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Sample records for confinement time

  1. Space-time symmetries of confined quarks

    SciTech Connect

    Han, D.; Noz, M.E.; Kim, Y.S.; Son, D.

    1982-03-15

    The first paragraph of Rotbart's recent paper is amplified. It is shown that the minimum symmetry for the spacetime separation of the confined quarks is that of the O(3)-like little group of the Poincare group for massive hadrons. It is then pointed out that the existence of additional coordinate dependences is determined from the way in which specific models are constructed.

  2. Coupling of transit time instabilities in electrostatic confinement fusion devices

    NASA Astrophysics Data System (ADS)

    Gruenwald, J.; Fröhlich, M.

    2015-07-01

    A model of the behavior of transit time instabilities in an electrostatic confinement fusion reactor is presented in this letter. It is demonstrated that different modes are excited within the spherical cathode of a Farnsworth fusor. Each of these modes is dependent on the fusion products as well as the acceleration voltage applied between the two electrodes and they couple to a resulting oscillation showing non-linear beat phenomena. This type of instability is similar to the transit time instability of electrons between two resonant surfaces but the presence of ions and the occurring fusion reactions alter the physics of this instability considerably. The physics of this plasma instability is examined in detail for typical physical parameter ranges of electrostatic confinement fusion devices.

  3. Real-time dynamics of the confining string

    NASA Astrophysics Data System (ADS)

    Loshaj, Frasher

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

  4. 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.

  5. Long time impurity confinement as a precursor to disruptions

    SciTech Connect

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

    1988-01-01

    The confinement time of laser-ablated test impurities in tokamaks lengthens considerably as operation approaches the density-limit boundary. Observations on the TEXT takamak indicate that a sharp change in the balance of diffusion and inward convection mechanisms governing impurity transport, at least in the interior of plasmas, occurs as a precursor of both partial and major disruptions in Ohmically heated discharges. Similar phenomena have been observed on other tokamaks, albeit with certain chartacteristics peculiar to each individual machine. These transitions can induce partial disruptions through impurity accumulation. Further study is required to ascertain whether they are a contributing factor major disruptions. Corresponding changes in the transport of the working gas ions have also been documented in TEXT. 11 refs., 9 figs.

  6. Full-f gyrokinetic simulation over a confinement time

    SciTech Connect

    Idomura, Yasuhiro

    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.

  7. Improvement of confinement times of lithium ion and electron plasmas in BX-U

    NASA Astrophysics Data System (ADS)

    Himura, H.; Noichi, T.; Nakata, S.; Kawai, S.; Sanpei, A.

    2015-06-01

    Confinements of both electron (e-) and Lithium ion (Li+) plasmas in the BX-U machine are improved experimentally. For the e- plasma, the longest confinement time so far has been 10 s, which is much longer than the classical electron-electron collision time: ?ee 0.6 s. On the other hand, for the Li+ plasma, the longest confinement time has been about 0.5 s, which is still much shorter than the classical ion-ion collision time.

  8. Time and space resolved neutron diagnostic systems for magnetically confined plasmas

    NASA Astrophysics Data System (ADS)

    Slaughter, D. R.; Spracklen, H. S.; Delvasto, R.

    1983-10-01

    Neutron spectrometer/counter systems have been developed for diagnostic measurements on magnetically confined deuterium and deuterium-tritium plasmas. An early version was used to determine the mean ion energy as well as the ion-energy confinement time in the endplugs of the Tandem Mirror Experiment. A recent upgrade includes a 10 MHz pulse height analysis and particle identification capability for time- and space-resolved neutron spectrum measurements. Resolution is adequate for a neutron Doppler-width measurement of mean ion energy in near-future confinement experiments such as the Mirror Fusion Test Facility.

  9. Quantum confinement in 1D systems through an imaginary-time evolution method

    NASA Astrophysics Data System (ADS)

    Roy, Amlan K.

    2015-09-01

    Quantum confinement is studied by numerically solving time-dependent (TD) Schrdinger equation (SE). An imaginary-time evolution technique is employed in conjunction with the minimization of an expectation value, to reach the global minimum. Excited states are obtained by imposing the orthogonality constraint with all lower states. Applications are made on three important model quantum systems, namely, harmonic, repulsive and quartic oscillators; enclosed inside an impenetrable box. The resulting diffusion equation is solved using finite-difference method. Both symmetric and asymmetric confinement are considered for attractive potential; for others only symmetrical confinement. Accurate eigenvalue, eigenfunction and position expectation values are obtained, which show excellent agreement with existing literature results. Variation of energies with respect to box length is followed for small, intermediate and large sizes. In essence, a simple accurate and reliable method is proposed for confinement in quantum systems.

  10. Confinement time of electrons and H(-)/D(-) ions in the Uramoto type sheet plasma

    NASA Astrophysics Data System (ADS)

    Uramoto, Joshin

    1987-10-01

    Confinement times of electrons and H(-)/D(-) ions in the Uramoto type sheet plasma as a H(-)/D(-) ion source of volume production are determined from e-folding decay times of negative current to a Langmuir probe, after a discharge for the sheet plasma production is stopped through SCR connected between the anode and the cathode. The confinement times depend mainly on a bias potential of the metal vacuum chamber outside of the sheet plasma, which are ranging from about 40 microsec (for plus bias voltage with respect to the anode) to about 300 microsec (for minus bias voltage). Then, in order to extract a volume produced H(-)/D(-) ion current in high efficiency, it is shown that a long confinement time is an important necessary condition with the two necessary conditions (high electron density in low electron temperature and electron beam components) reported already.

  11. Exponential time differencing methods with Chebyshev collocation for polymers confined by interacting surfaces

    NASA Astrophysics Data System (ADS)

    Liu, Yi-Xin; Zhang, Hong-Dong

    2014-06-01

    We present a fast and accurate numerical method for the self-consistent field theory calculations of confined polymer systems. It introduces an exponential time differencing method (ETDRK4) based on Chebyshev collocation, which exhibits fourth-order accuracy in temporal domain and spectral accuracy in spatial domain, to solve the modified diffusion equations. Similar to the approach proposed by Hur et al. [Macromolecules 45, 2905 (2012)], non-periodic boundary conditions are adopted to model the confining walls with or without preferential interactions with polymer species, avoiding the use of surface field terms and the mask technique in a conventional approach. The performance of ETDRK4 is examined in comparison with the operator splitting methods with either Fourier collocation or Chebyshev collocation. Numerical experiments show that our exponential time differencing method is more efficient than the operator splitting methods in high accuracy calculations. This method has been applied to diblock copolymers confined by two parallel flat surfaces.

  12. Exponential time differencing methods with Chebyshev collocation for polymers confined by interacting surfaces.

    PubMed

    Liu, Yi-Xin; Zhang, Hong-Dong

    2014-06-14

    We present a fast and accurate numerical method for the self-consistent field theory calculations of confined polymer systems. It introduces an exponential time differencing method (ETDRK4) based on Chebyshev collocation, which exhibits fourth-order accuracy in temporal domain and spectral accuracy in spatial domain, to solve the modified diffusion equations. Similar to the approach proposed by Hur et al. [Macromolecules 45, 2905 (2012)], non-periodic boundary conditions are adopted to model the confining walls with or without preferential interactions with polymer species, avoiding the use of surface field terms and the mask technique in a conventional approach. The performance of ETDRK4 is examined in comparison with the operator splitting methods with either Fourier collocation or Chebyshev collocation. Numerical experiments show that our exponential time differencing method is more efficient than the operator splitting methods in high accuracy calculations. This method has been applied to diblock copolymers confined by two parallel flat surfaces. PMID:24929368

  13. A model for inferring transport rates from observed confinement times in field-reversed configurations

    NASA Astrophysics Data System (ADS)

    Steinhauer, Loren C.; Milroy, Richard D.; Slough, John T.

    1985-03-01

    A one-dimensional transport model is developed to simulate the confinement of plasma and magnetic flux in a field-reversed configuration. Given the resistivity, the confinement times can be calculated. Approximate expressions are found which yield the magnitude and gross profile of the resistivity if the confinement times are known. These results are applied to experimental data from experiments, primarily TRX-1, to uncover trends in the transport properties. Several important conclusions emerge. The transport depends profoundly, and inexplicably, on the plasma formation mode. The inferred transport differs in several ways from the predictions of local lower-hybrid-drift turbulence theory. Finally, the gross resistivity exhibits an unusual trend with xs (separatrix radius rs divided by the conducting wall radius rc ), and is peaked near the magnetic axis for certain predictable conditions.

  14. Exponential time differencing methods with Chebyshev collocation for polymers confined by interacting surfaces

    SciTech Connect

    Liu, Yi-Xin Zhang, Hong-Dong

    2014-06-14

    We present a fast and accurate numerical method for the self-consistent field theory calculations of confined polymer systems. It introduces an exponential time differencing method (ETDRK4) based on Chebyshev collocation, which exhibits fourth-order accuracy in temporal domain and spectral accuracy in spatial domain, to solve the modified diffusion equations. Similar to the approach proposed by Hur et al. [Macromolecules 45, 2905 (2012)], non-periodic boundary conditions are adopted to model the confining walls with or without preferential interactions with polymer species, avoiding the use of surface field terms and the mask technique in a conventional approach. The performance of ETDRK4 is examined in comparison with the operator splitting methods with either Fourier collocation or Chebyshev collocation. Numerical experiments show that our exponential time differencing method is more efficient than the operator splitting methods in high accuracy calculations. This method has been applied to diblock copolymers confined by two parallel flat surfaces.

  15. Confinement and cavity effects in time-domain photoionization and recombination of Kr@C60

    NASA Astrophysics Data System (ADS)

    Magrakvelidze, Maia; Dixit, Gopal; Madjet, Mohamed; Chakraborty, Himadri

    2014-05-01

    Photoionization (PI) and radiative recombination (RR) of the endofullerene molecule, Kr@C60, are studied in a framework of time-dependent local density approximation (TDLDA) augmented by the Leeuwen and Baerends exchange-correlation functional. Phases of the dipole matrix elements corresponding to transitions to (PI) and from (RR) the continuum, involving atomic-type, fullerene-type and atom-fullerene hybrid levels of the molecule, are considered. Associated Wigner-Smith time-delays are extracted. Effects of the confinement on the phase and time-delay at Kr Cooper minima, and that of the C60 cavity at C60 cross section minima have been examined. Further, intercoulombic decay (ICD) and hybrid Auger-ICD resonances, direct results of the confinement, are found to considerably enrich the time-domain response of the molecule. This work was supported by the National Science Foundation.

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

    NASA Astrophysics Data System (ADS)

    Vitancol, Roberto S.; Galapon, Eric A.

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

  17. 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.

  18. Analysis of the neutron time-of-flight spectra from inertial confinement fusion experiments

    SciTech Connect

    Hatarik, R.; Sayre, D. B.; Caggiano, J. A.; Phillips, T.; Eckart, M. J.; Bond, E. J.; Cerjan, C.; Grim, G. P.; Hartouni, E. P.; Knauer, J. P.; Mcnaney, J. M.; Munro, D. H.

    2015-11-12

    For a long time, neutron time-of-flight diagnostics been used to characterize the neutron spectrum produced by inertial confinement fusion experiments. The primary diagnostic goals are to extract the d+t→n+α (DT) and d+d→n+³He (DD) neutron yields and peak widths, and the amount DT scattering relative to its unscattered yield, which is also known as the down-scatter ratio (DSR). These quantities are used to infer yield weighted plasma conditions, such as ion temperature (Tion) and cold fuel areal density. We explain such novel methodologies used to determine neutron yield, apparent Tion and DSR.

  19. Analysis of the neutron time-of-flight spectra from inertial confinement fusion experiments

    DOE PAGESBeta

    Hatarik, R.; Sayre, D. B.; Caggiano, J. A.; Phillips, T.; Eckart, M. J.; Bond, E. J.; Cerjan, C.; Grim, G. P.; Hartouni, E. P.; Knauer, J. P.; et al

    2015-11-12

    For a long time, neutron time-of-flight diagnostics been used to characterize the neutron spectrum produced by inertial confinement fusion experiments. The primary diagnostic goals are to extract the d+t→n+α (DT) and d+d→n+³He (DD) neutron yields and peak widths, and the amount DT scattering relative to its unscattered yield, which is also known as the down-scatter ratio (DSR). These quantities are used to infer yield weighted plasma conditions, such as ion temperature (Tion) and cold fuel areal density. We explain such novel methodologies used to determine neutron yield, apparent Tion and DSR.

  20. Ergodicity breaking, ageing, and confinement in generalized diffusion processes with position and time dependent diffusivity

    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.

  1. Real time reciprocal space mapping of nano-islands induced by quantum confinment.

    SciTech Connect

    Hong, H.; Gray, A.; 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 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.

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

    PubMed Central

    Ruprecht, Verena; Wieser, Stefan; Marguet, Didier; Schtz, GerhardJ.

    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

  3. Electron density and temperature determination using the concept of particle confinement time uniqueness

    NASA Astrophysics Data System (ADS)

    Daltrini, A. M.; Machida, M.

    2005-05-01

    The use of atomic hydrogen line emission to determine the particle confinement time ?p of a tokamak plasma is a well-known diagnostic technique. Using such a method, for any one of the emission lines, be it from Lyman, Balmer, or Paschen series, the same (i.e., unique) value of ?p must be obtained. Furthermore, this measurement is directly related to the local values of the electron temperature and density. We have developed a method based on the H?, H?, and H? hydrogen line emissions and on the concept of ?p uniqueness for a tokamak plasma, to determine the local electron density and temperature. The technique has been applied to plasma discharges generated in the NOVA-UNICAMP tokamak. The results show good agreement with measurements from multichannel Thomson scattering and Langmuir probe. A procedure to simulate the H? emissivity radial profile using the obtained results is also discussed.

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

    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.

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

    SciTech Connect

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

    2015-02-15

    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.

  6. Experimental studies on E [times] B drift rotational transform and confinement in the bumpy torus NBT-1M

    SciTech Connect

    Iguchi, H.; Hosokawa, M.; Komori, A.; Fujiwara, M.; Ikegami, H. ); Takasugi, K. . Atomic Energy Research Inst.); Shoji, T. . Plasma Science Center)

    1994-08-01

    Experimental studies on E[times]B drift rotational transform for toroidal plasma confinement were carried out using a bumpy torus NBT-1M. An inward radial electric field was observed, which induced E[times]B poloidal precession and formed closed drift surfaces in a conventional ECH configuration. However, the confinement was degraded by the plasma convective loss due to the asymmetric potential profile and core electrostatic fluctuations. By the use of a combination of two frequencies for ECH (18 GHz and 8.5 GHz), the authors could reduce both the potential asymmetry and the fluctuation. In this operation, the plasma confinement by E[times]B drift rotational transform was demonstrated more clearly than that in the conventional single frequency operation.

  7. Analysis of the neutron time-of-flight spectra from inertial confinement fusion experiments

    NASA Astrophysics Data System (ADS)

    Hatarik, R.; Sayre, D. B.; Caggiano, J. A.; Phillips, T.; Eckart, M. J.; Bond, E. J.; Cerjan, C.; Grim, G. P.; Hartouni, E. P.; Knauer, J. P.; Mcnaney, J. M.; Munro, D. H.

    2015-11-01

    Neutron time-of-flight diagnostics have long been used to characterize the neutron spectrum produced by inertial confinement fusion experiments. The primary diagnostic goals are to extract the d + t ? n + ? (DT) and d + d ? n + 3He (DD) neutron yields and peak widths, and the amount DT scattering relative to its unscattered yield, also known as the down-scatter ratio (DSR). These quantities are used to infer yield weighted plasma conditions, such as ion temperature (Tion) and cold fuel areal density. We report on novel methodologies used to determine neutron yield, apparent Tion, and DSR. These methods invoke a single temperature, static fluid model to describe the neutron peaks from DD and DT reactions and a spline description of the DT spectrum to determine the DSR. Both measurements are performed using a forward modeling technique that includes corrections for line-of-sight attenuation and impulse response of the detection system. These methods produce typical uncertainties for DT Tion of 250 eV, 7% for DSR, and 9% for the DT neutron yield. For the DD values, the uncertainties are 290 eV for Tion and 10% for the neutron yield.

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

    NASA Astrophysics Data System (ADS)

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

    1986-08-01

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

  9. Confinement marries correlation to control time delays in valence-photoemissions of Ar taken hostage in C60

    NASA Astrophysics Data System (ADS)

    Chakraborty, Himadri; Dixit, Gopal; Madjet, Mohamed

    2014-05-01

    Effects of confinement and electron correlations on the relative time delay between the 3s and 3p photoemissions of Ar confined endohedrally in C60 are investigated using the time dependent local density approximation - a method that is also found to mostly agree with recent time delay measurements between the 3s and 3p subshells in atomic Ar. The Leeuwen and Baerends exchange-correlation functional to produce accurate asymptotic behavior is employed to calculate the dynamical response of the system to the photon field. At energies in the neighborhood of 3p Cooper minimum, correlations with C60 electrons are found to induce opposite temporal effects in the emission of Ar 3p hybridized symmetrically versus that of Ar 3p hybridized antisymmetrically with C60. A recoil-type interaction model mediated by the confinement is found to best describe the phenomenon. We suggest that future experiments be performed on the time delay in Ar and Ar@C60 over broader photon energy ranges including the 3p Cooper minimum to unravel new physics from confinement and correlations. Supported by the National Science Foundation.

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

    PubMed Central

    Chen, A.; Sooryakumar, R.

    2013-01-01

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

  11. Comparison of confinement in resistive-shell reversed-field pinch devices with two different magnetic shell penetration times

    NASA Astrophysics Data System (ADS)

    Gravestijn, R. M.; Drake, J. R.; Hedqvist, A.; Rachlew, E.

    2004-01-01

    A loop voltage is required to sustain the reversed-field pinch (RFP) equilibrium. The configuration is characterized by redistribution of magnetic helicity but with the condition that the total helicity is maintained constant. The magnetic field shell penetration time, tgrs, has a critical role in the stability and performance of the RFP. Confinement in the EXTRAP device has been studied with two values of tgrs, first (EXTRAP-T2) with tgrs of the order of the typical relaxation cycle timescale and then (EXTRAP-T2R) with tgrs much longer than the relaxation cycle timescale, but still much shorter than the pulse length. Plasma parameters show significant improvements in confinement in EXTRAP-T2R. The typical loop voltage required to sustain comparable electron poloidal beta values is a factor of 3 lower in the EXTRAP-T2R device. The improvement is attributed to reduced magnetic turbulence.

  12. Application of symbolic regression to the derivation of scaling laws for tokamak energy confinement time in terms of dimensionless quantities

    NASA Astrophysics Data System (ADS)

    Murari, A.; Peluso, E.; Lungaroni, M.; Gelfusa, M.; Gaudio, P.

    2016-02-01

    In many scientific applications, it is important to investigate how certain properties scale with the parameters of the systems. The experimental studies of scalings have traditionally been addressed with log regression, which limits the results to power laws and to theoretical and not data-driven dimensionless quantities. This has also been the case in nuclear fusion, in which the scaling of the energy confinement time is a crucial aspect in understanding the physics of transport and in the design of future devices. Traditionally two main assumptions are at the basis of the most widely accepted empirical scaling laws for the confinement time: (a) the dimensionless variables used are the ones derived from the symmetries of the Vlasov equation; (b) the final scalings have the mathematical form of power laws. In this paper, it is shown how symbolic regression (SR), implemented with genetic programming (GP) techniques, can be used to test these hypotheses. Neither assumption is confirmed by the available data of the multi-machine International Tokamak Physics Activity (ITPA) of validated tokamak discharges. The statistically soundest expressions are not power laws and cannot be formulated in terms of the traditional dimensionless quantities. The consequences of the data-driven scaling laws obtained are both practical and theoretical: the confinement time for the ITER can be significantly shorter than foreseen by power laws and different dimensionless variables should be considered for theoretical investigations. On the other hand, higher quality databases should be built to reduce the uncertainties in the extrapolations. It is also worth emphasising that the proposed methodology is fully general and therefore can be applied to any field of science.

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

    NASA Astrophysics Data System (ADS)

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

    2012-10-01

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

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

    SciTech Connect

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

    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.

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

    NASA Astrophysics Data System (ADS)

    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.

  16. Extended gyrokinetic field theory for time-dependent magnetic confinement fields

    SciTech Connect

    Sugama, H.; Watanabe, T.-H.; Nunami, M.

    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.

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

    PubMed

    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

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

    SciTech Connect

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

    2010-11-09

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

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

    SciTech Connect

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

    2008-04-15

    The physics issues of developing model-based control of plasma etching are presented. A novel methodology for incorporating real-time model-based control of plasma processing systems is developed. The methodology is developed for control of two dependent variables (ion flux and chemical densities) by two independent controls (27 MHz power and O{sub 2} flow). A phenomenological physics model of the nonlinear coupling between the independent controls and the dependent variables of the plasma is presented. By using a design of experiment, the functional dependencies of the response surface are determined. In conjunction with the physical model, the dependencies are used to deconvolve the sensor signals onto the control inputs, allowing compensation of the interaction between control paths. The compensated sensor signals and compensated set-points are then used as inputs to proportional-integral-derivative controllers to adjust radio frequency power and oxygen flow to yield the desired ion flux and chemical density. To illustrate the methodology, model-based real-time control is realized in a commercial semiconductor dielectric etch chamber. The two radio frequency symmetric diode operates with typical commercial fluorocarbon feed-gas mixtures (Ar/O{sub 2}/C{sub 4}F{sub 8}). Key parameters for dielectric etching are known to include ion flux to the surface and surface flux of oxygen containing species. Control is demonstrated using diagnostics of electrode-surface ion current, and chemical densities of O, O{sub 2}, and CO measured by optical emission spectrometry and/or mass spectrometry. Using our model-based real-time control, the set-point tracking accuracy to changes in chemical species density and ion flux is enhanced.

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

    SciTech Connect

    Friedrich, Jochen; Fu Jinmei; Hendrickson, Christopher L.; Marshall, Alan G.; Wang Yisheng

    2004-11-01

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

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

    SciTech Connect

    Schmitt, A.J.; Afeyan, B.B.

    1998-02-01

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

  2. Galactic Confinement Time of Iron-Group Cosmic Rays Derived from the {sup 54}Mn Chronometer

    SciTech Connect

    Zaerpoor, K.; Dragowsky, M.R.; Krane, K.S.; Chan, Y.D.; Isaac, M.C.; Larimer, R.M.; Macchiavelli, A.O.; Macleod, R.W.; Norman, E.B.; DiGregorio, D.E.; Hindi, M.M.; Miocinovic, P.

    1997-12-01

    The {beta} -decay half-life of {sup 54}Mn is needed to employ this isotope as a cosmic ray chronometer. We have determined the partial half-life of {sup 54}Mn for positron emission by counting a highly purified 35-{mu}Ci source of {sup 54}Mn in GAMMASPHERE to search for the astrophysically interesting {beta}{sup +} decay branch through the observation of coincident positron-annihilation {gamma} rays. A careful analysis of 97hours of source counting and 61hours of background shows a net signal of 24{plus_minus}10 back-to-back 511-511keV coincident events. Based on this result, the branch for this decay mode is (2.2{plus_minus}0.9){times}10{sup {minus}7}{percent} . The implications of this result for the {sup 54}Mn cosmic-ray chronometer problem are discussed. {copyright} {ital 1997} {ital The American Physical Society}

  3. Overdamped motion of interacting particles in general confining potentials: time-dependent and stationary-state analyses

    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.

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

    PubMed

    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

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

    SciTech Connect

    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.

  6. Analysis of time-resolved PIV measurements of a confined turbulent jet using POD and Koopman modes

    NASA Astrophysics Data System (ADS)

    Semeraro, Onofrio; Bellani, Gabriele; Lundell, Fredrik

    2012-11-01

    We present a comparative analysis of proper orthogonal decomposition (POD) and dynamic mode decomposition (DMD) computed from experimental data of a turbulent, quasi 2-D, confined jet with co-flow ( Re = 11,500, co-flow ratio inner-to-outer flow ?2:1). The experimental data come from high-speed 2-D particle image velocimetry. The flow is fully turbulent, and it contains geometry-dependent large-scale coherent structures; thus, it provides an interesting benchmark case for the comparison between POD and DMD. In this work, we address issues related to snapshot selections (1), convergence (2) and the physical interpretation (3) of both POD and DMD modes. We found that the convergence of POD modes follows the criteria of statistical convergence of the autocovariance matrix. For the computation of DMD modes, we suggest a methodology based on two criteria: the analysis of the residuals to optimize the sampling parameters of the snapshots, and a time-shifting procedure that allows us to identify the spurious modes and retain the modes that consistently appear in the spectrum. These modes are found to be the ones with nearly null growth rate. We then present the selected modes, and we discuss the way POD and DMD rank them. POD analysis reveals that the most energetic spatial structures are related to the large-scale oscillation of the inner jet (flapping); from the temporal analysis emerges that these modes are associated with a low-frequency peak at St = 0.02. At this frequency, DMD identifies a similar mode, where oblique structures from the walls appear together with the flapping mode. The second most energetic group of modes identified is associated with shear-layer oscillations, and to a recirculation zone near the inner jet. Temporal analysis of these modes shows that the flapping of the inner jet might be sustained by the recirculation. In the DMD, the shear-layer modes are separated from the recirculation modes. These have large amplitudes in the DMD. In conclusion, the DMD modes with eigenvalues on the unit circle are found to be similar to the most energetic POD modes, although differences appear due to the fact that DMD isolates structures associated with one frequency only.

  7. Steady-shear-enhanced microdiffusion with multiple time scales of confined, mesoscopic, two-dimensional dusty-plasma liquids

    NASA Astrophysics Data System (ADS)

    Io, Chong-Wai; I, Lin

    2009-09-01

    We experimentally investigate the multitime scale diffusion and the spatiotemporal behaviors of the degrees of enhancement for the longitudinal and the transverse diffusions in a confined mesoscopic quasi-two-dimensional dusty-plasma liquid sheared by two parallel counterpropagating laser beams. The steady external drive directly enhances the longitudinal cooperative hopping, associated with the shear bands that have high shear rate near boundaries. It drastically excites the slow hopping modes to high fluctuation level in the outer band region, accompanied by the enhanced superdiffusion. Through cascaded many-body interaction, the excitation flows from the outer region toward the center region, from the longitudinal modes to the transverse mode, and from the slow hopping modes to the fast caging modes, which are in better contact with the thermal bath. It causes the weaker enhancement of fluctuation level, and diffusion for the center region and the fast modes. The boundary confinement further breaks the system symmetry and enhances anisotropy. It has much stronger effect on the suppression of the transverse hopping modes than the longitudinal hopping mode. The degrees of enhancement of the fluctuations by the shear stress are highly anisotropic for the large amplitude slow modes, especially in the outer region but are more isotropic in the inner band.

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

    PubMed

    Li, Yue

    2012-05-30

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

  9. Detection of magnetic barriers in a chaotic domain: first application of finite time Lyapunov exponent method to a magnetic confinement configuration

    NASA Astrophysics Data System (ADS)

    Rubino, G.; Borgogno, D.; Veranda, M.; Bonfiglio, D.; Cappello, S.; Grasso, D.

    2015-08-01

    Magnetic field lines embedded in a plasma confinement system are often characterized by a chaotic motion. This weakens the confinement properties of any magnetic configuration. However, even in case of chaotic domains, magnetic barriers can emerge and limit the field line motion itself. In the context of the numerical simulation of a Reversed-Field Pinch configuration a new magnetic topology analysis, borrowed from previous fluid dynamic studies, is discussed. This methodology relies on the behavior of the Finite Time Lyapunov Exponent (FTLE) associated with the magnetic field. By referring to a previous work in which the magnetic field is given in terms of analytical function (Borgogno et al 2011 Phys. Plasmas 18 102307) the FTLE field shows the presence of ridges, special gradient lines normal to the direction of minimum curvature, forming magnetic barriers. These ridges can be recognized as Lagrangian Coherent Structures (LCSs) for the system, actually opposing the penetration of magnetic field lines across them. In this article a more general numerical scheme for the detection of the LCSs has been adopted that allows analysis of realistic cases in which the magnetic fields are numerically known on a discrete mesh. After a validation test performed on the analytical case, a first application to a numerical magnetohydrodynamics simulation of the RFP, characterized by a broad chaotic region, has been performed. A strong magnetic barrier has been observed that effectively limits the field lines motion inside the chaotic sea.

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

    PubMed

    Dhar, Jayabrata; Ghosh, Uddipta; Chakraborty, Suman

    2014-03-01

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

  11. Relativistic scalar particle subject to a confining potential and Lorentz symmetry breaking effects in the cosmic string space-time

    NASA Astrophysics Data System (ADS)

    Belich, H.; Bakke, K.

    2016-03-01

    The behavior of a relativistic scalar particle subject to a scalar potential under the effects of the violation of the Lorentz symmetry in the cosmic string space-time is discussed. It is considered two possible scenarios of the Lorentz symmetry breaking in the CPT-even gauge sector of the Standard Model Extension defined by a tensor (KF)μναβ. Then, by introducing a scalar potential as a modification of the mass term of the Klein-Gordon equation, it is shown that the Klein-Gordon equation in the cosmic string space-time is modified by the effects of the Lorentz symmetry violation backgrounds and bound state solution to the Klein-Gordon equation can be obtained.

  12. Confined helium on Lagrange meshes.

    PubMed

    Baye, D; Dohet-Eraly, J

    2015-12-21

    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. PMID:25732054

  13. Investigation of gamma-ray time shifts caused by capsule areal density variations in inertial confinement fusion experiments at the national ignition facility and the omega facility

    NASA Astrophysics Data System (ADS)

    Grafil, Elliot M.

    This thesis describes work on Cherenkov based gamma detectors used as diag- nostics at Inertial Confinement Fusion (ICF) facilities. The first part describes the calibration and commissioning of the Gamma Reaction History diagnostic which is a four cell Cherenkov detector array used to characterize the ICF implosion at the National Ignition Facility (NIF) by measuring the gamma rays generated during the fusion event. Two of the key metrics which the GRH measures are Gamma Bang Time (GBT) generated from the D(T,α)n thermonuclear burn and Ablator Peak Time (APT) caused by (n,n‧)gamma reactions in the surrounding capsule ablator. Simulations of ignition capsules predict that GBT and APT should be time synchronized. After GRH commissioning, the array was used during first year of NIF operation in the National Ignition Campaign. Contrary to expectations, time shifts between GBT and APT of order 10s of picoseconds were observed. In order to further investigate the possibility of these time shifts in view of testing both instrument and code credibility an ICF shot campaign at the smaller OMEGA facility in Rochester was devised. It was performed during two full shot days in April of 2013 and 2014 and confirmed in principle the viability of the Cherenkov detector approach but raised additional questions regarding the credibility of the simulation codes used to describe ICF experiments. Specifically the measurements show that the understanding of temporal behavior of GBT vs APT may not be properly modeled in the DRACO code used at OMEGA. In view of the OMEGA results which showed no time shifts between GBT and APT, the readout and timing synchronization system of the GRH setup at the NIF was reevaluated in the framework of this thesis. Motivated by the results, which highlighted the use of wrong optical fiber diameters and possible problems with the installed variable optical attenuators, the NIF equipment has been updated over the recent months and new timing tests will be performed during the next years.

  14. Precision of Inhibition: Dendritic Inhibition by Individual GABAergic Synapses on Hippocampal Pyramidal Cells Is Confined in Space and Time.

