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1

Structured luminescence conversion layer  

DOEpatents

An apparatus device such as a light source is disclosed which has an OLED device and a structured luminescence conversion layer deposited on the substrate or transparent electrode of said OLED device and on the exterior of said OLED device. The structured luminescence conversion layer contains regions such as color-changing and non-color-changing regions with particular shapes arranged in a particular pattern.

Berben, Dirk; Antoniadis, Homer; Jermann, Frank; Krummacher, Benjamin Claus; Von Malm, Norwin; Zachau, Martin

2012-12-11

2

Original article Tree canopy and herb layer transpiration in three Scots  

E-print Network

Original article Tree canopy and herb layer transpiration in three Scots pine stands with different - To evaluate the impact of herb layer structure on the transpiration of Scots pine ecosystems in north-eastern Germany, we measured tree canopy and herb layer transpiration in three stands. Parameters of tree

Paris-Sud XI, Université de

3

Three Possible Origins for the Gas Layer on Gj 1214b  

E-print Network

We present an analysis of the bulk composition of the MEarth transiting super-Earth exoplanet GJ 1214b using planet interior structure models. We consider three possible origins for the gas layer on GJ 1214b: direct accretion ...

Rogers, Leslie Anne

4

The Layered Structure of The Universe  

NASA Astrophysics Data System (ADS)

It has now become a habit for the cosmologists to introduce attraction or repulsion generating substances to describe the observed cosmological behavior of matter. Examples are dark energy to provide repulsive force to cause increasing acceleration accompanying the expansion of the universe, quintessence providing repulsive force. In this paper we believe that what is needed in the final analysis is attraction and repulsion. We show here that universe can be conceived to consist of attractive and repulsive layers of matter expanding with increasing acceleration. The generalized theory of gravitation as developed originally by Einstein and Schrödinger as a non-symmetric theory was modified by this author using Bianchi-Einstein Identities yielding coupling between the field and electric charge as well as between the field and magnetic charge, and there appears a fundamental length parameter ro where quintessence constitute magnetic repulsive layers while dark energy and all other kinds of names invented by cosmologists refer to attractive electric layers. This layered structure of the universe resembles the layered structure of the elementary particle predicted by this theory decades ago (1, 3, and 6). This implies a layer Doughnut structure of the universe. We have therefore, obtained a unification of the structure of the universe and the structure of elementary particles. Overall the forces consist of long range attractive, long range repulsive, short-range attractive, and short-range repulsive variety. We further discovered the existence of space oscillations whose roles in the expansion of the universe with increasing acceleration and further the impact in the propagation of the gravitational waves can be expected to play a role in their observation.

Kursunoglu, Behram N.

2003-06-01

5

Buffer layer for thin film structures  

DOEpatents

A composite structure including a base substrate and a layer of a mixture of strontium titanate and strontium ruthenate is provided. A superconducting article can include a composite structure including an outermost layer of magnesium oxide, a buffer layer of strontium titanate or a mixture of strontium titanate and strontium ruthenate and a top-layer of a superconducting material such as YBCO upon the buffer layer.

Foltyn, Stephen R.; Jia, Quanxi; Arendt, Paul N.; Wang, Haiyan

2006-10-31

6

Buffer layer for thin film structures  

DOEpatents

A composite structure including a base substrate and a layer of a mixture of strontium titanate and strontium ruthenate is provided. A superconducting article can include a composite structure including an outermost layer of magnesium oxide, a buffer layer of strontium titanate or a mixture of strontium titanate and strontium ruthenate and a top-layer of a superconducting material such as YBCO upon the buffer layer.

Foltyn, Stephen R.; Jia, Quanxi; Arendt, Paul N.; Wang, Haiyan

2010-06-15

7

Structurized surface layers of normal alkanes  

NASA Astrophysics Data System (ADS)

The elevated viscosity of micron interlayers of certain normal alkanes compared to their viscosity in the "volume" is determined experimentally in shear flow using a rotational viscometer. The observed difference is considered to be caused by the manifestation, in such interlayers, of structural inhomogeneity due to the presence of structurized polymolecular surface layers on the substrates bounding them. The structural parameters of such layers, i.e., their equilibrium initial thickness and "hydrodynamic strength," are calculated in the model of a constant-viscosity layer. The measured effective viscosity of the interlayers diminishes with growth in the shear-flow velocity, which is attributed to the "cutting" of the structurized layer. Surfactant doping of the liquids leads to an increase in the effective viscosity of the interlayers, which is produced by the strengthening of the layer structure.

Altoiz, B. A.; Kiriyan, S. V.

2010-07-01

8

The origin of rhythmic layering in the Cape Neddick Plutonic Complex, Maine  

SciTech Connect

The Cape Neddick Plutonic Complex located along the southwestern coast of Maine is a small layered gabbroic body. It contains four concentric gabbros of differing composition, From the center to the exterior these are Cortlandtitic, Anorthositic, Normal, and Pegmatitic gabbros. They vary slightly in the proportion of essential minerals; plagioclase, clinopyroxene, hornblende, and biotite [+-] opaques and olivine. Rhythmic layering is seen in all four gabbros. This layering is also concentric around the center of the complex. The best exposure of the layering is along the coast where non-graded and graded rhythmic layering is seen extensively in the Normal gabbro. Only non-graded layering is seen in the Anorthositic gabbro. Non-graded layers were sampled at two localities. One locality is on Cape Nubble Island in the Normal gabbro. The second locality is in the Anorthositic gabbro along the northern coast. The layers are roughly 5--8 cm in width and are continuous around the complex. They are identified on weathered surfaces as alternating bands of felsic and mafic minerals. Layers are not obvious in hand sample. Approximately 15--20 layers were sampled perpendicular to layering. Petrographic and geochemical studies will help constrain the origin of rhythmic layering in the Cape Neddick Complex. Crystal settling or structural processes seem highly unlikely due to the small distance between the layers and the fact that they are not graded. Possible models include multiple pulses of magma within the same magma chamber, density currents, or in situ fractionation by a nucleation-diffusion process. Modal and chemical analysis of mineral phases within individual layers will allow comparison of the bulk composition of each layer. Analysis of coexisting pyroxene and plagioclase can be used to estimate compositional variations in the parent liquid.

Shipley, J. (Hartwick Coll., Oneonta, NY (United States). Dept. of Geology)

1993-03-01

9

Turbulence structure in a hypersonic boundary layer  

NASA Astrophysics Data System (ADS)

This dissertation provides new insights into the structure of compressible turbulent boundary layers in the hypersonic regime. Previous studies of compressible turbulent boundary layers have indicated that subtle differences may exist between subsonic and supersonic layers with respect to their structure angles, length scales, and intermittency functions. It was believed that a study at hypersonic speeds would provide information on characteristic differences attributable to Mach number effects. Towards this goal, a Mach 8 wind tunnel with a 9' axisymmetric test section was built at the Gas Dynamics Laboratory at Princeton University. The Mach 8 facility can produce flows with stagnation temperatures up to 1050 F (840 K) and stagnation pressures up to 1300 psi (9 MPa). Unit Reynolds numbers obtainable in the facility range from 3×106/m to 20×106/m. The focus of this dissertation is the zero-pressure- gradient hypersonic turbulent boundary layer on a flat plate. Mean pitot pressure and stagnation temperature surveys of the boundary layer at a Reynolds number Re/sb/theta/approx 3600 under moderately cold wall boundary conditions were performed and compared with theoretical predictions and previous experiments. Cross-sectional images of a hypersonic turbulent boundary layer were produced using filtered Rayleigh scattering to study the instantaneous structure of the boundary layer (previous visualizations of hypersonic boundary layers have relied on shadow-graph or schlieren techniques). The resulting images provided qualitative and quantitative information about turbulent structure which were then compared with those of sub- and supersonic data.

Baumgartner, Mark Lawrence

1997-10-01

10

The kinematics of turbulent boundary layer structure  

NASA Technical Reports Server (NTRS)

The long history of research into the internal structure of turbulent boundary layers has not provided a unified picture of the physics responsible for turbulence production and dissipation. The goals of the present research are to: (1) define the current state of boundary layer structure knowledge; and (2) utilize direct numerical simulation results to help close the unresolved issues identified in part A and to unify the fragmented knowledge of various coherent motions into a consistent kinematic model of boundary layer structure. The results of the current study show that all classes of coherent motion in the low Reynolds number turbulent boundary layer may be related to vortical structures, but that no single form of vortex is representative of the wide variety of vortical structures observed. In particular, ejection and sweep motions, as well as entrainment from the free-streem are shown to have strong spatial and temporal relationships with vortical structures. Disturbances of vortex size, location, and intensity show that quasi-streamwise vortices dominate the buffer region, while transverse vortices and vortical arches dominate the wake region. Both types of vortical structure are common in the log region. The interrelationships between the various structures and the population distributions of vortices are combined into a conceptual kinematic model for the boundary layer. Aspects of vortical structure dynamics are also postulated, based on time-sequence animations of the numerically simulated flow.

Robinson, Stephen Kern

1991-01-01

11

Structure of the low latitude boundary layer  

NASA Technical Reports Server (NTRS)

Observations at high temporal resolution of the frontside magnetopause and plasma boundary layer, made with the LASL/MPE fast plasma analyzer onboard the ISEE 1 and 2 spacecraft, revealed a complex quasiperiodic structure of some of the observed boundary layers. A cool tailward streaming boundary layer plasma was seen intermittently, with intervening periods of hot tenuous plasma which has properties similar to the magnetospheric population. While individual encounters with the boundary layer plasma last only a few minutes, the total observation time may extend over one hour or more.

Sckopke, N.; Paschmann, G.; Haerendel, G.; Sonnerup, B. U. O.; Bame, S. J.; Forbes, T. G.; Hones, E. W., Jr.; Russell, C. T.

1980-01-01

12

Nanoasperity: structure origin of nacre-inspired nanocomposites.  

PubMed

Natural nacre with superior mechanical property is generally attributed to the layered "brick-and-mortar" nanostructure. However, the role of nanograins on the hard aragonite platelets, which is so-called nanoasperity, is rarely addressed. Herein, we prepared silica platelets with aragonite-like nanoasperities via biomineralization strategy and investigated the effects of nanoasperity on the mechanical properties of resulting layered nanocomposites composed of roughened silica platelets and poly(vinyl alcohol). The tensile deformation behavior of the nanocomposites demonstrates that nanograins on silica platelets are responsive for strain hardening, improved strength, and toughness. The structure origin is attributed to the nanoasperity-controlled platelet sliding. PMID:25625593

Xia, Shuang; Wang, Zuoning; Chen, Hong; Fu, Wenxin; Wang, Jianfeng; Li, Zhibo; Jiang, Lei

2015-02-24

13

The coherent structure of atmospheric surface layers  

Microsoft Academic Search

The structure of two-point correlation statistics in the atmospheric surface layer are studied from measurements on the western Utah salt flats at the SLTEST facility. Large-scale features in the stable, neutral and unstable surface layers that adhere to Monin-Obukhov similarity (-10

Kapil Chauhan; Nick Hutchins; Ivan Marusic; Jason Monty

2010-01-01

14

Simulation of plasma double-layer structures  

SciTech Connect

Electrostatic plasma double layers are numerically simulated by means of a magnetized 2 1/2-dimensional particle-in-cell method. The investigation of planar double layers indicates that these one-dimensional potential structures are susceptible to periodic disruption by instabilities in the low-potential plasmas. Only a slight increase in the double-layer thickness with an increase in its obliqueness to the magnetic field is observed. Weak magnetization results in the double-layer electric-field alignment of accelerated particles and strong magnetization results in their magnetic-field alignment. The numerial simulations of spatially periodic two-dimensional double layers also exhibit cyclical instability. A morphological invariance in two-dimensional double layers with respect to the degree of magnetization implies that the potential structures scale with Debye lengths rather than with gyroradii. Electron-beam excited electrostatic electron-cyclotron waves and (ion-beam driven) solitary waves are present in the plasmas adjacent to the double layers.

Borovsky, J.E.; Joyce, G.

1982-01-01

15

Structural rearrangements in self-assembled surfactant layers at surfaces  

SciTech Connect

The transition from compact to extended configuration in ionic surfactant layers under the influence of salt, surfactant surface density and temperature is studied using the classical density functional theory (cDFT). The increase in ionic strength of aqueous salt solution or in surfactant surface density leads to the transition from the hemicylindrical to the perpendicular monolayer configuration of the molecules. Although producing the same structural rearrangement in the surfactant layer the origin of the effect of salt and surface density is different. While the addition of salt increases the out-of-plane attractive interactions with the solvent, the increase in density results in the increase in the in-plane repulsion in surfactant layer. The temperature effects are subtler and are mainly manifested in the reduction of the solution structuring at elevated temperatures.

Sushko, Maria L.; Liu, Jun

2010-03-25

16

Layered chalcogenide glass structures for IR lenses  

NASA Astrophysics Data System (ADS)

A technique for fabricating novel infrared (IR) lenses can enable a reduction in the size and weight of IR imaging optics through the use of layered glass structures. These structures can range from having a few thick glass layers, mimicking cemented doublets and triplets, to having many thin glass layers approximating graded index (GRIN) lenses. The effectiveness of these structures relies on having materials with diversity in refractive index (large ?n) and dispersion and similar thermo-viscous behavior (common glass transition temperature, ?Tg = 10°C). A library of 13 chalcogenide glasses with broad IR transmission (NIR through LWIR bands) was developed to satisfy these criteria. The lens fabrication methodology, including glass design and synthesis, sheet fabrication, preform making, lens molding and surface finishing are presented.

Gibson, Daniel; Bayya, Shyam; Sanghera, Jas; Nguyen, Vinh; Scribner, Dean; Maksimovic, Velimir; Gill, John; Yi, Allen; Deegan, John; Unger, Blair

2014-07-01

17

A sporadic layer in the Venus lower ionosphere of meteoric origin M. Patzold,1  

E-print Network

A sporadic layer in the Venus lower ionosphere of meteoric origin M. Pa¨tzold,1 S. Tellmann,1 B. Ha meteor layer electron densities increase with decreasing solar zenith angle. Layer shapes are symmetric in the Venus lower ionosphere of meteoric origin, Geophys. Res. Lett., 36, L05203, doi:10.1029/ 2008GL035875. 1

Mendillo, Michael

18

Nanomanufacturing : nano-structured materials made layer-by-layer.  

SciTech Connect

Large-scale, high-throughput production of nano-structured materials (i.e. nanomanufacturing) is a strategic area in manufacturing, with markets projected to exceed $1T by 2015. Nanomanufacturing is still in its infancy; process/product developments are costly and only touch on potential opportunities enabled by growing nanoscience discoveries. The greatest promise for high-volume manufacturing lies in age-old coating and imprinting operations. For materials with tailored nm-scale structure, imprinting/embossing must be achieved at high speeds (roll-to-roll) and/or over large areas (batch operation) with feature sizes less than 100 nm. Dispersion coatings with nanoparticles can also tailor structure through self- or directed-assembly. Layering films structured with these processes have tremendous potential for efficient manufacturing of microelectronics, photovoltaics and other topical nano-structured devices. This project is designed to perform the requisite R and D to bring Sandia's technology base in computational mechanics to bear on this scale-up problem. Project focus is enforced by addressing a promising imprinting process currently being commercialized.

Cox, James V.; Cheng, Shengfeng; Grest, Gary Stephen; Tjiptowidjojo, Kristianto (University of New Mexico); Reedy, Earl David, Jr.; Fan, Hongyou; Schunk, Peter Randall; Chandross, Michael Evan; Roberts, Scott A.

2011-10-01

19

Scattering in structured two-layered medium  

NASA Astrophysics Data System (ADS)

Multiple scattering in two-layered medium was modeled using Monte Carlo numerical simulation. Special case of group formation in such layers was considered. To estimate the impact of structure factor on the overall results, the rigorous calculation of single scattering phase function was used. Comparison with the Monte Carlo simulations for the respective model phase function shows that there were some differences in the scattered radiance. These differences had no significant energy redistribution in the angular dependence of the scattered radiance, but different elongation in the zero-direction occurred. So it was shown that the group formation and special structure still leaded to some changes in the scattering process, even if the medium had several layers with different parameters and had rather large width.

Dolganova, Irina N.; Neganova, Aleksandra S.; Karasik, Valeriy E.; Zaytsev, Kirill I.; Yurchenko, Stanislav O.

2015-01-01

20

Multi-Layer Laminated Thin Films for Inflatable Structures  

NASA Technical Reports Server (NTRS)

Special-purpose balloons and other inflatable structures would be constructed as flexible laminates of multiple thin polymeric films interspersed with layers of adhesive, according to a proposal. In the original intended application, the laminate would serve as the envelope of the Titan Aerobot a proposed robotic airship for exploring Titan (one of the moons of Saturn). Potential terrestrial applications for such flexible laminates could include blimps and sails. In the original application, the multi-layered laminate would contain six layers of 0.14-mil (0.0036-mm)-thick Mylar (or equivalent) polyethylene terephthalate film with a layer of adhesive between each layer of Mylar . The overall thickness and areal density of this laminate would be nearly the same as those of 1-mil (0.0254-mm)-thick monolayer polyethylene terephthalate sheet. However, the laminate would offer several advantages over the monolayer sheet, especially with respect to interrelated considerations of flexing properties, formation of pinholes, and difficulty or ease of handling, as discussed next. Most of the damage during flexing of the laminate would be localized in the outermost layers, where the radii of bending in a given bend would be the largest and, hence, the bending stress would be the greatest. The adverse effects of formation of pinholes would be nearly completely mitigated in the laminate because a pinhole in a given layer would not propagate to adjacent layers. Hence, the laminate would tend to remain effective as a barrier to retain gas. Similar arguments can be made regarding cracks: While a crack could form as a result of stress or a defect in the film material, a crack would not propagate into adjacent layers, and the adjacent layer(s) would even arrest propagation of the crack. In the case of the monolayer sheet, surface damage (scratches, dents, permanent folds, pinholes, and the like) caused by handling would constitute or give rise to defects that could propagate through the thickness as cracks or pinholes that would render the sheet less effective or ineffective as a barrier. In contrast, because damage incurred during handling of the laminate would ordinarily be limited to the outermost layers, the barrier properties of the laminate would be less likely to be adversely affected. Therefore, handling of the laminate would be easier because there would be less of a need to exercise care to ensure against surface damage.

Yavrouian, Andre; Plett, Gary; Mannella, Jerami

2005-01-01

21

Origin of voltage decay in high-capacity layered oxide electrodes  

NASA Astrophysics Data System (ADS)

Although Li-rich layered oxides (Li1+xNiyCozMn1?x?y?zO2 > 250 mAh g?1) are attractive electrode materials providing energy densities more than 15% higher than today’s commercial Li-ion cells, they suffer from voltage decay on cycling. To elucidate the origin of this phenomenon, we employ chemical substitution in structurally related Li2RuO3 compounds. Li-rich layered Li2Ru1?yTiyO3 phases with capacities of ~240 mAh g?1 exhibit the characteristic voltage decay on cycling. A combination of transmission electron microscopy and X-ray photoelectron spectroscopy studies reveals that the migration of cations between metal layers and Li layers is an intrinsic feature of the charge–discharge process that increases the trapping of metal ions in interstitial tetrahedral sites. A correlation between these trapped ions and the voltage decay is established by expanding the study to both Li2Ru1?ySnyO3 and Li2RuO3; the slowest decay occurs for the cations with the largest ionic radii. This effect is robust, and the finding provides insights into new chemistry to be explored for developing high-capacity layered electrodes that evade voltage decay.

Sathiya, M.; Abakumov, A. M.; Foix, D.; Rousse, G.; Ramesha, K.; Saubanère, M.; Doublet, M. L.; Vezin, H.; Laisa, C. P.; Prakash, A. S.; Gonbeau, D.; Vantendeloo, G.; Tarascon, J.-M.

2015-02-01

22

Origin of voltage decay in high-capacity layered oxide electrodes.  

PubMed

Although Li-rich layered oxides (Li1+xNiyCozMn1-x-y-zO2 > 250 mAh g(-1)) are attractive electrode materials providing energy densities more than 15% higher than today's commercial Li-ion cells, they suffer from voltage decay on cycling. To elucidate the origin of this phenomenon, we employ chemical substitution in structurally related Li2RuO3 compounds. Li-rich layered Li2Ru1-yTiyO3 phases with capacities of ~240 mAh g(-1) exhibit the characteristic voltage decay on cycling. A combination of transmission electron microscopy and X-ray photoelectron spectroscopy studies reveals that the migration of cations between metal layers and Li layers is an intrinsic feature of the charge-discharge process that increases the trapping of metal ions in interstitial tetrahedral sites. A correlation between these trapped ions and the voltage decay is established by expanding the study to both Li2Ru1-ySnyO3 and Li2RuO3; the slowest decay occurs for the cations with the largest ionic radii. This effect is robust, and the finding provides insights into new chemistry to be explored for developing high-capacity layered electrodes that evade voltage decay. PMID:25437258

Sathiya, M; Abakumov, A M; Foix, D; Rousse, G; Ramesha, K; Saubanère, M; Doublet, M L; Vezin, H; Laisa, C P; Prakash, A S; Gonbeau, D; VanTendeloo, G; Tarascon, J-M

2015-02-01

23

The coherent structure of atmospheric surface layers  

NASA Astrophysics Data System (ADS)

The structure of two-point correlation statistics in the atmospheric surface layer are studied from measurements on the western Utah salt flats at the SLTEST facility. Large-scale features in the stable, neutral and unstable surface layers that adhere to Monin-Obukhov similarity (-10structure inclination angle. Both streamwise and spanwise integral length scales show consistent logarithmic trends that increase with decreasing stability. Further, the structure inclination angle in the wall-normal plane also shows a logarithmic increase with increasing -z/? for the unstable surface layers. The changes in structure of Ruu can be characterized by z/? making it feasible to incorporate the trends in near-wall models of LES of atmospheric flows under stable and unstable conditions.

Chauhan, Kapil; Hutchins, Nick; Marusic, Ivan; Monty, Jason

2010-11-01

24

Local diffuse reflectance from three-layered skin tissue structures  

NASA Astrophysics Data System (ADS)

We consider two different skin structure models. The first structure consists of epidermis, dermis/blood, and subcutaneous tissue. The second structure consists of epidermis/dermis, adipose tissue and muscle tissue. A new solution based on diffusion theory of the cw local diffuse reflectance from a three-layered skin tissue structure is presented. Comparisons with Monte Carlo simulations are carried out favorably. It is shown that the functional form of the radial dependence of the diffuse reflectance from multilayer and single layer models are identical. We use a modified expression originating from diffusion theory to fit the diffuse reflectance. We discuss the sensitivity of the local diffuse reflectance as a function of the optical properties of separate layers in both structures. Moreover, we investigate the influence on the local diffuse reflectance with changes in the optical properties corresponding to normal changes in tissue glucose concentration and blood volume. The necessity of multilayer models lies within their ability to provide a detailed description of the light-tissue interaction rate than their applicability to practical data analysis of the local diffuse reflectance measurements.

Andersen, Peter E.; Dam, Jan S.; Petersen, Paul M.; Bjerring, Peter

1997-08-01

25

Ion transport and structure of layer-by-layer assemblies  

E-print Network

Layer-by-layer (LbL) films of various architectures were examined as potential solid state electrolytes for electrochemical systems (e.g. batteries and fuel cells). The relationship between materials properties and ion ...

Lutkenhaus, Jodie Lee

2007-01-01

26

Modelling apparent low thermal inertia by layered structure  

NASA Astrophysics Data System (ADS)

Thermal inertia of planetary surface is a physical property that controls the diurnal and seasonal cycles in the surface temperature. At the same time it provides a unique window into geologic structure of the surface and the nature of geologic processes that shapes the planetary surface. Especially on Mars, it has been extensively derived from spacecraft remote-sensing observations. It shows existence of the area with very low thermal inertia in the equatorial and middle latitudes, which at the same time display complicated heterogeneous characteristics(Putzig and Mellon, 2007). This is one of the enigma about the surface state of Mars. Physical interpretation about the origin of this heterogeneous nature of the thermal inertia is needed. In this study, we discuss a possibility of apparent low thermal inertia when there exists a layered structure having contrasting thermal conductivities based on laboratory experiments. The layered structure we examined in the experiments are an acrylic plate(3.2mm , 5mm , 10mm in thickness) on top of Polystyrene foam block or vesiculated particle layer. In both cases the lower layer has lower thermal conductivity. They are heated periodically by a infrared lump from above(period from 10 to 600 sec.). We measured the temperature at the surface, bottom of the acrylic plate and inside the lower Polystyrene foam and the granular layer using the thermocouples and infrared thermometer. From amplitude of temperature variation, we estimated the thermal inertia. The important controlling factor in this experimental design is a thermal relaxation time of the surface layer, which is controlled by period of the applied heating cycle and the thickness. At the fixed layer thickness thermal structure changes drastically between the periods below and above the relaxation time. We estimated variation of apparent thermal inertia with period. In a homogeneous semi-infinite layer the amplitude of variation of the surface temperature induced by periodic heating under controlled situation is proportional to square root of the period and inversely proportional to the thermal inertia(Wang et al 2010). We utilized their formula to determine apparent thermal inertia. At the periods below thermal relaxation time unique value for thermal inertia was obtained while above the relaxation time it decreases even below the value of the lower layer. This is caused by the effect of finite layer thickness,which reduces thermal gradient in the surface layer. This leads to apparent low thermal inertia value. In our experiments we can demonstrate a simple layered structure; a thin layer having higher thermal conductivity on top of a layer with low thermal conductivity can produce apparent low thermal inertia. In the martian situation the thermal inertia is obtained mostly by diurnal heating cycle, which has a penetration depth(Thermal relaxation depth) of several to 10 cm. We discuss several geological processes to produce layered structure in this depth range in the presentation.

Yoshida, Akari; Toyota, Takenori; Kurita, Kei

2013-04-01

27

Structural origin of light emission in germanium quantum dots  

PubMed Central

We used a combination of optically-detected x-ray absorption spectroscopy with molecular dynamics simulations to explore the origins of light emission in small (5?nm to 9?nm) Ge nanoparticles. Two sets of nanoparticles were studied, with oxygen and hydrogen terminated surfaces. We show that optically-detected x-ray absorption spectroscopy shows sufficient sensitivity to reveal the different origins of light emission in these two sets of samples. We found that in oxygen terminated nanoparticles its the oxide-rich regions that are responsible for the light emission. In hydrogen terminated nanoparticles we established that structurally disordered Ge regions contribute to the luminescence. Using a combination of molecular dynamics simulations and optically-detected x-ray absorption spectroscopy we show that these disordered regions correspond to the disordered layer a few Å thick at the surface of the simulated nanoparticle. PMID:25487681

Little, W.; Karatutlu, A.; Bolmatov, D.; Trachenko, K.; Sapelkin, A. V.; Cibin, G.; Taylor, R.; Mosselmans, F.; Dent, A. J.; Mountjoy, G.

2014-01-01

28

Structural origin of light emission in germanium quantum dots.  

PubMed

We used a combination of optically-detected x-ray absorption spectroscopy with molecular dynamics simulations to explore the origins of light emission in small (5?nm to 9?nm) Ge nanoparticles. Two sets of nanoparticles were studied, with oxygen and hydrogen terminated surfaces. We show that optically-detected x-ray absorption spectroscopy shows sufficient sensitivity to reveal the different origins of light emission in these two sets of samples. We found that in oxygen terminated nanoparticles its the oxide-rich regions that are responsible for the light emission. In hydrogen terminated nanoparticles we established that structurally disordered Ge regions contribute to the luminescence. Using a combination of molecular dynamics simulations and optically-detected x-ray absorption spectroscopy we show that these disordered regions correspond to the disordered layer a few Å thick at the surface of the simulated nanoparticle. PMID:25487681

Little, W; Karatutlu, A; Bolmatov, D; Trachenko, K; Sapelkin, A V; Cibin, G; Taylor, R; Mosselmans, F; Dent, A J; Mountjoy, G

2014-01-01

29

Unstable flow structures in the Blasius boundary layer.  

PubMed

Finite amplitude coherent structures with a reflection symmetry in the spanwise direction of a parallel boundary layer flow are reported together with a preliminary analysis of their stability. The search for the solutions is based on the self-sustaining process originally described by Waleffe (Phys. Fluids 9, 883 (1997)). This requires adding a body force to the Navier-Stokes equations; to locate a relevant nonlinear solution it is necessary to perform a continuation in the nonlinear regime and parameter space in order to render the body force of vanishing amplitude. Some states computed display a spanwise spacing between streaks of the same length scale as turbulence flow structures observed in experiments (S.K. Robinson, Ann. Rev. Fluid Mech. 23, 601 (1991)), and are found to be situated within the buffer layer. The exact coherent structures are unstable to small amplitude perturbations and thus may be part of a set of unstable nonlinear states of possible use to describe the turbulent transition. The nonlinear solutions survive down to a displacement thickness Reynolds number Re * = 496 , displaying a 4-vortex structure and an amplitude of the streamwise root-mean-square velocity of 6% scaled with the free-stream velocity. At this Re* the exact coherent structure bifurcates supercritically and this is the point where the laminar Blasius flow starts to cohabit the phase space with alternative simple exact solutions of the Navier-Stokes equations. PMID:24771239

Wedin, H; Bottaro, A; Hanifi, A; Zampogna, G

2014-04-01

30

Structure and origin of cometary nuclei  

NASA Technical Reports Server (NTRS)

There is strong evidence that a comet nucleus consists of a single object whose basic structure is Whipple's icy conglomerate. A number of cometary phenomena indicate that the nucleus is a low density, fragile object with a large degree of radial uniformity in structure and composition. Details of the ice-dust pattern are more uncertain. A working model is proposed which is based on theories of accumulation of larger objects from grains. This nucleus is a distorted spherical aggregate of a hierarchy of ice-dust cometesimals. These cometesimals retain some separate identity which lead to comet fragmentation when larger components break off. The outer layers of new comets were modified by cosmic ray irradiation in the Oort Cloud. The evidence for meteorite-comet association is steill controversial. Current dynamical studies do not seem to require a cometary source of meteorites.

Donn, B.; Rahe, J.

1981-01-01

31

Structure of the surface layer of the methanogenic archaean Methanosarcina acetivorans  

SciTech Connect

Archaea have a self-assembling proteinaceous surface (S-) layer as the primary and outermost boundary of their cell envelopes. The S-layer maintains structural rigidity, protects the organism from adverse environmental elements, and yet provides access to all essential nutrients. We have determined the crystal structure of one of the two 'homologous' tandem polypeptide repeats that comprise the Methanosarcina acetivorans S-layer protein and propose a high-resolution model for a microbial S-layer. The molecular features of our hexameric S-layer model recapitulate those visualized by medium resolution electron microscopy studies of microbial S-layers and greatly expand our molecular view of S-layer dimensions, porosity, and symmetry. The S-layer model reveals a negatively charged molecular sieve that presents both a charge and size barrier to restrict access to the cell periplasmic-like space. The {beta}-sandwich folds of the S-layer protein are structurally homologous to eukaryotic virus envelope proteins, suggesting that Archaea and viruses have arrived at a common solution for protective envelope structures. These results provide insight into the evolutionary origins of primitive cell envelope structures, of which the S-layer is considered to be among the most primitive: it also provides a platform for the development of self-assembling nanomaterials with diverse functional and structural properties.

Arbing, Mark A.; Chan, Sum; Shin, Annie; Phan, Tung; Ahn, Christine J.; Rohlin, Lars; Gunsalus, Robert P. (UCLA)

2012-09-05

32

Wave reflection by a periodic layered metamaterial Reflection by a semi-infinite layered structure  

Microsoft Academic Search

A technique incorporating the reflection matrix of a semi-infinite discrete layered periodic structure is employed to analyze the electromagnetic properties of a half-space filled with a layered metamaterial.

L. M. Lytvynenko; S. L. Prosvirnina

33

Wave reflection by a periodic layered metamaterial. Reflection by a semi-infinite layered structure  

Microsoft Academic Search

A technique incorporating the reflection matrix of a semi-infinite discrete layered periodic structure is employed to analyze the electromagnetic properties of a half-space filled with a layered metamaterial.

L. M. Lytvynenko; S. L. Prosvirnin

2009-01-01

34

Origin and consequences of silicate glass passivation by surface layers  

PubMed Central

Silicate glasses are durable materials, but are they sufficiently durable to confine highly radioactive wastes for hundreds of thousands years? Addressing this question requires a thorough understanding of the mechanisms underpinning aqueous corrosion of these materials. Here we show that in silica-saturated solution, a model glass of nuclear interest corrodes but at a rate that dramatically drops as a passivating layer forms. Water ingress into the glass, leading to the congruent release of mobile elements (B, Na and Ca), is followed by in situ repolymerization of the silicate network. This material is at equilibrium with pore and bulk solutions, and acts as a molecular sieve with a cutoff below 1?nm. The low corrosion rate resulting from the formation of this stable passivating layer enables the objective of durability to be met, while progress in the fundamental understanding of corrosion unlocks the potential for optimizing the design of nuclear glass-geological disposal. PMID:25695377

Gin, Stéphane; Jollivet, Patrick; Fournier, Maxime; Angeli, Frédéric; Frugier, Pierre; Charpentier, Thibault

2015-01-01

35

Origin and consequences of silicate glass passivation by surface layers.  

PubMed

Silicate glasses are durable materials, but are they sufficiently durable to confine highly radioactive wastes for hundreds of thousands years? Addressing this question requires a thorough understanding of the mechanisms underpinning aqueous corrosion of these materials. Here we show that in silica-saturated solution, a model glass of nuclear interest corrodes but at a rate that dramatically drops as a passivating layer forms. Water ingress into the glass, leading to the congruent release of mobile elements (B, Na and Ca), is followed by in situ repolymerization of the silicate network. This material is at equilibrium with pore and bulk solutions, and acts as a molecular sieve with a cutoff below 1?nm. The low corrosion rate resulting from the formation of this stable passivating layer enables the objective of durability to be met, while progress in the fundamental understanding of corrosion unlocks the potential for optimizing the design of nuclear glass-geological disposal. PMID:25695377

Gin, Stéphane; Jollivet, Patrick; Fournier, Maxime; Angeli, Frédéric; Frugier, Pierre; Charpentier, Thibault

2015-01-01

36

Origin and consequences of silicate glass passivation by surface layers  

NASA Astrophysics Data System (ADS)

Silicate glasses are durable materials, but are they sufficiently durable to confine highly radioactive wastes for hundreds of thousands years? Addressing this question requires a thorough understanding of the mechanisms underpinning aqueous corrosion of these materials. Here we show that in silica-saturated solution, a model glass of nuclear interest corrodes but at a rate that dramatically drops as a passivating layer forms. Water ingress into the glass, leading to the congruent release of mobile elements (B, Na and Ca), is followed by in situ repolymerization of the silicate network. This material is at equilibrium with pore and bulk solutions, and acts as a molecular sieve with a cutoff below 1?nm. The low corrosion rate resulting from the formation of this stable passivating layer enables the objective of durability to be met, while progress in the fundamental understanding of corrosion unlocks the potential for optimizing the design of nuclear glass-geological disposal.

Gin, Stéphane; Jollivet, Patrick; Fournier, Maxime; Angeli, Frédéric; Frugier, Pierre; Charpentier, Thibault

2015-02-01

37

Titan's planetary boundary layer structure at the Huygens landing site  

Microsoft Academic Search

Huygens Atmospheric Structure Instrument (HASI) for the first time performed an in situ measurement of the thermal structure in Titan's atmosphere with a vertical resolution sufficient to analyze the planetary boundary layer (PBL). The vertical potential temperature profile reveals the presence of a weakly convective PBL, with a surface layer thickness of 10 m and an outer layer with a

Tetsuya Tokano; Francesca Ferri; Giacomo Colombatti; Teemu Mäkinen; Marcello Fulchignoni

2006-01-01

38

Origin of the Accumulation Layer at the InN/a-In2O3 Interface.  

PubMed

We perform first-principles Density Functional Theory calculations for the amorphous In2O3/InN (11?00) heterostructure. Our results suggest that the interface between InN and its native amorphous oxide is a type "I" interface as observed in X-ray photoemission spectroscopy data for the same materials in the crystalline form. The microscopic analysis of the system reveals the presence of peculiar structural features localized at the interface, such as the formation of N-O bonds and the existence of N dangling bonds, that are responsible for donor states. These findings shed light on the origin of the electron accumulation layer occurring at the interface in spontaneously oxidized InN nanowires, recently associated with the observed increase in conductivity for such systems. PMID:25692685

Aliano, Antonio; Cicero, Giancarlo; Catellani, Alessandra

2015-03-11

39

Mercury: Remote Estimation of Surface Layer Structure  

NASA Astrophysics Data System (ADS)

Results of the optical observations of Mercury and the Moon confirm the close simi- larity of photometric properties of the bodies. Experience of lunar studies shows that space weathering processes on the Mercury (such as micrometeorite bombardment, solar wind ion bombardment etc.) can form properties of the upper layer of regolith. The amount of fused glassy particles and others agglutinates in the lunar upper layer is the direct index of the soil reworking caused be the micrometeorite bombardment. Besides, this micrometeorite bombardment is also responsible for the mechanical pro- cess through which the large particles are broken down into smaller ones. For lunar re- golith was showed that increasingly mature soils become progressively finer-grained, better-sorted, and composed of a greater proportion of agglutinates. The increasing rate of the fused glassy fragments, of agglutinates, and of fine size fraction in the regolith during its space weathering affects the polarization of the light reflected by an exposed lunar or Mercurian soil. Therefore, polarimetric properties of the regolith may be modified by the soil reworking process in the course of time. Comparison of the lunar and Mercurian optic observations confirms the remarkable similarity of the polarimetric properties of Mercury and the Moon. From of summary of polarization measurements of whole disk of Mercury it is possible to conclude that maturity of the soil on the Mercurian surface in scale of whole disk is similar to one in large old craters on the lunar highland. Comparison of the lunar and Mercurian disk-integrated photometric functions indicates the likeness of the surface layer structures of the bod- ies. Analysis of the phase curve inclination and magnitude of the opposition effect shows that Mercurian relief in scale of meter details is smoother than lunar one. It was measured brightness of number of small plots (10x10 cm) on the lunar surface (Luna-13 data). The range of phase angles was from 68 to 75 deg. These values close correlate with corresponding part of the Mercurian disk-integrated phase function. ItSs possible if Mercurian phase function received from Earth-based telescopes and lunar one received in cm-scale is coincided the structures of regolith may be similar in both cases. These conclusions may be used for planning BepiColombo mission. This work was supported by INTAS-ESA grant No. 99-00403.

Shevchenko, V. V.

40

Origin of the outer layer of martian low-aspect ratio layered ejecta craters  

NASA Astrophysics Data System (ADS)

Low-aspect ratio layered ejecta (LARLE) craters are one of the most enigmatic types of martian layered ejecta craters. We propose that the extensive outer layer of these craters is produced through the same base surge mechanism as that which produced the base surge deposits generated by near-surface, buried nuclear and high-explosive detonations. However, the LARLE layers have higher aspect ratios compared with base surge deposits from explosion craters, a result of differences in thicknesses of these layers. This characteristics is probably caused by the addition of large amounts of small particles of dust and ice derived from climate-related mantles of snow, ice and dust in the areas where LARLE craters form. These deposits are likely to be quickly stabilized (order of a few days to a few years) from eolian erosion by formation of duricrust produced by diffusion of water vapor out of the deposits.

Boyce, Joseph M.; Wilson, Lionel; Barlow, Nadine G.

2015-01-01

41

Representation of dry tropical layers and their origins in ERA-40 data  

E-print Network

an anomalous cooling in the underlying moist air, thus stabilizing the bottom of the dry intrusion there is substantial radiative cooling. [3] In this paper the origin of dry intrusions as inferred using the ECMWF 40Representation of dry tropical layers and their origins in ERA-40 data Piero Cau, John Methven

Hoskins, Brian

42

Planetary Rings: Structure, Evolution and Origin  

NASA Astrophysics Data System (ADS)

Using spacecraft and telescopic observations, I review the gross physical and morphological properties of the distinctive ring systems of each of the giant planets. In addition to their intrinsic interest, planetary rings provide proximate, but imperfect, analogs for more distant and massive structures, such as accretion and protoplanetary disks, which are of considerable current astronomical interest. Jupiter's dusty rings, strongly influenced by electromagnetic forces, appear to be derived of debris sloughed off small exterior satellites. Uranus's nine surprisingly narrow, eccentric and inclined rings hint at a role for self-gravitational effects. Neptune's most massive ring contains several clumps, likely due to satellite interactions. Saturn's resplendent rings display aspects of all the other systems. As time allows, I will mention observations planned for Cassini, a spacecraft mission just now starting a 4+-year tour of Saturn. Structures that develop owing to gravitational forces and collective effects can be destroyed by physical collisions and tidal shear. Satellites --near and far-- play important roles in sculpting planetary rings. Embedded satellites can be sources but also sinks for ring material. Moons generate clumps and kinks in narrow rings, and gravitational wakes and waves in continuous disks. The frequencies contained in the epicyclic motion of nearby satellites can resonate with the epicyclic frequencies of ring particles, thereby initiating spiral density and bending waves at some locations; from such features, one can infer ring surface density and viscosity. The resultant angular momentum transfer can open gaps or terminate rings. Besides moons, non-uniform magnetic or gravity fields can generate noticeable features. I provide simple illustrations of such phenomena, and supplement them with numerical simulations. Several lines of evidence indicate that planetary rings are considerably younger than the solar system. The jury is still out on possible ring origin(s).

Burns, J. A.

2004-12-01

43

Origin and effect of nonlocality in a layered composite.  

SciTech Connect

A simple demonstration of nonlocality in a heterogeneous material is presented. By analysis of the microscale deformation of a two-component layered medium, it is shown that nonlocal interactions necessarily appear in a homogenized model of the system. Explicit expressions for the nonlocal forces are determined. The way these nonlocal forces appear in various nonlocal elasticity theories is derived. The length scales that emerge involve the constituent material properties as well as their geometrical dimen- sions. A peridynamic material model for the smoothed displacement eld is derived. It is demonstrated by comparison with experimental data that the incorporation of non- locality in modeling dramatically improves the prediction of the stress concentration in an open hole tension test on a composite plate.

Silling, Stewart Andrew

2014-01-01

44

Boron-Based Layered Structures for Energy Storage  

SciTech Connect

Based on Density Functional Theory simulations, we have studied the boron-based graphite-like materials, i.e., LiBC and MgB2 for energy storage. First, when half of the Li-ions in the LiBC are removed, the BC layered structure is still preserved. The Li intercalation potential (equilibrium lithium-insertion voltage of 2.3-2.4 V relative to lithium metal) is significantly higher than that in graphite, allowing Li0.5BC to function as a cathode material. The reversible electrochemical reaction, LiBC = Li0.5BC + 0.5Li, enables a specific energy density of 1088 Wh/kg and a volumetric energy density of 2463 Wh/L. Second, 75% of the Mg ions in MgB2 can be removed and reversibly inserted with the layered boron structures being preserved through an in-plane topological transformation between the hexagonal lattice domains and triangular domains. The mechanism of such a charge-driven transformation originates from the versatile valence state of boron in its planar form.

Zhao, Y.; Wei, S. H.

2012-01-01

45

Towards Automatically Improving Package Structure While Respecting Original Design  

E-print Network

Towards Automatically Improving Package Structure While Respecting Original Design Decisions Hani approach that improves packages structure with regard to the well-known design principles, cohesion packages structure. This paper presents a novel multi-objective optimization approach for improving

Paris-Sud XI, Université de

46

Origins of microspherules from the Permian-Triassic boundary event layers in South China  

NASA Astrophysics Data System (ADS)

Volcanism and impact scenarios are two of the most plausible ways of interpreting the causes of the largest biological mass extinction at the end-Permian. Microspherules have previously been widely reported from tens of different Permian-Triassic boundary (PTB) sections in South China and some other regions. These microspherules have been interpreted as either the product of volcanic eruptions or an impact event. In order to test these scenarios, we collected 60 samples from 12 intensively-studied PTB sections in South China. In addition, four soil samples close to these PTB layers were also collected for comparison. Our investigation indicates that abundant microspherules with mosaic or dot shape crystals on rounded surface are present in the surface samples in the PTB layers at Meishan, Meili, and Shatian sections and most soil background samples in South China. Those microspherules consist of four different types based on their main chemical composition, surface features, and internal structure including iron, magnetite-silicate, glassy, pyrite microspherules and framboids. In contrast, microspherules have not been found in a few sections in remote areas such as the Selong Xishan section in Tibet and the Dalongkou section in Xinjiang, Northwest China, in the deeply-excavated samples at the Shangsi section and the hard tuff layers around the PTB at the Xiaochehe Section in Guiyang. Microspherules decrease in abundance with depth in PTB clay beds. All these microspherules except the pyrite microspherules and framboids are found in both the PTB layers and the nearby soil background samples. The iron microspherules are pure iron oxides such as magnetite, hematite or maghemite and contain low concentrations of nickel and chromium, and lack an Ni-Fe core and general extraterrestrial mineral wüstite. All these external and chemical characteristics suggest that most of iron microspherules previously reported from PTB sections in South China are modern industrial fly ashes. A low ratio of Fe3 +/FeTotal in crystals of magnetite-silicate microspherules and high ZnO contents can identify them as industrial contaminants. The pyrite microspherules and framboidal pyrite found from bed 24e and bed 26 at the Meishan sections are of depositional or/and diagenetic origins, and only the rounded quartz and the fragments containing extremely high SiO2 and TiO2 are possibly of volcanic origin.

Zhang, Hua; Shen, Shu-zhong; Cao, Chang-qun; Zheng, Quan-feng

2014-09-01

47

What is the Age and Origin of the Spherule Bearing Layer in some Ross Sea Cores?  

NASA Astrophysics Data System (ADS)

L.P. Khyranina (1985) was the first to suggest that there were two structures present on the Antarctic continental shelf beneath the Ross Sea. One was the ~100 km Bowers impact crater candidate. However, there was no solid evidence that proved an extraterrestrial impact produced the Bowers structure. Debate has ensued for decades on whether the Bowers structure was an impact crater. Now we have come close to finding an answer. We used core samples taken near the crater and sieved into four size fractions (>250,>125,>63,>38 ?m). Impact ejecta candidates were then picked from cores ELT 32-08, ELT 32-03, ELT 32-43, ELT 32-06, DSDP 273, DSDP 274, and NPB 95-01 39KC and were analyzed for chemical composition and physical features. All but DSDP site 274 contain pure SiO2 glasses that resemble tektites. We also found candidates for flow textured impact glass and shocked quartz. This led us to conclude that the origin of the spherule-bearing layer was from an impact. With the use of dated core NBP 95-01 39KC, we have constrained the age to lie between 7,305±80 BP and 11,150±95 BP (corrected radiocarbon ages) (Cunningham et al., 1999).

Yeh, C.; Abbott, D. H.; Anders, M. H.; Breger, D.

2012-12-01

48

Quasi-Coherent Structures In Turbulent Boundary Layers  

NASA Technical Reports Server (NTRS)

Two-part report reviews knowledge of coherent structures in turbulent boundary layers. Part I describes processes and status of cooperative project to summarize data from research on boundary-layer turbulence. Part II presents results of study of numerically simulated flat-plate canonical turbulent boundary layer.

Robinson, S. K.; Kline, S. J.; Spalart, P. R.

1992-01-01

49

The nature and origin of lateral composition modulations in short-period strained-layer superlattices  

SciTech Connect

The nature and origin of lateral composition modulations in (AlAs){sub m}(InAs){sub n} SPSs grown by MBE on InP substrates have been investigated by XRD, AFM, and TEM. Strong modulations were observed for growth temperatures between {approx} 540 and 560 C. The maximum strength of modulations was found for SPS samples with InAs mole fraction x (=n/(n+m)) close to {approx} 0.50 and when n {approx} m {approx} 2. The modulations were suppressed at both high and low values of x. For x >0.52 (global compression) the modulations were along the <100> directions in the (001) growth plane. For x < 0.52 (global tension) the modulations were along the two <310> directions rotated {approx} {+-} 27{degree} from [110] in the growth plane. The remarkably constant wavelength of the modulations, between {approx} 20--30 nm, and the different modulation directions observed, suggest that the origin of the modulations is due to surface roughening associated with the high misfit between the individual SPS layers and the InP substrate. Highly uniform unidirectional modulations have been grown, by control of the InAs mole fraction and growth on suitably offcut substrates, which show great promise for application in device structures.

NORMAN,A.G.; AHRENKIEL,S.P.; MOUTINHO,H.R.; BALLIF,C.; ALJASSIM,M.M.; MASCARENHAS,A.; FOLLSTAEDT,DAVID M.; LEE,STEPHEN R.; RENO,JOHN L.; JONES,ERIC D.; MIRECKI-MILLUNCHICK,J.; TWESTEN,R.D.

2000-01-27

50

A series of bismuth layer-structured ferroelectrics  

Microsoft Academic Search

The general formula, Srm?3+xBi4?xTim?xTaxO3m+3 (m=2 and 3) is a phase relation between well-known bismuth layer-structured ferroelectrics (BLSF) such as Bi4Ti3O12 and SrBi2Ta2O9 including a perovskite compound SrTiO3. The series was discussed to form the layer structure with the numbers m=2 and 3 of layer, where x is the number of Ta ions in the layer structure and 1?x?2 for m=2

Hajime Nagata; Takeshi Takahashi; Naohito Chikushi; Tadashi Takenaka

2000-01-01

51

Materials issues for layered tunnel barrier structures Julie D. Caspersona)  

E-print Network

Materials issues for layered tunnel barrier structures Julie D. Caspersona) Thomas J. Watson the program/erase speeds of nonvolatile floating gate memory devices and could allow both nanosecond program. A numerical model has been developed to assess potential layered tunnel barrier materials and structures

Atwater, Harry

52

Multi-layer laminate structure and manufacturing method  

SciTech Connect

The present invention is premised upon a multi-layer laminate structure and method of manufacture, more particularly to a method of constructing the multi-layer laminate structure utilizing a laminate frame and at least one energy activated flowable polymer.

Keenihan, James R. (Midland, MI); Cleereman, Robert J. (Midland, MI); Eurich, Gerald (Merrill, MI); Graham, Andrew T. (Midland, MI); Langmaid, Joe A. (Caro, MI)

2012-04-24

53

Multi-layer laminate structure and manufacturing method  

DOEpatents

The present invention is premised upon a multi-layer laminate structure and method of manufacture, more particularly to a method of constructing the multi-layer laminate structure utilizing a laminate frame and at least one energy activated flowable polymer.

Keenihan, James R.; Cleereman, Robert J.; Eurich, Gerald; Graham, Andrew T.; Langmaid, Joe A.

2013-01-29

54

Electroluminescent apparatus having a structured luminescence conversion layer  

DOEpatents

An apparatus such as a light source is disclosed which has an OLED device and a structured luminescence conversion layer disposed on the substrate or transparent electrode of said OLED device and on the exterior of said OLED device. The structured luminescence conversion layer contains color-changing and non-color-changing regions arranged in a particular pattern.

Krummacher, Benjamin Claus (Sunnyvale, CA)

2008-09-02

55

Turbulence Structure of the Unstable Atmospheric Surface Layer and Transition to the Outer Layer  

NASA Astrophysics Data System (ADS)

We present a new model of the structure of turbulence in the unstable atmospheric surface layer, and of the structural transition between this and the outer layer. The archetypal element of wall-bounded shear turbulence is the Theodorsen ejection amplifier (TEA) structure, in which an initial ejection of air from near the ground into an ideal laminar and logarithmic flow induces vortical motion about a hairpin-shaped core, which then creates a second ejection that is similar to, but larger than, the first. A series of TEA structures form a TEA cascade. In real turbulent flows TEA structures occur in distorted forms as TEA-like (TEAL) structures. Distortion terminates many TEAL cascades and only the best-formed TEAL structures initiate new cycles. In an extended log layer the resulting shear turbulence is a complex, self-organizing, dissipative system exhibiting self-similar behaviour under inner scaling. Spectral results show that this structure is insensitive to instability. This is contrary to the fundamental hypothesis of Monin--Obukhov similarity theory. All TEAL cascades terminate at the top of the surface layer where they encounter, and are severely distorted by, powerful eddies of similar size from the outer layer. These eddies are products of the breakdown of the large eddies produced by buoyancy in the outer layer. When the outer layer is much deeper than the surface layer the interacting eddies are from the inertial subrange of the outer Richardson cascade. The scale height of the surface layer, zs, is then found by matching the powers delivered to the creation of emerging TEAL structures to the power passing down the Richardson cascade in the outer layer. It is zs = u* 3ks, where u*s friction velocity, k is the von Káán constant and s is the rate of dissipation of turbulence kinetic energy in the outer layer immediately above the surface layer. This height is comparable to the Obukhov length in the fully convective boundary layer. Aircraft and tower observations confirm a strong qualitative change in the structure of the turbulence at about that height. The tallest eddies within the surface layer have height zs, so zs is a new basis parameter for similarity models of the surface layer.

McNaughton, K. G.

56

69. PHOTOCOPY OF ORIGINAL DRAWING OF 1904 STRUCTURE, NORTH CAROLINA ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

69. PHOTOCOPY OF ORIGINAL DRAWING OF 1904 STRUCTURE, NORTH CAROLINA AVENUE ELEVATION C BUILDING. ADDISON HUTTON COLLECTION - Chalfonte Hotel, Pacific & North Carolina Avenues, Atlantic City, Atlantic County, NJ

57

68. PHOTOCOPY OF ORIGINAL DRAWING OF 1904 STRUCTURE, SEA FRONT ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

68. PHOTOCOPY OF ORIGINAL DRAWING OF 1904 STRUCTURE, SEA FRONT ELEVATION (NOT AS BUILT). ADDISON HUTTON COLLECTION - Chalfonte Hotel, Pacific & North Carolina Avenues, Atlantic City, Atlantic County, NJ

58

70. PHOTOCOPY OF ORIGINAL DRAWING OF 1904 STRUCTURE, BACK AND ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

70. PHOTOCOPY OF ORIGINAL DRAWING OF 1904 STRUCTURE, BACK AND SIDE ELEVATION, E BUILDING. ADDISION HUTTON COLLECTION - Chalfonte Hotel, Pacific & North Carolina Avenues, Atlantic City, Atlantic County, NJ

59

Crystal structure of the eukaryotic origin recognition complex.  

