Sample records for original layered structure

  1. Origin of the polygons and underground structures in Southern layered deposits and Utopia Planitia on Mars

    Microsoft Academic Search

    K. Yoshikawa; S. Laderach; L. Hinzman

    2001-01-01

    Patterned ground is a common feature in the cold and\\/or arid regions of Earth, but similar features are also found on Mars. Polygons on the Martian surface have been classified into three different size classes: big (giant polygons, 1-20 km diameter), middle size (100-200 m diameter) and small size (5-20 m diameter). Many of small-scale polygons on the southern layered

  2. Original article Tree canopy and herb layer transpiration in three Scots

    E-print Network

    Paris-Sud XI, Université de

    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

  3. Origin of the dielectric dead layer in nanoscale capacitors.

    PubMed

    Stengel, Massimiliano; Spaldin, Nicola A

    2006-10-12

    Capacitors are a mainstay of electronic integrated circuits and devices, where they perform essential functions such as storing electrical charge, and blocking direct current while allowing alternating currents to propagate. Because they are often the largest components in circuits, extensive efforts are directed at reducing their size through the use of high-permittivity insulators such as perovskite-structure SrTiO3 (refs 1, 2), which should provide more capacitance per unit area of device. Unfortunately, most experiments on thin-film SrTiO3 capacitors have yielded capacitance values that are orders of magnitude smaller than expected. The microscopic origin of this reduced capacitance, which is often discussed in terms of a low-permittivity interfacial 'dead layer', is not well understood. Whether such a dead layer exists at all, and if so, whether it is an intrinsic property of an ideal metal-insulator interface or a result of processing issues such as defects and strains, are controversial questions. Here we present fully ab initio calculations of the dielectric properties of realistic SrRuO3/SrTiO3/SrRuO3 nanocapacitors, and show that the observed dramatic capacitance reduction is indeed an intrinsic effect. We demonstrate the existence of a dielectric dead layer by calculating the dielectric profile across the interface and analyse its origin by extracting the ionic and electronic contributions to the electrostatic screening. We establish a correspondence between the dead layer and the hardening of the collective SrTiO3 zone-centre polar modes, and determine the influence of the electrode by repeating our calculations for Pt/SrTiO3/Pt capacitors. Our results provide practical guidelines for minimizing the deleterious effects of the dielectric dead layer in nanoscale devices. PMID:17036000

  4. ORIGINAL PAPER On the origin of mixed-layered clay minerals from the

    E-print Network

    ORIGINAL PAPER On the origin of mixed-layered clay minerals from the San Andreas Fault at 2.5­3 km. The characteristics of authigenic illite­smectite (I­S) and chlorite­smectite (C­S) mixed- layer mineral clays of the dominant authigenic clay species across the San Andreas Fault zone (sampled at 3,066 and 3,436 m measured

  5. Planetary Origin Evolution and Structure

    NASA Technical Reports Server (NTRS)

    Stevenson, David J.

    2005-01-01

    This wide-ranging grant supported theoretical modeling on many aspects of the formation, evolution and structure of planets and satellites. Many topics were studied during this grant period, including the evolution of icy bodies; the origin of magnetic fields in Ganymede; the thermal histories of terrestrial planets; the nature of flow inside giant planets (especially the coupling to the magnetic field) and the dynamics of silicate/iron mixing during giant impacts and terrestrial planet core formation. Many of these activities are ongoing and have not reached completion. This is the nature of this kind of research.

  6. Wavy structures in compressible mixing layers

    NASA Astrophysics Data System (ADS)

    Chen, Jun; Shi, Xiao-Tian; Wang, Tie-Jin; She, Zhen-Su

    2013-10-01

    Semi-periodic structures namely inclined wavy structures (IWS) are experimentally observed in compressible mixing layers at two convective Mach numbers ( M c = 0.11 and 0.47). Flow structures are visualized by the laserinduced planar laser Mie scattering (PLMS) technique. Two methods are developed to investigate the spatial distribution and geometry of IWS: (1) the dominant mode extraction (DME) method, to extract the dominant modes of IWS from the streamwise gray-level fluctuation, and (2) the phase tracking (PT) method, to identify the shape of IWS. The results suggest that pressure perturbations account for the formation of IWS in the initialmixing region and the joint effect of dilatation and coherent vortices enhances IWS in the welldeveloped region. The large transverse (cross-flow) scale of the IWS and their relation to coherent vortices (CV) indicate that the disturbance originated from CV in the mixing center propagates far into the free streams. The DME and the PT method are shown to be the effective tools to study the geometrical features of wavy structures in compressible shear flows.

  7. Lattice Vibrations and Superconductivity in Layered Structures

    E-print Network

    Allen, Roland E.; Alldredg, GP; WETTE, FWD.

    1970-01-01

    PHYSICAL REVIEW B VOLUME 2, NUMBER 7 1 OCTOB ER, 1970 Lattice Vibrations and Superconductivity in Layered Structures* B. E. Allen, G. P. Alldredge, and F. W. de bette DePartment of Physics, University of Texas, Austin, Texas 78712 (Received 18... May 1970) In order to estimate the influence of both surface and interface effects on phonon frequencies and superconducting transition temperatures in layered structures, we have calculated the vibrational modes of structures composed...

  8. Understanding the Origin of Enhanced Performances in Core-Shell and Concentration-Gradient Layered Oxide Cathode Materials.

    PubMed

    Song, Dawei; Hou, Peiyu; Wang, Xiaoqing; Shi, Xixi; Zhang, Lianqi

    2015-06-17

    Core-shell and concentration-gradient layered oxide cathode materials deliver superior electrochemical properties such as long cycle life and outstanding thermal stability. However, the origin of enhanced performance is not clear and seldom investigated until now. Here, a specific structured layered oxide (LiNi0.5Co0.2Mn0.3O2) consisting of concentration-gradient core, transition layer, and stable outer shell, is designed and achieved from double-shelled precursors to overcome the great challenge by comparison with the normal layered LiNi0.5Co0.2Mn0.3O2. As expected, the specific structured layered oxide displays excellent cycle life and thermal stability. After numerous cycles, the valence state of Ni and Co at normal layered oxide surface tends to a higher oxidation state than that of the specific structured oxide, and the spinel phase is observed on particle surface of normal layered oxide. Also, the deficient spinel/layered mixed phases lead to high surface film and charge-transfer resistance for normal layered oxide, whereas the specific structured one still remains a layered structure. Those results first illustrate the origin of improved electrochemical performance of layered core-shell and concentration-gradient cathode materials for lithium-ion batteries. PMID:26017733

  9. Radiative Impacts of Elevated Aerosol Layers from Different Origins

    NASA Astrophysics Data System (ADS)

    Sauer, D. N.; Weinzierl, B.; Gasteiger, J.; Heimerl, K.

    2014-12-01

    Aerosol particles are omnipresent in the Earth's atmosphere and have important impacts on weather and climate by their effects on the atmospheric radiative balance. With the advent of more and more sophisticated representations of atmospheric processes in earth system models, the lack of reliable input data on aerosols leads to significant uncertainties in the prediction of future climate scenarios. In recent years large discrepancies in radiative forcing estimates from aerosol layers in modeling studies have been revealed emphasizing the need for detailed and systematic observations of aerosols. Airborne in-situ measurements represent an important pillar for validating both model results and retrievals of aerosol distributions and properties from remote sensing methods on global scales. However, detailed observations are challenging and therefore are subject to substantial uncertainties themselves. Here we use data from airborne in-situ measurements of elevated aerosol layers from various field experiments in different regions of the world. The data set includes Saharan mineral dust layers over Africa, the Atlantic Ocean and the Caribbean from the SALTRACE and the SAMUM campaigns as well as long-range transported biomass burning aerosol layers from wild fires in the Sahel region and North America measured over the tropical Atlantic Ocean, Europe and the Arctic detected during SAMUM2, CONCERT2011, DC3 and ACCESS 2012. We aim to characterize the effects of the measured aerosol layers, in particular with respect to ageing, mixing state and vertical structure, on the overall atmospheric radiation budget as well as local heating and cooling rates. We use radiative transfer simulations of short and long-wave radiation and aerosol optical properties derived in a consistent way from the in-situ observations of microphysical properties using T-matrix calculations. The results of this characterization will help to improve the parameterization of the effects of elevated aerosol layers in earth system models. In addition, we assess uncertainties in radiative forcing estimates introduced by uncertainties in the measured aerosol properties.

  10. Origin and Structure of Dynamic Cooperative Networks

    E-print Network

    Hauert, Christoph

    Origin and Structure of Dynamic Cooperative Networks Lucas Wardil & Christoph Hauert Department the local structure of the social network. Here we propose a simple theoretical framework to model dynamic among coop- erators2­4 . Social networks represent a dynamical abstraction of social structures

  11. Water Content and Deformation Microstructure of Layered Panzhihua Gabbro: Implications for the Origin of Rhythmic Layering

    NASA Astrophysics Data System (ADS)

    Zhang, J.; Wang, F.; Wang, Z.; Song, S.

    2014-12-01

    The Panzhihua, Hongge and Baima mafic-ultramafic layered intrusions host three giant Fe-Ti oxide deposites in the Pangzhihua-Xichang (Panxi) region, SW China. Various proportions of silicates (plagioclase, pyroxene and olivine), ilmenite and magnitite form rhythmic layering in the upper part of the intrusions. The origin of rhythmic layering in mafic-ultramafic layered intrusions has been debated for a long time in the literatures. Here we provide detailed FTIR and EBSD studies on the water content and deformation microstructure of gabbros from the Panzhihua intrusion. The FTIR analyses revealed a significant amount of hydroxyls in both clinopyroxene (411-775 ppm) and plagioclase (328-716 ppm), suggesting a high water content mantle plume source. The EBSD analyses show: 1) a weak clinopyroxene fabric of (100) parallel to foliation and [001] parallel to lineation; 2) a strong plagioclase fabric of (010) parallel to foliation and [100] parallel to lineation; 3) a weak ilmenite fabric of (001) parallel to foliation and [hk0] parallel to lieantion; 4) a near random magnitite fabric. These results suggest weak plagioclase is the main strain accommedation phase in lower crustal rocks under hydrous conditions, which is also consistent with previous deformation experiments on plagioclase and clinoproxene. Water plays an important role in deteriming the rheology contrast between plagioclase and clinoproxene. Our results revealed strong layer-parallel shearing deformation during the formation of the Panxi layered intrusions. We propose that the formation of the rhythmic layering is mainly caused by rheological stratification rather than chemical stratification of Fe-Ti oxides and gabbros.

  12. The structure of APG turbulent boundary layers

    NASA Astrophysics Data System (ADS)

    Gungor, Ayse G.; Maciel, Yvan; Simens, Mark P.; Soria, Julio

    2013-11-01

    A boundary layer under influence of a strong APG is studied using DNS. Transition to turbulence is triggered using a trip wire which is modelled using the immersed boundary method. The Reynolds number close to the exit of the numerical domain is Re? = 2175 and the shape-factor H = 2 . 5 . Two dimensional two-point spatial correlation functions are obtained in this region and close to the transition region. Cvu with a reference point close to the transition region shows a flow periodicity until Re? ~ 1600 . This periodicity is related to the shear layer instability of the separation bubble created as a result of the APG. The Cvv and Cww correlations obtained far from the transition region at Re? = 2175 and at y / ? = 0 . 4 coincide with results obtained for a ZPG boundary layer. Implying that the structure of the v , w fluctuations is the same as in ZPG. However, Cuu indicates that the structure of the u fluctuation in an APG boundary layer is almost twice as short as the ZPG structures. The APG structures are also less correlated with the flow at the wall. The near wall structure of strong APG flows is different from ZPG flows in that streaks are much shorter or absent. A boundary layer under influence of a strong APG is studied using DNS. Transition to turbulence is triggered using a trip wire which is modelled using the immersed boundary method. The Reynolds number close to the exit of the numerical domain is Re? = 2175 and the shape-factor H = 2 . 5 . Two dimensional two-point spatial correlation functions are obtained in this region and close to the transition region. Cvu with a reference point close to the transition region shows a flow periodicity until Re? ~ 1600 . This periodicity is related to the shear layer instability of the separation bubble created as a result of the APG. The Cvv and Cww correlations obtained far from the transition region at Re? = 2175 and at y / ? = 0 . 4 coincide with results obtained for a ZPG boundary layer. Implying that the structure of the v , w fluctuations is the same as in ZPG. However, Cuu indicates that the structure of the u fluctuation in an APG boundary layer is almost twice as short as the ZPG structures. The APG structures are also less correlated with the flow at the wall. The near wall structure of strong APG flows is different from ZPG flows in that streaks are much shorter or absent. Funded in part by ITU, NSERC of Canada, ARC Discovery Grant, and Multiflow program of the ERC.

  13. Fast two-layer image watermarking without referring to the original image and watermark

    E-print Network

    Salvaggio, Carl

    Fast two-layer image watermarking without referring to the original image and watermark Jian 24 April 2001; accepted 7 June 2001 Abstract A fast two-layer image watermarking without referring to the original image and watermark is proposed in this study. Two layers of algorithms are employed

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

    SciTech Connect

    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

    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.

  15. Earth Structure: Layers of the Earth

    NSDL National Science Digital Library

    Smoothstone

    This interactive Flash allows users to explore Earth's structure and processes that occur on Earth such as earthquakes and plate tectonics and how scientists know the composition and state of the Earth's layers. Interactive diagrams and animations with supplementary information make this a helpful overview or review for high school and undergraduate introductory-level courses in physical geology and Earth sciences.

  16. Multi-Layer Laminated Thin Films for Inflatable Structures

    NASA Technical Reports Server (NTRS)

    Yavrouian, Andre; Plett, Gary; Mannella, Jerami

    2005-01-01

    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.

  17. Electronic structure of bacterial surface protein layers

    SciTech Connect

    Maslyuk, Volodymyr V.; Mertig, Ingrid; Bredow, Thomas; Mertig, Michael; Vyalikh, Denis V.; Molodtsov, Serguei L. [Martin-Luther-Universitaet Halle-Wittenberg, Fachbereich Physik, D-06099 Halle (Germany); Institut fuer Physikalische und Theoretische Chemie, Universitaet Bonn, D-53115 Bonn (Germany); Max-Bergmann-Zentrum fuer Biomaterialien, Technische Universitaet Dresden, D-01062 Dresden (Germany); Institut fuer Festkoerperphysik, Technische Universitaet Dresden, D-01062 Dresden (Germany)

    2008-01-15

    We report an approach for the calculation of the electronic density of states of the dried two-dimensional crystalline surface protein layer (S layer) of the bacterium Bacillus sphaericus NCTC 9602. The proposed model is based on the consideration of individual amino acids in the corresponding conformation of the peptide chain which additively contribute to the electronic structure of the entire protein complex. The derived results agree well with the experimental data obtained by means of photoemission (PE), resonant PE, and near-edge x-ray absorption spectroscopy.

  18. Persistent Structures in the Turbulent Boundary Layer

    NASA Technical Reports Server (NTRS)

    Palumbo, Dan; Chabalko, Chris

    2005-01-01

    Persistent structures in the turbulent boundary layer are located and analyzed. The data are taken from flight experiments on large commercial aircraft. An interval correlation technique is introduced which is able to locate the structures. The Morlet continuous wavelet is shown to not only locates persistent structures but has the added benefit that the pressure data are decomposed in time and frequency. To better understand how power is apportioned among these structures, a discrete Coiflet wavelet is used to decompose the pressure data into orthogonal frequency bands. Results indicate that some structures persist a great deal longer in the TBL than would be expected. These structure contain significant power and may be a primary source of vibration energy in the airframe.

  19. A challenging interpretation of a hexagonally layered protein structure

    SciTech Connect

    Thompson, Michael C.; Yeates, Todd O., E-mail: yeates@mbi.ucla.edu [UCLA, Los Angeles, CA 90095 (United States)

    2014-01-01

    The authors describe the structure determination of a hexagonally layered protein structure that suffered from a complicated combination of translational non-crystallographic symmetry and hemihedral twinning. This case serves as a reminder that broken crystallographic symmetry resulting from doubling of a unit-cell axis often requires a new choice of origin. The carboxysome is a giant protein complex that acts as a metabolic organelle in cyanobacteria and some chemoautotrophs. Its outer structure is formed by the assembly of thousands of copies of hexameric shell protein subunits into a molecular layer. The structure determination of a CcmK1 shell protein mutant (L11K) from the ?-carboxysome of the cyanobacterium Synechocystis PCC6803 led to challenges in structure determination. Twinning, noncrystallographic symmetry and packing of hexameric units in a special arrangement led to initial difficulties in space-group assignment. The correct space group was clarified after initial model refinement revealed additional symmetry. This study provides an instructive example in which broken symmetry requires a new choice of unit-cell origin in order to identify the highest symmetry space group. An additional observation related to the packing arrangement of molecules in this crystal suggests that these hexameric shell proteins might have lower internal symmetry than previously believed.

  20. Photon Management Structures Originated by Interference Lithography

    Microsoft Academic Search

    Benedikt Bläsi; Hubert Hauser; Oliver Höhn; Volker Kübler; Marius Peters; Andreas J. Wolf

    2011-01-01

    Since micro- and nanostructures for photon management are of increasing importance in novel high efficiency solar cell concepts, structuring techniques with up-scaling potential play a key role for the realization of these concepts.Interference lithography is reviewed as a technology for the origination of fine-tailored two and three dimensional photonic structures on large areas. With the interference pattern of two or

  1. Modelling apparent low thermal inertia by layered structure

    NASA Astrophysics Data System (ADS)

    Yoshida, Akari; Toyota, Takenori; Kurita, Kei

    2013-04-01

    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.

  2. Nucleomorph genomes: structure, function, origin and evolution

    E-print Network

    Archibald, John

    Nucleomorph genomes: structure, function, origin and evolution John M. Archibald Summary and four genomes--two nuclear genomes, an endosymbiont- derived plastid genome and a mitochondrial genome derived from the host cell. Like mitochondrial and plastid genomes, the genome of the endosymbiont nucleus

  3. Plane mixing layer vortical structure kinematics

    NASA Technical Reports Server (NTRS)

    Leboeuf, Richard L.

    1993-01-01

    The objective of the current project was to experimentally investigate the structure and dynamics of the streamwise vorticity in a plane mixing layer. The first part of this research program was intended to clarify whether the observed decrease in mean streamwise vorticity in the far-field of mixing layers is due primarily to the 'smearing' caused by vortex meander or to diffusion. Two-point velocity correlation measurements have been used to show that there is little spanwise meander of the large-scale streamwise vortical structure. The correlation measurements also indicate a large degree of transverse meander of the streamwise vorticity which is not surprising since the streamwise vorticity exists in the inclined braid region between the spanwise vortex core regions. The streamwise convection of the braid region thereby introduces an apparent transverse meander into measurements using stationary probes. These results corroborated with estimated secondary velocity profiles in which the streamwise vorticity produces a signature which was tracked in time.

  4. Ion transport and structure of layer-by-layer assemblies

    E-print Network

    Lutkenhaus, Jodie Lee

    2007-01-01

    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 ...

  5. A sporadic layer in the Venus lower ionosphere of meteoric origin

    Microsoft Academic Search

    M. Pätzold; S. Tellmann; B. Häusler; M. K. Bird; G. L. Tyler; A. A. Christou; P. Withers

    2009-01-01

    The Venus Express Radio Science (VeRa) experiment aboard Venus Express has detected, by means of radio occultation, distinct, low-lying layers of electron density below the base (115 km altitude) of the ionosphere of Venus. A plausible origin of these lowest layers is ionization by the influx of meteoroids into the atmosphere. The layers appeared only occasionally during the 2006 and

  6. The Origins of Subsurface Layers below Tribological Contacts: A Historical Perspective on Research and Understanding

    SciTech Connect

    Blau, Peter Julian [ORNL

    2006-01-01

    Inspired by Sir George Beilby's research on polished surfaces in the 1920's, continuing progress in microscopy and surface probes has furthered understanding of tribo-formed layers. Known by various names, these highly-deformed and textured layers vary in thickness, defect arrangement, and uniformity. Their nature depends on the type of material being deformed and the type of wear process to which the surface is subjected. Under otherwise similar sliding conditions, different highly-deformed structures form in different materials because of the effects of stacking fault energy, the arrangement of phases, and the partition of frictional work into heat, fracture, and deformation. Third-body deposits originating from adhesive transfer and wear can shield the deformed layers, and the periodic growth and removal of plateaus can result in time-dependent variations in friction and wear. Combinations of tribo-contact modes, like impact with fretting, can also affect the nature of the near surface layers and their attendant effects on wear and friction.

  7. Lattice Vibrations and Superconductivity in Layered Structures 

    E-print Network

    Allen, Roland E.; Alldredg, GP; WETTE, FWD.

    1970-01-01

    PHYSICAL REVIEW B VOLUME 2, NUMBER 7 1 OCTOB ER, 1970 Lattice Vibrations and Superconductivity in Layered Structures* B. E. Allen, G. P. Alldredge, and F. W. de bette DePartment of Physics, University of Texas, Austin, Texas 78712 (Received 18... with fre- quency e, and the other symbols have been defined previously. As before, ' all the quantities with which we are presently concerned (e. g. , &u) can be scaled in terms of M and the potential parameters 0 and e, so we will take M=o = & =1...

  8. Electroluminescence in organic films with three-layer structure

    Microsoft Academic Search

    Chihaya Adachi; Shizuo Tokito; Tetsuo Tsutsui; Shogo Saito

    1988-01-01

    A stable organic electroluminescent (EL) device was successfully fabricated with a three-layer structure consisting of hole transport layer\\/emitting layer\\/electron transport layer. The EL device was prepared by vacuum evaporation. Efficient carrier double injection into the emitting layer was realized by the use of separate hole and electron transport layers. Bright EL emission was observed in a darkened room at the

  9. Layered graphene structure of a hexagonal carbon

    NASA Astrophysics Data System (ADS)

    Zhang, Bin

    2013-06-01

    Experiments show that there is a novel hexagonal carbon polymorph restricted to the space group of P-62c, but the detailed atomic structure is not determined. Here we set carbon atoms occupying P-62c 4f or P-62c 2c and 2d Wyckoff positions, and calculate the total energy of the different cell structures changing the internal parameter by first-principles calculations, which demonstrates that the stable structures in energy (at local minima) are hexagonal carbon (P-62c 2c and 2d) and hexagonal diamond (P-62c 4f, z=1/16). The calculated bulk modulus 437±16 GPa and interlayer distance 2.062 Å of the layered graphene structure P-62c 2c and 2d are in good agreement with those of the proposed new carbon, which indicates that P-62c 2c and 2d is a possible precursor or intermediate hard phase during the structural transformation of carbon.

  10. Structural origin of light emission in germanium quantum dots

    PubMed Central

    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

    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

  11. Structural origin of light emission in germanium quantum dots.

    PubMed

    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

    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

  12. Structure and origin of cometary nuclei

    NASA Technical Reports Server (NTRS)

    Donn, B.; Rahe, J.

    1981-01-01

    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.

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

    Microsoft Academic Search

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

    2006-01-01

    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

  14. The formation and evolution of layered structures in porous media

    Microsoft Academic Search

    Stan Schoofs; Ron A. Trompert; Ulrich Hansen

    1998-01-01

    Horizontally layered structures can develop in porous or partially molten environments, such as magma chambers, the early Earth's mantle, and hydrothermal systems. We have studied the generation and evolution of these horizontally layered structures in a rigid porous medium by heating a compositionally stably stratified fluid from below. Growth of a convective layer through entrainment, the formation of a vertical

  15. Sporadic structures in the atmospheric sodium layer

    Microsoft Academic Search

    Barclay R. Clemesha; Paulo P. Batista; Dale M. Simonich; Inez S. Batista

    2004-01-01

    The sporadic occurrence of layers of enhanced concentration of meteoric metals in the vicinity of the mesopause has been observed by lidar at many locations. These layers are much thinner than the background layer, last between a few minutes and many hours, and appear to be related to ionospheric sporadic E. A much more rare type of transient layer has

  16. On the origin of charge-density waves in select layered transition-metal dichalcogenides.

    PubMed

    Rossnagel, K

    2011-06-01

    The occurrence of charge-density waves in three selected layered transition-metal dichalcogenides-1T-TaS(2), 2H-TaSe(2) and 1T-TiSe(2)-is discussed from an experimentalist's point of view with a particular focus on the implications of recent angle-resolved photoelectron spectroscopy results. The basic models behind charge-density-wave formation in low-dimensional solids are recapitulated, the experimental and theoretical results for the three selected compounds are reviewed, and their band structures and spectral weight distributions in the commensurate charge-density-wave phases are calculated using an empirical tight-binding model. It is explored whether the origin of charge-density waves in the layered transition-metal dichalcogenides can be understood in a unified way on the basis of a few measured and calculated parameters characterizing the interacting electron-lattice system. It is found that the predictions of the standard mean-field model agree only semi-quantitatively with the experimental data and that there is not one generally dominant factor driving charge-density-wave formation in this family of layer compounds. The need for further experimental and theoretical scrutiny is emphasized. PMID:21558606

  17. Origin and consequences of silicate glass passivation by surface layers

    NASA Astrophysics Data System (ADS)

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

    2015-02-01

    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.

  18. Origin and consequences of silicate glass passivation by surface layers

    PubMed Central

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

    2015-01-01

    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

  19. Origin and consequences of silicate glass passivation by surface layers.

    PubMed

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

    2015-01-01

    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

  20. Typhoon kinematic and thermodynamic boundary layer structure from dropsonde composites

    NASA Astrophysics Data System (ADS)

    Ming, Jie; Zhang, Jun A.; Rogers, Robert F.

    2015-04-01

    The data from 438 Global Positioning System dropsondes in six typhoons are analyzed to investigate the mean atmospheric boundary layer structure in a composite framework. Following a recent study on boundary layer height in Atlantic hurricanes, we aim to quantify characteristics of boundary layer height scales in Western Pacific typhoons including the inflow layer depth (hinflow), height of the maximum tangential wind speed (hvtmax), and thermodynamic mixed layer depth. In addition, the kinematic and thermodynamic boundary layer structures are compared between the dropsonde composites using data in typhoons and hurricanes. Our results show that similar to the hurricane composite, there is a separation between the kinematic and thermodynamic boundary layer heights in typhoons, with the thermodynamic boundary layer depth being much smaller than hinflow and hvtmax in the typhoon boundary layer. All three boundary layer height scales tend to decrease toward the storm center. Our results confirm that the conceptual model of Zhang et al. (2011a) for boundary layer height variation is applicable to typhoon conditions. The kinematic boundary layer structure is generally similar between the typhoon and hurricane composites, but the typhoon composite shows a deeper inflow layer outside the eyewall than the hurricane composite. The thermodynamic structure of the typhoon boundary layer composite is warmer and moister outside the radius of maximum wind speed than the hurricane composite. This difference is attributed to different environmental conditions associated with typhoons compared to the hurricanes studied here.

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

    E-print Network

    Mendillo, Michael

    A sporadic layer in the Venus lower ionosphere of meteoric origin M. Pa¨tzold,1 S. Tellmann,1 B. Ha October 2008; accepted 29 October 2008; published 12 March 2009. [1] The Venus Express Radio Science (VeRa) experiment aboard Venus Express has detected, by means of radio occultation, distinct, low-lying layers

  2. A dynamic explanation for the origin of the western Mediterranean organic-rich layers

    Microsoft Academic Search

    M. Rogerson; I. Cacho; F. Jimenez-Espejo; M. I. Reguera; F. J. Sierro; F. Martinez-Ruiz; J. Frigola; M. Canals

    2008-01-01

    The eastern Mediterranean sapropels are among the most intensively investigated phenomena in the paleoceanographic record, but relatively little has been written regarding the origin of the equivalent of the sapropels in the western Mediterranean, the organic-rich layers (ORLs). ORLs are recognized as sediment layers containing enhanced total organic carbon that extend throughout the deep basins of the western Mediterranean and

  3. The origin of consistent protein structure refinement from structural averaging.

    PubMed

    Park, Hahnbeom; DiMaio, Frank; Baker, David

    2015-06-01

    Recent studies have shown that explicit solvent molecular dynamics (MD) simulation followed by structural averaging can consistently improve protein structure models. We find that improvement upon averaging is not limited to explicit water MD simulation, as consistent improvements are also observed for more efficient implicit solvent MD or Monte Carlo minimization simulations. To determine the origin of these improvements, we examine the changes in model accuracy brought about by averaging at the individual residue level. We find that the improvement in model quality from averaging results from the superposition of two effects: a dampening of deviations from the correct structure in the least well modeled regions, and a reinforcement of consistent movements towards the correct structure in better modeled regions. These observations are consistent with an energy landscape model in which the magnitude of the energy gradient toward the native structure decreases with increasing distance from the native state. PMID:25960407

  4. Origin and effect of nonlocality in a layered composite.

    SciTech Connect

    Silling, Stewart Andrew

    2014-01-01

    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.

  5. Structural studies on layered alkylpyridinium iodopalladate networks.

    PubMed

    Neve, F; Crispini, A; Francescangeli, O

    2000-03-20

    The reaction of alkylpyridinium (CnH2n + 1NC5H5, hereafter Cn-Py) iodide salts in aqueous acetonitrile with a preformed palladium iodide precursor afforded two different types of organic-inorganic phases depending on the molar ratio. A 2:1 ratio yielded the phase [Cn-Py]2[PdI4] (3, n = 14, 16), which crystallized in the triclinic crystal system. The X-ray crystal structure of 3, (n = 14), refined in the space group P1 (a = 8.918(3) A, b = 9.894(3) A, c = 29.062(12) A, alpha = 93.51(3) degrees, beta = 94.17(3) degrees, gamma = 115.60(3) degrees, and Z = 2), consists of interdigitated bilayers with a basal spacing of 29.0 A. The aliphatic chains of the cations, which run almost parallel to the stacking direction, are fully stretched between polar planes built on isolated [PdI4]2- anions and cation headgroups. Changing the organic cation to palladium ratio to 1:1 led to a new phase [Cn-Py]2[Pd2I6] (4, n = 14, 16), which crystallizes in the triclinic P1 space group (a = 9.399(4) A, b = 14.264(6) A, c = 29.415(13) A, alpha = 92.11(4) degrees, beta = 90.07(4) degrees, gamma = 104.53(3) degrees, Z = 3 for 4(n = 14); a = 9.417(2) A, b = 14.215(3) A, c = 31.552(6) A, alpha = 87.96(3) degrees, beta = 87.63(3) degrees, gamma = 75.67(3) degrees, Z = 3 for 4(n = 16)). The layered structure is basically of a continuously interdigitated single-layer type, with a bilayer sublattice superimposed. Isolated [Pd2I6]2- anions contribute to the inorganic planes. A high degree of interdigitation and tilting of the aliphatic chains lead to basal spacings of 29.4 and 31.5 A for 4(n = 14) and 4(n = 16), respectively. The [Cn-Py]2[PdI4] and [Cn-Py]2[Pd2I6] phases were characterized by thermal analysis. Mesomorphic behavior was observed only for 3(n = 16), which was confirmed by variable-temperature powder XRD and optical microscopy. PMID:12526409

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

    SciTech Connect

    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

    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.

  7. DUAL ORIGIN OF AEROSOLS IN TITAN'S DETACHED HAZE LAYER

    SciTech Connect

    Cours, T.; Burgalat, J.; Rannou, P. [Groupe de Spectrometrie Moleculaire et Atmospherique (GSMA), CNRS UMR-6089, Universite de Reims Champagne-Ardenne, 51687 Reims Cedex 2 (France); Rodriguez, S.; Brahic, A. [Laboratoire AIM, Universite Paris 7, CNRS UMR-7158, CEA-Saclay/DSM/IRFU/SAp, 91191 Gif/Yvette (France); West, R. A., E-mail: thibaud.cours@univ-reims.fr [Jet Propulsion Laboratory M/S 169-237, Pasadena, CA 91109 (United States)

    2011-11-10

    We have analyzed scattered light profiles from the Cassini Imaging Science Subsystem, taken at the limb and at several large phase angles. We also used results from an occultation observed by Ultraviolet Imaging Spectrograph in the ultraviolet. We found that particles responsible for the scattering in the detached haze have an effective radius around 0.15 {mu}m and the aerosol size distribution follows a power law (exponent about -4.5). We discuss these results along with microphysical constraints and thermal equilibrium of the detached haze, and we conclude that only a strong interaction with atmospheric dynamics can explain such a structure.

  8. Multi-layer laminate structure and manufacturing method

    DOEpatents

    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

    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.

  9. Multi-layer laminate structure and manufacturing method

    DOEpatents

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

    2013-01-29

    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.

  10. Mass exchange in the stable boundary layer by coherent structures

    E-print Network

    Leclerc, Monique Y.

    Mass exchange in the stable boundary layer by coherent structures D.I. Cooper a,*, M.Y. Leclerc b December 2004 Abstract Observations of multi-dimensional water vapor structures in the first 75 m of the stable boundary layer (SBL) were made using a high resolution scanning Raman lidar in October 2000 during

  11. Investigating the origin of intense photoluminescence in Si capping layer on Ge1-xSnx nanodots by transmission electron microscopy

    NASA Astrophysics Data System (ADS)

    Kikkawa, Jun; Nakamura, Yoshiaki; Fujinoki, Norihito; Ichikawa, Masakazu

    2013-02-01

    The authors investigated the annealing effects on atomic structures and elemental compositions in a stacking structure, Si capping layer on Ge1-xSnx nanodots on Si substrate covered with ultrathin SiO2 film, to clarify the origin of intense photoluminescence at ˜0.8 eV from the structure, using transmission electron microscopy. After the annealing, it was found that decay of Ge1-xSnx nanodots, formation of SiOx precipitates embedded in Si-rich Si1-xGex layer at the Si cap/Si substrate interface, formation of SnO2 nanoparticles on the oxidized surface of the Si capping layer, and morphological change of dislocations in the Si capping layer occur. Reaction products that appear as a result of the movement of dislocations can be related to the origin of intense photoluminescence.

  12. 1. Building #3, original structure and first addition, north side, ...

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

    1. Building #3, original structure and first addition, north side, looking south. Photo shows (from left) the original 1911 structure, the 1939 infill addition, and the 1934 structure. - S. W. Shattuck Chemical Company, Incorporated, Building No. 3, 1805 South Bannock Street, Denver, Denver County, CO

  13. Zipper layer method for linking two dissimilar structured meshes

    NASA Astrophysics Data System (ADS)

    Wang, Yibin; Qin, Ning; Carnie, Greg; Shahpar, Shahrokh

    2013-12-01

    A novel meshing method named the zipper layer method is presented, which links two topologically different multi-block structured meshes together without overlapping or hanging nodes. It can either locally or globally connect two dissimilar structured meshes with a small number of tetrahedra and pyramids on either side of the interface to form a conformal mesh. To test the method, the results using a zipper layer mesh and a fully structured mesh are compared regarding solution accuracy and convergence. This method has been demonstrated for several applications of turbomachinery interest, where quality multi-block structured meshes are connected and the numerical flow solutions on these zipper layer meshes are also shown.

  14. Tracing Heliospheric Structures to Their Solar Origin

    NASA Astrophysics Data System (ADS)

    Wimmer-Schweingruber, R. F.

    2014-12-01

    The solar wind creates a giant plasma bubble in our immediate, very local interstellar medium (VLISM), the heliosphere. As is true for every physical system, its structure is determined by dynamic processes and by the boundary conditions at the Sun and in the VLISM. Because of the supersonic expansion of the solar wind the structure of the inner (several AU) heliosphere is (nearly) exclusively determined by the Sun. As simple as this may all appear, the problem of linking heliospheric structure to solar features is remarkably complex and has so far eluded satisfactory solutions. ESA and NASA have implemented the Solar Orbiter and Solar Probe Plus missions to tackle and solve the mystery of how the Sun creates and controls the heliosphere. Previous missions, especially the twin Helios mission, lacked two crucial elements, remote-sensing of solar features and their dynamics, and composition measurements of the solar plasma, wind, and energetic particles. Solar Orbiter has both elements in its highly sophisticated payload and will allow us to link solar features to the solar wind sampled in situ by using composition and energetic particles as tracers. The composition of the solar wind is altered from its photospheric origin by two processes very probably acting at different altitudes in the solar atmosphere. Elemental composition of the solar wind appears to be fractionated by its First Ionization Potential (FIP) or time (FIT), indicating that some mechanism separates neutral atoms from ions. This requires temperatures low enough to allow a substantial neutral fraction of the solar plasma and therefore the FIP-effect is believed to act primarily in the chromosphere. Charge states on the other hand are determined by the expansion and acceleration of the solar wind and the electron temperature high in the corona. Solar Orbiter will allow remote-sensing measurements of the elemental composition of solar features and comparison with that measured in situ after the solar wind has traveled from the Sun to the spacecraft. Further information about the linkage between Sun and heliosphere will come from energetic particles which are tightly bound to magnetic field lines and therefore serve as good tracers for the magnetic connection between Sun and heliosphere.

  15. High-pressure layered structure of carbon disulfide

    NASA Astrophysics Data System (ADS)

    Naghavi, S. Shahab; Crespo, Yanier; MartoÅák, Roman; Tosatti, Erio

    2015-06-01

    Solid CS2 is superficially similar to CO2, with the same C m c a molecular crystal structure at low pressures, which has suggested similar phases also at high pressures. We carried out an extensive first-principles evolutionary search in order to identify the zero-temperature lowest-enthalpy structures of CS2 for increasing pressure up to 200 GPa. Surprisingly, the molecular C m c a phase does not evolve into ? -cristobalite as in CO2 but transforms instead into phases HP2 and HP1, both recently described in high-pressure SiS2. HP1 in particular, with a wide stability range, is a layered P 21/c structure characterized by pairs of edge-sharing tetrahedra and is theoretically more robust than all other CS2 phases discussed so far. Its predicted Raman spectrum and pair correlation function agree with experiment better than those of ? -cristobalite, and further differences are predicted between their respective IR spectra. The band gap of HP1-CS2 is calculated to close under pressure, yielding an insulator-metal transition near 50 GPa, in agreement with experimental observations. However, the metallic density of states remains modest above this pressure, suggesting a different origin for the reported superconductivity.

  16. Composite S-layer lipid structures

    PubMed Central

    Schuster, Bernhard; Sleytr, Uwe B.

    2010-01-01

    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

  17. Epitaxial niobium nitride\\/insulator layered structures

    Microsoft Academic Search

    J. Talvacchio; J. R. Gavaler; A. I. Braginski

    1988-01-01

    The properties of niobium nitride\\/insulator multilayers are reviewed. The NbN layers were polycrystalline or (100), (111), (110) or (135) single crystal films. The insulator was a 3 to 50 A thick epitaxial layer of A1âOâ, MgO, or a metastable pseudo-binary compound, Mg1-xCaxO. The particular composition, x=0.27, was chosen to match the oxide lattice constant to that NbN. Superconductive tunneling measurements

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

    SciTech Connect

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

    2014-01-15

    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.

  19. Crystal structure of the eukaryotic origin recognition complex.

    PubMed

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

    2015-03-19

    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

  20. Structural Characterization of Doped Thick Gainnas Layers - Ambiguities and Challenges

    NASA Astrophysics Data System (ADS)

    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

    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

  1. The Levantine Basin—crustal structure and origin

    NASA Astrophysics Data System (ADS)

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

    2006-06-01

    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.

  2. Experimental hydration of two synthetic glassy blast furnace slags in water and alkaline solutions (NaOH and KOH 0.1 N) at 40° C: structure, composition and origin of the hydrated layer

    Microsoft Academic Search

    Z. Rajaokarivony-Andriambololona; J. H. Thomassin; P. Baillif; J. C. Touray

    1990-01-01

    The hydration of blast furnace slags has been modelled using two synthetic (CaO, SiO2, Al2O3, MgO) glasses with different Al2O3\\/MgO values. Experiments (duration: 16 h to 150 d) were performed at 40° C in deionized water (pH 6.5) and in NaOH and KOH (0.1 N) solutions (pH=12.9). The hydrated layer was characterized from a combination of several techniques at different

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

    SciTech Connect

    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

    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.

  4. Prolonged reorganization of thiol-capped Au nanoparticles layered structures

    NASA Astrophysics Data System (ADS)

    Kundu, Sarathi; Das, Kaushik; Konovalov, Oleg

    2013-09-01

    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.

  5. Construction and asymptotic stability of structurally stable internal layer solutions

    Microsoft Academic Search

    Xiao-Biao Lin

    2001-01-01

    We introduce a geometric\\/asymptotic method to treat structurally stable internal layer solutions. We consider asymptotic expansions of the inter- nal layer solutions and the critical eigenvalues that determine their stability. Proofs of the existence of exact solutions and eigenvalue-eigenfunctions are outlined. Multi-layered solutions are constructed by a new shooting method through a sequence of pseudo Poincar e mappings that do

  6. Layer selective control of the lattice structure in oxide superlattices.

    PubMed

    Frano, Alex; Benckiser, Eva; Lu, Yi; Wu, Meng; Castro-Colin, Miguel; Reehuis, Manfred; Boris, Alexander V; Detemple, Eric; Sigle, Wilfried; van Aken, Peter; Cristiani, Georg; Logvenov, Gennady; Habermeier, Hanns-Ulrich; Wochner, Peter; Keimer, Bernhard; Hinkov, Vladimir

    2014-01-15

    A combined synchrotron X-ray diffraction and transmission electron microscopy study reveals a structural phase transition controlled by the overall thickness of epitaxial nickelate-aluminate superlattices. The transition between uniform and twin-domain states is confined to the nickelate layers and leaves the aluminate layers unaffected. PMID:24155253

  7. Turbulence Structure and Wall Signature in Hypersonic Turbulent Boundary Layer

    E-print Network

    Martín, Pino

    Turbulence Structure and Wall Signature in Hypersonic Turbulent Boundary Layer Yin-Chiu Kan , Clara and hypersonic turbulent boundary layer datasets from direct numerical simulation (DNS). Contour plots and Marusic5 and Mathis, Hutchins and Marusic16 ). In contrast to supersonic and hypersonic flow regimes

  8. Optimal shape design for a layered periodic structure 

    E-print Network

    Flanagan, Michael Brady

    2004-09-30

    A multi-layered periodic structure is investigated for optimal shape design in diffraction gratings. A periodic dielectric material is used as the scattering profile for a planar incident wave. Designing optimal profiles for scattering is a...

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

    SciTech Connect

    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

    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.

  10. Efficient vertical mode expansion method for scattering by arbitrary layered cylindrical structures.

    PubMed

    Shi, Hualiang; Lu, Ya Yan

    2015-06-01

    A relatively simple and efficient numerical method is developed for analyzing the scattering of light by a layered cylindrical structure of arbitrary cross section surrounded by a layered background. The method significantly extends an existing vertical mode expansion method (VMEM) for circular or elliptic cylindrical structures. The original VMEM and its extension give rise to effective two-dimensional formulations for the three-dimensional scattering problems of layered cylindrical structures. The extended VMEM developed in this paper uses boundary integral equations to handle the two-dimensional Helmholtz equations that appear in the vertical mode expansion process. The method is applied to analyze the transmission of light through subwavelength apertures in metallic films and the scattering of light by metallic nanoparticles. PMID:26072822

  11. Framework structures of interconnected layers in calcium iron arsenides.

    PubMed

    Stürzer, Tobias; Hieke, Christine; Löhnert, Catrin; Nitsche, Fabian; Stahl, Juliane; Maak, Christian; Pobel, Roman; Johrendt, Dirk

    2014-06-16

    The new calcium iron arsenide compounds Ca(n(n+1)/2)(Fe(1-x)M(x))(2+3n)M'(n(n-1)/2)As((n+1)(n+2)/2) (n = 1-3; M = Nb, Pd, Pt; M' = ?, Pd, Pt) were synthesized and their crystal structures determined by single-crystal X-ray diffraction. The series demonstrates the structural flexibility of iron arsenide materials, which otherwise prefer layered structures, as is known from the family of iron-based superconductors. In the new compounds, iron arsenide tetrahedral layers are bridged by iron-centered pyramids, giving rise to so far unknown frameworks of interconnected FeAs layers. Channels within the structures are occupied with calcium and palladium or platinum, respectively. Common basic building blocks are identified that lead to a better understanding of the building principles of these structures and their relation to CaFe4As3. PMID:24884132

  12. Superconducting structure with layers of niobium nitride and aluminum nitride

    DOEpatents

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

    1989-01-01

    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.

  13. Origin and evolution of the layered deposits in the Valles Marineris, Mars

    NASA Astrophysics Data System (ADS)

    Nedell, S. S.; Squyres, S. W.; Andersen, D. W.

    1987-06-01

    Four hypotheses are discussed concerning the origin of the layered deposits in the Martian Valles Marineris, whose individual thicknesses range from about 70 to 300 m. The hypothesized processes are: (1) aeolian deposition; (2) deposition of remnants of the material constituting the canyon walls; (3) deposition of volcanic eruptions; and (4) deposition in standing bodies of water. The last process is chosen as most consistent with the rhythm and lateral continuity of the layers, as well as their great thickness and stratigraphic relationship with other units in the canyons. Attention is given to ways in which the sediments could have entered an ice-covered lake; several geologically feasible mechanisms are identified.

  14. Structural Origins of Fibrin Clot Rheology

    Microsoft Academic Search

    Esther A. Ryan; Lyle F. Mockros; John W. Weisel; Laszlo Lorand

    1999-01-01

    The origins of clot rheological behavior associated with network morphology and factor XIIIa-induced cross-linking were studied in fibrin clots. Network morphology was manipulated by varying the concentrations of fibrinogen, thrombin, and calcium ion, and cross-linking was controlled by a synthetic, active-center inhibitor of FXIIIa. Quantitative measurements of network features (fiber lengths, fiber diameters, and fiber and branching densities) were made

  15. Population Structure and Modern Human Origins

    Microsoft Academic Search

    Alan R. Rogers

    1997-01-01

    This paper reviews statistical methods for inferring population his- tory from mitochondrial mismatch distributions and extends them to the case of geographically structured populations. Inference is based on a geographically structured version of the coalescent algorithm that allows for temporal variation in population size, in the number of subdivisions, and in the rate of migration between subdivisions. Confidence regions are

  16. Manipulation by exchange coupling in layered magnetic structures

    SciTech Connect

    Moskalenko, M. A. [St. Petersburg National Research University of Information Technologies, Mechanics and Optics, St. Petersburg 197101 (Russian Federation); Science Institute and Faculty of Science, VR-III, University of Iceland, 107 Reykjavík (Iceland); Uzdin, V. M. [St. Petersburg National Research University of Information Technologies, Mechanics and Optics, St. Petersburg 197101 (Russian Federation); St.-Petersburg State University, Ul'yanovskaya ul.1, Petrodvorets, St.-Petersburg 198904 (Russian Federation); Zabel, H. [Department of Physics and Astronomy, Ruhr-University Bochum, 44780 Bochum (Germany)

    2014-02-07

    Exchange coupling in magnetic heterostructures can be modified via introduction of additional magnetic spacer layers at the interfaces. The magnetic characteristics and the spacer layer thickness determine the functional properties of the whole system. We show that the hysteresis loop area of trilayer spring magnets with two different soft magnetic layers (s1, s2) and one hard magnetic layer (h) with the sequence s1/s2/h can be increased as compared to both bilayer structures s1/h and s2/h with the same total thickness of the soft layers and for definite thickness ratios of the soft layers and their sequences. For ferrimagnetic spin valves, the perpendicular exchange bias effect can be tuned via the thickness of non-magnetic spacer layers at the interface, which determine the exchange coupling between ferrimagnets. A simple quasi one-dimensional phenomenological model is able to describe the magnetic hysteresis of even complex layered structures and to predict optimal geometrical and magnetic parameters of such heterostructures.

  17. Super-hydrophobic surfaces of layer-by-layer structured film-coated electrospun nanofibrous membranes

    Microsoft Academic Search

    Tasuku Ogawa; Bin Ding; Yuji Sone; Seimei Shiratori

    2007-01-01

    We have recently fabricated super-hydrophobic membrane surfaces based on the inspiration of self-cleaning silver ragwort leaves. This biomimetic super-hydrophobic surface was composed of fluoroalkylsilane (FAS)-modified layer-by-layer (LBL) structured film-coated electrospun nanofibrous membranes. The rough fibre surface caused by the electrostatic LBL coating of TiO2 nanoparticles and poly(acrylic acid) (PAA) was used to imitate the rough surface of nanosized grooves along

  18. Structure analysis of layer-by-layer multilayer films of colloidal particles

    NASA Astrophysics Data System (ADS)

    Batys, Piotr; Nosek, Magdalena; Wero?ski, Pawe?

    2015-03-01

    We have mimicked the layer-by-layer self-assembling process of monodisperse colloidal particles at a solid-liquid interface using the extended random sequential adsorption model of hard spheres. We have studied five multilayer structures of similar thickness, each created at a different single-layer surface coverage. For each multilayer, we have determined its particle volume fraction as a function of distance from the interface. Additionally, we have characterized the film structure in terms of 2D and 3D pair-correlation functions. We have found that the coverage of about 0.3 is optimal for producing a uniform, constant-porosity multilayer in a minimum number of adsorption cycles. The single-layer coverage has also a significant effect on the primary maximum of 2D radial distribution function. In the case of multilayer with the coverage lower than 0.30 the 2D pair-correlation functions of even layers exhibit maxima decreasing with the increase in the layer number. We have verified our theoretical predictions experimentally. We have used fluorescence microscopy to determine the 2D pair-correlation functions for the second, third, and fourth layers of multilayer formed of micron-sized spherical latex particles. We have found a good agreement between our theoretical and experimental results, which confirms the validity of the extended RSA model.

  19. The structure of a three-dimensional turbulent boundary layer

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

    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.

  20. 79. EAST END OF ORIGINAL 1883 STRUCTURE. LEFT HAND WINDOW ...