    PubMed

    Mllner, Fiona E; Wierenga, Corette J; Bonhoeffer, Tobias

    2015-08-01

    Inhibition plays a fundamental role in controlling neuronal activity in the brain. While perisomatic inhibition has been studied in detail, the majority of inhibitory synapses are found on dendritic shafts and are less well characterized. Here, we combine paired patch-clamp recordings and two-photon Ca(2+) imaging to quantify inhibition exerted by individual GABAergic contacts on hippocampal pyramidal cell dendrites. We observed that Ca(2+) transients from back-propagating action potentials were significantly reduced during simultaneous activation of individual nearby inhibitory contacts. The inhibition of Ca(2+) transients depended on the precise spike-timing (time constant< 5ms) and declined steeply in the proximal and distal direction (length constants 23-28?m). Notably, Ca(2+) amplitudes in spines were inhibited to the same degree as in the shaft. Given the known anatomical distribution of inhibitory synapses, our data suggest that the collective inhibitory input to a pyramidal cell is sufficient to control Ca(2+) levels across the entire dendritic arbor with micrometer and millisecond precision. PMID:26247864

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

    PubMed Central

    2010-01-01

    Background Selection programs for growth and stress traits in cultured fish are fundamental to the improvement of aquaculture production. The gilthead sea bream (Sparus aurata) is the main aquacultured species in the Mediterranean area and there is considerable interest in the genetic improvement of this species. With the aim of increasing the genomic resources in gilthead sea bream and identifying genes and mechanisms underlying the physiology of the stress response, we developed a cDNA microarray for gilthead sea bream that is enriched by suppression substractive hybridization with stress and immunorelevant genes. This microarray is used to analyze the dynamics of gilthead sea bream liver expression profile after confinement exposure. Results Groups of confined and control juvenile fish were sampled at 6, 24, 72 and 120 h post exposure. GeneSpring analyses identified 202 annotated genes that appeared differentially expressed at least at one sampling time (P < 0.05). Gene expression results were validated by quantitative PCR of 10 target genes, and K-means clustering of differently expressed genes identified four major temporal gene expression profiles. Set 1 encompassed a rapid metabolic readjustment with enhanced uptake and intracellular transport of fatty acids as metabolic fuels. Set 2 was associated with a wide variety of tissue repair and remodeling processes that were mostly mediated by the stress response of the endoplasmic reticulum (ER). Sets 3 and 4 encompassed the re-establishment of cellular homeostasis with increased intracellular trafficking and scavenging of reactive oxygen species (ROS), accompanied by a bidirectional regulation of the immune system and a general decline of ROS production. Conclusions Collectively, these findings show the complex nature of the adaptive stress response with a clear indication that the ER is an important control point for homeostatic adjustments. The study also identifies metabolic pathways which could be analyzed in greater detail to provide new insights regarding the transcriptional regulation of the stress response in fish. PMID:20307314

  16. E{times}B flow shear effects on radial correlation length of turbulence and gyroradius scaling of confinement

    SciTech Connect

    Hahm, T.S.; Burrell, K.H.

    1996-01-01

    The radial correlation length of the turbulence responsible for transport can have a different gyroradius scaling in low (L)-mode and high (H)-mode plasmas due to {bold E{times}B} flow shear effects, as predicted by the two-point nonlinear analysis in general tokamak geometry [Phys. Plasmas {bold 2}, 1648 (1995)]. This difference offers a possible understanding of the recent {rho}{sub {asterisk}}-scan experiment results on DIII-D [Fusion Technol. {bold 8}, 441 (1985)] L-mode and H-mode plasmas [Phys. Plasmas {bold 2}, 2342 (1995)]. Within our model, thermal diffusivity in H-mode plasmas scales like gyro-Bohm, independent of the scaling in L-mode plasmas. {copyright} {ital 1996 American Institute of Physics.}

  17. Demonstration of a time-integrated short line of sight neutron imaging system for inertial confinement fusion

    NASA Astrophysics Data System (ADS)

    Simpson, R.; Christensen, K.; Danly, C.; Fatherley, V. E.; Fittinghoff, D.; Grim, G. P.; Izumi, N.; Jedlovec, D.; Merrill, F. E.; Skulina, K.; Volegov, P.; Wilde, C.

    2015-12-01

    The Neutron Imaging System (NIS) is an important diagnostic for understanding implosions of deuterium-tritium capsules at the National Ignition Facility. While the detectors for the existing system must be positioned 28 m from the source to produce sufficient imaging magnification and resolution, recent testing of a new short line of sight neutron imaging system has shown sufficient resolution to allow reconstruction of the source image with quality similar to that of the existing NIS on a 11.6 m line of sight. The new system used the existing pinhole aperture array and a stack of detectors composed of 2 mm thick high-density polyethylene converter material followed by an image plate. In these detectors, neutrons enter the converter material and interact with protons, which recoil and deposit energy within the thin active layer of the image plate through ionization losses. The described system produces time-integrated images for all neutron energies passing through the pinhole. We present details of the measurement scheme for this novel technique to produce energy-integrated neutron images as well as source reconstruction results from recent experiments at NIF.

  18. Demonstration of a time-integrated short line of sight neutron imaging system for inertial confinement fusion.

    PubMed

    Simpson, R; Christensen, K; Danly, C; Fatherley, V E; Fittinghoff, D; Grim, G P; Izumi, N; Jedlovec, D; Merrill, F E; Skulina, K; Volegov, P; Wilde, C

    2015-12-01

    The Neutron Imaging System (NIS) is an important diagnostic for understanding implosions of deuterium-tritium capsules at the National Ignition Facility. While the detectors for the existing system must be positioned 28 m from the source to produce sufficient imaging magnification and resolution, recent testing of a new short line of sight neutron imaging system has shown sufficient resolution to allow reconstruction of the source image with quality similar to that of the existing NIS on a 11.6 m line of sight. The new system used the existing pinhole aperture array and a stack of detectors composed of 2 mm thick high-density polyethylene converter material followed by an image plate. In these detectors, neutrons enter the converter material and interact with protons, which recoil and deposit energy within the thin active layer of the image plate through ionization losses. The described system produces time-integrated images for all neutron energies passing through the pinhole. We present details of the measurement scheme for this novel technique to produce energy-integrated neutron images as well as source reconstruction results from recent experiments at NIF. PMID:26724078

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

    NASA Astrophysics Data System (ADS)

    Frydel, Derek; Rice, Stuart A.

    2007-12-01

    We report a hydrodynamic analysis of the long-time behavior of the linear and angular velocity autocorrelation functions of an isolated colloid particle constrained to have quasi-two-dimensional motion, and compare the predicted behavior with the results of lattice-Boltzmann simulations. Our analysis uses the singularity method to characterize unsteady linear motion of an incompressible fluid. For bounded fluids we construct an image system with a discrete set of fundamental solutions of the Stokes equation from which we extract the long-time decay of the velocity. For the case that there are free slip boundary conditions at walls separated by H particle diameters, the time evolution of the parallel linear velocity and the perpendicular rotational velocity following impulsive excitation both correspond to the time evolution of a two-dimensional (2D) fluid with effective density ?2D=?H . For the case that there are no slip boundary conditions at the walls, the same types of motion correspond to 2D fluid motions with a coefficient of friction ?=?2?/H2 modulo a prefactor of order 1, with ? the kinematic viscosity. The linear particle motion perpendicular to the walls also experiences an effective frictional force, but the time dependence is proportional to t-2 , which cannot be related to either pure 3D or pure 2D fluid motion. Our incompressible fluid model predicts correct self-diffusion constants but it does not capture all of the effects of the fluid confinement on the particle motion. In particular, the linear motion of a particle perpendicular to the walls is influenced by coupling between the density flux and the velocity field, which leads to damped velocity oscillations whose frequency is proportional to cs/H , with cs the velocity of sound. For particle motion parallel to no slip walls there is a slowing down of a density flux that spreads diffusively, which generates a long-time decay proportional to t-1 .

  20. Study of the 3D Coronal Magnetic Field of Active Region 11117 Around the Time of a Confined Flare Using a Data-Driven CESE-MHD Model

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

    Non-potentiality of the solar coronal magnetic field accounts for the solar explosion like flares and CMEs. We apply a data-driven CESE-MHD model to investigate the three-dimensional (3D) coronal magnetic field of NOAA active region (AR) 11117 around the time of a C-class confined flare occurred on 2010 October 25. The CESE-MHD model, based on the spacetime conservation-element and solution-element scheme, is designed to focus on the magnetic-field evolution and to consider a simplified solar atomsphere with finite plasma β. Magnetic vector-field data derived from the observations at the photoshpere is inputted directly to constrain the model. Assuming that the dynamic evolution of the coronal magnetic field can be approximated by successive equilibria, we solve a time sequence of MHD equilibria basing on a set of vector magnetograms for AR 11117 taken by the Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamic Observatory (SDO) around the time of flare. The model qualitatively reproduces the basic structures of the 3D magnetic field, as supported by the visual similarity between the field lines and the coronal loops observed by the Atmospheric Imaging Assembly (AIA), which shows that the coronal field can indeed be well characterized by the MHD equilibrium in most time. The magnetic configuration changes very limited during the studied time interval of two hours. A topological analysis reveals that the small flare is correlated with a bald patch (BP, where the magnetic field is tangent to the photoshpere), suggesting that the energy release of the flare can be understood by magnetic reconnection associated with the BP separatrices. The total magnetic flux and energy keep increasing slightly in spite of the flare, while the magnetic free energy drops during the flare with an amount of 1.7 × 1030 erg, which can be interpreted as the energy budget released by the minor C-class flare.

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

    SciTech Connect

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

    1991-06-01

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

  2. Confinement contains condensates

    NASA Astrophysics Data System (ADS)

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

    2012-06-01

    Dynamical chiral symmetry breaking and its connection to the generation of hadron masses has historically been viewed as a vacuum phenomenon. We argue that confinement makes such a position untenable. If quark-hadron duality is a reality in QCD, then condensates, those quantities that have commonly been viewed as constant empirical mass scales that fill all space-time, are instead wholly contained within hadrons; i.e., they are a property of hadrons themselves and expressed, e.g., in their Bethe-Salpeter or light-front wave functions. We explain that this paradigm is consistent with empirical evidence and incidentally expose misconceptions in a recent Comment.

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

    NASA Astrophysics Data System (ADS)

    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.

  4. A Review of Quantum Confinement

    NASA Astrophysics Data System (ADS)

    Connerade, Jean-Patrick

    2009-12-01

    A succinct history of the Confined Atom problem is presented. The hydrogen atom confined to the centre of an impenetrable sphere counts amongst the exactly soluble problems of physics, alongside much more noted exact solutions such as Black Body Radiation and the free Hydrogen atom in absence of any radiation field. It shares with them the disadvantage of being an idealisation, while at the same time encapsulating in a simple way particular aspects of physical reality. The problem was first formulated by Sommerfeld and Welker [1]henceforth cited as SWin connection with the behaviour of atoms at very high pressures, and the solution was published on the occasion of Pauli's 60th birthday celebration. At the time, it seemed that there was not much other connection with physical reality beyond a few simple aspects connected to the properties of atoms in solids, for which more appropriate models were soon developed. Thus, confined atoms attracted little attention until the advent of the metallofullerene, which provided the first example of a confined atom with properties quite closely related to those originally considered by SW. Since then, the problem has received much more attention, and many more new features of quantum confinement, quantum compression, the quantum Faraday cage, electronic reorganisation, cavity resonances, etc have been described, which are relevant to real systems. Also, a number of other situations have been uncovered experimentally to which quantum confinement is relevant. Thus, studies of the confined atom are now more numerous, and have been extended both in terms of the models used and the systems to which they can be applied. Connections to thermodynamics are explored through the properties of a confined two-level atom adapted from Einstein's celebrated model, and issues of dynamical screening of electromagnetic radiation by the confining shell are discussed in connection with the Faraday cage produced by a confining conducting shell. The conclusions are shown to be relevant to a proposed `quantum computer'. The description of the actual geometry of C60, as opposed to a purely spherical approximation, leads to some qualification of the computed results.

  5. Momentum Confinement at Low Torque

    SciTech Connect

    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.

  6. Vortex rings in radially confined domains

    NASA Astrophysics Data System (ADS)

    Stewart, Kelley C.; Vlachos, Pavlos P.

    2012-10-01

    The dynamics of vortex rings generated within confined domains are relevant to important hydrodynamic processes such as flow past heart valves or severe arterial constrictions. However, despite their importance, these flows have not received much attention to date. This study examines the development and evolution of radially confined vortex rings. Time-resolved digital particle image velocimetry was used to investigate two levels of radial confinement and a range of vortex ring strengths. We found that for severely confined vortex rings, the formation time and peak circulation values were unaffected for L/D 0 < 4 cases and slightly affected for larger L/D 0 cases. After pinch-off, circulation decay was observed with an approximately constant normalized circulation decay rate. We found that with increasing circulation strength, the nondimensional time delay between the pinch-off and the onset of circulation decay reduced due to an increased vortex ring diameter within the confinement domain and a reduction in the necessary time for the surface induced and core vorticity regions to interact. This study uncovers the dynamics of radially confined vortex rings and show that the nondimensional rate of circulation decay is dependent on the vortex ring confinement ratio (ratio of the vortex ring orifice diameter to the diameter of the outer cylinder), and the time delay between the vortex pinch-off and the onset of circulation is dependent on the vortex ring circulation strength.

  7. 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…

  8. 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

  9. Indoor Confined Feedlots.

    PubMed

    Grooms, Daniel L; Kroll, Lee Anne K

    2015-07-01

    Indoor confined feedlots offer advantages that make them desirable in northern climates where high rainfall and snowfall occur. These facilities increase the risk of certain health risks, including lameness and tail injuries. Closed confinement can also facilitate the rapid spread of infectious disease. Veterinarians can help to manage these health risks by implementing management practices to reduce their occurrence. PMID:26139194

  10. Enhancement of confinement in tokamaks

    SciTech Connect

    Furth, H.P.

    1986-05-01

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

  11. Coaxial cable stripper for confined areas

    NASA Technical Reports Server (NTRS)

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

    1968-01-01

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

  12. Polymers in Confined Geometry

    NASA Astrophysics Data System (ADS)

    Brochard-Wyart, Francoise

    2008-03-01

    Thanks to P. G. de Genne's famous ``n = 0'' theorem (relating the configuration of a polymer chain to a magnetic phase transition with an order parameter of n = 0 component), the swelling exponent ? (R=N^?a) was calculated in terms of space dimension d and fitted the qualitative Flory calculation. Using scaling laws, or the ``blob'' picture, it became possible to derive the conformation of a chain confined in a tube or a slit. The dynamics of confined polymers followed immediately. The new feature was the screening of the hydrodynamic interactions in confined geometry leading to Rouse-like behaviour. In a third step, de Gennes focused on the forced penetration of polymers (linear, branched, stars, neutral or charged) in narrow tubes, when they are submitted to a flow (or an electrical field for DNA). From all these calculations, the conclusion was that the threshold velocity (or field) corresponds to the penetration of the first blob. Afterwards, the friction force increases linearly with the penetrated length, whereas the confinement force remains constant. In the last few years, with his collaboration we studied the penetration of DNA in ``soft'' tubes. We predicted a transition from extended to globular DNA observed experimentally. We also showed that semi flexible polymer chains, like DNA, are ideal in 3d, but swollen effects are more pronounced in confined geometries. We will also discuss experiments inspired by his work on confined polymers, in the last thirty years.

  13. Fusion, magnetic confinement

    SciTech Connect

    Berk, H.L.

    1992-08-06

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

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

    NASA Astrophysics Data System (ADS)

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

    2012-11-01

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

  15. The Physics Basis of ITER Confinement

    NASA Astrophysics Data System (ADS)

    Wagner, F.

    2009-02-01

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

  16. The Physics Basis of ITER Confinement

    SciTech Connect

    Wagner, F.

    2009-02-19

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

  17. Confined subdiffusion in three dimensions

    NASA Astrophysics Data System (ADS)

    Qin, Shan-Lin; He, Yong

    2014-11-01

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

  18. Plasma confinement at JET

    NASA Astrophysics Data System (ADS)

    Nunes, I.; ">the JET Contributors, confinement with respect to the carbon wall (JET-C). The main differences observed were (1) strong accumulation of W in the plasma core and (2) the need to mitigate the divertor target temperature to avoid W sputtering by Be and other low Z impurities and (3) a decrease of plasma energy confinement. A major difference is observed on the pedestal pressure, namely a reduction of the pedestal temperature which, due to profile stiffness the plasma core temperature is also reduced leading to a degradation of the global confinement. This effect is more pronounced in low β N scenarios. At high β N, the impact of the wall on the plasma energy confinement is mitigated by the weaker plasma energy degradation with power relative to the IPB98(y, 2) scaling calculated empirically for a CFC first wall. The smaller tolerable impurity concentration for tungsten (<10‑5) compared to that of carbon requires the use of electron heating methods to prevent W accumulation in the plasma core region as well as gas puffing to avoid W entering the plasma core by ELM flushing and reduction of the W source by decreasing the target temperature. W source and the target temperature can also be controlled by impurity seeding. Nitrogen and Neon have been used and with both gases the reduction of the W source and the target temperature is observed. Whilst more experiments with Neon are necessary to assess its impact on energy confinement, a partial increase of plasma energy confinement is observed with Nitrogen, through the increase of edge temperature. The challenge for scenario development at JET is to extend the pulse length curtailed by its transient behavior (W accumulation or MHD), but more importantly by the divertor target temperature limits. Re-optimisation of the scenarios to mitigate the effect of the change of wall materials maintaining high global energy confinement similar to JET-C is underway and JET has successfully achieved H 98(y,2)  =  1 for plasma currents up to 2.5 MA at moderate β N.

  19. Confined Space Imager (CSI) Software

    SciTech Connect

    2013-07-03

    The software provides real-time image capture, enhancement, and display, and sensor control for the Confined Space Imager (CSI) sensor system The software captures images over a Cameralink connection and provides the following image enhancements: camera pixel to pixel non-uniformity correction, optical distortion correction, image registration and averaging, and illumination non-uniformity correction. The software communicates with the custom CSI hardware over USB to control sensor parameters and is capable of saving enhanced sensor images to an external USB drive. The software provides sensor control, image capture, enhancement, and display for the CSI sensor system. It is designed to work with the custom hardware.

  20. Scaling Theory of Polymer Translocation into Confined Regions

    PubMed Central

    Wong, Chiu Tai Andrew; Muthukumar, Murugappan

    2008-01-01

    We examine the voltage-driven polymer translocation from a spacious region into a confined region imposed by two parallel planes, so that the entry is impeded by the entropic confinement but aided by the electric field inside the confined region. Two modes of entry are examined: linear translocation where a chain enters the confined region with chain ends, and hairpin translocation where a chain enters the confined region by forming a hairpin. Our calculation shows that translocation time increases with polymer length for linear entries but decreases with polymer length for hairpin entries. Applying to electrophoresis of DNA molecules through periodic spacious and confined regions, our theory shows that the dominance of hairpin translocations leads to the experimentally observed faster migration of longer DNA molecules. Our theory predicts experimental conditions for the validity of this law in terms of polymer length, size of the confined region, and solution conditions. PMID:18621833

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

    SciTech Connect

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

    2013-12-04

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

  2. Bifurcated equilibria in centrifugally confined plasma

    SciTech Connect

    Shamim, I.; Teodorescu, C.; Guzdar, P. N.; Hassam, A. B.; Clary, R.; Ellis, R.; Lunsford, R.

    2008-12-15

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

  3. Influence of the Nuclear Electric Quadrupolar Interaction on the Coherence Time of Hole and Electron Spins Confined in Semiconductor Quantum Dots

    NASA Astrophysics Data System (ADS)

    Hackmann, J.; Glasenapp, Ph.; Greilich, A.; Bayer, M.; Anders, F. B.

    2015-11-01

    The real-time spin dynamics and the spin noise spectra are calculated for p and n -charged quantum dots within an anisotropic central spin model extended by additional nuclear electric quadrupolar interactions and augmented by experimental data. Using realistic estimates for the distribution of coupling constants including an anisotropy parameter, we show that the characteristic long time scale is of the same order for electron and hole spins strongly determined by the quadrupolar interactions even though the analytical form of the spin decay differs significantly consistent with our measurements. The low frequency part of the electron spin noise spectrum is approximately 1 /3 smaller than those for hole spins as a consequence of the spectral sum rule and the different spectral shapes. This is confirmed by our experimental spectra measured on both types of quantum dot ensembles in the low power limit of the probe laser.

  4. Totally confined explosive welding

    NASA Technical Reports Server (NTRS)

    Bement, L. J. (inventor)

    1978-01-01

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

  5. Laser-confined fusion.

    PubMed

    Shen, Baifei; Zhang, Xiaomei; Yu, M Y

    2005-01-01

    An approach for producing a large quantity of neutrons is proposed. It involves compression of a fuel foil and confinement of the resulting plasma between two intense laser pulses. It is shown that two circularly polarized laser pulses of amplitude a = 7 illuminating a deuterium-tritium foil of areal density 3.3 x 10(18) cm(-2) can produce about 4.2 x 10(6) neutrons per joule of the input laser energy. PMID:15697649

  6. Classical confined particles

    NASA Technical Reports Server (NTRS)

    Horzela, Andrzej; Kapuscik, Edward

    1993-01-01

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

  7. 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.

  8. Topological confinement and superconductivity

    SciTech Connect

    Al-hassanieh, Dhaled A; Batista, Cristian D

    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.

  9. Anomalous thermal confinement in ohmically heated tokamaks

    SciTech Connect

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

    1986-02-01

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

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

    SciTech Connect

    Nelson, Alan J.; Cooper, Gary Wayne; 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.

  11. Cylindrical confinement of semiflexible polymers

    NASA Astrophysics Data System (ADS)

    Vzquez-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.

  12. Shear relaxations of confined liquids

    SciTech Connect

    Carson, G.A. Jr.

    1992-01-01

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

  13. Shear Relaxations of Confined Liquids.

    NASA Astrophysics Data System (ADS)

    Carson, George Amos, Jr.

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

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

    NASA Astrophysics Data System (ADS)

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

    2009-04-01

    Modern data logger and sensor technology enable well responses to barometric pressure changes to be monitored at a high frequency and precision. In this presentation, we demonstrate that such monitoring data can be utilized not just for the conventional calculation of a well's barometric efficiency but also to provide valuable information for site characterization applications. We investigate the water-level responses of wells in confined and semi-confined aquifers to changes in barometric pressure and show how simple analytical solutions can be fit to experimentally determined barometric response functions to place bounds on the properties of the confining bed. We demonstrate our approach at the Larned Research Site, located along the Arkansas River in south-central Kansas in the Great Plains region of the United States. The site contains monitoring wells tapping an unconsolidated, semi-confined aquifer (High Plains Aquifer) overlain by a clay unit and a shallow, unconfined aquifer. Water levels and atmospheric pressure have been monitored in the wells at 15-minute intervals for up to seven years. The spatial and temporal changes in the barometric response functions provide important insights on the degree of confinement and its change in space and time. Short term (hour or less) response functions indicate a classical confined aquifer, whereas long term responses (day) show semi-confined behavior, an indication that the air pressure exerted on the water table is being transmitted downward through the confining bed. The barometric response functions vary little in space, indicating the homogeneity of the confining bed, but do vary temporally as a function of the water table elevation and the pneumatic diffusivity of the vadose zone.

  15. Holographic collisions in confining theories

    NASA Astrophysics Data System (ADS)

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

    2014-01-01

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

  16. Response measurement of single-crystal chemical vapor deposition diamond radiation detector for intense X-rays aiming at neutron bang-time and neutron burn-history measurement on an inertial confinement fusion with fast ignition

    SciTech Connect

    Shimaoka, T. Kaneko, J. H.; Tsubota, M.; Arikawa, Y.; Nagai, T.; Kojima, S.; Abe, Y.; Sakata, S.; Fujioka, S.; Nakai, M.; Shiraga, H.; Azechi, H.; Isobe, M.; Sato, Y.; Chayahara, A.; Umezawa, H.; Shikata, S.

    2015-05-15

    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{sup 7} cm/s and 1.0 ± 0.3 × 10{sup 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{sup 9} neutrons/shot.

  17. Response measurement of single-crystal chemical vapor deposition diamond radiation detector for intense X-rays aiming at neutron bang-time and neutron burn-history measurement on an inertial confinement fusion with fast ignition

    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.

  18. Confined vortex scrubber

    SciTech Connect

    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.

  19. 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.

  20. Confinement Contains Condensates

    SciTech Connect

    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.

  1. Confinement Vessel Dynamic Analysis

    SciTech Connect

    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.

  2. Structure of confined water

    NASA Astrophysics Data System (ADS)

    Bellissent-Funel, M.-C.

    2001-10-01

    Water is essential for the stability and function of biological macromolecules. In living systems, essential water-related phenomena occur in restricted geometry in cells, and at active sites of proteins and membranes or at their surface. In this paper, we present the more recent results on the structure of confined water as compared with that of bulk supercooled water. In particular, the combined effects of the hydration level and the temperature on the change of the structure of water are discussed in the light of powerful techniques.

  3. Dynamics of ultracold molecules in confined geometry and electric field

    SciTech Connect

    Quemener, Goulven; Bohn, John L.

    2011-01-15

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

  4. 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.

  5. Spontaneous Circulation of Confined Active Suspensions

    NASA Astrophysics Data System (ADS)

    Woodhouse, Francis; Goldstein, Raymond

    2012-11-01

    Many active fluid systems encountered in biology are set in total geometric confinement; cytoplasmic streaming is a prominent and ubiquitous example. Using the simple paradigm of a dilute dipolar swimmer suspension, we demonstrate that the two key constraints of circular confinement and fluid incompressibility yield qualitatively new dynamics, effectively quantizing the behaviour regimes. We show analytically that there is an activity threshold for spontaneous auto-circulation and verify this numerically. Long-time non-linear behaviour is investigated via simulations, which reveal steady states displaying nematic defect separation and a high-activity bifurcation to an oscillatory regime.

  6. Static current profile control and RFP confinement

    NASA Astrophysics Data System (ADS)

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

    2013-11-01

    Static current profile control (CPC) is shown numerically to substantially enhance plasma confinement in the reversed-field pinch (RFP). By suitable application of an auxiliary electric field and adjustment of its internal location, width and amplitude, strongly decreased levels of dynamo fluctuations are obtained. The simulations are performed using a fully non-linear, resistive magnetohydrodynamic model, including the effects of ohmic heating as well as parallel and perpendicular heat conduction along stochastic field lines. The importance of controlling the parallel current profile in the core plasma to minimize the effects of tearing modes on confinement is thus confirmed. A near three-fold increase in energy confinement is found and poloidal plasma beta increases by 30% from 0.20 to 0.27. The edge heat flux is reduced to a third of that of the conventional RFP. The high-confinement phase is interrupted here by a crash, characterized by a rapid decrease in confinement. A detailed study of the crash phase is carried out by the standard ?? theory and a fully resistive linearized time-spectral method; the generalized weighted residual method. The analysis suggests that the instability is caused by pressure-driven, resistive g-modes. Inclusion of anisotropic thermal conduction reduces the linear growth rates. As compared with our earlier numerical studies of CPC in the RFP, employing feedback control, the present static control scheme should be more easily implemented experimentally.

  7. Experimental relation between particle and energy confinement in reversed-field pinches

    SciTech Connect

    Mazur, S.; Nordlund, P. ); Zastrow, K. ); Brzozowski, J.H.; Drake, J.R. )

    1993-08-01

    Confinement studies have been performed on the high-aspect-ratio, high-current-density Extrap-T1 reversed-field pinch. Experimental evidence is presented that the scaling of the particle confinement time is not dominated by the dynamo activity. This results in an anticorrelation between particle confinement time and energy confinement time, which becomes apparent in this experiment, as the ratio of Spitzer to total input power is varied over the wide range 0.4--0.8.

  8. Confined placental mosaicism.

    PubMed Central

    Kalousek, D K; Vekemans, M

    1996-01-01

    In most pregnancies the chromosomal complement detected in the fetus is also present in the placenta. The detection of an identical chromosomal complement in both the fetus and its placenta has always been expected as both develop from the same zygote. However, in approximately 2% of viable pregnancies studied by chorionic villus sampling (CVS) at 9 to 11 weeks of gestation, the cytogenetic abnormality, most often trisomy, is confined to the placenta. This phenomenon is known as confined placental mosaicism (CPM). It was first described by Kalousek and Dill in term placentas of infants born with unexplained intrauterine growth restriction (IUGR). Contrary to generalised mosaicism, which is characterised by the presence of two or more karyotypically different cell lines within both the fetus and its placenta, CPM represents tissue specific chromosomal mosaicism affecting the placenta only. The diagnosis of CPM is most commonly made when, after the diagnosis of chromosomal mosaicism in a CVS sample, the second prenatal testing (amniotic fluid culture or fetal blood culture analysis) shows a normal diploid karyotype. PMID:8818935

  9. Preface: Special Topic on Interfacial and Confined Water

    NASA Astrophysics Data System (ADS)

    Molinero, Valeria; Kay, Bruce D.

    2014-11-01

    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.

  10. Preface: Special Topic on Interfacial and Confined Water

    SciTech Connect

    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.

  11. Confined Space Imager (CSI) Software

    Energy Science and Technology Software Center (ESTSC)

    2013-07-03

    The software provides real-time image capture, enhancement, and display, and sensor control for the Confined Space Imager (CSI) sensor system The software captures images over a Cameralink connection and provides the following image enhancements: camera pixel to pixel non-uniformity correction, optical distortion correction, image registration and averaging, and illumination non-uniformity correction. The software communicates with the custom CSI hardware over USB to control sensor parameters and is capable of saving enhanced sensor images to anmore » external USB drive. The software provides sensor control, image capture, enhancement, and display for the CSI sensor system. It is designed to work with the custom hardware.« less

  12. Amoeboid motion in confined geometry

    NASA Astrophysics Data System (ADS)

    Wu, Hao; Thiébaud, M.; Hu, W.-F.; Farutin, A.; Rafaï, S.; Lai, M.-C.; Peyla, P.; Misbah, C.

    2015-11-01

    Many eukaryotic cells undergo frequent shape changes (described as amoeboid motion) that enable them to move forward. We investigate the effect of confinement on a minimal model of amoeboid swimmer. A complex picture emerges: (i) The swimmer's nature (i.e., either pusher or puller) can be modified by confinement, thus suggesting that this is not an intrinsic property of the swimmer. This swimming nature transition stems from intricate internal degrees of freedom of membrane deformation. (ii) The swimming speed might increase with increasing confinement before decreasing again for stronger confinements. (iii) A straight amoeoboid swimmer's trajectory in the channel can become unstable, and ample lateral excursions of the swimmer prevail. This happens for both pusher- and puller-type swimmers. 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. In this study, we combine numerical and theoretical analyses.

  13. Modeling confined jet flow

    NASA Astrophysics Data System (ADS)

    Yule, A. J.; Damou, M.; Kostopoulos, D.

    1993-03-01

    The prediction of confined jet mixing, which occurs in many processes from jet pumps to furnaces, is studied by testing and improving turbulence models. Numerical simulations of axisymmetric parabolic jet flows, with the two-equation k-epsilon eddy-viscosity model and the second-moment closure in its algebraic form, are compared with measurements. This leads to the identification of defects that cause high rates of mixing, similar to those shown in earlier work with free jets. Modifications to the dissipation rate equation, proposed for the free jet, are addressed by examining the effects of anisotropy-related proposals and the sensitization to irrotational strains. The involvement of large structures in transport phenomena is also considered via bulk-convection-based models. A combination of 20 percent gradient diffusion and 80 percent bulk convection appears to mimic the transport process for turbulent energy reasonably well.

  14. Confinement vessel analysis final report

    SciTech Connect

    Lewis, B.B.

    1992-05-06

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

  15. Cylindrical confinement of semiflexible polymers.

    PubMed

    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 ≈pE(0)(nE(0)), with E(0) the energy of a circular loop with same radius as the cylinder; in long loops the axial torque vanishes. Confined bound excited states are initially unstable; however, above a critical length 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. PMID:26172814

  16. Response measurement of single-crystal chemical vapor deposition diamond radiation detector for intense X-rays aiming at neutron bang-time and neutron burn-history measurement on an inertial confinement fusion with fast ignition.

