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Sample records for original layered structure

  1. Origin of interfacial perpendicular magnetic anisotropy in MgO/CoFe/metallic capping layer structures.

    PubMed

    Peng, Shouzhong; Wang, Mengxing; Yang, Hongxin; Zeng, Lang; Nan, Jiang; Zhou, Jiaqi; Zhang, Youguang; Hallal, Ali; Chshiev, Mairbek; Wang, Kang L; Zhang, Qianfan; Zhao, Weisheng

    2015-12-11

    Spin-transfer-torque magnetic random access memory (STT-MRAM) attracts extensive attentions due to its non-volatility, high density and low power consumption. The core device in STT-MRAM is CoFeB/MgO-based magnetic tunnel junction (MTJ), which possesses a high tunnel magnetoresistance ratio as well as a large value of perpendicular magnetic anisotropy (PMA). It has been experimentally proven that a capping layer coating on CoFeB layer is essential to obtain a strong PMA. However, the physical mechanism of such effect remains unclear. In this paper, we investigate the origin of the PMA in MgO/CoFe/metallic capping layer structures by using a first-principles computation scheme. The trend of PMA variation with different capping materials agrees well with experimental results. We find that interfacial PMA in the three-layer structures comes from both the MgO/CoFe and CoFe/capping layer interfaces, which can be analyzed separately. Furthermore, the PMAs in the CoFe/capping layer interfaces are analyzed through resolving the magnetic anisotropy energy by layer and orbital. The variation of PMA with different capping materials is attributed to the different hybridizations of both d and p orbitals via spin-orbit coupling. This work can significantly benefit the research and development of nanoscale STT-MRAM.

  2. Origin of interfacial perpendicular magnetic anisotropy in MgO/CoFe/metallic capping layer structures

    PubMed Central

    Peng, Shouzhong; Wang, Mengxing; Yang, Hongxin; Zeng, Lang; Nan, Jiang; Zhou, Jiaqi; Zhang, Youguang; Hallal, Ali; Chshiev, Mairbek; Wang, Kang L.; Zhang, Qianfan; Zhao, Weisheng

    2015-01-01

    Spin-transfer-torque magnetic random access memory (STT-MRAM) attracts extensive attentions due to its non-volatility, high density and low power consumption. The core device in STT-MRAM is CoFeB/MgO-based magnetic tunnel junction (MTJ), which possesses a high tunnel magnetoresistance ratio as well as a large value of perpendicular magnetic anisotropy (PMA). It has been experimentally proven that a capping layer coating on CoFeB layer is essential to obtain a strong PMA. However, the physical mechanism of such effect remains unclear. In this paper, we investigate the origin of the PMA in MgO/CoFe/metallic capping layer structures by using a first-principles computation scheme. The trend of PMA variation with different capping materials agrees well with experimental results. We find that interfacial PMA in the three-layer structures comes from both the MgO/CoFe and CoFe/capping layer interfaces, which can be analyzed separately. Furthermore, the PMAs in the CoFe/capping layer interfaces are analyzed through resolving the magnetic anisotropy energy by layer and orbital. The variation of PMA with different capping materials is attributed to the different hybridizations of both d and p orbitals via spin-orbit coupling. This work can significantly benefit the research and development of nanoscale STT-MRAM. PMID:26656721

  3. Origin of interfacial perpendicular magnetic anisotropy in MgO/CoFe/metallic capping layer structures

    NASA Astrophysics Data System (ADS)

    Peng, Shouzhong; Wang, Mengxing; Yang, Hongxin; Zeng, Lang; Nan, Jiang; Zhou, Jiaqi; Zhang, Youguang; Hallal, Ali; Chshiev, Mairbek; Wang, Kang L.; Zhang, Qianfan; Zhao, Weisheng

    2015-12-01

    Spin-transfer-torque magnetic random access memory (STT-MRAM) attracts extensive attentions due to its non-volatility, high density and low power consumption. The core device in STT-MRAM is CoFeB/MgO-based magnetic tunnel junction (MTJ), which possesses a high tunnel magnetoresistance ratio as well as a large value of perpendicular magnetic anisotropy (PMA). It has been experimentally proven that a capping layer coating on CoFeB layer is essential to obtain a strong PMA. However, the physical mechanism of such effect remains unclear. In this paper, we investigate the origin of the PMA in MgO/CoFe/metallic capping layer structures by using a first-principles computation scheme. The trend of PMA variation with different capping materials agrees well with experimental results. We find that interfacial PMA in the three-layer structures comes from both the MgO/CoFe and CoFe/capping layer interfaces, which can be analyzed separately. Furthermore, the PMAs in the CoFe/capping layer interfaces are analyzed through resolving the magnetic anisotropy energy by layer and orbital. The variation of PMA with different capping materials is attributed to the different hybridizations of both d and p orbitals via spin-orbit coupling. This work can significantly benefit the research and development of nanoscale STT-MRAM.

  4. Dynamical origins of the community structure of an online multi-layer society

    NASA Astrophysics Data System (ADS)

    Klimek, Peter; Diakonova, Marina; Eguíluz, Víctor M.; San Miguel, Maxi; Thurner, Stefan

    2016-08-01

    Social structures emerge as a result of individuals managing a variety of different social relationships. Societies can be represented as highly structured dynamic multiplex networks. Here we study the dynamical origins of the specific community structures of a large-scale social multiplex network of a human society that interacts in a virtual world of a massive multiplayer online game. There we find substantial differences in the community structures of different social actions, represented by the various layers in the multiplex network. Community sizes distributions are either fat-tailed or appear to be centered around a size of 50 individuals. To understand these observations we propose a voter model that is built around the principle of triadic closure. It explicitly models the co-evolution of node- and link-dynamics across different layers of the multiplex network. Depending on link and node fluctuation probabilities, the model exhibits an anomalous shattered fragmentation transition, where one layer fragments from one large component into many small components. The observed community size distributions are in good agreement with the predicted fragmentation in the model. This suggests that several detailed features of the fragmentation in societies can be traced back to the triadic closure processes.

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

    NASA Astrophysics Data System (ADS)

    Yoshikawa, K.; Laderach, S.; Hinzman, L.

    2001-12-01

    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 deposits near the South Pole possibly originated through thermal contraction as predicted by image analysis and statistical analysis, but many of the middle and small size polygons from Utopia Planitia may not be caused by thermal contraction. Polygons from southern layered deposits display characteristic shape factors, such as form factor, roundness, and aspect ratio, which are very similar to terrestrial frost polygons. Nearest-neighbor analyses of polygonal network distributions also yield comparable results with terrestrial polygonal networks. However, one significant difference is the spacing of the cracks, which is on the order of 5 - 10 times bigger than those on Earth. Polygon size provides some hints on the surface materials of the southern layered deposits. The polygonal patterns in Utopia Planitia have frequently been associated with collapsed features such as ancient subsurface channels (the width of the underground channel is estimated to be approximately 400-500 m) or a talik (unfrozen layer in the permafrost). These features also display linear structure, associated with lower surface albedo. The area of lower albedo has a higher density of polygonal patterns. These patterns potentially suggest that 1) the polygonal pattern is caused primarily by ground heaving and collapsing, 2) darker albedo materials had higher tensile strength and 3) liquid water or melt water (from ice rich materials) was running through the talik or near surface channel.

  6. Origin of Structural Transformation in Mono- and Bi-Layered Molybdenum Disulfide

    NASA Astrophysics Data System (ADS)

    Sun, Xiaoli; Wang, Zhiguo; Li, Zhijie; Fu, Y. Q.

    2016-05-01

    Mono- and multi-layered molybdenum disulfide (MoS2) is considered to be one of the next generation anode materials for rechargeable ion batteries. Structural transformation from trigonal prismatic (2H) to octahedral (1T) upon lithium or sodium intercalation has been in-situ observed experimentally using transmission electron microscope during studies of their electrochemical dynamics processes. In this work, we explored the fundamental mechanisms of this structural transformation in both mono- and bi-layered MoS2 using density functional theory. For the intercalated MoS2, the Li and Na donate their electrons to the MoS2. Based on the theoretical analysis, we confirmed that, for the first time, electron transfer is dominant in initiating this structural transformation, and the results provide an in-depth understanding of the transformation mechanism induced by the electron doping. The critical values of electron concentrations for this structural transformation are decreased with increasing the layer thickness.

  7. Origin of Structural Transformation in Mono- and Bi-Layered Molybdenum Disulfide

    PubMed Central

    Sun, Xiaoli; Wang, Zhiguo; Li, Zhijie; Fu, Y. Q.

    2016-01-01

    Mono- and multi-layered molybdenum disulfide (MoS2) is considered to be one of the next generation anode materials for rechargeable ion batteries. Structural transformation from trigonal prismatic (2H) to octahedral (1T) upon lithium or sodium intercalation has been in-situ observed experimentally using transmission electron microscope during studies of their electrochemical dynamics processes. In this work, we explored the fundamental mechanisms of this structural transformation in both mono- and bi-layered MoS2 using density functional theory. For the intercalated MoS2, the Li and Na donate their electrons to the MoS2. Based on the theoretical analysis, we confirmed that, for the first time, electron transfer is dominant in initiating this structural transformation, and the results provide an in-depth understanding of the transformation mechanism induced by the electron doping. The critical values of electron concentrations for this structural transformation are decreased with increasing the layer thickness. PMID:27225416

  8. Origins of Igneous Layering

    NASA Astrophysics Data System (ADS)

    Marsh, Bruce

    Anyone who has ever seen a photo of a layered intrusion, let alone visited one first hand, or even seen a thin section from one, cannot help but be impressed by the stunning record of crystal growth and deposition. Such bodies stand as majestic monuments of undeniable evidence that intricate magmatic processes exist, processes that couple crystallization, convection, and crystal sorting to form rocks so highly ordered and beautiful that they are a wonder to behold. These are the altars to which petrologists must carry their conceived petrologic processes for approval.Although significant in number, the best layered intrusions seem to be found almost always in remote places. Their names, Bushveld, Muskox, Kiglapait, Stillwater, Duke Island, Skaergaard, Rhum, ring through igneous petrology almost as historic military battles (Saratoga, Antietam, Bull Run, Manassas, Gettysburg) do through American history. People who have worked on such bodies are almost folk heros: Wager, Deer, Brown, Jackson, Hess, Irvine, McBirney, Morse; these names are petrologic household words. Yet with all this fanfare and reverence, layered instrusions are nearly thought of as period pieces, extreme examples of what can happen, but not generally what does. This is now all changing with the increasing realization that these bodies are perhaps highly representative of all magmatic bodies. They are simply more dynamically complete, containing more of the full range of interactions, and of course, exposing a more complete record. They are one end of a spectrum containing lava flows, lava lakes, large sills, plutons, and layered intrusions. This book uniquely covers this range with an abundance of first-hand field observations and a good dose of process conceptualization, magma physics, and crystal growth kinetics.

  9. 'Blueberry' Layers Indicate Watery Origins

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This microscopic image, taken at the outcrop region dubbed 'El Capitan' near the Mars Exploration Rover Opportunity's landing site, reveals millimeter-scale (.04 inch-scale) layers in the lower portion. This same layering is hinted at by the fine notches that run horizontally across the sphere-like grain or 'blueberry' in the center left. The thin layers do not appear to deform around the blueberry, indicating that these geologic features are concretions and not impact spherules or ejected volcanic material called lapilli. Concretions are balls of minerals that form in pre-existing wet sediments. This image was taken by the rover's microscopic imager on the 29th martian day, or sol, of its mission. The observed area is about 3 centimeters (1.2 inches) across.

  10. Structured luminescence conversion layer

    DOEpatents

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

    2012-12-11

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

  11. Origins of Ripples in CVD-Grown Few-layered MoS2 Structures under Applied Strain at Atomic Scales

    PubMed Central

    Wang, Jin; Namburu, Raju R.; Dubey, Madan; Dongare, Avinash M.

    2017-01-01

    The potential of the applicability of two-dimensional molybdenum disulfide (MoS2) structures, in various electronics, optoelectronics, and flexible devices requires a fundamental understanding of the effects of strain on the electronic, magnetic and optical properties. Particularly important is the recent capability to grow large flakes of few-layered structures using chemical vapor deposition (CVD) wherein the top layers are relatively smaller in size than the bottom layers, resulting in the presence of edges/steps across adjacent layers. This paper investigates the strain response of such suspended few-layered structures at the atomic scales using classic molecular dynamics (MD) simulations. MD simulations suggest that the suspended CVD-grown structures are able to relax the applied in-plane strain through the nucleation of ripples under both tensile and compressive loading conditions. The presence of terraced edges in these structures is the cause for the nucleation of ripples at the edges that grow towards the center of the structure under applied in-plane strains. The peak amplitudes of ripples observed are in excellent agreement with the experimental observations. The study provides critical insights into the mechanisms of strain relaxation of suspended few-layered MoS2 structures that determine the interplay between the mechanical response and the electronic properties of CVD-grown structures. PMID:28102351

  12. Origins of Ripples in CVD-Grown Few-layered MoS2 Structures under Applied Strain at Atomic Scales

    NASA Astrophysics Data System (ADS)

    Wang, Jin; Namburu, Raju R.; Dubey, Madan; Dongare, Avinash M.