PubMed

Initiation of cellular DNA replication is tightly controlled to sustain genomic integrity. In eukaryotes, the heterohexameric origin recognition complex (ORC) is essential for coordinating replication onset. Here we describe the crystal structure of Drosophila ORC at 3.5 Å resolution, showing that the 270 kilodalton initiator core complex comprises a two-layered notched ring in which a collar of winged-helix domains from the Orc1-5 subunits sits atop a layer of AAA+ (ATPases associated with a variety of cellular activities) folds. Although canonical inter-AAA+ domain interactions exist between four of the six ORC subunits, unanticipated features are also evident. These include highly interdigitated domain-swapping interactions between the winged-helix folds and AAA+ modules of neighbouring protomers, and a quasi-spiral arrangement of DNA binding elements that circumnavigate an approximately 20 Å wide channel in the centre of the complex. Comparative analyses indicate that ORC encircles DNA, using its winged-helix domain face to engage the mini-chromosome maintenance 2-7 (MCM2-7) complex during replicative helicase loading; however, an observed out-of-plane rotation of more than 90° for the Orc1 AAA+ domain disrupts interactions with catalytic amino acids in Orc4, narrowing and sealing off entry into the central channel. Prima facie, our data indicate that Drosophila ORC can switch between active and autoinhibited conformations, suggesting a novel means for cell cycle and/or developmental control of ORC functions. PMID:25762138

Bleichert, Franziska; Botchan, Michael R; Berger, James M

2015-03-19

60

Composite S-layer lipid structures  

PubMed Central

Designing and utilization of biomimetic membrane systems generated by bottom-up processes is a rapidly growing scientific and engineering field. Elucidation of the supramolecular construction principle of archaeal cell envelopes composed of S-layer stabilized lipid membranes led to new strategies for generating highly stable functional lipid membranes at meso- and macroscopic scale. In this review, we provide a state of the art survey how S-layer proteins, lipids, and polysaccharides may be used as basic building blocks for the assembly of S-layer supported lipid membranes. These biomimetic membrane systems are distinguished by a nanopatterned fluidity, enhanced stability and longevity and thus, provide a dedicated reconstitution matrix for membrane-active peptides and transmembrane proteins. Exciting areas for application of composite S-layer membrane systems concern sensor systems involving specific membrane functions. PMID:19303933

Schuster, Bernhard; Sleytr, Uwe B.

2010-01-01

61

The Levantine Basin—crustal structure and origin  

NASA Astrophysics Data System (ADS)

The origin of the Levantine Basin in the Southeastern Mediterranean Sea is related to the opening of the Neo-Tethys. The nature of its crust has been debated for decades. Therefore, we conducted a geophysical experiment in the Levantine Basin. We recorded two refraction seismic lines with 19 and 20 ocean bottom hydrophones, respectively, and developed velocity models. Additional seismic reflection data yield structural information about the upper layers in the first few kilometers. The crystalline basement in the Levantine Basin consists of two layers with a P-wave velocity of 6.0-6.4 km/s in the upper and 6.5-6.9 km/s in the lower crust. Towards the center of the basin, the Moho depth decreases from 27 to 22 km. Local variations of the velocity gradient can be attributed to previously postulated shear zones like the Pelusium Line, the Damietta-Latakia Line and the Baltim-Hecateus Line. Both layers of the crystalline crust are continuous and no indication for a transition from continental to oceanic crust is observed. These results are confirmed by gravity data. Comparison with other seismic refraction studies in prolongation of our profiles under Israel and Jordan and in the Mediterranean Sea near Greece and Sardinia reveal similarities between the crust in the Levantine Basin and thinned continental crust, which is found in that region. The presence of thinned continental crust under the Levantine Basin is therefore suggested. A ?-factor of 2.3-3 is estimated. Based on these findings, we conclude that sea-floor spreading in the Eastern Mediterranean Sea only occurred north of the Eratosthenes Seamount, and the oceanic crust was later subducted at the Cyprus Arc.

Netzeband, G. L.; Gohl, K.; Hübscher, C. P.; Ben-Avraham, Z.; Dehghani, G. A.; Gajewski, D.; Liersch, P.

2006-06-01

62

Hybrid inorganic–organic superlattice structures with atomic layer deposition/molecular layer deposition  

SciTech Connect

A combination of the atomic layer deposition (ALD) and molecular layer deposition (MLD) techniques is successfully employed to fabricate thin films incorporating superlattice structures that consist of single layers of organic molecules between thicker layers of ZnO. Diethyl zinc and water are used as precursors for the deposition of ZnO by ALD, while three different organic precursors are investigated for the MLD part: hydroquinone, 4-aminophenol and 4,4?-oxydianiline. The successful superlattice formation with all the organic precursors is verified through x-ray reflectivity studies. The effects of the interspersed organic layers/superlattice structure on the electrical and thermoelectric properties of ZnO are investigated through resistivity and Seebeck coefficient measurements at room temperature. The results suggest an increase in carrier concentration for small concentrations of organic layers, while higher concentrations seem to lead to rather large reductions in carrier concentration.

Tynell, Tommi; Yamauchi, Hisao; Karppinen, Maarit, E-mail: maarit.karppinen@aalto.fi [Department of Chemistry, Aalto University, FI-00076 Aalto (Finland)

2014-01-15

63

Structural Characterization of Doped Thick Gainnas Layers - Ambiguities and Challenges  

NASA Astrophysics Data System (ADS)

GaInNAs alloys are mostly used as an active part of light sources for long wavelength telecom applications. Beside this, these materials are used as thin quantum wells (QWs), and a need is to grow thick layers of such semiconductor alloys for photodetectors and photovoltaic cells applications. However, structural characterization of the GaInNAs layers is hindered by non-homogeneity of the In and N distributions along the layer. In this work the challenges of the structural characterization of doped thick GaInNAs layers grown by atmospheric pressure metalorganic vapour phase epitaxy (APMOVPE) will be presented

Pucicki, Damian; Bielak, Katarzyna; ?ciana, Beata; Dawidowski, Wojciech; ?elazna, Karolina; Serafi?czuk, Jaros?aw; Ková?, Jaroslav; Vincze, Andrej; Gelczuk, ?ukasz; D?u?ewski, Piotr

2014-09-01

64

Origin of ferromagnetism enhancement in bi-layer chromium-doped indium zinc oxides  

SciTech Connect

This work demonstrates that by controlling the rapid thermal annealing temperature, amorphous chromium-doped indium zinc oxide films develop an amorphous-crystalline bi-layer structure and show magnetization up to {approx}30 emu/cm{sup 3}. The crystalline layer arises from significant out-diffusion of Zn from surfaces, leading to a large difference in the Zn:In ratio in amorphous and crystalline layers. Doped Cr ions in amorphous and crystalline layers form different valence configurations, creating a charge reservoir which transfers electrons through amorphous-crystalline interfaces and in turn enhances ferromagnetism.

Hsu, C. Y. [Physics Department, National Sun Yat-Sen University, Kaohsiung 804, Taiwan (China)

2012-08-06

65

ORIGINAL PAPER Population genetic structure of the European kestrel  

E-print Network

ORIGINAL PAPER Population genetic structure of the European kestrel Falco tinnunculus in Central revealed the presence of a genetic structure in the population investigated. Bayesian clustering indicated that samples originated from more than one population. Genetic differentiation was less pronounced among

Paris-Sud XI, Université de

66

Elastodynamic behavior of the three dimensional layer-by-layer metamaterial structure  

NASA Astrophysics Data System (ADS)

In this work, we numerically investigate for the first time the elastodynamic behavior of a three dimensional layer-by-layer rod structure, which is easy to fabricate and has already proved to be very efficient as a photonic crystal. The Finite Difference Time Domain method was used for the numerical calculations. For the rods, several materials were examined and the effects of all the geometric parameters of the structure were also numerically investigated. Additionally, two modifications of the structure were included in our calculations. The results obtained here (for certain geometric parameters), exhibiting a high ratio of longitudinal over transverse sound velocity and therefore a close approach to ideal pentamode behavior over a frequency range, clearly show that the layer-by-layer rod structure, besides being an efficient photonic crystal, is a very serious contender as an elastodynamic metamaterial.

Aravantinos-Zafiris, N.; Sigalas, M. M.; Economou, E. N.

2014-10-01

67

Elastodynamic behavior of the three dimensional layer-by-layer metamaterial structure  

SciTech Connect

In this work, we numerically investigate for the first time the elastodynamic behavior of a three dimensional layer-by-layer rod structure, which is easy to fabricate and has already proved to be very efficient as a photonic crystal. The Finite Difference Time Domain method was used for the numerical calculations. For the rods, several materials were examined and the effects of all the geometric parameters of the structure were also numerically investigated. Additionally, two modifications of the structure were included in our calculations. The results obtained here (for certain geometric parameters), exhibiting a high ratio of longitudinal over transverse sound velocity and therefore a close approach to ideal pentamode behavior over a frequency range, clearly show that the layer-by-layer rod structure, besides being an efficient photonic crystal, is a very serious contender as an elastodynamic metamaterial.

Aravantinos-Zafiris, N.; Sigalas, M. M. [Department of Materials Science, University of Patras, 26504 Patras (Greece); Economou, E. N. [Institute of Electronic Structure and Laser (IESL), Foundation for Research and Technology—Hellas (FORTH), P.O. Box 1385, Heraklion GR-71110, Greece and Department of Physics, University of Crete, Heraklion GR-71003 (Greece)

2014-10-07

68

Prolonged reorganization of thiol-capped Au nanoparticles layered structures  

NASA Astrophysics Data System (ADS)

Prolonged reorganization behaviour of mono-, di-, tri- and multi-layer films of Au nanoparticles prepared by Langmuir-Blodgett method on hydrophobic Si(001) substrates have been studied by using X-ray scattering techniques. Out-of-plane study shows that although at the initial stage the reorganization occurs through the compaction of the films keeping the layered structure unchanged but finally all layered structures modify to monolayer structure. Due to this reorganization the Au density increases within the nanometer thick films. In-plane study shows that inside the reorganized films Au nanoparticles are distributed randomly and the particle size modifies as the metallic core of Au nanoparticles coalesces.

Kundu, Sarathi; Das, Kaushik; Konovalov, Oleg

2013-09-01

69

The Triple Layer Structure of a Transitional Wall-Jet  

Microsoft Academic Search

Wall-jets are commonly found in heating and cooling applications such as gas turbine blade cooling as well as flow control [i]. The structure of wall-jets can be described by three distinct regimes: near wall boundary layer, mixing layer, and outer shear layer [ii]. Previously, wall-jet studies have focused on the self-similar fully developed length scale regime. This study examines the

Sam Raben; Wing Ng; Pavlos Vlachos

2008-01-01

70

The Structure of the Near-Neutral Atmospheric Surface Layer  

Microsoft Academic Search

Recent observational data (turbulence variables by sonic anemometers and three-dimensional flow pattern by Doppler lidar), obtained during the Cooperative Atmosphere Surface Exchange Study field campaign in October 1999 (CASES-99), show evidence of a layered structure of the near-neutral surface layer: (i) the eddy surface layer (ESL), which is the lower sublayer where blocking of impinging eddies is the dominating mechanism;

Philippe Drobinski; Pierre Carlotti; Rob K. Newsom; Robert M. Banta; Ralph C. Foster; Jean-Luc Redelsperger

2004-01-01

71

Magnetoelectric effect in thin films and layered toroidal structures  

NASA Astrophysics Data System (ADS)

A calculation of the magnetoelectric and dielectric susceptibilities is carried out for a layered structure in which thin toroidal layers alternate with dielectric layers not found in a state of spontaneous toroidal ordering. The toroic considered is nickel iodine boracite. It is shown that an anomalous increase of the magnetoelectric and dielectric susceptibilities can occur in the vicinity of the temperature of the induced toroidal phase transition.

Chupis, I. E.

2003-04-01

72

Phonon localization in ultrathin layered structures  

NASA Astrophysics Data System (ADS)

An efficient way for minimizing phonon thermal conductivity in solids is to nanostructure them by means of reduced phonon mean free path, phonon scattering and phonon reflection at interfaces. A sophisticated approach toward this lies in the fabrication of thin multilayer films of different materials. In this paper, we show by femtosecond-pump-probe reflectivity measurements that in different multilayer systems with varying acoustic mismatch (consisting of metals, semiconductors, oxides and polymers), oscillations due to phonon localization can be observed. For the growth of multilayer films with well-defined layer thicknesses, we used magnetron sputtering, evaporation and pulsed laser deposition. By altering the material combinations and reducing the layer thicknesses down to 3 nm, we observed different mechanisms of phonon blocking, reaching in the frequency regime up to 360 GHz.

Döring, F.; Eberl, C.; Schlenkrich, S.; Schlenkrich, F.; Hoffmann, S.; Liese, T.; Krebs, H. U.; Pisana, S.; Santos, T.; Schuhmann, H.; Seibt, M.; Mansurova, M.; Ulrichs, H.; Zbarsky, V.; Münzenberg, M.

2015-04-01

73

Chemical and Magnetic Study of Layered Strontium Lanthanum Manganate Structures  

Microsoft Academic Search

Previously published work describes the magnetic properties of the calcium manganate (IV) phases having tetragonal structures consisting of perovskite layers separated along the 001 direction by non-magnetic layers. Anomalous magnetic behavior exhibited by these was attributed to a persistence of short-range, two-dimensional order above the Ne´el temperature. In the present study, phases having similar structures were prepared having the general

J. B. MacChesney; J. F. Potter; R. C. Sherwood

1969-01-01

74

Origin and Structure of Dynamic Cooperative Networks  

PubMed Central

Societies are built on social interactions among individuals. Cooperation represents the simplest form of a social interaction: one individual provides a benefit to another one at a cost to itself. Social networks represent a dynamical abstraction of social interactions in a society. The behaviour of an individual towards others and of others towards the individual shape the individual's neighbourhood and hence the local structure of the social network. Here we propose a simple theoretical framework to model dynamic social networks by focussing on each individual's actions instead of interactions between individuals. This eliminates the traditional dichotomy between the strategy of individuals and the structure of the population and easily complements empirical studies. As a consequence, altruists, egoists and fair types are naturally determined by the local social structures, while globally egalitarian networks or stratified structures arise. Cooperative interactions drive the emergence and shape the structure of social networks. PMID:25030202

Wardil, Lucas; Hauert, Christoph

2014-01-01

75

Effects of buffer layer structure on polysilicon buffer LOCOS for the isolation of submicron silicon devices  

Microsoft Academic Search

The effects of a buffer layer structure on polysilicon buffered LOCOS were shown and analyzed. Sample wafers are classified into four groups to show the effect of the buffer layer structure. The structures of the four different buffer layers are monolayer polysilicon (typical), monolayer amorphous silicon (?-Si), double layer ?-Si, and triple layer ?-Si. Total buffer layer thickness of each

Jong-Ho Lee; Jong-Son Lyu; Tae Moon Roh; Bo Woo Kim

1998-01-01

76

Metal diphosphonates with double-layer and pillared layered structures based on N-cyclohexylaminomethanediphosphonate  

SciTech Connect

Based on N-cyclohexylaminomethanediphosphonic acid (cmdpH{sub 4}), four new metal diphosphonate compounds with formula M{sub 3}(cmdpH){sub 2}(H{sub 2}O){sub 2} [M=Zn(1), Co(2)] and M{sub 2}(cmdpH{sub 2}){sub 2}(4,4'-bipy){sub 0.5}(H{sub 2}O) [M=Co(3), Mn(4)] have been obtained and structurally determined. Compounds 1 and 2 are isostructural. Within the structure, the M(2)O{sub 6} octahedra are each corner-shared with four PO{sub 3}C tetrahedra to form a single layer containing 3- and 7-member rings. Neighboring single layers are pillared by M(1)O{sub 4} tetrahedra, resulting in a novel double-layer structure. The organic moieties of cmdpH{sup 3-} are grafted on the two sides of the double layer. Compounds 3 and 4 are also isostructural, displaying a pillared layered structure. Within the inorganic layer, the M(1)O{sub 5} tetragonal pyramids and M(2)NO{sub 5} octahedra are each linked by PO{sub 3}C tetrahedra through corner-sharing, forming a layer in the ab plane which contains 3- and 10-member rings. These layers are pillared by 4,4'-bipyridine via coordination with the M(2) atoms from the adjacent layers, leading to a three-dimensional open framework structure with channels generated along the a-axis. The organic groups of cmdpH{sub 2}{sup 2-} locate within the channels. Magnetic studies show that antiferromagnetic interactions are dominant in compounds 2-4. Field dependent magnetization reveals a spin flop behavior for 2. - Graphical abstract: Based on N-cyclohexylaminomethanediphosphonate (cmdp{sup 4-}), compounds Zn{sub 3}(cmdpH){sub 2}(H{sub 2}O){sub 2} (1) and Co{sub 3}(cmdpH){sub 2}(H{sub 2}O){sub 2} (2) with a double-layer structure and compounds Co{sub 2}(cmdpH{sub 2}){sub 2}(4,4'-bipy){sub 0.5}(H{sub 2}O) (3) and Mn{sub 2}(cmdpH{sub 2}){sub 2}(4,4'-bipy){sub 0.5}(H{sub 2}O) (4) with a pillared layered structure are reported in this paper. Dominant antiferromagnetic interactions are found in compounds 2-4 and an interesting spin flop behavior is observed in 2.

Su Yanhui; Cao Dengke; Duan Yan; Li Yizhi [State Key Laboratory of Coordination Chemistry, Coordination Chemistry Institute, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093 (China); Zheng Limin, E-mail: lmzheng@nju.edu.c [State Key Laboratory of Coordination Chemistry, Coordination Chemistry Institute, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093 (China)

2010-07-15

77

Superconducting structure with layers of niobium nitride and aluminum nitride  

DOEpatents

A superconducting structure is formed by depositing alternate layers of aluminum nitride and niobium nitride on a substrate. Deposition methods include dc magnetron reactive sputtering, rf magnetron reactive sputtering, thin-film diffusion, chemical vapor deposition, and ion-beam deposition. Structures have been built with layers of niobium nitride and aluminum nitride having thicknesses in a range of 20 to 350 Angstroms. Best results have been achieved with films of niobium nitride deposited to a thickness of approximately 70 Angstroms and aluminum nitride deposited to a thickness of approximately 20 Angstroms. Such films of niobium nitride separated by a single layer of aluminum nitride are useful in forming Josephson junctions. Structures of 30 or more alternating layers of niobium nitride and aluminum nitride are useful when deposited on fixed substrates or flexible strips to form bulk superconductors for carrying electric current. They are also adaptable as voltage-controlled microwave energy sources.

Murduck, James M. (Lisle, IL); Lepetre, Yves J. (Lauris, FR); Schuller, Ivan K. (Woodridge, IL); Ketterson, John B. (Evanston, IL)

1989-01-01

78

Superconducting structure with layers of niobium nitride and aluminum nitride  

DOEpatents

A superconducting structure is formed by depositing alternate layers of aluminum nitride and niobium nitride on a substrate. Deposition methods include dc magnetron reactive sputtering, rf magnetron reactive sputtering, thin-film diffusion, chemical vapor deposition, and ion-beam deposition. Structures have been built with layers of niobium nitride and aluminum nitride having thicknesses in a range of 20 to 350 Angstroms. Best results have been achieved with films of niobium nitride deposited to a thickness of approximately 70 Angstroms and aluminum nitride deposited to a thickness of approximately 20 Angstroms. Such films of niobium nitride separated by a single layer of aluminum nitride are useful in forming Josephson junctions. Structures of 30 or more alternating layers of niobium nitride and aluminum nitride are useful when deposited on fixed substrates or flexible strips to form bulk superconductors for carrying electric current. They are also adaptable as voltage-controlled microwave energy sources. 8 figs.

Murduck, J.M.; Lepetre, Y.J.; Schuller, I.K.; Ketterson, J.B.

1989-07-04

79

ORIGINAL PAPER Population genetic structure of the Daubenton's bat  

E-print Network

ORIGINAL PAPER Population genetic structure of the Daubenton's bat (Myotis daubentonii) in western. Migration . Lyssavirus . Myotis daubentonii Introduction The Daubenton's bat, Myotis daubentonii, has been bats (Myotis dasycneme) suggesting that these are the normal maintenance hosts for the virus

Paris-Sud XI, Université de

80

72. PHOTOCOPY OF ORIGINAL DRAWING OF 1904 STRUCTURE, GROUND FLOOR ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

72. PHOTOCOPY OF ORIGINAL DRAWING OF 1904 STRUCTURE, GROUND FLOOR PLAN, E, B, AND K BUILDINGS. ADDISON HUTTON COLLECTION - Chalfonte Hotel, Pacific & North Carolina Avenues, Atlantic City, Atlantic County, NJ

81

Evaluation of layer-by-layer graphene structures as supercapacitor electrode materials  

NASA Astrophysics Data System (ADS)

Very less attention has been paid recently to the electrochemical properties of graphene films with intrinsic flat structure prepared by chemical vapor deposition (CVD). In this work, button supercapacitors were fabricated using ionic liquid as electrolytes and layer-by-layer graphene structures as electrodes. The specific capacitances of the supercapacitors increased with the increase of layer number. The areal specific capacitance of ten-layer graphene supercapacitor was 0.29 mF/cm2 at the scan rate of 50 mV/s, which was about three times of that of monolayer graphene supercapacitor (0.1 mF/cm2). The sandwiched multi-layer structures with oxide deposition further improved the device performance. However, the polycrystalline nature of CVD-grown graphene films introduced structural instability during charge-discharge process, resulting in degraded capacitive performance and cycling stability. Our results suggest that graphene films with intrinsic "in-plane" structure might not be ideal candidates for electrode materials.

Zang, Xiaobei; Li, Peixu; Chen, Qiao; Wang, Kunlin; Wei, Jinquan; Wu, Dehai; Zhu, Hongwei

2014-01-01

82

Novel nanoscroll structures from carbon nitride layers.  

PubMed

Nanoscrolls (papyrus-like nanostructures) are very attractive structures for a variety of applications, owing to their tunable diameter and large accessible surface area. They have been successfully synthesized from different materials. In this work, we investigate, through fully atomistic molecular dynamics simulations, the dynamics of scroll formation for a series of graphene-like carbon nitride (CN) two-dimensional systems: g-CN, triazine-based g-C3 N4 , and heptazine-based g-C3 N4 . Our results show that stable nanoscrolls can be formed for each of these structures. Possible synthetic routes to produce these nanostructures are also addressed. PMID:24819427

Perim, Eric; Galvao, Douglas S

2014-08-01

83

Nucleomorph genomes: structure, function, origin and evolution  

E-print Network

:147­175) Eukaryotic genome diversity--the big picture The nuclear genome is tremendously diverse in size and structure. Taking into account the full breadth of eukaryotic diversity, nuclear genomes vary in size 200,000 fold(1- similation of eukaryotic endosymbionts. As a result, they possess two distinct cytosolic compartments

Archibald, John

84

Original Articles The Nested Structure of Cancer  

E-print Network

, and degree of nested- ness of the symptoms based on the most fre- quently co-occurring symptoms for different and distribution. Results: The cancer symptoms tended to co- occur in a nested structure,where there was a small set of symptoms that co-occurred in many patients, and progressively larger sets of symptoms that co-occurred

Bhavnani, Suresh K.

85

The structure of a three-dimensional turbulent boundary layer  

NASA Technical Reports Server (NTRS)

The three-dimensional turbulent boundary layer is shown to have a self-consistent two-layer asymptotic structure in the limit of large Reynolds number. In a streamline coordinate system, the streamwise velocity distribution is similar to that in two-dimensional flows, having a defect-function form in the outer layer which is adjusted to zero at the wall through an inner wall layer. An asymptotic expansion accurate to two orders is required for the cross-stream velocity which is shown to exhibit a logarithmic form in the overlap region. The inner wall-layer flow is collateral to leading order but the influence of the pressure gradient, at large but finite Reynolds numbers, is not negligible and can cause substantial skewing of the velocity profile near the wall. Conditions under which the boundary layer achieves self-similarity and the governing set of ordinary differential equations for the outer layer are derived. The calculated solution of these equations is matched asymptotically to an inner wall-layer solution and the composite profiles so formed describe the flow throughout the entire boundary layer. The effects of Reynolds number and cross-stream pressure gradient on the crossstream velocity profile are discussed and it is shown that the location of the maximum cross-stream velocity is within the overlap region.

Degani, A. T.; Smith, F. T.; Walker, J. D. A.

1993-01-01

86

GPR determination of physical parameters of railway structural layers  

NASA Astrophysics Data System (ADS)

The paper studies the possibility of quantitative processing of the GPR data for determining the refractive index and conductivity of motor road and railway constructional layers. The main objective of the work is to develop a method of obtaining quantitative information on chosen physical properties of soil layers from regular GPR surveys. Theoretical study of plane electromagnetic wave propagation is made for the model of layered soil structure. As a result of the study appropriate equation systems are derived for the calculations of refractive index and conductivity of structural layers. Based on these equations the method of quantitative processing of radargrams is proposed. The method includes the GPR data processing algorithm and theoretical techniques for determination of refractive index and conductivity of the structural layers. The applicability of the proposed method was initially validated by lab experiments using radargrams of the soil samples with specified values of moisture and conductivity and reliable results were achieved. The methods were also successfully used while monitoring the long term seasonal changes in structural layers of several Russian railways sections. The contamination of ballast material is also evaluated by this method in addition to the refractive index and conductivity.

Khakiev, Zelimkhan; Shapovalov, Vladimir; Kruglikov, Alexander; Yavna, Victor

2014-07-01

87

Complex layered arrays as photonic band-gap structures  

Microsoft Academic Search

The reflective and transmitting properties of several layers of double-periodic arrays are studied. In the arrays, elements are conducting inclusions of various shapes. It is shown that in these structures all the phenomena recently found in dense wire grids with periodical defects (so called photonic band-gap structures) can be observed and explained in simple terms of interlayer and inclusion resonances.

S. L. Prosvirnin; S. A. Tretyakov; T. D. Vasilyeva; A. Fourrier-Lamer; S. Zouhdi

2000-01-01

88

The structure of turbulent boundary layers along mildly curved surfaces  

Microsoft Academic Search

The structure of turbulence in boundary layers along mildly curved convex and concave surfaces is studied. Measurements of turbulent energy balance, autocorrelations, auto- and cross-power spectra, amplitude probability distributions, and conditional correlations are reported. It is observed that even mild curvature has very strong effects on the various aspects of the turbulent structure. For example, convex curvature suppresses the diffusion

B. R. Ramaprian; B. G. Shivaprasad

1978-01-01

89

The simulation of coherent structures in a laminar boundary layer  

NASA Technical Reports Server (NTRS)

Coherent structures in turbulent shear flows were studied extensively by several techniques, including the VITA technique which selects rapidly accelerating or decelerating regions in the flow. The evolution of a localized disturbance in a laminar boundary layer shows strong similarity to the evolution of coherent structures in a turbulent-wall bounded flow. Starting from a liftup-sweep motion, a strong shear layer develops which shares many of the features seen in conditionally-sampled turbulent velocity fields. The structure of the shear layer, Reynolds stress distribution, and wall pressure footprint are qualitatively the same, indicating that the dynamics responsible for the structure's evolution are simple mechanisms dependent only on the presence of a high mean shear and a wall and independent of the effects of local random fluctuations and outer flow effects. As the disturbance progressed, the development of streak-like-high- and low-speed regions associated with the three-dimensionality.

Breuer, Kenny; Landahl, Marten T.; Spalart, Philippe R.

1987-01-01

90

Structural origins of morphing in plant tissues  

NASA Astrophysics Data System (ADS)

Plant tissues are able to generate complex movements via shape modifications. These effects are tightly related to distinctive multi-scale composite architectures of the plant material, and can therefore largely be interpreted by composite mechanics principles. Here, we propose a generic framework for the analysis and prediction of the shape morphing of intricate biological composite materials, arising from changes in humidity. We have examined in depth the hierarchical structures of three types of seed pods for which we propose a theoretical scheme that is able to accurately simulate the relevant shape deformations. The validity and generality of this approach are confirmed by means of laboratory scale synthetic models with similar architectures leading to equivalent morphing patterns. Such synthetic configurations could pave the way to future morphing architectures of advanced materials and structures.

Bar-On, Benny; Sui, Xiaomeng; Livanov, Konstantin; Achrai, Ben; Kalfon-Cohen, Estelle; Wiesel, Erica; Daniel Wagner, H.

2014-07-01

91

Prediction of silicon-based layered structures for optoelectronic applications.  

PubMed

A method based on the particle swarm optimization algorithm is presented to design quasi-two-dimensional materials. With this development, various single-layer and bilayer materials of C, Si, Ge, Sn, and Pb were predicted. A new Si bilayer structure is found to have a more favored energy than the previously widely accepted configuration. Both single-layer and bilayer Si materials have small band gaps, limiting their usages in optoelectronic applications. Hydrogenation has therefore been used to tune the electronic and optical properties of Si layers. We discover two hydrogenated materials of layered Si8H2 and Si6H2 possessing quasidirect band gaps of 0.75 and 1.59 eV, respectively. Their potential applications for light-emitting diode and photovoltaics are proposed and discussed. Our study opened up the possibility of hydrogenated Si layered materials as next-generation optoelectronic devices. PMID:25314126

Luo, Wei; Ma, Yanming; Gong, Xingao; Xiang, Hongjun

2014-11-12

92

Spatial structures and scaling in the Convective Boundary Layer  

NASA Astrophysics Data System (ADS)

We performed an investigation on spatial features of the Convective Boundary Layer (CBL) of the atmosphere, which was simulated in a laboratory model and analyzed by means of image analysis techniques. This flow is dominated by large, anisotropic vortical structures, whose spatial organization affects the scalar transport and therefore the fluxes across the boundary layer. With the aim of investigating the spatial structure and scaling in the Convective Boundary Layer, two-dimensional velocity fields were measured, on a vertical plane, by means of a pyramidal Lucas-Kanade algorithm. The coherent structures characterizing the turbulent convection were educed by analyzing the Finite-Time Lyapunov Exponent fields, which also revealed interesting phenomenological features linked to the mixing processes occurring in the Convective Boundary Layer. Both velocity and vorticity fields were analyzed in a scale-invariance framework. Data analysis showed that normalized probability distribution functions for velocity differences are dependent on the scale and tend to become Gaussian for large separations. Extended Self Similarity holds true for velocity structure functions computed within the mixing layer, and their scaling exponents are interpreted well in the phenomenological framework of the Hierarchical Structure Model. Specifically, ? parameter, which is related to the similarity between weak and strong vortices, reveals a higher degree of intermittency for the vertical velocity component with respect to the horizontal one. On the other hand, the analysis of circulation structure functions shows that scaling exponents are fairly constant in the lowest part of the mixed layer, and their values are in agreement with those reported in Benzi et al. (Phys Rev E 55:3739-3742, 1997) for shear turbulence. Moreover, the relationship between circulation and velocity scaling exponents is analyzed, and it is found to be linear in the bottom part of the mixing layer. The investigation of the CBL spatial features, which has seldom been studied experimentally, has important implications for the comprehension of the mixing dynamics, as well as in turbulence closure models.

Badas, M. G.; Querzoli, G.

2011-04-01

93

Structure of the regular surface layer of Sporosarcina ureae.  

PubMed Central

Optical diffraction and computer image processing of electron micrographs were employed to analyze the structure of the regular surface layer of Sporosarcina ureae at high resolution. Negatively stained preparations of regular surface layer fragments showed two types of tetragonal pattern, each having p4 symmetry in projection with a = 12.8 nm. Although the two patterns differed greatly in overall appearance, both had a common pattern of areas of high stain density which we interpret as arising from gaps or holes in the structure. We speculate that these holes may be related to a protective role of the regular surface layer, whereby hostile environmental agents (such as muramidases) larger than about 2 nm would be screened from the underlying layers of the bacterial surface, while the free passage of nutrients and waste products into and out of the cell would still be allowed. Images PMID:7372574

Stewart, M; Beveridge, T J

1980-01-01

94

Lactobacillus surface layer proteins: structure, function and applications.  

PubMed

Bacterial surface (S) layers are the outermost proteinaceous cell envelope structures found on members of nearly all taxonomic groups of bacteria and Archaea. They are composed of numerous identical subunits forming a symmetric, porous, lattice-like layer that completely covers the cell surface. The subunits are held together and attached to cell wall carbohydrates by non-covalent interactions, and they spontaneously reassemble in vitro by an entropy-driven process. Due to the low amino acid sequence similarity among S-layer proteins in general, verification of the presence of an S-layer on the bacterial cell surface usually requires electron microscopy. In lactobacilli, S-layer proteins have been detected on many but not all species. Lactobacillus S-layer proteins differ from those of other bacteria in their smaller size and high predicted pI. The positive charge in Lactobacillus S-layer proteins is concentrated in the more conserved cell wall binding domain, which can be either N- or C-terminal depending on the species. The more variable domain is responsible for the self-assembly of the monomers to a periodic structure. The biological functions of Lactobacillus S-layer proteins are poorly understood, but in some species S-layer proteins mediate bacterial adherence to host cells or extracellular matrix proteins or have protective or enzymatic functions. Lactobacillus S-layer proteins show potential for use as antigen carriers in live oral vaccine design because of their adhesive and immunomodulatory properties and the general non-pathogenicity of the species. PMID:23677442

Hynönen, Ulla; Palva, Airi

2013-06-01

95

Structural Origins of Aminoglycoside Specificity for Prokaryotic Ribosomes  

E-print Network

Structural Origins of Aminoglycoside Specificity for Prokaryotic Ribosomes Stephen R. Lynch of a prokaryotic decoding region A-site oligonucleotide free in solution and bound to the aminogly- cosides to the prokaryotic A-site-paromomycin structure. A con- formational change in three adenosine residues of an internal

Puglisi, Joseph

96

A New View on Origin, Role and Manipulation of Large Scales in Turbulent Boundary Layers  

NASA Technical Reports Server (NTRS)

The potential of passive 'manipulators' for altering the large scale turbulent structures in boundary layers was investigated. Utilizing smoke wire visualization and multisensor probes, the experiment verified that the outer scales could be suppressed by simple arrangements of parallel plates. As a result of suppressing the outer scales in turbulent layers, a decrease in the streamwise growth of the boundary layer thickness was achieved and was coupled with a 30 percent decrease in the local wall friction coefficient. After accounting for the drag on the manipulator plates, the net drag reduction reached a value of 20 percent within 55 boundary layer thicknesses downstream of the device. No evidence for the reoccurrence of the outer scales was present at this streamwise distance thereby suggesting that further reductions in the net drag are attainable. The frequency of occurrence of the wall events is simultaneously dependent on the two parameters, Re2 delta sub 2 and Re sub x. As a result of being able to independently control the inner and outer boundary layer characteristics with these manipulators, a different view of these layers emerged.

Corke, T. C.; Nagib, H. M.; Guezennec, Y. G.

1982-01-01

97

An origin of marginal reversal of the Fongen-Hyllingen layered intrusion by prolonged magma emplacement  

NASA Astrophysics Data System (ADS)

The ~100 m thick marginal zone of the Fongen-Hyllingen Intrusion (FHI) consists of nonlayered, highly iron-enriched ferrodiorites that are overlain by a ~6 km thick layered sequence of gabbroic to dioritic rocks of the Layered Series. From the base upwards the marginal zone become more primitive as exemplified by a significant increase in whole-rock MgO, Mg-number, and normative An. The reverse trends are also evident from an upward increase in An-content of plagioclase (from ~30 to ~43 at.%) and Mg-number of amphibole (from ~9 to ~23 at.%) and clinopyroxene (from ~23 to ~37 at.%). The marginal zone is abruptly terminated at the contact with the overlying Layered Series as is evident from a step-like increase in Mg-number of mafic minerals and An-content of plagioclase, as well as a sharp increase in whole-rock MgO and Mg-number in overlying olivine gabbronorites of the Layered Series. Based on these features the marginal zone of the FHI can be interpreted as an aborted marginal reversal. Reverse trends in whole-rock and mineral compositions, as well as a sharp break in these parameters are indicative of its formation in an open system with the involvement of the prolonged emplacement of magma that became increasingly more primitive. Such development of the marginal reversal was interrupted by the emplacement of a major influx of more primitive magma that produced the Layered Series. The open system evolution of a basaltic magma chamber may represent a general mechanism for the origin of marginal reversals in mafic sills and layered intrusions.

Egorova, V.; Latypov, R.

2012-04-01

98

TEMPERATURE STRUCTURE OF PROTOPLANETARY DISKS UNDERGOING LAYERED ACCRETION  

SciTech Connect

We calculate the temperature structures of protoplanetary disks (PPDs) around T Tauri stars heated by both incident starlight and viscous dissipation. We present a new algorithm for calculating the temperatures in disks in hydrostatic and radiative equilibrium, based on Rybicki's method for iteratively calculating the vertical temperature structure within an annulus. At each iteration, the method solves for the temperature at all locations simultaneously, and converges rapidly even at high (>>10{sup 4}) optical depth. The method retains the full frequency dependence of the radiation field. We use this algorithm to study for the first time disks evolving via the magnetorotational instability. Because PPD midplanes are weakly ionized, this instability operates preferentially in their surface layers, and disks will undergo layered accretion. We find that the midplane temperatures T{sub mid} are strongly affected by the column density {Sigma}{sub a} of the active layers, even for fixed mass accretion rate M-dot . Models assuming uniform accretion predict midplane temperatures in the terrestrial planet forming region several x 10{sup 2} K higher than our layered accretion models do. For M-dot < 10{sup -7} M{sub sun} yr{sup -1} and the column densities {Sigma}{sub a} < 10 g cm{sup -2} associated with layered accretion, disk temperatures are indistinguishable from those of a passively heated disk. We find emergent spectra are insensitive to {Sigma}{sub a}, making it difficult to observationally identify disks undergoing layered versus uniform accretion.

Lesniak, M. V. [Department of Physics, Arizona State University, P.O. Box 1504, Tempe, AZ 85287-1504 (United States); Desch, S. J., E-mail: mvl@asu.edu [School of Earth and Space Exploration, Arizona State University, P.O. Box 871404, Tempe, AZ 85287-1404 (United States)

2011-10-20

99

Ternary metal-rich sulfide with a layered structure  

DOEpatents

A ternary Nb-Ta-S compound is provided having the atomic formula, Nb.sub.1.72 Ta.sub.3.28 S.sub.2, and exhibiting a layered structure in the sequence S-M3-M2-M1-M2-M3-S wherein S represents sulfur layers and M1, M2, and M3 represent Nb/Ta mixed metal layers. This sequence generates seven sheets stacked along the [001] direction of an approximate body centered cubic crystal structure with relatively weak sulfur-to-sulfur van der Waals type interactions between adjacent sulfur sheets and metal-to-metal bonding within and between adjacent mixed metal sheets.

Franzen, Hugo F. (Ames, IA); Yao, Xiaoqiang (Ames, IA)

1993-08-17

100

Strained layer superlattice focal plane array having a planar structure  

DOEpatents

An infrared focal plane array (FPA) is disclosed which utilizes a strained-layer superlattice (SLS) formed of alternating layers of InAs and In.sub.xGa.sub.1-xSb with 0.ltoreq.x.ltoreq.0.5 epitaxially grown on a GaSb substrate. The FPA avoids the use of a mesa structure to isolate each photodetector element and instead uses impurity-doped regions formed in or about each photodetector for electrical isolation. This results in a substantially-planar structure in which the SLS is unbroken across the entire width of a 2-D array of the photodetector elements which are capped with an epitaxially-grown passivation layer to reduce or eliminate surface recombination. The FPA has applications for use in the wavelength range of 3-25 .mu.m.

Kim, Jin K; Carroll, Malcolm S; Gin, Aaron; Marsh, Phillip F; Young, Erik W; Cich, Michael J

2012-10-23

101

A New Series of Bismuth Layer-Structured Ferroelectrics  

Microsoft Academic Search

The general formula of a phase relation between well-known bismuth layer-structured ferroelectrics (BLSF) such as Bi3TiNbO9, Na0.5Bi2.5Nb2O9, Bi4Ti3O12, and Na0.5Bi4.5Ti4O15 including perovskite compounds (Bi0.5Na0.5) TiO3 and NaNbO3, that is, Na(m-3+x)\\/2 Bi(m+5-x)\\/2 Tim-x Nbx O3m+3 (2<=m<=5), was discussed to form the layer structure with the numbers m=3, 4 and 5 of layer, where x is the number of Nb ions in

Tadashi Takenaka; Takahiro Gotoh; Sigeo Mutoh; Takeshi Sasaki

1995-01-01

102

Structure evolution of implanted polymers: Buried conductive layer formation  

NASA Astrophysics Data System (ADS)

The polarization, temperature and frequency dependence of the conductivity of polyethylene and poliamide-6 films implanted with B + ions at 60-100 keV to various fluences were investigated. The phenomenon of hysteresis was observed in the d.c. current-voltage dependence for the polymers implanted with moderate fluences. This effect was attributed to the aligning of electric dipoles (attributed to the carbon-rich clusters) in the implanted layer by the applied electric field. The possibility of fabrication of a sandwich structure insulator/conductive layer/insulator combining the ion implantation with the electrochemical deposition of dielectric polymer poly-ortho-phenylenediamine from solution was demonstrated. The spatial characteristics of this structure enable the control of the conductance of the concealed carbonaceous layer by applying an external electric field that opens the way for fabrication of a transistor-like electronic switch.

Popok, V. N.; Karpovich, I. A.; Odzhaev, V. B.; Sviridov, D. V.

1999-01-01

103

Coherent structures in compressible free-shear-layer flows  

SciTech Connect

Large scale coherent structures are intrinsic fluid mechanical characteristics of all free-shear flows, from incompressible to compressible, and laminar to fully turbulent. These quasi-periodic fluid structures, eddies of size comparable to the thickness of the shear layer, dominate the mixing process at the free-shear interface. As a result, large scale coherent structures greatly influence the operation and efficiency of many important commercial and defense technologies. Large scale coherent structures have been studied here in a research program that combines a synergistic blend of experiment, direct numerical simulation, and analysis. This report summarizes the work completed for this Sandia Laboratory-Directed Research and Development (LDRD) project.

Aeschliman, D.P.; Baty, R.S. [Sandia National Labs., Albuquerque, NM (United States). Engineering Sciences Center; Kennedy, C.A.; Chen, J.H. [Sandia National Labs., Livermore, CA (United States). Combustion and Physical Sciences Center

1997-08-01

104

Structural reinforcement of microvascular networks using electrostatic layer-by-layer assembly with halloysite nanotubes.  

PubMed

We demonstrate a method for tailoring local mechanical properties near channel surfaces of vascular structural polymers in order to achieve high structural performance in microvascular systems. While synthetic vascularized materials have been created by a variety of manufacturing techniques, unreinforced microchannels act as stress concentrators and lead to the initiation of premature failure. Taking inspiration from biological tissues such as dentin and bone, these mechanical deficiencies can be mitigated by complex hierarchical structural features near to channel surfaces. By employing electrostatic layer-by-layer assembly (ELbL) to deposit films containing halloysite nanotubes onto scaffold surfaces followed by matrix infiltration and scaffold removal, we are able to controllably deposit nanoscale reinforcement onto 200 micron diameter channel surface interiors in microvascular networks. High resolution strain measurements on reinforced networks under load verify that the halloysite reduces strain concentrations and improves mechanical performance. PMID:24652338

Olugebefola, Solar C; Hamilton, Andrew R; Fairfield, Daniel J; Sottos, Nancy R; White, Scott R

2014-01-28

105

Layered Structure and Management in Internet of Things  

Microsoft Academic Search

The development for Internet of Things and RFID technology is described in this paper. A feasible scheme and layered structure is proposed for Internet of Things. Its management is presented according to the demand for Internet of Things in China. The general system contains two parts: computer information subsystem and RFID terminal subsystem, the latter of which is the main

Huansheng Ning; Na Ning; Shenfeng Qu; Yan Zhang; Huiping Yang

2007-01-01

106

Inverse magnetoelectric effects in a ferromagnetic piezoelectric layered structure  

E-print Network

Inverse magnetoelectric effects in a ferromagnetic­ piezoelectric layered structure Y.K. Fetisov, V 18 December 2006; accepted 9 March 2007) Measurements of inverse magnetoelectric (ME) effects in lead are in excellent agreement with values determined from data on induced voltage. I. INTRODUCTION Magnetoelectric (ME

Srinivasan, Gopalan

107

Using Layer-Cake Geology to Illustrate Structural Topographic Relationships.  

ERIC Educational Resources Information Center

Discusses some of the difficulties of visualizing underlying geologic structural patterns by using maps or wooden blocks. Suggests the use of a modified layer cake to show dipping beds, folds, faults and differential erosion, as well as the relationships of stream valleys to outcrop patterns. (TW)

Wagner, John Robert

1987-01-01

108

Pyroelectric properties of bismuth layer-structured ferroelectric ceramics  

Microsoft Academic Search

Pyroelectric properties of a bismuth layer-structured ferroelectric (BLSF) family are studied on ordinarily fired (OF) (nonoriented) and grain-oriented ceramics for pyrosensor materials. The pyroelectric figure of merit, Fv and FD, are evaluated from the measured values of the pyroelectric coefficient, p, the dielectric constant, ? = ?33 \\/?0, and the loss tangent, tan ?. Infrared frequency response measurements give the

Tadashi Takenaka; Koichiro Sakata

1991-01-01

109

Bismuth Layer Structured Ferroelectric Ceramics with High Mechanical Quality Factor  

Microsoft Academic Search

The piezoelectric properties in some bismuth layer-structured ferroelectric (BLSF) ceramics were investigated focusing on a mechanical quality factor, Qm. Many BLSF compositions with various Curie temperature, Tc, were selected in this study, and the Qm values of (33) mode were plotted as a function of their Curie temperature, Tc. The Qm increased with increasing the Tc in the low Tc

Hajime Nagata; Yuji Hiruma; Muneyasu Suzuki; Tadashi Takenaka

2007-01-01

110

Vertical velocity structure of nonprecipitating continental boundary layer stratocumulus clouds  

Microsoft Academic Search

Continental boundary layer (BL) stratocumulus clouds affect the local weather by modulating the surface energy and moisture budgets and are also intimately tied to the diurnal cycle of the turbulence in the BL. Vertical velocity structure of these clouds is studied using data from the Atmospheric Radiation Measurement Program's Southern Great Plains observing facility located near Lamont, Oklahoma. Data from

Virendra P. Ghate; Bruce A. Albrecht; Pavlos Kollias

2010-01-01

111

Large-Scale Streamwise Turbulent Structures in Hypersonic Boundary Layers  

E-print Network

Velocimetry in a M = 4.9 blow-down wind tunnel accompanied by a series of data analysis in order to identify the existence of streamwise-elongated large-scale turbulence structures in a hypersonic boundary layer. Furthermore, this study identified physical...

English, Benjamin L.

2013-04-22

112

Oblique along path toward structures at rear of parcel. Original ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

Oblique along path toward structures at rear of parcel. Original skinny mosaic path along edge of structures was altered (delineation can be seen in concrete) path was widened with a newer mosaic to make access to the site safer. Structures (from right) edge of Round House (with "Spring Garden"), Pencil house, Shell House, School House, wood lattice is attached to chain-link fence along north (rear) property line. These structures were all damaged by the 1994 Northridge earthquake. Camera facing northeast. - Grandma Prisbrey's Bottle Village, 4595 Cochran Street, Simi Valley, Ventura County, CA

113

Origin of Martian Interior Layered Deposits (ILDs) by atmospherically driven processes  

NASA Astrophysics Data System (ADS)

Since the first photogeologic exploration of Mars, vast mounds of layered sediments found within the Valles Marineris canyon system (Interior Layered Deposits or ILDs) have remained unexplained. Recent spectroscopic results showing that these materials contain coarse-grained hematite [1] and sulfate [2-8] suggest that they are fundamentally similar to layered sulfate deposits seen elsewhere on Mars [3], and are therefore a key piece of Mars' global aqueous history. Layered sulfate deposits (including ILDs) are often considered to have formed in association with transient, wet surface environments caused by groundwater upwelling [9] in the Hesperian. Here, we use spectroscopic mapping along with geomorphic observations and mass balance calculations to demonstrate that the sulfate-bearing ILDs likely did not form due to groundwater upwelling or any similar playa-lacustrine scenario. Instead, the ILDs likely formed from atmospherically driven processes in a configuration similar to that observed today. We suggest that Hesperian layered sulfate deposits formed in response to massive amounts of pyroclastic volcanism and SO2-outgassing that peaked near 3.5-3.7 Ga in a Martian climate that was largely cold and dry. This origin for the ILDs is also applicable to other layered terrain of similar age and characteristics, including sulphate-bearing crater fill, chaos terrains, and the Meridiani Planum sediments. [1] Weitz, C. M., Lane, M. D., Staid, M. & Dobrea, E. N. Gray hematite distribution and formation in Ophir and Candor chasmata. Journal of Geophysical Research-Planets 113, doi:E02016 10.1029/2007je002930 (2008). [2] Wendt, L. et al. Sulfates and iron oxides in Ophir Chasma, Mars, based on OMEGA and CRISM observations. Icarus 213, 86-103, doi:10.1016/j.icarus.2011.02.013 (2011). [3] Murchie, S. et al. Evidence for the origin of layered deposits in Candor Chasma, Mars, from mineral composition and hydrologic modeling. Journal of Geophysical Research-Planets 114, doi:E00d05 10.1029/2009je003343 (2009). [4] Mangold, N. et al. Spectral and geological study of the sulfate-rich region of West Candor Chasma, Mars. Icarus 194, 519-543, doi:10.1016/j.icarus.2007.10.021 (2008). [5] Le Deit, L. et al. Morphology, stratigraphy, and mineralogical composition of a layered formation covering the plateaus around Valles Marineris, Mars: Implications for its geological history. Icarus 208, 684-703, doi:10.1016/j.icarus.2010.03.012 (2010). [6] Gendrin, A. et al. Suffates in martian layered terrains: the OMEGA/Mars Express view. Science 307, 1587-1591, doi:10.1126/science.1109087 (2005). [7] Bibring, J.-P. et al. Coupled Ferric Oxides and Sulfates on the Martian Surface. Science 317, 1206-1210, doi:10.1126/science.1144174 (2007). [8] Roach, L. H., Mustard, J. F., Lane, M. D., Bishop, J. L. & Murchie, S. L. Diagenetic haematite and sulfate assemblages in Valles Marineris. Icarus 207, 659-674, doi:10.1016/j.icarus.2009.11.029 (2010). [9] Andrews-Hanna, J. C. & Lewis, K. W. Early Mars hydrology: 2. Hydrological evolution in the Noachian and Hesperian epochs. Journal of Geophysical Research-Planets 116, doi:E02007 10.1029/2010je003709 (2011).

Michalski, J. R.; Niles, P. B.

2011-12-01

114

Origins of unintentional incorporation of gallium in InAlN layers during epitaxial growth, part II: Effects of underlying layers and growth chamber conditions  

NASA Astrophysics Data System (ADS)

We systematically study the origins and mechanisms for unintentional incorporation of gallium (Ga) during epitaxial growth of ternary InAlN thin-film layers. The origins of auto-incorporation of Ga have been investigated by using different underlying layers, regrown layers, and growth chamber conditions. It is shown that Ga-containing deposition on a wafer susceptor/carrier and on surrounding surfaces of uncooled parts in a growth chamber can be responsible for Ga in the InAl(Ga)N layers, while a GaN underlying layer below an InAl(Ga)N layer does not contribute to the auto-incorporation of Ga in the InAl(Ga)N layers. Especially, the Ga-containing deposition on the surfaces inside the chamber is believed to be the dominant source of auto-incorporated Ga, possibly due to the high vapor pressure of a liquid phase as a result of eutectic system formation between indium (In) and Ga. The pressure of liquid-phase Ga, pGa=~3.67×10-4 Torr, can be significant as compared to precursor partial pressures with pTMAl=3.7×10-4 Torr and pTMIn=2.4×10-5 Torr. In addition, magnesium (Mg) or magnesium precursor (Cp2Mg) in the growth chamber is shown to promote the auto-incorporation of Ga in the InAl(Ga)N layers.

Kim, Jeomoh; Lochner, Zachary; Ji, Mi-Hee; Choi, Suk; Kim, Hee Jin; Kim, Jin Soo; Dupuis, Russell D.; Fischer, Alec M.; Juday, Reid; Huang, Yu; Li, Ti; Huang, Jingyi Y.; Ponce, Fernando A.; Ryou, Jae-Hyun

2014-02-01

115

Multi-functional layered structure having structural and radiation shielding attributes  

NASA Technical Reports Server (NTRS)

A cosmic and solar radiation shielding structure that also has structural attributes is comprised of three layers. The first layer is 30-42 percent by volume of ultra-high molecular weight (UHMW) polyethylene fibers, 18-30 percent by volume of graphite fibers, and a remaining percent by volume of an epoxy resin matrix. The second layer is approximately 68 percent by volume of UHMW polyethylene fibers and a remaining percent by volume of a polyethylene matrix. The third layer is a ceramic material.

Kaul, Raj K. (Inventor); Barghouty, Abdulnasser Fakhri (Inventor); Penn, Benjamin G. (Inventor); Hulcher, Anthony Bruce (Inventor)

2010-01-01

116

Origin of perpendicular magnetic anisotropy in Co/Ni multilayers on Ti layer  

NASA Astrophysics Data System (ADS)

Magnetic materials in which their magnetic moment direction is oriented perpendicular to the plane of the magnetic layers in thin film heterostructures have been much studied for their potential application to spintronic devices. In particular, theories of current induced excitation, via the phenomenon of spin torque transfer, show that perpendicularly magnetized layers can be more easily excited or their magnetization direction switched than in-plane magnetized layers. In particular, Co/Ni multilayers are promising due to high spin polarization and small Gilbert damping compared to Co/Pt or Fe/Pt. However, their perpendicular magnetic anisotropy (PMA) is highly sensitive to the underlayer that is critical in device performance because, for instance, the current shunting can substantially reduce the spin transfer torque in magnetic racetrack memory. We observed an excellent PMA in annealed Co/Ni on Ti underlayer whose resistance is significantly greater than those of Co/Ni, thereby minimizing the current shunting. It is found that the PMA does not simply originate from magneto-crystalline effect (spin-orbit interaction) but mainly from magnetoelastic effect caused by compressive strain along (111) direction. We will present systematic results and quantitative analyses.

Yang, See-Hun; Thoms, Kuei-Hung; Thomas, Luc; Parkin, Stuart

2012-02-01

117

Stable single-layer honeycomblike structure of silica.  

