Science.gov

Sample records for high confinement influence

  1. Effects of high sound speed confiners on ANFO detonations

    NASA Astrophysics Data System (ADS)

    Kiyanda, Charles; Jackson, Scott; Short, Mark

    2011-06-01

    The interaction between high explosive (HE) detonations and high sound speed confiners, where the confiner sound speed exceeds the HE's detonation speed, has not been thoroughly studied. The subsonic nature of the flow in the confiner allows stress waves to travel ahead of the main detonation front and influence the upstream HE state. The interaction between the detonation wave and the confiner is also no longer a local interaction, so that the confiner thickness now plays a significant role in the detonation dynamics. We report here on larger scale experiments in which a mixture of ammonium nitrate and fuel oil (ANFO) is detonated in aluminium confiners with varying charge diameter and confiner thickness. The results of these large-scale experiments are compared with previous large-scale ANFO experiments in cardboard, as well as smaller-scale aluminium confined ANFO experiments, to characterize the effects of confiner thickness.

  2. 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.

  3. QCD-like behavior of high-temperature confining strings.

    PubMed

    Diamantini, M C; Trugenberger, C A

    2002-06-24

    We show that, contrary to previous string models, the high-temperature behavior of the recently proposed confining strings reproduces exactly the correct large- N QCD result, a necessary condition for any string model of confinement.

  4. Magnetic confinement of a high-density cylindrical plasma

    SciTech Connect

    Ahedo, Eduardo

    2011-10-15

    The stationary structure of a weakly collisional plasma column, confined by an axial magnetic field and a cylindrical vessel, is studied for the high-density case, when the diamagnetic azimuthal current is large enough to demagnetize partially the plasma. The plasma response is characterized mainly by two dimensionless parameters: the ratios of the electron gyroradius and the electron skin-depth to the plasma radius, and each of them measures the independent influence of the applied magnetic field and the plasma density on the plasma response. The strong magnetic confinement regime, characterized by very small wall losses, is limited to the small gyroradius and large skin-depth ranges. In the high-density case, when the electron skin-depth is smaller than the electron gyroradius, the skin-depth turns out to be the magnetic screening length, so that the bulk of the plasma behaves as unmagnetized.

  5. The Influence of Electric Field and Confinement on Cell Motility

    PubMed Central

    Huang, Yu-Ja; Samorajski, Justin; Kreimer, Rachel; Searson, Peter C.

    2013-01-01

    The ability of cells to sense and respond to endogenous electric fields is important in processes such as wound healing, development, and nerve regeneration. In cell culture, many epithelial and endothelial cell types respond to an electric field of magnitude similar to endogenous electric fields by moving preferentially either parallel or antiparallel to the field vector, a process known as galvanotaxis. Here we report on the influence of dc electric field and confinement on the motility of fibroblast cells using a chip-based platform. From analysis of cell paths we show that the influence of electric field on motility is much more complex than simply imposing a directional bias towards the cathode or anode. The cell velocity, directedness, as well as the parallel and perpendicular components of the segments along the cell path are dependent on the magnitude of the electric field. Forces in the directions perpendicular and parallel to the electric field are in competition with one another in a voltage-dependent manner, which ultimately govern the trajectories of the cells in the presence of an electric field. To further investigate the effects of cell reorientation in the presence of a field, cells are confined within microchannels to physically prohibit the alignment seen in 2D environment. Interestingly, we found that confinement results in an increase in cell velocity both in the absence and presence of an electric field compared to migration in 2D. PMID:23555674

  6. The influence of electric field and confinement on cell motility.

    PubMed

    Huang, Yu-Ja; Samorajski, Justin; Kreimer, Rachel; Searson, Peter C

    2013-01-01

    The ability of cells to sense and respond to endogenous electric fields is important in processes such as wound healing, development, and nerve regeneration. In cell culture, many epithelial and endothelial cell types respond to an electric field of magnitude similar to endogenous electric fields by moving preferentially either parallel or antiparallel to the field vector, a process known as galvanotaxis. Here we report on the influence of dc electric field and confinement on the motility of fibroblast cells using a chip-based platform. From analysis of cell paths we show that the influence of electric field on motility is much more complex than simply imposing a directional bias towards the cathode or anode. The cell velocity, directedness, as well as the parallel and perpendicular components of the segments along the cell path are dependent on the magnitude of the electric field. Forces in the directions perpendicular and parallel to the electric field are in competition with one another in a voltage-dependent manner, which ultimately govern the trajectories of the cells in the presence of an electric field. To further investigate the effects of cell reorientation in the presence of a field, cells are confined within microchannels to physically prohibit the alignment seen in 2D environment. Interestingly, we found that confinement results in an increase in cell velocity both in the absence and presence of an electric field compared to migration in 2D.

  7. Confinement of hydrogen at high pressure in carbon nanotubes

    DOEpatents

    Lassila, David H.; Bonner, Brian P.

    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.

  8. 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.

  9. 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.

  10. 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.

  11. Simulation of transition dynamics to high confinement in fusion plasmas

    NASA Astrophysics Data System (ADS)

    Nielsen, A. H.; Xu, G. S.; Madsen, J.; Naulin, V.; Juul Rasmussen, J.; Wan, B. N.

    2015-12-01

    The transition dynamics from the low (L) to the high (H) confinement mode in magnetically confined plasmas is investigated using a first-principles four-field fluid model. Numerical results are in agreement with measurements from the Experimental Advanced Superconducting Tokamak - EAST. Particularly, the slow transition with an intermediate dithering phase is well reproduced at proper parameters. The model recovers the power threshold for the L-H transition as well as the decrease in power threshold switching from single to double null configuration observed experimentally. The results are highly relevant for developing predictive models of the transition, essential for understanding and optimizing future fusion power reactors.

  12. 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.

  13. Numerical modeling of the transition from low to high confinement in magnetically confined plasma

    NASA Astrophysics Data System (ADS)

    Rasmussen, J. Juul; Nielsen, A. H.; Madsen, J.; Naulin, V.; Xu, G. S.

    2016-01-01

    The transition dynamics from low (L) to high (H) mode confinement in magnetically confined plasmas is investigated using a four-field drift fluid model—HESEL (Hot Edge-Sol-Electrostatic). The model includes profile evolution and is solved in a 2D domain at the out-board mid-plane of a tokamak including both open and closed field lines. The results reveal different types of L-H-like transitions in response to ramping up the input power by increasing the ion temperature in the edge region. For a fast rising input power we obtain an abrupt transition, and for a slow rising power we obtain a L-I-H transition with an intermediate I-phase displaying limit-cycle oscillations (LCO). The model recovers the power threshold for the L-H transition, the scaling of the threshold with the density and with the loss-rate in the SOL, indicating a decrease in power threshold when switching from single to double null configuration. The results hold promises for developing full predictive modeling of the L-H transition, which is an essential step in understanding and optimizing fusion devices.

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

    SciTech Connect

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

    2011-04-18

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

  15. The Radioelectric effect in doped superlattices under the influence of confined phonon

    NASA Astrophysics Data System (ADS)

    Quang Bau, Nguyen; Thu Hang, Dao; Long, Do Tuan

    2016-06-01

    The Radioelectric effect in doped superlattices under the influence of confined phonon has been theoretically studied. The analytical expression for the Radioelectric field is obtained by quantum kinetic equation method. The theoretical expression shows that the Radioelectric field in doped superlattices depends on the frequencies and amplitudes of the laser and the linearly polarized electromagnetic wave, the period of the superlattices and especially the quantum number m characterizing the phonon confinement. Numerical calculation is also applied for GaAs:Si/GaAs:Be doped superlattices. It is found that the Radioelectric field is different from that in the normal bulk semiconductor as well as two-dimensional systems in case of unconfined phonon and in case of confined phonon when the contribution of confined potential of doped superlattices and confined phonon is remarkable. The Radioelectric field has multiple resonance peaks and increases as the increasing of quantum number m.

  16. Energy confinement in Doublet III with high-Z limiters

    SciTech Connect

    Marcus, F.B.; Adcock, S.J.; Baker, D.R.; Blau, F.P.; Brooks, N.H.; Chase, R.P.; DeBoo, J.C.; Ejima, S.; Fairbanks, E.S.; Fisher, R.K.

    1980-02-01

    This report describes the experimental measurements and data analysis techniques used to evaluate the energy confinement in noncircular plasmas produced in Doublet III. Major aspects of the confinement measurements and analysis techniques are summarized. Machine parameters, diagnostic systems and discharge parameters relavent to the confinement measurements are given. Magnetic analysis techniques used to determine the plasma shape are reviewed. Scaling of the on-axis values of electron temperature, confinement time and Z/sub eff/ with plasma density is presented. Comparison with scaling results from other circular tokamaks is discussed. Numerical and analytic techniques developed for calculating the plasma energy confinement time and self-consistent profiles of density, temperature, current, and flux in non-circular geometries are described. These techniques are applied to the data and used to determine the central and global electron energy confinement time for a typical doublet plasma. Additional aspects of the confinement such as the radial dependence of the electron thermal conductivity and the estimated ion temperature are explored with the aid of a non-circular transport simulation code. The results of the confinement measurements are summarized and discussed. A brief summary of the theoretically expected effects of noncircularity on plasma confinement is included for reference as Appendix I.

  17. 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.

  18. Influence of Homopolymers on the Microdomain Behavior of Block Copolymers in 2D Confinement

    NASA Astrophysics Data System (ADS)

    Kim, Youngkeol; Hwang, Sungyoul; Yu, Guiduk; Char, Kookheon

    Constraints imposed by nanometer scale confinement lead to changes in bulk equilibrium behavior of block copolymers (BCPs). Cylindrical pores with diameters corresponding to the length equivalent of several copolymer chains have been employed to investigate the influence of two-dimensional confinement on the behavior of BCPs. In this study, we expand the scope to homopolymer-BCP binary blends. Given fraction of homopolymers, the phase behavior of blends is dependent on molecular weight (Mw) of homopolymers. Lamella- and cylinder-forming poly(styrene-b-butadiene) (PS-b-PBD) and PS homopolymers (hPS) were drawn into the pores of anodized aluminum oxide (AAO) membranes in the melt by capillary forces. Based on the detailed observation of the morphologies within porous columns, we analyzed the structural transition of BCPs induced by the presence of hPS and confinement. The effect of hPS on the micro-domain of BCPs is greatly accentuated in nanoscale confinement compared to the bulk state due to the entropic loss of polymer chains. Pore diameters of AAO and Mw of the PS-b-PBD are also controlled so as to examine the effects of confinement on the phase transition of PS-b-PBD/hPS blends.

  19. Influence of the confining pressure on precursory and rupture processes of Westerly granite.

    NASA Astrophysics Data System (ADS)

    Passelegue, Francois; Nicolas, Aurelien; Madonna, Claudio; Schubnel, Alexandre

    2016-04-01

    In the shallow crust, brittle deformation mechanisms lead to damage and rupture of rocks. These mechanisms are generally described by non-linear stress relations and decrease of the elastic moduli due to microcrak opening and sliding. However, failure mode depends on confining pressure and ranges from axial splitting to shear localization. Here we report experiments on Westerly granite samples deformed under controlled upper crustal stress conditions in the laboratory. Experiments were conducted under triaxial loading (σ1>σ2=σ3) at confining pressures (σ3) ranging from 2 to 50 MPa (similar to upper crustal stress conditions) and at constant axial strain rate 10-5/s. Usual a dual gain system, a high frequency acoustic monitoring array recorded particles acceleration during macroscopic rupture of the intact specimen and premonitory background microseismicity. Secondly, acoustic sensors were used in an active way to measure the evolution of elastic wave velocities. In addition, we used an amplified strain gage to record the dynamic stress change during the dynamic rupture. Our preliminary results show that increasing confining pressure leads to the transition between axial cracks opening to shear localization. This result is supported by the moment tensor solutions of acoustic emissions and CT scan imaging of the post mortem sample. In addition, we systematically observe an exponential increase of the premonitory activity up to the shear failure of the sample. While the intensity of this precursory activity increase with the confining pressure in term of energy, the crack density leading to the failure of the sample is independent of the confinement. We show that the dynamic rupture occurs in only few microseconds, suggesting a rupture speed close to the shear wave velocity. In addition, the ratio between the stress drop and the peak of stress increases with the confinement. This result suggest that the weakening of faulting increases with the confinement. Finally

  20. 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

  1. Confined crystallization in compatibilized Polyamide 6/High Density Polyethylene blends

    NASA Astrophysics Data System (ADS)

    Ceccia, Simona; Argoud, Alexandra; Trouillet-Fonti, Lise; Long, Didier R.; Sotta, Paul

    2012-02-01

    Blending polymers can be considered the easiest way to obtain new materials with tuned properties thanks to the possibility to control blend morphologies. The blend characteristics depend on the properties of each component, on composition and on morphologies developed during polymers processing. In case of semi-crystalline blended polymers, mechanical performances are closely related to the crystalline morphology. Therefore, it is essential that crystallinity is maintained after blending in order to keep or enhance the properties. This may be a challenge when the blends exhibit multiphase morphologies with sub-micrometer domain sizes. In this work, we study the crystallization behavior of compatibilized Polyamide 6/High Density Polyethylene (PA6/PE) blends by means of the Differential Scanning Calorimetry technique. Blends with various morphologies (dispersed, stretched dispersed, fibrillar and co-continuous) are obtained by reactive extrusion and varying blend composition and processing parameters. Blend composition and morphology turn out to greatly affect the bulk crystallization temperatures of both PA6 and PE. When the polymer is confined in domains of a few micrometers the crystallization temperature peak shifts to lower temperatures. Thus, the smaller the domain size the lower the crystallization temperature in case of dispersed morphologies. Moreover, in multi-scale morphologies showing polymer droplets in the nanometer range, fractionated crystallization (multiple crystallization peaks) is observed.

  2. Deflagration to detonation in HMX under high confinement. [HMX confined in steel tubes

    SciTech Connect

    McAfee, J.M.; Campbell, A.W.; Asay, B.W.

    1987-01-01

    The deflagration-to-detonation behavior of HMX confined in steel tubes was studied by means of x radiography, light emission, and various pin techniques. Unlike most reported experiments, the HMX bed was ignited by driving a piston (initially at rest and in contact with the HMX) into the bed with the pressure generated from burning, low-density HMX on the opposite side of the piston. Because a gasless igniter is used to start the burning of the low-density HMX, the piston has a relatively smooth initial motion. Analysis of the data from these experiments gives a rather detailed picture of the DDT process under these conditions. 2 refs., 19 figs.

  3. 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.

  4. High energy and particle confinement times in PDX scoop discharges

    NASA Astrophysics Data System (ADS)

    Budny, R.; Bol, K.; Fonck, R.; Goldston, R.; Grek, B.; Heidbrink, W.; Heifetz, D.; Johnson, D.; Kaita, R.; Kaye, S.; Kugel, H.; Manos, D.; Mccune, D.; Mikkelsen, D.; Owens, K.; Post, D.; Redi, M.; Singer, C.; Strachan, J.

    1984-12-01

    Scoop limited discharges in PDX with neutral beam heating achieved energy and particle confinement times higher than those inferred from similar poloidal rail limiter discharges. We present transport simulations using TRANSP and BALDUR and neutral simulations using DEGAS. Large neutral densities and ionization rates localized near the scoop are inferred. Thermal neutral ionization increases the edge electron density substantially, resulting in a flattened density profile. Fueling from the scoop limiter is deeper than from simple limiters.

  5. 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.

  6. Impurity accumulation in plasma regimes with high energy confinement

    NASA Astrophysics Data System (ADS)

    Ran, L. B.; Roberts, D. E.; Yang, H. R.; Dodel, G.; Gentle, K.; Von Goeler, S.; Holzhauer, E.; Hübner, K.; Keilhacker, M.; Korotkov, A.; Luce, T. C.; Miura, Y.; Tsois, N.; Würz, H.; Fussmann, G.; Hofmann, J.; Janeschitz, G.; Krieger, K.; Müller, E. R.; Nolte, R.; Röhr, H.; Steuer, K. H.; Becker, G.; Bomba, B.; Bruhns, H.; Büchl, K.; Carlson, A.; Eberhagen, A.; Fahrbach, H.-U.; Gehre, O.; Gernhardt, J.; Giannone, L.; Von Gierke, G.; Glock, E.; Gruber, O.; Haas, G.; Herrmann, H.; Kaesdorf, S.; Karger, F.; Kaufmann, M.; Klüber, O.; Kornherr, M.; Lackner, K.; Lang, R.; Lee, P.; Lisitano, G.; Mast, F.; Mayer, H. M.; McCormick, K.; Meisel, D.; Mertens, V.; Murmann, H.; Neuhauser, J.; Niedermeyer, H.; Noterdaeme, J. M.; Poschenrieder, W.; Preis, R.; Rapp, H.; Rudyj, A.; Sandmann, W.; Schneider, F.; Schnider, U.; Siller, G.; Simmet, E.; Speth, E.; Söldner, F.; Stäbler, A.; Steinmetz, K.; Stroth, U.; Vollmer, O.; Zasche, D.

    1989-04-01

    Investigations of impurity accumulation phenomena in ASDEX are reviewed. There are four different operating regimes where pronounced accumulation is observed and these regimes are also characterized by improved energy confinement. In particular, medium-Z metallic ions are involved in accumulation processes whereas low-Z ions appear almost unaffected. The rapid accumulation observed in the case of metallic ions may be explained by neoclassical inward drifts if we assume that the anomalous diffusion is sufficiently suppressed, some indication of this being found from laser blow-off studies. The present results, however, can only be partly explained by neoclassical theory, according to which accumulation of low-Z impurities should also occur. The temporal behaviour of accumulation and the retarding effect of proton dilution for collision dominated transport are also discussed. Finally, we conclude that the full benefits of improved energy confinement can be achieved only if the impurity influxes are kept to a sufficiently low level. Expressed in terms of concentrations under low confinement conditions we have to postulate, for ASDEX, concentrations ≲ 10 -4 for metals and ≲ 2% for all light impurities.

  7. Stability analysis of confined V-shaped flames in high-velocity streams.

    PubMed

    El-Rabii, Hazem; Joulin, Guy; Kazakov, Kirill A

    2010-06-01

    The problem of linear stability of confined V-shaped flames with arbitrary gas expansion is addressed. Using the on-shell description of flame dynamics, a general equation governing propagation of disturbances of an anchored flame is obtained. This equation is solved analytically for V-flames anchored in high-velocity channel streams. It is demonstrated that dynamics of the flame disturbances in this case is controlled by the memory effects associated with vorticity generated by the perturbed flame. The perturbation growth rate spectrum is determined, and explicit analytical expressions for the eigenfunctions are given. It is found that the piecewise linear V structure is unstable for all values of the gas expansion coefficient. Despite the linearity of the basic pattern, however, evolutions of the V-flame disturbances are completely different from those found for freely propagating planar flames or open anchored flames. The obtained results reveal strong influence of the basic flow and the channel walls on the stability properties of confined V-flames. PMID:20866527

  8. Ventilation, air confinement and high radon level in an underground gallery studied from profiles measurements.

    NASA Astrophysics Data System (ADS)

    Richon, P.; Perrier, F.; Sabroux, J.-C.; Pili, E.; Ferry, C.; Dezayes, C.; Voisin, V.

    2003-04-01

    An horizontal closed-end tunnel, 128 m long and 2 m in diameter, located within the eastern margin of the Belledonne crystalline basement, French Alps, near the west shore of the Roselend artificial lake, 600 m NE of the dam, has been instrumented since 1995 for radon emanation and deformation measurements. Radon bursts are repeatedly associated with transient deformation events induced by variations in lake levels (Trique et al., 1999). This high radon anomalies (up to 30,000 Bq.m-3) in the air of the tunnel result from its particular geometry, its excellent confinement, the water and radium-226 contents of rocks, and the crossing of several faults. We calculated the equilibrium factor F, directly proportional to air ventilation, from the ratios of radon-222 gas activity measured with an AlphaGUARDTM, and the Potential Alpha Energy Concentration (PAEC, in μJ.m-3) of its short-lived daughters measured with a TracerlabTM, simultaneously in five locations along the tunnel. The calculated equilibrium factors of 0.60 to 0.78 show that confinement is very good all along the tunnel. Fast Fourier Transform of the radon-222 signals measured during six months simultaneously with six BarasolTM distributed along the tunnel shows also the poor ventilation and the weak influence of atmospheric pressure and air temperature.

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

    PubMed

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

    2016-09-02

    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.

  10. 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.

  11. 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.

  12. 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

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

    PubMed

    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

  14. Influence of the confinement on laser-induced dry etching at the rear side of fused silica

    NASA Astrophysics Data System (ADS)

    Pan, Yunxiang; Ehrhardt, Martin; Lorenz, Pierre; Han, Bing; Hopp, Bela; Vass, Csaba; Ni, Xiaowu; Zimmer, Klaus

    2016-04-01

    Laser-induced etching at the rear side of transparent material enables high-quality machining results. However, the mechanism is still not completely recognized which would allow further optimization. Therefore, multi-pulsed laser-induced backside dry etching with different thick photoresist films was studied experimentally for air (MP-LIBDE) and water confinements (cMP-LIBDE). The water confinement causes differences in photoresist ablation morphology and etching rate in dependence on laser fluence, film thickness and pulse number. Owing to the water confinement, the extent of photoresist film spallation and the etching rate slope difference in low and high fluence ranges are reduced. In particular, the etching rate of cMP-LIBDE keeps constant with different film thicknesses in contrast to MP-LIBDE. Two effects that are related to the water confinement, mechanical confinement and heat transfer alterations, are analysed and discussed in relation to the differences between MP-LIBDE and cMP-LIBDE.

  15. High-power semiconductor separate-confinement double heterostructure lasers

    SciTech Connect

    Tarasov, I S

    2010-10-15

    The review is devoted to high-power semiconductor lasers. Historical reference is presented, physical and technological foundations are considered, and the concept of high-power semiconductor lasers is formulated. Fundamental and technological reasons limiting the optical power of a semiconductor laser are determined. The results of investigations of cw and pulsed high-power semiconductor lasers are presented. Main attention is paid to inspection of the results of experimental studies of single high-power semiconductor lasers. The review is mainly based on the data obtained in the laboratory of semiconductor luminescence and injection emitters at the A.F. Ioffe Physicotechnical Institute. (review)

  16. JET confinement studies and their scaling to high βN, ITER scenarios

    NASA Astrophysics Data System (ADS)

    McDonald, D. C.; Laborde, L.; DeBoo, J. C.; Ryter, F.; Brix, M.; Challis, C. D.; de Vries, P.; Giroud, C.; Hobirk, J.; Howell, D.; Joffrin, E.; Luce, T. C.; Mailloux, J.; Pericoli-Ridolfini, V.; Sips, A. C. C.; Thomsen, K.; EFDA Contributors, JET

    2008-12-01

    The ITER hybrid scenario aims to exploit non-inductive current drive to enable burn times in excess of 1000 s. To achieve this, and optimize fusion performance, requires high βN (the plasma pressure normalized to a stability scaling) and energy confinement equal to or greater than that predicted for the baseline scenario. This paper discusses results from the JET candidate hybrid scenario, where βN,MHD <= 3.6 plasmas have been produced. Despite a different initial phase, confinement relevant plasma parameters evolve rapidly towards those of equivalent ELMy H-modes and are well described by IPB98(y, 2). In contrast to previous ELMy H-mode studies, a dedicated β scan experiment in the JET hybrid candidate scenario shows a strong negative dependence of global confinement on βN. Analysis indicates that the core transport remains consistent with weakly dependent electrostatic transport, whilst the edge confinement decreases strongly with increasing βN. By combining global confinement data from ASDEX Upgrade, DIII-D and JET hybrid scenario discharges, a multi-machine database is produced. In contrast to the JET case, confinement in ASDEX Upgrade and DIII-D is shown to be inconsistent with IPB98(y, 2) and alternative dependences are explored.

  17. 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.

  18. 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. PMID:27273454

  19. 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)

  20. Confinement of high energy trapped particles in tokamaks

    SciTech Connect

    Goldston, R.J.; White, R.B.; Boozer, A.H.

    1981-04-01

    The banana orbits of high energy trapped particles in tokamaks are found to diffuse rapidly in the radial direction if the toroidal ripple exceeds a low critical value. During this diffusion the energy, the magnetic moment, and the value of the magnetic field strength at the banana tips are conserved.

  1. Confinement of high-energy trapped particles in tokamaks

    SciTech Connect

    Goldston, R.J.; White, R.B.; Boozer, A.H.

    1981-08-31

    The banana orbits of high-energy trapped particles in tokamaks are found to diffuse rapidly in the radial direction if the toroidal ripple exceeds a low critical value. During this diffusion the energy, the magnetic moment, and the value of the magnetic field strength at the banana tips are conserved.

  2. Highly active nanoreactors: nanomaterial encapsulation based on confined catalysis.

    PubMed

    Sanlés-Sobrido, Marcos; Pérez-Lorenzo, Moisés; Rodríguez-González, Benito; Salgueiriño, Verónica; Correa-Duarte, Miguel A

    2012-04-16

    It happens inside: highly active nanoreactors are prepared by encapsulating dendritic Pt nanoparticles (NPs) grown on a polystyrene template inside hollow porous silica capsules. The catalytic activity of these Pt NPs is preserved after encapsulation and template removal. Different metals, such as Ni, can thus be reduced inside the capsules, thereby leading to the formation of composites with tunable magnetic properties.

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

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

    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.

  4. 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.

  5. Simulation of Microdamage in Ceramics Deformed under High Confinement

    NASA Astrophysics Data System (ADS)

    Zhang, Dongmei; Feng, Ruqiang

    2004-06-01

    A polycrystalline ceramic may display high strength under dynamic compression but fails catastrophically during load reversal to tension. One plausible mechanism is that heterogeneous plasticity in some of the crystals under compression induces microdamage during load reversal. To examine this possibility quantitatively, we developed a computational method, in which the polycrystalline microstructure is realistically simulated using Voronoi crystals having grain boundary layer. Both anisotropic elasticity and plastic slip in limited crystallographic planes are considered in crystal modeling. The grain boundary material is treated as an isotropic glassy solid, which has pressure-dependent shear strength under compression and fractures in Mode I when the threshold is reached. The structural and material models have been implemented into ABAQUS/Explicit code. Model simulations have been performed to analyze the intragranular microplasticity, intergranular microdamage, and their interactions in polycrystalline α-6H silicon carbide subjected to dynamic unaxial-strain compression and then load reversal to tension. It is found that microplasticity is more favorable than intergranular shear damage during compression. However, both the microplasticity-induced heterogeneity and the grain boundary damage affect strongly microcracking during load reversal, which leads to fragmentation or spallation depending on the level of compression. The significance of these findings is discussed.

  6. Experimental and Numerical Studies on Rock Breaking with TBM Tools under High Stress Confinement

    NASA Astrophysics Data System (ADS)

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

    2007-10-01

    The understanding of rock breaking and chipping due to the TBM cutter disks mechanism in deep tunnels is considered in this paper. The interest stems from the use of TBMs for the excavation of long Trans-Alpine tunnels. Some tests that simulate the disk cutter action at the tunnel face by means of an indenter, acting on a rock specimen are proposed. The rock specimen is confined through a flat-jack and a confinement-free area on one side of the specimen simulates the formation of a groove near the indenter, like it occurs in TBM excavation conditions. Results show a limited influence of the confinement stress versus the thrust increment required for breaking the rock between the indenter and the free side of the specimen. Numerical modelling of the cutter disk action on confined material has also been carried out in order to investigate further aspects of the fracture initiation. Also in this case the importance of the relative position between disk cutter and groove is pointed out.

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

    PubMed

    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

  8. 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

  9. 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.

  10. 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

  11. Influence of poly-L-lysine on the biomimetic growth of silica tubes in confined media.

    PubMed

    Gautier, Clémentine; Lopez, Pascal J; Livage, Jacques; Coradin, Thibaud

    2007-05-01

    Pore channels of polycarbonate membranes were recently used as biomimetic models to study the effect of confinement on silicate condensation, leading to the formation of silica tubes exhibiting a core-shell structure. In this work, we preimmobilized poly-L-lysine on the membrane pores, leading to modification of the tube shell formation process and variation in core particle size. These data strengthen previous assumptions on the role of confinement on silica growth, i.e., interfacial interactions and perturbation of the diffusion coefficient. They also suggest that this approach is suitable to investigate in more detail the contribution of confinement effects on silica biomineralization.