    PubMed

    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

  17. Inertial confinement fusion

    SciTech Connect

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

    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.

  18. Energy Confinement in the Advanced RFP

    NASA Astrophysics Data System (ADS)

    Scheffel, J.; Dahlin, J.-E.; Schnack, D. D.; Drake, J. R.

    2003-10-01

    In earlier numerical studies [1,2] of confinement in the optimized, conventional reversed-field pinch (RFP), the scaling of energy confinement time with plasma current and density was found to be too weak to lead into fusion relevant regimes. In the advanced RFP, however, the detrimental magnetic (dynamo) fluctuations are largely eliminated by the presence of an externally applied electric field. This field is adjusted to generate a tearing mode stable parallel current density profile. Previous studies [3,4] used a gaussian shaped electric field with given width and amplitude that was localised at some minor radius of the plasma. A threefold increase in energy confinement was found, but the three associated parameters made further optimisation difficult. In the present work a new, parameter free scheme for current profile control is introduced. An automatic control system continuously replaces the dynamo electric field. Early results indicate strong energy confinement enhancement. [1] J. Scheffel and D. D. Schnack, Phys. Rev. Lett. 85 (2000) 322. [2] J. Scheffel and D. D. Schnack, Nucl. Fusion 40 (2000) 1885. [3] C. R. Sovinec and S. C. Prager, Nucl. Fusion 39 (1999) 777. [4] J. Scheffel and D. D. Schnack, International RFP Workshop, Stockholm 2002.

  19. Partial confinement photonic crystal waveguides

    SciTech Connect

    Saini, S.; Hong, C.-Y.; Pfaff, N.; Kimerling, L. C.; Michel, J.

    2008-12-29

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

  20. Alpha particle confinement in tokamaks

    SciTech Connect

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

    1988-11-01

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

  1. Confinement scaling and ignition in tokamaks

    SciTech Connect

    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.

  2. Rheology of Confined Non-Brownian Suspensions

    NASA Astrophysics Data System (ADS)

    Fornari, Walter; Brandt, Luca; Chaudhuri, Pinaki; Lopez, Cyan Umbert; Mitra, Dhrubaditya; Picano, Francesco

    2016-01-01

    We study the rheology of confined suspensions of neutrally buoyant rigid monodisperse spheres in plane-Couette flow using direct numerical simulations. We find that if the width of the channel is a (small) integer multiple of the sphere diameter, the spheres self-organize into two-dimensional layers that slide on each other and the effective viscosity of the suspension is significantly reduced. Each two-dimensional layer is found to be structurally liquidlike but its dynamics is frozen in time.

  3. 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.

  4. Confined explosive joining of tubes

    NASA Technical Reports Server (NTRS)

    Bement, L. J.

    1979-01-01

    Technique uses explosive ribbon to join and seal tubes hermetically while totally confining explosive products, such as smoke, light, and sound. Only click is audible. Process yields joints of the same strengths as parent metal.

  5. Impurity confinement and transport in high confinement regimes without edge localized modes on DIII-D

    SciTech Connect

    Grierson, B. A. Nazikian, R. M.; Solomon, W. M.; Burrell, K. H.; Garofalo, A. M.; Belli, E. A.; Staebler, G. M.; Evans, T. E.; Smith, S. P.; Chrobak, C.; Fenstermacher, M. E.; McKee, G. R.; Orlov, D. M.; Chrystal, C.

    2015-05-15

    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 τ{sub p}/τ{sub 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 ρ=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.

  6. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2009-06-01

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

  8. Confined aquifer vulnerability induced by a pumping well in a leakage area

    NASA Astrophysics Data System (ADS)

    Meng, X.; Deng, B.; Shao, J.; Yin, M.; Liu, D.; Hu, Q.

    2015-05-01

    Due to the pollution of shallow groundwater and the rapid development of society and economy which consume more freshwater, the exploitation of confined groundwater is steadily increasing in north China. Therefore, the rapid decline of the confined groundwater head increases the risk of confined aquifer pollution by leaky recharge from shallow aquifers. In this paper, a quantitative method for assessing confined aquifer vulnerability to contamination due to pumping has been developed. This method is based on the shallow and confined groundwater flow model and the advection and dispersion in the aquitard, including sorption. The cumulative time for the pollutant concentration at the top boundary of confined aquifer exceeding the maximum allowable level is defined as the confined aquifer vulnerability index, which can be obtained by numerically solving the solute transport equation. A hypothetical example is chosen as a case study to illustrate the whole process. The results indicate that the proposed method is a practical and reasonable assessment method of confined aquifer vulnerability.

  9. Dissipation-driven behavior of nonpropagating hydrodynamic solitons under confinement.

    PubMed

    Gordillo, Leonardo; Garca-ustes, Mnica A

    2014-04-25

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

  10. Confined separated-swirling flows in diffusing ducts

    NASA Technical Reports Server (NTRS)

    Anderson, Bernhard H.

    1987-01-01

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

  11. 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.

  12. PREFACE: Water in confined geometries

    NASA Astrophysics Data System (ADS)

    Rovere, Mauro

    2004-11-01

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

  13. Single-molecule mobility in confined and crowded femtoliter chambers

    SciTech Connect

    Collier, Pat; Fowlkes, Jason Davidson

    2013-01-01

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

  14. Tgermonuclear Ignition in Inertial Confinement Fusion and Comparison with Magnetic Confinement

    SciTech Connect

    Betti, R.; Chang, P.Y.; Spears, B.K.; Anderson, K.S.; Edwards, J.; Fatenejad, M.; Lindl, J.D.; McCrory, R.L.; Nora, R.; Shvarts, D.

    2010-04-23

    The physics of thermonuclear ignition in inertial confinement fusion (ICF) is presented in the familiar frame of a Lawson-type criterion. The product of the plasma pressure and confinement time Ptau for ICF is cast in terms of measurable parameters and its value is estimated for cryogenic implosions. An overall ignition parameter chi including pressure, confinement time, and temperature is derived to complement the product Ptau. A metric for performance assessment should include both chi and Ptau. The ignition parameter and the product Ptau are compared between inertial and magnetic-confinement fusion. It is found that cryogenic implosions on OMEGA [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)] have achieved Ptau ~ 1.5 atm s comparable to large tokamaks such as the Joint European Torus [P. H. Rebut and B. E. Keen, Fusion Technol. 11, 13 (1987)] where Ptau ~ 1 atm s. Since OMEGA implosions are relatively cold (T ~ 2 keV), their overall ignition parameter chi ~ 0.020.03 is ~5X lower than in JET (chi ~ 0.13), where the average temperature is about 10 keV.

  15. Gas solubility in hydrophobic confinement.

    PubMed

    Luzar, Alenka; Bratko, Dusan

    2005-12-01

    Measured forces between apolar surfaces in water have often been found to be sensitive to exposure to atmospheric gases despite low gas solubilities in bulk water. This raises questions as to how significant gas adsorption is in hydrophobic confinement, whether it is conducive to water depletion at such surfaces, and ultimately if it can facilitate the liquid-to-gas phase transition in the confinement. Open Ensemble molecular simulations have been used here to determine saturated concentrations of atmospheric gases in water-filled apolar confinements as a function of pore width at varied gas fugacities. For paraffin-like confinements of widths barely exceeding the mechanical instability threshold (spinodal) of the liquid-to-vapor transition of confined water (aqueous film thickness between three and four molecular diameters), mean gas concentrations in the pore were found to exceed the bulk values by a factor of approximately 30 or approximately 15 in cases of N2 and CO2, respectively. At ambient conditions, this does not result in visible changes in the water density profile next to the surfaces. Whereas the barrier to capillary evaporation has been found to decrease in the presence of dissolved gas (Leung, K.; Luzar, A.; and Bratko, D. Phys. Rev. Lett. 2003, 90, 065502), gas concentrations much higher than those observed at normal atmospheric conditions would be needed to produce noticeable changes in the kinetics of capillary evaporation. In simulations, dissolved gas concentrations corresponding to fugacities above approximately 40 bar for N2, or approximately 2 bar for CO2, were required to trigger expulsion of water from a hydrocarbon slit as narrow as 1.4 nm. For nanosized pore widths corresponding to the mechanical instability threshold or above, no significant coupling between adsorption layers at opposing confinement walls was observed. This finding explains the approximately linear increase in gas solubility with inverse confinement width and the apparent validity of Henry's law in the pores over a broad fugacity range. PMID:16853936

  16. 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.

  17. 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. 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.

  18. Water confined in hydrophobic environments

    NASA Astrophysics Data System (ADS)

    Han, Sungho

    This thesis applies statistical physics approaches and computer simulation methods to investigate the dynamical properties and phase transitions of water confined in hydrophobic environments. A diffusion anomaly, an increase of diffusion upon compression, is one of many unexpected behaviors observed in water. To calculate the diffusion coefficient of confined water in the confining direction, we use the concept of the continuous random walk. We find that a diffusion anomaly of water is absent in the direction perpendicular to the confining walls down to 220 K, whereas there is a diffusion anomaly, similar to that in bulk water, in the direction parallel to the walls. Anomalous behaviors of water compared to simple liquids are generally ascribed to a hydrogen bond. From investigations of confinement effects on a hydrogen bond, we find that even if the average number and the lifetime of hydrogen bonds are affected by nanoconfinement, the characteristics of hydrogen bond dynamics in hydrophobic confined water are the same as in bulk water. The different physical properties of water in hydrophobic confinement compared to bulk water---such as 40 K temperature shift---may be primarily due to the reduction of the lifetime of hydrogen bonds in confined environments. We also find that the hydrogen bond autocorrelation function exhibits a power-law tail characterized by an exponent which depends on the system dimensionality. Vapor and liquid may transform into each other either discontinuously by crossing a first-order transition line or continuously without crossing a transition line, indicating an existence of the vapor-liquid critical point. In contrast to the phase transition line between vapor and liquid, the first-order transition line between solid and liquid is believed to persist indefinitely without terminating at a critical point. We show that either a first-order transition or a continuous transition between solid and liquid can occur for water confined in a quasi-two-dimensional hydrophobic nanopore slit. This finding indicates that the connection point between first-order and continuous transition lines might be a solid-liquid critical point with a tricritical nature.

  19. Confined PBX 9501 gap reinitiation studies

    SciTech Connect

    Salyer, Terry R; Hill, Larry G; Lam, Kin

    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.

  20. Confined PBX 9501 Gap Reinitiation Studies

    NASA Astrophysics Data System (ADS)

    Salyer, Terry

    2009-06-01

    For explosive systems that exhibit gaps or cracks between their internal components (either by design or mechanical failure), measureable time delays exist for detonation waves crossing them. Reinitiation across such gaps is dependent on the type of explosive, gap width, 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 established Pop plots and 1-D calculations, making it possible to estimate detonation run-up distances as well. These results are beneficial for the design and evaluation of explosive systems that require precision timing and performance.

  1. Thermodynamics of confined gallium clusters.

    PubMed

    Chandrachud, Prachi

    2015-11-11

    We report the results of ab initio molecular dynamics simulations of Ga13 and Ga17 clusters confined inside carbon nanotubes with different diameters. The cluster-tube interaction is simulated by the Lennard-Jones (LJ) potential. We discuss the geometries, the nature of the bonding and the thermodynamics under confinement. The geometries as well as the isomer spectra of both the clusters are significantly affected. The degree of confinement decides the dimensionality of the clusters. We observe that a number of low-energy isomers appear under moderate confinement while some isomers seen in the free space disappear. Our finite-temperature simulations bring out interesting aspects, namely that the heat capacity curve is flat, even though the ground state is symmetric. Such a flat nature indicates that the phase change is continuous. This effect is due to the restricted phase space available to the system. These observations are supported by the mean square displacement of individual atoms, which are significantly smaller than in free space. The nature of the bonding is found to be approximately jellium-like. Finally we note the relevance of the work to the problem of single file diffusion for the case of the highest confinement. PMID:26452011

  2. Thermodynamics of confined gallium clusters

    NASA Astrophysics Data System (ADS)

    Chandrachud, Prachi

    2015-11-01

    We report the results of ab initio molecular dynamics simulations of Ga13 and Ga17 clusters confined inside carbon nanotubes with different diameters. The cluster-tube interaction is simulated by the Lennard-Jones (LJ) potential. We discuss the geometries, the nature of the bonding and the thermodynamics under confinement. The geometries as well as the isomer spectra of both the clusters are significantly affected. The degree of confinement decides the dimensionality of the clusters. We observe that a number of low-energy isomers appear under moderate confinement while some isomers seen in the free space disappear. Our finite-temperature simulations bring out interesting aspects, namely that the heat capacity curve is flat, even though the ground state is symmetric. Such a flat nature indicates that the phase change is continuous. This effect is due to the restricted phase space available to the system. These observations are supported by the mean square displacement of individual atoms, which are significantly smaller than in free space. The nature of the bonding is found to be approximately jellium-like. Finally we note the relevance of the work to the problem of single file diffusion for the case of the highest confinement.

  3. Coronal electron confinement by double layers

    SciTech Connect

    Li, T. C.; Drake, J. F.; Swisdak, M.

    2013-12-01

    In observations of flare-heated electrons in the solar corona, a longstanding problem is the unexplained prolonged lifetime of the electrons compared to their transit time across the source. This suggests confinement. Recent particle-in-cell (PIC) simulations, which explored the transport of pre-accelerated hot electrons through ambient cold plasma, showed that the formation of a highly localized electrostatic potential drop, in the form of a double layer (DL), significantly inhibited the transport of hot electrons. The effectiveness of confinement by a DL is linked to the strength of the DL as defined by its potential drop. In this work, we investigate the scaling of the DL strength with the hot electron temperature by PIC simulations and find a linear scaling. We demonstrate that the strength is limited by the formation of parallel shocks. Based on this, we analytically determine the maximum DL strength, and also find a linear scaling with the hot electron temperature. The DL strength obtained from the analytic calculation is comparable to that from the simulations. At the maximum strength, the DL is capable of confining a significant fraction of hot electrons in the source.

  4. Plasma confinement studies in open systems

    NASA Astrophysics Data System (ADS)

    Yatsu, Kiyoshi

    1999-03-01

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

  5. Random Matrices in Non-confining Potentials

    NASA Astrophysics Data System (ADS)

    Allez, Romain; Dumaz, Laure

    2015-08-01

    We consider invariant matrix processes diffusing in non-confining cubic potentials of the form . 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 at a critical value . If , then the potential presents a well near deep enough to confine all the particles inside, and the spectral density is supported on a compact interval. If however, the steady state is in fact dynamical with a macroscopic stationary flux of particles flowing across the system. We prove that this flux displays a second order phase transition at the critical value such that when where is an explicit constant. In the subcritical regime, the eigenvalues allocate according to a stationary density profile with full support in , flanked with heavy tails such that as . Our method applies to other non-confining 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.

  6. Combinational concentration gradient confinement through stagnation flow.

    PubMed

    Alicia, Toh G G; Yang, Chun; Wang, Zhiping; Nguyen, Nam-Trung

    2016-01-01

    Concentration gradient generation in microfluidics is typically constrained by two conflicting mass transport requirements: short characteristic times (?) for precise temporal control of concentration gradients but at the expense of high flow rates and hence, high flow shear stresses (?). To decouple the limitations from these parameters, here we propose the use of stagnation flows to confine concentration gradients within large velocity gradients that surround the stagnation point. We developed a modified cross-slot (MCS) device capable of feeding binary and combinational concentration sources in stagnation flows. We show that across the velocity well, source-sink pairs can form permanent concentration gradients. As source-sink concentration pairs are continuously supplied to the MCS, a permanently stable concentration gradient can be generated. Tuning the flow rates directly controls the velocity gradients, and hence the stagnation point location, allowing the confined concentration gradient to be focused. In addition, the flow rate ratio within the MCS rapidly controls (? ? 50 ms) the location of the stagnation point and the confined combinational concentration gradients at low flow shear (0.2 Pa < ? < 2.9 Pa). The MCS device described in this study establishes the method for using stagnation flows to rapidly generate and position low shear combinational concentration gradients for shear sensitive biological assays. PMID:26671507

  7. Status of global energy confinement studies

    SciTech Connect

    Kaye, S.M.; Bell, M.G. . Plasma Physics Lab.); Barnes, C.W. ); DeBoo, J.C.; Waltz, R. ); Greenwald, M.; Sigmar, D. . Plasma Fusion Center); Riedel, K. . Courant Inst. of Mathematical Sciences); Uckan, N. (Oak Ridge National L

    1990-02-01

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

  8. CORRELATIONS IN CONFINED QUANTUM PLASMAS

    SciTech Connect

    DUFTY J W

    2012-01-11

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

  9. Confinement of multiply charged ions in an ECRH mirror plasma

    NASA Astrophysics Data System (ADS)

    Petty, Clinton Craig

    1989-06-01

    This thesis is an experimental study of multiply charged ions in the Constance B mirror experiment. By measuring the ion densities, end loss fluxes and ion temperatures, the parallel confinement times for the first five charge states of oxygen and neon plasmas are determined. The parallel ion confinement times increase with charge state and peak on axis, both indications of an ion-confining potential dip created by the hot electrons. The radial profile of ion end loss is usually hollow due to large ion radial transport (tau sub parallel(i) is approximately tau sub perpendicular(i)), with the peak fluxes occurring at the edge of the electron cyclotron resonance zone. Several attempts are made to increase the end loss of selected ion species. Using minority ICRH, the end loss flux of resonant ions increases by 20 percent in cases when radial transport induced by ICRH is not too severe. A large antenna voltage can also extinguish the plasma. By adding helium to an oxygen plasma, the end loss of O(6+) increases by 80 due to decreased ion radial transport. An ion model is developed to predict the ion densities, end loss fluxes and confinement times in the plasma center using the ion particle balance equations, the quasineutrality condition and theoretical confinement time formulas. The model generally agrees with the experimental data for oxygen and neon plasmas to within experimental error. Under certain conditions spatial diffusion appears to determine the parallel ion confinement time of the highest charge states. For oxygen plasmas during ICRH, the measured parallel confinement time of the resonant ions is much shorter than their theoretical value, probably due to rf diffusion of the ions into the loss cone.

  10. Special topics in plasma confinement

    NASA Astrophysics Data System (ADS)

    Taylor, J. B.; Newton, S. L.

    2015-10-01

    > These notes are based on lectures given by one of us (J.B.T.) at the University of Texas in Austin in 1991. Part I concerns some basic features of plasma confinement by magnetic fields as an introduction to an account of plasma relaxation in Part II. Part III discusses confinement by magnetic mirrors, especially minimum- systems. It also includes a general discussion of adiabatic invariants and of the principle of maximal ordering in perturbation theory. Part IV is devoted to the analysis of perturbations in toroidal plasmas and the stability of ballooning modes.

  11. Building solids inside nano-space: from confined amorphous through confined solvate to confined 'metastable' polymorph.

    PubMed

    Nartowski, K P; Tedder, J; Braun, D E; Fbin, L; Khimyak, Y Z

    2015-10-14

    The nanocrystallisation of complex molecules inside mesoporous hosts and control over the resulting structure is a significant challenge. To date the largest organic molecule crystallised inside the nano-pores is a known pharmaceutical intermediate - ROY (259.3 g mol(-1)). In this work we demonstrate smart manipulation of the phase of a larger confined pharmaceutical - indomethacin (IMC, 357.8 g mol(-1)), a substance with known conformational flexibility and complex polymorphic behaviour. We show the detailed structural analysis and the control of solid state transformations of encapsulated molecules inside the pores of mesoscopic cellular foam (MCF, pore size ca. 29 nm) and controlled pore glass (CPG, pore size ca. 55 nm). Starting from confined amorphous IMC we drive crystallisation into a confined methanol solvate, which upon vacuum drying leads to the stabilised rare form V of IMC inside the MCF host. In contrast to the pure form, encapsulated form V does not transform into a more stable polymorph upon heating. The size of the constraining pores and the drug concentration within the pores determine whether the amorphous state of the drug is stabilised or it recrystallises into confined nanocrystals. The work presents, in a critical manner, an application of complementary techniques (DSC, PXRD, solid-state NMR, N2 adsorption) to confirm unambiguously the phase transitions under confinement and offers a comprehensive strategy towards the formation and control of nano-crystalline encapsulated organic solids. PMID:26280634

  12. 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

  13. Mirror Confinement Systems: project summaries

    SciTech Connect

    Not Available

    1980-07-01

    This report contains descriptions of the projects supported by the Mirror Confinement Systems (MCS) Division of the Office of Fusion Energy. The individual project summaries were prepared by the principal investigators, in collaboration with MCS staff office, and include objectives and milestones for each project. In addition to project summaries, statements of Division objectives and budget summaries are also provided.

  14. 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.

  15. Inertial confinement fusion (ICF) review

    SciTech Connect

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

    1996-03-01

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

  16. Limiting Spectra from Confining Potentials.

    ERIC Educational Resources Information Center

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

    1979-01-01

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

  17. Time

    ERIC Educational Resources Information Center

    Circle, David

    2005-01-01

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

  18. Confinement Studies of Auxiliary Heated NSTX Plasmas

    SciTech Connect

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

    2003-05-06

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

  19. Polymer ejection from strong spherical confinement

    NASA Astrophysics Data System (ADS)

    Piili, J.; Linna, R. P.

    2015-12-01

    We examine the ejection of an initially strongly confined flexible polymer from a spherical capsid through a nanoscale pore. We use molecular dynamics for unprecedentedly high initial monomer densities. We show that the time for an individual monomer to eject grows exponentially with the number of ejected monomers. By measurements of the force at the pore we show this dependence to be a consequence of the excess free energy of the polymer due to confinement growing exponentially with the number of monomers initially inside the capsid. This growth relates closely to the divergence of mixing energy in the Flory-Huggins theory at large concentration. We show that the pressure inside the capsid driving the ejection dominates the process that is characterized by the ejection time growing linearly with the lengths of different polymers. Waiting time profiles would indicate that the superlinear dependence obtained for polymers amenable to computer simulations results from a finite-size effect due to the final retraction of polymers' tails from capsids.

  20. Dynamics of Confined Water Molecules in Aqueous Salt Hydrates

    SciTech Connect

    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 liquids 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.

  1. Response of marine bacterioplankton to differential filtration and confinement.

    PubMed Central

    Ferguson, R L; Buckley, E N; Palumbo, A V

    1984-01-01

    The bacterioplankton community of confined seawater at 25 degrees C changed significantly within 16 h of collection. Confinement increased CFU, total cell number (by epifluorescence microscopy), and average cell volume of bacterioplankton and increased the turnover rate of amino acids in seawater sampled at Frying Pan Shoals, N.C. The bacterioplankton community was characterized by two components: differential doubling times during confinement shifted dominance from bacteria which were nonculturable to bacteria which were culturable on a complex nutrient medium. Culturable cells (especially those of the genera Pseudomonas, Alcaligenes, and Acinetobacter) increased from 0.08% of the total cell number in the seawater immediately after collection to 13% at 16 h and 41% at 32 h of confinement. Differential filtration before confinement indicated that particles passing through a 3.9-microns-, but retained by a 0.2-micron-, pore-size Nuclepore filter may be a major source of primary amines to the confined population. The 3.0-microns filtration increased growth rate and ultimate numbers of culturable cells through the removal of bacterial predators or the release of primary amines from cells damaged during filtration or both. PMID:6696422

  2. H-mode confinement of Heliotron J

    NASA Astrophysics Data System (ADS)

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

    2005-12-01

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

  3. 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.

  4. Physics of magnetic confinement fusion

    NASA Astrophysics Data System (ADS)

    Wagner, F.

    2013-06-01

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

  5. Theory of rheology in confinement.

    PubMed

    Aerov, Artem A; Krüger, Matthias

    2015-10-01

    The viscosity of fluids is generally understood in terms of kinetic mechanisms, i.e., particle collisions, or thermodynamic ones as imposed through structural distortions upon, e.g., applying shear. Often the latter are more relevant, which allows a simpler theoretical description, and, e.g., (damped) Brownian particles can be considered good fluid model systems. We formulate a general theoretical approach for rheology in confinement, based on microscopic equations of motion and classical density functional theory. Specifically, we discuss the viscosity for the case of two parallel walls in relative motion as a function of the wall-to-wall distance, analyzing its relation to the slip length found for a single wall. The previously observed [A. A. Aerov and M. Krüger, J. Chem. Phys. 140, 094701 (2014).] deficiency of inhomogeneous (unphysical) stresses under naive application of shear in confinement is healed when hydrodynamic interactions are included. PMID:26565234

  6. Theory of rheology in confinement

    NASA Astrophysics Data System (ADS)

    Aerov, Artem A.; Krüger, Matthias

    2015-10-01

    The viscosity of fluids is generally understood in terms of kinetic mechanisms, i.e., particle collisions, or thermodynamic ones as imposed through structural distortions upon, e.g., applying shear. Often the latter are more relevant, which allows a simpler theoretical description, and, e.g., (damped) Brownian particles can be considered good fluid model systems. We formulate a general theoretical approach for rheology in confinement, based on microscopic equations of motion and classical density functional theory. Specifically, we discuss the viscosity for the case of two parallel walls in relative motion as a function of the wall-to-wall distance, analyzing its relation to the slip length found for a single wall. The previously observed [A. A. Aerov and M. Krüger, J. Chem. Phys. 140, 094701 (2014)., 10.1063/1.4866450] deficiency of inhomogeneous (unphysical) stresses under naive application of shear in confinement is healed when hydrodynamic interactions are included.

  7. Plasma Confinement in the UCLA Electric Tokamak.

    NASA Astrophysics Data System (ADS)

    Taylor, Robert J.

    2001-10-01

    The main goal of the newly constructed large Electric Tokamak (R = 5 m, a = 1 m, BT < 0.25 T) is to access an omnigeneous, unity beta(S.C. Cowley, P.K. Kaw, R.S. Kelly, R.M. Kulsrud, Phys. fluids B 3 (1991) 2066.) plasma regime. The design goal was to achieve good confinement at low magnetic fields, consistent with the high beta goal. To keep the program cost down, we adopted the use of ICRF as the primary heating source. Consequently, antenna surfaces covering 1/2 of the surface of the tokamak has been prepared for heating and current drive. Very clean hydrogenic plasmas have been achieved with loop voltage below 0.7 volt and densities 3 times above the Murakami limit, n(0) > 8 x 10^12 cm-3 when there is no MHD activity. The electron temperature, derived from the plasma conductivity is > 250 eV with a central electron energy confinement time > 350 msec in ohmic conditions. The sawteeth period is 50 msec. Edge plasma rotation is induced by plasma biasing via electron injection in an analogous manner to that seen in CCT(R.J. Taylor, M.L. Brown, B.D. Fried, H. Grote, J.R. Liberati, G.J. Morales, P. Pribyl, D. Darrow, and M. Ono. Phys. Rev Lett. 63 2365 1989.) and the neoclassical bifurcation is close to that described by Shaing et al(K.C. Shaing and E.C. Crume, Phys. Rev. Lett. 63 2369 (1989).). In the ohmic phase the confinement tends to be MHD limited. The ICRF heating eliminates the MHD disturbances. Under second harmonic heating conditions, we observe an internal confinement peaking characterized by doubling of the core density and a corresponding increase in the central electron temperature. Charge exchange data, Doppler data in visible H-alpha light, and EC radiation all indicate that ICRF heating works much better than expected. The major effort is focused on increasing the power input and controlling the resulting equilibrium. This task appears to be easy since our current pulses are approaching the 3 second mark without RF heating or current drive. Our initial experience with current profile control, needed for high beta plasma equilibrium, will be also discussed.

  8. Ion beam inertial confinement target

    DOEpatents

    Bangerter, Roger O.; Meeker, Donald J.

    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.

  9. Improved Confinement During Magnetic Levitation in LDX

    NASA Astrophysics Data System (ADS)

    Mauel, M. E.

    2008-11-01

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

  10. Preliminary Analysis of HL-2A Global Energy Confinement

    NASA Astrophysics Data System (ADS)

    Dong, Chunfeng; Cui, Zhengying; Ji, Xiaoquan; Zhou, Hangyu; Feng, Beibin; Sun, Hongjuan; Li, Yonggao; Yang, Qingwei

    2009-02-01

    Energy confinement time taken from 135 discharges of the 2006 campaign in HL-2A is studied. The data obtained from the measurements are verified by comparing diamagnetic energy with the electronic kinetic energy calculated from both the electron temperature and density profiles. Two data sets for supporting the ITER L-Mode confinement database are generated from the 2006 campaign. The dependence of ?E on the line-averaged electron density during ohmic phases is analysed. The comparison of ?E in electron cyclotron resonance heating (ECRH) plasma as well as the existing ITER L-mode scalings is made. The results show that the energy confinement time is consistent with the ITER L-mode scalings.

  11. Viscoelastic Transient of Confined Red Blood Cells

    NASA Astrophysics Data System (ADS)

    Prado, Gal; 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, $\\eta_{mem}^{2D}\\sim 10^{-7}$ 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.

  12. Viscoelastic transient of confined red blood cells.

    PubMed

    Prado, Gal; 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

  13. 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, τ, 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.

  14. Time?

    NASA Astrophysics Data System (ADS)

    Amoroso, Richard L.

    2013-09-01

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

  15. Criticality in confined ionic fluids

    SciTech Connect

    Flores-Mena, J. E.; Barbosa, Marcia C.; Levin, Yan

    2001-06-01

    A theory of a confined two-dimensional electrolyte is presented. The positive and negative ions, interacting by a 1/r potential, are constrained to move on an interface separating two solvents with dielectric constants {epsilon}{sub 1} and {epsilon}{sub 2}. It is shown that the Debye-Huckel type of theory predicts that this two-dimensional Coulomb fluid should undergo a phase separation into a coexisting liquid (high-density) and gas (low-density) phases. We argue, however, that the formation of polymerlike chains of alternating positive and negative ions can prevent this phase transition from taking place.

  16. Rheology of confined granular flows

    SciTech Connect

    Richard, Patrick; Valance, Alexandre; Metayer, Jean-Francois; Crassous, Jerome; Delannay, Renaud; Louge, Michel

    2010-05-05

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

  17. Electromelting of confined monolayer ice.

    PubMed

    Qiu, Hu; Guo, Wanlin

    2013-05-10

    In sharp contrast to the prevailing view that electric fields promote water freezing, here we show by molecular dynamics simulations that monolayer ice confined between two parallel plates can melt into liquid water under a perpendicularly applied electric field. The melting temperature of the monolayer ice decreases with the increasing strength of the external field due to the field-induced disruption of the water-wall interaction induced well-ordered network of the hydrogen bond. This electromelting process should add an important new ingredient to the physics of water. PMID:23705718

  18. Sustained operations in confined-space military vehicles.

    PubMed

    Delleman, Nico J; Colaciuri, Vronique; Wiederkehr, Emeric; Valk, Pierre J L

    2008-01-01

    This paper reports 2 baseline studies and one experiment performed in a confined-space military vehicle concerning the effects on fitness and performance of time in a sitting posture and workstation characteristics. On average physical fitness decreased by slightly more than 10% per hour, the observation performance decreased by 30% per hour, and the technical performance (of gunners) showed a relatively small decrease, i.e., less than 5% per hour. So-called active breaks (changing sitting into standing and walking) led to a significant reduction in the decrease of physical fitness, almost reducing it to zero. Furthermore, the level of confinement was shown to affect physical fitness. PMID:18954541

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

    SciTech Connect

    Besserer, U.; Doerr, L.; Glugla, M.

    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)

  20. Effect of magnetic confinement on manybody nonlinearities of Lorentzian excitons

    SciTech Connect

    Kner, P.; Bar-Ad, S.; Marquezini, M.V.; Chemla, D.S.