PubMed

Silica or SiO(2), the main constituent of Earth's rocks has several 3D complex crystalline and amorphous phases, but it does not have a graphitelike layered structure in 3D. Our theoretical analysis and numerical calculations from the first principles predict a single-layer honeycomblike allotrope, h? silica, which can be viewed to be derived from the oxidation of silicene and it has intriguing atomic structure with reentrant bond angles in hexagons. It is a wide band gap semiconductor, which attains remarkable electromechanical properties showing geometrical changes under an external electric field. In particular, it is an auxetic metamaterial with a negative Poisson's ratio and has a high piezoelectric coefficient. While it can form stable bilayer and multilayer structures, its nanoribbons can show metallic or semiconducting behavior depending on their chirality. Coverage of dangling Si orbitals by foreign adatoms can attribute new functionalities to h? silica. In particular, Si(2)O(5), where Si atoms are saturated by oxygen atoms from top and bottom sides alternatingly can undergo a structural transformation to make silicatene, another stable, single layer structure of silica. PMID:24996101

Özçelik, V Ongun; Cahangirov, S; Ciraci, S

2014-06-20

118

Stable Single-Layer Honeycomblike Structure of Silica  

NASA Astrophysics Data System (ADS)

Silica or SiO2, the main constituent of Earth's rocks has several 3D complex crystalline and amorphous phases, but it does not have a graphitelike layered structure in 3D. Our theoretical analysis and numerical calculations from the first principles predict a single-layer honeycomblike allotrope, h? silica, which can be viewed to be derived from the oxidation of silicene and it has intriguing atomic structure with reentrant bond angles in hexagons. It is a wide band gap semiconductor, which attains remarkable electromechanical properties showing geometrical changes under an external electric field. In particular, it is an auxetic metamaterial with a negative Poisson's ratio and has a high piezoelectric coefficient. While it can form stable bilayer and multilayer structures, its nanoribbons can show metallic or semiconducting behavior depending on their chirality. Coverage of dangling Si orbitals by foreign adatoms can attribute new functionalities to h? silica. In particular, Si2O5, where Si atoms are saturated by oxygen atoms from top and bottom sides alternatingly can undergo a structural transformation to make silicatene, another stable, single layer structure of silica.

Özçelik, V. Ongun; Cahangirov, S.; Ciraci, S.

2014-06-01

119

A New Series of Bismuth Layer-Structured Ferroelectrics  

NASA Astrophysics Data System (ADS)

The general formula of a phase relation between well-known bismuth layer-structured ferroelectrics (BLSF) such as Bi3TiNbO9, Na0.5Bi2.5Nb2O9, Bi4Ti3O12, and Na0.5Bi4.5Ti4O15 including perovskite compounds (Bi0.5Na0.5) TiO3 and NaNbO3, that is, Na(m-3+x)/2 Bi(m+5-x)/2 Tim-x Nbx O3m+3 (2?m?5), was discussed to form the layer structure with the numbers m=3, 4 and 5 of layer, where x is the number of Nb ions in the layer structure and 1?x?2 for m=2 and 0?x?m for 3?m?5. A new BLSF series is found for m=3 and x=1, 2 and 3. The ferroelectricity for m=4 (x=3 and 4) was very weak and no single phase with m=5 was obtained.

Takenaka, Tadashi; Gotoh, Takahiro; Mutoh, Sigeo; Sasaki, Takeshi

1995-09-01

120

Structural characterisation of a layered double hydroxide nanosheet  

NASA Astrophysics Data System (ADS)

We report the atomic-scale structure of a Zn2Al-borate layered double hydroxide (LDH) nanosheet, as determined by reverse Monte Carlo (RMC) modelling of X-ray total scattering data. This study involves the extension of the RMC method to enable structural refinement of two-dimensional nanomaterials. The refined LDH models show the intra-layer geometry in this highly-exfoliated phase to be consistent with that observed in crystalline analogues, with the reciprocal-space scattering data suggesting a disordered arrangement of the Zn2+ and Al3+ cations within the nanosheet. The approach we develop is generalisable and so offers a method of characterising the structures of arbitrary nanosheet phases, including systems that support complex forms of disorder within the nanosheets themselves.We report the atomic-scale structure of a Zn2Al-borate layered double hydroxide (LDH) nanosheet, as determined by reverse Monte Carlo (RMC) modelling of X-ray total scattering data. This study involves the extension of the RMC method to enable structural refinement of two-dimensional nanomaterials. The refined LDH models show the intra-layer geometry in this highly-exfoliated phase to be consistent with that observed in crystalline analogues, with the reciprocal-space scattering data suggesting a disordered arrangement of the Zn2+ and Al3+ cations within the nanosheet. The approach we develop is generalisable and so offers a method of characterising the structures of arbitrary nanosheet phases, including systems that support complex forms of disorder within the nanosheets themselves. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr01265h

Funnell, Nicholas P.; Wang, Qiang; Connor, Leigh; Tucker, Matthew G.; O'Hare, Dermot; Goodwin, Andrew L.

2014-06-01

121

Crystallographic structure and superconductive properties of Nb-Ti films with an artificially layered structure  

SciTech Connect

Artificially layered niobium-titanium (Nb-Ti) films with various thickness ratios (3/1--1/3) and periodicities (2--100 A) are made in an argon or in a mixed argon/nitrogen atmosphere by a dc magnetron sputtering method. Films with small periodicities (less than 30 A) have an artificial superlattice structure (ASL) with crystallographic coherence between constituent layers, where Nb and Ti grow epitaxially on the closest planes. The crystallographic structures of films are bcc with the (110) plane parallel to the film for films with the same or a thicker Nb layer than a Ti layer, and hcp with the (001) plane parallel to the film for films with a thinner Nb layer than a Ti layer. Films with large periodicities have an artificial superstructure (ASS) with only periodic stacking of constituent layers. Films deposited in the Ar/N atmosphere also have the artificially layered structures of ASL or ASS. The artificially layered structure is thermally stable at temperatures up to 500 {degree}C. The superconducting properties of the films depend strongly on the periodicity and thickness ratio of Nb and Ti layers. The dependence of the transition temperature on the periodicity and thickness ratio is qualitatively explained by a proximity effect with a three-region model. Films with periodicities less than 20 A, composed of the same or a thicker Nb layer than a Ti layer, show high transition temperatures (above 9.3 K). The highest {ital T}{sub {ital c}} of about 13.6 K is obtained in the film composed of monatomic layers of constituents deposited in an Ar atmosphere including 30 vol % N.

Sato, N. (SONY Corporation, Research Center, 7-35 Kitashinagawa-6, Shinagawa-ku, Tokyo 141, Japan (JP))

1990-06-15

122

ORIGINAL PAPER Population genetic structure of Juniperus phoenicea  

E-print Network

ORIGINAL PAPER Population genetic structure of Juniperus phoenicea (Cupressaceae) in the western and diversity of ten natural populations of Juniperus phoenicea L. from the western part of the species range. phoenicea, without seed exchange on large distance. Keywords Biogeography. Cupressaceae . Juniperus

Paris-Sud XI, Université de

123

ORIGINAL PAPER When invasion increases population genetic structure  

E-print Network

Centaurea diffusa Á Centaurea maculosa Á Centaurea stoebe Á Diffuse knapweed Á Genetic diversity Á InvasiveORIGINAL PAPER When invasion increases population genetic structure: a study with Centaurea diffusa of a prominent North American rangeland weed, Centaurea diffusa (Aster- aceae). We found that the total number

Hufbauer, Ruth A.

124

Original article Genetic structure of the Marseilles cat  

E-print Network

Original article Genetic structure of the Marseilles cat population: is there really a strong 4 February 1992; accepted 21 December 1993) Summary - In a previous study on the Marseilles cat population it was concluded that the small cat colonies were subject to a strong founder effect. A more

Paris-Sud XI, Université de

125

Original article Structure and fractal dimensions of root systems  

E-print Network

Original article Structure and fractal dimensions of root systems of four co-occurring fruit tree, Bangor, Gwynedd LL57 2UW, UK (Received 1 February 1999; accepted 29 October 1999) Abstract ­ Coarse root-auto- matically digitized. Spatial distributions of root length were determined from the digitally

Paris-Sud XI, Université de

126

ORIGINAL PAPER Strong genetic structure among populations of the invasive  

E-print Network

ORIGINAL PAPER Strong genetic structure among populations of the invasive avocado pest Pseudacysta Abstract In 2004, the avocado lace bug (ALB) Pseudacysta perseae, was discovered in San Diego County, CA, USA. Historically, California avocado producers have relied on biological control for sup- pression

Hoddle, Mark S.

127

Lactobacillus helveticus MIMLh5-Specific Antibodies for Detection of S-Layer Protein in Grana Padano Protected-Designation-of-Origin Cheese  

PubMed Central

Single-chain variable-fragment antibodies (scFvs) have considerable potential in immunological detection and localization of bacterial surface structures. In this study, synthetic phage-displayed antibody libraries were used to select scFvs against immunologically active S-layer protein of Lactobacillus helveticus MIMLh5. After three rounds of panning, five relevant phage clones were obtained, of which four were specific for the S-layer protein of L. helveticus MIMLh5 and one was also capable of binding to the S-layer protein of L. helveticus ATCC 15009. All five anti-S-layer scFvs were expressed in Escherichia coli XL1-Blue, and their specificity profiles were characterized by Western blotting. The anti-S-layer scFv PolyH4, with the highest specificity for the S-layer protein of L. helveticus MIMLh5, was used to detect the S-layer protein in Grana Padano protected-designation-of-origin (PDO) cheese extracts by Western blotting. These results showed promising applications of this monoclonal antibody for the detection of immunomodulatory S-layer protein in dairy (and dairy-based) foods. PMID:24242242

Brockmann, Eeva-Christine; Huovinen, Tuomas; Guglielmetti, Simone; Mora, Diego; Taverniti, Valentina; Arioli, Stefania; De Noni, Ivano; Lamminmäki, Urpo

2014-01-01

128

Chasma Australe Mars: Structural Framework for a Catastrophic Outflow Origin  

NASA Technical Reports Server (NTRS)

Chasma Australe is the most remarkable of the martian south pole erosional reentrants carved in the polar layered deposits. Ms chasma originates near the south pole and runs across the polar troughs over a distance of about 500 km. Its width varies between 20 and 80 km and, with a depth up to 1000 m, it reaches the bedrock. Following an idea put forward originally for Chasma Boreale, we propose for the genesis of Chasma Australe a mechanism of catastrophic outflow preceded by a tectonically induced powerful sapping process. A detailed geomorphological analysis of Chasma Australe shows erosional and depositional features that can be interpreted as produced by the motion of a fluid. Like other polar reentrants, Chasma Australe is clearly assymetric, with a steep eastern margin where basal and lateral erosion prevailed, and a gentler western side, where the stepped topography and bedrock spurs favored deposition.

Anguita, F.; Babin, R.; Benito, G.; Collado, A.; Gomez, D.; Rice, J. W.

1998-01-01

129

Ferrite-ferroelectric layered structures for electrically and magnetically tunable microwave resonators  

E-print Network

Ferrite-ferroelectric layered structures for electrically and magnetically tunable microwave filters and oscillators based on ferrite- ferroelectric structures will be "magnetically" tunable and barium strontium titanate BST films in the layered structure. The planar straight-edge ferrite

Demokritov, S.O.

130

Original size of the Vredefort structure, South Africa  

NASA Technical Reports Server (NTRS)

The Vredefort structure is located approximately 120 km southwest of Johannesburg, South Africa, and is deeply eroded. Controversies remain on the origin of this structure with the most popular hypotheses being: (1) by impact cratering about 2.0 Ga; (2) as a cryptoexplosion structure about 2.0 Ga; and (3) by purely tectonic processes starting at about 3.0 Ga and ending with the Vredefort event at 2.0 Ga. In view of recent work in which the granophyre dikes are interpreted as the erosional remants of a more extensive impact melt sheet, injected downward into the underlying country rocks, the impact origin hypothesis for Vredefort is adopted. In order to estimate the original dimensions of the Vredefort impact structure, it is assumed that the structure was initially circular, that its predeformation center corresponds to the center of the granitic core, and that the pre-Vredefort geology of the area prior to approximately 2.0 Ga ago is as suggested by Fletcher and Reimold. The spatial relationship between shock metamorphic effects, the shock pressures they record, and the morphological features of the crater were established for a number of large terrestrial craters. The principles of crater formation at large complex impact structures comparable in size to Vredefort were also established, although many details remain unresolved. An important conclusion is that the transient crater, which is formed directly by excavation and displacement by the shock-induced cratering flow-field (i.e., the particle velocity flow field existing in the region of the transient crater but behind the initial outgoing shock front), is highly modified during the late stage processes. The original transient crater diameter lies well within the final rim of the crater, which is established by structural movements during late-stage cavity modification.

Therriault, A. M.; Reid, A. M.; Reimold, W. U.

1993-01-01

131

Effects of image charges on double layer structure and forces  

NASA Astrophysics Data System (ADS)

The study of the electrical double layer lies at the heart of soft matter physics and biophysics. Here, we address the effects of the image charges on the double layer structure and forces. For electrolyte solutions between two neutral plates, we show that depletion of the salt ions by the image charge repulsion results in short-range attractive and long-range repulsive forces. If cations and anions are of different valency, the asymmetric depletion leads to the formation of an induced electrical double layer. In comparison to a 1:1 electrolyte solution, both the attractive and the repulsive parts of the interaction are stronger for the 2:1 electrolyte solution. For two charged plates, the competition between the surface charge and the image charge effect can give rise to like-charge attraction and charge inversion. These results are in stark contrast with predictions from the Poisson-Boltzmann theory.

Wang, Rui; Wang, Zhen-Gang

2013-09-01

132

Accurate characterization of a thick multilayer structure using the marking-layer-based scanning electron microscopy method  

NASA Astrophysics Data System (ADS)

A multilayer Laue lens (MLL) is a promising optics to advance the focusing resolution of hard x-rays to below 10 nm with high efficiency. It consists of a thickness-graded multilayer with hundreds or thousands of layers. To realize this nano-focusing optics, a high-precision characterization method is needed to measure the position and thickness of each layer. Scanning electron microscopy (SEM) combined with a marking layer method is illustrated in this paper. By inserting WSi2 layers as marking layers in the original MLL structure, the layer positions in different areas can be determined. All the SEM images can be stitched seamlessly and the thickness-graded multilayer is characterized more precisely compared with the conventional method. This new method can help in depositing a more accurate MLL to achieve near-theoretical focusing performance.

Huang, Qiushi; Li, Haochuan; Zhu, Jingtao; Wang, Zhanshan; Chen, Hong

2013-07-01

133

Impact origin of the Sudbury structure: Evolution of a theory  

NASA Technical Reports Server (NTRS)

This paper reviews the origin, development, and present status of the widely accepted theory, proposed by Robert S. Dietz in 1962, that the Sudbury structure was formed by meteoritic or asteroidal impact. The impact theory for the origin of the Sudbury structure seems supported by a nearly conclusive body of evidence. However, even assuming an impact origin to be correct, at least three major questions require further study: (1) the original size and shape of the crater, before tectonic deformation and erosion; (2) the source of the melt now forming the Sudbury Igneous Complex; and (3) the degree, if any, to which the Ni-Cu-platinum group elements are meteoritic. The history of the impact theory illustrates several under-appreciated aspects of scientific research: (1) the importance of cross-fertilization between space research and terrestrial geology; (2) the role of the outsider in stimulating thinking by insiders; (3) the value of small science, at least in the initial stages of an investigation, Dietz's first field work having been at his own expense; and (4) the value of analogies (here, between the Sudbury Igneous Complex and the maria), which although incorrect in major aspects, may trigger research on totally new lines. Finally, the Sudbury story illustrates the totally unpredictable and, by implication, unplannable nature of basic research, in that insight to the origin of the world's then-greatest Ni deposit came from the study of tektites and the Moon.

Lowman, Paul D., Jr.

1992-01-01

134

Polymer layered silicate nanocomposites: Structure, morphology, and properties  

NASA Astrophysics Data System (ADS)

Layered silicates are important fillers for improving various mechanical, flame retardant, and barrier properties of polymers, which can be attributed to their sheet-like morphology. Layered silicates can be modified with organic surfactants to render them compatible with polymer matrices. Organically modified silicates (organoclays) having large surface areas are very cost-efficient non-toxic nanofillers effective at very low loads and are readily available. Upon amalgamation of organoclays with polymer matrix nanocomposites, polymer chains can penetrate in between the silicate layers and result in an intercalated structure where the clay stack remains intact but the interlayer spacing is increased. When penetration becomes more severe, disintegration of clay stacks can occur, resulting in an exfoliated structure. It has often been observed that exfoliation is not complete down to the level of isolated silicate layers; rather, the large clay stacks are broken up into shorter stacks termed 'tactoids' together with a few individual silicate layers, resulting in a kind of mixed intercalated-exfoliated structure. Organoclay particles are mostly intercalated, having a preferred orientation with the clay gallery planes being preferentially parallel to the plane of the pressed film. Preferential orientation of organoclays affects the barrier properties of polymer membranes. Additional fillers like carbon black can induce a change in the orientation of organoclays. The effect of carbon black on the orientation of organoclays was elucidated and a relationship between orientation and permeability of air through such membranes was established. We have also investigated the flammability properties of a series of polymer nanocomposites, containing various Transition Metal Ion (TMI) modified organoclays. The improved fire retardation in nanocomposites with TMI-modified organoclays can be attributed to enhanced carbonaceous char formation during combustion, i.e., charring promoted by the presence of catalytically active TMI. Polymer nanocomposite materials depend not only on the properties of individual components but also on their morphology and interfacial interactions. In polymer nanocomposites, the interfacial interactions are maximized due to the large surface area of the filler particles exposed to the polymer matrix, resulting in unique anisotropic properties. Thus, it will be of great importance to achieve exfoliation of the lamellar stacks prior to mixing with the polymer matrix, in the dry powder state or in a solution state. In layered silicates the lamellar stacks are held by electrostatic interactions between the basal charges and ions present within the basal spacing. Lamellar stacks of layered silicates can be exfoliated if the amount of energy gained by them is higher than the electrostatic energy required to hold the lamellar stacks together. Using 'Microwave radiation', exfoliation of organoclays was achieved. Various characterization techniques were used to evaluate structure, morphology and properties of fillers and polymer nanocomposites.

Nawani, Pranav

135

Composition, structure, and properties of iron-rich nontronites of different origins  

SciTech Connect

The composition, structure, and properties of smectites of different origins have been studied by X-ray diffraction, IR spectroscopy, scanning electron microscopy, and microprobe analysis. The results showed that nontronites of different origins differ in composition, properties, morphology, and IR spectroscopic characteristics. Depending on the degree of structural order and the negative charge of iron-silicate layers in nontronites, the shift of the 001 reflection to smaller angles as a result of impregnation with ethylene glycol (this shift is characteristic of the smectite group) occurs differently. The calculated values of the parameter b (from 9.11 to 9.14A) are valid for the extreme terms of dioctahedral smectite representatives: nontronites.

Palchik, N. A., E-mail: nadezhda@igm.nsc.ru; Grigorieva, T. N.; Moroz, T. N. [Russian Academy of Sciences, Sobolev Institute of Geology and Mineralogy, Siberian Branch (Russian Federation)] [Russian Academy of Sciences, Sobolev Institute of Geology and Mineralogy, Siberian Branch (Russian Federation)

2013-03-15

136

Three-Dimensional Structure of Plane Mixing Layers.  

NASA Astrophysics Data System (ADS)

Recent studies have shown the existence of an organized and persistent streamwise vortex structure in plane mixing layers, which is believed to take the form of a row of alternating-sign streamwise vortices. So far, this streamwise vortex structure has been studied mostly through flow-visualization at relatively low Reynolds numbers. The main objective of the present work was to obtain quantitative measurements of the streamwise vorticity at Reynolds numbers more comparable to those commonly found in practical applications. In the first experiment, the artificially induced streamwise vortex was observed to decay as approximately 1/X^2 within the mixing layer. The effect of the vortex was to locally distort the mean strain distribution in the mixing layer, thus altering the production of the Reynolds stresses. Peak values of the normal stresses were increased by about 20% over the undisturbed case in the region of the streamwise vortex. In particular a strong, pronounced peak was generated in the secondary shear stress, (overline{u^' w^ '}).. In the second experiment, "naturally-occurring" streamwise vorticity was clearly observed in a two-stream mixing layer. Concentrated streamwise vortices appeared just downstream of the first roll-up of the spanwise vorticity, with an initial circulation which was roughly half that of the spanwise vortex circulation. The streamwise vortices first appeared in "clusters", the positions of which seemed to be related to small disturbances in one of the upstream boundary layers. The clusters quickly reorganized into a single row of alternating-sign vortices under the influence of vortex dynamics and changes in the normal stress anisotropy. The streamwise vortex spacing increased in a stepwise fashion, at least partially through the amalgamation of like-sign vortices. The wavelength of the streamwise vortices increased approximately as the mixing layer vorticity thickness, while their strength decayed as roughly 1/X^ {1.5}. In the near-field, the streamwise vortices grossly distorted the mean velocity and turbulence distributions within the mixing layer. In particular, the vortices were well-correlated in both position and strength with peaks in overline{u^ ' w^'}. Although continuing to decay, the streamwise vorticity appeared to persist into what would be conventionally regarded as the self-similar region of the mixing layer. (Abstract shortened with permission of author.).

Bell, James Horatio

137

The Turbulent Structure of Drag Reducing Boundary Layer Flows  

Microsoft Academic Search

The turbulent structure of wall-bounded drag reduced flow has been studied with particle image velocimetry (PIV) in a zero-pressure-gradient boundary layer. Drag reduction was achieved by injection of a concentrated polymer solution through a spanwise slot along the test wall at a distance approximately 2 m upstream of the PIV measurement station. For comparison, water was injected at the same

C. M. White; V. Somandepalli; M. G. Mungal

138

The Structure of the Astron E-layer  

Microsoft Academic Search

The structure of the field-reversing layer of circulating relativistic electrons which constitutes the plasma trap of the Astron has been calculated self-consistently using a model embodying the simplifying assumptions: (1) uniformity over an infinite length so that end-effects are absent, (2) uniformity of impressed field, i.e., no plasma diamagnetism, (3) dynamical friction from the trapped plasma but no scattering, (4)

Lewi Tonks

1961-01-01

139

Turbulence structure of the surface layer Boun 2247-03D TURBULENCE STRUCTURE OF THE UNSTABLE ATMOSPHERIC  

E-print Network

, and of the structural transition between this and the outer layer. The archetypal element of wall-bounded shear structures initiate new cycles. In an extended log layer the resulting shear turbulence is a complex, selfTurbulence structure of the surface layer Boun 2247-03D TURBULENCE STRUCTURE OF THE UNSTABLE

Moncrieff, John B.

140

Origin of superconductivity in layered centrosymmetric LaNiGa{sub 2}  

SciTech Connect

We have examined the origin of superconductivity in layered centrosymmetric LaNiGa{sub 2} by employing a linear response approach based on the density functional perturbation theory. Our results indicate that this material is a conventional electron-phonon superconductor with intermediate level of coupling strength, with the electron-phonon coupling parameter of 0.70, and the superconducting critical temperature of 1.90?K in excellent accordance with experimental value of 1.97?K. The largest contribution to the electron-phonon coupling comes from the La d and Ga p electrons near the Fermi energy and the B{sub 3g} phonon branch resulting from vibrations of these atoms along the ?-Z symmetry line in the Brillouin zone.

Tütüncü, H. M. [Sakarya Üniversitesi, Fen-Edebiyat Fakültesi, Fizik Bölümü, 54187 Adapazar? (Turkey); Srivastava, G. P. [School of Physics, University of Exeter, Stocker Road, Exeter EX4 4QL (United Kingdom)

2014-01-13

141

Structure of the magnetopause current layer at the subsolar point  

SciTech Connect

A one-dimensional electromagnetic particle simulation model developed for the magnetopause current layer between the shocked solar wind and the dipole magnetic field at the subsolar point has been extended to include the interplanetary magnetic field (IMF) in the solar wind. Interaction of the solar wind with the vacuum dipole field as well as the dipole field filled with a low density magnetospheric plasma are studied. It is found that the width and the structure of the magnetopause current layer differ markedly depending on the direction of the IMF. When the IMF is pointing southward, the current layer between the solar wind and the dipole field is narrow and the magnetic field has a single ramp structure caused by the reflection of the solar wind at that point. The current layer becomes several times wider and the magnetic field developes a multiple ramp structure when the IMF is northward. This broadening of the current layer is caused by the multiple reflection of the solar wind by the magnetic field. For the northward IMF, the magnetic field does not change its sign across the current layer so that the E {times} B drift of the solar wind electrons remains the same direction while for the southward IMF, it reverses the sign. This results in a single reflection of the solar wind for the southward IMF and multiple reflections for the northward IMF. When a low density mangetospheric plasma is present in the dipole magnetic field, a small fraction of the solar wind ions are found to penetrate into the dipole magnetic field beyond the reflection point of the solar wind electrons. The width of the ion current layer is of the order of the solar wind ion gyroradius, however, the current associated with the ions remains much smaller than the electron current so long as the density of the magnetospheric plasma is much smaller than the density of the solar wind. Comparisons of our simulation results with the magnetopause crossing near the subsolar point are provided.

Okuda, H.

1991-12-01

142

Origin of structures in disc galaxies: internal or external processes?  

NASA Astrophysics Data System (ADS)

Disc galaxies have a number of structures, such as bars, spirals, rings, discy bulges, m = 1 asymmetries, thick discs, warps etc. I will summarise what is known about their origin and in particular whether it is due to an external or an internal process. The former include interactions, major or minor mergers etc, while the latter include instabilities, or driving by another component of the same galaxy, as e.g. the bar or the halo. In cases where more than one process is eligible, I will analyse whether it is possible to distinguish between different origins, and what it would take to do so. This discussion will show that, at least in some cases, it is difficult to distinguish between an internal and an external origin.

Athanassoula, E.

2015-03-01

143

Streamwise vortices originating from synthetic jet-turbulent boundary layer interaction  

NASA Astrophysics Data System (ADS)

The interaction between a flat plate turbulent boundary layer and a synthetic jet issuing from a rectangular slot slanted with respect to the free stream was studied experimentally using digital particle image velocimetry. Instantaneous flow fields were sampled in a cross-plane downstream of the slot. Results concerning the effects of varying the synthetic jet velocity ratio at fixed stroke length L0 and yaw angle, and the effects of varying the orifice yaw angle ? at a fixed frequency are presented. The formation of a pair of counter-rotating vortical structures, completely embedded in the boundary layer, was observed in the mean flow field when the slot was aligned with the cross-flow. As the slot yaw angle was increased, the leeward vortex intensified while the other became weaker. These vortical structures are the traces of streamwise vortices forming upstream, at the slot exit, during the blowing phases. As the jet velocity ratio and the slot yaw angle were increased the vortices grew in size and intensity. The vortex identification technique showed that these vortical structures are intermittently present in the instantaneous flow fields with a percentage growing with the frequency but not influenced by the yaw angle. Conditional averages showed that while the rotational core of the identified vortices is nearly unaffected, their outer region is greatly modified and grows in size and intensity as the jet velocity ratio and the yaw angle increases.

Lasagna, D.; Orazi, M.; Iuso, G.

2014-02-01

144

Hierarchical layered double hydroxide nanocomposites: structure, synthesis and applications.  

PubMed

Layered double hydroxide (LDH)-based nanocomposites, constructed by interacting LDH nanoparticles with other nanomaterials (e.g. silica nanoparticles and magnetic nanoparticles) or polymeric molecules (e.g. proteins), are an emerging yet active area in healthcare, environmental remediation, energy conversion and storage. Combining advantages of each component in the structure and functions, hierarchical LDH-based nanocomposites have shown great potential in biomedicine, water purification, and energy storage and conversion. This feature article summarises the recent advances in LDH-based nanocomposites, focusing on their synthesis, structure, and application in drug delivery, bio-imaging, water purification, supercapacitors, and catalysis. PMID:25562489

Gu, Zi; Atherton, John James; Xu, Zhi Ping

2015-02-01

145

Acoustic structure and propagation in highly porous, layered, fibrous materials  

NASA Technical Reports Server (NTRS)

The acoustic structure and propagation of sound in highly porous, layered, fine fiber materials is examined. Of particular interest is the utilization of the Kozeny number for determining the static flow resistance and the static structure factor based on flow permeability measurements. In this formulation the Kozeny number is a numerical constant independent of volume porosity at high porosities. The other essential parameters are then evaluated employing techniques developed earlier for open cell foams. The attenuation and progressive phase characteristics in bulk samples are measured and compared with predicted values. The agreements on the whole are very satisfactory.

Lambert, R. F.; Tesar, J. S.

1984-01-01

146

Plasmon and exciton superconductivity mechanisms in layered structures  

NASA Technical Reports Server (NTRS)

Plasmon and exciton superconductivity mechanisms are discussed. Superconductivity in a three layer metal semiconductor metal and insulator semimetal insulator sandwich structure was described in terms of the temperature dependent Green function of the longitudinal (Coulomb) field. The dependences of the superconducting transition temperature on structure parameters were obtained. In a semiconducting film, as a result of interactions of degenerate free carriers with excitons, superconductivity exists only in a certain range of parameter values, and the corresponding critical temperature is much lower than in the plasmon mechanism of superconductivity.

Gabovich, A. M.; Pashitskiy, E. A.; Uvarova, S. K.

1977-01-01

147

Propagation of waves in layered structures viewed as number recognition  

NASA Astrophysics Data System (ADS)

We propose to consider multilayer spatial structures as numbers. An arbitrary finite sequence of layers with N values of a material parameter which determines the speed of wave propagation is considered as a number written in the numeration system with base N. Within the framework of this approach propagation of classical waves and quantum particles can be treated as number recognition. A problem is formulated of identification of a type among spatial sequences featuring unique spectral portraits versus spatial structure. It is shown possible to perform certain arithmetic operations by means of sequential propagation of waves through several structures. Using fractal Cantor structures as a representative example, spectral properties of waves are shown to reproduce certain properties of the corresponding numbers. A possibility is outlined to use the above approach for data storage. If a set of numbers possessing unique spectral portraits forms a complete set, then compact coding of arbitrary numbers will become possible.

Gaponenko, S. V.; Zhukovsky, S. V.; Lavrinenko, A. V.; Sandomirskii, K. S.

2002-04-01

148

Electroluminescent Device Comprising a Transparent Structured Electrode Layer Made From a Conductive Polymer  

Microsoft Academic Search

An electroluminescent (EL) device is (1) composed of polymeric LEDs comprising an active layer (7) of a conjugated polymer and a transparent polymeric electrode layer (5) having electroconductive areas (51) as electrodes. Like the active layer (7), the electrode layer (5) can be manufactured in a simple manner by spin coating. The electrode layer (5) is structured into conductive electrodes

Aemilianus G. J. Staring; David Braun

1998-01-01

149

Evaluating Satiated Copepod Behavioral Responses to Thin Layer Flow Structure  

NASA Astrophysics Data System (ADS)

Zooplankton exploit a variety of chemical and fluid mechanical cues in foraging, mate-seeking, and habitat partitioning contexts. To examine the influence of environmental cues on zooplankton aggregations in coastal marine thin layers, a laboratory thin layer mimic was built. The apparatus uses a laminar, planar jet (the Bickley jet) to produce ecologically-relevant layers of chemical (beneficial and harmful phytoplankton) and fluid mechanical (shear strain rate) cues for zooplankton behavioral assays. Particle image velocimetry (PIV) and laser-induced fluorescence (LIF) were employed to fully quantify the spatial structure of the chemical and fluid mechanical cues, ensuring a close match to in situ conditions and allowing for investigations into threshold cue levels responsible for inducing behavioral responses. Evaluating the effect of hunger level on behavioral responses is particularly important for producing accurate individual-based simulations of zooplankton population dynamics. Behavioral assays with the calanoid copepod Temora longicornis have produced digitized trajectories and, subsequently, path kinematics. Observed behaviors include increased turn frequency and decreased relative swimming speed, which result in increased residence time in the free jet shear layer. Cue-induced individual behaviors have the potential to produce population-scale aggregations.

True, Aaron C.; Webster, Donald R.; Weissburg, Marc J.; Yen, Jeannette

2011-11-01

150

Structural Changes in Individual Retinal Layers in Diabetic Macular Edema  

PubMed Central

Optical coherence tomography (OCT) has enabled objective measurement of the total retinal thickness in diabetic macular edema (DME). The central retinal thickness is correlated modestly with visual impairment and changes paradoxically after treatments compared to the visual acuity. This suggests the clinical relevance of the central retinal thickness in DME and the presence of other factors that affect visual disturbance. Recent advances in spectral-domain (SD) OCT have provided better delineation of the structural changes and fine lesions in the individual retinal layers. Cystoid spaces in the inner nuclear layer and outer plexiform layer are related to quantitative and qualitative parameters in fluorescein angiography. OCT often shows vitreoretinal interface abnormalities in eyes with sponge-like retinal swelling. Serous retinal detachment is sometimes accompanied by hyperreflective foci in the subretinal fluid, which exacerbates the pathogenesis at the interface of the photoreceptors and retinal pigment epithelium. Photoreceptor damage at the fovea is thought to be represented by disruption of the external limiting membrane or the junction between the inner and outer segment lines and is correlated with visual impairment. Hyperreflective foci in the outer retinal layers on SD-OCT images, another marker of visual disturbance, are associated with foveal photoreceptor damage. PMID:24073417

Yoshimura, Nagahisa

2013-01-01

151

Multiple maternal origins and weak phylogeographic structure in domestic goats  

PubMed Central

Domestic animals have played a key role in human history. Despite their importance, however, the origins of most domestic species remain poorly understood. We assessed the phylogenetic history and population structure of domestic goats by sequencing a hypervariable segment (481 bp) of the mtDNA control region from 406 goats representing 88 breeds distributed across the Old World. Phylogeographic analysis revealed three highly divergent goat lineages (estimated divergence >200,000 years ago), with one lineage occurring only in eastern and southern Asia. A remarkably similar pattern exists in cattle, sheep, and pigs. These results, combined with recent archaeological findings, suggest that goats and other farm animals have multiple maternal origins with a possible center of origin in Asia, as well as in the Fertile Crescent. The pattern of goat mtDNA diversity suggests that all three lineages have undergone population expansions, but that the expansion was relatively recent for two of the lineages (including the Asian lineage). Goat populations are surprisingly less genetically structured than cattle populations. In goats only ?10% of the mtDNA variation is partitioned among continents. In cattle the amount is ?50%. This weak structuring suggests extensive intercontinental transportation of goats and has intriguing implications about the importance of goats in historical human migrations and commerce. PMID:11344314

Luikart, Gordon; Gielly, Ludovic; Excoffier, Laurent; Vigne, Jean-Denis; Bouvet, Jean; Taberlet, Pierre

2001-01-01

152

Mechanisms of Texture Development in Bismuth Layer-Structured Ferroelectrics Prepared by Templated Grain Growth  

Microsoft Academic Search

The mechanism for texture development in bismuth layer-structured ferroelectrics prepared by the templated grain growth method was examined using template and matrix grains with different chemical compositions. The template particles used were platelike Bi4Ti3O12 and Ba6Ti17O40 for SrBi4Ti4O15-matrix composites and platelike Ba6Ti17O40 and Sr3Ti2O7 for BaBi4Ti4O15-matrix. The -texture developed in all composites examined. The origins of texture development were the

Yoshiyuki Sakuma; Toshio Kimura

2004-01-01

153

Vortical structure in a forced plane mixing layer  

NASA Technical Reports Server (NTRS)

The objective of this phase of an ongoing study is to obtain detailed three dimensional phase-averaged measurements of forced mixing layer vorticity development and evolution. Acoustic forcing is being used to phase-lock the initial development and subsequent pairing of the span wise vortical structures. Phase averaged measurements of the three velocity components will permit the study of three dimensional vorticity distributions without invoking Taylor's hypothesis which is known to introduce uncertainty. Currently two sine waves, one at the fundamental roll-up frequency and the second, its subharmonic, are being used to force the initial roll-up and first pairing of the span wise rollers. The two dimensional measurements described in this report were obtained in order to determine the best operating conditions for the detailed three dimensional study of the mixing layer undergoing pairing via various pairing mechanisms.

Leboeuf, Richard L.

1993-01-01

154

Flexural strength and failure modes of layered ceramic structures  

PubMed Central

Objective to evaluate the effect of the specimen design on the flexural strength (?f) and failure mode of ceramic structures, testing the hypothesis that the ceramic material under tension controls the mechanical performance of the structure. Methods Three ceramics used as framework materials for fixed partial dentures (YZ - Vita In-Ceram YZ; IZ - Vita In-Ceram Zirconia; AL - Vita In-Ceram AL) and two veneering porcelains (VM7 and VM9) were studied. Bar-shaped specimens were produced in three different designs (n=10): monolithic, two layers (porcelain-framework) and three layers (TRI) (porcelain-framework-porcelain). Specimens were tested for three-point flexural strength at 1 MPa/s in 37°C artificial saliva. For bi-layered design, the specimens were tested in both conditions: with porcelain (PT) or framework ceramic (FT) layer under tension. Fracture surfaces were analyzed using stereomicroscope and scanning electron microscopy (SEM). Young’s modulus (E) and Poisson’s ratio (?) were determined using ultrasonic pulse-echo method. Results were statistically analyzed by Kruskal-Wallis and Student-Newman-Keuls tests. Results Except for VM7 and VM9, significant differences were observed for E values among the materials. YZ showed the highest ? value followed by IZ and AL. YZ presented the highest ?f. There was no statistical difference in the ?f value between IZ and IZ-FT and between AL and AL-FT. ?f values for YZ-PT, IZ-PT, IZ-TRI, AL-PT, AL-TRI were similar to the results obtained for VM7 and VM9. Two types of fracture mode were identified: total and partial failure. Significance The mechanical performance of the specimens was determined by the material under tension during testing, confirming the study hypothesis. PMID:21982199

Borba, Márcia; de Araújo, Maico D.; de Lima, Erick; Yoshimura, Humberto N.; Cesar, Paulo F.; Griggs, Jason A.; Bona, Álvaro Della

2011-01-01

155

Maintaining network security: how macromolecular structures cross the peptidoglycan layer.  

PubMed

Peptidoglycan plays a vital role in bacterial physiology, maintaining cell shape and resisting cellular lysis from high internal turgor pressures. Its integrity is carefully maintained by controlled remodeling during growth and division by the coordinated activities of penicillin-binding proteins, lytic transglycosylases, and N-acetylmuramyl-l-alanine amidases. However, its small pore size (?2 nm) and covalently closed structure make it a formidable barrier to the assembly of large macromolecular cell-envelope-spanning complexes involved in motility and secretion. Here, we review the strategies used by Gram-negative bacteria to assemble such macromolecular complexes across the peptidoglycan layer, while preserving its essential structural role. In addition, we discuss evidence that suggests that peptidoglycan can be integrated into cell-envelope-spanning complexes as a structural and functional extension of their architecture. PMID:21276045

Scheurwater, Edie M; Burrows, Lori L

2011-05-01

156

Changes in the turbulent boundary layer structure associated with net drag reduction by outer layer manipulators  

NASA Technical Reports Server (NTRS)

A specially designed wind tunnel was used to examine the effects of tandemly arranged parallel plate manipulators (TAPPMs) on a turbulent boundary-layer structure and the associated drag. Momentum balances, as well as measurements of the local shear stress from the velocity gradient near the wall, were used to obtain the net drag and local skin friction changes. Two TAPPMs, identical except for the thickness of their plates, were used in the study. Results with .003 inch plates were a maximum net drag reduction of 10 percent at 58 beta sub o (using a momentum balance). At 20 beta sub o, simultaneous laser sheet flow visualization and hot-wire anemometry data showed that the Reynolds stress in the large eddies was significantly reduced, as were the streamwise and normal velocity components. Using space-time correlations the reductions were again identified. Furthermore, quantitative flow visualization showed that the outward normal velocity of the inner region was also significantly decreased in the region around 20 beta sub o. However, throughout the first 130 beta sub o, the measured sublayer thickness with the TAPPMs in place was 15 to 20 percent greater. The data showed that the skin friction, as well as the structure of the turbulence, was strongly modified in the first 35 beta sub o, but that they both significantly relaxed toward unmanipulated boundary layer values by 50 beta sub o.

Rashidnia, N.; Falco, R. E.

1987-01-01

157

Impact origin of the Newporte structure, Williston basin, North Dakota  

SciTech Connect

The Newporte field is located just south of the United States-Canada border in Renville County, North Dakota, in the north-central portion of the Williston basin. Integration of seismic, well-log, and core data supports the interpretation of an impact origin for the Newporte structure. The structure involves both Precambrian basement and lower Paleozoic sedimentary units. Oil and gas production began in 1977 from brecciated basement rocks along the rim of the 3.2-km-diameter circular structure. Both well logs and seismic data were used to determine thickness changes of sedimentary units overlying the structure. Resulting isopach maps reveal a circular, bowl-shaped feature with a recognizable rim. Microscopic shock metamorphic features in quartz and feldspar are visible in basement clasts that form a mixed breccia with Cambrian Deadwood sandstone within the western rim of the structure. A Late Cambrian-Early Ordovician age is suggested for the structure because of the presence of flatlying Deadwood sandstone overlying mixed basement/sandstone breccia along portions of the rim. Identification of the Newporte structure as an impact crater adds to the growing base of evidence revealing the relevance of impact craters to petroleum exploration.

Forsman, N.F.; Gerlach, T.R. [Univ. of North Dakota, Grand Forks, ND (United States); Anderson, N.L. [Univ. of Missouri, Rolla, MO (United States)

1996-05-01

158

Layers  

NASA Astrophysics Data System (ADS)

The temperature-dependent photoresponse characteristics of MnAl2S4 layers have been investigated, for the first time, by use of photocurrent (PC) spectroscopy. Three peaks were observed at all temperatures. The electronic origin of these peaks was associated with band-to-band transitions from the valence-band states ?4( z), ?5( x), and ?5( y) to the conduction-band state ?1( s). On the basis of the relationship between PC-peak energy and temperature, the optical band gap could be well expressed by the expression E g( T) = E g(0) - 2.80 × 10-4 T 2/(287 + T), where E g(0) was estimated to be 3.7920 eV, 3.7955 eV, and 3.8354 eV for the valence-band states ?4( z), ?5( x), and ?5( y), respectively. Results from PC spectroscopy revealed the crystal-field and spin-orbit splitting were 3.5 meV and 39.9 meV. The gradual decrease of PC intensity with decreasing temperature can be explained on the basis of trapping centers associated with native defects in the MnAl2S4 layers. Plots of log J ph, the PC current density, against 1/ T, revealed a dominant trap level in the high-temperature region. By comparing PC and the Hall effect results, we confirmed that this trap level is a shallow donor 18.9 meV below the conduction band.

Hong, K. J.; Jeong, T. S.; Youn, C. J.

2014-09-01

159

Nanosized Ni–Al layered double hydroxides—Structural characterization  

SciTech Connect

Highlights: ? The takovite anionic clays were obtained using the sol–gel method. ? The effect of samples’ composition on the structural and textural characteristics has been investigated. ? X-ray analysis. ? FTIR spectroscopy evidenced a disordered interlayer structure. ? FESEM and TEM analysis showed that the samples have high porosity. - Abstract: Takovite, a natural mineral with the formula Ni{sub 6}Al{sub 2}(OH){sub 6}CO{sub 3}·5H{sub 2}O belongs to the large class of layered double hydroxides (LDHs) and contains positively charged Ni(II) and Al(III) layers alternating with layers containing carbonate ions and water molecules. Mesoporous takovite-type layered double hydroxides (LDH) of the general formula [Ni{sub 1?x}Al{sub x}(OH){sub 2}]{sup x+}(CO{sub 3}{sup 2?}){sub x/2}·nH{sub 2}O with different Ni/Al molar ratios (1.9–2.8) have been successfully synthesized by the sol–gel method, followed by anionic exchange using nickel acetylacetonate and aluminum isopropylate as cation precursors. A single LDH phase and an anisotropic growth of very small crystallites (below 4 nm) have been evidenced by X-ray diffraction. The effect of samples’ composition on their structural and textural characteristics has been investigated. The BET surface area values are in the range of 100–122 m{sup 2}/g. BJH pore radius decreased with increase in the Al(III) content in the LDHs. FESEM micrographs show large aggregates of highly porous LDH particles, while TEM analysis reveals irregular agglomerates of crystallites, among which some of them displayed a developing hexagonal shape. The average particle size variation with the Al(III) content in the samples follows the same trend as the pore radius, the sample with the highest Ni/Al ratio displaying also the smallest particle size. This sample becomes even more interesting, since TEM analysis shows agglomerates with inside circular structures, feature not observed for the other Ni/Al ratios investigated.

Jitianu, Mihaela, E-mail: jitianum@wpunj.edu [William Paterson University, Department of Chemistry, 300 Pompton Road, Wayne, NJ 07470 (United States); Gunness, Darren C. [William Paterson University, Department of Chemistry, 300 Pompton Road, Wayne, NJ 07470 (United States); Aboagye, Doreen E. [Lehman College – City University of New York, Department of Chemistry, Davis Hall, 250 Bedford Boulevard West, Bronx, NY 10468 (United States); Zaharescu, Maria [Institute of Physical Chemistry, 202 Splaiul Independentei, 060021 Bucharest (Romania); Jitianu, Andrei, E-mail: andrei.jitianu@lehman.cuny.edu [Lehman College – City University of New York, Department of Chemistry, Davis Hall, 250 Bedford Boulevard West, Bronx, NY 10468 (United States)

2013-05-15

160

Plasma resonant terahertz photomixers based on double graphene layer structures  

NASA Astrophysics Data System (ADS)

We propose terahertz (THz) photomixers based on double graphene layer (DGL) structures, utilizing the interband absorption of modulated optical radiation, tunneling or thermionic inter-GL transitions, and resonant excitation of plasma oscillations. Using the developed device model, we substantiate the operation of the photomixers and calculate their characteristics. We demonstrate that the output frequency-dependent power of THz radiation exhibits pronounced resonant peaks at the plasmonic resonant frequencies. The proposed THz photomixer can surpass the pertinent devices based on the standard heterostructures.

Ryzhii, Maxim; Shur, Michael S.; Mitin, Vladimir; Satou, Akira; Ryzhii, Victor; Otsuji, Taiichi

2014-03-01

161

Electrical properties of bismuth layer-structured ferroelectrics  

Microsoft Academic Search

Bismuth layer-structured ferroelectrics (BLSF), Srm-3+xBi4-xTim-xTaxO3m+3 (m=2, x = 1?2 m=3, x=0?2) [SBTTm(x)] ceramics are studied on their ferroelectric and piezoelectric properties. From the measurement of D-E hysteresis, the remanent polarization, Pr of SBTT3(0.3) was the largest (Pr=12.3 ?C\\/cm) in the SBTT3(x) system and coercive field, Ec of SBTT2 becomes larger with decreasing the amount of Ta concentration. The electromechanical coupling

Hajime Nagata; Takeshi Takahashi; Yuzuru Yano; Tadashi Takenaka

2001-01-01

162

Surface-plasmons lasing in double-graphene-layer structures  

SciTech Connect

We consider the concept of injection terahertz lasers based on double-graphene-layer (double-GL) structures with metal surface-plasmon waveguide and study the conditions of their operation. The laser under consideration exploits the resonant radiative transitions between GLs. This enables the double-GL laser room temperature operation and the possibility of voltage tuning of the emission spectrum. We compare the characteristics of the double-GL lasers with the metal surface-plasmon waveguides with those of such laser with the metal-metal waveguides.

Dubinov, A. A. [Research Institute for Electrical Communication, Tohoku University, Sendai 980-8577 (Japan); Institute for Physics of Microstructures of Russian Academy of Sciences, and Lobachevsky State University of Nizhny Novgorod, Nizhny Novgorod 603950 (Russian Federation); Aleshkin, V. Ya. [Institute for Physics of Microstructures of Russian Academy of Sciences, and Lobachevsky State University of Nizhny Novgorod, Nizhny Novgorod 603950 (Russian Federation); Ryzhii, V. [Research Institute for Electrical Communication, Tohoku University, Sendai 980-8577 (Japan); Center for Photonics and Infrared Engineering, Bauman Moscow State Technical University, Moscow 105005 (Russian Federation); Shur, M. S. [Department of Electrical, Electronics, and System Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States); Otsuji, T. [Research Institute for Electrical Communication, Tohoku University, Sendai 980-8577 (Japan)

2014-01-28

163

S4 : A free electromagnetic solver for layered periodic structures  

NASA Astrophysics Data System (ADS)

We describe S4, a free implementation of the Fourier modal method (FMM), which has also been commonly referred to as rigorous coupled wave analysis (RCWA), for simulating electromagnetic propagation through 3D structures with 2D periodicity. We detail design aspects that allow S4 to be a flexible platform for these types of simulations. In particular, we highlight the ability to select different FMM formulations, user scripting, and extensibility of program capabilities for eigenmode computations. Program summary Program title: S4 Catalogue identifier: AEMO_v1_0. Program summary URL: http://cpc.cs.qub.ac.uk/summaries/AEMO_v1_0..html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: GNU General Public License, version 2 No. of lines in distributed program, including test data, etc.: 56910 No. of bytes in distributed program, including test data, etc.: 433883 Distribution format: Programming language: C, C++. Computer: Any computer with a Unix-like environment and a C++ compiler. Developed on 2.3 GHz AMD Phenom 9600. Operating system: Any Unix-like environment; developed under MinGW32 on Windows 7. Has the code been vectorized or parallelized?: Yes. Parallelized using MPI. RAM: Problem dependent (linearly proportional to number of layers and quadratic in number of Fourier components). A single layer calculation with approximately 100 Fourier components uses approximately 10 MB. Classification: 10. Electrostatics and Electromagnetics. External routines: Lua [1] and optionally exploits additional free software packages: FFTW [2], CHOLMOD [3], MPI message-passing interface [4], LAPACK and BLAS linear-algebra software [5], and Kiss FFT [6]. Nature of problem: Time-harmonic electromagnetism in layered bi-periodic structures. Solution method: The Fourier modal method (rigorous coupled wave analysis) and the scattering matrix method. Running time: Problem dependent and highly dependent on quality of the BLAS implementation (linearly proportional to number of layers and cubic in number of Fourier components). A single layer calculation with approximately 100 Fourier components takes 4 s on the development machine using the reference BLAS.

Liu, Victor; Fan, Shanhui

2012-10-01

164

Electrical characteristics of rare-earth oxides stacked-layer structures  

Microsoft Academic Search

In this paper, Lu2O3\\/La2O3 stacked layer structures of rare earth oxides were investigated. The La2O3 layer would be expected to form a uniform silicate layer with relatively high dielectric constant compared to SiO2 after the annealing process so that the leakage current characteristics would be improved for the stacked layer structures compared to those of the single Lu2O3 layer.

S. Ohmi; I. Ueda; Y. Kobayashi; K. Tsutsui; H. Iwai

2003-01-01

165

Original Size and Shape of the Sudbury Structure  

NASA Technical Reports Server (NTRS)

This paper presents new evidence bearing on the original size and shape of the Sudbury impact structure. Current opinion is almost unanimous that the structure is a multiring basin with an original diameter of about 200 km and a circular shape that has since been shortened in a northwest-southeast direction by Penokean deformation Evidence for this interpretation, collected chiefly from north of the Sudbury Igneous Complex (SIC), includes supposed outer rings on Landsat imagery, distant occurrences of "Sudbury breccia" (generally defined as pseudotachylite), shatter cone occurrences, and outliers of Huronian sedimentary rock thought to be down-faulted rings. New data from imaging radar and field work north of the SIC, however, contradict this evidence. Radar imagery shows no signs of the supposed outer rings mapped by earlier workers on Landsat images. The most prominent ring has been found to be a chance alignment of two independent fracture sets. Radar imagery from the CCRS Convair 580, with look direction almost normal to the north rim of the SIC, shows no evidence of the rings despite strong look azimuth highlighting. Radar imagery has shown many unmapped diabase dikes north of the SIC. Several exposures of supposed Sudbury breccia are associated with these dikes or with Nipissing diabase intrusions, in some cases actually inside the dikes or directly continuous with them. They appear to be igneous intrusion breccias with no relation to impact. Shock-wave interaction at lithologic contacts cannot be invoked for most of these, because they are part of a northwest trending swarm cutting the SIC in the North Range, and hence too young for an impact origin. Similar diabase-related breccias and pseudotachylite-like veins have been found far outside the Sudbury area between Chapleau and Thessalon. Shatter cones north of the SIC are few and poorly developed, perhaps due to the coarse-grained Footwall rock, and cannot be considered a continuous zone analogous to their occurrence on the South Range in Huronian rocks. Supposed down-faulted outliers of Huronian rocks north of the SIC show no consistent relation to faulting, and the Huronian/Archean contact is locally erosional. Radar imagery and field-checking confirm Rousell's conclusion that the North Range has undergone little or no Penokean deformation. T'his implies that the plan view outline of the crater (floor of the SIC) is original. Extrapolation of the North Range as part of a circular arc leads to an impossibly great diameter. It is concluded that although Penokean deformation largely accounts for the structure's shape, the original crater was not circular and was much smaller than 200 km across.

Lowman, P. D., Jr.

1997-01-01

166

Atomistic origin of an ordered superstructure induced superconductivity in layered chalcogenides  

NASA Astrophysics Data System (ADS)

Interplay among various collective electronic states such as charge density wave and superconductivity is of tremendous significance in low-dimensional electron systems. However, the atomistic and physical nature of the electronic structures underlying the interplay of exotic states, which is critical to clarifying its effect on remarkable properties of the electron systems, remains elusive, limiting our understanding of the superconducting mechanism. Here, we show evidence that an ordering of selenium and sulphur atoms surrounding tantalum within star-of-David clusters can boost superconductivity in a layered chalcogenide 1T-TaS2?xSex, which undergoes a superconducting transition in the nearly commensurate charge density wave phase. Advanced electron microscopy investigations reveal that such an ordered superstructure forms only in the x area, where the superconductivity manifests, and is destructible to the occurrence of the Mott metal–insulator transition. The present findings provide a novel dimension in understanding the relationship between lattice and electronic degrees of freedom.

Ang, R.; Wang, Z. C.; Chen, C. L.; Tang, J.; Liu, N.; Liu, Y.; Lu, W. J.; Sun, Y. P.; Mori, T.; Ikuhara, Y.

2015-01-01

167

Structure dependence of ferroelectric properties of bismuth layer-structured ferroelectric single crystals  

Microsoft Academic Search

Ferroelectric properties along the a(b) axis and c axis in single crystals of various bismuth layer-structured ferroelectrics (BLSFs) were investigated. By measuring saturated P-E hysteresis curves of BLSFs, values of the saturated remanent polarization and the coercive electric field were found to be related to the Curie temperature and the number of BO6 octahedra (m) between bismuth layers, respectively, along

Hiroshi Irie; Masaru Miyayama; Tetsuichi Kudo

2001-01-01

168

High resolution structural characterization of giant magnetoresistance structures containing a nano-oxide layer  

NASA Astrophysics Data System (ADS)

The microstructure and chemistry of a current-perpendicular-to-plane giant magnetoresistance structure containing a nano-oxide layer (NOL) have been studied using a combination of high resolution transmission electron microscopy and three-dimensional atom probe analysis. It was found that the morphology of the NOL changes from a planar layer to discrete particles on annealing, indicating the dominance of surface energy on the morphology evolution. Direct evidence was obtained for significant Mn diffusion from the IrMn antiferromagnetic layer and partitioning to the oxide region during annealing.

You, C. Y.; Cerezo, A.; Clifton, P. H.; Folks, L.; Carey, M. J.; Petford-Long, A. K.