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

    79. EAST END OF ORIGINAL 1883 STRUCTURE. LEFT HAND WINDOW ON SECOND FLOOR IS ACTUALLY A SLIDING DOOR, ORIGINALLY USED TO MOVE WAGONS TO AND FROM PAINT SHOP AND STORAGE ON SECOND FLOOR VIA A RAMP. - Gruber Wagon Works, Pennsylvania Route 183 & State Hill Road at Red Bridge Park, Bernville, Berks County, PA

  1. Structure of the regular surface layer of Sporosarcina ureae.

    PubMed Central

    Stewart, M; Beveridge, T J

    1980-01-01

    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

  2. 2. VIEW LOOKING WEST SHOWING STRUCTURE WHICH WAS ORIGINALLY A ...

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

    2. VIEW LOOKING WEST SHOWING STRUCTURE WHICH WAS ORIGINALLY A METHODIST CHURCH AND ONCE THE GARFIELD REFRACTORIES COMPANY OFFICE ON WASHINGTON STREET. - Town of Bolivar, Bolivar, Westmoreland County, PA

  3. 3. Building #3, original structure, east end of south side, ...

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

    3. Building #3, original structure, east end of south side, looking north. Photo shows (on left) the east edge of the second addition. - S. W. Shattuck Chemical Company, Incorporated, Building No. 3, 1805 South Bannock Street, Denver, Denver County, CO

  4. 5. Building #3, original structure, second addition, and first addition ...

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

    5. Building #3, original structure, second addition, and first addition (from right to left), south and east sides, looking northwest. - S. W. Shattuck Chemical Company, Incorporated, Building No. 3, 1805 South Bannock Street, Denver, Denver County, CO

  5. 9. Building #3, interior original structure, south room, looking from ...

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

    9. Building #3, interior original structure, south room, looking from north wall, south. - S. W. Shattuck Chemical Company, Incorporated, Building No. 3, 1805 South Bannock Street, Denver, Denver County, CO

  6. 4. Building #3, original structure, east end of north side, ...

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

    4. Building #3, original structure, east end of north side, looking south. Photo shows (on right) the east edge of the second addition. - S. W. Shattuck Chemical Company, Incorporated, Building No. 3, 1805 South Bannock Street, Denver, Denver County, CO

  7. Lactobacillus surface layer proteins: structure, function and applications.

    PubMed

    Hynönen, Ulla; Palva, Airi

    2013-06-01

    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

  8. Fabrication, structure and properties of aluminum-aluminide layered composites

    SciTech Connect

    Alman, D.E. [Dept. of Energy, Albany, OR (United States). Albany Research Center

    1996-12-31

    The fabrication of aluminum-aluminide layered composites by reactive bonding of elemental Al and Ni foils was investigated. It was observed that after hot-pressing, thin Ni foils were converted to NiAl. The as-processed Al-NiAl layered structure could be heat-treated to produce an equilibrium Al-Al{sub 3}Ni layered composite. Tensile tests revealed that composites could be produced that failed in a tough manner and were stronger and stiffer than aluminum.

  9. Prediction of Silicon-Based Layered Structures for Optoelectronic Applications

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

    A method based on the particle swarm optimization (PSO) algorithm is presented to design quasi-two-dimensional (Q2D) materials. With this development, various single-layer and bi-layer materials in C, Si, Ge, Sn, and Pb were predicted. A new Si bi-layer structure is found to have a much-favored energy than the previously widely accepted configuration. Both single-layer and bi-layer 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 Si8H2andSi6H2 possessing quasi-direct band gaps of 0.75 eV 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.

  10. Gel structure of the corrosion layer on cladding pipes of nuclear fuel

    NASA Astrophysics Data System (ADS)

    Medek, Ji?í; Weishauptová, Zuzana

    2009-09-01

    The fuel material in a nuclear reactor is protected by cladding pipes made of alloyed zirconium. In contact with water near its critical temperature, a corrosion layer of hydrated zirconium dioxide ZrO 2· nH 2O, probably with an amorphous gel structure under given conditions, is formed on the cladding. To verify the presence of the gel structure, an analysis was made by water vapour desorption of the original corrosion oxide layers stored in a given autoclave liquid, their dehydrated modifications, and modifications rehydrated in an aqueous medium. This analysis enabled the varying water content to be determined as a characteristic quantity reflecting the nature of its binding. Microhardness values as a measure of plastic deformation of the crystalline and amorphous forms of zirconium dioxide were also determined. Unambiguous agreement of the results obtained by sorption analysis and by microhardness measurement allows us to conclude that the corrosion layer in situ has properties corresponding to a reversible xerogel.

  11. Structural origins of morphing in plant tissues

    NASA Astrophysics Data System (ADS)

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

    2014-07-01

    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.

  12. Effects of mussel filtering activity on boundary layer structure

    NASA Astrophysics Data System (ADS)

    van Duren, Luca A.; Herman, Peter M. J.; Sandee, Adri J. J.; Heip, Carlo H. R.

    2006-01-01

    The structure of the benthic boundary layer over a bed of mussels ( Mytilus edulis) was investigated in a large racetrack flume. Flow was observed to be modified both by the physical roughness of the mussel bed and by the momentum input of the exhalent jets of the mussels. Particularly when the mussels were closed, and filtering activity was reduced to a minimum, we observed an internal boundary layer, around 4 cm thick, within the log layer. This internal boundary layer was often masked when the mussels were filtering actively. The presence of an internal boundary layer indicates that the boundary layer is not only structured by friction drag, but that form drag due to roughness elements also plays an important role. Consequently, estimates of bed shear stress based on velocity or Reynolds stress measurements carried out more than a few cm above the bed may be inaccurate. Over inactive mussels the shear velocity in the internal boundary layer (the roughness sub-layer) is smaller and bed shear stress is consequently reduced. Filtration activity of the mussels increased the velocity gradient in the lower layer at low and intermediate velocities, but at higher flow rates velocity profiles were not affected. Clear effects of the exhalent jets on absolute levels of TKE could be measured at all ambient velocities, while the effect on the Reynolds stress was limited. Velocity normalised TKE and Reynolds stress also indicated that the effect of the siphonal currents was limited at high velocities. Our results indicate that mussel filtration activity may have an important effect on exchange processes at the sediment-water interface, but that the extent of the effect is highly dependent on the ambient flow conditions.

  13. Memory effect from charge trapping in layered organic structures

    Microsoft Academic Search

    Sung Hoon Kang; Todd Crisp; Ioannis Kymissis; Vladimir Bulovic

    2004-01-01

    We demonstrate organic light emitting devices (OLEDs) with a charge trap layer that show memory behavior. These OLEDs demonstrate that organic heterojunction structures can controllably trap and release electronic charges. The trap layer is either 5-nm-thick clustered silver islands, or a 10-nm-thick organic laser dye DCM2 ([2-methyl-6-[2-(2,3,6,7-tetrahydro-1H,5H-benzo[i,j]quinolizin-9-yl)-ethenyl]-4H-pyran-4-ylidene] propane-dinitrile) doped into TPD (N,N'-diphenyl-N,N'-bis(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine). Predictions of the energy band structure indicate that

  14. Microscopic origins for stabilizing room-temperature ferromagnetism in ultrathin manganite layers

    PubMed Central

    Kourkoutis, L. Fitting; Song, J. H.; Hwang, H. Y.; Muller, D. A.

    2010-01-01

    La0.7Sr0.3MnO3 is a conducting ferromagnet at room temperature. Combined with thin SrTiO3 layers, the resulting heterostructures could be used as highly spin-polarized magnetic-tunnel-junction memories. However, when shrunk to dimensions below an apparent critical thickness, the structures become insulating and ferromagnetic ordering is suppressed. Interface spin and charge modulations are thought to create an interfacial dead layer, thus fundamentally limiting the use of this material in atomic-scale devices. The thickness of this dead layer, and whether it is intrinsic, is still controversial. Here we use atomic-resolution electron spectroscopy to demonstrate that the degradation of the magnetic and transport properties of La0.7Sr0.3MnO3/SrTiO3 multilayers correlates with atomic intermixing at the interfaces, and the presence of extended two-dimensional cation defects in the La0.7Sr0.3MnO3 layers (in contrast to three-dimensional precipitates in thick films). When these extrinsic defects are eliminated, metallic ferromagnetism at room temperature can be stabilized in five-unit-cell-thick manganite layers in superlattices, placing the upper limit for any intrinsic dead layer at two unit cells per interface. PMID:20547875

  15. TEMPERATURE STRUCTURE OF PROTOPLANETARY DISKS UNDERGOING LAYERED ACCRETION

    SciTech Connect

    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

    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.

  16. Structural Origins of Aminoglycoside Specificity for Prokaryotic Ribosomes

    E-print Network

    Puglisi, Joseph

    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

  17. Population Structure and Modern Human Origins Alan R. Rogers

    E-print Network

    Rogers, Alan R.

    Population Structure and Modern Human Origins Alan R. Rogers 1997 Abstract This paper reviews statistical methods for inferring population his- tory from mitochondrial mismatch distributions and extends them to the case of geographically structured populations. Inference is based on a geographically

  18. ORIGINAL PAPER Biotic and abiotic factors affecting the genetic structure

    E-print Network

    ORIGINAL PAPER Biotic and abiotic factors affecting the genetic structure and diversity. To manage the remaining pop- ulations effectively, information regarding how butternut's population genetic structure is affected by environmental and historical factors is needed. In this study, we assessed genetic

  19. Original article Genetic diversity and population structure of Plasmodium falciparum

    E-print Network

    are causative agents in humans, Plasmodium falciparum, P. vivax, P. malariae and P. ovale, the first accountsOriginal article Genetic diversity and population structure of Plasmodium falciparum isolates from the genetic diversity and the population structure of 32 Plasmodium falciparum blood sample isolates (25 from

  20. Structural properties of replication origins in yeast DNA sequences

    NASA Astrophysics Data System (ADS)

    Cao, Xiao-Qin; Zeng, Jia; Yan, Hong

    2008-09-01

    Sequence-dependent DNA flexibility is an important structural property originating from the DNA 3D structure. In this paper, we investigate the DNA flexibility of the budding yeast (S. Cerevisiae) replication origins on a genome-wide scale using flexibility parameters from two different models, the trinucleotide and the tetranucleotide models. Based on analyzing average flexibility profiles of 270 replication origins, we find that yeast replication origins are significantly rigid compared with their surrounding genomic regions. To further understand the highly distinctive property of replication origins, we compare the flexibility patterns between yeast replication origins and promoters, and find that they both contain significantly rigid DNAs. Our results suggest that DNA flexibility is an important factor that helps proteins recognize and bind the target sites in order to initiate DNA replication. Inspired by the role of the rigid region in promoters, we speculate that the rigid replication origins may facilitate binding of proteins, including the origin recognition complex (ORC), Cdc6, Cdt1 and the MCM2-7 complex.

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

    NASA Astrophysics Data System (ADS)

    Egorova, V.; Latypov, R.

    2012-04-01

    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.

  2. Coherent structures in compressible free-shear-layer flows

    SciTech Connect

    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

    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.

  3. Improvement in photoconductor film properties by changing dielectric layer structures

    NASA Astrophysics Data System (ADS)

    Kim, S.; Oh, K.; Lee, Y.; Jung, J.; Cho, G.; Jang, G.; Cha, B.; Park, J.; Nam, S.

    2011-01-01

    In recent times, digital X-ray detectors have been actively applied to the medical field; for example, digital radiography offers the potential of improved image quality and provides opportunities for advances in medical image management, computer-aided diagnosis and teleradiology. In this study, two candidate materials (HgI2 and PbI2) have been employed to study the influence of the dielectric structure on the performance of fabricated X-ray photoconducting films. Parylene C with high permittivity was deposited as a dielectric layer using a parylene deposition system (PDS 2060). The structural and morphological properties of the samples were evaluated field emission scanning electron microscopy and X-ray diffraction. Further, to investigate improvements in the electrical characteristics, a dark current in the dark room and sensitivity to X-ray exposure in the energy range of general radiography diagnosis were measured across the range of the operating voltage. The electric signals varied with the dielectric layer structure of the X-ray films. The PbI2 film with a bottom dielectric layer showed optimized electric properties. On the other hand, in the case of HgI2, the film with a top dielectric layer showed superior electric characteristics. Further, although the sensitivity of the film decreased, the total electrical efficiency of the film improved as a result of the decrease in dark current. When a dielectric layer is deposited on a photoconductor, the properties of the photoconductor, such as hole-electron mobility, should be considered to improve the image quality in digital medical imaging application. In this study, we have thus demonstrated that the use of dielectric layer structures improves the performance of photoconductors.

  4. Love wave propagation in layered magneto-electro-elastic structures

    E-print Network

    Wang, Ji

    Love wave propagation in layered magneto-electro-elastic structures with initial stress J. Du, X: April 11, 2007 Ó Springer-Verlag 2007 Summary. An analytical approach is taken to investigate Love wave of the Love wave is numerically calculated for the magneto-electrically open and short cases, respectively

  5. Using Layer-Cake Geology to Illustrate Structural Topographic Relationships.

    ERIC Educational Resources Information Center

    Wagner, John Robert

    1987-01-01

    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)

  6. Layered Structure and Management in Internet of Things

    Microsoft Academic Search

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

    2007-01-01

    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

  7. Effects of mussel filtering activity on boundary layer structure

    Microsoft Academic Search

    Luca A. van Duren; Peter M. J. Herman; Adri J. J. Sandee; Carlo H. R. Heip

    2006-01-01

    The structure of the benthic boundary layer over a bed of mussels (Mytilus edulis) was investigated in a large racetrack flume. Flow was observed to be modified both by the physical roughness of the mussel bed and by the momentum input of the exhalent jets of the mussels. Particularly when the mussels were closed, and filtering activity was reduced to

  8. Large-Scale Streamwise Turbulent Structures in Hypersonic Boundary Layers

    E-print Network

    English, Benjamin L.

    2013-04-22

    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...

  9. Turbulence Structure and Wall Signature in Hypersonic Boundary Layer

    E-print Network

    Martín, Pino

    Turbulence Structure and Wall Signature in Hypersonic Boundary Layer Yin-Chiu Kan , Beekman Izaak and low- speed features, found in subsonic experiments, are present in our supersonic and hypersonic and hypersonic regimes due to the lack of detailed flow field data, and the studies have been mostly restricted

  10. Large-Scale Streamwise Turbulent Structures in Hypersonic Boundary Layers 

    E-print Network

    English, Benjamin L.

    2013-04-22

    Prior research in the field of boundary layer turbulence has identified streamwise-elongated large-scale turbulence structures in both low speed compressible and high speed (M=2.0) flow. No experimental work has been done in any flow of M> or =3...

  11. Thermal and wind structure of the monsoon trough boundary layer

    NASA Astrophysics Data System (ADS)

    Rajkumar, G.; Narasimha, R.; Singal, S. P.; Gera, B. S.

    1996-09-01

    Radiosonde data from Jodhpur, taken at 0530, 1730 and around 1100 hr IST during MONTBLEX 1990, reveal that the distribution of virtual potential temperature 0 v below about 500 hPa has a structure characterized by up to three layers each of approximately constant gradient. We are thus led to introduce a characterization of the observed thermal structure through a sequence of the symbols N, S and U, standing respectively for neutral, stable or unstable conditions in the different layers, beginning with the one closest to the ground. It is found that, of the 29 combinations possible, only the seven classes, S, SS', SNS', NS, NSS', USS' and UNS are observed, where S' stands for a stable layer with a different gradient of 0 r. than in the layer S. It is also found that, in 90% of the launches at 0530 hr, 48% of the launches at 1730 hr and 69% of the launches around 1100 hr, the first radiosonde layer near the ground is stable; the classical mixed layer was found in only 11 % of the data set analysed, and, if present on other occasions, must have been less than 250 m in height, the first level at which radiosonde data are available. Supplementing the above data, sodar echograms, available during 82% of the time between June and August 1990, suggest a stable layer up to a few tens of metres 48% of the time. A comparative study of the radiosonde data at Ranchi shows that the frequent prevalence of stability near the surface at Jodhpur cannot be attributed entirely to the large scale subsidence known to be characteristic of the Rajasthan area. Further, data at Jodhpur reveal a weak low level jet at heights generally ranging from 400 to 900 m with wind speeds of 6 to 15 m/s. Based on these results, it is conjectured that the lowest layers in the atmosphere during the monsoons, especially with heavy clouding or rain, may frequently be closer to the classical nocturnal boundary layer than to the standard convective mixed layer, although often with shallow plumes that penetrate such a stable layer during daytime.

  12. Structure change, layer sliding, and metallization in high-pressure MoS2

    NASA Astrophysics Data System (ADS)

    Tosatti, Erio; Hromadova, Liliana; Martonak, Roman

    2013-03-01

    Based on ab initio calculations and metadynamics simulations, we predict that 2H-MoS2, a layered insulator, will metallize under pressures in excess of 20-30 GPa. In the same pressure range, simulations and enthalpy optimization predict a structural transition. Reminiscent of this material's frictional properties, free mutual sliding of layers takes place at this transition, where the original 2Hc stacking changes to a 2Ha stacking typical of 2H-NbSe2, a transformation which explains for the first time previously mysterious X-ray diffraction data. Phonon and electron phonon calculations suggest that metallic pristine MoS2 will require ultrahigh pressures in order to develop superconductivity. Based on ab initio calculations and metadynamics simulations, we predict that 2H-MoS2, a layered insulator, will metallize under pressures in excess of 20-30 GPa. In the same pressure range, simulations and enthalpy optimization predict a structural transition. Reminiscent of this material's frictional properties, free mutual sliding of layers takes place at this transition, where the original 2Hc stacking changes to a 2Ha stacking typical of 2H-NbSe2, a transformation which explains for the first time previously mysterious X-ray diffraction data. Phonon and electron phonon calculations suggest that metallic pristine MoS2 will require ultrahigh pressures in order to develop superconductivity. Supported by EU-Japan Project LEMSUPER, by a SNF Sinergia Project, and by the Slovak Research and Development Agency

  13. Investigation Of Boundary Layers Fine Structure In Arid Regions

    NASA Astrophysics Data System (ADS)

    Golitsyn, G. S.; Granberg, I. G.; Andronova, A. V.; Zilitinkevich, S. S.; Smirnov, V. V.; Ponomarev, V. M.

    In connection with insufficiency of the quantitative items of information about the structure of surface and boundary layers structure of the atmosphere in the periods previous dusty ejection, and also absence of the description of an arid atmospheres micrometeorological mode, when the dry spreading surface thermally is non-uniform, that is characteristic for midday hours, the forwarding researches of fine structure of boundary layers in deserted regions of Kalmykia (1995-1997) and on dried bottom of the Aral sea (1991-1992 and in 1998) were carried out. Is was established that in dry hot weather above sandy "saucers" at heights of 1-2 meters there are micro- inversions of temperature and humidity. On our supervisions, this process occurs at temperatures of air above 25 deg.C and relative humidity less than 40%. Thus the gra- dient of temperature in bottom (5 cm) layer in absence of an external wind reaches 200-500 , i.e., arises strongly unstable subsurface boundary layer. Thus during dehydration of aggregate particles consisting, as has shown the soil anal- ysis, from particles of size 80-150 microns, the organic-mineral compositions (OMC) are allocated, and the thin-dispersion aerosol is formed. These thin-dispersion par- ticles (0.01-0.1 microns) first accumulate in this layer, and then at the expense of strong temperature (vertical and horizontal) gradient pass through viscous sub-layer and rise above, as whirlwinds - standing motionless thermics, or dust-devils, or as sim- ple convective of flows. During investigations, is was established, that in a hot season in absence of dusty storms convective processes lift into air from sandy landscapes of Kalmykia and Sub-Aral regions, consisting from aggregate particles, significant amounts of long-living aerosol of size less than 5 microns (including thin-dispersion (0.01-0.1 microns) aerosol), which renders essential influence on formation of aerosol pollution of an atmosphere and, thus, on a climate. Is was established, that the in- termediate condition between unstable and homogeneous atmosphere is characteristic for a structure of a boundary layer during dusty ejection. The analysis of the basic characteristics of boundary layers fine structure in deserted regions was carried out.

  14. Natural large-scale structures in the axisymmetric mixing layer

    NASA Technical Reports Server (NTRS)

    Zaman, K. B. M. Q.; Hussain, A. K. M. F.

    1984-01-01

    The present study is concerned with the optimization of conditional sampling techniques for eduction of naturally occurring large-scale structures in an axisymmetric mixing layer, and a comparison of the natural structure with that induced by means of controlled excitation. Questions regarding the sensitivity of the educed structure to the excitation amplitude are also explored. Aspects regarding the eduction with the high-speed-side reference signal are considered, taking into account structure identification, the smearing effect and a comparison with the structure under excitation, the effects of the threshold level, and the effect of a trigger-level window. Attention is given to structure characteristics and their dependence on Reynolds number and initial condition.

  15. 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)

    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

    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.

  16. Electronic Structures of Single-Layer Boron Pnictides

    NASA Astrophysics Data System (ADS)

    Zhuang, Houlong L.; Hennig, Richard G.

    2013-03-01

    Single layered materials such as graphene and boron nitride promise alternative routes to electronic devices. We use density-functional calculations to identify potential novel 2D materials in the boron pnictide family and determine their stability and electronic properties.[1] Hybrid density functional calculations show that BN, BP, BAs and BSb in this family exhibit a direct bandgap of 6.1, 1.4, 1.2 and 0.6 eV, respectively, that originates from the energy difference of the pz orbitals of the species and is tunable by strain. The bandgap linearly decreases with strain for BN, while it increases non-linearly for BP, BAs, and BSb. The calculated natural band offsets between the various boron pnictides are all of type I. We expect that these results will provide valuable guidance in designing electronic devices based on single-layer boron pnictides.

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

    PubMed Central

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

    2014-01-01

    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

  18. 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

  19. Effects of image charges on double layer structure and forces.

    PubMed

    Wang, Rui; Wang, Zhen-Gang

    2013-09-28

    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. PMID:24089790

  20. Photothermoacoustic oscillations in a solid-piezoelectric layered structure

    NASA Astrophysics Data System (ADS)

    Kozachenko, V. V.; Kucherov, I. Ya.

    2004-03-01

    Photothermoacoustic oscillations in a thin plane-layered structure consisting of an isotropic solid and a piezoelectric crystal of class 6 mm (or piezoelectric ceramics) are studied theoretically and experimentally. Expressions for the potential difference across an arbitrary layer of the piezoelectric transducer are derived. For the case of a two-layer transducer, the amplitude-frequency and phase-frequency dependences of the signal are analyzed. It is shown that, from these experimental dependences, one can determine certain elastic and thermal parameters of a solid. An experiment is performed with samples of Cu, Zn, and TsTS-19 piezoceramics in the frequency range within 9 1000 Hz. The experimental data are used to determine the values of the reduced Young’s modulus and the thermal diffusivity of the materials under study.

  1. The origins of planar magnetic structures in the solar wind

    NASA Technical Reports Server (NTRS)

    Neugebauer, M.; Clay, D. R.; Gosling, J. T.

    1993-01-01

    It is shown that the solar-wind settings of planar magnetic structures (PMSs) are generally inconsistent with their interpretation by Nakagawa et al. (1989) as magnetic loops or tongues resulting from newly emerging magnetic flux in the photosphere. It is suggested that PMS events have two origins: (1) compression and/or draping of preexisting magnetic structures on the leading edge of high-speed streams, especially ahead of coronal mass ejections; and (2) discontinuities near the heliospheric current sheet.

  2. Influence of Coulomb collisions on the structure of reconnection layers

    SciTech Connect

    Daughton, W.; Roytershteyn, V.; Albright, B. J.; Yin, L.; Bowers, Kevin J. [Los Alamos National Laboratory, Los Alamos, New Mexico 87544 (United States); Karimabadi, H. [University of California, San Diego, La Jolla, California 92093 (United States)

    2009-07-15

    The influence of Coulomb collisions on the structure of reconnection layers is examined in neutral sheet geometry using fully kinetic simulations with a Monte Carlo treatment of the Fokker-Planck operator. The algorithm is first carefully benchmarked against key predictions from transport theory, including the parallel and perpendicular resistivities as well as the thermal force. The results demonstrate that the collisionality is accurately specified, thus allowing the initial Lundquist number to be chosen as desired. For modest Lundquist numbers S < or approx. 1000, the classic Sweet-Parker solution is recovered. Furthermore, a distinct transition to a faster kinetic regime is observed when the thickness of the resistive layer {delta}{sub SP} falls below the ion inertial length d{sub i}. For higher Lundquist numbers S > or approx. 1000, plasmoids (secondary islands) are observed within the elongated resistive layers. These plasmoids give rise to a measurable increase in the reconnection rate and for certain cases induce a transition to kinetic regimes sooner than expected from the {delta}{sub SP}{approx_equal}d{sub i} condition. During this transition, the reconnection electric field exceeds the runaway limit, leading to electron scale current layers in which the nonideal electric field is supported predominantly by off-diagonal components in the electron pressure tensor, along with a residual contribution from electron-ion momentum exchange. These weakly collisional electron layers are also unstable to the formation of new plasmoids.

  3. Boundary Layer Dynamical Structure During Secondary Eyewall Formation

    NASA Astrophysics Data System (ADS)

    Abarca, S. F.; Montgomery, M. T.; McWilliams, J. C.

    2014-12-01

    Secondary eyewall formation (SEF) is widely recognized as an important research problem in the dynamics of mature tropical cyclones. It has been shown that the development of the wind maxima in SEF occurs within the boundary layer and that it follows a chain of events initiated by a substantial radial expansion of the tangential wind field. In this context, there is not yet a consensus on the phenomenon's essential physics. It has been proposed that the boundary-layer dynamics of a maturing hurricane vortex is an important controlling element in SEF. However, recent literature also argues that hurricane boundary layers and the related coupling with the interior flow can be described through an Ekman-like balance and that shock-like structures are relevant in the swirling boundary layer of the inner core of mature storms. We analyze the radial and vertical structure of the specific forces and accelerations in in the boundary layer in a mature hurricane that includes a canonical eyewall replacement cycle. The case occurred in a mesoscale, convection-permitting numerical simulation of a tropical cyclone, integrated from an initial weak mesoscale vortex in an idealized quiescent environment. The simulation has been studied extensively in the literature. We find that momentum advection is almost everywhere important (some of it is associated with asymmetric eddies). We discuss the implication of our findings on the proposed importance of Ekman-like balance dynamics during SEF. Finally, our analysis does not support the recently proposed idea that the radial advection of radial momentum, and shock-like structures, are closely related to the supergradient wind phenomena observed during SEF.

  4. Nonlinear Stability and Structure of Compressible Reacting Mixing Layers

    NASA Technical Reports Server (NTRS)

    Day, M. J.; Mansour, N. N.; Reynolds, W. C.

    2000-01-01

    The parabolized stability equations (PSE) are used to investigate issues of nonlinear flow development and mixing in compressible reacting shear layers. Particular interest is placed on investigating the change in flow structure that occurs when compressibility and heat release are added to the flow. These conditions allow the 'outer' instability modes- one associated with each of the fast and slow streams-to dominate over the 'central', Kelvin-Helmholtz mode that unaccompanied in incompressible nonreacting mixing layers. Analysis of scalar probability density functions in flows with dominant outer modes demonstrates the ineffective, one-sided nature of mixing that accompany these flow structures. Colayer conditions, where two modes have equal growth rate and the mixing layer is formed by two sets of vortices, offer some opportunity for mixing enhancement. Their extent, however, is found to be limited in the mixing layer's parameter space. Extensive validation of the PSE technique also provides a unique perspective on central- mode vortex pairing, further supporting the view that pairing is primarily governed perspective sheds insight on how linear stability theory is able to provide such an accurate prediction of experimentally-observed, fully nonlinear flow phenomenon.

  5. ORIGINAL PAPER Colony social structure in native and invasive populations

    E-print Network

    Goodisman, Michael

    the most inva- sive of terrestrial species. The success of invasive social insects stems, in part, from understand variation in social phenotype in invasive social species. We found that (1) nestmate workersORIGINAL PAPER Colony social structure in native and invasive populations of the social wasp

  6. Original article Structure and fractal dimensions of root systems

    E-print Network

    Paris-Sud XI, Université de

    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

  7. Original article Structure and development of vegetative buds,

    E-print Network

    Paris-Sud XI, Université de

    Original article Structure and development of vegetative buds, from the lower crown of Picea abies in the development of Norway spruce (Picea abies (L) Karst) vege- tative buds in the lower crown position of 4 18-year-old free standing grafts in the climatic conditions of Poland are described. Bud awakening varies

  8. ORIGINAL ARTICLE The phylogenetic composition and structure of

    E-print Network

    Minnesota, University of

    .99; published online 28 July 2011 Subject Category: microbial population and community ecology Keywords: soilORIGINAL ARTICLE The phylogenetic composition and structure of soil microbial communities shifts and primary productivity have been established, its impacts on the diversity and function of soil microbial

  9. ORIGINAL ARTICLE The phylogenetic composition and structure of

    E-print Network

    Weiblen, George D

    :10.1038/ismej.2011.99 Subject Category: microbial population and community ecology Keywords: soilORIGINAL ARTICLE The phylogenetic composition and structure of soil microbial communities shifts and primary productivity have been established, its impacts on the diversity and function of soil microbial

  10. 10. KIDNER BRIDGE STRUCTURAL STEEL DETAIL SHEET (original plan sheet ...

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

    10. KIDNER BRIDGE STRUCTURAL STEEL DETAIL SHEET (original plan sheet is in possession of Ball State University, Drawings and Documents Archive, COllege of Architecture and Planing, Ball State University, Muncie, Indiana, 47306 - Kidner Bridge, Spanning Mississinewa River at County Road 700 South, Upland, Grant County, IN

  11. The origin of layered gabbros from the mid lower ocean crust, Hess Deep, East Pacific Rise

    NASA Astrophysics Data System (ADS)

    Cheadle, M. J.; Brown, T. C.; Ceuleneer, G.; Meyer, R.

    2014-12-01

    IODP Exp. 345 Holes U1415 I & J cored a ~30m thick unit of conspicuously layered gabbroic rocks from the lower plutonic crust at Hess Deep. These rocks likely come from >1500m below the dike gabbro transition and thus provide an unique opportunity to study the origin of layering and the formation of relatively deep, fast spread plutonic crust formed at the EPR. Here we report the initial results of a comprehensive high-resolution petrologic, geochemical and petrographic study of this unit, which focuses on a fairly continuous 1.5m long section recovered at Hole I. The rocks consist of opx-bearing olivine gabbro, olivine gabbro and gabbro and exhibit 1-10cm scale modal layering. Some layers host spectacular 2-3 cm diameter cpx oikocrysts encapsulating partially resorbed plagioclase laths. Downhole variations in mineral chemistry are complicated. Olivine, cpx and opx Mg#'s partly reflect equilibration and show a subtle metre-scale variation (1-2 Mg#), whereas, for example, plagioclase anorthite, and cpx TiO2 contents reveal a more complicated 10-20 cm-scale variation (2-4 An, and 0.2 TiO2). Mineral zonation, for all but Mg# in equilibrated olivine, is of higher magnitude than downhole variations in average mineral compositions. Trace element geochemistry reveals rather homogeneous plagioclase and opx compositions; however cpx exhibits variation at the mineral scale. Cpx shows an increased range of, and highest REE concentrations, in the more olivine rich, near cotectic, composition gabbros, whereas the more plagioclase rich, cumulates show no variation of, and low REE, concentrations.Plagioclase fabrics are moderate to weak and partially modally controlled, but the strength of the plagioclase crystallographic preferred orientation (CPO) varies dramatically, within the 1.5m core showing a significant part of the variation recorded by Oman ophiolite plutonic crust. Plagioclase shape preferred orientation and CPO match well suggesting that diffusion enabled compaction was not significant. Overall, our combined observations and the similarity of composition and textures to those found in the Rum layered mafic intrusion (Scotland); an intrusion built by multiple ~100m thick replenishments of magma, suggests that the studied layered sequence is best interpreted as having formed in a lower crustal sill.

  12. Redox Active Layer-by-Layer Structures containing MnO2 Nanoparticles

    SciTech Connect

    Bazito, Fernanda; O'Brien, Robert; Buttry, Daniel A.

    2005-02-01

    Nanoscale materials provide unique properties that will enable new technologies and enhance older ones. One area of intense activity in which nanoscale materials are being used is in the development of new functional materials for battery applications. This effort promises superior materials with properties that circumvent many of the problems associated with traditional battery materials. Previously we have worked on several approaches for using nanoscale materials for application as cathode materials in rechargeable Li batteries. Our recent work has focused on synthesizing MnO2 nanoparticles and using these in layer-by-layer (LbL) structures to probe the redox properties of the nanoparticles. We show that the aqueous colloidal nanoparticles produced by butanol reduction of tetramethylammonium permanganate can be trapped in thin films using a layer-by-layer deposition approach, and that these films are both redox active and exhibit kinetically facile electrochemical responses. We show cyclic voltammetry of MnO2 colloidal nanoparticles entrapped in a LbL thin film at an ITO electrode surface using poly(diallyldimethylammonium chloride) (PDDA). CV experiments demonstrate that Li+ insertion accompanies Mn(IV) reduction in LiClO4 supporting electrolytes, and that reduction is hindered in supporting electrolytes containing only tetrabutylammonium cations. We also show that electron propagation through multilayer films is facile, suggesting that electrons percolate through the films via electron exchange between nanoparticles.

  13. Original size of the Vredefort structure, South Africa

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

    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.

  14. Structure of polymer layers adsorbed from concentrated solutions

    NASA Astrophysics Data System (ADS)

    Auvray, Loïc; Auroy, Philippe; Cruz, Margarida

    1992-06-01

    We study by neutron scattering the interfacial strucuture of poly(dimethylsiloxane) layers irreversibly adsorbed from concentrated solutions or melts. We first measure the thickness h of the layers swollen by a good solvent as a function of the chain polymerisation index N and of the polymer volume fraction in the initial solution ?. The relation h ? N^{0.8}?^{0.3}, recently predicted from an analogy between irreversibly adsorbed layers and grafted polymer brushes, describes well our results. We can therefore deduce that there is at least one large loop of about N monomers per adsorbed chain. We also study the shape of the polymer concentration profile in the layers by measuring on two samples the polymer-solid partial structure factor, that is proportional to the Fourier transform of the profile. The model of pseudobrushes predicts a concentration decay varying with the distance of the wall z as z^{-2/5}. This power law profile accounts quantitatively for the angular variation of the polymer-solid cross structure factor but it is difficult to distinguish it without anbiguity from less singular profiles. It implies that the adsorption of PDMS onto silica is sufficiently strong and fast to quench completely the loop distribution in the initial layer. Nous étudions par diffusion de neutrons la structure interfaciale de couches de poly(diméthylsiloxane) irréversiblement adsorbées sur de la silice à partir de solutions semidiluées et de fondus. Nous mesurons d'abord l'épaisseur h des couches gonflées par un bon solvant en fonction du degré de polymérisation des chaînes N et de la fraction volumique dans la solution initiale ?. La relation h? N^{0.8}?^{0.3} récemment prédite à partir de l'analogie entre couches irréversiblement adsorbées et brosses de polymères greffés décrit bien nos résultats. Nous en déduisons qu'il existe au moins une grande boucle d'environ N monomères par chaîne adsorbée. Nous étudions aussi la forme du profil de concentration en polymère près de la paroi en mesurant sur deux échantillons le facteur de structure partiel polymère-solide qui est proportionnel à la transformée de Fourier du profil. Le modèle de pseudo-brosse prévoit une décroissance de la concentration avec la distance à la paroi z en z^{-2/5}. Ce profil en loi de puissance rend quantitativement compte de la dépendance angulaire du facteur de structure croisé polymère-solide, mais il est difficile de le distinguer sans ambiguïté de profils moins singuliers. Il implique que l'adsorption du PDMS sur la silice est suffisamment forte et rapide pour geler complètement la structure des boucles dans la couche adsorbée initiale.

  15. Effect of layered composite meta-structures on the optical activity and ellipticity of structural biomolecules

    NASA Astrophysics Data System (ADS)

    Khoo, E. H.; Hor, Y. Li; Leong, Eunice S. P.; Liu, Y. J.

    2014-09-01

    In this paper, we design layered composite meta-structures to investigate its' effect on the optical activity and circular dichroism (CD). The layered composite meta-structures consist of thin gammadion nanostructure with thickness ?/10, where ? is the incident wavelength. The layered meta-structures are alternate between a dielectric and gold (AU) material. Each layered composite meta-gammadion is arranged together in an array of pitch 700 nm. In the first case, 3 layers of meta-gammadion, with metal-insulator-metal (MIM) and insulator-metal-insulator (IMI) configuration are simulated with material properties from optical hand book. There are 3 modes in the CD spectrum, which can be characterized into Bloch CD mode and hybrid CD modes. Compared with the CD spectrum of whole structure of gammadion in gold with same total height, the CD of the MIM layered composite are larger. When the number layer increase to 5, it is observed that the CD is reduced by 30% and there is a red shift in the Bloch CD mode and a slight blue shift in the hybrid CD modes. By further increasing the number of layers to 7, we observed further CD increment and larger wavelength shift in the CD modes. The layered composite meta-gammadion is fabricated using template stripping method. Experimental results also show excellent agreement with the simulation results for CD and wavelength shift. We submerge the layered meta-gammadion into a solution of chiral molecules. The CD spectrum of the meta-gammadion shows a larger wavelength shift compared to pure metal structures. This indicate a more sensitive and robust detection of chiral molecules.

  16. Impact origin of the Sudbury structure: Evolution of a theory

    NASA Technical Reports Server (NTRS)

    Lowman, Paul D., Jr.

    1992-01-01

    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.

  17. Micromechanical behavior of adhesive granular silica layers: Structure deformation.

    PubMed

    Uricanu, V I; Duits, M H G

    2006-08-29

    We studied the mechanical behavior of packed layers of 1-mum-sized silica particles immersed in liquids, upon indentation with a 10-mum glass sphere, attached to the cantilever of an atomic force microscope (AFM). Simultaneously, a confocal scanning laser microscope (CSLM) was used to study the deformations in the material. Our liquids consisted of (nearly) refractive-index-matching water-DMSO mixtures. Particle layers were formed by sedimentation in normal gravity. In the absence of (added) electrolyte, the collective behavior of the layer is reminiscent of that of a simple liquid. Crystal-like structures were observed, with the individual particles showing positional fluctuations. Carefully adding 2 wt % LiCl to this system leads to the formation of a weakly aggregated network, in which the crystal-like order gets lost and the particles lose their mobility. On indenting into these aggregated layers, the CSLM recordings showed imprints that closely resembled the size and shape of the indenter. A more accurate inspection of the structural changes was allowed after localizing all silica particles in three dimensions. Calculated local concentrations and coordination numbers showed that even at the level of these highly local quantities, no deformation gradients could be observed in the vicinity of the probe. Particle image velocimetry analysis suggested that deformation occurs mostly in the lateral directions. On pulling the indenter out, adhesion between the silica particles and the glass indenter became manifest via a distortion of the initially spherical dent and lower coordination numbers under the dent. Together all these behaviors indicate that the aggregated layers behave like yield-stress materials, which are solidlike up to a critical stress and liquidlike above it. The results of this study also illustrate the potential of the AFM-CSLM combination to study the detailed 3D deformation in other types of systems, like granular packings or more open particle networks. PMID:16922564

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

    Microsoft Academic Search

    Aemilianus G. J. Staring; David Braun

    1998-01-01

    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

  19. Streamwise vortices originating from synthetic jet-turbulent boundary layer interaction

    NASA Astrophysics Data System (ADS)

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

    2014-02-01

    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.

  20. Electronic structure of the surfaces of layered copper oxides

    SciTech Connect

    Prosandeyev, S.A.; Tennenboum, I.M. [Department of Physics, Rostov State University, 5 Zorge Street, 344104 Rostov on Don (Russian Federation)] [Department of Physics, Rostov State University, 5 Zorge Street, 344104 Rostov on Don (Russian Federation)

    1995-08-01

    The electronic structure of the surfaces of layered copper oxides has been investigated in the framework of a tight-binding model together with the unrestricted Hartree-Fock method. The main element of the layered copper oxides, namely the CuO{sub 2} layer, was supposed to lie parallel with the surface, as well as to be trimmed at a boundary of crystal. In the former case, the electrons at the surface were considered to be in an additional (surface) potential. A mode of the calculation of this potential has been developed on the basis of a method being similar to Ewald`s transformation. As an example, the surface of La{sub 2}CuO{sub 4} was studied. In the latter case, when the CuO{sub 2} layer is semi-infinite due to its cutting at the surface, the formation of electronic surface bands was carefully investigated. Both the metal and dielectric phases were examined. For the metal phase, we took into account the possible freezing of the spin-density wave at the surface. In all the cases, surface bands were present in the vicinity of the Fermi level. They had inherent, in the one-dimensional systems, peculiarities.

  1. Boundary Layer Structure and Processes in Mid - Ocean Storms.

    NASA Astrophysics Data System (ADS)

    Bond, Nicholas A.

    Measurements taken during the Storm Transfer and Response Experiment (STREX) are used to analyze boundary layer structures and processes in the vicinity of North Pacific storms. Case studies are carried out for the pre -frontal, post-frontal, and frontal sectors of storms. The effects of sub-grid scale processes on the boundary layer and the overlying atmosphere receive special emphasis. The pre-frontal boundary layers are nearly neutrally stratified and the surface heat and moisture fluxes are small. The surface fluxes tend to be downward just ahead of the fronts and are of greater magnitude during stronger storms. Even though the actual entrainment velocities are small, the entrainment fluxes are generally the most important sources of total heat for the pre-frontal boundary layers. Entrainment rates determined from budgets compare well with results calculated from relationships determined in laboratory studies of shear-driven entrainment. Heat and moisture budgets are evaluated in two post-frontal situations. In both cases surface heat and moisture fluxes are the dominant sources of total heating within the boundary layers. The entrainment velocities are larger in post-frontal than pre-frontal regions, but entrainment has only a small and positive net effect on the total heat content of the post-frontal boundary layers. Penetrative convection represents the major sink of boundary layer moisture for the case with a long atmospheric fetch over the ocean. A single strong cold front is analysed. The Sawyer Eliassen secondary circulation equation is used to compare the effects of geostrophic forcing, diabatic heating, and friction on the synoptic-scale ageostrophic flow at the front. Friction is found to be the primary process forcing the low-level updraft at the front. Combined kinematic and thermodynamic analyses show strong relative inflow of warm boundary layer air toward the front from the east and a weaker inflow of cold air from the west. The frontogenetical processes are evaluated and compared with those from previous studies. It is proposed that the intensity of turbulent mixing limits the scale of a front.

  2. Origin of weak layer contraction in de Vries smectic liquid crystals

    NASA Astrophysics Data System (ADS)

    Agra-Kooijman, Dena M.; Yoon, HyungGuen; Dey, Sonal; Kumar, Satyendra

    2014-03-01

    Structural investigations of the de Vries smectic-A (SmA) and smectic-C (SmC) phases of four mesogens containing a trisiloxane end segment reveal a linear molecular conformation in the SmA phase and a bent conformation resembling a hockey stick in the SmC phase. The siloxane and the hydrocarbon parts of the molecule tilt at different angles relative to the smectic layer normal and are oriented along different directions. For the compounds investigated, the shape of orientational distribution function (ODF) is found to be sugarloaf shaped and not the widely expected volcano like with positive orientational order parameters: ?P2? = 0.53-0.78, ?P4? = 0.14-0.45, and ?P6?˜0.10. The increase in the effective molecular length, and consequently in the smectic layer spacing caused by reduced fluctuations and the corresponding narrowing of the ODF, counteracts the effect of molecular tilt and significantly reduces the SmC layer contraction. Maximum tilt of the hydrocarbon part of the molecule lies between approximately 18° and 25° and between 6° and 12° for the siloxane part. The critical exponent of the tilt order parameter, ?˜0.25, is in agreement with tricritical behavior at the SmA-SmC transition for two compounds and has lower value for first-order transition in the other compounds with finite enthalpy of transition.

  3. Vortical structure in a forced plane mixing layer

    NASA Technical Reports Server (NTRS)

    Leboeuf, Richard L.

    1993-01-01

    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.

  4. Flexural strength and failure modes of layered ceramic structures

    PubMed Central

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

    2011-01-01

    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

  5. Omnidirectional phononic reflection and selective transmission in one-dimensional acoustic layered structures

    Microsoft Academic Search

    A. Bousfia; E. H. El Boudouti; B. Djafari-Rouhani; D. Bria; A. Nougaoui; V. R. Velasco

    2001-01-01

    We report the theoretical evidence for the occurrence of omnidirectional reflection in one-dimensional phononic crystal structures, namely, a layered periodic structure that may exhibit total reflection of waves for all incident angles and polarizations in a given frequency range “the omnidirectional band gap”. By introducing a defect layer in the finite-size layered structure, selective waves falling within this omnidirectional band

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

    E-print Network

    Demokritov, S.O.

    and barium strontium titanate BST films in the layered structure. The planar straight-edge ferriteFerrite-ferroelectric layered structures for electrically and magnetically tunable microwave It is demonstrated experimentally that a layered structure consisting of ferrite and ferroelectric thin films can

  7. Origin of the Vredefort structure, South Africa: Impact model

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

    A model is presented for the evolution of the Vredefort structure, based on reasoned constraints on the original size of the Vredefort structure from observational data and comparison with other terrestrial impact craters. The models for complex craters (ring and multi-ring basins) of Croft, Grieve, and co-workers, and Schultz and co-workers, were used to reconstruct the Vredefort impact event, using a final crater diameter of 300 km, as estimated by Therriault. The sequence of events (stages 2-5) is illustrated diagramatically. The stages are: initial penetration, excavation and compression, dynamic rebound and uplift, maximum radial growth and collapse, and final crater form.

  8. Appearance of layered structures in numerical simulations of polydisperse bodies accretion: Application to cometary nuclei

    NASA Astrophysics Data System (ADS)

    Lasue, J.; Botet, R.; Levasseur-Regourd, A. C.; Hadamcik, E.; Kofman, W.

    2011-05-01

    A model for the aggregation of size distribution of cometesimals (Gaussian or power law) into cometary nuclei is developed. Upon disruption induced by collisions, sticking and evolution of the tensile strength and density of the cometesimals by sintering processes are taken into account. The resulting cometary nuclei present specific internal structures that have been quantified to allow the comparison with observational constraints and future in situ observations and cometary nucleus sounding with the CONSERT radar on-board the Rosetta mission. A parameter called the homogeneity exponent, ?, determines different aggregation regimes. Fractal aggregates are formed for ? < 0.4. Radial variations in tensile strength appear for 0.4 < ? < 0.6 and vanish for larger values of ?. The initial size distribution (following a Gaussian or power law) of aggregating cometesimals does not influence strongly these values but can change the extent of corresponding layers. If the layering observed on the surface of some cometary nuclei occurs often and originates from primordial structures, this constrains the velocity distribution of aggregating bodies to follow v?m-0.25, while a differential size distribution following a power law with exponent between -2 and -3 should result for large bodies, in agreement with current estimations of the size distributions. Such a layered structure would lead to more cohesive, dense and less porous material located near the center of mass of the nucleus predicting an increase of bulk density of comet nuclei with their erosion state.

  9. Perpendicular magnetic anisotropy in FePt/AlN layered structure

    NASA Astrophysics Data System (ADS)

    Zhang, Cong; Sannomiya, Takumi; Muraishi, Shinji; Shi, Ji; Nakamura, Yoshio

    2014-09-01

    FePt/AlN layered structures were deposited onto fused quartz substrate by magnetron sputtering method and found to show in-plane anisotropy. However, annealing of the films leads to a transition of magnetic anisotropy from in-plane to perpendicular direction, and the perpendicular anisotropy gets stronger as the annealing temperature increases. Structural analysis shows that the FePt and AlN layers are textured with (111) and (002) orientations, respectively, along the film normal, and no ordering transformation is found for FePt alloy. To study the origin of the developed anisotropy, stress condition was analyzed with an equal biaxial stress model using X-ray diffraction 2 ?- ? scan method and interface quality was evaluated by X-ray reflectivity measurement and transmission electron microscopy observation. The results reveal that perpendicular magnetic anisotropy of the annealed FePt/AlN layered structure can be attributed to the enhanced interface anisotropy, which is due to flattening of the interfaces through annealing.

  10. Packet Structure of Surface Eddies in the Atmospheric Boundary Layer

    NASA Astrophysics Data System (ADS)

    Hommema, Scott E.; Adrian, Ronald J.

    A smoke visualization experiment has beenperformed in the first 3,m ofneutral and unstable atmospheric boundary layersat very large Reynolds number(Re > 106). Under neutral atmosphericconditions mean wind profiles agreewell with those in the canonical flatplate zero-pressure-gradient turbulentboundary layer. The experiment was designedto minimize the temperaturedifference between the passive marker (smoke)and the air to ensure that anyobserved structures were due to vortical, ratherthan buoyant, motions. Imagesacquired in the streamwise-wall-normal planeusing a planar laser light-sheetare strikingly similar to those observed inlaboratory experiments at low to moderate Reynolds numbers. They reveal large-scaleramp-like structures withdownstream inclination of 3°-35°.This inclination isinterpreted as the hairpin packet growthangle following the hairpin vortexpacket model ofAdrian, Meinhart, and Tomkins.The distribution of this characteristicangle agrees with the results of experiments at far lower Reynolds numbers,suggesting a similarity in structures among low, moderate, and high Reynoldsnumber boundary layers at vastly different scales. These results indicate thatthe hairpin vortex packet model extends over a large range of scales. Theeffect of vertical heat transport in an unstable atmosphere on wall structuresis investigated in terms of the hairpin vortex packet model.

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

    NASA Technical Reports Server (NTRS)

    Rashidnia, N.; Falco, R. E.

    1987-01-01

    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.

