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Sample records for layer influence des

  1. Influence of corrosion layers on quantitative analysis

    NASA Astrophysics Data System (ADS)

    Denker, A.; Bohne, W.; Opitz-Coutureau, J.; Rauschenberg, J.; Röhrich, J.; Strub, E.

    2005-09-01

    Art historians and restorers in charge of ancient metal objects are often reluctant to remove the corrosion layer evolved over time, as this would change the appearance of the artefact dramatically. Therefore, when an elemental analysis of the objects is required, this has to be done by penetrating the corrosion layer. In this work the influence of corrosion was studied on Chinese and Roman coins, where removal of oxidized material was possible. Measurements on spots with and without corrosion are presented and the results discussed.

  2. Influence des interactions du couple ciment/adjuvant dispersant sur les proprietes des betons: Importance du mode d'introduction des adjuvants

    NASA Astrophysics Data System (ADS)

    Baalbaki, Moussa

    1998-12-01

    Les travaux de recherche de cette these de doctorat ont porte sur les phenomenes d'incompatibilite (ou de compatibilite) ciment/adjuvant dispersant en mettant l'accent sur l'influence du mode d'introduction des adjuvants sur les proprietes des betons frais et durcis. Les aspects physiques et chimiques de l'interaction ciment/adjuvant a ete relies aux proprietes des betons en tenant compte du rapport E/C, de la teneur en C3A du ciment ainsi que du type d'adjuvant dispersant. Le programme experimental propose debute par une etude rheologique et mecanique sur pate et sur beton. Le comportement du superplastifiant a base de polynaphtalene (PNS) depend surtout de son interaction avec les premiers produits d'hydratation du ciment. Cette interaction du superplastifiant PNS avec le ciment est remarquablement differente dans le cas ou l'ajout du PNS est differe de quelques minutes. Lorsque le superplastifiant PNS est introduit directement avec l'eau de gachage, on remarque la formation d'un gel blanc compose d'ettringite, de CaCO 3 et de polynaphtalene et ce compose organo-mineral est presque inexistant lorsque le superplastifiant PNS est ajoute en mode differe. Ce gel organo-mineral se forme a partir de la solution entre les aluminates de calcium hydrates, les sulfates et le PNS, et est responsable de la perte d'affaissement du beton. Les analyses au microscope electronique a balayage montrent que l'introduction du superplastifiant PNS en mode S1 (ajout direct) engendre la precipitation d'une plus grande quantite d'ettringite et de produit organo-mineral. Cette ettringite finement cristallisee, abondante et enchevetree aura pour consequence de diminuer les proprietes rheologiques des betons et des pates. Ce phenomene ne s'observe pas lorsque le superplastifiant PNS est introduit en mode differe. Le mode d'introduction du superplastifiant a base de polyacrylate (PAE) n'affecte nullement le comportement rheologique du beton. Par ailleurs, le gel organo-mineral n'apparait pas

  3. Les reseaux de politique publique comme facteur d'influence du choix des instruments de politique energetique canadienne a des fins environnementales de 1993 a nos jours

    NASA Astrophysics Data System (ADS)

    Fathy El Dessouky, Naglaa

    l'agenda politique du pays. Notre projet de recherche, par le truchement de l'approche des reseaux de politique publique, s'attarde a decrire et a expliquer le processus de la formulation d'une politique particuliere, soit la politique energetique a des fins de protection de l'environnement, elaboree en 1993. Il s'agit de mettre en evidence les facteurs affectant le choix des instruments de ces politiques publiques dans leur contexte national. Ainsi, la question generale de cette recherche est: Comment les phases evolutives de la formation d'un reseau de politique, en l'occurrence le Conseil canadien de l'energie (CCE), menent a des caracteristiques particulieres a ce reseau; et comment celles-ci determinent-elles les types des instruments de politique publique choisis, particulierement ceux de la recente orientation des politiques energetiques canadiennes a des fins environnementales elaborees en 1993? Afin d'atteindre l'objectif de notre recherche, deux facteurs primordiaux sont utilises, soit la circulation de l'information et l'exercice du controle sur les ressources des acteurs. L'analyse des caracteristiques du reseau en fonction des liens forts et des liens faibles autant que la presence ou l'absence des trous structuraux nous permettent de bien identifier les positions des differents acteurs, etatiques et non etatiques, sur le plan de l'information et du controle, qui a leur tour, nous semble-t-il, constituent des facteurs affectant les types des instruments des politiques publiques choisis: instruments substantifs, qui indiquent le degre de l'intervention du gouvernement, et instruments proceduraux, qui mettent plutot l'accent sur le degre de l'influence du gouvernement sur les acteurs non etatiques. L'etude soutient que l'approche des reseaux se distingue notamment par son potentiel a expliquer l'interrelation relative entre idees, interets et institutions, ce qui a son tour est susceptible de permettre une meilleure comprehension des processus de l

  4. Surface layer influences on supercell thunderstorms

    NASA Astrophysics Data System (ADS)

    Nowotarski, C. J.

    2016-12-01

    While low-level (nominally 0-1 km) environmental kinematic and thermodynamic properties have been shown to have some skill in discriminating between tornadic and nontornadic supercells, a growing body of work suggests that aspects of the near-storm environment (e.g., the wind profile, temperature lapse rate, surface roughness, soil moisture, and low-level relative humidity) in even shallower layers (<500 m) may be important in supercell tornadogenesis. Supercell thunderstorms are simulated with and without full surface physics in idealized environments varying surface and near-surface (i.e., surface layer) characteristics that may affect both the ambient and internal flow within the storms. The effects of horizontal variations in surface-layer characteristics on supercell dynamics will also be explored. Results from this and previous studies examining the effects of shallow changes in the near-storm environment on both observed and simulated storms will be presented.

  5. Influence of Mach Number and Incoming Boundary Layer on Shock Boundary Layer Interaction

    NASA Astrophysics Data System (ADS)

    Stab, Ilona; Threadgill, James; Little, Jesse

    2016-11-01

    Wall pressure fluctuations, schlieren imaging, oil flow visualization and PIV measurements have been performed on the shock boundary layer interaction (SBLI) formed by a 10° compression ramp. The incoming Mach number and boundary layer characteristics are varied to examine their influence on the SBLI. Focus is placed on understanding the effect of these parameters on the structure and unsteadiness of the resultant interaction. Lower Mach numbers M = 2 . 3 (δ0 = 1 . 7 mm , θ = 0 . 29 mm , Reθ = 3115 , H = 1 . 4) and M = 3 (δ0 = 1 . 3 mm , θ = 0 . 25 mm , Reθ = 1800 , H = 1 . 8) show a turbulent or transitional approach boundary layer with no apparent separation at the ramp. Mach 4 has a large separated region which is seemingly a result of a now laminar or transitional approach boundary layer. Pulsations in the separated region correspond to the expected low frequency SBLI dynamics showing a broad peak around a Strouhal number of St = fLint /U∞ = 0 . 27 which is lower than the characteristic frequency of the turbulent boundary layer. Additional results examining the influence of boundary layer modifications (e.g. sweep) and wind tunnel side-walls are also included. Supported by Raytheon Missile Systems.

  6. The influence of soft layer electrokinetics on bacterial electroporation

    NASA Astrophysics Data System (ADS)

    Moran, Jeffrey; Dingari, Naga Neehar; Buie, Cullen

    2015-11-01

    Electroporation of mammalian cells has received a significant amount of theoretical attention over the last decade because of its ability to deliver biologically active molecules into cells using short and strong electric field pulses. However, application of the same theory to bacterial electroporation presents significant challenges because of the presence of charged soft layers around bacteria. The soft layer charge distribution has been found to significantly influence bacterial electrophoretic mobility and polarizability because it alters the electric potential spatial distribution around the cell envelope. In addition, the RC charging time scale of both the soft layer and electric double layer is of the order of microseconds, which is also of similar order of magnitude as the pore creation time scale. Therefore in this study, we investigate the influence of soft layer electrokinetics on the spatial pore distribution and the temporal pore radius evolution during bacteria electroporation, which are quantitative measures of a bacterium's amenability to electroporation. The study will have significant impact on designing and optimizing bacteria electroporation platforms for gene and drug delivery applications.

  7. Dépistage des maladies cardiovasculaires chez des étudiants de l'Université de Douala et influence des activités physiques et sportives

    PubMed Central

    Ewane, Marielle Epacka; Mandengue, Samuel Honoré; Priso, Eugene Belle; Tamba, Stéphane Moumbe; Ahmadou; Fouda, André Bita

    2012-01-01

    Introduction Les maladies cardiovasculaires (MCV) constituent l'une des principales causes de mortalité dans les pays en développement. Le dépistage de ces dernières chez des jeunes est un défi dans la lutte contre leur expansion. Le but de cette étude était de dépister ces maladies au sein d'une population jeunes d’étudiants camerounais. Methodes Deux mille six cent cinquante-huit étudiants de l'Université de Douala (23,6 ± 2,9 ans, sex-ratio H/F = 0,9) ont en Avril - Mai 2011 participé à une campagne de dépistage gratuit du diabète, de l'hypertension artérielle (HTA) et de l'obésité. Ils ont également été soumis à une d'enquête évaluant leur niveau en activités physiques et sportives (APS). Resultats 12,7% des participants avaient une pression artérielle (PA) ≥ 140/90 mmHg, 3,6% étaient obèses et 0,9% avaient une glycémie ≥1,26 g/L. Des corrélations ont été trouvées entre certains facteurs de risque (diabète, hypertension et obésité) et le niveau académique d'une part (r =0,366; p < 0,0001) et le temps passé devant la télévision d'autres part (r = 0,411; p < 0,0001). L‘APS était inversement corrélée à l‘âge (r =-0,015; p < 0,0001) et au temps passé devant la télévision (r = -0,059; p = 0,002). Conclusion La présence des MCV et leurs facteurs de risque mis en évidence dans cette étude réalisée en milieu estudiantin camerounais interpelle à une prévention et une éducation dans la lutte contre ces dernières. PMID:22655111

  8. Influence des inclusions sur la rupture d'un acier faiblement allié

    NASA Astrophysics Data System (ADS)

    Hausild, P.; Berdin, C.; Bompard, P.; Prioul, C.

    2003-03-01

    L'étude de la rupture d'un acier faiblement allié dans le domaine de la transition ductile fragile a permis de mettre en évidence la présence croissante, avec la température de sollicitation, d'amas d'inclusions de seconde phase sur les surfaces de rupture. On montre, à l'aide de modélisations par éléments finis, que ces amas jouent néanmoins un rôle mineur dans le déclenchement du clivage. En revanche, leur influence sur la propagation de la rupture ductile est importante. On peut alors expliquer l'anisotropie de la résilience en prenant en compte la géométrie des inclusions et leur répartition spatiale.

  9. 20 March 2015 solar eclipse influence on sporadic E layer

    NASA Astrophysics Data System (ADS)

    Pezzopane, M.; Pietrella, M.; Pignalberi, A.; Tozzi, R.

    2015-11-01

    This paper shows how the solar eclipse occurred on 20 March 2015 influenced the sporadic E (Es) layer as recorded by the Advanced Ionospheric Sounder by Istituto Nazionale di Geofisica e Vulcanologia (AIS-INGV) ionosondes installed at Rome (41.8°N, 12.5°E) and Gibilmanna (37.9°N, 14.0°E), Italy. In these locations, the solar eclipse was only partial, with the maximum area of the solar disk obscured by the Moon equal to ∼54% at Rome and ∼45% at Gibilmanna. Nevertheless, it is shown that the strong thermal gradients that usually accompany a solar eclipse, have significantly influenced the Es phenomenology. Specifically, the solar eclipse did not affect the Es layer in terms of its maximum intensity, which is comparable with that of the previous and next day, but rather in terms of its persistence. In fact, both at Rome and Gibilmanna, contrary to what typically happens in March, the Es layer around the solar eclipse time is always present. On the other hand, this persistence is also confirmed by the application of the height-time-intensity (HTI) technique. A detailed analysis of isoheight ionogram plots suggests that traveling ionospheric disturbances (TIDs) likely caused by gravity wave (GW) propagation have played a significant role in causing the persistence of the Es layer.

  10. The influence of bulges on boundary-layer instability

    NASA Astrophysics Data System (ADS)

    Elli, S.; Vandam, C. P.

    Local disturbances caused by a spanwise surface corrugation affect the position of the boundary-layer transition, and so the drag, of an object. This premature transition from laminar to turbulent flow is often associated with a separation of the laminar boundary-layer from its surface. Also the roughness-induced separation bubble provides an important link between the pressure and velocity fluctuations in the environment and the development of the disturbance in the laminar boundary-layer, i.e., the receptivity problem. To investigate the influence of a laminar separation bubble on boundary-layer instability, a separated flow generated by a velocity gradient over a flat plate was analyzed by direct numerical simulation using finite-difference solutions of the Navier-Stokes equations. The bubble acts as a strong amplifier of the instability waves and a highly nonlinear flow field is shown to develop downstream of the bubble. Consequently, the results of the direct numerical simulation differ noticeably from those of the classical linear stability theory proving the fact that the nonparallel effects together with the nonlinear interactions are crucial to this flow development. In the present paper, the effect of physical perturbations such as humps and hollows on boundary-layer instability is analyzed. This problem has been considered theoretically by several researchers (e.g., Nayfeh et al., 1987 and 1990; Cebeci et al., 1988). They used linear stability theory in their approach which does not include the nonparallel nor the nonlinear effects. Therefore, to account for these important effects in studying flow over humps and hollows the direct simulation technique is being implemented in generalized coordinates.

  11. Influence du comportement des accompagnants sur le vécu des patients admis pour hémorragies digestives hautes au CHU campus de Lomé (Togo)

    PubMed Central

    Bagny, Aklesso; Dusabe, Angelique; Bouglouga, Oumboma; Lawson-ananisoh, Mawuli Late; Kaaga, Yeba Laconi; Djibril, Mohaman Awalou; Soedje, Kokou Mensah; Dassa, Simliwa Kolou; Redah, Datouda

    2014-01-01

    Introduction L'hémorragie digestive haute est une urgence, qui constitue souvent pour les patients un danger mortel suscitant inquiétude et agitation. Dans cet état, le patient dépend de ses accompagnants pour ses soins et pour honorer le traitement; mais souvent, il a été observé une discordance entre l'urgence et les comportements des accompagnants. Le but de cette étude était de décrire les facteurs socioéconomiques et psychologiques pouvant influencer les comportements des accompagnants des patients admis pour HDH, estimer l'indice de relation entre ces comportements et les facteurs associés d'une part et le vécu des patients admis pour HDH d'autre part. Méthodes Il s'agit d'une étude prospective menée de Septembre 2010 à Juin 2011 (soit 10 mois). Nous avions utilisé l'entretien semi-dirigé et l'observation directe pour collecter nos données, ces dernières avaient été traitées par les méthodes statistiques et d'analyse de contenu. Résultats Dans la présente étude, les comportements des accompagnants des patients admis pour HDH sont en majorité marqués par l'abandon (84%) et le manque de sollicitude (80,2%). Ces comportements sont souvent stimulés par les facteurs socioéconomiques tels que les difficultés économiques (83,2%), des conflits intrafamiliaux (85,1%) et des représentations (maladie incurable ou envoûtement) de la maladie par les accompagnants (73,3%) des cas. Quant aux patients, ils vivent ces comportements comme étant des menaces de mort ou des rejets (77,20%) et comme étant une dévalorisation ou une humiliation de la part de leurs accompagnants (70,30%). Les résultats confirment l'existence de lien significatif entre les comportements des accompagnants et les facteurs socio économiques, entre les comportements des accompagnants et des facteurs psychologiques, et entre le vécu des patients admis pour l'HDH et les comportements des accompagnants. Conclusion Des études ultérieures devraient aborder les points

  12. Reynolds number influences on turbulent boundary layer momentum transport

    NASA Astrophysics Data System (ADS)

    Priyadarshana, Paththage A.

    There are many engineering applications at Reynolds numbers orders of magnitude higher than existing turbulent boundary layer studies. Currently, the mechanisms for turbulent transport and the Reynolds number dependence of these mechanisms are not well understood. This dissertation presents Reynolds number influences on velocity and vorticity statistics, Reynolds shear stress, and velocity-vorticity correlations for turbulent boundary layers. Well resolved hot-wire data for this study were acquired in the atmospheric surface layer at the SLTEST facility in western Utah. It is shown that during near neutral thermal stability, the flow behaves as a canonical zero pressure gradient turbulent boundary layer, in which the Reynolds number based on momentum thickness, Rtheta, is approximately 2 x 106. The present study also provides information regarding the effects of wall roughness over a limited range of roughness. It is observed that with increasing Rtheta, the inner normalized streamwise intensity increases. This statistic is less sensitive to wall roughness away from the roughness sublayer. In contrast, the inner normalized wall normal intensity is less sensitive to the variation of Rtheta, and it is significantly sensitive to wall roughness. Outside the viscous sublayer, the inner normalized vorticity intensity is less sensitive to both Rtheta and roughness. A primary observation of the Reynolds stress study is that the predominant motions underlying the Reynolds shear stress undergo a significant shift from large to intermediate scales as Rtheta becomes large, irrespective of surface roughness. Quadrant analysis shows that types of motions contributing to the Reynolds stress change significantly at comparable wall normal locations with increasing Rtheta. The mean wall normal gradients of the Reynolds shear stress and the turbulent kinetic energy have direct connections to the transport mechanisms of the turbulent boundary layer. These gradients can be expressed in

  13. Oceanographic influences on Deep Scattering Layers across the North Atlantic

    NASA Astrophysics Data System (ADS)

    Fennell, Sheena; Rose, George

    2015-11-01

    The distribution and density of Deep Scattering Layers (DSLs) were quantified along North Atlantic transits from Ireland to the Grand Banks of Newfoundland in the springs of 2012, 2013 and 2014 employing a calibrated Simrad EK60 echo sounder at 38 kHz. Concurrently, Sippican T5 XBTs (eXpendable Bathy Thermographs) were used to profile temperatures to 1800 m. In each year the scattering layers spanned the deep basin at depths ranging from near surface to approximately 900 m, but annual mean densities differed significantly. Higher DSL densities were recorded during years that exhibited higher sea temperatures at the depths of major DSL concentration (400-600 m), higher sea level anomalies and stronger eastward geostrophic currents. The highest concentration of the DSLs in each year was found in the area east of the Grand Banks that corresponded with areas of anticyclonic eddies. In this region DSL densities in 2014 were among the highest recorded worldwide (>7000 m2 nautical mile-2). Midwater fishing indicated DSLs were dominated by Myctophids and Sternoptychids. Anticyclonic eddy formation is discussed as a possible means of transport and aggregation of the DSLs in that region, where oceanographic influences may play a dominant role in the distribution and density of the DSLs and upper trophic level fishes.

  14. Influence of Cemented Layers on Contaminant Transport in Mine Tailings

    NASA Astrophysics Data System (ADS)

    Ptacek, C.; Blowes, D.; Jambor, J.; Moncur, M.; Gunsinger, M.; Doerr, N.

    2004-12-01

    Exposure of sulfide-mine tailings to atmospheric oxygen leads to the initiation of a series of reactions, including sulfide oxidation, acid neutralization and metal attenuation reactions. As oxygen ingresses into the tailings, the oxidation front moves downward and inward from the edges of the tailings surface. At or near the acid neutralization front, secondary phases can accumulate, leading to the formation of hardpan layers. Field studies were conducted at three mine sites to evaluate the role of cemented layers in influencing contaminant transport from oxidized tailings. Detailed field measurements were made, including collection of water and gas samples from the vadose and groundwater zones. Cores were collected for mineralogical and chemical analyses to evaluate the extent of sulfide mineral oxidation and accumulation of secondary phases. Calculations of mineral saturation indices were made using ion-pair and ion-interaction models that were modified to account for the very high solute concentrations observed in the tailings pore waters. At a site that has been oxidizing for 25 years, a massive Fe(III)-bearing hardpan, containing gypsum, goethite and jarosite, has formed over the last 15 years. At a site that has been oxidizing for 35 years, an Fe(III)-bearing hardpan is also present. At a site that has been oxidizing for 70 years, a massive Fe(II)-bearing hardpan containing melanterite and gypsum is present below the zone of active oxidation. Above this zone, there are discontinuous Fe(III)-bearing cemented layers that are likely oxidized remnants of the original Fe(II) hardpan. Calculated mineral saturation indices are consistent with the observed accumulations of secondary phases. Transient perched water table conditions have developed above the massive Fe(II) hardpan, leading to the lateral transport of sulfide oxidation products along the hardpan and the formation of seepage zones above the permanent water table. Chemical extractions and mineralogical

  15. [The influences of lactose as an inducer on expression of plant des-pGlu1-brazzein in Escherichia coli].

    PubMed

    Li, Chun-Li; Chen, Qi-Xin; He, Guo-Qing

    2006-11-01

    Expression strain of des-pGlu1-brazzein was constructed and the conditions using lactose as inducer was also optimized. The Influences of three factors which were lactose concentration, induction time and inducing temperature on the growth of strain and on the yield of des-pGlul-Brazzein was analyzed in detail. The result indicated that high lactose concentration inhibit the growth of strains (P < 0.01) but made no difference on expression of target protein between 0.5%-5% (P > 0.05), Biomass would be improved as time passed (P < 0.01), but the yield of target protein didn't increase obviously at 30 degrees C compared with at 37 degrees C. Further result showed that the greater expressed level of des-pGlul-Brazzein, as high as about 20% of total cell protein, could be achieved after the strain had been induced with 0.5% lactose under 28 degrees C - 30 degrees C for 4 h.

  16. Influence of transverse surface waves on turbulent boundary layers

    NASA Technical Reports Server (NTRS)

    Balasubramanian, R.; Ash, R. L.; Cary, A. M., Jr.; Bushnell, D. M.

    1977-01-01

    Wavy wall experiments using solid waves and progressive waves have been reported. For this paper, the major effects of waviness of the wall on the flow are identified as due to oscillatory curvature (convex-concavity) and oscillatory acceleration/deceleration of the flow, which imposes a highly nonequilibrium influence upon the turbulence structure. The theoretical analysis in this presentation takes into account proper turbulence modeling (including the nonequilibrium effects) for the wavy wall problem. The analysis proceeds in three stages: (1) inviscid solution for induced pressure due to the physical wall, (2) solution of a turbulent boundary layer with pressure gradients and curvature effects in the modeling from which the profile correction is computed, and (3) induced pressure computations for the corrected profile. The phase shift of pressure perturbations with respect to the physical wall can be predicted, and pressure drag and skin friction drag can be estimated, with nonlinear viscous effects included. Comparison of the theoretical estimates with experimental data are also presented.

  17. Influence de l'environnement sur la tenue des ciments alumineux

    NASA Astrophysics Data System (ADS)

    Coatanlem, P.; Jauberthie, R.

    2004-11-01

    Le fondu alumineux est un ciment à prise rapide, bonne tenue à l'eau de mer, aux solutions sulfatées et aux sols alcalins. Actuellement, il est communément utilisé pour des applications à des ouvrages requérant une exécution rapide. Sa très bonne résistance mécanique à très courte échéance décroît ensuite après quelques années de service. Le but de notre étude est de relier ces observations à l'évolution des phases cristallines et ceci dans des conditions extérieures plus ou moins agressives. Le CA (aluminate de calcium CaOAl{2}O{3}) est le constituant principal du ciment fondu anhydre. A 20circC, la phase hydratée est le CAH{10} (CaO Al{2}O{3},10H{2}O). Cette phase métastable disparaît totalement à 60circC. Elle est remplacée par C{3}AH{6 }(3CaO, Al{2}O{3}, 6H{2}O) et Al(OH){3}. La transformation est très rapide. L'objectif de cette étude est d'observer par diffraction X l'évolution des phases hydratées du fondu alumineux soumis à des environnements agressifs : température élevée, atmosphère humide, solutions acides et solutions sulfatiques pour lesquelles ce ciment est couramment préconisé. Les observations au MEB mettent clairement en évidence l'évolution de la microstructure de la pâte cimentaire lors du changement de phase. Nous avons montré que cette transformation de phase observée à 60circC apparaît à des températures beaucoup plus basses (dès 20circC) liées à l'environnement. Ceci explique pourquoi certains pays ont proscrit l'utilisation d'un tel ciment, la durabilité n'étant pas correcte avec ce type de matériau.

  18. Corrosion influencée par les micro-organismes : influence du biofilm sur la corrosion des aciers, techniques et résultats recents

    NASA Astrophysics Data System (ADS)

    Feugeas, F.; Magnin, J. P.; Cornet, A.; Rameau, J. J.

    1997-03-01

    Microbiologically Influenced Corrosion (M.I.C.) studied since the beginning of this century, is responsible for the degradation of many metallic equipments. This study is a review of results dealing with M.I.C. on several types of steels as: carbon steels, stainless steels, welded steels and covered steels. M.I.C. occurs only in presence of a biofilm. The first part of this study describes chemical and physical factors involved in its development, technical methods for studying biofilms, and its contribution in the corrosion process. The second part is devoted to the study of M.I.C. cases linked with metal nature and different aqueous environments and the last part reviews the mainly mecanisms of biocorrosion. La Corrosion Influencée par les Micro-organismes (C.I.M.) ou biocorrosion, phénomène étudié depuis le début du siècle, est responsable de la dégradation d'un grand nombre d'ouvrages métalliques. Cette étude a pour but de faire le point des connaissances sur la corrosion influencée microbiologiquement de divers types d'aciers au carbone, d'aciers inoxydables, d'assemblages soudés et d'aciers revêtus. La C.I.M. n'apparaît qu'en présence d'un biofilm. La première partie de cette étude décrit les facteurs physico-chimiques impliqués dans la formation du biofilm, ces moyens d'études ainsi que son action dans le processus de biocorrosion. La seconde partie est consacrée à la description des cas de biocorrosion classés en fonction de la nature des métaux et des milieux avec lesquels ils sont en contact. La dernière partie de ce document passe en revue les principaux mécanismes de biocorrosion décrits.

  19. Electrical resistivity of assembled transparent inorganic oxide nanoparticle thin layers: influence of silica, insulating impurities, and surfactant layer thickness.

    PubMed

    Bubenhofer, Stephanie B; Schumacher, Christoph M; Koehler, Fabian M; Luechinger, Norman A; Sotiriou, Georgios A; Grass, Robert N; Stark, Wendelin J

    2012-05-01

    The electrical properties of transparent, conductive layers prepared from nanoparticle dispersions of doped oxides are highly sensitive to impurities. Production of cost-effective thin conducting films for consumer electronics often employs wet processing such as spin and/or dip coating of surfactant-stabilized nanoparticle dispersions. This inherently results in entrainment of organic and inorganic impurities into the conducting layer leading to largely varying electrical conductivity. Therefore, this study provides a systematic investigation on the effect of insulating surfactants, small organic molecules and silica in terms of pressure dependent electrical resistivity as a result of different core/shell structures (layer thickness). Application of high temperature flame synthesis gives access to antimony-doped tin oxide (ATO) nanoparticles with high purity. This well-defined starting material was then subjected to representative film preparation processes using organic additives. In addition ATO nanoparticles were prepared with a homogeneous inorganic silica layer (silica layer thickness from 0.7 to 2 nm). Testing both organic and inorganic shell materials for the electronic transport through the nanoparticle composite allowed a systematic study on the influence of surface adsorbates (e.g., organic, insulating materials on the conducting nanoparticle's surface) in comparison to well-known insulators such as silica. Insulating impurities or shells revealed a dominant influence of a tunneling effect on the overall layer resistance. Mechanical relaxation phenomena were found for 2 nm insulating shells for both large polymer surfactants and (inorganic) SiO(2) shells.

  20. Influence of haze layers upon remotely-sensed surface properties

    NASA Technical Reports Server (NTRS)

    Jurica, G. M.; Murray, W. L.

    1972-01-01

    The possibility that the presence of hazy layers contributes to anomalous effects in airplane remote sensing data on corn blight distribution is studied. Computations of scattering angles along flightlines are used to estimate reflected intensity variations as observed in bright and dark sides along flightline of the aircraft.

  1. Influence of localised double suction on a turbulent boundary layer

    NASA Astrophysics Data System (ADS)

    Oyewola, O.; Djenidi, L.; Antonia, R. A.

    2007-07-01

    The effects of localised suction applied through a pair of porous wall strips on a turbulent boundary layer have been quantified through the measurements of mean velocity and Reynolds stresses. The results indicate that the use of second strip extends the pseudo-relaminarisation zone but also reduces the overshoot in the longitudinal and normal r.m.s. velocities. While the minimum r.m.s. occurs at x/δo=3.0 (one strip) and x/δo=12 (two strips), the reduction observed for the latter case is larger. Relative to no suction, the turbulence level is modified by suction and the effect is enhanced with double suction. This increased effectiveness reflects the fact that the second strip acts on a boundary layer whose near-wall active motion has been seriously weakened by the first strip.

  2. Impinging Turbulent Boundary Layer Influence on Horseshoe Vortex Periodicity

    NASA Astrophysics Data System (ADS)

    Smith, Charles; Sabatino, Daniel

    2000-11-01

    The spatial-temporal flow-field and associated surface heat transfer for a turbulent juncture flow were experimentally examined in a water channel using PIV and thermochromic liquid crystals. Turbulent boundary layer "burst" events, which have been previously described as hairpin vortex "packets," are shown to interact and periodically strengthen the juncture-region horseshoe vortex (HV). This strengthening of the HV precipitates its movement upstream and toward the surface. This process that induces the ejection of a secondary vortex, which weakens the HV, with the strengthen-ejection-weakening cycle repeating quasi-periodically. The dominant period of motion for the HV correlates closely to the impinging turbulent boundary layer bursting frequency. This vortex-bursting interaction is responsible for the elevated endwall surface heat transfer upstream of the corner vortex region. The temporal endwall surface heat transfer behavior for a linear turbine cascade juncture was also determined to be essentially the same as that for a simple bluff body, with the impinging boundary layer bursting frequency again being the controlling parameter.

  3. Number of graphene layers exhibiting an influence on oxidation of DNA bases: analytical parameters.

    PubMed

    Goh, Madeline Shuhua; Pumera, Martin

    2012-01-20

    This article investigates the analytical performance of double-, few- and multi-layer graphene upon oxidation of adenine and guanine. We observed that the sensitivity of differential pulse voltammetric response of guanine and adenine is significantly higher at few-layer graphene surface than single-layer graphene. We use glassy carbon electrode as substrate coated with graphenes. Our findings shall have profound influence on construction of graphene based genosensors.

  4. The influence of the atmospheric boundary layer on nocturnal layers of noctuids and other moths migrating over southern Britain.

    PubMed

    Wood, Curtis R; Chapman, Jason W; Reynolds, Donald R; Barlow, Janet F; Smith, Alan D; Woiwod, Ian P

    2006-03-01

    Insects migrating at high altitude over southern Britain have been continuously monitored by automatically operating, vertical-looking radars over a period of several years. During some occasions in the summer months, the migrants were observed to form well-defined layer concentrations, typically at heights of 200-400 m, in the stable night-time atmosphere. Under these conditions, insects are likely to have control over their vertical movements and are selecting flight heights that are favourable for long-range migration. We therefore investigated the factors influencing the formation of these insect layers by comparing radar measurements of the vertical distribution of insect density with meteorological profiles generated by the UK Meteorological Office's (UKMO) Unified Model (UM). Radar-derived measurements of mass and displacement speed, along with data from Rothamsted Insect Survey light traps, provided information on the identity of the migrants. We present here three case studies where noctuid and pyralid moths contributed substantially to the observed layers. The major meteorological factors influencing the layer concentrations appeared to be: (a) the altitude of the warmest air, (b) heights corresponding to temperature preferences or thresholds for sustained migration and (c) on nights when air temperatures are relatively high, wind-speed maxima associated with the nocturnal jet. Back-trajectories indicated that layer duration may have been determined by the distance to the coast. Overall, the unique combination of meteorological data from the UM and insect data from entomological radar described here show considerable promise for systematic studies of high-altitude insect layering.

  5. The Influence of Laser Induced Consolidation on the Ablation Threshold of Nanoparticulate ITO-layers

    NASA Astrophysics Data System (ADS)

    Mikschl, Florian; Baum, Marcus; Heberle, Johannes; Alexeev, Ilya; Schmidt, Michael

    Indium tin oxide (ITO) is one of the few materials, which combines optical transparency in the wavelength range of visible light and electrical conductivity. It offers a wide range of applications in the field of optoelectronic devices such as solar cells or displays. To the present day, ITO is commonly deposited in a vacuum environment. Deposition under vacuum atmosphere is a cost-intensive process and not compatible with modern manufacturing techniques, like roll-to-roll processing. To overcome this limitation we propose the generation of ITO layers by deposition of ITO nanoparticles under atmospheric conditions.For the generation of functional devices structured layers are required. The exact damage threshold of nanoparticulate ITO layers is essential to minimize influence of the structuring process on the substrate.In our measurements we used three different substrates, spin coated layers, annealed layers and consolidated layers.

  6. Aerosol influences on marine atmospheric surface layer optics

    NASA Astrophysics Data System (ADS)

    Walker, Philip L.

    1998-11-01

    Shipboard optical system are used as passive sensors for threat detection. When a threat is at low altitude part of the optical path from it may lie in the marine surface layer where it is distorted by refractivity gradients caused by large vertical changes in temperature and humidity in the first several meters above the sear surface. In addition, the poorly characterized giant sea salt aerosols in this region not only contribute to scattering but add to atmospheric refractivity by an amount equal to the product of water refractivity and aerosol contribution to atmospheric liquid water content. The added refractivity is about 10 percent of that due to water vapor, depending on relative humidity. These aerosols are created from bubble fragments and jet droplets caused by air bubbles bursting at the sea surface and can be hundreds of micrometers in size. Their size and number depend on wind speed and turbulent diffusivity. Because of the droplets' large size the vertical profile of liquid water content decreases more rapidly than exponential leading to correspondingly larger ray bending. As for scattering the large size of the droplets means that Beer's law of extinction does not apply. Part of this work has been presented previously, but the current work will incorporate more up-to-date size distribution data for near sear surface aerosols, obtained from a literature review in progress, into calculations of forward scattering and vertical refractivity profiles using selected wind speeds, relative humidity and air-sea temperature differences.

  7. Influence of tableting forces and lubricant concentration on the adhesion strength in complex layer tablets.

    PubMed

    Dietrich, P; Bauer-Brandl, A; Schubert, R

    2000-07-01

    The strength of adhesion in complex two-layer tablets is assessed using statistical methods with respect to the applied tableting forces for the first layer and for applying the second layer on the first, as well as regarding the fraction of the lubricant. These results, obtained on a single-punch tablet press, are compared with the results for three-layer tablets produced on a rotary press at production scale. The strongest negative influence on adhesion strength was exerted by the amount of lubricant in the central layer. As expected, compression forces for central-layer tableting also had a negative effect, whereas the compression forces for complex layer tableting exerted a positive effect on layer adhesion. The validity of the derived model equation was proved by experiments: It was shown that the adhesion strength in complex layer tablets produced in production scale can be predicted from laboratory-scale experiments. This makes optimization of the formulation and parameter settings at an early stage of development possible.

  8. The influence of free-stream turbulence on turbulent boundary layers with mild adverse pressure gradients

    NASA Technical Reports Server (NTRS)

    Hoffmann, J. A.; Kassir, S. M.; Larwood, S. M.

    1989-01-01

    The influence of near isotropic free-stream turbulence on the shape factors and skin friction coefficients of turbulent boundary layers is presented for the cases of zero and mild adverse pressure gradients. With free-stream turbulence, improved fluid mixing occurs in boundary layers with adverse pressure gradients relative to the zero pressure gradient condition, with the same free-stream turbulence intensity and length scale. Stronger boundary layers with lower shape factors occur as a result of a lower ratio of the integral scale of turbulence to the boundary layer thickness, and to vortex stretching of the turbulent eddies in the free-stream, both of which act to improve the transmission of momentum from the free-stream to the boundary layers.

  9. The influence of free-stream turbulence on turbulent boundary layers with mild adverse pressure gradients

    NASA Technical Reports Server (NTRS)

    Hoffmann, Jon A.

    1988-01-01

    The influence of near isotropic free-stream turbulence on the shape factors and skin friction coefficients of turbulent bounday layers is presented for the cases of zero and mild adverse pressure gradients. With free-stream turbulence, improved fluid mixing occurs in boundary layers with adverse pressure gradients relative to the zero pressure gradient condition, with the same free-stream turbulence intensity and length scale. Stronger boundary layers with lower shape factors occur as a result of a lower ratio of the integral scale of turbulence to the boundary layer thickness, and to vortex stretching of the turbulent eddies in the free stream, both of which act to improve the transmission of momentum from the free stream to the boundary layers.

  10. Influence of thin alien layers on hydrogen reflection and trapping by PFM

    NASA Astrophysics Data System (ADS)

    Golubeva, A. V.; Kurnaev, V. A.; Levchuk, D. V.; Trifonov, N. N.

    2003-03-01

    Investigations of the influence of carbon and hydrocarbon layers on the trapping and reflection of hydrogen isotopes by tungsten were carried out with BCA based computer code SCATTER. It is shown that for small layer thickness the trapping efficiency depends on the hydrocarbon film composition. At layer thickness of a few nanometers energy dependence of the trapping efficiency has a non-monotonous character with a minimum at primary energies about 100-1000 eV and continuous increment with energy at higher energies. The possible reason of this effect is briefly discussed. Comparison between the trapping efficiencies of different hydrogen isotopes in a C-W target is also presented.

  11. Influence of orientation on the evolution of small perturbations in compressible shear layers with inflection points

    NASA Astrophysics Data System (ADS)

    Karimi, Mona; Girimaji, Sharath S.

    2017-03-01

    We investigate the influence of orientation on the evolution of small perturbations in compressible shear layers with inflection points. By using linear analysis, we demonstrate that perturbations along the shear plane are most affected by compressibility. The influence of compressibility gradually diminishes with increasing obliqueness of the perturbations with respect to the shear plane. It is demonstrated that the effective gradient Mach number is an appropriate compressibility parameter. We establish that spanwise perturbations, orthogonal to the shear plane, are impervious to compressibility effects. Direct numerical simulations of compressible mixing layers subject to the perturbations at various obliqueness angles verify the analytical findings.

  12. The influence of layers number on the structure and ferroelectric properties of BZT films

    SciTech Connect

    Andika, Rachmat Toresano, La Ode Husein Z.; Soegijono, Bambang

    2016-04-19

    In recent study, the number of BaZrTiO{sub 3} layers were successively deposited on the Si-substrate by spin-coating process. The increasing of layers number affects the films structure which has been observed in XRD, while the ferroelectric properties have been analyzed by Sawyer-Tower. Perovskite tetragonal is observed in all films by the c-a axis ratio around 1.002 to 1.018, and the crystallite sizes were calculated from 75 nm to 129 nm. The maximum polarization value was found to be decreased during the increase of numbers of layers from 3 to 4 layers. On the contrary, the value was noticeably increased to the highest value when 5 layers film was applied. The highest maximum polarization were recorded at 31.68 µC/cm{sup 2} and 34.12 µC/cm{sup 2} respectively for 5 layer BZT films in each 8 at.% and 10 at.% Zr content under electrical fields injection as triangle signal of Alternating Current (AC) 50 V/60 Hz. As the number of layers increases, the polarization field magnitude is significantly decreased. The general results of structure and ferroelectric properties of BZT films have been studied in the influence of layers number to enhance the electrical behavior.

  13. Layering

    NASA Image and Video Library

    2011-04-01

    At the bottom of this image from NASA Mars Odyssey is the cliff-face that is the sidewall of Ophir Chasma. Layering is easily visible in the upper cliff wall, with the thickness of the surface clearly visible.

  14. The influence of surface layer salinity on wintertime convection in Wilkinson Basin, Gulf of Maine

    NASA Astrophysics Data System (ADS)

    Taylor, Maureen H.; Mountain, David G.

    2009-02-01

    Observations suggest that the interannual variability of wintertime convection in Wilkinson Basin (WB) during 1977-2005 is related to the variation in the surface layer salinity in the western Gulf of Maine (wGOM). When the winter convection is stronger (weaker), the resulting deep-layer temperatures in the wGOM are colder (warmer), and the likelihood of deep winter mixing is greater when the wGOM salinities are high. This hypothesis was tested using a one-dimensional mixed layer model to simulate the water column structure over the cooling period. Comparisons were made between the convection potential for the range of observed late-fall salinity values. Model results indicated that the mixed layer depth could deepen by as much as 50% when the surface layer salinities in the wGOM were high. Sensitivity tests revealed that the surface layer salinity variability, and its influence on the water column density structure, was a significant factor, along with local climate variability, in determining the observed time series trend in springtime bottom layer temperatures. Density distributions in the wGOM in high salinity years suggested that winter-cooled water from the adjacent shallow coastal areas could become sufficiently dense to cascade into the deeper layers of WB and enhanced the convective cooling. The interannual variation in wintertime convection and in the resulting density structure has important implications for biological processes. The associated variation in deeper layer temperatures has been shown to influence the spatial distribution, timing of spawning, and growth rates of many demersal and mid-water fishery populations.

  15. Modelisation de la chimie d'une couche limite atmospherique non polluee. influence des hydrocarbures naturels emis par la vegetation

    NASA Astrophysics Data System (ADS)

    Lopez, A.; Prieur, S.; Fontan, J.; Barthomeuf, M. O.

    We present here the development of a physicochemical model of the unpolluted planetary boundary layer in which reactive mechanisms and intensity of vertical exchange of matter are taken into account. This is a box model which allows the study of evolution of concentration of trace constituents in an air mass over a large homogeneous source. Cycles of ozone, nitrogen oxides, methane, carbon monoxide and isoprene, a biogenic hydrocarbon, are considered in the chemical part. The dynamic aspect is constituted by a time variable equivalent mixing height. Experiments on photochemical formation of ozone in the lower layer of the atmosphere are conducted with this model with various initial and boundary conditions. These experiments show the influence of a ground removal and of vertical exchanges on the variations of ozone concentrations at ground level. They put forward a photochemical formation in which intensity varies with the intensity of NO x and isoprene source according to a nonlinear law.

  16. Modeling the Influence of Interaction Layer Formation on Thermal Conductivity of U–Mo Dispersion Fuel

    SciTech Connect

    Burkes, Douglas; Casella, Andrew M.; Huber, Tanja K.

    2015-01-01

    The Global Threat Reduction Initiative Program continues to develop existing and new plate- and rod-type research and test reactor fuels with maximum attainable uranium loadings capable of potentially converting a number of the world’s remaining high-enriched uranium fueled reactors to low-enriched uranium fuel. Currently, the program is focused on assisting with the development and qualification of an even higher density fuel type consisting of a uranium-molybdenum (U-Mo) alloy dispersed in an aluminum matrix. Thermal conductivity is an important consideration in determining the operational temperature of the fuel plate and can be influenced by interaction layer formation between the fuel and matrix, porosity that forms during fabrication of the fuel plates, and upon the concentration of the dispersed phase within the matrix. This paper develops and validates a simple model to study the influence of interaction layer formation and conductivity, fuel particle size, and volume fraction of fuel dispersed in the matrix on the effective conductivity of the composite. The model shows excellent agreement with results previously presented in the literature. In particular, the thermal conductivity of the interaction layer does not appear to be important in determining the overall conductivity of the composite, while formation of the interaction layer and subsequent consumption of the matrix reveals a rather significant effect. The effective thermal conductivity of the composite can be influenced by the fuel particle distribution by minimizing interaction layer formation and preserving the higher thermal conductivity matrix.

  17. Influence of bulk turbulence and entrance boundary layer thickness on the curved duct flow field

    NASA Astrophysics Data System (ADS)

    Crawford, R. A.

    1988-11-01

    The influence of bulk turbulence and boundary layer thickness on the secondary flow development in a square, 90 degree turning duct was investigated. A three-dimensional laser velocimetry system was utilized to measure the mean and fluctuating components of velocity at six cross-planes in the duct. The results from this investigation, with entrance boundary layer thickness of 20 percent, were compared with the thin boundary layer results documented in NASA CR-174811. The axial velocity profiles, cross-flow velocities, and turbulence intensities were compared and evaluated with regard to the influence of bulk turbulence intensity and boundary layer thickness, and the influence was significant. The results of this investigation expand the 90 degree curved duct experimental data base to higher turbulence levels and thicker entrance boundary layers. The experimental results provide a challenging benchmark data base for computational fluid dynamics code development and validation. The variation of inlet bulk turbulence intensity provides additional information to aid in turbulence model evaluation.

  18. Influence of bulk turbulence and entrance boundary layer thickness on the curved duct flow field

    NASA Technical Reports Server (NTRS)

    Crawford, R. A.

    1988-01-01

    The influence of bulk turbulence and boundary layer thickness on the secondary flow development in a square, 90 degree turning duct was investigated. A three-dimensional laser velocimetry system was utilized to measure the mean and fluctuating components of velocity at six cross-planes in the duct. The results from this investigation, with entrance boundary layer thickness of 20 percent, were compared with the thin boundary layer results documented in NASA CR-174811. The axial velocity profiles, cross-flow velocities, and turbulence intensities were compared and evaluated with regard to the influence of bulk turbulence intensity and boundary layer thickness, and the influence was significant. The results of this investigation expand the 90 degree curved duct experimental data base to higher turbulence levels and thicker entrance boundary layers. The experimental results provide a challenging benchmark data base for computational fluid dynamics code development and validation. The variation of inlet bulk turbulence intensity provides additional information to aid in turbulence model evaluation.

  19. Influences and interactions of inundation, peat, and snow on active layer thickness

    DOE PAGES

    Atchley, Adam L.; Coon, Ethan T.; Painter, Scott L.; ...

    2016-05-18

    The effect of three environmental conditions: 1) thickness of organic soil, 2) snow depth, and 3) soil moisture content or water table height above and below the soil surface, on active layer thickness (ALT) are investigated using an ensemble of 1D thermal hydrology models. Sensitivity analyses of the ensemble exposed the isolated influence of each environmental condition on ALT and their multivariate interactions. The primary and interactive influences are illustrated in the form of color maps of ALT change. Results show that organic layer acts as a strong insulator, and its thickness is the dominant control of ALT, but themore » strength of the effect of organic layer thickness is dependent on the saturation state. Snow depth, subsurface saturation, and ponded water depth are strongly codependent and positively correlated to ALT.« less

  20. Influences and interactions of inundation, peat, and snow on active layer thickness

    SciTech Connect

    Atchley, Adam L.; Coon, Ethan T.; Painter, Scott L.; Harp, Dylan R.; Wilson, Cathy J.

    2016-05-18

    The effect of three environmental conditions: 1) thickness of organic soil, 2) snow depth, and 3) soil moisture content or water table height above and below the soil surface, on active layer thickness (ALT) are investigated using an ensemble of 1D thermal hydrology models. Sensitivity analyses of the ensemble exposed the isolated influence of each environmental condition on ALT and their multivariate interactions. The primary and interactive influences are illustrated in the form of color maps of ALT change. Results show that organic layer acts as a strong insulator, and its thickness is the dominant control of ALT, but the strength of the effect of organic layer thickness is dependent on the saturation state. Snow depth, subsurface saturation, and ponded water depth are strongly codependent and positively correlated to ALT.

  1. Influence of absorber layer dopants on performance of Ge/Si single photon avalanche diodes

    NASA Astrophysics Data System (ADS)

    Pilgrim, Neil J.; Ikonic, Zoran; Kelsall, Robert W.

    2013-04-01

    Monte Carlo electronic transport simulations are applied to investigate the influence of the Ge absorber layer on the performance of Ge/Si single photon avalanche diodes. Ge dopant type and concentration control the internal electric field gradients, which directly influence the probabilistic distribution of times from the point of charge photo-generation to that of transmission over the Ge/Si heterojunction. The electric field adjacent to the heterointerface is found to be the dominant factor in achieving rapid transmission, leading to a preference for p-type dopants in the Ge absorber. The contribution to jitter from the Ge layer is estimated and appears relatively independent of bias, though scales near-linearly with layer height.

  2. Determination of mixing layer heights by ceilometer and influences upon air quality at Mexico City airport

    NASA Astrophysics Data System (ADS)

    Schäfer, Klaus; Flores-Jardines, Edgar; Emeis, Stefan; Grutter, Michel; Kurtenbach, Ralf; Wiesen, Peter; Münkel, Christoph

    2009-09-01

    Monitoring of mixing layer height (MLH) was performed during different measurement campaigns in urban and suburban area (Hannover, Munich, Budapest, Zürich, Augsburg) by the Vaisala ceilometer LD40. It is an eye-safe commercial lidar and designed originally to detect cloud base heights and vertical visibility for aviation safety purposes. Software for routine retrieval of mixing layer height from ceilometer data was developed and improved continuously. MLH was determined during a one-week-campaign at the airport Mexico City. Air pollutants like NO, NOx, CO and O3 as well as meteorological parameters like wind, temperature and irradiance are measured at the airport in addition to the air quality monitoring network RAMA in Mexico City. The influence of MLH together with wind, temperature and cloudiness upon air pollution is investigated. These continuous MLH and meteorological data are correlated with simultaneous measured air pollutants. The influence of mixing layer height upon air quality is shown.

  3. Influences and interactions of inundation, peat, and snow on active layer thickness

    SciTech Connect

    Atchley, Adam L.; Coon, Ethan T.; Painter, Scott L.; Harp, Dylan R.; Wilson, Cathy J.

    2016-05-18

    The effect of three environmental conditions: 1) thickness of organic soil, 2) snow depth, and 3) soil moisture content or water table height above and below the soil surface, on active layer thickness (ALT) are investigated using an ensemble of 1D thermal hydrology models. Sensitivity analyses of the ensemble exposed the isolated influence of each environmental condition on ALT and their multivariate interactions. The primary and interactive influences are illustrated in the form of color maps of ALT change. Results show that organic layer acts as a strong insulator, and its thickness is the dominant control of ALT, but the strength of the effect of organic layer thickness is dependent on the saturation state. Snow depth, subsurface saturation, and ponded water depth are strongly codependent and positively correlated to ALT.

  4. Layer-by-layer introduction of poly(phenylenevinylene) onto microspheres and probing the influence from the weak/strong polyanion spacer-layers.

    PubMed

    Song, Jing; Qiu, Tian; Chen, Yun; Zhang, Wei; Fan, Li-Juan

    2015-08-15

    The layer-by-layer (LBL) technique was employed for preparing fluorescent microspheres with a core-shell structure by the alternating adsorption of positively charged poly(p-phenylenevinylene) precursor (pre-PPV) and the polyanions onto polymer substrate spheres, followed by the thermal elimination to convert pre-PPV into fluorescent poly(p-phenylenevinylene) (PPV). Weak polyelectrolytes poly(acrylic acid) (PAA) (usually in a partly ionized form) and strong polyelectrolytes poly(sodium-p-styrenesulfonate) (PSS) were used as the anions to space the PPV layers and reduce the fluorescence self-quenching. Flow cytometry, combined with spectroscopy and microscopy, were used to study the structure and photophysical properties of the resulting microspheres. Optimization of the processing factors was carried out. PAA and PSS as weak and strong polyelectrolytes, respectively, displayed very different influence on the final emission of the spheres. Such difference was attributed to different inherent characteristics of PAA and PSS after detailed investigation in many aspects. In addition, the fluorescent spheres were found to have excellent photostability and thermal stability. Copyright © 2015 Elsevier Inc. All rights reserved.

  5. Accurate NIRS measurement of muscle oxygenation by correcting the influence of a subcutaneous fat layer

    NASA Astrophysics Data System (ADS)

    Yamamoto, Katsuyuki; Niwayama, Masatsugu; Lin, Ling; Shiga, Toshikazu; Kudo, Nobuki; Takahashi, Makoto

    1998-01-01

    Although the inhomogeneity of tissue structure affects the sensitivity of tissue oxygenation measurement by reflectance near-infrared spectroscopy, few analyses of this effect have been reported. In this study, the influence of a subcutaneous fat layer on muscle oxygenation measurement was investigated by Monte Carlo simulation and experimental studies. In the experiments, measurement sensitivity was examined by measuring the falling rate of oxygenation in occlusion tests on the forearm using a tissue oxygen monitor. The fat layer thickness was measured by ultrasonography. Results of the simulation and occlusion tests clearly showed that the presence of a fat layer greatly decreases the measurement sensitivity and increases the light intensity at the detector. The correction factors of sensitivity were obtained from this relationship and were successfully validated by experiments on 12 subjects whose fat layer thickness ranged from 3.5 to 8 mm.

  6. Accurate NIRS measurement of muscle oxygenation by correcting the influence of a subcutaneous fat layer

    NASA Astrophysics Data System (ADS)

    Yamamoto, Katsuyuki; Niwayama, Masatsugu; Lin, Ling; Shiga, Toshikazu; Kudo, Nobuki; Takahashi, Makoto

    1997-12-01

    Although the inhomogeneity of tissue structure affects the sensitivity of tissue oxygenation measurement by reflectance near-infrared spectroscopy, few analyses of this effect have been reported. In this study, the influence of a subcutaneous fat layer on muscle oxygenation measurement was investigated by Monte Carlo simulation and experimental studies. In the experiments, measurement sensitivity was examined by measuring the falling rate of oxygenation in occlusion tests on the forearm using a tissue oxygen monitor. The fat layer thickness was measured by ultrasonography. Results of the simulation and occlusion tests clearly showed that the presence of a fat layer greatly decreases the measurement sensitivity and increases the light intensity at the detector. The correction factors of sensitivity were obtained from this relationship and were successfully validated by experiments on 12 subjects whose fat layer thickness ranged from 3.5 to 8 mm.

  7. Non-local sub-characteristic zones of influence in unsteady interactive boundary-layers

    NASA Technical Reports Server (NTRS)

    Rothmayer, A. P.

    1992-01-01

    The properties of incompressible, unsteady, interactive, boundary layers are examined for a model hypersonic boundary layer and internal flow past humps or, equivalently, external flow past short-scaled humps. Using a linear high frequency analysis, it is shown that the domains of dependence within the viscous sublayer may be a strong function of position within the sublayer and may be strongly influenced by the pressure displacement interaction, or the prescribed displacement condition. Detailed calculations are presented for the hypersonic boundary layer. This effect is found to carry over directly to the fully viscous problem as well as the nonlinear problem. In the fully viscous problem, the non-local character of the domains of dependence manifests itself in the sub-characteristics. Potential implications of the domain of dependence structure on finite difference computations of unsteady boundary layers are briefly discussed.

  8. Influence of silicon dioxide capping layers on pore characteristics in nanocrystalline silicon membranes.

    PubMed

    Qi, Chengzhu; Striemer, Christopher C; Gaborski, Thomas R; McGrath, James L; Fauchet, Philippe M

    2015-02-06

    Porous nanocrystalline silicon (pnc-Si) membranes are a new class of membrane material with promising applications in biological separations. Pores are formed in a silicon film sandwiched between nm thick silicon dioxide layers during rapid thermal annealing. Controlling pore size is critical in the size-dependent separation applications. In this work, we systematically studied the influence of the silicon dioxide capping layers on pnc-Si membranes. Even a single nm thick top oxide layer is enough to switch from agglomeration to pore formation after annealing. Both the pore size and porosity increase with the thickness of the top oxide, but quickly reach a plateau after 10 nm of oxide. The bottom oxide layer acts as a barrier layer to prevent the a-Si film from undergoing homo-epitaxial growth during annealing. Both the pore size and porosity decrease as the thickness of the bottom oxide layer increases to 100 nm. The decrease of the pore size and porosity is correlated with the increased roughness of the bottom oxide layer, which hinders nanocrystal nucleation and nanopore formation.

  9. Influence of tides and gravity waves on layering processes in the polar summer mesopause region

    NASA Astrophysics Data System (ADS)

    Hoffmann, P.; Rapp, M.; Fiedler, J.; Latteck, R.

    2008-12-01

    Polar Mesosphere Summer Echoes (PMSE) have been studied at Andenes (69° N, 16° E), Norway, using VHF radar observations since 1994. One remarkable feature of these observations is the fact that {during 50% of the time,} the radar echoes occur in the form of two or more distinct layers. In the case of multiple PMSE layers, statistical analysis shows that the lower layer occurs at a mean height of 83.4 km, which is almost identical to the mean height of noctilucent clouds (NLC) derived from observation with the ALOMAR Rayleigh/Mie/Raman lidar at the same site. To investigate the layering processes microphysical model simulations under the influence of tidal and gravity waves were performed. In the presence of long period gravity waves, these model investigations predict an enhanced formation of multiple PMSE layer structures, where the lower layer is a consequence of the occurrence of the largest particles at the bottom of the ice cloud. This explains the coincidence of the lowermost PMSE layers and NLC. During periods with enhanced amplitudes of the semidiurnal tide, the observed NLC and PMSE show pronounced tidal structures comparable to the results of corresponding microphysical simulations. At periods with short period gravity waves there is a tendency for a decreasing occurrence of NLC and for variable weak PMSE structures.

  10. Vacuum infusion equipment design and the influence of reinforcement layers addition to the resin infusion time

    NASA Astrophysics Data System (ADS)

    Saputra, A. H.; Setyarso, G.

    2016-11-01

    The characteristic of composite material is greatly influenced by the manufacture method of composite. The conventional method that has been used such as hand lay-up and spray up are simple and easy to apply but the composite tend to have a void in it because of the air trapped during the manufacture process. Vacuum infusion is one of the modern composite manufacture process which can replace the conventional method. The problem of this method happens when the resin infusion time become longer due to the addition of reinforcement layers. When the resin infusion time is longer than the resin's gel time, the resin will become gel and not able to flow into the mold. In order to overcome this problem, a study that observe the influence of reinforcement layers addition to the resin infusion time is needed. In this study, vacuum infusion equipment for composite materials manufacturing process that are designed consists of: 1×1m glass as the mold, 1L PVC tube for the resin container, 1L glass tube for the resin trap, and ‘A HP vacuum pump with 7 CFM vacuum speed. The resin that is used in this study is unsaturated polyester resin (UPR) and the fiber used as reinforcement is fiber glass. It is observed that the more number of reinforcement layers the longer resin infusion time will be. The resin infusion time (in seconds) from two until six layers respectively for the area of 15×20cm are: 88, 115, 145, 174, 196; for the area of 15×25cm are: 119, 142, 168, 198, 235; and for the area of 15×35cm are: 181, 203, 235, 263, 303. The maximum reinforcement layers that can be accommodated for each 15×20cm, 15×25cm, and 15×35cm area are respectively 31 layers, 29 layers, and 25 layers.

  11. Injectabilite des coulis de ciment dans des milieux fissures

    NASA Astrophysics Data System (ADS)

    Mnif, Thameur

    Le travail presente ici est un bilan du travaux de recherche effectues sur l'injectabilite des coulis de ciment dans lu milieux fissures. Un certain nombre de coulis a base de ciment Portland et microfin ont ete selectionnes afin de caracteriser leur capacite a penetrer des milieux fissures. Une partie des essais a ete menee en laboratoire. L'etude rheologique des differents melanges a permis de tester l'influence de l'ajout de superplastifiant et/ou de fumee de silice sur la distribution granulometrique des coulis et par consequent sur leur capacite a injecter des colonnes de sable simulant un milieu fissure donne. La classe granulometrique d'un coulis, sa stabilite et sa fluidite sont apparus comme les trois facteurs principaux pour la reussite d'une injection. Un facteur de finesse a ete defini au cours de cette etude: base sur la classe granulometrique du ciment et sa stabilite, il peut entrer dans la formulation theorique du debit d'injection avant application sur chantier. La deuxieme et derniere partie de l'etude presente les resultats de deux projets de recherche sur l'injection realises sur chantier. L'injection de dalles de beton fissurees a permis le suivi de l'evolution des pressions avec la distance au point d'injection. L'injection de murs de maconnerie a caractere historique a montre l'importance de la definition de criteres de performance des coulis a utiliser pour traiter un milieu donne et pour un objectif donne. Plusieurs melanges peuvent ainsi etre predefinis et mis a disposition sur le chantier. La complementarite des ciments traditionnels et des ciments microfins devient alors un atout important. Le choix d'utilisation de ces melanges est fonction du terrain rencontre. En conclusion, cette recherche etablit une methodologie pour la selection des coulis a base de ciment et des pressions d'injection en fonction de l'ouverture des fissures ou joints de construction.

  12. The study of the influence of the layer resistivity of thin epitaxial Si cells

    SciTech Connect

    Evrard, O.; Vermeulen, T.; Poortmans, J.; Caymax, M.; Laermans, P.; Nijs, J.; Mertens, R.

    1994-12-31

    Epitaxial layers on heavily doped CZ substrates were grown in an APCVD epitaxial system with different epitaxial layer resistivities: 0.2, 0.5, 1.0 and 2.5 ohm.cm, in order to investigate the influence of the resistivity on the solar cell characteristics. Textured and untextured layers were compared. I-V characteristics under normalized AM 1.5 illumination, dark I-V and spectral response were measured. The efficiencies and the photogenerated current were found to increase with increasing layer resistivities in the range of their investigations. The authors have proven experimentally that for epitaxial cells, varying the resistivity of the layer has a great impact on the photogenerated current and the efficiency (from 13.3% in average for 0.2 ohm.cm to 14.5% in average for 2 ohm.cm). With a resistivity of 2 ohm.cm, they have succeeded to reach a device efficiency of 14.9%. If a constant lifetime is modeled, the lack of variation of the Voc over the investigated resistivity range is difficult to explain. With a simple p/p{sup ++} modeling, the fitting of the Voc data leads to an effective bulk lifetime between 2 and 20 microseconds. The authors therefore witness a variation of the effective lifetime which could be either due to the variation of the SHR layer lifetime or to the presence of interfacial regions. Defect etching on beveled samples has revealed the existence of defective regions which could be caused by lattice mismatch at the p/p{sup ++} interface. The growing of 2--3 {micro}m of a p{sup ++} buffer layer, having an intermediate doping level between the doping level of the layer and the carrier substrate before carrying the epitaxy of the base p layer, is therefore of potential interest in order to screen off any possible defective regions.

  13. Simulation of MLI concerning the influence of an additional heat load on intermediate layers

    SciTech Connect

    Funke, Thomas; Golle, Steffen; Haberstroh, Christoph

    2014-01-29

    Multilayer insulation (MLI) is commonly used in most cryogenic devices such as LHe cryostats or storage vessels. Numerical and experimental studies of such insulation systems are known from literature. The temperature distribution of intermediate layers has been investigated as well. Experiments using temperature sensors, for example thermocouples, to determine the temperature of intermediate layers had been described. Naturally such wiring causes additional heat load on the respective layer and influences the equilibrium temperature. A mathematical model of heat transfer through MLI has been developed to investigate the temperature distribution across the MLI layers. The model comprises a combination of radiation, residual gas conduction and conductive heat flux. An analysis for variable cold and warm boundary temperatures and various residual gases and pressures is carried out. In addition to the model an experimental test rig will be built for the verification of the model. The paper presents the influence of an additional heat load on an intermediate layer on the temperature distribution and on the overall thermal performance of MLI.

  14. Influence des caracteristiques geomecaniques du reseau de fractures sur les pressions d'injection limites

    NASA Astrophysics Data System (ADS)

    Lim, Sophie

    Grouting jointed rock masses improves their water tightness and strength for civil infrastructure foundations such as hydroelectric dams. In North America, the most common method involves injecting grout in fractures at a pressure given by a rule of thumb of 25 kPa per meter of rock cover. The criterion used to define the limit pressure is conservative because it considers a state of stress due to gravity only and does not take into account the geomechanical characteristics of the rock mass and the properties of the injection grout. The objective of this study is to verify the influence of geomechanical parameters on maximum injection pressures and compare it to the empirical criterion of 25 kPa /m using UDEC, a distinct element code for 2D modelling of fractured rock masses. The hydrojacking mechanism during fracture injection is sensitive not only to the grout pressure but also to its rheological parameters as well as the strength and the opening of the fractures. In this study, grouting in different rock mass models is simulated with conditions (constant-width fractures openings and horizontal stress equivalent to the vertical stress) favorable to hydrojacking. With the numerical model, hydrojacking was observed at injection pressures slightly higher than those prescribed by the industry. The jacking mechanism is mainly related to fractures near the surface. Because the model does not include the possibility of introducing time dependent grout parameters, grout flows at larger distances than what is observed in the field. In addition, the two-dimensional model has certain limitations and requires assumptions restricting the direct transposition of results to the field due to the complexity of fracture geometries and the grout spreading in 3D. A relative comparison of limit grouting pressures is nonetheless possible and it highlights the effects of certain geomechanical parameters on its magnitude.

  15. Influence of cooling intensity on shock wave boundary layer interaction region in turbine cascade

    NASA Astrophysics Data System (ADS)

    Kaczyński, P.; Szwaba, R.

    2016-10-01

    The shock wave boundary layer interaction on the suction side of a transonic turbine blade was one of the main objectives of the TFAST project. For this purpose a model of a turbine passage was designed, manufactured and assembled in a transonic wind tunnel. The paper presents the experimental investigations concerning the flow structure on the transonic turbine blade. A clean case (without a cooling system) with a normal shock wave interacting with a laminar boundary layer and also the influence of the blade cooling system with three different coolant blowing intensities on the laminar interaction region were investigated.

  16. Influence of an electric field on the ferromagnetic resonance in a plane-layered magnetic system

    NASA Astrophysics Data System (ADS)

    Karashtin, E. A.; Fraerman, A. A.

    2016-11-01

    The influence of an electric field on the ferromagnetic resonance (FMR) in a multilayer magnetic system consisting of two magnetic layers separated by a thin nonmagnetic interlayer has been investigated. It has been shown that, upon the excitation of magnetization oscillations by a microwave magnetic field, the eigenfrequencies of the ferromagnetic resonance depend on the stationary electric field applied in the plane of the layers. It has also been demonstrated that, in this system, high-frequency magnetization oscillations can be excited by an electric microwave field. The results of the investigation of the polarization properties of the excitation mechanism indicate that this effect can be observed experimentally.

  17. Large influence of capping layers on tunnel magnetoresistance in magnetic tunnel junctions

    NASA Astrophysics Data System (ADS)

    Zhou, Jiaqi; Zhao, Weisheng; Wang, Yin; Peng, Shouzhong; Qiao, Junfeng; Su, Li; Zeng, Lang; Lei, Na; Liu, Lei; Zhang, Youguang; Bournel, Arnaud

    2016-12-01

    It has been reported in experiments that capping layers, which enhance the perpendicular magnetic anisotropy (PMA) of magnetic tunnel junctions (MTJs), induce a great impact on the tunnel magnetoresistance (TMR). To explore the essential influence caused by the capping layers, we carry out ab initio calculations on TMR in the X(001)|CoFe(001)|MgO(001)|CoFe(001)|X(001) MTJ, where X represents the capping layer material, which can be tungsten, tantalum, or hafnium. We report TMR in different MTJs and demonstrate that tungsten is an ideal candidate for a giant TMR ratio. The transmission spectrum in Brillouin zone is presented. It can be seen that in the parallel condition of MTJ, sharp transmission peaks appear in the minority-spin channel. This phenomenon is attributed to the resonant tunnel transmission effect, and we explained it by the layer-resolved density of states. In order to explore transport properties in MTJs, the density of scattering states was studied from the point of band symmetry. It has been found that CoFe|tungsten interface blocks scattering states transmission in the anti-parallel condition. This work reports TMR and transport properties in MTJs with different capping layers and proves that tungsten is a proper capping layer material, which would benefit the design and optimization of MTJs.

  18. The influence of protein level in the diet on cannibalism and quality of plumage of layers.

    PubMed

    Ambrosen, T; Petersen, V E

    1997-04-01

    A factorial experiment, with seven levels of protein and seven strains of layers, was conducted to determine the effect of protein level on plumage condition and mortality due to cannibalism. The experiment was carried out with a total of 3,136 layers. The protein content of the feed varied from 11.1 to 19.3%. The experiment revealed that protein levels had an effect (P < 0.0001) on plumage condition, and that the plumage condition also varies (P < 0.01) with strain of layers. A strain by protein levels interaction occurred (P < 0.01) between strains of Leghorn layers, but not between strains of layers of medium body size. The requirement for energy to maintenance was reduced by 10.8 kcal ME per bird per d each time the plumage condition was improved by one point. Mortality due to cannibalism was influenced by protein level (P < 0.001) and strains of layers (P < 0.001). No significant improvement in plumage condition or reduction in cannibalism was obtained with 15.2% or more protein in the feed. The reason for the unsatisfactory plumage condition and the high mortality rate due to cannibalism for the diets low in protein could be inadequate lysine, methionine, and threonine in the diets. But the possibility of an amino acid imbalance in that protein, which is available for the birds after the egg production has taken place, may not be ignored.

  19. Influence of water layer thickness on hard tissue ablation with pulsed CO2 laser

    NASA Astrophysics Data System (ADS)

    Zhang, Xianzeng; Zhan, Zhenlin; Liu, Haishan; Zhao, Haibin; Xie, Shusen; Ye, Qing

    2012-03-01

    The theory of hard tissue ablation reported for IR lasers is based on a process of thermomechanical interaction, which is explained by the absorption of the radiation in the water component of the tissue. The microexplosion of the water is the cause of tissue fragments being blasted from hard tissue. The aim of this study is to evaluate the influence of the interdependence of water layer thickness and incident radiant exposure on ablation performance. A total of 282 specimens of bovine shank bone were irradiated with a pulse CO2 laser. Irradiation was carried out in groups: without a water layer and with a static water layer of thickness ranging from 0.2 to 1.2 mm. Each group was subdivided into five subgroups for different radiant exposures ranging from 18 to 84 J/cm2, respectively. The incision geometry, surface morphology, and microstructure of the cut walls as well as thermal injury were examined as a function of the water layer thickness at different radiant exposures. Our results demonstrate that the additional water layer is actually a mediator of laser-tissue interaction. There exists a critical thickness of water layer for a given radiant exposure, at which the additional water layer plays multiple roles, not only acting as a cleaner to produce a clean cut but also as a coolant to prevent bone heating and reduce thermal injury, but also helping to improve the regularity of the cut shape, smooth the cut surface, and enhance ablation rate and efficiency. The results suggest that desired ablation results depend on optimal selection of both water layer thickness and radiant exposure.

  20. Influence of water layer thickness on hard tissue ablation with pulsed CO2 laser.

    PubMed

    Zhang, Xianzeng; Zhan, Zhenlin; Liu, Haishan; Zhao, Haibin; Xie, Shusen; Ye, Qing

    2012-03-01

    The theory of hard tissue ablation reported for IR lasers is based on a process of thermomechanical interaction, which is explained by the absorption of the radiation in the water component of the tissue. The microexplosion of the water is the cause of tissue fragments being blasted from hard tissue. The aim of this study is to evaluate the influence of the interdependence of water layer thickness and incident radiant exposure on ablation performance. A total of 282 specimens of bovine shank bone were irradiated with a pulse CO(2) laser. Irradiation was carried out in groups: without a water layer and with a static water layer of thickness ranging from 0.2 to 1.2 mm. Each group was subdivided into five subgroups for different radiant exposures ranging from 18 to 84 J/cm(2), respectively. The incision geometry, surface morphology, and microstructure of the cut walls as well as thermal injury were examined as a function of the water layer thickness at different radiant exposures. Our results demonstrate that the additional water layer is actually a mediator of laser-tissue interaction. There exists a critical thickness of water layer for a given radiant exposure, at which the additional water layer plays multiple roles, not only acting as a cleaner to produce a clean cut but also as a coolant to prevent bone heating and reduce thermal injury, but also helping to improve the regularity of the cut shape, smooth the cut surface, and enhance ablation rate and efficiency. The results suggest that desired ablation results depend on optimal selection of both water layer thickness and radiant exposure.

  1. Influence of Atomic Layer Deposition Temperatures on TiO2/n-Si MOS Capacitor

    SciTech Connect

    Wei, Daming; Hossain, T; Garces, N. Y.; Nepal, N.; Meyer III, Harry M; Kirkham, Melanie J; Eddy, C.R., Jr.; Edgar, J H

    2013-01-01

    This paper reports on the influence of temperature on the structure, composition, and electrical properties of TiO2 thin films deposited on n-type silicon (100) by atomic layer deposition (ALD). TiO2 layers around 20nm thick, deposited at temperatures ranging from 100 to 300 C, were studied. Samples deposited at 250 C and 200 C had the most uniform coverage as determined by atomic force microscopy. The average carbon concentration throughout the oxide layer and at the TiO2/Si interface was lowest at 200 C. Metal oxide semiconductor capacitors (MOSCAPs) were fabricated, and profiled by capacitance-voltage techniques. Negligible hysteresis was observed from a capacitance-voltage plot and the capacitance in the accumulation region was constant for the sample prepared at a 200 C ALD growth temperature. The interface trap density was on the order of 1013 eV-1cm-2 regardless of the deposition temperature.

  2. The turbulent bottom boundary layer and its influence on local dynamics over the continental shelf

    NASA Astrophysics Data System (ADS)

    Dewey, Richard D.; Leblond, Paul H.; Crawford, William R.

    1988-11-01

    We report on measurements of the structure of the bottom boundary layer on the continental shelf off Vancouver Island. A time series of vertical profiles obtained with the microstructure profiler FLY II revealed large temporal variations in the dissipation rate and in the density structure. The near-bottom current structure was simultaneously measured at fixed heights with conventional current meters. The data reveal the association between the predominantly diurnal tide and the variations in the structure of the bottom boundary layer. A clear distinction appears between the turbulent bottom boundary layer (8-40 m deep in a total water depth of 138 m) and the well-mixed layer (20-40 m deep). The two layers vary independently, with horizontal advection dominating the fluctuations in the thickness of the well-mixed layer while local dissipation is more closely related to the thickness of the turbulent layer. Variations in the density structure of the bottom layer are related to the strength and direction of the vertical shear and to the regional distribution of isopycnals. Current veering is commonly concentrated above the well-mixed layer. The evolution of the characteristics of the bottom layers is followed through a tidal cycle and related to local dissipation and other variables. Microstructure measurements from six locations over the southern portion of the Vancouver Island continental shelf are used to estimate the influence of turbulent energy dissipation on regional-scale flows. That fraction of the dissipation taking place in the bottom boundary layer is attributed to barotropic tidal flows, while that occurring above it is associated with nearly geostrophic baroclinic flows. Results give a lower limit of ˜ 1070 km for the length scale of shelf wave decay, in good agreement with current models; the estimates of tidal friction based on our dissipation measurements are however much lower than required by astronomical observations. An estimate of 230 h is

  3. Bovine and porcine transscleral solute transport: influence of lipophilicity and the Choroid-Bruch's layer.

    PubMed

    Cheruvu, Narayan P S; Kompella, Uday B

    2006-10-01

    To determine the influence of the choroid-Bruch's layer and solute lipophilicity on in vitro transscleral drug permeability in bovine and porcine eyes. The in vitro permeability of two VEGF inhibitory drugs, budesonide and celecoxib, which are lipophilic and neutral at physiologic pH, and of three marker solutes, 3H-mannitol (hydrophilic, neutral), sodium fluorescein (hydrophilic, anionic), and rhodamine 6G (lipophilic, cationic), were determined across freshly excised scleras, with or without the underlying choroid-Bruch's layer. Select studies were performed using porcine sclera with and without choroid-Bruch's layer. Neural retina was removed by exposure of the eyecup to isotonic buffer and wherever required, the retinal pigment epithelial (RPE) layer of the preparation was disrupted and removed by exposure to hypertonic buffer. Because of the poor solubility of celecoxib and budesonide, permeability studies were conducted with 5% wt/vol of hydroxypropyl-beta-cyclodextrin (HPbetaCD). For other solutes, permeability studies were conducted, with and without HPbetaCD. Partitioning of the solutes into bovine sclera and choroid-Bruch's layer was also determined. The calculated log (distribution coefficient) values were -2.89, -0.68, 2.18, 3.12, and 4.02 for mannitol, sodium fluorescein, budesonide, celecoxib, and rhodamine 6G, respectively. Removal of RPE was confirmed by transmission electron microscopy and differences in the transport of mannitol. The order of the permeability coefficients (Papp) across sclera and sclera-choroid-Bruch's layers in bovine and porcine models was 3H-mannitol > fluorescein > budesonide > celecoxib > rhodamine 6G, with HPbetaCD, and 3H-mannitol > fluorescein > rhodamine 6G, without HPbetaCD. The presence of choroid-Bruch's layer reduced the bovine scleral permeability by 2-, 8-, 16-, 36-, and 50-fold and porcine tissue permeability by 2-, 7-, 15-, 33-, and 40-fold, respectively, for mannitol, sodium fluorescein, budesonide, celecoxib

  4. Investigation on the influences of layer structure and nanoporosity of light scattering TiO2 layer in DSSC

    NASA Astrophysics Data System (ADS)

    Apriani, T.; Arsyad, W. S.; Wulandari, P.; Hidayat, R.