2007-07-01

169

Evidence for the origin of layered deposits in Candor Chasma, Mars, from mineral composition and hydrologic modeling  

Microsoft Academic Search

New results from the Compact Reconnaissance Imaging Spectrometer for Mars and High Resolution Imaging Science Experiment and Context Imager cameras on Mars Reconnaissance Orbiter provide insights into the origin of interior layered deposits in Valles Marineris from analysis of a thick, well-exposed section in western Candor Chasma. Most of the deposit is dominated spectrally by nanophase ferric oxide like that

Scott Murchie; Leah Roach; Frank Seelos; Ralph Milliken; John Mustard; Raymond Arvidson; Sandra Wiseman; Kimberly Lichtenberg; Jeffrey Andrews-Hanna; Janice Bishop; Jean-Pierre Bibring; Mario Parente; Richard Morris

2009-01-01

170

One-seeded fruits in the core Caryophyllales: their origin and structural diversity.  

PubMed

The core Caryophyllales consist of approximately 30 families (12,000 species) distributed worldwide. Many members evolved one-seeded or conjoined fruits, but their origin and structural diversity have not been investigated. A comparative anatomical investigation of the one-seeded fruits within the core Caryophyllales was conducted. The origin of the one-seeded fruits and the evolutionary reconstructions of some carpological characters were traced using a tree based on rbcl and matK data in order to understand the ancestral characters and their changes. The one-seeded fruit type is inferred to be an ancestral character state in core Caryophyllales, with a subsequent increase in the seed number seen in all major clades. Most representatives of the 'Earlier Diverging' clade are distinguished in various carpological traits. The organization of the pericarp is diverse in many groups, although fruits with a dry, many-layered pericarp, consisting of sclerenchyma as outer layers and a thin-walled parenchyma below, with seeds occupying a vertical embryo position, are likely ancestral character states in the core Caryophyllales clade. Several carpological peculiarities in fruit and seed structure were discovered in obligate one-seeded Achatocarpaceae, Chenopodiaceae, Nyctaginaceae, Seguieriaceae and Sarcobataceae. The horizontal embryo evolved in only certain groups of Chenopodiaceae. The bar-thickening of endotegmen cells appears to be an additional character typical of core Caryophyllales. The syncarpy-to-lysicarpy paradigm in Caryophyllaceae needs to be reinterpreted. PMID:25710481

Sukhorukov, Alexander P; Mavrodiev, Evgeny V; Struwig, Madeleen; Nilova, Maya V; Dzhalilova, Khalima Kh; Balandin, Sergey A; Erst, Andrey; Krinitsyna, Anastasiya A

2015-01-01

171

One-Seeded Fruits in the Core Caryophyllales: Their Origin and Structural Diversity  

PubMed Central

The core Caryophyllales consist of approximately 30 families (12 000 species) distributed worldwide. Many members evolved one-seeded or conjoined fruits, but their origin and structural diversity have not been investigated. A comparative anatomical investigation of the one-seeded fruits within the core Caryophyllales was conducted. The origin of the one-seeded fruits and the evolutionary reconstructions of some carpological characters were traced using a tree based on rbcl and matK data in order to understand the ancestral characters and their changes. The one-seeded fruit type is inferred to be an ancestral character state in core Caryophyllales, with a subsequent increase in the seed number seen in all major clades. Most representatives of the ‘Earlier Diverging’ clade are distinguished in various carpological traits. The organization of the pericarp is diverse in many groups, although fruits with a dry, many-layered pericarp, consisting of sclerenchyma as outer layers and a thin-walled parenchyma below, with seeds occupying a vertical embryo position, are likely ancestral character states in the core Caryophyllales clade. Several carpological peculiarities in fruit and seed structure were discovered in obligate one-seeded Achatocarpaceae, Chenopodiaceae, Nyctaginaceae, Seguieriaceae and Sarcobataceae. The horizontal embryo evolved in only certain groups of Chenopodiaceae. The bar-thickening of endotegmen cells appears to be an additional character typical of core Caryophyllales. The syncarpy-to-lysicarpy paradigm in Caryophyllaceae needs to be reinterpreted. PMID:25710481

Sukhorukov, Alexander P.; Mavrodiev, Evgeny V.; Struwig, Madeleen; Nilova, Maya V.; Dzhalilova, Khalima Kh.; Balandin, Sergey A.; Erst, Andrey; Krinitsyna, Anastasiya A.

2015-01-01

172

Clouds, Precipitation and Marine Boundary Layer Structure during MAGIC (Invited)  

NASA Astrophysics Data System (ADS)

Marine boundary layer clouds in the subtropics play a key role in cloud-climate feedbacks that are poorly understood and are key elements in biases in seasonally coupled model forecasts and simulated mean climate. In particular, the representation of the transition from the stratocumulus (Sc) regime, to shallow cumulus (Cu) underlines one of the most challenging problems to the modeling community In MAGIC, the Marine ARM (Atmospheric Radiation Measurement) GPCI (Global Energy and Water Cycle Experiment [GEWEX] Cloud System Studies [GCSS] Pacific Cross-section Intercomparison) Investigation of Clouds study the second Atmospheric Radiation Measurement (ARM) Mobile Facility (AMF2) during the Marine ARM GPCI Investigation of Clouds (MAGIC) provided an unparalleled dataset to study the statistical properties of MBL clouds and the transitions between Sc and Cu. Utilizing AMF2, we develop an objective scheme to identify MBL cloud occurrence across each leg and to recognize some important properties of different MBL cloud (e.g. Sc and Cu) and precipitation types. The variability and frequency of occurrence of the different cloud and precipitation events is presented with emphasis on the various MBL cloud structures. A statistical analysis of macroscopic properties (e.g. Inversion and transition layer) and cloud structure (e.g. cloud boundaries) is preformed relating to the thermodynamic profiles. Further emphasis is placed on the differentiation between Cu and Sc regimes as well as the presence of decoupling.

Kollias, P.; Zhou, X.; Lewis, E. R.

2013-12-01

173

Supersonic Boundary-Layer Control: Bleed-Induced Shock Structure  

NASA Astrophysics Data System (ADS)

Bleed of a supersonic boundary layer through rows of normal and inclined circular holes has been found to be effective in controlling flow separation and in minimizing flow distortions caused by adverse pressure gradients from incident and reflected shock waves and from curvatures in geometry. This is accomplished by not just removing low momentum fluid next to walls but also through the formation of what are referred to as barrier shocks, one about each bleed hole, which collectively can block downstream adverse pressure gradients from propagating upstream. Unfortunately, these shocks also introduce considerable disturbances into the flow by curving and bending three-dimensionally incident and reflected shock waves. The structure of these barrier shocks is quite complicated because of the spanwise convex geometry of the holes and the interactions with the flow in neighboring bleed holes. Computations based on the low-Reynolds-number shear-stress-transport k-omega turbulence model were used to study the structure of the barrier shocks. Parameters investigated include rows of aligned and misaligned normal and inclined circular holes in which the diameter of the holes is comparable to the displacement thickness of the approaching boundary-layer flow.

Shih, Tom; Flores, Andrew

1999-11-01

174

TAKING THE OCEAN'S TEMPERATURE Much of the ocean has a layered temperature structure. Thermal layers may be revealed by measur-  

E-print Network

- perature to the ocean floor. The top of this deep layer is found at a depth of (less than 1,000 m) (more1 TAKING THE OCEAN'S TEMPERATURE Much of the ocean has a layered temperature structure. Thermal to the ocean bottom. The follow- ing activity uses a set of temperature versus depth measurements, called

Waliser, Duane E.

175

Structural and electronic origin of the magnetic structures in hexagonal LuFeO3  

NASA Astrophysics Data System (ADS)

Using combined theoretical and experimental approaches, we studied the structural and electronic origin of the magnetic structure in hexagonal LuFeO3. Besides showing the strong exchange coupling that is consistent with the high magnetic ordering temperature, the previously observed spin reorientation transition is explained by the theoretically calculated magnetic phase diagram. The structural origin of this spin reorientation that is responsible for the appearance of spontaneous magnetization, is identified by theory and verified by x-ray diffraction and absorption experiments.

Wang, Hongwei; Solovyev, Igor V.; Wang, Wenbin; Wang, Xiao; Ryan, Philip J.; Keavney, David J.; Kim, Jong-Woo; Ward, Thomas Z.; Zhu, Leyi; Shen, Jian; Cheng, X. M.; He, Lixin; Xu, Xiaoshan; Wu, Xifan

2014-07-01

176

Wave Shaping and Lateral Spreading of Impact Loads Using Layered Materials and Structures  

Microsoft Academic Search

The overall objective of our work is to explore a new concept for developing resilient armor using high wave speed layers to rapidly spread the loads arising from projectile impacts. Because layered structures involve many additional geometrical and material variables, and because layers affect stress distribution and energy absorption capability of the target, a fundamental issue in determining layering effects

J. L. Ding; J. Robbins; Y. M. Gupta; M. K. Wong

1999-01-01

177

Constraints on the Origin of Fine Layers in Ganges Mensa and Hebes Mensa, Mars  

NASA Astrophysics Data System (ADS)

These mensae have been proposed to have steeply dipping layers. The dip angle and direction of these layers can be constrained with MOC and MOLA data. We find no evidence that steep layers are present, most are much shallower than thirty degrees.

Beyer, R. A.; McEwen, A. S.

2005-03-01

178

Structural origin of the colored reflections from the black-billed magpie feathers  

NASA Astrophysics Data System (ADS)

The structural origin of the weak iridescence on some of the dark feathers of the black-billed magpie, Pica pica (Corvidae), is found in the structure of the ribbon-shaped barbules. The cortex of these barbules contains cylindrical holes distributed as the nodes of an hexagonal lattice in the hard layer cross section. The cortex optical properties are described starting from a photonic-crystal film theory. The yellowish-green coloration of the bird’s tail can be explained by the appearance of a reflection band related to the photonic-crystal lowest-lying gap. The bluish reflections from the wings are produced by a more complicated mechanism, involving the presence of a cortex second gap.”

Pol Vigneron, Jean; Colomer, Jean-François; Rassart, Marie; Ingram, Abigail L.; Lousse, Virginie

2006-02-01

179

Atmospheric boundary-layer structure from simultaneous SODAR, RASS, and ceilometer measurements  

Microsoft Academic Search

A comparison of the determination of boundary-layer structures by a SODAR, by a RASS, and by a ceilometer is presented. One important structure is the mixing-layer height (MLH). The comparison is focused on 3 days with an evolution of a convective boundary layer over a larger city in Germany. The three instruments give information that partly agree and partly complement

Stefan Emeis; Christoph Münkel; Siegfried Vogt; Wolfgang J Müller; Klaus Schäfer

2004-01-01

180

Journal of the Atmospheric Sciences Comments on "Symmetric and Asymmetric Structures of Hurricane Boundary Layer in  

E-print Network

Boundary Layer in Coupled Atmosphere-Wave-Ocean Models and Observations" --Manuscript Draft-- Manuscript symmetric and asymmetric hurricane boundary-layer structures in a fully coupled atmosphere-28 wave Number: Full Title: Comments on "Symmetric and Asymmetric Structures of Hurricane Boundary Layer

Smith, Roger K.

181

Structure of the Entrainment Zone Capping the Convective Atmospheric Boundary Layer  

Microsoft Academic Search

The authors use large-eddy simulation (LES) to investigate entrainment and structure of the inversion layer of a clear convectively driven planetary boundary layer (PBL) over a range of bulk Richardson numbers, Ri. The LES code uses a nested grid technique to achieve fine resolution in all three directions in the inversion layer.Extensive flow visualization is used to examine the structure

Peter P. Sullivan; Chin-Hoh Moeng; Bjorn Stevens; Donald H. Lenschow; Shane D. Mayor

1998-01-01

182

Bose-Einstein condensation in low dimensional layered structures  

NASA Astrophysics Data System (ADS)

Bose-Einstein condensation critical temperature, among other thermodynamic properties are reported for an ideal boson gas inside layered structures created by trapping potential of the Kronig-Penney type. We start with a big box where we introduce the Kronig-Penney potential in three directions to get a honey comb of cubes of side a size and walls of variable penetrability (P=mV0ab/^2), with bosons instead of bees. We are able to reduce the dimensions of the cubes to simulate bosons inside quantum dots. The critical temperature, starting from that of an ideal boson gas inside the big box, decreases as the small cube wall impenetrability increases arriving to a tiny but different from zero when the penetrability is zero (P-->?). We also calculate the internal energy and the specific heat, and compare them to the ones obtained for the case of the same Kronig-Penney potential in one direction (simulating layers), and two directions (nanotubes).

Salas, Patricia; Solis, M. A.

2008-03-01

183

Magnetic structures inside boundary layers of magnetic clouds  

NASA Astrophysics Data System (ADS)

We analyze 23 magnetic cloud boundary layers (BLs) in Feb. 1995-Oct. 1998 and find that: (1) the distribution functions of fluctuations in the southward field component inside the boundary layer, ?BzL, is very different from ?BzS in the background solar wind and ?BzM inside the cloud, with the enhancement in the fluctuation amplitude and the variation of the magnitude and direction of the average field. (2) in the maximum variance plane (MVP) composed of the maximum and medium variance directions, the walk of the tips of the magnetic field vectors in the BL could be classified into two types based on: (a) field vectors vibrate along a circle arc, which is possibly related with Alfven fluctuations inside the BL; (b) field vectors walk randomly in the MVP, which could be correlated with the turbulence inside the BL. (3) In the ?-? plane, fields inside the BL exhibits a `U' or inverse `U' shape with a spacing of about 180 degree in the azimuthal angle, which indicate the existence of a field reverse region and are often associated with the Alfvenic fluctuations. The results above suggest that the cloud's BL owns the magnetic structure different from that in the solar wind and cloud body, which is a manifestation for the interaction of the magnetic cloud (MC) with the solar wind (SW).

Wei, Fengsi; Liu, Rui; Feng, Xueshang; Zhong, Dingkun; Yang, Fang

2003-12-01

184

The Development of Layered Photonic Band Gap Structures Using a Micro-Transfer Molding Technique  

SciTech Connect

Photonic band gap (PBG) crystals are periodic dielectric structures that manipulate electromagnetic radiation in a manner similar to semiconductor devices manipulating electrons. Whereas a semiconductor material exhibits an electronic band gap in which electrons cannot exist, similarly, a photonic crystal containing a photonic band gap does not allow the propagation of specific frequencies of electromagnetic radiation. This phenomenon results from the destructive Bragg diffraction interference that a wave propagating at a specific frequency will experience because of the periodic change in dielectric permitivity. This gives rise to a variety of optical applications for improving the efficiency and effectiveness of opto-electronic devices. These applications are reviewed later. Several methods are currently used to fabricate photonic crystals, which are also discussed in detail. This research involves a layer-by-layer micro-transfer molding ({mu}TM) and stacking method to create three-dimensional FCC structures of epoxy or titania. The structures, once reduced significantly in size can be infiltrated with an organic gain media and stacked on a semiconductor to improve the efficiency of an electronically pumped light-emitting diode. Photonic band gap structures have been proven to effectively create a band gap for certain frequencies of electro-magnetic radiation in the microwave and near-infrared ranges. The objective of this research project was originally two-fold: to fabricate a three dimensional (3-D) structure of a size scaled to prohibit electromagnetic propagation within the visible wavelength range, and then to characterize that structure using laser dye emission spectra. As a master mold has not yet been developed for the micro transfer molding technique in the visible range, the research was limited to scaling down the length scale as much as possible with the current available technology and characterizing these structures with other methods.

Kevin Jerome Sutherland

2001-05-01

185

Remote estimation of the Mercury surface layer structure  

NASA Astrophysics Data System (ADS)

Results of the optical observations of Mercury and the Moon confirm the close similarity of photometric properties of the bodies. Experience of lunar studies shows that space weathering processes on the Mercury (such as micrometeorite bombardment, solar wind ion bombardment etc.) can form properties of the upper layer of regolith. The amount of fused glassy particles and others agglutinates in the lunar upper layer is the direct index of the soil reworking caused be the micrometeorite bombardment. Besides, this micrometeorite bombardment is also responsible for the mechanical process through which the large particles are broken down into smaller ones. For lunar regolith was showed that increasingly mature soils become progressively finer-grained, better-sorted, and composed of a greater proportion of agglutinates. The increasing rate of the fused glassy fragments, of agglutinates, and of fine size fraction in the regolith during its space weathering affects the polarization of the light reflected by an exposed lunar or Mercurian soil. Therefore, polarimetric properties of the regolith may be modified by the soil reworking process in the course of time. Comparison of the lunar and Mercurian optic observations confirms the remarkable similarity of the polarimetric properties of Mercury and the Moon. From of summary of polarization measurements of whole disk of Mercury it is possible to conclude that maturity of the soil on the Mercurian surface in scale of whole disk is similar to one in large old craters on the lunar highland. Comparison of the lunar and Mercurian disk-integrated photometric functions indicates the likeness of the surface layer structures of the bodies. Analysis of the phase curve inclination and magnitude of the opposition effect shows that Mercurian relief in scale of meter details is smoother than lunar one. It was measured brightness of number of small plots (10x10 cm) on the lunar surface (Luna-13 data). The range of phase angles was from 68 to 75 deg. These values close correlate with corresponding part of the Mercurian disk-integrated phase function. ItSs possible if Mercurian phase function received from Earth-based telescopes and lunar one received in cm-scale is coincided the structures of regolith may be similar in both cases. These conclusions may be used for planning BepiColombo mission. This work was supported by INTAS-ESA grant No. 99-00403.

Shevchenko, V.

186

Structure Identification Within a Transitioning Swept-Wing Boundary Layer  

NASA Technical Reports Server (NTRS)

Extensive measurements are made in a transitioning swept-wing boundary layer using hot-film, hot-wire and cross-wire anemometry. The crossflow-dominated flow contains stationary vortices that breakdown near mid-chord. The most amplified vortex wavelength is forced by the use of artificial roughness elements near the leading edge. Two-component velocity and spanwise surface shear-stress correlation measurements are made at two constant chord locations, before and after transition. Streamwise surface shear stresses are also measured through the entire transition region. Correlation techniques are used to identify stationary structures in the laminar regime and coherent structures in the turbulent regime. Basic techniques include observation of the spatial correlations and the spatially distributed auto-spectra. The primary and secondary instability mechanisms are identified in the spectra in all measured fields. The primary mechanism is seen to grow, cause transition and produce large-scale turbulence. The secondary mechanism grows through the entire transition region and produces the small-scale turbulence. Advanced techniques use Linear Stochastic Estimation (LSE) and Proper Orthogonal Decomposition (POD) to identify the spatio-temporal evolutions of structures in the boundary layer. LSE is used to estimate the instantaneous velocity fields using temporal data from just two spatial locations and the spatial correlations. Reference locations are selected using maximum RMS values to provide the best available estimates. POD is used to objectively determine modes characteristic of the measured flow based on energy. The stationary vortices are identified in the first laminar modes of each velocity component and shear component. Experimental evidence suggests that neighboring vortices interact and produce large coherent structures with spanwise periodicity at double the stationary vortex wavelength. An objective transition region detection method is developed using streamwise spatial POD solutions which isolate the growth of the primary and secondary instability mechanisms in the first and second modes, respectively. Temporal evolutions of dominant POD modes in all measured fields are calculated. These scalar POD coefficients contain the integrated characteristics of the entire field, greatly reducing the amount of data to characterize the instantaneous field. These modes may then be used to train future flow control algorithms based on neural networks.

Chapman, Keith; Glauser, Mark

1996-01-01

187

Corrosion detection in multi-layered rotocraft structures  

SciTech Connect

Rotorcraft structures do not readily lend themselves to quantifiable inspection methods due to airframe construction techniques. Periodic visual inspections are a common practice for detecting corrosion. Unfortunately, when the telltale signs of corrosion appear visually, extensive repair or refurbishment is required. There is a need to nondestructively evaluate airframe structures in order to recognize and quantify corrosion before visual indications are present. Nondestructive evaluations of rotorcraft airframes face inherent problems different from those of the fixed wing industry. Most rotorcraft lap joints are very narrow, contain raised fastener heads, may possess distortion, and consist of thinner gage materials ({approximately}0.012--0.125 inches). In addition the structures involve stack-ups of two and three layers of thin gage skins that are separated by sealant of varying thickness. Industry lacks the necessary data techniques, and experience to adequately perform routine corrosion inspection of rotorcraft. In order to address these problems, a program is currently underway to validate the use of eddy current inspection on specific rotorcraft lap joints. Probability of detection (POD) specimens have been produced that simulate two lap joint configurations on a model TH-57/206 helicopter. The FAA's Airworthiness Assurance Center (AANC) at Sandia Labs and Bell Helicopter have applied single and dual frequency eddy current (EC) techniques to these test specimens. The test results showed enough promise to justify beta site testing of the eddy current methods evolved in this study. The technique allows users to distinguish between corrosion signals and those caused by varying gaps between the assembly of skins. Specific structural joints were defined as prime corrosion areas and a series of corrosion specimens were produced with 5--20% corrosion distributed among the layers of each joint. Complete helicopter test beds were used to validate the laboratory findings. This paper will present the laboratory and field results that quantify the EC technique's corrosion detection performance. Plans for beta site testing, adoption of the new inspection procedure into routine rotorcraft maintenance, and NDI training issues will also be discussed.

ROACH,DENNIS P.; WALKINGTON,PHILLIP D.; HOHMAN,ED; MARSHALL,GREG

2000-04-25

188

The Development of Layered Photonic Band Gap Structures Using a Micro-Transfer Molding Technique  

SciTech Connect

Over the last ten years, photonic band gap (PBG) theory and technology have become an important area of research because of the numerous possible applications ranging from high-efficiency laser diodes to optical circuitry. This research concentrates on reducing the length scale in the fabrication of layered photonic band gap structures and developing procedures to improve processing consistency. Various procedures and materials have been used in the fabrication of layered PBG structures. This research focused on an economical micro transfer molding approach to create the final PBG structure. A poly dimethylsiloxane (PDMS) rubber mold was created from a silicon substrate. It was filled with epoxy and built layer-by-layer to create a 3-D epoxy structure. This structure was infiltrated with nanoparticle titania or a titania sol-gel, then fired to remove the polymer mold, leaving a monolithic ceramic inverse of the epoxy structure. The final result was a lattice of titania rolds that resembles a face-centered tetragonal structure. The original intent of this research was to miniaturize this process to a bar size small enough to create a photonic band gap for wavelengths of visible electro-magnetic radiation. The factor limiting progress was the absence of a silicon master mold of small enough dimensions. The Iowa State Microelectronics Research Center fabricated samples with periodicities of 2.5 and 1.0 microns with the existing technology, but a sample was needed on the order of 0.3 microns or less. A 0.4 micron sample was received from Sandia National Laboratory, which was made through an electron beam lithography process, but it contained several defects. The results of the work are primarily from the 2.5 and 1.0 micron samples. Most of the work focused on changing processing variables in order to optimize the infiltration procedure for the best results. Several critical parameters were identified, ranging from the ambient conditions to the specifics of the procedure. It is believed that most critical for fabrication of high quality samples is control of the temperature of the sample during and after infiltration, and the rate and amount of time spent applying epoxy to the PDMS.

Kevin Jerome Sutherland

2001-06-27

189

The structural origin of second harmonic generation in fascia  

PubMed Central

Fascia tissue is rich in collagen type I proteins and can be imaged by second harmonic generation (SHG) microscopy. While identifying the overall alignment of the collagen fibrils is evident from those images, the tridimensional structural origin for the observation of SHG signal is more complex than it apparently seems. Those images reveal that the noncentrosymmetric (piezoelectric) structures are distributed heterogeneously on spatial dimensions inferior to the resolution provided by the nonlinear optical microscope (sub-micron). Using piezoresponse force microscopy (PFM), we show that an individual collagen fibril has a noncentrosymmetric structural organization. Fibrils are found to be arranged in nano-domains where the anisotropic axis is preserved along the fibrillar axis, while across the collagen sheets, the phase of the second order nonlinear susceptibility is changing by 180 degrees between adjacent nano-domains. This complex architecture of noncentrosymmetric nano-domains governs the coherent addition of 2? light within the focal volume and the observed features in the SHG images taken in fascia. PMID:21326632

Rivard, Maxime; Laliberté, Mathieu; Bertrand-Grenier, Antony; Harnagea, Catalin; Pfeffer, Christian P.; Vallières, Martin; St-Pierre, Yves; Pignolet, Alain; El Khakani, My Ali; Légaré, François

2011-01-01

190

Atomistic origin of an ordered superstructure induced superconductivity in layered chalcogenides.  

PubMed

Interplay among various collective electronic states such as charge density wave and superconductivity is of tremendous significance in low-dimensional electron systems. However, the atomistic and physical nature of the electronic structures underlying the interplay of exotic states, which is critical to clarifying its effect on remarkable properties of the electron systems, remains elusive, limiting our understanding of the superconducting mechanism. Here, we show evidence that an ordering of selenium and sulphur atoms surrounding tantalum within star-of-David clusters can boost superconductivity in a layered chalcogenide 1T-TaS2-xSex, which undergoes a superconducting transition in the nearly commensurate charge density wave phase. Advanced electron microscopy investigations reveal that such an ordered superstructure forms only in the x area, where the superconductivity manifests, and is destructible to the occurrence of the Mott metal-insulator transition. The present findings provide a novel dimension in understanding the relationship between lattice and electronic degrees of freedom. PMID:25625438

Ang, R; Wang, Z C; Chen, C L; Tang, J; Liu, N; Liu, Y; Lu, W J; Sun, Y P; Mori, T; Ikuhara, Y

2015-01-01

191

Real-Time Experimental Investigation on Dynamic Failure of Sandwich Structures and Layered Materials  

Microsoft Academic Search

\\u000a We present a systematic experimental investigation of the generation and subsequent evolution of dynamic failure modes in\\u000a sandwich structures and layered materials subjected to out-of-plane low-speed impact. Model sandwich specimens involving a\\u000a compliant polymer core sandwiched between two metal layers and other model layered materials were designed to simulate failure\\u000a evolution mechanisms in real sandwich structures and layered materials. High-speed

L. Roy Xu; Ares J. Rosakis

192

Substrate Structures For Growth Of Highly Oriented And/Or Epitaxial Layers Thereon  

DOEpatents

A composite substrate structure including a substrate, a layer of a crystalline metal oxide or crystalline metal oxynitride material upon the substrate, a layer of an oriented cubic oxide material having a rock-salt-like structure upon the crystalline metal oxide or crystalline metal oxynitride material layer is provided together with additional layers such as one or more layers of a buffer material upon the oriented cubic oxide material layer. Jc's of 2.3×106 A/cm2 have been demonstrated with projected Ic's of 320 Amperes across a sample 1 cm wide for a superconducting article including a flexible polycrystalline metallic substrate, an inert oxide material layer upon the surface of the flexible polycrystalline metallic substrate, a layer of a crystalline metal oxide or crystalline metal oxynitride material upon the layer of the inert oxide material, a layer of an oriented cubic oxide material having a rock-salt-like structure upon the crystalline metal oxide or crystalline metal oxynitride material layer, a layer of a buffer material upon the oriented cubic oxide material layer, and, a top-layer of a high temperature superconducting material upon the layer of a buffer material.

Arendt, Paul N. (Los Alamos, NM); Foltyn, Stephen R. (Los Alamos, NM); Groves, James R. (Los Alamos, NM); Jia, Quanxi (Los Alamos, NM)

2005-07-26

193

Noise and vibration level reduction by covering metal structures with layers of damping materials. [considering viscoelastic insulation layers  

NASA Technical Reports Server (NTRS)

One of the most important methods of reducing the noise and vibration level is the damping of the secondary sources, such as metal plates, often used in vehicle structures, by means of covering materials with high internal viscosity. Damping layers are chosen at an optimum thickness corresponding to the frequency and temperature range in which a certain structure works. The structure's response corresponding to various real situations is analyzed by means of a measuring chain including electroacoustical or electromechanical transducers. The experimental results provide the dependence of the loss factor and damping transmission coefficient as a function of the damping layer thickness or of the frequency for various viscoelastic covering materials.

Rugina, I.; Paven, H. T. O.

1974-01-01

194

Enhancement of perpendicular magnetic anisotropy and transmission of spin-Hall-effect-induced spin currents by a Hf spacer layer in W/Hf/CoFeB/MgO layer structures  

SciTech Connect

We report that strong perpendicular magnetic anisotropy of the ferromagnetic layer in a W/CoFeB/MgO multilayer structure can be established by inserting a Hf layer as thin as 0.25?nm between the W and CoFeB layers. The Hf spacer also allows transmission of spin currents generated by an in-plane charge current in the W layer to apply strong spin torque on the CoFeB, thereby enabling current-driven magnetic switching. The antidamping-like and field-like components of the spin torque exerted on a 1?nm CoFeB layer are of comparable magnitudes in this geometry. Both components originate from the spin Hall effect in the underlying W layer.

Pai, Chi-Feng; Nguyen, Minh-Hai; Vilela-Leão, Luis Henrique; Buhrman, R. A., E-mail: rab8@cornell.edu [Cornell University, Ithaca, New York 14853 (United States); Belvin, Carina [Department of Physics, Wellesley College, Massachusetts 02481 (United States); Ralph, D. C. [Cornell University, Ithaca, New York 14853 (United States); Kavli Institute at Cornell, Ithaca, New York 14853 (United States)

2014-02-24

195

Self-organization of local magnetoplasma structures in the upper layers of the solar convection zone  

SciTech Connect

Self-organization and evolution of magnetoplasma structures in the upper layers of the solar convection zone are discussed as a process of diffuse aggregation of magnetic flux tubes. Equations describing the tube motion under the action of magnetic interaction forces, hydrodynamic forces, and random forces are written explicitly. The process of aggregation of magnetic flux tubes into magnetic flux clusters of different shapes and dimensions is simulated numerically. The obtained structures are compared with the observed morphological types of sunspot groups. The quantitative comparison with the observational data was performed by comparing the fractal dimensions of the photospheric magnetic structures observed in solar active regions with those of structures obtained in the numerical experiment. The model has the following free parameters: the numbers of magnetic flux tubes with opposite polarities on the considered area element (Nn and Ns), the average radius of the cross section of the magnetic flux tube (a), its effective length (l), the twist factor of the tube field (k), and the absolute value of the average velocity of chaotic tube displacements (d). Variations in these parameters in physically reasonable limits leads to the formation of structures (tube clusters of different morphological types) having different fractal dimensions. Using the NOAA 10488 active region, which appeared and developed into a complicated configuration near the central meridian, as an example, it is shown that good quantitative agreement between the fractal dimensions is achieved at the following parameters of the model: Nn = Ns = 250 ± 50; a = 150 ± 50 km; l ? 5000 km, and d = 80 ± 10 m/s. These results do not contradict the observational data and theoretical estimates obtained in the framework of the Parker “spaghetti” model and provide new information on the physical processes resulting in the origin and evolution of local magnetic plasma structures in the near-photospheric layers of the solar convection zone.

Chumak, O. V., E-mail: chuo@yandex.ru [Moscow State University, Sternberg Astronomical Institute (Russian Federation)

2013-08-15

196

Intercalation of cellulase enzyme into a hydrotalcite layer structure  

NASA Astrophysics Data System (ADS)

A new inorganic-organic hybrid material whereby cellulase enzyme is incorporated into a hydrotalcite type layered double hydroxide (LDH) structure is reported. The Mg2Al-cellulase-LDH was synthesized via co-precipitation from Mg/Al nitrate at pH=9.6. Characterization was performed using X-ray powder diffraction (XRD), small angle X-ray scattering (SAXS), elemental analysis, infrared spectroscopy (IR) and thermogravimetry (TG). From XRD and SAXS measurements, a d-value of ~5.0 nm was identified for the basal spacing of the Mg2Al-cellulase-LDH. Consequently, the cellulase enzyme (hydrodynamic diameter ~6.6 nm) attains a slightly compressed conformation when intercalated. Formation of the LDH hybrid was also confirmed via scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Mg2Al-cellulase-LDH phases appear as ~20 nm thin foils which are intergrown to flower-like aggregates. Activity of the enzyme was retained after deintercalation from the Mg2Al-LDH framework using anion exchange. Accordingly, cellulase is not denatured during the intercalation process, and LDH presents a suitable host structure for time-controlled release of the biomolecule.

Zou, N.; Plank, J.

2015-01-01

197

Thermoacoustic effects on layered structures for the evaluation of structural parameters  

NASA Astrophysics Data System (ADS)

The temperature dependent material characteristics of a layered panel are experimentally measured using a Thermal Mechanical Analysis (TMA) configuration. The temperature dependent wave dispersion characteristics of the panel are subsequently computed using a Wave Finite Element Method (WFEM). The WFEM predictions are eventually used within a wave context SEA approach in order to calculate the temperature dependent Sound Transmission Loss (STL) of the layered panel. Results on the STL for temperatures varying between -100 °C to 160 °C are computed for a structure operating at sea level. The importance of the glass transition region on the panel's vibroacoustic response is exhibited and discussed.

Bareille, Olivier A.; Chronopoulos, Dimitrios; Ichchou, Mohamed N.; Troclet, Bernard

2014-03-01

198

The origin of SH-wave resonance frequencies in sedimentary layers  

NASA Astrophysics Data System (ADS)

Resonance frequencies are often analysed in geo-engineering studies to evaluate seismic risk and microzonation in urban areas. The Nakamura technique constitutes a popular approach that computes the spectral ratio of horizontal-to-vertical ground motion in ambient noise recordings to reveal the existence of any site resonance frequencies. Its theoretical basis remains however unclear with some authors arguing that the method de-emphasizes any Rayleigh-wave contributions and that the resonance frequencies are solely caused by vertically incident SH waves. Other authors explain the same resonance frequencies by the ellipticity of the fundamental Rayleigh wave. Recent numerical simulations reveal that the magnitude of the peak frequency is proportional to the relative portion of Love waves present. This study demonstrates that Love waves alone can be responsible for any observed resonance frequencies in sedimentary layers. Yet sharp SH-wave resonance frequencies are only excited by a source in the bedrock. These resonance frequencies are caused by inhomogeneous waves excited by the bedrock source that tunnel through the high-velocity bedrock to emerge in the low-velocity sediments with a very reduced range of slownesses. The resulting SH waves are then free to interfere constructively thereby creating the observed resonance frequencies. This general trigger mechanism leads to resonances that are almost offset independent. The resulting resonance frequencies map onto points of maximum curvature in the Love-wave phase-velocity dispersion curves at or just beyond the critical horizontal slowness. They can be analysed with the quarter-wavelength law if a large velocity contrast exists between the unconsolidated sediments and the bedrock. A minor modification of the quarter-wavelength law provides more accurate predictions, also for smaller velocity contrasts. Multisource simulations show that site amplification factors as determined by horizontal-over-vertical (H/V) spectral ratios would not only depend on the relative portion of Love waves in the total wavefield but also on the depth distribution and the relative strength of the SH sources inside the bedrock compared with those in the sediments. An accurate interpretation of site amplification factors by means of H/V peak frequencies would thus require in-depth knowledge of the causes and origins of the local microseismic noise field.

van der Baan, Mirko

2009-09-01

199

Modeling a Possible Volcanic Origin for Interior Layered Deposits on Mars  

NASA Astrophysics Data System (ADS)

This study was undertaken to examine the valid range of temperatures required for sub-ice volcanic origin of interior layered deposits (ILDs) in Valles Marineris. To this end, using GIS the volume estimates of Ophir Chasma and its 4 ILDs were mapped and measured. The GIS volumes in this study are based on high-res HRSC topography overlain on MOLA. We determined the void space of Ophir Chasma sans ILDs to be 92,319 km3. Volumes for each ILD mound were determined to be 6,185 km3, 4,833 km3, 2,628 km3, and 0.2 km3 (negligible); totaling 13,642 km3. A sub-ice volcano requires eruption beneath an existing ice sheet or ponded ice. If during the formation of a sub-ice volcano the associated unstable englacial meltwater lake is drained by jökulhlaups or if the volcano rises above the meltwater, effused subaerial lava will cap the tuff cone forming resistant sheet lavas. Hence, the lava cap horizon can be used to estimate the minimum height of ice. Three resistant ILD caprock locales (found only on the 2 largest ILDs) were mapped and the hypothetical ice volumes measured beneath their elevations are 77,391 km3, 79,899 km3, and 51,695 km3. Following the equation from Chapman et al. (2003), if the known ILDs in Ophir are assumed to be basaltic subice volcanoes, calorimetry can be used to estimate the volumes of meltwater generated by their eruption [Allen, 1980; Björnsson, 1988; Gudmundsson and Björnsson, 1991; Gudmundsson et al., 1997; Höskuldsson and Sparks, 1997]. These estimates are based on (1) the volume and likely mound density, (2) the heat content of basaltic magmas, and (3) the specific heat capacity and the latent heat of fusion for ice. The ice that can be melted by a mass of magma as it solidifies and cools can be calculated by equating the heat content of the magma with the heat used for melting. Two possible end member cases were used. In the first case it is assumed that the chasma contained ice at its melting point of 273 K and in the other case the present day temperature at the latitude of Juventae Chasma of 150 K [Haberle et al., 1999] is assumed. At 273 K the predicted volume of melted ice = 96,465 km3 exceeds the void volume, so at this temperature it would be fairly impossible for ILD sub-ice edifices to form unless the ice greatly exceeded plateau height. At 150 K, the predicted volume of melted ice = 55,755 km3, and this plus the measured volume of the ILD mounds (13,642 km3) = 69,401 km3 or 22,918 km3 less than the volume of the Ophir void. So, at this temperature sub-ice volcano formation is within the realm of possibility. Also, the equivalent meltwater volume of 51,152 km3 is close to that calculated to lie beneath the lowest caprock height. The additional missing 22,918 km3 may represent loss due to ash escaping the chasma, ILD erosion, and sublimation of remaining ice. In conclusion, modeling indicates that the possibility the ILDs may have been sub-ice volcanoes increases in validity as temperature near 150 K. A sub-ice origin also implies prolonged volcanically-induced hydrothermal systems.

Chapman, M. G.; Kneissl, T.

2011-12-01

200

The Roles of Large- and Small-Scale Structures in Turbulent Free Shear Layers  

NASA Technical Reports Server (NTRS)

The occurrence of large-scale coherent structures in turbulent free shear flows (especially the planar mixing layer) has been recognized for some time. Indeed, the observation of such structures in mixing layers did much to promote interest in the study of coherent structures in turbulence. It has been widely assumed that the large-scale structures in these flows are responsible for the entrainment of free-stream fluid and the overall growth of the layer, while the small-scale structures provide mixing and dissipation. A model of scalar mixing based on these ideas was proposed for these flows. However, recent experimental and computational evidence suggests that the dominance of the large-scale structures in turbulent mixing layers is not universal. In addition, there is a substantial variation among experiments in several statistical measures of self-similar mixing layers, for example growth rate and velocity variances. To investigate the importance of large-scale structures, several free shear flows (mixing layers and wakes) have been simulated via direct numerical simulation. The simulations are designed to mimic experimental mixing layers in which the splitter plate boundary layers are turbulent. Different levels of two-dimensional forcing are included resulting in large-scale structures of differing strength and importance. These simulations are used to investigate the role of large-scale coherent structures in free shear layers and the effect of these structures on relevant turbulence statistics and scalar mixing. It is found that the statistics and structures in several experiments involving turbulent mixing layers are in better agreement with simulations that do not exhibit dominant large-scale structures than those in which the common mixing layer structures do dominate. It is also found that the level of forcing can have a profound effect on the qualitative and quantitative features of these shear layer, even when they are nominally self-similar.

Moser, Robert D.; Richardso, Pamela F. (Technical Monitor)

1994-01-01

201

Theory of spin waves in magnetic interfaces, superlattices and disordered layer structures  

Microsoft Academic Search

A general recursion method for calculating the exact local spin-wave Green function in an arbitrary ferromagnetic interface, superlattice and disordered layer structure is developed. The method is applied to magnetic insulator structures described by a nearest-neighbour exchange Hamiltonian. It is shown that the complete response function of an arbitrary layer structure can be generated from a single matrix element of

J. Mathon

1989-01-01

202

The motor origins of human and avian song structure  

PubMed Central

Human song exhibits great structural diversity, yet certain aspects of melodic shape (how pitch is patterned over time) are widespread. These include a predominance of arch-shaped and descending melodic contours in musical phrases, a tendency for phrase-final notes to be relatively long, and a bias toward small pitch movements between adjacent notes in a melody [Huron D (2006) Sweet Anticipation: Music and the Psychology of Expectation (MIT Press, Cambridge, MA)]. What is the origin of these features? We hypothesize that they stem from motor constraints on song production (i.e., the energetic efficiency of their underlying motor actions) rather than being innately specified. One prediction of this hypothesis is that any animals subject to similar motor constraints on song will exhibit similar melodic shapes, no matter how distantly related those animals are to humans. Conversely, animals who do not share similar motor constraints on song will not exhibit convergent melodic shapes. Birds provide an ideal case for testing these predictions, because their peripheral mechanisms of song production have both notable similarities and differences from human vocal mechanisms [Riede T, Goller F (2010) Brain Lang 115:69–80]. We use these similarities and differences to make specific predictions about shared and distinct features of human and avian song structure and find that these predictions are confirmed by empirical analysis of diverse human and avian song samples. PMID:21876156

Tierney, Adam T.; Russo, Frank A.; Patel, Aniruddh D.

2011-01-01

203

Effect of low-temperature annealing on the electronic- and band-structures of (Ga,Mn)As epitaxial layers  

SciTech Connect

The effect of outdiffusion of Mn interstitials from (Ga,Mn)As epitaxial layers, caused by post-growth low-temperature annealing, on their electronic- and band-structure properties has been investigated by modulation photoreflectance (PR) spectroscopy. The annealing-induced changes in structural and magnetic properties of the layers were examined with high-resolution X-ray diffractometry and superconducting quantum interference device magnetometry, respectively. They confirmed an outdiffusion of Mn interstitials from the layers and an enhancement in their hole concentration, which were more efficient for the layer covered with a Sb cap acting as a sink for diffusing Mn interstitials. The PR results demonstrating a decrease in the band-gap-transition energy in the as-grown (Ga,Mn)As layers, with respect to that in the reference GaAs one, are interpreted by assuming a merging of the Mn-related impurity band with the GaAs valence band. Whereas an increase in the band-gap-transition energy caused by the annealing treatment of the (Ga,Mn)As layers is interpreted as a result of annealing-induced enhancement of the free-hole concentration and the Fermi level location within the valence band. The experimental results are consistent with the valence-band origin of itinerant holes mediating ferromagnetic ordering in (Ga,Mn)As, in agreement with the Zener model for ferromagnetic semiconductors.

Yastrubchak, O., E-mail: yastrub@hektor.umcs.lublin.pl; Gluba, L.; ?uk, J. [Institute of Physics, Maria Curie-Sklodowska University, 20-031 Lublin (Poland); Wosinski, T., E-mail: wosin@ifpan.edu.pl; Andrearczyk, T.; Domagala, J. Z. [Institute of Physics, Polish Academy of Sciences, 02-668 Warsaw (Poland); Sadowski, J. [Institute of Physics, Polish Academy of Sciences, 02-668 Warsaw (Poland); MAX-IV Laboratory, Lund University, 221 00 Lund (Sweden)

2014-01-07

204

Antireflection efficiency comparison of single- and double-layered structures for photovoltaic glass covers.  

PubMed

For single-layer antireflection (AR) on glass, a low refractive index (n) AR layer is required to achieve high AR efficiency, which limits the selection of materials. The double-layered AR structure has a lower requirement on materials' n but is typically used for narrow waveband AR, and photovoltaic glass covers require broadband AR to increase the whole-spectrum solar energy transmittance. With the help of a multilayered optical simulation, we optimized the n and thickness of the single and double layered AR structure and found that, for broadband AR, double-layered structure only showed AR efficiency advantages in very high or low top layers' n compared to single AR layer structure. For a n=1.45 top layer of the double layer structure, the optimized reflectance is 2.57% (single side), while the optimized reflectance of a single AR layer with n=1.45 is 2.87%, which is a negligible AR efficiency advantage (0.30%) when considering production costs. Moreover, in our experiment, using SiO2 and SiO2 and TiO2 composite layers, the absorption of short wavelengths by TiO2 ostensibly cancelled this advantage out (92.87% compare to the single layer's 92.98% for single side AR). PMID:24921132

Chen, Zhang; Gao, Yanfeng

2014-06-10

205

PHYSIOLOGICAL ECOLOGY -ORIGINAL RESEARCH Responses of leaf structure and photosynthetic properties  

E-print Network

PHYSIOLOGICAL ECOLOGY - ORIGINAL RESEARCH Responses of leaf structure and photosynthetic properties global inter- specific relationships between photosynthesis, nitrogen, and leaf structure identified between photosynthesis, nitrogen, and leaf structure reported previously also exists in a dataset com

Minnesota, University of

206

Fundamental character of the field structure in formation of atmospheric and ionospheric layers: unified field of waves  

NASA Astrophysics Data System (ADS)

The suggested direction of research is based on the original methodology where plasma, gas, planetary and star systems are considered as a trial (experimental) material. This material is reactive to the changes of the environment according to the law of conservation of symmetry. It was discovered through the algorithm of symmetry conservation that the layered structure of the atmospher and the iososphere is generated by the thin structure of deformation of closed (stable, fixed) waves of density of space-mass continuum, which carry the Earth. In space the continuation of this thin structure is demonstrated by the phenomenon of LDE, inside the planet - by the spheres of compression and underpressure. Cases of closing of corresponding star deformations are seen in novas and supernovas, cases of closing of planet deformations are seen in asteroid belts. The Earth has a deformation, known as layer F2 in ionosphere, on the verge of closing a new wave.

Rusinov, Yu. I.

2004-02-01

207

Bismuth Layer Structured Ferroelectric Ceramics with High Mechanical Quality Factor  

NASA Astrophysics Data System (ADS)

The piezoelectric properties in some bismuth layer-structured ferroelectric (BLSF) ceramics were investigated focusing on a mechanical quality factor, Qm. Many BLSF compositions with various Curie temperature, Tc, were selected in this study, and the Qm values of (33) mode were plotted as a function of their Curie temperature, Tc. The Qm increased with increasing the Tc in the low Tc compositions below 500°C. It is considered to relate with the domain wall pinning because the coercive field, Ec also increased with increasing the Tc. However, in the high Tc compositions above 750°C, the Qm decreased with increasing the Tc contrary, because of the difficulties in poling treatment due to the Ec. On the other hand, high Qm values more than 10,000 were obtained in the intermediate Tc compositions between at 500 to 750°C. These values are quite high as the piezoelectric ceramics. The key point of the high Qm in these compositions is the poling process at high temperature of 300°C.

Nagata, Hajime; Hiruma, Yuji; Suzuki, Muneyasu; Takenaka, Tadashi

208

Structure and Response to Flow of the Glycocalyx Layer  

PubMed Central

The glycocalyx is a sugar-rich layer located at the luminal part of the endothelial cells. It is involved in key metabolic processes and its malfunction is related to several diseases. To understand the function of the glycocalyx, a molecular level characterization is necessary. In this article, we present large-scale molecular-dynamics simulations that provide a comprehensive description of the structure and dynamics of the glycocalyx. We introduce the most detailed, to-date, all-atom glycocalyx model, composed of lipid bilayer, proteoglycan dimers, and heparan sulfate chains with realistic sequences. Our results reveal the folding of proteoglycan ectodomain and the extended conformation of heparan sulfate chains. Furthermore, we study the glycocalyx response under shear flow and its role as a flypaper for binding fibroblast growth factors (FGFs), which are involved in diverse functions related to cellular differentiation, including angiogenesis, morphogenesis, and wound healing. The simulations show that the glycocalyx increases the effective concentration of FGFs, leading to FGF oligomerization, and acts as a lever to transfer mechanical stimulus into the cytoplasmic side of endothelial cells. PMID:24411255

Cruz-Chu, Eduardo R.; Malafeev, Alexander; Pajarskas, Tautrimas; Pivkin, Igor V.; Koumoutsakos, Petros

2014-01-01

209

Self-Restoration by Smectic Layer Structures of Monostable Ferroelectric Liquid Crystal in Flexible Devices  

Microsoft Academic Search

In this paper, we discuss a self-restoration phenomenon affecting smectic layer deformation and molecular alignment in monostable ferroelectric liquid crystals used for flexible displays. First, the mechanical stability of tilted `bookshelf' structures of smectic layers anchored on substrates using alignment layers was examined by precisely shearing two substrates. The microscopic texture of a monostable ferroelectric liquid crystal showed tolerance to

Hideo Fujikake; Hiroto Sato; Fumito Isaka; Takeshi Murashige; Hiroshi Kikuchi; Taiichiro Kurita; Fumio Sato

2004-01-01

210

Observed Boundary Layer Wind Structure and Balance in the Hurricane Core. Part I: Hurricane Georges  

Microsoft Academic Search

The GPS dropsonde allows observations at unprecedentedly high horizontal and vertical resolution, and of very high accuracy, within the tropical cyclone boundary layer. These data are used to document the boundary layer wind field of the core of Hurricane Georges (1998) when it was close to its maximum intensity. The spatial variability of the boundary layer wind structure is found

Jeffrey D. Kepert

2006-01-01

211

Modelling of the acoustic radiation of a structure covered by a porous layer  

E-print Network

Modelling of the acoustic radiation of a structure covered by a porous layer O. Doutres and N To predict noise in enclosure containing treated vibrating panels, porous layer effect has to be taken into account. This study propose an analytical model of the effects of a porous layer on a vibrating plate

Paris-Sud XI, Université de

212

One-Dimensional Structures in Ferrocholesteric Film with Weak Homeotropic Anchoring on the Layer Boundaries  

Microsoft Academic Search

We consider one-dimensional structures of a ferrocholesteric film with weak anchoring of homeotropic type on the boundaries of the layer. We assume that the external magnetic field is oriented normal to the plane of the layer and diamagnetic anisotropy of cholesteric liquid crystal matrix is positive. We find that two kinds of ordering can exist in the layer with weak

V. S. Shavkunov; A. N. Zakhlevnykh

2001-01-01

213

STOCHASTIC COMPUTATIONAL DYNAMICAL MODEL OF UNCERTAIN STRUCTURE COUPLED WITH AN INSULATION LAYER  

E-print Network

STOCHASTIC COMPUTATIONAL DYNAMICAL MODEL OF UNCERTAIN STRUCTURE COUPLED WITH AN INSULATION LAYER the effect of insulation layers in complex dynamical systems for low- and medium-frequency ranges such as car booming noise analysis, one introduces a sim- plified stochastic model of insulation layers based

Boyer, Edmond

214

Layered zinc hydroxide nanocones: synthesis, facile morphological and structural modification, and properties  

NASA Astrophysics Data System (ADS)

Layered zinc hydroxide nanocones intercalated with DS- have been synthesized for the first time via a convenient synthetic approach, using homogeneous precipitation in the presence of urea and sodium dodecyl sulfate (SDS). SDS plays a significant role in controlling the morphologies of as-synthesized samples. Conical samples intercalated with various anions were transformed through an anion-exchange route in ethanol solution, and the original conical structure was perfectly maintained. Additionally, these DS--inserted nanocones can be transformed into square-like nanoplates in aqueous solution at room temperature, fulfilling the need for different morphology-dependent properties. Corresponding ZnO nanocones and nanoplates have been further obtained through the thermal calcination of NO3--intercalating zinc hydroxide nanocones/nanoplates. These ZnO nanostructures with different morphologies exhibit promising photocatalytic properties.Layered zinc hydroxide nanocones intercalated with DS- have been synthesized for the first time via a convenient synthetic approach, using homogeneous precipitation in the presence of urea and sodium dodecyl sulfate (SDS). SDS plays a significant role in controlling the morphologies of as-synthesized samples. Conical samples intercalated with various anions were transformed through an anion-exchange route in ethanol solution, and the original conical structure was perfectly maintained. Additionally, these DS--inserted nanocones can be transformed into square-like nanoplates in aqueous solution at room temperature, fulfilling the need for different morphology-dependent properties. Corresponding ZnO nanocones and nanoplates have been further obtained through the thermal calcination of NO3--intercalating zinc hydroxide nanocones/nanoplates. These ZnO nanostructures with different morphologies exhibit promising photocatalytic properties. Electronic supplementary information (ESI) available: Typical SEM images, TGA curves and XRD patterns of as-prepared samples. See DOI: 10.1039/c4nr04166f

Ma, Wei; Ma, Renzhi; Liang, Jianbo; Wang, Chengxiang; Liu, Xiaohe; Zhou, Kechao; Sasaki, Takayoshi

2014-10-01

215

Electronic transport and layer engineering in multilayer graphene structures  

NASA Astrophysics Data System (ADS)

We demonstrate a reproducible layer engineering technique for multilayer graphene through controllable oxidation via a SiO2 capping layer. The oxidation method is able to reduce the thickness of few layer graphene to a single layer, as determined by a combination of contrast and Raman spectroscopies. We have also studied the electrical transport properties of graphene sheets with different thicknesses by focusing on their minimum conductivity. The average minimum conductivity of single layer graphene was found to be 0.3×4e2/h, while that of multilayer graphene consisting of n layers is approximately 1.2×4e2/h for n =2, 2.4×4e2/h for n =3, and 4ne2/h for n >3. The results suggest that the substrate plays an important role in determining the transport properties of thin graphene sheets with n <3, while its influence is relatively small in thicker graphene sheets.

Wang, H. M.; Wu, Y. H.; Ni, Z. H.; Shen, Z. X.

2008-02-01

216

Effect of thin oxide layers incorporated in spin valve structures  

NASA Astrophysics Data System (ADS)

The enhancement of the magnetoresistance effect, induced by incorporating nano-oxide layers (NOLs) in a bottom-type spin valve, was studied for various preparation conditions. The effect of a NOL in the Co90Fe10 pinned layer was found to depend critically on the oxygen pressure applied to form the thin oxide film. Pressures over 10-3 Torr O2 yield oxides thicker than about 0.7 nm, which apparently deteriorate the biasing field which exists over the oxide. The magnetoresistance values can further be raised by forming a specular reflecting oxide on top of the sense layer. Promising results were obtained with an Al2O3 capping layer formed in a solid-state oxidation reaction that occurs spontaneously when a thin Al layer is deposited on the oxidized surface of the Co90Fe10 sense layer.

Gillies, M. F.; Kuiper, A. E. T.; Leibbrandt, G. W. R.

