Gerard T. Barkema; Robin C. Ball
2007-11-19
Polymer translocation in three dimensions out of planar confinements is studied in this paper. Three membranes are located at $z=-h$, $z=0$ and $z=h_1$. These membranes are impenetrable, except for the middle one at $z=0$, which has a narrow pore. A polymer with length $N$ is initially sandwiched between the membranes placed at $z=-h$ and $z=0$ and translocates through this pore. We consider strong confinement (small $h$), where the polymer is essentially reduced to a two-dimensional polymer, with a radius of gyration scaling as $R^{\\tinytext{(2D)}}_g \\sim N^{\
Tension of confining strings at low temperature
NASA Astrophysics Data System (ADS)
Giataganas, Dimitrios; Goldstein, Kevin
2015-02-01
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.
Wellhead protection in confined, semi-confined, fractured and karst aquifer settings
Not Available
1993-09-01
Protection areas around wells producing from confined, fractured, and karst aquifers are, because of their complex hydrogeology, more difficult to define than protection areas for wells in porous media settings. The factsheet provides background information explaining the need to define protection areas for wells that draw public drinking water from several complex hydrogeologic settings: confined, semi-confined, fractured, and karst aquifers. These settings include aquifers in which the ground water is not open to the atmosphere, or the aquifer does not consist of unconsolidated porous media. Several figures illustrate these settings in a general way.
Dynamics of propylene glycol and its oligomers confined to a single molecular layer
NASA Astrophysics Data System (ADS)
Swenson, J.; Engberg, D.; Howells, W. S.; Seydel, T.; Juranyi, F.
2005-06-01
The dynamics of propylene glycol (PG) and its oligomers 7-PG and poly-propylene glycol (PPG), with Mw=4000 (?70 monomers), confined in a Na-vermiculite clay have been investigated by quasielastic neutron scattering. The liquids are confined to single molecular layers between clay platelets, giving a true two-dimensional liquid. Data from three different spectrometers of different resolutions were Fourier transformed to S(Q,t) and combined to give an extended dynamical time range of 0.3-2000 ps. An attempt was made to distinguish the diffusive motion from the methyl group rotation and a fast local motion of hydrogen in the polymer backbone. The results show that the average relaxation time ??d? of this diffusive process is, as expected, larger than the relaxation time ??? averaged over all dynamical processes observed in the experimental time window. More interesting, it is evident that the severe confinement has a relatively small effect on ??d? at T =300K, this holds particularly for the longest oligomer, PPG. The most significant difference is that the chain-length dependence of ??d? is weaker for the confined liquids, although the slowing down in bulk PG due to the formation of a three-dimensional network of OH-bonded end groups reduces this difference. The estimated average relaxation time ??? at Q =0.92Å-1 for all the observed processes is in excellent agreement with the previously reported dielectric ? relaxation time in the studied temperature range of 260-380 K. The average relaxation time ??? (as well as the dielectric ? relaxation time) is also almost unaffected by the confinement to a single molecular layer, suggesting that the interaction with the clay surfaces is weak and that the reduced dimensionality has only a weak influence on the time scale of all the dynamical processes observed in this study.
NASA Astrophysics Data System (ADS)
Perry, W. Lee; Dickson, Peter M.; Parker, Gary R.; Asay, B. W.
2005-01-01
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.
Magnetic Confinement Fusion Science Status and Challenges
by centrifugal force of particles moving along curved magnetic field plasma magnetic field Centrifugal force #12;Centrifugal force in a torus centrifugal force magnetic field #12;Stability theory is highly developed - no local damage #12;Plasma confinement is an optimization problem with many physics and engineering
Structure of confined films of chain alcohols
Mugele, Friedrich; Baldelli, Steven; Somorjai, Gabor A.; Salmeron, Miquel
1999-09-30
The structure of thin films of simple chain alcohols (1-octanol and 1-undecanol) confined between two atomically smooth mica surfaces has been investigated using a surface forces apparatus (SFA). In both systems, the substrate-molecule interaction leads to a strongly bound first layer on each surface. Additional liquid organizes into highly compressible bilayers, which could be expelled by applying sufficiently high pressure.
Confinement effects on thin polymer films
Karoly J. T. Dalnoki-Veress
1998-01-01
We present the results of four projects investigating the effects of confinement on polymeric systems. The first study dealt with polymer blends that are quenched using a spincoating technique rather than a temperature quench. The mass fraction of two blends was varied to determine the effect of the substrate-blend interface on the thin film phase separation morphology. Quantitative measurements of
Analysis of thermally-degrading, confined HMX
Hobbs, M.L.; Schmitt, R.G.; Renlund, A.M.
1996-12-01
The response of a thermally-degrading, confined HMX pellet is analyzed using a Reactive Elastic-Plastic (REP) constitutive model which is founded on the collapse and growth of internal inclusions resulting from physical and chemical processes such as forced displacement, thermal expansion, and/or decomposition. Axial stress predictions compare adequately to data. Deficiencies in the model and future directions are discussed.
Electrostatic-Dipole (ED) Fusion Confinement Studies
NASA Astrophysics Data System (ADS)
Miley, George H.; Shrestha, Prajakti J.; Yang, Yang; Thomas, Robert
2004-11-01
The Electrostatic-Dipole (ED) concept significantly differs from a "pure" dipole confinement device [1] in that the charged particles are preferentially confined to the high-pressure region interior of the dipole coil by the assistance of a surrounding spherical electrostatic grid. In present ED experiments, a current carrying coil is embedded inside the grid of an IEC such as to produce a magnetic dipole field. Charged particles are injected axisymmetrically from an ion gun (or duo-plasmatron) into the center of the ED confinement grid/dipole ring where they oscillate along the magnetic field lines and pass the peak field region at the center of the dipole region. As particles begin accelerating away from the center region towards the outer electrostatic grid region, they encounter a strong electrostatic potential (order of 10's of kilovolts) retarding force. The particles then decelerate, reverse direction and re-enter the dipole field region where again magnetic confinement dominates. This process continues, emulating a complex harmonic oscillator motion. The resulting pressure profile averaged over the field curvature offers good plasma stability in the ED configuration. The basic concept and results from preliminary experiments will be described. [1] M.E. Mauel, et al. "Dipole Equilibrium and Stability," 18th IAEA Conference of Plasma Phys. and Control. Nuclear Fusion, Varenna, Italy 2000, IAEA-F1-CN-70/TH
Polymer Statics and Dynamics in Confined Geometries
NASA Astrophysics Data System (ADS)
Kalb, Joshua; Chakraborty, Bulbul
2006-03-01
Current work on biological systems and glass forming polymers (JCP 106, 6176 (1997)) has led to an interest in the study of single polymer systems. The main questions concern relaxation phenomena and the shape adopted by single polymers under hard and soft boundaries. Little is known about the possibility of inducing a glass transition through pure dimensional confinement. We are concerned with whether or not there is a critical value of the confining length scale. Both structure and relaxation can be described using scaling arguments and tested with Monte Carlo simulations using the bond-fluctuation algorithm (Macromolecules 21,2819 (1988)), which uses a lattice representation of the polymer chain with excluded volume effects. We look at the effects of confinement on a single polymer chain by measuring quantities such as the magnitude end-to-end vector, the radius of gyration, and single monomer motion (JACS 124, 20 (2004)). A primary question is whether the self-avoidance constraint manifests itself in a manner similar to kinetically constrained models of the glass transition. Understanding how these quantities change with various confining geometries will lead to a deeper understanding of biological structures and glass formation. Work supported by NSF-DMR 0403997.
Polymer Statics and Dynamics Under Box Confinement
NASA Astrophysics Data System (ADS)
Kalb, Joshua; Chakraborty, Bulbul
2007-03-01
Current work on biological systems and glass forming polymers (JCP 106, 6176 (1997)) has led to an interest in the study of single polymer systems. The main questions concern relaxation phenomena and the shape adopted by single polymers under hard and soft boundaries. We are concerned with whether or not there is a critical length scale for a confined polymer system. Both structure and relaxation can be described using scaling arguments and tested with Monte Carlo simulations using the bond-fluctuation algorithm (Macromolecules 21,2819 (1988)), which uses a lattice representation of the polymer chain with excluded volume effects. We look at the effects of confinement on a single polymer chain confined to a box by measuring dynamical quantities such as the end-to-end vector and single monomer positions (JACS 124, 20 (2004)). A primary question is how spatial correlations between monomers, `blob's, influence the dynamics. Understanding how these quantities change with various confining geometries will lead to a deeper understanding of biological structures and glass formation. Work supported by NSF-DMR 0403997.
Generalized equipartition theorem and confining walls
NASA Astrophysics Data System (ADS)
Rey, Rossend
2015-06-01
It is shown that the generalized equipartition theorem as applied to the momentum may fail, even though the usual conditions of validity are met. This failure is linked to the nature of the confining walls, with ideal walls constituting a singular case. The corresponding analysis illustrates the use of proper sets of canonical coordinates, and the utility of canonical transformations other than point transformations.
Degenerate crystals from colloidal dimers under confinement.
Muangnapoh, Kullachate; Avendaño, Carlos; Escobedo, Fernando A; Liddell Watson, Chekesha M
2014-12-28
Colloidal aperiodic phases (i.e., entropy stabilized degenerate crystals, DCs) are realized via self-assembly of hollow fluorescent silica dimers under wedge-cell confinement. The dimer building blocks approximate two tangent spheres and their arrangements are studied via laser scanning confocal microscopy. In the DCs, the individual lobes tile a lattice and five distinct DC arrangements with square, triangular or rectangular layer symmetry are determined as a function of confinement height. Moreover, Monte Carlo simulations are used to construct the phase diagram for DCs up to two layer confinements and to analyze structural order in detail. Just as for spheres, the DC structural transitions under confinement are attributed to the ability or frustration to accommodate an integral number of particle layers between hard walls. Unlike spheres, dimers can also experience transitions involving changes in orientation. DCs are among the unconventional structures (e.g., semi-regular tilings, quasicrystals, plastic crystals) expected to enhance the properties of photonic solids. PMID:25366128
SIGNIFICANCE OF MHD EFFECTS IN STELLARATOR CONFINEMENT
Hudson, Stuart
and LHD on the future stellarator pro- gram will be discussed, including the relationship to tokamak milestone in future fusion re- search based on magnetic confinement. The considerable progress achieved engineering" has consti- tuted an innovative approach to meet desired physics*E-mail: arthur
Beam optics in inertial electrostatic confinement fusion
Masami Ohnishi; Chikara Hoshino; Kiyoshi Yoshikawa; Kai Masuda; Yasushi Yamamoto
2000-01-01
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
Inertial electrostatic confinement for fusion applications
R. A. Nebel; C. P. Munson; W. G. Rellergert; M. D. Sekora
2003-01-01
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.
Negative ions in inertial electrostatic confinement devices
D. R. Boris; J. F. Santarius; G. L. Kulcinski
2009-01-01
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,
Transitions Within a Vertically Confined Plasma Crystal
Ke Qiao; Truell Hyde
2004-01-01
Dusty plasmas consist of an ionized gas containing small (usually negatively charged) particles. Dusty plasmas are of interest in both astrophysics and space physics as well as in research in plasma processing and nanofabrication. In this work, the formation of plasma crystals confined in an external one-dimensional parabolic potential well is simulated for a normal experimental environment employing a computer
Confinement enclosure, notably for a nuclear reactor
Costes, D.
1983-07-26
A confinement enclosure is disclosed notably for a nuclear reactor, of the type consisting of reinforced, possibly prestressed concrete, comprising in the body of the wall a drainage network consisting of tubular channels provided in the concrete, wherein the tubular channels of the drainage network, which may be grouped in sub-groups, are connected to a system of filters located inside the enclosure.
cap alpha. Particle confinement in compact tori
Bozhokin
1986-01-01
The motion of high-energy ..cap alpha.. particles in compact tori is studied. The classically accessible regions of motion of charged particles are found. The conditions are formulated under which the ..cap alpha.. particles produced in fusion reactions are absolutely confined. An ..cap alpha.. particle starting in a region enclosed by a ''critical'' surface will never, in the course of its
Target plane imager for inertial confinement fusion
C. D. Swift; E. S. Bliss; W. A. Jones; L. G. Seppala
1985-01-01
The Nova laser, completed in December 1984 at Lawrence Livermore National Laboratory, is being used to conduct inertial confinement fusion experiments. It is capable of focusing more than 100 kJ of energy on small fusion targets. This paper discusses an optical system called the target plane imager that is used during the beam alignment phase of these experiments. The TPI
Cold Neutrons Confined in External Fields
Stefano Gandolfi; Joe Carlson; Steven C. Pieper
2010-01-01
Advances in computational techniques and facilities now allow us to calculate the properties of N=8 to 54 neutrons with realistic interactions confined in external fields. By examining the shell structure, spin orbit, and pairing properties of these systems we can provide input to constrain nuclear density functionals, particularly their properties in the extreme isospin limit where the density functionals are
Nuclear diagnostics for inertial confinement fusion implosions
Murphy, T.J.
1997-11-01
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.
Measurements of uranium mass confined in high density plasmas
NASA Technical Reports Server (NTRS)
Stoeffler, R. C.
1976-01-01
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.
Layer-resolved relaxation dynamics of confined water analyzed through subnanometer shear measurement
NASA Astrophysics Data System (ADS)
Kageshima, Masami
2014-09-01
The relaxation dynamics of thin water layers confined between hydrophilic surfaces was analyzed through shear relaxation measurement at room temperature. With the well-characterized shear motion of atomic force microscopy (AFM) probe with subnanometer amplitude, the viscoelastic response of water confined between hydrophilic substrate and probe was measured. Obtained data showed a stepwise variation with a typical spacing of water monolayer thickness. Relaxation time for water monolayer and bilayer derived from viscoelasticity exhibited a marked decrease with strain rate. A slightly faster relaxation of the bilayer than that of the monolayer was observed. The lower limit for the intrinsic thermal relaxation time was roughly evaluated to be as long as 0.2 ms. The possibility of a glassy state at room temperature is discussed considering the effects of intramolecular hydrogen bonds, of the hydrophilicity of the confining surfaces, and of the compressive force.
Phase Transformations in Confined Nanosystems
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
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.
Polar Confinement of Saturn's Magnetosphere Revealed by in-situ Cassini Observations
Pilkington, Nathan M; Arridge, Christopher S; Masters, Adam; Sergis, Nick; Coates, Andrew J; Dougherty, Michele K
2014-01-01
Plasma rotation plays a large role in determining the size and shape of Saturn's disc-like magnetosphere. A magnetosphere more confined to the equator in the polar regions is expected as a result of the interaction between this type of obstacle and the solar wind. In addition, at times away from equinox, a north-south asymmetry is expected where the magnetopause will be further confined in one hemisphere but less confined in the opposite hemisphere. Examining the extent of this confinement has been limited by a lack of high-latitude spacecraft observations. Here, for the first time, direct evidence for polar confinement of Saturn's magnetopause has been observed using in-situ data obtained by the Cassini spacecraft during a series of high-inclination orbits between 2007 and 2009. Following techniques established by previous authors, we assume an equilibrium between the solar wind dynamic pressure (which Cassini is generally unable to measure directly), and the magnetic plus plasma pressure inside the magnetos...
Ion confinement and transport in a toroidal plasma with externally imposed radial electric fields
NASA Technical Reports Server (NTRS)
Roth, J. R.; Krawczonek, W. M.; Powers, E. J.; Kim, Y. C.; Hong, H. Y.
1979-01-01
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.
Cho, Jae-Hie [ORNL; Smith, Gregory Scott [ORNL; Hamilton, William A. [ANSTO; Mulder, D. [University of California, Davis; Kuhl, T. L. [University of California, Davis; Mays, Jimmy [ORNL
2008-01-01
In this paper, we describe the construction of a new neutron surface force confinement cell (NSFCC). The NSFCC is equipped with hydraulically powered in-situ, temporally stable, force control system for simultaneous neutron reflectometry studies of nano-confined complex fluid systems. Test measurements with deuterated toluene confined between two opposing diblock copolymer (polystyrene + poly 2-vinylpyridine) coated quartz substrates demonstrate the capabilities of the NSFCC. With increasing hydraulically-applied force, a series of well-defined decreasing separations were observed from neutron reflectivity measurements. No noticeable changes in the hydraulic pressure used for controlling the surface separation were observed during the measurements, demonstrating the high stability of the apparatus. This newly designed NSFCC introduces a higher level of control for studies of confinement and consequent finite size effects on nano-scale structure in a variety of complex fluid and soft condensed matter systems.
Diffusion and surface excess of a confined nanoswimmer dispersion
NASA Astrophysics Data System (ADS)
Xiao, Song; Wang, Zhengjia; Chen, Hsuan-Yi; Sheng, Yu-Jane; Tsao, Heng-Kwong
2014-11-01
The diffusivity and surface excess of nanoswimmers which are confined in two plates with the separation H are explored by dissipative particle dynamics. Both mean squared displacement and velocity autocorrelation function methods are used to study the diffusive behavior of nanoswimmers with the Brownian diffusivity D0 and the results obtained from both methods are consistent. The active diffusivity of confined nanoswimmers (D - D0) depends on the wall separation, swimming speed va, and run time ?. Our simulation results show that (D-D0)/va2? is a function of va?/H. The reduction in the diffusivity of active colloids is more significant than that of passive particles. The distribution of nanoswimmers between two parallel walls is acquired and two regions can be identified. The accumulation of nanoswimmers near walls is quantitatively described by the surface excess ?. It is found that ? grows as the nanoswimmer concentration cb, swimming speed va, and run time ? are increased. The coupling between the ballistic trajectory of nanoswimmers and the walls results in nanoswimmer accumulation. The simulation outcomes indicate that ?/Hcb is a function of H/va?.
28 CFR 115.263 - Reporting to other confinement facilities.
Code of Federal Regulations, 2014 CFR
2014-07-01
...confinement facilities. 115.263 Section 115.263 Judicial Administration DEPARTMENT OF JUSTICE (CONTINUED) PRISON RAPE ELIMINATION ACT NATIONAL STANDARDS Standards for Community Confinement Facilities Official Response Following A...
28 CFR 115.263 - Reporting to other confinement facilities.
Code of Federal Regulations, 2013 CFR
2013-07-01
...confinement facilities. 115.263 Section 115.263 Judicial Administration DEPARTMENT OF JUSTICE (CONTINUED) PRISON RAPE ELIMINATION ACT NATIONAL STANDARDS Standards for Community Confinement Facilities Official Response Following A...
Reorientation and Solvation Dynamics of Bulk and Confined Alcohols
Vartia, Anthony Andrew
2012-12-31
of the additional timescales, appear in free energy profiles for reorientation, solvent viscosity must also be considered. Ethanol and a Stockmayer model solute were confined within a roughly cylindrical silica pore to investigate the effect of confinement...
System Description for the Double Shell Tank (DST) Confinement System
ROSSI, H.
2000-01-12
This document provides a description of the Double-Shell Tank (DST) Confinement System. This description will provide a basis for developing functional, performance and test requirements (i.e., subsystem specification), as necessary, for the DST Confinement System.
Interpretation of earth tide response of three deep, confined aquifers
Narasimhan, T.N.; Kanehiro, B.Y.; Witherspoon, P.A.
1984-03-10
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.
Quantum Confined Silicon Clathrate Quantum Dots
NASA Astrophysics Data System (ADS)
Lusk, Mark; Brawand, Nicholas
2013-03-01
Silicon (Si) allotropes can be synthesized in such a way that tetrahedrally bonded atoms form cage-like structures with bulk mechanical and opto-electronic properties distinct from those of diamond silicon (dSi). We use DFT, supplemented with many-body Green function analysis, to explore the structural stability of clathrate Si quantum dots (QDs) and to characterize their confinement as a function of crystal symmetry and size. Our results show that that there is a simple relationship between the confinement character of the QDs and the effective mass of the associated bulk crystals. Clathrate QDs and dSiQDs of the same size can exhibit differences of gap energies by as much as 2 eV. This offers the potential of synthesizing Si dots on the order of 1 nm that have optical gaps in the visible range but that do not rely on high-pressure routes such as those explored for the metastable BC8 and R8 phases. These results prompt the question as to how minimal quantum confinement can be in dots composed of Si. More broadly, clathrate QDs can in principle be synthesized for a wide range of semiconductors, and the design space can be further enriched via doping. Silicon (Si) allotropes can be synthesized in such a way that tetrahedrally bonded atoms form cage-like structures with bulk mechanical and opto-electronic properties distinct from those of diamond silicon (dSi). We use DFT, supplemented with many-body Green function analysis, to explore the structural stability of clathrate Si quantum dots (QDs) and to characterize their confinement as a function of crystal symmetry and size. Our results show that that there is a simple relationship between the confinement character of the QDs and the effective mass of the associated bulk crystals. Clathrate QDs and dSiQDs of the same size can exhibit differences of gap energies by as much as 2 eV. This offers the potential of synthesizing Si dots on the order of 1 nm that have optical gaps in the visible range but that do not rely on high-pressure routes such as those explored for the metastable BC8 and R8 phases. These results prompt the question as to how minimal quantum confinement can be in dots composed of Si. More broadly, clathrate QDs can in principle be synthesized for a wide range of semiconductors, and the design space can be further enriched via doping. NSF Renewable Energy Materials Research Science and Engineering Center (REMRSEC) and the Golden Energy Computing Organization (GECO)
Inertial electrostatic confinement: Theoretical and experimental studies of spherical devices
Ryan Meyer
2007-01-01
Inertial Electrostatic Confinement (IEC) is a means to confine ions for fusion purposes with electrostatic fields in a converging geometry. Its engineering simplicity makes it appealing when compared to magnetic confinement devices. It is hoped that such a device may one day be a net energy producer, but it has near term applications as a neutron generator. We study spherical
Author's personal copy Protein folding in confined and crowded environments
Weston, Ken
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
Concrete Cylinders Confined with Basalt Fibre Reinforced Polymer Eythor Thorhallsson
Karlsson, Brynjar
1 Concrete Cylinders Confined with Basalt Fibre Reinforced Polymer Eythor Thorhallsson M that was done on concrete cylinders confined with basalt fibre reinforced polymer (BFRP) and examination of its of more ductile behaviour. Key words: Concrete, confinement, basalt, BFRP and strengthening. 1
Microstructure and viscoelasticity of confined semiflexible polymer networks
Bausch, Andreas
LETTERS Microstructure and viscoelasticity of confined semiflexible polymer networks M. M. A. E of polymers to external confinement has potential implications both for technology and for our understanding-filament fluctuations. Enforcing progressively narrower confinement is found to induce a reduction of polymer
Helium in confinement: the filling A Neutron Scattering investigation.
Glyde, Henry R.
Helium in confinement: the filling parameter. A Neutron Scattering investigation. Francesco Albergamo Institut Laue-Langevin, France Helium in confinement: the filling parameter. Â p.1/13 #12;outline introduction and motivation Helium in confinement: the filling parameter. Â p.2/13 #12;outline introduction
Industrial Applications to the Inertial Electrostatic Confinement Configuration
Elijah Martin; Steve Shannon; Mohamed Bourham
2009-01-01
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
Confined Turbulent Swirling Recirculating Flow Predictions. Ph.D. Thesis
NASA Technical Reports Server (NTRS)
Abujelala, M. T.
1984-01-01
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.
Effects of polydispersity on confined homopolymer melts: A Monte Carlo study
NASA Astrophysics Data System (ADS)
Rorrer, Nicholas A.; Dorgan, John R.
