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Sample records for high confinement influence

  1. CONFINEMENT OF HIGH TEMPERATURE PLASMA

    DOEpatents

    Koenig, H.R.

    1963-05-01

    The confinement of a high temperature plasma in a stellarator in which the magnetic confinement has tended to shift the plasma from the center of the curved, U-shaped end loops is described. Magnetic means are provided for counteracting this tendency of the plasma to be shifted away from the center of the end loops, and in one embodiment this magnetic means is a longitudinally extending magnetic field such as is provided by two sets of parallel conductors bent to follow the U-shaped curvature of the end loops and energized oppositely on the inside and outside of this curvature. (AEC)

  2. The influence of divertor geometry on access to high confinement regimes on the Alcator C-Mod tokamak

    NASA Astrophysics Data System (ADS)

    Hughes, J. W.; Labombard, B.; Hubbard, A.; Marmar, E.; Terry, J.; Rice, J.; Walk, J.; Whyte, D.; Ma, Y.; Cziegler, I.; Edlund, E.; Theiler, C.

    2014-10-01

    The placement of X-point and strike points in a diverted tokamak can have a remarkable impact on properties of the discharge, including thermal and particle confinement. The distinctive divertor of Alcator C-Mod allows us to demonstrate these effects experimentally, as we vary equilibrium shaping to obtain substantial variation of divertor leg length, field line attack angle and divertor baffling. In response to these changes, we observe differences in both L-mode confinement and access to high-confinement regimes (i.e. ELMy H-mode and I-mode). With the ion grad-B drift directed toward the divertor, scanning the strike point can induce ~2× reductions in H-mode power threshold, and can produce a window for I-mode operation with H98 > 1. Recent experiments seek to explore these effects using improved diagnostics, and to extend them to the case with ion grad-B drift directed away from the divertor. Supported by USDoE award DE-FC02-99ER54512.

  3. Access to high-confinement regimes on Alcator C-Mod and the complex influence of divertor geometry

    NASA Astrophysics Data System (ADS)

    Hughes, J. W.; Labombard, B.; Brunner, D.; Hubbard, A.; Terry, J.; Rice, J.; Walk, J.; Cziegler, I.; Edlund, E.; Theiler, C.

    2015-11-01

    Placement of X-points and strike points in a diverted tokamak can have a remarkable impact on plasma properties, including thermal and particle confinement. The distinctive divertor of Alcator C-Mod allows substantial variation of divertor leg length, field line attack angle and divertor baffling, allowing us to induce changes in both L-mode confinement and access to both H-mode and I-mode. With the ion ∇B drift directed toward the divertor, scanning the strike point can induce ~ 2 × reductions in H-mode power threshold, and can produce a window for I-mode operation with H98 > 1 . Detailed high-resolution measurements, spanning the last closed flux surface, provide profiles of key quantities (n, T, ϕ) and their gradients, which are of likely importance in determining whether a discharge evolves an edge transport barrier, or remains in an L-mode state. Advances in Langmuir probes have enabled characterization of both radial profiles and fast (< 1 MHz) fluctuations in L-mode as the L-H threshold power is approached. These data allow new tests of models for H-mode access, especially those attempting to explain the non-monotonic density dependence of the H-mode power threshold through changes in transport and/or turbulence. Supported by U.S. Department of Energy award DE-FC02-99ER54512, using Alcator C-Mod, a DOE Office of Science User Facility.

  4. Influence of the radial profile of the electric potential on the confinement of a high-{beta} two-component plasma in a gas-dynamic trap

    SciTech Connect

    Soldatkina, E. I.; Bagryansky, P. A.; Solomakhin, A. L.

    2008-04-15

    One of the most important problems to be studied in the gas-dynamic trap (GDT) facility is the investigation of MHD stability and cross-field transport in a plasma with a relatively high value of {beta} = {pi}p/B{sup 2}. Recent experiments demonstrated that the radial electric field produced in the plasma by using radial limiters and coaxial end plasma collectors improves plasma stability in axisymmetric magnetic mirror systems without applying special MHD stabilizers. The experimental data presented in this work show that stable plasma confinement can be achieved by producing a radial potential drop across a narrow region near the plasma boundary. Creating radial electric fields of strength 15-40 V/cm causes a shear plasma flow, thereby substantially increasing the plasma confinement time. When all the radial electrodes were grounded, the confinement was unstable and the plasma confinement time was much shorter than the characteristic time of plasma outflow through the magnetic mirrors. Measurements of cross-field plasma fluxes with the use of a specially designed combined probe show that, in confinement modes with differential plasma rotation, transverse particle losses are negligibly small as compared to longitudinal ones and thus can be ignored. It is also shown that, when the GDT plasma is in electric contact with the radial limiters and end collectors, the growth rate of interchange instability decreases considerably; such a contact, however, does not ensure complete MHD stability when the electrodes are at the same potential.

  5. High Efficiency Targets for High Gain Inertial Confinement Fusion.

    DTIC Science & Technology

    1986-09-19

    Inertial Confinement Fusion JOHN H. GARDNER AND STEPHEN E. BODNER Laboratory for Computational Physics DTIC CD ELECTEf OCT 241986 j NU Aproedfr...81425 " 11 TITLE (include Security Classification) High Efficiency Targets for High Gain Inertial Confinement Fusion 12. PERSONAL AUTHOR(S) Gardner, John ...ArearCod) 22c OFFICE SYMBOL % John H. Gardner (202) 767-3055 Code 4040 DO FORM 1473. 84 MAR 83 APR edtion may be used until exhausted SECURITY

  6. High beta and confinement studies on TFTR

    SciTech Connect

    Navratil, G.A.; Bhattacharjee, A.; Iacono, R.; Mauel, M.E.; Sabbagh, S.A. ); Kesner, J. )

    1992-01-01

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

  7. Highly confined photonic nanojet from elliptical particles

    NASA Astrophysics Data System (ADS)

    Jalali, T.; Erni, D.

    2014-07-01

    Elliptically shaped particles with different size and refractive indices have been studied under plane wave illumination using simulation tools such as 2D-FDTD, 2D-MMP, and 3D-MMP. Owing to careful manipulation, the power distribution in the vicinity of the particles opposite boundary resulted in a tightly focused photonic nanojet. Their waists are significantly smaller than the diffraction limit while propagating over several optical wavelengths without significant divergence. In this paper, we report on the manipulation of the particles elliptical shapes and the underlying refractive indices with respect to a maximally confined power distribution in the resulting nanojet which has been parameterized according to both, the beam waist and the beam divergence. The result that elliptical particles (i.e. oblate spheroids) turned out to be superior to spherical ones was underpinned within a highly accurate and fast 3D-MMP simulation using ring multipoles.

  8. Liquid water confined in carbon nanochannels at high temperatures.

    PubMed

    Nagy, G; Gordillo, M C; Guàrdia, E; Martí, J

    2007-11-01

    Structure, hydrogen bonding, electrostatics, dielectric, and dynamical properties of liquid water confined in flat graphene nanochannels are investigated by molecular dynamics simulations. A wide range of temperatures (between 20 and 360 degrees C) have been considered. Molecular structure suffers substantial changes when the system is heated, with a significant loss of structure and hydrogen bonding. In such case, the interface between adsorbed and bulk-like water has a marked tendency to disappear, and the two preferential orientations of water nearby the graphite layers at room temperature are essentially merging above the boiling point. The general trend for the static dielectric constant is its reduction at high temperature states, as compared to ambient conditions. Similarly, residence times of water molecules in adsorbed and bulk-like regions are significantly influenced by temperature, as well. Finally, we observed relevant changes in water diffusion and spectroscopy along the range of temperatures analyzed.

  9. Confinement of hydrogen at high pressure in carbon nanotubes

    DOEpatents

    Lassila, David H [Aptos, CA; Bonner, Brian P [Livermore, CA

    2011-12-13

    A high pressure hydrogen confinement apparatus according to one embodiment includes carbon nanotubes capped at one or both ends thereof with a hydrogen-permeable membrane to enable the high pressure confinement of hydrogen and release of the hydrogen therethrough. A hydrogen confinement apparatus according to another embodiment includes an array of multi-walled carbon nanotubes each having first and second ends, the second ends being capped with palladium (Pd) to enable the high pressure confinement of hydrogen and release of the hydrogen therethrough as a function of palladium temperature, wherein the array of carbon nanotubes is capable of storing hydrogen gas at a pressure of at least 1 GPa for greater than 24 hours. Additional apparatuses and methods are also presented.

  10. Confinement Studies in High Temperature Spheromak Plasmas

    SciTech Connect

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

    2006-10-23

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

  11. 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.

  12. 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.

  13. Velocity alignment leads to high persistence in confined cells

    NASA Astrophysics Data System (ADS)

    Camley, Brian A.; Rappel, Wouter-Jan

    2014-06-01

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

  14. Confined microbubbles at high capillary numbers

    NASA Astrophysics Data System (ADS)

    Sauzade, Martin; Cubaud, Thomas

    2014-11-01

    We experimentally investigate the flow behavior of bubbles in highly viscous silicone oils within various microgeometries. A square focusing section is used to examine the bubble generation process at large capillary numbers. We notably vary the continuous phase viscosity from 1 to 10,000 cS and study the dynamics of interfacial cusps during bubble pinch-off. The resulting segmented flows are then scrutinized in straight microchannels for both dissolving and non-dissolving bubbles. Finally, we examine the motion of bubbles in periodically constricted microchannels over a wide range of flow conditions. Our findings highlight the possibility to control and exploit the interplay between capillary and mass transfer phenomena with highly viscous fluids in microsystems. This work is supported by NSF (CBET-1150389).

  15. Transitions Out of High-Confinement Mode to Lower Confinement Regimes in Tokamaks

    NASA Astrophysics Data System (ADS)

    Eldon, David

    A high-resolution edge Thomson Scattering (TS) system was developed and installed on the DIII-D tokamak, and was then used to study the back transition from High Confinement (H-mode) to Low Confinement (L-mode) in DIII-D. The transient event seen to initiate some back transition sequences is superficially similar to a large type-I ELM, which is described by the linear ideal MHD theory of peeling-ballooning modes. Detailed edge pedestal profile evolution studies during the back transition show that the plasma does not exceed this linear stability limit during the back transition, indicating that the transient is not a type-I ELM event. The E x B shearing rate oE x B and turbulence decorrelation rate oT were then compared before the H-L sequence. The results show that the back transition sequence begins while oE x B is still well above oT, indicating that the sequences observed in these experiments are not triggered by the collapse of the E x B shear layer. Further investigation is made to characterize a coherent density fluctuation whose behavior is linked to back transition sequences. Strategies for avoiding the transient are tested and a reliable method for producing a "soft'' back transition is identified. Such cases are compared to the class of "hard'' transitions in which the pedestal pressure gradient rapidly relaxes.

  16. Influence of rotating resonant magnetic perturbations on particle confinement

    NASA Astrophysics Data System (ADS)

    Hu, Qiming; Yu, Q.; Wang, Nengchao; Shi, Peng; Yi, Bin; Ding, Yonghua; Rao, Bo; Chen, Zhipeng; Gao, Li; Hu, Xiwei; Jin, Hai; Li, Mao; Li, Jianchao; Yu, Kexun; Zhuang, Ge; the J-TEXT Team

    2014-12-01

    The effect of resonant magnetic perturbations (RMPs) on particle confinement is studied in J-TEXT tokamak by using externally applied rotating RMPs. It is found that RMPs cause improved (degraded) particle confinement when its frequency is higher (lower) than the natural m/n = 2/1 tearing mode frequency, and the amount of change in electron density is proportional to the difference between these two frequencies, where m and n are the poloidal and toroidal mode number, respectively. These results reveal the important role of the relative rotation between RMPs and the electron fluid in affecting the particle confinement. The experimental results are compared to numerical ones based on nonlinear two-fluid equations, and quantitative agreement is found.

  17. Influence of confined acoustic phonons on the Radioelectric field in a Quantum well

    NASA Astrophysics Data System (ADS)

    Long, Do Tuan; Quang Bau, Nguyen

    2015-06-01

    The influence of confined acoustic phonons on the Radioelectric field in a quantum well has been studied in the presence of a linearly polarized electromagnetic wave and a laser radiation. By using the quantum kinetic equation for electrons with confined electrons - confined acoustic phonons interaction, the analytical expression for the Radio electric field is obtained. The formula of the Radio electric field contains the quantum number m characterizing the phonons confinement and comes back to the case of unconfined phonons when m reaches to zero. The dependence of the Radio electric field on the frequency of the laser radiation, in case of confined acoustic phonons, is also achieved by numerical method for a specific quantum well AlGaAs/GaAs/AlGaAs. Results show that the Radio electric field has a peak and reaches saturation as the frequency of the laser radiation increases.

  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. High confinement dissipative divertor operation on Alcator C-Mod

    NASA Astrophysics Data System (ADS)

    Goetz, J. A.; LaBombard, B.; Lipschultz, B.; Pitcher, C. S.; Terry, J. L.; Boswell, C.; Gangadhara, S.; Pappas, D.; Weaver, J.; Welch, B.; Boivin, R. L.; Bonoli, P.; Fiore, C.; Granetz, R.; Greenwald, M.; Hubbard, A.; Hutchinson, I.; Irby, J.; Marmar, E.; Mossessian, D.; Porkolab, M.; Rice, J.; Rowan, W. L.; Schilling, G.; Snipes, J.; Takase, Y.; Wolfe, S.; Wukitch, S.

    1999-05-01

    Alcator C-Mod [I. H. Hutchinson et al., Phys. Plasmas 1, 1511 (1994)] has operated a High-confinement-mode (H-mode) plasma together with a dissipative divertor and low core Zeff. The initially attached plasma is characterized by steady-state enhancement factor, HITER89P [P. N. Yushmanov et al., Nucl. Fusion 30, 1999 (1990)], of 1.9, central Zeff of 1.1, and a radiative fraction of ˜50%. Feedback control of a nitrogen gas puff is used to increase radiative losses in both the core/edge and divertor plasmas in almost equal amounts. Simultaneously, the core plasma maintains HITER89P of 1.6 and Zeff of 1.4 in this nearly 100% radiative state. The power and particle flux to the divertor plates have been reduced to very low levels while the core plasma is relatively unchanged by the dissipative nature of the divertor.

  20. Generating High-Brightness Ion Beams for Inertial Confinement Fusion

    NASA Astrophysics Data System (ADS)

    Cuneo, M. E.

    1997-11-01

    The generation of high current density ion beams with applied-B ion diodes showed promise in the late-1980's as an efficient, rep-rate, focusable driver for inertial confinement fusion. These devices use several Tesla insulating magnetic fields to restrict electron motion across anode-cathode gaps of order 1-2 cm, while accelerating ions to generate ≈ 1 kA/cm^2, 5 - 15 MeV beams. These beams have been used to heat hohlraums to about 65 eV. However, meeting the ICF driver requirements for low-divergence and high-brightness lithium ion beams has been more technically challenging than initially thought. Experimental and theoretical work over the last 5 years shows that high-brightness beams meeting the requirements for inertial confinement fusion are possible. The production of these beams requires the simultaneous integration of at least four conditions: 1) rigorous vacuum cleaning techniques for control of undesired anode, cathode, ion source and limiter plasma formation from electrode contaminants to control impurity ions and impedance collapse; 2) carefully tailored insulating magnetic field geometry for uniform beam generation; 3) high magnetic fields (V_crit/V > 2) and other techniques to control the electron sheath and the onset of a high divergence electromagnetic instability that couples strongly to the ion beam; and 4) an active, pre-formed, uniform lithium plasma for low source divergence which is compatible with the above electron-sheath control techniques. These four conditions have never been simultaneously present in any lithium beam experiment, but simulations and experimental tests of individual conditions have been done. The integration of these conditions is a goal of the present ion beam generation program at Sandia. This talk will focus on the vacuum cleaning techniques for ion diodes and pulsed power devices in general, including experimental results obtained on the SABRE and PBFA-II accelerators over the last 3 years. The current status of

  1. Influence of cylindrical submicrometer confinement on the static and dynamic properties in nonyloxycyanobiphenyl (9OCB).

    PubMed

    Pérez-Jubindo, M A; de la Fuente, M R; Diez-Berart, S; López, D O; Salud, J

    2008-05-29

    Broadband dielectric spectroscopy (10(2)-1.9 x 10(9) Hz) and specific heat measurements have been performed on nonyloxycyanobiphenyl (9OCB) in the isotropic (I), nematic (N), and smectic A (SmA) phases confined to 200 nm diameter parallel cylindrical pores of Anopore membranes. Untreated and HTBA-treated membranes have been found to obtain axial and radial confinements, respectively. However, structural or configurational transitions in untreated membranes have been reported to exist in the SmA-mesophase of 9OCB. Both confinements clearly affect the N-I and SmA-N phase transitions. In the axial confinement, the analysis of the specific heat and static dielectric permittivity data leads to a second order SmA-N phase transition, which is known to be weakly first order for bulk 9OCB. Dynamic dielectric measurements have accounted for the different molecular motions in both confinements. On both mesophases, either N or SmA, the relaxation processes in axial configuration are faster than in the bulk. However, in radial confinement, they are either equal or slower than in the bulk. Additionally, there are no differences in the energy barrier hindering the molecular motions between the axial and radial confinements and even in relation to bulk. Likewise, dielectric results suggest that the extension inside the pores of the surface pinned molecular layer (proved to be temperature-dependent) persists at high enough temperature as a residual-thin layer adjacent to the pore wall.

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

    SciTech Connect

    Grierson, Brian A.; Burrell, Keith H.; Nazikian, Raffi M.; Solomon, Wayne M.; Garofalo, Andrea M.; Belli, Emily A.; Staebler, Gary M.; Fenstermacher, Max E.; McKee, George R.; Evans, Todd E.; Orlov, D. M.; Smith, S. P.; Chrobak, C.; Chrystal, C.

    2015-04-17

    Here, impurity transport in the DIII-D tokamak 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 τpe ≈ 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 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.

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

    DOE PAGES

    Grierson, Brian A.; Burrell, Keith H.; Nazikian, Raffi M.; ...

    2015-04-17

    Here, impurity transport in the DIII-D tokamak 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 τp/τe ≈ 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 thanmore » 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 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.« less

  4. Mixing Diagnostics in Confined, High-Speed Droplet Collisions

    NASA Astrophysics Data System (ADS)

    Carroll, Brian; Hidrovo, Carlos

    2012-11-01

    Fast mixing remains a major challenge in droplet-based microfluidics. The low Reynolds number operating regime of most mixing devices signifies orderly flows that are devoid of any inertial characteristics. To increase droplet mixing rates, a novel technique is under development that uses a high Reynolds number gaseous phase for droplet generation and transport and promotes mixing through binary droplet collisions at velocities near 1m/s. Limitations in existing mixing diagnostic methodologies has persuaded cultivation of a new technique for measuring droplet collision mixing in confined microchannels. The technique employs single fluorophore laser-induced fluorescence, custom image processing, and meaningful statistical analysis for monitoring and quantifying mixing in high-speed droplet collisions. Mixing progress is revealed through two statistics that separate the roles of convective rearrangement and molecular diffusion during the mixing process. The end result is a viewing window into the rich dynamics of droplet collisions with spatial and temporal resolutions of 1 μm and 25 μs, respectively. Experimental results obtained across a decade of Reynolds and Peclet numbers reveal a direct link between droplet mixing time and the collision convective timescale. This work provides valuable insight into the emerging field of two-phase gas-liquid microfluidics and opens the door to fundamental research possibilities not offered by traditional oil-based architectures.

  5. Rock Deformation at High Confining Pressure and Temperature.

    DTIC Science & Technology

    debugged, delivered and installed to the contracting agency. Clay specimens of illite, kaolinite and montmorillonite were deformed in tri-axial compression...at 25 and 3000C at a constant confining pressure of 2 kb and a constant strain rate of .0001 sec. The illite and kaolinite are stronger under these...conditions than montmorillonite . Cores from dolomite single crystals were deformed at a confining pressure of 7 kb and temperatures of 300 and 500C

  6. Fault gouge rheology under confined, high-velocity conditions

    NASA Astrophysics Data System (ADS)

    Reches, Z.; Madden, A. S.; Chen, X.

    2012-12-01

    We recently developed the experimental capability to investigate the shear properties of fine-grain gouge under confined conditions and high-velocity. The experimental system includes a rotary apparatus that can apply large displacements of tens of meters, slip velocity of 0.001- 2.0 m/s, and normal stress of 35 MPa (Reches and Lockner, 2010). The key new component is a Confined ROtary Cell (CROC) that can shear a gouge layer either dry or under pore-pressure. The pore pressure is controlled by two syringe pumps. CROC includes a ring-shape gouge chamber of 62.5 mm inner diameter, 81.25 mm outer diameter, and up to 3 mm thick gouge sample. The lower, rotating part of CROC contains the sample chamber, and the upper, stationary part includes the loading, hollow cylinder and setting for temperature, and dilation measurements, and pore-pressure control. Each side of the gouge chamber has two pairs of industrial, spring-energized, self-lubricating, teflon-graphite seals, built for particle media and can work at temperature up to 250 ded C. The space between each of the two sets of seals is pressurized by nitrogen. This design generates 'zero-differential pressure' on the inner seal (which is in contact with the gouge powder), and prevents gouge leaks. For the preliminary dry experiments, we used ~2.0 mm thick layers of room-dry kaolinite powder. Total displacements were on the order of meters and normal stress up to 4 MPa. The initial shear was accommodated by multiple internal slip surfaces within the kaolinite layer accommodated as oriented Riedel shear structures. Later, the shear was localized within a thin, plate-parallel Y-surface. The kaolinite layer was compacted at a quasi-asymptotic rate, and displayed a steady-state friction coefficient of ~ 0.5 with no clear dependence on slip velocity up to 0.15 m/s. Further experiments with loose quartz sand (grain size ~ 125 micron) included both dry runs and pore-pressure (distilled water) controlled runs. The sand was

  7. Influence of Ambient Temperature and Confinement on the Chemical Immobilization of Fallow Deer ( Dama dama ).

    PubMed

    Costa, Giovanna Lucrezia; Nastasi, Bernadette; Musicò, Marcello; Spadola, Filippo; Morici, Manuel; Cucinotta, Giuseppe; Interlandi, Claudia

    2017-04-01

    We used physiological parameters and the duration and quality of anesthesia to compare the effects of two ambient temperatures and of the duration of pre-immobilization confinement on the chemical immobilization of fallow deer. We divided 45 free-ranging fallow deer ( Dama dama ) into two groups: Group A were deer captured in winter (average 12 C), using 1 mg/kg of xylazine and 1 mg/kg of tiletamine-zolazepam; and Group B were deer captured in spring (average 24 C), using 2 mg/kg of xylazine and 1.5 mg/kg of tiletamine-zolazepam, after being confined in a pen. We observed lower mean respiratory rate and oxygen saturation in Group B. In contrast, the mean body temperature and the mean blood lactate concentration were significantly higher in Group B, and quality of anesthesia was better in Group A. Mean induction time (time to achieve recumbency) and durations of recumbency were the same in Groups A and B: approximately 8 and 50 min, respectively. Despite the lower drug dosage, better sedation was obtained in Group A than in group B. The time of year, most likely associated with differences in ambient temperature and in confinement, influenced the recommended dosage for xylazine and tiletamine-zolazepam in fallow deer. As all the animals were sound, we concluded that the only factors that influenced the outcome of the present study were the ambient temperature and the level of stress caused by confinement in the pen.

  8. Residual Confinement in High-Temperature Yang-Mills Theory

    NASA Astrophysics Data System (ADS)

    Maas, A.; Wambach, J.; Grüter, B.; Alkofer, R.

    2005-01-01

    The infrared behavior of Landau gauge gluon and ghost propagators are investigated in Yang-Mills theory at non-vanishing temperatures. Self-consistent solutions are presented for temperatures below the presumed phase transition and in the infinite temperature limit. Gluon confinement is manifest in the infrared behavior of these propagators. As expected confinement prevails below the phase transition. In the infinite-temperature limit a qualitative change is observed: the chromoelectric sector exhibits a near-perturbative behavior while long-range chromomagnetic interactions, mediated by soft ghost modes, are still present. The latter behavior is in agreement with corresponding lattice results. It furthermore implies that part of the gluons are still confined.

  9. Rheology of red blood cells under flow in highly confined microchannels. II. Effect of focusing and confinement.

    PubMed

    Lázaro, Guillermo R; Hernández-Machado, Aurora; Pagonabarraga, Ignacio

    2014-10-07

    We study the focusing of red blood cells and vesicles in pressure-driven flows in highly confined microchannels (10-30 μm), identifying the control parameters that dictate the cell distribution along the channel. Our results show that an increase in the flow velocity leads to a sharper cell distribution in a lateral position of the channel. This position depends on the channel width, with cells flowing at outer (closer to the walls) positions in thicker channels. We also study the relevance of the object shape, exploring the different behaviour of red blood cells and different vesicles. We also analyze the implications of these phenomena in the cell suspension rheology, highlighting the crucial role of the wall confinement in the rheological properties of the suspension.

  10. Influence of boundary conditions and confinement on nonlocal effects in flows of wormlike micellar systems.

    PubMed

    Masselon, Chloé; Colin, Annie; Olmsted, Peter D

    2010-02-01

    In this paper we report on the influence of different geometric and boundary constraints on nonlocal (spatially inhomogeneous) effects in wormlike micellar systems. In a previous paper, nonlocal effects were observable by measuring the local rheological flow curves of micelles flowing in a microchannel under different pressure drops, which appeared to differ from the flow curve measured using conventional rheometry. Here we show that both the confinement and the boundary conditions can influence those nonlocal effects. The role of the nature of the surface is analyzed in detail using a simple scalar model that incorporates inhomogeneities, which captures the flow behavior in both wide and confined geometries. This leads to an estimate for the nonlocal "diffusion" coefficient (i.e., the shear curvature viscosity) which corresponds to a characteristic length from 1 to 10 microm.

  11. Time-dependent Brittle Creep in Rock: The Influence of Confining Pressure and Temperature

    NASA Astrophysics Data System (ADS)

    Meredith, P. G.; Heap, M. J.; Baud, P.; Bell, A. F.; Main, I. G.

    2009-12-01

    The characterization of time-dependent brittle creep deformation is fundamental to understanding the long-term evolution and dynamics of the Earth’s crust. The presence of water promotes environment-dependent stress corrosion cracking that allows rock to deform at a constant stress below its short-term failure stress over extended periods of time. Here we report illustrative results from an experimental study of the influence of an elevated temperature on time-dependent brittle creep in water-saturated samples of Bentheim sandstone (initial porosity, Φ = 23%), Darley Dale sandstone (Φ = 13%) and Crab Orchard sandstones (Φ = 4%). We present data obtained from both conventional, constant stress creep experiments and from stress-stepping creep experiments performed under effective confining pressures in the range 10 MPa to 50 MPa and at temperatures from 20° to 75°C. Deformation was monitored throughout each experiment by measuring simultaneously three proxies for evolving crack damage: (1) axial strain, (2) porosity change and (3) the output of acoustic emission (AE) energy, all as functions of time. Results from conventional creep experiments demonstrate that the primary control on creep strain rate and time-to-failure is the applied differential stress. They also suggest the existence of a critical level of crack damage beyond which deformation accelerates and ultimately leads to sample failure on a localized fault. The influence of effective confining pressure was investigated in stress-stepping experiments. In addition to the expected mechanical influence of elevated effective pressure, our results also demonstrate that stress corrosion cracking is inhibited at higher effective confining pressures, with creep strain rates reduced by about 3 orders of magnitude as effective confining pressure is increased from 10 to 50MPa. We have used the same technique to investigate the influence of an elevated temperature. Our results show that, for the same applied

  12. The influence of electrode biasing on plasma confinement in the J-TEXT tokamak

    NASA Astrophysics Data System (ADS)

    Sun, Yue; Chen, Z. P.; Zhu, T. Z.; Yu, Q.; Zhuang, G.; Nan, J. Y.; Ke, X.; Liu, H.; the J-TEXT Team

    2014-01-01

    The influence of both positive and negative bias on global and plasma-edge parameters has been comparatively studied with a newly designed electrode biasing system in the J-TEXT tokamak. Compared to the 0 V bias case, the global particle confinement of plasma is enhanced under bias with both polarities, with the increments of the central line-averaged density and the soft x-ray emission, as well as the reduction of the edge Hα radiation level. The suppression of plasma-edge fluctuations and turbulent particle transport are obviously observed under bias, in different degrees with different polarities. The potential fluctuation amplitude is observed to be increased at the vicinity of the limiter under positive bias, with the existence of a peaked low-frequency mode characterized as high coherence and near-zero cross-phase poloidally in the edge region, which is not found in the negative bias case. The poloidal correlation length of turbulence is greatly enhanced under bias with both polarities; it shows a positive correlation with the amplitude of the poloidal phase velocity, which is mainly driven by the local Jr × B torque at the plasma edge under bias. The characteristic parameters of intermittent events (i.e. blobs), including amplitude, radial velocity, related particle flux and radial size, decreased dramatically under bias in the edge region.

  13. Highly confined ions store charge more efficiently in supercapacitors.

    PubMed

    Merlet, C; Péan, C; Rotenberg, B; Madden, P A; Daffos, B; Taberna, P-L; Simon, P; Salanne, M

    2013-01-01

    Liquids exhibit specific properties when they are adsorbed in nanoporous structures. This is particularly true in the context of supercapacitors, for which an anomalous increase in performance has been observed for nanoporous electrodes. This enhancement has been traditionally attributed in experimental studies to the effect of confinement of the ions from the electrolyte inside sub-nanometre pores, which is accompanied by their partial desolvation. Here we perform molecular dynamics simulations of realistic supercapacitors and show that this picture is correct at the microscopic scale. We provide a detailed analysis of the various environments experienced by the ions. We pick out four different adsorption types, and we, respectively, label them as edge, planar, hollow and pocket sites upon increase of the coordination of the molecular species by carbon atoms from the electrode. We show that both the desolvation and the local charge stored on the electrode increase with the degree of confinement.

  14. Highly confined ions store charge more efficiently in supercapacitors

    NASA Astrophysics Data System (ADS)

    Merlet, C.; Péan, C.; Rotenberg, B.; Madden, P. A.; Daffos, B.; Taberna, P.-L.; Simon, P.; Salanne, M.

    2013-10-01

    Liquids exhibit specific properties when they are adsorbed in nanoporous structures. This is particularly true in the context of supercapacitors, for which an anomalous increase in performance has been observed for nanoporous electrodes. This enhancement has been traditionally attributed in experimental studies to the effect of confinement of the ions from the electrolyte inside sub-nanometre pores, which is accompanied by their partial desolvation. Here we perform molecular dynamics simulations of realistic supercapacitors and show that this picture is correct at the microscopic scale. We provide a detailed analysis of the various environments experienced by the ions. We pick out four different adsorption types, and we, respectively, label them as edge, planar, hollow and pocket sites upon increase of the coordination of the molecular species by carbon atoms from the electrode. We show that both the desolvation and the local charge stored on the electrode increase with the degree of confinement.

  15. Ground-water ages in confined and unconfined aquifers beneath the High Plains, U. S. A

    SciTech Connect

    Dutton, A.R. . Bureau of Economic Geology)

    1992-01-01

    Ages of confined and unconfined ground waters beneath the High Plains must be better known to evaluate water resources, explain differences in delta D and delta O-18 between the unconfined and confined aquifers, and help interpret Pleistocene and Holocene hydrologic history of the continental interior. Eighteen water samples were collected from a confined aquifer in Dockum Group (Triassic) sandstones beneath the southern High Plains in TX and NM from a confined aquifer in Dakota Formation (Cretaceous) sandstones beneath the central High Plains in southwestern KS, and from a sequence of confined aquifers in Upper Cretaceous to Tertiary rocks beneath the northern Great Plains in eastern WY and western NE. Seven samples were collected from the unconfined High Plains aquifer in the Ogallala Formation (Neogene) beneath the central and northern High Plains. Preliminary calculated ages suggest that waters in the High Plains aquifer are very young, probably less than 1,000 yr, and locally as young as 25 yr. Age of ground water in the deep confined aquifers appears to be 20,000 to 32,000 yr in the different study areas. Age of confined ground water appears to increase with predominant direction of ground-water flow beneath the central and northern High Plains but not beneath the southern High Plains, possibly reflecting greater downward leakage from the unconfined aquifer in the latter area.

  16. Polymer segregation under confinement: Influences of macromolecular crowding and the interaction between the polymer and crowders

    NASA Astrophysics Data System (ADS)

    Chen, Yuhao; Yu, Wancheng; Wang, Jiajun; Luo, Kaifu

    2015-10-01

    Entropy driven polymer segregation in confinements as a model for chromosome separation in bacteria has attracted wide attention; however, the effects of macromolecular crowding and the interaction between the binding protein and the newly replicated DNA on the segregation dynamics are not clear. Using Langevin dynamics simulations, we investigate the influences of crowders and the attractive interaction between the polymer and a small number of crowders on segregation of two overlapping polymers under a cylindrical confinement. We find that the segregation time increases with increasing the volume fraction of crowders due to the slower chain diffusion in crowded environments. For a fixed volume fraction of crowders, the segregation time decreases with increasing the size of crowders. Moreover, the attractive interaction between the polymer and a small number of crowders can significantly facilitate the chain segregation. These results are important for understanding the chromosome segregation in living cells.

  17. Metallic tin quantum sheets confined in graphene toward high-efficiency carbon dioxide electroreduction

    NASA Astrophysics Data System (ADS)

    Lei, Fengcai; Liu, Wei; Sun, Yongfu; Xu, Jiaqi; Liu, Katong; Liang, Liang; Yao, Tao; Pan, Bicai; Wei, Shiqiang; Xie, Yi

    2016-09-01

    Ultrathin metal layers can be highly active carbon dioxide electroreduction catalysts, but may also be prone to oxidation. Here we construct a model of graphene confined ultrathin layers of highly reactive metals, taking the synthetic highly reactive tin quantum sheets confined in graphene as an example. The higher electrochemical active area ensures 9 times larger carbon dioxide adsorption capacity relative to bulk tin, while the highly-conductive graphene favours rate-determining electron transfer from carbon dioxide to its radical anion. The lowered tin-tin coordination numbers, revealed by X-ray absorption fine structure spectroscopy, enable tin quantum sheets confined in graphene to efficiently stabilize the carbon dioxide radical anion, verified by 0.13 volts lowered potential of hydroxyl ion adsorption compared with bulk tin. Hence, the tin quantum sheets confined in graphene show enhanced electrocatalytic activity and stability. This work may provide a promising lead for designing efficient and robust catalysts for electrolytic fuel synthesis.

  18. Laboratory tests to study the influence of rock stress confinement on the performances of TBM discs in tunnels

    NASA Astrophysics Data System (ADS)

    Innaurato, N.; Oggeri, C.; Oreste, P.; Vinai, R.

    2011-06-01

    To clarify some aspects of rock destruction with a disc acting on a high confined tunnel face, a series of tests were carried out to examine fracture mechanisms under an indenter that simulates the tunnel boring machine (TBM) tool action, in the presence of an adjacent groove, when a state of stress (lateral confinement) is imposed on a rock sample. These tests proved the importance of carefully establishing the optimal distance of grooves produced by discs acting on a confined surface, and the value (as a mere order of magnitude) of the increase of the thrust to produce the initiation of chip formation, as long as the confinement pressure becomes greater.

  19. Influence of Aging and Environment on Nanoparticle Chemistry: Implication to Confinement Effects in Nanoceria

    SciTech Connect

    Kuchibhatla, Satyanarayana V N T; Karakoti, Ajay S.; Baer, Donald R.; Samudrala, Saritha; Engelhard, Mark H.; Amonette, James E.; Thevuthasan, Suntharampillai; Seal, Sudipta

    2012-07-05

    The oxidation state switching of cerium in cerium oxide nanoparticles is studied in detail. The influence of synthesis medium, aging time and local environment on the oxidation state switching, between +3 and + 4, is analyzed by tracking the absorption edge using UV-Visible spectroscopy. It is observed that by tuning the local environment, the chemistry of the nanoparticles could be altered. These time dependent, environmentally induced changes likely contribute to inconsistencies in the literature regarding quantum-confinement effects for ceria nanoparticles. The results in this article indicate that there is a need to carry out comprehensive analysis of nanoparticles while considering the influence of synthesis and processing conditions, aging time and local environment.

  20. Influence of Aging and Environment on Nanoparticle Chemistry – Implication to Confinement Effects in Nanoceria

    PubMed Central

    Kuchibhatla, Satyanarayana VNT; Karakoti, A. S.; Baer, D. R.; Samudrala, S.; Engelhard, M. H.; Amonette, J. E.; Thevuthasan, S.; Seal, S.

    2013-01-01

    The oxidation state switching of cerium in cerium oxide nanoparticles is studied in detail. The influence of synthesis medium, aging time and local environment on the oxidation state switching, between +3 and + 4, is analyzed by tracking the absorption edge using UV-Visible spectroscopy. It is observed that by tuning the local environment, the chemistry of the nanoparticles could be altered. These time dependent, environmentally induced changes likely contribute to inconsistencies in the literature regarding quantum-confinement effects for ceria nanoparticles. The results in this article indicate that there is a need to carry out comprehensive analysis of nanoparticles while considering the influence of synthesis and processing conditions, aging time and local environment. PMID:23573300

  1. PCF Based Sensor with High Sensitivity, High Birefringence and Low Confinement Losses for Liquid Analyte Sensing Applications

    PubMed Central

    Ademgil, Huseyin; Haxha, Shyqyri

    2015-01-01

    In this paper, we report a design of high sensitivity Photonic Crystal Fiber (PCF) sensor with high birefringence and low confinement losses for liquid analyte sensing applications. The proposed PCF structures are designed with supplementary elliptical air holes in the core region vertically-shaped V-PCF and horizontally-shaped H-PCF. The full vectorial Finite Element Method (FEM) simulations performed to examine the sensitivity, the confinement losses, the effective refractive index and the modal birefringence features of the proposed elliptical air hole PCF structures. We show that the proposed PCF structures exhibit high relative sensitivity, high birefringence and low confinement losses simultaneously for various analytes. PMID:26694408

  2. 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, 100μm wide stripe LDs with large effective spot size of 1.5μm 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.

  3. Influence of confinement by smooth and rough walls on particle dynamics in dense hard-sphere suspensions.

    PubMed

    Eral, H B; van den Ende, D; Mugele, F; Duits, M H G

    2009-12-01

    We used video microscopy and particle tracking to study the dynamics of confined hard-sphere suspensions. Our fluids consisted of 1.1-microm-diameter silica spheres suspended at volume fractions of 0.33-0.42 in water-dimethyl sulfoxide. Suspensions were confined in a quasiparallel geometry between two glass surfaces: a millimeter-sized rough sphere and a smooth flat wall. First, as the separation distance (H) is decreased from 18 to 1 particle diameter, a transition takes place from a subdiffusive behavior (as in bulk) at large H, to completely caged particle dynamics at small H. These changes are accompanied by a strong decrease in the amplitude of the mean-square displacement (MSD) in the horizontal plane parallel to the confining surfaces. In contrast, the global volume fraction essentially remains constant when H is decreased. Second, measuring the MSD as a function of distance from the confining walls, we found that the MSD is not spatially uniform but smaller close to the walls. This effect is the strongest near the smooth wall where layering takes place. Although confinement also induces local variations in volume fraction, the spatial variations in MSD can be attributed only partially to this effect. The changes in MSD are predominantly a direct effect of the confining surfaces. Hence, both the wall roughness and the separation distance (H) influence the dynamics in confined geometries.

  4. High-Performance of Gas Hydrates in Confined Nanospace for Reversible CH4 /CO2 Storage.

    PubMed

    Casco, Mirian E; Jordá, José L; Rey, Fernando; Fauth, François; Martinez-Escandell, Manuel; Rodríguez-Reinoso, Francisco; Ramos-Fernández, Enrique V; Silvestre-Albero, Joaquín

    2016-07-11

    The molecular exchange of CH4 for CO2 in gas hydrates grown in confined nanospace has been evaluated for the first time using activated carbons as a host structure. The nano-confinement effects taking place inside the carbon cavities and the exceptional physicochemical properties of the carbon structure allows us to accelerate the formation and decomposition process of the gas hydrates from the conventional timescale of hours/days in artificial bulk systems to minutes in confined nanospace. The CH4 /CO2 exchange process is fully reversible with high efficiency at practical temperature and pressure conditions. Furthermore, these activated carbons can be envisaged as promising materials for long-distance natural gas and CO2 transportation because of the combination of a high storage capacity, a high reversibility, and most important, with extremely fast kinetics for gas hydrate formation and release.

  5. 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)

  6. High ionic conductivity in confined bismuth oxide-based heterostructures

    NASA Astrophysics Data System (ADS)

    Sanna, Simone; Esposito, Vincenzo; Christensen, Mogens; Pryds, Nini

    2016-12-01

    Bismuth trioxide in the cubic fluorite phase ( δ - Bi 2 O 3 ) exhibits the highest oxygen ionic conductivity. In this study, we were able to stabilize the pure δ - Bi 2 O 3 at low temperature with no addition of stabilizer but only by engineering the interface, using highly coherent heterostructures made of alternative layers of δ - Bi 2 O 3 and Yttria Stabilized Zirconia (YSZ), deposited by pulsed laser deposition. The resulting [ δ - Bi 2 O 3 / YSZ ] heterostructures are found to be stable over a wide temperature range (500-750 °C) and exhibits stable high ionic conductivity over a long time comparable to the value of the pure δ - Bi 2 O 3 , which is approximately two orders of magnitude higher than the conductivity of YSZ bulk.

  7. Phase behaviour and correlations of parallel hard squares: from highly confined to bulk systems.

    PubMed

    González-Pinto, Miguel; Martínez-Ratón, Yuri; Varga, Szabolcs; Gurin, Peter; Velasco, Enrique

    2016-06-22

    We study a fluid of two-dimensional parallel hard squares in bulk and under confinement in channels, with the aim of evaluating the performance of fundamental-measure theory (FMT). To this purpose, we first analyse the phase behaviour of the bulk system using FMT and Percus-Yevick (PY) theory, and compare the results with molecular dynamics and Monte Carlo simulations. In a second step, we study the confined system and check the results against those obtained from the transfer matrix method and from our own Monte Carlo simulations. Squares are confined to channels with parallel walls at angles of 0° or 45° relative to the diagonals of the parallel hard squares, respectively, which allows for an assessment of the effect of the external-potential symmetry on the fluid structural properties. In general FMT overestimates bulk correlations, predicting the existence of a columnar phase (absent in simulations) prior to crystallization. The equation of state predicted by FMT compares well with simulations, although the PY approach with the virial route is better in some range of packing fractions. The FMT is highly accurate for the structure and correlations of the confined fluid due to the dimensional crossover property fulfilled by the theory. Both density profiles and equations of state of the confined system are accurately predicted by the theory. The highly non-uniform pair correlations inside the channel are also very well described by FMT.

  8. Influence of stochastic magnetic fields on the confinement of runaway electrons and thermal electron energy in tokamaks

    SciTech Connect

    Mynick, H.E.; Strachan, J.D.

    1980-07-01

    The ratio of the runaway electron confinement to thermal electron energy confinement is derived for tokamaks where both processes are determined by free streaming along stochastic magnetic field lines. The runaway electron confinement is enhanced at high runaway electron energies due to phase averaging over the magnetic perturbations when the runaway electron drift surfaces are dislaced from the magnetic surfaces. Comparison with experimental data from LT-3, ORMAK, PLT, ST, and TM-3 indicates that magnetic stochasticity may explain the relative transport rates of runaways and thermal electron energy.

  9. High convergence, indirect drive inertial confinement fusion experiments at Nova

    SciTech Connect

    Lerche, R.A.; Cable, M.D.; Hatchett, S.P.

    1995-06-02

    High convergence, indirect drive implosion experiments have been done at the Nova Laser Facility. The targets were deuterium and deuterium/tritium filled, glass microballoons driven symmetrically by x rays produced in a surrounding uranium hohlraum. Implosions achieved convergence ratios of 24:1 with fuel densities of 19 g/cm{sup 3}; this is equivalent to the range required for the hot spot of ignition scale capsules. The implosions used a shaped drive and were well characterized by a variety of laser and target measurements. The primary measurement was the fuel density using the secondary neutron technique (neutrons from the reaction {sup 2}H({sup 3}H,n){sup 4}He in initially pure deuterium fuel). Laser measurements include power, energy and pointing. Simultaneous measurement of neutron yield, fusion reaction rate, and x-ray images provide additional information about the implosion process. Computer models are in good agreement with measured results.

  10. Metallic tin quantum sheets confined in graphene toward high-efficiency carbon dioxide electroreduction

    PubMed Central

    Lei, Fengcai; Liu, Wei; Sun, Yongfu; Xu, Jiaqi; Liu, Katong; Liang, Liang; Yao, Tao; Pan, Bicai; Wei, Shiqiang; Xie, Yi

    2016-01-01

    Ultrathin metal layers can be highly active carbon dioxide electroreduction catalysts, but may also be prone to oxidation. Here we construct a model of graphene confined ultrathin layers of highly reactive metals, taking the synthetic highly reactive tin quantum sheets confined in graphene as an example. The higher electrochemical active area ensures 9 times larger carbon dioxide adsorption capacity relative to bulk tin, while the highly-conductive graphene favours rate-determining electron transfer from carbon dioxide to its radical anion. The lowered tin–tin coordination numbers, revealed by X-ray absorption fine structure spectroscopy, enable tin quantum sheets confined in graphene to efficiently stabilize the carbon dioxide radical anion, verified by 0.13 volts lowered potential of hydroxyl ion adsorption compared with bulk tin. Hence, the tin quantum sheets confined in graphene show enhanced electrocatalytic activity and stability. This work may provide a promising lead for designing efficient and robust catalysts for electrolytic fuel synthesis. PMID:27585984

  11. Observation of sub-detonative responses in confined high density HMX-based PBXs

    NASA Astrophysics Data System (ADS)

    Cumming, Andrew; Wood, Andrew; Steward, Paul; Ottley, Philip; Gould, Peter; Lewtas, Ian

    2015-06-01

    This paper describes experiments and modelling aimed at understanding the behaviour of highly loaded (90%-95%) pressed HMX-based PBXs, when subjected to shock compression and ignition by means of distinct mechanical and thermal insults under confinement. In order to separate the role of the stimuli, a test has been designed where a metal impactor is propelled at test samples using a well characterised propellant over a range of velocities to produce various levels of mechanical damage. The impactor is then heated using a characterised pyrotechnic composition which ignites the mechanically damaged explosive. Tubes have been designed to examine the effect of confinement at burst pressures of 218.5MPa and 120MPa. The high confinement tubes employ polycarbonate windows and the low confinement tubes are manufactured from polycarbonate blocks to allow the reaction of the energetic material to be captured using high-speed video. Tests carried out using these tubes have given a good insight into the processes occurring. Modelling runs have predicted an oscillating compressive wave in the explosive and considerable damage at either end of the explosive column. The latter leads to potential deconsolidation once the donor charge has burnt out allowing increased burning and violence.

  12. Improved confinement in JET high β plasmas with an ITER-like wall

    NASA Astrophysics Data System (ADS)

    Challis, C. D.; Garcia, J.; Beurskens, M.; Buratti, P.; Delabie, E.; Drewelow, P.; Frassinetti, L.; Giroud, C.; Hawkes, N.; Hobirk, J.; Joffrin, E.; Keeling, D.; King, D. B.; Maggi, C. F.; Mailloux, J.; Marchetto, C.; McDonald, D.; Nunes, I.; Pucella, G.; Saarelma, S.; Simpson, J.; Contributors, JET

    2015-05-01

    The replacement of the JET carbon wall (C-wall) by a Be/W ITER-like wall (ILW) has affected the plasma energy confinement. To investigate this, experiments have been performed with both the C-wall and ILW to vary the heating power over a wide range for plasmas with different shapes. It was found that the power degradation of thermal energy confinement was weak with the ILW; much weaker than the IPB98(y,2) scaling and resulting in an increase in normalized confinement from H98 ˜ 0.9 at βN ˜ 1.5 to H98 ˜ 1.2-1.3 at βN ˜ 2.5 - 3.0 as the power was increased (where H98 = τE/τIPB98(y,2) and βN = βTBT/aIP in % T/mMA). This reproduces the general trend in JET of higher normalized confinement in the so-called ‘hybrid’ domain, where normalized β is typically above 2.5, compared with ‘baseline’ ELMy H-mode plasmas with βN ˜ 1.5 - 2.0. This weak power degradation of confinement, which was also seen with the C-wall experiments at low triangularity, is due to both increased edge pedestal pressure and core pressure peaking at high power. By contrast, the high triangularity C-wall plasmas exhibited elevated H98 over a wide power range with strong, IPB98(y,2)-like, power degradation. This strong power degradation of confinement appears to be linked to an increase in the source of neutral particles from the wall as the power increased, an effect that was not reproduced with the ILW. The reason for the loss of improved confinement domain at low power with the ILW is yet to be clarified, but contributing factors may include changes in the rate of gas injection, wall recycling, plasma composition and radiation. The results presented in this paper show that the choice of wall materials can strongly affect plasma performance, even changing confinement scalings that are relied upon for extrapolation to future devices.

  13. Angle of Observation Influence on Emission Signal from Spatially Confined Laser-Induced Plasmas.

    PubMed

    Weiss, Jiri; Cabalín, Luisa Maria; Laserna, J Javier

    2017-01-01

    The present work focuses on the influence of the angle of observation on the emission signal from copper plasmas. Plasma plumes have been generated inside a home-made chamber consisting of two parallel glass windows spaced by 2.5 mm. This chamber allows observing plasma plumes from different collection angles throughout their perimeter, spanning from 20° to 80° with respect to the surface of the Cu target. In order to minimize the observed volume of the plasma, measurements were made from the closest distance possible through a metallic hollow tube. Single-pulse and collinear double-pulse excitation schemes with a Nd:YAG laser (1064 nm, 5 ns) have been investigated. The results have shown that the selection of the best angle to collect light from the plasma is related to the excitation mode. On the other hand, the shot-to-shot signal variability has been found to depend on the shape of plasma plumes. In single-pulse excitation, a good correlation between the observed laser-induced breakdown spectroscopy (LIBS) emission (from spatially confined plumes) and their integrated signal of plasma image has been ascertained. However, this fact was less evident in double-pulse LIBS, which could be due to a different mechanism involved in the ablation process.

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

    PubMed

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

    2014-08-19

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

  15. Current-confinement structure and extremely high current density in organic light-emitting transistors.

    PubMed

    Sawabe, Kosuke; Imakawa, Masaki; Nakano, Masaki; Yamao, Takeshi; Hotta, Shu; Iwasa, Yoshihiro; Takenobu, Taishi

    2012-12-04

    Extremely high current densities are realized in single-crystal ambipolar light-emitting transistors using an electron-injection buffer layer and a current-confinement structure via laser etching. Moreover, a linear increase in the luminance was observed at current densities of up to 1 kA cm(-2) , which is an efficiency-preservation improvement of three orders of magnitude over conventional organic light-emitting diodes (OLEDs) at high current densities.

  16. Confined Tension and Triaxial Extension Tests on Eglin High-Strength Concrete

    DTIC Science & Technology

    2014-10-17

    AFRL-RW-EG-TR-2014-120 Confined Tension and Triaxial Extension Tests on Eglin High-Strength Concrete Lance...EXTENSION TESTS ON EGLIN HIGH-STRENGTH CONCRETE FA8651-12-D-0309, Task 005 N/A 2502 9210 W0DT (1) Lance Besaw, Applied Research Associates, Inc. (2...models. All concretes exhibit higher strength in compression than in tension, therefore it is critical to understand the tensile properties of such

  17. Sequential Indentation Tests to Investigate the Influence of Confining Stress on Rock Breakage by Tunnel Boring Machine Cutter in a Biaxial State

    NASA Astrophysics Data System (ADS)

    Liu, Jie; Cao, Ping; Han, Dongya

    2016-04-01

    The influence of confining stress on rock breakage by a tunnel boring machine cutter was investigated by conducting sequential indentation tests in a biaxial state. Combined with morphology measurements of breaking grooves and an analysis of surface and internal crack propagation between nicks, the effects of maximum confining stress and minimum stress on indentation efficiency, crack propagation and chip formation were investigated. Indentation tests and morphology measurements show that increasing a maximum confining stress will result in increased consumed energy in indentations, enlarged groove volumes and promoted indentation efficiency when the corresponding minimum confining stress is fixed. The energy consumed in indentations will increase with increase in minimum confining stress, however, because of the decreased groove volumes as the minimum confining stress increases, the efficiency will decrease. Observations of surface crack propagation show that more intensive fractures will be induced as the maximum confining stress increases, whereas the opposite occurs for an increase of minimum confining stress. An observation of the middle section, cracks and chips shows that as the maximum confining stress increases, chips tend to form in deeper parts when the minimum confining stress is fixed, whereas they tend to formed in shallower parts as the minimum confining stress increases when the maximum confining stress is fixed.

  18. The influence of the stagnation zone on the fluid dynamics at the nozzle exit of a confined and submerged impinging jet

    NASA Astrophysics Data System (ADS)

    Jeffers, Nicholas; Stafford, Jason; Conway, Ciaran; Punch, Jeff; Walsh, Edmond

    2016-02-01

    Low profile impinging jets provide a means to achieve high heat transfer coefficients while occupying a small quantity of space. Consequently, they are found in many engineering applications such as electronics cooling, annealing of metals, food processing, and others. This paper investigates the influence of the stagnation zone fluid dynamics on the nozzle exit flow condition of a low profile, submerged, and confined impinging water jet. The jet was geometrically constrained to a round, 16-mm diameter, square-edged nozzle at a jet exit to target surface spacing ( H/ D) that varied between 0.25 < {{ H}{/}{ D}} < 8.75. The influence of turbulent flow regimes is the main focus of this paper; however, laminar flow data are also presented between 1350 < Re < 17{,}300. A custom measurement facility was designed and commissioned to utilise particle image velocimetry in order to quantitatively measure the fluid dynamics both before and after the jet exits its nozzle. The velocity profiles are normalised with the mean velocity across the nozzle exit, and turbulence statistics are also presented. The primary objective of this paper is to present accurate flow profiles across the nozzle exit of an impinging jet confined to a low H/ D, with a view to guide the boundary conditions chosen for numerical simulations confined to similar constraints. The results revealed in this paper suggest that the fluid dynamics in the stagnation zone strongly influences the nozzle exit velocity profile at confinement heights between 0 < {{ H}{/}{ D}} < 1. This is of particular relevance with regard to the choice of inlet boundary conditions in numerical models, and it was found that it is necessary to model a jet tube length {{ L}{/}{ D}} > 0.5—where D is the inner diameter of the jet—in order to minimise modelling uncertainty.

  19. Influence of the rotation on the natural frequencies of a submerged-confined disk in water

    NASA Astrophysics Data System (ADS)

    Presas, Alexandre; Valentin, David; Egusquiza, Eduard; Valero, Carme; Seidel, Ulrich

    2015-02-01

    In this paper, the effect of the rotation on the natural frequencies and mode shapes of a submerged-confined disk inside a casing with water is studied analytically, numerically and experimentally. To analyze the disk behavior, an analytical model is developed. The model assumes the thin-plate theory for the disk vibration and the Laplace Equation for the velocity potential of the flow on the upper and lower parts of the disk, considering a constant rotating speed of water for each part. A CFD simulation of the flow inside the tank has been performed in order to determine the averaged rotating speed of the water on the upper and lower parts of the disk for different velocities. The averaged rotating speed is introduced in the analytical model and in a FEM numerical model of the test rig. For the experimental investigation a test rig has been developed. It consists of a disk rotating inside a casing filled with water; the rotating speed can be varied from 0 to 8 Hz. The disk is made of stainless steel having a diameter of 400 mm and a thickness of 8 mm. The radial gap between the disk and the casing is of 7 mm, and the axial gap between the disk surface and the upper cover is 10 mm. For the excitation, four piezoelectric patches attached on the disk have been used. In order to measure the response miniature accelerometers are placed on the disk surface at several locations. Signals are transmitted from the rotating to the stationary system through a slip ring located at the tip of the shaft. Natural frequencies and mode shapes of the rotating disk are obtained experimentally for several rotating speeds. These results are discussed in detail and compared with those ones obtained with the analytical model and numerical simulation. The influence of the rotation of the surrounding water with respect to the disk is determined in this paper.

  20. Observation of the hot electron interchange instability in a high beta dipolar confined plasma

    NASA Astrophysics Data System (ADS)

    Ortiz, Eugenio Enrique

    In this thesis the first study of the high beta, hot electron interchange (HEI) instability in a laboratory, dipolar confined plasma is presented. The Levitated Dipole Experiment (LDX) is a new research facility that explores the confinement and stability of plasma created within the dipole field produced by a strong superconducting magnet. In initial experiments long-pulse, quasi-steady state microwave discharges lasting more than 10 sec have been produced with equilibria having peak beta values of 20%. Creation of high-pressure, high beta plasma is possible only when intense HEI instabilities are stabilized by sufficiently high background plasma density. LDX plasma exist within one of three regimes characterized by its response to heating and fueling. The observed HEI instability depends on the regime and can take one of three forms: as quasiperiodic bursts during the low density, low beta plasma regime, as local high beta relaxation events in the high beta plasma regime, and as global, intense energy relaxation bursts, both in the high beta and afterglow plasma regimes. Measurements of the HEI instability are made using high-impedance, floating potential probes and fast Mirnov coils. Analysis of these signals reveals the extent of the transport during high beta plasmas. During intense high beta HEI instabilities, fluctuations at the edge significantly exceed the magnitude of the equilibrium field generated by the high beta electrons and energetic electron confinement ends in under 100 musec. For heated plasmas, one of the consequences of the observed high beta transport is the presence of hysteresis in the neutral gas fueling required to stabilize and maintain the high beta plasma. Finally, a nonlinear, self-consistent numerical simulation of the growth and saturation of the HEI instability has been adapted for LDX and compared to experimental observations.

  1. High pressure induced phase transition and superdiffusion in anomalous fluid confined in flexible nanopores

    SciTech Connect

    Bordin, José Rafael; Krott, Leandro B. Barbosa, Marcia C.

    2014-10-14

    The behavior of a confined spherical symmetric anomalous fluid under high external pressure was studied with Molecular Dynamics simulations. The fluid is modeled by a core-softened potential with two characteristic length scales, which in bulk reproduces the dynamical, thermodynamical, and structural anomalous behavior observed for water and other anomalous fluids. Our findings show that this system has a superdiffusion regime for sufficient high pressure and low temperature. As well, our results indicate that this superdiffusive regime is strongly related with the fluid structural properties and the superdiffusion to diffusion transition is a first order phase transition. We show how the simulation time and statistics are important to obtain the correct dynamical behavior of the confined fluid. Our results are discussed on the basis of the two length scales.

  2. Investigation of physical processes limiting plasma density in high confinement mode discharges on DIII-D

    NASA Astrophysics Data System (ADS)

    Maingi, R.; Mahdavi, M. A.; Jernigan, T. C.; La Haye, R. J.; Hyatt, A. W.; Baylor, L. R.; Whyte, D. G.; Wade, M. R.; Petrie, T. W.; Cuthbertson, J. W.; Leonard, A. W.; Murakami, M.; Snider, R. T.; Stambaugh, R. D.; Watkins, J. G.; West, W. P.; Wood, R. D.

    1997-05-01

    A series of experiments was conducted on the DIII-D tokamak [J. L. Luxon and L. G. Davis, Fusion Technol. 8, 441 (1985)] to investigate the physical processes which limit density in high confinement mode (H-mode) discharges. The typical H-mode to low confinement mode (L-mode) transition limit at high density near the empirical Greenwald density limit [M. Greenwald et al., Nucl. Fusion 28, 2199 (1988)] was avoided by divertor pumping, which reduced divertor neutral pressure and prevented formation of a high density, intense radiation zone (MARFE) near the X-point. It was determined that the density decay time after pellet injection was independent of density relative to the Greenwald limit and increased nonlinearly with the plasma current. Magnetohydrodynamic (MHD) activity in pellet-fueled plasmas was observed at all power levels, and often caused unacceptable confinement degradation, except when the neutral beam injected (NBI) power was ⩽3 MW. Formation of MARFEs on closed field lines was avoided with low safety factor (q) operation but was observed at high q, qualitatively consistent with theory. By using pellet fueling and optimizing discharge parameters to avoid each of these limits, an operational space was accessed in which density ˜1.5×Greenwald limit was achieved for 600 ms, and good H-mode confinement was maintained for 300 ms of the density flat-top. More significantly, the density was successfully increased to the limit where a central radiative collapse was observed, the most fundamental density limit in tokamaks.