  12. 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.

  13. Different behavior of water in confined solutions of high and low solute concentrations.

    PubMed

    Elamin, Khalid; Jansson, Helén; Kittaka, Shigeharu; Swenson, Jan

    2013-11-14

    Water-glycerol solutions confined in 21 Å pores of the silica matrix MCM-41 C10 have been studied using differential scanning calorimetry (DSC) and broadband dielectric spectroscopy (BDS). The results suggest a micro-phase separation caused by the confinement. Likely the water molecules coordinate to the hydroxyl surface groups of the pores, leaving most of the glycerol molecules in the centre of the pores. This makes the dynamics of glycerol almost concentration independent up to water concentrations of about 85 wt%. However, at higher water concentrations no substantial clustering of glycerol molecules should occur and the glass transition related dynamics exhibit an anomalous behaviour. Instead of a common plasticization effect of water, as for the corresponding bulk solutions (when no ice is formed), it is evident that water acts as an anti-plasticizer in the confinement at high water concentrations. We propose that the increased water concentration slows down the glass transition related dynamics in the deeply supercooled regime due to that a rigid hydrogen bonded network structure of water molecules is formed at low temperatures and low glycerol concentrations. This is in contrast to the situation in a homogenously mixed bulk solution of a high solute concentration where the water molecules will be less hydrogen bonded, and therefore are typically more mobile than the surrounding solute molecules. An almost complete hydrogen bonded network of water molecules may, even in confinements, be sufficiently rigid to slow down the relaxation of embedded solute molecules. It can also be expressed the other way around, i.e. small amounts of glycerol act as a plasticizer for water, due to its breaking up of the nearly tetrahedral network structure. From the here observed concentration dependent behaviour of the deeply supercooled bulk and confined solutions it seems, furthermore, evident that the Tg value of bulk water cannot be estimated from extrapolations of aqueous

  14. 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.

  15. The Influence of Silica Nanoparticles on Ionic Liquid Behavior: A Clear Difference between Adsorption and Confinement

    PubMed Central

    Wang, Yaxing; Li, Cheng; Guo, Xiaojing; Wu, Guozhong

    2013-01-01

    The phase behaviors of ionic liquids (ILs) confined in nanospace and adsorbed on outer surface of nanoparticles are expected to be different from those of the bulk. Anomalous phase behaviors of room temperature ionic liquid tributylhexadecylphosphonium bromide (P44416Br) confined in ordered mesoporous silica nanoparticles with average pore size 3.7 nm and adsorbed on outer surface of the same silica nanoparticles were reported. It was revealed that the melting points (Tm) of confined and adsorbed ILs depressed significantly in comparison with the bulk one. The Tm depressions for confined and adsorbed ILs are 8 °C and 14 °C, respectively. For comparison with the phase behavior of confined P44416Br, 1-butyl-3-methylimidazolium bromide (BmimBr) was entrapped within silica nanopores, we observed an enhancement of 50 °C in Tm under otherwise similar conditions. The XRD analysis indicates the formation of crystalline-like phase under confinement, in contrast to the amorphous phase in adsorbed IL. It was confirmed that the behavior of IL has clear difference. Moreover, the complex π-π stacking and H-bonding do not exist in the newly proposed phosphonium-based IL in comparison with the widely studied imidazolium-based IL. The opposite change in melting point of P44416Br@SiO2 and BmimBr@SiO2 indicates that the cationic species plays an important role in the variation of melting point. PMID:24145752

  16. High-confinement photonic structures for light propagation in the visible range

    NASA Astrophysics Data System (ADS)

    Turner, Amy C.; Almeida, Vilson R.; Lipson, Michal F.

    2004-10-01

    Planar integrated photonic devices are typically designed for telecommunications wavelengths in the 1.55 micron range. For strong mode-confinement at these wavelengths, very high index contrasts are required and semiconductor materials are often used for the waveguide core. Recently, planar devices designed for the visible range were demonstrated with relatively large dimensions on the order of 0.5 - 5 mm. Here in contrast we demonstrate micron-size photonic devices with single-mode operation in the visible range. Devices made for light propagation in the visible range are designed for tapping specific wavelengths of light vertically out of the plane of integration. The structures are based on high confinement waveguides with an effective mode size on the order of 0.5 μm2.

  17. Attainment of high confinement in neutral beam heated divertor discharges in the PDX tokamak

    NASA Astrophysics Data System (ADS)

    Kaye, S. M.; Bell, M. G.; Bol, K.; Boyd, D.; Brau, K.; Buchenauer, D.; Budny, R.; Cavallo, A.; Couture, P.; Crowley, T.; Darrow, D. S.; Eubank, H.; Fonck, R. J.; Goldston, R.; Grek, B.; Jaehnig, K. P.; Johnson, D.; Kaita, R.; Kugel, H.; Leblanc, B.; Manickam, J.; Manos, D.; Mansfield, D.; Mazzucato, E.; McCann, R.; McCune, D.; McGuire, K.; Mueller, D.; Murdock, A.; Okabayashi, M.; Okano, K.; Owens, D. K.; Post, D. E.; Reusch, M.; Schmidt, G. L.; Sesnic, S.; Slusher, R.; Suckewer, S.; Surko, C.; Takahashi, H.; Tenney, F.; Towner, H.; Valley, J.

    1984-05-01

    The PDX divertor configuration has recently been converted from an open to a closed geometry to inhibit the return of neutral gas from the divertor region to the main chamber. Since then, operation in a regime with high energy confinement in neutral beam heated discharges (ASDEX H-mode) has been routine over a wide range of operating conditions. These H-mode discharges are characterized by a sudden drop in divertor density and H α emission and a spontaneous rise in main chamber plasma density during neutral beam injection. The confinement time is found to scale nearly linearly with plasma current, but can be degraded due either to the presence of edge instabilities or heavy gas puffing. Detailed Thomson scattering temperature profiles show high values of Tc near the plasma edge (˜ 450 eV) with sharp radial gradients (˜ 400 eV/cm) near the separatrix. Density profiles are broad and also exhibit steep gradients close to the separatrix.

  18. Energy Confinement of High-Density Pellet-Fueled Plasmas in the Alcator C Tokamak

    NASA Astrophysics Data System (ADS)

    Greenwald, M.; Gwinn, D.; Milora, S.; Parker, J.; Parker, R.; Wolfe, S.; Besen, M.; Camacho, F.; Fairfax, S.; Fiore, C.; Foord, M.; Gandy, R.; Gomez, C.; Granetz, R.; Labombard, B.; Lipschultz, B.; Lloyd, B.; Marmar, E.; McCool, S.; Pappas, D.; Petrasso, R.; Pribyl, P.; Rice, J.; Schuresko, D.; Takase, Y.; Terry, J.; Watterson, R.

    1984-07-01

    A series of pellet-fueling experiments has been carried out on the Alcator C tokamak. High-speed hydrogen pellets penetrate to within a few centimeters of the magnetic axis, raise the plasma density, and produce peaked density profiles. Energy confinement is observed to increase over similar discharges fueled only by gas puffing. In this manner record values of electron density, plasma pressure, and Lawson number (n τ) have been achieved.

  19. Observation of a high-confinement regime in a tokamak plasma with ion cyclotron resonance heating

    NASA Astrophysics Data System (ADS)

    Steinmetz, K.; Noterdaeme, J.-M.; Wagner, F.; Wesner, F.; Bäumler, J.; Becker, G.; Bosch, H. S.; Brambilla, M.; Braun, F.; Brocken, H.; Eberhagen, A.; Fritsch, R.; Fussmann, G.; Gehre, O.; Gernhardt, J.; v. Gierke, G.; Glock, E.; Gruber, O.; Haas, G.; Hofmann, J.; Hofmeister, F.; Izvozchikov, A.; Janeschitz, G.; Karger, F.; Keilhacker, M.; Klüber, O.; Kornherr, M.; Lackner, K.; Lisitano, G.; van Mark, E.; Mast, F.; Mayer, H. M.; McCormick, K.; Meisel, D.; Mertens, V.; Müller, E. R.; Murmann, H.; Niedermeyer, H.; Poschenrieder, W.; Puri, S.; Rapp, H.; Röhr, H.; Ryter, F.; Schmitter, K.-H.; Schneider, F.; Setzensack, C.; Siller, G.; Smeulders, P.; Söldner, F.; Speth, E.; Steuer, K.-H.; Vollmer, O.; Wedler, H.; Zasche, D.

    1987-01-01

    The H mode in ion cyclotron-resonance-heated plasmas has been investigated with and without additional neutral beam injection. Ion cyclotron-resonance heating can cause the transition into a high-confinement regime (H mode) in combination with beam heating. The H mode, however, has also been realized-for the first time-with ion cyclotron-resonance heating alone in the D (H)-hydrogen minority scheme at an absorbed rf power of 1.1 MW.

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

    SciTech Connect

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

    2008-01-15

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

  1. Entropy-driven spatial organization of highly confined polymers: Lessons for the bacterial chromosome

    NASA Astrophysics Data System (ADS)

    Jun, Suckjoon; Mulder, Bela

    2006-08-01

    Despite recent progress in visualization experiments, the mechanism underlying chromosome segregation in bacteria still remains elusive. Here we address a basic physical issue associated with bacterial chromosome segregation, namely the spatial organization of highly confined, self-avoiding polymers (of nontrivial topology) in a rod-shaped cell-like geometry. Through computer simulations, we present evidence that, under strong confinement conditions, topologically distinct domains of a polymer complex effectively repel each other to maximize their conformational entropy, suggesting that duplicated circular chromosomes could partition spontaneously. This mechanism not only is able to account for the spatial separation per se but also captures the major features of the spatiotemporal organization of the duplicating chromosomes observed in Escherichia coli and Caulobacter crescentus. bacterial chromosome segregation | Caulobacter crescentus | Escherichia coli | polymer physics

  2. 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.

  3. High energy x-ray imager for inertial confinement fusion at the National Ignition Facility

    NASA Astrophysics Data System (ADS)

    Tommasini, Riccardo; Koch, Jeffrey A.; Young, Bruce; Ng, Ed; Phillips, Tom; Dauffy, Lucile

    2006-10-01

    X-ray imaging is a fundamental diagnostic tool for inertial confinement fusion (ICF) research and provides data on the size and the shape of the core in implosions. We report on the feasibility and performance analyses of an ignition x-ray imager to be used on cryogenic deuterium-tritium implosions at the National Ignition Facility. The system is intended to provide time-integrated, broadband, moderate-energy x-ray core images of imploding inertial confinement fusion capsules. It is optimized with respect to spatial-resolution, signal-to-background, and signal-to-noise ratios, taking into account the extreme operating conditions expected at NIF due to high expected neutrons yields, gamma rays, and x rays from laser-plasma interactions.

  4. New steady-state quiescent high-confinement plasma in an experimental advanced superconducting tokamak.

    PubMed

    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

    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. Influence of the nanoparticles agglomeration state in the quantum-confinement effects: Experimental evidences

    SciTech Connect

    Lorite, I.; Romero, J. J.; Fernandez, J. F.

    2015-03-15

    The agglomeration state facilitates particle-particle interaction which produces important effects in the phonon confinement effects at the nanoscale. A partial phonon transmission between close nanoparticles yields a lower momentum conservation relaxation than in a single isolated nanoparticle. It means a larger red shift and broadening of the Raman modes than the expected ones for Raman quantum confinement effects. This particle-particle interaction can drive to error when Raman responses are used to estimate the size of the nanoscaled materials. In this work different corrections are suggested to overtake this source of error.

  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. Calculation of bending losses for highly confined modes of optical waveguides with transformation optics.

    PubMed

    Han, Zhanghua; Zhang, Pu; Bozhevolnyi, Sergey I

    2013-06-01

    We revisited the fundamental problem of bending loss calculation in optical waveguide theory using transformation optics (TOs). Due to the fact that TOs is based on the form invariance property of Maxwell equations, this new approach provides more accurate calculation of waveguide bending loss compared to the conventional refractive index conformal mapping method, especially for small bending radii typical for plasmonic waveguides or photonic waveguides with high-index contrast. We believe our results provide a simple yet reliable way of bending loss calculation for highly confined optical (including plasmonic) waveguides.

  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. Confinement dependent chemotaxis in two-photon polymerized linear migration constructs with highly definable concentration gradients.

    PubMed

    Hjortø, Gertrud Malene; Olsen, Mark Holm; Svane, Inge Marie; Larsen, Niels B

    2015-04-01

    Dendritic cell chemotaxis is known to follow chemoattractant concentration gradients through tissue of heterogeneous pore sizes, but the dependence of migration velocity on pore size and gradient steepness is not fully understood. We enabled chemotaxis studies for at least 42 hours at confinements relevant to tissue models by two-photon polymerization of linear channel constructs with cross-sections from 10 × 10 μm(2) to 20 × 20 μm(2) inside commercially available chemotaxis analysis chips. Faster directed migration was observed with decreasing channel dimensions despite substantial cell deformation in the narrower channels. Finite element modeling of a cell either partly or fully obstructing chemokine diffusion in the narrow channels revealed strong local accentuation of the chemokine concentration gradients. The modeled concentration differences across a cell correlated well with the observed velocity dependence on channel cross-section. However, added effects due to spatial confinement could not be excluded. The design freedom offered by two-photon polymerization was exploited to minimize the accentuated concentration gradients in cell-blocked channels by introducing "venting slits" to the surrounding medium at a length scale too small (≤500 nm) for the cells to explore, thereby decoupling effects of concentration gradients and spatial confinement. Studies in slitted 10 × 10 μm(2) channels showed significantly reduced migration speeds indistinguishable from speeds observed in unslitted 20 × 20 μm(2) channel. This result agrees with model predictions of very small concentration gradient variations in slitted channels, thus indicating a strong influence of the concentration gradient steepness, not the channel size, on the directed migration velocity. PMID:25681048

  11. Design of high-perveance confined-flow guns for periodic-permanent-magnet-focused tubes

    NASA Technical Reports Server (NTRS)

    Stankiewicz, N.

    1979-01-01

    An approach to the design of high perveance, low compression guns is described in which confinement is used to stabilize the beam for subsequent periodic-permanent-magnet focusing. The computed results for two cases are presented. A magnetic boundary value problem was solved for the scalar potential from which the axial magnetic field was computed. A solution was found by iterating between Poisson's equation and the electron trajectory calculations. Magnetic field values were varied in magnitude until a laminar beam with minimum scalloping was produced.

  12. First Observation of the High Field Side Sawtooth Crash and Heat Transfer during Driven Reconnection Processes in Magnetically Confined Plasmas

    SciTech Connect

    Park, HK; Luhmann, NC; Donne, AJH; Classen, IGJ; Domier, CW; Mazzucato, E; Munsat, T; van de Pol, MJ; Xia, Z

    2005-12-01

    High resolution (temporal and spatial), two-dimensional images of electron temperature fluctuations during sawtooth oscillations were employed to study driven reconnection processes in magnetically confined toroidal plasmas. The combination of kink and local pressure driven instabilities leads to an "X-point" reconnection process that is localized in the toroidal and poloidal planes. The reconnection is not always confined to the magnetic surfaces with minimum energy. The heat transport process from the core is demonstrated to be highly collective rather than stochastic.

  13. Effect of Aluminium Confinement on ANFO Detonation

    NASA Astrophysics Data System (ADS)

    Short, Mark; Jackson, Scott; Kiyanda, Charles; Shinas, Mike; Hare, Steve; Briggs, Matt

    2013-06-01

    Detonations in confined non-ideal high explosives often have velocities below the confiner sound speed. The effect on detonation propagation of the resulting subsonic flow in the confiner (such as confiner stress waves traveling ahead of the main detonation front or upstream wall deflection into the HE) has yet to be fully understood. Previous work by Sharpe and Bdzil (J. Eng. Math, 2006) has shown that for subsonic confiner flow, there is no limiting thickness for which the detonation dynamics are uninfluenced by further increases in wall thickness. The critical parameters influencing detonation behavior are the wall thickness relative to the HE reaction zone size, and the difference in the detonation velocity and confiner sound speed. Additional possible outcomes of subsonic flow are that for increasing thickness, the confiner is increasingly deflected into the HE upstream of the detonation, and that for sufficiently thick confiners, the detonation speed could be driven up to the sound speed in the confiner. We report here on a further series of experiments in which a mixture of ammonium nitrate and fuel oil (ANFO) is detonated in aluminum confiners with varying HE charge diameter and confiner thickness, and compare the results with the outcomes suggested by Sharpe and Bdzil.

  14. Electrofreezing of confined water.

    PubMed

    Zangi, Ronen; Mark, Alan E

    2004-04-15

    We report results from molecular dynamics simulations of the freezing transition of TIP5P water molecules confined between two parallel plates under the influence of a homogeneous external electric field, with magnitude of 5 V/nm, along the lateral direction. For water confined to a thickness of a trilayer we find two different phases of ice at a temperature of T=280 K. The transformation between the two, proton-ordered, ice phases is found to be a strong first-order transition. The low-density ice phase is built from hexagonal rings parallel to the confining walls and corresponds to the structure of cubic ice. The high-density ice phase has an in-plane rhombic symmetry of the oxygen atoms and larger distortion of hydrogen bond angles. The short-range order of the two ice phases is the same as the local structure of the two bilayer phases of liquid water found recently in the absence of an electric field [J. Chem. Phys. 119, 1694 (2003)]. These high- and low-density phases of water differ in local ordering at the level of the second shell of nearest neighbors. The results reported in this paper, show a close similarity between the local structure of the liquid phase and the short-range order of the corresponding solid phase. This similarity might be enhanced in water due to the deep attractive well characterizing hydrogen bond interactions. We also investigate the low-density ice phase confined to a thickness of 4, 5, and 8 molecular layers under the influence of an electric field at T=300 K. In general, we find that the degree of ordering decreases as the distance between the two confining walls increases. PMID:15267616

  15. 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

    2015-11-01

    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). PMID:26470838

  16. Site-specific patterning of highly ordered nanocrystal superlattices through biomolecular surface confinement.

    PubMed

    Noh, Hyunwoo; Choi, Chulmin; Hung, Albert M; Jin, Sungho; Cha, Jennifer N

    2010-09-28

    With the increasing demand in recent years for high-performance devices for both energy and health applications, there has been extensive research to direct the assembly of nanoparticles into meso- or macroscale single two- and three-dimensional crystals of arbitrary configuration or orientation. Inorganic nanoparticle arrays can have intriguing physical properties that differ from either individual nanoparticles or bulk materials. For most device applications, it is necessary to fabricate two-dimensional nanoparticle superlattices at programmed sites on a surface. However, it has remained a significant challenge to generate patterned arrays with long-range positional order because most highly ordered close-packed nanocrystal arrays are typically obtained by kinetically driven evaporation processes. In this report, we demonstrate a method to generate patterned nanocrystal superlattices by confining nanoparticles to geometrically defined 2-D DNA sites on a surface and using associative biomolecular interparticle interactions to produce thermodynamically stable arrays of hexagonally packed nanocrystals with significant long-range order observed over 1-2 μm. We also demonstrate the role of chemical and geometrical confinement on particle packing and obtaining long-range order. Finally, we also demonstrate that the formation of DNA-mediated nanocrystal superlattices requires both interparticle DNA hybridization and solvent-less thermal annealing.

  17. 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.

  18. Attainment of high confinement in neutral beam heated divertor discharges in the PDX tokamak

    SciTech Connect

    Kaye, S.M.; Bell, M.; Bol, K.; Boyd, D.; Brau, K.; Buchenauer, D.; Budny, R.; Cavallo, A.; Couture, P.; Crowley, T.

    1983-11-01

    The PDX divertor configuration has recently been converted from an open to a closed geometry to inhibit the return of neutral gas from the divertor region to the main chamber. Since then, operation in a regime with high energy confinement in neutral beam heated discharges (ASDEX H-mode) has been routine over a wide range of operating conditions. These H-mode discharges are characterized by a sudden drop in divertor density and H/sub ..cap alpha../ emission and a spontaneous rise in main chamber plasma density during neutral beam injection. The confinement time is found to scale nearly linearly with plasma current, but it can be degraded due to either the presence of edge instabilities or heavy gas puffing. Detailed Thomson scattering temperature profiles show high values of Te near the plasma edge (approx. 450 eV) with sharp radial gradients (approx. 400 eV/cm) near the separatrix. Density profiles are broad and also exhibit steep gradients close to the separatrix.

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

    SciTech Connect

    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.; and others

    2015-05-15

    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. 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.

  1. Thin shell, high velocity inertial confinement fusion implosions on the national ignition facility.

    PubMed

    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

    2015-04-10

    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. Early results have shown good repeatability, with up to 1/2 the neutron yield coming from α-particle self-heating. PMID:25910132

  2. 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.

  3. 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.

  4. Influence of surface scattering on the thermal properties of spatially confined GaN nanofilm

    NASA Astrophysics Data System (ADS)

    Hou, Yang; Zhu, Lin-Li

    2016-08-01

    Gallium nitride (GaN), the notable representative of third generation semiconductors, has been widely applied to optoelectronic and microelectronic devices due to its excellent physical and chemical properties. In this paper, we investigate the surface scattering effect on the thermal properties of GaN nanofilms. The contribution of surface scattering to phonon transport is involved in solving a Boltzmann transport equation (BTE). The confined phonon properties of GaN nanofilms are calculated based on the elastic model. The theoretical results show that the surface scattering effect can modify the cross-plane phonon thermal conductivity of GaN nanostructures completely, resulting in the significant change of size effect on the conductivity in GaN nanofilm. Compared with the quantum confinement effect, the surface scattering leads to the order-of-magnitude reduction of the cross-plane thermal conductivity in GaN nanofilm. This work could be helpful for controlling the thermal properties of GaN nanostructures in nanoelectronic devices through surface engineering. Project supported by the National Natural Science Foundation of China (Grant Nos. 11302189 and 11321202) and the Doctoral Fund of Ministry of Education of China (Grant No. 20130101120175).

  5. Influence of surface scattering on the thermal properties of spatially confined GaN nanofilm

    NASA Astrophysics Data System (ADS)

    Hou, Yang; Zhu, Lin-Li

    2016-08-01

    Gallium nitride (GaN), the notable representative of third generation semiconductors, has been widely applied to optoelectronic and microelectronic devices due to its excellent physical and chemical properties. In this paper, we investigate the surface scattering effect on the thermal properties of GaN nanofilms. The contribution of surface scattering to phonon transport is involved in solving a Boltzmann transport equation (BTE). The confined phonon properties of GaN nanofilms are calculated based on the elastic model. The theoretical results show that the surface scattering effect can modify the cross-plane phonon thermal conductivity of GaN nanostructures completely, resulting in the significant change of size effect on the conductivity in GaN nanofilm. Compared with the quantum confinement effect, the surface scattering leads to the order-of-magnitude reduction of the cross-plane thermal conductivity in GaN nanofilm. This work could be helpful for controlling the thermal properties of GaN nanostructures in nanoelectronic devices through surface engineering. Project supported by the National Natural Science Foundation of China (Grant Nos. 11302189 and 11321202) and the Doctoral Fund of Ministry of Education of China (Grant No. 20130101120175).

  6. Hydraulic head response of a confined aquifer influenced by river stage fluctuations and mechanical loading

    NASA Astrophysics Data System (ADS)

    Pacheco, F. A. L.; Fallico, C.

    2015-12-01

    The response to river stage fluctuation of a drilled well penetrating a confined aquifer was simulated using a stream-aquifer interaction algorithm. Because the confined aquifer is overlaid by a water table aquifer, the algorithm was coupled with formulae used to correct the heads for mechanical loading. The coupling of stream-aquifer interaction and mechanical loading models was tried for the first time in this study. The test site was a drilled well installed on the Montalto Uffugo aquifer located at the Calabria University groundwater test field (Calabria region, south of Italy). This aquifer comprises a 44 m-thick sand bank bounded on bottom and top by clay layers and covered by a 7 m-thick sandy conglomerate, being adjacent to the Mavigliano River. Overall, the head changes caused by a river stage raise represented a contribution of 49.3-57.8% to the total head, while mechanical loading accounted for the remaining 50.7-32.2%. The loading was triggered by a sequence of short-spaced rainfall events lasting for a total of 167 days, which caused recharge to the unconfined aquifer thickening the water column by some 3.1 m.

  7. Influence of the added mass effect and boundary conditions on the dynamic response of submerged and confined structures

    NASA Astrophysics Data System (ADS)

    Valentín, D.; Presas, A.; Egusquiza, E.; Valero, C.

    2014-03-01

    The dynamic response of submerged and confined disk-like structures is of interest in the flied of hydraulic machinery, especially in hydraulic turbine runners. This response is difficult to be estimated with accuracy due to the strong influence of the boundary conditions. Small radial gaps as well as short axial distances to rigid surfaces greatly modify the dynamic response because the fact of the added mass and damping effects. Moreover, the effect of the shaft coupling is also important for certain mode-shapes of the structure. In the present study, the influence of the added mass effect and boundary conditions on the dynamic behavior of a submerged disk attached to a shaft is evaluated through experimental tests and structural- acoustic coupling numerical simulations. For the experimentation, a test rig has been developed. It consists of a confined disk attached to a shaft inside a cylindrical container full of water. The disk can be fixed at different axial positions along the shaft. Piezoelectric patches are used to excite the disk and the response is measured with submersible accelerometers. For each configuration tested, the natural frequencies of the disk and the shaft are studied. Numerical results have been compared with experimental results.

  8. 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.

  9. Influence of the interface on the optical activity of confined glucose films.

    PubMed

    Emile, Olivier; Emile, Janine; Ghoufi, Aziz

    2016-09-01

    We report on the time evolution of the optical activity of a thinning liquid film containing glucose, and confined between two glass slides. This dynamics strongly depends on the presence of surfactant molecules. With sodium dodecyl sulfate (SDS), we evidence favorable interactions of sugar molecules with the sulfate group. As previously observed for a freely suspended soap film in the air (see Emile et al., 2013), this corresponds to an anchoring of glucose molecules at the interface. For glucose alone, we also highlight a molecular rearrangement that is not instantaneous and occurs after several minutes. This interfacial organization leads to an unusual giant optical activity that is different with or without SDS. Molecular simulations confirm the anchoring of the glucose molecules at the glass/liquid interface, and show a different molecular orientation in each case. PMID:27254252

  10. A High Energy X-ray Imager for Inertial Confinement Fusion at the National Ignition Facility

    SciTech Connect

    Tommasini, R; Koch, J A; Young, B; Ng, E; Phillips, T; Dauffy, L

    2006-05-03

    X-ray imaging is a fundamental diagnostic tool for inertial confinement fusion (ICF) research, and provides data on the size and the shape of the core in implosions. We report on the feasibility and performance analysis of an ignition x-ray imager to be used on cryogenic DT implosions at the National Ignition Facility. The system is intended to provide time-integrated, broadband, moderate-energy x-ray core images of imploding ICF capsules. It is optimized with respect to spatial-resolution, signal-to-background and signal-to-noise ratios, taking into account the extreme operating conditions expected at NIF due to high expected neutrons yields, gamma-rays, and x-rays from laser-plasma interactions.

  11. A highly efficient neutron time-of-flight detector for inertial confinement fusion experiments

    NASA Astrophysics Data System (ADS)

    Izumi, N.; Yamaguchi, K.; Yamagajo, T.; Nakano, T.; Kasai, T.; Urano, T.; Azechi, H.; Nakai, S.; Iida, T.

    1999-01-01

    We have developed the highly efficient neutron detector system MANDALA for the inertial-confinement-fusion experiment. The MANDALA system consists of 842 elements plastic scintillation detectors and data acquisition electronics. The detection level is the yield of 1.2×105 for 2.5 MeV and 1×105 for 14.1 MeV neutrons (with 100 detected hits). We have calibrated the intrinsic detection efficiencies of the detector elements using a neutron generator facility. Timing calibration and integrity test of the system were also carried out with a 60Co γ ray source. MANDALA system was applied to the implosion experiments at the GEKKO XII laser facility. The integrity test was carried out by implosion experiments.