    2016-08-01

    Dye-sensitized solar cell (DSSC) is one of promising photovoltaic materials due to its simplicity in fabrication process and rich variety of possible sensitizer molecules. DSSC cell is commonly constructed of TiO2 layer as photoelectrode, dye as photosensitizer, electrolyte as redox mediator, and platinum layer as counter electrode. TiO2 layer is often constructed from different types of layers, such as blocking layer, transparent layer, microchannel or light scattering layer, which is made usually by successive layer-by-layer process. In this work, different TiO2 layers with different thickness and heat treatment were prepared and then used to build a complete sandwich-type DSSC. The characterization results show that the power conversion efficiency (PCE) is slightly reduced when using TiO2 layer with multiple scattering layers. This reduction is caused by an increase in the resistance from charge transport and charge transfer inside the mesoporous TiO2 layer, as revealed from the electrochemical impedance spectroscopy measurement results. Additional heat treatment introduced at the final step in the TiO2 layer preparation process, however, slightly improve the cell performance. Although this heat treatment does not produce significant change in porosity or pore size distribution of the TiO2 layer, it might be able to improve the contact between the TiO2 nanoparticles. The best PCE achieved in this work is about 5.3%, which was observed in the cell using TiO2 layer with one scattering layer and additional heat treatment.

  5. Influence of different nucleation layers on the initial grain structure of multicrystalline silicon ingots

    NASA Astrophysics Data System (ADS)

    Kupka, I.; Lehmann, T.; Trempa, M.; Kranert, C.; Reimann, C.; Friedrich, J.

    2017-05-01

    The grain structure of high-performance (HP) multicrystalline silicon (mc-Si) is characterized by a small initial grain size with randomly oriented grains and a high length fraction of random grain boundaries. However, the remaining unmelted feedstock at the ingot bottom used as seeding layer for achieving the HP mc-Si properties in the standard crystallization procedure causes yield loss. To overcome this disadvantage, the influence of wetting angle, and surface roughness of non-Si nucleation layers at the crucible bottom on the grain structure properties of mc-Si ingots with a weight of 14.5 kg was investigated and compared to classical HP mc-Si. For that purpose, SiC and SiO2 nucleation layers realized by spraying and embedding of particles with different sizes resulting in different surface morphologies and wetting angles were studied. Nucleation on rough layers of both materials with a root mean square roughness value greater than 100 μm yielded an initially fine grain structure comparable to HP mc-Si. This did not necessarily result in a random orientation distribution and high length fraction of random grain boundaries. Nucleation on SiC layers caused random grain boundary length fractions between 20 and 30% and non-uniform grain distributions. But, nucleation on SiO2 layers yielded increased random grain boundary length fractions between 50 and 70% and homogenous grain distributions, both values are similar to HP mc-Si. These differences are discussed in terms of the thermal conductivity of the different nucleation layers.

  6. Magnetic and magnetoresistance studies of nanometric electrodeposited Co films and Co/Cu layered structures: Influence of magnetic layer thickness

    NASA Astrophysics Data System (ADS)

    Zsurzsa, S.; Péter, L.; Kiss, L. F.; Bakonyi, I.

    2017-01-01

    The magnetic properties and the magnetoresistance behavior were investigated for electrodeposited nanoscale Co films, Co/Cu/Co sandwiches and Co/Cu multilayers with individual Co layer thicknesses ranging from 1 nm to 20 nm. The measured saturation magnetization values confirmed that the nominal and actual layer thicknesses are in fairly good agreement. All three types of layered structure exhibited anisotropic magnetoresistance for thick magnetic layers whereas the Co/Cu/Co sandwiches and Co/Cu multilayers with thinner magnetic layers exhibited giant magnetoresistance (GMR), the GMR magnitude being the largest for the thinnest Co layers. The decreasing values of the relative remanence and the coercive field when reducing the Co layer thickness down to below about 3 nm indicated the presence of superparamagnetic (SPM) regions in the magnetic layers which could be more firmly evidenced for these samples by a decomposition of the magnetoresistance vs. field curves into a ferromagnetic and an SPM contribution. For thicker magnetic layers, the dependence of the coercivity (Hc) on magnetic layer thickness (d) could be described for each of the layered structure types by the usual equation Hc=Hco+a/dn with an exponent around n=1. The common value of n suggests a similar mechanism for the magnetization reversal by domain wall motion in all three structure types and hints also at the absence of coupling between magnetic layers in the Co/Cu/Co sandwiches and Co/Cu multilayers.

  7. Influence of atomic layer deposition valve temperature on ZrN plasma enhanced atomic layer deposition growth

    SciTech Connect

    Muneshwar, Triratna Cadien, Ken

    2015-11-15

    Atomic layer deposition (ALD) relies on a sequence of self-limiting surface reactions for thin film growth. The effect of non-ALD side reactions, from insufficient purging between pulses and from precursor self-decomposition, on film growth is well known. In this article, precursor condensation within an ALD valve is described, and the effect of the continuous precursor source from condensate evaporation on ALD growth is discussed. The influence of the ALD valve temperature on growth and electrical resistivity of ZrN plasma enhanced ALD (PEALD) films is reported. Increasing ALD valve temperature from 75 to 95 °C, with other process parameters being identical, decreased both the growth per cycle and electrical resistivity (ρ) of ZrN PEALD films from 0.10 to 0.07 nm/cycle and from 560 to 350 μΩ cm, respectively. Our results show that the non-ALD growth resulting from condensate accumulation is eliminated at valve temperatures close to the pressure corrected boiling point of precursor.

  8. The influence of surface forces on the formation of structural peculiarities in the boundary layers of liquids and boundary phases

    NASA Astrophysics Data System (ADS)

    Derjaguin, B. V.

    1992-05-01

    This article, mentioning the influence of surface forces on the formation and the properties of diffuse adsorption layers on the boundary of solution-substrate, is mainly about the influence of surface forces on the structure and properties of boundary layers of the liquid. It deals with the phenomena of formation of homogeneous liquid crystalline layers of nonmesogenic liquids, boundary phases and the properties of boundary nonhomogeneous layers of water and alcohols. In the conclusion the data on surface forces are given with the radius of action up to 100 μm, which are generated by leucocytes of blood plasma with the addition of a concentrated salt solution.

  9. Influence of Plant Communities on Active Layer Depth in Boreal Forest

    NASA Astrophysics Data System (ADS)

    Phoenix, G. K.; Fisher, J. P.; Estop-Aragones, C.; Thierry, A.; Hartley, I. P.; Murton, J.; Charman, D.; Williams, M.

    2014-12-01

    Vegetation plays a crucial role in determining active layer depth (ALD) and hence also the extent that permafrost may thaw under climate change. Such influences are multifaceted and include, for example, promotion of shallow ALD by insulation from moss or shading by plant canopies in summer, or trapping of snow in evergreen tree canopies that reduces snow insulation of soil in winter. However, while the role of different vegetation components are understood at a conceptual level, quantitative understanding of the relative importance of different vegetation components and how they interact to determine active layer depth is lacking. In addition, major abiotic factors such as fire and soil hydrological properties will considerably influence the role of vegetation in mediating ALD, though again this is not well understood. To address this we surveyed multiple plots across 4 sites of contrasting vegetation and fire status, including a range of soil moisture and organic matter thickness, in the discontinuous permafrost zone near Yellowknife, NT, Canada. In each plot we measured ALD and a range of vegetation and soil parameters to understand how key characteristics of the understory and canopy vegetation, and soil properties influence ALD. Measurements included moss depth, tree canopy LAI, understory LAI, understory height, vegetation composition, soil organic matter depth, slope and soil moisture. By undertaking these surveys in sites with contrasting hydrological conditions in both burned and unburned areas we have also been able to determine which characteristics of the vegetation and soil are important for protecting permafrost, which characteristics emerge as the most important factors across sites (i.e. irrespective of site conditions) and which factors have site (ecosystem) specific influences. This work provides a major insight into how ecosystem properties influence ALD and therefore also how changes in ecosystems properties arising from climate change may

  10. Influence of Plant Communities on Active Layer Depth in Boreal Forest

    NASA Astrophysics Data System (ADS)

    Fisher, James; Estop Aragones, Cristian; Thierry, Aaron; Hartley, Iain; Murton, Julian; Charman, Dan; Williams, Mathew; Phoenix, Gareth

    2015-04-01

    Vegetation plays a crucial role in determining active layer depth (ALD) and hence the extent to which permafrost may thaw under climate change. Such influences are multifaceted and include, for example, promotion of shallow ALD by insulation from moss or shading by plant canopies in summer, or trapping of snow in evergreen tree canopies that reduces snow insulation of soil in winter. However, while the role of different vegetation components are understood at a conceptual level, quantitative understanding of the relative importance of different vegetation components and how they interact to determine active layer depth is lacking. In addition, major abiotic factors such as fire and soil hydrological properties will considerably influence the role of vegetation in mediating ALD, though again this is not well understood. To address this we surveyed 60 plots across 4 sites of contrasting vegetation and fire status, encompassing a range of soil moisture and organic matter thickness, in the discontinuous permafrost zone near Yellowknife, NT, Canada. In each plot we measured ALD and a range of vegetation and soil parameters to understand how key characteristics of the understory and canopy vegetation, and soil properties influence ALD. Measurements included moss depth, tree canopy LAI, understory LAI, understory height, vegetation composition, soil organic matter depth, slope and soil moisture. By undertaking these surveys in sites with contrasting hydrological conditions in both burned and unburned areas we have also been able to determine which characteristics of the vegetation and soil are important for protecting permafrost, which characteristics emerge as the most important factors across sites (i.e. irrespective of site conditions) and which factors have site (ecosystem) specific influences. This work provides a major insight into how ecosystem properties influence ALD and therefore also how changes in ecosystems properties arising from climate change may influence

  11. Factors Influencing Pitot Probe Centerline Displacement in a Turbulent Supersonic Boundary Layer

    NASA Technical Reports Server (NTRS)

    Grosser, Wendy I.

    1997-01-01

    When a total pressure probe is used for measuring flows with transverse total pressure gradients, a displacement of the effective center of the probe is observed (designated Delta). While this phenomenon is well documented in incompressible flow and supersonic laminar flow, there is insufficient information concerning supersonic turbulent flow. In this study, three NASA Lewis Research Center Supersonic Wind Tunnels (SWT's) were used to investigate pitot probe centerline displacement in supersonic turbulent boundary layers. The relationship between test conditions and pitot probe centerline displacement error was to be determined. For this investigation, ten circular probes with diameter-to-boundary layer ratios (D/delta) ranging from 0.015 to 0.256 were tested in the 10 ft x 10 ft SWT, the 15 cm x 15 cm SWT, and the 1 ft x 1 ft SWT. Reynolds numbers of 4.27 x 10(exp 6)/m, 6.00 x 10(exp 6)/in, 10.33 x 10(exp 6)/in, and 16.9 x 10(exp 6)/m were tested at nominal Mach numbers of 2.0 and 2.5. Boundary layer thicknesses for the three tunnels were approximately 200 mm, 13 mm, and 30 mm, respectively. Initial results indicate that boundary layer thickness, delta, and probe diameter, D/delta play a minimal role in pitot probe centerline offset error, Delta/D. It appears that the Mach gradient, dM/dy, is an important factor, though the exact relationship has not yet been determined. More data is needed to fill the map before a conclusion can be drawn with any certainty. This research provides valuable supersonic, turbulent boundary layer data from three supersonic wind tunnels with three very different boundary layers. It will prove a valuable stepping stone for future research into the factors influencing pitot probe centerline offset error.

  12. Near-infrared muscle oximeter that can correct the influence of a subcutaneous fat layer

    NASA Astrophysics Data System (ADS)

    Yamamoto, Katsuyuki; Niwayama, Masatsugu; Lin, Ling; Shiga, Toshikazu; Kudo, Nobuki; Takahashi, Makoto

    1998-04-01

    The inhomogeneity of tissue structure greatly affects the sensitivity of tissue oxygenation measurement by reflectance NIRS. We have proposed a method for correcting the influence of a subcutaneous fat layer on muscle oxygenation measurement. In this study, this method was validated by measuring the peak-to-peak variation of muscle oxygenation in periodic exercise tests on the vastus lateralis and the falling rate of oxygenation in ischemia tests on the forearm. A newly developed multisensor probe with source- detector distances of 7-40 mm was used. THe probe, consisting of a two-wavelength LED and four photodiodes, was connected to a 4-channel tissue oxygen monitor. The fat layer thickness was also measured by ultrasonography. Results of the tests clearly showed that the presence of a fat layer greatly decreases the sensitivity of measurement and increases the light intensity at a detector. The correction factors of sensitivity were determined from this relationship and Monte Carlo simulation. The corrected oxygenation levels were quantitatively compared among subjects in spite of different fat layer thicknesses.

  13. Influence of heat conducting substrates on explosive crystallization in thin layers

    NASA Astrophysics Data System (ADS)

    Schneider, Wilhelm

    2017-09-01

    Crystallization in a thin, initially amorphous layer is considered. The layer is in thermal contact with a substrate of very large dimensions. The energy equation of the layer contains source and sink terms. The source term is due to liberation of latent heat in the crystallization process, while the sink term is due to conduction of heat into the substrate. To determine the latter, the heat diffusion equation for the substrate is solved by applying Duhamel's integral. Thus, the energy equation of the layer becomes a heat diffusion equation with a time integral as an additional term. The latter term indicates that the heat loss due to the substrate depends on the history of the process. To complete the set of equations, the crystallization process is described by a rate equation for the degree of crystallization. The governing equations are then transformed to a moving co-ordinate system in order to analyze crystallization waves that propagate with invariant properties. Dual solutions are found by an asymptotic expansion for large activation energies of molecular diffusion. By introducing suitable variables, the results can be presented in a universal form that comprises the influence of all non-dimensional parameters that govern the process. Of particular interest for applications is the prediction of a critical heat loss parameter for the existence of crystallization waves with invariant properties.

  14. Influence of heat conducting substrates on explosive crystallization in thin layers

    NASA Astrophysics Data System (ADS)

    Schneider, Wilhelm

    2017-03-01

    Crystallization in a thin, initially amorphous layer is considered. The layer is in thermal contact with a substrate of very large dimensions. The energy equation of the layer contains source and sink terms. The source term is due to liberation of latent heat in the crystallization process, while the sink term is due to conduction of heat into the substrate. To determine the latter, the heat diffusion equation for the substrate is solved by applying Duhamel's integral. Thus, the energy equation of the layer becomes a heat diffusion equation with a time integral as an additional term. The latter term indicates that the heat loss due to the substrate depends on the history of the process. To complete the set of equations, the crystallization process is described by a rate equation for the degree of crystallization. The governing equations are then transformed to a moving co-ordinate system in order to analyze crystallization waves that propagate with invariant properties. Dual solutions are found by an asymptotic expansion for large activation energies of molecular diffusion. By introducing suitable variables, the results can be presented in a universal form that comprises the influence of all non-dimensional parameters that govern the process. Of particular interest for applications is the prediction of a critical heat loss parameter for the existence of crystallization waves with invariant properties.

  15. Influence of C or In buffer layer on photoluminescence behaviour of ultrathin ZnO film

    SciTech Connect

    Saravanan, K. Jayalakshmi, G.; Krishnan, R.; Sundaravel, B.; Panigrahi, B. K.

    2016-09-07

    We study the effect of the indium or carbon buffer layer on the photoluminescence (PL) property of ZnO ultrathin films deposited on a Si(100) substrate. The surface morphology of the films obtained using scanning tunnelling microscopy shows spherical shaped ZnO nanoparticles of size ∼8 nm in ZnO/C/Si and ∼22 nm in ZnO/Si samples, while the ZnO/In/Si sample shows elliptical shaped ZnO particles. Further, the ZnO/C/Si sample shows densely packed ZnO nanoparticles in comparison with other samples. Strong band edge emission has been observed in the presence of In or C buffer layer, whereas the ZnO/Si sample exhibits poor PL emission. The influence of C and In buffer layers on the PL behaviour of ZnO films is studied in detail using temperature dependent PL measurements in the range of 4 K–300 K. The ZnO/C/Si sample exhibits a multi-fold enhancement in the PL emission intensity with well-resolved free and bound exciton emission lines. Our experimental results imply that the ZnO films deposited on the C buffer layer showed higher particle density and better exciton emission desired for optoelectronic applications.

  16. [The influence of simulated acid rain on acidity and K+ leaching regulation of different soil layers].

    PubMed

    Wang, Daizhang; Jiang, Xin; Bian, Yongrong; Sun, Lei; Li, Rui; He, Jizheng

    2003-03-01

    The influence of simulated acid rain on acidity and K+ release of different soil layers of red soil from Jiangxi was investigated in the lab when surface soil was mixed with KCl. The results indicated that pH of leaching solution first decreased, then increased in the different soil layers, but pH at the beginning moment of leaching existed prominent differences and pH of leachate of pH 2.5 acid rain in A and AB layers again decreased during subsequent stage. There was a peak value of EC of leachate appearing at the beginning stage, it showed that nutrient ions in soil rapidly moved downwards into lower depth of profile. K+ concentration of effluent solution was related to acidity of acid rain and the pH2.5 value of acid rain accelerated K+ transportation downwards along profile. K+ release of A soil layer was divided into two moments which one was the rapid rate of K+ release process at the moment of beginning and then into the middle rate of release process. As to pH 4.5 value of acid rain, it also existed rapid and slow rate processes.

  17. Influence of a stratospheric turbulence layer on the penetration of mountain waves into the middle atmosphere

    NASA Astrophysics Data System (ADS)

    Doernbrack, A.; Bramberger, M.; Rapp, M.; Wagner, J.; Kaifler, B.; Kaifler, N.

    2015-12-01

    During the DEEPWAVE campaign, large-amplitude mesospheric temperaturefluctuations were observed by the ground-based Rayleigh lidar at Lauder,NZ on July 4 2014. For the same day, coordinated aircraft observations ofthe DLR Falcon and the NSF/NCAR GV report one of the largest wave eventsmeasured by both aircraft with vertical velocity amplitudes in excess of6 m/s around the tropopause level at around 11 km altitude.Mesoscale numerical simulations indicate the existence of breakinghydrostatic gravity waves between about 15 km to 25 km altitudeabove the southern island. In most cases, the breaking regionsare linked with individual orographic peaks. As time evolves, theygenerate a stratospheric turbulent layer extending over the wholeisland. Nevertheless, the wave attenuation in this layer cannot preventthe penetration of mountain waves to higher altitudes and the simulationsreveal a boost of wave amplitudes above about 30 km altitude. Furthermore,the mesoscale numerical model simulates the excitation of secondarygravity waves from the turbulent layer.Obviously, the small-scale dynamics in this stratospheric turbulencelayer influences the momentum deposition and the spatial scales of thewaves. Therefore, this layer plays a central role in defining the spectrumof gravity waves penetrating to the mesosphere. By a combination of amultitude of ground-based and airborne measurements, mesoscale (ECMWF'sIFS, WRF and Unified Model of UK MetOffice) as well as idealized numericalsimulations we investigate the role of the breaking region on the deeppropagation of mountain waves over New Zealand.

  18. Influence of substrate preparation on the shaping of the topography of the surface of nanoceramic oxide layers

    NASA Astrophysics Data System (ADS)

    Bara, Marek; Kubica, Marek

    2014-02-01

    The paper discusses the shaping mechanism and changes occurring in the structure and topography of the surface of nanoceramic oxide layers during their formation. The paper presents the influence of substrate preparation on the surface topography of oxide layers. The layers were produced via hard anodizing on the EN AW-5251 aluminum alloy. The layers obtained were subjected to microscope examinations, image and chemical composition analyses, and stereometric examinations. Heredity of substrate properties in the topography of the surface of nanoceramic oxide layers formed as a result of electrochemical oxidation has been shown.

  19. Ion adsorption and its influence on direct current electric field induced deformations of flexoelectric nematic layers

    NASA Astrophysics Data System (ADS)

    Derfel, Grzegorz; Buczkowska, Mariola

    2011-07-01

    The influence of ion adsorption on the behavior of the nematic liquid crystal layers is studied numerically. The homeotropic flexoelectric layer subjected to the dc electric field is considered. Selective adsorption of positive ions is assumed. The analysis is based on the free energy formalism for ion adsorption. The distributions of director orientation angle, electric potential, and ion concentrations are calculated by numerical resolving of suitable torques equations and Poisson equation. The threshold voltages for the deformations are also determined. It was shown that adsorption affects the distributions of both cations and anions. Sufficiently large number of adsorbed ions leads to spontaneous deformation arising without any threshold if the total number of ions creates sufficiently strong electric field with significant field gradients in the neighborhood of electrodes. The spontaneous deformations are favored by strong flexoelectricity, large thickness, large ion concentrations, weak anchoring, and large adsorption energy.

  20. Influence of geometrical parameters on convective flows in non-uniformly heated cylindrical fluid layers

    NASA Astrophysics Data System (ADS)

    Evgrafova, A.; Sukhanovskii, A.; Kuchinskii, M.; Popova, E.

    2017-06-01

    Convection in a fluid layer with a free surface in a cylindrical container non-homogeneously heated from below was studied experimentally. The heater has a circular form and was placed in the center of the vessel. Such a system in the presents of rotation is very promising for studying the nature of tropical cyclones. In current paper we considered the influence of different geometric parameters on the dynamics of convection flows. For it two experimental setups of different sizes were used. Measurements were done for fluids with different values of Prandtl number and heating powers. It was shown that the structure and intensity of mean flow producing by a horizontal temperature gradient are defined by Rayleigh number Ra. The basic flow leads to unstable temperature stratification over the heating area and the formation of a system of secondary flows. The formation of secondary flows depends on characteristics of thermal boundary layer and is described by local Rayleigh number Raδ .

  1. Calculating acoustical properties of cells: influence of surface topography and liquid layer between cell and substrate.

    PubMed

    Kundu, T; Bereiter-Hahn, J; Hillmann, K

    1992-05-01

    In this paper, a mathematical formulation is presented to compute the V(z) of a tapering layered solid and applying this formulation to the determination of acoustic properties of biological cells and tissues. The formulation is adopted in the simplex inversion algorithm to obtain the acoustic properties of a tapering cell from its V(z) values. The influence of two parameters had been considered: The tapering angle and the presence of a thin liquid layer present between cells and the substratum to which they adhere. Up to a tapering angle less than 10 degrees, it can be safely neglected. However, if a larger angle is neglected, then the acoustic wave velocity in the cell is overestimated. Cell thickness estimation is not affected significantly when the tapering angle is ignored. The calculations of acoustic properties of cells are considerably influenced by the introduction of a thin fluid layer between the solid substratum and the overlying cell, neglecting the presence of at least a very thin layer (20-30 nm), in general, results in a considerable overestimation of sound velocity. The reliability of the data calculated from V(z) values was ascertained using an independent method to determine cell thickness by calculating it from the interference fringe pattern obtained with the reflection-interference light microscope. The shape of the glutaraldehyde-fixed cells was similar to fried eggs. The highest sound velocities were found close to the periphery of the dome-shaped cell center. In the very center and over most of the area of the thin periphery, sound velocity was close to that in saline.

  2. Influence of tall vegetation canopy on turbulence kinetic energy budget in the stable boundary layer

    NASA Astrophysics Data System (ADS)

    Babić, Karmen; Rotach, Mathias W.

    2017-04-01

    While a considerable amount of research has been done on turbulence kinetic energy (TKE) budget studies in the surface layer over horizontally homogeneous and flat (HHF) surfaces, little research focused on budgets above heterogeneous and rough surfaces. Only few studies have investigated TKE budgets above fetch-limited forest focusing on statically neutral conditions, while studies in the stable boundary layer (SBL) are still scarce in the literature. Therefore, we present turbulence characteristics above tall, deciduous forest in the wintertime SBL and make a comparison with a well-known results of HHF terrain. Turbulence measurements performed at five levels above the canopy height (approximately h = 18 m) allowed the investigation of combined influence of the roughness sublayer (RSL) found above tall vegetation and the internal boundary layer (IBL) on the TKE budget terms. Each term of the TKE budget is investigated within the framework of local similarity theory. Kolomogorov's similarity hypothesis assumes local isotropy within the inertial subrange. Testing the local isotropy hypothesis more thoroughly resulted in a ratio of the horizontal spectral densities (Sv/Su) approaching the 4/3, while the ratio of the vertical to the longitudinal spectral density (Sw/Su) was less than 1 for all levels indicating an anisotropic turbulence above the canopy. As a consequence, estimated values of TKE dissipation rate (ɛ) for the vertical component (ɛw) were smaller (underestimated) compared to the ɛ estimates obtained from the horizontal velocity components. This finding has a direct influence on the applicability of classical Kansas spectral models valid for HHF terrain as well as on the budget of wind variances. Additionally, the dimensionless wind shear function associated with "Kolmogorov turbulence" (existence of a well-defined inertial subrange with -5/3 slopes) was found to depart from linear prediction suggesting that the stability is a stronger determinant of

  3. Solid-state transformation of nanocrystalline phyllomanganate into tectomanganate: influence of initial layer and interlayer structure.

    PubMed

    Grangeon, Sylvain; Lanson, Bruno; Lanson, Martine

    2014-10-01

    In surficial environments, the fate of many elements is influenced by their interactions with the phyllomanganate vernadite, a nano-sized and turbostratic variety of birnessite. To advance our understanding of the surface reactivity of vernadite as a function of pH, synthetic vernadite (δ-MnO2) was equilibrated at pH ranging from 3 to 10 and characterized structurally using chemical methods, thermogravimetry and modelling of powder X-ray diffraction (XRD) patterns. With decreasing pH, the number of vacant layer sites increases in the octahedral layers of δ-MnO2 (from 0.14 per layer octahedron at pH 10 to 0.17 at pH 3), whereas the number of layer Mn(3+) is, within errors, equal to 0.12 per layer octahedron over the whole pH range. Vacant layer sites are capped by interlayer Mn(3+) sorbed as triple corner-sharing surface complexes (TC sites). The increasing number of interlayer Mn(3+) with decreasing pH (from 0.075 per layer octahedron at pH 10 to 0.175 at pH 3) results in the decrease of the average Mn oxidation degree (from 3.80 ± 0.01 at pH 10 to 3.70 ± 0.01 at pH 3) and in the lowering of the Na/Mn ratio (from 27.66 ± 0.20 at pH 10 to 6.99 ± 0.16 at pH 3). In addition, in-plane unit-cell parameters are negatively correlated to the number of interlayer Mn at TC sites and decrease with decreasing pH (from b = 2.842 Å at pH 10 to b = 2.834 Å at pH 3), layer symmetry being systematically hexagonal with a = b × 3(1/2). Finally, modelling of X-ray diffraction (XRD) patterns indicates that crystallite size in the ab plane and along the c* axis decreases with decreasing pH, ranging respectively from 7 nm to 6 nm, and from 1.2 nm to 1.0 nm (pH 10 and 3, respectively). Following their characterization, dry samples were sealed in polystyrene vials, kept in the dark, and re-analysed 4 and 8 years later. With ageing time and despite the dry state, layer Mn(3+) extensively migrates to the interlayer most likely to minimize steric strains

  4. A new rapid and non-destructive method to detect tephra layers and cryptotephras: applying to the first distal tephrostratigraphic record of the Chaîne des Puys volcanic field (France).

    NASA Astrophysics Data System (ADS)

    Jouannic, Gwénolé; Walter-Simonnet, Anne-Véronique; Bossuet, Gilles; Delabrousse, Eric; Cubizolle, Hervé

    2014-05-01

    Tephrostratigraphy has been considerably developed for 30 years, mainly in palaeo-environmental studies. In such studies, distal tephra layers are important chronological markers, but they are also tools to establish or specify record of past eruptions of a volcanic field. Nowadays, development of effective rapid methods to detect tephra layers in sedimentary records of various compositions is a challenge. Many classic methods for detection of tephra layers, like regular sampling or magnetic susceptibility measurements, have shown their limits. Regular sampling takes a long time, and finding tephra layers remains uncertain. Moreover, magnetic susceptibility maesurements, although it is a non-destructive method, is ineffective when tephra layers are made of volcanic glass shards with differentiated magma composition. X-ray fluorescence (XRF) is also a non-destructive method but it takes a very long time to analyze a core with sufficient high resolution, and measurements only concern the surface of the sediment. We propose a new method allows detection of tephra layers with, for the first time, a 3D resolution: the Computed Tomography Scan (CT- Scan). This method, regularly used in medicine, allows there to obtain pictures of materials density on 3D with inframillimetric measurement ranges. Then, it is possible to detect tephras, cryptotephras (invisible by naked eye), reworked tephra layers even when tephra layers don't outcrop at the surface of the sediment (and are therefore undetectable by usual methods like XRF and magnetic susceptibility). This method has been tried out on tephras sedimented in different types of sediments (silicated, carbonated and organic matter). Our results show that this method is very efficient for peaty environment. Used on coring carried out in Forez Mountains (French Massif Central), CT-Scan allows to detect more tephra layers than usual methods (XRF and magnetic susceptibility). Results presented here allow to build the first

  5. Influence of depositional setting and sedimentary fabric on mechanical layer evolution in carbonate aquifers

    USGS Publications Warehouse

    Graham, Wall B.R.

    2006-01-01

    Carbonate aquifers in fold-thrust belt settings often have low-matrix porosity and permeability, and thus groundwater flow pathways depend on high porosity and permeability fracture and fault zones. Methods from sedimentology and structural geology are combined to understand the evolution of fracture controlled flow pathways and determine their spatial distribution. Through this process bed-parallel pressure-solution surfaces (PS1) are identified as a fracture type which influences fragmentation in peritidal and basinal carbonate, and upon shearing provides a major flow pathway in fold - thrust belt carbonate aquifers. Through stratigraphic analysis and fracture mapping, depositional setting is determined to play a critical role in PS1 localization and spacing where peritidal strata have closer spaced and less laterally continuous PS1 than basinal strata. In the peritidal platform facies, units with planar lamination have bed-parallel pressure-solution seams along mudstone laminae. In contrast, burrowed units of peritidal strata have solution seams with irregular and anastamosing geometries. Laminated units with closely spaced bed-parallel solution seams are more fragmented than bioturbated units with anastamosing solution seams. In the deeper-water depositional environment, pelagic settling and turbidity currents are the dominant sedimentation processes, resulting in laterally continuous deposits relative to the peritidal platform environment. To quantify the fracture patterns in the basinal environment, mechanical layer thickness values were measured from regions of low to high bed dip. The results define a trend in which mechanical layer thickness decreases as layer dip increases. A conceptual model is presented that emphasizes the link between sedimentary and structural fabric for the peritidal and basinal environments, where solution seams localize in mud-rich intervals, and the resulting pressure-solution surface geometry is influenced by sedimentary geometry

  6. Influence of nonelectrostatic ion-ion interactions on double-layer capacitance

    NASA Astrophysics Data System (ADS)

    Zhao, Hui

    2012-11-01

    Recently a Poisson-Helmholtz-Boltzmann (PHB) model [Bohinc , Phys. Rev. EPLEEE81539-375510.1103/PhysRevE.85.031130 85, 031130 (2012)] was developed by accounting for solvent-mediated nonelectrostatic ion-ion interactions. Nonelectrostatic interactions are described by a Yukawa-like pair potential. In the present work, we modify the PHB model by adding steric effects (finite ion size) into the free energy to derive governing equations. The modified PHB model is capable of capturing both ion specificity and ion crowding. This modified model is then employed to study the capacitance of the double layer. More specifically, we focus on the influence of nonelectrostatic ion-ion interactions on charging a double layer near a flat surface in the presence of steric effects. We numerically compute the differential capacitance as a function of the voltage under various conditions. At small voltages and low salt concentrations (dilute solution), we find out that the predictions from the modified PHB model are the same as those from the classical Poisson-Boltzmann theory, indicating that nonelectrostatic ion-ion interactions and steric effects are negligible. At moderate voltages, nonelectrostatic ion-ion interactions play an important role in determining the differential capacitance. Generally speaking, nonelectrostatic interactions decrease the capacitance because of additional nonelectrostatic repulsion among excess counterions inside the double layer. However, increasing the voltage gradually favors steric effects, which induce a condensed layer with crowding of counterions near the electrode. Accordingly, the predictions from the modified PHB model collapse onto those computed by the modified Poisson-Boltzmann theory considering steric effects alone. Finally, theoretical predictions are compared and favorably agree with experimental data, in particular, in concentrated solutions, leading one to conclude that the modified PHB model adequately predicts the diffuse

  7. Vertical distribution and composition of phytoplankton under the influence of an upper mixed layer.

    PubMed

    Ryabov, Alexei B; Rudolf, Lars; Blasius, Bernd

    2010-03-07

    The vertical distribution of phytoplankton is of fundamental importance for the dynamics and structure of aquatic communities. Here, using an advection-reaction-diffusion model, we investigate the distribution and competition of phytoplankton species in a water column, in which inverse resource gradients of light and a nutrient can limit growth of the biomass. This problem poses a challenge for ecologists, as the location of a production layer is not fixed, but rather depends on many internal parameters and environmental factors. In particular, we study the influence of an upper mixed layer (UML) in this system and show that it leads to a variety of dynamic effects: (i) Our model predicts alternative density profiles with a maximum of biomass either within or below the UML, thereby the system may be bistable or the relaxation from an unstable state may require a long-lasting transition. (ii) Reduced mixing in the deep layer can induce oscillations of the biomass; we show that a UML can sustain these oscillations even if the diffusivity is less than the critical mixing for a sinking phytoplankton population. (iii) A UML can strongly modify the outcome of competition between different phytoplankton species, yielding bistability both in the spatial distribution and in the species composition. (iv) A light limited species can obtain a competitive advantage if the diffusivity in the deep layers is reduced below a critical value. This yields a subtle competitive exclusion effect, where the oscillatory states in the deep layers are displaced by steady solutions in the UML. Finally, we present a novel graphical approach for deducing the competition outcome and for the analysis of the role of a UML in aquatic systems. 2009 Elsevier Ltd. All rights reserved.

  8. Influence des melanges complexes organiques sur le sort des dioxines et furanes: Implications dans le developpement de facteurs de caracterisation en analyse du cycle de vie

    NASA Astrophysics Data System (ADS)

    Taing, Eric

    The environmental fate of dioxins and furans, or polychlorodibenzo-p-dioxins and -furans (PCDD/Fs), leaching from wood poles treated with pentachlorophenol (PCP) oil is modified by the presence of oil. Interactions between co-contaminants, which also exist for other pollutants within the mixtures, were shown in the specific context of risk analysis, but have never been taken into account for the generic context of life cycle assessment (LCA). This decision-making tool relies on characterization factors (CF) to estimate the potential impacts of an emitted amount of a pollutant in different impact categories such as aquatic ecotoxicity and human toxicity. For these two impact categories, CFs are calculated from a cause-effect chain that models the environmental fate, exposure and effects of the pollutant (represented by a matrix of fate FF, exposure XF and effect EF, respectively), meaning that a modification of PCDD/Fs fate induces a change in PCDD/Fs CFs. The research question is therefore as follows: In life cycle impact assessment (LCIA), to what extent would the potential impacts of PCDD/Fs on aquatic ecotoxicity and human toxicity change when taking into account the influence of a complex organic mixture on PCDD/Fs fate?. Thus, the main objective is to develop CFs of PCDD/Fs when their fate is influenced by PCP oil and compare them with the CFs of PCDD/Fs without oil for the aquatic ecotoxicity and human toxicity impact categories. A mathematic approach is established to determine the new environmental distribution of PCDD/Fs in the presence of oil and a new FF' matrix is calculated from this new distribution to obtain new CFs' integrating oil influence. FF' and CF' are then compared to FF and CF of PCDD/Fs without the oil. Finally, potential (eco)toxic impacts of the PCDD/F Canadian emissions are calculated with the new CFs' of PCDD/Fs in presence of oil. By only focusing on the results for an emission into air, freshwater and natural soil on a continental

  9. Influence of Direct Current Electric Field on Corrosion Behavior of Tin Under a Thin Electrolyte Layer

    NASA Astrophysics Data System (ADS)

    Huang, H. L.; Bu, F. R.; Tian, J.; Liu, D.

    2017-08-01

    The influence of a direct current electric field (DCEF) on corrosion behavior of tin under a thin electrolyte layer was investigated based on an array electrode technology by polarization, electrochemical impedance spectroscopy and surface analysis. The experimental results indicate that the corrosion rate of tin near the positive plate of DCEF increases with increased electric field intensity, which could be attributed to the acceleration of the migration of ions, the removal of corrosion products under DCEF and the damage of tin surface oxide film. Furthermore, tin at different positions in a DCEF exhibits different corrosion behavior, which could be ascribed to the difference of the local corrosion environment caused by the DCEF.

  10. Influence of Gas Turbulence on the Instability of an Air-Water Mixing Layer.

    PubMed

    Matas, Jean-Philippe; Marty, Sylvain; Dem, Mohamed Seydou; Cartellier, Alain

    2015-08-14

    We present the first evidence of the direct influence of gas turbulence on the shear instability of a planar air-water mixing layer. We show with two different experiments that increasing the level of velocity fluctuations in the gas phase continuously increases the frequency of the instability, up to a doubling of frequency for the largest turbulence intensity investigated. A modified spatiotemporal stability analysis taking turbulence into account via a simple Reynolds stress closure provides the right trend and magnitude for this effect.

  11. Instability of a compressible circular free jet with consideration of the influence of the jet boundary layer thickness

    NASA Technical Reports Server (NTRS)

    Michalke, A.

    1977-01-01

    The instability of a circular jet was investigated by means of the inviscid linearized stability theory. By variation of a jet parameter which takes the ratio of jet radius to boundary layer thickness into account, the influence of axisymmetry on the spatial growth rate and disturbance phase velocity is studied. The influence of Mach number and temperature ratio is discussed. A comparison with measurements shows that the instability of a turbulent jet boundary layer may also be explained by these results.

  12. Influence of a fat layer on the near infrared spectra of human muscle: quantitative analysis based on two-layered Monte Carlo simulations and phantom experiments

    NASA Astrophysics Data System (ADS)

    Yang, Ye; Soyemi, Olusola O.; Landry, Michelle R.; Soller, Babs R.

    2005-03-01

    Continuous wave near-IR spectroscopy (CW-NIRS) has been increasingly applied for the noninvasive, in vivo measurement of tissue and blood chemistry. It is hypothesized that there is a quantifiable relationship between fat thickness and near infrared diffuse reflectance spectra at all wavelengths, and this relationship can be used to remove the spectral influence of the overlying fat layer from the muscle spectrum. The hypothesis was investigated at a single wavelength using Monte Carlo simulations of a two-layer structure and with phantom experiments. The influence of a range of optical coefficients (absorption and reduced scattering) for fat and muscle over the known range of human physiological values was also investigated. A polynomial relationship was established between the fat thickness and the detected diffuse reflectance. It is also shown that the optical properties of the muscle and fat layers influence this relationship under certain conditions. Subject-to-subject variation in the fat optical coefficients and thickness can be ignored if the fat thickness is less than 5 mm, such as on the forearm. If NIRS measurement is to be performed on an anatomical region with a thicker fat layer, a spectral correction for fat will be needed to account for its thickness and the variation in optical coefficients for both the fat and the muscle layers.

  13. The influence of geometric imperfections on the stability of three-layer beams with foam core

    NASA Astrophysics Data System (ADS)

    Wstawska, Iwona

    2017-01-01

    The main objective of this work is the numerical analysis (FE analysis) of stability of three-layer beams with metal foam core (alumina foam core). The beams were subjected to pure bending. The analysis of the local buckling was performed. Furthermore, the influence of geometric parameters of the beam and material properties of the core (linear and non-linear model) on critical loads values and buckling shape were also investigated. The calculations were made on a family of beams with different mechanical properties of the core (elastic and elastic-plastic material). In addition, the influence of geometric imperfections on deflection and normal stress values of the core and the faces has been evaluated.

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

    NASA Astrophysics Data System (ADS)

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

    2016-10-01

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

  15. Etude de l'influence de la temperature et de l'humidite sur les proprietes mecaniques en traction des fibres de chanvre et de coco

    NASA Astrophysics Data System (ADS)

    Ho Thi, Thu Nga

    L'objectif de cette etude fut d'etablir l'effet de l'humidite et de la temperature sur la resistance en traction et le module elastique des fibres de chanvre et de coco. Deux etudes ont ete realisees afin d'atteindre cet objectif. La premiere vise l'absorption de l'humidite dans ces fibres en exposition dans l'air (de 0%RH a 80%RH) ainsi que l'absorption de l'eau dans ces fibres immergees dans l'eau aux differentes temperatures. La deuxieme consiste a mesurer la resistance en traction et le module elastique de ces fibres sous differentes conditions d'humidite et de temperature. En basant sur les resultats experimentaux obtenus, les methodes semi empiriques et de reseaux de neurones ont ete utilisees pour but de predire les proprietes en traction (resistance et module d'elasticite) des fibres de chanvre et de coco sous l'influence de l'humidite et de la temperature.

  16. Influence of layer thickness on the strength of angle-ply laminates

    NASA Technical Reports Server (NTRS)

    Herakovich, C. T.

    1982-01-01

    Experimental results are presented showing that the strength and toughness of finite width angle-ply laminates can be increased significantly by using an alternating layer stacking sequence as opposed to a clustered configuration. The ultimate tensile stress of an alternating plus/minus theta laminate of the form (+ or - theta) sub 2 sub s can be much as 1.5 times that of a clustered configuration of the form theta sub 2/-theta sub 2 sub s. Further, the toughness of the alternating layer configuration can be as much as 2.7 times that of the clustered configuration. These differences are explained analytically through consideration of the influence of layer thickness on the magnitude of the interlaminar shear stress and by examination of failed specimens. It is shown that the two laminate configurations exhibit distinctly different failure modes for some fiber angles. Both laminate configurations exhibit catastrophic failure with the damage limited essentially to a small region defined by the length of a single crack across the width of the specimen, parallel to the fiber direction. Results are presented for T300/5208 graphite-epoxy for fiber orientations of 10, 30, and 45 deg.

  17. Influence of a high aerosol concentration on the thermal structure of the atmospheric boundary layer

    NASA Astrophysics Data System (ADS)

    Khaikin, M. N.; Kuznetsova, I. N.; Kadygrov, E. N.

    2006-12-01

    The influence of increased concentrations of submicron aerosol produced by forest fires on thermal characteristics of the atmospheric boundary layer (ABL) in Moscow and its remote vicinity (the town of Zvenigorod) are analyzed on the basis of regular remote measurements of the ABL temperature profile with the use of MTP-5 profilers. In the air basin of a large city, additional aerosol and accompanying pollutants in early morning hours (at small heights of the Sun) most frequently did not cause substantial changes in the ABL thermal structure. In the locality remote from the megalopolis (Zvenigorod), the atmospheric pollution by aerosol led to noticeable changes in the ABL thermal characteristics. Especially strong changes were observed in the daytime, during the maximum supply of solar radiation. In morning hours, the heating rate of the lower 100-m layer of the polluted air exceeded the heating rate of a relatively pure air by more than one degree. In higher layers, the differences between the rates of temperature changes in a relatively clean atmosphere and in an atmosphere polluted by aerosol (in the suburb) were insignificant.

  18. Influence of superoleophobic layer on the lubrication performance of partially textured bearing including cavitation

    NASA Astrophysics Data System (ADS)

    Tauviqirrahman, M.; Bayuseno, A. P.; Muchammad, Jamari, J.

    2016-04-01

    Surfaces with high superoleophobicity have attracted important attention because of their potential applications in scientific and industrial field. Especially classical metal bearing are faced with lubrication problem, because metal surface shows typically oleophilicity. The development of superolephobic metal surfaces which repel oil liquid droplet have significant applications in preventing the stiction. In addition, for classical bearing with texturing, the cavitation occurence is often considered as the main cause of the deterioration of the lubrication performance and thus shorten the lifetime of the bearing. In the present study, the exploration of the influence of adding the superoleophobic layer on the improvement of the performance of partially textured bearing in preventing the cavitation was performed. Navier slip model was used to model the behavior of the superoleophobic layer. A formulation of the modified Reynolds equation with mass-conserving boundary conditions was derived and the pressure distribution was of particular interest. The equations of lubrication were discretized using a finite volume method and solved using a tri-diagonal-matrix-algortihm. In this calculation, it was shown that after introducing the superoleophobic layer at the leading edge of the contact, the cavitation occurence can be prevented and thus the increased hydrodynamic pressure is found. However, the results showed that for deeper texture, the deterioration of the load support is noted. This findings may have useful implications to extend the life time of textured bearing.

  19. Influence of hydrogen pre-growth flow on indium incorporation into InGaN layers

    NASA Astrophysics Data System (ADS)

    Czernecki, Robert; Grzanka, Ewa; Strak, Pawel; Targowski, Greg; Krukowski, Stanislaw; Perlin, Piotr; Suski, Tadeusz; Leszczynski, Mike

    2017-04-01

    In metalorganic vapour phase epitaxy (MOVPE) hydrogen is not commonly used in the carrier gas during growth of InGaN layers since it interferes with indium incorporation. However, hydrogen leads to a smoother surface morphology of the growing layers which is beneficial in many optoelectronic devices. The influence of hydrogen on indium incorporation was studied here. This study concludes that hydrogen alters the state of the GaN surface to the one, that does not favor indium incorporation. However, this change of the surface state by hydrogen is not immediate but occurs during the exposition of the GaN surface to H2 flow and leading to a significant In-content gradient in the InGaN layer grown with 1% (of total flow) of hydrogen in the carrier gas. We showed, that indium content on the GaN/InGaN interface is different in the case, when hydrogen is present or absent during pre-growth vent. For the InGaN sample grown without hydrogen in the carrier gas, In-content gradient was not observed.

  20. Influences of an Aluminum Covering Layer on the Performance of Cross-Like Hall Devices.

    PubMed

    Lyu, Fei; Liu, Xinfu; Ding, Yinjie; Toh, Eng-Huat; Zhang, Zhenyan; Pan, Yifan; Wang, Zhen; Li, Chengjie; Li, Li; Sha, Jin; Pan, Hongbing

    2016-01-15

    This work studies the effects of an aluminum covering on the performance of cross-like Hall devices. Four different Hall sensor structures of various sizes were designed and fabricated. The sensitivity and offset of the Hall sensors, two key points impacting their performance, were characterized using a self-built measurement system. The work analyzes the influences of the aluminum covering on those two aspects of the performance. The aluminum layer covering mainly leads to an eddy-current effect in an unstable magnetic field and an additional depletion region above the active region. Those two points have influences on the sensitivity and the offset voltage, respectively. The analysis guides the designer whether to choose covering with an aluminum layer the active region of the Hall sensor as a method to reduce the flicker noise and to improve the stability of the Hall sensor. Because Hall devices, as a reference element, always suffer from a large dispersion, improving their stability is a crucial issue.

  1. Fabric controls on strain accommodation in naturally deformed mylonites: The influence of interconnected micaceous layers

    NASA Astrophysics Data System (ADS)

    Hunter, Nicholas J. R.; Hasalová, Pavlína; Weinberg, Roberto F.; Wilson, Christopher J. L.

    2016-02-01

    We present microstructural analyses demonstrating how the geometrical distribution and interconnectivity of mica influences quartz crystallographic preferred orientation (CPO) development in naturally deformed rocks. We use a polymineralic (Qtz + Pl + Kfs + Bt + Ms ± Grt ± Tur) mylonite from the Zanskar Shear Zone, a section of the South Tibetan Detachment (NW Himalaya), to demonstrate how quartz CPO intensity decreases from quartz-dominated domains to micaceous domains, independently of whether or not quartz grains are pinned by mica grains. We then use a bimineralic (Qtz + Ms) mylonite from the Main Central Thrust (NW Himalaya) to show how increasing mica grain connectivity is concomitant with a systematic weakening of quartz CPO. Our results draw distinctions between CPO weakening due to: (i) second phase drag, leading to ineffective recovery in quartz; and (ii) increased transmission and localisation of strain between interconnected mica grains. In the latter case, well-connected micaceous layers take up most of the strain, weakening the rock and preventing straining of the stronger quartz matrix. Our findings suggest that rock weakening in quartz-rich crustal rocks is influenced not only by the presence of mica-rich layers but also the degree of mica grain connectivity, which allows for more effective strain localization through the entire rock mass.

  2. Mixing layer height measurements determines influence of meteorology on air pollutant concentrations in urban area

    NASA Astrophysics Data System (ADS)

    Schäfer, Klaus; Blumenstock, Thomas; Bonn, Boris; Gerwig, Holger; Hase, Frank; Münkel, Christoph; Nothard, Rainer; von Schneidemesser, Erika

    2015-10-01

    Mixing layer height (MLH) is a key parameter to determine the influence of meteorological parameters upon air pollutants such as trace gas species and particulate concentrations near the surface. Meteorology, and MLH as a key parameter, affect the budget of emission source strengths, deposition, and accumulation. However, greater possibilities for the application of MLH data have been identified in recent years. Here, the results of measurements in Berlin in 2014 are shown and discussed. The concentrations of NO, NO2, O3, CO, PM1, PM2.5, PM10 and about 70 volatile organic compounds (anthropogenic and biogenic of origin) as well as particle size distributions and contributions of SOA and soot species to PM were measured at the urban background station of the Berlin air quality network (BLUME) in Nansenstr./Framstr., Berlin-Neukölln. A Vaisala ceilometer CL51, which is a commercial mini-lidar system, was applied at that site to detect the layers of the lower atmosphere in real time. Special software for these ceilometers with MATLAB provided routine retrievals of MLH from vertical profiles of laser backscatter data. Five portable Bruker EM27/SUN FTIR spectrometers were set up around Berlin to detect column averaged abundances of CO2 and CH4 by solar absorption spectrometry. Correlation analyses were used to show the coupling of temporal variations of trace gas compounds and PM with MLH. Significant influences of MLH upon NO, NO2, PM10, PM2.5, PM1 and toluene (marker for traffic emissions) concentrations as well as particle number concentrations in the size modes 70 - 100 nm, 100 - 200 nm and 200 - 500 nm on the basis of averaged diurnal courses were found. Further, MLH was taken as important auxiliary information about the development of the boundary layer during each day of observations, which was required for the proper estimation of CO2 and CH4 source strengths from Berlin on the basis of atmospheric column density measurements.

  3. Influence of boundary-layer dynamics on pollen dispersion and viability

    NASA Astrophysics Data System (ADS)

    Arritt, Raymond W.; Viner, Brian J.; Westgate, Mark E.

    2013-04-01

    Adoption of genetically modified (GM) crops has raised concerns that GM traits can accidentally cross into conventional crops or wild relatives through the transport of wind-borne pollen. In order to evaluate this risk it is necessary to account both for dispersion of the pollen grains and environmental influences on pollen viability. The Lagrangian approach is suited to this problem because it allows tracking the environmental temperature and moisture that pollen grains experience as they travel. Taking advantage of this capability we have combined a high-resolution version of the WRF meteorological model with a Lagrangian particle dispersion model to predict maize pollen dispersion and viability. WRF is used to obtain fields of wind, turbulence kinetic energy, temperature, and humidity which are then used as input to the Lagrangian dispersion model. The dispersion model in turn predicts transport of a statistical sample of a pollen cloud from source plants to receptors. We also use the three-dimensional temperature and moisture fields from WRF to diagnose changes in moisture content of the pollen grains and consequent loss of viability. Results show that turbulent motions in the convective boundary layer counteract the large terminal velocity of maize pollen grains and lift them to heights of several hundred meters, so that they can be transported long distances before settling to the ground. We also found that pollen lifted into the upper part of the boundary layer remains more viable than has been inferred using surface observations of temperature and humidity. This is attributed to the thermal and moisture structure that typifies the daytime atmospheric boundary layer, producing an environment of low vapor pressure deficit in the upper boundary layer which helps maintain pollen viability.

  4. Estimation of the Influence of Thin Air Layers on Structures by the Use of Qualitative One-Dimensional Models

    NASA Astrophysics Data System (ADS)

    Chimeno Manguan, M.; Roibas Millan, E.; Simon Hidalgo, F.

    2014-06-01

    Air layers are regions of air between structural elements than can be found in numerous spacecraft structures. The space between folded solar panels and between antennas and a satellite's body are cases of air layers. For some cases, depending on the flexibility of the contiguous structures, the contribution of air layers can modify noticeably the dynamic response of a spacecraft structure. The analysis of these problems in detailed numerical models as Finite and Boundary Element models are characterised by a very small element size because of the requirements imposed by the thickness of the air layers and the fluid-structure interface. Then, a preliminary assessment of the influence of the air layer allows optimizing the development work flow of these elements. This work presents a methodology to preliminarily assess the influence of air layers in the structural response. The methodology is based on the definition of simplified one-dimensional models for the structure and the air gaps. The study of these simple models can be a useful tool to determine the degree of influence of the air layers in the system. Along with the introduction of the methodology a study on several of the model parameters as the number of degrees of freedom for the air layer or the structure is presented. The performance of the methodology is illustrated with results for several cases including actual spacecraft structures.

  5. Influence of vibrational relaxation on perturbations in a shock layer on a plate

    NASA Astrophysics Data System (ADS)

    Kirilovskiy, S. V.; Maslov, A. A.; Poplavskaya, T. V.; Tsyryul'nikov, I. S.

    2015-05-01

    The influence of excitation of molecular vibrational degrees of freedom on the mean flow and perturbation development in a hypersonic (M = 6-14) viscous shock layer is studied. The layer originates on a plate placed in a flow of air, carbon dioxide, or their mixture at high stagnation temperatures (2000-3000 K). The mean flow and pressure pulsation on the surface of the plate are measured in an IT-302M pulsed wind tunnel (Khristianovich Institute of Theoretical and Applied Mechanics, Siberian Branch, Russian Academy of Sciences). Numerical simulation is carried out in terms of a model of a thermally perfect gas using the ANSYS Fluent program package based on solving nonstationary two-dimensional Navier-Stokes equations. External flow perturbations are introduced into the computational domain in the form of plane monochromatic acoustic waves using UDF modules built in the computational code. It is shown that the excitation of vibrational degrees of freedom in carbon dioxide molecules considerably influences the position of the head wave and intensifies perturbations in contrast to air in which the fraction of vibrationally excited molecules is low at the same parameters of the oncoming low. The influence of the excitation of vibrational degrees of freedom is studied both for equilibrium gas and for a vibrationally nonequilibrium gas. Nonequilibrium vibrational degrees of freedom are simulated using a two-temperature model of relaxation flows in which the time variation of the vibrational energy is described by the Landau-Teller equation with regard to a finite time of energy exchange between vibrational and translational-rotational degrees of freedom of molecules. It is found that the vibrational nonequilibrium has a damping effect on perturbations.

  6. Étude par diffraction des rayons X de la nitruration plasma d'un acier 304L Influence sur l'oxydation à 1000 ^{circ}C

    NASA Astrophysics Data System (ADS)

    Marot, L.; Buscail, H.; Straboni, A.; Riffard, F.; Caudron, E.; Cueff, R.

    2002-07-01

    This work presents the influence of various nitridation parameters on the 304L steel oxidation at 1000 ^{circ}C, in air under atmospheric pressure. Nitridation temperatures were ranging between 300 ^{circ}C and 430 ^{circ}C with exposure times lasting from 2 to 8 hours. At 300 and 430 ^{circ}C, the nitridation treatment leads to the solid solution surface formation γ-N without any nitride formation. After oxidation at 1000 ^{circ}C of blank specimens, X ray diffraction reveals the FeCr2O4 spinel formation. This oxide does not act as a good diffusion barrier. With nitrogen treated specimens, the higher the nitridation temperature is and the longer the exposure time is, better is the oxidation behaviour at 1000 ^{circ}C. We then observe that the Cr{1,3}Fe{0,7}O3 oxide is more present in the oxide sale from the very beginning of the oxidation test which is correlated to a final lower mass gain. Cette étude porte sur l'influence des paramètres de nitruration plasma sur l'oxydation de l'acier 304L à 1000 ^{circ}C, sous air, à la pression atmosphérique. Les températures employées lors de la nitruration ont été de 300 ^{circ}C et 430 ^{circ}C pour des durées de nitruration variant entre 2 et 8 heures. A 300 et 430 ^{circ}C, la nitruration conduit à la formation d'une solution solide γ-N en surface sans provoquer la formation de nitrures. Après oxydation à 1000 ^{circ}C du 304L non nitruré, la diffraction des rayons X révèle la formation d'une couche de type spinelle FeCr2O4 qui ne semble pas jouer le rôle de barrière de diffusion. Pour les échantillons préalablement nitrurés, plus la température de nitruration est élevée et plus la durée du traitement est longue, meilleur est le comportement en oxydation. Nous observons alors l'oxyde Cr{1,3}Fe{0,7}O3 en proportion importante dès le début de l'oxydation et une prise de masse finale plus faible.

  7. Influence of annealing on composition and optical properties of CdTe nanoparticle layer-by-layer films.

    PubMed

    Briscoe, Joe; Gallardo, Diego E; Lesnyak, Vladimir; Dunn, Steve

    2011-06-01

    CdTe nanoparticle-polymer composite films were deposited conformally using a layer-by-layer (LbL) process onto planar or ZnO nanorod-coated substrates. Films were annealed between 150-450 degrees C. Under air this led to oxidation of the nanoparticles while under vacuum their composition was retained. Annealing at 450 degrees C led to complete removal of the polymer with a loss of quantum confinement as shown by UV-vis spectroscopy. Annealing at 350 degrees C gave partial removal of the polymer and retained quantum confinement. Such annealed nanoparticle composite systems may have application in photovoltaics.

  8. Influencing factors on the cooling effect of coarse blocky top-layers on relict rock glaciers

    NASA Astrophysics Data System (ADS)

    Pauritsch, Marcus; Wagner, Thomas; Mayaud, Cyril; Thalheim, Felix; Kellerer-Pirklbauer, Andreas; Winkler, Gerfried

    2017-04-01

    Coarse blocky material widely occurs in alpine landscapes particularly at the surface of bouldery rock glaciers. Such blocky layers are known to have a cooling effect on the subjacent material because of the enhanced non-conductive heat exchange with the atmosphere. This effect is used for instance by the construction of blocky embankments in the building of railways and roads in permafrost regions to prevent thawing processes. In alpine regions, this cooling effect may have a strong influence on the distribution and conservation of permafrost related to climate warming. The thermal regimes of the blocky surface layers of two comparable - in terms of size, elevation and geology - relict rock glaciers with opposing slope aspects are investigated. Therefore, the influence of the slope aspect-related climatic conditions (mainly the incident solar radiation, wind conditions and snow cover) on the cooling effect of the blocky layers is investigated. Air temperature, ground surface temperature and ground temperature at one meter depth were continuously measured over a period of four years at several locations at the NE-oriented Schöneben Rock Glacier and the adjacent SW-oriented Dürrtal Rock Glacier. At the former, additional data about wind speed and wind direction as well as precipitation are available, which are used to take wind-forced convection and snow cover into consideration. Statistical analyses of the data reveal that the blocky top layer of the Dürrtal Rock Glacier generally exhibits lower temperatures compared to the Schöneben Rock Glacier despite the more radiation-exposed aspect and the related higher solar radiation. However, the data show that the thermal regimes of the surface layers are highly heterogeneous and that data from the individual measurement sites have to be interpreted with caution. High Rayleigh numbers at both rock glaciers show that free convection occurs particularly during winter. Furthermore, wind-forced convection has a high

  9. Influence of active layer and support layer surface structures on organic fouling propensity of thin-film composite forward osmosis membranes.

    PubMed

    Lu, Xinglin; Arias Chavez, Laura H; Romero-Vargas Castrillón, Santiago; Ma, Jun; Elimelech, Menachem

    2015-02-03

    In this study, we investigate the influence of surface structure on the fouling propensity of thin-film composite (TFC) forward osmosis (FO) membranes. Specifically, we compare membranes fabricated through identical procedures except for the use of different solvents (dimethylformamide, DMF and N-methyl-2-pyrrolidinone, NMP) during phase separation. FO fouling experiments were carried out with a feed solution containing a model organic foulant. The TFC membranes fabricated using NMP (NMP-TFC) had significantly less flux decline (7.47 ± 0.15%) when compared to the membranes fabricated using DMF (DMF-TFC, 12.70 ± 2.62% flux decline). Water flux was also more easily recovered through physical cleaning for the NMP-TFC membrane. To determine the fundamental cause of these differences in fouling propensity, the active and support layers of the membranes were extensively characterized for physical and chemical characteristics relevant to fouling behavior. Polyamide surface roughness was found to dominate all other investigated factors in determining the fouling propensities of our membranes relative to each other. The high roughness polyamide surface of the DMF-TFC membrane was also rich in larger leaf-like structures, whereas the lower roughness NMP-TFC membrane polyamide layer contained more nodular and smaller features. The support layers of the two membrane types were also characterized for their morphological properties, and the relation between support layer surface structure and polyamide active layer formation was discussed. Taken together, our findings indicate that support layer structure has a significant impact on the fouling propensity of the active layer, and this impact should be considered in the design of support layer structures for TFC membranes.

  10. The influence of a model subglacial lake on ice dynamics and internal layering

    NASA Astrophysics Data System (ADS)

    Gudlaugsson, Eythor; Humbert, Angelika; Kleiner, Thomas; Kohler, Jack; Andreassen, Karin

    2016-04-01

    As ice flows over a subglacial lake, the drop in bed resistance leads to an increase in ice velocities and a draw down of isochrones and cold ice. The ice surface flattens as it adjusts to the lack of resisting forces at the base. The rapid transition in velocity induces changes in ice viscosity and releases deformation energy that can raise the temperature locally. Recent studies of Antarctic subglacial lakes indicate that many lakes experience very fast and possibly episodic drainage, during which the lake size is rapidly reduced as water flows out. Questions that arise are what effect this would have on internal layers within the ice and whether such past drainage events could be inferred from isochrone structures downstream. Here, we study the effect of a subglacial lake on ice dynamics as well as the influence that such short timescale drainage would have on the internal layers of the ice. To this end, we use a full Stokes, polythermal ice flow model. An enthalpy-gradient method is used to account for the evolution of temperature and water content within the ice. We find that a rapid transition between slow-moving ice outside the lake, and full sliding over the lake, can release considerable amounts of deformational energy, with the potential to form a temperate layer at depth in the transition zone. In addition, we provide an explanation for a characteristic surface feature commonly seen at the edges of subglacial lakes, a hummocky surface depression in the transition zone between little to full sliding. We also conclude that rapid changes in the horizontal extent of subglacial lakes and slippery patches, compared to the average ice column velocity, can create a traveling wave at depth within the isochrone structure that transfers downstream with the advection of ice, thus indicating the possibility of detecting past drainage events with ice penetrating radar.

  11. The influence of a model subglacial lake on ice dynamics and internal layering

    NASA Astrophysics Data System (ADS)

    Gudlaugsson, E.; Humbert, A.; Kleiner, T.; Kohler, J.; Andreassen, K.

    2015-07-01

    As ice flows over a subglacial lake, the drop in bed resistance leads to an increase in ice velocities and a subsequent draw-down of isochrones and cold ice from the surface. The ice surface flattens as it adjusts to the lack of resisting forces at the base. The rapid transition in velocity induces changes in temperature and ice viscosity, releasing deformation energy which raises the temperature locally. Recent studies of Antarctic subglacial lakes indicate that many lakes experience very fast and possibly episodic drainage, during which the lake size is rapidly reduced as water flows out. A question is what effect this would have on internal layers within the ice, and whether such past events could be inferred from isochrone structures downstream. Here, we study the effect of a subglacial lake on the dynamics of a model ice stream as well as the influence that such short timescale drainage would have on the internal layers of the ice. To this end, we use a Full-Stokes, polythermal ice flow model. An enthalpy gradient method is used to account for the evolution of temperature and water content within the ice. We find that the rapid transition between slow-moving ice outside the lake, and full sliding over the lake, releases large amounts of deformational energy, which has the potential to form a temperate layer at depth in the transition zone. In addition, we provide an explanation for a characteristic surface feature, commonly seen at the edges of subglacial lakes, a hummocky surface depression in the transition zone between little to full sliding. We also conclude that rapid changes in lake geometry or basal friction create a travelling wave at depth within the isochrone structure that transfers downstream with the advection of ice, thus indicating the possibility of detecting past events with ice penetrating radar.

  12. Influence of tides and planetary waves on E sporadic layer at mid latitudes

    NASA Astrophysics Data System (ADS)

    Pezzopane, Michael; Pignalberi, Alessio; Zuccheretti, Enrico

    This paper describes the influence that tides and planetary waves have on the variability shown by the main characteristics of the E sporadic (Es) layer, that is the top frequency (ftEs) and the lowest virtual height (h’Es). The study is based on ionograms recorded during the summertime of 2013, a year falling in the maximum of solar activity of cycle 24, and precisely in June, July, August and September, by the Advanced Ionospheric Sounder by Istituto Nazionale di Geofisica e Vulcanologia (AIS-INGV) ionosondes installed at Rome (41.8°N, 12.5°E) and Gibilmanna (37.9°N, 14.0°E), Italy. We applied the height-time-intensity (HTI) methodology proposed by Haldoupis et al. (2006) to investigate how tides control the Es dynamics. As a whole, the HTI analysis showed that a well-defined semidiurnal periodicity characterizes the Es layer descent and occurrence for all the considered months, although in September some cases which showed a prevailing diurnal periodicity were recorded. Through the application of the wavelet analysis it was also found that the tidal oscillations shown by ftEs and h’Es are affected by a strong amplitude modulation with periods of several days but with important differences between the two parameters. This amplitude modulation is a proof that Es layers are indirectly affected by planetary waves through their nonlinear interaction with tides at lower altitudes; this nonlinear interaction produces the presence of secondary waves with frequencies that are the sum and difference of the primary waves frequencies involved in the interaction as proposed by Teitelbaum and Vial [1991]. This work adds to those that were already done by Haldoupis et al. (2004, 2006), and confirms that ionosonde data, especially those registered in summertime, can be used as a powerful tool for studying tidal and planetary waves properties, as well as their climatology, in the mesosphere-low-termosphere region.

  13. A conceptual framework to quantify the influence of convective boundary layer development on carbon dioxide mixing ratios

    NASA Astrophysics Data System (ADS)

    Pino, D.; Vilà-Guerau de Arellano, J.; Peters, W.; Schroter, J.; van Heerwaarden, C. C.; Krol, M.

    2011-12-01

    Interpretation of observed diurnal carbon dioxide (CO2) mixing ratios near the surface requires knowledge of the local dynamics of the planetary boundary layer. In this paper, we quantify the relationship between the boundary layer dynamics and the CO2 budget in convective conditions through a newly derived set of analytical equations. From these equations, we are able to quantify how uncertainties in boundary layer dynamical variables or in the morning CO2 distribution in the mixed-layer or in the free atmosphere influence the bulk CO2 mixing ratio. We find that the largest uncertainty incurred on the mid-day CO2 mixing ratio comes from the prescribed early morning CO2 mixing ratios in the stable boundary layer, and in the free atmosphere. Errors in these values influence CO2 mixing ratios inversely proportional to the boundary layer depth (h), just like uncertainties in the assumed initial boundary layer depth and surface CO2 flux. The influence of uncertainties in the boundary layer depth itself are one order of magnitude smaller. If we "invert" the problem and calculate CO2 surface exchange from observed or simulated CO2 mixing ratios, the sensitivities to errors in boundary layer dynamics also invert: they become linearly proportional to the boundary layer depth. We demonstrate these relations for a typical well characterized situation at the Cabauw tower in the Netherlands, and conclude that knowledge of the temperature and carbon dioxide vertical profiles in the early morning are of vital importance to correctly interpret observed CO2 mixing ratios during midday.

  14. A conceptual framework to quantify the influence of convective boundary layer development on carbon dioxide mixing ratios

    NASA Astrophysics Data System (ADS)

    Pino, D.; Vilà-Guerau de Arellano, J.; Peters, W.; Schröter, J.; van Heerwaarden, C. C.; Krol, M. C.

    2012-03-01

    Interpretation of observed diurnal carbon dioxide (CO2) mixing ratios near the surface requires knowledge of the local dynamics of the planetary boundary layer. In this paper, we study the relationship between the boundary layer dynamics and the CO2 budget in convective conditions through a newly derived set of analytical equations. From these equations, we are able to quantify how uncertainties in boundary layer dynamical variables or in the morning CO2 distribution in the mixed-layer or in the free atmosphere (FA) influence the bulk CO2 mixing ratio. We find that the largest uncertainty incurred on the mid-day CO2 mixing ratio comes from the prescribed early morning CO2 mixing ratios in the stable boundary layer, and in the free atmosphere. Errors in these values influence CO2 mixing ratios inversely proportional to the boundary layer depth (h), just like uncertainties in the assumed initial boundary layer depth and surface CO2 flux. The influence of uncertainties in the boundary layer depth itself is one order of magnitude smaller. If we "invert" the problem and calculate CO2 surface exchange from observed or simulated CO2 mixing ratios, the sensitivities to errors in boundary layer dynamics also invert: they become linearly proportional to the boundary layer depth. We demonstrate these relations for a typical well characterized situation at the Cabauw site in The Netherlands, and conclude that knowledge of the temperature and carbon dioxide profiles of the atmosphere in the early morning are of vital importance to correctly interpret observed CO2 mixing ratios during midday.

  15. Influence of Evaporating Droplets in the Turbulent Marine Atmospheric Boundary Layer

    NASA Astrophysics Data System (ADS)

    Peng, Tianze; Richter, David

    2017-08-01

    Sea-spray droplets ejected into the marine atmospheric boundary layer take part in a series of complex transport processes. By capturing the air-droplet coupling and feedback, we focus on how droplets modify the total heat transfer across a turbulent boundary layer. We implement a high-resolution Eulerian-Lagrangian algorithm with varied droplet size and mass loading in a turbulent open-channel flow, revealing that the influence from evaporating droplets varies for different dynamic and thermodynamic characteristics of droplets. Droplets that both respond rapidly to the ambient environment and have long suspension times are able to modify the latent and sensible heat fluxes individually, however the competing signs of this modification lead to an overall weak effect on the total heat flux. On the other hand, droplets with a slower thermodynamic response to the environment are less subjected to this compensating effect. This indicates a potential to enhance the total heat flux, but the enhancement is highly dependent on the concentration and suspension time.

  16. Influence of pressure gradient on streamwise skewness factor in turbulent boundary layer

    NASA Astrophysics Data System (ADS)

    Dróżdż, Artur

    2014-08-01

    The paper shows an effect of favourable and adverse pressure gradients on turbulent boundary layer. The skewness factor of streamwise velocity component was chosen as a measure of the pressure gradient impact. It appears that skewness factor is an indicator of convection velocity of coherent structures, which is not always equal to the average flow velocity. The analysis has been performed based upon velocity profiles measured with hot-wire technique in turbulent boundary layer with pressure gradient corresponding to turbomachinery conditions. The results show that the skewness factor decreases in the flow region subjected to FPG and increases in the APG conditions. The changes of convection velocity and skewness factor are caused by influence of large-scale motion through the mechanism called amplitude modulation. The large-scale motion is less active in FPG and more active in APG, therefore in FPG the production of vortices is random (there are no high and low speed regions), while in the APG the large-scale motion drives the production of vortices. Namely, the vortices appear only in the high-speed regions, therefore have convection velocity higher than local mean velocity. The convection velocity affects directly the turbulent sweep and ejection events. The more flow is dominated by large-scale motion the higher values takes both the convection velocity of small-scale structures and sweep events induced by them.

  17. Influence of emulsification process on the properties of Pickering emulsions stabilized by layered double hydroxide particles.

    PubMed

    Zhang, Nana; Zhang, Li; Sun, Dejun

    2015-04-28

    This paper reports the influence of emulsification process on the packing of layered double hydroxide (LDH) particles at the aqueous/oil phase interface and the properties of the resulting Pickering emulsions. Emulsions prepared by ultrasonication display superior long-term stability and gel-like characteristics at the dispersed phase volume fraction well below the random close packing limit, whereas emulsions with same compositions prepared by vortex mixing show some extent of sedimentation and liquid-like behaviors. Rheological measurements demonstrate that the zero-shear elastic modulus and yield stress of gel-like emulsions exhibit power-law dependences on particle concentration and independence on aqueous/oil phase ratio. The microstructural origin of this behavior is investigated by optical microscopy, revealing the droplets become strongly adhesive and a heterogeneous percolating network is formed among neighboring droplets. Fluorescent confocal microscopy measurements further confirm that the droplet adhesion is due to particle layers bridging opposite interfaces. In contrast, homogeneous, isolated, and densely packed droplets are present in emulsions prepared by vortex mixing, which results in these systems being dominantly viscous like the suspending fluid. This study shows that the emulsification process can be used as a trigger to modify long-term stability and rheology of solid-stabilized multiphase mixtures, which greatly expands their potential technological applications.

  18. Dust aerosol radiative effect and influence on urban atmospheric boundary layer

    NASA Astrophysics Data System (ADS)

    Zhang, L.; Chen, M.; Li, L.

    2007-11-01

    An 1.5-level-closure and 3-D non-stationary atmospheric boundary layer (ABL) model and a radiation transfer model with the output of Weather Research and Forecast (WRF) Model and lidar AML-1 are employed to simulate the dust aerosol radiative effect and its influence on ABL in Beijing for the period of 23-26 January 2002 when a dust storm occurred. The simulation shows that daytime dust aerosol radiative effect heats up the ABL at the mean rate of about 0.68 K/h. The horizontal wind speed from ground to 900 m layer is also overall increased, and the value changes about 0.01 m/s at 14:00 LT near the ground. At night, the dust aerosol radiative effect cools the ABL at the mean rate of -0.21 K/h and the wind speed lowers down at about -0.19 m/s at 02:00 LT near the ground.

  19. Influence of weak layer heterogeneity on slab avalanche release. Application to the evaluation of avalanche release depths.

    NASA Astrophysics Data System (ADS)

    Gaume, J.; Chambon, G.; Eckert, N.; Naaim, M.

    2012-04-01

    Slab avalanches are generally caused by the collapse of a weak layer underlying a cohesive slab. The two key ingredients for the mechanical description of such slab avalanche releases are the heterogeneity of the weak layer and the redistribution of stresses via the elasticity of the slab. The finite element code Cast3M is used to build a complete full-scale mechanical model of the slab-weak layer system including inertial effects. The weak layer is modeled as a cohesive Mohr-Coulomb interface with cohesion softening which accounts for shear-induced collapse. The overlying slab is represented by an elastic layer. The system is loaded by increasing the slope angle until rupture. We first study the influence of a single weak spot in the weak layer in order to validate the model against analytical solutions. The interaction between two weak spots is also analyzed. The case of heterogeneous weak layers represented through Gaussian stochastic distributions of the cohesion with a spherical spatial covariance is then studied. Several simulations for different realizations of the heterogeneity of the weak layer are carried out and the influence of slab depth and heterogeneity correlation length on avalanche release angle distributions is examined. In particular a heterogeneity smoothing effect caused by slab elasticity and characterized by a typical length scale of the system is evidenced. Finally the model is coupled with extreme snowfall distributions belonging to the GEV class, which allows to recover with very good accuracy release depth distributions obtained from field data.