  3. Enhancement of high harmonic generation by confining electron motion in plasmonic nanostrutures.

    PubMed

    Ciappina, M F; Aćimović, Srdjan S; Shaaran, T; Biegert, J; Quidant, R; Lewenstein, M

    2012-11-19

    We study high-order harmonic generation (HHG) resulting from the illumination of plasmonic nanostructures with a short laser pulse of long wavelength. We demonstrate that both the confinement of the electron motion and the inhomogeneous character of the laser electric field play an important role in the HHG process and lead to a significant increase of the harmonic cutoff. In particular, in bow-tie nanostructures with small gaps, electron trajectories with large excursion amplitudes experience significant confinement and their contribution is essentially suppressed. In order to understand and characterize this feature, we combine the numerical solution of the time-dependent Schrödinger equation (TDSE) with the electric fields obtained from 3D finite element simulations. We employ time-frequency analysis to extract more detailed information from the TDSE results and classical tools to explain the extended harmonic spectra. The spatial inhomogeneity of the laser electric field modifies substantially the electron trajectories and contributes also to cutoff increase.

  4. New Steady-State Quiescent High-Confinement Plasma in an Experimental Advanced Superconducting Tokamak

    NASA Astrophysics Data System (ADS)

    Hu, J. S.; Sun, Z.; Guo, H. Y.; Li, J. G.; Wan, B. N.; Wang, H. Q.; Ding, S. Y.; Xu, G. S.; Liang, Y. F.; Mansfield, D. K.; Maingi, R.; Zou, X. L.; Wang, L.; Ren, J.; Zuo, G. Z.; Zhang, L.; Duan, Y. M.; Shi, T. H.; Hu, L. Q.; East Team

    2015-02-01

    A critical challenge facing the basic long-pulse high-confinement operation scenario (H mode) for ITER is to control a magnetohydrodynamic (MHD) instability, known as the edge localized mode (ELM), which leads to cyclical high peak heat and particle fluxes at the plasma facing components. A breakthrough is made in the Experimental Advanced Superconducting Tokamak in achieving a new steady-state H mode without the presence of ELMs for a duration exceeding hundreds of energy confinement times, by using a novel technique of continuous real-time injection of a lithium (Li) aerosol into the edge plasma. The steady-state ELM-free H mode is accompanied by a strong edge coherent MHD mode (ECM) at a frequency of 35-40 kHz with a poloidal wavelength of 10.2 cm in the ion diamagnetic drift direction, providing continuous heat and particle exhaust, thus preventing the transient heat deposition on plasma facing components and impurity accumulation in the confined plasma. It is truly remarkable that Li injection appears to promote the growth of the ECM, owing to the increase in Li concentration and hence collisionality at the edge, as predicted by GYRO simulations. This new steady-state ELM-free H -mode regime, enabled by real-time Li injection, may open a new avenue for next-step fusion development.

  5. Observation of sub-detonation response in confined high density HMX based PBXs

    NASA Astrophysics Data System (ADS)

    Cook, M. D.; Wood, A. D.; Ottley, P. R.; Cheese, P. J.

    2014-05-01

    This paper describes experiments and modelling aimed at understanding the behaviour of highly loaded (90%-95%) pressed HMX-based PBX compositions, when subjected to shock compression and ignition, by means of a propellant donor charge, under confinement. Such tests are routinely carried out in the UK on new formulations to determine their burn to violent reaction characteristics. The Bullseye propellant donor charge has been characterised in terms of pressure and temperature output. A range of tubes have been designed to examine the contribution of tube material properties (steel versus aluminium, 218.5 MPa) and to examine the effect of reduced confinement (120 MPa). For the reduced confinement scenario polycarbonate as well as steel and aluminium vessels have been designed which allow the reaction of the energetic material to be captured using a Phantom high-speed camera. In particular, tests carried out in the polycarbonate tubes have given a good insight of the processes occurring. Preliminary hydrocode modelling runs predicted an oscillating compressive wave in the explosive and considerable damage at either end of the explosive column. The latter leads to potential deconsolidation once the donor charge has burnt out allowing increased burning and violence.

  6. Formation of High-Beta Plasma and Stable Confinement of Toroidal Electron Plasma in RT-1

    NASA Astrophysics Data System (ADS)

    Saitoh, Haruhiko

    2010-11-01

    The Ring Trap 1 (RT-1) device is a laboratory magnetosphere generated by a levitated superconducting magnet. The goals of RT-1 are to realize stable formation of ultra high-beta plasma suitable for burning advanced fusion fuels, and confinement of toroidal non-neutral plasmas including antimatter particles. RT- 1 has produced high-beta plasma in the magnetospheric configuration. The effects of coil levitation and geomagnetic field compensation [Y. Yano et al., Plasma Fusion Res. 4, 039] resulted drastic improvements of the plasma properties, and a maximum local beta value exceeded 70%. Because plasma is generated by electron cyclotron resonance heating (ECH) in the present experiment, the plasma pressure is mainly due to hot electrons, whose bremsstrahlung was observed with an x-ray CCD camera. The pressure profiles have rather steep gradient near the superconducting coil in the strong field region. The decay rates of magnetic probe and interferometer signals have different time constants, suggesting multiple temperature components. The energy confinement time estimated from the input RF power and stored magnetic energy is on the order of 1s, which is comparable to the decay time constant of the density of hot electron component. Pure electron plasma experiments are also conducted in RT-1. Radial profiles of electrostatic potential and electron density showed that the plasma rigidly rotates in the toroidal direction in the stable confinement phase. Long time confinement of toroidal non- neutral plasma for more than 300s and inward particle diffusion to strong field regions, caused by the activation of the diocotron (Kelvin-Helmholtz) instability, have been realized [Z. Yoshida et al., Phys. Rev. Lett. 104, 235004].

  7. Bubble confinement in flow boiling of FC-72 in a ''rectangular'' microchannel of high aspect ratio

    SciTech Connect

    Barber, Jacqueline; Brutin, David; Tadrist, Lounes; Sefiane, Khellil

    2010-11-15

    Boiling in microchannels remains elusive due to the lack of full understanding of the mechanisms involved. A powerful tool in achieving better comprehension of the mechanisms is detailed imaging and analysis of the two-phase flow at a fundamental level. Boiling is induced in a single microchannel geometry (hydraulic diameter 727 {mu}m), using a refrigerant FC-72, to investigate the effect of channel confinement on bubble growth. A transparent, metallic, conductive deposit has been developed on the exterior of the rectangular microchannel, allowing simultaneous uniform heating and visualisation to be achieved. The data presented in this paper is for a particular case with a uniform heat flux applied to the microchannel and inlet liquid mass flowrate held constant. In conjunction with obtaining high-speed images and videos, sensitive pressure sensors are used to record the pressure drop across the microchannel over time. Bubble nucleation and growth, as well as periodic slug flow, are observed in the microchannel test section. The periodic pressure fluctuations evidenced across the microchannel are caused by the bubble dynamics and instances of vapour blockage during confined bubble growth in the channel. The variation of the aspect ratio and the interface velocities of the growing vapour slug over time, are all observed and analysed. We follow visually the nucleation and subsequent both 'free' and 'confined' growth of a vapour bubble during flow boiling of FC-72 in a microchannel, from analysis of our results, images and video sequences with the corresponding pressure data obtained. (author)

  8. Combining reactive and configurational-bias Monte Carlo: Confinement influence on the propene metathesis reaction system in various zeolites

    NASA Astrophysics Data System (ADS)

    Jakobtorweihen, S.; Hansen, N.; Keil, F. J.

    2006-12-01

    In order to efficiently calculate chemical equilibria of large molecules in a confined environment the reactive Monte Carlo technique is combined with the configurational-bias Monte Carlo approach. To prove that detailed balance is fulfilled the acceptance rule for this combination of particular Monte Carlo techniques is derived in detail. Notably, by using this derivation all other acceptance rules of any Monte Carlo trial moves usually carried out in combination with the configurational-bias Monte Carlo approach can be deduced from it. As an application of the combination of reactive and configurational-bias Monte Carlo the influence of different zeolitic confinements (MFI, TON, LTL, and FER) on the reaction equilibrium and the selectivity of the propene metathesis reaction system was investigated. Compared to the bulk phase the conversion is increased significantly. The authors study this reaction system in the temperature range between 300 and 600K, and the pressure range from 1to7bars. In contrast to the bulk phase, pressure and temperature have a strong influence on the composition of the reaction mixture in confinement. At low pressures and temperatures both conversion and selectivity are highest. Furthermore, the equilibrium composition is strongly dependent on the type of zeolite. This demonstrates the important role of the host structure in catalytic systems.

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

    SciTech Connect

    Garnier, D.T.; Hansen, A.; Mauel, M.E.; Ortiz, E.; Boxer, A.C.; Ellsworth, J.; Karim, I.; Kesner, J.; Mahar, S.; Roach, A.

    2006-05-15

    The Levitated Dipole Experiment (LDX) [J. Kesner et al., in Fusion Energy 1998, 1165 (1999)] is a new research facility that is exploring the confinement and stability of plasma created within the dipole field produced by a strong superconducting magnet. Unlike other configurations in which stability depends on curvature and magnetic shear, magnetohydrodynamic stability of a dipole derives from plasma compressibility. Theoretically, the dipole magnetic geometry can stabilize a centrally peaked plasma pressure that exceeds the local magnetic pressure ({beta}>1), and the absence of magnetic shear allows particle and energy confinement to decouple. In initial experiments, long-pulse, quasi-steady-state microwave discharges lasting more than 10 s have been produced that are consistent with equilibria having peak beta values of 20%. Detailed measurements have been made of discharge evolution, plasma dynamics and instability, and the roles of gas fueling, microwave power deposition profiles, and plasma boundary shape. In these initial experiments, the high-field superconducting floating coil was supported by three thin supports. The plasma is created by multifrequency electron cyclotron resonance heating at 2.45 and 6.4 GHz, and a population of energetic electrons, with mean energies above 50 keV, dominates the plasma pressure. Creation of high-pressure, high-beta plasma is possible only when intense hot electron interchange instabilities are stabilized by sufficiently high background plasma density. A dramatic transition from a low-density, low-beta regime to a more quiescent, high-beta regime is observed when the plasma fueling rate and confinement time become sufficiently large.

  10. Polymorphism and polyamorphism in bilayer water confined to slit nanopore under high pressure

    PubMed Central

    Bai, Jaeil; Zeng, Xiao Cheng

    2012-01-01

    A distinctive physical property of bulk water is its rich solid-state phase behavior, which includes 15 crystalline (ice I–ice XIV) and at least 3 glassy forms of water, namely, low-density amorphous, high-density amorphous, and very-high-density amorphous (VHDA). Nanoscale confinement adds a new physical variable that can result in a wealth of new quasi-2D phases of ice and amorphous ice. Previous computer simulations have revealed that when water is confined between two flat hydrophobic plates about 7–9 Å apart, numerous bilayer (BL) ices (or polymorphs) can arise [e.g., BL-hexagonal ice (BL-ice I)]. Indeed, growth of the BL-ice I through vapor deposition on graphene/Pt(111) substrate has been achieved experimentally. Herein, we report computer simulation evidence of pressure-induced amorphization from BL-ice I to BL-amorphous and then to BL-VHDA2 at 250 K and 3 GPa. In particular, BL-VHDA2 can transform into BL-VHDA1 via decompression from 3 to 1.5 GPa at 250 K. This phenomenon of 2D polyamorphic transition is akin to the pressure-induced amorphization in 3D ice (e.g., from hexagonal ice to HDA and then to VHDA via isobaric annealing). Moreover, when the BL-ice I is compressed instantly to 6 GPa, a new very-high-density BL ice is formed. This new phase of BL ice can be viewed as an array of square ice nanotubes. Insights obtained from pressure-induced amorphization and crystallization of confined water offer a guide with which to seek a thermodynamic path to grow a new form of methane clathrate whose BL ice framework exhibits the Archimedean 4⋅82 (square-octagon) pattern. PMID:23236178

  11. HZE particle shielding using confined magnetic fields. [high-energy heavy ions

    NASA Technical Reports Server (NTRS)

    Townsend, L. W.

    1983-01-01

    The great rigidities characteristic of high energy heavy ion (HZE) particles are judged to preclude near term use of confined magnetic fields of reasonable dimensions and strengths for small spacecraft shielding on long duration manned missions. It is noted that a Mars mission-class shield, although effective against solar protons, would be useless for HZE particles unless the mass and size of the shield are increased by several orders of magnitude (to yield a shield comparable to those contemplated for permanent space stations).

  12. Turbulent Transport at High Reynolds Numbers in an Inertial Confinement Fusion Context

    DTIC Science & Technology

    2014-09-01

    of Turbulent Mixing ,” Phys. Scr ., T142, p. 014014. Fig. 4 Turbulent transport as a fraction of total transport plotted versus Re for each of four...Diffusion in Turbulent Mixing ,” Phys. Scr ., T142, p. 014062. [9] George, E., Glimm, J., Grove, J. W., Li, X.-L., Liu, Y.-J., Xu, Z.-L., and Zhao, N., 2003...ABSTRACT Turbulent Transport at High Reynolds Numbers in an Inertial Confinement Fusion Context Report Title Mix is a critical input to hydro

  13. Dielectric confinement influenced screened Coulomb potential for a semiconductor quantum wire

    NASA Astrophysics Data System (ADS)

    Aharonyan, K. H.; Margaryan, N. B.

    2016-01-01

    A formalism of the Thomas-Fermi method has been applied for studying the screening effect due to quasi-one-dimensional electron gas in a semiconductor cylindrical quantum wire embedded in the barrier environment. With taking into account of strongly low dielectric properties of the barrier material, an applicability of the quantum wire effective interaction potential of the confined charge carriers has been revealed. Both screened quasi- one-dimensional interaction potential and effective screening length analytical expressions are derived in the first time. It is shown that in the long wavelength moderate limit dielectric confinement effect enhances strength of the screening potential depending on the both radius of the wire and effective screening length, whereas in the long wavelength strong limit the screening potential solely is determined by barrier environment dielectric properties.

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

    PubMed

    Dowgiallo, Anne-Marie; Knappenberger, Kenneth L

    2012-11-28

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

  15. Oxide confined 850-nm VCSELs for high-speed datacom applications

    NASA Astrophysics Data System (ADS)

    Moser, Philip; Mutig, Alex; Lott, James A.; Blokhin, Sergey; Fiol, Gerrit; Nadtochiy, Alexey M.; Ledentsov, Nikolai N.; Bimberg, Dieter

    2010-04-01

    Vertical cavity surface emitting lasers (VCSELs) are low cost and reliable light sources for high-speed local area and storage area network (LAN/SAN) optical fiber data communication systems and all other short-reach high-speed data transfer applications. The intrinsic limitations of copper-based electrical links at data rates exceeding 10 Gbit/s leads to a progressive movement wherein optical communication links replace traditional short-reach (300 m or shorter) copper interconnects. The wavelength of 850 nm is the standard for LAN/SAN applications as well as for several other evolving short-reach application areas including Fibre Channel, InfiniBand, Universal Serial Bus (optical USB), and active optical cables. Here we present our recent results on 850 nm oxide-confined VCSELs operating at data bit rates up to 40 Gbit/s at low current densities of ~10 kA/cm2 ensuring device reliability and long-term stability based on conventional industry certification specifications. The relaxation resonance frequencies, damping factors, and parasitic cut-off frequencies are determined for VCSELs with oxide-confined apertures of various diameters. At the highest optical modulation rates the VCSELs' high speed operation is limited by parasitic cut-off frequencies of 24-28 GHz. We believe that by further reducing device parasitics we will produce current modulated VCSELs with optical modulation bandwidths larger than 30 GHz and data bit rates beyond 40 Gbit/s.

  16. Highly confined low-loss plasmons in graphene-boron nitride heterostructures.

    PubMed

    Woessner, Achim; Lundeberg, Mark B; Gao, Yuanda; Principi, Alessandro; Alonso-González, Pablo; Carrega, Matteo; Watanabe, Kenji; Taniguchi, Takashi; Vignale, Giovanni; Polini, Marco; Hone, James; Hillenbrand, Rainer; Koppens, Frank H L

    2015-04-01

    Graphene plasmons were predicted to possess simultaneous ultrastrong field confinement and very low damping, enabling new classes of devices for deep-subwavelength metamaterials, single-photon nonlinearities, extraordinarily strong light-matter interactions and nano-optoelectronic switches. Although all of these great prospects require low damping, thus far strong plasmon damping has been observed, with both impurity scattering and many-body effects in graphene proposed as possible explanations. With the advent of van der Waals heterostructures, new methods have been developed to integrate graphene with other atomically flat materials. In this Article we exploit near-field microscopy to image propagating plasmons in high-quality graphene encapsulated between two films of hexagonal boron nitride (h-BN). We determine the dispersion and plasmon damping in real space. We find unprecedentedly low plasmon damping combined with strong field confinement and confirm the high uniformity of this plasmonic medium. The main damping channels are attributed to intrinsic thermal phonons in the graphene and dielectric losses in the h-BN. The observation and in-depth understanding of low plasmon damping is the key to the development of graphene nanophotonic and nano-optoelectronic devices.

  17. Reinforced Conductive Confinement of Sulfur for Robust and High-Performance Lithium-Sulfur Batteries.

    PubMed

    Lai, Chao; Wu, Zhenzhen; Gu, Xingxing; Wang, Chao; Xi, Kai; Kumar, R Vasant; Zhang, Shanqing

    2015-11-04

    Sulfur is an attractive cathode material in energy storage devices due to its high theoretical capacity of 1672 mAh g(-1). However, practical application of lithium-sulfur (Li-S) batteries can be achieved only when the major barriers, including the shuttling effect of polysulfides (Li2Sx, x = 3-8), significant volume change (∼80%), and the resultant rapid deterioration of electrodes, are tackled. Here, we propose an "inside-out" synthesis strategy by mimicking the structure of the pomegranate fruit to achieve conductive confinement of sulfur to address these issues. In the proposed pomegranate-like structure, sulfur and carbon nanotubes composite is encapsulated by the in situ formed amorphous carbon network, which allows the regeneration of electroactive material sulfur and the confinement of the sulfur as well as the lithium polysulfide within the electrical conductive carbon network. Consequently, a highly robust sulfur cathode is obtained, delivering remarkable performance in a Li-S battery. The obtained composite cathode shows a reversible capacity of 691 mAh g(-1) after 200 cycles with impressive cycle stability at the current density of 1600 mA g(-1).

  18. Highly confined low-loss plasmons in graphene-boron nitride heterostructures

    NASA Astrophysics Data System (ADS)

    Woessner, Achim; Lundeberg, Mark B.; Gao, Yuanda; Principi, Alessandro; Alonso-González, Pablo; Carrega, Matteo; Watanabe, Kenji; Taniguchi, Takashi; Vignale, Giovanni; Polini, Marco; Hone, James; Hillenbrand, Rainer; Koppens, Frank H. L.

    2015-04-01

    Graphene plasmons were predicted to possess simultaneous ultrastrong field confinement and very low damping, enabling new classes of devices for deep-subwavelength metamaterials, single-photon nonlinearities, extraordinarily strong light-matter interactions and nano-optoelectronic switches. Although all of these great prospects require low damping, thus far strong plasmon damping has been observed, with both impurity scattering and many-body effects in graphene proposed as possible explanations. With the advent of van der Waals heterostructures, new methods have been developed to integrate graphene with other atomically flat materials. In this Article we exploit near-field microscopy to image propagating plasmons in high-quality graphene encapsulated between two films of hexagonal boron nitride (h-BN). We determine the dispersion and plasmon damping in real space. We find unprecedentedly low plasmon damping combined with strong field confinement and confirm the high uniformity of this plasmonic medium. The main damping channels are attributed to intrinsic thermal phonons in the graphene and dielectric losses in the h-BN. The observation and in-depth understanding of low plasmon damping is the key to the development of graphene nanophotonic and nano-optoelectronic devices.

  19. Nonlinear gyrokinetic simulations of the I-mode high confinement regime and comparisons with experimenta)

    NASA Astrophysics Data System (ADS)

    White, A. E.; Howard, N. T.; Creely, A. J.; Chilenski, M. A.; Greenwald, M.; Hubbard, A. E.; Hughes, J. W.; Marmar, E.; Rice, J. E.; Sierchio, J. M.; Sung, C.; Walk, J. R.; Whyte, D. G.; Mikkelsen, D. R.; Edlund, E. M.; Kung, C.; Holland, C.; Candy, J.; Petty, C. C.; Reinke, M. L.; Theiler, C.

    2015-05-01

    For the first time, nonlinear gyrokinetic simulations of I-mode plasmas are performed and compared with experiment. I-mode is a high confinement regime, featuring energy confinement similar to H-mode, but without enhanced particle and impurity particle confinement [D. G. Whyte et al., Nucl. Fusion 50, 105005 (2010)]. As a consequence of the separation between heat and particle transport, I-mode exhibits several favorable characteristics compared to H-mode. The nonlinear gyrokinetic code GYRO [J. Candy and R. E. Waltz, J Comput. Phys. 186, 545 (2003)] is used to explore the effects of E × B shear and profile stiffness in I-mode and compare with L-mode. The nonlinear GYRO simulations show that I-mode core ion temperature and electron temperature profiles are more stiff than L-mode core plasmas. Scans of the input E × B shear in GYRO simulations show that E × B shearing of turbulence is a stronger effect in the core of I-mode than L-mode. The nonlinear simulations match the observed reductions in long wavelength density fluctuation levels across the L-I transition but underestimate the reduction of long wavelength electron temperature fluctuation levels. The comparisons between experiment and gyrokinetic simulations for I-mode suggest that increased E × B shearing of turbulence combined with increased profile stiffness are responsible for the reductions in core turbulence observed in the experiment, and that I-mode resembles H-mode plasmas more than L-mode plasmas with regards to marginal stability and temperature profile stiffness.

  20. Thin Shell, High Velocity Inertial Confinement Fusion Implosions on the National Ignition Facility

    NASA Astrophysics Data System (ADS)

    Ma, T.; Hurricane, O. A.; Callahan, D. A.; Barrios, M. A.; Casey, D. T.; Dewald, E. L.; Dittrich, T. R.; Döppner, T.; Haan, S. W.; Hinkel, D. E.; Berzak Hopkins, L. F.; Le Pape, S.; MacPhee, A. G.; Pak, A.; Park, H.-S.; Patel, P. K.; Remington, B. A.; Robey, H. F.; Salmonson, J. D.; Springer, P. T.; Tommasini, R.; Benedetti, L. R.; Bionta, R.; Bond, E.; Bradley, D. K.; Caggiano, J.; Celliers, P.; Cerjan, C. J.; Church, J. A.; Dixit, S.; Dylla-Spears, R.; Edgell, D.; Edwards, M. J.; Field, J.; Fittinghoff, D. N.; Frenje, J. A.; Gatu Johnson, M.; Grim, G.; Guler, N.; Hatarik, R.; Herrmann, H. W.; Hsing, W. W.; Izumi, N.; Jones, O. S.; Khan, S. F.; Kilkenny, J. D.; Knauer, J.; Kohut, T.; Kozioziemski, B.; Kritcher, A.; Kyrala, G.; Landen, O. L.; MacGowan, B. J.; Mackinnon, A. J.; Meezan, N. B.; Merrill, F. E.; Moody, J. D.; Nagel, S. R.; Nikroo, A.; Parham, T.; Ralph, J. E.; Rosen, M. D.; Rygg, J. R.; Sater, J.; Sayre, D.; Schneider, M. B.; Shaughnessy, D.; Spears, B. K.; Town, R. P. J.; Volegov, P. L.; Wan, A.; Widmann, K.; Wilde, C. H.; Yeamans, C.

    2015-04-01

    Experiments have recently been conducted at the National Ignition Facility utilizing inertial confinement fusion capsule ablators that are 175 and 165 μ m in thickness, 10% and 15% thinner, respectively, than the nominal thickness capsule used throughout the high foot and most of the National Ignition Campaign. These three-shock, high-adiabat, high-foot implosions have demonstrated good performance, with higher velocity and better symmetry control at lower laser powers and energies than their nominal thickness ablator counterparts. Little to no hydrodynamic mix into the DT hot spot has been observed despite the higher velocities and reduced depth for possible instability feedthrough. Early results have shown good repeatability, with up to 1 /2 the neutron yield coming from α -particle self-heating.

  1. Thin Shell, High Velocity Inertial Confinement Fusion Implosions on the National Ignition Facility

    SciTech Connect

    Ma, T.; Hurricane, O. A.; Callahan, D. A.; Barrios, M. A.; Casey, D. T.; Dewald, E. L.; Dittrich, T. R.; Doppner, T.; Haan, S. W.; Hinkel, D. E.; Berzak Hopkins, L. F.; Le Pape, S.; MacPhee, A. G.; Pak, A.; Park, H. S.; Patel, P. K.; Remington, B. A.; Robey, H. F.; Salmonson, J. D.; Springer, P. T.; Tommasini, R.; Benedetti, L. R.; Bionta, R.; Bond, E.; Bradley, D. K.; Caggiano, J.; Celliers, P.; Cerjan, C. J.; Church, J. A.; Dixit, S.; Dylla-Spears, R.; Edgell, D.; Edwards, M. J.; Field, J.; Fittinghoff, D. N.; Frenje, J. A.; Gatu Johnson, M.; Grim, G.; Guler, N.; Hatarik, R.; Herrmann, H. W.; Hsing, W. W.; Izumi, N.; Jones, O. S.; Khan, S. F.; Kilkenny, J. D.; Knauer, J.; Kohut, T.; Kozioziemski, B.; Kritcher, A.; Kyrala, G.; Landen, O. L.; MacGowan, B. J.; Mackinnon, A. J.; Meezan, N. B.; Merrill, F. E.; Moody, J. D.; Nagel, S. R.; Nikroo, A.; Parham, T.; Ralph, J. E.; Rosen, M. D.; Rygg, J. R.; Sater, J.; Sayre, D.; Schneider, M. B.; Shaughnessy, D.; Spears, B. K.; Town, R.P. J.; Volegov, P. L.; Wan, A.; Widmann, K.; Wilde, C. H.; Yeamans, C.

    2015-04-06

    Experiments have recently been conducted at the National Ignition Facility utilizing inertial confinement fusion capsule ablators that are 175 and 165 μm in thickness, 10% and 15% thinner, respectively, than the nominal thickness capsule used throughout the high foot and most of the National Ignition Campaign. These three-shock, high-adiabat, high-foot implosions have demonstrated good performance, with higher velocity and better symmetry control at lower laser powers and energies than their nominal thickness ablator counterparts. Little to no hydrodynamic mix into the DT hot spot has been observed despite the higher velocities and reduced depth for possible instability feedthrough. Earlier results have shown good repeatability, with up to 1/2 the neutron yield coming from α-particle self-heating.

  2. Rheology of red blood cells under flow in highly confined microchannels: I. effect of elasticity.

    PubMed

    Lázaro, Guillermo R; Hernández-Machado, Aurora; Pagonabarraga, Ignacio

    2014-10-07

    We analyze the rheology of dilute red blood cell suspensions in pressure driven flows at low Reynolds number, in terms of the morphologies and elasticity of the cells. We focus on narrow channels of width similar to the cell diameter, when the interactions with the walls dominate the cell dynamics. The suspension presents a shear-thinning behaviour, with a Newtonian-behaviour at low shear rates, an intermediate region of strong decay of the suspension viscosity, and an asymptotic regime at high shear rates in which the effective viscosity converges to that of the solvent. We identify the relevant aspects of cell elasticity that contribute to the rheological response of blood at high confinement. In a second paper, we will explore the focusing of red blood cells while flowing at high shear rates and how this effect is controlled by the geometry of the channel.

  3. The role of the radial electric field for the transition to high confinement regimes

    NASA Astrophysics Data System (ADS)

    Testa, D.; Garzotti, L.; Giroud, C.; contributors, JET-EFDA

    2006-05-01

    The radial electric field Er(x, t), and particularly its gradient, has been invoked by various theories and empirical models as a crucial parameter 'per se' for determining the transition to high confinement regimes, such as the onset of an internal transport barrier (ITB) in the plasma core and of the H-mode pedestal at the plasma edge. This idea, however, does not consider the basic fact that in most experiments the transition to a steady-state higher confinement regimes is produced by applying sufficient additional heating onto a given target density and current profile. In order to test this ansatz on a more routine basis, we have developed here an analytical approximation to the neoclassical calculation of the radial electric field, adapted for the 2D toroidal geometry of JET to describe all collisionality regimes (banana, banana-plateau, Pfirsch-Schlüter) and to include averaging over the potato orbits. An analytic calculation of the error bars on Er(x, t) has also been developed, which has allowed us to compare and successfully benchmark our calculations with the results of neoclassical codes such as JETTO and NCLASS. We are then able to demonstrate a striking similarity in the shape of Er(x, t) in steady-state L-mode, H-mode and ITB plasmas when normalizing Er(x, t) with respect to the total heating power flux. This clearly indicates that, experimentally, there is no direct causality relation between changes in Er(x, t) and steady-state improved confinement, as these are brought about together by changes in the power deposition profile. Only two cases do not satisfy this general rule. First, localized and rapid transients (i.e. occurring on time scales much shorter than the momentum and energy confinement time) could be linked to non-neoclassical changes in Er(x, t), possibly due to turbulence suppression mechanisms. Second, when comparing H-mode plasmas with forward and reversed ion ∇B-drift direction, we demonstrate the role of prompt fast ion losses

  4. Application of spatially resolved high resolution crystal spectrometry to inertial confinement fusion plasmas

    SciTech Connect

    Hill, K. W.; Bitter, M.; Delgado-Aparacio, L.; Pablant, N. A.; Beiersdorfer, P.; Schneider, M.; Widmann, K.; Sanchez del Rio, M.; Zhang, L.

    2012-10-15

    High resolution ({lambda}/{Delta}{lambda}{approx} 10 000) 1D imaging x-ray spectroscopy using a spherically bent crystal and a 2D hybrid pixel array detector is used world wide for Doppler measurements of ion-temperature and plasma flow-velocity profiles in magnetic confinement fusion plasmas. Meter sized plasmas are diagnosed with cm spatial resolution and 10 ms time resolution. This concept can also be used as a diagnostic of small sources, such as inertial confinement fusion plasmas and targets on x-ray light source beam lines, with spatial resolution of micrometers, as demonstrated by laboratory experiments using a 250-{mu}m {sup 55}Fe source, and by ray-tracing calculations. Throughput calculations agree with measurements, and predict detector counts in the range 10{sup -8}-10{sup -6} times source x-rays, depending on crystal reflectivity and spectrometer geometry. Results of the lab demonstrations, application of the technique to the National Ignition Facility (NIF), and predictions of performance on NIF will be presented.

  5. Rotational dynamics of confined C60 from near-infrared Raman studies under high pressure.

    PubMed

    Zou, Yonggang; Liu, Bingbing; Wang, Liancheng; Liu, Dedi; Yu, Shidan; Wang, Peng; Wang, Tianyi; Yao, Mingguang; Li, Quanjun; Zou, Bo; Cui, Tian; Zou, Guangtian; Wågberg, Thomas; Sundqvist, Bertil; Mao, Ho-Kwang

    2009-12-29

    Peapods present a model system for studying the properties of dimensionally constrained crystal structures, whose dynamical properties are very important. We have recently studied the rotational dynamics of C(60) molecules confined inside single walled carbon nanotube (SWNT) by analyzing the intermediate frequency mode lattice vibrations using near-infrared Raman spectroscopy. The rotation of C(60) was tuned to a known state by applying high pressure, at which condition C(60) first forms dimers at low pressure and then forms a single-chain, nonrotating, polymer structure at high pressure. In the latter state the molecules form chains with a 2-fold symmetry. We propose that the C(60) molecules in SWNT exhibit an unusual type of ratcheted rotation due to the interaction between C(60) and SWNT in the "hexagon orientation," and the characteristic vibrations of ratcheted rotation becomes more obvious with decreasing temperature.

  6. A simple formula to predict the influence of the near-field in the optical control of confined electron systems

    NASA Astrophysics Data System (ADS)

    Takeuchi, Takashi; Ohnuki, Shinichiro; Sako, Tokuei

    2017-02-01

    A simple formula for predicting the ratio between the field strengths of the incident laser pulse and of the near-field created in the vicinity of the target electron system has been proposed, in the context of optically controlling confined electron systems. The formula is easy to use and does not involve elaborate computation, thus enabling one to judge whether to use the time-consuming Maxwell–Schrödinger hybrid simulation or to stay with the conventional time-dependent Schrödinger equation approach that takes no near-field effect into account. As a demonstration we have examined in detail the system of an electron confined in a quasi-one-dimensional nanoscale potential well. The highly accurate Maxwell–Schrödinger hybrid simulation has been employed to demonstrate the usefulness of the proposed formula in predicting the significance of the near-field effect. The near-field effect has shown to depend sensitively on the characteristics of the laser pulse and of the geometry of the confined electron system, which can be predicted well by the proposed formula.

  7. High-speed 850 nm oxide-confined VCSELs for DATACOM applications

    NASA Astrophysics Data System (ADS)

    Mutig, Alex; Blokhin, Sergey; Nadtochiy, Alexey M.; Fiol, Gerrit; Lott, James A.; Shchukin, Vitaly A.; Ledenstov, Nikolai N.; Bimberg, Dieter

    2010-02-01

    Vertical cavity surface emitting lasers (VCSELs) are low cost and reliable light sources for high-speed local area and storage area network (LAN/SAN) optical fiber data communication systems and short-reach computer interconnects. The continuing rapid increase of serial transmission data rates driven by multi-core microprocessor's bandwidth upgrades cannot be sustained via conventional copper-based links as bit rates move beyond 10 Gbit/s and distances greater than 1 m. The intrinsic limitation of copper at high single-channel data rates facilitates the need to transition to optical fiberbased links at ever shorter distances. For LAN/SAN applications the 850 nm wavelength is standard. This same wavelength is also the standard for several other evolving short-reach application areas including Fibre Channel, CEI, USB, InfiniBand, and HDMI optical link systems. Herein we present our recent results on 850 nm oxide-confined VCSELs operating at data bit rates up to 40 Gbit/s. The low operational current density in the range of ~10 kA/cm2 ensures viable device reliability and long-term stability based on well-known industry certification specifications. Key VCSEL device parameters including the relaxation resonance frequency, damping, and parasitic cut-off frequency are determined for VCSELs with oxide-confined apertures of various diameters. We find that a parasitic cut-off frequency of 24-28 GHz limits the VCSEL's high speed operation at the highest optical modulation rates. We believe that with some effort the device parasitics can be further reduced such that current modulated VCSELs can be realized with larger than 30 GHz optical modulation bandwidth and reliable and practical operation beyond 40 Gbit/s.

  8. The influence of large-scale motion on turbulent transport for confined coaxial jets

    NASA Technical Reports Server (NTRS)

    Brondum, D. C.; Bennett, J. C.

    1984-01-01

    The existence of large-scale coherent structures in turbulent shear flows has been well documented in the literature. The importance of these structures in flow entrainment, momentum transport and mass transport in the shear layer has been suggested by several researchers. Comparisons between existing models and experimental data for shear flow in confined coaxial jets reinforce the necessity of further investigation of the large scale structures. These comparisons show the greatest discrepancy between prediction and actual results in the developing flow region where the large scales exist. It was also observed that the momentum transport rate comparisons were very bad. Finally, Schetz has reviewed mixing flows and concluded that large-scale structures were essential aspects of future modeling efforts.

  9. Plasmonic plano-semi-cylindrical nanocavities with high-efficiency local-field confinement

    NASA Astrophysics Data System (ADS)

    Liu, Feifei; Zhang, Xinping; Fang, Xiaohui

    2017-01-01

    Plasmonic nanocavity arrays were achieved by producing isolated silver semi-cylindrical nanoshells periodically on a continuous planar gold film. Hybridization between localized surface plasmon resonance (LSPR) in the Ag semi-cylindrical nanoshells (SCNS) and surface plasmon polaritons (SPP) in the gold film was observed as split bonding and anti-bonding resonance modes located at different spectral positions. This led to strong local field enhancement and confinement in the plano-concave nanocavites. Narrow-band optical extinction with an amplitude as high as 1.5 OD, corresponding to 97% reduction in the transmission, was achieved in the visible spectrum. The resonance spectra of this hybrid device can be extended from the visible to the near infrared by adjusting the structural parameters.

  10. Plasmonic plano-semi-cylindrical nanocavities with high-efficiency local-field confinement

    PubMed Central

    Liu, Feifei; Zhang, Xinping; Fang, Xiaohui

    2017-01-01

    Plasmonic nanocavity arrays were achieved by producing isolated silver semi-cylindrical nanoshells periodically on a continuous planar gold film. Hybridization between localized surface plasmon resonance (LSPR) in the Ag semi-cylindrical nanoshells (SCNS) and surface plasmon polaritons (SPP) in the gold film was observed as split bonding and anti-bonding resonance modes located at different spectral positions. This led to strong local field enhancement and confinement in the plano-concave nanocavites. Narrow-band optical extinction with an amplitude as high as 1.5 OD, corresponding to 97% reduction in the transmission, was achieved in the visible spectrum. The resonance spectra of this hybrid device can be extended from the visible to the near infrared by adjusting the structural parameters. PMID:28074853

  11. An on-chip study on the influence of geometrical confinement and chemical gradient on cell polarity.

    PubMed

    Zheng, Wenfu; Xie, Yunyan; Sun, Kang; Wang, Dong; Zhang, Yi; Wang, Chen; Chen, Yong; Jiang, Xingyu

    2014-09-01

    Cell polarity plays key roles in tissue development, regeneration, and pathological processes. However, how the cells establish and maintain polarity is still obscure so far. In this study, by employing microfluidic techniques, we explored the influence of geometrical confinement and chemical stimulation on the cell polarity and their interplay. We found that teardrop shape-induced anterior/posterior polarization of cells displayed homogeneous distribution of epidermal growth factor receptor, and the polarity could be maintained in a uniform epidermal growth factor (EGF) solution, but be broken by a reverse gradient of EGF, implying different mechanism of geometrical and chemical cue-induced cell polarity. Further studies indicated that a teardrop pattern could cause polarized distribution of microtubule-organization center and nucleus-Golgi complex, and this polarity was weakened when the cells were released from the confinement. Our study provides the evidence regarding the difference between geometrical and chemical cue-induced cell polarity and would be useful for understanding relationship between polarity and directional migration of cells.

  12. Experimental evaluation of connectivity influence on dispersivity under confined and unconfined radial convergent flow conditions

    NASA Astrophysics Data System (ADS)

    Guzzi, Silvia; Molinari, Antonio; Fallico, Carmine; Pedretti, Daniele

    2014-05-01

    Heterogeneity and connectivity have a significant impact on the fate and transport of contaminants due to the occurrence of formations with largest permeability than the surrounding geological materials, which can originate preferential pathways in groundwater system. These issues are usually addressed by tracer tests and a radial convergent (RC) flow setting is typically selected for convenience but more complicated for model interpretation than uniform flow transport. An experimental investigation was performed using RC tracer tests in a 3D intermediate scale physical model to illustrate the role of connected features on the estimation of dispersivity using the classical Sauty solution and the method of moments, under confined and unconfined aquifer conditions. The physical model consists of 26 piezometers located at difference distances from a constant-discharge central pumping well. The box is filled with gravel channels embedded in a sandy matrix and organized in different layers. Materials have been well characterized before and after the test. For the confined configuration, a silt layer was placed above the previous layers. Tracer tests were performed using potassium iodide solutions with concentration of 3•10-3 M and under a constant pumping flow rate of 0.05 L/s. To mimic a pulse injection in each piezometer we used syringes and pipes, whereas a probe allowed continuous measuring of tracer concentration. Average velocity and longitudinal dispersion coefficient were defined from the first and second central moment of the observed breakthrough curves for each piezometer (integrated over the outflow boundary of the domain) and using the classical curve matching from the Sauty's solution at different Péclet numbers. Results reveal in some cases that estimates of hydrodynamic parameters from the Sauty solution and the method of moments seem to be different. This is related to the different basic assumptions of the two methods applied, and especially because

  13. Observations of PAN and its confinement in the Asian Monsoon Anticyclone in high spatial resolution

    NASA Astrophysics Data System (ADS)

    Ungermann, Joern; Ploeger, Felix; Spang, Reinhold; Riese, Martin

    2016-04-01

    This talk presents a set of observations by the CRyogenic Infrared Spectrometers and Telescopes for the Atmosphere (CRISTA) infrared limb sounder on the SPAS platform in low-earth orbit. The spatially highly resolved trace gas measurements of six days in August 1997 allow a close look on the confinement of air masses within the Asian Summer Monsoon (ASM) anticyclone. Peroxyacetyl nitrate (PAN) is a secondary pollutant without sources in the stratosphere and acts as a tropospheric tracer. In combination with ozone as a stratospheric tracer, an eddy-shedding event of the ASM could be observed. The measured PAN volume mixing ratios (VMR) correlate well with potential vorticity (PV) derived from ECMWF ERA-Interim model data. Computing the gradient of PAN over PV on isentropes reveals that PAN VMR exhibit the strongest decrease at each isentrope for an increasing value of PV, which may be used to identify the extent of the ASM on that isentrope. CRISTA measurements also provide the temperature of measured air parcels and thus allow to derive the location of the thermal tropopause. We find that the thermal tropopause coincides with the border of the positive PAN anomaly both horizontally and vertically within the ASM anticyclone. In contrast, the shed eddy exhibits enhanced PAN VMRs for 1 to 2 km above the thermal tropopause. The amount of mixing may also be characterised by projecting the derived air parcels into tracer-tracer space using PAN and ozone as tropospheric and stratospheric tracer, respectively. This reveals that the anticyclone contains few mixed parcels in contrast to the region between the anticyclone and the shed eddy. This implies that while the anticyclone confines polluted air masses well, eddy shedding provides a very rapid horizontal transport pathway of Asian pollution into the extratropical lowermost stratosphere with a time scale of only a few days.

  14. Observations of PAN and its confinement in the Asian summer monsoon anticyclone in high spatial resolution

    NASA Astrophysics Data System (ADS)

    Ungermann, Jörn; Ern, Mandfred; Kaufmann, Martin; Müller, Rolf; Spang, Reinhold; Ploeger, Felix; Vogel, Bärbel; Riese, Martin

    2016-07-01

    This paper presents an analysis of trace gases in the Asian summer monsoon (ASM) region on the basis of observations by the CRISTA infrared limb sounder taken in low-earth orbit in August 1997. The spatially highly resolved measurements of peroxyacetyl nitrate (PAN) and O3 allow a detailed analysis of an eddy-shedding event of the ASM anticyclone. We identify enhanced PAN volume mixing ratios (VMRs) within the main anticyclone and within the eddy, which are suitable as a tracer for polluted air originating in India and China. Plotting the retrieved PAN VMRs against potential vorticity (PV) and potential temperature reveals that the PV value at which the PAN VMRs exhibit the strongest decrease with respect to PV increases with potential temperature. These PV values might be used to identify the extent of the ASM. Using temperature values also derived from CRISTA measurements, we also computed the location of the thermal tropopause according to the WMO criterion and find that it confines the PAN anomaly vertically within the main ASM anticyclone. In contrast, the shed eddy exhibits enhanced PAN VMRs for 1 to 2 km above the thermal tropopause. Using the relationship between PAN as a tropospheric tracer and O3 as a stratospheric tracer to identify mixed air parcels, we further found the anticyclone to contain few such air parcels, whereas the region between the anticyclone and the eddy as well as the eddy itself contains many mixed air parcels. In combination, this implies that while the anticyclone confines polluted air masses well, eddy shedding provides a very rapid horizontal transport pathway of Asian pollution into the extratropical lowermost stratosphere with a timescale of only a few days.

  15. Two dimensional impinging jet cooling of high heat flux surface in magnetic confinement fusion reactor

    SciTech Connect

    Inoue, A.; Tanno, T.; Takahashi, M.

    1994-12-31

    Divertor surface of a magnetic confinement fusion reactor is exposed to strong radiation heating by high flux charged particles. According to standard design of the ITER, the heat flux of the divertor surface becomes average 15MW/m{sup 2} or more. In this study, a cooling by a two dimensional impinging jet flow is proposed to cool such high heat flux surface. For an impinging jet flow to flat heated surface, such as CHF is obtained only in the limited surface region where the jet flow hits directly. Apart from the region, the CHF decreases abruptly with the distance from the center. The main reason is that the pressure decreases abruptly as apart from the center region and the liquid flow is spread away from the heated surface region by the strong boiling. To overcome these difficulties, the authors propose that the impinging jet is applied to the heat transfer wall with a concave surface, because the pressure change becomes mild by the centrifugal force along the curved surface. The increase of the radial pressure gradient in the vertical direction to the curved surface promotes the departure of vapor bubbles near the wall region. It is expected that this mechanism as well as keeping high pressure along the flow works to enhance the CHF. To obtain the high heat flux in the wide region, a use of a two-dimensional impinging jet is suitable instead of a round jet.

  16. The influence of electron confinement, quantum size effects, and film morphology on the dispersion and the damping of plasmonic modes in Ag and Au thin films

    NASA Astrophysics Data System (ADS)

    Politano, Antonio; Chiarello, Gennaro

    2015-05-01

    Plasmons are collective longitudinal modes of charge fluctuation in metal samples excited by an external electric field. Surface plasmons (SPs) are waves that propagate along the surface of a conductor. SPs find applications in magneto-optic data storage, optics, microscopy, and catalysis. The investigation of SPs in silver and gold is relevant as these materials are extensively used in plasmonics. The theoretical approach for calculating plasmon modes in noble metals is complicated by the existence of localized d electrons near the Fermi level. Nevertheless, recent calculations based on linear response theory and time-dependent local density approximation adequately describe the dispersion and damping of SPs in noble metals. Furthermore, in thin films the electronic response is influenced by electron quantum confinement. Confined electrons modify the dynamical screening processes at the film/substrate interface by introducing novel properties with potential applications. The presence of quantum well states in the Ag and Au overlayer affects both the dispersion relation of SP frequency and the damping processes of the SP. Recent calculations indicate the emergence of acoustic surface plasmons (ASP) in Ag thin films exhibiting quantum well states. The slope of the dispersion of ASP decreases with film thickness. High-resolution electron energy loss spectroscopy (HREELS) is the main experimental technique for investigating collective electronic excitations, with adequate resolution in both the energy and momentum domains to investigate surface modes. Herein we review on recent progress of research on collective electronic excitations in Ag and Au films deposited on single-crystal substrates.

  17. A landscape perspective on bat foraging ecology along rivers: does channel confinement and insect availability influence the response of bats to aquatic resources in riverine landscapes?

    PubMed

    Hagen, Elizabeth M; Sabo, John L

    2011-07-01

    River and riparian areas provide an important foraging habitat for insectivorous bats owing to high insect availability along waterways. However, structural characteristics of the riverine landscape may also influence the location of foraging bats. We used bat detectors to compare bat activity longitudinally along river reaches with contrasting channel confinement, ratio of valley floor width to active channel width, and riparian vegetation, and laterally with distance from the river along three different reach types. We measured rates of insect emergence from the river and aerial insect availability above the river and laterally up to 50-m into the riparian habitat in order to assess the relationship between food resources and insectivorous bat activity. Longitudinally, bat activity was concentrated along confined reaches in comparison to unconfined reaches but was not related to insect availability. Laterally, bats tracked exponential declines in aquatic insects with distance from the river. These data suggest that along the lateral dimension bats track food resources, but that along the longitudinal dimension channel shape and landscape structure determine bat distributions more than food resources.

  18. Improved Confinement in Highly Powered Advanced Tokamak Scenarios on DIII-D

    NASA Astrophysics Data System (ADS)

    Petrie, T. W.; Leonard, A.; Luce, T.; Osborne, T.; Solomon, W.; Turco, F.; Fenstermacher, M. E.; Holcomb, C.; Lasnier, C.; Makowski, M.

    2016-10-01

    DIII-D has recently demonstrated improved energy confinement by injecting neutral gas into high performance Advanced Tokamak (AT) plasmas during high power operation. Representative parameters are: q95 = 6, PIN up to 15 MW, H98 = 1.4-1.8, and βN = 2.8-4.2. Unlike in lower and moderate powered AT plasmas, τE and βN increased (and νELM decreased) as density was increased by deuterium gas puffing. We discuss how the interplay between pedestal density and temperature with fueling can lead to higher ballooning stability and a peeling/kink current limit that increasers as the pressure gradient increases. Comparison of neon, nitrogen, and argon as ``seed'' impurities in high PIN ATs in terms of their effects on core dilution, τE, and heat flux (q⊥) reduction favors argon. In general, the puff-and-pump radiating divertor was not as effective in reducing q⊥ while maintaining density control at highest PIN than it was at lower PIN. Work supported by the US DOE under DE-FC02-04ER54698, DE-AC05-00OR22725, DE-AC04-94AL85000, DE-AC52-07NA27344, and DE-FG02-07ER54917.

  19. Highly confined, enhanced surface fluorescence imaging with two-dimensional silver nanoparticle sheets

    SciTech Connect

    Usukura, Eiji; Shinohara, Shuhei; Okamoto, Koichi; Tamada, Kaoru; Lim, Jaehoon; Char, Kookheon

    2014-03-24

    A method of obtaining highly confined, enhanced surface fluorescence imaging is proposed using two-dimensional (2D) silver nanoparticle (AgMy) sheets. This technique is based on the localized surface plasmon resonance excited homogeneously on a 2D silver nanoparticle sheet. The AgMy sheets are fabricated at the air–water interface by self-assembly and transferred onto hydrophobic glass substrates. These sheets can enhance the fluorescence only when the excitation wavelength overlaps with the plasmon resonance wavelength. To confirm the validity of this technique, two separate test experiments are performed. One is the epifluorescence microscope imaging of a quantum dot 2D sheet on the AgMy 2D sheet with a SiO{sub 2} spacer layer, where the fluorescence is maximized with the 20 nm SiO{sub 2} layer, determined by the Förster resonance energy transfer distances. The second experiment is the imaging of a single fluorescence bead with a total internal reflection fluorescent microscope. We confirmed that the AgMy sheet provides a 4-fold increase in fluorescence with a 160-nm spatial resolution at 30 ms/frame snapshot. The AgMy sheet will be a powerful tool for high sensitivity and high-resolution real time bioimaging at nanointerfaces.

  20. Measurement of high-frequency, small scale density fluctuations in improved confinement RFP plasmas

    NASA Astrophysics Data System (ADS)

    Duff, J. R.; Chapman, B. E.; Sarff, J. S.; Carmody, D.; Terry, P. W.; den Hartog, D. J.; Morton, L. A.; Lin, L.; Ding, W. X.; Brower, D. L.; MST Team

    2014-10-01

    In standard MST RFP plasmas, core transport is governed by magnetic fluctuations associated with global tearing modes. Using pulsed parallel current drive, tearing is significantly reduced and smaller-scale fluctuations are likely important to electron particle and heat transport for these improved confinement plasmas. On MST, an 11-chord FIR laser-based interferometry diagnostic, with ~ 8 cm chord spacing, is used to measure electron density fluctuations with wavenumbers k < 1-2 cm-1. An upgrade underway will allow resolution up to k ~ 15 cm-1. A fast magnetic coil array is employed for magnetic fluctuations. High-frequency (>50 kHz) small-scale (n > 15) density and magnetic fluctuations have been observed in the edge plasma, where density and temperature gradients are largest. These fluctuations are distinct from tearing and have amplitudes that correlate with the density gradient and electron beta. The MST is well suited to explore beta scaling given the large dynamic range (9-26%) found in the device. Correlation of the measured density fluctuations with plasma parameters in high beta plasmas will serve to identify the drive and contribute to validation of gyrokinetic codes. Work supported by DOE and NSF.

  1. Measurement of high-frequency density fluctuations in improved confinement RFP plasmas

    NASA Astrophysics Data System (ADS)

    Duff, J. R.; Chapman, B. E.; Anderson, J. K.; Sarff, J. S.; Lin, L.; Ding, W. X.; Brower, D. L.

    2013-10-01

    In standard RFP plasmas, transport is dominated by global magnetic tearing modes. For improved-confinement plasmas using inductive current profile control (PPCD), smaller-scale fluctuations at higher frequencies (>50 kHz) may become more important as the global tearing modes are significantly reduced. In particular, drift-wave-like instabilities are theoretically unstable to the higher temperature and density gradients achieved during PPCD discharges. On the MST, an eleven chord Far-Infrared (FIR) laser-based diagnostic system with ~ 8 cm spacing is used to measure electron density fluctuations by interferometry and far-forward collective scattering. The existing diagnostic measures line-integrated density fluctuations within the divergence of the probe beam covering a wavenumber range k-< 1.3 cm-1, corresponding to k-ρs < 1.3 (ρs is the ion-sound Larmor radius). Experimentally, in PPCD plasmas, global tearing modes are reduced while high frequency coherent modes (50 < f < 140 kHz) emerge among broadband fluctuations. Correlations of these modes with sources of free energy, such as temperature and density gradients, will be investigated. Additionally, effects of increased plasma flow from a 1MW tangential NBI on high frequency density fluctuations will also be explored. Work Supported by U.S.D.O.E.

  2. Microstability in a ``MAST-like'' high confinement mode spherical tokamak equilibrium

    NASA Astrophysics Data System (ADS)

    Applegate, D. J.; Roach, C. M.; Cowley, S. C.; Dorland, W. D.; Joiner, N.; Akers, R. J.; Conway, N. J.; Field, A. R.; Patel, A.; Valovic, M.; Walsh, M. J.

    2004-11-01

    Gyrokinetic microstability analyses, with and without electromagnetic effects, are presented for a spherical tokamak plasma equilibrium closely resembling that from a high confinement mode (H mode) discharge in the mega-ampere spherical tokamak (MAST) [A. Sykes et al., Nucl. Fusion 41, 1423 (2001)]. Electrostatic ion temperature gradient driven modes (ITG modes) were found to be unstable on all surfaces, though they are likely to be substantially stabilized by equilibrium E×B flow shear. Electron temperature gradient driven modes (ETG modes) have stronger growth rates that substantially exceed the equilibrium flow shearing rates. Mixing length arguments suggest that ITG modes would give rise to significant transport if they are not stabilized by sheared flows, and predict weak transport from ETG turbulence. Significant plasma flows have been neglected in this first analysis, and are probably important in the delicate balance between ITG growth rates and flow shear, and in the formation of internal transport barriers on MAST. Electromagnetic effects are found to be important even in this low β discharge, especially for longer length-scale modes with k⊥ρihighly extended along the magnetic field, and have been reported in a number of spherical tokamak equilibria.

  3. Rotational dynamics of confined C60 from near-infrared Raman studies under high pressure

    SciTech Connect

    Zou, Y.; Liu, B.; Wang, L.; Liu, D.; Yu, S.; Wang, P.; Wang, T.; Yao, M.; Li, Q.; Zou, B.; Cui, T.; Zou, G.; Wagberg, T.; Sundqvist, B.; Mao, H.-K.

    2009-12-29

    Peapods present a model system for studying the properties of dimensionally constrained crystal structures, whose dynamical properties are very important. We have recently studied the rotational dynamics of C60 molecules confined inside single walled carbon nanotube (SWNT) by analyzing the intermediate frequency mode lattice vibrations using near-infrared Raman spectroscopy. The rotation of C60 was tuned to a known state by applying high pressure, at which condition C60 first forms dimers at low pressure and then forms a single-chain, nonrotating, polymer structure at high pressure. In the latter state the molecules form chains with a 2-fold symmetry. We propose that the C60 molecules in SWNT exhibit an unusual type of ratcheted rotation due to the interaction between C60 and SWNT in the “hexagon orientation,” and the characteristic vibrations of ratcheted rotation becomes more obvious with decreasing temperature.

  4. Neoclassical Tearing Mode Locking Avoidance by 3D Fields and Recovery of High Confinement

    NASA Astrophysics Data System (ADS)

    Okabayashi, M.; Budny, B.; Brennan, D.; Ferraro, N.; Grierson, B.; Jardin, S.; Logan, N.; Nazikian, R.; Tobias, B.; Wang, Z.; Strait, E.; de Grassie, J.; La Haye, R.; Paz-Soldan, C.; Taylor, Z.; Shiraki, D.; Hanson, J.; Holcomb, C.; Liu, Y.

    2016-10-01

    A slowly rotating n=1 helical magnetic field has been applied for Neoclassical Tearing Mode (NTM) locking avoidance in the DIII-D tokamak. This 3D field applied through feedback recovered a high performance configuration by rebuilding a H-mode edge and high ion temperature internal transport barrier in the plasma core, although, at present, the βn was reduced by 30%. The m/n=2/1 component of 3D field served to avoid NTM locking, while the m/n=1 and the m/n=(4-5)/1 components recover core confinement and H-mode edge. Preliminary analysis shows a quasi-steady helical plasma flow was built up around the core, mostly parallel to the equilibrium magnetic field. The optimization of m-components with n=1 is a promising approach for integrating optimizations of MHD stability from core to edge. Supported in part by the US DOE under DE-AC02-09CH11466, DE-FG02-99ER54531, DE-SC0003913 and DE-FC02-04ER54698.

  5. Operation Hardtack. Project 3. 2. Response of earth-confined flexible-arch structures in high-overpressure regions

    SciTech Connect

    LeDoux, J.C.; Rush, P.J.

    1985-09-01

    The purpose of this project was to determine structural responses and failure criteria of earth-confined corrugated-steel flexible arches subjected to high overpressure blast loading from nuclear detonations. A flexible arch is considered as an arch structure whose ultimate supporting capacity is dependent upon confinement within a surrounding earth configuration. A collateral objective was to determine the radiation-shielding effectiveness of such structures with a minimum cover of five feet of coral sand. Because the soil and ground-water conditions at Eniwetok did not permit the placing of the steel arches below natural-grade level, the structures were confined within massive non-drag sensitive earthwork configurations of coral sand. Empirical determinations were made of the responses of (1) three earth-confined prefabricated corrugated-steel flexible arches when subjected to relatively long-duration blast loadings from a megaton range detonation; and (2) one similar earth-confined flexible-arch when subjected to relatively short-duration blast loadings from a kiloton-range detonation.

  6. Public Data Set: High Confinement Mode and Edge Localized Mode Characteristics in a Near-Unity Aspect Ratio Tokamak

    SciTech Connect

    Thome, Kathreen E.; Bongard, Michael W.; Barr, Jayson L.; Bodner, Grant M.; Burke, Marcus G.; Fonck, Raymond J.; Kriete, David M.; Perry, Justin M.; Schlossberg, David J.

    2016-04-27

    This data set contains openly-documented, machine readable digital research data corresponding to figures published in K.E. Thome et al., 'High Confinement Mode and Edge Localized Mode Characteristics in a Near-Unity Aspect Ratio Tokamak,' Phys. Rev. Lett. 116, 175001 (2016).

  7. Programmable high voltage power supply with regulation confined to the high voltage section

    NASA Technical Reports Server (NTRS)

    Castell, Karen D. (Inventor); Ruitberg, Arthur P. (Inventor)

    1994-01-01

    A high voltage power supply in a dc-dc converter configuration includes a pre-regulator which filters and regulates the dc input and drives an oscillator which applies, in turn, a low voltage ac signal to the low side of a step-up high voltage transformer. The high voltage side of the transformer drives a voltage multiplier which provides a stepped up dc voltage to an output filter. The output voltage is sensed by a feedback network which then controls a regulator. Both the input and output of the regulator are on the high voltage side, avoiding isolation problems. The regulator furnishes a portion of the drive to the voltage multiplier, avoiding having a regulator in series with the load with its attendant, relatively high power losses. This power supply is highly regulated, has low power consumption, a low parts count and may be manufactured at low cost. The power supply has a programmability feature that allows for the selection of a large range of output voltages.

  8. Progress in laboratory high gain ICF (inertial confinement fusion): Prospects for the future

    SciTech Connect

    Storm, E.; Lindl, J.D.; Campbell, E.M.; Bernat, T.P.; Coleman, L.W.; Emmett, J.L.; Hogan, W.J.; Hunt, J.T.; Krupke, W.F.; Lowdermilk, W.H.

    1988-01-01

    Inertial confinement fusion (ICF), a thermonuclear reaction in a small (/approximately/5 mm diameter) fuel capsule filled with a few milligrams of deuterium and tritium, has been the subject of very fruitful experimentation since the early 1970's. High gain ICF is now on the threshold of practical applications. With a Laboratory Microfusion Facility (LMF), these applications will have major implications for national defense, basic and applied science, and power production. With a driver capable of delivering about 10 MJ in a 10-ns pulse at an intensity of /approximately/3 /times/ 10/sup 14/ W/cm/sup 2/, an appropriately configured cryogenic capsule could be compressed to a density of about 200 g/cm/sup 3/ and a temperature of 3--5 keV. Under these conditions, up to 10 mg of DT could be ignited, and with a burn efficiency of about 30%, release up to 1000 MJ of fusion energy, an energy gain of about 100. A thousand megajoules is equivalent to about one quarter ton of TNT, or about 7 gallons of oil--an amount of energy tractable under laboratory conditions and potentially very useful for a variety of applications. 61 refs., 33 figs.