  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. Quiescent double barrier high-confinement mode plasmas in the DIII-D tokamak

    NASA Astrophysics Data System (ADS)

    Burrell, K. H.; Austin, M. E.; Brennan, D. P.; DeBoo, J. C.; Doyle, E. J.; Fenzi, C.; Fuchs, C.; Gohil, P.; Greenfield, C. M.; Groebner, R. J.; Lao, L. L.; Luce, T. C.; Makowski, M. A.; McKee, G. R.; Moyer, R. A.; Petty, C. C.; Porkolab, M.; Rettig, C. L.; Rhodes, T. L.; Rost, J. C.; Stallard, B. W.; Strait, E. J.; Synakowski, E. J.; Wade, M. R.; Watkins, J. G.; West, W. P.

    2001-05-01

    High-confinement (H-mode) operation is the choice for next-step tokamak devices based either on conventional or advanced tokamak physics. This choice, however, comes at a significant cost for both the conventional and advanced tokamaks because of the effects of edge localized modes (ELMs). ELMs can produce significant erosion in the divertor and can affect the beta limit and reduced core transport regions needed for advanced tokamak operation. Experimental results from DIII-D [J. L. Luxon et al., Plasma Physics and Controlled Nuclear Fusion Research 1986 (International Atomic Energy Agency, Vienna, 1987), Vol. I, p. 159] this year have demonstrated a new operating regime, the quiescent H-mode regime, which solves these problems. We have achieved quiescent H-mode operation that is ELM-free and yet has good density and impurity control. In addition, we have demonstrated that an internal transport barrier can be produced and maintained inside the H-mode edge barrier for long periods of time (>3.5 s or >25 energy confinement times τE), yielding a quiescent double barrier regime. By slowly ramping the input power, we have achieved βNH89=7 for up to 5 times the τE of 150 ms. The βNH89 values of 7 substantially exceed the value of 4 routinely achieved in the standard ELMing H mode. The key factors in creating the quiescent H-mode operation are neutral beam injection in the direction opposite to the plasma current (counter injection) plus cryopumping to reduce the density. Density and impurity control in the quiescent H mode is possible because of the presence of an edge magnetohydrodynamic (MHD) oscillation, the edge harmonic oscillation, which enhances the edge particle transport while leaving the energy transport unaffected.

  14. Highly Active Nanoreactors: Patchlike or Thick Ni Coating on Pt Nanoparticles Based on Confined Catalysis.

    PubMed

    Qi, Xinhong; Li, Xiangcun; Chen, Bo; Lu, Huilan; Wang, Le; He, Gaohong

    2016-01-27

    Catalyst-containing nanoreactors have attracted considerable attention for specific applications. Here, we initially report preparation of PtNi@SiO2 hollow microspheres based on confined catalysis. The previous encapsulation of dispersed Pt nanoparticles (NPs) in hollow silica microspheres ensures the formation of Pt@Ni coreshell NPs inside the silica porous shell. Thus, the Pt NPs not only catalyze the reduction of Ni ions but also direct Ni deposition on the Pt cores to obtain Pt@Ni core-shell catalyst. It is worthy to point out that this synthetic approach helps to form a patchlike or thick Ni coating on Pt cores by controlling the penetration time of Ni ions from the bulk solution into the SiO2 microspheres (0.5, 1, 2, or 4 h). Notably, the Pt@Ni core-shell NPs with a patch-like Ni layer on Pt cores (0.5 and 1 h) show a higher H2 generation rate of 1221-1475 H2 mL min(-1) g(-1)cat than the Pt@Ni NPs with a thick Ni layer (2 and 4 h, 920-1183 H2 mL min(-1) g(-1)cat), and much higher than that of pure Pt NPs (224 H2 mL min(-1) g(-1)cat). In addition, the catalyst possesses good stability and recyclability for H2 generation. The Pt@Ni core-shell NPs confined inside silica nanocapsules, with well-defined compositions and morphologies, high H2 generation rate, and recyclability, should be an ideal catalyst for specific applications in liquid phase reaction.

  15. 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.

  16. 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.

  17. Quantum Confinement Induced Oscillatory Electric Field on a Stepped Pb(111) Film and Its Influence on Surface Reactivity

    SciTech Connect

    Liu, Xiaojie; Wang, Cai-Zhuang; Hupalo, Myron; Lin, Hai-Quing; Ho, Kai-Ming; Tringides, Michael C.

    2014-01-06

    When the thickness of ultrathin metal films approaches the nanometer scale comparable to the coherence length of the electrons, significant effects on the structure stability and the electronic properties of the metal films emerge due to electron confinement and quantization of the allowed electronic states in the direction perpendicular to the film. Using first-principles calculations, we showed that such quantum size effects can induce oscillatory electrostatic potential and thus alternating electric field on the surface of the wedge-shaped Pb(111) films. The alternating electric field has significant influence on surface reactivity, leading to selective even- or odd-layer adsorption preference depending on the charge state of the adatoms, consistent with the odd-layer preference of higher Mg coverage on wedge-shaped Pb(111) films, as observed in experiment.

  18. 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.

  19. 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.

  20. Regime of Improved Confinement and High Beta in Neutral-Beam-Heated Divertor Discharges of the ASDEX Tokamak

    NASA Astrophysics Data System (ADS)

    Wagner, F.; Becker, G.; Behringer, K.; Campbell, D.; Eberhagen, A.; Engelhardt, W.; Fussmann, G.; Gehre, O.; Gernhardt, J.; Gierke, G. V.; Haas, G.; Huang, M.; Karger, F.; Keilhacker, M.; Klüber, O.; Kornherr, M.; Lackner, K.; Lisitano, G.; Lister, G. G.; Mayer, H. M.; Meisel, D.; Müller, E. R.; Murmann, H.; Niedermeyer, H.; Poschenrieder, W.; Rapp, H.; Röhr, H.; Schneider, F.; Siller, G.; Speth, E.; Stäbler, A.; Steuer, K. H.; Venus, G.; Vollmer, O.; Yü, Z.

    1982-11-01

    A new operational regime has been observed in neutral-injection-heated ASDEX divertor discharges. This regime is characterized by high βp values comparable to the aspect ratio A (βp<=0.65A) and by confinement times close to those of Ohmic discharges. The high-βp regime develops at an injection power >=1.9 MW, a mean density n¯e>=3×1013 cm-3, and a q(a) value >=2.6. Beyond these limits or in discharges with material limiter, low βp values and reduced particle and energy confinement times are obtained compared to the Ohmic heating phase.

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

    NASA Astrophysics Data System (ADS)

    Rossi, M.; Vidal, O.; Wunder, B.; Renard, F.

    2007-08-01

    Theoretical models of compaction processes, such as for example intergranular pressure-solution (IPS), focus on deformation occurring at the contacts between spherical grains that constitute an aggregate. In order to investigate the applicability of such models, and to quantify the deformation of particles within an aggregate, isostatic experiments were performed in cold-sealed vessels on glass sphere aggregates at 200 MPa confining pressure and 350 °C with varying amounts of fluid. Several runs were performed in order to investigate the effects of time, fluid content, pressure and temperature, by varying one of these parameters and holding the others fixed. In order to compare the aggregates with natural materials, similar experiments were also performed using quartz sand instead of glass spheres. Experiments with quartz show evidence of IPS, but the strain could not be quantified. Experiments with glass spheres show evidence of several types of deformation processes: both brittle (fracturing) and ductile (plastic flow and fluid-enhanced deformation, such as IPS). In experiments with a large amount of water (≥ 5 vol.%), dissolution and recrystallization of the glass spheres also occurred, coupled with crystallization of new material filling the initial porosity. Experiments performed with a fluid content of less than 1 vol.% indicate creep behavior that is typical of glass deformation, following an exponential law. These experiments can also be made to fit a power law for creep, with a stress exponent of n = 10.5 ± 2.2 in both dry and wet experiments. However, the pre-factor of the power law creep increases 5 times with the addition of water, showing the strong effect of water on the deformation rate. These simple and low-cost experiments provide new insights on the rheology of soda-lime glass, which is used in analogue experiments, and of glass-bearing rocks under mid-crustal P- T conditions. They also highlight the strong enhancement of plasticity of natural

  2. Traction and nonequilibrium phase behavior of confined sheared liquids at high pressure

    NASA Astrophysics Data System (ADS)

    Gattinoni, Chiara; Heyes, David M.; Lorenz, Christian D.; Dini, Daniele

    2013-11-01

    Nonequilibrium molecular dynamics simulations of confined model liquids under pressure and sheared by the relative sliding of the boundary walls have been carried out. The relationship between the time-dependent traction coefficient, μ(t), and the state of internal structure of the film is followed from commencement of shear for various control parameters, such as applied load, global shear rate, and solid-liquid atom interaction parameters. Phase diagrams, velocity and temperature profiles, and traction coefficient diagrams are analyzed for pure Lennard-Jones (LJ) liquids and a binary LJ mixture. A single component LJ liquid is found to form semicrystalline arrangements with high-traction coefficients, and stick-slip behavior is observed for high pressures and low-shear velocities, which is shown to involve periodic deformation and stress release of the wall atoms and slip in the solid-liquid boundary region. A binary mixture, which discourages crystallization, gives a more classical tribological response with the larger atoms preferentially adsorbing commensurate with the wall. The results obtained are analyzed in the context of tribology: the binary mixture behaves like a typical lubricant, whereas the monatomic system behaves like a traction fluid. It is discussed how this type of simulation can give insights on the tribological behavior of realistic systems.

  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. Nanoscale High Energetic Materials: A Polymeric Nitrogen Chain N8 Confined inside a Carbon Nanotube

    NASA Astrophysics Data System (ADS)

    Abou-Rachid, Hakima; Hu, Anguang; Timoshevskii, Vladimir; Song, Yanfeng; Lussier, Louis-Simon

    2008-05-01

    We present a theoretical study of a new hybrid material, nanostructured polymeric nitrogen, where a polymeric nitrogen chain is encapsulated in a carbon nanotube. The electronic and structural properties of the new system are studied by means of ab initio electronic structure and molecular dynamics calculations. Finite temperature simulations demonstrate the stability of this nitrogen phase at ambient pressure and room temperature using carbon nanotube confinement. This nanostructured confinement may open a new path towards stabilizing polynitrogen or polymeric nitrogen at ambient conditions.

  5. 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.

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

    NASA Astrophysics Data System (ADS)

    Castell, Karen D.; Ruitberg, Arthur P.

    1994-11-01

    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.

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

    DOE Data Explorer

    Thome, Kathreen E. [University of Wisconsin-Madison] (ORCID:0000000248013922); Bongard, Michael W. [University of Wisconsin-Madison] (ORCID:0000000231609746); Barr, Jayson L. [University of Wisconsin-Madison] (ORCID:0000000177685931); Bodner, Grant M. [University of Wisconsin-Madison] (ORCID:0000000324979172); Burke, Marcus G. [University of Wisconsin-Madison] (ORCID:0000000176193724); Fonck, Raymond J. [University of Wisconsin-Madison] (ORCID:0000000294386762); Kriete, David M. [University of Wisconsin-Madison] (ORCID:0000000236572911); Perry, Justin M. [University of Wisconsin-Madison] (ORCID:0000000171228609); Schlossberg, David J. [University of Wisconsin-Madison] (ORCID:0000000287139448)

    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).

  8. High-Adiabat High-Foot Inertial Confinement Fusion Implosion Experiments on the National Ignition Facility

    NASA Astrophysics Data System (ADS)

    Park, H.-S.; Hurricane, O. A.; Callahan, D. A.; Casey, D. T.; Dewald, E. L.; Dittrich, T. R.; Döppner, T.; Hinkel, D. E.; Berzak Hopkins, L. F.; Le Pape, S.; Ma, T.; Patel, P. K.; Remington, B. A.; Robey, H. F.; Salmonson, J. D.; Kline, J. L.

    2014-02-01

    This Letter reports on a series of high-adiabat implosions of cryogenic layered deuterium-tritium (DT) capsules indirectly driven by a "high-foot" laser drive pulse at the National Ignition Facility. High-foot implosions have high ablation velocities and large density gradient scale lengths and are more resistant to ablation-front Rayleigh-Taylor instability induced mixing of ablator material into the DT hot spot. Indeed, the observed hot spot mix in these implosions was low and the measured neutron yields were typically 50% (or higher) of the yields predicted by simulation. On one high performing shot (N130812), 1.7 MJ of laser energy at a peak power of 350 TW was used to obtain a peak hohlraum radiation temperature of ˜300 eV. The resulting experimental neutron yield was (2.4±0.05)×1015 DT, the fuel ρR was (0.86±0.063) g/cm2, and the measured Tion was (4.2±0.16) keV, corresponding to 8 kJ of fusion yield, with ˜1/3 of the yield caused by self-heating of the fuel by α particles emitted in the initial reactions. The generalized Lawson criteria, an ignition metric, was 0.43 and the neutron yield was ˜70% of the value predicted by simulations that include α-particle self-heating.

  9. 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.

  10. 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.

  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. PMID:24679357

  12. 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.

  13. Quark matter at high density based on an extended confined isospin-density-dependent mass model

    NASA Astrophysics Data System (ADS)

    Qauli, A. I.; Sulaksono, A.

    2016-01-01

    We investigate the effect of the inclusion of relativistic Coulomb terms in a confined-isospin-density-dependent-mass (CIDDM) model of strange quark matter (SQM). We found that if we include the Coulomb term in scalar density form, the SQM equation of state (EOS) at high densities is stiffer but if we include the Coulomb term in vector density form it is softer than that of the standard CIDDM model. We also investigate systematically the role of each term of the extended CIDDM model. Compared with what was reported by Chu and Chen [Astrophys. J. 780, 135 (2014)], we found the stiffness of SQM EOS is controlled by the interplay among the oscillator harmonic, isospin asymmetry and Coulomb contributions depending on the parameter's range of these terms. We have found that the absolute stable condition of SQM and the mass of 2 M⊙ pulsars can constrain the parameter of oscillator harmonic κ1≈0.53 in the case the Coulomb term is excluded. If the Coulomb term is included, for the models with their parameters are consistent with SQM absolute stability condition, the 2.0 M⊙ constraint more prefers the maximum mass prediction of the model with the scalar Coulomb term than that of the model with the vector Coulomb term. On the contrary, the high densities EOS predicted by the model with the vector Coulomb is more compatible with the recent perturbative quantum chromodynamics result [1] than that predicted by the model with the scalar Coulomb. Furthermore, we also observed the quark composition in a very high density region depends quite sensitively on the kind of Coulomb term used.

  14. Fast Ion Confinement in High Beta, Steady-State Scenario Plasmas

    NASA Astrophysics Data System (ADS)

    Heidbrink, W. W.; Chen, X.; Ferron, J. R.; van Zeeland, M. A.; Grierson, B. A.; Holcomb, C. T.

    2013-10-01

    Fast-ion confinement is studied for qmin between 1.2-2.8 in plasmas with normalized β > 2 . 6 . Fast-ion D-alpha (FIDA), neutron, and neutral-particle diagnostics measure the confined fast ions. Tearing modes and a ``sea'' of unstable Alfvén eigenmodes (AE) are observed. In preliminary analysis, the degradation in fast-ion confinement increases with qmin ; increased AE activity appears responsible. Predictions of a model that assumes that AE-induced fast-ion transport is stiff are compared with the data. Work supported by the US Department of Energy under SC-G903402, DE-FC-02-04ER54698, DE-AC02-09CH11466, and DE-AC52-07NA27344.

  15. High-speed repetitive pellet injector for plasma fueling of magnetic confinement fusion devices

    SciTech Connect

    Combs, S.K.; Baylor, L.R.; Foust, C.R.

    1993-11-01

    The projected fueling requirements of future magnetic confinement devices for controlled thermonuclear research [e.g., the International Thermonuclear Experimental Reactor (ITER)] indicate that a flexible plasma fueling capability is required. This includes a mix of traditional gas puffing and low- and high-velocity deuterium-tritium pellets. Conventional pellet injectors (based on light gas guns or centrifugal accelerators) can reliably provide frozen hydrogen pellets (1- to 6-mm-diam sizes tested) up to {approximately}1.3-km/s velocity at the appropriate pellet fueling rates (1 to 10 Hz or greater). For long-pulse operation in a higher velocity regime (>2 km/s), an experiment in collaboration between Oak Ridge National Laboratory (ORNL) and ENEA Frascati is under way. This activity will be carried out in the framework of a collaborative agreement between the US Department of Energy and European Atomic Energy Community -- ENEA Association. In this experiment, an existing ORNL hydrogen extruder (equipped with a pellet chambering mechanism/gun barrel assembly) and a Frascati two-stage light gas gun driver have been combined on a test facility at ORNL. Initial testing has been carried out with single deuterium pellets accelerated up to 2.05 km/s with the two-stage driver; in addition, some preliminary repetitive testing (to commission the diagnostics) was performed at reduced speeds, including sequences at 0.5 to 1 Hz and 10 to 30 pellets. The primary objective of this study is to demonstrate repetitive operation (up to {approximately}1 Hz) with speeds in the 2- to 3-km/s range. In addition, the strength of extruded hydrogen ice as opposed to that produced in situ by direct condensation in pipe guns can be investigated. The equipment and initial experimental results are described.

  16. 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.

  17. Collisions between Dark Matter Confined High Velocity Clouds and Magnetized Galactic Disks: The Smith Cloud

    NASA Astrophysics Data System (ADS)

    Galyardt, Jason; Shelton, Robin L.

    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 × 106M⊙ and dark matter minihalo masses of 0, 3 × 108, or 1 × 109 M⊙. 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 × 105 M⊙ 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.

  18. A low cost and high throughput magnetic bead-based immuno-agglutination assay in confined droplets.

    PubMed

    Teste, Bruno; Ali-Cherif, Anaïs; Viovy, Jean Louis; Malaquin, Laurent

    2013-06-21

    Although passive immuno-agglutination assays consist of one step and simple procedures, they are usually not adapted for high throughput analyses and they require expensive and bulky equipment for quantitation steps. Here we demonstrate a low cost, multimodal and high throughput immuno-agglutination assay that relies on a combination of magnetic beads (MBs), droplets microfluidics and magnetic tweezers. Antibody coated MBs were used as a capture support in the homogeneous phase. Following the immune interaction, water in oil droplets containing MBs and analytes were generated and transported in Teflon tubing. When passing in between magnetic tweezers, the MBs contained in the droplets were magnetically confined in order to enhance the agglutination rate and kinetics. When releasing the magnetic field, the internal recirculation flows in the droplet induce shear forces that favor MBs redispersion. In the presence of the analyte, the system preserves specific interactions and MBs stay in the aggregated state while in the case of a non-specific analyte, redispersion of particles occurs. The analyte quantitation procedure relies on the MBs redispersion rate within the droplet. The influence of different parameters such as magnetic field intensity, flow rate and MBs concentration on the agglutination performances have been investigated and optimized. Although the immuno-agglutination assay described in this work may not compete with enzyme linked immunosorbent assay (ELISA) in terms of sensitivity, it offers major advantages regarding the reagents consumption (analysis is performed in sub microliter droplet) and the platform cost that yields to very cheap analyses. Moreover the fully automated analysis procedure provides reproducible analyses with throughput well above those of existing technologies. We demonstrated the detection of biotinylated phosphatase alkaline in 100 nL sample volumes with an analysis rate of 300 assays per hour and a limit of detection of 100 pM.

  19. Radiative power losses from impurities in high-density plasmas confined by high magnetic fields

    NASA Astrophysics Data System (ADS)

    May, Mark Joseph

    1998-07-01

    Quantifying and controlling the radiative power losses from impurities in the tokamak fusion plasma is crucial for obtaining ignition conditions. In the present work, therefore, losses from impurities have been measured in different operating regimes of the Alcator C-Mod Tokamak and the Frascati Tokamak Upgrade (FTU) plasmas. The major radiating intrinsic impurity in both tokamaks was molybdenum sputtered from the armor tiles covering all the plasma facing surfaces. The radiative power losses from the molybdenum ions accounted for [>]80/% of the total radiative power losses in ICRF heated plasmas and ~60/% in ohmically heated plasmas. Molybdenum could radiate as much as several thousand kW with concentrations as high as ~1× 1011/ particles/cm3 or ~0.001 of the plasma (electron) density. The radiative losses were found to increase linearly with increasing ICRF power and to vary weakly with the central electron density of the plasma. The other major intrinsic impurities in Alcator C-Mod Tokamak, carbon and boron, radiated at most ~100 kW from the plasma and had concentrations in ohmically heated plasmas of ~1.7× 10/ particles/cm3 and ~6.3× 1011/ particles/cm3, respectively. At Alcator C-Mod Tokamak, the total radiative power losses were measured with bolometric systems. The contribution to the total radiative losses from each major impurity and the impurity concentrations were determined spectroscopically from the line brightnesses of XUV (soft X-ray and extreme ultraviolet) transitions. The line brightnesses were interpreted via a detailed atomic physics model which included the Multiple Ionization State Transport (MIST) code, the ab initio atomic rates from the Hebrew University-Jerusalem Lawrence Livermore Atomic Code (HULLAC) and a collisional radiative model. At the FTU Tokamak, brightnesses from impurity emission measured with an X-ray crystal spectrometer were interpreted with a similar atomic physics model which included the molybdenum rates from HULLAC

  20. 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

  1. Pulsed-Power-Driven High Energy Density Physics and Inertial Confinement Fusion Research

    NASA Astrophysics Data System (ADS)

    Matzen, M. Keith

    2004-11-01

    There continues to be dramatic progress in applying pulsed-power drivers to research in High Energy Density Physics (HEDP) and Inertial Confinement Fusion (ICF). The Z facility at Sandia National Laboratories delivers 20-MA load currents to create high magnetic fields (> 1000 T) and pressures (Mbar to Gbar). In a z-pinch configuration, the magnetic pressure (Lorentz Force) supersonically implodes a plasma created from a cylindrical wire array, which at stagnation generates a plasma with energy densities of 10 MJ/cm^3 and temperatures exceeding 1 keV at 0.1% of solid density. These HED plasmas produce x-ray energies approaching 2 MJ at powers greater than 200 TW for ICF, radiation hydrodynamics, radiation-material interactions, Inertial Fusion Energy, astrophysics, and opacity experiments. In an alternate configuration, the large magnetic pressure is used to directly drive Isentropic Compression Experiments (ICE) to pressures greater than 3 Mbar and accelerate flyer plates to 27 km/s for equation of state (EOS) experiments at pressures up to 10 Mbar in Al. The challenge to model these complex geometric configurations over multiple orders of magnitude in spatial scale, temperatures, densities, and radiation fluxes is daunting. Nevertheless, development of multi-dimensional radiation-MHD codes (e.g. ALEGRA) coupled with more accurate material models (e.g. quantum molecular dynamics calculations within density functional theory) has resulted in a productive synergy between validating the simulations and guiding the experiments. The Z facility is now routinely used to drive ICF capsules (focusing on implosion symmetry and neutron production) and several different HEDP experiments (including radiation-driven hydrodynamic jets; material EOS, phase transitions, and strength; and the detailed behavior of z-pinch wire array initiation and implosion). This research is performed in collaboration with many other groups from around the world. A $60M, five-year project to enhance

  2. 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

  3. 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.; Shah, Rahul C.; Forrest, Chad J.; Silverstein, Kevin; Marshall, Frederic J.; Boswell, Melissa; Fowler, Malcolm M.; Gore, Robert A.; et al

    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

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. Observation of High-Field-Side Crash and Heat Transfer during Sawtooth Oscillation in Magnetically Confined Plasmas

    SciTech Connect

    Park, H.K.; Mazzucato, E.; Luhmann, N.C. Jr.; Domier, C.W.; Xia, Z.; Donne, A.J.H.; Classen, I.G.J.; Pol, M.J. van de; Munsat, T.

    2006-05-19

    High resolution (temporal and spatial), two-dimensional images of electron temperature fluctuations during sawtooth oscillations were employed to study the crash process and heat transfer in magnetically confined toroidal plasmas. The combination of kink and local pressure driven instabilities leads to a small poloidally localized puncture in the magnetic surface at both the low and the high field sides of the poloidal plane. This observation closely resembles the 'fingering event' of the ballooning mode model with the high-m mode only predicted at the low field side.

  9. 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

  10. Role of quantum confinement in giving rise to high electron mobility in GaN nanowall networks

    NASA Astrophysics Data System (ADS)

    Bhasker, H. P.; Thakur, Varun; Shivaprasad, S. M.; Dhar, S.

    2015-10-01

    Origin of unprecedentedly high electron mobility observed in the c-axis oriented GaN nanowall networks is investigated by studying the depth distribution of structural, electrical and optical properties of several such high mobility samples grown by molecular beam epitaxy (MBE) technique for different time durations. It has been found that in two hour grown samples, walls are tapered continuously from the bottom to the top. While in four hour grown samples, walls are flat-topped with the top surface containing certain secondary tip structures. These additional features run along the length of the walls to form a well-connected network. Our study reveals that the carriers are quantum mechanically confined not only in the secondary tip structures but also in the wider part of the walls. The secondary tip structures, which are found to offer higher mobility than the rest of the network, are also identified as the regions of stronger confinement. The effect of mobility enhancement observed in these samples has been attributed to a 2D quantum confinement of electrons in the central vertical plane of the walls.

  11. 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. PMID:27225944

  12. 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. PMID:11117739

  13. The influence of toroidal Alfvén modes on the confinement of fast particles in the Globus-M spherical tokamak

    NASA Astrophysics Data System (ADS)

    Petrov, Yu. V.; Bakharev, N. N.; Gusev, V. K.; Minaev, V. B.; Kornev, V. A.; Mel'nik, A. D.; Patrov, M. I.; Sakharov, N. V.; Tolstyakov, S. Yu.; Kurskiev, G. S.; Chernyshev, F. V.; Shchegolev, P. B.

    2014-12-01

    Neutral beam injection into the Globus-M spherical tokamak at the early stage of discharge leads to the development of instabilities in a frequency range of 50-200 kHz, which have been identified as toroidal Alfvén eigenmodes (TAEs) [1]. The influence of these modes on the confinement of fast particles has been studied with the aid of a neutral particle analyzer (NPA) and a neutron detector. The isotope effect was studied using hydrogen and deuterium both in the injected beam and in the target plasma. A correlation analysis of signals from magnetic probes showed that the observed modes in most cases contain a single harmonic with toroidal number n = 1. Upon the injection of deuterium into deuterium plasma, the development of TAEs led to a decrease in the neutron flux by 25%, whereas the fluxes of high-energy recharge atoms decreased by 75%. After the injection of hydrogen, a decrease in the flux measured by NPA did not exceed 25%.

  14. 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).].

  15. 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.; 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.

  16. 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.

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

    NASA Astrophysics Data System (ADS)

    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.

    2016-04-01

    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 PL H 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 Jedge(R ,t ) measurements through an ELM that show a complex multimodal collapse and the ejection of a current-carrying filament.

  18. 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.; 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 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

  19. 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

  20. 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

  1. 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

  2. PRODUCTION OF HIGHLY-ALIGNED COLLAGEN LAMELLAE BY COMBINING SHEAR FORCE AND THIN-FILM CONFINEMENT

    PubMed Central

    Saeidi, Nima; Sander, Edward A.; Zareian, Ramin

    2012-01-01

    Load-bearing tissues owe their mechanical strength to their highly-anisotropic collagenous structure. To date, attempts to engineer mechanically strong connective tissue have failed mainly due to the lack of the ability to reproduce native collagen organization in constructs synthesized by cultured cells in vitro. The ability to influence the direction of the self-assembling collagen molecules and produce highly anisotropic structures has applications ranging from de novo engineering of complex tissues to the production of organized scaffolds for cell culture contact guidance. In this investigation we have used the simple technique of spin coating to produce highly-aligned arrays of collagen fibrils. By a simple modification of the method we have also successfully produced orthogonal collagen lamellae. Alternating collagen lamellae are frequently seen in load-bearing tissues such as cornea, annulus fibrosus, and cortical bone. Culturing of corneal fibroblasts onto aligned collagen shows that the cells adopt the organization of the fibrils. In this investigation, we observed the reversal of fibrillar growth direction or “hook” formation similar to those seen previously in a microfluidic shear-flow chamber. Although the results of this investigation clearly show that it is possible to produce small areas (O) 1 cm2 of collagen fibrils with enough alignment to guide fibroblasts, there is evidence that thin film instabilities are likely to be a significant barrier to producing organized collagen fibrils over larger areas. Successful application of this method to produce highly-controlled and organized collagenous structures will require the development of techniques to control thin film instability and will be the subject of the future work. PMID:21362500

  3. 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.

  4. 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.

