Science.gov

Sample records for quasi-elastic barrier distributions

  1. Quasi-elastic scattering and transfer angular distribution for B,1110+232Th systems at near-barrier energies

    NASA Astrophysics Data System (ADS)

    Dubey, Shradha; Biswas, D. C.; Mukherjee, S.; Patel, D.; Gupta, Y. K.; Prajapati, G. K.; Joshi, B. N.; Danu, L. S.; Mukhopadhyay, S.; John, B. V.; Suryanarayana, S. V.; Vind, R. P.

    2016-12-01

    Quasi-elastic scattering and transfer angular distributions for B,1110+232Th reactions have been measured simultaneously in a wide range of bombarding energies around the Coulomb barrier. The quasi-elastic angular distribution data are analyzed using the optical model code ecis with phenomenological Woods-Saxon potentials. The obtained potential parameters suggest the presence of usual threshold anomaly, confirming tightly bound characteristics for both the projectiles. The reaction cross sections are obtained from the fitting of quasi-elastic angular distribution data. The reduced cross sections at sub-barrier energies compared with Li,76+232Th systems show a systematic dependence on projectile breakup energy. The angular distribution of the transfer products show similar behavior for both the systems.

  2. Breakup coupling effects on near-barrier quasi-elastic scattering of {sup 6,7}Li on {sup 144}Sm

    SciTech Connect

    Otomar, D. R.; Lubian, J.; Gomes, P. R. S.; Monteiro, D. S.; Niello, J. O. Fernandez; Guimaraes, V.; Chamon, L. C.

    2009-09-15

    Excitation functions of quasi-elastic scattering at backward angles have been measured for the {sup 6,7}Li+{sup 144}Sm systems at near-barrier energies, and fusion barrier distributions have been extracted from the first derivatives of the experimental cross sections with respect to the bombarding energies. The data have been analyzed in the framework of continuum discretized coupled-channel calculations, and the results have been obtained in terms of the influence exerted by the inclusion of different reaction channels, with emphasis on the role played by the projectile breakup.

  3. Swimming speed distributions of bull spermatozoa as determined by quasi-elastic light scattering.

    PubMed Central

    Hallett, F R; Craig, T; Marsh, J

    1978-01-01

    88 semen samples from 39 bulls have been investigated by the quasi-elastic light scattering technique. Normal, defective, and dead cells each yielded characteristic autocorrelation functions. The form of these functions indicates that the swimming speed distribution of normal cells is a gamma distribution with two degrees of freedom while that for defective or circular swimmers is a gamma distribution with one degree of freedom. The resulting analysis of the experimental autocorrelation functions yields the fraction of the sample that is normal, the fraction that is defective, and the average speed of each group. The average helical swimming speed of normal cells was found to be 384 micron/s, while the average trajectory speed of the circular swimmers was found to be 103 micron/s. The overall quality of the semen samples as determined by light scattering is compared to quality determination on the same samples by technicians from the artificial insemination industry. PMID:630041

  4. How well do we understand quasi-elastic reactions at energies close to the barrier

    SciTech Connect

    Rehm, K.E.

    1988-01-01

    In collisions between too heavy nuclei a wide spectrum of different reaction modes is observed covering the range from simple processes like elastic scattering to complicated multistep transfers and fusion. On the theoretical side heavy ion reactions are usually analyzed using models that were developed first for light ion induced reactions: the optical model for elastic scattering and the DWBA for more inelastic processes like transfer and inelastic scattering. Some of the assumptions going into these approximations, however, are not valid for heavy ion induced reactions. The region between fusion and quasi-elastic reactions is not well understood theoretically. This region is associated with deep inelastic collisions, which are complex multiparticle reactions involving transfer of several protons and neutrons. In this paper, the author discusses to what extent experiments in the field of quasi-elastic scattering are understood within the framework of various theoretical models and in what areas more work is needed.

  5. Important influence of single neutron stripping coupling on near-barrier 8Li + 90Zr quasi-elastic scattering

    NASA Astrophysics Data System (ADS)

    Pakou, A.; Keeley, N.; Pierroutsakou, D.; Mazzocco, M.; Acosta, L.; Aslanoglou, X.; Boiano, A.; Boiano, C.; Carbone, D.; Cavallaro, M.; Grebosz, J.; La Commara, M.; Manea, C.; Marquinez-Duran, G.; Martel, I.; Parascandolo, C.; Rusek, K.; Sánchez-Benítez, A. M.; Sgouros, O.; Signorini, C.; Soramel, F.; Soukeras, V.; Stiliaris, E.; Strano, E.; Torresi, D.; Trzcińska, A.; Watanabe, Y. X.; Yamaguchi, H.

    2015-07-01

    Quasi-elastic scattering data were obtained for the radioactive nucleus 8Li on a 90Zr target at the near-barrier energy of 18.5MeV over the angular range to 80°. They were analyzed within the coupled channels and coupled reaction channels frameworks pointing to a strong coupling effect for single neutron stripping, in contrast to 6, 7 Li + 90 Zr elastic scattering at similar energies, a non-trivial result linked to detailed differences in the structure of these Li isotopes.

  6. Spectroscopic study of sub-barrier quasi-elastic nuclear reactions

    SciTech Connect

    Pass, C.N.; Evans, P.M.; Smith, A.E.; Stuttge, L.; Betts, R.R.; Lilley, J.S.; Connell, K.A.; Simpson, J.; Smith, J.R.; James, A.N.

    1988-01-01

    The technique developed in this paper is particularly well suited to the detailed spectroscopic study of low energy quasi-elastic nuclear reactions and by overcoming the limitations of conventional procedure, the prospect of detailed studies of inclusive reaction mechanism may be realised. With only limited statistics we find evidence for strong multistep character in the transfer of a single nucleon from spherical vibrational target to spherical projectile nuclei. The suggestive measurements reported here may be made definitive through extended runs based on this technique and experiments planned for the future offer the real prospect of developing a quantified interpretation of the reaction process. 9 refs. 5 figs.

  7. Quasi-elastic light scattering determination of the size distribution of extruded vesicles.

    PubMed

    Kölchens, S; Ramaswami, V; Birgenheier, J; Nett, L; O'Brien, D F

    1993-04-01

    The size distribution of phospholipid vesicles prepared by the freeze thaw-extrusion method were determined by the non-perturbing technique of quasi-elastic light scattering (QELS) and compared to latex particles of known size. Multiangle QELS experiments were performed to avoid errors due to the angular dependence of the scattering function of the particles. The experimentally determined autocorrelation function was analyzed by multiple mathematical procedures, i.e. single exponential, CUMULANT, exponential sampling, non-negatively constrained least square and CONTIN, in order to select suitable models for vesicle characterization. The most consistent results were obtained with CUMULANT, non-negatively constrained least square and CONTIN. In many instances single exponential analysis gave comparable results to these procedures, which indicates the vesicles have a narrow distribution of sizes. The influence of filter pore size, extrusion pressure and lipid concentration on the size and size distribution of extruded vesicles was determined. Extrusion through 100-, 200- and 400-nm pore size filters produced a unimodal distribution of vesicles, with somewhat smaller diameters as the extrusion pressure increased. The larger the filter pore size, the more dependent the vesicle size was on applied pressure. The observed vesicle size was independent of the lipid concentration between 0.1 and 10 mg ml-1.

  8. Influence of breakup on fusion barrier distributions

    NASA Astrophysics Data System (ADS)

    Patel, D.; Nayak, B. K.; Mukherjee, S.; Biswas, D. C.; Mirgule, E. T.; John, B. V.; Gupta, Y. K.; Mukhopadhyay, S.; Prajapati, G.; Danu, L. S.; Rath, P. K.; Desai, V.; Deshmukh, N.; Saxena, A.

    2013-04-01

    Fusion barrier distributions have been extracted from the quasi-elastic scattering excitation functions, measured at backward angle θlab = 160° in reactions of 6,7Li+209Bi. The present results have been compared with the barrier distributions obtained from the fusion excitation function measurements for the above mentioned systems. The fusion barrier distributions from the quasi-elastic scattering excitation functions have been analyzed with simplified Coupled Channels calculations using Fresco. Inclusions of resonant states for both 6,7Li projectiles improve the predictions to describe the measured quasi-elastic scattering excitation functions and barrier distributions. For both the reactions peak positions of fusion barrier distributions are shifted towards a lower energy side in comparison to that obtained from the fusion excitation function measurements. The observed discrepancy in peak positions of barrier distributions obtained from quasi-elastic scattering and fusion excitation function measurements has been discussed in terms of total reaction threshold distribution.

  9. Quasi-Elastic Reactions of SILICON-28 and Chlorine -37 with LEAD-208 at Energies in the Range of 1 TO 3 Times the Coulomb Barrier

    NASA Astrophysics Data System (ADS)

    Dixit, Sunil

    Measurements have been made for the quasi-elastic scattering of ^{28}Si on ^{208}Pb at 280 and 420 MeV, and of ^{37}Cl on ^{208}Pb at 190, 330 and 433 MeV incident projectile energies. The elastic and inelastic scattering data, along with existing data at 152, 162, 166, 210, and 225 MeV, for the ^ {28}Si + ^{208} Pb system, and existing data at 250 MeV for the ^{37}Cl + ^ {208}Pb system have been analyzed using a collective model CCBA formalism. The data are well reproduced within this model at the higher energies. However, the ^{208}Pb(3_1 ^-) state predictions require an additional rotational quadrupole reorientation term at the lower energies which exhibit a striking energy dependence in the extracted effective quadrupole moment, the nuclear deformations, and the ratio (M_{rm N} /M_{rm P}) of the neutron to proton multipole matrix elements. These results suggest the possibility of threshold anomalies in the reorientation channel, highlighting the inadequacy of the collective model in describing the inelastic excitation process for heavy-ion reactions near the Coulomb barrier, at least for this state. The transfer data show large quasi-elastic yields for the one-neutron pickup channel, contributing between 50%-87% and 55%-71% of the total neutron transfer cross section as a function of decreasing projectile energy for the ^{28}Si,^ {37}Cl + ^{208} Pb reactions, respectively. The one nucleon transfer data has been analyzed using the finite range DWBA with optical-model parameters deduced from CCBA analysis and spectroscopic factors obtained from the literature. These transfer processes display a strong dependence on the ground state reaction Q-value, projectile mass, and charge. At the higher energies there is a strong deep-inelastic component (Q <= -30 MeV). This corresponds to angular distributions that are predominantly exponential for charged particle transfer greater than two. Finally, the recently observed "slope anomaly" between the one- and two

  10. Fusion and quasi-elastic scattering in the Li6,7+Au197 systems

    NASA Astrophysics Data System (ADS)

    Palshetkar, C. S.; Thakur, Shital; Nanal, V.; Shrivastava, A.; Dokania, N.; Singh, V.; Parkar, V. V.; Rout, P. C.; Palit, R.; Pillay, R. G.; Bhattacharyya, S.; Chatterjee, A.; Santra, S.; Ramachandran, K.; Singh, N. L.

    2014-02-01

    Fusion and quasi-elastic scattering measurements have been carried out for Li6,7+Au197 systems in the energy range E /Vb˜0.7 to 1.5. Coupled-channel calculations including coupling to inelastic states of the target and projectiles are able to explain an enhancement in measured fusion cross sections at energies below the barrier. At energies above the barrier the complete fusion cross sections are found to be suppressed compared to the coupled-channel predictions for both systems. A systematic comparison of fusion cross sections of the weakly bound stable nuclei Li6,7 and halo nuclei He6,8 on a Au197 target is presented. Barrier distributions from quasi-elastic scattering are seen to shift towards higher energies with respect to fusion after inclusion of the breakup-α channel for both Li6 and Li7.

  11. Transition from quasi-elastic to deep-inelastic reactions

    SciTech Connect

    Rehm, K.E.

    1986-01-01

    Heavy ion induced transfer reactions are usually considered to fall into two categories. Quasi-elastic processes, on one hand, are characterized by small energy transfers, with one-nucleon transfer reactions being a typical example. These processes are dominant for grazing collisions, and are generally described within simple one-step DWBA calculations. Deep inelastic reactions, on the other hand, occur for more central collisions where the interaction time is longer and subsequently more energy and particles can be exchanged. Quasi-elastic collisions dominate transfer reactions induced by light heavy ions (e.g., /sup 16/O) at energies not too high above the barrier, while deep inelastic collisions are observed mainly in reactions induced by heavier projectiles (Kr, Xe). In this contribution, we discuss the transition between these two processes for the system /sup 48/Ti + /sup 208/Pb. /sup 48/Ti is located between light (/sup 16/O) and heavy (Kr) projectiles and should be well suited for a study of the interrelation between quasi- and deep-inelastic reactions. The experiments were performed with a 300 MeV /sup 48/Ti beam obtained from the Argonne National Laboratory superconducting linac. The outgoing particles were momentum analyzed in a split pole magnetic spectrograph and detected in the focal plane by a position sensitive ionization chamber. The specific energy loss, the magnetic rigidity and the total energy of the outgoing particles were measured enabling mass and Z-identification. The energy resolution was about 3 MeV, determined by the thickness of the /sup 208/Pb target, and thus excluded study of transfer reactions to discrete final states. Angular distributions were measured in the range theta/sub lab/ = 20/sup 0/ to 80/sup 0/ in steps of 5/sup 0/. 8 refs.

  12. Extracting the hexadecapole deformation from backward quasi-elastic scattering

    NASA Astrophysics Data System (ADS)

    Jia, H. M.; Lin, C. J.; Yang, F.; Xu, X. X.; Zhang, H. Q.; Liu, Z. H.; Wu, Z. D.; Yang, L.; Ma, N. R.; Bao, P. F.; Sun, L. J.

    2014-09-01

    Background: The hexadecapole deformation β4 is usually difficult to determine experimentally, especially its sign. The rapidly accumulated knowledge of β2 inspires the desire of β4 for radioactive nuclei, but the current low-quality beam is a severe experimental challenge. Therefore, a simple but sensitive method to extract β4 in such a condition is urgently called for. Purpose: To study the feasibility of extracting β4 from the lower-energy backward quasi-elastic (QEL) scattering. Methods: The QEL scattering at sub-barrier energy region is sensitive to the coupled-channels (CC) effect and consequently may be used to extract β4. The QEL scattering excitation functions for O16+Sm152,Er170, and Yb174 were measured at a backward angle with small energy intervals at energies near the Coulomb barrier. Experimental fusion barrier distributions were also derived. The lower-energy data were analyzed to extract β4 with the help of the CC calculations. Results: The obtained β4 agrees with the available results reasonably well. Conclusions: We have demonstrated that the QEL scattering at sub-barrier energies provides a feasible and sensitive method to extract the value of β4, which is essentially meaningful for the radioactive nucleus because of its low beam intensity.

  13. Barrier distribution functions for the system 6Li+64Ni and the effect of channel coupling

    NASA Astrophysics Data System (ADS)

    Shaikh, Md. Moin; Roy, Subinit; Rajbanshi, S.; Pradhan, M. K.; Mukherjee, A.; Basu, P.; Pal, S.; Nanal, V.; Pillay, R. G.; Shrivastava, A.

    2015-03-01

    Background: The barrier distribution function is an important observable in low-energy nucleus-nucleus collisions because it carries the distinct signature of the channel-coupling effect that is dominant at low energies. It can be derived from the fusion excitation function as well as from the back-angle quasi-elastic excitation function. The barrier distribution functions derived from the two complimentary measurements, in general, appear to peak at an energy close to the Coulomb barrier for strongly bound systems. But for weakly bound projectiles, like 6Li, a relative shift is observed between the distributions. Purpose: The present work investigates the barrier distribution functions from fusion as well as from the back-angle quasi-elastic excitation function for the 6Li+64Ni system. The purpose is to look for the existence of a shift, if any, between the two measured distribution functions, as reported for 6Li collision with heavy targets. A detailed coupled-channel calculation to probe the behavior of the distribution functions and their relative shift has been attempted. Measurement: A simultaneous measurement of fusion and back-angle quasi-elastic excitation functions for the system 6Li+64Ni was performed. The fusion excitation function was measured for the energy range of 11 to 28 MeV while the quasi-elastic excitation function measurement extended from 11 to 20 MeV. The barrier distribution functions were subsequently extracted from both the excitation functions and compared. Results: A small shift of around 450 keV peak to peak is observed between the barrier distribution functions derived from the complementary measurements. Detailed coupled channel and coupled reaction channel calculations reproduced both the excitation functions and barrier distributions. The shift of about 550 keV resulted from the model predictions corroborate the experimentally observed value for 6Li+64Ni system. Conclusions: The coupling to inelastic channels are found to be

  14. Studying neutrino oscillations using quasi-elastic events in MINOS

    SciTech Connect

    Kumaratunga, Sujeewa Terasita

    2008-02-01

    MINOS (Main Injector Neutrino Oscillation Search), is a long baseline neutrino experiment designed to search for neutrino oscillations using two detectors at Fermi National Accelerator Laboratory, IL (Near Detector) and Soudan, MN (Far Detector). It will study vμ → vτ oscillations and make a measurement on the oscillation parameters, Δm$2\\atop{23}$ and sin223, via a vμ beam made at Fermilab. Charge current neutrino interactions in the MINOS detectors are of three types: quasi-elastic scattering (QEL), resonance scattering (RES) and deep inelastic scattering (DIS). Of these, quasi-elastic scattering leaves the cleanest signal with just one μ and one proton in the final state, thus rendering the reconstruction of the neutrino energy more accurate. This thesis will outline a method to separate QEL events from the others in the two detectors and perform a calculation of Δm$2\\atop{23}$ and sin223 using those events. The period under consideration was May 2005 to February 2006. The number of observed quasi-elastic events with energies below 10 GeV was 29, where the expected number was 60 ± 3. A fit to the energy distribution of these events gives Δm$2\\atop{23}$ = 2.91$+0.49\\atop{-0.53}$(stat)$+0.08\\atop{-0.09}$(sys) x 10-3 eV2 and sin223 = 0.990-0.180(stat)-0.030(sys).

  15. Energy dissipation in heavy systems: the transition from quasi-elastic to deep-inelastic scattering

    SciTech Connect

    Rehm, K.E.; van den Berg, A.; Kolata, J.J.; Kovar, D.G.; Kutschera, W.; Rosner, G.; Stephans, G.S.F.; Yntema, J.L.; Lee, L.L.

    1984-01-01

    The interaction of medium mass projectiles (A = 28 - 64) with /sup 208/Pb has been studied using a split-pole spectrograph which allows single mass and charge identification. The reaction process in all systems studied so far is dominated by quasi-elastic neutron transfer reactions, especially at incident energies in the vicinity of the Coulomb barrier. In addition to the quasi-elastic component deep inelastic contributions are present in all reaction channels. The good mass and charge separation allows to generate Wilczynski plots for individual channels; for the system /sup 48/Ti + /sup 208/Pb we observe that the transition between the quasi-elastic and deep-inelastic reactions occurs around Q = -(30 to 35) MeV.

  16. Quasi-Elastic Light Scattering in Ophthalmology

    NASA Astrophysics Data System (ADS)

    Ansari, Rafat R.

    The eye is not just a "window to the soul"; it can also be a "window to the human body." The eye is built like a camera. Light which travels from the cornea to the retina traverses through tissues that are representative of nearly every tissue type and fluid type in the human body. Therefore, it is possible to diagnose ocular and systemic diseases through the eye. Quasi-elastic light scattering (QELS) also known as dynamic light scattering (DLS) is a laboratory technique routinely used in the characterization of macromolecular dispersions. QELS instrumentation has now become more compact, sensitive, flexible, and easy to use. These developments have made QELS/DLS an important tool in ophthalmic research where disease can be detected early and noninvasively before the clinical symptoms appear.

  17. Quasi-elastic neutrino-nucleus reactions

    NASA Astrophysics Data System (ADS)

    Valverde, M.; Nieves, J.; Amaro, J. E.

    2006-05-01

    The quasi-elastic contribution of the nuclear inclusive electron scattering model developed in [A. Gil, J. Nieves, and E. Oset: Nucl. Phys. A 627 (1997) 543] is extended to the study of electroweak charged current induced nuclear reactions at intermediate energies of interest for future neutrino oscillation experiments. The model accounts for long-range nuclear (RPA) correlations, final state interaction and Coulomb corrections. RPA correlations are shown to play a crucial role in the whole range of neutrino energies, up to 500 MeV, studied in this work. Predictions for inclusive muon capture for different nuclei, and for the reactions 12C(ν μ , μ -)X and 12C(ν e, e-)X near threshold are also given.

  18. Quasi-elastic X-ray scattering divergence analysis calculation

    NASA Astrophysics Data System (ADS)

    Reid, John S.; Milne, Gordon J.

    1989-08-01

    A FORTRAN 77 program is described that enables a numerical investigation to be made of the variation of instrumental resolution corrections with apparatus configuration for quasi-elastic X-ray scattering. The program is useful for scattering from phonons, defects, low angle Comptom processes and all instances where the energy change on scattering is at most a small fraction of the incident energy. Account can be taken of an irregular incident beam distribution (in angle and in space), a sample crystal mosaic spread and a finite area detector. The numerical convolutions for each smearing effect are performed separately but cumulatively, allowing the effects of individual processes to be investigated or treated in variant fashion. The program provides a shell of organisation that could be adapted to related problems.

  19. Quasi-elastic neutron scattering studies of protein dynamics

    SciTech Connect

    Rorschach, H.E.

    1993-05-25

    Results that shed new light on the study of protein dynamics were obtained by quasi-elastic neutron scattering. The triple axis instrument H-9 supplied by the cold source was used to perform a detailed study of the quasi-elastic spectrum and the Debye-Waller factor for trypsin in powder form, in solution, and in crystals. A preliminary study of myoglobin crystals was also done. A new way to view the results of quasi-elastic scattering experiments is sketched, and the data on trypsin are presented and analyze according to this new picture.

  20. Measurement of quasi-elastic 12C(p,2p) scattering at high momentum transfer

    NASA Astrophysics Data System (ADS)

    Mardor, Y.; Aclander, J.; Alster, J.; Barton, D.; Bunce, G.; Carroll, A.; Christensen, N.; Courant, H.; Durrant, S.; Gushue, S.; Heppelmann, S.; Kosonovsky, E.; Mardor, I.; Marshak, M.; Makdisi, Y.; Minor, E. D.; Navon, I.; Nicholson, H.; Piasetzky, E.; Roser, T.; Russell, J.; Sutton, C. S.; Tanaka, M.; White, C.; Wu, J.-Y.

    1998-10-01

    We measured the high-momentum transfer [Q2=4.8 and 6.2 (GeV/c)2] quasi-elastic 12C(p,2p) reaction at θcm~=90 deg for 6 and 7.5 GeV/c incident protons. The momentum components of both outgoing protons and the missing energy and momentum of the proton in the nucleus were measured. We verified the validity of the quasi-elastic picture for ground state momenta up to about 0.5 GeV/c. Transverse and longitudinal momentum distributions of the target proton were measured. They have the same shape with a large momentum tail which is not consistent with independent particle models. We observed that the transverse distribution gets wider as the longitudinal component increases in the beam direction.

  1. Cross section measurements for quasi-elastic neutrino-nucleus scattering with the MINOS near detector

    SciTech Connect

    Dorman, Mark Edward

    2008-04-01

    The Main Injector Neutrino Oscillation Search (MINOS) is a long baseline neutrino oscillation experiment based at the Fermi National Accelerator Laboratory (FNAL) in Chicago, Illinois. MINOS measures neutrino interactions in two large iron-scintillator tracking/sampling calorimeters; the Near Detector on-site at FNAL and the Far Detector located in the Soudan mine in northern Minnesota. The Near Detector has recorded a large number of neutrino interactions and this high statistics dataset can be used to make precision measurements of neutrino interaction cross sections. The cross section for charged-current quasi-elastic scattering has been measured by a number of previous experiments and these measurements disagree by up to 30%. A method to select a quasi-elastic enriched sample of neutrino interactions in the MINOS Near Detector is presented and a procedure to fit the kinematic distributions of this sample and extract the quasi-elastic cross section is introduced. The accuracy and robustness of the fitting procedure is studied using mock data and finally results from fits to the MINOS Near Detector data are presented.

  2. Quasi-elastic nuclear scattering at high energies

    NASA Technical Reports Server (NTRS)

    Cucinotta, Francis A.; Townsend, Lawrence W.; Wilson, John W.

    1992-01-01

    The quasi-elastic scattering of two nuclei is considered in the high-energy optical model. Energy loss and momentum transfer spectra for projectile ions are evaluated in terms of an inelastic multiple-scattering series corresponding to multiple knockout of target nucleons. The leading-order correction to the coherent projectile approximation is evaluated. Calculations are compared with experiments.

  3. Improved Optics For Quasi-Elastic Light Scattering

    NASA Technical Reports Server (NTRS)

    Cheung, Harry Michael

    1995-01-01

    Improved optical train devised for use in light-scattering measurements of quasi-elastic light scattering (QELS) and laser spectroscopy. Measurements performed on solutions, microemulsions, micellular solutions, and colloidal dispersions. Simultaneous measurements of total intensity and fluctuations in total intensity of light scattered from sample at various angles provides data used, in conjunction with diffusion coefficients, to compute sizes of particles in sample.

  4. Color Transparency in Quasi-Elastic

    NASA Astrophysics Data System (ADS)

    Greenberg, William Ross

    The role of Color Transparency (CT) in high momentum transfer knockout reactions is explored. The main focus of this study is the escape process of the ejectile from the nucleus. We use a hadronic basis to describe the struck proton as a wavepacket of physical baryon resonances. The ideas of CT are embedded into the usual Glauber treatment. We first ignore the effects of spin and consider the resulting ejectile-nucleus scattering cross sections. We assume two representative forms for the ejectile-nucleon interaction. Explicit forms for the distorted waves are presented in the context of a multiple scattering formalism. New approximation techniques are developed and applied to predict the production of nucleons and N^*'s in (e,e^' p) experiments. The consequences of the non-zero size of the wavepacket are examined. Next, we replace the assumption of a specific form for the interaction with the ansatz that a zero-size wavepacket does not interact. As the wavepacket expands, the nuclear interactions grow. Exact solutions to the scattering equation are obtained. The resulting sum rules are rendered semi-realistic by demanding consistency with pp and pd data. We also use the sum rule method to analyze double scattering events from ^3He. These events are of particular interest since the effects of CT may be easier to see experimentally. Finally, we upgrade our model and consider the full effects of photon and proton spin and polarization. The polarization of the ejected proton is interesting because, due to general symmetry principles, it must vanish in the limit of full CT. These are the first calculations of the spin observables to include CT. Several new effects, due exclusively to the relativistic Dirac structure, are described. Explicit forms for the distorted waves are presented. We apply these wavefunctions to predict total cross sections, normal polarizations and other differential distributions. We also examine the effects of non-zero wavepacket size and of

  5. Effect of coupling in the 28Si+154Sm reaction studied by quasi-elastic scattering

    NASA Astrophysics Data System (ADS)

    Kaur, Gurpreet; Behera, B. R.; Jhingan, A.; Nayak, B. K.; Dubey, R.; Sharma, Priya; Thakur, Meenu; Mahajan, Ruchi; Saneesh, N.; Banerjee, Tathagata; Khushboo, Kumar, A.; Mandal, S.; Saxena, A.; Sugathan, P.; Rowley, N.

    2016-09-01

    The study of the coupling to collective states of the 28Si projectile and 154Sm target in fusion mechanism is reported. Understanding such couplings is important as they influence the barrier height and the formation probability of the compound nuclei, which in turn may be related to the synthesis of superheavy elements in heavier systems. In the present work, before performing the coupled-channel calculations, we wish to obtain an experimental signature of coupling to projectile and target excitation through barrier distribution (BD) study. To this end, the BDs of the 28Si+154Sm and 16O+154Sm systems have been compared using existing fusion data, scaled to compensate for the differences between the nominal Coulomb barriers and the respective coupling strengths. However, the large error bars on the high-energy side of the fusion BD prevent any definite identification of such signatures. We have, therefore, performed a quasi-elastic (QE) scattering experiment for the heavier 28Si+154Sm system and compared its results with existing QE data for the 16O projectile. Since QE BDs are precise at higher energies, the comparison has shown that the BD of 28Si+154Sm is similar to that of 16O+154Sm to a large extent except for a peaklike structure on the higher energy side. The similarity shows that the 154Sm deformation plays a major role in the fusion mechanism of 28Si+154Sm system. The peaklike structure is attributed to 28Si excitation. In contrast with previous studies, it is found that a coupled-channel calculation with vibrational coupling to the first 2+ state of 28Si reproduces this structure rather well. However, an almost identical result is found with the rotational coupling scheme if one considers the large positive hexadecapole deformation of the projectile. A value around that given by Möller and Nix (β4≈0.25 ) leads to a strong cancellation in the re-orientation term that couples the 2+ state back to itself, making that state look vibrational in this

  6. Quasi-elastic electron scattering from polarized 3He

    SciTech Connect

    H. J. Bulten; Ricardo Alarcon; Th. Bauer; D. Boersma; T. Botto; J. F. J. van den Brand; L. van Buuren; Rolf Ent; M. Ferro-Luzzi; D. Geurts; M. Harvey; Peter Heimberg; D. Highinbotham; Kees de Jager; Blaine Norum; I. Passchier; H. R. Poolman; M. van den Putte; E. Six; J. Steijger; D. Szczerba; H. de Vries

    1997-08-01

    Quasi-elastic electron scattering may provide precise information on the S and the D-wave parts of the {sup 3}He ground-state wave function, the neutron form factors, and the role of spin-dependent reaction mechanism effects. An experiment is being performed at the AmPS storage ring at NIKHEF (Amsterdam, the Netherlands), where polarized electrons (up to 900 MeV) are used in combination with large acceptance electron and hadron detectors. Preliminary results from data at four-momentum transfer squared Q{sup 2} = 0.15 GeV{sup 2} are presented.

  7. Desmin filaments studied by quasi-elastic light scattering.

    PubMed Central

    Hohenadl, M; Storz, T; Kirpal, H; Kroy, K; Merkel, R

    1999-01-01

    We studied polymers of desmin, a muscle-specific type III intermediate filament protein, using quasi-elastic light scattering. Desmin was purified from chicken gizzard. Polymerization was induced either by 2 mM MgCl(2) or 150 mM NaCl. The polymer solutions were in the semidilute regime. We concluded that the persistence length of the filaments is between 0.1 and 1 microm. In all cases, we found a hydrodynamic diameter of desmin filaments of 16-18 nm. The filament dynamics exhibits a characteristic frequency in the sense that correlation functions measured on one sample but at different scattering vectors collapse onto a single master curve when time is normalized by the experimentally determined initial decay rate. PMID:10512839

  8. Measurement of Neutrino Induced Quasi-Elastic Cross Section

    NASA Astrophysics Data System (ADS)

    Kim, Jae

    2006-04-01

    The measurement of the weak mixing angle is the goal, using the data collected in the NOMAD experiment at CERN. Studying the neutrino induced Quasi-Elastic (QE) scattering, in which neutrino hits neutron and results in a muon and a proton, would enhance our understanding of the `higher-twist effect' -- an effect that parameterizes the weak mixing angle. Toward this, I developed a likelihood probability density function that enabled me to eliminate a significant portion of the background, resonance and deep inelastic scattering events. As the Monte Carlo (MC) is only reliable to a precision not better than 15 -- 20 percent, I developed several techniques to make sure that MC and DATA agreed around 5 percent. The axial mass and QE cross section can then be calculated. Techniques and the preliminary results relevant to the calculation will be presented.

  9. Quasi-Elastic Scattering with Neutrinos in MINERvA

    NASA Astrophysics Data System (ADS)

    Osta, Jyotsna; Hurtado, Kenyi; Minerva Collaboration

    2014-09-01

    MINERvA is a few GeV neutrino-nucleus scattering experiment designed to study low energy neutrino interactions both in support of neutrino oscillation experiments as well as a pure weak probe of the nuclear medium. The experiment uses a fine-grained, high resolution detector. The active region is composed of plastic scintillator with additional targets of helium, carbon, iron, lead and water placed upstream of the active region. We present preliminary results from the double differential cross section analysis that aims to study quasi-elastic scattering of neutrinos in the phase space of the muon transverse and longitudinal momenta. This analysis uses the low energy neutrino dataset recorded from November 2009 to April 2012.

  10. Anharmonic behavior in the multisubunit protein apoferritin as revealed by quasi-elastic neutron scattering.

    PubMed

    Telling, Mark T F; Neylon, Cameron; Kilcoyne, Susan H; Arrighi, Valeria

    2008-09-04

    Quasi-elastic neutron scattering (QENS) has been used to study the deviation from Debye-law harmonic behavior in lyophilized and hydrated apoferritin, a naturally occurring, multisubunit protein. Whereas analysis of the measured mean squared displacement (msd) parameter reveals a hydration-dependent inflection above 240 K, characteristic of diffusive motion, a hydration-independent inflection is observed at 100 K. The mechanism responsible for this low-temperature anharmonic response is further investigated, via analysis of the elastic incoherent neutron scattering intensity, by applying models developed to describe side-group motion in glassy polymers. Our results suggest that the deviation from harmonic behavior is due to the onset of methyl group rotations which exhibit a broad distribution of activated processes ( E a,ave = 12.2 kJ.mol (-1), sigma = 5.0 kJ x mol (-1)). Our results are likened to those reported for other proteins.

  11. Maximum likelihood techniques applied to quasi-elastic light scattering

    NASA Technical Reports Server (NTRS)

    Edwards, Robert V.

    1992-01-01

    There is a necessity of having an automatic procedure for reliable estimation of the quality of the measurement of particle size from QELS (Quasi-Elastic Light Scattering). Getting the measurement itself, before any error estimates can be made, is a problem because it is obtained by a very indirect measurement of a signal derived from the motion of particles in the system and requires the solution of an inverse problem. The eigenvalue structure of the transform that generates the signal is such that an arbitrarily small amount of noise can obliterate parts of any practical inversion spectrum. This project uses the Maximum Likelihood Estimation (MLE) as a framework to generate a theory and a functioning set of software to oversee the measurement process and extract the particle size information, while at the same time providing error estimates for those measurements. The theory involved verifying a correct form of the covariance matrix for the noise on the measurement and then estimating particle size parameters using a modified histogram approach.

  12. Rhodopsin photoactivation dynamics revealed by quasi-elastic neutron scattering

    DOE PAGES

    Bhowmik, Debsindhu; Shrestha, Utsab; Perera, Suchithranga M.d.c.; ...

    2015-01-27

    Rhodopsin is a G-protein-coupled receptor (GPCR) responsible for vision under dim light conditions. During rhodopsin photoactivation, the chromophore retinal undergoes cis-trans isomerization, and subsequently dissociates from the protein yielding the opsin apoprotein [1]. What are the changes in protein dynamics that occur during the rhodopsin photoactivation process? Here, we studied the microscopic dynamics of the dark-state rhodopsin and the ligand-free opsin using quasi-elastic neutron scattering (QENS). The QENS technique tracks the individual hydrogen atom motions in the protein molecules, because the neutron scattering cross-section of hydrogen is much higher than other atoms [2-4]. We used protein (rhodopsin/opsin) samples with CHAPSmore » detergent hydrated with heavy water. The solvent signal is suppressed due to the heavy water, so that only the signals from proteins and detergents are detected. The activation of proteins is confirmed at low temperatures up to 300 K by the mean-square displacement (MSD) analysis. Our QENS experiments conducted at temperatures ranging from 220 K to 300 K clearly indicate that the protein dynamic behavior increases with temperature. The relaxation time for the ligand-bound protein rhodopsin was longer compared to opsin, which can be correlated with the photoactivation. Moreover, the protein dynamics are orders of magnitude slower than the accompanying CHAPS detergent, which forms a band around the protein molecule in the micelle. Unlike the protein, the CHAPS detergent manifests localized motions that are the same as in the bulk empty micelles. Furthermore QENS provides unique understanding of the key dynamics involved in the activation of the GPCR involved in the visual process.« less

  13. Rhodopsin photoactivation dynamics revealed by quasi-elastic neutron scattering

    SciTech Connect

    Bhowmik, Debsindhu; Shrestha, Utsab; Perera, Suchithranga M.d.c.; Chawla, Udeep; Mamontov, Eugene; Brown, Michael F.; Chu, Xiang -Qiang

    2015-01-27

    Rhodopsin is a G-protein-coupled receptor (GPCR) responsible for vision under dim light conditions. During rhodopsin photoactivation, the chromophore retinal undergoes cis-trans isomerization, and subsequently dissociates from the protein yielding the opsin apoprotein [1]. What are the changes in protein dynamics that occur during the rhodopsin photoactivation process? Here, we studied the microscopic dynamics of the dark-state rhodopsin and the ligand-free opsin using quasi-elastic neutron scattering (QENS). The QENS technique tracks the individual hydrogen atom motions in the protein molecules, because the neutron scattering cross-section of hydrogen is much higher than other atoms [2-4]. We used protein (rhodopsin/opsin) samples with CHAPS detergent hydrated with heavy water. The solvent signal is suppressed due to the heavy water, so that only the signals from proteins and detergents are detected. The activation of proteins is confirmed at low temperatures up to 300 K by the mean-square displacement (MSD) analysis. Our QENS experiments conducted at temperatures ranging from 220 K to 300 K clearly indicate that the protein dynamic behavior increases with temperature. The relaxation time for the ligand-bound protein rhodopsin was longer compared to opsin, which can be correlated with the photoactivation. Moreover, the protein dynamics are orders of magnitude slower than the accompanying CHAPS detergent, which forms a band around the protein molecule in the micelle. Unlike the protein, the CHAPS detergent manifests localized motions that are the same as in the bulk empty micelles. Furthermore QENS provides unique understanding of the key dynamics involved in the activation of the GPCR involved in the visual process.

  14. Study of the deuteron structure in quasi-elastic breakup reaction pd --> ppn at 1 GeV

    NASA Astrophysics Data System (ADS)

    Aleshin, N. P.; Belostotski, S. L.; Grebenyuk, O. G.; Gordeev, V. A.; Komarov, E. N.; Kochenda, L. M.; Lasarev, V. I.; Manayenkov, S. I.; Miklukho, O. V.; Nelyubin, V. V.; Nikulin, V. N.; Prokofiev, O. E.; Sulimov, V. V.; Vikhrov, V. V.; Boudard, A.; Laget, J.-M.

    1994-02-01

    Quasi-elastic deuteron break-up reactions pd → pp( n) and pd → pn( p) have been studied in complete kinematics at 1 GeV. Two outgoing nucleons were detected in coincidence by means of a two-arm spectrometer. After a correction to the impulse approximation for double scattering and Δ-excitation effects, a good agreement with data is found using a momentum distribution of nucleons in the deuteron computed from nucleon-nucleon potentials. This good agreement is obtained up to 0.5 GeV/ c.

  15. Study of quasi-elastic scattering in the NOνA near detector prototype

    SciTech Connect

    Betancourt, M.

    2015-05-15

    NOvA is a 14 kTon long-baseline neutrino oscillation experiment currently being installed in the NuMI off-axis neutrino beam produced at Fermilab. A 222 Ton prototype NOνA detector was built and operated in the neutrino beam for over a year to understand the response of the detector and its construction. Muon neutrino interaction data collected in this test are being analyzed to identify quasi-elastic charged-current interactions and measure the behavior of the quasi-elastic muon neutrino cross section.

  16. Study of the Quasi-Elastic Scattering in the NOvA Detector Prototype

    SciTech Connect

    Betancourt, Minerba

    2013-06-01

    NOvA is a 810 km long base-line neutrino oscillation experiment with two detectors (far 14 KTon and near detector 300 Ton) currently being installed in the NUMI o -axis neutrino beam produced at Fermilab. A 222 Ton prototype NOvA detector (NDOS) was built and operated in the neutrino beam for over a year to understand the response of the detector and its construction. The goal of this thesis is to study the muon neutrino interaction data collected in this test, specifically the identification of quasi-elastic charged-current interactions and measure the behavior of the quasi-elastic muon neutrino cross section.

  17. Inclusive nucleon emission induced by quasi-elastic neutrino-nucleus interactions

    NASA Astrophysics Data System (ADS)

    Nieves, J.; Valverde, M.; Vicente-Vacas, M. J.

    2006-05-01

    A previous model on inclusive charged-current quasi-elastic nuclear reactions [J. Nieves, J.E. Amaro and M. Valverde, Phys. Rev. C 70 (2004) 055503] is extended to include neutral- and charged-current nucleon emission reactions. The problem of outgoing nucleon propagation is treated by means of a Monte Carlo simulation.

  18. Quasi-elastic neutron scattering reveals ligand-induced protein dynamics of a G-protein-coupled receptor

    SciTech Connect

    Shrestha, Utsab R.; Perera, Suchithranga M. D. C.; Bhowmik, Debsindhu; Chawla, Udeep; Mamontov, Eugene; Brown, Michael F.; Chu, Xiang -Qiang

    2016-09-15

    Light activation of the visual G-protein-coupled receptor (GPCR) rhodopsin leads to significant structural fluctuations of the protein embedded within the membrane yielding the activation of cognate G-protein (transducin), which initiates biological signaling. Here, we report a quasi-elastic neutron scattering study of the activation of rhodopsin as a GPCR prototype. Our results reveal a broadly distributed relaxation of hydrogen atom dynamics of rhodopsin on a picosecond–nanosecond time scale, crucial for protein function, as only observed for globular proteins previously. Interestingly, the results suggest significant differences in the intrinsic protein dynamics of the dark-state rhodopsin versus the ligand-free apoprotein, opsin. These differences can be attributed to the influence of the covalently bound retinal ligand. Moreover, an idea of the generic free-energy landscape is used to explain the GPCR dynamics of ligand-binding and ligand-free protein conformations, which can be further applied to other GPCR systems.

  19. Quasi-elastic neutron scattering studies of protein dynamics. Progress report, November 1, 1992--May 25, 1993

    SciTech Connect

    Rorschach, H.E.

    1993-05-25

    Results that shed new light on the study of protein dynamics were obtained by quasi-elastic neutron scattering. The triple axis instrument H-9 supplied by the cold source was used to perform a detailed study of the quasi-elastic spectrum and the Debye-Waller factor for trypsin in powder form, in solution, and in crystals. A preliminary study of myoglobin crystals was also done. A new way to view the results of quasi-elastic scattering experiments is sketched, and the data on trypsin are presented and analyze according to this new picture.

  20. Two Photon Exchange in Quasi-elastic and Deep-inelastic Scattering

    SciTech Connect

    Averett, Todd D.; Katich, Joseph; Zhao Bo

    2011-10-24

    In this paper, I present an overview and preliminary results from three experiments at Jefferson Lab that were recently completed using a {sup 3}He gas target with polarization oriented normal to the scattering plane of unpolarized incident electrons. A target single spin asymmetry was formed by periodically flipping the direction of the target spin. In the reaction {up_arrow}{sup 3}He(e,e'), the Born contribution is expected to be zero, giving direct sensitivity to two photon exchange. This asymmetry was measured in the quasi-elastic and deep-inelastic regimes with 0.1 < Q{sup 2} < 1.0 GeV{sup 2}. The asymmetry is predicted to decrease by two-orders of magnitude for deep-inelastic versus quasi-elastic scattering. Preliminary results from these experiments will be presented.

  1. Charged current quasi-elastic neutrino analysis at MINERνA

    SciTech Connect

    Fiorentini, G. A.

    2015-05-15

    MINERνA (Main INjector Experiment for ν-A) is a neutrino scattering experiment in the NuMI high-intensity neutrino beam at the Fermi National Accelerator Laboratory. MINERvA was designed to make precision measurements of low energy neutrino and antineutrino cross sections on a variety of different materials (plastic scintillator, C, Fe, Pb, He and H2O). We present the current status of the charged current quasi-elastic scattering in plastic scintillator.

  2. Charged current quasi-elastic neutrino analysis at MINERνA

    NASA Astrophysics Data System (ADS)

    Fiorentini, G. A.

    2015-05-01

    MINERνA (Main INjector Experiment for ν-A) is a neutrino scattering experiment in the NuMI high-intensity neutrino beam at the Fermi National Accelerator Laboratory. MINERvA was designed to make precision measurements of low energy neutrino and antineutrino cross sections on a variety of different materials (plastic scintillator, C, Fe, Pb, He and H2O). We present the current status of the charged current quasi-elastic scattering in plastic scintillator.

  3. A study of quasi-elastic muon neutrino and antineutrino scattering in the NOMAD experiment

    NASA Astrophysics Data System (ADS)

    Lyubushkin, V.; Popov, B.; Kim, J. J.; Camilleri, L.; Levy, J.-M.; Mezzetto, M.; Naumov, D.; Alekhin, S.; Astier, P.; Autiero, D.; Baldisseri, A.; Baldo-Ceolin, M.; Banner, M.; Bassompierre, G.; Benslama, K.; Besson, N.; Bird, I.; Blumenfeld, B.; Bobisut, F.; Bouchez, J.; Boyd, S.; Bueno, A.; Bunyatov, S.; Cardini, A.; Cattaneo, P. W.; Cavasinni, V.; Cervera-Villanueva, A.; Challis, R.; Chukanov, A.; Collazuol, G.; Conforto, G.; Conta, C.; Contalbrigo, M.; Cousins, R.; Daniels, D.; Degaudenzi, H.; Del Prete, T.; de Santo, A.; Dignan, T.; di Lella, L.; Do Couto E Silva, E.; Dumarchez, J.; Ellis, M.; Feldman, G. J.; Ferrari, R.; Ferrère, D.; Flaminio, V.; Fraternali, M.; Gaillard, J.-M.; Gangler, E.; Geiser, A.; Geppert, D.; Gibin, D.; Gninenko, S.; Godley, A.; Gomez-Cadenas, J.-J.; Gosset, J.; Gößling, C.; Gouanère, M.; Grant, A.; Graziani, G.; Guglielmi, A.; Hagner, C.; Hernando, J.; Hubbard, D.; Hurst, P.; Hyett, N.; Iacopini, E.; Joseph, C.; Juget, F.; Kent, N.; Kirsanov, M.; Klimov, O.; Kokkonen, J.; Kovzelev, A.; Krasnoperov, A.; Kulagin, S.; Kustov, D.; Lacaprara, S.; Lachaud, C.; Lakić, B.; Lanza, A.; La Rotonda, L.; Laveder, M.; Letessier-Selvon, A.; Ling, J.; Linssen, L.; Ljubičić, A.; Long, J.; Lupi, A.; Marchionni, A.; Martelli, F.; Méchain, X.; Mendiburu, J.-P.; Meyer, J.-P.; Mishra, S. R.; Moorhead, G. F.; Nédélec, P.; Nefedov, Yu.; Nguyen-Mau, C.; Orestano, D.; Pastore, F.; Peak, L. S.; Pennacchio, E.; Pessard, H.; Petti, R.; Placci, A.; Polesello, G.; Pollmann, D.; Polyarush, A.; Poulsen, C.; Rebuffi, L.; Rico, J.; Riemann, P.; Roda, C.; Rubbia, A.; Salvatore, F.; Samoylov, O.; Schahmaneche, K.; Schmidt, B.; Schmidt, T.; Sconza, A.; Seaton, M.; Sevior, M.; Sillou, D.; Soler, F. J. P.; Sozzi, G.; Steele, D.; Stiegler, U.; Stipčević, M.; Stolarczyk, Th.; Tareb-Reyes, M.; Taylor, G. N.; Tereshchenko, V.; Toropin, A.; Touchard, A.-M.; Tovey, S. N.; Tran, M.-T.; Tsesmelis, E.; Ulrichs, J.; Vacavant, L.; Valdata-Nappi, M.; Valuev, V.; Vannucci, F.; Varvell, K. E.; Veltri, M.; Vercesi, V.; Vidal-Sitjes, G.; Vieira, J.-M.; Vinogradova, T.; Weber, F. V.; Weisse, T.; Wilson, F. F.; Winton, L. J.; Wu, Q.; Yabsley, B. D.; Zaccone, H.; Zuber, K.; Zuccon, P.

    2009-10-01

    We have studied the muon neutrino and antineutrino quasi-elastic (QEL) scattering reactions ( ν μ n→ μ - p and bar{ν }_{μ}ptoμ+n ) using a set of experimental data collected by the NOMAD Collaboration. We have performed measurements of the cross-section of these processes on a nuclear target (mainly carbon) normalizing it to the total ν μ ( bar{ν}_{μ} ) charged-current cross section. The results for the flux-averaged QEL cross sections in the (anti)neutrino energy interval 3-100 GeV are < σ_{qel}rangle_{ν_{μ}}=(0.92±0.02(stat)±0.06(syst))×10^{-38} cm2 and <σ_{qel}rangle_{bar{ν}_{μ}}=(0.81±0.05(stat)±0.09(syst))×10^{-38} cm2 for neutrino and antineutrino, respectively. The axial mass parameter M A was extracted from the measured quasi-elastic neutrino cross section. The corresponding result is M A =1.05±0.02(stat)±0.06(syst) GeV. It is consistent with the axial mass values recalculated from the antineutrino cross section and extracted from the pure Q 2 shape analysis of the high purity sample of ν μ quasi-elastic 2-track events, but has smaller systematic error and should be quoted as the main result of this work. Our measured M A is found to be in good agreement with the world average value obtained in previous deuterium filled bubble chamber experiments. The NOMAD measurement of M A is lower than those recently published by K2K and MiniBooNE Collaborations. However, within the large errors quoted by these experiments on M A , these results are compatible with the more precise NOMAD value.

  4. A study of quasi-elastic muon (anti)neutrino scattering in he NOMAD experiment

    NASA Astrophysics Data System (ADS)

    Lyubushkin, Vladimir

    2009-11-01

    We have studied the muon neutrino and antineutrino quasi-elastic (QEL) scattering reactions (vμn→μ-p and v¯μp→μ+n using a set of experimental data collected by the NOMAD collaboration. We have performed measurements of the cross-section of these processes on a nuclear target (mainly Carbon) normalizing it to the total vμ (v¯μ) charged current cross-section. The results for the flux averaged QEL cross-sections in the (anti)neutrino energy interval 3-100 GeV are <σqel>vμ = (0.92±0.02(stat)±0.06(syst))×10-38 cm2 and <σqel>v¯μ = (0.81±0.05(stat)±0.09(syst))×10-38 cm2 for neutrino and antineutrino, respectively. The axial mass parameter MA was extracted from the measured quasi-elastic neutrino cross-section. The corresponding result is MA = 1.05±0.02(stat)±0.06(syst) GeV. It is consistent with the axial mass values recalculated from the antineutrino cross-section and extracted from the pure Q2 shape analysis of the high purity sample of vμ quasi-elastic 2-track events, but has smaller systematic error and should be quoted as the main result of this work. Our measured MA is found to be in good agreement with the world average value obtained in previous deuterium filled bubble chamber experiments. The NOMAD measurement of MA is lower than those recently published by K2K and MiniBooNE collaborations. However, within the large errors quoted by these experiments on MA, these results are compatible with the more precise NOMAD value.

  5. Dynamical properties of α-synuclein in soluble and fibrillar forms by Quasi Elastic Neutron Scattering.

    PubMed

    Bousset, Luc; Brewee, Clémence; Melki, Ronald; Migliardo, Federica

    2014-07-01

    In the present paper, Quasi Elastic Neutron Scattering (QENS) results, gathered at different energy resolution values at the ISIS Facility (RAL, UK), on α-synuclein in soluble and fibrillar forms as a function of temperature and exchanged wave-vector Q are shown. The measurements reveal a different dynamic behavior of the soluble and fibrillar forms of α-synuclein as a function of thermal stress. In more detail, the dynamics of each protein form reflects its own complex conformational heterogeneity. Furthermore, the effect of a well known bioprotectant, trehalose, that influences α-synuclein fibrillation, on both soluble and fibrillar forms of α-synuclein is discussed.

  6. Measurement of Neutrino Induced Exclusive Quasi-Elastic Cross Section in NOMAD

    NASA Astrophysics Data System (ADS)

    Kim, Jae

    2007-04-01

    The measurement of neutrino induced charged current Quasi-Elastic (QE) cross section using the NOMAD data will be presented. The signature of the νμ QE interaction is an outgoing -circ and a proton. I developed a likelihood probability density function to separate QE from background - two track resonance and deep inelastic scattering events. Data themselves were used to help constrain the background estimate. By kinematic comparison to the measured QE data, the axial mass was also measured. This preliminary result is among the most precise measurements of the QE process.

  7. Short Range Correlations in Nuclei at Large xbj through Inclusive Quasi-Elastic Electron Scattering

    SciTech Connect

    Ye, Zhihong

    2013-12-01

    The experiment, E08-014, in Hall-A at Jefferson Lab aims to study the short-range correlations (SRC) which are necessary to explain the nuclear strength absent in the mean field theory. The cross sections for 2H, 3He, 4He, 12C, 40Ca and 48Ca, were measured via inclusive quasi-elastic electron scattering from these nuclei in a Q2 range between 0.8 and 2.8 (GeV/c)2 for x>1. The cross section ratios of heavy nuclei to 2H were extracted to study two-nucleon SRC for 1

  8. Measuring Quasi-Elastic e-n and e-p Scattering from Deuterium

    NASA Astrophysics Data System (ADS)

    Balsamo, Alexander; Sherman, Keegan; Gilfoyle, Gerard

    2016-09-01

    The main physics goal of Jefferson Lab is to understand how quarks and gluons form nuclei. We are developing algorithms to extract the relative amounts of electron-neutron (e-n) to electron-proton (e-p) scattering events from deuterium in quasi-elastic (QE) kinematics for an approved experiment with the CLAS12 detector. Our analysis focuses on neutrons detected in the CLAS12 calorimeters and protons measured with the CLAS12 toroidal magnetic field. Events were generated with the Quasi-Elastic Event Generator (QUEEG) and passed through the Monte Carlo code gemc to simulate the CLAS12 response. These simulated events were then reconstructed using CLAS12 Common Tools. We first match the solid angle for e-n and e-p events. The electron information is used to predict the trajectory of both a neutron and proton through CLAS12. If both particles would interact in the CLAS12 volume, we know the sample has the same solid angle for e-n and e-p events. We then select QE events by searching for a nucleon near the predicted position. The angle between the predicted 3-momentum of the nucleon and the measured value, θpq, reaches a peak near zero for QE events, but not for other inelastic events. A cut on θpq separates QE events from inelastic ones. Work supported by the University of Richmond and the US Department of Energy.

  9. Looking at hydrogen motions in confinement. The uniqueness of Quasi-Elastic Neutron Scattering

    NASA Astrophysics Data System (ADS)

    Fischer, J.; Tsapatsaris, N.; de Paula, E.; Bordallo, H. N.

    2014-09-01

    Why in a barren and hot desert, clays can contain a significant fraction of water? Why does concrete crack? How can we demonstrate that complexation of a drug does not alter its conformation in a way that affects its functionality? In this paper we present results on various studies using Quasi-Elastic Neutron Scattering aimed at clarifying these questions. To allow for a better understanding of neutron scattering, a brief introduction to the basics of its theory is presented. Following the theoretical part, experimental results dealing with the effects of confinement on the water dynamics caused by the interfaces in clays and the nano- and micro-pores of concrete are reviewed in detail. At the end, recent Quasi-Elastic Neutron Scattering investigations on the complexation of the local anesthetics Bupivacaine (BVC.HCl, C18H28N20.HCl.H2O) and Ropivacaine (RVC.HCl, C17H26N20.HCl.H2O) into the cyclic β-cyclodextrin oligosaccharide are presented. To conclude, the perspectives that the European Spallation Source brings to this subject are discussed.

  10. Quasi-elastic neutron scattering reveals ligand-induced protein dynamics of a G-protein-coupled receptor

    DOE PAGES

    Shrestha, Utsab R.; Perera, Suchithranga M. D. C.; Bhowmik, Debsindhu; ...

    2016-09-15

    Light activation of the visual G-protein-coupled receptor (GPCR) rhodopsin leads to significant structural fluctuations of the protein embedded within the membrane yielding the activation of cognate G-protein (transducin), which initiates biological signaling. Here, we report a quasi-elastic neutron scattering study of the activation of rhodopsin as a GPCR prototype. Our results reveal a broadly distributed relaxation of hydrogen atom dynamics of rhodopsin on a picosecond–nanosecond time scale, crucial for protein function, as only observed for globular proteins previously. Interestingly, the results suggest significant differences in the intrinsic protein dynamics of the dark-state rhodopsin versus the ligand-free apoprotein, opsin. These differencesmore » can be attributed to the influence of the covalently bound retinal ligand. Moreover, an idea of the generic free-energy landscape is used to explain the GPCR dynamics of ligand-binding and ligand-free protein conformations, which can be further applied to other GPCR systems.« less

  11. Characteristic Features of Water Dynamics in Restricted Geometries Investigated with Quasi-Elastic Neutron Scattering

    DOE PAGES

    Osti, Naresh C.; Mamontov, Eugene; Ramirez-cuesta, A.; ...

    2015-12-10

    Understanding the molecular behavior of water in spatially restricted environments is important to better understanding its role in many biological, chemical and geological processes. Here we examine the translational diffusion of water confined to a variety of substrates, from flat surfaces to nanoporous media, in the context of a recently proposed universal scaling law (Chiavazzo 2014) [1]. Using over a dozen previous neutron scattering results, we test the validity of this law, evaluating separately the influence of the hydration amount, and the effects of the size and morphology of the confining medium. Additionally, we investigate the effects of changing instrumentmore » resolutions and fitting models on the applicability of this law. Finally, we perform quasi-elastic neutron scattering measurements on water confined inside nanoporous silica to further evaluate this predictive law, in the temperature range 250≤T≤290 K.« less

  12. Quasi-elastic light scattering of platinum dendrimer-encapsulated nanoparticles.

    PubMed

    Wales, Christina H; Berger, Jacob; Blass, Samuel; Crooks, Richard M; Asherie, Neer

    2011-04-05

    Platinum dendrimer-encapsulated nanoparticles (DENs) containing an average 147 atoms were prepared within sixth-generation, hydroxyl-terminated poly(amidoamine) dendrimers (G6-OH). The hydrodynamic radii (R(h)) of the dendrimer/nanoparticle composites (DNCs) were determined by quasi-elastic light scattering (QLS) at high (pH ∼10) and neutral pH for various salt concentrations and identities. At high pH, the size of the DNC (R(h) ∼4 nm) is close to that of the empty dendrimer. At neutral pH, the size of the DNC approximately doubles (R(h) ∼8 nm) whereas that of the empty dendrimer remains unchanged. Changes in ionic strength also alter the size of the DNCs. The increase in size of the DNC is likely due to electrostatic interactions involving the metal nanoparticle.

  13. Search for neutrino oscillations in the MINOS experiment by using quasi-elastic interactions

    SciTech Connect

    Piteira, Rodolphe

    2005-09-29

    The enthusiasm of the scientific community for studying oscillations of neutrinos is equaled only by the mass of their detectors. The MINOS experiment determines and compares the near spectrum of muonic neutrinos from the NUMI beam to the far one, in order to measure two oscillation parameters: Δm$2\\atop{23}$ and sin2 (2θ23). The spectra are obtained by analyzing the charged current interactions which difficulty lies in identifying the interactions products (e.g. muons). An alternative method identifying the traces of muons, bent by the magnetic field of the detectors, and determining their energies is presented in this manuscript. The sensitivity of the detectors is optimal for the quasi-elastic interactions, for which a selection method is proposed, to study their oscillation. Even though it reduces the statistics, such a study introduces fewer systematic errors, constituting the ideal method on the long range.

  14. Hydration of NaDNA by neutron quasi-elastic scattering.

    PubMed Central

    Schreiner, L J; Pintar, M M; Dianoux, A J; Volino, F; Rupprecht, A

    1988-01-01

    Preliminary results of neutron quasi-elastic scattering experiments are reported for hydrated paracrystals of sodium deoxyribonucleic acid (NaDNA). The samples were investigated at two water contents: 3.5 +/- 1.0 and 9.5 +/- 1.5 mol H2O per mole nucleotide. The results of the scattering experiments were almost independent of whether the NaDNA fibers were oriented parallel or perpendicular to the momentum transfer. The data indicate that at the lower hydration the water molecules do not diffuse appreciably on the time scale of the neutron measurements (approximately 3 X 10(-10) s). At the higher hydration the water molecules diffuse isotropically in a sphere of 9 A in diameter with a diffusion coefficient of (5 +/- 2) X 10(-6) cm2 s-1. PMID:3342269

  15. Fast proton hopping detection in ice I{sub h} by quasi-elastic neutron scattering.

    SciTech Connect

    Presiado, I.; Lal, J.; Mamontov, E.; Kolesnikov, A. I.; Huppert, D.

    2011-01-01

    Quasi-elastic neutron scattering was employed on samples of HCl-doped polycrystalline ice I{sub h}. The analysis of the scattering signal provides the excess proton hopping time, {tau}{sub hop}, in the temperature range of 140-195 K. The hopping time strongly depends on the temperature of the sample, and the activation energy of a hopping step is 17 kJ/mol. The values of {tau}{sub hop} of the current experiment are in good agreement with calculated values derived from previous photochemical experiments, in which we found that the proton hopping time at T > 242 K is on the order of 200 fs, roughly 10 times shorter than in liquid water at room temperature.

  16. Fast Proton Hopping Detection in Ice Ih by Quasi-Elastic Neutron Scattering

    SciTech Connect

    Presiado, Itay; Lal, Jyotsana; Mamontov, Eugene; Kolesnikov, Alexander I; Huppert, Dan I

    2011-01-01

    Quasi-elastic neutron scattering was employed on samples of HCl-doped polycrystalline ice I{sub h}. The analysis of the scattering signal provides the excess proton hopping time, {tau}{sub hop}, in the temperature range of 140-195 K. The hopping time strongly depends on the temperature of the sample, and the activation energy of a hopping step is 17 kJ/mol. The values of {tau}{sub hop} of the current experiment are in good agreement with calculated values derived from previous photochemical experiments,(1) in which we found that the proton hopping time at T > 242 K is on the order of 200 fs, roughly 10 times shorter than in liquid water at room temperature.

  17. Spin-Momentum Correlations in Quasi-Elastic Electron Scattering from Deuterium

    SciTech Connect

    I. Passchier; L.D. van Buuren; D. Szczerba; R. Alarcon; Th.S. Bauer; D. Boersma; J.F.J. van den Brand; H.J. Bulten; R. Ent; M. Ferro-Luzzi; M. Harvey; P. Heimberg; D.W. Higinbotham; S. Klous; H. Kolster; J. Lang; B.L. Militsyn; D. Nikolenko; G.J.L. Nooren; B.E. Norum; H.R. Poolman; I. Rachek; M.C. Simani; E. Six; H. de Vries; K. Wang; Z.-L. Zhou

    2002-02-25

    We report on a measurement of spin-momentum correlations in quasi-elastic scattering of longitudinally polarized electrons with an energy of 720 MeV from vector-polarized deuterium. The spin correlation parameter A{sub ed}{sup V} was measured for the 2{rvec H}({rvec e},e{prime}p)n reaction for missing momenta up to 350 MeV/c at a four-momentum transfer squared of 0.21 (GeV/c){sup 2}. The data give detailed information about the spin structure of the deuteron, and are in good agreement with the predictions of microscopic calculations based on realistic nucleon-nucleon potentials and including various spin-dependent reaction mechanism effects. The experiment demonstrates in a most direct manner the effects of the D-state in the deuteron ground-state wave function and shows the importance of isobar configurations for this reaction.

  18. mQfit, a new program for analyzing quasi-elastic neutron scattering data

    NASA Astrophysics Data System (ADS)

    Martinez, Nicolas; Natali, Francesca; Peters, Judith

    2015-01-01

    Analysis of Quasi-elastic Neutron Scattering (QENS) data of complex systems such as biological or soft matter samples in a comprehensive and explicit way often requires great efforts. Most popular software only allows to fit spectra originating from one single instrument and does not permit to extract parameters from a model that is fitted simultaneously to data taken at different instrumental resolutions. We present here a new program, mQfit (multiple QENS dataset fitting), that enables to fit QENS data taken at different spectrometers (with typical resolutions between 0.01 and 0.1 meV) and momentum transfer ranges. This allows drastically reducing the number of fitting parameters. The routine is implemented with a user friendly Graphical User's Interface (GUI), and freely available. As an example, we will present results obtained on E. coli bacterial pellets, and compare them to values published in the literature.

  19. Extraction of structure functions for lepton-nucleus scattering in the quasi-elastic region

    NASA Astrophysics Data System (ADS)

    Kim, K. S.; Kim, Hungchong; Cheoun, Myung-Ki; So, W. Y.

    2016-12-01

    Within the framework of a relativistic single-particle model, we calculate inclusive electron-nucleus scattering by electromagnetic current, and neutrino-nucleus scattering by neutral and charged current in the quasi-elastic region. The longitudinal, the transverse, and the transverse-interference structure functions are extracted from the theoretical cross section by using the Rosenbluth separation method at fixed momentum transfer and scattering angle and then compared with each other from the viewpoint of these current interactions. The position of peak for the electron scattering shifts to higher energy transfer than that for the neutrino scattering. The axial and pseudoscalar terms turn out to play an important role in the neutrino-nucleus scattering.

  20. Characteristic Features of Water Dynamics in Restricted Geometries Investigated with Quasi-Elastic Neutron Scattering

    SciTech Connect

    Osti, Naresh C.; Mamontov, Eugene; Ramirez-cuesta, A.; Wesolowski, David J.; Diallo, S. O.

    2015-12-10

    Understanding the molecular behavior of water in spatially restricted environments is important to better understanding its role in many biological, chemical and geological processes. Here we examine the translational diffusion of water confined to a variety of substrates, from flat surfaces to nanoporous media, in the context of a recently proposed universal scaling law (Chiavazzo 2014) [1]. Using over a dozen previous neutron scattering results, we test the validity of this law, evaluating separately the influence of the hydration amount, and the effects of the size and morphology of the confining medium. Additionally, we investigate the effects of changing instrument resolutions and fitting models on the applicability of this law. Finally, we perform quasi-elastic neutron scattering measurements on water confined inside nanoporous silica to further evaluate this predictive law, in the temperature range 250≤T≤290 K.

  1. Study of Quasi-Elastic vμ (bar vμ ) Scattering in the Nomad Experiment

    NASA Astrophysics Data System (ADS)

    Levy, Jean-Michel

    2011-10-01

    The legacy of the NOMAD neutrino oscillation experiment is a unique data set with a large physics studies potential. We present here the results obtained for the quasi-elastic νμn → μ-p and bar vμ {p} -> μ ^ + {n} reactions.