2014-12-01
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.
Waliser, Duane E.
TIIE CONFINED HELIUM EXPERlblENT(CI117X1: TtIE SUCCESSFULRErURN OFTHE LOWTEMPERATURE PLAFORM F the Confined Helium experiment (CHeX). The CHeX mission was a success because theLTPF functioned as expected temperatures near 2K. The LTPF hadflown two times prior tothismostrecentflight: in 1984 as theSuperfluid Helium
Applications of group-invariant analytic solutions to inertial confinement fusion
Coggeshall, S.V.
1992-01-01
Analytic solutions to 1-,2-, and 3-D hydrodynamics are presented which can be applied to specific aspects of Inertial Confinement Fusion target evolutions. These solutions include drive source time profiles for 1-D isentropic implosions, 2-D P{sub 2} asymmetric compressions, 1- and 2-D solutions for the stagnation phase of implosions, and a 3-D spinning (mixing) solution.
Applications of group-invariant analytic solutions to inertial confinement fusion
Coggeshall, S.V.
1992-09-01
Analytic solutions to 1-,2-, and 3-D hydrodynamics are presented which can be applied to specific aspects of Inertial Confinement Fusion target evolutions. These solutions include drive source time profiles for 1-D isentropic implosions, 2-D P{sub 2} asymmetric compressions, 1- and 2-D solutions for the stagnation phase of implosions, and a 3-D spinning (mixing) solution.
Applications of group-invariant analytic solutions to inertial confinement fusion
S. V. Coggeshall
1992-01-01
Analytic solutions to 1-,2-, and 3-D hydrodynamics are presented which can be applied to specific aspects of inertial confinement fusion target evolutions. These solutions include drive source time profiles for 1-D isentropic implosions, 2-D P(sub 2) asymmetric compressions, 1- and 2-D solutions for the stagnation phase of implosions, and a 3-D spinning (mixing) solution.
Inward transport of a toroidally confined plasma subject to strong radial electric fields
NASA Technical Reports Server (NTRS)
Roth, J. R.; Krawczonek, W. M.; Powers, E. J.; Hong, J.; Kim, Y. H.
1977-01-01
Digitally implemented spectral analysis techniques were used to investigate the frequency-dependent fluctuation-induced particle transport across a toroidal magnetic field. When the electric field pointed radially inward, the transport was inward and a significant enhancement of the plasma density and confinement time resulted.
Victor Adrian Chiriac; Jorge Luis Rosales
2006-01-01
The unsteady laminar flow and heat transfer characteristics for a pair of opposed confined impinging air jets in a channel were studied numerically. The space and time-averaged heat transfer coefficients for a pair of heat sources arranged at different locations on opposite target walls was determined together with the oscillating jet frequency. The present study continues the authors' previous investigations,
Inertial Confinement Fusion quarterly report, April--June 1995. Volume 5, No. 3
NONE
1995-12-31
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.
Observation of the Dynamical Structure of Turbulence in Plasma Confined by a Dipole Magnetic Field
Mauel, Michael E.
Observation of the Dynamical Structure of Turbulence in Plasma Confined by a Dipole Magnetic Field in time and cause chaotic plasma fluctuations. The predominance of large scale structures represents energy cascade and a linear damping of small scale structures. PACS numbers: 52.35Mw, 52.35.Ra, 52.55.Hc
Capture and Confinement Stress in White Sucker Exposed to Bleached Kraft Pulp Mill Effluent
J. J. Jardine; G. J. Van Der Kraak; K. R. Munkittrick
1996-01-01
This study evaluates the effects of handling and confinement stress and a 3-day recovery period on a number of biochemical parameters used to monitor exposure of fish to bleached kraft mill effluent (BKME). Plasma was collected at four times of the day from male and female white sucker subjected to four levels of handling stress during their spawning migration at
Type II ELMy H modes on ASDEX Upgrade with good confinement at high density
J. Stober; M. Maraschek; G. D. Conway; O. Gruber; A. Herrmann; A. C. C. Sips; W. Treutterer; H. Zohm
2001-01-01
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
Spiral precipitation patterns in confined chemical gardens.
Haudin, Florence; Cartwright, Julyan H E; Brau, Fabian; De Wit, A
2014-12-01
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
Atypical quantum confinement effect in silicon nanowires.
Sorokin, Pavel B; Avramov, Pavel V; Chernozatonskii, Leonid A; Fedorov, Dmitri G; Ovchinnikov, Sergey G
2008-10-01
The quantum confinement effect (QCE) of linear junctions of silicon icosahedral quantum dots (IQD) and pentagonal nanowires (PNW) was studied using DFT and semiempirical AM1 methods. The formation of complex IQD/PNW structures leads to the localization of the HOMO and LUMO on different parts of the system and to a pronounced blue shift of the band gap; the typical QCE with a monotonic decrease of the band gap upon the system size breaks down. A simple one-electron one-dimensional Schrodinger equation model is proposed for the description and explanation of the unconventional quantum confinement behavior of silicon IQD/PNW systems. On the basis of the theoretical models, the experimentally discovered deviations from the typical QCE for nanocrystalline silicon are explained. PMID:18785695
Institutional games played by confined juveniles.
Bartollas, C; Sieverdes, C M
1983-01-01
This study examined the games played by 561 juvenile offenders confined in six coeducational correctional facilities in one state. The types of games these residents used against staff and peers within the confines of the institution varied considerably. The study documented nineteen games used by males and females, twelve to deal with staff and seven to deal with peers. The games were defined as therapeutic games, material games, psychological games, and physical games. Peer-oriented games included attention-seeking activities and a variety of dominance games. Additionally, these games were described and tabulated according to the sex and race of the residents. The conclusion was that game-playing behavior was no less frequent in coeducational institutions than it was in single-sex institutions. PMID:6650271
Micelle fragmentation and wetting in confined flow
Mona Habibi; Colin Denniston; Mikko Karttunen
2014-09-30
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.
Inertial electrostatic confinement (IEC) neutron sources
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
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.
Morphogenesis of filaments growing in flexible confinements
Roman Vetter; Falk K. Wittel; Hans J. Herrmann
2014-07-17
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.
Confinement and stability of a Crystalline Beam
Ruggiero, A.G.
1993-05-10
This technical report defines and describes a Crystalline Beam. This is an ordered state of matter made of electrically charged ions which are moving together in a storage ring with very high density and small velocity spread. In particular, the paper analyses the requirements for the confinement and the stability of the Beam. It is demonstrated that a storage ring made of one circular weak-focusing magnet, similar to a Betatron, is the most suitable for the confinement and stability of the Crystalline Beam. The disruptive effects of drift insertions have also been investigated. Requirements on final densities and velocity spreads are also calculated and reported. A matrix formalism is developed for the design of the storage ring. The important issue of the disruption caused by the curvature of the closed trajectory is not here discussed; it is the subject of a subsequent paper.
Compaction of granular material inside confined geometries
Benjy Marks; Bjørnar Sandnes; Guillaume Dumazer; Jon Alm Eriksen; Knut Jørgen Måløy
2015-05-15
In both nature and engineering, loosely packed granular materials are often compacted inside confined geometries. Here, we explore such behaviour in a quasi-two dimensional geometry, where parallel rigid walls provide the confinement. We use the discrete element method to investigate the stress distribution developed within the granular packing as a result of compaction due to the displacement of a rigid piston. We observe that the stress within the packing increases exponentially with the length of accumulated grains, and show an extension to current analytic models which fits the measured stress. The micromechanical behaviour is studied for a range of system parameters, and the limitations of existing analytic models are described. In particular, we show the smallest sized systems which can be treated using existing models. Additionally, the effects of increasing piston rate, and variations of the initial packing fraction, are described.
Dynamics of two-dimensional monolayer water confined in hydrophobic and charged environments
NASA Astrophysics Data System (ADS)
Kumar, Pradeep; Han, Sungho
2012-09-01
We perform molecular dynamics simulations to study the effect of charged surfaces on the intermediate and long time dynamics of water in nanoconfinements. Here, we use the transferable interaction potential with five points (TIP5P) model of a water molecule confined in both hydrophobic and charged surfaces. For a single molecular layer of water between the surfaces, we find that the temperature dependence of the lateral diffusion constant of water up to very high temperatures remains Arrhenius with a high activation energy. In case of charged surfaces, however, the dynamics of water in the intermediate time regime is drastically modified presumably due to the transient coupling of dipoles of water molecules with electric field fluctuations induced by charges on the confining surfaces. Specifically, the lateral mean square displacements display a distinct super-diffusive behavior at intermediate time scale, defined as the time scale between ballistic and diffusive regimes. This change in the intermediate time-scale dynamics in the charged confinement leads to the enhancement of long-time dynamics as reflected in increasing diffusion constant. We introduce a simple model for a possible explanation of the super-diffusive behavior and find it to be in good agreement with our simulation results. Furthermore, we find that confinement and the surface polarity enhance the low frequency vibration in confinement compared to bulk water. By introducing a new effective length scale of coupling between translational and orientational motions, we find that the length scale increases with the increasing strength of the surface polarity. Further, we calculate the correlation between the diffusion constant and the excess entropy and find a disordering effect of polar surfaces on the structure of water. Finally, we find that the empirical relation between the diffusion constant and the excess entropy holds for a monolayer of water in nanoconfinement.
Effect of internal magnetic structure on energetic ion confinement in tokamaks
Roberts, D.W.; Kaita, R.; Levinton, F.; Asakura, N.; Bell, R.; Chance, M.; Duperrex, P.; Gammel, G.; Hatcher, R.; Holland, A.; Kaye, S.; Kessel, C.; Kugel, H.; LeBlanc, B.; Manickam, J.; Okabayashi, M.; Paul, S.; Pomphrey, N.; Powell, E.; Sauthoff, N.; Sesnic, S.; Takahashi, H.; White, R. (Plasma Physics Laboratory, Princeton University, Princeton, New Jersey 08543 (United States))
1993-08-16
For the tokamak magnetic confinement concept, theory has predicted a distinct relationship between the plasma shape, the internal magnetic structure, and the presence or absence of fast ion losses in the presence of plasma instabilities. We have, for the first time, carried out measurements of the magnetic safety factor profile, [ital q]([ital r]), in plasmas unstable to a specific instability, the so-called fishbone'' mode. The experimental equilibria reconstructed from these data have been used to demonstrate that when the plasma is unstable to fishbones, the fast ion confinement properties depend strongly on the radius of the magnetic surface where [ital q]([ital r])=1.
Dynamics and statistics of wave-particle interactions in a confined geometry
NASA Astrophysics Data System (ADS)
Gilet, Tristan
2014-11-01
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.
Dynamics of a particle confined in a two-dimensional dilating and deforming domain
NASA Astrophysics Data System (ADS)
Anzà, Fabio; Di Martino, Sara; Messina, Antonino; Militello, Benedetto
2015-06-01
Some recent results concerning a particle confined in a one-dimensional box with moving walls are briefly reviewed. By exploiting the same techniques used for the 1D problem, we investigate the behavior of a quantum particle confined in a two-dimensional box (a 2D billiard) whose walls are moving by recasting the relevant mathematical problem with moving boundaries in the form of a problem with fixed boundaries and time-dependent Hamiltonian. Changes of the shape of the box are shown to be important, as it clearly emerges from the comparison between the ‘pantographic’ case (same shape of the box through the entire process) and the case with deformation.
Enhanced confinement regimes and control technology in the DIII-D tokamak
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
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.
Light ion driven inertial confinement fusion
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
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
Yukawa particles in a confining potential
Girotto, Matheus, E-mail: matheus.girotto@ufrgs.br; Levin, Yan, E-mail: levin@if.ufrgs.br [Instituto de Física, Universidade Federal do Rio Grande do Sul, Caixa Postal 15051, CEP 91501-970, Porto Alegre, RS (Brazil); Santos, Alexandre P. dos, E-mail: alexandreps@ufcspa.edu.br [Departamento de Educação e Informação em Saúde, Universidade Federal de Ciências da Saúde de Porto Alegre, 90050-170, Porto Alegre, RS (Brazil); Departamento de Física, Universidade Federal de Santa Catarina, 88040-900, Florianópolis, Santa Catarina (Brazil); Colla, Thiago, E-mail: thiago.colla@ufrgs.br [Faculty of Physics, University of Vienna, Boltzmanngasse 5, A-1090 Vienna (Austria)
2014-07-07
We study the density distribution of repulsive Yukawa particles confined by an external potential. In the weak coupling limit, we show that the mean-field theory is able to accurately account for the particle distribution. In the strong coupling limit, the correlations between the particles become important and the mean-field theory fails. For strongly correlated systems, we construct a density functional theory which provides an excellent description of the particle distribution, without any adjustable parameters.
Target support for inertial confinement fusion
Schultz, K.R.
1995-08-01
General Atomics (GA) plays an important industrial support role for the US Inertial Confinement Fusion (ICF) program in the area of target technology. This includes three major activities: target fabrication support, target handling systems development, and target chamber design. The work includes target fabrication for existing ICF experiments, target and target system development for future experiments, and target research and target chamber design for experiments on future machines, such as the National Ignition Facility (NIF).
Waveforms Measured in Confined Thermobaric Explosion
Reichenbach, H; Neuwald, P; Kuhl, A L
2007-05-04
Experiments with 1.5-g Shock-Dispersed-Fuel (SDF) charges have been conducted in six different chambers. Both flake Aluminum and TNT were used as the fuel. Static pressure gauges on the chamber wall were the main diagnostic. Waveforms for explosions in air were significantly larger than those in nitrogen - thereby demonstrating a strong thermobaric (combustion) effect. This effect increases as the confinement volume decreases and the mixture richness approaches 1.
Deuterium anions in inertial electrostatic confinement devices
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
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.
Pulse star inertial confinement fusion reactor
J. A. Blink; W. J. Hogan
1985-01-01
Pulse Star is a pool-type inertial confinement fusion reactor that emphasizes low cost and high safety levels. The reactor consists of a vacuum chamber (belljar) submerged in a compact liquid metal (Li17Pb83 or lithium) pool which also contains the heat exchangers and liquid metal pumps. The shielding efficiency of the liquid metal pool is high enough to allow hands-on maintenance
Chapter 2: Plasma confinement and transport
NASA Astrophysics Data System (ADS)
Doyle, E. J.; Houlberg, W. A.; Kamada, Y.; Mukhovatov, V.; Osborne, T. H.; Polevoi, A.; Bateman, G.; Connor, J. W.; Cordey, J. G.; Fujita, T.; Garbet, X.; Hahm, T. S.; Horton, L. D.; Hubbard, A. E.; Imbeaux, F.; Jenko, F.; Kinsey, J. E.; Kishimoto, Y.; Li, J.; Luce, T. C.; Martin, Y.; Ossipenko, M.; Parail, V.; Peeters, A.; Rhodes, T. L.; Rice, J. E.; Roach, C. M.; Rozhansky, V.; Ryter, F.; Saibene, G.; Sartori, R.; Sips, A. C. C.; Snipes, J. A.; Sugihara, M.; Synakowski, E. J.; Takenaga, H.; Takizuka, T.; Thomsen, K.; Wade, M. R.; Wilson, H. R.; ITPA Transport Physics Topical Group; Confinement Database, ITPA; Modelling Topical Group; Pedestal, ITPA; Edge Topical Group
2007-06-01
The understanding and predictive capability of transport physics and plasma confinement is reviewed from the perspective of achieving reactor-scale burning plasmas in the ITER tokamak, for both core and edge plasma regions. Very considerable progress has been made in understanding, controlling and predicting tokamak transport across a wide variety of plasma conditions and regimes since the publication of the ITER Physics Basis (IPB) document (1999 Nucl. Fusion 39 2137-2664). Major areas of progress considered here follow. (1) Substantial improvement in the physics content, capability and reliability of transport simulation and modelling codes, leading to much increased theory/experiment interaction as these codes are increasingly used to interpret and predict experiment. (2) Remarkable progress has been made in developing and understanding regimes of improved core confinement. Internal transport barriers and other forms of reduced core transport are now routinely obtained in all the leading tokamak devices worldwide. (3) The importance of controlling the H-mode edge pedestal is now generally recognized. Substantial progress has been made in extending high confinement H-mode operation to the Greenwald density, the demonstration of Type I ELM mitigation and control techniques and systematic explanation of Type I ELM stability. Theory-based predictive capability has also shown progress by integrating the plasma and neutral transport with MHD stability. (4) Transport projections to ITER are now made using three complementary approaches: empirical or global scaling, theory-based transport modelling and dimensionless parameter scaling (previously, empirical scaling was the dominant approach). For the ITER base case or the reference scenario of conventional ELMy H-mode operation, all three techniques predict that ITER will have sufficient confinement to meet its design target of Q = 10 operation, within similar uncertainties.
Evaporation rate of water in hydrophobic confinement
Sharma, Sumit; Debenedetti, Pablo G.
2012-01-01
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
Fast ion JET diagnostics: confinement and losses
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
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.
Reverse Monte Carlo modeling in confined systems
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
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.
Simulating tumor growth in confined heterogeneous environments
NASA Astrophysics Data System (ADS)
Gevertz, Jana L.; Gillies, George T.; Torquato, Salvatore
2008-09-01
The holy grail of computational tumor modeling is to develop a simulation tool that can be utilized in the clinic to predict neoplastic progression and propose individualized optimal treatment strategies. In order to develop such a predictive model, one must account for many of the complex processes involved in tumor growth. One interaction that has not been incorporated into computational models of neoplastic progression is the impact that organ-imposed physical confinement and heterogeneity have on tumor growth. For this reason, we have taken a cellular automaton algorithm that was originally designed to simulate spherically symmetric tumor growth and generalized the algorithm to incorporate the effects of tissue shape and structure. We show that models that do not account for organ/tissue geometry and topology lead to false conclusions about tumor spread, shape and size. The impact that confinement has on tumor growth is more pronounced when a neoplasm is growing close to, versus far from, the confining boundary. Thus, any clinical simulation tool of cancer progression must not only consider the shape and structure of the organ in which a tumor is growing, but must also consider the location of the tumor within the organ if it is to accurately predict neoplastic growth dynamics.
Kimichika Fukushima; Hikaru Sato
2014-10-04
This article reports an explicit function form for confining classical Yang-Mills vector potentials and quantum fluctuations around the classical field. The classical vector potential, which is composed of a confining localized function and an unlocalized function, satisfies the classical Yang-Mills equation. The confining localized function contributes to the Wilson loop, while the unlocalized function makes no contribution to this loop. The confining linear potential between a heavy fermion and antifermion is due to (1) the Lie algebra and (2) the form of the confining localized function which has opposite signs at the positions of the particle and antiparticle along the Wilson loop in the time direction. Some classical confining parts of vector potentials also change sign on inversion of the coordinates of the axis perpendicular to the axis joining the two particles. The localized parts of the vector potentials are squeezed around the axis connecting the two particles, and the string tension of the confining linear potential is derived. Quantum fluctuations are formulated using a field expression in terms of local basis functions in real spacetime. The quantum path integral gives the Coulomb potential between the two particles in addition to the linear potential due to the classical fields.
Single particle dynamics of water confined in a hydrophobically modified MCM-41-S nanoporous matrix
NASA Astrophysics Data System (ADS)
Faraone, Antonio; Liu, Kao-Hsiang; Mou, Chung-Yuan; Zhang, Yang; Chen, Sow-Hsin
2009-04-01
The single particle dynamics of water confined in a hydrophobically modified MCM-41-S sample has been studied using three high resolution quasielastic neutron scattering spectrometers in the temperature range from 300 to 210 K. A careful modeling of the dynamics allowed us to obtain good agreement among the results obtained with the three instruments, which have very different energy resolutions. The picture arising from the data is that, because of the heterogenous environment experienced by the water molecules, the dynamics show a broad distribution of relaxation times. However, the Fickian diffusive behavior is retained. In the investigated temperature range we found no evidence of the dynamic crossover, from a non-Arrhenius to an Arrhenius behavior, which was detected for water confined in hydrophilic MCM-41-S. This finding is in agreement with what was reported by Chu et al. [Phys. Rev. E 76, 021505 (2007)] for water confined in other hydrophobic confining media that the dynamic crossover takes place at a much lower temperature. The results reported in the paper help clarify the role that the chemical interaction between the water molecules and the walls of the confining host plays in determining the characteristics of the water dynamics, as compared to purely geometric constraints such as the size and shape of the pores.
Distribution of transverse chain fluctuations in harmonically confined semiflexible polymers
NASA Astrophysics Data System (ADS)
Sharma, Rati; Cherayil, Binny J.
2012-05-01
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.
Measurements of classical fast ion confinement with fusion product diagnostics
NASA Astrophysics Data System (ADS)
Magee, Richard; Clary, Ryan; Korepanov, Sergey; Smirnov, Artem; Garate, Eusebio; Allfrey, Ian; Valentine, Travis; the TAE Team
2014-10-01
Neutral beam injected fast ions play a critical role in the C-2 field reversed configuration plasma, helping to sustain magnetic flux against resistive decay and heating the plasma via Coulomb collisions. The fast ions are well confined; due to the relatively low magnetic field strength the fast ions have large, machine-size orbits that permit them to average over otherwise deleterious fluctuations. These same orbits however, have large radial excursions that result in greater interaction of fast ions with edge neutrals and a greater potential for charge exchange losses. In this presentation, the fast ion slowing down time is determined from the decay in neutron flux following beam termination. It is found that the slowing down scaling is close to classical (i.e., ? ~Te3/2/ne) and that charge exchange losses are only significant for ions with 1.5× the nominal injection energy. We will also present initial data from a newly installed proton detector, which complements the temporal resolution of the neutron detector with spatial resolution. The detector will be used to diagnose the axial profile of confined fast ions.
Confinement transitions in predator-prey models for tokamak plasmas
NASA Astrophysics Data System (ADS)
Dendy, Richard; Zhu, Hao; Chapman, Sandra
2013-10-01
Energy transport in tokamak plasmas is mainly determined by small-scale turbulence and larger coherent nonlinear structures, and their interactions. Zero-dimensional models of this offer a simple direct way of capturing the physical origins of enhanced energy confinement and transitions between regimes. The prime zero-dimensional paradigm is predator-prey. We have extended a three-variable (temperature gradient; microturbulence level; one class of coherent structure) model, by adding a fourth variable representing a second class of coherent structure. We investigate the degree of invariance of the phenomenology generated by the two models given this change. We compare the long-time behavior of the systems, their evolution to the final state, and their attractive fixed points and limit cycles. We explore the sensitivity of paths to attractors. Having thus confirmed that the model approach is robust, we investigate transitions to enhanced confinement regimes triggered by sharp changes in external heating, and relate this aspect of model phenomenology to tokamaks.
Initial confinement studies of ohmically heated plasmas in the Tokamak Fusion Test Reactor
Efthimion, P.C.; Bell, M.; Blanchard, W.R.; Bretz, N.; Cecchi, J.L.; Coonrod, J.; Davis, S.; Dylla, H.F.; Fonck, R.; Furth, H.P.
1984-06-01
Initial operation of the Tokamak Fusion Test Reactor (TFTR) has concentrated upon confinement studies of ohmically heated hydrogen and deuterium plasmas. Total energy confinement times (tau/sub E/) are 0.1 to 0.2 s for a line-average density range (anti n/sub e/) of 1 to 2.5 x 10/sup 19/ m/sup -3/ with electron temperatures of T/sub e/(o) approx. 1.2 to 2.2 keV, ion temperatures of T/sub i/(o) approx. 0.9 to 1.5 keV, and Z/sub eff/ approx. 3. A comparison of PLT, PDX, and TFTR plasma confinement supports a dimension-cubed scaling law.