  5. E-H mode transition of a high-power inductively coupled plasma torch at atmospheric pressure with a metallic confinement tube

    NASA Astrophysics Data System (ADS)

    Altenberend, Jochen; Chichignoud, Guy; Delannoy, Yves

    2012-08-01

    Inductively coupled plasma torches need high ignition voltages for the E-H mode transition and are therefore difficult to operate. In order to reduce the ignition voltage of an RF plasma torch with a metallic confinement tube the E-H mode transition was studied. A Tesla coil was used to create a spark discharge and the E-H mode transition of the plasma was then filmed using a high-speed camera. The electrical potential of the metallic confinement tube was measured using a high-voltage probe. It was found that an arc between the grounded injector and the metallic confinement tube is maintained by the electric field (E-mode). The transition to H-mode occurred at high magnetic fields when the arc formed a loop. The ignition voltage could be reduced by connecting the metallic confinement tube with a capacitor to the RF generator.

  6. Second Harmonic Generation and Confined Acoustic Phonons in HighlyExcited Semiconductor Nanocrystals

    SciTech Connect

    Son, Dong Hee; Wittenberg, Joshua S.; Banin, Uri; Alivisatos, A.Paul

    2006-03-30

    The photo-induced enhancement of second harmonic generation, and the effect of nanocrystal shape and pump intensity on confined acoustic phonons in semiconductor nanocrystals, has been investigated with time-resolved scattering and absorption measurements. The second harmonic signal showed a sublinear increase of the second order susceptibility with respect to the pump pulse energy, indicating a reduction of the effective one-electron second-order nonlinearity with increasing electron-hole density in the nanocrystals. The coherent acoustic phonons in spherical and rod-shaped semiconductor nanocrystals were detected in a time-resolved absorption measurement. Both nanocrystal morphologies exhibited oscillatory modulation of the absorption cross section, the frequency of which corresponded to their coherent radial breathing modes. The amplitude of the oscillation also increased with the level of photoexcitation, suggesting an increase in the amplitude of the lattice displacement as well.

  7. Near-integrability and confinement for high-energy hadron-hadron collisions

    SciTech Connect

    Orland, Peter

    2008-03-01

    We investigate an effective Hamiltonian for QCD at large s, in which longitudinal gauge degrees of freedom are suppressed, but not eliminated. In an axial gauge the effective field theory is a set of coupled (1+1)-dimensional principal-chiral models, which are completely integrable. The confinement problem is solvable in this context, and we find the longitudinal and transverse string tensions with techniques already used for a similar Hamiltonian in (2+1) dimensions. We find some a posteriori justification for the effective Hamiltonian as an eikonal approximation. Hadrons in this approximation consist of partons, which are quarks and solitonlike excitations of the sigma models. Diffractive hadron-hadron scattering appears primarily due to exchange of longitudinal flux between partons.

  8. Carrier dynamics in highly quantum-confined, colloidal indium antimonide nanocrystals.

    PubMed

    Chang, Angela Y; Liu, Wenyong; Talapin, Dmitri V; Schaller, Richard D

    2014-08-26

    Nanometer-sized particles of indium antimonide (InSb) offer opportunities in areas such as solar energy conversion and single photon sources. Here, we measure electron-hole pair dynamics, spectra, and absorption cross sections of strongly quantum-confined colloidal InSb nanocrystal quantum dots using femtosecond transient absorption. For all samples, we observe a bleach feature that develops on ultrafast time scales, which notably moves to lower energy during the first several picoseconds following excitation. We associate this unusual red shift, which becomes larger for larger particles and more distinct at lower sample temperatures, with hot exciton cooling through states that we suggest arise from energetically proximal conduction band levels. From controlled optical excitation intensities, we determine biexciton lifetimes, which range from 2 to 20 ps for the studied 3-6 nm diameter particle sizes. PMID:25106893

  9. 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.

  10. Confinement of bunched beams

    NASA Astrophysics Data System (ADS)

    Hess, Mark; Chen, Chiping

    2001-05-01

    The non-relativistic motion is analyzed for a highly bunched beam propagating through a perfectly conducting cylindrical pipe confined radially by a constant magnetic field parallel to the conductor axis, using a Green's function technique and Hamiltonian dynamics analysis. It is shown that for the confinement of beams with the same charge per unit length, the maximum value of the effective self-field parameter for a highly bunched beam is significantly lower than the Brillouin density limit for an unbunched beam.

  11. 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

  12. 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

  13. 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.

  14. Phase-controlled synthesis of α-NiS nanoparticles confined in carbon nanorods for high performance supercapacitors.

    PubMed

    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

  15. Confined Porous Graphene/SnOx Frameworks within Polyaniline-Derived Carbon as Highly Stable Lithium-Ion Battery Anodes.

    PubMed

    Zhou, Dan; Song, Wei-Li; Li, Xiaogang; Fan, Li-Zhen

    2016-06-01

    Tin oxides are promising anode materials for their high theoretical capacities in rechargeable lithium-ion batteries (LIBs). However, poor stability usually limits the practical application owing to the large volume variation during the cycling process. Herein, a novel carbon confined porous graphene/SnOx framework was designed using a silica template assisted nanocasting method followed by a polyaniline-derived carbon coating process. In this process, silica served as a template to anchor SnOx nanoparticles on porous framework and polyaniline was used as the carbon source for coating on the porous graphene/SnOx framework. The synthesized carbon confined porous graphene/SnOx frameworks demonstrate substantially improved rate capacities and enhanced cycling stability as the anode materials in LIBs, showing a high reversible capacity of 907 mAh g(-1) after 100 cycles at 100 mA g(-1) and 555 mAh g(-1) after 400 cycles at 1000 mA g(-1). The remarkably improved electrochemical performance could be assigned to the unique porous architecture, which effectively solves the drawbacks of SnOx including poor electrical conductivity and undesirable volume expansion during cycling process. Consequently, such design concept for promoting SnOx performance could provide a novel stage for improving anode stability in LIBs.

  16. 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.

  17. Simulation of High Re Boundary Layer Flows on Uniform Grids Using Immersed Boundaries with Vorticity Confinement

    NASA Astrophysics Data System (ADS)

    Chitta, Subhashini; Steinhoff, John

    2015-11-01

    This paper describes the use of Vorticity Confinement (VC) to efficiently treat complex blunt bodies with thin shed vortex sheets and attached boundary layers. Because these flows involve turbulence in the vortical regions, there is currently no ab initio method to treat them on current or foreseeable computers. In fact, in spite of years of turbulence modeling efforts (such as LES or RANS), serious flaws in aerodynamic design involving vortex shedding may still be left undetected until the expensive prototype or production stage. Our basic premise is that, for a class of real-world problems requiring simulating ensembles of flow conditions for overall accuracy, conventional turbulence models suffer cost constraints. For these reasons, VC is used to rapidly simulate many operating conditions, as is often done in expensive testing programs for flying prototypes, and in realistic simulations. To achieve dramatically lower computational cost, VC treats the entire flow in a uniform, coarse grid with solid surfaces ``immersed'' in the grid so that they can be quickly generated for many configurations with no requirement for adaptive or conforming fine grids. Also, the VC method has the efficiency of panel methods, but the generality and ease of use of Euler equation methods. We would like to thank Dr. Frank Caradonna for his suggestions and support.

  18. 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.

  19. Hitherto unknown shear rupture mechanism as a source of instability in intact hard rocks at highly confined compression

    NASA Astrophysics Data System (ADS)

    Tarasov, Boris G.

    2014-05-01

    Today, frictional shear resistance along pre-existing faults is considered to be the lower limit on rock shear strength for confined conditions corresponding to the seismogenic layer. This paper introduces a recently identified shear rupture mechanism providing a paradoxical feature of hard rocks - the possibility of shear rupture propagation through the highly confined intact rock mass at shear stress levels significantly less than frictional strength. In the new mechanism, the rock failure associated with consecutive creation of small slabs (known as ‘domino-blocks') from the intact rock in the rupture tip is driven by a fan-shaped domino structure representing the rupture head. The fan-head combines such unique features as: extremely low shear resistance, self-sustaining stress intensification, and self-unbalancing conditions. Due to this the failure process caused by the mechanism is very dynamic and violent. This makes it impossible to directly observe and study the mechanism and can explain why the mechanism has not been detected before. This paper provides physical motivation for the mechanism, based upon side effects accompanying the failure process. Physical and mathematical models of the mechanism presented in the paper explain unique and paradoxical features of the mechanism. The new shear rupture mechanism allows a novel point of view for understanding the nature of spontaneous failure processes in hard rocks including earthquakes.

  20. 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.

  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. Evidence of the existence of the high-density and low-density phases in deeply-cooled confined heavy water under high pressures

    SciTech Connect

    Wang, Zhe; Chen, Sow-Hsin; Liu, Kao-Hsiang; Harriger, Leland; Leão, Juscelino B.

    2014-07-07

    The average density of D{sub 2}O confined in a nanoporous silica matrix (MCM-41-S) is studied with neutron scattering. We find that below ∼210 K, the pressure-temperature plane of the system can be divided into two regions. The average density of the confined D{sub 2}O in the higher-pressure region is about 16% larger than that in the lower-pressure region. These two regions could represent the so-called “low-density liquid” and “high-density liquid” phases. The dividing line of these two regions, which could represent the associated 1st order liquid-liquid transition line, is also determined.

  3. 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

  4. 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.

  5. Thermal Cook-Off Experiments of the HMX Based High Explosive LX-04 to Characterize Violence with Varying Confinement

    NASA Astrophysics Data System (ADS)

    Garcia, Frank; Vandersall, Kevin S.; Forbes, Jerry W.; Tarver, Craig M.; Greenwood, Daniel

    2006-07-01

    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.

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

    PubMed

    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. PMID:27078402

  7. 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.

  8. 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.

  9. Low-to-High Confinement Transition Mediated by Turbulence Radial Wave Number Spectral Shift in a Fusion Plasma.

    PubMed

    Xu, G S; Wan, B N; Wang, H Q; Guo, H Y; Naulin, V; Rasmussen, J Juul; Nielsen, A H; Wu, X Q; Yan, N; Chen, L; Shao, L M; Chen, R; Wang, L; Zhang, W

    2016-03-01

    A new model for the low-to-high (L-H) confinement transition has been developed based on a new paradigm for turbulence suppression by velocity shear [G. M. Staebler et al., Phys. Rev. Lett. 110, 055003 (2013)]. The model indicates that the L-H transition can be mediated by a shift in the radial wave number spectrum of turbulence, as evidenced here, for the first time, by the direct observation of a turbulence radial wave number spectral shift and turbulence structure tilting prior to the L-H transition at tokamak edge by direct probing. This new mechanism does not require a pretransition overshoot in the turbulent Reynolds stress, shunting turbulence energy to zonal flows for turbulence suppression as demonstrated in the experiment.

  10. Low-to-High Confinement Transition Mediated by Turbulence Radial Wave Number Spectral Shift in a Fusion Plasma

    NASA Astrophysics Data System (ADS)

    Xu, G. S.; Wan, B. N.; Wang, H. Q.; Guo, H. Y.; Naulin, V.; Rasmussen, J. Juul; Nielsen, A. H.; Wu, X. Q.; Yan, N.; Chen, L.; Shao, L. M.; Chen, R.; Wang, L.; Zhang, W.

    2016-03-01

    A new model for the low-to-high (L -H ) confinement transition has been developed based on a new paradigm for turbulence suppression by velocity shear [G. M. Staebler et al., Phys. Rev. Lett. 110, 055003 (2013)]. The model indicates that the L -H transition can be mediated by a shift in the radial wave number spectrum of turbulence, as evidenced here, for the first time, by the direct observation of a turbulence radial wave number spectral shift and turbulence structure tilting prior to the L -H transition at tokamak edge by direct probing. This new mechanism does not require a pretransition overshoot in the turbulent Reynolds stress, shunting turbulence energy to zonal flows for turbulence suppression as demonstrated in the experiment.

  11. Influence of the Dzyaloshinskii-Moriya interaction on the FMR spectrum of magnonic crystals and confined structures

    NASA Astrophysics Data System (ADS)

    Mruczkiewicz, M.; Krawczyk, M.

    2016-07-01

    We study the effect of surface-induced Dzyaloshinskii-Moriya interaction (DMI) on the ferromagnetic resonance (FMR) spectrum of thickness-modulated one-dimensional magnonic crystals and isolated stripes. The DMI is found to substantially increases the intensity of absorption peaks and shifts the frequencies of the laterally quantized modes. The role of the DMI is determined by analyzing the amplitude and phase distributions of dynamic magnetic excitations calculated with frequency- and time-domain calculation methods. We propose experimentally realizable magnonic crystals and confined structures with multiple FMR absorption peaks. The frequency or magnetic field separation between FMR lines is exploited to propose a method for estimation of the DMI strength.

  12. Thermal Cook-Off Experiments of the HMX Based High Explosive LX-04 to Characterize Violence with Varying Confinement

    NASA Astrophysics Data System (ADS)

    Garcia, Frank; Forbes, Jerry W.

    2005-07-01

    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. Modeling was also performed using Ignition and Growth kinetics with reasonable agreement to the experiment. These results suggest that controlling the overall system confinement can modify the relative safety in a given scenario. This work was performed under the auspices of the U. S. Department of Energy by the University of California, Lawrence Livermore National Laboratory under Contract No. W-7405-Eng-48.

  13. 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

  14. 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.

  15. 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.

  16. HIGH CHARGE EFFECTS IN SILICON DRIFT DETECTORS WITH LATERAL CONFINEMENT OF ELECTRONS.

    SciTech Connect

    CASTOLDI,A.; REHAK,P.

    1995-10-21

    A new drift detector prototype which provides suppression of the lateral diffusion of electrons has been tested as a function of the signal charge up to high charge levels, when electrostatic repulsion is not negligible. The lateral diffusion of the electron cloud has been measured for injected charges up to 2 {center_dot} 10{sup 5} electrons. The maximum number of electrons for which the suppression of the lateral spread is effective is obtained.

  17. In Situ Confinement of Ultrasmall Pd Clusters within Nanosized Silicalite-1 Zeolite for Highly Efficient Catalysis of Hydrogen Generation.

    PubMed

    Wang, Ning; Sun, Qiming; Bai, Risheng; Li, Xu; Guo, Guanqi; Yu, Jihong

    2016-06-22

    Well-dispersed and ultrasmall Pd clusters in nanosized silicalite-1 (MFI) zeolite have been prepared under direct hydrothermal conditions using [Pd(NH2CH2CH2NH2)2]Cl2 as precursor. High-resolution scanning transmission electron microscopy studies indicate that the Pd clusters are encapsulated within the intersectional channels of MFI, and the Pd clusters in adjacent channels visually aggregate, forming nanoparticles (NPs) of ∼1.8 nm. The resultant catalysts show an excellent activity and highly efficient H2 generation toward the complete decomposition of formic acid (FA) under mild conditions. Notably, thanks to the further reduced Pd NP size (∼1.5 nm) and the additionally introduced basic sites, the Pd/S-1-in-K catalyst affords turnover frequency values up to 856 h(-1) at 25 °C and 3027 h(-1) at 50 °C. The easy in situ confinement synthesis of metal clusters in zeolites endows the catalysts with superior catalytic activities, excellent recyclability, and high thermal stability, thus opening new perspectives for the practical application of FA as a viable and effective H2 storage material for use in fuel cells. PMID:27248462

  18. High Density Plasma Beam Target Fusion: An Alternative form of Inertial Confinement to Ignition

    NASA Astrophysics Data System (ADS)

    Cheng, Dah Yu

    2005-10-01

    A scaling law has been demonstrated for a plasma gun in a 30 m diameter space chamber. Using a specific combination of delay time between the gas valve opening and operation of a capacitor bank switch, and the capacitor bank's voltage, the deflagration gun (Ref. 1) is capable of producing high kinetic energy and at a high density beam. Using a convergent gun barrel it is possible to compress beam density by a factor of 100. A 10^17/c.c.beam was obtained. If the kinetic energy is at 280 Kev (fusion threshold) Neutron flux up to 5 x 10^19 could be produced in a 1 micro-second period. This represents 500 MJ of energy yield. If the classical fusion energy data were in error by a factor of 100 that still would yield 5 MJ of fusion energy. Results obtained from experiments in the 30 m diameter space chamber have demonstrated such a capability using a 120 KV capacitor bank with 200 KJ of stored energy (Ref. 1). A very small scale experiment has demonstrated a yield of 10^15 neutrons using less than 10 kJ of capacitor energy.References:1. Cheng, D.Y. 1970 Plasma Deflagration and the Properties of a Coaxial Plasma Deflagration Gun. Nuclear Fusion, 10, pp. 305- 317

  19. High illumination uniformity scheme with 32 beams configuration for direct-drive inertial confinement fusion

    NASA Astrophysics Data System (ADS)

    Li, Li; Gu, Chun; Xu, Lixin; Zhou, Shenlei

    2016-04-01

    The self-adapting algorithms are improved to optimize a beam configuration in the direct drive laser fusion system with the solid state lasers. A configuration of 32 laser beams is proposed for achieving a high uniformity illumination, with a root-mean-square deviation at 10-4 level. In our optimization, the parameters such as beam number, beam arrangement, and beam intensity profile are taken into account. The illumination uniformity robustness versus the parameters such as intensity profile deviations, power imbalance, intensity profile noise, the pointing error, and the target position error is also discussed. In this study, the model is assumed a solid-sphere illumination, and refraction effects of incident light on the corona are not considered. Our results may have a potential application in the design of the direct-drive laser fusion of the Shen Guang-II Upgrading facility (SG-II-U, China).

  20. 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.

  1. 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.

  2. 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.

  3. 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. PMID:25010457

  4. 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.

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

    PubMed

    Larrea, Christian R; Baddeley, Christopher J

    2016-04-01

    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. PMID:26773305

  6. 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. PMID:23824982

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

    NASA Astrophysics Data System (ADS)

    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 H1,δH1,H1,δH1,..., 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 (H1>3), H1tr/J=3, δtr=-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×Tcb. Furthermore, we also recorded phase diagrams for fixed values of δ, i.e., plots of the critical field at the wetting transition (H1w) versus T showing, on the one hand, that the exact results of Abraham [Abraham, Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.44.1165 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 λ≪M, e.g., [H1(x,λ)>0], one can obtain the effective field Heff at a λ coarse-grained level

  8. 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/

  9. Photon detectors with high quantum efficiency at NUV range using a confinement of wavelength-shifted signals and optical couplers

    NASA Astrophysics Data System (ADS)

    Takahashi, Y.; Hadaway, J.; Pakhomov, A.; Takizawa, Y.

    Near-UV wavelengths 300 - 400 nm have been in a death-valley for photon detectors due to very low quantum efficiencies QE in this range Conventional bi-alkali photocathodes of PMTs do not have QE better than 20-26 Much better photo-cathodes like GaAsP GaN and similar give better efficiencies but only at wavelengths 400nm and are severely plagued by very short lifetimes Avalanche Photo-diodes perform better at low temperatures but no better than 35 QE in the NUV region Silicon Photo-multipliers at Geiger mode SiPM with micro-pixels have high QEs 90 like CCD and CMOS as bare silicon but are severely plagued by very poor geometrical fill-factors 30 and their overallQMis limited to no better than 20 at NUV regime An optical interference-filter works as a half-mirror passing more than 90 of NUV lights 300-400 nm and reflect more than 90 of longer wavelength lights 400 nm UV photons after converted into blue-green lights by wavelength-shifter are reflected back and confined without much loss back into space A specific dichroic interference mirror with WLS was made by RIKEN Japan H Shimizu Y Takahashi Y Takizawa Patent pending 2000-399940 for this optical principle It also allows a better use of limited photo-sensitive micro-cells of SiPM overcoming the past serious problem of its very poor fill-factor As a result Half-mirror SiPM yields high final efficiency for NUV photons This new detector TRAPPER with optical couplers for SiPM or by GaAsP PMTs could be used for photon-hungry space experiments at NUV range TRAPPER

  10. 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.

  11. Discovery of stationary operation of quiescent H-mode plasmas with net-zero neutral beam injection torque and high energy confinement on DIII-D

    NASA Astrophysics Data System (ADS)

    Burrell, K. H.; Barada, K.; Chen, X.; Garofalo, A. M.; Groebner, R. J.; Muscatello, C. M.; Osborne, T. H.; Petty, C. C.; Rhodes, T. L.; Snyder, P. B.; Solomon, W. M.; Yan, Z.; Zeng, L.

    2016-05-01

    Recent experiments in DIII-D [J. L. Luxon et al., in Plasma Physics and Controlled Nuclear Fusion Research 1996 (International Atomic Energy Agency, Vienna, 1987), Vol. I, p. 159] have led to the discovery of a means of modifying edge turbulence to achieve stationary, high confinement operation without Edge Localized Mode (ELM) instabilities and with no net external torque input. Eliminating the ELM-induced heat bursts and controlling plasma stability at low rotation represent two of the great challenges for fusion energy. By exploiting edge turbulence in a novel manner, we achieved excellent tokamak performance, well above the H98y2 international tokamak energy confinement scaling (H98y2 = 1.25), thus meeting an additional confinement challenge that is usually difficult at low torque. The new regime is triggered in double null plasmas by ramping the injected torque to zero and then maintaining it there. This lowers E × B rotation shear in the plasma edge, allowing low-k, broadband, electromagnetic turbulence to increase. In the H-mode edge, a narrow transport barrier usually grows until MHD instability (a peeling ballooning mode) leads to the ELM heat burst. However, the increased turbulence reduces the pressure gradient, allowing the development of a broader and thus higher transport barrier. A 60% increase in pedestal pressure and 40% increase in energy confinement result. An increase in the E × B shearing rate inside of the edge pedestal is a key factor in the confinement increase. Strong double-null plasma shaping raises the threshold for the ELM instability, allowing the plasma to reach a transport-limited state near but below the explosive ELM stability boundary. The resulting plasmas have burning-plasma-relevant βN = 1.6-1.8 and run without the need for extra torque from 3D magnetic fields. To date, stationary conditions have been produced for 2 s or 12 energy confinement times, limited only by external hardware constraints. Stationary operation with

  12. 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

  13. Plasma confinement at JET

    NASA Astrophysics Data System (ADS)

    Nunes, I.; JET Contributors

    2016-01-01

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

  14. 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.

  15. 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.

  16. 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.

  17. Confined flow of polymer blends.

    PubMed

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

    2008-05-01

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

  18. 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.

  19. An experimental method of measuring the confined compression strength of high-performance concretes to analyse their ballistic behaviour

    NASA Astrophysics Data System (ADS)

    Forquin, P.; Árias, A.; Zaera, R.

    2006-08-01

    The test known as “quasi-oedometric compression” consists of the compression of a cylindrical specimen confined in a thick vessel. In this work, an original methodology is proposed to deduce the radial stress and strain within the specimen using hoop strains measured on the external surface of the vessel, taking into account its elasto-plastic deformation. On one hand the spherical and deviatoric behaviours of two concretes are deduced. On the other hand, their ballistic behaviour is analysed using impact tests. These experiments are simulated numerically by the plasticity model of Krieg, Swenson and Taylor, and the features of the model are identified by the previous confined compression tests. The capacity of the model to describe the ballistic behaviour of such materials is shown in a comparison of the numerical simulations with the ballistic tests.

  20. 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.

  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. Thermal noise in confined fluids.

    PubMed

    Sanghi, T; Aluru, N R

    2014-11-01

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

  4. Thermal noise in confined fluids

    NASA Astrophysics Data System (ADS)

    Sanghi, T.; Aluru, N. R.

    2014-11-01

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

  5. 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.

  6. Tiny Pd@Co core-shell nanoparticles confined inside a metal-organic framework for highly efficient catalysis.

    PubMed

    Chen, Yu-Zhen; Xu, Qiang; Yu, Shu-Hong; Jiang, Hai-Long

    2015-01-01

    A new strategy to pre-incorporate metal precursors followed by their in situ reduction is established to prepare tiny core-shell nanoparticles (NPs) stabilized by a metal-organic framework (MOF). The obtained Pd@Co core-shell NPs of ∼2.5 nm confined in the pores of a mesoporous MOF, MIL-101, exhibit synergistic and superior catalytic performance in hydrolytic dehydrogenation of NH3 BH3 under mild conditions compared to their monometallic and alloy counterparts as well as Pd@Co NPs located on a MOF surface. PMID:25201445

  7. Experimental Investigation on the Influence of High Pressure and High Temperature on the Mechanical Properties of Deep Reservoir Rocks

    NASA Astrophysics Data System (ADS)

    Zhang, Peng; Mishra, Brijes; Heasley, Keith A.

    2015-11-01

    Deep and ultra-deep resources extraction has resulted in the challenge of drilling into high-pressure, high-temperature (HPHT) environments. Drilling challenges at such extreme conditions prompted NETL to develop a specialized ultra-deep drilling simulator (UDS) for investigating drill behavior in such conditions. Using the UDS apparatus, complex laboratory tests were performed on Carthage marble (Warsaw limestone) and Crab Orchard sandstone, which represent the rocks in the basins of the Tuscaloosa trend in southern Louisiana and the Arbuckle play in Oklahoma and North Texas. Additionally, numerical models of the UDS were developed for performing parametric analyses that would be impossible with the UDS alone. Subsequently, it was found that the input properties for these two rock types at such extreme pressure and temperature conditions were unavailable. Therefore, a suite of unconfined compressive strength, indirect tensile strength, and triaxial compression tests ( σ 1 > σ 2 = σ 3) were performed on Carthage marble and Crab Orchard sandstone for investigating their behavior in HPHT environments. The HPHT experiments were performed at confining pressures ranging from atmospheric to 200 MPa, and with temperatures ranging from 25 to 180 °C. The influences of confining pressure and temperature on the mechanical properties of two rocks were investigated.

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

    PubMed

    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.

  9. 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.

  10. 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

  11. 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.

  12. 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. PMID:27522865

  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. 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.

  15. 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.

  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. 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.

  18. 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.

  19. 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.

  20. Confined vortex scrubber

    SciTech Connect

    Not Available

    1990-07-01

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

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

    PubMed

    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. PMID:27213955

  2. Transport processes in well confined high temperature plasmas and collective modes in their partially ionized edge region

    NASA Astrophysics Data System (ADS)

    Daughton, William Scott

    1998-12-01

    of conditions, a novel form of a thermal transport coefficient which reproduces both ohmic and auxiliary heated L-mode discharges has been identified. This thermal transport coefficient involves the difference of two terms, one representing the normal outward diffusion of thermal energy and the other corresponding to a process reducing the outward flux. The coefficient includes the constraint of profile consistency. In a series of transport simulations for plasmas produced by the Alcator C-Mod machine, the thermal transport coefficient is shown to reproduce the observed electron temperature profile, stored energy and loop voltage. The relevant scaling for the energy confinement time is also composed of two terms. The L- mode database assembled for the ITER project is used to compare DIII-D, JET, JT60, PDX, TFTR, FTU, and Alcator C- Mod with this analysis. With the exception of PDX, the comparison is substantially better than standard L-mode power law scalings. Based on this analysis, an extrapolation is made for the confinement time of two proposed ignition experiments. (Copies available exclusively from MIT Libraries, Rm. 14-0551, Cambridge, MA 02139-4307. Ph. 617-253-5668; Fax 617-253-1690.) (Abstract shortened by UMI.)

  3. High-resolution dielectric study reveals pore-size-dependent orientational order of a discotic liquid crystal confined in tubular nanopores.

    PubMed

    Całus, Sylwia; Kityk, Andriy V; Borowik, Lech; Lefort, Ronan; Morineau, Denis; Krause, Christina; Schönhals, Andreas; Busch, Mark; Huber, Patrick

    2015-07-01

    We report a high-resolution dielectric study on a pyrene-based discotic liquid crystal (DLC) in the bulk state and confined in parallel tubular nanopores of monolithic silica and alumina membranes. The positive dielectric anisotropy of the DLC molecule at low frequencies (in the quasistatic case) allows us to explore the thermotropic collective orientational order. A face-on arrangement of the molecular discs on the pore walls and a corresponding radial arrangement of the molecules is found. In contrast to the bulk, the isotropic-to-columnar transition of the confined DLC is continuous, shifts with decreasing pore diameter to lower temperatures, and exhibits a pronounced hysteresis between cooling and heating. These findings corroborate conclusions from previous neutron and x-ray-scattering experiments as well as optical birefringence measurements. Our study also indicates that the relative simple dielectric technique presented here is a quite efficient method in order to study the thermotropic orientational order of DLC-based nanocomposites. PMID:26274191

  4. How ship wave action influences the sediment budget of a nature friendly bank protection in a confined, non-tidal waterway

    NASA Astrophysics Data System (ADS)

    De Roo, S.; Vanhaute, L.; Troch, P.