    1995-11-01

    100-fs time- and frequency-resolved four-wave mixing in GaAs at T=1.6K under magnetic field, 0{<=}|{rvec B}|{<=}12T, is used for investigating how magnetic confinement modifies the processes that govern the manybody nonlinearities of the Lorentzian excitons.

  1. 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 β (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 β 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 β . This represents critical progress toward an understanding of the plasma dynamics in a high-β 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-β cusp configuration with electrostatic fusion for a compact, power-producing nuclear fusion reactor.

  2. Ingestive Behavior of Lambs Confined in Individual and Group Stalls

    PubMed Central

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

    2014-01-01

    The experiment was conducted to evaluate the ingestive behavior of lambs confined in individual and group stalls. We used thirty-four lambs in their growing phase, aged an average of three months, with mean initial live weight of 17.85.2 kg. They were allotted in a completely randomized design with 24 animals kept in individual stalls and 10 animals confined as a group. The experiment lasted for a total of 74 days, and the first 14 days were dedicated to the animals adaption to the management, facilities and diets. The data collection period lasted 60 days, divided into three 20-d periods for the behavior evaluation. The animals were subjected to five days of visual observation during the experiment period, by the quantification of 24 h a day, with evaluations on the 15th day of each period and an interim evaluation consisting of two consecutive days on the 30th and 31st day of the experiment. The animals confined as a group consumed less (p<0.05) fiber. However, the animals confined individually spent less (p<0.05) time on feeding, rumination and chewing activities and longer in idleness. Therefore, the lower capacity of lambs confined in groups to select their food negatively affects their feeding behavior. PMID:25049953

  3. Issues in tokamak/stellarator transport and confinement enhancement mechanisms

    SciTech Connect

    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.

  4. Dynamics of Ice/Water Confined in Nanoporous Alumina.

    PubMed

    Suzuki, Yasuhito; Steinhart, Martin; Graf, Robert; Butt, Hans-Jrgen; Floudas, George

    2015-11-19

    Dielectric (DS), IR spectroscopy, and (1)H MAS NMR are employed in the study of ice/water confined in nanoporous alumina with pore diameters ranging from 400 nm down to 25 nm. Within nanoporous alumina there is a transformation from heterogeneous nucleation of hexagonal ice in the larger pores to homogeneous nucleation of cubic ice in the smaller pores. DS and IR show excellent agreement in the temperature interval and pore size dependence of the transformation. DS further revealed two dynamic processes under confinement. The "fast" and "slow" processes with an Arrhenius temperature dependence are attributed to ice and supercooled water relaxation, respectively. The main relaxation process of ice under confinement ("slow" process) has an activation energy of 44 2 kJ/mol. The latter is in agreement with the reported relaxation times and activation energy of cubic ice prepared following a completely different route (by pressure). (1)H MAS NMR provided new insight in the state of ice structures as well as of supercooled water. Under confinement, a layer of liquid-like water coexists with ice structures. In addition, both ice structures under confinement appear to be more ordered than bulk hexagonal ice. Supercooled water in the smaller pores is different from bulk water. It shows a shift of the signal toward higher chemical shift values which may suggest stronger hydrogen bonding between the water molecules or increasing interactions with the AAO walls. PMID:26511073

  5. Diffusional spread and confinement of newly exocytosed synaptic vesicle proteins

    PubMed Central

    Gimber, Niclas; Tadeus, Georgi; Maritzen, Tanja; Schmoranzer, Jan; Haucke, Volker

    2015-01-01

    Neurotransmission relies on the calcium-triggered exocytic fusion of non-peptide neurotransmitter-containing small synaptic vesicles (SVs) with the presynaptic membrane at active zones (AZs) followed by compensatory endocytic retrieval of SV membranes. Here, we study the diffusional fate of newly exocytosed SV proteins in hippocampal neurons by high-resolution time-lapse imaging. Newly exocytosed SV proteins rapidly disperse within the first seconds post fusion until confined within the presynaptic bouton. Rapid diffusional spread and confinement is followed by slow reclustering of SV proteins at the periactive endocytic zone. Confinement within the presynaptic bouton is mediated in part by SV protein association with the clathrin-based endocytic machinery to limit diffusional spread of newly exocytosed SV proteins. These data suggest that diffusion, and axonal escape of newly exocytosed vesicle proteins, are counteracted by the clathrin-based endocytic machinery together with a presynaptic diffusion barrier. PMID:26399746

  6. Measurement of the orthopositronium confinement energy in mesoporous thin films

    SciTech Connect

    Crivelli, Paolo; Gendotti, Ulisse; Rubbia, Andre; Liszkay, Laszlo; Perez, Patrice; Corbel, Catherine

    2010-05-15

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

  7. On the confinement of lunar induced magnetic fields

    NASA Astrophysics Data System (ADS)

    Fatemi, S.; Fuqua, H. A.; Poppe, A. R.; Delory, G. T.; Halekas, J. S.; Farrell, W. M.; Holmström, M.

    2015-09-01

    We examine the confinement of induced magnetic fields on the lunar dayside and nightside, when the Moon is in the solar wind. We use a three-dimensional hybrid model of plasma and place a dipole magnetic field at the center of the Moon to mimic the induced magnetic field, which is the response of the lunar interior to the time-varying interplanetary magnetic field. Consistent with previous observations and theoretical predictions, we show that the induced magnetic fields on the dayside are confined within the lunar surface through a dayside current sheet. In contrast to previous work, we show that the induced magnetic fields are not confined in the lunar wake, and they leak out, sometimes even appearing as lunar limb compressions. Finally, we identify favorable places to observe induced magnetic fields by electromagnetic sounding techniques, which will help to better constrain the lunar electrical conductivity profile, and interior structure.

  8. Collective waves in dense and confined microfluidic droplet arrays.

    PubMed

    Schiller, Ulf D; Fleury, Jean-Baptiste; Seemann, Ralf; Gompper, Gerhard

    2015-08-01

    Excitation mechanisms for collective waves in confined dense one-dimensional microfluidic droplet arrays are investigated by experiments and computer simulations. We demonstrate that distinct modes can be excited by creating specific 'defect' patterns in flowing droplet trains. Excited longitudinal modes exhibit a short-lived cascade of pairs of laterally displacing droplets. Transversely excited modes obey the dispersion relation of microfluidic phonons and induce a coupling between longitudinal and transverse modes, whose origin is the hydrodynamic interaction of the droplets with the confining walls. Moreover, we investigate the long-time behaviour of the oscillations and discuss possible mechanisms for the onset of instabilities. Our findings demonstrate that the collective dynamics of microfluidic droplet ensembles can be studied particularly well in dense and confined systems. Experimentally, the ability to control microfluidic droplets may allow the modulation of the refractive index of optofluidic crystals, which is a promising approach for the production of dynamically programmable metamaterials. PMID:26107262

  9. Quasielastic neutron scattering study of water confined in carbon nanopores

    SciTech Connect

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

    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.

  10. 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).

  11. Confinement effects in semimagnetic semiconductors

    NASA Astrophysics Data System (ADS)

    Dietl, Tomasz

    1998-02-01

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

  12. Failure Diameter of Confined Explosive Rods

    NASA Astrophysics Data System (ADS)

    Partom, Yehuda

    1999-06-01

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

  13. Mixed confinement regimes during equilibrium confinement spectroscopy of DNA

    PubMed Central

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

    2014-01-01

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

  14. Confining standing waves in optical corrals.

    SciTech Connect

    Babayan, Y.; McMahon, J. M.; Li, S.; Gray, S. K.; Schatz, G. C.; Odom, T. W.; Northwestern Univ.

    2009-03-01

    Near-field scanning optical microscopy images of solid wall, circular, and elliptical microscale corrals show standing wave patterns confined inside the structures with a wavelength close to that of the incident light. The patterns inside the corrals can be tuned by changing the size and material of the walls, the wavelength of incident light, and polarization direction for elliptical corrals. Finite-difference time-domain calculations of the corral structures agree with the experimental observations and reveal that the electric and magnetic field intensities are out of phase inside the corral. A theoretical modal analysis indicates that the fields inside the corrals can be attributed to p- and s-polarized waveguide modes, and that the superposition of the propagating and evanescent modes can explain the phase differences between the fields. These experimental and theoretical results demonstrate that electromagnetic fields on a dielectric surface can be controlled in a predictable manner.

  15. Diffusive dynamics of nanoparticles in ultra-confined media.

    PubMed

    Jacob, Jack Deodato C; He, Kai; Retterer, Scott T; Krishnamoorti, Ramanan; Conrad, Jacinta C

    2015-10-14

    Differential dynamic microscopy (DDM) was used to investigate the diffusive dynamics of nanoparticles of diameter 200-400 nm that were strongly confined in a periodic square array of cylindrical nanoposts. The minimum distance between posts was 1.3-5 times the diameter of the nanoparticles. The image structure functions obtained from the DDM analysis were isotropic and could be fit by a stretched exponential function. The relaxation time scaled diffusively across the range of wave vectors studied, and the corresponding scalar diffusivities decreased monotonically with increased confinement. The decrease in diffusivity could be described by models for hindered diffusion that accounted for steric restrictions and hydrodynamic interactions. The stretching exponent decreased linearly as the nanoparticles were increasingly confined by the posts. Together, these results are consistent with a picture in which strongly confined nanoparticles experience a heterogeneous spatial environment arising from hydrodynamics and volume exclusion on time scales comparable to cage escape, leading to multiple relaxation processes and Fickian but non-Gaussian diffusive dynamics. PMID:26278883

  16. A helium-3 refrigerator employing capillary confinement of liquid cryogen

    NASA Technical Reports Server (NTRS)

    Ennis, D. J.; Kittel, P.; Brooks, W.; Miller, A.; Spivak, A. L.

    1983-01-01

    A condensation refrigerator suitable for operation in a zero gravity space environment was constructed. The condensed liquid refrigerant is confined by surface tension inside a porous metal matrix. Helium-4 and helium-3 gases were condensed and held in a copper matrix. Evaporative cooling of confined liquid helium-4 resulted in a temperature of 1.4K. Using a zeolite adsorption pump external to the cryostat, a temperature of 0.6 K was achieved through evaporative cooling of liquid helium-3. The amount of time required for complete evaporation of a controlled mass of liquid helium-4 contained in the copper matrix was measured as a function of the applied background power. For heating powers below 18 mW the measured times are consistent with the normal boiling of the confined volume of liquid refrigerant. At background powers above 18 mW the rapid rise in the temperature of the copper matrix the signature of the absence of confined liquid occurs in a time a factor of two shorter than that expected on the basis of an extrapolation of the low power data.

  17. Failure diameter of confined explosive rods

    NASA Astrophysics Data System (ADS)

    Partom, Yehuda

    2000-04-01

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

  18. Elmo bumpy square plasma confinement device

    DOEpatents

    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.

  19. Quark confinement in a constituent quark model

    SciTech Connect

    Langfeld, K.; Rho, M.

    1995-07-01

    On the level of an effective quark theory, we define confinement by the absence of quark anti-quark thresholds in correlation function. We then propose a confining Nambu-Jona-Lasinio-type model. The confinement is implemented in analogy to Anderson localization in condensed matter systems. We study the model`s phase structure as well as its behavior under extreme conditions, i.e. high temperature and/or high density.

  20. DNA statics and dynamics in nanoscale confinement

    NASA Astrophysics Data System (ADS)

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

    2005-01-01

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

  1. Multishell inertial confinement fusion target

    DOEpatents

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

    1984-01-01

    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 reaction accomplished through the porous ceramic cover prior to enclosing of the outer sphere by addition of an outer coating. The multishell target comprises the inner fuel pellet concentrically arranged within a surrounding coated cover or shell by fiber nets imbedded within the cover material.

  2. Multishell inertial confinement fusion target

    DOEpatents

    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.

  3. 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.

  4. Are polymers glassier upon confinement?

    PubMed

    Spice, Jean; Martnez-Tong, Daniel E; Sferrazza, Michele; Nogales, Aurora; Napolitano, Simone

    2015-08-21

    Glass forming systems are characterized by a stability against crystallization upon heating and by the easiness with which their liquid phase can be transformed into a solid lacking of long-range order upon cooling (glass forming ability). Here, we report the thickness dependence of the thermal phase transition temperatures of poly(l-lactide acid) thin films supported onto solid substrates. The determination of the glass transition, cold crystallization and melting temperatures down to a thickness of 6 nm, permitted us to build up parameters describing glass stability and glass forming ability. We observed a strong influence of the film thickness on the latter, while the former is not affected by 1D confinement. Further experiments permitted us to highlight key structural morphology features giving insights to our ellipsometric results via a physical picture based on the changes in the free volume content in proximity of the supporting interfaces. PMID:26086889

  5. Knots along DNA Confined in Nanochannels

    NASA Astrophysics Data System (ADS)

    Renner, C. Benjamin; Dai, Liang; Doyle, Patrick

    2015-03-01

    We study the size distribution of spontaneous knots on semiflexible chains confined in square channels using Monte Carlo simulations. The most probable knot size is shown to vary non-monotonically with the channel size. For knotted polymers confined in channels larger than the size of a knot in bulk, our analysis reveals that the metastable knot size in weak confinement is larger than the knot size in absence of confinement because the confinement free energy gained by shrinking the knot is lessened when the chain experiences the confinement of a channel. In the case of strong confinement, the metastable knot size is smaller than the knot size in the absence of confinement because the segments in the core of the knot experience more confinement free energy, and the channels pushes the segments out of the core of the knot. We demonstrate that a simple theory can capture this non-monotonic behavior and quantitatively explain the metastable knot size as a function of the channel size. These results may have implications for tuning the channel size to either generate or screen knots. NSF CBET #1335938 and SMART's research program in BioSystems and Micromechanics.

  6. Structure and Dynamics of Octamethylcyclotetrasiloxane Confined between Mica Surfaces.

    PubMed

    Vadhana, V; Ayappa, K G

    2016-03-24

    Using a molecular model for octamethylcyclotetrasiloxane (OMCTS), molecular dynamics simulations are carried out to probe the phase state of OMCTS confined between two mica surfaces in equilibrium with a reservoir. Molecular dynamics simulations are carried out for elevations ranging from 5 to 35 K above the melting point for the OMCTS model used in this study. The Helmholtz free energy is computed for a specific confinement using the two-phase thermodynamic (2PT) method. Analysis of the in-plane pair correlation functions did not reveal signatures of freezing even under an extreme confinement of two layers. OMCTS is found to orient with a wide distribution of orientations with respect to the mica surface, with a distinct preference for the surface parallel configuration in the contact layers. The self-intermediate scattering function is found to decay with increasing relaxation times as the surface separation is decreased, and the two-step relaxation in the scattering function, a signature of glassy dynamics, distinctly evolves as the temperature is lowered. However, even at 5 K above the melting point, we did not observe a freezing transition and the self-intermediate scattering functions relax within 200 ps for the seven-layered confined system. The self-diffusivity and relaxation times obtained from the Kohlrausch-Williams-Watts stretched exponential fits to the late α-relaxation exhibit power law scalings with the packing fraction as predicted by mode coupling theory. A distinct discontinuity in the Helmholtz free energy, potential energy, and a sharp change in the local bond order parameter, Q4, was observed at 230 K for a five-layered system upon cooling, indicative of a first-order transition. A freezing point depression of about 30 K was observed for this five-layered confined system, and at the lower temperatures, contact layers were found to be disordered with long-range order present only in the inner layers. These dynamical signatures indicate that confined OMCTS undergoes a slowdown akin to a fluid approaching a glass transition upon increasing confinement, and freezing under confinement would require substantial subcooling below the bulk melting point of OMCTS. PMID:26916475

  7. Thermalization in a holographic confining gauge theory

    NASA Astrophysics Data System (ADS)

    Ishii, Takaaki; Kiritsis, Elias; Rosen, Christopher

    2015-08-01

    Time dependent perturbations of states in the holographic dual of a 3+1 dimensional confining theory are considered. The perturbations are induced by varying the coupling to the theory's most relevant operator. 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.

  8. Fast Ion Confinement in the MST Reversed Field Pinch

    NASA Astrophysics Data System (ADS)

    Fiksel, Gennady

    2005-10-01

    The influence of magnetic fluctuations and consequent magnetic stochasticity on transport and confinement of fast ions is important for fusion plasmas as well as for astrophysical situations. In fusion plasmas it affects the feasibility of neutral atom injection as a means to heat the plasma and will determine the confinement of fusion produced alpha-particles during magnetic reconnection. For astrophysical plasmas, energetic particle transport in stochastic fields can be important in thermal conduction in galaxy-cluster plasmas and cosmic ray propagation. We use the reversed field pinch laboratory plasma to measure transport of fast particles in a stochastic magnetic field. The standard RFP plasma contains a stochastic magnetic field which becomes particularly ergodic during reconnection events. We measure the confinement of fast ions generated by injection of energetic neutral atoms. The confinement is determined through detection of neutrons from the fusion reaction between the beam-produced deuterium ions and the background deuterium plasma. The results indicate that even for a level of magnetic fluctuations at which the magnetic field is stochastic the fast ions energy loss is consistent with the classical slowing down rate and their confinement time is at least 20 ms. This is much longer than expected (1 ms) from the simple picture of the ions streaming along the stochastic magnetic field. However, a several-fold increase in the magnetic stochasticity, as observed during reconnection events in MST, can significantly deteriorate the ion confinement These observation are in agreement with numerical simulation of ion trajectories as well as with analysis of the overlapping of islands in the ion guiding center trajectories.

  9. Enzymatic reactivity of glucose oxidase confined in nanochannels.

    PubMed

    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

  10. The effects of confinement on neuronalgrowth cone morphology and velocity

    PubMed Central

    Smirnov, Michael S.; Cabral, Katelyn A.; Geller, Herbert M.; Urbach, Jeffrey S.

    2014-01-01

    Optimizing growth cone guidance through the use of patterned substrates is important for designing regenerative substrates to aid in recovery from neuronal injury. Using laser ablation, we designed micron-scale patterns capable of confining dissociated mouse cerebellar granule neuron growth cones to channels of different widths ranging from 1.5 to 12 ?m. Growth cone dynamics in these channels were observed using time lapse microscopy. Growth cone area was decreased in channels between 1.5 and 6 ?m as compared to that in 12 ?m and unpatterned substrates. Growth cone aspect ratio was also affected as narrower channels forced growth cones into a narrow, elongated shape. There was no difference in the overall rate of growth cone advance in uniform channels between 1.5 and 12 ?m as compared to growth on unpatterned substrates. The percentage of time growth cones advanced, paused, and retracted was also similar. However, growth cones did respond to changes in confinement: growth cones in narrow lanes rapidly sped up when encountering a wide region and then slowed down as they entered another narrow region. Our results suggest that the rate of neurite extension is not affected by the degree of confinement, but does respond to changes in confinement. PMID:24840617

  11. Negative Pressure Vitrification of the Isochorically Confined Liquid in Nanopores.

    PubMed

    Adrjanowicz, K; Kaminski, K; Koperwas, K; Paluch, M

    2015-12-31

    Dielectric relaxation studies for model glass-forming liquids confined to nanoporous alumina matrices were examined together with high-pressure results. For confined liquids which show the deviation from bulk dynamics upon approaching the glass transition (the change from the Vogel-Fulcher-Tammann to the Arrhenius law), we have observed a striking agreement between the temperature dependence of the ?-relaxation time in the Arrhenius-like region and the isochoric relaxation times extrapolated from the positive range of pressure to the negative pressure domain. Our finding provides strong evidence that glass-forming liquid confined to native nanopores enters the isochoric conditions once the mobility of the interfacial layer becomes frozen in. This results in the negative pressure effects on cooling. We also demonstrate that differences in the sensitivity of various glass-forming liquids to the "confinement effects" can be rationalized by considering the relative importance of thermal energy and density contributions in controlling the ?-relaxation dynamics (the E_{v}/E_{p} ratio). PMID:26765007

  12. Negative Pressure Vitrification of the Isochorically Confined Liquid in Nanopores

    NASA Astrophysics Data System (ADS)

    Adrjanowicz, K.; Kaminski, K.; Koperwas, K.; Paluch, M.

    2015-12-01

    Dielectric relaxation studies for model glass-forming liquids confined to nanoporous alumina matrices were examined together with high-pressure results. For confined liquids which show the deviation from bulk dynamics upon approaching the glass transition (the change from the Vogel-Fulcher-Tammann to the Arrhenius law), we have observed a striking agreement between the temperature dependence of the ? -relaxation time in the Arrhenius-like region and the isochoric relaxation times extrapolated from the positive range of pressure to the negative pressure domain. Our finding provides strong evidence that glass-forming liquid confined to native nanopores enters the isochoric conditions once the mobility of the interfacial layer becomes frozen in. This results in the negative pressure effects on cooling. We also demonstrate that differences in the sensitivity of various glass-forming liquids to the "confinement effects" can be rationalized by considering the relative importance of thermal energy and density contributions in controlling the ? -relaxation dynamics (the Ev/Ep ratio).

  13. Confinement studies of ohmically heated plasmas in TFTR

    SciTech Connect

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

    1985-03-01

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

  14. Order in very cold confined plasmas

    SciTech Connect

    Schiffer, J.P. |

    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.

  15. 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...

  16. Wettability and Coalescence of Cu Droplets Subjected to Two-Wall Confinement

    PubMed Central

    Li, Xiongying; Ren, Hongru; Wu, Weikang; Li, Hui; Wang, Long; He, Yezeng; Wang, Junjun; Zhou, Yi

    2015-01-01

    Controlling droplet dynamics via wettability or movement at the nanoscale is a significant goal of nanotechnology. By performing molecular dynamics simulations, we study the wettability and spontaneous coalescence of Cu droplets confined in two carbon walls. We first focus on one drop in the two-wall confinement to reveal confinement effects on wettability and detaching behavior of metallic droplets. Results show that Cu droplets finally display three states: non-detachment, semi-detachment and full detachment, depending on the height of confined space. The contact angle ranges from 125° to 177°, and the contact area radius ranges from 12 to ~80 Å. The moving time of the detached droplet in the full detachment state shows a linear relationship with the height of confined space. Further investigations into two drops subjected to confinement show that the droplets, initially distant from each other, spontaneously coalesce into a larger droplet by detachment. The coalescing time and final position of the merged droplet are precisely controlled by tailoring surface structures of the carbon walls, the height of the confined space or a combination of these approaches. These findings could provide an effective method to control the droplet dynamics by confinement. PMID:26459952

  17. Wettability and Coalescence of Cu Droplets Subjected to Two-Wall Confinement

    NASA Astrophysics Data System (ADS)

    Li, Xiongying; Ren, Hongru; Wu, Weikang; Li, Hui; Wang, Long; He, Yezeng; Wang, Junjun; Zhou, Yi

    2015-10-01

    Controlling droplet dynamics via wettability or movement at the nanoscale is a significant goal of nanotechnology. By performing molecular dynamics simulations, we study the wettability and spontaneous coalescence of Cu droplets confined in two carbon walls. We first focus on one drop in the two-wall confinement to reveal confinement effects on wettability and detaching behavior of metallic droplets. Results show that Cu droplets finally display three states: non-detachment, semi-detachment and full detachment, depending on the height of confined space. The contact angle ranges from 125 to 177, and the contact area radius ranges from 12 to ~80?. The moving time of the detached droplet in the full detachment state shows a linear relationship with the height of confined space. Further investigations into two drops subjected to confinement show that the droplets, initially distant from each other, spontaneously coalesce into a larger droplet by detachment. The coalescing time and final position of the merged droplet are precisely controlled by tailoring surface structures of the carbon walls, the height of the confined space or a combination of these approaches. These findings could provide an effective method to control the droplet dynamics by confinement.

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

    SciTech Connect

    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.; Doyle, E.J.; Rettig, C.; James, R.; Wroblewski, D.; Lazarus, E.A.; Zohm, H.

    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.

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

    SciTech Connect

    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. ); Doyle, E.J.; Rettig, C. ); 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.

  20. Studies of global energy confinement in TFTR supershots

    SciTech Connect

    Strachan, J.D.

    1993-08-01

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

  1. Millisecond burning of confined energetic materials during cookoff

    SciTech Connect

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

    1997-11-01

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

  2. Mobility in geometrically confined membranes

    PubMed Central

    Domanov, Yegor A.; Aimon, Sophie; Toombes, Gilman E. S.; Renner, Marianne; Quemeneur, Franois; Triller, Antoine; Turner, Matthew S.; Bassereau, Patricia

    2011-01-01

    Lipid and protein lateral mobility is essential for biological function. Our theoretical understanding of this mobility can be traced to the seminal work of Saffman and Delbrck, who predicted a logarithmic dependence of the protein diffusion coefficient (i) on the inverse of the size of the protein and (ii) on the membrane size for membranes of finite size [Saffman P, Delbrck M (1975) Proc Natl Acad Sci USA 72:31113113]. Although the experimental proof of the first prediction is a matter of debate, the second has not previously been thought to be experimentally accessible. Here, we construct just such a geometrically confined membrane by forming lipid bilayer nanotubes of controlled radii connected to giant liposomes. We followed the diffusion of individual molecules in the tubular membrane using single particle tracking of quantum dots coupled to lipids or voltage-gated potassium channels KvAP, while changing the membrane tube radius from approximately 250 to 10nm. We found that both lipid and protein diffusion was slower in tubular membranes with smaller radii. The protein diffusion coefficient decreased as much as 5-fold compared to diffusion on the effectively flat membrane of the giant liposomes. Both lipid and protein diffusion data are consistent with the predictions of a hydrodynamic theory that extends the work of Saffman and Delbrck to cylindrical geometries. This study therefore provides strong experimental support for the ubiquitous SaffmanDelbrck theory and elucidates the role of membrane geometry and size in regulating lateral diffusion. PMID:21768336

  3. Hydrodynamics of DNA confined in nanoslits and nanochannels

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  4. 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.

  5. Human enteric viruses in groundwater from a confined bedrock aquifer

    USGS Publications Warehouse

    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.

  6. Ohmic Confinement Studies in the Pegasus Toroidal Experiment

    NASA Astrophysics Data System (ADS)

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

    2011-10-01

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

  7. Reduced Edge Instability and Improved Confinement in the MST Reversed-Field Pinch

    SciTech Connect

    Chapman, B.E.; Anderson, J.K.; Biewer, T.M.; Brower, D.L.; Castillo, S.; Chattopadhyay, P.K.; Chiang, C.S.; Cragi, D.; Den Hartog, D.J.; Fiksel, G.; Fontana, P.W.; Forest, C.B.; Gerhardt, S.; Hansen, A.K.; Holly, D.; Jiang, Y.; Lanier, N.E.; Prager, S.C.; Reardon, J.C.; Sarff, J.S.

    2001-01-01

    Improved confinement has been achieved in the MST through control of the poloidal electric field, but it is now known that the improvement has been limited by bursts of an edge-resonant instability. Through refined poloidal electric field control, plus control of the toroidal electric field, we have suppressed these bursts. This has led to a total beta of 14% and an RFP-record estimated energy confinement time of 9 ms, a nine-fold increase over the standard value which for the first time substantially exceeds the confinement scaling that has characterized most reversed-field pinch plasmas.

  8. Human adaptation to isolated and confined environments

    NASA Technical Reports Server (NTRS)

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

    1987-01-01

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

  9. Human Adaptation to Isolated and Confined Environments

    NASA Technical Reports Server (NTRS)

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

    1987-01-01

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

  10. Spatially Confined Bloch Oscillations in Semiconductor Superlattices

    NASA Astrophysics Data System (ADS)

    Carretero, M.; lvaro, M.; Bonilla, L. L.

    2011-09-01

    Bloch oscillations are coherent oscillations of the position of electrons (and therefore also of the electric current) inside energy bands of a crystal under an applied constant electric field. Their frequency is proportional to the lattice constant and to the field and therefore can be tuned by an applied voltage. Damped Bloch oscillations have been observed by optical means in undoped semiconductor superlattices which are artificial crystal structures formed by growing a succession of equal periods comprising layers of at least two different semiconductors. We model Bloch oscillations in a doped superlattice by using Boltzmann-Poisson equations and derive hydrodynamic equations for the electron, current and energy densities. For a superlattice with long scattering times, we show that the damping of Bloch oscillations is so small that nonlinearities may compensate it and provide stable oscillations of the current and energy densities. In this case, numerical solutions show that there are stable Bloch oscillations spatially confined to part of the superlattice, thereby having inhomogeneous field, charge, current density and energy density profiles. These Bloch oscillations disappear as scattering times become sufficiently short.

  11. Simulation of spheromak evolution and energy confinement

    SciTech Connect

    Cohen, B.I.; Hooper, E.B.; Cohen, R.H.; Hill, D.N.; McLean, H.S.; Wood, R.D.; Woodruff, S.; Sovinec, C.R.; Cone, G.A.

    2005-05-15

    Simulation results are presented that illustrate the formation and decay of a spheromak plasma driven by a coaxial electrostatic plasma gun, and model the plasma energy confinement. The physics of magnetic reconnection during formation is also illuminated. The simulations are performed with the three-dimensional, time-dependent, resistive magnetohydrodynamic NIMROD code [C. R. Sovinec, A. H. Glasser, T. A. Gianakon, D. C. Barnes, R. A. Nebel, S. E. Kruger, D. D. Schnack, S. J. Plimpton, A. Tarditi, and M. S. Chu, J. Comput. Phys. 195, 355 (2004)]. The simulation results are compared to data from the Sustained Spheromak Physics Experiment (SSPX) [E. B. Hooper, L. D. Pearlstein, and R. H. Bulmer, Nucl. Fusion 39, 863 (1999)]. The simulation results are tracking SSPX with increasing fidelity (e.g., improved agreement with measured magnetic fields, fluctuation amplitudes, and electron temperature) as the simulation has been improved in its representations of the experimental geometry, the magnetic bias coils, and the detailed time dependence of the current source driving the plasma gun, and uses realistic parameters. The simulations confirm that controlling the magnetic fluctuations is influenced by the current drive history and by matching the gun current in sustainment approximately to the value corresponding to the eigenvalue in the flux-conserver for the parallel current in a force-free equilibrium.

  12. Simulation of Spheromak Evolution and Energy Confinement

    SciTech Connect

    Cohen, B; Hooper, E; Cohen, R; Hill, D; McLean, H; Wood, R; Woodruff, S

    2004-11-12

    Simulation results are presented that illustrate the formation and decay of a spheromak plasma driven by a coaxial electrostatic plasma gun, and that model the energy confinement of the plasma. The physics of magnetic reconnection during spheromak formation is also illuminated. The simulations are performed with the three-dimensional, time-dependent, resistive magnetohydrodynamic NIMROD code. The dimensional, simulation results are compared to data from the SSPX spheromak experiment at the Lawrence Livermore National Laboratory. The simulation results are tracking the experiment with increasing fidelity (e.g., improved agreement with measurements of the magnetic field, fluctuation amplitudes, and electron temperature) as the simulation has been improved in its representations of the geometry of the experiment (plasma gun and flux conserver), the magnetic bias coils, and the detailed time dependence of the current source driving the plasma gun, and uses realistic parameters. The simulations are providing a better understanding of the dominant physics in SSPX, including when the flux surfaces close and the mechanisms limiting the efficiency of electrostatic drive.

  13. Simulation of Spheromak Evolution and Energy Confinement

    SciTech Connect

    Cohen, B; Hooper, E; Cohen, R; Hill, D; McLean, H; Wood, R; Woodruff, S; Sovinec, C; Cone, G

    2004-11-09

    Simulation results are presented that illustrate the formation and decay of a spheromak plasma driven by a coaxial electrostatic plasma gun, and that model the energy confinement of the plasma. The physics of magnetic reconnection during spheromak formation is also illuminated. The simulations are performed with the three-dimensional, time-dependent, resistive magnetohydrodynamic NIMROD code. The simulation results are compared to data from the SSPX spheromak experiment at the Lawrence Livermore National Laboratory. The simulation results are tracking the experiment with increasing fidelity (e.g., improved agreement with measurements of the magnetic field, fluctuation amplitudes, and electron temperature) as the simulation has been improved in its representations of the geometry of the experiment (plasma gun and flux conserver), the magnetic bias coils, and the detailed time dependence of the current source driving the plasma gun, and uses realistic parameters. The simulations are providing a better understanding of the dominant physics in SSPX, including when the flux surfaces close and the mechanisms limiting the efficiency of electrostatic drive.