Li, Min; Xu, Weixin; Zhang, John Z H; Xia, Fei
2014-12-01
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
Low beta confinement in a Polywell modelled with conventional point cusp theories
NASA Astrophysics Data System (ADS)
Carr, Matthew; Gummersall, David; Cornish, Scott; Khachan, Joe
2011-11-01
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.
Low beta confinement in a Polywell modelled with conventional point cusp theories
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
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.
Electron Energy Confinement for HHFW Heating and Current Drive Phasing on NSTX
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
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.
NASA Astrophysics Data System (ADS)
Murari, A.; Peluso, E.; Gelfusa, M.; Lupelli, I.; Gaudio, P.
2015-07-01
The extrapolation of the energy confinement time to the next generation of devices has been investigated both theoretically and experimentally for several decades in the tokamak community. Various scaling expressions have been proposed using dimensional and dimensionless quantities. They are all based on the assumption that the scalings are in power law form. In this paper, an innovative methodology is proposed to extract the scaling expressions for the energy confinement time in tokamaks directly from experimental databases, without any previous assumption about the mathematical form of the scalings. The approach to obtain the scaling expressions is based on genetic programming and symbolic regression. These techniques have been applied to the ITPA database of H-mode discharges and the results have been validated with a series of established statistical tools. The soundest results, using dimensional variables, are not in the form of power laws but contain a multiplicative saturation term. Also the scalings, expressed in terms of the traditional dimensionless quantities, are not in power law form and contain additive saturation terms. The extrapolation to ITER of both dimensional and dimensionless quantities indicate that the saturation effects are quite significant and could imply a non-negligible reduction in the confinement time to be expected in the next generation of devices. The results obtained with the proposed techniques therefore motivate a systematic revisiting of the scaling expressions for plasma confinement in tokamaks.
L- to H-mode power threshold and confinement characteristics of H-modes in KSTAR
NASA Astrophysics Data System (ADS)
Kim, Hyun-Seok; Jeon, Young-Mu; Ahn, Joon-Wook; Yoon, Si; Terzolo, Laurent; Kim, Ki; Na, Yong-Su; Kstar Team
2011-10-01
The KSTAR project has achieved H-mode with about 0.9 ~1.4 MW of NBI heating and about 0.25 MW of ECRH in the 3rd and 4th campaigns of KSTAR experiments. In this work, the L- to H-mode threshold power(PTH) , the energy confinement time(?E) and the confinement enhancement factor(H) were calculated in KSTAR. Firstly, in the procedure to calculate the power loss to the separatrix, the ohmic heating power, the fast ion loss power and the radiation loss power were simulated using a 1.5-D integrated plasma transport code, ASTRA and a Monte-Carlo code for NBI simulation, NUBEAM. With respect to PTH, a trend of discrepancy between the PTH of KSTAR and that of multi-machine empirical scaling was observed in the regime of relatively low plasma density. Secondly, in order to evaluate confinement of KSTAR H-modes, a Hexp was introduced defined as the ratio of total energy confinement time between the L-mode phase and the H-mode phase and compared with conventional H factors such as H89-p.
Energy confinement scaling in the low aspect ratio National Spherical Torus Experiment (NSTX)
NASA Astrophysics Data System (ADS)
Kaye, S. M.; Bell, M. G.; Bell, R. E.; Fredrickson, E. D.; LeBlanc, B. P.; Lee, K. C.; Lynch, S.; Sabbagh, S. A.
2006-10-01
Systematic and statistical studies have been conducted in order to develop an understanding of the parametric dependences of both the global and thermal energy confinement times at low aspect ratio in high power National Spherical Torus Experiment discharges. The global and thermal confinement times of both L- and H-mode discharges can exceed values given by H-mode scalings developed for conventional aspect ratio. Results of systematic scans in the H-mode indicate that the confinement times exhibit a nearly linear dependence on plasma current and a power degradation weaker than that observed at conventional aspect ratio. In addition, the dependence on the toroidal magnetic field is stronger than that seen in conventional aspect ratio tokamaks. This latter trend is also evident in statistical analyses of the available dataset. These statistical studies also indicate a weaker parametric dependence on plasma current than found in the systematic scans, due to correlations among the predictor variables. Regressions based on engineering variables, when transformed to dimensionless physics variables, indicate that the dependence of B?E on ?t can range from being negative to null. Regressions based directly on the dimensionless physics variables are inexact because of large correlations among these variables. Scatter in the confinement data, at otherwise fixed operating parameters, is found to be due to variations in ELM activity, low frequency density fluctuations and plasma shaping.
Confinement of a Dirac Particle to a Hard-Wall Confining Potential Induced by Noninertial Effects
NASA Astrophysics Data System (ADS)
Bakke, K.
2013-01-01
In this contribution, we discuss the influence of noninertial effects on a Dirac particle in the Minkowski spacetime by showing that the geometry of the manifold can play the role of a hard-wall confining potential. Thus, we discuss a limit case where the relativistic bound states can be achieved in analogous way to having a Dirac particle confined to a quantum dot. We discuss the application of this mathematical model in studies of noninertial effects on condensed matter systems described by the Dirac equation, and compare the nonrelativistic limit of the energy levels with the spectrum of energy of a spin-½ particle confined to a quantum dot [E. Tsitsishvili et al., Phys. Rev. B70 (2004) 115316].
NASA Astrophysics Data System (ADS)
Mohri, Akihiro; Yuyama, Tetsumori; Kiwamoto, Yasuhito; Yamazawa, Yohei; Michishita, Toshinori
1998-12-01
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.
NASA Astrophysics Data System (ADS)
Ahmad, Muhammad Raza; Jamil, Yasir; Qaiser Zakaria, M.; Hussain, Tousif; Ahmad, Riaz
2015-07-01
We introduce for the first time the novel idea of manipulating the momentum coupling coefficient using plasma confinement and shock wave reflection from the cavity walls. The plasma was confined using cylindrical geometries of various cavity aspect ratios to manipulate the momentum coupling coefficient (C m ). The Nd: YAG laser (532?nm, 5?ns pulse duration) was focused on the ferrite sample surface to produce plasma in a region surrounded by cylindrical cavity walls. The multiple reflections of the shockwaves from the cavity walls confined the laser-induced plasma to the central region of the cavity that subsequently resulted in a significant enhancement of the momentum coupling coefficient values. The plasma shielding effect has also been observed for particular values of laser fluencies and cavity aspect ratios. Compared with the direct ablation, the confined ablation provides an effective way to obtain high C m values.
Hershberger, P.; Hart, A.; Gregg, J.; Elder, N.; Winton, J.
2006-01-01
Capture of wild, juvenile herring Clupea pallasii from Puget Sound (Washington, USA) and confinement in laboratory tanks resulted in outbreaks of viral hemorrhagic septicemia (VHS), viral erythrocytic necrosis (VEN) and ichthyophoniasis; however, the timing and progression of the 3 diseases differed. The VHS epidemic occurred first, characterized by an initially low infection prevalence that increased quickly with confinement time, peaking at 93 to 98% after confinement for 6 d, then decreasing to negligible levels after 20 d. The VHS outbreak was followed by a VEN epidemic that, within 12 d of confinement, progressed from undetectable levels to 100% infection prevalence with >90% of erythrocytes demonstrating inclusions. The VEN epidemic persisted for 54 d, after which the study was terminated, and was characterized by severe blood dyscrasias including reduction of mean hematocrit from 42 to 6% and replacement of mature erythrocytes with circulating erythroblasts and ghost cells. All fish with ichthyophoniasis at capture died within the first 3 wk of confinement, probably as a result of the multiple stressors associated with capture, transport, confinement, and progression of concomitant viral diseases. The results illustrate the differences in disease ecology and possible synergistic effects of pathogens affecting marine fish and highlight the difficulty in ascribing a single causation to outbreaks of disease among populations of wild fishes. ?? Inter-Research 2006.
NASA Astrophysics Data System (ADS)
Neumann, R. F.; Bahiana, M.; Allende, S.; Escrig, J.; Altbir, D.
2012-01-01
The possibility of confining magnetic nanoparticles inside multisegmented nanotubes by using strong field gradients is considered by means of Monte Carlo simulations. The problem is reduced to the random walk performed by the nanoparticle on the energy landscape produced by the tube's magnetic field. The role of tube material, number of segments, and spacer thickness in the amount of time spent by the particle inside the tube is examined, concluding that it is possible to control the encapsulation time by using different architectures.
Clustering of branching Brownian motions in confined geometries
NASA Astrophysics Data System (ADS)
Zoia, A.; Dumonteil, E.; Mazzolo, A.; de Mulatier, C.; Rosso, A.
2014-10-01
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.
Nonvolatile semiconductor memory having three dimension charge confinement
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
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.
How spermatozoa come to be confined to surfaces.
Cosson, J; Huitorel, P; Gagnon, C
2003-01-01
In most detailed studies, sea urchin sperm movement has been analyzed mainly from observations of spermatozoa swimming at the interface between two media: water/air or water/glass. When spermatozoa are placed on a microscope slide, they rapidly appear to swim near those interfaces. The aim of this article is to determine how they become confined to the vicinity of surfaces. High-speed observations of moving spermatozoa reveal blurred portions in the flagellum images that propagate from base to tip, suggesting that flagellar waves contain an out-of-plane component. The model we have developed depicts how this tri-dimensional component tends to keep spermatozoa close to interfaces and, as a consequence, increases the time of contact between the egg surface and spermatozoa. PMID:12451595
Phase transitions in ultracold Bose gases confined in optical lattices
NASA Astrophysics Data System (ADS)
Caballero-Benítez, Santiago F.; Paredes, Rosario
2015-06-01
We address the study of quantum Bose fluids confined in optical lattices subject to the influence of a time varying disordered external potential. The aim is to elucidate the interplay among lattice structure, interparticle interactions and the influence of structural disorder on dynamical and stationary ground state properties. The analysis in quasi one-dimension systems is done combining both mean field and Bose–Hubbard schemes to capture the essence of the quantum many body problem. Our predictions include the manifestation of superfluid, Mott and Anderson-like phases. We also present a natural extension of our technique to investigate two-dimensions systems. A general panorama of the current studies in bosonic systems is also given.
Confined Dirac particles in a constant and tilted magnetic field
NASA Astrophysics Data System (ADS)
Alhaidari, Abdulaziz D.; Bahlouli, Hocine; Jellal, Ahmed
2015-04-01
We study the confinement of charged Dirac particles in a plane embedded in 3 + 1 space-time due to the presence of a constant magnetic field that is tilted on the given plane. We focus on the nature of the solutions of the Dirac equation and on how they depend on the choice of vector potential that gives rise to the magnetic field. In particular, we select a "Landau gauge" such that the momentum is conserved along the direction of the vector potential yielding spinor wave functions, which are localized in the plane containing the magnetic field and normal to the vector potential. These wave functions are expressed in terms of the Hermite polynomials. We point out the relevance of these findings to the relativistic quantum Hall effect and compare with the results obtained for a constant magnetic field normal to the plane in 2 + 1 dimensions.
Cation exchange dynamics confined in a synthetic clay mineral
NASA Astrophysics Data System (ADS)
Grassi, G.; Michels, L.; Rozynek, Z.; Altoé, M. A. S.; dos Santos, E. C.; da Fonseca, C. L. S.; Droppa, R.; Gholamipour-Shirazi, A.; Fossum, J. O.; da Silva, G. J.
2014-09-01
In this work we report X-Ray Diffraction (XRD) and Energy Dispersive X-Ray Spectroscopy (EDS) measurements to investigate the confined cation exchange process in saline aqueous suspensions of a synthetic clay mineral from Lithium-Fluorohectorite to Nickel-Fluorohectorite, as well as the reverse process from Nickel-Fluorohectorite to Lithium-Fluorohectorite and also from Lithium-Fluorohectorite to Sodium-Fluorohectorite. The dynamics of these cation exchanges was followed and it was observed that these processes can be faster than 1 minute. The results are compared to the observations on samples prepared by cation exchange procedures for which the exchange process was performed on the time-scale of months.
Integrated diagnostic analysis of inertial confinement fusion capsule performancea)
NASA Astrophysics Data System (ADS)
Cerjan, Charles; Springer, Paul T.; Sepke, Scott M.
2013-05-01
A conceptual model is developed for typical inertial confinement fusion implosion conditions that integrates available diagnostic information to determine the stagnation properties of the interior fill and surrounding shell. Assuming pressure equilibrium at peak compression and invoking radiative and equation-of-state relations, the pressure, density, and electron temperature are obtained by optimized fitting of the experimental output to smooth, global functional forms. Typical observational data that may be used includes x-ray self-emission, directional neutron time-of-flight signals, neutron yield, high-resolution x-ray spectra, and radiographic images. This approach has been validated by comparison with radiation-hydrodynamic simulations, producing semi-quantitative agreement. Model results implicate poor kinetic energy coupling to the hot core as the primary cause of the observed low thermonuclear burn yields.
Clustering of branching Brownian motions in confined geometries.
Zoia, A; Dumonteil, E; Mazzolo, A; de Mulatier, C; Rosso, A
2014-10-01
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
Confinement and focusing of geodesics in warped spacetimes
NASA Astrophysics Data System (ADS)
Kar, S.; Das Gupta, A.; Ghosh, S.; Nandan, H.
2014-03-01
We have explored certain characteristic features of test particle trajectories in five dimensional, warped bulk geometries with a single thick brane. After a brief introduction on such spacetimes, we have first discussed timelike geodesic motion. The geodesic equations, which reduce to a first order autonomous dynamical system, have been solved using analytical and numerical methods. We have demonstrated how a growing (decaying) warp factor leads to oscillatory (runaway) trajectories, suggesting confinement (deconfinement). Further, we have pointed out differences that arise when we have a cosmological brane and/or a time-dependent extra dimension. Next, we have moved on to the kinematics of geodesic congruences. The evolution of the kinematical variables (expansion, rotation and shear) along geodesic flows have been obtained using analytical and numerical approaches, with particular emphasis on the required conditions and occurence of geodesic focusing.
Sequential detection of temporal communities by estrangement confinement
Kawadia, Vikas; Sreenivasan, Sameet
2012-01-01
Temporal communities are the result of a consistent partitioning of nodes across multiple snapshots of an evolving network, and they provide insights into how dense clusters in a network emerge, combine, split and decay over time. To reliably detect temporal communities we need to not only find a good community partition in a given snapshot but also ensure that it bears some similarity to the partition(s) found in the previous snapshot(s), a particularly difficult task given the extreme sensitivity of community structure yielded by current methods to changes in the network structure. Here, motivated by the inertia of inter-node relationships, we present a new measure of partition distance called estrangement, and show that constraining estrangement enables one to find meaningful temporal communities at various degrees of temporal smoothness in diverse real-world datasets. Estrangement confinement thus provides a principled approach to uncovering temporal communities in evolving networks. PMID:23145317
Integrated diagnostic analysis of inertial confinement fusion capsule performance
Cerjan, Charles; Springer, Paul T.; Sepke, Scott M. [Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550 (United States)] [Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550 (United States)
2013-05-15
A conceptual model is developed for typical inertial confinement fusion implosion conditions that integrates available diagnostic information to determine the stagnation properties of the interior fill and surrounding shell. Assuming pressure equilibrium at peak compression and invoking radiative and equation-of-state relations, the pressure, density, and electron temperature are obtained by optimized fitting of the experimental output to smooth, global functional forms. Typical observational data that may be used includes x-ray self-emission, directional neutron time-of-flight signals, neutron yield, high-resolution x-ray spectra, and radiographic images. This approach has been validated by comparison with radiation-hydrodynamic simulations, producing semi-quantitative agreement. Model results implicate poor kinetic energy coupling to the hot core as the primary cause of the observed low thermonuclear burn yields.
Pathways to dewetting in hydrophobic confinement.
Remsing, Richard C; Xi, Erte; Vembanur, Srivathsan; Sharma, Sumit; Debenedetti, Pablo G; Garde, Shekhar; Patel, Amish J
2015-07-01
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 intersurface 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 nonclassical 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. PMID:26100866
Isolation and confinement - Considerations for colonization
NASA Technical Reports Server (NTRS)
Akins, F. R.
1978-01-01
This paper discusses three types of isolation (sensory/perceptual, temporal, and social) that could adversely affect mankind in space. The literature dealing with laboratory and field experiments relevant to these areas is summarized and suggestions are given for dealing with these problems within the space colony community. Also, consideration is given to the potential effects of physical confinement and the need for usable space. Finally, a modification of Maslow's hierarchy of needs is proposed as a theoretical framework to understand and investigate mankind's psychological needs in space.
Quark number susceptibilities, strangeness and dynamical confinement
Rajiv V. Gavai; Sourendu Gupta
2001-03-15
We report first results on the strange quark number susceptibility, chi_s, over a large range of temperatures, mainly in the plasma phase of QCD. Chi_s jumps across the phase transition temperature, T_c, and grows rapidly with temperature above but close to T_c. For all quark masses and susceptibilities in the entire temperature range studied, we found significant departures from ideal-gas values. We also observed a strong correlation between these quantities and the susceptibility in the scalar/pseudo-scalar channel, supporting ideas of ``dynamical confinement'' in the high temperature phase of the QCD plasma.
Anomalous diffusion in confined turbulent convection.
Boffetta, G; De Lillo, F; Musacchio, S
2012-06-01
Turbulent convection in quasi-one-dimensional geometry is studied by means of high-resolution direct numerical simulations within the framework of Rayleigh-Taylor turbulence. Geometrical confinement has dramatic effects on the dynamics of the turbulent flow, inducing a transition from superdiffusive to subdiffusive evolution of the mixing layer and arresting the growth of kinetic energy. A nonlinear diffusion model is shown to reproduce accurately the above phenomenology. The model is used to predict, without free parameters, the spatiotemporal evolution of the heat flux profile and the dependence of the Nusselt number on the Rayleigh number. PMID:23005221
On the Higgs-Confinement Complementarity
Seiler, Erhard
2015-01-01
It has been noticed long ago that in Higgs models with `complete symmetry breaking' one can move from the confinement to the Higgs regime without crossing a phase boundary, a fact sometimes called referred to as `complementarity'. In a recent paper some doubt was raised about the correctness of the mathematics underlying this fact and it was claimed that the supposed `flaw' would resolve the `paradox' seen in this complementarity. Here we briefly revisit the facts both from a mathematical and a physical point of view and point out that (a) there is no paradox and (b) there is no flaw in the mathematical reasoning.
On the Higgs-Confinement Complementarity
Erhard Seiler
2015-06-02
It has been noticed long ago that in Higgs models with `complete symmetry breaking' one can move from the confinement to the Higgs regime without crossing a phase boundary, a fact sometimes called referred to as `complementarity'. In a recent paper some doubt was raised about the correctness of the mathematics underlying this fact and it was claimed that the supposed `flaw' would resolve the `paradox' seen in this complementarity. Here we briefly revisit the facts both from a mathematical and a physical point of view and point out that (a) there is no paradox and (b) there is no flaw in the mathematical reasoning.
Elastic building blocks for confined sheets
Robert D. Schroll; Eleni Katifori; Benny Davidovitch
2010-12-17
We study the behavior of thin elastic sheets that are bent and strained under the influence of weak, smooth confinement. We show that the emerging shapes exhibit the coexistence of two types of domains that differ in their characteristic stress distributions and energies, and reflect different constraints. A focused-stress patch is subject to a geometric, piecewise-inextensibility constraint, whereas a diffuse-stress region is characterized by a mechanical constraint - the dominance of a single component of the stress tensor. We discuss the implications of our findings for the analysis of elastic sheets that are subject to various types of forcing.
Compaction force in a confined granular column.
Arroyo-Cetto, D; Pulos, G; Zenit, R; Jiménez-Zapata, M A; Wassgren, C R
2003-11-01
Experiments to determine the force required to push a granular column confined within a cylinder were performed. The experimental apparatus was mounted on a material testing system machine in order to obtain force and displacement measurements simultaneously. Experiments were performed for two different sphere diameters, two different cylinder diameters and for a range of piston displacement velocities. The force necessary to displace the column increases rapidly with the column height, in accordance with Janssen's theory. More importantly, we found that this force also increases with the displacement velocity. This unexpected behavior is an indication of the transition to rate-dependent behavior in dense granular flows. PMID:14682792
Colloids confined to a flexible container
NASA Astrophysics Data System (ADS)
Maibaum, Lutz; Schmidt, Matthias; Löwen, Hartmut
2001-05-01
A model of hard spheres trapped inside a container of fluctuating shape is proposed to describe colloidal particles in a vesicle or in an emulsion droplet. The container is assumed to be the convex hull of the particles and is described by an integral geometric approach including volume and surface terms. In the limit of large volume coupling, the model reduces to the well-known geometric problem of natural bin packing. Using computer simulations and cell theory, we calculate equilibrium properties for various finite numbers of confined particles in conformations ranging from clusters to planar and linear structures and identify transitions between these different conformations.
Colloids confined to a flexible container.
Maibaum, L; Schmidt, M; Löwen, H
2001-05-01
A model of hard spheres trapped inside a container of fluctuating shape is proposed to describe colloidal particles in a vesicle or in an emulsion droplet. The container is assumed to be the convex hull of the particles and is described by an integral geometric approach including volume and surface terms. In the limit of large volume coupling, the model reduces to the well-known geometric problem of natural bin packing. Using computer simulations and cell theory, we calculate equilibrium properties for various finite numbers of confined particles in conformations ranging from clusters to planar and linear structures and identify transitions between these different conformations. PMID:11414900
Confinement transitions (H-mode) in JET inner wall limiter plasmas
NASA Astrophysics Data System (ADS)
Borba, D.; Alper, B.; Conway, G. D.; Nunes, I.; Hacquin, S.; McDonald, D. C.; Maddison, G.; Lomas, P.; Pinches, S. D.; JET EFDA contributors
2006-06-01
Transitions in confinement with characteristics of H-mode are observed in JET inner wall limited plasmas in experiments performed at a magnetic field of 0.8 T and at a current of 0.9 MA, using up to 7 MW of auxiliary heating power. These transitions in confinement are short lived, with durations of up to 20 ms, but the overall stored energy increases by up to 5% and edge density by up to 20%. The termination of the period of good confinement correlates with the observation of a burst of magnetic fluctuations, similar to those associated with edge localized modes (ELMs). These transitions in confinement also correlate with a significant decrease in the density fluctuations measured by the microwave reflectometer and a small decrease in the magnetic fluctuations measured using 'Mirnov' probes, accompanied by a reduction of the D(alpha) emission. The comparison of the fluctuations in the limiter H-mode in JET with the divertor H-modes shows a similar behaviour, in particular the reduction of the fluctuation levels at high frequencies (f > 10 kHz) and an increase in the fluctuation levels at lower frequencies (f < 10 kHz). The strong electrostatic nature of the plasma edge turbulence is confirmed, where a reduction of up to ~50% in the density fluctuation levels correlates with an increase of up to 50% in the confinement time during the transition to H-mode. However, the importance of instabilities with a dominant magnetic component (such as ELMs) is also highlighted, which cause significant increase in transport, including the loss of the good confinement phase in limiter H-modes.
Anomalous Debye-like dielectric relaxation of water in micro-sized confined polymeric systems.