  2. A sub-GeV charged-current quasi-elastic $\

    SciTech Connect

    Walding, Joseph James

    2009-12-01

    Neutrino-nucleus charged-current quasi-elastic scattering is the signal interaction used by many neutrino oscillation experiments. For muon disappearance studies the signal mode is νμn → μp. Modern oscillation experiments, such as T2K, produce neutrino beams with peak beam energies of order a few-GeV. It is therefore vitally important to have accurate measurements of the charged-current quasi-elastic crosssection for future neutrino oscillation experiments. Neutrino-nucleus cross-sections in the few-GeV region are not well understood, with the main uncertainties coming from understanding of the neutrino beam flux and the final state interactions within nuclei. SciBooNE is a sub-GeV neutrino-nucleus cross-section experiment based at Fermilab, Batavia, USA, with the goal to measure neutrino cross-sections with precision of order 5%. SciBooNE took data from June 2007 until August 2008, in total 0.99×1020 and 1.53×1020 protons on target were collected in neutrino and anti-neutrino mode, respectively. In this thesis a νμ charged-current quasi-elastic (CCQE) cross-section contained within the SciBar sub-detector is presented. A method to tag muons in SciBar was developed and three samples were isolated. An excess in backwards tracks in the one-track sample is observed. A Poisson maximum likelihood is used to extract the CCQE cross-section. The fit was applied using a basic fit parameter model, successfully used to obtain the cross-section in the SciBar-MRD matched CCQE analysis. This method was found to be insufficient in describing the data for the SciBarcontained CCQE analysis. By adding two migration parameters the cross-section was calculated to be 1.004 ± 0.031 (stat)+0.101 -0.150(sys) × 10-38 cm2/neutron, excluding backwards tracks with a χ2 = 203.8/76 d.o.f. and 1.083 ± 0.030(stat)+0.115 -0.177(sys) × 10-38 cm2

  3. Investigation of processes involved in quasi-elastic and Delta excitation region with (e,e'p) reaction on carbon- 12 nuclei

    NASA Astrophysics Data System (ADS)

    Yadav, Mahesh Kumar

    We have studied the 12C(e,e'X) reaction with an incident electron energy of 705 MeV and electron scattering angle of 34.4o. A large solid angle detector, the LAMPF BGO ball, was used to detect protons, pions, deuterons, photons, and neutrons in coincidence with the electron. The electron energy loss was varied from 40 to 450 MeV, thus covering kinematical regions from quasi-elastic scattering to the Δ(1232) resonance. The main focus of the thesis is a study of the Δ region with one or two protons in coincidence with the electron. A simulation program, ENIGMA, was used to model various reactions leading to emission of one or more protons plus neutrons or pions. We found that only two channels were required to reproduce the energy spectra and angular distributions of the (e,e' p) final state: (e,e' p/pi) and (e,e' pnn). The two nucleon final state (e,e' pn) was less than 10% of the cross section. The peak of the Δ(1232) resonance for various coincidences was found to be close to the position of the inclusive spectrum, except for the (e,e' pp) reaction where it increases to the highest measured values in energy loss, in contrast to proton induced reactions. The cross section for (e,e' pp) was found to be small and does not appear to result from direct two nucleon decay of the Δ(1232) resonance. In the quasi-elastic region we found that the kinetic energy spectrum of the proton could be reproduced by a combination of 80% (e,e' p) and 20% (e,e' pn). We were not able to determine whether or not the pn final state was due to final state interactions or two nucleon absorption.

  4. Antineutrino-induced charge current quasi-elastic neutral hyperon production in ArgoNeuT

    NASA Astrophysics Data System (ADS)

    Farooq, Saima

    This dissertation presents the first topological study of the charge current quasi-elastic (CCQE) neutral hyperon production induced by antineutrinos in the ArgoNeuT detector, a liquid argon time projection chamber (LArTPC) at Fermilab, using 1.20 x 1020 protons-on- target (POT), in the NuMI beam operating in the low energy antineutrino mode. The total cross section for the CCQE neutral hyperon production is reported at the mean production energy of 3.42 GeV. The event yield in data is consistent with the predicted cross section, sigma = 2.7 x 10-40 cm2: sigma(CCQELambda0+Sigma0 ) = 3.7 +/- 1.9(stat.) +/- 1.5 (sys.) x 10 -40 cm2. The study sets a 90% confidence level (C.L.) upper limit on the total cross section of CCQE neutral hyperon production: sigma(CCQE Lambda0+Sigma0) < 7.3 x10-40 cm 2 at 90% C.L.

  5. Quasi-elastic neutron scattering studies of the slow dynamics of supercooled and glassy aspirin

    NASA Astrophysics Data System (ADS)

    Zhang, Yang; Tyagi, Madhusudan; Mamontov, Eugene; Chen, Sow-Hsin

    2012-02-01

    Aspirin, also known as acetylsalicylic acid (ASA), is not only a wonderful drug, but also a good glass former. Therefore, it serves as an important molecular system to study the near-arrest and arrested phenomena. In this paper, a high-resolution quasi-elastic neutron scattering (QENS) technique is used to investigate the slow dynamics of supercooled liquid and glassy aspirin from 410 down to 350 K. The measured QENS spectra can be analyzed with a stretched exponential model. We find that (i) the stretched exponent β(Q) is independent of the wavevector transfer Q in the measured Q range and (ii) the structural relaxation time τ(Q) follows a power-law dependence on Q. Consequently, the Q-independent structural relaxation time τ0 can be extracted for each temperature to characterize the slow dynamics of aspirin. The temperature dependence of τ0 can be fitted with the mode-coupling power law, the Vogel-Fulcher-Tammann equation and a universal equation for fragile glass forming liquids recently proposed by Tokuyama in the measured temperature range. The calculated dynamic response function χT(Q, t) using the experimentally determined self-intermediate scattering function of the hydrogen atoms of aspirin shows direct evidence of the enhanced dynamic fluctuations as the aspirin is increasingly supercooled, in agreement with the fixed-time mean squared displacement langx2rang and the non-Gaussian parameter α2 extracted from the elastic scattering.

  6. Diffusive properties of water in Artemia cysts as determined from quasi-elastic neutron scattering spectra.

    PubMed Central

    Trantham, E C; Rorschach, H E; Clegg, J S; Hazlewood, C F; Nicklow, R M; Wakabayashi, N

    1984-01-01

    Results have been obtained on the quasi-elastic spectra of neutrons scattered from pure water, a 20% agarose gel (hydration four grams H2O per gram of dry solid) and cysts of the brine shrimp Artemia for hydrations between 0.10 and 1.2 grams H2O per gram of dry solids. The spectra were interpreted using a two-component model that included contributions from the covalently bonded protons and the hydration water, and a mobile water fraction. The mobile fraction was described by a jump-diffusion correlation function for the translation motion and a simple diffusive orientational correlation function. The results for the line widths gamma (Q2) for pure water were in good agreement with previous measurements. The agarose results were consistent with NMR measurements that show a slightly reduced translational diffusion for the mobile water fraction. The Artemia results show that the translational diffusion coefficient of the mobile water fraction was greatly reduced from that of pure water. The line width was determined mainly by the rotational motion, which was also substantially reduced from the pure water value as determined from dielectric relaxation studies. The translational and rotational diffusion parameters were consistent with the NMR measurements of diffusion and relaxation. Values for the hydration fraction and the mean square thermal displacement [u2] as determined from the Q-dependence of the line areas were also obtained. PMID:6733243

  7. Quasi-Elastic Neutron Scattering Studies of the Slow Dynamics of Supercooled and Glassy Aspirin

    SciTech Connect

    Zhang, Yang; Tyagi, M.; Mamontov, Eugene; Chen, Sow-hsin H

    2011-01-01

    Aspirin, also known as acetylsalicylic acid (ASA), is not only a wonderful drug, but also a good glass former. Therefore, it serves as an important molecular system to study the near-arrest and arrested phenomena. In this paper, a high-resolution quasi-elastic neutron scattering (QENS) technique is used to investigate the slow dynamics of supercooled liquid and glassy aspirin from 410 K down to 350 K. The measured QENS spectra can be analyzed with a stretched exponential model. We find that (i) the stretched exponent (Q) is independent of the wave vector transfer Q in the measured Q-range, and (ii) the structural relaxation time (Q) follows a power law dependence on Q. Consequently, the Q-independent structural relaxation time 0 can be extracted for each temperature to characterize the slow dynamics of aspirin. The temperature dependence of 0 can be fitted with the mode coupling power law, the Vogel-Fulcher-Tammann equation and a universal equation for fragile glass forming liquids recently proposed by M. Tokuyama in the measured temperature range. The calculated dynamic response function T(Q,t) using the experimentally determined self-intermediate scattering function of the hydrogen atoms of aspirin shows a direct evidence of the enhanced dynamic fluctuations as the aspirin is increasingly supercooled, in agreement with the fixed-time mean squared displacement x2 and non-Gaussian parameter 2 extracted from the elastic scattering.

  8. Molecular dynamics force-field refinement against quasi-elastic neutron scattering data

    SciTech Connect

    Borreguero Calvo, Jose M.; Lynch, Vickie E.

    2015-11-23

    Quasi-elastic neutron scattering (QENS) is one of the experimental techniques of choice for probing the dynamics at length and time scales that are also in the realm of full-atom molecular dynamics (MD) simulations. This overlap enables extension of current fitting methods that use time-independent equilibrium measurements to new methods fitting against dynamics data. We present an algorithm that fits simulation-derived incoherent dynamical structure factors against QENS data probing the diffusive dynamics of the system. We showcase the difficulties inherent to this type of fitting problem, namely, the disparity between simulation and experiment environment, as well as limitations in the simulation due to incomplete sampling of phase space. We discuss a methodology to overcome these difficulties and apply it to a set of full-atom MD simulations for the purpose of refining the force-field parameter governing the activation energy of methyl rotation in the octa-methyl polyhedral oligomeric silsesquioxane molecule. Our optimal simulated activation energy agrees with the experimentally derived value up to a 5% difference, well within experimental error. We believe the method will find applicability to other types of diffusive motions and other representation of the systems such as coarse-grain models where empirical fitting is essential. In addition, the refinement method can be extended to the coherent dynamic structure factor with no additional effort.

  9. Molecular dynamics force-field refinement against quasi-elastic neutron scattering data

    DOE PAGES

    Borreguero Calvo, Jose M.; Lynch, Vickie E.

    2015-11-23

    Quasi-elastic neutron scattering (QENS) is one of the experimental techniques of choice for probing the dynamics at length and time scales that are also in the realm of full-atom molecular dynamics (MD) simulations. This overlap enables extension of current fitting methods that use time-independent equilibrium measurements to new methods fitting against dynamics data. We present an algorithm that fits simulation-derived incoherent dynamical structure factors against QENS data probing the diffusive dynamics of the system. We showcase the difficulties inherent to this type of fitting problem, namely, the disparity between simulation and experiment environment, as well as limitations in the simulationmore » due to incomplete sampling of phase space. We discuss a methodology to overcome these difficulties and apply it to a set of full-atom MD simulations for the purpose of refining the force-field parameter governing the activation energy of methyl rotation in the octa-methyl polyhedral oligomeric silsesquioxane molecule. Our optimal simulated activation energy agrees with the experimentally derived value up to a 5% difference, well within experimental error. We believe the method will find applicability to other types of diffusive motions and other representation of the systems such as coarse-grain models where empirical fitting is essential. In addition, the refinement method can be extended to the coherent dynamic structure factor with no additional effort.« less

  10. Spin correlations in quasi-elastic electron scattering from a (3)He internal target

    NASA Astrophysics Data System (ADS)

    Six, R. Edward, III

    The measurement of spin observables in the 3He-> (e->,e' ,d) and 3He-> (e->,e' ,p) reactions have been carried out at the Internal Target Facility of the Dutch National Institute for Nuclear and High Energy Physics (NIKHEF) in Amsterdam, The Netherlands, with a 720-MeV stored electron beam having a longitudinal polarization of 65% and an average current of 80 mA. This was the first measurement of the spin correlation parameters for the reaction 3He-> (e->,e' ,d) . The average target polarization was 45% with a thickness of 5 × 1014 atoms/cm2. The scattered electrons were detected in a large-acceptance, nonfocusing magnetic spectrometer located at a central angle of 40°. The knockout hadrons were detected in a non-magnetic detector located at a central angle of -56°. The central positions of the detectors correspond to quasi-elastic kinematics. The asymmetries A'x and A'x provide information on small components of the 3He ground-state wave function and on the isoscalar/isovector structure of the nuclear electromagnetic current. The results are compared with model calculations.

  11. Capture barrier distributions: Some insights and details

    SciTech Connect

    Rowley, N.; Grar, N.; Trotta, M.

    2007-10-15

    The 'experimental barrier distribution' provides a parameter-free representation of experimental heavy-ion capture cross sections that highlights the effects of entrance-channel couplings. Its relation to the s-wave transmission is discussed, and in particular it is shown how the full capture cross section can be generated from an l=0 coupled-channels calculation. Furthermore, it is shown how this transmission can be simply exploited in calculations of quasifission and evaporation-residue cross sections. The system {sup 48}Ca+{sup 154}Sm is studied in detail. A calculation of the compound-nucleus spin distribution reveals a possible energy dependence of barrier weights due to polarization arising from target and projectile quadrupole phonon states; this effect also gives rise to an entrance-channel 'extra-push'.

  12. Measurement of the nu(mu) Charged Current pi+ Production to Quasi-elastic Scattering Cross Section

    SciTech Connect

    Nowak, Jaroslaw A.; /Louisiana State U.

    2009-09-01

    Using high statistics samples of charged current interactions, MiniBooNE reports a model independent measurement of the single charged pion production to quasi-elastic cross section ratio on mineral oil without corrections for pion re-interactions in the target nucleus [1]. The result is provided as a function of neutrino energy in the range 0.4 GeV < E < 2.4 GeV with 11% precision in the region of highest statistics.

  13. Moments of fusion-barrier distributions

    NASA Astrophysics Data System (ADS)

    Rehm, K. E.; Esbensen, H.; Jiang, C. L.; Back, B. B.; Stefanini, A. M.; Montagnoli, G.

    2016-10-01

    A study of fusion-barrier distributions through an analysis of their moments is presented. The moments can be obtained from least-squares fits of the energy-weighted fusion cross sections without the need of calculating second derivatives. The zeroth and first moments determine the fusion radius R and the Coulomb barrier VC. These two quantities are the same as the parameters R and VC that are used in the well-known expression, E σ =π R2(E -VC) , for the fusion cross section at high energies. The second and third moments, M2 and M3, determine the width and skewness of the barrier distribution, respectively. From these global parameters new correlations for the study of heavy-ion-induced fusion reactions can be obtained. Systems exhibiting a large coupling to transfer reactions show a small fusion radius as well as a large second moment. A negative third moment is correlated with a prolate deformation of the target nucleus.

  14. A measurement of neutrino induced quasi-elastic cross section in NOMAD

    NASA Astrophysics Data System (ADS)

    Kim, Jae

    NOMAD (Neutrino Oscillation MAgnetic Detector) is a short baseline neutrino experiment at CERN (the European Laboratory for Particle physics) West Area Neutrino Facility (WANF) with a neutrino beam provided by the super proton synchrotron (SPS) accelerator [98]. In this dissertation, we present a measurement of the muon-neutrino induced quasi-elastic (QEL), nu mu + n → mu- + p, cross-section off an isoscalar target in the NOMAD detector. The incident neutrino energy in NOMAD experiment spans from 2.5 to 300 GeV. The measurement of the cross-section is conducted in a two-track topology where both a muon and a proton are fully reconstructed, and a one-track topology where only a muon is reconstructed. The QEL cross-section as a function of the incoming neutrino energy is consistent for the two different topologies, and within errors, constant as a function of the neutrino energy. We determine the energy-averaged cross-section, sigma = 0:908 +/- 0:012 (stat) +/-0:035 (syst) 10-38cm2, where the first is the averaged energy-dependent error (statistical error is dominant one), and the second is the energy-independent, or overall, error. From the shape-comparisons of kinematics of QEL events, the axial mass parameter is determined. It is in good agreement with the result from the measurement of QEL cross-section. Using the chi2 of the shapes of four independent kinematic variables between data and MC, we determine MA = 1:03 +/- 0:05 GeV. The cross-section and the axial mass presented in this thesis have the best precision to date.

  15. Anti-Neutrino Charged Current Quasi-Elastic Scattering in MINER$\

    SciTech Connect

    Chvojka, Jesse John

    2012-01-01

    The phenomenon of neutrino oscillation is becoming increasingly understood with results from accelerator-based and reactor-based experiments, but unanswered questions remain. The proper ordering of the neutrino mass eigenstates that compose the neutrino avor eigenstates is not completely known. We have yet to detect CP violation in neutrino mixing, which if present could help explain the asymmetry between matter and anti-matter in the universe. We also have not resolved whether sterile neutrinos, which do not interact in any Standard Model interaction, exist. Accelerator-based experiments appear to be the most promising candidates for resolving these questions; however, the ability of present and future experiments to provide answers is likely to be limited by systematic errors. A significant source of this systematic error comes from limitations in our knowledge of neutrino-nucleus interactions. Errors on cross-sections for such interactions are large, existing data is sometimes contradictory, and knowledge of nuclear effects is incomplete. One type of neutrino interaction of particular interest is charged current quasi-elastic (CCQE) scattering, which yields a final state consisting of a charged lepton and nucleon. This process, which is the dominant interaction near energies of 1 GeV, is of great utility to neutrino oscillation experiments since the incoming neutrino energy and the square of the momentum transferred to the final state nucleon, Q2, can be reconstructed using the final state lepton kinematics. To address the uncertainty in our knowledge of neutrino interactions, many experiments have begun making dedicated measurements. In particular, the MINER A experiment is studying neutrino-nucleus interactions in the few GeV region. MINERvA is a fine-grained, high precision, high statistics neutrino scattering experiment that will greatly improve our understanding of neutrino cross-sections and nuclear effects that affect the final state particles

  16. New Results from MiniBooNE Charged-Current Quasi-Elastic Anti-Neutrino Data

    SciTech Connect

    Grange, Joseph

    2011-07-01

    MiniBooNE anti-neutrino charged-current quasi-elastic (CCQE) data is compared to model predictions. The main background of neutrino-induced events is examined first, where three independent techniques are employed. Results indicate the neutrino flux is consistent with a uniform reduction of {approx}20% relative to the largely uncertain prediction. After background subtraction, the Q{sup 2} shape of {bar v}{sub {mu}} CCQE events is consistent with the model parameter MA = 1.35 GeV determined from MiniBooNE v{sub {mu}} CCQE data, while the normalization is {approx} 20% high compared to the same prediction.

  17. Recent Advances and Open Questions in Neutrino-induced Quasi-elastic Scattering and Single Photon Production

    SciTech Connect

    Garvey, G. T.; Harris, D. A.; Tanaka, H. A.; Tayloe, R.; Zeller, G. P.

    2015-06-15

    The study of neutrino–nucleus interactions has recently seen rapid development with a new generation of accelerator-based neutrino experiments employing medium and heavy nuclear targets for the study of neutrino oscillations. A few unexpected results in the study of quasi-elastic scattering and single photon production have spurred a revisiting of the underlying nuclear physics and connections to electron–nucleus scattering. A thorough understanding and resolution of these issues is essential for future progress in the study of neutrino oscillations.

  18. Results for quasi-elastic anti-neutrino scattering on scintillator from the MINERvA experiment

    NASA Astrophysics Data System (ADS)

    Schellman, Heidi; Minerva Collaboration

    2016-09-01

    We present a new preliminary measurement of the charge-current quasi-elastic scattering cross section for anti-neutrinos on scintillator (CH) over the energy range 1.5-10 GeV. The data were taken with the MINERvA detector in the NuMI beamline at Fermilab and cover the energy range of interest for the proposed DUNE long-baseline neutrino oscillation experiment and of JLAB elastic scattering experiments. Of particular interest to the nuclear community are possible signatures for short range correlations and/or meson exchange currents in these data. We present comparisons to a range of nuclear models.

  19. Meaurement of the target single-spin asymmetry in quasi-elastic region from the reaction {sup 3}He{up_arrow}(e,e')

    SciTech Connect

    Zhang, Yawei

    2013-10-01

    A measurement of the inclusive target single-spin asymmetry has been performed using the quasi-elastic {sup 3}He{up_arrow}(e,e') reaction with a vertically polarized {sup 3}He target at Q{sup 2} values of 0.13, 0.46 and 0.97 GeV{sup 2}. This asymmetry vanishes under the one photon exchange assumption. But the interference between two-photon exchange and one-photon exchange gives rise to an imaginary amplitude, so that a non-zero A{sub y} is allowed. The experiment, conducted in Hall A of Jefferson Laboratory in 2009, used two independent spectrometers to simultaneously measure the target single-spin asymmetry. Using the effective polarization approximation, the neutron single-spin asymmetries were extracted from the measured {sup 3}He asymmetries. The measurement is to establish a non-vanishing A{sub y}. Non-zero asymmetries were observed at all Q{sup 2} points, and the overall precision is an order of magnitude improved over the existing proton data. The data provide new constraints on Generalized Parton Distribution (GPD) models and new information on the dynamics of the two-photon exchange process.

  20. Barrier distributions for the 7Li+27Al reaction

    NASA Astrophysics Data System (ADS)

    Cárdenas, W. H. Z.

    2010-08-01

    Barrier distributions can be obtained from the first derivative of the elastic and quasielastic (QEL) backward angle excitation functions [1]. In this work we present a study of the barrier distribution for the 7Li+27Al reaction from a Coupled-Channels Born Approximation (CCBA) calculations using the code FRESCO [2].

  1. Effects of citral on Aspergillus flavus spores by quasi-elastic light scattering and multiplex microanalysis techniques.

    PubMed

    Luo, Man; Jiang, Li-Ke; Huang, Yao-Xiong; Xiao, Ming; Li, Bo; Zou, Guo-Lin

    2004-04-01

    Citral refined from Litsea cubeba oil has been found to have a strong influence on fungi, especially Aspergillus flavus. Multiplex microanalysis and quasi-elastic light scattering techniques were applied to study the effects of citral on Aspergillus flavus spores from the levels of membrane, organelle and intracellular macromolecule. It was found that citral injured the wall and the membrane of A. flavus spore, resulting in decrease of its elasticity. After entering the cell, citral not only influenced the genetic expression of mitochondrion reduplication and its morphology, but also changed the aggregation of protein-like macromolecules. As a result, cells, organelles and macromolecules lost their normal structures and functions, eventually leading to the loss of germination ability of A. flavus spores. Since Litsea cubeba oil as food additive and antifungal agent is safe and less poisonous, it is important to elucidate the inhibitory mechanisms of Litsea cubeba oil on the germination ability of A. flavus spore.

  2. Effect of ethanol on dimyristoylphosphatidylcholine large unilamellar vesicles investigated by quasi-elastic light scattering and vibrational spectroscopy.

    PubMed

    Hantz, E; Cao, A; Taillandier, E

    1988-12-01

    The gel-like liquid phase transition of dimyristoylphosphatidylcholine (DMPC) large unilamellar vesicles prepared by reverse phase evaporation has been investigated in buffers containing ethanol by quasi-elastic light scattering (QLS) and vibrational (infrared and Raman) spectroscopy. With the QLS technique, the relative change in the vesicles area (which is related to the molecular cross-sectional area of lipid molecules) was followed versus both temperature and ethanol concentration. When the latter was low, the depression of the transition point was a linear function of the alcohol concentration, c, but the vesicles area was practically unmodified. At alcohol concentration 10% v/v, an abrupt change of the vesicles area was observed and for c greater than 10% the depression of the transition point was a non-linear function of c. The infrared and Raman spectra showed a perturbation of the hydrophobic regions, including the terminal methyl groups of the acyl tails.

  3. Uncontained νμ charged-current quasi-elastic events at the NOvA far detector

    NASA Astrophysics Data System (ADS)

    Sepulveda-Quiroz, Jose; NOvA Collaboration

    2017-01-01

    NOvA is a long-baseline neutrino oscillation experiment that uses an upgraded neutrino beam from Fermilab and two highly active, segmented, liquid scintillator off-axis detectors that offer a remarkable capability in event identification. In its first and second analysis results, NOvA has used only events with an interaction vertex and all secondary particles fully contained in the detectors. I will present studies of the potential sensitivity improvement of the sin2 2θ23 and Δm322 neutrino oscillation parameters from the νμ-disappearance measurement when including uncontained events in the sample. In particular, this study focuses on incorporating νμ charged current quasi-elastic interactions of the type νμ + n -> μ + p where the muon is uncontained but the proton is contained.

  4. The Transverse Asymmetry A{sub T}, from Quasi-elastic {sup 3}{ovr He}({rvec e}, e{prime}) Process and the Neutron Magnetic Form Factor

    SciTech Connect

    Wang Xu; Dipangkar Dutta; Feng Xiong; Brian Anderson; Leonard Auerbach; Todd Averett; William Bertozzi; Tim Black; John Calarco; Lawrence Cardman; Gordon Cates; Zhengwei Chai; Jian-ping Chen; Seonho Choi; Eugene Chudakov; Steve Churchwell; G.S. Corrado; C. Crawford; Daniel Dale; Alexandre Deur; Pibero Djawotho; Bradley Filippone; John Finn; Haiyan Gao; Ronald Gilman; Oleksandr Glamazdin; Charles Glashausser; Walter Gloeckle; J. Golak; Javier Gomez; Viktor Gorbenko; Jens-ole Hansen; F. Hersman; Douglas Higinbotham; Richard Holmes; Calvin Howell; Emlyn Hughes; Thomas Humensky; Sebastien Incerti; Cornelis De Jager; John Jensen; Xiaodong Jiang; C.E. Jones; Mark Jones; R. Kahl; H. Kamada; A. Kievsky; Ioannis Kominis; Wolfgang Korsch; Kevin Kramer; Gerfried Kumbartzki; Michael Kuss; Enkeleida Lakuriqi; Meihua Liang; Nilanga Liyanage; John Lerose; Sergey Malov; Demetrius Margaziotis; J.W. Martin; Kathy Mccormick; Robert Mckeown; Kevin Mcilhany; Zein-eddine Meziani; Robert Michaels; G.W. Miller; Joseph Mitchell; Sirish Nanda; E. Pace; Tina Pavlin; Gerassimos Petratos; Roman Pomatsalyuk; D. Pripstein; David Prout; Ronald Ransome; Yves Roblin; Marat Rvachev; Arunava Saha; G. Salme; Michael Schnee; Taeksu Shin; Karl Slifer; Paul Souder; Steffen Strauch; Riad Suleiman; Mark Sutter; Bryan Tipton; Luminita Todor; Michele Viviani; Branislav Vlahovic; J. Watson; Claude Williamson; H. Witala; Bogdan Wojtsekhowski; Jen-chuan Yeh; Piotr Zolnierczuk

    2000-10-01

    We have measured the transverse asymmetry from inclusive scattering of longitudinally polarized electrons from polarized {sup 3}He nuclei at quasi-elastic kinematics in Hall A at Jefferson Lab with high statistical and systematic precision. The neutron magnetic form factor was extracted based on Faddeev calculations with an experimental uncertainty of less than 2%.

  5. Using Quasi-Elastic Events to Measure Neutrino Oscillations with MINOS Detectors in the NuMI Neutrino Beam

    SciTech Connect

    Watabe, Masaki

    2010-05-01

    MINOS (Main Injector Neutrino Oscillation Search) experiment has been designed to search for a change in the avor composition of a beam of muon neutrinos as they travel between the Near Detector at Fermi National Accelerator Laboratory and the Far Detector in the Soudan mine in Minnesota, 735 km from the target. The MINOS oscillation analysis is mainly performed with the charged current (CC) events and sensitive to constrain high- Δm2 values. However, the quasi-elastic (QEL) charged current interaction is dominant in the energy region important to access low- m2 values. For further improvement, the QEL oscillation analysis is performed in this dissertation. A data sample based on a total of 2.50 x 1020 POT is used for this analysis. In summary, 55 QEL-like events are observed at the Far detector while 87.06 ± 13.17 (syst:) events are expected with null oscillation hypothesis. These data are consistent with disappearance via oscillation with m2 = 2:10 0.37 (stat:) ± 0.24 (syst:) eV2 and the maximal mixing angle.

  6. Theory of quasi-elastic secondary emission from a quantum dot in the regime of vibrational resonance.

    PubMed

    Rukhlenko, Ivan D; Fedorov, Anatoly V; Baymuratov, Anvar S; Premaratne, Malin

    2011-08-01

    We develop a low-temperature theory of quasi-elastic secondary emission from a semiconductor quantum dot, the electronic subsystem of which is resonant with the confined longitudinal-optical (LO) phonon modes. Our theory employs a generalized model for renormalization of the quantum dot's energy spectrum, which is induced by the polar electron-phonon interaction. The model takes into account the degeneration of electronic states and allows for several LO-phonon modes to be involved in the vibrational resonance. We give solutions to three fundamental problems of energy-spectrum renormalization--arising if one, two, or three LO-phonon modes resonantly couple a pair of electronic states--and discuss the most general problem of this kind that admits an analytical solution. With these results, we solve the generalized master equation for the reduced density matrix, in order to derive an expression for the differential cross section of secondary emission from a single quantum dot. The obtained expression is then analyzed to establish the basics of optical spectroscopy for measuring fundamental parameters of the quantum dot's polaron-like states.

  7. Measurement of the Antineutrino Double-Differential Charged-Current Quasi-Elastic Scattering Cross Section at MINERvA

    SciTech Connect

    Patrick, Cheryl

    2016-01-01

    Next-generation neutrino oscillation experiments, such as DUNE and Hyper-Kamiokande, hope to measure charge-parity (CP) violation in the lepton sector. In order to do this, they must dramatically reduce their current levels of uncertainty, particularly those due to neutrino-nucleus interaction models. As CP violation is a measure of the difference between the oscillation properties of neutrinos and antineutrinos, data about how the less-studied antineutrinos interact is especially valuable. We present the MINERvA experiment's first double-differential scattering cross sections for antineutrinos on scintillator, in the few-GeV range relevant to experiments such as DUNE and NOvA. We also present total antineutrino-scintillator quasi-elastic cross sections as a function of energy, which we compare to measurements from previous experiments. As well as being useful to help reduce oscillation experiments' uncertainty, our data can also be used to study the prevalence of various cor relation and final-state interaction effects within the nucleus. We compare to models produced by different model generators, and are able to draw first conclusions about the predictions of these models.

  8. Ay0 Measurement from Quasi-Elastic 3He ↑ (e ,e' n) Scattering at Jefferson Lab

    NASA Astrophysics Data System (ADS)

    Long, Elena; Jefferson Lab Hall A Collaboration

    2016-03-01

    Due to the lack of free neutron targets, studies of the structure of the neutron are typically made by scattering electrons from either 2H or 3He targets. In order to extract useful neutron information from a 3He target, one must first understand how the neutron in a 3He system differs from a free neutron by taking into account nuclear effects such as final state interactions and meson exchange currents. The target single spin asymmetry Ay0 is an ideal probe of such effects, as any deviation from zero indicates effects beyond plane wave impulse approximation. When nuclear effects within the 3He wave function are taken into account, calculations show that this asymmetry can become large (> 50 %). New measurements of the target single spin asymmetry Ay0 were made at Jefferson Lab using the quasi-elastic 3He↑ (e ,e' n) reaction. The measured asymmetry decreases by over two orders of magnitude, from > 70 % at Q2 = 0 . 1 (GeV/c)2 to nearly zero at Q2 = 1 (GeV/c)2, providing evidence of the dominance and fall-off of nuclear effects when studying neutron structure by electron scattering from 3He. Details of the measurement will be presented.

  9. Measurement of the antineutrino double-differential charged-current quasi-elastic scattering cross section at MINERvA

    NASA Astrophysics Data System (ADS)

    Patrick, Cheryl Elizabeth

    Next-generation neutrino oscillation experiments, such as DUNE and Hyper-Kamiokande, hope to measure charge-parity (CP) violation in the lepton sector. In order to do this, they must dramatically reduce their current levels of uncertainty, particularly those due to neutrino-nucleus interaction models. As CP violation is a measure of the difference between the oscillation properties of neutrinos and antineutrinos, data about how the less-studied antineutrinos interact is especially valuable. We present the MINERvA experiment's first double-differential scattering cross sections for antineutrinos on scintillator, in the few-GeV range relevant to experiments such as DUNE and NOvA. We also present total antineutrino-scintillator quasi-elastic cross sections as a function of energy, which we compare to measurements from previous experiments. As well as being useful to help reduce oscillation experiments' uncertainty, our data can also be used to study the prevalence of various correlation and final-state interaction effects within the nucleus. We compare to models produced by different model generators, and are able to draw first conclusions about the predictions of these models.

  10. Nuclear Effects in Quasi-Elastic and Delta Resonance Production at Low Momentum Transfer

    NASA Astrophysics Data System (ADS)

    Demgen, John Gibney

    Analysis of data collected by the MINERvA experiment is done by showing the distribution of charged hadron energy for interactions that have low momentum transfer. This distribution reveals major discrepancies between the detector data and the standard MINERvA interaction model with only a simple global Fermi gas model. Adding additional model elements, the random phase approximation (RPA), meson exchange current (MEC), and a reduction of resonance delta production improve this discrepancy. Special attention is paid to resonance delta production systematic uncertainties, which do not make up these discrepancies even when added with resolution and biasing systematic uncertainties. Eye- scanning of events in this region also show a discrepancy, but we were insensitive to two-proton events, the predicted signature of the MEC process.

  11. Dynamics of iodine anions in KI and LiI aqueous solutions studied by 127I nuclear resonant quasi-elastic scattering

    NASA Astrophysics Data System (ADS)

    Haruki, Rie; Koshimizu, Masanori; Nishikido, Fumihiko; Masuda, Ryo; Kobayashi, Yasuhiro; Seto, Makoto; Yoda, Yoshitaka; Kishimoto, Shunji

    2016-12-01

    The dynamics of iodine ions in potassium iodide (KI) and lithium iodide (LiI) aqueous solutions have been studied through 127I nuclear resonant quasi-elastic scattering (NRQES). A newly developed Si (12 2 2) double crystal monochromator for 127I 57.6 keV excitation is used. Broadening due to a diffusive motion is measured in the energy spectra of the NRQES from the solutions.

  12. Sub-barrier reactions measured using a recoil mass separator

    SciTech Connect

    Betts, R.R.

    1988-01-01

    Few data exist in the sub-barrier region for reaction channels other than fusion. In particular, our experimental knowledge of quasi-elastic transfer reactions is sparse, despite the belief that this particular channel may be dominant in determining some features of the sub-barrier fusion enhancement. Transfer reactions are governed primarily by the closet approach of the colliding nuclei which, at low energies, results in a strong backward peaking of the angular distribution in the center-of-mass frame. For situations where the projectile has a significant fraction of the target mass, as is so in most cases of interest, the backscattered projectile-like fragment has such low energy that the usual techniques of measurement and identification become invalid. Here, we report on a solution to this problem which allows a systematic study of many aspects of transfer reactions in the energy regime of interest. We exploit the fact that associated with the low-energy backscattered projectile-like fragment is a complementary target-like fragment which recoils to forward angles with a large fraction of the incident beam energy. These target-like fragments were detected and identified using the Daresbury Recoil Mass Separator thus allowing the measurement of quasi-elastic transfer over hitherto inaccessible energy range from the vicinity of the barrier to several tens of MeV below. The experiments described here used VYNi beams of energies ranging from 180 to 260 MeV provided by the Daresbury Laboratory Nuclear Structure Facility tandem accelerator. Data on sub-barrier transfer for targets of /sup 116,118,120,122,124/Sn and /sup 144,148,150,152,154/Sm were obtained. 16 refs., 10 figs., 2 tabs.

  13. Solvent Dynamics in Solutions of PNIPAM in Water/Methanol Mixtures-A Quasi-Elastic Neutron Scattering Study.

    PubMed

    Kyriakos, Konstantinos; Philipp, Martine; Silvi, Luca; Lohstroh, Wiebke; Petry, Winfried; Müller-Buschbaum, Peter; Papadakis, Christine M

    2016-05-26

    The solvent dynamics of concentrated solutions of poly(N-isopropylacrylamide) (PNIPAM, 25 wt %) in water/methanol mixtures (85:15 v/v) are measured with the aim of shedding light onto the cononsolvency effect. Quasi-elastic neutron scattering (QENS) with contrast variation has been carried out at temperatures below and above the cloud point by using in the first set of experiments the mixture H2O:d-MeOD (d-MeOD denotes fully deuterated methanol) as a solvent and in the second set of experiments the mixture D2O:MeOH (MeOH denotes methanol). As a reference, bulk H2O, bulk MeOH and the mixtures H2O:d-MeOD and D2O:MeOH (both 85:15 v/v) have been investigated as well. In the PNIPAM solution in H2O:d-MeOD, two water populations are identified, namely strongly and less strongly arrested water. At the cloud point, the former is partially released from PNIPAM. The diffusion coefficient of the latter one is similar to the one in the water/methanol mixture, and its residence time decreases at the cloud point. The PNIPAM solution in D2O:MeOH reveals similar dynamics to the one in H2O:d-MeOD which may reflect that the dynamics of MeOH near the PNIPAM chain is similar to the one of H2O. The similarity may, however, partially be due to H/D exchange between D2O and MeOH. In both PNIPAM solutions, the mean-square displacement of the PNIPAM chain decreases gradually above the cloud point.

  14. Translational and rotational dynamics of water contained in aged Portland cement pastes studied by quasi-elastic neutron scattering.

    PubMed

    Li, Hua; Zhang, Li-Li; Yi, Zhou; Fratini, Emiliano; Baglioni, Piero; Chen, Sow-Hsin

    2015-08-15

    Cement is a widely used construction material in the world. The quality and durability of aged cement pastes have a strong relationship with the water contained in it. The translational and rotational dynamics of water in ordinary Portland cement (OPC) pastes cured for 7, 14 and 30days were studied by analyzing Quasi-elastic Neutron Scattering (QENS) data. The effect of a new super-plasticizer (SP) additive was also studied by comparing the samples with and without the additive. By fitting the QENS spectra with the Jump-diffusion and Rotation-diffusion Model (JRM), six important parameters including the bound water index (BWI), the self-diffusion coefficient, D(t), the average residence time, τ0, the rotational diffusion constant, D(r), the rotational residence time, τ(r), and the mean squared displacement (MSD), 〈u(2)〉, were obtained. From these parameters, we can quantitatively follow the evolution of the bound water fraction (BWI). We can clearly see the different time ranges for the translational and rotational dynamics of water contained in the OPC pastes by τ0 and τ(r). From the MSD values compared with those of molecular dynamics simulation, we can distinguish between immobile water (mainly bound water) and mobile water, which includes confined water and ultraconfined water. Furthermore, by the fitted parameters' values and their change of slopes with increasing setting time for cement pastes with and without additive SP, it becomes clear that the effect of additive SP is to make the mobile water more confined and induce a more uniform the aging process during the evolution of the OPC pastes.

  15. Distributions of methyl group rotational barriers in polycrystalline organic solids

    SciTech Connect

    Beckmann, Peter A. E-mail: wangxianlong@uestc.edu.cn; Conn, Kathleen G.; Mallory, Clelia W.; Mallory, Frank B.; Rheingold, Arnold L.; Rotkina, Lolita; Wang, Xianlong E-mail: wangxianlong@uestc.edu.cn

    2013-11-28

    We bring together solid state {sup 1}H spin-lattice relaxation rate measurements, scanning electron microscopy, single crystal X-ray diffraction, and electronic structure calculations for two methyl substituted organic compounds to investigate methyl group (CH{sub 3}) rotational dynamics in the solid state. Methyl group rotational barrier heights are computed using electronic structure calculations, both in isolated molecules and in molecular clusters mimicking a perfect single crystal environment. The calculations are performed on suitable clusters built from the X-ray diffraction studies. These calculations allow for an estimate of the intramolecular and the intermolecular contributions to the barrier heights. The {sup 1}H relaxation measurements, on the other hand, are performed with polycrystalline samples which have been investigated with scanning electron microscopy. The {sup 1}H relaxation measurements are best fitted with a distribution of activation energies for methyl group rotation and we propose, based on the scanning electron microscopy images, that this distribution arises from molecules near crystallite surfaces or near other crystal imperfections (vacancies, dislocations, etc.). An activation energy characterizing this distribution is compared with a barrier height determined from the electronic structure calculations and a consistent model for methyl group rotation is developed. The compounds are 1,6-dimethylphenanthrene and 1,8-dimethylphenanthrene and the methyl group barriers being discussed and compared are in the 2–12 kJ mol{sup −1} range.

  16. Measurement of the Charged-Current Quasi-Elastic Cross-Section for Electron Neutrinos on a Hydrocarbon Target

    SciTech Connect

    Wolcott, Jeremy

    2016-01-01

    Appearance-type neutrino oscillation experiments, which observe the transition from muon neutrinos to electron neutrinos, promise to help answer some of the fundamental questions surrounding physics in the post-Standard-Model era. Because they wish to observe the interactions of electron neutrinos in their detectors, and because the power of current results is typically limited by their systematic uncertainties, these experiments require precise estimates of the cross-section for electron neutrino interactions. Of particular interest is the charged-current quasi-elastic (CCQE) process, which gures signi cantly in the composition of the reactions observed at the far detector. However, no experimental measurements of this crosssection currently exist for electron neutrinos; instead, current experiments typically work from the abundance of muon neutrino CCQE cross-section data and apply corrections from theoretical arguments to obtain a prediction for electron neutrinos. Veri cation of these predictions is challenging due to the di culty of constructing an electron neutrino beam, but the advent of modern high-intensity muon neutrino beams|together with the percent-level electron neutrino impurity inherent in these beams| nally presents the opportunity to make such a measurement. We report herein the rst-ever measurement of a cross-section for an exclusive state in electron neutrino scattering, which was made using the MINER A detector in the NuMI neutrino beam at Fermilab. We present the electron neutrino CCQE di erential cross-sections, which are averaged over neutrinos of energies 1-10 GeV (with mean energy of about 3 GeV), in terms of various kinematic variables: nal-state electron angle, nal-state electron energy, and the square of the fourmomentum transferred to the nucleus by the neutrino , Q2. We also provide a total cross-section vs. neutrino energy. While our measurement of this process is found to be in agreement with the predictions of the GENIE

  17. A new apparatus design for high temperature (up to 950 °C) quasi-elastic neutron scattering in a controlled gaseous environment

    SciTech Connect

    Al-Wahish, Amal; Armitage, D.; Hill, B.; Mills, R.; Santodonato, L.; Herwig, K. W.; Al-Binni, U.; Jalarvo, N.; Mandrus, D.

    2015-09-15

    A design for a sample cell system suitable for high temperature Quasi-Elastic Neutron Scattering (QENS) experiments is presented. The apparatus was developed at the Spallation Neutron Source in Oak Ridge National Lab where it is currently in use. The design provides a special sample cell environment under controlled humid or dry gas flow over a wide range of temperature up to 950 °C. Using such a cell, chemical, dynamical, and physical changes can be studied in situ under various operating conditions. While the cell combined with portable automated gas environment system is especially useful for in situ studies of microscopic dynamics under operational conditions that are similar to those of solid oxide fuel cells, it can additionally be used to study a wide variety of materials, such as high temperature proton conductors. The cell can also be used in many different neutron experiments when a suitable sample holder material is selected. The sample cell system has recently been used to reveal fast dynamic processes in quasi-elastic neutron scattering experiments, which standard probes (such as electrochemical impedance spectroscopy) could not detect. In this work, we outline the design of the sample cell system and present results demonstrating its abilities in high temperature QENS experiments.

  18. Quasi-elastic pn scattering in 6LiD and 6LiH targets from 1.1 to 2.4 GeV

    NASA Astrophysics Data System (ADS)

    de Lesquen, A.; Allgower, C. E.; Ball, J.; Beddo, M.; Bystrický, J.; Combet, M.; Demierre, Ph.; Durand, G.; Fontaine, J.-M.; Grosnick, D.; Hess, R.; Janout, Z.; Janout, Z. F.; Kalinnikov, V. A.; Kasprzyk, T. E.; Khachaturov, B. A.; Kunne, R.; Lehar, F.; Lopiano, D.; Matafonov, V. N.; Pisarev, I. L.; Popov, A. A.; Prokofiev, A. N.; Rapin, D.; Sans, J.-L.; Spinka, H. M.; Usov, Yu. A.; Vikhrov, V. V.; Vuaridel, B.; Zhdanov, A. A.

    1999-11-01

    A polarized proton beam from SATURNE II, the Saclay polarized targets with ^6Li compounds, and an unpolarized CH_2 target were used to measure spin-dependent observables for protons scattered on bound nucleons. The beam and target polarizations were oriented vertically. The analyzing power A_{oono} and the depolarization D_{nono} were determined at seven energies between 1.1 and 2.4 GeV. The spin correlation parameter A_{oonn} was measured at only 1.1 and 1.6 GeV. Measurements with the CH_2 target at 1.1 GeV provided A_{oono} data for scattering of polarized protons on neutrons in carbon. The quasi-elastic observables are compared with previous elastic scattering measurements and at 1.1 GeV with predictions of phase shift analyses.

  19. Quasi-elastic Coulomb response function for finite systems and elimination of the Landau ghost in the relativistic σ-ω model

    NASA Astrophysics Data System (ADS)

    Kazuhiro, Tanaka; Wolfgang, Bentz; Akito, Arima

    1990-11-01

    The quasi-elastic Coulomb response function of finite nuclei including vacuum polarization effects is investigated in the relativistic σ-ω model. For the consistent elimination of the Landau ghost in meson propagators, the description of the ground state and the response function of the system is formulated utilizing the effective action method, and the effects of the ghost elimination on the nuclear matter response function are discussed. Finite system calculations are performed for 12C (|q|= 300, 400, 550 MeV) and 40Ca (|q|= 410, 500, 550 MeV) , in which particle-hole continuum states are fully taken into account by the method of continuum RPA, while the vacuum polarization effects are included by the local density approximation. The effects of the particle-hole effective interaction and the medium modified single-nucleon form factor on the response function are also discussed.

  20. Asymmetrical flow field-flow fractionation with multi-angle light scattering and quasi-elastic light scattering for characterization of polymersomes: comparison with classical techniques.

    PubMed

    Till, Ugo; Gaucher-Delmas, Mireille; Saint-Aguet, Pascale; Hamon, Glenn; Marty, Jean-Daniel; Chassenieux, Christophe; Payré, Bruno; Goudounèche, Dominique; Mingotaud, Anne-Françoise; Violleau, Frédéric

    2014-12-01

    Polymersomes formed from amphiphilic block copolymers, such as poly(ethyleneoxide-b-ε-caprolactone) (PEO-b-PCL) or poly(ethyleneoxide-b-methylmethacrylate), were characterized by asymmetrical flow field-flow fractionation coupled with quasi-elastic light scattering (QELS), multi-angle light scattering (MALS), and refractive index detection, leading to the determination of their size, shape, and molecular weight. The method was cross-examined with more classical ones, like batch dynamic and static light scattering, electron microscopy, and atomic force microscopy. The results show good complementarities between all the techniques; asymmetrical flow field-flow fractionation being the most pertinent one when the sample exhibits several different types of population.

  1. Barrier distributions for the {sup 7}Li+{sup 27}Al reaction

    SciTech Connect

    Cardenas, W. H. Z.

    2010-08-04

    Barrier distributions can be obtained from the first derivative of the elastic and quasielastic (QEL) backward angle excitation functions [1]. In this work we present a study of the barrier distribution for the {sup 7}Li+{sup 27}Al reaction from a Coupled-Channels Born Approximation (CCBA) calculations using the code FRESCO [2].

  2. A Study of the Quasi-elastic (e,e'p) Reaction on {sup 12}C, {sup 56}Fe and {sup 197}Au

    SciTech Connect

    D. Dutta; D. van Westrum; et al

    2003-12-09

    We report the results from a systematic study of the quasi-elastic (e,e'p) reaction on {sup 12}C, {sup 56}Fe and {sup 197}Au performed at Jefferson Lab. We have measured nuclear transparency and extracted spectral functions (corrected for radiation) over a Q{sup 2} range of 0.64 - 3.25 (GeV/c){sup 2} for all three nuclei. In addition we have extracted separated longitudinal and transverse spectral functions at Q{sup 2} of 0.64 and 1.8 (GeV/c){sup 2} for these three nuclei (except for {sup 197}Au at the higher Q{sup 2}). The spectral functions are compared to a number of theoretical calculations. The measured spectral functions differ in detail but not in overall shape from most of the theoretical models. In all three targets the measured spectral functions show considerable excess transverse strength at Q{sup 2} = 0.64 (GeV/c){sup 2}, which is much reduced at 1.8 (GeV/c){sup 2}.

  3. Measurement of double polarized asymmetries in quasi-elastic processes ${}^3\\vec{He}(\\vec{e},e' d)$ and ${}^3\\vec{He}(\\vec{e},e' p)$

    SciTech Connect

    Mihovilovic, Miha

    2012-01-01

    This thesis is dedicated to a study of a spin-isospin structure of the polarized 3He. First, an introduction to the spin structure of 3He is given, followed by a brief overview of past experiments. The main focus of the thesis is the E05-102 experiment at Jefferson Lab, in which the reactions ${}^3\\vec{He}(\\vec{e},e' d)$ and ${}^3\\vec{He}(\\vec{e},e' p)$ in the quasi-elastic region were studied. The purpose of this experiment was to better understand the effects of the S'- and D-state contributions to the 3He ground-state wave-functions by a precise measurement of beam-target asymmetries Ax and Az in the range of recoil momenta from 0 to about 300 MeV/c. The experimental equipment utilized in these measurements is described, with special attention devoted to the calibration of the hadron spectrometer, BigBite. Results on the measured asymmetries are presented, together with first attempts at their comparison to the state-of-the art Faddeev calculations. The remaining open problems and challenges for future work are also discussed.

  4. How mobile are dye adsorbates and acetonitrile molecules on the surface of TiO2 nanoparticles? A quasi-elastic neutron scattering study

    NASA Astrophysics Data System (ADS)

    Vaissier, Valerie; Sakai, Victoria Garcia; Li, Xiaoe; Cabral, João T.; Nelson, Jenny; Barnes, Piers R. F.

    2016-12-01

    Motions of molecules adsorbed to surfaces may control the rate of charge transport within monolayers in systems such as dye sensitized solar cells. We used quasi-elastic neutron scattering (QENS) to evaluate the possible dynamics of two small dye moieties, isonicotinic acid (INA) and bis-isonicotinic acid (BINA), attached to TiO2 nanoparticles via carboxylate groups. The scattering data indicate that moieties are immobile and do not rotate around the anchoring groups on timescales between around 10 ps and a few ns (corresponding to the instrumental range). This gives an upper limit for the rate at which conformational fluctuations can assist charge transport between anchored molecules. Our observations suggest that if the conformation of larger dye molecules varies with time, it does so on longer timescales and/or in parts of the molecule which are not directly connected to the anchoring group. The QENS measurements also indicate that several layers of acetonitrile solvent molecules are immobilized at the interface with the TiO2 on the measurement time scale, in reasonable agreement with recent classical molecular dynamics results.

  5. How mobile are dye adsorbates and acetonitrile molecules on the surface of TiO2 nanoparticles? A quasi-elastic neutron scattering study

    PubMed Central

    Vaissier, Valerie; Sakai, Victoria Garcia; Li, Xiaoe; Cabral, João T.; Nelson, Jenny; Barnes, Piers R. F.

    2016-01-01

    Motions of molecules adsorbed to surfaces may control the rate of charge transport within monolayers in systems such as dye sensitized solar cells. We used quasi-elastic neutron scattering (QENS) to evaluate the possible dynamics of two small dye moieties, isonicotinic acid (INA) and bis-isonicotinic acid (BINA), attached to TiO2 nanoparticles via carboxylate groups. The scattering data indicate that moieties are immobile and do not rotate around the anchoring groups on timescales between around 10 ps and a few ns (corresponding to the instrumental range). This gives an upper limit for the rate at which conformational fluctuations can assist charge transport between anchored molecules. Our observations suggest that if the conformation of larger dye molecules varies with time, it does so on longer timescales and/or in parts of the molecule which are not directly connected to the anchoring group. The QENS measurements also indicate that several layers of acetonitrile solvent molecules are immobilized at the interface with the TiO2 on the measurement time scale, in reasonable agreement with recent classical molecular dynamics results. PMID:27991538

  6. Measurement of the $M_A^{QE}$ parameter using multiple quasi-elastic dominated sub-samples in the minos near detector

    SciTech Connect

    Mayer, Nathan Samuel

    2011-12-05

    The Main Injector Neutrino Oscillation Search (MINOS) is a two detector, long baseline neutrino oscillation experiment. The MINOS near detector is an ironscintillator tracking/sampling calorimeter and has recorded the world’s largest data set of neutrino interactions in the 0-5 GeV region. This high statistics data set is used to make precision measurements of neutrino interaction cross-sections on iron. The Q2 dependence in charged current quasi-elastic (CCQE) scattering probes the axial and vector structure (form factor) of the nucleon/nuclear target, and nuclear effects in neutrino scattering. Presented here is a study of the MINOS Data that will introduce a method that improves the existing MINOS CCQE analysis. This analysis uses an additional CCQE dominated sub-sample from a different kinematic region to reduce correlations between fit parameters in the existing MINOS CCQE analysis. The measured value of the axial-vector mass is MQE A = 1.312+0.037 -0.038(fit)+0.123 -0.265(syst.) GeV.

  7. Study of the (e,e'p) quasi-elastic reaction in complex nuclei: theory and experiment

    SciTech Connect

    Herraiz, Joaquin Lopez

    2010-03-01

    Experimental coincidence cross section and transverse-longitudinal asymmetry ATL have been obtained for the quasielastic (e,e'p) reaction in 16O, 12C, and {sup 208}Pb in constant q-ω kinematics in the missing momentum range -350 < pmiss < 350 MeV/c. In these experiments, performed in experimental Hall A of the Thomas Jefferson National Accelerator Facility (JLAB), the beam energy and the momentum and angle of the scattered electrons were kept fixed, while the angle between the proton momentum and the momentum transfer q was varied in order to map out the missing momentum distribution. The experimental cross section and ATL asymmetry have been compared with Monte Carlo simulations based on Distorted Wave Impulse Approximation (DWIA) calculations with both relativistic and non-relativistic spinor structure. The spectroscopic factors obtained for both models are in agreement with previous experimental values, while ATL measurements favor the relativistic DWIA calculation. This thesis describes the details of the experimental setup, the calibration of the spectrometers, the techniques used in the data analysis to derive the final cross sections and the ATL, the ingredients of the theoretical calculations employed and the comparison of the results with the simulations based on these theoretical models.

  8. The role of ceramide chain length distribution on the barrier properties of the skin lipid membranes.

    PubMed

    Mojumdar, E H; Kariman, Z; van Kerckhove, L; Gooris, G S; Bouwstra, J A

    2014-10-01

    The skin barrier function is provided by the stratum corneum (SC). The lipids in the SC are composed of three lipid classes: ceramides (CERs), cholesterol (CHOL) and free fatty acids (FFAs) which form two crystalline lamellar structures. In the present study, we investigate the effect of CER chain length distribution on the barrier properties of model lipid membranes mimicking the lipid composition and organization of SC. The membranes were prepared with either isolated pig CERs (PCERs) or synthetic CERs. While PCERs have a wide chain length distribution, the synthetic CERs are quite uniform in chain length. The barrier properties were examined by means of permeation studies using hydrocortisone as a model drug. Our studies revealed a reduced barrier in lipid membranes prepared with PCERs compared to synthetic CERs. Additional studies revealed that a wider chain length distribution of PCERs results in an enhanced hexagonal packing and increased conformational disordering of the lipid tails compared to synthetic CERs, while the lamellar phases did not change. This demonstrates that the chain length distribution affects the lipid barrier by reducing the lipid ordering and density within the lipid lamellae. In subsequent studies, the effect of increased levels of FFAs or CERs with a long acyl chain in the PCERs membranes was also studied. These changes in lipid composition enhanced the level of orthorhombic packing, reduced the conformational disordering and increased the barrier of the lipid membranes. In conclusion, the CER chain length distribution is an important key factor for maintaining a proper barrier.

  9. Monitoring the dynamics of miscible P3HT:PCBM blends: A quasi elastic neutron scattering study of organic photovoltaic active layers

    DOE PAGES

    Etampawala, Thusitha; Ratnaweera, Dilru; Morgan, Brian; ...

    2015-02-02

    Our work reports on the detailed molecular dynamic behavior of miscible blends of Poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) and their pure counterparts by quasi-elastic neutron scattering measurements (QENS). The study provides the measure of relaxation processes on pico-to-nanosecond time scales. A single relaxation process was observed in pure P3HT and PCBM while two relaxation processes, one fast and one slow, were observed in the blends. The fast process was attributed to the dynamics of P3HT while the slow process was correlated to the dynamics of PCBM. The results show that the relaxation process is a balance betweenmore » two opposing effects: increased mobility due to thermal activation of P3HT molecules and decrease mobility due to the presence of PCBM which is correlated to the percent crystallinity of P3HT and local packing density of PCBM in the amorphous phase. The threshold for the domination of the thermally activated relaxation is between 5 and 9 vol.% of PCBM loading. Two distinct spatial dependences of the relaxation processes, in which the crossover length scale depends neither on temperature nor composition, were observed for all the samples. They were attributed to the collective motions of the hexyl side chains and the rotational motions of the C-C single bonds of the side chains. Finally, these results provide an understanding of the effects of PCBM loading and temperature on the dynamics of the polymer-fullerene blends which provides a tool to optimize the efficiency of charge carrier and exciton transport within the organic photovoltaic (OPV) active layer to improve the high performance of organic solar cells.« less

  10. Monitoring the dynamics of miscible P3HT:PCBM blends: A quasi elastic neutron scattering study of organic photovoltaic active layers

    SciTech Connect

    Etampawala, Thusitha; Ratnaweera, Dilru; Morgan, Brian; Diallo, Souleymane; Mamontov, Eugene; Dadmun, Mark

    2015-02-02

    Our work reports on the detailed molecular dynamic behavior of miscible blends of Poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) and their pure counterparts by quasi-elastic neutron scattering measurements (QENS). The study provides the measure of relaxation processes on pico-to-nanosecond time scales. A single relaxation process was observed in pure P3HT and PCBM while two relaxation processes, one fast and one slow, were observed in the blends. The fast process was attributed to the dynamics of P3HT while the slow process was correlated to the dynamics of PCBM. The results show that the relaxation process is a balance between two opposing effects: increased mobility due to thermal activation of P3HT molecules and decrease mobility due to the presence of PCBM which is correlated to the percent crystallinity of P3HT and local packing density of PCBM in the amorphous phase. The threshold for the domination of the thermally activated relaxation is between 5 and 9 vol.% of PCBM loading. Two distinct spatial dependences of the relaxation processes, in which the crossover length scale depends neither on temperature nor composition, were observed for all the samples. They were attributed to the collective motions of the hexyl side chains and the rotational motions of the C-C single bonds of the side chains. Finally, these results provide an understanding of the effects of PCBM loading and temperature on the dynamics of the polymer-fullerene blends which provides a tool to optimize the efficiency of charge carrier and exciton transport within the organic photovoltaic (OPV) active layer to improve the high performance of organic solar cells.

  11. Dynamic behaviors of water contained in calcium-silicate-hydrate gel at different temperatures studied by quasi-elastic neutron scattering spectroscopy

    NASA Astrophysics Data System (ADS)

    Yi, Zhou; Deng, Pei-Na; Zhang, Li-Li; Li, Hua

    2016-10-01

    The dynamic behaviors of water contained in calcium-silicate-hydrate (C-S-H) gel with different water content values from 10% to 30% (by weight), are studied by using an empirical diffusion model (EDM) to analyze the experimental data of quasi-elastic neutron scattering (QENS) spectra at measured temperatures ranging from 230 K to 280 K. In the study, the experimental QENS spectra with the whole Q-range are considered. Several important parameters including the bound/immobile water elastic coefficient A, the bound water index BWI, the Lorentzian with a half-width at half-maximum (HWHM) Γ 1(Q) and Γ 2(Q), the self-diffusion coefficients D t1 and D t2 of water molecules, the average residence times τ 01 and τ 02, and the proton mean squared displacement (MSD) are obtained. The results show that the QENS spectra can be fitted very well not only for small Q (≤ 1 Å-1) but also for large Q. The bound/immobile water fraction in a C-S-H gel sample can be shown by the fitted BWI. The distinction between bound/immobile and mobile water, which includes confined water and ultra-confined water, can be seen by the fitted MSD. All the MSD tend to be the smallest value below 0.25 Å2 (the MSD of bound/immobile water) as the Q increases to 1.9 Å-1, no matter what the temperature and water content are. Furthermore, by the abrupt changes of the fitted values of D t1, τ 01, and Γ 1(Q), a crossover temperature at 250 K, namely the liquid-to-crystal-like transition temperature, can be identified for confined water in large gel pores (LGPs) and/or small gel pores (SGPs) contained in the C-S-H gel sample with 30% water content.

  12. Influence of underwater barriers on the distribution of tsunami waves

    NASA Astrophysics Data System (ADS)

    Chugunov, V.; Fomin, S.; Shankar, R.

    2014-11-01

    Solitary wave propagation over underwater shelves and bumps is examined using straightforward analytical methods. Explicit solutions for wave propagation are obtained. Using the nonlinear shallow-water equations, it was found that propagation of small amplitude long waves can be well described by a linear approximation. The effects of topographical variety and proportion of underwater barriers (steps, bumps, multiple bumps) on the incident wave are demonstrated using linear wave theory. At a step, the incident wave is shown to be more strongly reflected for increased barrier size. The incident wave also transmits an amplified wave with smaller wavelength onto the obstacle. After propagating off of a bump, the wave experiences an amplitude decay. The decay rate is shown to be exponential with a variable number of bumps. Accounting for the presence of the small parameter, which represents the wave amplitude/water depth ratio, the nonlinear shallow-water equations were solved by the method of asymptotic expansions. Using the method of renormalization, a uniformly valid solution was obtained accounting for nonlinear effects in the vicinity of the sharp depth change. Far-field comparisons of the constructed solutions with the associated Riemann waves show good accuracy of the obtained solutions. Over an infinitely long shelf, the amplified transmitted wave breaks.

  13. Breaking through: The effects of a velocity distribution on barriers to dust growth

    NASA Astrophysics Data System (ADS)

    Windmark, F.; Birnstiel, T.; Ormel, C. W.; Dullemond, C. P.

    2012-08-01

    Context. It is unknown how far dust growth can proceed by coagulation. Obstacles to collisional growth are the fragmentation and bouncing barriers. However, in all previous simulations of the dust-size evolution, only the mean collision velocity has been considered, neglecting that a small but possibly important fraction of the collisions will occur at both much lower and higher velocities. Aims: We study the effect of the probability distribution of impact velocities on the collisional dust growth barriers. Methods: We assume a Maxwellian velocity distribution for colliding particles to determine the fraction of sticking, bouncing, and fragmentation, and implement this in a dust-size evolution code. We also calculate the probability of growing through the barriers and the growth timescale in these regimes. Results: We find that the collisional growth barriers are not as sharp as previously thought. With the existence of low-velocity collisions, a small fraction of the particles manage to grow to masses orders of magnitude above the main population. Conclusions: A particle velocity distribution softens the fragmentation barrier and removes the bouncing barrier. It broadens the size distribution in a natural way, allowing the largest particles to become the first seeds that initiate sweep-up growth towards planetesimal sizes.

  14. Gaussian distribution of inhomogeneous barrier height in Al/p-GaAs Schottky Barrier Diodes (SBDs)

    NASA Astrophysics Data System (ADS)

    Alialy, Sahar; Altindal, Semsettin

    2015-03-01

    The forward bias current-voltage (I-V) characteristics of Al/p-GaAs SBDs have been investigated in the temperature range of 240-360 K. The main electrical parameters such as zero-bias barrier height (ΦBo) , ideality factor (n) and series resistance (Rs) determined from the forward bias I-V data. These values are strong function of temperature and voltage. The analysis of I-V data based on the thermionic emission (TE) mechanism show that while the n decreases, the ΦBo and Rs increases with increasing temperature. ΦBo and n versus q/2kT plots were drown to obtain an evidence of GD of BH. The mean value of BH and standard deviation (σo) values were found from the intercept and slope of ΦBo vs q/2kT plot, respectively. Furthermore, the mean value of BH and the effective Richardson constant A* were obtained from the intercept and slope of the modified ln(Io/T2) -q2σ02 /2(kT)2 versus q/kT plot. The obtained value of A* is closed to theoretical value of p-GaAs. As a result, the I-V characteristics in Al/p-GaAs successfully have been explained based on TE theory with GD of BHs.

  15. Software Based Barriers To Integration Of Renewables To The Future Distribution Grid

    SciTech Connect

    Stewart, Emma; Kiliccote, Sila

    2014-06-01

    The future distribution grid has complex analysis needs, which may not be met with the existing processes and tools. In addition there is a growing number of measured and grid model data sources becoming available. For these sources to be useful they must be accurate, and interpreted correctly. Data accuracy is a key barrier to the growth of the future distribution grid. A key goal for California, and the United States, is increasing the renewable penetration on the distribution grid. To increase this penetration measured and modeled representations of generation must be accurate and validated, giving distribution planners and operators confidence in their performance. This study will review the current state of these software and modeling barriers and opportunities for the future distribution grid.

  16. Transition path time distribution and the transition path free energy barrier.

    PubMed

    Pollak, Eli

    2016-10-19

    The recent experimental measurement of the transition path time distributions of proteins presents several challenges to theory. Firstly, why do the fits of the experimental data to a theoretical expression lead to barrier heights which are much lower than the free energies of activation of the observed transitions? Secondly, there is the theoretical question of determining the transition path time distribution, without invoking the Smoluchowski limit. In this paper, we derive an exact expression for a transition path time distribution which is valid for arbitrary memory friction using the normal mode transformation which underlies Kramers' rate theory. We then recall that for low barriers, there is a noticeable difference between the transition path time distribution obtained with absorbing boundary conditions and free boundary conditions. For the former, the transition times are shorter, since recrossings of the boundaries are disallowed. As a result, if one uses the distribution based on absorbing boundary conditions to fit the experimental data, one will find that the transition path barrier will be larger than the values found based on a theory with free boundary conditions. We then introduce the paradigm of a transition path barrier height, and show that one should always expect it to be much smaller than the activation energy.