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

    NASA Astrophysics Data System (ADS)

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

    2014-09-01

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

  15. Probing Non-Gaussianity in Confined Diffusion of Nanoparticles.

    PubMed

    Xue, Chundong; Zheng, Xu; Chen, Kaikai; Tian, Yu; Hu, Guoqing

    2016-02-01

    Confined diffusion is ubiquitous in nature. Ever since the "anomalous yet Brownian" motion was observed, the non-Gaussianity in confined diffusion has been unveiled as an important issue. In this Letter, we experimentally investigate the characteristics and source of non-Gaussian behavior in confined diffusion of nanoparticles suspended in polymer solutions. A time-varied and size-dependent non-Gaussianity is reported based on the non-Gaussian parameter and displacement probability distribution, especially when the nanoparticle's size is smaller than the typical polymer mesh size. This non-Gaussianity does not vanish even at the long-time Brownian stage. By inspecting the displacement autocorrelation, we observe that the nanoparticle-structure interaction, indicated by the anticorrelation, is limited in the short-time stage and makes little contribution to the non-Gaussianity in the long-time stage. The main source of the non-Gaussianity can therefore be attributed to hopping diffusion that results in an exponential probability distribution with the large displacements, which may also explain certain processes dominated by rare events in the biological environment. PMID:26784864

  16. Review of Inertial Confinement Fusion

    NASA Astrophysics Data System (ADS)

    Haines, M. G.

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

  17. Carrier Spin Polarization in Quantum Confined System

    NASA Astrophysics Data System (ADS)

    Long, Gen

    In this dissertation, systematic studies of magneto-photoluminescence of manganese-doped lead salt (Mn doped lead sulfide and lead selenide) quantum dots and core/shell quantum dots will be presented. It was observed that large carrier spin polarization can be obtained in manganese doped IV-VI lead salt quantum dots upon excitation by circularly polarized light; and a clear dependence of spin polarization on the sizes of quantum dots and thickness of core/shell quantum dots was observed as well. The quantum dots in this study were synthesized by solution-phase chemical method. The sizes of the quantum dots could be controlled by the growth temperature (50 to 150) and growth time (1min to 24hr). The doping concentrations in the compounds Pb1-xMn xS (or Pb1-xMnxSe) ranging from x = 0 to 8% can be adjusted by varying synthesis conditions as well. Studies on size dependence (from 3 to 10 nm), temperature dependence (from 7K to 50K), magnetic field dependence (from 0 to 7T), and laser power dependence (from 1mW to 20mW) of photoluminescence intensities and peak positions were systematically carried out. The spin-polarization, which was directly calculated from magneto-luminescence measurements, was studied as a function of quantum dot sizes, temperatures and magnetic fields. It was observed that, depending on the sizes and growth conditions (growth temperature and time), the spin polarization, as large as 40% at 7K in a 7T magnetic field, could be tuned in magnitude. Core/shell structured quantum dots with Mn2+ ions doped in the inner core or outer shell were also studied. The spin polarization was observed in core/shell system to decrease as thickness of the shell increases. We believe the wave function overlap between carriers and dopants can be tuned by quantum confinement and therefore the magnitude of exchange interactions can be tuned via varying the sizes of quantum dots or the shell thickness of core/shell quantum dots. There are a couple of measurements that showed inversion of spin polarization but the reproducibility is low. Further studies are needed to verify the possibility of reversing the sign of spin polarization through quantum confinement, i.e., varying the sizes of quantum dots or the shell thickness of core/shell quantum dots.

  18. 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.

  19. Toroidal membrane vesicles in spherical confinement.

    PubMed

    Bouzar, Lila; Menas, Ferhat; Müller, Martin Michael

    2015-09-01

    We investigate the morphology of a toroidal fluid membrane vesicle confined inside a spherical container. The equilibrium shapes are assembled in a geometrical phase diagram as a function of scaled area and reduced volume of the membrane. For small area the vesicle can adopt its free form. When increasing the area, the membrane cannot avoid contact and touches the confining sphere along a circular contact line, which extends to a zone of contact for higher area. The elastic energies of the equilibrium shapes are compared to those of their confined counterparts of spherical topology to predict under which conditions a topology change is favored energetically. PMID:26465512

  20. Elastic scattering using an artificial confining potential.

    PubMed

    Mitroy, J; Zhang, J Y; Varga, K

    2008-09-19

    The discrete energies of a scattering Hamiltonian calculated under the influence of an artificial confining potential of almost arbitrary functional form can be used to determine its phase shifts. The method exploits the result that two short-range Hamiltonians having the same energy will have the same phase shifts upon removal of the confining potential. An initial verification is performed on a simple model problem. Then the stochastic variational method is used to determine the energies of the confined e(-)-He(2)S(e) system and thus determine the low energy phase shifts. PMID:18851369

  1. Toroidal membrane vesicles in spherical confinement

    NASA Astrophysics Data System (ADS)

    Bouzar, Lila; Menas, Ferhat; Mller, Martin Michael

    2015-09-01

    We investigate the morphology of a toroidal fluid membrane vesicle confined inside a spherical container. The equilibrium shapes are assembled in a geometrical phase diagram as a function of scaled area and reduced volume of the membrane. For small area the vesicle can adopt its free form. When increasing the area, the membrane cannot avoid contact and touches the confining sphere along a circular contact line, which extends to a zone of contact for higher area. The elastic energies of the equilibrium shapes are compared to those of their confined counterparts of spherical topology to predict under which conditions a topology change is favored energetically.

  2. Confinement of translated field-reversed configurations

    NASA Astrophysics Data System (ADS)

    Tuszewski, M.; Armstrong, W. T.; Chrien, R. E.; Klingner, P. L.; McKenna, K. F.; Rej, D. J.; Sherwood, E. G.; Siemon, R. E.

    1986-03-01

    The confinement properties of translating field-reversed configurations (FRC) in the FRX-C/T device [Phys. Fluids 29, (1986)] are analyzed and compared to previous data without translation and to available theory. Translation dynamics do not appear to appreciably modify the FRC confinement. Some empirical scaling laws with respect to various plasma parameters are extracted from the data. These are qualitatively similar to those obtained in the TRX-1 device [Phys. Fluids 28, 888 (1985)] without translation and with a different formation method. Translation with a static gas fill offers new opportunities such as improved particle confinement or refueling of the FRC particle inventory.

  3. Propagating confined states in phase dynamics

    NASA Technical Reports Server (NTRS)

    Brand, Helmut R.; Deissler, Robert J.

    1992-01-01

    Theoretical treatment is given to the possibility of the existence of propagating confined states in the nonlinear phase equation by generalizing stationary confined states. The nonlinear phase equation is set forth for the case of propagating patterns with long wavelengths and low-frequency modulation. A large range of parameter values is shown to exist for propagating confined states which have spatially localized regions which travel on a background with unique wavelengths. The theoretical phenomena are shown to correspond to such physical systems as spirals in Taylor instabilities, traveling waves in convective systems, and slot-convection phenomena for binary fluid mixtures.

  4. NMR investigation of gaseous SF6 confinement into EPDM rubber.

    PubMed

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

    2005-02-01

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

  5. Numerical Investigations On The Seismic Behaviour Of Confined Masonry Walls

    SciTech Connect

    Calderini, Chiara; Cattari, Serena; Lagomarsino, Sergio

    2008-07-08

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

  6. Numerical Investigations On The Seismic Behaviour Of Confined Masonry Walls

    NASA Astrophysics Data System (ADS)

    Calderini, Chiara; Cattari, Serena; Lagomarsino, Sergio

    2008-07-01

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

  7. Influence of confinement on polymer-electrolyte relaxational dynamics.

    SciTech Connect

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

    2004-01-01

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

  8. 915nm high-power broad area laser diodes with ultra-small optical confinement based on Asymmetric Decoupled Confinement Heterostructure (ADCH)

    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.

  9. Communication: Folding of glycosylated proteins under confinement

    NASA Astrophysics Data System (ADS)

    Shental-Bechor, Dalit; Levy, Yaakov

    2011-10-01

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

  10. 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.

  11. Model for melting of confined DNA

    NASA Astrophysics Data System (ADS)

    Werner, E.; Reiter-Schad, M.; Ambjrnsson, 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.

  12. Nutrient balance on Nebraska livestock confinement systems.

    PubMed

    Koelsch, R; Lesoing, G

    1999-01-01

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

  13. Vorticity confinement technique for drag prediction

    NASA Astrophysics Data System (ADS)

    Povitsky, Alex; Snyder, Troy

    2011-11-01

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

  14. Loop calculations in confined QCD.I

    NASA Astrophysics Data System (ADS)

    Baacke, Jrgen; Igarashi, Yuji; Kasperidus, Gerhard

    1983-06-01

    We present a method for calculating one loop corrections in QCD confined to a spherical cavity with bag boundary conditions. We use euclidean Greens functions separated into free space and boundary parts and use oldfashioned perturbation theory. As a first application we calculate that part of the quark self energy that gives rese to the confining mirror charge potential in the nonrelativistic approximation. We obtain a weaker potential for relativistic massive quarks. Some consequences are discussed.

  15. Quark propagators in confinement and deconfinement phases

    SciTech Connect

    Hamada, Masatoshi; Yahiro, Masanobu; Kouno, Hiroaki; Nakamura, Atsushi; Saito, Takuya

    2010-05-01

    We study quark propagators near the confinement/deconfinement phase transition temperature in quenched-lattice simulation of QCD. We find that there is no qualitative change for the quark propagators in both phases. In the confinement phase, those effective quark masses in units of the critical temperature behave as a constant as a function of the temperature, while above the critical temperature, the value of the effective quark mass drops to circa half value.

  16. Chiral symmetry, massive gluons and confinement

    SciTech Connect

    Natale, A. A.

    2013-03-25

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

  17. Programmed environment management of confined microsocieties

    NASA Technical Reports Server (NTRS)

    Emurian, Henry H.

    1988-01-01

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

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

    SciTech Connect

    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.

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

    SciTech Connect

    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.

  20. Heterogeneous dynamics of ionic liquids in confined films with varied film thickness.

    PubMed

    Wang, Yong-Lei; Lu, Zhong-Yuan; Laaksonen, Aatto

    2014-10-14

    Dynamical behavior and characteristics of 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]) ionic liquid (IL) in confined films with varied film thickness have been investigated using atomistic molecular dynamics simulations. Simulation results indicate that the dynamics of confined ionic groups in interfacial regions is highly heterogeneous and depends strongly on their relative layered positions in the confined IL film. The dynamics and relaxation times of the ionic groups in the bulk region of confined IL films are very similar to that in the corresponding pure bulk simulation. In contrast, the diffusion of the corresponding ionic groups slows down and can be characterized by slaved diffusion while the corresponding relaxation times increase remarkably as these ionic groups come closer to the neutral graphene surface. While at the IL-vacuum interface, the diffusion and relaxation of terminal carbon atoms of butyl chains of [BMIM] cations are much faster than in other layers of the confined IL film and in the bulk region of the simulation system without confinement, due to their librated motion in this interfacial region. The dynamical heterogeneity of the confined ionic groups is intrinsically related to microscopic ionic structures and the orientational preference of [BMIM][PF6] ion pairs in interfacial regions. PMID:25162673

  1. Neutral penetration in centrifugally confined plasmas

    SciTech Connect

    Ng, Sheung-wah; Hassam, A. B.

    2007-10-15

    Plasma-neutral interactions along the magnetic field are considered for a centrifugally confined plasma wherein a cross-field plasma rotation inhibits plasma escape along the magnetic field. Analytic and numerical solutions from a simple one-dimensional isothermal model are obtained. It is shown that for perfect recycling, the neutral density at the wall is exponentially smaller than the central plasma density for strong centrifugal confinement compared to the case of no confinement, for which the neutral wall density equals the central plasma density. The exponential factor is effectively exp(-M{sub s}{sup 2}/2), where M{sub s} is the sonic Mach number of the rotation speed. The effective neutral penetration depth along the field, of the same order as the cross-field penetration depth in the zero confinement limit, increases significantly in the strong confinement case. Estimates are given of plasma transverse momentum loss rates for centrifugally confined plasmas from plasma particle outfluxes and charge-exchange friction.

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

    PubMed

    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

  3. Confinement studies of neutral beam heated discharges in TFTR

    SciTech Connect

    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.

  4. Pellet-fueled, high-?, improved confinement RFP plasmas

    NASA Astrophysics Data System (ADS)

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

    2008-11-01

    Pellet fueling of improved confinement MST plasmas has resulted in a four-fold increase in the density, reaching 4x10^19 m-3, and a total beta of up to 26%. At high beta, the Mercier limit for interchange stability is exceeded, but there is as yet no experimental evidence of interchange modes. The linear stability threshold for pressure-driven tearing modes is also exceeded, and one does observe increased tearing mode amplitudes. At high density, the energy confinement time is still improved, but the degree of improvement is reduced. This may be due to the tearing modes, suggesting that pressure-driven tearing could ultimately limit the achievable beta in the RFP. MST's pellet injector has now been upgraded to accommodate pellets with roughly twice the particle inventory used to achieve the above results. Tests with these larger pellets are underway. Work supported by U.S.D.O.E.

  5. 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.

  6. Microscale Confinement features in microfluidic devices can affect biofilm

    SciTech Connect

    Kumar, Aloke; Karig, David K; Neethirajan, Suresh; Acharya, Rajesh K; Mukherjee, Partha P; Retterer, Scott T; Doktycz, Mitchel John

    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.

  7. Defect topologies in chiral liquid crystals confined to mesoscopic channels

    SciTech Connect

    Schlotthauer, Sergej Skutnik, Robert A.; Stieger, Tillmann; Schoen, Martin

    2015-05-21

    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.

  8. Confinement and power balance in the S-1 spheromak

    SciTech Connect

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

    1989-07-01

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

  9. Polarization beam smoothing for inertial confinement fusion

    SciTech Connect

    Rothenberg, Joshua E.

    2000-04-15

    For both direct and indirect drive approaches to inertial confinement fusion (ICF) it is imperative to obtain the best possible drive beam uniformity. The approach chosen for the National Ignition Facility uses a random-phase plate to generate a speckle pattern with a precisely controlled envelope on target. A number of temporal smoothing techniques can then be employed to utilize bandwidth to rapidly change the speckle pattern, and thus average out the small-scale speckle structure. One technique which generally can supplement other smoothing methods is polarization smoothing (PS): the illumination of the target with two distinct and orthogonally polarized speckle patterns. Since these two polarizations do not interfere, the intensity patterns add incoherently, and the rms nonuniformity can be reduced by a factor of ((sq root)2). A number of PS schemes are described and compared on the basis of the aggregate rms and the spatial spectrum of the focused illumination distribution. The ({radical}2) rms nonuniformity reduction of PS is present on an instantaneous basis and is, therefore, of particular interest for the suppression of laser plasma instabilities, which have a very rapid response time. When combining PS and temporal methods, such as smoothing by spectral dispersion (SSD), PS can reduce the rms of the temporally smoothed illumination by an additional factor of ({radical}2). However, it has generally been thought that in order to achieve this reduction of ({radical}2), the increased divergence of the beam from PS must exceed the divergence of SSD. It is also shown here that, over the time scales of interest to direct or indirect drive ICF, under some conditions PS can reduce the smoothed illumination rms by nearly ({radical}2) even when the PS divergence is much smaller than that of SSD. (c) 2000 American Institute of Physics.

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

    NASA Astrophysics Data System (ADS)

    Amitai, A.; Holcman, D.

    2013-06-01

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

  11. Surface-Activated Coupling Reactions Confined on a Surface.

    PubMed

    Dong, Lei; Liu, Pei Nian; Lin, Nian

    2015-10-20

    Chemical reactions may take place in a pure phase of gas or liquid or at the interface of two phases (gas-solid or liquid-solid). Recently, the emerging field of "surface-confined coupling reactions" has attracted intensive attention. In this process, reactants, intermediates, and products of a coupling reaction are adsorbed on a solid-vacuum or a solid-liquid interface. The solid surface restricts all reaction steps on the interface, in other words, the reaction takes place within a lower-dimensional, for example, two-dimensional, space. Surface atoms that are fixed in the surface and adatoms that move on the surface often activate the surface-confined coupling reactions. The synergy of surface morphology and activity allow some reactions that are inefficient or prohibited in the gas or liquid phase to proceed efficiently when the reactions are confined on a surface. Over the past decade, dozens of well-known "textbook" coupling reactions have been shown to proceed as surface-confined coupling reactions. In most cases, the surface-confined coupling reactions were discovered by trial and error, and the reaction pathways are largely unknown. It is thus highly desirable to unravel the mechanisms, mechanisms of surface activation in particular, of the surface-confined coupling reactions. Because the reactions take place on surfaces, advanced surface science techniques can be applied to study the surface-confined coupling reactions. Among them, scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS) are the two most extensively used experimental tools. The former resolves submolecular structures of individual reactants, intermediates, and products in real space, while the latter monitors the chemical states during the reactions in real time. Combination of the two methods provides unprecedented spatial and temporal information on the reaction pathways. The experimental findings are complemented by theoretical modeling. In particular, density-functional theory (DFT) transition-state calculations have been used to shed light on reaction mechanisms and to unravel the trends of different surface materials. In this Account, we discuss recent progress made in two widely studied surface-confined coupling reactions, aryl-aryl (Ullmann-type) coupling and alkyne-alkyne (Glaser-type) coupling, and focus on surface activation effects. Combined experimental and theoretical studies on the same reactions taking place on different metal surfaces have clearly demonstrated that different surfaces not only reduce the reaction barrier differently and render different reaction pathways but also control the morphology of the reaction products and, to some degree, select the reaction products. We end the Account with a list of questions to be addressed in the future. Satisfactorily answering these questions may lead to using the surface-confined coupling reactions to synthesize predefined products with high yield. PMID:26317241

  12. Circularly confined microswimmers exhibit multiple global patterns.

    PubMed

    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. PMID:25974581

  13. Stiffness and Confinement Ratios of SMA Wire Jackets for Confining Concrete

    NASA Astrophysics Data System (ADS)

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

    2014-07-01

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

  14. 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.

  15. Molecular simulation of chevrons in confined smectic liquid crystals

    NASA Astrophysics Data System (ADS)

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

    2003-08-01

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

  16. Transient temperature measurements of a plume in a confined space

    SciTech Connect

    Hsu, C.H.; Hsieh, C.F.; Teng, J.T.

    1995-12-31

    The objective of the present study is to measure the transient temperature profiles of a plume in a confined space and to develop an empirical formula relating heat transfer and buoyancy. The transient natural convective phenomenon, resulting from the buoyant effect, exists in confined spaces. This phenomenon is of practical importance in many fields, such as the formation process of material, cooling of electronic parts, design of solar collectors, cooling of fins, physics of space, fire plume in a compartment and movement of ocean current, etc. The present work is to study the transient natural convection phenomenon of a thermal plume. The plume is generated by locating a constant heat flux annular cylinder heater at the bottom of a confined cubic enclosure filled with water. The temperature profiles in the plume are measured and collected by six T-type thermocouples and a set of data acquisition system. Each test run lasts about 200 minutes and the measurement time step is 1 minute. The results indicate that the heat transfer mechanism in the plume is characterized by up-moving buoyancy-driven energy envelopes. Stratified temperature structure, which is caused by the retarding motion of the plume near the top surface, is also observed. An empirical correlation along local Nusselt number, Fourier number and modified Rayleigh number is obtained and written as Nu{sub x}/Ra{sub x}*{sup 1/4} = 0.00422Fo{sub L}{sup {minus}0.893}.

  17. Theory of Activated Relaxation in Nanoscale Confined Liquids

    NASA Astrophysics Data System (ADS)

    Mirigian, Stephen; Schweizer, Kenneth

    2014-03-01

    We extend the recently developed Elastically Cooperative Nonlinear Langevin Equation(ECNLE) theory of activated relaxation in supercooled liquids to treat the case of geometrically confined liquids. Generically, confinement of supercooled liquids leads to a speeding up of the dynamics(with a consequent depression of the glass transition temperature) extending on the order of tens of molecular diameters away from a free surface. At present, this behavior is not theoretically well understood. Our theory interprets the speed up in dynamics in terms of two coupled effects. First, a direct surface effect, extending two to three molecular diameters from a free surface, and related to a local rearrangement of molecules with a single cage. The second is a longer ranged ``confinement'' effect, extending tens of molecular diameters from a free surface and related to the long range elastic penalty necessary for a local rearrangement. The theory allows for the calculation of relaxation time and Tg profiles within a given geometry and first principles calculations of relevant length scales. Comparison to both dynamic and pseudo-thermodynamic measurements shows reasonable agreement to experiment with no adjustable parameters.

  18. COLLIMATION AND CONFINEMENT OF MAGNETIC JETS BY EXTERNAL MEDIA

    SciTech Connect

    Levinson, Amir; Begelman, Mitchell C. E-mail: mitch@jila.colorado.edu

    2013-02-20

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

  19. Emerging Functionality in Complex Oxides Driven by Spatial Confinement

    NASA Astrophysics Data System (ADS)

    Plummer, Ward

    2010-03-01

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

  20. Confinement and water quality-induced stress in largemouth bass

    SciTech Connect

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

    1984-11-01

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

  1. Physics of Improved Core Confinement with Lithium Injection in TFTR

    NASA Astrophysics Data System (ADS)

    Ernst, D. R.; TFTR Team

    2000-10-01

    Lithium pellet injection and laser ablation of lithium produced dramatically improved ion thermal, toroidal momentum, and particle confinement in very high temperature TFTR supershot plasmas. Attained continously through a gradual reduction of the edge particle influx from the plasma facing surfaces, the supershot regime is characterized by an energy confinement time strongly and inversely correlated with edge particle influx. Lithium injection reduces both the hydrogenic and carbon influxes, with improved confinement persisting over successive disharges. Core ion thermal diffusion nearly vanishes, leaving outward convection dominant, often producing flat-topped temperature profiles. These effects are reproduced by a model describing toroidal ITG turbulence, suppressed by self-consistent neoclassical E B shear, which plays a strongly self-reinforcing role [D. R. Ernst, et al., Phys. Rev. Lett. 81 (1998) 2454]. Because the E B shearing rate increases quadratically with density peakedness n_e0/< ne >, a strong sensitivity to edge conditions arises. Combined with strong central fueling, reductions in edge density lead to increases in ion temperature through coupling of particle and energy transport by toroidal ITG stability and E B shear. Simulations of Li pellet recycling scans with constant edge temperature are presented.

  2. Single-molecule microscopy using tunable nanoscale confinement

    NASA Astrophysics Data System (ADS)

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

    2013-09-01

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

  3. Global energy confinement studies on the Pegasus Toroidal Experiment

    NASA Astrophysics Data System (ADS)

    Battaglia, D. J.; Frost, M. J.; Garstka, G. D.; Sontag, A. C.; Unterberg, E. A.; Winz, G. R.

    2007-11-01

    Recent studies have shown that low-recycling walls significantly enhance L-mode energy confinement [1]. Discharges on Pegasus suggest a low-recycling regime is obtained using titanium gettering and cryogenic pumping. When the external gas supply is terminated during an established discharge, tangential H? and visible light signals drop to 5% of their initial levels within 5 ms. Wall recycling is measured using the density decay rate, and its effect on particle and energy confinement on Pegasus is explored. Initial global energy confinement times of ?E = 2 -- 4 ms were calculated for IP 0.15 MA L-mode discharges. Scans of plasma current and line-averaged density are used to benchmark ?E measurements against empirical L-mode scaling laws. These initial ?E measurements indicate the H-mode power threshold as given by the ITPA04 scaling [2] can be exceeded in diverted Ohmic discharges on Pegasus. [1] Majeski, R. et al. Phy. Rev. Lett. 97 2006 075002 [2] Takizuka, T. et al. Plasma Phys. Control. Fusion 46 2004 A227

  4. The glass transition and fragility of supercooled confined water

    NASA Astrophysics Data System (ADS)

    Swenson, J.

    2004-11-01

    In this paper we discuss the glass transition and fragility of supercooled confined water. We have used vermiculite clay, a molecular sieve and purple membrane as host materials in order to obtain confinements that are severe enough to avoid crystallization of the water, even in the (for bulk water) experimentally inaccessible temperature range 150-235 K. The clay and membrane have a 2D structure with a water layer thickness of 6 and 9 , respectively, whereas the molecular sieve contains cylindrical pores with a diameter of 10 . We show that one dielectric relaxation process, observed in the deeply supercooled regime, is very similar for the three investigated systems, as well as for water confined in other types of host materials, suggesting that it is relevant, although not identical, also for bulk water. At the lowest temperatures this process follows an Arrhenius temperature dependence with a relaxation time of 100 s at a temperature of approximately 130 K. However, an interesting crossover to a non-Arrhenius behaviour seems to occur at T>185 K. We discuss the possible origins of the observed dielectric relaxation process and its relation to the present controversy regarding the glass-transition temperature of hyperquenched water, as well as a proposed fragile to strong transition of supercooled water.

  5. Silver nanoparticles confined in carbon nanotubes: on the understanding of the confinement effect and promotional catalysis for the selective hydrogenation of dimethyl oxalate

    NASA Astrophysics Data System (ADS)

    Zheng, Jianwei; Duan, Xinping; Lin, Haiqiang; Gu, Zhengqiang; Fang, Huihuang; Li, Jianhui; Yuan, Youzhu

    2016-03-01

    A confined Ag nanomaterial in the channels of herringbone multi-walled carbon nanotubes (Ag-in/hCNT) was effectively prepared. The space restriction induces morphological changes of Ag nanoparticles into rough nanowires with an estimated aspect ratio of 60 : 8 (nm/nm). Dihydrogen activation is enhanced through the vacancy-enriched wire-like Ag nanocatalyst, as well as the confinement effect. The grain boundaries of Ag and rolled-up graphene layers of CNTs are speculated to play vital roles in the diffusion of activated hydrogen species. The Ag-in/hCNT catalyst exhibits an activity that is three times higher than that of Ag nanoparticles located on the CNT exterior walls in DMO hydrogenation. This finding may insinuate that interplanar spaces provide available access to the external surface of CNTs. Designed experiments further confirm the importance of herringbone CNTs with higher reaction rate than parallel CNTs, and confined Ag produces considerably more activated hydrogen species, thereby benefiting the reduction of surface copper nanoparticles or DMO molecules during hydrogenation. This paper presents a study of the effective utilization of hydrogen over herringbone CNT confined Ag and an understanding of the confinement and promotional catalytic effects.A confined Ag nanomaterial in the channels of herringbone multi-walled carbon nanotubes (Ag-in/hCNT) was effectively prepared. The space restriction induces morphological changes of Ag nanoparticles into rough nanowires with an estimated aspect ratio of 60 : 8 (nm/nm). Dihydrogen activation is enhanced through the vacancy-enriched wire-like Ag nanocatalyst, as well as the confinement effect. The grain boundaries of Ag and rolled-up graphene layers of CNTs are speculated to play vital roles in the diffusion of activated hydrogen species. The Ag-in/hCNT catalyst exhibits an activity that is three times higher than that of Ag nanoparticles located on the CNT exterior walls in DMO hydrogenation. This finding may insinuate that interplanar spaces provide available access to the external surface of CNTs. Designed experiments further confirm the importance of herringbone CNTs with higher reaction rate than parallel CNTs, and confined Ag produces considerably more activated hydrogen species, thereby benefiting the reduction of surface copper nanoparticles or DMO molecules during hydrogenation. This paper presents a study of the effective utilization of hydrogen over herringbone CNT confined Ag and an understanding of the confinement and promotional catalytic effects. Electronic supplementary information (ESI) available: Details of the XRD patterns of Ag on different carriers. See DOI: 10.1039/c5nr08651e

  6. Progress in toroidal confinement and fusion research

    SciTech Connect

    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.

  7. Properties of Water Confined in Ionic Liquids

    PubMed Central

    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

  8. Cylindrical fabric-confined soil structures

    NASA Astrophysics Data System (ADS)

    Harrison, Richard A.

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

  9. Neutron Assay System for Confinement Vessel Disposition

    SciTech Connect

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

    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.

  10. TOPICAL REVIEW: Biopolymer organization upon confinement

    NASA Astrophysics Data System (ADS)

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

    2010-07-01

    Biopolymers in vivo are typically subject to spatial restraints, either as a result of molecular crowding in the cellular medium or of direct spatial confinement. DNA in living organisms provides a prototypical example of a confined biopolymer. Confinement prompts a number of biophysics questions. For instance, how can the high level of packing be compatible with the necessity to access and process the genomic material? What mechanisms can be adopted in vivo to avoid the excessive geometrical and topological entanglement of dense phases of biopolymers? These and other fundamental questions have been addressed in recent years by both experimental and theoretical means. A review of the results, particularly of those obtained by numerical studies, is presented here. The review is mostly devoted to DNA packaging inside bacteriophages, which is the best studied example both experimentally and theoretically. Recent selected biophysical studies of the bacterial genome organization and of chromosome segregation in eukaryotes are also covered.

  11. Energy Confinement of both Ohmic and LHW Plasma on EAST

    NASA Astrophysics Data System (ADS)

    Yang, Yao; Gao, Xiang; EAST Team

    2011-06-01

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

  12. Neutral Beam Ion Confinement in NSTX

    SciTech Connect

    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.

  13. Entropy, confinement, and chiral symmetry breaking

    SciTech Connect

    Cornwall, John M.

    2011-04-01

    This paper studies the way in which confinement leads to chiral symmetry breaking (CSB) through a gap equation. We argue that a combination of entropic effects, related to fluctuations of Wilson loops with massless constituents, and an Abelian gauge invariance of the confinement action as expressed in terms of the usual confining effective propagator 8{pi}K{sub F{delta}{mu}{nu}}/k{sup 4}, in effect removes infrared singularities coming from use of this propagator in a standard gap equation (K{sub F} is the string tension). Beginning from an Abelian gauge-invariant description of CSB that differs from this standard gap equation, we show how to extract a corresponding gap equation that incorporates both entropic effects and Abelian gauge invariance by replacement of the confining propagator with 8{pi}K{sub F{delta}{mu}{nu}}/(k{sup 2}+m{sup 2}){sup 2}. Here the finite mass m turns out to be {approx_equal}M(0)[M(p{sup 2}) is the running quark mass], based on an extension of an old calculation of the author. This massive propagator gives semiquantitatively two critical properties of confinement: (1) a negative contribution to the confining potential coming from entropy; (2) an infrared cutoff required by Abelian gauge invariance. Entropic effects lead to a qq condensate and contribute a negative term {approx}-K{sub F}/M(0), essential for a massless pion, to the pion Hamiltonian. The resulting gap equation leads to M{sup 2}(0){approx_equal}K{sub F}/{pi}. We argue that one-gluon exchange is not strong enough in the IR to drive quark CSB, but in any case is necessary to get the correct renormalization-group ultraviolet behavior. We find the standard renormalization-group result with the improvement that the prefactor (related to ) can be calculated from the confining solution. Finally, we briefly point out the Minkowski-space virtues of using a principal-part propagator to describe confinement.

  14. Experimental Achievements on Plasma Confinement and Turbulence

    SciTech Connect

    Fujisawa, A.

    2009-02-19

    This article presents a brief review of the experimental studies on turbulence and resultant transport in toroidal plasmas. The article focuses on two topics, physics of transport barrier and the role of mesoscale structure on plasma confinement, i.e. zonal flows. The two topics show the important roles of the mutual interactions between sheared flows, zonal flows and drift waves for plasma turbulence and transport. The findings can lead us to further generalized concept of the disparate scale interactions which could give a fundamental understanding of the plasma confinement from the first principle.