Colosi, C; Costantini, M; Barbetta, A; Cametti, C; Dentini, M
2013-12-14
While it is well known that spatial confinement on a nm scale affects the molecular dynamics of water resulting in a hindered dipolar reorientation, question of whether these effects could result at length scales larger than these, i.e., in confined regions of the order of ?m or more, is still under debate. Here we use dielectric relaxation spectroscopy techniques to study the relaxation orientation dynamics of water entrapped in different polymeric matrices with pore sizes of the order of 100 ?m, analyzing the frequency relaxation behaviour of the dielectric response. Our results show that, contrary to what has been generally thought, even in confinements which are not particularly high such as those realized here, regions typically hundred micrometers in size can affect the water structure, inducing a water phase with properties different from those of bulk water. In particular, we observe a dielectric dispersion centered in the range 10(5)-10(7) Hz, in between the one characteristic of ice (8.3 kHz at T = 0 °C) and the one of bulk water (19.2 GHz at T = 25 °C). The analysis of the dependence on temperature of the relaxation time of this unexpected contribution rules out the possibility that it can be attributed to an interfacial polarization (Maxwell-Wagner effect) and suggests a dipolar Debye-like origin due to a slow-down of the hydrogen-bonded network orientational polarization. Also at these scales, the confinement alters the structure of water, leading to a hindered reorientation. These properties imply that water confined within these polymeric porous matrices is more ordered than bulk water. These findings may be important in order to understand biological processes in cells and in different biological compartments, where water is physiologically confined. PMID:24162131
Confinement and Localization on Domain Walls
R. Auzzi; S. Bolognesi; M. Shifman; A. Yung
2008-12-19
We continue the studies of localization of the U(1) gauge fields on domain walls. Depending on dynamics of the bulk theory the gauge field localized on the domain wall can be either in the Coulomb phase or squeezed into flux tubes implying (Abelian) confinement of probe charges on the wall along the wall surface. First, we consider a simple toy model with one flavor in the bulk at weak coupling (a minimal model) realizing the latter scenario. We then suggest a model presenting an extension of the Seiberg--Witten theory which is at strong coupling, but all theoretical constructions are under full control if we base our analysis on a dual effective action. Finally, we compare our findings with the wall in a "nonminimal" theory with two distinct quark flavors that had been studied previously. In this case the U(1) gauge field trapped on the wall is exactly massless because it is the Goldstone boson of a U(1) symmetry in the bulk spontaneously broken on the wall. The theory on the wall is in the Coulomb phase. We explain why the mechanism of confinement discussed in the first part of the paper does not work in this case, and strings are not formed on the walls.
Confined magnetic monopoles in dense QCD
Gorsky, A. [Theory Department, Institute for Theoretical and Experimental Physics, Moscow (Russian Federation); William I. Fine Theoretical Physics Institute, University of Minnesota, Minneapolis, Minnesota 55455 (United States); Shifman, M. [William I. Fine Theoretical Physics Institute, University of Minnesota, Minneapolis, Minnesota 55455 (United States); Center for Theoretical Physics, Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Yung, A. [William I. Fine Theoretical Physics Institute, University of Minnesota, Minneapolis, Minnesota 55455 (United States); Petersburg Nuclear Physics Institute, Gatchina, St. Petersburg 188300 (Russian Federation)
2011-04-15
Non-Abelian strings exist in the color-flavor locked phase of dense QCD. We show that kinks appearing in the world-sheet theory on these strings, in the form of the kink-antikink bound pairs, are the magnetic monopoles-descendants of the 't Hooft-Polyakov monopoles surviving in such a special form in dense QCD. Our consideration is heavily based on analogies and inspiration coming from certain supersymmetric non-Abelian theories. This is the first ever analytic demonstration that objects unambiguously identifiable as the magnetic monopoles are native to non-Abelian Yang-Mills theories (albeit our analysis extends only to the phase of the monopole confinement and has nothing to say about their condensation). Technically, our demonstration becomes possible due to the fact that low-energy dynamics of the non-Abelian strings in dense QCD is that of the orientational zero modes. It is described by an effective two-dimensional CP(2) model on the string world sheet. The kinks in this model representing confined magnetic monopoles are in a highly quantum regime.
Fire Risk Analysis for Armenian NPP Confinement
Poghosyan, Shahen; Malkhasyan, Albert; Bznuni, Surik; Amirjanyan, Armen [Armenian Nuclear Regulatory Authority - Armgosatomnadzor (Armenia)
2006-07-01
Major fire occurred at Armenian NPP (ANPP) in October 1982 showed that fire-induced initiating events (IE) can have dominant contribution in overall risk of core damage. Probabilistic Safety Assessment study for fire-induced initiating events for ANPP was initiated in 2002. Analysis was performed for compartments fires in which could result in failure of components which are necessary for reactor cold shutdown. Analysis shows that main risk from fire at ANPP is conditioned by fire in cable tunnels 61-64. Meanwhile fire in confinement compartments don't have significant contribution to overall risk of core damage. The exception is so called 'confinement valves compartment' (room no.A-013/2) fire (more than 7.5% of CDF) in which fire could result in the loss of coolant accident with unavailability of primary makeup system, which directly leads to core damage. Detailed analysis of this problem that is common for typical WWER-440/230 reactors with no hermetic MCPs and recommendations for solution are presented in this paper. (authors)
Polymer escape from a confining potential
Mökkönen, Harri, E-mail: harri.mokkonen@aalto.fi [Department of Applied Physics and COMP CoE, Aalto University School of Science, P.O. Box 11100, FIN-00076 Aalto, Espoo (Finland) [Department of Applied Physics and COMP CoE, Aalto University School of Science, P.O. Box 11100, FIN-00076 Aalto, Espoo (Finland); Faculty of Physical Sciences, University of Iceland, Reykjavík (Iceland); Ikonen, Timo [Department of Applied Physics and COMP CoE, Aalto University School of Science, P.O. Box 11100, FIN-00076 Aalto, Espoo (Finland) [Department of Applied Physics and COMP CoE, Aalto University School of Science, P.O. Box 11100, FIN-00076 Aalto, Espoo (Finland); VTT Technical Research Centre of Finland, P.O. Box 1000, FI-02044 VTT (Finland); Jónsson, Hannes [Department of Applied Physics and COMP CoE, Aalto University School of Science, P.O. Box 11100, FIN-00076 Aalto, Espoo (Finland) [Department of Applied Physics and COMP CoE, Aalto University School of Science, P.O. Box 11100, FIN-00076 Aalto, Espoo (Finland); Faculty of Physical Sciences, University of Iceland, Reykjavík (Iceland); Department of Physics, Brown University, Providence, Rhode Island 02912-1843 (United States); Ala-Nissila, Tapio [Department of Applied Physics and COMP CoE, Aalto University School of Science, P.O. Box 11100, FIN-00076 Aalto, Espoo (Finland) [Department of Applied Physics and COMP CoE, Aalto University School of Science, P.O. Box 11100, FIN-00076 Aalto, Espoo (Finland); Department of Physics, Brown University, Providence, Rhode Island 02912-1843 (United States)
2014-02-07
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.
Deuterium anions in inertial electrostatic confinement devices.
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
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
Neutron confinement cell for investigating complex fluids
Kuhl, Tonya L.; Smith, Gregory S.; Israelachvili, Jacob N.; Majewski, Jaroslaw; Hamilton, William
2001-03-01
We describe an apparatus for measuring the molecular density and orientation of confined, ultrathin complex fluids under static and dynamic flow conditions. The device essentially couples the utility of the surface forces apparatus -- ability to control surface separation and alignment under applied loads -- with in situ structural characterization of the intervening material utilizing neutron reflectivity measurements. The apparatus is designed such that single crystal substrates of quartz or sapphire with areas up to tens of square centimeters can be kept parallel at controlled and well-defined separations from millimeters to less than 100 nm. The large substrate surface area enables direct structural measurements of the density profile of ''soft'' material placed between the aligned substrates. In addition, the cell is also designed to enable steady shear rates from 0.001 to 20 Hz to be applied in order to follow the dynamic structural response of the confined material, especially at the solid-solution interface. Faster shear rates of order 10{sup 4} can be obtained using oscillatory motion. Current design specifications focus on the use of neutron reflectivity to characterize the structure of end-grafted polymer brush layers, but the device can be employed to probe the structure of any complex fluid of interest and is amenable to other characterization techniques.
Fractional Brownian motion and generalized Langevin equation motion in confined geometries
Jae-Hyung Jeon; Ralf Metzler
2010-01-06
Motivated by subdiffusive motion of bio-molecules observed in living cells we study the stochastic properties of a non-Brownian particle whose motion is governed by either fractional Brownian motion or the fractional Langevin equation and restricted to a finite domain. We investigate by analytic calculations and simulations how time-averaged observables (e.g., the time averaged mean squared displacement and displacement correlation) are affected by spatial confinement and dimensionality. In particular we study the degree of weak ergodicity breaking and scatter between different single trajectories for this confined motion in the subdiffusive domain. The general trend is that deviations from ergodicity are decreased with decreasing size of the movement volume, and with increasing dimensionality. We define the displacement correlation function and find that this quantity shows distinct features for fractional Brownian motion, fractional Langevin equation, and continuous time subdiffusion, such that it appears an efficient measure to distinguish these different processes based on single particle trajectory data.
NASA Astrophysics Data System (ADS)
Berrod, Quentin; Lyonnard, Sandrine; Guillermo, Armel; Ollivier, Jacques; Frick, Bernhard; Gébel, Gérard
2015-01-01
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.
Confinement and Tritium Stripping Systems for APT Tritium Processing
Hsu, R.H. [Westinghouse Savannah River Company, AIKEN, SC (United States); Heung, L.K.
1997-10-20
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.
Confinement dynamics of a semiflexible chain inside nano-spheres
Arman Fathizadeh; Maziar Heidari; Behrouz Eslami-Mossallam; Mohammad Reza Ejtehadi
2014-09-26
We study the conformations of a semiflexible chain, confined in nano-scaled spherical cavities, under two distinct processes of confinement. Radial contraction and packaging are employed as two confining procedures. The former method is performed by gradually decreasing the diameter of a spherical shell which envelopes a confined chain. The latter procedure is carried out by injecting the chain inside a spherical shell through a hole on the shell surface. The chain is modeled with a rigid body molecular dynamics simulation and its parameters are adjusted to DNA base-pair elasticity. Directional order parameter is employed to analyze and compare the confined chain and the conformations of the chain for two different sizes of the spheres are studied in both procedures. It is shown that for the confined chains in the sphere sizes of our study, they appear in spiral or tennis-ball structures, and the tennis-ball structure is more likely to be observed in more compact confinements. Our results also show that the dynamical procedure of confinement and the rate of the confinement are influential parameters of the structure of the chain inside spherical cavities.
The cruel and unusual phenomenology of solitary confinement
Gallagher, Shaun
2014-01-01
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
Quasielastic neutron scattering of propylene glycol and its 7-mer confined in clay
NASA Astrophysics Data System (ADS)
Swenson, J.; Howells, W. S.
2002-07-01
The dynamics of propylene glycol (PG) and its 7-mer confined in a Na-vermiculite clay have been investigated by quasielastic neutron scattering. Experiments were carried out in the temperature range 300-420 K and in two different scattering geometries in order to make the elastic Q-vector parallel and perpendicular to the clay platelets for a scattering angle of 90deg (Qapproximately1.33 A-1). The results indicate that at least three dynamical processes are present in the experimental time window of approximately 3-80 ps, although only two processes could be resolved at a given temperature. The fast process is independent of the chain length as well as the confinement, and in accordance with previous studies of the bulk liquids it is assigned to a rapid local motion of hydrogens in the polymeric backbone. The slow process has mainly a rotational character at T=300 K and it is assigned to the methyl group rotation. At higher temperatures this rotational motion is hidden behind a Q-dependent jump diffusion process. The calculated diffusion constant is roughly the same for our confined PG and 7-PG, and also similar to the corresponding bulk liquids (except for PG at high temperatures where the bulk liquid shows a considerably faster diffusion). However, the diffusion seems to increase slightly faster for confined 7-PG with increasing temperature. This is an interesting finding since a clear opposite trend was observed for the bulk liquids. The methyl group rotation at low temperatures (approximately300 K) is significantly faster in the confined liquids. Both the methyl group rotation and the jump diffusion process seem to be present also in the direction perpendicular to the clay platelets for the 7-mers, but not for the monomers where only the fast local motion of hydrogens is observed in that direction. Furthermore, the pure translational diffusion (with a quasielastic broadening proportional to Q2) observed for the bulk liquids was never obtained for our confined liquids. The different results for the confined and bulk liquids are discussed in terms of confinement and free volume effects and surface interactions.
NASA Astrophysics Data System (ADS)
Takenaga, H.; Mahdavi, M. A.; Baker, D. R.
2001-05-01
Particle confinement was compared for the high confinement mode plasmas with the edge localized mode in the Japan Atomic Energy Research Institute Tokamak-60 Upgrade (JT-60U) [S. Ishida, JT-60 Team, Nucl. Fusion 39, 1211 (1999)] and the DIII-D tokamak [J. L. Luxon et al., Plasma Physics and Controlled Nuclear Fusion Research 1986 (International Atomic Energy Agency, Vienna, 1987), Vol. 1, p. 159] considering separate confinement times for particles supplied by neutral beam injection (NBI) (center fueling) and by recycling and gas-puffing (edge fueling). Similar dependence on the NBI power was obtained in JT-60U and DIII-D. The particle confinement time for center fueling in DIII-D was smaller by a factor of 4 in the low density discharges and by a factor of 1.8 in the high density discharges than JT-60U scaling, respectively, suggesting the stronger dependence on the density in DIII-D. The particle confinement time for edge fueling in DIII-D was comparable with JT-60U scaling in the low density discharges. However, it decreased to a much smaller value in the high density discharges.
Inertial Confinement Fusion Target Component Fabrication and Technology Development Support
Steinman, D. (ed.)
1993-03-01
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.
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
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
Echoes and revival echoes in systems of anharmonically confined atoms
NASA Astrophysics Data System (ADS)
Herrera, M.; Antonsen, T. M.; Ott, E.; Fishman, S.
2012-08-01
We study echoes and what we call “revival echoes” for a collection of atoms that are described by a single quantum wave function and are confined in a weakly anharmonic trap. The echoes and revival echoes are induced by applying two successive temporally localized potential perturbations to the confining potential, one at time t=0, and a smaller one at time t=?. Pulselike responses in the expectation value of position
Fernandez, J.C.; Wysocki, F.J.; Jarboe, T.R.; Barnes, C.W.; Henins, I.; Knox, S.O.; Marklin, G.J.
1989-01-01
The 0.67 m radius mesh flux conserver (MFC) in CTX was replaced by a solid flux conserver (SFC), resulting in greatly reduced field errors. Decreased spheromak open flux led to vastly improved decaying discharges, including increased global energy confinement times /tau//sub E/ (from 20 to 180 ..mu..s) and corresponding magnetic energy decay times /tau//sub B/sup 2// (from 0.7 to 2 ms). Improved confinement allowed the observation of a pressure-driven instability which ejects plasma from the spheromak interior to the wall. 9 refs., 3 figs.
Influence of confined fluids on nanoparticle-to-surroundings energy transfer.
Dowgiallo, Anne-Marie; Knappenberger, Kenneth L
2012-11-28
Energy transfer from photoexcited nanoparticles to their surroundings was studied for both hollow and solid gold nanospheres (HGNs and SGNs, respectively) using femtosecond time-resolved transient extinction spectroscopy. HGNs having outer diameters ranging from 17 to 78 nm and fluid-filled cavities were synthesized by a sacrificial galvanic replacement method. The HGNs exhibited energy transfer half times that ranged from 105 ± 10 ps to 1010 ± 80 ps as the total particle surface area increased from 1005 to 28,115 nm(2). These data showed behaviors that were categorized into two classes: energy transfer from HGNs to interior fluids that were confined to cavities with radii <15 nm and ?15 nm. Energy transfer times were also determined for solid gold nanospheres (SGNs) having radii spanning 9-30 nm, with a similar size dependence where the relaxation times increased from 140 ± 10 to 310 ± 15 ps with increasing nanoparticle size. Analysis of the size-dependent energy transfer half times revealed that the distinct relaxation rate constants observed for particle-to-surroundings energy transfer for HGNs with small cavities were the result of reduced thermal conductivity of confined fluids. These data indicate that the thermal conductivity of HGN cavity-confined fluids is approximately one-half as great as it is for bulk liquid water. For all HGNs and SGNs studied, energy dissipation through the solvent and transfer across the particle/surroundings interface both contributed to the energy relaxation process. The current data illustrated the potential of fluid-filled hollow nanostructures to gain insight into the properties of confined fluids. PMID:23110583
Effects of confinement on short-period surface waves: Observations from a new dataset
Hooper, H.; Bonner, J.; Leidig, M. [Weston Geophysics Corp., Lexington, MA (United States)
2006-04-15
The Source Phenomenology Experiment (SPE) was conducted during the summer of 2003 in Arizona. Single-fired chemical shots were detonated and recorded at two locations, including a coal mine in the Black Mesa district of northern Arizona. This article reports on research into the effects of confinement on the generation of short-period, fundamental-mode Rayleigh waves (Rg), using a subset of the SPE data. Results show important differences between the Rg amplitudes of confined and unconfined explosions which must be understood to develop discriminants for mining explosions, which are an important aspect of nuclear test monitoring. Rg energy and frequency content depend on explosive weight and confinement, and unconfined explosions generate up to eight times less energy than equivalent confined explosions. For this reason, unconfined mining explosions cannot be simulated using a Mueller and Murphy (1971) source without including an empirical chemical decoupling factor. Rg chemical decoupling factors for unconfined shots vary from 0.5 to 8.2 at frequencies between 0.5 and 11 Hz. The effects of the bench free face are evident in radiation patterns. Explosions on the topographic bench show increased spectral energies for Rg (by a factor of 1.5) at azimuths behind the bench. This suggests that a discriminant based on the relative azimuthal spectral energies of Rg may be a possibility.
Structural integrity of a confinement vessel for testing nuclear fuels for space propulsion
NASA Astrophysics Data System (ADS)
Bergmann, V. L.
Nuclear propulsion systems for rockets could significantly reduce the travel time to distant destinations in space. However, long before such a concept can become reality, a significant effort must be invested in analysis and ground testing to guide the development of nuclear fuels. Any testing in support of development of nuclear fuels for space propulsion must be safely contained to prevent the release of radioactive materials. This paper describes analyses performed to assess the structural integrity of a test confinement vessel. The confinement structure, a stainless steel pressure vessel with bolted flanges, was designed for operating static pressures in accordance with the ASME Boiler and Pressure Vessel Code. In addition to the static operating pressures, the confinement barrier must withstand static overpressures from off-normal conditions without releasing radioactive material. Results from axisymmetric finite element analyses are used to evaluate the response of the confinement structure under design and accident conditions. For the static design conditions, the stresses computed from the ASME code are compared with the stresses computed by the finite element method.
Two-dimensional confined jet thrust vector control: Operating mechanisms and performance
NASA Astrophysics Data System (ADS)
Caton, Jeffrey L.
1989-03-01
An experimental investigation of two-dimensional confined jet thrust vector control nozzles was performed. Thrust vector control was accomplished by using secondary flow injection in the diverging section of the nozzle. Schlieren photographs and video tapes were used to study flow separation and internal shock structures. Nozzle performance parameters were determined for nozzle flow with and without secondary flows. These parameters included nozzles forces, vector angles, thrust efficiencies, and flow switching response times. Vector angles as great as 18 degrees with thrust efficiencies of 0.79 were measured. Several confined jet nozzles with variations in secondary flow port design were tested and results were compared to each other. Converging-diverging nozzles of similar design to the confined jet nozzles were also tested and results were compared to the confined jet nozzle results. Existing prediction models for nozzle side to axial force ratio were evaluated. A model for nozzle total forces based on shock losses that predicted values very close to actual results was developed.
Role of the confinement of a root canal on jet impingement during endodontic irrigation
NASA Astrophysics Data System (ADS)
Verhaagen, B.; Boutsioukis, C.; Heijnen, G. L.; van der Sluis, L. W. M.; Versluis, M.
2012-12-01
During a root canal treatment the root canal is irrigated with an antimicrobial fluid, commonly performed with a needle and a syringe. Irrigation of a root canal with two different types of needles can be modeled as an impinging axisymmetric or non-axisymmetric jet. These jets are investigated experimentally with high-speed Particle Imaging Velocimetry, inside and outside the confinement (concave surface) of a root canal, and compared to theoretical predictions for these jets. The efficacy of irrigation fluid refreshment with respect to the typical reaction time of the antimicrobial fluid with a biofilm is characterized with a non-dimensional Damköhler number. The pressure that these jets induce on a wall or at the apex of the root canal is also measured. The axisymmetric jet is found to be stable and its velocity agrees with the theoretical prediction for this type of jet, however, a confinement causes instabilities to the jet. The confinement of the root canal has a pronounced influence on the flow, for both the axisymmetric and non-axisymmetric jet, by reducing the velocities by one order of magnitude and increasing the pressure at the apex. The non-axisymmetric jet inside the confinement shows a cascade of eddies with decreasing velocities, which at the apex does not provide adequate irrigation fluid refreshment.
Aggregation and segregation of confined active particles.
Yang, Xingbo; Manning, M Lisa; Marchetti, M Cristina
2014-09-14
We simulate a model of self-propelled disks with soft repulsive interactions confined to a box in two dimensions. For small rotational diffusion rates, monodisperse disks spontaneously accumulate at the walls. At low densities, interaction forces between particles are strongly inhomogeneous, and a simple model predicts how these inhomogeneities alter the equation of state. At higher densities, collective effects become important. We observe signatures of a jamming transition at a packing fraction ? ? 0.88, which is also the jamming point for non-active athermal monodisperse disks. At this ?, the system develops a critical finite active speed necessary for wall aggregation. At packing fractions above ? ? 0.6, the pressure decreases with increasing density, suggesting that strong interactions between particles are affecting the equation of state well below the jamming transition. A mixture of bidisperse disks segregates in the absence of any adhesion, identifying a new mechanism that could contribute to cell sorting in embryonic development. PMID:25046587
Relativistic constituent quark model with infrared confinement
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
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.
Fabrication issues of oxide-confined VCSELs
NASA Astrophysics Data System (ADS)
Geib, Kent M.; Choquette, Kent D.; Hou, Hong Q.; Hammons, B. E.
1997-04-01
To insert high performance oxide-confined vertical-cavity surface-emitting lasers (VCSELs) into the manufacturing arena, we have examined the critical parameters that must be controlled to establish a repeatable and uniform wet thermal oxidation process for AlGaAs. These parameters include the AlAs mole fraction, the sample temperature, the carrier gas flow and the bubbler water temperature. Knowledge of these critical parameters has enabled the compilation of oxidation rate data for AlGaAs which exhibits an Arrhenius rate dependence. The compositionally dependent activation energies for AlxGa1-xAs layers of x equals 1.00, 0.98 and 0.92 are found to be 1.24, 1.75, and 1.88 eV, respectively.
From topological insulators to superconductors and Confinement
M. Cristina Diamantini; Pasquale Sodano; Carlo A. Trugenberger
2012-02-01
Topological matter in 3D is characterized by the presence of a topological BF term in its long-distance effective action. We show that, in 3D, there is another marginal term that must be added to the action in order to fully determine the physical content of the model. The quantum phase structure is governed by three parameters that drive the condensation of topological defects: the BF coupling, the electric permittivity and the magnetic permeability of the material. For intermediate levels of electric permittivity and magnetic permeability the material is a topological insulator. We predict, however, new states of matter when these parameters cross critical values: a topological superconductor when electric permittivity is increased and magnetic permeability is lowered and a charge confinement phase in the opposite case of low electric permittivity and high magnetic permeability. Synthetic topological matter may be fabricated as 3D arrays of Josephson junctions.