  20. The Influence of Stable Boundary Layer Flows on Wind Turbine Fatigue Loads

    NASA Astrophysics Data System (ADS)

    Sim, C.; Basu, S.; Manuel, L.

    2008-12-01

    This study aims to address two main issues: (i) the generation of high-resolution four-dimensional inflow turbulence fields for a range of atmospheric stability conditions; and (ii) the comparison of fatigue loads on utility-scale turbines for different atmospheric flows (e.g., night-time stable boundary layers and associated low-level jet events). Presented here is an attempt to exploit recent computational, observational, and statistical developments with a view to gaining a better understanding of atmospheric boundary layer flows and its influence on wind turbine loads and design. Over the last two decades, there has been considerable wind energy development in the Great Plains region of the U.S. Nocturnal low-level jets (LLJs) occur quite frequently in this region. The peaks (local wind maxima) of LLJs are typically centered 100-1,000 m above the ground level and make the Great Plains' wind resources very favorable for wind energy production. At the same time, though, the presence of LLJs can significantly modify vertical shear and night-time turbulence environments in the vicinities of wind turbine hub heights and have detrimental effects on rotors. Thus, accurate numerical modeling and forecasting of LLJs are needed for robust wind turbine design and more reliable power-generation prediction. Since stable stratification is a prerequisite for the occurrence of nocturnal LLJs, this then requires an improved modeling capability of stable boundary layers (SBLs). By statistically merging different types of LES-generated flow data sets, it is hoped that a consistent atmospheric turbulence database can be created for various wind turbine loads studies planned. The need for such a database is important in simulating wind turbine loads since it can provide an opportunity to examine the influence of realistic inflow turbulence over the rotor in different atmospheric conditions. Wind turbine aeroelastic simulations are carried out; these are employed to quantify turbine

  1. Influences of spatial and temporal variability of sound scattering layers on deep diving odontocete behavior

    NASA Astrophysics Data System (ADS)

    Copeland, Adrienne Marie

    Patchiness of prey can influence the behavior of a predator, as predicted by the optimal foraging theory which states that an animal will maximize the energy gain while minimizing energy loss. While this relationship has been studied and is relatively well understood in some terrestrial systems, the same is far from true in marine systems. It is as important to investigate this in the marine realm in order to better understand predator distribution and behavior. Micronekton, organisms from 2-20 cm, might be a key component in understanding this as it is potentially an essential link in the food web between primary producers and higher trophic levels, including cephalopods which are primary prey items of deep diving odontocetes (toothed whales). My dissertation assesses the spatial and temporal variability of micronekton in the Northwestern Hawaiian Islands (NWHI), the Main Hawaiian Islands' (MHI) Island of Hawaii, and the Gulf of Mexico (GOM). Additionally it focuses on understanding the relationship between the spatial distribution of micronekton and environmental and geographic factors, and how the spatial and temporal variability of this micronekton relates to deep diving odontocete foraging. I used both an active Simrad EK60 echosounder system to collect water column micronekton backscatter and a passive acoustic system to detect the presence of echolocation clicks from deep diving beaked, sperm, and short-finned pilot whales. My results provide insight into what might be contributing to hotspots of micronekton which formed discrete layers in all locations, a shallow scattering layer (SSL) from the surface to about 200 m and a deep scattering layer (DSL) starting at about 350 m. In both the GOM and the NWHI, the bathymetry and proximity to shore influenced the amount of micronekton backscatter with locations closer to shore and at shallower depths having higher backscatter. We found in all three locations that some species of deep diving odontocetes were

  2. Influence of the microporous layer on carbon corrosion in the catalyst layer of a polymer electrolyte membrane fuel cell

    NASA Astrophysics Data System (ADS)

    Spernjak, Dusan; Fairweather, Joseph; Mukundan, Rangachary; Rockward, Tommy; Borup, Rodney L.

    2012-09-01

    Corrosion of the catalyst support reduces PEM fuel cell performance via catalyst layer (CL) degradation (loss of porosity, catalyst connectivity, and active catalyst surface area). Carbon corrosion was investigated in a segmented cell for cathode gas diffusion layers (GDLs) with and without a microporous layer (MPL) to investigate the spatial aspects of GDL effect on corrosion. The cells were aged in situ using an accelerated stress test (AST) for carbon-support corrosion consisting of consecutive holds at 1.3 V. Carbon corrosion was quantified by measuring CO2 evolution during the AST. Performance degradation was substantial both with and without cathode MPL, but the degradation of the CL after prolonged corrosion was lower in the presence of an MPL. This was corroborated by better cell performance, higher remaining Pt active area, lower kinetic losses and smaller Pt particle size. The cell with an MPL showed increasingly nonuniform current distribution with corrosion time, which is correlated to the distribution of the Pt particle growth across the active area. This cell also showed an increase in mass-transport resistance due to MPL degradation. Without an MPL, GDL carbon fibers caused localized thinning in the cathode CL, originating from the combined effects of compression and corrosion.

  3. Des Moines.

    ERIC Educational Resources Information Center

    Gore, Deborah, Ed.

    1988-01-01

    This document, intended for elementary students, contains articles and activities designed to acquaint young people with the history of Des Moines, Iowa. The articles are short, and new or difficult words are highlighted and defined for young readers. "The Raccoon River Indian Agency" discusses the archeological exploration of the indian…

  4. Des Moines.

    ERIC Educational Resources Information Center

    Gore, Deborah, Ed.

    1988-01-01

    This document, intended for elementary students, contains articles and activities designed to acquaint young people with the history of Des Moines, Iowa. The articles are short, and new or difficult words are highlighted and defined for young readers. "The Raccoon River Indian Agency" discusses the archeological exploration of the indian…

  5. Influence of refractive profile on the reaction of modes with sensor layer in the planar amplitude chemical sensor

    NASA Astrophysics Data System (ADS)

    Karasinski, Pawel; Rogozinski, Roman

    2003-04-01

    The paper presents the theoretical and experimental results involving the influence of refractive profile on the reaction of modes with the absorption sensor layer. The investigation studies concerned the planar structure in which the waveguides were producd using the ion-exchange technique in glass, and the sensor layer was produced with the application of sol-gel technology. The results of experimental investigations confirm the theoretical predictions.

  6. Growth of micro- and nanocrystalline dual layer composite diamond films by microwave plasma CVD: Influence of CO2 concentration on growth of nano-layer

    NASA Astrophysics Data System (ADS)

    Liu, Cong; Wang, Jian-Hua; Weng, Jun

    2015-01-01

    The high quality and smooth micro-and nanocrystalline dual layer composite diamond films were successfully prepared using H2/CH4/Ar/CO2 plasma with a synthesis process of nucleation/MCD growth/nucleation/NCD growth. The carbon dioxide content is demonstrated to be important in controlling the NCD layer grain size and growth rate. The influences of carbon dioxide concentration on the morphology, microstructure and growth rate of the deposited NCD layer are investigated by using scanning electron microscopy (SEM), X-ray diffraction (XRD) and Raman spectroscopy. It is found that the additional carbonaceous sources supplied by CO2 are favourable to increase the growth rate, and meanwhile, the oxygen related species generated would enhance the etching effect not only to eliminate the non-diamond phase of NCD but also to decrease the growth rate. The appropriate addition of CO2 can increase the high quality and growth rate, decrease the surface roughness. It is demonstrated that adding CO2 strongly affects the contents of various reaction species in plasma, which would determine the growth features of NCD layers. The deposited highly smooth and quality micro-/nano-crystal layered diamond film is also expected to be applicable in surface aroustic wave (SAW) devices and micro-electromechanical systems (MEMS).

  7. Influence of the summer marine layer on patterns of chaparral diversity in west central California

    NASA Astrophysics Data System (ADS)

    Vasey, M. C.; Parker, V.; Loik, M. E.; Holl, K. D.; Hiatt, S.

    2012-12-01

    The central coast of California is renowned for its high concentration of narrow endemic shrub species, particularly in maritime chaparral. We investigated the possible influence of the summer marine layer on patterns of chaparral diversity in this region. Using field meteorological stations, water potential measurements, and stable isotopes of carbon for Arctostaphylos species, we tested the hypothesis that there is a pronounced late dry season coast-to-interior moisture gradient at a regional scale which impacts the water relations of these evergreen shrubs. Concurrently, we sampled species composition in 87 0.1-ha chaparral stands throughout the region so that we could evaluate the relationship between species diversity patterns and environmental variables. We found a pronounced late dry season coast-to-interior moisture gradient in west central California. Coastal chaparral sites had significantly higher mean percent leaf wetness, lower vapor pressure deficit, and less negative atmospheric water potential than chaparral sites in the interior. Likewise, Arctostaphylos shrubs along the coast had significantly less negative stem water potential than congeners in the interior, and stable carbon isotopes demonstrated that interior shrubs have greater water use efficiency. Chaparral composition plots clustered into three groups which we characterized as maritime, transition, and interior. A principle components analysis demonstrated that these plots were most strongly associated with estimated dry season climate variables. Non-metric multi-dimensional scaling revealed that interior plots were least dissimilar whereas transition and maritime plots here highly dissimilar, suggesting that maritime and transition plots had greater beta diversity than interior plots. A multivariate analysis of dispersion confirmed that maritime and transition plots differed significantly from interior plots but not from each other. Using one-way ANOVA, we found that mean alpha diversity

  8. Finite element analysis of influence of passivation layer on Cu/low-k structure during thermosonic Cu wire bonding

    NASA Astrophysics Data System (ADS)

    Bai, Xiaoyi; Chang, Baohua; Du, Dong

    2014-08-01

    An incrementally coupled "mechanical-ultrasonic" finite element model, in which both the ultrasound vibration and the bonding force are considered simultaneously, is used to model the thermosonic Cu wire-bonding process on Cu/low-k structures and to study the influence of the passivation layer on the stress condition in the Cu/low-k layer. Results show that the passivation layer acts as a stress buffer layer during the wirebonding process. The introduction of a passivation layer alleviates some of the impact effect from the free air ball (FAB). Increasing the passivation thickness can lead to significant stress alleviation. However, as the elastic modulus of passivation increases, the alleviation effect increases notably at first and then decreases.

  9. Rotor wake segment influence on stator-surface boundary layer development in an axial-flow compressor stage

    NASA Astrophysics Data System (ADS)

    Hansen, J. L.; Okiishi, T. H.

    1987-06-01

    The boundary layer development on blades in an axial-flow compressor is an important design consideration. The influence of upstream-blade wake segments on downstream-blade boundary layers is not yet satisfactorily modeled for design purposes. Surface hot-film gages were used to sense the influence of rotor wake segments on stator-surface boundary layers at midspan in a low-speed, axial-flow compressor stage. It was clear that rotor wake segments moved along the stator-blade pressure and suction surfaces much like a turbulent spot would; the region of influence of each wake segment became larger further downstream. Boundary layer transition was not expected on the low-speed stator blade surface till about midchord. Nevertheless, the laminar boundary-layer flow on the forward portion of the stator blade appeared to be turbulent when a rotor wake segment was present. This periodic alternating of the stator boundary-layer flow was observed further aft on the blade also.

  10. Layer-by-layer assembly of mucin and chitosan--Influence of surface properties, concentration and type of mucin.

    PubMed

    Svensson, Olof; Lindh, Liselott; Cárdenas, Marité; Arnebrant, Thomas

    2006-07-15

    Bovine submaxillary mucin (BSM) and chitosan were used to build layer-by-layer structures on solid substrates. The build-up was monitored using in situ ellipsometry to obtain time resolved values of the thickness and adsorbed amount. Additionally surface morphology during build-up was studied by atomic force microscopy (AFM). It was found that the adsorbed amount of the film increases approximately linearly with each deposition cycle on hydrophobized silica whereas construction on silica was found not to be possible at the experimental conditions used. We conclude that sufficient amount of the first mucin layer is crucial for the subsequent multilayer formation. The complex build-up kinetics on hydrophobized silica is characterized by adsorption and redissolution processes and the overall growth is the sum of both processes. AFM imaging on hydrophobized silica also confirmed the presence of redissolution processes and chitosan addition led to a reduction both in the number of surface aggregates and in the roughness of the surface. The present work also shows that by adjusting the relative concentrations of the polyelectrolytes it is possible to change the growth rate considerably. The final structures after deposition of 8 bilayers were found to have a high content of water and film stability test revealed that a substantial amount dissolves when increasing electrolyte concentration or pH of the ambient solution. Human mucin from saliva (MUC5B) was also used to create multilayers with chitosan on hydrophobized silica and it was revealed that no redissolution appears to be present in this system.

  11. The biodegradation of layered silicates under the influence of cyanobacterial-actinomycetes associations

    NASA Astrophysics Data System (ADS)

    Ivanova, Ekaterina

    2013-04-01

    substrate. The associative growth of S. cyaneofuscatus and A. variabilis led to the transformation of minerals indicated by the significant decreasing of the intensity of the reflections of vermiculite as well as biotite. Reduction in the intensity of the basal reflections of vermiculite (d001, d004 and d005) three times indicates the process of biodestruction of this component of the rock. The formation of the swelling phase - the product of biotite transformation into the mica-vermicullite mixed-layer formation was revealed. The study demonstrates the differences in the transformation of clay minerals under the influence of cyanobacterial-actinomycetes association, depending on minerals' crystal chemistry and it's resistance to weathering. The rate of the process transformation of micas into the mixed-layer formation depends on their structure - trioctahedral mica (biotite, part of vermiculite sample) are transformated much faster than dioctahedral. The growth of associative thallus and monocultures of cyanobacterium and actinomycete promoted the removal of potassium (?), magnesium (Mg) and aluminum (Al) from the crystal lattice of the rock sample of vermiculite. Leaching of elements due to the influence of associative thallus exceeded the release of cations observed in the sample under the influence of the growth of cyanobacterium and streptomycete monocultures and in the control sample of vermiculite. Therefore, the association's biodegradation impact on the mineral structure was significantly greater than the influence of the monocultures of cyanobacteria and actinomycetes.

  12. Influences on the Height of the Stable Boundary Layer as seen in Large-Eddy Simulations

    SciTech Connect

    Kosovic, B; Lundquist, J K

    2004-03-29

    Numerical weather prediction (NWP) models and atmospheric dispersion models rely on parameterizations of planetary boundary layer height. In the case of a stable boundary layer, errors in boundary layer height estimation can result in gross errors in boundary-layer evolution and in prediction of turbulent mixing within the boundary layer. We use large-eddy simulations (LES) of moderately stable boundary layers to characterize the effects of various physical processes on stable boundary layers. The stable boundary layer height is assumed to be a function of surface friction velocity, geostrophic wind, Monin-Obukhov length, and the strength of the temperature inversion atop the stable boundary layer. This temperature inversion induces gravity waves with a frequency determined by the strength of the temperature inversion.

  13. Movement Rate Is Encoded and Influenced by Widespread, Coherent Activity of Cerebellar Molecular Layer Interneurons.

    PubMed

    Gaffield, Michael A; Christie, Jason M

    2017-05-03

    Inhibition from molecular layer interneurons (MLIs) is thought to play an important role in cerebellar function by sharpening the precision of Purkinje cell spike output. Yet the coding features of MLIs during behavior are poorly understood. To study MLI activity, we used in vivo Ca(2+) imaging in head-fixed mice during the performance of a rhythmic motor behavior, licking during water consumption. MLIs were robustly active during lick-related movement across a lobule-specific region of the cerebellum showing high temporal correspondence within their population. Average MLI Ca(2+) activity strongly correlated with movement rate but not to the intentional, or unexpected, adjustment of lick position or to sensory feedback that varied with task condition. Chemogenetic suppression of MLI output reduced lick rate and altered tongue movements, indicating that activity of these interneurons not only encodes temporal aspects of movement kinematics but also influences motor outcome pointing to an integral role in online control of rhythmic behavior.SIGNIFICANCE STATEMENT The cerebellum helps fine-tune coordinated motor actions via signaling from projection neurons called Purkinje cells. Molecular layer interneurons (MLIs) provide powerful inhibition onto Purkinje cells, but little is understood about how this inhibitory circuit is engaged during behavior or what type of information is transmitted through these neurons. Our work establishes that MLIs in the lateral cerebellum are broadly activated during movement with calcium activity corresponding to movement rate. We also show that suppression of MLI output slows and disorganizes the precise movement pattern. Therefore, MLIs are an important circuit element in the cerebellum allowing for accurate motor control. Copyright © 2017 the authors 0270-6474/17/374751-15$15.00/0.

  14. Sporadic E layer at mid-latitudes: average properties and influence of atmospheric tides

    NASA Astrophysics Data System (ADS)

    Pignalberi, A.; Pezzopane, M.; Zuccheretti, E.

    2014-11-01

    This paper describes a study of the daily variability shown by the main characteristics of the sporadic E (Es) layer, that is the top frequency (ftEs) and the lowest virtual height (h'Es). The study is based on ionograms recorded by the Advanced Ionospheric Sounder by the Istituto Nazionale di Geofisica e Vulcanologia (AIS-INGV) ionosondes installed in the ionospheric stations at Rome (41.8° N, 12.5° E) and Gibilmanna (37.9° N, 14.0° E), Italy, during the summer (June, July, August and September) of 2013, a year falling in the ascending phase of solar cycle 24. The ftEs presents a diurnal variation characterized by two maxima, the first around noon is very well defined and the second in the evening/night is much less defined; the amplitude of both maxima decreases from June to September accompanied by a general decrease of the ftEs values which is more pronounced in the daytime than in the nighttime. h'Es also presents a diurnal variation characterized by two maxima but, unlike ftEs, these present the same amplitude which is independent from the considered month. Assuming that both ftEs and h'Es trends are influenced by the atmospheric tides, the height-time-intensity (HTI) technique was applied to deeply investigate how these waves control the Es dynamics. The HTI study, along with a fast Fourier transform analysis, show that a well-defined semidiurnal periodicity characterizes the Es layer dynamics most accurately in June and July, while in August and September the daytime semidiurnal periodicity becomes weaker and the role of the diurnal periodicity is consequently highlighted.

  15. Corrosion inhibition performance of imidazolium ionic liquids and their influence on surface ferrous carbonate layer formation

    NASA Astrophysics Data System (ADS)

    Yang, Dongrui

    Corrosion inhibitors as effective anti-corrosion applications were widely studied and drawn much attention in both academe and industrial area. In this work, a systematic work, including inhibitors selection, anti-corrosion property and characterization, influence on scale formation, testing system design and so on, were reported. The corrosion inhibition performance of four imidazolium ionic liquids in carbon dioxide saturated NaCl solution was investigated by using electrochemical and surface analysis technologies. The four compounds are 1-ethyl-3-methylimidazolium chloride (a), 1-butyl-3-methylimidazolium chloride (b), 1-hexyl-3-methylimidazolium chloride (c), 1-decyl-3-methylimidazolium chloride (d). Under the testing conditions, compound d showed the highest inhibition efficiency and selected as the main object of further study. As a selected representative formula, 1-decyl-3-methylimidazolium chloride was studied in detail about its corrosion inhibition performance on mild steel in carbon dioxide saturated NaCl brine at pH 3.8 and 6.8. Electrochemical and surface analysis techniques were used to characterize the specimen corrosion process during the immersion in the blank and inhibiting solutions. The precorrosion of specimen surface showed significant and different influences on the anti-corrosion property of DMICL at pH 3.8 and 6.8. The corrosion inhibition efficiency (IE) was calculated based on parameters obtained from electrochemical techniques; the achieved IE was higher than 98% at the 25th hour for the steel with a well-polished surface at pH 3.8. The fitting parameters obtained from electrochemical data helped to account for the interfacial changes. As proved in previous research, 1-decyl-3-methylimidazolium chloride could be used as good corrosion inhibitors under certain conditions. However, under other conditions, such chemicals, as well as other species in oil transporting system, could be a factor influencing the evolution of protective surface

  16. Influence of wind velocity on pollen concentration in urban canopy layer

    NASA Astrophysics Data System (ADS)

    Pospisil, J.; Jícha, M.

    2009-09-01

    POLLEN RELEASE Temperature is the basic parameter for prediction of the beginning of the pollen season and identification days with good potential for pollen release. Different approaches are used for determination of the start of the pollen season: i) the sum of daily pollen counts = x criterion (Arnold 2002), ii) the mean temperature method during pre-defined period (Sparks, 2000), iii) the temperature sum method (Jones 1992). Another parameters influencing pollen release are: day light length, morning temperature gradient, relative humidity. The mentioned parameters enable to create the "statistical” model for determination of timing of pollen potential release. But, the correct determination of pollen release timing is only the first step to correct prediction of pollen concentration in air. The above mentioned collection of parameters isn't complete for correct pollen production prediction without inclusion of the actual wind velocity. The wind velocity directly influences the pollen release rate from mother plant and subsequently transport of pollen grains. From this reason, influence of wind conditions has to be considered as exactly as possible in complex prediction models. WIND VELOCITY AND POLLEN CONCENTRATION Results of in-situ measurements were used for carried out analysis of the relation between wind velocity and pollen concentration in an urban canopy layer. The mean daily wind velocities and the mean daily pollen concentrations were used as the input data describing the pollen season 2005 in an inner part of the city of Brno (pop. 400 000). The mean daily pollen concentrations were matched to corresponding mean daily wind velocity and depicted in graphs. This procedure was done for all locally monitored aeroallergens, namely Alnus, Ambrosia, Betula, Artemis, Corylus, Fraxinus, Poaceae and Quercus. Only days with significant pollen concentration (above 10% of maximal pollen season concentration) were considered for detail analysis. Clear

  17. Influence of a fat layer on the near infrared spectra of human muscle: quantitative analysis based on two-layered Monte Carlo simulations and phantom experiments

    NASA Technical Reports Server (NTRS)

    Yang, Ye; Soyemi, Olusola O.; Landry, Michelle R.; Soller, Babs R.

    2005-01-01

    The influence of fat thickness on the diffuse reflectance spectra of muscle in the near infrared (NIR) region is studied by Monte Carlo simulations of a two-layer structure and with phantom experiments. A polynomial relationship was established between the fat thickness and the detected diffuse reflectance. The influence of a range of optical coefficients (absorption and reduced scattering) for fat and muscle over the known range of human physiological values was also investigated. Subject-to-subject variation in the fat optical coefficients and thickness can be ignored if the fat thickness is less than 5 mm. A method was proposed to correct the fat thickness influence. c2005 Optical Society of America.

  18. Influence of a fat layer on the near infrared spectra of human muscle: quantitative analysis based on two-layered Monte Carlo simulations and phantom experiments

    NASA Technical Reports Server (NTRS)

    Yang, Ye; Soyemi, Olusola O.; Landry, Michelle R.; Soller, Babs R.

    2005-01-01

    The influence of fat thickness on the diffuse reflectance spectra of muscle in the near infrared (NIR) region is studied by Monte Carlo simulations of a two-layer structure and with phantom experiments. A polynomial relationship was established between the fat thickness and the detected diffuse reflectance. The influence of a range of optical coefficients (absorption and reduced scattering) for fat and muscle over the known range of human physiological values was also investigated. Subject-to-subject variation in the fat optical coefficients and thickness can be ignored if the fat thickness is less than 5 mm. A method was proposed to correct the fat thickness influence. c2005 Optical Society of America.

  19. Influence of the Entrainment Interface Layer on Cloud Microphysical Properties near Stratocumulus Top

    NASA Astrophysics Data System (ADS)

    Chuang, P. Y.; Carman, J. K.; Rossiter, D. L.

    2010-12-01

    Entrainment across the stratocumulus-topped boundary layer is a key process governing the cloud properties and evolution. This process is not well-represented even in high-resolution large-eddy simulations, in part due to the sharp gradients in temperature, buoyancy and (usually) humidity that occur at the top of the boundary layer. In summer 2008, the Physics of Stratocumulus Top (POST) field campaign conduct extensive measurements in the vicinity of cloud top, including the so-called entrainment interface layer or EIL that separates boundary layer and free tropospheric air. Roughly half of the fifteen flights occurred during the day (near solar noon) while the remaining flights occurred during late evening-to-night when solar input was minimal. A wide diversity of EIL properties has been revealed over the course of the campaign. EIL vertical thickness diagnosed using total water varies from fairly thin (~20 m) to very thick (>100 m). The thickness and intensity of the turbulent layer in this interfacial region also varies substantially, with the top of the significantly turbulent region ranging from 10 m to 50 m above cloud top. Shear in the vicinity of cloud top also varied strongly from day-to-day. While almost all cases exhibited strong jumps in potential temperature, there are a number of cases where the jump in total water was very small-to-none, and one case where total water was higher in the free troposphere by 1.4 g/kg. POST thus demonstrates that the cloud-top interfacial region exhibits a rich and diverse range of properties. This study focuses on how this EIL diversity affects the stratocumulus cloud itself. We build on our study of the EIL dynamic and thermodynamic properties to investigate the influence of the EIL on the microphysical properties of the stratocumulus in the vicinity of cloud top. Entrainment of the overlying warmer and (usually) drier air can strongly impact the amount of liquid water as well as the size and concentration of cloud

  20. The influence of the depth of k-core layers on the robustness of interdependent networks against cascading failures

    NASA Astrophysics Data System (ADS)

    Dong, Zhengcheng; Fang, Yanjun; Tian, Meng; Kong, Zhengmin

    The hierarchical structure, k-core, is common in various complex networks, and the actual network always has successive layers from 1-core layer (the peripheral layer) to km-core layer (the core layer). The nodes within the core layer have been proved to be the most influential spreaders, but there is few work about how the depth of k-core layers (the value of km) can affect the robustness against cascading failures, rather than the interdependent networks. First, following the preferential attachment, a novel method is proposed to generate the scale-free network with successive k-core layers (KCBA network), and the KCBA network is validated more realistic than the traditional BA network. Then, with KCBA interdependent networks, the effect of the depth of k-core layers is investigated. Considering the load-based model, the loss of capacity on nodes is adopted to quantify the robustness instead of the number of functional nodes in the end. We conduct two attacking strategies, i.e. the RO-attack (Randomly remove only one node) and the RF-attack (Randomly remove a fraction of nodes). Results show that the robustness of KCBA networks not only depends on the depth of k-core layers, but also is slightly influenced by the initial load. With RO-attack, the networks with less k-core layers are more robust when the initial load is small. With RF-attack, the robustness improves with small km, but the improvement is getting weaker with the increment of the initial load. In a word, the lower the depth is, the more robust the networks will be.

  1. Influence of layer charge and charge distribution of smectites on the flow behaviour and swelling of bentonites

    USGS Publications Warehouse

    Christidis, G.E.; Blum, A.E.; Eberl, D.D.

    2006-01-01

    The influence of layer charge and charge distribution of dioctahedral smectites on the rheological and swelling properties of bentonites is examined. Layer charge and charge distribution were determined by XRD using the LayerCharge program [Christidis, G.E., Eberl, D.D., 2003. Determination of layer charge characteristics of smectites. Clays Clay Miner. 51, 644-655.]. The rheological properties were determined, after sodium exchange using the optimum amount of Na2CO3, from free swelling tests. Rheological properties were determined using 6.42% suspensions according to industrial practice. In smectites with layer charges of - 0.425 to - 0.470 per half formula unit (phfu), layer charge is inversely correlated with free swelling, viscosity, gel strength, yield strength and thixotropic behaviour. In these smectites, the rheological properties are directly associated with the proportion of low charge layers. By contrast, in low charge and high charge smectites there is no systematic relation between layer charge or the proportion of low charge layers and rheological properties. However, low charge smectites yield more viscous suspensions and swell more than high charge smectites. The rheological properties of bentonites also are affected by the proportion of tetrahedral charge (i.e. beidellitic charge), by the existence of fine-grained minerals having clay size, such as opal-CT and to a lesser degree by the ionic strength and the pH of the suspension. A new method for classification of smectites according to the layer charge based on the XRD characteristics of smecites is proposed, that also is consistent with variations in rheological properties. In this classification scheme the term smectites with intermediate layer charge is proposed. ?? 2006 Elsevier B.V. All rights reserved.

  2. Influence of wet chemical treatments on the evolution of epoxy polymer layer surface roughness for use as a build-up layer

    NASA Astrophysics Data System (ADS)

    Siau, Sam; Vervaet, Alfons; Calster, Andre Van; Swennen, Ives; Schacht, Etienne

    2004-10-01

    The adhesion of plated metal layers to polymer surfaces is of prime importance for the reliability of interconnections in electronics. An increase in the roughness of the polymer surface, caused by chemical treatment, plays an important part in the adhesion strength of plated metal layers by increasing the total area of interface between both layers. Hence, the evolution of polymer surface roughness, with time, due to the chemical treatment is of prime importance for determining the reliability of interconnections. The surface roughness changes due to chemical treatment. In this paper, we consider wet solution swellers and oxidizers. These changes are examined by means of AFM roughness measurements. Each chemical treatment, or combination thereof in a certain sequence, has its influence on the evolution of the roughness. Swellers increase roughness over treatment time without etching the surface. Oxidizers, on the other hand, etch part of the surface away and have a more profound influence on roughness. The evolution of surface roughness with treatment time indicates the mechanisms that cause the formation of roughness on the surface. This work is an original contribution to the understanding of the evolution of roughness on photo-imageable dielectrics.

  3. Urban Heat Island and Its Influence on Atmospheric Boundary Layer Temperature Field

    NASA Astrophysics Data System (ADS)

    Kadygrov, N.; Kruchenitsky, G.; Lykov, A.

    2006-12-01

    The effect of megacity on atmospheric boundary layer (ABL) temperature is a well known phenomenon called "Urban Heat Island" revealed in increasing temperature over megacity relative to its suburb. Until recently the only way to investigate and gather the data about its vertical distribution was to observe temperature on the meteorological, TV towers and by radiosonde. The available information appears to be irregular in time and space. The situation has changed in recent years since the advent of temperature profiler based on microwave radiometer, which can produce the vertical distribution of ABL temperature up to 600 meters ASL with 5 minute sampling period. The station in the center of Moscow megacity and 2 observation sites near Moscow (20 km and 50 km away from city center) were equipped by MTP-5 radiometer in order to get quantitative estimations of the Heat Island Effect on ABL temperature field. Three sites were selected in order to look at transition from megacity to suburb. The main aim was not to get the climatological averages but to get the differences between Heat Island and its background (suburb). The period of observation was from beginning of 2000 till the middle of 2004. The ABL temperature model was developed separately for each station in the multiplicative manner as the product of seasonal and diurnal variations of ABL temperature in order to obtain the differences between Urban Heat Island and suburb ABL temperatures. As the result of data analysis, the amplitudes and phases of seasonal and diurnal harmonics, average annual noon temperature value, average temperature gradients and daily altitude-time crossection of ABL temperature were obtained. The analysis performed in this work has given us a better insight into the mechanism of Urban Heat Island influence on ABL temperature field with quantitative estimations of such influence.

  4. Influence de la dépendance en température des propriétés optiques des matériaux sur la force de Casimir

    NASA Astrophysics Data System (ADS)

    Joulain, K.; Henkel, C.; Greffet, J.-J.

    2006-10-01

    Nous évaluons la force de Casimir entre deux surfaces planes métalliques constituées d'argent. Nous prenons, pour effectuer cette évaluation, des propriétés optiques de l'argent à différentes températures [1]. Nous montrons que cette dépendance en température modifie la force de Casimir (de 0.2%) y compris à des distances inférieures à la longueur d'onde thermique.

  5. Comprendre l'influence des facteurs contextuels sur la participation communautaire à la santé : une étude de cas dans le district sanitaire de Tenkodogo, au Burkina Faso.

    PubMed

    Sombié, Issa; Ilboudo, David O S; Soubeiga, André Kamba; Samuelsen, Helle

    2015-08-07

    Le Burkina Faso met en œuvre depuis plusieurs années la stratégie de la participation communautaire. Des comités de gestion (CoGes) ont été mis en place dans les centres de santé de la première ligne et doivent participer aux prises de décisions. L'objectif principal de cette stratégie est de favoriser l'utilisation des services de santé et une adhésion massive des communautés aux activités de promotion de la santé. Seulement, on constate que les résultats escomptés par les autorités sanitaires tardent à se réaliser. Le présent article convoque les facteurs liés au contexte socioculturel du district sanitaire, pour analyser le phénomène de la participation communautaire.L'étude s'est déroulée dans le district sanitaire de Tenkodogo, situé dans la région administrative du Centre-est, à environ 190 km de la capitale. Cette étude exclusivement qualitative, a utilisé deux méthodes de collecte : les entretiens individuels et les focus groups. Les participants à l'étude sont les chefs de ménage (n = 48), les membres des CoGes (n = 10), les agents de santé (n = 8) et les agents de santé communautaire (n = 24). La méthode de l'analyse de contenu a été utilisée pour l'analyse des données.Les résultats de l'étude montrent que plusieurs facteurs socioculturels influencent la dynamique de la participation communautaire dans le district. Ce sont les conditions économiques, la perception négative des services de santé, les inégalités sociales de sexe et d'âge, le faible ancrage social des organisations communautaires, les rivalités inter-villages et les conflits coutumiers. L'étude relève également que les communautés ne perçoivent pas leur implication dans le processus décisionnel des services de santé comme une priorité. Leurs principales attentes s'orientent vers la disponibilité de soins de qualité et à coût réduit.

  6. Platelets to rings: Influence of sodium dodecyl sulfate on Zn-Al layered double hydroxide morphology

    SciTech Connect

    Yilmaz, Ceren; Unal, Ugur; Yagci Acar, Havva

    2012-03-15

    In the current study, influence of sodium dodecyl sulfate (SDS) on the crystallization of Zn-Al layered double hydroxide (LDH) was investigated. Depending on the SDS concentration coral-like and for the first time ring-like morphologies were obtained in a urea-hydrolysis method. It was revealed that the surfactant level in the starting solution plays an important role in the morphology. Concentration of surfactant equal to or above the anion exchange capacity of the LDH is influential in creating different morphologies. Another important parameter was the critical micelle concentration (CMC) of the surfactant. Surfactant concentrations well above CMC value resulted in ring-like structures. The crystallization mechanism was discussed. - Graphical abstract: Dependence of ZnAl LDH Morphology on SDS concentration. Highlights: Black-Right-Pointing-Pointer In-situ intercalation of SDS in ZnAl LDH was achieved via urea hydrolysis method. Black-Right-Pointing-Pointer Morphology of ZnAl LDH intercalated with SDS depended on the SDS concentration. Black-Right-Pointing-Pointer Ring like morphology for SDS intercalated ZnAl LDH was obtained for the first time. Black-Right-Pointing-Pointer Growth mechanism was discussed. Black-Right-Pointing-Pointer Template assisted growth of ZnAl LDH was proposed.

  7. Caribbean sclerosponges reveal solar influence on mixed layer temperatures for the past 500 years

    NASA Astrophysics Data System (ADS)

    Estrella, J.; Winter, A.; Sherman, C.; Mangini, A.

    2013-05-01

    We present a high-resolution (annual) record of the Caribbean mixed layer temperature at different depths derived from oxygen isotopic ratios obtained from the sclerosponge Ceratoporella nicholsoni. Sclerosponges precipitate their calcium carbonate skeleton in equilibrium with their surrounding environment and are capable of living at depths down to 200 m. The sponges for this project were collected off the coasts of Puerto Rico and the US Virgin Islands in northeastern Caribbean Sea. The records obtained extend from the early 1500's to the present and suggest that the northeastern Caribbean was 1 - 2 °C cooler than present during the Little Ice Age. Wavelet time-series analysis of our sclerosponge records indicates that when the total solar irradiance (TSI) reaches a threshold value of 1365.29 Wm-2 there is a coupling of the eleven-year sunspot cycle with SST variability such that TSI was able to explain more than 35% of the decadal variability observed in our records. Our findings also suggest a local SST response to solar influence of 0.62 °C (Wm-2)-1 for the 20th century which is similar to previously published global values of climate sensitivity for solar radiation.

  8. Anomalous or regular capacitance? The influence of pore size dispersity on double-layer formation

    NASA Astrophysics Data System (ADS)

    Jäckel, N.; Rodner, M.; Schreiber, A.; Jeongwook, J.; Zeiger, M.; Aslan, M.; Weingarth, D.; Presser, V.

    2016-09-01

    The energy storage mechanism of electric double-layer capacitors is governed by ion electrosorption at the electrode surface. This process requires high surface area electrodes, typically highly porous carbons. In common organic electrolytes, bare ion sizes are below one nanometer but they are larger when we consider their solvation shell. In contrast, ionic liquid electrolytes are free of solvent molecules, but cation-anion coordination requires special consideration. By matching pore size and ion size, two seemingly conflicting views have emerged: either an increase in specific capacitance with smaller pore size or a constant capacitance contribution of all micro- and mesopores. In our work, we revisit this issue by using a comprehensive set of electrochemical data and a pore size incremental analysis to identify the influence of certain ranges in the pore size distribution to the ion electrosorption capacity. We see a difference in solvation of ions in organic electrolytes depending on the applied voltage and a cation-anion interaction of ionic liquids in nanometer sized pores.

  9. Assessing the Influence of Adsorbed-State Conformation on the Bioactivity of Adsorbed Enzyme Layers

    PubMed Central

    Fears, Kenan P.; Latour, Robert A.

    2013-01-01

    Systems using immobilized enzymes are attractive for a wide range of industrial and medical applications because they allow for the fabrication of stable, reusable substrates with highly specific functionality. The performance of these systems is greatly dependent upon the orientation and conformation of the adsorbed enzymes. To investigate these relationships, we have developed and applied methods to quantitatively assess the secondary structure of adsorbed enzyme layers on planar surfaces using circular dichroism (CD) spectroscopy and evaluate their bioactivity using colorimetric assays. These combined measurements provide molecular-level insights regarding whether observed changes in adsorbed enzyme bioactivity are due to the adsorbed orientation of an enzyme or adsorption-induced changes in its conformation. Using this approach, we investigated the adsorption behavior of lysozyme (HEWL), xylanase (XYL), and glucose oxidase (GOx) on OH-, CH3-, NH2-, and COOH-terminated alkanethiol self-assembled monolayer (SAM) surfaces. The bioactivities of the small enzymes, HEWL and XYL, had pronounced variations between the different SAM surfaces despite their structural stability, highlighting the role of adsorbed orientation on bioactivity. In contrast, GOx, which is a much larger enzyme, exhibited wide variations in both its structure and bioactivity after adsorption, with adsorption-induced conformational changes actually enhancing its bioactivity. These results provide new insights into protein-surface interactions at the molecular level and demonstrate that adsorption can either promote or inhibit bioactivity depending on how the surface chemistry influences the orientation and conformational state of the enzyme on the surface. PMID:19499935

  10. The Characters of Dry Soil Layer on the Loess Plateau in China and Their Influencing Factors.

    PubMed

    Yan, Weiming; Deng, Lei; Zhong, Yangquanwei; Shangguan, Zhouping

    2015-01-01

    A dry soil layer (DSL) is a common soil desiccation phenomenon that generally forms at a particular depth in the soil profile because of climatic factors and poor land management, and this phenomenon can influence the water cycle and has been observed on the Loess Plateau of China and other similar regions around the world. Therefore, an investigation of the DSL formation depth (DSLFD), thickness (DSLT) and mean water content (MWDSL) on the Loess Plateau can provide valuable information. This paper synthesized 69 recent publications (1,149 observations of DSLs from 73 sites) that focused on DSLs in this region, and the results indicated that DSLs are significantly affected by climatic and vegetation factors. The mean annual precipitation had a significant positive relationship with DSLFD (p = 0.0003) and MWDSL (p<0.0001) and a negative relationship with DSLT (p = 0.0071). Crops had the lowest DSLT and highest MWDSL values compared with other vegetation types. A significant correlation was observed between the occurrence of DSLs and the years since planting for grasses, shrubs, trees and orchards, and the severity of DSLs increased with increasing planting years and wheat yield. Our results suggest that optimizing land-use management can mitigate DSL formation and development on the Loess Plateau. Understanding the dominant factors affecting DSLs will provide information for use in guidelines for the sustainable development of economies and restoration of natural environments experiencing water deficiencies.

  11. The Characters of Dry Soil Layer on the Loess Plateau in China and Their Influencing Factors

    PubMed Central

    Yan, Weiming; Deng, Lei; Zhong, Yangquanwei; Shangguan, Zhouping

    2015-01-01

    A dry soil layer (DSL) is a common soil desiccation phenomenon that generally forms at a particular depth in the soil profile because of climatic factors and poor land management, and this phenomenon can influence the water cycle and has been observed on the Loess Plateau of China and other similar regions around the world. Therefore, an investigation of the DSL formation depth (DSLFD), thickness (DSLT) and mean water content (MWDSL) on the Loess Plateau can provide valuable information. This paper synthesized 69 recent publications (1,149 observations of DSLs from 73 sites) that focused on DSLs in this region, and the results indicated that DSLs are significantly affected by climatic and vegetation factors. The mean annual precipitation had a significant positive relationship with DSLFD (p = 0.0003) and MWDSL (p<0.0001) and a negative relationship with DSLT (p = 0.0071). Crops had the lowest DSLT and highest MWDSL values compared with other vegetation types. A significant correlation was observed between the occurrence of DSLs and the years since planting for grasses, shrubs, trees and orchards, and the severity of DSLs increased with increasing planting years and wheat yield. Our results suggest that optimizing land-use management can mitigate DSL formation and development on the Loess Plateau. Understanding the dominant factors affecting DSLs will provide information for use in guidelines for the sustainable development of economies and restoration of natural environments experiencing water deficiencies. PMID:26241046

  12. Thermal Infrared Emission Spectra of Terrestrial Exoplanets Influenced by Multi-layer Clouds

    NASA Astrophysics Data System (ADS)

    Schreier, Franz; Vasquez, Mayte; Gimeno Garcia, Sebastian; Kitzmann, Daniel

    2016-04-01

    Clouds play an important role in the radiative transfer of planetary atmospheres: they are key elements of the climate system and influence the planet's spectral appearance. Given the thousands of exoplanets discovered so far, including some dozens of Earth-sized exoplanets, the feasibility of remote sensing of exoplanet atmospheres is attracting increasing attention. Here we present a study of the thermal emission of cloud-covered Earth-like exoplanets orbiting in the habitable zone of F, G, K, and M-type stars. A line-by-line model for molecular absorption has been coupled to a discrete ordinate multiple scattering radiative transfer solver. Pressure, temperature, and molecular concentration profiles were taken from a consistent radiative-convective climate model including a parameterized cloud description (Kitzmann et al., A&A, 2010). The main focus of the current work is the impact of multi-layer clouds on emission spectra in the thermal infrared. The effects of low-level water clouds and high level ice clouds simultaneously on signatures of H2O, CO2, O3, etc will be studied for various resolutions. Furthermore, comparisons with spectra resulting from a low-resolution code will be shown.

  13. Influence of electron transport layer thickness on optical properties of organic light-emitting diodes

    NASA Astrophysics Data System (ADS)

    Liu, Guohong; Liu, Yong; Li, Baojun; Zhou, Xiang

    2015-06-01

    We investigate experimentally and theoretically the influence of electron transport layer (ETL) thickness on properties of typical N,N'-diphenyl-N,N'-bis(1-naphthyl)-[1,1'-biphthyl]-4,4'-diamine (NPB)/tris-(8-hydroxyquinoline) aluminum (Alq3) heterojunction based organic light-emitting diodes (OLEDs), where the thickness of ETL is varied to adjust the distance between the emitting zone and the metal electrode. The devices showed a maximum current efficiency of 3.8 cd/A when the ETL thickness is around 50 nm corresponding to an emitter-cathode distance of 80 nm, and a second maximum current efficiency of 2.6 cd/A when the ETL thickness is around 210 nm corresponding to an emitter-cathode distance of 240 nm. We adopt a rigorous electromagnetic approach that takes parameters, such as dipole orientation, polarization, light emitting angle, exciton recombination zone, and diffusion length into account to model the optical properties of devices as a function of varying ETL thickness. Our simulation results are accurately consistent with the experimental results with a widely varying thickness of ETL, indicating that the theoretical model may be helpful to design high efficiency OLEDs.

  14. Influence of electron transport layer thickness on optical properties of organic light-emitting diodes

    SciTech Connect

    Liu, Guohong; Liu, Yong; Li, Baojun; Zhou, Xiang

    2015-06-07

    We investigate experimentally and theoretically the influence of electron transport layer (ETL) thickness on properties of typical N,N′-diphenyl-N,N′-bis(1-naphthyl)-[1,1′-biphthyl]-4,4′-diamine (NPB)/tris-(8-hydroxyquinoline) aluminum (Alq{sub 3}) heterojunction based organic light-emitting diodes (OLEDs), where the thickness of ETL is varied to adjust the distance between the emitting zone and the metal electrode. The devices showed a maximum current efficiency of 3.8 cd/A when the ETL thickness is around 50 nm corresponding to an emitter-cathode distance of 80 nm, and a second maximum current efficiency of 2.6 cd/A when the ETL thickness is around 210 nm corresponding to an emitter-cathode distance of 240 nm. We adopt a rigorous electromagnetic approach that takes parameters, such as dipole orientation, polarization, light emitting angle, exciton recombination zone, and diffusion length into account to model the optical properties of devices as a function of varying ETL thickness. Our simulation results are accurately consistent with the experimental results with a widely varying thickness of ETL, indicating that the theoretical model may be helpful to design high efficiency OLEDs.

  15. Ab-initio investigation of the influence of chemical compounds on graphene layer properties in fabricated IR detector

    NASA Astrophysics Data System (ADS)

    Ruta, L.; Wozny, J.; Szczecinska, N.; Lisik, Z.

    2016-11-01

    In this work, the influence of H2O, NaOH and propanol on properties of graphene layer placed on SiO2 has been investigated. These chemical particles are present during technological steps required for a device fabrication and may lead to significant changes of graphene properties. The investigation has been done by means of ab-initio simulation based on the DFT method. A MedeA-VASP package was used to investigate behavior of graphene layer in the vicinity of chemical compounds. Presented studies show that properties of graphene are significantly modified when particles of H2O and NaOH are captured in-between graphene layer and SiO2. Special attention should be paid to NaOH which, according to simulations, decays and modifies the properties of graphene layer.

  16. Influence of the chemical nature of implanted ions on the structure of a silicon layer damaged by implantation

    SciTech Connect

    Shcherbachev, K. D. Voronova, M. I.; Bublik, V. T.; Mordkovich, V. N. Pazhin, D. M.; Zinenko, V. I.; Agafonov, Yu. A.

    2013-12-15

    The influence of the implantation of silicon single crystals by fluorine, nitrogen, oxygen, and neon ions on the distribution of strain and the static Debye-Waller factor in the crystal lattice over the implanted-layer depth has been investigated by high-resolution X-ray diffraction. The density depth distribution in the surface layer of native oxide has been measured by X-ray reflectometry. Room-temperature implantation conditions have ensured the equality of the suggested ranges of ions of different masses and the energies transferred by them to the target. It is convincingly shown that the change in the structural parameters of the radiation-damaged silicon layer and the native oxide layer depend on the chemical activity of the implanted ions.

  17. Numerical study on the standing morphology of an oblique detonation wave under the influence of an incoming boundary layer

    NASA Astrophysics Data System (ADS)

    Zhou, Jin; Liu, Yu; Lin, Zhi-yong

    2015-01-01

    The influence of an incoming boundary layer to the standing morphology of an oblique detonation wave (ODW) induced by a compression ramp is numerically studied in this paper. The Spalart-Allmaras (SA) turbulence model is used to perform simulation of detonationboundary- layer interactions. Three different wall conditions are applied to realize control on the boundary-layer separation scales. Accordingly, different standing morphologies of the ODWs are obtained, including smooth ODW (without transverse wave) under no-slip, adiabatic wall condition with large-scale separation, abrupt ODW (with transverse wave) under no-slip, cold wall condition with moderate-scale separation, and bow-shaped detached ODW under slipwall condition without a boundary layer.

  18. Influence of osmotic stress on the profile and gene expression of surface layer proteins in Lactobacillus acidophilus ATCC 4356.

    PubMed

    Palomino, María Mercedes; Waehner, Pablo M; Fina Martin, Joaquina; Ojeda, Paula; Malone, Lucía; Sánchez Rivas, Carmen; Prado Acosta, Mariano; Allievi, Mariana C; Ruzal, Sandra M

    2016-10-01

    In this work, we studied the role of surface layer (S-layer) proteins in the adaptation of Lactobacillus acidophilus ATCC 4356 to the osmotic stress generated by high salt. The amounts of the predominant and the auxiliary S-layer proteins SlpA and SlpX were strongly influenced by the growth phase and high-salt conditions (0.6 M NaCl). Changes in gene expression were also observed as the mRNAs of the slpA and slpX genes increased related to the growth phase and presence of high salt. A growth stage-dependent modification on the S-layer protein profile in response to NaCl was observed: while in control conditions, the auxiliary SlpX protein represented less than 10 % of the total S-layer protein, in high-salt conditions, it increased to almost 40 % in the stationary phase. The increase in S-layer protein synthesis in the stress condition could be a consequence of or a way to counteract the fragility of the cell wall, since a decrease in the cell wall thickness and envelope components (peptidoglycan layer and lipoteichoic acid content) was observed in L. acidophilus when compared to a non-S-layer-producing species such as Lactobacillus casei. Also, the stationary phase and growth in high-salt medium resulted in increased release of S-layer proteins to the supernatant medium. Overall, these findings suggest that pre-growth in high-salt conditions would result in an advantage for the probiotic nature of L. acidophilus ATCC 4356 as the increased amount and release of the S-layer might be appropriate for its antimicrobial capacity.

  19. Influence Of Clear-cutting On Thermal and hydrological Regime In The Active Layer Near Yakutsk, Eastern Siberia

    NASA Astrophysics Data System (ADS)

    Iwahana, G.; Kobayashi, Y.; Machimura, T.; Fedorov, A. N.; Fukuda, M.

    2004-12-01

    Thermal and hydrological conditions in the active layer were investigated simultaneously at a mature larch forest (control site) and a cutover, which experienced clear-cutting in November 2000 during the thawing periods from 2001 to 2003, near Yakutsk, Eastern Siberia. The two sites were located about 100m apart and the cutover was formerly a part of the control larch forest site. The aims were to clarify the characteristics of heat and water budget in the active layer, and to assess the influence of clear-cutting on permafrost and active layer conditions, based on field observations at both intact and clear-cut forest. Clear-cutting enhanced ground thawing and the difference in the active layer thickness between the forest and the cutover (1-year) was 14cm. The soil water content drastically decreased at the forest, while that at the cutover was retained in during the first thawing season after clear-cutting. Marked changes in the active layer conditions were limited only to the first thawing season. The difference in the maximum thaw depth did not expand significantly in the second thawing season despite the increased ground heat flux at the cutover site. Thermal and hydrological analyses of the active layer revealed that the storage of latent heat was a predominant component in the energy balance in the active layer. Thus, the soil moisture condition, especially spring ice content in the active layer, plays an important role in controlling the energy balance of the active layer. Further increases in the maximum thaw depth at the cutover site were inhibited by the thermal inertial effect of the larger amount of ice in the second spring after disturbance.

  20. The influence of boundary layers on supersonic inlet flow unstart induced by mass injection

    NASA Astrophysics Data System (ADS)

    Do, Hyungrok; Im, Seong-Kyun; Mungal, M. Godfrey; Cappelli, Mark A.

    2011-09-01

    A transverse jet is injected into a supersonic model inlet flow to induce unstart. Planar laser Rayleigh scattering from condensed CO2 particles is used to visualize flow dynamics during the unstart process, while in some cases, wall pressure traces are simultaneously recorded. Studies conducted over a range of inlet configurations reveal that the presence of turbulent wall boundary layers strongly affect the unstart dynamics. It is found that relatively thick turbulent boundary layers in asymmetric wall boundary layer conditions prompt the formation of unstart shocks; in symmetric boundary conditions lead to the propagation of pseudo-shocks; and in both cases facilitate fast inlet unstart, when compared with thin, laminar boundary layers. Incident shockwaves and associated reflections are found to affect the speed of pressure disturbances. These disturbances, which induce boundary layer separation, are found to precede the formation of unstart shocks. The results confirm the importance of and need to better understand shock-boundary layer interactions in inlet unstart dynamics.

  1. Characterizing the Influence of the General Circulation on Marine Boundary Layer Clouds

    NASA Technical Reports Server (NTRS)

    Rozendaal, Margaret A.; Rossow, William B.; Hansen, James E. (Technical Monitor)

    2001-01-01

    The seasonal and intraseasonal variability of boundary layer cloud in the subtropical eastern oceans are studied using combined data from the International Satellite Cloud Climatology Project (ISCCP) and the European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis. Spectral analysis reveals that most of the time variability of cloud properties occurs on seasonal to annual time scales. The variance decreases one to two orders of magnitude for each decade of time scale decrease, indicating that daily to monthly time scales have smaller, but non-negligible variability. The length of these dominant time scales suggests that the majority of the variability is influenced by the general circulation and its interaction with boundary layer turbulence, rather than a product of boundary layer turbulence alone. Previous datasets have lacked the necessary resolution in either time or in space to properly characterize variability on synoptic scales; this is remedied by using global satellite-retrieved cloud properties. We characterize the intraseasonal subtropical cloud variability in both hemispheres and in different seasons. In addition to cloud fraction, we examine variability of cloud optical thickness - cloud top pressure frequency distributions. Despite the large concentration of research on the variability of Northern Hemisphere (NH) regions during summer, it is noted that the largest amplitude intraseasonal variability in the NH regions occurs during local winter. The effect of intraseasonal variability on the calculation and interpretation of seasonal results is investigated. Decreases in seasonally averaged cloud cover, optical thickness and cloud top pressure from the May-through-September season to the November-through-March season are most apparent in the NH regions. Further analysis indicates that these changes are due to an increase in frequency, but a decrease in the persistence of synoptic events. In addition, changes in cloud top pressure and

  2. Influence of interdiffusion layer on magnetostriction of Fe/CoNbZr multilayers

    NASA Astrophysics Data System (ADS)

    Ż; uberek, R.; Szymczak, H.; Krishnan, R.; Tessier, M.

    1994-05-01

    The results of measurements of the magnetostriction constant λ S of multilayer Fe/CoNbZr sputtered films are reported, performed at room temperature using the strain-modulated ferromagnetic resonance method. Experimental evidence for an interdiffusion layer in the multilayer with iron layer thickness of 12 nm is demonstrated. The magnetostriction of the total multilayer is determined by the balance in magnetostriction among Fe, CoNbZr and the interdiffusion layer.

  3. The sub-ice platelet layer and its influence on freeboard to thickness conversion of Antarctic sea ice

    NASA Astrophysics Data System (ADS)

    Price, D.; Rack, W.; Langhorne, P. J.; Haas, C.; Leonard, G.; Barnsdale, K.

    2014-02-01

    This is an investigation to quantify the influence of the sub-ice platelet layer on satellite measurements of total freeboard and their conversion to thickness of Antarctic sea ice. The sub-ice platelet layer forms as a result of the seaward advection of supercooled ice shelf water from beneath ice shelves. This ice shelf water provides an oceanic heat sink promoting the formation of platelet crystals which accumulate at the sea ice-ocean interface. The build-up of this porous layer increases sea ice freeboard, and if not accounted for, leads to overestimates of sea ice thickness from surface elevation measurements. In order to quantify this buoyant effect, the solid fraction of the sub-ice platelet layer must be estimated. An extensive in situ data set measured in 2011 in McMurdo Sound in the south-western Ross Sea is used to achieve this. We use drill-hole measurements and the hydrostatic equilibrium assumption to estimate a mean value for the solid fraction of this sub-ice platelet layer of 0.16. This is highly dependent upon the uncertainty in sea ice density. We test this value with independent Global Navigation Satellite System (GNSS) surface elevation data to estimate sea ice thickness. We find that sea ice thickness can be overestimated by up to 19%, with a mean deviation of 12% as a result of the influence of the sub-ice platelet layer. It is concluded that in close proximity to ice shelves this influence should be considered universally when undertaking sea ice thickness investigations using remote sensing surface elevation measurements.

  4. The sub-ice platelet layer and its influence on freeboard to thickness conversion of Antarctic sea ice

    NASA Astrophysics Data System (ADS)

    Price, D.; Rack, W.; Langhorne, P. J.; Haas, C.; Leonard, G.; Barnsdale, K.

    2014-06-01

    This is an investigation to quantify the influence of the sub-ice platelet layer on satellite measurements of total freeboard and their conversion to thickness of Antarctic sea ice. The sub-ice platelet layer forms as a result of the seaward advection of supercooled ice shelf water from beneath ice shelves. This ice shelf water provides an oceanic heat sink promoting the formation of platelet crystals which accumulate at the sea ice-ocean interface. The build-up of this porous layer increases sea ice freeboard, and if not accounted for, leads to overestimates of sea ice thickness from surface elevation measurements. In order to quantify this buoyant effect, the solid fraction of the sub-ice platelet layer must be estimated. An extensive in situ data set measured in 2011 in McMurdo Sound in the southwestern Ross Sea is used to achieve this. We use drill-hole measurements and the hydrostatic equilibrium assumption to estimate a mean value for the solid fraction of this sub-ice platelet layer of 0.16. This is highly dependent upon the uncertainty in sea ice density. We test this value with independent Global Navigation Satellite System (GNSS) surface elevation data to estimate sea ice thickness. We find that sea ice thickness can be overestimated by up to 19%, with a mean deviation of 12% as a result of the influence of the sub-ice platelet layer. It is concluded that within 100 km of an ice shelf this influence might need to be considered when undertaking sea ice thickness investigations using remote sensing surface elevation measurements.

  5. The influence of seagrass on shell layers and Florida Bay mudbanks

    USGS Publications Warehouse

    Prager, E.J.; Halley, R.B.

    1999-01-01

    Aerial photography indicates that sometime since the early 1970's, an emergent ridge of shell debris developed on a mudbank north of Calusa Key in Florida Bay. Coarse shell deposits on and within the Bay's shallow mudbanks are believed to be the product of transport during major storm events and subsequent winnowing. However, shell material from the ridge contains nuclear bomb 14C, supporting formation within the past 30 years and the last major hurricanes to influence Florida Bay were Donna and Betsy (1960 and 1965). Results from this study suggest that the Calusa ridge and other coarse shell deposits in Florida Bay can result from, 1) periodic seagrass mortality and wave-induced transport during frequent winter cold fronts and/or 2) mollusc blooms and subsequent burial. A survey of bottom types indicates that dense to intermediate beds of seagrass, mainly Thalassia testudinum (turtle grass), occur within the shallow basins of western Florida Bay and along the margins of Bay mudbanks. Wave measurements and modeling indicate that Thalassia along mudbank margins can reduce incoming wave-energy by over 80%. Seagrass beds also host particularly dense populations of molluscs from periodic 'blooms' and are believed to be the major source of coarse sediments in the Bay. Thus, if bank-edge seagrass dies, sediments, including shell debris, become exposed and subject to greatly increased wave energy. Modeling indicates that winds typical of winter cold fronts in South Florida can produce near-bottom velocities and shear stress at a grass-free bank edge which are sufficient to transport coarse carbonate grains. Shell layers found at depth in mudbank cores can also be explained by previous episodes of sediment accretion over mollusc-rich seagrass beds or grass bed mortality at the edge of a mudbank and shell transport during cold front passage. The latter implies that mortality of marginal seagrass beds has occurred throughout the history of Florida Bay and that the

  6. The Influence of High Aerosol Concentration on Atmospheric Boundary Layer Temperature Stratification

    SciTech Connect

    Khaykin, M.N.; Kadygrove, E.N.; Golitsyn, G.S.

    2005-03-18

    Investigations of the changing in the atmospheric boundary layer (ABL) radiation balance as cased by natural and anthropogenic reasons is an important topic of the U.S. Department of Energy's Atmospheric Radiation Measurement (ARM) program. The influence of aerosol on temperature stratification of ABL while its concentration was extremely high within a long period of time was studied experimentally. The case was observed in Moscow region (Russia) with the transport of combustion products from peat-bog and forest fires in July-September, 2002. At this time the visibility was some times at about 100-300 m. Aerosol concentration measured by Moscow University Observatory and A.M. Obukhov Institute of Atmospheric Physics field station in Zvenigorod (55.7 N; 36.6 E) for several days was in 50-100 times more than background one (Gorchakov at al 2003). The high aerosol concentration can change the radiation balance at ABL, and so to change thermal stratification in ABL above the mega lopolis. For the analysis the data were used of synchronous measurements by MTP-5 (Microwave Temperature Profiler operating at wavelength 5 mm) in two locations, namely: downtown Moscow and country-side which is 50 km apart to the West (Zvenigorod station). (Kadygrov and Pick 1998; Westwater at al 1999; Kadygrov at al 2002). Zvenigorod station is located in strongly continental climate zone which is in between of the climates of ARM sites (NSANorth Slope of Alaska and SGP-Southern Great Plains). The town of Zvenigorod has little industry, small traffic volume and topography conductive to a good air ventilation of the town. For these reasons Zvenigorod can be considered as an undisturbed rural site. For the analysis some days were chosen with close meteorological parameters (average temperature, humidity, wind, pressure and cloud form) but strongly differing in aerosol concentration level.

  7. Influence des macles sur le courant critique de transport selon c et sur la ligne d'irréversibilité dans les plans ab étudiée dans des échantillons monodomaines texturés d'YBaCuO

    NASA Astrophysics Data System (ADS)

    Sanfilippo, S.; Sulpice, A.; Bourgault, D.; Villard, C.; Gautier-Picard, P.; Chaud, X.; Beaugnon, E.; Tournier, R.

    1998-02-01

    Direct transport measurements at 77 K of the critical current density along the c-axis (J_c) and magnetic measurements are performed on the same bulk textured single domain YBaCuO samples with the longest dimension along the c-axis. A strong influence of the Twin Planes (TP) on J_c and on the ab-plane irreversibility line B(T^*) is reported when the field is rotated in the ab-planes perpendicularly to the c-axis. The different unusual behaviors observed for J_c and the B(T^*), depending on the range of temperature and field are explained by the strong influence of these extended correlated defects on the pinning of the flux lines. La densité de courant critique selon l'axe c (J_c) est mesurée à 77 K en transport et par des mesures magnétiques sur les mêmes échantillons texturés monodomaines d'YBaCuO. L'influence des plans de macles (TP) sur J_c et sur la ligne d'irréversibilité B(T^*) est étudiée en faisant tourner le champ dans les plans ab, perpendiculairement à l'axe c. Les résultats montrent que dans ces composés, J_c et B(T^*) sont fortement influencés par le piégeage par les TP. Divers comportements des lignes de flux résultant de l'influence de ces défauts corrélés sont proposés selon les gammes de température et de champ étudiées.

  8. Influence of rheological layering on the formation of offset basins at inherited weak zones during continental rifting: effects of stiff and pliable layers

    NASA Astrophysics Data System (ADS)

    Chenin, Pauline; Beaumont, Christopher

    2013-04-01

    We use numerical modelling to investigate the influence of lithosphere rheological layering on the reactivation of inherited crust and mantle weak zones during continental rifting. Such reactivation often leads to the formation of offset basins, ie. basins whose development is concomitant with the rifting event, but whose location is offset/set off the main rift/locus of the breakup. Offset rift basins are ubiquitous features of rifted continental margins and are often located at inherited sutures and their fold-and-thrust belts. We use the software Sopale nested to test the effects of different lithospheres comprising Stiff and/or Pliable crust and mantle layers. Here Stiff (S) implies a nonlinear flow law with a high stress exponent (n ~> 10,000), a plastic material, and Pliable (P) means a low stress exponent (n~ 2 - 5) as in ductile, power-law creep of rocks. To achieve this rheological change without modifying the thermal structure of the model, we introduce a scaling factor f in the power-law creep parametrization of the viscosity, such that large values of f result in Coulomb frictional-plastic failure of a layer and small values result in power-law creep. One weak (ie. with reduced internal angle of friction, φ = 2°) zone is embedded in the central part of the uppermost mantle lithosphere and two weak zones are embedded in the upper crust, offset on either side of the mantle weak zone by 150 km in most models. During extension of the model lithosphere weak zones embedded in a stiff layer are preferentially and rapidly reactivated, whereas the same zones are either ignored or slowly reactivated when embedded in pliable layers. This is because necking instabilities grow much more rapidly in stiff layers than in pliable ones. Moreover, the intensity of coupling between the crust and the mantle determines which layer controls the morphology of the model continental margin. When the crust is strongly coupled to the underlying mantle, offset basins only form at

  9. Influence of humidity on high temperature oxidation of Inconel 600 alloy: Oxide layers and residual stress study

    NASA Astrophysics Data System (ADS)

    Xiao, J.; Prud'homme, N.; Li, N.; Ji, V.

    2013-11-01

    In order to understand the influence of humidity on high temperature oxidation of Inconel 600 alloy, in this work, water vapour (absolute humidity varying from 0% to 19%) was introduced in the thermal gravimetric analysis (TGA) system under artificial air between 600 °C and 900 °C. The oxides identification and the residual stress in the oxide layers have been studied by X-ray diffraction method in each of two oxide phases, simultaneously. The oxide surface morphology, cross-section microstructure and the chemical composition of the oxide layers were determined by FEG-SEM (Field Emission Gun Scanning Electron Microscope) observation and FEG-SEM EDS (Energy-dispersive X-ray spectroscopy) analysis. Depending on the oxidation temperature, the humidity and the oxidation duration, the oxide layer differed significantly. The residual stress levels in the different oxide layers (NiO-type layer and Cr2O3-type layer) have also been affected by the introduction of the water vapour. According to the analysis results, the residual stresses on oxide mainly came from the growth stress and thermomechanical stress; and the oxide growth stress was especially affected by humidity at high temperature.

  10. An Observational Case Study on the Influence of Atmospheric Boundary-Layer Dynamics on New Particle Formation

    NASA Astrophysics Data System (ADS)

    Platis, Andreas; Altstädter, Barbara; Wehner, Birgit; Wildmann, Norman; Lampert, Astrid; Hermann, Markus; Birmili, Wolfram; Bange, Jens

    2016-01-01

    We analyze the influence of atmospheric boundary-layer development on new particle formation (NPF) during the morning transition. Continuous in-situ measurements of vertical profiles of temperature, humidity and aerosol number concentrations were quasi-continously measured near Melpitz, Germany, by unmanned aerial systems to investigate the potential connection between NPF and boundary-layer dynamics in the context of turbulence, temperature and humidity fluctuations. On 3 April 2014 high number concentrations of nucleation mode particles up to 6.0 × 10^4 cm^{-3} were observed in an inversion layer located about 450 m above ground level. The inversion layer exhibited a spatial temperature structure parameter C_T^2 15 times higher and a spatial humidity structure parameter C_q^2 5 times higher than in the remaining part of the vertical profile. The study provides hints that the inversion layer is responsible for creating favorable thermodynamic conditions for a NPF event. In addition, this layer showed a strong anti-correlation of humidity and temperature fluctuations. Using estimates of the turbulent mixing and dissipation rates, it is concluded that the downward transport of particles by convective mixing was also the reason of the sudden increase of nucleation mode particles measured on ground. This work supports the hypothesis that many of the NPF events that are frequently observed near the ground may, in fact, originate at elevated altitude, with newly formed particles subsequently being mixed down to the ground.

  11. Influence of cutting parameters on the depth of subsurface deformed layer in nano-cutting process of single crystal copper.

    PubMed

    Wang, Quanlong; Bai, Qingshun; Chen, Jiaxuan; Su, Hao; Wang, Zhiguo; Xie, Wenkun

    2015-12-01

    Large-scale molecular dynamics simulation is performed to study the nano-cutting process of single crystal copper realized by single-point diamond cutting tool in this paper. The centro-symmetry parameter is adopted to characterize the subsurface deformed layers and the distribution and evolution of the subsurface defect structures. Three-dimensional visualization and measurement technology are used to measure the depth of the subsurface deformed layers. The influence of cutting speed, cutting depth, cutting direction, and crystallographic orientation on the depth of subsurface deformed layers is systematically investigated. The results show that a lot of defect structures are formed in the subsurface of workpiece during nano-cutting process, for instance, stair-rod dislocations, stacking fault tetrahedron, atomic clusters, vacancy defects, point defects. In the process of nano-cutting, the depth of subsurface deformed layers increases with the cutting distance at the beginning, then decreases at stable cutting process, and basically remains unchanged when the cutting distance reaches up to 24 nm. The depth of subsurface deformed layers decreases with the increase in cutting speed between 50 and 300 m/s. The depth of subsurface deformed layer increases with cutting depth, proportionally, and basically remains unchanged when the cutting depth reaches over 6 nm.

  12. Influence of Carbon in Metalorganic Chemical Vapor Deposition of Few-Layer WSe2 Thin Films

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaotian; Al Balushi, Zakaria Y.; Zhang, Fu; Choudhury, Tanushree H.; Eichfeld, Sarah M.; Alem, Nasim; Jackson, Thomas N.; Robinson, Joshua A.; Redwing, Joan M.

    2016-12-01

    Metalorganic chemical vapor deposition (MOCVD) is a promising technique to form large-area, uniform films of monolayer or few-layer transition metal dichalcogenide (TMD) thin films; however, unintentional carbon incorporation is a concern. In this work, we report the presence of a defective graphene layer that forms simultaneously during MOCVD growth of tungsten diselenide (WSe2) on sapphire at high growth temperature and high Se:W ratio when using tungsten hexacarbonyl (W(CO)6) and dimethyl selenide ((CH3)2Se, DMSe) as precursors. The graphene layer alters the surface energy of the substrate reducing the lateral growth and coalescence of WSe2 domains. The use of hydrogen selenide (H2Se) instead of DMSe eliminates the defective graphene layer enabling coalesced monolayer and few-layer WSe2 films.

  13. On the Influence of a Fuel Side Heat-Loss (Soot) Layer on a Planar Diffusion Flame

    NASA Technical Reports Server (NTRS)

    Wichman, Indrek S.

    1994-01-01

    A model of the response of a diffusion flame (DF) to an adjacent heat loss or 'soot' layer on the fuel side is investigated. The thermal influence of the 'soot' or heat-loss layer on the DF occurs through the enthalpy sink it creates. A sink distribution in mixture-fraction space is employed to examine possible DF extinction. It is found that (1) the enthalpy sink (or soot layer) must touch the DF for radiation-induced quenching to occur; and (2) for fuel-rich conditions extinction is possible only for a progressively narrower range of values ot the characteristic heat-loss parameter, N(sub R)(Delta Z(sub R)) Various interpretations ot the model are discussed. An attempt is made to place this work into the context created by previous experimental and computational studies.

  14. The chemistry influencing ODEs in the Polar Boundary Layer in spring: a model study

    NASA Astrophysics Data System (ADS)

    Piot, M.; von Glasow, R.

    2008-04-01

    Near-total depletions of ozone have been observed in the Arctic spring since the mid 1980s. The autocatalytic cycles involving reactive halogens are now recognized to be of main importance for Ozone Depletion Events (ODEs) in the Polar Boundary Layer (PBL). We present sensitivity studies using the model MISTRA in the box-model mode on the influence of chemical species on these ozone depletion processes. In order to test the sensitivity of the chemistry under polar conditions, we compared base runs undergoing fluxes of either Br2, BrCl, or Cl2 to induce ozone depletions, with similar runs including a modification of the chemical conditions. The role of HCHO, H2O2, DMS, Cl2, C2H4, C2H6, HONO, NO2, and RONO2 was investigated. Cases with elevated mixing ratios of HCHO, H2O2, DMS, Cl2, and HONO induced a shift in bromine speciation from Br/BrO to HOBr/HBr, while high mixing ratios of C2H6 induced a shift from HOBr/HBr to Br/BrO. Cases with elevated mixing ratios of HONO, NO2, and RONO2 induced a shift to BrNO2/BrONO2. The shifts from Br/BrO to HOBr/HBr accelerated the aerosol debromination, but also increased the total amount of deposited bromine at the surface (mainly via increased deposition of HOBr). These shifts to HOBr/HBr also hindered the BrO self-reaction. In these cases, the ozone depletion was slowed down, where increases in H2O2 and HONO had the greatest effect. The tests with increased mixing ratios of C2H4 highlighted the decrease in HOx which reduced the production of HOBr from bromine radicals. In addition, the direct reaction of C2H4 with bromine atoms led to less available reactive bromine. The aerosol debromination was therefore strongly reduced. Ozone levels were highly affected by the chemistry of C2H4. Cl2-induced ozone depletions were found unrealistic compared to field measurements due to the rapid production of CH3O2, HOx, and ROOH which rapidly convert reactive chlorine to HCl in a "chlorine counter-cycle". This counter-cycle efficiently reduces

  15. Influence of Passivation Layers for Metal Grating-Based Quantum Well Infrared Photodetectors

    NASA Astrophysics Data System (ADS)

    Liu, Dong; Fu, Yong-Qi; Yang, Le-Chen; Zhang, Bao-Shun; Li, Hai-Jun; Fu, Kai; Xiong, Min

    2012-06-01

    To improve absorption of quantum well infrared photodetectors (QWIPs), a coupling layer with metallic grating is designed and fabricated above the quantum well. The metal grating is composed of 100 nm Au film on top, and a 20-nm Ti thin layer between the Au film and the sapphire substrate is coated as an adhesion/buffer layer. To protect the photodetector from oxidation and to decrease leakage, a SiO2 film is deposited by means of plasma-enhanced chemical vapor deposition. A value of about 800 nm is an optimized thickness for the SiO2 applied in the metallic grating-based mid-infrared QWIP. In addition, a QWIP passivation layer is studied experimentally. The results demonstrate that the contribution from the layer is positive for metal grating coupling with the quantum well. The closer the permittivity of the two dielectric layers (SiO2 and the passivation layers), and the closer the two transmission peaks, the greater the QWIP enhancement will be.

  16. Influences of the geometry and acoustic parameter on acoustic radiation forces on three-layered nucleate cells

    NASA Astrophysics Data System (ADS)

    Wang, Yuan-Yuan; Yao, Jie; Wu, Xue-Wei; Wu, Da-Jian; Liu, Xiao-Jun

    2017-09-01

    Acoustic radiation forces (ARFs) on three-layered micro-shells (TLSs) are investigated using Mie scattering theory. The TLS is proposed to simulate a nucleate cell with nucleus, cytoplasm, and membrane. It is found that the existence of the inner core or outer shell greatly influences ARFs on nucleate cells. We focus on the influences of the geometry, acoustic parameters, and the surrounding medium on ARFs on TLSs. With increasing inner core radius or outer shell thickness, the ARF on the TLS shows a distinct increase. We find that the impedance of each layer of the TLS plays a dominant role with regard to the ARF, while the density and the sound velocity separately provide distinct modulations. In addition, it is found that the higher impedance of the surrounding medium induces larger ARF on the TLS. Our work may be beneficial for the acoustic manipulation of nucleate cells.

  17. Influence of material parameters on acoustic wave propagation modes in ZnO/Si bi-layered structures.

    PubMed

    Gao, Hui-dong; Zhang, Shu-Yi; Qi, Xue; Wasa, Kiyotaka; Wu, Hao-Dong

    2005-12-01

    The influences of material properties on acoustic wave propagation modes in ZnO/Si bi-layered structures are studied. The transfer matrix method is used to calculate dispersion relations, wave field distributions, and electromechanical coupling coefficients of acoustic wave propagation modes in ZnO/Si bi-layered systems, in which the thickness of the substrate is of the same order of magnitude as the wavelength of the propagating wave modes. The influences of the thin film parameters on the acoustic wave propagation modes and their electromechanical coupling coefficients of the wave modes also are obtained. In addition, some experimental results for characterizing the wave propagation modes and their frequencies have also been obtained, which agree well with the theoretical predictions.

  18. Influence of vibration amplitude on dynamic triggering of slip in sheared granular layers.

    PubMed

    Griffa, M; Ferdowsi, B; Guyer, R A; Daub, E G; Johnson, P A; Marone, C; Carmeliet, J

    2013-01-01

    We perform a systematic statistical investigation of the effect of harmonic boundary vibrations on a sheared granular layer undergoing repetitive, fully dynamic stick-slip motion. The investigation is performed using two-dimensional discrete element method simulations. The main objective consists of improving the understanding of dynamic triggering of slip events in the granular layer. Here we focus on how the vibration amplitude affects the statistical properties of the triggered slip events. The results provide insight into the granular physical controls of dynamic triggering of failure in sheared granular layers.