  12. Electroluminescence of ZnSe enhanced by improved layered optimization structure

    Microsoft Academic Search

    W. W. Jiang; S. L. Zhao; F. J. Zhang; Z. Xu

    The electroluminescence thin-film device with layered optimization structure based on ZnSe emitting layer was deposited by electron-beam evaporation. Electroluminescence of ZnSe film, which has not appeared in device with traditional double insulator structure, was observed. According to this phenomenon, SiO2 ultra-thin layer was inserted into the middle of ZnSe layer and the device with this kind of improved layered optimization

  13. Nanosized Ni–Al layered double hydroxides—Structural characterization

    SciTech Connect

    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

    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.

  14. S4 : A free electromagnetic solver for layered periodic structures

    NASA Astrophysics Data System (ADS)

    Liu, Victor; Fan, Shanhui

    2012-10-01

    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.

  15. Origin of micro-layering in a deep magma chamber: Evidence from two ultramafic mafic layered xenoliths from Puy Beaunit (French Massif Central)

    NASA Astrophysics Data System (ADS)

    Féménias, Olivier; Ohnenstetter, Daniel; Coussaert, Nicolas; Berger, Julien; Demaiffe, Daniel

    2005-08-01

    The origin of magmatic layering is still hotly debated. To try to shed some light on this problem, two ultramafic-mafic layered xenoliths from Puy Beaunit (French Massif Central) were investigated in detail. The nodules belong to a stratiform intrusion emplaced in the deep crust during the Permian (257 ± 6 Ma; Féménias, O., Coussaert, N., Bingen, B., Whitehouse, M., Mercier, J.-C., Demaiffe, D., 2003. A Permian underplating event in late- to post-orogenic tectonic setting. Evidence from the mafic-ultramafic layered xenoliths from Beaunit (French Massif Central). Chem. Geol. 199 293-315.). The 3 to 5 cm thick nodules have, in common, a central orthopyroxenite layer; the succession of layers is, respectively, norite-orthopyroxenite-norite (PBN 00-01) and norite-orthopyroxenite-harzburgite (PBN 00-03). The variations of both major (by electron microprobe) and trace, essentially the RE, elements (by LA-ICP-MS) were measured in major mineral phases (orthopyroxene, clinopyroxene, plagioclase, spinel) along cross-section perpendicular to the layering. Strong grain size, chemical and textural variations occur along these sections: they can be continuous or discontinuous, symmetrical or asymmetrical. Such complex variations cannot be solely related to a single magmatic history (fractional crystallisation, mineral sorting). Other processes such as element enrichment by residual liquid channelling along layer boundaries and/or sub-solidus recrystallisation and element redistribution must be invoked. It appears, in particular, that element distribution in the central orthopyroxenite layer could result from the injection of micro-sills of orthopyroxene-rich liquid between previously consolidated layers.

  16. Structure from the critical layer framework in turbulent flow

    NASA Astrophysics Data System (ADS)

    Sharma, Ati; McKeon, Beverley

    2010-11-01

    We extend the critical layer framework for turbulent pipe flow proposed by McKeon & Sharma (J. Fluid Mech, 2010) to investigate vortical structure generated at particular streamwise/azimuthal wavenumber and frequency combinations, (k,n,?). This framework utilizes an input-output formulation of the Navier-Stokes equations in a divergence-free basis to analyze the transfer function (the "resolvent") and identify the dominant forcing and response mode shapes at each (k,n,?) combination relevant to experimental spectra. It is shown that the hairpin vortex is a natural constituent of the velocity field associated with so-called wall modes, such that our model gives important predictive information about both the statistical and structural make-up of wall turbulence. Thus the dominant response mode shapes form a suitable basis by which to decompose the full turbulent velocity field. Acknowledgements: This research is sponsored by an Imperial College Junior Research Fellowship and the AFOSR (program manager J. Schmisseur).

  17. Model-based damage evaluation of layered CFRP structures

    NASA Astrophysics Data System (ADS)

    Munoz, Rafael; Bochud, Nicolas; Rus, Guillermo; Peralta, Laura; Melchor, Juan; Chiachío, Juan; Chiachío, Manuel; Bond, Leonard J.

    2015-03-01

    An ultrasonic evaluation technique for damage identification of layered CFRP structures is presented. This approach relies on a model-based estimation procedure that combines experimental data and simulation of ultrasonic damage-propagation interactions. The CFPR structure, a [0/90]4s lay-up, has been tested in an immersion through transmission experiment, where a scan has been performed on a damaged specimen. Most ultrasonic techniques in industrial practice consider only a few features of the received signals, namely, time of flight, amplitude, attenuation, frequency contents, and so forth. In this case, once signals are captured, an algorithm is used to reconstruct the complete signal waveform and extract the unknown damage parameters by means of modeling procedures. A linear version of the data processing has been performed, where only Young modulus has been monitored and, in a second nonlinear version, the first order nonlinear coefficient ? was incorporated to test the possibility of detection of early damage. The aforementioned physical simulation models are solved by the Transfer Matrix formalism, which has been extended from linear to nonlinear harmonic generation technique. The damage parameter search strategy is based on minimizing the mismatch between the captured and simulated signals in the time domain in an automated way using Genetic Algorithms. Processing all scanned locations, a C-scan of the parameter of each layer can be reconstructed, obtaining the information describing the state of each layer and each interface. Damage can be located and quantified in terms of changes in the selected parameter with a measurable extension. In the case of the nonlinear coefficient of first order, evidence of higher sensitivity to damage than imaging the linearly estimated Young Modulus is provided.

  18. Modulated structures of flexoelectric origin in nematic liquid crystals.

    PubMed

    Barbero, G; Lelidis, I

    2003-06-01

    A structural instability of flexoelectric origin is predicted in a homeotropic cell, of insulating nematic liquid crystal, by the action of an electric field applied in the direction of the initially nonperturbed nematic director. The instability gives rise to a two-dimensional periodic structure. The critical field to observe the predicted modulated structure as well as the wavelength at the threshold are evaluated. Both vary as the inverse square root of the cell thickness. The role of the dielectric anisotropy on the phenomenon is investigated. Our analysis is performed in the limit of weak anchoring energy strength, where the extrapolation length is large with respect to the thickness of the nematic sample. PMID:16241245

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

    NASA Astrophysics Data System (ADS)

    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

    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.

  20. Time-Dependent Structural Phase Transitions of Two-dimensional Intercalated Layered Oxides

    NASA Astrophysics Data System (ADS)

    Koski, Kristie; Zucker, Philip; Reed, Bryan

    2014-03-01

    We demonstrate time-dependent phase transitions in metal-intercalated 2D layered MoO3. Copper metal atoms are chemically intercalated into ultrathin 2D nanocrystalline MoO3 using a novel method we developed to intercalate high densities of zero-valent atomic species. In-situ transmission electron microscopy (TEM), operating on a timescale of seconds, and Dynamic TEM, operating on nanosecond time scales show that unique, time-dependent phase transitions can be driven in these two-dimensional layered oxide nanoribbons. Very different structures arise on different time scales, indicating a competition between kinetics and thermodynamics in determining the resulting structure. Control experiments in pure MoO3 show no such transitions, thus it appears that the copper intercalant is an essential part of the process. Measurements of the nanosecond-scale transformation are consistent with a local reordering of material within the original unit cell, while the slower transition is characterized by an incommensurate superlattice possibly associated with a charge density wave. This work opens new ground for accessing novel phases of matter in two-dimensional layered nanomaterials.

  1. The Electronic Structure of Single-Layer Graphene

    NASA Astrophysics Data System (ADS)

    Siegel, David Alan

    Single-layer graphene has been widely researched in recent years due to its perceived technological applicability and its scientific importance as a unique model system with relativistic Dirac Fermions. Because of its unique geometric and electronic structure, the properties of graphene can be tuned or manipulated in several ways. This tunability is important for technological applications in its own right, and it also allows us to study the fundamental properties of Dirac Fermions, including unique many-body interactions and the nature of the quasiparticles at half-filling. This thesis is a detailed examination of the electronic and structural properties of graphene, studied with angle-resolved photoemission spectroscopy (ARPES) and other surface science techniques like low-energy electron microscopy and diffraction. This thesis is organized as follows. Chapter 1 gives an introduction to the electronic and structural properties of single-layer graphene. It provides a brief historical overview of major theoretical and experimental milestones and sets the stage for the important theoretical and experimental questions that this thesis addresses. Chapters 2 and 3 describe the experimental setup. Chapter 2 discusses the experimental techniques used in this thesis with particular focus on the mechanics of ARPES. Chapter 3 discusses the different graphene growth techniques that were used to create our sample with particular focus on our characterization of epitaxial graphene on SiC(0001). Chapters 4 and 5 form the meat of this thesis: they provide a thorough discussion of the electronic properties of graphene as studied by ARPES. Chapter 4 describes how various perturbations can result in the manipulation of the bare electronic band structure, including the deposition of atomic or molecular species on top of an epitaxial graphene sheet as well as the interactions between graphene and its substrate. Chapter 5 describes the many-body physics in single-layer graphene. It begins with a discussion of the electron-electron interaction in undoped graphene, demonstrating that these interactions qualitatively differ from ordinary metals and semiconductors and depart from the standard Fermi liquid picture for quasiparticles; it then continues by describing how screening the electron-electron and electron-impurity interactions can impact the electronic properties of graphene. Chapter 5 ends with a discussion of the doping-dependent coupling strength of the electron-phonon interaction.

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

    Microsoft Academic Search

    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

    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

  3. Original Size and Shape of the Sudbury Structure

    NASA Technical Reports Server (NTRS)

    Lowman, P. D., Jr.

    1997-01-01

    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.

  4. Perforated Layer Structures in Liquid Crystalline Rod-Coil Block Copolymers

    E-print Network

    Wan, Xin-hua

    Perforated Layer Structures in Liquid Crystalline Rod-Coil Block Copolymers Kishore K. Tenneti of the tetragonal perforated layer structures in a series of rod- coil liquid crystalline block copolymers (BCPs microscopy (TEM) techniques were used to investigate these rod-coil molecules, and a perforated layer

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

    Microsoft Academic Search

    Stefan Emeisa

    A comparison ofthe determination ofboundary-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 ofa convective boundary layer over a larger city in Germany. The three instruments give inf ormation that partly agree and partly complement each other.

  6. Reduction of protein adsorption on well-characterized polymer brush layers with varying chemical structures

    Microsoft Academic Search

    Yuuki Inoue; Kazuhiko Ishihara

    2010-01-01

    To clarify protein adsorption behavior on polymer brush layers, surface characteristics and protein adsorption repellency on polymer brush layers should be precisely determined. Here, we clearly delineated the chemical structure of the polymer brush layers containing various hydrophilic groups, namely, phosphorylcholine, sulfoxybetaine, carboxybetaine (zwitterionic), and hydroxyl group (nonionic) and examined the effects of the chemical structure on initial protein adsorption

  7. Buried oxide layers formed by oxygen implantation on screened oxide silicon wafers: structural analysis

    Microsoft Academic Search

    J. Samitier; S. Martinez; A. Pérez-Rodríguez; B. Garrido; J. R. Morante; A. M. Papon; J. Margail

    1993-01-01

    In this work the structural analysis of the buried oxide layers formed by high dose oxygen ion implantation into Si through a screen oxide layer and annealing has been performed by infrared absorption, X-ray photoelectron spectroscopy and ellipsometry measurements. The correlation between the measurements from the different techniques points out the high structural quality of the buried oxide layers from

  8. On the quantum origin of the seeds of cosmic structure

    E-print Network

    Alejandro Perez; Hanno Sahlmann; Daniel Sudarsky

    2006-02-25

    The current understanding of the quantum origin of cosmic structure is discussed critically. We point out that in the existing treatments a transition from a symmetric quantum state to an (essentially classical) non-symmetric state is implicitly assumed, but not specified or analyzed in any detail. In facing the issue we are led to conclude that new physics is required to explain the apparent predictive power of the usual schemes. Furthermore we show that the novel way of looking at the relevant issues opens new windows from where relevant information might be extracted regarding cosmological issues and perhaps even clues about aspects of quantum gravity.

  9. Study on top layer structure of composite membranes

    Microsoft Academic Search

    A. E. Polotsky; G. A. Polotskaya

    1998-01-01

    The study of composite membranes with top layers of different thickness is essentially a method of integral layer scanning. Two-layer composite membranes were formed by coating polymer solution on porous support. Poly(phenylene oxide) (PPO) of different molecular weight and sulfonated PPO were used as top layer polymers. Gas transport properties were examined by gas chromatography and used for calculation of

  10. Developmental origin and fate of middle ear structures.

    PubMed

    Sienknecht, Ulrike J

    2013-07-01

    Results from developmental and phylogenetic studies have converged to facilitate insight into two important steps in vertebrate evolution: (1) the ontogenetic origin of articulating elements of the buccal skeleton, i.e., jaws, and (2) the later origins of middle ear impedance-matching systems that convey air-borne sound to the inner ear fluids. Middle ear ossicles and other skeletal elements of the viscerocranium (i.e., gill suspensory arches and jaw bones) share a common origin both phylogenetically and ontogenetically. The intention of this brief overview of middle-ear development is to emphasize the intimate connection between evolution and embryogenesis. Examples of developmental situations are discussed in which cells of different provenance, such as neural crest, mesoderm or endoderm, gather together and reciprocal interactions finally determine cell fate. Effects of targeted mutagenesis on middle ear development are described to illustrate how the alteration of molecularly-controlled morphogenetic programs led to phylogenetic modifications of skeletal development. Ontogenetic plasticity has enabled the diversification of jaw elements as well as middle ear structures during evolution. This article is part of a special issue entitled "MEMRO 2012". PMID:23396272

  11. Detecting distortions of the time structure of an optical pulse that has passed through an aerosol layer

    NASA Astrophysics Data System (ADS)

    Gavrikov, V. K.; Korenev, V. G.

    1981-07-01

    The passage of short light pulses through an aerosol layer is associated with the spatial and temporal distortions of the signal. The propagation of an isolated pulse of coherent radiation, having a wavelength of 0.53 micron, is studied in an artificial fog. An observed increase in the duration of the light pulse is described by formulas of Bucher (1973), Ishimaru (1975), and Stotts (1978). Oscillograms of pulses of radiation, passing through a water aerosol layer are compared to the original time structures of pulses at various values of optical thickness. The dependence of the temporal broadening of the optical pulse on the optical thickness of the fog is examined.

  12. Electronic structure origins of the extremely large magnetoresistance in tungsten ditelluride

    NASA Astrophysics Data System (ADS)

    Pletikosic, Ivo; Ali, Mazhar; Cava, Robert; Valla, Tonica

    2015-03-01

    WTe2 is a layered transition metal dichalcogenide showing a structural reduction to one-dimensional tellurium-surrounded tungsten chains. The material exhibits an extremely large positive anisotropic magnetoresistance of a few million percent that increases as the square of the field and shows no saturation up to 60 T. We explored the possible electronic structure origins of the magnetoresistance by means of angle-resolved photoelectron spectroscopy (ARPES) and found electron and hole pockets of equal size along the direction of tungsten chains, forming a highly anisotropic quasi-twodimensional Fermi surface. The perfect carrier compensation at low temperatures has been identified as the primary source of the magnetoresistive effect, and the change of the Fermi surface shape as well as a high-density-of-states band slightly below the Fermi level recognized as the cause of its diminishing at rising temperatures.

  13. Origin of the Low Energy Structure in Above Threshold Ionization

    E-print Network

    Titi, Atef S

    2015-01-01

    We present an ab initio analytic theory to account for both the very low energy structure (VLES) [C. Y. Wu et al., Phys. Rev. Lett. 109, 043001 (2012); W. Quan et al., Phys. Rev. Lett. 103, 093001 (2009)], and the low energy structure (LES) [W. Quan et al. Phys. Rev. Lett. 103, 093001 (2009); C.I. Blaga et al., Nat. Phys. 5, 335 2009)] of above threshold ionization. The origin of both VLES and LES lies in a forward scattering mechanism by the Coulomb potential. We parameterize the S matrix in terms of ?, which is the displacement of the the classical motion of an electron in the laser field. When ? = 0, the S matrix is singular, which we attribute to be forward Coulomb scattering without absorption of light quanta. By devising a regularization scheme, the resulting S matrix is non-singular when ? = 0, and the origins of VLES and LES are revealed. We attribute VLES to multiple forward scattering of near-threshold electrons by the Coulomb potential, with no absorption of light quanta, signifying the role of the...

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

    SciTech Connect

    Kevin Jerome Sutherland

    2001-05-01

    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.

  15. Cation Effects on the Layer Structure of Biogenic Mn-Oxides

    E-print Network

    Sparks, Donald L.

    Cation Effects on the Layer Structure of Biogenic Mn-Oxides M E N G Q I A N G Z H U , * M A T T H E 26, 2010. Biologically catalyzed Mn(II) oxidation produces biogenic Mn- oxides(BioMnOx)andmayserveasoneofthemajorformation pathways for layered Mn-oxides in soils and sediments. The structure of Mn octahedral layers in layered Mn

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

    SciTech Connect

    Kevin Jerome Sutherland

    2001-06-27

    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.

  17. kz Dependent Electronic Structure Studies of CaC6 and Inter Layer State Driven Superconductivity

    NASA Astrophysics Data System (ADS)

    Kyung, Wonshik; Kim, Yeongkwan; Han, Garam; Leem, Choonshik; Kim, Chul; Koh, Yoonyoung; Kim, Beomyoung; Kim, Yeongwook; Kim, Junsung; Kim, Keunsu; Rotenberg, Eli; Denlinger, Jonathan; Kim, Changyoung; Yonsei University Team; Postech Collaboration; Advanced light source Collaboration

    2015-03-01

    We performed angle-resolved photoemission experiments on CaC6 and measured kz dependent electronic structures to investigate the interlayer states. The results reveal a spherical interlayer Fermi surface centered at the ? point. We also find the graphene driven band possesses a weak kz dispersion. The overall electronic structure shows a peculiar single graphene layer periodicity in the kz direction although CaC6 unit cell is supposed to contain three graphene layers. This suggests that c-axis ordering of Ca has little effect on the electronic structure of CaC6. In addition to CaC6, we also studied the non-superconducting BaC6. For BaC6, the graphene band Dirac point energy is smaller than that of CaC6. Based on data from CaC6 and BaC6, we rule out Cxy phonon mode as the origin of the superconductivity in CaC6, which strongly suggests interlayer state driven supercondutivity.

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

    DOEpatents

    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

    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.

  19. Structure identification within a transitioning swept-wing boundary layer

    NASA Astrophysics Data System (ADS)

    Chapman, Keith Lance

    1997-08-01

    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.

  20. 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

    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

    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.

  1. Fabrication of three-dimensional (3D) woodpile structure photonic crystal with layer by layer e-beam lithography

    NASA Astrophysics Data System (ADS)

    Wang, Li; Zhang, Sasa; Wang, Qingpu; Chen, Jiaqi; Jiang, Wei; Chen, Ray T.

    2009-05-01

    Photonic crystal based superprism offers a way to design new optical components for beam steering and DWDM (Dense Wavelength Division Multiplexing) application. Three-dimensional (3D) photonic crystals are especially attractive as they could offer more control of the light beam. A FCT (Face-Centered-Tetragonal) woodpile structure has been fabricated using layer by layer stacking techniques with E-Beam lithography. Special planarizations and processes have been introduced to ensure the survivability and good alignment of the fabricated nanostructures. Scanning electron microscopy results proved the structure uniformity. With the proper design, the structure exhibits superprism effects around 1550 nm, and such effects have been observed in the experiments.

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

    NASA Technical Reports Server (NTRS)

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

    1974-01-01

    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.

  3. The structure of periglacial layers in the uplands of Rhineland-Palatinate (West Germany)

    NASA Astrophysics Data System (ADS)

    Stolz, Christian; Grunert, Jörg

    2010-05-01

    The poster presents several examples taken from Taunus, Hunsrück and Westerwald Mts. (Rhenish Slate Massif), the Palatinate Forest (Bunter Sandstone) and the Donnersberg monolith (porphyry). Extended research activities during the last years were carried on to specify the well known differentiation of periglacial slope deposits into three layers: Basic layer, medium layer and main layer on the top. At several places the medium layer is missing but, at a few places the basic layer and where it occurs, also the medium layer can be divided in two or more sublayers. The typical sediment of the medium layer and the main layer is fine silt, originating from periglacial loess deposits. Typically, the medium layer is more silty than the main layer. Exclusively involved in the main layer is Laacher Bims tephra of different content. Several problems are under discussion, such as: The different ages of the basal and medium layers at various places and the existence of a top layer (Oberlage). Another problem is the distinction between the main layer and Holocene colluvia.

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

    NASA Astrophysics Data System (ADS)

    Chumak, O. V.

    2013-08-01

    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.

  5. Thermoacoustic effects on layered structures for the evaluation of structural parameters

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

    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.

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

    PubMed

    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

    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

  7. Nonanolides of natural origin: structure, synthesis, and biological activity.

    PubMed

    Sun, P; Lu, S; Ree, T V; Krohn, K; Li, L; Zhang, W

    2012-01-01

    Naturally occurring nonanolides (synonym decanolides) are a large family of secondary metabolites with an interesting 10- membered macrolide subunit. Metabolites of the nonanolide family have been found to have various biological activities, including cytotoxic, phytotoxic, antimalarial, antifungal, antibacterial, and antimicrofilament activities. An early review of the chemistry and bioactivity of nonanolides was presented in 1996, covering the literature published between 1975 and 1995. During the past decades, the broad spectrum of bioactivity and the intriguing structure of the medium-sized ring in nonanolide analogues have continuously drawn the attention of biologists and natural product and synthetic chemists, resulting in a great number of publications. This review summarizes in whole the recent progress in the field of the nonanolides of natural origin, aiming to give the readers a brief view of the compounds, concerning their natural occurrence, structural elucidation, biological activities, total synthesis, and structure-activity relationships. The article covers the literature published in the period from the beginning of 1996 to July 2011. PMID:22612710

  8. Generation of mesoscale F layer structure and electric fields by the combined Perkins and Es layer instabilities, in simulations

    NASA Astrophysics Data System (ADS)

    Cosgrove, R. B.

    2007-07-01

    The generic equilibrium configuration of the nighttime midlatitude ionosphere consists of an F layer held up against gravity by winds and/or electric fields, and a sporadic E (Es) layer located by a sheared wind field, which experiences the same electric fields as the F layer. This configuration is subject to two large-scale (e.g. >10 km) "layer instabilities": one of the F layer known as the Perkins instability, and another of the Es layer which has been called the Es layer instability. Electric fields on scales larger than (about) 10 km map very efficiently between the Es and F layers, and the two instabilities have a similar geometry, allowing them to interact with one another. As shown through a linear growth rate analysis, the two most important parameters governing the interaction are the relative horizontal velocity between the Es and F layers, and the integrated conductivity ratio ?H/?PF, where ?H and ?PF are the field line integrated Hall conductivity of the Es layer, and the field line integrated Pedersen conductivity of the F layer, respectively. For both large and small relative velocities the growth rate was found to be more than double that of the Perkins instability alone, when ?H ?PF. However, the characteristic eigenmode varies considerably with relative velocity, and different nonlinear behavior is expected in these two cases. As a follow up to the linear growth rate analysis, we explore in this article the nonlinear evolution of the unstable coupled system subject to a 200 km wavelength initial perturbation of the F layer, using a two-dimensional numerical solution of the two-fluid equations, as a function of relative horizontal velocity and ?H ?PF. We find that when ?H ?PF ? 0.5 the Perkins instability is able to control the dynamics and modulate the F layer altitude in 2 to 3 h time. However, the electric fields remain small until the altitude modulation is extremely large, and even then they are not large enough to account for the observations of large midlatitude electric fields. When ?H ?PF ?1 the Es layer becomes a major contributor to the F layer dynamics. The Es layer response involves the breaking of a wave, with associated polarization electric fields, which modulate the F layer. Larger electric fields form when the relative velocity between the Es and F layers is large, whereas larger modulations of the F layer altitude occur when the relative velocity is small. In the latter case the F layer modulation grows almost twice as fast (for ?H ?PF >=1) as when no Es layer is present. In the former case the electric fields associated with the Es layer are large enough to explain the observations (~10 mV/m) , but occur over relatively short temporal and spatial scales. In the former case also there is evidence that the F layer structure may present with a southwestward trace velocity induced by Es layer motion.

  9. Terpenoid hydrocarbons in Hula peat: Structure and origins

    NASA Astrophysics Data System (ADS)

    Venkatesan, M. I.; Ruth, E.; Kaplan, I. R.

    1986-06-01

    Tri- and tetracyclic diterpenoid and pentacyclic triterpenoid hydrocarbons have been identified in the lipid extracts of three peat samples from the Hula Basin, Israel. Tentative structures for the diterpenoids have been proposed based on mass spectral studies and on extrapolation of known mass spectral fragmentation patterns of most probable biological precursors. The identification of ent-kaurenes in one peat sample appears to be a unique observation. Kaurenes most likely originated from higher plant resins. The triterpenoids in the three samples consist mainly of 17?-hopanes and hopenes, derived from recent biogenic activity. The preponderance of the 17?(H)-hopanes indicates the geological immaturity of the samples and implies that they have undergone only a mild thermal history.

  10. On the origin of stress in magnetron sputtered TiN layers

    NASA Astrophysics Data System (ADS)

    Kamminga, J.-D.; de Keijser, Th. H.; Delhez, R.; Mittemeijer, E. J.

    2000-12-01

    A recently proposed model has been used to describe the state of stress in magnetron sputtered TiN layers in which the stresses are believed to be caused by atomic peening. The state of stress in the layer is described by a combination of: (i) a hydrostatic state of stress, caused by the introduction of the misfitting atoms, and (ii) a biaxial state of stress induced by the equalization of the lateral dimensions of the substrate and the layer, dilated due to the misfitting atoms and the thermal misfit due to the cooling down of the layer/substrate assembly to room temperature. The implications of the thus obtained total state of stress on x-ray diffraction measurements have been clarified and a quantitative elaboration of the growth stress as a function of the amount and type of misfitting particles has been given. It has been deduced that the growth stresses are caused by about 1 wt % Ti atoms on nitrogen sites in the TiN lattice. By comparing x-ray diffraction results of layers of different thickness, deposited simultaneously on two different substrates, it has been concluded that the growth stress in the layers depends on the layer thickness, whereas the thermal stress is equal for all layers on a given substrate. The observed layer thickness dependence of the growth stress has been associated with a (macro)strain depth profile in the layers. The distinct diffraction line broadening observed for all layers cannot be due to smallness of crystallite size and the macrostrain-depth profiles, it is ascribed to (localized) lattice defects as dislocations and low angle grain boundaries.

  11. Modeling a Possible Volcanic Origin for Interior Layered Deposits on Mars

    NASA Astrophysics Data System (ADS)

    Chapman, M. G.; Kneissl, T.

    2011-12-01

    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.

  12. Development of titanium oxide layer containing nanocrystalline zirconia particles with tetragonal structure: Structural and biological characteristics.

    PubMed

    Shin, Ki Ryong; Kim, Yeon Sung; Kim, Gye Won; Ko, Young Gun; Shin, Dong Hyuk

    2015-07-01

    This study investigated the microstructural, mechanical and biological properties of oxide layers containing tetragonal zirconia (t-ZrO2) particles on pure titanium produced by plasma electrolytic oxidation (PEO) process. For this purpose, PEO processes were carried out at an AC current density of 200mA/cm(2) for 180s in potassium pyrophosphate (K4P2O7) electrolytes with and without t-ZrO2 powder. Structural investigations using transmission electron microscopy exhibited that the present nanocrystalline oxide layer evidenced the successful incorporation of a myriad of t-ZrO2 particles working as an intermediate medium to reinforce the adhesion strength between the substrate and oxide layer. Regarding biomimetic apatite formation, the t-ZrO2 particles uniformly spread were of considerable importance in triggering the nucleation and growth of biomimetic apatite on the surface of the oxide layer immersed in a simulated body fluid solution. The growth and proliferation rates of the osteoblasts (MC3T3-E1) cultured on the oxide layer with t-ZrO2 particles were higher than that without t-ZrO2 particles due to the higher roughness providing the better sites for the filopodia extension and interlocking. PMID:25956745

  13. Layered magnetic structures: Evidence for antiferromagnetic coupling of Fe layers across Cr interlayers

    Microsoft Academic Search

    P. Grünberg; R. Schreiber; Y. Pang; M. B. Brodsky; H. Sowers

    1986-01-01

    We investigated exchange coupling of Fe layers across Au and Cr interlayers by means of light scattering from spin waves. For Au interlayers we find a continuous decrease of this coupling to zero as the Au thickness is increased from 0 to ~=20 Å. For Cr interlayers of prpoer thickness we find antiferromagnetic coupling of the Fe layers. In small

  14. Structure and growth of the mixing layer over the Amazonian rain forest

    NASA Technical Reports Server (NTRS)

    Martin, Charles L.; Fitzjarrald, David; Garstang, Michael; Greco, Steve; Oliveira, Amauri P.; Browell, Edward

    1988-01-01

    The structure and growth of the atmospheric mixed layer over the Amazonian rain forest were examined using measurements obtained during the NASA Amazon Boundary Layer Experiment. Measurements of temperature, moisture, and horizontal wind were carried out in and above the mixed layer by means of a tethered balloon, rawinsonde, and aircraft; fluxes of sensible and latent heat were measured at the top of the canopy. It was found that the mixing layer grows rapidly, at 5-8 cm/sec, soon after sunrise to a mean maximum height of 1200 m by 1300 LT; during undisturbed conditions, mixed layer heights of 1000 are common between 1000 and 1600 LT. No horizontal inhomogeneities in the mixed layer structure or depth were found over large distances. A simple mixed layer model was applied to show how fluxes of species might be estimated using only quantities measured at the surface and prescribing an initial condition and boundary condition for the mixed layer.

  15. Dynamics of generalized Gaussian polymeric structures in random layered flows

    NASA Astrophysics Data System (ADS)

    Katyal, Divya; Kant, Rama

    2015-04-01

    We develop a formalism for the dynamics of a flexible branched polymer with arbitrary topology in the presence of random flows. This is achieved by employing the generalized Gaussian structure (GGS) approach and the Matheron-de Marsily model for the random layered flow. The expression for the average square displacement (ASD) of the center of mass of the GGS is obtained in such flow. The averaging is done over both the thermal noise and the external random flow. Although the formalism is valid for branched polymers with various complex topologies, we mainly focus here on the dynamics of the flexible star and dendrimer. We analyze the effect of the topology (the number and length of branches for stars and the number of generations for dendrimers) on the dynamics under the influence of external flow, which is characterized by their root-mean-square velocity, persistence flow length, and flow exponent ? . Our analysis shows two anomalous power-law regimes, viz., subdiffusive (intermediate-time polymer stretching and flow-induced diffusion) and superdiffusive (long-time flow-induced diffusion). The influence of the topology of the GGS is unraveled in the intermediate-time regime, while the long-time regime is only weakly dependent on the topology of the polymer. With the decrease in the value of ? , the magnitude of the ASD decreases, while the temporal exponent of the ASD increases in both the time regimes. Also there is an increase in both the magnitude of the ASD and the crossover time (from the subdiffusive to the superdiffusive regime) with an increase in the total mass of the polymeric structure.

  16. Dynamics of generalized Gaussian polymeric structures in random layered flows.

    PubMed

    Katyal, Divya; Kant, Rama

    2015-04-01

    We develop a formalism for the dynamics of a flexible branched polymer with arbitrary topology in the presence of random flows. This is achieved by employing the generalized Gaussian structure (GGS) approach and the Matheron-de Marsily model for the random layered flow. The expression for the average square displacement (ASD) of the center of mass of the GGS is obtained in such flow. The averaging is done over both the thermal noise and the external random flow. Although the formalism is valid for branched polymers with various complex topologies, we mainly focus here on the dynamics of the flexible star and dendrimer. We analyze the effect of the topology (the number and length of branches for stars and the number of generations for dendrimers) on the dynamics under the influence of external flow, which is characterized by their root-mean-square velocity, persistence flow length, and flow exponent ?. Our analysis shows two anomalous power-law regimes, viz., subdiffusive (intermediate-time polymer stretching and flow-induced diffusion) and superdiffusive (long-time flow-induced diffusion). The influence of the topology of the GGS is unraveled in the intermediate-time regime, while the long-time regime is only weakly dependent on the topology of the polymer. With the decrease in the value of ?, the magnitude of the ASD decreases, while the temporal exponent of the ASD increases in both the time regimes. Also there is an increase in both the magnitude of the ASD and the crossover time (from the subdiffusive to the superdiffusive regime) with an increase in the total mass of the polymeric structure. PMID:25974520

  17. Structure and dynamics of a layer of sedimented Brownian particles

    E-print Network

    Adar Sonn Segev; Jerzy B. lawzdziewicz; Eligiusz Wajnryb; Maria L. Ekiel Jezewska; Haim Diamant; Yael Roichman

    2015-04-13

    We investigate experimentally and theoretically thin layers of colloid particles held adjacent to a solid substrate by gravity. Epifluorescence, confocal, and holographic microscopy, combined with Monte Carlo and hydrodynamic simulations, are applied to infer the height distribution function of particles above the surface, and their diffusion coefficient parallel to it. As the particle area fraction is increased, the height distribution becomes bimodal, indicating the formation of a distinct second layer. In our theory we treat the suspension as a series of weakly coupled quasi-two-dimensional layers in equilibrium with respect to particle exchange. We experimentally, numerically, and theoretically study the changing occupancies of the layers as the area fraction is increased. The decrease of the particle diffusion coefficient with concentration is found to be weakened by the layering. We demonstrate that particle polydispersity strongly affects the properties of the sedimented layer, because of particle size segregation due to gravity.

  18. Structure and properties of thin iron phosphide films on carburised layers

    Microsoft Academic Search

    Jerzy Nowacki

    2004-01-01

    Iron phosphate layers on the carbuised layer structure and properties on the carburised layer have been studied. The layers were generated as a result of a gas phosphorcarburising of Armco iron and 0.2% C steel. Calculations have been done on the Gibbs energy of phosphates Fe3P, Fe2P and FeP synthesis reactions. In terms of the value of the Gibbs energy,

  19. Lack of evidence for glial cells originating from the external granular layer in mouse cerebellum.

    PubMed

    Swarz, J R; Del Cerro, M

    1977-04-01

    In 25 day mice cerebella, a quantitative electron microscopic analysis showed that glial cells were not seen among 749 cells counted in the molecular layer. Likewise, a light microscopic autoradiographic study showed that labelled oligodendroglia and/or astroglia in the cerebellum were not derived from the external granular layer (EGL). Previous claims, that these cells derived from the EGL, may have arisen because other cell types, i.e., endothelial cells, pericytes, microglia, and other ectopic granule cells may have been misidentified as oligodendroglia and/or astroglia. It seems likely that the EGL is a unique germinal cell layer in the mammalian nervous system because it gives rise only to neurons, whereas cerebellar astrocytes and oligodendrocytes are derived from the subventricular layer of the fourth ventricle, as first suggested by Cajal in 1911. PMID:856952

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

    SciTech Connect

    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

    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.

  1. Tunable Photonic Devices in Ferroelectric-Based Layered Structures

    NASA Astrophysics Data System (ADS)

    Xin, Jianzhuo

    This thesis presents the studies on the optical properties of perovskite ferroelectric thin films, as well as the preparation and applications of ferroelectrics in tunable photonic devices. Ba(Zr,Ti)O3 (BZT) thin films with different Zr concentration were grown on MgO substrates by pulsed laser deposition, and their structural and optical properties in the visible range were systematically characterized, including the out-of-plane lattice constant, grain size, refractive index, optical band gap energy, electro-optic coefficient, optical loss and absorption coefficient. The obtained results provide information for the design of BZT thin film-based optical devices. One-dimensional photonic crystal filter working in the terahertz (THz) range was studied. The transmission properties of SrTiO3 (STO) crystals were first characterized by THz time-domain spectroscopy. Si/STO multilayers with different STO defect thicknesses were designed by the transfer matrix method and then constructed by polishing and stacking. The shift of defect mode was observed and comparable with the calculations. Two-dimensional photonic structures in the optical and infra-red range were then attempted. A combination of nanoimprint lithography and inductively coupled plasma etching were investigated on (Ba,Sr)TiO3 thin films. Then, in order to simplify the nanoimprint process and allow thick metal sacrificial layer deposition for high aspect-ratio etching, a transfer imprint lithography technique was developed. Finally, surface plasmon resonance (SPR) tuning via thermally-induced refractive index changes in ferroelectrics was investigated. Ag stripes with periodicity 750 nm were fabricated on flat BST surface by nanoimprint lithography and subsequent lift-off. (-1), (2) and (-2) SP modes from Ag/BST interface were observed in visible range. Red shift of the modes up to 3.9 nm was obtained with increasing temperature. Then continuous Au film on corrugated BST surface with periodicity of 1 mum was obtained by nanoimprint lithography and subsequent dry etching. Thermal tuning of the (-1) SP mode from Au/BST interface by 1 nm was observed in the near infrared range. All the measurement results were comparable with the calculation by Rigorous coupled wave analysis and a simple analytical model. These results indicated the feasibility of active modulation in SPR in solid-state structures.

  2. Structured Analysis of a Layered Manufacturing Decision Support System

    Microsoft Academic Search

    M. M. Ghazy; K. W. Dalgarno

    Layer manufacturing technologies produce 3D physical parts directly from CAD solid models. Since 3D Systems Inc. introduced the first rapid prototyping system (stereolithography, SL) in 1988, many system manufacturers have developed layer manufacturing technologies and techniques, with SL, selective laser sintering (SLS), fused deposition modelling (FDM), and 3D printing (3DP) being the most common. At start, these technologies were initially

  3. The detection and measurement of turbulent structures in the atmospheric surface layer

    Microsoft Academic Search

    J. L. J. Schols

    1984-01-01

    Turbulence data from the planetary boundary layer (PBL) indicate the presence of deterministic turbulent structures. These structures often show up as asymmetric ramp patterns in measurements of the turbulent fluctuations of a scalar quantity in the atmospheric surface layer (ASL). The sign of the slope of the sharp upstream edge of such a triangular pattern depends on the thermal stability

  4. Investigation of Planetary Boundary Layer Structure over a topical Station using an Acoustic Sounder

    Microsoft Academic Search

    Ojo Mathew Olugoke

    2008-01-01

    An Acoustic sounder data were used to investigate the Planetary Boundary Layer (PBL) structure over Ile Ife , Nigeria. The study aimed at an understanding of the PBL structure and the associated atmospheric stability. It is also to validate the applicability of the Acoustic Sounder in monitoring the depth of the mixed layer. Case studies examined are based on the

  5. 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

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

    E-print Network

    Newman, David

    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

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

    E-print Network

    Arnold, Frances H.

    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

  8. Layered structures in twodimensional nonequilibrium systems G. Dewel (*), D. Walgraef (*) and P. Borckmans (*)

    E-print Network

    Boyer, Edmond

    of the problem. The field E tends to orient the layers perpendicu- larly to the z axis. It mimics the anisotropies which raise the orientational degeneracy of the structure in many convective instabilities embedded in a layered structure is given by L is the size of the systems, a the core diameter

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

    NASA Astrophysics Data System (ADS)

    Day, J. M.; Pearson, D.

    2013-12-01

    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.

  10. Toward the origin of exciton electronic structure in phycobiliproteins

    NASA Astrophysics Data System (ADS)

    Womick, Jordan M.; Miller, Stephen A.; Moran, Andrew M.

    2010-07-01

    Femtosecond laser spectroscopies are used to examine the electronic structures of two proteins found in the phycobilisome antenna of cyanobacteria, allophycocyanin (APC) and C-phycocyanin (CPC). The wave function composition involving the pairs of phycocyanobilin pigments (i.e., dimers) found in both proteins is the primary focus of this investigation. Despite their similar geometries, earlier experimental studies conducted in our laboratory and elsewhere observe clear signatures of exciton electronic structure in APC but not CPC. This issue is further investigated here using new experiments. Transient grating (TG) experiments employing broadband quasicontinuum probe pulses find a redshift in the signal spectrum of APC, which is almost twice that of CPC. Dynamics in the TG signal spectra suggest that the sub-100 fs dynamics in APC and CPC are respectively dominated by internal conversion and nuclear relaxation. A specialized technique, intraband electronic coherence spectroscopy (IECS), photoexcites electronic and nuclear coherences with nearly full suppression of signals corresponding to electronic populations. The main conclusion drawn by IECS is that dephasing of intraband electronic coherences in APC occurs in less than 25 fs. This result rules out correlated pigment fluctuations as the mechanism enabling exciton formation in APC and leads us to propose that the large Franck-Condon factors of APC promote wave function delocalization in the vibronic basis. For illustration, we compute the Hamiltonian matrix elements involving the electronic origin of the ?84 pigment and the first excited vibronic level of the ?84 pigment associated with a hydrogen out-of-plane wagging mode at 800 cm-1. For this pair of vibronic states, the -51 cm-1 coupling is larger than the 40 cm-1 energy gap, thereby making wave function delocalization a feasible prospect. By contrast, CPC possesses no pair of vibronic levels for which the intermolecular coupling is larger than the energy gap between vibronic states. This study of APC and CPC may be important for understanding the photophysics of other phycobiliproteins, which generally possess large vibronic couplings.

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

    SciTech Connect

    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

    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.

  12. Charge carrier transport properties in layer structured hexagonal boron nitride

    SciTech Connect

    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

    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.

  13. Charge carrier transport properties in layer structured hexagonal boron nitride

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

    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.

  14. Measuring Electron-Spin Relaxation in Layered Metallic Structures

    NASA Astrophysics Data System (ADS)

    Baxter, David V.

    2000-03-01

    The twin phenomena of Giant Magnetoresistance (GMR) and tunnel Junction Magnetoresistance (JMR) promise to give birth to a new field of information processing ("spintronics"). Both GMR and JMR devices rely on spin-polarized electron currents which traverse two or more interfaces, and yet perhaps the least-investigated aspect of either phenomenon is the possibility of spin-relaxation taking place at those interfaces. A new technique for measuring spin-relaxation rates in non-magnetic metals and at interfaces between non-magnetic materials will be described. The technique uses an exchange-biased spin valve in which the measuring current travels perpendicular to the interfaces (the so-called CPP current geometry). The theory of Valet and Fert may be used to describe the magnetoresistance of such devices in terms of the spin-diffusion lengths within the layers of the structure and other independently-measured parameters. Using this technique, spin-relaxation rates have been measured for sputtered films of Ag, V, Nb, W, CuPt(6at.%), and FeMn, and in [Cu/Ag]_N, [Cu/V]_N, [Cu/Nb]_N, and [Cu/W]N multilayers. Little spin relaxation is seen near Cu/Ag interfaces, but fractional losses in spin-direction memory of roughly 7, 18, and 60% are observed at Cu/V, Cu/Nb, and Cu/W interfaces respectively. These rates are consistent with order-of-magnitude estimates for spin-orbit-scattering-induced relaxation in thin, highly resistive, alloys at each interface.

  15. Cosmic Origins Spectrograph: On-Orbit Structural and Thermal Stability.

    NASA Astrophysics Data System (ADS)

    Smith, T. Ed; Keyes, C.; Penton, S.; Green, J.; Sahnow, D.; COS/STIS STScI Team; COS IDT Team

    2010-01-01

    After installation of the Cosmic Origins Spectrograph (COS) on the Hubble Space Telescope, two of the experiments characterizing the on-orbit performance of COS were the COS/NUV and the COS/FUV Structural and Thermal Stability programs (IDs 11480,11493). In each of three observations, the COS shutter was held open for approximately 8 hours of nearly continuous time-tag readouts. 23000s of FUV spectra were obtained of the SMC symbiotic star, Lindsay 358. 23500s of NUV spectra were obtained of the galactic symbiotic star, AG Draconis. The solar analog and HST standard star, P177D, was observed for 18000s in NUV image mode. We report our measurements of the time variation in along-dispersion and cross-dispersion positions and of the FWHM of the spectra and images on the detectors. We report long-term multi-orbit shifts and periodic variations on orbital as well as shorter time-scales. We relate these variations to variations in thermal conditions of the spacecraft and the COS instrument.

  16. Inner Plasma Structure of the Low-Latitude Reconnection Layer

    NASA Technical Reports Server (NTRS)

    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

    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.

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

    DOEpatents

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

    2011-12-20

    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.

  18. Structure design and manufacturing of layered bioceramic scaffolds for load-bearing bone reconstruction.

    PubMed

    Yang, Jing-Zhou; Hu, Xiao-Zhi; Sultana, Rumana; Edward Day, Robert; Ichim, Paul

    2015-01-01

    Bioceramic scaffolds with desired bone regeneration functions have the potential to become real alternatives to autologous bone grafts for reconstruction of load-bearing and critical-sized segmental bone defects. The aim of this paper was to develop a layered scaffold structure that has the biodegradable function of common monolithic scaffolds and adequate mechanical function for surgical fixing and after surgery support. The exemplary case of this study is assumed to be a large-segment tibia or femur bone repair. The layered scaffold structure consists of a macro porous hydroxyapatite-wollastonite layer and a strong dense zirconia matrix dense layer. The bio-functional scaffold layer with interconnected freeze-dried porous structures shows excellent apatite formation, cell attachment, and cell proliferation capabilities. The mechanical functional layer provides a bending strength matching that of the compact bone. PMID:26154898

  19. Omnidirectional phononic reflection and selective transmission in one-dimensional acoustic layered structures

    NASA Astrophysics Data System (ADS)

    Bousfia, A.; El Boudouti, E. H.; Djafari-Rouhani, B.; Bria, D.; Nougaoui, A.; Velasco, V. R.

    2001-06-01

    We report the theoretical evidence for the occurrence of omnidirectional reflection in one-dimensional phononic crystal structures, namely, a layered periodic structure that may exhibit total reflection of waves for all incident angles and polarizations in a given frequency range "the omnidirectional band gap". By introducing a defect layer in the finite-size layered structure, selective waves falling within this omnidirectional band gap may be transmitted through the structure. Such acoustic materials could be used for designing high-quality acoustic mirrors and filters in many frequency ranges of interest.

  20. Cobalt silicide layers on Si. I. Structure and growth

    Microsoft Academic Search

    G. J. van Gurp; C. Langereis

    1975-01-01

    Cobalt silicide layers have been grown by electron-beam vacuum deposition of Co onto Si wafers, and subsequent thermal treatment above 400 °C. The compounds Co2Si, CoSi, and CoSi2 were found by x-ray diffraction. The compounds grow as successive layers with a thickness ratio of about 3:1:0.1, as was found from comparison with powder diagrams. The silicide growth proceeds faster along

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

    NASA Astrophysics Data System (ADS)

    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

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2010-11-01

    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.

  3. Statistical Analysis of Coherent Vortical Structures in a Supersonic Turbulent Boundary Layer

    NASA Astrophysics Data System (ADS)

    Wang, Li; Lu, Xi-Yun

    2011-03-01

    Characteristics of coherent vortical structures in a compressible turbulent boundary layer are statistically analyzed by means of direct numerical simulation of the compressible Navier-Stokes equations for Mach number M=2 and Reynolds number Re? ? 1000 based on the inlet momentum thickness. It is found that a large variety of hairpin-like and cane-like vortical structures exist in the boundary layer and the most popular structure is the cane-like one. The injection and sweep events contribute a major proportion of the total Reynolds stress. This study indicates structural similarities with the incompressible case. Moreover, the length scales of coherent structures in the streamwise and spanwise directions increase with the distance from the wall. The inclination angle of coherent vortical structures with respect to the streamwise direction increases from the sublayer to the buffer layer and then decreases from the buffer layer to the wake region.

  4. Inversion of thicknesses of multi-layered structures from eddy current testing measurements.

    PubMed

    Huang, Ping-jie; Wu, Zhao-tong

    2004-01-01

    Luquire et al.'s impedance change model of a rectangular cross section probe coil above a structure with an arbitrary number of parallel layers was used to study the principle of measuring thicknesses of multi-layered structures in terms of eddy current testing voltage measurements. An experimental system for multi-layered thickness measurement was developed and several fitting models to formulate the relationships between detected impedance/voltage measurements and thickness are put forward using least square method. The determination of multi-layered thicknesses was investigated after inversing the voltage outputs of the detecting system. The best fitting and inversion models are presented. PMID:14663858

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

    SciTech Connect

    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

    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.

  6. The effects of expansion strength on large-scale structures in compressible free shear layers

    NASA Astrophysics Data System (ADS)

    Smith, K. M.; Dutton, J. C.

    2001-07-01

    Planar visualizations of two compressible free shear layers were performed immediately downstream of centered expansions of differing strengths in order to assess the influence of expansion strength on the embedded large-scale structures. The free shear layers studied here were formed through the separation of an approach flow, either a Mach 2.0 stream or a Mach 2.5 stream, from a planar backstep. In addition to side-view and end-view visualizations, spatial correlations (computed from large image ensembles) and laser Doppler velocimetry surveys of the free shear layers were also examined to discern relationships between the structure dynamics and the underlying pre- and postexpansion velocity fields. The instantaneous images clearly illustrate that ellipsoidal, highly coherent structures were present in both shear layers downstream of the expansion corner. The dissimilar expansion strengths did not appear to produce qualitatively different structures in the shear layers; however, as compared to the weaker expansion, the stronger expansion did result in an increase in the growth rate of the large-scale structures, apparently from an augmentation of the ?U/?y production term in the TKE equation. Furthermore, quantitative measurements of the mean structure geometry, as determined from the spatial correlation fields, revealed that a stronger expansion strength resulted in a larger aspect ratio of the mean structures (i.e., the structures were stretched preferentially in the streamwise and transverse directions as compared to the spanwise direction during the expansion process). Quadrant decompositions of the instantaneous velocity fluctuations within the approach boundary layers and within the free shear layers indicated a definite increase in structure organization across the expansion region, which is in contrast with studies of expanded supersonic boundary layers without separation. The instantaneous image data, spatial correlations, and velocity decompositions uniformly suggest that the separation process itself, and not the expansion strength, is the primary influence on initial eddy structure in the postexpansion free shear layer.