  17. Stress Distribution on Blasting Gallery Barrier Pillar due to Goaf Formation During Extraction

    NASA Astrophysics Data System (ADS)

    Kumar Reddy, Sandi; Sastry, Vedala Rama

    2016-10-01

    Semi-mechanised blasting gallery mining is a sustainable option to achieve higher production and productivity from underground thick coal seams. Judicious design of underground blasting gallery panel requires understanding of stress distribution on barrier pillars during different stages of extraction. This paper presents a study of stress distribution in and around barrier pillar for the different stages of extraction in the blasting gallery panel. Finite difference analysis taken up for final excavation (depillaring) in the panel with different stages of extraction. Analysis revealed that the stress transferred on barrier pillar increased as progress of excavation increased. Maximum stress was observed at a distance of 10 and 12 m from the pillar edge for virgin and goaved out panel sideby respectively, which gradually decreased towards centre of the pillar.

  18. Measurement of the Muon Neutrino Double-Differential Charged Current Quasi-Elastic Like Cross Section on a Hydrocarbon Target at Ev ~ 3.5 GeV

    SciTech Connect

    Hurtado Anampa, Kenyi Paolo

    2016-01-01

    The MINERvA Experiment (Main Injector Experiment v ₋ A interaction) [1] is a highly segmented detector of neutrinos, able to record events with high precision (over than thirteen million event in a four year run), using the NuMI Beam (Neutrino Main Injector) at the Fermi National Accelerator Laboratory [2]. This thesis presents a measurement of the Charged Current Quasi-Elastic Like1 vμ interaction on polystyrene scintillator (CH) in the MINERvA experiment with neutrino energies between 1.5 and 10 GeV. We use data taken between2 March 2010 and April 2012. The interactions were selected by requiring a negative muon, a reconstructed and identified proton, no michel electrons in the final state (in order to get rid of soft pions decaying) and a low calorimetric recoil energy away from the interaction vertex. The analysis is performed on 66,214 quasi-elastic like event candidates in the detectors tracker region with an estimated purity of 74%. The final measurement reported is a double differential cross sections in terms of the muon longitudinal and transversal momentum observables.

  19. Concordant genetic structure in two species of woodpecker distributed across the primary West African biogeographic barriers.

    PubMed

    Fuchs, Jérôme; Bowie, Rauri C K

    2015-07-01

    The lowland forests of western and central tropical Africa are separated by several potential biogeographic barriers to dispersal for forest adapted vertebrates. The two primary barriers are (1) the Dahomey Gap, a savanna corridor that reaches the coast of southern Ghana, Togo and Benin, and separates the West African rainforest into the Upper (Ghana west to Guinea) and Lower Guinea (Nigeria to Uganda and Angola) forest blocks, and (2) the Lower Niger River, a large delta that separates Western and Eastern Nigeria. Previous studies on terrestrial vertebrates (lizards, mammals and birds) have highlighted a genetic break in the Dahomey Gap/Lower Niger River area although the relative importance of each barrier has not been assessed due to limitations in geographic sampling. We compared the phylogeographic history of two co-distributed sister-species of woodpeckers (Campethera caroli and C. nivosa) using data from three loci representing all inheritance modes. Our analyses revealed that both the Dahomey Gap and possibly the Lower Niger River acted as strong biogeographic barriers for the two woodpecker species, with the Lower Niger River being the first barrier to have formed, leading to three distinct populations of C. nivosa. Our divergence time analyses revealed that both these biogeographic barriers formed during the Pleistocene, supporting the Pleistocene refuge hypothesis, with the Dahomey Gap likely appearing about 0.5 myr BP. No genetic structure was recovered among sampled populations in either the Upper or the Lower Guinea Forest Block for both species, despite the considerable geographic area covered.

  20. Total reaction cross sections for 8Li + 90Zr at near-barrier energies

    NASA Astrophysics Data System (ADS)

    Pakou, A.; Pierroutsakou, D.; Mazzocco, M.; Acosta, L.; Aslanoglou, X.; Boiano, A.; Boiano, C.; Carbone, D.; Cavallaro, M.; Grebosz, J.; Keeley, N.; La Commara, M.; Manea, C.; Marquinez-Duran, G.; Martel, I.; Parascandolo, C.; Rusek, K.; Sánchez-Benítez, A. M.; Sgouros, O.; Signorini, C.; Soramel, F.; Soukeras, V.; Stiliaris, E.; Strano, E.; Torresi, D.; Trzcinska, A.; Watanabe, Y. X.; Yamaguchi, H.

    2015-05-01

    Total reaction cross sections for the radioactive nucleus 8Li on 90Zr are reported at the near-barrier energies of 18.5 and 21.5MeV, derived from quasi-elastic scattering measurements. An analysis of the quasi-elastic scattering results is performed within an optical model framework using the BDM3Y1 interaction and total reaction cross sections are deduced. These quantities, appropriately reduced, are compared with previous data obtained in elastic scattering measurements with well and weakly bound projectiles on various targets and a formula for predicting total reaction cross sections with an uncertainty of % is obtained. Further on, the ratios of direct to total reaction cross sections are estimated for 6,8Li on various targets and are compared with CDCC or CRC calculations. The energy dependence of the optical potential is also discussed.

  1. A Precision Measurement of the Transverse Asymmetry AT from Quasi-elastic 3He(e,e') process, and the Neutron Magnetic Form Factor GNM at low Q2

    SciTech Connect

    Xu, Wang

    2002-06-01

    Electromagnetic form factors are fundamental quantities in describing the underlying electromagnetic structure of nucleons. While proton electromagnetic form factors have been determined with good precision, neutron form factors are known poorly, largely due to the lack of free neutron targets. Jefferson Lab Hall A experiment E95-001, a ''precise measurement of the transverse asymmetry AT' from the quasielastic 3He(e, e') process,'' was therefore designed to determine precisely the neutron magnetic form factor, G$n\\atop{M}$ at low momentum transfer values and was successfully completed in Spring 1999. High precision AT'data in the quasi-elastic region at Q2 values of 0.1 to 0.6 (GeV/c)2 were obtained using a high-pressure spin-exchange optically-pumped polarized 3He gas target with an average polarization of 30%, a longitudinally polarized e- beam, and two High Resolution Spectrometers: HRSe and HRSh. HRSe was employed to detect scattered electrons from the quasi-elastic kinematic region, and HRSh was employed as a elastic polarimetry to monitor the product of the beam and target polarizations. The extraction of form factors is usually model-dependent. Significant constraints on theoretical calculations are provided bu additional high precision quasi-elastic asymmetry data at Q2 values of 0.1 and 0.2 (GeV/c)2 in 3He breakup region, where effects of final state interactions (FSI) and meson exchange currents (MEC) are expected to be large [71]. G$n\\atop{M}$ is extracted from a non-relativistic Faddeev calculation which includes both FSI and MEC at Q2 values of 0.1 and 0.2 (GeV/c)2. The uncertainties of G$n\\atop{M}$ at these Q2 values are comparable to those of recent experiments with deuterium targets [58]. At the higher Q2 values from this experiment, G$n\\atop{M}$ is extracted from Plane-Wave Impulsive

  2. Effect of parallax distribution and crosstalk on visual comfort in parallax barrier autostereoscopic display

    NASA Astrophysics Data System (ADS)

    Kim, Donghyun; Lee, Hyoung; Kim, Sung-Kyu; Sohn, Kwanghoon

    2015-05-01

    Although autostereoscopic display is considered to be mainstream in the three-dimensional (3-D) display market for the near future, practical quality problems still exist due to various challenges such as the accommodation-vergence conflict and crosstalk. A number of studies have shown that these problems reduce the visual comfort and reliability of the perceived workload. We present two experiments for investigating the effect of parallax distribution, which affects the behavior of the accommodation and vergence responses and crosstalk on visual comfort in autostereoscopic display. We measured the subjective visual scores and perceived depth position for watching under various conditions that include foreground parallax, background parallax, and crosstalk levels. The results show that the viewers' comfort is significantly influenced by parallax distribution that induces a suitable conflict between the accommodation and vergence responses of the human visual system. Moreover, we confirm that crosstalk changes significantly affect visual comfort in parallax barrier autostereoscopic display. Consequently, the results can be used as guidelines to produce or adjust the 3-D image in accordance with the characteristics of parallax barrier autostereoscopic display.

  3. Patterns in the distribution of soft corals across the central Great Barrier Reef

    NASA Astrophysics Data System (ADS)

    Dinesen, Z. D.

    1983-05-01

    Distribution patterns of soft coral genera were examined at 11 reefs situated in a broad transect from inshore to the Coral Sea in the central region of the Great Barrier Reef. Twenty-five genera representing the Orders Alcyonacea and Stolonifera were recorded, and the survey also included one genus of the Order Gorgonacea. Total living soft coral cover is greatest on outershelf reef slopes, and is often less than and inversely related to the cover by stony corals. Soft coral diversity is generally low on reef flats, where soft coral cover is low or nil except in protected, inshore areas. The most diverse assemblages occur on reef slopes in midshelf and outershelf areas, where Efflatounaria and nephtheid genera predominate, and widely distributed alcyoniid genera are common. These richer assemblages are less well represented in the Coral Sea, while innershelf reefs support a less diverse fauna of somewhat different generic composition. Distribution patterns of soft corals across the transect broadly match similar variations in the distributions of stony corals and fishes, inshore reefs being generally depauperate. Such variations across the continental shelf are closely associated with changes in prevailing environmental conditions, but further research will be required to elucidate the effects of environmental parameters on benthic community structure.

  4. Testing charged current quasi-elastic and multinucleon interaction models in the NEUT neutrino interaction generator with published datasets from the MiniBooNE and MINERνA experiments

    NASA Astrophysics Data System (ADS)

    Wilkinson, C.; Terri, R.; Andreopoulos, C.; Bercellie, A.; Bronner, C.; Cartwright, S.; de Perio, P.; Dobson, J.; Duffy, K.; Furmanski, A. P.; Haegel, L.; Hayato, Y.; Kaboth, A.; Mahn, K.; McFarland, K. S.; Nowak, J.; Redij, A.; Rodrigues, P.; Sánchez, F.; Schwehr, J. D.; Sinclair, P.; Sobczyk, J. T.; Stamoulis, P.; Stowell, P.; Tacik, R.; Thompson, L.; Tobayama, S.; Wascko, M. O.; Żmuda, J.

    2016-04-01

    There has been a great deal of theoretical work on sophisticated charged current quasi-elastic (CCQE) neutrino interaction models in recent years, prompted by a number of experimental results that measured unexpectedly large CCQE cross sections on nuclear targets. As the dominant interaction mode at T2K energies, and the signal process in oscillation analyses, it is important for the T2K experiment to include realistic CCQE cross section uncertainties in T2K analyses. To this end, T2K's Neutrino Interaction Working Group has implemented a number of recent models in NEUT, T2K's primary neutrino interaction event generator. In this paper, we give an overview of the models implemented and present fits to published νμ and ν¯ μ CCQE cross section measurements from the MiniBooNE and MINER ν A experiments. The results of the fits are used to select a default cross section model for future T2K analyses and to constrain the cross section uncertainties of the model. We find strong tension between datasets for all models investigated. Among the evaluated models, the combination of a modified relativistic Fermi gas with multinucleon CCQE-like interactions gives the most consistent description of the available data.

  5. Precise Extraction of the Neutron Magnetic Form Factor from Quasi-elastic 3He(pol)(e(pol),e') at Q^2 = 0.1-0.6 (GeV/c)^2

    SciTech Connect

    Jens-ole Hansen; Brian Anderson; Leonard Auerbach; Todd Averett; William Bertozzi; Tim Black; John Calarco; Lawrence Cardman; Gordon Cates; Zhengwei Chai; Jiang-Ping Chen; Seonho Choi; Eugene Chudakov; Steve Churchwell; G Corrado; Christopher Crawford; Daniel Dale; Alexandre Deur; Pibero Djawotho; Dipangkar Dutta; John Finn; Haiyan Gao; Ronald Gilman; Oleksandr Glamazdin; Charles Glashausser; Walter Gloeckle; Jacek Golak; Javier Gomez; Viktor Gorbenko; F. Hersman; Douglas Higinbotham; Richard Holmes; Calvin Howell; Emlyn Hughes; Thomas Humensky; Sebastien Incerti; Piotr Zolnierczuk; Cornelis De Jager; John Jensen; Xiaodong Jiang; Cathleen Jones; Mark Jones; R Kahl; H Kamada; A Kievsky; Ioannis Kominis; Wolfgang Korsch; Kevin Kramer; Gerfried Kumbartzki; Michael Kuss; Enkeleida Lakuriqi; Meihua Liang; Nilanga Liyanage; John LeRose; Sergey Malov; Demetrius Margaziotis; Jeffery Martin; Kathy McCormick; Robert McKeown; Kevin McIlhany; Zein-Eddine Meziani; Robert Michaels; Greg Miller; Joseph Mitchell; Sirish Nanda; Emanuele Pace; Tina Pavlin; Gerassimos Petratos; Roman Pomatsalyuk; David Pripstein; David Prout; Ronald Ransome; Yves Roblin; Marat Rvachev; Giovanni Salme; Michael Schnee; Charles Seely; Taeksu Shin; Karl Slifer; Paul Souder; Steffen Strauch; Riad Suleiman; Mark Sutter; Bryan Tipton; Luminita Todor; M Viviani; Branislav Vlahovic; John Watson; Claude Williamson; H Witala; Bogdan Wojtsekhowski; Feng Xiong; Wang Xu; Jen-chuan Yeh

    2006-05-05

    We have measured the transverse asymmetry A{sub T'} in the quasi-elastic {sup 3}/rvec He/(/rvec e/,e') process with high precision at Q{sup 2}-values from 0.1 to 0.6 (GeV/c){sup 2}. The neutron magnetic form factor G{sub M}{sup n} was extracted at Q{sup 2}-values of 0.1 and 0.2 (GeV/c){sup 2} using a non-relativistic Faddeev calculation which includes both final-state interactions (FSI) and meson-exchange currents (MEC). Theoretical uncertainties due to the FSI and MEC effects were constrained with a precision measurement of the spin-dependent asymmetry in the threshold region of {sup 3}/rvec He/(/rvec e/,e'). We also extracted the neutron magnetic form factor G{sub M}{sup n} at Q{sup 2}-values of 0.3 to 0.6 (GeV/c){sup 2} based on Plane Wave Impulse Approximation calculations.

  6. Precision measurement of longitudinal and transverse response functions of quasi-elastic electron scattering in the momentum transfer range 0.55GeV/c lte math| lte 0.9GeV/c

    SciTech Connect

    Huan Yao, Jefferson Lab Hall A Collaboration, E05-110 Collaboration

    2012-04-01

    In order to test the Coulomb sum rule in nuclei, a precision measurement of inclusive electron scattering cross sections in the quasi-elastic region was performed at Jefferson Lab. Incident electrons of energies ranging from 0.4 GeV/c to 4 GeV/c scattered off {sup 4}He, {sup 12}C, {sup 56}Fe and {sup 208}Pb nuclei at four scattering angles (15deg., 60deg., 90deg., 120deg.) and scattered energies ranging from 0.1 GeV/c to 4 GeV/c. The Rosenbluth method with proper Coulomb corrections is used to extract the transverse and longitudinal response functions at three-momentum transfers 0.55 GeV/c {le} |q{yields}| {le} 1.0 GeV/c. The Coulomb Sum is determined in the same |q{yields}| range as mentioned above and will be compared to predictions. Analysis progress and preliminary results will be presented.

  7. Measurement of the νμ Charged Current π+ to Quasi-Elastic Cross Section Ratio on Mineral Oil in a 0.8 GeV Neutrino Beam

    SciTech Connect

    Linden, Steven K.

    2011-01-01

    Charged current single pion production (CCπ+) and charged current quasi-elastic scattering (CCQE) are the most abundant interaction types for neutrinos at energies around 1 GeV, a region of great interest to oscillation experiments. The cross-sections for these processes, however, are not well understood in this energy range. This dissertation presents a measurement of the ratio of CCπ+ to CCQE cross-sections for muon neutrinos on mineral oil (CH2) in the MiniBooNE experiment. The measurement is presented here both with and without corrections for hadronic re-interactions in the target nucleus and is given as a function of neutrino energy in the range 0.4 GeV < Eν < 2.4 GeV. With more than 46,000 CCπ+ events collected in MiniBooNE, and with a fractional uncertainty of roughly 11% in the region of highest statistics, this measurement represents a dramatic improvement in statistics and precision over previous CCπ+ and CCQE measurements.

  8. Mitochondrial evidence for panmixia despite perceived barriers to gene flow in a widely distributed waterbird.

    PubMed

    Oomen, Rebekah A; Reudink, Matthew W; Nocera, Joseph J; Somers, Christopher M; Green, M Clay; Kyle, Christopher J

    2011-01-01

    We examined the mitochondrial genetic structure of American white pelicans (Pelecanus erythrorhynchos) to: 1) verify or refute whether American white pelicans are panmictic and 2) understand if any lack of genetic structure is the result of contemporary processes or historical phenomena. Sequence analysis of mitochondrial DNA control region haplotypes of 367 individuals from 19 colonies located across their North American range revealed a lack of population genetic or phylogeographic structure. This lack of structure was unexpected because: 1) Major geographic barriers such as the North American Continental Divide are thought to limit dispersal; 2) Differences in migratory behavior are expected to promote population differentiation; and 3) Many widespread North American migratory bird species show historic patterns of differentiation resulting from having inhabited multiple glacial refugia. Further, high haplotype diversity and many rare haplotypes are maintained across the species' distribution, despite frequent local extinctions and recolonizations that are expected to decrease diversity. Our findings suggest that American white pelicans have a high effective population size and low natal philopatry. We suggest that the rangewide panmixia we observed in American white pelicans is due to high historical and contemporary gene flow, enabled by high mobility and a lack of effective physical or behavioral barriers.

  9. Evidence of Subdivisions on Evolutionary Timescales in a Large, Declining Marsupial Distributed across a Phylogeographic Barrier.

    PubMed

    Alpers, Deryn L; Walker, Faith M; Taylor, Andrea C; Sunnucks, Paul; Bellman, Steven; Hansen, Birgita D; Sherwin, William B

    2016-01-01

    Major prehistoric forces, such as the climatic shifts of the Pleistocene, can remain visible in a species' population genetics. Inference of refuges via genetic tools is useful for conservation management as it can identify populations whose preservation may help retain a species' adaptive potential. Such investigation is needed for Australia's southern hairy-nosed wombat (Lasiorhinus latifrons), whose conservation status has recently deteriorated, and whose phylogeographic history during the Pleistocene may be atypical compared to other species. Its contemporary range spans approximately 2000 km of diverse habitat on either side of the Spencer Gulf, which was a land bridge during periods of Pleistocene aridity that may have allowed for migration circumventing the arid Eyrean barrier. We sampled from animals in nearly all known sites within the species' current distribution, mainly using non-invasive methods, and employed nuclear and mitochondrial DNA analyses to assess alternative scenarios for Pleistocene impacts on population structure. We found evidence for mildly differentiated populations at the range extremes on either side of Spencer Gulf, with secondary contact between locations neighbouring each side of the barrier. These extreme western and eastern regions, and four other regions in between, were genetically distinct in genotypic clustering analyses. Estimates indicate modest, but complex gene flow patterns among some of these regions, in some cases possibly restricted for several thousand years. Prior to this study there was little information to aid risk assessment and prioritization of conservation interventions facilitating gene flow among populations of this species. The contributions of this study to that issue are outlined.

  10. Barrier distributions and signatures of transfer channels in the Ca40+Ni58,64 fusion reactions at energies around and below the Coulomb barrier

    NASA Astrophysics Data System (ADS)

    Bourgin, D.; Courtin, S.; Haas, F.; Stefanini, A. M.; Montagnoli, G.; Goasduff, A.; Montanari, D.; Corradi, L.; Fioretto, E.; Huiming, J.; Scarlassara, F.; Rowley, N.; Szilner, S.; Mijatović, T.

    2014-10-01

    Background: The nuclear structure of colliding nuclei is known to influence the fusion process. Couplings of the relative motion to nuclear shape deformations and vibrations lead to an enhancement of the sub-barrier fusion cross section in comparison with the predictions of one-dimensional barrier penetration models. This enhancement is explained by coupled-channels calculations including these couplings. The sub-barrier fusion cross section is also affected by nucleon transfer channels between the colliding nuclei. Purpose: The aim of the present experiment is to investigate the influence of the projectile and target nuclear structures on the fusion cross sections in the Ca40+Ni58 and Ca40+Ni64 systems. Methods: The experimental and theoretical fusion excitation functions as well as the barrier distributions were compared for these two systems. Coupled-channels calculations were performed using the ccfull code. Results: Good agreement was found between the measured and calculated fusion cross sections for the Ca40+Ni58 system. The situation is different for the Ca40+Ni64 system where the coupled-channels calculations with no nucleon transfer clearly underestimate the fusion cross sections below the Coulomb barrier. The fusion excitation function was, however, well reproduced at low and high energies by including the coupling to the neutron pair-transfer channel in the calculations. Conclusions: The nuclear structure of the colliding nuclei influences the fusion cross sections below the Coulomb barrier for both Ca40+Ni58,64 systems. Moreover, we highlighted the effect of the neutron pair-transfer channel on the fusion cross sections in Ca40+Ni64.

  11. Diversity and distribution of the bioactive actinobacterial genus Salinispora from sponges along the Great Barrier Reef.

    PubMed

    Vidgen, M E; Hooper, J N A; Fuerst, J A

    2012-03-01

    Isolates from the marine actinobacterial genus Salinispora were cultured from marine sponges collected from along the length of the Great Barrier Reef (GBR), Queensland, Australia. Strains of two species of Salinispora, Salinispora arenicola and "Salinispora pacifica", were isolated from GBR sponges Dercitus xanthus, Cinachyrella australiensis and Hyattella intestinalis. Phylogenetic analysis of the 16S rRNA gene sequences of representative strains, selected via BOX-PCR screening, identified previously unreported phylotypes of the species "S. pacifica". The classification of these microdiverse 16S rRNA groups was further confirmed by analysis of the ribonuclease P RNA (RNase P RNA) gene through both phylogenetic and secondary structure analysis. The use of RNase P RNA sequences combined with 16S rRNA sequences allowed distinction of six new intraspecies phylotypes of "S. pacifica" within the geographical area of the GBR alone. One of these new phylotypes possessed a localised regional distribution within the GBR.

  12. Numerical investigation of the spatiotemporal distribution of chemical species in an atmospheric surface barrier-discharge

    NASA Astrophysics Data System (ADS)

    Hasan, M. I.; Walsh, J. L.

    2016-05-01

    Using a one dimensional time dependent convection-reaction-diffusion model, the temporal and spatial distributions of species propagating downstream of an atmospheric pressure air surface barrier discharge was studied. It was found that the distribution of negatively charged species is more spatially spread compared to positive ions species, which is attributed to the diffusion of electrons that cool down and attach to background gas molecules, creating different negative ions downstream of the discharge region. Given the widespread use of such discharges in applications involving the remote microbial decontamination of surfaces and liquids, the transport of plasma generated reactive species away from the discharge region was studied by implementing mechanical convection through the discharge region. It was shown that increased convection causes the spatial distribution of species density to become uniform. It was also found that many species have a lower density close to the surface of the discharge as convection prevents their accumulation. While for some species, such as NO2, convection causes a general increase in the density due to a reduced residence time close to the discharge region, where it is rapidly lost through reactions with OH. The impact of the applied power was also investigated, and it was found that the densities of most species, whether charged or neutral, are directly proportional to the applied power.

  13. A multilayer ΔE-E R telescope for breakup reactions at energies around the Coulomb barrier

    NASA Astrophysics Data System (ADS)

    Ma, Nan-Ru; Lin, Cheng-Jian; Wang, Jian-Song; Yang, Lei; Wang, Dong-Xi; Zheng, Lei; Xu, Shi-Wei; Sun, Li-Jie; Jia, Hui-Ming; Ma, Jun-Bing; Ma, Peng; Jin, Shi-Lun; Bai, Zhen; Yang, Yan-Yun; Xu, Xin-Xing; Zhang, Gao-Long; Yang, Feng; He, Jian-Jun; Zhang, Huan-Qiao; Liu, Zu-Hua

    2016-11-01

    The breakup reactions of weakly-bound nuclei at energies around the Coulomb barrier and the corresponding coupling effect on the other reaction channels are hot topics nowadays. To overcome the difficulty in identifying both heavier and lighter fragments simultaneously, a new kind of ionization-chamber based detector telescope has been designed and manufactured. It consists of a PCB ionization chamber and three different thickness silicon detectors installed inside the chamber, which form a multilayer ΔE-E R telescope. The working conditions were surveyed by using an α source. An in-beam test experiment shows that the detector has good particle identification for heavy particles like 17F and 16O as well as light particles like protons and alpha particles. The measured quasi-elastic scattering angular distribution and the related discussions for 17F+208Pb are presented. Supported by National Key Basic Research Development Program of China (2013CB834404) and National Natural Science Foundation of China (11375268, 11475263, U1432127, U1432246).

  14. Horizontal mixing of Great Barrier Reef waters: Offshore diffusivity determined from radium isotope distribution

    NASA Astrophysics Data System (ADS)

    Hancock, Gary J.; Webster, Ian. T.; Stieglitz, Thomas C.

    2006-12-01

    The Great Barrier Reef (GBR), northern Australia, is the largest coral reef system in the world and provides habitat for highly diverse tropical marine ecosystems. Mixing in the coastal waters of the GBR is an important parameter influencing the health of these ecosystems. We have used the distribution of the four naturally occurring radium isotopes to determine the rate of mixing of nearshore waters of the central part of the GBR lagoon with water from the Coral Sea. The observed radium distribution is modeled using a one-dimensional diffusion model. The model improves on previous radium offshore mixing models by incorporating the benthic flux of radium diffusing across the sediment-water interface and offshore changes in water column depth. We find that the inner lagoon diffusivity (<20 km offshore) is best estimated using the short-lived isotopes 224Ra and 223Ra. The concordance of Kx estimated using the two different isotopes and the apparent consistency between measured riverine inflows to the lagoon and inflows inferred from the modeled salinity distribution provide confidence in the results. The mean value of Kx for the inner lagoon region of the southern central zone between latitudes 15.8°S and 19.0°S (265 ± 36 m2 s-1) is more than twice that in the northern central zone (14.3°S to 15.8°S). This difference likely reflects the different reef matrix density in the two zones. The distribution of the longer-lived isotope 228Ra indicates more rapid mixing in the middle and outer lagoon. These results indicate that central GBR water within 20 km of coast is flushed with outer lagoon water on a timescale of 18-45 days, with the flushing time increasing northward.

  15. Distribution, abundance and diversity of crustose coralline algae on the Great Barrier Reef

    NASA Astrophysics Data System (ADS)

    Dean, Angela J.; Steneck, Robert S.; Tager, Danika; Pandolfi, John M.

    2015-06-01

    The Great Barrier Reef (GBR) is the world's largest coral reef ecosystem. Crustose coralline algae (CCA) are important contributors to reef calcium carbonate and can facilitate coral recruitment. Despite the importance of CCA, little is known about species-level distribution, abundance, and diversity, and how these vary across the continental shelf and key habitat zones within the GBR. We quantified CCA species distributions using line transects ( n = 127) at 17 sites in the northern and central regions of the GBR, distributed among inner-, mid-, and outer-shelf regions. At each site, we identified CCA along replicate transects in three habitat zones: reef flat, reef crest, and reef slope. Taxonomically, CCA species are challenging to identify (especially in the field), and there is considerable disagreement in approach. We used published, anatomically based taxonomic schemes for consistent identification. We identified 30 CCA species among 12 genera; the most abundant species were Porolithon onkodes, Paragoniolithon conicum (sensu Adey), Neogoniolithon fosliei, and Hydrolithon reinboldii. Significant cross-shelf differences were observed in CCA community structure and CCA abundance, with inner-shelf reefs exhibiting lower CCA abundance than outer-shelf reefs. Shelf position, habitat zone, latitude, depth, and the interaction of shelf position and habitat were all significantly associated with variation in composition of CCA communities. Collectively, shelf position, habitat, and their interaction contributed to 22.6 % of the variation in coralline communities. Compared to mid- and outer-shelf sites, inner-shelf sites exhibited lower relative abundances of N. fosliei and Lithophyllum species. Reef crest habitats exhibited greater abundance of N. fosliei than reef flat and reef slope habitats. Reef slope habitats exhibited lower abundance of P. onkodes, but greater abundance of Neogoniolithon clavycymosum than reef crest and reef slope habitats. These findings

  16. Brain Distribution of Cediranib Is Limited by Active Efflux at the Blood-Brain Barrier

    PubMed Central

    Wang, Tianli; Agarwal, Sagar

    2012-01-01

    Cediranib is an orally active tyrosine kinase inhibitor that targets the vascular endothelial growth factor receptor family. Because of its potent antiangiogenic and antitumor activities, cediranib has been evaluated for therapy in glioma, a primary brain tumor. This study investigated the influence of two important efflux transporters at the blood-brain barrier, P-glycoprotein (P-gp) and breast cancer resistance protein (Bcrp), on the delivery of cediranib to the central nervous system. In vitro studies indicated that cediranib is a dual substrate for both P-gp and Bcrp. It is noteworthy that in spite of the in vitro data the in vivo mouse disposition studies conclusively showed that P-gp was the dominant transporter restricting the brain distribution of cediranib. The brain-to-plasma partitioning (AUCbrain/AUCplasma, where AUC is area under the curve) and the steady-state brain-to-plasma concentration ratio of cediranib were approximately 20-fold higher in Mdr1a/b(−/−) and Mdr1a/b(−/−)Bcrp1(−/−) mice compared with wild-type and Bcrp1(−/−) mice. Moreover, there was no significant difference in brain distribution of cediranib between wild-type and Bcrp1(−/−) mice and between Mdr1a/b(−/−) and Mdr1a/b(−/−)Bcrp1(−/−) mice. These results show that, unlike other tyrosine kinase inhibitors that are dual substrates for P-gp and Bcrp, Bcrp does not restrict the distribution of cediranib across the blood-brain barrier. We also show that inhibition of P-gp using specific or nonspecific inhibitors resulted in significantly enhanced delivery of cediranib to the brain. Concurrent administration of cediranib with chemical modulators of efflux transporters can be used as a strategy to enhance delivery and thus efficacy of cediranib in the brain. These findings are clinically relevant to the efficacy of cediranib chemotherapy in glioma. PMID:22323823

  17. Definition of preclinical and clinical character of human symptomatic status by quasi-elastic light scattering (QELS) investigations of blood plasma

    NASA Astrophysics Data System (ADS)

    Ivanova, Mariya A.; Klopov, Nicolay V.; Lebedev, Andrei D.; Noskin, Leonid A.; Noskin, Valentin A.; Pavlov, Michail Y.

    1997-05-01

    We discuss the use of the QELS method for screening of population groups for verified pathologies. For mathematical analysis of experimental data the regularization procedure have been used. This allows us to determine the histograms of particle size distribution of blood plasma samples. For the interpretation of the histogram data the special program of the mathematical processing - 'semiotic classifier' - have been created. The main idea of the 'semiotic classifier' is based on the fact, that formation of the pathological trace in human organism depends not only on concrete disease nature but also on the interaction between the organism sanogenetic mechanisms. We separate five pathological symptomatic complexes of organism status: allergic diseases, intoxications, organism catabolic shifts, auto-immune diseases and degenerative-dystrophy processes. The use of this 'semiotic classifier' in the system of monitoring investigations allows to solve the next problems: (1) to separate the persons with the expressed initial level of pathological processes to the risk groups for the special clinical investigations, (2) to set up the predisposition of the concrete individual towards definite pathologies at the preclinical stage, (3) under the conditions of expressed clinical pathology to study the dynamics of pathology processes.

  18. Evidence of Subdivisions on Evolutionary Timescales in a Large, Declining Marsupial Distributed across a Phylogeographic Barrier

    PubMed Central

    Alpers, Deryn L.; Walker, Faith M.; Taylor, Andrea C.; Sunnucks, Paul; Hansen, Birgita D.; Sherwin, William B.

    2016-01-01

    Major prehistoric forces, such as the climatic shifts of the Pleistocene, can remain visible in a species’ population genetics. Inference of refuges via genetic tools is useful for conservation management as it can identify populations whose preservation may help retain a species’ adaptive potential. Such investigation is needed for Australia’s southern hairy-nosed wombat (Lasiorhinus latifrons), whose conservation status has recently deteriorated, and whose phylogeographic history during the Pleistocene may be atypical compared to other species. Its contemporary range spans approximately 2000 km of diverse habitat on either side of the Spencer Gulf, which was a land bridge during periods of Pleistocene aridity that may have allowed for migration circumventing the arid Eyrean barrier. We sampled from animals in nearly all known sites within the species’ current distribution, mainly using non-invasive methods, and employed nuclear and mitochondrial DNA analyses to assess alternative scenarios for Pleistocene impacts on population structure. We found evidence for mildly differentiated populations at the range extremes on either side of Spencer Gulf, with secondary contact between locations neighbouring each side of the barrier. These extreme western and eastern regions, and four other regions in between, were genetically distinct in genotypic clustering analyses. Estimates indicate modest, but complex gene flow patterns among some of these regions, in some cases possibly restricted for several thousand years. Prior to this study there was little information to aid risk assessment and prioritization of conservation interventions facilitating gene flow among populations of this species. The contributions of this study to that issue are outlined. PMID:27732594

  19. Ring distributions leading to species formation: a global topographic analysis of geographic barriers associated with ring species

    PubMed Central

    2012-01-01

    importance of features that define barriers, (ii) can be replicated using any kind of continuously distributed environmental variable, and (iii) generates spatially explicit hypotheses of geographic species formation. The methods developed here - combined with study of the geographical ecology and genetics of taxa in their environments - should enable recognition of ring species phenomena throughout the world. PMID:22410314

  20. Performance of distributed bagged stone dust barrier in combating coal-dust explosions

    SciTech Connect

    Plessis, J.J.L. du; Vassard, P.S.

    1999-07-01

    The Kloppersbos Research Facility of the CSIR's Division of Mining Technology has developed a new method of building stone dust barriers. The new barrier makes use of a previous concept of containing stone dust in a bag, but incorporates a new method of rupturing the bag. This was achieved by adapting the closing mechanism and by balancing the stone dust content with the void in the bag. The bagged barrier was extensively tested in the 200-m test gallery. During these tests, it became evident that these bags could be made to rupture and spread stone dust when subjected to smaller forces than those required for the most commonly used passive barrier, the Polish light barrier. To validate this, as well as to gain international acceptance of this new barrier, tests were conducted in the German experimental mine, DMT Tremonia, Dortmund. The barrier was evaluated against numerous methane-initiated coal-dust explosions. The paper describes the successful inhibition of coal-dust explosions at Kloppersbos and DMT tremonia. The barrier has been proven successfully for static pressures of 44 to 82 kpa, dynamic pressures of 12 to 36 kpa and for flame speeds as low as 23 m/s. This barrier is now accepted by the South African government and has been implemented in numerous South African collieries.

  1. Effects of airflow on the distribution of filaments in atmospheric AC dielectric barrier discharge

    NASA Astrophysics Data System (ADS)

    Fan, Zhihui; Qi, Haicheng; Liu, Yidi; Yan, Huijie; Ren, Chunsheng

    2016-12-01

    Atmospheric-pressure dielectric barrier discharge (DBD) accompanied by airflow has attracted a significant attention for its extensive applications. In this paper, the effects of airflow on the characteristics of the atmospheric air DBD plasma are experimentally investigated using the DBD reactor excited by a 15 kHz AC power source. In order to study the discharge filaments distribution at different flow rates, transparent conductive indium tin oxide film is used as the upper electrode, and quartz glasses are used as insulated dielectrics. Experiment results prove that the breakdown voltage is decreased and more current pulses with declined amplitudes are produced when the airflow is introduced into the discharge gap. It is confirmed that although the discharge seems to be diffuse in the presence of airflow to the naked eyes, the discharge mode remains filamentary in the intensified charge-coupled device images within a single AC cycle. By acquiring the images with a different exposure time, it can be recognized that the discharge filaments move along the flow field direction with a velocity less than the corresponding flow rate. The movement of discharge filaments is attributed to the motion of the charge induced by the airflow.

  2. Microbubble type and distribution dependence of focused ultrasound-induced blood-brain barrier opening.

    PubMed

    Wang, Shutao; Samiotaki, Gesthimani; Olumolade, Oluyemi; Feshitan, Jameel A; Konofagou, Elisa E

    2014-01-01

    Focused ultrasound, in the presence of microbubbles, has been used non-invasively to induce reversible blood-brain barrier (BBB) opening in both rodents and non-human primates. This study was aimed at identifying the dependence of BBB opening properties on polydisperse microbubble (all clinically approved microbubbles are polydisperse) type and distribution by using a clinically approved ultrasound contrast agent (Definity microbubbles) and in-house prepared polydisperse (IHP) microbubbles in mice. A total of 18 C57 BL/6 mice (n = 3) were used in this study, and each mouse was injected with either Definity or IHP microbubbles via the tail vein. The concentration and size distribution of activated Definity and IHP microbubbles were measured, and the microbubbles were diluted to 6 × 10(8)/mL before injection. Immediately after microbubble administration, mice were subjected to focused ultrasound with the following parameters: frequency = 1.5 MHz, pulse repetition frequency = 10 Hz, 1000 cycles, in situ peak rarefactional acoustic pressures = 0.3, 0.45 and 0.6 MPa for a sonication duration of 60 s. Contrast-enhanced magnetic resonance imaging was used to confirm BBB opening and allowed for image-based analysis. Permeability of the treated region and volume of BBB opening did not significantly differ between the two types of microbubbles (p > 0.05) at peak rarefractional acoustic pressures of 0.45 and 0.6 MPa, whereas IHP microbubbles had significantly higher permeability and opening volume (p < 0.05) at the relatively lower pressure of 0.3 MPa. The results from this study indicate that microbubble type and distribution could have significant effects on focused ultrasound-induced BBB opening at lower pressures, but less important effects at higher pressures, possibly because of the stable cavitation that governs the former. This difference may have become less significant at higher pressures, where inertial cavitation typically occurs.

  3. Double Gaussian distribution of barrier height observed in densely packed GaN nanorods over Si (111) heterostructures

    SciTech Connect

    Mohan, Lokesh; Chandan, Greeshma; Mukundan, Shruthi; Krupanidhi, S. B.; Roul, Basanta

    2014-12-21

    GaN nanorods were grown by plasma assisted molecular beam epitaxy on intrinsic Si (111) substrates which were characterized by powder X-ray diffraction, field emission scanning electron microscopy, and photoluminescence. The current–voltage characteristics of the GaN nanorods on Si (111) heterojunction were obtained from 138 to 493 K which showed the inverted rectification behavior. The I-V characteristics were analyzed in terms of thermionic emission model. The temperature variation of the apparent barrier height and ideality factor along with the non-linearity of the activation energy plot indicated the presence of lateral inhomogeneities in the barrier height. The observed two temperature regimes in Richardson's plot could be well explained by assuming two separate Gaussian distribution of the barrier heights.

  4. Distribution and abundance of stream fishes in relation to barriers: implications for monitoring stream recovery after barrier removal

    USGS Publications Warehouse

    Zydlewski, Joseph; Coghlan Jr., Stephen M.; Gardner, C.; Saunders, R.

    2011-01-01

    Dams are ubiquitous in coastal regions and have altered stream habitats and the distribution and abundance of stream fishes in those habitats by disrupting hydrology, temperature regime and habitat connectivity. Dam removal is a common restoration tool, but often the response of the fish assemblage is not monitored rigorously. Sedgeunkedunk Stream, a small tributary to the Penobscot River (Maine, USA), has been the focus of a restoration effort that includes the removal of two low-head dams. In this study, we quantified fish assemblage metrics along a longitudinal gradient in Sedgeunkedunk Stream and also in a nearby reference stream. By establishing pre-removal baseline conditions and associated variability and the conditions and variability immediately following removal, we can characterize future changes in the system associated with dam removal. Over 2 years prior to dam removal, species richness and abundance in Sedgeunkedunk Stream were highest downstream of the lowest dam, lowest immediately upstream of that dam and intermediate farther upstream; patterns were similar in the reference stream. Although seasonal and annual variation in metrics within each site was substantial, the overall upstream-to-downstream pattern along the stream gradient was remarkably consistent prior to dam removal. Immediately after dam removal, we saw significant decreases in richness and abundance downstream of the former dam site and a corresponding increase in fish abundance upstream of the former dam site. No such changes occurred in reference sites. Our results show that by quantifying baseline conditions in a small stream before restoration, the effects of stream restoration efforts on fish assemblages can be monitored successfully. These data set the stage for the long-term assessment of Sedgeunkedunk Stream and provide a simple methodology for assessment in other restoration projects.

  5. Organisational Learning Barriers in Distributed Product Development: Observations from a Multinational Corporation.

    ERIC Educational Resources Information Center

    Gieskes, Jose F. B.; Hyland, Paul W.; Magnusson, Mats G.

    2002-01-01

    Using the Continuous Improvement for Global Innovation Management model, organizational learning in a multinational corporation was investigated. Barriers included time pressures, cultural differences, and inflexible hierarchy. Units with different operational foci emphasized different types of learning. Participants represented different…

  6. SPATIAL DISTRIBUTION OF CARBON AND SULFUR PRECIPITATING WITHIN PERMEABLE REACTIVE BARRIERS: DEVELOPMENT OF ANALYTICAL METHODS

    EPA Science Inventory

    A permeable reactive barrier (PRB) is a wall of porous reactive material placed in the path of a dissolved contaminant plume for the purpose of removing contaminants from ground water. Chemical processes within these reactive materials remove both inorganic and organic contamina...

  7. Defect distribution and Schottky barrier at metal/Ge interfaces: Role of metal-induced gap states

    NASA Astrophysics Data System (ADS)

    Sasaki, Shogo; Nakayama, Takashi

    2016-11-01

    The defect distribution and Schottky barrier at metal/Ge interfaces were studied using first-principles calculation. It was shown that the defect density markedly increases around the interface owing to the stabilization caused by the hybridization of defect electronic states with metal-induced gap states (MIGS) and by the associated small elastic energy loss around the interface. By comparing the formation energies of various defects at a variety of metal/substrate interfaces, we showed that MIGS not only control the Schottky barrier but also promote a defect-density increase at most metal/semiconductor interfaces. Moreover, we showed that interface oxide layers block MIGS penetration into the Ge substrate and promote the observed breakdown of Fermi-level pinning.

  8. New constraints on the spatial distribution and morphology of the Halimeda bioherms of the Great Barrier Reef, Australia

    NASA Astrophysics Data System (ADS)

    McNeil, Mardi A.; Webster, Jody M.; Beaman, Robin J.; Graham, Trevor L.

    2016-12-01

    Halimeda bioherms occur as extensive geological structures on the northern Great Barrier Reef (GBR), Australia. We present the most complete, high-resolution spatial mapping of the northern GBR Halimeda bioherms, based on new airborne lidar and multibeam echosounder bathymetry data. Our analysis reveals that bioherm morphology does not conform to the previous model of parallel ridges and troughs, but is far more complex than previously thought. We define and describe three morphological sub-types: reticulate, annulate, and undulate, which are distributed in a cross-shelf pattern of reduced complexity from east to west. The northern GBR bioherms cover an area of 6095 km2, three times larger than the original estimate, exceeding the area and volume of calcium carbonate in the adjacent modern shelf-edge barrier reefs. We have mapped a 1740 km2 bioherm complex north of Raine Island in the Cape York region not previously recorded, extending the northern limit by more than 1° of latitude. Bioherm formation and distribution are controlled by a complex interaction of outer-shelf geometry, regional and local currents, coupled with the morphology and depth of continental slope submarine canyons determining the delivery of cool, nutrient-rich water upwelling through inter-reef passages. Distribution and mapping of Halimeda bioherms in relation to Great Barrier Reef Marine Park Authority bioregion classifications and management zones are inconsistent and currently poorly defined due to a lack of high-resolution data not available until now. These new estimates of bioherm spatial distribution and morphology have implications for understanding the role these geological features play as structurally complex and productive inter-reef habitats, and as calcium carbonate sinks which record a complete history of the Holocene post-glacial marine transgression in the northern GBR.

  9. Host-Specific Interactions with Environmental Factors Shape the Distribution of Symbiodinium across the Great Barrier Reef

    PubMed Central

    Tonk, Linda; Sampayo, Eugenia M.; Weeks, Scarla; Magno-Canto, Marites; Hoegh-Guldberg, Ove

    2013-01-01

    Background The endosymbiotic dinoflagellates (genus Symbiodinium) within coral reef invertebrates are critical to the survival of the holobiont. The genetic variability of Symbiodinium may contribute to the tolerance of the symbiotic association to elevated sea surface temperatures (SST). To assess the importance of factors such as the local environment, host identity and biogeography in driving Symbiodinium distributions on reef-wide scales, data from studies on reef invertebrate-Symbiodinium associations from the Great Barrier Reef (GBR) were compiled. Methodology/Principal Findings The resulting database consisted of 3717 entries from 26 studies. It was used to explore ecological patterns such as host-specificity and environmental drivers structuring community complexity using a multi-scalar approach. The data was analyzed in several ways: (i) frequently sampled host species were analyzed independently to investigate the influence of the environment on symbiont distributions, thereby excluding the influence of host specificity, (ii) host species distributions across sites were added as an environmental variable to determine the contribution of host identity on symbiont distribution, and (iii) data were pooled based on clade (broad genetic groups dividing the genus Symbiodinium) to investigate factors driving Symbiodinium distributions using lower taxonomic resolution. The results indicated that host species identity plays a dominant role in determining the distribution of Symbiodinium and environmental variables shape distributions on a host species-specific level. SST derived variables (especially SSTstdev) most often contributed to the selection of the best model. Clade level comparisons decreased the power of the predictive model indicating that it fails to incorporate the main drivers behind Symbiodinium distributions. Conclusions/Significance Including the influence of different host species on Symbiodinium distributional patterns improves our understanding

  10. Optical heterodyne measurement of cloud droplet size distributions.

    PubMed

    Gollub, J P; Chabay, L; Flygare, W H

    1973-12-01

    Optical heterodyne spectra of laser light quasi-elastically scattered by falling water droplets (1-10-micro radius) in a diffusion cloud chamber were used to determine the droplet size distribution. The rate of fall depends on radius in a known way, thus yielding a heterodyne spectrum manifesting a distribution of Doppler shifts. This spectrum, in conjunction with the calculated Mie scattering intensity as a function of droplet radius, provides a direct measure of the droplet size distribution for droplets large enough that Brownian motion is negligible. The experiments described in this paper demonstrate the technique and establish the potential for further more quantitative studies of size distributions.

  11. Nanoscale potential barrier distributions and their effect on current transport in Ni/n type Si Schottky diode

    NASA Astrophysics Data System (ADS)

    Yeganeh, M.; Balkanian, N.; Rahmatallahpur, Sh.

    2015-12-01

    We have experimentally studied the Ni/n-Si nano Schottky barrier height (SBH) and potential difference between patches in the nano Schottky diodes (SD) using contact atomic force microscopy (C-AFM) in tapping mode and scanning tunneling microscopy (STM). Topology measurement of the surface with C-AFM showed that, a single Ni/n-Si SD consists of many patches with different sizes. These patches are sets of parallel diodes and electrically interacting contacts of 5 to 50 nm sizes and between these individual diodes, there exists an additional electric field. In real metal semiconductor contacts (MSC), patches with quite different configurations, various geometrical sizes and local work functions were randomly distributed on the surface of the metal. The direction and intensity of the additional electric field are distributed in homogenously along the contact metal surface. SBH controls the electronic transport across the MS interface and therefore, is of vital importance to the successful operation of semiconductor devices.

  12. Patterns in the distribution of coral communities across the central Great Barrier Reef

    NASA Astrophysics Data System (ADS)

    Done, T. J.

    1982-10-01

    Despite the pre-eminence of the Great Barrier Reef, there has been little systematic description of its biotic communities, and in particular, of the corals themselves. Only recently have the problems of coral taxonomy been sufficiently resolved to allow a beginning to be made in rectifying this deficiency. The present study describes seventeen assemblages of corals which occupy the major habitat types found in and near the central Great Barrier Reef. The habitats studied range from the wave swept reef flats of Coral Sea atolls to the slopes of small reefs occupying sheltered, muddy conditions near the coast. These, and the array of reefs between, have characteristic suites of coral communities which provide the basis for a classification of reefs into non- Acropora reefs and various Acropora reefs. It is speculated that the faunistic differences are maintained because reefs are primarily self-seeded and because the majority of larvae from external sources are of species which are already present. The greatest diversity of both species and community types was found on reefs near the middle of the continental shelf, while the oceanic atolls and nearshore silt-affected reefs are almost equally depauperate.

  13. Influence of capillary barrier effect on biogas distribution at the base of passive methane oxidation biosystems: Parametric study.

    PubMed

    Ahoughalandari, Bahar; Cabral, Alexandre R

    2016-12-05

    The efficiency of methane oxidation in passive methane oxidation biosystems (PMOBs) is influenced by, among other things, the intensity and distribution of the CH4 loading at the base of the methane oxidation layer (MOL). Both the intensity and distribution are affected by the capillary barrier that results from the superposition of the two materials constituting the PMOB, namely the MOL and the gas distribution layer (GDL). The effect of capillary barriers on the unsaturated flow of water has been well documented in the literature. However, its effect on gas flow through PMOBs is still poorly documented. In this study, sets of numerical simulations were performed to evaluate the effect of unsaturated hydraulic characteristics of the MOL material on the value and distribution of moisture and hence, the ease and uniformity in the distribution of the upward flow of biogas along the GDL-MOL interface. The unsaturated hydraulic parameters of the materials used to construct the experimental field plot at the St-Nicephore landfill (Quebec, Canada) were adopted to build the reference simulation of the parametric study. The behavior of the upward flow of biogas for this particular material was analyzed based on its gas intrinsic permeability function, which was obtained in the laboratory. The parameters that most influenced the distribution and the ease of biogas flow at the base of the MOL were the saturated hydraulic conductivity and pore size distribution of the MOL material, whose effects were intensified as the slope of the interface increased. The effect of initial dry density was also assessed herein. Selection of the MOL material must be made bearing in mind that these three parameters are key in the effort to prevent unwanted restriction in the upward flow of biogas, which may result in the redirection of biogas towards the top of the slope, leading to high CH4 fluxes (hotspots). In a well-designed PMOB, upward flow of biogas across the GDL-MOL interface is

  14. Suberin-associated fatty alcohols in Arabidopsis: distributions in roots and contributions to seed coat barrier properties.

    PubMed

    Vishwanath, Sollapura J; Kosma, Dylan K; Pulsifer, Ian P; Scandola, Sabine; Pascal, Stéphanie; Joubès, Jérôme; Dittrich-Domergue, Franziska; Lessire, René; Rowland, Owen; Domergue, Frédéric

    2013-11-01

    Suberin is found in a variety of tissues, such as root endoderms and periderms, storage tuber periderms, tree cork layer, and seed coats. It acts as a hydrophobic barrier to control the movement of water, gases, and solutes as well as an antimicrobial barrier. Suberin consists of polymerized phenolics, glycerol, and a variety of fatty acid derivatives, including primary fatty alcohols. We have conducted an in-depth analysis of the distribution of the C18:0 to C22:0 fatty alcohols in Arabidopsis (Arabidopsis thaliana) roots and found that only 20% are part of the root suberin polymer, together representing about 5% of its aliphatic monomer composition, while the remaining 80% are found in the nonpolymeric (soluble) fraction. Down-regulation of Arabidopsis FATTY ACYL REDUCTASE1 (FAR1), FAR4, and FAR5, which collectively produce the fatty alcohols found in suberin, reduced their levels by 70% to 80% in (1) the polymeric and nonpolymeric fractions from roots of tissue culture-grown plants, (2) the suberin-associated root waxes from 7-week-old soil-grown plants, and (3) the seed coat suberin polymer. By contrast, the other main monomers of suberin were not altered, indicating that reduced levels of fatty alcohols did not influence the suberin polymerization process. Nevertheless, the 75% reduction in total fatty alcohol and diol loads in the seed coat resulted in increased permeability to tetrazolium salts and a higher sensitivity to abscisic acid. These results suggest that fatty alcohols and diols play an important role in determining the functional properties of the seed coat suberin barrier.

  15. Suberin-Associated Fatty Alcohols in Arabidopsis: Distributions in Roots and Contributions to Seed Coat Barrier Properties1[W

    PubMed Central

    Vishwanath, Sollapura J.; Kosma, Dylan K.; Pulsifer, Ian P.; Scandola, Sabine; Pascal, Stéphanie; Joubès, Jérôme; Dittrich-Domergue, Franziska; Lessire, René; Rowland, Owen; Domergue, Frédéric

    2013-01-01

    Suberin is found in a variety of tissues, such as root endoderms and periderms, storage tuber periderms, tree cork layer, and seed coats. It acts as a hydrophobic barrier to control the movement of water, gases, and solutes as well as an antimicrobial barrier. Suberin consists of polymerized phenolics, glycerol, and a variety of fatty acid derivatives, including primary fatty alcohols. We have conducted an in-depth analysis of the distribution of the C18:0 to C22:0 fatty alcohols in Arabidopsis (Arabidopsis thaliana) roots and found that only 20% are part of the root suberin polymer, together representing about 5% of its aliphatic monomer composition, while the remaining 80% are found in the nonpolymeric (soluble) fraction. Down-regulation of Arabidopsis FATTY ACYL REDUCTASE1 (FAR1), FAR4, and FAR5, which collectively produce the fatty alcohols found in suberin, reduced their levels by 70% to 80% in (1) the polymeric and nonpolymeric fractions from roots of tissue culture-grown plants, (2) the suberin-associated root waxes from 7-week-old soil-grown plants, and (3) the seed coat suberin polymer. By contrast, the other main monomers of suberin were not altered, indicating that reduced levels of fatty alcohols did not influence the suberin polymerization process. Nevertheless, the 75% reduction in total fatty alcohol and diol loads in the seed coat resulted in increased permeability to tetrazolium salts and a higher sensitivity to abscisic acid. These results suggest that fatty alcohols and diols play an important role in determining the functional properties of the seed coat suberin barrier. PMID:24019425

  16. Patterns in the distribution of sponge populations across the central Great Barrier Reef

    NASA Astrophysics Data System (ADS)

    Wilkinson, Clive R.; Cheshire, Anthony C.

    1989-12-01

    Coral reef sponge populations were surveyed at two spatial scales: different depths and different reef locations across the continental shelf of the central Great Barrier Reef. The surveys were conducted on the forereef slopes of 12 reefs from land-influenced, inner-shelf reefs to those in the oligotrophic waters of the Coral Sea. Few sponges occur in shallow waters and the largest populations are found between 10 and 30 m depth. Sponges are apparently excluded from shallow waters because of excessive turbulence and possibly by high levels of damaging light. Sponge biomass is highest on the innershelf reefs and decreases away from the coast, whereas abundance is generally higher on middle-shelf reefs. There are considerable overlaps in the species composition on middle-, outer-shelf and Coral Sea reefs, but those on inner-shelf reefs are significantly different. The nature and size of sponge populations reflect environmental conditions across the continental shelf. The larger inner-shelf populations probably reflect higher levels of organic and inorganic nutrients and reduced amounts of physical turbulence, whereas sponges on reefs further from shore may be able to resist greater turbulence but appear more sensitive to the effects of fine sediments. These latter populations are smaller, reflecting the reduced availability of organic matter, however, many of these sponges rely on cyanobacterial symbionts to augment nutrition in these clearer, more oligotrophic waters.

  17. Environmental Factors Controlling the Distribution of Symbiodinium Harboured by the Coral Acropora millepora on the Great Barrier Reef

    PubMed Central

    Cooper, Timothy F.; Berkelmans, Ray; Ulstrup, Karin E.; Weeks, Scarla; Radford, Ben; Jones, Alison M.; Doyle, Jason; Canto, Marites; O'Leary, Rebecca A.; van Oppen, Madeleine J. H.

    2011-01-01

    Background The Symbiodinium community associated with scleractinian corals is widely considered to be shaped by seawater temperature, as the coral's upper temperature tolerance is largely contingent on the Symbiodinium types harboured. Few studies have challenged this paradigm as knowledge of other environmental drivers on the distribution of Symbiodinium is limited. Here, we examine the influence of a range of environmental variables on the distribution of Symbiodinium associated with Acropora millepora collected from 47 coral reefs spanning 1,400 km on the Great Barrier Reef (GBR), Australia. Methodology/Principal Findings The environmental data included Moderate Resolution Imaging Spectroradiometer (MODIS) satellite data at 1 km spatial resolution from which a number of sea surface temperature (SST) and water quality metrics were derived. In addition, the carbonate and mud composition of sediments were incorporated into the analysis along with in situ water quality samples for a subset of locations. Analyses were conducted at three spatio-temporal scales [GBR (regional-scale), Whitsunday Islands (local-scale) and Keppel Islands/Trunk Reef (temporal)] to examine the effects of scale on the distribution patterns. While SST metrics were important drivers of the distribution of Symbiodinium types at regional and temporal scales, our results demonstrate that spatial variability in water quality correlates significantly with Symbiodinium distribution at local scales. Background levels of Symbiodinium types were greatest at turbid inshore locations of the Whitsunday Islands where SST predictors were not as important. This was not the case at regional scales where combinations of mud and carbonate sediment content coupled with SST anomalies and mean summer SST explained 51.3% of the variation in dominant Symbiodinium communities. Conclusions/Significance Reef corals may respond to global-scale stressors such as climate change through changes in their resident symbiont

  18. Double Gaussian distribution of barrier height for FeCrNiC alloy Schottky contacts on p-Si substrates

    NASA Astrophysics Data System (ADS)

    Beştaş, A. N.; Yazıcı, S.; Aktaş, F.; Abay, B.

    2014-11-01

    The electrical properties of Schottky contact with a quadripartite alloy FeCrNiC on p-Si have been investigated in the temperature range of 80-320 K, for the first time. An abnormal decrease in the apparent barrier height (φap.) and an increase in the apparent ideality factor (nap.) with a decrease in the temperature were elucidated by the current-voltage (I-V) characteristic of the FeCrNiC/p-Si structure. The conventional Richardson plot exhibits non-linear behaviour at temperature below 180 K with the linear portion to be used for the calculation of activation energy and Richardson constant (A*) as 0.352 eV and 8.3 × 10-3 A K-2 cm-2, respectively. The observed anomalies were explained on the basis of the thermionic emission (TE) theory by incorporating the concept of inhomogeneous multiple barriers at Metal-Semiconductor (MS) interface. It has been seen that the apparent barrier height φap. exhibits double Gaussian distribution (DGD) feature with the mean BH (ϕbarb0) of 0.695 and 0.646 eV, accompanied by their standard deviations (σ0) of 0.082 and 0.070 eV in 320-180 K and 180-80 K regions, respectively. These values of the ϕbarb0 have been confirmed with the modified Richardson plot [ln (J0 /T2) - (q2σ02 / 2k2T2)   vs .    1 / T ] as 0.690 eV and 0.633 eV at the demarcated temperature regions, respectively. Richardson constant A* has also been calculated from the modified Richardson plots as 33.43 A K-2 cm-2 and 28.47 A K-2 cm-2 that belong to two distinct temperature ranges. Their average value exactly matched the theoretical value of 31.6 A K-2 cm-2 for the holes in p-type Si. Our results confirm the predictions of the multiple GD approach of nanoscale spatial BH inhomogeneities at the MS interface.

  19. Blood-nerve barrier: distribution of anionic sites on the endothelial plasma membrane and basal lamina of dorsal root ganglia.

    PubMed

    Bush, M S; Reid, A R; Allt, G

    1991-09-01

    Previous investigations of the blood-nerve barrier have correlated the greater permeability of ganglionic endoneurial vessels, compared to those of nerve trunks, with the presence of fenestrations and open intercellular junctions. Recent studies have demonstrated reduced endothelial cell surface charge in blood vessels showing greater permeability. To determine the distribution of anionic sites on the plasma membranes and basal laminae of endothelial cells in dorsal root ganglia, cationic colloidal gold and cationic ferritin were used. Electron microscopy revealed the existence of endothelial microdomains with differing labelling densities. Labelling indicated that caveolar and fenestral diaphragms and basal laminae are highly anionic at physiological pH, luminal plasma membranes and endothelial processes are moderately charged and abluminal plasma membranes are weakly anionic. Tracers did not occur in caveolae or cytoplasmic vesicles. In vitro tracer experiments at pH values of 7.3, 5.0, 3.5 and 2.0 indicated that the anionic charge on the various endothelial domains was contributed by chemical groups with differing pKa values. In summary, the labelling of ganglionic and sciatic nerve vessels was similar except for the heavy labelling of diaphragms in a minority of endoneurial vessels in ganglia. This difference is likely to account in part for the greater permeability of ganglionic endoneurial vessels. The results are discussed with regard to the blood-nerve and -brain barriers and vascular permeability in other tissues and a comparison made between the ultrastructure and anionic microdomains of epi-, peri- and endoneurial vessels of dorsal root ganglia and sciatic nerves.

  20. Reproduction and distribution of two species of Goniastrea (Scleractinia) from the Great Barrier Reef province

    NASA Astrophysics Data System (ADS)

    Babcock, Russell C.

    1984-04-01

    The reproductive biology of Goniastrea aspera at Magnetic Island was compared with that of a very similar sympatric species, G. favulus as reported by Kojis and Quinn at Heron Island. The development of gametes was similar in both species, but there was no evidence for an adolescent protandrous period of development in G. aspera such as that recorded for G. favulus at Heron Island. Other reproductive differences between the two species were found in egg size and the mode of spawning. The eggs of G. aspera are smaller and more numerous than those of G. favulus. Goniastrea aspera expelled buoyant packets of eggs and sperm, while G. favulus had sticky sinking eggs which were released separately from the sperm. The spatial pattern of the two species was examined on the reef flat at Magnetic Island to determine whether the observed differences in spawning behaviour and egg buoyancy might have an effect on egg retention and the distribution of adult colonies. The results of this comparison failed to detect any difference in the degree of aggregation of the two species. This is not the result which would be expected if sticky sinking eggs helped retain developing larvae in the vicinity of the adult. These results, together with evidence from a wide range of coelenterates and observations on the larvae of G. aspera point to post spawning larval behaviour as the most likely factor in determining where these species will settle.

  1. Effects of a small natural barrier on the spatial distribution of the fish assemblage in the Verde River, Upper Paraná River Basin,Brazil.

    PubMed

    Silva, J C; Gubiani, É A; Piana, P A; Delariva, R L

    2016-01-01

    Geographical barriers influence species distribution and play an important role in the segregation of fish assemblages. The present study aims to test the influence of a small natural barrier on the spatial distribution of fish species in the Verde River, Upper Paraná River Basin, Brazil, considering two biotopes: upstream and downstream of the Branca Waterfall. We observed the highest species richness downstream of the Branca Waterfall, which also had the highest number of exclusive species. Richness, evenness, and abundance varied significantly among biotopes. The composition and structure of the fish assemblage differed between biotopes, which were characterized by different indicator species, mainly downstream of the Branca Waterfall. Physical and chemical variables and geographical distance between sites were not responsible for the differences observed. Hence, the present study shows that small barriers can also be crucial in structuring fish fauna and play a key role in the segregation of fish assemblages.

  2. Diet and cross-shelf distribution of rabbitfishes (f. Siganidae) on the northern Great Barrier Reef: implications for ecosystem function

    NASA Astrophysics Data System (ADS)

    Hoey, A. S.; Brandl, S. J.; Bellwood, D. R.

    2013-12-01

    Herbivorous fishes are a critical functional group on coral reefs, and there is a clear need to understand the role and relative importance of individual species in reef processes. While numerous studies have quantified the roles of parrotfishes and surgeonfishes on coral reefs, the rabbitfishes (f. Siganidae) have been largely overlooked. Consequently, they are typically viewed as a uniform group of grazing or browsing fishes. Here, we quantify the diet and distribution of rabbitfish assemblages on six reefs spanning the continental shelf in the northern Great Barrier Reef. Our results revealed marked variation in the diet and distribution of rabbitfish species. Analysis of stomach contents identified four distinct groups: browsers of leathery brown macroalgae ( Siganus canaliculatus, S. javus), croppers of red and green macroalgae ( S. argenteus, S. corallinus, S. doliatus, S. spinus) and mixed feeders of diverse algal material, cyanobacteria, detritus and sediment ( S. lineatus, S. punctatissimus, S. punctatus, S. vulpinus). Surprisingly, the diet of the fourth group ( S. puellus) contained very little algal material (22.5 %) and was instead dominated by sponges (69.1 %). Together with this variation in diet, the distribution of rabbitfishes displayed clear cross-shelf variation. Biomass was greatest on inner-shelf reefs (112.7 ± 18.2 kg.ha-1), decreasing markedly on mid- (37.8 ± 4.6 kg.ha-1) and outer-shelf reefs (9.7 ± 2.2 kg.ha-1). This pattern was largely driven by the browsing S. canaliculatus that accounted for 50 % of the biomass on inner-shelf reefs, but was absent in mid- and outer-shelf reefs. Mixed feeders, although primarily restricted to the reef slope and back reef habitats, also decreased in abundance and biomass from inshore to offshore, while algal cropping taxa were the dominant group on mid-shelf reefs. These results clearly demonstrate the extent to which diet and distribution vary within the Siganidae and emphasise the importance of

  3. Gaussian distribution of inhomogeneous barrier height in Al/SiO2/p-Si Schottky diodes

    NASA Astrophysics Data System (ADS)

    Yıldız, D. E.; Altındal, Ş.; Kanbur, H.