  15. Inertial-confinement-fusion targets

    SciTech Connect

    Hendricks, C.D.

    1982-08-10

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

  16. Phase Transformations in Confined Nanosystems

    SciTech Connect

    Shield, Jeffrey E.; Belashchenko, Kirill

    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.

  17. Spinal cord compression following traditional confinement massage.

    PubMed

    Sahathevan, R; Tan, H J; Abdullah, Suhail; Shahizon, A M M; Hamidon, B B; Raymond, A A

    2011-12-01

    We describe a case of tetraparesis in a 33-year-old woman following neck manipulation performed by a traditional confinement mid-wife. An MRI of the cervical spine revealed a fracture of the second cervical vertebra with atlanto-axial subluxation that resulted in cord compression. PMID:22390109

  18. Analysis of thermally-degrading, confined HMX

    SciTech Connect

    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.

  19. Clusters of polyhedra in spherical confinement.

    PubMed

    Teich, Erin G; van Anders, Greg; Klotsa, Daphne; Dshemuchadse, Julia; Glotzer, Sharon C

    2016-02-01

    Dense particle packing in a confining volume remains a rich, largely unexplored problem, despite applications in blood clotting, plasmonics, industrial packaging and transport, colloidal molecule design, and information storage. Here, we report densest found clusters of the Platonic solids in spherical confinement, for up to [Formula: see text] constituent polyhedral particles. We examine the interplay between anisotropic particle shape and isotropic 3D confinement. Densest clusters exhibit a wide variety of symmetry point groups and form in up to three layers at higher N. For many N values, icosahedra and dodecahedra form clusters that resemble sphere clusters. These common structures are layers of optimal spherical codes in most cases, a surprising fact given the significant faceting of the icosahedron and dodecahedron. We also investigate cluster density as a function of N for each particle shape. We find that, in contrast to what happens in bulk, polyhedra often pack less densely than spheres. We also find especially dense clusters at so-called magic numbers of constituent particles. Our results showcase the structural diversity and experimental utility of families of solutions to the packing in confinement problem. PMID:26811458

  20. Nuclear diagnostics for inertial confinement fusion implosions

    SciTech Connect

    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.

  1. Crystallization of carbon tetrachloride in confined geometries.

    PubMed

    Meziane, Adil; Grolier, Jean-Pierre E; Baba, Mohamed; Nedelec, Jean-Marie

    2007-01-01

    The thermal behaviour of carbon tetrachloride confined in silica gels of different porosities was studied by differential scanning calorimetry. Both the melting point and the low temperature phase transition were measured and found to be inextricably dependant on the degree of confinement. The amount of solvent was varied through two sets of experiments, sequential addition and original progressive evaporation allowing the measurement of DSC signals for the various transitions as a function of the amount of CCl4. These experiments allowed the determination of the transition enthalpies in the confined state, which in turn allowed the determination of the exact quantities of solvent undergoing these transitions. A clear correlation was found between the amounts of solvent (both free and confined) undergoing the two transitions, demonstrating that the formation of the adsorbed layer t does not interfere with the second transition. The thickness of this layer and the porous volumes of the two silica samples were measured and found to be in very close agreement with the values determined by gas sorption. PMID:17955822

  2. Hohlraum manufacture for inertial confinement fusion

    SciTech Connect

    Foreman, L.R.; Gobby, P.; Bartos, J.

    1994-07-01

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

  3. National Ignition Facility for Inertial Confinement Fusion

    SciTech Connect

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

    1997-10-08

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

  4. Degenerate crystals from colloidal dimers under confinement.

    PubMed

    Muangnapoh, Kullachate; Avendao, 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

  5. Somersault of Paramecium in extremely confined environments

    PubMed Central

    Jana, Saikat; Eddins, Aja; Spoon, Corrie; Jung, Sunghwan

    2015-01-01

    We investigate various swimming modes of Paramecium in geometric confinements and a non-swimming self-bending behavior like a somersault, which is quite different from the previously reported behaviors. We observe that Paramecia execute directional sinusoidal trajectories in thick fluid films, whereas Paramecia meander around a localized region and execute frequent turns due to collisions with adjacent walls in thin fluid films. When Paramecia are further constrained in rectangular channels narrower than the length of the cell body, a fraction of meandering Paramecia buckle their body by pushing on the channel walls. The bucking (self-bending) of the cell body allows the Paramecium to reorient its anterior end and explore a completely new direction in extremely confined spaces. Using force deflection method, we quantify the Youngs modulus of the cell and estimate the swimming and bending powers exerted by Paramecium. The analysis shows that Paramecia can utilize a fraction of its swimming power to execute the self-bending maneuver within the confined channel and no extra power may be required for this new kind of self-bending behavior. This investigation sheds light on how micro-organisms can use the flexibility of the body to actively navigate within confined spaces. PMID:26286234

  6. Disproportionate Minority Confinement (DMC). A Special Report.

    ERIC Educational Resources Information Center

    Bumbarger, Brian, Ed.

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

  7. Energy confinement and profile consistency in TFTR

    SciTech Connect

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

    1987-04-01

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

  8. Somersault of Paramecium in extremely confined environments

    NASA Astrophysics Data System (ADS)

    Jana, Saikat; Eddins, Aja; Spoon, Corrie; Jung, Sunghwan

    2015-08-01

    We investigate various swimming modes of Paramecium in geometric confinements and a non-swimming self-bending behavior like a somersault, which is quite different from the previously reported behaviors. We observe that Paramecia execute directional sinusoidal trajectories in thick fluid films, whereas Paramecia meander around a localized region and execute frequent turns due to collisions with adjacent walls in thin fluid films. When Paramecia are further constrained in rectangular channels narrower than the length of the cell body, a fraction of meandering Paramecia buckle their body by pushing on the channel walls. The bucking (self-bending) of the cell body allows the Paramecium to reorient its anterior end and explore a completely new direction in extremely confined spaces. Using force deflection method, we quantify the Youngs modulus of the cell and estimate the swimming and bending powers exerted by Paramecium. The analysis shows that Paramecia can utilize a fraction of its swimming power to execute the self-bending maneuver within the confined channel and no extra power may be required for this new kind of self-bending behavior. This investigation sheds light on how micro-organisms can use the flexibility of the body to actively navigate within confined spaces.

  9. Somersault of Paramecium in extremely confined environments.

    PubMed

    Jana, Saikat; Eddins, Aja; Spoon, Corrie; Jung, Sunghwan

    2015-01-01

    We investigate various swimming modes of Paramecium in geometric confinements and a non-swimming self-bending behavior like a somersault, which is quite different from the previously reported behaviors. We observe that Paramecia execute directional sinusoidal trajectories in thick fluid films, whereas Paramecia meander around a localized region and execute frequent turns due to collisions with adjacent walls in thin fluid films. When Paramecia are further constrained in rectangular channels narrower than the length of the cell body, a fraction of meandering Paramecia buckle their body by pushing on the channel walls. The bucking (self-bending) of the cell body allows the Paramecium to reorient its anterior end and explore a completely new direction in extremely confined spaces. Using force deflection method, we quantify the Young's modulus of the cell and estimate the swimming and bending powers exerted by Paramecium. The analysis shows that Paramecia can utilize a fraction of its swimming power to execute the self-bending maneuver within the confined channel and no extra power may be required for this new kind of self-bending behavior. This investigation sheds light on how micro-organisms can use the flexibility of the body to actively navigate within confined spaces. PMID:26286234

  10. Torque-Wrench Adapter For Confined Spaces

    NASA Technical Reports Server (NTRS)

    Littlefield, Alan

    1993-01-01

    Adapter for torque wrench tightens nuts in confined spaces. Allows full rotation of nuts with minimum clearance of wrench. Adapter, spanner-type attachment that fits on end of standard torque wrench. Pair of dowel pins centers and locks wrench onto nut. Used to apply torque of 40 lb-in, also withstands torques up to 100 lb-ft.

  11. Confinement property in SU(3) gauge theory

    SciTech Connect

    Zayakin, A. V.; Rafelski, J.

    2009-08-01

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

  12. Wellhead protection in confined, semi-confined, fractured and karst aquifer settings

    SciTech Connect

    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.

  13. KrF lasers for inertial confinement fusion

    SciTech Connect

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

    1989-01-01

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

  14. Magnetospheric Vortex Formation: Self-Organized Confinement of Charged Particles

    NASA Astrophysics Data System (ADS)

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

    2010-06-01

    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.

  15. Anisotropic confinement effects in a two-dimensional plasma crystal

    NASA Astrophysics Data System (ADS)

    Laut, I.; Zhdanov, S. K.; Rth, C.; Thomas, H. M.; Morfill, G. E.

    2016-01-01

    The spectral asymmetry of the wave-energy distribution of dust particles during mode-coupling-induced melting, observed for the first time in plasma crystals by Coudel et al. [Phys. Rev. E 89, 053108 (2014), 10.1103/PhysRevE.89.053108], is studied theoretically and by molecular-dynamics simulations. It is shown that an anisotropy of the well confining the microparticles selects the directions of preferred particle motion. The observed differences in intensity of waves of opposed directions are explained by a nonvanishing phonon flux. Anisotropic phonon scattering by defects and Umklapp scattering are proposed as possible reasons for the mean phonon flux.

  16. Multibeam Stimulated Raman Scattering in Inertial Confinement Fusion Conditions

    NASA Astrophysics Data System (ADS)

    Michel, P.; Divol, L.; Dewald, E. L.; Milovich, J. L.; Hohenberger, M.; Jones, O. S.; Hopkins, L. Berzak; Berger, R. L.; Kruer, W. L.; Moody, J. D.

    2015-07-01

    Stimulated Raman scattering from multiple laser beams arranged in a cone sharing a common daughter wave is investigated for inertial confinement fusion (ICF) conditions in a inhomogeneous plasma. It is found that the shared electron plasma wave (EPW) process, where the lasers collectively drive the same EPW, can lead to an absolute instability when the electron density reaches a matching condition dependent on the cone angle of the laser beams. This mechanism could explain recent experimental observations of hot electrons at early times in ICF experiments, at densities well below quarter critical when two plasmon decay is not expected to occur.

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

    PubMed

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

    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. PMID:20867249

  18. Extreme optical confinement in a slotted photonic crystal waveguide

    SciTech Connect

    Caër, Charles; Le Roux, Xavier; Cassan, Eric; Combrié, Sylvain De Rossi, Alfredo

    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 μm{sup 2}. This is nearly 10 times below the diffraction limit at λ = 1.5 μm, and it enables an effective interaction with a very small volume of functionalized matter.

  19. High-performance inertial confinement fusion target implosions on OMEGA

    SciTech Connect

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

    2011-04-18

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

  20. Multibeam Stimulated Raman Scattering in Inertial Confinement Fusion Conditions.

    PubMed

    Michel, P; Divol, L; Dewald, E L; Milovich, J L; Hohenberger, M; Jones, O S; Hopkins, L Berzak; Berger, R L; Kruer, W L; Moody, J D

    2015-07-31

    Stimulated Raman scattering from multiple laser beams arranged in a cone sharing a common daughter wave is investigated for inertial confinement fusion (ICF) conditions in a inhomogeneous plasma. It is found that the shared electron plasma wave (EPW) process, where the lasers collectively drive the same EPW, can lead to an absolute instability when the electron density reaches a matching condition dependent on the cone angle of the laser beams. This mechanism could explain recent experimental observations of hot electrons at early times in ICF experiments, at densities well below quarter critical when two plasmon decay is not expected to occur. PMID:26274426

  1. Magnetospheric Vortex Formation: Self-Organized Confinement of Charged Particles

    SciTech Connect

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

    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.

  2. 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.

  3. Monopoles and confinement in lattice gauge theory

    SciTech Connect

    Singh, V.

    1992-01-01

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

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

    SciTech Connect

    Tsai, Jung-Hui

    2015-02-09

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

  5. Computational Support for Alternative Confinement Concepts Basic Plasma Science

    SciTech Connect

    Dalton D. Schnack

    2002-12-09

    This is the final report for contract DE-FG03-99ER54528, ''Computational Support for Alternative Confinement Concepts''. Progress was made in the following areas of investigation: (1) Extensive studies of the confinement properties of conventional Reversed-field Pinch (RFP) configurations (i.e., without current profile control) were performed in collaboration with the Royal Institute of Technology (KTH) in Stockholm, Sweden. These studies were carried out using the full 3-dimensional, finite-{beta}, resistive MHD model in the DEBS code, including ohmic heating and anisotropic heat conduction, and thus for the first time included the self-consistent effects of the dynamo magnetic fluctuations on the confinement properties of the RFP. By using multi-variant regression analysis of these results, scaling laws for various properties characterizing the conventional RFP were obtained. In particular, it was found that the, for constant ratio of I/N (where I is the current and N = na{sup 2} is the line density), and over a range of Lundquist numbers S that approaches 10{sup 6}, the fluctuations scale as {delta}B/B {approx} S{sup -0.14}, the temperature scales as T {approx} I{sup 0.56}, the poloidal beta scales as {beta}{sub {theta}} {approx} I{sup -0.4}, and the energy confinement time scales as {tau}{sub E} {approx} I{sup 0.34}. The degradation of poloidal beta with current is a result of the weak scaling of the fluctuation level with the Lundquist number, and leads to the unfavorable scaling laws for temperature and energy confinement time. These results compare reasonably well with experimental data, and emphasize the need for external control of the dynamo fluctuations in the RFP. (2) Studies of feedback stabilization of resistive wall modes in the RFP were performed with the DEBS code in collaboration with the CNR/RFX group in Padua, Italy. The ideal growth rates are ''passively'' reduced by the presence of a resistive wall within the radius for perfectly conducting wall stabilization of these modes. In this work we consider cases with up to two resistive walls. Moreover the feedback system is assumed to react to any given Fourier harmonic with an ideal response, in the sense that no spurious harmonics are generated. Successful feedback schemes are shown to be possible. However, a careful choice of the gains, along with the simultaneous feedback on at least 4 or 5 modes, is found to be necessary. (3) Studies of a stable rampdown operating regime for the RFP were performed in collaboration with Los Alamos National Laboratory and the University of Wisconsin. It was found that completely stable mean profiles can be obtained by properly tailoring the decaying time dependence of the toroidal current and magnetic flux. Deviations from optimal decay rates were shown to lead to single helicity (SH) and quasi-single helicity (QSH) states. In all cases the prospects for improved confinement properties were obtained. These results may account for the experimental observation of QSH states when the toroidal current is allowed to decay.

  6. Confinement matrices for low- and intermediate-level radioactive waste

    NASA Astrophysics Data System (ADS)

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

    2012-02-01

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

  7. Glass-like dynamics in confined and congested ant traffic.

    PubMed

    Gravish, Nick; Gold, Gregory; Zangwill, Andrew; Goodisman, Michael A D; Goldman, Daniel I

    2015-09-01

    The collective movement of animal groups often occurs in confined spaces. As animal groups are challenged to move at high density, their mobility dynamics may resemble the flow of densely packed non-living soft materials such as colloids, grains, or polymers. However, unlike inert soft-materials, self-propelled collective living systems often display social interactions whose influence on collective mobility are only now being explored. In this paper, we study the mobility of bi-directional traffic flow in a social insect (the fire ant Solenopsis invicta) as we vary the diameter of confining foraging tunnels. In all tunnel diameters, we observe the emergence of spatially heterogeneous regions of fast and slow traffic that are induced through two phenomena: physical obstruction, arising from the inability of individual ants to interpenetrate, and time-delay resulting from social interaction in which ants stop to briefly antennate. Density correlation functions reveal that the relaxation dynamics of high density traffic fluctuations scale linearly with fluctuation size and are sensitive to tunnel diameter. We separate the roles of physical obstruction and social interactions in traffic flow using cellular automata based simulation. Social interaction between ants is modeled as a dwell time (Tint) over which interacting ants remain stationary in the tunnel. Investigation over a range of densities and Tint reveals that the slowing dynamics of collective motion in social living systems are consistent with dynamics near a fragile glass transition in inert soft-matter systems. In particular, flow is relatively insensitive to density until a critical density is reached. As social interaction affinity is increased (increasing Tint) traffic dynamics change and resemble a strong glass transition. Thus, social interactions play an important role in the mobility of collective living systems at high density. Our experiments and model demonstrate that the concepts of soft-matter physics aid understanding of the mobility of collective living systems, and motivate further inquiry into the dynamics of densely confined social living systems. PMID:26106969

  8. 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-Prot 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.

  9. Silver nanoparticles confined in carbon nanotubes: on the understanding of the confinement effect and promotional catalysis for the selective hydrogenation of dimethyl oxalate.

    PubMed

    Zheng, Jianwei; Duan, Xinping; Lin, Haiqiang; Gu, Zhengqiang; Fang, Huihuang; Li, Jianhui; Yuan, Youzhu

    2016-03-10

    A confined Ag nanomaterial in the channels of herringbone multi-walled carbon nanotubes (Ag-in/hCNT) was effectively prepared. The space restriction induces morphological changes of Ag nanoparticles into rough nanowires with an estimated aspect ratio of 60 : 8 (nm/nm). Dihydrogen activation is enhanced through the vacancy-enriched wire-like Ag nanocatalyst, as well as the confinement effect. The grain boundaries of Ag and rolled-up graphene layers of CNTs are speculated to play vital roles in the diffusion of activated hydrogen species. The Ag-in/hCNT catalyst exhibits an activity that is three times higher than that of Ag nanoparticles located on the CNT exterior walls in DMO hydrogenation. This finding may insinuate that interplanar spaces provide available access to the external surface of CNTs. Designed experiments further confirm the importance of herringbone CNTs with higher reaction rate than parallel CNTs, and confined Ag produces considerably more activated hydrogen species, thereby benefiting the reduction of surface copper nanoparticles or DMO molecules during hydrogenation. This paper presents a study of the effective utilization of hydrogen over herringbone CNT confined Ag and an understanding of the confinement and promotional catalytic effects. PMID:26924186

  10. The Evaporation Regime in a Confined Flare

    NASA Astrophysics Data System (ADS)

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

    2006-12-01

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

  11. Confinement induced binding of noble gas atoms

    SciTech Connect

    Khatua, Munmun; Pan, Sudip; Chattaraj, Pratim K.

    2014-04-28

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

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

    NASA Astrophysics Data System (ADS)

    McMahon, P. B.

    2010-12-01

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

  13. Temporary confinement of loose-housed hyperprolific sows reduces piglet mortality.

    PubMed

    Hales, J; Moustsen, V A; Nielsen, M B F; Hansen, C F

    2015-08-01

    The objective of this study was to investigate piglet mortality in a commercial setting where sows were accommodated in a loose-housed system with an option to confine the sow for a few days around farrowing and during early lactation. The study was conducted in a Danish piggery where records were obtained from 2,139 farrowings. Sows were randomly allocated to 1 of 3 treatments: loose-loose (LL), loose-confined (LC), and confined-confined (CC). In LL, sows were loose housed from the time they entered the farrowing pens to weaning. In LC, sows were loose housed until farrowing was finished and then confined to d 4 after farrowing. In CC, sows were confined at d 114 of gestation to d 4 after farrowing. All sows were loose housed from d 5 to weaning. Total piglet mortality was analyzed at batch level to include piglets fostered by nurse sows and at sow level to analyze the effects of confinement during different time periods. Total piglet mortality was greater in LL (26.0%) and LC (25.4%) compared with CC (22.1%; < 0.001). The proportion of stillborn piglets was not different between treatments ( = 0.21) but a larger proportion was crushed in LL (10.7%) compared with LC (9.7%; = 0.03), which again was greater than CC (7.8%; < 0.001). Piglet mortality before equalization was lower in CC (3.7%) than in LL (7.5%) and LC (7.0%; < 0.001). Confinement reduced mortality from litter equalization to d 4 (7.6% for LL vs. 6.7% for LC; = 0.01) but more so in CC (5.6%) than in LC ( < 0.001). From d 4 to weaning, LL had lower mortality (5.6%) than LC (6.9%) and CC (6.6%; = 0.01). A larger proportion of sows in CC were classified as "low mortality" compared with LL and LC both before ( < 0.001) and after ( = 0.002) litter equalization. The results in this study emphasize that the period of time from the birth of the first piglet to litter equalization is important in relation to piglet mortality. The results also suggest that confinement for 4 d after farrowing can reduce mortality in this specific period, but only confinement from d 114 of gestation to d 4 after farrowing reduced total piglet mortality. PMID:26440187

  14. Confined disordered strictly jammed binary sphere packings

    NASA Astrophysics Data System (ADS)

    Chen, D.; Torquato, S.

    2015-12-01

    Disordered jammed packings under confinement have received considerably less attention than their bulk counterparts and yet arise in a variety of practical situations. In this work, we study binary sphere packings that are confined between two parallel hard planes and generalize the Torquato-Jiao (TJ) sequential linear programming algorithm [Phys. Rev. E 82, 061302 (2010), 10.1103/PhysRevE.82.061302] to obtain putative maximally random jammed (MRJ) packings that are exactly isostatic with high fidelity over a large range of plane separation distances H , small to large sphere radius ratio α , and small sphere relative concentration x . We find that packing characteristics can be substantially different from their bulk analogs, which is due to what we term "confinement frustration." Rattlers in confined packings are generally more prevalent than those in their bulk counterparts. We observe that packing fraction, rattler fraction, and degree of disorder of MRJ packings generally increase with H , though exceptions exist. Discontinuities in the packing characteristics as H varies in the vicinity of certain values of H are due to associated discontinuous transitions between different jammed states. When the plane separation distance is on the order of two large-sphere diameters or less, the packings exhibit salient two-dimensional features; when the plane separation distance exceeds about 30 large-sphere diameters, the packings approach three-dimensional bulk packings. As the size contrast increases (as α decreases), the rattler fraction dramatically increases due to what we call "size-disparity" frustration. We find that at intermediate α and when x is about 0.5 (50-50 mixture), the disorder of packings is maximized, as measured by an order metric ψ that is based on the number density fluctuations in the direction perpendicular to the hard walls. We also apply the local volume-fraction variance στ2(R ) to characterize confined packings and find that these packings possess essentially the same level of hyperuniformity as their bulk counterparts. Our findings are generally relevant to confined packings that arise in biology (e.g., structural color in birds and insects) and may have implications for the creation of high-density powders and improved battery designs.

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

    SciTech Connect

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

    1980-01-01

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

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

    SciTech Connect

    Martin, R.J.; Noel, J.S.; Boyd, P.J.; Price, R.H.

    1996-02-01

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

  17. Yang-Mills streamlines and semi-classical confinement

    SciTech Connect

    Langfeld, Kurt; Ilgenfritz, Ernst-Michael

    2011-05-23

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

  18. 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.

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

    SciTech Connect

    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.

  20. System and method of operating toroidal magnetic confinement devices

    DOEpatents

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

    1984-08-30

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

  1. Compaction of granular material inside confined geometries

    NASA Astrophysics Data System (ADS)

    Marks, Benjy; Sandnes, Bjornar; Dumazer, Guillaume; Eriksen, Jon Alm; Måløy, Knut Jørgen

    2015-06-01

    In both nature and the laboratory, 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.

  2. Spontaneous circulation of confined active suspensions.

    PubMed

    Woodhouse, Francis G; Goldstein, Raymond E

    2012-10-19

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

  3. Spontaneous Circulation of Confined Active Suspensions

    NASA Astrophysics Data System (ADS)

    Woodhouse, Francis G.; Goldstein, Raymond E.

    2012-10-01

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

  4. Spiral precipitation patterns in confined chemical gardens

    PubMed Central

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

    2014-01-01

    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 reactiondiffusion 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

  5. Scanning gate imaging in confined geometries

    NASA Astrophysics Data System (ADS)

    Steinacher, R.; Kozikov, A. A.; Rössler, C.; Reichl, C.; Wegscheider, W.; Ensslin, K.; Ihn, T.

    2016-02-01

    This article reports on tunable electron backscattering investigated with the biased tip of a scanning force microscope. Using a channel defined by a pair of Schottky gates, the branched electron flow of ballistic electrons injected from a quantum point contact is guided by potentials of a tunable height well below the Fermi energy. The transition from injection into an open two-dimensional electron gas to a strongly confined channel exhibits three experimentally distinct regimes: one in which branches spread unrestrictedly, one in which branches are confined but the background conductance is affected very little, and one where the branches have disappeared and the conductance is strongly modified. Classical trajectory-based simulations explain these regimes at the microscopic level. These experiments allow us to understand under which conditions branches observed in scanning gate experiments do or do not reflect the flow of electrons.

  6. Spiral precipitation patterns in confined chemical gardens.

    PubMed

    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

  7. Confinement of Fractional Quantum Hall States

    NASA Astrophysics Data System (ADS)

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

    2008-03-01

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

  8. Pressure-confined Lyman-alpha clouds

    SciTech Connect

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

    1989-02-01

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

  9. Multiscale confining dynamics from holographic RG flows

    NASA Astrophysics Data System (ADS)

    Elander, Daniel; Faedo, Anton F.; Hoyos, Carlos; Mateos, David; Piai, Maurizio

    2014-05-01

    We consider renormalization group flows between conformal field theories in five (six) dimensions with a string (M-theory) dual. By compactifying on a circle (torus) with appropriate boundary conditions, we obtain continuous families of confining fourdimensional theories parametrized by the ratio Λflow/ΛQCD, with Λflow the scale at which the flow between fixed points takes place and ΛQCD the confinement scale. We construct the dual geometries explicitly and compute the spectrum of scalar bound states (glueballs). We find a `universal' subset of states common to all the models. We comment on the modifications of these models, and the corresponding fine-tuning, required for a parametrically light `dilaton' state to be present. We also comment on some aspects of these theories as probed by extended objects such as strings and branes.

  10. 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?.

  11. Waveforms Measured in Confined Thermobaric Explosion

    SciTech Connect

    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.

  12. Yukawa particles in a confining potential

    SciTech Connect

    Girotto, Matheus Levin, Yan; Santos, Alexandre P. dos; Colla, Thiago

    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.

  13. LDV Measurement of Confined Parallel Jet Mixing

    SciTech Connect

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

    2001-01-31

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

  14. Designing the Cascade inertial confinement fusion reactor

    SciTech Connect

    Pitts, J.H.

    1987-02-09

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

  15. Target support for inertial confinement fusion

    SciTech Connect

    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).

  16. Theoretical aspects of energy confinement in spheromaks

    SciTech Connect

    Fowler, T.K.

    1994-11-16

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

  17. Neoclassical transport in enhanced confinement toroidal plasmas

    SciTech Connect

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

    1996-11-01

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

  18. Simulating tumor growth in confined heterogeneous environments.

    PubMed

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

    2008-01-01

    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. PMID:18824788

  19. 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.

  20. Water nanodroplets confined in zeolite pores.

    PubMed

    Coudert, Franois-Xavier; Cailliez, Fabien; Vuilleumier, Rodolphe; Fuchs, Alain H; Boutin, Anne

    2009-01-01

    We provide a comprehensive depiction of the behaviour of a nanodroplet of approximately equal to 20 water molecules confined in the pores of a series of 3D-connected isostructural zeolites with varying acidity, by means of molecular simulations. Both grand canonical Monte Carlo simulations using classical interatomic forcefields and first-principles Car-Parrinello molecular dynamics were used in order to characterise the behaviour of confined water by computing a range of properties, from thermodynamic quantities to electronic properties such as dipole moment, including structural and dynamical information. From the thermodynamic point of view, we have identified the all-silica zeolite as hydrophobic, and the cationic zeolites as hydrophilic; the condensation transition in the first case was demonstrated to be of first order. Furthermore, in-depth analysis of the dynamical and electronic properties of water showed that water in the hydrophobic zeolite behaves as a nanodroplet trying to close its hydrogen-bond network onto itself, with a few short-lived dangling OH groups, while water in hydrophilic zeolites "opens up" to form weak hydrogen bonds with the zeolite oxygen atoms. Finally, the dipole moment of confined water is studied and the contributions of water self-polarisation and the zeolite electric field are discussed. PMID:19227366

  1. Radioactivity Confinement Studies Within the SEAL Program

    NASA Astrophysics Data System (ADS)

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

    1997-09-01

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

  2. Fast ion JET diagnostics: confinement and losses

    NASA Astrophysics Data System (ADS)

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

    2008-03-01

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

  3. "Soft" confinement of graphene in hydrogel matrixes.

    PubMed

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

    2015-02-01

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

  4. 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. NSF Renewable Energy Materials Research Science and Engineering Center (REMRSEC) and the Golden Energy Computing Organization (GECO)

  5. Density Shock Waves in Confined Microswimmers

    NASA Astrophysics Data System (ADS)

    Tsang, Alan Cheng Hou; Kanso, Eva

    2016-01-01

    Motile and driven particles confined in microfluidic channels exhibit interesting emergent behavior, from propagating density bands to density shock waves. A deeper understanding of the physical mechanisms responsible for these emergent structures is relevant to a number of physical and biomedical applications. Here, we study the formation of density shock waves in the context of an idealized model of microswimmers confined in a narrow channel and subject to a uniform external flow. Interestingly, these density shock waves exhibit a transition from "subsonic" with compression at the back to "supersonic" with compression at the front of the population as the intensity of the external flow increases. This behavior is the result of a nontrivial interplay between hydrodynamic interactions and geometric confinement, and it is confirmed by a novel quasilinear wave model that properly captures the dependence of the shock formation on the external flow. These findings can be used to guide the development of novel mechanisms for controlling the emergent density distribution and the average population speed, with potentially profound implications on various processes in industry and biotechnology, such as the transport and sorting of cells in flow channels.

  6. Density Shock Waves in Confined Microswimmers.

    PubMed

    Tsang, Alan Cheng Hou; Kanso, Eva

    2016-01-29

    Motile and driven particles confined in microfluidic channels exhibit interesting emergent behavior, from propagating density bands to density shock waves. A deeper understanding of the physical mechanisms responsible for these emergent structures is relevant to a number of physical and biomedical applications. Here, we study the formation of density shock waves in the context of an idealized model of microswimmers confined in a narrow channel and subject to a uniform external flow. Interestingly, these density shock waves exhibit a transition from "subsonic" with compression at the back to "supersonic" with compression at the front of the population as the intensity of the external flow increases. This behavior is the result of a nontrivial interplay between hydrodynamic interactions and geometric confinement, and it is confirmed by a novel quasilinear wave model that properly captures the dependence of the shock formation on the external flow. These findings can be used to guide the development of novel mechanisms for controlling the emergent density distribution and the average population speed, with potentially profound implications on various processes in industry and biotechnology, such as the transport and sorting of cells in flow channels. PMID:26871357

  7. Fast ion JET diagnostics: confinement and losses

    SciTech Connect

    Kiptily, V. G.; Pinches, S. D.; Sharapov, S. E.; Syme, D. B.; Cecconello, M.; Darrow, D.; Hill, K.; Goloborod'ko, V.; Yavorskij, V.; Johnson, T.; Murari, A.; Reich, M.; Gorini, G.; Zoita, V.

    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.

  8. Counterpropagating Rossby waves in confined plane wakes

    NASA Astrophysics Data System (ADS)

    Biancofiore, L.; Gallaire, F.

    2012-07-01

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

  9. Confinement of nonneutral plasma in unconventional geometries

    SciTech Connect

    Turner, L.