  9. High-resolution Electrical Resistivity Tomography monitoring of a tracer test in a confined aquifer

    NASA Astrophysics Data System (ADS)

    Wilkinson, P. B.; Meldrum, P. I.; Kuras, O.; Chambers, J. E.; Holyoake, S. J.; Ogilvy, R. D.

    2010-04-01

    A permanent geoelectrical subsurface imaging system has been installed at a contaminated land site to monitor changes in groundwater quality after the completion of a remediation programme. Since the resistivities of earth materials are sensitive to the presence of contaminants and their break-down products, 4-dimensional resistivity imaging can act as a surrogate monitoring technology for tracking and visualising changes in contaminant concentrations at much higher spatial and temporal resolution than manual intrusive investigations. The test site, a municipal car park built on a former gasworks, had been polluted by a range of polycyclic aromatic hydrocarbons and dissolved phase contaminants. It was designated statutory contaminated land under Part IIA of the UK Environmental Protection Act due to the risk of polluting an underlying minor aquifer. Resistivity monitoring zones were established on the boundaries of the site by installing vertical electrode arrays in purpose-drilled boreholes. After a year of monitoring data had been collected, a tracer test was performed to investigate groundwater flow velocity and to demonstrate rapid volumetric monitoring of natural attenuation processes. A saline tracer was injected into the confined aquifer, and its motion and evolution were visualised directly in high-resolution tomographic images in near real-time. Breakthrough curves were calculated from independent resistivity measurements, and the estimated seepage velocities from the monitoring images and the breakthrough curves were found to be in good agreement with each other and with estimates based on the piezometric gradient and assumed material parameters.

  10. High Confinement and High Density with Stationary Plasma Energy and Strong Edge Radiation Cooling in Textor-94

    NASA Astrophysics Data System (ADS)

    Messiaen, A. M.

    1996-11-01

    A new discharge regime has been observed on the pumped limiter tokamak TEXTOR-94 in the presence of strong radiation cooling and for different scenarii of additional hearing. The radiated power fraction (up to 90%) is feedback controlled by the amount of Ne seeded in the edge. This regime meets many of the necessary conditions for a future fusion reactor. Energy confinement increases with increasing densities (reminiscent of the Z-mode obtained at ISX-B) and as good as ELM-free H-mode confinement (enhancement factor verus ITERH93-P up to 1.2) is obtained at high densities (up to 1.2 times the Greenwald limit) with peaked density profiles showing a peaking factor of about 2 and central density values around 10^14cm-3. In experiments where the energy content of the discharges is kept constant with an energy feedback loop acting on the amount of ICRH power, stable and stationary discharges are obtained for intervals of more than 5s, i.e. 100 times the energy confinement time or about equal to the skin resistive time, even with the cylindrical q_α as low as 2.8 β-values up to the β-limits of TEXTOR-94 are achieved (i.e. β n ≈ 2 of and β p ≈ 1.5) and the figure of merit for ignition margin f_Hqa in these discharges can be as high as 0.7. No detrimental effects of the seeded impurity on the reactivity of the plasma are observed. He removal in these discharges has also been investigated. [1] Laboratoire de Physique des Plasmas-Laboratorium voor Plasmafysica, Association "EURATOM-Belgian State", Ecole Royale Militaire-Koninklijke Militaire School, Brussels, Belgium [2] Institut für Plasmaphysik, Forschungszentrum Jülich, GmbH, Association "EURATOM-KFA", Jülich, Germany [3] Fusion Energy Research Program, Mechanical Engineering Division, University of California at San Diego, La Jolla, USA [4] FOM Institüt voor Plasmafysica Rijnhuizen, Associatie "FOM-EURATOM", Nieuwegein, The Netherlands [*] Researcher at NFSR, Belgium itemize

  11. Economics of fertility in high-yielding dairy cows on confined TMR systems.

    PubMed

    Cabrera, V E

    2014-05-01

    The objective of this review paper was to summarise the latest findings in dairy cattle reproductive economics with an emphasis on high yielding, confined total mixed ration systems. The economic gain increases as the reproductive efficiency improves. These increments follow the law of diminishing returns, but are still positive even at high reproductive performance. Reproductive improvement results in higher milk productivity and, therefore, higher milk income over feed cost, more calf sales and lower culling and breeding expenses. Most high-yielding herds in the United States use a combination of timed artificial insemination (TAI) and oestrous detection (OD) reproductive programme. The ratio of achievable pregnancies between OD and TAI determines the economic value difference between both and their combinations. Nonetheless, complex interactions between reproductive programme, herd relative milk yield, and type of reproductive programme are reported. For example, higher herd relative milk yield would favour programme relying more on TAI. In addition, improved reproductive efficiency produces extra replacements. The availability of additional replacements could allow more aggressive culling policies (e.g. less services for non-pregnant cows) to balance on-farm supply and demand of replacements. Balancing heifer replacement availability in an efficient reproductive programme brings additional economic benefits. New technologies such as the use of earlier chemical tests for pregnancy diagnosis could be economically effective depending on the goals and characteristics of the farm. Opportunities for individual cow reproductive management within defined reproductive programme exist. These decisions would be based on economic metrics derived from the value of a cow such as the value of a new pregnancy, the cost of a pregnancy loss, or the cost of an extra day open.

  12. Tokamak-like confinement at a high beta and low toroidal field in the MST reversed field pinch

    NASA Astrophysics Data System (ADS)

    Sarff, J. S.; Almagri, A. F.; Anderson, J. K.; Biewer, T. M.; Blair, A. P.; Cengher, M.; Chapman, B. E.; Chattopadhyay, P. K.; Craig, D.; Den Hartog, D. J.; Ebrahimi, F.; Fiksel, G.; Forest, C. B.; Goetz, J. A.; Holly, D.; Hudson, B.; Lovell, T. W.; McCollam, K. J.; Nonn, P. D.; O'Connell, R.; Oliva, S. P.; Prager, S. C.; Reardon, J. C.; Thomas, M. A.; Wyman, M. D.; Brower, D. L.; Ding, W. X.; Terry, S. D.; Carter, M. D.; Davydenko, V. I.; Ivanov, A. A.; Harvey, R. W.; Pinsker, R. I.; Xiao, C.

    2003-12-01

    Energy confinement comparable with tokamak quality is achieved in the Madison Symmetric Torus (MST) reversed field pinch (RFP) at a high beta and low toroidal magnetic field. Magnetic fluctuations normally present in the RFP are reduced via parallel current drive in the outer region of the plasma. In response, the electron temperature nearly triples and beta doubles. The confinement time increases ten-fold (to ~10 ms), which is comparable with L- and H-mode scaling values for a tokamak with the same plasma current, density, heating power, size and shape. Runaway electron confinement is evidenced by a 100-fold increase in hard x-ray bremsstrahlung. Fokker-Planck modelling of the x-ray energy spectrum reveals that the high energy electron diffusion is independent of the parallel velocity, uncharacteristic of magnetic transport and more like that for electrostatic turbulence. The high core electron temperature correlates strongly with a broadband reduction of resonant modes at mid-radius where the stochasticity is normally most intense. To extend profile control and add auxiliary heating, rf current drive and neutral beam heating are in development. Low power lower-hybrid and electron Bernstein wave injection experiments are underway. Dc current sustainment via ac helicity injection (sinusoidal inductive loop voltages) is also being tested. Low power neutral beam injection shows that fast ions are well-confined, even in the presence of relatively large magnetic fluctuations. Presented at the 19th IAEA Fusion Energy Conference with the title Overview of Improved Confinement and Plasma Control in the MST Reversed Field Pinch.

  13. COLLISIONS BETWEEN DARK MATTER CONFINED HIGH VELOCITY CLOUDS AND MAGNETIZED GALACTIC DISKS: THE SMITH CLOUD

    SciTech Connect

    Galyardt, Jason; Shelton, Robin L. E-mail: rls@physast.uga.edu

    2016-01-01

    The Galaxy’s population of High Velocity Clouds (HVCs) may include a subpopulation that is confined by dark matter minihalos and falling toward the Galactic disk. We present the first magnetohydrodynamic simulational study of dark-matter-dominated HVCs colliding with a weakly magnetized galactic disk. Our HVCs have baryonic masses of 5 × 10{sup 6}M{sub ⊙} and dark matter minihalo masses of 0, 3 × 10{sup 8}, or 1 × 10{sup 9} M{sub ⊙}. They are modeled on the Smith Cloud, which is said to have collided with the disk 70 Myr ago. We find that, in all cases, the cloud’s collision with the galactic disk creates a hole in the disk, completely disperses the cloud, and forms a bubble-shaped structure on the far side of the disk. In contrast, when present, the dark matter minihalo continues unimpeded along its trajectory. Later, as the minihalo passes through the bubble structure and galactic halo, it accretes up to 6.0 × 10{sup 5} M{sub ⊙} in baryonic material, depending on the strengths of the magnetic field and minihalo gravity. These simulations suggest that if the Smith Cloud is associated with a dark matter minihalo and collided with the Galactic disk, the minihalo has accreted the observed gas. However, if the Smith Cloud is dark-matter-free, it is on its first approach toward the disk. These simulations also suggest that the dark matter is most concentrated either at the head of the cloud or near the cloud, depending upon the strength of the magnetic field, a point that could inform indirect dark matter searches.

  14. THE SMITH CLOUD: HIGH-VELOCITY ACCRETION AND DARK MATTER CONFINEMENT

    SciTech Connect

    Nichols, M.; Bland-Hawthorn, J.

    2009-12-20

    The Smith Cloud is a massive system of metal-poor neutral and ionized gas (M{sub gas} approx> 2 x 10{sup 6} M{sub sun}) that is presently moving at high velocity (V{sub GSR}approx 300 km s{sup -1}) with respect to the Galaxy at a distance of 12 kpc from the Sun. The kinematics of the cloud's cometary tail indicates that the gas is in the process of accretion onto the Galaxy, as first discussed by Lockman et al. Here, we re-investigate the cloud's orbit by considering the possibility that the cloud is confined by a dark matter halo. This is required for the cloud to survive its passage through the Galactic corona. We consider three possible models for the dark matter halo (Navarro-Frenk-White (NFW), Einasto, and Burkert) including the effects of tidal disruption and ram pressure stripping during the cloud's infall onto and passage through the Galactic disk. For the NFW and Einasto dark matter models, we are able to determine reasonable initial conditions for the Smith Cloud, although this is only marginally possible with the Burkert model. For all three models, the progenitor had an initial (gas+dark matter) mass that was an order-of-magnitude higher than inferred today. In agreement with Lockman et al., the cloud appears to have punched through the disk approx70 Myr ago. For our most successful models, the baryon-to-dark matter ratio is fairly constant during an orbital period but drops by a factor of 2-5 after transiting the disk. The cloud appears to have only marginally survived its transit and is unlikely to retain its integrity during the next transit approx 30 Myr from now.

  15. A case study of the carbon footprint of milk from high-performing confinement and grass-based dairy farms.

    PubMed

    O'Brien, D; Capper, J L; Garnsworthy, P C; Grainger, C; Shalloo, L

    2014-03-01

    Life-cycle assessment (LCA) is the preferred methodology to assess carbon footprint per unit of milk. The objective of this case study was to apply an LCA method to compare carbon footprints of high-performance confinement and grass-based dairy farms. Physical performance data from research herds were used to quantify carbon footprints of a high-performance Irish grass-based dairy system and a top-performing United Kingdom (UK) confinement dairy system. For the US confinement dairy system, data from the top 5% of herds of a national database were used. Life-cycle assessment was applied using the same dairy farm greenhouse gas (GHG) model for all dairy systems. The model estimated all on- and off-farm GHG sources associated with dairy production until milk is sold from the farm in kilograms of carbon dioxide equivalents (CO2-eq) and allocated emissions between milk and meat. The carbon footprint of milk was calculated by expressing GHG emissions attributed to milk per tonne of energy-corrected milk (ECM). The comparison showed that when GHG emissions were only attributed to milk, the carbon footprint of milk from the Irish grass-based system (837 kg of CO2-eq/t of ECM) was 5% lower than the UK confinement system (884 kg of CO2-eq/t of ECM) and 7% lower than the US confinement system (898 kg of CO2-eq/t of ECM). However, without grassland carbon sequestration, the grass-based and confinement dairy systems had similar carbon footprints per tonne of ECM. Emission algorithms and allocation of GHG emissions between milk and meat also affected the relative difference and order of dairy system carbon footprints. For instance, depending on the method chosen to allocate emissions between milk and meat, the relative difference between the carbon footprints of grass-based and confinement dairy systems varied by 3 to 22%. This indicates that further harmonization of several aspects of the LCA methodology is required to compare carbon footprints of contrasting dairy systems. In

  16. Development of a Binary Mixture Gas Composition Instrument for Use in a Confined High Temperature Environment

    NASA Astrophysics Data System (ADS)

    Cadell, Seth R.

    , or used to measure the purity of the coolant itself. This work details the efforts conducted to develop such an instrument. While the concept of designing a capacitance sensor to measure a gas mixture is not unique, the application of using a capacitance sensor within a nuclear reactor is a new application. This application requires the development of an instrument that will survive a high temperature nuclear reactor environment and operate at a sensitivity not found in current applications. To prove this technique, instrument prototypes were built and tested in confined environments and at high temperatures. This work discusses the proof of concept testing and outlines an application in the High Temperature Test Facility to increase the operational understanding of the instrument. This work is the first step toward the ultimate outcome of this work, which is to provide a new tool to the gas reactor community allowing real-time measurements of coolant properties within the core.

  17. Influence of confining pressure and impact loading on mechanical properties of amphibolite and sericite-quartz schist

    NASA Astrophysics Data System (ADS)

    Liu, Shi; Xu, Jinyu; Lv, Xiaocong

    2014-06-01

    In order to investigate the dynamic mechanical properties of amphibolite and sericite-quartz schist under confining pressure, two rocks are subjected to impact loadings with different strain rates and confining pressures by using split Hopkinson pressure bar equipment with a confining pressure device. Based on the experimental results, the stress-strain curves are analyzed and the effects of confining pressure and strain rates on the dynamic compressive strength, peak strain and failure mode are summarized. The results show that: (1) The characteristics of two rocks in the ascent stage of the stress-strain curve are basically the same, but in the descent stage, the rocks gradually show plastic deformation characteristics as the confining pressure increases. (2) The dynamic compressive strength and peak strain of two rocks increase as the strain rate increases and the confining pressure effects are obvious. (3) Due to the effect of confining pressure, the normal stress on the damage surface of the rock increases correspondingly, the bearing capacity of the crack friction exceeds the material cohesion and the slippage of the fractured rock is controlled, which all lead to the compression and shear failure mode of rock. The theoretical analysis and experimental methods to study the dynamic failure mode and other related characteristics of rock are useful in developing standards for engineering practice.

  18. 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.

  19. Detailed high-resolution three-dimensional simulations of OMEGA separated reactants inertial confinement fusion experiments

    NASA Astrophysics Data System (ADS)

    Haines, Brian M.; Grim, Gary P.; Fincke, James R.; Shah, Rahul C.; Forrest, Chad J.; Silverstein, Kevin; Marshall, Frederic J.; Boswell, Melissa; Fowler, Malcolm M.; Gore, Robert A.; Hayes-Sterbenz, Anna C.; Jungman, Gerard; Klein, Andreas; Rundberg, Robert S.; Steinkamp, Michael J.; Wilhelmy, Jerry B.

    2016-07-01

    We present results from the comparison of high-resolution three-dimensional (3D) simulations with data from the implosions of inertial confinement fusion capsules with separated reactants performed on the OMEGA laser facility. Each capsule, referred to as a "CD Mixcap," is filled with tritium and has a polystyrene (CH) shell with a deuterated polystyrene (CD) layer whose burial depth is varied. In these implosions, fusion reactions between deuterium and tritium ions can occur only in the presence of atomic mix between the gas fill and shell material. The simulations feature accurate models for all known experimental asymmetries and do not employ any adjustable parameters to improve agreement with experimental data. Simulations are performed with the RAGE radiation-hydrodynamics code using an Implicit Large Eddy Simulation (ILES) strategy for the hydrodynamics. We obtain good agreement with the experimental data, including the DT/TT neutron yield ratios used to diagnose mix, for all burial depths of the deuterated shell layer. Additionally, simulations demonstrate good agreement with converged simulations employing explicit models for plasma diffusion and viscosity, suggesting that the implicit sub-grid model used in ILES is sufficient to model these processes in these experiments. In our simulations, mixing is driven by short-wavelength asymmetries and longer-wavelength features are responsible for developing flows that transport mixed material towards the center of the hot spot. Mix material transported by this process is responsible for most of the mix (DT) yield even for the capsule with a CD layer adjacent to the tritium fuel. Consistent with our previous results, mix does not play a significant role in TT neutron yield degradation; instead, this is dominated by the displacement of fuel from the center of the implosion due to the development of turbulent instabilities seeded by long-wavelength asymmetries. Through these processes, the long

  20. Detailed high-resolution three-dimensional simulations of OMEGA separated reactants inertial confinement fusion experiments

    DOE PAGES

    Haines, Brian Michael; Grim, Gary P.; Fincke, James R.; ...

    2016-07-29

    Here, we present results from the comparison of high-resolution three-dimensional (3D) simulations with data from the implosions of inertial confinement fusion capsules with separated reactants performed on the OMEGA laser facility. Each capsule, referred to as a “CD Mixcap,” is filled with tritium and has a polystyrene (CH) shell with a deuterated polystyrene (CD) layer whose burial depth is varied. In these implosions, fusion reactions between deuterium and tritium ions can occur only in the presence of atomic mix between the gas fill and shell material. The simulations feature accurate models for all known experimental asymmetries and do not employmore » any adjustable parameters to improve agreement with experimental data. Simulations are performed with the RAGE radiation-hydrodynamics code using an Implicit Large Eddy Simulation (ILES) strategy for the hydrodynamics. We obtain good agreement with the experimental data, including the DT/TT neutron yield ratios used to diagnose mix, for all burial depths of the deuterated shell layer. Additionally, simulations demonstrate good agreement with converged simulations employing explicit models for plasma diffusion and viscosity, suggesting that the implicit sub-grid model used in ILES is sufficient to model these processes in these experiments. In our simulations, mixing is driven by short-wavelength asymmetries and longer-wavelength features are responsible for developing flows that transport mixed material towards the center of the hot spot. Mix material transported by this process is responsible for most of the mix (DT) yield even for the capsule with a CD layer adjacent to the tritium fuel. Consistent with our previous results, mix does not play a significant role in TT neutron yield degradation; instead, this is dominated by the displacement of fuel from the center of the implosion due to the development of turbulent instabilities seeded by long-wavelength asymmetries. Through these processes, the long

  1. Detailed high-resolution three-dimensional simulations of OMEGA separated reactants inertial confinement fusion experiments

    SciTech Connect

    Haines, Brian Michael; Grim, Gary P.; Fincke, James R.; Shah, Rahul C.; Forrest, Chad J.; Silverstein, Kevin; Marshall, Frederic J.; Boswell, Melissa; Fowler, Malcolm M.; Gore, Robert A.; Hayes-Sterbenz, Anna Catherine; Jungman, Gerard; Klein, Andreas; Rundberg, Robert S.; Steinkamp, Michael James; Wilhelmy, Jerry B.

    2016-07-29

    Here, we present results from the comparison of high-resolution three-dimensional (3D) simulations with data from the implosions of inertial confinement fusion capsules with separated reactants performed on the OMEGA laser facility. Each capsule, referred to as a “CD Mixcap,” is filled with tritium and has a polystyrene (CH) shell with a deuterated polystyrene (CD) layer whose burial depth is varied. In these implosions, fusion reactions between deuterium and tritium ions can occur only in the presence of atomic mix between the gas fill and shell material. The simulations feature accurate models for all known experimental asymmetries and do not employ any adjustable parameters to improve agreement with experimental data. Simulations are performed with the RAGE radiation-hydrodynamics code using an Implicit Large Eddy Simulation (ILES) strategy for the hydrodynamics. We obtain good agreement with the experimental data, including the DT/TT neutron yield ratios used to diagnose mix, for all burial depths of the deuterated shell layer. Additionally, simulations demonstrate good agreement with converged simulations employing explicit models for plasma diffusion and viscosity, suggesting that the implicit sub-grid model used in ILES is sufficient to model these processes in these experiments. In our simulations, mixing is driven by short-wavelength asymmetries and longer-wavelength features are responsible for developing flows that transport mixed material towards the center of the hot spot. Mix material transported by this process is responsible for most of the mix (DT) yield even for the capsule with a CD layer adjacent to the tritium fuel. Consistent with our previous results, mix does not play a significant role in TT neutron yield degradation; instead, this is dominated by the displacement of fuel from the center of the implosion due to the development of turbulent instabilities seeded by long-wavelength asymmetries. Through these processes, the long

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

    SciTech Connect

    Hartley, J.H.

    1997-09-01

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

  3. Graphene/Si-quantum-dot heterojunction diodes showing high photosensitivity compatible with quantum confinement effect.

    PubMed

    Shin, Dong Hee; Kim, Sung; Kim, Jong Min; Jang, Chan Wook; Kim, Ju Hwan; Lee, Kyeong Won; Kim, Jungkil; Oh, Si Duck; Lee, Dae Hun; Kang, Soo Seok; Kim, Chang Oh; Choi, Suk-Ho; Kim, Kyung Joong

    2015-04-24

    Graphene/Si quantum dot (QD) heterojunction diodes are reported for the first time. The photoresponse, very sensitive to variations in the size of the QDs as well as in the doping concentration of graphene and consistent with the quantum-confinement effect, is remarkably enhanced in the near-ultraviolet range compared to commercially available bulk-Si photodetectors. The photoresponse proves to be dominated by the carriertunneling mechanism.

  4. Influence of confinement layers in the emitting layer of the blue phosphorescent organic light-emitting diodes

    NASA Astrophysics Data System (ADS)

    Ji, Chang-Yan; Gu, Zheng-Tian; Kou, Zhi-Qi

    2016-10-01

    The electrical and optical properties of the blue phosphorescent organic light-emitting diodes (PHOLEDs) can be affected by the various structure of confinement layer in the emitting layer (EML). A series of devices with different electron or hole confinement layer (TCTA or Bphen) are fabricated, it is more effective to balance charge carriers injection for the device with the double electron confinement layers structure, the power efficiency and luminance can reach 17.7 lm/W (at 103 cd/m2) and 3536 cd/m2 (at 8 V). In case of the same double electron confinement layers, another series of devices with different profile of EML are fabricated by changing the confinement layers position, the power efficiency and luminance can be improved to 21.7 lm/W (at 103 cd/m2) and 7674 cd/m2 (at 8 V) when the thickness of EML separated by confinement layers increases gradually from the hole injection side to the electron injection side, the driving voltage can also be reduced.

  5. Geometric conductive filament confinement by nanotips for resistive switching of HfO2-RRAM devices with high performance.

    PubMed

    Niu, Gang; Calka, Pauline; Auf der Maur, Matthias; Santoni, Francesco; Guha, Subhajit; Fraschke, Mirko; Hamoumou, Philippe; Gautier, Brice; Perez, Eduardo; Walczyk, Christian; Wenger, Christian; Di Carlo, Aldo; Alff, Lambert; Schroeder, Thomas

    2016-05-16

    Filament-type HfO2-based RRAM has been considered as one of the most promising candidates for future non-volatile memories. Further improvement of the stability, particularly at the "OFF" state, of such devices is mainly hindered by resistance variation induced by the uncontrolled oxygen vacancies distribution and filament growth in HfO2 films. We report highly stable endurance of TiN/Ti/HfO2/Si-tip RRAM devices using a CMOS compatible nanotip method. Simulations indicate that the nanotip bottom electrode provides a local confinement for the electrical field and ionic current density; thus a nano-confinement for the oxygen vacancy distribution and nano-filament location is created by this approach. Conductive atomic force microscopy measurements confirm that the filaments form only on the nanotip region. Resistance switching by using pulses shows highly stable endurance for both ON and OFF modes, thanks to the geometric confinement of the conductive path and filament only above the nanotip. This nano-engineering approach opens a new pathway to realize forming-free RRAM devices with improved stability and reliability.

  6. Graphene-Analogues Boron Nitride Nanosheets Confining Ionic Liquids: A High-Performance Quasi-Liquid Solid Electrolyte.

    PubMed

    Li, Mingtao; Zhu, Wenshuai; Zhang, Pengfei; Chao, Yanhong; He, Qian; Yang, Bolun; Li, Huaming; Borisevich, Albinab; Dai, Sheng

    2016-07-01

    Solid electrolytes are one of the most promising electrolyte systems for safe lithium batteries, but the low ionic conductivity of these electrolytes seriously hinders the development of efficient lithium batteries. Here, a novel class of graphene-analogues boron nitride (g-BN) nanosheets confining an ultrahigh concentration of ionic liquids (ILs) in an interlayer and out-of-layer chamber to give rise to a quasi-liquid solid electrolyte (QLSE) is reported. The electron-insulated g-BN nanosheet host with a large specific surface area can confine ILs as much as 10 times of the host's weight to afford high ionic conductivity (3.85 × 10(-3) S cm(-1) at 25 °C, even 2.32 × 10(-4) S cm(-1) at -20 °C), which is close to that of the corresponding bulk IL electrolytes. The high ionic conductivity of QLSE is attributed to the enormous absorption for ILs and the confining effect of g-BN to form the ordered lithium ion transport channels in an interlayer and out-of-layer of g-BN. Furthermore, the electrolyte displays outstanding electrochemical properties and battery performance. In principle, this work enables a wider tunability, further opening up a new field for the fabrication of the next-generation QLSE based on layered nanomaterials in energy conversion devices.

  7. Geometric conductive filament confinement by nanotips for resistive switching of HfO2-RRAM devices with high performance

    PubMed Central

    Niu, Gang; Calka, Pauline; Auf der Maur, Matthias; Santoni, Francesco; Guha, Subhajit; Fraschke, Mirko; Hamoumou, Philippe; Gautier, Brice; Perez, Eduardo; Walczyk, Christian; Wenger, Christian; Di Carlo, Aldo; Alff, Lambert; Schroeder, Thomas

    2016-01-01

    Filament-type HfO2-based RRAM has been considered as one of the most promising candidates for future non-volatile memories. Further improvement of the stability, particularly at the “OFF” state, of such devices is mainly hindered by resistance variation induced by the uncontrolled oxygen vacancies distribution and filament growth in HfO2 films. We report highly stable endurance of TiN/Ti/HfO2/Si-tip RRAM devices using a CMOS compatible nanotip method. Simulations indicate that the nanotip bottom electrode provides a local confinement for the electrical field and ionic current density; thus a nano-confinement for the oxygen vacancy distribution and nano-filament location is created by this approach. Conductive atomic force microscopy measurements confirm that the filaments form only on the nanotip region. Resistance switching by using pulses shows highly stable endurance for both ON and OFF modes, thanks to the geometric confinement of the conductive path and filament only above the nanotip. This nano-engineering approach opens a new pathway to realize forming-free RRAM devices with improved stability and reliability. PMID:27181525

  8. First-order transition in confined water between high-density liquid and low-density amorphous phases.

    PubMed

    Koga, K; Tanaka, H; Zeng, X C

    2000-11-30

    Supercooled water and amorphous ice have a rich metastable phase behaviour. In addition to transitions between high- and low-density amorphous solids, and between high- and low-density liquids, a fragile-to-strong liquid transition has recently been proposed, and supported by evidence from the behaviour of deeply supercooled bilayer water confined in hydrophilic slit pores. Here we report evidence from molecular dynamics simulations for another type of first-order phase transition--a liquid-to-bilayer amorphous transition--above the freezing temperature of bulk water at atmospheric pressure. This transition occurs only when water is confined in a hydrophobic slit pore with a width of less than one nanometre. On cooling, the confined water, which has an imperfect random hydrogen-bonded network, transforms into a bilayer amorphous phase with a perfect network (owing to the formation of various hydrogen-bonded polygons) but no long-range order. The transition shares some characteristics with those observed in tetrahedrally coordinated substances such as liquid silicon, liquid carbon and liquid phosphorus.

  9. Formation of high-{beta} plasma and stable confinement of toroidal electron plasma in Ring Trap 1

    SciTech Connect

    Saitoh, H.; Yoshida, Z.; Morikawa, J.; Furukawa, M.; Yano, Y.; Kawai, Y.; Kobayashi, M.; Vogel, G.; Mikami, H.

    2011-05-15

    Formation of high-{beta} electron cyclotron resonance heating plasma and stable confinement of pure electron plasma have been realized in the Ring Trap 1 device, a magnetospheric configuration generated by a levitated dipole field magnet. The effects of coil levitation resulted in drastic improvements of the confinement properties, and the maximum local {beta} value has exceeded 70%. Hot electrons are major component of electron populations, and its particle confinement time is 0.5 s. Plasma has a peaked density profile in strong field region [H. Saitoh et al., 23rd IAEA Fusion Energy Conference EXC/9-4Rb (2010)]. In pure electron plasma experiment, inward particle diffusion is realized, and electrons are stably trapped for more than 300 s. When the plasma is in turbulent state during beam injection, plasma flow has a shear, which activates the diocotron (Kelvin-Helmholtz) instability. The canonical angular momentum of the particle is not conserved in this phase, realizing the radial diffusion of charged particles across closed magnetic surfaces. [Z. Yoshida et al., Phys Rev. Lett. 104, 235004 (2010); H. Saitoh et al., Phys. Plasmas 17, 112111 (2010).].

  10. High Confinement Mode and Edge Localized Mode Characteristics in a Near-Unity Aspect Ratio Tokamak.

    PubMed

    Thome, K E; Bongard, M W; Barr, J L; Bodner, G M; Burke, M G; Fonck, R J; Kriete, D M; Perry, J M; Schlossberg, D J

    2016-04-29

    Tokamak experiments at near-unity aspect ratio A≲1.2 offer new insights into the self-organized H-mode plasma confinement regime. In contrast to conventional A∼3 plasmas, the L-H power threshold P_{LH} is ∼15× higher than scaling predictions, and it is insensitive to magnetic topology, consistent with modeling. Edge localized mode (ELM) instabilities shift to lower toroidal mode numbers as A decreases. These ultralow-A operations enable heretofore inaccessible J_{edge}(R,t) measurements through an ELM that show a complex multimodal collapse and the ejection of a current-carrying filament.

  11. High confinement mode and edge localized mode characteristics in a near-unity aspect ratio tokamak

    DOE PAGES

    Thome, Kathreen E.; Bongard, Michael W.; Barr, Jayson L.; ...

    2016-04-27

    Tokamak experiments at near-unity aspect ratio A ≲ 1.2 offer new insights into the self-organized H-mode plasma confinement regime. In contrast to conventional A ~ 3 plasmas, the L–H power threshold PLH is ~15× higher than scaling predictions, and it is insensitive to magnetic topology, consistent with modeling. Edge localized mode (ELM) instabilities shift to lower toroidal mode numbers as A decreases. Furthermore, these ultralow-A operations enable heretofore inaccessible Jedge(R,t) measurements through an ELM that show a complex multimodal collapse and the ejection of a current-carrying filament.

  12. High confinement mode and edge localized mode characteristics in a near-unity aspect ratio tokamak

    SciTech Connect

    Thome, Kathreen E.; Bongard, Michael W.; Barr, Jayson L.; Bodner, Grant M.; Burke, Marcus G.; Fonck, Raymond J.; Kriete, David M.; Perry, Justin M.; Schlossberg, David J.

    2016-04-27

    Tokamak experiments at near-unity aspect ratio A ≲ 1.2 offer new insights into the self-organized H-mode plasma confinement regime. In contrast to conventional A ~ 3 plasmas, the L–H power threshold PLH is ~15× higher than scaling predictions, and it is insensitive to magnetic topology, consistent with modeling. Edge localized mode (ELM) instabilities shift to lower toroidal mode numbers as A decreases. Furthermore, these ultralow-A operations enable heretofore inaccessible Jedge(R,t) measurements through an ELM that show a complex multimodal collapse and the ejection of a current-carrying filament.

  13. Improved confinement in high-density H-modes via modification of the plasma boundary with lower hybrid wavesa)

    NASA Astrophysics Data System (ADS)

    Terry, J. L.; Reinke, M. L.; Hughes, J. W.; LaBombard, B.; Theiler, C.; Wallace, G. M.; Baek, S. G.; Brunner, D.; Churchill, R. M.; Edlund, E.; Ennever, P.; Faust, I.; Golfinopoulos, T.; Greenwald, M.; Hubbard, A. E.; Irby, J.; Lin, Y.; Parker, R. R.; Rice, J. E.; Shiraiwa, S.; Walk, J. R.; Wukitch, S. J.; Xu, P.

    2015-05-01

    Injecting Lower Hybrid Range of Frequency (LHRF) waves into Alcator C-Mod's high-density H-mode plasmas has led to enhanced global energy confinement by increasing pedestal temperature and pressure gradients, decreasing the separatrix density, modifying the pedestal radial electric field and rotation, and decreasing edge turbulence. These experiments indicate that edge LHRF can be used as an actuator to increase energy confinement via modification of boundary quantities. H98-factor increases of up to ˜35% (e.g., H98 from 0.75 to 1.0) are seen when moderate amounts of LH power (PLH/Ptot ˜ 0.15) are applied to H-modes of densities n ¯ e ˜ 3 × 1020 m-3, corresponding to values ˜0.5 of the Greenwald density. However, the magnitude of the improvement is reduced if the confinement quality of the target H-mode plasma is already good (i.e., H98target ˜ 1). Ray-tracing modeling and accessibility calculations for the LH waves indicate that they do not penetrate to the core. The LHRF power appears to be deposited in plasma boundary region, with a large fraction of the injected power increment appearing promptly on the outer divertor target. There is no evidence that the LH waves are driving current in these plasmas. The LHRF-actuated improvements are well correlated with suppressed pedestal density fluctuations in the 100-300 kHz range. There is also a correlation between the improved confinement and a drop in separatrix density, a correlation that is consistent with previous H-mode results with no LHRF.

  14. The Influence of Short-Range Correlation on the Phonon Confinement of a Single ZnO Nanowire.

    PubMed

    Shih, Po-Hsun; Wu, Sheng Yun

    2017-12-01

    Plenty of researches have been performed to probe the diverse properties of ZnO nanowires, but only a few have focused on the physical properties of a single nanowire since to analyze the optical confinement and their correlation lengths along a single nanowire is difficult. In this study, a single ZnO nanowire was synthesized using a Ti-assisted chemical vapor deposition (CVD) method to avoid the appearance of catalytic contamination. Confocal Raman spectroscopy is a powerful tool for probing the phonon confinement effect in a single ZnO nanowire. A confinement model was used to calculate the correlation lengths along the growth direction. The Raman mapping of ZnO nanowires was obtained by a confocal Raman spectrometer. A phonon confinement model was used to fit the Raman curves of the E2 mode and to obtain the correlation lengths along the growth direction of the ZnO nanowire. The correlation lengths are related to the phonon confined region by boundaries and/or defects.

  15. Equilibrium drives of the low and high field side n = 2 plasma response and impact on global confinement

    DOE PAGES

    Paz-Soldan, C.; Logan, N. C.; Haskey, S. R.; ...

    2016-03-31

    The nature of the multi-modal n=2 plasma response and its impact on global confinement is studied as a function of the axisymmetric equilibrium pressure, edge safety factor, collisionality, and L-versus H-mode conditions. Varying the relative phase (ΔΦUL) between upper and lower in-vessel coils demonstrates that different n=2 poloidal spectra preferentially excite different plasma responses. These different plasma response modes are preferentially detected on the tokamak high-field side (HFS) or low-field side (LFS) midplanes, have different radial extents, couple differently to the resonant surfaces, and have variable impacts on edge stability and global confinement. In all equilibrium conditions studied, the observedmore » confinement degradation shares the same ΔΦUL dependence as the coupling to the resonant surfaces given by both ideal (IPEC) and resistive (MARS-F) MHD computation. Varying the edge safety factor shifts the equilibrium field-line pitch and thus the ΔΦUL dependence of both the global confinement and the n=2 magnetic response. As edge safety factor is varied, modeling finds that the HFS response (but not the LFS response), the resonant surface coupling, and the edge displacements near the X-point all share the same ΔΦUL dependence. The LFS response magnitude is strongly sensitive to the core pressure and is insensitive to the collisionality and edge safety factor. This indicates that the LFS measurements are primarily sensitive to a pressure-driven kink-ballooning mode that couples to the core plasma. MHD modeling accurately reproduces these (and indeed all) LFS experimental trends and supports this interpretation. In contrast to the LFS, the HFS magnetic response and correlated global confinement impact is unchanged with plasma pressure, but is strongly reduced in high collisionality conditions in both H- and L-mode. This experimentally suggests the bootstrap current drives the HFS response through the kink-peeling mode drive, though

  16. High-Energy Cosmic Ray Self-Confinement Close to Extra-Galactic Sources.

    PubMed

    Blasi, Pasquale; Amato, Elena; D'Angelo, Marta

    2015-09-18

    The ultrahigh-energy cosmic rays observed on the Earth are most likely accelerated in extra-Galactic sources. For the typical luminosities invoked for such sources, the electric current associated to the flux of cosmic rays that leave them is large. The associated plasma instabilities create magnetic fluctuations that can efficiently scatter particles. We argue that this phenomenon forces cosmic rays to be self-confined in the source proximity for energies Econfined close to their sources for energies E

  17. High-Energy Cosmic Ray Self-Confinement Close to Extra-Galactic Sources

    NASA Astrophysics Data System (ADS)

    Blasi, Pasquale; Amato, Elena; D'Angelo, Marta

    2015-09-01

    The ultrahigh-energy cosmic rays observed on the Earth are most likely accelerated in extra-Galactic sources. For the typical luminosities invoked for such sources, the electric current associated to the flux of cosmic rays that leave them is large. The associated plasma instabilities create magnetic fluctuations that can efficiently scatter particles. We argue that this phenomenon forces cosmic rays to be self-confined in the source proximity for energies E confined close to their sources for energies E

  18. Measurement of RF electric field in high- β plasma using a Pockels detector in magnetosphere plasma confinement device RT-1

    NASA Astrophysics Data System (ADS)

    Mushiake, Toshiki; Nishiura, M.; Yoshida, Z.; Yano, Y.; Kawazura, Y.; Saitoh, H.; Yamasaki, M.; Kashyap, A.; Takahashi, N.; Nakatsuka, M.; Fukuyama, Atsushi

    2015-11-01

    The magnetosphere plasma confinement device RT-1 generates a dipole magnetic field that can confine high- β plasma by using a levitated superconducting coil. So far it is reported that high temperature electrons (up to 50keV) exist and that the local electron βe value exceeds more than 100%. However, the ion β value βi remains low in the present high- β state. To realize a high-βi state, we have started Ion Cyclotron Heating (ICH) experiments. For efficient ICH in a dipole topology, it is important to measure RF electric fields and characterize the propagation of RF waves in plasmas. On this viewpoint, we started direct measurement of local RF electric fields in RT-1 with a Pockels sensor system. A non-linear optical crystal in the Pockels sensor produces birefringence in an ambient electric field. The refractive index change of the birefringence is proportional to the applied electric field strength, which can be used to measure local electric fields. RF electric field distribution radiated from an ICH antenna was measured inside RT-1 in air, and was compared with numerical results calculated by TASK code. Results on the measurement of electric field distribution in high- β plasma and evaluation of the absorbed RF power into ions will be reported. Supported by JSPS KAKENHI Grant Numbers 23224014.

  19. Exploring the potential high energy locations and intensities in confined work spaces of waveguide dimensions

    NASA Astrophysics Data System (ADS)

    Rodriguez, Ricardo; Lewis, Winston G.

    2014-07-01

    review visits the likelihood for potential energy build-up due to RF propagation in confined spaces that are of waveguide design but with larger dimensions. Such confined spaces include silos, tanks, pipes, manholes, air-condition ducts, tunnels, wells, engine rooms and operator rooms on board vessels. In these confined spaces waves reflect off of the walls and combine constructively or destructively with incident waves producing reinforcement or cancellation respectively. Where there is reinforcement, the intensity of the wave for a particular distance in accordance with the standard, may exceed the exposure limit for this distance from the source thereby exposing the worker to larger intensities than the accepted limit and presenting a potential health and safety threat.

  20. Confinement and the Pomeron

    SciTech Connect

    White, A.R.

    1989-09-25

    The importance of confinement for obtaining a unitary high-energy limit for QCD is discussed. Minijets'' are argued to build up non-unitary behavior{endash}when k{sub T} {gt} {Lambda} is imposed. For minijets to mix with low k{sub T} Pomeron Field Theory describing confinement, and give consistent asymptotic behavior, new quarks'' must enter the theory above the minijet transverse momentum scale. The Critical Pomeron is the resulting high-energy limit. 22 refs.

  1. High-Capacity Te Anode Confined in Microporous Carbon for Long-Life Na-Ion Batteries.

    PubMed

    Zhang, Juan; Yin, Ya-Xia; Guo, Yu-Guo

    2015-12-23

    Sodium-ion batteries (SIBs) have attracted considerable attention as an alternative energy-storage technology in recent years. Developing advanced sodium storage anode materials with appropriate working potential, high capacity, and good cycling performance is very important. Herein, we demonstrate a nanostructured tellurium@carbon (nano-Te@C) composite by confining nano-Te molecules in the space of carbon micropores as an attractive anode material for SIBs. The nano-Te@C anode presents an appropriate redox potential in the range of 1.05-1.35 V (vs Na(+)/Na), which avoids the Na dendrite problem and achieves a high reversible capacity of 410 mA h g(-1) on the basis of a two-electron redox reaction mechanism. Notably, the nano-Te@C exhibits an admirable long-term cycling stability with a high capacity retention of 90% for 1000 cycles (i.e., ultralow capacity decay of 0.01% per cycle). The excellent electrochemical property of nano-Te@C benefits from the high electroactivity from the nanostructure design and the effective confinement of the microporous carbon host. In addition, a Na-ion full cell by using nano-Te@C as anode and Na2/3Ni1/3Mn2/3O2 as cathode is demonstrated for the first time and exhibits a remarkable capacity retention up to 95% after 150 cycles. The results put new insights for the development of advanced SIBs with long-cycle lifespan.

  2. Generation of highly confined optical bottle beams by exploiting the photonic nanojet effect

    NASA Astrophysics Data System (ADS)

    Kim, Myun-Sik; Scharf, Toralf; Mühlig, Stefan; Rockstuhl, Carsten; Herzig, Hans Peter

    2012-03-01

    We report on the generation of photonic nanojets, which resemble optical bottle beams. They are realized by manipulating the illumination of dielectric microspheres. As illumination we use the outer region of deliberately truncated Bessel-Gauss beam or a focused Gaussian beam with intentionally induced spherical aberrations. For the Bessel-Gauss beam possessing a single side lobe only, the nanojet spot resembles an optical bottle beam with a strong confinement due to the nanojet effect. When multiple side lobes of the aberrated focal spot are used, a chain of 3D optical bottle beams appears. We show the 3D intensity distributions close to the spot and discuss the main characteristics of such optical bottle beams.

  3. Experimental study of magnetically confined hollow electron beams in the Tevatron as collimators for intense high-energy hadron beams

    SciTech Connect

    Stancari, G.; Annala, G.; Shiltsev, V.; Still, D.; Valishev, A.; Vorobiev, L.; /Fermilab

    2011-03-01

    Magnetically confined hollow electron beams for controlled halo removal in high-energy colliders such as the Tevatron or the LHC may extend traditional collimation systems beyond the intensity limits imposed by tolerable losses. They may also improve collimation performance by suppressing loss spikes due to beam jitter and by increasing capture efficiency. A hollow electron gun was designed and tested at Fermilab for this purpose. It was installed in one of the Tevatron electron lenses in the summer of 2010. We present the results of the first experimental tests of the hollow-beam collimation concept on 980-GeV antiproton bunches in the Tevatron.

  4. An Overview of the Los Alamos Inertial Confinement Fusion and High-Energy-Density Physics Research Programs

    SciTech Connect

    Batha, Steven H.

    2016-07-15

    The Los Alamos Inertial Confinement Fusion and Science Programs engage in a vigorous array of experiments, theory, and modeling. We use the three major High Energy Density facilities, NIF, Omega, and Z to perform experiments. These include opacity, radiation transport, hydrodynamics, ignition science, and burn experiments to aid the ICF and Science campaigns in reaching their stewardship goals. The ICF program operates two nuclear diagnostics at NIF, the neutron imaging system and the gamma reaction history instruments. Both systems are being expanded with significant capability enhancements.

  5. Demonstration of Radiation Pulse Shaping with Nested-Tungsten-Wire-Array Z Pinches for High-Yield Inertial Confinement Fusion

    SciTech Connect

    Cuneo, M.E.; Vesey, R.A.; Sinars, D.B.; Waisman, E.M.; Lemke, R.W.; Bliss, D.E.; Stygar, W.A.; Porter, J.L.; Mazarakis, M.G.; Chandler, G.A.; Mehlhorn, T.A.; Chittenden, J.P.; Lebedev, S.V.; Schroen, D.G.

    2005-10-28

    Nested wire-array Z pinches are shown to generate soft x-ray radiation pulse shapes required for three-shock isentropic compression and hot-spot ignition of high-yield inertial confinement fusion capsules. We demonstrate a reproducible and tunable foot pulse (first shock) produced by interaction of the outer and inner arrays. A first-step pulse (second shock) is produced by inner array collision with a central CH{sub 2} foam target. Stagnation of the inner array at the axis produces the third shock. Capsules optimized for several of these shapes produce 290-900 MJ fusion yields in 1D simulations.

  6. Highly alloyed PtRu nanoparticles confined in porous carbon structure as a durable electrocatalyst for methanol oxidation.

    PubMed

    Yang, Chunzhen; Zhou, Ming; Gao, Liang

    2014-11-12

    The state-of-the-art carbon-supported PtRu catalysts are widely used as the anode catalysts in polymer electrolyte fuel cells (PEMFCs) but suffer from instability issues. Severe ruthenium dissolution occurring at potentials higher than 0.5 V vs NHE would result in a loss of catalytic activity of PtRu hence a worse performance of the fuel cell. In this work, we report an ultrastable PtRu electrocatalyst for methanol oxidation by confining highly alloyed PtRu nanoparticles in a hierarchical porous carbon structure. The structural characteristics, e.g., the surface composition and the morphology evolution, of the catalyst during the accelerated degradation test were characterized by the Cu-stripping voltammetry and the TEM/SEM observations. From the various characterization results, it is revealed that both the high alloying degree and the pore confinement of PtRu nanoalloys play significant roles in suppressing the degradation processes, including Ru dissolution and particle agglomeration/migration. This report provides an opportunity for efficient design and fabrication of highly stable bimetallic or trimetallic electrocatalysts in a large variety of applications.

  7. Magneto-optical absorption in semiconducting spherical quantum dots: Influence of the dot-size, confining potential, and magnetic field

    SciTech Connect

    Kushwaha, Manvir S.

    2014-12-15

    Semiconducting quantum dots – more fancifully dubbed artificial atoms – are quasi-zero dimensional, tiny, man-made systems with charge carriers completely confined in all three dimensions. The scientific quest behind the synthesis of quantum dots is to create and control future electronic and optical nanostructures engineered through tailoring size, shape, and composition. The complete confinement – or the lack of any degree of freedom for the electrons (and/or holes) – in quantum dots limits the exploration of spatially localized elementary excitations such as plasmons to direct rather than reciprocal space. Here we embark on a thorough investigation of the magneto-optical absorption in semiconducting spherical quantum dots characterized by a confining harmonic potential and an applied magnetic field in the symmetric gauge. This is done within the framework of Bohm-Pines’ random-phase approximation that enables us to derive and discuss the full Dyson equation that takes proper account of the Coulomb interactions. As an application of our theoretical strategy, we compute various single-particle and many-particle phenomena such as the Fock-Darwin spectrum; Fermi energy; magneto-optical transitions; probability distribution; and the magneto-optical absorption in the quantum dots. It is observed that the role of an applied magnetic field on the absorption spectrum is comparable to that of a confining potential. Increasing (decreasing) the strength of the magnetic field or the confining potential is found to be analogous to shrinking (expanding) the size of the quantum dots: resulting into a blue (red) shift in the absorption spectrum. The Fermi energy diminishes with both increasing magnetic-field and dot-size; and exhibits saw-tooth-like oscillations at large values of field or dot-size. Unlike laterally confined quantum dots, both (upper and lower) magneto-optical transitions survive even in the extreme instances. However, the intra-Landau level

  8. Magneto-optical absorption in semiconducting spherical quantum dots: Influence of the dot-size, confining potential, and magnetic field

    NASA Astrophysics Data System (ADS)

    Kushwaha, Manvir S.

    2014-12-01

    Semiconducting quantum dots - more fancifully dubbed artificial atoms - are quasi-zero dimensional, tiny, man-made systems with charge carriers completely confined in all three dimensions. The scientific quest behind the synthesis of quantum dots is to create and control future electronic and optical nanostructures engineered through tailoring size, shape, and composition. The complete confinement - or the lack of any degree of freedom for the electrons (and/or holes) - in quantum dots limits the exploration of spatially localized elementary excitations such as plasmons to direct rather than reciprocal space. Here we embark on a thorough investigation of the magneto-optical absorption in semiconducting spherical quantum dots characterized by a confining harmonic potential and an applied magnetic field in the symmetric gauge. This is done within the framework of Bohm-Pines' random-phase approximation that enables us to derive and discuss the full Dyson equation that takes proper account of the Coulomb interactions. As an application of our theoretical strategy, we compute various single-particle and many-particle phenomena such as the Fock-Darwin spectrum; Fermi energy; magneto-optical transitions; probability distribution; and the magneto-optical absorption in the quantum dots. It is observed that the role of an applied magnetic field on the absorption spectrum is comparable to that of a confining potential. Increasing (decreasing) the strength of the magnetic field or the confining potential is found to be analogous to shrinking (expanding) the size of the quantum dots: resulting into a blue (red) shift in the absorption spectrum. The Fermi energy diminishes with both increasing magnetic-field and dot-size; and exhibits saw-tooth-like oscillations at large values of field or dot-size. Unlike laterally confined quantum dots, both (upper and lower) magneto-optical transitions survive even in the extreme instances. However, the intra-Landau level transitions are seen

  9. Phase-controlled synthesis of α-NiS nanoparticles confined in carbon nanorods for High Performance Supercapacitors

    NASA Astrophysics Data System (ADS)

    Sun, Chencheng; Ma, Mingze; Yang, Jun; Zhang, Yufei; Chen, Peng; Huang, Wei; Dong, Xiaochen

    2014-11-01

    A facile and phase-controlled synthesis of α-NiS nanoparticles (NPs) embedded in carbon nanorods (CRs) is reported by in-situ sulfurating the preformed Ni/CRs. The nanopore confinement by the carbon matrix is essential for the formation of α-NiS and preventing its transition to β-phase, which is in strong contrast to large aggregated β-NiS particles grown freely without the confinement of CRs. When used as electrochemical electrode, the hybrid electrochemical charge storage of the ultrasmall α-NiS nanoparticels dispersed in CRs is benefit for the high capacitor (1092, 946, 835, 740 F g-1 at current densities of 1, 2, 5, 10 A g-1, respectively.). While the high electrochemical stability (approximately 100% retention of specific capacitance after 2000 charge/discharge cycles) is attributed to the supercapacitor-battery electrode, which makes synergistic effect of capacitor (CRs) and battery (NiS NPs) components rather than a merely additive composite. This work not only suggests a general approach for phase-controlled synthesis of nickel sulfide but also opens the door to the rational design and fabrication of novel nickel-based/carbon hybrid supercapacitor-battery electrode materials.

  10. Phase-controlled synthesis of α-NiS nanoparticles confined in carbon nanorods for High Performance Supercapacitors

    PubMed Central

    Sun, Chencheng; Ma, Mingze; Yang, Jun; Zhang, Yufei; Chen, Peng; Huang, Wei; Dong, Xiaochen

    2014-01-01

    A facile and phase-controlled synthesis of α-NiS nanoparticles (NPs) embedded in carbon nanorods (CRs) is reported by in-situ sulfurating the preformed Ni/CRs. The nanopore confinement by the carbon matrix is essential for the formation of α-NiS and preventing its transition to β-phase, which is in strong contrast to large aggregated β-NiS particles grown freely without the confinement of CRs. When used as electrochemical electrode, the hybrid electrochemical charge storage of the ultrasmall α-NiS nanoparticels dispersed in CRs is benefit for the high capacitor (1092, 946, 835, 740 F g−1 at current densities of 1, 2, 5, 10 A g−1, respectively.). While the high electrochemical stability (approximately 100% retention of specific capacitance after 2000 charge/discharge cycles) is attributed to the supercapacitor-battery electrode, which makes synergistic effect of capacitor (CRs) and battery (NiS NPs) components rather than a merely additive composite. This work not only suggests a general approach for phase-controlled synthesis of nickel sulfide but also opens the door to the rational design and fabrication of novel nickel-based/carbon hybrid supercapacitor-battery electrode materials. PMID:25394517

  11. Simulation study on structure of water in aqueous solutions confined between graphene electrodes under very high applied electric field

    NASA Astrophysics Data System (ADS)

    Leuty, Gary; Tsige, Mesfin; Talapatra, Saikat

    2011-03-01

    Arising from questions regarding electric double-layer capacitors utilizing graphene electrodes and aqueous electrolyte (KOH solution), atomistic MD simulations of electrolyte confined between graphene electrodes were performed to understand the behavior of electrolyte as a function of electric field strength and solution concentration, from pure water to 6M KOH. It was noted that the strength of the electric field had a demonstrable effect on the structure of pure water between the electrodes (as has previously been seen in highly confined multilayer water systems), creating regularly spaced channels and densely packed sheets of highly ordered molecules. We also saw a clear effect due to the presence of electrolyte ions and their separation from the water due to the action of the field; different field strengths appear to greatly alter the distribution of ions, which in turn affects the structure and ordering of the water. Time dependence in the strength of the electric field was also studied to determine what effect, if any, it has on induced structure. Authors gratefully acknowledge support from the ACS Petroleum Research Fund and the National Science Foundation.

  12. High-efficiency Köhler photovoltaic concentrators with external light confinement

    NASA Astrophysics Data System (ADS)

    Zamora, Pablo; Benítez, Pablo; Miñano, Juan C.; Li, Yang; Buljan, Marina

    2011-10-01

    Metal grid lines are a vital element in multijunction solar cells in order to take out from the cell the generated photocurrent. Nevertheless all this implies certain shadowing factor and thus certain reflectivity on cells surface that lowers its light absorption. This reflectivity produces a loss in electrical efficiency and thus a loss in global energy production for CPV systems. We present here an optical design for recovering this portion of reflected light, and thus leading to a system efficiency increase. This new design is based on an external confinement cavity, an optical element able to redirect the light reflected by the cell towards its surface again. It has been possible thanks to the recent invention of the advanced Köhler concentrators by LPI, likely to integrate one of these cavities easily. We have proven the excellent performance of these cavities integrated in this kind of CPV modules offering outstanding results: 33.2% module electrical efficiency @Tcell=25ºC and relative efficiency and Isc gains of over 6%.

  13. Normal and anomalous diffusion in highly confined hard disk fluid mixtures.

    PubMed

    Ball, C D; MacWilliam, N D; Percus, J K; Bowles, R K

    2009-02-07

    Monte Carlo simulation is used to study binary mixtures of two-dimensional hard disks, confined to long, narrow, structureless pores with hard walls, in a regime of pore sizes where the large particles exhibit single file diffusion while the small particles diffuse normally. The dynamics of the small particles can be understood in the context of a hopping time, tau(21), that measures the time it takes for a small particle to escape the single file cage formed by its large particle neighbors, and can be linked to the long time diffusion coefficient. We find that tau(21) follows a power law as a function of the reduced pore radius for a wide range of particle size ratios with an exponent, alpha, that is independent of the size ratio, but linearly dependent on the Monte Carlo step size used in the dynamic scheme. The mean squared displacement of the small particles as a function of time exhibits two dynamic crossovers. The first, from normal to anomalous diffusion, occurs at intermediate times then the system returns to normal diffusion in the long time limit. We also find that the diffusion coefficient is related to tau(21) through a power law with exponent beta=-0.5, as predicted by theory. Finally, we show that particle separation in a binary mixture will be optimal at the pore radius that causes the large particles to undergo their transition from normal to anomalous diffusion.

  14. Reversible optical switching of highly confined phonon-polaritons with an ultrathin phase-change material

    NASA Astrophysics Data System (ADS)

    Li, Peining; Yang, Xiaosheng; Maß, Tobias W. W.; Hanss, Julian; Lewin, Martin; Michel, Ann-Katrin U.; Wuttig, Matthias; Taubner, Thomas

    2016-08-01

    Surface phonon-polaritons (SPhPs), collective excitations of photons coupled with phonons in polar crystals, enable strong light-matter interaction and numerous infrared nanophotonic applications. However, as the lattice vibrations are determined by the crystal structure, the dynamical control of SPhPs remains challenging. Here, we realize the all-optical, non-volatile, and reversible switching of SPhPs by controlling the structural phase of a phase-change material (PCM) employed as a switchable dielectric environment. We experimentally demonstrate optical switching of an ultrathin PCM film (down to 7 nm, <λ/1,200) with single laser pulses and detect ultra-confined SPhPs (polariton wavevector kp > 70k0, k0 = 2π/λ) in quartz. Our proof of concept allows the preparation of all-dielectric, rewritable SPhP resonators without the need for complex fabrication methods. With optimized materials and parallelized optical addressing we foresee application potential for switchable infrared nanophotonic elements, for example, imaging elements such as superlenses and hyperlenses, as well as reconfigurable metasurfaces and sensors.

  15. Experimental observations of detonation in ammonium-nitrate-fuel-oil (ANFO) surrounded by a high-sound speed, shockless, aluminum confiner

    SciTech Connect

    Jackson, Scott I; Klyanda, Charles B; Short, Mark

    2010-01-01

    Detonations in explosive mixtures of ammonium-nitrate-fuel-oil (ANFO) confined by aluminum allow for transport of detonation energy ahead of the detonation front due to the aluminum sound speed exceeding the detonation velocity. The net effect of this energy transport on the detonation is unclear. It could enhance the detonation by precompressing the explosive near the wall. Alternatively, it could desensitize the explosive by crushing porosity required for shock initiation or destroying confinement ahead of the detonation. As these phenomena are not well understood, most numerical explosive models are unable to account for them. But with slowly detonating, non-ideal high explosive (NIHE) systems becoming increasing prevalent, proper understanding and prediction of the performance of these metal-confined NIHE systems is desirable. Experiments are discussed that measured the effect of this ANFO detonation energy transported upstream of the front by an aluminum confining tube. Detonation velocity, detonation front curvature, and aluminum response are recorded as a function of confiner wall thickness and length. Front curvature profiles display detonation acceleration near the confining surface, which is attributed to energy transported upstream modifying the flow. Average detonation velocities were seen to increase with increasing confiner thickness due to the additional inertial confinement of the reaction zone flow. Significant radial sidewall tube motion was observed immediately ahead of the detonation. Axial motion was also detected which interfered with the front curvature measurements in some cases. It was concluded that the confiner was able to transport energy ahead of the detonation and that this transport has a definite effect on the detonation.

  16. High confinement and high density with stationary plasma energy and strong edge radiation cooling in the upgraded Torus Experiment for Technology Oriented Research (TEXTOR-94)

    SciTech Connect

    Messiaen, A.M.; Ongena, J.; Unterberg, B.; Boedo, J.; Fuchs, G.; Jaspers, R.; Konen, L.; Koslowski, H.R.; Mank, G.; Rapp, J.; Samm, U.; Vandenplas, P.E.; Van Oost, G.; Van Wassenhove, G.; Waidmann, G.; Weynants, R.R.; Wolf, G.H.; Bertschinger, G.; Bonheure, G.; Brix, M.; Dumortier, P.; Durodie, F.; Finken, K.H.; Giesen, B.; Hillis, D.; Hutteman, P.; Koch, R.; Kramer-Flecken, A.; Lyssoivan, A.; Mertens, P.; Pospieszczyk, A.; Post-Zwicker, A.; Sauer, M.; Schweer, B.; Schwelberger, J.; Telesca, G.; Tokar, M.Z.; Uhlemann, R.; Vervier, M.; Winter, J. ||||

    1997-05-01

    An overview of the results obtained so far for the radiative I-mode regime on the upgraded Torus Experiment for Technology Oriented Research (TEXTOR-94) [{ital Proceedings of the 16th IEEE Symposium on Fusion Engineering} (Institute of Electrical and Electronics Engineers, Piscataway, NJ, 1995), Vol. 1, p. 470] is given. This regime is obtained under quasistationary conditions with edge neon seeding in a pumped limiter tokamak with circular cross section. It combines high confinement and high {beta} (up to a normalized beta, {beta}{sub n}=2) with low edge q values (down to q{sub a}=2.8) and high density even above the Greenwald limit together with dominant edge radiative heat exhaust, and therefore shows promise for the future of fusion research. Bulk and edge properties of these discharges are described, and a detailed account is given of the energy and particle confinement and their scaling. Energy confinement scales linearly with density as for the nonsaturated Ohmic Neo-Alcator scaling, but the usual degradation with total power remains. No deleterious effects of the neon seeding on fusion reactivity and plasma stability have been observed. {copyright} {ital 1997 American Institute of Physics.}

  17. Numerical study of density functional theory with mean spherical approximation for ionic condensation in highly charged confined electrolytes

    NASA Astrophysics Data System (ADS)

    Joubaud, R.; Bernard, O.; Delville, A.; Ern, A.; Rotenberg, B.; Turq, P.