Nonideal magnetohydrodynamic instabilities and toroidal magnetic confinement
Furth, H.P.
1985-05-01
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.
Making confining strings out of mesons
NASA Astrophysics Data System (ADS)
Kitano, Ryuichiro; Nakamura, Mitsutoshi; Yokoi, Naoto
2012-07-01
The light mesons such as ?, ?, ?, f0, and a0 are possible candidates of magnetic degrees of freedom, if a magnetic dual picture of QCD exists. We construct a linear sigma model to describe spontaneous breaking of the magnetic gauge group, in which there is a stable vortex configuration of vector and scalar mesons. We numerically examine whether such a string can be interpreted as the confining string. By using meson masses and couplings as inputs, we calculate the tension of the string as well as the strength of the Coulomb force between static quarks. They are found to be consistent with those inferred from the quarkonium spectrum and the Regge trajectories of hadrons. By using the same Lagrangian, the critical temperature of the QCD phase transition is estimated, and a nontrivial flavor dependence is predicted. We also discuss a possible connection between the Seiberg duality and the magnetic model we studied.
28 CFR 523.13 - Community corrections center good time.
Code of Federal Regulations, 2011 CFR
2011-07-01
...Time § 523.13 Community corrections center good time. Extra good time for an inmate in a Federal or contract Community Corrections Center is awarded automatically...and continuing as long as the inmate is confined at the Center,...
28 CFR 523.13 - Community corrections center good time.
Code of Federal Regulations, 2010 CFR
2010-07-01
...Time § 523.13 Community corrections center good time. Extra good time for an inmate in a Federal or contract Community Corrections Center is awarded automatically...and continuing as long as the inmate is confined at the Center,...
High beta and confinement studies on TFTR
Navratil, G.A.; Bhattacharjee, A.; Iacono, R.; Mauel, M.E.; Sabbagh, S.A. (Columbia Univ., New York, NY (United States)); Kesner, J. (Massachusetts Inst. of Tech., Cambridge, MA (United States))
1992-01-01
A new regime of high poloidal beta operation in TFTR was developed in the course of the first two years of this project (9/25/89 to 9/24/91). Our proposal to continue this successful collaboration between Columbia University and the Massachusetts Institute of Technology with the Princeton Plasma Physics Laboratory for a three year period (9/25/91 to 9/24/94) to continue to investigate improved confinement and tokamak performance in high poloidal beta plasmas in TFTR through the DT phase of operation was approved by the DOE and this is a report of our progress during the first 9 month budget period of the three year grant (9/25/91 to 6/24/92). During the approved three year project period we plan to (1) extend and apply the low current, high QDD discharges to the operation of TFTR using Deuterium and Tritium plasma; (2) continue the analysis and plan experiments on high poloidal beta phenomena in TFTR including: stability properties, enhanced global confinement, local transport, bootstrap current, and divertor formation; (3) plan and carry out experiments on TFTR which attempt to elevate the central q to values > 2 where entry to the second stability regime is predicted to occur; and (4) collaborate on high beta experiments using bean-shaped plasmas with a stabilizing conducting shell in PBX-M. In the seven month period covered by this report we have made progress in each of these four areas through the submission of 4 TFTR Experimental Proposals and the partial execution of 3 of these using a total of 4.5 run days during the August 1991 to February 1992 run.
Vortices and quark confinement in non-abelian gauge theories
S. Mandelstam
1975-01-01
It is shown that finite-length vortices in an SU(n) Nielsen-Olesen model require explicit introduction of monopoles, which are confined in multiples of n by the Meissner effect. The model therefore possesses a natural explanation of quark confinement.
Holographic confining gauge theory and response to the electric field
Kazuo Ghoroku; Masafumi Ishihara; Tomoki Taminato
2010-01-01
We study the response of confining gauge theory to the external electric field by using holographic Yang-Mills theories in the large Nc limit. Although the theories are in the confinement phase, we find a transition from the insulator to the conductor phase when the electric field exceeds its critical value. Then, the baryon number current is generated in the conductor
Holographic confining gauge theory and response to the electric field
Kazuo Ghoroku; Masafumi Ishihara; Tomoki Taminato
2010-01-01
We study the response of confining gauge theory to the external electric field by using holographic Yang-Mills theories in the large N{sub c} limit. Although the theories are in the confinement phase, we find a transition from the insulator to the conductor phase when the electric field exceeds its critical value. Then, the baryon number current is generated in the
LAGOON WATER FROM CONFINED ANIMAL FEED OPERATIONS AND AMPHIBIAN DEVELOPMENT
Lagoon Water from Confined Animal Feed Operations and Amphibian Development. Dumont, J. N.* and Slagle, S., Oklahoma State University, Stillwater, OK, and Hutchins, S. R., U.S. Environmental Protection Agency (NRMRL/SPRD), Ada, OK. There is some evidence that confined anima...
Protein Simulations in Confined Environments Murat Cetinkaya1
Demirel, Melik C.
Protein Simulations in Confined Environments Murat Cetinkaya1 , Jorge Sofo2 , Melik C. Demirel1 1 Calculations, Protein Simulations Abstract Materials surfaces mimic cell like architecture and proteins can of surface interactions, this confine environment could destroy the protein or help it maintain its
Zero-point energy in flux-tube confinement
Paul M. Fishbane; Stephen G. Gasiorowicz; Peter Kaus
1988-01-01
We discuss the zero-point energy associated with a heavy-quark-antiquark system confined to a cylindrical cavity through the dielectric vacuum picture of confinement. The correction to the string tension and the universal Coulomb-type behavior produced by the Casimir forces are treated.
Zero-point energy in flux-tube confinement
Paul Fishbane; Stephen Gasiorowicz; Peter Kaus
1988-01-01
We discuss the zero-point energy associated with a heavy-quark--antiquark system confined to a cylindrical cavity through the dielectric vacuum picture of confinement. The correction to the string tension and the universal Coulomb-type behavior produced by the Casimir forces are treated.
Hydrodynamics of Confined Active Fluids Tommaso Brotto,1
Lauga, Eric
of their specific swimming mechanism. We also show that, due to friction with the nearby rigid walls, confined external actuation [59]. From a theoretical perspective, such systems are com- monly separated into two to friction with the walls, rigidly confined polar swimmers are not only prone to align along the local
Plutonium Finishing Plant assessment of confinement system bypass leakage
Dick, J.D.
1996-09-30
The purpose of this report is to document walk-through`s of the safety class confinement systems at the Plutonium Finishing Plant (PFP). In addition this document outlines the actions taken to assess the confinement system for bypass leakage as well as establishing disposition for discovered deficiencies at the PFP.
Inhibited emission of electromagnetic modes confined in subwavelength cavities
Le Thomas, N.; Houdre, R. [Institut de Physique de la Matiere Condensee, Ecole Polytechnique Federale de Lausanne (EPFL), Station 3, CH-1015 Lausanne (Switzerland)
2011-07-15
We experimentally demonstrate the active inhibition of subwavelength confined cavity modes emission and quality factor enhancement by controlling the cavity optical surrounding. The intrinsic radiation angular spectrum of modes confined in planar photonics crystal cavities as well as its modifications depending on the environment are inferred via a transfer matrix modeling and k-space imaging.
Atomic processes in Inertial Electrostatic Confinement (IEC) devices
R. A. Nebel; L. Turner; T. N. Tiouririne; D. C. Barnes; W. D. Nystrom; R. W. Bussard; G. H. Miley; J. Javedani; Y. Yamamoto
1993-01-01
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
Atomic Processes in Inertial Electrostatic Confinement (IEC) Devices
R. A. Nebel; L. Turner; T. N. Tiouririne; D. C. Barnes; W. D. Nystrom; R. W. Bussard; G. H. Miley; J. Javedani; Y. Yamamoto
1995-01-01
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
Modelling the confinement of spilled oil with floating booms
Song-Ping Zhu; Dmitry Strunin
2001-01-01
An effective mechanical method of confining the oil spills in an open ocean is to use barriers such as floating booms. However, the confined oil may leak beneath a boom if either the towing speed of the boom or the amount of oil is too large. In this paper a simple mathematical model based on the potential theory is presented
Prospects of confined flow boiling in thermal management of microsystems
S. Lin; K. Sefiane; J. R. E. Christy
2002-01-01
This paper presents a review of prospects of confined flow boiling in future thermal management of microsystems such as microelectronics, optoelectronics, and microreactors. With the trend towards miniaturisation, heat removal has become the major bottleneck in microsystem development. In view of this we briefly discuss available cooling strategies, then assess studies of confined flow boiling and potential applications in heat
Confinement at large-N. [N = number of colors
Klinkhamer, F.R.
1985-06-01
Recent numerical results indicate that QCD in the limit of an infinite number (N) of colors also has confinement and moreover that it looks rather similar to normal QCD with N = 3 colors. This imposes severe restrictions on what the mechanism of confinement can be.
Apparatus for Demonstrating Confined and Unconfined Aquifer Characteristics.
ERIC Educational Resources Information Center
Gillham, Robert W.; O'Hannesin, Stephanie F.
1984-01-01
Students in hydrogeology classes commonly have difficulty appreciating differences between the mechanisms of water release from confined and unconfined aquifers. Describes a simple and inexpensive laboratory model for demonstrating the hydraulic responses of confined and unconfined aquifers to pumping. Includes a worked example to demonstrate the…
Enhancement of high harmonic generation by confining electron motion in plasmonic nanostrutures.
Ciappina, M F; A?imovi?, Srdjan S; Shaaran, T; Biegert, J; Quidant, R; Lewenstein, M
2012-11-19
We study high-order harmonic generation (HHG) resulting from the illumination of plasmonic nanostructures with a short laser pulse of long wavelength. We demonstrate that both the confinement of the electron motion and the inhomogeneous character of the laser electric field play an important role in the HHG process and lead to a significant increase of the harmonic cutoff. In particular, in bow-tie nanostructures with small gaps, electron trajectories with large excursion amplitudes experience significant confinement and their contribution is essentially suppressed. In order to understand and characterize this feature, we combine the numerical solution of the time-dependent Schrödinger equation (TDSE) with the electric fields obtained from 3D finite element simulations. We employ time-frequency analysis to extract more detailed information from the TDSE results and classical tools to explain the extended harmonic spectra. The spatial inhomogeneity of the laser electric field modifies substantially the electron trajectories and contributes also to cutoff increase. PMID:23187480
Evidence for Critical Energy for Ion Confinement in Magnetic Fusion Reactors
NASA Astrophysics Data System (ADS)
Maglich, Bogdan; Hester, Tim; Scott, Dan; Calsec Collaboration
2015-03-01
It is shown here that fusion test reactors could not ignite for half-a-century because trials were conducted at thermonuclear ion energies 10-30 KeV, an order of magnitude lower than critical energy, Ec ~ 200 KeV. At subcritical energies, plasma is destroyed by neutralization of ions via overlooked atomic (non-nuclear) charge transfer collisions with giant cross-section, 109 barns, 100 times greater than that for ionization collisions that counters neutralization. Neutral injection sets limit on ion magnetic confinement time <10-6 s vs. >1 s required for ignition. In contrast, at energies above Ec, ionization prevails; near ~ 1 MeV, stable confinement of 20 s was routinely observed with charged injection. - To render ITER viable, ion energy must be increased to >/ = 1 MeV; neutral radioactive DT fuel replaced with charged, nonradioactive deuterium, giving rise to compact aneutronicreactor with direct conversion into RF power.
High-field penning-malmberg trap: confinement properties and use in positron accumulation
Hartley, J.H.
1997-09-01
This dissertation reports on the development of the 60 kG cryogenic positron trap at Lawrence Livermore National Laboratory, and compares the trap`s confinement properties with other nonneutral plasma devices. The device is designed for the accumulation of up to 2{times}10{sup 9} positrons from a linear-accelerator source. This positron plasma could then be used in Bhabha scattering experiments. Initial efforts at time-of-flight accumulation of positrons from the accelerator show rapid ({approximately}100 ms) deconfinement, inconsistent with the long electron lifetimes. Several possible deconfinement mechanisms have been explored, including annihilation on residual gas, injection heating, rf noise from the accelerator, magnet field curvature, and stray fields. Detailed studies of electron confinement demonstrate that the empirical scaling law used to design the trap cannot be extrapolated into the parameter regime of this device. Several possible methods for overcoming these limitations are presented.
Stochastic resonance in bistable confining potentials. On the role of confinement
NASA Astrophysics Data System (ADS)
Heinsalu, E.; Patriarca, M.; Marchesoni, F.
2009-05-01
We study the effects of the confining conditions on the occurrence of stochastic resonance (SR) in continuous bistable systems. We model such systems by means of double-well potentials that diverge like |x|q for |x|??. For super-harmonic (hard) potentials with q > 2 the SR peak sharpens with increasing q, whereas for sub-harmonic (soft) potentials, q < 2, it gets suppressed.
Yuming Wang; Jie Zhang
2008-08-21
We examine the two kinds of major energetic phenomena that occur in the solar atmosphere: eruptive and confined events. The former describes flares with associated coronal mass ejections (CMEs), while the latter denotes flares without associated CMEs. We find that about 90% of X-class flares are eruptive, but the remaining 10% are confined. To probe why the largest energy releases could be either eruptive or confined, we investigate four X-class events from each of the two types. Both sets of events are selected to have very similar intensities (X1.0 to X3.6) and duration (rise time under 13 minutes and decay time not over 9 minutes) in soft X-ray observations, to reduce any bias due to flare size on CME occurrence. We find that the occurrence of eruption (or confinement) is sensitive to the displacement of the location of the energy release, defined as the distance between the flare site and the flux-weighted magnetic center of the source active region. The displacement is 6 - 17 Mm for confined events but as large as 22 - 37 Mm for eruptive events. This means that confined events occur closer to the magnetic center, while the eruptive events tend to occur close to the edge of active regions. We use the potential field source-surface model to infer the coronal magnetic field above the source active regions and calculate the flux ratio of low (1.1 Rs) corona. We find that the confined events have a lower ratio (7.1). These results imply that a stronger overlying arcade field may prevent energy releases in the low corona from being eruptive, resulting in flares, but without CMEs.
Highly confined water: two-dimensional ice, amorphous ice, and clathrate hydrates.
Zhao, Wen-Hui; Wang, Lu; Bai, Jaeil; Yuan, Lan-Feng; Yang, Jinlong; Zeng, Xiao Cheng
2014-08-19
Understanding phase behavior of highly confined water, ice, amorphous ice, and clathrate hydrates (or gas hydrates), not only enriches our view of phase transitions and structures of quasi-two-dimensional (Q2D) solids not seen in the bulk phases but also has important implications for diverse phenomena at the intersection between physical chemistry, cell biology, chemical engineering, and nanoscience. Relevant examples include, among others, boundary lubrication in nanofluidic and lab-on-a-chip devices, synthesis of antifreeze proteins for ice-growth inhibition, rapid cooling of biological suspensions or quenching emulsified water under high pressure, and storage of H2 and CO2 in gas hydrates. Classical molecular simulation (MD) is an indispensable tool to explore states and properties of highly confined water and ice. It also has the advantage of precisely monitoring the time and spatial domains in the sub-picosecond and sub-nanometer scales, which are difficult to control in laboratory experiments, and yet allows relatively long simulation at the 10(2) ns time scale that is impractical with ab initio molecular dynamics simulations. In this Account, we present an overview of our MD simulation studies of the structures and phase behaviors of highly confined water, ice, amorphous ice, and clathrate, in slit graphene nanopores. We survey six crystalline phases of monolayer (ML) ice revealed from MD simulations, including one low-density, one mid-density, and four high-density ML ices. We show additional supporting evidence on the structural stabilities of the four high-density ML ices in the vacuum (without the graphene confinement), for the first time, through quantum density-functional theory optimization of their free-standing structures at zero temperature. In addition, we summarize various low-density, high-density, and very-high-density Q2D bilayer (BL) ice and amorphous ice structures revealed from MD simulations. These simulations reinforce the notion that the nanoscale confinement not only can disrupt the hydrogen bonding network in bulk water but also can allow satisfaction of the ice rule for low-density and high-density Q2D crystalline structures. Highly confined water can serve as a generic model system for understanding a variety of Q2D materials science phenomena, for example, liquid-solid, solid-solid, solid-amorphous, and amorphous-amorphous transitions in real time, as well as the Ostwald staging during these transitions. Our simulations also bring new molecular insights into the formation of gas hydrate from a gas and water mixture at low temperature. PMID:25088018
Chain dynamics in mesoscopically confined polymer melts. A field-cycling NMR relaxometry study
NASA Astrophysics Data System (ADS)
Kausik, R.; Mattea, C.; Kimmich, R.; Fatkullin, N.
2007-02-01
Polymer chain dynamics were studied with the aid of field-cycling NMR relaxometry (time scale: 10-9s... 10-4s) supplemented by field gradient NMR diffusometry (time scale: 10-4s...100s). Three sorts of samples of mesoscopically confined polymer melts were examined. In the first sample series, linear poly(ethylene oxide) was incorporated in strands embedded in a quasi-solid and impenetrable methacrylate matrix. The strand diameters ranged from 10 to 60 nm. It was shown that chain dynamics becomes dramatically different from bulk behavior. This so-called “corset effect” occurs both above and below the critical molecular mass and reveals dynamic features predicted for reptation. On the time scale of spin-lattice relaxation, the frequency and molecular weight, signature of reptation, T1 ˜M0 ?3/4, that is limit II of the Doi/Edwards formalism corresponding to the mean squared segment displacement law
Confined space entry program for the Westinghouse Hanford Company
Cornell, T.M.
1993-11-01
To comply with anticipated OSHA regulatory requirements concerning Permit-Required Confined Spaces, Westinghouse Hanford Company (WHC) created a Confined Spaces Task Team. The primary focus of the task team was to prepare a formal Confined Space Entry (CSE) Program that would ensure full compliance with the anticipated OSHA requirements. A comprehensive training plan was also prepared and submitted for approval as soon as the new CSE Program was approved and released for implementation. On January 14, 1993, OSHA released their final ruling which contained several further changes, requiring the WHC Confined Space Entry Program and Training Plan to be revised. The revised training manual and lessons learned in establishing a Confined Space Entry Program are presented.
Entropic competition in polymeric systems under geometrical confinement
Arash Azari; Kristian K. Müller-Nedebock
2015-06-11
Using molecular dynamics simulation, we investigate the effect of confinement on a system that comprises several stiff segmented polymer chains where each chain has similar segments, but length and stiffness of the segments vary among the chains which makes the system inhomogeneous. The translational and orientational entropy loss due to the confinement plays a crucial role in organizing the chains which can be considered as an entropy-driven segregation mechanism to differentiate the components of the system. Due to the inhomogeneity, both weak and strong confinement regimes show the competition in the system and we see segregation of chains as the confining volume is decreased. In the case of strong spherical confinement, a chain at the periphery shows higher angular mobility than other chains, despite being more radially constrained.
Radial Distribution Function for Semiflexible Polymers Confined in Microchannels
Patrick Levi; Klaus Mecke
2006-12-22
An analytic expression is derived for the distribution $G(\\vec{R})$ of the end-to-end distance $\\vec{R}$ of semiflexible polymers in external potentials to elucidate the effect of confinement on the mechanical and statistical properties of biomolecules. For parabolic confinement the result is exact whereas for realistic potentials a self-consistent ansatz is developed, so that $G(\\vec{R})$ is given explicitly even for hard wall confinement. The theoretical result is in excellent quantitative agreement with fluorescence microscopy data for actin filaments confined in rectangularly shaped microchannels. This allows an unambiguous determination of persistence length $L_P$ and the dependence of statistical properties such as Odijk's deflection length $\\lambda$ on the channel width $D$. It is shown that neglecting the effect of confinement leads to a significant overestimation of bending rigidities for filaments.
Theory of plasma confinement in non-axisymmetric magnetic fields.
Helander, Per
2014-08-01
The theory of plasma confinement by non-axisymmetric magnetic fields is reviewed. Such fields are used to confine fusion plasmas in stellarators, where in contrast to tokamaks and reversed-field pinches the magnetic field generally does not possess any continuous symmetry. The discussion is focussed on magnetohydrodynamic equilibrium conditions, collisionless particle orbits, and the kinetic theory of equilbrium and transport. Each of these topics is fundamentally affected by the absence of symmetry in the magnetic field: the field lines need not trace out nested flux surfaces, the particle orbits may not be confined, and the cross-field transport can be very large. Nevertheless, by tailoring the magnetic field appropriately, well-behaved equilibria with good confinement can be constructed, potentially offering an attractive route to magnetic fusion. In this article, the mathematical apparatus to describe stellarator plasmas is developed from first principles and basic elements underlying confinement optimization are introduced. PMID:25047050
Confined compression of dental composites for Class I restorations
Patki, Amol S.; Vural, Murat; Gosz, Mike
2011-01-01
This study focuses on the mechanical response of a particle-reinforced restorative dental composite (Renew™) under proportional transverse confinement to understand the effects of stress multiaxiality on its mechanical and failure behaviors. We describe the confining ring technique as an experimental tool to introduce multiaxial compressive stress states in dental composites that realistically mimic three-dimensional stress states commonly experienced by dental restorations in the oral cavity. Effect of initial radial misfit between confining ring and specimen is analyzed through computational finite element simulations, and an analytical treatment of problem is also provided to compute the confining stress during elasto-plastic expansion of confining ring. Experimental results suggest that inelastic response of Renew composite is significantly influenced by hydrostatic stress component, and pressure-dependent yield functions are required to analyze plastic deformations and internal damage accumulation process. PMID:21857744
Prediction of Anomalous Blood Viscosity in Confined Shear Flow
NASA Astrophysics Data System (ADS)
Thiébaud, Marine; Shen, Zaiyi; Harting, Jens; Misbah, Chaouqi
2014-06-01
Red blood cells play a major role in body metabolism by supplying oxygen from the microvasculature to different organs and tissues. Understanding blood flow properties in microcirculation is an essential step towards elucidating fundamental and practical issues. Numerical simulations of a blood model under a confined linear shear flow reveal that confinement markedly modifies the properties of blood flow. A nontrivial spatiotemporal organization of blood elements is shown to trigger hitherto unrevealed flow properties regarding the viscosity ?, namely ample oscillations of its normalized value [?]=(?-?0)/(?0?) as a function of hematocrit ? (?0=solvent viscosity). A scaling law for the viscosity as a function of hematocrit and confinement is proposed. This finding can contribute to the conception of new strategies to efficiently detect blood disorders, via in vitro diagnosis based on confined blood rheology. It also constitutes a contribution for a fundamental understanding of rheology of confined complex fluids.
Onset of flow in a confined colloidal glass under an imposed shear stress
Pinaki Chaudhuri; Jürgen Horbach
2014-10-26
A confined colloidal glass, under the imposition of a uniform shear stress, is investigated using numerical simulations. Both at macro- and microscales, the consequent dynamics during the onset of flow is studied. When the imposed stress is gradually decreased, the time scale for the onset of steady flow diverges, associated with long-lived spatial heterogeneities. Near this yield-stress regime, persistent creep in the form of shear-banded structures is observed.