    1990-01-01

    Our interest in efficient storage of cold, nonneutral plasma has been motivated by the elegant studies on cryogenic nonneutral electron plasmas at UCSD and by the remarkable results obtained from the laser-cooled ion plasmas at the NIST, Boulder, Colorado. Also motivating our study is the perceived need to develop the most expedient means of storing antimatter, whether it be antiprotons for gravitational studies or positrons for a variety of physics experiments and diagnostic purposes. One of the most explored technologies of confining nonneutral plasmas is the Penning trap. The maximum number density of cold nonneutral plasma that can be stored in such a trap is B{sup 2}/2{mu}{sub 0}mc{sup 2}, in which B{sup 2}/2{mu}{sub 0} is the (homogeneous) magnetic energy density and mc{sup 2} is the rest energy of the stored charges. In this paper, we shall present a synopsis of the results of our theoretical exploration of the effect on this hydrostatic limit, the so-called Brillouin'' limit, of altering the geometry of the confining vacuum magnetic field while maintaining the field's azimuthal symmetry. In particular, we shall analyze equilibrium confinement by, first, a poloidal magnetic field, B{sub 4}(r,z){cflx r} + B{sub z}(r,z){cflx z}, and second, a toroidal magnetic field, along with the concomitant electrostatic fields.

  10. Dynamics of Hyperbranched Polymers under Confinement

    NASA Astrophysics Data System (ADS)

    Androulaki, Krystallenia; Chrissopoulou, Kiriaki; Anastasiadis, Spiros H.; Prevosto, Daniele; Labardi, Massimiliano

    2015-03-01

    The effect of severe confinement on the dynamics of three different generations of hyperbranched polyesters (Boltorns) is investigated by Dielectric Spectroscopy. The polymers are intercalated within the galleries of natural Na+-MMT, thus, forming 1nm polymer films confined between solid walls. The Tg's of the polymers determined by DSC show a clear dependence on the generation whereas the transition is completely suppressed when all the polymer chains are intercalated. The dynamic investigation of the bulk polymers reveals two sub-Tg processes, with similar behavior for the three polymers with the segmental relaxation observed above the Tg of each. For the nanocomposites, where all polymers are severely confined, the dynamics show significant differences compared to that of the bulk polymers. The sub-Tg processes are similar for the three generations but significantly faster and with weaker temperature dependence than those in the bulk. The segmental process appears at temperatures below the bulk polymer Tg, it exhibits an Arrhenius temperature dependence and shows differences for the three generations. A slow process that appears at higher temperatures is due to interfacial polarization. Co-financed by the EU and Greek funds through the Operational Program ``Education and Lifelong Learning'' of the NSRF-Research Funding Program: THALES-Investing in knowledge society through the Eur. Social Fund (MIS 377278) and COST Action MP0902-COINAPO.

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

    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.

  12. 46 CFR 148.86 - Confined space entry.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 46 Shipping 5 2014-10-01 2014-10-01 false Confined space entry. 148.86 Section 148.86 Shipping... MATERIALS THAT REQUIRE SPECIAL HANDLING Minimum Transportation Requirements § 148.86 Confined space entry. (a) Except in an emergency, no person may enter a confined space unless that space has been tested...

  13. 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.

  14. 46 CFR 148.86 - Confined space entry.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 5 2013-10-01 2013-10-01 false Confined space entry. 148.86 Section 148.86 Shipping... MATERIALS THAT REQUIRE SPECIAL HANDLING Minimum Transportation Requirements § 148.86 Confined space entry. (a) Except in an emergency, no person may enter a confined space unless that space has been tested...

  15. 46 CFR 148.86 - Confined space entry.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 46 Shipping 5 2012-10-01 2012-10-01 false Confined space entry. 148.86 Section 148.86 Shipping... MATERIALS THAT REQUIRE SPECIAL HANDLING Minimum Transportation Requirements § 148.86 Confined space entry. (a) Except in an emergency, no person may enter a confined space unless that space has been tested...

  16. 25 CFR 141.21 - Trade confined to premises.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 25 Indians 1 2012-04-01 2011-04-01 true Trade confined to premises. 141.21 Section 141.21 Indians... NAVAJO, HOPI AND ZUNI RESERVATIONS General Business Practices 141.21 Trade confined to premises. The licensee shall confine all trade on the reservation to the premises specified in the license, except,...

  17. 25 CFR 141.21 - Trade confined to premises.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 25 Indians 1 2013-04-01 2013-04-01 false Trade confined to premises. 141.21 Section 141.21 Indians... NAVAJO, HOPI AND ZUNI RESERVATIONS General Business Practices 141.21 Trade confined to premises. The licensee shall confine all trade on the reservation to the premises specified in the license, except,...

  18. 25 CFR 141.21 - Trade confined to premises.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 25 Indians 1 2014-04-01 2014-04-01 false Trade confined to premises. 141.21 Section 141.21 Indians... NAVAJO, HOPI AND ZUNI RESERVATIONS General Business Practices 141.21 Trade confined to premises. The licensee shall confine all trade on the reservation to the premises specified in the license, except,...

  19. 25 CFR 141.21 - Trade confined to premises.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 25 Indians 1 2011-04-01 2011-04-01 false Trade confined to premises. 141.21 Section 141.21 Indians... NAVAJO, HOPI AND ZUNI RESERVATIONS General Business Practices 141.21 Trade confined to premises. The licensee shall confine all trade on the reservation to the premises specified in the license, except,...

  20. 25 CFR 141.21 - Trade confined to premises.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 25 Indians 1 2010-04-01 2010-04-01 false Trade confined to premises. 141.21 Section 141.21 Indians... NAVAJO, HOPI AND ZUNI RESERVATIONS General Business Practices 141.21 Trade confined to premises. The licensee shall confine all trade on the reservation to the premises specified in the license, except,...

  1. 46 CFR 148.86 - Confined space entry.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 5 2011-10-01 2011-10-01 false Confined space entry. 148.86 Section 148.86 Shipping... MATERIALS THAT REQUIRE SPECIAL HANDLING Minimum Transportation Requirements § 148.86 Confined space entry. (a) Except in an emergency, no person may enter a confined space unless that space has been tested...

  2. Numerical study of a confined slot impinging jet with nanofluids

    PubMed Central

    2011-01-01

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

  3. Interpretation of earth tide response of three deep, confined aquifers

    SciTech Connect

    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.

  4. 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.

  5. Confinement-induced vitrification of aqueous sodium chloride solutions

    NASA Astrophysics Data System (ADS)

    Zhao, Lishan; Pan, Liqing; Cao, Zexian; Wang, Qiang

    2016-03-01

    Bulk aqueous solution of NaCl is a poor glass former, it vitrifies only under high pressure. Here we report the investigation of glass transition of NaCl solutions confined in nanopores. By inspecting the dependence of glass transition temperature and heat flow jump at transition it is concluded that vitrification of confined NaCl solutions involves only the eutectic phase and the precipitated ice core may help furnish the demanded confinement strength. Ion-water interaction still plays a dominant role in determining vitrification of solutions even under nano-confinement, as under exactly the same confinement conditions vitrification of aqueous KCl solutions was not detected.

  6. Stationary shapes of confined rotating magnetic liquid droplets.

    PubMed

    Lira, Srgio A; Miranda, Jos A; Oliveira, Rafael M

    2010-09-01

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

  7. B activation enhancement in submicron confined implants in Si

    SciTech Connect

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

    2005-09-26

    We implanted 3 keV B ions into a crystalline Si film, grown by molecular-beam epitaxy and masked by SiO{sub 2} stripes with opening widths ranging from 3.2 {mu}m down to 0.38 {mu}m. Thermal anneals were performed at 800 deg. C for several times. By quantitative high-resolution scanning capacitance microscopy, we demonstrated that the electrical reactivation of inactive B after postimplant annealing is obtained at faster rates as the window width decreases. Total electrical activation is gained first in the narrowest window, with times shorter by nearly a factor of 4 compared to the widest one. In addition, since inactive B seems to be caused by B clustering induced by implantation, our results put in evidence a strong effect of implantation confinement also on B clusters dissolution mechanism. These results have a strong impact on the modern silicon-based device engineering.

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

    SciTech Connect

    Grossnickle, J. A.; Vlases, G. C.; Hoffman, A. L.; Melnik, P. A.; Milroy, R. D.; Tankut, A.; Velas, K. M.

    2010-03-15

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

  9. Classical scattering of charged particles confined on an inhomogeneous helix.

    PubMed

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

    2013-10-01

    We explore the effects arising due to the coupling of the center of mass and relative motion of two charged particles confined on an inhomogeneous helix with a locally modified radius. It is first proven that a separation of the center of mass and the relative motion is provided if and only if the confining manifold represents a homogeneous helix. In this case, bound states of repulsively Coulomb interacting particles occur. For an inhomogeneous helix, the coupling of the center of mass and relative motion induces an energy transfer between the collective and relative motion, leading to dissociation of initially bound states in a scattering process. Due to the time reversal symmetry, a binding of the particles out of the scattering continuum is thus equally possible. We identify the regimes of dissociation for different initial conditions and provide an analysis of the underlying phase space via Poincar surfaces of section. Bound states inside the inhomogeneity as well as resonant states are identified. PMID:24229295

  10. Confinement and propagation characteristics of subwavelength plasmonic modes

    NASA Astrophysics Data System (ADS)

    Oulton, R. F.; Bartal, G.; Pile, D. F. P.; Zhang, X.

    2008-10-01

    We have studied subwavelength confinement of the surface plasmon polariton modes of various plasmonic waveguides and examined their relative merits using a graphical parametric representation of their confinement and propagation characteristics. While the same plasmonic phenomenon governs mode confinement in all these waveguides, the various architectures can exhibit distinctive behavior in terms of effective mode area and propagation distance. We found that the waveguides based on metal and one dielectric material show a similar trade-off between energy confinement and propagation distance. However, a hybrid plasmon waveguide, incorporating metal, low index and high index dielectric materials, exhibits longer propagation distances for the same degree of confinement. We also point out that plasmonic waveguides with sharp features can provide an extremely strong local field enhancement, which is not necessarily accompanied by strong confinement of the total electromagnetic energy. In these waveguides, a mode may couple strongly to nearby atoms, but suffer relatively low propagation losses due to weak confinement.

  11. Photoluminescence of quantum-confined semiconductor structures

    NASA Astrophysics Data System (ADS)

    Mosor, Sorin

    Different aspects of the photoluminescence from semiconductor quantum-confined structures are studied in this dissertation, for a better understanding of fundamental physics of semiconductors. The precursor of any photoluminescence study is the characterization of the linear optical properties of the semiconductor structures. High resolution absorption measurements were performed in order to study the interplay of disorder and acoustic phonon scattering in a quantum well. Also, reflectivity measurements, together with a fitting procedure based on the transfer matrix formalism, are used to determine the thickness of samples. Excitons are atom-like quasi-particles, formed from a bound electron-hole pair. They follow a Bose-Einstein statistic, so in principle it is possible to achieve an excitonic Bose-Einstein condensate. Time resolved photoluminescence measurements were performed over an extensive range of lattice temperatures and carrier concentrations, in order to determine the fraction of excitons formed from the electron-hole plasma in a quantum well, after non-resonant excitation. The experimental spectra were compared to a pure plasma calculation first, then excitons were taken into account-The highest fraction of formed excitons is found for low temperatures and intermediate carrier densities. This fraction is found to be very small, and this has clear implications on the excitonic Bose-Einstein condensation studies. The photoluminescence emitted left and right from a quantum well is interfered in a modified Mach-Zender interferometer. It is shown that the light emitted on the two paths will interfere for a V-shape geometry and will not for any other paths. A structure formed by placing a quantum well in a field antinode of a resonant planar microcavity exhibits normal mode coupling: splitting of the resonance spectral line. For the case of resonant excitation, a third peak appears at higher excitation levels. The coherence properties of the photoluminescence from a normal-mode-coupling microcavity are studied using another version of the Mach-Zender interferometer. The degree of coherence measured in this way depends greatly on the pump wavelength and intensity, ranging from zero to 0.8. However, direct observation of the emission speckle shows significant coherence in all cases. The difference is explained by the different methods used to evaluate the coherence. The strong coupling between a quantum dot and a photonic crystal nanocavity is investigated by observation of photoluminescence. A new method of tunning the cavity wavelength by deposition of a thin film of solid Xenon on all the surfaces of the sample is presented. The method allows the scanning of the cavity wavelength with about 5 nm without a decrease in the quality factor and without changing the temperature. Finally, an extensive study of the quality factors of quantum dot photonic crystal nanocavities is presented. The role of the quantum dot ensemble absorption is investigated. At higher excitation levels, lasing is observed and discussed.

  12. Trigonal warping effect on velocity and transverse confinement length of topologically confined states in bilayer graphene

    NASA Astrophysics Data System (ADS)

    Cosma, Diana A.; Fal'ko, Vladimir I.

    2015-10-01

    In bilayer graphene an interface between regions with opposite sign of the interlayer asymmetry gap leads to the spatial confinement of low-energy chiral modes [I. Martin, Y. M. Blanter, and A. F. Morpurgo, Phys. Rev. Lett. 100, 036804 (2008), 10.1103/PhysRevLett.100.036804]. Here we study the influence of trigonal warping on the properties of the interface-guided stats and find that in the vicinity of the band edges the group velocity and transverse confinement length exhibit a nonmonotonic dependence on the crystallographic orientation of the crystal with respect to the interface.

  13. Pathways to dewetting in hydrophobic confinement.

    PubMed

    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

  14. Spherical microwave confinement and ball lightning

    NASA Astrophysics Data System (ADS)

    Robinson, William Richard

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

  15. Pathways to dewetting in hydrophobic confinement

    PubMed Central

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

    2015-01-01

    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

  16. Inverted critical adsorption of polyelectrolytes in confinement.

    PubMed

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

    2015-06-14

    What are the fundamental laws for the adsorption of charged polymers onto oppositely charged surfaces, for convex, planar, and concave geometries? This question is at the heart of surface coating applications, various complex formation phenomena, as well as in the context of cellular and viral biophysics. It has been a long-standing challenge in theoretical polymer physics; for realistic systems the quantitative understanding is however often achievable only by computer simulations. In this study, we present the findings of such extensive Monte-Carlo in silico experiments for polymer-surface adsorption in confined domains. We study the inverted critical adsorption of finite-length polyelectrolytes in three fundamental geometries: planar slit, cylindrical pore, and spherical cavity. The scaling relations extracted from simulations for the critical surface charge density σc-defining the adsorption-desorption transition-are in excellent agreement with our analytical calculations based on the ground-state analysis of the Edwards equation. In particular, we confirm the magnitude and scaling of σc for the concave interfaces versus the Debye screening length 1/κ and the extent of confinement a for these three interfaces for small κa values. For large κa the critical adsorption condition approaches the known planar limit. The transition between the two regimes takes place when the radius of surface curvature or half of the slit thickness a is of the order of 1/κ. We also rationalize how σc(κ) dependence gets modified for semi-flexible versus flexible chains under external confinement. We examine the implications of the chain length for critical adsorption-the effect often hard to tackle theoretically-putting an emphasis on polymers inside attractive spherical cavities. The applications of our findings to some biological systems are discussed, for instance the adsorption of nucleic acids onto the inner surfaces of cylindrical and spherical viral capsids. PMID:25940939

  17. Viscous fingering and liquid crystals in confinement

    NASA Astrophysics Data System (ADS)

    Zacharoudiou, Ioannis

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

  18. Thermodynamic Properties of Alkanes in Confined Geometries

    NASA Astrophysics Data System (ADS)

    Sheehan, Joseph F., III

    1995-11-01

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

  19. 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.

  20. Alpha particle confinement in tandem mirrors

    SciTech Connect

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

    1980-10-10

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

  1. Spatiotemporal instability of a confined capillary jet.

    PubMed

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

    2008-10-01

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

  2. Magnetohydrodynamically generated velocities in confined plasma

    SciTech Connect

    Morales, Jorge A. Bos, Wouter J. T.; Schneider, Kai; Montgomery, David C.

    2015-04-15

    We investigate by numerical simulation the rotational flows in a toroid confining a conducting magnetofluid in which a current is driven by the application of externally supported electric and magnetic fields. The computation involves no microscopic instabilities and is purely magnetohydrodynamic (MHD). We show how the properties and intensity of the rotations are regulated by dimensionless numbers (Lundquist and viscous Lundquist) that contain the resistivity and viscosity of the magnetofluid. At the magnetohydrodynamic level (uniform mass density and incompressible magnetofluids), rotational flows appear in toroidal, driven MHD. The evolution of these flows with the transport coefficients, geometry, and safety factor are described.

  3. Graviton confinement inside hypermonopoles of any dimension

    SciTech Connect

    Murray, Seán; Ringeval, Christophe; Zonetti, Simone E-mail: christophe.ringeval@uclouvain.be

    2010-09-01

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

  4. Critical Behavior of Magnetically Confined Plasma Regimes

    SciTech Connect

    Garcia, J.; Giruzzi, G.

    2010-05-21

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

  5. Microwave Reflectometry for Magnetically Confined Plasmas

    SciTech Connect

    Mazzucato, E.

    1998-02-01

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

  6. Micromachining of inertial confinement fusion targets

    SciTech Connect

    Gobby, P.L.; Salzer, L.J.; Day, R.D.

    1996-12-31

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

  7. Magnetohydrodynamically generated velocities in confined plasma

    NASA Astrophysics Data System (ADS)

    Morales, Jorge A.; Bos, Wouter J. T.; Schneider, Kai; Montgomery, David C.

    2015-04-01

    We investigate by numerical simulation the rotational flows in a toroid confining a conducting magnetofluid in which a current is driven by the application of externally supported electric and magnetic fields. The computation involves no microscopic instabilities and is purely magnetohydrodynamic (MHD). We show how the properties and intensity of the rotations are regulated by dimensionless numbers (Lundquist and viscous Lundquist) that contain the resistivity and viscosity of the magnetofluid. At the magnetohydrodynamic level (uniform mass density and incompressible magnetofluids), rotational flows appear in toroidal, driven MHD. The evolution of these flows with the transport coefficients, geometry, and safety factor are described.

  8. Perlite for permanent confinement of cesium

    NASA Astrophysics Data System (ADS)

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

    2006-06-01

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

  9. Anomalous diffusion in confined turbulent convection.

    PubMed

    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

  10. Summary of progress in inertial confinement fusion

    SciTech Connect

    Younger, S.M.

    1992-01-01

    Progress in inertial confinement fusion (ICF) has been very rapid over the past two years. Significant advances have been made in the production of smooth laser beams, the focusing of light ions beams, and the development of heavy ion accelerators. The availability of advanced target diagnostics on several major drivers has resulted in an extensive database of target performance over a wide range of conditions. Theoretical models of ICF targets are approaching the predictive level with two and even three dimensional calculations becoming routine. Within the next several years information should be available to allow confident extrapolation to ignition on the next generation driver.

  11. Summary of progress in inertial confinement fusion

    SciTech Connect

    Younger, S.M.

    1992-12-31

    Progress in inertial confinement fusion (ICF) has been very rapid over the past two years. Significant advances have been made in the production of smooth laser beams, the focusing of light ions beams, and the development of heavy ion accelerators. The availability of advanced target diagnostics on several major drivers has resulted in an extensive database of target performance over a wide range of conditions. Theoretical models of ICF targets are approaching the predictive level with two and even three dimensional calculations becoming routine. Within the next several years information should be available to allow confident extrapolation to ignition on the next generation driver.

  12. Nanofabricated cells for confined 3He

    NASA Astrophysics Data System (ADS)

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

    2013-03-01

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

  13. Central cell confinement in MFTF-B

    SciTech Connect

    Jong, R.A.

    1981-05-05

    The point code TANDEM has been used to survey the range of plasma parameters which can be attained in MFTF-B. The code solves for the electron and ion densities and temperatures in the central cell, yin-yang, barrier, and A-cell regions as well as the plasma potential in each region. In these studies, the A-cell sloshing ion beams were fixed while the neutral beams in the yin-yang and central cell, the gas feed in the central cell, and the applied ECRH power ..beta.., central cell ion density and temperature, and the confining potential are discussed.

  14. 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.

  15. Phonon confinement effect in calcium fluoride nanoparticles

    NASA Astrophysics Data System (ADS)

    Ricci, Pier Carlo; Casu, Alberto; Giudici, Giovanni De; Scardi, Paolo; Anedda, Alberto

    2007-08-01

    Nanocrystalline CaF 2 were obtained by ball-milled synthetic fluorite powders. Raman spectra of nanocrystals with average sizes of 10-25 nm are reported and the correlation between the band shape of the only allowed Raman mode at 322 cm -1 and the crystals dimensions is discussed. While in such systems local temperature and pressure effects play a minor role, variations in the shape of the Raman band can be correctly reproduced by a model based on the phonon confinement that effectively takes into account the anisotropy of the phonon dispersion curve.

  16. Double-Current-Confined CSP Laser

    NASA Technical Reports Server (NTRS)

    Connolly, John C.

    1992-01-01

    Improved channeled-substrate-planar (CSP) lasers that emit at wavelengths between 860 and 880 nm grown by liquid-phase epitaxy (LPE). Exhibit record high output powers and efficiencies, attained without sacrifice of desirable characteristics of lasers. In fabrication, second reverse-bias p/n junction incorporated to reduce required current. By incorporating two reverse-bias junctions in CSP structure, one doubly confines current. Lasers used eventually as sources of light in intersatellite communications systems and, specifically, NASA Advanced Communications Technology Satellite (ACTS) System.

  17. Confinement of knotted polymers in a slit

    NASA Astrophysics Data System (ADS)

    Matthews, R.; Louis, A. A.; Yeomans, J. M.

    2011-04-01

    We investigate the effect of knot type on the properties of a ring polymer confined to a slit. For relatively wide slits, the more complex the knot, the more the force exerted by the polymer on the walls is decreased compared to an unknotted polymer of the same length. For more narrow slits the opposite is true. The crossover between these two regimes is, to first order, at smaller slit width for more complex knots. However, knot topology can affect these trends in subtle ways. Besides the force exerted by the polymers, we also study other quantities such as the monomer-density distribution across the slit and the anisotropic radius of gyration.

  18. Nanoscale light confinement and nonlinearity of hybrid plasmonic waveguide with a metal cap

    NASA Astrophysics Data System (ADS)

    Li, Kai; Yun, Maojin; Wang, Mei; Wu, Xingxing; Liu, Chao; Kong, Weijin; Chen, Shu; Dong, Lifeng

    2015-10-01

    A nonlinear hybrid plasmonic waveguide (HPW) with a metal cap on a nonlinear material-on-insulator rib is proposed. By using a finite-difference time-domain method, its light confinement and effective nonlinearity coefficient of the Kerr effect for all-optical switches are analyzed in detail. Numerical simulations illustrate that the nonlinear HPW structure has nanoscale confinement and high effective nonlinearity coefficient at the wavelength of 1550 nm. Consequently, the HPW can be used in all-optical signal processing of integrated photonics.

  19. Stark-assisted quantum confinement of wavepackets. A coupling of nonadiabatic interaction and CW-laser

    NASA Astrophysics Data System (ADS)

    Arasaki, Yasuki; Mizuno, Yuta; Scheit, Simona; Takatsuka, Kazuo

    2016-01-01

    When a nonadiabatic system that has an ionic state (large dipole moment) and a covalent state (small dipole moment) is located in a strong laser field, the crossing point of the two potential energy curves is forced to oscillate due to the oscillating laser field and to meet wavepackets moving on the potential curves many times. This leads to additional transitions between the two states, and under favorable conditions, the wavepacket may be confined in a spatial region rich in nonadiabatic interaction. In this paper, taking the LiF molecule system in a continuous-wave driving field as a prototypical example, the dynamical origins of the wavepacket confinement are theoretically investigated.

  20. Lateral carrier confinement in InGaN quantum-well nanorods

    SciTech Connect

    Shi, Chentian; Zhang, Chunfeng; Wang, Xiaoyong; Xiao, Min

    2015-07-15

    We review our studies on lateral carrier diffusion in micro-fabricated samples of InGaN nanorods and their parent quantum wells. The carrier diffusion is observed to be strongly confined in nanorods, as manifested by the reduction in the delayed-rise component of time-resolved photoluminescence traces. We further argue that the confinement of carrier diffusion can be applied to suppress the efficiency droop related to defect state recombination and to assist in the energy transfer between InGaN nanorods and nanocrystal phosphors for color conversion.

  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.

  2. Analysis of Confined Random Walkers with Applications to Processes Occurring in Molecular Aggregates and Immunological Systems.

    PubMed

    Chase, Matthew; Spendier, Kathrin; Kenkre, V M

    2016-03-31

    Explicit solutions are presented in the Laplace and time domains for a one-variable Fokker-Planck equation governing the probability density of a random walker moving in a confining potential. Illustrative applications are discussed in two unrelated physical contexts: quantum yields in a doped molecular crystal or photosynthetic system, and the motion of signal receptor clusters on the surface of a cell encountered in a problem in immunology. An interesting counterintuitive effect concerning the consequences of confinement is found in the former, and some insights into the driving force for microcluster centralization are gathered in the latter application. PMID:26885727

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

    PubMed

    Wesley, David; Cox, Hugh F

    2007-01-01

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

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

    PubMed

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

    2013-08-15

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

  5. Applications of group-invariant analytic solutions to inertial confinement fusion

    SciTech Connect

    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.

  6. 28 CFR 541.31 - Conditions of confinement in the SHU.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... confinement in the SHU. Your living conditions in the SHU will meet or exceed standards for healthy and humane... the Administrative Remedy Program, 28 CFR part 542, subpart B. ... and shave at least three times per week. You will have access to hair care services as necessary....

  7. 28 CFR 541.31 - Conditions of confinement in the SHU.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... confinement in the SHU. Your living conditions in the SHU will meet or exceed standards for healthy and humane... the Administrative Remedy Program, 28 CFR part 542, subpart B. ... and shave at least three times per week. You will have access to hair care services as necessary....

  8. 28 CFR 541.31 - Conditions of confinement in the SHU.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... confinement in the SHU. Your living conditions in the SHU will meet or exceed standards for healthy and humane... the Administrative Remedy Program, 28 CFR part 542, subpart B. ... and shave at least three times per week. You will have access to hair care services as necessary....

  9. 28 CFR 541.31 - Conditions of confinement in the SHU.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... confinement in the SHU. Your living conditions in the SHU will meet or exceed standards for healthy and humane... the Administrative Remedy Program, 28 CFR part 542, subpart B. ... and shave at least three times per week. You will have access to hair care services as necessary....

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

    DOEpatents

    Coppi, B.; Montgomery, D.B.

    1973-12-11

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

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

    SciTech Connect

    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.

  12. 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.

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

    SciTech Connect

    Skalyga, V.; Zorin, V.

    2005-03-15

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

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

    SciTech Connect

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

    2013-08-15

    Dynamics of Li plasma plume created by laser-blow-off technique in air ambient is reported. Plasma plume dynamics and its optical emission are investigated in planar and confined geometries using time resolved shadowgraph imaging and optical emission spectroscopy. Significant differences in the plasma characteristics in confined geometry are quantitatively investigated by comparing the plasma parameters (temperature and density) in free expansion and confined geometry configurations. Dynamics and physical parameters of the primary as well as the reflected shock waves (in confined geometry) and their interactions with expanding plasma are briefly addressed. A large enhancement in the emission intensities of Li I 610.3 nm (2p {sup 2}P{sub 1/2,3/2}? 3d {sup 2}P{sub 3/2,5/2}) and 670.8 nm (2s {sup 2}S{sub 1/2}? 2p {sup 2}P{sub 1/2,3/2}) is correlated with the shock wave dynamics in the two geometries. Strong self reversal in the neutral emission infers an increase in the population density of neutrals within the confined plasma plume.

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

    SciTech Connect

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

    1988-09-01

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

  16. Sub-diffusion and population dynamics of water confined in soft environments.

    PubMed

    Hanot, Samuel; Lyonnard, Sandrine; Mossa, Stefano

    2016-02-01

    We have studied by using molecular dynamics computer simulations the dynamics of water confined in ionic surfactant phases, ranging from well ordered lamellar structures to micelles at low and high water loading, respectively. We have analysed in depth the main dynamical features in terms of mean-squared displacements and intermediate scattering functions, and found clear evidence of sub-diffusive behaviour. We have identified water molecules lying at the charged interface with the hydrophobic confining matrix as the main factor responsible for this unusual feature, and given a comprehensive picture of dynamics based on a very precise analysis of lifetimes at the interface. We conclude by providing, for the first time to our knowledge, a unique framework for rationalizing the existence of important dynamical heterogeneities in fluids adsorbed in soft confining environments. PMID:26690685

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

    SciTech Connect

    Wyman, M. D.; Chapman, B. E.; Ahn, J. W.; Almagri, A. F.; Anderson, J. K.; Den Hartog, D. J.; Ebrahimi, F.; Ennis, D. A.; Fiksel, G.; Gangadhara, S.; Goetz, J. A.; O'Connell, R.; Oliva, S. P.; Prager, S. C.; Reusch, J. A.; Sarff, J. S.; Stephens, H. D.; Bonomo, F.; Franz, P.; Brower, D. L.

    2008-01-15

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

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

    SciTech Connect

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

    2008-01-01

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

  19. Using Quantum Confinement to Uniquely Identify Devices

    NASA Astrophysics Data System (ADS)

    Roberts, J.; Bagci, I. E.; Zawawi, M. A. M.; Sexton, J.; Hulbert, N.; Noori, Y. J.; Young, M. P.; Woodhead, C. S.; Missous, M.; Migliorato, M. A.; Roedig, U.; Young, R. J.

    2015-11-01

    Modern technology unintentionally provides resources that enable the trust of everyday interactions to be undermined. Some authentication schemes address this issue using devices that give a unique output in response to a challenge. These signatures are generated by hard-to-predict physical responses derived from structural characteristics, which lend themselves to two different architectures, known as unique objects (UNOs) and physically unclonable functions (PUFs). The classical design of UNOs and PUFs limits their size and, in some cases, their security. Here we show that quantum confinement lends itself to the provision of unique identities at the nanoscale, by using fluctuations in tunnelling measurements through quantum wells in resonant tunnelling diodes (RTDs). This provides an uncomplicated measurement of identity without conventional resource limitations whilst providing robust security. The confined energy levels are highly sensitive to the specific nanostructure within each RTD, resulting in a distinct tunnelling spectrum for every device, as they contain a unique and unpredictable structure that is presently impossible to clone. This new class of authentication device operates with minimal resources in simple electronic structures above room temperature.

  20. Regimes of DNA confined in a nanochannel

    NASA Astrophysics Data System (ADS)

    Dai, Liang; Doyle, Patrick

    2014-03-01

    Scaling regimes for polymers confined to tubular channels are well established when the channel cross-sectional dimension is either very small (Odjik regime) or large (classic de Gennes regime) relative to the polymer Kuhn length. In the literature, there is no clear consensus regarding the intermediate region and if subregimes even exist to connect these two classic bounding regimes. The confluence of emerging single DNA mapping technologies and a resurged interest in the fundamental properties of confined polymers has led to extensive research in this area using DNA as a model system. Due to the DNA molecule's properties and limitations of nanofabrication, most experiments are performed in this intermediate regime with channel dimensions of a few Kuhn lengths. Here we use simulations and theory to reconcile conflicting theories and show that there are indeed extended de Gennes, partial alignment and hairpin regimes located between the two classic regimes. Simulations results for both chain extension and free energy support the existence of these regimes. This research was supported by the National Research Foundation Singapore through the Singapore MIT Alliance for Research and Technology's research program in BioSystems and Micromechanics, the National Science Foundation (CBET-1335938).

  1. Neutron imaging for inertial confinement fusion experiments

    NASA Astrophysics Data System (ADS)

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

    2007-09-01

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

  2. Deuterium anions in inertial electrostatic confinement devices.

    PubMed

    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

  3. Deuterium anions in inertial electrostatic confinement devices

    NASA Astrophysics Data System (ADS)

    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?A/cm2 have been measured at the wall of the UW-IEC device, 40 cm from the surface of the device cathode with a detector assembly of admittance area 0.7cm2 . Energy spectra obtained using a magnetic deflection-energy analyzer diagnostic indicate the presence of D2- , and D- ions produced through thermal electron attachment near the device cathode, as well as D- ions produced via charge-transfer processes between the anode and cathode of the device.