    2014-06-01

    We investigate numerically a density functional theory (DFT) for strongly confined ionic solutions in the canonical ensemble by comparing predictions of ionic concentration profiles and pressure for the double-layer configuration to those obtained with Monte Carlo (MC) simulations and the simpler Poisson-Boltzmann (PB) approach. The DFT consists of a bulk (ion-ion) and an ion-solid part. The bulk part includes nonideal terms accounting for long-range electrostatic and short-range steric correlations between ions and is evaluated with the mean spherical approximation and the local density approximation. The ion-solid part treats the ion-solid interactions at the mean-field level through the solution of a Poisson problem. The main findings are that ionic concentration profiles are generally better described by PB than by DFT, although DFT captures the nonmonotone co-ion profile missed by PB. Instead, DFT yields more accurate pressure predictions than PB, showing in particular that nonideal effects are important to describe highly confined ionic solutions. Finally, we present a numerical methodology capable of handling nonconvex minimization problems so as to explore DFT predictions when the reduced temperature falls below the critical temperature.

  18. A simple structure of all circular-air-holes photonic crystal fiber for achieving high birefringence and low confinement loss

    SciTech Connect

    Chou Chau, Yuan-Fong Lim, Chee Ming; Yoong, Voo Nyuk; Syafi'ie Idris, Muhammad Nur

    2015-12-28

    We propose a simple structure of photonic crystal fibers (PCFs) with high birefringence and low confinement loss based on one rectangular centric ring of smaller circular air holes (CAHs) in the fiber core, and three rings of larger CAHs in the fiber cladding. This simple geometry (using all CAHs with two different air hole sizes) is capable of achieving a flexible control of the birefringence, B = 5.501 × 10{sup −3}, and ultra-low confinement loss, 7.30 × 10{sup −5 }dB/km, at an excitation wavelength of λ = 1550 nm. The birefringence value is ∼5.0 times greater than that obtained for conventional CAH PCF. This simple structure has the added advantage from the view point of easy fabrication, robustness, and cost. A full-vector finite element method combined with anisotropic perfectly matched layers was used to analyze the various fiber structures. We have analyzed four cases of CAH PCFs, focusing on the core asymmetry design as opposed to the conventional approach of CAHs or elliptical air holes on the cladding and core. The robustness against manufacturing inaccuracies of the proposed structure has also been further investigated in this work.

  19. Slip-localization within confined gouge powder sheared at moderate to high slip-velocity

    NASA Astrophysics Data System (ADS)

    Reches, Zeev; Chen, Xiaofeng; Morgan, Chance; Madden, Andrew

    2015-04-01

    Slip along faults in the upper crust is always associated with comminution and formation of non-cohesive gouge powder that can be lithified to cataclasite. Typically, the fine-grained powders (grain-size < 1 micron) build a 1-10 cm thick inner-core of a fault-zone. The ubiquitous occurrence of gouge powder implies that gouge properties may control the dynamic weakening of faults. Testing these properties is the present objective. We built a Confined ROtary Cell, CROC, with a ring-shape, ~3 mm thick gouge chamber, with 62.5 and 81.2 mm of inner and outer diameters. The sheared powder is sealed by two sets of seals pressurized by nitrogen. In CROC, we can control the pore-pressure and to inject fluids, and to monitor CO2 and H2O concentration; in addition, we monitor the standard mechanical parameters (slip velocity, stresses, dilation, and temperature). We tested six types of granular materials (starting grain-size in microns): Talc (<250), Kasota dolomite (125-250), ooides grains (125-250), San Andreas fault zone powder (< 840), montmorillonite powder (1-2), kaolinite powder and gypsum. The experimental slip-velocity ranged 0.001-1 m/s, slip distances from a few tens of cm to tens of m, effective normal stress up to 6.1 MPa. The central ultra-microscopic (SEM) observation is that almost invariably the slip was localized along principal-slip-zone (PSZ) within the granular layer. Even though the starting material was loose, coarse granular material, the developed PSZ was cohesive, hard, smooth and shining. The PSZ is about 1 micron thick, and built of agglomerated, ultra-fine grains (20-50 nm) that were pulverized from the original granular material. We noted that PSZs of the different tested compositions display similar characteristics in terms of structure, grain size, and roughness. Further, we found striking similarities between PSZ in the granular samples and the PZS that developed along experimental faults made of solid rock that were sheared at similar

  20. High Flux FRC Facility for the Stability, Confinement and ITER Divertor Studies

    SciTech Connect

    Hoffman, Alan L.; Milroy, Richard D.

    2014-01-31

    The TCS (Translation, Confinement, & Sustainment) program was begun on 7 August, 1996 to renew basic studies of the Field Reversed Configuration (FRC). The program made use of the old LSX (Large s Experiment) device, which was constructed at STI during the period from 1986 to 1990, but only operated for one year due to a DOE decision at the time to focus exclusively on the tokamak configuration. LSX was transferred to the University of Washington in 1992 and modified (LSX/mod) to perform Tokamak Refueling by Accelerated Plasmoids (TRAP) experiments. The TRAP program was funded from 7 August, 1992 until 6 August, 1996, but was utilized for an additional year while TCS was being constructed. During the first TCS funding period TCS was completed and initial experiments were begun. A large multi-megawatt RF power supply was built by Los Alamos National Laboratory (LANL) for use with a Rotating Magnetic Field (RMF) system, and LANL has been a continuing participant in our experimental program. A smaller prototype facility, called the Star Thrust Experiment (STX) was also built and operated in this period, partly with NASA funding, before TCS came on-line. A final report for this construction period was submitted in September 2000. A first renewal period (2.5 years) provided operating funds for the period between July 7, 2000 and January 6, 2003. A great deal of progress was made in understanding the use of RMF to both form and sustain FRCs during this period. The principal result of the experimental program was the formation of quasi steady-state (as long as RMF power was available) FRCs with densities in the 1-3x1019 m-3 range. However, the plasma temperature (Te or Ti) was limited to sub-25 eV, except transiently during start-up, by the rapid accumulation of impurities. This is not surprising since TCS was only designed to demonstrate RMF flux build-up and was not provided with either fueling capabilities or modern vacuum

  1. Reported Pain During Labour – A Qualitative Study of Influencing Factors among Parturient During Confinement in Private or Government Hospital

    PubMed Central

    Ravishankar, M.; Hemanthkumar, V.R.

    2016-01-01

    Introduction Labour pain is distressing and it produces undue side effects both to the mother and the baby. The incidence is high in developing countries like India where the awareness about labour analgesia is still lacking. Aim It is to find out the incidence of labour pain and the influence of various described factors on pain with a comparison between patients admitted in a government set up with a private set up in a south Indian semi-urban area. Materials and Methods Two hundred continuous uneventful normal deliveries each in a Government (group G) and a private hospital (group P) were enrolled for the study. The reported pain during labour was noted 6-7 hours after delivery by interacting with the patient. The factors like age of the mother, sex and weight of the baby, literacy, socioeconomic status, the use of oxytocics and analgesia were evaluated. Results The incidence of severe pain was more in group G (43.5%) than group P (12%). There was no analgesic intervention in 68.5% in group G while it was 13.5% (27/200) in group P. Even among these 27 patients who did not receive analgesics, only three parturients reported severe pain. Even administration of analgesics in a Government set up did not decrease pain to a significant extent. There were richer and more literate patients in group P. Booked cases were less in group G. Logistic regression analyses to find out factors which influenced pain in either group was used. Gravida, analgesic intervention and admission in a Govt. hospital influenced the pain experience of the parturient. There was minimal antenatal preparation in both the groups. There were no post partum complications. Conclusion Mothers suffered from labour pain to a significant extent and there is an urgent need for awareness about labour analgesia. Primigravida, admission in a Govt. set up and analgesic interventions were the factors which influenced pain than others. Patients admitted in Govt. hospitals suffered more pain with less analgesic

  2. Influence of confinement in controlled-pore glass on the layer spacing of smectic- A liquid crystals

    NASA Astrophysics Data System (ADS)

    Cordoyiannis, George; Zidanšek, Aleksander; Lahajnar, Gojmir; Kutnjak, Zdravko; Amenitsch, Heinz; Nounesis, George; Kralj, Samo

    2009-05-01

    A detailed x-ray scattering study has been performed in the temperature range of the smectic- A phase for the liquid crystal compounds dodecylcyanobiphenyl (12CB) and octylcyanobiphenyl (8CB) confined in different controlled-pore glasses (CPGs) characterized by their average void radius R . On decreasing the temperature in bulk samples the layer thickness is increasing for 12CB and decreasing for 8CB, respectively. In nontreated CPG samples the layers dilate significantly with respect to the bulk liquid crystal. In order to explain the layer thickness behavior on varying temperature and R , one has to take into account molecular details of the liquid crystalline samples as well as memory effects.

  3. THERMAL COOK-OFF EXPERIMENTS OF THE HMX BASED HIGH EXPLOSIVE LX-04 TO CHARACTERIZE VIOLENCE WITH VARYING CONFINEMENT

    SciTech Connect

    Garcia, F; Vandersall, K S; Forbes, J W; Tarver, C M; Greenwood, D

    2005-07-25

    Thermal cook-off experiments were carried out using LX-04 explosive (85% HMX and 15% Viton by weight) with different levels of confinement to characterize the effect of confinement on the reaction violence. These experiments involved heating a porous LX-04 sample in a stainless steel container with varying container end plate thickness and assembly bolt diameter to control overall confinement. As expected, detonation did not occur and reducing the overall confinement lowered the reaction violence. This is consistent with modeling results that predict that a lower confinement will act to lower the cook-off pressure and thus the overall burn rate which lowers the overall violence. These results suggest that controlling the overall system confinement can modify the relative safety in a given scenario.

  4. Confined Brownian ratchets

    NASA Astrophysics Data System (ADS)

    Malgaretti, Paolo; Pagonabarraga, Ignacio; Rubi, J. Miguel

    2013-05-01

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

  5. High-pressure behavior of bromine confined in the one-dimensional channels of zeolite AlPO4-5 single crystals

    NASA Astrophysics Data System (ADS)

    Liu, Zhaodong; Yao, Zhen; Yao, Mingguang; Lv, Jiayin; Chen, Shuanglong; Li, Quanjun; Lv, Hang; Wang, Tianyi; Lu, Shuangchen; Liu, Ran; Liu, Bo; Liu, Jing; Chen, Zhiqiang; Zou, Bo; Cui, Tian; Liu, Bingbing

    2016-09-01

    We present a joint experimental and theoretical study on the high-pressure behavior of bromine confined in the one-dimensional (1D) nanochannels of zeolite AlPO4-5 (AFI) single crystals. Raman scattering experiments indicate that loading bromine into AFI single crystals can lead to the formation of bromine molecular chains inside the nanochannels of the crystals. High-pressure Raman and X-ray diffraction studies demonstrate that high pressure can increase the length of the confined bromine molecular chains and modify the inter- and intramolecular interactions of the molecules. The confined bromine shows a considerably different high-pressure behavior to that of bulk bromine. The pressure-elongated bromine molecular chains can be preserved when the pressure is reduced to ambient pressure. Theoretical simulations explain the experimental results obtained from the Raman spectroscopy and X-ray diffraction studies. Furthermore, we find that the intermolecular distance between confined bromine molecules gradually becomes comparable to the intramolecular bond length in bromine molecules upon compression. This may result in the dissociation of the bromine molecules and the formation of 1D bromine atomic chains at pressures above 24 GPa. Our study suggests that the unique nanoconfinement has a considerable effect on the high-pressure behavior of bromine, and the confined bromine species concomitantly enhance the structural stability of the host AFI single crystals.

  6. Influence of substrate interaction and confinement on electric-field-induced transition in symmetric block-copolymer thin films

    NASA Astrophysics Data System (ADS)

    Mukherjee, Arnab; Mukherjee, Rajdip; Ankit, Kumar; Bhattacharya, Avisor; Nestler, Britta

    2016-03-01

    In the present work, we study morphologies arising due to competing substrate interaction, electric field, and confinement effects on a symmetric diblock copolymer. We employ a coarse-grained nonlocal Cahn-Hilliard phenomenological model taking into account the appropriate contributions of substrate interaction and electrostatic field. The proposed model couples the Ohta-Kawasaki functional with Maxwell equation of electrostatics, thus alleviating the need for any approximate solution used in previous studies. We calculate the phase diagram in electric-field-substrate strength space for different film thicknesses. In addition to identifying the presence of parallel, perpendicular, and mixed lamellae phases similar to analytical calculations, we also find a region in the phase diagram where hybrid morphologies (combination of two phases) coexist. These hybrid morphologies arise either solely due to substrate affinity and confinement or are induced due to the applied electric field. The dependence of the critical fields for transition between the various phases on substrate strength, film thickness, and dielectric contrast is discussed. Some preliminary 3D results are also presented to corroborate the presence of hybrid morphologies.

  7. Experimental studies of high-confinement mode plasma response to non-axisymmetric magnetic perturbations in ASDEX Upgrade

    SciTech Connect

    Suttrop, Wolfgang; Kirk, A.; Nazikian, R.; Leuthold, N.; Strumberger, E.; Willensdorfer, M.; Cavedon, M.; Dunne, M.; Fischer, R.; Fietz, S.; Fuchs, J. C.; Liu, Y. Q.; McDermott, R. M.; Orain, F.; Ryan, D. A.; Viezzer, E.

    2016-11-22

    Here, the interaction of externally applied small non-axisymmetric magnetic perturbations (MP) with tokamak high-confinement mode (H-mode) plasmas is reviewed and illustrated by recent experiments in ASDEX Upgrade. The plasma response to the vacuum MP field is amplified by stable ideal kink modes with low toroidal mode number n driven by the H-mode edge pressure gradient (and associated bootstrap current) which is experimentally evidenced by an observable shift of the poloidal mode number m away from field alignment (m = qn, with q being the safety factor) at the response maximum. A torque scan experiment demonstrates the importance of the perpendicular electron flow for shielding of the resonant magnetic perturbation, as expected from a two-fluid MHD picture. Two significant effects of MP occur in H-mode plasmas at low pedestal collisionality, $\

  8. Experimental studies of high-confinement mode plasma response to non-axisymmetric magnetic perturbations in ASDEX Upgrade

    DOE PAGES

    Suttrop, Wolfgang; Kirk, A.; Nazikian, R.; ...

    2016-11-22

    Here, the interaction of externally applied small non-axisymmetric magnetic perturbations (MP) with tokamak high-confinement mode (H-mode) plasmas is reviewed and illustrated by recent experiments in ASDEX Upgrade. The plasma response to the vacuum MP field is amplified by stable ideal kink modes with low toroidal mode number n driven by the H-mode edge pressure gradient (and associated bootstrap current) which is experimentally evidenced by an observable shift of the poloidal mode number m away from field alignment (m = qn, with q being the safety factor) at the response maximum. A torque scan experiment demonstrates the importance of the perpendicular electron flow for shielding of the resonant magnetic perturbation, as expected from a two-fluid MHD picture. Two significant effects of MP occur in H-mode plasmas at low pedestal collisionality,more » $$\

  9. Factors Influencing High School Students' Career Aspirations

    ERIC Educational Resources Information Center

    Tang, Mei; Pan, Wei; Newmeyer, Mark D.

    2008-01-01

    This article explores the factors influencing high school students' career aspirations with a study analyzing 141 high school students. The Social Cognitive Career Development Model was utilized to examine the interactive relationships among learning experiences, career self-efficacy, outcome expectations, career interests, and career choices. The…

  10. Silicon Nano-well Arrays for Reliable Pattern Transfer and Locally Confined High Temperature Reactions

    PubMed Central

    Wi, Jung-Sub; Wilson, Robert J.; Lee, Donkoun; White, Robert M.; Wang, Shan X.

    2011-01-01

    Si nano-well arrays, with precisely controlled undercut Si sidewall profiles and flat bottomed pockets, enable uniform nanoscale pattern transfer from resists to metal deposits without degradation of the initial lithographic resolution, as verified by formation of arrays of Au nano-dots with 10 nm diameter. An additional functionality of the Si nano-wells as local nano-reactors, where the patterned material is enclosed in a Si pocket during high temperature reaction, is demonstrated by thermally inducing a phase transformation of the as-deposited A1 phase of FePt nano-dots to the high coercivity, chemically ordered L10 phase. PMID:21709347

  11. Kinetic instabilities in a mirror-confined plasma sustained by high-power microwave radiation

    NASA Astrophysics Data System (ADS)

    Shalashov, A. G.; Viktorov, M. E.; Mansfeld, D. A.; Golubev, S. V.

    2017-03-01

    This paper summarizes the studies of plasma kinetic instabilities in the electron cyclotron frequency range carried out over the last decade at the Institute of Applied Physics in Nizhny Novgorod. We investigate the nonequilibrium plasma created and sustained by high-power microwave radiation of a gyrotron under the electron cyclotron resonance condition. Resonant plasma heating results in the formation of at least two electron components, one of which, more dense and cold, determines the dispersion properties of the high-frequency waves, and the other, a small group of energetic electrons with a highly anisotropic velocity distribution, is responsible for the excitation of unstable waves. Dynamic spectra and the intensity of stimulated electromagnetic emission are studied with high temporal resolution. Interpretation of observed data is based on the cyclotron maser paradigm; in this context, a laboratory modeling of non-stationary wave-particle interaction processes has much in common with similar processes occurring in the magnetosphere of Earth, planets, and solar coronal loops.

  12. Team dynamics in isolated, confined environments - Saturation divers and high altitude climbers

    NASA Technical Reports Server (NTRS)

    Kanki, Barbara G.; Gregorich, Steven E.

    1992-01-01

    The effects of leadership dynamics and social organization factors on team performance under conditions of high altitude climbing and deep sea diving are studied. Teams of two to four members that know each other well and have a relaxed informal team structure with much sharing of responsibilities are found to do better than military teams with more than four members who do not know each other well and have a formal team structure with highly specialized rules. Professionally guided teams with more than four members, a formally defined team structure, and clearly designated role assignments did better than 'club' teams of more than four members with a fairly informal team structure and little role specialization.

  13. High-resolution spectroscopy used to measure inertial confinement fusion neutron spectra on Omega (invited)

    SciTech Connect

    Forrest, C. J.; Radha, P. B.; Glebov, V. Yu.; Goncharov, V. N.; Knauer, J. P.; Pruyne, A.; Romanofsky, M.; Sangster, T. C.; Shoup, M. J. III; Stoeckl, C.; Casey, D. T.; Gatu-Johnson, M.; Gardner, S.

    2012-10-15

    The areal density ({rho}R) of cryogenic DT implosions on Omega is inferred by measuring the spectrum of neutrons that elastically scatter off the dense deuterium (D) and tritium (T) fuel. Neutron time-of-flight (nTOF) techniques are used to measure the energy spectrum with high resolution. High signal-to-background data has been recorded on cryogenic DT implosions using a well-collimated 13.4-m line of sight and an nTOF detector with an advanced liquid scintillator compound. An innovative method to analyze the elastically scattered neutron spectra was developed using well-known cross sections of the DT nuclear reactions. The estimated areal densities are consistent with alternative {rho}R measurements and 1-D simulations.

  14. Main drive optimization of a high-foot pulse shape in inertial confinement fusion implosions

    NASA Astrophysics Data System (ADS)

    Wang, L. F.; Ye, W. H.; Wu, J. F.; Liu, Jie; Zhang, W. Y.; He, X. T.

    2016-12-01

    While progress towards hot-spot ignition has been made achieving an alpha-heating dominated state in high-foot implosion experiments [Hurricane et al., Nat. Phys. 12, 800 (2016)] on the National Ignition Facility, improvements are needed to increase the fuel compression for the enhancement of the neutron yield. A strategy is proposed to improve the fuel compression through the recompression of a shock/compression wave generated by the end of the main drive portion of a high-foot pulse shape. Two methods for the peak pulse recompression, namely, the decompression-and-recompression (DR) and simple recompression schemes, are investigated and compared. Radiation hydrodynamic simulations confirm that the peak pulse recompression can clearly improve fuel compression without significantly compromising the implosion stability. In particular, when the convergent DR shock is tuned to encounter the divergent shock from the capsule center at a suitable position, not only the neutron yield but also the stability of stagnating hot-spot can be noticeably improved, compared to the conventional high-foot implosions [Hurricane et al., Phys. Plasmas 21, 056314 (2014)].

  15. Behavior Of A Confined Tension Lap Splice In High-Strength Reinforced Concrete Beams

    NASA Astrophysics Data System (ADS)

    Abdel-Kareem, Ahmed H.; Abousafa, Hala; El-Hadidi, Omaia S.

    2015-09-01

    The results of an experimental program conducted on seventeen simply supported concrete beams to study the effect of transverse reinforcement on the behavior of the lap splice of a steel reinforcement in tension zones in high-strength concrete beams are presented. The parameters included in the experimental program were the concrete compressive strength, the lap splice length, the amount of transverse reinforcement provided within the splice region, and the shape of the transverse reinforcement around the spliced bars. The experimental results showed that the displacement ductility increased and the mode of failure changed from a splitting bond failure to a flexural failure when the amount of the transverse reinforcement in the splice region increased, and the compressive strength increased up to 100 MPa. The presence of the transverse reinforcement around the spliced bars had a pronounced effect on increasing the ultimate load, the ultimate deflection, and the displacement ductility. The prediction of maximum steel stresses for spliced bars using the ACI 318-05 building code was compared with the experimental results. The comparison showed that the effect of the transverse reinforcement around spliced bars has to be considered into the design equations for lap splice length in high-strength concrete beams.

  16. Electron confinement in drift detectors by means of ``channel-stop`` implants: Characterization at high signal charges

    SciTech Connect

    Castoldi, A.; Rehak, P.; Strueder, L.

    1996-12-01

    Electron confinement in the direction transverse to the drift can be implemented in silicon drift detectors by means of deep p-implants. The reduced broadening of the electron cloud due to the deep p-implants has been tested as a function of the signal amplitude up to 200,000 electrons. The maximum number of electrons for which full confinement is achieved has been measured. The dependence of this threshold charge on the potential barrier generated by the deep p-implants, the size of the confinement, and the detector operating conditions are reported.

  17. New concept for a high-repetition-rate reactor for inertial-confinement fusion

    SciTech Connect

    Monsler, M.J.

    1980-11-01

    A new design concept was developed that has three additional features that are very important in reducing program risk: (1) through a proper choice of the working temperature (400 to 540/sup 0/C) and of the liquid metal (lithium or lead-lithium eutectic alloy), we can select a chamber pressure within the range of 10/sup -1/ to 10/sup -4/ Torr, required for the propagation of either a laser-beam or a heavy-ion-beam driver; (2) presently available ferritic steels can be used for the structural material; and (3) the new concept allows flexibility in irradiaton geometry. Although two-sided irradiation at high f/Nos. seems most attractive from the standpoints of minimizing the number of chamber penetrations and of simplifing the layout of the balance of plant, we must provide for the possibility that target-implosion physics will require a more symmetrical illumination geometry.

  18. Diels–Alder reactions in confined spaces: the influence of catalyst structure and the nature of active sites for the retro-Diels–Alder reaction

    PubMed Central

    Cantín, Ángel

    2016-01-01

    Summary Diels–Alder cycloaddition between cyclopentadiene and p-benzoquinone has been studied in the confined space of a pure silica zeolite Beta and the impact on reaction rate due to the concentration effect within the pore and diffusion limitations are discussed. Introduction of Lewis or Brønsted acid sites on the walls of the zeolite strongly increases the reaction rate. However, contrary to what occurs with mesoporous molecular sieves (MCM-41), Beta zeolite does not catalyse the retro-Diels–Alder reaction, resulting in a highly selective catalyst for the cycloaddition reaction. PMID:27829925

  19. Comparative analysis of low- and high-swirl confined flames and jets by proper orthogonal and dynamic mode decompositions

    NASA Astrophysics Data System (ADS)

    Markovich, D. M.; Abdurakipov, S. S.; Chikishev, L. M.; Dulin, V. M.; Hanjalić, K.

    2014-06-01

    Low-order coherent structures of non-reacting and combusting low- and high-swirl (swirl rates S = 0.41 and S = 1.0) jet flows in an open-ended cylindrical model combustor have been studied using the proper orthogonal decomposition (POD) and the dynamic mode decomposition (DMD) of high-repetition stereoscopic particle image velocimetry (PIV) velocity measurements. Lean methane-air mixture with the equivalence ratio of 0.6 was chosen for the reacting case as lean flames are generally less stable and more receptive to active control. The nonreacting and reacting flows at the same swirl rates exhibit qualitatively similar overall features characterized by highly turbulent annular jets enveloping the central retarding zone (for S = 0.41) or a recirculating bubble (for S = 1.0). At low swirl the dominant coherent structures appeared in the form of tilted ring vortices, evolving into helices as the swirl rate increases. The high-swirl flows are characterized by a pair of well-organized counter-rotating co-winding helical vortices originating in the inner and outer jet shear layers. Vortex cores were detected in both cases, but at low swirl it was less energetic and not associated with a distinct precession frequency. The core region of the low-swirl flame shows intermittent mild flow reversal without permanent central recirculation zone. The thermal expansion enhances the spreading of the reacting flow, especially at the high swirl number. Here the helices pitch is smaller and some neighbouring vortices merge into vortical sheets that act as shear shield confining the flame within the inner shear layer. Despite the significant effects of combustion on the time-averaged characteristics for the high-swirl, the dynamics of both flows were dominated by the global inviscid helical instability mode with a DMD detected conspicuous frequencies of 223 Hz for the nonreacting jet and 257 Hz for the flame.

  20. High methane natural gas/air explosion characteristics in confined vessel.

    PubMed

    Tang, Chenglong; Zhang, Shuang; Si, Zhanbo; Huang, Zuohua; Zhang, Kongming; Jin, Zebing

    2014-08-15

    The explosion characteristics of high methane fraction natural gas were investigated in a constant volume combustion vessel at different initial conditions. Results show that with the increase of initial pressure, the peak explosion pressure, the maximum rate of pressure rise increase due to a higher amount (mass) of flammable mixture, which delivers an increased amount of heat. The increased total flame duration and flame development time result as a consequence of the higher amount of flammable mixture. With the increase of the initial temperature, the peak explosion pressures decrease, but the pressure increase during combustion is accelerated, which indicates a faster flame speed and heat release rate. The maximum value of the explosion pressure, the maximum rate of pressure rise, the minimum total combustion duration and the minimum flame development time is observed when the equivalence ratio of the mixture is 1.1. Additionally, for higher methane fraction natural gas, the explosion pressure and the maximum rate of pressure rise are slightly decreased, while the combustion duration is postponed. The combustion phasing is empirically correlated with the experimental parameters with good fitting performance. Furthermore, the addition of dilute gas significantly reduces the explosion pressure, the maximum rate of pressure rise and postpones the flame development and this flame retarding effect of carbon dioxide is stronger than that of nitrogen.

  1. Dynamic formation of a hot field reversed configuration with improved confinement by supersonic merging of two colliding high-β compact toroids.

    PubMed

    Binderbauer, M W; Guo, H Y; Tuszewski, M; Putvinski, S; Sevier, L; Barnes, D; Rostoker, N; Anderson, M G; Andow, R; Bonelli, L; Brandi, F; Brown, R; Bui, D Q; Bystritskii, V; Ceccherini, F; Clary, R; Cheung, A H; Conroy, K D; Deng, B H; Dettrick, S A; Douglass, J D; Feng, P; Galeotti, L; Garate, E; Giammanco, F; Glass, F J; Gornostaeva, O; Gota, H; Gupta, D; Gupta, S; Kinley, J S; Knapp, K; Korepanov, S; Hollins, M; Isakov, I; Jose, V A; Li, X L; Luo, Y; Marsili, P; Mendoza, R; Meekins, M; Mok, Y; Necas, A; Paganini, E; Pegoraro, F; Pousa-Hijos, R; Primavera, S; Ruskov, E; Qerushi, A; Schmitz, L; Schroeder, J H; Sibley, A; Smirnov, A; Song, Y; Sun, X; Thompson, M C; Van Drie, A D; Walters, J K; Wyman, M D

    2010-07-23

    A hot stable field-reversed configuration (FRC) has been produced in the C-2 experiment by colliding and merging two high-β plasmoids preformed by the dynamic version of field-reversed θ-pinch technology. The merging process exhibits the highest poloidal flux amplification obtained in a magnetic confinement system (over tenfold increase). Most of the kinetic energy is converted into thermal energy with total temperature (T{i}+T{e}) exceeding 0.5 keV. The final FRC state exhibits a record FRC lifetime with flux confinement approaching classical values. These findings should have significant implications for fusion research and the physics of magnetic reconnection.

  2. Experimental studies of high-confinement mode plasma response to non-axisymmetric magnetic perturbations in ASDEX Upgrade

    NASA Astrophysics Data System (ADS)

    Suttrop, W.; Kirk, A.; Nazikian, R.; Leuthold, N.; Strumberger, E.; Willensdorfer, M.; Cavedon, M.; Dunne, M.; Fischer, R.; Fietz, S.; Fuchs, J. C.; Liu, Y. Q.; McDermott, R. M.; Orain, F.; Ryan, D. A.; Viezzer, E.; The ASDEX Upgrade Team; The DIII-D Team; The Eurofusion MST1 Team

    2017-01-01

    The interaction of externally applied small non-axisymmetric magnetic perturbations (MP) with tokamak high-confinement mode (H-mode) plasmas is reviewed and illustrated by recent experiments in ASDEX Upgrade. The plasma response to the vacuum MP field is amplified by stable ideal kink modes with low toroidal mode number n driven by the H-mode edge pressure gradient (and associated bootstrap current) which is experimentally evidenced by an observable shift of the poloidal mode number m away from field alignment (m  =  qn, with q being the safety factor) at the response maximum. A torque scan experiment demonstrates the importance of the perpendicular electron flow for shielding of the resonant magnetic perturbation, as expected from a two-fluid MHD picture. Two significant effects of MP occur in H-mode plasmas at low pedestal collisionality, ν \\text{ped}\\ast≤slant 0.4 : (a) a reduction of the global plasma density by up to 61 % and (b) a reduction of the energy loss associated with edge localised modes (ELMs) by a factor of up to 9. A comprehensive database of ELM mitigation pulses at low {ν\\ast} in ASDEX Upgrade shows that the degree of ELM mitigation correlates with the reduction of pedestal pressure which in turn is limited and defined by the onset of ELMs, i. e. a modification of the ELM stability limit by the magnetic perturbation.

  3. Fabrication of a High-Quality, Porous, Surface-Confined Covalent Organic Framework on a Reactive Metal Surface.

    PubMed

    Larrea, Christian R; Baddeley, Christopher J

    2016-04-04

    A major goal of heterogeneous catalysis is to optimize catalytic selectivity. Selectivity is often limited by the fact that most heterogeneous catalysts possess sites with a range of reactivities, resulting in the formation of unwanted by-products. The construction of surface-confined covalent organic frameworks (sCOFs) on catalytically active surfaces is a desirable strategy, as pores can be tailored to operate as catalytic nanoreactors. Direct modification of reactive surfaces is impractical, because the strong molecule-surface interaction precludes monomer diffusion and formation of extended architectures. Herein, we describe a protocol for the formation of a high-quality sCOF on a Pd-rich surface by first fabricating a porous sCOF through Ullmann coupling on a Au-rich bimetallic surface on Pd(111). Once the sCOF has formed, thermal processing induces a Pd-rich surface while preserving the integrity of the sCOF architecture, as evidenced by scanning tunneling microscopy and titration of Pd sites through CO adsorption.

  4. Surface Interactions and Confinement of Methane: A High Pressure Magic Angle Spinning NMR and Computational Chemistry Study

    DOE PAGES

    Ok, Salim; Hoyt, David W.; Andersen, Amity; ...

    2017-01-18

    Characterization and modeling of the molecular-level behavior of simple hydrocarbon gases, such as methane, in the presence of both nonporous and nanoporous mineral matrices allows for predictive understanding of important processes in engineered and natural systems. In this study, we observed changes in local electromagnetic environments of the carbon atoms in methane under conditions of high pressure (up to 130 bar) and moderate temperature (up to 346 K) with 13C magic-angle spinning (MAS) NMR spectroscopy while the methane gas was mixed with two model solid substrates: a fumed nonporous, 12 nm particle size silica and a mesoporous silica with 200more » nm particle size and 4 nm average pore diameter. Examination of the interactions between methane and the silica systems over temperatures and pressures that include the supercritical regime was allowed by a novel high pressure MAS sample containment system, which provided high resolution spectra collected under in situ conditions. There was no significant thermal effects were found for the observed 13C chemical shifts at all pressures studied here (28.2, 32.6, 56.4, 65.1, 112.7, and 130.3 bar) for pure methane. However, the 13C chemical shifts of resonances arising from confined methane changed slightly with changes in temperature in mixtures with mesoporous silica. The chemical shift values of 13C nuclides in methane change measurably as a function of pressure both in the pure state and in mixtures with both silica matrices, with a more pronounced shift when meso-porous silica is present. Molecular-level simulations utilizing GCMC, MD, and DFT confirm qualitatively that the experimentally measured changes are attributed to interactions of methane with the hydroxylated silica surfaces as well as densification of methane within nanopores and on pore surfaces.« less

  5. Youth pathways to placement: the influence of gender, mental health need and trauma on confinement in the juvenile justice system.

    PubMed

    Espinosa, Erin M; Sorensen, Jon R; Lopez, Molly A

    2013-12-01

    Although the juvenile crime rate has generally declined, the involvement of girls in the juvenile justice system has been increasing. Possible explanations for this gender difference include the impact of exposure to trauma and mental health needs on developmental pathways and the resulting influence of youth's involvement in the justice system. This study examined the influence of gender, mental health needs and trauma on the risk of out-of-home placement for juvenile offenders. The sample included youth referred to three urban juvenile probation departments in Texas between January 1, 2007 and December 31, 2008 and who received state-mandated mental health screening (N = 34,222; 30.1 % female). The analysis revealed that, for both genders, elevated scores on the seven factor-analytically derived subscales of a mental health screening instrument (Alcohol and Drug Use, Depressed-Anxious, Somatic Complaints, Suicidal Ideation, Thought Disturbance, and Traumatic Experiences), especially related to past traumatic experiences, influenced how deeply juveniles penetrated the system. The findings suggest that additional research is needed to determine the effectiveness of trauma interventions and the implementation of trauma informed systems for youth involved with the juvenile justice system.

  6. INSTALLATION OF A POST-ACCIDENT CONFINEMENT HIGH-LEVEL RADIATION MONITORING SYSTEM IN THE KOLA NUCLEAR POWER STATION (UNIT 2) IN RUSSIA

    SciTech Connect

    GREENE,G.A.; GUPPY,J.G.

    1998-09-01

    This is the final report on the INSP project entitled, ``Post-Accident Confinement High-Level Radiation Monitoring System'' conducted by BNL under the authorization of Project Work Plan WBS 1.2.2.6 (Attachment 1). This project was initiated in February 1993 to assist the Russians in reducing risks associated with the continued operation of older Soviet-designed nuclear power plants, specifically the Kola VVER-440/230 Unit 2, through improved accident detection capability, specifically by the installation of a dual train high-level radiation detection system in the confinement of Unit 2 of the Kola NPP. The major technical objective of this project was to provide, install and make operational the necessary hardware inside the confinement of the Kola NPP Unit 2 to provide early and reliable warning of the release of radionuclides from the reactor into the confinement air space as an indication of the occurrence of a severe accident at the plant. In addition, it was intended to provide hands-on experience and training to the Russian plant workers in the installation, operation, calibration and maintenance of the equipment in order that they may use the equipment without continued US assistance as an effective measure to improve reactor safety at the plant.

  7. Influence of nonuniform surface magnetic fields in wetting transitions in a confined two-dimensional Ising ferromagnet.

    PubMed

    Trobo, Marta L; Albano, Ezequiel V

    2013-11-01

    Wetting transitions are studied in the two-dimensional Ising ferromagnet confined between walls where competitive surface fields act. In our finite samples of size L×M, the walls are separated by a distance L, M being the length of the sample. The surface fields are taken to be short-range and nonuniform, i.e., of the form H(1),δH(1),H(1),δH(1),..., where the parameter -1≤δ≤1 allows us to control the nonuniformity of the fields. By performing Monte Carlo simulations we found that those competitive surface fields lead to the occurrence of an interface between magnetic domains of different orientation that runs parallel to the walls. In finite samples, such an interface undergoes a localization-delocalization transition, which is the precursor of a true wetting transition that takes place in the thermodynamic limit. By exactly working out the ground state (T=0), we found that besides the standard nonwet and wet phases, a surface antiferromagnetic-like state emerges for δ<-1/3 and large fields (H(1)>3), H(1)(tr)/J=3, δ(tr)=-1/3,T=0, being a triple point where three phases coexist. By means of Monte Carlo simulations it is shown that these features of the phase diagram remain at higher temperatures; e.g., we examined in detail the case T=0.7×T(cb). Furthermore, we also recorded phase diagrams for fixed values of δ, i.e., plots of the critical field at the wetting transition (H(1w)) versus T showing, on the one hand, that the exact results of Abraham [Abraham, Phys. Rev. Lett. 44, 1165 (1980)] for δ=1 are recovered, and on the other hand, that extrapolations to T→0 are consistent with our exact results. Based on our numerical results we conjectured that the exact result for the phase diagram worked out by Abraham can be extended for the case of nonuniform fields. In fact, by considering a nonuniform surface field of some period λ, with λ0], one can obtain the effective field H(eff) at a λ coarse-grained level given by H(eff)=1/

  8. Cell Blebbing in Confined Microfluidic Environments

    PubMed Central

    Ibo, Markela; Srivastava, Vasudha; Robinson, Douglas N.; Gagnon, Zachary R.

    2016-01-01

    Migrating cells can extend their leading edge by forming myosin-driven blebs and F-actin-driven pseudopods. When coerced to migrate in resistive environments, Dictyostelium cells switch from using predominately pseudopods to blebs. Bleb formation has been shown to be chemotactic and can be influenced by the direction of the chemotactic gradient. In this study, we determine the blebbing responses of developed cells of Dictyostelium discoideum to cAMP gradients of varying steepness produced in microfluidic channels with different confining heights, ranging between 1.7 μm and 3.8 μm. We show that microfluidic confinement height, gradient steepness, buffer osmolarity and Myosin II activity are important factors in determining whether cells migrate with blebs or with pseudopods. Dictyostelium cells were observed migrating within the confines of microfluidic gradient channels. When the cAMP gradient steepness is increased from 0.7 nM/μm to 20 nM/μm, cells switch from moving with a mixture of blebs and pseudopods to moving only using blebs when chemotaxing in channels with confinement heights less than 2.4 μm. Furthermore, the size of the blebs increases with gradient steepness and correlates with increases in myosin-II localization at the cell cortex. Reduction of intracellular pressure by high osmolarity buffer or inhibition of myosin-II by blebbistatin leads to a decrease in bleb formation and bleb size. Together, our data reveal that the protrusion type formed by migrating cells can be influenced by the channel height and the steepness of the cAMP gradient, and suggests that a combination of confinement-induced myosin-II localization and cAMP-regulated cortical contraction leads to increased intracellular fluid pressure and bleb formation. PMID:27706201

  9. Improved confinement in ELM-suppressed high-density H-modes at the ITER field via modification of the plasma boundary with Lower Hybrid RF

    NASA Astrophysics Data System (ADS)

    Terry, J. L.

    2014-10-01

    Injecting Lower Hybrid (LH) power into Alcator C-Mod's high-density H-mode plasmas has enhanced global confinement by increasing pedestal temperature gradients, modifying edge rotation, and decreasing edge and SOL turbulence. These new experiments indicate that edge LHRF can be used as a tool to increase confinement via direct modification of boundary quantities. Ray-tracing modeling and accessibility calculations for the LH waves indicate that the LH waves do not penetrate to regions inside the top of the pedestal and are not driving current in these plasmas; instead the LH power modifies the boundary conditions. When moderate amounts of LH power (PLH/Ptot = 20%) are applied to high-density EDA H-modes (neo = 3.5×1020 m-3) , we observe the following effects: edge/SOL fluctuation power decreases by roughly an order of magnitude; pedestal temperature gradients are increased; global energy confinement time and H-factor increase by 30-40% (H98 from 0.7 to 1.0); co-current core and pedestal rotation velocities increase; power to the (outer) divertor target increases promptly with an increment that is roughly 1/2 of the injected LH power, qualitatively consistent with the inaccessibility of the LH waves; and the central frequency of the edge-localized Quasi-Coherent Mode down-shifts and becomes much more coherent. These H-mode confinement improvements brought about by the edge LHRF are the result of changes in the pedestal (e.g. changes in rotation/shear and increased pedestal temperature gradients), with no substantial change in peaking of core density or temperature profiles. There is not perfect correlation with edge turbulence suppression, indicating that the turbulence decrease may be a necessary, but not sufficient, condition for the pedestal and confinement improvements. Supported by US DoE Awards DE-FC02-99ER54512 and DE-AC02-09CH11466.

  10. 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.

  11. Enhanced second-harmonic generation by means of high-power confinement in a photovoltaic soliton-induced waveguide.

    PubMed

    Lou, Cibo; Xu, Jingjun; Qiao, Haijun; Zhang, Xinzheng; Chen, Yunlin; Chen, Zhigang

    2004-05-01

    We present the first experimental demonstration of enhanced second-harmonic generation (SHG) by means of power confinement with a femtosecond laser in a photovoltaic soliton-induced waveguide. A dark spatial soliton created with a weak cw laser beam in a photovoltaic lithium niobate crystal induces an efficient waveguide for SHG, leading to a 60% enhancement of the conversion efficiency.

  12. Influence of finite size and wetting on nematic and smectic phase behavior of liquid crystal confined to controlled-pore matrices

    NASA Astrophysics Data System (ADS)

    Kutnjak, Zdravko; Kralj, Samo; Lahajnar, Gojmir; Žumer, Slobodan

    2004-11-01

    The high-resolution calorimetric study was carried out on octylcyanobiphenyl liquid crystal (LC) confined to various controlled-pore glass (CPG) matrices with silane-treated surface. The diameter of the voids cross section ranged between 23.7 and 395nm . The results are compared to those obtained previously on CPG voids nontreated with silane. We found a striking similarity between the shifts in the isotropic to nematic and nematic to smectic- A phase transition temperatures as a function of the void radius in which order parameter variations at the LC-void interface play the dominant role. Weaker temperature shifts are observed in silane-treated samples, where surface ordering tendency is larger. In nontreated samples, a finite-size scaling law in the maximum value of the heat capacity at the nematic to smectic- A transition was observed for void diameters larger than 20nm . In silane-treated samples, this behavior is considerably changed by surface wetting interactions.

  13. Assessing confinement in coastal lagoons.

    PubMed

    Canu, Donata Melaku; Solidoro, Cosimo; Umgiesser, Georg; Cucco, Andrea; Ferrarin, Christian

    2012-11-01

    Measures of transport scale in aquatic systems can contribute to the formulation of definitions of indicators of the system's ecological properties. This paper addresses confinement, a specific transport scale proposed by biological scientists as a parameter that can capture and synthesize the principal properties that determine the spatial structure of biological communities in transitional environments. Currently, there is no direct experimental measure of confinement. In this study, a methodology based on the accumulation rate within a lagoon of a passive tracer of marine origin is proposed, the influences of different factors in the calculation of confinement are analyzed, and general recommendations are derived. In particular, we analyze the spatial and the temporal variability of confinement and its sensitivity to the seasonal variability of climatic forcing, the inputs from rivers and the parameterization of the tidal exchanges. The Lagoon of Venice is used as a case study.

  14. Interplay of explosive thermal reaction dynamics and structural confinement

    NASA Astrophysics Data System (ADS)

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

    2007-04-01

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

  15. Dynamics of High Sound-Speed Metal Confiners Driven By Non-Ideal High-Explosive Detonation

    DOE PAGES

    Short, Mark; Jackson, Scott I.

    2015-01-23

    . The range of wall velocities where the overlap occurs increases as the ratio of the wall thickness to inner diameter decreases. In conclusion, this is in contrast to ideal high explosives, where the outer wall velocity histories are only similar when the geometric scale factor (in this case a factor of 2) is applied to the wall velocity motion.« less

  16. Dynamics of High Sound-Speed Metal Confiners Driven By Non-Ideal High-Explosive Detonation

    SciTech Connect

    Short, Mark; Jackson, Scott I.

    2015-01-23

    range of wall velocities where the overlap occurs increases as the ratio of the wall thickness to inner diameter decreases. In conclusion, this is in contrast to ideal high explosives, where the outer wall velocity histories are only similar when the geometric scale factor (in this case a factor of 2) is applied to the wall velocity motion.

  17. Influence of quantum-confined Stark effect on optical properties within trench defects in InGaN quantum wells with different indium content

    SciTech Connect

    Vaitkevičius, A. Mickevičius, J.; Dobrovolskas, D.; Tamulaitis, G.; Tuna, Ö.; Giesen, C.; Heuken, M.

    2014-06-07

    The trench defects in InGaN/GaN multiple quantum well structures are studied using confocal photoluminescence (PL) spectroscopy and atomic force microscopy. A strong blueshift (up to ∼280 meV) and an intensity increase (by up to a factor of 700) of the emission are demonstrated for regions enclosed by trench loops. The influence of the difference in the well width inside and outside the trench loops observed by transmission electron microscopy, the compositional pulling effect, the strain relaxation inside the loop, and corresponding reduction in the built-in field on the PL band peak position and intensity were estimated. The competition of these effects is mainly governed by the width of the quantum wells in the structure. It is shown that the PL band blueshift observed within the trench defect loops in the InGaN structures with wide quantum wells is mainly caused by the reduction in efficiency of the quantum-confined Stark effect due to strain relaxation.

  18. Highly efficient photothermal effect by atomic-thickness confinement in two-dimensional ZrNCl nanosheets.

    PubMed

    Feng, Feng; Guo, Hongyan; Li, Dianqi; Wu, Changzheng; Wu, Junchi; Zhang, Wenshuai; Fan, Shaojuan; Yang, Yuchen; Wu, Xiaojun; Yang, Jinlong; Ye, Bangjiao; Xie, Yi

    2015-02-24

    We report a giant photothermal effect arising from quantum confinement in two-dimensional nanomaterials. ZrNCl ultrathin nanosheets with less than four monolayers of graphene-like nanomaterial successfully generated synergetic effects of larger relaxation energy of photon-generated electrons and intensified vibration of surface bonds, offering predominantly an enhancement of the electron-phonon interaction to a maximized extent. As a result, they could generate heat flow reaching an ultrahigh value of 5.25 W/g under UV illumination with conversion efficiency up to 72%. We anticipate that enhanced electron-phonon coupling in a quantum confinement system will be a powerful tool for optimizing photothermal conversion of inorganic semiconductors.

  19. Graphene/sulfur hybrid nanosheets from a space-confined "sauna" reaction for high-performance lithium-sulfur batteries.

    PubMed

    Fei, Linfeng; Li, Xiaogang; Bi, Wentuan; Zhuo, Zhiwen; Wei, Wenfei; Sun, Li; Lu, Wei; Wu, Xiaojun; Xie, Keyu; Wu, Changzheng; Chan, Helen L W; Wang, Yu

    2015-10-21

    A space-confined "sauna" reaction system is introduced for the simultaneous reduction and functionalization of graphene oxide to unique graphene-sulfur hybrid nanosheets, in which thin layers of amorphous sulfur are tightly anchored on the graphene sheet via strong chemical bonding. Upon being used as the cathode material in lithium-sulfur batteries, the as-synthesized composite shows an excellent electrochemical performance.

  20. Two- and three-phase equilibria of polydisperse Yukawa hard-sphere fluids confined in random porous media: high temperature approximation and scaled particle theory.

    PubMed

    Hvozd, Taras V; Kalyuzhnyi, Yurij V

    2017-02-15

    We have studied the phase behavior of polydisperse Yukawa hard-sphere fluid confined in random porous media using extension and combination of high temperature approximation and scaled particle theory. The porous media are represented by the matrix of randomly placed hard-sphere obstacles. Due to the confinement, polydispersity effects are substantially enhanced. At an intermediate degree of fluid polydispersity and low density of the matrix, we observe two-phase coexistence with two critical points, and cloud and shadow curves forming closed loops of ellipsoidal shape. With the increase of the matrix density and the constant degree of polydispersity, these two critical points merge and disappear, and at lower temperatures the system fractionates into three coexisting phases. A similar phase behavior was observed in the absence of the porous media caused, however, by the increase of the polydispersity.

  1. The dynamics of short-scale turbulent fluctuations across low-intermediate-high-confinement transition with lower hybrid current drive in the EAST superconducting tokamak

    SciTech Connect

    Cao, G. M.; Li, Y. D.; Zhang, X. D.; Sun, P. J.; Wu, G. J.; Hu, L. Q.

    2015-02-15

    Two different confinement transition discharges, the low-intermediate-high (L-I-H) and the low-intermediate-low (L-I-L) confinement transitions, respectively, have been obtained by lower hybrid current drive with lithium wall conditioning in the EAST superconducting tokamak. The dynamic features of short-scale turbulent fluctuations in the two discharges are investigated by a tangential CO{sub 2} laser collective scattering system. It is found that the great changes of broadband fluctuations in amplitude and structure characteristics are closely related to the choice of the final transition to H-mode. These results could shed light on the understanding of the L-H transition mechanism.

  2. Review of energy confinement and local transport scaling results in neutral-beam-heated tokamaks

    SciTech Connect

    Kaye, S.M.

    1985-05-01

    Over the past several years, tokamak neutral beam injection experiments have evolved from the brute force study of the effects of global discharge characteristics (I/sub p/, anti n/sub e/, P/sub heat/, etc.) on energy confinement to the appreciation that there are effects more subtle, yet controllable, that may influence confinement dramatically. While this evolution from first to second generation experiments is derived from an empirical understanding of low and high energy confinement modes and how to achieve them operationally, the underlying physics is still unknown. Several theories with different physical bases appear to describe the global scaling of the low confinement mode discharges quite well. On the other hand, little agreement has been found between theoretical and experimentally deduced values of local transport coefficients. While it is known operationally how to achieve any one of several types of high confinement mode discharges, here too, the underlying physics of the transport associated with these modes is poorly understood.

  3. Influence of particle size and water coverage on the thermodynamic properties of water confined on the surface of SnO2 cassiterite nanoparticles

    SciTech Connect

    Spencer, Elinor; Ross, Dr. Nancy; Parker, Stewart F.; Kolesnikov, Alexander I; Woodfield, Brian; Woodfield, K; Rytting, M; Boerio-Goates, Juliana; Navrotsky, Alexandra

    2011-01-01

    Inelastic neutron scattering (INS) data for SnO2 nanoparticles of three different sizes and varying hydration levels are presented. Data were recorded on five nanoparticle samples that had the following compositions: 2 nm SnO2*0.82H2O, 6 nm SnO2*0.055H2O, 6 nm SnO2*0.095H2O, 20 nm SnO2*0.072H2O, and 20 nm SnO2*0.092H2O. The isochoric heat capacity and vibrational entropy values at 298 K for the water confined on the surface of these nanoparticles were calculated from the vibrational density of states that were extracted from the INS data. This study has shown that the hydration level of the SnO2 nanoparticles influences the thermodynamic properties of the water layers and, most importantly, that there appears to be a critical size limit for SnO2 between 2 and 6 nm below which the particle size also affects these properties and above which it does not. These results have been compared with those for isostructural rutile-TiO2 nanoparticles [TiO2*0.22H2O and TiO2*0.37H2O], which indicated that water on the surface of TiO2 nanoparticles is more tightly bound and experiences a greater degree of restricted motion with respect to water on the surface of SnO2 nanoparticles. This is believed to be a consequence of the difference in chemical composition, and hence surface properties, of these metal oxide nanoparticles.

  4. Social support and depressed mood in isolated and confined environments

    NASA Astrophysics Data System (ADS)

    Palinkas, Lawrence A.; Johnson, Jeffrey C.; Boster, James S.

    2004-05-01

    The influence of isolation and confinement on social support and depressed mood was examined in a study of 235 men and women who spent a year at McMurdo Station in Antarctica, and a study of 77 men and women who spent a year at the Amundson-Scott South Pole Station. Although availability of support remained unchanged, there was a significant decrease in reported satisfaction with support obtained, as well as a significant increase in depressed mood. Satisfaction with support was inversely associated with depressed mood at the beginning and end of isolation and confinement. At the end of winter, this association varied by source of support. High levels of tension-anxiety, depression and anger preceded an increase in advice seeking, but high levels of advice seeking also preceded an increase in tension-anxiety and depression. Results suggest a significant erosion of social support under conditions of prolonged isolation and confinement, leading to an increase in depressed mood.

  5. Equilibrium drives of the low and high field side n  =  2 plasma response and impact on global confinement

    NASA Astrophysics Data System (ADS)

    Paz-Soldan, C.; Logan, N. C.; Haskey, S. R.; Nazikian, R.; Strait, E. J.; Chen, X.; Ferraro, N. M.; King, J. D.; Lyons, B. C.; Park, J.-K.

    2016-05-01

    The nature of the multi-modal n  =  2 plasma response and its impact on global confinement is studied as a function of the axisymmetric equilibrium pressure, edge safety factor, collisionality, and L-versus H-mode conditions. Varying the relative phase (Δ {φ\\text{UL}} ) between upper and lower in-vessel coils demonstrates that different n  =  2 poloidal spectra preferentially excite different plasma responses. These different plasma response modes are preferentially detected on the tokamak high-field side (HFS) or low-field side (LFS) midplanes, have different radial extents, couple differently to the resonant surfaces, and have variable impacts on edge stability and global confinement. In all equilibrium conditions studied, the observed confinement degradation shares the same Δ {φ\\text{UL}} dependence as the coupling to the resonant surfaces given by both ideal (IPEC) and resistive (MARS-F) MHD computation. Varying the edge safety factor shifts the equilibrium field-line pitch and thus the Δ {φ\\text{UL}} dependence of both the global confinement and the n  =  2 magnetic response. As edge safety factor is varied, modeling finds that the HFS response (but not the LFS response), the resonant surface coupling, and the edge displacements near the X-point all share the same Δ {φ\\text{UL}} dependence. The LFS response magnitude is strongly sensitive to the core pressure and is insensitive to the collisionality and edge safety factor. This indicates that the LFS measurements are primarily sensitive to a pressure-driven kink-ballooning mode that couples to the core plasma. MHD modeling accurately reproduces these (and indeed all) LFS experimental trends and supports this interpretation. In contrast to the LFS, the HFS magnetic response and correlated global confinement impact is unchanged with plasma pressure, but is strongly reduced in high collisionality conditions in both H- and L-mode. This experimentally suggests the bootstrap

  6. Equilibrium drives of the low and high field side n = 2 plasma response and impact on global confinement

    SciTech Connect

    Paz-Soldan, C.; Logan, N. C.; Haskey, S. R.; Nazikian, R.; Strait, E. J.; Chen, X.; Ferraro, N. M.; King, J. D.; Lyons, B. C.; Park, J. -K.

    2016-03-31

    The nature of the multi-modal n=2 plasma response and its impact on global confinement is studied as a function of the axisymmetric equilibrium pressure, edge safety factor, collisionality, and L-versus H-mode conditions. Varying the relative phase (ΔΦUL) between upper and lower in-vessel coils demonstrates that different n=2 poloidal spectra preferentially excite different plasma responses. These different plasma response modes are preferentially detected on the tokamak high-field side (HFS) or low-field side (LFS) midplanes, have different radial extents, couple differently to the resonant surfaces, and have variable impacts on edge stability and global confinement. In all equilibrium conditions studied, the observed confinement degradation shares the same ΔΦUL dependence as the coupling to the resonant surfaces given by both ideal (IPEC) and resistive (MARS-F) MHD computation. Varying the edge safety factor shifts the equilibrium field-line pitch and thus the ΔΦUL dependence of both the global confinement and the n=2 magnetic response. As edge safety factor is varied, modeling finds that the HFS response (but not the LFS response), the resonant surface coupling, and the edge displacements near the X-point all share the same ΔΦUL dependence. The LFS response magnitude is strongly sensitive to the core pressure and is insensitive to the collisionality and edge safety factor. This indicates that the LFS measurements are primarily sensitive to a pressure-driven kink-ballooning mode that couples to the core plasma. MHD modeling accurately reproduces these (and indeed all) LFS experimental trends and supports this interpretation. In contrast to the LFS, the HFS magnetic response and correlated global confinement impact is unchanged with plasma pressure, but is strongly reduced in high collisionality conditions in both H- and L-mode. This experimentally suggests the bootstrap current drives the HFS response through

  7. Development of an NDA system for high-level waste from the Chernobyl new safe confinement construction site

    SciTech Connect

    Lee, Sang-yoon; Browne, Michael C; Rael, Carlos D; Carroll, Colin J; Sunshine, Alexander; Novikov, Alexander; Lebedev, Evgeny

    2010-01-01

    In early 2009, preliminary excavation work has begun in preparation for the construction of the New Safe Confinement (NSC) at the Chernobyl Nuclear Power Plant (ChNPP) in Ukraine. The NSC is the structure that will replace the present containment structure and will confine the radioactive remains of the ChNPP Unit-4 reactor for the next 100 years. It is expected that special nuclear material (SNM) that was ejected from the Unit-4 reactor during the accident in 1986 could be uncovered and would therefore need to be safeguarded. ChNPP requested the assistance of the United States Department of Energy/National Nuclear Security Administration (NNSA) with developing a new non-destructive assay (NDA) system that is capable of assaying radioactive debris stored in 55-gallon drums. The design of the system has to be tailored to the unique circumstances and work processes at the NSC construction site and the ChNPP. This paper describes the Chernobyl Drum Assay System (CDAS), the solution devised by Los Alamos National Laboratory, Sonalysts Inc., and the ChNPP, under NNSA's International Safeguards and Engagement Program (INSEP). The neutron counter measures the spontaneous fission neutrons from the {sup 238}U, {sup 240}Pu, {sup 244}Cm in a waste drum and estimates the mass contents of the SNMs in the drum by using of isotopic compositions determined by fuel burnup. The preliminary evaluation on overall measurement uncertainty shows that the system meets design performance requirements imposed by the facility.

  8. Exposure to Indoor Allergens in Different Residential Settings and Its Influence on IgE Sensitization in a Geographically Confined Austrian Cohort

    PubMed Central

    Stemeseder, Teresa; Schweidler, Bettina; Doppler, Patrick; Klinglmayr, Eva; Moser, Stephanie; Lueftenegger, Lisa; Himly, Martin; Lang, Roland; Zumbach, Joerg; Oostingh, Gertie J.; Hawranek, Thomas; Bathke, Arne C.

    2017-01-01

    Background Exposure to indoor allergens is crucial for IgE sensitization and development of allergic symptoms. Residential settings influence the allergen amount in house dust and hence allergic sensitization. Within this study, we investigated allergen exposure and molecule-based IgE levels in a geographically confined region and evaluated the impact of housing, pets and cleaning. Methods 501 adolescents from Salzburg, Austria participated in this cross-sectional study. House dust samples were examined regarding major mite, cat, dog, and mold allergens using a multiplex assay. Serum samples of participants were analyzed for specific IgE to Der p 1, Der p 2, Fel d 1, Can f 1 and Alt a 1 using the multiplex array ImmunoCAP ISAC. Information on allergies, living areas, dwelling form (house, flat, farm), pets, and household cleanliness were obtained by a questionnaire. Results In investigated house dust samples, the concentration of cat allergen was highest while the prevalence of mold allergens was very low. Participants showed IgE sensitization to Der p 1 (13.2%), Der p 2 (18.2%), Fel d 1 (14.4%), Can f 1 (2.4%) and Alt a 1 (2.0%). In alpine regions, lower mite allergen concentrations were detected which correlated with reduced IgE levels. A trend for increased sensitization prevalence from rural to alpine to urban regions was noted. Living on farms resulted in lower sensitization prevalence to mite and cat allergens, even though exposure to mites was significantly elevated. The presence of cats was associated with a lower sensitization rate and IgE levels to cat and mite allergens, and less frequent allergic diseases. Cleaning did not impact allergen concentrations, while IgE reactivity to mites and allergic diseases were more pronounced when living in cleaner homes. Conclusion Allergen exposure to indoor allergens was influenced by setting of homes. Living in a farm environment and having a cat at home showed a protective effect for IgE sensitization and allergies

  9. Perceived Influences on High School Students' Current Career Expectations.

    ERIC Educational Resources Information Center

    Paa, Heidi K.; McWhirter, Ellen Hawley

    2000-01-01

    Presents descriptive data on high school students' (N=464) perceptions of various factors that might influence their current career expectations. Analysis suggests that high school students are aware of a variety of internal and external influences on their current career expectations. Girls endorsed more types of influence from same sex parent,…

  10. 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.