  7. On the origin of the electron blocking effect by an n-type AlGaN electron blocking layer

    SciTech Connect

    Zhang, Zi-Hui; Ji, Yun; Liu, Wei; Tiam Tan, Swee; Kyaw, Zabu; Ju, Zhengang; Zhang, Xueliang; Hasanov, Namig; Lu, Shunpeng; Zhang, Yiping; Zhu, Binbin; Wei Sun, Xiao, E-mail: exwsun@ntu.edu.sg, E-mail: volkan@stanfordalumni.org [LUMINOUS Centre of Excellence for Semiconductor Lighting and Displays, School of Electrical and Electronic Engineering, School of Physical and Mathematical Sciences, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore); Volkan Demir, Hilmi, E-mail: exwsun@ntu.edu.sg, E-mail: volkan@stanfordalumni.org [LUMINOUS Centre of Excellence for Semiconductor Lighting and Displays, School of Electrical and Electronic Engineering, School of Physical and Mathematical Sciences, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore); Department of Electrical and Electronics, Department of Physics, and UNAM-Institute of Material Science and Nanotechnology, Bilkent University, TR-06800, Ankara (Turkey)

    2014-02-17

    In this work, the origin of electron blocking effect of n-type Al{sub 0.25}Ga{sub 0.75}N electron blocking layer (EBL) for c+ InGaN/GaN light-emitting diodes has been investigated through dual-wavelength emission method. It is found that the strong polarization induced electric field within the n-EBL reduces the thermal velocity and correspondingly the mean free path of the hot electrons. As a result, the electron capture efficiency of the multiple quantum wells is enhanced, which significantly reduces the electron overflow from the active region and increases the radiative recombination rate with holes.

  8. Structural investigations of RTA boron-doped thin aSi layers

    Microsoft Academic Search

    L. Popova; St. Peneva; P. Aleksandrova; G. Beshkov

    2005-01-01

    The structural changes in as- sputtered thin a-Si layer, and after boron doping with rapid thermal annealing are investigated by transmission electron microscopy. Stable hexagonal amorphous\\/crystalline series of SiO2 structures, as signed as SiO2 (SnO2-V), not revealed in high temperature SiO2 layers, are observed in all films investigated. Different types of crystalline and high ordered SiO2 structures are obtained in

  9. Fundamentals of layered nanoparticle covered pyramidal structures formed on nickel during femtosecond laser surface interactions

    NASA Astrophysics Data System (ADS)

    Zuhlke, Craig A.; Anderson, Troy P.; Alexander, Dennis R.

    2013-10-01

    The formation of nanoparticle covered pyramidal structures using femtosecond laser pulses with a fluence near the ablation threshold is reported for the first time. These unique structures form through a combination of preferential ablation of flat regions around the pyramids and redeposition of nanoparticles created during the ablation process. The structures are demonstrated on nickel and stainless steel 316. When produced by rastering Gaussian pulses across the sample, layers of nanoparticles join together by sintering to form unique layered shells.

  10. Monitoring of hidden damage in multi-layered aerospace structures using high-frequency guided waves

    Microsoft Academic Search

    A. Semoroz; B. Masserey; P. Fromme

    2011-01-01

    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

  11. Toward the origin of exciton electronic structure in phycobiliproteins.

    PubMed

    Womick, Jordan M; Miller, Stephen A; Moran, Andrew M

    2010-07-14

    Femtosecond laser spectroscopies are used to examine the electronic structures of two proteins found in the phycobilisome antenna of cyanobacteria, allophycocyanin (APC) and C-phycocyanin (CPC). The wave function composition involving the pairs of phycocyanobilin pigments (i.e., dimers) found in both proteins is the primary focus of this investigation. Despite their similar geometries, earlier experimental studies conducted in our laboratory and elsewhere observe clear signatures of exciton electronic structure in APC but not CPC. This issue is further investigated here using new experiments. Transient grating (TG) experiments employing broadband quasicontinuum probe pulses find a redshift in the signal spectrum of APC, which is almost twice that of CPC. Dynamics in the TG signal spectra suggest that the sub-100 fs dynamics in APC and CPC are respectively dominated by internal conversion and nuclear relaxation. A specialized technique, intraband electronic coherence spectroscopy (IECS), photoexcites electronic and nuclear coherences with nearly full suppression of signals corresponding to electronic populations. The main conclusion drawn by IECS is that dephasing of intraband electronic coherences in APC occurs in less than 25 fs. This result rules out correlated pigment fluctuations as the mechanism enabling exciton formation in APC and leads us to propose that the large Franck-Condon factors of APC promote wave function delocalization in the vibronic basis. For illustration, we compute the Hamiltonian matrix elements involving the electronic origin of the alpha84 pigment and the first excited vibronic level of the beta84 pigment associated with a hydrogen out-of-plane wagging mode at 800 cm(-1). For this pair of vibronic states, the -51 cm(-1) coupling is larger than the 40 cm(-1) energy gap, thereby making wave function delocalization a feasible prospect. By contrast, CPC possesses no pair of vibronic levels for which the intermolecular coupling is larger than the energy gap between vibronic states. This study of APC and CPC may be important for understanding the photophysics of other phycobiliproteins, which generally possess large vibronic couplings. PMID:20632763

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

    NASA Astrophysics Data System (ADS)

    Ming, Jie; Wang, Yuan

    2015-04-01

    This study 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 "post-convective"). Data analyses show that the thermodynamic mixed-layer depth and inflow layer depth are higher during the convective period than the post-convective 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 post-convective period. The results suggest that convective downdrafts may play an important role in modulating turbulent flux, TKE, vertical mixing and boundary layer recovery processes.

  13. Origin of Berreman effect in GaN layers on sapphire substrates

    Microsoft Academic Search

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

    2011-01-01

    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

  14. Electronic structure of a dual-layered organic charge transfer salt

    NASA Astrophysics Data System (ADS)

    Jeschke, Harald; Altmeyer, Michaela; Valenti, Roser

    2015-03-01

    We examine the electronic properties of polymorphs of (BEDT-TTF)2Ag(CF3)4(TCE) (1,1,2-trichloroethane) within density functional theory (DFT). While a phase with low superconducting transition temperature Tc = 2 . 6 K exhibits a ? packing motif, two high Tc phases are layered structures consisting of ?' and ? packed layers. We determine the electronic structures and discuss the influence of the insulating ?' layer on the conducting ? layer. We find that the stripes of high and low charge in the ?' layer correspond to a stripe pattern of hopping parameters in the ? layer. This finding is the basis for studying the effect of the different underlying Hamiltonians on the superconducting properties. Research funded within DFG Transregio 49.

  15. Local Structure Analysis and Interface Layer Effect of Phase-Change Recording Material Using Actual Media

    NASA Astrophysics Data System (ADS)

    Nakai, Tsukasa; Yoshiki, Masahiko; Satoh, Yasuhiro; Ashida, Sumio

    2008-07-01

    The influences of the interface layer on crystal structure, the local atomic arrangement, and the electronic and chemical structure of a GeBiTe (GBT) phase-change recording material have been investigated using X-ray diffraction (XRD), X-ray absorption fine structure (XAFS), and hard X-ray photoelectron spectroscopy (HX-PES) methods using actual rewritable high-speed HD DVD media without special sample processing. XRD results showed that the crystal structure of laser-crystallized GBT alloy in the actual HD DVD media is the same as that of GeSbTe (GST) alloy, which has a NaCl-type structure. No differences between samples with and without interface layers were found. The lattice constant of GBT is larger than that of GST. Bi increases the lattice constant of GST with respect to the Bi substitution ratio of Sb. According to HX-PES, the DOS of in the recording film amorphous state with an interface layer is closer to that of the crystalline state than the recording film without an interface layer. From XAFS results, clear differences between amorphous (Amo.) and crystalline states (Cry.) were observed. The interatomic distance of amorphous recording material is independent of the existence of an interface layer. On the other hand, the coordination number varied slightly due to the presence of the interface layer. Therefore, the electronic state of the recording layer changes because of the interface layer, although the local structure changes only slightly except for the coordination number. Combining these results, we conclude that the interface layer changes the electronic state of the recording layer and promotes crystallization, but only affects the local structure of the atomic arrangement slightly.

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

    NASA Astrophysics Data System (ADS)

    Shen, Mingrong; Cao, Wenwu

    1999-12-01

    The transmission coefficient of a layered structure made of glass and water was calculated using transfer matrix method and also measured as a function of frequency. It was found that acoustic band gaps can be created using only 3-4 cells of a two-phase layered structure. By introducing two or more periods into the layered structure, very sharp passbands and very broad stopbands can be engineered for acoustic waves. Such acoustic band-gap materials could be used for making high-quality acoustic filters, acoustic mirrors and vibration insulation devices in selective frequency range.

  17. Origin of n-type conduction at the interface between epitaxial-grown layer and InP substrate and its suppression by heating in phosphine atmosphere

    Microsoft Academic Search

    Hideto Ishikawa; Shiro Miwa; Toshiyuki Maruyama; Mikio Kamada

    1992-01-01

    The origin of unintentionally introduced n-type conduction at the interface of epitaxially grown layer-InP substrate is identified. From the relation between the sheet carrier concentration and the etching depth, an n-type conducting layer was found at the epitaxial layer-substrate interface. The sheet carrier concentration and the sheet Si concentration at the surface of the InP substrate, which was obtained by

  18. Suppression of embedded shocks in supersonic free-shear-layer structures

    Microsoft Academic Search

    A. Umemura; K. Miura; K. Takada

    1996-01-01

    Although the suppressed instability of supersonic free shear layer flow has been documented by many investigators, the underlying\\u000a physics are still ambiguous. In the present study, numerical simulations were performed to cast physical insight into the\\u000a two-dimensional large-scale structure which is organized in a supersonic free shear layer. It is found that an acoustic interaction\\u000a of the disturbed shear layer

  19. Crystal Chemistry and Atomic Order in Brucite-related Double-layer Structures

    Microsoft Academic Search

    W. Hofmeister; H. Von Platen

    1992-01-01

    Brucite-related double layer structures are characterized by a regular but distinct stacking of [MexMe (OH)2x+2]+ octahedral layers with ordered cation distribution and usually x = 2 or x = 3, alternating with anionic {A·nH2O}- interlayers. The stacking sequence of the layers is rhombohedral (3R) or hexagonal (2H) parallel to [001]. Evidence of order by X-ray experiments is largely prohibited by

  20. Model for evolution of periodic layered structure in the SiO 2\\/Mg system

    Microsoft Academic Search

    I. Gutman; L. Klinger; I. Gotman; M. Shapiro

    2009-01-01

    A mathematical model for the growth of MgO\\/Mg2Si periodic layered structure (PLS) is presented based on Fick's diffusion law and conservation of matter. The model explains the temporal evolution of the width of periodic layers at different temperatures, for layers distant enough from the Mg source. It is demonstrated that the difference in thickness of a pair of any two

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

    PubMed

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

    2015-02-01

    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

  2. Turbulent structure of scalars in the eddy surface layer over land and sea

    NASA Astrophysics Data System (ADS)

    Smedman, Ann-Sofi; Sahlee, Erik

    2015-04-01

    Turbulent structure of scalars in the 'eddy surface layer' over land and sea. In a study of the kinematic structure of the near neutral atmospheric surface layer, Högström, Hunt and Smedman, 2002, it was demonstrated that a model with detached eddies from above the surface layer impinging on to the surface (Hunt and Morison, 2000) could explain some of the observed features in the neutral atmospheric boundary layer. Thus the detached eddy model proved successful in explaining the dynamic structure of the near neutral atmospheric surface layer (eddy surface layer), especially the shape of the spectra of the wind components and corresponding fluxes. However, the structure of temperature and humidity fluctuations in the eddy surface layer shows quite different behaviour. In particular the efficiency of turbulent exchange of sensible and latent heat is observed to be more strongly enhanced than is consistent with standard similarity theory. Also the profiles of dissipation of turbulent kinetic energy and temperature fluctuation variance are found to depend on the height of the eddy surface layer and not the height above the surface. All these features are found to be similar in measurements at a marine site, a flat land site and during hurricane conditions (hurricane Fabian and Isabel). Hunt, J.C.R and Morrison, J.F., 2000: Eddy structure in turbulent boundary layers, Euro. J. Mech. B-Fluids, 19, 673-694.. Högström, U., Hunt, J.C.R., and Smedman, A., 2002: Theory and measurements for turbulence spectra and variances in the atmospheric neutral surface layer, Bound.-Layer Meteorol., 103,101-124.

  3. Layered Alkyltrimethylammonium Chromates: Thermal and Structural Investigations and Crystal Structure of the Anhydrous Bisoctyltrimethylammonium Dichromate

    NASA Astrophysics Data System (ADS)

    Fosse, N.; Caldes, M.; Joubert, O.; Ganne, M.; Brohan, L.

    1998-09-01

    New mesostructured bisalkyltrimethylammonium dichromates of formula (C nH 2 n+1 (CH 3) 3N) 2Cr 2O 7· xH 2O ( n=12, 14, 16, 18; 0? x?2) were prepared at 80°C from an aqueous solution of alkyltrimethylammonium salt and K 2Cr 2O 7. The chemical composition and phase transitions have been determined by thermogravimetric analysis (TGA) coupled with differential scanning calorimetry (DSC) and mass spectrometry (MS). As suggested by X-ray diffraction and transmission electron microscopy studies, the lamellar hydrated and anhydrous bisalkyltrimethylammonium dichromates crystallize in the triclinic system, with space group P-1. The structure of the anhydrous bisoctyltrimethylammonium dichromate, (C 18H 37(CH 3) 3N) 2Cr 2O 7, was determined from single-crystal X-ray diffraction data. The compound crystallizes in the triclinic system, space group P-1, with 2 formula units in a cell a=7.197(1) Å, b=8.816(2) Å, c=43.400(9) Å, ?=93.43(3)°, ?=90.00(3)°, ?=113.98(3)°. The structure consists of discrete dichromate anions stacking up in a layer, separated by a double layer of octyltrimethylammonium surfactant chains lying in parallel. The interlayer spacing of 43.4 Å, smaller than the expected value for the fully extended molecular model, is achieved through a tilting of the surfactant chains of about 37.5° from the normal to the (Cr 2O 7) 2-plane.

  4. Inner plasma structure of the low latitude reconnection layer

    NASA Astrophysics Data System (ADS)

    Zhang, Q.-H.; Dunlop, M. W.; Lockwood, M.; Lavraud, B.; Bogdanova, Y.; Pu, Z.; Hasegawa, H.; 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.; Eastwood, J.; Wild, J.

    2012-04-01

    We report a clear transition through a low-latitude reconnection layer which shows a complete traversal across all reconnected field lines and the associated plasma populations, confirming details of the electron and ion mixing, time history and acceleration through the current layer, during north-westward interplanetary magnetic field (IMF) conditions. With a strong guide field, the reconnection layer has a single density cavity on the magentosheath side with super-Alfvénic nearly field-aligned manetosheath flows. In the reconnection layer, there are four sharp plasma boundaries, associated with the separatrices (Ssp and Ssh) and Alfvén waves (or Rotational Discontinuities (RD), RDsp and RDsh) on the magnetosphere and magnetosheath sides. There are deemed to be launched from the reconnection site and confirm the time elapsed since reconnection. In each sublayer between the boundaries the plasma distribution is different. We show convincing evidence for a velocity dispersion effect in the electron anisotropy that is consistent with the time elapsed since reconnection of the given field lines crossed. We further give new evidence for the occurrence of partial reflection of magnetosheath electrons at the magnetopause.

  5. Horizontal structures in sporadic sodium layers at 23°S

    Microsoft Academic Search

    Paulo P. Batista; Barclay R. Clemesha; Dale M. Simonich

    1991-01-01

    During 1979 and 1980 the INPE lidar located at So Jos6 dos Campos, Brazil was operated in a steer- able mode, measuring the sodium profiles sequentially at three points in the sky. Twelve sporadic sodium layer events (SSLs) wb_ich occurred in this period are studied in the present work. The evolution of the sporadic peaks at the three positions shows

  6. Structure and dynamics of the oceanic bottom boundary layer

    Microsoft Academic Search

    Georges L. Weatherly; Paul J. Martin

    1978-01-01

    The Mellor and Yamada (1974) Level II turbulence closure scheme is used to study the oceanic bottom boundary layer (BBL). The model is tested against observations of the BBL obtained on the western Florida Shelf reported in Weatherly and Van Leer (1977) and in turn conclusions about the BBL made in that paper are tested against the model. The agreement

  7. Tangling Turbulence and Semi-Organized Structures in Convective Boundary Layers

    NASA Astrophysics Data System (ADS)

    Elperin, T.; Kleeorin, N.; Rogachevskii, I.; Zilitinkevich, S. S.

    2006-06-01

    A new mean-field theory of turbulent convection is developed based on the idea that only the small-scale region of the spectrum is considered as turbulence, whereas its large-scale part, including both regular and semi-organized motions, is treated as the mean flow. In the shear-free regime, this theory predicts the convective wind instability, which causes the formation of large-scale semi-organized motions in the form of cells. In the presence of wind shear, the theory predicts another type of instability, which causes the formation of large-scale semi-organized structures in the form of rolls and the generation of convective-shear waves propagating perpendicular to the convective rolls. The spatial characteristics of these structures, such as the minimum size of the growing perturbations and the size of perturbations with the maximum growth rate, are determined. This theory might be useful for understanding the origin of large-scale cells and rolls observed in the convective boundary layer and laboratory turbulent convection

  8. Role of metallic substrate on the plasmon modes in double-layer graphene structures

    NASA Astrophysics Data System (ADS)

    Cruz, G. Gonzalez de la

    2015-07-01

    Novel heterostructures combining different layered materials offer new opportunities for applications and fundamental studies of collective excitations driven by interlayer Coulomb interactions. In this work, we have investigated the influence of the metallic-like substrate on the plasmon spectrum of a double layer graphene system and a structure consisting of conventional two-dimensional electron gas (2DEG) immersed in a semiconductor quantum well and a graphene sheet with an interlayer separation of d. Long-range Coulomb interactions between substrate and graphene layered systems lead a new set of spectrum plasmons. At long wavelengths (q?0) the acoustic modes (?~q) depend, besides on the carrier density in each layer, on the distance between the first carrier layer and the substrate in both structures. Furthermore, in the relativistic/nonrelativistic layered structure an undamped acoustic mode emerges for a certain interlayer critical distance dc. On the other hand, the optical plasmon modes emerging from the coupling of the double-layer systems and the substrate, both start at finite frequency at q=0 in contrast to the collective excitation spectrum ?~q1/2 reported in the literature for double-layer graphene structures.

  9. Application of compound matrices to the study of SAW and PSAW propagation in layered structures

    Microsoft Academic Search

    V. I. Fedosov; Yu. V. Gulyaev; I. I. Chusov; M. Benetti; D. Cannata; F. Di Pietrantonio; E. Verona

    2008-01-01

    It was demonstrated in, that the use of compound matrices in the matrix formalism makes it possible to calculate acoustic mode velocities in a layered structure with thick film layers and is an useful tool to derive the analytic expressions for the acoustic mode propagation. The advantages, as well as the weak points related to the use of compound matrices

  10. An Extremely Low Contact-Resistance MEMS Relay Using Meshed Drain Structure and Soft Insulating Layer

    Microsoft Academic Search

    Yong-Ha Song; Dong-Hoon Choi; Hyun-Ho Yang; Jun-Bo Yoon

    2011-01-01

    This paper presents an electrostatically actuated microelectromechanical systems (MEMS) relay with a stacked- electrode structure having meshed drain electrode and a soft dielectric layer under the contact material to achieve high contact force and low hardness simultaneously, with the aim of providing ultralow contact resistance. In particular, a novel method for lay- ing benzocyclobutene polymer under the contact layer to

  11. Effects of Large Eddies on the Structure of the Marine Boundary Layer under Strong Wind Conditions

    Microsoft Academic Search

    Isaac Ginis; Alexander P. Khain; Elena Morozovsky

    2004-01-01

    A model of the atmospheric boundary layer (BL) is presented that explicitly calculates a two-way interaction of the background flow and convective motions. The model is utilized for investigation of the formation of large eddies (roll vortices) and their effects on the structure of the marine boundary layer under conditions resembling those of tropical cyclones. It is shown that two

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

    NASA Technical Reports Server (NTRS)

    Palumbo, Dan

    2008-01-01

    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.

  13. 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)

    Pitz, R. W.

    1981-01-01

    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%.

  14. Anisotropic Structure and Transport in Self-Assembled Layered Polymer-Clay Nanocomposites

    E-print Network

    Sadoway, Donald Robert

    Anisotropic Structure and Transport in Self-Assembled Layered Polymer-Clay Nanocomposites Jodie L a polymer-clay structure from a unique combination of LbL materials: poly(ethylene imine), Laponite clay transport in LbL assemblies and its correlation to structural anisotropy. Introduction Synthetic clays

  15. Evaluation of reflection and transmission coefficients for multi-layered chiral structures

    NASA Technical Reports Server (NTRS)

    Tamirisa, P.; Uslenghi, P. L. E.; Yu, C. L.

    1989-01-01

    The paper examines a structure consisting of an arbitrary number of layers of different chiral materials, backed by either a perfect conductor or a penetrable half-space. A plane electromagnetic wave of arbitrary polarization is obliquely incident on the structure. The reflection and transmission coefficients of the structure can be determined by a chain-matrix algorithm.

  16. Structure of atmospheric turbulence in the friction layer below 500 meters 

    E-print Network

    Maas, Stephan Joseph

    1975-01-01

    ' SCIENCE May i97S Major Subject: Meteorology STRUCTURE OF ATMOSPHERIC TURBULENCE IN THE FRICTION LAYER BELOW 500 METERS A Thesis by STEPHAN JOSEPH MAAS Approved as to style and content by: Chairman of Commit ) (Head of, Depar ent) (Member...

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

    SciTech Connect

    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

    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.

  18. Dynamics of coherent structures in a plane mixing layer

    NASA Technical Reports Server (NTRS)

    Hussain, Fazle; Moser, R. D.; Colonius, T.; Moin, P.; Rogers, M. M.

    1988-01-01

    An incompressible, time developing 3-D mixing layer with idealized initial conditions was simulated numerically. Consistent with the suggestions from experimental measurements, the braid region between the dominant spanwise vortices or rolls develops longitudinal vortices or ribs, which are aligned upstream and downstream of a roll and produce spanwise distortion of the rolls. The process by which this distortion occurs is explained by studying a variety of quantities of dynamic importance (e.g., production of enstrophy, vortex stretching). Other quantities of interest (dissipation, helicity density) are also computed and discussed. The currently available simulation only allows the study of the early evolution (before pairing) of the mixing layer. New simulations in progress will relieve this restriction.

  19. On the Origin of the Aflou Structure (Algeria)

    NASA Astrophysics Data System (ADS)

    Chabou, M. C.; Laghouag, M. Y.

    2014-09-01

    Here we report the results of our field observations in the Aflou structure (Algeria). This structure is interpreted as a Triassic diapir. The igneous rocks that outcrop in the area are Triassic/Jurassic ophites within the Triassic formation.

  20. Functional Nano-Structures Using Atomic Layer Deposition

    E-print Network

    Salgård Cunha, Pedro

    2014-05-27

    and the fabrication of the active material to be optimised separately. Given the separation of the template fabrication and the replica- tion a range of different replication techniques can be used, including electrochemistry, sol-gel and atomic layer deposition. One... -state electrolyte cells will be described, together with the advantages and disadvantages of these device geometries. 2.1 Conventional photovoltaic devices The word photovoltaic stems from the Greek word photo meaning ‘light’ and voltaic designating ‘electricity...

  1. Mechanically activating formation of layered structured bismuth titanate

    Microsoft Academic Search

    Biljana D. Stojanovic; C. O. Paiva-Santos; C. Jovalekic; A. Z. Simoes; F. M. Filho; Z. Lazarevic; J. A. Varela

    2006-01-01

    Bismuth titanate—Bi4Ti3O12 (BIT) with wide application in the electronic industry as capacitors, memory devices and sensors is the simplest compound in the Aurivillius family, which consists of (Bi2O2)2+ sheets alternating with (Bi2Ti3O10)2? perovskite-like layers. The synthesis of more resistive BIT ceramics would be preferable advance in obtaining of well-densified ceramic with small grains randomly oriented to limit the conductivity along

  2. Addendum: Improvement in photoconductor film properties by changing dielectric layer structures Addendum: Improvement in photoconductor film properties by changing dielectric layer structures

    NASA Astrophysics Data System (ADS)

    Kim, S.; Oh, K.; Lee, Y.; Jung, J.; Cho, G.; Jang, G.; Cha, B.; Park, J.; Nam, S.

    2011-02-01

    In recent times, digital X-ray detectors have been actively applied to the medical field; for example, digital radiography offers the potential of improved image quality and provides opportunities for advances in medical image management, computer-aided diagnosis and teleradiology. In this study, two candidate materials (HgI2 and PbI2) have been employed to study the influence of the dielectric structure on the performance of fabricated X-ray photoconducting films. Parylene C with high permittivity was deposited as a dielectric layer using a parylene deposition system (PDS 2060). The structural and morphological properties of the samples were evaluated field emission scanning electron microscopy and X-ray diffraction. Further, to investigate improvements in the electrical characteristics, a dark current in the dark room and sensitivity to X-ray exposure in the energy range of general radiography diagnosis were measured across the range of the operating voltage. The electric signals varied with the dielectric layer structure of the X-ray films. The PbI2 film with a bottom dielectric layer showed optimized electric properties. On the other hand, in the case of HgI2, the film with a top dielectric layer showed superior electric characteristics. Further, although the sensitivity of the film decreased, the total electrical efficiency of the film improved as a result of the decrease in dark current. When a dielectric layer is deposited on a photoconductor, the properties of the photoconductor, such as hole-electron mobility, should be considered to improve the image quality in digital medical imaging application. In this study, we have thus demonstrated that the use of dielectric layer structures improves the performance of photoconductors

  3. ORIGINAL PAPER Genetic diversity and colony breeding structure in native

    E-print Network

    Vargo, Ed

    is recognized as one of the most important invasive pest species. Originating from China, C. formosanus has the patterns of invasion and effects of introduction on the population genetics of this species is largely and ant species. Keywords Isoptera Á Invasive insect Á Microsatellites Á Bottleneck Á Genetic diversity

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

    PubMed

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

    2015-01-01

    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

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

    NASA Astrophysics Data System (ADS)

    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

    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.

  6. Gust structure in the neutral surface boundary layer

    SciTech Connect

    Doran, J.C.; Powell, D.C.

    1982-01-01

    Measured characteristics of gust amplitudes and times in the neutral surface boundary layer are presented. The probability of gust amplitudes exceeding a prescribed level is shown to decrease exponentially with amplitude, provided the amplitude is scaled with the root-mean-square turbulent speed. The 25 and 75 percentile conditional probabilities of gust duration obey power laws in the scaled amplitudes if the durations are normalized by N/sub 0/, the frequency of occurance of all gusts. These relationships are nearly independent of mean wind speed and measurement height. The effects of digital filtering of the data also are discussed.

  7. Aliphatic structure of humic acids; a clue to their origin

    USGS Publications Warehouse

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

    1981-01-01

    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.

  8. The dependence of magnetic properties of Co/FeMn bilayer structure on the magnitude of magnetic field applied during the layer deposition

    NASA Astrophysics Data System (ADS)

    Dzhun, I. O.; Dushenko, S. A.; Chechenin, N. G.; Konstantinova, E. A.

    2011-07-01

    By measuring the angular dependence of ferromagnetic resonance field at room and low temperatures, it is demonstrated that the magnitude of magnetic field applied during magnetron deposition of Ta/Co/FeMn/Ta structures influences their magnetic properties such as uniaxial and unidirectional anisotropy, magnetization and the exchange bias blocking temperature. The deposition field effects on the bilayer structure are compared with the effects on a similar structure, but without antiferromagnetic layer. The exchange bias blocking temperature of investigated structures is found to be significantly lower than the Néel temperature of a bulk antiferromagnet. The origin of the observed effects is shortly discussed.

  9. Coherent structures in a turbulent mixing layer - A comparison between direct numerical simulations and experiments

    NASA Technical Reports Server (NTRS)

    Metcalfe, R. W.; Menon, S.; Hussain, A. K. M. F.

    1985-01-01

    An eduction scheme has been developed in an attempt to determine the characteristics of large-scale vortical structures in a turbulent mixing layer. This analysis scheme has been applied to a set of experimental data taken in a new, larger mixing layer facility designed to minimize boundary and resonance effects. A similar scheme has been developed to apply to the results of a direct numerical simulation of a temporally growing mixing layer. A comparison of the two approaches shows important similarities in the coherent structures. The numerical simulations indicate that low levels of coherent forcing can dramatically change the evolution of the mixing layer. In the absence of such forcing, the numerical simulations and experiments show a lack of regularity in the transverse position, spacing, amplitude, shape and spanwise coherence of the large-scale vortical structures.

  10. Boundary layer structure over areas of heterogeneous heat fluxes

    SciTech Connect

    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

    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.

  11. Boundary layer structure over areas of heterogeneous heat fluxes

    SciTech Connect

    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

    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.

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

    E-print Network

    Sottos, Nancy R.

    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

  13. ORIGINAL PAPER Population genetic structure of the European kestrel

    E-print Network

    Paris-Sud XI, Université de

    the effects of isolation and reduced gene flow between habitat fragments within urban areas. However that were isolated by patches of less suitable or unsuitable habitat. Meanwhile, some species actively as environmental barriers and the spatial structure of habitat may all influence the genetic structure

  14. ORIGINAL PAPER Changes in forest structure and composition on Changbai

    E-print Network

    Paris-Sud XI, Université de

    in forest structure and tree species composition and (2) population dynamics of the dominant tree species natural disturbance affecting the forest structure and dynamics, especially for the coniferous forest in maintaining their respective populations. Keywords China forestry. Long-term study. Forest dynamics . Wind

  15. Vesicle layering in solidified intrusive magma bodies: a newly recognized type of igneous structure

    NASA Astrophysics Data System (ADS)

    Toramaru, Atsushi; Ishiwatari, Akira; Matsuzawa, Maki; Nakamura, Masaru; Arai, Shoji

    1996-12-01

    We report a novel type of layering structure in igneous rocks. The layering structure in the Ogi picrite sill in Sado Island, Japan, is spatially periodic, and appears to be caused by the variation in vesicle volume fraction. The gas phase forming the vesicles apparently exsolved from the interstitial melt at the final stage of solidification of the magma body. We call this type of layering caused by periodic vesiculation in the solidifying magma body "vesicle layering." The presence of vesicle layering in other basic igneous bodies (pillow lava at Ogi and dolerite sill at Atsumi, Japan) implies that it may be a fairly common igneous feature. The width of individual layers slightly, but regularly, increases with distance from the upper contact. The layering plane is perpendicular to the long axes of columnar joints, regardless of gravitational direction, suggesting that the formation of vesicles is mainly controlled by the temperature distribution in the cooling magma body. We propose a model of formation of vesicle layering which is basically the same as that for Liesegang rings. The interplay between the diffusion of heat and magmatic volatiles in melt, and the sudden vesiculation upon supersaturation, both play important roles.

  16. Probing structural inhomogeneity of graphene layers via nonlinear optical scattering.

    PubMed

    Bykov, Anton Y; Rusakov, Pavel S; Obraztsova, Elena D; Murzina, Tatiana V

    2013-11-15

    Incoherent optical second harmonic generation (SHG) is studied from series of multilayer graphene samples of various thickness manufactured by chemical vapor deposition technique and deposited over 150 ?m thick glass slides. Two different values of the correlation lengths are obtained from the linear and SHG indicatrices and reveal the existence of two types of optical scatterers. The first one is associated with homogeneous graphene areas, while the second one originates from wrinkles at the interdomain boundaries. Second harmonic imaging microscopy used to map the distribution of the second-order polarization at the nanoscale confirms the results of the nonlinear scattering data. PMID:24322081

  17. Variance of the Boundary Layer Structure in Dependence of distinct Circulation Types

    NASA Astrophysics Data System (ADS)

    Philipp, Andreas; Beck, Christoph; Jacobeit, Jucundus

    2015-04-01

    Variability of local climate features is related on the one hand to large scale circulation patterns, but is modified additionally by regional or local influences. This is true for basic climate variables like temperature and precipitation but also for more complex environmental conditions like air quality, e.g. PM10 concentration. Regional and local influences are to a large extend represented by the atmosperic boundary structure, i.e. the height of the mixed layer or its stability determining fluxes of temperature and impulse as well as water vapor etc. The presented study focusses on the interaction between the boundary layer structure and large scale circulation types for selected radiosonde stations. Crculation is described by a k-means cluster analysis of European circulation fields, retrieved from the NCEP/NCAR reanalysis. The boundary layer structure is derived from European radiosonde data collected in the Integrated Global Radiosonde Archive (IGRA). Here the mixed layer heigth and stability indices are anaylsed for within-type variance in a first step for different circulation types created independently from any other information. In a second step circulation types are created including boundary layer information. Both kinds of types are then realted to local impact variables in order to achieve conclusions about the interdependence of both, the large scale circulation and the boundary layer structure in modifying local climate variables.

  18. The effects of vortex structure and vortex translation on the tropical cyclone boundary layer wind field

    NASA Astrophysics Data System (ADS)

    Williams, Gabriel J.

    2015-03-01

    The effects of vortex translation and radial vortex structure in the distribution of boundary layer winds in the inner core of mature tropical cyclones are examined using a high-resolution slab model and a multilevel model. It is shown that the structure and magnitude of the wind field (and the corresponding secondary circulation) depends sensitively on the radial gradient of the gradient wind field above the boundary layer. Furthermore, it is shown that vortex translation creates low wave number asymmetries in the wind field that rotate anticyclonically with height. A budget analysis of the steady state wind field for both models was also performed in this study. Although the agradient force drives the evolution of the boundary layer wind field for both models, it is shown that the manner in which the boundary layer flow responds to this force differs between the two model representations. In particular, the inner core boundary layer flow in the slab model is dominated by the effects of horizontal advection and horizontal diffusion, leading to the development of shock structures in the model. Conversely, the inner core boundary layer flow in the multilevel model is primarily influenced by the effects of vertical advection and vertical diffusion, which eliminates shock structures in this model. These results further indicate that special care is required to ensure that qualitative applications from slab models are not unduly affected by the neglect of vertical advection. This article was corrected on 31 MAR 2015. See the end of the full text for details.

  19. Layered structure and related magnetic properties for annealed Fe/Ir(111) ultrathin films

    NASA Astrophysics Data System (ADS)

    Jiang, Pei-Cheng; Chen, Wei-Hsiang; Hsieh, Chen-Yuan; Tsay, Jyh-Shen

    2015-05-01

    After annealing treatments for fcc-Fe/Ir(111) below 600 K, the surface layers remain pseudomorphic. The Ir(111) substrate plays an important role on the expanded Fe lattice. At temperatures between 750 and 800 K, the surface composition shows a stable state and a c(2 × 4) structure is observed. We discover a layered structure composed of some Fe atoms on the top of a Fe0.5Ir0.5 interfacial alloy supported on the Ir(111) substrate. The competition between the negative formation heat of Fe0.5Ir0.5 and surface free energy of Fe causes the formation of layered structure. The existence of ferromagnetic dead layer coincides with the formation of fcc-Fe for ultrathin Fe on Fe0.5Ir0.5/Ir(111). For Fe films thicker than three monolayers, the linear increase of the Kerr intensity versus the Fe coverage is related to the growing of bcc-Fe on the surface where the Fe layer is incoherent to the underlying Fe0.5Ir0.5/Ir(111). These results emphasize the importance of the substrate induced strain and layered structure of Fe/Fe0.5Ir0.5/Ir(111) on the magnetic properties and provide valuable information for future applications.

  20. Computational methods in eddy current crack detection at fastener sites in multi-layer structures

    Microsoft Academic Search

    Jeremy S. Knopp; John C. Aldrin; Kumar V. Jata

    2009-01-01

    Reliable detection of both surface and subsurface cracks around fastener sites continues to be a need for maintaining ageing aircraft structures. In this work, a comprehensive overview of both experimental and modelling work addressing eddy current crack detection around fastener holes in multi-layer structures is presented. This overview consists of a strategy for the application of computational methods along with

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

    E-print Network

    Cao, Wenwu

    Acoustic band-gap engineering using finite-size layered structures of multiple periodicity Mingrong and also measured as a function of frequency. It was found that acoustic band gaps can be created using structure, very sharp passbands and very broad stopbands can be engineered for acoustic waves. Such acoustic

  2. Double-layer structure, corrosion and corrosion inhibition of copper in aqueous solution

    Microsoft Academic Search

    O. M. Magnussen; M. R. Vogt; J. Scherer; R. J. Behm

    1998-01-01

    In situ STM results on the surface structure of Cu(100) electrodes in sulfuric and hydrochloric acid solution, both at potentials in the double-layer range and at the onset of anodic Cu dissolution, are presented. The Cu surface structure, morphology and dynamic behavior are found to depend strongly on the anion species and on the potential. In both electrolytes dissolution of

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

    E-print Network

    Vu-Quoc, Loc

    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

  4. Love wave propagation in piezoelectric layered structure with dissipation Jianke Du a,b,*, Kai Xian a

    E-print Network

    Wang, Ji

    Love wave propagation in piezoelectric layered structure with dissipation Jianke Du a,b,*, Kai Xian October 2008 Keywords: Love waves Piezoelectric Viscous Dissipation Sensors a b s t r a c t We investigate characteristics of Love wave propagation in a layered structure, which involves a thin pie- zoelectric layer

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

    NASA Astrophysics Data System (ADS)

    Deinega, Alexei; Valuev, Ilya

    2011-01-01

    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.

  6. Layers and tubes of fluorographene C4F: Stability, structural and electronic properties from DFTB calculations

    NASA Astrophysics Data System (ADS)

    Enyashin, A. N.; Ivanovskii, A. L.

    2013-06-01

    By means of the DFTB band structure calculations we have explored the layers' isomerism of fluorographene C4F. The relative stability, structural and electronic properties of the C4F layers and nanotubes have been revealed depending on the possible types of fluorine coverage: single-sided, double-sided or so-called non-uniform variants. Our main finding is that the aforementioned types of fluorine coverage are crucial for the morphology of these materials. At the non-uniform or single-sided coverage types the C4F structures aspire to the spontaneous folding in order to minimize their surface tension.

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

    SciTech Connect

    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

    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.

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

    NASA Technical Reports Server (NTRS)

    Koontz, Steven L. (inventor)

    1994-01-01

    A microporous structure with layered interstitial surface treatments, and method and apparatus for preparation thereof is presented. 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 atomic 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.

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

    NASA Technical Reports Server (NTRS)

    Koontz, Steven L. (inventor)

    1992-01-01

    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.

  10. Instantaneous wavenumber estimation for damage quantification in layered plate structures

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

    Guided wavefield detection is at the basis of a number of promising techniques for the identification and the characterization of damage in plate structures. Among the processing techniques proposed, the estimation of instantaneous and local wavenumbers can lead to effective metrics that quantify the extent of delaminations in composite plates. 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 approach for damage assessment in composites.

  11. Beyond Phonics: Integrated Decoding and Spelling Instruction Based on Word Origin and Structure.

    ERIC Educational Resources Information Center

    Henry, Marcia K.

    1988-01-01

    A discussion-oriented, direct approach to teaching decoding and spelling based on word origin and structure is proposed. The instruction leads students to a comparison and contrast of letter-sound correspondences, syllable patterns, and morpheme patterns in English words of Anglo-Saxon, Romance, and Greek origin. (Author/JDD)

  12. Spiraling spin structure in an exchange-coupled antiferromagnetic layer

    PubMed

    Yang; Chien

    2000-09-18

    Using trilayers of permalloy/FeMn/Co with various thicknesses t(AF) of the antiferromagnetic FeMn, we have observed evidence of a spiraling spin structure within FeMn. For t(AF)<90 A, the turn angle straight theta of the spiral varies as straight theta = (1.76 degrees /A)t(AF). PMID:10978116

  13. Polar cap F layer patches: structure and dynamics

    Microsoft Academic Search

    E. J. Weber; J. A. Klobuchar; J. Buchau; R. C. Livingston; O. De La Beaujardiere; M. McCready; J. G. Moore; G. J. Bishop

    1986-01-01

    Coordinated measurements of F-region plasma patches were conducted on February 3\\/4, 1984, from Thule and Sondrestrom, Greenland. Optical, ionsonde, amplitude scintillation, total electron content (TEC), and incoherent scatter radar measurements were combined to reveal several new aspects of the structure and transport of these localized regions of enhanced F region ionization. For the first time, these patches were directly tracked

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

    E-print Network

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

    2005-09-05

    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.

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

    E-print Network

    Diederik Aerts; Sandro Sozzo

    2015-03-10

    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.

  16. On the origin of irregular structure in Saturn's rings

    E-print Network

    Scott Tremaine

    2002-11-07

    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.

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

    SciTech Connect

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

    1996-02-29

    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.

  18. Influence of relaxation processes on the structure of a thermal boundary layer in partially ionized argon

    NASA Astrophysics Data System (ADS)

    van Dongen, M. E. H.; van Eck, R. B. P.; Hagebeuk, H. J. L.; Hirschberg, A.; Hutten-Mansfeld, A. C. B.; Jager, H. J.; Willems, J. F. H.

    1981-08-01

    A model for the unsteady thermal boundary layer development at the end wall of a shock tube in partially ionized atmospheric argon is proposed. Consideration is given to ionization and thermal relaxation processes. In order to obtain some insight into the influence of the relaxation processes on the structure of the boundary layer, a study of the frozen and equilibrium limits has been carried out. The transition from a near-equilibrium situation in the outer part of the boundary layer towards a frozen situation near the wall has been determined numerically. Experimental data on the electron and atom density profiles obtained from laser schlieren and absorption measurements are presented. A quantitative agreement between theory and experiment is found for a moderate degree of ionization (3%). At a higher degree of ionization, the structure of the boundary layer is dominated by the influence of radiation cooling, which has been neglected in the model.

  19. Resonance cone structure in a warm inhomogeneous bounded plasma with lower-hybrid resonance layers

    NASA Technical Reports Server (NTRS)

    Grabbe, C. L.

    1985-01-01

    The paper presents a theoretical study of the problem of the wave fields excited by a gap source at the edge of an inhomogeneous magnetized plasma with a pair of lower-hybrid resonance layers present and bounded by conducting walls. The approach used is that of a solution as a sum of multiply reflected extraordinary mode and ion-thermal resonance cones as an alternative to the guided-wave mode approach. A diagrammatic scheme for writing the solution is given which can be used to determine in great detail the structure and properties of the resonance cones and the way they transform across the back-to-back hybrid layers. Evanescent resonance cones are shown to exist in the high-density region between the hybrid resonance layers and to tunnel through to the other side, maintaining this general structure if the layer is relatively thin.

  20. Structural diagnostics of the tropopause inversion layer and its evolution

    NASA Astrophysics Data System (ADS)

    Gettelman, A.; Wang, T.

    2015-01-01

    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.

  1. Synaptic deficits in layer 5 neurons precede overt structural decay in 5xFAD mice

    PubMed Central

    Buskila, Yossi; Crowe, Sarah E; Ellis-Davies, Graham C.R.

    2014-01-01

    Synaptic decay and neurodegeneration are hallmarks of Alzheimer’s disease that are thought to precede dementia. Recently, we have reported that the first signs of neuritic dystrophy in a new transgenic mouse model of familial Alzheimer’s disease called the “5xFAD” are axonal dystrophy followed by loss of spines on basal dendrites. The 5xFAD mouse has profound loss of layer 5 neurons by 12 months, and these initial structural insults appear between 4 to 6 months of age. Here, we test, for the first time, if synaptic failure of layer 5 neurons in the 5xFAD mouse precedes these structural changes. We used longitudinal, in vivo two-photon fluorescence imaging of bigenic 5xFAD/YFP mice to assess the overall structural stability of layer 5 neurons in young mice (age less than 14 weeks). We found these neurons to be structurally and morphologically sound. In parallel, we used in vitro, whole-cell patch clamp electrophysiology of layer 5 pyramidal neurons, from mice aged 8-12 weeks, to reveal significant pre- and postsynaptic defects in these cells. Thus our data suggest that layer 5 neurons in the 5xFAD mouse model have synaptic deficits at an early time point, before any overt structural dystrophy, and that such synaptic failure, with co-temporal biochemical changes, may be an early step in neuronal loss. PMID:24055684

  2. Structure of multi-layer spherical crystals of graphite in cast iron

    NASA Astrophysics Data System (ADS)

    Kurepina, V. V.; Chernovol, A. V.

    A careful investigation of the structure of graphite inclusions in an yttrium-inoculated hyper-eutectic cast iron was carried out. It was established that the outer zone of two-layer spheroidal inclusions is formed on account of group growth of individual graphite crystallites that were nucleated on the surface of the primary core. Indications were obtained on how the rarely-encountered three-layer inclusions might be formed.

  3. Formation of Metal\\/Ferroelectric\\/Insulator\\/Semiconductor Structure with a CeO2 Buffer Layer

    Microsoft Academic Search

    Tadahiko Hirai; Kazuhiro Teramoto; Takeharu Nishi; Takaaki Goto; Yasuo Tarui

    1994-01-01

    Experimental results derived from the capacitance vs voltage (C-V) characteristics of metal\\/ferroelectric\\/insulator\\/semiconductor (MFIS) structures are described. PbTiO3 ferroelectric films of 600 Å thickness were grown on CeO2\\/Si(100) substrate by digital chemical vapor deposition (digital CVD). As the buffer layer between ferroelectric and Si substrate, 150-Å-thick CeO2 intermediate epitaxial layers were grown on a (100) silicon substrate by vacuum evaporation. The

  4. Preparation and photoluminescence of SiC\\/Si\\/SiO 2 multi-layer structure

    Microsoft Academic Search

    L. Wang; Z. J. Liang; Z. B. Wang; F. L. Zhao; Z. H. He; Dihu Chen

    2007-01-01

    A multi-layer structure of SiC\\/Si\\/SiO2 was fabricated by successive deposition of SiC and Si using plasma-enhanced chemical vapor deposition and post-deposition thermal oxidation of the part as-deposited Si surface layer. The samples oxidized at 900°C for various annealing times exhibit two strong photoluminescence peaks in the blue-light range, one is a stable PL peak at 433nm and the other is

  5. Dynamical origin and the pole structure of X(3872)

    E-print Network

    I. V. Danilkin; Yu. A. Simonov

    2010-08-25

    The dynamical mechanism of channel coupling with the decay channels is applied to the case of coupled charmonium - $DD^*$ states with $J^{PC}=1^{++}$. A pole analysis is done and the $DD^*$ production cross section is calculated in qualitative agreement with experiment. The sharp peak at the $D_0D^*_0$ threshold and flat background are shown to be due to Breit-Wigner resonance, shifted by channel coupling from the original position of 3954 MeV for the $2^3P_1$, $Q\\bar Q$ state. A similar analysis, applied to the $n=2$, $^3P_2$, $^1P_1$, $^3P_0$, allows us to associate the first one with the observed $Z(3930)$ J=2 and explains the destiny of $^3P_0$.

  6. S-layers at second glance? Altiarchaeal grappling hooks (hami) resemble archaeal S-layer proteins in structure and sequence

    PubMed Central

    Perras, Alexandra K.; Daum, Bertram; Ziegler, Christine; Takahashi, Lynelle K.; Ahmed, Musahid; Wanner, Gerhard; Klingl, Andreas; Leitinger, Gerd; Kolb-Lenz, Dagmar; Gribaldo, Simonetta; Auerbach, Anna; Mora, Maximilian; Probst, Alexander J.; Bellack, Annett; Moissl-Eichinger, Christine

    2015-01-01

    The uncultivated “Candidatus Altiarchaeum hamiconexum” (formerly known as SM1 Euryarchaeon) carries highly specialized nano-grappling hooks (“hami”) on its cell surface. Until now little is known about the major protein forming these structured fibrous cell surface appendages, the genes involved or membrane anchoring of these filaments. These aspects were analyzed in depth in this study using environmental transcriptomics combined with imaging methods. Since a laboratory culture of this archaeon is not yet available, natural biofilm samples with high Ca. A. hamiconexum abundance were used for the entire analyses. The filamentous surface appendages spanned both membranes of the cell, which are composed of glycosyl-archaeol. The hami consisted of multiple copies of the same protein, the corresponding gene of which was identified via metagenome-mapped transcriptome analysis. The hamus subunit proteins, which are likely to self-assemble due to their predicted beta sheet topology, revealed no similiarity to known microbial flagella-, archaella-, fimbriae- or pili-proteins, but a high similarity to known S-layer proteins of the archaeal domain at their N-terminal region (44–47% identity). Our results provide new insights into the structure of the unique hami and their major protein and indicate their divergent evolution with S-layer proteins. PMID:26106369

  7. A parametric analysis of radiative structure in aerobrake shock layers

    NASA Technical Reports Server (NTRS)

    Greendyke, Robert B.

    1992-01-01

    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.

  8. Structural correlations: Design levers for performance and durability of catalyst layers

    NASA Astrophysics Data System (ADS)

    Artyushkova, Kateryna; Atanassov, Plamen; Dutta, Monica; Wessel, Silvia; Colbow, Vesna

    2015-06-01

    Durability of the catalyst layer (CL) is of vital importance in the large-scale deployment of PEMFCs. It is necessary to determine parameters that represent properties of catalysts layer and other cathode components for optimization of fuel cell performance and durability. The structure, morphology and surface chemistry of the catalyst powder affects the ionomer and catalyst interaction, ionomer dispersion in the catalyst layer and, for this reason, its morphology and chemistry. These, in turn, affect the catalyst layer effective properties such as thickness, porosity, tortuosity, diffusivity, conductivity and others, directly influencing electrode performance and durability. In this study, X-ray Photoelectron Spectroscopy and SEM are used to quantify surface species and morphology of membrane electrode assemblies (MEAs) tested under different accelerated stress test (AST) conditions. Correlations between composition, structure and morphological properties of cathode components and the catalyst layer have been developed and linked to catalyst layer performance losses. The key relationships between the catalyst layer effective properties and performance and durability provide design and optimization levers for making MEAs for different operating regimes.