Applications of a general random-walk theory for confined diffusion
NASA Astrophysics Data System (ADS)
Calvo-Muñoz, Elisa M.; Selvan, Myvizhi Esai; Xiong, Ruichang; Ojha, Madhusudan; Keffer, David J.; Nicholson, Donald M.; Egami, Takeshi
2011-01-01
A general random walk theory for diffusion in the presence of nanoscale confinement is developed and applied. The random-walk theory contains two parameters describing confinement: a cage size and a cage-to-cage hopping probability. The theory captures the correct nonlinear dependence of the mean square displacement (MSD) on observation time for intermediate times. Because of its simplicity, the theory also requires modest computational requirements and is thus able to simulate systems with very low diffusivities for sufficiently long time to reach the infinite-time-limit regime where the Einstein relation can be used to extract the self-diffusivity. The theory is applied to three practical cases in which the degree of order in confinement varies. The three systems include diffusion of (i) polyatomic molecules in metal organic frameworks, (ii) water in proton exchange membranes, and (iii) liquid and glassy iron. For all three cases, the comparison between theory and the results of molecular dynamics (MD) simulations indicates that the theory can describe the observed diffusion behavior with a small fraction of the computational expense. The confined-random-walk theory fit to the MSDs of very short MD simulations is capable of accurately reproducing the MSDs of much longer MD simulations. Furthermore, the values of the parameter for cage size correspond to the physical dimensions of the systems and the cage-to-cage hopping probability corresponds to the activation barrier for diffusion, indicating that the two parameters in the theory are not simply fitted values but correspond to real properties of the physical system.
Particle Dynamics in Neutral-Gas Confined Laser-Produced Plasmas
Yong W. Kim
2001-01-01
Laser-produced plasma from a metallic target can be confined to higher plasma densities by immersing the target in an inert gas medium at increasingly high density. The plasma becomes Rayleigh-Taylor unstable, however, when the mass density of the neutral gas exceeds the plasma mass density substantially.[1] A new plasma diagnostic method is developed to help examine the early time development
A URA coded aperture camera for the inertial confinement fusion experiments
Yamanaka, C.; Niki, H.; Yamada, A.; Yamamoto, Y.; Yamanaka, M.; Yamanaka, T.
1984-02-01
A coded aperture camera using m-sequence URA (uniformly redundant arrays) pattern has been constructed for the inertial confinement fusion (ICF) images. The URA camera is much brighter than a single pinhole camera, and then has high S/N. This URA camera has been successfully applied for the first time to take an X-ray image on a cannonball target. The tomographic capability of URA camera is improved by applying an iterative method.
Plasma confinement by a radio frequency plugging potential in an axisymmetric mirror-cusp device
R. Kumazawa; S. Okamura; K. Adati; T. Aoki; H. Fujita; K. Hattori; S. Hidekuma; T. Kawamoto; Y. Okubo; T. Sato
1986-01-01
The RFC-XX-M is a magnetohydrodynamic (MHD) stable and axisymmetric mirror-cusp device with radio frequency (RF) plugging. The plasma is produced by ion cyclotron resonant heating (ICRH) with gas puffing at the central mirror. The total ion energy confinement time including axial loss, electron drag, and charge exchange is improved by a factor of three by the RF plugging and reaches
Narrative survival: personal and institutional accounts of asylum confinement.
Hanganu-Bresch, Cristina; Berkenkotter, Carol
2012-01-01
This essay has been conceptually eclectic in that we have integrated concepts from genre theory and discourse analysis. In our interpretation of Merivale and Marshall's narratives, we have also drawn upon Frye's Anatomy of criticism, a canonical text in literary genre theory. Such an eclectic approach seems warranted by both the contextual and textual features of Merivale's and Marshall's narratives, and in particular by Merivale's use of Mennipean satire with its encyclopedic detail. In our discussion of Merivale and Marshall's Admissions Records we have drawn on speech act theory to suggest that the Order (to admit a patient), the two medical certificates that follow, and finally, the notice to admit a patient constitute a constellation of texts, a genre suite, with a powerful illocutionary force. These texts are the prelude to and the means of confinement; they are both act and process. At the heart of our comparison of the asylum records of Merivale and Marshall with their "survivor narratives" is our analytic conclusion that the Ticehurst case histories can be said to constitute a linear "chronicle" of what Hayes Newington, the writer of the two case histories observed and inferred about his two patients. As chronicles, the Ticehurst Asylum case histories are linear representations or realistic accounts. As such, these archival documents provide a genuine insight into the "ways that that reality offers itself to perception". The institutional accounts exist in--and mark a--"flat time," equalized by each dated entry depicting the writer's mechanical act of observing/noting in brief, stereotypical sentences, e.g., "Patient is better [or, conversely, no] better today." We dubbed this metronomic time: beating regularly and evenly, flattening out the individual trajectories of each patient's illness. Metronomic time is normative. Each beat is calculated precisely to be the same as next. The dispassionate nature of clinical observations and the metronymic rhythms of the asylum fit with this flat, regular, uniform view of time. Once metronomic, institutional time is set in motion by the precipitating event of the certificates of insanity, entries are logged with regularity and observations are made in a formulaic, abbreviated, and predictable manner. By contrast, the passage of time recorded in both Merivale's memoir and Marshall's oral account is irregular, unpredictable, marked by acute catastrophes and long anxious periods of waiting for a resolution, by peaks of conflict and turmoil alternating with valleys of dazed stupor or inaction. Time in their accounts is also recursive; events are re-lived, sometimes more than once, as the patients recount their feelings about their confinement. Time for Merivale and Marshall (and presumably other patients as well) acquires a symphonic pattern: recursive, with dramatic highs and lows, unfolding multiple variations of a central theme-in both of these cases, denial of insanity. Both metronome and symphonic time have similar rhythmic "deep structures," but while one is simply a repetitive drumbeat of the quotidian, the other takes off into richer, more elaborate arrangements invested with personal meaning. PMID:22870607
Convex Lens-Induced Confinement for Imaging Single Molecules
Leslie, Sabrina R.; Fields, Alexander P.; Cohen, Adam E.
2011-01-01
Fluorescence imaging is used to study the dynamics of a wide variety of single molecules in solution or attached to a surface. Two key challenges in this pursuit are (1) to image immobilized single molecules in the presence of a high level of fluorescent background and (2) to image freely diffusing single molecules for long times. Strategies that perform well by one measure often perform poorly by the other. Here, we present a simple modification to a wide-field fluorescence microscope that addresses both challenges and dramatically improves single-molecule imaging. The technique of convex lens-induced confinement (CLIC) restricts molecules to a wedge-shaped gap of nanoscale depth, formed between a plano-convex lens and a planar coverslip. The shallow depth of the imaging volume leads to 20-fold greater rejection of background fluorescence than is achieved with total internal reflection fluorescence (TIRF) imaging. Elimination of out-of-plane diffusion leads to an approximately 10 000-fold longer diffusion-limited observation time per molecule than is achieved with confocal fluorescence correlation spectroscopy. The CLIC system also provides a new means to determine molecular size. The CLIC system does not require any nanofabrication, nor any custom optics, electronics, or computer control. PMID:20557026
Transition to coarsening for confined one-dimensional membranes
Thomas Le Goff; Paolo Politi; Olivier Pierre-Louis
2015-04-28
We discuss the dynamics of membranes confined between two attractive walls with arbitrary permeabilities. We use a two-dimension model, so that the membrane is effectively a one-dimensional object. In a previous work, we have shown that this model predicts frozen states caused by bending rigidity-induced oscillatory interactions between kinks (or domain walls). We here demonstrate that in the presence of membrane tension, potential asymmetry, or thermal noise, there is a finite threshold above which frozen states disappear, and perpetual coarsening is restored. Depending on the driving force, the transition to coarsening exhibits different scenarios. First, for membranes under tension, small tensions can only lead to transient coarsening or partial disordering, while above a finite threshold, membrane oscillations disappear and perpetual coarsening is found. Second, potential asymmetry is relevant in the non-conserved case only, i.e. for permeable walls, where it induces a drift force on the kinks, leading to a fast coarsening process via kink-antikink annihilation. However, below some threshold, the drift force can be balanced by the oscillatory interactions between kinks, and frozen adhesion patches can still be observed. Finally, noise always induces coarsening with standard exponents related to mass conservation, but the typical time for the appearance of coarsening exhibits an Arrhenius form. As a consequence, a finite noise amplitude is needed in order to observe coarsening in observable time.
T-T Neutron Spectrum from Inertial Confinement Implosions
NASA Astrophysics Data System (ADS)
Caggiano, Joseph; Sayre, Daniel; Brune, Carl; Gatu Johnson, Maria; McNabb, Dennis; Bacher, Andrew
2014-03-01
Measurements of the T(t , 2 n) ? fusion reaction (TT) have been conducted using high-purity (~99 percent) tritium, gas-filled glass capsules in inertial confinement fusion implosions. In these experiments, which were conducted at both the NIF and the OMEGA laser facilities, spectral measurements of the TT neutrons were carried out using two well-established instruments: the neutron-time-of-flight (nTOF) and the magnet-based Magnetic Recoil Spectrometer (MRS). The resolutions of these systems were improved significantly for the nTOF facility by using a crystal with much faster decay time and for the MRS by using a thinner, more uniform CD2 recoil foil. At OMEGA, charged particle energy spectra were also measured using a magnetic charged particle spectrometer and the Thompson Parabola Ion Energy spectrometer. These measurements at reactant central-mass energies in the range of 10-30 keV can be used to study the TT reaction mechanism near astrophysical energies. This work was reported at the 2013 APS April meeting, where we used basic R-matrix line shapes. Since then we have updated and improved the fitting method by including the proper quantum interferences from fermion symmetry and decay channels. The implications of these effects on our understanding of the spectrum also will be discussed.
T-T Neutron Spectrum from Inertial Confinement Implosions
NASA Astrophysics Data System (ADS)
Caggiano, Joseph; Gatu Johnson, Maria; Bacher, Andrew; McNabb, Denns
2013-04-01
Measurements of the T(2n,)^4He reaction (TT) have been conducted using high-purity tritium, gas-filled capsules in inertial confinement fusion (ICF) implosions. At the OMEGA laser facility, TT neutron spectra were measured using two instruments: the neutron-time-of-flight (nTOF) facility and the Magnetic Recoil Spectrometer (MRS) facility. The resolutions of these systems were improved for nTOF by using a crystal with much faster decay time and for MRS by using a thinner, more uniform CD2 recoil foil. Measurements at c.m. energies of 10-30 keV can be used to study the TT three-body reaction mechanism near astrophysical energies. With both nTOF and MRS, we observe a small, narrow peak starting at the 9.44 MeV endpoint, corresponding to the n + ^5He (g.s.) reaction channel. Most of the TT reaction proceeds through other reaction channels which produce broad, continuous neutron spectra in the range 0 - 9.5 MeV. Implications for ICF experiments at the National Ignition Facility will be discussed. Work in collaboration with J. A. Frenje, D. T. Casey, M. J.-E. Manuel, N. Sinenian, A. B. Zylstra, F. H. Seguin, C. K. Li, R. D. Petrasso, V. Yu Glebov, P. B. Radha, D. D. Meyerhofer, T. C. Sangster, P. A. Amendt, R. Hatarik, D. B. Sayre, J. R. Rygg, H. W. Herrmann and Y. H. Kim.
An ICF (Inertial Confinement Fusion) power plant development program
Storm, E.; Hogan, W.J.; Lindl, J.D.
1990-06-05
The development of Inertial Confinement Fusion (ICF) as a power source will require demonstrating four principal objectives: ignition and propagating burn, adequate gain ({eta}G {approx gt} 10) at low drive energy for the reactor driver, reactor pulse rates of a few Hz, and the long-term reliability and economics of a reactor. Additionally, the potential value and applicability of special-purpose ICF reactors, such as tritium breeding reactors and reactors for burning high level fission waste (actinide and fission products) should be investigated. To keep development time and costs to a minimum these should be accomplished with as few major facilities as possible, and subsystems should be developed only as they are needed. A viable scenario for Inertial Fusion Energy (IFE) would include establishing the first milestone in the National Academy of Sciences (NAS) and Fusion Policy Advisory Committee (FPAC) recommended Nova Upgrade, and the latter three in an Engineering Test Facility (ETF)/Demonstration Power Plant (DPP), i.e. two major facilities. To be successful in so short a time, operations at the major facilities would have to be supported by off-line reactor driver and other technology development. The program plan discussed here assumes that enhanced funding is available beginning in FY 1992. It is estimated that such a program could provide a prototype IFE power plant by the second decade of the 21st century and make commercial power available in mid to late 2020s.
Transport efficiency studies for light-ion inertial confinement fusion
NASA Astrophysics Data System (ADS)
Rose, D. V.; Ottinger, P. F.; Olson, C. L.
1994-09-01
The proposed Laboratory Microfusion Facility (LMF) will require greater than or equal to 10 MJ of 30 MeV lithium ions to be transported and focused onto high-gain, high-yield inertial confinement fusion targets. The light-ion LMF approach used a multimodular system with individual ion extraction diodes as beam sources. Several transport schemes are being considered to deliver the individual ion beams to the centrally located target. Previous work P.F. Ottinger, D.V. Rose, and C.L. Olson, J. Appl. Phys. 75, 4402 (1994) examined the effect of time-of-flight bunching on energy transport efficiency, eta sub t, under realistic constraints on diode operation, beam transport, and packing. Target design considerations suggest that the instantaneous power efficiency, gamma sub t, be maximized near peak power. Because of time-of-flight bunching, peak power occurs at the end of the power pulse for LMF designs. This work examines the effect of power efficiency tuning on eta sub t for three transport schemes. Results indicate that tuning the power pulse to maximize eta sub t, at about three-quarters through the pulse provides high power efficiency at the end of the pulse while still maintaining high eta sub t. In addition to power efficiency tuning, effects on eta sub t from variations of the diode impedance model and the diode voltage waveform are also examined.
Dynamically slow processes in supercooled water confined between hydrophobic plates.
Franzese, Giancarlo; Santos, Francisco de Los
2009-12-16
We study the dynamics of water confined between hydrophobic flat surfaces at low temperature. At different pressures, we observe different behaviors that we understand in terms of the hydrogen bond dynamics. At high pressure, the formation of the open structure of the hydrogen bond network is inhibited and the surfaces can be rapidly dried (dewetted) by formation of a large cavity with decreasing temperature. At lower pressure we observe strong non-exponential behavior of the correlation function, but with no strong increase of the correlation time. This behavior can be associated, on the one hand, to the rapid ordering of the hydrogen bonds that generates heterogeneities and, on the other hand, to the lack of a single timescale as a consequence of the cooperativity in the vicinity of the liquid-liquid critical point that characterizes the phase diagram at low temperature of the water model considered here. At very low pressures, the gradual formation of the hydrogen bond network is responsible for the large increase of the correlation time and, eventually, the dynamical arrest of the system, with a strikingly different dewetting process, characterized by the formation of many small cavities. PMID:21836218
Robustness of predator-prey models for confinement regime transitions in fusion plasmas
Zhu, H. [Department of Physics, Centre for Fusion, Space and Astrophysics, University of Warwick, Coventry CV4 7AL (United Kingdom); Chapman, S. C. [Department of Physics, Centre for Fusion, Space and Astrophysics, University of Warwick, Coventry CV4 7AL (United Kingdom); Department of Mathematics and Statistics, University of Tromso (Norway); Dendy, R. O. [Euratom/CCFE Fusion Association, Culham Science Centre, Abingdon, Oxfordshire OX14 3DB (United Kingdom); Department of Physics, Centre for Fusion, Space and Astrophysics, University of Warwick, Coventry CV4 7AL (United Kingdom)
2013-04-15
Energy transport and confinement in tokamak fusion plasmas is usually determined by the coupled nonlinear interactions of small-scale drift turbulence and larger scale coherent nonlinear structures, such as zonal flows, together with free energy sources such as temperature gradients. Zero-dimensional models, designed to embody plausible physical narratives for these interactions, can help to identify the origin of enhanced energy confinement and of transitions between confinement regimes. A prime zero-dimensional paradigm is predator-prey or Lotka-Volterra. Here, we extend a successful three-variable (temperature gradient; microturbulence level; one class of coherent structure) model in this genre [M. A. Malkov and P. H. Diamond, Phys. Plasmas 16, 012504 (2009)], by adding a fourth variable representing a second class of coherent structure. This requires a fourth coupled nonlinear ordinary differential equation. We investigate the degree of invariance of the phenomenology generated by the model of Malkov and Diamond, given this additional physics. We study and compare the long-time behaviour of the three-equation and four-equation systems, their evolution towards the final state, and their attractive fixed points and limit cycles. We explore the sensitivity of paths to attractors. It is found that, for example, an attractive fixed point of the three-equation system can become a limit cycle of the four-equation system. Addressing these questions which we together refer to as 'robustness' for convenience is particularly important for models which, as here, generate sharp transitions in the values of system variables which may replicate some key features of confinement transitions. Our results help to establish the robustness of the zero-dimensional model approach to capturing observed confinement phenomenology in tokamak fusion plasmas.
Modeling Non-Confined Coronal Flares: Dynamics and X-Ray Diagnostics
F. Reale; F. Bocchino; G. Peres
2001-12-14
Long-lasting, intense, stellar X-ray flares may approach conditions of breaking magnetic confinement and evolving in open space. We explore this hypothesis with hydrodynamic simulations of flares occurring in a non-confined corona: model flares are triggered by a transient impulsive heating injected in a plane-parallel stratified corona. The plasma evolution is described by means of a numerical 2-D model in cylindrical geometry R,Z. We explore the space of fundamental parameters. As a reference model, we consider a flare triggered by a heating pulse that would cause a 20 MK flare if delivered in a 40000 km long closed loop. The modeled plasma evolution is described. The X-ray emission, spectra and light curves at the ASCA/SIS focal plan, and in two intense X-ray lines (Mg XI at 9.169 A and Fe XXI at 128.752 A), have been synthesized from the models. The results are discussed and compared to features of confined events, and scaling laws are derived. The light curves invariably show a very rapid rise, a constant phase as long as the constant heating is on, and then a very fast decay, on time scales of few seconds, followed by a more gradual one (few minutes). We show that this evolution of the emission, and especially the fast decay, together with other potentially observable effects, are intrinsic to the assumption of non-confinement. Their lack indicates that observed long-lasting stellar X-ray flares should involve plasma strongly confined by magnetic fields.
Robustness of predator-prey models for confinement regime transitions in fusion plasmas
NASA Astrophysics Data System (ADS)
Zhu, H.; Chapman, S. C.; Dendy, R. O.
2013-04-01
Energy transport and confinement in tokamak fusion plasmas is usually determined by the coupled nonlinear interactions of small-scale drift turbulence and larger scale coherent nonlinear structures, such as zonal flows, together with free energy sources such as temperature gradients. Zero-dimensional models, designed to embody plausible physical narratives for these interactions, can help to identify the origin of enhanced energy confinement and of transitions between confinement regimes. A prime zero-dimensional paradigm is predator-prey or Lotka-Volterra. Here, we extend a successful three-variable (temperature gradient; microturbulence level; one class of coherent structure) model in this genre [M. A. Malkov and P. H. Diamond, Phys. Plasmas 16, 012504 (2009)], by adding a fourth variable representing a second class of coherent structure. This requires a fourth coupled nonlinear ordinary differential equation. We investigate the degree of invariance of the phenomenology generated by the model of Malkov and Diamond, given this additional physics. We study and compare the long-time behaviour of the three-equation and four-equation systems, their evolution towards the final state, and their attractive fixed points and limit cycles. We explore the sensitivity of paths to attractors. It is found that, for example, an attractive fixed point of the three-equation system can become a limit cycle of the four-equation system. Addressing these questions which we together refer to as "robustness" for convenience is particularly important for models which, as here, generate sharp transitions in the values of system variables which may replicate some key features of confinement transitions. Our results help to establish the robustness of the zero-dimensional model approach to capturing observed confinement phenomenology in tokamak fusion plasmas.
NASA Astrophysics Data System (ADS)
Schönhals, A.; Goering, H.; Schick, Ch.; Frick, B.; Zorn, R.
2003-09-01
The glassy dynamics of poly(propylene glycol) (PPG) and poly(dimethyl siloxane) (PDMS) confined to a nanoporous host system revealed by dielectric spectroscopy, temperature-modulated DSC and neutron scattering is compared. For both systems the relaxation rates estimated from dielectric spectroscopy and temperature-modulated DSC agree quantitatively indicating that both experiments sense the glass transition. For PPG the segmental dynamics is determined by a counterbalance of adsorption and confinement effect. The former results form an interaction of the confined macromolecules with the internal surfaces. A confinement effect originates from an inherent length scale on which the underlying molecular motions take place. The increment of the specific-heat capacity ? c_ab{p} at the glass transition vanishes at a finite length scale of 1.8 nm. Both results support the conception that a characteristic length scale is relevant for glassy dynamics. For PDMS only a confinement effect is observed which is much stronger than that for PPG. Down to a pore size of 7.5 nm, the temperature dependence of the relaxation times follows the Vogel-Fulcher-Tammann dependence. At a pore size of 5 nm this changes to an Arrhenius-like behaviour with a low activation energy. At the same pore size ? c_ab{p} vanishes for PDMS. Quasielastic neutron scattering experiments reveal that also the diffusive character of the relevant molecular motions —found to be characteristic above the glass transition— seems to disappear at this length scale. These results gives further strong support that the glass transition has to be characterised by an inherent length scale of the relevant molecular motions.
Axisymmetric Tandem Mirrors: Stabilization and Confinement Studies
Post, R.F.; Fowler, T.K.; Bulmer, R.; Byers, J.; Hua, D.; Tung, L. [Lawrence Livermore National Laboratory (United States)
2005-01-15
The 'Kinetic Stabilizer' has been proposed as a means of MHD stabilizing an axisymmetric tandem mirror system. The K-S concept is based on theoretical studies by Ryutov, confirmed experimentally in the Gas Dynamic Trap experiment in Novosibirsk. In the K-S beams of ions are directed into the end of an 'expander' region outside the outer mirror of a tandem mirror. These ions, slowed, stagnated, and reflected as they move up the magnetic gradient, produce a low-density stabilizing plasma.At the Lawrence Livermore National Laboratory we have been conducting theoretical and computational studies of the K-S Tandem Mirror. These studies have employed a low-beta code written especially to analyze the beam injection/stabilization process,and a new code SYMTRAN (by Hua and Fowler)that solves the coupled radial and axial particle and energy transport in a K-S T-M. Also, a 'legacy' MHD stability code, FLORA, has been upgraded and employed to benchmark the injection/stabilization code and to extend its results to high beta values.The FLORA code studies so far have confirmed the effectiveness of the K-S in stabilizing high-beta (40%) plasmas with stabilizer plasmas the peak pressures of which are several orders of magnitude smaller than those of the confined plasma.Also the SYMTRAN code has shown D-T plasma ignition from alpha particle energy deposition in T-M regimes with strong end plugging.Our studies have confirmed the viability of the K-S T-M concept with respect to MHD stability and radial and axial confinement. We are continuing these studies in order to optimize the parameters and to examine means for the stabilization of possible residual instability modes, such as drift modes and 'trapped-particle' modes. These modes may in principle be controlled by tailoring the stabilizer plasma distribution and/or the radial potential distribution.In the paper the results to date of our studies are summarized and projected to scope out possible fusion-power versions of the K-S T-M.