  11. De-confinement in small systems: Clustering of color sources in high multiplicity p¯p collisions at s = 1.8TeV

    NASA Astrophysics Data System (ADS)

    Gutay, L. J.; Hirsch, A. S.; Scharenberg, R. P.; Srivastava, B. K.; Pajares, C.

    2015-12-01

    It is shown that de-confinement can be achieved in high multiplicity nonjet p¯p collisions at s = 1.8TeV Fermi National Accelerator Laboratory (FNAL- E735) experiment. Previously, the evidence for de-confinement was demonstrated by the constant freeze out energy density in high multiplicity events. In this paper, we use the same but analyze the transverse momentum spectrum in the framework of the clustering of color sources. This frame work naturally predicts the reduction in the charged particle multiplicity with respect to the value expected from the number of independent strings. The charged particle pseudorapidity densities in the range 7.0 ≤≤ 26.0 are considered. Results are presented for both thermodynamic and transport properties. The initial temperature and energy density are obtained from the data via the color reduction factor F(ξ) and the associated string density parameter ξ. The Bjorken ideal fluid description of the QGP, when modified by the color reduction factor and the trace anomaly Δ is in remarkable agreement with the lattice quantum chromo dynamics (LQCD) simulations. The energy density (ɛ/T4) ˜ 11.5 for ˜ 25.0 is close to the value for 0-10% central events in Au+Au collisions at sNN = 200GeV. The shear viscosity to entropy density ratio (η/s) is ˜0.2 at the transition temperature of 167MeV. The result for the trace anomaly Δ is in excellent agreement with LQCD simulations. These results confirm our earlier observation that the de-confined state of matter was created in high multiplicity events in p¯p collisions at s = 1.8TeV.

  12. QUIESCENT H-MODE, AN ELM-FREE HIGH-CONFINEMENT MODE ON DIII-D WITH POTENTIAL FOR STATIONARY STATE OPERATION

    SciTech Connect

    WEST,WP; BURRELL,KH; deGRASSIE,JS; DOYLE,EJ; GREENFIELD,CM; LASNIER,CJ; SNYDER,PB; ZENG,L

    2003-08-01

    OAK-B135 The quiescent H-mode (QH-mode) is an ELM-free and stationary state mode of operation discovered on DIII-D. This mode achieves H-mode levels of confinement and pedestal pressure while maintaining constant density and radiated power. The elimination of edge localized modes (ELMs) and their large divertor loads while maintaining good confinement and good density control is of interest to next generation tokamaks. This paper reports on the correlations found between selected parameters in a QH-mode database developed from several hundred DIII-D counter injected discharges. Time traces of key plasma parameters from a QH-mode discharge are shown. On DIII-D the negative going plasma current (a) indicates that the beam injection direction is counter to the plasma current direction, a common feature of all QH-modes. The D{sub {alpha}} time behavior (c) shows that soon after high powered beam heating (b) is applied, the discharge makes a transition to ELMing H-mode, then the ELMs disappear, indicating the start of the QH period that lasts for the remainder of the high power beam heating (3.5 s). Previously published work showing density and temperature profiles indicates that long-pulse, high-triangularity QH discharges develop an internal transport barrier in combination with the QH edge barrier. These discharges are known as quiescent, double-barrier discharges (QDB). The H-factor (d) and stored energy (c) rise then saturate at a constant level and the measured axial and minimum safety factors remain above 1.0 for the entire QH duration. During QDB operation the performance of the plasma can be very good, with {beta}{sub N}*H{sub 89L} product reaching 7 for > 10 energy confinement times. These discharges show promise that a stationary state can be achieved.

  13. Heteroatomic SenS8-n Molecules Confined in Nitrogen-Doped Mesoporous Carbons as Reversible Cathode Materials for High-Performance Lithium Batteries.

    PubMed

    Sun, Fugen; Cheng, Hongye; Chen, Jianzhuang; Zheng, Nan; Li, Yongsheng; Shi, Jianlin

    2016-09-27

    A reversible cathode material in an ether-based electrolyte for high-energy lithium batteries was successfully fabricated by homogeneously confining heteroatomic SenS8-n molecules into nitrogen-doped mesoporous carbons (NMCs) via a facile melt-impregnation route. The resultant SenS8-n/NMC composites exhibit highly reversible electrochemical behavior, where selenium sulfides are recovered through the reversible conversion of polysulfoselenide intermediates during discharge-charge cycles. The recovery of selenium sulfide molecules endows the SenS8-n/NMC cathodes with the rational integration of S and Se cathodes. Density functional theory calculations further reveal that heteroatomic selenium sulfide molecules with higher polarizability could bind more strongly with NMCs than homoatomic sulfur molecules, which provides more efficient suppression of the shuttling phenomenon. Therefore, with further assistance of mesopore confinement of the nitrogen-doped carbons, the Se2S6/NMC composite with an optimal Se/S mole ratio of 2/6 presents excellent cycle stability with a high initial Coulombic efficiency of 96.5% and a high reversible capacity of 883 mAh g(-1) after 100 cycles and 780 mAh g(-1) after 200 cycles at 250 mA g(-1). These encouraging results suggest that the heteroatomization of chalcogen (such as S, Se, or Te) molecules in mesostructured carbon hosts is a promising strategy in enhancing the electrochemical performances of chalcogen/carbon-based cathodes for Li batteries.

  14. A highly accurate and efficient algorithm for electrostatic interactions of charged particles confined by parallel metallic plates

    NASA Astrophysics Data System (ADS)

    Rostami, Samare; Ghasemi, S. Alireza; Nedaaee Oskoee, Ehsan

    2016-09-01

    We present an accurate and efficient algorithm to calculate the electrostatic interaction of charged point particles with partially periodic boundary conditions that are confined along the non-periodic direction by two parallel metallic plates. The method preserves the original boundary conditions, leading to an exact solution of the problem. In addition, the scaling complexity is quasilinear O ( N ln ( N ) ) , where N is the number of particles in the simulation box. Based on the superposition principle in electrostatics, the problem is split into two electrostatic problems where each can be calculated by the appropriate Poisson solver. The method is applied to NaCl ultra-thin films where its dielectric response with respect to an external bias voltage is investigated. Furthermore, the total charge induced on the metallic boundaries can be calculated to an arbitrary precision.

  15. 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.

  16. Formation of two-dimensionally confined superparamagnetic (Mn, Ga)As nanocrystals in high-temperature annealed (Ga, Mn)As/GaAs superlattices.

    PubMed

    Sadowski, Janusz; Domagala, Jaroslaw Z; Mathieu, Roland; Kovacs, Andras; Dłużewski, Piotr

    2013-05-15

    The annealing-induced formation of (Mn, Ga)As nanocrystals in (Ga, Mn)As/GaAs superlattices was studied by x-ray diffraction, transmission electron microscopy and magnetometry. The superlattice structures with 50 Å thick (Ga, Mn)As layers separated by 25, 50 and 100 Å thick GaAs spacers were grown by molecular beam epitaxy at low temperature (250 °C), and then annealed at high temperatures of 400, 560 and 630 °C. The high-temperature annealing causes decomposition to a (Ga, Mn)As ternary alloy and the formation of (Mn, Ga)As nanocrystals inside the GaAs matrix. The nanocrystals are confined in the planes that were formerly occupied by (Ga, Mn)As layers for the up to 560 °C annealing and diffuse throughout the GaAs spacer layers at 630 °C annealing. The two-dimensionally confined nanocrystals exhibit a superparamagnetic behavior which becomes high-temperature ferromagnetism (~350 K) upon diffusion.

  17. High-energy X-ray diffuse scattering studies on deformation-induced spatially confined martensitic transformations in multifunctional Ti-24Nb-4Zr-8Sn alloy

    SciTech Connect

    Liu, J. P.; Wang, Y. D.; Hao, Y. L.; Wang, H. L.; Wang, Y.; Nie, Z. H.; Su, R.; Wang, D.; Ren, Y.; Lu, Z. P.; Wang, J. G.; Hui, X. D.; Yang, R.

    2014-12-01

    Two main explanations exist for the deformation mechanisms in Ti-Nb-based gum metals, i.e. the formation of reversible nanodisturbance and reversible stress-induced martensitic transformation. In this work, we used the in situ synchrotron-based high-energy X-ray diffuse-scattering technique to reveal the existence of a specific deformation mechanism, i.e. deformation-induced spatially confined martensitic transformations, in Ti-24Nb-4Zr-8Sn-0.10O single crystals with cubic 13 parent phase, which explains well some anomalous mechanical properties of the alloy such as low elastic modulus and nonlinear superelasticity. Two kinds of nanosized martensites with different crystal structures were found during uniaxial tensile loading along the [11 0](beta) axis at room temperature and 190 K, respectively. The detailed changes in the martensitic phase transformation characteristics and the transformation kinetics were experimentally observed at different temperatures. The domain switch from non-modulated martensite to a modulated one occurred at 190 K, with its physical origin attributed to the heterogeneity of local phonon softening depending on temperature and inhomogeneous composition in the parent phase. An in-depth understanding of the formation of stress-induced spatially confined nanosized martensites with a large gradient in chemical composition may benefit designs of high-strength and high-ductility alloys. (C) 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  18. De-Confinement in small systems: Clustering of color sources in high multiplicity p¯p collisions at √s = 1.8 TeV

    NASA Astrophysics Data System (ADS)

    Gutay, L. J.

    2016-07-01

    It is shown that de-confinement can be achieved in high multiplicity non jet p¯p collisions at √s = 1.8 TeV Fermi National Accelerator Laboratory(FNAL- E735) experiment. In this paper we have analyzed the transverse momentum spectrum in the framework of the clustering of color sources. This frame-work naturally predicts the reduction in the charged particle multiplicity with respect to the value expected from the number of independent strings. Results are presented for both thermodynamic and transport properties. The initial temperature and energy density are obtained from the data via the color reduction factor F(ξ) and the associated string density parameter ξ. The results for he trace anomaly Δ and shear viscosity to entropy density ratio(η/s) are presented. These results confirm our earlier observation that the de-confined state of matter was created in high multiplicity events in p¯p collisions at √s = 1.8 TeV.

  19. 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 SW—in connection with the behaviour of atoms at very high pressures, and the solution was published on the occasion of Pauli's 60th birthday celebration. At the time, it seemed that there was not much other connection with physical reality beyond a few simple aspects connected to the properties of atoms in solids, for which more appropriate models were soon developed. Thus, confined atoms attracted little attention until the advent of the metallofullerene, which provided the first example of a confined atom with properties quite closely related to those originally considered by SW. Since then, the problem has received much more attention, and many more new features of quantum confinement, quantum compression, the quantum Faraday cage, electronic reorganisation, cavity resonances, etc have been described, which are relevant to real systems. Also, a number of other situations have been uncovered experimentally to which quantum confinement is relevant. Thus, studies of the confined atom are now more numerous, and have been extended both in terms of the models used and the systems to which they can be applied. Connections to thermodynamics are explored through the properties of a confined two-level atom adapted from Einstein's celebrated model, and issues of dynamical screening of electromagnetic radiation by the confining shell are discussed in connection with the Faraday cage produced by a confining conducting shell

  20. A Review of Quantum Confinement

    SciTech Connect

    Connerade, Jean-Patrick

    2009-12-03

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

  1. Semiflexible chains in confined spaces

    NASA Astrophysics Data System (ADS)

    Morrison, Greg; Thirumalai, D.

    2009-01-01

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

  2. Bimetallic Microswimmers Speed Up in Confining Channels

    NASA Astrophysics Data System (ADS)

    Liu, Chang; Zhou, Chao; Wang, Wei; Zhang, H. P.

    2016-11-01

    Synthetic microswimmers are envisioned to be useful in numerous applications, many of which occur in tightly confined spaces. It is therefore important to understand how confinement influences swimmer dynamics. Here we study the motility of bimetallic microswimmers in linear and curved channels. Our experiments show swimmer velocities increase, up to 5 times, with the degree of confinement, and the relative velocity increase depends weakly on the fuel concentration and ionic strength in solution. Experimental results are reproduced in a numerical model which attributes the swimmer velocity increase to electrostatic and electrohydrodynamic boundary effects. Our work not only helps to elucidate the confinement effect of phoretic swimmers, but also suggests that spatial confinement may be used as an effective control method for them.

  3. Size Dependant Nucleation of Confined 2-Decanol

    NASA Astrophysics Data System (ADS)

    Amanuel, Samuel; Bauer, Hillary; Safiq, Alexandrea; Dulmaa, Jargalsaikhan; Khraisat, Amer

    2012-02-01

    We have studied freezing and melting of physically confined 2-decanol in nano porous silica using a Differential Scanning Calorimeter (DSC). Both melting and freezing temperatures are suppressed for physically confined 2-decanol. In the presence of bulk, freezing of the confined system is triggered by freezing of the bulk where nucleation is heterogeneous. There is, however, a cutoff size between 100 nm and 300 nm where phase transition is no longer initiated through heterogeneous nucleation. Below the cutoff size, nucleation is homogeneous where the confined system has to be supercooled further before any phase transition can occur. Melting of the confined system, on the other hand, is not influenced by the presence or absence of the bulk.

  4. Acoustic confinement in superlattice cavities

    NASA Astrophysics Data System (ADS)

    Garcia-Sanchez, Daniel; Déleglise, Samuel; Thomas, Jean-Louis; Atkinson, Paola; Lagoin, Camille; Perrin, Bernard

    2016-09-01

    The large coupling rate between the acoustic and optical fields confined in GaAs/AlAs superlattice cavities makes them appealing systems for cavity optomechanics. We have developed a mathematical model based on the scattering matrix that allows the acoustic guided modes to be predicted in nano and micropillar superlattice cavities. We demonstrate here that the reflection at the surface boundary considerably modifies the acoustic quality factor and leads to significant confinement at the micropillar center. Our mathematical model also predicts unprecedented acoustic Fano resonances on nanopillars featuring small mode volumes and very high mechanical quality factors, making them attractive systems for optomechanical applications.

  5. Trophic dynamics influence climate at high latitudes

    NASA Astrophysics Data System (ADS)

    Oksanen, L.; Tuomi, M.; Hoset, K.; Oksanen, T.; Olofsson, J.; Dahlgren, J.; Nordic Center of Excellence-Tundra

    2011-12-01

    Abundance relationships between tall woody plants and low herbaceous plants influence ground albedo. Increasing abundance of erect woody plants on the tundra increase the amount of solar energy converted to heat, thus speeding up global warming. By transplanting vegetation blocks from an island with predatory mammals and gray-sided voles (Myodes rufocanus) to similar habitats on islands with gray-sided voles but no resident predators and to islands with neither voles nor predators, we show that changing trophic dynamics radically change the abundance relationships between woody and herbaceous plants. Impacts of food limited gray-sided voles result to devastation of all erect woody plants, regardless of their palatability, thus differing both quantitatively and qualitatively from the selective impacts of the same species in the presence of predators. The shift from vegetation dominated by erect woody plants to vegetation dominated by herbs or trailing dwarf shrubs also increases ground albedo. The relationship between climate and trophic dynamics is thus no one way street. Rather than responding passively to changes in climate, food webs can also influence climate via their impacts on ground albedo.

  6. Influence of nanopores of MCM-41 and SBA-15 confining (n-BuCp)2ZrCl2 on copolymerization of ethylene-alpha-olefin.

    PubMed

    Ko, Young Soo; Lee, Jeong Suk; Yim, Jin-Heong; Jeon, Jong-Ki; Jung, Kyeong Youl

    2010-01-01

    The effect of nanopore in mesoporous materials confining (n-BuCp),ZrCl2 and methylaluminoxane (MAO) on ethylene-1-hexene and ethylene-1-octene copolymerization was investigated on the basis of the copolymerization results, and the analysis of the supported catalyst and the copolymers. SBA-15 and MCM-41 together with amorphous silica were employed as supports, which are capable of confining (n-BuCp)2ZrCl2 and MAO in the nanopore. The copolymerization activities of MCM-41-supported (n-BuCp)2ZrCl2 were higher than those of SBA-15 and SiO2 although that its Zr content was quite lower than those of SBA-15 and SiO2. SBA-15 and MCM-41 showed a remarkable decrease in BET surface area after confining MAO and (n-BuCp)2ZrCl2 compared to SiO2, explaining an even adsorption of MAO and (n-BuCp)2ZrCl2 complexes on the nanopore surface. Temperature rising elution fractionation (TREF) results showed bimodal curves of MCM-41-supported (n-BuCp)2ZrCl2 at the C6/C2 and C8/C2 molar ratios of 0.6 and 0.5, respectively, which was attributed to the differences in ethylene and alpha-olefin concentrations along with the cylindrical nanopore of MCM-41 due to the narrow nanospace.

  7. High surface area Au-SBA-15 and Au-MCM-41 materials synthesis: tryptophan amino acid mediated confinement of gold nanostructures within the mesoporous silica pore walls.

    PubMed

    Selvakannan, Pr; Mantri, Kshudiram; Tardio, James; Bhargava, Suresh K

    2013-03-15

    Advantages of confining the gold nanostructures formation within the mesoporous silica pore walls during its silica condensation and consequent improvement in the textural properties such as specific surface area, pore volume, pore diameter have been demonstrated, while retaining gold nanostructures within the silica walls. This has been achieved by tryptophan mediated confinement of gold nanoparticles formation within the condensing silica framework, to obtain Au-SBA-15 (SSA 1247 m(2)/g, V(t)~1.37 cm(3)/g) and Au-MCM-41 (SSA 1287 m(2)/g, V(t)~1.1 cm(3)/g), mesoporous silica materials having the combination of very high surface area from the porous support as well as gold nanoparticles infiltrated silica walls. Choice of tryptophan for this purpose is that it has an indole group, which was known to reduce gold ions to form gold nanoparticles and its amine and carboxylic acid groups, catalyze the hydrolysis of silica precursors in a wide range of pH. These properties have been utilized in restricting the gold nanostructures formation inside the condensing silica phase without affecting the self assembly between the silica precursors and the triblock copolymer (for SBA-15) or cetyltrimethylammonium bromide template (for MCM-41). The polytryptophan and the gold nanostructures, which were encapsulated within the silica framework and upon removal of the template by calcination resulting in the formation mesoporous materials wherein the silica walls become microporous due to the removal of occluded polytryptophan and the resulting microchannels contain very small gold nanostructures. Hence, the resulting materials have very high surface area, high pore volume and narrow pore size distribution as compared to their parent SBA-15, MCM-41 and SBA-15, MCM-41 post functionalized with gold nanoparticles inside the pores.

  8. Increasing the critical speed of wetting failure through meniscus confinement

    NASA Astrophysics Data System (ADS)

    Vandre, Eric; Kumar, Satish; Carvalho, Marcio

    2010-11-01

    Dynamic wetting is a crucial step of fluid-fluid displacement along a solid surface, such as the deposition of a coating liquid onto a moving substrate. At some critical process speed wetting fails and the displaced phase (e.g. air) is entrained within the displacing phase. Improving upon current industrial production speeds requires a better understanding of how system parameters influence wetting failure. Confinement of the wetting meniscus is one such parameter commonly found in high-speed coating methods, though its influence remains unclear. In this study, we explore the effects of confinement on wetting failure with a laboratory-scale plunge-coating system. Our experimental apparatus consists of a steel roll that plunges into a bath of glycerol. Confinement is imposed by bringing a coating die near the wetting line, and liquid is injected through the die to compensate for liquid being dragged away with the roll. Flow visualization is used to record the critical roll speed at which wetting failure occurs. The data show a clear increase in the critical speed with increasing confinement. A model based on the lubrication approximation does a remarkable job in accurately predicting the increase in the critical speed relative to the unconfined value.

  9. Home versus hospital confinement

    PubMed Central

    Barry, C. N.

    1980-01-01

    The case for hospital rather than home delivery has been powerfully argued, especially in and since the Report of the Peel Committee. Nevertheless, evidence of comparison with other countries, notably the Netherlands, suggests the choice is not necessarily simple. Some general practitioner units are now reporting perinatal mortality rates which are consistently lower than those of specialist units, and recent statistical analyses suggest that the presence of more high risk cases in consultant units does not explain this. The only big controlled home-versus-hospital trial did not lead to a significantly lower perinatal mortality rate in the hospital group. The onus of proof now seems to lie with those who advocate 100 per cent hospital confinement. PMID:7373581

  10. Using ensembles of simulations to find high-fidelity post-shot models of inertial confinement implosions at the National Ignition Facility

    NASA Astrophysics Data System (ADS)

    Nora, Ryan; Field, John E.; Spears, Brian; Thomas, Cliff A.

    2016-10-01

    The inertial confinement fusion program at the National Ignition Facility is performing subscale experiments for a variety of implosion designs. Successful designs, those with experiments that are similar to postshot simulation, will be fielded at larger scale. This work supports the program's effort by establishing high fidelity post-shot simulations matching all experimental observables: scalar data, such as the neutron yield and areal densities; vector data, such as flange nuclear activation diagnostics; and image data, such as time-dependent x-ray self-emission images. We will present a metric for measuring the nearness of postshot simulations to experiments. In particular, we will emphasize area-based (as opposed to contour-based) image analysis metrics (e.g., Zernike moments) for comparison of x-ray self-emission images. The postshot metrics and methodology will be applied to the Big Foot implosion design as an example.

  11. 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…

  12. Influence of quantum confinement and strain on orbital polarization of four-layer LaNiO3 superlattices: A DFT+DMFT study

    NASA Astrophysics Data System (ADS)

    Park, Hyowon; Millis, Andrew J.; Marianetti, Chris A.

    2016-06-01

    Atomically precise superlattices involving transition-metal oxides provide a unique opportunity to engineer correlated electron physics using strain (modulated by choice of substrate) and quantum confinement (controlled by layer thickness). Here we use the combination of density-functional theory and dynamical mean-field theory (DFT+DMFT) to study Ni Egd -orbital polarization in strained LaNiO3/LaAlO3 superlattices consisting of four layers of nominally metallic NiO2 and four layers of insulating AlO2 separated by LaO layers. The layer-resolved orbital polarization is calculated as a function of strain and analyzed in terms of structural, quantum confinement, and correlation effects. The effect of strain is determined from the dependence of the results on the Ni-O bond-length ratio and the octahedral rotation angles, quantum confinement is studied by comparison to bulk calculations with similar degrees of strain, and correlation effects are inferred by varying interaction parameters within our DFT+DMFT calculations. The calculated dependence of orbital polarization on strain in superlattices is qualitatively consistent with recent x-ray-absorption spectroscopy and resonant reflectometry data. However, interesting differences of detail are found between theory and experiment. Under tensile strain, the two inequivalent Ni ions display orbital polarization similar to that calculated for strained bulk LaNiO3 and observed in experiment. Compressive strain produces a larger dependence of orbital polarization on Ni position, and even the inner Ni layer exhibits orbital polarization different from that calculated for strained bulk LaNiO3.

  13. 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.

  14. Elastic anisotropy and pore space geometry of schlieren granite: direct 3-D measurements at high confining pressure combined with microfabric analysis

    NASA Astrophysics Data System (ADS)

    Staněk, Martin; Géraud, Yves; Lexa, Ondrej; Špaček, Petr; Ulrich, Stanislav; Diraison, Marc

    2013-07-01

    Pore space geometry of granitic rocks and its evolution with depth are key factors in large-scale seismics or in projects of enhanced geothermal systems or of deep hazardous waste repositories. In this study, we studied macroscopically anisotropic schlieren-bearing granite by experimental P-wave velocity (VP) measurements on spherical sample in 132 directions at seven different confining pressures in the range 0.1-400 MPa. In order to discriminate the phenomena affecting the rock elastic properties we analysed the orientation of microcracks and of grain boundaries and we measured the anisotropy of magnetic susceptibility of the rock. Three sets of microcracks were defined, with two of them linked to the massif exfoliation process and one to cooling contraction of the massif. During pressurization the measured mean VP and VP anisotropy degree at ambient pressure and at highest confinement (400 MPa) yielded 3.3 km s-1 and 24 per cent, and 6.2 km s-1 and 3 per cent, respectively. The associated VP anisotropy pattern was transversely isotropic and governed by the schlieren, with a minimum VP direction perpendicular to them and a girdle of high VP directions parallel to them. The highest change in VP was observed between 0.1 and 10 MPa, suggesting a significant closure of porosity below depths of 500 m. Change of the VP anisotropy pattern to orthorhombic together with increase of mean VP and VP anisotropy degree during depressurization was attributed to inelastic response of one of the sets of microcracks to the loading-unloading cycle.

  15. 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.

  16. Influence of heterogeneity of confined water on photophysical behavior of acridine with amines: a time-resolved fluorescence and laser flash photolysis study.

    PubMed

    Sarangi, Manas Kumar; Dey, Debarati; Basu, Samita

    2011-01-20

    The photophysical behavior of acridine (Acr) shows facilitated water-assisted protonation equilibrium between its deprotonted (Acr* ∼ 10 ns) and protonated forms (AcrH(+*) ∼ 28 ns) within confined region of ordered water molecules inside AOT/H(2)O/n-heptane reverse micelles (RMs). The time-resolved-area-normalized-emission spectra confirm both Acr* and AcrH(+*), while time-resolved-emission spectra depict time evolution between them. Quenching of AcrH(+*) with N,N-dimethylaniline (DMA) is a purely diffusion-controlled bimolecular quenching with linear Stern-Volmer (S-V) plot, while nonlinearity arises with triethylamine (TEA) that forms ground state complex with AcrH(+) (AcrH(+)··H(2)O··TEA) indicating both static and dynamic quenching. Transient intermediates, DMA(•+) and AcrH(•) infer photoinduced electron transfer from DMA to Acr, while those from AcrH(+)··H(2)O··TEA complex suggest water mediated excited-state proton transfer (ESPT) between AcrH(+) and TEA. The ESPT becomes faster in larger RMs due to enhanced mobility of hydronium ions in AcrH(+)··H(2)O··TEA, which reduces in smaller RMs as water becomes much more constrained owing to stronger complexation by excess confinement.

  17. Queries, Influencers and Vocational Interests of Junior High School Students

    ERIC Educational Resources Information Center

    Woal, S. Theodore

    1974-01-01

    The study, based on questionnaire results from 207 ninth grade students, investigates: student familiarity with occupations; influencers of their tentative occupational choices; post high school plans; and student queries and concerns pertinent to preparation for entry into a job. (MW)

  18. 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.

  19. 2D Confined-Space Assisted Growth of Molecular-Level-Thick Polypyrrole Sheets with High Conductivity and Transparency.

    PubMed

    Yang, Yang; Wang, Dong; Wu, Yongjin; Tian, Xiaorui; Qin, Haili; Hu, Liang; Zhang, Ting; Ni, Weihai; Jin, Jian

    2016-04-01

    Herein, the use of a 2D soft template system composed of hundred-nanometer-thick water/ethanol mixed layers sandwiched by lamellar bilayer membranes of a self-assembled amphiphilic molecule to produce ultrathin polyprrole (PPy) with a uniform thickness as thin as 3.8 nm and with large dimensions (>2 μm(2)) is presented. The obtained PPy nanosheets exhibit regioregularity with ordered chain alignment where the polymer chains in the nanosheets produced are well aligned with a clear interchain spacing as confirmed by small-angle X-ray scattering measurement. The molecular-level-thick PPy nanosheets exhibit extremely high conductivity up to 1330 S m(-1), thanks to the ordered alignment of polymer chains in the nanosheets, and a high transparency in both the visible region (transmittance >99%) and near-infrared region (transmittance >93%).

  20. Enhanced second-harmonic generation from metal-integrated semiconductor nanowires via highly confined whispering gallery modes.

    PubMed

    Ren, Ming-Liang; Liu, Wenjing; Aspetti, Carlos O; Sun, Liaoxin; Agarwal, Ritesh

    2014-11-12

    Coherent and tunable nanoscale light sources utilizing optical nonlinearities are required for applications ranging from imaging and bio-sensing to on-chip all-optical signal processing. However, owing to their small sizes, the efficiency of nanostructures even with high nonlinear coefficients is poor, therefore requiring very high excitation energies. Although surface-plasmon resonances of metal nanostructures can enhance surface nonlinear processes such as second-harmonic generation, they still suffer from low conversion efficiencies owing to their intrinsically low nonlinear coefficients. Here we show highly enhanced and directional second-harmonic generation from individual CdS nanowires integrated with silver nanocavities (>1,000 times higher external efficiency compared with bare CdS), in which the lowest-order whispering gallery mode is engineered to concentrate light in the nonlinear material while minimizing Ohmic losses. The directional nonlinear signal is redirected into another waveguide, which is then utilized to configure an optical router that can potentially serve as a tunable coherent light source to enable on-chip signal processing for integrated nanophotonic systems.

  1. Elastic membranes in confinement

    NASA Astrophysics Data System (ADS)

    Bostwick, Joshua; Miksis, Michael; Davis, Stephen

    2014-11-01

    An elastic membrane stretched between two walls takes a shape defined by its length and the volume of fluid it encloses. Many biological structures, such as cells, mitochondria and DNA, have finer internal structure in which a membrane (or elastic member) is geometrically ``confined'' by another object. We study the shape stability of elastic membranes in a ``confining'' box and introduce repulsive van der Waals forces to prevent the membrane from intersecting the wall. We aim to define the parameter space associated with mitochondria-like deformations. We compare the confined to `unconfined' solutions and show how the structure and stability of the membrane shapes changes with the system parameters.

  2. Prepartum and postpartum nutritional management to optimize fertility in high-yielding dairy cows in confined TMR systems.

    PubMed

    Drackley, J K; Cardoso, F C

    2014-05-01

    The 6 to 8-week period centered on parturition, known as the transition or periparturient period, is critical to welfare and profitability of individual cows. Fertility of high-producing cows is compromised by difficult transitions. Deficiencies in either nutritional or non-nutritional management increase risk for periparturient metabolic disorders and infectious diseases, which decrease subsequent fertility. A primary factor impeding fertility is the extent of negative energy balance (NEB) early postpartum, which may inhibit timing of first ovulation, return to cyclicity, and oocyte quality. In particular, pronounced NEB during the first 10 days to 2 weeks (the time of greatest occurrence of health problems) is critical for later reproductive efficiency. Avoiding over-conditioning and preventing cows from over-consuming energy relative to their requirements in late gestation result in higher dry matter intake (DMI) and less NEB after calving. A pooled statistical analysis of previous studies in our group showed that days to pregnancy are decreased (by 10 days) by controlling energy intake to near requirements of cows before calving compared with allowing cows to over-consume energy. To control energy intake, total mixed rations (TMR) must be well balanced for metabolizable protein, minerals and vitamins yet limit total DM consumed, and cows must uniformly consume the TMR without sorting. Dietary management to maintain blood calcium and rumen health around and after calving also are important. Opportunities may exist to further improve energy status in fresh cows. Recent research to manipulate the glucogenic to lipogenic balance and the essential fatty acid content of tissues are intriguing. High-producing cows that adapt successfully to lactation can have high reproductive efficiency, and nutritional management of the transition period both pre- and post-calving must facilitate that adaptation.

  3. Composite mesostructures by nano-confinement.

    PubMed

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

    2004-11-01

    In a physically confined environment, interfacial interactions, symmetry breaking, structural frustration and confinement-induced entropy loss can play dominant roles in determining molecular organization. Here we present a systematic study of the confined assembly of silica-surfactant composite mesostructures within cylindrical nanochannels of varying diameters. Using exactly the same precursors and reaction conditions that form the two-dimensional hexagonal SBA-15 mesostructured thin film, unprecedented silica mesostructures with chiral mesopores such as single- and double-helical geometries spontaneously form inside individual alumina nanochannels. On tightening the degree of confinement, a transition is observed in the mesopore morphology from a coiled cylindrical to a spherical cage-like geometry. Self-consistent field calculations carried out to account for the observed mesostructures accord well with experiment. The mesostructures produced by confined syntheses are useful as templates for fabricating highly ordered mesostructured nanowires and nanowire arrays.

  4. An X-ray absorption study of selenium confined in channels of cancrinite: Evidence for dimerisation in highly oriented chains

    NASA Astrophysics Data System (ADS)

    Kolobov, Alexander V.; Oyanagi, Hiroyuki; Poborchii, Vladimir V.; Tanaka, Kazunobu

    1997-09-01

    Local structure of one-dimensional selenium chains in cancrinite channels have been studied by polarised X-ray absorption. Polarised EXAFS reveals that selenium atoms are one-fold coordinated and well-aligned along the c-axis of cancrinite. The obtained SeSe bond length is 2.40 ± 0.01 Å. The results provide direct evidence for dimerisation of selenium chains and suggest incommensurate intercalation of dimers which do not form a triplet (π-bond) state or a dangling bond state. Highly anisotropic polarisation dependence of XANES demonstrate that antibonding 4p(σ ∗) states are partially filled suggesting a charge transfer from Na cations located in the channels.

  5. Confinement Effects for Lithium Borohydride: Comparing Silica and Carbon Scaffolds.

    PubMed

    Suwarno; Ngene, Peter; Nale, Angeloclaudio; Eggenhuisen, Tamara M; Oschatz, Martin; Embs, Jan Peter; Remhof, Arndt; de Jongh, Petra E

    2017-03-02

    LiBH4 is a promising material for hydrogen storage and as a solid-state electrolyte for Li ion batteries. Confining LiBH4 in porous scaffolds improves its hydrogen desorption kinetics, reversibility, and Li(+) conductivity, but little is known about the influence of the chemical nature of the scaffold. Here, quasielastic neutron scattering and calorimetric measurements were used to study support effects for LiBH4 confined in nanoporous silica and carbon scaffolds. Pore radii were varied from 8 Å to 20 nm, with increasing confinement effects observed with decreasing pore size. For similar pore sizes, the confinement effects were more pronounced for silica than for carbon scaffolds. The shift in the solid-solid phase transition temperature is much larger in silica than in carbon scaffolds with similar pore sizes. A LiBH4 layer near the pore walls shows profoundly different phase behavior than crystalline LiBH4. This layer thickness was 1.94 ± 0.13 nm for the silica and 1.41 ± 0.16 nm for the carbon scaffolds. Quasi-elastic neutron scattering confirmed that the fraction of LiBH4 with high hydrogen mobility is larger for the silica than for the carbon nanoscaffold. These results clearly show that in addition to the pore size the chemical nature of the scaffold also plays a significant role in determining the hydrogen mobility and interfacial layer thickness in nanoconfined metal hydrides.

  6. Confinement Effects for Lithium Borohydride: Comparing Silica and Carbon Scaffolds

    PubMed Central

    2017-01-01

    LiBH4 is a promising material for hydrogen storage and as a solid-state electrolyte for Li ion batteries. Confining LiBH4 in porous scaffolds improves its hydrogen desorption kinetics, reversibility, and Li+ conductivity, but little is known about the influence of the chemical nature of the scaffold. Here, quasielastic neutron scattering and calorimetric measurements were used to study support effects for LiBH4 confined in nanoporous silica and carbon scaffolds. Pore radii were varied from 8 Å to 20 nm, with increasing confinement effects observed with decreasing pore size. For similar pore sizes, the confinement effects were more pronounced for silica than for carbon scaffolds. The shift in the solid–solid phase transition temperature is much larger in silica than in carbon scaffolds with similar pore sizes. A LiBH4 layer near the pore walls shows profoundly different phase behavior than crystalline LiBH4. This layer thickness was 1.94 ± 0.13 nm for the silica and 1.41 ± 0.16 nm for the carbon scaffolds. Quasi-elastic neutron scattering confirmed that the fraction of LiBH4 with high hydrogen mobility is larger for the silica than for the carbon nanoscaffold. These results clearly show that in addition to the pore size the chemical nature of the scaffold also plays a significant role in determining the hydrogen mobility and interfacial layer thickness in nanoconfined metal hydrides. PMID:28286596

  7. Polymer Crystallization under Confinement

    NASA Astrophysics Data System (ADS)

    Floudas, George

    Recent efforts indicated that polymer crystallization under confinement can be substantially different from the bulk. This can have important technological applications for the design of polymeric nanofibers with tunable mechanical strength, processability and optical clarity. However, the question of how, why and when polymers crystallize under confinement is not fully answered. Important studies of polymer crystallization confined to droplets and within the spherical nanodomains of block copolymers emphasized the interplay between heterogeneous and homogeneous nucleation. Herein we report on recent studies1-5 of polymer crystallization under hard confinement provided by model self-ordered AAO nanopores. Important open questions here are on the type of nucleation (homogeneous vs. heterogeneous), the size of critical nucleus, the crystal orientation and the possibility to control the overall crystallinity. Providing answers to these questions is of technological relevance for the understanding of nanocomposites containing semicrystalline polymers. In collaboration with Y. Suzuki, H. Duran, M. Steinhart, H.-J. Butt.

  8. Confined Formation of Ultrathin ZnO Nanorods/Reduced Graphene Oxide Mesoporous Nanocomposites for High-Performance Room-Temperature NO2 Sensors.

    PubMed

    Xia, Yi; Wang, Jing; Xu, Jian-Long; Li, Xian; Xie, Dan; Xiang, Lan; Komarneni, Sridhar

    2016-12-28

    Here we demonstrate high-performance room-temperature NO2 sensors based on ultrathin ZnO nanorods/reduced graphene oxide (rGO) mesoporous nanocomposites. Ultrathin ZnO nanorods were loaded on rGO nanosheets by a facile two-step additive-free solution synthesis involving anchored seeding followed by oriented growth. The ZnO nanorod diameters were simply controlled by the seed diameters associated with the spatial confinement effects of graphene oxide (GO) nanosheets. Compared to the solely ZnO nanorods and rGO-based sensors, the optimal sensor based on ultrathin ZnO nanorods/rGO nanocomposites exhibited higher sensitivity and quicker p-type response to parts per million level of NO2 at room temperature, and the sensitivity to 1 ppm of NO2 was 119% with the response and recovery time being 75 and 132 s. Moreover, the sensor exhibited full reversibility, excellent selectivity, and a low detection limit (50 ppb) to NO2 at room temperature. In addition to the high transport capability of rGO as well as excellent NO2 adsorption ability derived from ultrathin ZnO nanorods and mesoporous structures, the superior sensing performance of the nanocomposites was attributed to the synergetic effect of ZnO and rGO, which was realized by the electron transfer across the ZnO-rGO interfaces through band energy alignment.

  9. Self-phase modulation in highly confined submicron Ta2O5 channel waveguides.

    PubMed

    Lin, Yuan-Yao; Wu, Chung-Lun; Chi, Wen-Chun; Chiu, Yi-Jen; Hung, Yung-Jr; Chu, Ann-Kuo; Lee, Chao-Kuei

    2016-09-19

    Optical spectra broadening as a result self-phase modulation in a channel waveguide fabricated on a high quality tantalum pentoxide (Ta2O5) film by using RF sputtering is measured. The full-width at half maximum of the optical spectra for transverse electric (TE)/transverse magnetic (TM) polarizations of 42.5/31.7 nm is obtained using pulses of 10 nm at a wavelength of 800 nm with a peak-coupled power of 43.77 W. The nonlinear Kerr coefficients of 2.14 × 10-14 cm2/W and 1.92 × 10-14 cm2/W for TE and TM polarizations, respectively, are then extracted from the experiments using a theoretical model based on the method of moments. The obtained results on the nonlinearity further suggest that Ta2O5 is a promising material to develop nonlinear waveguide devices for integrated photonics.

  10. Ruthenium nanoparticles confined in SBA-15 as highly efficient catalyst for hydrolytic dehydrogenation of ammonia borane and hydrazine borane

    PubMed Central

    Yao, Qilu; Lu, Zhang-Hui; Yang, Kangkang; Chen, Xiangshu; Zhu, Meihua

    2015-01-01

    Ultrafine ruthenium nanoparticles (NPs) within the mesopores of the SBA-15 have been successfully prepared by using a “double solvents” method, in which n-hexane is used as a hydrophobic solvent and RuCl3 aqueous solution is used as a hydrophilic solvent. After the impregnation and reduction processes, the samples were characterized by XRD, TEM, EDX, XPS, N2 adsorption-desorption, and ICP techniques. The TEM images show that small sized Ru NPs with an average size of 3.0 ± 0.8 nm are uniformly dispersed in the mesopores of SBA-15. The as-synthesized Ru@SBA-15 nanocomposites (NCs) display exceptional catalytic activity for hydrogen generation by the hydrolysis of ammonia borane (NH3BH3, AB) and hydrazine borane (N2H4BH3, HB) at room temperature with the turnover frequency (TOF) value of 316 and 706 mol H2 (mol Ru min)−1, respectively, relatively high values reported so far for the same reaction. The activation energies (Ea) for the hydrolysis of AB and HB catalyzed by Ru@SBA-15 NCs are measured to be 34.8 ± 2 and 41.3 ± 2 kJ mol−1, respectively. Moreover, Ru@SBA-15 NCs also show satisfied durable stability for the hydrolytic dehydrogenation of AB and HB, respectively. PMID:26471355

  11. Confinement improvement in the high poloidal beta regime on DIII-D and application to steady-state H-mode on EAST

    NASA Astrophysics Data System (ADS)

    Ding, S.

    2016-10-01

    Systematic experimental and modeling investigations on DIII-D and EAST show attractive transport properties of fully non-inductive high βP plasmas. The improved understanding is used to develop steady state scenarios for ITER and CFETR. Experiments on DIII-D show that the large-radius internal transport barrier (ITB), a key feature providing improved performance in the high βP regime, is maintained when the scenario is extended from q95 10 to 7 and from rapid to near-zero plasma rotation. The robustness of confinement versus rotation was predicted by gyrofluid modeling showing dominant neoclassical ion energy transport even without E ×B shear effect on turbulence suppression. Measured electron turbulent transport is large when ion turbulent transport is low, consistent with recent multi-scale simulations. With decreasing q95, dominant turbulent transport shifts from electrons to ions, which exceeds the neoclassical ion transport level, and may set a q95 limit for the large-radius ITB regime. Experiments also show that the ITB is lost below βN 1.5 , when long wavelength turbulence increases in agreement with predictions of turbulence suppression by Shafranov shift. In DIII-D, a broad current profile enabling large radius ITB is accessed via early heating and sustained with high bootstrap current fraction. Experiments on EAST show that a broad current profile can be accessed and sustained exploiting a large fraction of lower hybrid wave current drive (LHCD). Results show that as the electron density is increased, the fully non-inductive current profile broadens on EAST. Overall, these results provide encouragement that high performance high βP regimes can be extended to lower safety factor and very low rotation, providing potential paths to steady state in ITER and CFETR. Supported in part by the US DOE under DE-FC02-04ER54698 and the NNSF of China under 11575248.

  12. 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.

  13. Walking droplets in confined domains

    NASA Astrophysics Data System (ADS)

    Sáenz, Pedro; Bush, John

    2016-11-01

    A millimetric liquid drop can walk spontaneously along the surface of a vibrating fluid bath, propelled by a resonant interaction with its own wave field. These walking droplets exhibit features previously thought to be exclusive to the microscopic quantum realm. We here explore experimentally the dynamics and statistics of this macroscopic wave-particle system in confined domains, or 'corrals'. Particular attention is given to characterizing the influence of the corral geometry on the emergent probability distributions. The relation to analogous quantum systems (specifically, quantum corrals, the quantum mirage and scarring in Bose-Einstein condensates) is discussed. NSF support via CMMI-1333242.

  14. A Survey of Factors Influencing High School Start Times

    ERIC Educational Resources Information Center

    Wolfson, Amy R.; Carskadon, Mary A.

    2005-01-01

    The present study surveyed high school personnel regarding high school start times, factors influencing school start times, and decision making around school schedules. Surveys were analyzed from 345 secondary schools selected at random from the National Center for Educational Statistics database. Factors affecting reported start times included…

  15. Confined Selective Withdrawal

    NASA Astrophysics Data System (ADS)

    Evangelio, Alvaro; Campo-Cortes, Francisco; Gordillo, Jose Manuel

    2014-11-01

    It is well known that the controlled production of monodisperse simple and composite emulsions possesses uncountable applications in medicine, pharmacy, materials science and industry. Here we present both experiments and slender-body theory regarding the generation of simple emulsions using a configuration that we have called Confined Selective Withdrawal, since it is an improved configuration of the classical Selective Withdrawal. We consider two different situations, namely, the cases when the outer flow Reynolds number is high and low, respectively. Several geometrical configurations and a wide range of viscosity ratios are analyzed so that the physics behind the phenomenon can be fully understood. In addition, we present both experiments and theory regarding the generation of composite emulsions. This phenomenon is only feasible when the outer flow Reynolds number is low enough. In this case, we propose a more complex theory which requires the simultaneous resolution of two interfaces in order to predict the shape of the jet and the sizes of the drops formed. The excellent agreement between our slender-body approximation and the experimental evidence fully validates our theories.

  16. 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.

  17. High-power low-threshold graded-index separate confinement heterostructure AlGaAs single quantum well lasers on Si substrates

    NASA Technical Reports Server (NTRS)

    Kim, Jae-Hoon; Lang, Robert J.; Radhakrishnan, Gouri; Katz, Joseph; Narayanan, Authi A.

    1989-01-01

    A high-power low-threshold graded-index separate confinement heterostructure AlGaAs single quantum well laser on Si substrates has been demonstrated for the first time by a hybrid growth of migration-enhanced molecular beam epitaxy followed by metalorganic vapor phase epitaxy. The quantum well laser showed an output power of more than 400 mW per facet under pulsed conditions. A room-temperature threshold current of 300 mA was obtained with a differential quantum efficiency of 40 percent without facet coating. The threshold current density was 550 A/sq cm for a cavity length of 500 microns. These results show the highest peak power reported to date for low-threshold lasers on Si substrates. The full width at half maximum of the far-field pattern parallel to the junction was 6 deg. Threshold current densities as low as 250 A/sq cm were obtained for lasers on GaAs substrates.

  18. Enzymatic reactions in confined environments

    NASA Astrophysics Data System (ADS)

    Küchler, Andreas; Yoshimoto, Makoto; Luginbühl, Sandra; Mavelli, Fabio; Walde, Peter

    2016-05-01

    Within each biological cell, surface- and volume-confined enzymes control a highly complex network of chemical reactions. These reactions are efficient, timely, and spatially defined. Efforts to transfer such appealing features to in vitro systems have led to several successful examples of chemical reactions catalysed by isolated and immobilized enzymes. In most cases, these enzymes are either bound or adsorbed to an insoluble support, physically trapped in a macromolecular network, or encapsulated within compartments. Advanced applications of enzymatic cascade reactions with immobilized enzymes include enzymatic fuel cells and enzymatic nanoreactors, both for in vitro and possible in vivo applications. In this Review, we discuss some of the general principles of enzymatic reactions confined on surfaces, at interfaces, and inside small volumes. We also highlight the similarities and differences between the in vivo and in vitro cases and attempt to critically evaluate some of the necessary future steps to improve our fundamental understanding of these systems.

  19. Confined aquifers as viral reservoirs.

    PubMed

    Smith, Renee J; Jeffries, Thomas C; Roudnew, Ben; Seymour, Justin R; Fitch, Alison J; Simons, Keryn L; Speck, Peter G; Newton, Kelly; Brown, Melissa H; Mitchell, James G

    2013-10-01

    Knowledge about viral diversity and abundance in deep groundwater reserves is limited. We found that the viral community inhabiting a deep confined aquifer in South Australia was more similar to reclaimed water communities than to the viral communities in the overlying unconfined aquifer community. This similarity was driven by high relative occurrence of the single-stranded DNA viral groups Circoviridae, Geminiviridae and Microviridae, which include many known plant and animal pathogens. These groups were present in a 1500-year-old water situated 80 m below the surface, which suggests the potential for long-term survival and spread of potentially pathogenic viruses in deep, confined groundwater. Obtaining a broader understanding of potentially pathogenic viral communities within aquifers is particularly important given the ability of viruses to spread within groundwater ecosystems.

  20. Enzymatic reactions in confined environments.

    PubMed

    Küchler, Andreas; Yoshimoto, Makoto; Luginbühl, Sandra; Mavelli, Fabio; Walde, Peter

    2016-05-05

    Within each biological cell, surface- and volume-confined enzymes control a highly complex network of chemical reactions. These reactions are efficient, timely, and spatially defined. Efforts to transfer such appealing features to in vitro systems have led to several successful examples of chemical reactions catalysed by isolated and immobilized enzymes. In most cases, these enzymes are either bound or adsorbed to an insoluble support, physically trapped in a macromolecular network, or encapsulated within compartments. Advanced applications of enzymatic cascade reactions with immobilized enzymes include enzymatic fuel cells and enzymatic nanoreactors, both for in vitro and possible in vivo applications. In this Review, we discuss some of the general principles of enzymatic reactions confined on surfaces, at interfaces, and inside small volumes. We also highlight the similarities and differences between the in vivo and in vitro cases and attempt to critically evaluate some of the necessary future steps to improve our fundamental understanding of these systems.

  1. Simulations of Enhanced Confinement

    NASA Astrophysics Data System (ADS)

    Dorland, W.; Kotschenreuther, M.; Liu, Q. P.; Jones, C. S.; Beer, M. A.; Hammett, G. W.

    1996-11-01

    Most existing tokamaks routinely achieve enhanced confinement regimes. Designs for new, larger tokamaks therefore are typically predicated upon reliable enhanced confinement performance. However, most enhanced confinement regimes rely (to some degree) upon sheared E×B flows to stabilize the turbulence that otherwise limits the confinement. For example, the pedestal H-mode transport barrier is typically attributed to shear stabilization [Biglari, Diamond and Terry, Phys. Fl. B, 2 1 (1990)]. Unfortunately, it is easily shown that sheared E×B stabilization of microinstabilities such as the ITG mode does not scale favorably with machine size. Here, using nonlinear gyrofluid simulations in general geometry, we attempt to quantify the confinement enhancement that can be expected from velocity shear stabilization for conventional reactor plasmas. We also consider other microinstability stabilization mechanisms(See related presentations by Beer, Kotschenreuther, Manickam, and Ramos, this conference.) (strong density peaking, Shafranov shift stabilization, dots) and unconventional reactor configurations.^2 Experimental datasets from JET, DIII-D, C-Mod and TFTR are analyzed, and ITER operation is considered.

  2. Small-angle neutron scattering studies of hemoglobin confined inside silica tubes of varying sizes.

    PubMed

    Mandal, Soumit S; Cristiglio, Viviana; Lindner, Peter; Bhattacharyya, Aninda J

    2014-02-03

    In addition to the chemical nature of the surface, the dimensions of the confining host exert a significant influence on confined protein structures; this results in immense biological implications, especially those concerning the enzymatic activities of the protein. This study probes the structure of hemoglobin (Hb), a model protein, confined inside silica tubes with pore diameters that vary by one order of magnitude (≈20-200 nm). The effect of confinement on the protein structure is probed by comparison with the structure of the protein in solution. Small-angle neutron scattering (SANS), which provides information on protein tertiary and quaternary structures, is employed to study the influence of the tube pore diameter on the structure and configuration of the confined protein in detail. Confinement significantly influences the structural stability of Hb and the structure depends on the Si-tube pore diameter. The high radius of gyration (Rg) and polydispersity of Hb in the 20 nm diameter Si-tube indicates that Hb undergoes a significant amount of aggregation. However, for Si-tube diameters greater or equal to 100 nm, the Rg of Hb is found to be in very close proximity to that obtained from the protein data bank (PDB) reported structure (Rg of native Hb=23.8 Å). This strongly indicates that the protein has a preference for the more native-like non-aggregated state if confined inside tubes of diameter greater or equal to 100 nm. Further insight into the Hb structure is obtained from the distance distribution function, p(r), and ab initio models calculated from the SANS patterns. These also suggest that the Si-tube size is a key parameter for protein stability and structure.

  3. Non-monotonic effect of confinement on the glass transition.

    PubMed

    Varnik, Fathollah; Franosch, Thomas

    2016-04-06

    The relaxation dynamics of glass forming liquids and their structure are influenced in the vicinity of confining walls. This effect has mostly been observed to be a monotonic function of the slit width. Recently, a qualitatively new behaviour has been uncovered by Mittal and coworkers, who reported that the single particle dynamics in a hard-sphere fluid confined in a planar slit varies in a non-monotonic way as the slit width is decreased from five to roughly two particle diametres (Mittal et al 2008 Phys. Rev. Lett. 100 145901). In view of the great potential of this effect for applications in those fields of science and industry, where liquids occur under strong confinement (e.g. nano-technology), the number of researchers studying various aspects and consequences of this non-monotonic behaviour has been rapidly growing. This review aims at providing an overview of the research activity in this newly emerging field. We first briefly discuss how competing mechanisms such as packing effects and short-range attraction may lead to a non-monotonic glass transition scenario in the bulk. We then analyse confinement effects on the dynamics of fluids using a thermodynamic route which relates the single particle dynamics to the excess entropy. Moreover, relating the diffusive dynamics to the Widom's insertion probability, the oscillations of the local dynamics with density at moderate densities are fairly well described. At high densities belonging to the supercooled regime, however, this approach breaks down signaling the onset of strongly collective effects. Indeed, confinement introduces a new length scale which in the limit of high densities and small pore sizes competes with the short-range local order of the fluid. This gives rise to a non-monotonic dependence of the packing structure on confinement, with a corresponding effect on the dynamics of structural relaxation. This non-monotonic effect occurs also in the case of a cone-plate type channel, where the degree

  4. Non-monotonic effect of confinement on the glass transition

    NASA Astrophysics Data System (ADS)

    Varnik, Fathollah; Franosch, Thomas

    2016-04-01

    The relaxation dynamics of glass forming liquids and their structure are influenced in the vicinity of confining walls. This effect has mostly been observed to be a monotonic function of the slit width. Recently, a qualitatively new behaviour has been uncovered by Mittal and coworkers, who reported that the single particle dynamics in a hard-sphere fluid confined in a planar slit varies in a non-monotonic way as the slit width is decreased from five to roughly two particle diametres (Mittal et al 2008 Phys. Rev. Lett. 100 145901). In view of the great potential of this effect for applications in those fields of science and industry, where liquids occur under strong confinement (e.g. nano-technology), the number of researchers studying various aspects and consequences of this non-monotonic behaviour has been rapidly growing. This review aims at providing an overview of the research activity in this newly emerging field. We first briefly discuss how competing mechanisms such as packing effects and short-range attraction may lead to a non-monotonic glass transition scenario in the bulk. We then analyse confinement effects on the dynamics of fluids using a thermodynamic route which relates the single particle dynamics to the excess entropy. Moreover, relating the diffusive dynamics to the Widom’s insertion probability, the oscillations of the local dynamics with density at moderate densities are fairly well described. At high densities belonging to the supercooled regime, however, this approach breaks down signaling the onset of strongly collective effects. Indeed, confinement introduces a new length scale which in the limit of high densities and small pore sizes competes with the short-range local order of the fluid. This gives rise to a non-monotonic dependence of the packing structure on confinement, with a corresponding effect on the dynamics of structural relaxation. This non-monotonic effect occurs also in the case of a cone-plate type channel, where the degree

  5. Magnetic microsphere-confined graphene for the extraction of polycyclic aromatic hydrocarbons from environmental water samples coupled with high performance liquid chromatography-fluorescence analysis.

    PubMed

    Wang, Weina; Ma, Ruiyang; Wu, Qiuhua; Wang, Chun; Wang, Zhi

    2013-06-07

    In this paper, a magnetic microsphere-confined graphene adsorbent (Fe3O4@SiO2-G) was fabricated and used for the extraction of five polycyclic aromatic hydrocarbons (fluorene, anthracene, phenanthrene, fluoranthene and pyrene) from environmental water samples prior to high performance liquid chromatography with fluorescence detection. The Fe3O4@SiO2-G was characterized by various instrumental methods. Various experimental parameters that could affect the extraction efficiencies, such as the amount of Fe3O4@SiO2-G, the pH and ionic strength of sample solution, the extraction time and the desorption conditions, were investigated. Due to the high surface area and excellent adsorption capacity of the Fe3O4@SiO2-G, satisfactory extraction can be achieved with only 15mg of the adsorbent per 250mL solution and 5min extraction. Under the optimum conditions, a linear response was observed in the concentration range of 5-1500ngL(-1) for fluorene, 2.5-1500ngL(-1) for anthracene and 15-1500ngL(-1) for phenanthrene, fluoranthene and pyrene, with the correlation coefficients (r) ranging from 0.9897 to 0.9961. The limits of detection (S/N=3) of the method were between 0.5 and 5.0ngL(-1). The relative standard deviations (RSDs) were less than 5.6%. The recoveries of the method were in the range between 83.2% and 108.2%. The results indicated that this graphene-based magnetic nanocomposite had a great adsorptive ability toward the five polycyclic aromatic hydrocarbons from environmental water samples.

  6. Influence of steric confinement within zeolite Y on photoinduced energy transfer between [Ru(bpy)3]2+ and iron polypyridyl complexes.

    PubMed

    Sewell, Gavin; Forster, Robert J; Keyes, Tia E

    2008-02-07

    The spectroscopic and photophysical properties of zeolite-Y-entrapped [Ru(bpy)3]2+ co-doped with either [Fe(bpy)3]2+ or [Fe(tpy)2]2+ over a range of iron complex loadings are presented. In solution, [Ru(bpy)3]2+ undergoes efficient bimolecular energy transfer to [Fe(bpy)3]2+, whereas only radiative or trivial energy transfer occurs between [Ru(bpy)3]2+ and [Fe(tpy)2]2+. In sharp contrast, within zeolite Y, both [Fe(bpy)3]2+ and [Fe(tpy)2]2+ were found to effectively quench the donor emission. Fitting the Perrin model to the photophysical data yields an effective quenching radius of 32 and 27 A, respectively, for [Fe(bpy)3]2+ and [Fe(tpy)2]2+. The long-range nature of the quenching suggests Förster energy transfer. Detailed spectroscopic investigations indicate that [Fe(tpy)2]2+ bound within zeolite Y undergoes significant distortion from octahedral geometry. This distortion results in increased oscillator strength and enhanced spectral overlap, between the [Ru(bpy)3]2+ (3)d pi-pi* donor emission and the co-incident acceptor (1)T2-(1)A1 ligand field absorption compared with solution. This turns on an efficient energy transfer to [Fe(tpy)2]2+ within the confinement of the zeolite Y supercage. Overall, this is an interesting example of the ability of the zeolite environment to provoke new photophysical processes not possible in solution.

  7. Improved confinement in JET hybrid discharges

    NASA Astrophysics Data System (ADS)

    Hobirk, J.; Imbeaux, F.; Crisanti, F.; Buratti, P.; Challis, C. D.; Joffrin, E.; Alper, B.; Andrew, Y.; Beaumont, P.; Beurskens, M.; Boboc, A.; Botrugno, A.; Brix, M.; Calabro', G.; Coffey, I.; Conroy, S.; Ford, O.; Frigione, D.; Garcia, J.; Giroud, C.; Hawkes, N. C.; Howell, D.; Jenkins, I.; Keeling, D.; Kempenaars, M.; Leggate, H.; Lotte, P.; de la Luna, E.; Maddison, G. P.; Mantica, P.; Mazzotta, C.; McDonald, D. C.; Meigs, A.; Nunes, I.; Rachlew, E.; Rimini, F.; Schneider, M.; Sips, A. C. C.; Stober, J. K.; Studholme, W.; Tala, T.; Tsalas, M.; Voitsekhovitch, I.; de Vries, P. C.; EFDA contributors, JET

    2012-09-01

    A new technique has been developed to produce plasmas with improved confinement relative to the H98,y2 scaling law (ITER Physics Expert Groups on Confinement and Transport and Confinement Modelling and Database ITER Physics Basics Editors and ITER EDA 1999 Nucl. Fusion 39 2175) on the JET tokamak. In the mid-size tokamaks ASDEX upgrade and DIII-D heating during the current formation is used to produce a flat q-profile with a minimum close to 1. On JET this technique leads to q-profiles with similar minimum q but opposite to the other tokamaks not to an improved confinement state. By changing the method utilizing a faster current ramp with temporary higher current than in the flattop (current overshoot) plasmas with improved confinement (H98,y2 = 1.35) and good stability (βN ≈ 3) have been produced and extended to many confinement times only limited by technical constraints. The increase in H98,y2-factor is stronger with more heating power as can be seen in a power scan. The q-profile development during the high power phase in JET is reproduced by current diffusion calculated by TRANSP and CRONOS. Therefore the modifications produced by the current overshoot disappear quickly from the edge but the confinement improvement lasts longer, in some cases up to the end of the heating phase.