  9. Bi-layered calcium phosphate cement-based composite scaffold mimicking natural bone structure

    NASA Astrophysics Data System (ADS)

    He, Fupo; Ye, Jiandong

    2013-08-01

    In this study, a core/shell bi-layered calcium phosphate cement (CPC)-based composite scaffold with adjustable compressive strength, which mimicked the structure of natural cortical/cancellous bone, was fabricated. The dense tubular CPC shell was prepared by isostatic pressing CPC powder with a specially designed mould. A porous CPC core with unidirectional lamellar pore structure was fabricated inside the cavity of dense tubular CPC shell by unidirectional freeze casting, followed by infiltration of poly(lactic-co-glycolic acid) and immobilization of collagen. The compressive strength of bi-layered CPC-based composite scaffold can be controlled by varying thickness ratio of dense layer to porous layer. Compared to the scaffold without dense shell, the pore interconnection of bi-layered scaffold was not obviously compromised because of its high unidirectional interconnectivity but poor three dimensional interconnectivity. The in vitro results showed that the rat bone marrow stromal cells attached and proliferated well on the bi-layered CPC-based composite scaffold. This novel bi-layered CPC-based composite scaffold is promising for bone repair.

  10. Satellited Y chromosomes: Structure, origin, and clinical significance

    Microsoft Academic Search

    M. Schmid; T. Haaf; Eva Solleder; W. Schempp; M. Leipoldt; H. Heilbronner

    1984-01-01

    Three cases of inherited satellited Y chromosomes (Yqs) were analysed using several cytogenetic techniques. The cytogenetic data of the 14 cases of Yqs chromosomes described to date were reviewed. All Yqs chromosomes carry an active nucleolus organizer region (NOR) in their long arm and must have developed from translocations involving the short arms of the acrocentric autosomes. The structure of

  11. ORIGINAL PAPER Synthesis and Crystal Structure of the Azoxydichinyl Helicene,

    E-print Network

    Gates, Kent. S.

    serve to link the he- licenes into a one dimensional chain structure forming a hydrogen bonded bridge The compound, 6-hydroxylaminoquinoline (100 mg, 0.625 mmol), was dissolved in DMF (1 mL) and sprayed into warm, USA 123 J Chem Crystallogr (2011) 41:1712­1716 DOI 10.1007/s10870-011-0162-z #12;solution, warm sodium

  12. Electroluminescent devices using a layered organic-inorganic perovskite structure as emitter

    Microsoft Academic Search

    Michael Coelle; Wolfgang Bruetting; Markus Schwoerer; Masayuki Yahiro; Tetsuo Tsutsui

    2001-01-01

    12 Self-organizing layered perovskite compounds like (C6H5C2H4NH3)2PbI4 naturally form a dielectric quantum-well structure in which semiconducting PbI4 layers and organic (C6H5C2H4NH3) layers are alternately piled up. Due to their low- dimensional semiconductor nature they exhibit a strong absorption and sharp photoluminescence from the exciton band. In electroluminescent devices pure green emission peaking at 520 nm with a very narrow half-width

  13. Bragg resonances of magnetostatic surface spin waves in a layered structure: Magnonic crystal-dielectric-metal

    NASA Astrophysics Data System (ADS)

    Beginin, E. N.; Filimonov, Yu. A.; Pavlov, E. S.; Vysotskii, S. L.; Nikitov, S. A.

    2012-06-01

    It is experimentally shown that metal cladding of the surface of a one-dimensional magnonic crystal destroys the Bragg band gaps in microwave transmission spectra of propagating magnetostatic surface spin waves in magnonic crystal. This is a consequence of violating a phase synchronism condition of forward and reflected by a magnonic crystal magnetostatic surface wave. When a magnetostatic surface wave propagates in a layered structure, ferromagnetic film with a magnonic crystal-dielectric layer-metal cladding this synchronism condition can also be fulfilled, not depending on the thickness of a dielectric layer.

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

    SciTech Connect

    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

    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.

  15. X-ray reflectivity analysis of giant-magnetoresistance spin-valve layered structures

    Microsoft Academic Search

    T. C. Huang; J.-P. Nozieres; V. S. Speriosu; H. Lefakis; B. A. Gurney

    1992-01-01

    The amount of intermixing at the interfaces of sputter-deposited spin-valve layered structures, comprising Si\\/Ta (50 A?)\\/NiFe (75 A?)\\/Cu (22.5 A?)\\/NiFe (50 A?)\\/FeMn (110 A?)\\/Ta (50 A?), were obtained from least-squares refinement of x-ray reflectivity data. The observations were modeled by layers of nominal composition with compositional inhomogeneity at the interfaces. Layer thicknesses deduced from x-ray analysis were generally within a

  16. First-principles based semi-classical model for transport in magnetic layered structures

    SciTech Connect

    Butler, W.H.; Zhang, X.G. [Oak Ridge National Lab., TN (United States). Metals and Ceramics Div.] [Oak Ridge National Lab., TN (United States). Metals and Ceramics Div.; MacLaren, J.M. [Tulane Univ., New Orleans, LA (United States). Dept. of Physics] [Tulane Univ., New Orleans, LA (United States). Dept. of Physics

    1998-07-01

    The authors present a first principles based semiclassical model for transport in an inhomogeneous magnetic layered structure. The approach solves the Boltzmann transport equation using the band structure, Bloch wave velocities and scattering matrices, describing the reflection and transmission of Bloch waves from interfaces, derived from ab-initio local spin density electronic structure calculations. The model has been tested for thick Co and Cu films as well as for a set of Co{vert_bar}Cu{vert_bar}Co spin valves.

  17. Fabrication and Mechanical Evaluation of Anatomically-Inspired Quasilaminate Hydrogel Structures with Layer-Specific Formulations

    PubMed Central

    Tseng, Hubert; Cuchiara, Maude L.; Durst, Christopher A.; Cuchiara, Michael P.; Lin, Chris J.; West, Jennifer L.; Grande-Allen, K. Jane

    2012-01-01

    A major tissue engineering challenge is the creation of multilaminate scaffolds with layer-specific mechanical properties representative of native tissues, such as heart valve leaflets, blood vessels, and cartilage. For this purpose, poly(ethylene glycol) diacrylate (PEGDA) hydrogels are attractive materials due to their tunable mechanical and biological properties. This study explored the fabrication of trilayer hydrogel quasilaminates. A novel sandwich method was devised to create quasilaminates with layers of varying stiffnesses. The trilayer structure was comprised of two “stiff” outer layers and one “soft” inner layer. Tensile testing of bilayer quasilaminates demonstrated that these scaffolds do not fail at the interface. Flexural testing showed that the bending modulus of acellular quasilaminates fell between the bending moduli of the “stiff” and “soft” hydrogel layers. The bending modulus and swelling of trilayer scaffolds with the same formulations were not significantly different than single layer gels of the same formulation. The encapsulation of cells and the addition of phenol red within the hydrogel layers decreased bending modulus of the trilayer scaffolds. The data presented demonstrates that this fabrication method can make quasilaminates with robust interfaces, integrating layers of different mechanical properties and biofunctionalization, and thus forming the foundation for a multilaminate scaffold that more accurately represents native tissue. PMID:23053300

  18. Very-large-scale coherent structures in the wall pressure field beneath a supersonic turbulent boundary layer.

    SciTech Connect

    Beresh, Steven Jay; Spillers, Russell Wayne; Henfling, John Francis; Pruett, Brian Owen Matthew

    2010-11-01

    Previous wind tunnel experiments up to Mach 3 have provided fluctuating wall-pressure spectra beneath a supersonic turbulent boundary layer, which essentially are flat at low frequency and do not exhibit the theorized {psi}{sup 2} dependence. The flat portion of the spectrum extends over two orders of magnitude and represents structures reaching at least 100 {delta} in scale, raising questions about their physical origin. The spatial coherence required over these long lengths may arise from very-large-scale structures that have been detected in turbulent boundary layers due to groupings of hairpin vortices. To address this hypothesis, data have been acquired from a dense spanwise array of fluctuating wall pressure sensors, then invoking Taylor's Hypothesis and low-pass filtering the data allows the temporal signals to be converted into a spatial map of the wall pressure field. This reveals streaks of instantaneously correlated pressure fluctuations elongated in the streamwise direction and exhibiting spanwise alternation of positive and negative events that meander somewhat in tandem. As the low-pass filter cutoff is lowered, the fluctuating pressure magnitude of the coherent structures diminishes while their length increases.

  19. Shallow-marine impact origin of the Wetumpka structure (Alabama, USA)

    Microsoft Academic Search

    David T. King Jr.; Thornton L. Neathery; Lucille W. Petruny; Christian Koeberl; Willis E. Hames

    2002-01-01

    The Wetumpka structure, an arcuate, 7.6 km diameter, rimmed feature of the inner Coastal Plain, Alabama, is a Late Cretaceous shallow-marine impact crater. In this paper, we show unequivocal evidence of Wetumpka’s impact origin. Within and about this structure, pre-existing Upper Cretaceous stratigraphy was resedimented and(or) deformed, thus creating distinctive intra-structure and extra-structure terrains. These terrains are located, respectively, within

  20. Shallow-marine impact origin of the Wetumpka structure (Alabama, USA)

    Microsoft Academic Search

    David T. King; Thornton L. Neathery; Lucille W. Petruny; Christian Koeberl; Willis E. Hames

    2002-01-01

    The Wetumpka structure, an arcuate, 7.6 km diameter, rimmed feature of the inner Coastal Plain, Alabama, is a Late Cretaceous shallow-marine impact crater. In this paper, we show unequivocal evidence of Wetumpka's impact origin. Within and about this structure, pre-existing Upper Cretaceous stratigraphy was resedimented and(or) deformed, thus creating distinctive intra-structure and extra-structure terrains. These terrains are located, respectively, within

  1. Observing the Origins of Galaxy Structure in the Illustris Simulation

    NASA Astrophysics Data System (ADS)

    Snyder, Greg

    2014-10-01

    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.

  2. Measuring the atomic-scale structure of a Helmholtz `double layer'

    NASA Astrophysics Data System (ADS)

    Hayes, T. M.; Lurio, L. B.; Pant, J.; Wang, L.; Furtak, T. E.

    1997-03-01

    We propose a powerful new technique to measure the structure of the Helmholtz `double layer' formed in an aqueous electrolyte in contact with a metal electrode. The critical innovation is to couple a structural probe which is specific to the environment of a particular atom species with a `tag' layer of metal atoms electrodeposited in underpotential conditions on an unlike-metal electrode. The efficacy of our approach is illustrated through a measurement of the double layer in a dilute sulfuric acid electrolyte in contact with a Pt electrode decorated with Cu atoms, the surface structure of which we have studied extensively.( T E Furtak, L Wang, J Pant, K Pansewicz, and T M Hayes, J Electrochem Soc 141) 2369 (1994); L B Lurio, J Pant, T M Hayes, L Wang, and T E Furtak, Physica B 208 413 (1995)

  3. Instantaneous Wavenumber Estimation for Damage Quantification in Layered Plate Structures

    NASA Technical Reports Server (NTRS)

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

    2014-01-01

    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.

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

    PubMed

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

    2015-03-01

    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

  5. Structural analysis and characterization of layer perovskite oxynitrides made from Dion Jacobson oxide precursors

    NASA Astrophysics Data System (ADS)

    Schottenfeld, Joshua A.; Benesi, Alan J.; Stephens, Peter W.; Chen, Gugang; Eklund, Peter C.; Mallouk, Thomas E.

    2005-07-01

    A three-layer oxynitride Ruddlesden-Popper phase Rb 1+xCa 2Nb 3O 10-xN x· yH 2O ( x=0.7-0.8, y=0.4-0.6) was synthesized by ammonialysis at 800 °C from the Dion-Jacobson phase RbCa 2Nb 3O 10 in the presence of Rb 2CO 3. Incorporation of nitrogen into the layer perovskite structure was confirmed by XPS, combustion analysis, and MAS NMR. The water content was determined by thermal gravimetric analysis and the rubidium content by ICP-MS. A similar layered perovskite interconversion occurred in the two-layer Dion-Jacobson oxide RbLaNb 2O 7 to yield Rb 1+xLaNb 2O 7-xN x· yH 2O ( x=0.7-0.8, y=0.5-1.0). Both compounds were air- and moisture-sensitive, with rapid loss of nitrogen by oxidation and hydrolysis reactions. The structure of the three-layer oxynitride Rb 1.7Ca 2Nb 3O 9.3N 0.7·0.5H 2O was solved in space group P4 /mmm with a=3.887(3) and c=18.65(1) Å, by Rietveld refinement of X-ray powder diffraction data. The two-layer oxynitride structure Rb 1.8LaNb 2O 6.3N 0.7·1.0H 2O was also determined in space group P4 /mmm with a=3.934(2) and c=14.697(2) Å. GSAS refinement of synchrotron X-ray powder diffraction data showed that the water molecules were intercalated between a double layer of Rb+ ions in both the two- and three-layer Ruddlesden-Popper structures. Optical band gaps were measured by diffuse reflectance UV-vis for both materials. An indirect band gap of 2.51 eV and a direct band gap of 2.99 eV were found for the three-layer compound, while an indirect band gap of 2.29 eV and a direct band gap of 2.84 eV were measured for the two-layer compound. Photocatalytic activity tests of the three-layer compound under 380 nm pass filtered light with AgNO 3 as a sacrificial electron acceptor gave a quantum yield of 0.025% for oxygen evolution.

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

    PubMed

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

    2013-01-01

    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

  7. Structural-acoustic optimization of structures excited by turbulent boundary layer flow

    NASA Astrophysics Data System (ADS)

    Shepherd, Micah R.

    In order to reduce noise radiation of aircraft or marine panels, a general structural-acoustic optimization technique is presented. To compute the structural-acoustic response, a modal approach based on finite element / boundary element analysis is used which can easily incorporate fluid loading, added structures and static pre-loads. Simple deterministic or complex random forcing functions are included in the analysis by transforming their cross-spectral density matrices to modal space. Particular emphasis is placed in this dissertation on structures excited by the fluctuating pressures due to turbulent boundary layer (TBL) flow. An efficient frequency-spacing is also used to minimize evaluation time but ensure accuracy. The response from the structural-acoustic analysis is coupled to an evolutionary strategy with covariance matrix adaptation (CMA-ES) to find the best design for low noise and weight. CMA-ES, a stochastic optimizer with robust search properties, samples candidate solutions from a multi-variate normal distribution and adapts the covariance matrix to favor good solutions. The optimization procedure is validated by minimizing the sound radiated by a point-driven ribbed panel and comparing the optimization results to an exhaustive search of the design space. Structural-acoustic optimization is then performed on a curved marine panel with heavy fluid loading excited by slow TBL flow. A weighted combination of noise radiation and mass are minimized by changing the thickness of strips and patches of elements. An uncorrelated pressure approximation is used to estimate the modal force due to TBL flow thus reducing the evaluation time required to compute the objective function. The results show that the best noise reduction is achieved by minimizing the modal acceptance of energy by the panel. This is equivalent to pushing the structural modes away from the peak frequency range of the forcing function. Additionally, the Pareto trade-off curve between total sound power and panel mass is estimated to show the best designs which will simultaneously reduce both noise and weight. As a final case, the sound power radiated is minimized for a ribbed aircraft panel excited by TBL flow at typical cruise conditions. A static pressure load is applied to the panel to simulate cabin pressurization during flight and the rib locations and cross-sectional area are used as the design variables during optimization. Nearly 10 dB of reduction is achieved by pushing the ribs to the edge of the panel, thus lowering the modal amplitudes excited by the forcing function. The optimal configuration is also found for a higher speed and a larger downstream distance. The design variables are then separated, and the optimization is repeated to determine the coupling between the design variables. Finally, a static constraint is included in the procedure using a very low-frequency dynamic calculation to approximate a static response. The constraint limits the amount of reduction that can be achieved by the optimizer. Guidance for designing quiet aircraft panels is then presented.

  8. Analysis of mixed-layer clay mineral structures

    USGS Publications Warehouse

    Bradley, W.F.

    1953-01-01

    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.

  9. Saturn layered structure and homogeneous evolution models with different EOSs

    NASA Astrophysics Data System (ADS)

    Nettelmann, Nadine; Püstow, Robert; Redmer, Ronald

    2013-07-01

    The core mass of Saturn is commonly assumed to be 10-25M? as predicted by interior models with various equations of state (EOSs) and the Voyager gravity data, and hence larger than that of Jupiter (0-10M?). We here re-analyze Saturn's internal structure and evolution by using more recent gravity data from the Cassini mission and different physical equations of state: the ab initio LM-REOS which is rather soft in Saturn's outer regions but stiff at high pressures, the standard Sesame-EOS which shows the opposite behavior, and the commonly used SCvH-i EOS. For all three EOS we find similar core mass ranges, i.e. of 0-20M? for SCvH-i and Sesame EOS and of 0-17M? for LM-REOS. Assuming an atmospheric helium mass abundance of 18%, we find maximum atmospheric metallicities, Zatm of 7× solar for SCvH-i and Sesame-based models and a total mass of heavy elements, MZ of 25-30M?. Some models are Jupiter-like. With LM-REOS, we find MZ = 16-20M?, less than for Jupiter, and Zatm ? 3× solar. For Saturn, we compute moment of inertia values ? = 0.2355(5). Furthermore, we confirm that homogeneous evolution leads to cooling times of only ˜2.5 Gyr, independent on the applied EOS. Our results demonstrate the need for accurately measured atmospheric helium and oxygen abundances, and of the moment of inertia for a better understanding of Saturn's structure and evolution.

  10. The structure of nanoscale polaron correlations in the layered manganites

    NASA Astrophysics Data System (ADS)

    Campbell, Branton

    2002-03-01

    Recent x-ray and neutron scattering experiments have uncovered nanoscale polaron correlations that play an essential role in the colossal magnetoresistive (CMR) behavior of the perovskite manganites. Short-range polaronic order decreases the charge-carrier mobility of the high-temperature paramagnetic state, and subsequently becomes unstable at the ferromagnetic transition, contributing to a pronounced resistivity decrease at T_C. In the bilayered perovskite system La_2-2xSr_1+2xMn_2O7 (0.3 < x < 0.5), weak x-ray diffuse scattering maxima reveal a one-dimensional incommensurate structural modulation with wavevector q = (0.3, 0, ± 1) and a correlation length of 10 to 30 Angstroms. A crystallographic analysis of the diffuse satellite intensities yields a longitudinal Jahn-Teller stretch mode suggestive of charge-density-wave fluctuations. Within the correlated regions, polaronic eg electrons form a striped pattern of occupied d(3x^2-r^2) orbitals. Dynamic polaron correlations of the zig-zag orbital type are also observed above TC and exhibit distinctly glassy behavior. These structures provide unique insights into the nature of strongly correlated polaronic systems. Collaborators: R. Osborn, D.N. Argyriou, S. Rosenkranz, L. Vasiliu-Doloc, J.F. Mitchell, S.K. Sinha, J.W. Lynn, C.D. Ling, Z. Islam, U. Ruett, and A. Berger. This work was supported by the U.S. DOE Office of Science contract No. W-31-109-ENG-38.

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

    PubMed

    Xu, Yan; Wu, Weiying; Chang, Eric I-Chao; Chen, Danny; Mu, Jian; Lee, Peter P; Blenman, Kim R M; Tu, Zhuowen

    2015-04-01

    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

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

    NASA Astrophysics Data System (ADS)

    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

    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.

  13. Spatial properties of entangled photon pairs generated in nonlinear layered structures

    SciTech Connect

    Perina, Jan Jr. [Palacky University, RCPTM, Joint Laboratory of Optics, 17. listopadu 12, 771 46 Olomouc (Czech Republic)

    2011-11-15

    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 antibunching and anticoalescence 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.

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

    NASA Astrophysics Data System (ADS)

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

    2013-07-01

    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.

  15. The structure and chemical layering of Proterozoic stromatolites in the Mojave Desert

    NASA Astrophysics Data System (ADS)

    Douglas, Susanne; Perry, Meredith E.; Abbey, William J.; Tanaka, Zuki; Chen, Bin; McKay, Christopher P.

    2015-07-01

    The Proterozoic carbonate stromatolites of the Pahrump Group from the Crystal Spring formation exhibit interesting layering patterns. In continuous vertical formations, there are sections of chevron-shaped stromatolites alternating with sections of simple horizontal layering. This apparent cycle of stromatolite formation and lack of formation repeats several times over a vertical distance of at least 30 m at the locality investigated. Small representative samples from each layer were taken and analysed using X-ray diffraction (XRD), X-ray fluorescence (XRF), environmental scanning electron microscopy - energy dispersive X-ray spectrometry, and were optically analysed in thin section. Optical and spectroscopic analyses of stromatolite and of non-stromatolite samples were undertaken with the objective of determining the differences between them. Elemental analysis of samples from within each of the four stromatolite layers and the four intervening layers shows that the two types of layers are chemically and mineralogically distinct. In the layers that contain stromatolites the Ca/Si ratio is high; in layers without stromatolites the Ca/Si ratio is low. In the high Si layers, both K and Al are positively correlated with the presence and levels of Si. This, together with XRD analysis, suggested a high K-feldspar (microcline) content in the non-stromatolitic layers. This variation between these two types of rocks could be due to changes in biological growth rates in an otherwise uniform environment or variations in detrital influx and the resultant impact on biology. The current analysis does not allow us to choose between these two alternatives. A Mars rover would have adequate resolution to image these structures and instrumentation capable of conducting a similar elemental analysis.

  16. Strong, macroporous, and in situ-setting calcium phosphate cement-layered structures

    PubMed Central

    Xu, Hockin H.K.; Burguera, Elena F.; Carey, Lisa E.

    2009-01-01

    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

  17. Effects of seed layers on structural, morphological, and optical properties of ZnO nanorods.

    PubMed

    Lee, Geon Joon; Min, Soon-Ki; Oh, Cha-Hwan; Leel, YoungPak; Lim, Hyunjin; Cheong, Hyeonsik; Nam, Hyun Jung; Hwangbo, Chang Kwon; Min, Sun-Ki; Han, Sung-Hwan

    2011-01-01

    We studied the effects of seed layers on the structural and optical properties of ZnO nanorods. ZnO and Ag-doped ZnO (ZnO:Ag) seed layers were deposited on glass substrates by magnetron co-sputtering. ZnO nanorods were grown on these seed layers by the chemical bath deposition in an aqueous solution of Zn(NO3)2 and hexamethyltetramine. SEM micrographs clearly reveal that ZnO nanorods were successfully grown on both kinds of seed layers. The XRD patterns indicate that crystallization of ZnO nanorods is along the c-axis. Meanwhile, the packing density and the vertical alignment of the ZnO nanorods on the ZnO seed layer are better than those of the ZnO nanorods on ZnO:Ag. The enhanced growth of nanorods is thought to be due to the fact that the ZnO layer exhibits a higher crystalline quality than the ZnO:Ag layer. According to the low-temperature photoluminescence spectra, the ZnO nanorods on the ZnO seed layer show a narrow strong ultraviolet emission band centered at 369 nm, while those on ZnO:Ag exhibit multiple bands. These results are thought to be related with the crystallinity of ZnO nanorods, the morphologies of ZnO nanorods, and the reflectivities of seed layers. More detailed studies for clarification of the seed layer effect on the growth of ZnO nanorods are desirable. PMID:21446487

  18. Turbulence structure and polymer drag reduction in adverse pressure gradient boundary layers

    NASA Astrophysics Data System (ADS)

    Koskie, John Edward

    1991-05-01

    One zero pressure gradient Newtonian boundary layer and two adverse pressure gradient equilibrium boundary layers in a water channel were examined. The momentum thickness Reynolds numbers, Re(sub theta), were in the range 1360 to 4980. The adverse pressure gradient boundary layers were characterized by equilibrium parameters, beta of 1.8 and 2.4. These boundary layers were modified by injecting a drag reducing polymer solution at 2.6 and 5.1 times the flow rate of the undisturbed flows inside of y(+) = 5. The sum of the viscous and Reynolds shear stresses was sometimes less than the total shear stress in the drag reduced boundary layer and in these cases the production of Reynolds shear and normal stresses was virtually eliminated. The mean streamwise velocity measurements in the drag reduced boundary layers showed that both parameters, kappa and B, of the logarithmic velocity profile changed. The slope parameter, kappa, varied directly with the percent drag reduction. The peak in the root-mean-square streamwise velocities remained essentially unchanged in the presence of polymer but its location moved away from the wall. The root-mean-square normal velocities and the Reynolds shear stress were reduced in the inner region of the boundary layer during drag reduction. The adverse pressure gradient boundary layers did not separate during drag reduction even when large amounts of polymer were injected. The influence of the polymer on the turbulent boundary layer structure was greatly reduced, but the effects of polymer were consistent with those in the zero pressure gradient boundary layer. The hypothesis that the extensional motions in the flow must be strong enough to stretch the polymer molecules so that stretched molecules will form an anisotropic viscosity that damps the small scales of the turbulence (Hinch, 1977) was supported by the present data. Walker's (1985) modified mixing length model correctly predicted the wall shear stress coefficient, c(sub f), in all the drag reduced boundary layers as long as the measured polymer concentration in the linear sublayer was within the range of concentrations for which the model was derived and the non-Newtonian shear stresses in the boundary layer were small. Mixed scaling of the average time between bursts best scaled the present zero and adverse pressure gradient Newtonian boundary layer data. The data was consistent with the hypothesis that the method of tripping the boundary layer affects the average burst period at very low Reynolds numbers.

  19. The effect of transverse curvature on the fluctuating wall pressure and structure of boundary layer turbulence

    NASA Astrophysics Data System (ADS)

    Snarski, Stephen R.

    1993-08-01

    This document consists of the text and viewgraphs of a paper presented at the ONR Workshop on Nonequilibrium Turbulence held at Arizona State University in Tempe, Arizona, from 10-12 Mar. 1993. This workshop was the first step of an ONR Accelerated Research Initiative (ARI) to establish the state-of-the-art for theory, computation, and experimentation relevant to turbulence in a nonequilibrium state, or, more generally, to turbulence in complex flows. The overall goal of the initiative is to understand the behavior of turbulence in such complex conditions in order to advance our prediction and control capabilities. When a cylinder in axial flow is sufficiently long and thin, the growth of the boundary layer results in its thickness exceeding the radius of the cylinder such that the three-dimensional effects due to transverse curvature cannot be neglected. With this condition, the wall of the cylinder provides less constraint on the outer flow and motion of eddies than is experienced in an equilibrium flat plate boundary layer introducing an avenue for enhanced inner-layer/outer-layer interaction and modified turbulence activity. In this paper, we present results of measurements of the fluctuating wall pressure and turbulent streamwise velocity in the turbulent boundary layer on a cylinder in axial flow to identify the coherent structures that contribute to the fluctuating pressure at the wall. Determining the influence of transverse curvature on the relationship between the wall pressure and velocity field allows examination of its effect on the structure of equilibrium boundary layer turbulence.

  20. Inner Structure of Atmospheric Inversion Layers over Haifa Bay in the Eastern Mediterranean

    NASA Astrophysics Data System (ADS)

    Haikin, N.; Galanti, E.; Reisin, T. G.; Mahrer, Y.; Alpert, P.

    2015-05-01

    Capping inversions act as barriers to the vertical diffusion of pollutants, occasionally leading to significant low-level air pollution episodes in the lower troposphere. Here, we conducted two summer campaigns where global positioning system radiosondes were operated in Haifa Bay on the eastern Mediterranean coast, a region of steep terrain with significant pollution. The campaigns provided unique high resolution measurements related to capping inversions. It was found that the classical definition of a capping inversion was insufficient for an explicit identification of a layer; hence additional criteria are required for a complete spatial analysis of inversion evolution. Based on the vertical temperature derivative, an inner fine structure of inversion layers was explored, and was then used to track inversion layers spatially and to investigate their evolution. The exploration of the inner structure of inversion layers revealed five major patterns: symmetric peak, asymmetric peak, double peak, flat peak, and the zig-zag pattern. We found that the symmetric peak is related to the strongest inversions, double peak inversions tended to break apart into two layers, and the zig-zag pattern was related to the weakest inversions. Employing this classification is suggested for assistance in following the evolution of inversion layers.

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

    DOEpatents

    Spahn, O.B.; Lear, K.L.

    1998-03-10

    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.

  2. Thermal properties of composite two-layer systems with a fractal inclusion structure

    NASA Astrophysics Data System (ADS)

    Reyes-Salgado, J. J.; Dossetti, V.; Bonilla-Capilla, B.; Carrillo, J. L.

    2015-01-01

    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.

  3. Structural Origin of Circularly Polarized Iridescence in Jeweled Beetles

    NASA Astrophysics Data System (ADS)

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

    2009-07-01

    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.

  4. Structural origin of circularly polarized iridescence in jeweled beetles

    NASA Astrophysics Data System (ADS)

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

    2010-03-01

    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.

  5. Evidence of an Impact Origin for the Azuara Structure (spain)

    NASA Astrophysics Data System (ADS)

    Ernstson, K.; Hammann, W.; Fiebag, J.; Graup, G.

    Some 50 km south of Zaragoza (northeast Spain) there is a tectonically peculiar area, which is suspected to be a large impact site. It has a morphologically conspicuous ring structure with a diameter of roughly 30 km and consists mainly of Mesozoic sediments emerging from the Ebro Tertiary Basin, and partly of Palaeozoic rocks from the Iberian System. The strata of the ring, in general, dip to the center and are highly folded and faulted. Intense and unusual deformation is indicated by abundant mixed and monomict breccias. A single poorly exposed outcrop of a mixed breccia with sedimentary fragments exhibits shock-metamorphic effects. Within quartz grains, systems of crystallographically oriented microscopic planar features and planar fractures can be observed, as well as kink bands in micas within the breccia matrix. The age of the impact is estimated to be between Lower Cretaceous and Miocene.

  6. Mirror instability and origin of morningside auroral structure

    NASA Technical Reports Server (NTRS)

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

    1983-01-01

    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. A theory of morningside auroras consistent with these features was constructed. 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.

  7. Saturn layered structure and homogeneous evolution models with different EOSs

    E-print Network

    Nettelmann, N; Redmer, R

    2013-01-01

    The core mass of Saturn is commonly assumed to be 10-25 ME as predicted by interior models with various equations of state (EOSs) and the Voyager gravity data, and hence larger than that of Jupiter (0-10 ME). We here re-analyze Saturn's internal structure and evolution by using more recent gravity data from the Cassini mission and different physical equations of state: the ab initio LM-REOS which is rather soft in Saturn's outer regions but stiff at high pressures, the standard Sesame-EOS which shows the opposite behavior, and the commonly used SCvH-i EOS. For all three EOS we find similar core mass ranges, i.e. of 0-20 ME for SCvH-i and Sesame EOS and of 0-17 ME for LM-REOS. Assuming an atmospheric helium mass abundance of 18%, we find maximum atmospheric metallicities, Zatm of 7x solar for SCvH-i and Sesame-based models and a total mass of heavy elements, MZ of 25-30 ME. Some models are Jupiter-like. With LM-REOS, we find MZ=16-20 ME, less than for Jupiter, and Zatm less than 3x solar. For Saturn, we comput...

  8. Molluscan shell proteins: primary structure, origin, and evolution.

    PubMed

    Marin, Frédéric; Luquet, Gilles; Marie, Benjamin; Medakovic, Davorin

    2008-01-01

    In the last few years, the field of molluscan biomineralization has known a tremendous mutation, regarding fundamental concepts on biomineralization regulation as well as regarding the methods of investigation. The most recent advances deal more particularly with the structure of shell biominerals at nanoscale and the identification of an increasing number of shell matrix protein components. Although the matrix is quantitatively a minor constituent in the shell of mollusks (less than 5% w/w), it is, however, the major component that controls different aspects of the shell formation processes: synthesis of transient amorphous minerals and evolution to crystalline phases, choice of the calcium carbonate polymorph (calcite vs aragonite), organization of crystallites in complex shell textures (microstructures). Until recently, the classical paradigm in molluscan shell biomineralization was to consider that the control of shell synthesis was performed primarily by two antagonistic mechanisms: crystal nucleation and growth inhibition. New concepts and emerging models try now to translate a more complex reality, which is remarkably illustrated by the wide variety of shell proteins, characterized since the mid-1990s, and described in this chapter. These proteins cover a broad spectrum of pI, from very acidic to very basic. The primary structure of a number of them is composed of different modules, suggesting that these proteins are multifunctional. Some of them exhibit enzymatic activities. Others may be involved in cell signaling. The oldness of shell proteins is discussed, in relation with the Cambrian appearance of the mollusks as a mineralizing phylum and with the Phanerozoic evolution of this group. Nowadays, the extracellular calcifying shell matrix appears as a whole integrated system, which regulates protein-mineral and protein-protein interactions as well as feedback interactions between the biominerals and the calcifying epithelium that synthesized them. Consequently, the molluscan shell matrix may be a source of bioactive molecules that would offer interesting perspectives in biomaterials and biomedical fields. PMID:17950376

  9. Effect of compositional gradient on mechanical properties in aluminum/duralumin multi-layered clad structures

    NASA Astrophysics Data System (ADS)

    Tsukamoto, Hideaki; Komiya, Yoshiki; Sato, Hisashi; Watanabe, Yoshimi

    2013-12-01

    This study aims to investigate the effect of compositional gradient on nano-, micro- and macro-mechanical properties in aluminum (A1050)/ duralumin (A2017) multi-layered clad structures fabricated by hot rolling. Such multilayered clad structures are possibly adopted to a new type of automobile crash boxes to effectively absorb the impact forces generated when automobiles having collisions. 2- and 6-layered clad structures with asymmetric lay-ups from one side of aluminum to another side of duralumin have been fabricated, which have been suffering three different heattreatments such as (1) as-rolled (no heat-treatment), (2) annealed at 400°C and (3) homogenized at 500°C followed by water quenching and aging (T4 heat treatment). For nano- and micro-scale mechanical properties proved by nanoindentation, higher hardness and elastic modulus correspond to higher Cu content at the interface in annealed and aged samples. For macro-scale mechanical properties, internal friction of 2-layered clad structures is higher than that of 6-layered clad structures in any heat-treatment samples. Deep drawing formability of annealed samples is considerably high compared to as-rolled and aged ones.

  10. Monitoring of hidden damage in multi-layered aerospace structures using high-frequency guided waves

    NASA Astrophysics Data System (ADS)

    Semoroz, A.; Masserey, B.; Fromme, P.

    2011-04-01

    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.

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

    Microsoft Academic Search

    R. M. Woollacott; R. L. Zimmer

    1972-01-01

    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

  12. A Comparison of Aerosol-Layer and Convective Boundary-Layer Structure over a Mountain Range during STAAARTE '97

    SciTech Connect

    De Wekker, Stephan; Steyn, D. G.; Nyeki, Stephan

    2004-11-01

    The temporal evolution and spatial structure of the aerosol layer (AL) height as observed with an airborne downlooking lidar over the Swiss Alps was investigated with a three dimensional mesoscale numerical model and a particle dispersion model. Convective boundary layer (CBL) heights were derived from the mesoscale model output, and the behavior of surface-released particles was investigated with the particle dispersion model. While a previous investigation, using data from the same field study, equated the observed AL height with the CBL height, the results of the current investigation indicate that there is a considerable difference between AL and CBL heights caused by mixing and transport processes between the CBL and the free atmosphere. CBL heights show a more terrain-following behavior and are lower than AL heights. We argue that processes causing the difference between AL and CBL heights are common over mountainous terrain and that the AL height is a length scale that needs t o be considered in air pollution studies in mountainous terrain.

  13. Structure Analyses of Ti-Based Self-Formed Barrier Layers

    NASA Astrophysics Data System (ADS)

    Kohama, Kazuyuki; Ito, Kazuhiro; Sonobayashi, Yutaka; Ohmori, Kazuyuki; Mori, Kenichi; Maekawa, Kazuyoshi; Shirai, Yasuharu; Murakami, Masanori

    2011-04-01

    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.

  14. Can we neglect the multi-layer structure of functional networks?

    NASA Astrophysics Data System (ADS)

    Zanin, Massimiliano

    2015-07-01

    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.

  15. Capillary layer structure effect upon heat transfer in flat heat pipes

    NASA Astrophysics Data System (ADS)

    Sprinceana, Silviu; Mihai, Ioan; Beniuga, Marius; Suciu, Cornel

    2015-02-01

    The research presented in this paper aimed to determine the maximum heat transfer a heat pipe can achieve. To that purpose the structure of the capillary layer which can be deposited on the walls of the heat pipe was investigated. For the analysis of different materials that can produce capillarity, the present study takes into account the optimal thickness needed for this layer so that the accumulated fluid volume determines a maximum heat transfer. Two materials that could be used to create a capillary layer for the heat pipes, were investigated, one formed by sintered copper granules (the same material by which the heat pipe is formed) and a synthetic material (cellulose sponge) which has high absorbing proprieties. In order to experimentally measure and visualize the surface characteristics for the considered capillary layers, laser profilometry was employed.

  16. Incoherent scatter radar observations of irregular structure in mid-latitude sporadic E layers

    NASA Technical Reports Server (NTRS)

    Miller, K. L.; Smith, L. G.

    1978-01-01

    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.

  17. Boundary Layer and Mesoscale Structure over Lake Michigan during a Wintertime Cold Air Outbreak.

    NASA Astrophysics Data System (ADS)

    Agee, Ernest M.; Hart, Mary L.

    1990-10-01

    An investigation of a cloud-topped boundary layer during a wintertime cold air outbreak over Lake Michigan has been conducted based on research aircraft 1 and 20 Hz data for five vertically-stacked levels within the boundary layer. Mean east-west cross sections for this northerly flow event have been prepared for heat, moisture, and momentum fields along with spectral decomposition and turbulent flux statistics. Results have been interpreted on the basis of three generalized spatial domains: mesoscale 5 km, large eddies from 100 m to <5 km, and higher frequency turbulence <100 m. Mesoscale structures identified in the mean cross-sections include the lower Michigan land breeze, a strong offshore convergence snow band, cloud streets and precipitation bands over the lake, and entrainment spikes in the vicinity of the inversion layer. Analyses of particle concentrations, sizes, and liquid water content have also been presented in mean cross sections, which correspond well with all identifiable mesoscale structures.This study has also examined a `hand-picked' data set in the mixed layer over the middle of the lake not affected by the land breeze and inversion layer phenomena. Analysis of this 20 Hz data set shows convergence in the turbulence statistics for different 15 km flight segments, which also introduces an analysis technique called telescoping skewness. Also included are two independently derived vertical profiles of vertical velocity skewness that are seen to be nearly identical. Differences and similarities in numerical model results and observations are discussed that suggest a modeling weakness in predicting convective turbulent transport in the cloud layer when driven by strong surface heating. Analysis shows the subcloud layer of the mixed layer to be characterized by large eddies arranged in accordance with open cell geometry (narrow strong updrafts with weak broad regions of downdraft). This positive skewness in the subcloud layer is about twice that in the cloud layer indicative of a modulating effect by cloud layer processes such as condensational heating. The vertical profile of the normalized buoyant production of turbulence kinetic energy is also presented, which agrees well with Deardorff's model results with strong surface heating and cloud-top cooling. The role of the mean vertical velocity is also considered in the mathematical expansion of skewness, which is seen to agree with Deardorff's model results with strong surface heating and cloud-top cooling. The role of the mean vertical velocity is also considered in the mathematical expansion of skewness, which is seen to agree with Deardorff's results if is set equal to zero (a feature of numerical models, but not necessarily a feature of the real planetary boundary layer as evidenced by this study).

  18. Origin of Permeability and Structure of Flows in Fractured Media

    NASA Astrophysics Data System (ADS)

    De Dreuzy, J.; Darcel, C.; Davy, P.; Erhel, J.; Le Goc, R.; Maillot, J.; Meheust, Y.; Pichot, G.; Poirriez, B.

    2013-12-01

    After more than three decades of research, flows in fractured media have been shown to result from multi-scale geological structures. Flows result non-exclusively from the damage zone of the large faults, from the percolation within denser networks of smaller fractures, from the aperture heterogeneity within the fracture planes and from some remaining permeability within the matrix. While the effect of each of these causes has been studied independently, global assessments of the main determinisms is still needed. We propose a general approach to determine the geological structures responsible for flows, their permeability and their organization based on field data and numerical modeling [de Dreuzy et al., 2012b]. Multi-scale synthetic networks are reconstructed from field data and simplified mechanical modeling [Davy et al., 2010]. High-performance numerical methods are developed to comply with the specificities of the geometry and physical properties of the fractured media [Pichot et al., 2010; Pichot et al., 2012]. And, based on a large Monte-Carlo sampling, we determine the key determinisms of fractured permeability and flows (Figure). We illustrate our approach on the respective influence of fracture apertures and fracture correlation patterns at large scale. We show the potential role of fracture intersections, so far overlooked between the fracture and the network scales. We also demonstrate how fracture correlations reduce the bulk fracture permeability. Using this analysis, we highlight the need for more specific in-situ characterization of fracture flow structures. Fracture modeling and characterization are necessary to meet the new requirements of a growing number of applications where fractures appear both as potential advantages to enhance permeability and drawbacks for safety, e.g. in energy storage, stimulated geothermal energy and non-conventional gas productions. References Davy, P., et al. (2010), A likely universal model of fracture scaling and its consequence for crustal hydromechanics, Journal of Geophysical Research-Solid Earth, 115, 13. de Dreuzy, J.-R., et al. (2012a), Influence of fracture scale heterogeneity on the flow properties of three-dimensional Discrete Fracture Networks (DFN), J. Geophys. Res.-Earth Surf., 117(B11207), 21 PP. de Dreuzy, J.-R., et al. (2012b), Synthetic benchmark for modeling flow in 3D fractured media, Computers and Geosciences(0). Pichot, G., et al. (2010), A Mixed Hybrid Mortar Method for solving flow in Discrete Fracture Networks, Applicable Analysis, 89(10), 1729-1643. Pichot, G., et al. (2012), Flow simulation in 3D multi-scale fractured networks using non-matching meshes, SIAM Journal on Scientific Computing (SISC), 34(1). Figure: (a) Fracture network with a broad-range of fracture lengths. (b) Flows (log-scale) with homogeneous fractures. (c) Flows (log-scale) with heterogeneous fractures [de Dreuzy et al., 2012a]. The impact of the fracture apertures (c) is illustrated on the organization of flows.

  19. THE STRUCTURE, ORIGIN, AND EVOLUTION OF INTERSTELLAR HYDROCARBON GRAINS

    SciTech Connect

    Chiar, J. E.; Ricca, A. [SETI Institute, Carl Sagan Center, 189 Bernardo Avenue, Mountain View, CA 94043 (United States); Tielens, A. G. G. M. [Leiden Observatory, P.O. Box 9513, NL-2300 RA Leiden (Netherlands); Adamson, A. J., E-mail: jchiar@seti.org, E-mail: Alessandra.Ricca@1.nasa.gov, E-mail: tielens@strw.leidenuniv.nl, E-mail: aadamson@gemini.edu [Gemini Observatory, Northern Operations Center, 670 North A'ohoku Place, Hilo, HI 96729 (United States)

    2013-06-10

    Many materials have been considered for the carrier of the hydrocarbon absorption bands observed in the diffuse interstellar medium (ISM). In order to refine the model for ISM hydrocarbon grains, we analyze the observed aromatic (3.28, 6.2 {mu}m) and aliphatic (3.4 {mu}m) hydrocarbon absorption features in the diffuse ISM along the line of sight toward the Galactic center Quintuplet Cluster. Observationally, sp {sup 2} bonds can be measured in astronomical spectra using the 6.2 {mu}m CC aromatic stretch feature, whereas the 3.4 {mu}m aliphatic feature can be used to quantify the fraction of sp {sup 3} bonds. The fractional abundance of these components allows us to place the Galactic diffuse ISM hydrocarbons on a ternary phase diagram. We conclude that the Galactic hydrocarbon dust has, on average, a low H/C ratio and sp {sup 3} content and is highly aromatic. We have placed the results of our analysis within the context of the evolution of carbon dust in the ISM. We argue that interstellar carbon dust consists of a large core of aromatic carbon surrounded by a thin mantle of hydrogenated amorphous carbon (a-C:H), a structure that is a natural consequence of the processing of stardust grains in the ISM.

  20. The Nature and Origin of Time-Asymmetric Spacetime Structures

    NASA Astrophysics Data System (ADS)

    Zeh, H. Dieter

    Time-asymmetric spacetime structures, in particular those representing black holes and the expansion of the universe, are intimately related to other arrows of time, such as the second law and the retardation of radiation. The nature of the quantum arrow, often attributed to a collapse of the wave function, is essential, in particular, for understanding the much discussed black hole information loss paradox. This paradox assumes a new form and can possibly be avoided in a consistent causal treatment that may be able to avoid horizons and singularities. The master arrow that would combine all arrows of time does not have to be identified with a direction of the formal time parameter that serves to formulate the dynamics as a succession of global states (a trajectory in configuration or Hilbert space). It may even change direction with respect to a fundamental physical clock such as the cosmic expansion parameter if this was formally extended either into a future contraction era or to negative pre-big-bang values.

  1. Formation of Structured Dayside Boundary Layers under Different Solar Wind Conditions: THEMIS Observations

    NASA Technical Reports Server (NTRS)

    Avanov, Levon A.; Chandler, Michael O.

    2008-01-01

    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.

  2. Mg intercalation in layered and spinel host crystal structures for mg batteries.

    PubMed

    Emly, Alexandra; Van der Ven, Anton

    2015-05-01

    We investigate electrochemical properties of Mg in layered and spinel intercalation compounds from first-principles using TiS2 as a model system. Our calculations predict that MgxTiS2 in both the layered and spinel crystal structures exhibits sloping voltage profiles with steps at stoichiometric compositions due to Mg-vacancy ordering. Mg ions are predicted to occupy the octahedral sites in both layered and spinel TiS2 with diffusion mediated by hops between octahedral sites that pass through adjacent tetrahedral sites. Predicted migration barriers are substantially higher than typical Li-migration barriers in intercalation compounds. The migration barriers are shown to be very sensitive to lattice parameters of the host crystal structure. We also discuss the possible role of rehybridization between the transition metal and the anion in affecting migration barriers. PMID:25905428

  3. Strained-layer superlattice focal plane array having a planar structure

    DOEpatents

    Kim, Jin K. (Albuquerque, NM); Carroll, Malcolm S. (Albuquerque, NM); Gin, Aaron (Albuquerque, NM); Marsh, Phillip F. (Lowell, MA); Young, Erik W. (Albuquerque, NM); Cich, Michael J. (Albuquerque, NM)

    2010-07-13

    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.

  4. Inferring the mesoscale structure of layered, edge-valued and time-varying networks

    E-print Network

    Peixoto, Tiago P

    2015-01-01

    Many network systems are composed of interdependent but distinct types of interactions, which cannot be fully understood in isolation. These different types of interactions are often represented as layers, attributes on the edges or as a time-dependence of the network structure. Although they are crucial for a more comprehensive scientific understanding, these representations offer substantial challenges. Namely, it is an open problem how to precisely characterize the large or mesoscale structure of network systems in relation to these additional aspects. Furthermore, the direct incorporation of these features invariably increases the effective dimension of the network description, and hence aggravates the problem of overfitting, i.e. the use of overly-complex characterizations that mistake purely random fluctuations for actual structure. In this work, we propose a robust and principled method to tackle these problems, by constructing generative models of modular network structure, incorporating layered, attr...

  5. ISO 14000: Origin, Structure, and Potential Barriers to Implementation.

    PubMed

    Casto; Ellisen; Trnovec; Kross; Ginter

    1996-04-01

    The ISO 14000 is likely to become the international standard for environmental management. At present, it is an evolving series of individual voluntary standards and guideline reference documents that provide business management with the structure for managing environmental impacts. These encompass environmental management systems, environmental audits, eco-labeling, environmental performance evaluations, life-cycle assessment, and environmental aspects in product standards. The authors present the rationale for the ISO 14000 and the steps in its evolution so far, as well as its present provisions and their implications and its position with regard to regulatory agencies. Particular attention is paid to the consequences of voluntary disclosure and correction of violations. Hanley & Belfus, Inc. Int J Occup Environ Health 1077-3525 2 2 1996 April/June Perspectives on Rural Environmental Health in Central Europe 125 134 EN Tomas Trnovec Burton C. Kross CIREH-Room 352, International Center, University of Iowa, Iowa City, IA 52242, USA. Emil Ginter Life expectancy is about five to seven years less in Central European countries than in comparable countries in Western Europe. Environmental and occupational health risk factors, along with the socioeconomic and political conditions that have prevailed in this region for the past 40 years, are suspected contributing factors to this condition. The initial impression among observers was that environmental pollution by industry was the primary source of contamination leading to human health effects. Current thinking by the authors recognizes that combinations of personal habits, local environmental emissions (home heating), and occupational risk factors are more likely to be influencing the health of this region, particularly in rural areas. A predictive model for standard mortality rates determined that only three potential risk factors were statistically significant: consumption of alcoholic beverages, consumption of citrus fruits, and consumption of cereals. Additional emphasis should be placed on defining risk factors in rural areas of Central Europe, and designing intervention strategies to address these factors. PMID:9933869

  6. ORIGINAL PAPER Electronic Structure of Unsaturated V2O5(001) and (100)

    E-print Network

    ORIGINAL PAPER Electronic Structure of Unsaturated V2O5(001) and (100) Surfaces: Ab Initio Density. In the present study the electronic structure of V2O5(001) and (100) surfaces are determined by ab ini- tio DFTO40H20, V14O46H22, V16O52H24 for the (100) surface. Detailed analyses of the electronic structure

  7. Structural, Compositional and Electrical Characterization of buried silicon oxide insulating layers synthesized by SIMOX process

    NASA Astrophysics Data System (ADS)

    Patel, A. P.; Yadav, A. D.; Dubey, S. K.; Panigrahi, B. K.; Nair, K. G. M.; Kumar, P.