  19. The influence of dual-substrate-layer extensive green roofs on rainwater runoff quantity and quality.

    PubMed

    Wang, Xiaoou; Tian, Yimei; Zhao, Xinhua

    2017-08-15

    This study investigates the ability of dual-substrate-layer extensive green roofs to retain rainwater and reduce pollutant leaching. The substrates in dual-substrate-layer green roofs consist of an upper organic nutrition layer for plant growth and a lower inorganic adsorption layer for water retention and pollutant reduction. One traditional single-substrate-layer extensive green roof was built for comparison with dual-substrate-layer green roofs. During the experimental period, dual-substrate-layer green roofs supported better natural vegetation growth, with coverage exceeding 90%, while the coverage in single-substrate-layer green roof was over 80%. Based on the average retention value of the total rainfall for four types of simulated rains (the total rainfall depth (mm) was 43.2, 54.6, 76.2 and 86.4, respectively), the dual-substrate-layer green roofs, which used the mixture of activated charcoal with perlite and vermiculite as the adsorption substrate, possessed better rainfall retention performance (65.9% and 55.4%) than the single-substrate-layer green roof (52.5%). All of the dual-substrate-layer green roofs appeared to be sinks for organics, heavy metals and all forms of nitrogen in all cases, while acted as sources of phosphorus contaminants in the case of heavy rains. In consideration of the factors of water retention, pollution reduction and service life of the green roof, a mixture of activated charcoal and/or pumice with perlite and vermiculite is recommended as the adsorption substrate. The green roofs were able to mitigate mild acid rain, raising the pH from approximately 5.6 in rainfall to 6.5-7.6 in green roof runoff. No signs of a first flush effect for phosphate, total phosphorus, ammonia nitrogen, nitrate nitrogen, total nitrogen, organics, zinc, lead, chromium, manganese, copper, pH or turbidity were found in the green roof runoff. Cost analysis further proved the practicability of dual-substrate-layer green roofs in retaining rainwater, and

  20. Influence of Computational Drop Representation in LES of a Droplet-Laden Mixing Layer

    NASA Technical Reports Server (NTRS)

    Bellan, Josette; Radhakrishnan, Senthilkumaran

    2013-01-01

    Multiphase turbulent flows are encountered in many practical applications including turbine engines or natural phenomena involving particle dispersion. Numerical computations of multiphase turbulent flows are important because they provide a cheaper alternative to performing experiments during an engine design process or because they can provide predictions of pollutant dispersion, etc. Two-phase flows contain millions and sometimes billions of particles. For flows with volumetrically dilute particle loading, the most accurate method of numerically simulating the flow is based on direct numerical simulation (DNS) of the governing equations in which all scales of the flow including the small scales that are responsible for the overwhelming amount of dissipation are resolved. DNS, however, requires high computational cost and cannot be used in engineering design applications where iterations among several design conditions are necessary. Because of high computational cost, numerical simulations of such flows cannot track all these drops. The objective of this work is to quantify the influence of the number of computational drops and grid spacing on the accuracy of predicted flow statistics, and to possibly identify the minimum number, or, if not possible, the optimal number of computational drops that provide minimal error in flow prediction. For this purpose, several Large Eddy Simulation (LES) of a mixing layer with evaporating drops have been performed by using coarse, medium, and fine grid spacings and computational drops, rather than physical drops. To define computational drops, an integer NR is introduced that represents the ratio of the number of existing physical drops to the desired number of computational drops; for example, if NR=8, this means that a computational drop represents 8 physical drops in the flow field. The desired number of computational drops is determined by the available computational resources; the larger NR is, the less computationally

  1. Preliminary Results on the Influence of Engineered Artificial Mucus Layer on Phonation

    ERIC Educational Resources Information Center

    Döllinger, Michael; Gröhn, Franziska; Berry, David A.; Eysholdt, Ulrich; Luegmair, Georg

    2014-01-01

    Purpose: Previous studies have confirmed the influence of dehydration and an altered mucus (e.g., due to pathologies) on phonation. However, the underlying reasons for these influences are not fully understood. This study was a preliminary inquiry into the influences of mucus architecture and concentration on vocal fold oscillation. Method: Two…

  2. Preliminary Results on the Influence of Engineered Artificial Mucus Layer on Phonation

    ERIC Educational Resources Information Center

    Döllinger, Michael; Gröhn, Franziska; Berry, David A.; Eysholdt, Ulrich; Luegmair, Georg

    2014-01-01

    Purpose: Previous studies have confirmed the influence of dehydration and an altered mucus (e.g., due to pathologies) on phonation. However, the underlying reasons for these influences are not fully understood. This study was a preliminary inquiry into the influences of mucus architecture and concentration on vocal fold oscillation. Method: Two…

  3. Influence of intermediate layers on the surface condition of laser crystallized silicon thin films and solar cell performance

    NASA Astrophysics Data System (ADS)

    Höger, Ingmar; Himmerlich, Marcel; Gawlik, Annett; Brückner, Uwe; Krischok, Stefan; Andrä, Gudrun

    2016-01-01

    The intermediate layer (IL) between glass substrate and silicon plays a significant role in the optimization of multicrystalline liquid phase crystallized silicon thin film solar cells on glass. This study deals with the influence of the IL on the surface condition and the required chemical surface treatment of the crystallized silicon (mc-Si), which is of particular interest for a-Si:H heterojunction thin film solar cells. Two types of IL were investigated: sputtered silicon nitride (SiN) and a layer stack consisting of silicon nitride and silicon oxide (SiN/SiO). X-ray photoelectron spectroscopy measurements revealed the formation of silicon oxynitride (SiOxNy) or silicon oxide (SiO2) layers at the surface of the mc-Si after liquid phase crystallization on SiN or SiN/SiO, respectively. We propose that SiOxNy formation is governed by dissolving nitrogen from the SiN layer in the silicon melt, which segregates at the crystallization front during crystallization. This process is successfully hindered, when additional SiO layers are introduced into the IL. In order to achieve solar cell open circuit voltages above 500 mV, a removal of the formed SiOxNy top layer is required using sophisticated cleaning of the crystallized silicon prior to a-Si:H deposition. However, solar cells crystallized on SiN/SiO yield high open circuit voltage even when a simple wet chemical surface treatment is applied. The implementation of SiN/SiO intermediate layers facilitates the production of mesa type solar cells with open circuit voltages above 600 mV and a power conversion efficiency of 10%.

  4. Influence of intermediate layers on the surface condition of laser crystallized silicon thin films and solar cell performance

    SciTech Connect

    Höger, Ingmar Gawlik, Annett; Brückner, Uwe; Andrä, Gudrun; Himmerlich, Marcel; Krischok, Stefan

    2016-01-28

    The intermediate layer (IL) between glass substrate and silicon plays a significant role in the optimization of multicrystalline liquid phase crystallized silicon thin film solar cells on glass. This study deals with the influence of the IL on the surface condition and the required chemical surface treatment of the crystallized silicon (mc-Si), which is of particular interest for a-Si:H heterojunction thin film solar cells. Two types of IL were investigated: sputtered silicon nitride (SiN) and a layer stack consisting of silicon nitride and silicon oxide (SiN/SiO). X-ray photoelectron spectroscopy measurements revealed the formation of silicon oxynitride (SiO{sub x}N{sub y}) or silicon oxide (SiO{sub 2}) layers at the surface of the mc-Si after liquid phase crystallization on SiN or SiN/SiO, respectively. We propose that SiO{sub x}N{sub y} formation is governed by dissolving nitrogen from the SiN layer in the silicon melt, which segregates at the crystallization front during crystallization. This process is successfully hindered, when additional SiO layers are introduced into the IL. In order to achieve solar cell open circuit voltages above 500 mV, a removal of the formed SiO{sub x}N{sub y} top layer is required using sophisticated cleaning of the crystallized silicon prior to a-Si:H deposition. However, solar cells crystallized on SiN/SiO yield high open circuit voltage even when a simple wet chemical surface treatment is applied. The implementation of SiN/SiO intermediate layers facilitates the production of mesa type solar cells with open circuit voltages above 600 mV and a power conversion efficiency of 10%.

  5. Influence of light and darkness on the behaviour of Dermanyssus gallinae on layer farms.

    PubMed

    Sokół, R; Szkamelski, A; Barski, D

    2008-01-01

    The behaviour of Dermanyssus gallinae was investigated on two layer farms where two different light programs were introduced in the 40th week of hen life. In layer house No. 1, light was applied continuously for 16 hours during the day, while layer house No. 2 was subjected to 4 hours of light and 2 hours of darkness applied alternately during the day. To monitor the level of red mite infestation, 30 tube traps were placed in every layer house corridor at a height of 1.5 m above the floor. In the first layer house, 280 Dermanyssus gallinae females, 50 nymph larvae and 198 eggs were found in 100 mg of tube trap material during 16 hours of the light phase, while during the 8-hour darkness phase, 1240 females, 70 nymph larvae and 110 eggs were collected. In the other layer house (with an alternating light phase of 4 hours and a darkness phase of 2 hours per day), 387 Dermanyssus gallinae females, 401 nymph larvae and 1060 eggs were found in trap tubes over the 8-hour dark phase, while 343 females, 202 nymph larvae and 1106 eggs were discovered over the 16-hour light phase.

  6. Influence of capping layers on CoFeB anisotropy and damping

    SciTech Connect

    Natarajarathinam, A.; Tadisina, Z. R.; Gupta, S.; Mewes, T.; Watts, S.; Chen, E.

    2012-09-01

    Magnetic behavior of CoFeB at various thicknesses ranging from 2 nm to 8 nm capped with different materials, such as MgO, Ta, Ru, and V have been studied. The films were sputter-deposited and subsequently characterized by magnetometry and broadband ferromagnetic resonance (FMR). There are magnetically dead layers at the interface observed with Ru and Ta capping layers, while MgO and V have almost no effect on the magnetization of the CoFeB. As the ferromagnetic layer is made thinner, the effective magnetization decreases, indicating an interfacial perpendicular anisotropy. Particularly in the case of MgO, V/Ru, and V/Ta capping layers, interfacial perpendicular anisotropy is induced in CoFeB, and the Gilbert damping parameter is also reduced. The origin of this perpendicular magnetic anisotropy (PMA) is understood to be caused by the interface anisotropy between the free layer and the capping layer. The effect of post-deposition annealing and CoFeB thickness on the anisotropy and damping of V/Ta capped samples are reported. Doping CoFeB with vanadium (V) greatly reduced the 4{pi}M{sub s} and 4{pi}M{sub eff} values, resulting in an effective increase in the PMA.

  7. Influence of capping layers on CoFeB anisotropy and damping

    NASA Astrophysics Data System (ADS)

    Natarajarathinam, A.; Tadisina, Z. R.; Mewes, T.; Watts, S.; Chen, E.; Gupta, S.

    2012-09-01

    Magnetic behavior of CoFeB at various thicknesses ranging from 2 nm to 8 nm capped with different materials, such as MgO, Ta, Ru, and V have been studied. The films were sputter-deposited and subsequently characterized by magnetometry and broadband ferromagnetic resonance (FMR). There are magnetically dead layers at the interface observed with Ru and Ta capping layers, while MgO and V have almost no effect on the magnetization of the CoFeB. As the ferromagnetic layer is made thinner, the effective magnetization decreases, indicating an interfacial perpendicular anisotropy. Particularly in the case of MgO, V/Ru, and V/Ta capping layers, interfacial perpendicular anisotropy is induced in CoFeB, and the Gilbert damping parameter is also reduced. The origin of this perpendicular magnetic anisotropy (PMA) is understood to be caused by the interface anisotropy between the free layer and the capping layer. The effect of post-deposition annealing and CoFeB thickness on the anisotropy and damping of V/Ta capped samples are reported. Doping CoFeB with vanadium (V) greatly reduced the 4πMs and 4πMeff values, resulting in an effective increase in the PMA.

  8. Convectively-driven cold layer and its influences on moisture in the UTLS

    NASA Astrophysics Data System (ADS)

    Kim, J.; Randel, W. J.; Birner, T.

    2016-12-01

    Characteristics of the cold anomaly in the tropical tropopause layer (TTL) that is commonly observed with deep convection are examined using CloudSat and Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC) GPS radio occultation measurements. Deep convection is sampled based on the cloud top height (>17 km) from CloudSat 2B-CLDCLASS, and then temperature profiles from COSMIC are composited around the deep convection. The composite temperature shows anomalously warm troposphere (up to 14 km) and a significantly cold layer near the tropopause (at 16-18 km) in the regions of deep convection. Generally in the tropics, the cold layer has very large horizontal scale (2,000 - 6,000 km) compared to that of mesoscale convective cluster, and it lasts one or two weeks with minimum temperature anomaly of - 2K. The cold layer shows slight but clear eastward-tilted vertical structure in the deep tropics indicating a large-scale Kelvin wave response. Further analyses on circulation patterns suggest that the anomaly can be explained as a part of Gill-type response in the TTL to deep convective heating in the troposphere. Response of moisture to the cold layer is also examined in the upper troposphere and lower stratosphere using microwave limb sounder (MLS) measurements. The water vapor anomalies show coherent structures with the temperature and circulation anomalies. A clear dry anomaly is found in the cold layer and its outflow region, implying a large-scale dehydration process due to the convectively driven cold layer in the upper TTL.

  9. Reticulation des fibres lignocellulosiques

    NASA Astrophysics Data System (ADS)

    Landrevy, Christel

    Pour faire face à la crise économique la conception de papier à valeur ajoutée est développée par les industries papetières. Le but de se projet est l'amélioration des techniques actuelles de réticulation des fibres lignocellulosiques de la pâte à papier visant à produire un papier plus résistant. En effet, lors des réactions de réticulation traditionnelles, de nombreuses liaisons intra-fibres se forment ce qui affecte négativement l'amélioration anticipée des propriétés physiques du papier ou du matériau produit. Pour éviter la formation de ces liaisons intra-fibres, un greffage sur les fibres de groupements ne pouvant pas réagir entre eux est nécessaire. La réticulation des fibres par une réaction de « click chemistry » appelée cycloaddition de Huisgen entre un azide et un alcyne vrai, catalysée par du cuivre (CuAAC) a été l'une des solutions trouvée pour remédier à ce problème. De plus, une adaptation de cette réaction en milieux aqueux pourrait favoriser son utilisation en milieu industriel. L'étude que nous désirons entreprendre lors de ce projet vise à optimiser la réaction de CuAAC et les réactions intermédiaires (propargylation, tosylation et azidation) sur la pâte kraft, en milieu aqueux. Pour cela, les réactions ont été adaptées en milieu aqueux sur la cellulose microcristalline afin de vérifier sa faisabilité, puis transférée à la pâte kraft et l'influence de différents paramètres comme le temps de réaction ou la quantité de réactifs utilisée a été étudiée. Dans un second temps, une étude des différentes propriétés conférées au papier par les réactions a été réalisée à partir d'une série de tests papetiers optiques et physiques. Mots Clés Click chemistry, Huisgen, CuAAC, propargylation, tosylation, azidation, cellulose, pâte kraft, milieu aqueux, papier.

  10. Influence of electronic energy deposition on the structural modification of swift heavy-ion-irradiated amorphous germanium layers

    SciTech Connect

    Steinbach, T.; Schnohr, C. S.; Wesch, W.; Kluth, P.; Giulian, R.; Araujo, L. L.; Sprouster, D. J.; Ridgway, M. C.

    2011-02-01

    Swift heavy-ion (SHI) irradiation of amorphous germanium (a-Ge) layers leads to a strong volume expansion accompanied by a nonsaturating irreversible plastic deformation (ion hammering), which are consequences of the high local electronic energy deposition within the region of the a-Ge layer. We present a detailed study of the influence of SHI irradiation parameters on the effect of plastic deformation and structural modification. Specially prepared a-Ge layers were irradiated using two SHI energies and different angles of incidence, thus resulting in a variation of the electronic energy deposition per depth {epsilon}{sub e} between 14.0 and 38.6 keV nm{sup -1}. For all irradiation parameters used a strong swelling of the irradiated material was observed, which is caused by the formation and growth of randomly distributed voids, leading to a gradual transformation of the amorphous layer into a sponge-like porous structure as established by cross-section scanning electron microscopy investigations. The swelling depends linearly on the ion fluence and on the value of {epsilon}{sub e}, thus clearly demonstrating that the structural changes are determined solely by the electronic energy deposited within the amorphous layer. Plastic deformation shows a superlinear dependence on the ion fluence due to the simultaneous volume expansion. This influence of structural modification on plastic deformation is described by a simple approach, thus allowing estimation of the deformation yield. With these results the threshold values of the electronic energy deposition for the onset of both structural modification and plastic deformation due to SHI irradiation are determined. Furthermore, based on these results, the longstanding question concerning the reason for the structural modification observed in SHI-irradiated crystalline Ge is answered.

  11. Influence of confining layers' heterogeneity on the barometric response functions in semi-confined aquifers

    NASA Astrophysics Data System (ADS)

    Redaelli, Marco; Perulero Serrano, Raul

    2017-04-01

    It has been shown that Barometric Response Functions (BRFs) can provide a useful tool for detecting the occurrence of highly conducive bodies which span across aquifer confining layers and can potentially give rise to pathways for pollutant migration (Hussein et al 2013, Odling et al 2015). Analytical models employed to estimate BRFs from geological system properties assume homogeneity within the aquifer and its confining layer. These assumptions are rarely satisfied in practice. Our study focusses on the impact on predicted BRFs of heterogeneous distribution of high conductivity geomaterials within the confining layer. The work is grounded on a suite of three-dimensional, transient numerical computations of groundwater flow in a confining layer-aquifer system for i) a perfectly homogeneous two-layer setting where a single highly conducive block is fully penetrating the confining layer and ii) a heterogeneous two-layer system where hydraulic conductivity in the confining layer is modelled as a stochastic process. Our numerical results are interpreted through a comparison against those associated with an analytical model which assumes system homogeneity. Monitoring points located in the middle of the modelled aquifer domain, mimicking screened boreholes in field conditions, are used to extract water level records. The output is used to obtain the corresponding BRFs (in terms of gain and phase components) and compared vis-a-vis the selected analytical solution. The results show a wide variety of BRF responses, especially in the gain component, which vary from almost confined to unconfined scenarios. Our simulations show that the BRFs are a viable tool to improve understanding of the degree of spatial continuity within low permeability heterogeneous geological materials such as glacial till which is frequently found overlying water bearing units across the UK and other localities worldwide. As such, it has the potential to improve groundwater vulnerability assessment

  12. The influence of vegetation and soil characteristics on active-layer thickness of permafrost soils in boreal forest.

    PubMed

    Fisher, James P; Estop-Aragonés, Cristian; Thierry, Aaron; Charman, Dan J; Wolfe, Stephen A; Hartley, Iain P; Murton, Julian B; Williams, Mathew; Phoenix, Gareth K

    2016-09-01

    Carbon release from thawing permafrost soils could significantly exacerbate global warming as the active-layer deepens, exposing more carbon to decay. Plant community and soil properties provide a major control on this by influencing the maximum depth of thaw each summer (active-layer thickness; ALT), but a quantitative understanding of the relative importance of plant and soil characteristics, and their interactions in determine ALTs, is currently lacking. To address this, we undertook an extensive survey of multiple vegetation and edaphic characteristics and ALTs across multiple plots in four field sites within boreal forest in the discontinuous permafrost zone (NWT, Canada). Our sites included mature black spruce, burned black spruce and paper birch, allowing us to determine vegetation and edaphic drivers that emerge as the most important and broadly applicable across these key vegetation and disturbance gradients, as well as providing insight into site-specific differences. Across sites, the most important vegetation characteristics limiting thaw (shallower ALTs) were tree leaf area index (LAI), moss layer thickness and understory LAI in that order. Thicker soil organic layers also reduced ALTs, though were less influential than moss thickness. Surface moisture (0-6 cm) promoted increased ALTs, whereas deeper soil moisture (11-16 cm) acted to modify the impact of the vegetation, in particular increasing the importance of understory or tree canopy shading in reducing thaw. These direct and indirect effects of moisture indicate that future changes in precipitation and evapotranspiration may have large influences on ALTs. Our work also suggests that forest fires cause greater ALTs by simultaneously decreasing multiple ecosystem characteristics which otherwise protect permafrost. Given that vegetation and edaphic characteristics have such clear and large influences on ALTs, our data provide a key benchmark against which to evaluate process models used to predict

  13. Effect of velocity ratio on plane mixing layer development - Influence of the splitter plate wake

    NASA Technical Reports Server (NTRS)

    Mehta, R. D.

    1991-01-01

    The effect of the velocity ratio on the approach of a plane mixing layer to self-similarity was investigated experimentally. In the experiment, plane mixing layers with velocity ratios 0.5, 0.6, 0.7, 0.8, and 0.9 were generated in a mixing-layer wind tunnel consisting of two individually driven legs, in which the two streams were allowed to merge at the sharp edge of a tappered splitter plate. The leg driven by the bigger blower was operated at a free-stream velocity in the test section of 21 m/s, while the flow speed in the other leg was varied to change the velocity ratio. For each velocity ratio, the mean flow- and turbulence measurements were carried out at eight streamwise locations. Results showed that, for velocity ratios between 0.5 and 0.7, self-similarity of the mixing layer was achieved, with the asymptotic states comparable; mixing layers with higher velocity ratios failed to achieve a self-similar state within the measurement domain.

  14. Influence of the layer thickness in plasmonic gold nanoparticles produced by thermal evaporation

    PubMed Central

    Gaspar, D.; Pimentel, A. C.; Mateus, T.; Leitão, J. P.; Soares, J.; Falcão, B. P.; Araújo, A.; Vicente, A.; Filonovich, S. A.; Águas, H.; Martins, R.; Ferreira, I.

    2013-01-01

    Metallic nanoparticles (NPs) have received recently considerable interest of photonic and photovoltaic communities. In this work, we report the optoelectronic properties of gold NPs (Au-NPs) obtained by depositing very thin gold layers on glass substrates through thermal evaporation electron-beam assisted process. The effect of mass thickness of the layer was evaluated. The polycrystalline Au-NPs, with grain sizes of 14 and 19 nm tend to be elongated in one direction as the mass thickness increase. A 2 nm layer deposited at 250°C led to the formation of Au-NPs with 10-20 nm average size, obtained by SEM images, while for a 5 nm layer the wide size elongates from 25 to 150 nm with a mean at 75 nm. In the near infrared region was observed an absorption enhancement of amorphous silicon films deposited onto the Au-NPs layers with a corresponding increase in the PL peak for the same wavelength region. PMID:23552055

  15. Beryllium deposition on International Thermonuclear Experimental Reactor first mirrors: Layer morphology and influence on mirror reflectivity

    SciTech Connect

    De Temmerman, G.; Baldwin, M. J.; Doerner, R. P.; Nishijima, D.; Seraydarian, R.; Schmid, K.; Kost, F.; Linsmeier, Ch.; Marot, L.

    2007-10-15

    Metallic mirrors will be essential components of the optical diagnostic systems in the International Thermonuclear Experimental Reactor (ITER). Reliability of these systems may be affected by mirror reflectivity changes induced by erosion and/or deposition of impurities (carbon, beryllium). The present study aims to assess the effect of beryllium (Be) deposition on the reflectivity of metallic mirrors and to collect data on the optical quality of these layers in terms of morphology, roughness, etc. Mirrors from molybdenum and copper were exposed in the PISCES-B linear plasma device to collect eroded material from graphite and beryllium targets exposed to beryllium-seeded deuterium plasma. After exposure, relative reflectivity of the mirrors was measured and different surface analysis techniques were used to investigate the properties of the deposited layers. Be layers formed in PISCES-B exhibit high levels of porosity which makes the reflectivity of the Be layers much lower than the reflectivity of pure Be. It is found that if Be deposition occurs on ITER first mirrors, the reflectivity of the coated mirrors will strongly depend on the layer morphology, which in turn depends on the deposition conditions.

  16. Influence of interphase layer on the overall elasto-plastic behaviors of HA/PEEK biocomposite.

    PubMed

    Fan, J P; Tsui, C P; Tang, C Y; Chow, C L

    2004-10-01

    A three-dimensional finite element unit cell model has been designed and constructed for studying mechanical properties of hydroxyapatite (HA) reinforced polyetheretherketone (PEEK) biocomposite. The model consists of an elastic-brittle HA spherical particle, an elasto-plastic matrix and an interphase layer between the particle and the matrix. The interphase layers with four different kinds of material behaviors have been taken into consideration to examine their effects on the overall properties of the composite. The damage evolution in the matrix and the interphase layer, and the interface failure, were also taken into account. Some other factors, such as mesh sensitivity, loading velocity and mass scale scheme, were also discussed in this investigation. A general-purpose finite element software package, ABAQUS, incorporated with a user-defined material subroutine, was used to perform the analysis. The predicted results were compared with the experimental data obtained from existing literatures. The results predicted by using the cell model with consideration of the matrix degradation and the effects of the damage and failure on the interphase layer are in good agreement with the experimental ones. Hence, the suitability of our proposed cell model incorporated with an appropriate type of the interphase layer for modeling the mechanical properties of the particulate biocomposite could be verified. Copyright 2004 Elsevier Ltd.

  17. The Influence of Free Tropospheric Aerosol on the Boundary Layer Aerosol Budget in the Arctic

    NASA Astrophysics Data System (ADS)

    Igel, A. L.; Ekman, A.; Leck, C.; Savre, J.; Tjernstrom, M. K. H.; Sedlar, J.

    2015-12-01

    Large-eddy simulations of the summertime high Arctic boundary layer with mixed-phase stratus clouds have been performed based on observations taken during the ASCOS[1] campaign. The model includes a prognostic aerosol scheme where accumulation mode aerosol particles can be activated into cloud droplets, impaction scavenged, and regenerated upon cloud droplet evaporation or ice crystal sublimation. Two sets of simulations were performed, one with a constant aerosol concentration in the boundary layer and free troposphere, and one with enhanced free tropospheric concentrations based on observed aerosol concentration profiles. We find that the rate of aerosol depletion in the boundary layer is an order of magnitude larger than the median surface emission rates measured over the open water, indicating that for the present case the surface emissions are unlikely to compensate for aerosol loss due to interactions with clouds. In this case study, when the enhanced free troposphere aerosol concentrations are included, the entrainment of these particles into the boundary layer is able to offset the loss of particles from aerosol-cloud interactions. These results suggest that enhanced levels of accumulation mode particles, if located at the cloud top, may be an important source of accumulation mode particles in the Arctic boundary layer. [1] The Arctic Summer Cloud Ocean Study (ASCOS) was conducted in 2008 with the overall aim to improve our understanding of stratus cloud formation and possible climate feedback processes over the central Arctic Ocean. Tjernström et al., 2014 give more details.

  18. Influence of material impurities in the hole-blocking layer on the lifetime of organic light-emitting diodes

    NASA Astrophysics Data System (ADS)

    Fujimoto, Hiroshi; Yahiro, Masayuki; Yukiwaki, Satoshi; Kusuhara, Keiko; Nakamura, Nozomi; Suekane, Takashi; Wei, Hong; Imanishi, Katsuya; Inada, Ko; Adachi, Chihaya

    2016-12-01

    We evaluated the influence of impurities in an organic material used for the fabrication of organic light-emitting diodes (OLEDs) on the lifetime of the fabricated devices. Despite no differences in the current-density-voltage characteristics and external quantum efficiencies of the devices, the lifetime was approximately nine times longer for devices with high-purity 2,4,6-tris(biphenyl-3-yl)-1,3,5-triazine (T2T), which was used as a hole-block layer. Chlorine-containing impurities derived from T2T had the greatest influence on the lifetime of the OLEDs even though the amount of halogen in the source material was at most 0.9 ppm. On the other hand, the lifetime was not greatly influenced by other impurities even with concentrations up to 0.2%. Therefore, the purities of materials other than the emitter must also be closely controlled.

  19. Influence of a Magnetically Permeable Surface Layer on Transient Fields for a Thin Circular Loop Antenna

    NASA Astrophysics Data System (ADS)

    Sami, Ghada M.

    2004-04-01

    The transient fields, in the time-domain, of a thin circular loop antenna, on a two-layered earth’s model are reexamined when the usually neglected magnetic permeability contrast is considered. It is shown that for a two-layered earth model, where the upper layer is permeable, the transient fields are modified over the nonpermeable case. The fields in the time domain are obtained as the inverse Laplace transforms of derived full wave time-harmonic solution. These time-domain solutions are obtained as a summation of waveguide modes plus contributions from branch cuts in the complex plane of the longitudinal wave number. The results should be useful for interpreting airborne electromagnetic systems and in cases where super-paramagnetic mineral constant is present.

  20. Influence of external disturbances and compressibility on free turbulent mixing. [in free shear layers

    NASA Technical Reports Server (NTRS)

    Oh, Y. H.; Bushnell, D. M.

    1975-01-01

    It is shown that disturbances in external flow can significantly affect, by as much as an order of magnitude, the turbulent mixing rate in free shear layers and that the length scale of the external flow disturbances is as important as the amplitude. The difference between the effect of wide-band and narrow-band disturbances is stressed. The model for pressure fluctuation term in the kinetic energy equation is included in a two-equation model. The reduced spreading rate in high Mach number, high Reynolds number, adiabatic, free turbulent shear layers is predicted.

  1. The influence of winding direction of two-layer HTS DC cable on the critical current

    NASA Astrophysics Data System (ADS)

    Vyatkin, V. S.; Kashiwagi, K.; Ivanov, Y. V.; Otabe, E. S.; Yamaguchi, S.

    2017-09-01

    The design of twist pitch and direction of winding in multilayer HTS coaxial cable is important. For HTS AC transmitting cables, the main condition of twist pitch is the balance of inductances of each layer for providing the current balance between layers. In this work, the finite element method analysis for the coaxial cables with both same and opposite directions winding is used to calculate magnetic field distribution, and critical current of the cable is estimated. It was found that the critical current of the cable with same direction winding is about 10 percent higher than that in the case of the cable with the opposite direction winding.

  2. Influence of surface layer removal of shade guide tabs on the measured color by spectrophotometer and spectroradiometer.

    PubMed

    Kim, Jin-Cheol; Yu, Bin; Lee, Yong-Keun

    2008-12-01

    To determine the changes in color parameters of Vitapan 3D-Master shade guide tabs by a spectrophotometer (SP) or a spectroradiometer (SR), and by the removal of the surface layer of the tabs that was performed to make a flat measuring surface for the SP color measurement. Color of the shade tabs was measured before and after removing the surface layer of the tabs using SP and SR. Correlations between the color parameters between the original (OR) and the surface layer removed (RM) tabs and between the SP and the SR measurements were determined (alpha=0.05). Based on SP, the lightness, chroma, CIE a* and b* values measured after the surface layer removal were higher than those of the original tabs except a few cases. Based on SR, the chroma and CIE a* and b* values measured after surface layer removal were higher than those of the original tabs except a few cases; however, in case of the lightness, the changes varied by the shade designation. Type of instrument influenced the changes in color parameters based on paired t-test (p<0.05). The color parameters of the OR and RM tabs showed correlations based on both SP and SR measurements (r=0.952-0.997 and p<0.01); however, color difference between the SP-RM and SR-OR tabs was in the range of 18.1-27.0 DeltaE(ab)(*) units (mean: 23.3+/-2.2). When the color of tooth-shaped objects is measured with a spectrophotometer or a spectroradiometer, measurement protocols should be specified because color difference by the surface layer removal and the instrument was high.

  3. Exploring the influence of boundary layer stability on wind farms and their interplay with the surrounding environment

    NASA Astrophysics Data System (ADS)

    Vanderwende, Brian Joseph

    There is growing awareness in the wind power industry that boundary-layer stability influences wind turbine performance in meaningful ways. Stability is inextricably tied to the diurnal ebb and flow of heat, momentum, and moisture that drives weather. Boundary-layer stability is closely linked to low-level wind speeds, wind shear, wind veer, and turbulence. It is these myriad consequences of stability which directly impact turbines, both modifying performance and contributing to structural fatigue. I describe the influence of near-surface stability on the aggregate power output of a utility-scale wind farm in central North America. During convective conditions, the wind farm produced more power than during neutral conditions, while in stable conditions the farm underperformed. These results are statistically significant, despite the uncertainty involved in using nacelle anemometer measurements of wind speed. Next, I use lidar measurements from Iowa to categorize low-level jets and their impact on rotor-layer winds. Observed jets are similar to those studied in the Great Plains, though regional sloping terrain forcing is absent in Iowa. Rotor-layer wind speeds intensify during jet periods, but detrimental wind shear and veer also increase when jets occur. Simulations using the Weather Research and Forecasting (WRF) model with various input data and boundary-layer physics favorably reproduce jet features. I then utilize the same model to examine the impact of switching from maize to soybeans on rotor-layer winds during the peak of the growing season. The crop change was represented in the simulation by surface roughness. The switch produces a statistically significant increase in both wind speed and power output. Finally, I evaluate the performance of the wind farm parameterization (WFP) in WRF using high-resolution large eddy simulations (LES) from the same model. The wind speed and turbulence impacts estimated by the WFP compare favorably to LES flow for both

  4. Impact de la preparation des anodes crues et des conditions de cuisson sur la fissuration dans des anodes denses

    NASA Astrophysics Data System (ADS)

    Amrani, Salah

    fabriquees industriellement. Cette technique a consiste a determiner le profil des differentes proprietes physiques. En effet, la methode basee sur la mesure de la distribution de la resistivite electrique sur la totalite de l'echantillon est la technique qui a ete utilisee pour localiser la fissuration et les macro-pores. La microscopie optique et l'analyse d'image ont, quant a elles, permis de caracteriser les zones fissurees tout en determinant la structure des echantillons analyses a l'echelle microscopique. D'autres tests ont ete menes, et ils ont consiste a etudier des echantillons cylindriques d'anodes de 50 mm de diametre et de 130 mm de longueur. Ces derniers ont ete cuits dans un four a UQAC a differents taux de chauffage dans le but de pouvoir determiner l'influence des parametres de cuisson sur la formation de la fissuration dans ce genre de carottes. La caracterisation des echantillons d'anodes cuites a ete faite a l'aide de la microscopie electronique a balayage et de l'ultrason. La derniere partie des travaux realises a l'UQAC contient une etude sur la caracterisation des anodes fabriquees au laboratoire sous differentes conditions d'operation. L'evolution de la qualite de ces anodes a ete faite par l'utilisation de plusieurs techniques. L'evolution de la temperature de refroidissement des anodes crues de laboratoire a ete mesuree; et un modele mathematique a ete developpe et valide avec les donnees experimentales. Cela a pour objectif d'estimer la vitesse de refroidissement ainsi que le stress thermique. Toutes les anodes fabriquees ont ete caracterisees avant la cuisson par la determination de certaines proprietes physiques (resistivite electrique, densite apparente, densite optique et pourcentage de defauts). La tomographie et la distribution de la resistivite electrique, qui sont des techniques non destructives, ont ete employees pour evaluer les defauts internes des anodes. Pendant la cuisson des anodes de laboratoire, l'evolution de la resistivite

  5. A study of the influence of a gravel subslab layer on radon entry rate using two basement structures

    SciTech Connect

    Robinson, A.L.; Sextro, R.G.; Fisk, W.J.; Garbesi, K.; Wooley, J.; Wollenberg, H.A.

    1993-01-01

    In buildings with elevated radon concentrations, the dominant transport mechanism of radon is advective flow of soil gas into the building substructure. However, the building-soil system is often complex, making detailed studies of the radon source term difficult. In order to examine radon entry into buildings, the authors have constructed two room-size, precisely-fabricated basement structures at a site with relatively homogeneous, moderately permeable soil. The basements are identical except that one lies directly on native soil whereas the other lies on a high permeability aggregate layer. The soil pressure field and radon entry rate have been measured for different basement pressures and environmental conditions. The subslab gravel layer greatly enhances the advective entry of radon into the structure; when the structures are depressurized, the radon entry rate into the structure with the subslab gravel layer is more than a factor of 3 times the radon entry rate into the other structure for the same depressurization. The gravel subslab layer also spreads the pressure field around the structure, extending the field of influence of the structure and the region from which it draws radon.

  6. A study of the influence of a gravel subslab layer on radon entry rate using two basement structures

    SciTech Connect

    Robinson, A.L.; Sextro, R.G.; Fisk, W.J.; Garbesi, K.; Wooley, J.; Wollenberg, H.A.

    1993-01-01

    In buildings with elevated radon concentrations, the dominant transport mechanism of radon is advective flow of soil gas into the building substructure. However, the building-soil system is often complex, making detailed studies of the radon source term difficult. In order to examine radon entry into buildings, the authors have constructed two room-size, precisely-fabricated basement structures at a site with relatively homogeneous, moderately permeable soil. The basements are identical except that one lies directly on native soil whereas the other lies on a high permeability aggregate layer. The soil pressure field and radon entry rate have been measured for different basement pressures and environmental conditions. The subslab gravel layer greatly enhances the advective entry of radon into the structure; when the structures are depressurized, the radon entry rate into the structure with the subslab gravel layer is more than a factor of 3 times the radon entry rate into the other structure for the same depressurization. The gravel subslab layer also spreads the pressure field around the structure, extending the field of influence of the structure and the region from which it draws radon.

  7. The Influence of Irradiation Time and Layer Thickness on Elution of Triethylene Glycol Dimethacrylate from SDR® Bulk-Fill Composite.

    PubMed

    Łagocka, Ryta; Jakubowska, Katarzyna; Chlubek, Dariusz; Buczkowska-Radlińska, Jadwiga

    2016-01-01

    Objective. This study aimed to evaluate triethylene glycol dimethacrylate (TEGDMA) elution from SDR bulk-fill composite. Methods. Three groups of samples were prepared, including samples polymerized in a 4 mm layer for 20 s, in a 4 mm layer for 40 s, and in a 2 mm layer for 20 s. Elution of TEGDMA into 100% ethanol, a 75% ethanol/water solution, and distilled water was studied. The TEGDMA concentration was measured using HPLC. Results. The TEGDMA concentration decreased in the following order: 100% ethanol > 75% ethanol > distilled water. Doubling the energy delivered to the 4 mm thick sample caused decrease (p < 0.05) in TEGDMA elution to distilled water. In ethanol solutions, the energy increase had no influence on TEGDMA elution. Decreasing the sample thickness resulted in decrease (p < 0.05) in TEGDMA elution for all the solutions. Conclusions. The concentration of eluted TEGDMA and the elution time were both strongly affected by the hydrophobicity of the solvent. Doubling the energy delivered to the 4 mm thick sample did not decrease the elution of TEGDMA but did decrease the amount of the monomer available to less aggressive solvents. Elution of TEGDMA was also correlated with the exposed sample surface area. Clinical Relevance. Decreasing the SDR layer thickness decreases TEGDMA elution.

  8. Influence of land-surface and turbulent parameterization schemes on regional-scale boundary layer characteristics over northern India

    NASA Astrophysics Data System (ADS)

    Panda, Jagabandhu; Sharan, Maithili

    2012-08-01

    The influence of turbulent and land-surface parameterizations on regional scale boundary layer features over north India is analyzed using the Weather Research and Forecasting (WRF) modeling system during two contrasting cases of summer and winter. The model predicted surface temperatures, wind speeds, potential temperature profiles and wind speed profiles are compared with the observations from India Meteorological Department and Wyoming Weather Web data archive. The qualitative and quantitative analyses indicate that the model predictions are relatively better over three north Indian cities namely Delhi, Ahmedabad and Jodhpur when the Mellor-Yamada-Janjic boundary layer scheme along with Noah land-surface model is used. The near surface flow features during both summer and winter cases indicate the major role of land surface models (LSMs) as compared to the boundary layer parameterizations in governing the regional scale flow fields. The role of the LSMs and boundary layer parameterizations in the regional scale transport of dust particles from Thar region toward Delhi and its neighborhood depends upon their point of origin during summer. However, the flow trajectories travel in the opposite direction during the winter case because of the contrasting nature of the flow patterns and consequently, the formation of haze-like conditions over Delhi due to Thar dusts is not expected.

  9. The Influence of Irradiation Time and Layer Thickness on Elution of Triethylene Glycol Dimethacrylate from SDR® Bulk-Fill Composite

    PubMed Central

    Jakubowska, Katarzyna; Chlubek, Dariusz; Buczkowska-Radlińska, Jadwiga

    2016-01-01

    Objective. This study aimed to evaluate triethylene glycol dimethacrylate (TEGDMA) elution from SDR bulk-fill composite. Methods. Three groups of samples were prepared, including samples polymerized in a 4 mm layer for 20 s, in a 4 mm layer for 40 s, and in a 2 mm layer for 20 s. Elution of TEGDMA into 100% ethanol, a 75% ethanol/water solution, and distilled water was studied. The TEGDMA concentration was measured using HPLC. Results. The TEGDMA concentration decreased in the following order: 100% ethanol > 75% ethanol > distilled water. Doubling the energy delivered to the 4 mm thick sample caused decrease (p < 0.05) in TEGDMA elution to distilled water. In ethanol solutions, the energy increase had no influence on TEGDMA elution. Decreasing the sample thickness resulted in decrease (p < 0.05) in TEGDMA elution for all the solutions. Conclusions. The concentration of eluted TEGDMA and the elution time were both strongly affected by the hydrophobicity of the solvent. Doubling the energy delivered to the 4 mm thick sample did not decrease the elution of TEGDMA but did decrease the amount of the monomer available to less aggressive solvents. Elution of TEGDMA was also correlated with the exposed sample surface area. Clinical Relevance. Decreasing the SDR layer thickness decreases TEGDMA elution. PMID:27366742

  10. Interannual Variability of Deep-Layer Hydrologic Memory and Mechanisms of Its Influence on Surface Energy Fluxes.

    NASA Astrophysics Data System (ADS)

    Amenu, Geremew G.; Kumar, Praveen; Liang, Xin-Zhong

    2005-12-01

    The characteristics of deep-layer terrestrial memory are explored using observed soil moisture data and simulated soil temperature from the Illinois Climate Network stations. Both soil moisture and soil temperature are characterized by exponential decay in amplitude, linear lag in phase, and increasing persistence with depth. Using spectral analysis, four dominant low-frequency modes are identified in the soil moisture variability. These signals have periods of about 12, 17, 34, and 60 months, which correspond to annual cycle, (4/3) ENSO, quasi-biennial (QB) ENSO, and quasi-quadrennial (QQ) ENSO signals, respectively. For deep layers, the interannual modes are dominant over the annual cycle, and vice versa for the near-surface layer. There are inherently two mechanisms by which deep-layer moisture impacts the surface fluxes. First, its temporal variability sets the lower boundary condition for the transfer of moisture and heat fluxes from the surface. Second, this temporal variability influences the uptake of moisture by plant roots, resulting in the variability of the transpiration and, therefore, the entire energy balance. Initial results suggest that this second mechanism may be more predominant.

  11. The influence of equivalence ratio and Soret effect on the ignition of hydrogen-air mixtures in supersonic boundary layers

    SciTech Connect

    Figueira da Silva, L.F.; Deshaies, B.

    1994-12-31

    As a result of viscous heating, spontaneous ignition of a supersonic flow of premixed combustible gases can occur in boundary layers. In a previous numerical study, the main structure of the reacting flow related to this specific type of ignition was given in the case of a laminar boundary layer of hydrogen and air developing over a flat plate. To complete the first mapping of the ignition as a function of the boundary conditions, the authors present in this paper the results of a specific study of the influence of the equivalence ratio of the mixture on ignition. The equivalence ratio is found to modify the chemical induction time in the boundary layer as follows: (1) in a direct way, (2) via the dependence of the wall temperature on the composition. Because of these combined effects, the minimum induction length is obtained for unusually lead mixtures. As it modifies local composition, the Soret effect is also found to change the boundary-layer induction length.

  12. Influence of human skin specimens consisting of different skin layers on the result of in vitro permeation experiments.

    PubMed

    Henning, A; Neumann, D; Kostka, K-H; Lehr, C-M; Schaefer, U F

    2008-01-01

    The literature exhibits high variation in results from drug permeation experiments across human skin. Our purpose was to investigate the influence of human skin specimens, consisting of different skin layers and resulting from different skin preparation techniques, on the in vitro permeation of a model drug, i.e. flufenamic acid (FFA). FFA permeation across human (1) trypsin-isolated stratum corneum, (2) heat-separated epidermis and (3) dermis, (4) dermatomized skin and (5) full-thickness skin (FTS) from either a hydrophilic or lipophilic donor was investigated in Franz-type diffusion cells. Cumulative permeated drug amounts were plotted versus time, and a fit to Fick's 2nd law of diffusion was performed. Since performing skin diffusion experiments in the laboratory is time consuming and expensive, especially when using FTS, we also investigated the possibility of calculating the resistances of composite skin layers from the diffusion resistances of the individual skin layers. Due to short lag time, practical handling and economic preparation, heat-separated epidermis appears to be superior in human skin in vitro permeation experiments compared to separated stratumcorneum sheets, dermatomized skin and FTS. Furthermore, we found a good correlation between calculated and experimental resistances which underlines that calculation of the total diffusion resistance of composed skin preparations from resistances of individual skin layers is legitimate and useful. Considering our findings, improved interpretation of literature data and more consistent results for future permeation experiments are possible.

  13. Buffer influence on magnetic dead layer, critical current, and thermal stability in magnetic tunnel junctions with perpendicular magnetic anisotropy

    NASA Astrophysics Data System (ADS)

    Frankowski, Marek; Żywczak, Antoni; Czapkiewicz, Maciej; Zietek, Sławomir; Kanak, Jarosław; Banasik, Monika; Powroźnik, Wiesław; Skowroński, Witold; Checiński, Jakub; Wrona, Jerzy; Głowiński, Hubert; Dubowik, Janusz; Ansermet, Jean-Philippe; Stobiecki, Tomasz

    2015-06-01

    We present a detailed study of Ta/Ru-based buffers and their influence on features crucial from the point of view of applications of Magnetic Tunnel Junctions (MTJs) such as critical switching current and thermal stability. We study buffer/FeCoB/MgO/Ta/Ru and buffer/MgO/FeCoB/Ta/Ru layers, investigating the crystallographic texture, the roughness of the buffers, the magnetic domain pattern, the magnetic dead layer thickness, and the perpendicular magnetic anisotropy fields for each sample. Additionally, we examine the effect of the current induced magnetization switching for complete nanopillar MTJs with lateral dimensions of 270 × 180 nm. Buffer Ta 5/Ru 10/Ta 3 (thicknesses in nm), which has the thickest dead layer, exhibits a much larger thermal stability factor (63 compared to 32.5) while featuring a slightly lower critical current density value (1.25 MA/cm2 compared to 1.5 MA/cm2) than the buffer with the thinnest dead layer Ta 5/Ru 20/Ta 5. We can account for these results by considering the difference in damping which compensates for the difference in the switching barrier heights.

  14. Influence of layering on the formation and growth of solution pipes

    NASA Astrophysics Data System (ADS)

    Petrus, Karine; Szymczak, Piotr

    2015-12-01

    In karst systems, hydraulic conduits called solution pipes (or wormholes) are formed as a result of the dissolution of limestone rocks by the water surcharged with CO2. The solution pipes are the end result of a positive feedback between spatial variations in porosity in the rock matrix and the local dissolution rate. Here, we investigate numerically the effect of rock stratification on the solution pipe growth, using a simple model system with a number of horizontal layers, which are less porous than the rest of the matrix. Stratification is shown to affect the resulting piping patterns in a variety of ways. First of all, it enhances the competition between the pipes, impeding the growth of the shorter ones and enhancing the flow in the longer ones, which therefore grow longer. This is reflected in the change of the pipe length distribution, which becomes steeper as the porosity contrast between the layers is increased. Additionally, stratification affects the shapes of individual solution pipes, with characteristic widening of the profiles in between the layers and narrowing within the layers. These results are in qualitative agreement with the piping morphologies observed in nature.

  15. Laser cleaning of calcareous stones: influence of laser irradiation in colour changes of different layers

    NASA Astrophysics Data System (ADS)

    Amaral, Sandra S.; Pires, Margarida; Carvalho, M. D.; Costa, F. M.

    2008-10-01

    Experimental laser cleaning of black crusted calcareous stones, carried on to study the laser yellowing of petreous surfaces, showed different colour alterations on the exposed surface, after laser irradiation, depending not only on the incident fluence but also with the crust or stone irradiated layer.

  16. Influence of layered structure of the lower ionosphere on nonmonotonic spectrum behavior of ELF atmospheric noise

    SciTech Connect

    Molchanov, O.A. |; Nickolaenko, A.P.; Rafalsky, V.A. |; Schecotov, A.Yu.; Hayakawa, M.

    1994-11-15

    The authors present studies related to resonance phenomena occurring between and within different layers in the ionosphere, and the effect these resonances can have on the amplitude of extremely low frequency (ELF) wave propagation through the ionosphere. They follow several model problems to illustrate the impact of theses effects.

  17. Influence of layer microstructure on the double nucleation process in Cu/Mg multilayers

    SciTech Connect

    Gonzalez-Silveira, M.; Rodriguez-Viejo, J.; Garcia, G.; Pi, F.; Ager, F. J.; Labar, J. L.; Barna, A.; Menyhard, M.; Kotis, L.

    2006-12-01

    We have investigated by differential scanning calorimetry the thermal evolution of Cu/Mg multilayers with different modulation lengths, ranging from 7/28 to 30/120 nm. The Cu and Mg layers were grown by sequential evaporation in an electron beam deposition system. The phase identification and layer microstructure were determined by cross-section transmission electron microscopy, Rutherford backscattering, and scanning electron microscopy with focused ion beam for sample preparation. Upon heating, the intermetallic CuMg{sub 2} forms at the interfaces until coalescence is reached and thickens through a diffusion-limited process. Cross-section transmission electron microscopy observations show a distinct microstructure at the top and bottom of the as-prepared Mg layers, while no significant differences were seen in the Cu layers. We show that this effect is responsible for the observed asymmetry in the nucleation process between the Cu on Mg and the Mg on Cu interfaces. By modeling the calorimetric data we determine the role of both interfaces in the nucleation and lateral growth stages. We also show that vertical growth proceeds by grain development of the product phase, increasing significantly the roughness of the interfaces.

  18. Influence of Surface-Based Stable Layer Development on Asian Dust Behaviour Over Tokyo

    NASA Astrophysics Data System (ADS)

    Tsunematsu, Nobumitsu; Iwai, Hironori; Ishii, Shoken; Yasui, Motoaki; Murayama, Yasuhiro; Mizutani, Kohei

    2009-05-01

    The relationship between local meteorological fields and the behaviour of airborne Asian dust that arrived in the Tokyo metropolitan area on 1 April 2007 with the passage of a synoptic-scale cold front has been investigated through Doppler lidar observations, experiments using a regional atmospheric numerical model, and analyses of surface and upper-air meteorological observations. Results of the Doppler lidar observations showed that the Asian dust passed above the metropolitan area with strong south-westerly winds with speeds of 15-26 m s-1. Meteorological fields reproduced by the numerical experiments showed the development of a surface-based stable layer in the metropolitan area caused by nocturnal radiational cooling near the ground surface and south-westerly warm air advection at upper levels. The blocking effect of the mountainous region located to the west of the metropolitan area induced an area of stagnant air inside the metropolitan area and promoted the stable layer development. Although strong downdrafts prevailed in the upper air, the airborne Asian dust did not spread to the ground when the stable layer was formed. These results strongly indicate that the developed stable layer prevented strong downdrafts from spreading to the ground, acting as an obstacle to the transport of the Asian dust particles from the upper air towards the ground. This is considered to be one of the main causes of the low appearance frequency of Asian dust phenomena near the ground in the Tokyo metropolitan area and eastern Japan.

  19. Influence of patterning the TCO layer on the series resistance of thin film HIT solar cells

    NASA Astrophysics Data System (ADS)

    Champory, Romain; Mandorlo, Fabien; Seassal, Christian; Fave, Alain

    2017-01-01

    Thin HIT solar cells combine efficient surface passivation and high open circuit voltage leading to high conversion efficiencies. They require a TCO layer in order to ease carriers transfer to the top surface fingers. This Transparent Conductive Oxide layer induces parasitic absorption in the low wavelength range of the solar spectrum that limits the maximum short circuit current. In case of thin film HIT solar cells, the front surface is patterned in order to increase the effective life time of photons in the active material, and the TCO layer is often deposited with a conformal way leading to additional material on the sidewalls of the patterns. In this article, we propose an alternative scheme with a local etching of both the TCO and the front a-Si:H layers in order to reduce the parasitic absorption. We study how the local resistivity of the TCO evolves as a function of the patterns, and demonstrate how the increase of the series resistance can be compensated in order to increase the conversion efficiency.

  20. Influence of intermediate aminodextran layers on the signal response of surface acoustic wave biosensors.

    PubMed

    Länge, Kerstin; Rapp, Michael

    2008-06-15

    Surface acoustic wave (SAW) devices based on horizontally polarized surface shear waves enable direct and label-free detection of proteins in real time. Binding reactions on the sensor surface are detected by determining changes in surface wave velocity caused mainly by mass adsorption or change of viscoelasticity in the sensing layer. Intermediate hydrogel layers have been proven to be useful to immobilize capture molecules or ligands corresponding to the analyte. However, the SAW signal response strongly depends on the morphology of the hydrogel due to different relative changes of its acoustomechanical parameters such as viscoelasticity and density. In this work five aminodextrans (AMD) and one diamino polyethylene glycol (DA-PEG) were used as intermediate hydrogel layers. Sensors with immobilized streptavidin and samples containing biotinylated bovine serum albumin were used to exemplify affinity assays based on immobilized capture molecules for protein detection. The effects of the three-dimensional AMDs and the two-dimensional (2D) DA-PEG on the SAW signal response were investigated. The signal height decreased with increasing molar mass and increasing amount of immobilized AMD. Consequently, thin hydrogel layers are ideal to obtain optimum signal responses in this type of assay, whereas it is not necessarily a 2D hydrogel that gives the best results.

  1. Linear and weakly nonlinear aspects of free shear layer instability, roll-up, subharmonic interaction and wall influence

    NASA Technical Reports Server (NTRS)

    Cain, A. B.; Thompson, M. W.

    1986-01-01

    The growth of the momentum thickness and the modal disturbance energies are examined to study the nature and onset of nonlinearity in a temporally growing free shear layer. A shooting technique is used to find solutions to the linearized eigenvalue problem, and pseudospectral weakly nonlinear simulations of this flow are obtained for comparison. The roll-up of a fundamental disturbance follows linear theory predictions even with a 20 percent disturbance amplitude. A weak nonlinear interaction of the disturbance creates a finite-amplitude mean shear stress which dominates the growth of the layer momentum thickness, and the disturbance growth rate changes until the fundamental disturbance dominates. The fundamental then becomes an energy source for the harmonic, resulting in an increase in the growth rate of the subharmonic over the linear prediction even when the fundamental has no energy to give. Also considered are phase relations and the wall influence.

  2. A comparative study of the influence of nickel oxide layer on the FTO surface of organic light emitting diode

    NASA Astrophysics Data System (ADS)

    Saikia, Dhrubajyoti; Sarma, Ranjit

    2017-09-01

    The influence of thin layer of nickel oxide (NiO) over the fluorine-doped tin oxide (FTO) surface on the performance of Organic light-emitting diode (OLED) is reported. With an optimal thickness of NiO (10 nm), the luminance efficiency is found to be increased as compared to the single FTO OLED. The performance of OLED is studied by depositing NiO films at different thicknesses on the FTO surface and analyzed their J-V and L-V characteristics. Further analysis is carried out by measuring sheet resistance and optical transmittance. The surface morphology is studied with the help of FE-SEM images. Our results indicate that NiO (10 nm) buffer layer is an excellent choice to increase the efficiency of FTO based OLED devices within the charge tunneling region. The maximum value of current efficiency is found to be 7.32 Cd/A.

  3. The influence of flow parameters on the transition to turbulence in supersonic boundary layer on swept wing

    NASA Astrophysics Data System (ADS)

    Semionov, N. V.; Yermolaev, Yu. G.; Kosinov, A. D.; Dryasov, A. D.; Semenov, A. N.; Yatskikh, A. A.

    2016-10-01

    The paper is devoted to an experimental study of laminar-turbulent transition in a three-dimensional supersonic boundary layer. The experiments were conducted at the low nose supersonic wind tunnel T-325 of ITAM at Mach numbers M=2 - 4. Model is a symmetrical wing with a 45° sweep angle, a 3 percent-thick circular-arc airfoil. The influence of flow parameters, such as the Mach number, unit Reynolds number, angle of attack, level of perturbations on the transitions to turbulence are on the consideration. Transition Reynolds numbers are obtained. Analysis of all obtained data allow to determine reliable value of Retr of swept wing supersonic boundary layer, that especially important at consideration of experiments fulfilled at different flow conditions in different wind tunnels.

  4. Linear and weakly nonlinear aspects of free shear layer instability, roll-up, subharmonic interaction and wall influence

    NASA Technical Reports Server (NTRS)

    Cain, A. B.; Thompson, M. W.

    1986-01-01

    The growth of the momentum thickness and the modal disturbance energies are examined to study the nature and onset of nonlinearity in a temporally growing free shear layer. A shooting technique is used to find solutions to the linearized eigenvalue problem, and pseudospectral weakly nonlinear simulations of this flow are obtained for comparison. The roll-up of a fundamental disturbance follows linear theory predictions even with a 20 percent disturbance amplitude. A weak nonlinear interaction of the disturbance creates a finite-amplitude mean shear stress which dominates the growth of the layer momentum thickness, and the disturbance growth rate changes until the fundamental disturbance dominates. The fundamental then becomes an energy source for the harmonic, resulting in an increase in the growth rate of the subharmonic over the linear prediction even when the fundamental has no energy to give. Also considered are phase relations and the wall influence.

  5. Cap Layer Influence on Impurity-Free Vacancy Disordering of InGaAs/InP Quantum Well Structure

    NASA Astrophysics Data System (ADS)

    An, Yu-Peng; Yang, Hua; Mei, Ting; Wang, Yi-Ding; Teng, Jing-Hua; Xu, Cheng-Dong

    2010-01-01

    Quantum well intermixing (QWI) by the impurity-free vacancy disordering (IFVD) technique is an important and effective approach for the monolithic integration of optoelectronic devices based on InGaAs/InP quantum well structures. We experimentally investigate the influence of the capping layer SiO2 and Si3N4 on the QWI by IFVD. The results show that for all the samples with three-types differently doped (P, N and I) top InP layers, Si3N4 can always induce a larger photoluminescence blueshift than SiO2 in the IFVD QWI process, which attributes more to the group III and V vacancies point defects created in the interface of Si3N4-InP than that of SiO2-InP, proved by the SIMS measurements. The inherent mechanisms for explaining these properties are further discussed.

  6. Surface-sensitive reflection-mode EXAFS from layered sample systems: the influence of surface and interface roughness.

    PubMed

    Keil, P; Lützenkirchen-Hecht, D

    2009-07-01

    The calculation of reflection-mode grazing-incidence X-ray absorption spectra from single surfaces and (multi-)layered systems is studied here. In particular, the influence of the surface and interface roughness was investigated in detail. Simulations of grazing-incidence reflection-mode EXAFS spectra using a simple Fresnel theory neglecting any effect of roughness are compared with the Névot-Croce model and the elaborated distorted-wave Born approximation which both include surface and interface roughness. Data are presented for clean gold surfaces, where the strong influence of the surface roughness on the resulting spectra is demonstrated. Furthermore, in the case of layered systems, the influence of both the outer (air or vacuum side) surface roughness and the inner interface roughness on the reflection-mode EXAFS spectra is evaluated. The practical consequences of the observed correlations are discussed, and a quantitative data analysis of a copper sample that was oxidized in ambient air for several months is shown, including the evaluation of specular reflectivity profiles at fixed energy.

  7. Influence of electric-double-layer structure on the transient response of nanochannels

    NASA Astrophysics Data System (ADS)

    Schiffbauer, Jarrod; Yossifon, Gilad

    2014-05-01

    A fundamental Poisson-Nernst-Planck-Stokes model is presented for the impedance response of a long nanochannel under zero bias, capturing the effects of surface conduction and the coupling between transverse momentum and axial ion distribution in a manner reminiscent of Taylor dispersion. This is shown to result in a shift of the impedance frequency spectrum with bulk concentration similar to previous experimental observation [Schiffbauer, Liel, and Yossifon, Phys. Rev. E 89, 033017 (2014), 10.1103/PhysRevE.89.033017]. It further predicts an additional downward shift in frequency with increasing viscosity. Finally, the introduction of a phenomenological model for the impedance response of a dynamic Stern layer in parallel with the diffuse layer transport model is shown to yield good agreement between theory and experiment. As a result, we are able to obtain an equivalent circuit model based on the fundamental model and proposed corrections.

  8. On the Influence of Internal Density Variations on the Linear Stability Characteristics of Planar Shear Layers

    DTIC Science & Technology

    2014-01-01

    PROJECT NUMBER Hajesfandiari, A. and Forliti, D. J. 5e. TASK NUMBER 5f. WORK UNIT NUMBER Q0YA 7. PERFORMING ORGANIZATION NAME(S) AND...ADDRESS(ES) 8. PERFORMING ORGANIZATION REPORT NO. Air Force Research Laboratory (AFMC) AFRL/RQRC 10 E. Saturn Blvd. Edwards AFB, CA, 93524-7680...the right to use, modify, reproduce, release, perform , display, or disclose the work. 14. ABSTRACT Planar shear layers are known to be sensitive to

  9. Influence of the Halogen Activation on the Ozone Layer in XXIst Century

    NASA Astrophysics Data System (ADS)

    Larin, Igor; Aloyan, Artash; Yermakov, Alexandr

    2016-04-01

    The aim of the work is to evaluate a possible effect of heterophase chemical reactions (HCR) with participation of reservoir gases (ClONO2, HCl) and sulfate particles of the Junge layer on the ozone layer at mid-latitudes in the XXI century, which could be relevant for more accurate predicting a recovery of the ozone layer, taking into account that just these processes were the main cause of the ozone depletion at the end of XXth century. Required for calculating the dynamics of GHR data on the specific volume/surface of the sulfate aerosols in the lower stratosphere were taken from the data of field experiments. Their physico-chemical properties (chemical composition, density, water activity and free protons activity et al.) have been obtained with help of thermodynamic calculations (Atmospheric Inorganic Model, AIM). Altitude concentration profiles of individual gas components, as well as temperature and relative humidity (RH) at a given geographic location and season have been calculated using a two-dimensional model SOCRATES. The calculations have been made for the conditions of June 1995, 2040 and 2080 at 15 km altitude and 50° N latitude. It has been shown that the rate of ozone depletion as a result of processes involving halogen activation for the given conditions in 2040, 2080 is about 35% lower than a corresponding value in 1995 (a year of maximum effect of halogen activation). From this we can conclude that in the XXI century, despite the natural decline of ozone-depleting chlorofluorocarbons. processes of halogen activation of the ozone depletion with participation of sulfate aerosols should be taken into account in the calculations of the recovery of the ozone layer at mid-latitudes.

  10. The influence of nanoclay on the durability properties of asphalt mixtures for top and base layers

    NASA Astrophysics Data System (ADS)

    Blom, Johan; De Kinder, Bram; Meeusen, Jannes; Van den bergh, Wim

    2017-09-01

    To avoid traffic congestion, due to road works, a continuous research into asphalt pavement and especially its durability is of great importance. This research focuses on improving the mechanical performance and the durability of asphalt mixtures by nanoclay modified bitumen. This promising technique of introducing nanoclays or nano particles into bitumen could offer an significant improvement on the fatigue properties and rutting performance and thus the durability of the asphalt top layer.

  11. Influence of (phospho)lipases on properties of mica supported phospholipid layers

    NASA Astrophysics Data System (ADS)

    Jurak, Malgorzata; Chibowski, Emil

    2010-08-01

    The effect of enzymes: lipase from Candida cylindracea (L Cc), phospholipase A 2 from hog pancreas (PLA 2) and phospholipase C from Bacillus cereus (PLC) to modulate wetting properties of solid supported phospholipid bilayers was studied via advancing and receding contact angle measurements of water, formamide and diiodomethane, and calculation of the surface free energy and its components from van Oss et al. (LWAB) and contact angle hysteresis (CAH) approaches. Simultaneously, topography of the studied layers was determined by Atomic Force Microscopy (AFM). The investigated lipid bilayers were transferred on mica plates from subphase of pure water by means of Langmuir-Blodgett and Langmuir-Schaefer techniques. The investigated phospolipid layers were: saturated DPPC (1,2-dipalmitoyl- sn-glycero-3-phosphocholine), unsaturated DOPC (1,2-dioleoyl- sn-glycero-3-phosphocholine), and their mixture DPPC/DOPC. The obtained results revealed that the lipid membrane degradation by the enzymes caused increase in its surface free energy due to the amphiphilic hydrolysis products, which may accumulate in the lipid bilayer. In result activity of the enzymes may increase and then break down the bilayer structure takes place. It is likely that after dissolution of the hydrolysis reaction products in the bulk phase, patches of bare mica surface are accessible, which contribute to the apparent surface free energy changes. Comparison of AFM images and the free energy changes of the layers gives better insight into changes of their properties. The observed gradual increase in the layer surface free energy allows controlling of the hydrolysis process to obtain the surfaces of defined properties.

  12. Factors Influencing the Nearshore Sound-Scattering Layer in Hawaiian Waters

    DTIC Science & Technology

    2005-09-30

    autonomous profiler was deployed at the 26 m site (Figure 2A). The autonomous profiler (the Seahorse ; Brooke Ocean Technology) uses wave energy to power...autonomous profiler (the Seahorse ; Brooke Ocean Technology), (B) 200 kHz echosounder, thermistor chain with 3 temperature units. (C) 200 kHz... SeaHorse is given in Figure 8. There are 576 continuous profiles in this record, with < 1 cm vertical resolution. A thin optical layer was observed for the

  13. Influence of attached bacteria and biofilm on double-layer capacitance during biofilm monitoring by electrochemical impedance spectroscopy.

    PubMed

    Kim, Taeyoung; Kang, Junil; Lee, Joon-Hee; Yoon, Jeyong

    2011-10-01

    Development of an effective strategy for biofilm control in water-related system has become a matter of significant concern nowadays. Electrochemical monitoring, especially electrochemical impedance spectroscopy (EIS), is one of the efficient approaches to dealing with biofilm-related issues. However, currently used EIS methods without a redox probe intend to detect all effects generated from media components, bacteria, and bacterial metabolites, which used to make the signals from the attached bacteria and biofilm weakened. In this study, we tried improved EIS measurement to monitor bacterial adhesion and biofilm maturation using a double-layer capacitance. In this improved method, we minimized background signal by subtracting the interference of electrolyte caused by bacterial metabolism. Pseudomonas aeruginosa PA14 wild type and wspF mutant that form the biofilm of distinct nature were used for the model strains to test our method. During bacterial adhesion and biofilm maturation, EIS data were collected and equivalent circuit analysis was carried out to obtain constant phase element (CPE) values representing double-layer capacitance. Since the influence by the bacterial growth-related culture media condition was eliminated by adopting fresh electrolyte at the measurement, the contribution of attached bacteria and biofilm was exclusively measured. As a result, the bacterial adhesion at the early stage of biofilm development was specifically monitored from reduction in double-layer capacitance. Particularly, the plateau in double-layer capacitance appeared upon biofilm maturation, indicating that biofilm maturation could be expected beyond this point. In conclusion, this study found that measurement of double-layer capacitance based on EIS could provide a monitoring parameter suggesting bacterial adhesion and the initiation point of biofilm maturation.

  14. Influence of Idealized Heterogeneity on Wet and Dry Planetary Boundary Layers Coupled to the Land Surface. 2; Phase-Averages

    NASA Technical Reports Server (NTRS)

    Houser, Paul (Technical Monitor); Patton, Edward G.; Sullivan, Peter P.; Moeng, Chin-Hoh

    2003-01-01

    We examine the influence of surface heterogeneity on boundary layers using a large-eddy simulation coupled to a land-surface model. Heterogeneity, imposed in strips varying from 2-30 km (1 less than lambda/z(sub i) less than 18), is found to dramatically alter the structure of the free convective boundary layer by inducing significant organized circulations. A conditional sampling technique, based on the scale of the surface heterogeneity (phase averaging), is used to identify and quantify the organized surface fluxes and motions in the atmospheric boundary layer. The impact of the organized motions on turbulent transport depends critically on the scale of the heterogeneity lambda, the boundary layer height zi and the initial moisture state of the boundary layer. Dynamical and scalar fields respond differently as the scale of the heterogeneity varies. Surface heterogeneity of scale 4 less than lamba/z(sub i) less than 9 induces the strongest organized flow fields (up, wp) while heterogeneity with smaller or larger lambda/z(sub i) induces little organized motion. However, the organized components of the scalar fields (virtual potential temperature and mixing ratio) grow continuously in magnitude and horizontal scale, as lambda/z(sub i) increases. For some cases, the organized motions can contribute nearly 100% of the total vertical moisture flux. Patch-induced fluxes are shown to dramatically impact point measurements that assume the time-average vertical velocity to be zero. The magnitude and sign of this impact depends on the location of the measurement within the region of heterogeneity.

  15. The influence of magnesium oxide interfacial layer on photovoltaic properties of dye-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Asemi, M.; Ghanaatshoar, M.

    2016-09-01

    In the present study, to enhance the power conversion efficiency of the DSSCs, we introduce MgO insulating layers at the interface between TiO2 and electrolyte to decrease charge recombination rate by suppressing the electron transfer from TiO2 to the electrolyte. The thickness of the MgO layer plays a vital role in the kinetics of dye-sensitized solar cells and affects their overall efficiency. The cell with optimized thickness of MgO layer exhibits the highest conversion efficiency ( η = 5.12 %) with a high short-circuit current density (18.15 mA/cm2) and open-circuit voltage (0.571 V). Open-circuit voltage decay measurement results verify the improvement of the electrons lifetime in the DSSCs fabricated with surface-modified photoanodes due to the retarding the charge recombination. In order to explore the reasons for the J SC improvement, incident photon-to-current conversion efficiency measurement was taken. Our results show that the enhancement in the photoinjected electron lifetime can contribute to an increase in the electron collection efficiency, leading to the improved J SC value. Furthermore, the enhancement in the photoinjected electron recombination rate is also demonstrated by electrochemical impedance spectroscopy.

  16. Influence of oxygen content on the crystallinity of MgO layers in magnetic tunnel junctions

    NASA Astrophysics Data System (ADS)

    Yongle, Lou; Yuming, Zhang; Daqing, Xu; Hui, Guo; Yimen, Zhang; Yuchen, Li

    2014-08-01

    With RF sputtering process, Si/SiO2/Ta/Ru/Ta/CoFeB/MgO/CoFeB/Ta/Ru structure has been grown on Si (100) substrate. Attempting different targets and adjusting the oxygen dose, the crystallization quality of the MgO layer is studied. The X-ray diffraction measurements demonstrate that crystal structure and crystallization quality of MgO layers are related to the type of target and concentration of oxygen in sputtering process. With the method sputtering Mg in an ambient flow of oxygen, not only the crystallization quality of a normal MgO layer with lattice constant of 0.421 nm is improved, but also a new MgO crystal with lattice constant of 0.812 nm is formed and the perpendicular magnetic anisotropy of CoFeB is enhanced. Also it is found that crystallization quality for both the normal MgO and new MgO is more improved with MgO target and same oxygen dose, which means that this new method is helpful to form a new structure of MgO with lattice constant of 0.812 nm. All of the samples were annealed at 400 °C in vacuum.

  17. Vegetation type and layer depth influence nitrite-dependent methane-oxidizing bacteria in constructed wetland.

    PubMed

    Yang, Mengxi; Guo, Qingwei; Tong, Tianli; Li, Ningning; Xie, Shuguang; Long, Yan

    2017-04-01

    Nitrite-dependent anaerobic methane oxidation (n-damo) process might be an important methane sink in wetland system. However, information on n-damo microorganisms in constructed wetland (CW) system for water treatment is still lacking. The present study investigated the n-damo communities in five full-scale vertical-flow CW systems with different plants. N-damo bacterial abundance did not show a considerable shift in CW planted with Cyperus papyrus, but varied greatly in other CW systems. However, the evident vertical change of n-damo community diversity occurred in each CW system. These CW systems displayed the different vertical change trends for either n-damo community abundance or diversity. In addition, CW n-damo community structure could change with wetland layer depth. At a given wetland layer depth, the evident difference of n-damo community abundance, diversity and structure could be observed in the five different CW systems. Both wetland layer depth and vegetation type could contribute to the shift of n-damo bacterial abundance and community structure in CWs.

  18. The influence of a very large wind farm on turbulent transport in the atmospheric boundary layer

    NASA Astrophysics Data System (ADS)

    Abkar, M.; Porté-Agel, F.

    2012-04-01

    Predicting wind and turbulent transport of heat, water vapor and pollutants through wind farms is of great importance for wind engineering, wind energy and environmental applications. It requires detailed knowledge of atmospheric boundary-layer (ABL) over a wide range of spatial and temporal scales. The complexity of such flows makes it difficult to obtain all the needed information through field experiments alone, and often necessitates high-resolution eddy-resolving numerical tools such as large-eddy simulation (LES). In this study, Large-eddy simulation is used to simulate atmospheric boundary-layer flow through a very large wind farm. To do this, tuning-free Lagrangian scale-dependent dynamic models (Stoll and Porte-Agel 2006) are used to model the subgrid-scale fluxes and the turbine-induced forces are parameterized using the actuator disk model (Wu and Porte-Agel 2011). The effect of large arrays of wind turbines on local/regional fluxes of momentum and scalar quantities under different stability conditions is assessed. Also, it will be shown how wind farms can change the vertical distribution of momentum and scalar fluxes inside the ABL. Particular attention is placed on the growth of the boundary layer height due to the presence of the wind turbines.

  19. Light source distribution and scattering phase function influence light transport in diffuse multi-layered media

    NASA Astrophysics Data System (ADS)

    Vaudelle, Fabrice; L'Huillier, Jean-Pierre; Askoura, Mohamed Lamine

    2017-06-01

    Red and near-Infrared light is often used as a useful diagnostic and imaging probe for highly scattering media such as biological tissues, fruits and vegetables. Part of diffusively reflected light gives interesting information related to the tissue subsurface, whereas light recorded at further distances may probe deeper into the interrogated turbid tissues. However, modelling diffusive events occurring at short source-detector distances requires to consider both the distribution of the light sources and the scattering phase functions. In this report, a modified Monte Carlo model is used to compute light transport in curved and multi-layered tissue samples which are covered with a thin and highly diffusing tissue layer. Different light source distributions (ballistic, diffuse or Lambertian) are tested with specific scattering phase functions (modified or not modified Henyey-Greenstein, Gegenbauer and Mie) to compute the amount of backscattered and transmitted light in apple and human skin structures. Comparisons between simulation results and experiments carried out with a multispectral imaging setup confirm the soundness of the theoretical strategy and may explain the role of the skin on light transport in whole and half-cut apples. Other computational results show that a Lambertian source distribution combined with a Henyey-Greenstein phase function provides a higher photon density in the stratum corneum than in the upper dermis layer. Furthermore, it is also shown that the scattering phase function may affect the shape and the magnitude of the Bidirectional Reflectance Distribution (BRDF) exhibited at the skin surface.

  20. The influence of an In0.52Al0.48As transition layer design on the transport characteristics of a metamorphic high-electron-mobility transistor

    NASA Astrophysics Data System (ADS)

    Lazarenko, A. A.; Nikitina, E. V.; Pirogov, E. V.; Sobolev, M. S.; Egorov, A. Yu.