    2017-01-01

    The potential of the applicability of two-dimensional molybdenum disulfide (MoS2) structures, in various electronics, optoelectronics, and flexible devices requires a fundamental understanding of the effects of strain on the electronic, magnetic and optical properties. Particularly important is the recent capability to grow large flakes of few-layered structures using chemical vapor deposition (CVD) wherein the top layers are relatively smaller in size than the bottom layers, resulting in the presence of edges/steps across adjacent layers. This paper investigates the strain response of such suspended few-layered structures at the atomic scales using classic molecular dynamics (MD) simulations. MD simulations suggest that the suspended CVD-grown structures are able to relax the applied in-plane strain through the nucleation of ripples under both tensile and compressive loading conditions. The presence of terraced edges in these structures is the cause for the nucleation of ripples at the edges that grow towards the center of the structure under applied in-plane strains. The peak amplitudes of ripples observed are in excellent agreement with the experimental observations. The study provides critical insights into the mechanisms of strain relaxation of suspended few-layered MoS2 structures that determine the interplay between the mechanical response and the electronic properties of CVD-grown structures.

  13. Origin and evolution of asthenospheric layers

    NASA Astrophysics Data System (ADS)

    Czechowski, Leszek; Grad, Marek

    2013-04-01

    is probably in the range from 3 to 5. We investigate the processes of formation and evolution of low viscosity layers ("asthenospheric layers") in the upper mantle. The time scale of the temperature changes is of the order of 10 Myr. The characteristic time of stress changes could be much shorter depending on tectonic processes. Eventually processes of formation and vanishing of low viscosity layers is very dynamical. In a relatively short time (below 1 Myr) the pattern the viscosity distribution and velocity gradient could change substantially. Using results from deep seismic sounding and surface wave tomography we have found that below some regions there are structures in the mantle that could be a forming/vanishing low viscosity layers. Reflectors in the lower lithosphere are observed beneath Trans-European suture zone between Precambrian and Palaeozoic platforms. In a thick Baltic shield lithosphere (200 km or more) low velocity zones and seismic reflectors are observed in the depth range 60-100 km, which could be interpreted as mechanical low Vp velocity zones, in contrast to thermal velocity zone in deeper asthenosphere.

  14. 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.

  15. Structural Origins of Silk Piezoelectricity

    PubMed Central

    Yucel, Tuna; Cebe, Peggy

    2012-01-01

    Uniaxially oriented, piezoelectric silk films were prepared by a two-step method that involved: (1) air drying aqueous, regenerated silk fibroin solutions into films, and (2) drawing the silk films to a desired draw ratio. The utility of two different drawing techniques, zone drawing and water immersion drawing were investigated for processing the silk for piezoelectric studies. Silk films zone drawn to a ratio of λ= 2.7 displayed relatively high dynamic shear piezoelectric coefficients of d14 = −1.5 pC/N, corresponding to over two orders of magnitude increase in d14 due to film drawing. A strong correlation was observed between the increase in the silk II, β-sheet content with increasing draw ratio measured by FTIR spectroscopy (Cβ∝ e2.5 λ), the concomitant increasing degree of orientation of β-sheet crystals detected via WAXD (FWHM = 0.22° for λ= 2.7), and the improvement in silk piezoelectricity (d14∝ e2.4 λ). Water immersion drawing led to a predominantly silk I structure with a low degree of orientation (FWHM = 75°) and a much weaker piezoelectric response compared to zone drawing. Similarly, increasing the β-sheet crystallinity without inducing crystal alignment, e.g. by methanol treatment, did not result in a significant enhancement of silk piezoelectricity. Overall, a combination of a high degree of silk II, β-sheet crystallinity and crystalline orientation are prerequisites for a strong piezoelectric effect in silk. Further understanding of the structural origins of silk piezoelectricity will provide important options for future biotechnological and biomedical applications of this protein. PMID:23335872

  16. On The Physical Mechanism At The Origin Of Multiple Double Layers Appearance In Plasma

    SciTech Connect

    Dimitriu, D. G.; Gurlui, S.; Aflori, M.; Ivan, L. M.

    2006-01-15

    Double layer in plasma are nonlinear potential structures consisting of two adjacent layers of positive and negative space charges, respectively. Between these layers a potential jump exists, creating an electric field. A common way to obtain a double layer structure is to positively bias an electrode immersed into stable plasma. Under certain experimental conditions, a more complex structure in form of two or more subsequent double layers was observed, which was called multiple double layers. It appears as several bright and concentric plasma shells attached to the electrode. The successive double layers are located at the abrupt changes of luminosity between two adjacent plasma shells. However, if the electrode is large, the multiple double layers structure appears non-concentrically, as a network of plasma spots, near each other, almost equally distributed on the electrode surface. Each of the plasma spots is confined by an electrical double layer. Here, we will present experimental results on the appearance and dynamics of concentric, as well as non-concentric multiple double layers. The results prove that the same physical mechanism is at the origin of their appearance in plasma. In this mechanism, the electron-neutral impact excitations and ionizations play the key role.

  17. Buffer layer for thin film structures

    SciTech Connect

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

    2010-06-15

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

  18. Buffer layer for thin film structures

    DOEpatents

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

    2006-10-31

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

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

    SciTech Connect

    Shipley, J. . Dept. of Geology)

    1993-03-01

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

  20. 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

  1. 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.

  2. Visualizing Evaluation Structures using Layered Graph Drawings.

    PubMed

    Onoue, Yosuke; Kukimoto, Nobuyuki; Sakamoto, Naohisa; Misue, Kazuo; Koyamada, Koji

    2016-03-18

    We propose a method for visualizing evaluation structures that is based on layered graph drawing techniques. An evaluation structure is a hierarchical structure of human cognition extracted from interviews based on the evaluation grid method. An evaluation structure can be defined as a directed acyclic graph (DAG). The Sugiyama framework is a popular method for constructing DAGs. A new layer assignment method that is a part of the Sugiyama framework is proposed to satisfy the requirements for drawing evaluation structures. We formulate a layer assignment problem by considering the sum of squares of arc lengths to be an integer quadratic programming (IQP) problem. Moreover, we transform the IQP problem into an equivalent integer linear programming (ILP) problem for computational efficiency. Evaluations demonstrate that the layered graph drawing with the proposed layer assignment method is preferred by users and aids in the understanding of evaluation structures.

  3. Simulation of plasma double-layer structures

    NASA Technical Reports Server (NTRS)

    Borovsky, J. E.; Joyce, G.

    1982-01-01

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

  4. Nanoasperity: structure origin of nacre-inspired nanocomposites.

    PubMed

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

    2015-02-24

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

  5. Marine Toxins Origin, Structure, and Molecular Pharmacology

    DTIC Science & Technology

    1990-01-01

    thin-layer chromatography (TLC) were instrumental in the initial isolation and purification processes. Mass spectrometry (MS), infrared spectroscopy ...Frederick, MD 21701-5011 Methods of detection, metabolism, and pathophysiology of the brevetoxins, PbTx-2 and PbTx-3, are summarized. Infrared spectros...1R), circular dichroism (CD), nuclear magnetic resonance spectroscopy (NMR), and X-ray crystal- lography all played important roles in structure

  6. The Kinematics of Turbulent Boundary Layer Structure

    NASA Technical Reports Server (NTRS)

    Robinson, Stephen Kern

    1991-01-01

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

  7. Crystal structure of britvinite [Pb7(OH)3F(BO3)2(CO3)][Mg4.5(OH)3(Si5O14)]: A new layered silicate with an original type of silicon-oxygen networks

    NASA Astrophysics Data System (ADS)

    Yakubovich, O. V.; Massa, W.; Chukanov, N. V.

    2008-03-01

    The crystal structure of a new mineral britvinite Pb7.1Mg4.5(Si4.8Al0.2O14)(BO3)(CO3)[(BO3)0.7(SiO4)0.3](OH, F)6.7 from the Lángban iron-manganese skarn deposit (Värmland, Sweden) is determined at T = 173 K using X-ray diffraction (Stoe IPDS diffractometer, λMo Kα, graphite monochromator, 2θmax = 58.43°, R = 0.052 for 6262 reflections). The main crystal data are as follows: a = 9.3409(8) Å, b = 9.3579(7) Å, c = 18.8333(14) Å, α = 80.365(6)°, β = 75.816(6)°, γ = 59.870(5)°, V = 1378.7(2) Å3, space group P1, Z = 2, and ρcalcd = 5.42 g/cm3. The idealized structural formula of the mineral is represented as [Pb7(OH)3F(BO3)2(CO3)][Mg4.5(OH)3(Si5O14)]. It is demonstrated that the mineral britvinite is a new representative of the group of mica-like layered silicates with structures in which three-layer (2: 1) "sandwiches" composed of tetrahedra and octahedra alternate with blocks of other compositions, such as oxide, oxide-carbonate, oxide-carbonate-sulfate, and other blocks. The tetrahedral networks (Si5O14)∞∞ consisting of twelve-membered rings are fragments of the britvinite structure. Similar networks also form crystal structures of the mineral zeophyllite and the synthetic phase Rb6Si10O23. In the crystal structures under consideration, the tetrahedral networks differ in the rotation of tetrahedra with respect to the layer plane.

  8. Structure of relaminarizing turbulent boundary layers

    NASA Astrophysics Data System (ADS)

    Ramesh, O.; Patwardhan, Saurabh

    2014-11-01

    Relaminarization of a turbulent boundary layer in a strongly accelerated flow has received a great attention in recent times. It has been found that such relaminarization is a general and regularly occurring phenomenon in the leading-edge region of a swept wing of an airplane (van Dam et al., 1993). In this work, we investigate the effect of initial Reynolds number on the process of relaminarization in turbulent boundary layers. The experimental and numerical investigation of relaminarizing turbulent boundary layers undergoing same history reveals that the boundary layer with higher initial Reynolds number relaminarizes at a lower pressure gradient value compared to the one with lower Reynolds number. This effect can be explained on the inviscid theory proposed earlier in the literature. Further, various parameter criteria proposed to predict relaminarization, are assessed and the structure of relaminarizing boundary layers is investigated. A mechanism for stabilization of near-wall low speed streaks is proposed.

  9. Energy gap structure of layered superconductors

    SciTech Connect

    Liu, S.H.; Klemm, R.A.

    1993-11-01

    We report the energy gap structure and density-of-states (DOS) of a model layered superconductor with one superconducting layer and one normal layer in a unit cell along the c-axis. In the physically interesting parameter range where the interlayer hopping strengths of the quasiparticles are comparable to the critical temperature, the peaks in the DOS curve do not correspond to the order parameter (OP) of the superconducting layer, but depend on the OP and the band dispersion in the c-direction in a complex manner. In contrast to a BCS superconductor, the DOS of layered systems have logarithmic singularities. Our simulated tunneling characteristics bear close resemblance to experimental results.

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

    PubMed

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

    2015-02-01

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

  11. 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.

  12. Conserved variable analysis of the convective boundary layer thermodynamic structure over the tropical oceans

    NASA Technical Reports Server (NTRS)

    Betts, Alan K.; Albrecht, Bruce A.

    1987-01-01

    An analysis of FGGE dropwindsonde data using conserved thermodynamic variables shows mixing line structures for the convective boundary layer over the equatorial Pacific. Deeper boundary layers show a double structure. Reversals of the gradients of mixing ratio and equivalent potential temperature above the boundary-layer top are present in all the averages and suggest that the origin of the air sinking into the boundary layer needs further study.

  13. Some new aspects of the transient ionization layer of comet Siding Spring origin in the Martian upper atmosphere

    NASA Astrophysics Data System (ADS)

    Venkateswara Rao, N.; ManasaMohana, P.; Jayaraman, A.; Rao, S. V. B.

    2016-04-01

    The close encounter of comet Siding Spring with Mars resulted in the formation of a dense transient ionization layer in the Martian upper atmosphere at altitudes between 80 and 120 km. Instruments on three spacecraft orbiting Mars detected the presence of this layer, as reported in previous publications. In this study, we reanalyzed the ionograms of the Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) instrument on Mars Express to get further insight about the recurrence of the layer. For this purpose, data from three periapsis passes of MARSIS that took place 5 h, 12 h, and 19 h after peak dust deposition are used. We found that the transient ionization layer was sustained at least for 19 h on the nightside and 12 h on the dayside. While the peak density of the layer on the nightside gradually decreases from orbit to orbit, it does not change much on the dayside. Some ionograms in all three orbits show two transient ionization layers that are separated by ~60 km in apparent altitude. These double layers occur preferentially in regions of strong vertical magnetic fields. The bottom layer of the double structure is probably an oblique echo due to reflections from ionization bulges (formed in regions of vertical magnetic fields) at altitudes of the transient ionization layer. Horizontal bifurcation of the original layer is considered as another plausible mechanism for explaining the double-layer structure.