29 CFR 1915.94 - Work in confined or isolated spaces.
Code of Federal Regulations, 2011 CFR
2011-07-01
...Work in confined or isolated spaces. 1915.94 Section 1915...Work in confined or isolated spaces. The provisions of this section shall apply to ship repairing, shipbuilding...is performed in a confined space, except as provided...
29 CFR 1915.94 - Work in confined or isolated spaces.
Code of Federal Regulations, 2010 CFR
2010-07-01
...Work in confined or isolated spaces. 1915.94 Section 1915...Work in confined or isolated spaces. The provisions of this section shall apply to ship repairing, shipbuilding...is performed in a confined space, except as provided...
Light-Front Holographic QCD and the Confinement Potential
NASA Astrophysics Data System (ADS)
Brodsky, Stanley J.; de Téramond, Guy F.; Dosch, Hans Günter
2014-06-01
Light-Front Hamiltonian theory, derived from the quantization of the QCD Lagrangian at fixed light-front time ?=t+z/c, provides a rigorous frame-independent framework for solving nonperturbative QCD. The eigenvalues of the light-front QCD Hamiltonian predict the hadronic mass spectrum, and the corresponding eigensolutions provide the light-front wavefunctions which describe hadron structure. The valence Fock-state wavefunctions of the light-front QCD Hamiltonian satisfy a single-variable relativistic equation of motion, analogous to the nonrelativistic radial Schrödinger equation, with an effective confining potential U which systematically incorporates the effects of higher quark and gluon Fock states. In fact, the potential U has a unique form if one requires that the action for zero quark mass remains conformally invariant. We also show that the holographic mapping of gravity in AdS space to QCD with a specific soft-wall dilaton yields the same light-front Schrödinger equation. Light-front holography also leads to a precise relation between the bound-state amplitudes in the fifth dimension z of AdS space and the boost-invariant light-front wavefunctions describing the internal structure of hadrons in physical space-time. The elastic and transition form factors of the pion and the nucleons are found to be well described in this framework. The predictions of the LF equations of motion include a zero-mass pion in the chiral mq?0 limit, and linear Regge trajectories M2(n,L)?n+L with the same slope in the radial quantum number n and orbital angular momentum L. The light-front AdS/QCD holographic approach thus gives a frame-independent representation of color-confining dynamics, Regge spectroscopy, and the excitation spectra of relativistic light-quark meson and baryon bound states in QCD in terms of a single mass parameter. We also briefly discuss the implications of the underlying conformal template of QCD for renormalization scale-setting and the implications of light-front quantization for the value of the cosmological constant.
NMR Studies on the Temperature-Dependent Dynamics of Confined Water
Matthias Sattig; Stefan Reutter; Franz Fujara; Mayke Werner; Gerd Buntkowsky; Michael Vogel
2014-07-16
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 $\\alpha$ process-like dynamics is probed above the crossover temperature, whereas $\\beta$ 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 $\\beta$ process of supercooled liquids during the glass transition, suggesting a value of $T_g\\!\\approx\\!185$ 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 $\\alpha$ 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 $E_a\\!\\approx\\!0.5\\ $eV in the low-temperature range, $T\\!water.
Hydrodynamic instabilities in inertial confinement fusion
Hoffman, N.M.
1994-12-01
The focus of the paper is on buoyancy-driven instabilities of the Rayleigh-Taylor type, which are commonly regarded as the most important kind of hydrodynamic instability in inertial-confinement-fusion implosions. The paper is intended to be pedagogical rather than research-oriented, and so is by no means a comprehensive review of work in this field. Rather, it is hoped that the student will find here a foundation on which to build an understanding of current research, and the experienced researcher will find a compilation of useful results. The aim of the paper is to discuss the evolution of a single Rayleigh-Taylor-unstable mode, from its linear phase to its late-stage constant-velocity bubble growth, with a brief consideration of the saturation of linear growth. The influence of other modes in invoked only in the short-range sense (in wavenumber space) of the Haan saturation model. Owing to limitations of space, the treatment of other instabilities such as Richtmyer-Meshkov and Kelvin-Helmholtz is necessarily very brief, and entirely inadequate as an introductory discussion. Likewise, there is no reference to the effect of convergent geometry, to long-range mode coupling, or to shape effects in three-dimensional growth. Furthermore, there is no reference to the large body of experimental research related to hydrodynamic instabilities.
Numerical Studies of Properties of Confined Helium
NASA Technical Reports Server (NTRS)
Manousakis, Efstratios
2003-01-01
We carry out state of the art simulations of properties of confined liquid helium near the superfluid transition to a degree of accuracy which allows to make predictions for the outcome of fundamental physics experiments in microgravity. First we report our results for the finite-size scaling behavior of heat capacity of superfluids for cubic and parallel-plate geometry. This allows us to study the crossover from zero and two dimensions to three dimensions. Our calculated scaling functions are in good agreement with recently measured specific heat scaling functions for the above mentioned geometries. We also present our results of a quantum simulation of submonolayer of molecular hydrogen deposited on an ideal graphite substrate using path-integral quantum Monte Carlo simulation. We find that the monolayer phase diagram is rich and very similar to that of helium monolayer. We are able to uncover the main features of the complex monolayer phase diagram, such as the commensurate solid phases and the commensurate to incommensurate transition, in agreement with the experiments and to find some features which are missing from the experimental analysis.
A numerical study of confined turbulent jets
NASA Technical Reports Server (NTRS)
Zhu, J.; Shih, T.-H.
1993-01-01
A numerical investigation is reported of turbulent incompressible jets confined in two ducts, one cylindrical and the other conical with a 5 degree divergence. In each case, three Craya-Curtet numbers are considered which correspond, respectively, to flow situations with no moderate and strong recirculation. Turbulence closure is achieved by using the k-epsilon model and a recently proposed realizable Reynolds stress algebraic equation model that relates the Reynolds stresses explicitly to the quadratic terms of the mean velocity gradients and ensures the positiveness of each component of the turbulent kinetic energy. Calculations are carried out with a finite-volume procedure using boundary-fitted curvilinear coordinates. A second-order accurate, bounded convection scheme and sufficiently fine grids are used to prevent the solutions from being contaminated by numerical diffusion. The calculated results are compared extensively with the available experimental data. It is shown that the numerical methods presented are capable of capturing the essential flow features observed in the experiments and that the realizable Reynolds stress algebraic equation model performs much better than the k-epsilon model for this class of flows of great practical importance.
Droplet microfluidics driven by gradients of confinement
Dangla, Rémi; Kayi, S. Cagri; Baroud, Charles N.
2013-01-01
The miniaturization of droplet manipulation methods has led to drops being proposed as microreactors in many applications of biology and chemistry. In parallel, microfluidic methods have been applied to generate monodisperse emulsions for applications in the pharmaceuticals, cosmetics, and food industries. To date, microfluidic droplet production has been dominated by a few designs that use hydrodynamic forces, resulting from the flowing fluids, to break drops at a junction. Here we present a platform for droplet generation and manipulation that does not depend on the fluid flows. Instead, we use devices that incorporate height variations to subject the immiscible interfaces to gradients of confinement. The resulting curvature imbalance along the interface causes the detachment of monodisperse droplets, without the need for a flow of the external phase. Once detached, the drops are self-propelled due to the gradient of surface energy. We show that the size of the drops is determined by the device geometry; it is insensitive to the physical fluid properties and depends very weakly on the flow rate of the dispersed phase. This allows us to propose a geometric theoretical model that predicts the dependence of droplet size on the geometric parameters, which is in agreement with experimental measurements. The approach presented here can be applied in a wide range of standard applications, while simplifying the device operations. We demonstrate examples for single-droplet operations and high-throughput generation of emulsions, all of which are performed in simple and inexpensive devices. PMID:23284169
Inertial confinement fusion reactor cavity analysis
NASA Astrophysics Data System (ADS)
Peterson, R. R.; Macfarlane, J. J.; Moses, G. A.; El-Afify, M.; Corradini, M. L.
1987-07-01
This is a process report for research performed from July 1, 1986 to June 30, 1987, for Lawrence Livermore National Laboratory under subcontract number 9265205 with the project title: Inertial Confinement Fusion Reactor Cavity Analysis. This research generally considers the problems of vaporization and condensation of liquid metal or solid first surface materials in high yield ICF facilities such as reactors or high yield target test experiments. The past year's research consisted of 1.2 man years of effort on three tasks. These tasks were: verify the current vaporization-condensation models in CONRAD through literature surveys of relevant published data, and evaluation and comparison of these data with predictions by CONRAD on condensation phenomena, and with predictions by CONRAD, ZPINCH, and/or MIXERG on radiation phenomena, design a small-scale vaporization experiment by evaluating existing experimental facilities, selecting a primary facility, and conceptually designing an experiment complete with facility parameters and measurables, and design a small-scale condensation experiment including experimental parameters, measurables, and diagnostics.
Stellarator approach to fusion plasma confinement
Harris, J.H.
1985-01-01
The stellarator is a toroidal fusion plasma confinement device with nested magnetic flux surfaces. The required twist of the field lines is produced by external helical coils rather than by plasma current, as in a tokamak. Stellarator devices are attractive fusion reactor candidates precisely because they offer the prospect of steady-state operation without plasma current. In the last few years the excellent results achieved with currentless stellarator plasmas of modest minor radius (10 to 20 cm) at Kyoto University (Japan) and the Max Planck Institute (West Germany) have made the stellarator second only to the tokamak in its progress toward fusion breakeven, with temperatures T/sub e/, T/sub i/ approx. 1 KeV, Lawson products n tau approx. 2 to 5 x 10/sup 12/ cm/sup -3/.s, and volume-averaged beta values approx. = 2%. The Advanced Toroidal Facility (ATF), now under construction at Oak Ridge Natioal Laboratory (ORNL) and scheduled to operate in 1986, represents a significant advance in stellarator research, with a plasma major radius of 2.1 m, an average minor radius of 0.3 m, and a magnetic field of 2 T for 5 s or 1 T at steady state. ATF replaces the Impurity Study Experiment (ISX-B) tokamak at ORNL and will use the ISX-B heating and diagnostic system.
Quantum confinement in GaP nanoclusters
Laurich, B.K.; Smith, D.C.; Healy, M.D.
1994-06-01
We have prepared GaP and GaAs nanoclusters from organometallic condensation reactions of E[Si(ChH{sub 3})3]3 (E = P, As) and GaCl{sub 3}. The size of the as synthesized clusters is 10 {Angstrom} to 15 {Angstrom}. Larger clusters of 20 {Angstrom} to 30 {Angstrom} size were obtained by thermal annealing of the as grown material. X-ray diffraction and transmission electron microscopy confirm the high crystalline quality. A lattice contraction of 6.7% could be seen for 10 {Angstrom} sized GaAs clusters. The clusters are nearly spherical in shape. Optical absorption spectra show a distinct line which can be assigned to the fundamental transition of the quantum confined electronic state. The measured blue shift, with respect to the GaP bulk absorption edge is 0.53 eV. As the cluster is smaller than the exciton radius, we can calculate the cluster size from this blue shift and obtain 20.2 {Angstrom}, consistent with the results from X-ray diffraction of 19.5 {Angstrom} for the same sample.
Species separation in inertial confinement fusion fuels
NASA Astrophysics Data System (ADS)
Bellei, C.; Amendt, P. A.; Wilks, S. C.; Haines, M. G.; Casey, D. T.; Li, C. K.; Petrasso, R.; Welch, D. R.
2013-01-01
It is shown by means of multi-fluid particle-in-cell simulations that convergence of the spherical shock wave that propagates through the inner gas of inertial confinement fusion-relevant experiments is accompanied by a separation of deuterium (D) and tritium (T) ions across the shock front. Deuterons run ahead of the tritons due to their lower mass and higher charge-to-mass ratio and can reach the center several tens of picoseconds before the tritons. The rising edge of the DD and TT fusion rate is also temporally separated by the same amount, which should be an observable in experiments and would be a direct proof of the "stratification conjecture" on the shock front [Amendt et al., Phys. Plasmas 18, 056308 (2011)]. Moreover, dephasing of the D and T shock components in terms of density and temperature leads to a degradation of the DT fusion yield as the converging shock first rebounds from the fuel center (shock yield). For the parameters of this study, the second peak in the fusion yield (compression yield) is strongly dependent on the choice of the flux limiter.
Auxiliary Heating of Inertial Confinement Fusion Targets
NASA Astrophysics Data System (ADS)
Norreys, Peter
2014-10-01
The role of collisionless ion heating arising from the propagation of petawatt-laser driven relativistic electron beams in dense plasma will be discussed. The energy cascade mechanism begins first with the rapid growth of electrostatic waves near the electron plasma frequency. These waves reach high amplitudes and break, which then results in the generation of a strongly driven turbulent Langmuir spectrum. Parametric decay of these waves, particularly via the modulational instability, then gives rise to a coupled turbulent ion acoustic spectrum. These waves, in turn, experience significant Landau damping, resulting in the rapid heating of the background ion population. In this talk, I will review the evidence for this cascade process in laboratory plasmas and describe the theoretical background that underpins this process. I will then present the most recent analytic modelling, particle-in-cell and Vlasov-Poisson simulation results of my team within Oxford Physics and the Central Laser Facility that explores the optimum parameter space for this process, focusing in particular on the requirements for auxiliary heating of the central hot spot in inertial confinement fusion target experiments now underway on the National Ignition Facility. I will also describe new methods for hole-boring through the coronal plasma surrounding the fuel using strongly relativistic laser beams that demonstrates the strong suppression of the hosing instability under these conditions.
Small perturbations in magnetically confined plasmas
NASA Astrophysics Data System (ADS)
Sugiyama, Linda
2012-03-01
Two types of small perturbation theories exist for plasmas confined in strong toroidal magnetic fields. Both are well developed and provide useful insights into plasma behavior. The MHD plasma equations can be linearized to predict exponential growth rates for small disturbances.footnotetextI.B. Bernstein et al., Proc. Roy. Soc. London, Ser. A 244 1765 (1958). The toroidal magnetic field can be described as a Hamiltonian system with two degrees of freedeom, as long as the toroidal field component is nonzero. Small perturbations produce magnetic island chains at low order rational surfaces and characteristic stochasticity around magnetic X-points (homoclinic or heteroclinic tangles around hyperbolic saddle points in Hamiltonian dynamics), The X-points can be induced by the perturbations or exist in the equilibrium configuration). The two descriptions appear to predict different behavior for small plasma perturbations. The explanation of this apparent paradox has important implications for linear and nonlinear small plasma perturbations and for plasma models, that extend beyond MHD. The cases of magnetic tearing modes on interior flux surfaces and edge instabilities in plasmas with X-poinhts on the plasma separatrix are discussed.
An extragalactic supernebula confined by gravity.
Turner, J L; Beck, S C; Crosthwaite, L P; Larkin, J E; McLean, I S; Meier, D S
2003-06-01
Little is known about the origins of globular clusters, which contain hundreds of thousands of stars in a volume only a few light years across. Radiation pressure and winds from luminous young stars should disperse the star-forming gas and disrupt the formation of the cluster. Globular clusters in our Galaxy cannot provide answers; they are billions of years old. Here we report the measurement of infrared hydrogen recombination lines from a young, forming super star cluster in the dwarf galaxy NGC5253. The lines arise in gas heated by a cluster of about one million stars, including 4,000-6,000 massive, hot 'O' stars. It is so young that it is still enshrouded in gas and dust, hidden from optical view. The gases within the cluster seem bound by gravity, which may explain why the windy and luminous O stars have not yet blown away those gases. Young clusters in 'starbursting' galaxies in the local and distant Universe may also be gravitationally confined and cloaked from view. PMID:12789332
Dipole Transport: a New Confinement Paradigm
NASA Astrophysics Data System (ADS)
Kesner, J.; Garnier, D.; Mauel, M.
2014-10-01
In a tokamak-like device turbulence will grow up to a level determined by non-linear processes. The associated transport, in combination with particle and energy sources then determines the density and temperature profiles of the plasma. This paradigm is fundamentally different for a plasma that is confined in a dipole field. In a dipole, levitated to avoid losses to the supports, the plasma will assume a stationary profile determined only by the specific volume, V (?) , (which is determined by the magnetic geometry). Independent of the source and sink profiles for particles and energy, turbulence will grow up to a sufficient level so that diffusion and pinch dynamics will establish stationary profiles characterized by ne ~ 1 / V and p ~ 1 /V 5 / 3 . This process is observed in magnetospheric plasmas and we have observed it in the laboratory in LDX. For example, with edge fueling in LDX we observed that the stationary (peaked) density profile (n ~ 1 / V) was established by a turbulence-driven density pinch whereas in recent experiments with core (pellet) fueling turbulence was observed to relax the density back to the stationary profile on a similar timescale. Supported by the NSF-DOE Partnership in Plasma Science Grants DE-FG02-00ER54585 and PHY-1201896.
Azimuthal field instability in a confined ferrofluid.
Dias, Eduardo O; Miranda, José A
2015-02-01
We report the development of interfacial ferrohydrodynamic instabilities when an initially circular bubble of a nonmagnetic inviscid fluid is surrounded by a viscous ferrofluid in the confined geometry of a Hele-Shaw cell. The fluid-fluid interface becomes unstable due to the action of magnetic forces induced by an azimuthal field produced by a straight current-carrying wire that is normal to the cell plates. In this framework, a pattern formation process takes place through the interplay between magnetic and surface tension forces. By employing a perturbative mode-coupling approach we investigate analytically both linear and intermediate nonlinear regimes of the interface evolution. As a result, useful analytical information can be extracted regarding the destabilizing role of the azimuthal field at the linear level, as well as its influence on the interfacial pattern morphology at the onset of nonlinear effects. Finally, a vortex sheet formalism is used to access fully nonlinear stationary solutions for the two-fluid interface shapes. PMID:25768610
Azimuthal field instability in a confined ferrofluid
NASA Astrophysics Data System (ADS)
Dias, Eduardo O.; Miranda, José A.
2015-02-01
We report the development of interfacial ferrohydrodynamic instabilities when an initially circular bubble of a nonmagnetic inviscid fluid is surrounded by a viscous ferrofluid in the confined geometry of a Hele-Shaw cell. The fluid-fluid interface becomes unstable due to the action of magnetic forces induced by an azimuthal field produced by a straight current-carrying wire that is normal to the cell plates. In this framework, a pattern formation process takes place through the interplay between magnetic and surface tension forces. By employing a perturbative mode-coupling approach we investigate analytically both linear and intermediate nonlinear regimes of the interface evolution. As a result, useful analytical information can be extracted regarding the destabilizing role of the azimuthal field at the linear level, as well as its influence on the interfacial pattern morphology at the onset of nonlinear effects. Finally, a vortex sheet formalism is used to access fully nonlinear stationary solutions for the two-fluid interface shapes.
Particle focusing mechanisms in curving confined flows.
Gossett, Daniel R; Di Carlo, Dino
2009-10-15
Particles in finite-inertia confined channel flows are known to segregate and focus to equilibrium positions whose number corresponds with the fold of symmetry of the channel's cross section. The addition of curvature into channels presumably modifies these equilibrium inertial focusing positions, because of the secondary flow induced in curved channels. Here, we identify the critical interaction of the secondary flow field with inertial lift forces to create complex sets of particle focusing positions that vary with the channel Reynolds number (Re(C)) and the inertial force ratio, which is a new dimensionless parameter that is based on the ratio of inertial lift to drag forces from the secondary flow. We use these results to identify microfluidic channel geometries to focus particles at rates an order of magnitude higher than previously shown (channel Reynolds number, Re(C) = 270) and develop design criteria for the focusing of potentially arbitrary-sized particles. In addition, our results indicate that channel curvature can lead to microfluidic designs with reduced fluidic resistance, useful for lower power inertial focusing or separation. These results will enable design of practical particle/cell separation, filtration, and focusing systems for critical applications in biomedicine and environmental cleanup. PMID:19761190
Precursor detonation wave development in ANFO due to aluminum confinement
Jackson, Scott I [Los Alamos National Laboratory; Klyanda, Charles B [Los Alamos National Laboratory; Short, Mark [Los Alamos National Laboratory
2010-01-01
Detonations in explosive mixtures of ammonium-nitrate-fuel-oil (ANFO) confined by aluminum allow for transport of detonation energy ahead of the detonation front due to the aluminum sound speed exceeding the detonation velocity. The net effect of this energy transport on the detonation is unclear. It could enhance the detonation by precompressing the explosive near the wall. Alternatively, it could decrease the explosive performance by crushing porosity required for initiation by shock compression or destroying confinement ahead of the detonation. At present, these phenomena are not well understood. But with slowly detonating, non-ideal high explosive (NIHE) systems becoming increasing prevalent, proper understanding and prediction of the performance of these metal-confined NIHE systems is desirable. Experiments are discussed that measured the effect of this ANFO detonation energy transported upstream of the front by a 76-mm-inner-diameter aluminum confining tube. Detonation velocity, detonation-front shape, and aluminum response are recorded as a function of confiner wall thickness and length. Detonation shape profiles display little curvature near the confining surface, which is attributed to energy transported upstream modifying the flow. Average detonation velocities were seen to increase with increasing confiner thickness, while wavefront curvature decreased due to the stiffer, subsonic confinement. Significant radial sidewall tube motion was observed immediately ahead of the detonation. Axial motion was also detected, which interfered with the front shape measurements in some cases. It was concluded that the confiner was able to transport energy ahead of the detonation and that this transport has a definite effect on the detonation by modifying its characteristic shape.
Interplay of explosive thermal reaction dynamics and structural confinement
NASA Astrophysics Data System (ADS)
Perry, W. Lee; Zucker, Jonathan; Dickson, Peter M.; Parker, Gary R.; Asay, Blaine W.
2007-04-01
Explosives play a significant role in human affairs; however, their behavior in circumstances other than intentional detonation is poorly understood. Accidents may have catastrophic consequences, especially if additional hazardous materials are involved. Abnormal ignition stimuli, such as impact, spark, friction, and heat may lead to a very violent outcome, potentially including detonation. An important factor influencing the behavior subsequent to abnormal ignition is the strength and inertia of the vessel confining the explosive, i.e., the near-field structural/mechanical environment, also known as confinement (inertial or mechanical). However, a comprehensive and quantified understanding of how confinement affects reaction violence does not yet exist. In the research discussed here, we have investigated a wide range of confinement conditions and related the explosive response to the fundamentals of the combustion process in the explosive. In our experiments, a charge of an octahydrotetranitrotetrazine-based plastic bonded explosive (PBX 9501) was loaded into a gun assembly having variable confinement conditions and subjected to a heating profile. The exploding charge breached the confinement and accelerated a projectile down the gun barrel. High bandwidth pressure and volume measurements were made and a first-law analysis was used to obtain enthalpy and power from the raw data. These results were then used to quantify reaction violence. Enthalpy change and power ranged from 0-1.8 kJ and 0-12 MW for 300 mg charges, respectively. Below a confinement strength of 20 MPa, violence was found to decline precipitously with decreasing confinement, while the violence for the heaviest confinement experiments was found to be relatively constant. Both pressure and pressurization rate were found to have critical values to induce and sustain violent reaction.