    2008-06-01

    The forward and reverse bias current-voltage (I-V) characteristics of Al/SiO2/p-Si (metal-insulator-semiconductor) type Schottky diodes (SDs) were measured in the temperature range of 200-400 K. Evaluation of the experimental I-V data reveals a decrease in ΦB0 and Rs but an increase in n, with a decrease in temperature. To explain this behavior of ΦB0 with temperature, we have reported a modification which included n and the tunneling parameter αχ1/2δ in the expression of reverse saturation current I0. Thus, a corrected effective barrier height ΦB eff(I -V) vs T has a negative temperature coefficient (α ≈-5×10-4 eV/K), and it is in good agreement with α=-4.73×10-4 eV/K of Si band gap. Such behavior of Rs estimated from Cheung's method could be expected for semiconductors in the temperature region, where there is no carrier freezing out, which is non-negligible at low temperatures. Also, there is a linear correlation between ΦB0(I -V) and n due to the inhomogeneities of the barrier heights (BHs). The conventional activation energy (Ea) plot exhibits nonlinearity below 320 K with the linear portion corresponding to Ea of 0.275 eV. An A∗ value of 1.45×10-5 A cm-2 K-2,which is much lower than the known value of 32 A cm-2 K-2 for p-type Si, is determined from the intercept at the ordinate of this experimental plot. Such behavior is attributed to Schottky barrier inhomogeneities by assuming a Gaussian distribution (GD) of BHs due to BH inhomogeneities that prevail at the interface. We attempted to draw a ΦB0 vs q /2kT plot to obtain evidence of a GD of the BHs, and the values of Φ¯B0=1.136 eV and σ0=0.159 V for the mean BH and standard deviation at zero bias have been obtained from this plot. Therefore, the modified ln (I0/T2)-q2σ02/2k2T2 vs q /kT plot gives Φ¯B0 and A∗ values of 1.138 eV and 37.23 A cm-2 K-2, respectively, without using the temperature coefficient of the BH. This A∗ value of 37.23 A cm-2 K-2 is very close to the theoretical

  4. Influence of riffle characteristics, surficial geology, and natural barriers on the distribution of the channel darter, Percina copelandi, in the Lake Ontario basin

    USGS Publications Warehouse

    Reid, S.M.; Carl, L.M.; Lean, J.

    2005-01-01

    The channel darter, Percina copelandi, is a small benthic fish with a wide but disjunct distribution across central North America. The development of conservation and recovery strategies for Canadian populations is limited by a lack of knowledge regarding ecology, population size and other factors that affect its distribution and abundance. We sampled five rivers in the Lake Ontario basin to test whether the distribution of P. copelandi reflected riffle habitat characteristics or landscape-scale factors such as surficial geology and natural barriers (waterfalls). At most sites yielding P. copelandi, riffles flowed into deep sand bottomed run or pool habitats. Despite a lack of association with local surficial geology or riffle habitat characteristics, both the upstream limits of P. copelandi occurrence and distribution of suitable habitats reflected the distribution of waterfalls, chutes and bedrock outcroppings. In contrast to P. copelandi, distributions of Etheostoma flabellare, P. caprodes and Rhinichthys cataractae reflected among site differences in riffle habitat. ?? Springer 2005.

  5. Changes in expression and distribution of claudin 2, 5 and 8 lead to discontinuous tight junctions and barrier dysfunction in active Crohn's disease

    PubMed Central

    Zeissig, S; Bürgel, N; Günzel, D; Richter, J; Mankertz, J; Wahnschaffe, U; Kroesen, A J; Zeitz, M; Fromm, M; Schulzke, J‐D

    2007-01-01

    Background Epithelial barrier function is impaired in Crohn's disease. Aim To define the underlying cellular mechanisms with special attention to tight junctions. Methods Biopsy specimens from the sigmoid colon of patients with mild to moderately active or inactive Crohn's disease were studied in Ussing chambers, and barrier function was determined by impedance analysis and conductance scanning. Tight junction structure was analysed by freeze fracture electron microscopy, and tight junction proteins were investigated immunohistochemically by confocal laser scanning microscopy and quantified in immunoblots. Epithelial apoptosis was analysed in terminal deoxynucleotidyl transferase‐mediated deoxyuridine triphosphate nick‐end labelling and 4′,6‐diamidino‐2‐phenylindole staining. Results Patients with active Crohn's disease showed an impaired intestinal barrier function as indicated by a distinct reduction in epithelial resistance. As distribution of conductivity was even, focal epithelial lesions (eg, microerosions) did not contribute to barrier dysfunction. Instead, freeze fracture electron microscopy analysis showed reduced and discontinuous tight junction strands. Occludin and the sealing tight junction proteins claudin 5 and claudin 8 were downregulated and redistributed off the tight junction, whereas the pore‐forming tight junctions protein claudin 2 was strongly upregulated, which constitute the molecular basis of tight junction changes. Other claudins were unchanged (claudins 1, 4 and 7) or not detectable in sigmoid colon (claudins 11, 12, 14, 15 and 16). Claudin 2 upregulation was less pronounced in active Crohn's disease compared with active ulcerative colitis and was inducible by tumour necrosis factor α. As a second source of impaired barrier function, epithelial apoptosis was distinctly increased in active Crohn's disease (mean (SD) 5.2 (0.5)% v 1.9 (0.2)% in control). By contrast, barrier function, tight junction proteins and apoptosis

  6. Correlated distributions in the photodissociation of HNCO to NH(X 3Σ-, a 1Δ) + CO(X 1Σ+) near the barrier on S 1

    NASA Astrophysics Data System (ADS)

    Droz-Georget, Thierry; Zyrianov, Mikhail; Reisler, Hanna; Chandler, David W.

    1997-09-01

    The photodissociation of HNCO is examined at 230.1 nm, near the threshold to NH(a 1Δ) + CO(X 1Σ+). CO products are generated from NH(X 3Σ-) + CO(X 1Σ+) and NH(a 1Δ) + CO(X 1Σ+). Although the two contributions overlap spectroscopically, they are resolved in velocity space when using photofragment ion imaging. For both channels the CO rotational distribution is cold and non-statistical. A high resolution variant of imaging is employed to obtain NH(a 1Δ) distributions correlating with specific JCO levels. Combining these measurements with NH(a 1Δ) photofragment yield spectra and rotational distributions, we establish that decomposition to NH(a 1Δ) + CO(X 1 Σ) evolves over a small barrier on S 1, estimated at 400-600 cm -1.

  7. Depletion of Caco-2 cell cholesterol disrupts barrier function by altering the detergent solubility and distribution of specific tight-junction proteins

    PubMed Central

    2004-01-01

    In the present study, we have investigated the role of cholesterol in maintaining the barrier properties of the model intestinal cell line Caco-2. We have extracted membrane cholesterol using methyl-β-cyclodextrin and demonstrated that maximally, methyl-β-cyclodextrin lowered cell cholesterol levels by 40–45%. Depletion of cell cholesterol was accompanied by an 80–90% decrease in monolayer transepithelial electrical resistance and a significant increase in the paracellular permeability of dextrans of 4, 10 and 40 kDa. The increase in dextran permeability was most pronounced for the two lower molecular mass species. In addition to the decline in the barrier properties of the monolayers, extraction of cell cholesterol produced an increase in the Triton X-100 solubility of claudin 3, claudin 4 and occludin, and the loss of all three proteins from the plasma membrane (tight junctions). In contrast, removal of cholesterol had no detectable influence on the detergent solubility or morphological distribution of claudin 1. These results indicate that membrane cholesterol is a critical factor in maintaining the barrier property of epithelial monolayers. More specifically, cholesterol appears to stabilize the association of certain proteins with the tight junctions. PMID:15500448

  8. Distribution of sea snakes in the Great Barrier Reef Marine Park: observations from 10 yrs of baited remote underwater video station (BRUVS) sampling

    NASA Astrophysics Data System (ADS)

    Udyawer, Vinay; Cappo, Mike; Simpfendorfer, Colin A.; Heupel, Michelle R.; Lukoschek, Vimoksalehi

    2014-09-01

    The distributions of three species of sea snake (olive sea snake: Aipysurus laevis, spine-bellied sea snake: Lapemis curtus, and ornate sea snake: Hydrophis ocellatus) were estimated over 14° of latitude within the Great Barrier Reef Marine Park (GBRMP) using data from baited remote underwater video stations (BRUVS). A total of 2,471 deployments of BRUVS were made in a range of locations, in sites open and closed to trawl fishing. Sightings of sea snakes were analysed alongside six spatial factors [depth, relative distance across (longitude) and along (latitude) the GBRMP, proximity to land, proximity to the nearest reef, and habitat complexity] to determine the factors that most strongly influenced the distribution and abundance of sea snakes. The results showed a strong latitudinal effect on the distribution of all three sea snake species, with the highest densities and diversities occurring in central and southern GBRMP locations, while the northern Great Barrier Reef was relatively depauperate in terms of both occurrence and diversity. Shallow inshore areas were identified as key habitats for A. laevis and L. curtus, whereas deeper offshore habitats were most important for H. ocellatus. No significant difference was found in the mean number of snakes sighted per hour between sites open and closed to trawling. There was a high degree of congruence in the distribution of sea snakes estimated from the BRUVS data and results from previous trawl and underwater visual surveys, demonstrating the utility of BRUVS to estimate distribution and relative abundance in these species of sea snake at broad spatial scales in a non-extractive manner.

  9. Rhodopsin Photoactivation Dynamics Revealed by Quasi-Elastic Neutron Scattering

    NASA Astrophysics Data System (ADS)

    Bhowmik, Debsindhu; Shrestha, Utsab; Perera, Suchhithranga M. C. D.; Chawla, Udeep; Mamontov, Eugene; Brown, Michael; Chu, Xiang-Qiang

    2015-03-01

    Rhodopsin is a G-protein-coupled receptor (GPCR) responsible for vision. During photoactivation, the chromophore retinal dissociates from protein yielding the opsin apoprotein. What are the changes in protein dynamics that occur during the photoactivation process? Here, we studied the microscopic dynamics of dark-state rhodopsin and the ligand-free opsin using quasielastic neutron scattering (QENS). The QENS technique tracks individual hydrogen atom motion because of the much higher neutron scattering cross-section of hydrogen than other atoms. We used protein with CHAPS detergent hydrated with heavy water. The activation of proteins is confirmed at low temperatures up to 300 K by mean-square displacement (MSD) analysis. The QENS experiments at temperatures ranging from 220 K to 300 K clearly indicate an increase in protein dynamic behavior with temperature. The relaxation time for the ligand-bound protein rhodopsin is faster compared to opsin, which can be correlated with the photoactivation. Moreover, the protein dynamics are orders of magnitude slower than the accompanying CHAPS detergent, which unlike protein, manifests localized motions.

  10. Influence of time to achieve substrate distribution equilibrium between brain tissue and blood on quantitation of the blood-brain barrier P-glycoprotein effect.

    PubMed

    Padowski, Jeannie M; Pollack, Gary M

    2011-12-02

    Active efflux transport processes at the blood-brain barrier (BBB), such as P-glycoprotein (P-gp)-mediated efflux, can limit brain uptake of therapeutics. Accurate determination of the consequent impact on brain uptake is assumed to require sampling post-attainment of brain-to-blood distribution equilibrium. Because this approach is not always feasible, understanding the relationship between apparent degree of efflux (e.g., calculated BBB P-gp effect) and the fraction of time remaining until distribution equilibrium is achieved (FTDE) would be advantageous. This study employed simulation strategies to explore this relationship in the simplest relevant system (absence of protein binding, saturable uptake, or metabolism at the BBB). Concentration-time profiles were simulated with a 4-compartment system (blood, peripheral tissues, BBB endothelium and brain parenchyma). A unidirectional endothelium-to-blood rate constant, PS(e), represented P-gp-mediated efflux. A parameter space was selected to simulate an 18-fold P-gp effect, (K(p,brain) at distribution equilibrium in the absence [K(p,brain)=82] vs. presence [K(p,brain)=4.5] of P-gp-mediated flux), as observed for paclitaxel in P-gp-deficient vs. P-gp-competent mice. Hypothetical compounds with different P-gp effects, peripheral compartment distribution kinetics, or times to achieve distribution equilibrium were simulated by perturbing the values of relevant model parameters. P-gp effects calculated prior to attainment of distribution equilibrium may be substantially erroneous. However, reasonably accurate estimates can be obtained relatively early in the net distributional phase (under 20% error at FTDE>0.36 or 0.11 for bolus or infusion administration, respectively). Potential errors associated with non-equilibrium calculations are dependent on both P-gp-mediated and P-gp-independent components of flux across the BBB.

  11. Diffusion barriers

    NASA Technical Reports Server (NTRS)

    Nicolet, M. A.

    1983-01-01

    The choice of the metallic film for the contact to a semiconductor device is discussed. One way to try to stabilize a contact is by interposing a thin film of a material that has low diffusivity for the atoms in question. This thin film application is known as a diffusion barrier. Three types of barriers can be distinguished. The stuffed barrier derives its low atomic diffusivity to impurities that concentrate along the extended defects of a polycrystalline layer. Sacrificial barriers exploit the fact that some (elemental) thin films react in a laterally uniform and reproducible fashion. Sacrificial barriers have the advantage that the point of their failure is predictable. Passive barriers are those most closely approximating an ideal barrier. The most-studied case is that of sputtered TiN films. Stuffed barriers may be viewed as passive barriers whose low diffusivity material extends along the defects of the polycrystalline host.

  12. Improving hole injection and carrier distribution in InGaN light-emitting diodes by removing the electron blocking layer and including a unique last quantum barrier

    SciTech Connect

    Cheng, Liwen Chen, Haitao; Wu, Shudong

    2015-08-28

    The effects of removing the AlGaN electron blocking layer (EBL), and using a last quantum barrier (LQB) with a unique design in conventional blue InGaN light-emitting diodes (LEDs), were investigated through simulations. Compared with the conventional LED design that contained a GaN LQB and an AlGaN EBL, the LED that contained an AlGaN LQB with a graded-composition and no EBL exhibited enhanced optical performance and less efficiency droop. This effect was caused by an enhanced electron confinement and hole injection efficiency. Furthermore, when the AlGaN LQB was replaced with a triangular graded-composition, the performance improved further and the efficiency droop was lowered. The simulation results indicated that the enhanced hole injection efficiency and uniform distribution of carriers observed in the quantum wells were caused by the smoothing and thinning of the potential barrier for the holes. This allowed a greater number of holes to tunnel into the quantum wells from the p-type regions in the proposed LED structure.

  13. Atelectrauma disrupts pulmonary epithelial barrier integrity and alters the distribution of tight junction proteins ZO-1 and claudin 4

    PubMed Central

    Jacob, Anne-Marie

    2012-01-01

    Mechanical ventilation inevitably exposes the delicate tissues of the airways and alveoli to abnormal mechanical stresses that can induce pulmonary edema and exacerbate conditions such as acute respiratory distress syndrome. The goal of our research is to characterize the cellular trauma caused by the transient abnormal fluid mechanical stresses that arise when air is forced into a liquid-occluded airway (i.e., atelectrauma). Using a fluid-filled, parallel-plate flow chamber to model the “airway reopening” process, our in vitro study examined consequent increases in pulmonary epithelial plasma membrane rupture, paracellular permeability, and disruption of the tight junction (TJ) proteins zonula occludens-1 and claudin-4. Computational analysis predicts the normal and tangential surface stresses that develop between the basolateral epithelial membrane and underlying substrate due to the interfacial stresses acting on the apical cell membrane. These simulations demonstrate that decreasing the velocity of reopening causes a significant increase in basolateral surface stresses, particularly in the region between neighboring cells where TJs concentrate. Likewise, pulmonary epithelial wounding, paracellular permeability, and TJ protein disruption were significantly greater following slower reopening. This study thus demonstrates that maintaining a higher velocity of reopening, which reduces the damaging fluid stresses acting on the airway wall, decreases the mechanical stresses on the basolateral cell surface while protecting cells from plasma membrane rupture and promoting barrier integrity. PMID:22898551

  14. Dependence of Ozone Generation on Gas Temperature Distribution in AC Atmospheric Pressure Dielectric Barrier Discharge in Oxygen

    NASA Astrophysics Data System (ADS)

    Takahashi, Go; Akashi, Haruaki

    AC atmospheric pressure multi-filament dielectric barrier discharge in oxygen has been simulated using two dimensional fluid model. In the discharge, three kinds of streamers have been obtained. They are primary streamers, small scale streamers and secondary streamers. The primary streamers are main streamers in the discharge and the small scale streamers are formed after the ceasing of the primary streamers. And the secondary streamers are formed on the trace of the primary streamers. In these streamers, the primary and the small scale streamers are very effective to generate O(3P) oxygen atoms which are precursor of ozone. And the ozone is generated mainly in the vicinity of the dielectrics. In high gas temperature region, ozone generation decreases in general. However, increase of the O(3P) oxygen atom density in high gas temperature region compensates decrease of ozone generation rate coefficient. As a result, amount of ozone generation has not changed. But if the effect of gas temperature was neglected, amount of ozone generation increases 10%.

  15. Study of Schultz distribution to model polydispersity of microemulsion droplets

    SciTech Connect

    Kotlarchyk, M.; Stephens, R.B.; Huang, J.S.

    1988-03-24

    The authors have employed a histogram analysis method to study the spectra obtained by small-angle neutron scattering (SANS) in order to investigate the size distribution of a model water-in-oil three-component microemulsion. It is found that the often used Schultz distribution function is indeed one of the reasonable choices to represent the moderately polydispersed droplet system. Analysis based on mean spherical approximations of the SANS data and inverse Laplace transformation of quasi-elastic light scattering data, assuming a Schultz distribution, yield consistent results compared with the histogram method. The polydispersity index, ..delta..R/anti R, found in the model microemulsion is roughly constant at larger R, but increases at small R, consistent with a theory proposed by Safran.

  16. Parallax adjustment for visual comfort enhancement using the effect of parallax distribution and cross talk in parallax-barrier autostereoscopic three-dimensional display

    NASA Astrophysics Data System (ADS)

    Kim, Donghyun; Lee, Hyoung; Kim, Sung-Kyu; Sohn, Kwanghoon

    2015-12-01

    Visual discomfort is a common problem in three-dimensional (3D) videos, and this issue is the subject of many current studies. Among the methods to overcome visual discomfort presented in current research, parallax adjustment methods provide little guidance in determining the condition for parallax control. We propose a parallax adjustment based on the effects of parallax distribution and cross talk on visual comfort, where the visual comfort level is used as the adjustment parameter, in parallax-barrier-type autostereoscopic 3D displays. We use the horizontal image shift method for parallax adjustment to enhance visual comfort. The speeded-up robust feature is used to estimate the parallax distribution of 3D sequences, and the required amount for parallax control is chosen based on the predefined effect of parallax distribution and cross talk on visual comfort. To evaluate the performance of the proposed method, we used commercial 3D equipment with various intrinsic cross-talk levels. Subjective tests were conducted at the fixed optimal viewing distance for each piece of equipment. The results show that comfortable videos were generated based on the proposed parallax adjustment method.

  17. Distribution and abundance of anadromous Sea Lamprey Spawners in a fragmented stream: Current status and potential range expansion following barrier removal

    USGS Publications Warehouse

    Zydlewski, Joseph; Gardner, Cory; Coghlan Jr., Stephen M.

    2012-01-01

    Dams fragment watersheds and prevent anadromous fishes from reaching historic spawning habitat. Sedgeunkedunk Stream, a small tributary to the Penobscot River (Maine), has been the focus of efforts to reestablish marine-freshwater connectivity and restore anadromous fishes via the removal of two barriers to fish migration. Currently, Petromyzon marinus (Sea Lamprey) is the only anadromous fish known to spawn successfully in the stream downstream of the lowermost dam. Here, we describe the distribution and abundance of a spawning population of Sea Lamprey in Sedgeunkedunk Stream, prior to and in anticipation of habitat increase after the completion of one barrier removal. In 2008, we estimated the abundance of Sea Lamprey and its nests using daily stream surveys and an open-population mark-recapture model. We captured 47 Sea Lamprey and implanted each with a PIT tag so that we could track movements and nest associations of individual fish. The spawning migration began on 18 June, and the last living individual was observed on 27 June. We located 31 nests, distributed from head-of-tide to the lowermost dam; no spawners or nests were observed in the tidally influenced zone or upstream of this dam. Mean longevity in the stream and the number of nests attended were correlated with arrival date; early migrants were alive longer and attended more nests than later migrants. Males were more likely to be observed away from a nest, or attending three or more nests, than were females, which attended usually one or two nests. We observed a negative association between nest abundance and substrate cover by fine sediment. Based on their observed movements in the system, and the extent of their habitat use, we anticipate that spawning Sea Lamprey will recolonize formerly inaccessible habitat after dam removals.

  18. The consequences of air flow on the distribution of aqueous species during dielectric barrier discharge treatment of thin water layers

    NASA Astrophysics Data System (ADS)

    Tian, Wei; Lietz, Amanda M.; Kushner, Mark J.

    2016-10-01

    The desired outcomes of wet tissue treatment by dielectric barrier discharges (DBDs) strongly depend on the integrated fluences of reactive species incident onto the tissue, which are determined by power, frequency and treatment time. The reactivity produced by such plasmas is often expected to be proportional to treatment time due to the accumulation of radicals in the liquid over the tissue. However, one of the typically uncontrolled parameters in DBD treatment of liquids and tissue is gas flow, which could affect the delivery of plasma produced radicals to the tissue. Gas flow can redistribute long-lived, plasma produced gas phase species prior to solvating in the liquid, while not greatly affecting the solvation of short-lived species. Gas flow can therefore potentially be a control mechanism for tailoring the fluences of reactive species to the tissue. In this paper, we report on a computational investigation of the consequences of gas flow on treatment of liquid layers covering tissue by atmospheric DBDs by up to 100 pulses. We found that gas flow (through residence time of the gas) can control the production of gas phase species requiring many collisions to form, such as reactive nitrogen species (RNS). The resulting solvation of the RNS in turn controls the production of aqueous species such as \\text{NO}\\text{3aq}- and \\text{ONOO}\\text{aq}- (aq denotes an aqueous species). With the exception of O3 and O3aq, reactive oxygen species (ROS) are less sensitive to gas flow, and so OHaq and H2O2aq, are determined primarily by discharge properties.

  19. Historical habitat barriers prevent ring-like genetic continuity throughout the distribution of threatened Alameda Striped Racers (Coluber lateralis euryxanthus)

    USGS Publications Warehouse

    Richmond, Jonathan Q.; Wood, Dustin A.; Swaim, Karen; Fisher, Robert N.; Vandergast, Amy

    2016-01-01

    We used microsatellites and mtDNA sequences to examine the mixed effects of geophysical, habitat, and contemporary urban barriers on the genetics of threatened Alameda Striped Racers (Coluber lateralis euryxanthus), a species with close ties to declining coastal scrub and chaparral habitat in the eastern San Francisco Bay area of California. We used cluster assignments to characterize population genetic structuring with respect to land management units and approximate Bayesian analysis to rank the ability of five alternative evolutionary hypotheses to explain the inferred structure. Then, we estimated rates of contemporary and historical migration among the major clusters and measured the fit of different historical migration models to better understand the formation of the current population structure. Our results reveal a ring-like pattern of historical connectivity around the Tri-Valley area of the East Bay (i.e., San Ramon, Amador, and Livermore valleys), with clusters largely corresponding to different management units. We found no evidence of continuous gene flow throughout the ring, however, and that the main gap in continuity is centered across the Livermore Valley. Historical migration models support higher rates of gene flow away from the terminal ends of the ring on the north and south sides of the Valley, compared with rates into those areas from western sites that border the interior San Francisco Bay. We attribute the break in ring-like connectivity to the presence of unsuitable habitat within the Livermore Valley that has been reinforced by 20th century urbanization, and the asymmetry in gene flow rates to spatial constraints on movement and east–west environmental gradients influenced by the proximity of the San Francisco Bay.

  20. Distribution of two species of sea snakes, Aipysurus laevis and Emydocephalus annulatus, in the southern Great Barrier Reef: metapopulation dynamics, marine protected areas and conservation

    NASA Astrophysics Data System (ADS)

    Lukoschek, V.; Heatwole, H.; Grech, A.; Burns, G.; Marsh, H.

    2007-06-01

    Aipysurus laevis and Emydocephalus annulatus typically occur in spatially discrete populations, characteristic of metapopulations; however, little is known about the factors influencing the spatial and temporal stability of populations or whether specific conservation strategies, such as networks of marine protected areas, will ensure the persistence of species. Classification tree analyses of 35 years of distribution data (90 reefs, surveyed 1-11 times) in the southern Great Barrier Reef (GBR) revealed that longitude was a major factor determining the status of A. laevis on reefs (present = 38, absent = 38 and changed = 14). Reef exposure and reef area were also important; however, these factors did not specifically account for the population fluctuations and the recent local extinctions of A. laevis in this region. There were no relationships between the status of E. annulatus (present = 16, absent = 68 and changed = 6) and spatial or physical variables. Moreover, prior protection status of reefs did not account for the distribution of either species. Biotic factors, such as habitat and prey availability and the distribution of predators, which may account for the observed patterns of distribution, are discussed. The potential for inter-population exchange among sea snake populations is poorly understood, as is the degree of protection that will be afforded to sea snakes by the recently implemented network of No-take areas in the GBR. Data from this study provide a baseline for evaluating the responses of A. laevis and E. annulatus populations to changes in biotic factors and the degree of protection afforded on reefs within an ecosystem network of No-take marine protected areas in the southern GBR.

  1. c-Yes regulates cell adhesion at the apical ectoplasmic specialization-blood-testis barrier axis via its effects on protein recruitment and distribution.

    PubMed

    Xiao, Xiang; Mruk, Dolores D; Cheng, C Yan

    2013-01-15

    During spermatogenesis, extensive restructuring takes place at the cell-cell interface since developing germ cells migrate progressively from the basal to the adluminal compartment of the seminiferous epithelium. Since germ cells per se are not motile cells, their movement relies almost exclusively on the Sertoli cell. Nonetheless, extensive exchanges in signaling take place between these cells in the seminiferous epithelium. c-Yes, a nonreceptor protein tyrosine kinase belonging to the Src family kinases (SFKs) and a crucial signaling protein, was recently shown to be upregulated at the Sertoli cell-cell interface at the blood-testis barrier (BTB) at stages VIII-IX of the seminiferous epithelial cycle of spermatogenesis. It was also highly expressed at the Sertoli cell-spermatid interface known as apical ectoplasmic specialization (apical ES) at stage V to early stage VIII of the epithelial cycle during spermiogenesis. Herein, it was shown that the knockdown of c-Yes by RNAi in vitro and in vivo affected both Sertoli cell adhesion at the BTB and spermatid adhesion at the apical ES, causing a disruption of the Sertoli cell tight junction-permeability barrier function, germ cell loss from the seminiferous epithelium, and also a loss of spermatid polarity. These effects were shown to be mediated by changes in distribution and/or localization of adhesion proteins at the BTB (e.g., occludin, N-cadherin) and at the apical ES (e.g., nectin-3) and possibly the result of changes in the underlying actin filaments at the BTB and the apical ES. These findings implicate that c-Yes is a likely target of male contraceptive research.

  2. c-Yes regulates cell adhesion at the apical ectoplasmic specialization-blood-testis barrier axis via its effects on protein recruitment and distribution

    PubMed Central

    Xiao, Xiang; Mruk, Dolores D.

    2013-01-01

    During spermatogenesis, extensive restructuring takes place at the cell-cell interface since developing germ cells migrate progressively from the basal to the adluminal compartment of the seminiferous epithelium. Since germ cells per se are not motile cells, their movement relies almost exclusively on the Sertoli cell. Nonetheless, extensive exchanges in signaling take place between these cells in the seminiferous epithelium. c-Yes, a nonreceptor protein tyrosine kinase belonging to the Src family kinases (SFKs) and a crucial signaling protein, was recently shown to be upregulated at the Sertoli cell-cell interface at the blood-testis barrier (BTB) at stages VIII–IX of the seminiferous epithelial cycle of spermatogenesis. It was also highly expressed at the Sertoli cell-spermatid interface known as apical ectoplasmic specialization (apical ES) at stage V to early stage VIII of the epithelial cycle during spermiogenesis. Herein, it was shown that the knockdown of c-Yes by RNAi in vitro and in vivo affected both Sertoli cell adhesion at the BTB and spermatid adhesion at the apical ES, causing a disruption of the Sertoli cell tight junction-permeability barrier function, germ cell loss from the seminiferous epithelium, and also a loss of spermatid polarity. These effects were shown to be mediated by changes in distribution and/or localization of adhesion proteins at the BTB (e.g., occludin, N-cadherin) and at the apical ES (e.g., nectin-3) and possibly the result of changes in the underlying actin filaments at the BTB and the apical ES. These findings implicate that c-Yes is a likely target of male contraceptive research. PMID:23169788

  3. Barriers and benefits: implications of artificial night-lighting for the distribution of common bats in Britain and Ireland.

    PubMed

    Mathews, Fiona; Roche, Niamh; Aughney, Tina; Jones, Nicholas; Day, Julie; Baker, James; Langton, Steve

    2015-05-05

    Artificial lighting is a particular problem for animals active at night. Approximately 69% of mammal species are nocturnal, and one-third of these are bats. Due to their extensive movements-both on a nightly basis to exploit ephemeral food supplies, and during migration between roosts-bats have an unusually high probability of encountering artificial light in the landscape. This paper reviews the impacts of lighting on bats and their prey, exploring the direct and indirect consequences of lighting intensity and spectral composition. In addition, new data from large-scale surveys involving more than 265 000 bat calls at more than 600 locations in two countries are presented, showing that prevalent street-lighting types are not generally linked with increased activity of common and widespread bat species. Such bats, which are important to ecosystem function, are generally considered 'light-attracted' and likely to benefit from the insect congregations that form at lights. Leisler's bat (Nyctalus leisleri) may be an exception, being more frequent in lit than dark transects. For common pipistrelle bats (Pipistrellus pipistrellus), lighting is negatively associated with their distribution on a landscape scale, but there may be local increases in habitats with good tree cover. Research is now needed on the impacts of sky glow and glare for bat navigation, and to explore the implications of lighting for habitat matrix permeability.

  4. Barriers and benefits: implications of artificial night-lighting for the distribution of common bats in Britain and Ireland

    PubMed Central

    Mathews, Fiona; Roche, Niamh; Aughney, Tina; Jones, Nicholas; Day, Julie; Baker, James; Langton, Steve

    2015-01-01

    Artificial lighting is a particular problem for animals active at night. Approximately 69% of mammal species are nocturnal, and one-third of these are bats. Due to their extensive movements—both on a nightly basis to exploit ephemeral food supplies, and during migration between roosts—bats have an unusually high probability of encountering artificial light in the landscape. This paper reviews the impacts of lighting on bats and their prey, exploring the direct and indirect consequences of lighting intensity and spectral composition. In addition, new data from large-scale surveys involving more than 265 000 bat calls at more than 600 locations in two countries are presented, showing that prevalent street-lighting types are not generally linked with increased activity of common and widespread bat species. Such bats, which are important to ecosystem function, are generally considered ‘light-attracted’ and likely to benefit from the insect congregations that form at lights. Leisler's bat (Nyctalus leisleri) may be an exception, being more frequent in lit than dark transects. For common pipistrelle bats (Pipistrellus pipistrellus), lighting is negatively associated with their distribution on a landscape scale, but there may be local increases in habitats with good tree cover. Research is now needed on the impacts of sky glow and glare for bat navigation, and to explore the implications of lighting for habitat matrix permeability. PMID:25780236

  5. Vehicle barrier

    DOEpatents

    Hirsh, Robert A.

    1991-01-01

    A vehicle security barrier which can be conveniently placed across a gate opening as well as readily removed from the gate opening to allow for easy passage. The security barrier includes a barrier gate in the form of a cable/gate member in combination with laterally attached pipe sections fixed by way of the cable to the gate member and lateral, security fixed vertical pipe posts. The security barrier of the present invention provides for the use of cable restraints across gate openings to provide necessary security while at the same time allowing for quick opening and closing of the gate areas without compromising security.

  6. Ecology of the ciguatera causing dinoflagellates from the Northern Great Barrier Reef: changes in community distribution and coastal eutrophication.

    PubMed

    Skinner, Mark P; Lewis, Richard J; Morton, Steve

    2013-12-15

    Ciguatera fish poisoning (CFP) is known to be caused by the ciguatoxins from the dinoflagellate genus Gambierdiscus, however, there is the potential for other toxins such as okadaic acid and dinophysistoxins from the genus Prorocentrum, and palytoxin from the genus Ostreopsis, to contaminate seafood. These genera may also be indicators of ecosystem health and potentially impact on coral reef ecosystems and the role they may play in the succession of coral to macroalgae dominated reefs has not been researched. Sixteen GBR field sites spanning inshore, mid-lagoon and outer lagoon (offshore) regions were studied. Samples were collected from September 2006 to December 2007 and abundance of benthic dinoflagellates on different host macroalgae and concentration of nutrients present in the water column were determined. The maximum abundance of Prorocentrum, Ostreopsis and Gambierdiscus found was 112, 793 and 50 cells per gram wet weight of host macroalgae, respectively. The average level of Dissolved Inorganic Nitrogen (DIN) in the water column across all sites (0.03 mg/L) was found to be more than double the threshold critical value (0.013 mg/L) for healthy coral reefs. Compared to a previous study 1984, there is evidence of a major shift in the distribution and abundance of these dinoflagellates. Inshore reefs have either of Prorocentrum (as at Green Island) or Ostreopsis (as at Magnetic Island) dominating the macroalgal surface niche which was once dominated by Gambierdiscus, whilst at offshore regions Gambierdiscus is still dominant. This succession may be linked to the ongoing eutrophication of the GBR lagoon and have consequences for the sources of toxins for ongoing cases of ciguatera.

  7. From simple to complex reactions: Nuclear collisions near the Coulomb barrier

    SciTech Connect

    Rehm, K.E.

    1992-12-01

    Collisions between two heavy nuclei produce a diverse spectrum of reaction modes which is much wider than that observed in light ion studies. For the latter case, two processes are observed: direct reactions and compound nucleus formation. Heavy ion reaction studies on the other hand have identified additional processes such as deep-inelastic scattering, incomplete fusion and quasi-fission reactions. While the boundaries between the various processes are usually not well defined, it is generally accepted that with increasing overlap of the two nuclei the interaction evolves from distant collisions where only elastic scattering and Coulomb excitation processes occur, through grazing-type collisions associated with quasi-elastic reactions to deep-inelastic and fusion-fission processes requiring a substantial nuclear overlap. Varying the bombarding energy is a convenient way to change the overlap of the two nuclei. Measurements of excitation functions can thus probe the onset and the interplay of the various reaction modes. Experiments at bombarding energies in the vicinity of the Coulomb barrier are particularly suited for comparisons with theoretical predictions since the small number of degrees of freedom involved in the interaction greatly simplifies the calculations. In the first part of this contribution a short overview is given on the status of heavy ion reaction studies at energies in the vicinity of the Coulomb barrier. In the second part two experiments, one involving simple and the other studying complex reactions, are discussed in more detail.

  8. From simple to complex reactions: Nuclear collisions near the Coulomb barrier

    SciTech Connect

    Rehm, K.E.

    1992-01-01

    Collisions between two heavy nuclei produce a diverse spectrum of reaction modes which is much wider than that observed in light ion studies. For the latter case, two processes are observed: direct reactions and compound nucleus formation. Heavy ion reaction studies on the other hand have identified additional processes such as deep-inelastic scattering, incomplete fusion and quasi-fission reactions. While the boundaries between the various processes are usually not well defined, it is generally accepted that with increasing overlap of the two nuclei the interaction evolves from distant collisions where only elastic scattering and Coulomb excitation processes occur, through grazing-type collisions associated with quasi-elastic reactions to deep-inelastic and fusion-fission processes requiring a substantial nuclear overlap. Varying the bombarding energy is a convenient way to change the overlap of the two nuclei. Measurements of excitation functions can thus probe the onset and the interplay of the various reaction modes. Experiments at bombarding energies in the vicinity of the Coulomb barrier are particularly suited for comparisons with theoretical predictions since the small number of degrees of freedom involved in the interaction greatly simplifies the calculations. In the first part of this contribution a short overview is given on the status of heavy ion reaction studies at energies in the vicinity of the Coulomb barrier. In the second part two experiments, one involving simple and the other studying complex reactions, are discussed in more detail.

  9. Double exponential I-V characteristics and double Gaussian distribution of barrier heights in (Au/Ti)/Al2O3/ n-GaAs (MIS)-type Schottky barrier diodes in wide temperature range

    NASA Astrophysics Data System (ADS)

    Güçlü, Çiğdem Ş.; Özdemir, Ahmet Faruk; Altindal, Şemsettin

    2016-12-01

    In this study, current conduction mechanisms of the sample (Au/Ti)/Al2O3/ n-GaAs were investigated in detail using current-voltage (I-V) measurements in the temperature range of 80-380 K. The semilogarithmic I-V plots reveal two distinct linear regions with different slopes between 0.07-0.30 and 0.30-0.69 V which are called as Region I (RI) and Region II (RII), respectively. The ideality factor ( n) and zero-bias barrier height (Φ_{{bo}}) were found to be strong functions of temperature and voltage. In both regions, as the temperature increases, Φ_{{bo}} increases, whereas the value of n decreases. The high value of n at low temperatures is an evidence of deviation from thermionic emission, and it cannot be explained solely by tunneling mechanism, the existence of surface states and interfacial layer. Therefore, the Φ_{{bo}} versus q/kT plots were drawn for two linear regions of lnI-V plots, and these plots also revealed two distinct linear regions with different slopes between two temperature regions of 80-170 and 200-380 K which are called as low- and high-temperature range (LTR and HTR), respectively. Such behavior of these plots confirmed the existence of double Gaussian distribution (DGD) in the samples which in turn has mean barrier heights bar{Φ}_{{bo}} and standard deviations ( σ s). These values were obtained from the intercept and slope of these plots as 0.38 eV and 0.061 V for LTR and as 0.88 eV and 0.142 V for HTR (in RI), whereas they were obtained as 0.37 eV and 0.061 V for LTR and as 0.92 eV and 0.148 V for HTR (in RII), respectively. Thus, the modified ln( I s/ T 2)- q 2 σ s 2 /2 k 2 T 2 versus q/ kT plots were drawn, and the values of (bar{Φ}_{{bo}}) and effective Richardson constant ( A *) were extracted from the intercept and slope of these plots as 0.39 eV and 7.07 A/cm2 K2 for LTR and as 0.92 eV and 8.158 A/cm2 K2 for HTR (in RI), whereas they were extracted as 0.38 eV and 7.92 A/cm2 K2 for LTR and as 0.94 eV and 4.66 A/cm2 K2 for HTR

  10. U-Th age distribution of coral fragments from multiple rubble ridges within the Frankland Islands, Great Barrier Reef: Implications for past storminess history

    NASA Astrophysics Data System (ADS)

    Liu, Entao; Zhao, Jian-xin; Feng, Yue-xing; Leonard, Nicole D.; Clark, Tara R.; Roff, George

    2016-07-01

    Prograded coral rubble ridges have been widely used as archives for reconstructing long-term storm or storminess history. Chronologies of ridge systems in previous studies are often based on a limited number of low-resolution radiocarbon or optically-stimulated luminescence (OSL) ages per ridge (usually only one age per ridge), which carry intrinsic age uncertainties and make interpretation of storm histories problematic. To test the fidelity of storm ridges as palaeo-storm archives, we used high-precision U-Th dating to examine whether different samples from a single ridge are temporally constrained. We surveyed three transects of ridge systems from two continental islands (Normanby Island and High Island) within the Frankland Islands, Great Barrier Reef (GBR), and obtained 96 U-Th dates from coral rubble samples collected from within and between different ridges. Our results revealed significant differences in age ranges between the two islands. The steeper and more defined rubble ridges present on Normanby Island revealed that the majority of U-Th ages (over 60%) from a single ridge clustered within a narrow age range (∼100 years). By contrast, the lower and less defined ridges on High Island, which were more likely formed during both storm and non-storm high-energy events, revealed significant scatter in age distribution (>>200 years) with no notable clustering. The narrower age ranges obtained from the steeper and more defined rubble ridges suggest that previous approaches of using either limited samples from a single ridge or low-precision dating methods to establish chronologies are generally valid at centennial to millennial timescales, although caution must be taken to use such approaches for storm history reconstruction on shorter timescales (e.g. decadal). The correlation between U-Th mortality ages of coral rubble and historical stormy periods highlights the possibility of using coral rubble age distribution from rubble ridges to reconstruct the long

  11. The double Gaussian distribution of barrier heights in Al/TiO2/p-Si (metal-insulator-semiconductor) structures at low temperatures

    NASA Astrophysics Data System (ADS)

    Pakma, O.; Serin, N.; Serin, T.; Altındal, Ş.

    2008-07-01

    The current-voltage (I-V) characteristics of Al/TiO2/p-Si metal-insulator-semiconductor (MIS) structures have been investigated in the temperature range of 80-300 K. An abnormal decrease in the zero bias barrier height (BH) (ϕb0) and an increase in the ideality factor (n ) with decreasing temperature have been explained on the basis of the thermionic emission (TE) theory with Gaussian distribution (GD) of the BHs due to the BH inhomogeneities. The temperature dependence of the experimental I-V data of the Al/TiO2/p-Si (MIS) structures has revealed the existence of a double GD with mean BH values (ϕ¯b0) of 1.089 and 0.622 eV and standard deviations σs of 0.137 and 0.075 V, respectively. Thus, the modified ln(I0/T2)-q2σ02/2(kT)2 versus q /kT plot gives ϕ¯b0 values and Richardson constants (A∗) as 1.108 and 0.634 eV and 31.42 and 23.83 A/cm2 K2, respectively, without using the temperature coefficient of the BH. The value of the effective Richardson constant of 31.42 A/cm2 K2 is very close to the theoretical value of 32 A/cm2 K2 for p-Si. As a result, the temperature dependence of the forward bias I-V characteristics of the Al/TiO2/p-Si (MIS) structure can be successfully explained on the basis of the TE mechanism with a double GD of the BHs.

  12. Isomer-selective distribution of 3-n-butylphthalide (NBP) hydroxylated metabolites, 3-hydroxy-NBP and 10-hydroxy-NBP, across the rat blood-brain barrier

    PubMed Central

    Diao, Xing-xing; Zhong, Kan; Li, Xiu-li; Zhong, Da-fang; Chen, Xiao-yan

    2015-01-01

    Aim: To investigate the mechanisms underlying the isomer-selective distribution of 3-n-butylphthalide (NBP) hydroxylated metabolites, 3-hydroxy-NBP (3-OH-NBP) and 10-hydroxy-NBP (10-OH-NBP), across the blood brain barrier (BBB). Methods: After oral administration of NBP (20 mg/kg) to rats, the pharmacokinetics of two major hydroxylated metabolites, 3-OH-NBP and 10-OH-NBP, in plasma and brains were investigated. Plasma and brain protein binding of 3-OH-NBP and 10-OH-NBP was also assessed. To evaluate the influences of major efflux transporters, rats were pretreated with the P-gp inhibitor tariquidar (10 mg/kg, iv) and BCRP inhibitor pantoprazole (40 mg/kg, iv), then received 3-OH-NBP (12 mg/kg, iv) or 10-OH-NBP (3 mg/kg, iv). The metabolic profile of NBP was investigated in rat brain homogenate. Results: After NBP administration, the plasma exposure of 3-OH-NBP was 4.64 times that of 10-OH-NBP, whereas the brain exposure of 3-OH-NBP was only 11.8% of 10-OH-NBP. In the rat plasma, 60%±5.2% of 10-OH-NBP was unbound to proteins versus only 22%±2.3% of 3-OH-NBP being unbound, whereas in the rat brain, free fractions of 3-OH-NBP and 10-OH-NBP were 100%±9.7% and 49.9%±14.1%, respectively. In the rats pretreated with tariquidar and pantoprazole, the unbound partition coefficient Kp,uu of 3-OH-NBP was significantly increased, while that of 10-OH-NBP showed a slight but not statistically significant increase. Incubation of rat brain homogenate with NBP yielded 3-OH-NBP but not 10-OH-NBP. Conclusion: The isomer-selective distribution of 10-OH-NBP and 3-OH-NBP across the BBB of rats is mainly attributed to the differences in plasma and brain protein binding and the efflux transport of 3-OH-NBP. The abundant 10-OH-NBP is not generated in rat brains. PMID:26567730

  13. Elastic scattering measurement for the system 17O + 58Ni at Coulomb barrier energies with silicon strip detectors exploiting ASIC electronics

    NASA Astrophysics Data System (ADS)

    Signorini, C.; Mazzocco, M.; Molini, P.; Pierroutsakou, D.; Boiano, C.; Manea, C.; Strano, E.; Torresi, D.; Di Meo, P.; Nicoletto, M.; Boiano, A.; Glodariu, T.; Grebosz, J.; Guglielmetti, A.; La Commara, M.; Parascandolo, C.; Parascandolo, L.; Sandoli, M.; Soramel, F.; Stroe, L.; Toniolo, N.; Veronese, F.

    2013-03-01

    The quasi elastic scattering of a 17O projectile from a 58Ni target has been studied at beam energies ranging from 42.5 to 55.0 MeV in 2.5 MeV steps. The total reaction cross sections were derived from the measured angular distributions by using an optical model fit within the coupled-channel code FRESCO. These cross sections are very similar to those measured for 17F (loosely bound by 0.6 MeV), mirror nucleus of 17O (tightly bound by 4.14 MeV). This outcome points out that, in this energy range, the small binding energy of the 17F valence proton has negligible influence onto the reactivity of such a loosely bound projectile, contrary to simple expectations, and to what observed for other loosely bound nuclei. The reaction dynamics seems to be influenced mainly by the Coulomb interaction which is similar for both mirror projectiles.

  14. In situ determination of the pore opening point during wet-chemical etching of the barrier layer of porous anodic aluminum oxide: nonuniform impurity distribution in anodic oxide.

    PubMed

    Han, Hee; Park, Sang-Joon; Jang, Jong Shik; Ryu, Hyun; Kim, Kyung Joong; Baik, Sunggi; Lee, Woo

    2013-04-24

    Wet-chemical etching of the barrier oxide layer of anodic aluminum oxide (AAO) was systematically investigated by using scanning electron microscopy (SEM), secondary ion mass spectrometry (SIMS), and a newly devised experimental setup that allows accurate in situ determination of the pore opening point during chemical etching of the barrier oxide layer. We found that opening of the barrier oxide layer by wet-chemical etching can be significantly influenced by anodization time (tanodi). According to secondary ion mass spectrometry (SIMS) analysis, porous anodic aluminum oxide (AAO) samples formed by long-term anodization contained a lower level of anionic impurity in the barrier oxide layer compared to the short-term anodized one and consequently exhibited retarded opening of the barrier oxide layer during the wet-chemical etching. The observed compositional dependence on the anodization time (tanodi) in the barrier oxide layer is attributed to the progressive decrease of the electrolyte concentration upon anodization. The etching rate of the outer pore wall at the bottom part is lower than that of the one at the top part due to the lower level of impurity content in that region. This indicates that a concentration gradient of anionic impurity in the outer pore wall oxide may be established along both the vertical and radial directions of cylindrical pores. Apart from the effect of electrolyte concentration on the chemical composition of the barrier oxide layer, significantly decreased current density arising from the lowered concentration of electrolyte during the long-term anodization (~120 h) was found to cause disordering of pores. The results of the present work are expected to provide viable information not only for practical applications of nanoporous AAO in nanotechnology but also for thorough understanding of the self-organized formation of oxide nanopores during anodization.

  15. CD24 regulated gene expression and distribution of tight junction proteins is associated with altered barrier function in oral epithelial monolayers

    PubMed Central

    Ye, Ping; Nadkarni, Mangala A; Simonian, Mary; Hunter, Neil

    2009-01-01

    Background Control of intercellular penetration of microbial products is critical for the barrier function of oral epithelia. We demonstrated that CD24 is selectively and strongly expressed in the cells of the epithelial attachment to the tooth and the epithelial lining of the diseased periodontal pocket and studies in vitro showed that CD24 regulated expression of the epithelial intercellular adhesion protein E-cadherin. Results In the present study, the barrier function of oral epithelial cell monolayers to low molecular weight dextran was assayed as a model for the normal physiological function of the epithelial attachment to limit ingress of microbial products from oral microbial biofilms. Paracellular transfer of low molecular weight dextran across monolayers of oral epithelial cells was specifically decreased following incubation with anti-CD24 peptide antibody whereas passage of dextran across the monolayer was increased following silencing of mRNA for CD24. Changes in barrier function were related to the selective regulation of the genes encoding zonula occludens-1, zonula occludens-2 and occludin, proteins implicated in tight junctions. More particularly, enhanced barrier function was related to relocation of these proteins to the cell periphery, compatible with tight junctions. Conclusion CD24 has the constitutive function of maintaining expression of selected genes encoding tight junction components associated with a marginal barrier function of epithelial monolayers. Activation by binding of an external ligand to CD24 enhances this expression but is also effective in re-deployment of tight junction proteins that is aligned with enhanced intercellular barrier function. These results establish the potential of CD24 to act as a potent regulator of the intercellular barrier function of epithelia in response to local microbial ecology. PMID:19138432

  16. Language barriers

    PubMed Central

    Ngwakongnwi, Emmanuel; Hemmelgarn, Brenda R.; Musto, Richard; King-Shier, Kathryn M.; Quan, Hude

    2012-01-01

    Abstract Objective To assess use of regular medical doctors (RMDs), as well as awareness and use of telephone health lines or telehealth services, by official language minorities (OLMs) in Canada. Design Analysis of data from the 2006 postcensal survey on the vitality of OLMs. Setting Canada. Participants In total, 7691 English speakers in Quebec and 12 376 French speakers outside Quebec, grouped into those who experienced language barriers and those with no language barriers. Main outcome measures Health services utilization (HSU) by the presence of language barriers; HSU measures included having an RMD, use of an RMD’s services, and awareness of and use of telephone health lines or telehealth services. Multivariable models examined the associations between HSU and language barriers. Results After adjusting for age and sex, English speakers residing in Quebec with limited proficiency in French were less likely to have RMDs (adjusted odds ratio [AOR] 0.66, 95% CI 0.50 to 0.87) and to use the services of their RMDs (AOR 0.65, 95% CI 0.50 to 0.86), but were more likely to be aware of the existence of (AOR 1.50, 95% CI 1.16 to 1.93) and to use (AOR 1.43, 95% CI 0.97 to 2.11) telephone health lines or telehealth services. This pattern of having and using RMDs and telehealth services was not observed for French speakers residing outside of Quebec. Conclusion Overall we found variation in HSU among the language barrier populations, with lower use observed in Quebec. Age older than 45 years, male sex, being married or in common-law relationships, and higher income were associated with having RMDs for OLMs. PMID:23242902

  17. Distributions.

    ERIC Educational Resources Information Center

    Bowers, Wayne A.

    This monograph was written for the Conference of the New Instructional Materials in Physics, held at the University of Washington in summer, 1965. It is intended for students who have had an introductory college physics course. It seeks to provide an introduction to the idea of distributions in general, and to some aspects of the subject in…

  18. Barrier Formation

    PubMed Central

    Lyaruu, D.M.; Medina, J.F.; Sarvide, S.; Bervoets, T.J.M.; Everts, V.; DenBesten, P.; Smith, C.E.; Bronckers, A.L.J.J.

    2014-01-01

    Enamel fluorosis is an irreversible structural enamel defect following exposure to supraoptimal levels of fluoride during amelogenesis. We hypothesized that fluorosis is associated with excess release of protons during formation of hypermineralized lines in the mineralizing enamel matrix. We tested this concept by analyzing fluorotic enamel defects in wild-type mice and mice deficient in anion exchanger-2a,b (Ae2a,b), a transmembrane protein in maturation ameloblasts that exchanges extracellular Cl− for bicarbonate. Defects were more pronounced in fluorotic Ae2a,b−/− mice than in fluorotic heterozygous or wild-type mice. Phenotypes included a hypermineralized surface, extensive subsurface hypomineralization, and multiple hypermineralized lines in deeper enamel. Mineral content decreased in all fluoride-exposed and Ae2a,b−/− mice and was strongly correlated with Cl−. Exposure of enamel surfaces underlying maturation-stage ameloblasts to pH indicator dyes suggested the presence of diffusion barriers in fluorotic enamel. These results support the concept that fluoride stimulates hypermineralization at the mineralization front. This causes increased release of protons, which ameloblasts respond to by secreting more bicarbonates at the expense of Cl− levels in enamel. The fluoride-induced hypermineralized lines may form barriers that impede diffusion of proteins and mineral ions into the subsurface layers, thereby delaying biomineralization and causing retention of enamel matrix proteins. PMID:24170372

  19. Skin barrier disruptions in tape stripped and allergic dermatitis models have no effect on dermal penetration and systemic distribution of AHAPS-functionalized silica nanoparticles.

    PubMed

    Ostrowski, Anja; Nordmeyer, Daniel; Boreham, Alexander; Brodwolf, Robert; Mundhenk, Lars; Fluhr, Joachim W; Lademann, Jürgen; Graf, Christina; Rühl, Eckart; Alexiev, Ulrike; Gruber, Achim D

    2014-10-01

    The skin is a potential site of entry for nanoparticles (NP) but the role of disease-associated barrier disturbances on the path and extent of skin penetration of NP remains to be characterized. Silica nanoparticles (SiO2-NP) possess promising potential for various medical applications. Here, effects of different skin barrier disruptions on the penetration of N-(6-aminohexyl)-aminopropyltrimethoxysilane (AHAPS) functionalized SiO2-NP were studied. AHAPS-SiO2-NP (55±6 nm diameter) were topically applied on intact, tape stripped or on inflamed skin of SKH1 mice with induced allergic contact dermatitis for one or five consecutive days, respectively. Penetration of AHAPS-SiO2-NP through the skin was not observed regardless of the kind of barrier disruption. However, only after subcutaneous injection, AHAPS-SiO2-NP were incorporated by macrophages and transported to the regional lymph node only. Adverse effects on cells or tissues were not observed. In conclusion, AHAPS-SiO2-NP seem to not cross the normal or perturbed mouse skin. From the clinical editor: Skin is a potential site of entry for nanoparticles; however, it is poorly understood how skin diseases may alter this process. In tape-stripped skin and allergic contact dermatitis models the delivery properties of AHAPS-SiO2 nanoparticles remained unchanged, and in neither case were these NP-s able to penetrate the skin. No adverse effects were noted on the skin in these models and control mice.

  20. Differential distribution of tight junction proteins suggests a role for tanycytes in blood-hypothalamus barrier regulation in the adult mouse brain

    PubMed Central

    Mullier, Amandine; Bouret, Sébastien G.; Prevot, Vincent; Dehouck, Bénédicte

    2010-01-01

    The median eminence is one of the seven so-called circumventricular organs. It is located in the basal hypothalamus, ventral to the third ventricle and adjacent to the arcuate nucleus. This structure characteristically contains a rich capillary plexus and features a fenestrated endothelium, making it a direct target of blood-borne molecules. The median eminence also contains highly specialized ependymal cells called tanycytes which line the floor of the third ventricle. It has been hypothesized that one of the functions of these cells is to create a barrier that prevents substances in the portal capillary spaces from entering the brain. In this paper, we report on our use of immunohistochemistry to study the expression of tight junction proteins in the cells that compose the median eminence in adult mice. Our results indicate that tanycytes of the median eminence express occludin, ZO-1, and claudin 1 and 5, but not claudin 3. Remarkably, these molecules are organized as a continuous belt around the cell bodies of the tanycytes that line the ventral part of the third ventricle. In contrast, the tanycytes at the periphery of the arcuate nucleus do not express claudin 1 and instead exhibit a disorganized expression pattern of occludin, ZO-1 and claudin 5. Consistent with these observations, permeability studies using peripheral or central injections of Evans blue dye show that only the tanycytes of the median eminence are joined at their apices by functional tight junctions, whereas tanycytes located at the level of the arcuate nucleus form a permeable layer. In conclusion, this study reveals a unique expression pattern of tight junction proteins in hypothalamic tanycytes, which yields new insights into their barrier properties. PMID:20127760

  1. Differential distribution of tight junction proteins suggests a role for tanycytes in blood-hypothalamus barrier regulation in the adult mouse brain.

    PubMed

    Mullier, Amandine; Bouret, Sebastien G; Prevot, Vincent; Dehouck, Bénédicte

    2010-04-01

    The median eminence is one of the seven so-called circumventricular organs. It is located in the basal hypothalamus, ventral to the third ventricle and adjacent to the arcuate nucleus. This structure characteristically contains a rich capillary plexus and features a fenestrated endothelium, making it a direct target of blood-borne molecules. The median eminence also contains highly specialized ependymal cells called tanycytes, which line the floor of the third ventricle. It has been hypothesized that one of the functions of these cells is to create a barrier that prevents substances in the portal capillary spaces from entering the brain. In this paper, we utilize immunohistochemistry to study the expression of tight junction proteins in the cells that compose the median eminence in adult mice. Our results indicate that tanycytes of the median eminence express occludin, ZO-1, and claudin 1 and 5, but not claudin 3. Remarkably, these molecules are organized as a continuous belt around the cell bodies of the tanycytes that line the ventral part of the third ventricle. In contrast, the tanycytes at the periphery of the arcuate nucleus do not express claudin 1 and instead exhibit a disorganized expression pattern of occludin, ZO-1, and claudin 5. Consistent with these observations, permeability studies using peripheral or central injections of Evans blue dye show that only the tanycytes of the median eminence are joined at their apices by functional tight junctions, whereas tanycytes located at the level of the arcuate nucleus form a permeable layer. In conclusion, this study reveals a unique expression pattern of tight junction proteins in hypothalamic tanycytes, which yields new insights into their barrier properties.

  2. Nonclassical transport in fractal media with a diffusion barrier

    SciTech Connect

    Dvoretskaya, O. A. Kondratenko, P. S.

    2013-04-15

    We investigate the impurity transport in a randomly heterogeneous fractal medium with a diffusion barrier. The barrier is due to low permeable medium surrounding the source. The transport regimes and asymptotic (large-distance) concentration distributions are found. The presence of the diffusion barrier results in the retardation of the transport regimes at short times. As regards the asymptotic concentration distribution, the barrier influence persists for long times as well.

  3. Nanomedicine Faces Barriers

    PubMed Central

    Debbage, Paul; Thurner, Gudrun C.

    2010-01-01

    Targeted nanoparticles have the potential to improve drug delivery efficiencies by more than two orders of magnitude, from the ~ 0.1% which is common today. Most pharmacologically agents on the market today are small drug molecules, which diffuse across the body’s blood-tissue barriers and distribute not only into the lesion, but into almost all organs. Drug actions in the non-lesion organs are an inescapable part of the drug delivery principle, causing “side-effects” which limit the maximally tolerable doses and result in inadequate therapy of many lesions. Nanoparticles only cross barriers by design, so side-effects are not built into their mode of operation. Delivery rates of almost 90% have been reported. This review examines the significance of these statements and checks how far they need qualification. What type of targeting is required? Is a single targeting sufficient? What new types of clinical challenge, such as immunogenicity, might attend the use of targeted nanoparticles?

  4. Saturable Active Efflux by P-Glycoprotein and Breast Cancer Resistance Protein at the Blood-Brain Barrier Leads to Nonlinear Distribution of Elacridar to the Central Nervous System

    PubMed Central

    Sane, Ramola; Agarwal, Sagar; Mittapalli, Rajendar K.

    2013-01-01

    The study objective was to investigate factors that affect the central nervous system (CNS) distribution of elacridar. Elacridar inhibits transport mediated by P-glycoprotein (P-gp) and breast cancer resistance protein (Bcrp) and has been used to study the influence of transporters on brain distribution of chemotherapeutics. Adequate distribution of elacridar across the blood-brain barrier (BBB) and into the brain parenchyma is necessary to target tumor cells in the brain that overexpress transporters and reside behind an intact BBB. We examined the role of P-gp and Bcrp on brain penetration of elacridar using Friend leukemia virus strain B wild-type, Mdr1a/b(−/−), Bcrp1(−/−), and Mdr1a/b(−/−)Bcrp1(−/−) mice. Initially, the mice were administered 2.5 mg/kg of elacridar intravenously, and the plasma and brain concentrations were determined. The brain-to-plasma partition coefficient of elacridar in the wild-type mice was 0.82, as compared with 3.5 in Mdr1a/b(−/−) mice, 6.6 in Bcrp1(−/−) mice, and 15 in Mdr1a/b(−/−)Bcrp1(−/−) mice, indicating that both P-gp and Bcrp limit the brain distribution of elacridar. The four genotypes were then administered increasing doses of elacridar, and the CNS distribution of elacridar was determined. The observed and model predicted maximum brain-to-plasma ratios (Emax) at the highest dose were not significantly different in all genotypes. However, the ED50 was lower for Mdr1a/b(−/−) mice compared with Bcrp1(−/−) mice. These findings correlate with the relative expression of P-gp and Bcrp at the BBB in these mice and demonstrate the quantitative enhancement in elacridar CNS distribution as a function of its dose. Overall, this study provides useful concepts for future applications of elacridar as an adjuvant therapy to improve targeting of chemotherapeutic agents to tumor cells in the brain parenchyma. PMID:23397054

  5. Dynamic changes in the distribution and time course of blood-brain barrier-permeative nitroxides in the mouse head with EPR imaging: visualization of blood flow in a mouse model of ischemia.

    PubMed

    Emoto, Miho C; Sato-Akaba, Hideo; Hirata, Hiroshi; Fujii, Hirotada G

    2014-09-01

    Electron paramagnetic resonance (EPR) imaging using nitroxides as redox-sensitive probes is a powerful, noninvasive method that can be used under various physiological conditions to visualize changes in redox status that result from oxidative damage. Two blood-brain barrier-permeative nitroxides, 3-hydroxymethyl-2,2,5,5-tetramethylpyrrolidine-1-oxyl (HMP) and 3-methoxycarbonyl-2,2,5,5-tetramethylpyrrolidine-1-yloxy (MCP), have been widely used as redox-sensitive probes in the brains of small animals, but their in vivo distribution and properties have not yet been analyzed in detail. In this study, a custom-made continuous-wave three-dimensional (3D) EPR imager was used to obtain 3D EPR images of mouse heads using MCP or HMP. This EPR imager made it possible to take 3D EPR images reconstructed from data from 181 projections acquired every 60s. Using this improved EPR imager and magnetic resonance imaging, the distribution and reduction time courses of HMP and MCP were examined in mouse heads. EPR images of living mice revealed that HMP and MCP have different distributions and different time courses for entering the brain. Based on the pharmacokinetics of the reduction reactions of HMP and MCP in the mouse head, the half-lives of HMP and MCP were clearly and accurately mapped pixel by pixel. An ischemic mouse model was prepared, and the half-life of MCP was mapped in the mouse head. Compared to the half-life in control mice, the half-life of MCP in the ischemic model mouse brain was significantly increased, suggesting a shift in the redox balance. This in vivo EPR imaging method using BBB-permeative MCP is a useful noninvasive method for assessing changes in the redox status in mouse brains under oxidative stress.

  6. Puncture detecting barrier materials

    DOEpatents

    Hermes, R.E.; Ramsey, D.R.; Stampfer, J.F.; Macdonald, J.M.

    1998-03-31

    A method and apparatus for continuous real-time monitoring of the integrity of protective barrier materials, particularly protective barriers against toxic, radioactive and biologically hazardous materials has been developed. Conductivity, resistivity or capacitance between conductive layers in the multilayer protective materials is measured by using leads connected to electrically conductive layers in the protective barrier material. The measured conductivity, resistivity or capacitance significantly changes upon a physical breach of the protective barrier material. 4 figs.

  7. Puncture detecting barrier materials

    DOEpatents

    Hermes, Robert E.; Ramsey, David R.; Stampfer, Joseph F.; Macdonald, John M.

    1998-01-01

    A method and apparatus for continuous real-time monitoring of the integrity of protective barrier materials, particularly protective barriers against toxic, radioactive and biologically hazardous materials has been developed. Conductivity, resistivity or capacitance between conductive layers in the multilayer protective materials is measured by using leads connected to electrically conductive layers in the protective barrier material. The measured conductivity, resistivity or capacitance significantly changes upon a physical breach of the protective barrier material.

  8. The Barriers Project.

    ERIC Educational Resources Information Center

    Confederation Coll. of Applied Arts and Technology, Thunder Bay (Ontario).

    In 1987, the Barriers Project was initiated by Confederation College of Applied Arts and Technology to engage 31 selected community colleges in Canada in an organized self-appraisal of institutional barriers to the enrollment of part-time credit students. From the outset, colleges were encouraged to limit their investigation to barriers over which…

  9. Synthetic Eelgrass Oil Barrier

    NASA Astrophysics Data System (ADS)

    Curtis, T. G.

    2013-05-01

    Although surviving in situ micro-organisms eventually consume spilled oil, extensive inundation of shore biota by oil requires cleanup to enable ecological recovery within normal time scales. Although effective in calm seas and quiet waters, oil is advected over and under conventional curtain oil booms by wave actions and currents when seas are running. Most sorbent booms are not reusable, and are usually disposed of in landfills, creating excessive waste. A new concept is proposed for a floating oil barrier, to be positioned off vulnerable coasts, to interdict, contain, and sequester spilled oil, which can then be recovered and the barrier reused. While conventional oil boom designs rely principally on the immiscibility of oil in water and its relative buoyancy, the new concept barrier avoids the pitfalls of the former by taking advantage of the synergistic benefits of numerous fluid and material properties, including: density, buoyancy, elasticity, polarity, and surface area to volume ratio. Modeled after Zostera marina, commonly called eelgrass, the new barrier, referred to as synthetic eelgrass (SE), behaves analogously. Eelgrass has very long narrow, ribbon-like, leaves which support periphyton, a complex matrix of algae and heterotrophic microbes, which position themselves there to extract nutrients from the seawater flowing past them. In an analogous fashion, oil on, or in, seawater, which comes in contact with SE, is adsorbed on the surface and sequestered there. Secured to the bottom, in shoal waters, SE rises to the surface, and, if the tide is low enough, floats on the sea surface down wind, or down current to snare floating oil. The leaves of SE, called filaments, consist of intrinsically buoyant strips of ethylene methyl acrylate, aka EMA. EMA, made of long chain, saturated, hydrocarbon molecules with nearly homogeneous electron charge distributions, is a non-polar material which is oleophilic and hydrophobic. Oil must be in close proximity to the

  10. Extremal surface barriers

    NASA Astrophysics Data System (ADS)

    Engelhardt, Netta; Wall, Aron C.