  4. Thermodynamic properties of bulk and confined water

    SciTech Connect

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

    2014-11-14

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

  5. Condensate bright solitons under transverse confinement

    NASA Astrophysics Data System (ADS)

    Salasnich, L.; Parola, A.; Reatto, L.

    2002-10-01

    We investigate the dynamics of Bose-Einstein condensate bright solitons made of alkali-metal atoms with negative scattering length and under harmonic confinement in the transverse direction. Contrary to the one-dimensional (1D) case, the 3D bright soliton exists only below a critical attractive interaction that depends on the extent of confinement. Such a behavior is also found in multisoliton condensates with box boundary conditions. We obtain numerical and analytical estimates of the critical strength beyond which the solitons do not exist. By using an effective 1D nonpolynomial nonlinear Schrdinger equation, which accurately takes into account the transverse dynamics of cigarlike condensates, we numerically simulate the dynamics of the ``soliton train'' reported in a recent experiment [Nature (London) 417, 150 (2002)]. Then, analyzing the macroscopic quantum tunneling of the bright soliton on a Gaussian barrier, we find that its interference in the tunneling region is strongly suppressed with respect to nonsolitonic case; moreover, the tunneling through a barrier breaks the shape invariance of the matter wave. Finally, we show that the collapse of the soliton is induced by the scattering on the barrier or by the collision with another matter wave when the density reaches a critical value, for which we derive an accurate analytical formula.

  6. Polymer escape from a confining potential.

    PubMed

    Mkknen, Harri; Ikonen, Timo; Jnsson, Hannes; Ala-Nissila, Tapio

    2014-02-01

    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. PMID:24511979

  7. Confined Polymerization in Highly Ordered Mesoporous Organosilicas.

    PubMed

    Comotti, Angiolina; Bracco, Silvia; Beretta, Mario; Perego, Jacopo; Gemmi, Mauro; Sozzani, Piero

    2015-12-01

    Hybrid mesoporous organosilica exhibiting crystal-like order in the walls provided an ideal channel reaction vessel for the confined polymerization of acrylonitrile (PAN). The resulting high-molecular-mass PAN fills the channels at high yield and forms an ordered nanostructure of polymer nanobundles enclosed into the hybrid matrix. The in situ thermal transformation of PAN into rigid polyconjugated and, eventually, into condensed polyaromatic carbon nanofibers, retains the periodic architecture. Simultaneously, the matrix evolves showing the fusion of the p-phenylene rings and the cleavage of carbon?silicon bonds: this gives rise to graphitic-carbon/silica nanocomposites containing hyper-oxydrylated silica nanophases. Interestingly, the 3D hexagonal mesostructure survives in the carbonaceous material. The exploitation of porous materials of high capacity and a hybrid nature, for polymerization in the confined state, followed by high temperature treatments, allowed us to achieve unique and precisely fabricated nanostructures, thus paving the way for the construction of fine-tuned electronic and light-harvesting materials. PMID:26559381

  8. Polymer Dynamics in Nanocomposites and under Confinement

    NASA Astrophysics Data System (ADS)

    Richter, Dieter

    2013-03-01

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

  9. Using Quantum Confinement to Uniquely Identify Devices.

    PubMed

    Roberts, J; Bagci, I E; Zawawi, M A M; Sexton, J; Hulbert, N; Noori, Y J; Young, M P; Woodhead, C S; Missous, M; Migliorato, M A; Roedig, U; Young, R J

    2015-01-01

    Modern technology unintentionally provides resources that enable the trust of everyday interactions to be undermined. Some authentication schemes address this issue using devices that give a unique output in response to a challenge. These signatures are generated by hard-to-predict physical responses derived from structural characteristics, which lend themselves to two different architectures, known as unique objects (UNOs) and physically unclonable functions (PUFs). The classical design of UNOs and PUFs limits their size and, in some cases, their security. Here we show that quantum confinement lends itself to the provision of unique identities at the nanoscale, by using fluctuations in tunnelling measurements through quantum wells in resonant tunnelling diodes (RTDs). This provides an uncomplicated measurement of identity without conventional resource limitations whilst providing robust security. The confined energy levels are highly sensitive to the specific nanostructure within each RTD, resulting in a distinct tunnelling spectrum for every device, as they contain a unique and unpredictable structure that is presently impossible to clone. This new class of authentication device operates with minimal resources in simple electronic structures above room temperature. PMID:26553435

  10. Charge-Confining Gravitational Electrovacuum Shock Wave

    NASA Astrophysics Data System (ADS)

    Guendelman, Eduardo; Nissimov, Emil; Pacheva, Svetlana

    2014-01-01

    In previous publications, we have extensively studied spherically symmetric solutions of gravity coupled to a nonstandard type of nonlinear electrodynamics containing a square-root of the ordinary Maxwell Lagrangian (the latter is known to yield quantum chromodynamic (QCD)-like confinement in a flat spacetime). A class of these solutions describe nonstandard black holes of Reissner-Nordstrm-(anti-)-de Sitter type with an additional constant radial vacuum electric field, in particular, a non-asymptotically flat Reissner-Nordstrm-type black hole. Here, we study the ultra-relativistic boost (Lousto-Sanchez extension of Aichelburg-Sexl) limit of the latter and show that, unlike the ordinary Reissner-Nordstrm case, we obtain a gravitational electrovacuum shock wave as a result of the persistence of the gauge field due to the "square-root" Maxwell Lagrangian term. Next, we show that this gravitational electrovacuum shock wave confines charged test particles (both massive and massless) within a finite distance from its front.

  11. Polymer escape from a confining potential

    SciTech Connect

    Mkknen, Harri; Faculty of Physical Sciences, University of Iceland, Reykjavk ; Ikonen, Timo; VTT Technical Research Centre of Finland, P.O. Box 1000, FI-02044 VTT ; Jnsson, Hannes; Faculty of Physical Sciences, University of Iceland, Reykjavk; Department of Physics, Brown University, Providence, Rhode Island 02912-1843 ; Ala-Nissila, Tapio; Department of Physics, Brown University, Providence, Rhode Island 02912-1843

    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.

  12. Confined superadiabatic premixed flame-flow interaction

    SciTech Connect

    Najm, H.N.

    1995-12-31

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

  13. Viscosity of confined inhomogeneous nonequilibrium fluids.

    PubMed

    Zhang, Junfang; Todd, B D; Travis, Karl P

    2004-12-01

    We use the nonlocal linear hydrodynamic constitutive model, proposed by Evans and Morriss [Statistical Mechanics of Nonequilibrium Liquids (Academic, London, 1990)], for computing an effective spatially dependent shear viscosity of inhomogeneous nonequilibrium fluids. The model is applied to a simple atomic fluid undergoing planar Poiseuille flow in a confined channel of several atomic diameters width. We compare the spatially dependent viscosity with a local generalization of Newton's law of viscosity and the Navier-Stokes viscosity, both of which are known to suffer extreme inaccuracies for highly inhomogeneous systems. The nonlocal constitutive model calculates effective position dependent viscosities that are free from the notorious singularities experienced by applying the commonly used local constitutive model. It is simple, general, and has widespread applicability in nanofluidics where experimental measurement of position dependent transport coefficients is currently inaccessible. In principle the method can be used to predict approximate flow profiles of any arbitrary inhomogeneous system. We demonstrate this by predicting the flow profile for a simple fluid undergoing planar Couette flow in a confined channel of several atomic diameters width. PMID:15549963

  14. Fire Risk Analysis for Armenian NPP Confinement

    SciTech Connect

    Poghosyan, Shahen; Malkhasyan, Albert; Bznuni, Surik; Amirjanyan, Armen

    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)

  15. Hierarchical wrinkling in a confined permeable biogel

    PubMed Central

    Leocmach, Mathieu; Nespoulous, Mathieu; Manneville, Sébastien; Gibaud, Thomas

    2015-01-01

    Confined thin surfaces may wrinkle as a result of the growth of excess material. Elasticity or gravity usually sets the wavelength. We explore new selection mechanisms based on hydrodynamics. First, inspired by yoghurt-making processes, we use caseins (a family of milk proteins) as pH-responsive building blocks and the acidulent glucono-δ-lactone to design a porous biogel film immersed in a confined buoyancy-matched viscous medium. Under specific boundary conditions yet without any external stimulus, the biogel film spontaneously wrinkles in cascade. Second, using a combination of titration, rheology, light microscopy, and confocal microscopy, we demonstrate that, during continuous acidification, the gel first shrinks and then swells, inducing wrinkling. Third, taking into account both Darcy flow through the gel and Poiseuille flow in the surrounding solvent, we develop a model that correctly predicts the wrinkling wavelength. Our results should be universal for acid-induced protein gels because they are based on pH-induced charge stabilization/destabilization and therefore could set a benchmark to gain fundamental insights into wrinkled biological tissues, to texture food, or to design surfaces for optical purposes. PMID:26601296

  16. Hierarchical wrinkling in a confined permeable biogel.

    PubMed

    Leocmach, Mathieu; Nespoulous, Mathieu; Manneville, Sébastien; Gibaud, Thomas

    2015-10-01

    Confined thin surfaces may wrinkle as a result of the growth of excess material. Elasticity or gravity usually sets the wavelength. We explore new selection mechanisms based on hydrodynamics. First, inspired by yoghurt-making processes, we use caseins (a family of milk proteins) as pH-responsive building blocks and the acidulent glucono-δ-lactone to design a porous biogel film immersed in a confined buoyancy-matched viscous medium. Under specific boundary conditions yet without any external stimulus, the biogel film spontaneously wrinkles in cascade. Second, using a combination of titration, rheology, light microscopy, and confocal microscopy, we demonstrate that, during continuous acidification, the gel first shrinks and then swells, inducing wrinkling. Third, taking into account both Darcy flow through the gel and Poiseuille flow in the surrounding solvent, we develop a model that correctly predicts the wrinkling wavelength. Our results should be universal for acid-induced protein gels because they are based on pH-induced charge stabilization/destabilization and therefore could set a benchmark to gain fundamental insights into wrinkled biological tissues, to texture food, or to design surfaces for optical purposes. PMID:26601296

  17. On chiral symmetry breaking, topology and confinement

    NASA Astrophysics Data System (ADS)

    Shuryak, Edward

    2014-08-01

    We start with the relation between the chiral symmetry breaking and gauge field topology. New lattice results further enhance the notion of Zero Mode Zone, a very narrow strip of states with quasizero Dirac eigenvalues. Then we move to the issue of origin of mass and Brown-Rho scaling: a number of empirical facts contradicts to the idea that masses of quarks and such hadrons as ?,N decrease near Tc. We argue that while at T=0 the main contribution to the effective quark mass is chirally odd m??, near Tc it rotates to chirally-even component m?, because infinite clusters of topological solitons gets split into finite ones. Recent progress in understanding of topology require introduction of nonzero holonomy ?0, which splits instantons into Nc (anti)selfdual instanton-dyons. Qualitative progress, as well as first numerical studies of the dyon ensemble are reported. New connections between chiral symmetry breaking and confinement are recently understood, since instanton-dyons generate holonomy potential with a minimum at confining value, if the ensemble is dense enough.

  18. Improved Confinement Regimes and the Ignitor Experiment

    NASA Astrophysics Data System (ADS)

    Bombarda, F.; Coppi, B.; Detragiache, P.

    2013-10-01

    The Ignitor experiment is the only one designed and planned to reach ignition under controlled DT burning conditions. The machine prameters have been established on the basis of existing knowledge of the confinement properties of high density plasmas. The optimal plasma evolution in order to reach ignition by means of Ohmic heating only, without the contribution of transport barriers has been identified. Improved confinement regimes are expected to be accessible by means of the available ICRH additional heating power and the injection of pellets for density profile control. Moreover, ECRH of the outer edge of the (toroidal) plasma column has been proposed using very high frequency sources developed in Russia. Ignition can then be reached at slightly reduced machine parameters. Significant exploration of the behavior of burning, sub-ignited plasmas can be carried out in less demanding operational conditions than those needed for ignition with plasmas accessing the I or H-regimes. These conditions will be discussed together with the provisions made in order to maintain the required (for ignition) degree of plasma purity. Sponsored in part by the U.S. DOE.

  19. Polymer escape from a confining potential

    NASA Astrophysics Data System (ADS)

    Mkknen, Harri; Ikonen, Timo; Jnsson, Hannes; Ala-Nissila, Tapio

    2014-02-01

    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.

  20. Using Quantum Confinement to Uniquely Identify Devices

    PubMed Central

    Roberts, J.; Bagci, I. E.; Zawawi, M. A. M.; Sexton, J.; Hulbert, N.; Noori, Y. J.; Young, M. P.; Woodhead, C. S.; Missous, M.; Migliorato, M. A.; Roedig, U.; Young, R. J.

    2015-01-01

    Modern technology unintentionally provides resources that enable the trust of everyday interactions to be undermined. Some authentication schemes address this issue using devices that give a unique output in response to a challenge. These signatures are generated by hard-to-predict physical responses derived from structural characteristics, which lend themselves to two different architectures, known as unique objects (UNOs) and physically unclonable functions (PUFs). The classical design of UNOs and PUFs limits their size and, in some cases, their security. Here we show that quantum confinement lends itself to the provision of unique identities at the nanoscale, by using fluctuations in tunnelling measurements through quantum wells in resonant tunnelling diodes (RTDs). This provides an uncomplicated measurement of identity without conventional resource limitations whilst providing robust security. The confined energy levels are highly sensitive to the specific nanostructure within each RTD, resulting in a distinct tunnelling spectrum for every device, as they contain a unique and unpredictable structure that is presently impossible to clone. This new class of authentication device operates with minimal resources in simple electronic structures above room temperature. PMID:26553435

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

    SciTech Connect

    Travis, J.R.; Wilson, T.L.; Spore, J.W.; Lam, K.L.; Rao, D.V.

    1994-09-01

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

  2. Sub-diffusion and population dynamics of water confined in soft environments

    NASA Astrophysics Data System (ADS)

    Hanot, Samuel; Lyonnard, Sandrine; Mossa, Stefano

    2016-02-01

    We have studied by using molecular dynamics computer simulations the dynamics of water confined in ionic surfactant phases, ranging from well ordered lamellar structures to micelles at low and high water loading, respectively. We have analysed in depth the main dynamical features in terms of mean-squared displacements and intermediate scattering functions, and found clear evidence of sub-diffusive behaviour. We have identified water molecules lying at the charged interface with the hydrophobic confining matrix as the main factor responsible for this unusual feature, and given a comprehensive picture of dynamics based on a very precise analysis of lifetimes at the interface. We conclude by providing, for the first time to our knowledge, a unique framework for rationalizing the existence of important dynamical heterogeneities in fluids adsorbed in soft confining environments.We have studied by using molecular dynamics computer simulations the dynamics of water confined in ionic surfactant phases, ranging from well ordered lamellar structures to micelles at low and high water loading, respectively. We have analysed in depth the main dynamical features in terms of mean-squared displacements and intermediate scattering functions, and found clear evidence of sub-diffusive behaviour. We have identified water molecules lying at the charged interface with the hydrophobic confining matrix as the main factor responsible for this unusual feature, and given a comprehensive picture of dynamics based on a very precise analysis of lifetimes at the interface. We conclude by providing, for the first time to our knowledge, a unique framework for rationalizing the existence of important dynamical heterogeneities in fluids adsorbed in soft confining environments. Electronic supplementary information (ESI) available. See DOI: 10.1039/C5NR05853H

  3. Development of Compton Radiography Diagnostics for Inertial Confinement Fusion Implosions

    SciTech Connect

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

    2010-11-16

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

  4. Temperature measurements on a HSLA-100 steel confinement vessel

    SciTech Connect

    Lohsen, R.A.

    1998-05-07

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

  5. Nonvolatile semiconductor memory having three dimension charge confinement

    DOEpatents

    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.

  6. Antiproton powered propulsion with magnetically confined plasma engines

    NASA Technical Reports Server (NTRS)

    Lapointe, Michael R.

    1989-01-01

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

  7. Antiproton powered propulsion with magnetically confined plasma engines

    SciTech Connect

    Lapointe, M.R.

    1989-01-01

    The reaction of the matter-antimatter annihilation, with its specific energy being over 250 times the specific energy released in nuclear fusion, is considered as an energy source for spacecraft propulsion. A concept of a magnetically confined pulsed plasma engine is described. In this concept, antiproton beams are injected axially into a pulsed magnetic mirror system, where they annihilate with an initially neutral hydrogen gas; the resulting charge annihilation products transfer energy to the hydrogen propellant, which is then exhausted through one end of the pulsed mirror system to provide thrust. Numerical simulations were developed to calculate the annihilation rate of antiprotons in hydrogen and to follow the resulting ion, muon, and electron/positron number density evolutions. 22 refs.

  8. Investigation B: Laminar confined coaxial entrance flow with heat generation

    NASA Technical Reports Server (NTRS)

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

    1975-01-01

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

  9. 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.

  10. Enhanced Ps-Ps interactions due to quantum confinement.

    PubMed

    Cassidy, D B; Mills, A P

    2011-11-18

    Slow positrons implanted into a porous silica film may efficiently form positronium (Ps) atoms that diffuse through a network of interconnected pores. At high Ps densities, the long lifetime of ortho-positronium atoms is reduced due to Ps-Ps spin dependent interactions at a rate that implies an effective free-space scattering cross section, ?(e) = (3.4 0.5) 10(-14) cm(-2), at least 25 times larger than the theoretical value. This enhanced interaction rate may be explained if the quantum confinement of Ps results in interpore tunneling rates that depend critically on the distribution of pore sizes, so that rather than uniformly sampling the porous matrix Ps diffusion is limited to a small subset of the pores. PMID:22181877

  11. Hydrogen Confinement in Carbon Nanopores: Extreme Densification at Ambient Temperature

    SciTech Connect

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

    2011-01-01

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

  12. Anisotropic confinement effects in a two-dimensional plasma crystal.

    PubMed

    Laut, I; Zhdanov, S K; Rth, C; Thomas, H M; Morfill, G E

    2016-01-01

    The spectral asymmetry of the wave-energy distribution of dust particles during mode-coupling-induced melting, observed for the first time in plasma crystals by Coudel etal. [Phys. Rev. E 89, 053108 (2014)PLEEE81539-375510.1103/PhysRevE.89.053108], is studied theoretically and by molecular-dynamics simulations. It is shown that an anisotropy of the well confining the microparticles selects the directions of preferred particle motion. The observed differences in intensity of waves of opposed directions are explained by a nonvanishing phonon flux. Anisotropic phonon scattering by defects and Umklapp scattering are proposed as possible reasons for the mean phonon flux. PMID:26871180

  13. Turbulent Confinement Models and Transport Solvers for PTRANSP

    NASA Astrophysics Data System (ADS)

    St. John, H. E.; Lao, L. L.; Staebler, G. M.; McCune, D.

    2008-11-01

    The PTRANSP development project is a multi-institutional, multi-year, effort designed to ensure that PTRANSP has the best physics models and computational support possible. Here we describe the first year's contribution that the collaborators at GA have made to this project. The primary result is a standalone module, GCNMP, that is coupled to PTRANSP and makes possible the analysis and simulation of tokamak discharges currently using the most promising confinement models, TGLF and GLF23. The TGLF model is particularly challenging in terms of computational effort required and several MPI based parallel schemes were implemented in order to minimize the time required to obtain solutions to the particle and energy balance equations. Using a client server approach the single cpu environment of PTRANSP remains intact. The reformulation of the transport equations strictly in terms of flows rather than the awkward, unnatural decomposition into diffusivities is presented. Application of TGLF to ITER, DIII-D, and benchmarks against XPTOR are discussed.

  14. 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.

  15. A new approach to the formulation and validation of scaling expressions for plasma confinement in tokamaks

    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.

  16. Energy confinement scaling in the low aspect ratio National Spherical Torus Experiment (NSTX)

    SciTech Connect

    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

    Statistical and systematic 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 (NSTX) 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. Also, this latter trend is 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 BτE on βt 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.

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

    SciTech Connect

    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.

  18. Perspectives on water science: transport and application of confined water

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

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

  19. Fundamental limits of material toughening in molecularly confined polymers

    NASA Astrophysics Data System (ADS)

    Isaacson, Scott G.; Lionti, Krystelle; Volksen, Willi; Magbitang, Teddie P.; Matsuda, Yusuke; Dauskardt, Reinhold H.; Dubois, Geraud

    2016-03-01

    The exceptional mechanical properties of polymer nanocomposites are achieved through intimate mixing of the polymer and inorganic phases, which leads to spatial confinement of the polymer phase. In this study we probe the mechanical and fracture properties of polymers in the extreme limits of molecular confinement, where a stiff inorganic phase confines the polymer chains to dimensions far smaller than their bulk radius of gyration. We show that polymers confined at molecular length scales dissipate energy through a confinement-induced molecular bridging mechanism that is distinct from existing entanglement-based theories of polymer deformation and fracture. We demonstrate that the toughening is controlled by the molecular size and the degree of confinement, but is ultimately limited by the strength of individual molecules.

  20. The confinement effect of inert materials on insensitive high explosives

    NASA Astrophysics Data System (ADS)

    Sun, Yutao; Yu, Ming

    2013-06-01

    The paper aims at investing the confinement effect of inert materials on insensitive high explosives by means of shock polar curve and phenomenological reaction model. The confinement types are categorized by the shock polar theory, which built on the leading shock wave based on the detonation ZND model. If the sonic velocity of the confinement material is less than the CJ velocity of an explosive, the shock polar theory can be utilized. In general, there are several types of interactions that give a ``match'' of the pressure and streamline-deflection across the interface between IHE and confinement material. A two-dimensional Lagrangian hydrodynamic method with three-term Lee-Tarver rate law is used to numerically simulate all types of confinement interactions. The important character of confinement material include: compressibility, thickness, the representative assembled layers, such as bakelite-iron and iron-beryllium. Supported by NSFC No.11101046.

  1. Elevated-Confined Phase-Change Random Access Memory Cells

    NASA Astrophysics Data System (ADS)

    Lee; Koon, Hock; Shi; Luping; Zhao; Rong; Yang; Hongxin; Lim; Guan, Kian; Li; Jianming; Chong; Chong, Tow

    2010-04-01

    A new elevated-confined phase-change random access memory (PCRAM) cell structure to reduce power consumption was proposed. In this proposed structure, the confined phase-change region is sitting on top of a small metal column enclosed by a dielectric at the sides. Hence, more heat can be effectively sustained underneath the phase-change region. As for the conventional structure, the confined phase-change region is sitting directly above a large planar bottom metal electrode, which can easily conduct most of the induced heat away. From simulations, a more uniform temperature profile around the active region and a higher peak temperature at the phase-change layer (PCL) in an elevated-confined structure were observed. Experimental results showed that the elevated-confined PCRAM cell requires a lower programming power and has a better scalability than a conventional confined PCRAM cell.

  2. Simulation of Spheromak Evolution and Energy Confinement

    NASA Astrophysics Data System (ADS)

    Cohen, Bruce I.

    2004-11-01

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

  3. Confinement and Tritium Stripping Systems for APT Tritium Processing

    SciTech Connect

    Hsu, R.H.; 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.

  4. Multichannel effects near confinement-induced resonances in harmonic waveguides

    SciTech Connect

    Melezhik, Vladimir S.; Schmelcher, Peter

    2011-10-15

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

  5. Confinement in Yang Mills: Elements of a Big Picture

    SciTech Connect

    Shifman, M.; Unsal, Mithat; /SLAC /Stanford U., Phys. Dept.

    2008-10-22

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

  6. Generalized Lawson Criteria for Inertial Confinement Fusion

    SciTech Connect

    Tipton, Robert E.

    2015-08-27

    The Lawson Criterion was proposed by John D. Lawson in 1955 as a general measure of the conditions necessary for a magnetic fusion device to reach thermonuclear ignition. Over the years, similar ignition criteria have been proposed which would be suitable for Inertial Confinement Fusion (ICF) designs. This paper will compare and contrast several ICF ignition criteria based on Lawson’s original ideas. Both analytical and numerical results will be presented which will demonstrate that although the various criteria differ in some details, they are closely related and perform similarly as ignition criteria. A simple approximation will also be presented which allows the inference of each ignition parameter directly from the measured data taken on most shots fired at the National Ignition Facility (NIF) with a minimum reliance on computer simulations. Evidence will be presented which indicates that the experimentally inferred ignition parameters on the best NIF shots are very close to the ignition threshold.

  7. Relativistic constituent quark model with infrared confinement

    SciTech Connect

    Branz, Tanja; Faessler, Amand; Gutsche, Thomas; Lyubovitskij, Valery E.; Ivanov, Mikhail A.; Koerner, Juergen G.

    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.

  8. Innovative Confinement Concepts Workshop2002: Conference Report

    NASA Astrophysics Data System (ADS)

    Hooper, E. Bickford; Anderson, David T.; Greeley, John B.; Goldston, Robert J.; Hegna, Chris C.; Heidbrink, William W.; Hoffman, Alan L.; Jardin, Stephen C.; Kesner, Jay; Kirkpatrick, Ronald C.; Logan, B. Grant; Lyon, James F.; Navratil, Gerald A.; Peng, Martin; Perkins, L. John; Prager, Stewart C.; Sarff, John F.; Schaffer, Michael J.; Schoenberg, Kurt F.; Taylor, Robert J.; Tynan, George R.; Zarnstroff, Michael C.

    2001-06-01

    The Innovative Confinement Concepts Workshop, ICC2002, provided a forum for presentations and exchange of ideas on the science and status of innovative concepts in the U.S. Fusion Energy Program. The workshop, held at the University of Maryland on January 22-24, 2002, included oral presentations addressing the important science and status of the concepts, posters focussed on details of the work, a skunkworks for novel ideas, and breakout sessions preparing for the July 2002 fusion energy Snowmass meeting. This report summarizes the oral presentations. A web site (https://wormhole.ucllnl.org/ICC2002/) has been established with the abstracts and many of the presentations, both oral and poster, from the workshop.

  9. Fast ignition schemes for inertial confinement fusion

    NASA Astrophysics Data System (ADS)

    Deutsch, C.

    2003-11-01

    The controlled production of a local hot spot in supercompressed deuterium + tritium fuel is examined in details. Relativistic electron beams (REB) in the MeV and proton beams in the few tens MeV energy range produced by PW-lasers are respectively considered. A strong emphasis is given to the propagation issues due to large density gradients in the outer core of compressed fuel. A specific attention is also paid to the final and complete particle stopping resulting in hot spot generation as well as to the interplay of collective vs. particle stopping at the entrance channel on the low density side in plasma target. Moreover, REB production and fast acceleration mechanisms are also given their due attention. Proton fast ignition looks promising as well as the wedged (cone angle) approach circumventing most of transport uncertainties between critical layer and hot spot. Global engineering perspectives for fast ignition scenario (FIS) driven inertial confinement fusion are also detailed.

  10. Nonideal magnetohydrodynamic instabilities and toroidal magnetic confinement

    SciTech Connect

    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.

  11. Preliminary Results from the Confined Helium Experiment

    NASA Technical Reports Server (NTRS)

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

    1999-01-01

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

  12. Colloidal Organohalide Perovskite Nanoplatelets Exhibiting Quantum Confinement.

    PubMed

    Tyagi, Pooja; Arveson, Sarah M; Tisdale, William A

    2015-05-21

    We prepare colloidal nanoplatelets of methylammonium lead bromide (MAPbBr3) perovskite and compare the optical signatures of excitons in these two-dimensional systems to spherical perovskite nanocrystals and the corresponding bulk phase. We find that excitonic features that had previously been attributed to quantum confinement in MAPbBr3 nanocrystals are in fact a property of the bulk perovskite phase. Furthermore, we find that higher-energy absorption features originate from two-dimensional nanoplatelets, which are present in the nanocrystal reaction product. Upon further purification, we obtain colloidal nanoplatelets with predominantly single unit cell thickness and submicron lateral dimensions, which are stable in solution and exhibit a sharp excitonic absorption feature 0.5 eV blue-shifted from that of the three-dimensional bulk MAPbBr3 phase, representing a new addition to the growing family of colloidal two-dimensional nanostructures. PMID:26263268

  13. Engineering tube shapes to control confined transport

    NASA Astrophysics Data System (ADS)

    Reguera, D.; Rubi, J. M.

    2014-12-01

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

  14. Simulations of artificial swimmers in confined flows

    NASA Astrophysics Data System (ADS)

    Brandt, Luca; Zhu, Lailai; Gjølberg, Eerik

    2012-11-01

    Miniature swimmming robots are potentially powerful for microobject manipulation, such as flow control in lab-on-a-chip, localized drug delivery and screening for diseases. Magnetically driven artificial bacterial flagella (ABF) performing helical motion is advantegous due to high swimming speed and accurate control. Using boundary element method, we numerically investigate the propulsion of ABF in free space and near solid boundaries. Step-out at high actuation frequencies, wobbling and near-wall drifting are documented, in qualitative agreement with recent experiments. We aim to explore the effect of swimmer shape on the performance, thus benefiting design of efficient microswimmers. Propulsion of ABF confined by a solid wall with and without background shear flow is also studied, with a focus on wall-induced hydrodynamic interaction and its influence on the stability of the motion. Funding by VR (the Swedish Research Council) and Linne flow centre at KTH is acknowledged.

  15. Fabrication issues of oxide-confined VCSELs

    SciTech Connect

    Geib, K.M.; Choquette, K.D.; Hou, H.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, sample temperature, carrier gas flow, and bubbler water temperature. Knowledge of these parameters has enable the compilation of oxidation rate data for AlGaAs which exhibits an Arrhenius rate dependence. The compositionally dependent activation energies for Al{sub x}Ga{sub 1-x}As layers of x=1.00, 0.98, and 0.92 are found to be 1.24, 1.75, and 1.88 eV, respectively. 7 figs, 1 tab, 14 refs.

  16. Composite model with three confining hypercolor groups

    SciTech Connect

    Albright, C.H.

    1984-06-01

    A preon model of composite quarks, leptons, and weak bosons is constructed based on the hypercolor group G/sub HC/ = SU(2)/sub TC/ x SU(2) L x SU(2)/sub R/ with a chiral SU(4) hyperflavor symmetry. Two of the hypercolor forces confine the preons into composite fermions which are hypercolor singlets and technifermions belonging to four-, three-, and two-dimensional representations of technicolor. The most-attractive-channel hypothesis leads to technifermion condensates which (1) break the hyperflavor symmetry in stages providing 't Hooft anomaly matching at the first stage, (2) determine the generation structure through a resulting discrete axial Z(m)/sub A/ group, and (3) lead to light-fermion masses through techniboson-exchange graphs. At most three generations of standard quarks and leptons plus two ''mirror'' generations arise in the model with Q, B, and (optionally) L conserved quantum numbers.

  17. Light ion driven inertial confinement fusion

    SciTech Connect

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

    1992-01-01

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

  18. Light ion driven inertial confinement fusion

    SciTech Connect

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

    1992-05-01

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

  19. Confinement-induced resonances in low-dimensional quantum systems.

    PubMed

    Haller, Elmar; Mark, Manfred J; Hart, Russell; Danzl, Johann G; Reichsllner, Lukas; Melezhik, Vladimir; Schmelcher, Peter; Ngerl, Hanns-Christoph

    2010-04-16

    We report on the observation of confinement-induced resonances in strongly interacting quantum-gas systems with tunable interactions for one- and two-dimensional geometry. Atom-atom scattering is substantially modified when the s-wave scattering length approaches the length scale associated with the tight transversal confinement, leading to characteristic loss and heating signatures. Upon introducing an anisotropy for the transversal confinement we observe a splitting of the confinement-induced resonance. With increasing anisotropy additional resonances appear. In the limit of a two-dimensional system we find that one resonance persists. PMID:20481986

  20. Confinement dynamics of a semiflexible chain inside nano-spheres

    NASA Astrophysics Data System (ADS)

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

    2013-07-01

    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.