2001-06-01

217

Molecular analysis of neocortical layer structure in the ferret  

PubMed Central

Molecular markers that distinguish specific layers of rodent neocortex are increasingly employed to study cortical development and the physiology of cortical circuits. The extent to which these markers represent general features of neocortical cell type identity across mammals is, however, unknown. To assess the conservation of layer markers more broadly, we isolated orthologs for fifteen layer-enriched genes in the ferret, a carnivore with a large, gyrencephalic brain, and analyzed their patterns of neocortical gene expression. Our major findings are: (1) Many but not all layer markers tested show similar patterns of layer-specific gene expression between mouse and ferret cortex, supporting the view that layer-specific cell type identity is conserved at a molecular level across mammalian superorders; (2) Our panel of deep layer markers (ER81/ETV1, SULF2, PCP4, FEZF2/ZNF312, CACNA1H, KCNN2/SK2, SYT6, FOXP2, CTGF) provides molecular evidence that the specific stratifications of layer 5 and 6 into 5a, 5b, 6a and 6b are also conserved between rodents and carnivores. (3) Variations in layer-specific gene expression are more pronounced across areas of ferret cortex than between homologous areas of mouse and ferret cortex; (4) This variation of area gene expression was clearest with the superficial layer markers studied (SERPINE2, MDGA1, CUX1, UNC5D, RORB/NR1F2, EAG2/KCNH5). Most dramatically, the layer 4 markers RORB and EAG2 disclosed a molecular sublamination to ferret visual cortex and demonstrated a molecular dissociation among the so-called agranular areas of the neocortex. Our findings establish molecular markers as a powerful complement to cytoarchitecture for neocortical layer and cell-type comparisons across mammals. PMID:20575059

Rowell, Joanna J.; Mallik, Atul K.; Dugas-Ford, Jennifer; Ragsdale, Clifton W.

2010-01-01

218

Identifying the origin of groundwater samples in a multi-layer aquifer system with Random Forest classification  

NASA Astrophysics Data System (ADS)

Accurate identification of the origin of groundwater samples is not always possible in complex multilayered aquifers. This poses a major difficulty for a reliable interpretation of geochemical results. The problem is especially severe when the information on the tubewells design is hard to obtain. This paper shows a supervised classification method based on the Random Forest (RF) machine learning technique to identify the layer from where groundwater samples were extracted. The classification rules were based on the major ion composition of the samples. We applied this method to the Campo de Cartagena multi-layer aquifer system, in southeastern Spain. A large amount of hydrogeochemical data was available, but only a limited fraction of the sampled tubewells included a reliable determination of the borehole design and, consequently, of the aquifer layer being exploited. Added difficulty was the very similar compositions of water samples extracted from different aquifer layers. Moreover, not all groundwater samples included the same geochemical variables. Despite of the difficulty of such a background, the Random Forest classification reached accuracies over 90%. These results were much better than the Linear Discriminant Analysis (LDA) and Decision Trees (CART) supervised classification methods. From a total of 1549 samples, 805 proceeded from one unique identified aquifer, 409 proceeded from a possible blend of waters from several aquifers and 335 were of unknown origin. Only 468 of the 805 unique-aquifer samples included all the chemical variables needed to calibrate and validate the models. Finally, 107 of the groundwater samples of unknown origin could be classified. Most unclassified samples did not feature a complete dataset. The uncertainty on the identification of training samples was taken in account to enhance the model. Most of the samples that could not be identified had an incomplete dataset.

Baudron, Paul; Alonso-Sarría, Francisco; García-Aróstegui, José Luís; Cánovas-García, Fulgencio; Martínez-Vicente, David; Moreno-Brotóns, Jesús

2013-08-01

219

Origin of the Mackenzie large igneous province and sourcing of flood basalts from layered intrusions  

NASA Astrophysics Data System (ADS)

The 1.27 Ga Coppermine continental flood basalt (CFB) in northern Canada represents the extrusive manifestation of the Mackenzie large igneous province (LIP) that includes the Mackenzie dyke swarm and the Muskox layered intrusion. New Re-Os isotope and highly siderophile element (HSE: Re, Pd, Pt, Ru, Ir, Os) abundance data are reported together with whole-rock major- and trace-element abundances and Nd isotopes to examine the behaviour of the HSE during magmatic differentiation and to place constraints on the extent of crustal interaction with mantle-derived melts. Mineral-chemical data are also reported for an unusual andesite glass flow (4.9 wt.% MgO) found in proximity to newly recognised picrites (>20 wt.% MgO) in the lowermost stratigraphy of the Coppermine CFB. Compositions of mineral phases in the andesite are similar to equivalent phases found in Muskox Intrusion chromitites and the melt composition is identical to Muskox chromite melt inclusions. Elevated HSE contents (e.g., 3.8 ppb Os) and the mantle-like initial Os isotope composition of this andesitic glass contrast strongly with oxygen isotope and lithophile element evidence for extensive crustal contamination. These signatures implicate an origin for the glass as a magma mingling product formed within the Muskox Intrusion during chromitite genesis. The combination of crust and mantle signatures define roles for both these reservoirs in chromitite genesis, but the HSE appear to be dominantly mantle-sourced. Combined with Nd isotope data that places the feeder for lower Coppermine CFB picrites and basalts within the Muskox Intrusion, this provides the strongest evidence yet for direct processing of some CFB within upper-crustal magma chambers. Modeling of absolute and relative HSE abundances in CFB reveal that HSE concentrations decrease with increasing fractionation for melts with <8×1 wt.% MgO in the Coppermine CFB, with picrites (>13.5wt.% MgO) from CFB having higher Os abundances than ocean island basalt (OIB) equivalents. The differences between CFB and OIB picrite absolute Os abundances may result from higher degrees of partial melting to form CFB but may also reflect incorporation of trace sulphide in CFB picrites from magmas that reached S-saturation in shallow-level magma chambers. Significant inter-element fractionation between (Re+Pt+Pd)/(Os+Ir+Ru) are generated during magmatic differentiation in response to strongly contrasting partitioning of these two groups of elements into sulphides and/or HSE-rich alloys. Furthermore, fractional crystallization has a greater role on absolute and relative HSE abundances than crustal contamination under conditions of CFB petrogenesis due to the dilution effect of continental crust. The Coppermine CFB define a Re-Os isochron with an age of 1263 +16/-20 Ma and initial gamma Os = +2.2×0.8. Combined data for the basaltic and intrusive portions of the Mackenzie LIP indicate a mantle source broadly within the range of the primitive upper mantle. The majority of Archaean komatiites and Phanerozoic CFB also require mantle sources with primitive upper mantle to chondritic Re/Os evolution, with exceptions typically being from analyses of highly-fractionated MgO-poor basalts.

Day, J. M.; Pearson, D.

2013-12-01

220

Analysis of large structures in separated shear layers  

SciTech Connect

Large scale structures play an important role in the development of free shear layers and jets, and there is a large body of literature dealing with this subject. For meaningful interpretation of data, different analysis techniques have been used. However, these methods have been plagued with problems associated with phase jitter in the coherent modes. The primary goal of the data analysis techniques is to identify the individual modes present and to accurately determine the evolution of the amplitudes and phases of these modes. The goal of the present work is to develop suitable data analysis techniques for accurately evaluating the amplitude and phases of the coherent structures. In this paper, a pattern recognition technique that has the potential of computing the amplitudes of the large-scale structures correctly has been developed and further extended to include the calculation of the phase jitter. The pattern recognition technique is based on characterizing the coherent components in the form of a Fourier-cosine series with each mode identified by a frequency, amplitude and phase. The series is truncated by pre-selecting the modes (based on a spectral analysis of the signal). The evaluation of the Fourier components for the different modes is then made by segmenting the whole time-series into different segments such that in one segment one period of the corresponding wave is present. The mode corresponding to the lowest frequency is evaluated first, the coherent components corresponding to this mode is then subtracted from the signal, and then the components of the next higher mode is evaluated, and the process continued till all modes have been determined. A second approach has been used in the evaluation of phase jitter, and is based on an extension of a method proposed by Ho and co-workers (referred to as the HZFB method) in this paper. Using simulated data, the HZFB method is shown to produce inaccurate results in the presence of multiple modes and small scales. The HZFB technique is modified in this paper to eliminate the small scale effects in the phase jitter calculation. Both the pattern recognition technique and the modified-HZFB method were evaluated using simulated data and measurements for separated flow behind a rib mounted on the surface of a test plate. A hot-wire anemometer was used to collect the experimental data. The results of these techniques were compared with those obtained from a traditional Fourier Analysis and the HZFB method. The superior performance of the improved data analysis techniques was clearly demonstrated both in the simulated data and in the measurements.

Panigrahi, P.; Acharya, S.

1999-07-01

221

The structure of the near neutral atmospheric surface layer as observed during the CASES'99 experiment  

Microsoft Academic Search

Recent observational data obtained during the Cooperative Surface-Atmosphere Exchange Study field campaign in October 1999 (CASES'99), show evidence of layered structure of the near-neutral surface layer (SL): (i) the upper surface layer (USL) which corresponds to the upper part of the surface layer, where the mean velocity profile is logarithmic and the spectrum decays as k_1-5\\/3 (where k_1 is the

P. Drobinski; P. Carlotti; R. K. Newsom; R. M. Banta; R. C. Foster; J. L. Redelsperger

2003-01-01

222

Interface Structure Influence on Thermal Resistance Across Double-Layered Nanofilms  

Microsoft Academic Search

This work investigated the interface influence on the thermal resistance across double-layered thin films by non-equilibrium molecular dynamics (NEMD) with Lennard-Jones potential. Layer A is a solid argon with a face-centered cubic structure and Layer B is obtained by changing atomic mass only. A flat interface is formed when each of the contacting atomic planes from the two layers has

Xin-Gang Liang; Lin Sun

2005-01-01

223

Acoustic double layer structures in dense magnetized electron-positron-ion plasmas  

SciTech Connect

The acoustic double layer structures are studied using quantum hydrodynamic model in dense magnetized electron-positron-ion plasmas. The extended Korteweg-de Vries is derived using reductive perturbation method. It is found that increase in the ion concentration in dense magnetized electron-positron plasmas increases the amplitude as well as the steepness of the double layer structure. However, increase in the magnetic field strength and decrease in the obliqueness of the nonlinear acoustic wave enhances only the steepness of the double layer structures. The numerical results have also been shown by using the data of the outer layer regions of white dwarfs given in the literature.

Akhtar, N.; Mahmood, S. [Theoretical Plasma Physics Division, PINSTECH, P. O. Nilore, Islamabad 44000 (Pakistan); Department of Physics and Applied Mathematics, PIEAS, P. O. Nilore, Islamabad 44000 (Pakistan)

2011-11-15

224

New bismuth layer-structured ferroelectrics with niobium ions As B-site  

Microsoft Academic Search

A series of bismuth layer-structured oxides, Nam-1.5Bi2.5 Nbm O3m+3 [NBNm] (2layer-structured ferroelectric (BLSF), Na0.5Bi2.5Nb2O9 [NBN2], and a perovskite compound, NaNbO3, was studied on their dielectric and ferroelectric properties using normal and grain oriented ceramics. They form layer-structured ferroelectrics for layer-numbers m=2, 3, 4 and are new BLSFs.

Tadashi Takenaka; Takeshi Sasaki

1997-01-01

225

Origin of the Apollo 17 deep drill coarse-grained layer  

NASA Technical Reports Server (NTRS)

A depositional model of the coarse-grained layer of the Apollo 17 deep drill is described which takes into account thermoluminescence, tracks, Na-22 and Al-26 studies. On the basis of this evidence, it appears that the coarse-grained layer was emplaced some 100 m.y. ago associated either with Camelot Crater or the Central Cluster craters; at that time it was capped by some 25 cm of material which were recently (about 2 m.y.) excavated. The resulting depression has partially and gradually filled since.

Crozaz, G.; Plachy, A. L.

1976-01-01

226

Structure and phase transitions into ionic adsorption layers on liquid interfaces  

E-print Network

The structure of ionic adsorption layers is studied via a proper thermodynamic treatment of the electrostatic and non-electrostatic interactions between the surfactant ions as well as of the effect of thermodynamic non-locality. The analysis is also applied to phase transitions into the ionic adsorption layer, which interfere further with the oscillatory-diffusive structure of the electric double layer and hydrodynamic stability of squeezing waves in thin liquid films.

R. Tsekov

2014-10-25

227

Charge carrier transport properties in layer structured hexagonal boron nitride  

NASA Astrophysics Data System (ADS)

Due to its large in-plane thermal conductivity, high temperature and chemical stability, large energy band gap (˜ 6.4 eV), hexagonal boron nitride (hBN) has emerged as an important material for applications in deep ultraviolet photonic devices. Among the members of the III-nitride material system, hBN is the least studied and understood. The study of the electrical transport properties of hBN is of utmost importance with a view to realizing practical device applications. Wafer-scale hBN epilayers have been successfully synthesized by metal organic chemical deposition and their electrical transport properties have been probed by variable temperature Hall effect measurements. The results demonstrate that undoped hBN is a semiconductor exhibiting weak p-type at high temperatures (> 700 °K). The measured acceptor energy level is about 0.68 eV above the valence band. In contrast to the electrical transport properties of traditional III-nitride wide bandgap semiconductors, the temperature dependence of the hole mobility in hBN can be described by the form of ? ? (T/T0)-? with ? = 3.02, satisfying the two-dimensional (2D) carrier transport limit dominated by the polar optical phonon scattering. This behavior is a direct consequence of the fact that hBN is a layer structured material. The optical phonon energy deduced from the temperature dependence of the hole mobility is ?? = 192 meV (or 1546 cm-1), which is consistent with values previously obtained using other techniques. The present results extend our understanding of the charge carrier transport properties beyond the traditional III-nitride semiconductors.

Doan, T. C.; Li, J.; Lin, J. Y.; Jiang, H. X.

2014-10-01

228

Charge carrier transport properties in layer structured hexagonal boron nitride  

SciTech Connect

Due to its large in-plane thermal conductivity, high temperature and chemical stability, large energy band gap (~ 6.4 eV), hexagonal boron nitride (hBN) has emerged as an important material for applications in deep ultraviolet photonic devices. Among the members of the III-nitride material system, hBN is the least studied and understood. The study of the electrical transport properties of hBN is of utmost importance with a view to realizing practical device applications. Wafer-scale hBN epilayers have been successfully synthesized by metal organic chemical deposition and their electrical transport properties have been probed by variable temperature Hall effect measurements. The results demonstrate that undoped hBN is a semiconductor exhibiting weak p-type at high temperatures (> 700?°K). The measured acceptor energy level is about 0.68 eV above the valence band. In contrast to the electrical transport properties of traditional III-nitride wide bandgap semiconductors, the temperature dependence of the hole mobility in hBN can be described by the form of ? ? (T/T{sub 0}){sup ??} with ? = 3.02, satisfying the two-dimensional (2D) carrier transport limit dominated by the polar optical phonon scattering. This behavior is a direct consequence of the fact that hBN is a layer structured material. The optical phonon energy deduced from the temperature dependence of the hole mobility is ?? = 192 meV (or 1546 cm{sup -1}), which is consistent with values previously obtained using other techniques. The present results extend our understanding of the charge carrier transport properties beyond the traditional III-nitride semiconductors.

Doan, T. C.; Li, J.; Lin, J. Y.; Jiang, H. X., E-mail: hx.jiang@ttu.edu [Department of Electrical and Computer Engineering, Texas Tech University, Lubbock, Texas 79409 (United States)

2014-10-15

229

THE THEORETICAL AND APPLICATION STUDY ON A DOUBLE LAYER MICROPERFORATED SOUND ABSORPTION STRUCTURE  

Microsoft Academic Search

The calculation of resonance and anti-resonance frequencies of a double layer microperforated sound absorption structure is studied, and simplified analytical formulae which will be very useful for the design and analysis of wide bandwidth double layer microperforated sound absorption structures are derived. The results obtained provide an effective method for the design of wide bandwidth microperforated panel silencers.

Z. M. Zhang; X. T. Gu

1998-01-01

230

Bifurcation Structure of a Wind-Driven Shallow Water Model with Layer-Outcropping  

E-print Network

Bifurcation Structure of a Wind-Driven Shallow Water Model with Layer-Outcropping Fran¸cois W of the double-gyre wind-driven ocean circu- lation is examined in a shallow water model where the upper layer structure had hitherto remained unexplored. Preprint submitted to Elsevier 26 October 2006 #12;Key words: 1

Newman, David

231

OBSERVATIONS AND PARAMETERIZATION OF BOUNDARY LAYER STRUCTURES AND CLOUDS AT THE ARM TWP NAURU SITE  

E-print Network

OBSERVATIONS AND PARAMETERIZATION OF BOUNDARY LAYER STRUCTURES AND CLOUDS AT THE ARM TWP NAURU SITE National Laboratory P.O. Box 5000 Upton, NY 11973-5000 www.bnl.gov ABSTRACT Marine boundary layer clouds are fundamental in regulating the vertical structure of water vapor and entropy in the lowest 2 km of the Earth

232

Physical Structures of Lipid Layers X I A N G V . Z H A N G ,  

E-print Network

Physical Structures of Lipid Layers on Pyrite X I A N G V . Z H A N G , T R E A V O R A . K E N D at Stony Brook, Stony Brook, New York 11794 The physical structures of lipid layers on pyrite (FeS2 experimental observations show that this lipid formed bilayers on an atomically rough pyrite surface

233

Self-Organization, Layered Structure, and Aggregation Enhance Persistence of a Synthetic Biofilm Consortium  

E-print Network

Self-Organization, Layered Structure, and Aggregation Enhance Persistence of a Synthetic Biofilm consortium, we fortuitously observed such spatial self-organization. This consortium forms a biofilm and) Self-Organization, Layered Structure, and Aggregation Enhance Persistence of a Synthetic Biofilm

Arnold, Frances H.

234

The viscosity structure of the D00 layer of the Earth's mantle inferred  

E-print Network

The viscosity structure of the D00 layer of the Earth's mantle inferred from the analysis layer Core­mantle boundary Viscosity Maxwell body a b s t r a c t The viscosity structure of the D00-diurnal to 18.6 years tidal deformations combined with model viscosity­depth profiles corresponding to a range

235

Hydrothermal synthesis, structure and thermal stability of diamine templated layered uranyl-vanadates  

E-print Network

crystal structure and thermal behavior are reported herein. Experimental Synthesis Uranyl nitrate (UO2(NO31 Hydrothermal synthesis, structure and thermal stability of diamine templated layered uranyl. Murielle.rivenet@ensc-lille.fr Running Title : Diamine templated layered uranyl-vanadates. Figure for table

Paris-Sud XI, Université de

236

Spatial Variability of Atmospheric Boundary Layer Structure over the Eastern Equatorial Pacific  

Microsoft Academic Search

Variations in the atmospheric boundary layer structure over the eastern equatorial Pacific are analyzed using 916 soundings collected during the First Global Atmospheric Research Program Global Experiment. Unstable boundary layer structures are observed much more frequently in soundings north of the ocean front located near 2.5°N in the eastern equatorial Pacific than in soundings south of the front. An objective

Bingfan Yin; Bruce A. Albrecht

2000-01-01

237

Inner Plasma Structure of the Low-Latitude Reconnection Layer  

NASA Technical Reports Server (NTRS)

We report a clear transition through a reconnection layer at the low-latitude magnetopause which shows a complete traversal across all reconnected field lines during northwestward interplanetary magnetic field (IMF) conditions. The associated plasma populations confirm details of the electron and ion mixing and the time history and acceleration through the current layer. This case has low magnetic shear with a strong guide field and the reconnection layer contains a single density depletion layer on the magnetosheath side which we suggest results from nearly field-aligned magnetosheath flows. Within the reconnection boundary layer, there are two plasma boundaries, close to the inferred separatrices on the magnetosphere and magnetosheath sides (Ssp and Ssh) and two boundaries associated with the Alfvén waves (or Rotational Discontinuities, RDsp and RDsh). The data are consistent with these being launched from the reconnection site and the plasma distributions are well ordered and suggestive of the time elapsed since reconnection of the field lines observed. In each sub-layer between the boundaries the plasma distribution is different and is centered around the current sheet, responsible for magnetosheath acceleration. We show evidence for a velocity dispersion effect in the electron anisotropy that is consistent with the time elapsed since reconnection. In addition, new evidence is presented for the occurrence of partial reflection of magnetosheath electrons at the magnetopause current layer.

Zhang, Q.-H.; Dunlop, M. W.; Lockwood, M.; Lavraud, B.; Bogdanova, Y. V.; Hasegawa, H.; Yang, H. -G.; Liu, R. -Y.; Hu, H. -Q.; Zhang, B. -C.; Pu, Z. -Y.; Yang, Z. -W.; Wang, J.; Taylor, M. G. G. T.; Berchem, J.; Constantinescu, D.; Volwerk, M.; Frey, H.; Fazakerley, A. N.; Shen, C.; Shi, J. -K.; Sibeck, D.; Escoubet, P.; Wild, J. A.

2012-01-01

238

Local structure of Fe in Fe-doped misfit-layered calcium cobaltite: An X-ray absorption spectroscopy study  

SciTech Connect

Polycrystalline Ca{sub 3}Co{sub 4?x}Fe{sub x}O{sub 9+?} ceramics (x=0, 0.01, 0.03, 0.05) were fabricated using a simple thermal hydro-decomposition method and a spark plasma sintering technique. Thermoelectric property measurements showed that increasing Fe concentration resulted in a decrease in electrical resistivity, thermopower and thermal conductivity, leading to an improvement in the dimensionless figure-of-merit, >35% for x=0.05 at 1073 K. An X-ray absorption spectroscopy technique was used to investigate the local structure of Fe ions in the Ca{sub 3}Co{sub 4?x}Fe{sub x}O{sub 9+?} structure for the first time. By fitting data from the extended X-ray absorption fine structure (EXAFS) spectra and analyzing the X-ray absorption near-edge structure (XANES) spectra incorporated with first principle simulation, it was shown that Fe was substituted for Co in the the Ca{sub 2}CoO{sub 3} (rocksalt, RS) layer rather than in the CoO{sub 2} layer. Variation in the thermoelectric properties as a function of Fe concentration was attributed to charge transfer between the CoO{sub 2} and the RS layers. The origin of the preferential Fe substitution site was investigated considering the ionic radii of Co and Fe and the total energy of the system. - Graphical abstract: The Fe K-edge XANES spectra of: (a) experimental result in comparison to the simulated spectra when Fe atoms were substituted in the RS layer; (b) with magnetic moment; (c) without magnetic moment, and in the CoO{sub 2} layer; (d) with magnetic moment and (e) without magnetic moment. Highlights: • Synthesis, structural studies, and thermoelectric properties of Ca{sub 3}Co{sub 4?x}Fe{sub x}O{sub 9+?}. • Direct evidence for the local structure of the Fe ions in the Ca{sub 3}Co{sub 4?x}Fe{sub x}O{sub 9+?} using XAS analysis. • EXAFS and XANES analysis showed that Fe was likely to be situated in the RS layer structure. • Changes in TE property with Fe content was due to charge transfer between the CoO{sub 2} and the RS layers. • Total energy calculation showed energetically favorable Fe substitution in the RS layer.

Prasoetsopha, Natkrita [Materials Science and Nanotechnology Program, Faculty of Science, Khon Kaen University, Khon Kaen 40002 (Thailand); Pinitsoontorn, Supree, E-mail: psupree@kku.ac.th [Department of Physics, Faculty of Science, Khon Kaen University, Khon Kaen 40002 (Thailand); Thailand Center of Excellence in Physics (ThEP), CHE, Ministry of Education, Bangkok 10400 (Thailand); Bootchanont, Atipong [School of Physics, Institute of Science, Suranaree University of Technology, Nakhon Ratchasima 30000 (Thailand); Kidkhunthod, Pinit [Synchrotron Light Research Institute (Public Organization), 111 University Avenue, Muang District, Nakhon Ratchasima 30000 (Thailand); Srepusharawoot, Pornjuk; Kamwanna, Teerasak [Department of Physics, Faculty of Science, Khon Kaen University, Khon Kaen 40002 (Thailand); Amornkitbamrung, Vittaya [Department of Physics, Faculty of Science, Khon Kaen University, Khon Kaen 40002 (Thailand); Thailand Center of Excellence in Physics (ThEP), CHE, Ministry of Education, Bangkok 10400 (Thailand); Kurosaki, Ken; Yamanaka, Shinsuke [Graduate School of Engineering, Osaka University, Suita 565-0871 (Japan)

2013-08-15

239

Constraints on the origin and evolution of the layered mound in Gale Crater, Mars using Mars Reconnaissance Orbiter data  

NASA Astrophysics Data System (ADS)

Gale Crater contains a 5.2 km-high central mound of layered material that is largely sedimentary in origin and has been considered as a potential landing site for both the MER (Mars Exploration Rover) and MSL (Mars Science Laboratory) missions. We have analyzed recent data from Mars Reconnaissance Orbiter to help unravel the complex geologic history evidenced by these layered deposits and other landforms in the crater. Results from imaging data from the High Resolution Imaging Science Experiment (HiRISE) and Context Camera (CTX) confirm geomorphic evidence for fluvial activity and may indicate an early lacustrine phase. Analysis of spectral data from the CRISM (Compact Reconnaissance Imaging Spectrometer for Mars) instrument shows clay-bearing units interstratified with sulfate-bearing strata in the lower member of the layered mound, again indicative of aqueous activity. The formation age of the layered mound, derived from crater counts and superposition relationships, is ˜3.6-3.8 Ga and straddles the Noachian-Hesperian time-stratigraphic boundary. Thus Gale provides a unique opportunity to investigate global environmental change on Mars during a period of transition from an environment that favored phyllosilicate deposition to a later one that was dominated by sulfate formation.

Thomson, B. J.; Bridges, N. T.; Milliken, R.; Baldridge, A.; Hook, S. J.; Crowley, J. K.; Marion, G. M.; de Souza Filho, C. R.; Brown, A. J.; Weitz, C. M.

2011-08-01

240

Thin-film structures with nanocrystals: an origin of enhanced photo-response  

NASA Astrophysics Data System (ADS)

To discover well the properties of nanothin crystalline layers and nanometer-sized crystals, we investigated the relatively thick multilayer structures composed of high quantity of nanothin layers with nanocrystals. Alternate nanolayers of 150-10 nm thicknesses with LiF, CaF2 and CdS nanocrystals have been deposited onto irradiation-resistive substrates by thermal evaporation of pure crystals. Some multilayers were ?-irradiated in air at room temperature with dose of 83 kGy. X-ray diffraction and microscopy studies reveal that the multilayers consist of nanocrystals with cubic phase and defined size. Thin-film structures were oriented along the (111) plane. Absorption spectra of non-irradiated LiF nanocrystals of 100 nm size suggest evidence of metal colloids presence. We find that photoluminescence spectra of ?-irradiated nanostructures with metal colloids and various LiF contents show the enhancement of F3 +-colour centres excitation in the region of metal colloids absorption and the increase is observed of the emission intensities ratio of F3+ and F2 centers with respect to initial crystals ?-coloured in identical conditions. Emission intensities of both centers under excitation at 458 nm correlate with LiF content. These effects, which are related to high-quality nanostructures, but at the same time depend strongly on the defect content, especially as far as their 1-2 ps nonlinearities are concerned, could depend on nanocrystal purity and metal excess collection in their boundaries regions. Our results provide an original contribution to the understanding of the influence of the nanolayer-by-nanolayer deposition, ?-irradiation on these specific structures, and of the metal aggregates on the properties of nanocrystals and nanolayers.

Goncharova, O.; Montereali, R. M.; Baldacchini, G.

2010-11-01

241

Dynamic Instability of Solidification Fronts and Formation of Transverse Layered Structures  

NASA Technical Reports Server (NTRS)

A plane front of crystallization in a unidirectional process of solidification of a binary melt or a solution is shown to be unstable with respect to virtual perturbations of the front velocity within some region of physical and operating parameters. This dynamic instability has nothing in common with morphological instability of the front also possible under certain conditions. It gives rise to the origination of a self-oscillating regime of solidification. The oscillations of the front velocity are accompanied by oscillations of other relevant variables, such as the melt concentration and temperature at the front. What is most important is that this provides for a natural explanation of phenomena of the formation of ordered striations commonly observed when producing alloys and withdrawing crystals. A theory of nonlinear instability of the solidification front is developed which also allows for properties of both self-oscillating regimes of solidification and transverse layered structures it allows to be described in an explicit form, without introducing any additional hypotheses and empirical parameters. Apart from other things, the properties are strongly dependent on convective transport originated in consequence of a difference between the densities of the liquid melt and solid alloy. The theory results in a remarkably good agreement with experimental evidence on crystal withdrawal obtained in normal gravity and under space flight conditions. The problem of interplay between modes of the dynamic and morphological types of instability is also discussed. There are parametric regions in which either only one of these types occurs or both of them arise simultaneously.

Buyevich, Yu A.; Mansurov, Valery V.; Webbon, Bruce W. (Technical Monitor)

1995-01-01

242

Effect of thin oxide layers incorporated in spin valve structures  

SciTech Connect

The enhancement of the magnetoresistance effect, induced by incorporating nano-oxide layers (NOLs) in a bottom-type spin valve, was studied for various preparation conditions. The effect of a NOL in the Co{sub 90}Fe{sub 10} pinned layer was found to depend critically on the oxygen pressure applied to form the thin oxide film. Pressures over 10{sup {minus}3}Torr O{sub 2} yield oxides thicker than about 0.7 nm, which apparently deteriorate the biasing field which exists over the oxide. The magnetoresistance values can further be raised by forming a specular reflecting oxide on top of the sense layer. Promising results were obtained with an Al{sub 2}O{sub 3} capping layer formed in a solid-state oxidation reaction that occurs spontaneously when a thin Al layer is deposited on the oxidized surface of the Co{sub 90}Fe{sub 10} sense layer. {copyright} 2001 American Institute of Physics.

Gillies, M. F.; Kuiper, A. E. T.; Leibbrandt, G. W. R.

2001-06-01

243

Density of polymers in a layered structure: An exactly solvable model  

NASA Astrophysics Data System (ADS)

We have developed an exactly solvable model that makes it possible to calculate the density profile of polymers filled inside a chemically nonuniform structure that consists of alternating layers that have different affinity for polymers. It is shown that the mean density of polymers in this layered structure is in excess relative to that in the uniform system that has the same average affinity for polymers. The average excess density of polymers in the layered structure is calculated as a function of their degree of polymerization, layer thickness, and affinities of the layers for polymers. The developed theoretical model is shown to have relevance to several experimentally important chemically nonuniform layered systems like microphase separated diblock copolymers and selective mixed brushes.

Chervanyov, A. I.; Heinrich, G.

2007-02-01

244

Turbine airfoil with dual wall formed from inner and outer layers separated by a compliant structure  

DOEpatents

A turbine airfoil usable in a turbine engine with a cooling system and a compliant dual wall configuration configured to enable thermal expansion between inner and outer layers while eliminating stress formation is disclosed. The compliant dual wall configuration may be formed a dual wall formed from inner and outer layers separated by a compliant structure. The compliant structure may be configured such that the outer layer may thermally expand without limitation by the inner layer. The compliant structure may be formed from a plurality of pedestals positioned generally parallel with each other. The pedestals may include a first foot attached to a first end of the pedestal and extending in a first direction aligned with the outer layer, and may include a second foot attached to a second end of the pedestal and extending in a second direction aligned with the inner layer.

Campbell; Christian X. (Oviedo, FL), Morrison; Jay A. (Oviedo, FL)

2011-12-20

245

Modeling of Sporadic Layers Meteoritic in Origin in the Mars' Ionosphere  

NASA Astrophysics Data System (ADS)

Recent measurements of the Martian ionosphere has revealed the existence of low altitude layers at altitudes ranging from 70 and 90 km, well below the main photoionospheric peak. These peaks were detected by radio science experiments both Mars Global Surveyor (in 71 of 56000 profiles, [1]) and Mars Express (in 75 of 465 profiles, [2]). The presence of these layers was not limited to specific times of the day, longitude or latitude. Previous theoretical models [3,4] predicted the existence of a constant low altitude layer, with a maximum density of the same order of magnitude compared with the recent observations. Long-live metallic ions coming from meteoroid particles can increase the concentration of electrons. However, the models are not able to explain the huge variability of the observations. Similar layers have been observed in the Earth's atmosphere, especially during strong meteor shower and it is well known that they contain metallic ions coming from the ablation of extraterrestrial dust. Here we present a model of the vertical density profile of metallic species (magnesium and iron) between 60 and 120 km altitude. The model includes ablation of meteoroids, metal diffusion in the atmosphere, photoionization of neutrals by ultraviolet photons, and the chemistry of ions and neutrals including charge exchange between neutrals and ions. We have found that the presence of Mg and Fe reduces the concentration of the most abundant atmospheric ions and also increase the concentration of electrons below 90 km of altitude. Model results are compared with some selected electron density profiles observed by Mars Express in order to understand the existence of this sporadic layer. We obtain that in some conditions a low altitude layer can be formed which compared relatively well with the observations, even under steady state scenarios. However dynamic models or high meteoroid fluxes, i.e. meteor showers, are required to explain fully the observations. [1] Withers et al. (2008), J. Geophys. Res. 113, A12314. [2] Patzold et al. (2005), Science 310, 837-838. [3] Pesnell et al. (2000), J. Geophys. Res.105, 1695. [4] Molina-Cuberos et al. (2003), Planet. and Space Sci. 51, 239

Molina-Cuberos, G. J.; Peter, K.; Witasse, O. G.; Nuñez, M. J.; Paetzold, M.

2011-12-01

246

Origins.  

ERIC Educational Resources Information Center

Provides an annotated list of resources dealing with the theme of origins of life, the universe, and traditions. Includes Web sites, videos, books, audio materials, and magazines with appropriate grade levels and/or subject disciplines indicated; professional resources; and learning activities. (LRW)

Online-Offline, 1999

1999-01-01

247

Origin of Berreman effect in GaN layers on sapphire substrates  

NASA Astrophysics Data System (ADS)

Oblique incidence polarized IR reflectivity measurements of Metal Organic Chemical Vapor Deposition (MOCVD) grown GaN epitaxial layers on sapphire are discussed in the context of recent literature on Berreman effect. The dependence of the p-polarized reflectivity spectrum on incidence angle and thickness of the GaN films is analyzed theoretically and the results are compared with experiment. The "Berreman minimum" that is the reflectivity minimum near the longitudinal-optical (LO) phonon frequency is shown to be due to optical interference. Our calculations show that in GaN layers with thickness greater than 0.1 ?m and for high incidence angles, the frequency of "Berreman minimum" does not correspond to the A1 LO phonon frequency.

Raman, R.; Mishra, Puspashree; Kapoor, Ashok Kumar; Muralidharan, R.

2011-09-01

248

Using in situ isotopic analyses of crystals to investigate the origins of layered intrusions  

NASA Astrophysics Data System (ADS)

An important conclusion from recent detailed textural and geochemical work on many volcanic rocks is that the crystals they contain are largely allochtonous. Isotopic work in particular has shown that crystals grew largely from magmatic reservoirs different from the host in which they are erupted. The term “antecryst” has been adopted to describe such crystals - associated with the magma system in space and time, perhaps cumulates from earlier episodes, but not directly grown from the magma in which they are entrained. Given that layered intrusions are formed entirely from crystals we should surely ask to what degree to the crystals represent a common magma source, or to what degree are they the accumulated record of recycled earlier episodes? The Rum layered intrusion, NW Scotland, has been sampled across a unit boundary (9/10) over which large changes in bulk rock initial Sr isotope ratio had been recorded. Analyses were performed using a microdrill and analysing Sr isotopes following column chemistry. This approach gives superior precision and spatial resolution. Sr isotopic heterogeneity was recovered at mineral and even intra-mineral scale. The isotopic variations coincide with observed grain boundaries and are therefore considered primary. A similar exercise for the Ferrar Dais layered intrusion of the Dry Valleys in Antarctica also showed inter-mineral isotopic heterogeneity. These results indicate that the crystals in each case have grown in isotopically different magmas and mechanically aggregated subsequently. The isotopic heterogeneity suggests that diffusive re-equilibration did not take place and the intrusions must have cooled relatively quickly (closure to Sr diffusion in <1000 years). In principle, isotopic variations over small (crystal-scale) distances can be used to constrain not only the crystal ancestry, but also the cooling histories of layered intrusions.

Davidson, J. P.; Tepley, F. J.; Font, L.

2009-12-01

249

Fabrication of luminescent porous silicon with stain etches and evidence that luminescence originates in amorphous layers  

NASA Technical Reports Server (NTRS)

Simple immersion of Si in stain etches of HF:HNO3:H2O or NaNO2 in aqueous HF was used to produce films exhibiting luminescence in the visible similar to that of anodically-etched porous Si. All of the luminescent samples consist of amorphous porous Si in at least the near surface region. No evidence was found for small crystalline regions within these amorphous layers.

Fathauer, R. W.; George, T.; Ksendzov, A.; Lin, T. L.; Pike, W. T.; Vasquez, R. P.; Wu, Z.-C.

1992-01-01

250

Origin of the circular silverpit structure, UK North Sea : meteorite impact or salt withdrawal?   

E-print Network

The origin of the Silverpit structure, UK North Sea has been contested since its discovery on seismic data in 2002. The Silverpit structure consists of a 3 - 4km central zone of deformation, which includes a conical uplift. ...

Conway, Zana Kate

2007-06-25

251

Characteristics and Origin of Martian Low-Aspect-Ratio Layered Ejecta (LARLE) Craters  

NASA Astrophysics Data System (ADS)

An unusual crater morphology is found primarily at high latitudes on Mars. These craters display an extensive outer deposit beyond the normal layered ejecta blanket. This outer deposit extends up to 20 crater radii from the rim, terminates in a sinuous flame-like edge, and is extremely thin, leading to a low aspect ratio (A = thickness/length). These craters are thus called Low-Aspect-Ratio Layered Ejecta (LARLE) craters. We have conducted a survey of all LARLE craters 1-km-diameter and larger on Mars. We find 139 LARLE craters ranging in diameter from 1.0 to 12.2 km with a median of 2.8 km. Most (97%) are found poleward of 35N and 40S, with the remainder primarily found in the equatorial Medusae Fossae Formation. The surfaces of the freshest LARLE layers commonly exhibit radial, curvilinear ridges and dune-like landforms, and the LARLE deposit typically drapes over pre-existing terrain. We propose that the LARLE deposit is formed by a different mechanism than that responsible for the normal layered ejecta patterns. We suggest that impact into relatively-thick fine-grained ice-rich mantles enhances the formation of a base surge that is deposited after formation of the inner layered ejecta deposits. This base surge is similar to the density-driven, turbulent cloud of suspended fine-grained particles produced by impact erosion and mobilization of the surrounding surface material by ejecta from shallow-depth-of-burst nuclear and high-explosion craters. We have applied a base surge equation developed for terrestrial explosive events to two fresh LARLE craters. After adjustment of the equation for Martian conditions, it predicts runout distances that are within 99% of the observed values. All Martian craters likely produce a base surge during formation, but the presence of the obvious LARLE deposit is attributed to crater formation in thick, fine-grained, sedimentary deposits. These sediments are the source of the extra particulate debris incorporated into and deposited by the base surge.

Barlow, Nadine G.; Boyce, J. M.

2013-10-01

252

Ferromagnetism and the electronic band structure in (Ga,Mn)(Bi,As) epitaxial layers  

SciTech Connect

Impact of Bi incorporation into (Ga,Mn)As layers on their electronic- and band-structures as well as their magnetic and structural properties has been studied. Homogenous (Ga,Mn)(Bi,As) layers of high structural perfection have been grown by the low-temperature molecular-beam epitaxy technique. Post-growth annealing treatment of the layers results in an improvement of their structural and magnetic properties and an increase in the hole concentration in the layers. The modulation photoreflectance spectroscopy results are consistent with the valence-band model of hole-mediated ferromagnetism in the layers. This material combines the properties of (Ga,Mn)As and Ga(Bi,As) ternary compounds and offers the possibility of tuning its electrical and magnetic properties by controlling the alloy composition.

Yastrubchak, O., E-mail: yastrub@hektor.umcs.lublin.pl [Institute of Physics, Maria Curie-Sklodowska University in Lublin, Pl. M. Curie-Sk?odowskiej 1, 20-031 Lublin (Poland); Institute of Semiconductor Physics, National Academy of Sciences, 41 pr. Nauki, 03028 Kyiv (Ukraine); Sadowski, J. [MAX-IV Laboratory, Lund University, P.O. Box 118, SE-221 00 Lund (Sweden); Institute of Physics, Polish Academy of Sciences, Al. Lotnikow 32/46, 02-668 Warsaw (Poland); Gluba, L.; ?uk, J.; Kulik, M. [Institute of Physics, Maria Curie-Sklodowska University in Lublin, Pl. M. Curie-Sk?odowskiej 1, 20-031 Lublin (Poland); Domagala, J. Z.; Andrearczyk, T.; Wosinski, T. [Institute of Physics, Polish Academy of Sciences, Al. Lotnikow 32/46, 02-668 Warsaw (Poland); Rawski, M. [Analytical Laboratory, Maria Curie-Sklodowska University in Lublin, Pl. M. Curie-Sk?odowskiej 3, 20-031 Lublin (Poland)

2014-08-18

253

Effect of pore structure of catalyst layer in a PEMFC on its performance  

Microsoft Academic Search

Influence of pore structure of the cathode catalytic layer in a PEMFC in its performance has been studied. Membrane–electrode assemblies were prepared to have various kinds of porosities and pore structures using spray-drying method. From the I–V characteristics of catalytic layers, pore structure seems to be an important factor determining the cell performance. Addition of thermoplastic agent seems to indeed

Y.-G. Yoon; G.-G. Park; T.-H. Yang; J.-N. Han; W.-Y. Lee; C.-S. Kim

2003-01-01

254

Acceleration and deceleration of coherent structures in the initial shear layers of laminar circular jets  

NASA Astrophysics Data System (ADS)

The acceleration and deceleration of the shear layer mode coherent structures in the initial shear layers of two initially laminar subsonic circular air jets were measured by a novel method employing three hot-wires and the structure capturing scheme of the conditional sampling technique. Several modes of pairing, some of them axisymmetric and others involving tilted flow structures, were established and confirmed by flow visualization.

Chow, K. K.; Tang, S. K.; Ko, N. W. M.

2009-06-01

255

Influence of structural defects on carrier lifetime in 4H-SiC epitaxial layers: Optical lifetime mapping  

NASA Astrophysics Data System (ADS)

The influence of structural defects on carrier lifetime in 4H-SiC epilayers has been studied using high spatial resolution optically detected lifetime measurements. Full wafers mappings with 200 ?m spatial resolution revealed the carrier lifetime variations that can be associated with structural defects replicated from the substrate and variations in the epitaxial growth conditions due to the susceptor design. High resolution mappings over smaller regions with lateral step size down to 20 ?m, revealed local carrier lifetime reductions associated with different structural defects in the epitaxial layers. Identified defects that influence the carrier lifetime are the carrot defects and different types of in-grown stacking faults. Also clusters of threading screw dislocations in the epilayer probably originating from the dissociation of micropipe in the substrate are found to effectively reduce the carrier lifetime. Furthermore, optically detected lifetime mapping has been demonstrated as a nondestructive technique which allows nonvisible structural defects to be detected in as-grown epilayers.

Hassan, J.; Bergman, J. P.

2009-06-01

256

Anatomy of the auditory thalamocortical system in the Mongolian gerbil: nuclear origins and cortical field-, layer-, and frequency-specificities.  

PubMed

Knowledge of the anatomical organization of the auditory thalamocortical (TC) system is fundamental for the understanding of auditory information processing in the brain. In the Mongolian gerbil (Meriones unguiculatus), a valuable model species in auditory research, the detailed anatomy of this system has not yet been worked out in detail. Here, we investigated the projections from the three subnuclei of the medial geniculate body (MGB), namely, its ventral (MGv), dorsal (MGd), and medial (MGm) divisions, as well as from several of their subdivisions (MGv: pars lateralis [LV], pars ovoidea [OV], rostral pole [RP]; MGd: deep dorsal nucleus [DD]), to the auditory cortex (AC) by stereotaxic pressure injections and electrophysiologically guided iontophoretic injections of the anterograde tract tracer biocytin. Our data reveal highly specific features of the TC connections regarding their nuclear origin in the subdivisions of the MGB and their termination patterns in the auditory cortical fields and layers. In addition to tonotopically organized projections, primarily of the LV, OV, and DD to the AC, a large number of axons diverge across the tonotopic gradient. These originate mainly from the RP, MGd (proper), and MGm. In particular, neurons of the MGm project in a columnar fashion to several auditory fields, forming small- and medium-sized boutons, and also hitherto unknown giant terminals. The distinctive layer-specific distribution of axonal endings within the AC indicates that each of the TC connectivity systems has a specific function in auditory cortical processing. PMID:24435884

Saldeitis, Katja; Happel, Max F K; Ohl, Frank W; Scheich, Henning; Budinger, Eike

2014-07-01

257

Structure dependence of ferroelectric properties of bismuth layer-structured ferroelectric single crystals  

NASA Astrophysics Data System (ADS)

Ferroelectric properties along the a(b) axis and c axis in single crystals of various bismuth layer-structured ferroelectrics (BLSFs) were investigated. By measuring saturated P-E hysteresis curves of BLSFs, values of the saturated remanent polarization and the coercive electric field were found to be related to the Curie temperature and the number of BO6 octahedra (m) between bismuth layers, respectively, along the a(b) axis. The saturated remanent polarization was larger in the BLSF with a higher Curie temperature. This is attributed to a large atomic displacement accompanied by a high Curie temperature. In contrast, the saturated coercive electric field was smaller in the BLSF with a larger number of m. This phenomenon is assumed to be caused by the decrease in the strain energy of the octahedra from the bismuth layer, which leads to an easy movement of the octahedral cations in the direction of an applied external electric field. Along the c axis, the BLSFs with an odd number of m had the same relationship, that is, the saturated remanent polarization was larger with the high Curie temperature, and the saturated coercive field was smaller with the large m number. However, no remanent polarization was confirmed in the BLSFs with an even number of m.

Irie, Hiroshi; Miyayama, Masaru; Kudo, Tetsuichi

2001-10-01

258

Multiplatform observations of boundary layer structure in the outer rainbands of landfalling typhoons  

NASA Astrophysics Data System (ADS)

This paper analyzes data collected from a new set of observational platforms in the coastal area of China, which consist of a mobile observation system, meteorological tower, automatic weather station, and Doppler radars, to investigate the mean and turbulent boundary layer structure and evolution during the landfall of typhoons. An example of these data is provided from Typhoon Morakot (2009). Vertical profiles of wind velocities and thermodynamic parameters from the observed data allow us to identify different boundary layer structures during and after landfall. These structures, sampled in regions of the outer core, are stratified into periods where convection is occurring (termed "convective") and periods where convection has recently (<2 h) occurred (termed "postconvective"). Data analyses show that the thermodynamic mixed-layer depth and inflow layer depth are higher during the convective period than the postconvective period. The mixed-layer depth is found to be within the strong inflow layer, but the height of the maximum tangential wind speed is above the inflow layer during both periods, contrary to recent observational studies of the boundary-layer structure of tropical cyclones over water. High-frequency wind data show that momentum flux, turbulent kinetic energy (TKE) and integral length scales of wind velocities are all much larger during the convective period than the postconvective period. The results suggest that convective downdrafts may play an important role in modulating turbulent flux, TKE, vertical mixing, and boundary layer recovery processes.

Ming, Jie; Zhang, Jun A.; Rogers, Robert F.; Marks, Frank D.; Wang, Yuan; Cai, Ninghao

2014-07-01

259

Solvent-free synthesis of new metal phosphites with double-layered, pillared-layered, and framework structures  

NASA Astrophysics Data System (ADS)

Three new metal phosphites, formulated as (H3O)2·Mn2(HPO3)3 (1), Co(bpy) (H2O) (HPO3) (2), and H2tmpda·Zn3(HPO3)4 (3), have been synthesized under solvent-free conditions, where bpy = 4,4?-bipyridine, and tmpda = N,N,N?,N?-tetramethyl-1,3-propanediamine. Compound 1 has a double-layered structure with a thickness of 5.68 Å. Compound 2 has an inorganic-organic hybrid framework with cobalt phosphite layers pillared by bpy ligands. Compound 3 has a three-dimensional open-framework structure containing 8-ring channels. The temperature dependence of the magnetic susceptibility of compounds 1 and 2 were also investigated.

Liu, Lin; Zhang, Wei; Shi, Zhonghua; Chen, Yaoqiang; Lin, Zhien

2014-12-01

260

The atomic scale structure and the electronic properties of a graded composition semiconductor layer  

Microsoft Academic Search

We report the results of a study on the relationship between the structural and electronic properties of a graded layer of undoped AlxGa1?xAs, where x was specified to increase linearly from 0 to 0.2 over 50 nm. The layer was grown by molecular-beam epitaxy between layers of doped GaAs. A high-resolution dark-field transmission electron microscopy imaging technique of combining information

A. P. Long; M. J. Kelly; T. M. Kerr; K. M. Knowles; E. G. Britton; W. M. Stobbs

1988-01-01

261

Dependence of band structures on stacking and field in layered graphene  

Microsoft Academic Search

Novel systems of layered graphene are attracting interest for theories and applications. The stability, band structures of few-layer graphite films, and their dependence on electric field applied along the c-axis are examined within the density functional theory. We predict that those of Bernal type and also rhombohedral type tri- and tetra-layer graphite films exhibit stability. Rhombohedral-type systems, including AB-bilayer, show variable

Masato Aoki; Hiroshi Amawashi

2007-01-01

262

Dimensionality of intermolecular interactions in layered crystals by electronic-structure theory and geometric analysis.  

PubMed

Two-dimensional (2D) and layered structures gained a lot of attention in the recent years ("post-graphene era"). The chalcogen cyanides S(CN)(2) and Se(CN)(2) offer themselves as interesting model systems to study layered inorganic crystal structures; both are built up from cyanide molecules connected by chalcogen bonds (ChBs). Here, we investigate ChBs and their cooperativity directly within the layers of the S(CN)(2) and Se(CN)(2) crystal structures and, furthermore, in putative O(CN)(2) and Te(CN)(2) crystal structures derived therefrom. Moreover, we determine the energetic contributions of ChBs within the layers to the overall stabilization energy. To compare these structures not only energetically but also geometrically, we derive a direction-dependent root mean square of the Cartesian displacement, a possible tool for further computational investigations of layered compounds. The molecular chains connected by ChBs are highly cooperative but do not influence each other when combined to layers: the ChBs are nearly orthogonal in terms of energy when connected to the same chalcogen acceptor atom. Layers built up from ChBs account for 41% to 79% of the overall interaction energy in the crystal. This provides new, fundamental insight into the meaning of ChBs, and therefore directed intermolecular interactions, for the stability of crystal structures. PMID:25363246

George, Janine; Deringer, Volker L; Dronskowski, Richard

2015-02-01

263

Modification in drag of turbulent boundary layers resulting from manipulation of large-scale structures  

NASA Technical Reports Server (NTRS)

The effects of placing a parallel-plate turbulence manipulator in a boundary layer are documented through flow visualization and hot wire measurements. The boundary layer manipulator was designed to manage the large scale structures of turbulence leading to a reduction in surface drag. The differences in the turbulent structure of the boundary layer are summarized to demonstrate differences in various flow properties. The manipulator inhibited the intermittent large scale structure of the turbulent boundary layer for at least 70 boundary layer thicknesses downstream. With the removal of the large scale, the streamwise turbulence intensity levels near the wall were reduced. The downstream distribution of the skin friction was also altered by the introduction of the manipulator.

Corke, T. C.; Guezennec, Y.; Nagib, H. M.

1981-01-01

264

Deriving Lifetime Maps in the Time/Frequency Domain of Coherent Structures in the Turbulent Boundary Layer  

NASA Technical Reports Server (NTRS)

The lifetimes of coherent structures are derived from data correlated over a 3 sensor array sampling streamwise sidewall pressure at high Reynolds number (> 10(exp 8)). The data were acquired at subsonic, transonic and supersonic speeds aboard a Tupolev Tu-144. The lifetimes are computed from a variant of the correlation length termed the lifelength. Characteristic lifelengths are estimated by fitting a Gaussian distribution to the sensors cross spectra and are shown to compare favorably with Efimtsov s prediction of correlation space scales. Lifelength distributions are computed in the time/frequency domain using an interval correlation technique on the continuous wavelet transform of the original time data. The median values of the lifelength distributions are found to be very close to the frequency averaged result. The interval correlation technique is shown to allow the retrieval and inspection of the original time data of each event in the lifelength distributions, thus providing a means to locate and study the nature of the coherent structure in the turbulent boundary layer. The lifelength data are converted to lifetimes using the convection velocity. The lifetime of events in the time/frequency domain are displayed in Lifetime Maps. The primary purpose of the paper is to validate these new analysis techniques so that they can be used with confidence to further characterize the behavior of coherent structures in the turbulent boundary layer.

Palumbo, Dan

2008-01-01

265

AIP/123-QED Fuzzy structure theory modeling of sound-insulation layers in complex  

E-print Network

- and medium- frequency ranges. The sound-insulation layer is assumed to behave as a resonant continuous dynamical system in the frequency band of interest. In this paper, we will not consider the high frequencyAIP/123-QED Fuzzy structure theory modeling of sound-insulation layers in complex vibroacoustic

Paris-Sud XI, Université de

266

An observational study of the structure of the nocturnal boundary layer  

Microsoft Academic Search

In an effort to describe the basic vertical structure of the nocturnal boundary layer, observations from four experiments are analyzed. During the night, the depth of significant cooling appears to increase with time while the depth of the turbulence and height of the low level wind maximum tend to remain constant or decrease with time. Since the inversion layer extends

L. Mahrt; R. C. Heald; D. H. Lenschow; B. B. Stankov; Ib Troen

1979-01-01

267

Mechanism of the structure formation of the transition layers in cobalt films electroplated on copper  

NASA Astrophysics Data System (ADS)

The structure formation of the transition layers in electrolytic cobalt films on copper substrates is studied. It has been found that epitaxial growth and repeated twinning in the transition film/substrate layers form the nonequilibrium ? and ? cobalt phases, which cause additional reflections in electron and X-ray diffraction patterns.

Tochitskii, T. A.; Dmitrieva, A. E.

2008-08-01

268

Semiclassical Aspect of Collective Motion in a Layer-Structured Many Particle System  

Microsoft Academic Search

Semiclassical argument is presented for the layer vibration in the many particle system with a layer structure, which is expected to be realized in a dense nuclear matter. Within a toy model, the presence of this collective mode is shown to result in a small reduction of system's energy.