  14. Origins of serotonin innervation of forebrain structures

    NASA Technical Reports Server (NTRS)

    Kellar, K. J.; Brown, P. A.; Madrid, J.; Bernstein, M.; Vernikos-Danellis, J.; Mehler, W. R.

    1977-01-01

    The tryptophan hydroxylase activity and high-affinity uptake of (3H) serotonin ((3H)5-HT) were measured in five discrete brain regions of rats following lesions of the dorsal or median raphe nuclei. Dorsal raphe lesions reduced enzyme and uptake activity in the striatum only. Median raphe lesions reduced activities in the hippocampus, septal area, frontal cortex, and, to a lesser extent, in the hypothalamus. These data are consistent with the suggestion that the dorsal and median raphe nuclei are the origins of two separate ascending serotonergic systems - one innervating striatal structures and the other mesolimbic structures, predominantly. In addition, the data suggest that measurements of high-affinity uptake of (3H)5-HT may be a more reliable index of innervation than either 5-HT content or tryptophan hydroxylase activity.

  15. 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 Reθ = 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 Reθ ~ 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 Reθ = 2175 and at y / δ = 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.

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

    SciTech Connect

    Cox, James V.; Cheng, Shengfeng; Grest, Gary Stephen; Tjiptowidjojo, Kristianto; 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.

  17. Structural phase transitions in layered perovskitelike crystals

    SciTech Connect

    Aleksandrov, K.S.

    1995-03-01

    Possible symmetry changes due to small tilts of octahedra are considered for layered perovskite-like crystals containing slabs of several ({ell}) layers of comer-sharing octahedra. In the crystals with {ell} > 1, four types of distortions are possible; as a rule, these distortions correspond to the librational modes of the parent lattice. Condensation of these soft modes is the reason for structural phase transitions or sequences of phase transitions. The results obtained are compared with the known experimental data for a number of layered ferroelectric and ferroelastic perovskite-like compounds. An application of the results to the initial stage of determining unknown structures is discussed with particular attention paid to high-temperature superconductors. 76 refs., 9 figs., 7 tabs.

  18. 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

  19. 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

  20. 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.

  1. Structure and dynamics of layered molecular assemblies

    NASA Astrophysics Data System (ADS)

    Horne, Jennifer Conrad

    This dissertation focuses on the goal of understanding and controlling layered material properties from a molecular perspective. With this understanding, materials can be synthetically tailored to exhibit predetermined bulk properties. This investigation describes the optical response of a family of metal-phosphonate (MP) monolayers and multilayers, materials that are potentially useful because the films are easy to synthesize and are chemically and thermally stable. MP films have shown potential in a variety of chemical sensing and optical applications, and in this dissertation, the suitability of MP films for optical information storage is explored For this application, the extent of photonic energy transport within and between optically active layers is an important factor in determining the stability and specificity of optical modifications made to a material. Intralayer and interlayer energy transport processes can be studied selectively in MP films because the composition, and thus the properties, of each layer are controlled synthetically. It was determined by fluorescence relaxation dynamics in conjunction with atomic force microscopy (AFM) that the substrate and layer morphologies are key factors in determining the layer optical and physical properties. The initial MP layers in a multilayer are structurally heterogeneous, characterized by randomly distributed islands that are ~50 A in diameter. The population dynamics measured for these layers are non-exponential, chromophore concentration-independent, and identical for two different chromophores. The data is explained in the context of an excitation hopping model in a system where the surface is characterized by islands of aggregated chromophores as well as non-aggregated monomers. Within a MP monolayer, the dynamics are dominated by intra-island excitation hopping. Forster (dipolar) energy transfer between the energetically overlapped chromophores does not play a significant role in determining the

  2. 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

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

    PubMed

    Park, Hahnbeom; DiMaio, Frank; Baker, David

    2015-06-02

    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.

  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. 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.

  6. A challenging interpretation of a hexagonally layered protein structure

    SciTech Connect

    Thompson, Michael C.; Yeates, Todd O.

    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 β-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.

  7. Flow visualization of turbulent boundary layer structure

    NASA Astrophysics Data System (ADS)

    Head, M. R.; Bandyopadhyay, P.

    1980-01-01

    The results from flow visualization experiments performed using an argon-ion laser to illuminate longitudinal and transverse sections of the smoke filled boundary layer in zero pressure gradient are discussed. Most of the experiments were confined to the range 600 Re sub theta 10,000. Results indicate that the boundary layer consists almost exclusively of vortex loops or hairpins, some of which may extend through the complete boundary layer thickness and all of which are inclined at a more or less constant characteristic angle of approximately 45 deg to the wall. Since the cross-stream dimensions of the hairpins appear to scale roughly with the wall variables U sub tau and nu, while their length is limited only by the boundary layer thickness, there are very large scale effects on the turbulence structure. At high Reynolds numbers (Re sub theta = 10,000) there is little evidence of large-scale coherent motions, other than a slow overturning of random agglomerations of the hairpins just mentioned.

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

    SciTech Connect

    Cours, T.; Burgalat, J.; Rannou, P.; Rodriguez, S.; Brahic, A.

    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.

  9. Fungal catalases: function, phylogenetic origin and structure.

    PubMed

    Hansberg, Wilhelm; Salas-Lizana, Rodolfo; Domínguez, Laura

    2012-09-15

    Most fungi have several monofunctional heme-catalases. Filamentous ascomycetes (Pezizomycotina) have two types of large-size subunit catalases (L1 and L2). L2-type are usually induced by different stressors and are extracellular enzymes; those from the L1-type are not inducible and accumulate in asexual spores. L2 catalases are important for growth and the start of cell differentiation, while L1 are required for spore germination. In addition, pezizomycetes have one to four small-size subunit catalases. Yeasts (Saccharomycotina) do not have large-subunit catalases and generally have one peroxisomal and one cytosolic small-subunit catalase. Small-subunit catalases are inhibited by substrate while large-subunit catalases are activated by H(2)O(2). Some small-subunit catalases bind NADPH preventing inhibition by substrate. We present a phylogenetic analysis revealing one or two events of horizontal gene transfers from Actinobacteria to a fungal ancestor before fungal diversification, as the origin of large-size subunit catalases. Other possible horizontal transfers of small- and large-subunit catalases genes were detected and one from bacteria to the fungus Malassezia globosa was analyzed in detail. All L2-type catalases analyzed presented a secretion signal peptide. Mucorales preserved only L2-type catalases, with one containing a secretion signal if two or more are present. Basidiomycetes have only L1-type catalases, all lacking signal peptide. Fungal small-size catalases are related to animal catalases and probably evolved from a common ancestor. However, there are several groups of small-size catalases. In particular, a conserved group of fungal sequences resemble plant catalases, whose phylogenetic origin was traced to a group of bacteria. This group probably has the heme orientation of plant catalases and could in principle bind NADPH. From almost a hundred small-subunit catalases only one fourth has a peroxisomal localization signal and in fact many fungi lack

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

    NASA Astrophysics Data System (ADS)

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

    2014-09-01

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

  11. 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.

  12. Structures and Crystal Chemistry of Layered Materials

    NASA Astrophysics Data System (ADS)

    Partin, Daniel Edward

    The crystal chemistry of several layered materials has been explored using a variety of methods, with an emphasis on their structural aspects. In the second part of this work, the structure of several copper oxides that are of significance to the study of superconductors are described. The crystal structures of MgCl_2 and CdCl_2 have been refined using powder X-ray diffraction data. They have the space group Roverline{3}m. For magnesium chloride the unit cell constants are a = 3.6363(1) A, c = 17.6663(5) A. For cadmium chloride they are a = 3.8459(1) A, c = 17.4931(4) A. The structures and their relationship to that of fluorite are discussed within the framework of a Born-Mayer model. The crystal structure of Mg(OD)_2 has been refined from time-of flight (TOF) neutron diffraction data and found to be trigonal, Poverline {3}m1, a = 3.1455(1) A, c = 4.7646(3) A. The data were collected at 305 K. The O-D bond length is 0.937 (1) A (corrected for "riding" motion 0.948 A). An infrared/Raman study of Mg(OH)_2 was conducted in a diamond anvil cell in the pressure range from room pressure up to 7 Gpa. For layered crystals, it was found that as the internally fixed layers are moved apart the Madelung energy of the system becomes constant after a very short distance, although not necessarily that of the given crystal's energy at ambient conditions. The crystal structure of Sr(OD)_2 has been refined from time-of-flight neutron diffraction data and the deuterium positions found. Strontium deuteroxide crystallizes in the space group Pnma, with the unit cell constants of a = 9.8269(5) A, b = 3.9051(2) A, and c = 6.0733(3) A. The crystal structures of SrCuO_2 and Sr_2CuO_3 have been refined by time-of-flight neutron diffraction. For SrCuO_2 the space group is Cmcm, a = 3.57002(2), b = 16.32268(8), c = 3.91100(2); for Sr _2CuO_3 the space group is Immm, a = 3.49900(5), b = 12.7009(2), c = 3.91120(5). In both structures the strontium atoms are coordinated by seven oxygen atoms

  13. 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 β-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.

  14. Origin and Structure of Dynamic Cooperative Networks

    PubMed Central

    Wardil, Lucas; Hauert, Christoph

    2014-01-01

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

  15. Origin and Structure of Dynamic Cooperative Networks

    NASA Astrophysics Data System (ADS)

    Wardil, Lucas; Hauert, Christoph

    2014-07-01

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

  16. Three layers of skyrmions in the magnetic triple-layer structure without the Dzyaloshinsky-Moriya interaction

    NASA Astrophysics Data System (ADS)

    Xie, Kaixuan; Sang, Hai

    2014-12-01

    The skyrmionic state is an exciting realm of study and the skyrmions are being explored as the promising candidates of information carriers. In most systems, the skyrmions originate from the Dzyaloshinsky-Moriya interaction (DMI). However, in this work, it is demonstrated that in the triple-layer CoPt/Co/CoPt structure, the skyrmion-like state can be formed not only in the CoPt layers but also in the middle Co layer, without DMI. In this new structure, the skyrmion-like state in Co layer can exist in a large CoPt thickness range with thick Co. It can be very stable even against the external field from -500 to 200 mT along Z axis. The skyrmion number (S) in Co (SCo) can be as large as 0.9. These advanced properties make it high application potential for the future information-processing and storage devices.

  17. Complex structures of dense lithium: Electronic origin

    NASA Astrophysics Data System (ADS)

    Degtyareva, V. F.

    2016-11-01

    Lithium—the lightest alkali metal exhibits unexpected structures and electronic behavior at high pressures. Like the heavier alkali metals, Li is bcc at ambient pressure and transforms first to fcc (at 7.5 GPa). The post-fcc high-pressure form Li-cI 16 (at 40-60 GPa) is similar to Na-cI 16 and related to more complex structures of heavy alkalis Rb-oC52 and Cs- oC84. The other high pressure phases for Li (oC88, oC40, oC24) observed at pressures up to 130 GPa are found only in Li. The different route of Li high-pressure structures correlates with its special electronic configuration containing the only 3 electrons (at 1s and 2s levels). Crystal structures for Li are analyzed within the model of Fermi sphere-Brillouin zone interactions. Stability of post-fcc structures for Li are supported by the Hume-Rothery arguments when new diffraction plains appear close to the Fermi level producing pseudogaps near the Fermi level and decreasing the crystal energy. The filling of Brillouin-Jones zones by electron states for a given structure defines the physical properties as optical reflectivity, electrical resistivity and superconductivity. To understand the complexity of structural and physical properties of Li above 60 GPa it is necessary to assume the valence electron band overlap with the core electrons and increase the valence electron count under compression.

  18. Dry release of polymer structures with anti-sticking layer

    NASA Astrophysics Data System (ADS)

    Cheng, M. C.; Gadre, A. P.; Garra, J. A.; Nijdam, A. J.; Luo, C.; Schneider, T. W.; White, R. C.; Currie, J. F.; Paranjape, M.

    2004-05-01

    A dry release method using a thin Teflon™ layer for SU-8 multilayered polymeric microstructures is presented. The low surface energy of Teflon makes the adhesion of SU-8 and substrate poor, enabling the SU-8 polymer photoresist to be removed after the devices have been fully processed. The surface energy was measured using the open-crack method, and the surface roughness and deformation of the released SU-8 were minimized in our processing. The dry release technique eliminates the diffusion limited problem in wet etching and is suitable to package complex three-dimensional polymer microfluidic devices. One such example, which provided the original impetus to formulate a dry release process, is a multilayered SU-8 structure that encapsulates small quantities of fluid. This device is being developed for a biomedical application, and will be used throughout this article as an example of a complex SU-8 structure that uses the dry release process. .