    2016-03-01

    We have used the atomic force microscopy and Hall effect measurements to study the influence of In0.52Al0.48As transition layer design on the electron mobility in the InAlAs/InGaAs/GaAs channel of a highelectron- mobility transistor (HEMT) with the metamorphic buffer. The optimum buffer layer favors suppression of the misfit dislocation threading into upper layers of the HEMT heterostructure and prevents development of the surface microrelief.

  1. Influence of layering on the formation and growth of dissolution pipes in karst systems

    NASA Astrophysics Data System (ADS)

    Petrus, Karine; Pecelerowicz, Michal; Szymczak, Piotr

    2015-04-01

    In karst systems, hydraulic conduits called dissolution pipes (a.k.a. wormholes) are formed as a result of the dissolution of limestone rocks by the water surcharged with CO2. The dissolution pipes are the end result of a positive feedback between spatial variations in porosity in the initial matrix and the local dissolution rate. A small enhancement in porosity at some point in the reaction front increases the fluid flow in that region, which convects reactant further downstream. By this means any local variation in porosity is amplified as the reaction front passes through and propagates downstream with the front, eventually developing into dissolution pipes. As dissolution proceeds the growing pipes interact, competing for the available flow, and eventually the growth of the shorter ones ceases. Here, we investigate numerically the effect of rock stratification on the dissolution pipe growth, using a simple model system with a number of horizontal bedding planes, which are less porous than the rest of the matrix. Stratification is shown to affect the resulting piping patterns in a variety of ways. First of all, it enhances the competition between the pipes, impeding the growth of the shorter ones and enhancing the flow in the longer ones, which therefore grow longer. Next, it affects the shapes of individual dissolution pipes, with characteristic widening of the profiles in between the layers and narrowing within the layers. These results are in qualitative agreement with the piping morphologies observed in nature. Importantly, measuring the ratio between the pipe diameters in different layers can provide one with information on the conditions prevailing during the formation of the pattern as well as on the physical characteristics of the layers in a given natural system. Additionally, we have investigated the model with layers of the same porosity but a smaller dissolution rate. Interestingly, in this case, the stratification is shown to weaken the competition

  2. Influence of defect formation as a result of incorporation of a Mn {delta} layer on the photosensitiviy spectrum of InGaAs/GaAs quantum wells

    SciTech Connect

    Gorshkov, A. P. Karpovich, I. A.; Pavlova, E. D.; Kalenteva, I. L.

    2012-02-15

    The influence of defect formation upon the deposition of a Mn {delta} layer and a GaAs coating layer (with the use of laser evaporation) on the photosensitivity spectra of heterostructures with InGaAs/GaAs quantum wells located in the near-surface region has been studied.

  3. Influence of the spatial arrangement of the Si δ layer on the optoelectronic properties of InGaAs/GaAs quantum-well nanoheterostructures

    SciTech Connect

    Volkova, N. S. Gorshkov, A. P.; Tikhov, S. V.; Baidus, N. V.; Khazanova, S. V.; Degtyarev, V. E.; Filatov, D. O.

    2015-02-15

    The photosensitivity, photoluminescence, and electroluminescence spectra of InGaAs/GaAs diode nanoheterostructures with a Si δ layer formed at a distance of 10 nm from the InGaAs quantum well are studied. The influence of the arrangement of the δ layer with respect to the quantum well on the optoelectronic properties of the structures is established.

  4. Evidence of Deep Convective Transport of Reactive Constituents to the Tropical Tropopause Layer Using Convective Influence Calculations

    NASA Astrophysics Data System (ADS)

    Selkirk, H. B.; Pfister, L.; Ridley, B. A.; Atlas, E.

    2003-12-01

    Isentropic convective influence calculations are performed to identify upstream convective systems impacting air sampled just below the subtropical and tropical tropopause on a flight of the NASA WB-57F from Houston, Texas south to 5° N during the September 1999 airborne mission Atmospheric Chemistry of Combustion Effects Near the Tropopause (ACCENT). Interpretation of ensembles of in situ tracer measurements, in particular NOy, O3, and CH3I, have indicated that much of the air sampled on this flight had been recently injected by deep convection, although from non-pristine marine boundary layers. In addition there were more limited stretches of the flight track with evidence of biomass burning and industrial sources. Consistent with this finding, convective influence calculations indicate that the great majority of the parcels along the flight track had been affected by deep convective events at some time in the seven days preceding the flight; the majority of these were oceanic systems. Under the anticyclonic upper tropospheric flow pattern prevailing north of ˜11° N, the marine convective influence came from systems in the Gulf of Mexico, around Cuba and over the waters east of the Bahamas. Influence from continental systems was sporadic except for one extended portion of the track with air that the calculations indicated had been injected by land-based systems over Guatemala within the previous 12-24 hours. South of ˜11° N, a group of systems east of the Lesser Antilles were major contributors of marine influence. However, as the aircraft approached its turnaround at 5° N, the calculations also show influence from land-based systems over Colombia, consistent with the tracer measurements. One important feature of the results is that the convective influence over the course of the 2600-km flight track is derived from a relatively small number of systems. This is a direct result of the minimal dispersion of the trajectories, particularly those emanating from

  5. Influence of thickness and permeability of endothelial surface layer on transmission of shear stress in capillaries

    NASA Astrophysics Data System (ADS)

    Zhang, SongPeng; Zhang, XiangJun; Tian, Yu; Meng, YongGang; Lipowsky, Herbert

    2015-07-01

    The molecular coating on the surface of microvascular endothelium has been identified as a barrier to transvascular exchange of solutes. With a thickness of hundreds of nanometers, this endothelial surface layer (ESL) has been treated as a porous domain within which fluid shear stresses are dissipated and transmitted to the solid matrix to initiate mechanotransduction events. The present study aims to examine the effects of the ESL thickness and permeability on the transmission of shear stress throughout the ESL. Our results indicate that fluid shear stresses rapidly decrease to insignificant levels within a thin transition layer near the outer boundary of the ESL with a thickness on the order of ten nanometers. The thickness of the transition zone between free fluid and the porous layer was found to be proportional to the square root of the Darcy permeability. As the permeability is reduced ten-fold, the interfacial fluid and solid matrix shear stress gradients increase exponentially two-fold. While the interfacial fluid shear stress is positively related to the ESL thickness, the transmitted matrix stress is reduced by about 50% as the ESL thickness is decreased from 500 to 100 nm, which may occur under pathological conditions. Thus, thickness and permeability of the ESL are two main factors that determine flow features and the apportionment of shear stresses between the fluid and solid phases of the ESL. These results may shed light on the mechanisms of force transmission through the ESL and the pathological events caused by alterations in thickness and permeability of the ESL.

  6. Observing and modeling the influence of layering on bubble trapping in polar firn

    NASA Astrophysics Data System (ADS)

    Mitchell, Logan E.; Buizert, Christo; Brook, Edward J.; Breton, Daniel J.; Fegyveresi, John; Baggenstos, Daniel; Orsi, Anais; Severinghaus, Jeffrey; Alley, Richard B.; Albert, Mary; Rhodes, Rachael H.; McConnell, Joseph R.; Sigl, Michael; Maselli, Olivia; Gregory, Stephanie; Ahn, Jinho

    2015-03-01

    Interpretation of ice core trace gas records depends on an accurate understanding of the processes that smooth the atmospheric signal in the firn. Much work has been done to understand the processes affecting air transport in the open pores of the firn, but a paucity of data from air trapped in bubbles in the firn-ice transition region has limited the ability to constrain the effect of bubble closure processes. Here we present high-resolution measurements of firn density, methane concentrations, nitrogen isotopes, and total air content that show layering in the firn-ice transition region at the West Antarctic Ice Sheet (WAIS) Divide ice core site. Using the notion that bubble trapping is a stochastic process, we derive a new parameterization for closed porosity that incorporates the effects of layering in a steady state firn modeling approach. We include the process of bubble trapping into an open-porosity firn air transport model and obtain a good fit to the firn core data. We find that layering broadens the depth range over which bubbles are trapped, widens the modeled gas age distribution of air in closed bubbles, reduces the mean gas age of air in closed bubbles, and introduces stratigraphic irregularities in the gas age scale that have a peak-to-peak variability of ~10 years at WAIS Divide. For a more complete understanding of gas occlusion and its impact on ice core records, we suggest that this experiment be repeated at sites climatically different from WAIS Divide, for example, on the East Antarctic plateau.

  7. Assumptions about footprint layer heights influence the quantification of emission sources: a case study for Cyprus

    NASA Astrophysics Data System (ADS)

    Hüser, Imke; Harder, Hartwig; Heil, Angelika; Kaiser, Johannes W.

    2017-09-01

    Lagrangian particle dispersion models (LPDMs) in backward mode are widely used to quantify the impact of transboundary pollution on downwind sites. Most LPDM applications count particles with a technique that introduces a so-called footprint layer (FL) with constant height, in which passing air tracer particles are assumed to be affected by surface emissions. The mixing layer dynamics are represented by the underlying meteorological model. This particle counting technique implicitly assumes that the atmosphere is well mixed in the FL. We have performed backward trajectory simulations with the FLEXPART model starting at Cyprus to calculate the sensitivity to emissions of upwind pollution sources. The emission sensitivity is used to quantify source contributions at the receptor and support the interpretation of ground measurements carried out during the CYPHEX campaign in July 2014. Here we analyse the effects of different constant and dynamic FL height assumptions. The results show that calculations with FL heights of 100 and 300 m yield similar but still discernible results. Comparison of calculations with FL heights constant at 300 m and dynamically following the planetary boundary layer (PBL) height exhibits systematic differences, with daytime and night-time sensitivity differences compensating for each other. The differences at daytime when a well-mixed PBL can be assumed indicate that residual inaccuracies in the representation of the mixing layer dynamics in the trajectories may introduce errors in the impact assessment on downwind sites. Emissions from vegetation fires are mixed up by pyrogenic convection which is not represented in FLEXPART. Neglecting this convection may lead to severe over- or underestimations of the downwind smoke concentrations. Introducing an extreme fire source from a different year in our study period and using fire-observation-based plume heights as reference, we find an overestimation of more than 60  % by the constant FL

  8. Hydrography and bottom boundary layer dynamics: Influence on inner shelf sediment mobility, Long Bay, North Carolina

    USGS Publications Warehouse

    Davis, L.A.; Leonard, L.A.; Snedden, G.A.

    2008-01-01

    This study examined the hydrography and bottom boundary-layer dynamics of two typical storm events affecting coastal North Carolina (NC); a hurricane and the passages of two small consecutive extratropical storms during November 2005. Two upward-looking 1200-kHz Acoustic Doppler Current Profilers (ADCP) were deployed on the inner shelf in northern Long Bay, NC at water depths of less than 15 m. Both instruments profiled the overlying water column in 0.35 in bins beginning at a height of 1.35 in above the bottom (mab). Simultaneous measurements of wind speed and direction, wave and current parameters, and acoustic backscatter were coupled with output from a bottom boundary layer (bbl) model to describe the hydrography and boundary layer conditions during each event. The bbl model also was used to quantify sediment transport in the boundary layer during each storm. Both study sites exhibited similar temporal variations in wave and current magnitude, however, wave heights during the November event were higher than waves associated with the hurricane. Near-bottom mean and subtidal currents, however, were of greater magnitude during the hurricane. Peak depth-integrated suspended sediment transport during the November event exceeded transport associated with the hurricane by 25-70%. Substantial spatial variations in sediment transport existed throughout both events. During both events, along-shelf sediment transport exceeded across-shelf transport and was related to the magnitude and direction of subtidal currents. Given the variations in sediment type across the bay, complex shoreline configuration, and local bathymetry, the sediment transport rates reported here are very site specific. However, the general hydrography associated with the two storms is representative of conditions across northern Long Bay. Since the beaches in the study area undergo frequent renourishment to counter the effects of beach erosion, the results of this study also are relevant to coastal

  9. The Influence of Impurities and Metallic Capping Layers on the Microstructure of Copper Interconnects

    NASA Astrophysics Data System (ADS)

    Rizzolo, Michael

    As copper interconnects have scaled to ever smaller dimensions on semiconductor devices, the microstructure has become increasingly detrimental for performance and reliability. Small grains persist in interconnects despite annealing at high temperatures, leading to higher line resistance and more frequent electromigration-induced failures. Conventionally, it was believed that impurities from the electrodeposition pinned grain growth, but limitations in analytical techniques meant the effect was inferred rather than observed. Recent advances in analytical techniques, however, have enabled this work to quantify impurity content, location, and diffusion in relation to microstructural changes in electroplated copper. Surface segregation of impurities during the initial burst of grain growth was investigated. After no surface segregation was observed, a microfluidic plating cell was constructed to plate multilayer films with regions of intentionally high and low impurity concentrations to determine if grain growth could be pinned by the presence of impurities; it was not. An alternate mechanism for grain boundary pinning based on the texture of the seed layer is proposed, supported by time-resolved transmission electron microscopy and transmission electron backscatter diffraction data. The suggested model posits that the seed in narrow features has no preferred orientation, which results in rapid nucleation of subsurface grains in trench regions prior to recrystallization from the overburden down. These rapidly growing grains are able to block off several trenches from the larger overburden grains, inhibiting grain growth in narrow features. With this knowledge in hand, metallic capping layers were employed to address the problematic microstructure in 70nm lines. The capping layers (chromium, nickel, zinc, and tin) were plated on the copper overburden prior to annealing to manipulate the stress gradient and microstructural development during annealing. It appeared that

  10. Influence of irradiation upon few-layered graphene using electron-beams and gamma-rays

    NASA Astrophysics Data System (ADS)

    Wang, Yuqing; Feng, Yi; Mo, Fei; Qian, Gang; Chen, Yangming; Yu, Dongbo; Wang, Yang; Zhang, Xuebin

    2014-07-01

    Few-layered graphene (FLG) is irradiated by electron beams and gamma rays. After 100 keV electron irradiation, the edges of FLG start bending, shrinking, and finally generate gaps and carbon onions due to sputtering and knock-on damage mechanism. When the electron beam energy is increased further to 200 keV, FLG suffers rapid and catastrophic destruction. Unlike electron irradiation, Compton effect is the dominant damage mechanism in gamma irradiation. The irradiation results indicate the crystallinity of FLG decreases first, then restores as increasing irradiation doses, additionally, the ratio (O/C) of FLG surface and the relative content of oxygen groups increases after irradiation.

  11. Influence of irradiation upon few-layered graphene using electron-beams and gamma-rays

    SciTech Connect

    Wang, Yuqing; Feng, Yi Mo, Fei; Qian, Gang; Chen, Yangming; Yu, Dongbo; Wang, Yang; Zhang, Xuebin

    2014-07-14

    Few-layered graphene (FLG) is irradiated by electron beams and gamma rays. After 100 keV electron irradiation, the edges of FLG start bending, shrinking, and finally generate gaps and carbon onions due to sputtering and knock-on damage mechanism. When the electron beam energy is increased further to 200 keV, FLG suffers rapid and catastrophic destruction. Unlike electron irradiation, Compton effect is the dominant damage mechanism in gamma irradiation. The irradiation results indicate the crystallinity of FLG decreases first, then restores as increasing irradiation doses, additionally, the ratio (O/C) of FLG surface and the relative content of oxygen groups increases after irradiation.

  12. Atomic layer deposition precursor step repetition and surface plasma pretreatment influence on semiconductor–insulator–semiconductor heterojunction solar cell

    SciTech Connect

    Talkenberg, Florian Illhardt, Stefan; Schmidl, Gabriele; Schleusener, Alexander; Sivakov, Vladimir; Radnóczi, György Zoltán; Pécz, Béla; Dikhanbayev, Kadyrjan; Mussabek, Gauhar; Gudovskikh, Alexander

    2015-07-15

    Semiconductor–insulator–semiconductor heterojunction solar cells were prepared using atomic layer deposition (ALD) technique. The silicon surface was treated with oxygen and hydrogen plasma in different orders before dielectric layer deposition. A plasma-enhanced ALD process was applied to deposit dielectric Al{sub 2}O{sub 3} on the plasma pretreated n-type Si(100) substrate. Aluminum doped zinc oxide (Al:ZnO or AZO) was deposited by thermal ALD and serves as transparent conductive oxide. Based on transmission electron microscopy studies the presence of thin silicon oxide (SiO{sub x}) layer was detected at the Si/Al{sub 2}O{sub 3} interface. The SiO{sub x} formation depends on the initial growth behavior of Al{sub 2}O{sub 3} and has significant influence on solar cell parameters. The authors demonstrate that a hydrogen plasma pretreatment and a precursor dose step repetition of a single precursor improve the initial growth behavior of Al{sub 2}O{sub 3} and avoid the SiO{sub x} generation. Furthermore, it improves the solar cell performance, which indicates a change of the Si/Al{sub 2}O{sub 3} interface states.

  13. Influence of temperature on layer growth as measured by in situ XRD observation of nitriding of austenitic stainless steel

    NASA Astrophysics Data System (ADS)

    Manova, D.; Günther, C.; Bergmann, A.; Mändl, S.; Neumann, H.; Rauschenbach, B.

    2013-07-01

    Investigating the formation of expanded austenite has resulted in several, different models trying to explain the particular diffusion and phase formation behaviour. However, only ex situ information, influenced by cooling and annealing processes of the samples after ion implantation has been available until now. Here, the time and temperature dependent layer growth is reported using in situ XRD measurements obtained from low energy broadbeam nitrogen ion implantation into polycrystalline austenitic stainless steel 304 in the temperature range from 300 to 500 °C for a process time of up to 1 h. Expanded austenite was observed at all temperatures without any CrN, in agreement with already published lifetime data for this metastable phase. The layer growth was derived from the time evolution of the substrate peak intensity. Using the temperature dependence of the layer growth, an activation energy of nearly 0.8 eV was estimated for the nitrogen diffusion. In contrast, a complex behaviour was observed for the lattice expansion and peak width of the expanded peak, indicating additional dynamic annealing during implantation.

  14. Time-dependent supplementation of vitamin E influences leptin expression in the aortic layers of rats fed atherogenic diet.

    PubMed

    Krawczynska, A; Olczak, E; Rembiszewska, A; Herman, A P; Gromadzka-Ostrowska, J

    2014-02-01

    An excessive consumption of a diet rich in saturated fatty acids is a key factor in pathogenesis of cardiovascular diseases which are strictly connected with leptin imbalance in the vessels. However, whether vitamin E supplementation would influence leptin expression in aortic layers is still unknown. For 3 or 6 weeks male Wistar rats were fed a high-fat (20% w/w) diet with lard as dietary fat source with or without vitamin E supplementation (50 mg/100 g of diet). The 6-week intake of an atherogenic diet increased total cholesterol (TC) and high density lipoprotein cholesterol (HDL) plasma levels simultaneously lowering TC/HDL ratio (ANOVA p≤0.0001 for all three parameters). After longer period of feeding it was stated that leptin expression in all three aortic layers was enhanced (ANOVA p≤0.0001 for endothelium, tunica media and adventitia, respectively) with decreased leptin plasma concentration (ANOVA p≤0.0001). After both periods of feeding vitamin E supplementation caused an increase in plasma HDL content and a decrease of TC/HDL ratio. In the 3-week experiment vitamin E addition caused a decrease in leptin plasma levels (Fisher's test, 3L versus 3LE: p≤0.002) and an increase in leptin expression in all three aortic layers (Fisher's test, 3L versus 3LE p≤0.005, p≤0.01 and p≤0.05 respectively for endothelium, tunica media and adventitia). The contradictory results were observed in the 6-week experiment in which vitamin supplementation decreased leptin expression in the aortic endothelium (Fisher's test, 6L versus 6LE: p≤0.001) with lack of changes in the other two layers of the aorta and plasma. The study showed that vitamin E supplementation influenced leptin expression in aortic layers in rats fed atherogenic diet differently depending on the length of feeding period. It may suggest that vitamin E consumption plays an important role in the control of leptin status in the endothelium.

  15. Heat Transfer of Thermocapillary Convection in a Two-Layered Fluid System Under the Influence of Magnetic Field

    NASA Technical Reports Server (NTRS)

    Ramachandran, N.; Ludovisis, D.; Cha, S. S.

    2006-01-01

    Heat transfer of a two-layer fluid system has been of great importance in a variety of industrial applications. For example, the phenomena of immiscible fluids can be found in materials processing and heat exchangers. Typically in solidification from a melt, the convective motion is the dominant factor that affects the uniformity of material properties. In the layered flow, thermocapillary forces can come into an important play, which was first emphasized by a previous investigator in 1958. Under extraterrestrial environments without gravity, thermocapillary effects can be a more dominant factor, which alters material properties in processing. Control and optimization of heat transfer in an immiscible fluid system need complete understanding of the flow phenomena that can be induced by surface tension at a fluid interface. The present work is focused on understanding of the magnetic field effects on thermocapillary convection, in order to optimize material processing. That is, it involves the study of the complicated phenomena to alter the flow motion in crystal growth. In this effort, the Marangoni convection in a cavity with differentially heated sidewalls is investigated with and without the influence of a magnetic field. As a first step, numerical analyses are performed, by thoroughly investigating influences of all pertinent physical parameters. Experiments are then conducted, with preliminary results, for comparison with the numerical analyses.

  16. Heat Transfer of Thermocapillary Convection in a Two-Layered Fluid System Under the Influence of Magnetic Field

    NASA Technical Reports Server (NTRS)

    Ramachandran, N.; Ludovisis, D.; Cha, S. S.

    2006-01-01

    Heat transfer of a two-layer fluid system has been of great importance in a variety of industrial applications. For example, the phenomena of immiscible fluids can be found in materials processing and heat exchangers. Typically in solidification from a melt, the convective motion is the dominant factor that affects the uniformity of material properties. In the layered flow, thermocapillary forces can come into an important play, which was first emphasized by a previous investigator in 1958. Under extraterrestrial environments without gravity, thermocapillary effects can be a more dominant factor, which alters material properties in processing. Control and optimization of heat transfer in an immiscible fluid system need complete understanding of the flow phenomena that can be induced by surface tension at a fluid interface. The present work is focused on understanding of the magnetic field effects on thermocapillary convection, in order to optimize material processing. That is, it involves the study of the complicated phenomena to alter the flow motion in crystal growth. In this effort, the Marangoni convection in a cavity with differentially heated sidewalls is investigated with and without the influence of a magnetic field. As a first step, numerical analyses are performed, by thoroughly investigating influences of all pertinent physical parameters. Experiments are then conducted, with preliminary results, for comparison with the numerical analyses.

  17. Aminosilane layers on the plasma activated thermoplastics: influence of solvent on its structure and morphology.

    PubMed

    Sunkara, Vijaya; Cho, Yoon-Kyoung

    2013-12-01

    The chemistry and the structure of aminosilane layer on the plasma activated thermoplastic substrates, e.g., polycarbonate (PC), polystyrene (PS), poly(methyl methacrylate) (PMMA), and cyclic olefin co-polymer (COC) were investigated at the molecular level. The nature of the surface functional groups of the silane layers prepared by solution phase deposition in aqueous and anhydrous solvents were studied using various techniques including ellipsometry, goniometry, atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and attenuated total reflectance infrared spectroscopy (ATR-IR). The XPS analyses revealed the presence of various oxygen functionalities on the plasma activated thermoplastics. Considerable differences were observed for the structure of aminosilane depending on the solvent used for the reaction. Deposition from aqueous solution resulted in relatively flat and smooth surfaces with consistent thickness compared to the anhydrous solution deposition. In the former case, 33% of the total nitrogen accounted for protonated amine and 16% for the free amino groups. In the latter, only 6% accounted for the protonated amine. The point of zero charge (pzc), on the aminosilane modified PC was found to be around 7, indicated that the surface is positively charged below pH 7 and negatively charged above pH 7. The surface analysis data suggested that various interactions are possible between the plasma activated thermoplastic surface and the aminosilane. In general, they are bound to the surface through covalent bond formation between the oxygen functionalities on the thermoplastic surface and the amino or the silanol groups of the aminosilane.

  18. Influence of the bound polymer layer on nanoparticle diffusion in polymer melts

    SciTech Connect

    Griffin, Philip J.; Bocharova, Vera; Middleton, L. Robert; Composto, Russell J.; Clarke, Nigel; Schweizer, Kenneth S.; Winey, Karen I.

    2016-09-23

    We measure the center-of-mass diffusion of silica nanoparticles (NPs) in entangled poly(2-vinylpyridine) (P2VP) melts using Rutherford backscattering spectrometry. While these NPs are well within the size regime where enhanced, nonhydrodynamic NP transport is theoretically predicted and has been observed experimentally (2RNP/dtube ≈ 3, where 2RNP is the NP diameter and dtube is the tube diameter), we find that the diffusion of these NPs in P2VP is in fact well-described by the hydrodynamic Stokes–Einstein relation. The effective NP diameter 2Reff is significantly larger than 2RNP and strongly dependent on P2VP molecular weight, consistent with the presence of a bound polymer layer on the NP surface with thickness heff ≈ 1.1Rg. Our results show that the bound polymer layer significantly augments the NP hydrodynamic size in polymer melts with attractive polymer–NP interactions and effectively transitions the mechanism of NP diffusion from the nonhydrodynamic to hydrodynamic regime, particularly at high molecular weights where NP transport is expected to be notably enhanced. Lastly, these results provide the first experimental demonstration that hydrodynamic NP transport in polymer melts requires particles of size ≳5dtube, consistent with recent theoretical predictions.

  19. Influence of experimental parameters on physical properties of porous silicon and oxidized porous silicon layers

    NASA Astrophysics Data System (ADS)

    Charrier, J.; Alaiwan, V.; Pirasteh, P.; Najar, A.; Gadonna, M.

    2007-08-01

    This paper reports physical properties of porous silicon and oxidized porous silicon, manufactured by anodisation from heavily p-type doped silicon wafers as a function of experimental parameters. The growth rate and refractive index of the layers were studied at different applied current densities and glycerol concentrations in electrolyte. When the current density varied from 5 to 100 mA/cm 2, the refractive index was between 1.2 and 2.4 which corresponded to a porosity range from 42 to 85%. After oxidation, the porosity decreased and was between 2 and 45% for a refractive index range from 1.22 to 1.46. The thermal processing also induced an increase in thickness which was dependent on the initial porosity. This increase in thickness was more important for the lowest porosities. Lastly, the roughness of the porous layer/silicon substrate interface was studied at different applied current densities and glycerol concentrations in solution. Roughness decreased when the current density or glycerol concentration increased. Moreover, roughness was also reduced by thermal oxidation.

  20. On the influence of free-stream turbulence length scales on boundary-layer transition

    NASA Astrophysics Data System (ADS)

    Fransson, Jens; Shahinfar, Shahab

    2015-11-01

    A measurement campaign on the free-stream turbulence (FST) induced boundary layer transition has been carried out in the Minimum-Turbulence-Level wind tunnel at KTH. Previous numerical investigations where the turbulence intensity (Tu) has been kept constant, while the integral length scale (Λx) has been varied, have shown that the transition location is advanced for increasing Λx. The present measurement campaign has been carried out using hot-wire anemometry and consists of 42 unique FST conditions with thorough measurements throughout the transitional region. Unlike other extensive FST induced transition measurements the free-stream velocity was here kept constant for all cases, implying that the boundary layer scale is locked up to transition onset. Our measurements confirm previous results on the advancement of the transition location with increasing Λx for low to moderate Tu levels, but show the opposite effect for higher levels, i.e. a delay in the transition location for larger Λx, which to the knowledge of the present authors so far is unreported. In addition, the common belief that the FST length scales have a negligible effect on the transition location with regards to the Tu level does not seem to be fully true.

  1. Influence of the bound polymer layer on nanoparticle diffusion in polymer melts

    SciTech Connect

    Griffin, Philip J.; Bocharova, Vera; Middleton, L. Robert; Composto, Russell J.; Clarke, Nigel; Schweizer, Kenneth S.; Winey, Karen I.

    2016-09-23

    We measure the center-of-mass diffusion of silica nanoparticles (NPs) in entangled poly(2-vinylpyridine) (P2VP) melts using Rutherford backscattering spectrometry. While these NPs are well within the size regime where enhanced, nonhydrodynamic NP transport is theoretically predicted and has been observed experimentally (2RNP/dtube ≈ 3, where 2RNP is the NP diameter and dtube is the tube diameter), we find that the diffusion of these NPs in P2VP is in fact well-described by the hydrodynamic Stokes–Einstein relation. The effective NP diameter 2Reff is significantly larger than 2RNP and strongly dependent on P2VP molecular weight, consistent with the presence of a bound polymer layer on the NP surface with thickness heff ≈ 1.1Rg. Our results show that the bound polymer layer significantly augments the NP hydrodynamic size in polymer melts with attractive polymer–NP interactions and effectively transitions the mechanism of NP diffusion from the nonhydrodynamic to hydrodynamic regime, particularly at high molecular weights where NP transport is expected to be notably enhanced. Lastly, these results provide the first experimental demonstration that hydrodynamic NP transport in polymer melts requires particles of size ≳5dtube, consistent with recent theoretical predictions.

  2. Influence of Permafrost Active Layer Dynamics on Trace Metals in Two Small Alaskan Arctic Rivers

    NASA Astrophysics Data System (ADS)

    Barker, A. J.; Douglas, T. A.; Jacobson, A. D.; McClelland, J. W.; Ilgen, A. G.; Khosh, M. S.; Lehn, G. O.; Trainor, T. P.

    2011-12-01

    Permafrost underlies much of the Arctic landscape. Climate warming in the Arctic is expected to increase air temperatures which will likely cause major changes in permafrost dynamics: thawing of permafrost and the downward migration of the seasonally thawed active layer into previously frozen material. Some of these processes have been observed in Arctic watersheds. A variety of geochemical tracers, including major and trace elements, could yield insight into these processes. The primary goal of this study was to use trace metals to identify potential shifts in chemical signatures in watersheds and key surface water geochemistry to active layer dynamics. The geochemical composition of rivers in the Alaskan Arctic is controlled by a variety of factors, among which are the permafrost thickness, the depth of the seasonally thawed active layer, and the composition of underlying soils. Seasonally, the chemical composition of surface waters in the Arctic is controlled by a large influx of snowmelt in the spring with the chemical composition of ground and surface water changing during the summer as soil gradually thaws. Future expansion of the active layer downward into previously frozen soils would expose fresh soils to weathering. This enhanced weathering signal would most likely be evident in surface waters during late summer and early fall when the active layer is at its deepest yearly extent. We measured trace metal concentrations in two watersheds in the Alaskan Arctic: 2.2 km2 Imnavait Creek and 83.9 km2 Roche Mountanee Creek. The Imnavait catchment drains predominantly tussock tundra underlain by continuous permafrost with organic rich soils whereas Roche Mountanee drains mountainous bedrock with minor tussock tundra at the base of the watershed. We collected 60 water samples from both watersheds between early May and mid-October 2010. Three thermistor strings were installed in the Imnavait Creek watershed to continuously measure ground temperatures at depths from

  3. Influence of casein phosphopeptide-amorphous calcium phosphate application, smear layer removal, and storage time on resin-dentin bonding*

    PubMed Central

    Lin, Jun; Zheng, Wei-ying; Liu, Peng-ruo-feng; Zhang, Ning; Lin, Hui-ping; Fan, Yi-jing; Gu, Xin-hua; Vollrath, Oliver; Mehl, Christian

    2014-01-01

    The aim of this study is to evaluate the influence of Tooth Mousse (TM) application, smear layer removal, and storage time on resin-dentin microtensile bond strength (μTBS). Dentin specimens were divided into two groups: (1) smear layer covered; (2) smear layer removed using 15% EDTA for 90 s. In each group, half the specimens were treated once with TM for 60 min. After bonding procedures using a two-step self-etching adhesive (Clearfil SE Bond (CSE); Kuraray Medical, Tokyo, Japan), an all-in-one adhesive (G-Bond (GB); GC Corp, Tokyo, Japan), and a total-etch adhesive (Adper Single Bond 2 (SB); 3M ESPE, St. Paul, MN, USA), the specimens were stored for 3 d or 6 months in deionized water at 37 °C, and μTBS was tested and analyzed. With the exception of SB (no TM application) and GB, the μTBS was significantly increased for CSE and SB using EDTA pre-conditioning and 3 d of storage (P≤0.001). Bond strength of GB decreased significantly when using EDTA (3 d storage, P<0.05). TM application only increased the μTBS of GB (no EDTA) and SB (with EDTA) after 3 d (P≤0.02). Comparing the adhesives after 3 d of storage, CSE exhibited the greatest μTBS values followed by GB and SB (P≤0.02). The factors of adhesive, EDTA, and TM did not show any significant impact on μTBS when specimens were stored for 6 months (P>0.05). The additional application of TM and EDTA for cavity preparation seems only to have a short-term effect, and no influence on μTBS of dentin bonds after a period of 6 months. PMID:25001224

  4. Influence of the bluff body shear layers on the wake of a square prism in a turbulent flow

    NASA Astrophysics Data System (ADS)

    Lander, D. C.; Letchford, C. W.; Amitay, M.; Kopp, G. A.

    2016-08-01

    Despite a substantial body of literature dealing with the effects of free-stream turbulence (FST) on two-dimensional square prism, there remain some open questions regarding the influence of the bluff body shear layer development in a highly perturbed environment and the resulting impact on bluff body flow characteristics. Accordingly, flows with ambient and enhanced FST were studied at ReD=5.0 ×104 using long-duration time-resolved particle image velocimetry (PIV). The data indicate a narrowing and lengthening of the mean wake and an accompanying rise in base pressure. Using triple decomposition, the underlying dynamics of the wake reveal a streamwise lengthening of the individual von Kármán vortex structures, complementing the increase in mean wake length. Close inspection of the shear layer region, in the presence of FST, indicates a substantial increase in curvature towards the body but no pronounced increase in the growth rate. The loci of maximum turbulent kinetic energy and spanwise vorticity in the shear layer region further reveal that the most pronounced changes occur during the very initial stages follow separation. Inspection of a series of instantaneous PIV fields of Q criterion show that the conventional transition pathway, via the formation and subsequent pairing of the Kelvin-Helmholtz (KH) vortices, is bypassed. The KH vortices are observed to immediately cluster and amalgamate before breaking into smaller random eddies. The bypass transition is followed by shear layer reattachment in some cases. This is considered a primary mechanism responsible for the reported changes in the global flow characteristics and the altered wake dynamics. Furthermore, a quantitative definition of the diffusion length is implemented for the square prism wake and its relationship to the Strouhal number and wake formation length is considered.

  5. Surface-induced rearrangement of polyelectrolyte complexes: influence of complex composition on adsorbed layer properties.

    PubMed

    Ondaral, Sedat; Ankerfors, Caroline; Odberg, Lars; Wågberg, Lars

    2010-09-21

    The adsorption characteristics of two different types of polyelectrolyte complexes (PECs), prepared by mixing poly(allylamine hydrochloride) and poly(acrylic acid) in a confined impinging jet (CIJ) mixer, have been investigated with the aid of stagnation point adsorption reflectometry (SPAR), a quartz crystal microbalance with dissipation (QCM-D), and atomic force microscopy (AFM) using SiO(2) surfaces. The two sets of PEC were prepared by combining high molecular mass PAH/PAA (PEC-A) and low molecular mass PAH/PAA (PEC-B). The PEC-A showed a higher adsorption to the SiO(2) surfaces than the PEC-B. The adsorption of the PEC-A also showed a larger change in the dissipation (ΔD), according to the QCM-D measurements, suggesting that the adsorbed layer of these complexes had a relatively lower viscosity and a lower shear modulus. Complementary investigations of the adsorbed layer using AFM imaging showed that the adsorbed layer of PEC-A was significantly different from that of PEC-B and that the changes in properties with adsorption time were very different for the two types of PECs. The PEC-A complexes showed a coalescence into larger block of complexes on the SiO(2) surface, but this was not detected with the PEC-B. The size determinations of the complexes in solution showed that they were very stable over time, and it was therefore concluded that the coalescence of the complexes was induced by the interaction between the complexes and the surface. The results also indicated that polyelectrolytes can migrate between the different complexes adsorbed to the surface. The results also give indications that the preparation of PEC-B leads to the formation of two different types of polyelectrolyte complexes differing in the amount of polymer in the complexes; i.e., two populations of complexes were formed with similar sizes but with totally different adsorption structures at the solid-liquid interface.

  6. Birefringence measurement of glass ion-exchanged waveguides: burying depth or cover layer influence

    NASA Astrophysics Data System (ADS)

    Jamon, D.; Garayt, J. P.; Jordan, E.; Parsy, F.; Ghibaudo, E.; Neveu, S.; Broquin, J.-E.; Royer, F.

    2016-02-01

    This paper deals with an experimental non-destructive technique for the measurement of polarization behavior of integrated optical waveguides. It is based on a high resolution polarimeter associated to an ellipsometric-type calibration which allows determining the full state of polarization of the output light. A magneto-optic perturbation is also added to generate TE/TM mode beating, whose spatial period is directly linked to the modal TE/TM birefringence. This equipment is first qualified by the measurement of modal birefringence in totally or partially buried ion exchanged waveguides. The results show that the value of the birefringence varies as a function of the diffusion aperture width or with the burying depth. By adding a magneto-optical cover layer, consisting in magnetic nanoparticles doped silica matrix obtained by a sol gel process 1, we evidence a huge increase of the beating magnitude and a decrease of the modal birefringence.

  7. Influence of subsurface hydrogen on the properties of single layer graphene grown on Ru(0001)

    NASA Astrophysics Data System (ADS)

    Diaconescu, Bogdan; Hagelberg, Frank; Grady, Maxwell; Pohl, Karsten

    2012-02-01

    Graphene has aroused tremendous interest due to its remarkable electronic and mechanical properties. The lack of a band-gap, however, causes a serious challenge for implementing graphene as a material for electrical switches and therefore creative ways of inducing this band-gap are needed. We will present a STM/LEED/DFT study of the single layer graphene on Ru(0001) system in the presence of hydrogen. Structural studies show arrays of Moire superlattices with sizes ranging from 0.9 to 3.0 nm in the presence of hydrogen on the compact surface of ruthenium. First principle calculations help explain the appearance of these arrays of graphene reconstructions driven by the H presence at the Ru(0001) interface, and furthermore, predict the appearance of a bandgap with values correlated with the Moire superstructure sizes in the presence of hydrogen.

  8. The influence of Nunataks on atmospheric boundary layer convection during summer in Dronning Maud Land, Antarctica

    NASA Astrophysics Data System (ADS)

    Stenmark, Aurora; Hole, Lars Robert; Voss, Paul; Reuder, Joachim; Jonassen, Marius O.

    2014-06-01

    The effects of nunataks on temperature profiles and wind patterns are studied using simulations from the Weather Research and Forecasting model. Simulations are compared to hourly observations from an automatic weather station located at the Troll Research Station in Dronning Maud Land. Areas of bare ground have been implemented in the model, and the simulations correspond well with meteorological measurements acquired during the 4 day simulation period. The nunataks are radiatively heated during daytime, and free convection occurs in the overlying atmospheric boundary layer. The inflow below the updraft forces strong horizontal convergence at the surface, whereas weaker divergence appears aloft. In a control run with a completely ice-covered surface, the convection is absent. In situ observations carried out by a remotely controlled balloon and a small model airplane compare well with model temperature profiles, but these are only available over the ice field upwind to the nunatak.

  9. Influence of buoyant media on particle layer dynamics in microfiltration membranes.

    PubMed

    Aryal, R K; Vigneswaran, S; Kandasamy, Jaya

    2010-01-01

    This study forms a part of the physical study of the membrane bioreactor in presence of buoyancy media. Kaolin clay suspension with buoyancy media (anthracite) was used as a suspension and the particle layer development on membrane surface with evolution of time was studied. Presence of buoyancy media reduced the pressure development by almost two folds compared to in absence of the media. The particles deposition on membrane surface was size selective. The mean particle diameter (0.45 mum) deposited on the membrane surface remained almost similar in presence of the media after 7 hrs run where as in its absence the mean diameter finer particles deposition occurred at the beginning followed by coarser particles.

  10. An aerosol climatology for the Jungfraujoch, Part 1: Criteria for cloud presence and boundary layer influence

    NASA Astrophysics Data System (ADS)

    Herrmann, Erik; Weingartner, Ernest; Gysel, Martin; Bukowiecki, Nicolas; Hammer, Emanuel; Collaud Coen, Martine; Conen, Franz; Vuilleumier, Laurent; Baltensperger, Urs

    2014-05-01

    The high alpine research station at the Jungfraujoch in Switzerland is located at 3580 m asl. Depending on meteorological conditions, the station is in the planetary boundary layer or in the free troposphere; and often it is inside clouds. In one location, it is thus possible to study aerosols under very different conditions. These possibilities have been recognized early on, with aerosol measurements starting in 1995. Over the years, the instrumentation has been extended significantly, today including various measurements of aerosol optical properties (nephelometer, aethalometer, MAAP) as well as aerosol size distribution (SMPS, OPC, APS). Additionally, the station regularly hosts campaigns (e.g. CLACE) with a multitude of additional devices, mostly focusing on new particle formation, cloud condensation nuclei, and ice nuclei. However, there are no continuously operated direct measurements to determine whether the station is in the clouds or not, whether it is in the PBL or the free troposphere. As these are essential parameters to describe the aerosol observed at the station, we present approaches to describe them based on the observations available to us. The intuitive choices to look at in terms of clouds are relative humidity and dew point. When comparing dew point and ambient temperature, a clear criterion to identify clouds can be easily deducted. However, the determination of "no clouds" is more ambiguous. Based on longwave radiation measurements performed routinely at the site, it is possible to calculate the sky temperature, i.e. the temperature at the point of origin of the radiation. When within a cloud, the sky temperature should be identical or at least close to ambient temperature. The comparison of sky and ambient temperature shows two clear clusters which can be interpreted as "cloud" and "no cloud". One has to note that in case of inversion or clouds shortly above the research station, this approach will produce false positives. However, combining

  11. Influence of layer charge and charge location on the swelling pressure of dioctahedral smectites

    NASA Astrophysics Data System (ADS)

    Sun, Linlin; Ling, Chian Ye; Lavikainen, Lasse P.; Hirvi, Janne T.; Kasa, Seppo; Pakkanen, Tapani A.

    2016-07-01

    Swelling pressure of dioctahedral smectites in the montmorillonite - beidellite series was investigated by molecular dynamics simulations. The pressure was found to correlate inversely with the magnitude of the layer charge in the range of -0.5 to -1.0 per unit cell. The beidellite type smectites were found to have lower swelling pressure than the montmorillonite type smectites. A clear effect of the type of interlayer cations on the swelling pressure was found. The sodium smectites sustained significant pressure even at longer interlayer distances, while in calcium smectites the pressure decreased soon after the initial swelling. The simulation results are in good agreement with experimental observations and provide a tool for predicting macroscopic swelling behavior in smectites.

  12. Influence of the number of layers on the equilibrium of a granular packing

    PubMed

    Aguirre; Nerone; Calvo; Ippolito; Bideau

    2000-07-01

    This paper reports an experimental study on avalanches in a granular material contained in a confined geometry. The granular packing is made of monosize glass beads initially poured into a box that is slowly inclined until an avalanche takes place at a critical angle straight theta(M) (maximum angle of stability). The avalanche involves a decrease of the surface slope until a second critical angle straight theta(r) (angle of repose) is reached. Both angles and the mass displaced out of the box during the avalanche are studied as a function of the height of the granular packing. In order to avoid cohesion effects, experiments are carried out in a humidity controlled environment. For small packings, up to approximately ten layers, the stability of the system is significantly affected by the rough surface at the bottom. In contrast, for thicker systems, critical angles do not depend on the height.

  13. Influences and interactions of inundation, peat, and snow on active layer thickness: Modeling Archive

    DOE Data Explorer

    Scott Painter; Ethan Coon; Cathy Wilson; Dylan Harp; Adam Atchley

    2016-04-21

    This Modeling Archive is in support of an NGEE Arctic publication currently in review [4/2016]. The Advanced Terrestrial Simulator (ATS) was used to simulate thermal hydrological conditions across varied environmental conditions for an ensemble of 1D models of Arctic permafrost. The thickness of organic soil is varied from 2 to 40cm, snow depth is varied from approximately 0 to 1.2 meters, water table depth was varied from -51cm below the soil surface to 31 cm above the soil surface. A total of 15,960 ensemble members are included. Data produced includes the third and fourth simulation year: active layer thickness, time of deepest thaw depth, temperature of the unfrozen soil, and unfrozen liquid saturation, for each ensemble member. Input files used to run the ensemble are also included.

  14. History of cosmic ray influence on ozone layer-key steps

    NASA Astrophysics Data System (ADS)

    Krivolutsky, A. A.

    2003-05-01

    A review presents the history and present-day state of the theoretical and experimental studies of the interaction between corpuscular radiation of cosmic nature and the Earth's atmosphere. According to the current knowledge, ionization of the atmosphere due to solar and galactic cosmic rays can produce additional chemical sources and sinks of ozone molecules in the atmosphere, contributing to both short-period ozone variations after solar flares and its long-term variations. At present, the huge volume of satellite and ground-based data on the chemical composition of the atmosphere and the characteristics of cosmic rays, together with the theoretical approaches and numerical simulations, make possible to form a new view on the contribution of cosmic factors on the variability of the Earth's ozone layer.

  15. Influence of aligned MHD on convective boundary layer flow of viscoelastic fluid

    NASA Astrophysics Data System (ADS)

    Aziz, Laila Amera; Kasim, Abdul Rahman Mohd; Al-Sharifi, H. A. M.; Salleh, Mohd Zuki; Mohammad, Nurul Farahain; Shafie, Sharidan; Ali, Anati

    2017-05-01

    Effects of aligned Magnetohydrodynamics (MHD) on the mixed convection boundary layer flow of viscoelastic fluid past a circular cylinder with Newtonian heating is investigated. Appropriate transformation is applied to the governing partial differential equations to transform them into dimensionless forms which are then solved using finite difference method known as Keller box. For verification purpose, the preliminary numerical solutions of the model are compared with previous study with a particular condition that the magnetic and viscosity effect are both absent. With strong agreement between the previous and current results, the authors believe that the extended outcome produced from the present model is accurate. Findings from the study will be presented in tabular and graphical form.

  16. Leaf Area Influence on Surface Layer in a Deciduous Forest. Part I; Site Description

    NASA Technical Reports Server (NTRS)

    Sakai, Ricardo K.; Fitzjarrald, David R.; Moore, Kathleen E.; Sicker, John W.; Munger, William; Goulden, Michael L.; Wofsy, Steven C.

    1996-01-01

    A study over a deciduous forest located in middle Massachusetts (USA) has been performed to examine the role of leaves in the forest-atmosphere interaction. Due to the seasonal presence of leaves, a deciduous forest is a 'good laboratory' to study this interaction. In this first part, a description of a 30 m micrometeorological tower as well a qualitative description of some meteorological parameters are presented. The presence of leaves affects the forest in several ways. There is a decrease of upward PAR (Photosynthetically Active Radiation) due to absorption of visible light in the canopy. Water vapor concentration increases, and the CO2 concentration decreases in the surface layer as the canopy starts to be foliated. The physical presence of the leaves is felt in other quantities such as the global albedo and the subcanopy environment.

  17. Influence of the dissipation mechanism on collisionless magnetic reconnection in symmetric and asymmetric current layers

    SciTech Connect

    Aunai, Nicolas; Hesse, Michael; Black, Carrie; Evans, Rebekah; Kuznetsova, Maria

    2013-04-15

    Numerical studies implementing different versions of the collisionless Ohm's law have shown a reconnection rate insensitive to the nature of the non-ideal mechanism occurring at the X line, as soon as the Hall effect is operating. Consequently, the dissipation mechanism occurring in the vicinity of the reconnection site in collisionless systems is usually thought not to have a dynamical role beyond the violation of the frozen-in condition. The interpretation of recent studies has, however, led to the opposite conclusion that the electron scale dissipative processes play an important dynamical role in preventing an elongation of the electron layer from throttling the reconnection rate. This work re-visits this topic with a new approach. Instead of focusing on the extensively studied symmetric configuration, we aim to investigate whether the macroscopic properties of collisionless reconnection are affected by the dissipation physics in asymmetric configurations, for which the effect of the Hall physics is substantially modified. Because it includes all the physical scales a priori important for collisionless reconnection (Hall and ion kinetic physics) and also because it allows one to change the nature of the non-ideal electron scale physics, we use a (two dimensional) hybrid model. The effects of numerical, resistive, and hyper-resistive dissipation are studied. In a first part, we perform simulations of symmetric reconnection with different non-ideal electron physics. We show that the model captures the already known properties of collisionless reconnection. In a second part, we focus on an asymmetric configuration where the magnetic field strength and the density are both asymmetric. Our results show that contrary to symmetric reconnection, the asymmetric model evolution strongly depends on the nature of the mechanism which breaks the field line connectivity. The dissipation occurring at the X line plays an important role in preventing the electron current layer

  18. Transitional Benthic Boundary Layers and their Influence on Nutrient Flux in Tidal Estuaries

    NASA Astrophysics Data System (ADS)

    Koetje, K. M.; Foster, D. L.; Lippmann, T. C.; Kalnejais, L. H.

    2016-12-01

    Quantifying the coupled physical and geochemical processes in the fluid-sediment interface is critical to managing coastal resources. This is of particular importance during times of enhanced hydrodynamic forcing where extreme tide or wind events can have a significant impact on water quality. A combination of field and laboratory experiments were used to examine the relationship between large-scale fluid shear stresses and geochemical fluxes at the fluid-sediment interface in the Great Bay Estuary, New Hampshire. Sediment geochemical measurements paired with flow field observations along estuary-wide transects over several tidal cycles provide nutrient load estimates that can be scaled to represent the whole Bay. Three-dimensional flow field measurements collected using a maneuverable personal watercraft were used to determine the spatial and temporal variability of the shear stress throughout the Bay. High-resolution bottom boundary layer dynamics were observed using a suite of acoustic Doppler current profilers (ADCP) in order to improve the accuracy of diffusive flux estimates by directly measuring the thickness of the benthic boundary layer. Over the 2.5 m tidal range and at water depths ranging from 0.3 m to 1.5 m at mean lower low water, peak mean flows ranged from 0.2 m/s to 1 m/s at the sampling sites. The dominant contribution of hydrodynamic forcing to the Bay is due to tidal flows, which are largely unidirectional during flood tide. Sediment grain size analysis characterized the bed at sampling sites as fine-grained sandy mud (d50 = 47 μm). Sampling during typical tidal flow conditions, a smooth turbulent flow field was observed and the threshold of motion was not exceeded. Along with sediment characterization, porosity profiles and erosion chamber experiments were used to characterize nutrient release. This host of data provides shear stress estimates that can constrain nutrient loads under variable hydrodynamic conditions.

  19. Influence of the dissipation mechanism on collisionless magnetic reconnection in symmetric and asymmetric current layers

    NASA Astrophysics Data System (ADS)

    Aunai, Nicolas; Hesse, Michael; Black, Carrie; Evans, Rebekah; Kuznetsova, Maria

    2013-04-01

    Numerical studies implementing different versions of the collisionless Ohm's law have shown a reconnection rate insensitive to the nature of the non-ideal mechanism occurring at the X line, as soon as the Hall effect is operating. Consequently, the dissipation mechanism occurring in the vicinity of the reconnection site in collisionless systems is usually thought not to have a dynamical role beyond the violation of the frozen-in condition. The interpretation of recent studies has, however, led to the opposite conclusion that the electron scale dissipative processes play an important dynamical role in preventing an elongation of the electron layer from throttling the reconnection rate. This work re-visits this topic with a new approach. Instead of focusing on the extensively studied symmetric configuration, we aim to investigate whether the macroscopic properties of collisionless reconnection are affected by the dissipation physics in asymmetric configurations, for which the effect of the Hall physics is substantially modified. Because it includes all the physical scales a priori important for collisionless reconnection (Hall and ion kinetic physics) and also because it allows one to change the nature of the non-ideal electron scale physics, we use a (two dimensional) hybrid model. The effects of numerical, resistive, and hyper-resistive dissipation are studied. In a first part, we perform simulations of symmetric reconnection with different non-ideal electron physics. We show that the model captures the already known properties of collisionless reconnection. In a second part, we focus on an asymmetric configuration where the magnetic field strength and the density are both asymmetric. Our results show that contrary to symmetric reconnection, the asymmetric model evolution strongly depends on the nature of the mechanism which breaks the field line connectivity. The dissipation occurring at the X line plays an important role in preventing the electron current layer

  20. Les applications des faisceaux d'ions dans la physique des polymères

    NASA Astrophysics Data System (ADS)

    Ratier, B.; Moliton, A.; Lucas, B.; Guille, B.; Clamadieu, M.

    1998-06-01

    Experimental configurations of ions beams are illustrated by diagrams in the case of low energy implantation, Reactive Ion Beam Etching (RIBE), Ion Beam Assisted Deposition (IBAD) of molecular layers (or oligomers). Nous présentons les configurations expérimentales (illustrées par des schémas) de trois applications des faisceaux d'ions au traitement physique des polymères : dopage par implantation (cité pour mémoire), gravure par faisceaux d'ions réactifs (RIBE), dépôt des couches moléculaires (ou oligomères) assistés par faisceau (IBAD).

  1. Les effets des interfaces sur les proprietes magnetiques et de transport des multicouches nickel/iron et cobalt/silver

    NASA Astrophysics Data System (ADS)

    Veres, Teodor

    Cette these est consacree a l'etude de l'evolution structurale des proprietes magnetiques et de transport des multicouches Ni/Fe et nanostructures a base de Co et de l'Ag. Dans une premiere partie, essentiellement bibliographique, nous introduisons quelques concepts de base relies aux proprietes magnetiques et de transport des multicouches metalliques. Ensuite, nous presentons une breve description des methodes d'analyse des resultats. La deuxieme partie est consacree a l'etude des proprietes magnetiques et de transport des multicouches ferromagnetiques/ferromagnetiques Ni/Fe. Nous montrerons qu'une interpretation coherente de ces proprietes necessite la prise en consideration des effets des interfaces. Nous nous attacherons a mettre en evidence, a evaluer et a etudier les effets de ces interfaces ainsi que leur evolution, et ce, suite a des traitements thermiques tel que le depot a temperature elevee et l'irradiation ionique. Les analyses correlees de la structure et de la magnetoresistance nous permettront d'emettre des conclusions sur l'influence des couches tampons entre l'interface et le substrat ainsi qu'entre les couches elles-memes sur le comportement magnetique des couches F/F. La troisieme partie est consacree aux systemes a Magneto-Resistance Geante (MRG) a base de Co et Ag. Nous allons etudier l'evolution de la microstructure suite a l'irradiation avec des ions Si+ ayant une energie de 1 MeV, ainsi que les effets de ces changements sur le comportement magnetique. Cette partie debutera par l'analyse des proprietes d'une multicouche hybride, intermediaire entre les multicouches et les materiaux granulaires. Nous analyserons a l'aide des mesures de diffraction, de relaxation superparamagnetique et de magnetoresistance, les evolutions structurales produites par l'irradiation ionique. Nous etablirons des modeles qui nous aideront a interpreter les resultats pour une serie des multicouches qui couvrent un large eventail de differents comportements magnetiques

  2. The influence of higher harmonics on vortex pairing in an axisymmetric mixing layer

    NASA Technical Reports Server (NTRS)

    Petersen, R. A.; Clough, R. C.

    1992-01-01

    Strong forcing was used to produce vortex pairing in a submerged axisymmetric water jet. Phase-averaged hot-wire measurements were combined with phase-averaged flow visualization to identify the relevant nonlinear interactions. The leading resonant interaction was not a subharmonic resonance. Instead, it was a triad resonance involving the subharmonic, the fundamental and the 3/2 harmonic. The profound influence of higher harmonics on the amplification of the fundamental and subharmonic was demonstrated in a systematic way by successive truncation of the Fourier series representation of the excitation waveform.

  3. Influence of free-stream disturbances on boundary-layer transition

    NASA Technical Reports Server (NTRS)

    Harvey, W. D.

    1978-01-01

    Considerable experimental evidence exists which shows that free stream disturbances (the ratio of root-mean-square pressure fluctuations to mean values) in conventional wind tunnels increase with increasing Mach number at low supersonic to moderate hypersonic speeds. In addition to local conditions, the free stream disturbance level influences transition behavior on simple test models. Based on this observation, existing noise transition data obtained in the same test facility were correlated for a large number of reference sharp cones and flat plates and are shown to collapse along a single curve. This result is a significant improvement over previous attempts to correlate noise transition data.

  4. Aerosol properties and their influences on marine boundary layer cloud condensation nuclei at the ARM mobile facility over the Azores

    NASA Astrophysics Data System (ADS)

    Logan, Timothy; Xi, Baike; Dong, Xiquan

    2014-04-01

    A multiplatform data set from the Clouds, Aerosol, and Precipitation in the Marine Boundary Layer (MBL) Graciosa, Azores, 2009-2010 field campaign was used to investigate how continental aerosols can influence MBL cloud condensation nuclei (CCN) number concentration (NCCN). The seasonal variations of aerosol properties have shown that the winter and early spring months had the highest mean surface wind speed (> 5 m s-1) and greatest contribution of sea salt to aerosol optical depth (AOD), while continental fine mode aerosols were the main contributors to AOD during the warm season months (May-September). Five aerosol events consisting of mineral dust, pollution, biomass smoke, and volcanic ash particles were selected as case studies using Atmospheric Radiation Measurement (ARM) mobile facility measurements. The aerosols in Case I were found to primarily consist of coarse mode, Saharan mineral dust. For Case II, the aerosols were also coarse mode but consisted of volcanic ash. Case III had fine mode biomass smoke and pollution aerosol influences while Cases IV and V consisted of mixtures of North American pollution and Saharan dust that was advected by an extratropical cyclone to the Azores. Cases I, IV, and V exhibited weak correlations between aerosol loading and NCCN due to mineral dust influences, while Cases II and III had a strong relationship with NCCN likely due to the sulfate content in the volcanic ash and pollution particles. The permanent Eastern North Atlantic ARM facility over the Azores will aid in a future long-term study of aerosol effects on NCCN.

  5. Renouvellement des eaux du fjord du Saguenay

    NASA Astrophysics Data System (ADS)

    Belzile, Melany

    variabilite saisonniere dans les profondeurs des evenements de renouvellement peuvent etre expliques par le cycle saisonnier de salinite des eaux presentes au seuil, qui est lui-meme influence par la saisonnalite de la circulation estuarienne du Saint-Laurent. Nous avons estime un temps typique de renouvellement du bassin interne de 2 mois, mais pouvant aller jusqu' a 6 mois maximum.

  6. The different influence of the residual layer on the development of the summer convective boundary layer in two deserts in northwest China

    NASA Astrophysics Data System (ADS)

    Lin, Zhao; Bo, Han; Shihua, Lv; Lijuan, Wen; Xianhong, Meng; Zhaoguo, Li

    2016-12-01

    The development of the atmospheric boundary layer is closely connected with the exchange of momentum, heat, and mass near the Earth's surface, especially for a convective boundary layer (CBL). Besides being modulated by the buoyancy flux near the Earth's surface, some studies point out that a neutrally stratified residual layer is also crucial for the appearance of a deep CBL. To verify the importance of the residual layer, the CBLs over two deserts in northwest China (Badan Jaran and Taklimakan) were investigated. The summer CBL mean depth over the Taklimakan Desert is shallower than that over the Badan Jaran Desert, even when the sensible heat flux of the former is stronger. Meanwhile, the climatological mean residual layer in the Badan Jaran Desert is much deeper and neutrally stratified in summer. Moreover, we found a significant and negative correlation between the lapse rate of the residual layer and the CBL depth over the Badan Jaran Desert. The different lapse rates of the residual layer in the two regions are partly connected with the advection heating from large-scale atmospheric circulation. The advection heating tends to reduce the temperature difference in the 700 to 500-hPa layer over the Badan Jaran Desert, and it increases the stability in the same atmospheric layer over the Taklimakan Desert. The advection due to climatological mean atmospheric circulation is more effective at modulating the lapse rate of the residual layer than from varied circulation. Also, the interannual variation of planetary boundary layer (PBL) height over two deserts was found to covary with the wave train.

  7. On the Offshore Advection of Boundary-Layer Structures and the Influence on Offshore Wind Conditions

    NASA Astrophysics Data System (ADS)

    Dörenkämper, Martin; Optis, Michael; Monahan, Adam; Steinfeld, Gerald

    2015-06-01

    The coastal discontinuity imposes strong signals to the atmospheric conditions over the sea that are important for wind-energy potential. Here, we provide a comprehensive investigation of the influence of the land-sea transition on wind conditions in the Baltic Sea using data from an offshore meteorological tower, data from a wind farm, and mesoscale model simulations. Results show a strong induced stable stratification when warm inland air flows over a colder sea. This stratification demonstrates a strong diurnal pattern and is most pronounced in spring when the land-sea temperature difference is greatest. The strength of the induced stratification is proportional to this parameter and inversely proportional to fetch. Extended periods of stable stratification lead to increased influence of inertial oscillations and increased frequency of low-level jets. Furthermore, heterogeneity in land-surface roughness along the coastline is found to produce pronounced horizontal streaks of reduced wind speeds that under stable stratification are advected several tens of kilometres over the sea. The intensity and length of the streaks dampen as atmospheric stability decreases. Increasing sea surface roughness leads to a deformation of these streaks with increasing fetch. Slight changes in wind direction shift the path of these advective streaks, which when passing through an offshore wind farm are found to produce large fluctuations in wind power. Implications of these coastline effects on the accurate modelling and forecasting of offshore wind conditions, as well as damage risk to the turbine, are discussed.

  8. The Influence of Soft Layer Electrokinetics on Electroporation of Gram-positive Bacteria

    NASA Astrophysics Data System (ADS)

    Dingari, Naga Neehar; Moran, Jeffrey L.; Garcia, Paulo A.; Buie, Cullen R.

    2016-11-01

    Bacterial electroporation involves subjecting cells to intense ( 10 kV/cm) electric pulses, to open pores on the cell membrane for intracellular delivery of exogenous molecules. Its high efficiency in genetic transformation makes it an attractive tool for synthetic biology. While mammalian cell electroporation has received extensive theoretical and experimental investigation, bacterial electroporation has received markedly less attention. In this work, we develop a theoretical model of electroporation for gram-positive bacteria, taking into account the effect of the bacterial cell envelope on the cell's response to an electroporation pulse. We model the influence of the cell wall charge on the electrokinetic transport (and hence the pore properties) around the bacterial cell envelope using the Poisson-Nernst-Planck equations. Further, we account for the influence of the cell wall's mechanical elasticity on the pore radius evolution during electroporation, which is typically neglected in mammalian cell electroporation. This yields valuable information about favorable conditions for pore formation and will enable designing optimal platforms for bacteria electroporation.

  9. Influence of topography on the temperature variation around the tropical tropopause layer

    NASA Astrophysics Data System (ADS)

    Kubokawa, H.; Masaki, S.; Fujiwara, M.; Suzuki, J.

    2015-12-01

    Temperature variations in the Tropical Tropopause Layer (TTL) are an important factor for dehydration in the UTLS region. It is known that Kelvin waves induce large temperature variations in the TTL. We investigated the temperature variations in the TTL using both numerical data produced by the Nonhydrostatic Icosahedral Atmospheric Model (NICAM) and various observational data including satellite data (the Constellation Observing System for Meteorology, Ionosphere, and Climate; COSMIC), the reanalysis data of different resolution (ERA-40-interim, NCEP-CFSR, MERRA, YOTC-ECMWF), and radiosonde data for the Cooperative Indian Ocean experiment on intra-seasonal variability in the Year 2011 (CINDY). We found that all the data shows that the temperature variations become larger over the mountainous regions of the Indonesian maritime continent than over the oceanic regions and that the large temperature variations are associated with Kelvin waves. As, the horizontal resolution of the reanalysis becomes higher, the standard deviations of the TTL temperature near the mountains became larger. When Kelvin waves passed over the Indonesian maritime continent, the amplitude of temperature becomes about 2 K larger over the mountainous regions. The power spectrum for the periods between 7 days and 12 days was larger over the mountainous regions compared with that over the ocean. The sensitivity study using the stretch-NICAM shows that the height of mountains clearly affect the amplitude of temperature near the TTL.

  10. Influence of the bound polymer layer on nanoparticle diffusion in polymer melts

    DOE PAGES

    Griffin, Philip J.; Bocharova, Vera; Middleton, L. Robert; ...

    2016-09-23

    We measure the center-of-mass diffusion of silica nanoparticles (NPs) in entangled poly(2-vinylpyridine) (P2VP) melts using Rutherford backscattering spectrometry. While these NPs are well within the size regime where enhanced, nonhydrodynamic NP transport is theoretically predicted and has been observed experimentally (2RNP/dtube ≈ 3, where 2RNP is the NP diameter and dtube is the tube diameter), we find that the diffusion of these NPs in P2VP is in fact well-described by the hydrodynamic Stokes–Einstein relation. The effective NP diameter 2Reff is significantly larger than 2RNP and strongly dependent on P2VP molecular weight, consistent with the presence of a bound polymer layermore » on the NP surface with thickness heff ≈ 1.1Rg. Our results show that the bound polymer layer significantly augments the NP hydrodynamic size in polymer melts with attractive polymer–NP interactions and effectively transitions the mechanism of NP diffusion from the nonhydrodynamic to hydrodynamic regime, particularly at high molecular weights where NP transport is expected to be notably enhanced. Lastly, these results provide the first experimental demonstration that hydrodynamic NP transport in polymer melts requires particles of size ≳5dtube, consistent with recent theoretical predictions.« less

  11. Influence of the mole penetrator on measurements of heat flow in lunar subsurface layers

    NASA Astrophysics Data System (ADS)

    Wawrzaszek, Roman; Drogosz, Michal; Seweryn, Karol; Banaszkiewicz, Marek; Grygorczuk, Jerzy

    Measuring the thermal gradient in subsurface layers is a basic method of determination the heat flux from the interior of a planetary body to its surface. In case of the Moon, such measurements complemented with the results of theoretical analysis and modeling can significantly improve our understanding of the thermal and geological evolution of the Moon. In practice, temperature gradient measurements are performed by at least two sensors located at different depths under the surface. These sensors will be attached to a penetrator [1] or to a cable pulled behind the penetrator. In both cases the object that carries the sensors, e.g. penetrator, perturb temperature measurements. In our study we analyze a case of two thermal sensors attached to the ends of 350mm long penetrator made of a composite material. In agreement with the studies of other authors we have found that the penetrator should be placed at the depth of 2-3 meters, where periodic changes of the temperature due to variation of solar flux at the surface are significantly smaller than the error of temperature measurement. The most important result of our analysis is to show how to deconvolve the real gradient of the temperature from the measurements perturbed by the penetrator body. In this way it will be possible to more accurately determine heat flux in the lunar regolith. [1] Grygorczuk J., Seweryn K., Wawrzaszek R., Banaszkiewicz M., Insertion of a Mole Pene-trator -Experimental Results, /39th Lunar and Planetary Science Conference /League City, Texas 2008

  12. The Barrier Layer of the Atlantic Warmpool: Formation Mechanism and Influence on the Mean Climate

    SciTech Connect

    Balaguru, Karthik; Chang, P.; Saravanan, R.; Jang, C. J.

    2012-04-20

    Many Coupled General Circulation Models (CGCMs) tend to overestimate the salinity in the Atlantic warm pool or the Northwestern Tropical Atlantic (NWTA) and underestimate the surface salinity in the subtropical salinity maxima region. Most of these models also suffer from a sea-surface temperature (SST) bias in the NWTA region, leading to suggestions that the upper ocean salinity stratification may need to be improved in order to improve the Barrier Layer (BL) simulations and thus the SST through BL-SST-Intertropical Convergence Zone (ITCZ) feedbacks. In the present study, we use a CGCM to perform a set of idealized numerical experiments to test and understand the sensitivity of the BL and consequently SST in the NWTA region to freshwater flux and hence the upper ocean salinity stratification. We find that the BL of the NWTA is sensitive to upper ocean salinity changes in the Amazon river discharge region and the subtropical salinity maxima region. The BL phenomenon is further manifested by the formation of winter temperature inversions in our model simulations, the maximum magnitude of inversions being about 0.20 C. The atmo- spheric response causes a statistically significant reduction of mean precipitation and SST in the equatorial Atlantic region and helps improve the respective biases by 10-15 %. In the region of improved BL simulation, the SST change is positive and in the right direction of bias correction, albeit weak.

  13. The influence of bottom boundary layer hydrodynamics on sediment focusing in a contaminated bay.

    PubMed

    Graham, Neil D; Bouffard, Damien; Loizeau, Jean-Luc

    2016-12-01

    Understanding the dynamics and fate of particle bound contaminants is important for mitigating potential environmental, economic and health impacts linked to their presence. Vidy Bay, Lake Geneva (Switzerland), is contaminated due to the outfall and overflow from the wastewater treatment plant of the City of Lausanne. This study was designed to investigate the fate of particle-bound contaminants with the goal of providing a more complete picture of contaminant pathways within the bay and their potential spread to the main basin. This goal was achieved by investigating the sediment transport dynamics, using sediment traps and radionuclide tracers, and ascertaining how local bottom-boundary hydrodynamic conditions (temperature, turbidity, current velocity and direction) influence these dynamics. Results of the study indicated that sedimentation rates and lateral advections increased vertically with proximity to the lakebed and laterally with proximity to shore, indicating the presence of sediment focusing in the bay. Hydrodynamic measurements showed the persistent influence of a gyre within the bay, extending down to the lake bed, while just outside of the bay circulation was influenced by the seasonal patterns of the main basin. Calculated mean displacement distances in the bay indicated that suspended particles can travel ∼3 km per month, which is 1.7 times the width of the Vidy Bay gyre. This results in a residence time of approximately 21 days for suspended particles, which is much greater than previously modelled results. The calculated mobility Shield parameter never exceeded the threshold shear stress needed for resuspension in deeper parts of the bay. In such, increased lateral advections to the bay are not likely due to local resuspension but rather external particle sources, such as main basin or shallow, littoral resuspensions. These external sources coupled with an increased residence time and decreased current velocity within the bay are the

  14. Influence of Filler Alloy Composition and Process Parameters on the Intermetallic Layer Thickness in Single-Sided Cold Metal Transfer Welding of Aluminum-Steel Blanks

    NASA Astrophysics Data System (ADS)

    Silvayeh, Zahra; Vallant, Rudolf; Sommitsch, Christof; Götzinger, Bruno; Karner, Werner; Hartmann, Matthias

    2017-08-01

    Hybrid components made of aluminum alloys and high-strength steels are typically used in automotive lightweight applications. Dissimilar joining of these materials is quite challenging; however, it is mandatory in order to produce multimaterial car body structures. Since especially welding of tailored blanks is of utmost interest, single-sided Cold Metal Transfer butt welding of thin sheets of aluminum alloy EN AW 6014 T4 and galvanized dual-phase steel HCT 450 X + ZE 75/75 was experimentally investigated in this study. The influence of different filler alloy compositions and welding process parameters on the thickness of the intermetallic layer, which forms between the weld seam and the steel sheet, was studied. The microstructures of the weld seam and of the intermetallic layer were characterized using conventional optical light microscopy and scanning electron microscopy. The results reveal that increasing the heat input and decreasing the cooling intensity tend to increase the layer thickness. The silicon content of the filler alloy has the strongest influence on the thickness of the intermetallic layer, whereas the magnesium and scandium contents of the filler alloy influence the cracking tendency. The layer thickness is not uniform and shows spatial variations along the bonding interface. The thinnest intermetallic layer (mean thickness < 4 µm) is obtained using the silicon-rich filler Al-3Si-1Mn, but the layer is more than twice as thick when different low-silicon fillers are used.

  15. Electrophoresis of two spheres: Influence of double layer and van der Waals interactions.

    PubMed

    Tseng, Shiojenn; Huang, Chih-Hua; Hsu, Jyh-Ping

    2015-08-01

    Considering recent applications of electrophoresis conduced in nanoscaled devices, where particle-particle interaction can play a role, we studied for the first time the electrophoresis of two rigid spheres along their center line, taking account of the hydrodynamic, electric, and van der Waals interactions between them. Under the conditions of constant surface potential and surface charge density, the influences of the level of surface potential/charge density, the bulk salt concentration, and the particle-particle distance on their electrokinetic behaviors are examined. Numerical simulation reveals that these behaviors are much more complicated and interesting than those of isolated particles. In particular, we show that care must be taken in choosing an appropriate particle concentration in relevant experiment to avoid obtaining unreliable mobility data.

  16. Influence of buffer solutions in the adsorption of human serum proteins onto layered double hydroxide.

    PubMed

    Gondim, Diego R; Cecilia, Juan A; Santos, Santângela O; Rodrigues, Thainá N B; Aguiar, José E; Vilarrasa-García, Enrique; Rodríguez-Castellón, Enrique; Azevedo, Diana C S; Silva, Ivanildo J

    2017-08-07

    The adsorption of human immunoglobulin G (IgG) and human serum albumin (HSA) on a non-calcined Mg-Al layered double hydroxide (3:1 Mg-Al LDH) was studied in batch and fixed bed experiments, focusing on the effect of buffer solution and pH over sorbent uptake. Mg-Al LDH was synthesized and characterized by X-ray diffraction (XRD), N2 adsorption-desorption isotherms at -196°C, X-ray photoelectron spectroscopy (XPS), Zero point charge (pHzpc), particle size distribution and Fourier transform infra-red (FTIR). Batch adsorption experiments were performed in order to investigate the effects of pH on IgG and HSA adsorption with different buffers: sodium acetate (ACETATE), sodium phosphate (PHOSPHATE), 3-(N-morpholino) propanesulfonic acid (MOPS), 4-(2-Hydroxyethyl)piperazine-1-ethanesulfonic acid (HEPES) and trizma-hydrochloric acid (TRIS-HCl). Maximum adsorption capacities estimated by the Langmuir model were 239mgg(-1) for IgG and 105mgg(-1) for HSA in TRIS-HCl buffer. On the other hand, the highest selectivity for IgG adsorption over HSA was obtained with buffer PHOSPHATE (pH 6.5). The maximum IgG and HSA adsorption uptake in this case were 165 and 36mgg(-1), respectively. Fixed bed experiments were carried out with both proteins using PHOSPHATE buffer (pH 6.5), which confirmed that IgG was more selectively adsorbed than HSA on Mg-Al LDH and both could be fully recovered by elution with sodium chloride (NaCl). Copyright © 2017 Elsevier B.V. All rights reserved.

  17. In vitro corrosion of pure magnesium and AZ91 alloy—the influence of thin electrolyte layer thickness

    PubMed Central

    Zeng, Rong-Chang; Qi, Wei-Chen; Zhang, Fen; Li, Shuo-Qi

    2016-01-01

    In vivo degradation predication faces a huge challenge via in vitro corrosion test due to the difficulty for mimicking the complicated microenvironment with various influencing factors. A thin electrolyte layer (TEL) cell for in vitro corrosion of pure magnesium and AZ91 alloy was presented to stimulate the in vivo corrosion in the micro-environment built by the interface of the implant and its neighboring tissue. The results demonstrated that the in vivo corrosion of pure Mg and the AZ91 alloy was suppressed under TEL condition. The AZ91 alloy was more sensitive than pure Mg to the inhibition of corrosion under a TEL thickness of less than 200 µm. The TEL thickness limited the distribution of current, and thus localized corrosion was more preferred to occur under TEL condition than in bulk solution. The TEL cell might be an appropriate approach to simulating the in vivo degradation of magnesium and its alloys. PMID:26816655

  18. In vitro corrosion of pure magnesium and AZ91 alloy-the influence of thin electrolyte layer thickness.

    PubMed

    Zeng, Rong-Chang; Qi, Wei-Chen; Zhang, Fen; Li, Shuo-Qi

    2016-03-01

    In vivo degradation predication faces a huge challenge via in vitro corrosion test due to the difficulty for mimicking the complicated microenvironment with various influencing factors. A thin electrolyte layer (TEL) cell for in vitro corrosion of pure magnesium and AZ91 alloy was presented to stimulate the in vivo corrosion in the micro-environment built by the interface of the implant and its neighboring tissue. The results demonstrated that the in vivo corrosion of pure Mg and the AZ91 alloy was suppressed under TEL condition. The AZ91 alloy was more sensitive than pure Mg to the inhibition of corrosion under a TEL thickness of less than 200 µm. The TEL thickness limited the distribution of current, and thus localized corrosion was more preferred to occur under TEL condition than in bulk solution. The TEL cell might be an appropriate approach to simulating the in vivo degradation of magnesium and its alloys.