Koichi Takahashi; Tatsuo Tsukamoto

1992-01-01

269

Capacitance value control for metamaterial reflectarray using multi layer mushroom-structure with parasitic element  

Microsoft Academic Search

This paper proposes novel reflectarray design using multi layer mushroom structure with parasitic element based on capacitance value control of LC resonant circuit model. From the study of LC resonant circuit model, this paper shows the parallel setting capacitance value can be theoretically controlled by that the parasitic layer number. Next, this paper shows novel reflectarray design method for -70

Tamami Maruyama; Tasuo Furuno; Yasuhiro Oda; Jiyun Shen; Tomoyuki Ohya

2010-01-01

270

Scaling structure of the velocity statistics in atmospheric boundary layers Susan Kurien,1,2  

E-print Network

Scaling structure of the velocity statistics in atmospheric boundary layers Susan Kurien,1,2 Victor. INTRODUCTION The atmospheric boundary layer is a natural laboratory of turbulence that is unique to be universal in the limit Re , are thus attracted to atmospheric measurements. On the other hand, the boundary

Kurien, Susan

271

Structurally perfect silicon layers produced on sapphire by oxygen ion implantation  

Microsoft Academic Search

We demonstrate that the structural perfection of silicon layers on sapphire can be improved through high-temperature solid-state\\u000a recrystallization after preamorphization of the most imperfect silicon layer near the silicon\\/sapphire interface by high-energy\\u000a oxygen ions, followed by high-temperature recrystallization in an inert atmosphere.

V. M. Vorotyntsev; E. L. Shobolov; V. A. Gerasimov

2011-01-01

272

Vapor Solid Growth of One-Dimensional Layer-Structured Gallium  

E-print Network

-axis as shown in Figure 1 inset.1 There are two layers in a single GaS unit cell, in which the bonding between made GaS attractive in photoelectric devices, electrical sensors, and nonlinear optical applications direct bandgap semiconductor with uniform layered structure used in photoelectric devices, electrical

Zhou, Chongwu

273

A class of unsteady, three-dimensional flow structures in turbulent boundary layers  

NASA Technical Reports Server (NTRS)

A restricted class of mathematically admissible, unsteady, three dimensional flows was identified which may constitute part of the structure observed in turbulent boundary layers. The development of the model and some general results are discussed. The resulting solution has characteristics which suggest how upwelling low speed flow can trigger a downward jetting of irrotational high speed fluid into the boundary layer.

Ash, R. L.

1981-01-01

274

Effects of interfacial layer structures on crystal structural properties of ZnO films  

SciTech Connect

Single crystalline ZnO films were grown on Cr compound buffer layers on (0001) Al{sub 2}O{sub 3} substrates by plasma assisted molecular beam epitaxy. In terms of lattice misfit reduction between ZnO and substrate, the CrN and Cr{sub 2}O{sub 3}/CrN buffers are investigated. The structural and optical qualities of ZnO films suggest the feasibility of Cr compound buffers for high-quality ZnO films growth on (0001) Al{sub 2}O{sub 3} substrates. Moreover, the effects of interfacial structures on selective growth of different polar ZnO films are investigated. Zn-polar ZnO films are grown on the rocksalt CrN buffer and the formation of rhombohedral Cr{sub 2}O{sub 3} results in the growth of O-polar films. The possible mechanism of polarity conversion is proposed. By employing the simple patterning and regrowth procedures, a periodical polarity converted structure in lateral is fabricated. The periodical change of the polarity is clearly confirmed by the polarity sensitive piezo response microscope images and the opposite hysteretic characteristic of the piezo response curves, which are strict evidences for the validity of the polarity controlling method as well as the successful fabrication of the periodical polarity controlled ZnO structure.

Park, J. S.; Minegishi, T.; Lee, S. H.; Im, I. H.; Park, S. H.; Hanada, T.; Goto, T.; Cho, M. W.; Yao, T.; Hong, S. K.; Chang, J. H. [Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); School of Nanoscience and Technology, Chungnam National University, Daejeon 305-764 (Korea, Republic of); Major of Nano Semiconductor, Korea Maritime University, Youngdo-ku, Pusan 606-791 (Korea, Republic of)

2008-01-15

275

An experimental study of combustion: The turbulent structure of a reacting shear layer formed at a rearward-facing step. Ph.D. Thesis. Final Report  

NASA Technical Reports Server (NTRS)

A premixed propane-air flame is stabilized in a turbulent free shear layer formed at a rearward-facing step. The mean and rms averages of the turbulent velocity flow field were determined by LDV for both reacting and non-reacting flows. The reaching flow was visualized by high speed schlieren photography. Large scale structures dominate the reacting shear layer. The growth of the large scale structures is tied to the propagation of the flame. The linear growth rate of the reacting shear layer defined by the mean velocity profiles is unchanged by combustion but the virtual origin is shifted downstream. The reacting shear layer based on the mean velocity profiles is shifted toward the recirculation zone and the reattachments lengths are shortened by 30%.

Pitz, R. W.

1981-01-01

276

Effects of physical processes on structure and transport of thin zooplankton layers in the coastal ocean  

USGS Publications Warehouse

Thin layers of plankton are recurrent features in a variety of coastal systems. These layers range in thickness from a few centimeters to a few meters. They can extend horizontally for kilometers and have been observed to persist for days. Densities of organisms found within thin layers are far greater than those above or below the layer, and as a result, thin layers may play an important role in the marine ecosystem. The paramount objective of this study was to understand the physical processes that govern the dynamics of thin layers of zooplankton in the coastal ocean. We deployed instruments to measure physical processes and zooplankton distribution in northern Monterey Bay; during an 11 d period of persistent upwelling-favorable winds, 7 thin zooplankton layers were observed. These zooplankton layers persisted throughout daylight hours, but were observed to dissipate during evening hours. These layers had an average vertical thickness of 1.01 m. No layers were found in regions where the Richardson number was <0.25. In general, when the Richardson number is <0.25 the water column is unstable, and incapable of supporting thin layers. Thin zooplankton layers were also located in regions of reduced flow. In addition, our observations show that the vertical depth distribution of thin zooplankton layers is modulated by high-frequency internal waves, with periods of 18 to 20 min. Results from this study clearly show an association between physical structure, physical processes and the presence of thin zooplankton layers in Monterey Bay. With this new understanding we may identify other coastal regions that have a high probability of supporting thin layers. ?? Inter-Research 2005.

McManus, M.A.; Cheriton, O.M.; Drake, P.J.; Holliday, D.V.; Storlazzi, C.D.; Donaghay, P.L.; Greenlaw, C.F.

2005-01-01

277

Structure and electronic properties of ionic nano-layers MBE-grown on IIIV semiconductors  

E-print Network

Structure and electronic properties of ionic nano-layers MBE-grown on III±V semiconductors MSb semiconductors by means of molecular beam epitaxy (MBE). Electronic and structural properties of the freshly-insulator interface; Surface structure; Molecular beam epitaxy; III±V semiconductor compounds; Electron holography

Korecki, Pawe³

278

The origin and significance of hypersaline magmatic volatiles in giant layered intrusions  

NASA Astrophysics Data System (ADS)

Fluid and melt inclusions are preserved within pegmatite bodies and cumulus minerals within mafic-ultramafic layered intrusions that host economic concentrations of the platinum-group elements (e.g., Bushveld Complex, South Africa; Stillwater Complex, Montana). The inclusions indicate that the earliest volatile phase to have exsolved from the crystallizing intrusions was a relatively anhydrous carbonic fluid (CO2-dominated). As crystallization proceeded, volatiles appear to have become increasingly water-rich and saline, consistent with the relative saturation limits of carbonic and aqueous fluids in mafic silicate liquids. However, the latest stage volatiles in the layered intrusions were unusual halide melts (only slightly hydrous molten salts) of relatively simply composition (NaCl±KCl, CaCl2) with salinities in excess of 90 wt% eq. NaCl or CaCl2. These volatiles were trapped at minimum temperatures of ~750-800oC, near the eutectic temperature for water-saturated felsic (very late, intercumulate) liquid. Heterogeneous entrapment of late-stage silicate melt and halide melt provides unambiguous evidence for the coexistence of both phases. However, experimental constraints on the nature of exsolved volatiles from mafic silicate liquids suggest that the halide melt phases cannot represent an exsolved phase from that coexisting silicate liquid, since this would require unrealistically high (initial) Cl:H2O ratios for the parental silicate liquid (> 9). Analysis of rhyodacitic silicate melt inclusions that coexist with the halide melt inclusions show that the coevally-trapped silicate melt had a Cl:H2O ratios of only ~ 0.1 to 0.2. Similarily, the salt melt phases could not have evolved via the crystallization of hydrous magmatic minerals (e.g., biotite, apatite) since their abundance in the intrusion are very low. The most plausible explanation for the halide melt phases involves the "dehydration" of an initially lower salinity aqueous fluid. This may have occurred by the reaction of the aqueous fluid with nominally-anhydrous minerals such as pyroxene, or by the late-stage alteration of cumulus minerals to hydrous mineral assemblages. Through the use of conventional hydrothermal experimental techniques, it can be shown that the reaction of a volumetrically-minor CaCl2-rich aqueous fluid (20 wt% eq. CaCl2) with the assemblage diopside-enstatite-quartz at near-solidus conditions (700oC, 0.4 kbar) results in the formation of tremolite by the reaction of H2O with the initially anhydrous mafic mineral assemblage. The resulting salinity of the saline phase, trapped as synthetic inclusions in quartz, was > 96 wt% eq. CaCl2, consistent with the water-poor nature of the salt melt inclusions observed in most layered intrusions globally.

Hanley, Jacob; Adlakha, Erin

2013-04-01

279

XeF2 etching of Si(111): The geometric structure of the reaction layer  

NASA Astrophysics Data System (ADS)

Si(111)-7×7 is exposed to XeF2 in ultrahigh vacuum and examined with soft-x-ray photoelectron spectroscopy (SXPS) and photon-stimulated desorption (PSD). The exposures encompass the entire range from chemisorption to steady-state etching. By taking into account the different surface sensitivities of SXPS and PSD, the microscopic structure of the surface fluorosilyl reaction layer is obtained as a function of exposure, and the reaction process is modeled. It is found that the reaction-layer structure passes through four distinct exposure regimes. Steric hindrance between the F atoms of neighboring fluorosilyl groups and defects in the substrate are responsible for the evolution of the reaction-layer structure. When steady-state etching is reached, the reaction layer evolves to a ``tree'' structure of fluorosilyl chains terminated at the surface by SiF3 groups.

Lo, C. W.; Shuh, D. K.; Chakarian, V.; Durbin, T. D.; Varekamp, P. R.; Yarmoff, J. A.

1993-06-01

280

Structural simplicity and complexity of compressed calcium: electronic origin.  

PubMed

A simple cubic structure with one atom in the unit cell found in compressed calcium is counterintuitive to the traditional view of a tendency towards densely packed structures with an increase in pressure. To understand this unusual transformation it is necessary to assume electron transfer from the outer core band to the valence band, and an increase of valence electron number for calcium from 2 to ??3.5. This assumption is supported by the Fermi sphere-Brillouin zone interaction model that increases under compression. The recently found structure of Ca-VII with a tetragonal cell containing 32 atoms (tI32) is similar to that in the intermetallic compound In5Bi3 with 3.75 valence electrons per atom. Structural relations are analyzed in terms of electronic structure resemblance. Correlations of structure and physical properties of Ca are discussed. PMID:24892588

Degtyareva, Valentina F

2014-06-01

281

Aliphatic structure of humic acids; a clue to their origin  

USGS Publications Warehouse

Nuclear magnetic resonance spectra (both 1H and 13C) of humic acids from diverse depositional environments indicate the presence of aromatic chemical structures, most likely derived from lignin of vascular plants, and complex, paraffinic structures, most likely derived from algal or microbial sources. The latter components account for a major fraction of humic acid structures in both terrestrial and aquatic environments, suggesting that algae or microbes play a large role in humification of organic remains from both systems. ?? 1981.

Hatcher, P.G.; Maciel, G.E.; Dennis, L.W.

1981-01-01

282

Structural molecular components of septate junctions in cnidarians point to the origin of epithelial junctions in eukaryotes.  

PubMed

Septate junctions (SJs) insure barrier properties and control paracellular diffusion of solutes across epithelia in invertebrates. However, the origin and evolution of their molecular constituents in Metazoa have not been firmly established. Here, we investigated the genomes of early branching metazoan representatives to reconstruct the phylogeny of the molecular components of SJs. Although Claudins and SJ cytoplasmic adaptor components appeared successively throughout metazoan evolution, the structural components of SJs arose at the time of Placozoa/Cnidaria/Bilateria radiation. We also show that in the scleractinian coral Stylophora pistillata, the structural SJ component Neurexin IV colocalizes with the cortical actin network at the apical border of the cells, at the place of SJs. We propose a model for SJ components in Cnidaria. Moreover, our study reveals an unanticipated diversity of SJ structural component variants in cnidarians. This diversity correlates with gene-specific expression in calcifying and noncalcifying tissues, suggesting specific paracellular pathways across the cell layers of these diploblastic animals. PMID:25246700

Ganot, Philippe; Zoccola, Didier; Tambutté, Eric; Voolstra, Christian R; Aranda, Manuel; Allemand, Denis; Tambutté, Sylvie

2015-01-01

283

Air-coupled ultrasonic measurements of adhesively bonded multi-layer structures  

Microsoft Academic Search

An air-coupled ultrasonic system employing wideband micromachined capacitance transducers has been used for non-contact measurements of material properties in adhesively bonded multi-layer aluminum structures. By sweeping the frequency of the ultrasonic toneburst applied to the air-coupled source, while measuring the air-coupled receiver response, through-transmission spectra for normally incident ultrasound were obtained for various multi-layer structures at frequencies below 2MHz. Resonant

D. W. Schindel

1999-01-01

284

Terahertz and Infrared Photodetection using p-i-n Multiple-Graphene-Layer Structures  

Microsoft Academic Search

We propose to utilize multiple-graphene-layer structures with lateral p-i-n\\u000ajunctions for terahertz (THz) and infrared (IR) photodetection and substantiate\\u000athe operation of photodetectors based on these structures. Using the developed\\u000adevice model, we calculate the detector dc responsivity and detectivity as\\u000afunctions of the number of graphene layers and geometrical parameters and show\\u000athat the dc responsivity and detectivity can

V. Ryzhiiand; M. Ryzhii; V. Mitin; T. Otsuji

2009-01-01

285

Terahertz and infrared photodetection using p-i-n multiple-graphene-layer structures  

Microsoft Academic Search

We propose to utilize multiple-graphene-layer structures with lateral p-i-n junctions for terahertz and infrared (IR) photodetection and substantiate the operation of photodetectors based on these structures. Using the developed device model, we calculate the detector dc responsivity and detectivity as functions of the number of graphene layers and geometrical parameters and show that the dc responsivity and detectivity can be

V. Ryzhii; M. Ryzhii; V. Mitin; T. Otsuji

2010-01-01

286

Electronic Structure of a Chemisorbed Layer at Electrochemical Interface Copper Layer on Gold Electrode  

E-print Network

An appropriate model Hamiltonian based formalism is proposed for a random adsorbate layer with arbitrary coverage and the ensuing two-dimensional band formation by metallic adsorbates in the monolayer regime. The coherent potential approximation is employed to handle the randomness. The adsorbate self-energy is evaluated explicitly using the density of states for the substrate band. This takes us beyond the conventional wide-band approximation and removes the logarithmic divergence associated with the binding energy calculations. The formalism is applied to the electrosorption of copper ion on gold electrode, and the coverage dependence of adsorbate charge, binding energy, and adsorbate density of states are determined. The analysis predicts a unique charge configuration of copper adsorbate, having a net positive charge, in the high-coverage regime, and multiple charge states when the coverage is low. Though one of the charge configurations of copper is nearly neutral at small coverage, its positive charge st...

Mishra, A K

1999-01-01

287

Fuselage Structure Response to Boundary Layer, Tonal Sound, and Jet Noise  

NASA Technical Reports Server (NTRS)

Experiments have been conducted to study the response of curved aluminum and graphite-epoxy fuselage structures to flow and sound loads from turbulent boundary layer, tonal sound, and jet noise. Both structures were the same size. The aluminum structure was reinforced with tear stoppers, while the graphite-epoxy structure was not. The graphite-epoxy structure weighed half as much as the aluminum structure. Spatiotemporal intermittence and chaotic behavior of the structural response was observed, as jet noise and tonal sound interacted with the turbulent boundary layer. The fundamental tone distributed energy to other components via wave interaction with the turbulent boundary layer. The added broadband sound from the jet, with or without a shock, influenced the responses over a wider range of frequencies. Instantaneous spatial correlation indicates small localized spatiotemporal regions of convected waves, while uncorrelated patterns dominate the larger portion of the space. By modifying the geometry of the tear stoppers between panels and frame, the transmitted and reflected waves of the aluminum panels were significantly reduced. The response level of the graphite-epoxy structure was higher, but the noise transmitted was nearly equal to that of the aluminum structure. The fundamental shock mode is between 80 deg and 150 deg and the first harmonic is between 20 deg and 80 deg for the underexpanded supersonic jet impinging on the turbulent boundary layer influencing the structural response. The response of the graphite-epoxy structure due to the fundamental mode of the shock impingement was stabilized by an externally fixed oscillator.

Maestrello, L.

2004-01-01

288

Origin of p-type conductivity in layered nGeTe·mSb2Te3 chalcogenide semiconductors  

NASA Astrophysics Data System (ADS)

Ge2Sb2Te5, an extensively studied narrow-band-gap semiconductor for phase-change memories, always displays p-type conductivity. However, the defect physics and origin of the p-type conductivity are not yet clear. We have studied various types of defects in layered nGeTe·mSb2Te3 (GST) using ab initio calculations. The results show that the formation energies of VGe are always the lowest followed by SbTe in the studied GST. The majority defects are VGe and SbTe, which results in the p-type conductivity of GST. Although Ge2Sb2Te5 always has a p-type character, one can make both p- and n-type GeSb2Te4 and GeSb4Te7 by tuning the atomic chemical environments.

Sun, Zhimei; Pan, Yuanchun; Zhou, Jian; Sa, Baisheng; Ahuja, Rajeev

2011-03-01

289

Thermal cycling response of layered gold/polysilicon MEMS structures  

E-print Network

work in this area focused on understanding the stresses in thin films using wafer curvature the full-field deformed shapes of the Au­Si structures subjected to thermal cycles or hold periods. Depending on the Au­Si plate geometry, the structures deform in a non-linear manner and buckle when

Zhang, Katherine Yanhang

290

Domain structure of the Acetogenium kivui surface layer revealed by electron crystallography and sequence analysis.  

PubMed Central

The three-dimensional structure of the Acetogenium kivui surface layer (S-layer) has been determined to a resolution of 1.7 nm by electron crystallographic techniques. Two independent reconstructions were made from layers negatively stained with uranyl acetate and Na-phosphotungstate. The S-layer has p6 symmetry with a center-to-center spacing of approximately 19 nm. Within the layer, six monomers combine to form a ring-shaped core surrounded by a fenestrated rim and six spokes that point towards the axis of threefold symmetry and provide lateral connectivity to other hexamers in the layer. The structure of the A. kivui S-layer protein is very similar to that of the Bacillus brevis middle wall protein, with which it shares an N-terminal domain of homology. This domain is found in several other extracellular proteins, including the S-layer proteins from Bacillus sphaericus and Thermus thermophilus, Omp alpha from Thermotoga maritima, an alkaline cellulase from Bacillus strain KSM-635, and xylanases from Clostridium thermocellum and Thermoanaerobacter saccharolyticum, and may serve to anchor these proteins to the peptidoglycan. To our knowledge, this is the first example of a domain conserved in several S-layer proteins. Images PMID:8113161

Lupas, A; Engelhardt, H; Peters, J; Santarius, U; Volker, S; Baumeister, W

1994-01-01

291

Effect of electron collecting metal oxide layer in normal and inverted structure polymer solar cells  

SciTech Connect

We performed a systematic study of the effect of electron collecting metal oxide layer on the performance of P3HT: PCBM solar cells. Zinc oxide (ZnO) or titanium dioxide (TiO{sub 2}) buffer layers were prepared by either e-beam evaporation or solution processing method. We also compared the photovoltaic performance of inserting the buffer layer between indium tin oxide (ITO) and the polymer layer for the inverted structure (ITO/ ZnO or TiO{sub 2}/P3HT:PCBM/V{sub 2}O{sub 5}/Au) as well as inserting the buffers layers between the polymer and the aluminum electrode for the conventional structure (ITO/V{sub 2}O{sub 5}/P3HT:PCBM/ZnO or TiO{sub 2}/Al). The results are shown in detail.

Ng, A.; Liu, X.; Sun, Y. C.; Djuriši?, A. B. [Department of Physics, The University of Hong Kong, Pokfulam Road, Hong Kong, P. R. (China); Ng, A. M. C. [Department of Physics, The University of Hong Kong, Pokfulam Road, Hong Kong, P. R. China and Nanostructure Institute for Energy and Environmental Research, Division of Physical Sciences, South University of Science and Technology of China, Shenzhen (China); Chan, W. K. [Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong, P. R. (China)

2013-12-04

292

Patterned defect structures predicted for graphene are observed on single-layer silica films.  

PubMed

Topological defects in two-dimensional materials such as graphene are considered as a tool for tailoring their physical properties. Here, we studied defect structures on a single-layer silica (silicatene) supported on Ru(0001) using a low energy electron diffraction, scanning tunneling microscopy, infrared reflection-absorption spectroscopy, and photoelectron spectroscopy. The results revealed easy formation of periodic defect structures, which were previously predicted for graphene on a theoretical ground, yet experimentally unrealized. The structural similarities between single-layer materials (graphene, silicene, silicatene) open a new playground for deeper understanding and tailoring structural, electronic, and chemical properties of the truly two-dimensional systems. PMID:23937399

Yang, Bing; Boscoboinik, Jorge Anibal; Yu, Xin; Shaikhutdinov, Shamil; Freund, Hans-Joachim

2013-09-11

293

Metallic layered composite materials produced by explosion welding: Structure, properties, and structure of the transition zone  

NASA Astrophysics Data System (ADS)

The structure, morphology, and microhardness of the transition zone in multilayer metallic composite joints are studied, and the cohesion strength of the plates to be joined, the mechanical properties of the formed composite materials, and fracture surfaces are analyzed. The materials to be joined are plates (0.1-1 mm thick) made of D16 aluminum alloy, high-strength maraging ZI90-VI (03Kh12N9K4M2YuT) steel, BrB2 beryllium bronze, and OT4-1 titanium alloy. Composite materials made of different materials are shown to be produced by explosion welding. The dependence of the interface shape (smooth or wavelike) on the physicomechanical properties of the materials to be joined is found. The formation of a wavelike interface is shown to result in the formation of intense-mixing regions in transition zones. Possible mechanisms of layer adhesion are discussed.

Mal'tseva, L. A.; Tyushlyaeva, D. S.; Mal'tseva, T. V.; Pastukhov, M. V.; Lozhkin, N. N.; Inyakin, D. V.; Marshuk, L. A.

2014-10-01

294

Boundary layer structure over areas of heterogeneous heat fluxes  

SciTech Connect

In general circulation models (GCMs), some properties of a grid element are necessarily considered homogeneous. That is, for each grid volume there is associated a particular combination of boundary layer depth, vertical profiles of wind and temperature, surface fluxes of sensible and latent heat, etc. In reality, all of these quantities may exhibit significant spatial variations the grid area, and the larger the area the greater the likely variations. In balancing the benefits of higher resolution against increased computational time and expense, it is useful to consider what the consequences of such subgrid-scale variability may be. Moreover, in interpreting the results of a simulation, one must be able to define an appropriate average value over a grid. There are two aspects of this latter problem: (1) in observations, how does one take a set of discrete or volume-averaged measurements and relate these to properties of the entire domain, and (2) in computations, how can subgrid-scale features be accounted for in the model parameterizations? To address these and related issues, two field campaigns were carried out near Boardman, Oregon, in June 1991 and 1992. These campaigns were designed to measure the surface fluxes of latent and sensible heat over adjacent areas with strongly contrasting surface types and to measure the response of the boundary layer to those fluxes. This paper discusses some initial findings from those campaigns.

Doran, J.C. [Pacific Northwest Lab., Richland, WA (United States); Barnes, F.J. [Los Alamos National Lab., NM (United States); Coulter, R.L. [Argonne National Lab., IL (United States); Crawford, T.L. [National Oceanic and Atmospheric Administration, Oak Ridge, TN (United States). Air Resources Lab. Atmospheric Turbulence and Diffusion Div.

1993-01-01

295

Boundary layer structure over areas of heterogeneous heat fluxes  

SciTech Connect

In general circulation models (GCMs), some properties of a grid element are necessarily considered homogeneous. That is, for each grid volume there is associated a particular combination of boundary layer depth, vertical profiles of wind and temperature, surface fluxes of sensible and latent heat, etc. In reality, all of these quantities may exhibit significant spatial variations within the grid area, and the larger the area the greater the likely variations. In balancing the benefits of higher resolution against increased computational time and expense, it is useful to consider what the consequences of such subgrid-scale variability may be. Moveover, in interpreting the results of a simulation, one must be able to define an appropriate average value over a grid. There are two aspects of this latter problem: (1) in observations, how does one take a set of discrete or volume-averaged measurements and relate these to properties of the entire domain, and (2) in computations, how can subgrid-scale features be accounted for in the model parameterizations? To address these and related issues, two field campaigns were carried out near Boardman, Oregon, in June 1991 and 1992. These campaigns were designed to measure the surface fluxes of latent and sensible heat over adjacent areas with strongly contrasting surface types and to measure the response of the boundary layer to those fluxes. This paper discuses some initial findings from those campaigns.

Doran, J.C. [Pacific Northwest Lab., Richland, WA (United States); Barnes, F.J. [Los Alamos National Lab., NM (United States); Coulter, R.L. [Argonne National Lab., IL (United States); Crawford, T.L. [National Oceanic and Atmospheric Administration, Oak Ridge, TN (United States). Air Resources Lab. Atmospheric Turbulence and Diffusion Div.

1993-04-01

296

Boundary layer structure over areas of heterogeneous heat fluxes  

SciTech Connect

In general circulation models (GCMs), some properties of a grid element are necessarily considered homogeneous. That is, for each grid volume there is associated a particular combination of boundary layer depth, vertical profiles of wind and temperature, surface fluxes of sensible and latent heat, etc. In reality, all of these quantities may exhibit significant spatial variations the grid area, and the larger the area the greater the likely variations. In balancing the benefits of higher resolution against increased computational time and expense, it is useful to consider what the consequences of such subgrid-scale variability may be. Moreover, in interpreting the results of a simulation, one must be able to define an appropriate average value over a grid. There are two aspects of this latter problem: (1) in observations, how does one take a set of discrete or volume-averaged measurements and relate these to properties of the entire domain, and (2) in computations, how can subgrid-scale features be accounted for in the model parameterizations To address these and related issues, two field campaigns were carried out near Boardman, Oregon, in June 1991 and 1992. These campaigns were designed to measure the surface fluxes of latent and sensible heat over adjacent areas with strongly contrasting surface types and to measure the response of the boundary layer to those fluxes. This paper discusses some initial findings from those campaigns.

Doran, J.C. (Pacific Northwest Lab., Richland, WA (United States)); Barnes, F.J. (Los Alamos National Lab., NM (United States)); Coulter, R.L. (Argonne National Lab., IL (United States)); Crawford, T.L. (National Oceanic and Atmospheric Administration, Oak Ridge, TN (United States). Air Resources Lab. Atmospheric Turbulence and Diffusion Div.)

1993-01-01

297

Boundary layer structure over areas of heterogeneous heat fluxes  

SciTech Connect

In general circulation models (GCMs), some properties of a grid element are necessarily considered homogeneous. That is, for each grid volume there is associated a particular combination of boundary layer depth, vertical profiles of wind and temperature, surface fluxes of sensible and latent heat, etc. In reality, all of these quantities may exhibit significant spatial variations within the grid area, and the larger the area the greater the likely variations. In balancing the benefits of higher resolution against increased computational time and expense, it is useful to consider what the consequences of such subgrid-scale variability may be. Moveover, in interpreting the results of a simulation, one must be able to define an appropriate average value over a grid. There are two aspects of this latter problem: (1) in observations, how does one take a set of discrete or volume-averaged measurements and relate these to properties of the entire domain, and (2) in computations, how can subgrid-scale features be accounted for in the model parameterizations To address these and related issues, two field campaigns were carried out near Boardman, Oregon, in June 1991 and 1992. These campaigns were designed to measure the surface fluxes of latent and sensible heat over adjacent areas with strongly contrasting surface types and to measure the response of the boundary layer to those fluxes. This paper discuses some initial findings from those campaigns.

Doran, J.C. (Pacific Northwest Lab., Richland, WA (United States)); Barnes, F.J. (Los Alamos National Lab., NM (United States)); Coulter, R.L. (Argonne National Lab., IL (United States)); Crawford, T.L. (National Oceanic and Atmospheric Administration, Oak Ridge, TN (United States). Air Resources Lab. Atmospheric Turbulence and Diffusion Div.)

1993-01-01

298

Structural reinforcement of microvascular networks using electrostatic layer-by-layer assembly with  

E-print Network

particles at the channel surface. For self-healing materials the two most documented fabri- cation methods tissue for various functions including, but not limited to self-healing. We seek to create structures systems. While synthetic vascularized materials have been created by a variety of manufacturing techniques

Sottos, Nancy R.

299

Properties of transition metal oxides with layered perovskite structure  

Microsoft Academic Search

The manganates of Lan?nxSr1+nxMnnO3n+1(x=0.4; n=1, 2, ?) were prepared to study the relationship between their electronic properties and their crystal structure; two-dimensional structure with n=1, pseudo-two-dimensional with n=2 and three-dimensional with n=?. The n=1 manganate exhibits semiconducting behavior below room temperature. When the manganate has a higher dimensional structure with an increase in the value of n, the electric conduction

Minoru Takemoto; Tatsuya Miyajima; Kazuyoshi Takayanagi; Takeshi Ogawa; Hiroyuki Ikawa; Takahisa Omata

1998-01-01

300

9.14 Brain Structure and its Origins, Spring 2005  

E-print Network

This course covers major CNS structures with emphasis on systems being used as models for experimental studies of development and plasticity. Topics include basic patterns of connections in CNS, embryogenesis, PNS anatomy ...

Schneider, Gerald

301

ORIGINAL PAPER Observations on the population structure and behaviour  

E-print Network

) on the population structure, behaviour and ecology of these antelope with regard to population persistence antelopes of the world and of great economical value. It is an ungulate belonging to the family Bovidae

Paris-Sud XI, Université de

302

Origin of the filamentary structure in space plasmas  

NASA Astrophysics Data System (ADS)

We propose a scenario that filamentary structure appears together with propagating waves on the scale of ion gyroradius. The method is based on two-dimensional ion particle-in-cell (or hybrid) simulation in low-beta plasmas. Coherent, filamentary structures in space plasmas are found as the zero-frequency mode in the wavenumber-frequency domain. The existence of the wave modes might be the key to understand filament formation in space plasmas.

Comi?el, Horia; Constantinescu, Vlad; Narita, Yasuhito

2014-12-01

303

Evolution of the ring-like vortices and spike structure in transitional boundary layers  

NASA Astrophysics Data System (ADS)

At the late stage of transitional boundary layers, the nonlinear evolution of the ring-like vortices and spike structures and their effects on the surrounding flow were studied by means of direct numerical simulation with high order accuracy. A spatial transition of the flat-plate boundary layers in the compressible flow was conducted. Detailed numerical results with high resolution clearly represented the typical vortex structures, such as ring-like vortices and so on, and induced ejection and sweep events. It was verified that the formation of spike structures in transitional boundary layers had close relationship with ring-like vortices. Especially, compared to the newly observed positive spike structure in the experiments, the same structure was found in the present numerical simulations, and the mechanism was also studied and analyzed.

Chen, Lin; Tang, Dengbin; Liu, Xiaobing; Oliveira, Maria; Liu, Chaoqun

2010-03-01

304

Internal structure of event layers preserved on the Andaman Sea continental shelf, Thailand: tsunami vs. storm and flash flood deposits  

NASA Astrophysics Data System (ADS)

Tsunami, storm and flash event layers, which have been deposited over the last century on the shelf offshore from Khao Lak (Thailand, Andaman Sea), are identified in sediment cores based on sedimentary structures, grain size compositions, Ti / Ca ratios and 210Pb activity. Individual offshore tsunami deposits are 12 to 30 cm in thickness and originate from the 2004 Indian Ocean tsunami. They are characterized by (1) the appearance of sand layers enriched in shells and shell debris, (2) cross lamination and (3) the appearance of rip-up clasts. Storm deposits found in core depths between 5 and 82 cm could be attributed to individual storm events by using 210Pb dating in conjunction with historical data of typhoons and tropical storms and could thus be securely differentiated from tsunami deposits. Massive sand layers enriched in shells and shell debris characterize the storm deposits. The last classified type of event layer represents flash floods, which is characterized by a fining-upward sequence of muddy sediment. The most distinct difference between the storm and tsunami deposits is the lack of rip-up clasts, mud, and terrigenous material within the storm deposits. Terrigenous material transported offshore during the tsunami backwash is therefore an important indicator to distinguish between offshore storm and tsunami deposits.

Sakuna-Schwartz, D.; Feldens, P.; Schwarzer, K.; Khokiattiwong, S.; Stattegger, K.

2014-12-01

305

Unattended automatic monitoring of boundary layer structures with cost effective lidar ceilometers  

NASA Astrophysics Data System (ADS)

The vertical temperature and moisture distribution affect the layering of the atmospheric boundary layer and the existence of inversions within this layer or on the top of it. These layers have a strong influence on the development of episodes of high concentrations of air pollutants which might be harmful to people and ecosystems. The height of the mixing layer is defined as the height up to which due to the thermal structure of the boundary layer vertical dispersion by turbulent mixing of air pollutants takes place. Most of the aerosol particles in an atmospheric column are usually confined to atmospheric layers below this height, the knowledge on the mixing layer height can thus be employed to convert column-mean optical depths measured from satellites into near-surface air quality information. Eye-safe lidar ceilometers are reliable tools for unattended boundary layer structure monitoring around the clock up to heights exceeding 2500 m. Comparison to temperature, humidity, and wind profiles reported by RASS, sodar, radio soundings, and weather mast in-situ sensors has confirmed their ability to detect convective or residual layers. In addition, ceilometers with a single lens optical design enable precise assessment of inversion layers and nocturnal stable layers below 200 m. This design has been chosen for the Vaisala Ceilometer CL31, the standard cloud height indicator for the Automated Surface Observing System of the US National Weather Service (NWS). During a two years evaluation period, the NWS permanently collected backscatter profiles from at least three ceilometers at its test site in Sterling, VA. Based on these and on data from units running at the Vaisala test sites in Vantaa, Finland, and Hamburg, Germany, an automatic algorithm for online retrieval of aerosol layer heights within the boundary layer has been developed that covers not only ideal boundary layer diurnal evolution, but all situations involving clouds, fog, and precipitation. This algorithm is part of the Vaisala boundary layer reporting and analysis tool BL-VIEW. The algorithm is based on the gradient method looking for gradient minima of the backscatter intensity to mark upper edges of aerosol layers. Main additional features of the novel automatic algorithm are a cloud, fog and precipitation filter designed to avoid false hits, a noise and range dependant averaging scheme, and a variable detection threshold. Examples covering a variety of meteorological situations in all seasons will be presented that demonstrate the quality of the algorithm and its application in the field of air quality forecasting.

Münkel, Christoph; Roininen, Reijo

2010-05-01

306

Study on tribological mechanism for multi-layer porous structure of diatom frustule.  

PubMed

Tribological mechanism of the diatom frustule with multi-layers of pores is studied with the liquid-solid interaction (FSI) method. Based on the reconstructed representative Coscinodiscus sp. frustule with two-layer porous structure, the tribological performances for the diatom frustule at its different pore diameter ratios, pore depth ratios, and velocities are solved through governing equations involved with FSI method. The numerical result shows that the existence of the two-layer porous structure of the diatom helps to reduce the friction between it and ambient water, and to increase its ability to resist the ambient water pressure. The two-layer porous structure effectively improve the tribological performances for the diatom frustule due to the change in the frustule velocity. PMID:25204749

Meng, Fanming; Gao, Guixiang; Jia, Zhihong

2015-01-01

307

Unequal density effect on static structure factor of coupled electron layers  

NASA Astrophysics Data System (ADS)

In order to understand the ordered phase, if any, in a real coupled electron layers (CEL), there is a need to take into account the effect of unequal layer density. Such phase is confirmed by a strong peak in a static structure factor. With the aid of quantum/dynamical version of Singwi, Tosi, Land and Sjölander (so-called qSTLS) approximation, we have calculated the intra- and interlayer static structure factors, Sll(q) and S12(q), over a wide range of density parameter rsl and interlayer spacing d. In our present study, the sharp peak in S22(q) has been found at critical density with sufficiently lower interlayer spacing. Further, to find the resultant effect of unequal density on intra- and interlayer static structure factors, we have compared our results with that of the recent CEL system with equal layer density and isolated single electron layer.

Saini, L. K.; Nayak, Mukesh G.

2014-04-01

308

A novel cesium hydroxygallophosphate with a layered structure built up of rutile ribbons: CsGa 2(OH) 2[(PO 4)H(PO 4)  

NASA Astrophysics Data System (ADS)

A new cesium gallophosphate, CsGa 2(OH) 2[(PO 4)H(PO 4)], with an original layer structure has been synthesized by hydrothermal route and characterized by single-crystal X-ray diffraction ( R=0.0344, R=0.0319). Its structure crystallizes in the monoclinic space group P2 1/ a with cell parameters a=16.079(6) Å, b=5.9873(12) Å, c=4.5033(15) Å, ?=93.36(4)° and Z=2. It consists of [Ga(OH)PO 4] ? layers built up of rutile ribbons interconnected through PO 4 tetrahedra. The structure of CsGa 2(OH) 2[(PO 4)H(PO 4)] is closely related to those of (NH 4)Ga(OH)PO 4 and ( en)Ga 2(OH) 2(PO 4) 2 ( en=ethylenediamine [H 3N(CH 2) 2NH 3] 2+). The three structures differ mainly from each other by the relative positions and the spacing of the successive layers, which are governed by different hydrogen bonding modes between [Ga(OH)PO 4] ? layers and the interleaved species. The title compound presents strong symmetric hydrogen bonds O---H---O which bridge two PO 4 tetrahedra of two successive layers. As a consequence, the distance between the layers is significantly shorter than in the two other amine compounds.

Lesage, J.; Guesdon, A.; Raveau, B.

2006-12-01

309

Experiments on near-wall structure of three-dimensional boundary layers  

NASA Technical Reports Server (NTRS)

Investigations of three-dimensional turbulent boundary layers have shown basic differences between two- and three-dimensional flows. These differences can significantly impact the modeling of three-dimensional flows since many flow models are based on results from two-dimensional boundary layers. In many cases the shear stress vector direction has been shown to lag relative to the direction of the mean velocity gradient as the cross flow grows downstream. Coincidence of these vectors is necessary for a scalar eddy viscosity modeling assumption. A second effect is a reduction in magnitude of the shear stress and/or the shear stress to turbulence energy ratio, a(sub 1). This reduction has been observed in several experiments. Recent numerical simulations also indicate wall-layer structural differences between two- and three-dimensional boundary layers. The differences in structure between two- and three-dimensional boundary layers was also addressed in the experiment of Littell & Eaton. The experiment used two-point correlations to investigate the vortical structures in a three dimensional boundary layer on a spinning disk. It was found that each sign of longitudinal vortex is equally likely to exist, but one sign of vorticity is associated with a structure which is better at producing ejections. The goal of the current investigation is to study the structure of the inner layers. Among other questions, the differences between the effects deduced from the three-dimensional flow simulations and the effects seen in experiments can be examined. The research concentrates on the structure of the wall-layer through flow visualization and direct turbulence measurements down to y(+) = 5.

Flack, Karen A.; Johnston, J. P.

1993-01-01

310

Impact of urbanization on boundary layer structure in Beijing  

NASA Astrophysics Data System (ADS)

The Beijing meteorological tower is located in an area of Beijing, China, which has developed from a suburban to an inner city setting over the past 30 years. The impacts of this urbanization process on both the vertical profile and diurnal cycles of air temperature are investigated using hourly data collected from a series of monitoring levels (up to 325 m high) on the Beijing meteorological tower since 1984. We find that the inter-decadal temperature has increased gradually, and that a more significant increase occurred during the 1980s and 1990s due to the effects of urbanization. A well-defined change in temperature stratification was also observed over this period. The height of the temperature inversion layer decreased from the 1980s to the 2000s. A well-defined nighttime temperature inversion developed below 50 m during the summer in the 1980s, but this near-surface inversion is not seen in data from the 1990s and 2000s. This change can be related to an increase in turbulent mixing caused by urban roughness and surface heat storage that disturbs the near-surface temperature inversion layer. In addition, the diurnal change in temperature in the city in summer shows a maximum increase from sunrise to the early afternoon, which is mainly caused by the nature variability and global warming in both the summer and winter. The urbanization mainly contributes to the temperature increase in the afternoon and nighttime. Moreover the urbanization dominates the increase in daily mean near-surface temperature.

Liu, Y.; Yu, M.; Dai, Y.

2013-12-01

311

Two isostructural layered oxohalide compounds containing Mn2+, Te4+ and Si4+; crystal structure and magnetic susceptibility  

NASA Astrophysics Data System (ADS)

The new compounds Mn4(TeO3)(SiO4)X2 (X=Br, Cl) were synthesized by solid state reactions in sealed evacuated silica tubes. The compounds crystallize in the monoclinic space group P21/m with the unit cell parameters a=5.5463(3) Å (5.49434(7) Å), b=6.4893(4) Å (6.44184(9) Å), c=12.8709(7) Å (12.60451(18) Å), ?=93.559(5)° (94.1590(12)°) and Z=2 for the respective Br and Cl analogues. Manganese adopts various distorted coordination polyhedra; [MnO6] octahedra, [MnO5] tetragonal pyramids and [MnO2X2] tetrahedra. Other building blocks are [SiO4] tetrahedra and [TeO3] trigonal pyramids. The structure is made up from layers having no net charge that are connected via weak Van der Waal interactions. The layers that are parallel to (1 1 0) consist of two manganese oxide sheets which are separated by [SiO4] tetrahedra. On the outer sides of the sheets are the [MnO2X2] tetrahedra and the [TeO3] trigonal pyramids connected so that the halide ions and the stereochemically active lone pairs on the tellurium atoms protrude from the layers. Magnetic susceptibility measurements reveal a Curie law with a Weiss temperature of ?=-153(3) K for temperatures ?100 K and indicate antiferromagnetic ordering at TN ~4 K. Possible structural origins of the large frustration parameter of f=38 are discussed. The new compounds Mn4(TeO3)(SiO4)X2 (X=Br, Cl) are layered with weak Van der Waal interactions in between the layers. Manganese adopts various distorted coordination polyhedral, other building blocks are [SiO4] tetrahedra and [TeO3] trigonal pyramids. Magnetic susceptibility measurements indicate antiferromagnetic ordering at low temperatures and a large frustration parameter.

Zimmermann, Iwan; Kremer, Reinhard K.; Johnsson, Mats

2014-10-01

312

On a Pregeometric Origin for Spacetime Dimensionality and Metric Structure  

E-print Network

Motivated by Wheeler's bottom up pregeometry, we introduce a pregeometric approach that does not assume Wheeler's probability amplitudes for establishing spacetime neighborhoods. Rather, a non-trivial metric is produced via the concept of a uniformity base, which is generated with discrete topological groups over some arbitrary fundamental, denumerable set. We show how the concept of entourage multiplication for the elements of our uniformity base mirrors the underlying group structure. This fact is then exploited to create entourage sequences of maximal length, whence a fine metric structure. The resulting metric structure is, for certain group structures, consistent with E4-embeddable graphs. Examples over Z2 x Z4, D4, Z6, D3, Z8, and Z5 are provided. Euclidean embeddability over Z7 and Q8 is discussed. Unlike the statistical approaches typical of graph theory, this method generates dimensionality over low-order sets. Possible applications to the pregeometric modeling of quantum stochasticity and non-locality/non-separability, wave function collapse, and the M4 structure of spacetime are provided in the context of Z2 x Z2 x Z4.

W. M. Stuckey

2002-08-20

313

A structural origin for the cantaloupe terrain of Triton  

NASA Technical Reports Server (NTRS)

Cantaloupe terrain is unique to Triton. It is Triton's oldest terrain and includes about 250,000 km sq. region displaying sparsely cratered, closely spaced, nearly circular dimples about 30-40 km across. This terrain is found on no other planet because, only on Triton the final major global thermal pulse (1) caused completed (or nearly) interior melting resulting in a cooling history where large thermal stresses shattered and contorted a thin, weak lithosphere, and (2) occurred after heavy bombardment so that the surface features were preserved. The cantaloupe terrain is composed of intersecting sets of structures (folds and/or faults) that have developed as a result of global compression generated by volumetric changes associated with cooling of Triton's interior. Further, it is proposed that these structures developed after the period of heavy bombardment, and resulted from the last major global thermal epoch in Triton's unique history (either caused by tidal or radio metric heating). Initially, as the body cooled and the structures formed, their surface topography was most likely modified by thermal relaxation of the warm surface ices. In other bodies like Mercury, thermal stresses generated from global cooling and contraction have resulted in widely spaced thrust faults, whereas on Triton, thermal stresses produced more closely-spaced folds and faults sets. This difference in structural style is probably due to differences in lithospheric properties (thickness, strength, etc.), the magnitude of stress (directly dependent on the thermal history), and when the structures formed, relative to the period of heavy bombardment.

Boyce, Joseph M.

1993-01-01

314

On the origin of irregular structure in Saturn's rings  

E-print Network

We suggest that the irregular structure in Saturn's B ring arises from the formation of shear-free ring-particle assemblies of up to ~100 km in radial extent. The characteristic scale of the irregular structure is set by the competition between tidal forces and the yield stress of these assemblies; the required tensile strength of ~10^5 dyn/cm^2 is consistent with the sticking forces observed in laboratory simulations of frosted ice particles. These assemblies could be the nonlinear outcome of a linear instability that occurs in a rotating fluid disk in which the shear stress is a decreasing function of the shear. We show that a simple model of an incompressible, non-Newtonian fluid in shear flow leads to the Cahn-Hilliard equation, which is widely used to model the formation of structure in binary alloys and other systems.

Scott Tremaine

2002-11-07

315

Towards Automatically Improving Package Structure While Respecting Original Design Decisions  

E-print Network

Abstract—Recently, there has been an important progress in applying search-based optimization techniques to the problem of software re-modularization. Yet, a major part of the existing body of work addresses the problem of modularizing software systems from scratch, regardless of the existing packages structure. This paper presents a novel multi-objective optimization approach for improving existing packages structure. The optimization approach aims at increasing the cohesion and reducing the coupling and cyclic connectivity of packages, by modifying as less as possible the existing packages organization. Moreover, maintainers can specify several constraints to guide the optimization process with regard to extra design factors. To this contribution, we use the Non-Dominated Sorting Genetic Algorithm (NSGA-II). We evaluate the optimization approach through an experiment covering four real-world software systems. The results promise the effectiveness of our optimization approach for improving existing packages structure by doing very small modifications.

Hani Abdeen; Houari Sahraoui; Osama Shata; Nicolas Anquetil; Stéphane Ducasse

2013-01-01

316

Quantum Structure in Cognition, Origins, Developments, Successes and Expectations  

E-print Network

We provide an overview of the results we have attained in the last decade on the identification of quantum structures in cognition and, more specifically, in the formalization and representation of natural concepts. We firstly discuss the quantum foundational reasons that led us to investigate the mechanisms of formation and combination of concepts in human reasoning, starting from the empirically observed deviations from classical logical and probabilistic structures. We then develop our quantum-theoretic perspective in Fock space which allows successful modeling of various sets of cognitive experiments collected by different scientists, including ourselves. In addition, we formulate a unified explanatory hypothesis for the presence of quantum structures in cognitive processes, and discuss our recent discovery of further quantum aspects in concept combinations, namely, 'entanglement' and 'indistinguishability'. We finally illustrate perspectives for future research.

Diederik Aerts; Sandro Sozzo

2015-03-10

317

Origins of Structural Hole Traps in Hydrogenated Amorphous Silicon  

NASA Astrophysics Data System (ADS)

The inherently disordered nature of hydrogenated amorphous silicon (a-Si:H) obscures the influence of atomic features on the trapping of holes. To address this, we have created a set of over two thousand ab initio structures of a-Si:H and explored the influence of geometric factors on the occurrence of deep hole traps using density-functional theory. Statistical analysis of the relative contribution of various structures to the trap distribution shows that floating bonds and ionization-induced displacements correlate most strongly with hole traps in our ensemble.

Johlin, Eric; Wagner, Lucas K.; Buonassisi, Tonio; Grossman, Jeffrey C.

2013-04-01

318

Origins of structural hole traps in hydrogenated amorphous silicon.  

PubMed

The inherently disordered nature of hydrogenated amorphous silicon (a-Si:H) obscures the influence of atomic features on the trapping of holes. To address this, we have created a set of over two thousand ab initio structures of a-Si:H and explored the influence of geometric factors on the occurrence of deep hole traps using density-functional theory. Statistical analysis of the relative contribution of various structures to the trap distribution shows that floating bonds and ionization-induced displacements correlate most strongly with hole traps in our ensemble. PMID:25167024

Johlin, Eric; Wagner, Lucas K; Buonassisi, Tonio; Grossman, Jeffrey C

2013-04-01

319

Injection terahertz laser using the resonant inter-layer radiative transitions in double-graphene-layer structure  

NASA Astrophysics Data System (ADS)

We propose and substantiate the concept of terahertz (THz) laser enabled by the resonant electron radiative transitions between graphene layers (GLs) in double-GL structures. We estimate the THz gain for TM-mode exhibiting very low Drude absorption in GLs and show that the gain can exceed the losses in metal-metal waveguides at the low end of the THz range. The spectrum of the emitted photons can be tuned by the applied voltage. A weak temperature dependence of the THz gain promotes an effective operation at room temperature.

Ryzhii, V.; Dubinov, A. A.; Aleshkin, V. Ya.; Ryzhii, M.; Otsuji, T.

2013-10-01

320

Structure prediction of an S-layer protein by the mean force method  

NASA Astrophysics Data System (ADS)

S-layer proteins have a wide range of application potential due to their characteristic features concerning self-assembling, assembling on various surfaces, and forming of isoporous structures with functional groups located on the surface in an identical position and orientation. Although considerable knowledge has been experimentally accumulated on the structure, biochemistry, assemble characteristics, and genetics of S-layer proteins, no structural model at atomic resolution has been available so far. Therefore, neither the overall folding of the S-layer proteins—their tertiary structure—nor the exact amino acid or domain allocations in the lattices are known. In this paper, we describe the tertiary structure prediction for the S-layer protein SbsB from Geobacillus stearothermophilus PV72/p2. This calculation was based on its amino acid sequence using the mean force method (MF method) achieved by performing molecular dynamic simulations. This method includes mainly the thermodynamic aspects of protein folding as well as steric constraints of the amino acids and is therefore independent of experimental structure analysis problems resulting from biochemical properties of the S-layer proteins. Molecular dynamic simulations were performed in vacuum using the simulation software NAMD. The obtained tertiary structure of SbsB was systematically analyzed by using the mean force method, whereas the verification of the structure is based on calculating the global free energy minimum of the whole system. This corresponds to the potential of mean force, which is the thermodynamically most favorable conformation of the protein. Finally, an S-layer lattice was modeled graphically using CINEMA4D and compared with scanning force microscopy data down to a resolution of 1nm. The results show that this approach leads to a thermodynamically favorable atomic model of the tertiary structure of the protein, which could be verified by both the MF Method and the lattice model.

Horejs, C.; Pum, D.; Sleytr, U. B.; Tscheliessnig, R.

2008-02-01

321

Original article Monitoring the identity and the structure  

E-print Network

analysis and factorial discriminant analysis. From the trypto- phan fluorescence data set, a good levels. Structurally, cheese is a complex matrix of milk proteins, fats, min- erals and other components contribute to firmness and milk fats provide smoothness to cheese: the higher the fat content of cheese

Paris-Sud XI, Université de

322

Modern Structures in the 1906 Quake (Not from original site)  

NSDL National Science Digital Library

A series of QuickTime movies illustrating the deformation of modern Californian structures subjected to the 1906 earthquake. The deformation, exaggerated 100 times, is shown for the Golden Gate Bridge, the SF International Airport, and the San Francisco Marriot. Los Angeles City Hall is also simulated in order to show how buildings further from the epicenter were affected.

Computers & amp; amp; Structures, Inc.

323

Wintertime Boundary Layer Structure in the Grand Canyon  

Microsoft Academic Search

Wintertime temperature profiles in the Grand Canyon exhibit a neutral to isothermal stratification during both daytime and nighttime, with only rare instances of actual temperature inversions. The canyon warms during daytime and cools during nighttime more or less uniformly through the canyon's entire depth. This weak stability and temperature structure evolution differ from other Rocky Mountain valleys, which develop strong

C. David Whiteman; Shiyuan Zhong; Xindi Bian

1999-01-01

324

Acoustic Performance Analysis of Bionic Coupling Multi-layer Structure Yonghua Wang1,2,a  

E-print Network

bionic method to develop a new sound absorption structure. Inspired by the coupling absorption structure-perforated membrane backed with airspace. The impedance transfer method is applied to calculate the absorption coefficients and analyze the influences of different parameters of each layer on absorption coefficients

Boyer, Edmond

325

Optimal solid shell element for large-deformable composite structures with piezoelectric layers and  

E-print Network

Optimal solid shell element for large-deformable composite structures with piezoelectric layers-QUOC CLESMCLESMCLESMCLESMCLESMCLESMCLESMCLESMCLESMCLESMCLESMCLESMCLESMCLESMCLESMCLESMCLESMCLESMCLESMCLESM Computational Laboratory for Electromagnetics and Solid Mechanics To appear in the International 2005 #12;Optimal solid shell element for large-deformable composite structures with piezoelectric

Vu-Quoc, Loc

326

Evolution of Marine Atmospheric Boundary Layer Structure across the Cold Tongue-ITCZ Complex  

Microsoft Academic Search

The structure of the marine atmospheric boundary layer (MABL) over the tropical eastern Pacific Ocean is influenced by spatial variations of sea surface temperature (SST) in the region. As the MABL air is advected across a strong SST gradient associated with the cold tongue-ITCZ complex (CTIC), substantial changes occur in the thermodynamic structure, surface fluxes, and cloud properties. This study

Hollis E. Pyatt; Bruce A. Albrecht; Chris Fairall; J. E. Hare; Nicholas Bond; Patrick Minnis; J. Kirk Ayers

2005-01-01

327

Acoustic band-gap engineering using finite-size layered structures of multiple periodicity  

E-print Network

coefficient of a layered structure made of glass and water was calculated using transfer matrix method by using crystals with periodic structures.1,2 The fundamental principle is to use the periodic medium- magnetic waves cannot go through the crystal. In principle, the band-gap phenomena can be produced when

Cao, Wenwu

328

On the structure formation of hydrophobed particles in the boundary layer of water and octane phases  

Microsoft Academic Search

Two-dimensional aggregation of the surface modified glass beads was carried out in the boundary layer of water and octane phases. The effect of particles' hydrophobicity was investigated on the structure of forming aggregates and the growth process. The structure of the aggregates and their growth were characterized by a density function which demonstrates the change of mean particle density as

Z. Hórvölgyi; G. Medveczky; M. Zrinyi

1993-01-01

329

Ferromagnetic GaAs structures with single Mn delta-layer fabricated using laser deposition.  