    2014-03-01

    We present a generic condition for Lorentzian manifolds to have a barrier that limits the reach of boundary-anchored extremal surfaces of arbitrary dimension. We show that any surface with nonpositive extrinsic curvature is a barrier, in the sense that extremal surfaces cannot be continuously deformed past it. Furthermore, the outermost barrier surface has nonnegative extrinsic curvature. Under certain conditions, we show that the existence of trapped surfaces implies a barrier, and conversely. In the context of AdS/CFT, these barriers imply that it is impossible to reconstruct the entire bulk using extremal surfaces. We comment on the implications for the firewall controversy.

  11. Influence of cryomilling on the microstructural features in HVOF-sprayed NiCrAlY bond coats for thermal barrier coatings: Creation of a homogeneous distribution of nanoscale dispersoids

    NASA Astrophysics Data System (ADS)

    Ma, Kaka; Schoenung, Julie M.

    2010-10-01

    Previous research has revealed that thermal barrier coatings with cryomilled bond coats exhibit improved thermal cycling lifetime by growing a continuous and uniform oxide layer at a slower rate; yet the mechanism controlling the ultimate failure remains unclear. In an effort to provide a foundation for understanding the improved behavior, the influence of cryomilling on the microstructure of the NiCrAlY bond coat material is investigated in this article. Rather than focusing on the alumina scale formation, the microstructural features and their evolution within the high-velocity oxy-fuel (HVOF)-sprayed NiCrAlY bond coats themselves, prepared from conventional powder and cryomilled powder, were carefully compared through extensive scanning electron microscope/energy-dispersive X-ray spectroscopy characterization. In addition, the as-cryomilled NiCrAlY powder is characterized to provide evidence of the direct influence of cryomilling and to exclude the impact from the HVOF spraying. It is found that the essential change in microstructural features resulting from the cryomilling is the creation of a homogeneous distribution of ultrafine (nanoscale) Al-rich oxide/nitride dispersoids, which remain thermally stable even after exposure at 1100°C for 100 h. The TEM study on the as-cryomilled powder, prior to the HVOF spraying, indicates that some Al and Y-rich oxides are already present within the material as a direct result of the cryomilling process.

  12. Motility analysis of circularly swimming bull spermatozoa by quasi-elastic light scattering and cinematography.

    PubMed

    Craig, T; Hallett, F R; Nickel, B

    1982-04-01

    The Rayleigh-Gans-Debye approximation is used to predict the electric field autocorrelation functions of light scattered from circularly swimming bull spermatozoa. Using parameters determined from cinematography and modeling the cells as coated ellipsoids of semiaxes a = 0.5 micrometers, b = 2.3 micrometers, and c = 9.0 micrometers, we were able to obtain model spectra that mimic the data exactly. A coat is found to be a necessary attribute of the particle. It is also clear that these model functions at 15 degrees may be represented by the relatively simple function used before by Hallett et al. (1978) to fit data from circularly swimming cells, thus giving some physical meaning to these functional shapes. Because of this agreement the half-widths of experimental functions can now be interpreted in terms of an oscillatory frequency for the movement of the circularly swimming cell. The cinematographic results show a trend to chaotic behavior as the temperature of the sample is increased, with concomitant decrease in overall efficiency. This is manifested by a decrease in oscillatory frequency and translational speed.

  13. Motility analysis of circularly swimming bull spermatozoa by quasi-elastic light scattering and cinematography.

    PubMed Central

    Craig, T; Hallett, F R; Nickel, B

    1982-01-01

    The Rayleigh-Gans-Debye approximation is used to predict the electric field autocorrelation functions of light scattered from circularly swimming bull spermatozoa. Using parameters determined from cinematography and modeling the cells as coated ellipsoids of semiaxes a = 0.5 micrometers, b = 2.3 micrometers, and c = 9.0 micrometers, we were able to obtain model spectra that mimic the data exactly. A coat is found to be a necessary attribute of the particle. It is also clear that these model functions at 15 degrees may be represented by the relatively simple function used before by Hallett et al. (1978) to fit data from circularly swimming cells, thus giving some physical meaning to these functional shapes. Because of this agreement the half-widths of experimental functions can now be interpreted in terms of an oscillatory frequency for the movement of the circularly swimming cell. The cinematographic results show a trend to chaotic behavior as the temperature of the sample is increased, with concomitant decrease in overall efficiency. This is manifested by a decrease in oscillatory frequency and translational speed. PMID:7074199

  14. Water Dynamics in Shewanella oneidensis at Ambient and High Pressure using Quasi-Elastic Neutron Scattering

    PubMed Central

    Foglia, Fabrizia; Hazael, Rachael; Simeoni, Giovanna G.; Appavou, Marie-Sousai; Moulin, Martine; Haertlein, Michael; Trevor Forsyth, V.; Seydel, Tilo; Daniel, Isabelle; Meersman, Filip; McMillan, Paul F.

    2016-01-01

    Quasielastic neutron scattering (QENS) is an ideal technique for studying water transport and relaxation dynamics at pico- to nanosecond timescales and at length scales relevant to cellular dimensions. Studies of high pressure dynamic effects in live organisms are needed to understand Earth’s deep biosphere and biotechnology applications. Here we applied QENS to study water transport in Shewanella oneidensis at ambient (0.1 MPa) and high (200 MPa) pressure using H/D isotopic contrast experiments for normal and perdeuterated bacteria and buffer solutions to distinguish intracellular and transmembrane processes. The results indicate that intracellular water dynamics are comparable with bulk diffusion rates in aqueous fluids at ambient conditions but a significant reduction occurs in high pressure mobility. We interpret this as due to enhanced interactions with macromolecules in the nanoconfined environment. Overall diffusion rates across the cell envelope also occur at similar rates but unexpected narrowing of the QENS signal appears between momentum transfer values Q = 0.7–1.1 Å−1 corresponding to real space dimensions of 6–9 Å. The relaxation time increase can be explained by correlated dynamics of molecules passing through Aquaporin water transport complexes located within the inner or outer membrane structures. PMID:26738409

  15. Water Dynamics in Shewanella oneidensis at Ambient and High Pressure using Quasi-Elastic Neutron Scattering.

    PubMed

    Foglia, Fabrizia; Hazael, Rachael; Simeoni, Giovanna G; Appavou, Marie-Sousai; Moulin, Martine; Haertlein, Michael; Trevor Forsyth, V; Seydel, Tilo; Daniel, Isabelle; Meersman, Filip; McMillan, Paul F

    2016-01-07

    Quasielastic neutron scattering (QENS) is an ideal technique for studying water transport and relaxation dynamics at pico- to nanosecond timescales and at length scales relevant to cellular dimensions. Studies of high pressure dynamic effects in live organisms are needed to understand Earth's deep biosphere and biotechnology applications. Here we applied QENS to study water transport in Shewanella oneidensis at ambient (0.1 MPa) and high (200 MPa) pressure using H/D isotopic contrast experiments for normal and perdeuterated bacteria and buffer solutions to distinguish intracellular and transmembrane processes. The results indicate that intracellular water dynamics are comparable with bulk diffusion rates in aqueous fluids at ambient conditions but a significant reduction occurs in high pressure mobility. We interpret this as due to enhanced interactions with macromolecules in the nanoconfined environment. Overall diffusion rates across the cell envelope also occur at similar rates but unexpected narrowing of the QENS signal appears between momentum transfer values Q = 0.7-1.1 Å(-1) corresponding to real space dimensions of 6-9 Å. The relaxation time increase can be explained by correlated dynamics of molecules passing through Aquaporin water transport complexes located within the inner or outer membrane structures.

  16. Quasi-elastic light-scattering spectra of swimming spermatozoa. Rotational and translational effects.

    PubMed Central

    Craig, T; Hallett, F R; Nickel, B

    1979-01-01

    The electric field autocorrelation functions of light scattered from normal swimming bull spermatozoa are shown to be dependent on the mean head rotation frequency and not on the translational speed of the cells, as previously believed. This result was obtained from numerical generation of functions in which spermatozoa were modeled as Rayleigh-Gans-Debye ellipsoids having semiaxes a = 0.5 micrometer, b = 2.3 micrometer, and c = 9.0 micrometer. The magnitude of c required to achieve agreement with the experimental data is larger than the half-length of the head region of the cell. This implies that the midpiece, which also lies along c, contributes to the scattering power. Details regarding swimming trajectory and head orientation are included in the model. Analyses of the calculated functions and comparisons with experimentally determined ones suggest that at a scattering angle of 15 degrees the electric field autocorrelation function can be fit a simple Lorentzian whose half-width is inversely proportional to the scattering vector and the mean head rotational frequency. PMID:262561

  17. Population of high spin states by quasi-elastic and deep inelastic collisions

    NASA Astrophysics Data System (ADS)

    Takai, H.; Knott, C. N.; Winchell, D. F.; Saladin, J. X.; Kaplan, M. S.; de Faro, L.; Aryaeinejad, R.; Blue, R. A.; Ronningen, R. M.; Morrissey, D. J.; Lee, I. Y.; Dietzsch, O.

    1988-09-01

    The feasibility of populating high spin states using reactions induced by a 10 MeV/nucleon 22Ne beam on 170Er was studied. The experiment was carried out using a multidetector array for high resolution γ-ray spectroscopy, a 14 element sum-multiplicity spectrometer and six ΔE-E telescopes. Detailed information was obtained concerning the reaction mechanisms associated with various reaction channels. Deep inelastic collisions are shown to be a promising tool for high spin spectroscopy in regions of the chart of nuclides which are not accessible by other reactions.

  18. The excitation of high spin states with quasi-elastic and deep inelastic reactions

    SciTech Connect

    Knott, C.N.

    1988-01-01

    The feasibility of populating high spin states using reactions induced by a 220 MeV {sup 22}Ne beam on a {sup 170}Er target was studied. The experiment was carried out using a multidetector array for high resolution {gamma}-ray spectroscopy, a 14 element sum multiplicity spectrometer and six {Delta}E-E particle telescopes. Detailed information was obtained concerning the reaction mechanisms associated with various reaction channels. Deep inelastic collisions are shown to be a promising tool for high spin spectroscopy in regions of the chart of nuclides which are not accessible by other reactions.

  19. Population of high spin states by quasi-elastic and deep inelastic collisions

    SciTech Connect

    Takai, H.; Knott, C.N.; Winchell, D.F.; Saladin, J.X.; Kaplan, M.S.; de Faro, L.; Aryaeinejad, R.; Blue, R.A.; Ronningen, R.M.; Morrissey, D.J.; and others

    1988-09-01

    The feasibility of populating high spin states using reactions induced by a 10 MeV/nucleon /sup 22/Ne beam on /sup 170/Er was studied. The experiment was carried out using a multidetector array for high resolution ..gamma..-ray spectroscopy, a 14 element sum-multiplicity spectrometer and six ..delta..E-E telescopes. Detailed information was obtained concerning the reaction mechanisms associated with various reaction channels. Deep inelastic collisions are shown to be a promising tool for high spin spectroscopy in regions of the chart of nuclides which are not accessible by other reactions.

  20. Dynamics of Hydrated tRNA on Nanodiamond Surface Studied by Quasi-elastic Neutron Scattering

    NASA Astrophysics Data System (ADS)

    Dhindsa, Gurpreet; Mochalin, Vadym N.; O'Neill, Hugh; Gogotsi, Yury; Chu, Xiang Qiang

    2014-03-01

    Diamond is an outstanding material in many aspects, and nanodiamond (ND) inherits most of the superior properties of bulk diamond and delivers them at the nanoscale. ND has excellent properties that can be applied in biomedical field such as a good platform for drug delivery. In this study, we show that hydrated tRNA can be adsorbed on the surfaces of nanodiamonds and further demonstrate specific properties in its dynamics. We investigate the dynamics of the system by Quasielastic neutron scattering (QENS) technique. The dynamics of hydrated tRNA on ND surfaces exhibits a logarithmic-like decay within the time range of 10 ps to 1 ns, which has also been observed in the freestanding proteins and other biopolymers. We further compare the dynamics of tRNA hydrated with D2O on ND surface with that of freestanding hydrated tRNA molecules. Our results show that the relaxational dynamics of tRNA on ND surface is much faster than that of the freestanding tRNA molecules. This gives the hint that the folded states of tRNA is modified by ND surfaces to engage faster dynamics. The difference in the dynamics of the hydration water modified by ND is another possible reason which causes the faster dynamics in tRNA on ND surface.

  1. Coherent Dynamics of meta-Toluidine Investigated by QuasiElastic Neutron Scattering

    SciTech Connect

    Faraone, Antonio; Hong, Kunlun; Kneller, Larry; Ohl, Michael E; Copley, John R. D.

    2012-01-01

    The coherent dynamics of a typical fragile glass former, meta-toluidine, was investigated at the molecular level using quasielastic neutron scattering, with time-of-flight and neutron spin echo spectrometers. It is well known that the static structure factor of meta-toluidine shows a prepeak originating from clustering of the molecules through hydrogen bonding between the amine groups. The dynamics of meta-toluidine was measured for several values of the wavevector transfer Q, which is equivalent to an inverse length scale, in a range encompassing the prepeak and the structure factor peak. Data were collected in the temperature range corresponding to the liquid and supercooled states, down to the glass transition. At least two dynamical processes were identified. This paper focuses on the slowest relaxation process in the system, the {alpha}-relaxation, which was found to scale with the macroscopic shear viscosity at all the investigated Q values. No evidence of 'de Gennes' narrowing associated with the prepeak was observed, in contrast with what happens at the Q value corresponding to the interparticle distance. Moreover, using partially deuterated samples, the dynamics of the clusters was found to be correlated to the single-particle dynamics of the meta-toluidine molecules.

  2. Quasi-elastic neutron scattering studies on dynamics of water confined in nanoporous copper rubeanate hydrates.

    PubMed

    Yamada, Takeshi; Yonamine, Ryo; Yamada, Teppei; Kitagawa, Hiroshi; Tyagi, Madhusudan; Nagao, Michihiro; Yamamuro, Osamu

    2011-11-24

    We have investigated the mechanism of the first order transition and proton conductivity in copper rubeanate hydrates from microscopic and dynamical points of view. Three different types of neutron spectrometer-time-of-flight, backscattering, and neutron spin echo-were used to cover a wide dynamic range (1 ps to 100 ns). We found that the water molecules adsorbed in the pore are divided into "free water" having diffusion coefficients similar to those of bulk water at room temperature and "condensed water" which is about 10 times slower than bulk water owing to the interaction with the pore wall. The hydrogen atoms in the pore wall exhibited no relaxation within the measured time scales. The free water has, in the framework of the jump-diffusion model, smaller activation energy, longer residence time, and longer jump distance than bulk water. The neutron spin echo measurement revealed that the first order transition is a kind of liquid-liquid transition at which the free water is condensed on the pore surface in the low temperature phase. On cooling the condensed water, the relaxation time starts to deviate from the VFT equation around 200 K as previously observed in the water confined in nanoporous silicates. The free water plays an important role as the proton carrier but the proton conductivity is mainly governed by the number of protons provided into the adsorbed water from the pore wall.

  3. Production of Z0 bosons in elastic and quasi-elastic ep collisions at HERA

    NASA Astrophysics Data System (ADS)

    ZEUS Collaboration; Abramowicz, H.; Abt, I.; Adamczyk, L.; Adamus, M.; Aggarwal, R.; Antonelli, S.; Antonioli, P.; Antonov, A.; Arneodo, M.; Arslan, O.; Aushev, V.; Aushev, Y.; Bachynska, O.; Bamberger, A.; Barakbaev, A. N.; Barbagli, G.; Bari, G.; Barreiro, F.; Bartosik, N.; Bartsch, D.; Basile, M.; Behnke, O.; Behr, J.; Behrens, U.; Bellagamba, L.; Bertolin, A.; Bhadra, S.; Bindi, M.; Blohm, C.; Bokhonov, V.; Bołd, T.; Bondarenko, K.; Boos, E. G.; Borras, K.; Boscherini, D.; Bot, D.; Brock, I.; Brownson, E.; Brugnera, R.; Brümmer, N.; Bruni, A.; Bruni, G.; Brzozowska, B.; Bussey, P. J.; Bylsma, B.; Caldwell, A.; Capua, M.; Carlin, R.; Catterall, C. D.; Chekanov, S.; Chwastowski, J.; Ciborowski, J.; Ciesielski, R.; Cifarelli, L.; Cindolo, F.; Contin, A.; Cooper-Sarkar, A. M.; Coppola, N.; Corradi, M.; Corriveau, F.; Costa, M.; D'Agostini, G.; Dal Corso, F.; del Peso, J.; Dementiev, R. K.; De Pasquale, S.; Derrick, M.; Devenish, R. C. E.; Dobur, D.; Dolgoshein, B. A.; Dolinska, G.; Doyle, A. T.; Drugakov, V.; Durkin, L. S.; Dusini, S.; Eisenberg, Y.; Ermolov, P. F.; Eskreys, A.; Fang, S.; Fazio, S.; Ferrando, J.; Ferrero, M. I.; Figiel, J.; Foster, B.; Gach, G.; Galas, A.; Gallo, E.; Garfagnini, A.; Geiser, A.; Gialas, I.; Gizhko, A.; Gladilin, L. K.; Gladkov, D.; Glasman, C.; Gogota, O.; Golubkov, Yu. A.; Göttlicher, P.; Grabowska-Bołd, I.; Grebenyuk, J.; Gregor, I.; Grigorescu, G.; Grzelak, G.; Gueta, O.; Guzik, M.; Gwenlan, C.; Haas, T.; Hain, W.; Hamatsu, R.; Hart, J. C.; Hartmann, H.; Hartner, G.; Hilger, E.; Hochman, D.; Hori, R.; Hüttmann, A.; Ibrahim, Z. A.; Iga, Y.; Ingbir, R.; Ishitsuka, M.; Jakob, H.-P.; Januschek, F.; Jones, T. W.; Jüngst, M.; Kadenko, I.; Kahle, B.; Kananov, S.; Kanno, T.; Karshon, U.; Karstens, F.; Katkov, I. I.; Kaur, M.; Kaur, P.; Keramidas, A.; Khein, L. A.; Kim, J. Y.; Kisielewska, D.; Kitamura, S.; Klanner, R.; Klein, U.; Koffeman, E.; Kondrashova, N.; Kononenko, O.; Kooijman, P.; Korol, Ie.; Korzhavina, I. A.; Kotański, A.; Kötz, U.; Kowalski, H.; Kuprash, O.; Kuze, M.; Lee, A.; Levchenko, B. B.; Levy, A.; Libov, V.; Limentani, S.; Ling, T. Y.; Lisovyi, M.; Lobodzinska, E.; Lohmann, W.; Löhr, B.; Lohrmann, E.; Long, K. R.; Longhin, A.; Lontkovskyi, D.; Lukina, O. Yu.; Maeda, J.; Magill, S.; Makarenko, I.; Malka, J.; Mankel, R.; Margotti, A.; Marini, G.; Martin, J. F.; Mastroberardino, A.; Mattingly, M. C. K.; Melzer-Pellmann, I.-A.; Mergelmeyer, S.; Miglioranzi, S.; Mohamad Idris, F.; Monaco, V.; Montanari, A.; Morris, J. D.; Mujkic, K.; Musgrave, B.; Nagano, K.; Namsoo, T.; Nania, R.; Nigro, A.; Ning, Y.; Nobe, T.; Notz, D.; Nowak, R. J.; Nuncio-Quiroz, A. E.; Oh, B. Y.; Okazaki, N.; Olkiewicz, K.; Onishchuk, Yu.; Papageorgiu, K.; Parenti, A.; Paul, E.; Pawlak, J. M.; Pawlik, B.; Pelfer, P. G.; Pellegrino, A.; Perlański, W.; Perrey, H.; Piotrzkowski, K.; Pluciński, P.; Pokrovskiy, N. S.; Polini, A.; Proskuryakov, A. S.; Przybycień, M.; Raval, A.; Reeder, D. D.; Reisert, B.; Ren, Z.; Repond, J.; Ri, Y. D.; Robertson, A.; Roloff, P.; Rubinsky, I.; Ruspa, M.; Sacchi, R.; Samson, U.; Sartorelli, G.; Savin, A. A.; Saxon, D. H.; Schioppa, M.; Schlenstedt, S.; Schleper, P.; Schmidke, W. B.; Schneekloth, U.; Schönberg, V.; Schörner-Sadenius, T.; Schwartz, J.; Sciulli, F.; Shcheglova, L. M.; Shehzadi, R.; Shimizu, S.; Singh, I.; Skillicorn, I. O.; Słomiński, W.; Smith, W. H.; Sola, V.; Solano, A.; Son, D.; Sosnovtsev, V.; Spiridonov, A.; Stadie, H.; Stanco, L.; Stefaniuk, N.; Stern, A.; Stewart, T. P.; Stifutkin, A.; Stopa, P.; Suchkov, S.; Susinno, G.; Suszycki, L.; Sztuk-Dambietz, J.; Szuba, D.; Szuba, J.; Tapper, A. D.; Tassi, E.; Terrón, J.; Theedt, T.; Tiecke, H.; Tokushuku, K.; Tomaszewska, J.; Trusov, V.; Tsurugai, T.; Turcato, M.; Turkot, O.; Tymieniecka, T.; Vázquez, M.; Verbytskyi, A.; Viazlo, O.; Vlasov, N. N.; Walczak, R.; Wan Abdullah, W. A. T.; Whitmore, J. J.; Wichmann, K.; Wiggers, L.; Wing, M.; Wlasenko, M.; Wolf, G.; Wolfe, H.; Wrona, K.; Yagües-Molina, A. G.; Yamada, S.; Yamazaki, Y.; Yoshida, R.; Youngman, C.; Zabiegalov, O.; Żarnecki, A. F.; Zawiejski, L.; Zenaiev, O.; Zeuner, W.; Zhautykov, B. O.; Zhmak, N.; Zichichi, A.; Zolkapli, Z.; Zotkin, D. S.

    2013-01-01

    The production of Z0 bosons in the reaction ep→eZ0p, where p stands for a proton or a low-mass nucleon resonance, has been studied in ep collisions at HERA using the ZEUS detector. The analysis is based on a data sample collected between 1996 and 2007, amounting to 496 pb of integrated luminosity. The Z0 was measured in the hadronic decay mode. The elasticity of the events was ensured by a cut on ηmax<3.0, where ηmax is the maximum pseudorapidity of energy deposits in the calorimeter defined with respect to the proton beam direction. A signal was observed at the Z0 mass. The cross section of the reaction ep→eZ0p was measured to be σ(ep→eZ0p)=0.13±0.06(stat.)±0.01(syst.) pb, in agreement with the Standard Model prediction of 0.16 pb. This is the first measurement of Z0 production in ep collisions.

  4. Production of Z0 bosons in elastic and quasi-elastic ep collisions at HERA

    NASA Astrophysics Data System (ADS)

    Abramowicz, H.; Abt, I.; Adamczyk, L.; Adamus, M.; Aggarwal, R.; Antonelli, S.; Antonioli, P.; Antonov, A.; Arneodo, M.; Arslan, O.; Aushev, V.; Aushev, Y.; Bachynska, O.; Bamberger, A.; Barakbaev, A. N.; Barbagli, G.; Bari, G.; Barreiro, F.; Bartosik, N.; Bartsch, D.; Basile, M.; Behnke, O.; Behr, J.; Behrens, U.; Bellagamba, L.; Bertolin, A.; Bhadra, S.; Bindi, M.; Blohm, C.; Bokhonov, V.; Bołd, T.; Bondarenko, K.; Boos, E. G.; Borras, K.; Boscherini, D.; Bot, D.; Brock, I.; Brownson, E.; Brugnera, R.; Brümmer, N.; Bruni, A.; Bruni, G.; Brzozowska, B.; Bussey, P. J.; Bylsma, B.; Caldwell, A.; Capua, M.; Carlin, R.; Catterall, C. D.; Chekanov, S.; Chwastowski, J.; Ciborowski, J.; Ciesielski, R.; Cifarelli, L.; Cindolo, F.; Contin, A.; Cooper-Sarkar, A. M.; Coppola, N.; Corradi, M.; Corriveau, F.; Costa, M.; D'Agostini, G.; Dal Corso, F.; del Peso, J.; Dementiev, R. K.; De Pasquale, S.; Derrick, M.; Devenish, R. C. E.; Dobur, D.; Dolgoshein, B. A.; Dolinska, G.; Doyle, A. T.; Drugakov, V.; Durkin, L. S.; Dusini, S.; Eisenberg, Y.; Ermolov, P. F.; Eskreys, A.; Fang, S.; Fazio, S.; Ferrando, J.; Ferrero, M. I.; Figiel, J.; Foster, B.; Gach, G.; Galas, A.; Gallo, E.; Garfagnini, A.; Geiser, A.; Gialas, I.; Gizhko, A.; Gladilin, L. K.; Gladkov, D.; Glasman, C.; Gogota, O.; Golubkov, Yu. A.; Göttlicher, P.; Grabowska-Bołd, I.; Grebenyuk, J.; Gregor, I.; Grigorescu, G.; Grzelak, G.; Gueta, O.; Guzik, M.; Gwenlan, C.; Haas, T.; Hain, W.; Hamatsu, R.; Hart, J. C.; Hartmann, H.; Hartner, G.; Hilger, E.; Hochman, D.; Hori, R.; Hüttmann, A.; Ibrahim, Z. A.; Iga, Y.; Ingbir, R.; Ishitsuka, M.; Jakob, H.-P.; Januschek, F.; Jones, T. W.; Jüngst, M.; Kadenko, I.; Kahle, B.; Kananov, S.; Kanno, T.; Karshon, U.; Karstens, F.; Katkov, I. I.; Kaur, M.; Kaur, P.; Keramidas, A.; Khein, L. A.; Kim, J. Y.; Kisielewska, D.; Kitamura, S.; Klanner, R.; Klein, U.; Koffeman, E.; Kondrashova, N.; Kononenko, O.; Kooijman, P.; Korol, Ie.; Korzhavina, I. A.; Kotański, A.; Kötz, U.; Kowalski, H.; Kuprash, O.; Kuze, M.; Lee, A.; Levchenko, B. B.; Levy, A.; Libov, V.; Limentani, S.; Ling, T. Y.; Lisovyi, M.; Lobodzinska, E.; Lohmann, W.; Löhr, B.; Lohrmann, E.; Long, K. R.; Longhin, A.; Lontkovskyi, D.; Lukina, O. Yu.; Maeda, J.; Magill, S.; Makarenko, I.; Malka, J.; Mankel, R.; Margotti, A.; Marini, G.; Martin, J. F.; Mastroberardino, A.; Mattingly, M. C. K.; Melzer-Pellmann, I.-A.; Mergelmeyer, S.; Miglioranzi, S.; Mohamad Idris, F.; Monaco, V.; Montanari, A.; Morris, J. D.; Mujkic, K.; Musgrave, B.; Nagano, K.; Namsoo, T.; Nania, R.; Nigro, A.; Ning, Y.; Nobe, T.; Notz, D.; Nowak, R. J.; Nuncio-Quiroz, A. E.; Oh, B. Y.; Okazaki, N.; Olkiewicz, K.; Onishchuk, Yu.; Papageorgiu, K.; Parenti, A.; Paul, E.; Pawlak, J. M.; Pawlik, B.; Pelfer, P. G.; Pellegrino, A.; Perlański, W.; Perrey, H.; Piotrzkowski, K.; Pluciński, P.; Pokrovskiy, N. S.; Polini, A.; Proskuryakov, A. S.; Przybycień, M.; Raval, A.; Reeder, D. D.; Reisert, B.; Ren, Z.; Repond, J.; Ri, Y. D.; Robertson, A.; Roloff, P.; Rubinsky, I.; Ruspa, M.; Sacchi, R.; Samson, U.; Sartorelli, G.; Savin, A. A.; Saxon, D. H.; Schioppa, M.; Schlenstedt, S.; Schleper, P.; Schmidke, W. B.; Schneekloth, U.; Schönberg, V.; Schörner-Sadenius, T.; Schwartz, J.; Sciulli, F.; Shcheglova, L. M.; Shehzadi, R.; Shimizu, S.; Singh, I.; Skillicorn, I. O.; Słomiński, W.; Smith, W. H.; Sola, V.; Solano, A.; Son, D.; Sosnovtsev, V.; Spiridonov, A.; Stadie, H.; Stanco, L.; Stefaniuk, N.; Stern, A.; Stewart, T. P.; Stifutkin, A.; Stopa, P.; Suchkov, S.; Susinno, G.; Suszycki, L.; Sztuk-Dambietz, J.; Szuba, D.; Szuba, J.; Tapper, A. D.; Tassi, E.; Terrón, J.; Theedt, T.; Tiecke, H.; Tokushuku, K.; Tomaszewska, J.; Trusov, V.; Tsurugai, T.; Turcato, M.; Turkot, O.; Tymieniecka, T.; Vázquez, M.; Verbytskyi, A.; Viazlo, O.; Vlasov, N. N.; Walczak, R.; Wan Abdullah, W. A. T.; Whitmore, J. J.; Wichmann, K.; Wiggers, L.; Wing, M.; Wlasenko, M.; Wolf, G.; Wolfe, H.; Wrona, K.; Yagües-Molina, A. G.; Yamada, S.; Yamazaki, Y.; Yoshida, R.; Youngman, C.; Zabiegalov, O.; Żarnecki, A. F.; Zawiejski, L.; Zenaiev, O.; Zeuner, W.; Zhautykov, B. O.; Zhmak, N.; Zichichi, A.; Zolkapli, Z.; Zotkin, D. S.; ZEUS Collaboration

    2013-01-01

    The production of Z0 bosons in the reaction ep → eZ0p (*), where p (*) stands for a proton or a low-mass nucleon resonance, has been studied in ep collisions at HERA using the ZEUS detector. The analysis is based on a data sample collected between 1996 and 2007, amounting to 496 pb-1 of integrated luminosity. The Z0 was measured in the hadronic decay mode. The elasticity of the events was ensured by a cut on ηmax < 3.0, where ηmax is the maximum pseudorapidity of energy deposits in the calorimeter defined with respect to the proton beam direction. A signal was observed at the Z0 mass. The cross section of the reaction ep → eZ0p (*) was measured to be σ (ep → eZ0p (*)) = 0.13 ± 0.06 (stat.) ± 0.01 (syst.) pb, in agreement with the Standard Model prediction of 0.16 pb. This is the first measurement of Z0 production in ep collisions.

  5. Multilayer moisture barrier

    DOEpatents

    Pankow, Joel W; Jorgensen, Gary J; Terwilliger, Kent M; Glick, Stephen H; Isomaki, Nora; Harkonen, Kari; Turkulainen, Tommy

    2015-04-21

    A moisture barrier, device or product having a moisture barrier or a method of fabricating a moisture barrier having at least a polymer layer, and interfacial layer, and a barrier layer. The polymer layer may be fabricated from any suitable polymer including, but not limited to, fluoropolymers such as polyethylene terephthalate (PET) or polyethylene naphthalate (PEN), or ethylene-tetrafluoroethylene (ETFE). The interfacial layer may be formed by atomic layer deposition (ALD). In embodiments featuring an ALD interfacial layer, the deposited interfacial substance may be, but is not limited to, Al.sub.2O.sub.3, AlSiO.sub.x, TiO.sub.2, and an Al.sub.2O.sub.3/TiO.sub.2 laminate. The barrier layer associated with the interfacial layer may be deposited by plasma enhanced chemical vapor deposition (PECVD). The barrier layer may be a SiO.sub.xN.sub.y film.

  6. Barriers to screening mammography.

    PubMed

    Sarma, Elizabeth A

    2015-01-01

    Breast cancer (BRCA) is the second most commonly diagnosed cancer among women in the USA, and mammography is an effective means for the early detection of BRCA. Identifying the barriers to screening mammography can inform research, policy and practice aiming to increase mammography adherence. A literature review was conducted to determine common barriers to screening mammography adherence. PsycINFO and PubMed databases were searched to identify studies published between 2000 and 2012 that examined barriers associated with reduced mammography adherence. Three thematic groups of barriers, based on social ecology, were identified from the literature: healthcare system-level, social and individual-level barriers. Researchers must consider screening behaviour in context and, therefore, should simultaneously consider each level of barriers when attempting to understand screening behaviour and create interventions to increase mammography adherence.

  7. Transforming Education: Overcoming Barriers.

    ERIC Educational Resources Information Center

    David, Jane L.; Goren, Paul D.

    Barriers to progress in educational reform exist inside and outside the education system. Some arise where new practices encounter traditional expectations and boundaries, but others go much deeper than education, such as poverty, racism, local political conflicts, and human resistance to change. The following five categories of barriers are…

  8. OVERCOMING CULTURAL BARRIERS.

    ERIC Educational Resources Information Center

    BARRUTIA, RICHARD

    THE RELATIONSHIP OF LANGUAGE DEVELOPMENT TO CULTURAL BARRIERS AND THE TEACHING OF FOREIGN LANGUAGES IS DISCUSSED IN THIS ARTICLE. VARIOUS VIEWS OF THE MEANING OF CULTURE ARE MENTIONED IN ORDER TO SINGLE OUT ANTHROPOLOGICAL CULTURE AS A MAIN FOCAL POINT. INTERCULTURAL DIFFERENCES ARE SPELLED OUT WITH EXAMPLES OF LINGUISTIC BARRIERS, AND…

  9. Penetration resistant barrier

    DOEpatents

    Hoover, William R.; Mead, Keith E.; Street, Henry K.

    1977-01-01

    The disclosure relates to a barrier for resisting penetration by such as hand tools and oxy-acetylene cutting torches. The barrier comprises a layer of firebrick, which is preferably epoxy impregnated sandwiched between inner and outer layers of steel. Between the firebrick and steel are layers of resilient rubber-like filler.

  10. Liquid metal hydrogen barriers

    DOEpatents

    Grover, George M.; Frank, Thurman G.; Keddy, Edward S.

    1976-01-01

    Hydrogen barriers which comprise liquid metals in which the solubility of hydrogen is low and which have good thermal conductivities at operating temperatures of interest. Such barriers are useful in nuclear fuel elements containing a metal hydride moderator which has a substantial hydrogen dissociation pressure at reactor operating temperatures.

  11. Catalytic thermal barrier coatings

    DOEpatents

    Kulkarni, Anand A.; Campbell, Christian X.; Subramanian, Ramesh

    2009-06-02

    A catalyst element (30) for high temperature applications such as a gas turbine engine. The catalyst element includes a metal substrate such as a tube (32) having a layer of ceramic thermal barrier coating material (34) disposed on the substrate for thermally insulating the metal substrate from a high temperature fuel/air mixture. The ceramic thermal barrier coating material is formed of a crystal structure populated with base elements but with selected sites of the crystal structure being populated by substitute ions selected to allow the ceramic thermal barrier coating material to catalytically react the fuel-air mixture at a higher rate than would the base compound without the ionic substitutions. Precious metal crystallites may be disposed within the crystal structure to allow the ceramic thermal barrier coating material to catalytically react the fuel-air mixture at a lower light-off temperature than would the ceramic thermal barrier coating material without the precious metal crystallites.

  12. Cultural Barriers to Multinational C2 Decision Making

    DTIC Science & Technology

    2000-01-01

    present barriers to successful coalition command and control. The challenge is compounded by distributed decision making that characterizes many...national culture differences will need to be managed. Coalition Command and Control: The Nature of the Challenge There are many barriers to effective...easiest to fixate on behavioral differences and customs. We understand the barriers created by language. We recognize that others eat different food

  13. Retractable barrier strip

    DOEpatents

    Marts, Donna J.; Barker, Stacey G.; Wowczuk, Andrew; Vellenoweth, Thomas E.

    2002-01-01

    A portable barrier strip having retractable tire-puncture spikes for puncturing a vehicle tire. The tire-puncture spikes have an armed position for puncturing a tire and a retracted position for not puncturing a tire. The strip comprises a plurality of barrier blocks having the tire-puncture spikes removably disposed in a shaft that is rotatably disposed in each barrier block. The plurality of barrier blocks hare hingedly interconnected by complementary hinges integrally formed into the side of each barrier block which allow the strip to be rolled for easy storage and retrieval, but which prevent irregular or back bending of the strip. The shafts of adjacent barrier blocks are pivotally interconnected via a double hinged universal joint to accommodate irregularities in a roadway surface and to transmit torsional motion of the shaft from block to block. A single flexshaft cable is connected to the shaft of an end block to allow a user to selectively cause the shafts of a plurality of adjacently connected barrier blocks to rotate the tire-puncture spikes to the armed position for puncturing a vehicle tire, and to the retracted position for not puncturing the tire. The flexshaft is provided with a resiliently biased retracting mechanism, and a release latch for allowing the spikes to be quickly retracted after the intended vehicle tire is punctured.

  14. Vehicle barrier systems

    SciTech Connect

    Sena, P.A.

    1986-01-01

    The ground vehicle is one of the most effective tools available to an adversary force. Vehicles can be used to penetrate many types of perimeter barriers, transport equipment and personnel rapidly over long distances, and deliver large amounts of explosives directly to facilities in suicide missions. The function of a vehicle barrier system is to detain or disable a defined threat vehicle at a selected distance from a protected facility. Numerous facilities are installing, or planning to install, vehicle barrier systems and many of these facilities are requesting guidance to do so adequately. Therefore, vehicle barriers are being evaluated to determine their stopping capabilities so that systems can be designed that are both balanced and capable of providing a desired degree of protection. Equally important, many of the considerations that should be taken into account when establishing a vehicle barrier system have been identified. These considerations which pertain to site preparation, barrier selection, system integration and operation, and vehicle/barrier interaction, are discussed in this paper. 2 tabs.

  15. Vehicle barrier systems

    SciTech Connect

    Sena, P.A.

    1986-01-01

    The ground vehicle is one of the most effective tools available to an adversary force. Vehicles can be used to penetrate many types of perimeter barriers, transport equipment, and personnel rapidly over long distances, and deliver large amounts of explosives directly to facilities in suicide missions. The function of a vehicle barrier system is to detain or disable a defined threat vehicle at a selected distance from a protected facility. Numerous facilities are installing, or planning to install, vehicle barrier systems and many of these facilities are requesting guidance to do so adequately. Therefore, vehicle barriers are being evaluated to determine their stopping capabilities so that systems can be designed that are both balanced and capable of providing a desired degree of protection. Equally important, many of the considerations that should be taken into account when establishing a vehicle barrier system have been identified. These considerations which pertain to site preparation, barrier selection, system integration and operation, and vehicle/barrier interaction, are discussed in this paper.

  16. Vehicle barrier systems

    SciTech Connect

    Sena, P.A.

    1986-01-01

    The ground vehicle is one of the most effective tools available to an adversary force. Vehicles can be used to penetrate many types of perimeter barriers, transport equipment and personnel rapidly over long distances, and deliver large amounts of explosives directly to facilities in suicide missions. The function of a vehicle barrier system is to detain or disable a defined threat vehicle at a selected distance from a protected facility. Numerous facilities are installing, or planning to install, vehicle barrier systems and many of these facilities are requesting guidance to do so adequately. Therefore, vehicle barriers are being evaluated to determine their stopping capabilities so that systems can be designed that are both balanced and capable of providing a desired degree of protection. Equally important, many of the considerations that should be taken into account when establishing a vehicle barrier system have been identified. These considerations which pertain to site preparation, barrier selection, system integration and operation, and vehicle/barrier interaction, are discussed in this paper.

  17. Counseling for barrier methods.

    PubMed

    Guest, F

    1979-08-01

    Despite the less serious risks of barrier methods (diaphragm, condom, foam, and other vaginal spermicides) compared with other contraceptive methods, many family planning programs find that only a minority of patients accept barrier methods as primary contraceptive choices. Some misconceptions patients have about barrier methods are: 1) they are less effective compared to oral contraceptives or IUDs, 2) foam kills sperm that are still inside a man's body, and 3) you need a prescription to use a barrier method. This article provides the following information about barrier methods to use in counseling patients: 1) couples who use barriers exactly right all the time can achieve high levels of effectiveness; average effectiveness rates for longterm users are 87% for the diaphragm, 90% for condoms, and 85% for foam; 2) noncontraceptive benefits include protection against sexually transmitted infections; barrier methods are nonhormonal and nonsurgical and posters to that effect are recommended for the counselor's waiting room; 3) patients need to be encouraged to use barrier methods even though they are less convenient in certain situations; support groups could improve patients' success; 4) counselors may be able to help users by giving them permission not to use the method on certain cycle days as a tradeoff for diligent use at other times thereby relieving the contraceptive burden; 5) recurring problems that patients should be warned about include waiting too late to put on a condom, running out of foam, using too little cream with the diaphragm, and douching after intercourse; and 6) improper care and storage problems which could cause failure are storing latex near heat, separating the foam bottle from the applicator, using old condoms and diaphragms, and suppositories that fail to melt. Patients' 2 biggest complaints about vaginal suppositories are messiness and irritation and switching to condoms can help. The last page of the article is a one page handout for

  18. Recycler barrier RF buckets

    SciTech Connect

    Bhat, C.M.; /Fermilab

    2011-03-01

    The Recycler Ring at Fermilab uses a barrier rf systems for all of its rf manipulations. In this paper, I will give an overview of historical perspective on barrier rf system, the longitudinal beam dynamics issues, aspects of rf linearization to produce long flat bunches and methods used for emittance measurements of the beam in the RR barrier rf buckets. Current rf manipulation schemes used for antiproton beam stacking and longitudinal momentum mining of the RR beam for the Tevatron collider operation are explained along with their importance in spectacular success of the Tevatron luminosity performance.

  19. Thermal Barrier Coatings

    NASA Technical Reports Server (NTRS)

    1993-01-01

    In order to reduce heat transfer between a hot gas heat source and a metallic engine component, a thermal insulating layer of material is placed between them. This thermal barrier coating is applied by plasma spray processing the thin films. The coating has been successfully employed in aerospace applications for many years. Lewis Research Center, a leader in the development engine components coating technology, has assisted Caterpillar, Inc. in applying ceramic thermal barrier coatings on engines. Because these large engines use heavy fuels containing vanadium, engine valve life is sharply decreased. The barrier coating controls temperatures, extends valve life and reduces operating cost. Additional applications are currently under development.

  20. A mechanism study of sound wave-trapping barriers.

    PubMed

    Yang, Cheng; Pan, Jie; Cheng, Li

    2013-09-01

    The performance of a sound barrier is usually degraded if a large reflecting surface is placed on the source side. A wave-trapping barrier (WTB), with its inner surface covered by wedge-shaped structures, has been proposed to confine waves within the area between the barrier and the reflecting surface, and thus improve the performance. In this paper, the deterioration in performance of a conventional sound barrier due to the reflecting surface is first explained in terms of the resonance effect of the trapped modes. At each resonance frequency, a strong and mode-controlled sound field is generated by the noise source both within and in the vicinity outside the region bounded by the sound barrier and the reflecting surface. It is found that the peak sound pressures in the barrier's shadow zone, which correspond to the minimum values in the barrier's insertion loss, are largely determined by the resonance frequencies and by the shapes and losses of the trapped modes. These peak pressures usually result in high sound intensity component impinging normal to the barrier surface near the top. The WTB can alter the sound wave diffraction at the top of the barrier if the wavelengths of the sound wave are comparable or smaller than the dimensions of the wedge. In this case, the modified barrier profile is capable of re-organizing the pressure distribution within the bounded domain and altering the acoustic properties near the top of the sound barrier.

  1. Distributed Wind Energy in Idaho

    SciTech Connect

    Gardner, John; Johnson, Kathryn; Haynes, Todd; Seifert, Gary

    2009-01-31

    This project is a research and development program aimed at furthering distributed wind technology. In particular, this project addresses some of the barriers to distributed wind energy utilization in Idaho.

  2. Optimistic barrier synchronization

    NASA Technical Reports Server (NTRS)

    Nicol, David M.

    1992-01-01

    Barrier synchronization is fundamental operation in parallel computation. In many contexts, at the point a processor enters a barrier it knows that it has already processed all the work required of it prior to synchronization. The alternative case, when a processor cannot enter a barrier with the assurance that it has already performed all the necessary pre-synchronization computation, is treated. The problem arises when the number of pre-sychronization messages to be received by a processor is unkown, for example, in a parallel discrete simulation or any other computation that is largely driven by an unpredictable exchange of messages. We describe an optimistic O(log sup 2 P) barrier algorithm for such problems, study its performance on a large-scale parallel system, and consider extensions to general associative reductions as well as associative parallel prefix computations.

  3. [Vascular endothelial Barrier Function].

    PubMed

    Ivanov, A N; Puchinyan, D M; Norkin, I A

    2015-01-01

    Endothelium is an important regulator of selective permeability of the vascular wall for different molecules and cells. This review summarizes current data on endothelial barrier function. Endothelial glycocalyx structure, its function and role in the molecular transport and leukocytes migration across the endothelial barrier are discussed. The mechanisms of transcellular transport of macromolecules and cell migration through endothelial cells are reviewed. Special section of this article addresses the structure and function of tight and adherens endothelial junction, as well as their importance for the regulation of paracellular transport across the endothelial barrier. Particular attention is paid to the signaling mechanism of endothelial barrier function regulation and the factors that influence on the vascular permeability.

  4. Great Barrier Reef

    Atmospheric Science Data Center

    2013-04-16

    article title:  Australia's Great Barrier Reef     View Larger Image ... reef, but a vast maze of reefs, passages, and coral cays (islands that are part of the reef). This nadir true-color image was acquired by ...

  5. Barrier Island Hazard Mapping.

    ERIC Educational Resources Information Center

    Pilkey, Orrin H.; Neal, William J.

    1980-01-01

    Describes efforts to evaluate and map the susceptibility of barrier islands to damage from storms, erosion, rising sea levels and other natural phenomena. Presented are criteria for assessing the safety and hazard potential of island developments. (WB)

  6. Retractable barrier strip

    DOEpatents

    Marts, D.J.; Barker, S.G.; McQueen, M.A.

    1996-04-16

    A portable barrier strip is described having retractable tire-puncture means for puncturing a vehicle tire. The tire-puncture means, such as spikes, have an armed position for puncturing a tire and a retracted position for not puncturing a tire. The strip comprises a plurality of barrier blocks having the tire-puncture means removably disposed in a shaft that is rotatably disposed in each barrier block. The shaft removably and pivotally interconnects the plurality of barrier blocks. Actuation cables cause the shaft to rotate the tire-puncture means to the armed position for puncturing a vehicle tire and to the retracted position for not puncturing the tire. Each tire-puncture means is received in a hollow-bed portion of its respective barrier block when in the retracted position. The barrier strip rests in its deployed position and substantially motionless as a tire rolls thereon and over. The strip is rolled up for retrieval, portability, and storage purposes, and extended and unrolled in its deployed position for use. 13 figs.

  7. Retractable barrier strip

    DOEpatents

    Marts, Donna J.; Barker, Stacey G.; McQueen, Miles A.

    1996-01-01

    A portable barrier strip having retractable tire-puncture means for puncturing a vehicle tire. The tire-puncture means, such as spikes, have an armed position for puncturing a tire and a retracted position for not puncturing a tire. The strip comprises a plurality of barrier blocks having the tire-puncture means removably disposed in a shaft that is rotatably disposed in each barrier block. The shaft removably and pivotally interconnects the plurality of barrier blocks. Actuation cables cause the shaft to rotate the tire-puncture means to the armed position for puncturing a vehicle tire and to the retracted position for not puncturing the tire. Each tire-puncture means is received in a hollow-bed portion of its respective barrier block when in the retracted position. The barrier strip rests stable in its deployed position and substantially motionless as a tire rolls thereon and over. The strip is rolled up for retrieval, portability, and storage purposes, and extended and unrolled in its deployed position for use.

  8. Convective mixing in formations with horizontal barriers

    NASA Astrophysics Data System (ADS)

    Elenius, Maria T.; Gasda, Sarah E.

    2013-12-01

    It has been shown that convective mixing in porous media flow is important for applications such as saltwater intrusion and geological storage of carbon dioxide. In the latter case, dissolution from the injected phase to the resident brine is assisted by convective mixing, which leads to enhanced storage security through reduced buoyancy. Here, we focus on the effect of horizontal barriers on the efficiency of convective mixing. Previous investigations of the effect of heterogeneity on mixing efficiency have focused on random permeability fields or barriers of small extent compared to the intrinsic finger wavelength. The effect of horizontal barriers of larger extent, such as mudstone inclusions or thin shale deposits, has not been given sufficient attention. We perform detailed numerical investigations to represent the continuous solution of this problem in semi-infinite domains with barriers arranged in a periodic manner. The results show that mass flux into the domain, which is a measure of the efficiency of redistribution of the solute, is inversely proportional to the barrier length and proportional to the horizontal and vertical aperture between the barriers, for the cases studied. The flow structure is complex, and it depends not only on the total area of barriers but also largely on the distribution of barriers. Therefore, neither simple analytical models nor simple upscaling methods that lack information about the flow paths, can be used to predict the behavior. However, we compute the effective vertical permeability by flow-based upscaling and show that it can be used to directly obtain a first-order approximation to the mass flux into the domain.

  9. Noise control by sonic crystal barriers made of recycled materials.

    PubMed

    Sánchez-Dehesa, José; Garcia-Chocano, Victor M; Torrent, Daniel; Cervera, Francisco; Cabrera, Suitberto; Simon, Francisco

    2011-03-01

    A systematic study of noise barriers based on sonic crystals made of cylinders that use recycled materials like absorbing component is reported here. The barriers consist of only three rows of perforated metal shells filled with rubber crumb. Measurements of reflectance and transmittance by these barriers are reported. Their attenuation properties result from a combination of sound absorption by the rubber crumb and reflection by the periodic distribution of scatterers. It is concluded that the porous cylinders can be used as building blocks whose physical parameters can be optimized in order to design efficient barriers adapted to different noisy environments.

  10. Vacuum barrier for excimer lasers

    DOEpatents

    Shurter, Roger P.

    1992-01-01

    A barrier for separating the vacuum area of a diode from the pressurized gas area of an excimer laser. The barrier is a composite material comprising layers of a metal such as copper, along with layers of polyimide, and a matrix of graphite fiber yarns impregnated with epoxy. The barrier is stronger than conventional foil barriers, and allows greater electron throughput.

  11. Vacuum barrier for excimer lasers

    DOEpatents

    Shurter, R.P.

    1992-09-15

    A barrier for separating the vacuum area of a diode from the pressurized gas area of an excimer laser. The barrier is a composite material comprising layers of a metal such as copper, along with layers of polyimide, and a matrix of graphite fiber yarns impregnated with epoxy. The barrier is stronger than conventional foil barriers, and allows greater electron throughput. 3 figs.

  12. Micro heat barrier

    DOEpatents

    Marshall, Albert C.; Kravitz, Stanley H.; Tigges, Chris P.; Vawter, Gregory A.

    2003-08-12

    A highly effective, micron-scale micro heat barrier structure and process for manufacturing a micro heat barrier based on semiconductor and/or MEMS fabrication techniques. The micro heat barrier has an array of non-metallic, freestanding microsupports with a height less than 100 microns, attached to a substrate. An infrared reflective membrane (e.g., 1 micron gold) can be supported by the array of microsupports to provide radiation shielding. The micro heat barrier can be evacuated to eliminate gas phase heat conduction and convection. Semi-isotropic, reactive ion plasma etching can be used to create a microspike having a cusp-like shape with a sharp, pointed tip (<0.1 micron), to minimize the tip's contact area. A heat source can be placed directly on the microspikes. The micro heat barrier can have an apparent thermal conductivity in the range of 10.sup.-6 to 10.sup.-7 W/m-K. Multiple layers of reflective membranes can be used to increase thermal resistance.

  13. Method of installing subsurface barrier

    SciTech Connect

    Nickelson, Reva A.; Richardson, John G.; Kostelnik, Kevin M.; Sloan, Paul A.

    2007-10-09

    Systems, components, and methods relating to subterranean containment barriers. Laterally adjacent tubular casings having male interlock structures and multiple female interlock structures defining recesses for receiving a male interlock structure are used to create subterranean barriers for containing and treating buried waste and its effluents. The multiple female interlock structures enable the barriers to be varied around subsurface objects and to form barrier sidewalls. The barrier may be used for treating and monitoring a zone of interest.

  14. Intestinal Barrier and Behavior.

    PubMed

    Julio-Pieper, M; Bravo, J A

    2016-01-01

    The intestinal barrier function contributes to gut homeostasis by modulating absorption of water, electrolytes, and nutrients from the lumen into the circulation while restricting the passage of noxious luminal substances and microorganisms. Chronic conditions such as rheumatoid arthritis, inflammatory bowel disease, and celiac disease are associated to intestinal barrier dysfunction. Here, the hypothesis is that a leaky intestinal wall allowing for indiscriminate passage of intraluminal compounds to the vascular compartment could in turn lead to systemic inflammation. An increasing number of studies are now investigating the association between gut permeability and CNS disorders, under the premise that translocation of intestinal luminal contents could affect CNS function, either directly or indirectly. Still, it is unknown whether disruption of intestinal barrier is a causative agent or a consequence in these situations. Here, we discuss the latest evidence pointing to an association between increased gut permeability and disrupted behavioral responses.

  15. Skin barrier in rosacea.

    PubMed

    Addor, Flavia Alvim Sant'Anna

    2016-01-01

    Recent studies about the cutaneous barrier demonstrated consistent evidence that the stratum corneum is a metabolically active structure and also has adaptive functions, may play a regulatory role in the inflammatory response with activation of keratinocytes, angiogenesis and fibroplasia, whose intensity depends primarily on the intensity the stimulus. There are few studies investigating the abnormalities of the skin barrier in rosacea, but the existing data already show that there are changes resulting from inflammation, which can generate a vicious circle caused a prolongation of flare-ups and worsening of symptoms. This article aims to gather the most relevant literature data about the characteristics and effects of the state of the skin barrier in rosacea.

  16. Skin barrier in rosacea*

    PubMed Central

    Addor, Flavia Alvim Sant'Anna

    2016-01-01

    Recent studies about the cutaneous barrier demonstrated consistent evidence that the stratum corneum is a metabolically active structure and also has adaptive functions, may play a regulatory role in the inflammatory response with activation of keratinocytes, angiogenesis and fibroplasia, whose intensity depends primarily on the intensity the stimulus. There are few studies investigating the abnormalities of the skin barrier in rosacea, but the existing data already show that there are changes resulting from inflammation, which can generate a vicious circle caused a prolongation of flare-ups and worsening of symptoms. This article aims to gather the most relevant literature data about the characteristics and effects of the state of the skin barrier in rosacea. PMID:26982780

  17. Thermal barrier coating system

    NASA Technical Reports Server (NTRS)

    Stecura, S. (Inventor)

    1984-01-01

    A high temperature oxidation resistant, thermal barrier coating system is disclosed for a nickel cobalt, or iron base alloy substrate. An inner metal bond coating contacts the substrate, and a thermal barrier coating covers the bond coating. NiCrAlR, FeCrAlR, and CoCrAlR alloys are satisfactory as bond coating compositions where R=Y or Yb. These alloys contain, by weight, 24.9-36.7% chromium, 5.4-18.5% aluminum, and 0.05 to 1.55% yttrium or 0.05 to 0.53% ytterbium. The coatings containing ytterbium are preferred over those containing yttrium. An outer thermal barrier coating of partial stabilized zirconium oxide (zirconia) which is between 6% and 8%, by weight, of yttrium oxide (yttria) covers the bond coating. Partial stabilization provides a material with superior durability. Partially stabilized zirconia consists of mixtures of cubic, tetragonal, and monoclinic phases.

  18. Ice barrier construction

    SciTech Connect

    Finucane, R. G.; Jahns, H. O.

    1985-06-18

    A method is provided for constructing spray ice barriers to protect offshore structures in a frigid body of water from mobile ice, waves and currents. Water is withdrawn from the body of water and is sprayed through ambient air which is below the freezing temperature of the water so that a substantial amount of the water freezes as it passes through the air. The sprayed water is directed to build up a mass of ice having a size and shape adapted to protect the offshore structure. Spray ice barriers can also be constructed for the containment of pollutant spills.

  19. Barriers to cancer screening.

    PubMed

    Womeodu, R J; Bailey, J E

    1996-01-01

    Many barriers to cancer screening have been summarized and discussed. Barriers have been documented in all patient populations, but some groups such as ethnic minorities and the elderly face unique barriers. The barriers to cancer screening, are multifactorial, but much of the responsibility for change must lie with health care providers and the health care delivery industry. This is not to free the patient of all responsibility, but some significant barriers are beyond their direct control. Take, for example, socioeconomic status, disease knowledge, and culturally related perceptions and myths about cancer detection and treatment. The health care industry must do a better job identifying and overcoming these barriers. The significant effects of provider counseling and advice must not be underestimated. Patients must first be advised, and then further actions must be taken if they reject the screening advice. Did they refuse adherence to recommendations because they do not view themselves as susceptible, because of overwhelming personal barriers, or because of a fatalistic attitude toward cancer detection and treatment? If that is the case, physicians and health care institutions must attempt to change perceptions, educate, and personalize the message so that patients accept their disease susceptibility [table: see text]. Multiple patient and provider risk factors have been identified that can be used to target patients particularly at high risk for inadequate cancer screening and providers at high risk for performing inadequate screening. Research has clearly demonstrated the effectiveness of interventions to improve tracking of patient and physician compliance with screening recommendations. Further research is needed to show the impact of managed-care penetration and payer status on screening efforts, and incentive schemes need to be tested that reward institutions and third-party payers who develop uniform standards and procedures for cancer screening. The

  20. Thermal Barrier Coating Workshop

    NASA Technical Reports Server (NTRS)

    Brindley, W. J. (Compiler); Lee, W. Y. (Compiler); Goedjen, J. G. (Compiler); Dapkunas, S. J. (Compiler)

    1995-01-01

    This document contains the agenda and presentation abstracts for the Thermal Barrier Coating Workshop, sponsored by NASA, DOE, and NIST. The workshop covered thermal barrier coating (TBC) issues related to applications, processing, properties, and modeling. The intent of the workshop was to highlight the state of knowledge on TBC's and to identify critical gaps in knowledge that may hinder TBC use in advanced applications. The workshop goals were achieved through presentations by 22 speakers representing industry, academia, and government as well as through extensive discussion periods.

  1. Thermal barrier coating system

    NASA Technical Reports Server (NTRS)

    Stecura, S.; Leibert, C. H. (Inventor)

    1977-01-01

    A coating system which contains a bond coating and a thermal barrier coating is applied to metal surfaces such as turbine blades and provides both low thermal conductivity and improved adherence when exposed to high temperature gases or liquids. The bond coating contains NiCrAlY and the thermal barrier coating contains a reflective oxide. The reflective oxides ZrO2-Y2O3 and ZrO2-MgO have demonstrated significant utility in high temperature turbine applications.

  2. A double barrier memristive device

    PubMed Central

    Hansen, M.; Ziegler, M.; Kolberg, L.; Soni, R.; Dirkmann, S.; Mussenbrock, T.; Kohlstedt, H.

    2015-01-01

    We present a quantum mechanical memristive Nb/Al/Al2O3/NbxOy/Au device which consists of an ultra-thin memristive layer (NbxOy) sandwiched between an Al2O3 tunnel barrier and a Schottky-like contact. A highly uniform current distribution for the LRS (low resistance state) and HRS (high resistance state) for areas ranging between 70 μm2 and 2300 μm2 were obtained, which indicates a non-filamentary based resistive switching mechanism. In a detailed experimental and theoretical analysis we show evidence that resistive switching originates from oxygen diffusion and modifications of the local electronic interface states within the NbxOy layer, which influences the interface properties of the Au (Schottky) contact and of the Al2O3 tunneling barrier, respectively. The presented device might offer several benefits like an intrinsic current compliance, improved retention and no need for an electric forming procedure, which is especially attractive for possible applications in highly dense random access memories or neuromorphic mixed signal circuits. PMID:26348823

  3. Numerical investigation of dielectric barrier discharges

    NASA Astrophysics Data System (ADS)

    Li, Jing

    1997-12-01

    A dielectric barrier discharge (DBD) is a transient discharge occurring between two electrodes in coaxial or planar arrangements separated by one or two layers of dielectric material. The charge accumulated on the dielectric barrier generates a field in a direction opposite to the applied field. The discharge is quenched before an arc is formed. It is one of the few non-thermal discharges that operates at atmospheric pressure and has the potential for use in pollution control. In this work, a numerical model of the dielectric barrier discharge is developed, along with the numerical approach. Adaptive grids based on the charge distribution is used. A self-consistent method is used to solve for the electric field and charge densities. The Successive Overrelaxation (SOR) method in a non-uniform grid spacing is used to solve the Poisson's equation in the cylindrically-symmetric coordinate. The Flux Corrected Transport (FCT) method is modified to solve the continuity equations in the non-uniform grid spacing. Parametric studies of dielectric barrier discharges are conducted. General characteristics of dielectric barrier discharges in both anode-directed and cathode-directed streamer are studied. Effects of the dielectric capacitance, the applied field, the resistance in external circuit and the type of gases (O2, air, N2) are investigated. We conclude that the SOR method in an adaptive grid spacing for the solution of the Poisson's equation in the cylindrically-symmetric coordinate is convergent and effective. The dielectric capacitance has little effect on the g-factor of radical production, but it determines the strength of the dielectric barrier discharge. The applied field and the type of gases used have a significant role on the current peak, current pulse duration and radical generation efficiency, discharge strength, and microstreamer radius, whereas the external series resistance has very little effect on the streamer properties. The results are helpful in

  4. Barrier methods of contraception.

    PubMed

    Skrine, R L

    1985-05-01

    Barrier methods of contraception make up an essential part of the present contraceptive range, and doctors need to know in detail how to choose and fit them as well as how to instruct patients in their use. This discussion reviews the mode of action of the barrier method and then focuses on the vaginal diaphragm, the cervical or vault cap, the collatex (Today) sponge, condoms, emotionl problems associated with the use of barrier methods, advantages of barrier methods, and future developments. Barrier methods of contraception are only effective if used consistently and carefully. Failure rates vary greatly between studies, but in selected populations the failure rate for the diaphragm with spermicide can be as low as 1.9/100 woman years (wy) and for the condom 3.6 per 100wy (Vessey et al., 1982). If known user failures are removed, the figure for the condom can drop to as low as 0.4 per 100wy (John, 1973), which compares favorably with that of the combined oral contraceptive. Other studies quote failure rates of 10 per 100wy or more. These methods call for considerable participation by the patient at or before each act of intercourse and there is, therefore, great scope for inefficient use, either as a result of poor instruction or because couples find that they interfere with happy, relaxed sexual activity -- or fear that they may do so. Doctors need to understand the feelings of their patients before recommending them. The aim of a barrier method is to prevent live sperm from meeting the ovum. This is accomplished by the combination of a physical barrier with a spermicide. In the case of the condom, the integrity of the physical barrier is the most important factor, although some patients feel more secure with an additional spermicide. The vaginal barriers used at present do not produce a "water-tight" fit, and the principle is that the spermicide is held over the cervix by the barrier. It is also possible that the device acts partially by holding the alkaline

  5. Dissecting gene expression at the blood-brain barrier

    PubMed Central

    Huntley, Melanie A.; Bien-Ly, Nga; Daneman, Richard; Watts, Ryan J.

    2014-01-01

    The availability of genome-wide expression data for the blood-brain barrier is an invaluable resource that has recently enabled the discovery of several genes and pathways involved in the development and maintenance of the blood-brain barrier, particularly in rodent models. The broad distribution of published data sets represents a viable starting point for the molecular dissection of the blood-brain barrier and will further direct the discovery of novel mechanisms of blood-brain barrier formation and function. Technical advances in purifying brain endothelial cells, the key cell that forms the critical barrier, have allowed for greater specificity in gene expression comparisons with other central nervous system cell types, and more systematic characterizations of the molecular composition of the blood-brain barrier. Nevertheless, our understanding of how the blood-brain barrier changes during aging and disease is underrepresented. Blood-brain barrier data sets from a wider range of experimental paradigms and species, including invertebrates and primates, would be invaluable for investigating the function and evolution of the blood-brain barrier. Newer technologies in gene expression profiling, such as RNA-sequencing, now allow for finer resolution of transcriptomic changes, including isoform specificity and RNA-editing. As our field continues to utilize more advanced expression profiling in its ongoing efforts to elucidate the blood-brain barrier, including in disease and drug delivery, we will continue to see rapid advances in our understanding of the molecular mediators of barrier biology. We predict that the recently published data sets, combined with forthcoming genomic and proteomic blood-brain barrier data sets, will continue to fuel the molecular genetic revolution of blood-brain barrier biology. PMID:25414634

  6. Energy barriers and cell migration in confluent tissues

    NASA Astrophysics Data System (ADS)

    Bi, Dapeng; Lopez, J. H.; Schwarz, J. M.; Manning, M. Lisa

    2014-03-01

    Biological processes such as embryogensis, tumorigenesis and wound healing require cells to move within a tissue. While the migration of single cells has been extensively studied, it has remained unclear how single cell properties control migration through a confluent tissue. We develop numerical and theoretical models to calculate energy barriers to cell rearrangements, which govern cell motility. In contrast to sheared foams where energy barriers are power-law distributed, energy barriers in tissues are exponentially distributed and depend systematically on the cell's number of neighbors. Using simple extensions of `trap' and `Soft Glassy Rheology' models, we demonstrate that these energy barrier distributions give rise to glassy behavior and use the models to make testable predictions for two-time correlation functions and caging times. We incorporate these ideas into a continuum model that combines glassy rheology with active polarization to better understand collective migration in epithelial sheets.

  7. Thermal barrier coating

    DOEpatents

    Bowker, Jeffrey Charles; Sabol, Stephen M.; Goedjen, John G.

    2001-01-01

    A thermal barrier coating for hot gas path components of a combustion turbine based on a zirconia-scandia system. A layer of zirconium scandate having the hexagonal Zr.sub.3 Sc.sub.4 O.sub.12 structure is formed directly on a superalloy substrate or on a bond coat formed on the substrate.

  8. The Fission Barrier Landscape

    SciTech Connect

    Phair, L.; Moretto, L. G.

    2008-04-17

    Fission excitation functions have been measured for a chain of neighboring compound nuclei from {sup 207}Po to {sup 212}Po. We present a new analysis which provides a determination of the fission barriers and ground state shell effects with nearly spectroscopic accuracy. The accuracy achieved in this analysis may lead to a future detailed exploration of the saddle mass surface and its spectroscopy.