  8. The Influence of Social Networks on High School Students' Performance

    ERIC Educational Resources Information Center

    Abu-Shanab, Emad; Al-Tarawneh, Heyam

    2015-01-01

    Social networks are becoming an integral part of people's lives. Students are spending much time on social media and are considered the largest category that uses such application. This study tries to explore the influence of social media use, and especially Facebook, on high school students' performance. The study used the GPA of students in four…

  9. Interfacial electrofluidics in confined systems

    NASA Astrophysics Data System (ADS)

    Tang, Biao; Groenewold, Jan; Zhou, Min; Hayes, Robert A.; Zhou, Guofu (G. F.)

    2016-05-01

    Electrofluidics is a versatile principle that can be used for high speed actuation of liquid interfaces. In most of the applications, the fundamental mechanism of electro-capillary instability plays a crucial role, yet it’s potential richness in confined fluidic layers has not been well addressed. Electrofluidic displays which are comprised of thin pixelated colored films in a range of architectures are excellent systems for studying such phenomena. In this study we show theoretically and experimentally that confinement leads to the generation of a cascade of voltage dependent modes as a result of the electro-capillary instability. In the course of reconciling theory with our experimental data we have observed a number of previously unreported phenomena such as a significant induction time (several milliseconds) prior to film rupture as well as a rupture location not corresponding to the minimum electric field strength in the case of the standard convex water/oil interface used in working devices. These findings are broadly applicable to a wide range of switchable electrofluidic applications and devices having confined liquid films.

  10. Interfacial electrofluidics in confined systems

    PubMed Central

    Tang, Biao; Groenewold, Jan; Zhou, Min; Hayes, Robert A.; Zhou, Guofu (G.F.)

    2016-01-01

    Electrofluidics is a versatile principle that can be used for high speed actuation of liquid interfaces. In most of the applications, the fundamental mechanism of electro-capillary instability plays a crucial role, yet it’s potential richness in confined fluidic layers has not been well addressed. Electrofluidic displays which are comprised of thin pixelated colored films in a range of architectures are excellent systems for studying such phenomena. In this study we show theoretically and experimentally that confinement leads to the generation of a cascade of voltage dependent modes as a result of the electro-capillary instability. In the course of reconciling theory with our experimental data we have observed a number of previously unreported phenomena such as a significant induction time (several milliseconds) prior to film rupture as well as a rupture location not corresponding to the minimum electric field strength in the case of the standard convex water/oil interface used in working devices. These findings are broadly applicable to a wide range of switchable electrofluidic applications and devices having confined liquid films. PMID:27221211

  11. Nanoparticle Order through Entropic Confinement

    NASA Astrophysics Data System (ADS)

    Zhang, Ren; Lee, Bongjoon; Stafford, Christopher; Douglas, Jack; Bockstaller, Michael; Karim, Alamgir

    As has been addressed in colloidal science, visual order transitions can be achieved with entropy contributions alone. Herein, entropy-driven ordering of nanoparticle (NP) structures is generated where entropy increase and visual order are achieved simultaneously. We study an ``athermal'' NP-polymer blends where NPs are densely grafted with polymer brush of the same chemical composition as the polymer matrix. Visual order of the NPs is induced by geometrically confining the thin film blends with meso-scale topographic patterns. When the residual layer thickness of the patterned blend films approaches the nanoparticle dimension, exclusive segregation of NPs to less confining imprinted mesa region occurs. This preferential segregation of NPs, defined by partition coefficient K = 0, is attributed to purely entropic penalty, where K denotes the particle density ratio at highly confined residual layer to that at mesa region. We further demonstrate K is fully tunable and even invertible with increasing matrix chain dimension. The associated entropic free energy change (ΔF = - ln K) is calculated to explain NP segregation preference. Accordingly, variation of residual layer thickness and polymer matrix molecule size can both affect NP distribution among patterned thick and thin regions.

  12. Controlling the Electromagnetic Field Confinement with Metamaterials

    PubMed Central

    Bonache, Jordi; Zamora, Gerard; Paredes, Ferran; Zuffanelli, Simone; Aguilà, Pau; Martín, Ferran

    2016-01-01

    The definition of a precise illumination region is essential in many applications where the electromagnetic field should be confined in some specific volume. By using conventional structures, it is difficult to achieve an adequate confinement distance (or volume) with negligible levels of radiation leakage beyond it. Although metamaterial structures and metasurfaces are well-known to provide high controllability of their electromagnetic properties, this feature has not yet been applied to solve this problem. We present a method of electromagnetic field confinement based on the generation of evanescent waves by means of metamaterial structures. With this method, the confinement volume can be controlled, namely, it is possible to define a large area with an intense field without radiation leakage. A prototype working in the microwave region has been implemented, and very good agreement between the measurements and the theoretical prediction of field distribution has been obtained. PMID:27886230

  13. Controlling the Electromagnetic Field Confinement with Metamaterials

    NASA Astrophysics Data System (ADS)

    Bonache, Jordi; Zamora, Gerard; Paredes, Ferran; Zuffanelli, Simone; Aguilà, Pau; Martín, Ferran

    2016-11-01

    The definition of a precise illumination region is essential in many applications where the electromagnetic field should be confined in some specific volume. By using conventional structures, it is difficult to achieve an adequate confinement distance (or volume) with negligible levels of radiation leakage beyond it. Although metamaterial structures and metasurfaces are well-known to provide high controllability of their electromagnetic properties, this feature has not yet been applied to solve this problem. We present a method of electromagnetic field confinement based on the generation of evanescent waves by means of metamaterial structures. With this method, the confinement volume can be controlled, namely, it is possible to define a large area with an intense field without radiation leakage. A prototype working in the microwave region has been implemented, and very good agreement between the measurements and the theoretical prediction of field distribution has been obtained.

  14. The Influence of High-Frequency Gravitational Waves Upon Muscles

    SciTech Connect

    Moy, Lawrence S.; Baker, Robert M. L. Jr

    2007-01-30

    The objective of this paper is to present a theory for the possible influence of high-frequency gravitational waves or HFGWs and pulsed micro-current electromagnetic waves or EMs on biological matter specifically on muscle cells and myofibroblasts. The theory involves consideration of the natural frequency of contractions and relaxations of muscles, especially underlying facial skin, and the possible influence of HFGWs on that process. GWs pass without attenuation through all material thus conventional wisdom would dictate that GWs would have no influence on biological matter. On the other hand, GWs can temporarily modify a gravitational field in some locality if they are of high frequency and such a modification might have an influence in changing the skin muscles' natural frequency. Prior to the actual laboratory generation of HFGWs their influence can be emulated by micro-current EM pulses to the skin and some evidence presented here on that effect may predict the influence of HFGWs. We believe that the HFGW pulsations lead to increased muscle activity and may serve to reverse the aging process. A novel theoretical framework concerning these relaxation phenomena is one result of the paper. Another result is the analysis of the possible delivery system of the FBAR-generated HFGWs, the actual power of the generated HFGWs, and the system's application to nanostructural modification of the skin or muscle cells. It is concluded that a series of non-evasive experiments, which are identified, will have the potential to test theory by detecting and analyzing the possible HFGWs change in polarization, refraction, etc. after their interaction with the muscle cells.

  15. Are polymers glassier upon confinement?

    NASA Astrophysics Data System (ADS)

    Napolitano, Simone; Spiece, Jean; Martinez-Tong, Daniel E.; Sferrazza, Michele; Nogales, Aurora

    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 discuss on the 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 (Tg), cold crystallization (TCC) and melting (Tm) temperatures down to a thickness of 6 nm via ellipsometry, 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. Remarkably, the increase in Tg/Tm ratio, a parameter related to glass forming ability, is not accompanied by an increase in TCC-Tg, as observed on the contrary, in bulk metallic glasses. We explained this peculiar behavior of soft matter in confinement considering the impact of irreversible adsorption on local free volume content.

  16. Diffusion of micrometer-sized soft particles in confinement

    NASA Astrophysics Data System (ADS)

    Jordan, Benjamin; Aptowicz, Kevin

    We investigate the diffusion of micrometer sized poly(N-isopropylacrylamide) (PNIPAM) gel particles in confinement. The influence of confinement on the transport of small particles is becoming increasingly important for microfluidics and bio-fluidics. Analytical solutions to this problem are limited to very unique geometries or gross approximations. Computational methods have provided more insight into the problem as well as experimental investigations. However, most research has focused on the hard-sphere problem. In this work, we will explore the diffusion of soft particles in confinement. The dynamics of the particles confined between two parallel walls is captured with video-microscopy. In addition, we use a recently developed technique to measurement confinement of particles in-situ with a precision of 1%. This poster will present some preliminary results of how confinement affects the diffusion of these soft particles. We acknowledge support from Grant DMR-1206231.

  17. Color Confinement from Fluctuating Topology

    NASA Astrophysics Data System (ADS)

    Kharzeev, Dmitri E.

    QCD possesses a compact gauge group, and this implies a non-trivial topological structure of the vacuum. In this contribution to the Gribov-85 Memorial volume, we first discuss the origin of Gribov copies and their interpretation in terms of fluctuating topology in the QCD vacuum. We then describe the recent work with E. Levin that links the confinement of gluons and color screening to the fluctuating topology, and discuss implications for spin physics, high energy scattering, and the physics of quark-gluon plasma.

  18. Color confinement from fluctuating topology

    NASA Astrophysics Data System (ADS)

    Kharzeev, Dmitri E.

    2016-10-01

    QCD possesses a compact gauge group, and this implies a non-trivial topological structure of the vacuum. In this contribution to the Gribov-85 Memorial volume, we first discuss the origin of Gribov copies and their interpretation in terms of fluctuating topology in the QCD vacuum. We then describe the recent work with E. Levin that links the confinement of gluons and color screening to the fluctuating topology, and discuss implications for spin physics, high energy scattering, and the physics of quark-gluon plasma.

  19. The history of research into improved confinement regimes

    NASA Astrophysics Data System (ADS)

    Wagner, F.

    2017-01-01

    Increasing the pressure by additional heating of magnetically confined plasmas had the consequence that turbulent processes became more violent and plasma confinement degraded. Since this experience from the early 1980ies, fusion research was dominated by the search for confinement regimes with improved properties. It was a gratifying experience that toroidally confined plasmas are able to self-organise in such a way that turbulence diminishes, resulting in a confinement with good prospects to reach the objectives of fusion R&D. The understanding of improved confinement regimes revolutionized the understanding of turbulent transport in high-temperature plasmas. In this paper the story of research into improved confinement regimes will be narrated starting with 1980.

  20. 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.

  1. 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.

  2. Energy confinement in tokamaks

    SciTech Connect

    Sugihara, M.; Singer, C.

    1986-08-01

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

  3. 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.

  4. 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.

  5. Ionic structure in liquids confined by dielectric interfaces

    NASA Astrophysics Data System (ADS)

    Jing, Yufei; Jadhao, Vikram; Zwanikken, Jos W.; Olvera de la Cruz, Monica

    2015-11-01

    The behavior of ions in liquids confined between macromolecules determines the outcome of many nanoscale assembly processes in synthetic and biological materials such as colloidal dispersions, emulsions, hydrogels, DNA, cell membranes, and proteins. Theoretically, the macromolecule-liquid boundary is often modeled as a dielectric interface and an important quantity of interest is the ionic structure in a liquid confined between two such interfaces. The knowledge gleaned from the study of ionic structure in such models can be useful in several industrial applications, such as in the design of double-layer supercapacitors for energy storage and in the extraction of metal ions from wastewater. In this article, we compute the ionic structure in a model system of electrolyte confined by two planar dielectric interfaces using molecular dynamics simulations and liquid state theory. We explore the effects of high electrolyte concentrations, multivalent ions, dielectric contrasts, and external electric field on the ionic distributions. We observe the presence of non-monotonic ionic density profiles leading to a layered structure in the fluid which is attributed to the competition between electrostatic and steric (entropic) interactions. We find that thermal forces that arise from symmetry breaking at the interfaces can have a profound effect on the ionic structure and can oftentimes overwhelm the influence of the dielectric discontinuity. The combined effect of ionic correlations and inhomogeneous dielectric permittivity significantly changes the character of the effective interaction between the two interfaces.

  6. Spatially confined assembly of nanoparticles.

    PubMed

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

    2014-10-21

    an increasingly important role in the controllable assembly of NPs. In this Account, we summarize our approaches and progress in fabricating spatially confined assemblies of NPs that allow for the positioning of NPs with high resolution and considerable throughput. The spatially selective assembly of NPs at the desired location can be achieved by various mechanisms, such as, a controlled dewetting process, electrostatically mediated assembly of particles, and confined deposition and growth of NPs. Three nanofabrication techniques used to produce prepatterns on a substrate are summarized: the Langmuir-Blodgett (LB) patterning technique, e-beam lithography (EBL), and nanoimprint lithography (NPL). The particle density, particle size, or interparticle distance in NP assemblies strongly depends on the geometric parameters of the template structure due to spatial confinement. In addition, with smart design template structures, multiplexed NPs can be assembled into a defined structure, thus demonstrating the structural and functional complexity required for highly integrated and multifunction applications.

  7. Structure of confined films of chain alcohols

    SciTech Connect

    Mugele, Friedrich; Baldelli, Steven; Somorjai, Gabor A.; Salmeron, Miquel

    1999-09-30

    The structure of thin films of simple chain alcohols (1-octanol and 1-undecanol) confined between two atomically smooth mica surfaces has been investigated using a surface forces apparatus (SFA). In both systems, the substrate-molecule interaction leads to a strongly bound first layer on each surface. Additional liquid organizes into highly compressible bilayers, which could be expelled by applying sufficiently high pressure.

  8. 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.

  9. Confinement studies in TFTR

    SciTech Connect

    Murakami, M.; Arunasalam, V.; Bell, J.D.; Bell, M.G.; Bitter, M.; Blanchard, W.R.; Boody, F.; Boyd, D.; Bretz, N.; Bush, C.E.

    1985-06-01

    The paper describes the present (end of February 1985) status of the plasma confinement studies in the TFTR tokamak with emphasis on those with neutral beam injection (NBI). Recent improvements in the device capabilities have substantially extended operating parameters: B/sub T/ increased to 4.0 T, I/sub p/ to 2.0 MA, injection power (P/sub b/) to 5 MW with H/sup 0/ or D/sup 0/ beams anti n/sub e/ to 5 x 10/sup 19/ m/sup -3/, and Z/sub eff/ reduced to 1.4. With ohmic heating (OH) alone, the previously established scaling for gross energy confinement time (tau/sub E/ = anti n/sub e/q) has been confirmed at higher I/sub p/ and B/sub T/, and the maximum tau/sub E/ of 0.4 sec has been achieved. With NBI at P/sub b/ substantially (by factor >2) higher than P/sub OH/, excellent power and particle accountability have been established. This suggests that the less-than-expected increase in stored energy with NBI is not due to problems of power delivery, but due to problems of confinement deterioration. tau/sub E/ is observed to scale approximately as I/sub p/ P/sub b//sup -0.5/ (independent of anti n/sub e/), consistent with previous L-mode scalings. With NBI we have achieved the maximum tau/sub E/ of 0.2 sec and the maximum T/sub i/(o) of 4.4 keV in the normal operating regime, and even higher T/sub i/(o) in the energetic-ion regime with low-n/sub e/ and low-I/sub p/ operation.

  10. Quark confinement dynamics

    SciTech Connect

    Allen, T.J.; Olsson, M.G.; Veseli, S.; Williams, K. |

    1997-05-01

    Starting from Buchm{umlt u}ller{close_quote}s observation that a chromoelectric flux tube meson will exhibit only the Thomas-type spin-orbit interaction, we show that a model built upon the related assumption that a quark feels only a constant radial chromoelectric field in its rest frame implies a complete relativistic effective Hamiltonian that can be written explicitly in terms of quark canonical variables. The model yields linear Regge trajectories and exhibits some similarities to scalar confinement, but with the advantage of being more closely linked to QCD. {copyright} {ital 1997} {ital The American Physical Society}

  11. 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.

  12. Magnetic Fusion Energy Plasma Interactive and High Heat Flux Components: Volume 5, Technical assessment of critical issues in the steady state operation of fusion confinement devices

    SciTech Connect

    Not Available

    1988-01-01

    Critical issues for the steady state operation of plasma confinement devices exist in both the physics and technology fields of fusion research. Due to the wide range and number of these issues, this technical assessment has focused on the crucial issues associated with the plasma physics and the plasma interactive components. The document provides information on the problem areas that affect the design and operation of a steady state ETR or ITER type confinement device. It discusses both tokamaks and alternative concepts, and provides a survey of existing and planned confinement machines and laboratory facilities that can address the identified issues. A universal definition of steady state operation is difficult to obtain. From a physics point of view, steady state is generally achieved when the time derivatives approach zero and the operation time greatly exceeds the characteristic time constants of the device. Steady state operation for materials depends on whether thermal stress, creep, fatigue, radiation damage, or power removal are being discussed. For erosion issues, the fluence and availability of the machine for continuous operation are important, assuming that transient events such as disruptions do not limit the component lifetimes. The panel suggests, in general terms, that steady state requires plasma operation from 100 to 1000 seconds and an availability of more than a few percent, which is similar to the expectations for an ETR type device. The assessment of critical issues for steady state operation is divided into four sections: physics issues; technology issues; issues in alternative concepts; and devices and laboratory facilities that can address these problems.

  13. Topographic confinement of epithelial clusters induces epithelial-to-mesenchymal transition in compliant matrices

    PubMed Central

    Nasrollahi, Samila; Pathak, Amit

    2016-01-01

    Epithelial cells disengage from their clusters and become motile by undergoing epithelial-to-mesenchymal transition (EMT), an essential process for both embryonic development and tumor metastasis. Growing evidence suggests that high extracellular matrix (ECM) stiffness induces EMT. In reality, epithelial clusters reside in a heterogeneous microenvironment whose mechanical properties vary not only in terms of stiffness, but also topography, dimensionality, and confinement. Yet, very little is known about how various geometrical parameters of the ECM might influence EMT. Here, we adapt a hydrogel-microchannels based matrix platform to culture mammary epithelial cell clusters in ECMs of tunable stiffness and confinement. We report a previously unidentified role of ECM confinement in EMT induction. Surprisingly, confinement induces EMT even in the cell clusters surrounded by a soft matrix, which otherwise protects against EMT in unconfined environments. Further, we demonstrate that stiffness-induced and confinement-induced EMT work through cell-matrix adhesions and cytoskeletal polarization, respectively. These findings highlight that both the structure and the stiffness of the ECM can independently regulate EMT, which brings a fresh perspective to the existing paradigm of matrix stiffness-dependent dissemination and invasion of tumor cells. PMID:26728047

  14. Topographic confinement of epithelial clusters induces epithelial-to-mesenchymal transition in compliant matrices

    NASA Astrophysics Data System (ADS)

    Nasrollahi, Samila; Pathak, Amit

    2016-01-01

    Epithelial cells disengage from their clusters and become motile by undergoing epithelial-to-mesenchymal transition (EMT), an essential process for both embryonic development and tumor metastasis. Growing evidence suggests that high extracellular matrix (ECM) stiffness induces EMT. In reality, epithelial clusters reside in a heterogeneous microenvironment whose mechanical properties vary not only in terms of stiffness, but also topography, dimensionality, and confinement. Yet, very little is known about how various geometrical parameters of the ECM might influence EMT. Here, we adapt a hydrogel-microchannels based matrix platform to culture mammary epithelial cell clusters in ECMs of tunable stiffness and confinement. We report a previously unidentified role of ECM confinement in EMT induction. Surprisingly, confinement induces EMT even in the cell clusters surrounded by a soft matrix, which otherwise protects against EMT in unconfined environments. Further, we demonstrate that stiffness-induced and confinement-induced EMT work through cell-matrix adhesions and cytoskeletal polarization, respectively. These findings highlight that both the structure and the stiffness of the ECM can independently regulate EMT, which brings a fresh perspective to the existing paradigm of matrix stiffness-dependent dissemination and invasion of tumor cells.

  15. Dependency of hydromechanical properties of monzonitic granite on confining pressure and fluid pressure under compression

    NASA Astrophysics Data System (ADS)

    Wang, Huanling; Xu, Weiya; Lui, Zaobao; Chao, Zhiming; Meng, Qingxiang

    2016-05-01

    Monzonitic granite is a low-permeability rock. Monzonitic granite formations are ideal for underground storage of oil due to their low permeability and high mechanical strength. In this study, a series of coupled hydromechanical triaxial tests are carried out using monzonitic granite specimens. The influence of confining and fluid pressures on stress, strain, and permeability is investigated. Failure characteristics under different confining and fluid pressures are discussed based on the analysis of macro fracture planes and micro scanning electron microscopy (SEM). The test results show that the change of permeability with stress and strain reflects the deformation stages of compaction, compression, crack propagation, coalesce, and failure of cracks. Due to the low porosity, the change of permeability is small in the initial phases of compaction and compression, whereas there is a significant increase in permeability when new cracks start to develop and coalesce. Confining pressures have a significant impact on the strength and permeability, particularly the crack damage stress of the rock. Compared with confining pressure, the effect of fluid pressure on rock strength and crack damage stress is small. For the monzonitic granite specimens tested, changing the confining pressure results in different failure modes, whereas the fluid pressure has a relatively small effect on the failure modes.

  16. Study on Locally Confined Deposition of Si Nanocrystals in High-Aspect-Ratio Si Nano-Pillar Arrays for Nano-Electronic and Nano-Photonic Applications II

    DTIC Science & Technology

    2010-12-03

    photoluminescence characteristics of equivalent-size controlled silicon quantum dots by employing a nano- porous aluminum oxide membrane as the template for growing...characteristics of the equivalent-size controlled Si-QDs by employing the nano- porous AAO membrane as the template for growing Si-rich SiOx nano-rods...to achieve the spatially confined synthesis of Si-QD. The ultra-bright PL can be emitted from the SiOx nano-rod in nano- porous AAO membrane. In

  17. Spiral precipitation patterns in confined chemical gardens.

    PubMed

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

    2014-12-09

    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.

  18. 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 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

  19. Quark Confinement and Strings

    NASA Astrophysics Data System (ADS)

    't Hooft, Gerardus

    QCD was proposed as a theory for the strong interactions long before we had any idea as to how it could be that its fundamental constituents, the quarks, are never seen as physical particles. Massless gluons also do not exist as free particles. How can this be explained? The first indication that this question had to be considered in connection with the topological structure of a gauge theory came when Nielsen and Olesen observed the occurrence of stable magnetic vortex structures [1] in the Abelian Higgs model. Expanding on such ideas, the magnetic monopole solution was found [2]. Other roundabout attempts to understand confinement involve instantons. Today, we have better interpretations of these topological structures, including a general picture of the way they do lead to unbound potentials confining quarks. It is clear that these unbound potentials can be ascribed to a string-like structure of the vortices formed by the QCD field lines. Can string theory be used to analyze QCD? Many researchers think so. The leading expert on this is Sacha Polyakov. In his instructive account he adds how he experienced the course of events in Gauge Theory, emphasizing the fact that quite a few discoveries often ascribed to researchers from the West, actually were made independently by scientists from the Soviet Union…

  20. Influence of spatial temperature distribution on high accuracy interferometric metrology

    NASA Astrophysics Data System (ADS)

    Gu, Yongqiang; Miao, Erlong; Yan, Feng; Zhang, Jian; Yang, Huaijiang

    2010-10-01

    We calculate the influence of temperature change on the refractive index of air, establish a model of air temperature distribution and analyze the effect of different temperature distribution on the high accuracy interferometric metrology. First, a revised Edlen formula is employed to acquire the relation between temperature and refractive index of air, followed by introducing the fixed temperature gradient distribution among the spatial grid within the optical cavity between the reference flat and the test flat of the Fizeau interferometer, accompanied by a temperature change random function within each grid. Finally, all the rays through the air layer with different incident angles are traced by Matlab program in order to obtain the final output position, angle and OPD for each ray. The influence of different temperature distribution and the length of the optical cavity in on the testing accuracy can be analyzed through the RMS value that results from repeatable rays tracing. As a result, the horizontal distribution (vertical to optical axis) has a large effect on the testing accuracy. Thus, to realize the high accuracy figure metrology, the horizontal distribution of temperature must be rigorously controlled as well as to shorten the length of the optical cavity to a large extent. The results from our simulation are of great significant for the accuracy analysis of interferometric testing and the research of manufacturing a interferometer.

  1. Measurement of high-frequency density fluctuations using far-forward collective scattering and interferometric techniques in improved-confinement RFP plasmas

    NASA Astrophysics Data System (ADS)

    Duff, James; Chapman, Brett; Sarff, John; Ding, Weixing; Brower, David; Lin, Liang

    2012-10-01

    In standard RFP plasmas, transport is governed by magnetic fluctuations associated with global tearing modes. For improved-confinement plasmas using inductive current profile control (PPCD), smaller-scale fluctuations at higher frequencies might become important for transport, especially drift-wave-like instabilities which may be theoretically unstable for the larger temperature gradients achieved. On the MST-RFP, an 11-chord laser-based diagnostic with ˜8 cm chord spacing is and frequency 694 GHz used to measure electron density fluctuations both interferometrically and by far-forward collective scattering. The existing diagnostic configuration measures the line-integrated fluctuations within the divergence of the probe beam covering a wavenumber range k<1.3 cm-1, corresponding to kρs <1.3 (ρs is the ion-sound Larmor radius). Of particular interest is comparing fluctuations in standard and PPCD plasmas. Relative to standard plasmas, tearing mode and higher frequency broadband fluctuations (up to 600 kHz) are suppressed with PPCD. This suppression in PPCD plasmas corresponds to the improved confinement. A diagnostic upgrade, in progress, will improve sensitivity and cover shorter wavelengths. Work supported by U.S.D.O.E.

  2. Effects of confinement on nanoparticle flows

    NASA Astrophysics Data System (ADS)

    Conrad, Jacinta

    The transport properties of nanoparticles that are dispersed in complex fluids and flowed through narrow confining geometries affect a wide range of materials shaping and forming processes, including three-dimensional printing and nanocomposite processing. Here, I will describe two sets of experiments in which we use optical microscopy to probe the structure and transport properties of suspensions of particles that are confined geometrically. First, we investigate the structure and flow properties of dense suspensions of submicron particles, in which the particles interact via an entropic depletion attraction, that are confined in thin films and microchannels. Second, we characterize the transport properties of nanoparticles, dispersed at low concentration in water or in aqueous solutions of high-molecular weight polymers, that are confined in regular arrays of nanoposts or in disordered porous media. I will discuss our results and their practical implications for materials processing as well as for other applications that require confined transport of nanomaterials through complex media. Welch Foundation (E-1869) and NSF (CBET-1438204).

  3. Effects of quantum confinement in nanoscale superconductors: From electronic density of states to vortex matter

    NASA Astrophysics Data System (ADS)

    Zhang, Lingfeng

    Due to quantum confinement, nanoscale superconductivity exhibits richer phenomena than bulk superconductivity. This will allow us to artificially design the electronic properties by changing the size and geometry of the superconductor, leading to the desired control and enhancement of superconductivity. However, the interplay between superconductivity and quantum confinement effect has not been fully understood yet. In this thesis, we theoretically investigated several aspects of nanoscale superconductivity by solving the Bogoliubov-de Gennes equations. The topics that are covered range from vortex states under the influence of quantum confinement to the electronic structure in various nano-structures. The density of states (DOS) obtained in this thesis can be compared with results from Scanning tunneling microscope (STM) experiments. In Chapter. 3 and 4, we studied vortex states under the influence of quantum confinement effect. We found that the shape resonances of the order parameter results in an additional contribution to quantum topological confinement - leading to unconventional vortex configurations. Our results reveal a plethora of asymmetric, giant multi-vortex, and vortex-antivortex structures. They are relevant for high-Tc nanograins, confined Bose-Einstein condensates, and graphene fakes with proximity-induced superconductivity. In Chapter. 5, we studied the effect of non-magnetic impurities in superconducting nanowires. We found that: 1) impurities strongly affect the transport properties, 2) the effect is impurity position-dependent, and 3) it exhibits opposite behavior for resonant and off-resonant wire widths due to the sub-band energy spectrum induced by lateral quantum confinement. These effects can be used to manipulate the Josephson current, filter electrons by subband. In Chapter. 6, we investigated the Tomasch effect on the electronic structure in nanoscale superconductors. Here it is the quasiparticle interference effect induced by an

  4. Confined compression of dental composites for Class I restorations

    PubMed Central

    Patki, Amol S.; Vural, Murat; Gosz, Mike

    2011-01-01

    This study focuses on the mechanical response of a particle-reinforced restorative dental composite (Renew™) under proportional transverse confinement to understand the effects of stress multiaxiality on its mechanical and failure behaviors. We describe the confining ring technique as an experimental tool to introduce multiaxial compressive stress states in dental composites that realistically mimic three-dimensional stress states commonly experienced by dental restorations in the oral cavity. Effect of initial radial misfit between confining ring and specimen is analyzed through computational finite element simulations, and an analytical treatment of problem is also provided to compute the confining stress during elasto-plastic expansion of confining ring. Experimental results suggest that inelastic response of Renew composite is significantly influenced by hydrostatic stress component, and pressure-dependent yield functions are required to analyze plastic deformations and internal damage accumulation process. PMID:21857744

  5. 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.

  6. Amoeboid motion in confined geometry.

    PubMed

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

    2015-01-01

    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.

  7. Mechanical behavior of concrete columns confined by basalt FRP windings

    NASA Astrophysics Data System (ADS)

    Ciniņa, I.; Zīle, E.; Zīle, O.

    2012-11-01

    The results of an experimental investigation of round concrete columns confined by a wound basalt filament yarn are presented. Basalt is an attractive material for strengthening purposes due to its low cost coupled with a good mechanical performance, especially at high temperatures. It is shown that the basalt FRP confinement provides a considerable strengthening effect. The winding equipment employed in this study has the ability to set a desired pretension force of the yarn and thereby to produce a prestressed confinement. It is found that the prestressed confinement notably delays the onset of intense internal cracking of concrete.

  8. 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.

  9. Factors Influencing Migrant High School Students to Drop Out or Graduate from High School.

    ERIC Educational Resources Information Center

    Nelken, Ira; Gallo, Kathleen

    Factors influencing migrant students in decisions to drop out or graduate from high school were determined in interviews with 24 dropouts and potential dropouts and 22 students who had graduated. Profiles were compiled on each group. Data were collected from twelfth grade migrant students in northern California. The main appeal of school to the…

  10. 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.

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

    PubMed

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

    2015-09-07

    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

  12. Influence of load by high power on the optical coupler

    NASA Astrophysics Data System (ADS)

    Bednarek, Lukas; Poboril, Radek; Vanderka, Ales; Hajek, Lukas; Nedoma, Jan; Vasinek, Vladimir

    2016-12-01

    Nowadays, aging of the optical components is a very current topic. Therefore, some investigations are focused on this area, so that the aging of the optical components is accelerated by thermal, high power and gamma load. This paper deals by findings of the influence of the load by laser with high optical power on the transmission parameters of the optical coupler. The investigated coupler has one input and eight outputs (1x8). Load by laser with high optical power is realized using a fiber laser with a cascade configuration EDFA amplifiers. The output power of the amplifier is approximately 250 mW. Duration of the load is moving from 104 hours to 139 hours. After each load, input power and output powers of all branches are measured. Following parameters of the optical coupler are calculated using formulas: the insertion losses of the individual branches, split ratio, total losses, homogeneity of the losses and cross-talk between different branches. All measurements are performed at wavelengths 1310 nm and 1550 nm. Individual optical powers are measured 20 times, due to the exclusion of statistical error of the measurement. After measuring, the coupler is connected to the amplifier for next cycle of the load. The paper contains an evaluation of the results of the coupler before and after four cycles of the burden.

  13. Confinement-driven increase in ionomer thin-film modulus.

    PubMed

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

    2014-05-14

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

  14. NMR studies of metallic tin confined within porous matrices

    SciTech Connect

    Charnaya, E. V.; Tien, Cheng; Lee, M. K.; Kumzerov, Yu. A.

    2007-04-01

    {sup 119}Sn NMR studies were carried out for metallic tin confined within synthetic opal and porous glass. Tin was embedded into nanoporous matrices in the melted state under pressure. The Knight shift for liquid confined tin was found to decrease with decreasing pore size. Correlations between NMR line shapes, Knight shift, and pore filling were observed. The melting and freezing phase transitions of tin under confinement were studied through temperature dependences of NMR signals upon warming and cooling. Melting of tin within the opal matrix agreed well with the liquid skin model suggested for small isolated particles. The influence of the pore filling on the melting process was shown.

  15. Influences on shallow ground temperatures in high flux thermal systems

    NASA Astrophysics Data System (ADS)

    Lubenow, Brady L.; Fairley, Jerry P.; Lindsey, Cary R.; Larson, Peter B.

    2016-09-01

    Ground temperature measurements are a useful indication of subsurface processes and heat flux, particularly in volcanic and hydrothermal systems, but obtaining reliable data at sufficient resolution can be difficult. Investigators commonly use temperature measurements at 1 m depths to minimize land surface boundary impacts; however, these measurements are time-consuming and invasive, limiting the number of points that can be surveyed. Alternatively, shallow ground temperature measurements (≤ 25 cm depth) offer a rapid and minimally-invasive way to collect a large number of observations in a target area. Although this method has obvious appeal, changing atmospheric conditions can impact the observed temperatures, and thus may reasonably be expected to influence interpretations arising from the data. Here we examine the impact of precipitation and changing air temperature on shallow ground temperatures in the vicinity of a group of hot springs located in Yellowstone National Park, Wyoming. We find that the mean, the range, and the skewness of the observed temperatures were decreased by changing atmospheric conditions; however, the model variogram representing data taken after several days of moderate precipitation adequately described the spatial correlation of data taken before precipitation. We therefore conclude that the ability to differentiate between high- and low-flux areas may be somewhat reduced by moderate precipitation and changing atmospheric conditions, but that interpretations made on the basis of characteristics of the inferred variograms are likely to be robust to such perturbations in high heat flux environments.

  16. Highly conserved small subunit residues influence rubisco large subunit catalysis.

    PubMed

    Genkov, Todor; Spreitzer, Robert J

    2009-10-30

    The chloroplast enzyme ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco) catalyzes the rate-limiting step of photosynthetic CO(2) fixation. With a deeper understanding of its structure-function relationships and competitive inhibition by O(2), it may be possible to engineer an increase in agricultural productivity and renewable energy. The chloroplast-encoded large subunits form the active site, but the nuclear-encoded small subunits can also influence catalytic efficiency and CO(2)/O(2) specificity. To further define the role of the small subunit in Rubisco function, the 10 most conserved residues in all small subunits were substituted with alanine by transformation of a Chlamydomonas reinhardtii mutant that lacks the small subunit gene family. All the mutant strains were able to grow photosynthetically, indicating that none of the residues is essential for function. Three of the substitutions have little or no effect (S16A, P19A, and E92A), one primarily affects holoenzyme stability (L18A), and the remainder affect catalysis with or without some level of associated structural instability (Y32A, E43A, W73A, L78A, P79A, and F81A). Y32A and E43A cause decreases in CO(2)/O(2) specificity. Based on the x-ray crystal structure of Chlamydomonas Rubisco, all but one (Glu-92) of the conserved residues are in contact with large subunits and cluster near the amino- or carboxyl-terminal ends of large subunit alpha-helix 8, which is a structural element of the alpha/beta-barrel active site. Small subunit residues Glu-43 and Trp-73 identify a possible structural connection between active site alpha-helix 8 and the highly variable small subunit loop between beta-strands A and B, which can also influence Rubisco CO(2)/O(2) specificity.

  17. Size scaling of microtubule asters in confinement

    NASA Astrophysics Data System (ADS)

    Pelletier, James; Field, Christine; Krutkramelis, Kaspars; Fakhri, Nikta; Oakey, John; Gatlin, Jay; Mitchison, Timothy

    Microtubule asters are radial arrays of microtubules (MTs) nucleated around organizing centers (MTOCs). Across a wide range of cell types and sizes, aster positioning influences cellular organization. To investigate aster size and positioning, we reconstituted dynamic asters in Xenopus cytoplasmic extract, confined in fluorous oil microfluidic emulsions. In large droplets, we observed centering of MTOCs. In small droplets, we observed a breakdown in natural positioning, with MTOCs at the droplet edge and buckled or bundled MTs along the interface. In different systems, asters are positioned by different forces, such as pushing due to MT polymerization, or pulling due to bulk or cortical dynein. To estimate different contributions to aster positioning, we biochemically perturbed dynactin function, or MT or actin polymerization. We used carbon nanotubes to measure molecular motions and forces in asters. These experimental results inform quantitative biophysical models of aster size and positioning in confinement. JFP was supported by a Fannie and John Hertz Graduate Fellowship.

  18. High School Teachers and High School Reform: A Phenomenological Study of the Influence of Teachers' High School Experience regarding Their High School Teaching Experience

    ERIC Educational Resources Information Center

    Augustine, Dwaine Keith

    2009-01-01

    This study explored the effects of the lived high school experiences of high school teachers and how those experiences may inform researchers regarding high school reform. One aim was to investigate how teachers' experiences during high school influenced their thoughts or behaviors toward high school as a rite of passage, epiphany, or critical…

  19. Magneto-photon-phonon interaction in a parabolically confined quantum dot in the presence of high magnetic fields and intense terahertz radiation fields

    NASA Astrophysics Data System (ADS)

    Wang, W. Y.; Xu, W.

    2012-07-01

    We present a theoretical study on magneto-photon-phonon interaction in a parabolically confined quantum dot subjected simultaneously to static magnetic field and radiation field. A nonperturbative treatment for electron-photon interaction is proposed by solving analytically the time-dependent Schrödinger equation in which the magnetic field and the radiation field are included exactly. We employ the energy-balance equation approach on the basis of the Boltzmann equation to evaluate the energy transfer rate induced by optical transition events. It is found that for relatively low radiation levels, two peaks of the cyclotron resonance (CR) appear at two Kohn's frequencies ω±, and the strength and the width of the CR increase with radiation intensity. The CR at ω+ is more prominent than that at ω-. When the radiation become intense, the splitting of the CR peaks can be observed and the splitting increases with radiation intensity. The physics reasons behind these interesting findings are discussed. This study is pertinent to the application of intense terahertz radiation sources such as free-electron lasers in the investigation into low-dimensional semiconductor systems.

  20. Effects of Thermal Damage and Confining Pressure on the Mechanical Properties of Coarse Marble

    NASA Astrophysics Data System (ADS)

    Yao, Mengdi; Rong, Guan; Zhou, Chuangbing; Peng, Jun

    2016-06-01

    Heating treatment generally causes thermal damage inside rocks, and the influence of thermal damage on mechanical properties of rocks is an important topic in rock mechanics. The coarse marble specimens drilled out from a rock block were first heated to a specific temperature level of 200, 400 and 600 °C except the control group left at 20 °C. A series of triaxial compression tests subjected to the confining pressure of 0, 5, 10, 15, 20, 25, 30, 35 and 40 MPa were conducted. Coupling effects of thermal damage and confining pressure on the mechanical properties of marbles including post-peak behaviors and failure modes, strength and deformation parameters, characteristic stresses in the progressive failure process had been investigated. Meanwhile, accompanied tests of physical properties were carried out to study the effect of thermal damage on microstructure, porosity and P-wave velocity. Finally, the degradation parameter was defined and a strength-degradation model to describe the peak strength was proposed. Physical investigations show that porosity increases slowly and P-wave velocity reduces dramatically, which could be re-demonstrated by the microscopy results. As for the post-peak behaviors and the failure modes, there is a brittle to ductile transition trend with increasing confining pressure and thermal effect reinforces the ductility to some degree. The comparative study on strength and deformation parameters concludes that heating causes damage and confining pressure inhibits the damage to develop. Furthermore, crack damage stress and crack initiation stress increase, while the ratios of crack damage stress to peak strength and crack initiation stress to peak strength show a decreasing trend with the increase of confining pressure; the magnitude of crack damage stress or crack initiation stress shows a tendency of decrease with the increasing heating temperature and the tendency vanishes subjected to high confinement.

  1. Inertial Confinement Fusion Materials Science

    SciTech Connect

    Hamza, A V

    2004-06-01

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

  2. 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.

  3. Structure of confined films of chain alcohols

    SciTech Connect

    Mugele, F.; Baldelli, S.; Somorjai, G.A.; Salmeron, M.

    2000-04-13

    The structure of thin films of simple chain alcohols (1-octanol and 1-undecanol) confined between two atomically smooth mica surfaces has been investigated using a surface forces apparatus. Contact angle measurements and optical sum frequency generation were used for additional characterization. In both systems, the substrate-molecule interaction leads to a strongly bound first layer on each surface. Additional liquid organizes into highly compressible bilayers, which could be expelled by applying sufficiently high pressure.

  4. Psychopathological effects of solitary confinement.

    PubMed

    Grassian, S

    1983-11-01

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

  5. Spatial confinement of muonium atoms

    NASA Astrophysics Data System (ADS)

    Khaw, K. S.; Antognini, A.; Prokscha, T.; Kirch, K.; Liszkay, L.; Salman, Z.; Crivelli, P.

    2016-08-01

    We report the achievement of spatial confinement of muonium atoms (the bound state of a positive muon and an electron). Muonium emitted into a vacuum from mesoporous silica reflects between two SiO2 confining surfaces separated by 1 mm. From the data, one can extract that the reflection probability on the confining surfaces kept at 100 K is about 90% and the reflection process is well described by a cosine law. This technique enables new experiments with this exotic atomic system and is a very important step towards a measurement of the 1 S -2 S transition frequency using continuous-wave laser spectroscopy.

  6. Interface confined hydrogen evolution reaction in zero valent metal nanoparticles-intercalated molybdenum disulfide

    NASA Astrophysics Data System (ADS)

    Chen, Zhongxin; Leng, Kai; Zhao, Xiaoxu; Malkhandi, Souradip; Tang, Wei; Tian, Bingbing; Dong, Lei; Zheng, Lirong; Lin, Ming; Yeo, Boon Siang; Loh, Kian Ping

    2017-02-01

    Interface confined reactions, which can modulate the bonding of reactants with catalytic centres and influence the rate of the mass transport from bulk solution, have emerged as a viable strategy for achieving highly stable and selective catalysis. Here we demonstrate that 1T'-enriched lithiated molybdenum disulfide is a highly powerful reducing agent, which can be exploited for the in-situ reduction of metal ions within the inner planes of lithiated molybdenum disulfide to form a zero valent metal-intercalated molybdenum disulfide. The confinement of platinum nanoparticles within the molybdenum disulfide layered structure leads to enhanced hydrogen evolution reaction activity and stability compared to catalysts dispersed on carbon support. In particular, the inner platinum surface is accessible to charged species like proton and metal ions, while blocking poisoning by larger sized pollutants or neutral molecules. This points a way forward for using bulk intercalated compounds for energy related applications.

  7. Interface confined hydrogen evolution reaction in zero valent metal nanoparticles-intercalated molybdenum disulfide

    PubMed Central

    Chen, Zhongxin; Leng, Kai; Zhao, Xiaoxu; Malkhandi, Souradip; Tang, Wei; Tian, Bingbing; Dong, Lei; Zheng, Lirong; Lin, Ming; Yeo, Boon Siang; Loh, Kian Ping

    2017-01-01

    Interface confined reactions, which can modulate the bonding of reactants with catalytic centres and influence the rate of the mass transport from bulk solution, have emerged as a viable strategy for achieving highly stable and selective catalysis. Here we demonstrate that 1T′-enriched lithiated molybdenum disulfide is a highly powerful reducing agent, which can be exploited for the in-situ reduction of metal ions within the inner planes of lithiated molybdenum disulfide to form a zero valent metal-intercalated molybdenum disulfide. The confinement of platinum nanoparticles within the molybdenum disulfide layered structure leads to enhanced hydrogen evolution reaction activity and stability compared to catalysts dispersed on carbon support. In particular, the inner platinum surface is accessible to charged species like proton and metal ions, while blocking poisoning by larger sized pollutants or neutral molecules. This points a way forward for using bulk intercalated compounds for energy related applications. PMID:28230105

  8. Counterpropagating Rossby waves in confined plane wakes

    PubMed Central

    Biancofiore, L.; Gallaire, F.

    2012-01-01

    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. PMID:22865998

  9. Chemical reactions confined within carbon nanotubes.

    PubMed

    Miners, Scott A; Rance, Graham A; Khlobystov, Andrei N

    2016-08-22

    In this critical review, we survey the wide range of chemical reactions that have been confined within carbon nanotubes, particularly emphasising how the pairwise interactions between the catalysts, reactants, transition states and products of a particular molecular transformation with the host nanotube can be used to control the yields and distributions of products of chemical reactions. We demonstrate that nanoscale confinement within carbon nanotubes enables the control of catalyst activity, morphology and stability, influences the local concentration of reactants and products thus affecting equilibria, rates and selectivity, pre-arranges the reactants for desired reactions and alters the relative stability of isomeric products. We critically evaluate the relative advantages and disadvantages of the confinement of chemical reactions inside carbon nanotubes from a chemical perspective and describe how further developments in the controlled synthesis of carbon nanotubes and the incorporation of multifunctionality are essential for the development of this ever-expanding field, ultimately leading to the effective control of the pathways of chemical reactions through the rational design of multi-functional carbon nanoreactors.

  10. Shock Polar Angles and Confinement Effect on Detonation Propagation

    NASA Astrophysics Data System (ADS)

    Chiquete, Carlos; Short, Mark; Meyer, Chad; Quirk, James; Bdzil, John

    2016-11-01

    In high explosive (HE) engineering applications, the shape of a detonation front is influenced by the density and impedance of the inert material that surrounds the explosive. Where the detonation shock intersects the material boundary, a number of gasdynamic reflection patterns are possible involving shocks, Prandtl-Meyer fans and material interfaces. To leading-order, these reflection patterns can be predicted through a shock polar analysis. For the commonly used Detonation Shock Dynamics (DSD) front surface propagation model, the shape and evolution of the detonation wave is determined by the specification of the surface wave angle at the HE charge-confiner interface. Typically, the shock polar analysis is employed to approximate this necessary "edge angle" using specified equations of state for the HE-inert pair and a given phase velocity. For engineering applications, we need to evaluate how accurately a shock polar analysis can predict the DSD model edge-angle. We extend previous on this issue examining reactive flow simulations of detonation propagation in a confined HE compared to the predictions of a shock polar analysis.

  11. Effects of geometrical confinement in membrane pores on enzyme-based layer-by-layer assemblies

    NASA Astrophysics Data System (ADS)

    Ramírez-Wong, Diana G.; Coelho-Diogo, Cristina; Aimé, Carole; Bonhomme, Christian; Jonas, Alain M.; Demoustier-Champagne, Sophie

    2015-05-01

    Micro- and nanoporous systems incorporating bioactive molecules, such as enzymes, are very promising supports for biocatalysis. Here, we investigate the influence of geometrical confinement on the layer-by-layer (LbL) assembly of enzyme-based thin films, using the polyionic couple (chitosan/β-lactamase)n. Thin films with different number of layers were prepared on flat silicon wafers and within cylindrical submicron pores of polycarbonate membranes to determine the impact of the confinement of macromolecules on: (i) the LbL film growth, (ii) the enzyme loading, and (iii) the biocatalytic efficiency. Solid-state NMR is employed to estimate the amount of enzyme loaded in the different types of LbL films, and the enzyme activity is determined by the study of the kinetics of nitrocefin hydrolysis. Film growth and loading of enzyme occur faster in the confined medium, until pores reach saturation. Moreover, when LbL films are grown within nanopores, the weight fraction of enzyme is very high and remains constant along the build-up. Conversely, the relative amount of enzyme in flat films significantly decreases with the number of layers due to the partial exchange during the growth. Finally, our study emphasizes that the immobilization of enzymes through LbL assembly in confined media can lead to very active surfaces with a restricted number of LbL cycles.

  12. 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.

  13. Tandem mirror plasma confinement apparatus

    DOEpatents

    Fowler, T. Kenneth

    1978-11-14

    Apparatus and method for confining a plasma in a center mirror cell by use of two end mirror cells as positively charged end stoppers to minimize leakage of positive particles from the ends of the center mirror cell.

  14. Solvent cavitation under solvophobic confinement

    NASA Astrophysics Data System (ADS)

    Ashbaugh, Henry S.

    2013-08-01

    The stability of liquids under solvophobic confinement can tip in favor of the vapor phase, nucleating a liquid-to-vapor phase transition that induces attractive forces between confining surfaces. In the case of water adjacent to hydrophobic surfaces, experimental and theoretical evidence support confinement-mediated evaporation stabilization of biomolecular and colloidal assemblies. The macroscopic thermodynamic theory of cavitation under confinement establishes the connection between the size of the confining surfaces, interfacial free energies, and bulk solvent pressure with the critical evaporation separation and interfacial forces. While molecular simulations have confirmed the broad theoretical trends, a quantitative comparison based on independent measurements of the interfacial free energies and liquid-vapor coexistence properties has, to the best of our knowledge, not yet been performed. To overcome the challenges of simulating a large number of systems to validate scaling predictions for a three-dimensional fluid, we simulate both the forces and liquid-vapor coexistence properties of a two-dimensional Lennard-Jones fluid confined between solvophobic plates over a range of plate sizes and reservoir pressures. Our simulations quantitatively agree with theoretical predictions for solvent-mediated forces and critical evaporation separations once the length dependence of the solvation free energy of an individual confining plate is taken into account. The effective solid-liquid line tension length dependence results from molecular scale correlations for solvating microscopic plates and asymptotically decays to the macroscopic value for plates longer than 150 solvent diameters. The success of the macroscopic thermodynamic theory at describing two-dimensional liquids suggests application to surfactant monolayers to experimentally confirm confinement-mediated cavitation.

  15. 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.

  16. Particle dispersion in confined turbulent swirling flows

    NASA Astrophysics Data System (ADS)

    Chen, C. P.

    1986-06-01

    This paper reports a numerical investigation of confined swirling flows of gas-particle mixtures. A recently developed two-fluid, multiple-scale mixing model is applied to study the influence of particles on the intensity of the reverse flows of the gas phase and the effects of swirl on the particle dispersion in an annular expanding chamber under isothermal condition. The calculations were made for different swirl strength of injection of the annular jet into the mixing chamber. Results agree well qualitatively with experimental information available. It is also found that the calculated flow fields depend heavily on the prescription of the inlet flow conditions.

  17. Particle dispersion in confined turbulent swirling flows

    NASA Technical Reports Server (NTRS)

    Chen, C. P.

    1986-01-01

    This paper reports a numerical investigation of confined swirling flows of gas-particle mixtures. A recently developed two-fluid, multiple-scale mixing model is applied to study the influence of particles on the intensity of the reverse flows of the gas phase and the effects of swirl on the particle dispersion in an annular expanding chamber under isothermal condition. The calculations were made for different swirl strength of injection of the annular jet into the mixing chamber. Results agree well qualitatively with experimental information available. It is also found that the calculated flow fields depend heavily on the prescription of the inlet flow conditions.

  18. Estimation of Confined Peak Strength of Crack-Damaged Rocks

    NASA Astrophysics Data System (ADS)

    Bahrani, Navid; Kaiser, Peter K.

    2017-02-01

    It is known that the unconfined compressive strength of rock decreases with increasing density of geological features such as micro-cracks, fractures, and veins both at the laboratory specimen and rock block scales. This article deals with the confined peak strength of laboratory-scale rock specimens containing grain-scale strength dominating features such as micro-cracks. A grain-based distinct element model, whereby the rock is simulated with grains that are allowed to deform and break, is used to investigate the influence of the density of cracks on the rock strength under unconfined and confined conditions. A grain-based specimen calibrated to the unconfined and confined strengths of intact and heat-treated Wombeyan marble is used to simulate rock specimens with varying crack densities. It is demonstrated how such cracks affect the peak strength, stress-strain curve and failure mode with increasing confinement. The results of numerical simulations in terms of unconfined and confined peak strengths are used to develop semi-empirical relations that relate the difference in strength between the intact and crack-damaged rocks to the confining pressure. It is shown how these relations can be used to estimate the confined peak strength of a rock with micro-cracks when the unconfined and confined strengths of the intact rock and the unconfined strength of the crack-damaged rock are known. This approach for estimating the confined strength of crack-damaged rock specimens, called strength degradation approach, is then verified by application to published laboratory triaxial test data.

  19. Laser driven instabilities in inertial confinement fusion

    SciTech Connect

    Kruer, W.L.

    1990-06-04

    Parametric instabilities excited by an intense electromagnetic wave in a plasma is a fundamental topic relevant to many applications. These applications include laser fusion, heating of magnetically-confined plasmas, ionospheric modification, and even particle acceleration for high energy physics. In laser fusion, these instabilities have proven to play an essential role in the choice of laser wavelength. Characterization and control of the instabilities is an ongoing priority in laser plasma experiments. Recent progress and some important trends will be discussed. 8 figs.

  20. Enhanced ionic liquid mobility induced by confinement in 1D CNT membranes.

    PubMed

    Berrod, Q; Ferdeghini, F; Judeinstein, P; Genevaz, N; Ramos, R; Fournier, A; Dijon, J; Ollivier, J; Rols, S; Yu, D; Mole, R A; Zanotti, J-M

    2016-04-21

    Water confined within carbon nanotubes (CNT) exhibits tremendous enhanced transport properties. Here, we extend this result to ionic liquids (IL) confined in vertically aligned CNT membranes. Under confinement, the IL self-diffusion coefficient is increased by a factor 3 compared to its bulk reference. This could lead to high power battery separators.

  1. Confined synthesis of graphene wrapped LiMn0.5Fe0.5PO4 composite via two step solution phase method as high performance cathode for Li-ion batteries

    NASA Astrophysics Data System (ADS)

    Xiang, Wei; Wu, Zhen-Guo; Wang, En-Hui; Chen, Ming-Zhe; Song, Yang; Zhang, Ji-Bin; Zhong, Yan-Jun; Chou, Shu-Lei; Luo, Jian-Hong; Guo, Xiao-Dong

    2016-10-01

    A novel strategy for confined synthesis of graphene wrapped nano-sized LiMn0.5Fe0.5PO4 hybrid composite has been developed, including co-precipitation and solvothermal reactions. The LiMn0.5Fe0.5PO4 nanoparticles with a constrained diameter of 20 nm are homogeneously wrapped by a continuous interconnected graphene sheets. The mechanism and composite structure evolution during the process are carefully investigated and discussed. With the shortened Li+ diffusion paths and enhanced electron conductivity, the hybrid composite shows high discharge capacity and superior rate performance with the discharge capacities of 166 mA h g-1 at 0.1 C and 90 mA h g-1 at 20 C. Excellent cycle stability is also demonstrated with only about 7.8% capacity decay after 500 cycles at 1 C.

  2. 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

  3. 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

  4. Unusually high soil nitrogen oxide emissions influence air quality in a high-temperature agricultural region

    PubMed Central

    Oikawa, P. Y.; Ge, C.; Wang, J.; Eberwein, J. R.; Liang, L. L.; Allsman, L. A.; Grantz, D. A.; Jenerette, G. D.

    2015-01-01

    Fertilized soils have large potential for production of soil nitrogen oxide (NOx=NO+NO2), however these emissions are difficult to predict in high-temperature environments. Understanding these emissions may improve air quality modelling as NOx contributes to formation of tropospheric ozone (O3), a powerful air pollutant. Here we identify the environmental and management factors that regulate soil NOx emissions in a high-temperature agricultural region of California. We also investigate whether soil NOx emissions are capable of influencing regional air quality. We report some of the highest soil NOx emissions ever observed. Emissions vary nonlinearly with fertilization, temperature and soil moisture. We find that a regional air chemistry model often underestimates soil NOx emissions and NOx at the surface and in the troposphere. Adjusting the model to match NOx observations leads to elevated tropospheric O3. Our results suggest management can greatly reduce soil NOx emissions, thereby improving air quality. PMID:26556236

  5. Unusually high soil nitrogen oxide emissions influence air quality in a high-temperature agricultural region.

    PubMed

    Oikawa, P Y; Ge, C; Wang, J; Eberwein, J R; Liang, L L; Allsman, L A; Grantz, D A; Jenerette, G D

    2015-11-10

    Fertilized soils have large potential for production of soil nitrogen oxide (NOx=NO+NO2), however these emissions are difficult to predict in high-temperature environments. Understanding these emissions may improve air quality modelling as NOx contributes to formation of tropospheric ozone (O3), a powerful air pollutant. Here we identify the environmental and management factors that regulate soil NOx emissions in a high-temperature agricultural region of California. We also investigate whether soil NOx emissions are capable of influencing regional air quality. We report some of the highest soil NOx emissions ever observed. Emissions vary nonlinearly with fertilization, temperature and soil moisture. We find that a regional air chemistry model often underestimates soil NOx emissions and NOx at the surface and in the troposphere. Adjusting the model to match NOx observations leads to elevated tropospheric O3. Our results suggest management can greatly reduce soil NOx emissions, thereby improving air quality.

  6. Factors Influencing Females' Access to the High School Principalship

    ERIC Educational Resources Information Center

    Kruse, Rae Ann

    2012-01-01

    Scope and Method of Study: The purpose of this study was to identify the factors influencing females' access to the Oklahoma secondary school principalship. Although in the United States federal laws and policies are in place to promote equity, research indicates females are underrepresented in secondary school administration. Regardless of equity…

  7. Does Peer Group Identity Influence Absenteeism in High School Students?

    ERIC Educational Resources Information Center

    Hartnett, Sharon

    2008-01-01

    The focus of this piece is on exploring questions regarding school organizational structures and cultures and their unintentional encouragement of teenage absenteeism. The organizational structure and culture of a school setting contributes to how students experience the system. School characteristics and culture can influence student absenteeism…

  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. Confinement and stability of a Crystalline Beam

    SciTech Connect

    Ruggiero, A.G.

    1993-05-10

    This technical report defines and describes a Crystalline Beam. This is an ordered state of matter made of electrically charged ions which are moving together in a storage ring with very high density and small velocity spread. In particular, the paper analyses the requirements for the confinement and the stability of the Beam. It is demonstrated that a storage ring made of one circular weak-focusing magnet, similar to a Betatron, is the most suitable for the confinement and stability of the Crystalline Beam. The disruptive effects of drift insertions have also been investigated. Requirements on final densities and velocity spreads are also calculated and reported. A matrix formalism is developed for the design of the storage ring. The important issue of the disruption caused by the curvature of the closed trajectory is not here discussed; it is the subject of a subsequent paper.

  10. Nonlinear adhesion dynamics of confined lipid membranes

    NASA Astrophysics Data System (ADS)

    To, Tung; Le Goff, Thomas; Pierre-Louis, Olivier

    Lipid membranes, which are ubiquitous objects in biological environments are often confined. For example, they can be sandwiched between a substrate and the cytoskeleton between cell adhesion, or between other membranes in stacks, or in the Golgi apparatus. We present a study of the nonlinear dynamics of membranes in a model system, where the membrane is confined between two flat walls. The dynamics derived from the lubrication approximation is highly nonlinear and nonlocal. The solution of this model in one dimension exhibits frozen states due to oscillatory interactions between membranes caused by the bending rigidity. We develope a kink model for these phenomena based on the historical work of Kawasaki and Otha. In two dimensions, the dynamics is more complex, and depends strongly on the amount of excess area in the system. We discuss the relevance of our findings for experiments on model membranes, and for biological systems. Supported by the grand ANR Biolub.

  11. Self-Assembly under Confinement: Nanocorrals for Understanding Fundamentals of 2D Crystallization.

    PubMed

    Verstraete, Lander; Greenwood, John; Hirsch, Brandon E; De Feyter, Steven

    2016-12-27

    Nanocorrals with different size, shape, and orientation are created on covalently modified highly oriented pyrolytic graphite surfaces using scanning probe nanolithography, i.e., nanoshaving. Alkylated diacetylene molecules undergo laterally confined supramolecular self-assembly within these corrals. When nanoshaving is performed in situ, at the liquid-solid interface, the orientation of the supramolecular lamellae structure is directionally influenced by the gradual graphite surface exposure. Careful choice of the nanoshaving direction with respect to the substrate symmetry axes promotes alignment of the supramolecular lamellae within the corral. Self-assembly occurring inside corrals of different size and shape reveals the importance of geometric and kinetic constraints controlled by the nanoshaving process. Finally, seed-mediated crystallization studies demonstrate confinement control over nucleation and growth principles.