PubMed

The new technique combining metal-organic chemical vapor epitaxy with laser ablation of solid targets was used for fabrication of ferromagnetic GaAs structures with single Mn delta-doped layer. The structures demonstrated anomalous Hall effect, planar Hall effect, negative and anisotropic magnetoresistance in temperature range of 10-35 K. In GaAs structures with only single Mn delta-layer (without additional 2D hole gas channel or quantum well) ferromagnetism was observed for the first time. PMID:22905589

Danilov, Yuri A; Vikhrova, Olga V; Kudrin, Alexey V; Zvonkov, Boris N

2012-06-01

330

Quantum confinement in two dimensional layers of PbSe/ZnSe multiple quantum well structures  

NASA Astrophysics Data System (ADS)

The structural and optical properties of thermally evaporated PbSe/ZnSe multiple quantum well (MQW) structures as a function of the PbSe quantum well (QW) layer thickness in the range between 2.5 and 10 nm have been investigated. An ordered periodicity in the MQW structure was confirmed by transmission electron microscopy. The discrete linear resonances in the absorption spectra and the corresponding blue shift observed with decreasing well layer thickness unambiguously reflect the quantum confinement effect. The effective QW band gap is calculated from the infinite well approximation and compared to the experimentally observed value. The QW emission is identified and discussed.

Arivazhagan, V.; Manonmani Parvathi, M.; Rajesh, S.; Sæterli, Ragnhild; Holmestad, Randi

2013-06-01

331

Long-time behavior of PML absorbing boundaries for layered periodic structures  

NASA Astrophysics Data System (ADS)

In this work we consider a special case of the Perfectly Matched Layer (PML) divergence which is observed by the simulation of the planar periodic structures such as photonic crystal slabs or antenna arrays. This divergence is caused by an excitation of long-living artefact evanescent waves in these structures by an incident external pulse. We study the application of the known remedies to this problem: increasing the distance between the structure and PML, employing the ? parameter, employing non-PML absorbers. We also suggest a new simple and effective solution, where the usual PML is backed by an additional absorbing layer.

Deinega, Alexei; Valuev, Ilya

2011-01-01

332

Structure in multilayer films of zinc sulfide and copper sulfide via atomic layer deposition  

SciTech Connect

Multilayer film stacks of ZnS and Cu{sub x}S (x???2) were made via atomic layer deposition. The precursors were bis(2,2,6,6-tetramethyl-3,5-heptanedionato)zinc, bis(2,2,6,6-tetramethyl-3,5-heptanedionato)copper, and H{sub 2}S generated in situ for sulfur. Samples were deposited at 200?°C, in layers ranging from approximately 2 to 20 nm thick, based on binary growth rates. The properties of the film stacks were studied with atomic force microscopy, ultraviolet–visible spectroscopy, and extended x-ray absorption fine structure. The results demonstrate that the structure of films with the thinnest layers is dominated by Cu{sub x}S, whereas in the thicker films, the structure is determined by whichever material is first deposited. This can be attributed to the crystal structure mismatch of ZnS and Cu{sub x}S.

Short, Andrew; Jewell, Leila; Bielecki, Anthony; Keiber, Trevor; Bridges, Frank; Carter, Sue; Alers, Glenn, E-mail: galers@ucsc.edu [Department of Physics, University of California at Santa Cruz, 1156 High Street, Santa Cruz, California 95064 (United States)

2014-01-15

333

Microporous structure with layered interstitial surface treatment, and method and apparatus for preparation thereof  

NASA Technical Reports Server (NTRS)

A microporous structure with layered interstitial surface treatments, and the method and apparatus for its preparation are disclosed. The structure is prepared by sequentially subjecting a uniformly surface treated structure to atomic oxygen treatment to remove an outer layer of surface treatment to a generally uniform depth, and then surface treating the so exposed layer with another surface treating agent. The atomic oxygen/surface treatment steps may optionally be repeated, each successive time to a lesser depth, to produce a microporous structure having multilayered surface treatments. The apparatus employs at least one side arm from a main oxygen-containing chamber. The side arm has characteristic relaxation times such that a uniform atomic oxygen dose rate is delivered to a specimen positioned transversely in the side arm spaced from the main gas chamber.

Koontz, Steven L. (inventor)

1992-01-01

334

Defect Detection in Multi-Layered Structures Using High Frequency Guided Waves  

NASA Astrophysics Data System (ADS)

Aircraft structures contain multi-layered components connected by fasteners, where fatigue cracks and disbonds can develop due to cyclic loading conditions and stress concentration. High frequency guided waves propagating along the structure allow for the efficient non-destructive testing of components, such as aircraft wings. However, the sensitivity for the detection of small defects has to be ascertained. The type of multi-layered model structure investigated consists of two adhesively bonded aluminium plate-strips. High frequency ultrasonic wave propagation along the structure and the sensitivity to disbonds and small defects in the metallic layers was investigated and verified experimentally. Preliminary fatigue experiments were carried out and the sensitivity of the guided waves to monitor fatigue crack growth at a fastener hole during cyclic loading was investigated. The measurement setup has the potential for fatigue crack growth monitoring at critical and difficult to access fastener locations from a stand-off distance.

Masserey, B.; Kostson, E.; Fromme, P.

2011-06-01

335

Structural diagnostics of the tropopause inversion layer and its evolution  

NASA Astrophysics Data System (ADS)

The Tropopause Inversion Layer (TIL) is marked by a peak in static stability directly above the tropopause. The TIL is quantitatively defined with new diagnostics using Global Positioning System Radio Occultation temperature soundings and reanalysis data. A climatology of the TIL is developed from reanalysis data (1980-2011) using diagnostics for the position, depth, and strength of the TIL based on the TIL peak in static stability. TIL diagnostics have defined relationships to the synoptic situation in the Upper Troposphere and Lower Stratosphere. The TIL is present nearly all the time. The TIL becomes hard to define in the subtropics where tropical air overlies midlatitude air, in a region of complex static stability profiles. The mean position of the subtropical TIL gradient is sharp and is co-located with the subtropical tropopause break. Over the period 1980-2011 the TIL depth below the tropopause has decreased by 5% per decade and increased above the tropical tropopause by a similar percentage. Furthermore, the latitude of the abrupt change in the TIL from tropical to extratropical in the lower stratosphere appears to have shifted poleward in each hemisphere by ˜1° latitude per decade, depending on the diagnostic examined. Reanalysis trends should be treated with caution.

Gettelman, A.; Wang, T.

2015-01-01

336

Sliding contact fatigue damage in layered ceramic structures.  

PubMed

Porcelain-veneered restorations often chip and fracture from repeated occlusal loading, making fatigue studies relevant. Most fatigue studies are limited to uni-axial loading without sliding motion. We hypothesized that bi-axial loading (contact-load-slide-liftoff, simulating a masticatory cycle), as compared with uni-axial loading, accelerates the fatigue of layered ceramics. Monolithic glass plates were epoxy-joined to polycarbonate substrates as a transparent model for an all-ceramic crown on dentin. Uni-and bi-axial cyclic contact was applied through a hard sphere in water, by means of a mouth-motion simulator apparatus. The uni-axial (contact-load-hold-liftoff) and traditional R-ratio fatigue (indenter never leaves the specimen surface) produced similar lifespans, while bi-axial fatigue was more severe. The accelerated crack growth rate in bi-axial fatigue is attributed to enhanced tensile stresses at the trailing edges of a moving indenter. Fracture mechanics descriptions for damage evolution in brittle materials loaded repeatedly with a sliding sphere are provided. Clinical relevance is addressed. PMID:17959894

Kim, J-W; Kim, J-H; Thompson, V P; Zhang, Y

2007-11-01

337

Computer simulation study of the structural stability and materials properties of DNA-intercalated layered double hydroxides.  

PubMed

The intercalation of DNA into layered double hydroxides (LDHs) has various applications, including drug delivery for gene therapy and origins of life studies. The nanoscale dimensions of the interlayer region make the exact conformation of the intercalated DNA difficult to elucidate experimentally. We use molecular dynamics techniques, performed on high performance supercomputing grids, to carry out large-scale simulations of double stranded, linear and plasmid DNA up to 480 base pairs in length intercalated within a magnesium-aluminum LDH. Currently only limited experimental data have been reported for these systems. Our models are found to be in agreement with experimental observations, according to which hydration is a crucial factor in determining the structural stability of DNA. Phosphate backbone groups are found to align with aluminum lattice positions. At elevated temperatures and pressures, relevant to origins of life studies which maintain that the earliest life forms originated around deep ocean hydrothermal vents, the structural stability of LDH-intercalated DNA is substantially enhanced as compared to DNA in bulk water. We also discuss how the materials properties of the LDH are modified due to DNA intercalation. PMID:18345669

Thyveetil, Mary-Ann; Coveney, Peter V; Greenwell, H Chris; Suter, James L

2008-04-01

338

Observing the Origins of Galaxy Structure in the Illustris Simulation  

NASA Astrophysics Data System (ADS)

Many processes affect the appearance of galaxies, and it has recently become possible to predict how these processes set internal galaxy structure in significant populations. Such calculations are poised to clarify the physics of star formation quenching, the cosmological formation of bulges and disks, and the observability of galaxy mergers. To advance these goals, we propose to build and analyze a very large set of mock HST images based on the Illustris Project. This accurate continuous-volume hydrodynamical simulation formed thousands of structurally diverse Milky Way-mass galaxies in {106.5 Mpc}^3 with detail comparable to the resolution of HST at many cosmic times. We will mock-observe 41,000 model galaxies at 0 < z < 5 in broadband filters used by ACS, WFC3, and JWST/NIRCAM, and measure automated morphology diagnostics from each image. This will constitute a timely and effective tool to advance two key goals of observational cosmology with HST: linking the building blocks of galaxies across cosmic time, and understanding the implications of galaxy morphology and structure. It will allow us to study the emergence of the Hubble Sequence, estimate merger rates and consequences, and interpret star formation patterns in distant galaxies. Therefore this model dataset is ideally suited to enhance results from HST Treasury and Archival Legacy surveys, the Ultra Deep Fields, and Frontier Fields. To increase the science return, we will publicly release our model images and morphology catalogs, providing a tool that can directly link physical mechanisms to high redshift galaxy data.

Snyder, Greg

2014-10-01

339

A parametric analysis of radiative structure in aerobrake shock layers  

NASA Technical Reports Server (NTRS)

A broad-spectrum version of the NEQAIR code was modified to account for self-absorption and applied to AFE flowfields calculated by the LAURA code with a variety of kinetic models. The resulting radiative fluxes were obtained in a decoupled fashion from the flowfield solver along the vehicle's stagnation streamline. The radiative flux obtained was broken down by causative process to study the radiative structure of the AFE's flowfield for the various kinetic models. In addition, the radiative fluxes for several points on a typical AFE trajectory were analyzed to examine how the radiative structure changes as the vehicle completes its aeropass. Only two radiative processes dominated the stagnation radiative flux, and the flow field conditions near the wal were found to exert considerable influence over the radiative flux to the wall.

Greendyke, Robert B.

1992-01-01

340

Giant magnetoresistance of manganese oxides with a layered perovskite structure  

Microsoft Academic Search

MANGANESE oxides with the cubic perovskite structure (typified by LaMnO3) have stimulated considerable interest because of their magnetoresistive properties1-9 they exhibit extremely large changes in electrical resistance in response to applied magnetic fields, a property that is of technological relevance for the development of magnetic memory and switching devices. But for such applications to be viable, great improvements will be

Y. Moritomo; A. Asamitsu; H. Kuwahara; Y. Tokura

1996-01-01

341

Functional Nano-Structures Using Atomic Layer Deposition  

E-print Network

photovoltaic structures. The thesis begins by providing three background chapters. Chapter 1 covers pho- tovoltaics, with an emphasis on liquid and solid-state electrolyte dye-sensitised solar cells. Chapter 2 is concerned with the self-assembly of microphase... Blumei butterfly. v Contents Declaration iii Acknowledgements iv Abstract v 1 Introduction 1 2 Fundamentals of solar cells 5 2.1 Conventional photovoltaic devices . . . . . . . . . . . . . . . . . . . . . 5 2.2 Excitonic solar cells...

Salgård Cunha, Pedro

2014-05-27

342

Layered dielectric–magnetic composite structures for Rf-applications  

Microsoft Academic Search

In this paper multilayer magnetic–dielectric composite structures for high frequency applications are introduced. The 0–3 type dielectric and magnetic composites with homogeneously distributed ceramic inclusions were fabricated by mixing extrusion and injection moulding. Magnetic Yttrium Iron Garnet (YIG) and Z-type Hexaferrite (HexaZ) as well as paraelectric Barium Strontium Titanate (BST) powders were used to enhance the permittivity and permeability of

Merja Teirikangas; Jari Juuti; Heli Jantunen

2010-01-01

343

Anomalous absorption of bulk shear sagittal acoustic waves in a layered structure with viscous fluid  

E-print Network

It is demonstrated theoretically that the absorptivity of bulk shear sagittal waves by an ultra-thin layer of viscous fluid between two different elastic media has a strong maximum (in some cases as good as 100%) at an optimal layer thickness. This thickness is usually much smaller than the penetration depths and lengths of transverse and longitudinal waves in the fluid. The angular dependencies of the absorptivity are demonstrated to have significant and unusual structure near critical angles of incidence. The effect of non-Newtonian properties and non-uniformities of the fluid layer on the absorptivity is also investigated. In particular, it is shown that the absorption in a thin layer of viscous fluid is much more sensitive to non-zero relaxation time(s) in the fluid layer than the absorption at an isolated solid-fluid interface.

Dmitri K. Gramotnev; Melissa L. Mather; Timo A. Nieminen

2005-09-05

344

The stabilities and electronic structures of single-layer bismuth oxyhalides for photocatalytic water splitting.  

PubMed

The stabilities and electronic/band structures of single-layer bismuth oxyhalides have been investigated by employing first-principles calculations. The results indicate that the single-layer bismuth oxyhalide materials, except for BiOF, have robust energetic and dynamical stabilities because of their low formation energies and the absence of imaginary frequencies within the entire Brillouin zone. Furthermore, calculations of the electronic structures and optical absorptions indicate that single-layer BiOI possesses a favorable band gap, suitable band edge positions, different orbital characteristics and different effective masses at the valence band maximum (VBM) and conduction band minimum (CBM), thus presenting excellent photocatalytic activity for water splitting. Moreover, the resulting compressive strains can shift the band edge positions of the single-layer materials to more suitable places to enhance their photocatalytic activities. PMID:25354143

Zhang, Xue; Li, Baihai; Wang, Jianlin; Yuan, Yu; Zhang, Qiujie; Gao, Zhanzhong; Liu, Li-Min; Chen, Liang

2014-12-21

345

Large GMR values of sputtered Co/Cu multilayer structures with Co-Cu buffer layers  

SciTech Connect

We demonstrate large giant magnetoresistance (GMR) values of Co/Cu multilayers (MLs) sputtered on combined Co18{angstrom}/Cu48{angstrom} buffer layer. GMR values at room temperature reach 62% at the first antiferromagnetically (AF) coupling peak and 33% at the 2nd AF coupled peak, which are very close to those found in Co/Cu MLs sputtered on a Fe buffer layer. The large GMR effect is attributed to the superior superlattice structure of these samples, as evidenced by the x-ray reflectivity data as well as the TEM micrographs. In particular, the role of thin Co initial layer deposited beneath the Cu buffer layer on improved ML structure has been clarified from cross-sectional micrographs of high-resolution TEM.

Huai, Y.; Vernon, S.P.; Stearns, D.G.; Cerjan, C.; Kania, D.R.

1996-02-29

346

Internal structure of nanoporous TiO2/polyion thin films prepared by layer-by-layer deposition.  

PubMed

The internal structure of porous TiO2 films prepared by electrostatic layer-by-layer deposition was investigated. The films were prepared by alternate dipping of solid substrates into dispersions of TiO2 nanoparticles and polycations, polyanions, or pure buffer solution, respectively. The surface charge of the amphoteric TiO2 particles was controlled by the pH of the aqueous dispersions. The morphology of the film surface was investigated by means of scanning electron microscopy. It was found that the surface roughness strongly depends on the polymeric material used for the deposition process but is independent of the ionic strength of the solution or the molecular weight of the polyions. The samples with rough surfaces feature strong light scattering. The porosity and internal structure of the TiO2/polyelectrolyte films were investigated by adsorption/desorption of dye molecules. A crude estimate yields an internal surface that is up to 160 times the plane surface of the substrate for a film thickness of 1 microm. The composition of the films was investigated by X-ray photoelectron spectroscopy (XPS). Detection of the XPS signal after each deposition step of the first three dipping cycles shows a significant increase of the relative surface coverage of Ti after the TiO2 deposition step and of PSS after the PSS deposition step. For later dipping cycles, such an increase was also detectable but less prominent. PMID:17696454

Kniprath, R; Duhm, S; Glowatzki, H; Koch, N; Rogaschewski, S; Rabe, J P; Kirstein, S

2007-09-11

347

Investigation of Ti layer thickness dependent structural, magnetic, and photoemission study of nanometer range Ti/Ni multilayer structures.  

PubMed

Structural, magnetic, and electronic properties of Ti/Ni multilayer (ML) samples as a function of Ti layer thickness are studied and reported in this paper. For this purpose [Ti (t nm)/Ni (5 nm)] x 10 ML samples, where t = 3, 5, and 7 nm have been deposited by using electron beam evaporation technique under UHV conditions at room temperature. Structure of ML samples were determined by using XRD (X-ray diffraction) technique and observed that Titanium is deposited mainly in amorphous nature with FCC structure at lower Ti layer thickness of 3 nm, which transform to crystalline HCP structures above than this Ti layer thickness. Corresponding fitted GIXRR (grazing incidence X-ray reflectivity) patterns shows asymmetric nature of Ti-Ni and Ni-Ti interfaces because of heavy intermixing and interdiffusion of Ni and Ti atoms at Ti-Ni interfaces at lower Ti layer thickness. The depth profiling core level and valence band measurements carried out by using XPS (X-ray photoelectron spectroscopy) technique confirms the interdiffusion and intermixing leading to Ti-Ni alloy phase formation at interfaces during deposition, particularly at lower Ti layer thickness of 3 nm. The corresponding magnetization behavior of ML samples has been investigated using Magneto-Optical Kerr Effect (MOKE) technique and observed that, coercitivity decreases while saturation magnetization increases with Ti layer thickness variations. These results are interpreted and discussed in terms of observed micro-structural changes due to Ti layer thickness vitiations in Ti/Ni multilayer samples. PMID:17654996

Bhatt, Pramod; Prakash, Ram; Chaudhari, S M; Reddy, V R; Phase, D M

2007-06-01

348

Electric field measurements of DC and long wavelength structures associated with sporadic-E layers and QP radar echoes  

NASA Astrophysics Data System (ADS)

Electric field and plasma density data gathered on a sounding rocket launched from Uchinoura Space Center, Japan, reveal a complex electrodynamics associated with sporadic-E layers and simultaneous observations of quasi-periodic radar echoes. The electrodynamics are characterized by spatial and temporal variations that differed considerably between the rocket's upleg and downleg traversals of the lower ionosphere. Within the main sporadic-E layer (95 110 km) on the upleg, the electric fields were variable, with amplitudes of 2 4 mV/m that changed considerably within altitude intervals of 1 3 km. The identification of polarization electric fields coinciding with plasma density enhancements and/or depletions is not readily apparent. Within this region on the downleg, however, the direction of the electric field revealed a marked change that coincided precisely with the peak of a single, narrow sporadic-E plasma density layer near 102.5 km. This shear was presumably associated with the neutral wind shear responsible for the layer formation. The electric field data above the sporadic-E layer on the upleg, from 110 km to the rocket apogee of 152 km, revealed a continuous train of distinct, large scale, quasi-periodic structures with wavelengths of 10 15 km and wavevectors oriented between the NE-SW quadrants. The electric field structures had typical amplitudes of 3 5 mV/m with one excursion to 9 mV/m, and in a very general sense, were associated with perturbations in the plasma density. The electric field waveforms showed evidence for steepening and/or convergence effects and presumably had mapped upwards along the magnetic field from the sporadic-E region below. Candidate mechanisms to explain the origin of these structures include the Kelvin-Helmholtz instability and the Es-layer instability. In both cases, the same shear that formed the sporadic-E layer would provide the energy to generate the km-scale structures. Other possibilities include gravity waves or a combination of these processes. The data suggest that these structures were associated with the lower altitude density striations that were the seat of the QP radar echoes observed simultaneously. They also appear to have been associated with the mechanism responsible for a well-defined pattern of "whorls" in the neutral wind data that were revealed in a chemical trail released by a second sounding rocket launched 15min later. Short scale (<100 m) electric field irregularities were also observed and were strongest in the sporadic-E region below 110km. The irregularities were organized into 2 3 layers on the upleg, where the plasma density also displayed multiple layers, yet were confined to a single layer on the downleg where the plasma density showed a single, well-defined sporadic-E peak. The linear gradient drift instability involving the DC electric field and the vertical plasma gradient is shown to be incapable of driving the observed waves on the upleg, but may have contributed to the growth of short scale waves on the topside of the narrow unstable density gradient observed on the downleg. The data suggest that other sources of free energy may have been important factors for the growth of the short scale irregularities. Keywords. Ionosphere (Mid-latitude ionosphere; Electric fields and currents; Ionospheric irregularities)

Pfaff, R.; Freudenreich, H.; Yokoyama, T.; Yamamoto, M.; Fukao, S.; Mori, H.; Ohtsuki, S.; Iwagami, N.

2005-10-01

349

Sound transmission through finite lightweight multilayered structures with thin air layers.  

PubMed

The sound transmission loss (STL) of finite lightweight multilayered structures with thin air layers is studied in this paper. Two types of models are used to describe the vibro-acoustic behavior of these structures. Standard transfer matrix method assumes infinite layers and represents the plane wave propagation in the layers. A wave based model describes the direct sound transmission through a rectangular structure placed between two reverberant rooms. Full vibro-acoustic coupling between rooms, plates, and air cavities is taken into account. Comparison with double glazing measurements shows that this effect of vibro-acoustic coupling is important in lightweight double walls. For infinite structures, structural damping has no significant influence on STL below the coincidence frequency. In this frequency region, the non-resonant transmission or so-called mass-law behavior dominates sound transmission. Modal simulations suggest a large influence of structural damping on STL. This is confirmed by experiments with double fiberboard partitions and sandwich structures. The results show that for thin air layers, the damping induced by friction and viscous effects at the air gap surfaces can largely influence and improve the sound transmission characteristics. PMID:21218884

Dijckmans, A; Vermeir, G; Lauriks, W

2010-12-01

350

An effective structure prediction method for layered materials based on 2D particle swarm optimization algorithm  

NASA Astrophysics Data System (ADS)

A structure prediction method for layered materials based on two-dimensional (2D) particle swarm optimization algorithm is developed. The relaxation of atoms in the perpendicular direction within a given range is allowed. Additional techniques including structural similarity determination, symmetry constraint enforcement, and discretization of structure constructions based on space gridding are implemented and demonstrated to significantly improve the global structural search efficiency. Our method is successful in predicting the structures of known 2D materials, including single layer and multi-layer graphene, 2D boron nitride (BN) compounds, and some quasi-2D group 6 metals(VIB) chalcogenides. Furthermore, by use of this method, we predict a new family of mono-layered boron nitride structures with different chemical compositions. The first-principles electronic structure calculations reveal that the band gap of these N-rich BN systems can be tuned from 5.40 eV to 2.20 eV by adjusting the composition.

Wang, Yanchao; Miao, Maosheng; Lv, Jian; Zhu, Li; Yin, Ketao; Liu, Hanyu; Ma, Yanming

2012-12-01

351

Growth and properties III–V films and multilayered structures on fianite substrates and buffer layers  

Microsoft Academic Search

The opportunity of the use Si and GaAs with single and double buffer layers and YSZ substrates for III-V(GaAs, InAs, GaSb, InGaAs, AlGaAs, GaN, AlN) epitaxy by a MOCVD method is investigated. The technology of single YSZ and double (YSZ on porous material) buffer layers preparation on Si and GaAs substrates is developed. By using porous substrate, we improved structure

Yu. N. Buzynin; A. N. Buzynin; V. V. Osiko; M. N. Drozdov; E. E. Lomonova; O. I. Khrykin; B. N. Zvonkov

2010-01-01

352

Effect of seed layers on the structure of Co/ Cu(1 0 0) metallic multilayers  

NASA Astrophysics Data System (ADS)

The influence of Ti and Co seed layers on the structural and magnetic properties of Co/Cu multilayers was studied. The X-ray diffraction results proved that by using Ti and Co seed layers, the crystal orientation of Co/Cu multilayers was drastically changed to FCC (1 0 0) plane. The maximum giant magnetoresistance ratios of FCC (1 0 0) oriented Co/Cu multilayers were enhanced.

Chihaya, Hiroaki; Kamiko, Masao; Oh, Sang-Mun; Yamamoto, Ryoichi

2004-05-01

353

Failure Modes in Ceramic-Based Layer Structures: A Basis for Materials Design of Dental Crowns  

Microsoft Academic Search

A research program on failure modes induced by spherical in- denters in brittle layer structures bonded to polymeric sub- strates, in simulation of occlusal function in all-ceramic dental crowns, is surveyed. Tests are made on model flat and curved layers bonded onto a dentin-like polymer base, in bilayer (ce- ramic\\/polymer) and trilayer (ceramic\\/ceramic\\/polymer) config- urations. All-transparent systems using glass as

Brian Lawnw; Sanjit Bhowmick; Mark B. Bush; Tarek Qasim; E. Dianne Rekow; Yu Zhang

2007-01-01

354

An analysis of the structure of thunderstorm in the atmospheric boundary layer  

Microsoft Academic Search

The structure of thunderstorm in the atmospheric boundary layer in Beijing area is analysed by using three-year data of tower.\\u000a It is indicated that the outflow current of the thunderstorm in the lower layer is a sort of density current. An area of evident\\u000a wind direction shear is found at about half an hour to one hour before the arrival

Cuijuan Zhu; Xingsheng Li; Zhuojia Ye

1984-01-01

355

Retention of gold nanoparticles in the structure of quasinematic layers formed by DNA molecules  

Microsoft Academic Search

Gold nanoparticles are shown to get incorporated into double-stranded DNA molecules forming quasinematic layers in the cholesteric\\u000a liquid-crystalline dispersion particles. The process of nanoparticle incorporation results in distortion in an ordered arrangement\\u000a of the neighboring dsDNA molecules in a layer and in global spatial structure of particles of the dispersion, which may be\\u000a one of the possible causes of the

S. G. Skuridin; V. A. Dubinskaya; E. V. Shtykova; V. V. Volkov; V. M. Rudoy; O. V. Dement’eva; V. A. Kuzmin; E. S. Lisitsyna; S. T. Zakhidov; I. A. Zelenina; Yu. M. Yevdokimov

2011-01-01

356

Structure of Protein Layers in Polyelectrolyte Matrices Studied by Neutron Reflectivity  

SciTech Connect

Polyelectrolyte multilayer films obtained by localized incorporation of Green Fluorescent Protein (GFP) within electrostatically assembled matrices of poly(styrene sulfonate)/poly(allylamine hydrochloride) (PSS/PAH) via spin-assisted layer-by-layer growth were discovered to be highly structured, with closely packed monomolecular layers of the protein within the bio-hybrid films. The structure of the films was evaluated in both vertical and lateral directions with neutron reflectometry, using deuterated GFP as a marker for neutron scattering contrast. Importantly, the GFP preserves its structural stability upon assembly as confirmed by circular dichroism (CD) and in situ attenuated total reflection Fourier Transform Infrared spectroscopy (ATR-FTIR). Atomic force microscopy was complimented with X-ray reflectometry to characterize the external roughness of the biohybrid films. Remarkably, films assembled with a single GFP layer confined at various distances from the substrate exhibit a strong localization of the GFP layer without intermixing into the LbL matrix. However, partial intermixing of the GFP layers with polymeric material is evidenced in multiple-GFP layer films with alternating protein-rich and protein-deficient regions. We hypothesize that the polymer-protein exchange observed in the multiple-GFP layer films suggests the existence of a critical protein concentration which can be accommodated by the multilayer matrix. Our results yield new insights into the mechanism of GFP interaction with a polyelectrolyte matrix and open opportunities for fabrication of bio-hybrid films with well-organized structure and controllable function, a crucial requirement for advanced sensing applications.

Kozlovskaya, Veronika [University of Alabama, Birmingham; Ankner, John Francis [ORNL; O'Neill, Hugh Michael [ORNL; Zhang, Qiu [ORNL; Kharlampieva, Eugenia [University of Alabama, Birmingham

2011-01-01

357

Structure and Origin of the Columbia Hills, Gusev Crater, Mars  

NASA Astrophysics Data System (ADS)

The Mars Exploration Rover Spirit has yielded profound insights into features at millimeter to decimeter scales. However, the origin of the Columbia Hills has remained enigmatic given the traverse across one peak [1]. We present a geologic history of the Hills consistent with their morphology, bedding attitudes, and stratigraphy. The Columbia Hills form a triangle 4.2 by 2.3 km, are bounded by linear to slightly concave margins, lie near the center of Gusev Crater, and have peaks rising to 90 m. Bedding dips away from a NNE-SSW axis cutting the Tennessee Valley. Husband Hill dips (15-32°) are steeper than local topography ( 8-10°) and those on West Spur are conformable with greater scatter in strike and shallower dips (7-15°). Husband Hill is cored by volcaniclastic rocks and impact breccias altered to various extents (Wishstone, Watchtower and Descartes classes), ringed by ultramafic volcaniclastic rocks and sulfate-cemented sands (Algonquin and Peace classes), ringed by localized impact breccias and volcaniclastic deposits (West Spur and Home Plate) [2]. The Columbia Hills likely formed by (1) Uplift of the Gusev Crater central peak, raising the Hills to 3 km above the crater floor, assuming the Hills are deeply-rooted and subsequently buried. Uplift by overlapping crater rims is inconsistent with bedding attitudes, but may have modified the margins of the Hills. (2) Draping by impact and volcaniclastic rocks and sands with localized alteration and cementation. Fragile rocks (Peace) and in situ soils (Paso Robles) would not have survived Gusev Crater formation. (3) Mass wasting of the Tennessee Valley removed tens of meters from the peak of the Hills, exposing older units in the core, (4) Plains (Adirondack) basalts surrounded and embayed the Hills, and (5) Small impacts redistributed rocks. [1] Rice J.W. (2004) Fall AGU, #P23B-03. [2] Squyres S.W. et al. (2006) JGR 111, E02S11.

McCoy, Timothy; Sims, M.; Crumpler, L. S.; Cohen, B. A.; Blaney, D. L.; Schmidt, M. E.; Treguier, E.; d'Uston, C.; Rice, J. W.; Tornabene, L. L.; Squyres, S. W.; Arvidson, R. E.; Haldemann, A.

2007-10-01

358

Turbulent Structures and Coherence in the Atmospheric Surface Layer  

NASA Astrophysics Data System (ADS)

Organized structures in turbulent flow fields are a well-known and still fascinating phenomenon. Although these so-called coherent structures are obvious from visual inspection, quantitative assessment is a challenge and many aspects e.g., formation mechanisms and contribution to turbulent fluxes, are discussed controversially. During the "High Definition Clouds and Precipitation for Advancing Climate Prediction" Observational Prototype Experiment (HOPE) from April to May 2013, an advanced dual Doppler lidar technique was used to image the horizontal wind field near the surface for approximately 300 h. A visual inspection method, as well as a two-dimensional integral length scale analysis, were performed to characterize the observations qualitatively and quantitatively. During situations with forcing due to shear, the wind fields showed characteristic patterns in the form of clearly bordered, elongated areas of enhanced or reduced wind speed, which can be associated with near-surface streaks. During calm situations with strong buoyancy forcing, open cell patterns in the horizontal divergence field were observed. The measurement technique used enables the calculation of integral length scales of both horizontal wind components in the streamwise and cross-stream directions. The individual length scales varied considerably during the observation period but were on average shorter during situations with compared to strongly stable situations. During unstable situations, which were dominated by wind fields with structures, the streamwise length scales increased with increasing wind speed, whereas the cross-stream length scales decreased. Consequently, the anisotropy increased from 1 for calm situations to values of 2-3 for wind speeds of 8-10. During neutral to stable situations, the eddies were on average quite isotropic in the horizontal plane.

Träumner, K.; Damian, Th.; Stawiarski, Ch.; Wieser, A.

2015-01-01

359

Electronic band structure imaging of three layer twisted graphene on single crystal Cu(111)  

SciTech Connect

Few layer graphene (FLG) is grown on single crystal Cu(111) by Chemical Vapor Deposition, and the electronic valence band structure is imaged by Angle-Resolved Photo-Emission Spectroscopy. It is found that graphene essentially grows polycrystalline. Three nearly ideal Dirac cones are observed along the Cu ?{sup ¯}K{sup ¯} direction in k-space, attributed to the presence of ?4° twisted three layer graphene with negligible interlayer coupling. The number of layers and the stacking order are compatible with Raman data analysis demonstrating the complementarity of the two techniques for a more accurate characterization of FLG.

Marquez Velasco, J. [National Center for Scientific Research “Demokritos,” 15310 Athens (Greece) [National Center for Scientific Research “Demokritos,” 15310 Athens (Greece); Department of Physics, National Technical University of Athens, Athens (Greece); Kelaidis, N.; Xenogiannopoulou, E.; Tsoutsou, D.; Tsipas, P.; Speliotis, Th.; Pilatos, G.; Likodimos, V.; Falaras, P.; Dimoulas, A., E-mail: dimoulas@ims.demokritos.gr [National Center for Scientific Research “Demokritos,” 15310 Athens (Greece); Raptis, Y. S. [Department of Physics, National Technical University of Athens, Athens (Greece)] [Department of Physics, National Technical University of Athens, Athens (Greece)

2013-11-18

360

Effects of Earth's layered structure, gravity and curvature on coseismic deformation  

NASA Astrophysics Data System (ADS)

The effects of Earth's layered structure, gravity and curvature on coseismic deformation are systematically quantified for all fundamental point sources and some finite-fault sources, respectively. The point-source simulations show that the layering effect (about ?25 per cent) is significantly higher than the gravity effect (about ?11 per cent) and the curvature effect (about ?5 per cent). A case study on the 2011 Mw 9.0 Tohoku earthquake is made to quantify the uncertainties of the dislocation models of large earthquakes, in which the three different effects are neglected. Finally, it is investigated how geodetic finite-fault slip inversions are affected by neglecting the layering effect.

Dong, Jie; Sun, Wenke; Zhou, Xin; Wang, Rongjiang

2014-12-01

361

Structural origins of intrinsic stress in amorphous silicon thin films  

NASA Astrophysics Data System (ADS)

Hydrogenated amorphous silicon (a-Si:H) refers to a broad class of atomic configurations, sharing a lack of long-range order, but varying significantly in material properties, including optical constants, porosity, hydrogen content, and intrinsic stress. It has long been known that deposition conditions affect microstructure, but much work remains to uncover the correlation between these parameters and their influence on electrical, mechanical, and optical properties critical for high-performance a-Si:H photovoltaic devices. We synthesize and augment several previous models of deposition phenomena and ion bombardment, developing a refined model correlating plasma-enhanced chemical vapor deposition conditions (pressure and discharge power and frequency) to the development of intrinsic stress in thin films. As predicted by the model presented herein, we observe that film compressive stress varies nearly linearly with bombarding ion momentum and with a (-1/4) power dependence on deposition pressure, that tensile stress is proportional to a reduction in film porosity, and the net film intrinsic stress results from a balance between these two forces. We observe the hydrogen-bonding configuration to evolve with increasing ion momentum, shifting from a void-dominated configuration to a silicon-monohydride configuration. Through this enhanced understanding of the structure-property-process relation of a-Si:H films, improved tunability of optical, mechanical, structural, and electronic properties should be achievable.

Johlin, Eric; Tabet, Nouar; Castro-Galnares, Sebastián; Abdallah, Amir; Bertoni, Mariana I.; Asafa, Tesleem; Grossman, Jeffrey C.; Said, Syed; Buonassisi, Tonio

2012-02-01

362

The origin of oil in the Cretaceous succession from the South Pars Oil Layer of the Persian Gulf  

NASA Astrophysics Data System (ADS)

The origin of the oil in Barremian-Hauterivian and Albian age source rock samples from two oil wells (SPO-2 and SPO-3) in the South Pars oil field has been investigated by analyzing the quantity of total organic carbon (TOC) and thermal maturity of organic matter (OM). The source rocks were found in the interval 1,000-1,044 m for the Kazhdumi Formation (Albian) and 1,157-1,230 m for the Gadvan Formation (Barremian-Hauterivian). Elemental analysis was carried out on 36 samples from the source rock candidates (Gadvan and Kazhdumi formations) of the Cretaceous succession of the South Pars Oil Layer (SPOL). This analysis indicated that the OM of the Barremian-Hauterivian and Albian samples in the SPOL was composed of kerogen Types II and II-III, respectively. The average TOC of analyzed samples is less than 1 wt%, suggesting that the Cretaceous source rocks are poor hydrocarbon (HC) producers. Thermal maturity and Ro values revealed that more than 90 % of oil samples are immature. The source of the analyzed samples taken from Gadvan and Kazhdumi formations most likely contained a content high in mixed plant and marine algal OM deposited under oxic to suboxic bottom water conditions. The Pristane/nC17 versus Phytane/nC18 diagram showed Type II-III kerogen of mixture environments for source rock samples from the SPOL. Burial history modeling indicates that at the end of the Cretaceous time, pre-Permian sediments remained immature in the Qatar Arch. Therefore, lateral migration of HC from the nearby Cretaceous source rock kitchens toward the north and south of the Qatar Arch is the most probable origin for the significant oils in the SPOL.

Rahmani, Omeid; Aali, Jafar; Junin, Radzuan; Mohseni, Hassan; Padmanabhan, Eswaran; Azdarpour, Amin; Zarza, Sahar; Moayyed, Mohsen; Ghazanfari, Parviz

2013-07-01

363

Instantaneous Wavenumber Estimation for Damage Quantification in Layered Plate Structures  

NASA Technical Reports Server (NTRS)

This paper illustrates the application of instantaneous and local wavenumber damage quantification techniques for high frequency guided wave interrogation. The proposed methodologies can be considered as first steps towards a hybrid structural health monitoring/ nondestructive evaluation (SHM/NDE) approach for damage assessment in composites. The challenges and opportunities related to the considered type of interrogation and signal processing are explored through the analysis of numerical data obtained via EFIT simulations of damage in CRFP plates. Realistic damage configurations are modeled from x-ray CT scan data of plates subjected to actual impacts, in order to accurately predict wave-damage interactions in terms of scattering and mode conversions. Simulation data is utilized to enhance the information provided by instantaneous and local wavenumbers and mitigate the complexity related to the multi-modal content of the plate response. Signal processing strategies considered for this purpose include modal decoupling through filtering in the frequency/wavenumber domain, the combination of displacement components, and the exploitation of polarization information for the various modes as evaluated through the dispersion analysis of the considered laminate lay-up sequence. The results presented assess the effectiveness of the proposed wavefield processing techniques as a hybrid SHM/NDE technique for damage detection and quantification in composite, plate-like structures.

Mesnil, Olivier; Leckey, Cara A. C.; Ruzzene, Massimo

2014-01-01

364

Semiconductor structures having electrically insulating and conducting portions formed from an AlSb-alloy layer  

DOEpatents

A semiconductor structure. The semiconductor structure comprises a plurality of semiconductor layers formed on a substrate including at least one layer of a III-V compound semiconductor alloy comprising aluminum (Al) and antimony (Sb), with at least a part of the AlSb-alloy layer being chemically converted by an oxidation process to form superposed electrically insulating and electrically conducting portions. The electrically insulating portion formed from the AlSb-alloy layer comprises an oxide of aluminum (e.g. Al.sub.2 O.sub.3), while the electrically conducting portion comprises Sb. A lateral oxidation process allows formation of the superposed insulating and conducting portions below monocrystalline semiconductor layers for forming many different types of semiconductor structures having particular utility for optoelectronic devices such as light-emitting diodes, edge-emitting lasers, vertical-cavity surface-emitting lasers, photodetectors and optical modulators (waveguide and surface normal), and for electronic devices such as heterojunction bipolar transistors, field-effect transistors and quantum-effect devices. The invention is expected to be particularly useful for forming light-emitting devices for use in the 1.3-1.6 .mu.m wavelength range, with the AlSb-alloy layer acting to define an active region of the device and to effectively channel an electrical current therein for efficient light generation.

Spahn, Olga B. (Albuquerque, NM); Lear, Kevin L. (Albuquerque, NM)

1998-01-01

365

Spatiotemporal structure of wind farm-atmospheric boundary layer interactions  

NASA Astrophysics Data System (ADS)

Wind power is currently one of the fastest growing energy sources in the world. Most of the growth is in the utility sector consisting of large wind farms with numerous industrial-scale wind turbines. Wind turbines act as a sink of mean kinetic energy and a source of turbulent kinetic energy in the atmospheric boundary layer (ABL). In doing so, they modify the ABL profiles and land-atmosphere exchanges of energy, momentum, mass and moisture. This project explores theses interactions using remote sensing data and numerical model simulations. The domain is central Texas where 4 of the world's largest wind farms are located. A companion study of seasonally-averaged Land Surface Temperature data from the Moderate Resolution Imaging Spectroradiometer (MODIS) on TERRA and AQUA satellites shows a warming signal at night and a mixed cooling/warming signal during the daytime within the wind farms. In the present study, wind farm-ABL interactions are simulated with the Weather Research and Forecasting (WRF) model. The simulations show that the model is capable of replicating the observed signal in land surface temperature. Moreover, similar warming/cooling effect, up to 1C, was observed in seasonal mean 2m air temperature as well. Further analysis show that enhanced turbulent mixing in the rotor wakes is responsible for the impacts on 2m and surface air temperatures. The mixing is due to 2 reasons: (i) turbulent momentum transport to compensate the momentum deficit in the wakes of the turbines and (ii) turbulence generated due to motion of turbine rotors. Turbulent mixing also alters vertical profiles of moisture. Changes in land-atmosphere temperature and moisture gradient and increase in turbulent mixing leads to more than 10% change in seasonal mean surface sensible and latent heat flux. Given the current installed capacity and the projected installation across the world, wind farms are likely becoming a major driver of anthropogenic land use change on Earth. Hence, understanding WF-ABL interactions and its effects is of significant scientific and societal importance.

Cervarich, Matthew; Baidya Roy, Somnath; Zhou, Liming

2013-04-01

366

Electrical characteristics of silicon-rare-earth fluoride layered switching structures  

Microsoft Academic Search

Switching and memory effects in the electrical conductance of layered structures based on rare-earth fluorides are investigated.\\u000a These investigations reveal the existence of high-and low-resistance states in structures of metal-insulator-semiconductor\\u000a type. It is shown that the characteristics of the low-resistance state of such structures are described by a metal-tunneling\\u000a insulator-semiconductor model.

V. A. Rozhkov; M. B. Shalimova

1998-01-01

367

Structural origin of circularly polarized iridescence in jeweled beetles  

NASA Astrophysics Data System (ADS)

The iridescent metallic green beetle, Chrysina gloriosa, selectively reflects left circularly polarized light. The exoskeleton is decorated by hexagonal cells (˜10 micron) that coexist with pentagons and heptagons. We find that the fraction of hexagons decreases with an increase in curvature. In bright field microscopy, each cell contains a bright yellow core, placed in a greenish cell with yellowish border, but the core disappears in the dark field. Using confocal microscopy, we observe that these cells consist of nearly concentric, nested arcs that lie on surface of a shallow cone. We infer that the patterns are structurally and optically analogous to the focal conic domains formed spontaneously on the free surface of a cholesteric liquid crystal. The microstructure provides the bases for the morphogenesis as well as key insights for emulating the intricate optical response the exoskeleton of scarab beetles.

Crne, Matija; Sharma, Vivek; Park, Jung O.; Srinivasarao, Mohan

2010-03-01

368

Structural Origin of Circularly Polarized Iridescence in Jeweled Beetles  

NASA Astrophysics Data System (ADS)

The iridescent metallic green beetle, Chrysina gloriosa, which selectively reflects left circularly polarized light, possesses an exoskeleton decorated by hexagonal cells (~10 ?m) that coexist with pentagons and heptagons. The fraction of hexagons decreases with an increase in curvature. In bright field microscopy, each cell contains a bright yellow core, placed in a greenish cell with yellowish border, but the core disappears in dark field. With use of confocal microscopy, we observe that these cells consist of nearly concentric nested arcs that lie on the surface of a shallow cone. We infer that the patterns are structurally and optically analogous to the focal conic domains formed spontaneously on the free surface of a cholesteric liquid crystal. These textures provide the basis for the morphogenesis as well as key insights for emulating the intricate optical response of the exoskeleton of scarab beetles.

Sharma, Vivek; Crne, Matija; Park, Jung Ok; Srinivasarao, Mohan

2009-07-01

369

Structural origin of circularly polarized iridescence in jeweled beetles.  

PubMed

The iridescent metallic green beetle, Chrysina gloriosa, which selectively reflects left circularly polarized light, possesses an exoskeleton decorated by hexagonal cells (approximately 10 microm) that coexist with pentagons and heptagons. The fraction of hexagons decreases with an increase in curvature. In bright field microscopy, each cell contains a bright yellow core, placed in a greenish cell with yellowish border, but the core disappears in dark field. With use of confocal microscopy, we observe that these cells consist of nearly concentric nested arcs that lie on the surface of a shallow cone. We infer that the patterns are structurally and optically analogous to the focal conic domains formed spontaneously on the free surface of a cholesteric liquid crystal. These textures provide the basis for the morphogenesis as well as key insights for emulating the intricate optical response of the exoskeleton of scarab beetles. PMID:19628862

Sharma, Vivek; Crne, Matija; Park, Jung Ok; Srinivasarao, Mohan

2009-07-24

370

Structure and origin of the subtropical South Indian Ocean Countercurrent  

NASA Astrophysics Data System (ADS)

The structure of the subtropical South Indian Ocean Countercurrent (SICC) is revealed by altimeter-derived absolute geostrophic surface velocities. It is a narrow, eastward-flowing current between 22° and 26°S confined to planetary wave trains which propagate westward through the Indian Ocean. Multi-year averaging identifies it as a well-defined current between Madagascar and 80°E, continuing with lower intensity between 90° and 100°E. It virtually coincides with the northern limit of Subtropical Underwater subduction. Geostrophic currents from hydrographic sections closely correspond to these surface patterns. Volume transports of the countercurrent down to 800 dbar are of order (107 m3 s-1). Evidence is provided for a narrow branch of the South Equatorial Current (SEC) approaching Madagascar near 18°S and feeding the southern East Madagascar Current (EMC) which appears to continue westward around the southern tip of Madagascar. It then partially retroflects and nourishes the SICC.

Siedler, Gerold; Rouault, Mathieu; Lutjeharms, Johann R. E.

2006-12-01

371

Mirror instability and the origin of morningside auroral structure  

SciTech Connect

Auroral optical imagery shows marked differences between auroral features of the evening and morning sectors: The separation between diffuse and discrete auroras in the evening sector is not distinct in the morning sector, which is dominated by auroral patches and multiple banded structures aligned along some direction. Plasma distribution function signatures also show marked differences: downward electron beams and inverted-V signatures prefer the evening sector, while the electron spectra on the morning sector are similar to the diffuse aurora. We have constructed a theory of morningside auroras consistent with these features. The theory is based on modulation of the growth rates of electron cyclotron waves by the mirror instability, which is in turn driven by inward-convected ions that have become anisotropic. This modulation produces alternating bands of enhanced and reduced electron precipitation which approximate the observed multiple auroral bands and patches of the morning sector.

Chiu, Y.T.; Schulz, M.; Fennell, J.F.; Kishi, A.M.

1983-05-01

372

ORIGINAL PAPER Influence of the Metal Oxide Substrate Structure on Vanadium  

E-print Network

ORIGINAL PAPER Influence of the Metal Oxide Substrate Structure on Vanadium Oxide Monomer Formation 2013 � Springer Science+Business Media New York 2013 Abstract Vanadium oxide (VOx) molecular species nature of surface VOx species. Keywords Vanadium oxide Á Strontium titanate Á XPS Á Surface structure 1

Marks, Laurence D.

373

ORIGINS OF GENETIC VARIATION AND POPULATION STRUCTURE OF FOXSNAKES ACROSS SPATIAL AND TEMPORAL SCALES  

E-print Network

ORIGINS OF GENETIC VARIATION AND POPULATION STRUCTURE OF FOXSNAKES ACROSS SPATIAL AND TEMPORAL the population structure and genetic variation of foxsnakes (Pantherophis gloydi). First, I determine the likely suitability modeling with population genetics (589 individuals, 12 microsatellite loci) to infer how foxsnakes

Blouin-Demers, Gabriel

374

Amino acids equivalences within protein structures The original publication is available at www.springerlink.com  

E-print Network

Amino acids equivalences within protein structures 1 The original publication is available at www.springerlink.com A reduced amino acid alphabet for understanding and designing protein adaptation to mutation. C. Etchebest 1, 75251 Paris, France Short title: Amino acids equivalences within protein structures * Corresponding

Paris-Sud XI, Université de

375

Origin and structure of the brood chamber in Bugula neritina (Bryozoa)  

Microsoft Academic Search

The literature on bryozoan reproduction contains varying accounts of the origin and structure of the “hyperstomial” type of brood chamber (ooecium). Because of the widespread occurrence of hyperstomial ooecia in eurystome bryozoans and the discrepancies in previous descriptions of ooecial structure, a reexamination of this problem was initiated. Results of a light microscopic study of Bugula neritina indicate that the

R. M. Woollacott; R. L. Zimmer

1972-01-01

376

Analysis of mixed-layer clay mineral structures  

USGS Publications Warehouse

Among the enormously abundant natural occurrences of clay minerals, many examples are encountered in which no single specific crystallization scheme extends through a single ultimate grain. The characterization of such assemblages becomes an analysis of the distribution of matter within such grains, rather than the simple identification of mineral species. It having become established that the particular coordination complex typified by mica is a common component of many natural subcrystalline assemblages, the opportunity is afforded to analyze scattering from random associations of these complexes with other structural units. Successful analyses have been made of mixed hydration states of montmorillonite, of montmorillonite with mica, of vermiculite with mica, and of montmorillonite with chlorite, all of which are variants of the mica complex, and of halloysite with hydrated halloysite.

Bradley, W.F.

1953-01-01

377

Development of a low activation concrete shielding wall by multi-layered structure for a fusion reactor  

Microsoft Academic Search

A multi-layered concrete structure has been developed to reduce induced activity in the shielding for neutron generating facilities such as a fusion reactor. The multi-layered concrete structure is composed of: (1) an inner low activation concrete, (2) a boron-doped low activation concrete as the second layer, and (3) ordinary concrete as the outer layer of the neutron shield. With the

Satoshi Sato; Toshio Maegawa; Kenji Yoshimatsu; Koichi Sato; Akira Nonaka; Kosuke Takakura; Kentaro Ochiai; Chikara Konno

2011-01-01

378

Fabrication and atomic structure of size-selected, layered MoS2 clusters for catalysis  

NASA Astrophysics Data System (ADS)

Well defined MoS2 nanoparticles having a layered structure and abundant edges would be of considerable interest for applications including photocatalysis. We report the atomic structure of MoS2 size-selected clusters with mass in a range all the way from 50 to ~2000 MoS2 units. The clusters were prepared by magnetron sputtering and gas condensation prior to size selection and soft landing on carbon supports. Aberration-corrected scanning transmission electron microscopy (STEM) in high-angle annular dark-field (HAADF) mode reveals a layered structure and Mo-Mo spacing similar to the bulk material. The mean number of layers in these lamellar clusters increases from one to three with increasing mass, consistent with density functional theory calculations of the balance between edge energies and interlayer binding.

Cuddy, Martin J.; Arkill, Kenton P.; Wang, Zhi Wei; Komsa, Hannu-Pekka; Krasheninnikov, Arkady V.; Palmer, Richard E.

2014-10-01

379

Structural and electronic properties of the transition layer at the SiO2/4H-SiC interface  

NASA Astrophysics Data System (ADS)

Using first-principles methods, we generate an amorphous SiO2/4H-SiC interface with a transition layer. Based this interface model, we investigate the structural and electronic properties of the interfacial transition layer. The calculated Si 2p core-level shifts for this interface are comparable to the experimental data, indicating that various SiCxOy species should be present in this interface transition layer. The analysis of the electronic structures reveals that the tetrahedral SiCxOy structures cannot introduce any of the defect states at the interface. Interestingly, our transition layer also includes a C-C=C trimer and SiO5 configurations, which lead to the generation of interface states. The accurate positions of Kohn-Sham energy levels associated with these defects are further calculated within the hybrid functional scheme. The Kohn-Sham energy levels of the carbon trimer and SiO5 configurations are located near the conduction and valence band of bulk 4H-SiC, respectively. The result indicates that the carbon trimer occurred in the transition layer may be a possible origin of near interface traps. These findings provide novel insight into the structural and electronic properties of the realistic SiO2/SiC interface.

Li, Wenbo; Zhao, Jijun; Wang, Dejun

2015-01-01

380

Structural design of a double-layered porous hydrogel for effective mass transport.  

PubMed

Mass transport in porous materials is universal in nature, and its worth attracts great attention in many engineering applications. Plant leaves, which work as natural hydraulic pumps for water uptake, have evolved to have the morphological structure for fast water transport to compensate large water loss by leaf transpiration. In this study, we tried to deduce the advantageous structural features of plant leaves for practical applications. Inspired by the tissue organization of the hydraulic pathways in plant leaves, analogous double-layered porous models were fabricated using agarose hydrogel. Solute transport through the hydrogel models with different thickness ratios of the two layers was experimentally observed. In addition, numerical simulation and theoretical analysis were carried out with varying porosity and thickness ratio to investigate the effect of structural factors on mass transport ability. A simple parametric study was also conducted to examine unveiled relations between structural factors. As a result, the porosity and thickness ratio of the two layers are found to govern the mass transport ability in double-layered porous materials. The hydrogel models with widely dispersed pores at a fixed porosity, i.e., close to a homogeneously porous structure, are mostly turned out to exhibit fast mass transport. The present results would provide a new framework for fundamental design of various porous structures for effective mass transport. PMID:25825619

Kim, Hyejeong; Kim, Hyeon Jeong; Huh, Hyung Kyu; Hwang, Hyung Ju; Lee, Sang Joon

2015-03-01

381

Towards a unified model of passive drug permeation I: origins of the unstirred water layer with applications to ionic permeation.  