    2010-06-01

    Silicon oxide (SiO2) buried insulating layers were synthesized by SIMOX (separation by implanted oxygen) process using 140 keV 16O+ ion implantation at fluence levels ranging from 1.0×1017 to 1.0×1018 cm-2 into <111> single crystal silicon substrates at room temperature and at elevated temperature (325 °C). The post-implantation annealing was performed in order to recover the implantation-induced structural damage. The structural, compositional and electrical characterization of the ion-beam synthesized buried silicon oxide insulating layers were characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), Rutherford backscattering spectroscopy (RBS) measurements and Current-voltage (I-V) characteristics. The FTIR spectra of implanted samples reveal absorption band in the wavenumber range 1200-800 cm-1 associated with the stretching vibration of Si-O bonds indicating the formation of silicon oxide. The FTIR spectra of annealed samples revealed absorption band associated with one bending vibration in addition to the asymmetric stretching vibration of Si-O bonds. The FTIR studies show that the structures of ion-beam synthesized buried oxide layers are strongly dependent on total ion fluence. The XRD data show the formation of silicon oxide (SiO2) structure at all ion fluences. The concentration of the formed phases is found to increase with increase in the ion fluence as well as the annealing temperature. The RBS measurements show that the thickness of the buried oxide layer increases with increase in the oxygen fluence. However, the thickness of the top silicon layer was found to decrease with increase in the ion fluence. The I-V characteristics show that the currents flowing in buried oxide layers are ohmic in the low voltage region and space charge limited in the higher voltage range.

  8. Synthesis and single crystal structure refinement of the one-layer hydrate of sodium brittle mica

    SciTech Connect

    Kalo, Hussein; Milius, Wolfgang [Lehrstuhl fuer Anorganische Chemie I, University of Bayreuth, D-95440 Bayreuth (Germany)] [Lehrstuhl fuer Anorganische Chemie I, University of Bayreuth, D-95440 Bayreuth (Germany); Braeu, Michael [BASF Construction Chemicals GmbH, 83308 Trostberg (Germany)] [BASF Construction Chemicals GmbH, 83308 Trostberg (Germany); Breu, Josef, E-mail: Josef.Breu@uni-bayreuth.de [Lehrstuhl fuer Anorganische Chemie I, University of Bayreuth, D-95440 Bayreuth (Germany)] [Lehrstuhl fuer Anorganische Chemie I, University of Bayreuth, D-95440 Bayreuth (Germany)

    2013-02-15

    A sodium brittle mica with the ideal composition [Na{sub 4}]{sup inter}[Mg{sub 6}]{sup oct}[Si{sub 4}Al{sub 4}]{sup tet}O{sub 20}F{sub 4} was synthesized via melt synthesis in a gas tight crucible. This mica is unusual inasmuch as the known mica structure holds only room for two interlayer cations per unit cell and inasmuch as it readily hydrates despite the high layer charge while ordinary micas and brittle micas are non-swelling. The crystal structure of one-layer hydrate sodium brittle mica was determined and refined from single crystal X-ray data. Interlayer cations reside at the center of the distorted hexagonal cavities and are coordinated by the three inner basal oxygen atoms. The coordination of the interlayer cation is completed by three interlayer water molecules residing at the center of the interlayer region. The relative position of adjacent 2:1-layers thus is fixed by these octahedrally coordinated interlayer cations. Pseudo-symmetry leads to extensive twinning. In total five twin operations generate the same environment for the interlayer species and are energetically degenerate. - Graphical abstract: The sodium brittle mica has been successfully synthesized by melt synthesis and the crystal structure of the one-layer hydrate of sodium brittle mica was determined from single crystal X-ray diffraction data. Highlights: Black-Right-Pointing-Pointer Melt synthesis yielded coarse grained sodium brittle mica which showed little disorder. Black-Right-Pointing-Pointer Sodium brittle mica hydrated completely to the state of one-layer hydrate. Black-Right-Pointing-Pointer Structure of one-layer hydrate of sodium brittle mica could therefore be determined and refined. Black-Right-Pointing-Pointer Arrangement of upper and lower tetrahedral sheet encompassing interlayer cation were clarified.

  9. Observations of Coherent Turbulence Structures in the Near-Neutral Atmospheric Boundary Layer

    Microsoft Academic Search

    Mitsuaki Horiguchi; Taiichi Hayashi; Hiroyuki Hashiguchi; Yoshiki Ito; Hiromasa Ueda

    2010-01-01

    Turbulence structures of high Reynolds number flow in the near-neutral atmospheric boundary layer (ABL) are investigated based\\u000a on observations at Shionomisaki and Shigaraki, Japan. A Doppler sodar measured the vertical profiles of winds in the ABL.\\u000a Using the integral wavelet transform for the time series of surface wind data, the pattern of a descending high-speed structure\\u000a with large vertical extent

  10. Mode manipulation and near-THz absorptions in binary grating-graphene layer structures

    PubMed Central

    2014-01-01

    The excitation and absorption properties of grating coupled graphene surface plasmons were studied. It was found that whether a mode can be excited is mainly determined by the frequency of incident light and the duty ratio of gratings. In the structure consisting graphene bilayer, a blueshift of the excitation frequency existed when the distance between neighbor graphene layer were decreased gradually. In graphene-grating multilayer structures, a strong absorption (approximately 90% at maximum) was found in near-THz range. PMID:24559407

  11. Qualitative methods of structural analysis: Layer-based methods are informationally trivial

    Microsoft Academic Search

    Louis de MESNARD

    2000-01-01

    Some methods of qualitative structural analysis, as MFA, are based on the analysis of layers (flow matrices generated at each iteration when the equilibrium of an input-output model is computed). MFA mixes the analysis of the pure structure of production (the technical coefficients) and of the final demand. I have demonstrated that all column-coefficient matrices (or row-coefficient matrices) computed from

  12. Optimum design of substation grounding in a two layer earth structure: Part I?Analytical study

    Microsoft Academic Search

    F. Dawalibi; D. Mukhedkar

    1975-01-01

    The authors have developed a computer program which calculates the potential in earth, the resistance and the required potential probe position in field resistance measurements [1], for any complex electrode in a two layer earth structure. The first part of the study describes the theoretical basis of the programs and compares the two analytical methods of potential calculations, the summation

  13. Electric-field-induced local layer structure in plasticized PVC actuator.

    PubMed

    Xia, Hong; Hirai, Toshihiro

    2010-08-26

    In order to investigate the molecular vibrations and structure variations of PVC gels with applied electric fields, a mechanical measurement (combined tensile and shear test) was proposed, and the Fourier transform infrared (FT-IR) spectrometry and in situ Raman spectroscopy were conducted to clarify the mechanism of electric-field-induced local layer structure in PVC gel and its relationship to gel creeping deformation. As a result, the electric-field-induced local layer structure and the migration of the solvent-rich phase in PVC gels were clarified. The layer of PVC gel clinging to the anode is softer than that near the cathode. The peaks of FT-IR spectra were shifted and changed in the gel surface on the anode and cathode. Using the in situ Raman spectroscopy, it is found that the intensity of the whole Raman spectra was reduced from the cathode to the anode, and the elastic modulus of the gel on the anode was smaller than that on the cathode. All of the results indicated that the electric field induced the local layer structure and caused the asymmetric actuation behavior in PVC gel actuators. PMID:20684498

  14. Debye Length Structures and Slow Shocks in Earth's Reconnection Layer: Observations and Simulations

    NASA Astrophysics Data System (ADS)

    Scudder, J. D.; Ma, Z. W.; Mozer, F. S.

    2004-12-01

    Frequently abrupt (7.5ms FWHM), strong (150mV/m) electrostatic structures are detected nearly perpendicular to B, near local density depletions in magnetopause current layers. These electrostatic structures have been suggested [Mozer, et al., Geophys. Res. Lett., 31, L15802, doi:10.1029/2004GL020062,2004] to have either electron inertial or electron Debye length scales. Using a broader suite of observational diagnostics, tests of Rankine-Hugoniot conservation laws, and new, full particle simulations, we demonstrate that these structures are unanticipated Debye length substructures (L ? 5? De ) adjoining slow switch-off shock transition layers within the magnetopause proper. The electrostatic structures are found just inside the local density minimum and are perpendicular to the coplanarity plane of the adjacent slow shock layer. Electric layers of scale r? De will cause the demagnetization of thermal electrons of temperature Te , by pushing down the threshold for the electron demagnetization to ? e > Min(r2kTe/mec2,1) , thereby assisting topology change and the formation of Petschek slow shocks away from the separator where ? e is usually much less than unity.

  15. Cohesive layer models for predicting delamination growth and crack kinking in sandwich structures

    Microsoft Academic Search

    S. El-Sayed; S. Sridharan

    2002-01-01

    There are potentially two types of fracture that sandwich structures with strong and stiff facing sheets and lightweight cores are liable to suffer. These are the delamination growth at the face-sheet core interface and crack kinking into the sandwich core, respectively. The paper proposes computational models to simulate these failure mechanisms. The models employ the cohesive layer concept and are

  16. Remote sensing methods to investigate boundary-layer structures in proximity of urban areas

    Microsoft Academic Search

    A. Pelliccioni; C. Gariazzo

    2010-01-01

    The vertical stratification of thermal and mechanical properties of the lower side of atmosphere are described by atmospheric turbulence conditions and at each time of day they have some well defined characteristics. Remote sensing systems are often used to study boundary layer structures. One of the very attractive remote sensing tool is the ceilometer, which is based on the measurements

  17. Meteorological observations of the coastal boundary layer structure at the Bulgarian Black Sea coast

    Microsoft Academic Search

    D. Barantiev; M. Novitsky; E. Batchvarova

    2011-01-01

    Continuous wind profile and turbulence measurements were initiated in July 2008 at the coastal meteorological observatory of Ahtopol on the Black Sea (south-east Bulgaria) under a Bulgarian-Russian collaborative program. These observations are the start of high resolution atmospheric boundary layer vertical structure climatology at the Bulgarian Black Sea coast using remote sensing technology and turbulence measurements. The potential of the

  18. Optical fiber sensor layer embedded in smart composite material and structure

    NASA Astrophysics Data System (ADS)

    Pan, Xiao Wen; Liang, Da Kai; Li, Dongsheng

    2006-10-01

    A composite structure health monitoring system with optical fiber sensors is an important development in smart materials and structures. But it is difficult to embed a network of distributed optical fiber sensors in a smart composite structure, and the most effective method would be integrating the network of sensors with the polyimide film as a layer, called the optical fiber sensor layer, and then embedding the layer with optical fiber sensors in the composite material. This paper introduces three methods of making a distributed optical fiber sensor layer with polyimide. The first is to sandwich optical fiber sensors in two polyimide films. The second is to deposit the network of sensors in polyimide solution, and dry the polyimide solution. The last is to build thin-film optical waveguides and optical sensors by using fluorinated polyimide, which is expected to have high integration and high reliability. Some tests indicate that there is a little influence on the mechanical performance of the structure; however, optical fiber sensor built-in polyimide films work very well.

  19. Effect of interlayer on stress wave propagation in CMC\\/RHA multi-layered structure

    Microsoft Academic Search

    Yangwei Wang; Fuchi Wang; Xiaodong Yu; Zhuang Ma; Jubin Gao; Xiaopeng Kang

    2010-01-01

    Due to the significance of the propagation of stress wave in composite armor during projectile–target interaction, the characteristics of stress wave propagation in multi-layered composite structure under impact load were investigated by traditional Split Hopkinson Pressure Bar system in this study. The effect of interlayer characteristic on the stress wave propagation was discussed. The results show that the interlayer properties

  20. Structures of ultra-thin atomic-layer-deposited TaNx films

    Microsoft Academic Search

    Y. Y. Wu; A. Kohn; M. Eizenberg

    2004-01-01

    Atomic layer deposition (ALD) is an attractive technique in fabrication of microelectronics presently and in the future, for its accurate thickness control in atomic scale, excellent conformality, and uniformity over large areas at low temperature. It has been adapted and used in deposition of ultrathin TaNx films as diffusion barriers for Cu metallization. In this study, composition, structure, and stability

  1. The formation and evolution of layered structures in porous media: effects of porosity and mechanical dispersion

    Microsoft Academic Search

    Stan Schoofs; Ron A. Trompert; Ulrich Hansen

    2000-01-01

    Horizontally layered structures can develop in porous or partially molten environments, such as hydrothermal systems, magmatic intrusions and the early Earth's mantle. The porosity ? of these natural environments is typically small. Since dissolved chemical elements unlike heat cannot diffuse through the solid rocks, heat and solute influence the interstitial fluid density in a different manner: heat advects slower than

  2. Electronic and geometric structure of silver and palladium on aluminum (111) in monoatomic surface layers

    Microsoft Academic Search

    Bjoern Frick

    1987-01-01

    Geometric and electronic structures of Ag and Pd on Al (111) are observed by low energy electron diffraction, by Auger electron spectroscopy, and angle resolved UV photoelectron spectroscopy. The Al (111) substrate is well adapted for the observation of crystal formation. Vapor deposited Ag and Pd lead to 2D-crystal formation by the growth of a monoatomic surface layer. Both systems

  3. Research of intelligent information retrieval system based on three layers agent structure

    Microsoft Academic Search

    Shi-Yi Xie; Jia-Cun Liu; Han Wang

    2003-01-01

    With the development of Internet, we put forward high requests for information retrieval. First, efficiency; second, personalizing. In this paper a model and an algorithm are proposed which are according to the user's retrieval habit of learning and the intelligent information retrieval system that has inner relativity of three layers agent structure. This is a trend that using artificial intelligence

  4. A novel series of photocatalysts with an ion-exchangeable layered structure of niobate

    Microsoft Academic Search

    K. Domen; J. Yoshimura; T. Sekine; A. Tanaka; T. Onishi

    1990-01-01

    Ion-exchangeable niobates, A(Mn-1NbnO3n+1) (A = Na, K, Rb, Cs; M = La, Ca etc.), with a layered perovskite structure are found to show a unique photocatalytic activity, especially in those H+-exchanged forms, for H2 evolution from aqueous alcohol solutions as well as O2 evolution from an aqueous silver nitrate solution.

  5. Structure and elemental composition of layers of solid solutions in the EuS-Sm system

    Microsoft Academic Search

    V. E. Marincheva; M. N. Naboka; L. D. Finkelshtein; N. N. Efremova

    1987-01-01

    In this work the structure, valence of the cations and phase and elemental composition of the layers obtained by vacuum condensation of europium and samarium monosulfides simultaneously evaporating from two independent vaporizers were investigated. By varying the mutual disposition of the vaporizers and the substrate one could obtain samples of preassigned elemental composition.

  6. Structure and elemental composition of layers of solid solutions in the EuS-Sm system

    SciTech Connect

    Marincheva, V.E.; Naboka, M.N.; Finkel'shtein, L.D.; Efremova, N.N.

    1987-04-01

    In this work the structure, valence of the cations and phase and elemental composition of the layers obtained by vacuum condensation of europium and samarium monosulfides simultaneously evaporating from two independent vaporizers were investigated. By varying the mutual disposition of the vaporizers and the substrate one could obtain samples of preassigned elemental composition.

  7. Pressure induced metallization with absence of structural transition in layered molybdenum diselenide.

    PubMed

    Zhao, Zhao; Zhang, Haijun; Yuan, Hongtao; Wang, Shibing; Lin, Yu; Zeng, Qiaoshi; Xu, Gang; Liu, Zhenxian; Solanki, G K; Patel, K D; Cui, Yi; Hwang, Harold Y; Mao, Wendy L

    2015-01-01

    Layered transition-metal dichalcogenides have emerged as exciting material systems with atomically thin geometries and unique electronic properties. Pressure is a powerful tool for continuously tuning their crystal and electronic structures away from the pristine states. Here, we systematically investigated the pressurized behavior of MoSe2 up to ?60?GPa using multiple experimental techniques and ab-initio calculations. MoSe2 evolves from an anisotropic two-dimensional layered network to a three-dimensional structure without a structural transition, which is a complete contrast to MoS2. The role of the chalcogenide anions in stabilizing different layered patterns is underscored by our layer sliding calculations. MoSe2 possesses highly tunable transport properties under pressure, determined by the gradual narrowing of its band-gap followed by metallization. The continuous tuning of its electronic structure and band-gap in the range of visible light to infrared suggest possible energy-variable optoelectronics applications in pressurized transition-metal dichalcogenides. PMID:26088416

  8. Relating performance of thin-film composite forward osmosis membranes to support layer formation and structure

    Microsoft Academic Search

    Alberto Tiraferri; Ngai Yin Yip; William A. Phillip; Jessica D. Schiffman; Menachem Elimelech

    2011-01-01

    Osmotically driven membrane processes have the potential to treat impaired water sources, desalinate sea\\/brackish waters, and sustainably produce energy. The development of a membrane tailored for these processes is essential to advance the technology to the point that it is commercially viable. Here, a systematic investigation of the influence of thin-film composite membrane support layer structure on forward osmosis performance

  9. Scattering From Layered Structures With One Rough Interface: A Unified Formulation of Perturbative Solutions

    Microsoft Academic Search

    Giorgio Franceschetti; Pasquale Imperatore; Antonio Iodice; Daniele Riccio; Giuseppe Ruello

    2008-01-01

    In this paper, we investigate analytically the connection between the existing first-order small perturbation method solutions for the scattering from a layered structure with one rough interface. First of all, by using effectively the concept of generalized reflection coefficients, we cast the existing models in a unified more compact formulation and point out the connection between the different analytical solutions.

  10. A Shell Finite Element for Active-Passive Vibration Control of Composite Structures with Piezoelectric and Viscoelastic Layers

    Microsoft Academic Search

    Hakim Boudaoud; Salim Belouettar; El Mostafa Daya; Michel Potier-Ferry

    2008-01-01

    This paper presents an accurate shell finite element (FE) formulation to model composite shell structures with embedded viscoelastic and piezoelectric layers and an integrated active damping control mechanism. The five-layered finite element introduced in this paper uses the first order shear deformation theory in the viscoelastic core and Kirchoff theory for the elastic and piezoelectric layers. The corresponding coupled FE

  11. Structural origin of the brown color of barbules in male peacock tail feathers

    Microsoft Academic Search

    Yizhou Li; Zhihua Lu; Haiwei Yin; Xindi Yu; Xiaohan Liu; Jian Zi

    2005-01-01

    We report detailed optical measurements and numerical simulations of brown barbules in male peacock tail feathers. Our results indicate that brown coloration is predominantly produced structurally by the two-dimensional (2D) photonic-crystal structure in the cortex layer of a barbule. The constructing strategies of brown coloration revealed by numerical simulations are indeed subtle, which are of great significance in the artificial

  12. Sperm yield after single layer centrifugation with Androcoll-E is related to the potential fertility of the original ejaculate.

    PubMed

    Morrell, J M; Stuhtmann, G; Meurling, S; Lundgren, A; Winblad, C; Macias Garcia, B; Johannisson, A

    2014-05-01

    Many attempts have been made to identify laboratory tests that are predictive of sperm fertility, both to improve the quality of stallion semen doses for artificial insemination (AI) and to identify potential breeding sires if no fertility data are available. Sperm quality at the stud is mostly evaluated by assessing subjective motility, although this parameter can be poorly indicative of fertility. Sperm morphology and chromatin integrity in Swedish stallions are correlated to pregnancy rate after AI. Because single layer centrifugation (SLC) selects for spermatozoa with normal morphology and good chromatin, retrospective analysis was carried out to investigate whether sperm yield after SLC is linked to potential fertility. Commercial semen doses for AI from 24 stallions (five stallions with four ejaculates each, 19 stallions with three ejaculates each; n = 77) obtained during the breeding season were cooled, and sent overnight to the Swedish University of Agricultural Sciences in an insulated box for evaluation, with other doses being sent to studs for commercial AI. On arrival at Swedish University of Agricultural Sciences, the semen was used for SLC and also for evaluation of sperm motility, membrane integrity, chromatin integrity, and morphology. The seasonal pregnancy rates for each stallion were available. The yield of progressively motile spermatozoa after SLC (calculated as a proportion of the initial load) was found to be highly correlated with pregnancy rate (r = 0.75; P < 0.001). Chromatin damage was highly negatively correlated with pregnancy rate (r = -0.69; P < 0.001). Pregnancy rate was also correlated with membrane integrity (r = 0.58; P < 0.01), progressive motility (r = 0.63; P < 0.01), and normal morphology (r = 0.45; P < 0.05). In conclusion, these preliminary results show that sperm yield after SLC is related to the potential fertility of the original ejaculate, and could be an alternative indicator of stallion fertility if breeding data are not available. Single layer centrifugation is fast (30 minutes) and does not require expensive equipment, whereas other assays require a flow cytometer and/or specialist skills. An additional option could be to transport semen doses to a laboratory for SLC if the stud personnel do not want to perform the procedure themselves. PMID:24582376

  13. Intrusive origin of the Sudbury Igneous Complex: Structural and sedimentological evidence

    NASA Technical Reports Server (NTRS)

    Cowan, E. J.; Schwerdtner, W. M.

    1992-01-01

    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.

  14. Structural and electronic properties of manganese-doped Bi2Te3 epitaxial layers

    NASA Astrophysics Data System (ADS)

    R?ži?ka, J.; Caha, O.; Holý, V.; Steiner, H.; Volobuiev, V.; Ney, A.; Bauer, G.; Ducho?, T.; Veltruská, K.; Khalakhan, I.; Matolín, V.; Schwier, E. F.; Iwasawa, H.; Shimada, K.; Springholz, G.

    2015-01-01

    We show that in manganese-doped topological insulator bismuth telluride layers, Mn atoms are incorporated predominantly as interstitials in the van der Waals gaps between the quintuple layers and not substitutionally on Bi sites within the quintuple layers. The structural properties of epitaxial layers with Mn concentration of up to 13% are studied by high-resolution x-ray diffraction, evidencing a shrinking of both the in-plane and out-of plane lattice parameters with increasing Mn content. Ferromagnetism sets in for Mn contents around 3% and the Curie temperatures rises up to 15 K for a Mn concentration of 9%. The easy magnetization axis is along the c-axis perpendicular to the (0001) epilayer plane. Angle-resolved photoemission spectroscopy reveals that the Fermi level is situated in the conduction band and no evidence for a gap opening at the topological surface state with the Dirac cone dispersion is found within the experimental resolution at temperatures close to the Curie temperature. From the detailed analysis of the extended x-ray absorption fine-structure experiments (EXAFS) performed at the MnK-edge, we demonstrate that the Mn atoms occupy interstitial positions within the van der Waals gap and are surrounded octahedrally by Te atoms of the adjacent quintuple layers.

  15. Structural vs electronic origin of renormalized band widths in TTF-TCNQ: An angular dependent NEXAFS study

    SciTech Connect

    Sing, M.; Meyer, J.; Glawion, S.; Claessen, R. [Experimentelle Physik IV, Universitaet Wuerzburg, D-97074 Wuerzburg (Germany); Hoinkis, M. [Experimentelle Physik IV, Universitaet Wuerzburg, D-97074 Wuerzburg (Germany); Experimentalphysik II, Universitaet Augsburg, D-86135 Augsburg (Germany); Blaha, P. [Institute of Materials Chemistry, Vienna University of Technology, A-1060 Vienna (Austria); Gavrila, G. [Institut fuer Physik, Technische Universitaet Chemnitz, D-09107 Chemnitz (Germany); Jacobsen, C. S. [Department of Physics, Technical University of Denmark, DK-2800 Lyngby (Denmark)

    2007-12-15

    We have performed angle-dependent near-edge x-ray absorption fine structure measurements in the Auger electron yield mode on the correlated quasi-one-dimensional organic conductor tetrathiafulvalene-tetracyanoquinodimethane (TTF-TCNQ) in order to determine the orientation of the molecules in the topmost surface layer. We find that the tilt angles of the molecules with respect to the one-dimensional axis are essentially the same as in the bulk. Thus, we can rule out surface relaxation as the origin of the renormalized band widths which were inferred from the analysis of photoemission data within the one-dimensional Hubbard model. Thereby, recent theoretical results are corroborated which invoke long-range Coulomb repulsion as alternative explanation to understand the spectral dispersions of TTF-TCNQ quantitatively within an extended Hubbard model.

  16. X-ray reflectivity analysis of giant-magnetoresistance spin-valve layered structures

    NASA Astrophysics Data System (ADS)

    Huang, T. C.; Nozieres, J.-P.; Speriosu, V. S.; Lefakis, H.; Gurney, B. A.

    1992-03-01

    The amount of intermixing at the interfaces of sputter-deposited spin-valve layered structures, comprising Si/Ta (50 Å)/NiFe (75 Å)/Cu (22.5 Å)/NiFe (50 Å)/FeMn (110 Å)/Ta (50 Å), were obtained from least-squares refinement of x-ray reflectivity data. The observations were modeled by layers of nominal composition with compositional inhomogeneity at the interfaces. Layer thicknesses deduced from x-ray analysis were generally within a few percent of the nominal values. Interface widths between the two NiFe layers and the Cu spacer were 6.2-7.4 Å, indicating intermixing of atoms of about three monolayers at the interfaces. A 10.0-Å interface width was found at the FeMn interface suggesting a mixed-phase layer of ?- and ?-FeMn. Layer densities, except those of the less dense Ta underlayer and the oxidized Ta surface, agreed to within 10% of bulk values. The results were in agreement with those obtained from closely related Si/Ta/NiFe/Cu/NiFe/Ta, Si/Ta/NiFe/Cu/Ta, Si/Ta/NiFe/Ta, and Si/Ta films.

  17. Origin of the 'dike-like' structure and transitions in eruptive styles at Colton Crater, northern Arizona: San Francisco Volcanic Field REU

    NASA Astrophysics Data System (ADS)

    Witter, M. R.; Ort, M. H.; Leudemann, L. A.

    2013-12-01

    Colton Crater, located within the San Francisco Volcanic Field (SFVF) in northern Arizona, is one of over 600 scoria cones in the field. Unlike most other volcanoes in the SFVF, Colton Crater is characterized as a hybrid volcano that had Strombolian, Hawaiian, and Surtseyan explosions. Surtseyan explosions led to the excavation of the center of the volcano, creating a large 1.3-km-diameter crater with a 30-m post-phreatomagmatic scoria cone at its center. A vertical erosion-resistant feature along the northern rim of the crater, originally mapped as a dike, provides valuable information about the sequence and timing of the transition to phreatomagmatic eruptions because it disrupts the otherwise continuous spatter layers deposited just prior to that change. Stratigraphic sections and paleomagnetic analysis of Colton Crater reveal the origin and timing of emplacement of this vertical structure and its place in the transitional eruptive history. The prominent upper layers in the crater walls show some variation throughout the crater, but generally are composed of agglutinated spatter, welded scoria and bombs, and rootless lava flows. The uppermost portion of the outward-dipping spatter layers that lie between the two saddles on the northern rim closely match the layers observed in the vertical structure, revealing that the structure is a section of rotated spatter. The characteristic remanent magnetization (ChRM), identified using alternating field (AF) demagnetization, shows the timing of the displacement of sections of the agglutinated spatter and welded cinder. Sites along the vertical structure yield ChRMs statistically identical to non-rotated sites, which indicates that rotation of the vertical structure occurred before the ChRM had been set, i.e., the layers were above the Curie temperature during rotation. The eruption started as Strombolian and Hawaiian perhaps because the flux of magma overpowered the influx of water from local aquifer formations, creating a stable and sealed conduit. Lava flows associated with the Strombolian and Hawaiian activity breached the northern flank and destabilized the walls of the crater. Water may have been introduced to the magmatic system through conduit collapse beneath the water table or vent migration to a conduit location with greater water flux, leading to the Surtseyan explosions. As space was created on the northern rim, the destabilized spatter layers detached and rotated, creating the vertical structure. The eruption ended with a small Strombolian phase, forming the 30-m-high scoria cone in the bottom of the crater. The sequence of these events must have happened within a short time period because the rotated spatter layers of the vertical structure remained above 580 oC.

  18. Co layer fragmentation effect on magnetoresistive and structural properties of nanogranular Co/Cu multilayers

    SciTech Connect

    Spizzo, F.; Ronconi, F. [Dipartimento di Fisica and CNISM, Polo Scientifico e Tecnologico, Universita degli Studi di Ferrara, via Saragat, 1 I-44100 Ferrara (Italy); Ferrero, C.; Mazuelas, A.; Metzger, T. H. [ESRF, BP 220, F-38043 Grenoble (France); Albertini, F.; Casoli, F.; Nasi, L. [IMEM-CNR, Parco Area delle Scienze, 37/A I-43100 Parma (Italy)

    2009-06-15

    We deposited nanogranular Co/Cu multilayers made of thin fragmented Co layers separated by thicker Cu layers to study how the structure and the microstructure of magnetic nanogranular samples change as the average particle size is reduced and how these changes affect the giant magnetoresistive response of the samples. Indeed, thanks to the vertical periodicity of the structure, namely, to the fact that Co/Cu interfaces display an ordered stacking and are not randomly distributed within the samples as in conventional granular materials, their self-correlation and cross correlation can be investigated. In this way, the characteristic length scale of the Co/Cu interfacial roughness that is strictly related to the giant magnetoresistive response of the samples and the universality class of the growth mechanism that affects the systems structure can be both accessed. The Co/Cu nanogranular multilayers were characterized using different x-ray techniques, from specular reflectivity, which allows to probe the multilayer development in the vertical direction, to grazing incidence small angle diffuse scattering, which provides information on the self-correlation and cross correlation of the Co/Cu interfaces. Furthermore, diffraction measurements indicate that the degree of structural disorder increases by decreasing the thickness of the Co layers. Magnetoresistive and magnetization measurements are as well presented and discussed with the results of the structural characterization.

  19. Extraction of very-large scale structures in turbulent boundary layer

    NASA Astrophysics Data System (ADS)

    Roux, Stéphane; Kerhervé, Franck; Stanislas, Michel; Marc Foucaut, Jean; Delville, Joel; Team

    2012-11-01

    The examined flow is a zero-pressure gradient turbulent boundary layer. The data used are taken from the joined experimental campaign conducted during the european WALLTURB program in the large wind tunnel at Laboratoire de Mécanique de Lille (LML). The free-stream velocity is 10 m/s. At the investigated position, the boundary layer thickness is 30 cm and the Reynolds number based on the momentum thickness is 19100. A methodology for eduction of super-structures is presented. These structures are characterised by a large degree of persistance and are thought to participate actively to the turbulence regeneration in the near-wall region (Marusic et al. 2010). A time-resolved estimate of the three-dimensionnal structures is obtained by combining low-speed two-dimensional stereo-PIV at 4 Hz and a two-dimensionnal rake of 143 single hot-wire probes at 30 kHz. The very large scale structures are clearly reconstructed which exhibit a streamwise extent an order of magnitude larger than the boundary layer thickness. Interest is particulary focused on the low-speed species of these structures. Associated coounter-rotating vortices are also evidenced in good agreement with the litterature.

  20. Response of rocky invertebrate diversity, structure and function to the vertical layering of vegetation

    NASA Astrophysics Data System (ADS)

    Bustamante, María; Tajadura, Javier; Gorostiaga, José María; Saiz-Salinas, José Ignacio

    2014-06-01

    Macroalgae comprise a prominent part of the rocky benthos where many invertebrates develop, and are believed to be undergoing severe declines worldwide. In order to investigate how the vegetation structure (crustose, basal and canopy layers) contributes to the diversity, structure and function of benthic invertebrates, a total of 31 subtidal transects were sampled along the northeast Atlantic coast of Spain. Significant positive relationships were found between the canopy layer and faunal abundance, taxonomic diversity and functional group diversity. Canopy forming algae were also related to epiphytic invertebrates, medium size forms, colonial strategy and suspensivores. By contrast, basal algae showed negative relationships with all variables tested except for detritivores. Multivariate multiple regression analyses (DISTLM) point to crustose as well as canopy layers as the best link between seaweeds and invertebrate assemblage structure. A close relationship was found between taxonomic and functional diversities. In general, low levels of taxonomic redundancy were detected for functional groups correlated with vegetation structure. A conceptual model based on the results is proposed, describing distinct stages of invertebrate assemblages in relation to the vertical structure of vegetation.

  1. Three-dimensional cell manipulation and patterning using dielectrophoresis via a multi-layer scaffold structure.

    PubMed

    Chu, H K; Huan, Z; Mills, J K; Yang, J; Sun, D

    2015-02-01

    Cell manipulation is imperative to the areas of cellular biology and tissue engineering, providing them a useful tool for patterning cells into cellular patterns for different analyses and applications. This paper presents a novel approach to perform three-dimensional (3D) cell manipulation and patterning with a multi-layer engineered scaffold. This scaffold structure employed dielectrophoresis as the non-contact mechanism to manipulate cells in the 3D domain. Through establishing electric fields via this multi-layer structure, the cells in the medium became polarized and were attracted towards the interior part of the structure, forming 3D cellular patterns. Experiments were conducted to evaluate the manipulation and the patterning processes with the proposed structure. Results show that with the presence of a voltage input, this multi-layer structure was capable of manipulating different types of biological cells examined through dielectrophoresis, enabling automatic cell patterning in the time-scale of minutes. The effects of the voltage input on the resultant cellular pattern were examined and discussed. Viability test was performed after the patterning operation and the results confirmed that majority of the cells remained viable. After 7 days of culture, 3D cellular patterns were observed through SEM. The results suggest that this scaffold and its automated dielectrophoresis-based patterning mechanism can be used to construct artificial tissues for various tissue engineering applications. PMID:25501324

  2. Development of Layered Sediment Structure and its Effects on Pore Water Transport and Hyporheic Exchange

    SciTech Connect

    Packman, Aaron I.; Marion, Andrea; Zaramella, Mattia; Chen, Cheng; Gaillard, Jean-François; Keane, Denis T. (Padua); (NWU)

    2008-04-15

    Hyporheic exchange is known to provide an important control on nutrient and contaminant fluxes across the stream-subsurface interface. Similar processes also mediate interfacial transport in other permeable sediments. Recent research has focused on understanding the mechanics of these exchange processes and improving estimation of exchange rates in natural systems. While the structure of sediment beds obviously influences pore water flow rates and patterns, little is known about the interplay of typical sedimentary structures, hyporheic exchange, and other transport processes in fluvial/alluvial sediments. Here we discuss several processes that contribute to local-scale sediment heterogeneity and present results that illustrate the interaction of overlying flow conditions, the development of sediment structure, pore water transport, and stream-subsurface exchange. Layered structures are shown to develop at several scales within sediment beds. Surface sampling is used to analyze the development of an armor layer in a sand-and-gravel bed, while innovative synchrotron-based X-ray microtomography is used to observe patterns of grain sorting within sand bedforms. We show that layered bed structures involving coarsening of the bed surface increase interfacial solute flux but produce an effective anisotropy that favors horizontal pore water transport while limiting vertical penetration.

  3. High frequency guided waves for hidden fatigue crack growth monitoring in multi-layer aerospace structures

    NASA Astrophysics Data System (ADS)

    Chan, Henry; Fromme, Paul

    2015-03-01

    Varying loading conditions of aircraft structures result in stress concentration at fastener holes, where multi-layered components are connected, possibly leading to the development of fatigue cracks. High frequency guided waves propagating along the structure allow for the non-destructive testing of such components, e.g., aircraft wings. However, the sensitivity for the detection of small, potentially hidden, fatigue cracks has to be ascertained. The type of multi-layered model structure investigated consists of two adhesively bonded aluminium plate-strips. Fatigue experiments were carried out. The sensitivity of the high frequency guided wave modes to monitor fatigue crack growth at a fastener hole during cyclic loading was investigated, using both standard pulse-echo equipment and laser interferometry. The sensitivity and repeatability of the measurements were ascertained, having the potential for fatigue crack growth monitoring at critical and difficult to access fastener locations from a stand-off distance.

  4. A highly sensitive pressure sensor using a double-layered graphene structure for tactile sensing.

    PubMed

    Chun, Sungwoo; Kim, Youngjun; Oh, Hyeong-Sik; Bae, Giyeol; Park, Wanjun

    2015-07-21

    In this paper, we propose a graphene sensor using two separated single-layered graphenes on a flexible substrate for use as a pressure sensor, such as for soft electronics. The working pressure corresponds to the range in which human perception recognizes surface morphologies. A specific design of the sensor structure drives the piezoresistive character due to the contact resistance between two graphene layers and the electromechanical properties of graphene itself. Accordingly, sensitivity in resistance change is given by two modes for low pressure (-0.24 kPa(-1)) and high pressure (0.039 kPa(-1)) with a crossover pressure (700 Pa). This sensor can detect infinitesimal pressure as low as 0.3 Pa with uniformly applied vertical force. With the attachment of the artificial fingerprint structure (AFPS) on the sensor, the detection ability for both the locally generated shear force and actual human touch confirms recognition of the surface morphology constructed by periodic structures. PMID:26098064

  5. Mass Conservation in Modeling Moisture Diffusion in Multi-Layer Carbon Composite Structures

    NASA Technical Reports Server (NTRS)

    Nurge, Mark A.; Youngquist, Robert C.; Starr, Stanley O.

    2009-01-01

    Moisture diffusion in multi-layer carbon composite structures is difficult to model using finite difference methods due to the discontinuity in concentrations between adjacent layers of differing materials. Applying a mass conserving approach at these boundaries proved to be effective at accurately predicting moisture uptake for a sample exposed to a fixed temperature and relative humidity. Details of the model developed are presented and compared with actual moisture uptake data gathered over 130 days from a graphite epoxy composite sandwich coupon with a Rohacell foam core.

  6. Fabrication of organic photovoltaic cells with double-layer ZnO structure

    Microsoft Academic Search

    Xiaohui Ju; Wei Feng; Xuequan Zhang; Varutt Kittichungchit; Tetsuro Hori; Hiroki Moritou; Akihiko Fujii; Masanori Ozaki

    2009-01-01

    The fabrication process of a photovoltaic cell with a structure of indium-tin-oxide (ITO)\\/double ZnO\\/C60\\/poly(3-hexylthiophene) (PAT6)\\/Ag has been investigated. The C60\\/PAT6 heterojunction of this cell was fabricated by spin-coating a chloroform solution of PAT6 onto the C60 thin film formed on double-layer ZnO-coated ITO. The fabrication of this double-layer ZnO was a new method, which was a composite of a sputtered

  7. Three-layered models of Ganymede and Callisto - Compositions, structures, and aspects of evolution

    NASA Technical Reports Server (NTRS)

    Mueller, Steve; Mckinnon, William B.

    1988-01-01

    The structural models presently defined for Ganymede and Callisto, which encompass a pure-ice upper layer, a mixed ice/rock lower mantle, and a rock core, incorporate three alternative rock component candidates representing various degrees of silicate hydration and oxidation. The three-layered model facilitates close study of the radius increase required for the internal differentiation of an ice-rock satellite; such expansion is determined to be most significant early in the process, and less so as differentiation approaches completion. The probability of postaccretional melting due to radiogenic heating is calculated.

  8. Optical studies of the smectic-C*? phase layer structure in free-standing films

    NASA Astrophysics Data System (ADS)

    Olson, D. A.; Pankratz, S.; Johnson, P. M.; Cady, A.; Nguyen, H. T.; Huang, C. C.

    2001-06-01

    The layer structure of the smectic-C*? phase of one liquid-crystal compound has been acquired from both differential optical reflectivity and ellipsometry measurements in the free-standing film geometry. The data from both techniques display characteristic oscillations as a function of temperature, which can be described by a model for the film consisting of surface anticlinic layers and an interior short-pitched azimuthal helix. These results are consistent with those found previously for another compound. Depolarized reflected light microscopy is used to study the films when the unique features of the aforementioned oscillations occur.

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

    PubMed

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

    2015-02-01

    In this study, we investigate the influence of surface structure on the fouling propensity of thin-film composite (TFC) forward osmosis (FO) membranes. Specifically, we compare membranes fabricated through identical procedures except for the use of different solvents (dimethylformamide, DMF and N-methyl-2-pyrrolidinone, NMP) during phase separation. FO fouling experiments were carried out with a feed solution containing a model organic foulant. The TFC membranes fabricated using NMP (NMP-TFC) had significantly less flux decline (7.47 ± 0.15%) when compared to the membranes fabricated using DMF (DMF-TFC, 12.70 ± 2.62% flux decline). Water flux was also more easily recovered through physical cleaning for the NMP-TFC membrane. To determine the fundamental cause of these differences in fouling propensity, the active and support layers of the membranes were extensively characterized for physical and chemical characteristics relevant to fouling behavior. Polyamide surface roughness was found to dominate all other investigated factors in determining the fouling propensities of our membranes relative to each other. The high roughness polyamide surface of the DMF-TFC membrane was also rich in larger leaf-like structures, whereas the lower roughness NMP-TFC membrane polyamide layer contained more nodular and smaller features. The support layers of the two membrane types were also characterized for their morphological properties, and the relation between support layer surface structure and polyamide active layer formation was discussed. Taken together, our findings indicate that support layer structure has a significant impact on the fouling propensity of the active layer, and this impact should be considered in the design of support layer structures for TFC membranes. PMID:25564877

  10. Adaptive nonlinear polynomial neural networks for control of boundary layer/structural interaction

    NASA Technical Reports Server (NTRS)

    Parker, B. Eugene, Jr.; Cellucci, Richard L.; Abbott, Dean W.; Barron, Roger L.; Jordan, Paul R., III; Poor, H. Vincent

    1993-01-01

    The acoustic pressures developed in a boundary layer can interact with an aircraft panel to induce significant vibration in the panel. Such vibration is undesirable due to the aerodynamic drag and structure-borne cabin noises that result. The overall objective of this work is to develop effective and practical feedback control strategies for actively reducing this flow-induced structural vibration. This report describes the results of initial evaluations using polynomial, neural network-based, feedback control to reduce flow induced vibration in aircraft panels due to turbulent boundary layer/structural interaction. Computer simulations are used to develop and analyze feedback control strategies to reduce vibration in a beam as a first step. The key differences between this work and that going on elsewhere are as follows: that turbulent and transitional boundary layers represent broadband excitation and thus present a more complex stochastic control scenario than that of narrow band (e.g., laminar boundary layer) excitation; and secondly, that the proposed controller structures are adaptive nonlinear infinite impulse response (IIR) polynomial neural network, as opposed to the traditional adaptive linear finite impulse response (FIR) filters used in most studies to date. The controllers implemented in this study achieved vibration attenuation of 27 to 60 dB depending on the type of boundary layer established by laminar, turbulent, and intermittent laminar-to-turbulent transitional flows. Application of multi-input, multi-output, adaptive, nonlinear feedback control of vibration in aircraft panels based on polynomial neural networks appears to be feasible today. Plans are outlined for Phase 2 of this study, which will include extending the theoretical investigation conducted in Phase 2 and verifying the results in a series of laboratory experiments involving both bum and plate models.

  11. Comparison of Structural Models of Mixed-Layer Illite\\/Smectite and Reaction Mechanisms of Smectite Illitization

    Microsoft Academic Search

    Stephen P. Altaner; ROBERT E YLAGAN

    1997-01-01

    This paper compares mechanisms of the reaction of smectite to illite, in light of structural models for interstratified illite\\/smectite (US). The crystal structure of US has been described previously by a nonpolar and polar 2:1 layer model. In a nonpolar model, individual 2:1 layers are chemically homogeneous, whereas a polar model assumes a 2: l layer can have a smectite

  12. Preparation and characterization of conductor–insulator–semiconductor sandwich-structured MWCNT\\/double-layer polymer hybrid nanocomposites

    Microsoft Academic Search

    Bin Mu; Peng Liu; Xiaomin Yu; Fei Pan; Zhijun Gao; Xiang Liu

    2010-01-01

    The conductor–insulator–semiconductor sandwich-structured MWCNT\\/double-layer polymer hybrid nanocomposites (MWCNT-PS-PAA\\/PAn), multiwalled carbon nanotubes (MWCNTs) encapsulated with polystyrene (PS) inner layer and polyacrylic acid (PAA) doped polyaniline (PAn) outer layer via covalently linking, were fabricated through combining the successive surface-initiated atom transfer radical polymerization (SI-ATRP) and in situ chemical oxidative polymerization techniques. The sandwiched structure was confirmed by the XPS and TEM analysis.

  13. Si\\/Si 1? x Ge x epitaxial layers and superlattices. Growth and structural characteristics

    Microsoft Academic Search

    F. F. Sizov; V. P. Klad’ko; S. V. Plyatsko; A. P. Shevlyakov; Yu. N. Kozyrev; V. M. Ogenko

    1997-01-01

    Si, Ge, and Si1?x\\u000a Gex epitaxial layers and Si\\/Si1?x\\u000a Gex superlattices have been obtained on (100) and (111) silicon substrates by molecular-beam epitaxy. The growth processes and\\u000a the structural characteristics and chemical composition of the structures were studied by x-ray diffraction and Auger spectroscopy.\\u000a It is shown that under the experimental conditions for obtaining Si\\/Si1?x\\u000a Gex superlattices structurally perfect, strained

  14. On the origin of mixed-layered clay minerals from the San Andreas Fault at 2.5–3 km vertical depth (SAFOD drillhole at Parkfield, California)

    Microsoft Academic Search

    A. M. Schleicher; L. N. Warr; B. A. van der Pluijm

    2009-01-01

    A detailed mineralogical study is presented of the matrix of mudrocks sampled from spot coring at three key locations along\\u000a the San Andreas Fault Observatory at depth (SAFOD) drill hole. The characteristics of authigenic illite–smectite (I–S) and\\u000a chlorite–smectite (C–S) mixed-layer mineral clays indicate a deep diagenetic origin. A randomly ordered I–S mineral with ca.\\u000a 20–25% smectite layers is one of

  15. Highly Insulating Glazing Systems using Non-Structural Center Glazing Layers

    SciTech Connect

    Kohler, Christian; Arasteh, Dariush; Goudey, Howdy; Kohler, Christian

    2008-04-09

    Three layer insulating glass units with two low-e coatings and an effective gas fill are known to be highly insulating, with center-of-glass U-factors as low as 0.57 W/m{sup 2}-K (0.10 Btu/h-ft{sup 2}- F). Such units have historically been built with center layers of glass or plastic which extend all the way through the spacer system. This paper shows that triple glazing systems with non-structural center layers which do not create a hermetic seal at the edge have the potential to be as thermally efficient as standard designs, while potentially removing some of the production and product integration issues that have discouraged the use of triples.

  16. Interrelated structures of the transport shock and collisional relaxation layer in a multitemperature, multilevel ionized gas

    NASA Technical Reports Server (NTRS)

    Vinolo, A. R.; Clarke, J. H.

    1972-01-01

    The gas dynamic structures of the transport shock and the downstream collisional relaxation layer are evaluated for partially ionized monatomic gases. Elastic and inelastic collisional nonequilibrium effects are taken into consideration. Three electronic levels are accounted for in the microscopic model of the atom. Nonequilibrium processes with respect to population of levels and species plus temperature are considered. By using an asymptotic technique the shock morphology is found on a continuum flow basis. The asymptotic procedure gives two distinct layers in which the nonequilibrium effects to be considered are different. A transport shock appears as the inner solution to an outer collisional relaxation layer in which the gas reaches local equilibrium. A family of numerical examples is displayed for different flow regimes. Argon and helium models are used in these examples.

  17. Mesoscopic Structures Reveal the Network Between the Layers of Multiplex Datasets

    E-print Network

    Iacovacci, Jacopo; Bianconi, Ginestra

    2015-01-01

    Multiplex networks describe a large variety of complex systems, whose elements (nodes) can be connected by different types of interactions forming different layers (networks) of the multiplex. Multiplex networks include social networks, transportation networks or biological networks in the cell or in the brain. Extracting relevant information from these networks is of crucial importance for solving challenging inference problems and for characterizing the multiplex networks microscopic and mesoscopic structure. Here we propose an information theory method to extract the network between the layers of multiplex datasets, forming a "network of networks". We build an indicator function, based on the entropy of network ensembles, to characterize the mesoscopic similarities between the layers of a multiplex network and we use clustering techniques to characterize the communities present in this network of networks. We apply the proposed method to study the Multiplex Collaboration Network formed by scientists collab...

  18. A multi-layered thermal model of backup structures for mm-wavelength radio telescopes

    NASA Astrophysics Data System (ADS)

    Greve, A.; Smith, D. R.; Bremer, M.

    2006-06-01

    An unfavourable influence that degrades the performance of any millimeter wavelength radio telescope is the deformation of the reflector surface due to temperature differences in the supporting backup structure. To avoid, or at least reduce this influence, the backup structures are typically protected by a rear side cladding, insulation at the panel inner side, and ventilation or climatization of the air inside the backup structure. During the design of a mm-wavelength telescope, the layout of a thermal protection system is made, based on experience gained on other telescopes, and on thermal model calculations of the complete backup structure. The available thermal programs allow today the construction of a multi-layered backup structure model, consisting of the backup structure tube network, without and with ventilation/climatization, the panels, insulation behind the panels, and the rear side cladding. We provide a guideline for the construction of such a multi-layered thermal model, and demonstrate that realistic temperature gradients across and through a backup structure can be calculated. These gradients can be used in a finite element model to calculate the reflector surface deformations, which can be used in a diffraction program to calculate the radio beam pattern.