    2012-04-01

    Failure of the concrete slab revetment resulted in progressive bank erosion along the Lys (Belgium), a confined, non-tidal waterway subject to heavy shipping traffic. In an attempt to reconcile both the technical and environmental requirements related to a river bank, restoration was carried out using a more ecologically sound, 'soft' engineering method. A nature friendly bank protection, consisting of off-bank timber piling in combination with (reed)vegetation in the shallow water zone behind, was installed. As a consequence of this effort towards a more sustainable and ecological design of the waterway, sediment redistribution and transport processes are however altered distinctly. Being a waterway subject to heavy shipping traffic (on monthly average 1700 ship passages), hydrodynamic ship wave action on this open, semi-natural bank protection also induces sediment (re)suspension and acts as a main contributor to sediment transport (in normal weather conditions). In order to identify the relevant transport processes caused by ship-generated wave forcing, a field measurement campaign took place in April 2011. By measuring instantaneous water velocities, suspended sediment concentrations and wave hydrodynamics with a high temporal resolution, the effects on the sediment budget were quantified. It is found that the driving forces for these processes are the ship's speed, its blockage coefficient and the distance of the sailing ship to the timber piling. Bottom shear stresses significantly increase to values up to 10 N/m2 during a ship passage. Being much higher than the critical shear stress of 1.5 N/m2 and lasting for several minutes, the fine as well as coarser fractions of bottom sediment are dislodged and (re)suspended. Wave height also correlates well with the amount of sediment suspension. The best predictor for bank erosion is the velocity at which the displaced water mass hits the river bank. These experimental results indicate a reduced yet continuing

  5. Local transport in Joint European Tokamak edge-localized, high-confinement mode plasmas with H, D, DT, and T isotopes

    NASA Astrophysics Data System (ADS)

    Budny, R. V.; Ernst, D. R.; Hahm, T. S.; McCune, D. C.; Christiansen, J. P.; Cordey, J. G.; Gowers, C. G.; Guenther, K.; Hawkes, N.; Jarvis, O. N.; Stubberfield, P. M.; Zastrow, K.-D.; Horton, L. D.; Saibene, G.; Sartori, R.; Thomsen, K.; von Hellermann, M. G.

    2000-12-01

    The edge-localized, high-confinement mode regime is of interest for future Tokamak reactors since high performance has been sustained for long durations. Experiments in the Joint European Tokamak [M. Keilhacker et al., Nuclear Fusion 39, 209 (1999)] have studied this regime using scans with the toroidal field and plasma current varied together in H, D, DT, and T isotopes. The local energy transport in more than fifty of these plasmas is analyzed, and empirical scaling relations are derived for energy transport coefficients during quasi-steady state conditions using dimensionless parameters. Neither the Bohm nor gyro-Bohm expressions give the shapes of the profiles. The scalings with β and ν* are in qualitative agreement with Ion Temperature Gradient theory.

  6. Can High Altitude Influence Cytokines and Sleep?

    PubMed Central

    de Aquino Lemos, Valdir; dos Santos, Ronaldo Vagner Thomatieli; Lira, Fabio Santos; Rodrigues, Bruno; Tufik, Sergio; de Mello, Marco Tulio

    2013-01-01

    The number of persons who relocate to regions of high altitude for work, pleasure, sport, or residence increases every year. It is known that the reduced supply of oxygen (O2) induced by acute or chronic increases in altitude stimulates the body to adapt to new metabolic challenges imposed by hypoxia. Sleep can suffer partial fragmentation because of the exposure to high altitudes, and these changes have been described as one of the responsible factors for the many consequences at high altitudes. We conducted a review of the literature during the period from 1987 to 2012. This work explored the relationships among inflammation, hypoxia and sleep in the period of adaptation and examined a novel mechanism that might explain the harmful effects of altitude on sleep, involving increased Interleukin-1 beta (IL-1β), Interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-α) production from several tissues and cells, such as leukocytes and cells from skeletal muscle and brain. PMID:23690660

  7. 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.

  8. Efficient Activation of High-Loading Sulfur by Small CNTs Confined Inside a Large CNT for High-Capacity and High-Rate Lithium-Sulfur Batteries.

    PubMed

    Jin, Feiying; Xiao, Suo; Lu, Lijie; Wang, Yong

    2016-01-13

    Sulfur with a high specific capacity of 1673 mAh g(-1) is yet to be used as commercial cathode for lithium batteries because of its low utilization rate and poor cycle stability. In this work, a tube-in-tube carbon structure is demonstrated to relieve the critical problems with sulfur cathode: poor electrical conductivity, dissolution of lithium polysulfides, and large volume change during cycling. A number of small carbon nanotubes (∼20 nm in diameter) and a high loading amount of 85.2 wt % sulfur are both filled completely inside a large amorphous carbon nanotube (∼200 nm in diameter). Owing to the presence of these electrically conductive, highly flexible and structurally robust small CNTs and a large CNT overlayer, sulfur material exhibits a high utilization rate and delivers a large discharge capacity of 1633 mAh g(-1) (based on the mass of sulfur) at 0.1 C, approaching its theoretical capacity (1673 mAh g(-1)). The obtained S-CNTs@CNT electrode demonstrates superior high-rate cycling performances. Large discharge capacities of ∼1146, 1121, and 954 mAh g(-1) are observed after 150 cycles at large current rates of 1, 2, and 5 C, respectively. PMID:26675744

  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. Atomic processes in Inertial Electrostatic Confinement (IEC) devices

    SciTech Connect

    Nebel, R.A.; Turner, L.; Tiouririne, T.N.; Barnes, D.C.; Nystrom, W.D.; Bussard, R.W.

    1993-12-31

    Inertial Electrostatic Confinement (IEC) is one of the earliest plasma confinement concepts, having first been suggested by P. T. Farnsworth in the 1950s. The concept involves a simple apparatus of concentric spherical electrostatic grids or a combination of grids and magnetic fields. An electrostatic structure is formed from the confluence of electron or ion beams. Gridded IEC systems have demonstrated neutron yields as high as 2*10{sup 10} neutrons/sec. These systems have considerable potential as small, inexpensive, portable neutron sources for assaying applications. Neutron tomography is also a potential application. Atomic physics effects strongly influence the performance of all of these systems. Important atomic effects include elastic scattering, ionization, excitation, and charge exchange. This paper discusses how an IEC system is influenced by these effects and how to design around them. Theoretical modeling and experimental results are presented.

  11. 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.

  12. Elastic scattering using an artificial confining potential.

    PubMed

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

    2008-09-19

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

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

    NASA Astrophysics Data System (ADS)

    Park, Hyowon; Millis, Andrew; Marianetti, Chris

    Here we use the combination of density functional theory and dynamical mean field theory to study Ni d 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 analysed in terms of structural, quantum confinement, and correlation effects. The overall 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 depending on the sign of strain. 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. The quantum confinement effect is as important as the strain effect and more stronger for tensile strain. This work is supported by DOE ER-046169 and FAME, one of six centers of STARnet, a Semiconductor Research Corporation program sponsored by MARCO and DARPA.

  14. 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…

  15. Elastic membranes in confinement.

    PubMed

    Bostwick, J B; Miksis, M J; Davis, S H

    2016-07-01

    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 coiled DNA, have fine internal structure in which a membrane (or elastic member) is geometrically 'confined' by another object. Here, the two-dimensional shape of an elastic membrane in a 'confining' box is studied by introducing a repulsive confinement pressure that prevents the membrane from intersecting the wall. The stage is set by contrasting confined and unconfined solutions. Continuation methods are then used to compute response diagrams, from which we identify the particular membrane mechanics that generate mitochondria-like shapes. Large confinement pressures yield complex response diagrams with secondary bifurcations and multiple turning points where modal identities may change. Regions in parameter space where such behaviour occurs are then mapped. PMID:27440257

  16. 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…

  17. 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.

  18. 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%).

  19. 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.

  20. Photonic heterostructure High Contrast Grating as a novel polarization control and light confinement system in HCG VCSEL

    NASA Astrophysics Data System (ADS)

    Gebski, M.; Dems, M.; Chen, J.; Qijie, W.; Dao Hua, Z.; Czyszanowski, T.

    2014-05-01

    In this paper we present results of computer optical simulations of VCSEL with modified high refractive index contrast grating (HCG) as a top mirror. We consider the HCG of two different designs which determine the lateral aperture. Such HCG mirror provides selective guiding effect. We show that proper design of aperture of HCG results in almost sixfold increase in cavity Q-factor for zero order mode and a discrimination of higher order modes.

  1. Li2S Nanocrystals Confined in Free-Standing Carbon Paper for High Performance Lithium-Sulfur Batteries.

    PubMed

    Wu, Min; Cui, Yi; Fu, Yongzhu

    2015-09-30

    Lithium sulfide (Li2S) with a high theoretical capacity of 1166 mAh g(-1) is a promising cathode material for Li-S batteries as it allows for the use of lithium-free anodes. However, a large overpotential (~1 V) is usually needed to activate microsized Li2S particles due to their low electronic and ionic conductivities. Here, nano-Li2S/carbon paper electrodes are developed via a simple Li2S solution filtration method. Li2S nanocrystals with a size less than 10 nm are formed uniformly in the pores of carbon paper network. These electrodes show an unprecedented low potential difference (0.1 V) in the first and following charges, also show high discharge capacities, good rate capability, and excellent cycling performance. More specifically, the nano-Li2S/carbon nanotube paper electrodes show a reversible capacity of 634 mAh g(-1) with a capacity retention of 92.4% at 1C rate from the 4th to 100th cycle, corresponding to a low capacity fading rate of 0.078% per cycle. These results demonstrate a facile and scalable electrode fabrication process for making high performance nano-Li2S/carbon paper electrodes, and the superior performance makes them promising for use with lithium metal-free anodes in rechargeable Li-S batteries for practical applications. PMID:26349017

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

    NASA Astrophysics Data System (ADS)

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

    2014-11-01

    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.

  3. Novel double-confined polymeric ionic liquids as sorbents for solid-phase microextraction with enhanced stability and durability in high-ionic-strength solution.

    PubMed

    Feng, Juanjuan; Sun, Min; Xu, Lili; Wang, Shuai; Liu, Xia; Jiang, Shengxiang

    2012-12-14

    Because of the occurrence of ion exchange between high-ionic-strength solution and anions of polymeric ionic liquids (PILs), PILs based solid-phase microextraction (SPME) fibers were rarely used in direct immersion mode to high-salt-added samples. In this work, a novel double-confined PIL sorbent was prepared by co-polymerization of cation and anion of 1-vinyl-3-octylimidzaolium p-styrenesulfonate (VOIm(+)SS(-)). The poly(VOIm(+)-SS(-)) was chemically bonded onto functionalized stainless steel wire via surface radical chain-transfer reaction. Stability of poly(VOIm(+)-SS(-)) in high-ionic-strength solution was investigated and compared with that of poly(1-vinyl-3-octylimidzaolium benzenesulfonate) (poly(VOIm(+)BS(-))) by elemental analysis of sulfur element, and results turned out that the poly(VOIm(+)-SS(-)) was more stable. Coupled to gas chromatography (GC), the poly(VOIm(+)-SS(-)) fiber was used to extract three sorts of compounds including anilines, phenols and phthalate esters in aqueous solution. The as-established method showed good linearity, low detection limits, and acceptable repeatability. The direct immersion SPME-GC method was applied to determine the model phthalate esters in bottled mineral water. The determination results were satisfactory.

  4. Enhancement of confinement in tokamaks

    SciTech Connect

    Furth, H.P.

    1986-05-01

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

  5. Momentum Confinement at Low Torque

    SciTech Connect

    Solomon, W M; Burrell, K H; deGrassie, J S; Budny, R; Groebner, R J; Heidbrink, W W; Kinsey, J E; Kramer, G J; Makowski, M A; Mikkelsen, D; Nazikian, R; Petty, C C; Politzer, P A; Scott, S D; Van Zeeland, M A; Zarnstorff, M C

    2007-06-26

    Momentum confinement was investigated on DIII-D as a function of applied neutral beam torque at constant normalized {beta}{sub N}, by varying the mix of co (parallel to the plasma current) and counter neutral beams. Under balanced neutral beam injection (i.e. zero total torque to the plasma), the plasma maintains a significant rotation in the co-direction. This 'intrinsic' rotation can be modeled as being due to an offset in the applied torque (i.e. an 'anomalous torque'). This anomalous torque appears to have a magnitude comparable to one co-neutral beam source. The presence of such an anomalous torque source must be taken into account to obtain meaningful quantities describing momentum transport, such as the global momentum confinement time and local diffusivities. Studies of the mechanical angular momentum in ELMing H-mode plasmas with elevated q{sub min} show that the momentum confinement time improves as the torque is reduced. In hybrid plasmas, the opposite effect is observed, namely that momentum confinement improves at high torque/rotation. The relative importance of E x B shearing between the two is modeled using GLF23 and may suggest a possible explanation.

  6. 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.

  7. 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

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

    PubMed

    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

  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. PMID:27661901

  10. Ordering Single Cells and Single Embryos in 3D Confinement: A New Device for High Content Screening.

    PubMed

    Wollrab, Viktoria; Caballero, David; Thiagarajan, Raghavan; Riveline, Daniel

    2016-01-01

    Biological cells are usually observed on flat (2D) surfaces. This condition is not physiological, and phenotypes and shapes are highly variable. Screening based on cells in such environments have therefore serious limitations: cell organelles show extreme phenotypes, cell morphologies and sizes are heterogeneous and/or specific cell organelles cannot be properly visualized. In addition, cells in vivo are located in a 3D environment; in this situation, cells show different phenotypes mainly because of their interaction with the surrounding extracellular matrix of the tissue. In order to standardize and generate order of single cells in a physiologically-relevant 3D environment for cell-based assays, we report here the microfabrication and applications of a device for in vitro 3D cell culture. This device consists of a 2D array of microcavities (typically 10(5) cavities/cm(2)), each filled with single cells or embryos. Cell position, shape, polarity and internal cell organization become then normalized showing a 3D architecture. We used replica molding to pattern an array of microcavities, 'eggcups', onto a thin polydimethylsiloxane (PDMS) layer adhered on a coverslip. Cavities were covered with fibronectin to facilitate adhesion. Cells were inserted by centrifugation. Filling percentage was optimized for each system allowing up to 80%. Cells and embryos viability was confirmed. We applied this methodology for the visualization of cellular organelles, such as nucleus and Golgi apparatus, and to study active processes, such as the closure of the cytokinetic ring during cell mitosis. This device allowed the identification of new features, such as periodic accumulations and inhomogeneities of myosin and actin during the cytokinetic ring closure and compacted phenotypes for Golgi and nucleus alignment. We characterized the method for mammalian cells, fission yeast, budding yeast, C. elegans with specific adaptation in each case. Finally, the characteristics of this

  11. 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.

  12. Coupled chemical reactions in dynamic nanometric confinement: V. The influence of Li+ and F- ions on etching of nuclear tracks in polymers

    NASA Astrophysics Data System (ADS)

    Fink, D.; Muñoz Hernandez, G.; Ruiz, N. L.; Vacik, J.; Hnatowicz, V.; García-Arellano, H.; Alfonta, L.; Kiv, A.

    2014-05-01

    Etching of continuous nuclear tracks in thin polymer foils from both sides is known to lead to the formation of double-conical nanopores. In this work and related ones we try to find out how this etching kinetics is modified when materials are added which react with each other upon their contact towards some new product that influences the etching. For that purpose we have chosen here Li+ and F- ions as the additions, which react with each other to form LiF precipitations. The coupled etching and precipitation kinetics is recorded by measuring the electrical current that is transmitted through the foils upon application of a low-frequency alternating sinusoidal voltage. Depending on the etchant concentrations, the etching temperature and the time of Li+ and F- addition, different effects are found that range from (a) no alteration of the transmitted current at all, via (b) the emergence of an alternating current with a temperature-dependent amplitude, and (c) the complete vanishing of any transmitted current at all, towards (d) chaotic transmitted current histories with phases with strong current spike emission and (e) rather quiet phases, alternating with each other in a rather unsystematic way. The observed effects are ascribed to (a) the enhanced penetration efficiency of both the Li+ and F- ions through the polymeric bulk and/or latent ion tracks after the removal of the polymer's protective surface layer by the etchant, (b) the high mobility of preferentially the F- ions within the polymer, (c) the LiF precipitation within the polymer or on its surface upon encounter of Li+ and F- ions, (d) the nanofluidic properties of narrow etched tracks covered with Li+ ions on the wall surfaces and F- ions beyond, and/or (e) the formation of LiF membranes within the etched tracks.

  13. Bacteria in Confined Spaces

    NASA Astrophysics Data System (ADS)

    Wilking, Connie; Weitz, David

    2010-03-01

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

  14. Family Influences on the Development of High Ability.

    ERIC Educational Resources Information Center

    Herskovits, Maria

    2000-01-01

    A longitudinal study of 118 high ability Budapest children (ages 12-14) investigated family influences on child development. Three case studies are described that illustrate the differences in the sensitivity with which the parents recognized the various demands of their able children and how they responded to them. (Contains nine references.) (CR)

  15. 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.

  16. Global patterns of solar influence on high cloud cover

    NASA Astrophysics Data System (ADS)

    Dima, Mihai; Voiculescu, Mirela

    2016-07-01

    One of the main sources of uncertainty in climate projections is represented by clouds, which have a profound influence on the Earth's radiation budget through the feedbacks in which they are involved. The improvement of clouds representation in General Circulation Models relies largely on constraints derived from observations and on correct identification of processes that influence cloud formation or lifetime. Here we identify solar forced high cloud cover (HCC) patterns in reanalysis and observed data extending over the 1871-2009 period, based on their associations with known fingerprints of the same forcing on surface air temperature, sea surface temperature (SST) and sea level pressure fields. The solar influence on HCC has maximum amplitudes over the Pacific basin, where HCC anomalies are distributed in bands of alternating polarities. The colocation of the HCC and SST anomalies bands indicates a thermal influence on high clouds through convection and an amplification of the HCC anomalies by a positive feedback of long-wave fluxes, which increases the solar signal. Consistent with numerical simulations, the solar forced HCC pattern appears to be generated through a constructive interference between the so-called "top-down" and "bottom-up" mechanisms of solar influence on climate and is amplified by ocean-atmosphere positive feedbacks.

  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. Progress of ECRH by EBW in over-dense plasmas and controlling the confinement regime by ECCD with high power launching in LHD

    NASA Astrophysics Data System (ADS)

    Igami, H.; Yoshimura, Y.; Takahashi, H.; Shimozuma, T.; Kubo, S.; Idei, H.; Nishiura, M.; Ogasawara, S.; Makino, R.; Ohdachi, S.; Ida, K.; Yoshinuma, M.; Ido, T.; Shimizu, A.; Tamura, N.; Inagaki, S.; Mutoh, T.

    2012-09-01

    In the large helical device (LHD), fundamental electron cyclotron resonance heating (ECRH) by the electron Bernstein wave (EBW) excited via the ordinary-extraordinary-EBW (O-X-B) mode conversion process was performed with high power (~1MW) launching. Profiles of increase of the electron temperature (Te) and the soft X-ray signals during the power injection suggest power absorption in the core region. Effects of the local modification of the rotational transform l/2π(=1/q) by electron cyclotron current drive (ECCD) on the formation and sustainment of the electron internal transport barrier (e-ITB) was investigated for the first time. Co ECCD raised l/2π close to 0.5 in the core region and caused the flattening of the Te profile. Additional ECRH power is required to form the e-ITB. On the contrary, counter (cntr.) ECCD separates l/2π from 0.5 in the core region and avoids the flattening of the Te profile. The e-ITB can be formed and sustained without additional ECRH. Analysis of the heat pulse transport with use of the modulation ECRH (MECH) shows the good confinement region extends to the l/2π =0.5 rational surface in the case of cntr. ECCD.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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

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

    PubMed

    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. 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

  6. 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.

  7. Visualization of the influence of the air conditioning system to the high-power laser beam quality with the modulation coherent imaging method.

    PubMed

    Tao, Hua; Veetil, Suhas P; Pan, Xingchen; Liu, Cheng; Zhu, Jianqiang

    2015-08-01

    Air conditioning systems can lead to dynamic phase change in the laser beams of high-power laser facilities for the inertial confinement fusion, and this kind of phase change cannot be measured by most of the commonly employed Hartmann wavefront sensor or interferometry due to some uncontrollable factors, such as too large laser beam diameters and the limited space of the facility. It is demonstrated that this problem can be solved using a scheme based on modulation coherent imaging, and thus the influence of the air conditioning system on the performance of the high-power facility can be evaluated directly. PMID:26368074

  8. Visualization of the influence of the air conditioning system to the high-power laser beam quality with the modulation coherent imaging method.

    PubMed

    Tao, Hua; Veetil, Suhas P; Pan, Xingchen; Liu, Cheng; Zhu, Jianqiang

    2015-08-01

    Air conditioning systems can lead to dynamic phase change in the laser beams of high-power laser facilities for the inertial confinement fusion, and this kind of phase change cannot be measured by most of the commonly employed Hartmann wavefront sensor or interferometry due to some uncontrollable factors, such as too large laser beam diameters and the limited space of the facility. It is demonstrated that this problem can be solved using a scheme based on modulation coherent imaging, and thus the influence of the air conditioning system on the performance of the high-power facility can be evaluated directly.

  9. Confinement effects in semimagnetic semiconductors

    NASA Astrophysics Data System (ADS)

    Dietl, Tomasz

    1998-02-01

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

  10. 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.

  11. 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.

  12. Spin-Orbit Activated Confinement Resonances

    NASA Astrophysics Data System (ADS)

    Keating, David; Manson, Steven; Deshmukh, Pranawa

    2016-05-01

    At high enough Z relativistic effects become important contributors to even the qualitative nature of atomic properties. This is likely to be true for confined atoms as well. One relativistic effect of interest is the spin-orbit activated interchannel coupling of a pair of spin-orbit doublet channels. This interaction is possible owing to the spin-orbit interaction breaking the degenerancy among the electrons of a subshell allowing, for example, the 5p3/2 and 5p1/2 subshells of mercury (Z = 80) and the 6p3/2 and 6p1/2 of radon (Z = 86), to interact. To explore the effect confinement has on spin-orbit activated interchannel coupling, a theoretical study of the 5p subshell of mercury and the 6p subshell of radon both confined in a C60 cage has been performed using the relativistic-random-phase approximation (RRPA) methodology. The effects of the C60 potential modeled by a static spherical well which is reasonable in the energy region well above the C60 plasmons. It is found in the photoionization cross sections of the 5p3/2 of confined mercury and the 6p3/2 of confined radon an extra confinement resonance due to spin-orbit activated interchannel coupling with the respective np1/2 photoionization channels.

  13. The roles of electric field shear and Shafranov shift in sustaining high confinement in enhanced reversed shear plasmas on the TFTR tokamak

    SciTech Connect

    Synakowski, E.J.; Beer, M.A.; Batha, S.H.

    1997-02-01

    The relaxation of core transport barriers in TFTR Enhanced Reversed Shear plasmas has been studied by varying the radial electric field using different applied torques from neutral beam injection. Transport rates and fluctuations remain low over a wide range of radial electric field shear, but increase when the local E x B shearing rates are driven below a threshold comparable to the fastest linear growth rates of the dominant instabilities. Shafranov-shift-induced stabilization alone is not able to sustain enhanced confinement.

  14. 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.

  15. 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.

  16. Inertial Confinement fusion targets

    NASA Technical Reports Server (NTRS)

    Hendricks, C. D.

    1982-01-01

    Inertial confinement fusion (ICF) targets are made as simple flat discs, as hollow shells or as complicated multilayer structures. Many techniques were devised for producing the targets. Glass and metal shells are made by using drop and bubble techniques. Solid hydrogen shells are also produced by adapting old methods to the solution of modern problems. Some of these techniques, problems, and solutions are discussed. In addition, the applications of many of the techniques to fabrication of ICF targets is presented.

  17. 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.

  18. Topological confinement and superconductivity

    SciTech Connect

    Al-hassanieh, Dhaled A; Batista, Cristian D

    2008-01-01

    We derive a Kondo Lattice model with a correlated conduction band from a two-band Hubbard Hamiltonian. This mapping allows us to describe the emergence of a robust pairing mechanism in a model that only contains repulsive interactions. The mechanism is due to topological confinement and results from the interplay between antiferromagnetism and delocalization. By using Density-Matrix-Renormalization-Group (DMRG) we demonstrate that this mechanism leads to dominant superconducting correlations in aID-system.

  19. 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.

  20. Ionic structure in liquids confined by dielectric interfaces.

    PubMed

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

    2015-11-21

    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. PMID:26590543

  1. The influence of high-order dispersion on femesecond solitons

    NASA Astrophysics Data System (ADS)

    Wang, Zhi-bin; Li, Zhong-zhen; Liu, Yang; Chen, Jian-wei; Li, Zhi-quan

    2008-03-01

    In the nonlinear optical fiber, soliton is a pulse envelop that formed under the balance of group velocity dispersion(GVD) and self-phase modulation(SPM). It has the transmission characteristic that the pulse shape and amplitude are steady. The GVD causes the pulse stretch, but the SPM induces the high frequency elements to accumulate step by step, and the soliton pulse change steep. The two kind of opposition factors unit in together, mutually balances can maintain the pulse shape stabilization invariable. Along with the soliton research, it extends from picosecond (ps) to femesecond (fs). High order dispersion, in particular the third order dispersion (TOD) influences the soliton transmission very large. The high order dispersion is studied by the split step Fourier method (SSFM) numerical analysis the modified high order nonlinear Schrödinger equation(HNLSE). The results indicate that the TOD and the fourth order dispersion(FOD) can all affect the quality of the telecommunication. And the TOD plays the main role. It causes the pulse bottom vibration in one side, causes the pulse to stretch and to form vibration belt. The FOD causes the soliton bottom vibration in two sides, it causes the pulse stretch and the spectrum appears side lobe.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. Spiral precipitation patterns in confined chemical gardens.

    PubMed

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

    2014-12-01

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

  9. 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

  10. 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.

  11. 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

  12. Circularly confined microswimmers exhibit multiple global patterns.

    PubMed

    Tsang, Alan Cheng Hou; Kanso, Eva

    2015-04-01

    Geometric confinement plays an important role in the dynamics of natural and synthetic microswimmers from bacterial cells to self-propelled particles in high-throughput microfluidic devices. However, little is known about the effects of geometric confinement on the emergent global patterns in such self-propelled systems. Recent experiments on bacterial cells report that, depending on the cell concentration, cells either spontaneously organize into vortical motion in thin cylindrical and spherical droplets or aggregate at the inner boundary of the droplets. Our goal in this paper is to investigate, in the context of an idealized physical model, the interplay between geometric confinement and level of flagellar activity on the emergent collective patterns. We show that decreasing flagellar activity induces a hydrodynamically triggered transition in confined microswimmers from swirling to global circulation (vortex) to boundary aggregation and clustering. These results highlight that the complex interplay between confinement, flagellar activity, and hydrodynamic flows in concentrated suspensions of microswimmers could lead to a plethora of global patterns that are difficult to predict from geometric consideration alone. PMID:25974581

  13. 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).

  14. Active matter in lateral parabolic confinement: From subdiffusion to superdiffusion

    NASA Astrophysics Data System (ADS)

    Ribeiro, H. E.; Potiguar, F. Q.

    2016-11-01

    In this work we studied the diffusive behavior of active brownian particles under lateral parabolic confinement. The results showed that we go from subdiffusion to ballistic motion as we vary the angular noise strength and confinement intensity. We argued that the subdiffusion regimes appear as consequence of the restricted space available for diffusion (achieved either through large confinement and/or large noise); we saw that when there are large confinement and noise intensity, a similar configuration to single file diffusion appears; on the other hand, normal and superdiffusive regimes may occur due to low noise (longer persistent motion), either through exploring a wider region around the potential minimum in the transverse direction (low confinement), or by forming independent clusters (high confinement).

  15. 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. PMID:26651631

  16. 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.

  17. 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.