Ion-mediated RNA structural collapse: effect of spatial confinement
Zhi-Jie Tan; Shi-Jie Chen
2013-05-06
RNAs are negatively charged molecules residing in macromolecular crowding cellular environments. Macromolecular confinement can influence the ion effects in RNA folding. In this work, using the recently developed tightly bound ion model for ion fluctuation and correlation, we investigate the confinement effect on the ion-mediated RNA structural collapse for a simple model system. We found that, for both Na$^+$ and Mg$^{2+}$, ion efficiencies in mediating structural collapse/folding are significantly enhanced by the structural confinement. Such an enhancement in the ion efficiency is attributed to the decreased electrostatic free energy difference between the compact conformation ensemble and the (restricted) extended conformation ensemble due to the spatial restriction.
Temperature-resonant cyclotron spectra in confined geometries.
Pototsky, A; Hänggi, P; Marchesoni, F; Savel'ev, S
2011-07-01
We consider a two-dimensional gas of colliding charged particles confined to finite size containers of various geometries and subjected to a uniform orthogonal magnetic field. The gas spectral densities are characterized by a broad peak at the cyclotron frequency. Unlike for infinitely extended gases, where the amplitude of the cyclotron peak grows linearly with temperature, here confinement causes such a peak to go through a maximum for an optimal temperature. In view of the fluctuation-dissipation theorem, the reported resonance effect has a direct counterpart in the electric susceptibility of the confined magnetized gas. PMID:21867113
Role of center vortices in Gribov's confinement scenario
NASA Astrophysics Data System (ADS)
Quandt, M.; Reinhardt, H.; Burgio, G.
2010-03-01
The connection of Gribov’s confinement scenario in the Coulomb gauge with the center vortex picture of confinement is investigated. For this purpose we assume a vacuum wave functional that models the infrared properties of the theory and, in particular, shows strict confinement, i.e. an area law of the Wilson loop. We isolate the center vortex content of this wave functional by standard lattice methods and investigate their contributions to various static propagators of the Hamilton approach to Yang-Mills theory in the Coulomb gauge. We find that the infrared properties of these quantities, in particular, the infrared divergence of the ghost form factor, are dominated by center vortices.
Inherent Structures and Kauzmann Temperature of Confined Liquids
A. Attili; P. Gallo; M. Rovere
2005-04-06
Calculations of the thermodynamical properties of a supercooled liquid confined in a matrix are performed with an inherent structure analysis. The liquid entropy is computed by means of a thermodynamical integration procedure. The contributions to the free energy of the liquid can be decoupled also in confinement in the configurational and the vibrational part. We show that the vibrational entropy can be calculated in the harmonic approximation as in the bulk case. The Kauzmann temperature of the confined system is estimated from the behavior of the configurational entropy.
Spatial confinement effects in laser-induced breakdown spectroscopy
Shen, X. K.; Sun, J.; Ling, H.; Lu, Y. F. [Department of Electrical Engineering, University of Nebraska-Lincoln, Lincoln, Nebraska 68588-0511 (United States)
2007-08-20
The spatial confinement effects in laser-induced breakdown of aluminum (Al) targets in air have been investigated both by optical emission spectroscopy and fast photography. A KrF excimer laser was used to produce plasmas from Al targets in air. Al atomic emission lines show an obvious enhancement in the emission intensity when a pair of Al-plate walls were placed to spatially confine the plasma plumes. Images of the Al plasma plumes showed that the plasma plumes evolved into a torus shape and were compressed in the Al walls. The mechanism for the confinement effects was discussed using shock wave theory.
Confined geometry effects on reorientational dynamics of molecular liquids in porous silica glasses
NASA Astrophysics Data System (ADS)
Liu, G.; Li, Y.; Jonas, J.
1991-11-01
This work investigates the relative role of the pure geometrical confinement and the strength of the surface effect on the dynamics of liquids in porous silica glasses prepared by the sol-gel process. The deuteron NMR spin-lattice relaxation times T1 of several molecular liquids in porous silica glasses are reported as function of pore size in the range from 18 to 143 Å over the temperature range from 260 to 310 K. Molecular liquids studied include strongly interacting polar liquids such as pyridine-d5, aniline-d5, and nitrobenzene-d5, whereas the saturated cyclic hydrocarbon liquids of cyclohexane-d12 and cis-decalin-d18 represent the weakly interacting liquids. In a first approximation, toluene-d1 and dioxane-d18 are chosen as examples of liquids with intermediate interactions with the silica surface. The experimental relaxation data are analyzed by using the two-state, fast-exchange model which is found to be valid for the strongly interacting liquids and liquids with intermediate interactions. In terms of this model, the viscosity of the surface layer for pyridine-d5 is about 30 times higher than that for bulk liquid pyridine. The importance of the two-dimensional approach to describe motional dynamics of liquids confined to pores smaller than 30 Å is illustrated in the case of weakly interacting liquid of cyclohexane-d12. Additional information on the relative role of surface interactions and the pure topological effects on the dynamics of liquids in confined geometries was obtained by using surface-modified glasses in which the surface hydroxyl groups were replaced by OSi(CH3)2OC2H5 groups. Indeed, the effects of surface modifications on the 2H T-11 are most pronounced for strongly interacting liquids whereas they are absent for cyclohexane. In agreement with the concept of two-dimensional behavior of liquids in small pores, one finds that the low-frequency relaxation times, namely, the spin-spin relaxation time T2, and the spin-lattice relaxation time in the rotating coordinate frame, T1?, remain unchanged by surface modification. In fact, this is a consequence of logarithmic enhancement of the spectral density at low frequencies so that the effect of pure geometrical confinement on the T-12 and T-11? relaxation rates is much larger than any relaxation rate changes arising from surface modification. Several selected NMR T1 experiments on pyridine-d5 confined to anopore and zeolites are also presented.
Quantum confinement regime in silicon nanocrystals Julien Derr Ã, Kerry Dunn, Daria Riabinina of photoluminescence (PL) in Si nanocrystals embedded in a silicon-rich SiO2 matrix. PL properties as a function of time and temperature were investigated for nanocrystal diameters ðdÞ ranging from about 1.5 to 4 nm
Transient drawdown solution for a constant pumping test in finite two-zone confined aquifers
NASA Astrophysics Data System (ADS)
Wang, C.-T.; Yeh, H.-D.; Tsai, C.-S.
2012-02-01
The drawdown solution has been widely used to analyze pumping test data for the determination of aquifer parameters when coupled with an optimization scheme. The solution can also be used to predict the drawdown due to pumping and design the dewatering system. The drawdown solution for flow toward a finite-radius well with a skin zone in a confined aquifer of infinite extent in radial direction had been developed before. To our best knowledge, the drawdown solution in confined aquifers of finite extent with a skin zone so far has never before been presented in the groundwater literature. This article presents a mathematical model for describing the drawdown distribution due to a constant-flux pumping from a finite-radius well with a skin zone in confined aquifers of finite extent. The analytical solution of the model is developed by applying the methods of Laplace transforms, Bromwich contour integral, and residue theorem. This solution can be used to investigate the effects of finite boundary and conductivity ratio on the drawdown distribution. In addition, the inverse relationship between Laplace- and time-domain variables is used to develop the large time solution which can reduce to the Thiem solution if there is no skin zone.
Transient drawdown solution for a constant pumping test in finite two-zone confined aquifers
NASA Astrophysics Data System (ADS)
Wang, C.-T.; Yeh, H.-D.; Tsai, C.-S.
2011-10-01
The drawdown solution has been widely used to analyze pumping test data for the determination of aquifer parameters when coupled with an optimization scheme. The solution can also be used to predict the drawdown due to pumping and design the dewatering system. The drawdown solution for flow toward a finite-radius well with a skin zone in a confined aquifer of infinite extent in radial direction had been developed before. To our best knowledge, the drawdown solution in confined aquifers of finite extent so far has never before been presented in the groundwater literature. This article presents a mathematical model for describing the drawdown distribution due to a constant-flux pumping from a finite-radius well with a skin zone in confined aquifers of finite extent. The analytical solution of the model is developed by applying the methods of Laplace transforms and Bromwich contour integral. This solution can be used to investigate the effects of finite boundary and conductivity ratio on the drawdown distribution. In addition, the inverse relationship between Laplace- and time-domain variables is used to develop the large time solution which can reduce to the Thiem solution if there is no skin zone.
Plasma balls/kinks as solitons of large $N$ confining gauge theories
Pallab Basu; Bobby Ezhuthachan; Spenta R. Wadia
2006-10-24
We discuss finite regions of the deconfining phase of a confining gauge theory (plasma balls/kinks) as solitons of the large $N$, long wavelength, effective Lagrangian of the thermal gauge theory expressed in terms of suitable order parameters. We consider a class of confining gauge theories whose effective Lagrangian turns out to be a generic 1 dim. unitary matrix model. The dynamics of this matrix model can be studied by an exact mapping to a non-relativistic many fermion problem on a circle. We present an approximate solution to the equations of motion which corresponds to the motion (in Euclidean time) of the Fermi surface interpolating between the phase where the fermions are uniformly distributed on the circle (confinement phase) and the phase where the fermion distribution has a gap on the circle (deconfinement phase). We later self-consistently verify that the approximation is a good one. We discuss some properties and implications of the solution including the surface tension which turns out to be positive. As a by product of our investigation we point out the problem of obtaining time dependent solutions in the collective field theory formalism due to generic shock formation.
Bubble confinement in flow boiling of FC-72 in a ''rectangular'' microchannel of high aspect ratio
Barber, Jacqueline [School of Engineering, University of Edinburgh, The King's Buildings, Mayfield Road, Edinburgh, EH9 3JL (United Kingdom); Aix-Marseille Universite (UI, UII) - CNRS Laboratoire IUSTI, UMR 6595, 5 Rue Enrico Fermi, Marseille 13453 (France); Brutin, David; Tadrist, Lounes [Aix-Marseille Universite (UI, UII) - CNRS Laboratoire IUSTI, UMR 6595, 5 Rue Enrico Fermi, Marseille 13453 (France); Sefiane, Khellil [School of Engineering, University of Edinburgh, The King's Buildings, Mayfield Road, Edinburgh, EH9 3JL (United Kingdom)
2010-11-15
Boiling in microchannels remains elusive due to the lack of full understanding of the mechanisms involved. A powerful tool in achieving better comprehension of the mechanisms is detailed imaging and analysis of the two-phase flow at a fundamental level. Boiling is induced in a single microchannel geometry (hydraulic diameter 727 {mu}m), using a refrigerant FC-72, to investigate the effect of channel confinement on bubble growth. A transparent, metallic, conductive deposit has been developed on the exterior of the rectangular microchannel, allowing simultaneous uniform heating and visualisation to be achieved. The data presented in this paper is for a particular case with a uniform heat flux applied to the microchannel and inlet liquid mass flowrate held constant. In conjunction with obtaining high-speed images and videos, sensitive pressure sensors are used to record the pressure drop across the microchannel over time. Bubble nucleation and growth, as well as periodic slug flow, are observed in the microchannel test section. The periodic pressure fluctuations evidenced across the microchannel are caused by the bubble dynamics and instances of vapour blockage during confined bubble growth in the channel. The variation of the aspect ratio and the interface velocities of the growing vapour slug over time, are all observed and analysed. We follow visually the nucleation and subsequent both 'free' and 'confined' growth of a vapour bubble during flow boiling of FC-72 in a microchannel, from analysis of our results, images and video sequences with the corresponding pressure data obtained. (author)
Extreme Gain Enhancement in Surface-Confined Resonant Stimulated Brillouin Scattering
Dostart, Nathan; Bahl, Gaurav
2015-01-01
The notion that Stimulated Brillouin Scattering (SBS) is primarily defined by bulk material properties has been overturned by recent work on nanoscale waveguides. It is now understood that boundary forces of radiation pressure and electrostriction appearing in such highly confined waveguides can make a significant contribution to the Brillouin gain. Here, this concept is extended to show that gain enhancement does not require nanoscale or subwavelength features, but generally appears where optical and acoustic fields are simultaneously confined near a free surface or material interface. This situation routinely occurs in whispering gallery resonators (WGRs), making gain enhancements much more accessible than previously thought. To illustrate this concept, the first full-vectorial analytic model for SBS in WGRs is developed, including optical boundary forces, and the SBS gain in common WGR geometries is computationally evaluated. These results predict that gains 100 times greater than the predictions of scalar...
Thermal monopole condensation and confinement in finite temperature Yang-Mills theories
D'Alessandro, Alessio; D'Elia, Massimo [Dipartimento di Fisica, Universita di Genova and INFN, Via Dodecaneso 33, 16146 Genova (Italy); Shuryak, Edward V. [Department of Physics and Astronomy, State University of New York, Stony Brook, New York 11794-3800 (United States)
2010-05-01
We investigate the connection between color confinement and thermal Abelian monopoles populating the deconfined phase of SU(2) Yang-Mills theory, by studying how the statistical properties of the monopole ensemble change as the confinement/deconfinement temperature is approached from above. In particular, we study the distribution of monopole currents with multiple wrappings in the Euclidean time direction, corresponding to two or more particle permutations, and show that multiple wrappings increase as the deconfinement temperature is approached from above, in a way compatible with a condensation of such objects happening right at the deconfining transition. We also address the question of the thermal monopole mass, showing that different definitions give consistent results only around the transition, where the monopole mass goes down and becomes of the order of the critical temperature itself.
Broken-diabolo nanoantenna for co-enhancing and -confining optical electric and magnetic field
NASA Astrophysics Data System (ADS)
Yu, Zaihe; Gao, Zhen; Wang, Zhuoyuan
2015-07-01
In this letter, we introduce a broken-diabolo nanoantenna aimed at generating electric and magnetic hot spots in the near-infrared range, thus enhancing and confining the electric and magnetic optical field simultaneously. This nanoantenna different from the well-known diabolo nanoantenna and bowtie nanoantenna in that it can accumulate a large charge density at the upper air gap and a high optical current density within the lower central junction, leading to a large electric and magnetic field enhancement near the center of the nanoantenna at the same time. Numerical simulation results on this broken-diabolo nanoantenna show that a 5-fold enhancement of electric field (compare to the electric field enhancement of a diabolo nanoantenna) is achieved at a wavelength of 2353 nm, confined to a 40-by-40 nm region near the center of the nanoantenna.
Confinement engineering of s-d exchange interactions in GaMnAs quantum wells
NASA Astrophysics Data System (ADS)
Stern, N. P.; Myers, R. C.; Poggio, M.; Gossard, A. C.; Awschalom, D. D.
2006-03-01
Recent measurements of coherent electron spin dynamics have observed antiferromagnetic s-d exchange coupling between conduction band electrons and electrons localized on Mn^2+ impurities in GaMnAs quantum wells. Here we discuss systematic measurements of the s-d exchange interaction in Ga1-xMnxAs/AlyGa1-yAs quantum wells with different confinement potentials using time- resolved Kerr rotation spectroscopy. Extending previous investigations of the well width dependence of the s-d exchange, N0?, we find that the magnitude of the exchange parameter, N0?, varies as a function of both well width and well depth (y). Both phenomena reduce to a general dependence on confinement energy, which is well-fit to a model taking into account the effect of kinetic exchange and band mixing on the exchange parameters. R. C. Myers, M. Poggio, N. P. Stern, A. C. Gossard, and D. D. Awschalom, Phys. Rev. Lett. 95, 017204 (2005)
Overview of Milestone E activities, greater confinement than shallow land burial
Mezga, L.J.
1981-01-01
In summary, the objective of Milestone E is to provide the technology and documentation needed to open a site providing greater confinement than shallow land burial. To that end, ORNL has prepared a technical position paper defining greater confinement disposal, options for achieving it, and the need for this disposal technology. In order to meet the objective of the milestones, the LLWMP evaluated the full range of options to shallow land burial and decided to focus on a combination of greater depth solidification containment and engineered barriers. The program identified a series of research needs and then focused program efforts on resolving those needs. These tasks are proceeding on schedule at this time but budget reductions may have an impact on our ability to maintain the schedule.
Tommasini, R
2010-04-23
An important diagnostic tool for inertial confinement fusion is time-resolved imaging of the dense cold fuel surrounding the hot spot. Here we report on the source and diagnostic development of hard x-ray radiography and on the first radiographs of direct drive implosions obtained at photon energies up to about 100keV, where the Compton effect is the dominant contributor to the shell opacity. The radiographs of direct drive, plastic shell implosions obtained at the OMEGA laser facility have a spatial resolution of {approx}10um and a temporal resolution of {approx}10ps. This novel Compton Radiography is an invaluable diagnostic tool for Inertial Confinement Fusion targets, and will be integrated at the National Ignition Facility (NIF).
Franz, Dennis; Reich, Aina; Strelow, Christian; Wang, Zhe; Kornowski, Andreas; Kipp, Tobias; Mews, Alf
2014-11-12
One-dimensional semiconductor nanostructures combine electron mobility in length direction with the possibility of tailoring the physical properties by confinement effects in radial direction. Here we show that thin CdSe quantum nanowires exhibit low-temperature fluorescence spectra with a specific universal structure of several sharp lines. The structure strongly resembles the pattern of bulk spectra but show a diameter-dependent shift due to confinement effects. Also the fluorescence shows a pronounced complex blinking behavior with very different blinking dynamics of different emission lines in one and the same spectrum. Time- and space-resolved optical spectroscopy are combined with high-resolution transmission electron microscopy of the very same quantum nanowires to establish a detailed structure-property relationship. Extensive numerical simulations strongly suggest that excitonic complexes involving donor and acceptor sites are the origin of the feature-rich spectra. PMID:25343231
NASA Astrophysics Data System (ADS)
Shaughnessy, D. A.; Moody, K. J.; Gharibyan, N.; Grant, P. M.; Gostic, J. M.; Torretto, P. C.; Wooddy, P. T.; Bandong, B. B.; Despotopulos, J. D.; Cerjan, C. J.; Hagmann, C. A.; Caggiano, J. A.; Yeamans, C. B.; Bernstein, L. A.; Schneider, D. H. G.; Henry, E. A.; Fortner, R. J.
2014-06-01
We describe a radiochemical measurement of the ratio of isotope concentrations produced in a gold hohlraum surrounding an Inertial Confinement Fusion capsule at the National Ignition Facility (NIF). We relate the ratio of the concentrations of (n,?) and (n,2n) products in the gold hohlraum matrix to the down-scatter of neutrons in the compressed fuel and, consequently, to the fuel's areal density. The observed ratio of the concentrations of 198m+gAu and 196gAu is a performance signature of ablator areal density and the fuel assembly confinement time. We identify the measurement of nuclear cross sections of astrophysical importance as a potential application of the neutrons generated at the NIF.
Scaling law of electron confinement in a zero beta polywell device
Gummersall, David V.; Carr, Matthew; Cornish, Scott; Kachan, Joe [Department of Plasma Physics, School of Physics A28, University of Sydney, NSW 2006 (Australia)] [Department of Plasma Physics, School of Physics A28, University of Sydney, NSW 2006 (Australia)
2013-10-15
Orbital theory simulation was applied to an electron trap that uses a cube shaped magnetic cusp known as a Polywell device. The purpose of this device is to create a virtual cathode in order to achieve nuclear fusion using inertial electrostatic confinement. Analytical expressions of the electron confinement time and average position within the device were obtained in terms of the current in the field coils, the dimensions of the device, and the kinetic energy of the electrons. Comparisons with numerical simulations showed good agreement over a parameter range that spanned several orders of magnitude for the current. In addition, power loss from electrons exiting the trap was estimated in order to obtain minimum power requirement to maintain a virtual cathode within the device.
Morikawa, Kyojiro; Kazoe, Yutaka; Mawatari, Kazuma; Tsukahara, Takehiko; Kitamori, Takehiko
2015-02-01
Understanding liquid structure and the electrical properties of liquids confined in extended nanospaces (10-1000 nm) is important for nanofluidics and nanochemistry. To understand these liquid properties requires determination of the dielectric constant of liquids confined in extended nanospaces. A novel dielectric constant measurement method has thus been developed for extended nanospaces using a streaming potential method. We focused on the nonsteady-state streaming potential in extended nanospaces and successfully measured the dielectric constant of liquids within them without the use of probe molecules. The dielectric constant of water was determined to be significantly reduced by about 3 times compared to that of the bulk. This result contributes key information toward further understanding of the chemistry and fluidics in extended nanospaces. PMID:25569302
Scaling law of electron confinement in a zero beta polywell device
NASA Astrophysics Data System (ADS)
Gummersall, David V.; Carr, Matthew; Cornish, Scott; Kachan, Joe
2013-10-01
Orbital theory simulation was applied to an electron trap that uses a cube shaped magnetic cusp known as a Polywell device. The purpose of this device is to create a virtual cathode in order to achieve nuclear fusion using inertial electrostatic confinement. Analytical expressions of the electron confinement time and average position within the device were obtained in terms of the current in the field coils, the dimensions of the device, and the kinetic energy of the electrons. Comparisons with numerical simulations showed good agreement over a parameter range that spanned several orders of magnitude for the current. In addition, power loss from electrons exiting the trap was estimated in order to obtain minimum power requirement to maintain a virtual cathode within the device.
Slow dynamics of a confined supercooled binary mixture. II. Q space analysis
NASA Astrophysics Data System (ADS)
Gallo, P.; Pellarin, R.; Rovere, M.
2003-12-01
We report the analysis in the wave vector space of the density correlator of a Lennard-Jones binary mixture confined in a disordered matrix of soft spheres upon supercooling. In spite of the strong confining medium the behavior of the mixture is consistent with the mode-coupling theory predictions for bulk supercooled liquids. The relaxation times extracted from the fit of the density correlator to the stretched exponential function follow a unique power law behavior as a function of wave vector and temperature. The von Schweidler scaling properties are valid for an extended wave vector range around the peak of the structure factor. The parameters extracted in the present work are compared with the bulk values obtained in literature.
Communication: Local structure-mobility relationships of confined fluids reverse upon supercooling
NASA Astrophysics Data System (ADS)
Bollinger, Jonathan A.; Jain, Avni; Carmer, James; Truskett, Thomas M.
2015-04-01
We examine the structural and dynamic properties of confined binary hard-sphere mixtures designed to mimic realizable colloidal thin films. Using computer simulations, governed by either Newtonian or overdamped Langevin dynamics, together with other techniques including a Fokker-Planck equation-based method, we measure the position-dependent and average diffusivities of particles along structurally isotropic and inhomogeneous dimensions of the fluids. At moderate packing fractions, local single-particle diffusivities normal to the direction of confinement are higher in regions of high total packing fraction; however, these trends are reversed as the film is supercooled at denser average packings. Auxiliary short-time measurements of particle displacements mirror data obtained for experimental supercooled colloidal systems. We find that average dynamics can be approximately predicted based on the distribution of available space for particle insertion across orders of magnitude in diffusivity regardless of the governing microscopic dynamics.
Local structure-mobility relationships of confined fluids reverse upon supercooling
Jonathan A. Bollinger; Avni Jain; James Carmer; Thomas M. Truskett
2015-04-10
We examine the structural and dynamic properties of confined binary hard-sphere mixtures designed to mimic realizable colloidal thin films. Using computer simulations, governed by either Newtonian or overdamped Langevin dynamics, together with other techniques including a Fokker-Planck equation-based method, we measure the position-dependent and average diffusivities of particles along structurally isotropic and inhomogeneous dimensions of the fluids. At moderate packing fractions, local single-particle diffusivities normal to the direction of confinement are higher in regions of high total packing fraction; however, these trends are reversed as the film is supercooled at denser average packings. Auxiliary short-time measurements of particle displacements mirror data obtained for experimental supercooled colloidal systems. We find that average dynamics can be approximately predicted based on the distribution of available space for particle insertion across orders of magnitude in diffusivity regardless of the governing microscopic dynamics.