  12. Self-Assembly under Confinement: Nanocorrals for Understanding Fundamentals of 2D Crystallization

    PubMed Central

    2016-01-01

    Nanocorrals with different size, shape, and orientation are created on covalently modified highly oriented pyrolytic graphite surfaces using scanning probe nanolithography, i.e., nanoshaving. Alkylated diacetylene molecules undergo laterally confined supramolecular self-assembly within these corrals. When nanoshaving is performed in situ, at the liquid–solid interface, the orientation of the supramolecular lamellae structure is directionally influenced by the gradual graphite surface exposure. Careful choice of the nanoshaving direction with respect to the substrate symmetry axes promotes alignment of the supramolecular lamellae within the corral. Self-assembly occurring inside corrals of different size and shape reveals the importance of geometric and kinetic constraints controlled by the nanoshaving process. Finally, seed-mediated crystallization studies demonstrate confinement control over nucleation and growth principles. PMID:27749033

  13. Tuning the energetics and tailoring the optical properties of silver clusters confined in zeolites

    NASA Astrophysics Data System (ADS)

    Fenwick, Oliver; Coutiño-Gonzalez, Eduardo; Grandjean, Didier; Baekelant, Wouter; Richard, Fanny; Bonacchi, Sara; de Vos, Dirk; Lievens, Peter; Roeffaers, Maarten; Hofkens, Johan; Samorì, Paolo

    2016-09-01

    The integration of metal atoms and clusters in well-defined dielectric cavities is a powerful strategy to impart new properties to them that depend on the size and geometry of the confined space as well as on metal-host electrostatic interactions. Here, we unravel the dependence of the electronic properties of metal clusters on space confinement by studying the ionization potential of silver clusters embedded in four different zeolite environments over a range of silver concentrations. Extensive characterization reveals a strong influence of silver loading and host environment on the cluster ionization potential, which is also correlated to the cluster’s optical and structural properties. Through fine-tuning of the zeolite host environment, we demonstrate photoluminescence quantum yields approaching unity. This work extends our understanding of structure-property relationships of small metal clusters and applies this understanding to develop highly photoluminescent materials with potential applications in optoelectronics and bioimaging.

  14. Combinational concentration gradient confinement through stagnation flow.

    PubMed

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

    2016-01-21

    Concentration gradient generation in microfluidics is typically constrained by two conflicting mass transport requirements: short characteristic times (τ) for precise temporal control of concentration gradients but at the expense of high flow rates and hence, high flow shear stresses (σ). 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 (τ ∼ 50 ms) the location of the stagnation point and the confined combinational concentration gradients at low flow shear (0.2 Pa < σ < 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.

  15. Diamond Ablators for Inertial Confinement Fusion

    SciTech Connect

    Biener, J; Mirkarimi, P B; Tringe, J W; Baker, S L; Wang, Y M; Kucheyev, S O; Teslich, N E; Wu, K J; Hamza, A V; Wild, C; Woerner, E; Koidl, P; Bruehne, K; Fecht, H

    2005-06-21

    Diamond has a unique combination of physical properties for the inertial confinement fusion ablator application, such as appropriate optical properties, high atomic density, high yield strength, and high thermal conductivity. Here, we present a feasible concept to fabricate diamond ablator shells. The fabrication of diamond capsules is a multi-step process, which involves diamond chemical vapor deposition on silicon mandrels followed by polishing, microfabrication of holes, and removing of the silicon mandrel by an etch process. We also discuss the pros and cons of coarse-grained optical quality and nanocrystalline chemical vapor deposition diamond films for the ablator application.

  16. Modeling the response of a quartz crystal microbalance under nanoscale confinement and slip boundary conditions.

    PubMed

    Qiao, Xiaoxi; Zhang, Xiangjun; Tian, Yu; Meng, Yonggang

    2015-03-21

    Nanorheology and boundary slip play an important role in the micro/nanofluidics, and micro/nano-electromechanical systems, especially for research on DNA, proteins and polymers. Herein, a nanoscale confinement structure, called a nanocell, is established by assembling a parallel plate on the quartz crystal microbalance (QCM) chip to study the nanorheology of liquids and the boundary slip on the interface. The corresponding analytical models are established and verified experimentally with high consistency. We reveal that the responses of QCM with the nanocell assembled are dependent on the nanocell confinement thickness, the acoustic impedance of the nanocell lid (parallel plate), as well as the boundary slip on the interface. A critical influence thickness of the assembled nanocell d = 2δ is indicated, above which the assembly of a nanocell has no influence on the QCM response. And the interfacial boundary slip results in obvious decreases of relative frequency shift and relative half-bandwidth variation. We find that adopting a nanocell lid with the same acoustic impedance as the tested liquids will evidently simplify the experimental analysis. In the paper, the nanocell provides an effective method to investigate the nanorheology of confined liquids and the interfacial boundary slip, and the established models offer a theoretical basis for the analysis of the nanocell-assembled QCM response.

  17. Ubiquitous influence of waves on tropical high cirrus clouds

    NASA Astrophysics Data System (ADS)

    Kim, Ji-Eun; Alexander, M. Joan; Bui, T. Paul; Dean-Day, Jonathan M.; Lawson, R. Paul; Woods, Sarah; Hlavka, Dennis; Pfister, Leonhard; Jensen, Eric J.

    2016-06-01

    Cirrus clouds in the tropical tropopause layer (TTL) and water vapor transported into the stratosphere have significant impacts on the global radiation budget and circulation patterns. Climate models, however, have large uncertainties in representing dehydration and cloud processes in the TTL, and thus their feedback on surface climate, prohibiting an accurate projection of future global and regional climate changes. Here we use unprecedented airborne measurements over the Pacific to reveal atmospheric waves as a strong modulator of ice clouds in the TTL. Wave-induced cold and/or cooling conditions are shown to exert a nearly ubiquitous influence on cirrus cloud occurrence at altitudes of 14-18 km, except when air was very recently influenced by convective hydration. We further observe that various vertical scales of cloud layers are associated with various vertical scales of waves, suggesting the importance of representing TTL waves in models.

  18. 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

  19. To What Extent is Gluon Confinement an Empirical Fact?

    NASA Astrophysics Data System (ADS)

    Delgado, R. L.; Hidalgo-Duque, Carlos; Llanes-Estrada, Felipe J.

    2013-11-01

    Experimental verifications of confinement in hadron physics have established the absence of charges with a fraction of the electron's charge by studying the energy deposited in ionization tracks at high energies, and performing Millikan experiments with charged droplets at rest. These experiments test only the absence of particles with fractional charge in the asymptotic spectrum, and thus "Quark" Confinement. However what theory suggests is that Color is confined, that is, all asymptotic particles are color singlets. Since QCD is a non-Abelian theory, the gluon force carriers (indirectly revealed in hadron jets) are colored. We empirically examine what can be said about gluon confinement based on the lack of detection of appropriate events, aiming at an upper bound for high-energy free-gluon production.

  20. Automated entry technologies for confined space work activities: A survey.

    PubMed

    Botti, Lucia; Ferrari, Emilio; Mora, Cristina

    2017-04-01

    Work in confined spaces poses a significant risk to workers and rescuers involved in the emergency response when an accident occurs. Despite several standards and regulations define the safety requirements for such activities, injuries, and fatalities still occur. Furthermore, the on-site inspections after accidents often reveal that both employers and employees fail to implement safe entry procedures. Removing the risk is possible by avoiding the worker entry, but many activities require the presence of the operator inside the confined space to perform manual tasks. The following study investigates the available technologies for hazardous confined space work activities, e.g., cleaning, inspecting, and maintenance tasks. The aim is to provide a systematic review of the automated solutions for high-risk activities in confined spaces, considering the non-man entry as the most effective confined space safety strategy. Second, this survey aims to provide suggestions for future research addressing the design of new technologies. The survey consists of about 60 papers concerning innovative technologies for confined space work activities. The document review shows that several solutions have been developed and automation can replace the workers for a limited number of hazardous tasks. Several activities still require the manual intervention due to the complex characteristics of confined spaces, e.g., to remove the remains of the automatic cleaning process from the bottom of a tank. The results show that available technologies require more flexibility to adapt to such occupational environments and further research is needed.

  1. Nanoscopic Cellular Imaging: Confinement Broadens Understanding.

    PubMed

    Lee, Stephen A; Ponjavic, Aleks; Siv, Chanrith; Lee, Steven F; Biteen, Julie S

    2016-09-27

    In recent years, single-molecule fluorescence imaging has been reconciling a fundamental mismatch between optical microscopy and subcellular biophysics. However, the next step in nanoscale imaging in living cells can be accessed only by optical excitation confinement geometries. Here, we review three methods of confinement that can enable nanoscale imaging in living cells: excitation confinement by laser illumination with beam shaping; physical confinement by micron-scale geometries in bacterial cells; and nanoscale confinement by nanophotonics.

  2. Carbon-Confined SnO2-Electrodeposited Porous Carbon Nanofiber Composite as High-Capacity Sodium-Ion Battery Anode Material.

    PubMed

    Dirican, Mahmut; Lu, Yao; Ge, Yeqian; Yildiz, Ozkan; Zhang, Xiangwu

    2015-08-26

    Sodium resources are inexpensive and abundant, and hence, sodium-ion batteries are promising alternative to lithium-ion batteries. However, lower energy density and poor cycling stability of current sodium-ion batteries prevent their practical implementation for future smart power grid and stationary storage applications. Tin oxides (SnO2) can be potentially used as a high-capacity anode material for future sodium-ion batteries, and they have the advantages of high sodium storage capacity, high abundance, and low toxicity. However, SnO2-based anodes still cannot be used in practical sodium-ion batteries because they experience large volume changes during repetitive charge and discharge cycles. Such large volume changes lead to severe pulverization of the active material and loss of electrical contact between the SnO2 and carbon conductor, which in turn result in rapid capacity loss during cycling. Here, we introduce a new amorphous carbon-coated SnO2-electrodeposited porous carbon nanofiber (PCNF@SnO2@C) composite that not only has high sodium storage capability, but also maintains its structural integrity while ongoing repetitive cycles. Electrochemical results revealed that this SnO2-containing nanofiber composite anode had excellent electrochemical performance including high-capacity (374 mAh g(-1)), good capacity retention (82.7%), and large Coulombic efficiency (98.9% after 100th cycle).

  3. Evidence of low-density and high-density liquid phases and isochore end point for water confined to carbon nanotube.

    PubMed

    Nomura, Kentaro; Kaneko, Toshihiro; Bai, Jaeil; Francisco, Joseph S; Yasuoka, Kenji; Zeng, Xiao Cheng

    2017-04-03

    Possible transition between two phases of supercooled liquid water, namely the low- and high-density liquid water, has been only predicted to occur below 230 K from molecular dynamics (MD) simulation. However, such a phase transition cannot be detected in the laboratory because of the so-called "no-man's land" under deeply supercooled condition, where only crystalline ices have been observed. Here, we show MD simulation evidence that, inside an isolated carbon nanotube (CNT) with a diameter of 1.25 nm, both low- and high-density liquid water states can be detected near ambient temperature and above ambient pressure. In the temperature-pressure phase diagram, the low- and high-density liquid water phases are separated by the hexagonal ice nanotube (hINT) phase, and the melting line terminates at the isochore end point near 292 K because of the retracting melting line from 292 to 278 K. Beyond the isochore end point (292 K), low- and high-density liquid becomes indistinguishable. When the pressure is increased from 10 to 600 MPa along the 280-K isotherm, we observe that water inside the 1.25-nm-diameter CNT can undergo low-density liquid to hINT to high-density liquid reentrant first-order transitions.

  4. 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.

  5. Workpiece surface quality and the influence factors when high-speed milling of SiCp/2009Al composite

    NASA Astrophysics Data System (ADS)

    Ge, Yingfei; Xu, Jiuhua; Fu, Yucan

    2011-05-01

    Surface finish, surface generation and the influence factors were investigated when high speed milling SiCp/2009Al composites using polycrystalline diamond (PCD) tools. The results showed that the surface roughness Ra0.207-0.542μm and Rz2.02-5.20μm can be attained when tool flank wear VB is less than 0.09mm under the present cutting conditions. With the increasing wear of the cutting tools, the value of the machined surface roughness significantly increased. The machined surfaces included many defects of pits, voids, microcracks, grooves, protuberances, matrix tearing and smearing and so on. The depth of deformation layers were confined to 20-35μm. Among the factors which affected Ra, reinforcement volume fraction was the most significant factor and followed by cutting speed and feed rate. For the side face, the significance order of the factors which affected Rz can be ranged as reinforcement volume fraction, cutting speed, feed rate and radial depth of cut. Material swelling and side flow, tool-workpiece relative vibration, feed rate and tool nose radius, removal mode of SiC particles were the main mechanisms of surface generation.

  6. Workpiece surface quality and the influence factors when high-speed milling of SiCp/2009Al composite

    NASA Astrophysics Data System (ADS)

    Ge, Yingfei; Xu, Jiuhua; Fu, Yucan

    2010-12-01

    Surface finish, surface generation and the influence factors were investigated when high speed milling SiCp/2009Al composites using polycrystalline diamond (PCD) tools. The results showed that the surface roughness Ra0.207-0.542μm and Rz2.02-5.20μm can be attained when tool flank wear VB is less than 0.09mm under the present cutting conditions. With the increasing wear of the cutting tools, the value of the machined surface roughness significantly increased. The machined surfaces included many defects of pits, voids, microcracks, grooves, protuberances, matrix tearing and smearing and so on. The depth of deformation layers were confined to 20-35μm. Among the factors which affected Ra, reinforcement volume fraction was the most significant factor and followed by cutting speed and feed rate. For the side face, the significance order of the factors which affected Rz can be ranged as reinforcement volume fraction, cutting speed, feed rate and radial depth of cut. Material swelling and side flow, tool-workpiece relative vibration, feed rate and tool nose radius, removal mode of SiC particles were the main mechanisms of surface generation.

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

    PubMed

    Nartowski, K P; Tedder, J; Braun, D E; Fábián, 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.

  8. 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

  9. Dimensional reduction of duplex DNA under confinement to nanofluidic slits.

    PubMed

    Vargas-Lara, Fernando; Stavis, Samuel M; Strychalski, Elizabeth A; Nablo, Brian J; Geist, Jon; Starr, Francis W; Douglas, Jack F

    2015-11-14

    There has been much interest in the dimensional properties of double-stranded DNA (dsDNA) confined to nanoscale environments as a problem of fundamental importance in both biological and technological fields. This has led to a series of measurements by fluorescence microscopy of single dsDNA molecules under confinement to nanofluidic slits. Despite the efforts expended on such experiments and the corresponding theory and simulations of confined polymers, a consistent description of changes of the radius of gyration of dsDNA under strong confinement has not yet emerged. Here, we perform molecular dynamics (MD) simulations to identify relevant factors that might account for this inconsistency. Our simulations indicate a significant amplification of excluded volume interactions under confinement at the nanoscale due to the reduction of the effective dimensionality of the system. Thus, any factor influencing the excluded volume interaction of dsDNA, such as ionic strength, solution chemistry, and even fluorescent labels, can greatly influence the dsDNA size under strong confinement. These factors, which are normally less important in bulk solutions of dsDNA at moderate ionic strengths because of the relative weakness of the excluded volume interaction, must therefore be under tight control to achieve reproducible measurements of dsDNA under conditions of dimensional reduction. By simulating semi-flexible polymers over a range of parameter values relevant to the experimental systems and exploiting past theoretical treatments of the dimensional variation of swelling exponents and prefactors, we have developed a novel predictive relationship for the in-plane radius of gyration of long semi-flexible polymers under slit-like confinement. Importantly, these analytic expressions allow us to estimate the properties of dsDNA for the experimentally and biologically relevant range of contour lengths that is not currently accessible by state-of-the-art MD simulations.

  10. Quantum Confined Semiconductors

    DTIC Science & Technology

    2015-02-01

    45 34 SEM image of the quantum dots. The bar on the right hand side corresponds to 50 nm...structured type-II superlattice long-wave infrared photodiodes with high quantum efficiency ,” Appl. Phys. Lett. 89, 053519 (2006). 10 Distribution...active region. To achieve a wide depletion width (~5 µm) with low applied bias, and thus a good absorption quantum efficiency , the majority carrier

  11. MHD Stability of Centrifugally Confined Plasmas

    NASA Astrophysics Data System (ADS)

    Huang, Yi-Min

    2003-10-01

    Centrifugally confined plasmas utilize centrifugal forces from plasma rotation to augment magnetic confinement, as an alternative approach to fusion. One magnetic geometry is mirror-type, with rotation about the axis induced from a central, biased core conductor. The outward centrifugal forces from the rotation have a component along the field lines, thus confining ions to the center. The immediate concern, of course, is that the system could be flute unstable to the interchange. The antidote here is that the radial shear in the rotation could stabilize the flute. Our 2D simulations show, first, that plasma pressure is highly peaked at the center away from the mirror end coils. Next, 3D simulations show unequivocally that velocity shear is providing the stability. Further study indicates that the flute stability is sensitive to the density profile. A favorable density profile could be achieved by judiciously placing the particle source, also necessary for a steady state centrifuge. As flows approach the Alfven speed, electromagnetic modes could be involved. The latter is motivated by the question of whether magnetorotational instability, thought to be an angular momentum transporter in accretion disks, could be found in centrifugal plasmas, since all the ingredients are there. We show that the MRI as understood should be stable; however, a related astrophysical instability, the Parker instability, could arise. The Parker instability results in plasma accumulating in regions of bent field lines, further accentuating the bending.

  12. 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.

  13. Strong focusing influence on high gain FEL characteristics

    SciTech Connect

    Smirnov, A.; Varfolomeev, A.

    1995-12-31

    The use of intrinsic alternating focusing in a linac-driven FEL with planar undulator is considered numerically. The analysis is done on the basis of TDA code for soft X-ray FEL with FD lattice implementing focusing of quadrupole and periodic sextupole type. The influence of the focusing (type and phase advance) on FEL performance and the reasons of difference in FEL performance for focusing of two kinds are analyzed. A possibility of some kind of beam conditioning for intrinsic focusing is discussed.

  14. Precursor detonation wave development in ANFO due to aluminum confinement

    SciTech Connect

    Jackson, Scott I; Klyanda, Charles B; Short, Mark

    2010-01-01

    Detonations in explosive mixtures of ammonium-nitrate-fuel-oil (ANFO) confined by aluminum allow for transport of detonation energy ahead of the detonation front due to the aluminum sound speed exceeding the detonation velocity. The net effect of this energy transport on the detonation is unclear. It could enhance the detonation by precompressing the explosive near the wall. Alternatively, it could decrease the explosive performance by crushing porosity required for initiation by shock compression or destroying confinement ahead of the detonation. At present, these phenomena are not well understood. But with slowly detonating, non-ideal high explosive (NIHE) systems becoming increasing prevalent, proper understanding and prediction of the performance of these metal-confined NIHE systems is desirable. Experiments are discussed that measured the effect of this ANFO detonation energy transported upstream of the front by a 76-mm-inner-diameter aluminum confining tube. Detonation velocity, detonation-front shape, and aluminum response are recorded as a function of confiner wall thickness and length. Detonation shape profiles display little curvature near the confining surface, which is attributed to energy transported upstream modifying the flow. Average detonation velocities were seen to increase with increasing confiner thickness, while wavefront curvature decreased due to the stiffer, subsonic confinement. Significant radial sidewall tube motion was observed immediately ahead of the detonation. Axial motion was also detected, which interfered with the front shape measurements in some cases. It was concluded that the confiner was able to transport energy ahead of the detonation and that this transport has a definite effect on the detonation by modifying its characteristic shape.

  15. Environmental Influences and Perinatal Risk Factors in High Risk Children.

    ERIC Educational Resources Information Center

    Lindgren, Scott D.; And Others

    Children in a longitudinal high-risk infant follow-up program were evaluated at age 5 to determine whether they demonstrated behavior problems or cognitive deficits exceeding expectations based on conditions in their home environments. Normal expectations were determined through regression analyses on a group of age-matched controls. All high-risk…

  16. CUSP Energetic Particles: Confinement, Acceleration and Implications

    NASA Technical Reports Server (NTRS)

    Chen, Jiasheng

    1999-01-01

    The cusp energetic particle (CEP) event is a new magnetospheric phenomenon. The events were detected in the dayside cusp for hours, in which the measured helium ions had energies up to 8 MeV. All of these events were associated with a dramatic decrease and large fluctuations in the local magnetic field strength. During January 1999 - December 1999 covered by this report, I have studied the CEP events by analyzing the POLAR, GEOTAIL, and WIND particle and magnetic field data measured during the geomagnetic quiet periods in 1996 and one geomagnetic storm period in 1998. The simultaneous observations indicated that the ion fluxes in the CEP events were higher than that in both the upstream and the downstream from the bow shock. The pitch angle distribution of the helium ions in the CEP events was found to peak around 90 deg. It was found that the mirror parameter, defined as the ratio of the square root of the integration of the parallel turbulent power spectral component over the ultra-low frequency (ULF) ranges to the mean field in the cusp, is correlated with the intensity of the cusp MeV helium flux, which is a measure of the influence of mirroring interactions and an indication of local effect. It was also found that the turbulent power of the local magnetic field in the ultra-low frequency (ULF) ranges is correlated with the intensity of the cusp energetic helium ions. Such ULF ranges correspond to periods of about 0.33-500 seconds that cover the gyroperiods, the bounce periods, and the drift periods of the tens keV to MeV charged particles when they are temporarily confined in the high-altitude dayside cusp. These observations represent a discovery that the high-altitude dayside cusp is a new acceleration and dynamic trapping region of the magnetosphere. The cusp geometry is connected via gradient and curvature drift of these energized ions to the equatorial plasma sheet as close as the geostationary orbit at local midnight. It implies that the dayside cusp is

  17. Confinement and lattice gauge theory

    SciTech Connect

    Creutz, M

    1980-06-01

    The motivation for formulating gauge theories on a lattice to study non-perturbative phenomena is reviewed, and recent progress supporting the compatibility of asymptotic freedom and quark confinement in the standard SU(3) Yang-Mills theory of the strong interaction is discussed.

  18. Permit-Required Confined Spaces

    DTIC Science & Technology

    1998-01-01

    Permit-Required Confined Spaces U.S. Department of Labor Occupational Safety and Health Administration OSHA 3138 1998 (Revised) Report Documentation...Department of Labor Occupational Safety & Health Administration 200 Constitution Avenue Washington, DC 20210 Performing Organization Report Number OSHA 3138...determine compliance responsibili- ties, which are set forth in OSHA standards themselves and the Occupational Safety and Health Act. Moreover, because

  19. 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.

  20. Dynamical conductivity of confined water

    NASA Astrophysics Data System (ADS)

    Artemov, V. G.

    2017-01-01

    The electrodynamic response of water confined in nanoporous MCM-41 is measured in the frequency range 1 MHz-3 THz at room temperature. The results are analyzed in the context of a recently proposed ionic model of water. We found an increase in dc-conductivity of confined water by 3 orders of magnitude (3.3 · 10-3 Ω-1 · m-1) compared to bulk water (5.5 · 10-6 Ω-1 · m-1). This is attributed to the increase of H3O+ and OH- ion mobility, due to a decrease of the effective potential amplitude by walls of the confining environment. We found that the absorption in the microwave frequency range is much smaller in the medium with confined water than in the bulk water, and the quadratic dependence of the conductivity (σ) on frequency (ω) becomes less steep and tends to σ ~ ω. The results are of fundamental importance and can be used for understanding of the proton transport in systems with water in the nanoconfined state.

  1. Fat Quality Influences the Obesogenic Effect of High Fat Diets

    PubMed Central

    Crescenzo, Raffaella; Bianco, Francesca; Mazzoli, Arianna; Giacco, Antonia; Cancelliere, Rosa; di Fabio, Giovanni; Zarrelli, Armando; Liverini, Giovanna; Iossa, Susanna

    2015-01-01

    High fat and/or carbohydrate intake are associated with an elevated risk for obesity and chronic diseases such as diabetes and cardiovascular diseases. The harmful effects of a high fat diet could be different, depending on dietary fat quality. In fact, high fat diets rich in unsaturated fatty acids are considered less deleterious for human health than those rich in saturated fat. In our previous studies, we have shown that rats fed a high fat diet developed obesity and exhibited a decrease in oxidative capacity and an increase in oxidative stress in liver mitochondria. To investigate whether polyunsaturated fats could attenuate the above deleterious effects of high fat diets, energy balance and body composition were assessed after two weeks in rats fed isocaloric amounts of a high-fat diet (58.2% by energy) rich either in lard or safflower/linseed oil. Hepatic functionality, plasma parameters, and oxidative status were also measured. The results show that feeding on safflower/linseed oil diet attenuates the obesogenic effect of high fat diets and ameliorates the blood lipid profile. Conversely, hepatic steatosis and mitochondrial oxidative stress appear to be negatively affected by a diet rich in unsaturated fatty acids. PMID:26580650

  2. Design of indirectly driven, high-compression Inertial Confinement Fusion implosions with improved hydrodynamic stability using a 4-shock adiabat-shaped drive

    NASA Astrophysics Data System (ADS)

    Milovich, J. L.; Robey, H. F.; Clark, D. S.; Baker, K. L.; Casey, D. T.; Cerjan, C.; Field, J.; MacPhee, A. G.; Pak, A.; Patel, P. K.; Peterson, J. L.; Smalyuk, V. A.; Weber, C. R.

    2015-12-01

    Experimental results from indirectly driven ignition implosions during the National Ignition Campaign (NIC) [M. J. Edwards et al., Phys. Plasmas 20, 070501 (2013)] achieved a record compression of the central deuterium-tritium fuel layer with measured areal densities up to 1.2 g/cm2, but with significantly lower total neutron yields (between 1.5 × 1014 and 5.5 × 1014) than predicted, approximately 10% of the 2D simulated yield. An order of magnitude improvement in the neutron yield was subsequently obtained in the "high-foot" experiments [O. A. Hurricane et al., Nature 506, 343 (2014)]. However, this yield was obtained at the expense of fuel compression due to deliberately higher fuel adiabat. In this paper, the design of an adiabat-shaped implosion is presented, in which the laser pulse is tailored to achieve similar resistance to ablation-front instability growth, but with a low fuel adiabat to achieve high compression. Comparison with measured performance shows a factor of 3-10× improvement in the neutron yield (>40% of predicted simulated yield) over similar NIC implosions, while maintaining a reasonable fuel compression of >1 g/cm2. Extension of these designs to higher laser power and energy is discussed to further explore the trade-off between increased implosion velocity and the deleterious effects of hydrodynamic instabilities.

  3. Design of indirectly driven, high-compression Inertial Confinement Fusion implosions with improved hydrodynamic stability using a 4-shock adiabat-shaped drive

    SciTech Connect

    Milovich, J. L. Robey, H. F.; Clark, D. S.; Baker, K. L.; Casey, D. T.; Cerjan, C.; Field, J.; MacPhee, A. G.; Pak, A.; Patel, P. K.; Peterson, J. L.; Smalyuk, V. A.; Weber, C. R.

    2015-12-15

    Experimental results from indirectly driven ignition implosions during the National Ignition Campaign (NIC) [M. J. Edwards et al., Phys. Plasmas 20, 070501 (2013)] achieved a record compression of the central deuterium-tritium fuel layer with measured areal densities up to 1.2 g/cm{sup 2}, but with significantly lower total neutron yields (between 1.5 × 10{sup 14} and 5.5 × 10{sup 14}) than predicted, approximately 10% of the 2D simulated yield. An order of magnitude improvement in the neutron yield was subsequently obtained in the “high-foot” experiments [O. A. Hurricane et al., Nature 506, 343 (2014)]. However, this yield was obtained at the expense of fuel compression due to deliberately higher fuel adiabat. In this paper, the design of an adiabat-shaped implosion is presented, in which the laser pulse is tailored to achieve similar resistance to ablation-front instability growth, but with a low fuel adiabat to achieve high compression. Comparison with measured performance shows a factor of 3–10× improvement in the neutron yield (>40% of predicted simulated yield) over similar NIC implosions, while maintaining a reasonable fuel compression of >1 g/cm{sup 2}. Extension of these designs to higher laser power and energy is discussed to further explore the trade-off between increased implosion velocity and the deleterious effects of hydrodynamic instabilities.

  4. Statistical Contact Model for Confined Molecules

    NASA Astrophysics Data System (ADS)

    Santamaria, Ruben; de la Paz, Antonio Alvarez; Roskop, Luke; Adamowicz, Ludwik

    2016-08-01

    A theory that describes in a realistic form a system of atoms under the effects of temperature and confinement is presented. The theory departs from a Lagrangian of the Zwanzig type and contains the main ingredients for describing a system of atoms immersed in a heat bath that is also formed by atoms. The equations of motion are derived according to Lagrangian mechanics. The application of statistical mechanics to describe the bulk effects greatly reduces the complexity of the equations. The resultant equations of motion are of the Langevin type with the viscosity and the temperature of the heat reservoir able to influence the trajectories of the particles. The pressure effects are introduced mechanically by using a container with an atomic structure immersed in the heat bath. The relevant variables that determine the equation of state are included in the formulation. The theory is illustrated by the derivation of the equation of state for a system with 76 atoms confined inside of a 180-atom fullerene-like cage that is immersed in fluid forming the heat bath at a temperature of 350 K and with the friction coefficient of 3.0 {ps}^{-1}. The atoms are of the type believed to form the cores of the Uranus and Neptune planets. The dynamic and the static pressures of the confined system are varied in the 3-5 KBar and 2-30 MBar ranges, respectively. The formulation can be equally used to analyze chemical reactions under specific conditions of pressure and temperature, determine the structure of clusters with their corresponding equation of state, the conditions for hydrogen storage, etc. The theory is consistent with the principles of thermodynamics and it is intrinsically ergodic, of general use, and the first of this kind.

  5. Magnetic-confinement fusion

    NASA Astrophysics Data System (ADS)

    Ongena, J.; Koch, R.; Wolf, R.; Zohm, H.

    2016-05-01

    Our modern society requires environmentally friendly solutions for energy production. Energy can be released not only from the fission of heavy nuclei but also from the fusion of light nuclei. Nuclear fusion is an important option for a clean and safe solution for our long-term energy needs. The extremely high temperatures required for the fusion reaction are routinely realized in several magnetic-fusion machines. Since the early 1990s, up to 16 MW of fusion power has been released in pulses of a few seconds, corresponding to a power multiplication close to break-even. Our understanding of the very complex behaviour of a magnetized plasma at temperatures between 150 and 200 million °C surrounded by cold walls has also advanced substantially. This steady progress has resulted in the construction of ITER, a fusion device with a planned fusion power output of 500 MW in pulses of 400 s. ITER should provide answers to remaining important questions on the integration of physics and technology, through a full-size demonstration of a tenfold power multiplication, and on nuclear safety aspects. Here we review the basic physics underlying magnetic fusion: past achievements, present efforts and the prospects for future production of electrical energy. We also discuss questions related to the safety, waste management and decommissioning of a future fusion power plant.

  6. Order-disorder structural transition in a confined fluid

    NASA Astrophysics Data System (ADS)

    de la Calleja-Mora, E. M.; Krott, Leandro B.; Barbosa, M. C.

    2016-05-01

    In this paper we analyze the amorphous/solid to disordered liquid structural phase transitions of an anomalous confined fluid in terms of their fractal dimensions. The model studied is composed by particles interaction through a two-length scales potential confined by two infinite plates. This fluid that in the bulk exhibits water-like anomalies under confinement forms layers of particles. We show that the fluid at the contact layer forms at high densities structures and transitions that can be mapped into fractal dimensions. The multi-fractal singularity spectrum is obtained in all these cases and it is used as the order parameter to quantify the structural transitions for each stage on the confined liquid. This mapping shows that the fractal dimension increases with the density and with the temperature.

  7. High throughput CIGS solar cell fabrication via ultra-thin absorber layer with optical confinement and (Cd, CBD)-free heterojunction partner

    SciTech Connect

    Marsillac, Sylvain

    2015-11-30

    The main objective of this proposal was to use several pathways to reduce the production cost of Cu(In,Ga)Se2 (CIGS) PV modules and therefore the levelized cost of energy (LCOE) associated with this technology. Three high cost drivers were identified, nominally: 1) Materials cost and availability; 2) Large scale uniformity; 3) Improved throughput These three cost drivers were targeted using the following pathways: 1) Reducing the thickness of the CIGS layer while enhancing materials quality; 2) Developing and applying enhanced in-situ metrology via real time spectroscopic ellipsometry; 3) Looking into alternative heterojunction partner, back contact and anti-reflection (AR) coating Eleven main Tasks were then defined to achieve these goals (5 in Phase 1 and 6 in Phase 2), with 11 Milestones and 2 Go/No-go decision points at the end of Phase 1. The key results are summarized below

  8. Wang-Landau Simulations of Adsorbed and Confined Lattice Proteins

    NASA Astrophysics Data System (ADS)

    Pattanasiri, Busara; Li, Ying Wai; Landau, David P.; Wüst, Thomas

    2012-08-01

    The hydrophobic-polar (HP) model has emerged as one of the standard approaches for simulating protein folding. In this work, we used this model together with Wang-Landau (WL) sampling and appropriate Monte Carlo trial moves to determine the density of states and thermodynamics for two cases: Protein adsorption and protein confinement, in the vicinity of attractive surfaces. The influence on the adsorption behavior of surface attractive strength in the adsorption case and volumetric spaces in the confinement case will be discussed.

  9. Optical response of alkali metal atoms confined in nanoporous glass

    SciTech Connect

    Burchianti, A; Marinelli, C; Mariotti, E; Bogi, A; Marmugi, L; Giomi, S; Maccari, M; Veronesi, S; Moi, L

    2014-03-28

    We study the influence of optical radiation on adsorption and desorption processes of alkali metal atoms confined in nanoporous glass matrices. Exposure of the sample to near-IR or visible light changes the atomic distribution inside the glass nanopores, forcing the entire system to evolve towards a different state. This effect, due to both atomic photodesorption and confinement, causes the growth and evaporation of metastable nanoparticles. It is shown that, by a proper choice of light characteristics and pore size, these processes can be controlled and tailored, thus opening new perspectives for fabrication of nanostructured surfaces. (nanoobjects)

  10. Effect of laser supported detonation wave confinement on termination conditions

    NASA Astrophysics Data System (ADS)

    Ushio, Masato; Komurasaki, Kimiya; Kawamura, Koichi; Arakawa, Yoshihiro

    2008-06-01

    A laser supported detonation (LSD) wave was driven using line-focusing laser optics, in which an induced blast wave expanded laterally from the LSD region to surrounding air in two-dimensional space. The LSD wave was confined in quasi-1D space using a wedge nozzle to restrict the lateral expansion of a blast wave. The LSD termination threshold and the blast wave energy were deduced from shadowgraphs showing the blast wave expansion. The respective threshold laser intensities for cases with and without confinement were estimated as 17 and 34 GW/m2, indicating that the lateral expansion strongly influenced on the LSD termination condition.

  11. Boundary condition for toroidal plasma flow imposed at the separatrix in high confinement JT-60U plasmas with edge localized modes and the physics process in pedestal structure formation

    SciTech Connect

    Kamiya, K.; Honda, M.; Urano, H.; Yoshida, M.; Kamada, Y.; Itoh, K.

    2014-12-15

    Modulation charge eXchange recombination spectroscopy measurements with high spatial and temporal resolution have made the evaluation of the toroidal plasma flow of fully stripped carbon impurity ions (V{sub ϕ}{sup C6+}) in the JT-60U tokamak peripheral region (including, in particular, the separatrix) possible with a better signal-to-noise ratio. By comparing co- and counter-neutral beam injection discharges experimentally, we have identified the boundary condition of V{sub ϕ}{sup C6+} and radial electric field shear (∇E{sub r}) imposed at the separatrix in high confinement (H-mode) plasmas with edge localized modes (ELMs). The V{sub ϕ}{sup C6+} value at the separatrix is not fixed at zero but varies with the momentum input direction. On the other hand, the ∇E{sub r} value is nearly zero (or very weakly positive) at the separatrix. Furthermore, the edge localized mode perturbation does not appear to affect both V{sub ϕ}{sup C6+} and ∇E{sub r} values at the separatrix as strongly as that in the pedestal region. The above experimental findings based on the precise edge measurements have been used to validate a theoretical model and develop a new empirical model. A better understanding of the physical process in the edge transport barrier (ETB) formation due to the sheared E{sub r} formation is also discussed.

  12. Characteristics of confinement and fusion reactivity in JT-60U high-{beta}{rho} and TFTR supershot regimes with deuterium neutral beam injection

    SciTech Connect

    Park, H.K.; Bell, M.G.; Yamada, M.

    1995-03-01

    The high performance regimes achieved in JT-60U and TFTR have produced peak DD fusion neutron rates up to 5.6 {times} 10{sup 16}/s for similar heating beam powers, in spite of considerable differences in machine operation and plasma configuration. A common scaling for the DD fusion neutron rate (S{sub DD} {proportional_to} P{sub abs}{sup 2.0} H{sub ne} V{sub p}{sup {minus}0.9}) is obtained, where P{sub abs} and H{sub ne} are the absorbed beam power and beam fueling peaking factor, respectively, and V{sub p} is the plasma volume. The maximum stored energy obtained in each machine has been up to 5.4 MJ in TFTR and 8.7 MJ in JT-60U. Further improvements in the fusion neutron rate and the stored energy are limited by the {beta}-limit in Troyon range, {beta}{sub N} {approximately} 2.0--2.5. A common scaling for the stored energy (W{sub tot} {proportional_to} P{sub abs}V{sub p}H{sub ne}{sup 0.2}) is also proposed.

  13. Confined SnO2 quantum-dot clusters in graphene sheets as high-performance anodes for lithium-ion batteries

    PubMed Central

    Zhu, Chengling; Zhu, Shenmin; Zhang, Kai; Hui, Zeyu; Pan, Hui; Chen, Zhixin; Li, Yao; Zhang, Di; Wang, Da-Wei

    2016-01-01

    Construction of metal oxide nanoparticles as anodes is of special interest for next-generation lithium-ion batteries. The main challenge lies in their rapid capacity fading caused by the structural degradation and instability of solid-electrolyte interphase (SEI) layer during charge/discharge process. Herein, we address these problems by constructing a novel-structured SnO2-based anode. The novel structure consists of mesoporous clusters of SnO2 quantum dots (SnO2 QDs), which are wrapped with reduced graphene oxide (RGO) sheets. The mesopores inside the clusters provide enough room for the expansion and contraction of SnO2 QDs during charge/discharge process while the integral structure of the clusters can be maintained. The wrapping RGO sheets act as electrolyte barrier and conductive reinforcement. When used as an anode, the resultant composite (MQDC-SnO2/RGO) shows an extremely high reversible capacity of 924 mAh g−1 after 200 cycles at 100 mA g−1, superior capacity retention (96%), and outstanding rate performance (505 mAh g−1 after 1000 cycles at 1000 mA g−1). Importantly, the materials can be easily scaled up under mild conditions. Our findings pave a new way for the development of metal oxide towards enhanced lithium storage performance. PMID:27181691

  14. Confined SnO2 quantum-dot clusters in graphene sheets as high-performance anodes for lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Zhu, Chengling; Zhu, Shenmin; Zhang, Kai; Hui, Zeyu; Pan, Hui; Chen, Zhixin; Li, Yao; Zhang, Di; Wang, Da-Wei

    2016-05-01

    Construction of metal oxide nanoparticles as anodes is of special interest for next-generation lithium-ion batteries. The main challenge lies in their rapid capacity fading caused by the structural degradation and instability of solid-electrolyte interphase (SEI) layer during charge/discharge process. Herein, we address these problems by constructing a novel-structured SnO2-based anode. The novel structure consists of mesoporous clusters of SnO2 quantum dots (SnO2 QDs), which are wrapped with reduced graphene oxide (RGO) sheets. The mesopores inside the clusters provide enough room for the expansion and contraction of SnO2 QDs during charge/discharge process while the integral structure of the clusters can be maintained. The wrapping RGO sheets act as electrolyte barrier and conductive reinforcement. When used as an anode, the resultant composite (MQDC-SnO2/RGO) shows an extremely high reversible capacity of 924 mAh g‑1 after 200 cycles at 100 mA g‑1, superior capacity retention (96%), and outstanding rate performance (505 mAh g‑1 after 1000 cycles at 1000 mA g‑1). Importantly, the materials can be easily scaled up under mild conditions. Our findings pave a new way for the development of metal oxide towards enhanced lithium storage performance.

  15. Confinement and heating of high beta plasmas with emphasis on compact toroids: Task 2, Stellarator and heliac research: Annual report, October 1, 1985-September 30, 1986

    SciTech Connect

    Ribe, F.L.

    1986-12-31

    Progress over the past year has enabled us to complete the comprehensive experimental investigation of the equilibrium and stability of the linear heliac and the linear l = 1 stellarator configration. In the case of the heliac work, we discoverd axisymmetric hot plasma near the axial conductor (''hardcore'') in amounts which are comparable to the helically symmetric hot plasma centered on the magnetic axis. From this result came the motivation for an extended investigation which concentrates on the details of high-beta heliac formation. Important first results of the formation study have been obtained. In the case of the stellarator work, we have observed the flute-like m = 1 instability foe a specific set of experimental parameters and, for a different set, we have observed the mode stabilized by the combined effects of a finite ion Larmor radius and a nearby conducting wall. The single-discharge CV ion-temperature diagnostic system has been debugged and has yielded a heliac temperature measurement of (90 +- 10)eV. The plasma density diagnostic system based on cross-tube interferometry has been modified from its previous design for use with the somewhat wrinkly helical discharge tube.

  16. Food intake, milk production, and tissue changes of Holstein-Friesian and Jersey × Holstein-Friesian dairy cows within a medium-input grazing system and a high-input total confinement system.

    PubMed

    Vance, E R; Ferris, C P; Elliott, C T; McGettrick, S A; Kilpatrick, D J

    2012-03-01

    Although interest in crossbreeding within dairy systems has increased, the role of Jersey crossbred cows within high concentrate input systems has received little attention. This experiment was designed to examine the performance of Holstein-Friesian (HF) and Jersey × Holstein-Friesian (J × HF) cows within a high concentrate input total confinement system (CON) and a medium concentrate input grazing system (GRZ). Eighty spring-calving dairy cows were used in a 2 (cow genotype) × 2 (milk production system) factorial design experiment. The experiment commenced when cows calved and encompassed a full lactation. With GRZ, cows were offered diets containing grass silage and concentrates [70:30 dry matter (DM) ratio] until turnout, grazed grass plus 1.0 kg of concentrate/day during a 199-d grazing period, and grass silage and concentrates (75:25 DM ratio) following rehousing and until drying-off. With CON, cows were confined throughout the lactation and offered diets containing grass silage and concentrates (DM ratio; 40:60, 50:50, 40:40, and 75:25 during d 1 to 100, 101 to 200, 201 to 250, and 251 until drying-off, respectively). Full-lactation concentrate DM intakes were 791 and 2,905 kg/cow for systems GRZ and CON, respectively. Although HF cows had a higher lactation milk yield than J × HF cows, the latter produced milk with a higher fat and protein content, so that solids-corrected milk yield (SCM) was unaffected by genotype. Somatic cell score was higher with the J × HF cows. Throughout lactation, HF cows were on average 37 kg heavier than J × HF cows, whereas the J × HF cows had a higher body condition score. Within each system, food intake did not differ between genotypes, whereas full-lactation yields of milk, fat plus protein, and SCM were higher with CON than with GRZ. A significant genotype × environment interaction was observed for milk yield, and a trend was found for an interaction with SCM. Crossbred cows on CON gained more body condition than HF

  17. Childhood events and circumstances influencing high school completion.

    PubMed

    Haveman, R; Wolfe, B; Spaulding, J

    1991-02-01

    This paper is an empirical exploration of the effects of a variety of family and economic circumstances experienced during childhood on one indicator of success in young adulthood--high school completion. The estimates suggest that parental education and mother's work are positive and significant determinants of high school completion, whereas growing up in a family with more children (who compete for resources), being persistently poor and on welfare, and moving one's residence as a child have significant negative impacts on high school completion. The effects of some family stress and economic events differ depending on the age of the child when they occur. The results support the economic model of investment in children, as well as the welfare culture and socialization models.

  18. Factors Influencing Noncompletion of High School: A Comparison of Methodologies.

    ERIC Educational Resources Information Center

    Weng, Li-Jen; And Others

    1988-01-01

    Impacts of the parents' divorce and the student's academic potential and drug use on non-completion of high school were examined using 3 methods of structural equation modeling with latent variables. Data were collected from 706 adolescents (in grades 10 through 12). Maximum likelihood, asymptotically distribution-free, and categorical variable…

  19. Influencing College Chemistry Success through High School Chemistry Teaching

    ERIC Educational Resources Information Center

    Tai, Robert H.; Sadler, Philip M.; Loehr, John F.

    2006-01-01

    The connection between high school chemistry pedagogical experiences and introductory college chemistry performance has been a topic researched in published science education literature since the 1920s. However, analysis techniques have limited the generalizability of these results. This review discusses the findings of a large-scale,…

  20. Effects of strain rate and confining pressure on the deformation and failure of shale

    SciTech Connect

    Cook, J.M. ); Sheppard, M.C. ); Houwen, O.H. )

    1991-06-01

    Previous work on shale mechanical properties has focused on the slow deformation rates appropriate to wellbore deformation. Deformation of shale under a drill bit occurs at a very high rate, and the failure properties of the rock under these conditions are crucial in determining bit performance and in extracting lithology and pore-pressure information from drilling parameters. Triaxial tests were performed on two nonswelling shales under a wide range of strain rates and confining and pore pressures. At low strain rates, when fluid is relatively free to move within the shale, shale deformation and failure are governed by effective stress or pressure (i.e., total confining pressure minus pore pressure), as is the case for ordinary rock. If the pore pressure in the shale is high, increasing the strain rate beyond about 0.1%/sec causes large increases in the strength and ductility of the shale. Total pressure begins to influence the strength. At high stain rates, the influence of effective pressure decreases, except when it is very low (i.e., when pore pressure is very high); ductility then rises rapidly. This behavior is opposite that expected in ordinary rocks. This paper briefly discusses the reasons for these phenomena and their impact on wellbore and drilling problems.

  1. 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.

  2. Characteristics of inhomogeneous jets in confined swirling air flows

    NASA Astrophysics Data System (ADS)

    So, R. M. C.; Ahmed, S. A.

    1984-04-01

    An experimental program to study the characteristics of inhomogeneous jets in confined swirling flows to obtain detailed and accurate data for the evaluation and improvement of turbulent transport modeling for combustor flows is discussed. The work was also motivated by the need to investigate and quantify the influence of confinement and swirl on the characteristics of inhomogeneous jets. The flow facility was constructed in a simple way which allows easy interchange of different swirlers and the freedom to vary the jet Reynolds number. The velocity measurements were taken with a one color, one component DISA Model 55L laser-Doppler anemometer employing the forward scatter mode. Standard statistical methods are used to evaluate the various moments of the signals to give the flow characteristics. The present work was directed at the understanding of the velocity field. Therefore, only velocity and turbulence data of the axial and circumferential components are reported for inhomogeneous jets in confined swirling air flows.

  3. High pressure gas pipeline under the influence of radiation

    NASA Astrophysics Data System (ADS)

    Ilic, Marko N.; Ilic, Gradimir S.; Stefanovic, Velimir P.; Pavlovic, Sasa R.; Bojic, Milorad L. j.

    2012-11-01

    This paper presents one of the possible hazardous situations during transportation of gas through the international pipeline. It describes case when at high pressure gas pipeline, due to mechanical or chemical effect, the crack and gas leakage appears and gas is somehow triggered to combusting. As a consequence of heat impingement on the pipe surface will be, change of material properties (decreasing of strength) at high temperatures. In order to avoid greater rapture a reasonable pressure relief rate needs to be applied. Standards in this particular domain of depressurizing procedure are not so exact (DIN EN ISO 23251; API 521). The main part of the work consists of two calculations. First is the numerical simulation of heat radiation of combustible gas which affects the pipeline, done by software FLUENT, and second in Matlab. There are also given conclusions according to achieved results.

  4. Effect of confinement on droplet coalescence in shear flow.

    PubMed

    Chen, Dongju; Cardinaels, Ruth; Moldenaers, Paula

    2009-11-17

    The effect of confinement on the coalescence of Newtonian (polydimethylsiloxane) droplets in a Newtonian (polyisobutylene) matrix is investigated experimentally. A counter rotating parallel plate device, equipped with a microscopy setup, is used to visualize two interacting droplets during shear flow. The ratio of droplet-to-matrix viscosity is kept constant at 1.1. Droplet collisions are studied for a range of droplet sizes, both in bulk conditions and for gap spacings that are comparable to the droplet size. As a result, we present the first quantitative experimental data set for the coalescence of two equal-sized droplets in a pure shear flow with varying degrees of confinement. Compared to bulk conditions, for droplets smaller than roughly 0.2 times the gap spacing, a slight degree of confinement only decreases the orientation angle at which the droplets coalesce whereas the critical conditions for coalescence remain unaltered. For more confined conditions, the critical capillary number up to which coalescence can occur, increases. Therefore, confinement clearly promotes coalescence. In addition, the droplet trajectories, the time-dependent orientation angle of the droplet pair, and the droplet deformation prior to the coalescence event are systematically studied, and a comparison between the confined and the unconfined situation is provided. It is shown that the presence of two parallel walls can induce changes in the flow field around the droplet pair, which cause an increase of the interaction time between the droplets. Moreover, for sufficiently confined droplets, the additional force originating from the presence of the walls becomes comparable to the hydrodynamic force on the droplet pair, thus influencing the drainage of the matrix film between the droplet surfaces.

  5. Rapid identifying high-influence nodes in complex networks

    NASA Astrophysics Data System (ADS)

    Song, Bo; Jiang, Guo-Ping; Song, Yu-Rong; Xia, Ling-Ling

    2015-10-01

    A tiny fraction of influential individuals play a critical role in the dynamics on complex systems. Identifying the influential nodes in complex networks has theoretical and practical significance. Considering the uncertainties of network scale and topology, and the timeliness of dynamic behaviors in real networks, we propose a rapid identifying method (RIM) to find the fraction of high-influential nodes. Instead of ranking all nodes, our method only aims at ranking a small number of nodes in network. We set the high-influential nodes as initial spreaders, and evaluate the performance of RIM by the susceptible-infected-recovered (SIR) model. The simulations show that in different networks, RIM performs well on rapid identifying high-influential nodes, which is verified by typical ranking methods, such as degree, closeness, betweenness, and eigenvector centrality methods. Project supported by the National Natural Science Foundation of China (Grant Nos. 61374180 and 61373136), the Ministry of Education Research in the Humanities and Social Sciences Planning Fund Project, China (Grant No. 12YJAZH120), and the Six Projects Sponsoring Talent Summits of Jiangsu Province, China (Grant No. RLD201212).

  6. A New Approach Towards Characterizing Microstructural Influence on Material Behavior Under Very High Cycle

    DTIC Science & Technology

    2015-09-30

    vacuum and in controlled partial pressures of water vapor, high purity oxygen, and high purity hydrogen. 15. SUBJECT TERMS high cycle fatigue 16...Fatigue crack growth in laboratory air, high purity hydrogen, high purity oxygen, and water vapor environments. (top) Crack length (c) vs. cycle number...AFRL-AFOSR-VA-TR-2016-0144 A New Approach Towards Characterizing Microstructural Influence on Material Behavior Under Very High Cycle Samantha Daly

  7. 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.

  8. 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.

  9. Investigation of high-energy external influences on structural heredity of the Ti-Nb alloy

    NASA Astrophysics Data System (ADS)

    Khimich, M. A.; Parilov, E. A.; Kovalevskaya, Zh G.; Sharkeev, Yu P.

    2015-10-01

    The effects of high-energy external influences on structural heredity of Ti-Nb alloy is investigated in this paper. By the methods of XRD, SEM, EDX and optical microscopy it was founded that thermal treatment and severe plastic deformation lead to the phase transformations in the alloy, the dendritic segregation occurs and retains in the alloy under external influences.

  10. The Influence of Communicator Characteristics on the Nutrition Attitudes and Behavior of High School Students.

    ERIC Educational Resources Information Center

    Feldman, Robert H. L.

    1984-01-01

    School health educators can increase teaching effectiveness by emphasizing common interests with their students. High school students were studied to observe the influence of the communicator in a health program on nutrition. Results indicate that the greater the perceived similarities, the greater the influence of the communicator. Research…

  11. Precision platform for convex lens-induced confinement microscopy

    NASA Astrophysics Data System (ADS)

    Berard, Daniel; McFaul, Christopher M. J.; Leith, Jason S.; Arsenault, Adriel K. J.; Michaud, François; Leslie, Sabrina R.

    2013-10-01

    We present the conception, fabrication, and demonstration of a versatile, computer-controlled microscopy device which transforms a standard inverted fluorescence microscope into a precision single-molecule imaging station. The device uses the principle of convex lens-induced confinement [S. R. Leslie, A. P. Fields, and A. E. Cohen, Anal. Chem. 82, 6224 (2010)], which employs a tunable imaging chamber to enhance background rejection and extend diffusion-limited observation periods. Using nanopositioning stages, this device achieves repeatable and dynamic control over the geometry of the sample chamber on scales as small as the size of individual molecules, enabling regulation of their configurations and dynamics. Using microfluidics, this device enables serial insertion as well as sample recovery, facilitating temporally controlled, high-throughput measurements of multiple reagents. We report on the simulation and experimental characterization of this tunable chamber geometry, and its influence upon the diffusion and conformations of DNA molecules over extended observation periods. This new microscopy platform has the potential to capture, probe, and influence the configurations of single molecules, with dramatically improved imaging conditions in comparison to existing technologies. These capabilities are of immediate interest to a wide range of research and industry sectors in biotechnology, biophysics, materials, and chemistry.

  12. Effects of confinement on protein folding and protein stability

    NASA Astrophysics Data System (ADS)

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

    2003-05-01

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

  13. Enhanced fluctuations of interacting particles confined in a box

    NASA Astrophysics Data System (ADS)

    Delfau, Jean-Baptiste; Coste, Christophe; Saint Jean, Michel

    2012-04-01

    We study the position fluctuations of interacting particles aligned in a finite cell that avoid any crossing in equilibrium with a thermal bath. The focus is put on the influence of the confining force directed along the cell length. We show that the system may be modeled as a 1D chain of particles with identical masses, linked with linear springs of varying spring constants. The confining force may be accounted for by linear springs linked to the walls. When the confining force range is increased toward the inside of the chain, a paradoxical behavior is exhibited. The outermost particles fluctuations are enhanced, whereas those of the inner particles are reduced. A minimum of fluctuations is observed at a distance of the cell extremities that scales linearly with the confining force range. Those features are in very good agreement with the model. Moreover, the simulations exhibit an asymmetry in their fluctuations which is an anharmonic effect. It is characterized by the measurement of the skewness, which is found to be strictly positive for the outer particles when the confining force is short ranged.

  14. Inertial-confinement-fusion targets

    SciTech Connect

    Hendricks, C.D.

    1981-11-16

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

  15. Influences of High and Low Variability on Infant Word Recognition

    PubMed Central

    Singh, Leher

    2008-01-01

    Although infants begin to encode and track novel words in fluent speech by 7.5 months, their ability to recognize words is somewhat limited at this stage. In particular, when the surface form of a word is altered, by changing the gender or affective prosody of the speaker, infants begin to falter at spoken word recognition. Given that natural speech is replete with variability, only some of which is determines the meaning of a word, it remains unclear how infants might ever overcome the effects of surface variability without appealing to meaning. In the current set of experiments, consequences of high and low variability are examined in preverbal infants. The source of variability, vocal affect, is a common property of infant-directed speech with which young learners have to contend. Across a series of four experiments, infants' abilities to recognize repeated encounters of words, as well as to reject similar-sounding words, are investigated in the context of high and low affective variation. Results point to positive consequences of affective variation, both in creating generalizable memory representations for words, but also in establishing phonologically precise memories for words. Conversely, low variability appears to degrade word recognition on both fronts, compromising infants' abilities to generalize across different affective forms of a word and to detect similar-sounding items. Findings are discussed in the context of principles of categorization, both of a linguistic and non-linguistic variety, which may potentiate the early growth of a lexicon. PMID:17586482

  16. Nematode locomotion in unconfined and confined fluids

    NASA Astrophysics Data System (ADS)

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

    2013-08-01

    The millimeter-long soil-dwelling nematode Caenorhabditis elegans propels itself by producing undulations that propagate along its body and turns by assuming highly curved shapes. According to our recent study [V. Padmanabhan et al., PLoS ONE 7, e40121 (2012), 10.1371/journal.pone.0040121] all these postures can be accurately described by a piecewise-harmonic-curvature model. We combine this curvature-based description with highly accurate hydrodynamic bead models to evaluate the normalized velocity and turning angles for a worm swimming in an unconfined fluid and in a parallel-wall cell. We find that the worm moves twice as fast and navigates more effectively under a strong confinement, due to the large transverse-to-longitudinal resistance-coefficient ratio resulting from the wall-mediated far-field hydrodynamic coupling between body segments. We also note that the optimal swimming gait is similar to the gait observed for nematodes swimming in high-viscosity fluids. Our bead models allow us to determine the effects of confinement and finite thickness of the body of the nematode on its locomotion. These effects are not accounted for by the classical resistive-force and slender-body theories.

  17. Holographic confinement in inhomogeneous backgrounds

    NASA Astrophysics Data System (ADS)

    Marolf, Donald; Wien, Jason

    2016-08-01

    As noted by Witten, compactifying a d-dimensional holographic CFT on an S 1 gives a class of ( d - 1)-dimensional confining theories with gravity duals. The proto-typical bulk solution dual to the ground state is a double Wick rotation of the AdS d+1 Schwarzschild black hole known as the AdS soliton. We generalize such examples by allowing slow variations in the size of the S 1, and thus in the confinement scale. Coefficients governing the second order response of the system are computed for 3 ≤ d ≤ 8 using a derivative expansion closely related to the fluid-gravity correspondence. The primary physical results are that i) gauge-theory flux tubes tend to align orthogonal to gradients and along the eigenvector of the Hessian with the lowest eigenvalue, ii) flux tubes aligned orthogonal to gradients are attracted to gradients for d ≤ 6 but repelled by gradients for d ≥ 7, iii) flux tubes are repelled by regions where the second derivative along the tube is large and positive but are attracted to regions where the eigenvalues of the Hessian are large and positive in directions orthogonal to the tube, and iv) for d > 3, inhomogeneities act to raise the total energy of the confining vacuum above its zeroth order value.

  18. Sheared magnetofluids and Bernoulli confinement

    NASA Astrophysics Data System (ADS)

    Quevado, H. J.; Bengtson, Roger; Mahajan, S. M.; Valanju, P. M.

    2001-10-01

    New magnetofluid states that differ qualitatively from those accessible to either neutral fluids or to conventional MHD plasmas have been predited theoretically. They are predicted to appear if plasmas with strong velocity shear flows (with large initial values of both magnetic and magnetofluid helicity) are created and allowed to relax. The dynamic invariance of these two helicities will force the plasma to self-organize and relax to a long-lived quasi equilibrium state away from thermal equilibrium. The investigation of these states bears critically upon basic plasma confinement and heating issues in both natural and laboratory plasmas. We have built a magnetic mirror device designed to create and investigate these theoretically predicted pressure-confining magnetofluid states. The primary experimental challenge is to create an initial plasma (with significant flows and currents) which is relatively isolated from walls and embedded in a modest magnetic external field. Our machine has a central bias rod to create a radial electric field for generating fast plasma flow, a large mirror ratio for good centrifugal confinement, and magnetic, Langmuir, and Mach probes to measure the evolution of plasma rotation profiles and fluctuations. Initial results will be presented demonstrating plasma rotation.

  19. Influence of total cholesterol, high density lipoprotein cholesterol, and triglycerides on risk of cerebrovascular disease: the Copenhagen City Heart Study.

    PubMed Central

    Lindenstrøm, E.; Boysen, G.; Nyboe, J.

    1994-01-01

    OBJECTIVE--To estimate the influence of plasma total cholesterol, high density lipoprotein cholesterol, and triglycerides on risk of cerebrovascular disease. DESIGN--The Copenhagen City Heart Study is a prospective observational survey with two cardiovascular examinations at five year intervals. Non-fasting plasma lipids were measured in participants once at each examination, along with other variables. The Cox regression model was used to establish the effect of the factors recorded on cerebrovascular events of mostly, but not exclusively, ischaemic origin. SUBJECTS--19,698 women and men at least 20 years old, randomly selected after age stratification from an area of central Copenhagen. MAIN OUTCOME MEASURES--Initial cases of stroke and transient ischaemic attack recorded from hospital records and death certificates from 1976 through 1988. RESULTS--660 non-haemorrhagic and 33 haemorrhagic events were recorded. Total cholesterol was positively associated with risk of non-haemorrhagic events, but only for levels > 8 mmol/l, corresponding to the upper 5% of the distribution in the study population. For lower plasma cholesterol values the relative risk remained nearly constant. Plasma triglyceride concentration was significantly, positively associated with risk of non-haemorrhagic events. The relative risk corresponding to an increase of 1 mmol/l was 1.12 (95% confidence interval 1.07 to 1.16). There was a negative, log linear association between high density lipoprotein cholesterol and risk of non-haemorrhagic events (0.53 (0.34 to 0.83)). There was no indication that the effects of plasma lipids were different in women and men. CONCLUSIONS--The pattern of the association between plasma cholesterol and risk of ischaemic cerebrovascular disease was not log linear, and the increased risk was confined to the upper 5% of the cholesterol distribution. Further studies should concentrate on the association between plasma cholesterol and verified haemorrhagic stroke. PMID

  20. Non-equilibrium phase behavior and friction of confined molecular films under shear: A non-equilibrium molecular dynamics study

    NASA Astrophysics Data System (ADS)

    Maćkowiak, Sz.; Heyes, D. M.; Dini, D.; Brańka, A. C.