  19. Diverse and tunable electronic structures of single-layer metal phosphorus trichalcogenides for photocatalytic water splitting

    SciTech Connect

    Liu, Jian [School of Materials Science and Engineering, Hunan University, Changsha 410082, Hunan (China) [School of Materials Science and Engineering, Hunan University, Changsha 410082, Hunan (China); Beijing Computational Science Research Center, Beijing 100084 (China); College of Electrical and Information Engineering, Hunan Institute of Engineering, Xiangtan 411105, Hunan (China); Li, Xi-Bo; Wang, Da; Liu, Li-Min, E-mail: ppeng@hnu.edu.cn, E-mail: limin.liu@csrc.ac.cn [Beijing Computational Science Research Center, Beijing 100084 (China)] [Beijing Computational Science Research Center, Beijing 100084 (China); Lau, Woon-Ming [Beijing Computational Science Research Center, Beijing 100084 (China) [Beijing Computational Science Research Center, Beijing 100084 (China); Chengdu Green Energy and Green Manufacturing Technology R and D Center, Chengdu, Sichuan 610207 (China); Peng, Ping, E-mail: ppeng@hnu.edu.cn, E-mail: limin.liu@csrc.ac.cn [School of Materials Science and Engineering, Hunan University, Changsha 410082, Hunan (China)] [School of Materials Science and Engineering, Hunan University, Changsha 410082, Hunan (China)

    2014-02-07

    The family of bulk metal phosphorus trichalcogenides (APX{sub 3}, A = M{sup II}, M{sub 0.5}{sup I}M{sub 0.5}{sup III}; X = S, Se; M{sup I}, M{sup II}, and M{sup III} represent Group-I, Group-II, and Group-III metals, respectively) has attracted great attentions because such materials not only own magnetic and ferroelectric properties, but also exhibit excellent properties in hydrogen storage and lithium battery because of the layered structures. Many layered materials have been exfoliated into two-dimensional (2D) materials, and they show distinct electronic properties compared with their bulks. Here we present a systematical study of single-layer metal phosphorus trichalcogenides by density functional theory calculations. The results show that the single layer metal phosphorus trichalcogenides have very low formation energies, which indicates that the exfoliation of single layer APX{sub 3} should not be difficult. The family of single layer metal phosphorus trichalcogenides exhibits a large range of band gaps from 1.77 to 3.94 eV, and the electronic structures are greatly affected by the metal or the chalcogenide atoms. The calculated band edges of metal phosphorus trichalcogenides further reveal that single-layer ZnPSe{sub 3}, CdPSe{sub 3}, Ag{sub 0.5}Sc{sub 0.5}PSe{sub 3}, and Ag{sub 0.5}In{sub 0.5}PX{sub 3} (X = S and Se) have both suitable band gaps for visible-light driving and sufficient over-potentials for water splitting. More fascinatingly, single-layer Ag{sub 0.5}Sc{sub 0.5}PSe{sub 3} is a direct band gap semiconductor, and the calculated optical absorption further convinces that such materials own outstanding properties for light absorption. Such results demonstrate that the single layer metal phosphorus trichalcogenides own high stability, versatile electronic properties, and high optical absorption, thus such materials have great chances to be high efficient photocatalysts for water-splitting.

  20. The structure and tribological properties of gradient layers prepared by plasma-based ion implantation on 2024 Al alloy

    NASA Astrophysics Data System (ADS)

    Liao, J. X.; Xia, L. F.; Sun, M. R.; Liu, W. M.; Xu, T.; Xue, Q. J.

    2004-02-01

    Using plasma-based ion implantation, two types of gradient layers have been prepared on 2024 Al alloy. One is prepared by N-implantation then C-deposition, the other adds an interlayer composed of a Ti layer and a Ti-N layer between N-implantation and C-deposition. C-deposition is carried out at various implanting voltages or C2H2/H2 ratios. The composition depth profiles of these layers were characterized by x-ray photoelectron spectroscopy. The structure, morphologies and microstructure of the C layers were studied using Raman spectroscopy, atomic force microscope and transmission electron microscope, respectively. The surface hardness was measured with a Knoop tester and a mechanical property microprobe. The dry ball-on-disc wear tests were performed in ambient air. The gradient layer without interlayer is composed of an N-implanted layer rich in AlN and a diamond-like carbon (DLC) layer (film), and the two layers are connected with a C-Al transition layer containing Al4C3. The Ti layer rich in agr -Ti and the N-implanted layer are connected by a Ti-Al transition layer containing TiAl3, while the Ti-N layer rich in TiN and the DLC film are connected by a C-Ti transition layer containing TiC, TiCN, etc. Thus, the gradient layer with interlayers has optimized the gradient structure. DLC films are compact and amorphous, contain high sp3/sp2 ratios and depend on the implanting voltage and the C2H2/H2 ratio. Similarly, these gradient layers exhibit significant improvement in morphologies, surface hardness and tribological properties; the interlayer, the implanting voltage and the C2H2/H2 ratio all have prominent effects on these properties.

  1. A Markov chain model for characterizing medium heterogeneity and sediment layering structure

    NASA Astrophysics Data System (ADS)

    Ye, Ming; Khaleel, Raziuddin

    2008-09-01

    By leveraging use of "soft" data (e.g., initial moisture content, ?i), this study applies the transition probability (TP) based Markov chain (MC) model to sediment textural classes for characterizing the medium heterogeneity and sediment layering structure. The TP/MC method is evaluated by simulating the vadose zone moisture movement at a field site, where the stratigraphy consists of imperfectly stratified soil layers. Soil heterogeneity is characterized via spatial variability of the geometry of soil textural classes. When the ?i measurements, which carry signature about medium heterogeneity and stratigraphy, are not included in the TP/MC model, it is not possible to identify the horizontal TP. The ?i measurements, when transformed into soil classes, are necessary in mapping the soil layering structure prevalent at the site. The soil hydraulic parameters for each soil class are treated deterministically and are estimated on the basis of core samples. To evaluate uncertainty in characterizing geometry of the soil classes, multiple conditional realizations of the soil classes are generated. A Monte Carlo simulation shows that the simulated mean moisture contents agree well with corresponding field observations. The observed splitting of the moisture plume in a coarse sand layer that is sandwiched between two fine-textured layers, the southeastward movement of the plume during the redistribution period, and the near-zero fluid flux below the bottom fine layer are adequately simulated. Spatial variability of the field-measured moisture content is sufficiently captured by the 95% confidence intervals calculated from the Monte Carlo simulations. Investigating the effect of data conditioning on the simulated results shows that a reduction of conditioning data does not necessarily deteriorate simulation results if other conditioning data exist within the mean length of the soil classes. The TP/MC method is flexible so that other types of site characterization data (e.g., geophysical data) can be incorporated as they become available.

  2. Theoretical study of shear horizontal wave propagation in periodically layered piezoelectric structure

    NASA Astrophysics Data System (ADS)

    Zhao, J.; Pan, Y.; Zhong, Z.

    2012-03-01

    In this paper, the propagation of the shear horizontal wave (SH-wave) in the single piezoelectric layer and periodically layered piezoelectric structure is studied. Both the dispersion equation and transmission coefficients are derived to reveal the wave behavior of the corresponding structures when the piezoelectricity is ignored or the electrical circuit is open and closed. The zero-order mode of the piezoelectricity-ignored single plate is not dispersive and every higher order mode is dispersive with a cut-off frequency. Same features are found for the electrically open and closed cases except that the zero-order mode of the latter case is no more non-dispersive. The pass bands of the piezoelectricity-ignored periodically layered structure appear when the normalized frequency is an even integer under the normal incidence, and new stop bands will appear from the pass bands as the incident angle increases. The same features are observed for the band gaps of the electrically open and closed cases except that the zero-order mode of the latter case is dispersive. The stop bands of the periodic structure will change in a cycle as the geometric ratio increases from zero to one.

  3. Intercalation of dodecylamine into kaolinite and its layering structure investigated by molecular dynamics simulation.

    PubMed

    Zhang, Shuai; Liu, Qinfu; Cheng, Hongfei; Li, Xiaoguang; Zeng, Fangui; Frost, Ray L

    2014-09-15

    Dodecylamine was successfully intercalated into the layer space of kaolinite by utilizing the methanol treated kaolinite-dimethyl sulfoxide (DMSO) intercalation complex as an intermediate. The basal spacing of kaolinite, measured by X-ray diffraction (XRD), increased from 0.72 nm to 4.29 nm after the intercalation of dodecylamine. Also, the significant variation observed in the Fourier Transform Infrared Spectroscopy (FTIR) spectra of kaolinite when intercalated with dodecylamine verified the feasibility of intercalation of dodecylamine into kaolinite. Isothermal-isobaric (NPT) molecular dynamics simulation with the use of Dreiding force field was performed to probe into the layering behavior and structure of nanoconfined dodecylamine in the kaolinite gallery. The concentration profiles of the nitrogen atom, methyl group and methylene group of intercalated dodecylamine molecules in the direction perpendicular to the kaolinite basal surface indicated that the alkyl chains within the interlayer space of kaolinite exhibited an obvious layering structure. However, the unified bilayer, pseudo-trilayer, or paraffin-type arrangements of alkyl chains deduced based on their chain length combined with the measured basal spacing of organoclays were not found in this study. The alkyl chains aggregated to a mixture of ordered paraffin-type-like structure and disordered gauche conformation in the middle interlayer space of kaolinite, and some alkyl chains arranged in two bilayer structures, in which one was close to the silica tetrahedron surface, and the other was close to the alumina octahedron surface with their alkyl chains parallel to the kaolinite basal surface. PMID:24974247

  4. Soil sealing and vesicular layer formation as initial structure development and its effect on infiltration

    NASA Astrophysics Data System (ADS)

    Badorreck, A.; Gerke, H. H.; Weller, U.; Vontobel, P.

    2009-04-01

    In the Lusatia mining district (NE-Germany) an artificial catchment was constructed to study initial ecosystem development and runoff generation. As a key process in this early stage, we investigate the surface structure dynamics as it strongly influences erosion, infiltration, matter dynamics, and vegetation establishment. The presented work focuses on observations of soil pore structure formation at the surface at five sites in the catchment and in an adjacent "younger" area composed of comparable sediments. Moreover we've conducted infiltration experiments in the lab and field to relate the soil pore structure to the hydraulic properties. The surface soil was sampled in cylindrical rings (10 cm³) down to 2 cm depth from which bulk density profiles were obtained using X-ray computed tomography (CT) (at UFZ- Halle, Germany) with a resolution of 0.084 mm. The influence of structure on infiltration was investigated using neutron radiography (at the NEUTRA facility of the Paul-Scherrer-Institut, Villigen, Switzerland) to visualise two-dimensional (2D) infiltration patterns. The slab-type samples were equilibrated to different initial water contents and then exposed to drip irrigation (to simulate rainfall) while a series of neutron radiographs were taken. In addition, field measurements with a miniature tension infiltrometer were conduced. The micro-tomographies exhibit formation of surface sealing whose thickness and intensity vary with silt and clay content. The CT images show several coarser- and finer-textured micro-layers at the sample surfaces that were formed as a consequence of repeated washing in of finer particles in underlying coarser sediment. In micro-depressions, the uppermost layers consist of sorted fine sand and silt due to wind erosion. Similar as for desert pavements, a vesicular pore structure developed in these sediments on top, but also scattered in fine sand- and silt-enriched micro-layers. The infiltration rates were severely affected by the surface crusts; however, the rates were independent of the vesicular pore layer.

  5. Shear rheology of mixed protein adsorption layers vs their structure studied by surface force measurements.

    PubMed

    Danov, Krassimir D; Kralchevsky, Peter A; Radulova, Gergana M; Basheva, Elka S; Stoyanov, Simeon D; Pelan, Eddie G

    2014-05-01

    The hydrophobins are proteins that form the most rigid adsorption layers at liquid interfaces in comparison with all other investigated proteins. The mixing of hydrophobin HFBII with other conventional proteins is expected to reduce the surface shear elasticity and viscosity, Esh and ?sh, proportional to the fraction of the conventional protein. However, the experiments show that the effect of mixing can be rather different depending on the nature of the additive. If the additive is a globular protein, like ?-lactoglobulin and ovalbumin, the surface rigidity is preserved, and even enhanced. The experiments with separate foam films indicate that this is due to the formation of a bilayer structure at the air/water interface. The more hydrophobic HFBII forms the upper layer adjacent to the air phase, whereas the conventional globular protein forms the lower layer that faces the water phase. Thus, the elastic network formed by the adsorbed hydrophobin remains intact, and even reinforced by the adjacent layer of globular protein. In contrast, the addition of the disordered protein ?-casein leads to softening of the HFBII adsorption layer. Similar (an even stronger) effect is produced by the nonionic surfactant Tween 20. This can be explained with the penetration of the hydrophobic tails of ?-casein and Tween 20 between the HFBII molecules at the interface, which breaks the integrity of the hydrophobin interfacial elastic network. The analyzed experimental data for the surface shear rheology of various protein adsorption layers comply with a viscoelastic thixotropic model, which allows one to determine Esh and ?sh from the measured storage and loss moduli, G' and G?. The results could contribute for quantitative characterization and deeper understanding of the factors that control the surface rigidity of protein adsorption layers with potential application for the creation of stable foams and emulsions with fine bubbles or droplets. PMID:24828304

  6. Dynamical robustness of the conductivity of ultracold bosons confined in layered structures

    NASA Astrophysics Data System (ADS)

    Sajna, A. S.; Polak, T. P.

    2014-10-01

    We study dynamical conductivity of strongly correlated bosons loaded in an optical lattice with restricted geometry in which gauge fields are present. We show that dynamics influenced by the uniform synthetic magnetic field combined with layered lattice structures changes into rich insulator-metallic behavior in the strongly correlated regime. Especially, the amplitude of optical conductivity for a given frequency is a nonmonotonous function of the number of layers L. In particular, conductivity for frequency corresponding to on-site interaction energy can abruptly vanish for a special number of applied layers. Moreover, such an insulating behavior is stable in the whole range of parameters in the Mott phase. This robustness arises from the complex gaplike behavior or from Dirac-like physics reflected in the quasiparticle energy spectra. Furthermore we show that a large interlayer tunneling anisotropy destabilizes the absence of conducting state. We also investigate the critical conductivity on the Mott-insulator-superfluid phase boundary and show the correspondence between the number of Hofstadter subbands and the number of layers. The obtained results also reveal that the value of critical conductivity gradually goes to zero when a three-dimensional system is approached. The experimental setup for generation of layered optical lattices is also proposed.

  7. Identification and radio vision of the vertical structure of the layers and wave activity in the atmoshere

    NASA Astrophysics Data System (ADS)

    Alexander, Pavelyev; Kefei, Zhang; Vladimir, Gubenko; Erjiang, Fu; Chuan-Sheng, Wang; Yuei-An, Liou; Yuriy, Kuleshov

    2010-05-01

    Identification and radio vision of the vertical structure of the layers and wave activity in the atmosphere Alexander Pavelyev, Vladimir Gubenko Institute of Radio Engineering and Electronics, Russian Academy of Sciences, Fryazino, Russia Kefei Zhang, Erjiang Fu and Chuan-Sheng Wang School of Mathematical and Geospatial Sciences, RMIT University, Melbourne, Australia Yuei-An Liou Center for Space and Remote Sensing Research (CSRSR), National Central University, Jhongli, Taiwan Yuriy Kuleshov National Climate Centre, Bureau of Meteorology, Melbourne, Australia From an analysis of the CHAMP (Challenging Minisatellite Payload, Germany) and the FORMOSAT-3/COSMIC (FORMOSA Satellite Constellation Observing Systems for Meteorology, Ionosphere, and Climate mission, USA -Taiwan) satellite data it follows that the second-order time derivative of the eikonal (eikonal acceleration) and the Doppler frequency shift are two most important parameters indispensable for the radio vision of layers in the atmosphere and the ionosphere. Measurements of the temporal evolution of the Doppler shift permit one to study the vertical structure of the atmosphere under the condition of its spherical symmetry. Analysis of the amplitude and phase of interrelated variations in the eikonal acceleration and radio-wave intensity permits one to detect and identify the layers in the atmosphere and ionosphere. Therefore the eikonal acceleration/intensity technique can be applied to separate the influence of layered structures from contributions of irregularities and turbulence in the atmosphere. In many cases the layered structures in the atmosphere indicate quasi-periodical altitude dependence that reveals their wave origin. The altitude profile of the vertical gradient of refractivity in the layered structures can be used to find the main characteristics of the internal wave activity with a global coverage. When the type of internal waves are not known, the height dependence of the vertical gradient of refractivity can be applied for monitoring the temporal and spatial distributions of wave activity at different levels in the atmosphere. In the case of the internal gravity waves one can measure their important parameters by use of the vertical profile of the refractivity: the intrinsic phase speed, the horizontal wind perturbations and, under some assumptions, the intrinsic frequency as functions of height in the atmosphere. Advantages of the eikonal acceleration/intensity technique are validated by means of analysis of the CHAMP and FORMOSAT-3/COSMIC RO data. Eikonal variations may be converted into refraction attenuation variations, which allows the integral absorption to be determined with the refraction effect on the radio-wave intensity cancelled out. This is necessary for measurements of the water-vapor density and gas minorities during multifrequency radio-occultation sounding along the satellite-to-satellite paths. The obtained results can be of common value for other remote-sounding paths, as well.

  8. Crystal structure of La4Mg3W3O18 layered oxide

    NASA Astrophysics Data System (ADS)

    Khalyavin, D. D.; Senos, A. M. R.; Mantas, P. Q.

    2005-05-01

    The crystal structure of A-site deficient La4Mg3W3O18 perovskite has been solved by x-ray powder diffraction in combination with group theoretical analysis. Above 700 K, the crystal structure is orthorhombic (space group Ibam; 2ap × 4ap × 2ap type superstructure) and presents a sequence of [LaO]-[Mg1/2W1/2O2]-[La1/3O]'-[Mg1/2W1/2O2]-[LaO]- [Mg1/2W1/2O2]-[La1/3O]''-[Mg1/2W1/2O2] layers stacked along the b axis. The lanthanum ions and the vacancies in the [La1/3O]' and [La1/3O]'' layers are ordered and form rows along the c axis. A half-period shift along the a direction between these layers leads to a quadrupling of the primitive perovskite unit cell in the b direction. The ordering of the vacancies in the lanthanum poor layers is connected with the ionic ordering between Mg2+ and W6+ in the neighbouring [Mg1/2W1/2O2] blocks. Around 700 K, due to an anti-phase rotation of the octahedra, a continuous phase transition mediated by the ?2+ irreducible representation from orthorhombic (Ibam, a0b0c0) to monoclinic (C 2/m, a0b0c-) symmetry takes place.

  9. Pressure induced metallization with absence of structural transition in layered MoSe2

    NASA Astrophysics Data System (ADS)

    Zhao, Zhao; Zhang, Haijun; Yuan, Hongtao; Wang, Shibing; Lin, Yu; Zeng, Qiaoshi; Liu, Zhenxian; Patel, Kirit; Solanki, Gunvant; Cui, Yi; Hwang, Harold; Mao, Wendy

    2015-03-01

    Layered transition-metal dichalcogenides 2H-MX2 (M = Mo, W, and etc, X = S, Se, and Te) are emerging as exciting material systems with unique electronic properties and atomically thin geometries. Here, we systematically investigating the high pressure behavior of 2Hc-MoSe2 up to 60 GPa via a diamond anvil cell, we identified MoSe2 as a promising candidate for lattice and electronic engineering. In sharp contrast to MoS2, the crystal structure of MoSe2 evolves from an anisotropic two-dimensional layered network to a highly isotropic three-dimensional solid without any structural transition. The role of the chalcogenides anions in stabilizing either 2Ha or 2Hc layered patterns is underscored by our layer sliding calculations. MoSe2 possesses highly tunable optical and electrical transport properties as a function of pressure, which is essentially determined by the narrowing of its band gap followed by closure at around 40 GPa. Our ab-initio calculations further support the semiconductor to metal transition.

  10. Asymptotic structure and similarity solutions for three-dimensional turbulent boundary layers

    NASA Technical Reports Server (NTRS)

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

    1989-01-01

    The asymptotic structure of the three-dimensional turbulent boundary layer is investigated in the limit of large Reynolds numbers. A self-consistent, but relatively complex, two-layer structure exists and the simplest situation, corresponding to a plane of symmetry, is considered in this paper as a first step. The adjustment of the streamwise velocity to relative rest, through an outer defect layer and then an inner wall layer, is similar to that in two-dimensional flow. The adjustment of the cross-streamwise velocity is more complicated and it is shown that two terms in the expansion are required to obtain useful results, and in particular to obtain the velocity skew angle at the wall near the symmetry plane. The conditions under which self-similarity is achieved near a plane of symmetry are investigated. A set of ordinary differential equations is developed which describe the streamwise and cross-streamwise velocities near a plane of symmetry in a self-similar flow through two orders of magnitude. Calculated numerical solutions of these equations yield trends which are consistent with experimental observations.

  11. Ripple structure of crystalline layers in ion-beam-induced Si wafers

    SciTech Connect

    Hazra, S.; Chini, T.K.; Sanyal, M.K.; Grenzer, J.; Pietsch, U. [Surface Physics Division, Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700 064 (India); Institut fur Physik, Universitat Potsdam, 14415 Potsdam (Germany)

    2004-09-15

    Ion-beam-induced ripple formation in Si wafers was studied by two complementary surface sensitive techniques, namely atomic force microscopy (AFM) and depth-resolved x-ray grazing incidence diffraction (GID). The formation of ripple structure at high doses ({approx}7x10{sup 17} ions/cm{sup 2}), starting from initiation at low doses ({approx}1x10{sup 17} ions/cm{sup 2}) of ion beam, is evident from AFM, while that in the buried crystalline region below a partially crystalline top layer is evident from GID study. Such ripple structure of crystalline layers in a large area formed in the subsurface region of Si wafers is probed through a nondestructive technique. The GID technique reveals that these periodically modulated wavelike buried crystalline features become highly regular and strongly correlated as one increases the Ar ion-beam energy from 60 to 100 keV. The vertical density profile obtained from the analysis of a Vineyard profile shows that the density in the upper top part of ripples is decreased to about 15% of the crystalline density. The partially crystalline top layer at low dose transforms to a completely amorphous layer for high doses, and the top morphology was found to be conformal with the underlying crystalline ripple.

  12. Design maps for failure of all-ceramic layer structures in concentrated cyclic loading

    PubMed Central

    Bhowmick, Sanjit; Meléndez-Martínez, Juan José; Zhang, Yu; Lawn, Brian R.

    2009-01-01

    A study is made of the competition between failure modes in ceramic-based bilayer structures joined to polymer-based substrates, in simulation of dental crown-like structures with a functional but weak “veneer” layer bonded onto a strong “core” layer. Cyclic contact fatigue tests are conducted in water on model flat systems consisting of glass plates joined to glass, sapphire, alumina or zirconia support layers glued onto polycarbonate bases. Critical numbers of cycles to take each crack mode to failure are plotted as a function of peak contact load on failure maps showing regions in which each fracture mode dominates. In low-cycle conditions, radial and outer cone cracks are competitive in specimens with alumina cores, and outer cone cracks prevail in specimens with zirconia cores; in high-cycle conditions, inner cone cracks prevail in all cases. The roles of other factors, e.g. substrate modulus, layer thickness, indenter radius and residual stresses from specimen preparation, are briefly considered. PMID:19562095

  13. Organic and inorganic-organic thin film structures by molecular layer deposition: A review.

    PubMed

    Sundberg, Pia; Karppinen, Maarit

    2014-01-01

    The possibility to deposit purely organic and hybrid inorganic-organic materials in a way parallel to the state-of-the-art gas-phase deposition method of inorganic thin films, i.e., atomic layer deposition (ALD), is currently experiencing a strongly growing interest. Like ALD in case of the inorganics, the emerging molecular layer deposition (MLD) technique for organic constituents can be employed to fabricate high-quality thin films and coatings with thickness and composition control on the molecular scale, even on complex three-dimensional structures. Moreover, by combining the two techniques, ALD and MLD, fundamentally new types of inorganic-organic hybrid materials can be produced. In this review article, we first describe the basic concepts regarding the MLD and ALD/MLD processes, followed by a comprehensive review of the various precursors and precursor pairs so far employed in these processes. Finally, we discuss the first proof-of-concept experiments in which the newly developed MLD and ALD/MLD processes are exploited to fabricate novel multilayer and nanostructure architectures by combining different inorganic, organic and hybrid material layers into on-demand designed mixtures, superlattices and nanolaminates, and employing new innovative nanotemplates or post-deposition treatments to, e.g., selectively decompose parts of the structure. Such layer-engineered and/or nanostructured hybrid materials with exciting combinations of functional properties hold great promise for high-end technological applications. PMID:25161845

  14. Structure of nanofibrillated cellulose layers at the o/w interface.

    PubMed

    Xhanari, Klodian; Syverud, Kristin; Chinga-Carrasco, Gary; Paso, Kristofer; Stenius, Per

    2011-04-01

    The nature of layers formed by cellulose nanofibrils that had been surface modified (hydrophobized) at the oil/water (o/w) interface was investigated. The aim of the study was to clarify the mechanism underlying the excellent ability of these nanoparticles to stabilize emulsions. Layers of hydrophobized nanofibrillated cellulose spread at the o/w interface were deposited on glass slides by the Langmuir-Blodgett deposition technique. Overall evaluation of layer structures was performed by image analysis based on a Quadtree decomposition of images obtained from a flatbed scanner. A more detailed characterization of the layer structures was performed by Atomic Force Microscopy (AFM), and Field-Emission Scanning Electron Microscopy (FE-SEM). The results show that nanofibrils that were able to stabilize emulsions occur as single, dispersed fibrils or form large, network-like aggregates at the o/w interface. Fibrils that were insufficiently hydrophobized and therefore did not stabilize emulsions were only partially deposited and formed small, compact aggregates. We conclude that it is likely that the network formation is the main mechanism by which the fibrils prevent coalescence of emulsion droplets. PMID:21269639

  15. The evolution of electronic structure in few-layer graphene revealed by optical spectroscopy.

    PubMed

    Mak, Kin Fai; Sfeir, Matthew Y; Misewich, James A; Heinz, Tony F

    2010-08-24

    The massless Dirac spectrum of electrons in single-layer graphene has been thoroughly studied both theoretically and experimentally. Although a subject of considerable theoretical interest, experimental investigations of the richer electronic structure of few-layer graphene (FLG) have been limited. Here we examine FLG graphene crystals with Bernal stacking of layer thicknesses N = 1,2,3,...8 prepared using the mechanical exfoliation technique. For each layer thickness N, infrared conductivity measurements over the spectral range of 0.2-1.0 eV have been performed and reveal a distinctive band structure, with different conductivity peaks present below 0.5 eV and a relatively flat spectrum at higher photon energies. The principal transitions exhibit a systematic energy-scaling behavior with N. These observations are explained within a unified zone-folding scheme that generates the electronic states for all FLG materials from that of the bulk 3D graphite crystal through imposition of appropriate boundary conditions. Using the Kubo formula, we find that the complete infrared conductivity spectra for the different FLG crystals can be reproduced reasonably well within the framework a tight-binding model. PMID:20696939

  16. The evolution of electronic structure in few-layer graphene revealed by optical spectroscopy

    PubMed Central

    Mak, Kin Fai; Sfeir, Matthew Y.; Misewich, James A.; Heinz, Tony F.

    2010-01-01

    The massless Dirac spectrum of electrons in single-layer graphene has been thoroughly studied both theoretically and experimentally. Although a subject of considerable theoretical interest, experimental investigations of the richer electronic structure of few-layer graphene (FLG) have been limited. Here we examine FLG graphene crystals with Bernal stacking of layer thicknesses N = 1,2,3,…8 prepared using the mechanical exfoliation technique. For each layer thickness N, infrared conductivity measurements over the spectral range of 0.2–1.0 eV have been performed and reveal a distinctive band structure, with different conductivity peaks present below 0.5 eV and a relatively flat spectrum at higher photon energies. The principal transitions exhibit a systematic energy-scaling behavior with N. These observations are explained within a unified zone-folding scheme that generates the electronic states for all FLG materials from that of the bulk 3D graphite crystal through imposition of appropriate boundary conditions. Using the Kubo formula, we find that the complete infrared conductivity spectra for the different FLG crystals can be reproduced reasonably well within the framework a tight-binding model. PMID:20696939

  17. Tubercle loss in Spatangoids (Echinodermata, Echinoides): Original skeletal structures and underlying processes

    Microsoft Academic Search

    Bruno David; Didier Néraudeau

    1989-01-01

    Circular marks, flush with the test or slightly depressed, exist on the test surface of various echinoid species. Fifty-six species belonging to regular and irregular echinoids were examined in order to describe the diversity and structure of these marks and to discuss their origins, with particular emphasis being put on the spatangoids Heterobrissus niasicus and Maretia planulata. Investigations combine statistical,

  18. ORIGINAL PAPERS AID binds to transcription-induced structures in c-MYC that map to

    E-print Network

    Maizels, Nancy

    ORIGINAL PAPERS AID binds to transcription-induced structures in c-MYC that map to regions hypermutation of c-MYC are common in B-cell lymphomas. Activation-induced Cyti- dine Deaminase (AID) initiates. We show that transcription of the immunoglobulin S regions and c-MYC results in forma- tion

  19. Protein folding, protein structure and the origin of life: Theoretical methods and solutions of dynamical problems

    NASA Technical Reports Server (NTRS)

    Weaver, D. L.

    1982-01-01

    Theoretical methods and solutions of the dynamics of protein folding, protein aggregation, protein structure, and the origin of life are discussed. The elements of a dynamic model representing the initial stages of protein folding are presented. The calculation and experimental determination of the model parameters are discussed. The use of computer simulation for modeling protein folding is considered.

  20. The structure and origin of magnetic clouds in the solar wind V. Bothmer1

    E-print Network

    Boyer, Edmond

    The structure and origin of magnetic clouds in the solar wind V. Bothmer1 * and R. Schwenn2 1 Space in the surrounding solar wind. Minimum variance analysis (MVA) showed that MCs can best be described as large- scale to be proportional to RÀ2X4 , thus being stronger compared to the average solar wind. Four dierent magnetic con

  1. ORIGINAL PAPER Evolution of growth but not structural or chemical defense

    E-print Network

    Hufbauer, Ruth A.

    ORIGINAL PAPER Evolution of growth but not structural or chemical defense in Verbascum thapsus in a single defense) is associated with increased growth in introduced Verbascum thapsus populations. Intro that evolution of increased growth in V. thapsus is not fueled by decreased allocation to defense

  2. ORIGINAL PAPER Evolution of growth but not structural or chemical defense

    E-print Network

    Hufbauer, Ruth A.

    ORIGINAL PAPER Evolution of growth but not structural or chemical defense in Verbascum thapsus with increased growth in introduced Verbascum thapsus populations. Intro- duced populations had significantly growth in V. thapsus is not fueled by decreased allocation to defense, and that selection on defense may

  3. ORIGINAL RESEARCH MTHFR 677C>T effects on anterior cingulate structure

    E-print Network

    Manoach, Dara S.

    ORIGINAL RESEARCH MTHFR 677C>T effects on anterior cingulate structure and function during response heritable alterations of dACC function. We examined whether the hypofunctional 677C>T variant in MTHFR fractional anisotropy in bilateral dACC. These findings suggest that the MTHFR 677T allele blunts response

  4. ORIGINAL PAPER Long-term human impacts on genetic structure of Italian

    E-print Network

    ORIGINAL PAPER Long-term human impacts on genetic structure of Italian walnut inferred by SSR, and human activities can all shape the genetic diversity of a species. In Italy, walnut (Juglans regia L.) has a long history of cultivation both for wood and edible nuts. To better understand the genetic

  5. ORIGINAL PAPER On the canopy structure manipulation to buffer climate change

    E-print Network

    Giron, David - Institut de Recherche sur la Biologie de l'Insecte, Université François Rabelais

    by the insect, and the non-linear response of insect develop- ment rate to temperature. In this study, usingORIGINAL PAPER On the canopy structure manipulation to buffer climate change effects on insect online: 27 October 2012 Ó Springer-Verlag Berlin Heidelberg 2012 Abstract Insect pest development

  6. Origin, taxonomy and population structure of the allopolyploid peat moss Sphagnum majus

    Microsoft Academic Search

    S. M. Såstad; K. I. Flatberg; L. Hanssen

    2000-01-01

    The polyploid peat mossSphagnum majus shows considerable phenotypic plasticity along ecological gradients in mires. It is considered taxonomically heterogeneous, and two subspecies have been described. Isozyme analyses were carried out on populations ofS. majus from Central Norway and from eastern coast of North America in order to assess the origin, taxonomy and population structure of this species. High levels of

  7. Original article Structure and yield of all-sized and even-sized

    E-print Network

    Paris-Sud XI, Université de

    Original article Structure and yield of all-sized and even-sized conifer-dominated stands-1953) using a systematic temporary circular plot line survey. Each plot represented a particular stand. An all-sized whereas 25% were even-sized (resembling a normal distribution) and 13% were irregularly uneven-sized

  8. Local orderings in long-range-disordered bismuth-layered intergrowth structure

    NASA Astrophysics Data System (ADS)

    Zhang, Faqiang; Li, Yongxiang; Gu, Hui; Gao, Xiang

    2014-04-01

    A series of intergrowth bismuth-layered (Bi3TiNbO9)2(Bi4Ti3O12) (223) ceramics were prepared by conventional solid-state reaction to study the characteristics of the local orderings in long-range-disordered intergrowth structures. High-resolution high-angle annular dark-field (HAADF) imaging reveals the intergrowth structure composed of mixtures of -23-, -223-, -2223- and -22- sequences, while the -223- structure is the thermodynamic stable state of this intergrowth system. It was confirmed by the crystals of recurrent -223- structure prepared by self-flux method and the nature of the local ordering was discussed from their differences in repeating units. The statistics show that when repeating units reach 4 or higher, the independent -223- intergrowth ordering emerges clearly among the competing associated orderings. We infer it is the kinetic factor that induces local compositional variance to result in long-range disordered intergrowth structures.

  9. Uranium nitride chloride UNCl: 30 K-class ferromagnet with layered structure

    NASA Astrophysics Data System (ADS)

    Nakamura, Akio; Akabori, Mitsuo; Ogawa, Toru; Huntelaar, M.

    2005-04-01

    Uranium nitride chloride (UNCl) has an unique tetragonal crystal structure, in which the U/N/U trilayer is sandwiched by the chlorine (Cl) double layers. This structure is homologous to Hf(Zr)NCl, for which high- TC superconductivity ( T=25.5 K) has been recently discovered to result from the lithium (Li) intercalation. Recent specific heat measurements on this compound have revealed the existence of a lambda-type phase transition around 32 K. In the present study, this anomaly was confirmed to be correspondent for a ferromagnetic transition in the uranium ions having a localized 4f 2(U 4+) character: Its saturation moment ( ?B(sat)) attains a value of ?1.56 ?B at 2 K. Among varieties of actinide (An) compounds, UNCl and related systems, AnNX (X=halogens (Cl, Br, I)) may represent a novel class of layer mixed compounds with intriguing magnetic, electronic and chemical-bonding properties.

  10. Strong composite films with layered structures prepared by casting silk fibroin-graphene oxide hydrogels.

    PubMed

    Huang, Liang; Li, Chun; Yuan, Wenjing; Shi, Gaoquan

    2013-05-01

    Composite films of graphene oxide (GO) sheets and silk fibroin (SF) with layered structures have been prepared by facile solution casting of SF-GO hydrogels. The as-prepared composite film containing 15% (by weight, wt%) of SF shows a high tensile strength of 221 ± 16 MPa and a failure strain of 1.8 ± 0.4%, which partially surpass those of natural nacre. Particularly, this composite film also has a high modulus of 17.2 ± 1.9 GPa. The high mechanical properties of this composite film can be attributed to its high content of GO (85 wt%), compact layered structure and the strong hydrogen bonding interaction between SF chains and GO sheets. PMID:23538717

  11. Formation of conductive structures in insulate layers by selective removal of atoms technique

    NASA Astrophysics Data System (ADS)

    Gurovich, B.; Prikhodko, K.; Domantovsky, A.; Kuleshova, E.; Olshansky, E.; Maslakov, K.; Lunin, Y.

    2006-05-01

    The structure and electric properties of initial oxides and metals (Bi, Ag, Cu, Ni, Co, Mo and W) produced by Selective Removal of oxygen Atoms technique (SRA) were studied. It was found a correspondence of electrical conductivity of SRA metals and pure sputtered metals films. At the same time, low resistance of some oxides, for instance CuO, will initiate big leakage currents inside the layer. Among the investigated materials special attention will be paid to SRA Bi, Mo and W because of the high values of contact resistance and puncture potential with initial oxides. It is shown the adaptability of Selective Removal of Atoms technique for formation of conductive insulated structures in layers for new micro and nano-electronic devices.

  12. Structure of an electric double layer containing a 2:2 valency dimer electrolyte.

    PubMed

    Silvestre-Alcantara, Whasington; Henderson, Douglas; Wu, Jianzhong; Kaja, Monika; Lamperski, Stanis?aw; Bhuiyan, Lutful Bari

    2015-07-01

    The structure of a planar electric double layer formed by a 2:2 valency dimer electrolyte in the vicinity of a uniformly charged planar hard electrode is investigated using density functional theory and Monte Carlo simulations. The dimer electrolyte consists of a mixture of charged divalent dimers and charged divalent monomers in a dielectric continuum. A dimer is constructed by two tangentially tethered rigid spheres, one of which is divalent and positively charged and the other neutral, whereas the monomer is a divalent and negatively charged rigid sphere. The density functional theory reproduces well the simulation results for (i) the singlet distributions of the various ion species with respect to the electrode, and (ii) the mean electrostatic potential. Comparison with earlier results for a 2:1/1:2 dimer electrolyte shows that the double layer structure is similar when the counterion has the same valency. PMID:25529333

  13. Photoluminescence emission from Alq3 organic layer in metal-Alq3-metal plasmonic structure

    NASA Astrophysics Data System (ADS)

    Huang, Bohr-Ran; Liao, Chung-Chi; Fan, Wan-Ting; Wu, Jin-Han; Chen, Cheng-Chang; Lin, Yi-Ping; Li, Jung-Yu; Chen, Shih-Pu; Ke, Wen-Cheng; Chen, Nai-Chuan

    2014-06-01

    The emission properties of an organic layer embedded in a metal-organic-metal (MOM) structure were investigated. A partially radiative odd-SPW as well as a non-radiative even-SPW modes are supported by hybridization of the SPW modes on the opposite organic/metal interface in the structure. Because of the competition by this radiative SPW, the population of excitons that recombine to form non-radiative SPW should be reduced. This may account for why the photoluminescence intensity of the MOM sample is higher than that of an organic-metal sample even though the MOM sample has an additional metal layer that should intuitively act as a filter.

  14. Mode conversion of ultrafast pulses by grating structures in layered dielectric waveguides

    Microsoft Academic Search

    Tao Liang; Richard W. Ziolkowski

    1997-01-01

    Various grating configurations are introduced to develop structures for the mode conversion of an ultrafast, ultrawide-bandwidth optical pulse propagating in a layered dielectric waveguide. Introducing a new technique for efficient, real-time mode extraction, we examine these schemes with a full-wave, vector, finite difference time domain (FDTD) Maxwell equation simulator. The resulting FDTD simulator is very flexible and accurate; it is

  15. Synthesis and electrochemical properties of lithium iron oxides with layer-related structures

    Microsoft Academic Search

    Ryoji Kanno; Takayuki Shirane; Yukishige Inaba; Yoji Kawamoto

    1997-01-01

    Two modifications of layered lithium iron oxides were synthesized and characterized by X-ray diffractometry and electrochemical measurements. LiFeO2 with ?-NaFeO2 structure was synthesized by the ion-exchange reaction in molten salts; cationic distribution in the host, ?-NaFeO2, affects the disordering in the reaction product. However, lithium de-intercalation was not confirmed. The ion-exchange reaction in molten salts gave a whole range of

  16. Investigation of copper metallization induced failure of diode structures with and without a barrier layer

    Microsoft Academic Search

    J. Baumann; Ch. Kaufmann; M. Rennau; Th. Werner; T. Gessner

    1997-01-01

    Different metallization systems and were prepared on +p-diodes. After sequential annealing in H2-atmosphere these structures were investigated by electrical and analytical methods. For a metallization without barrier layer the electrical breakdown is caused by the formation of Cu3Si. Randomly distributed reaction spots are visible on the silicon surface. For Ti and W the electrical failure occurs after annealing at 450°C

  17. An experimental study of coherent structures in a three-dimensional turbulent boundary layer

    Microsoft Academic Search

    Siew-Mun Ha

    1993-01-01

    Measurements were performed in a three dimensional, pressure-driven turbulent boundary layer (Re(sub theta) = 5936) in the flow around a wing-body junction with a variety of multiple-sensor probes to examine the features of the coherent structures in the flow. The measurements were carried out with a hot-wire rake with sixteen sensors spaced approximately logarithmically over 25.4 mm (1 inch), a

  18. Search for high Tc in layered structures: The case of LiB Matteo Calandra

    E-print Network

    Curtarolo, Stefano

    Search for high Tc in layered structures: The case of LiB Matteo Calandra Institut de Minéralogie devised superconductor MS1-LiB LiB . We calculate the electron-phonon coupling =0.62 and the phonon fre- quency logarithmic average log=54.6 meV and show that the LiB critical temperature is in the range of 10

  19. Strong composite films with layered structures prepared by casting silk fibroin-graphene oxide hydrogels

    NASA Astrophysics Data System (ADS)

    Huang, Liang; Li, Chun; Yuan, Wenjing; Shi, Gaoquan

    2013-04-01

    Composite films of graphene oxide (GO) sheets and silk fibroin (SF) with layered structures have been prepared by facile solution casting of SF-GO hydrogels. The as-prepared composite film containing 15% (by weight, wt%) of SF shows a high tensile strength of 221 +/- 16 MPa and a failure strain of 1.8 +/- 0.4%, which partially surpass those of natural nacre. Particularly, this composite film also has a high modulus of 17.2 +/- 1.9 GPa. The high mechanical properties of this composite film can be attributed to its high content of GO (85 wt%), compact layered structure and the strong hydrogen bonding interaction between SF chains and GO sheets.Composite films of graphene oxide (GO) sheets and silk fibroin (SF) with layered structures have been prepared by facile solution casting of SF-GO hydrogels. The as-prepared composite film containing 15% (by weight, wt%) of SF shows a high tensile strength of 221 +/- 16 MPa and a failure strain of 1.8 +/- 0.4%, which partially surpass those of natural nacre. Particularly, this composite film also has a high modulus of 17.2 +/- 1.9 GPa. The high mechanical properties of this composite film can be attributed to its high content of GO (85 wt%), compact layered structure and the strong hydrogen bonding interaction between SF chains and GO sheets. Electronic supplementary information (ESI) available: XPS spectrum of the SF-GO hybrid film, SEM images of lyophilized GO dispersion and the failure surface of GO film. See DOI: 10.1039/c3nr00196b

  20. The effect of tropospheric layer structures on long-range VHF radio propagation

    Microsoft Academic Search

    Hsi-Tien Chang

    1971-01-01

    Long-distance radio communication at VHF is investigated by the waveguide mode theory taking into account the strong gradient, layered structure of the troposphere. A linear-segmented numerical method for the squared refractive index profile is developed to calculate the wave modes. This method reduces the reflection error from the discontinuities that occur in the conventional step-function approximation. The frequency at which

  1. Perfectly matched layer for the FDTD solution of wave-structure interaction problems

    Microsoft Academic Search

    Jean-Pierre Berenger

    1996-01-01

    The wave-structure interactions are the most usual applications of the finite-difference method, in electromagnetic compatibility and radar cross-section computations. The aim of this paper is to get a detailed insight into the implementation of the perfectly matched layer (PML) technique when dealing with such important applications. The PML is a new technique developed for the simulation of free space with

  2. Selective area atomic layer deposition of rhodium and effective work function characterization in capacitor structures

    Microsoft Academic Search

    K. J. Park; G. N. Parsons

    2006-01-01

    Atomic layer deposition (ALD) of rhodium was investigated using rhodium(III) acetylacetonate and oxygen, and capacitance versus voltage is used to extract the effective work function in metal\\/insulator\\/semiconductor structures. Self-limiting growth was observed, and the resistivity of Rh deposited at 300 °C is ?10 ?? cm, approximately a factor of 2 larger than the Rh bulk resistivity (4.3 ?? cm). Selective

  3. Selective area atomic layer deposition of rhodium and effective work function characterization in capacitor structures

    Microsoft Academic Search

    K. J. Park; G. N. Parsons

    2006-01-01

    Atomic layer deposition (ALD) of rhodium was investigated using rhodium(III) acetylacetonate and oxygen, and capacitance versus voltage is used to extract the effective work function in metal\\/insulator\\/semiconductor structures. Self-limiting growth was observed, and the resistivity of Rh deposited at 300 °C is ~10 muOmega cm, approximately a factor of 2 larger than the Rh bulk resistivity (4.3 muOmega cm). Selective

  4. Development of a low temperature MEMS process with a PECVD amorphous silicon structural layer

    Microsoft Academic Search

    Stella Chang; Siva Sivoththaman

    2006-01-01

    Amorphous silicon (a-Si:H) deposited at 150 °C by plasma-enhanced chemical vapor deposition (PECVD) is investigated as a structural layer for low temperature microelectromechanical system (MEMS) fabrication. The process development of depositing thick a-Si:H films and the material characterization of the film stress and hydrogen content is presented. To demonstrate a MEMS application, bimorph thermal actuators incorporating a-Si:H and aluminum were

  5. Structure of the edge flame in a methane–oxygen mixing layer

    Microsoft Academic Search

    S. K. Choi; J. Kim; S. H. Chung; J. S. Kim

    2009-01-01

    The structure of an edge flame in a mixing layer of two uniformly flowing pure CH4 and pure O2 streams has been investigated numerically by employing a detailed methane–oxidation mechanism in order to investigate the influence of using pure oxygen, instead of air, as the oxidizing agent. The results exhibited similar behaviour to the CH4-air counterpart in the premixed-flame front,

  6. Capacity of graphite's layered structure to suppress the sputtering yield: A molecular dynamics study

    NASA Astrophysics Data System (ADS)

    Tian, Jiting; Zheng, Tao; Yang, Jiangyan; Kong, Shuyan; Xue, Jianming; Wang, Yugang; Nordlund, Kai

    2015-05-01

    20-120 keV C60 bombardment on graphite and 20 keV C60 impact on diamond are studied by classical molecular dynamics (MD) simulations. The number of atoms ejected from graphite after a 20 keV C60 impact is found to be much smaller than that from diamond. By analyzing the microscopic sputtering process, we find this difference is due to the combined effects of graphite's low number density and layered structure. These two features of graphite make the pressure waves during the spike stage much weaker and the crater rim much more stable, compared to the case of diamond. While the role of atomic density on sputtering has been discussed in previous studies, effect of layered structure has not gained much attention yet. To affirm this effect and exclude the influence of density, we have also simulated C60 impact on an amorphous carbon (a-C) target whose density is very close to that of graphite. The yield of a-C is higher than that of graphite, certifying the capacity of graphite's layered structure to suppress the sputtering yield.

  7. Layered Structure and Swelling Behavior of a Multiple Hydrate-Forming Pharmaceutical Compound

    SciTech Connect

    Kiang, Y.; Xu, W; Stephens, P; Ball, R; Yasuda, N

    2009-01-01

    Investigation of one anhydrous and four hydrated forms of a pharmaceutical compound (1) using both single-crystal and high-resolution powder X-ray diffraction methods revealed a two-dimensional framework which, upon exposure to moisture, absorbed water between the layers, causing the lattice to expand by as much as 20% of the axial length along a. The single-crystal structure was solved and refined for the pentahydrate form in space group C2 with unit cell parameters a = 36.961(5) Angstroms, b = 7.458(2) Angstroms, c = 20.691(4) Angstroms, e = 99.461(1), and V = 5626(4) Angstroms3. In the single-crystal structure the water layers were parallel to the bc plane and sandwiched by the crystalline compound 1 framework. Upon a change of relative humidity, water goes in and out of the interlayer space with the retention of the layer structure of the development compound. Starting from the anhydrous form, each additional water of hydration increased the interlayer spacing of the pharmaceutical solid by 1.3 Angstroms, half the size of a water molecule. In an exploratory formulation, this expansion of interlayer spacing caused tablets to crack upon storage at high relative humidity.

  8. The turbulence structure of a reattaching axisymmetric compressible free shear layer

    NASA Astrophysics Data System (ADS)

    Herrin, J. L.; Dutton, J. C.

    1997-11-01

    The reattachment of a supersonic, axisymmetric shear layer downstream of a blunt-based afterbody is studied. Of primary interest are the effects of the "extra" strain rates, such as bulk compression, concave streamline curvature, and lateral streamline convergence associated with shear layer reattachment on the structure of the turbulence field. Experimental turbulence data obtained throughout the reattachment region with a two-component laser Doppler velocimeter are presented. In general, the axisymmetric compliant boundary reattachment process is shown to be different in character compared to the planar solid wall case. Most notably, significant reductions in the Reynolds stresses occur through the reattachment region due to the dominating effect of lateral streamline convergence as the flow approaches the axis. Similar to the planar solid wall case, however, a reduction in the mean turbulent transport toward the axis in the reattachment region was found, which suggests a radial containment of the large-scale eddies near the axis of symmetry. The reattachment process was also seen to have profound effects on the large-scale structures in the shear layer, primarily through reduced structural organization as indicated by instantaneous shear angle histograms.

  9. Ion irradiation temperature effect on HfO 2/MgO multi-layer structures

    NASA Astrophysics Data System (ADS)

    Usov, I. O.; Valdez, J. A.; Won, J.; Devlin, D. J.