  9. Thermal barrier coating system

    NASA Technical Reports Server (NTRS)

    Stecura, S. (Inventor)

    1985-01-01

    An oxide thermal barrier coating comprises ZrO3-Yb2O3 that is plasma sprayed onto a previously applied bond coating. The zirconia is partially stabilized with about 124 w/o ytterbia to insure cubic, monoclinic, and terragonal phases.

  10. Barriers Regarding Using Technology

    ERIC Educational Resources Information Center

    Boekenoogen, John Russell

    2014-01-01

    The University of Florida (UF) used an open-source course management system (CMS) called Sakai. Sakai was the fourth CMS the university has used to help teach live, blended (or hybrid), and online courses over the past ten years. The objective of this dissertation was to identify what barriers may be preventing university personnel from using…

  11. Overcoming Language Barriers

    PubMed Central

    De Buda, Yvonne

    1976-01-01

    Many family physicians in Canada experience language and cultural barriers between themselves and their patients. Several aspects of the ensuing problems are described and some practical suggestions for solutions are made. The importance of health education for new Canadians in the family physician's office as well as through the media and community projects is stressed. Imagesp68-ap68-bp70-a PMID:21308059

  12. Great Barrier Reef

    NASA Technical Reports Server (NTRS)

    2002-01-01

    A better than average view of the Great Barrier Reef was captured by SeaWiFS on a recent overpass. There is sunglint northeast of the reef and there appears to be some sort of filamentous bloom in the Capricorn Channel.

  13. Stability of barrier buckets with short barrier separations

    SciTech Connect

    Ng, K.Y.; /Fermilab

    2005-04-01

    A barrier bucket with very short or zero rf-barrier separation (relative to the barrier widths) has its synchrotron tune decreasing from a very large value towards the bucket boundary. As a result, chaotic region may form near the bucket center and extends outward under increasing modulation of rf voltage and/or rf phase. Application is made to those barrier buckets used in momentum mining at the Fermilab Recycler Ring.

  14. Chaotic correlations in barrier billiards with arbitrary barriers

    NASA Astrophysics Data System (ADS)

    Osbaldestin, A. H.; Adamson, L. N. C.

    2013-06-01

    We study autocorrelation functions in symmetric barrier billiards for golden mean trajectories with arbitrary barriers. Renormalization analysis reveals the presence of a chaotic invariant set and thus that, for a typical barrier, there are chaotic correlations. The chaotic renormalization set is the analogue of the so-called orchid that arises in a generalized Harper equation.

  15. Dynamics of cold atoms crossing a one-way barrier

    NASA Astrophysics Data System (ADS)

    Thorn, Jeremy J.; Schoene, Elizabeth A.; Li, Tao; Steck, Daniel A.

    2009-06-01

    We implemented an optical one-way potential barrier that allows ultracold R87b atoms to transmit through when incident on one side of the barrier but reflect from the other. This asymmetric barrier is a realization of Maxwell’s demon, which can be employed to produce phase-space compression and has implications for cooling atoms and molecules not amenable to standard laser-cooling techniques. The barrier comprises two focused Gaussian laser beams that intersect the focus of a far-off-resonant single-beam optical dipole trap that holds the atoms. The main barrier beam presents a state-dependent potential to incident atoms, while the repumping barrier beam optically pumps atoms to a trapped state. We investigated the robustness of the barrier asymmetry to changes in the barrier-beam separation, the initial atomic potential energy, the intensity of the second beam, and the detuning of the first beam. We performed simulations of the atomic dynamics in the presence of the barrier, showing that the initial three-dimensional momentum distribution plays a significant role, and that light-assisted collisions are likely the dominant loss mechanism. We also carefully examined the relationship to Maxwell’s demon and explicitly accounted for the apparent decrease in entropy for our particular system.

  16. Apoplastic Diffusion Barriers in Arabidopsis

    PubMed Central

    Schreiber, Lukas; Franke, Rochus Benni; Geldner, Niko; Reina-Pinto, José J.; Kunst, Ljerka

    2013-01-01

    During the development of Arabidopsis and other land plants, diffusion barriers are formed in the apoplast of specialized tissues within a variety of plant organs. While the cuticle of the epidermis is the primary diffusion barrier in the shoot, the Casparian strips and suberin lamellae of the endodermis and the periderm represent the diffusion barriers in the root. Different classes of molecules contribute to the formation of extracellular diffusion barriers in an organ- and tissue-specific manner. Cutin and wax are the major components of the cuticle, lignin forms the early Casparian strip, and suberin is deposited in the stage II endodermis and the periderm. The current status of our understanding of the relationships between the chemical structure, ultrastructure and physiological functions of plant diffusion barriers is discussed. Specific aspects of the synthesis of diffusion barrier components and protocols that can be used for the assessment of barrier function and important barrier properties are also presented. PMID:24465172

  17. Multilayer thermal barrier coating systems

    DOEpatents

    Vance, Steven J.; Goedjen, John G.; Sabol, Stephen M.; Sloan, Kelly M.

    2000-01-01

    The present invention generally describes multilayer thermal barrier coating systems and methods of making the multilayer thermal barrier coating systems. The thermal barrier coating systems comprise a first ceramic layer, a second ceramic layer, a thermally grown oxide layer, a metallic bond coating layer and a substrate. The thermal barrier coating systems have improved high temperature thermal and chemical stability for use in gas turbine applications.

  18. Modeling Catastrophic Barrier Island Dynamics

    NASA Astrophysics Data System (ADS)

    Whitley, J. W.; McNamara, D.

    2012-12-01

    Barrier islands, thin strips of sand lying parallel to the mainland coastline, along the U.S. Atlantic and Gulf Coasts appear to have maintained their form for thousands of years in the face of rising sea level. The mechanisms that allow barrier islands to remain robust are transport of sediment from the ocean side of barriers to the top and backside during storms, termed island overwash, and the growth and alongshore propagation of tidal deltas near barrier island inlets. Dynamically these processes provide the necessary feedbacks to maintain a barrier island in an attractor that withstands rising sea level within a phase space of barrier island geometrical characteristics. Current barrier island configurations along the Atlantic and Gulf coasts exist among a wide range of storm climate and underlying geologic conditions and therefore the environment that forces overwash and tidal delta dynamics varies considerably. It has been suggested that barrier islands in certain locations such as those between Avon and Buxton (losing 76% of island width since 1852) and Chandeleur islands (losing 85% of its surface area since 2005) along the Atlantic and Gulf coasts, respectively, may be subject to a catastrophic shift in barrier island attractor states - more numerous inlets cutting barriers in some locations and the complete disappearance of barrier islands in other locations. In contrast to common models for barrier islands that neglect storm dynamics and often only consider cross-shore response, we use an alongshore extended model for barrier island dynamics including beach erosion, island overwash and inlet cutting during storms, and beach accretion, tidal delta growth and dune and vegetation growth between storms to explore the response of barrier islands to a wide range of environmental forcing. Results will be presented that show how barrier island attractor states are altered with variations in the rate of sea level rise, storminess, and underlying geology. We will

  19. Evaluation of screen barriers on redbay trees to protect them from Xyleborus glabratus (Coleoptera: Curculionidae: Scolytinae) and distribution of initial attacks in relation to stem moisture content, diameter, and height.

    PubMed

    Maner, M Lake; Hanula, James L; Braman, S Kristine

    2013-08-01

    Fine mesh screen was used to create a physical barrier to prevent redbay ambrosia beetles, Xyleborus glabratus Eichhoff (Coleoptera: Curculionidae: Scolytinae), from accessing various parts of the boles of redbay trees, Persea borbonia (L.) Sprengel, and infecting them with the laurel wilt fungus, Raffaelea lauricola (T.C. Harrington, Fraedrich, & Aghayeva). Screen barriers prevented beetles from attacking boles of mature redbay trees from the ground to 1 or to 3 m and from 1 to 3 m above ground. Untreated control trees were sampled more extensively to determine how location of initial attacks varied with height, diameter, and moisture content of the wood. Screening did not affect tree survival, and all of the trees died within 243 d from the beginning of observation. Initial points of attack by X. glabratus varied from ground level to heights of at least 6.6 m. Trees showed characteristic laurel wilt symptoms with as few as two X. glabratus entry points. The number of attacks exhibited nonlinear relationships with diameter (P = 0.0004; r2 = 0.82) and height (P = 0.0013; r2 = 0.69) but were not correlated with moisture content. Attacks increased gradually with increasing stem diameter up to approximately 10 cm after which the attacks became more numerous. X. glabratus attacks were most numerous on the tree bole near the ground. Attacks then declined as tree height reached 2-3 m. From 3 to 8 m, attacks were relatively consistent.

  20. Can-Filled Crash Barrier

    NASA Technical Reports Server (NTRS)

    Wilson, A. H.

    1983-01-01

    Crash barrier composed largely of used aluminum beverage cans protects occupants of cars in collisions with poles or trees. Lightweight, can-filled barrier very effective in softening impact of an automobile in head-on and off-angle collisions. Preliminary results indicate barrier is effective in collisions up to 40 mi/h (64 km/h).

  1. Information Barriers: Identification and Seriousness.

    ERIC Educational Resources Information Center

    Haag, D. E.

    The project documented in this report identified barriers researchers encounter in gaining access to--i.e., identifying, acquiring, handling, and using--published information and measured the seriousness of the more significant barriers. Fifty-one barriers were identified, and a method of measuring their seriousness was developed. Thirty of the…

  2. Underground waste barrier structure

    DOEpatents

    Saha, Anuj J.; Grant, David C.

    1988-01-01

    Disclosed is an underground waste barrier structure that consists of waste material, a first container formed of activated carbonaceous material enclosing the waste material, a second container formed of zeolite enclosing the first container, and clay covering the second container. The underground waste barrier structure is constructed by forming a recessed area within the earth, lining the recessed area with a layer of clay, lining the clay with a layer of zeolite, lining the zeolite with a layer of activated carbonaceous material, placing the waste material within the lined recessed area, forming a ceiling over the waste material of a layer of activated carbonaceous material, a layer of zeolite, and a layer of clay, the layers in the ceiling cojoining with the respective layers forming the walls of the structure, and finally, covering the ceiling with earth.

  3. Amosphous diffusion barriers

    NASA Technical Reports Server (NTRS)

    Kolawa, E.; So, F. C. T.; Nicolet, M-A.

    1986-01-01

    Amorphous W-Zr and W-N alloys were investigated as diffusion barriers in silicon metallization schemes. Data were presented showing that amorphous W-Zr crystallizes at 900 C, which is 200 C higher than amorphous W-Ni films, and that both films react with metallic overlayers at temperatures far below the crystllization temperature. Also, W-N alloys (crystalline temperature of 600 C) were successfully incorporated as a diffusion barrier in contact structures with both Al and Ag overlayers. The thermal stability of the electrical characteristics of shallow n(+)p junctions significantly improved by incorporating W-N layers in the contact system. One important fact demonstated was the critical influence of the deposition parameters during formation of these carriers.

  4. Skin Barrier Function

    PubMed Central

    Elias, Peter M.

    2010-01-01

    Like other inflammatory dermatoses, the pathogenesis of atopic dermatitis (AD) has been largely attributed to abnormalities in adaptive immunity. T helper (Th) cell types 1 and 2 cell dysregulation, IgE production, mast cell hyperactivity, and dendritic cell signaling are thought to account for the chronic, pruritic, and inflammatory dermatosis that characterizes AD. Not surprisingly, therapy has been directed toward ameliorating Th2-mediated inflammation and pruritus. Here, we review emerging evidence that inflammation in AD occurs downstream to inherited and acquired insults to the barrier. Therapy based upon this new view of pathogenesis should emphasize approaches that correct the primary abnormality in barrier function, which drives downstream inflammation and allows unrestricted antigen access. PMID:18606081

  5. Barrier breaching device

    DOEpatents

    Honodel, C.A.

    1983-06-01

    A barrier breaching device that is designed primarily for opening holes in interior walls of buildings uses detonating fuse for explosive force. The fuse acts as the ribs or spokes of an umbrella-like device that may be opened up to form a cone. The cone is placed against the wall so that detonating fuse that rings the base of the device and which is ignited by the spoke-like fuses serves to cut a circular hole in the wall.

  6. Barrier infrared detector

    NASA Technical Reports Server (NTRS)

    Ting, David Z. (Inventor); Khoshakhlagh, Arezou (Inventor); Soibel, Alexander (Inventor); Hill, Cory J. (Inventor); Gunapala, Sarath D. (Inventor)

    2012-01-01

    A superlattice-based infrared absorber and the matching electron-blocking and hole-blocking unipolar barriers, absorbers and barriers with graded band gaps, high-performance infrared detectors, and methods of manufacturing such devices are provided herein. The infrared absorber material is made from a superlattice (periodic structure) where each period consists of two or more layers of InAs, InSb, InSbAs, or InGaAs. The layer widths and alloy compositions are chosen to yield the desired energy band gap, absorption strength, and strain balance for the particular application. Furthermore, the periodicity of the superlattice can be "chirped" (varied) to create a material with a graded or varying energy band gap. The superlattice based barrier infrared detectors described and demonstrated herein have spectral ranges covering the entire 3-5 micron atmospheric transmission window, excellent dark current characteristics operating at least 150K, high yield, and have the potential for high-operability, high-uniformity focal plane arrays.

  7. Simulation of the interaction of tsunami waves with underwater barriers

    NASA Astrophysics Data System (ADS)

    Boshenyatov, B. V.; Zhiltsov, K. N.

    2016-10-01

    This article examines the experimental and numerical simulation of the processes of distribution and interaction of tsunami-type gravitational waves with one barrier and a complex of two barriers. Experiments were conducted in a hydrodynamic channel using high-precision sensors for the measurement of the wave processes. Mathematical modelling was carried out using two-dimensional non-stationary Navier-Stokes equations for an incompressible fluid using the freely available software package OpenFOAM. It is shown that for small-amplitude waves, when their advance speed is described by the linear theory of shallow water, the interaction with the underwater barriers has important non-linear and viscous effects. Our results explain why a complex of two barriers spaced at a definite distance from each other has a significant impact on the power of the transmitted wave. The energy of the waves passing through the two barriers can be reduced to 35% of the incident wave.

  8. Deep inelastic scattering near the Coulomb barrier

    SciTech Connect

    Gehring, J.; Back, B.; Chan, K.

    1995-08-01

    Deep inelastic scattering was recently observed in heavy ion reactions at incident energies near and below the Coulomb barrier. Traditional models of this process are based on frictional forces and are designed to predict the features of deep inelastic processes at energies above the barrier. They cannot be applied at energies below the barrier where the nuclear overlap is small and friction is negligible. The presence of deep inelastic scattering at these energies requires a different explanation. The first observation of deep inelastic scattering near the barrier was in the systems {sup 124,112}Sn + {sup 58,64}Ni by Wolfs et al. We previously extended these measurements to the system {sup 136}Xe + {sup 64}Ni and currently measured the system {sup 124}Xe + {sup 58}Ni. We obtained better statistics, better mass and energy resolution, and more complete angular coverage in the Xe + Ni measurements. The cross sections and angular distributions are similar in all of the Sn + Ni and Xe + Ni systems. The data are currently being analyzed and compared with new theoretical calculations. They will be part of the thesis of J. Gehring.

  9. Stability of barrier buckets with zero RF-barrier separations

    SciTech Connect

    Ng, K.Y.; /Fermilab

    2005-03-01

    A barrier bucket with very small separation between the rf barriers (relative to the barrier widths) or even zero separation has its synchrotron tune decreasing rather slowly from a large value towards the boundary of the bucket. As a result, large area at the bucket edges can become unstable under the modulation of rf voltage and/or rf phase. In addition, chaotic regions may form near the bucket center and extend outward under increasing modulation. Application is made to those barrier buckets used in the process of momentum mining at the Fermilab Recycler Ring.

  10. Performing a local barrier operation

    DOEpatents

    Archer, Charles J; Blocksome, Michael A; Ratterman, Joseph D; Smith, Brian E

    2014-03-04

    Performing a local barrier operation with parallel tasks executing on a compute node including, for each task: retrieving a present value of a counter; calculating, in dependence upon the present value of the counter and a total number of tasks performing the local barrier operation, a base value, the base value representing the counter's value prior to any task joining the local barrier; calculating, in dependence upon the base value and the total number of tasks performing the local barrier operation, a target value of the counter, the target value representing the counter's value when all tasks have joined the local barrier; joining the local barrier, including atomically incrementing the value of the counter; and repetitively, until the present value of the counter is no less than the target value of the counter: retrieving the present value of the counter and determining whether the present value equals the target value.

  11. Performing a local barrier operation

    DOEpatents

    Archer, Charles J; Blocksome, Michael A; Ratterman, Joseph D; Smith, Brian E

    2014-03-04

    Performing a local barrier operation with parallel tasks executing on a compute node including, for each task: retrieving a present value of a counter; calculating, in dependence upon the present value of the counter and a total number of tasks performing the local barrier operation, a base value of the counter, the base value representing the counter's value prior to any task joining the local barrier; calculating, in dependence upon the base value and the total number of tasks performing the local barrier operation, a target value, the target value representing the counter's value when all tasks have joined the local barrier; joining the local barrier, including atomically incrementing the value of the counter; and repetitively, until the present value of the counter is no less than the target value of the counter: retrieving the present value of the counter and determining whether the present value equals the target value.

  12. Interdigital Schottky barrier capacitor apparatus

    NASA Astrophysics Data System (ADS)

    Bierig

    1985-05-01

    The present invention relates broadly to Schottky barrier capacitors, and in particular to an interdigital Schottky barrier capacitor apparatus. In the prior art, the Schottky barrier diode is rather well known. In general, a Schottky barrier device comprises a semiconductor substrate layer that is formed by a first layer of heavily doped materials and a second layer of lightly doped materials upon which a layer of barrier metal is deposited thereon. The maximum reverse bias voltage which can be appplied to the Schottky barrier device is determined by the thickness of the lightly doped layer of semiconductive material which is deposited upon the substrate layer. This is only one of the factors that determined the reverse bias voltage, When a guardring is diffused into the lightly doped layer of semiconductive substrate material, the thickness of the layer is reduced, and therefore, the reverse bias voltage that can be applied to the Schottky device is reduced.

  13. Problems in characterizing barrier performance

    NASA Technical Reports Server (NTRS)

    Jordan, Harry F.

    1988-01-01

    The barrier is a synchronization construct which is useful in separating a parallel program into parallel sections which are executed in sequence. The completion of a barrier requires cooperation among all executing processes. This requirement not only introduces the wait for the slowest process delay which is inherent in the definition of the synchronization, but also has implications for the efficient implementation and measurement of barrier performance in different systems. Types of barrier implementation and their relationship to different multiprocessor environments are described. Then the problem of measuring the performance of barrier implementations on specific machine architecture is discussed. The fact that the barrier synchronization requires the cooperation of all processes makes the problem of performance measurement similarly global. Making non-intrusive measurements of sufficient accuracy can be tricky on systems offering only rudimentary measurement tools.

  14. Irritants and Skin Barrier Function.

    PubMed

    Angelova-Fischer, Irena

    2016-01-01

    The barrier response to irritant challenge involves complex biologic events and can be modulated by various environmental, exposure and host-related factors. Irritant damage to the epidermal barrier elicits a cascade of homeostatic or pathologic responses that could be investigated by both in vitro and in vivo methods providing different information at biochemical and functional level. The present chapter summarizes the changes in key barrier function parameters following irritant exposure with focus on experimental controlled in vivo human skin studies.

  15. Barrier immunity and IL-17

    PubMed Central

    Marks, Benjamin R.; Craft, Joe

    2009-01-01

    CD4+ TH17 cells display a featured role in barrier immunity. This effector population of T cells is important for clearance of microorganisms but can also promote autoimmunity at barrier sites. Recent work has indicated that these effector cells share a pathway with CD4+ regulatory T cells (TR cells) that also have a critical function in barrier protection and immune regulation. The development and function of TH17 cells, and their relationship with TR cells are discussed. PMID:19386512

  16. Barriers of the peripheral nerve

    PubMed Central

    Peltonen, Sirkku; Alanne, Maria; Peltonen, Juha

    2013-01-01

    This review introduces the traditionally defined anatomic compartments of the peripheral nerves based on light and electron microscopic topography and then explores the cellular and the most recent molecular basis of the different barrier functions operative in peripheral nerves. We also elucidate where, and how, the homeostasis of the normal human peripheral nerve is controlled in situ and how claudin-containing tight junctions contribute to the barriers of peripheral nerve. Also, the human timeline of the development of the barriers of the peripheral nerve is depicted. Finally, potential future therapeutic modalities interfering with the barriers of the peripheral nerve are discussed. PMID:24665400

  17. Silicon Carbide Schottky Barrier Diode

    NASA Technical Reports Server (NTRS)

    Zhao, Jian H.; Sheng, Kuang; Lebron-Velilla, Ramon C.

    2004-01-01

    This chapter reviews the status of SiC Schottky barrier diode development. The fundamental of Schottky barrier diodes is first provided, followed by the review of high-voltage SiC Schottky barrier diodes, junction-barrier Schottky diodes, and merged-pin-Schottky diodes. The development history is reviewed ad the key performance parameters are discussed. Applications of SiC SBDs in power electronic circuits as well as other areas such as gas sensors, microwave and UV detections are also presented, followed by discussion of remaining challenges.

  18. Pharmacoproteomics-based reconstruction of in vivo P-glycoprotein function at blood-brain barrier and brain distribution of substrate verapamil in pentylenetetrazole-kindled epilepsy, spontaneous epilepsy, and phenytoin treatment models.

    PubMed

    Uchida, Yasuo; Ohtsuki, Sumio; Terasaki, Tetsuya

    2014-10-01

    The purpose of this study was to demonstrate experimentally that alterations of in vivo transporter function at the blood-brain barrier (BBB) in disease and during pharmacotherapy can be reconstructed from in vitro data based on our established pharmacoproteomic concept of reconstructing in vivo function by integrating intrinsic transport activity per transporter molecule and absolute protein expression level at the BBB. Pentylenetetrazole (PTZ)-kindled and spontaneous model of epilepsy (EL) mice were used as models of chemically induced and spontaneous epilepsy, respectively. A mouse model of antiepileptic drug treatment was prepared by consecutive 5-week administration of phenytoin (PHT). Quantitative targeted absolute proteomic analysis of 31 membrane proteins showed that P-glycoprotein (P-gp/mdr1a) protein expression levels were significantly increased in brain capillaries of PTZ (129%), EL (143%), and PHT mice (192%) compared with controls. The brain-to-plasma concentration ratios (Kp brain) of P-gp/mdr1a substrate verapamil were 0.563, 0.394, 0.432, and 0.234 in control, PTZ, EL, and PHT mice, respectively. In vivo P-gp/mdr1a function at the BBB was reconstructed from the measured P-gp/mdr1a protein expression levels and intrinsic transport activity for verapamil per P-gp/mdr1a previously reported by our group. Then, the reconstructed P-gp/mdr1a functional activities were integrated with unbound fractions of verapamil in plasma and brain to reconstruct Kp brain of verapamil. In all mice, reconstructed Kp brain values agreed well with the observed values within a 1.21-fold range. These results demonstrate that altered P-gp functions at the BBB in epilepsy and during pharmacotherapy can be reconstructed from in vitro data by means of our pharmacoproteomic approach.

  19. Thermal barrier coatings

    SciTech Connect

    Alvin, Mary Anne

    2010-06-22

    This disclosure addresses the issue of providing a metallic-ceramic overlay coating that potentially serves as an interface or bond coat layer to provide enhanced oxidation resistance to the underlying superalloy substrate via the formation of a diffusion barrier regime within the supporting base material. Furthermore, the metallic-ceramic coating is expected to limit the growth of a continuous thermally grown oxide (TGO) layer that has been primarily considered to be the principal cause for failure of existing TBC systems. Compositional compatibility of the metallic-ceramic with traditional yttria-stabilized zirconia (YSZ) top coats is provided to further limit debond or spallation of the coating during operational use. A metallic-ceramic architecture is disclosed wherein enhanced oxidation resistance is imparted to the surface of nickel-based superalloy or single crystal metal substrate, with simultaneous integration of the yttria stabilized zirconia (YSZ) within the metallic-ceramic overlayer.

  20. Schottky barrier solar cell

    NASA Technical Reports Server (NTRS)

    Stirn, R. J.; Yeh, Y. C. M. (Inventor)

    1981-01-01

    A method of fabricating a Schottky barrier solar cell is described. The cell consists of a thin substrate of low cost material with at least the top surface of the substrate being electrically conductive. A thin layer of heavily doped n-type polycrystalling germanium is deposited on the substrate after a passivation layer is deposited to prevent migration of impurities into the polycrystalline germanium. The polycrystalline germanium is recrystallized to increase the crystal sizes to serve as a base layer on which a thin layer of gallium arsenide is vapor-epitaxilly grown followed by a thermally-grown oxide layer. A metal layer is deposited on the oxide layer and a grid electrode is deposited to be in electrical contact with the top surface of the metal layer.

  1. Exposure, Uptake, and Barriers

    NASA Astrophysics Data System (ADS)

    Baeza-Squiban, Armelle; Lanone, Sophie

    The nanotechnologies market is booming, e.g., in the food industry (powder additives, etc.) and in medical applications (drug delivery, prosthetics, diagnostic imaging, etc.), but also in other industrial sectors, such as sports, construction, cosmetics, and so on. In this context, with an exponential increase in the number of current and future applications, it is particularly important to evaluate the problem of unintentional (i.e., non-medical) exposure to manufactured nanoparticles (so excluding nanoparticles found naturally in the environment). In this chapter, we begin by discussing the various parameters that must be taken into account in any serious assessment of exposure to man-made nanoparticles. We then list the potential routes by which nanoparticles might enter into the organism, and outline the mechanisms whereby they could get past the different biological barriers. Finally, we describe the biodistribution of nanoparticles in the organism and the way they are eliminated.

  2. Oxygen diffusion barrier coating

    NASA Technical Reports Server (NTRS)

    Unnam, Jalaiah (Inventor); Clark, Ronald K. (Inventor)

    1987-01-01

    A method for coating a titanium panel or foil with aluminum and amorphous silicon to provide an oxygen barrier abrogating oxidation of the substrate metal is developed. The process is accomplished with known inexpensive procedures common in materials research laboratories, i.e., electron beam deposition and sputtering. The procedures are conductive to treating foil gage titanium and result in submicron layers which virtually add no weight to the titanium. There are no costly heating steps. The coatings blend with the substrate titanium until separate mechanical properties are subsumed by those of the substrate without cracking or spallation. This method appreciably increases the ability of titanium to mechanically perform in high thermal environments such as those witnessed on structures of space vehicles during re-entry

  3. Identifying ecological barriers in marine environment: The case study of Dasyatis marianae.

    PubMed

    Costa, Tiego L A; Pennino, M Grazia; Mendes, Liana F

    2017-04-01

    Ecological barriers are important determinants of the evolution and distributions marine organisms, and a challenge for evolutionary ecologists seeking to understand population structure in the sea. Dasyatis marianae is an endemic Brazilian species that indicates certain restrictions on its distribution probably due to marine barriers. In this study, Bayesian hierarchical spatial models, jointly with environmental and occurrence species data, are used to identify, which elements could generate these barriers on Dasyatis marianae distribution. Results show that salinity and temperature are the most important drivers that play an essential role to limit the distribution of this species. Indeed, low salinity values restrict Dasyatis marianae distribution in the north of the Brazilian coast, while in the south are colder temperatures. These results highlight the need to better define the distribution of marine species, especially for the ones affected by ecological barriers that are more sensitive to environmental changes.

  4. Barriers to Women in Science

    ERIC Educational Resources Information Center

    Butler, Rosemary

    2013-01-01

    The Presiding Officer of the National Assembly for Wales, Rosemary Butler AM, has put the issue of barriers to women in public life at the top of the political agenda in Wales. She has held sessions with women across Wales to find out what those barriers are and how they can be tackled. On International Women's Day in February, she invited…

  5. Educator's Barriers to Using Technology

    ERIC Educational Resources Information Center

    Brown, April S.

    2012-01-01

    The study is an action research project focused on learning more about the barriers to using technology at one site in Southern California. Learning about the barriers for one school may assist this researcher in learning how to improve the changes of teachers and staff using technology in the field of education. The methodology of this study was…

  6. Psychological Barriers to Behavior Change

    PubMed Central

    Olson, James M.

    1992-01-01

    Adopting a healthy lifestyle often requires changing patterns of behavior. This article describes three categories of psychological barriers to behavior change: those that prevent the admission of a problem, those that interfere with initial attempts to change behavior, and those that make long-term change difficult. Strategies are identified that family physicians can use to overcome the barriers. PMID:21221258

  7. Determination of RL,RT, and RLT in the quasi-elastic 2H(e,e'p) reaction

    NASA Astrophysics Data System (ADS)

    Steenhoven, G. van der; van der Schaar, M.; Arenhövel, H.; Blok, H. P.; Hummel, E.; Jans, E.; Lapikás, L.; Tjon, J. A.; de Witt Huberts, P. K. A.

    1992-01-01

    Cross sections for the reaction 2H(e,e'p) have been measured at Q2=0.21 (GeV/c)2 under three kinematical conditions such that the longitudinal and transverse structure functions and the longitudinal-transverse interference structure function could be separately determined. The results are compared to a non-relativistic calculation by Arenhövel and a relativistic calculation by Hummel and Tjon. Whereas the longitudinal and transverse structure functions are well reproduced by both calculations, a discrepancy is observed between the data and the non-relativistic calculation for the interference structure function. The relativistic calculation is not in disagreement with the data.

  8. Quasi-elastic Raman scattering and free volume in isotropic pressure-densified atactic poly(methyl methacrylate) glasses

    NASA Astrophysics Data System (ADS)

    Schmidt, M.; Brodin, A.; Jacobsson, P.; Maurer, F. H. J.

    2000-01-01

    We have made a series of isotropic pressure-densified atactic poly(methyl methacrylate) (PMMA) glasses with densities ranging from 1.1823 g/cm3 to 1.1963 g/cm3, in order to investigate how the glassy dynamics, measured by Raman scattering in the frequency range of 0.1-10 THz, depends on the thermomechanical history of the glasses. In particular, we investigate whether there is a correlation between the strength of the fast relaxation dynamics and the free-volume characteristics, such as the average free-volume size and the free-volume fraction. The fast relaxation strength is deduced from the quasielastic light scattering (QES) intensity; the free-volume size is measured with positron annihilation lifetime spectroscopy (PALS); and the free-volume fraction is determined from pressure-volume-temperature (PVT) data and the Simha-Somcynsky equation-of-state (EOS) theory. Our temperature-dependent Raman and PALS measurements show that both the QES intensity and the ortho-positronium (o-Ps) lifetime increase smoothly with the temperature. On the other hand, the relaxation strength of the densified glasses at room temperature is, within experimental error, independent of the density, whereas both the o-Ps lifetime from PALS and the free volume fraction from the PVT data decrease significantly with pressure densification. We therefore conclude that the fast relaxation intensity cannot be explained on the basis of free-volume quantities, contrary to a recently suggested correlation between the QES intensity and the free volume [V. N. Novikov et al., J. Chem. Phys. 107, 1057 (1997)]. On the other hand, the observed behavior is consistent with another recently suggested model [V. N. Novikov, Phys. Rev. B 58, 8367 (1998)] which attributes the fast relaxations to vibration anharmonicity. Moreover, we show that the measured increase in the refractive index of the pressure-densified glasses fits the Lorentz-Lorenz equation and compares well to predictions of the relative change in refractive index with formation pressure from our own as well as published PVT data.

  9. Epistemological barriers to radical behaviorism.

    PubMed

    O'Donohue, W T; Callaghan, G M; Ruckstuhl, L E

    1998-01-01

    The historian and philosopher of science Gaston Bachelard proposed the concept of epistemological barriers to describe the intellectual challenges encountered by scientists in their work. In order to embrace novel ways of approaching a problem in science, scientists must overcome barriers or obstacles posed by their prior views. For example, Einsteinian physics presents scientists with claims that space is curved and that time and space are on the same continuum. We utilize Bachelard's concept of epistemological barriers to describe the differences between the intellectual journeys students pursuing advanced studies face when attempting to accept cognitive psychology or radical behaviorism. We contend that the folk psychological beliefs that students typically hold when entering these studies pose less challenge to cognitive psychology than to radical behaviorism. We also suggest that these barriers may also partly be involved in the problematic exegesis that has plagued radical behaviorism. In close, we offer some suggestions for dealing with these epistemological barriers.

  10. Epistemological barriers to radical behaviorism

    PubMed Central

    O'Donohue, William T.; Callaghan, Glenn M.; Ruckstuhl, L. E.

    1998-01-01

    The historian and philosopher of science Gaston Bachelard proposed the concept of epistemological barriers to describe the intellectual challenges encountered by scientists in their work. In order to embrace novel ways of approaching a problem in science, scientists must overcome barriers or obstacles posed by their prior views. For example, Einsteinian physics presents scientists with claims that space is curved and that time and space are on the same continuum. We utilize Bachelard's concept of epistemological barriers to describe the differences between the intellectual journeys students pursuing advanced studies face when attempting to accept cognitive psychology or radical behaviorism. We contend that the folk psychological beliefs that students typically hold when entering these studies pose less challenge to cognitive psychology than to radical behaviorism. We also suggest that these barriers may also partly be involved in the problematic exegesis that has plagued radical behaviorism. In close, we offer some suggestions for dealing with these epistemological barriers. PMID:22478314

  11. Hanford Protective Barriers Program asphalt barrier studies -- FY 1988

    SciTech Connect

    Freeman, H.D.; Gee, G.W.

    1989-05-01

    The Hanford Protective Barrier (HPB) Program is evaluating alternative barriers to provide a means of meeting stringent water infiltration requirements. One type of alternative barrier being considered is an asphalt-based layer, 1.3 to 15 cm thick, which has been shown to be very effective as a barrier for radon gas and, hence, should be equally effective as a barrier for the larger molecules of water. Fiscal Year 1988 studies focused on the selection and formulation of the most promising asphalt materials for further testing in small-tube lysimeters. Results of laboratory-scale formulation and hydraulic conductivity tests led to the selection of a rubberized asphalt material and an admixture of 24 wt% asphalt emulsion and concrete sand as the two barriers for lysimeter testing. Eight lysimeters, four each containing the two asphalt treatments, were installed in the Small Tube Lysimeter Facility on the Hanford Site. The lysimeter tests allow the performance of these barrier formulations to be evaluated under more natural environmental conditions.

  12. Barrier height fluctuations in InGaN polarization dipole diodes

    NASA Astrophysics Data System (ADS)

    Suntrup, Donald J.; Gupta, Geetak; Li, Haoran; Keller, Stacia; Mishra, Umesh K.

    2015-10-01

    We present an analysis of the effects of lateral barrier height fluctuations on the transport properties of an InGaN polarization dipole diode (PDD). Typical diode analysis proceeds by performing a linear fit to the data contained in a Richardson plot in order to extract the zero-bias barrier height ( ϕ B ) and the Richardson constant ( A * ). The experimental PDD Richardson plot, however, is highly nonlinear and we attribute this to a spatially nonuniform distribution of barrier heights. After modeling the barrier height distribution using a Gaussian, we fit the Richardson data with a modified, second-order function from which we extract the Richardson constant, mean barrier height, and standard deviation simultaneously. We propose that the physical cause of the observed barrier height inhomogeneity in the PDD is statistical nanoscale fluctuations in indium composition.

  13. The barrier within: endothelial transport of hormones.

    PubMed

    Kolka, Cathryn M; Bergman, Richard N

    2012-08-01

    Hormones are involved in a plethora of processes including development and growth, metabolism, mood, and immune responses. These essential functions are dependent on the ability of the hormone to access its target tissue. In the case of endocrine hormones that are transported through the blood, this often means that the endothelium must be crossed. Many studies have shown that the concentrations of hormones and nutrients in blood can be very different from those surrounding the cells on the tissue side of the blood vessel endothelium, suggesting that transport across this barrier can be rate limiting for hormone action. This transport can be regulated by altering the surface area of the blood vessel available for diffusion through to the underlying tissue or by the permeability of the endothelium. Many hormones are known to directly or indirectly affect the endothelial barrier, thus affecting their own distribution to their target tissues. Dysfunction of the endothelial barrier is found in many diseases, particularly those associated with the metabolic syndrome. The interrelatedness of hormones may help to explain why the cluster of diseases in the metabolic syndrome occur together so frequently and suggests that treating the endothelium may ameliorate defects in more than one disease. Here, we review the structure and function of the endothelium, its contribution to the function of hormones, and its involvement in disease.

  14. Tunnelling without barriers

    SciTech Connect

    Lee, K.

    1987-01-01

    The evolution in flat and curved space-time of quantum fields in theories with relative flat potential and its consequences are considered. It is shown that bubble nucleation, a quantum mechanical tunnelling process, may occur in flat space-time, having a bounce solution, even if V(phi) has no barrier. It is shown that bubble nucleation can also occur in curved space-time even though there is no bounce solution in the standard formalism for the bubble nucleation rate in curved space-time. Additionally, bubbles can nucleate during the slow rolling period on the potential in flat and curved space-time, in this case also there is no bounce solution. It is known in the new inflationary scenario that energy density perturbations caused by quantum fluctuations of the scalar field can satisfy the presently observed bounds on density perturbations. Bubble nucleation during the slow rolling period also gives rise to density perturbations. For a model potential density perturbations by bubbles are calculated at the horizon reentering. By applying the bound from the almost isotropic microwave black body radiation on these density perturbations, a constraint on the model potential is obtained. Finally, some further implications on the galaxy formation and applications in more realistic potential are discussed.

  15. Volumetric analysis of a New England barrier system using ground-penetrating-radar and coring techniques

    USGS Publications Warehouse

    Van Heteren, S.; FitzGerald, D.M.; Barber, D.C.; Kelley, J.T.; Belknap, D.F.

    1996-01-01

    Ground-penetrating-radar (GPR) profiles calibrated with core data allow accurate assessments of coastal barrier volumes. We applied this procedure successfully to the barrier system along Saco Bay, Maine (USA), as part of a sediment-budget study that focused on present-day sand volumes in various coastal, shoreface, and inner-shelf lith-osomes, and on sand fluxes that have affected the volume or distribution of sand in these sediment bodies through time. On GPR profiles, the components of the barrier lithosome are readily differentiated from other facies, except where the radar signal is attenuated by brackish or salty groundwater. Significant differences between dielectric properties of the barrier lithosome and other units commonly result in strong boundary reflectors. The mostly sandy barrier sediments allow deep penetration of GPR waves, in contrast to finer-grained strata and till-covered bedrock. Within the Saco Bay barrier system, 22 ??3 x 106 m3 of sediment are unevenly distributed. Two-thirds of the total barrier volume is contained within the northern and southern ends of the study area, in the Pine Point spit and the Ferry Beach/Goosefare complex, respectively. The central area around Old Orchard Beach is locally covered by only a thin veneer of barrier sand, averaging <3 m, that unconformably overlies shallow pre-Holocene facies. The prominence of barrier-spit facies and the distribution pattern of back-barrier sediments indicate that a high degree of segmentation, governed by antecedent topography, has affected the development of the Saco Bay barrier system. The present-day configuration of the barrier and back-barrier region along Saco Bay, however, conceals much of its early compartmentalized character.

  16. Moisture monitoring in waste disposal surface barriers.

    PubMed

    Brandelik, Alex; Huebner, Christof

    2003-05-01

    Surface barriers for waste disposal sites should prevent waste water and gas emission into the environment. It is necessary to assess their proper operation by monitoring the water regime of the containment. A set of three new water content measuring devices has been developed that provide an economical solution for monitoring the moisture distribution and water dynamic. They will give an early warning service if the barrier system is at risk of being damaged. The cryo soil moisture sensor 'LUMBRICUS' is an in situ self-calibrating absolute water content measuring device. It measures moisture profiles at spot locations down to 2.5 m depth with an accuracy of better than 1.5% and a depth resolution of 0.03 m. The sensor inherently measures density changes and initial cracks of shrinking materials like clay minerals. The large area soil moisture sensor 'TAUPE' is a moisture sensitive electric cable network to be buried in the mineral barrier material of the cover. A report will be given with results and experiences on an exemplary installation at the Waste Disposal Facility Karlsruhe-West. 800 m2 of the barrier construction have been continuously monitored since December 1997. Volumetric water content differences of 1.5% have been detected and localised within 4 m. This device is already installed in two other waste disposal sites. A modified 'TAUPE' was constructed for the control of tunnels and river dams as well. Thin sheet moisture sensor 'FORMI' is specifically designed for moisture measurements in liners like bentonite, textile and plastic. Due to its flexibility it follows the curvature of the liner. The sensor measures independently from neighbouring materials and can be matched to a wide range of different thickness of the material. The sensors are patented in several countries.

  17. Directed transport of active particles over asymmetric energy barriers.

    PubMed

    Koumakis, N; Maggi, C; Di Leonardo, R

    2014-08-21

    We theoretically and numerically investigate the transport of active colloids to target regions, delimited by asymmetric energy barriers. We show that it is possible to introduce a generalized effective temperature that is related to the local variance of particle velocities. The stationary probability distributions can be derived from a simple diffusion equation in the presence of an inhomogeneous effective temperature resulting from the action of external force fields. In particular, transition rates over asymmetric energy barriers can be unbalanced by having different effective temperatures over the two slopes of the barrier. By varying the type of active noise, we find that equal values of diffusivity and persistence time may produce strongly varied effective temperatures and thus stationary distributions.

  18. Tritium/hydrogen barrier development

    SciTech Connect

    Hollenberg, G.W.; Simonen, E.P.; Kalinen, G.; Terlain, A.

    1994-06-01

    A review of hydrogen permeation barriers that can be applied to structural metals used in fusion power plants is presented. Both implanted and chemically available hydrogen isotopes must be controlled in fusion plants. The need for permeation barriers appears strongest in Li17-Pb blanket designs, although barriers also appear necessary for other blanket and coolant systems. Barriers that provide greater than a 1000 fold reduction in the permeation of structural metals are desired. In laboratory experiments, aluminide and titanium ceramic coatings provide permeation reduction factors, PRFS, from 1000 to over 100,000 with a wide range of scatter. The rate-controlling mechanism for hydrogen permeation through these barriers may be related to the number and type of defects in the barriers. Although these barriers appear robust and resistant to liquid metal corrosion, irradiation tests which simulate blanket environments result in very low PRFs in comparison to laboratory experiments, i.e., <150. It is anticipated from fundamental research activities that the REID enhancement of hydrogen diffusion in oxides may contribute to the lower permeation reduction factors during in-reactor experiments.

  19. Vehicle barrier with access delay

    DOEpatents

    Swahlan, David J; Wilke, Jason

    2013-09-03

    An access delay vehicle barrier for stopping unauthorized entry into secure areas by a vehicle ramming attack includes access delay features for preventing and/or delaying an adversary from defeating or compromising the barrier. A horizontally deployed barrier member can include an exterior steel casing, an interior steel reinforcing member and access delay members disposed within the casing and between the casing and the interior reinforcing member. Access delay members can include wooden structural lumber, concrete and/or polymeric members that in combination with the exterior casing and interior reinforcing member act cooperatively to impair an adversarial attach by thermal, mechanical and/or explosive tools.

  20. Treatments Improving Skin Barrier Function.

    PubMed

    Lodén, Marie

    2016-01-01

    Moisturizers affect the stratum corneum architecture and barrier homeostasis, i.e. topically applied ingredients are not as inert to the skin as one might expect. A number of different mechanisms behind the barrier-influencing effects of moisturizers have been suggested, such as simple deposition of lipid material outside the skin. Ingredients in the moisturizers may also change the lamellar organization and the packing of the lipid matrix and thereby skin permeability. Topically applied substances may also penetrate deeper into the skin and interfere with the production of barrier lipids and the maturation of corneocytes. Furthermore, moisturizing creams may influence the desquamatory proteases and alter the thickness of the stratum corneum.

  1. Australia's Great Barrier Reef

    NASA Technical Reports Server (NTRS)

    2001-01-01

    The Great Barrier Reef extends for 2,000 kilometers along the northeastern coast of Australia. It is not a single reef, but a vast maze of reefs, passages, and coral cays (islands that are part of the reef). This nadir true-color image was acquired by the MISR instrument on August 26, 2000 (Terra orbit 3679), and shows part of the southern portion of the reef adjacent to the central Queensland coast. The width of the MISR swath is approximately 380 kilometers, with the reef clearly visible up to approximately 200 kilometers from the coast. It may be difficult to see the myriad details in the browse image, but if you retrieve the higher resolution version, a zoomed display reveals the spectacular structure of the many reefs.

    The more northerly coastal area in this image shows the vast extent of sugar cane cultivation, this being the largest sugar producing area in Australia, centered on the city of Mackay. Other industries in the area include coal, cattle, dairying, timber, grain, seafood, and fruit. The large island off the most northerly part of the coast visible in this image is Whitsunday Island, with smaller islands and reefs extending southeast, parallel to the coast. These include some of the better known resort islands such as Hayman, Lindeman, Hamilton, and Brampton Islands.

    Further south, just inland of the small semicircular bay near the right of the image, is Rockhampton, the largest city along the central Queensland coast, and the regional center for much of central Queensland. Rockhampton is just north of the Tropic of Capricorn. Its hinterland is a rich pastoral, agricultural, and mining region.

    MISR was built and is managed by NASA's Jet Propulsion Laboratory, Pasadena, CA, for NASA's Office of Earth Science, Washington, DC. The Terra satellite is managed by NASA's Goddard Space Flight Center, Greenbelt, MD. JPL is a division of the California Institute of Technology.

  2. New records of Cotylea (Polycladida, Platyhelminthes) from Lizard Island, Great Barrier Reef, Australia, with remarks on the distribution of the Pseudoceros Lang, 1884 and Pseudobiceros Faubel, 1984 species of the Indo-Pacific Marine Region.

    PubMed

    Marquina, Daniel; Aguado, M Teresa; Noreña, Carolina

    2015-09-18

    In the present work eleven polyclad species of Lizard Island are studied. Seven of them are new records for this locality of the Australian coral reef and one is new to science, Lurymare clavocapitata n. sp. (Family Prosthiostomidae). The remaining recorded species belong to the genera Pseudoceros (P. bimarginatus, P. jebborum, P. stimpsoni, P. zebra, P. paralaticlavus and P. prudhoei) and Pseudobiceros (Pb. hancockanus, Pb. hymanae, Pb. flowersi and Pb. uniarborensis). Regardless of the different distribution patterns, all pseudocerotid species show brilliant colours, but similar internal morphology. Furthermore, differences in the form and size of the stylet are characteristic, because it is a sclerotic structure that is not affected during fixation. In Pseudoceros, the distance between the sucker and the female pore also differs among species. These features do not vary enough to be considered as diagnostic, but they provide information that can help to disentangle similarly coloured species complexes. A key of the genera Pseudoceros and Pseudobiceros of the Indo-Pacific region is provided, in order to facilitate the identification of species from this area.

  3. The Secret of the Svalbard Sea Ice Barrier

    NASA Technical Reports Server (NTRS)

    Nghiem, Son V.; Van Woert, Michael L.; Neumann, Gregory

    2004-01-01

    An elongated sea ice feature called the Svalbard sea ice barrier rapidly formed over an area in the Barents Sea to the east of Svalbard posing navigation hazards. The secret of its formation lies in the bottom bathymetry that governs the distribution of cold Arctic waters masses, which impacts sea ice growth on the water surface.

  4. Poverty in Alabama. A Barrier to Postsecondary Education.

    ERIC Educational Resources Information Center

    Shannon, Mary Lee Rice

    This study was undertaken with the belief that financial need is not an isolated barrier to postsecondary education and that it is frequently accompanied by distinct motivational, academic, and geographic factors. The distribution of Alabama's poverty on a county level is shown and evaluated. It is noted that all of the countries with a…

  5. Comparing the Dimensions of Modern and Ancient Barrier Island Systems to Understand Controls on Preservation

    NASA Astrophysics Data System (ADS)

    Mulhern, J.; Johnson, C. L.; Stright, L.

    2015-12-01

    Commonly assumed to have low preservation potential, barrier islands are rarely interpreted in the rock record, and there is little consensus on the terminology and depositional models related to their interpretation. Prevalent on transgressive coastlines, the dimensions of modern barriers are used as analogs for the ancient; however, ancient examples are complicated by post-depositional processes, including thickening through amalgamation and removal by ravinement. Contrasting the dimensions of modern and ancient examples lends insight into the development and preservation of transgressive deposits, improving the ability to predict the size and distribution of barrier island sand bodies in the rock record as well as understanding the variables that control their architecture. Interpretation of barrier island deposits from the John Henry Member (Cretaceous Straight Cliffs Fm., Kaiparowits Plateau, southern Utah) motivated an investigation into both ancient and modern barrier islands. Traditional sequence stratigraphic models predict thin condensed deposition during transgression, not accounting for possible thick and laterally extensive accumulations of barrier island deposits. More recent models recognize the possible complexity and heterogeneity of transgressive deposits and the potential for barrier island accumulation. To better understand the relationship between modern and ancient barrier islands, the length (along strike), width (dip direction) and thickness (vertical) of >20 modern and >30 ancient barrier islands were compared. Ancient dimensions were gathered from the literature, while modern dimensions were aggregated from literature and a database of modern barrier islands currently being developed. Initial results suggest that ancient barrier island deposits record the motion of the shoreline during transgression. Ancient barriers are ~2-8 times wider and ~2-3 times thicker than modern islands. The dynamics of barrier island migration and sediment

  6. 30 CFR 75.819 - Motor-starter enclosures; barriers and interlocks.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Motor-starter enclosures; barriers and...-Voltage Distribution High-Voltage Longwalls § 75.819 Motor-starter enclosures; barriers and interlocks. Compartment separation and cover interlock switches for motor-starter enclosures must be maintained...

  7. 30 CFR 75.819 - Motor-starter enclosures; barriers and interlocks.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Motor-starter enclosures; barriers and...-Voltage Distribution High-Voltage Longwalls § 75.819 Motor-starter enclosures; barriers and interlocks. Compartment separation and cover interlock switches for motor-starter enclosures must be maintained...

  8. Low Conductivity Thermal Barrier Coatings

    NASA Technical Reports Server (NTRS)

    Zhu, Dong-Ming

    2005-01-01

    Thermal barrier coatings will be more aggressively designed to protect gas turbine engine hot-section components in order to meet future engine higher fuel efficiency and lower emission goals. In this presentation, thermal barrier coating development considerations and requirements will be discussed. An experimental approach is established to monitor in real time the thermal conductivity of the coating systems subjected to high-heat-flux, steady-state and cyclic temperature gradients. Advanced low conductivity thermal barrier coatings have also been developed using a multi-component defect clustering approach, and shown to have improved thermal stability. The durability and erosion resistance of low conductivity thermal barrier coatings have been improved utilizing advanced coating architecture design, composition optimization, in conjunction with more sophisticated modeling and design tools.

  9. INFORMATION BARRIERS - A HISTORICAL PERSPECTIVE

    SciTech Connect

    D. CLOSE; D. MACARTHUR; N. NICHOLAS

    2001-05-01

    The concept ''transparency'' was introduced into the safeguards lexicon in the early 1990s, and the term ''information barrier'' was introduced into the safeguards lexicon in the late 1990s. Although the terms might have been new, the concepts were not. Both concepts have been used by the International Atomic Energy Agency (IAEA) and its inspectors since the early 1980s, but the terms ''transparency'' and ''information barrier'' were not used for those concepts then. The definitions of these concepts have evolved in recent years, and these concepts have been applied to a broader category of special nuclear material measurement problems. The origin and features of the information barrier concept will be traced from an early implementation by the IAEA to the current state-of-the-art information barrier technology used in nonproliferation, arms control, and dismantlement.

  10. Subwavelength slit acoustic metamaterial barrier

    NASA Astrophysics Data System (ADS)

    Rubio, Constanza; Candelas, Pilar; Belmar, Francisco; Gomez-Lozano, Vicente; Uris, Antonio

    2015-10-01

    Reduction of noise in the transmission path is a very important environmental problem. The standard method to reduce this noise level is the use of acoustic barriers. In this paper, an acoustic metamaterial based on sound transmission through subwavelength slits, is tailored to be used as an acoustic barrier. This system consists of two rows of periodic repetition of vertical rigid pickets separated by a slit of subwavelength width, embedded in air. Here, both the experimental and the numerical analyses are presented. These analyses have facilitated the identification of the parameters that affect the insertion loss performance. The results demonstrated that the proposed barrier can be tuned to mitigate a band noise in a mechanical plant for buildings where openings for air flow are required as well as industrial noise, without excessive barrier thickness.

  11. Guided tissue regeneration. Absorbable barriers.

    PubMed

    Wang, H L; MacNeil, R L

    1998-07-01

    Over the past 15 years, techniques aimed at regeneration of lost periodontal tissue have become widely used and accepted in clinical practice. Among these techniques are those which use the principles of guided tissue regeneration (GTR), wherein barriers (i.e., membranes) are used to control cell and tissue repopulation of the periodontal wound. A variety of non-absorbable and absorbable barriers have been developed and used for this purpose, with a trend in recent years toward increased use of absorbable GTR materials. This article describes the evolution of absorbable barrier materials and overview materials available for clinical use today. In addition, advantages and disadvantages of these materials are discussed, as well as possible new developments in barrier-based GTR therapy.

  12. Ocean barrier layers' effect on tropical cyclone intensification.

    PubMed

    Balaguru, Karthik; Chang, Ping; Saravanan, R; Leung, L Ruby; Xu, Zhao; Li, Mingkui; Hsieh, Jen-Shan

    2012-09-04

    Improving a tropical cyclone's forecast and mitigating its destructive potential requires knowledge of various environmental factors that influence the cyclone's path and intensity. Herein, using a combination of observations and model simulations, we systematically demonstrate that tropical cyclone intensification is significantly affected by salinity-induced barrier layers, which are "quasi-permanent" features in the upper tropical oceans. When tropical cyclones pass over regions with barrier layers, the increased stratification and stability within the layer reduce storm-induced vertical mixing and sea surface temperature cooling. This causes an increase in enthalpy flux from the ocean to the atmosphere and, consequently, an intensification of tropical cyclones. On average, the tropical cyclone intensification rate is nearly 50% higher over regions with barrier layers, compared to regions without. Our finding, which underscores the importance of observing not only the upper-ocean thermal structure but also the salinity structure in deep tropical barrier layer regions, may be a key to more skillful predictions of tropical cyclone intensities through improved ocean state estimates and simulations of barrier layer processes. As the hydrological cycle responds to global warming, any associated changes in the barrier layer distribution must be considered in projecting future tropical cyclone activity.

  13. Ocean Barrier Layers’ Effect on Tropical Cyclone Intensification

    SciTech Connect

    Balaguru, Karthik; Chang, P.; Saravanan, R.; Leung, Lai-Yung R.; Xu, Zhao; Li, M.; Hsieh, J.

    2012-09-04

    Improving a tropical cyclone's forecast and mitigating its destructive potential requires knowledge of various environmental factors that influence the cyclone's path and intensity. Herein, using a combination of observations and model simulations, we systematically demonstrate that tropical cyclone intensification is significantly affected by salinity-induced barrier layers, which are 'quasi-permanent' features in the upper tropical oceans. When tropical cyclones pass over regions with barrier layers, the increased stratification and stability within the layer reduce storm-induced vertical mixing and sea surface temperature cooling. This causes an increase in enthalpy flux from the ocean to the atmosphere and, consequently, an intensification of tropical cyclones. On average, the tropical cyclone intensification rate is nearly 50% higher over regions with barrier layers, compared to regions without. Our finding, which underscores the importance of observing not only the upper-ocean thermal structure but also the salinity structure in deep tropical barrier layer regions, may be a key to more skillful predictions of tropical cyclone intensities through improved ocean state estimates and simulations of barrier layer processes. As the hydrological cycle responds to global warming, any associated changes in the barrier layer distribution must be considered in projecting future tropical cyclone activity.

  14. Thermal Barrier Coating Workshop, 1997

    NASA Technical Reports Server (NTRS)

    Brindley, William J. (Compiler)

    1998-01-01

    This document contains papers from the 1997 Thermal Barrier Coatings Workshop, sponsored by the TBC Interagency Coordination Committee. The Workshop was held in Fort Mitchell, Kentucky, May 19-21, 1997. The papers cover the topics of heat transfer and conductivity of thermal barrier coatings, failure mechanisms and characterization of the coatings as well as characterization of coating deposition methods. Speakers included research, development and user groups in academia, industry and government.

  15. Economic alternatives for containment barriers

    SciTech Connect

    Nicholson, P.J.; Jasperse, B.H.; Fisher, M.J.

    1997-12-31

    Fixation, barriers, and containment of existing landfills and other disposal areas are often performed by insitu auger type soil mixing and jet grouting. Cement or other chemical reagents are mixed with soil to form both vertical and horizontal barriers. Immobilization of contaminants can be economically achieved by mixing soil and the contaminants with reagents that solidify or stabilize the contaminated area. Developed in Japan, and relatively new to the United States, the first large scale application was for a vertical barrier at the Jackson Lake Dam project in 1986. This technology has grown in both the civil and environmental field since. The paper describes current United States practice for Deep Soil Mixing (over 12 meters in depth), and Shallow Soil Mixing for vertical barriers and stabilization/solidification, and Jet Grouting for horizontal and vertical barriers. Creating very low permeability barriers at depth with minimal surface return often makes these techniques economical when compared to slurry trenches. The paper will discuss equipment, materials, soil and strength parameters, and quality control.

  16. Global interrupt and barrier networks

    DOEpatents

    Blumrich, Matthias A.; Chen, Dong; Coteus, Paul W.; Gara, Alan G.; Giampapa, Mark E; Heidelberger, Philip; Kopcsay, Gerard V.; Steinmacher-Burow, Burkhard D.; Takken, Todd E.

    2008-10-28

    A system and method for generating global asynchronous signals in a computing structure. Particularly, a global interrupt and barrier network is implemented that implements logic for generating global interrupt and barrier signals for controlling global asynchronous operations performed by processing elements at selected processing nodes of a computing structure in accordance with a processing algorithm; and includes the physical interconnecting of the processing nodes for communicating the global interrupt and barrier signals to the elements via low-latency paths. The global asynchronous signals respectively initiate interrupt and barrier operations at the processing nodes at times selected for optimizing performance of the processing algorithms. In one embodiment, the global interrupt and barrier network is implemented in a scalable, massively parallel supercomputing device structure comprising a plurality of processing nodes interconnected by multiple independent networks, with each node including one or more processing elements for performing computation or communication activity as required when performing parallel algorithm operations. One multiple independent network includes a global tree network for enabling high-speed global tree communications among global tree network nodes or sub-trees thereof. The global interrupt and barrier network may operate in parallel with the global tree network for providing global asynchronous sideband signals.

  17. Investigation of special features of parameters of Schottky barrier contacts caused by a nonlinear bias dependence of the barrier height

    NASA Astrophysics Data System (ADS)

    Bozhkov, V. G.; Shmargunov, A. V.

    2012-03-01

    The results of studying the IV-characteristics (IVCs) of the contact Au-n-GaAs obtained by electrochemical deposition are presented. The observed characteristics - the bias dependence of the ideality factor (n), the measured (ϕbm) and effective (ϕbI) barrier heights, an inverse relationship between the measured barrier height and ideality factor, and the edge effects (the dependence of n, ϕbm, and ϕbI on the contact diameter) are explained by the nonlinear bias dependence on the effective barrier height. The explanation is given on the basis of the contact model with an intermediate layer and interface states (Bardeen model), and the intimate contact model with the subsurface states. The nonlinearity of the bias dependence on the barrier height is due to the inhomogeneous energy distribution of the interface states (a decrease in density from the edges to the middle of the bandgap) and the inhomogeneous energy and coordinate (from the surface to the depth) distribution of the subsurface states. An essential feature for every model is also the condition that the barrier height and ideality factor are measured at a constant current (or in a constant range of currents) while studying contacts with different diameters or when measuring the IVCs at different temperatures. This condition is not difficult to achieve, but gives the necessary certainty to different barrier height values used in examining experimental results. Some limitations and shortcomings of the widely used model of inhomogeneous Schottky barrier contact with the "saddle points" are also discussed.

  18. MODELING HOW A HURRICANE BARRIER IN NEW BEDFORD HARBOR, MASSACHUSETTS, AFFECTS THE HYDRODYNAMICS AND RESIDENCE TIMES

    EPA Science Inventory

    Two-dimensional hydrodynamic and transport models were used to simulate tidal and subtidal circulation, residence times, and the longitudinal distributions of conservative constituents in New Bedford Harbor, Massachusetts, before and after a hurricane barrier was constructed. The...

  19. Filaggrin and Skin Barrier Function.

    PubMed

    Kezic, Sanja; Jakasa, Ivone

    2016-01-01

    The skin barrier function is greatly dependent on the structure and composition of the uppermost layer of the epidermis, the stratum corneum (SC), which is made up of flattened anucleated cells surrounded by highly organized and continuous lipid matrix. The interior of the corneocytes consists mainly of keratin filaments aggregated by filaggrin (FLG) protein. Next, together with several other proteins, FLG is cross-linked into a mechanically robust cornified cell envelope providing a scaffold for the extracellular lipid matrix. In addition to its role for the SC structural and mechanical integrity, FLG degradation products account in part for the water-holding capacity and maintenance of acidic pH of the SC, both crucial for the epidermal barrier homoeostasis by regulating activity of multiple enzymes that control desquamation, lipid synthesis and inflammation. The major determinant of FLG expression in the skin are loss-of-function mutations in FLG, the strongest genetic risk factor for atopic dermatitis (AD), an inflammatory skin disease characterized by a reduced skin barrier function. The prevalence of FLG mutations varies greatly among different populations and ranges from about 10% in Northern Europeans to less than 1% in the African populations. An impaired skin barrier facilitates absorption of potentially hazardous chemicals, which might cause adverse effects in the skin, such as contact dermatitis, or systemic toxicity after their passage into blood. In another direction, a leaky epidermal barrier will lead to enhanced loss of water from the skin. A recent study has shown that even subtle increase in epidermal water loss in newborns increases the risk for AD. Although there are multiple modes of action by which FLG might affect skin barrier it is still unclear whether and how FLG deficiency leads to the reduced skin barrier function. This chapter summarizes the current knowledge in this field obtained from clinical studies, and animal and in vitro models

  20. Transport Barriers and Turbulent Equipartition

    NASA Astrophysics Data System (ADS)

    Volker, Naulin; Jonas, Nycander; Juul, Rasmussen Jens

    2000-10-01

    Turbulent equipartition and the formation and dynamics of transport barriers in the form of zonal flows are investigated. We consider pressure gradient driven flute modes in an inhomogeneous magnetic field with curvature. Numerical solutions of the model equations on a bounded domain with sources and sinks show that the turbulent fluctuations introduce an equipartition of the relevant Lagrangian invariants by effective mixing. The time averaged equilibrium density and temperature approach the profiles n ~ B and T ~ B^2/3 predicted by turbulent equipartition. However, below a critical aspect ration alpha = L_y/Lx = 3.8 large scale poloidal flows are found to develop. These so-called zonal flows quench the turbulence locally and form barriers for the turbulence flux. These barriers move on the timescale of diffusion. As the turbulence is quenched the Reynoldsstress driving the flows ceases. The transport barrier is then temporarily destroyed, triggering a large transport event. The formation and dynamics of the transport barrier and the related intermittent turbulent flux are investigated.

  1. Graphene-Based Environmental Barriers

    PubMed Central

    Guo, Fei; Silverberg, Gregory; Bowers, Shin; Kim, Sang-Pil; Datta, Dibakar; Shenoy, Vivek; Hurt, Robert H.

    2012-01-01

    Many environmental technologies rely on containment by engineered barriers that inhibit the release or transport of toxicants. Graphene is a new, atomically thin, two-dimensional sheet material, whose aspect ratio, chemical resistance, flexibility, and impermeability make it a promising candidate for inclusion in a next generation of engineered barriers. Here we show that ultrathin graphene oxide (GO) films can serve as effective barriers for both liquid and vapor permeants. First, GO deposition on porous substrates is shown to block convective flow at much lower mass loadings than other carbon nanomaterials, and can achieve hydraulic conductivities of 5×10−12 cm/s or lower. Second we show that ultrathin GO films of only 20 nm thickness coated on polyethylene films reduce their vapor permeability by 90% using elemental mercury as a model vapor toxicant. The barrier performance of GO in this thin-film configuration is much better than the Nielsen model limit, which describes ideal behavior of flake-like fillers uniformly imbedded in a polymer. The Hg barrier performance of GO films is found to be sensitive to residual water in the films, which is consistent with molecular dynamics (MD) simulations that show lateral diffusion of Hg atoms in graphene interlayer spaces that have been expanded by hydration. PMID:22717015

  2. Bioenergetic Progress and Heat Barriers

    NASA Astrophysics Data System (ADS)

    Zotin, A. A.; Lamprecht, I.; Zotin, A. I.

    2001-07-01

    Progressing biological evolution is discussed in the framework of nonequilibrium thermodynamics. It is connected with an increase of the mass specific standard metabolism given by coefficient a in the allometric relation (1) between oxygen consumption rate and body mass of an animal. Three “heat barriers” are found in the course of such a bioenergetic evolution. The first heat barrier concerns an animal's overheating during active movement and is overcome by the development of thermoregulation and the appearance of homeothermic animals. A second barrier arises when the coefficient a reaches values connected with lethal body temperatures. The transition across this second heat barrier occurs as result of reasonable activities and the appearance of civilization. The third heat barrier will arise during the further development of human civilization, connected with a highly increased energy production and a fatal warming of the Earth atmosphere. The manner to overcome this barrier will probably depend on the assimilation of space and the establishment of energy consuming industries outside the Earth. The bioenergetic evolution discussed in this paper does not exclude other trends of evolution, e.g. increase of size, and does not mean to be the only aspect of biological evolution.

  3. Electric current effect on the energy barrier of magnetic domain wall depinning: origin of the quadratic contribution.