  19. Structure of the surface layer of the methanogenic archaean Methanosarcina acetivorans

    SciTech Connect

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

    2012-09-05

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

  20. Structure of the surface layer of the methanogenic archaean Methanosarcina acetivorans.

    PubMed

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

    2012-07-17

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

  1. The structural origin of metabolic quantitative diversity

    PubMed Central

    Koshiba, Seizo; Motoike, Ikuko; Kojima, Kaname; Hasegawa, Takanori; Shirota, Matsuyuki; Saito, Tomo; Saigusa, Daisuke; Danjoh, Inaho; Katsuoka, Fumiki; Ogishima, Soichi; Kawai, Yosuke; Yamaguchi-Kabata, Yumi; Sakurai, Miyuki; Hirano, Sachiko; Nakata, Junichi; Motohashi, Hozumi; Hozawa, Atsushi; Kuriyama, Shinichi; Minegishi, Naoko; Nagasaki, Masao; Takai-Igarashi, Takako; Fuse, Nobuo; Kiyomoto, Hideyasu; Sugawara, Junichi; Suzuki, Yoichi; Kure, Shigeo; Yaegashi, Nobuo; Tanabe, Osamu; Kinoshita, Kengo; Yasuda, Jun; Yamamoto, Masayuki

    2016-01-01

    Relationship between structural variants of enzymes and metabolic phenotypes in human population was investigated based on the association study of metabolite quantitative traits with whole genome sequence data for 512 individuals from a population cohort. We identified five significant associations between metabolites and non-synonymous variants. Four of these non-synonymous variants are located in enzymes involved in metabolic disorders, and structural analyses of these moderate non-synonymous variants demonstrate that they are located in peripheral regions of the catalytic sites or related regulatory domains. In contrast, two individuals with larger changes of metabolite levels were also identified, and these individuals retained rare variants, which caused non-synonymous variants located near the catalytic site. These results are the first demonstrations that variant frequency, structural location, and effect for phenotype correlate with each other in human population, and imply that metabolic individuality and susceptibility for diseases may be elicited from the moderate variants and much more deleterious but rare variants. PMID:27528366

  2. Structure and morphology of submarine slab slides: clues to origin and behavior

    USGS Publications Warehouse

    O'Leary, D. W.

    1991-01-01

    Geologic features suggest that some slab slides probably result from long-term strength degradation of weak layers deep in the homoclinal section. Time-dependent strain in clay-rich layers can create potential slide surfaces of low frictional strength. Competent layers are weak in tension and probably fragment in the first instance of, or even prior to, translation, and the allochthonous mass is readily transformed into a high-momentum debris flow. The structure and geomorphology of slab slides provide important clues to their origin and behavior. -from Author

  3. Milia may originate from the outermost layers of the hair bulge of the outer root sheath: A case report

    PubMed Central

    Kurokawa, Ichiro; Kakuno, Ayako; Tsubura, Airo

    2016-01-01

    It has been hypothesized that milia originate from the hair bulge of the outer root sheath. To elucidate the histogenesis of milia, an immunohistochemical study was performed using anti-keratin and anti-filaggrin antibodies to determine the levels of keratin and filaggrin expression. Keratin expression was evaluated using anti-keratin antibodies against K1, K7, K8, K10, K14, K15, K16, K17, K18, K19 and K20. K1 and K10 expression were detected in the suprabasal layers of the more superficial section of the cyst walls, but not in the deeper section of the cyst walls. However, K14 and K17 were expressed in all layers of the cyst walls. Notably, K15 was expressed in the outermost layer of the deeper section of the cyst walls and hair germ structure, whereas filaggrin was expressed in the superficial layer of the more superficial section of the cyst walls. Therefore, the pattern of keratin and filaggrin expression indicates that milia may originate from the outermost cells of the hair bulge of the outer root sheath. PMID:28105227

  4. Structure and dynamics of electrical double layers in organic electrolytes

    SciTech Connect

    Huang, Jingsong; Sumpter, Bobby G; Meunier, Vincent; Qiao, Rui; Feng, Guang

    2010-01-01

    The organic electrolyte of tetraethylammonium tetrafluoroborate (TEABF{sub 4}) in the aprotic solvent of acetonitrile (ACN) is widely used in electrochemical systems such as electrochemical capacitors. In this paper, we examine the solvation of TEA{sup +} and BF{sub 4}{sup -} in ACN, and the structure, capacitance, and dynamics of the electrical double layers (EDLs) in the TEABF{sub 4}-ACN electrolyte using molecular dynamics simulations complemented with quantum density functional theory calculations. The solvation of TEA+ and BF4- ions is found to be much weaker than that of small inorganic ions in aqueous solutions, and the ACN molecules in the solvation shell of both types of ions show only weak packing and orientational ordering. These solvation characteristics are caused by the large size, charge delocalization, and irregular shape (in the case of TEA+ cation) of the ions. Near neutral electrodes, the double-layer structure in the organic electrolyte exhibits a rich organization: the solvent shows strong layering and orientational ordering, ions are significantly contact-adsorbed on the electrode, and alternating layers of cations/anions penetrate ca. 1.1 nm into the bulk electrolyte. The significant contact adsorption of ions and the alternating layering of cation/anion are new features found for EDLs in organic electrolytes. These features essentially originate from the fact that van der Waals interactions between organic ions and the electrode are strong and the partial desolvation of these ions occurs easily, as a result of the large size of the organic ions. Near charged electrodes, distinct counter-ion concentration peaks form, and the ion distribution cannot be described by the Helmholtz model or the Helmholtz + Poisson-Boltzmann model. This is because the number of counter-ions adsorbed on the electrode exceeds the number of electrons on the electrode, and the electrode is over-screened in parts of the EDL. The computed capacitances of the EDLs are in

  5. Structure and dynamics of electrical double layers in organic electrolytes.

    PubMed

    Feng, Guang; Huang, Jingsong; Sumpter, Bobby G; Meunier, Vincent; Qiao, Rui

    2010-01-01

    The organic electrolyte of tetraethylammonium tetrafluoroborate (TEABF(4)) in the aprotic solvent of acetonitrile (ACN) is widely used in electrochemical systems such as electrochemical capacitors. In this paper, we examine the solvation of TEA(+) and BF(4)(-) in ACN, and the structure, capacitance, and dynamics of the electrical double layers (EDLs) in the TEABF(4-)ACN electrolyte using molecular dynamics simulations complemented with quantum density functional theory calculations. The solvation of TEA(+) and BF(4)(-) ions is found to be much weaker than that of small inorganic ions in aqueous solutions, and the ACN molecules in the solvation shell of both types of ions show only weak packing and orientational ordering. These solvation characteristics are caused by the large size, charge delocalization, and irregular shape (in the case of TEA(+) cation) of the ions. Near neutral electrodes, the double-layer structure in the organic electrolyte exhibits a rich organization: the solvent shows strong layering and orientational ordering, ions are significantly contact-adsorbed on the electrode, and alternating layers of cations/anions penetrate ca. 1.1 nm into the bulk electrolyte. The significant contact adsorption of ions and the alternating layering of cation/anion are new features found for EDLs in organic electrolytes. These features essentially originate from the fact that van der Waals interactions between organic ions and the electrode are strong and the partial desolvation of these ions occurs easily, as a result of the large size of the organic ions. Near charged electrodes, distinct counter-ion concentration peaks form, and the ion distribution cannot be described by the Helmholtz model or the Helmholtz + Poisson-Boltzmann model. This is because the number of counter-ions adsorbed on the electrode exceeds the number of electrons on the electrode, and the electrode is over-screened in parts of the EDL. The computed capacitances of the EDLs are in good

  6. Boron-Based Layered Structures for Energy Storage

    SciTech Connect

    Zhao, Y.; Wei, S. H.

    2012-01-01

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

  7. 2-DE combined with two-layer feature selection accurately establishes the origin of oolong tea.

    PubMed

    Chien, Han-Ju; Chu, Yen-Wei; Chen, Chi-Wei; Juang, Yu-Min; Chien, Min-Wei; Liu, Chih-Wei; Wu, Chia-Chang; Tzen, Jason T C; Lai, Chien-Chen

    2016-11-15

    Taiwan is known for its high quality oolong tea. Because of high consumer demand, some tea manufactures mix lower quality leaves with genuine Taiwan oolong tea in order to increase profits. Robust scientific methods are, therefore, needed to verify the origin and quality of tea leaves. In this study, we investigated whether two-dimensional gel electrophoresis (2-DE) and nanoscale liquid chromatography/tandem mass spectroscopy (nano-LC/MS/MS) coupled with a two-layer feature selection mechanism comprising information gain attribute evaluation (IGAE) and support vector machine feature selection (SVM-FS) are useful in identifying characteristic proteins that can be used as markers of the original source of oolong tea. Samples in this study included oolong tea leaves from 23 different sources. We found that our method had an accuracy of 95.5% in correctly identifying the origin of the leaves. Overall, our method is a novel approach for determining the origin of oolong tea leaves.

  8. Structural Origins of Martian Pit Chains

    NASA Astrophysics Data System (ADS)

    Wyrick, D.; Ferrill, D. A.; Morris, A. P.; Colton, S. L.; Sims, D. W.

    2003-12-01

    Pit craters are circular to elliptical depressions found in alignments (chains), which in many cases coalesce into linear troughs, and are common on the surface of Mars. Pit craters lack an elevated rim, ejecta deposits, or lava flows that are associated with impact craters or calderas. It is generally agreed that these features are formed by collapse into a subsurface cavity. Hypotheses regarding the formation of pit crater chains require development of a substantial subsurface void to accommodate collapse of the overlying sediments. Suggested mechanisms of formation include: collapsed lava tubes, dike swarms, collapsed magma chamber, karst dissolution, fissuring beneath loose material, and dilational faulting. The research described here is intended to constrain current interpretations of pit crater chain formation by analyzing their distribution and morphology. The western hemisphere of Mars was systematically mapped using Mars Orbiter Camera (MOC) images to generate ArcView Geographic Information System (GIS) coverages. All visible pit crater chains were mapped, including their orientations and associations with other structures. We found that pit chains commonly occur in areas that show regional extension or local fissuring. There is a strong correlation between pit chains and fault-bounded grabens. Frequently, there are transitions along strike from (i) visible faulting to (ii) faults and pits to (iii) pits alone. We performed a detailed quantitative analysis of pit crater morphology using MOC narrow angle images, Thermal Emission Imaging System (THEMIS) visual images and Mars Orbiter Laser Altimeter (MOLA) data. This allowed us to interpret a pattern of pit chain evolution and calculate pit depth, slope, and volume. The information collected in the study was then compared with non-Martian examples of pit chains and physical analog models. We evaluated the various mechanisms for pit chain development based on the data collected and conclude that dilational

  9. 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

  10. Preservation of Archaeal Surface Layer Structure During Mineralization

    NASA Astrophysics Data System (ADS)

    Kish, Adrienne; Miot, Jennyfer; Lombard, Carine; Guigner, Jean-Michel; Bernard, Sylvain; Zirah, Séverine; Guyot, François

    2016-05-01

    Proteinaceous surface layers (S-layers) are highly ordered, crystalline structures commonly found in prokaryotic cell envelopes that augment their structural stability and modify interactions with metals in the environment. While mineral formation associated with S-layers has previously been noted, the mechanisms were unconstrained. Using Sulfolobus acidocaldarius a hyperthermophilic archaeon native to metal-enriched environments and possessing a cell envelope composed only of a S-layer and a lipid cell membrane, we describe a passive process of iron phosphate nucleation and growth within the S-layer of cells and cell-free S-layer “ghosts” during incubation in a Fe-rich medium, independently of metabolic activity. This process followed five steps: (1) initial formation of mineral patches associated with S-layer; (2) patch expansion; (3) patch connection; (4) formation of a continuous mineral encrusted layer at the cell surface; (5) early stages of S-layer fossilization via growth of the extracellular mineralized layer and the mineralization of cytosolic face of the cell membrane. At more advanced stages of encrustation, encrusted outer membrane vesicles are formed, likely in an attempt to remove damaged S-layer proteins. The S-layer structure remains strikingly well preserved even upon the final step of encrustation, offering potential biosignatures to be looked for in the fossil record.