  19. Influence of localized unsteady ejection on the scaling laws and intermittency in a turbulent boundary layer flow

    NASA Astrophysics Data System (ADS)

    Guo, H.; Huang, Q. M.; Liu, P. Q.; Feng, T.

    2015-08-01

    The effects of localized unsteady ejection by synthetic jet with slot-type exit on a turbulent boundary layer at zero pressure gradient conditions were investigated downstream of the slot using hot-wire anemometry. This work is to investigate the influence of unsteady disturbance on turbulent structures at small scales, i.e., in the isotropy recovery range (IRR) and the shear-dominated range (SDR). In the near-slot region, our results show that IRR is extended and SDR is shortened for the perturbed flow in the near-wall region, which contributes to the decrease in anisotropy and intermittency. For the perturbed flow, only one scaling behavior of the longitudinal structure functions similar to the classical Kolmogorov-like scaling is observed in IRR.

  20. Skin-friction measurements in a turbulent boundary layer under the influence of free-stream turbulence

    NASA Astrophysics Data System (ADS)

    Esteban, Luis Blay; Dogan, Eda; Rodríguez-López, Eduardo; Ganapathisubramani, Bharathram

    2017-09-01

    This experimental investigation deals with the influence of free-stream turbulence (FST) produced by an active grid on the skin friction of a zero-pressure-gradient turbulent boundary layer. Wall shear stress is obtained by oil-film interferometry. In addition, hot-wire anemometry was performed to obtain wall-normal profiles of streamwise velocity. This enables the skin friction to be deduced from the mean profile. Both methods show remarkable agreement for every test case. Although skin friction is shown to increase with FST, the trend with Reynolds number is found to be similar to cases without FST. Furthermore, once the change in the friction velocity is accounted for, the self-similarity of the logarithmic region and below (i.e. law of the wall) appears to hold for all FST cases investigated.

  1. Influence of growth conditions on irradiation induced defects in low doped 4H-SiC epitaxial layers

    SciTech Connect

    Pintilie, I.; Grossner, U.; Svensson, B. G.; Irmscher, K.; Thomas, B.

    2007-02-05

    Nitrogen doped 4H-SiC epitaxial layers were investigated by deep level transient spectroscopy after irradiation with 6 MeV electrons. The influence of C/Si ratio, N doping level, and growth rate on the behavior of the prominent Z{sub 1,2} and EH{sub 6,7} levels during irradiation and subsequent annealing was studied. Both Z{sub 1,2} and EH{sub 6,7} increase in concentration with the N doping as well as with the C/Si ratio. It is demonstrated that the growth conditions play a decisive role for the annihilation of the EH{sub 6,7} level and a possible identity of the EH{sub 6,7} defect is discussed.

  2. Influence of plasmonic array geometry on energy transfer from a quantum well to a quantum dot layer.

    PubMed

    Higgins, Luke J; Marocico, Cristian A; Karanikolas, Vasilios D; Bell, Alan P; Gough, John J; Murphy, Graham P; Parbrook, Peter J; Bradley, A Louise

    2016-10-27

    A range of seven different Ag plasmonic arrays formed using nanostructures of varying shape, size and gap were fabricated using helium-ion lithography (HIL) on an InGaN/GaN quantum well (QW) substrate. The influence of the array geometry on plasmon-enhanced Förster resonance energy transfer (FRET) from a single InGaN QW to a ∼80 nm layer of CdSe/ZnS quantum dots (QDs) embedded in a poly(methyl methacrylate) (PMMA) matrix is investigated. It is shown that the energy transfer efficiency is strongly dependent on the array properties and an efficiency of ∼51% is observed for a nanoring array. There were no signatures of FRET in the absence of the arrays. The QD acceptor layer emission is highly sensitive to the array geometry. A model was developed to confirm that the increase in the QD emission on the QW substrate compared with a GaN substrate can be attributed solely to plasmon-enhanced FRET. The individual contributions of direct enhancement of the QD layer emission by the array and the plasmon-enhanced FRET are separated out, with the QD emission described by the product of an array emission factor and an energy transfer factor. It is shown that while the nanoring geometry results in an energy transfer factor of ∼1.7 the competing quenching by the array, with an array emission factor of ∼0.7, results in only an overall gain of ∼14% in the QD emission. The QD emission was enhanced by ∼71% for a nanobox array, resulting from the combination of a more modest energy transfer factor of 1.2 coupled with an array emission factor of ∼1.4.

  3. Comparative research on the influence of varied Al component on the active layer of AlGaN photocathode

    NASA Astrophysics Data System (ADS)

    He, Minyou; Chen, Liang; Su, Lingai; Yin, Lin; Qian, Yunsheng

    2017-06-01

    To theoretically research the influence of a varied Al component on the active layer of AlGaN photocathodes, the first principle based on density functional theory is used to calculate the formation energy and band structure of Al x Ga1-x N with x at 0, 0.125, 0.25, 0.325, and 0.5. The calculation results show that the formation energy declines along with the Al component rise, while the band gap is increasing with Al component increasing. Al x Ga1-x N with x at 0, 0.125, 0.25, 0.325, and 0.5 are direct band gap semiconductors, and their absorption coefficient curves have the same variation tendency. For further study, we designed two kinds of reflection-mode AlGaN photocathode samples. Sample 1 has an Al x Ga1-x N active layer with varied Al component ranging from 0.5 to 0 and decreasing from the bulk to the surface, while sample 2 has an Al x Ga1-x N active layer with the fixed Al component of 0.25. Using the multi-information measurement system, we measured the spectral response of the activated samples at room temperature. Their photocathode parameters were obtained by fitting quantum efficiency curves. Results show that sample 1 has a better spectral response than sample 2 at the range of short-wavelength. This work provides a reference for the structure design of the AlGaN photocathode. Project supported by the National Natural Science Foundation of China (Nos. 61308089, 6144005) and the Public Technology Applied Research Project of Zhejiang Province (No. 2013C31068).

  4. Influence of tree cover on herbaceous layer development and carbon and water fluxes in a Portuguese cork-oak woodland

    NASA Astrophysics Data System (ADS)

    Dubbert, Maren; Mosena, Alexander; Piayda, Arndt; Cuntz, Matthias; Correia, Alexandra Cristina; Pereira, Joao Santos; Werner, Christiane

    2014-08-01

    Facilitation and competition between different vegetation layers may have a large impact on small-scale vegetation development. We propose that this should not only influence overall herbaceous layer yield but also species distribution and understory longevity, and hence the ecosystems carbon uptake capacity especially during spring. We analyzed the effects of trees on microclimate and soil properties (water and nitrate content) as well as the development of an herbaceous community layer regarding species composition, aboveground biomass and net water and carbon fluxes in a cork-oak woodland in Portugal, between April and November 2011. The presence of trees caused a significant reduction in photosynthetic active radiation of 35 mol m-2 d-1 and in soil temperature of 5 °C from April to October. At the same time differences in species composition between experimental plots located in open areas and directly below trees could be observed: species composition and abundance of functional groups became increasingly different between locations from mid April onwards. During late spring drought adapted native forbs had significantly higher cover and biomass in the open area while cover and biomass of grasses and nitrogen fixing forbs was highest under the trees. Further, evapotranspiration and net carbon exchange decreased significantly stronger under the tree crowns compared to the open during late spring and the die back of herbaceous plants occurred earlier and faster under trees. This was most likely caused by interspecific competition for water between trees and herbaceous plants, despite the more favorable microclimate conditions under the trees during the onset of summer drought.

  5. From single to multiple TiO{sub 2} nanotubes layers: Analysis of the parameters which influence the growth

    SciTech Connect

    Scaramuzzo, Francesca A. Pasquali, Mauro; Mura, Francesco; Dell’Era, Alessandro

    2015-06-23

    Highly-ordered vertically oriented TiO{sub 2} nanotube arrays (TiO{sub 2} NTs) are widely exploited in many different fields such as catalysis, electronics and biomedicine. TiO{sub 2} NTs can be synthetized by a number of methods; however, the synthesis via anodization in a fluoride-based electrolyte, proposed for the first time in 2001, has been proved to be the procedure which offers the best control over the nanotube dimensions. In literature, four generations of TiO{sub 2} NTs obtained with different types of anodization baths have been reported, each bath giving rise to TiO{sub 2} NTs with specific morphological features. In this work, we performed the growth of third generation TiO{sub 2} NTs by varying different parameters (i.e. voltage, temperature, anodization time, bath composition) and systematically analyzed their influence on NTs morphology. A deep knowledge of the effect of each parameter allowed their suitable combination in order to obtain double and triple NTs layers with different length and aspect ratio. The proposed method can be applied to synthetize multiple layers with predictable and well-defined features.

  6. Influence of supraglottal structures on the glottal jet exiting a two-layer synthetic, self-oscillating vocal fold model

    PubMed Central

    Drechsel, James S.; Thomson, Scott L.

    2008-01-01

    A synthetic two-layer, self-oscillating, life-size vocal fold model was used to study the influence of the vocal tract and false folds on the glottal jet. The model vibrated at frequencies, pressures, flow rates, and amplitudes consistent with human phonation, although some differences in behavior between the model and the human vocal folds are noted. High-speed images of model motion and flow visualization were acquired. Phase-locked ensemble-averaged glottal jet velocity measurements using particle image velocimetry (PIV) were acquired with and without an idealized vocal tract, with and without false folds. PIV data were obtained with varying degrees of lateral asymmetric model positioning. Glottal jet velocity magnitudes were consistent with those measured using excised larynges. A starting vortex was observed in all test cases. The false folds interfered with the starting vortex, and in some cases vortex shedding from the false folds was observed. In asymmetric cases without false folds, the glottal jet tended to skew toward the nearest wall; with the false folds, the opposite trend was observed. rms velocity calculations showed the jet shear layer and laminar core. The rms velocities were higher in the vocal tract cases compared to the open jet and false fold cases. PMID:18537394

  7. Influence of nature of precursors on the formation and structure of Cu Ni Cr mixed oxides from layered double hydroxides

    NASA Astrophysics Data System (ADS)

    Zhang, Lihong; Zhu, Jia; Jiang, Xiaorui; Evans, David G.; Li, Feng

    2006-08-01

    Analogous layered double hydroxides (LDHs) with the Cu2+/Ni2+/Cr3+ molar ratio of 1/2/1 on the brucite-like layers and interlayer anions (viz sulfate, nitrate and carbonate, respectively) were synthesized by a coprecipitation method. For the first time, the effects of interlayer anions on the structural properties of as-synthesized LDHs and resulting calcined products at 773 K were investigated by means of powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), simultaneous thermogravimetric and differential thermal analysis (TG-DTA), X-ray photoelectron spectroscopy (XPS) and temperature programmed reduction (TPR). The results indicate that the nature of interlayer anions involved within the hydrotalcite (HT)-like structure has a larger influence on the thermal stability of LDHs precursors. Calcination of well-crystallized LDHs leads to the formation of mixed metal oxides including CuO, NiO and Cu2+-, Ni2+- and Cr3+-containing spinel phases, the composition distributions of which obtained from LDHs precursors depend on the nature of interlayer anions, thus resulting in the difference of the reducibility of reducible metal species in the calcined LDHs. Moreover, the surface basicity of the calcined material, which is related to the different behaviour of LDHs precursors during the thermal decomposition depending on the interlayer anions, increases progressively following the order of calcined LDHs from sulfate to nitrate and carbonate.

  8. Influence of polymeric electron injection layers on the electrical properties of solution-processed multilayered polymer light-emitting diodes

    NASA Astrophysics Data System (ADS)

    Itoh, Eiji; Kurami, Kazuhiko

    2016-02-01

    In this study, we fabricated multilayered polymer-based light-emitting diodes (pLEDs) with various solution-processed electron-injection layers (EILs), and investigated the influence of the EILs on the electrical properties of pLEDs in indium tin oxide (ITO)/poly(3,4-ethylenedioxythiophene) doped with poly(styrene sulfonic acid) (PEDOT:PSS)/poly[(9,9-dioctylfluorene-alt-(1,4-phenylene((4-sec-butylphenyl)amino)-1,4-phenylene))] (TFB) (HTL)/poly(9,9-dioctylfluorene-alt-1,4-benzothiadiazole) (F8BT) (EML)/EIL/Al structures. We have used the quaternized ammonium π-conjugated polyelectrolyte derivative (poly[(9,9-di(3,3‧-N,N‧-trimethylammonium)propylfluorenyl-2,7-diyl)-co-(1,4-phenylene)]diiodide salt) (PF-PDTA), a mixture of PF-PDTA and CS2CO3, and the aliphatic-amine-based polymer poly(ethylene imine) (PEI) as solution-processed EILs, and compared them with LiF as a solvent-free EIL. The EILs enhanced the electron injection and improve the pLED performance. High external quantum efficiencies of nearly 4% were obtained in the pLEDs with the combination of a multilayered structure fabricated by a transfer printing technique and EILs of a PF-PDTA:CS2CO3 mixture and PEI. On the other hand, the device with PF-PDTA exhibited lower efficiency, higher driving voltage, and larger leakage current at lower voltage. The migration of ionic charges was suggested from the abnormal dielectric behaviors, and serious damage on the electrode material occurred when both an acid hole-injection layer (PEDOT:PSS) and PF-PDTA were used. On the other hand, the pLEDs with ultrathin PEI showed high performance and stable device operation in terms of the influence of ionic charges.

  9. Influence of Subpixel Scale Cloud Top Structure on Reflectances from Overcast Stratiform Cloud Layers

    NASA Technical Reports Server (NTRS)

    Loeb, N. G.; Varnai, Tamas; Winker, David M.

    1998-01-01

    Recent observational studies have shown that satellite retrievals of cloud optical depth based on plane-parallel model theory suffer from systematic biases that depend on viewing geometry, even when observations are restricted to overcast marine stratus layers, arguably the closest to plane parallel in nature. At moderate to low sun elevations, the plane-parallel model significantly overestimates the reflectance dependence on view angle in the forward-scattering direction but shows a similar dependence in the backscattering direction. Theoretical simulations are performed that show that the likely cause for this discrepancy is because the plane-parallel model assumption does not account for subpixel, scale variations in cloud-top height (i.e., "cloud bumps"). Monte Carlo simulation, comparing ID model radiances to radiances from overcast cloud field with 1) cloud-top height variation, but constant cloud volume extinction; 2) flat tops but horizontal variations in cloud volume extinction; and 3) variations in both cloud top height and cloud extinction are performed over a approximately equal to 4 km x 4 km domain (roughly the size of an individual GAC AVHRR pixel). The comparisons show that when cloud-top height variations are included, departures from 1D theory are remarkably similar (qualitatively) to those obtained observationally. In contrast, when clouds are assumed flat and only cloud extinction is variable, reflectance differences are much smaller and do not show any view-angle dependence. When both cloud-top height and cloud extinction variations are included, however, large increases in cloud extinction variability can enhance reflectance difference. The reason 3D-1D reflectance differences are more sensitive to cloud-top height variations in the forward-scattering direction (at moderate to low, sun elevations) is because photons leaving the cloud field in that direction experience fewer scattering events (low-order scattering) and are restricted to the

  10. Influence d'une substitution partielle du ciment par du laitier de hauts fourneaux sur la résistance des mortiers en milieu acide

    NASA Astrophysics Data System (ADS)

    Achoura, D.; Lanos, Ch.; Jauberthie, R.; Redjel, B.

    2004-11-01

    Le stockage de produits chimiques dans du béton présente souvent des problèmes de durabilité dus aux attaques chimiques. Inévitablement les concentrations élevées sont les plus dangereuses. Le but de notre étude est de déterminer les changements de phases qui apparaissent dans le béton lorsqu'on substitue une partie du ciment par du laitier de haut fourneaux. Les échantillons sont conservés dans des solutions acides différents anions (HCl, H{2}SO{4}, H{3}PO{4} et CH{3}COOH) et différentes concentrations (0,1; 0,25 et 0,5M). Les formations qui apparaissent sont déterminées par diffraction X et observées au MEB. Les solutions sulfatiques conduisent à une formation de gypse en surface et d'ettringite au contact de la matrice cimentaire. Avec l'acide acétique, il y a formation de calcium acétate hydrate sous forme spongieuse tandis que, avec l'acide phosphatique, la formation de calcium hydrogeno phosphate hydrate est très superficielle. Enfin, avec l'acide chlorhydrique, la surface du mortier est recouverte de chlorure de calcium dihydrate et d'hydroxyde de fer. Les résistances mécaniques sont plus ou moins affectées par la concentration mais aussi et surtout par la nature des acides avec dans l'ordre le plus agressif H{2}SO{4} puis HCl et CH{3}COOH enfin peu de modification pour H{3}PO{4}.

  11. Influence of GlidArc treatment on layers formation of biofouling

    NASA Astrophysics Data System (ADS)

    Hnatiuc, B.; Sabau, A.; Ghita, S.; Hnatiuc, M.; Dumitrache, C. L.; Pellerin, S.

    2015-02-01

    Corrosion in marine environment is a complex dynamic process influenced mainly by physical chemical, microbiological and mechanical parameters. Times for maintenance related to corrosion are greater than 80% of the total repair. Reducing this cost would be a significant saving, and an effective treatment can reduce times related to ships repairing. Biofouling is a main cause of corrosion and its formation contains four steps. To inhibit biofouling it is proposed a treatment based on non-thermal plasma produced by GlidArc, which can be applied before the immersion of small boats in the sea, as well as cleaning treatment of the hull after a period of time. This work presents the microbiological results of treatment of metal surfaces (naval OL36 steel) with GlidArc technology, according to the first, respectively the second phase formation of biofouling. Samples of naval steel were prepared with three specific naval paints and before the treatment have been introduced in seawater. Microbiological results have been compared for two types of treatments based on GlidArc. In the first case the painted samples are submitted to direct action of non-thermal plasma. In the second case the plasma produced by GlidArc technology is used to activate a solution (plasma activated water = PAW) and then the samples are introduced into this water.

  12. Compound microstructures and wax layer of beetle elytral surfaces and their influence on wetting properties.

    PubMed

    Sun, Mingxia; Liang, Aiping; Watson, Gregory S; Watson, Jolanta A; Zheng, Yongmei; Jiang, Lei

    2012-01-01

    A beetles' first line of defense against environmental hazards is their mesothoracic elytra--rigid, protective forewings. In order to study the interaction of these wings with water, the surface microstructures of various beetles' elytra were observed by Environment Scanning Electron Microscopy (ESEM) and Atomic Force Microscopy (AFM). Chemistry components were ascertained using X-ray photoelectron spectroscopy (XPS). All the beetles of various habitats (including desert, plant, dung, land and water) exhibited compound microstructures on their elytra. The wetting properties of these elytra were identified using an optical contact angle meter. In general the native elytra exhibited hydrophilic or weak hydrophobic properties with contact angles (CAs) ranging from 47.5° to 109.1°. After treatment with chloroform, the CAs all increased on the rougher elytral surfaces. The presence of wax is not the only determinant of hydrophobic properties, but rather a combination with microscopic structures found on the surfaces. Irregularities and the presence or absence of tiny cracks, hairs (or setae), pores and protrusions are important factors which influence the wetting properties. Rougher elytral surfaces tended to present a stronger hydrophobicity. Effects on hydrophobicity, such as surface microstructures, chemistry, environment and aging (referring to the time after emergence), are also included and discussed. Our results also provide insights into the motion of water droplets when in contact with beetle elytra.

  13. Compound Microstructures and Wax Layer of Beetle Elytral Surfaces and Their Influence on Wetting Properties

    PubMed Central

    Sun, Mingxia; Liang, Aiping; Watson, Gregory S.; Watson, Jolanta A.; Zheng, Yongmei; Jiang, Lei

    2012-01-01

    A beetles’ first line of defense against environmental hazards is their mesothoracic elytra – rigid, protective forewings. In order to study the interaction of these wings with water, the surface microstructures of various beetles’ elytra were observed by Environment Scanning Electron Microscopy (ESEM) and Atomic Force Microscopy (AFM). Chemistry components were ascertained using X-ray photoelectron spectroscopy (XPS). All the beetles of various habitats (including desert, plant, dung, land and water) exhibited compound microstructures on their elytra. The wetting properties of these elytra were identified using an optical contact angle meter. In general the native elytra exhibited hydrophilic or weak hydrophobic properties with contact angles (CAs) ranging from 47.5° to 109.1°. After treatment with chloroform, the CAs all increased on the rougher elytral surfaces. The presence of wax is not the only determinant of hydrophobic properties, but rather a combination with microscopic structures found on the surfaces. Irregularities and the presence or absence of tiny cracks, hairs (or setae), pores and protrusions are important factors which influence the wetting properties. Rougher elytral surfaces tended to present a stronger hydrophobicity. Effects on hydrophobicity, such as surface microstructures, chemistry, environment and aging (referring to the time after emergence), are also included and discussed. Our results also provide insights into the motion of water droplets when in contact with beetle elytra. PMID:23056414

  14. Etude microdosimetrique de l'influence des materiaux sur l'efficacite biologique d'une source d'iode-125

    NASA Astrophysics Data System (ADS)

    Taschereau, Richard

    Cette these concerne les implants permanents pour la prostate. Les isotopes employes, le 103Pd et l'125I, semblent produire les memes resultats cliniques: le premier a cause d'une radiation plus efficace et le second a cause de sa demi-vie plus longue. La recherche utilise le cadre theorique de la microdosimetrie et des simulations Monte Carlo. Elle propose d'employer le spectre d'ejection dans le calcul de l'efficacite; ce changement fait passer l'efficacite relative du 103Pd de 10% a 5%. Elle montre ensuite qu'il est possible d'ameliorer l'efficacite de la radiation de 125I par l'exploitation des rayons X caracteristiques de la capsule. Une source amelioree faite de molybdene et d'yttrium est donnee en exemple. Elle procure une radiation de 5--7% plus efficace, ce qui surclasse les deux sources existantes. Les applications ne se limitent pas au traitement de la prostate; le traitement du melanome oculaire et la curietherapie endovasculaire pourraient en beneficier.

  15. Influence of Dielectric Layers on Charge Transport through Diketopyrrolopyrrole-Containing Polymer Films: Dielectric Polarizability vs Capacitance.

    PubMed

    Lee, Jiyoul; Chung, Jong Won; Yoon, Gyu Bok; Lee, Moo Hyung; Kim, Do Hwan; Park, Jozeph; Lee, Jin-Kyun; Kang, Moon Sung

    2016-11-09

    Field-effect mobility of a polymer semiconductor film is known to be enhanced when the gate dielectric interfacing with the film is weakly polarizable. Accordingly, gate dielectrics with lower dielectric constant (k) are preferred for attaining polymer field-effect transistors (PFETs) with larger mobilities. At the same time, it is also known that inducing more charge carriers into the polymer semiconductor films helps in enhancing their field-effect mobility, because the large number of traps presented in such a disorder system can be compensated substantially. In this sense, it may seem that employing higher k dielectrics is rather beneficial because capacitance is proportional to the dielectric constant. This, however, contradicts with the statement above. In this study, we compare the impact of the two, i.e., the polarizability and the capacitance of the gate dielectric, on the transport properties of poly[(diketopyrrolopyrrole)-alt-(2,2'-(1,4-phenylene)bisthiophene)] (PDPPTPT) semiconductor layers in an FET architecture. For the study, three different dielectric layers were employed: fluorinated organic CYTOP (k = ∼2), poly(methyl methacrylate) (k = ∼4), and relaxor ferroelectric poly(vinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene) (k = ∼60). The beneficial influence of attaining more carriers in the PDPPTPT films on their charge transport properties was consistently observed from all three systems. However, the more dominant factor determining the large carrier mobility was the low polarizability of the gate dielectric rather than its large capacitance; field-effect mobilities of PDPPTPT films were always larger when lower k dielectric was employed than when higher k dielectric was used. The higher mobilities obtained when using lower k dielectrics could be attributed to the suppressed distribution of the density of localized states (DOS) near the transport level and to the resulting enhanced electronic coupling between the macromolecules.

  16. ILM peeling technique influences the degree of a dissociated optic nerve fibre layer appearance after macular hole surgery.

    PubMed

    Steel, David H W; Dinah, Christiana; Habib, Maged; White, Kathryn

    2015-05-01

    We sought to assess the effect of two different internal limiting membrane [ILM] peeling techniques carried out during surgery for idiopathic macular holes on the postoperative extent of a dissociated optic nerve fibre layer appearance [DONFL]. We collected prospective data of surgical records, videos, and pre- and postoperative imaging of a consecutive series of patients undergoing surgery for idiopathic macular hole with one of two surgeons. One surgeon used a forceps pinch-peel technique to peel the ILM, whereas the other surgeon used a diamond dusted membrane scraper. The extent of any DONFL was measured using spectral domain optical coherence tomography and blue reflectance imaging at three months postoperatively. A proportion of the ILMs removed were examined with transmission electron microscopy. Fifty-seven patients were studied, with 41 in the forceps group and 16 in the scraper group. The groups were well matched, with no significant difference in any preoperative parameters. Some degree of DONFL was observed on the 3-month blue reflectance images in 88 % of the forceps group and 100 % of the scraper group [p = 0.14]. There was a significant difference in the total number of depressions in the nerve fibre layer typical of DONFL on OCT between the two groups [p = 0.001], and general regression analysis showed that the peeling technique used had the only significant association with the degree of DONFL observed. Electron microscopy showed large patches of cellular debris on the retinal side of the peeled ILM in 3 out of 4 cases in the scraper group and 1 out of 12 cases in the forceps group. ILM peeling technique and possibly other surgeon-specific factors appear to influence the extent of DONFL observed after ILM peeling macular hole surgery.

  17. Influence of thermal expansion mismatch on residual stress profile in veneering ceramic layered on zirconia: Measurement by hole-drilling.

    PubMed

    Mainjot, Amélie K; Najjar, Achref; Jakubowicz-Kohen, Boris D; Sadoun, Michaël J

    2015-09-01

    Mismatch in thermal expansion coefficient between core and veneering ceramic (Δα=αcore-αveneer, ppm/°C) is reported as a crucial parameter influencing veneer fractures with Yttria-tetragonal-zirconia-polycrystal (Y-TZP) prostheses, which still constitutes a misunderstood problem. However, the common positive Δα concept remains empirical. The objective of this study is to investigate the Δα dependence of residual stress profiles in veneering ceramic layered on Y-TZP frameworks. The stress profile was measured with the hole-drilling method in bilayered disc samples of 20mm diameter with a 0.7mm thick Y-TZP framework and a 1.5mm thick veneer layer. 3 commercial and 4 experimental veneering ceramics (n=3 per group) were used to obtain different Δα varying from -1.3ppm/°C to +3.2ppm/°C, which were determined by dilatometric analyses. Veneer fractures were observed in samples with Δα≥+2.3 or ≤-0.3ppm/°C. Residual stress profiles measured in other groups showed compressive stresses in the surface, these stresses decreasing with depth and then becoming more compressive again near the interface. Small Δα variations were shown to induce significant changes in residual stress profiles. Compressive stress near the framework was found to decrease inversely to Δα. Veneer CTE close to Y-TZP (+0.2ppm/°C Δα) gived the most favorable stress profile. Yet, near the framework, Δα-induced residual stress varied inversely to predictions. This could be explained by the hypothesis of structural changes occurrence within the Y-TZP surface. Consequently, the optimum Δα value cannot be determined before understanding Y-TZP's particular behavior when veneered. Copyright © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  18. Passive buoyant tracers in the ocean surface boundary layer: 1. Influence of equilibrium wind-waves on vertical distributions

    NASA Astrophysics Data System (ADS)

    Kukulka, T.; Brunner, K.

    2015-05-01

    This paper is the first of a two part series that investigates passive buoyant tracers in the ocean surface boundary layer. The first part examines the influence of equilibrium wind-waves on vertical tracer distributions, based on large eddy simulations (LES) of the wave-averaged Navier-Stokes equation. The second part applies the model to investigate observations of buoyant microplastic marine debris, which has emerged as a major ocean pollutant. The LES model captures both Langmuir turbulence (LT) and enhanced turbulent kinetic energy input due to breaking waves (BW) by imposing equilibrium wind-wave statistics for a range of wind and wave conditions. Concentration profiles of LES agree well with analytic solutions obtained for an eddy diffusivity profile that is constant near the surface and transitions into the K-Profile Parameterization (KPP) profile shape at greater depth. For a range of wind and wave conditions, the eddy diffusivity normalized by the product of water-side friction velocity and mixed layer depth, h, mainly depends on a single nondimensional parameter, the peak wavelength (which is related to Stokes drift decay depth) normalized by h. For smaller wave ages, BW critically enhances near-surface mixing, while LT effects are relatively small. For greater wave ages, both BW and LT contribute to elevated near-surface mixing, and LT significantly increases turbulent transport at greater depth. We identify a range of realistic wind and wave conditions for which only Langmuir (and not BW or shear driven) turbulence is capable of deeply submerging buoyant tracers.

  19. Influence of the Saharan Air Layer on Atlantic tropical cyclone formation during the period 1-12 September 2003

    NASA Astrophysics Data System (ADS)

    Pan, Weiyu; Wu, Liguang; Shie, Chung-Lin

    2011-01-01

    Atmospheric Infrared Sounder (AIRS) data show that the Saharan air layer (SAL) is a dry, warm, and well-mixed layer between 950 and 500 hPa over the tropical Atlantic, extending westward from the African coast to the Caribbean Sea. The formations of both Hurricane Isabel and Tropical Depression 14 (TD14) were accompanied with outbreaks of SAL air during the period 1-12 September 2003, although TD14 failed to develop into a named tropical cyclone. The influence of the SAL on their formations is investigated by examining data from satellite observations and numerical simulations, in which AIRS data are incorporated into the MM5 model through the nudging technique. Analyses of the AIRS and simulation data suggest that the SAL may have played two roles in the formation of tropical cyclones during the period 1-12 September 2003. First, the outbreaks of SAL air on 3 and 8 September enhanced the transverse-vertical circulation with the rising motion along the southern edge of the SAL and the sinking motion inside the SAL, triggering the development of two tropical disturbances associated with Hurricane Isabel and TD14. Second, in addition to the reduced environmental humidity and enhanced static stability in the lower troposphere, the SAL dry air intruded into the inner region of these tropical disturbances as their cyclonic flows became strong. This effect may have slowed down the formation of Isabel and inhibited TD14 becoming a named tropical cyclone, while the enhanced vertical shear contributed little to tropical cyclone formation during this period. The 48-h trajectory calculations confirm that the parcels from the SAL can be transported into the inner region of an incipient tropical cyclone.

  20. Influence of a large-eddy breakup device on the frictional drag in a turbulent boundary layer

    NASA Astrophysics Data System (ADS)

    Kim, Joon-Seok; Hwang, Jinyul; Yoon, Min; Ahn, Junsun; Sung, Hyung Jin

    2017-06-01

    A direct numerical simulation of a spatially developing turbulent boundary layer with a large-eddy breakup (LEBU) device was performed to investigate the influence of the LEBU device on the near-wall turbulence and frictional drag. The LEBU device, which is thin and rectangular in shape, was located at 80% of the boundary layer thickness (δ). The LEBU device reduced the skin-friction coefficient (Cf) up to 17%. The breakdown of the outer structures passing through the LEBU device reduced the energy of the long wavelength motions (λz +>200) along the wall-normal direction. The reduction of Cf mainly arose from the contribution of the Reynolds shear stress by the difference in the spatial coherence of the outer high- and low-speed structures. We investigated the relationship between the large-scale motions and the velocity-vorticity correlations (⟨"/>v ωz<-w ωy>), which directly contribute to Cf. The contributions of accounted for 80% of the total Cf reduction. The amount of the Cf reduction induced by vortex stretching arose from the contributions of the intense positive uL (uL +≈2) and the relatively weak negative uL (uL +≈-0.7). Owing to the negative contribution of the advective vorticity transport, the total Cf reduction was obtained under the negative uL even though drag reduction was achieved by the suppression of vortex stretching under the intense positive uL.

  1. Influence of the shape of the layers in photo-cured dental restorations on the shrinkage stress peaks-FEM study.

    PubMed

    Kowalczyk, Piotr

    2009-12-01

    The aim of the paper is to analyse an influence of the shape of the layers in photo-cured dental restorations of Class I on distribution of shrinkage stresses along the tooth-restoration interface. The study is a continuation of the previous considerations (Kowalczyk and Gambin (2008) [1]), where techniques, which reduce stress concentration at the top of the tooth-restoration interface, were considered. The analysis leads to proposition of new layer forming techniques, which diminish the stress peaks at the interface and prevent the crack propagation process. To find the stress distributions in the dental restoration layers and the tooth tissues the finite element method implemented in the ABAQUS (Simulia, Providence, USA) software is used. For Class I restoration of the premolar tooth, the axisymmetrical model is assumed. The restoration is made of four layers of a photo-cured composite. Between the tooth tissues and the restoration, a layer of bonding agent 0.01mm thick is placed and modeled by FEM with help of the cohesive elements. The assumed model takes into account an influence of changes of elastic properties and viscous effects. For each case of the restoration layers system, the Huber-Mises stresses are analysed. The investigations show that the stresses near the restoration-tooth tissue interface are reduced due to viscous flow of the cured material and due to existence of a thin layer of the bonding agent. However, the stress distribution both, in the restoration and in the tooth tissues, is strongly dependent on a shape of the filling layers. Numerical simulations disclose that stress peaks are located at the top corners of each layer. The top corners of the last layer are the places where microleakage may occur. Stress concentrations at the corners of the preceding layers may lead to a growth of uprising crack. It will be shown that the flat layers in the restoration create relatively high values of the stress peaks. The rounded layers, with shapes

  2. The influence of a Si cap on self-organized SiGe islands and the underlying wetting layer

    SciTech Connect

    Brehm, M.; Grydlik, M.; Groiss, H.; Hackl, F.; Schaeffler, F.; Fromherz, T.; Bauer, G.

    2011-06-15

    For the prototypical SiGe/Si(001) Stranski-Krastanow (SK) growth system, the influence of intermixing caused by the deposition of a Si cap layer at temperatures T{sub cap} between 300 deg. C and 700 deg. C is studied both for the SiGe wetting layer (WL) and the SiGe islands. Systematic growth experiments were carried out with an ultrahigh resolution of down to 0.005 monolayers (ML) of deposited Ge. The properties of the samples were investigated via photoluminescence (PL) spectroscopy, atomic force microscopy (AFM), and transmission electron microscopy. We studied in detail the influence of T{sub cap} in the three main coverage regions of SiGe SK growth, which are (i) the WL build-up regime, (ii) the island nucleation regime, where most of the Ge is supplied via material transfer from the WL, and (iii) the saturation regime, where the WL thickness remains initially stable. At T{sub cap} = 300 deg. C, we found that both the WL and the island are essentially preserved in composition and shape, whereas at 500 deg. C the WL becomes heavily alloyed during capping, and at 700 deg. C the islands also become alloyed. At T{sub cap} = 500 deg. C we found enhanced WL intermixing in the presence of dome-shaped islands, whereas at T{sub cap} 700 deg. C the WL properties become dominated by the dissolution of pyramid-shaped islands upon capping. At Ge coverages above {approx_equal}6 ML, we found an unexpected thickening of the WL, almost independently of T{sub cap}. This finding suggests that the density and the volume of the dome-shaped islands have an upper limit, beyond which excess Ge from the external source again becomes incorporated into the WL. Finally, we compared PL spectra with AFM-based evaluations of the integral island volumes in order to determine in a straightforward manner the average composition of the SiGe islands.

  3. Diffusion des Metaux et Evolution Stellaire

    NASA Astrophysics Data System (ADS)

    Turcotte, Sylvain

    Nous presentons dans cette these des modeles d'evolution stellaire incorporant la diffusion microscopique de maniere consistante. Pour la premiere fois, on a calcule l'evolution d'etoiles en tenant compte en detail de l'impact des variations d'abondances sur leur structure. Nous utilisons des spectres monochromatiques pour chacun des elements les plus abondants dans un melange solaire pour recalculer l'opacite pour les abondances et les conditions locales dans l'interieur d'une etoile au cours de son evolution. Nos modeles montrent que la diffusion atomique des metaux a un effet important sur les opacites dan les etoiles de plus de 1.3Msolar ou l'abondance du fer et des autres elements du pic du fer varient substantiellement. Ces etoiles, sans rotation ou champ magnetique, sont proches des etoiles de type Fm-Am dans lesquelles on observe une legere surabondance d'elements du pic du fer en plus d'une sous-abondance de calcium, sous-abondance que l'on obtient egalement. Nous obtenons cependant des surabondances depassant un facteur 10 pour les etoiles de plus de 1.4Msolar ce qui suggere qu'il existe un ou plusieurs mecanismes limitant la diffusion microscopique. La surabondance du fer en surface cause une augmentation, qui peut atteindre un facteur sept, de l'opacite a la limite de la zone convective. Ceci cause un accroissement de la temperature effective et de la masse de la zone convective comparativement aux modeles n'incluant que la diffusion de l'helium. Il s'agit la du principal effet de la diffusion sur la structure interne de ces etoiles. La diffusions n'a pas d'influence sur l'evolution de coeur stellaire dans les etoiles significativement plus massives quie le Soleil. Nous avons verife que l'utilisation de modeles consistants avec diffusion n'apporte pas d'amelioration sensible aux modeles solaires. Les forces radiatives calculees a partir des spectres d'OPAL pour les elements du pic du fer representent une fraction importante de la gravite. On obtient des

  4. Influence of PEDOT:PSS on the effectiveness of barrier layers prepared by atomic layer deposition in organic light emitting diodes

    SciTech Connect

    Wegler, Barbara; Schmidt, Oliver; Hensel, Bernhard

    2015-01-15

    Organic light emitting diodes (OLEDs) are well suited for energy saving lighting applications, especially when thinking about highly flexible and large area devices. In order to avoid the degradation of the organic components by water and oxygen, OLEDs need to be encapsulated, e.g., by a thin sheet of glass. As the device is then no longer flexible, alternative coatings are required. Atomic layer deposition (ALD) is a very promising approach in this respect. The authors studied OLEDs that were encapsulated by 100 nm Al{sub 2}O{sub 3} deposited by ALD. The authors show that this coating effectively protects the active surface area of the OLEDs from humidity. However, secondary degradation processes still occur at sharp edges of the OLED stack where the extremely thin encapsulation layer does not provide perfect coverage. Particularly, the swelling of poly(3,4-ethylenedioxythiophene) mixed with poly(styrenesulfonate), which is a popular choice for the planarization of the bottom electrode and at the same time acts as a hole injection layer, affects the effectiveness of the encapsulation layer.

  5. Influences of Alq3 as electron extraction layer instead of Ca on the photo-stability of organic solar cells

    NASA Astrophysics Data System (ADS)

    Liu, Zhiyong; Tian, Miaomiao; Wang, Ning

    2014-03-01

    Calcium (Ca) is not a desirable candidate as electron extraction layer (EEL) for long-term stability organic photovoltaics (OPVs) on account of its nature of active metal. In this paper, we has selected thieno[3,4-b]thiophene/benzodithiophene (PTB7) and [6,6]-phenyl C71-butyric acid methyl ester (PC71BM) as donor and acceptor, respectively, and the device architecture is Glass/ITO/poly(ethylenedioxythiophene):polystyrene sulphonate (PEDOT:PSS)/PTB7:PC71BM/EEL/Aluminum. For comparison, tris (8-hydroxyquinoline) aluminum (Alq3) and Ca were used as EEL to reveal their influence on the performance [power conversion efficiency (PCE), short-circuit current density (JSC), open-circuit voltage (VOC) and fill factor (FF)] of the OPVs. As a result, PCE of the device with Ca as EEL rapidly reduced over 60% after three days due to the poor stability of Ca. The device with Alq3 as EEL shows favorable stability owing to the PCE moderate declined less than 30% after one month. Furthermore, PCE of the device with Alq3 as EEL was fully comparable to that with Ca as EEL. Our results indicate that Alq3 is an alternative candidate for high-performance and long-term photo-stability OPVs.

  6. Influence of Metal Contacts on Graphene Transport Characteristics and Its Removal with Nano-carbon Interfacial Layer

    NASA Astrophysics Data System (ADS)

    Kanda, Akinobu; Ito, Yu; Katakura, Kenta; Sonoda, Hiroki; Higuchi, Shoma; Tomori, Hikari; Ootuka, Youiti

    Graphene is a promising candidate for the next-generation electronic material. While considerable effort has been devoted to achieve higher mobility in graphene films, relatively little attention has been paid to the effect of metal contacts, which are indispensable to the electric devices. At a graphene/metal interface, mainly due to the difference in work functions, carriers are injected from the metal to graphene. The resulting shift of local Dirac point is not limited at the graphene/metal interface but extends into the graphene channel. This carrier doping affects more significantly the performance of graphene field effect devices with shorter channel, as well as may conceal Dirac physics at the graphene/metal interface. Here, we experimentally investigate the channel length dependence of graphene transport properties in a wide gate-voltage range and extract the effect of metal contact. Several metal species are investigated. We reveal the origin of electron-hole asymmetry and the effect of the chemical interaction between graphene and metal, and derive the effective work function of graphene (4.93 eV). Furthermore, we succeed in reducing the influence of metal contact by inserting a thin nano-carbon layer (amorphous carbon or multilayer graphene (MLG)) at the interface.

  7. Influence of an oxygen-inhibited layer on enamel bonding of dental adhesive systems: surface free-energy perspectives.

    PubMed

    Ueta, Hirofumi; Tsujimoto, Akimasa; Barkmeier, Wayne W; Oouchi, Hajime; Sai, Keiichi; Takamizawa, Toshiki; Latta, Mark A; Miyazaki, Masashi

    2016-02-01

    The influence of an oxygen-inhibited layer (OIL) on the shear bond strength (SBS) to enamel and surface free-energy (SFE) of adhesive systems was investigated. The adhesive systems tested were Scotchbond Multipurpose (SM), Clearfil SE Bond (CS), and Scotchbond Universal (SU). Resin composite was bonded to bovine enamel surfaces to determine the SBS, with and without an OIL, of adhesives. The SFE of cured adhesives with and without an OIL were determined by measuring the contact angles of three test liquids. There were no significant differences in the mean SBS of SM and CS specimens with or without an OIL; however, the mean SBS of SU specimens with an OIL was significantly higher than that of SU specimens without an OIL. For all three systems, the mean total SFE (γS), polarity force (γSp), and hydrogen bonding force (γSh) values of cured adhesives with an OIL were significantly higher than those of cured adhesives without an OIL. The results of this study indicate that the presence of an OIL promotes higher SBS of a single-step self-etch adhesive system, but not of a three-step or a two-step self-etch primer system. The SFE values of cured adhesives with an OIL were significantly higher than those without an OIL. The SFE characteristics of the OIL of adhesives differed depending on the type of adhesive. © 2015 Eur J Oral Sci.

  8. Influence of Particle Size Distribution on the Performance of Ionic Liquid-based Electrochemical Double Layer Capacitors

    PubMed Central

    Rennie, Anthony J. R.; Martins, Vitor L.; Smith, Rachel M.; Hall, Peter J.

    2016-01-01

    Electrochemical double layer capacitors (EDLCs) employing ionic liquid electrolytes are the subject of much research as they promise increased operating potentials, and hence energy densities, when compared with currently available devices. Herein we report on the influence of the particle size distribution of activated carbon material on the performance of ionic liquid based EDLCs. Mesoporous activated carbon was ball-milled for increasing durations and the resultant powders characterized physically (using laser diffraction, nitrogen sorption and SEM) and investigated electrochemically in the form of composite EDLC electrodes. A bi-modal particle size distribution was found for all materials demonstrating an increasing fraction of smaller particles with increased milling duration. In general, cell capacitance decreased with increased milling duration over a wide range of rates using CV and galvanostatic cycling. Reduced coulombic efficiency is observed at low rates (<25 mVs−1) and the efficiency decreases as the volume fraction of the smaller particles increases. Efficiency loss was attributed to side reactions, particularly electrolyte decomposition, arising from interactions with the smaller particles. The effect of reduced efficiency is confirmed by cycling for over 15,000 cycles, which has the important implication that diminished performance and reduced cycle life is caused by the presence of submicron-sized particles. PMID:26911531

  9. Influence of large-eddy breakup device on near-wall turbulent structures in turbulent boundary layer

    NASA Astrophysics Data System (ADS)

    Kim, Joon-Seok; Hwang, Jinyul; Yoon, Min; Ahn, Junsun; Sung, Hyung Jin; Flow Control Lab Team

    2016-11-01

    Direct numerical simulation of a large-eddy breakup (LEBU) device in a spatially developing turbulent boundary layer was performed to investigate the influence of outer structures on the near-wall turbulence. The thin and rectangular shaped LEBU device was placed on y / δ = 0 . 8 and the device reduced the skin-friction coefficient (Cf) up to 17%. Decomposition of Cf showed that the contribution of the Reynolds shear stress decreased along the wall-normal direction. The reduction of the Reynolds shear stress was associated with the decrease of the ejection and sweep events, and in particular the latter was significantly reduced compared to the former in the near-wall region. The spanwise length scale of high-speed structures was more shortened than that of low-speed very near the wall (y+ = 20). As a result, the dispersive motions induced by the outer sweeps were weakened leading to the reduction of Cf even the LEBU device located far from the wall. This work was supported by the Creative Research Initiatives (No. 2016-004749) program of the National Research Foundation of Korea (MSIP).

  10. CFD modelling of small particle dispersion: The influence of the turbulence kinetic energy in the atmospheric boundary layer

    NASA Astrophysics Data System (ADS)

    Gorlé, C.; van Beeck, J.; Rambaud, P.; Van Tendeloo, G.

    When considering the modelling of small particle dispersion in the lower part of the Atmospheric Boundary Layer (ABL) using Reynolds Averaged Navier Stokes simulations, the particle paths depend on the velocity profile and on the turbulence kinetic energy, from which the fluctuating velocity components are derived to predict turbulent dispersion. It is therefore important to correctly reproduce the ABL, both for the velocity profile and the turbulence kinetic energy profile. For RANS simulations with the standard k- ɛ model, Richards and Hoxey (1993. Appropriate boundary conditions for computational wind engineering models using the k-ɛ turbulence model. Journal of Wind Engineering and Industrial Aerodynamics 46-47, 145-153.) proposed a set of boundary conditions which result in horizontally homogeneous profiles. The drawback of this method is that it assumes a constant profile of turbulence kinetic energy, which is not always consistent with field or wind tunnel measurements. Therefore, a method was developed which allows the modelling of a horizontally homogeneous turbulence kinetic energy profile that is varying with height. By comparing simulations performed with the proposed method to simulations performed with the boundary conditions described by Richards and Hoxey (1993. Appropriate boundary conditions for computational wind engineering models using the k-ɛ turbulence model. Journal of Wind Engineering and Industrial Aerodynamics 46-47, 145-153.), the influence of the turbulence kinetic energy on the dispersion of small particles over flat terrain is quantified.

  11. Influence of Particle Size Distribution on the Performance of Ionic Liquid-based Electrochemical Double Layer Capacitors.

    PubMed

    Rennie, Anthony J R; Martins, Vitor L; Smith, Rachel M; Hall, Peter J

    2016-02-25

    Electrochemical double layer capacitors (EDLCs) employing ionic liquid electrolytes are the subject of much research as they promise increased operating potentials, and hence energy densities, when compared with currently available devices. Herein we report on the influence of the particle size distribution of activated carbon material on the performance of ionic liquid based EDLCs. Mesoporous activated carbon was ball-milled for increasing durations and the resultant powders characterized physically (using laser diffraction, nitrogen sorption and SEM) and investigated electrochemically in the form of composite EDLC electrodes. A bi-modal particle size distribution was found for all materials demonstrating an increasing fraction of smaller particles with increased milling duration. In general, cell capacitance decreased with increased milling duration over a wide range of rates using CV and galvanostatic cycling. Reduced coulombic efficiency is observed at low rates (<25 mVs(-1)) and the efficiency decreases as the volume fraction of the smaller particles increases. Efficiency loss was attributed to side reactions, particularly electrolyte decomposition, arising from interactions with the smaller particles. The effect of reduced efficiency is confirmed by cycling for over 15,000 cycles, which has the important implication that diminished performance and reduced cycle life is caused by the presence of submicron-sized particles.

  12. Diffusion incohérente des neutrons : modèles analytiques pour la dynamique interne des protéines

    NASA Astrophysics Data System (ADS)

    Bicout, D. J.

    2005-11-01

    La dynamique interne des protéines joue un rôle central dans la stabilité, la fonction et l'activité biologique de ces biomolécules. Il est maintenant établi que les fluctuations d'états conformationnels des protéines influencent fortement la plupart des réactions biochimiques et s'accompagnent d'une augmentation brutale des déplacements carrés moyens des atomes au dessus de la température de la transition dynamique. Dans cette contribution, nous présentons une revue critique de quelques modèles théoriques couramment utilisés dans la littérature pour l'analyse des mouvements internes des protéines et la description de la transition dynamique.

  13. Influence of a low-temperature GaN cap layer on the electron concentration in AlGaN/GaN heterostructure

    NASA Astrophysics Data System (ADS)

    Andreev, A. A.; Vavilova, E. A.; Ezubchenko, I. S.; Zanaveskin, M. L.; Maiboroda, I. O.

    2017-08-01

    The influence of low-temperature passivating GaN cap layers on the electrophysical parameters of a 2D electron gas (2DEG) in heterostructure high-electron mobility transistors has been studied. It has been found that thin GaN layers deposited in situ at 550°C do not exhibit polar properties and do not change the carrier concentration in the 2DEG. However, GaN layers deposited at 830°C decrease the carrier concentration in the 2DEG, which is in agreement with theoretical calculations. Using the reflected high-energy electron diffraction technique, it has been established that this effect may be associated with different structures and morphologies of GaN layers deposited at different temperatures.

  14. ACCURATE: Influence of Cloud Layers and Aerosol on Infrared Laser Occultation Signals for Sensing of Greenhouse Gases

    NASA Astrophysics Data System (ADS)

    Proschek, V.; Schweitzer, S.; Emde, C.; Ladstädter, F.; Fritzer, J.; Kirchengast, G.

    2009-04-01

    ACCURATE (Atmospheric Climate and Chemistry in the UTLS Region And climate Trends Explorer), a new climate satellite concept, enables simultaneous measurement of profiles of greenhouse gases, isotopes, wind and thermodynamic variables from Low Earth Orbit (LEO) satellites. The measurement principle applied is a combination of the novel LEO-LEO infrared laser occultation (LIO) technique and the well-studied but not yet flown LEO-LEO microwave occultation (LMO) technique. As intrinsic to the space-borne occultation technique, the measurements are evenly distributed around the world, have high vertical resolution and high accuracy and are stable over long time periods. The LIO uses near-monochromatic signals in the short-wave infrared range (~2-2.5 m in the case of ACCURATE) which are absorbed by various trace species in the Earth's atmosphere. From signal transmission measurements, profiles of the concentration of the absorbing species can be derived given that temperature and pressure are accurately known from LMO. The current ACCURATE mission design is arranged for the measurement of six greenhouse gases (H2O, CO2, CH4, N2O, O3, CO) and four isotopes (13CO2, C18OO, HDO, H218O) with focus on the upper troposphere/lower stratosphere region (UTLS, 5-35 km). Wind speed in line-of-sight can be derived from a line-symmetric transmission difference which is caused by wind-induced Doppler shift. By-products are information on cloud layering, aerosol extinction and scintillation strength. This contribution presents an overview on the ACCURATE mission design and the expected accuracy of retrieved atmospheric variables and further focuses on the influence of clouds and aerosols on propagating LIO signals. Special emphasis will be given to sub-visible cirrus clouds which are semi-transparent to infrared signals. A simple frequency dependent cloud extinction parametrization was included into the occultation propagation software EGOPS and evaluated against results of the

  15. Influence of the current through one turn of a multilayer coil on the nearest turn in a consecutive layer

    NASA Astrophysics Data System (ADS)

    Suárez, P.; Alvarez, A.; Pérez, B.; Ceballos, J. M.

    2008-02-01

    Many references on AC losses can be found for straight superconducting tapes with or without an external magnetic field. There are fewer references on AC losses for bent tapes such as we find it in a spire or solenoid. But even fewer are the references on the study of AC losses in multilayer coils or magnetically coupled coils wound close together. In these cases, the loss in each piece of tape depends on three factors: the transport current in it, the global magnetic field due to the complete coil, and the local magnetic field due to the current in the tape wound just over or under the piece in question -the main difference between multilayer coils and magnetically coupled coils is that the current in the former is the same in all the layers and the currents in magnetically coupled coils are different in amplitude and phase. In order to determine the losses due to the third factor above, the local magnetic fields, we propose in this paper an experiment that consists of the measurement of losses in two straight insulated superconducting tapes located one over the other as close together as possible. In this way, the effect of the global magnetic field of the coil disappears because the coil does not exist. Furthermore, one of the tapes is made to be twice as long as the other so that we can measure the part of the transport losses in the part of the tape independent on the influence of the other. This permits us to distinguish the component of the losses due to the interaction between the pair of tapes. BSCCO tape was used and the pieces were fed with two different power supplies each one giving a current adjustable in amplitude. Measurements of the voltages between taps and in contact-less loops were taken both between the tapes and, in the longer tape, away from the influence of the shorter one. The losses were calculated from the wave forms of the contact and contact-less voltages and the currents. The influence of the proximity of the tapes was determined.

  16. Des ballons pour demain

    NASA Astrophysics Data System (ADS)

    Régipa, R.

    A partir d'une théorie sur la détermination des formes et des contraintes globales d'un ballon de révolution, ou s'en rapprochant, une nouvelle famille de ballons a été définie. Les ballons actuels, dits de ``forme naturelle'', sont calculés en général pour une tension circonférencielle nulle. Ainsi, pour une mission donnée, la tension longitudinale et la forme de l'enveloppe sont strictement imposées. Les ballons de la nouvelle génération sont globalement cylindriques et leurs pôles sont réunis par un câble axial, chargé de transmettre une partie des efforts depuis le crochet (pôle inférieur), directement au pôle supérieur. De plus, la zone latérale cylindrique est soumise à un faible champ de tensions circonférencielles. Ainsi, deux paramètres permettent de faire évoluer la distribution des tensions et la forme de l'enveloppe: - la tension du câble de liaison entre pôles (ou la longueur de ce câble) - la tension circonférencielle moyenne désirée (ou le rayon du ballon). On peut donc calculer et réaliser: - soit des ballons de forme adaptée, comme les ballons à fond plat pour le bon fonctionnement des montgolfières infrarouge (projet MIR); - soit des ballons optimisés pour une bonne répartition des contraintes et une meilleure utilisation des matériaux d'enveloppe, pour l'ensemble des programmes stratosphériques. Il s'ensuit une économie sensible des coûts de fabrication, une fiabilité accrue du fonctionnement de ces ballons et une rendement opérationnel bien supérieur, permettant entre autres, d'envisager des vols à très haute altitude en matériaux très légers.

  17. Influence of C60 co-deposition on the growth kinetics of diindenoperylene-From rapid roughening to layer-by-layer growth in blended organic films

    NASA Astrophysics Data System (ADS)

    Lorch, C.; Novák, J.; Banerjee, R.; Weimer, S.; Dieterle, J.; Frank, C.; Hinderhofer, A.; Gerlach, A.; Carla, F.; Schreiber, F.

    2017-02-01

    We investigated the growth of the two phase-separating materials diindenoperylene (DIP) and buckminsterfullerene C60 with different mixing ratio in real-time and in situ by X-ray scattering experiments. We found that at room temperature, mixtures with an excess of DIP show a growth mode which is very close to the perfect layer-by-layer limit with DIP crystallites forming over the entire film thickness. An unexpected increase in the island size is observed for these mixtures as a function of film thickness. On the other hand, equimolar and C60 dominated mixtures grow with poor crystallinity but form very smooth films. Additionally, it is observed that higher substrate temperatures lead to an increase in the length scale of phase separation with film thickness.

  18. Influence of head size on the development of metallic wear and on the characteristics of carbon layers in metal-on-metal hip joints

    PubMed Central

    Sprecher, Christoph M; Wimmer, Markus A; Milz, Stefan; Taeger, Georg

    2009-01-01

    Background and purpose Particles originating from the articulating surfaces of hip endoprostheses often induce an inflammatory response, which can be related to implant failure. We therefore analyzed the metal content in capsular tissue from 44 McKee-Farrar metal-on-metal hip prostheses (with 3 different head sizes) and we also analyzed the morphological structure of layers located on articulating surfaces. Methods Atomic absorption spectrometry (AAS) was used to analyze the metal content in capsular tissue. Visually detectable carbon layers located on the articulating surfaces were evaluated using scanning electron microscopy (SEM), energy-dispersive Xray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS). Results Metallic debris was detected in all capsular tissue samples but no statistically significant differences in metal content were found in relation to implant head size. The morphological characteristics of the different layer zones allowed an exact analysis of contact and non-contact areas. Furthermore, surface layers appear to have a protective function because they can prevent sharp-edged particles from damaging the prostheses surface. Interpretation The implant head size does not appear to influence the amount of metallic debris. The layers obviously act like a lubricating agent because the protection function does not occur in regions without layers where the metal surface often shows numerous scratches. As layers are not generated immediately after the implantation of hip prostheses, these findings may at least partially explain the high amount of wear early after implantation. PMID:19421914

  19. Influence of growth temperature on laser molecular beam epitaxy and properties of GaN layers grown on c-plane sapphire

    NASA Astrophysics Data System (ADS)

    Dixit, Ripudaman; Tyagi, Prashant; Kushvaha, Sunil Singh; Chockalingam, Sreekumar; Yadav, Brajesh Singh; Sharma, Nita Dilawar; Kumar, M. Senthil

    2017-04-01

    We have investigated the influence of growth temperature on the in-plane strain, structural, optical and mechanical properties of heteroepitaxially grown GaN layers on sapphire (0001) substrate by laser molecular beam epitaxy (LMBE) technique in the temperature range 500-700 °C. The GaN epitaxial layers are found to have a large in-plane compressive stress of about 1 GPa for low growth temperatures but the strain drastically reduced in the layer grown at 700 °C. The nature of the in-plane strain has been analyzed using high resolution x-ray diffraction, atomic force microscopy (AFM), Raman spectroscopy and photoluminescence (PL) measurements. From AFM, a change in GaN growth mode from grain to island is observed at the high growth temperature above 600 °C. A blue shift of 20-30 meV in near band edge PL emission line has been noticed for the GaN layers containing the large in-plane strain. These observations indicate that the in-plane strain in the GaN layers is dominated by a biaxial strain. Using nanoindentation, it is found that the indentation hardness and Young's modulus of the GaN layers increases with increasing growth temperature. The results disclose the critical role of growth mode in determining the in-plane strain and mechanical properties of the GaN layers grown by LMBE technique.

  20. Influence du débit et de la répartition de dose sur l'incidence des cancers pulmonaires après inhalation d'émetteurs

    NASA Astrophysics Data System (ADS)

    Fritsch, P.; Dudoignon, N.; Morlier, J. P.; Monchaux, G.; Morin, M.

    1998-04-01

    We have discussed experimental results reported on the influence of dose rate and dose distribution on the incidence of lung tumors after inhalation exposure to α emitters. New experiments have been carried out to characterize the range of tumor risk which could vary over more than a factor 20 depending on the α activity of the inhaled particles. Long term effects induced in rats after inhalation of poorly soluble 237NpO2 and industrial PuO2 with a similar granulometry will be compared, the specific activities of which varying within a factor 500. Nous avons rapporté les différentes données expérimentales de cancérogenèse pulmonaire qui montrent une variation du risque d'induction des tumeurs après inhalation de radionucléides émetteurs α selon le débit et la répartition de dose. De nouvelles expérimentations ont été initiées afin de préciser ces variations qui s'étalent sur plus d'un facteur 20. Elles consistent à comparer les effets induits chez le rat après exposition à des aérosols de 237NpO2 et de PuO2 d'origine industrielle peu solubles et de granulométrie analogue dont les activités spécifiques diffèrent d'un facteur 500.

  1. Influence of water-layer thickness on Er:YAG laser ablation of enamel of bovine anterior teeth.

    PubMed

    Mir, Maziar; Meister, Joerg; Franzen, Rene; Sabounchi, Shabnam S; Lampert, Friedrich; Gutknecht, Norbert

    2008-10-01

    Different ideas have been presented to describe the mechanism of augmented laser ablation of dental enamel with different shapes by adding water to the working environment. In this study, the influence of water-laser interaction on the surface of enamel during ablation was investigated at a wavelength of 2.94 microm with different distances between the laser tip and the enamel surface. A motion-control system was used to produce linear incisions uniformly on flat enamel surfaces of bovine anterior teeth, with free-running Er:YAG laser very short pulses (pulse length = 90-120 micros, repetition rate = 10 pulses per second). Four different output energies (100, 200, 300 and 400 mJ) were radiated on samples under distilled water from different distances (0.5, 0.75, 1, 1.25, 1.75 and 2.00 mm). The tooth slices were prepared with a cutting machine, and the surfaces of the ablated areas were measured with software under a light microscope. The average and standard deviation of all cut areas in different groups were reported. There was no significant difference when using a different pulse ablation speed (cm(3)/J) and a water-layer thickness between the tip and enamel surface of 0.5-1.25 mm with energy densities of 30-60 J/cm(2) (200-400 mJ). However, using an output energy of 15 J/cm(2) (100 mJ) and a thicker water layer than 1 mm, a linear ablation did not take place. This information led to a clearer view of the efficiency of Er:YAG laser in the conditions of this study. There are several hypotheses which describe a hydrokinetic effect of Er,Cr:YSGG. These basic studies could guide us to have a correct attitude regarding hydro-mechanical effects of water, although the wavelength of 2.78 microm has a better absorption in hydroxyl branch of water molecules. Therefore, our results do not directly interrupt with the series of investigations done with Er,Cr:YSGG. Water propagation and channel formation under water are investigated during the ablation of tooth enamel with

  2. Transport quantique dans des nanostructures

    NASA Astrophysics Data System (ADS)

    Naud, C.

    2002-09-01

    structure des oscillations de conductance en fonction du flux du champ magnétique de période h/e dont l'amplitude est beaucoup plus importante que celle mesurée sur un réseau carré de même dimension. Cette différence constitue une signature d'un effet de localisation induit par le champ magnétique sur la topologie mathcal{T}3. Pour des valeurs spécifiques du champ magnétique, du fait des interférences destructives Aharonov-Bohm, la propagation des fonctions d'ondes est limitée à un ensemble fini de cellule du réseau appelé cage. De la dépendance en température des oscillations de période h/e mesurées sur le réseau mathcal{T}3 nous avons tiré une longueur caractéristique qui peut être rattachée au périmètre des cages. Un phénomène inattendu fut l'observation, pour des champs magnétiques plus importants, d'un doublement de fréquence des oscillations. Ces oscillations de période h/2e pouvant avoir une amplitude supérieure aux oscillations de période h/e, une interprétation en terme d'harmonique n'est pas possible. Enfin, l'influence de la largeur électrique des fils constituant le réseau et donc celle du nombre de canaux par brin a été étudiée en réalisant des grilles électrostatique. Les variations de l'amplitude des signaux en h/e et h/2e en fonction de la tension de grille ont été mesurés.

  3. Influences of thicknesses and structures of barrier cap layers on As ion profiles and implant damages in HgCdTe epilayers

    NASA Astrophysics Data System (ADS)

    Shi, Changzhi; Lin, Chun; Wei, Yanfeng; Chen, Lu; Ye, Zhenhua

    2016-05-01

    The barrier cap layer (BCL) is considered to be able to absorb partially implant induced damages during ion implantation, thus its structure and property could impact the result of ion implantation. In this paper, for As ion implantation in HgCdTe, the different BCLs were deposited on the CdZnTe-based (LPE) and GaAs-based (MBE) HgCdTe epilayers, respectively. Then, the influences of thicknesses and structures of these BCLs on dopant profiles and implant damages were investigated. The as-grown BCLs include thermally evaporated (TE) ZnS, TE CdTe, electron beam evaporated (EBE) CdTe and in-situ CdTe/ZnTe grown by MBE. The SIMS profiles and TEM characterization indicate: For TE ZnS BCLs, there exists an optimized thickness to obtain the deepest As indiffusion after high temperature annealing, and the end-of-range (EOR) depth is linearly proportional to the thickness ratio of a-MCT layer/damage layer. For TE CdTe BCLs, the barrier layer induced channeling effect (BLICE) occurs to the thin BCL samples, while this effect is suppressed in the thick BCL samples. The phenomenon might be due to that the blocking effect of the layered structure inside each crystal column becomes dominate in the thick BCL samples. Additionally, the EBE CdTe BCL with layered structure can suppress effectively the BLICE effect; in the in-situ CdTe/ZnTe BCL, the short defect layer generated in the CdTe buffer layer and the amorphization of the ZnTe layer during ion implantation also play a significant role in suppressing the BLICE effect.

  4. The Influence of Multiple Nested Layer Waviness on the Compression Strength of Double Nested Wave Formations in a Carbon Fiber Composite Laminate

    NASA Astrophysics Data System (ADS)

    Khan, Z. M.; Adams, D. O.; Anas, S.

    2016-01-01

    As advanced composite materials having superior physical and mechanical properties are being developed, the optimization of their processing techniques is eagerly sought. One of the most common defects arising during processing of structural composites is layer waviness. The layer waviness is more pronounced in thick-section flat and cylindrical laminates, which are extensively used in large wind turbine blades, submersibles, and space platforms. The layer waviness undulates the entire layer of a multidirectional laminate in the throughthe-thickness direction, leading to a gross deterioration of its compressive strength. This research investigates the influence of multiple layer waviness in a double nest formation on the compression strength of a composite laminate. Different wave fractions of wavy 0° layers were fabricated in an IM/8551-7 carbon-epoxy composite laminate on a steel mold by using a single-step fabrication procedure. The test laminates were cured on a heated press according to the specific curing cycle of epoxy. Their static compression testing was performed using a NASA short block compression fixture on an MTS servohydraulic machine. The purpose of these tests was to determine the effects of multiple layer wave regions on the compression strength of the composite laminate. The experimental and analytical results obtained revealed that the reduction in the compression strength of composite laminate was constant after the fraction of the wavy 0° layers exceeded 35%. This analysis indicated that the percentage of the 0° wavy layer may be used to estimate the reduction in the compression strength of a double nested wave formation in a composite laminate.

  5. The Influence of Gender, Age, Matriline and Hierarchical Rank on Individual Social Position, Role and Interactional Patterns in Macaca sylvanus at ‘La Forêt des Singes’: A Multilevel Social Network Approach

    PubMed Central

    Sosa, Sebastian

    2016-01-01

    A society is a complex system composed of individuals that can be characterized by their own attributes that influence their behaviors. In this study, a specific analytical protocol based on social network analysis was adopted to investigate the influence of four attributes (gender, age, matriline, and hierarchical rank) on affiliative (allogrooming) and agonistic networks in a non-human primate species, Macaca sylvanus, at the park La Forêt des Singes in France. The results show significant differences with respect to the position (i.e., centric, peripheral) and role (i.e., implication in the network cohesiveness) of an individual within a social network and hence interactional patterns. Females are more central, more active, and have a denser ego network in the affiliative social network tan males; thus, they contribute in a greater way to the cohesive structure of the network. High-ranking individuals are likely to receive fewer agonistic behaviors than low-ranking individuals, and high-ranking females receive more allogrooming. I also observe homophily for affiliative interactions regarding all attributes and homophily for agonistic interactions regarding gender and age. Revealing the positions, the roles, and the interactional behavioral patterns of individuals can help understand the mechanisms that shape the overall structure of a social network. PMID:27148137

  6. Influence of the foundation layer on the layer-by-layer assembly of poly-L-lysine and poly(styrenesulfonate) and its usage in the fabrication of 3D microscale features.

    PubMed

    Zhou, Dejian; Bruckbauer, Andreas; Batchelor, Matthew; Kang, Dae-Joon; Abell, Chris; Klenerman, David

    2004-10-12

    The layer-by-layer (LBL) assembly of a polypeptide, poly-L-lysine (PLL), with poly(styrenesulfonate) sodium salt (PSS) on flat template-stripped gold (TSG) surfaces precoated with a self-assembled monolayer of alkanethiols terminated with positive (pyridinium), negative (carboxylic acid), and neutral [hexa(ethylene glycol)] groups is investigated. Both the topography and the rate of film thickness growth are found to be strongly dependent on the initial surface foundation layer. LBL assembly of PLL and PSS on patterned TSG surfaces produced by micro contact printing leads to structurally distinct microscale features, including pillars, ridges, and wells, whose height can be controlled with nanometer precision.

  7. Influence of cathode opening size and wetting properties of diffusion layers on the performance of air-breathing PEMFCs

    NASA Astrophysics Data System (ADS)

    Schmitz, A.; Tranitz, M.; Eccarius, S.; Weil, A.; Hebling, C.

    Air-breathing PEMFCs consist of an open cathodic side to allow an entirely passive supply of oxygen by diffusion. Furthermore, a large fraction of the produced water is removed by evaporation from the open cathode. Gas diffusion layers (GDLs) and the opening size of the cathode have a crucial influence on the performance of an air-breathing PEMFC. In order to assure an unobstructed supply of oxygen the water has to be removed efficiently and condensation in the GDL has to be avoided. On the other hand good humidification of the membrane has to be achieved to obtain high protonic conductivity. In this paper the influence of varying cathodic opening sizes (33%, 50% and 80% opening ratios) and of GDLs with different wetting properties are analysed. GDLs with hydrophobic and hydrophilic properties are prepared by coating of untreated GDLs (Toray ® carbon paper TGP-H-120, thickness of 350 μm). The air-breathing PEMFC test samples are realised using printed circuit board (PCB) technology. The cell samples were characterised over the entire potential range (0-0.95 V) by extensive measurements of the current density, the temperature and the cell impedance at 1 kHz. Additionally, measurements of the water balance were carried out at distinct operation points. The best cell performance was achieved with the largest opening ratio (80%) and an untreated GDL. At the maximum power point, this cell sample achieved a power density of 100 mW cm -2 at a moderate cell temperature of 43 °C. Furthermore, it could be shown that GDLs with hydrophilic or intense hydrophobic properties do not improve the performance of an air-breathing PEMFC. Based on the extensive characterisations, two design rules for air-breathing PEMFCs could be formulated. Firstly, it is crucial to maximise the cathode opening as far as an appropriate compression pressure of the cell assembly and therewith low contact resistance can be assured. Secondly, it is advantageous to use an untreated, slightly hydrophobic

  8. Influence of the Oxygen-inhibited Layer on Bonding Performance of Dental Adhesive Systems: Surface Free Energy Perspectives.

    PubMed

    Tsujimoto, Akimasa; Barkmeier, Wayne W; Takamizawa, Toshiki; Latta, Mark A; Miyazaki, Masashi

    2016-01-01

    To examine the influence of the oxygen inhibited layer (OIL) on shear bond strength (SBS) to dentin and surface free energy (SFE) characteristics of different adhesive systems. Three adhesive systems were used: Scotchbond Multipurpose (SM), Clearfil SE Bond (CS), and Scotchbond Universal (SU). Resin composite was bonded to dentin surfaces to determine SBS with and without OIL of adhesives. The SFE, dispersion force (γSd), polarity force (γSp), and hydrogen bonding force (γSh) of cured adhesives with and without an OIL were measured. Two-way ANOVA and Tukey's honestly significant difference (HSD) test were used for analysis of SBS data, and one-way ANOVA and Tukey's HSD test were used for the SFE and contact angle data. The SBS of SM and CS showed no significant differences between specimens with and without the OIL. However, the SBS of SU with the OIL was significantly higher than without the OIL. The SFE, γSp, and γSh of cured adhesives with an OIL were significantly higher than those of cured adhesives without an OIL. The SFE, γSp, and γSh of SM and CS with an OIL were significantly higher than those of SU with an OIL. The results of this study indicate that the presence of an OIL with a single-step self-etching adhesive promotes higher SBS to dentin, unlike in the other types of adhesive systems. The SFE characteristics of the OIL of dental adhesives differed depending on the type of adhesive system.

  9. Influence of pH and oxygen-inhibited layer on fluoride release properties of fluoride sealant.

    PubMed

    Shen, C; Shokry, T E; Anusavice, K J

    2007-04-01

    This study tested the hypothesis that the oxygen-inhibited layer on a light-cured methacrylate based resin and the pH of the storage medium would increase significantly the initial fluoride release and long-term release rate from fluoride dental sealant. Forty-eight discs (16-mm diameter x 1-mm thick) were made from FluroShield (<5 wt% NaF) and Helioseal F (<30 wt% fluorosilicate glass) sealants. For each sealant, 24 discs were cured through a Mylar strip that covered the surface and the remaining 24 discs were cured in air allowing formation of the oxygen-inhibited surface. Each specimen in the 24-disc groups was stored individually in 25-mL vials, and divided into four six-vial groups to receive 10 mL of pH4-pH7 (designation of pH 4-7) lactate buffer solutions. The buffer solutions were replaced periodically up to 121 days. The cumulative fluoride release over time was used to determine the coefficients for short-term and long-term release. Two-way ANOVA showed that the mean coefficient values for either sealant were significantly influenced by the curing condition (p<0.0001) and pH (p<0.0001), except for short-term release from NaF sealant. The duration of short-term release was much longer for the fluorosilicate glass sealant. Both pH and the source of fluoride source incorporated in the sealant play significant roles in fluoride release.

  10. The influence of doping and post-treatment on optical-electrical properties of novel window layers

    NASA Astrophysics Data System (ADS)

    Liu, Xingzuo; Shen, Jiesheng; Zhao, Yue

    2016-10-01

    In this paper, vacuum thermal evaporation and direct current magnetron sputtering technique are used to produce a novel window layer with the structure of i-ZnO/AZO/Ag(In):AZO. Based on the traditional i-ZnO/AZO window layer, the metal Ag (In) thin film is deposited on the surface of this double-layer thin film to form a new window layer with the structure of i-ZnO/AZO/Ag (In):AZO. Comparing with the traditional i-ZnO/AZO window layer, the deposited metal Ag (In) thin film on the surface of traditional i-ZnO/AZO window layer may lead to the reduction in resistivity and transmittance, which can be attributed to high conductivity and high reflectivity of deposited metal Ag (In) thin film. After annealing, the resistance of novel window layer with the structure of i-ZnO/AZO/In:AZO has a large reduction, but the change of resistance of novel i-ZnO/AZO/Ag:AZO window layer shows a opposite trend. This phenomenon may be related to the different number of valence electron of doping element. Furthermore, the annealing process promotes the recrystallization process to decrease the internal stress and the crystal structure defects, which leads to an obvious decrease in the transmittance and the carrier scattering rate of novel window layer.