    PubMed

    Kim, Kab-Jin; Ryu, Jisu; Gim, Gi-Hong; Lee, Jae-Chul; Shin, Kyung-Ho; Lee, Hyun-Woo; Choe, Sug-Bong

    2011-11-18

    The energy barrier of a magnetic domain wall trapped at a defect is measured experimentally. When the domain wall is pushed by an electric current and/or a magnetic field, the depinning time from the barrier exhibits perfect exponential distribution, indicating that a single energy barrier governs the depinning. The electric current is found to generate linear and quadratic contributions to the energy barrier, which are attributed to the nonadiabatic and adiabatic spin-transfer torques, respectively. The adiabatic spin-transfer torque reduces the energy barrier and, consequently, causes depinning at lower current densities, promising a way toward low-power current-controlled magnetic applications.

  4. Large-scale field testing on flexible shallow landslide barriers

    NASA Astrophysics Data System (ADS)

    Bugnion, Louis; Volkwein, Axel; Wendeler, Corinna; Roth, Andrea

    2010-05-01

    Open shallow landslides occur regularly in a wide range of natural terrains. Generally, they are difficult to predict and result in damages to properties and disruption of transportation systems. In order to improve the knowledge about the physical process itself and to develop new protection measures, large-scale field experiments were conducted in Veltheim, Switzerland. Material was released down a 30° inclined test slope into a flexible barrier. The flow as well as the impact into the barrier was monitored using various measurement techniques. Laser devices recording flow heights, a special force plate measuring normal and shear basal forces as well as load cells for impact pressures were installed along the test slope. In addition, load cells were built in the support and retaining cables of the barrier to provide data for detailed back-calculation of load distribution during impact. For the last test series an additional guiding wall in flow direction on both sides of the barrier was installed to achieve higher impact pressures in the middle of the barrier. With these guiding walls the flow is not able to spread out before hitting the barrier. A special constructed release mechanism simulating the sudden failure of the slope was designed such that about 50 m3 of mixed earth and gravel saturated with water can be released in an instant. Analysis of cable forces combined with impact pressures and velocity measurements during a test series allow us now to develop a load model for the barrier design. First numerical simulations with the software tool FARO, originally developed for rockfall barriers and afterwards calibrated for debris flow impacts, lead already to structural improvements on barrier design. Decisive for the barrier design is the first dynamic impact pressure depending on the flow velocity and afterwards the hydrostatic pressure of the complete retained material behind the barrier. Therefore volume estimation of open shallow landslides by assessing

  5. Deceleration-Limiting Roadway Barrier

    NASA Technical Reports Server (NTRS)

    Schneider, William C. (Inventor); Locke, P. James (Inventor)

    2006-01-01

    Roadway barrier system and method are disclosed for decelerating a moving vehicle in a controlled manner and for retaining the decelerated vehicle. A net or mesh of the roadway barrier system receives and captures the moving vehicle. The net or mesh is secured to anchors by energy absorbing straps. The energy absorbing straps deploy under a tensional load to decelerate the moving vehicle, the straps providing a controlled resistance to the tensional load over a predefined displacement or stroke to bring the moving vehicle to rest. Additional features include a sacrificial panel or sheet in front of the net that holds up the net or mesh while deflecting vehicles that collide only tangentially with the roadway barrier system.

  6. Stem Cells behind the Barrier

    PubMed Central

    Cangkrama, Michael; Ting, Stephen B.; Darido, Charbel

    2013-01-01

    Epidermal stem cells sustain the adult skin for a lifetime through self-renewal and the production of committed progenitors. These stem cells generate progeny that will undergo terminal differentiation leading to the development of a protective epidermal barrier. Whereas the molecular mechanisms that govern epidermal barrier repair and renewal have been extensively studied, pathways controlling stem cell differentiation remain poorly understood. Asymmetric cell divisions, small non-coding RNAs (microRNAs), chromatin remodeling complexes, and multiple differentiation factors tightly control the balance of stem and progenitor cell proliferation and differentiation, and disruption of this balance leads to skin diseases. In this review, we summarize and discuss current advances in our understanding of the mechanisms regulating epidermal stem and progenitor cell differentiation, and explore new relationships for maintenance of skin barrier function. PMID:23812084

  7. Semiclassical Transport Theory For Quantum Barrier-Conductor Chains

    NASA Astrophysics Data System (ADS)

    Sinkkonen, Juha A. T.

    1988-08-01

    A simple semiclassical treatment of the vertical transport in barrier-conductor structures is presented. The distribution function is constructed by fitting the solutions of the Boltzmann equation for the conductor parts with the barrier reflection and transmission probabilities. This semiclassical theory describes multiple reflection in a random phase approximation leaving out the fine structure associated with the quantum interference. As an application we analyze single and double barrier structures in detail. We study the high frequency behaviour of various diode structures. For the hot electron transistors (HET) we derive simple formulas for the base transport factor, transconductance and other elements of the ac-small signal equivalent circuit. The transistor model is also valid for the resonant hot electron transistor (RHET).

  8. Sound propagation over curved barriers

    NASA Technical Reports Server (NTRS)

    Pierce, Allan D.; Main, Geoffrey L.; Kearns, James A.; Hsieh, H.-A.

    1986-01-01

    Wide barriers with curved tops are studied with emphasis placed on circumstances whereby the local radius of curvature R of the barrier is continuous along the surface and is large compared to a wavelength. Results analogous to those given by Hayek et al. (1978) are reviewed and extended to cases where the radius of curvature and the surface impedance may vary with position. Circumstances not easily interpreted within the framework of the model proposed by Keller (1956) and Hayek et al. are also considered.

  9. Sound propagation over curved barriers

    NASA Astrophysics Data System (ADS)

    Pierce, Allan D.; Main, Geoffrey L.; Kearns, James A.; Hsieh, H.-A.

    Wide barriers with curved tops are studied with emphasis placed on circumstances whereby the local radius of curvature R of the barrier is continuous along the surface and is large compared to a wavelength. Results analogous to those given by Hayek et al. (1978) are reviewed and extended to cases where the radius of curvature and the surface impedance may vary with position. Circumstances not easily interpreted within the framework of the model proposed by Keller (1956) and Hayek et al. are also considered.

  10. Enhanced tunneling through nonstationary barriers

    SciTech Connect

    Palomares-Baez, J. P.; Rodriguez-Lopez, J. L.; Ivlev, B.

    2007-11-15

    Quantum tunneling through a nonstationary barrier is studied analytically and by a direct numerical solution of Schroedinger equation. Both methods are in agreement and say that the main features of the phenomenon can be described in terms of classical trajectories which are solutions of Newton's equation in complex time. The probability of tunneling is governed by analytical properties of a time-dependent perturbation and the classical trajectory in the plane of complex time. Some preliminary numerical calculations of Euclidean resonance (an easy penetration through a classical nonstationary barrier due to an underbarrier interference) are presented.

  11. Blood-brain barrier delivery.

    PubMed

    Pardridge, William M

    2007-01-01

    Neuropharmaceutics is the largest potential growth sector of the pharmaceutical industry. However, this growth is blocked by the problem of the blood-brain barrier (BBB). Essentially 100% of large-molecule drugs and >98% of small-molecule drugs do not cross the BBB. The BBB can be traversed because there are multiple endogenous transporters within this barrier. Therefore, brain drug development programs of the future need to be re-configured so that drugs are formulated to enable transport into the brain via endogenous BBB transporters.

  12. Barrier mechanisms in the Drosophila blood-brain barrier

    PubMed Central

    Hindle, Samantha J.; Bainton, Roland J.

    2014-01-01

    The invertebrate blood-brain barrier (BBB) field is growing at a rapid pace and, in recent years, studies have shown a physiologic and molecular complexity that has begun to rival its vertebrate counterpart. Novel mechanisms of paracellular barrier maintenance through G-protein coupled receptor signaling were the first demonstrations of the complex adaptive mechanisms of barrier physiology. Building upon this work, the integrity of the invertebrate BBB has recently been shown to require coordinated function of all layers of the compound barrier structure, analogous to signaling between the layers of the vertebrate neurovascular unit. These findings strengthen the notion that many BBB mechanisms are conserved between vertebrates and invertebrates, and suggest that novel findings in invertebrate model organisms will have a significant impact on the understanding of vertebrate BBB functions. In this vein, important roles in coordinating localized and systemic signaling to dictate organism development and growth are beginning to show how the BBB can govern whole animal physiologies. This includes novel functions of BBB gap junctions in orchestrating synchronized neuroblast proliferation, and of BBB secreted antagonists of insulin receptor signaling. These advancements and others are pushing the field forward in exciting new directions. In this review, we provide a synopsis of invertebrate BBB anatomy and physiology, with a focus on insights from the past 5 years, and highlight important areas for future study. PMID:25565944

  13. Access to Barrier Perches Improves Behavior Repertoire in Broilers

    PubMed Central

    Ventura, Beth A.; Siewerdt, Frank; Estevez, Inma

    2012-01-01

    Restriction of behavioral opportunities and uneven use of space are considerable welfare concerns in modern broiler production, particularly when birds are kept at high densities. We hypothesized that increased environmental complexity by provision of barrier perches would help address these issues by encouraging perching and enhancing use of the pen space across a range of stocking densities. 2,088 day-old broiler chicks were randomly assigned to one of the following barrier and density treatment combinations over four replications: simple barrier, complex barrier, or control (no barrier) and low (8 birds/m2), moderate (13 birds/m2), or high (18 birds/m2) density. Data were collected on focal birds via instantaneous scan sampling from 2 to 6 weeks of age. Mean estimates per pen for percent of observations seen performing each behavior, as well as percent of observations in the pen periphery vs. center, were quantified and submitted to an analysis of variance with week as the repeated measure. Barrier perches, density and age affected the behavioral time budget of broilers. Both simple and complex barrier perches effectively stimulated high perching rates. Aggression and disturbances were lower in both barrier treatments compared to controls (P<0.05). Increasing density to 18 birds/m2 compared to the lower densities suppressed activity levels, with lower foraging (P<0.005), decreased perching (P<0.0001) and increased sitting (P = 0.001) earlier in the rearing period. Disturbances also increased at higher densities (P<0.05). Use of the central pen area was higher in simple barrier pens compared to controls (P<0.001), while increasing density above 8 birds/m2 suppressed use of the central space (P<0.05). This work confirms some negative effects of increasing density and suggests that barrier perches have the potential to improve broiler welfare by encouraging activity (notably by providing accessible opportunities to perch), decreasing aggression and disturbances

  14. Systems study on engineered barriers: barrier performance analysis

    SciTech Connect

    Stula, R.T.; Albert, T.E.; Kirstein, B.E.; Lester, D.H.

    1980-09-01

    A performance assessment model for multiple barrier packages containing unreprocessed spent fuel has been modified and applied to several package designs. The objective of the study was to develop information to be used in programmatic decision making concerning engineered barrier package design and development. The assessment model, BARIER, was developed in previous tasks of the System Study on Engineered Barriers (SSEB). The new version discussed in this report contains a refined and expanded corrosion rate data base which includes pitting, crack growth, and graphitization as well as bulk corrosion. Corrosion rates for oxic and anoxic conditions at each of the two temperature ranges are supplied. Other improvements include a rigorous treatment of radionuclide release after package failure which includes resistance of damaged barriers and backfill, refined temperature calculations that account for convection and radiation, a subroutine to calculate nuclear gamma radiation field at each barrier surface, refined stress calculations with reduced conservatism and various coding improvements to improve running time and core usage. This report also contains discussion of alternative scenarios to the assumed flooded repository as well as the impact of water exclusion backfills. The model was used to assess post repository closure performance for several designs which were all variation of basic designs from the Spent Unreprocessed Fuel (SURF) program. Many designs were found to delay the onset of leaching by at least a few hundreds of years in all geologic media. Long delay times for radionuclide release were found for packages with a few inches of sorption backfill. Release of uranium, plutonium, and americium was assessed.

  15. Concentric superlattice pattern in dielectric barrier discharge

    NASA Astrophysics Data System (ADS)

    Feng, Jianyu; Dong, Lifang; Wei, Lingyan; Fan, Weili; Li, Caixia; Pan, Yuyang

    2016-09-01

    The concentric superlattice pattern with three sub-lattices is observed in the dielectric barrier discharge in air/argon for the first time. Its spatiotemporal structure investigated by an intensified charge-coupled device shows that it is an interleaving of three different sub-lattices, which are concentric-ring, concentric-framework, and concentric-dot, respectively. The images of single-frame indicate that the concentric-ring and concentric-framework are composed of individual filaments. By using the optical emission spectrum method, it is found that plasma parameters of the concentric-dot are different from those of the concentric-ring and concentric-framework. The spatiotemporal dynamics of the concentric superlattice pattern is dependent upon the effective field of the distribution of the wall charges field and the applied field.

  16. Toppling Job Barriers for Offenders

    ERIC Educational Resources Information Center

    McNett, Ian

    1978-01-01

    Second in a series, this article discusses the applicability of the Comprehensive Employment and Training Act (CETA) to those persons with an arrest or conviction record, who usually lack education and training and who encounter employment barriers. Some resource materials for CETA sponsors are given. (MF)

  17. Processes of barrier island erosion

    SciTech Connect

    Sallenger, A.H. Jr. ); Williams, S.J. )

    1989-09-01

    During 1986, the US Geological Survey and the Louisiana Geological Survey began a 5-year study of the processes causing the extreme rates (up to 20 m/year) of erosion of Louisiana's barrier islands. These processes must be better understood in order to predict future erosion and to assess management and erosion mitigation plans. The study is divided into three parts: the geologic development of barrier islands, the critical processes leading to erosion, and applications of results. This paper provides an overview of the part of the study on critical processes. The process part includes modeling erosion of the barrier islands due to sea level rise, the net loss of sand offshore, gradients in longshore transport, and overwash. Evidence indicates that the low-lying barrier beaches on much of the Louisiana coast do not approach an equilibrium configuration. These beaches, which, in many places, are not protected by dunes, are overwashed even during moderate storms and apparently are not evolving to a configuration that limits overwash. As a result, even with stable sea level, the beaches will continue to overwash and migrate landward during storms. Commonly used methods of modeling beach response to rising sea level assume beaches approach an equilibrium configuration, hence applying these methods to coastal Louisiana is problematical.

  18. Barrier/Cu contact resistivity

    SciTech Connect

    Reid, J.S.; Nicolet, M.A.; Angyal, M.S.; Lilienfeld, D.; Shacham-Diamand, Y.; Smith, P.M.

    1995-10-17

    The specific contact resistivity of Cu with ({alpha} + {beta})-Ta, TiN, {alpha}-W, and amorphous-Ta{sub 36}Si{sub 14}N{sub 50} barrier films is measured using a novel four-point-probe approach. Geometrically, the test structures consist of colinear sets of W-plugs to act as current and voltage probes that contact the bottom of a planar Cu/barrier/Cu stack. Underlying Al interconnects link the plugs to the current source and voltmeter. The center-to-center distance of the probes ranges from 3 to 200 {micro}m. Using a relation developed by Vu et al., a contact resistivity of roughly 7 {times} 10{sup {minus}9} {Omega} cm{sup 2} is obtained for all tested barrier/Cu combinations. By reflective-mode small-angle X-ray scattering, the similarity in contact resistivity among the barrier films may be related to interfacial impurities absorbed from the deposition process.

  19. Injectable barriers for waste isolation

    SciTech Connect

    Persoff, P.; Finsterle, S.; Moridis, G.J.; Apps, J.; Pruess, K.; Muller, S.J.

    1995-03-01

    In this paper the authors report laboratory work and numerical simulation done in support of development and demonstration of injectable barriers formed from either of two fluids: colloidal silica or polysiloxane. Two principal problems addressed here are control of gel time and control of plume emplacement in the vadose zone. Gel time must be controlled so that the viscosity of the barrier fluid remains low long enough to inject the barrier, but increases soon enough to gel the barrier in place. During injection, the viscosity must be low enough to avoid high injection pressures which could uplift or fracture the formation. To test the grout gel time in the soil, the injection pressure was monitored as grouts were injected into sandpacks. When grout is injected into the vadose zone, it slumps under the influence of gravity, and redistributes due to capillary forces as it gels. The authors have developed a new module for the reservoir simulator TOUGH2 to model grout injection into the vadose zone, taking into account the increase of liquid viscosity as a function of gel concentration and time. They have also developed a model to calculate soil properties after complete solidification of the grout. The numerical model has been used to design and analyze laboratory experiments and field pilot tests. The authors present the results of computer simulations of grout injection, redistribution, and solidification.

  20. Alumina-Enhanced Thermal Barrier

    NASA Technical Reports Server (NTRS)

    Smith, Marnell; Leiser, Dan; Goldstein, Howard

    1989-01-01

    Rigid, fibrous ceramic tile material called "alumina-enhanced thermal barrier" (AETB) extends temperature capability of insulating materials. Material has obvious potential for terrestrial use in kilns, furnaces, heat engines, and other applications in which light weight and high operating temperature are specified. Three kinds of ceramic fibers are blended, molded, and sintered to make refractory tiles.

  1. Transforming Articulation Barriers in Nursing.

    ERIC Educational Resources Information Center

    Waters, Verle

    Barriers to educational mobility for nurses have existed since the mid-1960s. In 1963, the National League for Nursing (NLN) adopted a position that ruled out articulation of any kind between associate degree in nursing (ADN) and bachelors in science in nursing (BSN) programs. In the mid-1970s, a countermovement took shape, supporting open…

  2. Environmental barriers in mainstream schools.

    PubMed

    Hemmingson, H; Borell, L

    2002-01-01

    Research on students with disabilities in mainstream schools often focuses on the students' personal abilities rather than on the establishment itself. To promote inclusive education, the environmental prerequisite for participation has to be explored also. The aim of this study was to identify the barriers to participation in Swedish mainstream schools, from the personal perspective of students with physical disabilities. The study also investigated how gender, diagnosis, level of mobility, academic years and availability of an assistant were related to student-environment fit. A total of 34 students with physical disabilities, aged between 10 and 19 years, participated in the study. The students were assessed by 'The school-setting interview'. Results show that two-thirds of the students experienced barriers to participation in both the physical and the social environment. A majority of the barriers originated from the way in which school activities were organized and carried out in schools. Failure to provide adequate environmental adjustments resulted in restricted participation or exclusion from some of the activities in class. Older students experienced significantly more barriers than younger ones because the school organization was less favourable. The results suggest that the way in which activities are organized in school is the area in need of most improvements to promote participation of students with physical disabilities.

  3. Plastic Schottky barrier solar cells

    DOEpatents

    Waldrop, James R.; Cohen, Marshall J.

    1984-01-24

    A photovoltaic cell structure is fabricated from an active medium including an undoped, intrinsically p-type organic semiconductor comprising polyacetylene. When a film of such material is in rectifying contact with a magnesium electrode, a Schottky-barrier junction is obtained within the body of the cell structure. Also, a gold overlayer passivates the magnesium layer on the undoped polyacetylene film.

  4. Overcoming Barriers: Women in Superintendency

    ERIC Educational Resources Information Center

    Miller, Claire M.

    2009-01-01

    Women currently represent the largest number of teachers in the United States but remain underrepresented in the superintendent position. This suggests that the superintendency has been influenced by patriarchy. If women are to break through the barriers that prevent them from attaining a superintendency, we will need to understand the social…

  5. Vented Cavity Radiant Barrier Assembly And Method

    DOEpatents

    Dinwoodie, Thomas L.; Jackaway, Adam D.

    2000-05-16

    A vented cavity radiant barrier assembly (2) includes a barrier (12), typically a PV module, having inner and outer surfaces (18, 22). A support assembly (14) is secured to the barrier and extends inwardly from the inner surface of the barrier to a building surface (14) creating a vented cavity (24) between the building surface and the barrier inner surface. A low emissivity element (20) is mounted at or between the building surface and the barrier inner surface. At least part of the cavity exit (30) is higher than the cavity entrance (28) to promote cooling air flow through the cavity.

  6. Barriers to improvements in energy efficiency

    SciTech Connect

    Reddy, A.K.N.

    1991-10-01

    To promote energy-efficiency improvements, actions may be required at one or more levels -- from the lowest level of the consumer (residential, commercial, industrial, etc.) through the highest level of the global agencies. But barriers to the implementation of energy-efficiency improvements exist or can arise at all these levels. Taking up each one of these barriers in turn, the paper discusses specific measures that can contribute to overcoming the barriers. However, a one-barrier-one-measure approach must be avoided. Single barriers may in fact involve several sub-barriers. Also, combinations of measures are much more effective in overcoming barriers. In particular, combinations of measures that simultaneously overcome several barriers are most successful. The paper discusses the typology of barriers, explores their origin and suggests measures that by themselves or in combination with other measures, will overcome these barriers. Since most of the barriers dealt with can be found in the ``barriers`` literature, any originality in the paper lies in its systematic organization, synoptic view and holistic treatment of this issue. This paper is intended to initiate a comprehensive treatment of barriers, their origins and the measures that contribute to overcoming them. Hopefully, such a treatment will facilitate the implementation of energy-efficiency improvements involving a wide diversity of ever-changing energy end uses and consumer preferences.

  7. Barriers to improvements in energy efficiency

    SciTech Connect

    Reddy, A.K.N.

    1991-10-01

    To promote energy-efficiency improvements, actions may be required at one or more levels -- from the lowest level of the consumer (residential, commercial, industrial, etc.) through the highest level of the global agencies. But barriers to the implementation of energy-efficiency improvements exist or can arise at all these levels. Taking up each one of these barriers in turn, the paper discusses specific measures that can contribute to overcoming the barriers. However, a one-barrier-one-measure approach must be avoided. Single barriers may in fact involve several sub-barriers. Also, combinations of measures are much more effective in overcoming barriers. In particular, combinations of measures that simultaneously overcome several barriers are most successful. The paper discusses the typology of barriers, explores their origin and suggests measures that by themselves or in combination with other measures, will overcome these barriers. Since most of the barriers dealt with can be found in the barriers'' literature, any originality in the paper lies in its systematic organization, synoptic view and holistic treatment of this issue. This paper is intended to initiate a comprehensive treatment of barriers, their origins and the measures that contribute to overcoming them. Hopefully, such a treatment will facilitate the implementation of energy-efficiency improvements involving a wide diversity of ever-changing energy end uses and consumer preferences.

  8. Autostereoscopic display concept with time-sequential wavelength-selective filter-barrier

    NASA Astrophysics Data System (ADS)

    Jurk, Silvio; Kuhlmey, Mathias; Bartmann, Roland; Duckstein, Bernd; de la Barré, René

    2016-03-01

    A spatially multiplexed autostereoscopic 3D display design with a strip barrier consisting of RGB-color filters is presented. The wavelength selective filter barrier emits the light from a display area larger than that of common autostereoscopic barrier displays. However, such construction is still used rather rarely. The time sequential operation mode is a supplemental option. Wavelength selective filter barrier arrangements exhibit characteristics different from common barrier displays with similar barrier pitch and ascent. In particular these constructions show strong angular luminance dependency under barrier inclination specified by correspondent slant angle. In time sequential implementation it is important to avoid that quick eye or eyelid movement lead to visible color artifacts. Those circumstances limit the possibility to find well working and usable display designs superior to usual barrier displays. The newly introduced design is usable as a multi user display as well as a single user system with user adaptive control. In case of tracked single user mode the adaption in x-z-direction is continuously. The design has been modelled with simulation software developed for that purpose. The modelling of wavelength-selective barriers was used to calculate the light ray distribution properties of that arrangement. For the experimental verification of the image separation and evaluation of image quality, commercially available display components were combined for a display demonstrator.

  9. Barriers and facilitators of sports in Dutch Paralympic athletes: An explorative study.

    PubMed

    Jaarsma, E A; Geertzen, J H B; de Jong, R; Dijkstra, P U; Dekker, R

    2014-10-01

    The purpose of this study was to gain insight in barriers and facilitators of sports in paralympic athletes. An online questionnaire was distributed through the Netherlands Olympic Committee and National Sports Confederation to determine personal and environmental barriers and facilitators of sports participation. The International Classification of Functioning, Disability and Health model and theory of planned behavior were used to respectively categorize the results in environmental and personal factors, and attitude, subjective norm and perceived behavioral control. Seventy-six Dutch Paralympic athletes completed the questionnaire (51% response rate). Barriers and facilitators experienced by ambulant and wheelchair athletes were compared. Most frequently mentioned personal barrier was dependency of others (22%), while most frequently mentioned environmental barrier was lack of sports facilities (30%). Wheelchair athletes mentioned more barriers (median = 3, interquartile range: 0.5-6), than ambulant athletes (median = 1.0,interquartile range:0.0-3.0, P = 0.023). One-third of the athletes did not experience any barriers. Most frequently mentioned personal facilitators to initiate sports participation were fun (78%), health (61%), and competition (53%). Most frequently mentioned environmental facilitator was social support (40%). This study indicated that barriers of sport were mostly environmental, while facilitators were usually personal factors. Attitude and subjective norm were considered the most important components for intention to participation in sports. The facilitators outweighed the barriers and kept the athletes being active in sports.

  10. Geographical Barriers Impeded the Spread of a Parasitic Chromosome

    PubMed Central

    Manrique-Poyato, María Inmaculada; López-León, María Dolores; Cabrero, Josefa; Gómez, Ricardo; Perfectti, Francisco; Camacho, Juan Pedro M.

    2015-01-01

    Parasitic supernumerary (B) chromosomes show high capability to spread across populations. But the existence of abrupt discontinuities in their distribution demands an explanation. The grasshopper Eyprepocnemis plorans plorans harbour supernumerary chromosomes in all natural populations hitherto analyzed from the Circum-Mediterranean region, with the single exception of the headwaters of the Iberian Segura River and several of its tributaries. To ascertain the causes of this distribution pattern, we analyze here the genetic structure of five natural populations collected in this zone (two +B and three -B), by means of ISSR markers. We found significant population structure, with two kinds of populations coinciding with +B and -B ones, separated by strong barriers to gene flow. This gives strong support to the hypothesis that the non-B populations precede B origin, and that B-carrying individuals from coastal zones have been able to colonize upstream areas, until geographical barriers (usually narrow canyons and arid areas surrounding them) impeded their advance. PMID:26111020

  11. Sound barriers from materials of inhomogeneous impedance.

    PubMed

    Wang, Xu; Mao, Dongxing; Yu, Wuzhou; Jiang, Zaixiu

    2015-06-01

    Sound barriers are extensively used in environmental noise protection. However, when barriers are placed in parallel on opposite sides of a sound source, their performance deteriorates markedly. This paper describes a barrier made from materials of inhomogeneous impedance which lacks this drawback. The nonuniform impedance affects the way sound undergoes multiple reflections, and in the process traps acoustic energy. A proposed realization of the barrier comprises a closely spaced array of progressively tuned hollow narrow tubes which create a phase gradient. The acoustics of the barrier is theoretically examined and its superiority over conventional barriers is calculated using finite element modeling. Structural parameters of the barrier can be changed to achieve the required sound insertion loss, and the barrier has the potential to be widely used in environmental noise control.

  12. PERMEABLE REACTIVE BARRIER TECHNOLOGIES FOR CONTAMINANT REMEDIATION

    EPA Science Inventory

    Environmental scientists are generally familiar with the concept of barriers for restricting the movement of contaminant plumes in ground water. Such barriers are typically constructed of highly impermeable emplacements of materials such as grouts, slurries, or sheet pilings to ...

  13. Morphology and stratigraphy of small barrier-lagoon systems in Maine

    USGS Publications Warehouse

    Duffy, W.; Belknap, D.F.; Kelley, J.T.

    1989-01-01

    The coast of Maine contains over 200 individual barrier-lagoon systems, most quite small, with an aggregate length of nearly 100 km. Although they represent less than 5% of the tidally influenced coastline of Maine, they are widely distributed and occur in a variety of dynamic regimes and physiographic regions. Their morphology and backbarrier stratigraphy are different from better studied coastal plain systems, and provide important clues to the Holocene evolution of the Maine coast. In a study of geomorphic form and backbarrier stratigraphy, inlet processes and Holocene sea-level rise have been identified as the principal controls on coarse-grained barrier stratigraphy. Barriers in Maine are found in five distinct geomorphic forms, identified herein as: barrier spits, pocket barriers, double tombolos, cuspate barriers and looped barriers. The few long sandy beaches in southwestern Maine are mostly barrier spits. The remainder of the barrier types is composed primarily of gravel or mixed sand and gravel. The barriers protect a variety of backbarrier environments: fresh and brackish ponds, lagoons and fresh- and saltwater marshes. The barriers may or may not have inlets. Normal wave action, coarse-grain size and a deeply embayed coast result in barriers with steep, reflective profiles several meters above MHW. Occasional storm events completely wash over the barriers, building steep, lobate gravel fans along their landward margin. Few, if any, extensive storm layers are recognized as extending into the distal backbarrier environments, however. During sea-level rise and landward barrier retreat, this abrupt, storm-generated transition zone inters the backbarrier sediments. Statistical comparisons of barrier morphology, location and backbarrier environment type with backbarrier stratigraphy show that Holocene backbarrier stratigraphy is best predicted by the modern backbarrier environment type. This, in turn, is influenced most by the absence or presence, and long

  14. Dielectric barrier discharges applied for optical spectrometry

    NASA Astrophysics Data System (ADS)

    Brandt, S.; Schütz, A.; Klute, F. D.; Kratzer, J.; Franzke, J.

    2016-09-01

    The present review reflects the importance of dielectric barrier discharges for optical spectrometric detection in analytical chemistry. In contrast to usual discharges with a direct current the electrodes are separated by at least one dielectric barrier. There are two main features of the dielectric barrier discharges: they can serve as dissociation and excitation devices as well as ionization sources, respectively. This article portrays various application fields of dielectric barrier discharges in analytical chemistry used for elemental and molecular detection with optical spectrometry.

  15. 40 CFR 194.44 - Engineered barriers.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 26 2013-07-01 2013-07-01 false Engineered barriers. 194.44 Section 194.44 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) RADIATION PROTECTION... accessible environment. (b) In selecting any engineered barrier(s) for the disposal system, the...

  16. Barriers to Mammography among Inadequately Screened Women

    ERIC Educational Resources Information Center

    Stoll, Carolyn R. T.; Roberts, Summer; Cheng, Meng-Ru; Crayton, Eloise V.; Jackson, Sherrill; Politi, Mary C.

    2015-01-01

    Mammography use has increased over the past 20 years, yet more than 30% of women remain inadequately screened. Structural barriers can deter individuals from screening, however, cognitive, emotional, and communication barriers may also prevent mammography use. This study sought to identify the impact of number and type of barriers on mammography…

  17. Article Including Environmental Barrier Coating System

    NASA Technical Reports Server (NTRS)

    Lee, Kang N. (Inventor)

    2015-01-01

    An enhanced environmental barrier coating for a silicon containing substrate. The enhanced barrier coating may include a bond coat doped with at least one of an alkali metal oxide and an alkali earth metal oxide. The enhanced barrier coating may include a composite mullite bond coat including BSAS and another distinct second phase oxide applied over said surface.

  18. Security barriers with automated reconnaissance

    DOEpatents

    McLaughlin, James O; Baird, Adam D; Tullis, Barclay J; Nolte, Roger Allen

    2015-04-07

    An intrusion delaying barrier includes primary and secondary physical structures and can be instrumented with multiple sensors incorporated into an electronic monitoring and alarm system. Such an instrumented intrusion delaying barrier may be used as a perimeter intrusion defense and assessment system (PIDAS). Problems with not providing effective delay to breaches by intentional intruders and/or terrorists who would otherwise evade detection are solved by attaching the secondary structures to the primary structure, and attaching at least some of the sensors to the secondary structures. By having multiple sensors of various types physically interconnected serves to enable sensors on different parts of the overall structure to respond to common disturbances and thereby provide effective corroboration that a disturbance is not merely a nuisance or false alarm. Use of a machine learning network such as a neural network exploits such corroboration.

  19. Ductal barriers in mammary epithelium

    PubMed Central

    Owens, Mark B; Hill, Arnold DK; Hopkins, Ann M

    2013-01-01

    Tissue barriers play an integral role in the biology and pathobiology of mammary ductal epithelium. In normal breast physiology, tight and adherens junctions undergo dynamic changes in permeability in response to hormonal and other stimuli, while several of their proteins are directly involved in mammary tumorigenesis. This review describes first the structure of mammary ductal epithelial barriers and their role in normal mammary development, examining the cyclical changes in response to puberty, pregnancy, lactation and involution. It then examines the role of adherens and tight junctions and the participation of their constituent proteins in mammary tumorigenic functions such as migration, invasion and metastasis. Finally, it discusses the potential of these adhesion proteins as both prognostic biomarkers and potential therapeutic targets in breast cancer. PMID:24665412

  20. Psoriasis genetics: breaking the barrier

    PubMed Central

    Roberson, Elisha D.O.; Bowcock, Anne M.

    2010-01-01

    Psoriasis is a common incurable inflammatory skin disease affecting 2–3% of the European population. Psoriatic skin contains large numbers of immune cells which produce many cytokines, chemokines and inflammatory molecules. The epidermis divides much faster than normal and has a defective outer layer or barrier which under normal circumstances protects from infection and dehydration. Psoriatic skin is characterized by a distinct set of inflammation and epidermal proliferation and differentiation markers, and it has not been clear if the genetic basis of psoriasis is due to defects of the immune system or the skin. One genetic determinant lies within the major histocompatibility complex class 1 region. Genome-wide association studies have revealed genetic susceptibility factors that play a role in the formation of immune cells found in psoriasis lesions. Others affect epidermal proliferation and the formation of the skin’s barrier. Hence, genetic components of both the immune system and the epidermis predispose to disease. PMID:20692714

  1. Overcome barriers to career success

    SciTech Connect

    Raudsepp, E.

    1983-04-01

    A test is given to determine if an engineer suffers from one of the three barriers to technical success: fear of success, fear of failure, or perfectionism. As in most such tests, the middle way is best. Successful engineers know that perfection cannot be attained, that they don't have time to worry about failure or success, and that by aiming and perservering in doing things well, success can be achieved.

  2. Flexible pile thermal barrier insulator

    NASA Technical Reports Server (NTRS)

    Anderson, G. E.; Fell, D. M.; Tesinsky, J. S. (Inventor)

    1978-01-01

    A flexible pile thermal barrier insulator included a plurality of upstanding pile yarns. A generally planar backing section supported the upstanding pile yarns. The backing section included a plurality of filler yarns forming a mesh in a first direction. A plurality of warp yarns were looped around said filler yarns and pile yarns in the backing section and formed a mesh in a second direction. A binder prevented separation of the yarns in the backing section.

  3. Permanence of Temporary Security Barriers

    DTIC Science & Technology

    2009-05-01

    confidence among interface residents that the outcome of the process will be a lasting improvement in safety, security and quality of life adequate...most significant finding was that the most direct link to removal of barriers is risk tolerance regarding an improved security environment, but the...tolerance in regards to an improving security environment. This fell short of identifying specific conditions or criteria for the removal of security

  4. Great Barrier Reef, Queensland, Australia

    NASA Technical Reports Server (NTRS)

    1991-01-01

    Along the coast of Queensland, Australia (18.0S, 147.5E), timbered foothills of the Great Dividing Range separate the semi-arid interior of Queensland from the farmlands of the coastal plains. Prominent cleared areas in the forest indicate deforestation for farm and pasture lands. Offshore, islands and the Great Barrier Reef display sand banks along the southern sides of the structures indicating a dominant southerly wind and current direction.

  5. Improved performance thermal barrier coatings

    NASA Technical Reports Server (NTRS)

    Levine, S. R.; Miller, R. A.; Stecura, S.

    1983-01-01

    Thermal barrier coatings offer an attractive approach to improving the durability and efficiency of the hot section of heat engines. The coatings typically consist of an inner alloy bond coating about 0.01 cm thick resistant to oxidation and hot corrosion and an outer ceramic layer, usually a stabilized zirconia, 0.01-0.05 cm thick. Here, the materials, thermomechanical stress, and hot corrosion problems associated with thermal barrier coatings are reviewed along with the capabilities and limitations of current technology. The coatings discussed include ZrO2-Y2O3/NiCrAlY, ZrO2-Y2O3/NiCoCrAlY, ZrO2-MgO/NiCoCrAlY, CaO-SiO2/Co-Cr-Al-Y, and CaO-SiO2/NiCrAlY systems. It is emphasized that the performance of thermal barrier coatings is governed by many complex and interrelated factors, so that optimization of these coatings always involves certain tradeoffs.

  6. Skin Barrier Function and Allergens.

    PubMed

    Engebretsen, Kristiane Aasen; Thyssen, Jacob Pontoppidan

    2016-01-01

    The skin is an important barrier protecting us from mechanical insults, microorganisms, chemicals and allergens, but, importantly, also reducing water loss. A common hallmark for many dermatoses is a compromised skin barrier function, and one could suspect an elevated risk of contact sensitization (CS) and allergy following increased penetration of potential allergens. However, the relationship between common dermatoses such as psoriasis, atopic dermatitis (AD) and irritant contact dermatitis (ICD) and the development of contact allergy (CA) is complex, and depends on immunologic responses and skin barrier status. Psoriasis has traditionally been regarded a Th1-dominated disease, but the discovery of Th17 cells and IL-17 provides new and interesting information regarding the pathogenesis of the disease. Research suggests an inverse relationship between psoriasis and CA, possibly due to increased levels of Th17 cells and its associated cytokines. As for AD, a positive association to CS has been established in epidemiological studies, but is still unresolved. Experimental studies show, however, an inverse relationship between AD and CS. The opposing and antagonistic influences of Th1 (CS) and Th2 (AD) have been proposed as an explanation. Finally, there is convincing evidence that exposure to irritants increases the risk of CS, and patients with ICD are, therefore, at great risk of developing CA. Skin irritation leads to the release of IL-1 and TNF-α, which affects the function of antigen-presenting cells and promotes their migration to local lymph nodes, thus increasing the probability of CS and ultimately the development of CA.

  7. Development and Effectiveness of a Dairy Foods Curriculum Packet and Inservice and the Assessment of Barriers to Dairy Foods Education

    ERIC Educational Resources Information Center

    Kahnke, Sheri L.; Baer, Robert J.; Portillo, Matthew T.

    2006-01-01

    A Dairy Foods Curriculum Packet and inservice training were provided to South Dakota high school agricultural education instructors. Instructors rated barriers to implementation of teaching dairy foods as "small to medium barriers." After curriculum distribution and inservice training, more than half of instructors indicated an increase…

  8. Cryogenic Barrier Demonstration Project. Final report

    SciTech Connect

    Johnson, L.A.; Yarmak, E.; Long, E.L.

    2000-03-01

    A long-term frozen soil barrier was implemented at the HRE (Homogeneous Reactor Experiment) Pond facility at the Oak Ridge National Laboratory in 1997. This was performed to verify the technical feasibility and costs of deploying a frozen barrier at a radiologically contaminated site. Work began in September 1996 and progressed through to December 1999. The frozen barrier has been operational since November 1997. Verification of the barrier integrity was performed independently by the EPA's SITE Program. This project showed frozen barriers offer a proven technology to retain below grade hazardous substances at relatively low costs with minimal effect on the environment.

  9. Diffraction of sound by nearly rigid barriers

    NASA Technical Reports Server (NTRS)

    Hadden, W. J., Jr.; Pierce, A. D.

    1976-01-01

    The diffraction of sound by barriers with surfaces of large, but finite, acoustic impedance was analyzed. Idealized source-barrier-receiver configurations in which the barriers may be considered as semi-infinite wedges are discussed. Particular attention is given to situations in which the source and receiver are at large distances from the tip of the wedge. The expression for the acoustic pressure in this limiting case is compared with the results of Pierce's analysis of diffraction by a rigid wedge. An expression for the insertion loss of a finite impedance barrier is compared with insertion loss formulas which are used extensively in selecting or designing barriers for noise control.

  10. Testosterone perturbs epidermal permeability barrier homeostasis.

    PubMed

    Kao, J S; Garg, A; Mao-Qiang, M; Crumrine, D; Ghadially, R; Feingold, K R; Elias, P M

    2001-03-01

    Although there are no known gender-related differences in permeability barrier function in adults, estrogens accelerate whereas testosterone retards barrier development in fetal skin, and male fetuses demonstrate slower barrier development than female littermates. Moreover, prenatal administration of the androgen receptor antagonist, flutamide, equalizes developmental rates in male and female fetuses. Therefore, we evaluated the effects of changes in testosterone on barrier homeostasis in adult murine and human skin. Hypogonadal mice (whether by castration or by treatment with systemic flutamide) displayed significantly faster barrier recovery at 3, 6, and 12 h than did controls, and testosterone replacement slowed barrier recovery in castrated mice. Moreover, testosterone directly effects the skin, as topical flutamide also accelerated barrier recovery in normal male mice. These findings appear to be of physiologic significance, since prepubertal male mice (age 5 wk) displayed accelerated barrier recovery in comparison with adult postpubertal (11 wk) males. These studies also appear to be relevant for humans, as a hypopituitary human subject demonstrated repeated changes in barrier recovery in parallel with peaks and nadirs in serum testosterone levels during intermittent testosterone replacement. Mechanistic studies showed that differences in epidermal lipid synthesis do not account for the testosterone-induced functional alterations. Instead, epidermal lamellar body (LB) formation and secretion both decrease, resulting in decreased extracellular lamellar bilayers in testosterone-replete animals. These studies demonstrate that fluctuations in testosterone modulate barrier function, and that testosterone repletion can have negative consequences for permeability barrier homeostasis.

  11. Dielectric barrier discharges in analytical chemistry.

    PubMed

    Meyer, C; Müller, S; Gurevich, E L; Franzke, J

    2011-06-21

    The present review reflects the importance of dielectric barrier discharges in analytical chemistry. Special about this discharge is-and in contrast to usual discharges with direct current-that the plasma is separated from one or two electrodes by a dielectric barrier. This gives rise to two main features of the dielectric barrier discharges; it can serve as dissociation and excitation device and as ionization mechanism, respectively. The article portrays the various application fields for dielectric barrier discharges in analytical chemistry, for example the use for elemental detection with optical spectrometry or as ionization source for mass spectrometry. Besides the introduction of different kinds of dielectric barrier discharges used for analytical chemistry from the literature, a clear and concise classification of dielectric barrier discharges into capacitively coupled discharges is provided followed by an overview about the characteristics of a dielectric barrier discharge concerning discharge properties and the ignition mechanism.

  12. Retrostructural model to predict biomass formulations for barrier performance.

    PubMed

    Zhu Ryberg, Y Z; Edlund, U; Albertsson, A-C

    2012-08-13

    Barrier performance and retrostructural modeling of the macromolecular components demonstrate new design principles for film formulations based on renewable wood hydrolysates. Hardwood hydrolysates, which contain a fair share of lignin coexisting with poly- and oligosaccharides, offer excellent oxygen-barrier performance. A Hansen solubility parameter (HSP) model has been developed to convert the complex hydrolysate structural compositions into relevant matrix oxygen-permeability data allowing a systematic prediction of how the biomass should be formulated to generate an efficient barrier. HSP modeling suggests that the molecular packing ability plays a key role in the barrier performance. The actual size and distribution of free volume holes in the matrices were quantified in the subnanometer scale with Positron annihilation lifetime spectroscopy (PALS) verifying the affinity-driven assembly of macromolecular segments in a densely packed morphology and regulating the diffusion of small permeants through the matrix. The model is general and can be adapted to determine the macromolecular affinities of any hydrolysate biomass based on chemical composition.

  13. Heavy-Ion Fusion near and below the Coulomb Barrier: New Results

    NASA Astrophysics Data System (ADS)

    Stefanini, A. M.

    2009-03-01

    Fusion hindrance well below the Coulomb barrier has been observed in several systems in recent years showing systematic but also unsystematic behaviours. Our understanding of this phenomenon has greatly advanced in the last 2-3 years. Coupled-channel effects leading to barrier distributions, influence the threshold energy for hindrance. Very recent measurements on 36S+48Ca, 64Ni, performed at LNL, are presented. The two excitation functions are very different below the barrier, possibly due to the Q-value for CN formation. A few other systems, for which previous experiments were done, show interesting features, suggesting measurements at still lower energies.

  14. Double barrier system for an in situ conversion process

    DOEpatents

    McKinzie, Billy John [Houston, TX; Vinegar, Harold J [Bellaire, TX; Cowan, Kenneth Michael [Sugar land, TX; Deeg, Wolfgang Friedrich Johann [Houston, TX; Wong, Sau-Wai [Rijswijk, NL

    2009-05-05

    A barrier system for a subsurface treatment area is described. The barrier system includes a first barrier formed around at least a portion of the subsurface treatment area. The first barrier is configured to inhibit fluid from exiting or entering the subsurface treatment area. A second barrier is formed around at least a portion of the first barrier. A separation space exists between the first barrier and the second barrier.

  15. The Blood-Testis Barrier and Male Sexual Dysfunction following Spinal Cord Injury

    DTIC Science & Technology

    2014-10-01

    AWARD NUMBER: W81XWH-12-1-0481 TITLE: The Blood-Testis Barrier and Male Sexual Dysfunction following Spinal Cord Injury PRINCIPAL INVESTIGATOR...AND SUBTITLE: l The Blood-Testis Barrier and Male Sexual Dysfunction following Spinal Cord Injury 5a. CONTRACT NUMBER 5b. GRANT NUMBER W81XWH-12-1...for Public Release; Distribution Unlimited 13. SUPPLEMENTARY NOTES 14. ABSTRACT A majority of males exhibit a profound loss of fertility following

  16. Modeling, analysis, and validation of an active T-shaped noise barrier.

    PubMed

    Fan, Rongping; Su, Zhongqing; Cheng, Li

    2013-09-01

    With ever-increasing land traffic, abatement of traffic noise using noise barriers remains significant, yet it is a challenging task due to spatial competition with other infrastructure. In this study, a deep insight into the diffraction characteristics of acoustic fields near noise barriers of various geometries and surface conditions was achieved using numerical simulations. A T-shaped passive noise barrier with acoustically soft upper surfaces was demonstrated to outperform other candidates in a middle- or high-frequency range. Based on attributes of the acoustic field diffracted by T-shaped barriers, an active control strategy was developed to revamp the T-shaped barrier, in which a filtered minimax algorithm was established to drive the secondary sound sources. This algorithm resulted in more uniformly distributed residual sound fields than a filtered-X least mean square algorithm. Performance of the actively controlled barrier was evaluated at different positions and spacings of secondary sound sources and error sensors, leading to a series of optimal criteria for the design of active noise barriers. A prototype was fabricated and validated experimentally, manifesting particular effectiveness in insulating low-frequency noise, supplementing well the capacity of a passive T-shaped barrier which is effective in the middle- or high-frequency range.

  17. Thermal Conductivity of Ceramic Thermal Barrier and Environmental Barrier Coating Materials

    NASA Technical Reports Server (NTRS)

    Zhu, Dong-Ming; Bansal, Narottam P.; Lee, Kang N.; Miller, Robert A.

    2001-01-01

    Thermal barrier and environmental barrier coatings (TBC's and EBC's) have been developed to protect metallic and Si-based ceramic components in gas turbine engines from high temperature attack. Zirconia-yttria based oxides and (Ba,Sr)Al2Si2O8(BSAS)/mullite based silicates have been used as the coating materials. In this study, thermal conductivity values of zirconia-yttria- and BSAS/mullite-based coating materials were determined at high temperatures using a steady-state laser heat flux technique. During the laser conductivity test, the specimen surface was heated by delivering uniformly distributed heat flux from a high power laser. One-dimensional steady-state heating was achieved by using thin disk specimen configuration (25.4 mm diam and 2 to 4 mm thickness) and the appropriate backside air-cooling. The temperature gradient across the specimen thickness was carefully measured by two surface and backside pyrometers. The thermal conductivity values were thus determined as a function of temperature based on the 1-D heat transfer equation. The radiation heat loss and laser absorption corrections of the materials were considered in the conductivity measurements. The effects of specimen porosity and sintering on measured conductivity values were also evaluated.

  18. Fire resistant oil spill barrier

    SciTech Connect

    Lane, P.

    1986-08-12

    A fire-resistant, portable, barrier for the containment of marine oil spill, is described which consists of: (A) a continuous length of a fire-resistant fabric comprising interwoven yarns of heat-resistant material, coated with a liquid-impermeable film; the fabric being impermeable to a hydrocarbon petroleum oil; (B) buoyant bodies attached to the fabric in a quantity and at positions sufficient to buoy the length of fabric on a body of water; and (C) means for stabilizing the length of fabric when buoyed upon the body of water.

  19. Hydrogen-isotope permeation barrier

    DOEpatents

    Maroni, Victor A.; Van Deventer, Erven H.

    1977-01-01

    A composite including a plurality of metal layers has a Cu-Al-Fe bronze layer and at least one outer layer of a heat and corrosion resistant metal alloy. The bronze layer is ordinarily intermediate two outer layers of metal such as austenitic stainless steel, nickel alloys or alloys of the refractory metals. The composite provides a barrier to hydrogen isotopes, particularly tritium that can reduce permeation by at least about 30 fold and possibly more below permeation through equal thicknesses of the outer layer material.

  20. Monitoring of Zero-Valent Iron Permeable Reactive Barriers: Electrical Properties and Barrier Aging

    NASA Astrophysics Data System (ADS)

    Labrecque, D. J.; Adkins, P. L.; Slater, L. D.; Versteeg, R.; Sharpe, R.

    2007-12-01

    An innovative method of groundwater remediation invented in the 1990"s, Permeable Reactive Barriers, use sand-sized grains of scrap iron placed in trenches or injected under pressure to remediate a number of organic and inorganic contaminants. Monitoring the aging of these barriers becomes increasingly important as many of these barriers approach their predicted life spans. In-situ resistivity and induced polarization studies have been conducted at six barriers at four different sites: Monticello, Utah; the Denver Federal Center; Kansas City, Missouri; and East Helena, Montana. As some barriers tend to age dramatically faster than others, for this study we consider low permeability barriers as of greater age, as "old" barriers tend to loose permeability rather than exhaust reactive materials. One complicating factor is that two of the barriers studied appear to have issues related to installation. One site, the former Asarco Smelter Site near East Helena, Montana, has been instrumented with an autonomous monitoring system allowing continuous monitoring of the evolution of a relatively new (less than three years old) barrier. The barrier showed surprisingly rapid evolution over the first year of monitoring with changes in both resistivity and chargeability of tens of percent per month. In general, the electrical properties of all of the barriers studied follow a pattern. New barriers are fairly resistive with in-situ conductivity only a few times background (outside the barrier) values. Older barriers get increasingly conductive, with failed barriers showing values of over 100 S/m. The induced polarization response is more complicated. Chargeability values increase over time for young barriers, are largest for healthy barriers in the middle of their lifespan, and decrease as the barrier ages.

  1. Westinghouse thermal barrier coatings development

    SciTech Connect

    Goedjen, J.G.; Wagner, G.

    1995-10-01

    Westinghouse, in conjunction with the Department of Energy and Oak Ridge National Laboratory, has embarked upon a program for the development of advanced thermal barrier coatings for industrial gas turbines. Development of thermal barrier coatings (TBC`s) for industrial gas turbines has relied heavily on the transfer of technology from the aerospace industry. Significant differences in the time/temperature/stress duty cycles exist between these two coating applications. Coating systems which perform well in aerospace applications may not been optimized to meet power generation performance requirements. This program will focus on development of TBC`s to meet the specific needs of power generation applications. The program is directed at developing a state-of-the-art coating system with a minimum coating life of 25,000 hours at service temperatures required to meet increasing operating efficiency goals. Westinghouse has assembled a team of university and industry leaders to accomplish this goal. Westinghouse will coordinate the efforts of all program participants. Chromalloy Turbine Technologies, Inc. and Sermatech International, Inc. will be responsible for bond coat and TBC deposition technology. Praxair Specialty Powders, Inc. will be responsible for the fabrication of all bond coat and ceramic powders for the program. Southwest Research Institute will head the life prediction modelling effort; they will also be involved in coordinating nondestructive evaluation (NDE) efforts. Process modelling will be provided by the University of Arizona.

  2. PWM Converter Power Density Barriers

    NASA Astrophysics Data System (ADS)

    Kolar, Johann W.; Drofenik, Uwe; Biela, Juergen; Heldwein, Marcelo; Ertl, Hans; Friedli, Thomas; Round, Simon

    Power density of power electronic converters has roughly doubled every 10 years since 1970. Behind this trajectory is the continuous advancement of power semiconductor devices, which has increased the converter switching frequencies by a factor of 10 every decade. However, today's cooling concepts and passive components are major barriers for a continuation of this trend. To identify such technological barriers, this paper investigates the volume of the cooling system and passive components as a function of the switching frequency for power electronic converters and determines the switching frequency that minimizes the total volume. A power density limit of 28kW/dm3 at 300kHz is calculated for an isolated DC-DC converter, 44kW/dm3 at 820kHz for a three-phase unity power factor PWM rectifier, and 26kW/dm3 at 21kHz for a sparse matrix converter. For single-phase AC-DC conversion a general limit of 35kW/dm3 results from the DC link capacitor. These power density limits highlight the need to broaden the scope of power electronics research to include cooling systems, high frequency electromagnetics, interconnection and packaging technology, and multi-domain modelling and simulation to ensure further advancement along the power density trajectory.

  3. Pseudomonas aeruginosa: breaking down barriers.

    PubMed

    Berube, Bryan J; Rangel, Stephanie M; Hauser, Alan R

    2016-02-01

    Many bacterial pathogens have evolved ingenious ways to escape from the lung during pneumonia to cause bacteremia. Unfortunately, the clinical consequences of this spread to the bloodstream are frequently dire. It is therefore important to understand the molecular mechanisms used by pathogens to breach the lung barrier. We have recently shown that Pseudomonas aeruginosa, one of the leading causes of hospital-acquired pneumonia, utilizes the type III secretion system effector ExoS to intoxicate pulmonary epithelial cells. Injection of these cells leads to localized disruption of the pulmonary-vascular barrier and dissemination of P. aeruginosa to the bloodstream. We put these data in the context of previous studies to provide a holistic model of P. aeruginosa dissemination from the lung. Finally, we compare P. aeruginosa dissemination to that of other bacteria to highlight the complexity of bacterial pneumonia. Although respiratory pathogens use distinct and intricate strategies to escape from the lungs, a thorough understanding of these processes can lay the foundation for new therapeutic approaches for bacterial pneumonia.

  4. Richards Barrier LA Reference Design Feature Evaluation

    SciTech Connect

    N.E. Kramer

    1999-11-17

    The Richards Barrier is one of the design features of the repository to be considered for the License Application (LA), Richards was a soil scientist who first described the diversion of moisture between two materials with different hydrologic properties. In this report, a Richards Barrier is a special type of backfill with a fine-grained material (such as sand) overlaying a coarse-grained material (such as gravel). Water that enters an emplacement drift will first encounter the fine-grained material and be transported around the coarse-grained material covering the waste package, thus protecting the waste package from contact with most of the groundwater. The objective of this report is to discuss the benefits and liabilities to the repository by the inclusion of a Richards Barrier type backfill in emplacement drifts. The Richards Barrier can act as a barrier to water flow, can reduce the waste package material dissolution rate, limit mobilization of the radionuclides, and can provide structural protection for the waste package. The scope of this report is to: (1) Analyze the behavior of barrier materials following the intrusion of groundwater for influxes of 1 to 300 mm per year. The report will demonstrate diversion of groundwater intrusions into the barrier over an extended time period when seismic activity and consolidation may cause the potential for liquefaction and settlement of the Richards Barrier. (2) Review the thermal effects of the Richards Barrier on material behavior. (3) Analyze the effect of rockfall on the performance of the Richards Barrier and the depth of the barrier required to protect waste packages under the barrier. (4) Review radiological and heating conditions on placement of multiple layers of the barrier. Subsurface Nuclear Safety personnel will perform calculations to determine the radiation reduction-time relationship and shielding capacity of the barrier. (5) Evaluate the effects of ventilation on cooling of emplacement drifts and

  5. Potential corridors and barriers for plague spread in central Asia

    PubMed Central

    2013-01-01

    Background Plague (Yersinia pestis infection) is a vector-borne disease which caused millions of human deaths in the Middle Ages. The hosts of plague are mostly rodents, and the disease is spread by the fleas that feed on them. Currently, the disease still circulates amongst sylvatic rodent populations all over the world, including great gerbil (Rhombomys opimus) populations in Central Asia. Great gerbils are social desert rodents that live in family groups in burrows, which are visible on satellite images. In great gerbil populations an abundance threshold exists, above which plague can spread causing epizootics. The spatial distribution of the host species is thought to influence the plague dynamics, such as the direction of plague spread, however no detailed analysis exists on the possible functional or structural corridors and barriers that are present in this population and landscape. This study aims to fill that gap. Methods Three 20 by 20 km areas with known great gerbil burrow distributions were used to analyse the spatial distribution of the burrows. Object-based image analysis was used to map the landscape at several scales, and was linked to the burrow maps. A novel object-based method was developed – the mean neighbour absolute burrow density difference (MNABDD) – to identify the optimal scale and evaluate the efficacy of using landscape objects as opposed to square cells. Multiple regression using raster maps was used to identify the landscape-ecological variables that explain burrow density best. Functional corridors and barriers were mapped using burrow density thresholds. Cumulative resistance of the burrow distribution to potential disease spread was evaluated using cost distance analysis. A 46-year plague surveillance dataset was used to evaluate whether plague spread was radially symmetric. Results The burrow distribution was found to be non-random and negatively correlated with Greenness, especially in the floodplain areas. Corridors and

  6. The impact of ageing on the barriers to drug delivery.

    PubMed

    Perrie, Yvonne; Badhan, Raj K Singh; Kirby, Daniel J; Lowry, Deborah; Mohammed, Afzal R; Ouyang, Defang

    2012-07-20

    Generally, we like to see ageing as a process that is happening to people older than ourselves. However the process of ageing impacts on a wide range of functions within the human body. Whilst many of the outcomes of ageing can now be delayed or reduced, age-related changes in cellular, molecular and physiological functionality of tissues and organs can also influence how drugs enter, distribute and are eliminated from the body. Therefore, the changing profile of barriers to drug delivery should be considered if we are to develop more age-appropriate medicines. Changes in the drug dissolution and absorption in older patients may require the formulation of oral delivery systems that offer enhanced retention at absorption sites to improve drug delivery. Alternatively, liquid and fast-melt dosage systems may address the need of patients who have difficulties in swallowing medication. Ageing-induced changes in the lung can also result in slower drug absorption, which is further compounded by disease factors, common in an ageing population, that reduce lung capacity. In terms of barriers to drug delivery to the eye, the main consideration is the tear film, which like other barriers to drug delivery, changes with normal ageing and can impact on the bioavailability of drugs delivery using eye drops and suspensions. In contrast, whilst the skin as a barrier changes with age, no significant difference in absorption of drugs from transdermal drug delivery is observed in different age groups. However, due to the age-related pharmacokinetic and pharmacodynamic changes, dose adaptation should still be considered for drug delivery across the skin. Overall it is clear that the increasing age demographic of most populations, presents new (or should that be older) barriers to effective drug delivery.

  7. Barrier experiment: Shock initiation under complex loading

    SciTech Connect

    Menikoff, Ralph

    2016-01-12

    The barrier experiments are a variant of the gap test; a detonation wave in a donor HE impacts a barrier and drives a shock wave into an acceptor HE. The question we ask is: What is the trade-off between the barrier material and threshold barrier thickness to prevent the acceptor from detonating. This can be viewed from the perspective of shock initiation of the acceptor subject to a complex pressure drive condition. Here we consider key factors which affect whether or not the acceptor undergoes a shock-to-detonation transition. These include the following: shock impedance matches for the donor detonation wave into the barrier and then the barrier shock into the acceptor, the pressure gradient behind the donor detonation wave, and the curvature of detonation front in the donor. Numerical simulations are used to illustrate how these factors affect the reaction in the acceptor.

  8. Technical Basis for Evaluating Surface Barriers to Protect Groundwater from Deep Vadose Zone Contamination

    SciTech Connect

    Fayer, Michael J.; Ward, Anderson L.; Freedman, Vicky L.

    2010-02-03

    This document presents a strategy for evaluating the effectiveness of surface barriers for site-specific deep vadose zone remediation. The strategy provides a technically defensible approach to determine the depth to which a surface barrier can effectively isolate contaminants in the vadose at a specific site as a function of subsurface properties, contaminant distribution, barrier design, and infiltration control performance. The strategy also provides an assessment of additional data and information needs with respect to surface barrier performance for deep vadose zone applications. The strategy addresses the linkage between surface barriers and deep vadose zone in situ remediation activities, monitoring issues, and emerging science, technology, and regulatory objectives. In short, the report documents the existing knowledge base, identifies knowledge needs (based on data gaps), and suggests tasks whose outcomes will address those knowledge needs. More important, the report serves as a starting point to engage the regulator and stakeholder community on the viability of deploying surface barriers for deep vadose zone contamination. As that engagement unfolds, a systematic methodology can be formalized and instituted. The strategy is focused on deep vadose zone contamination and the methods needed to determine the impact to groundwater from those deep vadose zone contaminants. Processes that affect surface barrier performance, recharge in the areas surrounding the surface barrier, and the near-surface vadose zone beneath the barrier are acknowledged but are not addressed by this strategy. In addition, the collection of site-specific data on contaminant distribution and geologic structure and properties are programmatic responsibilities and are not provided by this strategy.

  9. A preliminary experimental study on virtual sound barrier system

    NASA Astrophysics Data System (ADS)

    Zou, Haishan; Qiu, Xiaojun; Lu, Jing; Niu, Feng

    2007-10-01

    Virtual sound barrier (VSB) is an array of loudspeakers and microphones forming an acoustic barrier, which creates a quiet zone without blocking air and light. A 16-channel cylindrical VSB system has been developed and its feasibility is verified by both numerical simulations and experiments. Experimental results in a normal room show that it can create a quiet zone larger than the size of a human head in the low-middle frequency, with a total sound pressure level reduction of more than 10 dB in the quiet zone. The control performance of the system with respect to the frequency, the distribution of the error sensors and the control sources are discussed.

  10. Assessing Controls on the Geometry and Dimensions of Modern Barrier Islands

    NASA Astrophysics Data System (ADS)

    Mulhern, J.; Johnson, C. L.; Martin, J. M.

    2015-12-01

    Barrier islands are highly ephemeral features, shaped by wave, tide, and storm energy. The processes that govern the size, shape, and motion of barrier islands are not well constrained, yet central to coastal dynamics. While the global distribution of barrier islands has been mapped and assessed, there is little consensus on the forces controlling barrier island formation, motion, or preservation. This study presents a new semi-global database of modern barrier islands to better understand their morphology and spatial distribution. We have mapped, in Google Earth, the subaerial extent of >350 barrier islands and spits, measuring spatial characteristic such as exposed area, perimeter, length, and width. These objects are cross-referenced with parameters that potentially control morphology, including tidal range, wave height, climate, distance from the continental shelf, proximity to fluvial output, and tectonic setting. This approach provides a more optimal framework to assess controls on coastal features, including barrier island morphology, and to investigate potential geometric scaling relationships. Preliminary analysis shows trends in the spatial characteristics of barrier islands. There is a strong linear relationship between the perimeter and length (y= -0.59 + 0.42x, R2=0.95). Linear trends also relate length to area when the data are separated by tidal range to wave height ratio. Assessment of barrier island shape supports the hypothesis of Hayes (1979) that barrier islands in wave-dominated settings are long and linear while those in mixed energy setting are more rounded. The barrier islands of the Texas Gulf of Mexico are larger than the global average for the database, with distinctly longer length values (41.16 km vs. 15.77 km respectively) and larger areas (103.81 km2 vs. 42.14 km2 respectively). Initial assessment shows that tidal range and wave height are primary controls barrier island dimensions. Future work will consider climate, latitude, fluvial

  11. Concepts for Functional Restoration of Barrier Islands

    DTIC Science & Technology

    2009-09-01

    Frisian barrier islands to sea-level rise: An investigation of past and future evolution. Geomorphology 15, 57-65. Farley, P. P. 1923. Coney Island ...ERDC/CHL CHETN-IV-74 September 2009 Concepts for Functional Restoration of Barrier Islands by Julie Dean Rosati PURPOSE: This Coastal and...Hydraulics Engineering Technical Note (CHETN) presents guid- ance for functional restoration of barrier islands . The concept of functional restoration

  12. Barrier paradox in the Klein zone

    SciTech Connect

    De Leo, Stefano; Rotelli, Pietro P.

    2006-04-15

    We study the solutions for a one-dimensional electrostatic potential in the Dirac equation when the incoming wave packet exhibits the Klein paradox (pair production). With a barrier potential we demonstrate the existence of multiple reflections (and transmissions). The antiparticle solutions which are necessarily localized within the barrier region create new pairs with each reflection at the potential walls. Consequently we encounter a new 'paradox' for the barrier because successive outgoing wave amplitudes grow geometrically.

  13. Identification of Key Barriers in Workforce Development

    SciTech Connect

    2008-03-31

    This report documents the identification of key barriers in the development of an adequate national security workforce as part of the National Security Preparedness Project, being performed under a Department of Energy/National Nuclear Security Administration grant. Many barriers exist that prevent the development of an adequate number of propertly trained national security personnel. Some barriers can be eliminated in a short-term manner, whereas others will involve a long-term strategy that takes into account public policy.

  14. Barrier Engineered Quantum Dot Infrared Photodetectors

    DTIC Science & Technology

    2015-06-01

    AFRL-RV-PS- AFRL-RV-PS- TR-2015-0111 TR-2015-0111 BARRIER ENGINEERED QUANTUM DOT INFRARED PHOTODETECTORS Sanjay Krishna Center for High Technology...2011 – 22 May 2012 4. TITLE AND SUBTITLE Barrier Engineered Quantum Dot Infrared Photodetectors 5a. CONTRACT NUMBER FA9453-12-1-0336 5b. GRANT...is Unlimited. 13. SUPPLEMENTARY NOTES 14. ABSTRACT To investigate barrier engineered designs to reduce the dark current in quantum dot infrared

  15. Probing barrier transmission in ballistic graphene

    NASA Astrophysics Data System (ADS)

    Gunlycke, Daniel; White, Carter T.

    2015-02-01

    We derive the local density of states from itinerant and boundary states around transport barriers and edges in graphene and show that the itinerant states lead to mesoscale undulations that could be used to probe their scattering properties in equilibrium without the need for lateral transport measurements. This finding will facilitate vetting of extended structural defects, such as grain boundaries or line defects as transport barriers for switchable graphene resonant tunneling transistors. We also show that barriers could exhibit double minima and that the charge density away from highly reflective barriers and edges scales as x-2.