  11. Preservation of Archaeal Surface Layer Structure During Mineralization

    PubMed Central

    Kish, Adrienne; Miot, Jennyfer; Lombard, Carine; Guigner, Jean-Michel; Bernard, Sylvain; Zirah, Séverine; Guyot, François

    2016-01-01

    Proteinaceous surface layers (S-layers) are highly ordered, crystalline structures commonly found in prokaryotic cell envelopes that augment their structural stability and modify interactions with metals in the environment. While mineral formation associated with S-layers has previously been noted, the mechanisms were unconstrained. Using Sulfolobus acidocaldarius a hyperthermophilic archaeon native to metal-enriched environments and possessing a cell envelope composed only of a S-layer and a lipid cell membrane, we describe a passive process of iron phosphate nucleation and growth within the S-layer of cells and cell-free S-layer “ghosts” during incubation in a Fe-rich medium, independently of metabolic activity. This process followed five steps: (1) initial formation of mineral patches associated with S-layer; (2) patch expansion; (3) patch connection; (4) formation of a continuous mineral encrusted layer at the cell surface; (5) early stages of S-layer fossilization via growth of the extracellular mineralized layer and the mineralization of cytosolic face of the cell membrane. At more advanced stages of encrustation, encrusted outer membrane vesicles are formed, likely in an attempt to remove damaged S-layer proteins. The S-layer structure remains strikingly well preserved even upon the final step of encrustation, offering potential biosignatures to be looked for in the fossil record. PMID:27221593

  12. Doubly slanted layer structures in holographic gelatin emulsions: solar concentrators

    NASA Astrophysics Data System (ADS)

    Hung, Jenny; Chan, Po Shan; Sun, Caiming; Wing Ho, Choi; Tam, Wing Yim

    2010-04-01

    We have fabricated doubly slanted layer structures in holographic gelatin emulsions using a double-exposure two-beam interference from two light sources with different wavelengths. The doubly slanted layers, with different spacings and overlapping with each other, are fabricated such that they are slanted in opposite directions making a 30° angle with the holographic plate. The doubly slanted layer structures exhibit photonic stop bands corresponding to the two layered structures. More importantly, diffracted light beams from the slanted layers travel in different directions and emerge, through internal reflections, at the opposite edges of the gelatin plate. The doubly slanted layer structures could be used as solar concentrators such that sunlight is separated into different components and steered directly to photovoltaics with the corresponding wavelength sensitivities to enhance energy conversion efficiency.

  13. Shear-layer structures in near-wall turbulence

    NASA Technical Reports Server (NTRS)

    Johansson, A. V.; Alfredsson, P. H.; Kim, J.

    1987-01-01

    The structure of internal shear layer observed in the near-wall region of turbulent flows is investigated by analyzing flow fields obtained from numerical simulations of channel and boundary-layer flows. It is found that the shear layer is an important contributor to the turbulence production. The conditionally averaged production at the center of the structure was almost twice as large as the long-time mean value. The shear-layer structure is also found to retain its coherence over streamwise distances on the order of a thousand viscous length units, and propagates with a constant velocity of about 10.6 u sub rho throughout the near wall region.

  14. Experimentally excellent beaming in a two-layer dielectric structure

    DOE PAGES

    Tasolamprou, Anna C.; Zhang, Lei; Kafesaki, Maria; ...

    2014-09-15

    We demonstrate both experimentally and theoretically that a two-layer dielectric structure can provide collimation and enhanced transmission of a Gaussian beam passing through it. This is due to formation of surface localized states along the layered structure and the coupling of these states to outgoing propagating waves. As a result, a system of multiple cascading two-layers can sustain the beaming for large propagation distances.

  15. Topologic connection between 2-D layered structures and 3-D diamond structures for conventional semiconductors

    PubMed Central

    Wang, Jianwei; Zhang, Yong

    2016-01-01

    When coming to identify new 2D materials, our intuition would suggest us to look from layered instead of 3D materials. However, since graphite can be hypothetically derived from diamond by stretching it along its [111] axis, many 3D materials can also potentially be explored as new candidates for 2D materials. Using a density functional theory, we perform a systematic study over the common Group IV, III–V, and II–VI semiconductors along different deformation paths to reveal new structures that are topologically connected to but distinctly different from the 3D parent structure. Specifically, we explore two major phase transition paths, originating respectively from wurtzite and NiAs structure, by applying compressive and tensile strain along the symmetry axis, and calculating the total energy changes to search for potential metastable states, as well as phonon spectra to examine the structural stability. Each path is found to further split into two branches under tensile strain–low buckled and high buckled structures, which respectively lead to a low and high buckled monolayer structure. Most promising new layered or planar structures identified include BeO, GaN, and ZnO on the tensile strain side, Ge, Si, and GaP on the compressive strain side. PMID:27090430

  16. Electroluminescent apparatus having a structured luminescence conversion layer

    DOEpatents

    Krummacher, Benjamin Claus

    2008-09-02

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

  17. 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.

  18. 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.

  19. 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 β -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 β -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.

  20. Failure modes and materials design for biomechanical layer structures

    NASA Astrophysics Data System (ADS)

    Deng, Yan

    Ceramic materials are finding increasing usage in the area of biomechanical replacements---dental crowns, hip and bone implants, etc.---where strength, wear resistance, biocompatibility, chemical durability and even aesthetics are critical issues. Aesthetic ceramic crowns have been widely used in dentistry to replace damaged or missing teeth. However, the failure rates of ceramic crowns, especially all-ceramic crowns, can be 1%˜6% per year, which is not satisfactory to patients. The materials limitations and underlying fracture mechanisms of these prostheses are not well understood. In this thesis, fundamental fracture and damage mechanisms in model dental bilayer and trilayer structures are studied. Principle failure modes are identified from in situ experimentation and confirmed by fracture mechanics analysis. In bilayer structures of ceramic/polycarbonate (representative of ceramic crown/dentin structure), three major damage sources are identified: (i) top-surface cone cracks or (ii) quasiplasticity, dominating in thick ceramic bilayers; (iii) bottom-surface radial cracks, dominating in thin ceramic bilayers. Critical load P for each damage mode are measured in six dental ceramics: Y-TZP zirconia, glass-infiltrated zirconia and alumina (InCeram), glass-ceramic (Empress II), Porcelain (Mark II and Empress) bonded to polymer substrates, as a function of ceramic thickness d in the range of 100 mum to 10 mm. P is found independent of d for mode (i) and (ii), but has a d 2 relations for mode (iii)---bottom surface radial cracking. In trilayer structures of glass/core-ceramic/polycarbonate (representing veneer porcelain/core/dentin structures), three inner fracture origins are identified: radial cracks from the bottom surface in the (i) first and (ii) second layers; and (iii) quasiplasticity in core-ceramic layer. The role of relative veneer/core thickness, d1/d 2 and materials properties is investigated for three core materials with different modulus (114--270GPa

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

    NASA Technical Reports Server (NTRS)

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

    1982-01-01

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

  2. 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.

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

    SciTech Connect

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

    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.

  5. Magnetism in structures with ferromagnetic and superconducting layers

    NASA Astrophysics Data System (ADS)

    Zhaketov, V. D.; Nikitenko, Yu. V.; Radu, F.; Petrenko, A. V.; Csik, A.; Borisov, M. M.; Mukhamedzhanov, E. Kh.; Aksenov, V. L.

    2017-01-01

    The influence of superconductivity on ferromagnetism in the layered Ta/V/Fe1- x V x /V/Fe1- x V x /Nb/Si structures consisting of ferromagnetic and superconducting layers is studied using polarized neutron reflection and scattering. It is experimentally shown that magnetic structures with linear sizes from 5 nm to 30 μm are formed in these layered structures at low temperatures. The magnetization of the magnetic structures is suppressed by superconductivity at temperatures below the superconducting transition temperatures in the V and Nb layers. The magnetic states of the structures are shown to undergo relaxation over a wide magnetic-field range, which is caused by changes in the states of clusters, domains, and Abrikosov vortices.

  6. 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

  7. Chasma Australe Mars: Structural Framework for a Catastrophic Outflow Origin

    NASA Technical Reports Server (NTRS)

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

    1998-01-01

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

  8. 52. Humbug Creek Diversion Dam showing original masonry structure at ...

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

    52. Humbug Creek Diversion Dam showing original masonry structure at right and concrete weir at left added later. Photographer James Eastwood, 1986. Source: Salt River Project. - Waddell Dam, On Agua Fria River, 35 miles northwest of Phoenix, Phoenix, Maricopa County, AZ

  9. 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.

  10. 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.

  11. Cocured damped layers in composite structure

    SciTech Connect

    Rotz, C.A. ); Barrett, D.J. )

    1992-01-01

    A study was made on the feasibility of laminating and cocuring graphite fiber-epoxy prepreg with plies of commercially available damping materials for form beams and hat-stiffened panels. Experiments showed that cocuring did not adversely affect the damping materials and that excellent structural damping properties could be obtained. The construction of the hat-stiffened panels proved that complex parts containing damping materials could be fabricated. Dynamic testing of these components showed that internal architectural features could be designed to promote damping in primary structure.

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

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

    Since the first photogeologic exploration of Mars, vast mounds of layered sediments found within the Valles Marineris canyon system (Interior Layered Deposits or ILDs) have remained unexplained. Recent spectroscopic results showing that these materials contain coarse-grained hematite [1] and sulfate [2-8] suggest that they are fundamentally similar to layered sulfate deposits seen elsewhere on Mars [3], and are therefore a key piece of Mars' global aqueous history. Layered sulfate deposits (including ILDs) are often considered to have formed in association with transient, wet surface environments caused by groundwater upwelling [9] in the Hesperian. Here, we use spectroscopic mapping along with geomorphic observations and mass balance calculations to demonstrate that the sulfate-bearing ILDs likely did not form due to groundwater upwelling or any similar playa-lacustrine scenario. Instead, the ILDs likely formed from atmospherically driven processes in a configuration similar to that observed today. We suggest that Hesperian layered sulfate deposits formed in response to massive amounts of pyroclastic volcanism and SO2-outgassing that peaked near 3.5-3.7 Ga in a Martian climate that was largely cold and dry. This origin for the ILDs is also applicable to other layered terrain of similar age and characteristics, including sulphate-bearing crater fill, chaos terrains, and the Meridiani Planum sediments. [1] Weitz, C. M., Lane, M. D., Staid, M. & Dobrea, E. N. Gray hematite distribution and formation in Ophir and Candor chasmata. Journal of Geophysical Research-Planets 113, doi:E02016 10.1029/2007je002930 (2008). [2] Wendt, L. et al. Sulfates and iron oxides in Ophir Chasma, Mars, based on OMEGA and CRISM observations. Icarus 213, 86-103, doi:10.1016/j.icarus.2011.02.013 (2011). [3] Murchie, S. et al. Evidence for the origin of layered deposits in Candor Chasma, Mars, from mineral composition and hydrologic modeling. Journal of Geophysical Research-Planets 114, doi

  13. Measurements of the streamwise vortical structures in a plane mixing layer

    NASA Technical Reports Server (NTRS)

    Bell, James H.; Mehta, Rabindra D.

    1992-01-01

    The 3D structure of a plane two-stream mixing layer of velocity ratio 0.6 and originating from laminar initial boundary layers was investigated through direct measurements made in a specially constructed mixing-layer wind tunnel. The main objective of the study was to establish quantitatively the presence and the role of the secondary streamwise vortex structure (of the kind that has been shown in past flow visualization investigations to ride among the primary spanwise vortices) in the development of a plane turbulent mixing layer at relatively high Reynolds numbers. Results indicate that the instability leading to the formation of streamwise vortices is initially amplified just downstream of the first spanwise roll-up. The streamwise vortices, which first appear in clusters containing vorticity of both signs, realign further downstream to form counterrotating pairs. Due to the amalgamation of like-sign vortices, the streamwise vortex spacing increases in a stepwise fashion.

  14. Structure and composition of the septal nacreous layer of Nautilus macromphalus L. (Mollusca, Cephalopoda).

    PubMed

    Dauphin, Yannicke

    2006-01-01

    The nacreous layer of Mollusca is the best-known aragonitic structure and is the usual model for biomineralization. However, data are based on less than 10 species. In situ observations of the septal nacreous layer of the cephalopod Nautilus shell has revealed that the tablets are composed of acicular laths. These laths are composed of round nanograins surrounded by an organic sheet. No hole has been observed in the decalcified interlamellar membranes. A set of combined analytical data shows that the organic matrices extracted from the nacreous layer are glycoproteins. In both soluble and insoluble matrices, S amino acids are rare and the soluble organic matrices have a higher sulfated sugar content than the insoluble matrices. It is possible that the observed differences in the structure and composition of the nacreous layers of the outer wall and septa of the Nautilus shell have a dual origin: evolution and functional adaptation. However, we have no appropriate data as yet to answer this question.

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

    DOEpatents

    Murduck, James M.; Lepetre, Yves J.; Schuller, Ivan K.; Ketterson, John B.

    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.

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

    DOEpatents

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

    1989-07-04

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

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

    NASA Astrophysics Data System (ADS)

    Athanassoula, E.