  18. Mixed-Metal-Organic Framework with Effective Lewis Acidic Sites for Sulfur Confinement in High-Performance Lithium-Sulfur Batteries.

    PubMed

    Wang, Ziqi; Wang, Buxue; Yang, Yu; Cui, Yuanjing; Wang, Zhiyu; Chen, Banglin; Qian, Guodong

    2015-09-23

    The mixed-metal-organic framework approach and a representative zirconium-metalloporphyrin framework (MOF-525) have been developed to create novel sulfur hosts and Li-S batteries. The different local environments at the centers of the porphyrin moieties in a series of MMOFs-MOF-525(2H), MOF-525(FeCl), and MOF-525(Cu)-have led to their different behaviors for the confinement of sulfur and thus Li-S batteries. The unique structure of MOF-525(Cu) has enabled each Cu(2+) site to offer two Lewis acidic sites, featuring it as a very powerful MOF host for the inclusion of sulfur and polysulfides. The S@MOF-525(Cu) cathode has demonstrated the best performance among all reported sulfur/MOFs composite cathode materials, with a reversible capacity of about 700 mAh/g at 0.5 C after 200 cycles. PMID:26323942

  19. 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.

  20. Confinement of a Dirac Particle to a Hard-Wall Confining Potential Induced by Noninertial Effects

    NASA Astrophysics Data System (ADS)

    Bakke, K.

    2013-01-01

    In this contribution, we discuss the influence of noninertial effects on a Dirac particle in the Minkowski spacetime by showing that the geometry of the manifold can play the role of a hard-wall confining potential. Thus, we discuss a limit case where the relativistic bound states can be achieved in analogous way to having a Dirac particle confined to a quantum dot. We discuss the application of this mathematical model in studies of noninertial effects on condensed matter systems described by the Dirac equation, and compare the nonrelativistic limit of the energy levels with the spectrum of energy of a spin-½ particle confined to a quantum dot [E. Tsitsishvili et al., Phys. Rev. B70 (2004) 115316].

  1. Planning for greater confinement disposal

    SciTech Connect

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

    1985-01-01

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

  2. Influences of High-Level Features, Gaze, and Scene Transitions on the Reliability of BOLD Responses to Natural Movie Stimuli.

    PubMed

    Lu, Kun-Han; Hung, Shao-Chin; Wen, Haiguang; Marussich, Lauren; Liu, Zhongming

    2016-01-01

    Complex, sustained, dynamic, and naturalistic visual stimulation can evoke distributed brain activities that are highly reproducible within and across individuals. However, the precise origins of such reproducible responses remain incompletely understood. Here, we employed concurrent functional magnetic resonance imaging (fMRI) and eye tracking to investigate the experimental and behavioral factors that influence fMRI activity and its intra- and inter-subject reproducibility during repeated movie stimuli. We found that widely distributed and highly reproducible fMRI responses were attributed primarily to the high-level natural content in the movie. In the absence of such natural content, low-level visual features alone in a spatiotemporally scrambled control stimulus evoked significantly reduced degree and extent of reproducible responses, which were mostly confined to the primary visual cortex (V1). We also found that the varying gaze behavior affected the cortical response at the peripheral part of V1 and in the oculomotor network, with minor effects on the response reproducibility over the extrastriate visual areas. Lastly, scene transitions in the movie stimulus due to film editing partly caused the reproducible fMRI responses at widespread cortical areas, especially along the ventral visual pathway. Therefore, the naturalistic nature of a movie stimulus is necessary for driving highly reliable visual activations. In a movie-stimulation paradigm, scene transitions and individuals' gaze behavior should be taken as potential confounding factors in order to properly interpret cortical activity that supports natural vision. PMID:27564573

  3. Influences of High-Level Features, Gaze, and Scene Transitions on the Reliability of BOLD Responses to Natural Movie Stimuli.

    PubMed

    Lu, Kun-Han; Hung, Shao-Chin; Wen, Haiguang; Marussich, Lauren; Liu, Zhongming

    2016-01-01

    Complex, sustained, dynamic, and naturalistic visual stimulation can evoke distributed brain activities that are highly reproducible within and across individuals. However, the precise origins of such reproducible responses remain incompletely understood. Here, we employed concurrent functional magnetic resonance imaging (fMRI) and eye tracking to investigate the experimental and behavioral factors that influence fMRI activity and its intra- and inter-subject reproducibility during repeated movie stimuli. We found that widely distributed and highly reproducible fMRI responses were attributed primarily to the high-level natural content in the movie. In the absence of such natural content, low-level visual features alone in a spatiotemporally scrambled control stimulus evoked significantly reduced degree and extent of reproducible responses, which were mostly confined to the primary visual cortex (V1). We also found that the varying gaze behavior affected the cortical response at the peripheral part of V1 and in the oculomotor network, with minor effects on the response reproducibility over the extrastriate visual areas. Lastly, scene transitions in the movie stimulus due to film editing partly caused the reproducible fMRI responses at widespread cortical areas, especially along the ventral visual pathway. Therefore, the naturalistic nature of a movie stimulus is necessary for driving highly reliable visual activations. In a movie-stimulation paradigm, scene transitions and individuals' gaze behavior should be taken as potential confounding factors in order to properly interpret cortical activity that supports natural vision.

  4. Influences of High-Level Features, Gaze, and Scene Transitions on the Reliability of BOLD Responses to Natural Movie Stimuli

    PubMed Central

    Lu, Kun-Han; Hung, Shao-Chin; Wen, Haiguang; Marussich, Lauren; Liu, Zhongming

    2016-01-01

    Complex, sustained, dynamic, and naturalistic visual stimulation can evoke distributed brain activities that are highly reproducible within and across individuals. However, the precise origins of such reproducible responses remain incompletely understood. Here, we employed concurrent functional magnetic resonance imaging (fMRI) and eye tracking to investigate the experimental and behavioral factors that influence fMRI activity and its intra- and inter-subject reproducibility during repeated movie stimuli. We found that widely distributed and highly reproducible fMRI responses were attributed primarily to the high-level natural content in the movie. In the absence of such natural content, low-level visual features alone in a spatiotemporally scrambled control stimulus evoked significantly reduced degree and extent of reproducible responses, which were mostly confined to the primary visual cortex (V1). We also found that the varying gaze behavior affected the cortical response at the peripheral part of V1 and in the oculomotor network, with minor effects on the response reproducibility over the extrastriate visual areas. Lastly, scene transitions in the movie stimulus due to film editing partly caused the reproducible fMRI responses at widespread cortical areas, especially along the ventral visual pathway. Therefore, the naturalistic nature of a movie stimulus is necessary for driving highly reliable visual activations. In a movie-stimulation paradigm, scene transitions and individuals’ gaze behavior should be taken as potential confounding factors in order to properly interpret cortical activity that supports natural vision. PMID:27564573

  5. 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.

  6. Recent results on heating and confinement in TEXTOR

    SciTech Connect

    Vandenplas, P.E.; Koch, R.; Messiaen, A.M.; Finken, K.H.; Ongena, J.; Philipps, V.; Samm, U.; Unterberg, B.; Van Oost, G.; Van Wassenhove, G.; Winter, J.; Dumortier, P.; Durodie, F.; Esser, H.G.; Euringer, H.; Giesen, B.; Hintz, E.; Lochter, M.; Tokar, M.Z.; Wolf, G.H.; Bertschinger, G.; Fuchs, G.; Hillis, D.L.; Hoenen, F.; Huettemann, P.; Koenen, L.; Koslowski, H.R.; Kraemer-Flecken, A.; Mank, G.; Pettiaux, D.

    1995-09-01

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

  7. Confinement stabilizes a bacterial suspension into a spiral vortex.

    PubMed

    Wioland, Hugo; Woodhouse, Francis G; Dunkel, Jörn; Kessler, John O; Goldstein, Raymond E

    2013-06-28

    Confining surfaces play crucial roles in dynamics, transport, and order in many physical systems, but their effects on active matter, a broad class of dynamically self-organizing systems, are poorly understood. We investigate here the influence of global confinement and surface curvature on collective motion by studying the flow and orientational order within small droplets of a dense bacterial suspension. The competition between radial confinement, self-propulsion, steric interactions, and hydrodynamics robustly induces an intriguing steady single-vortex state, in which cells align in inward spiraling patterns accompanied by a thin counterrotating boundary layer. A minimal continuum model is shown to be in good agreement with these observations.

  8. 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.

  9. Biomimetic growth of silica tubes in confined media.

    PubMed

    Gautier, Clémentine; Lopez, Pascal J; Hemadi, Miryana; Livage, Jacques; Coradin, Thibaud

    2006-10-24

    Polymer membranes were used as biomimetic environments to study the effect of confinement on silica formation. Within membrane pores, silica tubes were formed, consisting of a dense silica shell incorporating nanoparticle aggregates. The shell structure does not depend on the membrane pore size, suggesting that its formation proceeds via interfacial interactions with the pore surface. In contrast, the size of primary nanoparticles within core aggregates is influenced by pore dimensions, indicating an effect of confinement on the diffusion-limited growth of silica. A parallel can be drawn with reported roles of confinement in biomineralization processes, providing a basis for future developments in biosilicification mimetic approaches and biofunctional nanomaterials design.

  10. Working safely in confined spaces

    SciTech Connect

    Bush, C.; Versweyveld, J. )

    1992-08-13

    Working in confined spaces is a delicate balance of the correct equipment, hazard knowledge, proper training, and common sense. Anything less has potentially deadly consequences. The dangerous atmospheric and physical hazards often encountered in confined spaces must be recognized and accounted for. In addition, procedures and practices must conform to Occupational Safety and health Administration (OSHA) confined space regulations. Last year, three men were asphyxiated while surveying beneath a manhole in Boulder, CO. An area newspaper called the deaths the result of a freak accident. Whatever the cause, entering a manhole without first monitoring the air and posting an outside attendant is both extremely dangerous and a violation of safe entry procedures. The National Institute for Health and Occupational Safety (NIOSH) estimates that millions of workers from a wide range of occupations and industries are exposed to confined space hazards every year. Although confined space deaths are not a new phenomenon, only recently has the problem received serious study. Government regulatory agencies are becoming more involved OSHA recently proposed ruling 1910.146, Permit Required Confined Spaces, to mandate safe entry practices and procedures. The ruling requires all employers to develop a specific action plan for confined space entry, including entry procedures, worker training, safety equipment, and emergency action. This first article defines a confined space and examines some common hazards, including toxic, combustible, and oxygen-deficient atmospheres and combustible dusts. A subsequent article will review the use of test instruments, personal protective equipment, worker training, and emergency response.

  11. 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.

  12. Electric-field-induced phase transition of confined water nanofilms between two graphene sheets.

    PubMed

    Qian, Zhenyu; Wei, Guanghong

    2014-10-01

    A recent study reported that confined water nanofilms may freeze continuously or discontinuously depending on their densities. In this study, we report results from molecular dynamics simulations of the structures and the phase transition of water confined between two graphene sheets with a separation of 1.0 nm under the influence of an electric (E) field applied along the direction parallel to the sheets. We find that confined water can form three kinds of ice phases at atmospheric pressure: amorphous, hexagonal, or rhombic bilayer ice, depending on the E-field strength (0-1.5 V/nm). As the E-field strength changes, these ice configurations can transform into each other through a first-order phase transition. These E-field-induced water phases are different from those induced by high pressure (under high density). In addition, we find that all of the three ice nanofilms melt through a first-order transition. The heating and cooling processes are accompanied by a hysteresis loop between the solid and liquid phases. A phase diagram of confined water between two graphene sheets is given in the temperature-E-field plane. PMID:24831927

  13. 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.

  14. 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

  15. 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.

  16. 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

  17. 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

    2015-01-01

    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

  18. 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.

  19. Density shocks in confined microswimmers

    NASA Astrophysics Data System (ADS)

    Tsang, Alan Cheng Hou; Kanso, Eva; Biodynamics Team

    2014-11-01

    Motile microorganisms are often subject to different types of boundary confinement in their natural environment, but the effects of confinement on their dynamics are poorly understood. We consider an idealized model of confined microswimmers restricted to move in a two-dimensional Hele-Shaw cell. We then impose two different types of boundary confinement: circular and sidewalls confinement. We study how boundaries trigger the emergence of global modes. In the case of circular confinement, the microswimmers can spontaneously organize themselves into a single vortex state when the radius of the circular boundary is below a certain critical value, reminiscent to what have been observed in recent experiments of bacterial suspensions. In the case of sidewalls confinement in a rectangular channel, the microswimmers form density shock, via interaction with the sidewalls and background flow. We show that, through controlling the strength of background flow, we can manipulate the density shock to form at the back or front of the swimmer clusters or the suppression of the shock which gives rise to a uniform traveling wave of swimmers.

  20. Morphology of diblock copolymers under confinement

    NASA Astrophysics Data System (ADS)

    Ackerman, David; Ganapathysubramanian, Baskar

    The structure adopted by polymer chains is of particular intrest for materials design. In particular, a great deal of effort has been made to study diblock polymers due to the importance they have in industrial applications. The bulk structure of most systems has been the most widely studied. However, when under the effect of confinement, the polymer chains are forced to adopt structures differing from the familiar bulk phases. As many applications utilize polymers in sizes and shapes that lead to these non bulk structures, the confinement effects are important. A commonly used tool for computationally determining structures is the continuum self consistant field theory (SCFT). We discuss our highly scalable parallel framework for SCFT using real space methods (finite element) that is especially well suited to modelling complex geometries. This framework is capable of modeling both Gaussian and worm like chains. We illustate the use of the software framework in determining structures under varying degrees of confinement. We detail the method used and present selected results from a systematic study of confinement using arbitrary structures.

  1. 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.

  2. Partial confinement photonic crystal waveguides

    SciTech Connect

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

    2008-12-29

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

  3. 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.

  4. Role of the confinement of a root canal on jet impingement during endodontic irrigation

    NASA Astrophysics Data System (ADS)

    Verhaagen, B.; Boutsioukis, C.; Heijnen, G. L.; van der Sluis, L. W. M.; Versluis, M.

    2012-12-01

    During a root canal treatment the root canal is irrigated with an antimicrobial fluid, commonly performed with a needle and a syringe. Irrigation of a root canal with two different types of needles can be modeled as an impinging axisymmetric or non-axisymmetric jet. These jets are investigated experimentally with high-speed Particle Imaging Velocimetry, inside and outside the confinement (concave surface) of a root canal, and compared to theoretical predictions for these jets. The efficacy of irrigation fluid refreshment with respect to the typical reaction time of the antimicrobial fluid with a biofilm is characterized with a non-dimensional Damköhler number. The pressure that these jets induce on a wall or at the apex of the root canal is also measured. The axisymmetric jet is found to be stable and its velocity agrees with the theoretical prediction for this type of jet, however, a confinement causes instabilities to the jet. The confinement of the root canal has a pronounced influence on the flow, for both the axisymmetric and non-axisymmetric jet, by reducing the velocities by one order of magnitude and increasing the pressure at the apex. The non-axisymmetric jet inside the confinement shows a cascade of eddies with decreasing velocities, which at the apex does not provide adequate irrigation fluid refreshment.

  5. Computer simulation of polypeptides in a confinement.

    PubMed

    Sikorski, Andrzej; Romiszowski, Piotr

    2007-02-01

    A coarse-grained model of polypeptide chains confined in a slit formed by two parallel impenetrable surfaces was studied. The chains were flexible heteropolymers (polypeptides) built of two kinds of united atoms-hydrophobic and hydrophilic. The positions of the united atoms were restricted to the vertices of a [310] lattice. The force field consisted of a rigorous excluded volume, a long-distance potential between a pair of amino-acid residues and a local preference for forming secondary structure (helices). The properties of the chains were studied at a wide range of temperatures from good to bad solvent conditions. Monte-Carlo simulations were carried out using the algorithm based on the chain's local changes of conformation and employing the Replica Exchange technique. The influence of the chain length, the distances between the confining surfaces, the temperature and the force field on the dimension and the structure of chains were studied. It was shown that the presence of the confinement chain complicates the process of the chain collapse to low-temperature structures. For some conditions, one can find a rapid decrease of chain size and a second transition indicated by the rapid decrease of the total energy of the system.

  6. 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.

  7. 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.

  8. Collective excitations of a spherically confined Yukawa plasma

    SciTech Connect

    Kaehlert, H.; Bonitz, M.

    2011-05-15

    The complete spectrum of eigenmodes of a spherically confined Yukawa plasma is presented, based on first-principle molecular dynamics simulations. These results are compared with a recent fluid theory for the multipole modes of this system [H. Kaehlert and M. Bonitz, Phys. Rev. E 82, 036407 (2010)] and with the exact N-particle eigenmodes in the crystalline phase. Simulations confirm the existence of high-order modes found in cold fluid theory. We investigate the influence of screening, coupling, and friction on the mode spectra in detail. Good agreement between theory and simulation is found for weak to moderate screening and low-order modes. In addition, a number of new modes are observed which are missing in the fluid theory. The relations between the breathing mode in the fluid theory, simulation, and the crystal eigenmode are investigated in further detail.

  9. Confined explosive joining of tubes

    NASA Technical Reports Server (NTRS)

    Bement, L. J.

    1979-01-01

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

  10. 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.

  11. 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.

  12. Confining quark condensate model of the nucleon.

    SciTech Connect

    Frank, Michael; Tandy, Peter

    1992-07-01

    We obtain a mean-field solution for the nucleon as a quark-meson soliton obtained from the action of the global color-symmetry model of QCD. All dynamics is generated from an effective interaction of quark currents. At the quark-meson level there are two novel features: (1) absolute confinement is produced from the space-time structure of the dynamical self-energy in the vacuum quark propagator; and (2) the related scalar meson field is an extended q-barq composite that couples nonlocally to quarks. The influence of these features upon the nucleon mass contributions and other nucleon properties is presented.

  13. Dynamics of colloids in confined geometries.

    PubMed

    Almenar, L; Rauscher, M

    2011-05-11

    We discuss the Brownian dynamics of colloids in confinement with special emphasis on the influence of the solvent dynamics. We review the derivation of a dynamic density functional theory (DDFT) including some aspects of hydrodynamic interactions and its application to the micro-rheology of suspensions. In particular we discuss the failure of Stokes' law in suspensions and non-equilibrium solvent structure mediated interactions. With regard to hydrodynamic chromatography we also discuss the stationary transport of particles in narrow channels, and the reasons for the failure of DDFT in this situation.

  14. 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.

  15. Freezing of fluids confined between mica surfaces.

    PubMed

    Ayappa, K G; Mishra, Ratan K

    2007-12-27

    Using grand ensemble simulations, we show that octamethyl-cyclo-tetra-siloxane (OMCTS) confined between two mica surfaces can form a variety of frozen phases which undergo solid-solid transitions as a function of the separation between the surfaces. For atomically smooth mica surfaces, the following sequence of transitions 1[triangle up] --> 1[triangle up]b --> 2B --> 2 square --> 2[triangle up] are observed in the one- and two-layered regimes, where n[triangle up], n[square], and nB denote triangular, square, and buckled phases, respectively, with the prefix n denoting the number of confined layers. The presence of potassium on mica is seen to have a strong influence on the degree of order induced in the fluid. The sequence of solid-solid transitions that occurs with the smooth mica surface is no longer observed. When equilibrated with a state point near the liquid-solid transition, a counterintuitive freezing scenario is observed in the presence of potassium. Potassium disrupts in-plane ordering in the fluid in contact with the mica surface, and freezing is observed only in the inner confined layers. The largest mica separations at which frozen phases were observed ranged from separations that could accommodate six to seven fluid layers. The extent of freezing and the square-to-triangular lattice transition was found to be sensitive to the presence of potassium as well as the thermodynamic conditions of the bulk fluid. The implications of our results on interpretation of surface force experiments as well as the generic phase behavior of confined soft spheres is discussed. PMID:18092763

  16. Spontaneous Patterning of Confined Granular Rods

    NASA Astrophysics Data System (ADS)

    Galanis, Jennifer; Harries, Daniel; Sackett, Dan L.; Losert, Wolfgang; Nossal, Ralph

    2006-01-01

    Vertically vibrated rod-shaped granular materials confined to quasi-2D containers self-organize into distinct patterns. We find, consistent with theory and simulation, a density dependent isotropic-nematic transition. Along the walls, rods interact sterically to form a wetting layer. For high rod densities, complex patterns emerge as a result of competition between bulk and boundary alignment. A continuum elastic energy accounting for nematic distortion and local wall anchoring reproduces the structures seen experimentally.

  17. InAlN/InGaN/GaN double heterostructure with improved carrier confinement and high-temperature transport performance grown by metal-organic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Zhao, Yi; Shuai Xue, Jun; Zhang, Jin Cheng; Zhou, Xiao Wei; Chao Zhang, Ya; Hao, Yue

    2015-07-01

    A nearly lattice-matched InAlN/InGaN/GaN double heterostructure (DH) and traditional InAlN/GaN single heterostructure (SH) were grown by metal-organic chemical vapor deposition. The InN mole fraction of InGaN channel was deduced by XRD and photoluminescence. The electrical properties were characterized by capacitance-voltage and temperature-dependent Hall measurements. Both results revealed that the InAlN/InGaN/GaN DH possessed superior carrier confinement over traditional InAlN/GaN SH owing to the back barrier formed at the InGaN/GaN interface, which prevents the spilling over of carriers and thus remarkably improves the transport performance at high temperature. Furthermore, a thin InGaN layer was preferable for carrier channel applications to a thick one.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. Understanding the Antecedents of Korean High School Students’ Drinking Refusal Self-Efficacy: Parental Influence, Peer Influence, and Behavior

    PubMed Central

    Jang, Su Ahn; Cho, NamAuk; Yoo, Jina

    2012-01-01

    The current study examined the factors that influence Korean adolescents’ drinking refusal self-efficacy, which is known to be associated with alcohol use and drinking intentions. Specifically, this study considered parental monitoring, parent-child communication satisfaction, peer influence, and prior alcohol use as possible antecedents of Korean high school students’ drinking refusal self-efficacy. High school students (n = 538) in South Korea responded to the current study. The data revealed that parent-child communication satisfaction facilitated parental monitoring, and these factors indirectly predicted adolescents’ drinking behavior through peer influence. We also found that prior drinking, parental monitoring, and peer influence were directly associated with drinking refusal self-efficacy, and the self-efficacy, in turn, was associated with drinking intentions. These results not only suggest that drinking refusal self-efficacy are related to drinking behavior and intentions, but they also provide a theoretical explanation for how parental and peer influences are associated with adolescents’ drinking refusal self-efficacy. PMID:22980099

  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. Fat Quality Influences the Obesogenic Effect of High Fat Diets.

    PubMed

    Crescenzo, Raffaella; Bianco, Francesca; Mazzoli, Arianna; Giacco, Antonia; Cancelliere, Rosa; di Fabio, Giovanni; Zarrelli, Armando; Liverini, Giovanna; Iossa, Susanna

    2015-11-16

    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.

  5. 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

  6. Fat Quality Influences the Obesogenic Effect of High Fat Diets.

    PubMed

    Crescenzo, Raffaella; Bianco, Francesca; Mazzoli, Arianna; Giacco, Antonia; Cancelliere, Rosa; di Fabio, Giovanni; Zarrelli, Armando; Liverini, Giovanna; Iossa, Susanna

    2015-11-01

    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

  7. 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.

  8. 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.

  9. 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. PMID:26671507

  10. 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.

  11. Thermodynamics of confined gallium clusters

    NASA Astrophysics Data System (ADS)

    Chandrachud, Prachi

    2015-11-01

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

  12. 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). PMID:26252051

  13. 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).

  14. Universal chiral-triggered magnetization switching in confined nanodots

    PubMed Central

    Martinez, Eduardo; Torres, Luis; Perez, Noel; Hernandez, Maria Auxiliadora; Raposo, Victor; Moretti, Simone

    2015-01-01

    Spin orbit interactions are rapidly emerging as the key for enabling efficient current-controlled spintronic devices. Much work has focused on the role of spin-orbit coupling at heavy metal/ferromagnet interfaces in generating current-induced spin-orbit torques. However, the strong influence of the spin-orbit-derived Dzyaloshinskii-Moriya interaction (DMI) on spin textures in these materials is now becoming apparent. Recent reports suggest DMI-stabilized homochiral domain walls (DWs) can be driven with high efficiency by spin torque from the spin Hall effect. However, the influence of the DMI on the current-induced magnetization switching has not been explored nor is yet well-understood, due in part to the difficulty of disentangling spin torques and spin textures in nano-sized confined samples. Here we study the magnetization reversal of perpendicular magnetized ultrathin dots, and show that the switching mechanism is strongly influenced by the DMI, which promotes a universal chiral non-uniform reversal, even for small samples at the nanoscale. We show that ultrafast current-induced and field-induced magnetization switching consists on local magnetization reversal with domain wall nucleation followed by its propagation along the sample. These findings, not seen in conventional materials, provide essential insights for understanding and exploiting chiral magnetism for emerging spintronics applications. PMID:26062075

  15. Universal chiral-triggered magnetization switching in confined nanodots.

    PubMed

    Martinez, Eduardo; Torres, Luis; Perez, Noel; Hernandez, Maria Auxiliadora; Raposo, Victor; Moretti, Simone

    2015-01-01

    Spin orbit interactions are rapidly emerging as the key for enabling efficient current-controlled spintronic devices. Much work has focused on the role of spin-orbit coupling at heavy metal/ferromagnet interfaces in generating current-induced spin-orbit torques. However, the strong influence of the spin-orbit-derived Dzyaloshinskii-Moriya interaction (DMI) on spin textures in these materials is now becoming apparent. Recent reports suggest DMI-stabilized homochiral domain walls (DWs) can be driven with high efficiency by spin torque from the spin Hall effect. However, the influence of the DMI on the current-induced magnetization switching has not been explored nor is yet well-understood, due in part to the difficulty of disentangling spin torques and spin textures in nano-sized confined samples. Here we study the magnetization reversal of perpendicular magnetized ultrathin dots, and show that the switching mechanism is strongly influenced by the DMI, which promotes a universal chiral non-uniform reversal, even for small samples at the nanoscale. We show that ultrafast current-induced and field-induced magnetization switching consists on local magnetization reversal with domain wall nucleation followed by its propagation along the sample. These findings, not seen in conventional materials, provide essential insights for understanding and exploiting chiral magnetism for emerging spintronics applications.

  16. 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,…

  17. The High Citadel: The Influence of Harvard Law School.

    ERIC Educational Resources Information Center

    Seligman, Joel

    The history of Harvard Law School, a modern critique, and a proposed new model for American legal education are covered in this book by a Harvard Law graduate. Harvard Law School is called the "high citadel" of American legal education. Its admissions procedures, faculty selection, curriculum, teaching methods, and placement practices have served…

  18. 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.

  19. 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

  20. Influence of Tool Balancing in High Speed Machining

    NASA Astrophysics Data System (ADS)

    Bašovská, Klaudia; Peterka, Jozef

    2014-12-01

    The high speed machining (HSM) is now considered as one of the key manufacturing technologies for higher throughput and productivity. HSM used higher rotational speed of the spindle (40,000 min-1 and higher). With increasing high speed spindle rotations raises a number of dynamic forces. Even a small mass unbalance in the spindle and tooling generates tool vibration. Tool vibration shortens tool life and lowers the quality of the machined surface. It is necessary to minimize this vibration by balancing tool and tool holder. The balancing process improves the mass distribution of a cutting tool and its holder, allowing the combination of the two to rotate with the minimum amount of unbalanced centrifugal forces. Machining with balanced tool will provide better surface quality, accuracy and less tool and machine wear. In this study is focused on unbalance cutting tools, definitions, balancing techniques, sources, effects, processes and machineries. The aim of this article was to examine the relationship between unbalance and tool holders used in high speed metalworking machine tools

  1. 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).

  2. 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.

  3. Development of a strongly focusing high-intensity He{sup +} ion source for a confined alpha particle measurement at ITER

    SciTech Connect

    Kisaki, M.; Shinto, K.; Kobuchi, T.; Okamoto, A.; Kitajima, S.; Sasao, M.; Tsumori, K.; Nishiura, M.; Kaneko, O.; Matsuda, Y.; Wada, M.; Sakakita, H.; Kiyama, S.; Hirano, Y.