  11. Influences of alcoholic solvents on spray pyrolysis deposition of TiO{sub 2} blocking layer films for solid-state dye-sensitized solar cells

    SciTech Connect

    Jiang, Changyun; Koh, Wei Lin; Leung, Man Yin; Hong, Wei; Li, Yuning; Zhang, Jie

    2013-02-15

    Influences of alcoholic solvents for titanium diisopropoxide bis(acetylacetonate) (TPA) precursor solutions on the spray pyrolysis deposited TiO{sub 2} films and the photovoltaic performance of the solid-state dye-sensitized solar cells (SDSCs) using these TiO{sub 2} films as the blocking layers were investigated. Smooth TiO{sub 2} films were obtained by spray pyrolysis deposition of a TPA solution in isopropanol (IPA) at a relatively low temperature of 260 Degree-Sign C. On the other hand, when ethanol was used as solvent, the TiO{sub 2} films fabricated at the same temperature showed much rougher surfaces with many pinholes. Our results showed that ethanol reacts with TPA to form titanium diethoxide bis(acetylacetonate) (TEA), which requires a higher thermal decomposition temperature than that of TPA. SDSCs with TiO{sub 2} blocking layer films fabricated using a TPA solution in IPA showed higher power conversion efficiencies with smaller variations. - Graphical abstract: Alcoholic solvents used for the TiO{sub 2} precursor play a critical role in determining the surface morphology of blocking layers and thus the photovoltaic performance of the SDSCs. Highlights: Black-Right-Pointing-Pointer Solvent influences morphology of spray pyrolysis deposited TiO{sub 2} blocking layer. Black-Right-Pointing-Pointer Ethanol reacts with TPA, resulting poor quality of blocking layer. Black-Right-Pointing-Pointer Isopropanol is better than ethanol for obtaining smooth blocking layer. Black-Right-Pointing-Pointer SDSC with blocking layer made with isopropanol showed better performance.

  12. Study on the influence of the B4C layer thickness on the neutron flux and energy distribution shape in multi-electrode ionisation chamber.

    PubMed

    Tymińska, K; Maciak, M; Ośko, J; Tulik, P; Zielczyński, M; Gryziński, M A

    2014-10-01

    A model of a multi-electrode ionisation chamber, with polypropylene electrodes coated with a thin layer of B4C was created within Monte Carlo N-Particle Transport Code (MCNPX) and Fluktuierende Kaskade (FLUKA) codes. The influence of the layer thickness on neutron absorption in B4C and on the neutron spectra in the consecutive intra-electrode gas volumes has been studied using the MCNPX and FLUKA codes. The results will be used for designing the new type of the ionisation chamber.

  13. Influence of layer-by-layer assembled electrospun poly (L-lactic acid) nanofiber mats on the bioactivity of endothelial cells

    NASA Astrophysics Data System (ADS)

    Wu, Keke; Zhang, Xiazhi; Yang, Wufeng; Liu, Xiaoyan; Jiao, Yanpeng; Zhou, Changren

    2016-12-01

    Electrospun poly(L-lactic acid) (PLLA) nanofiber mats were successfully modified by deposition of multilayers with chitosan (CS), heparin (Hep) and graphene oxide (GO) through electrostatic layer-by-layer (LBL) self-assembly method. In this study, the surface properties of PLLA nanofiber mats before and after modification were investigated via scanning electron microscope (SEM), atomic force microscopy (AFM), attenuated total reflectance fourier transformation infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS) and water contact angle measurement. In addition, the cytocompatibility of the modified PLLA nanofiber mats were investigated by testing endothelial cells compatibility, including cell attachment, cell proliferation and cell cycle. The results revealed that the surfaces of modified PLLA nanofiber mats become much rougher, stifiness and the hydrophilicity of the LBL modified PLLA nanofiber mats were improved compared to original PLLA one. Moreover, the modified PLLA nanofiber mats had promoted the endothelial cells viability attachment significantly. Besides, we studied the PLLA nanofiber mats on the expression of necrosis factor (TNF-α), interleukine-1β (IL-1β), monocyte chemoattractant protein-1 (MCP-1) and vascular cell adhesion molecule-1 (VCAM-1) in endothelial cells. The results showed that modified PLLA nanofiber mats had inhibited the inflammatory response to some extent.

  14. Influence of annealing in H atmosphere on the electrical properties of Al2O3 layers grown on p-type Si by the atomic layer deposition technique

    NASA Astrophysics Data System (ADS)

    Kolkovsky, Vl.; Stübner, R.; Langa, S.; Wende, U.; Kaiser, B.; Conrad, H.; Schenk, H.

    2016-09-01

    In the present study the electrical properties of 100 nm and 400 nm alumina films grown by the atomic layer deposition technique on p-type Si before and after a post-deposition annealing at 440 °C and after a dc H plasma treatment at different temperatures are investigated. We show that the density of interface states is below 2 × 1010 cm-2 in these samples and this value is significantly lower compared to that reported previously in thinner alumina layers (below 50 nm). The effective minority carrier lifetime τg,eff and the effective surface recombination velocity seff in untreated p-type Si samples with 100 nm and 400 nm aluminum oxide is comparable with those obtained after thermal oxidation of 90 nm SiO2. Both, a post-deposition annealing in forming gas (nitrogen/hydrogen) at elevated temperatures and a dc H-plasma treatment at temperatures close to room temperature lead to the introduction of negatively charged defects in alumina films. The results obtained in samples annealed in different atmospheres at different temperatures or subjected to a dc H plasma treatment allow us to correlate these centers with H-related defects. By comparing with theory we tentatively assign them to negatively charged interstitial H atoms.

  15. CdSe quantum dot formation: alternative paths to relaxation of a strained CdSe layer and influence of the capping conditions.

    PubMed

    Robin, I C; Aichele, T; Bougerol, C; André, R; Tatarenko, S; Bellet-Amalric, E; Van Daele, B; Van Tendeloo, G

    2007-07-04

    CdSe/ZnSe quantum dot formation is investigated by studying different steps of the growth. To precisely control the critical thickness of CdSe grown on a ZnSe buffer layer, the CdSe self-regulated growth rate in atomic layer epitaxy growth mode is determined by reflection high-energy electron diffraction (RHEED) measurements for a temperature range between 180 and 280 °C. Then, the two-dimensional-three-dimensional (2D-3D) transition of a strained CdSe layer on (001)-ZnSe induced by the use of amorphous selenium is studied. The formation of CdSe islands is found when 3 monolayers (ML) of CdSe are deposited. When only 2.5 ML of CdSe are deposited, another relaxation mechanism is observed, leading to the appearance of strong undulations on the surface. We also studied the evolution of the surface morphology when 2.7 ML are deposited, to study the boundary between those two phenomena. The influence of capping on quantum dot morphology is investigated. It is found that cadmium is redistributed within the layer during capping. Our results show that the cadmium distribution after capping depends on the capping temperature and on the strain of the CdSe layer. Cadmium incorporation after capping is also studied. It is found that the amount of incorporated cadmium depends on the strain of the CdSe layer before capping.

  16. Influence of high-temperature AlN intermediate layer on the optical properties of MOCVD grown AlGaN films

    NASA Astrophysics Data System (ADS)

    Xie, Deng; Qiu, Zhi Ren; Liu, Yao; Talwar, Devki N.; Wan, Lingyu; Zhang, Xiong; Mei, Ting; Ferguson, Ian T.; Feng, Zhe Chuan

    2017-02-01

    By combining spectroscopic ellipsometry (SE) and optical transmission (OT) characterization methods we have systematically investigated the influence of AlN intermediate layer and AlN transition layer on the optical properties of AlGaN epilayers grown on sapphire by metalorganic chemical vapor deposition (MOCVD) method. Most dielectric functions of III-nitrides obtained by different research groups show significant band-tail absorption—which is not anticipated for such a direct band gap material. The dielectric functions are studied for a series of AlGaN/AlN/Al2O3 structures, with a four-layer model taking into account both high temperature grown AlN layer and low temperature grown AlN layer. The results obtained by fitting the optical parameters to experimental data show that the band-tail absorption should originate from the transition layer. AlGaN film without high temperature AlN epilayer exhibited a redshift of band gap around 0.24 eV.

  17. Observation studies on the influence of atmospheric boundary layer characteristics associate with air quality in dry season over the Pearl River Delta, China

    NASA Astrophysics Data System (ADS)

    Fan, Shaojia; Wu, Meng; Li, Haowen; Liao, Zhiheng; Fan, Qi; Zhu, Wei

    2016-04-01

    The characteristics of atmospheric boundary layer (ABL) is the very important factors influence on air quality in dry season over the Pearl River Delta (PRD), China. Based on the sounding data at six stations (Xinken,Dongguan, Sanshui, Nanhai, Shunde, and Heshan) which obtained from three times ABL experiments carried in dry season over PRD, the influence of wind and temperature vertical structure to the air quality over PRD has been studied with wind and temperature profiles, inversion layer, recirculation factor (RF), atmospheric boundary layer height (ABLH) and ventilation index (VI). It was found that the vertical wind of PRD could be divided in typical three layers according two wind shears appeared in 800 m and 1300 m. The thickness of calm or lower wind speed layer in pollution days was 500-1000m thicker than that of clean days, and its last time also much longer than that of clean days. The frequency of surface inversion in pollution days was about 35%,the mean thickness was about 100 m. With the influence of sea breeze, the frequency and thickness of surface inversion layer at Xinken station was a little lower than that in inland. Influenced by sea-land breezes and urban heat-island circulation, the RF of pollution days in coastal and urban area was quite smaller than that of clean days. During sea-land breezes days, the pollutants would be transported back to inland in nighttime with the influence of sea breeze, and resulted in 72.7% sea-land breezes was pollution days. The evolution of ABL was very typical in PRD during dry season. In pollution days, daily ABLH in PRD was lower than 500 m, daily VI was about 500-1500 m2/s. In clean days, daily VI was much larger than 2500 m2/s. An improved conceptual model of ABL influence on poor air quality and the parameters of the ABL characteristics associate with poor air quality in dry season over PRD had been summarized.

  18. Maladie des vibrations

    PubMed Central

    Shen, Shixin (Cindy); House, Ronald A.

    2017-01-01

    Résumé Objectif Permettre aux médecins de famille de comprendre l’épidémiologie, la pathogenèse, les symptômes, le diagnostic et la prise en charge de la maladie des vibrations, une maladie professionnelle importante et courante au Canada. Sources d’information Une recherche a été effectuée sur MEDLINE afin de relever les recherches et comptes rendus portant sur la maladie des vibrations. Une recherche a été effectuée sur Google dans le but d’obtenir la littérature grise qui convient au contexte canadien. D’autres références ont été tirées des articles relevés. Message principal La maladie des vibrations est une maladie professionnelle répandue touchant les travailleurs de diverses industries qui utilisent des outils vibrants. La maladie est cependant sous-diagnostiquée au Canada. Elle compte 3 éléments : vasculaire, sous la forme d’un phénomène de Raynaud secondaire; neurosensoriel; et musculosquelettique. Aux stades les plus avancés, la maladie des vibrations entraîne une invalidité importante et une piètre qualité de vie. Son diagnostic exige une anamnèse minutieuse, en particulier des antécédents professionnels, un examen physique, des analyses de laboratoire afin d’éliminer les autres diagnostics, et la recommandation en médecine du travail aux fins d’investigations plus poussées. La prise en charge consiste à réduire l’exposition aux vibrations, éviter les températures froides, abandonner le tabac et administrer des médicaments. Conclusion Pour assurer un diagnostic rapide de la maladie des vibrations et améliorer le pronostic et la qualité de vie, les médecins de famille devraient connaître cette maladie professionnelle courante, et pouvoir obtenir les détails pertinents durant l’anamnèse, recommander les patients aux cliniques de médecine du travail et débuter les demandes d’indemnisation de manière appropriée. PMID:28292812

  19. Canopy gap size influences niche partitioning of the ground-layer plant community in a northern temperate forest

    Treesearch

    Christel C. Kern; Rebecca A. Montgomery; Peter B. Reich; Terry F. Strong

    2013-01-01

    The Gap Partitioning Hypothesis (GPH) posits that gaps create heterogeneity in resources crucial for tree regeneration in closed-canopy forests, allowing trees with contrasting strategies to coexist along resource gradients. Few studies have examined gap partitioning of temperate, ground-layer vascular plants. We used a ground-layer plant community of a temperate...

  20. Influence of Smear Layer on the Antimicrobial Activity of a Sodium Hypochlorite/Etidronic Acid Irrigating Solution in Infected Dentin.

    PubMed

    Morago, Ana; Ordinola-Zapata, Ronald; Ferrer-Luque, Carmen María; Baca, Pilar; Ruiz-Linares, Matilde; Arias-Moliz, María Teresa

    2016-11-01

    The aim of this study was to evaluate the influence of the smear layer on the antimicrobial activity of a 2.5% sodium hypochlorite (NaOCl)/9% etidronic acid (HEBP) irrigating solution against bacteria growing inside dentin tubules. Dentin tubules were infected with Enterococcus faecalis by centrifugation. After 5 days of incubation, the smear layer had formed in half of the samples, which were then treated with 2.5% NaOCl either alone or combined with 9% HEBP for 3 minutes. The percentage of dead cells in infected dentinal tubules was measured using confocal laser scanning microscopy and the live/dead technique. The smear layer on the surface of the root canal wall was also observed by scanning electron microscopy. Results of the percentage of dead cells were compared using parametric tests after subjecting data to the normalized Anscombe transformation. The level of significance was P < .05. In the absence of the smear layer, 2.5% NaOCl alone and combined with 9% HEBP showed high antimicrobial activity without significant differences between the 2. The smear layer reduced the antimicrobial activity of 2.5% NaOCl significantly, whereas the solution with HEBP was not affected. No dentin tubules free of the smear layer were obtained in the 2.5% NaOCl group. In the case of 2.5% NaOCl/9% HEBP, 95.40% ± 3.63% of dentin tubules were cleaned. The presence of the smear layer reduced the antimicrobial activity of 2.5% NaOCl. The combination of 2.5% NaOCl/9% HEBP exerted antimicrobial activity that was not reduced by the smear layer. Copyright © 2016 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

  1. Influence of Idealized Heterogeneity on Wet and Dry Planetary Boundary Layers Coupled to the Land Surface. 1; Instantaneous Fields and Statistics

    NASA Technical Reports Server (NTRS)

    Houser, Paul (Technical Monitor); Patton, Edward G.; Sullivan, Peter P.; Moeng, Chin-Hoh

    2003-01-01

    This is the first in a two-part series of manuscripts describing numerical experiments on the influence of 2-30 km striplike heterogeneity on wet and dry boundary layers coupled to the land surface. The strip-like heterogeneity is shown to dramatically alter the structure of the free-convective boundary layer by inducing significant organized circulations that modify turbulent statistics. The coupling with the land-surface modifies the circulations compared to previous studies using fixed surface forcing. Total boundary layer turbulence kinetic energy increases significantly for surface heterogeneity at scales between Lambda/z(sub i) = 4 and 9, however entrainment rates for all cases are largely unaffected by the strip-like heterogeneity.

  2. The analysis of the influence of the material antifrictional layer frictional properties on the parameters of the spherical bearing contact zone

    NASA Astrophysics Data System (ADS)

    Kamenskikh, A. A.; Trufanov, N. A.

    2017-02-01

    The paper presents data on the influence of the frictional properties of a material antifrictional layer on the parameters of the spherical bearing contact zone. The dependences of the friction coefficient from the load were obtained as a result of the study. Series of numerical experiments were conducted to investigate the frictional properties of a materials contact pair in the work. Regularities of the relative contact pressure and relative contact tangential stress were obtained for seven variants of the load-friction coefficient for the spherical bearing with a layer of modified fluoroplastic. The study puts emphasis on the fact that that adhesion area of the contact surface is reduced and the load is increased taking into account the fact that the friction properties of the layer has been fixed in the study.

  3. Influence of relative rolling reduction and thickness layers bimetallic plate at the non-uniformity of the strain after rolling process

    NASA Astrophysics Data System (ADS)

    Rydz, D.; Stradomski, G.; Dyja, H.

    2017-02-01

    In the article were made numerical and laboratory tests of two-layers rolling process sheet composed of Al99,8 + M1E. Laboratory tests made with use of 150 mm diameter working rolls mill. To the modeling of the bimetallic plate rolling were taken the FEM Forge 2D software based on the theory of plasticity and MathCad program (in which to the rolling process modeling were used the mathematical model developed in the work [5] based on the theory of viscoelasticity). The aim of study was to determine the influence of layer thickness HT0/HM0 and relative deformation ε on the uneven distribution of steel sheet deformation after rolling process. Calculations based on the theory of viscoelasticity allowed additionally take into account the impact of the delayed effects of the variation of viscoelastic deformation of layers of the bimetallic plate rolling process.

  4. Des Vents et des Jets Astrophysiques

    NASA Astrophysics Data System (ADS)

    Sauty, C.

    well expected result from the theory. Although, collimation may be conical, paraboloidal or cylindrical (Part 4), cylindrical collimation is the more likely to occur. The shape of outflows may then be used as a tool to predict physical conditions on the flows or on their source. L'éjection continue de plasma autour d'objets massifs est un phénomène largement répandu en astrophysique, que ce soit sous la forme du vent solaire, de vents stellaires, de jets d'étoiles en formation, de jets stellaires autour d'objets compacts ou de jets extra-galactiques. Cette zoologie diversifiée fait pourtant l'objet d'un commun effort de modélisation. Le but de cette revue est d'abord de présenter qualitativement le développement, depuis leur origine, des diverses théories de vents (Partie 1) et l'inter disciplinarité dans ce domaine. Il s'agit d'une énumération, plus ou moins exhaustive, des idées proposées pour expliquer l'accélération et la morphologie des vents et des jets, accompagnée d'une présentation sommaire des aspects observationnels. Cette partie s'abstient de tout aspect faisant appel au formalisme mathématique. Ces écoulements peuvent être décrits, au moins partiellement, en résolvant les équations magnétohydrodynamiques, axisymétriques et stationnaires. Ce formalisme, à la base de la plupart des théories, est exposé dans la Partie 2. Il permet d'introduire quantitativement les intégrales premières qu'un tel système possède. Ces dernières sont amenées à jouer un rôle important dans la compréhension des phénomènes d'accélération ou de collimation, en particulier le taux de perte de masse, le taux de perte de moment angulaire ou l'énergie du rotateur magnétique. La difficulté de modélisation réside dans l'existence de points critiques, propres aux équations non linéaires, qu'il faut franchir. La nature physique et la localisation de ces points critiques fait l'objet d'un débat important car ils sont la clef de voute de la r

  5. Influence of p-doping hole transport layer on the performance of organic light-emitting devices

    NASA Astrophysics Data System (ADS)

    Khan, M. A.; Xu, Wei; Khizar-ul-Haq; Bai, Yu; Jiang, X. Y.; Zhang, Z. L.; Zhu, W. Q.

    2008-05-01

    We have demonstrated devices based on a p-doped layer consisting of 4,4',4''-tris(3-methylphenylphenylamono) triphenylamine (m-MTDATA) and tetrafluro-tetracyano-quinodimethane (F4-TCNQ) as a hole transport layer (HTL). The typical device structure is ITO/m-MTDATA: x% F4-TCNQ (40 nm)/N, N'-bis-[1-naphthy(-N, N' diphenyl-1,1'-biphenyl-4,4'-diamine)] (NPB) (10 nm)/tris (8-hydroxyquinoline) aluminum (Alq3) (50 nm)/LiF (10 nm)/Al (100 nm). Hole-only devices, where the current only consists of holes, are fabricated to observe the apparent improvement in the conductivity of the p-doped layers. We have observed that such layers lead to a striking improvement of the electrical properties of organic light-emitting devices. In particular, the electroluminescent onset voltage is observed to decrease continuously with increasing doping ratio and is greatly reduced compared to diodes with undoped layers. We have seen that the driving voltage of device 3 (m-MTDATA:4% F4-TCNQ) is reduced ~56% as compared with that of the control device (undoped). This improvement has been attributed to the increased conductivity of the p-doping hole transport layer. It is found that the current efficiency also decreases with increasing doping ratio. This can be attributed to the charge imbalance in the emission layer due to the excess hole injection.

  6. Influence of mill scale and rust layer on the corrosion resistance of low-alloy steel in simulated concrete pore solution

    NASA Astrophysics Data System (ADS)

    Shi, Jin-jie; Ming, Jing

    2017-01-01

    Electrochemical impedance spectroscopy, cyclic potentiodynamic polarization measurements, and scanning electron microscopy in conjunction with energy-dispersive X-ray spectroscopy were used to investigate the influence of mill scale and rust layer on the passivation capability and chloride-induced corrosion behaviors of conventional low-carbon (LC) steel and low-alloy (LA) steel in simulated concrete pore solution. The results show that mill scale exerts different influences on the corrosion resistance of both steels at various electrochemical stages. We propose that the high long-term corrosion resistance of LA steel is mainly achieved through the synergistic effect of a gradually formed compact, adherent and well-distributed Cr-enriched inner rust layer and the physical barrier protection effect of mill scale.

  7. Influence of the thickness and doping of the emission layer on the performance of organic light-emitting diodes with PiN structure

    NASA Astrophysics Data System (ADS)

    Huang, Jingsong; Blochwitz-Nimoth, Jan; Pfeiffer, Martin; Leo, Karl

    2003-01-01

    We have studied the behavior of various intrinsic emission zones on the characteristics of organic light-emitting diodes with a p-doped hole-transport layer and an n-doped electron-transport layer based on our previous work [J. S. Huang, M. Pfeiffer, A. Werner, J. Blochwitz, K. Leo, and S. Liu, Appl. Phys. Lett. 80, 139 (2002)]. This configuration is referred to as a PiN structure. Because the p- and n-doped regions occupy nearly 80% of the total thickness in our PiN device, the intrinsic region becomes a narrow layer between two doped regions. This intrinsic region includes the region where the radiative recombination occurs. Thus, the nature of this layer plays an important role in determining the actual device performance. Employing 8-tris-hydroxyquinoline aluminum as an emitter, we investigated the influence of the thickness of the emitter layer on the performance of the device. The optimum thickness of the emitter layer is found to be 20 nm. Combining the fluorescence dye doping method, we have optimized the PiN structure device. Two emitter systems have been used: Alq3 doped with two highly fluorescent laser dyes, Quinacridone or Coumarin 6, respectively. We have demonstrated the influence of the thickness and the doping of the emission zone on the characteristics of a doped emitter device with PiN structure, and obtained higher-efficiency PiN structure devices. The different properties of PiN devices corresponding to two different emitter dopants with different trapping effect are also discussed.

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

    NASA Astrophysics Data System (ADS)

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

    2009-05-01

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

  9. The dynamics of endometrial growth and the triple layer appearance in three different controlled ovarian hyperstimulation protocols and their influence on IVF outcomes.

    PubMed

    Kuć, Paweł; Kuczyńska, Agnieszka; Topczewska, Magdalena; Tadejko, Paweł; Kuczyński, Waldemar

    2011-11-01

    The impact of endometrial growth to the triple layer, endometrial thickness, and echogenicity on IVF outcomes was investigated in the study. A retrospective analysis of 583 ICSI patients was conducted: 385 with a long GnRH agonist protocol, 114 with a short GnRH agonist, and 84 with a GnRH antagonist protocol. The progression of endometrial growth to the appearance of the triple layer, endometrial thickness, and echogenicity was compared between protocols. At least one high quality blastocyst was transferred in a double embryo transfer. The time of the appearance of the endometrial triple layer was statistically significant for the pregnancy rate only in the GnRH antagonist protocol. The endometrial thickness on the day of the appearance of the triple layer had a statistically significant influence on the pregnancy rate in the GnRH antagonist and in the long GnRH agonist protocols. The highest pregnancy rate for the long GnRH agonist and the GnRH antagonist protocols was observed when the endometrium thickness was 12-13 mm (61.6% and 58.8%, respectively). The endometrial echogenicity had a significant influence on the pregnancy rate only in the long GnRH agonist protocol. Endometrial features could be helpful parameters in IVF outcomes in particular controlled ovarian hyperstimulation protocols.

  10. Application of CFD to Abrupt Wing Stall Using RANS and DES

    NASA Technical Reports Server (NTRS)

    Forsythe, Jim

    2004-01-01

    For DES, RANS is responsible for predicting boundary layer growth and separation. LES is responsible for predicting the geometry dependent turbulent flow features. Grid adaptation done using NASA Langley s RefineMesh program. Adaptation on time average of vorticity

  11. Heat diffusion and thermolastic vibration influence on the signal of an open photoacoustic cell for two layer systems

    NASA Astrophysics Data System (ADS)

    Pichardo-Molina, J. L.; Alvarado-Gil, J. J.

    2004-06-01

    Thermal diffusion and thermoelastic vibration in two layer systems is studied using photoacoustic spectroscopy. Three different two layer systems, copper/lead-tin (Cu/Pb-Sn), aluminum/paint (Al/paint) and aluminum/polyvinyl-chloride (Al/PVC) are studied. A model is developed considering that both layers present thermoelastic vibration and heat diffusion. It is shown that our equations can be used to obtain the theoretical photoacoustic signal independent of the mechanical properties when the thermal and thermomechanical properties of the composing layers are similar. It is shown that this approximation is much better suited for the study of metal/metal systems where the coupling of the thermoelastic bending is smooth. The restrictions of this approach and the possible extensions to study systems with different thermal expansion and mechanical behavior are discussed.

  12. Influence of passive ultrasonic irrigation on the efficiency of various irrigation solutions in removing smear layer: a scanning electron microscope study.

    PubMed

    Koçak, Sibel; Bağcı, Nur; Çiçek, Ersan; Türker, Sevinç Aktemur; Can Sağlam, Baran; Koçak, Mustafa Murat

    2017-05-01

    To evaluate the influence of passive ultrasonic irrigation (PUI) to remove the smear layer with different irrigation solutions. Seventy-eight single rooted mandibular premolars were used. The working lengths were measured and the root canals were prepared by using nickel titanium rotary files. The specimens were subjected to six different irrigation regimens: sodium hypochloride (NaOCl) with classic irrigation (CI); NaOCl with PUI; EDTA with CI; EDTA with PUI; QMix with CI; and QMix with PUI. The specimens were split longitudinally. Scanning electron microscopy images were taken to evaluate the amount of residual smear layer and scored. Statistical analysis was performed with the Kruskal-Wallis test. The Dunn's test was used for post hoc testing after the Kruskal-Wallis test. The smear layer scores of apical thirds were significantly higher than coronal and middle thirds except for NaOCl + CI group (p < 0.001). The irrigation with PUI improved the efficacy of all irrigation solutions on removal of smear layer in both coronal and middle thirds (p < 0.001). The PUI activation increased the activity of NaOCl, EDTA, and QMix, respectively without any significance. All irrigation regimens were significantly more effective in coronal and middle thirds compared to apical third. PUI significantly increased the efficacy of smear layer removal regardless of irrigation solution. © 2016 Wiley Periodicals, Inc.

  13. Influence of Covering on Critical Thickness of Strained In(x)Ga(1-x)As Layer

    DTIC Science & Technology

    2002-06-03

    Van der Pauw method, not only the channel layer lattice 3. Results and discussion relaxation but also electrical parameters of HEMT struc- tures with...parameters of these structures by the Van der Pauw Blakeslee limit and experimentally determined the value. method, the contact layer was not deposited...obtained by Van der Pauw measurements and placed in carrier scattering cause decreasing electron mobility with Table 1. going up channel thickness. A

  14. POU-III Transcription Factors (Brn1, Brn2, and Oct6) Influence Neurogenesis, Molecular Identity, and Migratory Destination of Upper-Layer Cells of the Cerebral Cortex

    PubMed Central

    Dominguez, Martin H.; Ayoub, Albert E.; Rakic, Pasko

    2013-01-01

    The upper layers (II–IV) are the most prominent distinguishing feature of mammalian neocortex compared with avian or reptilian dorsal cortex, and are vastly expanded in primates. Although the time-dependent embryonic generation of upper-layer cells is genetically instructed within their parental progenitors, mechanisms governing cell-intrinsic fate transitions remain obscure. POU-homeodomain transcription factors Pou3f3 and Pou3f2 (Brn1 and Brn2) are known to label postmitotic upper-layer cells, and are redundantly required for their production. We find that the onset of Pou3f3/2 expression actually occurs in ventricular zone (VZ) progenitors, and that Pou3f3/2 subsequently label neural progeny switching from deep-layer Ctip2+ identity to Satb2+ upper-layer fate as they migrate to proper superficial positions. By using an Engrailed dominant-negative repressor, we show that sustained neurogenesis after the deep- to upper-layer transition requires the proneual action of Pou3fs in VZ progenitors. Conversely, single-gene overexpression of any Pou3f in early neural progenitors is sufficient to specify the precocious birth of Satb2+ daughter neurons that extend axons to the contralateral hemisphere, as well as exhibit robust pia-directed migration that is characteristic of upper-layer cells. Finally, we demonstrate that Pou3fs influence multiple stages of neurogenesis by suppressing Notch effector Hes5, and promoting the expression of proneural transcription factors Tbr2 and Tbr1. PMID:22892427

  15. Influence of AZO stair-like transparent layers on GaN-based light-emitting diodes

    NASA Astrophysics Data System (ADS)

    Liou, Syuan-Hao; Tsai, Jung-Hui; Liu, Wen-Chau; Lin, Pao-Sheng; Chen, Yu-Chi

    2017-10-01

    The GaN-based light-emitting diodes (LEDs) with various height ratios of aluminum-doped zinc oxide (AZO) stair-like transparent layers are fabricated and comparatively investigated. The characteristics of the LEDs with conventional plane AZO transparent layer (device A) and AZO stair-like transparent layers having height ratios of 1:1:1 (device B), 1.5:1:0.5 (device C), and 0.5:1:1.5 (device D) are compared. Attributed that the lower resistance is formed in the thinner AZO film of the stair-like structure, the current crowding effect is improved for extending the whole current-spreading area. Experimentally, the forward turn-on voltages of the LEDs are reduced from 3.68 V to 3.42 V as the plane AZO transparent layer is processed to form the stair-like transparent layers with height ratio of 1:1:1. In addition, the light luminous flux, output power, external quantum efficiency, and wall-plug efficiency of the device B are enhanced by 30.5, 12.1, 22.2, and 20.7%, respectively, as compared to the traditional device with plane AZO transparent layer.

  16. Etude du processus de changement vecu par des familles ayant decide d'adopter volontairement des comportements d'attenuation des changements climatiques

    NASA Astrophysics Data System (ADS)

    Leger, Michel T.

    recension des ecrits sur le changement de comportement en environnement. Nous explorons egalement la famille comme systeme fonctionnel de sorte a mieux comprendre ce contexte d'action environnementale qui est, a notre connaissance, peu etudie. Dans le deuxieme article, nous presentons nos resultats de recherche concernant les facteurs d'influence observes ainsi que les competences manifestees au cours du processus d'adoption de nouveaux comportements environnementaux dans trois familles. Enfin, le troisieme article presente les resultats du cas d'une quatrieme famille ou les membres vivent depuis longtemps des modes de vie ecologique. Dans le cadre d'une demarche d'analyse par theorisation ancree, l'etude de ce cas modele nous a permis d'approfondir les categories conceptuelles identifiees dans le deuxieme article de sorte a produire une modelisation de l'integration de comportements environnementaux dans le contexte de la famille. Les conclusions degagees grace a la recension des ecrits nous ont permis d'identifier les elements qui pourraient influencer l'adoption de comportements environnementaux dans des familles. La recension a aussi permis une meilleure comprehension des divers facteurs qui peuvent affecter l'adoption de comportements environnementaux et, enfin, elle a permis de mieux cerner le phenomene de changement de comportement dans le contexte de la famille consideree comme un systeme. En appliquant un processus d'analyse inductif, a partir de nos donnees qualitatives, les resultats de notre etude multi-cas nous ont indique que deux construits conceptuels semblent influencer l'adoption de comportements environnementaux en famille : 1) les valeurs biospheriques communes au sein de la famille et 2) les competences collectivement mises a profit collectivement durant l'essai de nouveaux comportements environnementaux. Notre modelisation du processus de changement dans des familles indique aussi qu'une dynamique familiale collaborative et la presence d'un groupe de

  17. Influence of Clinical Factors and Magnification Correction on Normal Thickness Profiles of Macular Retinal Layers Using Optical Coherence Tomography

    PubMed Central

    Higashide, Tomomi; Ohkubo, Shinji; Hangai, Masanori; Ito, Yasuki; Shimada, Noriaki; Ohno-Matsui, Kyoko; Terasaki, Hiroko; Sugiyama, Kazuhisa; Chew, Paul; Li, Kenneth K. W.; Yoshimura, Nagahisa

    2016-01-01

    Purpose To identify the factors which significantly contribute to the thickness variabilities in macular retinal layers measured by optical coherence tomography with or without magnification correction of analytical areas in normal subjects. Methods The thickness of retinal layers {retinal nerve fiber layer (RNFL), ganglion cell layer plus inner plexiform layer (GCLIPL), RNFL plus GCLIPL (ganglion cell complex, GCC), total retina, total retina minus GCC (outer retina)} were measured by macular scans (RS-3000, NIDEK) in 202 eyes of 202 normal Asian subjects aged 20 to 60 years. The analytical areas were defined by three concentric circles (1-, 3- and 6-mm nominal diameters) with or without magnification correction. For each layer thickness, a semipartial correlation (sr) was calculated for explanatory variables including age, gender, axial length, corneal curvature, and signal strength index. Results Outer retinal thickness was significantly thinner in females than in males (sr2, 0.07 to 0.13) regardless of analytical areas or magnification correction. Without magnification correction, axial length had a significant positive sr with RNFL (sr2, 0.12 to 0.33) and a negative sr with GCLIPL (sr2, 0.22 to 0.31), GCC (sr2, 0.03 to 0.17), total retina (sr2, 0.07 to 0.17) and outer retina (sr2, 0.16 to 0.29) in multiple analytical areas. The significant sr in RNFL, GCLIPL and GCC became mostly insignificant following magnification correction. Conclusions The strong correlation between the thickness of inner retinal layers and axial length appeared to result from magnification effects. Outer retinal thickness may differ by gender and axial length independently of magnification correction. PMID:26814541

  18. Development of retinal layers.

    PubMed

    Nguyen-Ba-Charvet, Kim Tuyen; Chédotal, Alain

    2014-03-01

    A noticeable characteristic of nervous systems is the arrangement of synapses into distinct layers. Such laminae are fundamental for the spatial organisation of synaptic connections transmitting different kinds of information. A major example of this is the inner plexiform layer (IPL) of the vertebrate retina, which is subdivided into at least ten sublayers. Another noticeable characteristic of these retina layers is that neurons are displayed in the horizontal plane in a non-random array termed as mosaic patterning. Recent studies of vertebrate and invertebrate systems have identified molecules that mediate these interactions. Here, we review the last mechanisms and molecules mediating retinal layering. Copyright © 2013 Académie des sciences. Published by Elsevier SAS. All rights reserved.

  19. Surface-tension-driven convection in pure liquid layers evaporating into ambient air: influence of liquid volatility

    NASA Astrophysics Data System (ADS)

    Chauvet, Fabien; Dehaeck, Sam; Colinet, Pierre

    2011-11-01

    The spontaneous surface-tension-driven convective patterns induced by evaporation of a pure liquid layer are studied experimentally. A volatile liquid layer placed in a cylindrical container is left free to evaporate into air at rest under ambient conditions. The thermal dynamics of the evaporating liquid layer is visualized using an infrared camera. Evaporation rate and liquid thickness are measured by weighting. We focus on the transition between the convective state and the conductive state appearing at a certain instant during the drying of the liquid layer. The critical Marangoni number Mac associated to this transition is estimated from evaporation rate and layer thickness measurements at this instant. The effect of the evaporation rate on Mac and kc (the critical wavenumber) has been investigated by changing the container height and, separately, the effect of the liquid volatility has been studied by using different liquids. Interestingly, it appears that Mac does not depend on the evaporation rate while it depends strongly on the liquid volatility. Given the typical uncertainties associated with liquid properties, a quite reasonable agreement is found with a ``one-sided'' linear stability analysis of this problem. Supported by ESA & BELSPO, by the EU, by ULB, and by FRS - FNRS.

  20. Influence of carboxylic ion-pairing reagents on retention of peptides in thin-layer chromatography systems with C18 silica-based adsorbents.

    PubMed

    Gwarda, Radosław Ł; Aletańska-Kozak, Monika; Klimek-Turek, Anna; Ziajko-Jankowska, Agnieszka; Matosiuk, Dariusz; Dzido, Tadeusz H

    2016-04-01

    One of the main problems related to chromatography of peptides concerns adverse interactions of their strong basic groups with free silanol groups of the silica based stationary phase. Influence of type and concentration of ion-pairing regents on peptide retention in reversed-phase high-performance liquid chromatography (RP-HPLC) systems has been discussed before. Here we present influence of these mobile phase additives on retention of some peptide standards in high-performance thin-layer chromatography (HPTLC) systems with C18 silica-based adsorbents. We prove, that due to different characteristic of adsorbents used in both techniques (RP HPLC and HPTLC), influence of ion-pairing reagents on retention of basic and/or amphoteric compounds also may be quite different. C18 silica-based HPTLC adsorbents provide more complex mechanism of retention and should be rather considered as mixed-mode adsorbents. Copyright © 2016 Elsevier B.V. All rights reserved.

  1. Influence of Copper Layer Content in the Elastic and Damping Behavior of Glass-Fiber/Epoxy-Resin Composites

    NASA Astrophysics Data System (ADS)

    Carneiro, V. H.; Capela, P.; Teixeira, J. C.; Teixeira, S.; Cerqueira, F.; Macedo, F.; Ribas, L.; Soares, D.

    2016-12-01

    The impact in the elastic behavior and internal friction, caused by the introduction of Copper layers in Glass-Fiber/Epoxy Resin composites and temperature effects, were studied and evaluated recurring to Dynamic Mechanical Analysis. It is shown that the introduction of Copper layers increases the storage modulus of the composites and delays their glass transition temperature, however, it allows a faster transformation. Additionally, it is concluded that the introduction of Copper layers elevates the internal friction during the glass transition phase by the inversion of the deformation mechanism due to thermal expansion and increase in the Poisson's ratio of the epoxy resin to a value near 0.5 where its deformation is approximately isochoric. This increase in damping capacity is relevant in application with cyclic fatigue and mechanical vibration.

  2. The first biantennary bacterial secondary cell wall polymer and its influence on S-layer glycoprotein assembly.

    PubMed Central

    Steindl, Christian; Schäffer, Christina; Wugeditsch, Thomas; Graninger, Michael; Matecko, Irena; Müller, Norbert; Messner, Paul

    2002-01-01

    The cell surface of Aneurinibacillus thermoaerophilus DSM 10155 is covered with a square surface (S)-layer glycoprotein lattice. This S-layer glycoprotein, which was extracted with aqueous buffers after a freeze-thaw cycle of the bacterial cells, is the only completely water-soluble S-layer glycoprotein to be reported to date. The purified S-layer glycoprotein preparation had an overall carbohydrate content of 19%. Detailed chemical investigations indicated that the S-layer O-glycans of previously established structure accounted for 13% of total glycosylation. The remainder could be attributed to a peptidoglycan-associated secondary cell wall polymer. Structure analysis was performed using purified secondary cell wall polymer-peptidoglycan complexes. NMR spectroscopy revealed the first biantennary secondary cell wall polymer from the domain Bacteria, with the structure alpha-L-Glc p NAc-(1-->3)-beta-L-Man p NAc-(1-->4)-beta-L-Gal p NAc-(1-->3)-alpha-L-Glc p NAc-(1-->3)-beta-L-Man p NAc-(1-->4)-beta-L-Gal p NAc-(1-->3)-alpha-L-Glc p NAc-(1-->4)-[alpha-L-Glc p NAc-(1-->3)-beta-L-Man p NAc-(1-->4)-beta-L-Gal p NAc-(1-->3)-alpha-L-Glc p NAc-(1-->3)-beta-L-Man p NAc-(1-->4)-beta-L-Gal p NAc-(1-->3)-alpha-L-Glc p NAc-(1-->3)]-beta-L-Man p NAc-(1-->3)-alpha-L-Glc p NAc-(1-->3)-beta-L-Man p NAc-(1-->3)-alpha-L-Glc p NAc-(1-->3)-alpha-L-Glc p NAc-(1-->O)-PO(2)(-)-O-PO(2)(-)-(O-->6)-MurNAc- (where MurNAc is N -acetylmuramic acid). The neutral polysaccharide is linked via a pyrophosphate bond to the C-6 atom of every fourth N -acetylmuramic acid residue, in average, of the A1gamma-type peptidoglycan. In vivo, the biantennary polymer anchored the S-layer glycoprotein very effectively to the cell wall, probably due to the doubling of motifs for a proposed lectin-like binding between the polymer and the N-terminus of the S-layer protein. When the cellular support was removed during S-layer glycoprotein isolation, the co-purified polymer mediated the solubility of the S-layer

  3. Durability influence depending on the thickness and microhardness of AlTiN and TiN thin layers deposed on cutting inserts

    NASA Astrophysics Data System (ADS)

    Bădănac, A.; Lupescu, O.; Paraschiv, D.; Ungureanu, C.; Rotaru, A.

    2016-11-01

    During the exploitation process of cutting tools occurs phenomens as wear which leads to deterioration of functional parameters, performance and partial or total loss of the functioning capacity. The wear resistance of cutting tools depends by the nature of the material and by the working conditions (the quality of surface processing, lubrication quality, temperature). For increased the durability of cutting tools and increase the wear resistance are taken action which aim, improving the surface quality. For increase the surfaces quality are known different deposit methods in vacuum of materials by coating technology PVD as: aluminum-titanium nitride (AlTiN) and titanium nitride (TiN). The coatings realized by vacuum deposition have gained special attention because of their unique physical and chemical properties for example excellent resistance to oxidation at high temperatures. The most important characteristics which are checked in the deposition process of thin layers are: thickness and microhardness. The thickness and microhardness influence significantly the cutting tool durability. In this paper the authors carried out researches regarding the coatings of AlTiN and TiN in thin layers, on surface of some cutting inserts. It was studied the durability influence depending on the thickness and microhardness of AlTiN and TiN thin layers.

  4. Cartographie des disques

    NASA Astrophysics Data System (ADS)

    Hameury, Jean-Marie

    2001-01-01

    Two techniques are frequently used to produce images of the accretion disc in an eclipsing binary: eclipse mapping and Doppler tomography. From the light curve, one can deduce the radial distribution of the effective temperature, assuming axial symmetry. On the other hand, from the variation of the line profile one can reconstruct an image in the velocity space, which can be converted into a real image if one knows the kinematics of the system. Deux techniques sont couramment utilisées pour obtenir des images des disques dans les systèmes binaires à éclipses. En utilisant la courbe de lumière, on peut remonter à la distribution radiale de la brillance de surface, en supposant que celle-ci a une symètrie axiale. D'autre part, les profils de raies renseignent sur la distribution de vitesse des régions émissives leur variation temporelle permet de réaliser une image dans l'espace des vitesses, que l'on peut ensuite transformer en carte dans l'espace (x,y) si on connaît la cinématique du système.

  5. Influence of thin AlAs layer insertion on intersubband optical transitions in GaAs/AlGaAs quantum- well structures

    NASA Astrophysics Data System (ADS)

    Liu, Dongfeng; Wang, Everett X.; Guo, Kangxian

    2017-02-01

    In this work, we demonstrate the thin AlAs layer insertion into GaAs/AlGaAs quantum well (QW) structures and its influence in energy transition in the frequency range of mid-infrared. To realize the more accurate calculation, the graded interface model of QW structures is integrated into our self-consistent solving of Schrodinger and Poisson equations to obtain the energy level and envelope wave functions of QW. We find the thin AlAs layer inserted at various positions in the well can obviously tune intersubband optical transitions. The corresponding tuning range can be 50 meV. We find that the thicker AlAs layer (2 monolayers) can provide wider tuning range and larger oscillator strength between subbands 1 and 3, compared with the thinner one (1 monolayer). Our results suggest that thin semiconductor layer may be an idea optimization design for the quantum well terahertz lasers which are based on optical pumping with mid-infrared lasers.

  6. The influence of free-stream turbulence on separation of turbulent boundary layers in incompressible, two-dimensional flow

    NASA Technical Reports Server (NTRS)

    Potter, J. Leith; Barnett, R. Joel; Fisher, Carl E.; Koukousakis, Costas E.

    1986-01-01

    Experiments were conducted to determine if free-stream turbulence scale affects separation of turbulent boundary layers. In consideration of possible interrelation between scale and intensity of turbulence, the latter characteristic also was varied and its role was evaluated. Flow over a 2-dimensional airfoil in a subsonic wind tunnel was studied with the aid of hot-wire anemometry, liquid-film flow visualization, a Preston tube, and static pressure measurements. Profiles of velocity, relative turbulence intensity, and integral scale in the boundary layer were measured. Detachment boundary was determined for various angles of attack and free-stream turbulence. The free-stream turbulence intensity and scale were found to spread into the entire turbulent boundary layer, but the effect decreased as the airfoil surface was approached. When the changes in stream turbulence were such that the boundary layer velocity profiles were unchanged, detachment location was not significantly affected by the variations of intensity and scale. Pressure distribution remained the key factor in determining detachment location.

  7. Influence of layer orientation and interlayer bonding force on the mechanical behavior of shale under Brazilian test conditions

    NASA Astrophysics Data System (ADS)

    He, Jianming; Afolagboye, Lekan Olatayo

    2017-05-01

    The mechanical behavior of inherently anisotropic shale rocks under Brazilian test conditions are investigated in this study based on experimental studies and numerical simulations. The effects of the weak lamination planes and interlayer bonding force of these layers on the failure strength and fracture patterns are studied systematically. Numerical simulations using particle flow code in two dimensions based on the discrete element method showed a good agreement with the experimental results in the failure strength and fracture patterns. The shale revealed strong anisotropic behavior with the failure strength perpendicular to the lamination plane greater than failure strength parallel to lamination plane. The failure strength of the different interlayer bonding force against the layer orientations changed significantly. Four types of fracture patterns were observed: curved fracture, broken-linear fracture, layer-activated fracture, and central-linear fracture. The observed fracture patterns are either or a combination of tensile and/or shear fractures. Increase in interlayer bonding strength decreased the quantity of micro cracks and this directly led to reduction in the anisotropic behavior. Overall the layer orientation and interlayer bonding force of the shale thus play a very important role in the anisotropic behavior of the shale.

  8. On the influence of a single roughness element on the flow in supersonic boundary layer on a blunted cone

    NASA Astrophysics Data System (ADS)

    Kirilovskiy, S. V.; Poplavskaya, T. V.

    2016-11-01

    The work presents the results of numerical modeling of a supersonic flow around a blunted cone with an isolated cylindrical roughness on the forebody surface in the three-dimensional formulation. The roughness element is shown to distort the mean flow and to give rise to small-amplitude disturbances with distinguished spectral peaks in the boundary layer.

  9. Strain distribution in Si capping layers on SiGe islands: influence of cap thickness and footprint in reciprocal space.

    PubMed

    Hrauda, N; Zhang, J J; Süess, M J; Wintersberger, E; Holý, V; Stangl, J; Deiter, C; Seeck, O H; Bauer, G

    2012-11-23

    We present investigations on the strain properties of silicon capping layers on top of regular SiGe island arrays, in dependence on the Si-layer thickness. Such island arrays are used as stressors for the active channel in field-effect transistors where the desired tensile strain in the Si channel is a crucial parameter for the performance of the device. The thickness of the Si cap was varied from 0 to 30 nm. The results of high resolution x-ray diffraction experiments served as input to perform detailed strain calculations via finite element method models. Thus, detailed information on the Ge distribution within the buried islands and the strain interaction between the SiGe island and Si cap was obtained. It was found that the tensile strain within the Si capping layer strongly depends on its thickness, even if the Ge concentration of the buried dot remains unchanged, with tensile strains degrading if thicker Si layers are used.

  10. Influence of Cu and Ni on the morphology and composition of the rust layer of steels exposed to industrial environment

    NASA Astrophysics Data System (ADS)

    Ocampo C., L. M.; Mattos, O. R.; Margarit-Mattos, I. C. P.; Fabris, J. D.; Pereira, M. C.; Rechenberg, H. R.; de Faria, D. L. A.

    2006-01-01

    Four samples of steels with alloying elements were exposed to an industrial environment during 1,955 days, aiming to elucidate the effect of the alloying elements Cu and Ni on the resistance of weathering steels to corrosion processes. The samples were characterized with optical microscopy, scanning electron microscopy (SEM), powder X-ray diffraction (XRD), saturation magnetization measurements and with energy dispersive (EDS), infrared, Mössbauer and Raman spectroscopies. All the steels originated orange and dark corrosion layers; their thicknesses were determined from the SEM images. EDS data of such rust layers showed that the alloying element content decreases from the steel core towards the outer part of the rust layer. Moreover, in the dark rust layer some light-gray regions were identified in the W and Cu-alloy steel, where relatively higher Cr and Cu contents were found. XRD patterns, infrared, Raman and Mössbauer spectra (298, 110 and 4 K) indicated that the corrosion products are qualitatively the same, containing lepidocrocite (γFeOOH; hereinafter, it may be referred to as simply L), goethite (αFeOOH; G), feroxyhite (δ‧FeOOH; F), hematite (αFe2O3; H) and magnetite (Fe3O4; M) in all samples; this composition does not depend upon the steel type, but their relative concentrations is related to the alloying element. Mössbauer data reveal the presence of (super)paramagnetic iron oxides in the corrosion products. Saturation magnetization measurements suggest that feroxyhite may be an occurring ferrimagnetic phase in the rust layer.

  11. Detrimental influence of catalyst seeding on the device properties of CVD-grown 2D layered materials: A case study on MoSe{sub 2}

    SciTech Connect

    Utama, M. Iqbal Bakti; Lu, Xin; Yuan, Yanwen; Xiong, Qihua

    2014-12-22

    Seed catalyst such as perylene-3,4,9,10-tetracarboxylic acid tetrapotassium (PTAS) salt has been used for promoting the growth of atomically thin layered materials in chemical vapor deposition (CVD) synthesis. However, the ramifications from the usage of such catalyst are not known comprehensively. Here, we report the influence of PTAS seeding on the transistor device performance from few-layered CVD-grown molybdenum diselenide (MoSe{sub 2}) flakes. While better repeatability and higher yield can be obtained with the use of PTAS seeds in synthesis, we observed that PTAS-seeded flakes contain particle impurities. Moreover, devices from PTAS-seeded MoSe{sub 2} flakes consistently displayed poorer field-effect mobility, current on-off ratio, and subthreshold swing as compared to unseeded flakes.

  12. Influence of Layer Thickness, Raster Angle, Deformation Temperature and Recovery Temperature on the Shape-Memory Effect of 3D-Printed Polylactic Acid Samples

    PubMed Central

    Wu, Wenzheng; Ye, Wenli; Wu, Zichao; Geng, Peng; Wang, Yulei; Zhao, Ji

    2017-01-01

    The success of the 3D-printing process depends upon the proper selection of process parameters. However, the majority of current related studies focus on the influence of process parameters on the mechanical properties of the parts. The influence of process parameters on the shape-memory effect has been little studied. This study used the orthogonal experimental design method to evaluate the influence of the layer thickness H, raster angle θ, deformation temperature Td and recovery temperature Tr on the shape-recovery ratio Rr and maximum shape-recovery rate Vm of 3D-printed polylactic acid (PLA). The order and contribution of every experimental factor on the target index were determined by range analysis and ANOVA, respectively. The experimental results indicated that the recovery temperature exerted the greatest effect with a variance ratio of 416.10, whereas the layer thickness exerted the smallest effect on the shape-recovery ratio with a variance ratio of 4.902. The recovery temperature exerted the most significant effect on the maximum shape-recovery rate with the highest variance ratio of 1049.50, whereas the raster angle exerted the minimum effect with a variance ratio of 27.163. The results showed that the shape-memory effect of 3D-printed PLA parts depended strongly on recovery temperature, and depended more weakly on the deformation temperature and 3D-printing parameters. PMID:28825617

  13. Sea-Breeze and Topographic Influences on the Planetary Boundary Layer in the Coastal Upwelling Area of Cabo Frio (Brazil)

    NASA Astrophysics Data System (ADS)

    Ribeiro, F. N. D.; Soares, J.; Oliveira, A. P.

    2016-01-01

    We use a fully coupled oceanic-atmospheric model to investigate the sources and sinks of turbulent kinetic energy in the Cabo Frio coastal area and to determine the role of topography and the sea breeze in planetary boundary-layer (PBL) development. The study area presents similar boundary-layer characteristics than other coastal upwelling areas with complex topography, such as increased stability and low-level jets. The results show that the major effect of upwelling, over the investigated area, is to maintain low temperatures in the lower atmosphere over the coastal zone, sustaining a strong temperature inversion that precludes the vertical PBL development. Therefore, the cooling effect reduces the horizontal thermal contrast between land and water, generating a negative feedback between the intensity of the sea breeze and the intensity of the upwelling. The topography at Cabo Frio prevents this cooling effect from propagating inland, since it limits the penetration of the sea-breeze circulation.

  14. Mapping bound plasmon propagation on a nanoscale stripe waveguide using quantum dots: influence of spacer layer thickness.

    PubMed

    Perera, Chamanei S; Funston, Alison M; Cheng, Han-Hao; Vernon, Kristy C

    2015-01-01

    In this paper we image the highly confined long range plasmons of a nanoscale metal stripe waveguide using quantum emitters. Plasmons were excited using a highly focused 633 nm laser beam and a specially designed grating structure to provide stronger incoupling to the desired mode. A homogeneous thin layer of quantum dots was used to image the near field intensity of the propagating plasmons on the waveguide. We observed that the photoluminescence is quenched when the QD to metal surface distance is less than 10 nm. The optimised spacer layer thickness for the stripe waveguides was found to be around 20 nm. Authors believe that the findings of this paper prove beneficial for the development of plasmonic devices utilising stripe waveguides.

  15. Influence of the Hole Transporting Layer on the Thermal Stability of Inverted Organic Photovoltaics Using Accelerated-Heat Lifetime Protocols

    PubMed Central

    2017-01-01

    High power conversion efficiency (PCE) inverted organic photovoltaics (OPVs) usually use thermally evaporated MoO3 as a hole transporting layer (HTL). Despite the high PCE values reported, stability investigations are still limited and the exact degradation mechanisms of inverted OPVs using thermally evaporated MoO3 HTL remain unclear under different environmental stress factors. In this study, we monitor the accelerated lifetime performance under the ISOS-D-2 protocol (heat conditions 65 °C) of nonencapsulated inverted OPVs based on the thiophene-based active layer materials poly(3-hexylthiophene) (P3HT), poly[[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl][3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl

  16. Influence of the Hole Transporting Layer on the Thermal Stability of Inverted Organic Photovoltaics Using Accelerated-Heat Lifetime Protocols.

    PubMed

    Hermerschmidt, Felix; Savva, Achilleas; Georgiou, Efthymios; Tuladhar, Sachetan M; Durrant, James R; McCulloch, Iain; Bradley, Donal D C; Brabec, Christoph J; Nelson, Jenny; Choulis, Stelios A

    2017-04-26

    High power conversion efficiency (PCE) inverted organic photovoltaics (OPVs) usually use thermally evaporated MoO3 as a hole transporting layer (HTL). Despite the high PCE values reported, stability investigations are still limited and the exact degradation mechanisms of inverted OPVs using thermally evaporated MoO3 HTL remain unclear under different environmental stress factors. In this study, we monitor the accelerated lifetime performance under the ISOS-D-2 protocol (heat conditions 65 °C) of nonencapsulated inverted OPVs based on the thiophene-based active layer materials poly(3-hexylthiophene) (P3HT), poly[[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl][3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl

  17. Influence of the Compliance and Layering Method on the Wall Deflection of Simulated Cavities in Bulk-fill Composite Restoration.

    PubMed

    Kim, Y-J; Kim, R; Ferracane, J L; Lee, I-B

    The aim of this study was to investigate the effects of the layering method and compliance on the wall deflection of simulated cavities in bulk-fill and conventional composite restorations and to examine the relationships between the wall deflection and the polymerization shrinkage, flexural modulus, and polymerization shrinkage stress of composites. Six light-cured composites were used in this study. Two of these were conventional methacrylate-based composites (Filtek Z250 and Filtek Z350 XT Flowable [Z350F]), whereas four were bulk-fill composites (SonicFill, Tetric N-Ceram Bulk-Fill, SureFil SDR Flow [SDR], and Filtek Bulk-Fill). One hundred eighty aluminum molds simulating a mesio-occluso-distal cavity (6 W×8 L×4 D mm) were prepared and classified into three groups with mold wall thicknesses of 1, 2, and 3 mm. Each group was further subdivided according to the composite layering method (bulk or incremental layering). Linear variable differential transformer probes were used to measure the mold wall deflection of each composite (n=5) over a period of 2000 seconds (33.3 minutes). The polymerization shrinkage, flexural modulus, and polymerization shrinkage stress of the six composites were also measured. All groups with bulk filling exhibited significantly higher deflection compared with groups with incremental layering. The deflection decreased as mold wall thickness increased. The highest and lowest polymerization shrinkage stresses were recorded for Z350F (5.07 MPa) and SDR (1.70 MPa), respectively. The correlation between polymerization shrinkage and the mold wall deflection decreased with increasing wall thickness. On the other hand, the correlation between flexural modulus and the mold wall deflection increased with increasing wall thickness. For all groups, wall deflection correlated strongly with polymerization shrinkage stress.

  18. A Note on Eccentricities within a Single n-Layered Obstacle and their Influence on Time Harmonic SH Waves

    SciTech Connect

    Weber, Wolfgang; Zastrau, Bernd W.

    2010-09-30

    In this contribution some aspects of SH wave scattering due to a single eccentric n-layered obstacle are being looked at. Herewith, the basis solution is derived analytically for an elliptic inclusion as it occurs in civil engineering practice e. g. within textile reinforced concrete. Hence, (modified) MATHIEUfunctions have to be evaluated. Later on, the degenerate case of an eccentric circular obstacle is dealt with.

  19. Charge injection in thin dielectric layers by atomic force microscopy: influence of geometry and material work function of the AFM tip on the injection process

    NASA Astrophysics Data System (ADS)

    Villeneuve-Faure, C.; Makasheva, K.; Boudou, L.; Teyssedre, G.

    2016-06-01

    Charge injection and retention in thin dielectric layers remain critical issues for the reliability of many electronic devices because of their association with a large number of failure mechanisms. To overcome this drawback, a deep understanding of the mechanisms leading to charge injection close to the injection area is needed. Even though the charge injection is extensively studied and reported in the literature to characterize the charge storage capability of dielectric materials, questions about charge injection mechanisms when using atomic force microscopy (AFM) remain open. In this paper, a thorough study of charge injection by using AFM in thin plasma-processed amorphous silicon oxynitride layers with properties close to that of thermal silica layers is presented. The study considers the impact of applied voltage polarity, work function of the AFM tip coating and tip curvature radius. A simple theoretical model was developed and used to analyze the obtained experimental results. The electric field distribution is computed as a function of tip geometry. The obtained experimental results highlight that after injection in the dielectric layer the charge lateral spreading is mainly controlled by the radial electric field component independently of the carrier polarity. The injected charge density is influenced by the nature of electrode metal coating (work function) and its geometry (tip curvature radius). The electron injection is mainly ruled by the Schottky injection barrier through the field electron emission mechanism enhanced by thermionic electron emission. The hole injection mechanism seems to differ from the electron one depending on the work function of the metal coating. Based on the performed analysis, it is suggested that for hole injection by AFM, pinning of the metal Fermi level with the metal-induced gap states in the studied silicon oxynitride layers starts playing a role in the injection mechanisms.

  20. Influence of high-intensity turbulence on laminar boundary layer development on a cylindrical leading edge: Enhancement to eddy diffusivity

    NASA Astrophysics Data System (ADS)

    Pearson, Juli K.

    The growing demand for increased efficiency in turbine engine designs has sparked a growing interest for research of air flow around curved surfaces. The turbine's operating conditions result in material property constraints, especially in the first stage turbine vanes and blades. These turbine vane components experience extreme loading conditions of both high temperature and high turbulence intensities exiting the combustor. The surface of the turbine blades has cylindrical leading edges that promote stabilizing flow accelerations. These convex surfaces can cause a reduced eddy diffusivity across the boundary layer. This thesis reviews measurements of velocity and turbulence intensities taken just shy of the thirty degrees offset from the stagnation line of a two-dimensional cylindrical leading edge under a wide range of turbulence and flow conditions flow conditions. Flow conditions and velocity measurements were gathered with respect to the distance to the surface. The length of the measurements extended from the surface to beyond the boundary layer's edge. The instrumentation used to collect data was a single wire driven by a constant temperature anemometer bridge. The hot wire is specially modified to measure data near the cylindrical leading edges curved surface. The traversing system allowed the acquisition of high-resolution boundary layer data. The traversing system was installed internally to the cylindrical leading edge to reduce probe blockage.

  1. Influence of chemical and structural properties of functionalized polythiophene-based layers on electrochemical sensing of atrazine.

    PubMed

    Lattach, Youssef; Garnier, Francis; Remita, Samy

    2012-01-16

    Sensitive layers based on conducting homopolymer [poly(3,4-ethylenedioxythiophene), denoted PEDOT] and copolymers [molecularly imprinted and non-imprinted poly(EDOT-co-3-thiophene acetic acid), denoted MICP and NICP, respectively] are electrosynthesized on gold substrates and used for the electrochemical detection of atrazine. These layers are characterized by cyclic voltammetry, ATR-FTIR spectroscopy, optical profilemetry, and AFM microscopy in order to study the effect of the chemical functionalities and of the structural properties of these conducting polymers on the physical chemistry of the interaction with atrazine targets and with the aim to improve the sensitivity of the recognition process. In particular, due to the presence in their backbones of preshaped functionalized cavities which keep the molecular memory of the targets, MICP layers show remarkable sensitivity, a low detection limit (10(-9) mol  L(-1)), and a large linear range of detection (10(-8) to 10(-4) mol  L(-1)), as demonstrated by square-wave voltammetry.

  2. Influence of the thickness and surface composition on the electronic structure of FeS2 layers

    NASA Astrophysics Data System (ADS)

    Yakovkin, I. N.; Petrova, N. V.

    2016-07-01

    Electronic structures of bulk, bilayer and monolayer FeS2 are studied by DFT-GGA method. The band gap of the FeS2 monolayer is found to be of 0.73 eV, which is well below the estimated bulk value (0.85 eV). As a result, the gap reaches its maximum (1.39 eV) for the bilayer FeS2. It is confirmed that the hybridization of Fe d states in the Fe-rich layer can lead to the decrease of the band gap down to the metallization of the surface. However, the Fe enrichment required for metallization must be very large, which makes it unrealistic. In contrast, the S-rich pyrite surface is found to be inherently metallic. This conclusion follows, in particular, from the revealed metallicity of the FeS3/FeS2 bilayer slab, in which the metallic properties stem from d states of Fe and p states of S of the FeS3 layer, while the FeS2 layer remains essentially semiconducting. Thus, the known decrease of the open-circuit voltage of pyrite solar cells can be attributed to the S enrichment, caused, for example, by surface segregation of sulfur.

  3. High-Efficiency Perovskite Solar Cell Based on Poly(3-Hexylthiophene): Influence of Molecular Weight and Mesoscopic Scaffold Layer.

    PubMed

    Nia, Narges Yaghoobi; Matteocci, Fabio; Cina, Lucio; Di Carlo, Aldo

    2017-05-28

    Here, we investigated the effect of the molecular weight (MW) of poly 3-hexylthiophene (P3HT) hole-transport material on the performance of perovskite solar cells (PSCs). We found that by increasing the MW the photovoltaic performances of the cells are enhanced leading to an improvement of the overall efficiency. P3HT-based PSCs with a MW of 124 kDa can achieve an overall average efficiency of 16.2 %, double with respect to the ones with a MW of 44 kDa. Opposite to spiro-OMeTAD-based PSCs, the photovoltaic parameters of the P3HT-based devices are enhanced by increasing the mesoporous TiO2 layer thickness from 250 to 500 nm. Moreover, for a titania scaffold layer thickness of 500 nm, the efficiency of P3HT-based PSCs with high MW is larger than the spiro-OMeTAD based PSCs with the same scaffold layer thickness. Recombination reactions of the devices were also investigated by voltage decay and electrochemical impedance spectroscopy. We found that the relationship between P3HT MW and cell performance is related to the reduction of charge recombination and to the increase of the P3HT light absorption by increasing the MW. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Influence des erreurs de modele et de mesure sur les resultats d'interpretation d'un essai de reponse thermique

    NASA Astrophysics Data System (ADS)

    Jacques, Louis

    Prior to the design of a geothermal system for heating and cooling purposes, the thermal parameters in the vicinity of the borehole are established through the completion of a thermal response test. Various sources of error are causing uncertainties on the interpretation outcome. Among the sources of error, the impact of the interpretation model and the measurement errors had never been thoroughly demonstrated. To evaluate the accuracy of an interpretation, the real borehole thermal parameters need to be exactly known, which hinder use of real thermal response test data. Noiseless synthetic interpretation data is then produced through a geostatistical study and a numerical simulation of a three dimensional finite element model. Several stochastic inversions were performed in order to obtain statistic distribution for each unknown thermal parameters. The inversions are carried out with the finite line-source model (FLSM) and the thermal resistance and capacity model (TRCM), included in the interpretation tool TRT-SInterp. For each experiment, 100 inversions were realized with the same initial seed. The bias and precision of thermal parameters are obtained by comparing the average and the standard deviation of the posterior distributions with the reference thermal parameters. To analyze the model error, a stopping criteria is utilized to keep only the results allowing an error of adjustment under the model error. An additional experiment shows the influence of the recovery phase during the test. To consider the temperature probe error, the bias of the probe is included within the stopping criteria. For the watt-transducer, systematic errors and random noises are added to the signal at each inversion. The use of a stopping criteria for the model's error demonstrated a reduction of the uncertainty of the parameters for the TRCM and the identification error for the FLSM. Results indicated that the use of a recovery phase helps narrowing the interpretation results bias

  5. The influence of drinking water containing sodium chloride on performance and eggshell quality of a modern, colored layer strain.

    PubMed

    Chen, J; Balnave, D

    2001-01-01

    Hubbard ISA IsaBrown pullets were purchased from a commercial supplier at 16 wk of age and kept at a constant 18 C or a constant 30 C in temperature-controlled rooms. The purpose of our experiment was to determine the effect of ambient temperature on the eggshell quality responses of laying hens receiving saline drinking water with or without simultaneous supplementation of the diet with ascorbic acid or Zn methionine. Four treatments were investigated: 1) a basal layer diet (C) and local drinking water, 2) diet C and local drinking water containing 2 g NaCl/L, 3) diet C containing 200 mg ascorbic acid/kg and local drinking water containing 2 g NaCl/L, and 4) diet C with 360 mg Zinpro 100 (Zn methionine)/kg and local drinking water containing 2 g NaCl/L. The local drinking water contained <1 mmol Cl/ L. The pullets received a continuous daily photoperiod of 16 h from fluorescent lighting, and production measures were made between 20 and 60 wk of age. Production and eggshell quality were significantly reduced at 30 C compared with 18 C but were not significantly affected by the dietary and water treatments. The results indicated that the IsaBrown hens were relatively insensitive to intakes of NaCl from the drinking water at concentrations of 2 g/L. This lack of sensitivity in eggshell quality contrasts with the majority of published reports, including earlier work with local Australian layer strains. It is suggested that this contrasting sensitivity may relate to the concentration of dietary NaCl used during the selection of layer genotypes.

  6. The influence of matrix composition and ink layer thickness on iron gall ink determination by the PIXE method

    NASA Astrophysics Data System (ADS)

    Uršič, Mitja; Budnar, Miloš; Simčič, Jure; Pelicon, Primož

    2006-06-01

    The elemental composition of iron gall inks in historical documents can be effectively studied using the non-destructive proton induced X-ray emission (PIXE) method. The in-air proton beam experimental set-up installed at the Microanalytical Centre of the Jožef Stefan Institute was used for this purpose. The aim of the present investigation was to model and evaluate the uncertainties in the analysis due to the incompletely known matrix composition and iron gall ink layer thickness. Estimation of these uncertainties helped in quantifying the accuracy of multi-elemental PIXE analysis of historical documents.

  7. Influence of layer doping and thickness on predicted performance of NPN AlGaN/GaN HBTs

    NASA Astrophysics Data System (ADS)

    Lee, K. P.; Dabiran, A.; Chow, P. P.; Pearton, S. J.; Ren, F.

    2003-06-01

    The effects of base doping and thickness on dc current gain, collector-emitter saturation voltage, saturation current and collector-emitter breakdown voltage of GaN/AlGaN heterojunction bipolar transistors were investigated using a drift-diffusion transport model. Given the low ionization efficiency of Mg acceptors in the base, it is important to design structures that avoid depletion of the base layer. The presence of a resistive base causes current to flow directly to the collector, severely reducing gain. The effect of emitter doping on current gain and of collector doping on the breakdown voltage of the C-E junction were also investigated.

  8. The influence of a local wall deformation on the development of natural instabilities in a laminar boundary layer

    NASA Technical Reports Server (NTRS)

    Burnel, S.; Gougat, P.; Martin, F.

    1981-01-01

    The natural instabilities which propagate in the laminar boundary layer of a flat plate composed of intermittent wave trains are described. A spectral analysis determines the frequency range and gives a frequency and the harmonic 2 only if there is a wall deformation. This analysis provides the amplitude modulation spectrum of the instabilities. Plots of the evolution of power spectral density are compared with the numerical results obtained from the resolve of the Orr-Sommerfeld equation, while the harmonic is related to a micro-recirculating flow near the wall deformation.

  9. Grundlagen des Tissue Engineering

    NASA Astrophysics Data System (ADS)

    Mayer, Jörg; Blum, Janaki; Wintermantel, Erich

    Die Organtransplantation stellt eine verbreitete Therapie dar, um bei krankheitsoder unfallbedingter Schädigung eines Organs die Gesamtheit seiner Funktionen wieder herzustellen, indem es durch ein Spenderorgan ersetzt wird. Organtransplantationen werden für die Leber, die Niere, die Lunge, das Herz oder bei schweren grossflächigen Verbrennungen der Haut vorgenommen. Der grosse apparative, personelle und logistische Aufwand und die Risiken der Transplantationschirurgie (Abstossungsreaktionen) sowie die mangelnde Verfügbarkeit von immunologisch kompatiblen Spenderorganen führen jedoch dazu, dass der Bedarf an Organtransplantaten nur zu einem sehr geringen Teil gedeckt werden kann. Sind Spenderorgane nicht verfügbar, können in einzelnen Fällen lebenswichtige Teilfunktionen, wie beispielsweise die Filtrationsfunktion der Niere durch die Blutreinigung mittels Dialyse ersetzt oder, bei mangelnder Funktion der Bauchspeicheldrüse (Diabetes), durch die Verabreichung von Insulin ein normaler Zustand des Gesamtorganismus auch über Jahre hinweg erhalten werden. Bei der notwendigen lebenslangen Anwendung apparativer oder medikamentöser Therapie können für den Patienten jedoch häufig schwerwiegende, möglicherweise lebensverkürzende Nebenwirkungen entstehen. Daher werden in der Forschung Alternativen gesucht, um die Funktionen des ausgefallenen Organs durch die Implantation von Zellen oder in vitro gezüchteten Geweben möglichst umfassend wieder herzustellen. Dies erfordert biologisch aktive Implantate, welche die für den Stoffwechsel des Organs wichtigen Zellen enthalten und einen organtypischen Stoffwechsel entfalten.

  10. Influence of a compost layer on the attenuation of 28 selected organic micropollutants under realistic soil aquifer treatment conditions: insights from a large scale column experiment.

    PubMed

    Schaffer, Mario; Kröger, Kerrin Franziska; Nödler, Karsten; Ayora, Carlos; Carrera, Jesús; Hernández, Marta; Licha, Tobias

    2015-05-01

    Soil aquifer treatment is widely applied to improve the quality of treated wastewater in its reuse as alternative source of water. To gain a deeper understanding of the fate of thereby introduced organic micropollutants, the attenuation of 28 compounds was investigated in column experiments using two large scale column systems in duplicate. The influence of increasing proportions of solid organic matter (0.04% vs. 0.17%) and decreasing redox potentials (denitrification vs. iron reduction) was studied by introducing a layer of compost. Secondary effluent from a wastewater treatment plant was used as water matrix for simulating soil aquifer treatment. For neutral and anionic compounds, sorption generally increases with the compound hydrophobicity and the solid organic matter in the column system. Organic cations showed the highest attenuation. Among them, breakthroughs were only registered for the cationic beta-blockers atenolol and metoprolol. An enhanced degradation in the columns with organic infiltration layer was observed for the majority of the compounds, suggesting an improved degradation for higher levels of biodegradable dissolved organic carbon. Solely the degradation of sulfamethoxazole could clearly be attributed to redox effects (when reaching iron reducing conditions). The study provides valuable insights into the attenuation potential for a wide spectrum of organic micropollutants under realistic soil aquifer treatment conditions. Furthermore, the introduction of the compost layer generally showed positive effects on the removal of compounds preferentially degraded under reducing conditions and also increases the residence times in the soil aquifer treatment system via sorption. Copyright © 2015 Elsevier Ltd. All rights reserved.

  11. Revisiting methods to characterize bioelectrochemical systems: The influence of uncompensated resistance (iRu-drop), double layer capacitance, and junction potential

    NASA Astrophysics Data System (ADS)

    Madjarov, J.; Popat, S. C.; Erben, J.; Götze, A.; Zengerle, R.; Kerzenmacher, S.

    2017-07-01

    Bioelectrochemical systems (BES) are characterized with methods derived from the electrochemistry field, for e.g. linear sweep voltammetry (LSV), cyclic voltammetry (CV), and chronoamperometry. The limitations of electrochemical measurements are well known and described, but there are new challenges when these are applied to biological systems. For instance, the electrolyte conditions are predefined by the application involving the use of low conductivities, leading to an increase of two error sources: the iRu-drop and junction potential. Furthermore, the use of electrodes with high surface areas and thus high double layer capacitance lead to capacitive currents that superimpose the biocatalytic current of interest. Even though these problems have often been mentioned in the bioelectrochemistry field, they are seldom considered and reported in publications. The scope of this work is to present and discuss methods to quantify the Ru and double layer capacitance, and to demonstrate their significant influence on the recording of polarization curves. In a typical BES setup, it is exemplarily shown that due to iRu-drop measured potentials can deviate by more than 200 mV from the actual potential. Similarly, more than 40% of a recorded electrode current can originate from the electrode material's double layer capacitance.

  12. Study of the influence of semiconductor material parameters on acoustic wave propagation modes in GaSb/AlSb bi-layered structures by Legendre polynomial method

    NASA Astrophysics Data System (ADS)

    Othmani, Cherif; Takali, Farid; Njeh, Anouar; Ben Ghozlen, Mohamed Hédi

    2016-09-01

    The propagation of Rayleigh-Lamb waves in bi-layered structures is studied. For this purpose, an extension of the Legendre polynomial (LP) method is proposed to formulate the acoustic wave equation in the bi-layered structures induced by thin film Gallium Antimonide (GaSb) and with Aluminum Antimonide (AlSb) substrate in moderate thickness. Acoustic modes propagating along a bi-layer plate are shown to be quite different than classical Lamb modes, contrary to most of the multilayered structures. The validation of the LP method is illustrated by a comparison between the associated numerical results and those obtained using the ordinary differential equation (ODE) method. The convergency of the LP method is discussed through a numerical example. Moreover, the influences of thin film GaSb parameters on the characteristics Rayleigh-Lamb waves propagation has been studied in detail. Finally, the advantages of the Legendre polynomial (LP) method to analyze the multilayered structures are described. All the developments performed in this work were implemented in Matlab software.

  13. Influence of post-deposition annealing on interfacial properties between GaN and ZrO{sub 2} grown by atomic layer deposition

    SciTech Connect

    Ye, Gang; Wang, Hong Arulkumaran, Subramaniam; Ng, Geok Ing; Li, Yang; Ang, Kian Siong; Geok Ng, Serene Lay; Ji, Rong; Liu, Zhi Hong

    2014-10-13

    Influence of post-deposition annealing on interfacial properties related to the formation/annihilation of interfacial GaO{sub x} layer of ZrO{sub 2} grown by atomic layer deposition (ALD) on GaN is studied. ZrO{sub 2} films were annealed in N{sub 2} atmospheres in temperature range of 300 °C to 700 °C and analyzed by X-ray photoelectron spectroscopy and high-resolution transmission electron microscopy. It has been found that Ga-O bond to Ga-N bond area ratio decreases in the samples annealed at temperatures lower than 500 °C, which could be attributed to the thinning of GaO{sub x} layer associated with low surface defect states due to “clean up” effect of ALD-ZrO{sub 2} on GaN. However, further increase in annealing temperature results in deterioration of interface quality, which is evidenced by increase in Ga-O bond to Ga-N bond area ratio and the reduction of Ga-N binding energy.