  16. Barriers to Health Care for Transgender Individuals

    PubMed Central

    Safer, Joshua D.; Coleman, Eli; Feldman, Jamie; Garofalo, Robert; Hembree, Wylie; Radix, Asa; Sevelius, Jae

    2016-01-01

    Purpose of Review Transgender persons suffer significant health disparities and may require medical intervention as part of their care. The purpose of this manuscript is to briefly review the literature characterizing barriers to health care for transgender individuals and to propose research priorities to understand mechanisms of those barriers and interventions to overcome them. Recent Findings Current research emphasizes sexual minorities’ self report of barriers, rather than using direct methods. The biggest barrier to health care reported by transgender individuals is lack of access due to lack of providers who are sufficiently knowledgeable on the topic. Other barriers include: financial barriers, discrimination, lack of cultural competence by providers, health systems barriers and socioeconomic barriers. Summary National research priorities should include rigorous determination of the capacity of the United States health care system to provide adequate care for transgender individuals. Studies should determine knowledge and biases of the medical work force across the spectrum of medical training with regard to transgender medical care; adequacy of sufficient providers for the care required, larger social structural barriers and status of a framework to pay for appropriate care. As well, studies should propose and validate potential solutions to address identified gaps. PMID:26910276

  17. Tandem mirror thermal barrier experimental program plan

    SciTech Connect

    Coensgen, F.H.; Drake, R.P.; Simonen, T.C.

    1980-01-02

    This report describes an experimental plan for the development of the Tandem Mirror Thermal Barrier. Included is: (1) a description of thermal barrier related physics experiments; (2) thermal barrier related experiments in the existing TMX and Phaedrus experiments; (3) a thermal barrier TMX upgrade; and (4) initiation of investigations of axisymmetric magnetic geometry. Experimental studies of the first two items are presently underway. Results are expected from the TMX upgrade by the close of 1981 and from axisymmetric tandem mirror experiments at the end of 1983. Plans for Phaedrus upgrades are developing for the same period.

  18. Signalling of DNA damage and cytokines across cell barriers exposed to nanoparticles depends on barrier thickness

    NASA Astrophysics Data System (ADS)

    Sood, A.; Salih, S.; Roh, D.; Lacharme-Lora, L.; Parry, M.; Hardiman, B.; Keehan, R.; Grummer, R.; Winterhager, E.; Gokhale, P. J.; Andrews, P. W.; Abbott, C.; Forbes, K.; Westwood, M.; Aplin, J. D.; Ingham, E.; Papageorgiou, I.; Berry, M.; Liu, J.; Dick, A. D.; Garland, R. J.; Williams, N.; Singh, R.; Simon, A. K.; Lewis, M.; Ham, J.; Roger, L.; Baird, D. M.; Crompton, L. A.; Caldwell, M. A.; Swalwell, H.; Birch-Machin, M.; Lopez-Castejon, G.; Randall, A.; Lin, H.; Suleiman, M.-S.; Evans, W. H.; Newson, R.; Case, C. P.

    2011-12-01

    The use of nanoparticles in medicine is ever increasing, and it is important to understand their targeted and non-targeted effects. We have previously shown that nanoparticles can cause DNA damage to cells cultured below a cellular barrier without crossing this barrier. Here, we show that this indirect DNA damage depends on the thickness of the cellular barrier, and it is mediated by signalling through gap junction proteins following the generation of mitochondrial free radicals. Indirect damage was seen across both trophoblast and corneal barriers. Signalling, including cytokine release, occurred only across bilayer and multilayer barriers, but not across monolayer barriers. Indirect toxicity was also observed in mice and using ex vivo explants of the human placenta. If the importance of barrier thickness in signalling is a general feature for all types of barriers, our results may offer a principle with which to limit the adverse effects of nanoparticle exposure and offer new therapeutic approaches.

  19. Pratt & Whitney thermal barrier coatings

    SciTech Connect

    Bornstein, N.; Marcin, J.

    1995-10-01

    The objective of the Advanced Turbine Systems (ATS) Program is to develop ultra-high efficient, environmentally superior, and cost competitive gas turbine systems. The operating profiles of these industrial gas turbines are long, less cyclic with fewer transients-compared with those for aircraft gas turbine engines. Therefore, creep rather than thermal fatigue, becomes primary life-limiting for hot section components. Thermal barrier coatings (TBCs) will be used to achieve the objectives of the program. TBCs allow surface temperatures to increase without compromising the structural properties of the alloy. TBCs typically consist of a ceramic insulating layer, deposited onto the substrate with an intervening metallic layer, which imparts oxidation protection to the substrate and provides a surface to which the ceramic layer can adhere.

  20. Modeling of Thermal Barrier Coatings

    NASA Technical Reports Server (NTRS)

    Ferguson, B. L.; Petrus, G. J.; Krauss, T. M.

    1992-01-01

    The project examined the effectiveness of studying the creep behavior of thermal barrier coating system through the use of a general purpose, large strain finite element program, NIKE2D. Constitutive models implemented in this code were applied to simulate thermal-elastic and creep behavior. Four separate ceramic-bond coat interface geometries were examined in combination with a variety of constitutive models and material properties. The reason for focusing attention on the ceramic-bond coat interface is that prior studies have shown that cracking occurs in the ceramic near interface features which act as stress concentration points. The model conditions examined include: (1) two bond coat coefficient of thermal expansion curves; (2) the creep coefficient and creep exponent of the bond coat for steady state creep; (3) the interface geometry; and (4) the material model employed to represent the bond coat, ceramic, and superalloy base.

  1. Permeability Barrier Generation in the Martian Lithosphere

    NASA Astrophysics Data System (ADS)

    Schools, Joe; Montési, Laurent

    2015-11-01

    Permeability barriers develop when a magma produced in the interior of a planet rises into the cooler lithosphere and crystallizes more rapidly than the lithosphere can deform (Sparks and Parmentier, 1991). Crystallization products may then clog the porous network in which melt is propagating, reducing the permeability to almost zero, i.e., forming a permeability barrier. Subsequent melts cannot cross the barrier. Permeability barriers have been useful to explain variations in crustal thickness at mid-ocean ridges on Earth (Magde et al., 1997; Hebert and Montési, 2011; Montési et al., 2011). We explore here under what conditions permeability barriers may form on Mars.We use the MELTS thermodynamic calculator (Ghiorso and Sack, 1995; Ghiorso et al., 2002; Asimow et al., 2004) in conjunction with estimated Martian mantle compositions (Morgan and Anders, 1979; Wänke and Dreibus, 1994; Lodders and Fegley, 1997; Sanloup et al., 1999; Taylor 2013) to model the formation of permeability barriers in the lithosphere of Mars. In order to represent potential past and present conditions of Mars, we vary the lithospheric thickness, mantle potential temperature (heat flux), oxygen fugacity, and water content.Our results show that permeability layers can develop in the thermal boundary layer of the simulated Martian lithosphere if the mantle potential temperature is higher than ~1500°C. The various Martian mantle compositions yield barriers in the same locations, under matching variable conditions. There is no significant difference in barrier location over the range of accepted Martian oxygen fugacity values. Water content is the most significant influence on barrier development as it reduces the temperature of crystallization, allowing melt to rise further into the lithosphere. Our lower temperature and thicker lithosphere model runs, which are likely the most similar to modern Mars, show no permeability barrier generation. Losing the possibility of having a permeability

  2. Subsurface barrier verification technologies, informal report

    SciTech Connect

    Heiser, J.H.

    1994-06-01

    One of the more promising remediation options available to the DOE waste management community is subsurface barriers. Some of the uses of subsurface barriers include surrounding and/or containing buried waste, as secondary confinement of underground storage tanks, to direct or contain subsurface contaminant plumes and to restrict remediation methods, such as vacuum extraction, to a limited area. To be most effective the barriers should be continuous and depending on use, have few or no breaches. A breach may be formed through numerous pathways including: discontinuous grout application, from joints between panels and from cracking due to grout curing or wet-dry cycling. The ability to verify barrier integrity is valuable to the DOE, EPA, and commercial sector and will be required to gain full public acceptance of subsurface barriers as either primary or secondary confinement at waste sites. It is recognized that no suitable method exists for the verification of an emplaced barrier`s integrity. The large size and deep placement of subsurface barriers makes detection of leaks challenging. This becomes magnified if the permissible leakage from the site is low. Detection of small cracks (fractions of an inch) at depths of 100 feet or more has not been possible using existing surface geophysical techniques. Compounding the problem of locating flaws in a barrier is the fact that no placement technology can guarantee the completeness or integrity of the emplaced barrier. This report summarizes several commonly used or promising technologies that have been or may be applied to in-situ barrier continuity verification.

  3. Elastic scattering of Beryllium isotopes near the Coulomb barrier

    SciTech Connect

    Di Pietro, A.; Figuera, P.; Amorini, F.; Fisichella, M.; Lattuada, M.; Musumarra, A.; Pellegriti, M. G.; Randisi, G.; Rizzo, F.; Santonocito, D.; Scalia, G.; Scuderi, V.; Strano, E.; Torresi, D.; Papa, M.; Acosta, L.; Martel, I.; Perez-Bernal, F.; Borge, M. J. G.; Tengblad, O.

    2011-10-28

    In this contribution, results of experiments performed with the three Beryllium isotopes {sup 9,10,11}Be on a medium mass {sup 64}Zn target, at a center of mass energy of {approx_equal}1.4 the Coulomb barrier, will be discussed. Elastic scattering angular distributions have been measured for the {sup 9,10}Be reactions. In the {sup 11}Be case the quasielastic scattering angular distribution was obtained. In the halo nucleus case, the angular distribution exhibit a non-Fresnel-type pattern with a strong damping of the Coulomb-nuclear interference peak. Moreover, it is found that the total reaction cross-section for the halo nucleus induced collision is more than double the ones extracted in the collisions induced by the non-halo Beryllium isotopes. A large contribution to the total-reaction cross-section in the {sup 11}Be case could be attributed to transfer and/or break-up events.

  4. Passive Barriers to Inadvertent Human Intrusion for Use at the Nevada Test Site

    SciTech Connect

    NSTec Environmental Management

    2007-06-01

    In July1996, BN transmitted Passive Barriers to Inadvertent Human Intrusion for Use at the Nevada Test Site to the United States Department of Energy, under Contract DE-AC08-91NV10833. The 1996 paper had a limited distribution and was not reviewed for public release. In 2007, National Security Technologies LLC (NSTec) made minor revisions to conform to current editorial standards of the NNSA/NSO and to meet current security requirements for public release. The primary purpose of this study was to identify types of engineered passive barriers that could deter future intrusion into buried low-level radioactive waste, particularly intrusion by drilling water wells. The study considered drilling technology, many natural and man-made materials, and both underground and above-ground barriers. Based on cost and effectiveness, the report recommended underground barriers consisting of a layer of rubble or tires. An aboveground barrier mound might also prove effective, but would cost more, and may become an attractive nuisance (e.g., might, after their purpose has been forgotten, encourage exploration for the sake of satisfying curiosity). Advances in drilling technology could render any engineered barriers ineffective if there is motivation to penetrate the barriers.

  5. Energy management action plan: Developing a strategy for overcoming institutional barriers to municipal energy conservation

    SciTech Connect

    Not Available

    1992-12-31

    Energy offices working to improve efficiency of local government facilities face not only technical tasks, but institutional barriers, such as budget structures that do not reward efficiency, a low awareness of energy issues, and purchasing procedures based only on minimizing initial cost. The bureau, in working to remove such barriers in San Francisco, has identified 37 institutional barriers in areas such as operations & maintenance, purchasing, and facility design; these barriers were then reorganized into three groupings-- policy & attitudes, budget & incentives, and awareness & information-- and mapped. This map shows that the barriers mutually reinforce each other, and that a holistic approach is required for permanent change. The city`s recreation & parks department was used as a model department, and information about facility energy use was compiled into a departmental energy review. Staff interviews showed how barriers affect conservation. The bureau then generated ideas for projects to remove specific barriers and rated them according to potential impact and the resources required to implement them. Four of the six projects selected focused on maintenance staff: a cost- sharing lighting retrofit program, a boiler efficiency program, a departmental energy tracking system, and a budgetary incentive program for conservation. The other two projects are city-wide: promotion of a new term contract supplying energy-efficient light materials, and publication/distribution of ENERGY NEWS newsletter. A general methodology, the EMAP Strategy Guide, has been created to assist other energy offices in developing EMAPs.

  6. Improved epidermal barrier formation in human skin models by chitosan modulated dermal matrices

    PubMed Central

    Mieremet, Arnout; Rietveld, Marion; Absalah, Samira; van Smeden, Jeroen

    2017-01-01

    Full thickness human skin models (FTMs) contain an epidermal and a dermal equivalent. The latter is composed of a collagen dermal matrix which harbours fibroblasts. Current epidermal barrier properties of FTMs do not fully resemble that of native human skin (NHS), which makes these human skin models less suitable for barrier related studies. To further enhance the resemblance of NHS for epidermal morphogenesis and barrier formation, we modulated the collagen dermal matrix with the biocompatible polymer chitosan. Herein, we report that these collagen-chitosan FTMs (CC-FTMs) possess a well-organized epidermis and maintain both the early and late differentiation programs as in FTMs. Distinctively, the epidermal cell activation is reduced in CC-FTMs to levels observed in NHS. Dermal-epidermal interactions are functional in both FTM types, based on the formation of the basement membrane. Evaluation of the barrier structure by the organization of the extracellular lipid matrix of the stratum corneum revealed an elongated repeat distance of the long periodicity phase. The ceramide composition exhibited a higher resemblance of the NHS, based on the carbon chain-length distribution and subclass profile. The inside-out barrier functionality indicated by the transepidermal water loss is significantly improved in the CC-FTMs. The expression of epidermal barrier lipid processing enzymes is marginally affected, although more restricted to a single granular layer. The novel CC-FTM resembles the NHS more closely, which makes them a promising tool for epidermal barrier related studies. PMID:28333992

  7. Distributed Logics

    DTIC Science & Technology

    2014-10-03

    introduce distributed logics. Distributed logics lift the distribution structure of a distributed system directly into the logic, thereby parameterizing...the logic by the distribution structure itself. Each domain supports a “local modal logic.” The connections between domains are realized as...There are also multi- agent logic systems [12]. What distinguishes distributed logics from these are that the morphisms, i.e., the nbd maps, have

  8. Eliminating Barriers to Dual Enrollment in Oklahoma

    ERIC Educational Resources Information Center

    Roach, Rick; Gamez Vargas, Juanita; David, Kevin M.

    2015-01-01

    Policy, financial, and transportation barriers have limited participation in dual enrollment for marginalized (low-socioeconomic, first-generation, and ethnic minority) students in Oklahoma. This chapter presents a collaborative effort by education and community leaders that has successfully eliminated these barriers and increased the number of…

  9. Barriers to Adult Learning: Bridging the Gap

    ERIC Educational Resources Information Center

    Falasca, Marina

    2011-01-01

    A fundamental aspect of adult education is engaging adults in becoming lifelong learners. More often than not, this requires removing barriers to learning, especially those relating to the actual organisational or institutional learning process. This article explores some of the main barriers to adult learning discussed in the literature and…

  10. Reusable Thermal Barrier for Insulation Gaps

    NASA Technical Reports Server (NTRS)

    Saladee, C. E.

    1985-01-01

    Filler composed of resilient, heat-resistant materials. Thermal barrier nestles snugly in gap between two tiles with minimal protrusion beyond faces of surrounding tiles. When removed from gap, barrier springs back to nearly original shape. Developed for filling spaces between tiles on Space Shuttle, also used in furnaces and kilns.

  11. Rocket Motor Joint Construction Including Thermal Barrier

    NASA Technical Reports Server (NTRS)

    Steinetz, Bruce M. (Inventor); Dunlap, Patrick H., Jr. (Inventor)

    2002-01-01

    A thermal barrier for extremely high temperature applications consists of a carbon fiber core and one or more layers of braided carbon fibers surrounding the core. The thermal barrier is preferably a large diameter ring, having a relatively small cross-section. The thermal barrier is particularly suited for use as part of a joint structure in solid rocket motor casings to protect low temperature elements such as the primary and secondary elastomeric O-ring seals therein from high temperature gases of the rocket motor. The thermal barrier exhibits adequate porosity to allow pressure to reach the radially outward disposed O-ring seals allowing them to seat and perform the primary sealing function. The thermal barrier is disposed in a cavity or groove in the casing joint, between the hot propulsion gases interior of the rocket motor and primary and secondary O-ring seals. The characteristics of the thermal barrier may be enhanced in different applications by the inclusion of certain compounds in the casing joint, by the inclusion of RTV sealant or similar materials at the site of the thermal barrier, and/or by the incorporation of a metal core or plurality of metal braids within the carbon braid in the thermal barrier structure.

  12. Fracture mechanism of a thermal barrier coating

    NASA Astrophysics Data System (ADS)

    Samoilenko, V. M.; Ravilov, R. G.; Drevnyak, V. V.; Petrova, M. A.

    2016-06-01

    The fracture mechanism of the thermal barrier coating of gas turbine blades is studied. The causes of the fracture of the ceramic layer are discussed and the possible ways to increase the fatigue life of the thermal barrier coating are considered.

  13. Complementary Barrier Infrared Detector (CBIRD) Contact Methods

    NASA Technical Reports Server (NTRS)

    Ting, David Z.; Hill, Cory J.; Gunapala, Sarath D.

    2013-01-01

    The performance of the CBIRD detector is enhanced by using new device contacting methods that have been developed. The detector structure features a narrow gap adsorber sandwiched between a pair of complementary, unipolar barriers that are, in turn, surrounded by contact layers. In this innovation, the contact adjacent to the hole barrier is doped n-type, while the contact adjacent to the electron barrier is doped p-type. The contact layers can have wider bandgaps than the adsorber layer, so long as good electrical contacts are made to them. If good electrical contacts are made to either (or both) of the barriers, then one could contact the barrier(s) directly, obviating the need for additional contact layers. Both the left and right contacts can be doped either n-type or ptype. Having an n-type contact layer next to the electron barrier creates a second p-n junction (the first being the one between the hole barrier and the adsorber) over which applied bias could drop. This reduces the voltage drop over the adsorber, thereby reducing dark current generation in the adsorber region.

  14. Barriers to entrepreneurship in healthcare organizations.

    PubMed

    Phillips, Frank S; Garman, Andrew N

    2006-01-01

    Entrepreneurship has received little attention in the healthcare industry, perhaps in part because of barriers inherent in the structure and culture of healthcare organizations. Eliminating barriers can help promote entrepreneurial activities to drive continuing innovation and identify new sources of revenue.

  15. Overcoming Blocks and Barriers to Creativity.

    ERIC Educational Resources Information Center

    Raudsepp, Eugene

    1982-01-01

    Organizational barriers to creativity are examined. It is noted that resistance to change is a major impediment to creative problem solving in most organizations. Understanding the barriers to change that exist is viewed to help people exercise and develop their creativity more fully and effectively. (MP)

  16. Barriers to Accessing Services for Young Children

    ERIC Educational Resources Information Center

    Williams, Marian E.; Perrigo, Judith L.; Banda, Tanya Y.; Matic, Tamara; Goldfarb, Fran D.

    2013-01-01

    This study investigates barriers to accessing services for children under age 3 presenting with language delays and behavioral difficulties, including language barriers for Spanish-speaking families. Using a telephone script, researchers called 30 agencies in Los Angeles County, including regional centers (the state network of Part C agencies for…

  17. Nurses' barriers to learning: an integrative review.

    PubMed

    Santos, Marion C

    2012-07-01

    This integrative review of the literature describes nurses' barriers to learning. Five major themes emerged: time constraints, financial constraints, workplace culture, access/relevance, and competency in accessing electronic evidence-based practice literature. The nurse educator must address these barriers for the staff to achieve learning and competency.

  18. Geomembrane barriers using integral fiber optics to monitor barrier integrity

    DOEpatents

    Staller, George E.; Wemple, Robert P.

    1996-01-01

    This invention provides a geomembrane or geotextile with embedded optical sensors that are used to monitor the status of containment site barriers. Fiber optic strands are used to form the sensors that can detect and monitor conditions at the sites such as breaches, slope creep, subsidence, leachate levels, fires, and types of materials present or leaking from the site. The strands are integral to the membrane or textile materials. The geosythetic membrane is deployed at the site in a fashion similar to carpet laying. Edges of the membrane or textile are joined to form a liner and the ends of the membrane or textile become the connection zones for obtaining signals from the sensors. A connection interface with a control system to generate Optical Time Delay Response or other light signals for transmission to the optic fiber strands or sensors and also to receive reflected signals from the sensors is included in the system. Software to interpret the sensor signals can be used in the geosythetic monitoring system.

  19. Geomembrane barriers using integral fiber optics to monitor barrier integrity

    DOEpatents

    Staller, G.E.; Wemple, R.P.

    1996-10-22

    This invention provides a geomembrane or geotextile with embedded optical sensors that are used to monitor the status of containment site barriers. Fiber optic strands are used to form the sensors that can detect and monitor conditions at the sites such as breaches, slope creep, subsidence, leachate levels, fires, and types of materials present or leaking from the site. The strands are integral to the membrane or textile materials. The geosynthetic membrane is deployed at the site in a fashion similar to carpet laying. Edges of the membrane or textile are joined to form a liner and the ends of the membrane or textile become the connection zones for obtaining signals from the sensors. A connection interface with a control system to generate Optical Time Delay Response or other light signals for transmission to the optic fiber strands or sensors and also to receive reflected signals from the sensors is included in the system. Software to interpret the sensor signals can be used in the geosynthetic monitoring system. 6 figs.

  20. Multi-layer waste containment barrier

    SciTech Connect

    Smith, Ann Marie; Gardner, Bradley M.; Nickelson, David F.

    1999-01-01

    An apparatus for constructing an underground containment barrier for containing an in-situ portion of earth. The apparatus includes an excavating device for simultaneously (i) excavating earthen material from beside the in-situ portion of earth without removing the in-situ portion and thereby forming an open side trench defined by opposing earthen sidewalls, and (ii) excavating earthen material from beneath the in-situ portion of earth without removing the in-situ portion and thereby forming a generally horizontal underground trench beneath the in-situ portion defined by opposing earthen sidewalls. The apparatus further includes a barrier-forming device attached to the excavating device for simultaneously forming a side barrier within the open trench and a generally horizontal, multi-layer barrier within the generally horizontal trench. The multi-layer barrier includes at least a first layer and a second layer.

  1. Classical trajectory study of internal energy distributions in unimolecular processes

    NASA Technical Reports Server (NTRS)

    Mcdonald, J. D.; Marcus, R. A.

    1976-01-01

    Energy flow in a molecular system such as CD3Cl or CD3H representing a chemical activation experiment is studied by the method of classical trajectories. A correlation function method is used to obtain energy distributions before and after the breakup of the activated molecule. The energy distribution in the final product is found to be randomly distributed for a surface with no exit channel barrier or strong intermode couplings. Nonrandom energy distributions result when these special forces are present. Product channel barriers result in an excess of translational energy and exit channel intermode couplings result in nonrandom vibrational distributions.

  2. Barrier height inhomogeneity in electrical transport characteristics of InGaN/GaN heterostructure interfaces

    SciTech Connect

    Roul, Basanta; Mukundan, Shruti; Chandan, Greeshma; Mohan, Lokesh; Krupanidhi, S. B.

    2015-03-15

    We have grown InGaN/GaN heterostructures using plasma-assisted molecular beam epitaxy and studied the temperature dependent electrical transport characteristics. The barrier height (φ{sub b}) and the ideally factor (η) estimated using thermionic emission model were found to be temperature dependent. The conventional Richardson plot of ln(J{sub s}/T{sup 2}) versus 1/kT showed two temperature regions (region-I: 400–500 K and region-II: 200–350 K) and it provides Richardson constants (A{sup ∗}) which are much lower than the theoretical value of GaN. The observed variation in the barrier height and the presence of two temperature regions were attributed to spatial barrier inhomogeneities at the heterojunction interface and was explained by assuming a double Gaussian distribution of barrier heights with mean barrier height values 1.61 and 1.21 eV with standard deviation (σ{sub s}{sup 2}) of 0.044 and 0.022 V, respectively. The modified Richardson plot of ln(J{sub s}/T{sup 2}) − (q{sup 2}σ{sub s}{sup 2}/2k{sup 2}T{sup 2}) versus 1/kT for two temperature regions gave mean barrier height values as 1.61 eV and 1.22 eV with Richardson constants (A{sup ∗}) values 25.5 Acm{sup −2}K{sup −2} and 43.9 Acm{sup −2}K{sup −2}, respectively, which are very close to the theoretical value. The observed barrier height inhomogeneities were interpreted on the basis of the existence of a double Gaussian distribution of barrier heights at the interface.

  3. Representativeness Uncertainty in Chemical Data Assimilation Highlight Mixing Barriers

    NASA Technical Reports Server (NTRS)

    Lary, David John

    2003-01-01

    When performing chemical data assimilation the observational, representativeness, and theoretical uncertainties have very different characteristics. In this study we have accurately characterized the representativeness uncertainty by studying the probability distribution function (PDF) of the observations. The average deviation has been used as a measure of the width of the PDF and of the variability (representativeness uncertainty) for the grid cell. It turns out that for long-lived tracers such as N2O and CH4 the representativeness uncertainty is markedly different from the observational uncertainty and clearly delineates mixing barriers such as the polar vortex edge, the tropical pipe and the tropopause.

  4. Barriers to the utilization of synthetic fuels for transportation

    NASA Technical Reports Server (NTRS)

    Parker, H. W.; Reilly, M. J.

    1981-01-01

    The principal types of engines for transportation uses are reviewed and the specifications for conventional fuels are compared with specifications for synthetic fuels. Synfuel processes nearing the commercialization phase are reviewed. The barriers to using synfuels can be classified into four groups: technical, such as the uncertainty that a new engine design can satisfy the desired performance criteria; environmental, such as the risk that the engine emissions cannot meet the applicable environmental standards; economic, including the cost of using a synfuel relative to conventional transportation fuels; and market, involving market penetration by offering new engines, establishing new distribution systems and/or changing user expectations.

  5. Temperature-dependent electrical transport properties of (Au/Ni)/n-GaN Schottky barrier diodes

    NASA Astrophysics Data System (ADS)

    Dogan, Hulya; Elagoz, Sezai

    2014-09-01

    The temperature-dependent electrical properties of (Au/Ni)/n-GaN Schottky barrier diodes (SBDs)have been investigated in the wide temperature range of 40-400 K. The analysis of the main electrical characteristics such as zero-bias barrier height (ΦB0), ideality factor (n) and series resistance (Rs) were found strongly temperature dependent. Such behavior is attributed to barrier inhomogeneities by assuming a Gaussian distribution (GD) of barrier heights (BHs) at the interface. It is evident that the diode parameters such as zero-bias barrier height increases and the ideality factor decreases with increasing temperature. The values of series resistance that are obtained from Cheung's method are decreasing with increasing temperature. The temperature dependence of Schottky barrier height (SBD) and ideality factor (n) are explained by invoking three sets of Gaussian distribution of (SBH) in the temperature ranges of 280-400 K, 120-260 K and 40-100 K, respectively. (Au/Ni)/n-GaN Schottky barrier diode have been shown a Gaussian distribution giving mean BHs (ΦbarB0) of 1.167, 0.652 and 0.356 eV and standard deviation σs of 0.178, 0.087 and 0.133 V for the three temperature regions. A modified ln(I0/T2)-q2σ2/2k2T2 vs. 1/kT plot have given ΦbarB0 and A* as 1.173 eV and 34.750 A/cm2 K2, 0.671 eV and 26.293 A/cm2 K2, 0.354 eV and 10.199 A/cm2 K2, respectively.

  6. Thermal barrier coating evaluation needs

    NASA Technical Reports Server (NTRS)

    Brindley, William J.; Miller, Robert A.

    1990-01-01

    A 0.025 cm (0.010 in) thick thermal barrier coating (TBC) applied to turbine airfoils in a research gas turbine engine provided component temperature reductions of up to 190 C. These impressive temperature reductions can allow increased engine operating temperatures and reduced component cooling to achieve greater engine performance without sacrificing component durability. The significant benefits of TBCs are well established in aircraft gas turbine engine applications and their use is increasing. TBCs are also under intense development for use in the Low Heat Rejection (LHR) diesel engine currently being developed and are under consideration for use in utility and marine gas turbines. However, to fully utilize the benefits of TBCs it is necessary to accurately characterize coating attributes that affect the insulation and coating durability. The purpose there is to discuss areas in which nondestructive evaluation can make significant contributions to the further development and full utilization of TBCs for aircraft gas turbine engines and low heat rejection diesel engines.

  7. Advances in Information Barrier Design.

    SciTech Connect

    Williams, R. B.; Frame, K. C.; Landry, R. P.; MacArthur, D. W.; Smith, M. K.

    2005-01-01

    The concept of an information barrier, or IB, has been widely discussed for a number of years. An IB is used in a measurement system that contains classified information to prevent the release (either intentional or inadvertent) of the classified information while still allowing an inspecting party to reach independent conclusions as to the contents of a storage container. Typically, an IB would be used in a measurement system regime that requires the owner of certain storage containers to declare the contents of the containers (in unclassified terms) and an inspecting party to confirm this declaration. The IB allows the owner's declaration to be confirmed without releasing any classified information to the inspecting party. Most IB design concepts are based on two attribute measruement systems (AMSs) that were built and demonstrated in the US in 1999 and 2000. These IBs relied heavily on simple hardware implementations and performed well in a 'one-time' demonstration mode. However, implementation of an AMS in a long-term verification regime will place a different set of requirements on the entire AMS system - and the IB, in particular. In this paper, they will concentrate on the effects of changing constraints on IB design, new IB concepts that have been developed since the earlier demonstrations, and design concepts that have been developed within a number of related verification regimes.

  8. Transport in the barrier billiard

    NASA Astrophysics Data System (ADS)

    Saberi Fathi, S. M.; Ettoumi, W.; Courbage, M.

    2016-06-01

    We investigate transport properties of an ensemble of particles moving inside an infinite periodic horizontal planar barrier billiard. A particle moves among bars and elastically reflects on them. The motion is a uniform translation along the bars' axis. When the tangent of the incidence angle, α , is fixed and rational, the second moment of the displacement along the orthogonal axis at time n , , is either bounded or asymptotic to K n2 , when n →∞ . For irrational α , the collision map is ergodic and has a family of weakly mixing observables, the transport is not ballistic, and autocorrelation functions decay only in time average, but may not decay for a family of irrational α 's. An exhaustive numerical computation shows that the transport may be superdiffusive or subdiffusive with various rates or bounded strongly depending on the values of α . The variety of transport behaviors sounds reminiscent of well-known behavior of conservative systems. Considering then an ensemble of particles with nonfixed α , the system is nonergodic and certainly not mixing and has anomalous diffusion with self-similar space-time properties. However, we verified that such a system decomposes into ergodic subdynamics breaking self-similarity.

  9. The immunological barriers to xenotransplantation.

    PubMed

    Vadori, M; Cozzi, E

    2015-10-01

    The availability of cells, tissues and organs from a non-human species such as the pig could, at least in theory, meet the demand of organs necessary for clinical transplantation. At this stage, the important goal of getting over the first year of survival has been reported for both cellular and solid organ xenotransplantation in relevant preclinical primate models. In addition, xenotransplantation is already in the clinic as shown by the broad use of animal-derived medical devices, such as bioprosthetic heart valves and biological materials used for surgical tissue repair. At this stage, however, prior to starting a wide-scale clinical application of xenotransplantation of viable cells and organs, the important obstacle represented by the humoral immune response will need to be overcome. Likewise, the barriers posed by the activation of the innate immune system and coagulative pathway will have to be controlled. As far as xenogeneic nonviable xenografts, increasing evidence suggests that considerable immune reactions, mediated by both innate and adaptive immunity, take place and influence the long-term outcome of xenogeneic materials in patients, possibly precluding the use of bioprosthetic heart valves in young individuals. In this context, the present article provides an overview of current knowledge on the immune processes following xenotransplantation and on the possible therapeutic interventions to overcome the immunological drawbacks involved in xenotransplantation.

  10. Advanced thermal barrier coating systems

    NASA Technical Reports Server (NTRS)

    Dorfman, M. R.; Reardon, J. D.

    1985-01-01

    Current state-of-the-art thermal barrier coating (TBC) systems consist of partially stabilized zirconia coatings plasma sprayed over a MCrAlY bond coat. Although these systems have excellent thermal shock properties, they have shown themselves to be deficient for a number of diesel and aircraft applications. Two ternary ceramic plasma coatings are discussed with respect to their possible use in TBC systems. Zirconia-ceria-yttria (ZCY) coatings were developed with low thermal conductivities, good thermal shock resistance and improved resistance to vanadium containing environments, when compared to the baseline yttria stabilized zirconia (YSZ) coatings. In addition, dense zirconia-titania-yttria (ZTY) coatings were developed with particle erosion resistance exceeding conventional stabilized zirconia coatings. Both coatings were evaluated in conjunction with a NiCr-Al-Co-Y2O3 bond coat. Also, multilayer or hybrid coatings consisting of the bond coat with subsequent coatings of zirconia-ceria-yttria and zirconia-titania-yttria were evaluated. These coatings combine the enhanced performance characteristics of ZCY with the improved erosion resistance of ZTY coatings. Improvement in the erosion resistance of the TBC system should result in a more consistent delta T gradient during service. Economically, this may also translate into increased component life simply because the coating lasts longer.

  11. Engineered Barrier System Degradation, Flow, and Transport Process Model Report

    SciTech Connect

    E.L. Hardin

    2000-07-17

    The Engineered Barrier System Degradation, Flow, and Transport Process Model Report (EBS PMR) is one of nine PMRs supporting the Total System Performance Assessment (TSPA) being developed by the Yucca Mountain Project for the Site Recommendation Report (SRR). The EBS PMR summarizes the development and abstraction of models for processes that govern the evolution of conditions within the emplacement drifts of a potential high-level nuclear waste repository at Yucca Mountain, Nye County, Nevada. Details of these individual models are documented in 23 supporting Analysis/Model Reports (AMRs). Nineteen of these AMRs are for process models, and the remaining 4 describe the abstraction of results for application in TSPA. The process models themselves cluster around four major topics: ''Water Distribution and Removal Model, Physical and Chemical Environment Model, Radionuclide Transport Model, and Multiscale Thermohydrologic Model''. One AMR (Engineered Barrier System-Features, Events, and Processes/Degradation Modes Analysis) summarizes the formal screening analysis used to select the Features, Events, and Processes (FEPs) included in TSPA and those excluded from further consideration. Performance of a potential Yucca Mountain high-level radioactive waste repository depends on both the natural barrier system (NBS) and the engineered barrier system (EBS) and on their interactions. Although the waste packages are generally considered as components of the EBS, the EBS as defined in the EBS PMR includes all engineered components outside the waste packages. The principal function of the EBS is to complement the geologic system in limiting the amount of water contacting nuclear waste. A number of alternatives were considered by the Project for different EBS designs that could provide better performance than the design analyzed for the Viability Assessment. The design concept selected was Enhanced Design Alternative II (EDA II).

  12. River barriers and cryptic biodiversity in an evolutionary museum

    PubMed Central

    Voelker, G; Marks, B D; Kahindo, C; A'genonga, U; Bapeamoni, F; Duffie, L E; Huntley, J W; Mulotwa, E; Rosenbaum, S A; Light, J E

    2013-01-01

    The Riverine Barriers Hypothesis (RBH) posits that tropical rivers can be effective barriers to gene flow, based on observations that range boundaries often coincide with river barriers. Over the last 160 years, the RBH has received attention from various perspectives, with a particular focus on vertebrates in the Amazon Basin. To our knowledge, no molecular assessment of the RBH has been conducted on birds in the Afrotropics, despite its rich avifauna and many Afrotropical bird species being widely distributed across numerous watersheds and basins. Here, we provide the first genetic evidence that an Afrotropical river has served as a barrier for birds and for their lice, based on four understory bird species collected from sites north and south of the Congo River. Our results indicate near-contemporaneous, Pleistocene lineage diversification across the Congo River in these species. Our results further indicate differing levels of genetic variation in bird lice; the extent of this variation appears linked to the life-history of both the host and the louse. Extensive cryptic diversity likely is being harbored in Afrotropical forests, in both understory birds and their lice. Therefore, these forests may not be “museums” of old lineages. Rather, substantial evolutionary diversification may have occurred in Afrotropical forests throughout the Pleistocene, supporting the Pleistocene Forest Refuge Hypothesis. Strong genetic variation in birds and their lice within a small part of the Congo Basin forest indicates that we may have grossly underestimated diversity in the Afrotropics, making these forests home of substantial biodiversity in need of conservation. PMID:23532272

  13. Numerical simulations of capillary barrier field tests

    SciTech Connect

    Morris, C.E.; Stormont, J.C.

    1997-12-31

    Numerical simulations of two capillary barrier systems tested in the field were conducted to determine if an unsaturated flow model could accurately represent the observed results. The field data was collected from two 7-m long, 1.2-m thick capillary barriers built on a 10% grade that were being tested to investigate their ability to laterally divert water downslope. One system had a homogeneous fine layer, while the fine soil of the second barrier was layered to increase its ability to laterally divert infiltrating moisture. The barriers were subjected first to constant infiltration while minimizing evaporative losses and then were exposed to ambient conditions. The continuous infiltration period of the field tests for the two barrier systems was modelled to determine the ability of an existing code to accurately represent capillary barrier behavior embodied in these two designs. Differences between the field test and the model data were found, but in general the simulations appeared to adequately reproduce the response of the test systems. Accounting for moisture retention hysteresis in the layered system will potentially lead to more accurate modelling results and is likely to be important when developing reasonable predictions of capillary barrier behavior.

  14. Blood cells and endothelial barrier function

    PubMed Central

    Rodrigues, Stephen F; Granger, D Neil

    2015-01-01

    Abstract The barrier properties of endothelial cells are critical for the maintenance of water and protein balance between the intravascular and extravascular compartments. An impairment of endothelial barrier function has been implicated in the genesis and/or progression of a variety of pathological conditions, including pulmonary edema, ischemic stroke, neurodegenerative disorders, angioedema, sepsis and cancer. The altered barrier function in these conditions is often linked to the release of soluble mediators from resident cells (e.g., mast cells, macrophages) and/or recruited blood cells. The interaction of the mediators with receptors expressed on the surface of endothelial cells diminishes barrier function either by altering the expression of adhesive proteins in the inter-endothelial junctions, by altering the organization of the cytoskeleton, or both. Reactive oxygen species (ROS), proteolytic enzymes (e.g., matrix metalloproteinase, elastase), oncostatin M, and VEGF are part of a long list of mediators that have been implicated in endothelial barrier failure. In this review, we address the role of blood borne cells, including, neutrophils, lymphocytes, monocytes, and platelets, in the regulation of endothelial barrier function in health and disease. Attention is also devoted to new targets for therapeutic intervention in disease states with morbidity and mortality related to endothelial barrier dysfunction. PMID:25838983

  15. HgCdTe barrier infrared detectors

    NASA Astrophysics Data System (ADS)

    Kopytko, M.; Rogalski, A.

    2016-05-01

    In the last decade, new strategies to achieve high-operating temperature (HOT) detectors have been proposed, including barrier structures such as nBn devices, unipolar barrier photodiodes, and multistage (cascade) infrared detectors. The ability to tune the positions of the conduction and valence band edges independently in a broken-gap type-II superlattices is especially helpful in the design of unipolar barriers. This idea has been also implemented in HgCdTe ternary material system. However, the implementation of this detector structure in HgCdTe material system is not straightforward due to the existence of a valence band discontinuity (barrier) at the absorber-barrier interface. In this paper we present status of HgCdTe barrier detectors with emphasis on technological progress in fabrication of MOCVD-grown HgCdTe barrier detectors achieved recently at the Institute of Applied Physics, Military University of Technology. Their performance is comparable with state-of-the-art of HgCdTe photodiodes. From the perspective of device fabrication their important technological advantage results from less stringent surface passivation requirements and tolerance to threading dislocations.

  16. Implementation of power barrier option valuation

    NASA Astrophysics Data System (ADS)

    Cahyani, Agatha C. P.; Sumarti, Novriana

    2015-09-01

    Options are financial instruments that can be utilized to reduce risk in stock investment. Barrier options are one of the major types of options actively used in financial markets where its life period depends on the path of the underlying stock prices. The features of the barrier option can be used to modify other types of options. In this research, the barrier option will be implemented into power option, so it is called power barrier option. This option is an extension of the vanilla barrier options where the Call payoff being considered is defined as P C =max (STβ-Kβ,0 ) , and the Put payoff being considered is defined as P P =max (Kβ-STβ,0 ) . Here β > 0 and β ≠ 1, K is the strike price of the option, and ST is the price of the underlying stock at time maturity T. In this paper, we generate the prices of stock using binomial method which is adjusted to the power option. In the conclusion, the price of American power barrier option is more expensive than the price of European power barrier option.

  17. Telerobotics in rehabilitation: Barriers to a virtual existence

    NASA Technical Reports Server (NTRS)

    Leifer, Larry; Vanderloos, Machiel; Michalowski, Stefan

    1991-01-01

    The topics covered include the following: the need for telerobotics in rehabilitation; barriers to telerobotics technology in rehabilitation and health care; institutional barriers; technical barriers; and a partial view of the future.

  18. Barriers to Adult Learning: Does Anticipation Match Reality?

    ERIC Educational Resources Information Center

    Richter, Donna L.; Witten, Charles H.

    1984-01-01

    Examined barriers to learning in adult students (N=111) using the Adult Student Survey. Results indicated that in many cases students were able to predict barriers before enrolling. Lack of time was the most difficult barrier to anticipate correctly. (JAC)

  19. Permanent isolation surface barrier development plan

    SciTech Connect

    Wing, N.R.

    1994-01-01

    The exhumation and treatment of wastes may not always be the preferred alternative in the remediation of a waste site. In-place disposal alternatives, under certain circumstances, may be the most desirable alternatives to use in the protection of human health and the environment. The implementation of an in-place disposal alternative will likely require some type of protective covering that will provide long-term isolation of the wastes from the accessible environment. Even if the wastes are exhumed and treated, a long-term barrier may still be needed to adequately dispose of the treated wastes or any remaining waste residuals. Currently, no {open_quotes}proven{close_quotes} long-term barrier is available. The Hanford Site Permanent Isolation Surface Barrier Development Program (BDP) was organized to develop the technology needed to provide a long-term surface barrier capability for the Hanford Site. The permanent isolation barrier technology also could be used at other sites. Permanent isolation barriers use engineered layers of natural materials to create an integrated structure with redundant protective features. Drawings of conceptual permanent isolation surface barriers are shown. The natural construction materials (e.g., fine soil, sand, gravel, riprap, asphalt) have been selected to optimize barrier performance and longevity. The objective of current designs is to use natural materials to develop a maintenance-free permanent isolation surface barrier that isolates wastes for a minimum of 1,000 years by limiting water drainage to near-zero amounts; reducing the likelihood of plant, animal, and human intrusion; controlling the exhalation of noxious gases; and minimizing erosion-related problems.

  20. Method for forming a barrier layer

    DOEpatents

    Weihs, Timothy P.; Barbee, Jr., Troy W.

    2002-01-01

    Cubic or metastable cubic refractory metal carbides act as barrier layers to isolate, adhere, and passivate copper in semiconductor fabrication. One or more barrier layers of the metal carbide are deposited in conjunction with copper metallizations to form a multilayer characterized by a cubic crystal structure with a strong (100) texture. Suitable barrier layer materials include refractory transition metal carbides such as vanadium carbide (VC), niobium carbide (NbC), tantalum carbide (TaC), chromium carbide (Cr.sub.3 C.sub.2), tungsten carbide (WC), and molybdenum carbide (MoC).

  1. Tight junction proteins: from barrier to tumorigenesis.

    PubMed

    Runkle, E Aaron; Mu, David

    2013-08-28

    The tight junction is a multi-protein complex and is the apical most junctional complex in certain epithelial and endothelial cells. A great deal of attention has been devoted to the understanding of these proteins in contributing to the barrier function - that is, regulating the paracellular flux or permeability between adjacent cells. However, tight junction proteins are now recognized as having functions beyond the barrier. The focus of this review is to discuss the barrier function of the tight junction and to summarize the literature with a focus on the role of tight junction proteins in proliferation, transformation, and metastasis.

  2. Tight Junction Proteins: From Barrier to Tumorigenesis

    PubMed Central

    Runkle, E. Aaron; Mu, David

    2013-01-01

    The tight junction is a multi-protein complex and is the apical most junctional complex in certain epithelial and endothelial cells. A great deal of attention has been devoted to the understanding of these proteins in contributing to the barrier function - that is, regulating the paracellular flux or permeability between adjacent cells. However, tight junction proteins are now recognized as having functions beyond the barrier. The focus of this review is to discuss the barrier function of the tight junction and to summarize the literature with a focus on the role of tight junction proteins in proliferation, transformation, and metastasis. PMID:23743355

  3. Intestinal barriers to bacteria and their toxins

    SciTech Connect

    Walker, R.I.; Owen, R.L. )

    1990-01-01

    Immunologic and nonimmunologic processes work together to protect the host from the multitude of microorganisms residing within the intestinal lumen. Mechanical integrity of the intestinal epithelium, mucus in combination with secretory antibody, antimicrobial metabolites of indigenous microorganisms, and peristalsis each limit proliferation and systemic dissemination of enteric pathogens. Uptake of microorganisms by Peyer's patches and other intestinal lymphoid structures and translocation circumvent the mucosal barrier, especially in immunosuppressed individuals. Improved understanding of the composition and limitation of the intestinal barrier, coupled with advances in genetic engineering of immunogenic bacteria, development of oral delivery systems, and immunomodulators, now make enhancement of mucosal barriers feasible. 32 references.

  4. Wood-Based Paneling as Thermal Barriers,

    DTIC Science & Technology

    1982-06-01

    Forest Panelingi as Products Laboratory Research Thermal Barriers Paper ’> FPL 408 10 C-D Li-J _ LzstZibutio iOse flh SQe.it s V 82 1012 048 |stract...this paper, a small scale horizontal exposure furnace test for testing thermal barriers over a calcium silicate board was added to the Uniform Building...Results," by Robert H. White. United States Department of - a eArclueWood-Based Agriculture Forest Paneling as Products Laboratory, Par Thermal Barriers PaperFPL

  5. Market and Policy Barriers to Energy Storage Deployment

    SciTech Connect

    Bhatnagar, Dhruv; Currier, Aileen; Hernandez, Jacquelynne; Ma, Ookie; Kirby, Brendan

    2013-09-01

    Electric energy storage technologies can provide numerous grid services; there are a number of factors that restrict their current deployment. The most significant barrier to deployment is high capital costs, though several recent deployments indicate that capital costs are decreasing and energy storage may be the preferred economic alternative in certain situations. However, a number of other market and regulatory barriers persist, limiting further deployment. These barriers can be categorized into regulatory barriers, market (economic) barriers, utility and developer business model barriers, cross-cutting barriers and technology barriers.

  6. How-To-Do-It: A Transect Study of a Barrier Beach.

    ERIC Educational Resources Information Center

    Hamilton, Thomas R.

    1988-01-01

    Describes a field trip activity to measure changes in elevation across the dunes of a barrier beach, measure wind velocity along the transect line, and observe the distribution of ground cover in the study area. Discusses equipment, materials, procedures and follow-up activities for each study. (CW)

  7. Permeable Reactive Barrier: Technology Update

    DTIC Science & Technology

    2011-06-01

    Contrary to laboratory findings, breakdown products like TAT from TNT have not been observed under field conditions. 4.3 Organic Substrates (Biowalls...low frequency of injection required, and lower product cost relative to other slow- release substrate types. There is an economy of scale in large...fatty acids Biodegradation breakdown products and fermentation substrates . Indicator of substrate distribution. Phospholipid fatty acids Indicator of

  8. The BARRIERS scale -- the barriers to research utilization scale: A systematic review

    PubMed Central

    2010-01-01

    Background A commonly recommended strategy for increasing research use in clinical practice is to identify barriers to change and then tailor interventions to overcome the identified barriers. In nursing, the BARRIERS scale has been used extensively to identify barriers to research utilization. Aim and objectives The aim of this systematic review was to examine the state of knowledge resulting from use of the BARRIERS scale and to make recommendations about future use of the scale. The following objectives were addressed: To examine how the scale has been modified, to examine its psychometric properties, to determine the main barriers (and whether they varied over time and geographic locations), and to identify associations between nurses' reported barriers and reported research use. Methods Medline (1991 to September 2009) and CINHAL (1991 to September 2009) were searched for published research, and ProQuest® digital dissertations were searched for unpublished dissertations using the BARRIERS scale. Inclusion criteria were: studies using the BARRIERS scale in its entirety and where the sample was nurses. Two authors independently assessed the study quality and extracted the data. Descriptive and inferential statistics were used. Results Sixty-three studies were included, with most using a cross-sectional design. Not one study used the scale for tailoring interventions to overcome identified barriers. The main barriers reported were related to the setting, and the presentation of research findings. Overall, identified barriers were consistent over time and across geographic locations, despite varying sample size, response rate, study setting, and assessment of study quality. Few studies reported associations between reported research use and perceptions of barriers to research utilization. Conclusions The BARRIERS scale is a nonspecific tool for identifying general barriers to research utilization. The scale is reliable as reflected in assessments of internal

  9. A powerful electrohydrodynamic flow generated by a high-frequency dielectric barrier discharge in a gas

    SciTech Connect

    Nebogatkin, S. V.; Rebrov, I. E.; Khomich, V. Yu.; Yamshchikov, V. A.

    2016-01-15

    Theoretical and experimental studies of an electrohydrodynamic flow induced by a high-frequency dielectric barrier discharge distributed over a dielectric surface in a gas have been conducted. Dependences of the ion current, the gas flow velocity, and the spatial distributions thereof on the parameters of the power supply of the plasma ion emitter and an external electric field determined by the collector grid voltage have been described.

  10. A powerful electrohydrodynamic flow generated by a high-frequency dielectric barrier discharge in a gas

    NASA Astrophysics Data System (ADS)

    Nebogatkin, S. V.; Rebrov, I. E.; Khomich, V. Yu.; Yamshchikov, V. A.

    2016-01-01

    Theoretical and experimental studies of an electrohydrodynamic flow induced by a high-frequency dielectric barrier discharge distributed over a dielectric surface in a gas have been conducted. Dependences of the ion current, the gas flow velocity, and the spatial distributions thereof on the parameters of the power supply of the plasma ion emitter and an external electric field determined by the collector grid voltage have been described.

  11. Communicating across barriers at home and abroad

    SciTech Connect

    McDonald, J.W.

    1985-01-01

    This paper intends to catalyze the exchange of experience among technical communicators in meeting the challenge of communicating across a multitude of barriers: linguistic, disciplinary, cultural, political, intellectual, and emotional.

  12. Vapor-barrier Vacuum Isolation System

    NASA Technical Reports Server (NTRS)

    Weinstein, Leonard M. (Inventor); Taminger, Karen M. (Inventor)

    2014-01-01

    A system includes a collimated beam source within a vacuum chamber, a condensable barrier gas, cooling material, a pump, and isolation chambers cooled by the cooling material to condense the barrier gas. Pressure levels of each isolation chamber are substantially greater than in the vacuum chamber. Coaxially-aligned orifices connect a working chamber, the isolation chambers, and the vacuum chamber. The pump evacuates uncondensed barrier gas. The barrier gas blocks entry of atmospheric vapor from the working chamber into the isolation chambers, and undergoes supersonic flow expansion upon entering each isolation chamber. A method includes connecting the isolation chambers to the vacuum chamber, directing vapor to a boundary with the working chamber, and supersonically expanding the vapor as it enters the isolation chambers via the orifices. The vapor condenses in each isolation chamber using the cooling material, and uncondensed vapor is pumped out of the isolation chambers via the pump.

  13. CAPILLARY BARRIERS IN UNSATURATED FRACTURED ROCKS

    SciTech Connect

    Y.S. Wu; W. Zhang; L. Pan; J. Hinds; G. Bodvarsson

    2000-10-01

    This work presents modeling studies investigating the effects of capillary barriers on fluid-flow and tracer-transport processes in the unsaturated zone of Yucca Mountain, Nevada, a potential site for storing high-level radioactive waste. These studies are designed to identify factors controlling the formation of capillary barriers and to estimate their effects on the extent of possible large-scale lateral flow in unsaturated fracture rocks. The modeling approach is based on a continuum formulation of coupled multiphase fluid and tracer transport through fractured porous rock. Flow processes in fractured porous rock are described using a dual-continuum concept. In addition, approximate analytical solutions are developed and used for assessing capillary-barrier effects in fractured rocks. This study indicates that under the current hydrogeologic conceptualization of Yucca Mountain, strong capillary-barrier effects exist for significantly diverting moisture flow.

  14. ULTRA BARRIER TOPSHEET (UBT) FOR FLEXIBLE PHOTOVOLTAICS

    SciTech Connect

    DeScioli, Derek

    2013-06-01

    This slide-show presents 3M photovoltaic-related products, particularly flexible components. Emphasis is on the 3M Ultra Barrier Solar Films. Topics covered include reliability and qualification testing and flexible photovoltaic encapsulation costs.

  15. 24 CFR 574.645 - Coastal barriers.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ...) OFFICE OF ASSISTANT SECRETARY FOR COMMUNITY PLANNING AND DEVELOPMENT, DEPARTMENT OF HOUSING AND URBAN... financial assistance under this part may be made available within the Coastal Barrier Resources System....

  16. Barriers to Physical Activity on University Student

    NASA Astrophysics Data System (ADS)

    Jajat; Sultoni, K.; Suherman, A.

    2017-03-01

    The purpose of the research is to analyze the factors that become barriers to physical activity in university students based on physical activity level. An internet-based survey was conducted. The participants were 158 University students from Universitas Pendidikan Indonesia. Barriers to Physical Activity Quiz (BPAQ) were used to assessed the factors that become barriers to physical activity in university students. IPAQ (short form) were used to assessed physical activity level. The results show there was no differences BPAQ based on IPAQ level. But when analyzed further based on seven factors barriers there are differences in factors “social influence and lack of willpower” based IPAQ level. Based on this it was concluded that the “influence from other and lack of willpower” an inhibiting factor on students to perform physical activity.

  17. Evapotranspiration studies for protective barriers: Experimental plans

    SciTech Connect

    Link, S.O.; Waugh, W.J.

    1989-11-01

    This document describes a general theory and experimental plans for predicting evapotranspiration in support of the Protective Barrier Program. Evapotranspiration is the combined loss of water from plants and soil surfaces to the atmosphere. 45 refs., 1 fig., 4 tabs.

  18. Skin barrier in atopic dermatitis: beyond filaggrin*

    PubMed Central

    Zaniboni, Mariana Colombini; Samorano, Luciana Paula; Orfali, Raquel Leão; Aoki, Valéria

    2016-01-01

    Atopic dermatitis is a chronic inflammatory skin disease with a complex pathogenesis, where changes in skin barrier and imbalance of the immune system are relevant factors. The skin forms a mechanic and immune barrier, regulating water loss from the internal to the external environment, and protecting the individual from external aggressions, such as microorganisms, ultraviolet radiation and physical trauma. Main components of the skin barrier are located in the outer layers of the epidermis (such as filaggrin), the proteins that form the tight junction (TJ) and components of the innate immune system. Recent data involving skin barrier reveal new information regarding its structure and its role in the mechanic-immunological defense; atopic dermatitis (AD) is an example of a disease related to dysfunctions associated with this complex. PMID:27579743

  19. 40 CFR 194.44 - Engineered barriers.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... impact on worker exposure to radiation both during and after incorporation of engineered barriers; (iii) The increased ease or difficulty of removing the waste from the disposal system; (iv) The increased...

  20. 40 CFR 194.44 - Engineered barriers.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... impact on worker exposure to radiation both during and after incorporation of engineered barriers; (iii) The increased ease or difficulty of removing the waste from the disposal system; (iv) The increased...

  1. 40 CFR 194.44 - Engineered barriers.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... impact on worker exposure to radiation both during and after incorporation of engineered barriers; (iii) The increased ease or difficulty of removing the waste from the disposal system; (iv) The increased...

  2. Contamination Barrier For Contour-Molding Material

    NASA Technical Reports Server (NTRS)

    Adams, James F.

    1988-01-01

    Release agent prevents molding compound from adhering to or contaminating surface. Cleaning agent, Turco 4215 NCLT, forms barrier preventing silicone molding compound from sticking to surface and leaving contaminating residue. Also see MFS-29243.

  3. Photovoltaic and thermophotovoltaic devices with quantum barriers

    DOEpatents

    Wernsman, Bernard R.

    2007-04-10

    A photovoltaic or thermophotovoltaic device includes a diode formed by p-type material and n-type material joined at a p-n junction and including a depletion region adjacent to said p-n junction, and a quantum barrier disposed near or in the depletion region of the p-n junction so as to decrease device reverse saturation current density while maintaining device short circuit current density. In one embodiment, the quantum barrier is disposed on the n-type material side of the p-n junction and decreases the reverse saturation current density due to electrons while in another, the barrier is disposed on the p-type material side of the p-n junction and decreases the reverse saturation current density due to holes. In another embodiment, both types of quantum barriers are used.

  4. Thermal barrier coating for alloy systems

    DOEpatents

    Seals, Roland D.; White, Rickey L.; Dinwiddie, Ralph B.

    2000-01-01

    An alloy substrate is protected by a thermal barrier coating formed from a layer of metallic bond coat and a top coat formed from generally hollow ceramic particles dispersed in a matrix bonded to the bond coat.

  5. PERMEABLE REACTIVE BARRIERS FOR GROUNDWATER REMEDIATION

    EPA Science Inventory

    Permeable reactive barriers (PRB's) are an emerging, alternative in-situ approach for remediating groundwater contamination that combine subsurface fluid flow management with a passive chemical treatment zone. Removal of contaminants from the groundwater plume is achieved by alt...

  6. PERMEABLE REACTIVE BARRIERS FOR GROUND WATER REMEDIATION

    EPA Science Inventory

    Permeable reactive barriers (PRB's) are an emerging, alternative in-situ approach for remediating groundwater contamination that combine subsurface fluid flow management with a passive chemical treatment zone. Removal of contaminants from the groundwater plume is achieved by alt...

  7. [THE INTESTINAL BARRIER, THE MICROBIOTA, MICROBIOME].

    PubMed

    Mar'yanovich, A T

    2016-01-01

    The review examined modern condition of development directions physiology of digestion, like structure and function of the intestinal barrier, the microbiota of the digestive tract in its relations with the microorganism.

  8. Federal Policies in Barrier Island Development.

    ERIC Educational Resources Information Center

    Miller, H. Crane

    1980-01-01

    Current federal policy towards barrier islands is ambivalent, both favoring and regulating development. Alternate policies are presently being examined by Congress and the Department of Interior. Several of these options are discussed in this article. (WB)

  9. Epidermal Permeability Barrier Defects and Barrier Repair Therapy in Atopic Dermatitis

    PubMed Central

    Lee, Hae-Jin

    2014-01-01

    Atopic dermatitis (AD) is a multifactorial inflammatory skin disease perpetuated by gene-environmental interactions and which is characterized by genetic barrier defects and allergic inflammation. Recent studies demonstrate an important role for the epidermal permeability barrier in AD that is closely related to chronic immune activation in the skin during systemic allergic reactions. Moreover, acquired stressors (e.g., Staphylococcus aureus infection) to the skin barrier may also initiate inflammation in AD. Many studies involving patients with AD revealed that defective skin barriers combined with abnormal immune responses might contribute to the pathophysiology of AD, supporting the outside-inside hypothesis. In this review, we discuss the recent advances in human and animal models, focusing on the defects of the epidermal permeability barrier, its immunologic role and barrier repair therapy in AD. PMID:24991450

  10. Current evidence of skin barrier dysfunction in human and canine atopic dermatitis.

    PubMed

    Marsella, Rosanna; Olivry, Thierry; Carlotti, Didier-Noel

    2011-06-01

    Atopic dermatitis (AD) is a multifaceted disease resulting from a complex interaction between environmental and genetic factors. Both of these factors can shape skin barrier function and the immunological response of predisposed patients. There is increasing evidence that an impaired skin barrier plays a role in both human and canine AD. Although many primary skin barrier defects had already been documented in the past in humans, the recent identification of the filaggrin mutations and the fact that such mutations are now considered the most important risk factor for development of AD have further emphasized the relevance of epidermal dysfunction in human AD. Much less is known in veterinary medicine, but evidence is rapidly building to support a role for skin barrier dysfunction in canine AD. Canine AD shares many clinical and immunological similarities with its human counterpart. The similar distribution of clinical lesions and the importance of the epicutaneous route of allergen exposure provided the incentive to investigate the role of skin barrier impairments in canine AD. The purpose of this comparative review is to present the current evidence of barrier dysfunction in both human and canine AD.

  11. Frozen soil barriers for hazardous waste confinement

    SciTech Connect

    Dash, J.G.; Leger, R.; Fu, H.Y.

    1997-12-31

    Laboratory and full field measurements have demonstrated the effectiveness of artificial ground freezing for the containment of subsurface hazardous and radioactive wastes. Bench tests and a field demonstration have shown that cryogenic barriers are impenetrable to aqueous and non aqueous liquids. As a result of the successful tests the US Department of Energy has designated frozen ground barriers as one of its top ten remediation technologies.

  12. Composite Pressure Vessel Including Crack Arresting Barrier

    NASA Technical Reports Server (NTRS)

    DeLay, Thomas K. (Inventor)

    2013-01-01

    A pressure vessel includes a ported fitting having an annular flange formed on an end thereof and a tank that envelopes the annular flange. A crack arresting barrier is bonded to and forming a lining of the tank within the outer surface thereof. The crack arresting barrier includes a cured resin having a post-curing ductility rating of at least approximately 60% through the cured resin, and further includes randomly-oriented fibers positioned in and throughout the cured resin.

  13. Liquid junction schottky barrier solar cell

    DOEpatents

    Williams, Richard

    1980-01-01

    A mixture of ceric ions (Ce.sup.+4) and cerous ions (Ce.sup.+3) in an aqueous electrolyte solution forms a Schottky barrier at the interface between an active region of silicon and the electrolyte solution. The barrier height obtained for hydrogenated amorphous silicon using the Ce.sup.+4 /Ce.sup.+3 redox couple is about 1.7 eV.

  14. Transition Control with Dielectric Barrier Discharge Plasmas

    DTIC Science & Technology

    2013-01-01

    AFRL-AFOSR-UK-TR-2013-0007 Transition Control with Dielectric Barrier Discharge Plasmas Professor Cameron Tropea...Discharge Plasmas 5a. CONTRACT NUMBER FA8655-11-1-3067 5b. GRANT NUMBER Grant 11-3067 5c. PROGRAM ELEMENT NUMBER 61102F 6. AUTHOR(S...15. SUBJECT TERMS EOARD, Plasma Aerodynamic, transition control, Dielectric Barrier 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF

  15. Corrosion-resistant ceramic thermal barrier coating

    NASA Technical Reports Server (NTRS)

    Hodge, P. E.; Levine, S. R.; Miller, R. A.

    1980-01-01

    Two-layer thermal barrier coating, consisting of metal-CrA1Y bond coating and calcium silicate ceramic outer layer, greatly improves resistance of turbine parts to hot corrosion from fuel and air impurities. Both layers can be plasma sprayed, and ceramic layer may be polished to reduce frictional losses. Ceramic provides thermal barrier, so parts operate cooler metal temperatures, coolant flow can be reduced, or gas temperatures increased. Lower grade fuels also can be used.

  16. Nuclear structure and sub-barrier fusion

    SciTech Connect

    Esbensen, H. . Cyclotron Lab. Argonne National Lab., IL )

    1990-01-01

    The influence of nuclear structure on heavy-ion fusion and elastic scattering, at energies near and below the Coulomb barrier, is discussed within the coupled channels formalism. The coupled channels approach provides a consistent description of the enhancement of sub-barrier fusion and the energy dependence of the effective potential for elastic scattering. This is illustrated by comparison to the data for several systems. 48 refs., 4 figs.

  17. Iron Nanoparticles in Reactive Environmental Barriers

    SciTech Connect

    Nuxoll, Eric E.; Shimotori, Tsutomu; Arnold, William A.; Cussler, Edward L.

    2003-09-23

    Zero-valent iron is cheap, environmentally innocuous, and effective at reducing chlorinated organics. It has, as a result, become a popular candidate for remediating aquifers contaminated with trichloroethylene and other halogenated pollutants. In this paper, we discuss one such system, where iron nanoparticles are synthesized and incorporated into polyvinyl alcohol membranes, forming water-permeable barriers to these pollutants. These barriers are tested against a variety of contaminants, including carbon tetrachloride, copper, and chromate.

  18. Drywall construction as a dental radiation barrier

    SciTech Connect

    MacDonald, J.C.; Reid, J.A.; Berthoty, D.

    1983-03-01

    Six typical forms of drywall construction have been tested as barriers against primary and secondary dental x-radiation. It is concluded that this widely used type of wall construction is generally effective for this purpose, but with a heavy workload two thicknesses of wallboard on each side of the wall are required to provide a sufficient barrier. In general, no lead need be incorporated in the walls.

  19. Drywall construction as a dental radiation barrier.

    PubMed

    MacDonald, J C; Reid, J A; Berthoty, D

    1983-03-01

    Six typical forms of drywall construction have been tested as barriers against primary and secondary dental x-radiation. It is concluded that this widely used type of wall construction is generally effective for this purpose, but with a heavy workload two thicknesses of wallboard on each side of the wall are required to provide a sufficient barrier. In general, no lead need be incorporated in the walls.

  20. Porosity determination of thermal barrier coatings

    NASA Technical Reports Server (NTRS)

    Van Roode, Mark; Beardsley, Brad

    1988-01-01

    Coating porosity is believed to be a critical factor for the thermal conductivity of thermal barrier coatings (TBCs). A number of different techniques have been used to determine the porosities of thermal barrier coatings for diesel applications as part of a NASA/DOE sponsored study. A comparison is made between methods based on water immersion, optical microscopy, eddy current thickness measurements, and Archimedes principle for TBC porosity determination.