    2008-02-15

    A strongly focusing high-intensity He{sup +} ion source has been designed and constructed as a beam source for a high-energy He{sup 0} beam probe system for diagnosis of fusion produced alpha particles in the thermonuclear fusion plasmas. The He{sup +} beam was extracted from the ion source at an acceleration voltage of 18-35 kV. Temperature distributions of the beam target were observed with an IR camera. The 1/e-holding beam profile half-width was about 15 mm at optimum perveance (Perv) of 0.03 (I{sub beam}=2.4 A). A beam current about 3 A was achieved at an acceleration voltage of 26.7 kV with an arc power of 10 kW (Perv=0.023)

  4. 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

  5. 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. PMID:26280634

  6. Anomalous lasing of high-speed 850 nm InGaAlAs oxide-confined vertical-cavity surface-emitting lasers with a large negative gain-to-cavity wavelength detuning

    SciTech Connect

    Blokhin, S. A. Bobrov, M. A.; Maleev, N. A.; Sakharov, A. V.; Ustinov, V. M.; Kuzmenkov, A. G.; Blokhin, A. A.; Moser, P.; Lott, J. A.; Bimberg, D.

    2014-08-11

    The impact of a large negative quantum well gain-to-cavity etalon wavelength detuning on the static and dynamic characteristics of 850 nm InGaAlAs high-speed oxide-confined vertical-cavity surface-emitting lasers (VCSELs) was investigated. Three distinct lasing regimes were revealed in large square aperture (≥7 μm per side) devices with large detuning including: (1) an anomalous lasing via higher order Hermite–Gaussian modes at low forward bias current; (2) lasing via the lowest order Hermite–Gaussian modes at high bias current; and (3) simultaneous lasing via both types of transverse modes at intermediate bias currents. In contrast to conventional multimode VCSELs a two-resonance modulation response was observed for the case of co-lasing via multiple transverse modes with high spectral separation. The reduction in the oxide aperture area resulted in classical lasing via the lowest order modes with a conventional single-resonance frequency response.

  7. 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.

  8. Coronal Electron Confinement by Double Layers

    NASA Astrophysics Data System (ADS)

    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.

  9. Factors Influencing High School Students' Science Enrollments Patterns: Academic Abilities, Parental Influences, and Attitudes toward Science.

    ERIC Educational Resources Information Center

    Khoury, Ghada A.; Voss, Burton E.

    This study was designed, using a path analytic model, to assess the relative impact of different factors on science concentration decisions made by grade 10 high school students (N=237). Included in the model were selected demographic and socioeconomic factors, academic abilities factors (including logical thinking), indicators of home and school…

  10. 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.

  11. 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

  12. 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.

  13. 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.

  14. 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.

  15. 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

  16. Influence of high biomass concentrations on alkane solubilities.

    PubMed

    Davison, B H; Barton, J W; Klasson, K T; Francisco, A B

    2000-05-01

    Alkane solubilities were measured experimentally for high-density biomass. The resulting Henry's law constants for propane were found to decrease significantly for both dense yeast suspensions and an actual propane-degrading biofilm consortium. At the biomass densities of a typical biofilm, propane solubility was about an order of magnitude greater than that in pure water. For example, a dense biofilm had a propane Henry's law constant of 0.09+/-0.04 atm m(3) mol(-1) compared to 0.6+/-0.1 atm m(3) mol(-1) measured in pure water. The results were modeled with mixing rules and compared with octanol-water mixtures. Hydrogels (agar) and salts decreased the alkane solubility. By considering a theoretical solubility of propane in dry biomass, estimates were made of intrinsic Henry's law constants for propane in pure yeast and biomass, which were 13+/-2 and 5+/-2 atm kg biomass mol(-1) for yeast and biofilm consortium, respectively.

  17. The effect of confinement on the development of an axisymmetric wall-jet in confined jet impingement

    NASA Astrophysics Data System (ADS)

    Guo, Tianqi; Rau, Matthew J.; Vlachos, Pavlos P.; Garimella, Suresh V.

    2015-11-01

    An experimental study of a confined developing axisymmetric wall-jet is reported. The wall-jet is formed downstream of a circular, confined, impinging jet of water. Stereo particle image velocimetry (SPIV) experiments are conducted at three different nozzle-to-plate spacings (2, 4 and 8 jet diameters) and across Reynolds numbers ranging from 1000 to 9000. Special attention is paid to the development of the wall-jet. The growth rate of the boundary layer thickness, decay rate of the local maximum velocity, and velocity profile scaling for both the inner- and outer-layer are investigated. Measurements are obtained with a maximum spatial resolution of 25 μm and a temporal resolution of 750 Hz. Both ensemble-averaged and instantaneous time-resolved three-component, two-dimensional (3C-2D) flow fields are obtained and analyzed. The upper confinement plate is found to limit the supply of ambient liquid for both the impinging-jet and wall-jet entrainment, and thus significantly influences the wall-jet development; the growth and decay rate of the wall-jet are shown to be greatest at the smallest confinement height. The influence of these confining effects on recirculation patterns and coherent-structure evolution is also reported. These flow field measurements and analyses will serve to inform a variety of practical applications that use impinging jets.

  18. Principals’ Perception of Influence on Factors Affecting Student Achievement in Low- and High-Achieving Urban High Schools

    ERIC Educational Resources Information Center

    Bloom, Collette M.; Owens, Emiel W.

    2013-01-01

    The purpose of the study was to compare and contrast influences principals have on staffing, curriculum issues, and discipline policies in high- and low-performing urban high schools. The data for the present study were drawn from the first year follow up of the Educational Longitudinal Survey of 2002-2004 (ELS: 02), administered by the National…

  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. Limiting Spectra from Confining Potentials.

    ERIC Educational Resources Information Center

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

    1979-01-01

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

  1. 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

  2. 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.

  3. High Tg photorefractive polymers: Influence of the chromophores' β tensor

    NASA Astrophysics Data System (ADS)

    Acebal, P.; Blaya, S.; Carretero, L.

    2004-11-01

    In this paper we study the effect of the chromophores' β tensor active components on the diffraction efficiency of a high Tg photorefractive polymer. In particular, we study the two simplest structures with nonvanishing dipole moment, the one-dimension push-pull systems, and the Λ-shaped chromophores. We have developed a model that relate the diffraction efficiency expression with experimental conditions and microscopic properties of the molecules used. Using this model we determine the optimum experimental conditions for both kinds of chromophores and the criteria for the design of chromophores with improved microscopic properties. The model was also used to evaluate the diffraction efficiency of the chromophore Disperse Red 1 (DR1) with a good agreement with experimental data present in bibliography, and of other chromophores selected with the criteria derived from the model, using quantum mechanical calculations to obtain the microscopic properties. Using the designed chromophores diffraction efficiencies more than one order of magnitude higher than that calculated for DR1 with the experimental conditions has been obtained in simulations. These chromophores also exhibit a low dependency of η on the electric field polarization in contrast to the DR1 or the low Tg photoreactive materials.

  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. 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

  6. 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.

  7. 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.

  8. 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

  9. 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.

  10. Surfactant Two-Dimensional Self-Assembly under Confinement

    SciTech Connect

    Sushko, Maria L.; Liu, Jun

    2011-03-28

    Confinement-induced structural rearrangements in supported self-assembled surfactant layers in aqueous salt solutions are investigated using classical Density Functional Theory. The systematic study of the influence of the nature of electrolyte revealed that 2:1 electrolyte stabilizes the hemicylindrical configuration of ionic surfactant layers, while a confinement-induced transition to a tilted monolayer configuration was found in symmetric 1:1 and 2:2 electrolytes. On the basis of this study we formulate a general model for the energetics of structural rearrangements in supported surfactant layers.

  11. 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)

  12. Two blinking mechanisms in highly confined AgInS2 and AgInS2/ZnS quantum dots evaluated by single particle spectroscopy

    NASA Astrophysics Data System (ADS)

    Cichy, B.; Rich, R.; Olejniczak, A.; Gryczynski, Z.; Strek, W.

    2016-02-01

    Ternary AgInS2 quantum dots (QDs) have been found as promising cadmium-free, red-shifted, and tunable luminescent bio-probes with efficient Stokes and anti-Stokes excitations and luminescence lifetimes (ca. 100 ns) convenient for time resolved techniques like fluorescence life-time imaging. Although the spectral properties of the AgInS2 QDs are encouraging, the complex recombination kinetics in the QDs being still far from understood, limits their full utility. In this paper we report on a model describing the recombination pathways responsible for large deviations from the first-order decay law observed commonly in the ternary chalcogenides. The presented results were evaluated by means of individual AgInS2 QD spectroscopy aided by first principles calculations including the electronic structure and structural reconstruction of the QDs. Special attention was devoted to study the impact of the surface charge state on the excited state relaxation and effect of its passivation by Zn2+ ion alloying. Two different blinking mechanisms related to defect-assisted charge imbalance in the QD responsible for fast non-radiative relaxation of the excited states as well as surface recharging of the QD were found as the major causes of deviations from the first-order decay law. Careful optimization of the AgInS2 QDs would help to fabricate new red-shifted and tunable fluorescent bio-probes characterized by low-toxicity, high quantum yield, long luminescence lifetime, and time stability, leading to many novel in vitro and in vivo applications based on fluorescence lifetime imaging (FLIM) and time-gated detection.Ternary AgInS2 quantum dots (QDs) have been found as promising cadmium-free, red-shifted, and tunable luminescent bio-probes with efficient Stokes and anti-Stokes excitations and luminescence lifetimes (ca. 100 ns) convenient for time resolved techniques like fluorescence life-time imaging. Although the spectral properties of the AgInS2 QDs are encouraging, the complex

  13. Two blinking mechanisms in highly confined AgInS2 and AgInS2/ZnS quantum dots evaluated by single particle spectroscopy.

    PubMed

    Cichy, B; Rich, R; Olejniczak, A; Gryczynski, Z; Strek, W

    2016-02-21

    Ternary AgInS2 quantum dots (QDs) have been found as promising cadmium-free, red-shifted, and tunable luminescent bio-probes with efficient Stokes and anti-Stokes excitations and luminescence lifetimes (ca. 100 ns) convenient for time resolved techniques like fluorescence life-time imaging. Although the spectral properties of the AgInS2 QDs are encouraging, the complex recombination kinetics in the QDs being still far from understood, limits their full utility. In this paper we report on a model describing the recombination pathways responsible for large deviations from the first-order decay law observed commonly in the ternary chalcogenides. The presented results were evaluated by means of individual AgInS2 QD spectroscopy aided by first principles calculations including the electronic structure and structural reconstruction of the QDs. Special attention was devoted to study the impact of the surface charge state on the excited state relaxation and effect of its passivation by Zn(2+) ion alloying. Two different blinking mechanisms related to defect-assisted charge imbalance in the QD responsible for fast non-radiative relaxation of the excited states as well as surface recharging of the QD were found as the major causes of deviations from the first-order decay law. Careful optimization of the AgInS2 QDs would help to fabricate new red-shifted and tunable fluorescent bio-probes characterized by low-toxicity, high quantum yield, long luminescence lifetime, and time stability, leading to many novel in vitro and in vivo applications based on fluorescence lifetime imaging (FLIM) and time-gated detection.

  14. 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.

  15. Effect of an offshore sinkhole perforation in a coastal confined aquifer on submarine groundwater discharge

    USGS Publications Warehouse

    Fratesi, S.E.; Leonard, V.; Sanford, W.E.

    2007-01-01

    In order to explore submarine groundwater discharge in the vicinity of karst features that penetrate the confining layer of an offshore, partially confined aquifer, we constructed a three-dimensional groundwater model using the SUTRA (Saturated-Unsaturated TRAnsport) variable-density groundwater flow model. We ran a parameter sensitivity analysis, testing the effects of recharge rates, permeabilities of the aquifer and confining layer, and thickness of the confining layer. In all simulations, less than 20% of the freshwater recharge for the entire model exits through the sinkhole. Recirculated seawater usually accounts for 10-30% of the total outflow from the model. Often, the sinkhole lies seaward of the transition zone and acts as a recharge feature for recirculating seawater. The permeability ratio between aquifer and confining layer influences the configuration of the freshwater wedge the most; as confining layer permeability decreases, the wedge lengthens and the fraction of total discharge exiting through the sinkhole increases. Copyright ?? 2007 IAHS Press.

  16. Characteristics of inhomogeneous jets in confined swirling air flows

    NASA Technical Reports Server (NTRS)

    So, R. M. C.; Ahmed, S. A.

    1984-01-01

    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.

  17. Experimental investigation of a confined developing axisymmetric wall jet

    NASA Astrophysics Data System (ADS)

    Guo, Tianqi; Rau, Matthew; Vlachos, Pavlos; Garimella, Suresh

    2014-11-01

    The present work reports an experimental study of an axisymmetric, confined wall jet using planar particle image velocimetry (PIV) and the dielectric liquid HFE-7100. The wall jet is formed downstream from a confined and submerged impinging round jet, 3.75 mm in diameter. Both the developing region and self-similar region of the wall jet are investigated. The experiments are conducted for Reynolds numbers (Re = Ud/ υ) ranging from 1500 to 38000 and at a nozzle-to-plate spacing of four jet diameters. Image-preprocessing techniques are used to eliminate background noise and an ensemble correlation scheme is applied to improve the resolution of the measurement of the mean velocity field near the wall. A maximum measurement resolution of 36 μm is achieved. Profiles of the mean velocity, turbulent intensities, decay rate, spread rate and wall shear stress are used to characterize the influence of confinement on the wall jet development and inner layer scaling.

  18. Double-Current-Confined CSP Laser

    NASA Technical Reports Server (NTRS)

    Connolly, John C.

    1992-01-01

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

  19. Confinement and heating studies of field-reversed configurations

    NASA Astrophysics Data System (ADS)

    Chrien, Robert E.

    1990-10-01

    Confinement studies of field-reversed configurations (FRCs) have been actively pursued during the past ten years with the larger and longer-lived FRCs produced in the FRX-C and FRX-C/LSM devices. Confinement measurements have included the global FRC quantities and, in some cases, profiles of electron temperature and density. The inferred confinement times and transport coefficients are used for comparison with transport models as well as to find the best operating conditions in the experiment. Global power flow modelling shows that energy confinement during the equilibrium phase is usually dominated by particle losses, with a substantial secondary contribution from electron thermal conduction. Particle losses in present kinetic FRCs are strongly influenced by open field line confinement, which complicates the study of transport mechanisms. The electron thermal conduction is observed to be anomalous, as in other plasma devices. The bulk electrical resistivity is also anomalous and shows no evidence of classical Spitzer scaling. Recently, the resistive anomaly has been shown to correlate with tilt-like magnetic perturbations observed with Mirnov coils. FRC confinement studies have also been extended to a higher temperature regime during magnetic compression heating. In these experiments, translated FRCs are compressed by increasing the external magnetic flux up to a factor of seven on a time scale between the radial Alfven time and the FRC lifetime. Electron and ion temperatures up to 0.4 keV and 1.6 keV, respectively have been obtained. Confinement times scale roughly as r(exp 2) during compression.

  20. Chiral discrimination in the confined environment of biological nanospace

    NASA Astrophysics Data System (ADS)

    Nandi, Nilashis

    Although chiral discrimination in biological systems is overwhelmingly present, its molecular mechanism remained a puzzle. Why the basic blocks of life like L-amino acid and D-sugar are not being scrambled and retain enantiomeric purity since evolution is an unresolved question. In the present review we focus on the recent experimental and computational studies on the chiral discrimination in reactions such as peptide synthesis and aminoacylation. Experimental studies have shown that a clear homochiral preference exists favouring L-amino acid. Recent combined quantum mechanical/molecular mechanical studies explain the high level of stereospecificity of the processes and revealed multiple factors responsible for the discrimination and concomitant retention of the biological homochirality. Chirality of the relevant molecular segments and the intricate interaction between them as well as with the surrounding residues are important. The confinement of the chiral reactants within the biological nanospaces like the peptidyl transferase centre in tRNA and active site of the aminoacyl transferase as well as the nanoscale proximity are important for the manifestation of the discrimination. Multiple favourable influences of the stereochemistry of the natural chirality (D-form) of the sugar ring are noted. This explains the heterochiral relationship of the D-sugar and L-amino acid in biology. In addition to factors such as chirality, confinement and nanoscale proximity of the molecular segments, the network of electrostatic interaction present in the active site plays a significant role in the chiral discrimination in aminoacylation. Chiral discriminations in the biological cavities of nucleic acid and cyclodextrin are also briefly reviewed.

  1. 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.

  2. Thermodynamics of water structural reorganization due to geometric confinement

    NASA Astrophysics Data System (ADS)

    Stroberg, Wylie; Lichter, Seth

    2015-03-01

    Models of aqueous solvation have successfully quantified the behavior of water near convex bodies. However, many important processes occurring in aqueous solution involve interactions between solutes and surfaces with complicated non-convex geometries. Examples include the folding of proteins, hydrophobic association of solutes, ligand-receptor binding, and water confined within nanotubes and pores. For these geometries, models for solvation of convex bodies fail to account for the added interactions associated with structural confinement. Due to water's propensity to form networks of hydrogen bonds, small alterations to the confining geometry can induce large structural rearrangement within the water. We perform systematic Monte Carlo simulations of water confined to cylindrical cavities of varying aspect ratio to investigate how small geometric changes to the confining geometry may cause large changes to the structure and thermodynamic state of water. Using the Wang-Landau algorithm, we obtain free energies, enthalpies, entropies, and heat capacities across a broad range of temperatures, and show how these quantities are influenced by the structural rearrangement of water molecules due to geometric perturbations.

  3. Feynman amplitudes with confinement included

    NASA Astrophysics Data System (ADS)

    Simonov, Yu. A.

    2009-07-01

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

  4. Nanoparticle fabrication by geometrically confined nanosphere lithography

    NASA Astrophysics Data System (ADS)

    Denomme, Ryan C.; Iyer, Krishna; Kreder, Michael; Smith, Brendan; Nieva, Patricia M.

    2013-07-01

    Arrays of metal nanoparticles, typically gold or silver, exhibit localized surface plasmon resonance, a phenomenon that has many applications, such as chemical and biological sensing. However, fabrication of metal nanoparticle arrays with high uniformity and repeatability, at a reasonable cost, is difficult. Nanosphere lithography (NSL) has been used before to produce inexpensive nanoparticle arrays through the use of monolayers of self-assembled microspheres as a deposition mask. However, control over the size and location of the arrays, as well as uniformity over large areas is poor, thus limiting its use to research purposes. In this paper, a new NSL method, called here geometrically confined NSL (GCNSL), is presented. In GCNSL, microsphere assembly is confined to geometric patterns defined in photoresist, allowing high-precision and large-scale nanoparticle patterning while still remaining low cost. Using this new method, it is demonstrated that 400 nm polystyrene microspheres can be assembled inside of large arrays of photoresist patterns. Results show that optimal microsphere assembly is achieved with long and narrow rectangular photoresist patterns. The combination of microsphere monolayers and photoresist patterns is then used as a deposition mask to produce silver nanoparticles at precise locations on the substrate with high uniformity, repeatability, and quality.

  5. 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.

  6. Valence photoionization of small alkaline earth atoms endohedrally confined in C60

    NASA Astrophysics Data System (ADS)

    Javani, M. H.; McCreary, M. R.; Patel, A. B.; Madjet, M. E.; Chakraborty, H. S.; Manson, S. T.

    2012-07-01

    A theoretical study of photoionization from the outermost orbitals of Be, Mg and Ca atoms endohedrally confined in C60 is reported. The fullerene ion core, comprised of sixty C4+, is smudged into a continuous jellium charge distribution, while the delocalized cloud of carbon valence electrons plus the encaged atom are treated in the time-dependent local density approximation (TDLDA). Systematic evolution of the mixing of outer atomic level with states of the C60 valence band is found along the sequence. This is found to influence the plasmonic enhancement of atomic photoionization at low energies and the geometry-revealing confinement oscillations at high energies in significantly different ways: (a) the extent of enhancement is mainly determined by the strength of atomic ionization, giving the strongest enhancement for Be even though Ca suffers the largest mixing. But (b) strongest collateral oscillations are uncovered for Ca, since, relative to Be and Mg, the mixing causes the highest photoelectron production at confining boundaries of Ca. The study paints the first comparative picture of the atomic valence photospectra for alkaline earth metallofullerenes in a dynamical many-electron framework.

  7. 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.

  8. 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…

  9. 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.…

  10. 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.…

  11. 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…

  12. 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

  13. Simulation of detonation of ammonium nitrate fuel oil mixture confined by aluminum: edge angles for DSD

    SciTech Connect

    Short, Mark; Quirk, James J; Kiyanda, Charles B; Jackson, Scott I; Briggs, Matthew E; Shinas, Micheal A

    2010-01-01

    Non-ideal high explosives are typically porous, low-density materials with a low detonation velocity (3--5 km/s) and long detonation reaction zone ({approx} cms). As a result, the interaction of a non-ideal high explosive with an inert confiner can be markedly different than for a conventional high explosive. Issues arise, for example, with light stiff confiners where the confiner can drive the high explosive (HE) through a Prandtl-Meyer fan at the HE/confiner interface rather than the HE driving the confiner. For a non-ideal high explosive confined by a high sound speed inert such that the detonation velocity is lower than the inert sound speed, the flow is subsonic and thus shockless in the confiner. In such cases, the standard detonation shock dynamics methodology, which requires a positive edge-angle be specified at the HE/confiner interface in order that the detonation shape be divergent, cannot be directly utilized. In order to study how detonation shock dynamics can be utilized in such cases, numerical simulations of the detonation of ammonium nitrate-fuel oil (ANFO) confined by aluminum 6061 are conducted.

  14. Confinement Studies of Auxiliary Heated NSTX Plasmas

    SciTech Connect

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

    2003-05-06

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

  15. Spherical microwave confinement and ball lightning

    NASA Astrophysics Data System (ADS)

    Robinson, William Richard

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

  16. Confinement dynamics in the reversed field pinch

    SciTech Connect

    Schoenberg, K.F.

    1988-01-01

    The study of basic transport and confinement dynamics is central to the development of the reversed field pinch (RFP) as a confinement concept. Thus, the goal of RFP research is to understand the connection between processes that sustain the RFP configuration and related transport/confinement properties. Recently, new insights into confinement have emerged from a detailed investigation of RFP electron and ion physics. These insights derive from the recognition that both magnetohydrodynamic (MHD) and electron kinetic effects play an important and strongly coupled role in RFP sustainment and confinement dynamics. In this paper, we summarize the results of these studies on the ZT-40M experiment. 8 refs.

  17. Greater confinement disposal of radioactive wastes

    SciTech Connect

    Trevorrow, L.E.; Gilbert, T.L.; Luner, C.; Merry-Libby, P.A.; Meshkov, N.K.; Yu, C.

    1985-01-01

    Low-level radioactive waste (LLW) includes a broad spectrum of different radionuclide concentrations, half-lives, and hazards. Standard shallow-land burial practice can provide adequate protection of public health and safety for most LLW. A small volume fraction (approx. 1%) containing most of the activity inventory (approx. 90%) requires specific measures known as greater-confinement disposal (GCD). Different site characteristics and different waste characteristics - such as high radionuclide concentrations, long radionuclide half-lives, high radionuclide mobility, and physical or chemical characteristics that present exceptional hazards - lead to different GCD facility design requirements. Facility design alternatives considered for GCD include the augered shaft, deep trench, engineered structure, hydrofracture, improved waste form, and high-integrity container. Selection of an appropriate design must also consider the interplay between basic risk limits for protection of public health and safety, performance characteristics and objectives, costs, waste-acceptance criteria, waste characteristics, and site characteristics.

  18. 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.

  19. Cholesterol Modulates CFTR Confinement in the Plasma Membrane of Primary Epithelial Cells

    PubMed Central

    Abu-Arish, Asmahan; Pandzic, Elvis; Goepp, Julie; Matthes, Elizabeth; Hanrahan, John W.; Wiseman, Paul W.

    2015-01-01

    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. PMID:26153705

  20. Generic transport coefficients of a confined electrolyte solution.

    PubMed

    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.

  1. 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.

  2. 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.

  3. Cylindrical confinement of semiflexible polymers

    NASA Astrophysics Data System (ADS)

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

    2015-06-01

    Equilibrium states of a closed semiflexible polymer binding to a cylinder are described. This may be either by confinement or by constriction. Closed completely bound states are labeled by two integers: the number of oscillations, n , and the number of times it winds the cylinder, p , the latter being a topological invariant. We examine the behavior of these states as the length of the loop is increased by evaluating the energy, the conserved axial torque, and the contact force. The ground state for a given p is the state with n =1 ; a short loop with p =1 is an elliptic deformation of a parallel circle; as its length increases it elongates along the cylinder axis with two hairpin ends. Excited states with n ≥2 and p =1 possess n -fold axial symmetry. Short (long) loops possess energies ≈p E0 (n E0 ), with E0 the energy of a circular loop with same radius as the cylinder; in long loops the axial torque vanishes. Confined bound excited states are initially unstable; however, above a critical length each n -fold state becomes stable: The folded hairpin cannot be unfolded. The ground state for each p is also initially unstable with respect to deformations rotating the loop off the surface into the interior. A closed planar elastic curve aligned along the cylinder axis making contact with the cylinder on its two sides is identified as the ground state of a confined loop. Exterior bound states behave very differently, if free to unbind, as signaled by the reversal in the sign of the contact force. If p =1 , all such states are unstable. If p ≥2 , however, a topological obstruction to complete unbinding exists. If the loop is short, the bound state with p =2 and n =1 provides a stable constriction of the cylinder, partially unbinding as the length is increased. This motif could be relevant to an understanding of the process of membrane fission mediated by dynamin rings.

  4. Thermoelectricity in Confined Liquid Electrolytes.

    PubMed

    Dietzel, Mathias; Hardt, Steffen

    2016-06-01

    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. PMID:27314730

  5. Liquid Spreading under Nanoscale Confinement

    NASA Astrophysics Data System (ADS)

    Checco, Antonio

    2009-03-01

    Dynamic atomic force microscopy in the noncontact regime is used to study the morphology of a nonvolatile liquid (squalane) as it spreads along wettable nanostripes embedded in a nonwettable surface. Results show that the liquid profile depends on the amount of lateral confinement imposed by the nanostripes, and it is truncated at the microscopic contact line in good qualitative agreement with classical mesoscale hydrodynamics. However, the width of the contact line is found to be significantly larger than expected theoretically. This behavior may originate from small chemical inhomogeneity of the patterned stripes as well as from thermal fluctuations of the contact line.

  6. 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.

  7. Electromelting of Confined Monolayer Ice

    NASA Astrophysics Data System (ADS)

    Qiu, Hu; Guo, Wanlin

    2013-05-01

    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.

  8. Electromelting of confined monolayer ice.

    PubMed

    Qiu, Hu; Guo, Wanlin

    2013-05-10

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

  9. 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.

  10. 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.

  11. Space Weather and confined CME events

    NASA Astrophysics Data System (ADS)

    Thalmann, Julia; Temmer, Manuela; Veronig, Astrid; Su, Yang

    2016-04-01

    The unusually large NOAA active region (AR) 2192, observed in October and November 2014, was outstanding in its productivity of major flares (GOES class M5 and larger). During the time when the AR faced Earth, major Space Weather events would have been expected. However, none of the X-flares was associated to a coronal mass ejection. Observational evidence for the confinement of the flare are large initial separation of the flare ribbons, together with an almost absent growth in ribbon separation. The low dynamic of the ribbons also suggests a reconnection site high up in the corona. From NLFF modeling we show that the arcade overlying the AR had a predominantly north-south oriented magnetic system, which served as a strong, also lateral, confinement for the flares at the core of the active region. From the magnetic field modeling we derived the decay of the constraining background, and it was found that the overlying field was only slowly decaying with height. We conclude that observational data of the solar surface, especially of flare ribbon dynamics as well as magnetic field models support Space Weather predictions.

  12. Viscosity of confined inhomogeneous nonequilibrium fluids

    NASA Astrophysics Data System (ADS)

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

    2004-12-01

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

  13. 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

  14. Polymer ejection from strong spherical confinement

    NASA Astrophysics Data System (ADS)

    Piili, J.; Linna, R. P.

    2015-12-01

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

  15. Confined magnetic monopoles in dense QCD

    SciTech Connect

    Gorsky, A.; Shifman, M.; Yung, A.