    2015-03-01

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

  18. Structure and properties of ITQ-8: a hydrous layer silicate with microporous silicate layers.

    PubMed

    Marler, Bernd; Müller, Melanie; Gies, Hermann

    2016-06-21

    ITQ-8 is a new hydrous layer silicate (HLS) with a chemical composition of [C4H8(C7H13N)2]8 [Si64O128(OH)16]·48H2O per unit cell. The synthesis of ITQ-8 was first described in 2002 by Díaz-Cabañas et al., the structure of this material, however, remained unsolved at that time. Physico-chemical characterization using solid-state NMR spectroscopy, SEM, TG-DTA, and FTIR spectroscopy confirmed that ITQ-8 is a layer silicate. The XRD powder pattern was indexed in the monoclinic system with lattice parameters of a0 = 35.5168(5) Å, b0 = 13.3989(2) Å, c0 = 16.0351(2) Å, β = 106.74(2)°. The crystal structure was solved by simulated annealing. Rietveld refinement of the structure in space group C2/c converged to residual values of RBragg = 0.023, RF = 0.022 and chi(2) = 2.3 confirming the structure model. The structure of ITQ-8 contains silicate layers with a topology that resembles a (11-1) section of the framework of zeolite levyne. So far, this layer topology is unique among layer silicates. The layer can be regarded as made up of 4-, 6-, double-six and 8-rings which are interconnected to form cup-like "half-cages". Unlike other HLSs, which possess impermeable silicate layers, ITQ-8 contains 8-rings pores with a free diameter of 3.5 Å × 3.4 Å and can be regarded as a "small-pore layer silicate". In the crystal structure, the organic cations, 1,4-diquiniclidiniumbutane, used as structure directing agents during synthesis are intercalated between the silicate layers. Clusters (bands) of water molecules which are hydrogen bonded to each other and to the terminal Si-OH/Si-O(-) groups are located between the organic cations and interconnect the silicate layers. ITQ-8 is a very interesting material as precursor for the synthesis of microporous framework silicates by topotactic condensation or interlayer expansion reactions leading to 3D micro-pore systems which may be useful in applications as e.g. catalysts, catalyst supports and adsorbents of for separation.

  19. Manipulation by exchange coupling in layered magnetic structures

    SciTech Connect

    Moskalenko, M. A.; Uzdin, V. M.; Zabel, H.

    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.

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

    NASA Astrophysics Data System (ADS)

    Batys, Piotr; Nosek, Magdalena; Weroński, Paweł

    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.

  1. Two-Dimensional Layered Oxide Structures Tailored by Self-Assembled Layer Stacking via Interfacial Strain

    DOE PAGES

    Zhang, Wenrui; Li, Mingtao; Chen, Aiping; ...

    2016-06-13

    Two-dimensional (2D) nanostructures emerge as one of leading topics in fundamental materials science and could enable next generation nanoelectronic devices. Beyond graphene and molybdenum disulphide, layered complex oxides are another large group of promising 2D candidates because of their strong interplay of intrinsic charge, spin, orbital and lattice. As a fundamental basis of heteroepitaxial thin film growth, interfacial strain can be used to design materials exhibiting new phenomena beyond their conventional form. Here we report the strain-driven self-assembly of Bismuth-based supercells (SC) with a 2D layered structure, and elucidate the fundamental growth mechanism with combined experimental tools and first-principles calculations.more » The study revealed that the new layered structures were formed by the strain-enabled self-assembled atomic layer stacking, i.e., alternative growth of Bi2O2 layer and [Fe0.5Mn0.5]O6 layer. The strain-driven approach is further demonstrated in other SC candidate systems with promising room-temperature multiferroic properties. This well-integrated theoretical and experimental study inspired by the Materials Genome Initiatives opens up a new avenue in searching and designing novel 2D layered complex oxides with enormous promises.« less

  2. Two-Dimensional Layered Oxide Structures Tailored by Self-Assembled Layer Stacking via Interfacial Strain

    SciTech Connect

    Zhang, Wenrui; Li, Mingtao; Chen, Aiping; Li, Leigang; Zhu, Yuanyuan; Xia, Zhenhai; Lu, Ping; Boullay, Philippe; Wu, Lijun; Zhu, Yimei; MacManus-Driscoll, Judith L.; Jia, Quanxi; Zhou, Honghui; Narayan, Jagdish; Zhang, Xinghang; Wang, Haiyan

    2016-06-13

    Two-dimensional (2D) nanostructures emerge as one of leading topics in fundamental materials science and could enable next generation nanoelectronic devices. Beyond graphene and molybdenum disulphide, layered complex oxides are another large group of promising 2D candidates because of their strong interplay of intrinsic charge, spin, orbital and lattice. As a fundamental basis of heteroepitaxial thin film growth, interfacial strain can be used to design materials exhibiting new phenomena beyond their conventional form. Here we report the strain-driven self-assembly of Bismuth-based supercells (SC) with a 2D layered structure, and elucidate the fundamental growth mechanism with combined experimental tools and first-principles calculations. The study revealed that the new layered structures were formed by the strain-enabled self-assembled atomic layer stacking, i.e., alternative growth of Bi2O2 layer and [Fe0.5Mn0.5]O6 layer. The strain-driven approach is further demonstrated in other SC candidate systems with promising room-temperature multiferroic properties. This well-integrated theoretical and experimental study inspired by the Materials Genome Initiatives opens up a new avenue in searching and designing novel 2D layered complex oxides with enormous promises.

  3. 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

  4. Perturbation of the Heat Lateral Diffusion by Interface Resistance in Layered Structures

    NASA Astrophysics Data System (ADS)

    Frétigny, C.; Duquesne, J.-Y.; Fournier, D.

    2015-06-01

    It is well established that interface resistances do usually exist in layered structures, and their values strongly depend on their origin. They may arise from different vibrational properties of the layers, nonharmonic processes at the interface, surface chemical contamination, interfacial defects, etc. Numerous studies have been published to evaluate their values, most of the time, in a perpendicular heat diffusion scheme. In this paper, the effect of interface resistances on the lateral modulated surface temperature of a layered structure for cylindrical symmetry heat diffusion is studied. The thermoreflectance microscope is a particularly convenient tool to record heat lateral diffusion from a surface modulated heated point and thus to evidence the presence of such resistance interfaces. In a first part, the theoretical model of heat diffusion in cylindrical symmetry, in a layered structure exhibiting an interface resistance between the layer and the substrate, is briefly described. In a second part, the C/I configuration (good conductive layer deposited on an insulating substrate, with an interface resistance) is investigated. Experimental results illustrate the theory. In the third part, the reverse case I/C (insulating layer deposited on a conductive substrate, with an interface resistance) is discussed. To conclude, all the cases and the ability of the lateral diffusion to recover interface thermal resistances are compared.

  5. Decoupling a Reflecting Layer From Its Support Structure

    NASA Technical Reports Server (NTRS)

    Bamford, R. M.

    1984-01-01

    Mounting decouples thermal distortions of reflective surface so not transmitted to support structure. Reflecting layer consists of aluminum reflecting tiles attached to support structure by flexural mounting bend and twist to accommodate thermal expansion of tiles. Technique useful in microwave-antenna reflectors.

  6. Prediction of silicon-based layered structures for optoelectronic applications.

    PubMed

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

    2014-11-12

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

  7. Two-Dimensional Layered Oxide Structures Tailored by Self-Assembled Layer Stacking via Interfacial Strain.

    PubMed

    Zhang, Wenrui; Li, Mingtao; Chen, Aiping; Li, Leigang; Zhu, Yuanyuan; Xia, Zhenhai; Lu, Ping; Boullay, Philippe; Wu, Lijun; Zhu, Yimei; MacManus-Driscoll, Judith L; Jia, Quanxi; Zhou, Honghui; Narayan, Jagdish; Zhang, Xinghang; Wang, Haiyan

    2016-07-06

    Study of layered complex oxides emerge as one of leading topics in fundamental materials science because of the strong interplay among intrinsic charge, spin, orbital, and lattice. As a fundamental basis of heteroepitaxial thin film growth, interfacial strain can be used to design materials that exhibit new phenomena beyond their conventional forms. Here, we report a strain-driven self-assembly of bismuth-based supercell (SC) with a two-dimensional (2D) layered structure. With combined experimental analysis and first-principles calculations, we investigated the full SC structure and elucidated the fundamental growth mechanism achieved by the strain-enabled self-assembled atomic layer stacking. The unique SC structure exhibits room-temperature ferroelectricity, enhanced magnetic responses, and a distinct optical bandgap from the conventional double perovskite structure. This study reveals the important role of interfacial strain modulation and atomic rearrangement in self-assembling a layered singe-phase multiferroic thin film, which opens up a promising avenue in the search for and design of novel 2D layered complex oxides with enormous promise.

  8. Multiple maternal origins and weak phylogeographic structure in domestic goats

    PubMed Central

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

    2001-01-01

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

  9. Cloud Creek structure, central Wyoming, USA: Impact origin confirmed

    NASA Astrophysics Data System (ADS)

    Stone, D. S.; Therriault, A. M.

    2003-03-01

    The circular Cloud Creek structure in central Wyoming, USA is buried beneath ~1200 m of Mesozoic sedimentary rocks and has a current diameter of ~7 km. The morphology/morphometry of the structure, as defined by borehole, seismic, and gravity data, is similar to that of other buried terrestrial complex impact structures in sedimentary target rocks, e.g., Red Wing Creek in North Dakota, USA. The structure has a fault-bordered central peak with minimum diameter of ~1.4 km, composed predominantly of Paleozoic carbonates thickened by thrust faulting and brecciation, and is elevated some 520 m above equivalent strata beyond the outer rim of the structure. There is a ~1.6 km wide annular trough sloping away from the central peak (maximum structural relief, 300 m) and terminated by a detached, fault-bounded, rim anticline. The youngest rocks within the structure are Late Triassic (Norian?) clastics and these are overlain unconformably by post-impact Middle Jurassic (Bathonian?) sandstones and shales. Thus, the formation of the Cloud Creek structure is dated chronostratigraphicly as ~190 ± 20 Ma. Reported here for the first time are measurements of planar deformation features (PDFs) in shocked quartz grains in thin sections made from drill cuttings recovered in a borehole drilled at the southern perimeter of the central peak. Other, less definitive microstructures consistent with impact occur in samples collected from boreholes drilled into the central peak and rim anticline. The shock- metamorphic evidence confirms an impact origin for the Cloud Creek structure.

  10. Structural origin of magnetic birefringence in rutile-type antiferromagnets

    NASA Astrophysics Data System (ADS)

    Jauch, W.

    1991-10-01

    The microscopic origin of magnetic birefringence in the rutile-type antiferromagnets XF2 (X=Mn, Fe, Co, or Ni) is analyzed on the basis of the theory of structural birefringence developed by Ewald and Born. The general principles of the Ewald-Born theory are reviewed. The magnetic birefringence can be explained by a small exchange-induced internal displacement of the fluorine atoms. Predictions from theory are compared with accurate crystal-structure analyses based on γ-ray-diffraction data. The agreement found between theory and experiment is excellent.

  11. 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.

  12. Turbulence structures in a strongly decelerated boundary layer

    NASA Astrophysics Data System (ADS)

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

    2014-11-01

    The characteristics of three-dimensional intense Reynolds shear stress structures (Qs) are presented from a direct numerical simulation of an adverse pressure gradient boundary layer at Reθ = 1500 -2175. The intense Q2 (ejections) and Q4 (sweeps) structures separate into two groups: wall-attached and wall-detached structures. In the region where turbulent activity is maximal, between 0 . 2 δ and 0 . 6 δ , 94 % of the structures are detached structures. In comparison to canonical wall flows, the large velocity defect turbulent boundary layers are less efficient in extracting turbulent energy from the mean flow. There is, furthermore, much less turbulence activity and less velocity coherence near the wall. Additionally, the wall-detached structures are more frequent and carry a much larger amount of Reynolds shear stress. Funded in part by ITU, NSERC of Canada, and Multiflow program of the ERC.

  13. 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.

  14. S-layers as patterning structures and supporting layers for biomimetic membranes

    NASA Astrophysics Data System (ADS)

    Pum, Dietmar; Wetzer, Barbara; Schuster, Bernhard; Sleytr, Uwe B.

    1997-03-01

    A new approach in nanostructure technology particularly in the functionalization of surfaces has been developed on the basis of crystalline bacterial cell surface layers (S- layers). S-layers are composed of monomolecular arrays of identical (glyco)proteins showing high molecular order, defined mass distribution and isoporosity, and a high binding capacity for functional macromolecules. The possibility for recrystallizing isolated S-layer subunits into large isoporous, coherent lattices at solid supports, at the air/water interface or on lipid films and for handling such layers by standard Langmuir-Blodgett techniques opens a broad spectrum of applications in basic and applied membrane research. S-layer supported functional phospholipid bilayers or tetraether lipid films mimic the molecular architecture of those archaebacterial cell envelopes that are exclusively composed of an S-layer and a plasma membrane. This novel concept could lead to new techniques for exploiting large scale structural and functional principles of membrane associated and integrated molecules (e.g. ion channels, proton pumps, receptors).

  15. Lamb waves dispersion curves for diamond based piezoelectric layered structure

    NASA Astrophysics Data System (ADS)

    Sorokin, B. P.; Kvashnin, G. M.; Telichko, A. V.; Novoselov, A. S.; Burkov, S. I.