  14. Monte Carlo analysis of the influence of germanium dead layer thickness on the HPGe gamma detector experimental efficiency measured by use of extended sources.

    PubMed

    Chham, E; García, F Piñero; El Bardouni, T; Ferro-García, M Angeles; Azahra, M; Benaalilou, K; Krikiz, M; Elyaakoubi, H; El Bakkali, J; Kaddour, M

    2014-09-22

    We have carried out a study to figure out the influence of crystal inactive-layer thickness on gamma spectra measured by an HPGe detector. The thickness of this dead layer (DL) is not known (no information about it was delivered by the manufacturer) due to the existence of a transition zone where photons are increasingly absorbed. To perform this analyses a virtual model of a Canberra HPGe detector was produced with the aid of MCNPX 2.7 code. The main objective of this work is to produce an optimal modeling for our GPGe detector. To this end, the study included the analysis of the total inactive germanium layer thickness and the active volume that are needed in order to obtain the smallest discrepancy between calculated and experimental efficiencies. Calculations and measurements were performed for all of the radionuclides included in a standard calibration gamma cocktail solution. Different geometry sources were used: a Marinelli and two other new sources represented as S(1) and S(2). The former was used for the determination of the active volume, whereas the two latter were used for the determination of the face and lateral DL, respectively. The model was validated by comparing calculated and experimental full energy peak efficiencies in the 50-1900keV energy range. the results show that the insertion of the DL parameter in the modeling is absolutely essential to reproduce the experimental results, and that the thickness of this DL varies from one position to the other on the detector surface.

  15. Influence of micro-porous layer and operating conditions on the fluoride release rate and degradation of PEMFC membrane electrode assemblies

    NASA Astrophysics Data System (ADS)

    Kundu, Sumit; Karan, Kunal; Fowler, Michael; Simon, Leonardo C.; Peppley, Brant; Halliop, Ela

    2008-05-01

    In this study, the influence of micro-porous layers (MPL) on polymer electrolyte membrane fuel cell (PEMFC) durability was investigated. Two fuel cells were built, one with a micro-porous layer on the anode side, and a second cell with MPL on both sides. Experiments were conducted by varying operational parameters such as current density, reactant stoichiometry, and inlet relative humidity. Fuel cell degradation was evaluated by measuring fluoride release rates. The largest factor determining fluoride release rate was found to be the presence of MPL; the cell with MPLs on both sides exhibited significantly reduced fluoride release rates compared to that of cell with one MPL. Increasing the current density also reduced the fluoride release rate for cells with only one MPL whereas there was only a moderate effect on cells with two MPLs. Microscopy analysis showed small but significant changes in ionomer layer thickness. Polarization measurements indicated that there was little change in the performance for both cells over the test period.

  16. Influence of liquid medium with different absorption and its layer thickness on bovine bone tibia ablation induced by CO2 laser

    NASA Astrophysics Data System (ADS)

    Li, Xuwei; Chen, Chuanguo; Zhang, Xianzeng; Zhan, Zhenlin; Xie, Shusen

    2014-11-01

    Liquid-assisted laser ablation has been investigated in laser surface cleaning, laser osteotomy, and dental tissue ablation. However, the actual mechanism of liquid-assisted ablation is not clear yet. The purpose of this study was to investigate the influence of liquid medium with different absorption and the liquid thickness on laser ablation efficiency. A pulsed CO2 laser was employed to ablate bovine bone tibia under liquid layer which varied from 0.6 mm to 2 mm. The applied pulse power level was set at 5 w and each crater was produced with six laser pulses. The results showed that the ablation cross-section area produced with various levels of pure water thickness (0.6, 0.8, 1 and 2 mm)were lower than under ink, and the ablation depth gradually decreased as the water layer becoming thicker. The biggest cross-section area in liquid thickness of ink was 0.8mm, but as the layer thicker than 0.8 mm the ablation depth decreased suddenly. There was thermal damage seen on samples in all of the groups, but less in pure water.

  17. Influence of the heat treatment condition of alloy AlCu4Mg1 on the microstructure and properties of anodic oxide layers

    NASA Astrophysics Data System (ADS)

    Morgenstern, R.; Dietrich, D.; Sieber, M.; Lampke, T.

    2017-03-01

    Due to their outstanding specific mechanical properties, high-strength, age-hardenable aluminum alloys offer a high potential for lightweight security-related applications. However, the use of copper-alloyed aluminum is limited because of their susceptibility to selective corrosion and their low wear resistance. These restrictions can be overcome and new applications can be opened up by the generation of protective anodic aluminum oxide layers. In contrast to the anodic oxidation of unalloyed aluminum, oxide layers produced on copper-rich alloys exhibit a significantly more complex pore structure. It is the aim of the investigation to identify the influence of microstructural parameters such as size and distribution of the strengthening precipitations on the coating microstructure. The aluminum alloy EN AW-2024 (AlCu4Mg1) in different heat treatment conditions serves as substrate material. The influence of the strengthening precipitations’ size and distribution on the development of the pore structure is investigated by the use of high-resolution scanning electron microscopy. Integral coating properties are characterized by non-destructive and light-microscopic thickness measurements and instrumented indentation tests.

  18. Layered double hydroxide/polyethylene terephthalate nanocomposites. Influence of the intercalated LDH anion and the type of polymerization heating method

    SciTech Connect

    Herrero, M.; Martinez-Gallegos, S.; Labajos, F.M.; Rives, V.

    2011-11-15

    Conventional and microwave heating routes have been used to prepare PET-LDH (polyethylene terephthalate-layered double hydroxide) composites with 1-10 wt% LDH by in situ polymerization. To enhance the compatibility between PET and the LDH, terephthalate or dodecyl sulphate had been previously intercalated in the LDH. PXRD and TEM were used to detect the degree of dispersion of the filler and the type of the polymeric composites obtained, and FTIR spectroscopy confirmed that the polymerization process had taken place. The thermal stability of these composites, as studied by thermogravimetric analysis, was enhanced when the microwave heating method was applied. Dodecyl sulphate was more effective than terephthalate to exfoliate the samples, which only occurred for the terephthalate ones under microwave irradiation. - Graphical abstract: Conventional and microwave heating routes were used to prepare PET-LDH (polyethylene terephthalate-layered double hydroxide) composites with 1-10 wt% LDH by in situ polymerization. To enhance the compatibility between PET and the LDH, terephthalate or dodecyl sulphate was previously intercalated into the LDH. The microwave process improves the dispersion and the thermal stability of nanocomposites due to the interaction of the microwave radiation and the dipolar properties of EG and the homogeneous heating. Highlights: > LDH-PET compatibility is enhanced by preintercalation of organic anions. > Dodecylsulphate performance is much better than that of terephthalate. > Microwave heating improves the thermal stability of the composites. > Microwave heating improves as well the dispersion of the inorganic phase.

  19. Influence of the process parameters on the growth of YSZ-layers prepared by Ion Beam Assisted Deposition (IBAD)

    NASA Astrophysics Data System (ADS)

    Knierim, A.; Auer, R.; Geerk, J.; Lierk, Fuli. Y.; Linker, G.; Meyer, O.; Schweiss, P.; Smithey, R.; Reiner, J.

    1997-05-01

    Cubic yttria stabilized zirconia (YSZ) thin films were grown on amorphous quartz, r-plane sapphire and stainless steel substrates by ion beam sputtering from a planar target under simultaneous ion bombardment (IBAD) during film growth and sputtering employing the inverted cylindrical magnetron (ICM) gun. The formation and modification of preferred orientations was studied by X-ray diffraction and TEM investigations as a function of different deposition parameters like substrate temperature, total pressure, deposition rate, ion beam energy and current. A preferred (100)-orientation could be achieved on untextured substrates by ICM-deposition at substrate temperatures above 800°C and by IBAD without external heating of the substrates. In-plane orientation of YSZ films on untextured substrates was only achieved with IBAD for an ion impact angle αs between 30° and 70°. For αs = 55° the best mosaic spread was observed. The observation of significantly smaller texture distribution widths for epitaxially post-deposited material than measured at the basic YSZ buffer layer was found to be due to a gradual improvement of YSZ growth under ion bombardment with increasing layer thickness.

  20. Influence of electrode groove geometry on the passive control of the depletion layer in microfluidic fuel cells

    NASA Astrophysics Data System (ADS)

    Lee, Seung-Wu; Ahn, Yoomin

    2015-12-01

    Mitigation of the concentration boundary layer is an essential requirement to improve the power density of microfluidic fuel cells. In this study, the formation of a groove shape in the surface of the electrodes, located in parallel on the bottom of the channel, is proposed for the passive control of the depletion layer. The flow field inside the channel is numerically simulated and cell performance is experimentally measured for the various groove formation patterns (converging, parallel, or diverging) and tilt angles (30, 45, or 60°). Experimentally measured cell performance also shows superior results at the best conditions as determined by numerical modeling, where the interdiffusion zone at the fuel-oxidant interface is not significantly expanded and the flow in the direction normal to the electrode surface is large. Our results show that the depletion region is well-controlled when the groove angle is large and when the groove pattern is not parallel, due to the increase in chaotic mixing. At these conditions, with formic acid as the fuel and a platinum electrode, the maximum current density and peak power density are increased by 38.42% and 38.09%, respectively, compared to the values for flat electrodes. Even better cell performance is expected if the optimum design of the groove shape is determined using flow analysis.

  1. Influence of the magnetic dead layer thickness of Mg-Zn ferrites nanoparticle on their magnetic properties

    NASA Astrophysics Data System (ADS)

    El-Sayed, H. M.; Ali, I. A.; Azzam, A.; Sattar, A. A.

    2017-02-01

    Nanoparticle ferrite with chemical formula Mg(1-x)ZnxFe2O4 (where x=0.0, 0.2, 0.4, 0.6, 0.8 and 1) were prepared by sol-gel technique. Single phase structure of these ferrites was confirmed using X-ray diffraction (XRD). Transmission Electron Microscope (TEM) showed that the particle size of the samples in the range of (5.7-10.6 nm). The hysteresis studies showed superparamagnetic behaviour at room temperature. The magnetization behaviour with Zn-content is expressed in the light of Yafet-Kittel angles. The dead layer thickness (t) was calculated and its effect on the magnetization and magnetic losses was debated. The Specific Absorption Rate (SAR) in an alternating magnetic field with frequency 198 kHz for these ferrites has been studied. It is found that, the thickness of magnetic dead layer of the surface of the materials has greatly affected the SAR value of the samples.

  2. Anodic Behavior of the Aluminum Current Collector in Imide-Based Electrolytes: Influence of Solvent, Operating Temperature, and Native Oxide-Layer Thickness.

    PubMed

    Meister, Paul; Qi, Xin; Kloepsch, Richard; Krämer, Elisabeth; Streipert, Benjamin; Winter, Martin; Placke, Tobias

    2017-02-22

    The inability of imide salts to form a sufficiently effective passivation layer on aluminum current collectors is one of the main obstacles that limit their broad application in electrochemical energy-storage systems. However, under certain circumstances, the use of electrolytes with imide electrolyte salts in combination with the aluminum current collector is possible. In this contribution, the stability of the aluminum current collector in electrolytes containing either lithium bis(trifluoromethanesulfonyl) imide (LiTFSI) or lithium fluorosulfonyl-(trifluoromethanesulfonyl) imide (LiFTFSI) as conductive salt was investigated by electrochemical techniques, that is, cyclic voltammetry (CV) and chronocoulometry (CC) in either room-temperature ionic liquids or in ethyl methyl sulfone. In particular, the influence of the solvent, operating temperature, and thickness of the native oxide layer of aluminum on the pit formation at the aluminum current collector surface was studied by means of scanning electron microscopy. In general, a more pronounced aluminum dissolution and pit formation was found at elevated temperatures as well as in solvents with a high dielectric constant. An enhanced thickness of the native aluminum oxide layer increases the oxidative stability versus dissolution. Furthermore, we found a different reaction rate depending on dwell time at the upper cut-off potential for aluminum dissolution in TFSI- and FTFSI-based electrolytes during the CC measurements; the use of LiFTFSI facilitated the dissolution of aluminum compared to LiTFSI. Overall, the mechanism of anodic aluminum dissolution is based on: i) the attack of the Al2 O3 surface by acidic species and ii) the dissolution of bare aluminum into the electrolyte, which, in turn, is influenced by the electrolyte's dielectric constant.

  3. Influence of Dynamics and Chemistry on the Diurnal Variation of VOCs in the Planetary Boundary Layer above a Mixed Forest Canopy in the Southeastern United States

    NASA Astrophysics Data System (ADS)

    Guenther, A. B.; Su, L.; Patton, E. G.; Vila-Guerau Arellano, J.; Mak, J. E.

    2014-12-01

    The planetary boundary layer (PBL) is a region of inherent interest because reactive VOCs emitted from the forest canopy are mixed with the residual and free tropospheric air masses, oxidized, and/or otherwise removed in this region. The characterization of diurnal variation of VOCs in the PBL is limited due to the lack of appropriate sampling platforms that are able to probe all the regions of interest: from the surface to the entrainment zone. Here we present the application of the Whole Air Sample Profiler (WASP) system during the 2013 Southeast Atmosphere Study (SAS) campaign. A total of 41 research flights (RFs) were carried out during the 2013 SAS campaign between June 1 and June 14 over the Alabama Aquatic Biodiversity Center (AABC) site and the SEARCH site. During each RF, ambient air sampling started from 50-100 m above the canopy top and stopped at ~1200 m above the mean sea level (a.m.s.l). The air samples were subsequently analyzed by using a proton-transfer-reaction time-of-flight mass spectrometry (PTR-TOF-MS). Here we analyze the vertical profiles and averaged diurnal variation of the mixing ratios of several reactive VOC species, including isoprene, the sum of monoterpenes, and first generation oxidation products of isoprene: methyl vinyl ketone and methacrolein (MVK+MACR). A MiXed Layer Chemistry (MXLCH) model, guided by the meteorological and chemical observations during the SAS campaign, is used to study the influence of boundary layer dynamics and new isoprene oxidation mechanism on the diurnal variation of major biogenic VOCs emitted from the forest canopy. The new scheme includes OH recycling through two pathways under low-NOx regime: (1) hydroxyl peroxy radicals (HOC5H8OO•; ISOPO2) unimolecular isomerization, and (2) ISOPO2+HO2. The model is able to reproduce the evolution of the boundary layer dynamics (including potential temperature, and boundary layer height) during the selected simulation dates. Based on the model results, budget

  4. Environmental and physiological regulation of transpiration in tropical forest gap species: the influence of boundary layer and hydraulic properties.

    PubMed

    Meinzer, F C; Goldstein, G; Jackson, P; Holbrook, N M; Gutiérrez, M V; Cavelier, J

    1995-04-01

    Environmental and physiological regulation of transpiration were examined in several gap-colonizing shrub and tree species during two consecutive dry seasons in a moist, lowland tropical forest on Barro Colorado Island, Panama. Whole plant transpiration, stomatal and total vapor phase (stomatal + boundary layer) conductance, plant water potential and environmental variables were measured concurrently. This allowed control of transpiration (E) to be partitioned quantitatively between stomatal (g s) and boundary layer (g b) conductance and permitted the impact of invividual environmental and physiological variables on stomatal behavior and E to be assessed. Wind speed in treefall gap sites was often below the 0.25 m s(-1) stalling speed of the anemometer used and was rarely above 0.5 m s(-1), resulting in uniformly low g b (c. 200-300 mmol m(-2) s(-1)) among all species studied regardless of leaf size. Stomatal conductance was typically equal to or somewhat greater than g b. This strongly decoupled E from control by stomata, so that in Miconia argentea a 10% change in g s when g s was near its mean value was predicted to yield only a 2.5% change in E. Porometric estimates of E, obtained as the product of g s and the leaf-bulk air vapor pressure difference (VPD) without taking g b into account, were up to 300% higher than actual E determined from sap flow measurements. Porometry was thus inadequate as a means of assessing the physiological consequences of stomatal behavior in different gap colonizing species. Stomatal responses to humidity strongly limited the increase in E with increasing evaporative demand. Stomata of all species studied appeared to respond to increasing evaporative demand in the same manner when the leaf surface was selected as the reference point for determination of external vapor pressure and when simultaneous variation of light and leaf-air VPD was taken into account. This result suggests that contrasting stomatal responses to similar leaf

  5. La diffraction des neutrons et des rayons X pour l'étude structurale des liquides et des verres

    NASA Astrophysics Data System (ADS)

    Fischer, H. E.; Salmon, P. S.; Barnes, A. C.

    2003-02-01

    La compréhension de mainte propriété physique d'un verre ou d'un liquide nécessite la connaissance des facteurs de structure partiels (PSFs) qui décrivent chacun la distribution d'une espèce atomique autour d'une autre. La technique de diffraction des neutrons avec substitution isotopique (NDIS) [1,2,3], ayant bien réussi a déterminer les PSFs de certains composés [4,5], est pourtant restreinte aux isotopes présentant un contraste suffisant en longueur de diffusion. D'un autre cote, la technique de diffusion anomale des rayons X (AXS ou AXD) [6] permet de faire varier la longueur de diffusion d'une espèce atomique pourvu que son énergie d'absorption soit à la fois accessible et suffisamment élevée pour donner un assez grand transfert du moment. La combinaison des techniques de diffraction des neutrons (avec ou sans substitution isotopique) et de diffraction des rayons X (avec ou sans diffusion anomale) peut donc permettre d'obtenir un meilleur contraste en longueurs de diffusion pour un système donné, mais exige une analyse de données plus soignée pour pouvoir bien tenir compte des erreurs systématiques qui sont différentes pour les 2 techniques [7]. Pour les atomes ayant des distributions électroniques quasi-sphériques, e.g. dans le cas d'un alliage liquide, la combinaison des techniques de NDIS et de diffraction des rayons X s'est déjà montrée très avantageuse pour la détermination des PSFs [8,9]. Dans le cas des verres ayant d'importantes liaisons covalentes, l'effective combinaison des 2 techniques peut être moins directe mais facilitée lorsqu'il s'agit des atomes de grand Z [10,11]. Nous présentons ici un sommaire du méthode et quelques exemples des résultats.

  6. Influence of gravity waves and tides on mesospheric temperature inversion layers: simultaneous Rayleigh lidar and MF radar observations

    NASA Astrophysics Data System (ADS)

    Sridharan, S.; Sathishkumar, S.; Gurubaran, S.

    2008-11-01

    Three nights of simultaneous Rayleigh lidar temperature measurements over Gadanki (13.5° N, 79.2° E) and medium frequency (MF) radar wind measurements over Tirunelveli (8.7° N, 77.8° E) have been analyzed to illustrate the possible effects due to tidal-gravity wave interactions on upper mesospheric inversion layers. The occurrence of tidal gravity wave interaction is investigated using MF radar wind measurements in the altitude region 86 90 km. Of the three nights, it is found that tidal gravity wave interaction occurred in two nights. In the third night, diurnal tidal amplitude is found to be significantly larger. As suggested in Sica et al. (2007), mesospheric temperature inversion seems to be a signature of wave saturation in the mesosphere, since the temperature inversion occurs at heights, when the lapse rate is less than half the dry adiabatic lapse rate.

  7. Influence of oxidation on the composition and structure of the surface layer of hot-pressed boron carbide

    SciTech Connect

    Lavrenko, V.A.; Gogotsi, Yu.G.

    1988-04-01

    The oxidation of hot-pressed boron carbide under isothermal conditions and under conditions of programmed heating up to 1500/degrees/C was investigated. Oxidized samples were studied by secondary-ion mass spectrometry, X-ray photoelectron spectroscopy, scanning electron microscopy, energy-dispersive X-ray microanalysis, X-ray diffraction, and other methods. It has been demonstrated that oxidation starts above 600/degrees/C and results in the formation of a thin transparent B/sub 2/O/sub 3/ film that is cracked after cooling. Up to 1200/degrees/C, the oxidation process is limited by the diffusion of reagents through the oxide layer; at higher temperatures, it is determined by the rate of chemical reaction of carbide with oxygen in the air. During boron carbide oxidation the etching of grain boundaries occurs, it results in strength degradation at higher temperatures.

  8. Influence of a Localized Roughness Element on Disturbance Amplification in a Laminar Boundary Layer at Ma=4.8

    NASA Astrophysics Data System (ADS)

    Marxen, Olaf; Iaccarino, Gianluca; Shaqfeh, Eric

    2007-11-01

    Knowledge of heat load on the surface of vehicles (re-)entering a planetary atmosphere is important for heat-shield design. Prediction of laminar-turbulent transition is a key factor for the design. We carry out numerical simulations of a flat-plate boundary layer with and without localized roughness element (small hump). The compressible Navier-Stokes equations are solved for a calorically perfect gas. Small perturbations at a fixed frequency are triggered at the wall. Their downstream convective amplification is compared between flat-plate and hump case. The roughness element leads to increased disturbance amplification. Peak amplitude levels are reached in the vicinity of the hump. The effect of the roughness element seems similar to the effect of a shock impinging on a wall. The present study shall be extended to include high-temperature gas effects as well as three-dimensional disturbances (oblique waves).

  9. Influence of two different alcohols in the esterification of fatty acids over layered zinc stearate/palmitate.

    PubMed

    de Paiva, Eduardo José Mendes; Corazza, Marcos Lúcio; Sierakowski, Maria Rita; Wärnå, Johan; Murzin, Dmitry Yu; Wypych, Fernando; Salmi, Tapio

    2015-10-01

    In this work, esterification of fatty acids (oleic, linoleic and stearic acid) with a commercial zinc carboxylate (a layered compound formed by simultaneous intercalation of stearate and palmitate anions) was performed. Kinetic modeling using a quasi-homogeneous approach successfully fitted experimental data at different molar ratio of fatty acids/alcohols (1-butanol and 1-hexanol) and temperature. An apparent first-order reaction related to all reactants was found and activation energy of 66 kJ/mol was reported. The catalyst showed to be unique, as it can be easily recovered like a heterogeneous catalysts behaving like ionic liquids. In addition, this catalyst demonstrated a peculiar behavior, because higher reactivity was observed with the increase in the alcohols chain length compared to the authors' previous work using ethanol.

  10. Convergent crater circulations on Mars: Influence on the surface pressure cycle and the depth of the convective boundary layer

    NASA Astrophysics Data System (ADS)

    Tyler, Daniel; Barnes, Jeffrey R.

    2015-09-01

    Modeling of slope flow circulations in idealized axisymmetric craters is used to understand (1) the large surface pressure amplitude observed in Gale Crater by the Rover Environmental Monitoring Station and (2) the shallow convective boundary layer (CBL) suggested by Curiosity imagery. Air temperatures vary within craters with greater amplitudes than outside them, becoming warmer/colder during day/night. This crater circulation effect is most significant over the depth of the crater (key parameter). Within the idealized craters, a surface pressure cycle develops (in the real atmosphere it is enhanced). Partially caused by thermal expansion, a "surge" of mass away from the craters develops during daytime. Over crater floors, the CBL depth is inhibited by a capping inversion from the adiabatic warming of widespread daytime subsidence. For a variety of craters (radius, depth, and with or without a central mound), the results are very similar. In real-atmosphere simulations over canyons or large basins, similar circulations are seen.

  11. Polycation-exchanged clays as sorbents for organic pollutants: Influence of layer charge on pollutant sorption capacity

    SciTech Connect

    Breen, C.; Watson, R.

    1998-12-15

    The uptake curves for the adsorption of a polycation ([CH{sub 2}CH(OH)CH{sub 2}N(CH{sub 3}){sub 2}]{sub n}{sup n+}(Cl){sub n}{sup n{minus}}) onto a low iron Texas bentonite, WL, have been determined and compared with those onto two source smectites, SWy-1 and SAz-1. The polycation exhibited a marked affinity for all the smectite surfaces but polycation uptake was maximized on the fine fractions of Na{sup +}-WL. Variable temperature X-ray diffraction of the clay polycation complexes showed that the polycation was segregated into different interlayers at loadings below 30% of the CEC. The adsorption of benzene onto TMA{sup +}-exchanged SWy-1, SAz-1, and WL showed that, despite having a comparable layer charge to SWy-1, WL was as poor a sorbent for benzene as SAz-1, which has a much higher layer charge. The adsorption of p-nitrophenol (PNP) from aqueous solution onto the TMA{sup +}-exchanged sorbents exhibited the same trends, although a smaller amount was adsorbed due to the greater size of PNP. The amount of PNP adsorbed by polycation-treated SWy-1 depended upon the polycation loading, and PNP uptake maximized at loadings of 28 and 46 mg/(g clay). At higher loadings (80, 102, and 147 mg/(g clay)) the uptake curves became linear and the PNP uptake decreased with increased polycation loading. No polycation-treated clay was as effective as TMA{sup +}-exchanged SWy-1 for the removal of PNP from water.

  12. The Observed Relationship Between Water Vapor and Ozone in the Tropical Tropopause Saturation Layer and the Influence of Meridional Transport

    NASA Technical Reports Server (NTRS)

    Selkirk, Henry B.; Schoeberl, M. R.; Olsen, M. A.; Douglass, A. R.

    2011-01-01

    We examine balloonsonde observations of water vapor and ozone from three Ticosonde campaigns over San Jose, Costa Rica [10 N, 84 W] during northern summer and a fourth during northern winter. The data from the summer campaigns show that the uppermost portion of the tropical tropopause layer between 360 and 380 K, which we term the tropopause saturation layer or TSL, is characterized by water vapor mixing ratios from proximately 3 to 15 ppmv and ozone from approximately 50 ppbv to 250 ppbv. In contrast, the atmospheric water vapor tape recorder at 380 K and above displays a more restricted 4-7 ppmv range in water vapor mixing ratio. From this perspective, most of the parcels in the TSL fall into two classes - those that need only additional radiative heating to rise into the tape recorder and those requiring some combination of additional dehydration and mixing with drier air. A substantial fraction of the latter class have ozone mixing ratios greater than 150 ppbv, and with water vapor greater than 7 ppmv this air may well have been transported into the tropics from the middle latitudes in conjunction with high-amplitude equatorial waves. We examine this possibility with both trajectory analysis and transport diagnostics based on HIRDLS ozone data. We apply the same approach to study the winter season. Here a very different regime obtains as the ozone-water vapor scatter diagram of the sonde data shows the stratosphere and troposphere to be clearly demarcated with little evidence of mixing in of middle latitude air parcels.

  13. Influence of Dermanyssus gallinae (poultry red mite) invasion on the plasma levels of corticosterone, catecholamines and proteins in layer hens.

    PubMed

    Kowalski, A; Sokół, R

    2009-01-01

    The results of studies conducted in 2006 revealed that mass red mite (Dermanyssus gallinae) invasions cause somatic stress which may be responsible for the pathophysiological mechanism of decreased egg production, lower humoral immunity and higher mortality in layer hens. The aim of this study was to validate the above research results, to investigate whether in addition to somatic stress, red mite invasions cause psychogenic stress due to the activation of the sympatho-adrenomedullar system, and to determine the level of stress resulting from red mite infestations in comparison with a short, 1.5 h period of acute immobilisation stress. The study investigated 36 HY-Line Brown layer hens divided into three groups: a non-infested control group, an experimental group infested with red mites and a non-infested experimental group subjected to acute immobilisation stress for 1.5 h. Blood samples were taken from all hens for the determination of the levels of corticosterone, adrenaline, noradrenaline, albumin, and alpha-, beta- and gamma-globulins. The results validated the previous reports on the occurrence of somatic stress and on a significant decrease in y-globulin levels (p < or = 0.01) in the group of birds infested with red mites, in comparison with the control group. Adrenaline levels in infested hens were indicative of psychogenic stress. Based on a comparison of hormonal indicators in all hen groups, the level of somatic stress resulting from red mite infestation can be classified as moderate, while the level of psychogenic stress can be interpreted as high. A significant drop in y-globulin levels in the blood of birds infested with red mites also shows that the invasion induces chronic stress which lowers the humoral immunity of hens.

  14. Influences of initial plankton biomass and mixed-layer depths on the outcome of iron-fertilization experiments

    NASA Astrophysics Data System (ADS)

    Fujii, M.; Chai, F.

    2009-12-01

    Several in situ iron-enrichment experiments have been conducted, where the response of the phytoplankton community differed. We use a marine ecosystem model to investigate the effect of iron on phytoplankton in response to different initial plankton conditions and mixed-layer depths (MLDs). Sensitivity analysis of the model results to the MLDs reveals that the modeled response to the same iron enhancement treatment differed dramatically according to the different MLDs. The magnitude of the iron-induced biogeochemical responses in the surface water, such as maximum chlorophyll, is inversely correlated with MLD, as observed. The significant decrease in maximum surface chlorophyll with MLD results from the difference in diatom concentration in the mixed layer, which is determined by vertical mixing. The modeled column-integrated chlorophyll, on the other hand, is the highest with intermediate MLD cases, suggesting difference in iron-induced biogeochemical responses between volume and area considerations. The iron-induced diatom bloom is severely restricted below the compensation depth due to both light limitation and grazing pressure, irrespective of the MLD. Sensitivity of the model to initial mesozooplankton (as grazers on diatoms) biomass shows that column-integrated biomass, net community production and export production are strongly controlled by the initial mesozooplankton biomass. Higher initial mesozooplankton biomass yields high grazing pressure on diatoms, which results in less accumulation of diatom biomass and may account for notably lower surface chlorophyll during SEEDS (Subarctic Pacific Iron Experiment for Ecosystem Dynamics Study) II than during SEEDS. The initial diatom biomass is also important to the outcome of iron enrichment but is not as crucial as the MLD and the initial mesozooplankton biomass. This modeling study suggests that not only MLD but also the initial biomass of diatoms and its principle grazers are crucial factors in the response of

  15. Geophysical Investigations on Malta (Central Mediterranean) using Ambient Noise: Assessing Array Performance and Influence of a Thick Low Velocity Layer.

    NASA Astrophysics Data System (ADS)

    Farrugia, D.; Paolucci, E.; D'Amico, S.; Galea, P. M.

    2014-12-01

    The use of microtremors to obtain shear wave velocity (Vs) profiles of the subsurface is becoming a widespread approach due to its various advantages. Noise measurements were carried out at four sites on Malta (Central Mediterranean). Array techniques were first tested in an area where a ≈45 m layer of soft Blue Clay (BC) overlies the harder limestone. Three array configurations (two arrays of 17 geophones in an L-shape and circle respectively and one 42 geophone array in an L-shape) were tested and processed using the f-k and two SPAC techniques: Modified and Extended SPAC. No significant difference was observed in the dispersion curve from the two short arrays despite having different shapes. However, a significant variation was observed between the dispersion curve from the long and short arrays in the low frequency part. A joint inversion, using two direct search methods, of the dispersion and the H/V curve was then used to obtain the Vs profile for the site, with most of the profiles being in agreement both in terms of velocity and depth. A study was also conducted at three other sites on Malta where hard Upper Coralline Limestone (UCL) overlies the soft BC creating a velocity inversion in the soil profile. The shape of the effective dispersion curves obtained using ESAC show both an inverse dispersive trend and normal dispersion. This shape is tentatively explained in terms of the presence of higher mode Rayleigh waves. A Genetic Algorithm approach was then used to jointly invert the H/V and Rayleigh wave dispersion curve. It was observed that the BC velocity was higher when overlain by a large thickness of UCL. This could be linked to the effective pressure caused by the hard UCL, making the BC more compact, and having a higher velocity. The theoretical implications of a prominent low-velocity layer on site amplification and the interpretation of ambient noise data are investigated and discussed.

  16. Concentrations of PM 10, PM 2.5, and PM 1 influenced by atmospheric circulation and atmospheric boundary layer in the Korean mountainous coast during a duststorm

    NASA Astrophysics Data System (ADS)

    Choi, Hyo; Choi, Doo Sun

    2008-09-01

    Particle size concentrations of 100 ng m - 3 to 203" in the main text were changed to "100 ng m- 3". Please check if appropriate.--> μg m - 3 were measured at two sampling points over the eastern coastal region of Korea by two GRIMM aerosol samplers from March 7-17, 2004. One sampling point was located on the western upwind side of the mountains, and the other sampling point was located in the city of Kangnung in the coastal basin downwind and adjacent to the East Sea. Concentrations of PM 10, PM 2.5, and PM 1 were measured near the ground in Kangnung on March 8, 2004, until 1200 LST before the passage of a duststorm. Values of about 40, 35, and 30 μg m - 3 , respectively, were detected indicating little variation among sample concentrations. Before the duststorm, maximum concentrations for PM 10 occurred around 0800 and 1700 LST due to increased fuel combustion from road vehicles. From the afternoon of March 10-16 when the largest amount of dust from China had passed over Kangnung under the influence of a westerly wind, PM 10 concentration reached 340 μg m - 3 , and PM 2.5 and PM 1 concentrations reached 105 μg m - 3 and 60 μg m - 3 , respectively, indicating double the PM 10 concentration as compared to PM 2.5. Most of the dust transported from China consisted of particle sizes larger than PM 2.5 and PM 1. Dust transported from the western, upwind side of the mountains combined with the particulates emitted from road vehicles and industrial and residential boilers in the city after sunrise under the influence of westerly winds resulted in a high particulate concentration at 0900 LST. However, a low concentration of particulates in the city was detected near 1200 LST due to changes in the structure of the atmospheric boundary layer, while a high concentration over the mountains occurred due to a stable layer. High-particulate concentrations in the city occurred again after 1700 LST owing to increased fuel combustion from road vehicles and residential boilers

  17. Influence of Al{sub 2}O{sub 3} layer insertion on the electrical properties of Ga-In-Zn-O thin-film transistors

    SciTech Connect

    Kurishima, Kazunori; Nabatame, Toshihide; Shimizu, Maki; Mitoma, Nobuhiko; Kizu, Takio; Aikawa, Shinya; Tsukagoshi, Kazuhito; Ohi, Akihiko; Chikyow, Toyohiro; Ogura, Atsushi

    2015-11-15

    To investigate the influence of ionic/covalent interface of Al{sub 2}O{sub 3}/SiO{sub 2} gate insulator on the electrical properties of thin-film transistors (TFTs) with ionic Ga-In-Zn-O (GIZO) semiconducting channel layers, Al{sub 2}O{sub 3} layers of different thickness were introduced between SiO{sub 2} and GIZO using plasma-enhanced atomic layer deposition. The GIZO layers were obtained by DC magnetron sputtering using a GIZO target (Ga:In:Zn = 1:1:1 mol. %). The GIZO TFTs with an Al{sub 2}O{sub 3}/SiO{sub 2} gate insulator exhibited positive threshold voltage (V{sub th}) shift (about 1.1 V), V{sub th} hysteresis suppression (0.23 V), and electron mobility degradation (about 13%) compared with those of a GIZO TFT with SiO{sub 2} gate insulator by the influence of ionic/ionic and ionic/covalent interface at Al{sub 2}O{sub 3}/GIZO and Al{sub 2}O{sub 3}/SiO{sub 2}, respectively. To clarify the origin of the positive V{sub th} shift, the authors estimated the shifts of flatband voltage (0.4 V) due to the dipole and the fixed charge (−1.1 × 10{sup 11}/cm{sup 2}) at Al{sub 2}O{sub 3}/SiO{sub 2} interface, from capacitance–voltage data for Pt/Al{sub 2}O{sub 3}/SiO{sub 2}/p-Si capacitors. Based on these experimental data, the authors found that the positive V{sub th} shift (1.1 V) could be divided into three components: the dipole (−0.4 V) and fixed charge (0.15 V) at the SiO{sub 2}/Al{sub 2}O{sub 3} interface, and the fixed charge (1.35 V) at the Al{sub 2}O{sub 3}/GIZO interface. Finally, it is noted that heterointerface of SiO{sub 2}/Al{sub 2}O{sub 3}/GIZO stacks is important not only to recognize mechanism of V{sub th} shift but also to design future TFTs with high-k dielectrics and low operating voltage.

  18. The Influence of Vegetation Canopy Structure on Active Layer Thaw Within the Sub-Arctic Discontinuous Permafrost Zone

    NASA Astrophysics Data System (ADS)

    Chasmer, L.; Quinton, W.; Hopkinson, C.; Petrone, R.; Whittington, P.

    2009-05-01

    Much of the sub-arctic discontinuous permafrost zone is dominated by a range in peatland ecosystems, each with their own characteristic soil frost dynamics. Soil thaw within the discontinuous permafrost zones of the Canadian sub-arctic is driven by the surface energy balance. The following study examines the influence of canopy structure on frost table (FT) depth and rates of thaw by: 1. relating measurements of FT depth to canopy structure using airborne scanning light detection and ranging (lidar) and hemispherical photographs taken below vegetated canopies; and 2. quantifying the spatial influences of canopy structural characteristics on the radiation balance (direct and diffuse incident radiation) within raised peat plateaus, connected bogs, fens, and isolated bogs. The results of this study indicate that peat plateaus, being characterised by greater vegetation fractional cover, typically have shallower FT depths (r2 = 0.5, p = 0.03) than locations with lower biomass. Further, average ground surface elevation and canopy height are related to rates of FT thaw (r2 = 0.73, p < 0.01; and r2 = 0.22, p = 0.2, respectively). Within the larger basin, variability in the spatial extent of vegetation biomass has an important influence on cumulative direct and diffuse radiation incident on the ground surface, especially in areas where peat plateaus are adjacent to open fens, connected bogs, and isolated bogs. This indicates that rates of thaw at the edges of peat plateaus and areas surrounding isolated bogs will be exacerbated by increased incident radiation and less shadowing by the canopy, leading to the conversion of peat plateaus to fens or bogs. This hypothesis is tested by comparing the change in peat plateau area coverage in 2000 and 2008 using classified IKONOS imagery (2000) and airborne lidar (2008).

  19. Influence of topological defects on the structure of G and D spectral bands of a single-layer carbon nanotube

    NASA Astrophysics Data System (ADS)

    Ten, G. N.; Glukhova, O. E.; Slepchenkov, M. M.; Bobrinetskii, I. I.; Ibragimov, R. A.; Fedorov, G. E.; Baranov, V. I.

    2016-05-01

    A topological defect in a carbon nanotube grown by chemical vapor deposition from methane onto a silicon substrate with thermal oxide has been investigated and visualized (with a resolution of about 1.5 μm) by confocal Raman spectroscopy. Vibrational Raman spectra of molecular fragments of a single-wall carbon nanotube (SWCNT) without a defect and with Stone-Wales defects (two pentagonal and two heptagonal cells) are calculated. The influence of defects on the shape of G-band components (G+ and G-), which makes it possible to determine the nanotube conductivity type, is considered.

  20. Influence of the Aure valley on the boundary-layer features observed during the BLLAST experimental field campaign

    NASA Astrophysics Data System (ADS)

    Jimenez, Maria A.; Cuxart, Joan; Martinez-Villagrasa, Daniel

    2016-04-01

    Under clear-skies and weak-synoptic pressure gradients, the organization of the flow at lower levels is mainly controlled by the local effects, such as terrain or surface heterogeneities. This is the case of the thermal differences between the air adjacent to the slopes, within a valley and over the nearby plains that generate slope, valley and mountain winds with an opposite direction between day and night. The Aure valley, located at the north of the Pyrenees with the main axis pointing to North, and the surrounding foothills are selected to study the temporal and spatial scales of the thermally-driven flows during the BLLAST experimental field campaign (June-July 2011). A combined inspection of the observations in Lannemezan (located over a plateau at about 5 km from the exit of the Aure valley) and high-resolution mesoscale simulations is used to evaluate the effect of the Aure valley on the boundary-layer characteristics over Lannemezan. The inspection of some selected IOPs (clear-skies, no rain) show that the interaction between the Aure valley and the Lannemezan plateau takes place depending on the direction and intensity of the large-scale wind, enhancing or diminishing the thermally-driven flow. During day, a convective boundary layer is formed with associated strong turbulence at the foothills, valleys and plain. However, during the night-time turbulence is in general weaker with some episodes of strong turbulence associated to wind shear related to the presence of the exit valley jet of the drainage winds. It is found that when large-scale winds are weak the exit valley jet reach Lannemezan close to midnight and interacts with the locally-generated downslope winds already present. It is found that IOP11 shows a Foehn effect in the valley, that is warmer than the plain, resulting in up-valley flows during the night. The BLLAST dataset is an useful tool to evaluate the performance of the mesoscale model in a complex region, such as the valleys and

  1. Modelisations des effets de surface sur les jets horizontaux subsoniques d'hydrogene et de methane

    NASA Astrophysics Data System (ADS)

    Gomez, Luis Fernando

    Le developpement des codes et de normes bases sur une methodologie scientifique requiert la capacite de predire l'etendue inflammable de deversements gazeux d'hydrogene sous differentes conditions. Des etudes anterieures ont deja etabli des modeles bases sur les lois de conservation de la mecanique des fluides basees sur des correlations experimentales qui permettent de predire la decroissance de la concentration et de la vitesse d'un gaz le long de l'axe d'un jet libre vertical. Cette etude s'interesse aux effets de proximite a une surface horizontale parallele sur un jet turbulent. Nous nous interessons a son impact sur l'etendue du champ de la concentration et sur l'enveloppe inflammable en particulier. Cette etude est comparative : l'hydrogene est compare au methane. Ceci permet de degager l'influence des effets de difference de la densite sur le comportement du jet, et de comparer le comportement de l'hydrogene aux correlations experimentales, qui ont ete essentiellement etablies pour le methane. Un modele decrivant l'evolution spatio-temporelle du champ de concentration du gaz dilue est propose, base sur la mecanique des fluides computationnelle. Cette approche permet de varier systematiquement les conditions aux frontieres (proximite du jet a la surface, par exemple) et de connaitre en detail les proprietes de l'ecoulement. Le modele est implemente dans le code de simulations par volumes finis de FLUENT. Les resultats des simulations sont compares avec les lois de similitudes decoulant de la theorie des jets d'ecoulements turbulents libres ainsi qu'avec les resultats experimentaux disponibles. L'effet de la difference des masses molaires des constituantes du jet et des constituantes du milieu de dispersion est egalement etudie dans le contexte du comportement d'echelle de la region developpee du jet.

  2. Physical defect formation in few layer graphene-like carbon on metals: influence of temperature, acidity, and chemical functionalization.

    PubMed

    Schumacher, Christoph M; Grass, Robert N; Rossier, Michael; Athanassiou, Evagelos K; Stark, Wendelin J

    2012-03-06

    A systematical examination of the chemical stability of cobalt metal nanomagnets with a graphene-like carbon coating is used to study the otherwise rather elusive formation of nanometer-sized physical defects in few layer graphene as a result of acid treatments. We therefore first exposed the core-shell nanomaterial to well-controlled solutions of altering acidity and temperature. The release of cobalt into these solutions over time offered a simple tool to monitor the progress of particle degradation. The results suggested that the oxidative damage of the graphene-like coatings was the rate-limiting step during particle degradation since only fully intact or entirely emptied carbon shells were found after the experiments. If ionic noble metal species were additionally present in the acidic solutions, the noble metal was found to reduce on the surface of specific, defective particles. The altered electrochemical gradients across the carbon shells were however not found to lead to a faster release of cobalt from the particles. The suggested mechanistic insight was further confirmed by the covalent chemical functionalization of the particle surface with chemically inert aryl species, which leads to an additional thickening of the shells. This leads to reduced cobalt release rates as well as slower noble metal reduction rates depending on the augmentation of the shell thickness.

  3. Influence of the ionomer/carbon ratio for low-Pt loading catalyst layer prepared by reactive spray deposition technology

    NASA Astrophysics Data System (ADS)

    Yu, Haoran; Roller, Justin M.; Mustain, William E.; Maric, Radenka

    2015-06-01

    Proton exchange membrane fuel cell (PEMFC) catalyst layers (CLs) were fabricated by direct deposition of the catalyst onto Nafion® membranes using reactive spray deposition technique (RSDT) to reduce platinum (Pt) loading and reduce the number of catalyst synthesis and processing steps. Nitrogen adsorption, mercury porosimetry, and scanning electron microscopy (SEM) were used to investigate the effects of ionomer/carbon ratio (I/C) on the surface area, pore structure and morphology of the CLs; cyclic voltammetry and polarization curves were used to determine the electrochemically active area (ECSA) and PEMFC performance. The BET surface area and pore volume of the CLs decreased continuously with increasing I/C ratio regardless of the catalyst loading. Bimodal distribution of pores with diameters ranging from 1.7 to 10 nm and from 30 to 100 nm were observed from the pore-size distribution of the CLs. The catalyst-coated membrane (CCM) with an I/C ratio of 0.3 showed the highest ECSA of 62 m2 gPt-1 and the best performance at 0.6 V for oxygen (1400 mA cm-2) and air (650 mA cm-2) among all RSDT samples. The optimum I/C ratio is lower compared to ink-based methods, and Pt nanoparticles showed improved distribution on the carbon surface. The RSDT process shows promise in achieving better ionomer coverage and penetration in the CL microstructure, enhancing the performance of low Pt-loading PEMFCs.

  4. Influence of UV and visible laser light on the structure and composition of layered organic - inorganic zinc and copper nanocomposites

    SciTech Connect

    Borodina, T I; Val'yano, G E; Gololobova, O A; Karpukhin, Vyacheslav T; Malikov, Mikhail M; Strikanov, D A

    2013-06-30

    The effect of UV and visible laser light on the structure and composition of layered organic-inorganic nanocomposites of transition metals, zinc [zinc hydroxide/dodecyl sulfate, Zn(OH){sub 2}DS] and copper [copper hydroxide/dodecyl sulfate, Cu{sub 2}(OH){sub 3}DS], has been experimentally investigated. Nanocomposites have been synthesised by laser ablation of targets from the aforementioned materials in aqueous solutions of a surfactant: sodium dodecyl sulfate (SDS). The absorption and Raman spectra of the thus obtained colloids are analysed. The structural composition and morphology of the solid phase isolated from the colloids are determined using X-ray diffraction, atomic-force microscopy, and scanning electron microscopy. It is shown that exposure of nanocomposites to UV and visible laser light with intensities in the range of 5 Multiplication-Sign 10{sup 5}-10{sup 7} W cm{sup -2} or higher leads to their fragmentation and change in their composition. (optical nanostructures)

  5. Influences of internal resistance and specific surface area of electrode materials on characteristics of electric double layer capacitors

    NASA Astrophysics Data System (ADS)

    Suda, Yoshiyuki; Mizutani, Akitaka; Harigai, Toru; Takikawa, Hirofumi; Ue, Hitoshi; Umeda, Yoshito

    2017-01-01

    We fabricated electric double layer capacitors (EDLCs) using particulate and fibrous types of carbon nanomaterials with a wide range of specific surface areas and resistivity as an active material. The carbon nanomaterials used in this study are carbon nanoballoons (CNBs), onion-like carbon (OLC), and carbon nanocoils (CNCs). A commercially used activated carbon (AC) combined with a conductive agent was used as a comparison. We compared the EDLC performance using cyclic voltammetry (CV), galvanostatic charge/discharge testing, and electrochemical impedance spectroscopy (EIS). OLC showed a poor EDLC performance, although it has the lowest resistivity among the carbon nanomaterials. CNB, which has a 1/16 lower specific surface area than AC but higher specific surface area than CNC and OLC, had a higher specific capacitance than CNC and OLC. Moreover, at current densities of 1.5 Ag-1 and larger, the specific capacitance of the EDLC using CNB was almost the same as that using AC. Electrochemical impedance spectroscopy of the EDLCs revealed that the CNB and CNC electrodes had a much lower internal resistance than the AC electrode, which correlated with a low capacitance maintenance factor as the current density increased.

  6. Influence of surface chemistry on the structural organization of monomolecular protein layers adsorbed to functionalized aqueous interfaces.

    PubMed Central

    Lösche, M; Piepenstock, M; Diederich, A; Grünewald, T; Kjaer, K; Vaknin, D

    1993-01-01

    The molecular organization of streptavidin (SA) bound to aqueous surface monolayers of biotin-functionalized lipids and binary lipid mixtures has been investigated with neutron reflectivity and electron and fluorescence microscopy. The substitution of deuterons (2H) for protons (1H), both in subphase water molecules and in the alkyl chains of the lipid surface monolayer, was utilized to determine the interface structure on the molecular length scale. In all cases studied, the protein forms monomolecular layers underneath the interface with thickness values of approximately 40 A. A systematic dependence of the structural properties of such self-assembled SA monolayers on the surface chemistry was observed: the lateral protein density depends on the length of the spacer connecting the biotin moiety and its hydrophobic anchor. The hydration of the lipid head groups in the protein-bound state depends on the dipole moment density at the interface. Images FIGURE 1 FIGURE 2 FIGURE 3 FIGURE 5 FIGURE 11 FIGURE 12 FIGURE A1 PMID:8298041

  7. Influence of erythrocyte aggregation at pathological levels on cell-free marginal layer in a narrow circular tube.

    PubMed

    Namgung, Bumseok; Sakai, Hiromi; Kim, Sangho

    2015-01-01

    Human red blood cells (RBCs) were perfused in a circular micro-tube (inner diameter of 25 μm) to examine the dynamic changes of cell-free marginal region at both physiological (normal) and pathophysiological (hyper) levels of RBC aggregation. The cell-free area (CFA) was measured to provide additional information on the cell-free layer (CFL) width changes in space and time domains. A prominent enhancement in the mean CFL width was found in hyper-aggregating conditions as compared to that in non-aggregating conditions (P <  0.001). The frequent contacts between RBC and the tube wall were observed and the contact frequency was greatly decreased when the aggregation level was increased from none to normal (P <  0.05) and to hyper (P <  0.001) levels. In addition, the enhanced aggregation from none to hyper levels significantly enlarged the CFA (P <  0.01). We concluded that the RBC aggregation at pathophysiological levels could promote not only the CFL width (one-dimensional parameter) but also the spatiotemporal variation of CFA (two-dimensional parameter).

  8. Multiple layers of regulation influence cell integrity control by the PKC ortholog Pck2 in fission yeast.

    PubMed

    Madrid, Marisa; Jiménez, Rafael; Sánchez-Mir, Laura; Soto, Teresa; Franco, Alejandro; Vicente-Soler, Jero; Gacto, Mariano; Pérez, Pilar; Cansado, José

    2015-01-15

    The fission yeast protein kinase C (PKC) ortholog Pck2 controls cell wall synthesis and is a major upstream activator of the cell integrity pathway (CIP) and its core component, the MAP kinase Pmk1 (also known as Spm1), in response to environmental stimuli. We show that in vivo phosphorylation of Pck2 at the conserved T842 activation loop during growth and in response to different stresses is mediated by the phosphoinositide-dependent kinase (PDK) ortholog Ksg1 and an autophosphorylation mechanism. However, T842 phosphorylation is not essential for Pmk1 activation, and putative phosphorylation at T846 might play an additional role in Pck2 catalytic activation and downstream signaling. These events, together with turn motif autophosphorylation at T984 and binding to small GTPases Rho1 and/or Rho2, stabilize Pck2 and render it competent to exert its biological functions. Remarkably, the target of rapamycin complex 2 (TORC2) does not participate in the catalytic activation of Pck2, but instead contributes to de novo Pck2 synthesis, which is essential to activate the CIP in response to cell wall damage or glucose exhaustion. These results unveil a novel mechanism whereby TOR regulates PKC function at a translational level, and they add a new regulatory layer to MAPK signaling cascades. © 2015. Published by The Company of Biologists Ltd.

  9. Influence of inclined Lorentz forces on boundary layer flow of Casson fluid over an impermeable stretching sheet with heat transfer

    NASA Astrophysics Data System (ADS)

    Abdul Hakeem, A. K.; Renuka, P.; Vishnu Ganesh, N.; Kalaivanan, R.; Ganga, B.

    2016-03-01

    The inclined magnetic field effect on the boundary layer flow of a Casson model non-Newtonian fluid over a stretching sheet in the existence of thermal radiation and velocity slip boundary condition is investigated for both prescribed surface temperature and power law of surface heat flux cases. It is assumed that the magnetic field is applied with an aligned angle which varied from 0° to 90°. Both analytical and numerical solutions are obtained for the transformed non-dimensional ODE's using confluent hypergeometric function and fourth order Runge-Kutta method with shooting technique respectively. The combined effects of inclined magnetic field with other pertinent parameters such as Casson parameter, velocity slip parameter, radiation parameter and Prandtl number on velocity profile, temperature profile, local skin friction coefficient, local Nusselt number and non-dimensional wall temperature are discussed through graphs. It is found that the aligned angle plays a vital role in controlling the magnetic field strength on the Casson fluid flow region and the increasing values of aligned angle of the magnetic field lead to decrease the skin friction coefficient and the Nusselt number and increase the non-dimensional wall temperature.

  10. The influence of tertiary butyl hydrazine as a co-reactant on the atomic layer deposition of silver

    NASA Astrophysics Data System (ADS)

    Golrokhi, Zahra; Marshall, Paul A.; Romani, Simon; Rushworth, Simon; Chalker, Paul R.; Potter, Richard J.

    2017-03-01

    Ultra-thin conformal silver films are the focus of development for applications such as anti-microbial surfaces, optical components and electronic devices. In this study, metallic silver films have been deposited using direct liquid injection thermal atomic layer deposition (ALD) using (hfac)Ag(1,5-COD) ((hexafluoroacetylacetonato)silver(I)(1,5-cyclooctadiene)) as the metal source and tertiary butyl hydrazine (TBH) as a co-reactant. The process provides a 23 °C wide 'self-limiting' ALD temperature window between 105 and 128 °C, which is significantly wider than is achievable using alcohol as a co-reactant. A mass deposition rate of ∼20 ng/cm2/cycle (∼0.18 Å/cycle) is observed under self-limiting growth conditions. The resulting films are crystalline metallic silver with a near planar film-like morphology which are electrically conductive. By extending the temperature range of the ALD window by the use of TBH as a co-reactant, it is envisaged that the process will be exploitable in a range of new low temperature applications.

  11. Internal flow numerical simulation of double-suction centrifugal pump using DES model

    NASA Astrophysics Data System (ADS)

    Zhou, P. J.; Wang, F. J.; Yang, M.

    2012-11-01

    It is a challenging task for the flow simulation for a double-suction centrifugal pump, because the wall effects are strong in this type of pumps. Detached-eddy simulation (DES), referred as a hybrid RANS-LES approach, has emerged recently as a potential compromise between RANS based turbulence models and Large Eddy Simulation. In this approach, the unsteady RANS model is employed in the boundary layer, while the LES treatment is applied to the separated region. In this paper, S-A DES method and SST k-ω DES method are applied to the numerical simulation for the 3D flow in whole passage of a double-suction centrifugal pump. The unsteady flow field including velocity and pressure distributions is obtained. The head and efficiency of the pump are predicted and compared with experimental results. According to the calculated results, S-A DES model is easy to control the partition of the simulation when using near wall grid with 30 < y+<300 control approach. It also has better performance on efficiency and accuracy than SST k - ω DES method. S-A DES method is more suitable for solving the unsteady flow in double-suction centrifugal pump. S-A DES method can capture more flow phenomenon than SST k - ω DES method. In addition, it can accurately predict the power performance under different flow conditions, and can reflect pressure fluctuation characteristics.

  12. La participation des enfants et des adolescents à la boxe

    PubMed Central

    Purcell, Laura K; LeBlanc, Claire MA

    2012-01-01

    RÉSUMÉ Des milliers de garçons et de filles de moins de 19 ans font de la boxe en Amérique du Nord. Même si la boxe comporte des avantages pour ceux qui y participent, y compris l’exercice, l’autodiscipline et la confiance en soi, le sport lui-même favorise et récompense des coups délibérés à la tête et au visage. Les personnes qui font de la boxe risquent de subir des blessures à la tête, au visage et au cou, y compris des traumatismes neurologiques chroniques et même fatals. Les commotions cérébrales sont l’une des principales blessures causées par la boxe. En raison du risque de blessures crâniennes et faciales, la Société canadienne de pédiatrie et l’American Academy of Pediatrics s’opposent vigoureusement à la boxe comme activité sportive pour les enfants et les adolescents. Ces organismes recommandent que les médecins s’élèvent contre la boxe auprès des jeunes et les encouragent à participer à d’autres activités dans lesquelles les coups intentionnels à la tête ne constituent pas un élément essentiel du sport.

  13. Periodic bedforms generated by sublimation on terrestrial and martian ice sheets under the influence of the turbulent atmospheric boundary layer

    NASA Astrophysics Data System (ADS)

    Bordiec, Maï; Carpy, Sabrina; Perret, Laurent; Bourgeois, Olivier; Massé, Marion

    2017-04-01

    The redistribution of surface ice induced the wind flow may lead to the development and migration of periodic bedforms, or "ice ripples", at the surface of ice sheets. In certain cold and dry environments, this redistribution need not involve solid particle transport but may be dominated by sublimation and condensation, inducing mass transfers between the ice surface and the overlying steady boundary layer turbulent flow. These mass transfers diffuse the water vapour sublimated from the ice into the atmosphere and become responsible for the amplification and propagation of ripples in a direction perpendicular to their crests. Such ice ripples, 24 cm in wavelength, have been described in the so-called Blue Ice Areas of Antarctica. In order to understand the mechanisms that generate and develop these periodic bedforms on terrestrial glaciers and to evaluate the plausibility that similar bedforms may develop on Mars, we performed a linear stability analysis applied to a turbulent boundary layer flow perturbed by a wavy ice surface. The model is developed as follow. We first solve the flow dynamics using numerical methods analogous to those used in sand wave models assuming that the airflow is similar in both problems. We then add the transport/diffusion equation of water vapour following the same scheme. We use the Reynolds-averaged description of the equation with a Prandtl-like closure. We insert a damping term in the exponential formula of the Van Driest mixing length, depending on the pressure gradient felt by the flow and related to the thickness of the viscous sublayer at the ice-atmosphere interface. This formulation is an efficient way to properly represent the transitional regime under which the ripples grow. Once the mass flux of water vapour is solved, the phase shift between the ripples crests and the maximum of the flux can be deduced for different environments. The temporal evolution of the ice surface can be expressed from these quantities to infer the

  14. Influence of boundary layer dynamics and isoprene chemistry on the organic aerosol budget in a tropical forest

    NASA Astrophysics Data System (ADS)

    Janssen, R. H. H.; Vilà-Guerau de Arellano, J.; Jimenez, J. L.; Ganzeveld, L. N.; Robinson, N. H.; Allan, J. D.; Coe, H.; Pugh, T. A. M.

    2013-08-01

    We study the organic aerosol (OA) budget in a tropical forest by analyzing a case that is representative for the OP3 campaign at Borneo. A model is designed that combines the essential dynamical and chemical processes that drive the diurnal evolution of reactants in the atmospheric boundary layer (BL). In this way, the model simultaneously represents the effects and interactions of various dynamical and chemical factors on the OA budget. The model is able to reproduce the observed diurnal dynamics of the BL, including the evolution of most chemical species involved in secondary organic aerosol (SOA) formation. A budget analysis of the contributions of the dynamic and chemical processes reveals the significance of the entrainment process in the diurnal evolution of SOA. Further, we perform a series of sensitivity analyses to determine the effect of meteorological forcings and isoprene chemical pathways on the OA budget. Subsidence and advection of cool air have opposing effects on the OA concentration, although both suppress BL growth. Recycling of the OH radical in the oxidation of isoprene may affect the amount of SOA that is formed, but must be understood better before its impact can be definitely determined. SOA formation from isoprene is calculated for both the low- and high-NOx pathway, with the latter dominating the isoprene peroxy radical chemistry. Finally, we study the significance of SOA formation through the reactive uptake of isoprene epoxydiols on acidic sulfate aerosol. Despite the incorporation of these new pathways, the OA concentration is systematically underestimated by about a factor of 2.

  15. Influence of the voltage waveform during nanocomposite layer deposition by aerosol-assisted atmospheric pressure Townsend discharge

    SciTech Connect

    Profili, J.; Levasseur, O.; Stafford, L.; Naudé, N.; Gherardi, N.; Chaneac, C.

    2016-08-07

    This work examines the growth dynamics of TiO{sub 2}-SiO{sub 2} nanocomposite coatings in plane-to-plane Dielectric Barrier Discharges (DBDs) at atmospheric pressure operated in a Townsend regime using nebulized TiO{sub 2} colloidal suspension in hexamethyldisiloxane as the growth precursors. For low-frequency (LF) sinusoidal voltages applied to the DBD cell, with voltage amplitudes lower than the one required for discharge breakdown, Scanning Electron Microscopy of silicon substrates placed on the bottom DBD electrode reveals significant deposition of TiO{sub 2} nanoparticles (NPs) close to the discharge entrance. On the other hand, at higher frequencies (HF), the number of TiO{sub 2} NPs deposited strongly decreases due to their “trapping” in the oscillating voltage and their transport along the gas flow lines. Based on these findings, a combined LF-HF voltage waveform is proposed and used to achieve significant and spatially uniform deposition of TiO{sub 2} NPs across the whole substrate surface. For higher voltage amplitudes, in the presence of hexamethyldisiloxane and nitrous oxide for plasma-enhanced chemical vapor deposition of inorganic layers, it is found that TiO{sub 2} NPs become fully embedded into a silica-like matrix. Similar Raman spectra are obtained for as-prepared TiO{sub 2} NPs and for nanocomposite TiO{sub 2}-SiO{sub 2} coating, suggesting that plasma exposure does not significantly alter the crystalline structure of the TiO{sub 2} NPs injected into the discharge.

  16. Dipolar interactions and their influence on the critical single domain grain size of Ni in layered Ni/Al(2)O(3) composites.

    PubMed

    Das, R; Gupta, A; Kumar, D; Oh, S H; Pennycook, S J; Hebard, A F

    2008-09-24

    Pulsed laser deposition has been used to fabricate Ni/Al(2)O(3) multilayer composites in which Ni nanoparticles with diameters in the range of 3-60 nm are embedded as layers in an insulating Al(2)O(3) host. At fixed temperatures, the coercive fields plotted as a function of particle size show well-defined peaks, which define a critical size that delineates a crossover from coherently rotating single domain to multiple domain behavior. We observe a shift in peak position to higher grain size as temperature increases and describe this shift with theory that takes into account the decreasing influence of dipolar magnetic interactions from thermally induced random orientations of neighboring grains.

  17. Dipolar interactions and their influence on the critical single domain grain size of Ni in layered Ni/Al(2)O(3) composites

    SciTech Connect

    Das, R; Gupta, A.; Ho, S; Pennycook, Stephen J; Hebard, A.

    2008-01-01

    Pulsed laser deposition has been used to fabricate Ni/Al2O3 multilayer composites in which Ni nanoparticles with diameters in the range of 3 60 nm are embedded as layers in an insulating Al2O3 host. At fixed temperatures, the coercive fields plotted as a function of particle size show well-defined peaks, which define a critical size that delineates a crossover from coherently rotating single domain to multiple domain behavior. We observe a shift in peak position to higher grain size as temperature increases and describe this shift with theory that takes into account the decreasing influence of dipolar magnetic interactions from thermally induced random orientations of neighboring grains.

  18. Influence of surface static-pressure orifices on boundary-layer transition. [tests conducted in the Langley Low-Turbulence Pressure Tunnel

    NASA Technical Reports Server (NTRS)

    Somers, D. M.; Stack, J. P.; Harvey, W. D.

    1982-01-01

    An investigation of the interaction of a laminar boundary layer and surface static-pressure orifices was conducted on a natural laminar flow airfoil. The effects of both favorable and adverse pressure gradients were studied at Reynolds numbers based on airfoil chord from approximately 500,000 to 6,000,000 with Mach number varying accordingly from about 0.03 to 0.42. The smaller the diameter of the orifice, the less likely it will cause premature transition. Locating the orifices in a chord-wise row aligned with the flow appears to have an additive, adverse effect on transition. Tube length-to-orifice diameter ration does not seem to have a consistent influence on transition.

  19. The influence of process parameters and pulse ratio of precursors on the characteristics of La1 - x Al x O3 films deposited by atomic layer deposition

    NASA Astrophysics Data System (ADS)

    Fei, Chenxi; Liu, Hongxia; Wang, Xing; Fan, Xiaojiao

    2015-04-01

    The influence of processing parameters of aluminum oxide (Al2O3) and lanthanum oxide (La2O3) gate dielectric is investigated. Trimethylaluminum (TMA) and tris(isopropylcyclopentadienyl) lanthanum [La(iPrCp)3] were used as precursors separately, and H2O was used as oxidant. The ultra-thin La1 - x Al x O3 gate dielectric films are deposited on p-type silicon substrates by atom layer deposition (ALD) for different pulse ratios of precursors. Effects of different La/Al precursor pulse ratios on the physical properties and electrical characteristics of La1 - x Al x O3 films are studied. The preliminary testing results indicate that the increase of La precursor pulse can improve the characteristics of film, which has significant effects on the dielectric constant, equivalent oxide thickness (EOT), electrical properties, and stability of film.

  20. Influence of Layer Thickness and Raster Angle on the Mechanical Properties of 3D-Printed PEEK and a Comparative Mechanical Study between PEEK and ABS

    PubMed Central

    Wu, Wenzheng; Geng, Peng; Li, Guiwei; Zhao, Di; Zhang, Haibo; Zhao, Ji

    2015-01-01

    Fused deposition modeling (FDM) is a rapidly growing 3D printing technology. However, printing materials are restricted to acrylonitrile butadiene styrene (ABS) or poly (lactic acid) (PLA) in most Fused deposition modeling (FDM) equipment. Here, we report on a new high-performance printing material, polyether-ether-ketone (PEEK), which could surmount these shortcomings. This paper is devoted to studying the influence of layer thickness and raster angle on the mechanical properties of 3D-printed PEEK. Samples with three different layer thicknesses (200, 300 and 400 μm) and raster angles (0°, 30° and 45°) were built using a polyether-ether-ketone (PEEK) 3D printing system and their tensile, compressive and bending strengths were tested. The optimal mechanical properties of polyether-ether-ketone (PEEK) samples were found at a layer thickness of 300 μm and a raster angle of 0°. To evaluate the printing performance of polyether-ether-ketone (PEEK) samples, a comparison was made between the mechanical properties of 3D-printed polyether-ether-ketone (PEEK) and acrylonitrile butadiene styrene (ABS) parts. The results suggest that the average tensile strengths of polyether-ether-ketone (PEEK) parts were 108% higher than those for acrylonitrile butadiene styrene (ABS), and compressive strengths were 114% and bending strengths were 115%. However, the modulus of elasticity for both materials was similar. These results indicate that the mechanical properties of 3D-printed polyether-ether-ketone (PEEK) are superior to 3D-printed ABS. PMID:28793537

  1. Influence of Layer Thickness and Raster Angle on the Mechanical Properties of 3D-Printed PEEK and a Comparative Mechanical Study between PEEK and ABS.

    PubMed

    Wu, Wenzheng; Geng, Peng; Li, Guiwei; Zhao, Di; Zhang, Haibo; Zhao, Ji

    2015-09-01

    Fused deposition modeling (FDM) is a rapidly growing 3D printing technology. However, printing materials are restricted to acrylonitrile butadiene styrene (ABS) or poly (lactic acid) (PLA) in most Fused deposition modeling (FDM) equipment. Here, we report on a new high-performance printing material, polyether-ether-ketone (PEEK), which could surmount these shortcomings. This paper is devoted to studying the influence of layer thickness and raster angle on the mechanical properties of 3D-printed PEEK. Samples with three different layer thicknesses (200, 300 and 400 μm) and raster angles (0°, 30° and 45°) were built using a polyether-ether-ketone (PEEK) 3D printing system and their tensile, compressive and bending strengths were tested. The optimal mechanical properties of polyether-ether-ketone (PEEK) samples were found at a layer thickness of 300 μm and a raster angle of 0°. To evaluate the printing performance of polyether-ether-ketone (PEEK) samples, a comparison was made between the mechanical properties of 3D-printed polyether-ether-ketone (PEEK) and acrylonitrile butadiene styrene (ABS) parts. The results suggest that the average tensile strengths of polyether-ether-ketone (PEEK) parts were 108% higher than those for acrylonitrile butadiene styrene (ABS), and compressive strengths were 114% and bending strengths were 115%. However, the modulus of elasticity for both materials was similar. These results indicate that the mechanical properties of 3D-printed polyether-ether-ketone (PEEK) are superior to 3D-printed ABS.

  2. Numerical study of the influence of applied voltage on the current balance factor of single layer organic light-emitting diodes

    SciTech Connect

    Lu, Fei-ping Liu, Xiao-bin; Xing, Yong-zhong

    2014-04-28

    Current balance factor (CBF) value, the ratio of the recombination current density and the total current density of a device, has an important function in fluorescence-based organic light-emitting diodes (OLEDs), as well as in the performance of the organic electrophosphorescent devices. This paper investigates the influence of the applied voltage of a device on the CBF value of single layer OLED based on the numerical model of a bipolar single layer OLED with organic layer trap free and without doping. Results show that the largest CBF value can be achieved when the electron injection barrier (ϕ{sub n}) is equal to the hole injection barrier (ϕ{sub p}) in the lower voltage region at any instance. The largest CBF in the higher voltage region can be achieved in the case of ϕ{sub n} > ϕ{sub p} under the condition of electron mobility (μ{sub 0n}) > hole mobility (μ{sub 0p}), whereas the result for the case of μ{sub 0n} < μ{sub 0p}, is opposite. The largest CBF when μ{sub 0n} = μ{sub 0p} can be achieved in the case of ϕ{sub n} = ϕ{sub p} in the entire region of the applied voltage. In addition, the CBF value of the device increases with increasing applied voltage. The results obtained in this paper can present an in-depth understanding of the OLED working mechanism and help in the future fabrication of high efficiency OLEDs.

  3. Analysis of the substrate influence on the ordering of epitaxial molecular layers: The special case of point-on-line coincidence

    NASA Astrophysics Data System (ADS)

    Mannsfeld, S. C.; Fritz, T.

    2004-02-01

    The physical structure of organic-inorganic heteroepitaxial thin films is usually governed by a fine balance between weak molecule-molecule interactions and a weakly laterally varying molecule-substrate interaction potential. Therefore, in order to investigate the energetics of such a layer system one has to consider large molecular domains. So far, layer potential calculations for large domains of organic thin films on crystalline substrates were difficult to perform concerning the computational effort which stems from the vast number of atoms which have to be included. Here, we present a technique which enables the calculation of the molecule-substrate interaction potential for large molecular domains by utilizing potential energy grid files. This technique allows the investigation of the substrate influence in systems prepared by organic molecular beam epitaxy (OMBE), like 3,4,9,10-perylenetetracarboxylicdianhydride on highly oriented pyrolytic graphite. For this system the so-called point-on-line coincidence was proposed, a growth mode which has been controversially discussed in literature. Furthermore, we are able to provide evidence for a general energetic advantage of such point-on-line coincident domain orientations over arbitrarily oriented domains which substantiates that energetically favorable lattice structures in OMBE systems are not restricted to commensurate unit cells or coincident super cells.

  4. SiC layer microstructure in AGR-1 and AGR-2 TRISO fuel particles and the influence of its variation on the effective diffusion of key fission products

    NASA Astrophysics Data System (ADS)

    Gerczak, Tyler J.; Hunn, John D.; Lowden, Richard A.; Allen, Todd R.

    2016-11-01

    Tristructural isotropic (TRISO) coated particle fuel is a promising fuel form for advanced reactor concepts such as high temperature gas-cooled reactors (HTGR) and is being developed domestically under the US Department of Energy's Nuclear Reactor Technologies Initiative in support of Advanced Reactor Technologies. The fuel development and qualification plan includes a series of fuel irradiations to demonstrate fuel performance from the laboratory to commercial scale. The first irradiation campaign, AGR-1, included four separate TRISO fuel variants composed of multiple, laboratory-scale coater batches. The second irradiation campaign, AGR-2, included TRISO fuel particles fabricated by BWX Technologies with a larger coater representative of an industrial-scale system. The SiC layers of as-fabricated particles from the AGR-1 and AGR-2 irradiation campaigns have been investigated by electron backscatter diffraction (EBSD) to provide key information about the microstructural features relevant to fuel performance. The results of a comprehensive study of multiple particles from all constituent batches are reported. The observations indicate that there were microstructural differences between variants and among constituent batches in a single variant. Insights on the influence of microstructure on the effective diffusivity of key fission products in the SiC layer are also discussed.

  5. SiC layer microstructure in AGR-1 and AGR-2 TRISO fuel particles and the influence of its variation on the effective diffusion of key fission products

    DOE PAGES

    Gerczak, Tyler J.; Hunn, John D.; Lowden, Richard A.; ...

    2016-08-15

    Tristructural isotropic (TRISO) coated particle fuel is a promising fuel form for advanced reactor concepts such as high temperature gas-cooled reactors (HTGR) and is being developed domestically under the US Department of Energy’s Nuclear Reactor Technologies Initiative in support of Advanced Reactor Technologies. The fuel development and qualification plan includes a series of fuel irradiations to demonstrate fuel performance from the laboratory to commercial scale. The first irradiation campaign, AGR-1, included four separate TRISO fuel variants composed of multiple, laboratory-scale coater batches. The second irradiation campaign, AGR-2, included TRISO fuel particles fabricated by BWX Technologies with a larger coater representativemore » of an industrial-scale system. The SiC layers of as-fabricated particles from the AGR-1 and AGR-2 irradiation campaigns have been investigated by electron backscatter diffraction (EBSD) to provide key information about the microstructural features relevant to fuel performance. The results of a comprehensive study of multiple particles from all constituent batches are reported. The observations indicate that there were microstructural differences between variants and among constituent batches in a single variant. Finally, insights on the influence of microstructure on the effective diffusivity of key fission products in the SiC layer are also discussed.« less

  6. SiC layer microstructure in AGR-1 and AGR-2 TRISO fuel particles and the influence of its variation on the effective diffusion of key fission products

    SciTech Connect

    Gerczak, Tyler J.; Hunn, John D.; Lowden, Richard A.; Allen, Todd R.

    2016-08-15

    Tristructural isotropic (TRISO) coated particle fuel is a promising fuel form for advanced reactor concepts such as high temperature gas-cooled reactors (HTGR) and is being developed domestically under the US Department of Energy’s Nuclear Reactor Technologies Initiative in support of Advanced Reactor Technologies. The fuel development and qualification plan includes a series of fuel irradiations to demonstrate fuel performance from the laboratory to commercial scale. The first irradiation campaign, AGR-1, included four separate TRISO fuel variants composed of multiple, laboratory-scale coater batches. The second irradiation campaign, AGR-2, included TRISO fuel particles fabricated by BWX Technologies with a larger coater representative of an industrial-scale system. The SiC layers of as-fabricated particles from the AGR-1 and AGR-2 irradiation campaigns have been investigated by electron backscatter diffraction (EBSD) to provide key information about the microstructural features relevant to fuel performance. The results of a comprehensive study of multiple particles from all constituent batches are reported. The observations indicate that there were microstructural differences between variants and among constituent batches in a single variant. Finally, insights on the influence of microstructure on the effective diffusivity of key fission products in the SiC layer are also discussed.

  7. Growth and characterization of Escherichia coli DH5α biofilm on concrete surfaces as a protective layer against microbiologically influenced concrete deterioration (MICD).

    PubMed

    Soleimani, Sahar; Ormeci, Banu; Isgor, O Burkan

    2013-02-01

    Biofilms of selected bacteria strains were previously used on metal coupons as a protective layer against microbiologically influenced corrosion of metals. Unlike metal surfaces, concrete surfaces present a hostile environment for growing a protective biofilm. The main objective of this research was to investigate whether a beneficial biofilm can be successfully grown on mortar surfaces. Escherichia coli DH5α biofilm was grown on mortar surfaces for 8 days, and the structure and characteristics of the biofilm were studied using advanced microscopy techniques such as scanning electron microscopy and confocal laser scanning micro