PubMed

In this work, we provide a unified theoretical framework describing how drug molecules can permeate across membranes in neutral and ionized forms for unstirred in vitro systems. The analysis provides a self-consistent basis for the origin of the unstirred water layer (UWL) within the Nernst-Planck framework in the fully unstirred limit and further provides an accounting mechanism based simply on the bulk aqueous solvent diffusion constant of the drug molecule. Our framework makes no new assumptions about the underlying physics of molecular permeation. We hold simply that Nernst-Planck is a reasonable approximation at low concentrations and all physical systems must conserve mass. The applicability of the derived framework has been examined both with respect to the effect of stirring and externally applied voltages to measured permeability. The analysis contains data for 9 compounds extracted from the literature representing a range of permeabilities and aqueous diffusion coefficients. Applicability with respect to ionized permeation is examined using literature data for the permanently charged cation, crystal violet, providing a basis for the underlying mechanism for ionized drug permeation for this molecule as being due to mobile counter-current flow. PMID:24211511

Ghosh, Avijit; Scott, Dennis O; Maurer, Tristan S

2014-02-14

382

SbsB structure and lattice reconstruction unveil Ca2+ triggered S-layer assembly.  

PubMed

S-layers are regular two-dimensional semipermeable protein layers that constitute a major cell-wall component in archaea and many bacteria. The nanoscale repeat structure of the S-layer lattices and their self-assembly from S-layer proteins (SLPs) have sparked interest in their use as patterning and display scaffolds for a range of nano-biotechnological applications. Despite their biological abundance and the technological interest in them, structural information about SLPs is limited to truncated and assembly-negative proteins. Here we report the X-ray structure of the SbsB SLP of Geobacillus stearothermophilus PV72/p2 by the use of nanobody-aided crystallization. SbsB consists of a seven-domain protein, formed by an amino-terminal cell-wall attachment domain and six consecutive immunoglobulin-like domains, that organize into a ?-shaped disk-like monomeric crystallization unit stabilized by interdomain Ca(2+) ion coordination. A Ca(2+)-dependent switch to the condensed SbsB quaternary structure pre-positions intermolecular contact zones and renders the protein competent for S-layer assembly. On the basis of crystal packing, chemical crosslinking data and cryo-electron microscopy projections, we present a model for the molecular organization of this SLP into a porous protein sheet inside the S-layer. The SbsB lattice represents a previously undescribed structural model for protein assemblies and may advance our understanding of SLP physiology and self-assembly, as well as the rational design of engineered higher-order structures for biotechnology. PMID:22722836

Baranova, Ekaterina; Fronzes, Rémi; Garcia-Pino, Abel; Van Gerven, Nani; Papapostolou, David; Péhau-Arnaudet, Gérard; Pardon, Els; Steyaert, Jan; Howorka, Stefan; Remaut, Han

2012-07-01

383

Structural layers of ex vivo rat hippocampus at 7T MRI.  

PubMed

Magnetic resonance imaging (MRI) applied to the hippocampus is challenging in studies of the neurophysiology of memory and the physiopathology of numerous diseases such as epilepsy, Alzheimer's disease, ischemia, and depression. The hippocampus is a well-delineated cerebral structure with a multi-layered organization. Imaging of hippocampus layers is limited to a few studies and requires high magnetic field and gradient strength. We performed one conventional MRI sequence on a 7T MRI in order to visualize and to delineate the multi-layered hippocampal structure ex vivo in rat brains. We optimized a volumic three-dimensional T2 Rapid Acquisition Relaxation Enhancement (RARE) sequence and quantified the volume of the hippocampus and one of its thinnest layers, the stratum granulare of the dentate gyrus. Additionally, we tested passive staining by gadolinium with the aim of decreasing the acquisition time and increasing image contrast. Using appropriated settings, six discrete layers were differentiated within the hippocampus in rats. In the hippocampus proper or Ammon's Horn (AH): the stratum oriens, the stratum pyramidale of, the stratum radiatum, and the stratum lacunosum moleculare of the CA1 were differentiated. In the dentate gyrus: the stratum moleculare and the stratum granulare layer were seen distinctly. Passive staining of one brain with gadolinium decreased the acquisition time by four and improved the differentiation between the layers. A conventional sequence optimized on a 7T MRI with a standard receiver surface coil will allow us to study structural layers (signal and volume) of hippocampus in various rat models of neuropathology (anxiety, epilepsia, neurodegeneration). PMID:24086700

Kamsu, Jeanine Manuella; Constans, Jean-Marc; Lamberton, Franck; Courtheoux, Patrick; Denise, Pierre; Philoxene, Bruno; Coquemont, Maelle; Besnard, Stephane

2013-01-01

384

A two-layer structure prediction framework for microscopy cell detection.  

PubMed

The task of microscopy cell detection is of great biological and clinical importance. However, existing algorithms for microscopy cell detection usually ignore the large variations of cells and only focus on the shape feature/descriptor design. Here we propose a new two-layer model for cell centre detection by a two-layer structure prediction framework, which is respectively built on classification for the cell centres implicitly using rich appearances and contextual information and explicit structural information for the cells. Experimental results demonstrate the efficiency and effectiveness of the proposed method over competing state-of-the-art methods, providing a viable alternative for microscopy cell detection. PMID:25082065

Xu, Yan; Wu, Weiying; Chang, Eric I-Chao; Chen, Danny; Mu, Jian; Lee, Peter P; Blenman, Kim R M; Tu, Zhuowen

2015-04-01

385

Performance optimization of plate-mode sensors with bi-layered structure.  

PubMed

The acoustic characteristics of plate-mode sensors with bi-layered structures composed of a piezoelectric film and a non-piezoelectric substrate are studied by numerical calculations using the transfer matrix method. Performances of the sensors can be evaluated based on the theoretical calculations of the dispersion curves, electromechanical coupling coefficients and sensitivities of the plate-mode sensors with a bi-layered structure. In order to obtain the optimized operating conditions of the sensors, the operating mode, frequency and the ratios of thickness of piezoelectric film to that of the substrate are evaluated when the sensors are applied in gas and/or liquid conditions. PMID:16793105

Fan, Li; Zhang, Shu-yi; Cheng, Li-ping; Zhang, Hui

2006-12-22

386

The inviscid secondary instability of fully nonlinear longitudinal vortex structures in growing boundary layers  

NASA Technical Reports Server (NTRS)

The inviscid instability of a longitudinal vortex structure within a steady boundary layer is investigated. The instability has a wavelength comparable with the boundary layer thickness so that a quasi-parallel approach to the instability problem can be justified. The generalization of the Rayleigh equation to such a flow is obtained and solved for the case when the vortex structure is induced by curvature. Two distinct modes of instability are found; these modes correspond with experimental observations on the breakdown process for Goertler vortices.

Hall, Philip; Horseman, Nicola J.

1990-01-01

387

Finite element simulation of laser-induced guided wave in layered structure  

NASA Astrophysics Data System (ADS)

Ultrasonic field in layered structure excited by a nanosecond pulsed laser irradiation is numerically simulated by finite element method. Typical calculation is executed for a configuration of a zirconium nitride (ZrN) thin film with different thickness on a steel substrate. The waveforms of surface acoustic wave are presented and the dispersion properties of surface waves in two-layered structure are analyzed by the method of phase spectral analysis, and the results show that the surface wave is anomalous dispersive with the higher frequencies propagating fast than the lower frequencies, and that with the decrease of film thickness, the dispersion of surface wave becomes more serious.

Zhao, Yan; Xue, Liping

2014-11-01

388

Frequency separation of surface acoustic waves in layered structures with acoustic metamaterials  

NASA Astrophysics Data System (ADS)

We show theoretically that in elastic layered structures containing an upper layer of smoothly varied thickness and a substrate of a highly dispersive metametarial it is possible to significantly enhance spatial frequency separation of surface acoustic waves. Theory of Love surface acoustic waves propagation in waveguides with varied thickness, taking into account mutual modes coupling, is built. Appropriate structure of metamatererial with resonant frequency dependence of material parameters, making frequency separation effective, is provided. Efficiency of spatial frequency separation and modes coupling is calculated for various metamaterial parameters and wave frequencies.

Kalyabin, D.; Lisenkov, I.; Lee, Y. P.; Nikitov, S.

2014-06-01

389

Spatial properties of entangled photon pairs generated in nonlinear layered structures  

E-print Network

A spatial quantum model of spontaneous parametric down-conversion in nonlinear layered structures is developed expanding the interacting vectorial fields into monochromatic plane waves. A two-photon spectral amplitude depending on the signal- and idler-field frequencies and propagation directions is used to derive transverse profiles of the emitted fields as well as their spatial correlations. Intensity spatial profiles and their spatial correlations are mainly determined by the positions of transmission peaks formed in these structures with photonic bands. A method for geometry optimization of the structures with respect to efficiency of the nonlinear process is suggested. Several structures composed of GaN/AlN layers are analyzed as typical examples. They allow the generation of photon pairs correlated in several emission directions. Photon-pair generation rates increasing better than the second power of the number of layers can be reached. Also structures efficiently generated photon pairs showing anti-bunching and anti-coalescence can be obtained. Three reasons for splitting the correlated area in photonic-band-gap structures are revealed: zig-zag movement of photons inside the structure, spatial symmetry and polarization-dependent properties. Also spectral splitting can be observed in these structures.

Jan Perina Jr

2011-11-07

390

Pressure-induced phase transition of BiOF: novel two-dimensional layered structures.  

PubMed

Bismuth oxide haloids BiOXs (X = Cl, Br, I) have received attention as photocatalytic materials after TiO2 in recent years due to their unique layered structures. Using an ab initio evolutionary methodology structure search method, we systematically investigate the evolution of BiOF structures under pressure. It is found that BiOF can maintain its layered structure up to 300 GPa. Three stable new phases with Pnma, P3?m1 and Cmcm structure at a pressure of 10, 66, and 286 GPa have been identified for the first time. All the newly found phases are two-dimensional layered structures characterized by Bi-O slabs interleaved with F(-) anion slabs. Moreover, all three phases are indirect semiconductors with wide band gaps. It is found that pressure can cause great change in the band gaps of BiOF. The band gaps of the high-pressure phases of BiOF vary nearly linearly with pressure but exhibit different pressure trends. The electronic structure, structural stability, phase transition mechanisms and evolution of the Bi-O slabs of BiOF under pressure are discussed. PMID:25578959

Zhou, Dawei; Pu, Chunying; He, Chaozheng; Zhang, Feiwu; Lu, Cheng; Bao, Gang

2015-02-14

391

Strong, macroporous, and in situ-setting calcium phosphate cement-layered structures  

PubMed Central

Calcium phosphate cement (CPC) is highly promising for clinical uses due to its in situ-setting ability, excellent osteoconductivity and bone-replacement capability. However, the low strength limits its use to non-load-bearing applications. The objectives of this study were to develop a layered CPC structure by combining a macroporous CPC layer with a strong CPC layer, and to investigate the effects of porosity and layer thickness ratios. The rationale was for the macroporous layer to accept tissue ingrowth, while the fiber-reinforced strong layer would provide the needed early-strength. A biopolymer chitosan was incorporated to strengthen both layers. Flexural strength, S (mean±sd; n = 6) of CPC-scaffold decreased from (9.7±1.2) to (1.8±0.3) MPa (p<0.05), when the porosity increased from 44.6% to 66.2%. However, with a strong-layer reinforcement, S increased to (25.2±6.7) and (10.0±1.4) MPa, respectively, at these two porosities. These strengths matched/exceeded the reported strengths of sintered porous hydroxyapatite implants and cancellous bone. Relationships were established between S and the ratio of strong layer thickness/specimen thickness, a/h:S = (17.6 a/h+3.2) MPa. The scaffold contained macropores with a macropore length (mean±sd; n = 147) of (183±73) ?m, suitable for cell infiltration and tissue ingrowth. Nano-sized hydroxyapatite crystals were observed to form the scaffold matrix of CPC with chitosan. In summary, a layered CPC implant, combining a macroporous CPC with a strong CPC, was developed. Mechanical strength and macroporosity are conflicting requirements. However, the novel functionally graded CPC enabled a relatively high strength and macroporosity to be simultaneously achieved. Such an in situ-hardening nano-apatite may be useful in moderate stress-bearing applications, with macroporosity to enhance tissue ingrowth and implant resorption. PMID:17574665

Xu, Hockin H.K.; Burguera, Elena F.; Carey, Lisa E.

2009-01-01

392

The internal structure of Jupiter family cometary nuclei from Deep Impact observations: The “talps” or “layered pile” model  

NASA Astrophysics Data System (ADS)

We consider the hypothesis that the layering observed on the surface of Comet 9P/Tempel 1 from the Deep Impact spacecraft and identified on other comet nuclei imaged by spacecraft (i.e., 19P/Borrelly and 81P/Wild 2) is ubiquitous on Jupiter family cometary nuclei and is an essential element of their internal structure. The observational characteristics of the layers on 9P/Tempel 1 are detailed and considered in the context of current theories of the accumulation and dynamical evolution of cometary nuclei. The works of Donn [Donn, B.D., 1990. Astron. Astrophys. 235, 441 446], Sirono and Greenberg [Sirono, S.-I., Greenberg, J.M., 2000. Icarus 145, 230 238] and the experiments of Wurm et al. [Wurm, G., Paraskov, G., Krauss, O., 2005. Icarus 178, 253 263] on the collision physics of porous aggregate bodies are used as basis for a conceptual model of the formation of layers. Our hypothesis is found to have implications for the place of origin of the JFCs and their subsequent dynamical history. Models of fragmentation and rubble pile building in the Kuiper belt in a period of collisional activity (e.g., [Kenyon, S.J., Luu, J.X., 1998. Astron. J. 115, 2136 2160; 1999a. Astron. J. 118, 1101 1119; 1999b. Astrophys. J. 526, 465 470; Farinella, P., Davis, D.R., Stern, S.A., 2000. In: Mannings, V., Boss, A.P., Russell, S.S. (Eds.), Protostars and Planets IV. Univ. of Arizona Press, Tucson, pp. 1255 1282; Durda, D.D., Stern, S.J., 2000. Icarus 145, 220 229]) following the formation of Neptune appear to be in conflict with the observed properties of the layers and irreconcilable with the hypothesis. Long-term residence in the scattered disk [Duncan, M.J., Levison, H.F., 1997. Science 276, 1670 1672; Duncan, M., Levison, H., Dones, L., 2004. In: Festou, M., Keller, H.U., Weaver, H.A. (Eds.), Comets II. Univ. of Arizona Press, Tucson, pp. 193 204] and/or a change in fragmentation outcome modeling may explain the long-term persistence of primordial layers. In any event, the existence of layers places constraints on the environment seen by the population of objects from which the Jupiter family comets originated. If correct, our hypothesis implies that the nuclei of Jupiter family comets are primordial remnants of the early agglomeration phase and that the physical structure of their interiors, except for the possible effects of compositional phase changes, is largely as it was when they were formed. We propose a new model for the interiors of Jupiter family cometary nuclei, called the talps or “layered pile” model, in which the interior consists of a core overlain by a pile of randomly stacked layers. We discuss how several cometary characteristics—layers, surface texture, indications of flow, compositional inhomogeneity, low bulk density low strength, propensity to split, etc., might be explained in terms of this model. Finally, we make some observational predictions and suggest goals for future space observations of these objects.

Belton, Michael J. S.; Thomas, Peter; Veverka, J.; Schultz, Peter; A'Hearn, Michael F.; Feaga, Lori; Farnham, Tony; Groussin, Olivier; Li, Jian-Yang; Lisse, Casey; McFadden, Lucy; Sunshine, Jessica; Meech, Karen J.; Delamere, W. Alan; Kissel, Jochen

393

The internal structure of Jupiter family cometary nuclei from Deep Impact observations: The “talps” or “layered pile” model  

NASA Astrophysics Data System (ADS)

We consider the hypothesis that the layering observed on the surface of Comet 9P/Tempel 1 from the Deep Impact spacecraft and identified on other comet nuclei imaged by spacecraft (i.e., 19P/Borrelly and 81P/Wild 2) is ubiquitous on Jupiter family cometary nuclei and is an essential element of their internal structure. The observational characteristics of the layers on 9P/Tempel 1 are detailed and considered in the context of current theories of the accumulation and dynamical evolution of cometary nuclei. The works of Donn [Donn, B.D., 1990. Astron. Astrophys. 235, 441-446], Sirono and Greenberg [Sirono, S.-I., Greenberg, J.M., 2000. Icarus 145, 230-238] and the experiments of Wurm et al. [Wurm, G., Paraskov, G., Krauss, O., 2005. Icarus 178, 253-263] on the collision physics of porous aggregate bodies are used as basis for a conceptual model of the formation of layers. Our hypothesis is found to have implications for the place of origin of the JFCs and their subsequent dynamical history. Models of fragmentation and rubble pile building in the Kuiper belt in a period of collisional activity (e.g., [Kenyon, S.J., Luu, J.X., 1998. Astron. J. 115, 2136-2160; 1999a. Astron. J. 118, 1101-1119; 1999b. Astrophys. J. 526, 465-470; Farinella, P., Davis, D.R., Stern, S.A., 2000. In: Mannings, V., Boss, A.P., Russell, S.S. (Eds.), Protostars and Planets IV. Univ. of Arizona Press, Tucson, pp. 1255-1282; Durda, D.D., Stern, S.J., 2000. Icarus 145, 220-229]) following the formation of Neptune appear to be in conflict with the observed properties of the layers and irreconcilable with the hypothesis. Long-term residence in the scattered disk [Duncan, M.J., Levison, H.F., 1997. Science 276, 1670-1672; Duncan, M., Levison, H., Dones, L., 2004. In: Festou, M., Keller, H.U., Weaver, H.A. (Eds.), Comets II. Univ. of Arizona Press, Tucson, pp. 193-204] and/or a change in fragmentation outcome modeling may explain the long-term persistence of primordial layers. In any event, the existence of layers places constraints on the environment seen by the population of objects from which the Jupiter family comets originated. If correct, our hypothesis implies that the nuclei of Jupiter family comets are primordial remnants of the early agglomeration phase and that the physical structure of their interiors, except for the possible effects of compositional phase changes, is largely as it was when they were formed. We propose a new model for the interiors of Jupiter family cometary nuclei, called the talps or "layered pile" model, in which the interior consists of a core overlain by a pile of randomly stacked layers. We discuss how several cometary characteristics—layers, surface texture, indications of flow, compositional inhomogeneity, low bulk density low strength, propensity to split, etc., might be explained in terms of this model. Finally, we make some observational predictions and suggest goals for future space observations of these objects.

Belton, Michael J. S.; Thomas, Peter; Veverka, J.; Schultz, Peter; A'Hearn, Michael F.; Feaga, Lori; Farnham, Tony; Groussin, Olivier; Li, Jian-Yang; Lisse, Casey; McFadden, Lucy; Sunshine, Jessica; Meech, Karen J.; Delamere, W. Alan; Kissel, Jochen

2007-03-01

394

Semiconductor structures having electrically insulating and conducting portions formed from an AlSb-alloy layer  

DOEpatents

The semiconductor structure comprises a plurality of semiconductor layers formed on a substrate including at least one layer of a III-V compound semiconductor alloy comprising aluminum (Al) and antimony (Sb), with at least a part of the AlSb-alloy layer being chemically converted by an oxidation process to form superposed electrically insulating and electrically conducting portions. The electrically insulating portion formed from the AlSb-alloy layer comprises an oxide of aluminum (e.g., Al{sub 2}O{sub 3}), while the electrically conducting portion comprises Sb. A lateral oxidation process allows formation of the superposed insulating and conducting portions below monocrystalline semiconductor layers for forming many different types of semiconductor structures having particular utility for optoelectronic devices such as light-emitting diodes, edge-emitting lasers, vertical-cavity surface-emitting lasers, photodetectors and optical modulators (waveguide and surface normal), and for electronic devices such as heterojunction bipolar transistors, field-effect transistors and quantum-effect devices. The invention is expected to be particularly useful for forming light-emitting devices for use in the 1.3--1.6 {mu}m wavelength range, with the AlSb-alloy layer acting to define an active region of the device and to effectively channel an electrical current therein for efficient light generation. 10 figs.

Spahn, O.B.; Lear, K.L.

1998-03-10

395

Structure of the regular surface layer of Aquaspirillum serpens MW5.  

PubMed Central

The structure of the regular surface layer of Aquaspirillum serpens MW5 has been investigated by electon microscopy supplemented by computer image processing and least-squares analysis. The layer has a ribbed appearance, both on the bacterium and in isolated, negatively stained fragments. However, detailed analysis indicated that the layer was composed of two hexagonal sheets having p6mm symmetry and a = 16 nm. One sheet was staggered by one half repeat along a (1,0) line of the p6nm lattice relative to the second so that, in projection, the pattern of the composite layer was a translational moiré, characterized by a series of ribs spaced 16 nm apart. The ribbed layer had cmm symmetry with a = 32 nm and b = 18.5 nm. Analysis of this pattern indicated that the two p6nm hexagonal sheets were unevenly stained, and this was confirmed by using least-squares methods to simulate the observed pattern by combining two hexagonal patterns. The general structure of the layer was consistent with a role as a selective and protective barrier on the cell surface. Images PMID:7061396

Stewart, M; Murray, R G

1982-01-01

396

Electronic structure of realistically extended atomistically resolved disordered Si:P ?-doped layers  

NASA Astrophysics Data System (ADS)

The emergence of scanning tunneling microscope (STM) lithography and low temperature molecular beam epitaxy (MBE) opens the possibility of creating scalable donor based quantum computing architectures. In particular, atomically precise Si:P monolayer structures (?-doped layers) serve as crucial contact regions and in-plane gates in single impurity devices. In this paper we study highly confined ?-doped layers to explain the disorder in the P dopant placements in realistically extended systems. The band structure is computed using the tight-binding formalism and charge-potential self-consistency. The exchange-correlation corrected impurity potential pulls down subbands below the silicon valley minima to create impurity bands. Our methodology is benchmarked and validated against other theoretical methods for small ordered systems. The doping density is shown to linearly control the impurity bands. Disorder within the Si:P ?-doped layer is examined using an extended domain to describe the effects of experimentally unavoidable randomness through explicitly disordered dopant placement. Disorder in the ?-doped layer breaks the symmetry in the supercell and creates band splitting in every subband. Vertical segregation of dopants is shown to dramatically reduce valley splitting (VS). Such VS can be used as a measure of ideality of the fabricated Si:P ?-doped layer. Although the resulting disorder induces density of states fluctuations, this theoretical analysis shows that ?-doped layers can serve as quasimetallic 2D electron sources even in the presence of strong nonidealities.

Lee, Sunhee; Ryu, Hoon; Campbell, Huw; Hollenberg, Lloyd C. L.; Simmons, Michelle Y.; Klimeck, Gerhard

2011-11-01

397

Thermal properties of composite two-layer systems with a fractal inclusion structure  

NASA Astrophysics Data System (ADS)

In this work, we study the thermal transport properties of platelike composite two-layer samples made of polyester resin and magnetite inclusions. By means of photoacoustic spectroscopy and thermal relaxation, their effective thermal diffusivity and conductivity were experimentally measured. The composite layers were prepared under the action of a static magnetic field, resulting in anisotropic (fractal) inclusion structures with the formation of chain-like magnetite aggregates parallel to the faces of the layers. In one kind of the bilayers, a composite layer was formed on top of a resin layer while their relative thickness was varied. These samples can be described by known models. In contrast, bilayers with the same concentration of inclusions and the same thickness on both sides, where only the angle between their inclusion structures was systematically varied, show a nontrivial behaviour of their thermal conductivity as a function of this angle. Through a multifractal and lacunarity analysis, we explain the observed thermal response in terms of the complexity of the interface between the layers.

Reyes-Salgado, J. J.; Dossetti, V.; Bonilla-Capilla, B.; Carrillo, J. L.

2015-01-01

398

DNS study of large-scale structures in a separated turbulent boundary layer  

NASA Astrophysics Data System (ADS)

Direct numerical simulations (DNSs) of a separated flat-plate turbulent boundary layer have been carried out. The inlet data are prescribed by DNSs of a zero-pressure-gradient turbulent boundary layer with the rescaling-recycling method; blowing and suction are imposed at the upper boundary for producing a separation bubble. The Reynolds numbers at the inlet are set to be Re?=300, 600 and 900, where Re? is the Reynolds number based on the freestream velocity and the momentum thickness. Particular attention is given to large- scale structures existing in a separated region. Results indicate that large-scale organized structures of the streamwise velocity fluctuation appear in a detached shear layer when a large separated region is formed. The latter structures consist of positive and negative regions alternating in the spanwise direction with a spacing of about 2˜3 ?99 (?99 denotes the 99% boundary layer thickness at the inlet), which become more apparent with increasing Reynolds number. They are most likely associated with large-scale spanwise meandering of the separation line. There is also close relationship between the large-scale structures and vortical structures, the latter tending to form vortex clusters where hairpin-like vortices are also observed.

Abe, Hiroyuki; Mizobuchi, Yasuhiro; Matsuo, Yuichi

2011-11-01

399

Monitoring of hidden damage in multi-layered aerospace structures using high-frequency guided waves  

NASA Astrophysics Data System (ADS)

Aerospace structures contain multi-layered components connected by fasteners, where fatigue cracks and disbonds or localized lack of sealant can develop due to cyclic loading conditions and stress concentration. High frequency guided waves propagating along such a structure allow for the efficient non-destructive testing of large components, such as aircraft wings. The type of multi-layered model structure investigated in this contribution consists of two aluminium plates adhesively bonded with an epoxy based sealant layer. Using commercially available transducer equipment, specific high frequency guided ultrasonic wave modes that penetrate through the complete thickness of the structure were excited. The wave propagation along the structure was measured experimentally using a laser interferometer. Two types of hidden damage were considered: a localized lack of sealant and small surface defects in the metallic layer facing the sealant. The detection sensitivity using standard pulse-echo measurement equipment has been quantified and the detection of small hidden defects from significant stand-off distances has been shown. Fatigue experiments were carried out and the potential of high frequency guided waves for the monitoring of fatigue crack growth at a fastener hole during cyclic loading was discussed.

Semoroz, A.; Masserey, B.; Fromme, P.

2011-04-01

400

Origin of Degradation Phenomenon under Drain Bias Stress for Oxide Thin Film Transistors using IGZO and IGO Channel Layers  

NASA Astrophysics Data System (ADS)

Top-gate structured thin film transistors (TFTs) using In-Ga-Zn-O (IGZO) and In-Ga-O (IGO) channel compositions were investigated to reveal a feasible origin for degradation phenomenon under drain bias stress (DBS). DBS-driven instability in terms of VTH shift, deviation of the SS value, and increase in the on-state current were detected only for the IGZO-TFT, in contrast to the IGO-TFT, which did not demonstrate VTH shift. These behaviors were visually confirmed via nanoscale transmission electron microscopy and energy-dispersive x-ray spectroscopy observations. To understand the degradation mechanism, we performed ab initio molecular dynamic simulations on the liquid phases of IGZO and IGO. The diffusivities of Ga and In atoms were enhanced in IGZO, confirming the degradation mechanism to be increased atomic diffusion.

Bak, Jun Yong; Kang, Youngho; Yang, Shinhyuk; Ryu, Ho-Jun; Hwang, Chi-Sun; Han, Seungwu; Yoon, Sung-Min

2015-01-01

401

Origin of degradation phenomenon under drain bias stress for oxide thin film transistors using IGZO and IGO channel layers.  

PubMed

Top-gate structured thin film transistors (TFTs) using In-Ga-Zn-O (IGZO) and In-Ga-O (IGO) channel compositions were investigated to reveal a feasible origin for degradation phenomenon under drain bias stress (DBS). DBS-driven instability in terms of V(TH) shift, deviation of the SS value, and increase in the on-state current were detected only for the IGZO-TFT, in contrast to the IGO-TFT, which did not demonstrate V(TH) shift. These behaviors were visually confirmed via nanoscale transmission electron microscopy and energy-dispersive x-ray spectroscopy observations. To understand the degradation mechanism, we performed ab initio molecular dynamic simulations on the liquid phases of IGZO and IGO. The diffusivities of Ga and In atoms were enhanced in IGZO, confirming the degradation mechanism to be increased atomic diffusion. PMID:25601183

Bak, Jun Yong; Kang, Youngho; Yang, Shinhyuk; Ryu, Ho-Jun; Hwang, Chi-Sun; Han, Seungwu; Yoon, Sung-Min

2015-01-01

402

Effects of cropping history and origin of seed potatoes on population structure of Phytophthora infestans  

Microsoft Academic Search

The effects of origin of seed potatoes and the cropping history on the phenotypic structure of Phytophthora infestans populations was studied in northern Hessia, central Germany, from 2000 to 2002. Populations originating from fields with\\u000a a history of potato cropping with only short or no rotation (old fields) were compared with populations from new fields, i.e.,\\u000a where no potatoes had been

Heidi Bouws; Maria R. Finckh

2007-01-01

403

Structure Analyses of Ti-Based Self-Formed Barrier Layers  

NASA Astrophysics Data System (ADS)

Self-formed Ti-based barrier layer using Cu(Ti) alloy seed applied to 45-nm-node dual-damascene interconnects was reported to have sufficient barrier strength to prevent Cu diffusion into dielectrics. The constituent Ti compounds in the self-formed Ti-based barrier layers and the barrier structures in Cu(Ti)/dielectric samples were identified by X-ray photoelectron spectroscopy (XPS) analyses. Two types of SiOC with low dielectric constants, SiO2, and SiCN were used as dielectrics. The Ti-based barrier layers consisted mainly of amorphous Ti oxides such as TiO2, Ti2O3, and TiO, regardless of the dielectric. In addition to Ti oxides, barrier layers containing TiC, TiSi, and TiN were observed, depending on the dielectric. TiC and TiSi were in crystalline state. They were formed beneath the Cu(Ti) alloy films, and had orientation relationship with the crystalline Cu(Ti) alloy films. The amorphous Ti oxides were formed above the amorphous dielectric layers. The amorphous Ti oxides are believed to be formed continuously above the dielectric layers and prevent Cu diffusion into the dielectric layers.

Kohama, Kazuyuki; Ito, Kazuhiro; Sonobayashi, Yutaka; Ohmori, Kazuyuki; Mori, Kenichi; Maekawa, Kazuyoshi; Shirai, Yasuharu; Murakami, Masanori

2011-04-01

404

Ultra-fine structural characterization and bioactivity evaluation of TiO2 nanotube layers.  

PubMed

For an application as biomedical materials of high performance with a good biocompatibility, the TiO2 nanotube-type oxide film on Ti substrate has been fabricated by electrochemical method, and the effects of surface characteristics of TiO2 naotube layer have been investigated. The surface morphology of TiO2 nanotube layer depends on factors such as anodizing time, current density, and electrolyte temperature. Moreover, the cell and pore size gradually were increased with the passage of anodizing time. X-ray diffraction (XRD) results indicated that the TiO2 nanotube layer formed in acidic electrolytes was mainly composed of anatase structure containing rutile. From the analysis of chemical states of TiO2 nanotube layer using X-ray photoelectron spectroscopy (XPS), Ti2p, P2p and O1s were observed in the nanotubes layer, which were penetrated from the electrolyte into the oxide layer during anodic process. The incorporated phosphate species were found mostly in the forms of HPO4-, PO4-, and PO3-. From the result of biological evaluation in simulated body fluid (SBF) the TiO2 nanotube layer was effective for bioactive property. PMID:19198362

Jang, JaeMyung; Kwon, TaeYub; Kim, KyoHan

2008-10-01

405

Can we neglect the multi-layer structure of functional networks?  

E-print Network

Functional networks, i.e. networks representing dynamic relationships between the components of a complex system, have been instrumental for our understanding of, among others, the human brain. Due to limited data availability, the multi-layer nature of numerous functional networks has hitherto been neglected, and nodes are endowed with a single type of links even when multiple relationships coexist at different physical levels. A relevant problem is the assessment of the benefits yielded by studying a multi-layer functional network, against the simplicity guaranteed by the reconstruction and use of the corresponding single layer projection. Here, I tackle this issue by using as a test case, the functional network representing the dynamics of delay propagation through European airports. Neglecting the multi-layer structure of a functional network has dramatic consequences on our understanding of the underlying system, a fact to be taken into account when a projection is the only available information.

Zanin, Massimiliano

2015-01-01

406

A review of vortex structures and associated coherent motions in turbulent boundary layers  

NASA Technical Reports Server (NTRS)

The experimental and computational evidence for the existence and role of vortices in turbulent boundary layers is briefly reviewed. Quasi-streamwise and transverse vortices are considered, and various published conceptual models for horseshoe-like vortical structures are compared. The causes for upright and inverted horseshoe-shaped vorticity lines are discussed, and the distinction between vorticity lines and vortices is demonsrated. Finally, results from a numerically-simulated turbulent boundary layer are used to compute distributions of diameter, height, and strength for quasi-streamwise and spanwise vortices. These results confirm that quasi-streamwise vortices are clustered near the wall, while spanwise vortices are distributed throughout the layer. The variation of spanwise vortex core diameter with distance from the wall is found to be consistent with the mixing-length distribution for a boundary layer.

Robinson, Stephen K.

1990-01-01

407

Incoherent scatter radar observations of irregular structure in mid-latitude sporadic E layers  

NASA Technical Reports Server (NTRS)

The basic experiments used phase-coded pulses to record electron density profiles with a resolution of 600 m in range and 300 m in horizontal extent, while scanning in azimuth. Data from incoherent scatter radar were compared with simultaneous ionosonde observations. Observations of sporadic E layers by incoherent scatter radar were discussed in terms of the effects of the neutral wind system acting on metallic ions. Several features were noted in the data, which support the wind shear mechanism of layer formation. The sporadic E layers often contained a pronounced small-scale structure, especially at times when partially transparent echoes were observed by the ionosonde. Under specific conditions, the ions in a meteor trail can be converged by a shear in the neutral wind into a relatively small irregularity at the center of a sporadic E layer.

Miller, K. L.; Smith, L. G.

1978-01-01

408

Controlled gentamicin release from multi-layered electrospun nanofibrous structures of various thicknesses  

PubMed Central

Polyvinyl alcohol nanofibers incorporating the wide spectrum antibiotic gentamicin were prepared by Nanospider™ needleless technology. A polyvinyl alcohol layer, serving as a drug reservoir, was covered from both sides by polyurethane layers of various thicknesses. The multilayered structure of the nanofibers was observed using scanning electron microscopy, the porosity was characterized by mercury porosimetry, and nitrogen adsorption/desorption measurements were used to determine specific surface areas. The stability of the gentamicin released from the electrospun layers was proved by high-performance liquid chromatography (HPLC) and inhibition of bacterial growth. Drug release was investigated using in vitro experiments with HPLC/MS quantification, while the antimicrobial efficacy was evaluated on Gram-positive Staphylococcus aureus and Gram-negative Pseudomonas aeruginosa. Both experiments proved that the released gentamicin retained its activity and showed that the retention of the drug in the nanofibers was prolonged with the increasing thickness of the covering layers. PMID:23071393

Sirc, Jakub; Kubinova, Sarka; Hobzova, Radka; Stranska, Denisa; Kozlik, Petr; Bosakova, Zuzana; Marekova, Dana; Holan, Vladimir; Sykova, Eva; Michalek, Jiri

2012-01-01

409

A randomly nano-structured scattering layer for transparent organic light emitting diodes.  

PubMed

A random scattering layer (RSL) consisting of a random nano-structure (RNS) and a high refractive index planarization layer (HRI PL) is suggested and demonstrated as an efficient internal light-extracting layer for transparent organic light emitting diodes (TOLEDs). By introducing the RSL, a remarkable enhancement of 40% and 46% in external quantum efficiency (EQE) and luminous efficacy (LE) was achieved without causing deterioration in the transmittance. Additionally, with the use of the RSL, the viewing angle dependency of EL spectra was reduced to a marginal degree. The results were interpreted as the stronger influence of the scattering effect over the microcavity. The RSL can be applied widely in TOLEDs as an effective light-extracting layer for extracting the waveguide mode of confined light at the indium tin oxide (ITO)/OLED stack without introducing spectral changes in TOLEDs. PMID:25099663

Huh, Jin Woo; Shin, Jin-Wook; Cho, Doo-Hee; Moon, Jaehyun; Joo, Chul Woong; Park, Seung Koo; Hwang, Joohyun; Cho, Nam Sung; Lee, Jonghee; Han, Jun-Han; Chu, Hye Yong; Lee, Jeong-Ik

2014-09-21

410

Synthetic magnetic field effects on neutral bosonic condensates in quasi-three-dimensional anisotropic layered structures  

SciTech Connect

We discuss a system of dilute Bose gas confined in a layered structure of stacked square lattices (slab geometry). A derived phase diagram reveals a nonmonotonic dependence of the ratio of tunneling to on-site repulsion on the artificial magnetic field applied to the system. The effect is reduced when more layers are added, which mimics a two- to quasi-three-dimensional geometry crossover. Furthermore, we establish a correspondence between anisotropic infinite (quasi-three-dimensional) and isotropic finite (slab geometry) systems that share exactly the same critical values, which can be an important clue for choosing experimental setups that are less demanding, but still leading to the identical results. Finally, we show that the properties of the ideal Bose gas in a three-dimensional optical lattice can be closely mimicked by finite (slab) systems when the number of two-dimensional layers is larger than 10 for isotropic interactions, or even less when the layers are weakly coupled.

Zaleski, T. A.; Polak, T. P. [Institute of Low Temperatures and Structure Research, Polish Academy of Sciences, POB 1410, 50-950 Wroclaw 2 (Poland); Adam Mickiewicz University of Poznan, Faculty of Physics, Umultowska 85, 61-614 Poznan (Poland)

2011-02-15

411

Intrusive origin of the Sudbury Igneous Complex: Structural and sedimentological evidence  

NASA Technical Reports Server (NTRS)

In recent years, many geoscientists have come to believe that the Sudbury event was exogenic rather than endogenic. Critical to a recent exogenic hypothesis is the impact melt origin of the Sudbury Igneous Complex (SIC). Such origin implies that the SIC was emplaced before deposition of the Whitewater Group, in contrast to origins in which the SIC postdates the lithification of the Onaping Formation. Structural and sedimentological evidence is summarized herein that supports an intrusion of the SIC after lithification of all Whitewater Group strata, and conflicts with the hypothesis advanced by other researchers.

Cowan, E. J.; Schwerdtner, W. M.

1992-01-01

412

Optical properties of thin semiconductor device structures with reflective back-surface layers  

SciTech Connect

Ultrathin semiconductor device structures incorporating reflective internal or back surface layers have been investigated recently as a means of improving photon recuperation, eliminating losses associated with free carrier absorption in conductive substrates and increasing the above bandgap optical thickness of thermophotovoltaic device structures. However, optical losses in the form of resonance absorptions in these ultrathin devices have been observed. This behavior in cells incorporating epitaxially grown FeAl layers and in devices that lack a substrate but have a back-surface reflector (BSR) at the rear of the active layers has been studied experimentally and modeled effectively. For thermophotovoltaic devices, these resonances represent a significant loss mechanism since the wavelengths at which they occur are defined by the active TPV cell thickness of {approximately} 2--5 microns and are in a spectral range of significant energy content for thermal radiators. This study demonstrates that ultrathin semiconductor structures that are clad by such highly reflective layers or by films with largely different indices of refraction display resonance absorptions that can only be overcome through the implementation of some external spectral control strategy. Effective broadband, below-bandgap spectral control using a back-surface reflector is only achievable using a large separation between the TPV active layers and the back-surface reflector.

Clevenger, M.B.; Murray, C.S. [Westinghouse Electric Co., West Mifflin, PA (United States); Ringel, S.A.; Sachs, R.N.; Qin, L. [Ohio State Univ., Columbus, OH (United States). Dept. of Electrical Engineering; Charache, G.W.; Depoy, D.M. [Lockheed Martin, Inc., Schenectady, NY (United States)

1998-11-01

413

A randomly nano-structured scattering layer for transparent organic light emitting diodes  

NASA Astrophysics Data System (ADS)

A random scattering layer (RSL) consisting of a random nano-structure (RNS) and a high refractive index planarization layer (HRI PL) is suggested and demonstrated as an efficient internal light-extracting layer for transparent organic light emitting diodes (TOLEDs). By introducing the RSL, a remarkable enhancement of 40% and 46% in external quantum efficiency (EQE) and luminous efficacy (LE) was achieved without causing deterioration in the transmittance. Additionally, with the use of the RSL, the viewing angle dependency of EL spectra was reduced to a marginal degree. The results were interpreted as the stronger influence of the scattering effect over the microcavity. The RSL can be applied widely in TOLEDs as an effective light-extracting layer for extracting the waveguide mode of confined light at the indium tin oxide (ITO)/OLED stack without introducing spectral changes in TOLEDs.A random scattering layer (RSL) consisting of a random nano-structure (RNS) and a high refractive index planarization layer (HRI PL) is suggested and demonstrated as an efficient internal light-extracting layer for transparent organic light emitting diodes (TOLEDs). By introducing the RSL, a remarkable enhancement of 40% and 46% in external quantum efficiency (EQE) and luminous efficacy (LE) was achieved without causing deterioration in the transmittance. Additionally, with the use of the RSL, the viewing angle dependency of EL spectra was reduced to a marginal degree. The results were interpreted as the stronger influence of the scattering effect over the microcavity. The RSL can be applied widely in TOLEDs as an effective light-extracting layer for extracting the waveguide mode of confined light at the indium tin oxide (ITO)/OLED stack without introducing spectral changes in TOLEDs. Electronic supplementary information (ESI) available: Simulation results of total (bottom and top) radiance of TOLEDs with the RSL depending on HTL and ETL thicknesses. See DOI: 10.1039/c4nr01520g

Huh, Jin Woo; Shin, Jin-Wook; Cho, Doo-Hee; Moon, Jaehyun; Joo, Chul Woong; Park, Seung Koo; Hwang, Joohyun; Cho, Nam Sung; Lee, Jonghee; Han, Jun-Han; Chu, Hye Yong; Lee, Jeong-Ik

2014-08-01

414

The vertical turbulence structure of the coastal marine atmospheric boundary layer  

SciTech Connect

The vertical turbulence structure in the marine atmosphere along a shoreline has been investigated using data from tower and aircraft measurements performed along the Baltic coast in the southeast of Sweden. Two properties make the Baltic Sea particularly interesting. It is surrounded by land in all directions within moderate advection distances, and it features a significant annual lag in sea surface temperature as compared with inland surface temperature. The present data were collected mostly during spring or early summer, when the water is cool, i.e., with a stably or neutrally stratified marine boundary layer usually capped by an inversion. Substantial daytime heating over the land area results in a considerable horizontal thermal contrast. Measurements were made on a small island, on a tower with a good sea fetch, and with an airborne instrument package. The profile data from the aircraft is from 25 slant soundings performed in connection to low level boundary layer flights. The results from the profiles are extracted through filtering techniques on individual time (space) series (individual profiles), applying different normalization and finally averaging over all or over groups of profiles. The land-based data are from a low tower situated on the shoreline of a small island with a wide sector of unobstructed sea fetch. Several factors are found that add to the apparent complexity of the coastal marine environment: the state of the sea appears to have a major impact on the turbulence structure of the surface layer, jet-shaped wind speed profiles were very common at the top of the boundary layer (in about 50% of the cases) and distinct layers with increased turbulence were frequently found well above the boundary layer (in about 80% of the cases). The present paper will concentrate on a description of the experiment, the analysis methods, and a general description of the boundary layer turbulence structure over the Baltic Sea. 40 refs., 16 figs., 2 tabs.

Tjernstroem, M.; Smedman, A.S. (Uppsala Univ. (Sweden))

1993-03-15

415

The vertical turbulence structure of the coastal marine atmospheric boundary layer  

NASA Astrophysics Data System (ADS)

The vertical turbulence structure in the marine atmosphere along a shoreline has been investigated using data from tower and aircraft measurements performed along the Baltic coast in the southeast of Sweden. Two properties make the Baltic Sea particularly interesting. It is surrounded by land in all directions within moderate advection distances, and it features a significant annual lag in sea surface temperature as compared with inland surface temperature. The present data were collected mostly during spring or early summer, when the water is cool, i.e., with a stably or neutrally stratified marine boundary layer usually capped by an inversion. Substantial daytime heating over the land area results in a considerable horizontal thermal contrast. Measurements were made on a small island, on a tower with a good sea fetch, and with an airborne instrument package. The profile data from the aircraft is from 25 slant soundings performed in connection to low level boundary layer flights. The results from the profiles are extracted through filtering techniques on individual time (space) series (individual profiles), applying different normalization and finally averaging over all or over groups of profiles. The land-based data are from a low tower situated on the shoreline of a small island with a wide sector of unobstructed sea fetch. Several factors are found that add to the apparent complexity of the coastal marine environment: the state of the sea appears to have a major impact on the turbulence structure of the surface layer, jet-shaped wind speed profiles were very common at the top of the boundary layer (in about 50% of the cases) and distinct layers with increased turbulence were frequently found well above the boundary layer (in about 80% of the cases). The present paper will concentrate on a description of the experiment, the analysis methods, and a general description of the boundary layer turbulence structure over the Baltic Sea.

TjernströM, Michael; Smedman, Ann-Sofi

1993-03-01

416

Three-Layered Atmospheric Structure in Accretion Disks Around Stellar-Mass Black Holes  

E-print Network

Modeling of the x-ray spectra of the Galactic superluminal jet sources GRS 1915+105 and GRO J1655-40 reveal a three-layered atmospheric structure in the inner region of their accretion disks. Above the cold and optically thick disk of a temperature 0.2-0.5 keV, there is a warm layer with a temperature of 1.0-1.5 keV and an optical depth around 10. Sometimes there is also a much hotter, optically thin corona above the warm layer, with a temperature of 100 keV or higher and an optical depth around unity. The structural similarity between the accretion disks and the solar atmosphere suggest that similar physical processes may be operating in these different systems.

S. N. Zhang; Wei Cui; Wan Chen; Yangsen Yao; Xiaoling Zhang; Xuejun Sun; Xue-Bing Wu; Haiguang Xu

2000-02-24

417

An analysis of the structure of thunderstorm in the atmospheric boundary layer  

NASA Astrophysics Data System (ADS)

The structure of thunderstorm in the atmospheric boundary layer in Beijing area is analysed by using three-year data of tower. It is indicated that the outflow current of the thunderstorm in the lower layer is a sort of density current. An area of evident wind direction shear is found at about half an hour to one hour before the arrival of the gust front. The maximum intensity of the shear can reach 0.35sec-1 The inner structure within the density current is also very complicated. At the nocturnal stable boundary layer in summertime, the development of the convective motions is often triggered due to the instability of the Kelvin-Helmholtz wave.

Zhu, Cuijuan; Li, Xingsheng; Ye, Zhuojia

1984-05-01

418

Three-Layered Atmospheric Structure in Accretion Disks Around Stellar-Mass Black Holes  

NASA Technical Reports Server (NTRS)

Modeling of the x-ray spectra of the Galactic superluminal jet sources GRS 1915+105 and GRO J1655-40 reveals a three-layered atmospheric structure in the inner region of the inner accretion disks. Above the cold and optically thick disk with a temperature of 0.2 to 0.5 kiloelectron volts, there is a warm layer with a temperature of 1.0 to 1.5 kiloelectron volts and an optical depth around 10. Sometimes there is also a much hotter, optically thin corona above the warm layer, with a temperature of 100 kiloelectron volts or higher and an optical depth around unity. The structural similarity between the accretion disks and the solar atmosphere suggests that similar physical processes may be operating in these different systems.

Zhang, S. N.; Cui, Wei; Chen, Wan; Yao, Yangsen; Zhang, Xiaoling; Sun, Xuejun; Wu, Xue-Bing; Xu, Haiguang

2000-01-01

419

Three-layered atmospheric structure in accretion disks around stellar-mass black holes  

PubMed

Modeling of the x-ray spectra of the Galactic superluminal jet sources GRS 1915+105 and GRO J1655-40 reveals a three-layered atmospheric structure in the inner region of their accretion disks. Above the cold and optically thick disk with a temperature of 0.2 to 0.5 kiloelectron volts, there is a warm layer with a temperature of 1.0 to 1.5 kiloelectron volts and an optical depth around 10. Sometimes there is also a much hotter, optically thin corona above the warm layer, with a temperature of 100 kiloelectron volts or higher and an optical depth around unity. The structural similarity between the accretion disks and the solar atmosphere suggests that similar physical processes may be operating in these different systems. PMID:10678825

Zhang; Cui; Chen; Yao; Zhang; Sun; Wu; Xu

2000-02-18

420

EXAFS Signatures of Structural Zn at Trace Levels in Layered Minerals  

SciTech Connect

Many in situ XAFS studies have shown that zinc incorporated in layered minerals is a major form of zinc in Zn-contaminated soils. Quantitative information on the local structural environment(s) and ordering of Zn in these minerals is required to better understand its behavior in soils. In this study, EXAFS spectroscopy was used to assess the structural environment of zinc incorporated at trace levels (40 ppm to 4,000 ppm) within the octahedral sheets of various natural and synthetic layered minerals. Results indicate that EXAFS data analyzed using ab initio FEFF calculations (FEFF 8.10) can unambiguously distinguish between zinc incorporation within the octahedral sheet of dioctahedral versus trioctahedral layered minerals and can determine the distribution (random or ordered) of zinc cations within the octahedral sheets of these minerals.

Juillot, Farid; Morin, Guillaume; /Paris U., VI-VII, LMCP; Hazemann, Jean-Louis; Proux, Olivier; /ESRF, Grenoble; Belin, Stephanie; Briois, Valerie; /ESRF, Grenoble; Brown,; /Stanford U., Geo. Environ. Sci. /SLAC, SSRL; Calas, Georges; /Paris U., VI-VII, LMCP

2006-12-13

421

Formation of Structured Dayside Boundary Layers under Different Solar Wind Conditions: THEMIS Observations  

NASA Technical Reports Server (NTRS)

We have begun an investigation of the formation of the dayside low latitude boundary layer under different solar wind conditions using data from the THEMIS spacecraft. We present two cases of magnetopause/LLBL interface crossings made by the five spacecraft; one under long lasting northward IMF and a second for a period of southward IMF. All spacecraft during these observations traversed the dayside magnetosphere in a string-of-pearls configuration with the farthest distance between spacecraft less than approx.2 R(sub E). The sequence of observations from spacecraft, as they crossed the magnetopause, shows the development of a highly structured boundary layer regardless of the polarity of the IMF. We discuss possible scenarios for the development of such structured boundary layers, including low latitude reconnection under northward IMF as well as double reconnection in opposite hemispheres.

Avanov, Levon A.; Chandler, Michael O.

2008-01-01

422

A Long-Lived Tracer Perspective on the Origin of Air in the Tropical Tropopause Layer during ATTREX  

NASA Astrophysics Data System (ADS)

The origin of air in the tropical tropopause layer (TTL) and the subsequent transport pathways of these air masses play a critical role in the delivery of trace gases, including ozone depleting substances and water vapor, to the stratosphere. The Airborne Tropical Tropopause Experiment (ATTREX) is designed to study this transport and processing in the TTL over the Pacific Ocean, including how dehydration occurs in this region and how trace gases involved in ozone depletion and climate reach the tropical lower stratosphere. For this mission, the NASA Global Hawk aircraft is carrying a suite of in situ and remote sensing instruments for trace gases, aerosols, radiation, and meteorology. Two deployments have occurred from NASA/Dryden Flight Research Center, with flights to the eastern and central tropical Pacific. Two more deployments, targeting the western equatorial Pacific, are planned for 2014 from Guam and one other location. Over 100 vertical profiles from about 14 to 18 km have now been obtained from the tropics to midlatitudes, as well as long sections at nearly constant altitude. Results are shown here from the UAS Chromatograph for Atmospheric Trace Species (UCATS) instrument and other sensors. UCATS was configured to measure the long-lived tracers N2O, SF6, H2, and CH4, as well as water vapor, CO, and ozone. Results thus far have shown a mix of midlatitude and tropical air in the tropical and subtropical lower stratosphere, particularly for flights in November 2011. Recent results from February 2013 indicate much more homogeneous air masses in the TTL during this period. This homogeneity may be related to fact that these flights occurred in the middle of (northern) winter rather than fall, or to the 'sudden stratospheric warming' in January 2013, with sinking motion in the Arctic polar region and a corresponding rising motion and cooling in the tropics. Data will be presented in the context of trajectory model calculations of the origin and fate of the air masses sampled. These findings are relevant for understanding the composition of air rising through the TTL and into the tropical stratosphere, one of the central goals of ATTREX.

Hintsa, E. J.; Moore, F.; Dutton, G. S.; Hall, B. D.; Nance, J. D.; Elkins, J. W.; Gao, R.; Rollins, D. W.; Thornberry, T. D.; Watts, L.; Fahey, D. W.; Daube, B. C.; Pittman, J. V.; Wofsy, S. C.; Atlas, E. L.; Navarro, M. A.; Dessler, A. E.; Mahoney, M.

2013-12-01

423

Structure and chemical composition of layers adsorbed at interfaces with champagne.  

PubMed

The structure and the chemical composition of the layer adsorbed at interfaces involving champagne have been investigated using native champagne, as well as ultrafiltrate (UFch) and ultraconcentrate (UCch) obtained by ultrafiltration with a 10(4) nominal molar mass cutoff. The layer adsorbed at the air/liquid interface was examined by surface tension and ellipsometry kinetic measurements. Brewster angle microscopy demonstrated that the layer formed on polystyrene by adsorption or drop evaporation was heterogeneous, with a domain structure presenting similarities with the layer adsorbed at the air/liquid interface. The surface chemical composition of polystyrene with the adlayer was determined by X-ray photoelectron spectroscopy (XPS). The contribution of champagne constituents varied according to the liquid (native, UFch, and UCch) and to the procedure of adlayer formation (evaporation, adsorption, and adsorption + rinsing). However, their chemical composition was not significantly influenced either by ultrafiltration or by the procedure of deposition on polystyrene. Modeling this composition in terms of classes of model compounds gave approximately 35% (w/w) of proteins and 65% (w/w) of polysaccharides. In the adlayer, the carboxyl groups or esters represent about 18% of carbon due to nonpolypeptidic compounds, indicating the presence of either uronic acids in the complex structure of pectic polysaccharides or of polyphenolic esters. This structural and chemical information and its relationship with the experimental procedures indicate that proteins alone cannot be used as a realistic model for the macromolecules forming the adsorption layer of champagne. Polysaccharides, the other major macromolecular components of champagne wine, are assembled with proteins at the interfaces, in agreement with the heterogeneous character of the adsorbed layer at interfaces. PMID:19813745

Aguié-Béghin, V; Adriaensen, Y; Péron, N; Valade, M; Rouxhet, P; Douillard, R

2009-11-11