    2016-03-01

    The presence of spurious peaks in the amplitude-frequency response of diamond based piezoelectric layered structure was shown. Excitation of such peaks results in deterioration of an useful acoustical signal. It was shown that such spurious peaks should be associated with Lamb waves in a layered structure. By means of FEM analysis, the propagation of acoustic waves of different types in the piezoelectric layered structure "Al/AlN/Mo/(100) diamond" has been investigated in detail. By analyzing the elastic displacement patterns at frequencies from 0 up to 250 MHz, a set of all the possible acoustic waves, especially Lamb modes, have been studied, and dispersive curves of phase velocity have been plotted. A revised classification of Lamb modes has been introduced.

  16. 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, β˜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.

  17. Coherent X-ray radiation by relativistic electron in a structure “amorphous layer-vacuum-periodic layered medium”

    NASA Astrophysics Data System (ADS)

    Blazhevich, S. V.; Gladkikh, J. P.; Nemtsev, S. N.; Zagorodnyuk, R. A.; Noskov, A. V.

    2016-07-01

    The dynamic theory of coherent X-ray radiation by relativistic electron crossing a three-layer structure consisting of an amorphous substance layer, a layer of vacuum and a layer with artificial periodic structure has been developed. The process of radiation and propagation of X-ray waves in an artificial periodic structure have been considered based on two-wave approximation of dynamic diffraction theory in Laue scattering geometry.

  18. Structural origin of polymorphism of Alzheimer's amyloid β-fibrils.

    PubMed

    Agopian, Audrey; Guo, Zhefeng

    2012-10-01

    Formation of senile plaques containing amyloid fibrils of Aβ (amyloid β-peptide) is a pathological hallmark of Alzheimer's disease. Unlike globular proteins, which fold into unique structures, the fibrils of Aβ and other amyloid proteins often contain multiple polymorphs. Polymorphism of amyloid fibrils leads to different toxicity in amyloid diseases and may be the basis for prion strains, but the structural origin for fibril polymorphism is still elusive. In the present study we investigate the structural origin of two major fibril polymorphs of Aβ40: an untwisted polymorph formed under agitated conditions and a twisted polymorph formed under quiescent conditions. Using electron paramagnetic resonance spectroscopy, we studied the inter-strand side-chain interactions at 14 spin-labelled positions in the Aβ40 sequence. The results of the present study show that the agitated fibrils have stronger inter-strand spin-spin interactions at most of the residue positions investigated. The two hydrophobic regions at residues 17-20 and 31-36 have the strongest interactions in agitated fibrils. Distance estimates on the basis of the spin exchange frequencies suggest that inter-strand distances at residues 17, 20, 32, 34 and 36 in agitated fibrils are approximately 0.2 Å (1 Å=0.1 nm) closer than in quiescent fibrils. We propose that the strength of inter-strand side-chain interactions determines the degree of β-sheet twist, which then leads to the different association patterns between different cross β-units and thus distinct fibril morphologies. Therefore the inter-strand side-chain interaction may be a structural origin for fibril polymorphism in Aβ and other amyloid proteins.

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

    SciTech Connect

    Forsman, N.F.; Gerlach, T.R.; Anderson, N.L.

    1996-05-01

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

  20. Shock-like structures in the tropical cyclone boundary layer

    NASA Astrophysics Data System (ADS)

    Williams, Gabriel J.; Taft, Richard K.; McNoldy, Brian D.; Schubert, Wayne H.

    2013-06-01

    This paper presents high horizontal resolution solutions of an axisymmetric, constant depth, slab boundary layer model designed to simulate the radial inflow and boundary layer pumping of a hurricane. Shock-like structures of increasing intensity appear for category 1-5 hurricanes. For example, in the category 3 case, the u>(∂u/∂r>) term in the radial equation of motion produces a shock-like structure in the radial wind, i.e., near the radius of maximum tangential wind the boundary layer radial inflow decreases from approximately 22 m s-1 to zero over a radial distance of a few kilometers. Associated with this large convergence is a spike in the radial distribution of boundary layer pumping, with updrafts larger than 22 m s-1 at a height of 1000 m. Based on these model results, it is argued that observed hurricane updrafts of this magnitude so close to the ocean surface are attributable to the dry dynamics of the frictional boundary layer rather than moist convective dynamics. The shock-like structure in the boundary layer radial wind also has important consequences for the evolution of the tangential wind and the vertical component of vorticity. On the inner side of the shock the tangential wind tendency is essentially zero, while on the outer side of the shock the tangential wind tendency is large due to the large radial inflow there. The result is the development of a U-shaped tangential wind profile and the development of a thin region of large vorticity. In many respects, the model solutions resemble the remarkable structures observed in the boundary layer of Hurricane Hugo (1989).

  1. The ferrite/superconductor layered structure for tunable microwave devices

    NASA Astrophysics Data System (ADS)

    Bobyl, A.; Suris, R.; Karmanenko, S.; Semenov, A.; Melkov, A.; Konuhov, S.; Olshevski, A.

    2002-08-01

    The ferrite/superconductor (FS) structure composed from the separate ferrite garnet Y 3Fe 5O 12 epitaxial layers and superconducting films was used for development of such microwave devices as tunable pass-band filter, phase-shifter and delay line. Application of superconducting layer decreases the microwave losses and it provides new functions of magnetostatic waveguide FS structures. The central frequency of band-pass filter is tuned from 1.5 up to 3 GHz; bandwidth can be regulated by the geometry of antenna transducers (from 30 up to 300 MHz); band insertion loss is about 1.5-3 dB.

  2. 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

  3. Electronic origin of high-temperature superconductivity in single-layer FeSe superconductor.

    PubMed

    Liu, Defa; Zhang, Wenhao; Mou, Daixiang; He, Junfeng; Ou, Yun-Bo; Wang, Qing-Yan; Li, Zhi; Wang, Lili; Zhao, Lin; He, Shaolong; Peng, Yingying; Liu, Xu; Chen, Chaoyu; Yu, Li; Liu, Guodong; Dong, Xiaoli; Zhang, Jun; Chen, Chuangtian; Xu, Zuyan; Hu, Jiangping; Chen, Xi; Ma, Xucun; Xue, Qikun; Zhou, X J

    2012-07-03

    The recent discovery of high-temperature superconductivity in iron-based compounds has attracted much attention. How to further increase the superconducting transition temperature (T(c)) and how to understand the superconductivity mechanism are two prominent issues facing the current study of iron-based superconductors. The latest report of high-T(c) superconductivity in a single-layer FeSe is therefore both surprising and significant. Here we present investigations of the electronic structure and superconducting gap of the single-layer FeSe superconductor. Its Fermi surface is distinct from other iron-based superconductors, consisting only of electron-like pockets near the zone corner without indication of any Fermi surface around the zone centre. Nearly isotropic superconducting gap is observed in this strictly two-dimensional system. The temperature dependence of the superconducting gap gives a transition temperature T(c)~ 55 K. These results have established a clear case that such a simple electronic structure is compatible with high-T(c) superconductivity in iron-based superconductors.

  4. Velocity-vorticity correlation structures in compressible turbulent boundary layer

    NASA Astrophysics Data System (ADS)

    Chen, Jun; Li, Shi-Yao; She, Zhen-Su

    2016-11-01

    A velocity-vorticity correlation structure (VVCS) analysis is applied to analyze data of 3-dimensional (3-D) direct numerical simulations (DNS), to investigate the quantitative properties of the most correlated vortex structures in compressible turbulent boundary layer (CTBL) at Mach numbers, Ma = 2 . 25 and 6 . 0 . It is found that the geometry variation of the VVCS closely reflects the streamwise development of CTBL. In laminar region, the VVCS captures the instability wave number of the boundary layer. The transition region displays a distinct scaling change of the dimensions of VVCS. The developed turbulence region is characterized by a constant spatial extension of the VVCS. For various Mach numbers, the maximum correlation coefficient of the VVCS presents a clear multi-layer structure with the same scaling laws as a recent symmetry analysis proposed to quantifying the sublayer, the log-layer, and the wake flow. A surprising discovery is that the wall friction coefficient, Cf, holds a "-1"-power law of the wall normal distance of the VVCS, ys. This validates the speculation that the wall friction is determined by the near-wall coherent structure, which clarifies the correlation between statistical structures and the near-wall dynamics. Project 11452002 and 11172006 supported by National Natural Science Foundation of China.

  5. 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

  6. Layer-stacking effect on electronic structures of bilayer arsenene

    NASA Astrophysics Data System (ADS)

    Mi, Kui; Xie, Jiafeng; Si, M. S.; Gao, C. X.

    2017-01-01

    A monolayer of orthorhombic arsenic (arsenene) is a promising candidate for nano-electronic devices due to the uniquely electronic properties. To further extend its practical applications, an additional layer is introduced to tune the electronic structures. Four layer-stacking manners, namely AA-, AB-, AB‧-, and AC-stacking, are constructed and studied through using first-principles calculations. Compared with monolayer, an indirect-direct gap transition is realized in AB-stacking. More importantly, a semimetal feature appears in the AC- and AB‧-stacked bilayers, leaving the electronic structure of AA-stacking trivial. In addition, the energy dispersion around Γ is largely tuned from the layer-stacking effect. To understand the underlying physics, the \\textbf{k}\\cdot\\textbf{p} approximation is taken to address this issue. Our results show that the level repulsion from the additional layer domaintes the anisotropy of energy dispersion around Γ. The works like ours would shed new light on the tunability of the electronic structure in layered arsenene.

  7. Design of elliptic cylindrical thermal cloak with layered structure

    NASA Astrophysics Data System (ADS)

    Yuan, Xuebo; Lin, Guochang; Wang, Youshan

    2017-01-01

    Thermal cloak has potential applications in thermal protection and sensing. Based on the theories of spatial transformation and effective medium, layered structure of elliptic cylindrical thermal cloak was designed. According to theoretical analysis and numerical simulation, the layered structure has typical characteristics of perfect thermal cloak. The external temperature field remains unchanged, while the internal temperature gradient decreases obviously. Meanwhile, the cloaking effect is stable in any direction. The cloaking effect can be improved by increasing the number of discretization layers or reducing the cloak thickness. The elliptic cylindrical cloak can be considered as cylindrical cloak when the focal distance is close to zero. This study has provided an effective way for realizing thermal cloak with more complex shapes.

  8. Strained layer superlattice focal plane array having a planar structure

    DOEpatents

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

    2012-10-23

    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.

  9. Ternary metal-rich sulfide with a layered structure

    DOEpatents

    Franzen, Hugo F.; Yao, Xiaoqiang

    1993-08-17

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

  10. Structural complexities in the active layers of organic electronics.

    PubMed

    Lee, Stephanie S; Loo, Yueh-Lin

    2010-01-01

    The field of organic electronics has progressed rapidly in recent years. However, understanding the direct structure-function relationships between the morphology in electrically active layers and the performance of devices composed of these materials has proven difficult. The morphology of active layers in organic electronics is inherently complex, with heterogeneities existing across multiple length scales, from subnanometer to micron and millimeter range. A major challenge still facing the organic electronics community is understanding how the morphology across all of the length scales in active layers collectively determines the device performance of organic electronics. In this review we highlight experiments that have contributed to the elucidation of structure-function relationships in organic electronics and also point to areas in which knowledge of such relationships is still lacking. Such knowledge will lead to the ability to select active materials on the basis of their inherent properties for the fabrication of devices with prespecified characteristics.

  11. Stable single-layer structure of group-V elements

    NASA Astrophysics Data System (ADS)

    Ersan, F.; Aktürk, E.; Ciraci, S.

    2016-12-01

    In addition to stable single-layer buckled honeycomb and washboard structures of group-V elements (or pnictogens P, As, Sb, and Bi) we show that these elements can also form two-dimensional, single-layer structures consisting of buckled square and octagon rings. An extensive analysis comprising the calculation of mechanical properties, vibration frequencies, and finite-temperature ab initio molecular dynamics confirms that these structures are dynamically and thermally stable and suitable for applications at room temperature and above. All these structures are semiconductors with a fundamental band gap, which is wide for P but decreases with increasing row number. The effect of the spin-orbit coupling decreases the band gap and is found to be crucial for Sb and Bi. These results are obtained from first-principles calculations based on density functional theory.

  12. Hyperbolic Spirals as Surface Structures in Thin Layers.

    PubMed

    Weh, Lothar

    2001-03-15

    When thin layers of 4-chloro-3-methylphenol and a copolymer of methyl(methacrylate) and maleic acid dissolved in acetone are dried by solvent evaporation, various surface structures appear. Besides linear surface deformations that can ramify like fractals, spirals of the hyperbolic type have been found. The surface structures are due to crystallization processes and flows caused by surface tension differences. The spirals are surface elevations with grooves on both sides as shown by surface profile measurements by means of a microscope interferometer. The addition of surfactants reduces the structure formation. A large surfactant concentration prevents the structure formation. Copyright 2001 Academic Press.

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

    SciTech Connect

    Aeschliman, D.P.; Baty, R.S.; Kennedy, C.A.; Chen, J.H.

    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.

  14. 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".