    2016-10-01

    The phase behavior of a confined liquid at high pressure and shear rate, such as is found in elastohydrodynamic lubrication, can influence the traction characteristics in machine operation. Generic aspects of this behavior are investigated here using Non-equilibrium Molecular Dynamics (NEMD) simulations of confined Lennard-Jones (LJ) films under load with a recently proposed wall-driven shearing method without wall atom tethering [C. Gattinoni et al., Phys. Rev. E 90, 043302 (2014)]. The focus is on thick films in which the nonequilibrium phases formed in the confined region impact on the traction properties. The nonequilibrium phase and tribological diagrams are mapped out in detail as a function of load, wall sliding speed, and atomic scale surface roughness, which is shown can have a significant effect. The transition between these phases is typically not sharp as the external conditions are varied. The magnitude of the friction coefficient depends strongly on the nonequilibrium phase adopted by the confined region of molecules, and in general does not follow the classical friction relations between macroscopic bodies, e.g., the frictional force can decrease with increasing load in the Plug-Slip (PS) region of the phase diagram owing to structural changes induced in the confined film. The friction coefficient can be extremely low (˜0.01) in the PS region as a result of incommensurate alignment between a (100) face-centered cubic wall plane and reconstructed (111) layers of the confined region near the wall. It is possible to exploit hysteresis to retain low friction PS states well into the central localization high wall speed region of the phase diagram. Stick-slip behavior due to periodic in-plane melting of layers in the confined region and subsequent annealing is observed at low wall speeds and moderate external loads. At intermediate wall speeds and pressure values (at least) the friction coefficient decreases with increasing well depth of the LJ potential

  1. Influence of loading-rate and steel fibers on the shear strength of ultra high performance concrete

    NASA Astrophysics Data System (ADS)

    Bratislav, Lukic; Pascal, Forquin

    2015-09-01

    The paper describes quasi-static and dynamic experimental methods used to examine the confined shear strength of an Ultra High Performance Concrete, with and without the presence of steel fibers in the concrete composition. An experimental setup was created to investigate the concrete shear strength under quasi-static loading regime using a hydraulic press Schenk while dynamic shear strength was characterized by subjecting concrete samples to dynamic loading through a modified Split Hopkinson Pressure Bar. Both methods are based on a Punch Through Shear (PTS) test with a well-instrumented aluminum passive confinement ring that allows measuring the change of radial stress in the shear ligament throughout the test. Firstly, four equally distributed radial notches have been performed in order to deduce the radial stress by suppressing a self-confinement of the sample peripheral part. However, by analyzing the strain gauge data from the confinement ring, it has been noticed that these were apparently insufficient, especially for fiber-reinforced samples, resulting in subsequently practicing eight radial notches through the sample peripheral part. The results obtained from both procedures are reported and discussed.

  2. Influence of pore roughness on high-frequency permeability

    NASA Astrophysics Data System (ADS)

    Cortis, Andrea; Smeulders, David M. J.; Guermond, Jean Luc; Lafarge, Denis

    2003-06-01

    The high-frequency behavior of the fluid velocity patterns for smooth and corrugated pore channels is studied. The classical approach of Johnson et al. [J. Fluid Mech. 176, 379 (1987)] for smooth geometries is obtained in different manners, thus clarifying differences with Sheng and Zhou [Phys. Rev. Lett. 61, 1591 (1988)] and Avellaneda and Torquato [Phys. Fluids A 3, 2529 (1991)]. For wedge-shaped pore geometries, the classical approach is modified by a nonanalytic extension proposed by Achdou and Avellaneda [Phys. Fluids A 4, 2561 (1992)]. The dependency of the nonanalytic extension on the apex angle of the wedge was derived. Precise numerical computations for various apex angles in two-dimensional channels confirmed this theoretical dependency, which is somewhat different from the original Achdou and Avellaneda predictions. Moreover, it was found that the contribution of the singularities does not alter the parameters of the classical theory by Johnson et al..

  3. High tibial osteotomy: factors influencing the duration of satisfactory function.

    PubMed

    Giagounidis, E M; Sell, S

    1999-01-01

    In 94 patients 112 knees were examined after high tibial osteotomy for varus and valgus gonarthrosis. Preoperatively, there were 71 varus and 23 valgus deformities. The mean follow-up period was 9.0 years (range 2-21 years). Concerning the pain on walking and the pain at rest, we noted good and excellent results in 73% and 65%, respectively. The radiological evaluation showed an improvement or a persistence of the stage of arthrosis in 69.5% of the reviewed cases. The results according to the HSS score as an objective parameter showed in over 50% an improvement of the patients' situation. The data were subjected to multivariate statistical analysis in which three of four evaluated risk factors were found to be associated with the duration of pain-free survival: certain preoperative injuries, preoperative meniscopathies and a deterioration of the stage of arthrosis (P < 0.05). There was no significance for weight in excess of 10% above the normal body mass index (BMI) limits. However, in a Kaplan-Meier survival analysis this parameter could be determined as a significant factor for a reduced pain-free survival interval (P < 0.05): patients with a BMI of more than 10% above normal limits had a pain-free period of 5.07 years, whereas those with a BMI of less than 10% had a pain-free period of 7.80 years.

  4. An Analysis of Stimuli that Influence Compliance during the High-Probability Instruction Sequence

    ERIC Educational Resources Information Center

    Normand, Matthew P.; Kestner, Kathryn; Jessel, Joshua

    2010-01-01

    When we evaluated variables that influence the effectiveness of the high-probability (high-p) instruction sequence, the sequence was associated with a precipitous decrease in compliance with high-"p" instructions for 1 participant, thereby precluding continued use of the sequence. We investigated the reasons for this decrease. Stimuli associated…

  5. The Influence of High-Stakes Testing on Science Teacher Perceptions and Practices

    ERIC Educational Resources Information Center

    Davis, Melissa Ferman

    2011-01-01

    The purpose of this study was to examine influences of standards-based reform and high-stakes testing on teacher practices and perceptions in high school science classrooms. A literature review suggested that teacher practices and perceptions are affected by emphasis on standards-based reform and high-stakes testing and that state level…

  6. Fueling of magnetic-confinement devices

    SciTech Connect

    Milora, S.L.

    1981-01-01

    A general overview of the fueling of magnetic confinement devices is presented, with particular emphasis on recent experimental results. Various practical fueling mechanisms are considered, such as cold gas inlet (or plasma edge fueling), neutral beam injection, and injection of high speed cryogenic hydrogen pellets. The central role played by charged particle transport and recycle of plasma particles from material surfaces in contact with the plasma is discussed briefly. The various aspects of hydrogen pellet injection are treated in detail, including applications to the production of high purity startup plasmas for stellarators and other devices, refueling of tokamak plasmas, pellet ablation theory, and the technology and performance characteristics of low and high speed pellet injectors.

  7. Proving Nontrivial Topology of Pure Bismuth by Quantum Confinement

    NASA Astrophysics Data System (ADS)

    Ito, S.; Feng, B.; Arita, M.; Takayama, A.; Liu, R.-Y.; Someya, T.; Chen, W.-C.; Iimori, T.; Namatame, H.; Taniguchi, M.; Cheng, C.-M.; Tang, S.-J.; Komori, F.; Kobayashi, K.; Chiang, T.-C.; Matsuda, I.

    2016-12-01

    The topology of pure Bi is controversial because of its very small (˜10 meV ) band gap. Here we perform high-resolution angle-resolved photoelectron spectroscopy measurements systematically on 14-202 bilayer Bi films. Using high-quality films, we succeed in observing quantized bulk bands with energy separations down to ˜10 meV . Detailed analyses on the phase shift of the confined wave functions precisely determine the surface and bulk electronic structures, which unambiguously show nontrivial topology. The present results not only prove the fundamental property of Bi but also introduce a capability of the quantum-confinement approach.

  8. Cholesterol modulates CFTR confinement in the plasma membrane of primary epithelial cells.

    PubMed

    Abu-Arish, Asmahan; Pandzic, Elvis; Goepp, Julie; Matthes, Elizabeth; Hanrahan, John W; Wiseman, Paul W

    2015-07-07

    The cystic fibrosis transmembrane conductance regulator (CFTR) is a plasma-membrane anion channel that, when mutated, causes the disease cystic fibrosis. Although CFTR has been detected in a detergent-resistant membrane fraction prepared from airway epithelial cells, suggesting that it may partition into cholesterol-rich membrane microdomains (lipid rafts), its compartmentalization has not been demonstrated in intact cells and the influence of microdomains on CFTR lateral mobility is unknown. We used live-cell imaging, spatial image correlation spectroscopy, and k-space image correlation spectroscopy to examine the aggregation state of CFTR and its dynamics both within and outside microdomains in the plasma membrane of primary human bronchial epithelial cells. These studies were also performed during treatments that augment or deplete membrane cholesterol. We found two populations of CFTR molecules that were distinguishable based on their dynamics at the cell surface. One population showed confinement and had slow dynamics that were highly cholesterol dependent. The other, more abundant population was less confined and diffused more rapidly. Treatments that deplete the membrane of cholesterol caused the confined fraction and average number of CFTR molecules per cluster to decrease. Elevating cholesterol had the opposite effect, increasing channel aggregation and the fraction of channels displaying confinement, consistent with CFTR recruitment into cholesterol-rich microdomains with dimensions below the optical resolution limit. Viral infection caused the nanoscale microdomains to fuse into large platforms and reduced CFTR mobility. To our knowledge, these results provide the first biophysical evidence for multiple CFTR populations and have implications for regulation of their surface expression and channel function.

  9. Enhanced ionic liquid mobility induced by confinement in 1D CNT membranes

    NASA Astrophysics Data System (ADS)

    Berrod, Q.; Ferdeghini, F.; Judeinstein, P.; Genevaz, N.; Ramos, R.; Fournier, A.; Dijon, J.; Ollivier, J.; Rols, S.; Yu, D.; Mole, R. A.; Zanotti, J.-M.

    2016-04-01

    Water confined within carbon nanotubes (CNT) exhibits tremendous enhanced transport properties. Here, we extend this result to ionic liquids (IL) confined in vertically aligned CNT membranes. Under confinement, the IL self-diffusion coefficient is increased by a factor 3 compared to its bulk reference. This could lead to high power battery separators.Water confined within carbon nanotubes (CNT) exhibits tremendous enhanced transport properties. Here, we extend this result to ionic liquids (IL) confined in vertically aligned CNT membranes. Under confinement, the IL self-diffusion coefficient is increased by a factor 3 compared to its bulk reference. This could lead to high power battery separators. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr01445c

  10. Generic transport coefficients of a confined electrolyte solution

    NASA Astrophysics Data System (ADS)

    Yoshida, Hiroaki; Mizuno, Hideyuki; Kinjo, Tomoyuki; Washizu, Hitoshi; Barrat, Jean-Louis

    2014-11-01

    Physical parameters characterizing electrokinetic transport in a confined electrolyte solution are reconstructed from the generic transport coefficients obtained within the classical nonequilibrium statistical thermodynamic framework. The electro-osmotic flow, the diffusio-osmotic flow, the osmotic current, as well as the pressure-driven Poiseuille-type flow, the electric conduction, and the ion diffusion are described by this set of transport coefficients. The reconstruction is demonstrated for an aqueous NaCl solution between two parallel charged surfaces with a nanoscale gap, by using the molecular dynamic (MD) simulations. A Green-Kubo approach is employed to evaluate the transport coefficients in the linear-response regime, and the fluxes induced by the pressure, electric, and chemical potential fields are compared with the results of nonequilibrium MD simulations. Using this numerical scheme, the influence of the salt concentration on the transport coefficients is investigated. Anomalous reversal of diffusio-osmotic current, as well as that of electro-osmotic flow, is observed at high surface charge densities and high added-salt concentrations.

  11. Thermoelectricity in Confined Liquid Electrolytes.

    PubMed

    Dietzel, Mathias; Hardt, Steffen

    2016-06-03

    The electric field in an extended phase of a liquid electrolyte exposed to a temperature gradient is attributed to different thermophoretic mobilities of the ion species. As shown herein, such Soret-type ion thermodiffusion is not required to induce thermoelectricity even in the simplest electrolyte if it is confined between charged walls. The space charge of the electric double layer leads to selective ion diffusion driven by a temperature-dependent electrophoretic ion mobility, which-for narrow channels-may cause thermovoltages larger in magnitude than for the classical Soret equilibrium.

  12. Confined Space Imager (CSI) Software

    SciTech Connect

    Karelilz, David

    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.

  13. 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.

  14. 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.

  15. 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

  16. Length of the School Day and Its Influence on New Jersey High School Proficiency Assessment Scores

    ERIC Educational Resources Information Center

    deAngelis, Phyllis

    2016-01-01

    This paper presents results from an examination of the relationships between high school (HS) school day length and 2011 New Jersey High School Proficiency Assessment (HSPA) Math and Language Arts Literacy test results. Variables found to have an influence on standardized test scores in the extant literature were evaluated and reported.…

  17. Faculty Mobility and Its Influence on New Jersey High School Proficiency Assessment Scores

    ERIC Educational Resources Information Center

    Graziano, Dana; Babo, Gerard

    2014-01-01

    This paper presents results from an examination of the relationships between high school (HS) faculty mobility and 2009-2010 New Jersey High School Proficiency Assessment (HSPA) Math and Language Arts Literacy test results. Variables found to have an influence on standardized test scores in the extant literature were evaluated and reported.…

  18. Factors That Influence a Student Not To Enter into a High School Vocational Curriculum.

    ERIC Educational Resources Information Center

    Rossetti, Rosemarie

    In view of the steady decline in vocational enrollments since 1979, a study was conducted to identify factors that influence students not to enter into a high school vocational curriculum. The study questionnaire was given to 633 nonvocational 11th-grade students from 5 randomly selected southwestern Ohio high schools. One month after the student…

  19. The Influence of Performance Accountability Culture on the Work of High School Principals

    ERIC Educational Resources Information Center

    Cohen, Michael Ian

    2011-01-01

    This study examined the way performance accountability culture influenced the work of public high school principals. A qualitative multiple case study design was used to discover the way principals responded to, and coped with, performance accountability culture at the local level. Interviews of nine high school principals in the state of New…

  20. Influences on Students Selecting Cooperative Education Programs in Michigan High Schools. Final Report.

    ERIC Educational Resources Information Center

    Woloszyk, Carl A.

    Factors influencing the decision of high school students to enroll in cooperative education programs were investigated in a survey. The stratified random sample consisted of 275 high school students currently enrolled in cooperative education programs in five different types of communities throughout Michigan. The survey questionnaire included 8…

  1. 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).

  2. Analysis of Factors Influencing Interest in STEM Career: Comparison between American and Turkish High School Students with High Ability

    ERIC Educational Resources Information Center

    Bahar, Abdulkadir; Adiguzel, Tufan

    2016-01-01

    The low number of students studying or applying for STEM subjects and workforce demand has been prioritized in almost all countries policies. This study intended to examine factors that influenced American and Turkish students to pursue a degree or career in STEM-related fields. Participants of the study were 86 high-ability students selected from…

  3. Price and maternal obesity influence purchasing of low- and high-energy-dense foods2

    PubMed Central

    Epstein, Leonard H; Dearing, Kelly K; Paluch, Rocco A; Roemmich, James N; Cho, David

    2007-01-01

    Background Price can influence food purchases, which can influence consumption. Limited laboratory research has assessed the effect of price changes on food purchases, and no research on individual differences that may interact with price to influence purchases exists. Objective We aimed to assess the influence of price changes of low-energy-density (LED) and high-energy-density (HED) foods on mother’s food purchases in a laboratory food-purchasing analogue. Design Mothers were randomly assigned to price conditions in which the price of either LED or HED foods was manipulated from 75% to 125% of the reference purchase price, whereas the price of the alternative foods was kept at the reference value. Mothers completed purchases for 2 income levels ($15 or $30 per family member). Results Purchases were reduced when prices of LED (P < 0.01) and HED (P < 0.001) foods were increased. Maternal BMI interacted with price to influence purchases of HED foods when the price of HED foods increased (P = 0.016) and interacted with price to influence purchases of LED foods when the price of HED foods increased (P = 0.008). Conclusion These results show the relevance of considering price change as a way to influence food purchases of LED compared with HED foods and the possibility that individual differences may influence the own-price elasticity of HED foods and substitution of LED for HED foods. PMID:17921365

  4. Chain confinement drives the mechanical properties of nanoporous polymers

    NASA Astrophysics Data System (ADS)

    Tang, Shan; Greene, M. Steven; Peng, Xiang He; Liu, Wing Kam; Guo, Zao Yang

    2014-05-01

    Recent experiments using nanoindentation and buckling-based metrology (Stafford C. M. et al., Nat. Mater., 3 (2004) 545) have shown the elastic modulus of submicron-nano porous polymers to be lower than that predicted by classical homogenization or finite element simulations, especially at high porosities. This letter presents a model that captures the experimentally observed elastic modulus of nanoporous polymers by assuming that polymer chains are less confined in the interfacial layer close to the free surface of voids than in the bulk. The confinement assumption is incorporated into a recently proposed hyperelastic model, wherein low values of confinement parameters are needed to match the observed mechanical moduli of these materials. Evidence from molecular dynamics and physical experiments further supports the conclusion that variable chain confinement at material interfaces drives the mechanical behavior in nanoporous polymers due to the increasing importance of surface effects. The effect of confinement on instability under compression is also demonstrated since instability may be exploited to create porous polymers with tunable acoustic, electronic or optic properties.

  5. The effect of boundary adaptivity on hexagonal ordering and bistability in circularly confined quasi hard discs.

    PubMed

    Williams, Ian; Oğuz, Erdal C; Jack, Robert L; Bartlett, Paul; Löwen, Hartmut; Royall, C Patrick

    2014-03-14

    The behaviour of materials under spatial confinement is sensitively dependent on the nature of the confining boundaries. In two dimensions, confinement within a hard circular boundary inhibits the hexagonal ordering observed in bulk systems at high density. Using colloidal experiments and Monte Carlo simulations, we investigate two model systems of quasi hard discs under circularly symmetric confinement. The first system employs an adaptive circular boundary, defined experimentally using holographic optical tweezers. We show that deformation of this boundary allows, and indeed is required for, hexagonal ordering in the confined system. The second system employs a circularly symmetric optical potential to confine particles without a physical boundary. We show that, in the absence of a curved wall, near perfect hexagonal ordering is possible. We propose that the degree to which hexagonal ordering is suppressed by a curved boundary is determined by the "strictness" of that wall.

  6. Engineered Models of Confined Cell Migration

    PubMed Central

    Paul, Colin D.; Hung, Wei-Chien; Wirtz, Denis; Konstantopoulos, Konstantinos

    2017-01-01

    Cells in the body are physically confined by neighboring cells, tissues, and the extracellular matrix. Although physical confinement modulates intracellular signaling and the underlying mechanisms of cell migration, it is difficult to study in vivo. Furthermore, traditional two-dimensional cell migration assays do not recapitulate the complex topographies found in the body. Therefore, a number of experimental in vitro models that confine and impose forces on cells in well-defined microenvironments have been engineered. We describe the design and use of microfluidic microchannel devices, grooved substrates, micropatterned lines, vertical confinement devices, patterned hydrogels, and micropipette aspiration assays for studying cell responses to confinement. Use of these devices has enabled the delineation of changes in cytoskeletal reorganization, cell–substrate adhesions, intracellular signaling, nuclear shape, and gene expression that result from physical confinement. These assays and the physiologically relevant signaling pathways that have been elucidated are beginning to have a translational and clinical impact. PMID:27420571

  7. Methods for two-dimensional cell confinement.

    PubMed

    Le Berre, Maël; Zlotek-Zlotkiewicz, Ewa; Bonazzi, Daria; Lautenschlaeger, Franziska; Piel, Matthieu

    2014-01-01

    Protocols described in this chapter relate to a method to dynamically confine cells in two dimensions with various microenvironments. It can be used to impose on cells a given height, with an accuracy of less than 100 nm on large surfaces (cm(2)). The method is based on the gentle application of a modified glass coverslip onto a standard cell culture. Depending on the preparation, this confinement slide can impose on the cells a given geometry but also an environment of controlled stiffness, controlled adhesion, or a more complex environment. An advantage is that the method is compatible with most optical microscopy technologies and molecular biology protocols allowing advanced analysis of confined cells. In this chapter, we first explain the principle and issues of using these slides to confine cells in a controlled geometry and describe their fabrication. Finally, we discuss how the nature of the confinement slide can vary and provide an alternative method to confine cells with gels of controlled rigidity.

  8. Using off-diagonal confinement as a cooling method

    SciTech Connect

    Rousseau, V. G.; Hettiarachchilage, K.; Jarrell, M.; Moreno, J.; Sheehy, D. E.

    2010-12-15

    In a recent letter [Phys. Rev. Lett. 104, 167201 (2010)] we proposed a new confining method for ultracold atoms on optical lattices, which is based on off-diagonal confinement (ODC). This method was shown to have distinct advantages over the conventional diagonal confinement (DC), which makes use of a trapping potential, such as the existence of pure Mott phases and highly populated condensates. In this manuscript we show that the ODC method can also lead to lower temperatures than the DC method for a wide range of control parameters. Using exact diagonalization we determine this range of parameters for the hard-core case and then we extend our results to the soft-core case by performing quantum Monte Carlo (QMC) simulations for both DC and ODC systems at fixed temperature and analyzing the corresponding entropies. We also propose a method for measuring the entropy in QMC simulations.

  9. Self-organizing human cardiac microchambers mediated by geometric confinement

    NASA Astrophysics Data System (ADS)

    Ma, Zhen; Wang, Jason; Loskill, Peter; Huebsch, Nathaniel; Koo, Sangmo; Svedlund, Felicia L.; Marks, Natalie C.; Hua, Ethan W.; Grigoropoulos, Costas P.; Conklin, Bruce R.; Healy, Kevin E.

    2015-07-01

    Tissue morphogenesis and organ formation are the consequences of biochemical and biophysical cues that lead to cellular spatial patterning in development. To model such events in vitro, we use PEG-patterned substrates to geometrically confine human pluripotent stem cell colonies and spatially present mechanical stress. Modulation of the WNT/β-catenin pathway promotes spatial patterning via geometric confinement of the cell condensation process during epithelial-mesenchymal transition, forcing cells at the perimeter to express an OCT4+ annulus, which is coincident with a region of higher cell density and E-cadherin expression. The biochemical and biophysical cues synergistically induce self-organizing lineage specification and creation of a beating human cardiac microchamber confined by the pattern geometry. These highly defined human cardiac microchambers can be used to study aspects of embryonic spatial patterning, early cardiac development and drug-induced developmental toxicity.

  10. Electromagnetic confinement and movement of thin sheets of molten metal

    DOEpatents

    Lari, Robert J.; Praeg, Walter F.; Turner, Larry R.

    1990-01-01

    An apparatus capable of producing a combination of magnetic fields that can retain a metal in liquid form in a region having a smooth vertical boundary including a levitation magnet that produces low frequency magnetic field traveling waves to retain the metal and a stabilization magnet that produces a high frequency magnetic field to produce a smooth vertical boundary. As particularly adapted to the casting of solid metal sheets, a metal in liquid form can be continuously fed into one end of the confinement region produced by the levitation and stabilization magnets and removed in solid form from the other end of confinement region. An additional magnet may be included for support at the edges of the confinement region where eddy currents loop.

  11. The role of collisions and scattering in differential confinement

    NASA Astrophysics Data System (ADS)

    Ochs, Ian; Fisch, Nathaniel; Gueroult, Renaud; Zweben, Stewart

    2016-10-01

    Much of plasma physics is concerned with the overall confinement of all species present. However, in certain applications, it is desirable to confine some species while allowing others to escape, or to have different species escape to different regions. In this study, we examine one class of differential confinement system, the plasma mass filter, and evaluate the regimes of feasible operation given realistic confounding effects such as collisions with neutrals and ions, turbulence, and radiative losses. In schemes that rely on Larmor motion, we find that the low-temperature requirement imposed by line radiation necessitates a large ( 1 T) magnetic field at the densities required for high throughput, since the Coulomb collision frequency scales as T - 3 / 2. There are, however, a variety of ways that may be contemplated to achieve separation effects.

  12. 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

  13. Inertial-Electrostatic Confinement (IEC) Fusion for Space Propulsion

    NASA Technical Reports Server (NTRS)

    Nadler, Jon

    1999-01-01

    An Inertial-Electrostatic Confinement (IEC) device was assembled at the Marshall Space Flight Center (MSFC) Propulsion Research Center (PRC) to study the possibility of using EEC technology for deep space propulsion and power. Inertial-Electrostatic Confinement is capable of containing a nuclear fusion plasma in a series of virtual potential wells. These wells would substantially increase plasma confinement, possibly leading towards a high-gain, breakthrough fusion device. A one-foot in diameter IEC vessel was borrowed from the Fusion Studies Laboratory at the University of Illinois@Urbana-Champaign for the summer. This device was used in initial parameterization studies in order to design a larger, actively cooled device for permanent use at the PRC.

  14. Inertial-Electrostatic Confinement (IEC) Fusion For Space Propulsion

    NASA Technical Reports Server (NTRS)

    Nadler, Jon

    1999-01-01

    An Inertial-Electrostatic Confinement (IEC) device was assembled at the Marshall Space Flight Center (MSFC) Propulsion Research Center (PRC) to study the possibility of using IEC technology for deep space propulsion and power. Inertial-Electrostatic Confinement is capable of containing a nuclear fusion plasma in a series of virtual potential wells. These wells would substantially increase plasma confinement, possibly leading towards a high-gain, breakthrough fusion device. A one-foot in diameter IEC vessel was borrowed from the Fusion Studies Laboratory at the University of Illinois @ Urbana-Champaign for the summer. This device was used in initial parameterization studies in order to design a larger, actively cooled device for permanent use at the PRC.

  15. Confinement-dependent localization of diffusing aggregates in cellular geometries.

    PubMed

    Keramati, Mahdi Rezaei; Wasnik, Vaihbav; Ping, Liyan; Das, Dibyendu; Emberly, Eldon

    2015-01-01

    Confinement has a strong influence on diffusing nano-sized clusters. In particular, biomolecular aggregates within the shell-like confining space of a bacterial cell have been shown to display a variety of localization patterns, from being midcell to the poles. How does the confining space determine where the aggregate will localize? Here, using Monte Carlo simulations we have calculated the equilibrium spatial distribution of fixed-sized clusters diffusing in spherocylindrical shells. We find that localization to the poles depends strongly on shell thickness and the size of the cluster. Compared to being at midcell, polar clusters can be more bent and hence have higher energy, but they also can have a greater number of defects and hence have more entropy. Under certain conditions this can lead to polar clusters having a lower free energy than at midcell, favoring localization to the poles. Our findings suggest possible localization selection mechanisms within shell-like geometries that can arise purely from cluster confinement.

  16. Confinement effects on chemical reactions in nanostructured carbon materials

    NASA Astrophysics Data System (ADS)

    George, Aaron; Kostov, Milen; Buongiorno Nardelli, Marco

    2005-03-01

    Chemical reactions are frequently carried out in nano-structured media, such as micellar or colloidal solutions, nano-porous media, hydrogels or organogels, or in systems involving nano-particles. Nanostructured environments have been shown to enhance reaction rates through a variety of catalytic effects, such as high surface area, interactions with the nano-structure or confinement. In this work, we have used state-of-the-art electronic structure techniques to study the prototypical example of the hydrogen-producing reaction of formaldehyde dissociation (H2CO -> H2 + CO) within various configurations of a graphitic pore. Using the Nudged Elastic Band (NEB) method for transition states analysis, we have found that the activation energy of the dissociation can be influenced by the presence of a graphitic pore. In particular, while a graphene surface reduces the activation barrier for the reaction, this catalytic effect is enhanced by the presence of two planar sheets, which mimic the geometry of a nano-pore. These findings will be discussed in terms of the charge transfer and/or polarization mechanism associated with the catalytic process.

  17. Antibacterial performance of nanocrystallined titania confined in mesoporous silica nanotubes.

    PubMed

    Cendrowski, Krzysztof; Peruzynska, Magdalena; Markowska-Szczupak, Agata; Chen, Xuecheng; Wajda, Anna; Lapczuk, Joanna; Kurzawski, Mateusz; Kalenczuk, Ryszard J; Drozdzik, Marek; Mijowska, Ewa

    2014-06-01

    In this paper, we study synthesis and characteristics of mesoporous silica nanotubes modified by titanium dioxide, as well as their antimicrobial properties and influence on mitochondrial activity of mouse fibroblast L929. Nanocrystalized titania is confined in mesopores of silica nanotubes and its light activated antibacterial response is revealed. The analysis of the antibacterial effect on Escherichia coli. (ATCC 25922) shows strong enhancement during irradiation with the artificial visible and ultraviolet light in respect to the commercial catalyst and control sample free from the nanomaterials. In darkness, the mesoporous silica/titania nanostructures exhibited antibacterial activity dependent on the stirring speed of the suspension containing nanomaterials. Obtained micrograph proved internalization of the sample into the microorganism trough the cell membrane. The analysis of the mitochondrial activity and amount of lactate dehydrogenase released from mouse fibroblast cells L929 in the presence of the sample were determined with LDH and WST1 assays, respectively. The synthesized silica/titania antibacterial agent also exhibits pronounced photoinduced inactivation of the bacterial growth under the artificial visible and UV light irritation in respect to the commercial catalyst. Additionally, mesoporous silica/titania nanotubes were characterized in details by means of high resolution transmission electron microscopy (HR-TEM), XRD and BET Isotherm.

  18. Molecular Motion and Confined Polymers

    NASA Astrophysics Data System (ADS)

    Dobrynin, Andrey V.; Jeon, Junhwan

    2004-03-01

    Microorganisms such as myxobacteria, cyanobacteria, and flexibacteria move by gliding. The gliding has been described by two quite different mechanisms: social (S) motility and adventurous (A) motility. Though retraction of type 4-pili provides the force for the S motility, extrusion of slime, which may be associated with the A motility, is not well known. Nozzle-like structures recently found in cyanobacteria can support the A motility. However, complete understaning A motility is still lacking. To describe the A motility, we use molecular dynamics simulations of a polymer growing inside a cylindrically shaped tube with one end capped. Confined polymers provide a driving force for a tube motion as if a rocket flew with emitting gas. It is seen from the mean-squared displacement of a tube that its motion is ballistic under constant applied force.

  19. Multishell inertial confinement fusion target

    DOEpatents

    Holland, James R.; Del Vecchio, Robert M.

    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.

  20. Multishell inertial confinement fusion target

    DOEpatents

    Holland, James R.; Del Vecchio, Robert M.

    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.

  1. Confinement and heating of a deuterium-tritium plasma

    SciTech Connect

    Hawryluk, R. J.; Adler, H.; Alling, P.; Synakowski, E.

    1994-03-01

    The Tokamak Fusion Test Reactor (TFTR) has performed initial high-power experiments with the plasma fueled by deuterium and tritium to nominally equal densities. Compared to pure deuterium plasmas, the energy stored in the electron and ions increased by ~20%. These increases indicate improvements in confinement associated with the use of tritium and possibly heating of electrons by α-particles.

  2. 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.

  3. Coaxial Compound Helicopter for Confined Urban Operations

    NASA Technical Reports Server (NTRS)

    Johnson, Wayne; Elmore, Joshua F.; Keen, Ernest B.; Gallaher, Andrew T.; Nunez, Gerardo F.

    2016-01-01

    A rotorcraft was designed for military operations in a confined urban environment. The specifications included major increases in useful load, range, and speed relative current aircraft capabilities, with a size constraint based on the dimensions of urban streets and intersections. Analysis showed that this combination of requirements is best satisfied by a coaxial main-rotor configuration, with lift compounding to off-load the rotors at high speed, and ducted fans under the rotor disk for propulsion. The baseline design is described, and the aircraft performance is summarized for utility, attack, MEDEVAC, and cargo delivery missions. The impact on size and performance is examined for a number of excursions, including lift-offset main rotors. Technology development required to achieve this advance in capability is recommended.

  4. Normal modes of confined cold ionic systems

    SciTech Connect

    Schiffer, J.P.; Dubin, D.H.

    1995-08-01

    The normal modes of a cloud of confined ions forming a strongly-correlated plasma were investigated. The results of molecular-dynamics simulations were compared to predictions of a cold fluid mode. Mode frequencies are observed to shift slightly compared to the cold fluid predictions, and the modes are also observed to damp in time. Simulations also reveal a set of torsional oscillations which have no counterpart in cold fluid theory. The frequency shift, damping, and torsional effects are compared to a model that treats trapped plasmas as a visco-elastic spheroid. It may be possible to measure high-frequency bulk and shear moduli of a strongly-correlated plasma from mode excitation experiments on trapped non-neutral plasmas. An example of the results of the calculation is presented.

  5. The influence of high intensity terahertz radiation on mammalian cell adhesion, proliferation and differentiation

    NASA Astrophysics Data System (ADS)

    Williams, Rachel; Schofield, Amy; Holder, Gareth; Downes, Joan; Edgar, David; Harrison, Paul; Siggel-King, Michele; Surman, Mark; Dunning, David; Hill, Stephen; Holder, David; Jackson, Frank; Jones, James; McKenzie, Julian; Saveliev, Yuri; Thomsen, Neil; Williams, Peter; Weightman, Peter

    2013-01-01

    Understanding the influence of exposure of biological systems to THz radiation is becoming increasingly important. There is some evidence to suggest that THz radiation can influence important activities within mammalian cells. This study evaluated the influence of the high peak power, low average power THz radiation produced by the ALICE (Daresbury Laboratory, UK) synchrotron source on human epithelial and embryonic stem cells. The cells were maintained under standard tissue culture conditions, during which the THz radiation was delivered directly into the incubator for various exposure times. The influence of the THz radiation on cell morphology, attachment, proliferation and differentiation was evaluated. The study demonstrated that there was no difference in any of these parameters between irradiated and control cell cultures. It is suggested that under these conditions the cells are capable of compensating for any effects caused by exposure to THz radiation with the peak powers levels employed in these studies.

  6. Spatially Confined Propagation of Intense Ultraviolet Radiation in Plasmas.

    NASA Astrophysics Data System (ADS)

    Shi, Xiaomei

    X-ray amplification requires a high energy deposition rate in a high aspect-ratio volume. High power lasers for x-ray laser pumping have become available with the development of the short pulse and high intensity laser technology capable of producing pulses with a peak power as high as 10^{12} watts. Short pulses of high intensity x-ray have been observed in laser -plasma interactions, which encurages many scientists actively pursuing the goal of constructing practical x-ray lasers. Our approach has concentrated on producing high aspect ratio x-ray amplifying medium by spatially confined propagation of high power laser pulse in plasmas. A high intensity laser beam induces nonlinear refractive index changes in plasma. In the case of subpicosecond ultrahigh power laser-plasma interaction, the dominant mechanisms responsible for the refractive index change in plasmas are: (1) the relativistic free electron mass increase due to the increase of electron oscillation velocity in the intense electromagnetic field of the laser pulses; and (2) displacement of free electrons out of the high intensity region of the laser beam by ponderomotive force. Both of the above effects lead to a refractive index change of the plasma, which in turn has a positive lensing effect on the beam. If the focusing effect is strong enough to overcome diffraction the beam will stay in a spatially confined mode of propagation. This confined propagation provides an effective method of concentrating energy. The field intensity associated with the confined propagation is so high that the highly excited medium with high aspect ratio suitable for x-ray amplification can be achieved. In this research we have successfully demonstrated spatially confined propagation of 500 GW subpicosecond laser pulse in laser induced plasma. The measured diameter of the propagation is less than 2 μm and the aspect ratio of the confined propagation is over 1000. The filed intensity associated with the propagation is

  7. Utilizing STEM experiential learning to influence attitudes, skills, and knowledge in urban high school

    NASA Astrophysics Data System (ADS)

    Considine, Shannon L.

    This qualitative research study focused on the influence of experiential learning on urban students' performance in science classes. It also explored how experiential learning influenced the development of urban students' independent innovation skills and ability to explore topics in greater depth as required by STEM education. The experiential learning method that was investigated in this study was an Explore College program, which was a program created by a college in the same city as the urban high school that the student participants attended. This program was created with the intent to boost college readiness and aspirations among high-achieving, low-income students in urban schools. The student participants were asked eleven open-ended questions regarding their experience in the Explore College program; they were asked to reflect on the influence that participating that program had on their academic performance in science and on their perspective of science education. The teacher participants were asked ten open-ended questions regarding their opinion of whether student participation in this program influenced their performance in the classroom and in the development of their independent innovation skills. This study detailed the influence that experiential learning had on student academic performance and perspective of science education. Utilizing this type of education will improve student achievement, attitudes towards education and academic success. The completion of the study proved that experiential learning does in fact influence student performance in science, can influence students' perspective of science, and does indeed influence the development of independent innovation skills which are crucial in STEM education.

  8. The effect of confinement length on the stability of planar dense wakes

    NASA Astrophysics Data System (ADS)

    Si, Minqiang; Gupta, Vikrant; Li, Larry K. B.

    2016-11-01

    Planar dense wakes can be found in many industrial processes, such as combustion and paper-making. Confinement is known to make such wakes more locally absolutely unstable, but this destabilizing effect has not been comprehensively examined in real wakes bounded by a finite streamwise domain. For example, it is not known (i) how long the confinement walls should be and (ii) what the critical values of the operating parameters should be for global instability to occur. In this experimental study, we try to answer these questions by examining a planar dense wake consisting of a central stream of CO2 (dense gas) sandwiched by two identical outer streams of air (light gas). The wake is confined by solid walls of variable length, which act as an adjustable confinement. We find that the confinement length has a strong influence on the hydrodynamic stability of the wake: (a) self-excited global oscillations appear only when the confinement length exceeds a critical value and (b) the streamwise location of the wavemaker changes with confinement length. Knowledge of how long the confinement walls should be for global instability to occur under various conditions could be useful for optimizing industrial processes.

  9. Laboratory-scale uranium RF plasma confinement experiments

    NASA Technical Reports Server (NTRS)

    Roman, W. C.

    1976-01-01

    An experimental investigation was conducted using 80 kW and 1.2 MW RF induction heater facilities to aid in developing the technology necessary for designing a self-critical fissioning uranium plasma core reactor. Pure uranium hexafluoride (UF6) was injected into argon-confined, steady-state, RF-heated plasmas in different uranium plasma confinement tests to investigate the characteristics of plamas core nuclear reactors. The objectives were: (1) to confine as high a density of uranium vapor as possible within the plasma while simultaneously minimizing the uranium compound wall deposition; (2) to develop and test materials and handling techniques suitable for use with high-temperature, high-pressure gaseous UF6; and (3) to develop complementary diagnostic instrumentation and measurement techniques to characterize the uranium plasma and residue deposited on the test chamber components. In all tests, the plasma was a fluid-mechanically-confined vortex-type contained within a fused-silica cylindrical test chamber. The test chamber peripheral wall was 5.7 cm ID by 10 cm long.

  10. The Influence of Competence, Motivation, and Organisational Culture to High School Teacher Job Satisfaction and Performance

    ERIC Educational Resources Information Center

    Arifin, H. Muhammad

    2015-01-01

    The study aims to find out and analyze the influence of competence, motivation, and organizational competence to high school teacher job satisfaction and performance in Jayapura City, Papua, Indonesia. The study was conducted on 117 respondents of 346 teachers by means of questionnaire. Data is analyzed by SEM analysis method in AMOS program.…

  11. Response to "Exploring the Influence of the ROC Integrated High School Program"

    ERIC Educational Resources Information Center

    Elrick, Michael

    2007-01-01

    In this article, the author provides a response to Scott Caspell's article "Exploring the Influence of the ROC Integrated High School Program." The author states that Caspell picked an excellent time frame to interview former students as they had participated in the integrated program between 10 and 13 years ago. Ideally, then,…

  12. Students' High School Organizational Leadership Opportunities and Their Influences on Academic Achievement and Civic Participation

    ERIC Educational Resources Information Center

    Elemen, Jennifer E.

    2015-01-01

    The purpose of this quantitative study was to analyze high school leadership praxis for its inclusion of students in organizational leadership dialogue and decision-making and the influences of these factors on student achievement and civic participation. Survey questionnaire data were provided by 215 full-time enrolled undergraduate students from…

  13. Factors that Influence Career Choice among Native American and African American High School Students

    ERIC Educational Resources Information Center

    Bennett-Smith, Keisha K.

    2011-01-01

    There is a need for research in the area of career choice of minority students in the United States. This descriptive study examined the factors that may influence Native American and African American high school students' career choices. These factors include such variables as parental educational level, family composition, and potential grade…

  14. Influence of High School Physical Education on University Student's Physical Activity

    ERIC Educational Resources Information Center

    Kimball, Jessica; Jenkins, Jayne; Wallhead, Tristan

    2009-01-01

    The purpose of this study was to use the Lifelong Physical Activity (LLPA) framework to examine the influence of high school physical education (PE) on university students' level of physical activity (PA). Participants included 365 undergraduate students from the Rocky Mountain West of the USA enrolled in a university physical activity course.…

  15. Disentangling Ethnic and Contextual Influences among Parents Raising Youth in High-Risk Communities

    ERIC Educational Resources Information Center

    Pinderhughes, Ellen E.; Hurley, Sean

    2008-01-01

    This article reports on analyses examining contextual influences on parenting with an ethnically and geographically diverse sample of parents (predominantly mothers) raising 387 children (49% ethnic minority; 51% male) in high-risk communities. Parents and children were followed longitudinally from first through tenth grades. Contextual influences…

  16. Emiratii High School Students' Understandings of Stoichiometry and the Influence of Metacognition on Their Understanding

    ERIC Educational Resources Information Center

    Haidar, Abdullateef H.; Al Naqabi, Ali K.

    2008-01-01

    The aim of this study is to investigate Emiratii high school students' understandings of stoichiometry, their use of metacognitive strategies, and the influence of students' use of metacognitive strategies on their understandings of stoichiometry. Two instruments were used in this study, the first to measure students' understandings of…

  17. High Enrollment Course Success Factors in Virtual School: Factors Influencing Student Academic Achievement

    ERIC Educational Resources Information Center

    Liu, Feng; Cavanaugh, Cathy

    2011-01-01

    This paper describes a study of success factors in high enrollment courses in a K-12 virtual school learning environment. The influence of variables: time student spent in the learning management system (LMS), number of times logged into the LMS, teacher comment, participation in free or reduced lunch programs, student status in the virtual school…

  18. Influences on Member Assimilation in Work Groups in High-Reliability Organizations: A Multilevel Analysis

    ERIC Educational Resources Information Center

    Myers, Karen Kroman; McPhee, Robert D.

    2006-01-01

    This multilevel investigation examined the effect of group interaction and its influence on individual-level membership variables and group assimilation. The study is based on a model of group socialization developed by Moreland and Levine (1982) and was modified in this study to investigate the development and maintenance of highly interdependent…

  19. Glass transition and relaxation dynamics of propylene glycol-water solutions confined in clay

    NASA Astrophysics Data System (ADS)

    Elamin, Khalid; Björklund, Jimmy; Nyhlén, Fredrik; Yttergren, Madeleine; Mârtensson, Lena; Swenson, Jan

    2014-07-01

    The molecular dynamics of aqueous solutions of propylene glycol (PG) and propylene glycol methylether (PGME) confined in a two-dimensional layer-structured Na-vermiculite clay has been studied by broadband dielectric spectroscopy and differential scanning calorimetry. As typical for liquids in confined geometries the intensity of the cooperative α-relaxation becomes considerably more suppressed than the more local β-like relaxation processes. In fact, at high water contents the calorimetric glass transition and related structural α-relaxation cannot even be observed, due to the confinement. Thus, the intensity of the viscosity related α-relaxation is dramatically reduced, but its time scale as well as the related glass transition temperature Tg are for both systems only weakly influenced by the confinement. In the case of the PGME-water solutions it is an important finding since in the corresponding bulk system a pronounced non-monotonic concentration dependence of the glass transition related dynamics has been observed due to the growth of hydrogen bonded relaxing entities of water bridging between PGME molecules [J. Sjöström, J. Mattsson, R. Bergman, and J. Swenson, Phys. Chem. B 115, 10013 (2011)]. The present results suggest that the same type of structural entities are formed in the quasi-two-dimensional space between the clay platelets. It is also observed that the main water relaxation cannot be distinguished from the β-relaxation of PG or PGME in the concentration range up to intermediate water contents. This suggests that these two processes are coupled and that the water molecules affect the time scale of the β-relaxation. However, this is most likely true also for the corresponding bulk solutions, which exhibit similar time scales of this combined relaxation process below Tg. Finally, it is found that at higher water contents the water relaxation does not merge with, or follow, the α-relaxation above Tg, but instead crosses the

  20. Influence of ordering phenomena on the magnetostriction of high Si alloys for electrical applications

    SciTech Connect

    Ros-Yanez, Tanya; Ruiz, Daniel; Lopez, Diego; Hilgert, Tom; Dupre, Luc; Vandenberghe, Robert E.; Houbaert, Yvan

    2005-05-15

    The present work attempts to assess the influence of order phenomena on the magnetostriction of high Fe-Si alloys for electrical applications. The magnetostriction of high silicon electrical steels in the range of 4 to 6 wt. % Si was studied regarding the effect of processing and thermal treatment. In addition, power losses and saturation magnetization measurements were performed and {sup 57}Fe Moessbauer spectroscopy was used to evaluate and quantify the degree of order.

  1. Plasma confinement. [Physics for magnetic geometries

    SciTech Connect

    Boozer, A.H.

    1985-03-01

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

  2. Confinement and the safety factor profile

    SciTech Connect

    Batha, S.H.; Levinton, F.M.; Scott, S.D.

    1995-12-01

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

  3. 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...

  4. Method of high speed flow field influence and restrain on laser communication

    NASA Astrophysics Data System (ADS)

    Meng, Li-xin; Wang, Chun-hui; Qian, Cun-zhu; Wang, Shuo; Zhang, Li-zhong

    2013-08-01

    For laser communication performance which carried by airplane or airship, due to high-speed platform movement, the air has two influences in platform and laser communication terminal window. The first influence is that aerodynamic effect causes the deformation of the optical window; the second one is that a shock wave and boundary layer would be generated. For subsonic within the aircraft, the boundary layer is the main influence. The presence of a boundary layer could change the air density and the temperature of the optical window, which causes the light deflection and received beam spot flicker. Ultimately, the energy hunting of the beam spot which reaches receiving side increases, so that the error rate increases. In this paper, aerodynamic theory is used in analyzing the influence of the optical window deformation due to high speed air. Aero-optics theory is used to analyze the influence of the boundary layer in laser communication link. Based on this, we focused on working on exploring in aerodynamic and aero-optical effect suppression method in the perspective of the optical window design. Based on planning experimental aircraft types and equipment installation location, we optimized the design parameters of the shape and thickness of the optical window, the shape and size of air-management kit. Finally, deformation of the optical window and air flow distribution were simulated by fluid simulation software in the different mach and different altitude fly condition. The simulation results showed that the optical window can inhibit the aerodynamic influence after optimization. In addition, the boundary layer is smoothed; the turbulence influence is reduced, which meets the requirements of the airborne laser communication.

  5. 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.

  6. Azimuthal field instability in a confined ferrofluid.

    PubMed

    Dias, Eduardo O; Miranda, José A

    2015-02-01

    We report the development of interfacial ferrohydrodynamic instabilities when an initially circular bubble of a nonmagnetic inviscid fluid is surrounded by a viscous ferrofluid in the confined geometry of a Hele-Shaw cell. The fluid-fluid interface becomes unstable due to the action of magnetic forces induced by an azimuthal field produced by a straight current-carrying wire that is normal to the cell plates. In this framework, a pattern formation process takes place through the interplay between magnetic and surface tension forces. By employing a perturbative mode-coupling approach we investigate analytically both linear and intermediate nonlinear regimes of the interface evolution. As a result, useful analytical information can be extracted regarding the destabilizing role of the azimuthal field at the linear level, as well as its influence on the interfacial pattern morphology at the onset of nonlinear effects. Finally, a vortex sheet formalism is used to access fully nonlinear stationary solutions for the two-fluid interface shapes.

  7. Water confinement in nanoporous silica materials

    SciTech Connect

    Renou, Richard; Szymczyk, Anthony; Ghoufi, Aziz

    2014-01-28

    The influence of the surface polarity of cylindrical silica nanopores and the presence of Na{sup +} ions as compensating charges on the structure and dynamics of confined water has been investigated by molecular dynamics simulations. A comparison between three different matrixes has been included: a protonated nanopore (PP, with SiOH groups), a deprotonated material (DP, with negatively charged surface groups), and a compensated-charge framework (CC, with sodium cations compensating the negative surface charge). The structure of water inside the different pores shows significant differences in terms of layer organization and hydrogen bonding network. Inside the CC pore the innermost layer is lost to be replaced by a quasi bulk phase. The electrostatic field generated by the DP pore is felt from the surface to the centre of pore leading to a strong orientation of water molecules even in the central part of the pore. Water dynamics inside both the PP and DP pores shows significant differences with respect to the CC pore in which the sub-diffusive regime of water is lost for a superdiffusive regime.

  8. Confined ferrofluid droplet in crossed magnetic fields.

    PubMed

    Jackson, D P; Miranda, J A

    2007-08-01

    When a ferrofluid drop is trapped in a horizontal Hele-Shaw cell and subjected to a vertical magnetic field, a fingering instability results in the droplet evolving into a complex branched structure. This fingering instability depends on the magnetic field ramp rate but also depends critically on the initial state of the droplet. Small perturbations in the initial droplet can have a large influence on the resulting final pattern. By simultaneously applying a stabilizing (horizontal) azimuthal magnetic field, we gain more control over the mode selection mechanism. We perform a linear stability analysis that shows that any single mode can be selected by appropriately adjusting the strengths of the applied fields. This offers a unique and accurate mode selection mechanism for this confined magnetic fluid system. We present the results of numerical simulations that demonstrate that this mode selection mechanism is quite robust and "overpowers" any initial perturbations on the droplet. This provides a predictable way to obtain patterns with any desired number of fingers.

  9. The sensitivity of production temperatures and thermal recharge of low-enthalpy geothermal reservoirs to the thermal conductivity of the confining beds

    NASA Astrophysics Data System (ADS)

    Erbs Poulsen, Søren; Balling, Niels; Bom Nielsen, Søren

    2013-04-01

    The exploration and exploitation of low-enthalpy geothermal energy has increased globally within recent decades in the pursuit of sustainable, low carbon emission energy sources. In 2009 funding was dedicated to a national multi-disciplinary research project with the aim of quantifying the thermal properties and temperature distributions of geothermal reservoirs in Denmark and to develop models for utilisation. The Danish subsurface encompasses low-enthalpy geothermal reservoirs of Triassic, Jurassic, and Cretaceous age with formation temperatures between 40° C and 80° C. In previous literature it is shown that the ratio between the circulation rate in doublet well configurations and the vertical thermal conductivity of confining rocks significantly influences the temporal development in production temperatures in low-enthalpy geothermal reservoirs. We analyse the thermal interplay between a reservoir which is utilised by an injection- and production well, and its confining beds in four conceptual reservoir systems, inspired by the low-enthalpy reservoirs found in Denmark. The analysis is based on state-of-the-art high resolution finite element modelling. Three of the four conceptual reservoirs represent different geological settings in which the confining beds of the reservoir have different thermal conductivities. In the first case, no heat is conducted across the boundaries of the reservoir, which serves merely as a reference. In the three remaining cases, the matrix thermal conductivity of the confining beds is set equal to 1.5, 3 and 4.5 W/m/K. In one additional case study, the anisotropy of the thermal conductivity of the confining beds is increased from 1 (isotropic) to 1.7 (horizontal conductivity is set equal to 1.5 W/m/K). For the considered reservoirs, we calculate the ratio between the accumulated energy that can be attributed conductive heat flow from the confining beds to the reservoir and the accumulated extracted energy from the pumping well

  10. 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.

  11. Behavior of turbulent gas jets in an axisymmetric confinement

    NASA Technical Reports Server (NTRS)

    So, R. M. C.; Ahmed, S. A.

    1985-01-01

    The understanding of the mixing of confined turbulent jets of different densities with air is of great importance to many industrial applications, such as gas turbine and Ramjet combustors. Although there have been numerous studies on the characteristics of free gas jets, little is known of the behavior of gas jets in a confinement. The jet, with a diameter of 8.73 mm, is aligned concentrically in a tube of 125 mm diameter, thus giving a confinement ratio of approximately 205. The arrangement forms part of the test section of an open-jet wind tunnel. Experiments are carried out with carbon dioxide, air and helium/air jets at different jet velocities. Mean velocity and turbulence measurements are made with a one-color, one-component laser Doppler velocimeter operating in the forward scatter mode. Measurements show that the jets are highly dissipative. Consequently, equilibrium jet characteristics similar to those found in free air jets are observed in the first two diameters downstream of the jet. These results are independent of the fluid densities and velocities. Decay of the jet, on the other hand, is a function of both the jet fluid density and momentum. In all the cases studied, the jet is found to be completely dissipated in approximately 30 jet diameters, thus giving rise to a uniform flow with a very high but constant turbulence field across the confinement.

  12. Electrokinetic ion transport in confined micro-nanochannel.

    PubMed

    Wang, Junyao; Liu, Chong; Xu, Zheng

    2016-03-01

    In this paper, a confined micronanochannel is presented to concentrate ions in a restricted zone. A general model exploiting the Poisson-Nernst-Plank equations coupled with the Navier-Stokes equation is employed to simulate the electrokinetic ion transport. The influences of the micronanochannel dimension and the surface charge density on the potential distribution, the ion concentration, and the fluid flow are investigated. The numerical results show that the potential drop depends mainly on the nanochannel, instead of the confined channel. Both decreasing the width and increasing the length enhance the ion enrichment performance. For a given nanochannel, ultimate value of ion concentration may be determined by the potential at the center point of the nanochannel. The study also shows that the enrichment stability can be improved by increasing the micronanochannel width, decreasing the micronanochannel length and reducing the surface charge density.

  13. Quantum-confined Stark effects in semiconductor quantum dots

    NASA Astrophysics Data System (ADS)

    Wen, G. W.; Lin, J. Y.; Jiang, H. X.; Chen, Z.

    1995-08-01

    Quantum-confined Stark effects (QCSE) on excitons, i.e., the influence of a uniform electric field on the confined excitons in semiconductor quantum dots (QD's), have been studied by using a numerical matrix-diagonalization scheme. The energy levels and the wave functions of the ground and several excited states of excitons in CdS and CdS1-xSex quantum dots as functions of the size of the quantum dot and the applied electric field have been obtained. The electron and hole distributions and wave function overlap inside the QD's have also been calculated for different QD sizes and electric fields. It is found that the electron and hole wave function overlap decreases under an electric field, which implies an increased exciton recombination lifetime due to QCSE. The energy level redshift and the enhancement of the exciton recombination lifetime are due to the polarization of the electron-hole pair under the applied electric field.

  14. Fluid viscosity under confined conditions

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  15. Cell migration in confined environments.

    PubMed

    Irimia, Daniel

    2014-01-01

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

  16. A double-layer based model of ion confinement in electron cyclotron resonance ion source

    SciTech Connect

    Mascali, D. Neri, L.; Celona, L.; Castro, G.; Gammino, S.; Ciavola, G.; Torrisi, G.; Sorbello, G.

    2014-02-15

    The paper proposes a new model of ion confinement in ECRIS, which can be easily generalized to any magnetic configuration characterized by closed magnetic surfaces. Traditionally, ion confinement in B-min configurations is ascribed to a negative potential dip due to superhot electrons, adiabatically confined by the magneto-static field. However, kinetic simulations including RF heating affected by cavity modes structures indicate that high energy electrons populate just a thin slab overlapping the ECR layer, while their density drops down of more than one order of magnitude outside. Ions, instead, diffuse across the electron layer due to their high collisionality. This is the proper physical condition to establish a double-layer (DL) configuration which self-consistently originates a potential barrier; this “barrier” confines the ions inside the plasma core surrounded by the ECR surface. The paper will describe a simplified ion confinement model based on plasma density non-homogeneity and DL formation.

  17. Process influences and correction possibilities for high precision injection molded freeform optics

    NASA Astrophysics Data System (ADS)

    Dick, Lars; Risse, Stefan; Tünnermann, Andreas

    2016-08-01

    Modern injection molding processes offer a cost-efficient method for manufacturing high precision plastic optics for high volume applications. Besides form deviation of molded freeform optics, internal material stress is a relevant influencing factor for the functionality of a freeform optics in an optical system. This paper illustrates dominant influence parameters of an injection molding process relating to form deviation and internal material stress based on a freeform demonstrator geometry. Furthermore, a deterministic and efficient way for 3D mold correcting of systematic, asymmetrical shrinkage errors is shown to reach micrometer range shape accuracy at diameters up to 40 mm. In a second case, a stress-optimized parameter combination using unusual molding conditions was 3D corrected to reach high precision and low stress freeform polymer optics.

  18. Thickness of the upper and lower confining units of the Mississippi River alluvial aquifer in northwestern Mississippi

    USGS Publications Warehouse

    Arthur, J. Kerry

    1994-01-01

    The thickness of the upper and lower confining units of the Mississippi River alluvial aquifer in north- western Mississippi (the Delta) has a significant influence on the vertical recharge and contamination susceptibility of the aquifer. The upper confining unit is thicker in the southern part of the Delta, the upper confining unit is less than 10 feet thick in small areas in Bolivar, Coahoma, Sunflower, Quit- man, and Tallahatchie Counties. The lower confining units are characterized by the geologic units directly underlying the alluvial aquifer. The geologic units directly underlying the aquifer, from youngest to oldest, are the Jackson Group, Cockfield Formation, Cook Mountain Formation, Sparta Sand, and Zilpha Clay. The lower confining unit thickness is greatest (greater than 250 feet) in southern Issaquena and northwestern Warren Counties. The largest area where the lower confining unit is less than 10 feet thick is Quitman, southern Coahoma, western Panola, southern Tunica, and the northern one-half of Sunflower Counties.

  19. Annual survival and site fidelity of free-ranging white-tailed deer (Odocoileus virginianus): comparative demography before (1983-1992) and after (1993-2005) spatial confinement.

    PubMed

    Webb, Stephen L; Gee, Kenneth L

    2014-01-01

    Survival and movement are important demographic variables influencing the dynamics of large herbivores with implications for management and evolution of life-history strategies. Management practices such as spatial confinement and harvest regulation attempt to control survival and movement for the sustainability of harvested deer populations, but a paucity of long-term data exists on these management practices. We examined annual survival and site fidelity of free-ranging white-tailed deer (Odocoileus virginianus) over 10 years (1983-1992) to compare demographic parameters after spatial confinement (1993-2005). We used capture records (n = 174; 104 females, 70 males), marked deer recaptures (n = 42), and dead recoveries (n = 68) to estimate sex-specific, age-specific and time-specific parameters. We found that annual female survival was 50% from 1983-1987 during a period of intense harvest, but increased to 93.7% after intense harvesting was eliminated. Prior to spatial confinement, annual survival of marked male deer averaged 36.7%-42.5%. After spatial confinement, annual survival increased on average for males (58%-99%) and females (77%-98%). Females showed high levels of site fidelity (>99%) prior to spatial confinement, whereas males showed much less site fidelity (≤4.5% for the 2 top-ranking models). During spatial confinement, the semi-impermeable fence effectively increased site fidelity of males (≥56%). These results stem from long-term study (23 years) of a large herbivore experiencing changes to life-history, resulting from changes in management that were applied to the population and aimed at altering population demographics, for sustainability of a harvestable population of deer.

  20. Acculturation and Substance Use: Social Influence as a Mediator among Hispanic Alternative High School Youth*

    PubMed Central

    MYERS, RAQUEL; CHOU, CHIH-PING; SUSSMAN, STEVE; BAEZCONDE-GARBANATI, LOURDES; PACHON, HARRY; VALENTE, THOMAS W.

    2014-01-01

    Research suggests that acculturation increases the risk of substance use among Hispanic youth. However, this process is not well understood. This study examined associations between acculturation and several substance use indicators among a sample of 714 Hispanic youth attending alternative high schools in southern California. Peer social influence was assessed as a potential mediator Acculturation, measured by language use, was associated with increased risk of lifetime alcohol, marijuana, and current alcohol, cigarettes, marijuana, and hard drug use, controlling for age, socioeconomic status, and gender Results of mediation analyses indicate that peer social influence mediated the relationship between acculturation and lifetime alcohol, and current alcohol, cigarettes, and hard drug use. Evidence for partial mediation was observed with lifetime and current marijuana use. These results provide evidence that peer social influence is an important mediating variable that should be considered when examining the relationship between acculturation and substance use. PMID:19537458