    2011-04-15

    Non-Abelian strings exist in the color-flavor locked phase of dense QCD. We show that kinks appearing in the world-sheet theory on these strings, in the form of the kink-antikink bound pairs, are the magnetic monopoles-descendants of the 't Hooft-Polyakov monopoles surviving in such a special form in dense QCD. Our consideration is heavily based on analogies and inspiration coming from certain supersymmetric non-Abelian theories. This is the first ever analytic demonstration that objects unambiguously identifiable as the magnetic monopoles are native to non-Abelian Yang-Mills theories (albeit our analysis extends only to the phase of the monopole confinement and has nothing to say about their condensation). Technically, our demonstration becomes possible due to the fact that low-energy dynamics of the non-Abelian strings in dense QCD is that of the orientational zero modes. It is described by an effective two-dimensional CP(2) model on the string world sheet. The kinks in this model representing confined magnetic monopoles are in a highly quantum regime.

  16. 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).

  17. Influence of High Harmonics of Magnetic Fields on Trapped Magnetic Fluxes in HTS Bulk

    NASA Astrophysics Data System (ADS)

    Yamagishi, K.; Miyagi, D.; Tsukamoto, O.

    Various kinds of HTS bulk motors are proposed and have been developed. Generally, those motors are driven by semiconductor inverters and currents fed to the armature windings contain high harmonics. Therefore, the bulks are exposed to high harmonics magnetic fields and AC losses are produced in the bulks. The AC losses deteriorate the efficiency of the motors and cause temperature rise of the bulks which decrease the trapped magnetic fluxes of the bulks. Usually, electro-magnetic shielding devices are inserted between the bulks and armature windings. However, the shielding devices degrade compactness of the motors. Therefore, it is important to have knowledge of the influence of the high harmonics magnetic fields on the AC losses and trapped magnetic fluxes of the bulk for optimum design of the shielding devices. In this work, the authors experimentally study the influence of high harmonics magnetic fields.

  18. 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.…

  19. 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…

  20. 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…

  1. 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…

  2. 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…

  3. 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, participants would…

  4. 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.…

  5. 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…

  6. 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…

  7. 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.

  8. Legal briefing: coerced treatment and involuntary confinement for contagious disease.

    PubMed

    Pope, Thaddeus Mason; Bughman, Heather Michelle

    2015-01-01

    This issue's "Legal Briefing" column covers recent legal developments involving coerced treatment and involuntary confinement for contagious disease. Recent high profile court cases involving measles, tuberculosis, human immunodeficiency virus, and especially Ebola, have thrust this topic back into the bioethics and public spotlights. This has reignited debates over how best to balance individual liberty and public health. For example, the Presidential Commission for the Study of Bioethical Issues has officially requested public comments, held open hearings, and published a 90-page report on "ethical considerations and implications" raised by "U.S. public policies that restrict association or movement (such as quarantine)." Broadly related articles have been published in previous issues of The Journal of Clinical Ethics. We categorize recent legal developments on coerced treatment and involuntary confinement into the following six categories: 1. Most Public Health Confinement Is Voluntary 2. Legal Requirements for Involuntary Confinement 3. New State Laws Authorizing Involuntary Confinement 4. Quarantine Must Be as Least Restrictive as Necessary 5. Isolation Is Justified Only as a Last Resort 6. Coerced Treatment after Persistent Noncompliance. PMID:25794297

  9. Combined static potentials for confinement of neutral species

    SciTech Connect

    Ricci, Leonardo; Bassi, Davide; Bertoldi, Andrea

    2007-08-15

    We discuss the general problem of generating confining potentials for neutral matter by combining different kinds of static forces. The interactions taken into account are those having a linear or quadratic dependence on the modulus of an irrotational and solenoidal field. Particular attention is devoted to the combination of electric and magnetic forces for paramagnetic species. In this case, tight confinement can be achieved by enhancing and balancing the field gradients. Combined potentials turn out to be conveniently generated by configurations based on high permeability materials. Feasibility of combined electric-magnetic traps and guides for neutral alkali-metal atoms is discussed.

  10. Modelling Violent Reaction Following Low Speed Impact on Confined Explosives

    NASA Astrophysics Data System (ADS)

    Curtis, John; Jones, Andrew; Hughes, Christopher; Reaugh, John

    2011-06-01

    To ensure the safe storage and deployment of explosives it is important to understand the mechanisms that give rise to ignition and reaction growth in low speed impacts. The LLNL High Explosive Response to Mechanical Stimulus (HERMES) material model, integrated in LS-DYNA, has been developed to model the progress of the reaction after such an impact. The low speed impact characteristics of an HMX based formulation have been determined in the AWE Steven Test. Axisymmetric simulations have been performed to determine the characteristics of the model. The sensitivity study included looking at the influence of friction, material strength and confinement. By comparing the experimental and calculated results, the key parameters which determine the response in this configuration have been determined. The model qualitatively predicts the point of ignition within the vehicle. Future refinements are discussed. JER's activity was performed under the auspices of the US DOE by LLNL under Contract DE-AC52-07NA27344, and partially funded by the Joint US DoD/DOE Munitions Technology Development Program.

  11. Quantum confinement in Si and Ge nanostructures: Theory and experiment

    SciTech Connect

    Barbagiovanni, Eric G.; Lockwood, David J.; Simpson, Peter J.; Goncharova, Lyudmila V.

    2014-03-15

    The role of quantum confinement (QC) in Si and Ge nanostructures (NSs) including quantum dots, quantum wires, and quantum wells is assessed under a wide variety of fabrication methods in terms of both their structural and optical properties. Structural properties include interface states, defect states in a matrix material, and stress, all of which alter the electronic states and hence the measured optical properties. We demonstrate how variations in the fabrication method lead to differences in the NS properties, where the most relevant parameters for each type of fabrication method are highlighted. Si embedded in, or layered between, SiO{sub 2}, and the role of the sub-oxide interface states embodies much of the discussion. Other matrix materials include Si{sub 3}N{sub 4} and Al{sub 2}O{sub 3}. Si NSs exhibit a complicated optical spectrum, because the coupling between the interface states and the confined carriers manifests with varying magnitude depending on the dimension of confinement. Ge NSs do not produce well-defined luminescence due to confined carriers, because of the strong influence from oxygen vacancy defect states. Variations in Si and Ge NS properties are considered in terms of different theoretical models of QC (effective mass approximation, tight binding method, and pseudopotential method). For each theoretical model, we discuss the treatment of the relevant experimental parameters.

  12. 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.

  13. 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

  14. 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.

  15. Self-organizing human cardiac microchambers mediated by geometric confinement

    PubMed Central

    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.

    2015-01-01

    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. PMID:26172574

  16. 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.

  17. 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.

  18. Influence of low and high doses of fluoride on tooth germ development in rats.

    PubMed

    Maciejewska, I; Adamowicz-Klepalska, B

    2000-01-01

    The influence of fluoride on tooth germ development, especially mineralised tissue, is well documented in numerous dental publications, but there are few reports concerning the influence of fluoride on enamel organ and dental papilla cells. The aim of the study was to assess histologically the development of tooth germs of 20-day-old rat foetuses whose mothers drank water without fluoride or with low (10 mg) and high (110 mg) contents of natrium fluoride, starting from the 12th day of the pregnancy. The fluoride contained in drinking water in low as well as high concentration accelerated the development of enamel organ and dental papilla structures in rat foetuses. The acceleration was proportional to the content of fluoride in drinking water. No disturbances caused by high concentration of natrium fluoride were observed.

  19. 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.

  20. Computational Knowledge for Toroidal Confinement Physics: Part I

    SciTech Connect

    Chang, C. S.

    2009-02-19

    Basic high level computational knowledge for studying the toroidal confinement physics is discussed. Topics include the primacy hierarchy of simulation quantities in statistical plasma physics, importance of the nonlinear-multiscale self-organization phenomena in a computational study, different types of codes for different applications, and different types of computer architectures for different types of codes.

  1. Progress in Direct-Drive Inertial Confinement Fusion

    SciTech Connect

    Meyerhofer,D.D.

    2004-12-17

    Recent progress in direct-drive inertial confinement fusion research at LLE using the 60-beam, 30-kJUV OMEGA laser system and cryogenic target capability to perform ignition-scaled implosions will be reported. In addition, a new high-energy (2.6-kJ) petawatt capability is currently under construction.

  2. Improved mechanical stability of HKUST-1 in confined nanospace.

    PubMed

    Casco, M E; Fernández-Catalá, J; Martínez-Escandell, M; Rodríguez-Reinoso, F; Ramos-Fernández, E V; Silvestre-Albero, J

    2015-09-28

    One of the main concerns in the technological application of several metal-organic frameworks (MOFs) relates to their structural instability under pressure (after a conforming step). Here we report for the first time that mechanical instability can be highly improved via nucleation and growth of MOF nanocrystals in the confined nanospace of activated carbons.

  3. Recent results on heating and confinement in TEXTOR

    SciTech Connect

    Vandenplas, P.E.; Koch, R.; Messiaen, A.M.; Finken, K.H.; Ongena, J.; Philipps, V.; Samm, U.; Unterberg, B.; Oost, G.V.; Wassenhove, G.V.; Winter, J.; Bonheure, G.; Dumortier, P.; Durodie, F.; Esser, H.G.; Euringer, H.; Giesen, B.; Lochter, M.; Tokar, M.Z.; Wolf, G.H.; Bertschinger, G.; Fuchs, G.; Hillis, D.L.; Hoenen, F.; Huettemann, P.; Koenen, L.; Koslowski, H.R.; Kraemer-Flecken, A.; Mank, G.; Pospieszczyk, A.

    1996-02-01

    Experimentation with TEXTOP tokamak using the ICR plasma heating together with an auxiliary heating system involving the neutral beam injection have allowed to extend the improved confinement mode to the high density regime. The third harmonic D heating and a new reactor coating with edge radiative cooling have given a strong increase of the neutron yield. {copyright} {ital 1996 American Institute of Physics.}

  4. Improved mechanical stability of HKUST-1 in confined nanospace.

    PubMed

    Casco, M E; Fernández-Catalá, J; Martínez-Escandell, M; Rodríguez-Reinoso, F; Ramos-Fernández, E V; Silvestre-Albero, J

    2015-09-28

    One of the main concerns in the technological application of several metal-organic frameworks (MOFs) relates to their structural instability under pressure (after a conforming step). Here we report for the first time that mechanical instability can be highly improved via nucleation and growth of MOF nanocrystals in the confined nanospace of activated carbons. PMID:26256926

  5. Confined Space Imager (CSI) Software

    2013-07-03

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

  6. 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.

  7. 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.

  8. 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

  9. Shear Relaxations of Confined Liquids.

    NASA Astrophysics Data System (ADS)

    Carson, George Amos, Jr.

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

  10. 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.

  11. Planning for greater-confinement disposal

    SciTech Connect

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

    1984-01-01

    This contribution is a progress report for preparation of a document that will summarize procedures and technical information needed to plan for and implement greater-confinement disposal (GCD) of low-level radioactive waste. Selection of a site and a facility design (Phase I), and construction, operation, and extended care (Phase II) will be covered in the document. This progress report is limited to Phase I. Phase I includes determination of the need for GCD, design alternatives, and selection of a site and facility design. Alternative designs considered are augered shafts, deep trenches, engineered structures, high-integrity containers, hydrofracture, and improved waste form. Design considerations and specifications, performance elements, cost elements, and comparative advantages and disadvantages of the different designs are covered. Procedures are discussed for establishing overall performance objectives and waste-acceptance criteria, and for comparative assessment of the performance and cost of the different alternatives. 16 references.

  12. 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.

  13. 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.

  14. Tokamak confinement projections and performance goals

    SciTech Connect

    Uckan, N.A.

    1988-01-01

    One key quantity to be determined in the design of burning-plasma devices (CIT, ITER, reactors, etc.) is the level of plasma current (I) required to meet the desired plasma performance goals (ignition, high Q, etc.) and device objectives (fusion power, wall loading, current drive power, etc.). It is shown that these goals and objectives can be expressed in terms of the ''figure-of-merit'' parameter IA/sup alpha//R/sup x/(/approximately/f(LB/sup y/), where A is the aspect ratio, R is the major radius, L(= R, a) is the characteristic length, B is the toroidal magnetic field on axis, and the exponents ..cap alpha.. /approximately/ 1 +- 0.5 and x /approximately/ 0-0.5 (y /approximately/ 1-2) depend on the confinement assumptions and operational limits. To reach ignition or high Q, the main goal is to optimize IA/sup alpha//R/sup x/, subject to other engineering design constraints. In a CIT-like device (with R /approximately/ 2 m, kappa /approximately/ 2, q/sub psi/ greater than or equal to 3), the ignition requirements is I(A/3)/sup alpha/ /approximately/ 9-15 MA for ''enhanced'' L-mode (H-mode) confinement scaling expressions; an ITER-like device (with R /approximately/ 5-6 m, kappa /approximately/ 2, q/sub psi/ greater than or equal to 3) would require I(A/3)/sup alpha/ /approximately/ 15-25 MA. These requirements are embodied in the present CIT (with I /approximately/ 11 MA, A /approximately 3.25) and ITER (with I /approximately/ 18-22, A /approximately/ 3.1-2.6) designs. 12 refs., 1 fig., 3 tabs.

  15. Experimental Studies on Permeability of Intact and Singly Jointed Meta-Sedimentary Rocks Under Confining Pressure

    NASA Astrophysics Data System (ADS)

    Wong, Louis Ngai Yuen; Li, Diyuan; Liu, Gang

    2013-01-01

    Three different types of permeability tests were conducted on 23 intact and singly jointed rock specimens, which were cored from rock blocks collected from a rock cavern under construction in Singapore. The studied rock types belong to inter-bedded meta-sandstone and meta-siltstone with very low porosity and high uniaxial compressive strength. The transient pulse water flow method was employed to measure the permeability of intact meta-sandstone under a confining pressure up to 30 MPa. It showed that the magnitude order of meta-sandstone's intrinsic permeability is about 10-18 m2. The steady-state gas flow method was used to measure the permeability of both intact meta-siltstone and meta-sandstone in a triaxial cell under different confining pressures spanning from 2.5 to 10 MPa. The measured permeability of both rock types ranged from 10-21 to 10-20 m2. The influence of a single natural joint on the permeability of both rock types was studied by using the steady-state water flow method under different confining pressures spanning from 1.25 to 5.0 MPa, including loading and unloading phases. The measured permeability of both jointed rocks ranged from 10-13 to 10-11 m2, where the permeability of jointed meta-siltstone was usually slightly lower than that of jointed meta-sandstone. The permeability of jointed rocks decreases with increasing confining pressure, which can be well fitted by an empirical power law relationship between the permeability and confining pressure or effective pressure. The permeability of partly open cracked specimens is lower than that of open cracked specimens, but it is higher than that of the specimen with a dominant vein for the meta-sandstone under the same confining pressure. The permeability of open cracked rock specimens will partially recover during the unloading confining pressure process. The equivalent crack (joint) aperture is as narrow as a magnitude order of 10-6 m (1 μm) in the rock specimens under confining pressures

  16. 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.

  17. Influence of high pressure on the relative permittivity of oleic acid

    NASA Astrophysics Data System (ADS)

    Kościesza, R.; Siegoczyński, R. M.

    2011-03-01

    Oleic acid (OA) is a monounsaturated omega-9 fatty acid which undergoes a first-order phase transition when it is influenced by high pressures. The transition results in a change of molecular structure, which was investigated by means of X-ray techniques [J. Przedmojski and R.M. Siegoczyński, X-ray diffraction investigation of oleic acid under high pressure, Phase Transit. 75 (2002), pp. 373-377]. Despite a significant change in the structure, the permittivity of the acid remains barely influenced during and after the phase transition. A rise in relative permittivity has been observed due to the increasing number of molecules per volume unit within a compression cycle. However, no significant fall in the permittivity has been observed as a result of the transition which occurs in the case of edible oils. This may be caused by a strongly dimerised structure and dipole-dipole interaction in the liquid at ambient pressure.

  18. Structure and dynamics of supercooled water in neutral confinements

    NASA Astrophysics Data System (ADS)

    Klameth, F.; Vogel, M.

    2013-04-01

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

  19. The influence of IMF on the lower ionosphere plasma in high and middle latitudes

    NASA Technical Reports Server (NTRS)

    Bremer, J.

    1989-01-01

    As shown by ground-based absorption measurements, the lower ionospheric plasma is markedly controlled by the structure of the IMF. Whereas in high auroral and subauroral latitudes this effect is very pronounced, in midlatitudes its influence is less important. A comparison of these results with satellite data of the IMF and the solar wind speed confirms the important role of these components, not only during special events but also for the normal state of the ionospheric D region plasma.

  20. Gender differences in introductory university physics performance: The influence of high school physics preparation and affect

    NASA Astrophysics Data System (ADS)

    Hazari, Zahra Sana

    The attrition of females studying physics after high school is a concern to the science education community. Most undergraduate science programs require introductory physics coursework. Thus, success in introductory physics is necessary for students to progress to higher levels of science study. Success also influences attitudes; if females are well-prepared, feel confident, and do well in introductory physics, they may be inclined to study physics further. This quantitative study using multilevel modeling focused on determining factors from high school physics preparation (content, pedagogy, and assessment) and the affective domain that influenced female and male performance in introductory university physics. The study controlled for some university/course level characteristics as well as student demographic and academic background characteristics. The data consisted of 1973 surveys from 54 introductory physics courses within 35 universities across the US. The results highlight high school physics and affective experiences that differentially influenced female and male performance. These experiences include: learning requirements, computer graphing/analysis, long written problems, everyday world examples, community projects, cumulative tests/quizzes, father's encouragement, family's belief that science leads to a better career, and the length of time students believed that high school physics would help in university physics. There were also experiences that had a similar influence on female and male performance. Positively related to performance were: covering fewer topics for longer periods of time, the history of physics as a recurring topic, physics-related videos, and test/quiz questions that involved calculations and/or were drawn from standardized tests. Negatively related to performance were: student-designed projects, reading/discussing labs the day before performing them, microcomputer based laboratories, discussion after demonstrations, and family

  1. 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.

  2. 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.

  3. 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. PMID:25768610

  4. 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.

  5. Azimuthal field instability in a confined ferrofluid

    NASA Astrophysics Data System (ADS)

    Dias, Eduardo O.; Miranda, José A.

    2015-02-01

    We report the development of interfacial ferrohydrodynamic instabilities when an initially circular bubble of a nonmagnetic inviscid fluid is surrounded by a viscous ferrofluid in the confined geometry of a Hele-Shaw cell. The fluid-fluid interface becomes unstable due to the action of magnetic forces induced by an azimuthal field produced by a straight current-carrying wire that is normal to the cell plates. In this framework, a pattern formation process takes place through the interplay between magnetic and surface tension forces. By employing a perturbative mode-coupling approach we investigate analytically both linear and intermediate nonlinear regimes of the interface evolution. As a result, useful analytical information can be extracted regarding the destabilizing role of the azimuthal field at the linear level, as well as its influence on the interfacial pattern morphology at the onset of nonlinear effects. Finally, a vortex sheet formalism is used to access fully nonlinear stationary solutions for the two-fluid interface shapes.

  6. 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. PMID:26995194

  7. Confinement-induced resonances in anharmonic waveguides

    SciTech Connect

    Peng Shiguo; Hu Hui; Liu Xiaji; Drummond, Peter D.

    2011-10-15

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

  8. Understanding and improving confinement in CNT

    NASA Astrophysics Data System (ADS)

    Brenner, Paul; Pedersen, Thomas; Sarasola, Xabier; Durand de Gevigney, Benoit; Traverso, Peter

    2010-11-01

    Confinement studies in the Columbia Non-neutral Torus (CNT) are providing new insights into the physics of pure electron plasmas confined on magnetic surfaces. The confinement of pure electron plasmas has now been measured in the absence of internal objects . These transient plasmas exhibit confinement times that are shorter than expected and have a strong dependence on neutral pressure. Plasmas created by electron emission in one direction have been compared to those created by emission in two directions. The confinement is significantly longer when emitting in only one direction, suggesting that a two-stream instability is present and affects the radial transport rate. Progress on verifying the existence of a two-stream instability will be presented. Experimental results from previously unexplored stellarator configurations, with low shear and large islands will also be shown.

  9. 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.

  10. Growth patterns and shape development of zeolite nanocrystals in confined syntheses.

    PubMed

    Yoo, Won Cheol; Kumar, Sandeep; Penn, R Lee; Tsapatsis, Michael; Stein, Andreas

    2009-09-01

    The effects of confinement on the morphological development of the zeolite silicalite-1 were studied during hydrothermal synthesis in three-dimensionally ordered macroporous (3DOM) carbon monoliths. By scheduling multiple infiltration/hydrothermal reaction (IHT) steps using precursor solutions with high (H) or low nutrient content (L) in specific sequences, it was possible to obtain various zeolite morphologies of interest for technological applications. The special morphologies are also functions of shaping and templating effects by the 3DOM carbon reactor and functions of limited mass transport in the confined reaction environment. IHT steps employing high nutrient concentrations favor nucleation, whereas those using low nutrient concentrations provide growth-dominant conditions. Observed product morphologies include polycrystalline sphere arrays for the sequence HHH..., single crystal domains spanning dozens of macropores for the sequence LLL..., and faceted silicalite-1 crystallites with dimensions less than 100 nm with the sequence HLLL.... Most of these crystallites have dimensions less than 100 nm and would be suitable building blocks for seeded zeolite membrane growth. Finally, the sequence LLL...H introduces a secondary population of particles with smaller size, so that the size distribution of zeolite crystallites in the combined population may be tuned, for example, to optimize packing of particles. Hence, by choosing the appropriate infiltration program, it is possible to control grain sizes in polycrystalline particles (spheres and opaline arrays of spheres), which alters the concentration of grain boundaries in the particles and is expected to influence transport properties through the zeolite. PMID:19663496

  11. Three Southern high school biology teachers' perspectives on teaching evolution: Sociocultural influences

    NASA Astrophysics Data System (ADS)

    Kyzer, Peggy Mckewen

    Organizations in science and science education call for students to have a thorough understanding of the theory of evolution. Yet many high school biology teachers do not teach evolution and/or include creationism in their instruction (National Academy of Science, 1998). Historically, the controversy surrounding evolution has created tension for teachers. This case study explored the sociocultural influences related to teaching evolution in three Southern 10th-grade public high school biology classrooms. It also explored the socially and culturally embedded influences on teachers' instructional goals and personal perspectives toward evolution as well as modification of instruction when evolution is taught. Theoretically framed using symbolic interactionism and sociocultural theory, data were collected between October 2003 and April 2004 and included classroom observations two to three times per week, artifacts, and in-depth interviews of the participating teachers, their science department chairpersons, their students, and a Protestant minister. The classroom teachers were unaware of the focus of the study until after evolution was taught. The analysis used in this study was an inductive, interpretative approach that allowed exploration of the sociocultural influences that affect how teachers teach evolution. The sociocultural influences and the lived experiences of each teacher created a continuum for teaching evolution. One of the participating teachers who was heavily involved in the community and one of its fundamentalist churches elected to avoid teaching evolution. Another participating teacher at the same school integrated the theory of evolution in every unit. The third teacher who taught in another school elected to teach evolution in a superficial manner to avoid conflict. The data revealed that the participating teachers' sociocultural situatedness influenced their decisions and instruction on evolution. The influence of strong religious beliefs within

  12. Disentangling Ethnic and Contextual Influences Among Parents Raising Youth in High-Risk Communities.

    PubMed

    Hurley, Sean; Bierman, Karen L; Coie, John D; Dodge, Kenneth A; Greenberg, Mark T; Lochman, John E; McMahon, Robert J; Pinderhughes, Ellen E

    2008-10-01

    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 included geographical location, neighborhood risk, SES, and family stress. The cultural variable was racial socialization. Parenting constructs created through the consensus decision-making of the Parenting Subgroup of the Study Group on Race, Culture, and Ethnicity (see Le et al., 2008) included Monitoring, Communication, Warmth, Behavioral Control and Parenting Efficacy. Hierarchical regressions on each parenting construct were conducted for each grade for which data were available. Analyses tested for initial ethnic differences and then for remaining ethnic differences once contextual influences were controlled. For each construct, some ethnic differences did remain (Monitoring, ninth grade; Warmth, third grade; Communication, kindergarten; Behavioral Control, eighth grade; and Parenting Efficacy, kindergarten through fifth grade). Ethnic differences were explained by contextual differences in the remaining years. Analyses examining the impact of cultural influences revealed a negative relation between racial socialization messages and Communication or Monitoring.

  13. Positive Peer Support or Negative Peer Influence? the Role of Peers among Adolescents in Recovery High Schools

    ERIC Educational Resources Information Center

    Karakos, Holly L.

    2014-01-01

    Evidence from previous research suggests that peers at times exert negative influence and at other times exert positive influence on drug and alcohol use among adolescents in recovery. This study explores recovery high school staff members' perceptions of peer support among students in recovery high schools using qualitative interview data.…

  14. The Influence of Cyberbullying on the College Objectives of Female Undergraduates Who Were Victims in High School

    ERIC Educational Resources Information Center

    Vargas, Militza

    2012-01-01

    Cyberbullying has a negative influence on academic grades, school attendance, and graduation rates, and occurs more frequently among female high school students. The purpose of this study was to analyze the influence of cyberbullying on the college objectives of female undergraduates who were victims in high school. Goleman's theory of…

  15. An Examination of Variables Which Influence High School Students to Enroll in an Undergraduate Engineering or Physical Science Major

    ERIC Educational Resources Information Center

    Porter, Christopher H.

    2011-01-01

    The purpose of this study was to examine the variables which influence a high school student to enroll in an engineering discipline versus a physical science discipline. Data was collected utilizing the High School Activities, Characteristics, and Influences Survey, which was administered to students who were freshmen in an engineering or physical…

  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. 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.

  18. 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.

  19. Influence of spatial and temporal coherences on atomic resolution high angle annular dark field imaging.

    PubMed

    Beyer, Andreas; Belz, Jürgen; Knaub, Nikolai; Jandieri, Kakhaber; Volz, Kerstin

    2016-10-01

    Aberration-corrected (scanning) transmission electron microscopy ((S)TEM) has become a widely used technique when information on the chemical composition is sought on an atomic scale. To extract the desired information, complementary simulations of the scattering process are inevitable. Often the partial spatial and temporal coherences are neglected in the simulations, although they can have a huge influence on the high resolution images. With the example of binary gallium phosphide (GaP) we elucidate the influence of the source size and shape as well as the chromatic aberration on the high angle annular dark field (HAADF) intensity. We achieve a very good quantitative agreement between the frozen phonon simulation and experiment for different sample thicknesses when a Lorentzian source distribution is assumed and the effect of the chromatic aberration is considered. Additionally the influence of amorphous layers introduced by the preparation of the TEM samples is discussed. Taking into account these parameters, the intensity in the whole unit cell of GaP, i.e. at the positions of the different atomic columns and in the region between them, is described correctly. With the knowledge of the decisive parameters, the determination of the chemical composition of more complex, multinary materials becomes feasible.

  20. CMKLR1 deficiency influences glucose tolerance and thermogenesis in mice on high fat diet.

    PubMed

    Huang, Chen; Wang, Miaomiao; Ren, Lirong; Xiang, Liang; Chen, Jie; Li, Mengxia; Xiao, Tianxia; Ren, Peigen; Xiong, Likuan; Zhang, Jian V

    2016-04-29

    Obesity has become a global epidemic disease, contributing to increases in the prevalence of type 2 diabetes. CMKLR1, one of the receptors for chemerin, has a wide range of functions in physiological and pathological activity, including innate and adaptive immunity, inflammation, metabolism and reproduction. In our study, CMKLR1 deficiency did not influence the gain of body weight but did exacerbate glucose intolerance, increase serum insulin level, and promote insulin resistance in mice on high fat diets. The expression of thermogenesis related genes was examined and indicated to decrease in CMKLR1 knockout (KO) mice in both normal and cold environments, which indicated CMKLR1 influence the thermogenesis process. Cold exposure induced significant body mass decrease and improved glucose tolerance and insulin resistance in wild type HFD mice but had no obvious effect on CMKLR1 KO HFD mice. In vitro, loss of CMKLR1 did not significantly influence the differentiation of stromal vascular fibroblasts (SVFs) derived from adipose tissue, but did suppress the expression of thermogenesis related genes. Collectively, these data demonstrate that CMKLR1 deficiency induces inbalance of glucose metabolism and impairs the cold induced-thermogenesis process in high diet models. PMID:26972253