    2012-01-01

    Properties of nuclear materials may be improved by employing composite materials. However, these properties usually degrade during the operation in a nuclear reactor environment due to radiation damage accumulation. For this study we fabricated a multi-layer structure composed of MgO and HfO 2 thin films on a sapphire substrate. This multi-layer structure was designed to mimic a CERCER (ceramic-ceramic) composite fuel form. The goal of this study was to investigate features of radiation damage evolution cause by ion beam irradiation in a wide temperature range. We observed phase transformation in HfO 2 from monoclinic to the tetragonal polymorph and no changes in MgO. Formation of thin amorphous regions adjacent to the MgO/HfO 2 and HfO 2/sapphire substrate interfaces was identified in both cases. Phase and microstructural changes demonstrated pronounced dependence on irradiation temperature, which we attributed to either enhanced annihilation of irradiation induced point defects or intermixing between the components of our multi-layered structure.

  10. Layered nanocomposites inspired by the structure and mechanical properties of nacre.

    PubMed

    Wang, Jianfeng; Cheng, Qunfeng; Tang, Zhiyong

    2012-02-01

    Nacre (mother-of-pearl), made of inorganic and organic constituents (95 vol% aragonite calcium carbonate (CaCO(3)) platelets and 5 vol% elastic biopolymers), possesses a unique combination of remarkable strength and toughness, which is compatible for conventional high performance materials. The excellent mechanical properties are related to its hierarchical structure and precisely designed organic-inorganic interface. The rational design of aragonite platelet strength, aspect ratio of aragonite platelets, and interface strength ensures that the strength of nacre is maximized under platelet pull-out failure mode. At the same time, the synergy of strain hardening mechanisms acting over multiple scales results in platelets sliding on one another, and thus maximizes the energy dissipation of viscoplastic biopolymers. The excellent integrated mechanical properties with hierarchical structure have inspired chemists and materials scientists to develop biomimetic strategies for artificial nacre materials. This critical review presents a broad overview of the state-of-the-art work on the preparation of layered organic-inorganic nanocomposites inspired by nacre, in particular, the advantages and disadvantages of various biomimetic strategies. Discussion is focused on the effect of the layered structure, interface, and component loading on strength and toughness of nacre-mimic layered nanocomposites (148 references). PMID:21959863

  11. Born energy, acid-base equilibrium, structure and interactions of end-grafted weak polyelectrolyte layers

    NASA Astrophysics Data System (ADS)

    Nap, R. J.; Tagliazucchi, M.; Szleifer, I.

    2014-01-01

    This work addresses the effect of the Born self-energy contribution in the modeling of the structural and thermodynamical properties of weak polyelectrolytes confined to planar and curved surfaces. The theoretical framework is based on a theory that explicitly includes the conformations, size, shape, and charge distribution of all molecular species and considers the acid-base equilibrium of the weak polyelectrolyte. Namely, the degree of charge in the polymers is not imposed but it is a local varying property that results from the minimization of the total free energy. Inclusion of the dielectric properties of the polyelectrolyte is important as the environment of a polymer layer is very different from that in the adjacent aqueous solution. The main effect of the Born energy contribution on the molecular organization of an end-grafted weak polyacid layer is uncharging the weak acid (or basic) groups and consequently decreasing the concentration of mobile ions within the layer. The magnitude of the effect increases with polymer density and, in the case of the average degree of charge, it is qualitatively equivalent to a small shift in the equilibrium constant for the acid-base equilibrium of the weak polyelectrolyte monomers. The degree of charge is established by the competition between electrostatic interactions, the polymer conformational entropy, the excluded volume interactions, the translational entropy of the counterions and the acid-base chemical equilibrium. Consideration of the Born energy introduces an additional energetic penalty to the presence of charged groups in the polyelectrolyte layer, whose effect is mitigated by down-regulating the amount of charge, i.e., by shifting the local-acid base equilibrium towards its uncharged state. Shifting of the local acid-base equilibrium and its effect on the properties of the polyelectrolyte layer, without considering the Born energy, have been theoretically predicted previously. Account of the Born energy leads to systematic, but in general small, corrections to earlier theoretical predictions describing the behavior of weak polyelectrolyte layers. However, polyelectrolyte uncharging results in a decrease in the concentration of counterions and inclusion of the Born Energy can result in a substantial decrease of the counterion concentration. The effect of considering the Born energy contribution is explored for end-grafted weak polyelectrolyte layers by calculating experimental observables which are known to depend on the presence of charges within the polyelectrolyte layer: inclusion of the Born energy contribution leads to a decrease in the capacitance of polyelectrolyte-modified electrodes, a decrease of conductivity of polyelectrolyte-modified nanopores and an increase in the repulsion exerted by a planar polyelectrolyte layer confined by an opposing wall.

  12. Near-wake flow structure downwind of a wind turbine in a turbulent boundary layer

    NASA Astrophysics Data System (ADS)

    Zhang, Wei; Markfort, Corey D.; Porté-Agel, Fernando

    2012-05-01

    Wind turbines operate in the surface layer of the atmospheric boundary layer, where they are subjected to strong wind shear and relatively high turbulence levels. These incoming boundary layer flow characteristics are expected to affect the structure of wind turbine wakes. The near-wake region is characterized by a complex coupled vortex system (including helicoidal tip vortices), unsteadiness and strong turbulence heterogeneity. Limited information about the spatial distribution of turbulence in the near wake, the vortex behavior and their influence on the downwind development of the far wake hinders our capability to predict wind turbine power production and fatigue loads in wind farms. This calls for a better understanding of the spatial distribution of the 3D flow and coherent turbulence structures in the near wake. Systematic wind-tunnel experiments were designed and carried out to characterize the structure of the near-wake flow downwind of a model wind turbine placed in a neutral boundary layer flow. A horizontal-axis, three-blade wind turbine model, with a rotor diameter of 13 cm and the hub height at 10.5 cm, occupied the lowest one-third of the boundary layer. High-resolution particle image velocimetry (PIV) was used to measure velocities in multiple vertical stream-wise planes ( x- z) and vertical span-wise planes ( y- z). In particular, we identified localized regions of strong vorticity and swirling strength, which are the signature of helicoidal tip vortices. These vortices are most pronounced at the top-tip level and persist up to a distance of two to three rotor diameters downwind. The measurements also reveal strong flow rotation and a highly non-axisymmetric distribution of the mean flow and turbulence structure in the near wake. The results provide new insight into the physical mechanisms that govern the development of the near wake of a wind turbine immersed in a neutral boundary layer. They also serve as important data for the development and validation of numerical models.

  13. Boundary layer structure of oscillatory open-channel shallow flows over smooth and rough beds

    NASA Astrophysics Data System (ADS)

    Chen, Daoyi; Chen, Chaoquan; Tang, Fu-Ee; Stansby, Peter; Li, Ming

    2007-05-01

    The boundary layer structure of oscillatory shallow open channel flows has been studied in a wide flume. Fluorescence solution was released at a porous rough bed through a diffuser covered by gravel of 0.5 cm grain size. A planar laser-induced fluorescence (PLIF) system was used to visualise the dye plumes in both vertical and horizontal planes for a qualitative understanding of the roles of large-scale flow structures in mass transport. A variety of tests were conducted for a range of oscillatory periods (30-240 s), water depths (3-16 cm) and velocity amplitudes (0.027-0.325 m/s), which cover a wide range of oscillatory flows with Reynolds numbers Re a varied from 0.3 × 104 (laminar) to 2.1 × 106 (fully turbulent). For quantitative investigation, a novel technique, namely combined laser-induced fluorescence (LIF) and 2D laser Doppler velocimetry (LDV) (LIF/LDV), was developed and used to measure the velocity and solute concentration simultaneously in a vertical plane over 50 cycles. From the dye plumes revealed by the PLIF in transitional flows, there are different patterns of flow structure and solute transport with three representative stages of acceleration, deceleration and flow reversal. In the acceleration stage, turbulence was suppressed with dye layers adhering to the surface with little vertical mass transport. In the deceleration stage, flame-like turbulent structures occurred when turbulence generation was prominent. This was investigated quantitatively by recording the percentage occurrence of the adhered smooth layers per cycle. For those smooth bed cases with Re a < 1.8 × 105, the adhered smooth dye layers type of boundary layer occupied 100% of the oscillation period. Over a sufficiently high Re a , a rough bed can generate fully turbulent oscillatory flows without the appearance of adhering dye layers. Between these two extremes, a transitional flow regime occurs in a wide range of flow conditions: Re a > 2.7 × 104 over the rough bed and Re a > 8.3 × 106 over a smooth bed.

  14. Defect mode suppression in a photonic crystal structure with a resonance nanocomposite layer

    SciTech Connect

    Moiseev, Sergey G; Ostatochnikov, Vladimir A; Sementsov, Dmitrii I

    2012-06-30

    This paper examines the key features of the transmission and reflection spectra of a one-dimensional photonic crystal structure in which a nanocomposite layer is sandwiched between dielectric Bragg mirrors. Two orthogonal polarisations of an incident wave correspond to different plasmon resonance frequencies of the nanocomposite. If one of the plasmon frequencies coincides with the defect mode frequency in one of the photonic bandgaps, complete suppression of the defect mode in the transmission spectrum is possible, which makes the spectra of such structures polarisation-sensitive.

  15. Determining crustal structure beneath seismic stations overlying a low-velocity sedimentary layer using receiver functions

    NASA Astrophysics Data System (ADS)

    Yu, Youqiang; Song, Jianguo; Liu, Kelly H.; Gao, Stephen S.

    2015-05-01

    The receiver function (RF) technique has been widely applied to investigate crustal and mantle layered structures using P-to-S converted (Ps) phases from velocity discontinuities. However, the presence of low-velocity (relative to that of the bedrock) sediments can give rise to strong reverberations in the resulting RFs, frequently masking the Ps phases from crustal and mantle boundaries. Such reverberations are caused by P-to-S conversions and their multiples associated with the strong impedance contrast across the bottom of the low-velocity sedimentary layer. Here we propose and test an approach to effectively remove the near-surface reverberations and decipher the Ps phases associated with the Moho discontinuity. Autocorrelation is first applied on the observed RFs to determine the strength and two-way traveltime of the reverberations, which are then used to construct a resonance removal filter in the frequency domain to remove or significantly reduce the reverberations. The filtered RFs are time corrected to eliminate the delay effects of the sedimentary layer and applied to estimate the subsediment crustal thickness and VP/VSusing a H-k stacking procedure. The resulting subsediment crustal parameters (thickness and VP/VS) are subsequently used to determine the thickness and VP/VS of the sedimentary layer, using a revised version of the H-k stacking procedure. Testing using both synthetic and real data suggests that this computationally inexpensive technique is efficient in resolving subsediment crustal properties beneath stations sitting on a low-velocity sedimentary layer and can also satisfactorily determine the thickness and VP/VS of the sedimentary layer.

  16. High-frequency guided ultrasonic waves for hidden defect detection in multi-layered aircraft structures.

    PubMed

    Masserey, Bernard; Raemy, Christian; Fromme, Paul

    2014-09-01

    Aerospace structures often contain multi-layered metallic components where hidden defects such as fatigue cracks and localized disbonds can develop, necessitating non-destructive testing. Employing standard wedge transducers, high frequency guided ultrasonic waves that penetrate through the complete thickness were generated in a model structure consisting of two adhesively bonded aluminium plates. Interference occurs between the wave modes during propagation along the structure, resulting in a frequency dependent variation of the energy through the thickness with distance. The wave propagation along the specimen was measured experimentally using a laser interferometer. Good agreement with theoretical predictions and two-dimensional finite element simulations was found. Significant propagation distance with a strong, non-dispersive main wave pulse was achieved. The interaction of the high frequency guided ultrasonic waves with small notches in the aluminium layer facing the sealant and on the bottom surface of the multilayer structure was investigated. Standard pulse-echo measurements were conducted to verify the detection sensitivity and the influence of the stand-off distance predicted from the finite element simulations. The results demonstrated the potential of high frequency guided waves for hidden defect detection at critical and difficult to access locations in aerospace structures from a stand-off distance. PMID:24856653

  17. Structures of ultra-thin atomic-layer-deposited TaNx films

    NASA Astrophysics Data System (ADS)

    Wu, Y. Y.; Kohn, A.; Eizenberg, M.

    2004-06-01

    Atomic layer deposition (ALD) is an attractive technique in fabrication of microelectronics presently and in the future, for its accurate thickness control in atomic scale, excellent conformality, and uniformity over large areas at low temperature. It has been adapted and used in deposition of ultrathin TaNx films as diffusion barriers for Cu metallization. In this study, composition, structure, and stability of ultra-thin (1.5-10 nm) atomic layer deposited films are characterized by a set of complementary analytical techniques. The results indicate that the N to Ta atomic concentration ratio in the ALD TaNx films is approximately 2, independent of the film thickness and annealing up to 750 °C. Hydrogen, oxygen, and carbon are detected as impurities within the as-deposited films. The as-deposited ALD TaNx films have an fcc NaCl-type nanocrystalline structure even when the film thickness is 1.5 nm. Following thermal anneal at 600 °C and higher, the films do not undergo a structural change except for an increase in grain size and a decrease in the lattice constant. X-ray photoelectron spectra results indicate that all the Ta atoms in the films are bonded ionically with the surrounding N atoms. An ex situ thermal treatment at 600 °C for 1 h removes the O, which penetrated the layers, by a reduction reaction with the residual H and results in densification of the ALD films. Our analysis of the experimental results indicates that the excess of N atoms of the ALD TaNx films is mainly due to Ta vacancies in the fcc NaCl-type structure. The structural and compositional characteristics of the films explain why the films serve as good diffusion barriers to Cu metallization.

  18. Crystal and molecular structure of monomeric yttrium(III) dipivalylmethanate. Arrangement of adsorbed layers

    SciTech Connect

    Gromilov, S.A.; Baidina, I.A.; Prokhorova, S.A. [and others

    1995-11-01

    Crystal structure of monomeric yttrium(III) dipivalylmethanate, YO{sub 6}C{sub 33}H{sub 57}, has been studied by X-ray diffraction. Crystal data: a = 17.868(3), b = 9.977(2), c = 10.633(2) {angstrom}, V = 1895.7 {angstrom}{sup 3}, space group Pmn2{sub 1}, Z = 2, d{sub calc} = 1.116, d{sub exp} = 1.119 g/cm{sup 3}. The compound has a molecular structure and consists of monomeric molecules with a proper symmetry plane m. In the metallocycle lying in this plane, Y-O interatomic distances and O-Y-O bond angles markedly differ from the similar distances and angles in the other two planes. The average Y-O, O-C, and C-C distances are 2.22, 1.25, and 1.46 {angstrom}, respectively. As a result of comparative crystal-chemical analysis carried out for related compounds, the coordination polyhedra around the yttrium atoms were found to be trigonal prisms formed by six oxygen atoms of three bidentate ligands. Layers {approximately}1 {mu}m thick were obtained by vapor condensation of the complex on different support; the layers were investigated by XRD. Irrespective of the type of support, the layers are oriented polycrystalline films with texture axes. Arrangement of the adsorbed molecules of the complex is analyzed. The layers are self-organized into close-packed structures with C(CH{sub 3}){sub 3} groups oriented toward supports.

  19. Structural changes of anodic layer on titanium in sulfate solution as a function of anodization duration in constant current mode

    NASA Astrophysics Data System (ADS)

    Komiya, Shinji; Sakamoto, Kouta; Ohtsu, Naofumi

    2014-03-01

    The present study investigated the effect of anodization time, in constant current mode, on the anodic oxide layer formed on titanium (Ti). Anodization of the Ti substrate was?carried out in a 0.1 M (NH4)2SO4 aqueous solution with reaction times of various durations, after which the characteristics and photocatalytic activity were investigated in detail. The TiO2 layer fabricated in a short duration exhibited comparatively flat surface morphology and an anatase-type crystal structure. This layer acted as a photocatalyst only under ultraviolet light (UV) illumination. Upon prolonging the anodization, the layer structure changed drastically. The surface morphology became rough, and the crystal structure changed to rutile-type TiO2. Furthermore, the layer showed photocatalytic activity both under UV and visible light illumination. Further anodization increased the amount of methylene blue (MB) adsorbed on the surface, but did not cause additional change to the structure of the anodic layer. The surface morphology and crystal structure of the anodic layer were predominantly controlled by the anodization time; thus, the anodization time is an important parameter for controlling the characteristics of the anodic layer.

  20. Nanoimprinting lithography of a two-layer phase mask for three-dimensional photonic structure holographic fabrications via single exposure

    NASA Astrophysics Data System (ADS)

    Xu, Di; Chen, Kevin P.; Ohlinger, Kris; Lin, Yuankun

    2011-01-01

    We report a combined holographic and nanoimprinting lithography technique to produce three-dimensional woodpile photonic crystal templates through only one single exposure. The interference lithography process uses an integratable diffractive optical element for large throughout 3D pattern manufacturing. The diffractive optical element consists of two layers of phase grating separated by an intermediate layer, fabricated by repeated nanoimprinting lithography, followed by an SU8 photoresist bonding technique. Grating periods, relative orientation, diffraction angle, and efficiency, as well as layer to layer phase delay, are well designed during manufacturing. By thermally optimizing the thickness of the intermediate layer, this paper demonstrates the fabrication of interconnected 3D photonic structures with arbitrary symmetry through a single laser exposure. The two-layer phase mask approach enables a CMOS-compatible monolithic integration of 3D photonic structures with other integrated optical elements and waveguides.

  1. On atomic structure of Ge huts growing on the Ge/Si(001) wetting layer

    SciTech Connect

    Arapkina, Larisa V.; Yuryev, Vladimir A. [A. M. Prokhorov General Physics Institute of the Russian Academy of Sciences, 38 Vavilov Street, Moscow, 119991 (Russian Federation)] [A. M. Prokhorov General Physics Institute of the Russian Academy of Sciences, 38 Vavilov Street, Moscow, 119991 (Russian Federation)

    2013-09-14

    Structural models of growing Ge hut clusters—pyramids and wedges—are proposed on the basis of data of recent STM investigations of nucleation and growth of Ge huts on the Si(001) surface in the process of molecular beam epitaxy. It is shown that extension of a hut base along <110> directions goes non-uniformly during the cluster growth regardless of its shape. Growing pyramids, starting from the second monolayer, pass through cyclic formation of slightly asymmetrical and symmetrical clusters, with symmetrical ones appearing after addition of every fourth monolayer. We suppose that pyramids of symmetrical configurations composed by 2, 6, 10, etc., monolayers over the wetting layer are more stable than asymmetrical ones. This might explain less stability of pyramids in comparison with wedges in dense arrays forming at low temperatures of Ge deposition. Possible nucleation processes of pyramids and wedges on wetting layer patches from identical embryos composed by 8 dimers through formation of 1 monolayer high 16-dimer nuclei different only in their symmetry is discussed. Schematics of these processes are presented. It is concluded from precise STM measurements that top layers of wetting layer patches are relaxed when huts nucleate on them.

  2. Simulation and Implementation of Moth-eye Structures as a Broadband Anti-Reflective Layer

    NASA Astrophysics Data System (ADS)

    Deshpande, Ketan S.

    Conventional single layer thin anti-reflective coatings (ARCs) are only suitable for narrowband applications. A multilayer film stack is often employed for broadband applications. A coating of multiple layers with alternating low and high refractive index materials increases the overall cost of the system. This makes multilayer ARCs unsuitable for low-cost broadband applications. Since the discovery of moth-eye corneal nipple patterns and their potential applicability in the field of broadband ARCs, many studies have been carried out to fabricate these bio-inspired nanostructures with available manufacturing processes. Plasma etching processes used in microelectronic manufacturing are applied for creating these nanostructures at the Rochester Institute of Technology's Semiconductor & Microsystems Fabrication Laboratory (SMFL). Atomic Force Microscope (AFM) scanned surfaces of the nanostructure layer are simulated and characterized for their optical properties using a Finite-Difference Time Domain (FDTD) simulator from Lumerical Solutions, Inc. known as FDTD Solutions. Simulation results show that the layer is anti-reflective over 50 to 350 nm broadband of wavelengths at 0° angle of incidence. These simulation results were supported by ellipsometer reflection measurements off the actual samples at multiple angles of light incidence, which show a 10% to 15% decrease in reflection for 240 to 400 nm wavelengths. Further improvements in the optical efficiency of these structures can be achieved through simulation-fabrication-characterization cycles performed for this project. The optimized nanostructures can then serve the purpose of low-cost anti-reflective coatings for solar cells and similar applications.

  3. Efficiency Enhancement of Inverted Structure Perovskite Solar Cells via Oleamide Doping of PCBM Electron Transport Layer.

    PubMed

    Xia, Fei; Wu, Qiliang; Zhou, Pengcheng; Li, Yi; Chen, Xiang; Liu, Qing; Zhu, Jun; Dai, Songyuan; Lu, Yalin; Yang, Shangfeng

    2015-06-24

    An amphiphilic surfactant, oleamide, was applied to dope the PCBM electron transport layer (ETL) of inverted structure perovskite solar cells (ISPSCs), resulting in a dramatic efficiency enhancement. Under the optimized oleamide doping ratio of 5.0 wt %, the power conversion efficiency of the CH3NH3PbIxCl3-x perovskite-based ISPSC device is enhanced from 10.05% to 12.69%, and this is primarily due to the increases of both fill factor and short-circuit current. According to the surface morphology study of the perovskite/PCBM bilayer film, oleamide doping improves the coverage of PCBM ETL onto the perovskite layer, and this is beneficial for the interfacial contact between the perovskite layer and the Ag cathode and consequently the electron transport from perovskite to the Ag cathode. Such an improved electron transport induced by oleamide doping is further evidenced by the impedance spectroscopic study, revealing the prohibited electron-hole recombination at the interface between the perovskite layer and the Ag cathode. PMID:26053101

  4. Convection and correlation of coherent structure in turbulent boundary layer using tomographic particle image velocimetry

    NASA Astrophysics Data System (ADS)

    Wang, Wei; Guan, Xin-Lei; Jiang, Nan

    2014-10-01

    The present experimental work focuses on a new model for space—time correlation and the scale-dependencies of convection velocity and sweep velocity in turbulent boundary layer over a flat wall. A turbulent boundary layer flow at Re? = 2460 is measured by tomographic particle image velocimetry (tomographic PIV). It is demonstrated that arch, cane, and hairpin vortices are dominant in the logarithmic layer. Hairpins and hairpin packets are responsible for the elongated low-momentum zones observed in the instantaneous flow field. The conditionally-averaged coherent structures systemically illustrate the key roles of hairpin vortice in the turbulence dynamic events, such as ejection and sweep events and energy transport. The space—time correlations of instantaneous streamwise fluctuation velocity are calculated and confirm the new elliptic model for the space—time correlation instead of Taylor hypothesis. The convection velocities derived from the space—time correlation and conditionally-averaged method both suggest the scaling with the local mean velocity in the logarithmic layer. Convection velocity result based on Fourier decomposition (FD) shows stronger scale- dependency in the spanwise direction than in streamwise direction. Compared with FD, the proper orthogonal decomposition (POD) has a distinct distribution of convection velocity for the large- and small-scales which are separated in light of their contributions of turbulent kinetic energy.

  5. The structure of variable property, compressible mixing layers in binary gas mixtures

    NASA Technical Reports Server (NTRS)

    Kozusko, F.; Grosch, C. E.; Jackson, T. L.; Kennedy, Christipher A.; Gatski, Thomas B.

    1996-01-01

    We present the results of a study of the structure of a parallel compressible mixing layer in a binary mixture of gases. The gases included in this study are hydrogen (H2), helium (He), nitrogen (N2), oxygen (02), neon (Ne) and argon (Ar). Profiles of the variation of the Lewis and Prandtl numbers across the mixing layer for all thirty combinations of gases are given. It is shown that the Lewis number can vary by as much as a factor of eight and the Prandtl number by a factor of two across the mixing layer. Thus assuming constant values for the Lewis and Prandtl numbers of a binary gas mixture in the shear layer, as is done in many theoretical studies, is a poor approximation. We also present profiles of the velocity, mass fraction, temperature and density for representative binary gas mixtures at zero and supersonic Mach numbers. We show that the shape of these profiles is strongly dependent on which gases are in the mixture as well as on whether the denser gas is in the fast stream or the slow stream.

  6. Turbulence vertical structure of the boundary layer during the afternoon transition

    NASA Astrophysics Data System (ADS)

    Darbieu, Clara; Lohou, Fabienne; Lothon, Marie; Vilà-Guerau de Arellano, Jordi; Couvreux, Fleur; Durand, Pierre; Pino, David; Patton, Ned; Nilsson, Erik; Blay-Carreras, Estel; Gioli, Beniamino

    2015-04-01

    The transition from a well-mixed convective boundary layer to a residual layer overlying a stabilized nocturnal layer raises several issues, which remain difficult to address from both modeling and observational perspectives. The well mixed convective boundary layer is mainly forced by buoyancy, with fully developed turbulence. The daily decrease of the surface buoyancy flux leads to the decay of the turbulence kinetic energy (TKE), and a possible change of the structure of the turbulence before it reaches the stable regime, with more anisotropy and intermittency. It is important to better understand these processes, as they can impact on the dispersion of tracers in the atmosphere, and on the development of the nocturnal and daytime boundary layers of the following days. The presented work is based on both observations from the BLLAST (Boundary Layer Later Afternoon and Sunset Turbulence) experiment and Large-Eddy Simulation (NCAR LES code). The field campaign took place in summer 2011 in France, on the northern side of the Pyrenean foothills. A well-documented cloud-free weak wind day is considered here to analyze in details the evolution of the turbulence along the day, from midday to sunset. The case study combines observations of the mean structure and of the turbulence. It is the base of a complementary idealized numerical study with a large eddy simulation. From both observations and numerical simulations, the turbulence is described, according to time and height, with the characteristics of the spectral energy density, especially the typical turbulence lengthscales and the sharpness of the transition from energy-containing eddies to the inertial subrange. An analytical model proposed by Kristensen and Lenschow (1988) for homogeneous nonisotropic turbulence is used to approximate the observed and LES-modeled spectra and estimate their characteristics. The study points out the LES ability to reproduce th­e turbulence evolution throughout the afternoon. Two periods have been defined and caracterized: the "Early Afternoon", quasi-stationary, during which the TKE decays with a slow rate, with no significant change in the turbulence characteristics, and the "Late Afternoon", characterized by a larger TKE decay rate and a change of its spectral characteristics (increase of vertical velocity lengthscale, and change of the inertial spectral range slope). We also point out that the turbulent changes occur first in the upper part of the ABL. We have extended the analysis to several other days of aircraft observation, and to a LES sensitivity analysis with a TKE budget analysis, in order to confirm our findings and propose an explanation of these results with the role of the wind shear, entrainment, and by considering the effect of turbulent structures and anisotropy.

  7. Recrystallized S-layer protein of a probiotic Propionibacterium: structural and nanomechanical changes upon temperature or pH shifts probed by solid-state NMR and AFM.

    PubMed

    de sa Peixoto, Paulo; Roiland, Claire; Thomas, Daniel; Briard-Bion, Valérie; Le Guellec, Rozenn; Parayre, Sandrine; Deutsch, Stéphanie-Marie; Jan, Gwénaël; Guyomarc'h, Fanny

    2015-01-13

    Surface protein layers (S layers) are common constituents of the bacterial cell wall and originate from the assembly of strain-dependent surface layer proteins (Slps). These proteins are thought to play important roles in the bacteria's biology and to have very promising technological applications as biomaterials or as part of cell-host cross-talk in probiotic mechanism. The SlpA from Propionibacterium freudenreichii PFCIRM 118 strain was isolated and recrystallized to investigate organization and assembly of the protein using atomic force microscopy and solid-state (1)H and (13)C-nuclear magnetic resonance. SlpA was found to form hexagonal p1 monolayer lattices where the protein exhibited high proportions of disordered regions and of bound water. The lattice structure was maintained, but softened, upon mild heating or acidification, probably in relation with the increasing mobilities of the disordered protein regions. These results gave structural insights on the mobile protein regions exposed by S layer films, upon physiologically relevant changes of their environmental conditions. PMID:25479375

  8. Growth of magnetic materials and structures on Si(0 0 1) substrates using Co 2Si as a template layer

    Microsoft Academic Search

    S. Olive Mendez; V. Le Thanh; A. Ranguis; J. Derrien

    2008-01-01

    We report in this paper the use of Co2Si silicide as a template layer for the integration of magnetic materials and structures on silicon substrate. By undertaking Co deposition on silicon at a temperature of about 300°C, we show that it is possible to obtain a smooth and epitaxial Co2Si layer, which can act as a template layer preventing the

  9. Necking propagated deformation behavior of layer-structured steel prepared by co-warm rolled surface nanocrystallized 304 stainless steel

    Microsoft Academic Search

    A. Y. Chen; J. B. Zhang; J. Lu; W. Lun; H. W. Song

    2007-01-01

    Surface nanocrystallized 304ss sheets prepared by surface mechanical attrition technique were co-warm rolled at 500 °C to obtain layer-structured steel with alternate nanocrystalline layer and coarse grained layer. Tensile test results revealed that a novel tensile deformation behavior characterized by sliding and necking propagation were presented compared to the base material. In the process of tensile deformation, a sliding band occurred

  10. PREFACE: Ultrathin layers of graphene, h-BN and other honeycomb structures Ultrathin layers of graphene, h-BN and other honeycomb structures

    NASA Astrophysics Data System (ADS)

    Geber, Thomas; Oshima, Chuhei

    2012-08-01

    Since ancient times, pure carbon materials have been familiar in human society—not only diamonds in jewellery and graphite in pencils, but also charcoal and coal which have been used for centuries as fuel for living and industry. Carbon fibers are stronger, tougher and lighter than steel and increase material efficiency because of their lower weight. Today, carbon fibers and related composite materials are used to make the frames of bicycles, cars and even airplane parts. The two-dimensional allotrope, now called graphene, is just a single layer of carbon atoms, locked together in a strongly bonded honeycomb lattice. In plane, graphene is stiffer than diamond, but out-of-plane it is soft, like rubber. It is virtually invisible, may conduct electricity (heat) better than copper and weighs next to nothing. Carbon compounds with two carbon atoms as a base, such as graphene, graphite or diamond, have isoelectronic sister compounds made of boron-nitrogen pairs: hexagonal and cubic boron nitride, with almost the same lattice constant. Although the two 2D sisters, graphene and h-BN, have the same number of valence electrons, their electronic properties are very different: freestanding h-BN is an insulator, while charge carriers in graphene are highly mobile. The past ten years have seen a great expansion in studies of single-layer and few-layer graphene. This activity has been concerned with the ? electron transport in graphene, in electric and magnetic fields. More than 30 years ago, however, single-layer graphene and h-BN on solid surfaces were widely investigated. It was noted that they drastically changed the chemical reactivity of surfaces, and they were known to 'poison' heterogeneous catalysts, to passivate surfaces, to prevent oxidation of surfaces and to act as surfactants. Also, it was realized that the controlled growth of h-BN and graphene on substrates yields the formation of mismatch driven superstructures with peculiar template functionality on the nanometer scale. This special section contains interesting papers on graphene, h-BN and related 'honeycomb' compounds on solid surfaces, which are currently in development. Interfacial interaction strongly modifies the electronic and atomic structures of these overlayer systems and substrate surfaces. In addition, one can recognize a variety of growth phenomena by changing the surface and growth conditions, which are promising as regards fabricating those noble nanosystems. We have great pleasure in acknowledging the enthusiastic response and participation of our invited authors and their diligent preparation of the manuscripts. Ultrathin layers of graphene, h-BN and other honeycomb structures contents Ultrathin layers of graphene, h-BN and other honeycomb structuresThomas Geber and Chuhei Oshima Templating of arrays of Ru nanoclusters by monolayer graphene/Ru Moirés with different periodicitiesEli Sutter, Bin Wang, Peter Albrecht, Jayeeta Lahiri, Marie-Laure Bocquet and Peter Sutter Controllable p-doping of graphene on Ir(111) by chlorination with FeCl3N A Vinogradov, K A Simonov, A V Generalov, A S Vinogradov, D V Vyalikh, C Laubschat, N Mårtensson and A B Preobrajenski Optimizing long-range order, band gap, and group velocities for graphene on close-packed metal surfacesF D Natterer, S Rusponi, M Papagno, C Carbone and H Brune Epitaxial growth of graphene on transition metal surfaces: chemical vapor deposition versus liquid phase depositionSamuel Grandthyll, Stefan Gsell, Michael Weinl, Matthias Schreck, Stefan Hüfner and Frank Müller High-yield boron nitride nanosheets from 'chemical blowing': towards practical applications in polymer compositesXuebin Wang, Amir Pakdel, Chunyi Zhi, Kentaro Watanabe, Takashi Sekiguchi, Dmitri Golberg and Yoshio Bando BCx layers with honeycomb lattices on an NbB2(0001) surfaceChuhei Oshima Epitaxial growth of boron-doped graphene by thermal decomposition of B4CWataru Norimatsu, Koichiro Hirata, Yuta Yamamoto, Shigeo Arai and Michiko Kusunoki Mechanical exfoliation of epitaxial graphene on Ir(111) enabled by Br2 intercalationCh

  11. Titan: Predicted Bulk Chemical Composition and Interior Structure for a Capture Origin

    NASA Astrophysics Data System (ADS)

    Prentice, A. J.

    2004-12-01

    I report a predicted bulk chemical composition and internal structure for Titan based on the idea that this body is a captured satellite of Saturn which originally condensed within the gas ring shed by the proto-Solar cloud (PSC) at Saturn's initial helio-centric distance ˜ 8.1 AU . The case for capture rests on the large disparity (by a factor of ˜ 58) between the masses of Titan and Rhea. Rhea's mass (2.3 × 1024 g) is consistent with the mass mcond = 9.3 × 1024 of rock, H2O, and NH3 ices expected for a native moon of Saturn, had Rhea condensed from a gas ring shed by the proto-Saturnian cloud (Prentice, \\textit{JPL Pub.} 80-80 1980; \\textit{Proc. Astron. Soc. Australia} 4 164 1981; \\textit{Earth, Moon Planets} 30 209 1984). Here I assume an efficiency of 25% in the process of satellite accretion and adopt the proto-solar elemental abundances of Lodders (\\textit{Astrophys.J} 591 1220 2003). Titan's mass exceeds mcond by a factor of ˜ 14, so speaking against a native origin (http://www.aas.org/publications/baas/v36n2/aas204/887.htm). Previously it has been supposed that the process of shedding discrete gas rings by the parent gas cloud comes about solely through the action of large turbulent stresses arising from powerful convective motions (Prentice, \\textit{Moon & Planets} 19 341 1978, \\textit{Earth, Moon & Planets} 87 11 2001, http://www.lpi.usra.edu/meetings/mercury01/pdf/8061.pdf). This has necessitated convective speeds vt up to ˜ 5 times the local adiabatic sound speed vs, which is unacceptable. An exact numerical simulation of supersonic turbulent convection in a model atmosphere which represents the outer layers of the PSC shows, however, that the upper layers are strongly super-adiabatic (Prentice & Dyt, \\textit{MNRAS} 341 644 2003). This results in a natural density inversion at the top boundary . Gas ring shedding can now be achieved for speeds vt ? 3vs, which is OK. A new model for PSC has thus been constructed to include the influence of very strong super-adiabaticity. The controlling paramters are chosen so that the mean density of the condensate at the orbit of Mercury matches the inferred uncompressed value ? unc = 5.3 g/cm3 and that the fraction of water vapour in the gas ring at Jupiter's orbit which condenses is ? {H{2 O}} = 0.665. This later accounts for the densities of Ganymede and Callisto, following condensation from the gas rings shed by proto-Jovian cloud (Prentice 2001). At Saturn's initial orbit, where the gas ring temperature is Tn= 94 K and the mean orbit pressure pn= 4.7 × 10-7 bar, the bulk chemical constituents of the condensate are anhydrous rock (mass fraction 0.494), water ice (0.474) and graphite (0.032). The mean density is 1.52 g/cm3. Structural models for a present-day Titan based on this composition yield mean densities of 2.10 g/cm3 (homogeneous case) and 1.93 g/cm3 (differentiated 2-zone case). For the latter, C/MR2 = 0.32. Titan is thus most likely fully differentiated between its rock, graphite and water ice constituents. It is predicted that Titan has no internal ocean or induced magnetic field but it may possess a small magnetic dipole moment of magnitude ˜ 2× 1011 T m3. This was acquired through thermoremanence at ˜ 1.5 × 109 yr after satellite formation. Capture of Titan was achieved by gas drag within the proto-Saturnian envelope whose initial size was ˜ 60 RSat. Titan's surface should thus look much like that of Triton. I thank John D. Anderson [NASA/JPL] for much support, and Nicole Rappaport and Bob Jacobson for helpful discussions.

  12. Perforated Layer Structures in Liquid Crystalline Rod-coil Block Copolymers

    SciTech Connect

    Tenneti,K.; Chen, X.; Li, C.; Tu, Y.; Wan, X.; Zhou, Q.; Sics, I.; Hsiao, B.

    2005-01-01

    We report a novel observation of the tetragonal perforated layer structures in a series of rod-coil liquid crystalline block copolymers (BCPs), poly(styrene-block-(2, 5-bis[4-methoxyphenyl]oxycarbonyl)styrene) (PS-b-PMPCS). PMPCS forms rigid rods while PS forms the coil block. Differential scanning calorimetry (DSC), polarized light microscopy (PLM), small-angle X-ray scattering (SAXS), wide-angle X-ray diffraction (WAXD), and transmission electron microscopy (TEM) techniques were used to investigate these rod-coil molecules, and a perforated layer structure was observed at {sup fPMPCS} {approx} 0.37 in relatively low molecular weight (M{sub w}) samples and {approx}0.5 in high M{sub w} PS-b-PMPCS. This substantial phase boundary shift was attributed to the rod-coil nature of the BCP. The perforation obeys a tetragonal instead of hexagonal symmetry. The 'onset' of perforation was also observed in real space in sample PS{sub 272}-b-PMPCS{sub 93} ({sup fPMPCS} {approx} 0.52), in which few PS chains punctuate PMPCS layers. A slight increase in f{sub PS}, by blending with PS homopolymer, led to a dramatic change in the BCP morphology, and uniform tetragonal perforations were observed at {sup fPMPCS} {approx} 0.48.

  13. Summer Boundary Layer structure and circulations in the presence of a large man made lake

    NASA Astrophysics Data System (ADS)

    Salgado, Rui; Soares, Pedro; Policarpo, Carlos; Le Moigne, Patrick; Miranda, Pedro; Potes, Miguel

    2015-04-01

    The evolution of the thermodynamic structure of the atmospheric boundary layer over and in the vicinity of the Alqueva reservoir, a 250 km2 man made lake in south Portugal, is studied using mesoscale simulations and observations. The Observations were carried out during the intensive period (IOP) of the ALqueva hydro-meteorological Experiment, ALEX 2014 (www.alex2014.cge.uevora.pt), which took place between 22 and 24 July 2014. Twomodels were used, and the results have been inter-compared: The Weather Research and Forecasting, WRF, andthe non-hydrostatic Meso-NH. During the ALEX 2014 IOP, radiosondes were launched every tree hours and the near surface fluxes of energy, vapor and momentum were measured using an eddy covariance system installed on a floating platform in the lake. The ALEX field campaign includes also several surface meteorological stations, over water and land in order to characterize the local horizontal structure of the surface layer. The simulations, validated by the observations, allows the study of the effects of the lake in the boundary layer and on the atmospheric flow.

  14. Structural and Interaction Properties of Porphyrin Layers — A Quantum Chemical Study

    NASA Astrophysics Data System (ADS)

    Praveena, G.; Abiram, A.

    2015-05-01

    This paper is proposed to understand the interaction of porphyrin layers with diatomic molecules interacting at their interior regions by applying ab initio and density functional theory (DFT) methods. We have used NO, CO, and O2 diatomic molecules to interact with the porphyrin layers. The most common Fe-centered metalloporphyrin structure with tetra-pyrrlic rings having N4 core is chosen for the study. The optimization of Porphyrin-Porphyrin (PI-PII) and Porphyrin-Diatomic molecule-Porphyrin (PI-AB-PII) (AB = NO, CO, and O2) complexes are performed using HF method. In order to understand the planarity and appropriate stacking size of porphyrins and also to infer the separation of diatomic molecules between porphyrin layers the behavior of PI-AB-PII complexes (where AB = NO, CO, and O2) are analyzed using structural properties and molecular electrostatic potentials (MEP). The MEPs are calculated using hybrid exchange correlation functional B3PW91 of DFT along with 6-31+G* basis set for the PI-PII and PI-AB-PII complexes obtained from HF method.

  15. Genome Scan for Selection in Structured Layer Chicken Populations Exploiting Linkage Disequilibrium Information

    PubMed Central

    Gholami, Mahmood; Reimer, Christian; Erbe, Malena; Preisinger, Rudolf; Weigend, Annett; Weigend, Steffen; Servin, Bertrand; Simianer, Henner

    2015-01-01

    An increasing interest is being placed in the detection of genes, or genomic regions, that have been targeted by selection because identifying signatures of selection can lead to a better understanding of genotype-phenotype relationships. A common strategy for the detection of selection signatures is to compare samples from distinct populations and to search for genomic regions with outstanding genetic differentiation. The aim of this study was to detect selective signatures in layer chicken populations using a recently proposed approach, hapFLK, which exploits linkage disequilibrium information while accounting appropriately for the hierarchical structure of populations. We performed the analysis on 70 individuals from three commercial layer breeds (White Leghorn, White Rock and Rhode Island Red), genotyped for approximately 1 million SNPs. We found a total of 41 and 107 regions with outstanding differentiation or similarity using hapFLK and its single SNP counterpart FLK respectively. Annotation of selection signature regions revealed various genes and QTL corresponding to productions traits, for which layer breeds were selected. A number of the detected genes were associated with growth and carcass traits, including IGF-1R, AGRP and STAT5B. We also annotated an interesting gene associated with the dark brown feather color mutational phenotype in chickens (SOX10). We compared FST, FLK and hapFLK and demonstrated that exploiting linkage disequilibrium information and accounting for hierarchical population structure decreased the false detection rate. PMID:26151449

  16. Resolving fine structures of the electric double layer of electrochemical interfaces in ionic liquids with an AFM tip modification strategy.

    PubMed

    Zhong, Yun-Xin; Yan, Jia-Wei; Li, Mian-Gang; Zhang, Xiao; He, Ding-Wen; Mao, Bing-Wei

    2014-10-22

    We report enhanced force detection selectivity based on Coulombic interactions through AFM tip modification for probing fine structures of the electric double layer (EDL) in ionic liquids. When AFM tips anchored with alkylthiol molecular layers having end groups with different charge states (e.g., -CH3, -COO(-), and -NH3(+)) are employed, Coulombic interactions between the tip and a specified layering structure are intensified or diminished depending on the polarities of the tip and the layering species. Systematic potential-dependent measurements of force curves with careful inspection of layered features and thickness analysis allows the fine structure of the EDL at the Au(111)-OMIPF6 interface to be resolved at the subionic level. The enhanced force detection selectivity provides a basis for thoroughly understanding the EDL in ionic liquids. PMID:25291430

  17. Synthesis of carbon nano-structures using organic-molecule intercalated taeniolite layered silicates

    NASA Astrophysics Data System (ADS)

    Maezumi, Takaaki; Wada, Noboru

    2015-03-01

    By calcinating organic-molecule intercalated taeniolite layered silicates, carbon nano-structures were made between the 2:1 layered silicate sheets. Raman scattering, XRD, TGA and SEM were used to characterize the samples. Large taeniolite crystals (NaLiMg2Si4O10F) were first prepared by melting appropriate chemicals at high temperatures using a platinum crucible. Then, the taeniolite crystals made were cation-exchanged with Li+, K+, NH4+,Ca2+ + and Mg2+ in salt solution. Finally, various organic molecules such as ethylene glycol, pyridine and so on were intercalated into the taeniolite crystals, and calcinated under a N2 atmosphere at about 1000K. The resulting crystals are usually gray or black. X-ray (00l) diffraction patterns suggested that the carbon structures may be monolayer thick (i.e., graphene-like). Raman scattering spectra which exhibited a sharp G-band peak with a high G-band/D-band ratio indicated that the carbon structures were relatively well crystallized. Cation and organic-molecule dependence on the carbon structures will be discussed. In addition, evidence for stage-2 taeniolite will be presented.

  18. Kinematics and the origin of the internal structures in HL Tau jet (HH 151)

    E-print Network

    Movsessian, T A; Moiseev, A V

    2012-01-01

    Knotty structures of Herbig-Haro jets are common phenomena, and knowing the origin of these structures is essential for understanding the processes of jet formation. Basically, there are two theoretical approaches: different types of instabilities in stationary flow, and velocity variations in the flow. We investigate the structures with different radial velocities in the knots of the HL Tau jet as well as its unusual behaviour starting from 20 arcsec from the source. Collation of radial velocity data with proper motion measurements of emission structures in the jet of HL Tau makes it possible to understand the origin of these structures and decide on the mechanism for the formation of the knotty structures in Herbig-Haro flows. We present observations obtained with a 6 m telescope (Russia) using the SCORPIO camera with scanning Fabry-Perot interferometer. Two epochs of the observations of the HL/XZ Tau region in Halpha emission (2001 and 2007) allowed us to measure proper motions for high and low radial velo...

  19. Turbulence statistics and structures of drag-reducing turbulent boundary layer in homogeneous aqueous surfactant solutions

    NASA Astrophysics Data System (ADS)

    Tamano, Shinji; Itoh, Motoyuki; Inoue, Takefumi; Kato, Katsuo; Yokota, Kazuhiko

    2009-04-01

    In our earlier work [Itoh et al., Phys. Fluids 17, 075107 (2005)], the additional maximum of the streamwise turbulence intensity near the center of the drag-reducing turbulent boundary layer was found in the homogeneous dilute aqueous surfactant solution which was a mixture of cetyltrimethyl ammonium chloride with sodium salicylate as counterion. In this work, we systematically investigated the influence of the drag-reducing surfactant on the velocity fields of the turbulent boundary layer at various Reynolds numbers Re? from 301 to 1437 and the drag reduction ratio DR from 8% to 74% under different streamwise locations and concentration and temperature of solutions using a two-component laser-Doppler velocimetry (LDV) system. It was revealed that all data on DR versus the wall-shear rate obtained here were collapsed on a single curve. We verified the existence of the additional maximum of the streamwise turbulence intensity near the center of the boundary layer which appeared at relatively large drag reduction ratios and small Reynolds numbers. It was found that the additional maximum of streamwise turbulence intensity and its wall-normal location were independent of the streamwise location, wall-shear rate, Reynolds number, and drag reduction ratio. The additional maximum could be explained by the bilayered structure model proposed, in which the flow in the near-wall region is in shear-induced structure (SIS) and viscoelastic, whereas the flow in the region away from the wall is in non-SIS and nonviscoelastic. This model was based on measurements of the shear viscosity. We also performed particle image velocimetry measurements, which revealed that the fluctuating velocity vector fields showed two situations, with low and high activity. In low activity, the velocity fluctuations were attenuated largely across the turbulent boundary layer. In high activity, fluctuating velocity vectors were almost parallel to the wall and relatively large in both regions near the wall and the center of the boundary layer, which seemed to be a bilayered structure and supported the bilayered structure model.

  20. Stabilization and study of SrFe(1-x)Mn(x)O2 oxides with infinite-layer structure.

    PubMed

    Retuerto, María; Jiménez-Villacorta, Félix; Martínez-Lope, María J; Fernández-Díaz, María T; Alonso, José A

    2011-11-01

    A series of layered oxides of nominal composition SrFe(1-x)Mn(x)O(2) (x = 0, 0.1, 0.2, 0.3) have been prepared by the reduction of three-dimensional perovskites SrFe(1-x)Mn(x)O(3-?) with CaH(2) under mild temperature conditions of 583 K for 2 days. The samples with x = 0, 0.1, and 0.2 exhibit an infinite-layer crystal structure where all of the apical O atoms have been selectively removed upon reduction. A selected sample (x = 0.2) has been studied by neutron powder diffraction (NPD) and X-ray absorption spectroscopy. Both techniques indicate that Fe and Mn adopt a divalent oxidation state, although Fe(2+) ions are under tensile stress whereas Mn(2+) ions undergo compressive stress in the structure. The unit-cell parameters progressively evolve from a = 3.9932(4) Å and c = 3.4790(4) Å for x = 0 to a = 4.00861(15) Å and c = 3.46769(16) Å for x = 0.2; the cell volume presents an expansion across the series from V = 55.47(1) to 55.722(4) Å(3) for x = 0 and 0.2, respectively, because of the larger effective ionic radius of Mn(2+) versus Fe(2+) in four-fold coordination. Attempts to prepare Mn-rich compositions beyond x = 0.2 were unsuccessful. For SrFe(0.8)Mn(0.2)O(2), the magnetic properties indicate a strong magnetic coupling between Fe(2+) and Mn(2+) magnetic moments, with an antiferromagnetic temperature T(N) above room temperature, between 453 and 523 K, according to temperature-dependent NPD data. The NPD data include Bragg reflections of magnetic origin, accounted for with a propagation vector k = ((1)/(2), (1)/(2), (1)/(2)). A G-type antiferromagnetic structure was modeled with magnetic moments at the Fe/Mn position. The refined ordered magnetic moment at this position is 1.71(3) ?(B)/f.u. at 295 K. This is an extraordinary example where Mn(2+) and Fe(2+) ions are stabilized in a square-planar oxygen coordination within an infinite-layer structure. The layered SrFe(1-x)Mn(x)O(2) oxides are kinetically stable at room temperature, but in air at ~170 °C, they reoxidize and form the perovskites SrFe(1-x)Mn(x)O(3-?). A cubic phase is obtained upon reoxidation of the layered compound, whereas the starting precursor SrFeO(2.875) (Sr(8)Fe(8)O(23)) was a tetragonal superstructure of perovskite. PMID:21973275