  15. 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)

  16. Interfacial Atomic Structure of Twisted Few-Layer Graphene.

    PubMed

    Ishikawa, Ryo; Lugg, Nathan R; Inoue, Kazutoshi; Sawada, Hidetaka; Taniguchi, Takashi; Shibata, Naoya; Ikuhara, Yuichi

    2016-02-18

    A twist in bi- or few-layer graphene breaks the local symmetry, introducing a number of intriguing physical properties such as opening new bandgaps. Therefore, determining the twisted atomic structure is critical to understanding and controlling the functional properties of graphene. Combining low-angle annular dark-field electron microscopy with image simulations, we directly determine the atomic structure of twisted few-layer graphene in terms of a moiré superstructure which is parameterized by a single twist angle and lattice constant. This method is shown to be a powerful tool for accurately determining the atomic structure of two-dimensional materials such as graphene, even in the presence of experimental errors. Using coincidence-site-lattice and displacement-shift-complete theories, we show that the in-plane translation state between layers is not a significant structure parameter, explaining why the present method is adequate not only for bilayer graphene but also a few-layered twisted graphene.

  17. Exploring New RF Circuit Structures with Embedded Patterned Substrate Layers

    DTIC Science & Technology

    2013-06-12

    spaced microstrip lines are common in T/R module packages and other high density circuit packages. The work involved creating a method to reduce the...Jan-2013 Approved for Public Release; Distribution Unlimited Final Report: Exploring New RF Circuit Structures with Embedded Patterned Substrate...Report: Exploring New RF Circuit Structures with Embedded Patterned Substrate Layers Report Title This report presents the findings made under the ARO

  18. Morphology and origins of sedimentary structures on submarine slopes.

    PubMed

    Hulsemann, J

    1968-07-05

    Submarine slopes in deep water, such as continental slopes, are often indented by valleys or channels and made uneven by ridges or levees. The origins of many of these features are unknown or disputed. Morphologically, however, there is often great similarity between forms on deep slopes and forms on shallow slopes or on land. Structurally the slopes in deep water are less well explored, but several observations reveal features, such as lamination and crossbedding, that are known from shallow water also. Measurements of current indicate that periodically the movement of water near the bottom is fast enough to move particles of sediment from time to time. Morphology, fine structure, and currents suggest that internal waves and associated currents, as well as gravity, may control the shape of deep submarine slopes analogously to the shaping by surface waves of slopes in shallow water.

  19. Design of a three-dimensional photonic crystal nanocavity based on a \\langle 110\\rangle -layered diamond structure

    NASA Astrophysics Data System (ADS)

    Tajiri, Takeyoshi; Takahashi, Shun; Tandaechanurat, Aniwat; Iwamoto, Satoshi; Arakawa, Yasuhiko

    2014-01-01

    We design a three-dimensional (3D) photonic crystal (PC) nanocavity based on a \\langle 110\\rangle -layered diamond structure. The designed structure, comprised of self-sustainable layers, is suitable for fabrication by layer stacking techniques. Quality factors (Q-factors) of nanocavities were calculated for the \\langle 110\\rangle -layered diamond and a commonly-used woodpile structures, both of which are generated from the same diamond lattice with a lattice constant adiamond. The Q-factor of the designed nanocavity can reach as high as 230,000 with 35 stacked layers and a square in-plane PC area of the length of one side of 5\\sqrt{2} a^{\\text{diamond}}. This is 1.5 times higher than that of a 3D PC nanocavity based on the woodpile structure with the same in-plane PC size and with the same number of stacked layers. The higher Q-factor in the \\langle 110\\rangle -layered diamond structure originates from its stronger in-plane light confinement over the woodpile structure. The \\langle 110\\rangle -layered diamond structure will be beneficial for improving experimentally attainable Q-factors of 3D PC nanocavities particularly fabricated by a micromanipulation method.

  20. Nature, Origin, Potential Composition, and Climate Impact of the Asian Tropopause Aerosol Layer (ATAL)

    NASA Technical Reports Server (NTRS)

    Fairlie, T. D.; Vernier, J.-P.; Thomason, L. W.; Natarajan, M.; Bedka, K.; Wienhold, F.; Bian J.; Martinsson, B.

    2015-01-01

    Satellite observations from SAGE II and CALIPSO indicate that summertime aerosol extinction has more than doubled in the Asian Tropopause Aerosol Layer (ATAL) since the late 1990s. Here we show remote and in-situ observations, together with results from a chemical transport model (CTM), to explore the likely composition, origin, and radiative forcing of the ATAL. We show in-situ balloon measurements of aerosol backscatter, which support the high levels observed by CALIPSO since 2006. We also show in situ measurements from aircraft, which indicate a predominant carbonaceous contribution to the ATAL (Carbon/Sulfur ratios of 2- 10), which is supported by the CTM results. We show that the peak in ATAL aerosol lags by 1 month the peak in CO from MLS, associated with deep convection over Asia during the summer monsoon. This suggests that secondary formation and growth of aerosols in the upper troposphere on monthly timescales make a significant contribution to ATAL. Back trajectory calculations initialized from CALIPSO observations provide evidence that deep convection over India is a significant source for ATAL through the vertical transport of pollution to the upper troposphere.

  1. 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

    2015-01-27

    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.

  2. Structure of the active form of human origin recognition complex and its ATPase motor module

    PubMed Central

    Tocilj, Ante; On, Kin Fan; Yuan, Zuanning; Sun, Jingchuan; Elkayam, Elad; Li, Huilin; Stillman, Bruce; Joshua-Tor, Leemor

    2017-01-01

    Binding of the Origin Recognition Complex (ORC) to origins of replication marks the first step in the initiation of replication of the genome in all eukaryotic cells. Here, we report the structure of the active form of human ORC determined by X-ray crystallography and cryo-electron microscopy. The complex is composed of an ORC1/4/5 motor module lobe in an organization reminiscent of the DNA polymerase clamp loader complexes. A second lobe contains the ORC2/3 subunits. The complex is organized as a double-layered shallow corkscrew, with the AAA+ and AAA+-like domains forming one layer, and the winged-helix domains (WHDs) forming a top layer. CDC6 fits easily between ORC1 and ORC2, completing the ring and the DNA-binding channel, forming an additional ATP hydrolysis site. Analysis of the ATPase activity of the complex provides a basis for understanding ORC activity as well as molecular defects observed in Meier-Gorlin Syndrome mutations. DOI: http://dx.doi.org/10.7554/eLife.20818.001 PMID:28112645

  3. Hybrid transfer-matrix FDTD method for layered periodic structures.

    PubMed

    Deinega, Alexei; Belousov, Sergei; Valuev, Ilya

    2009-03-15

    A hybrid transfer-matrix finite-difference time-domain (FDTD) method is proposed for modeling the optical properties of finite-width planar periodic structures. This method can also be applied for calculation of the photonic bands in infinite photonic crystals. We describe the procedure of evaluating the transfer-matrix elements by a special numerical FDTD simulation. The accuracy of the new method is tested by comparing computed transmission spectra of a 32-layered photonic crystal composed of spherical or ellipsoidal scatterers with the results of direct FDTD and layer-multiple-scattering calculations.

  4. Stable single-layer honeycomblike structure of silica.

    PubMed

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

    2014-06-20

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

  5. Stable Single-Layer Honeycomblike Structure of Silica

    NASA Astrophysics Data System (ADS)

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

    2014-06-01

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

  6. Excitation of guided waves in layered structures with negative refraction.

    PubMed

    Shadrivov, Ilya; Ziolkowski, Richard; Zharov, Alexander; Kivshar, Yuri

    2005-01-24

    We study the electromagnetic beam reflection from layered structures that include the so-called double-negative metamaterials, also called left-handed metamaterials. We predict that such structures can demonstrate a giant lateral Goos-Hänchen shift of the scattered beam accompanied by a splitting of the reflected and transmitted beams due to the resonant excitation of surface waves at the interfaces between the conventional and double-negative materials as well as due to the excitation of leaky modes in the layered structures. The beam shift can be either positive or negative, depending on the type of the guided waves excited by the incoming beam. We also perform finite-difference time-domain simulations and confirm the major effects predicted analytically.

  7. Deep structure and origin of active volcanoes in China

    NASA Astrophysics Data System (ADS)

    Zhao, D.

    2010-12-01

    Recent geophysical studies have provided important constraints on the deep structure and origin of the active intraplate volcanoes in Mainland China. Magmatism in the western Pacific arc and back-arc areas is caused by the corner flow in the mantle wedge and dehydration of the subducting slab (e.g., Zhao et al., 2009a), while the intraplate magmatism in China has different origins. The active volcanoes in Northeast China (such as the Changbai and Wudalianchi) are caused by hot upwelling in the big mantle wedge (BMW) above the stagnant slab in the mantle transition zone and deep slab dehydration as well (Zhao et al., 2009b). The Tengchong volcano in Southwest China is caused by a similar process in the BMW above the subducting Burma microplate (or Indian plate) (Lei et al., 2009a). The Hainan volcano in southernmost China is a hotspot fed by a lower-mantle plume which may be associated with the Pacific and Philippine Sea slabs' deep subduction in the east and Indian slab's deep subduction in the west down to the lower mantle (Lei et al., 2009b; Zhao, 2009). The stagnant slab finally collapses down to the bottom of the mantle, which can trigger the upwelling of hot mantle materials from the lower mantle to the shallow mantle beneath the subducting slabs and may cause the slab-plume interactions (Zhao, 2009). References Lei, J., D. Zhao, Y. Su, 2009a. Insight into the origin of the Tengchong intraplate volcano and seismotectonics in southwest China from local and teleseismic data. J. Geophys. Res. 114, B05302. Lei, J., D. Zhao, B. Steinberger et al., 2009b. New seismic constraints on the upper mantle structure of the Hainan plume. Phys. Earth Planet. Inter. 173, 33-50. Zhao, D., 2009. Multiscale seismic tomography and mantle dynamics. Gondwana Res. 15, 297-323. Zhao, D., Z. Wang, N. Umino, A. Hasegawa, 2009a. Mapping the mantle wedge and interplate thrust zone of the northeast Japan arc. Tectonophysics 467, 89-106. Zhao, D., Y. Tian, J. Lei, L. Liu, 2009b. Seismic

  8. Optimization of SMA layers in composite structures to enhance damping

    NASA Astrophysics Data System (ADS)

    Haghdoust, P.; Cinquemani, S.; Lecis, N.; Bassani, P.

    2016-04-01

    The performance of lightweight structures can be severely affected by vibration. New design concepts leading to lightweight, slender structural components can increase the vulnerability of the components to failure due to excessive vibration. The intelligent approach to address the problem would be the use of materials which are more capable in dissipating the energy due to their high value of loss factor. Among the different materials available to achieve damping, much attention has been attached to the use of shape memory alloys (SMAs) because of their unique microstructure, leading to good damping capacity. This work describes the design and optimization of a hybrid layered composite structure for the passive suppression of flexural vibrations in slender and light structures. Embedding the SMA layers in composite structure allows to combine different properties: the lightness of the base composite (e.g. fiber glass), the mechanical strength of the insert of metallic material and the relevant damping properties of SMA, in the martensitic phase. In particular, we put our attention on embedding the CuZnAl in the form of thin sheet in a layered composite made by glass fiber reinforced epoxy. By appropriately positioning of the SMA sheets so that they are subjected to the maximum curvature, the damping of the hybrid system can be considerably enhanced. Accordingly analytical method for evaluating the energy dissipation of the thin sheets with different shapes and patterns is developed and is followed by a shape optimization based on genetic algorithm. Eventually different configurations of the hybrid beam structure with different patterns of SMA layer are proposed and compared in the term of damping capacity.

  9. Structural characterisation of a layered double hydroxide nanosheet

    NASA Astrophysics Data System (ADS)

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

    2014-06-01

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

  10. Multi-functional layered structure having structural and radiation shielding attributes

    NASA Technical Reports Server (NTRS)

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

    2010-01-01

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

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

    SciTech Connect

    Sato, N. )

    1990-06-15

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

  12. Origin, genetic diversity, and population structure of Chinese domestic sheep.

    PubMed

    Chen, Shan-Yuan; Duan, Zi-Yuan; Sha, Tao; Xiangyu, Jinggong; Wu, Shi-Fang; Zhang, Ya-Ping

    2006-07-19

    To characterize the origin, genetic diversity, and phylogeographic structure of Chinese domestic sheep, we here analyzed a 531-bp fragment of mtDNA control region of 449 Chinese autochthonous sheep from 19 breeds/populations from 13 geographic regions, together with previously reported 44 sequences from Chinese indigenous sheep. Phylogenetic analysis showed that all three previously defined lineages A, B, and C were found in all sampled Chinese sheep populations, except for the absence of lineage C in four populations. Network profiles revealed that the lineages B and C displayed a star-like phylogeny with the founder haplotype in the centre, and that two star-like subclades with two founder haplotypes were identified in lineage A. The pattern of genetic variation in lineage A, together with the divergence time between the two central founder haplotypes suggested that two independent domestication events have occurred in sheep lineage A. Considerable mitochondrial diversity was observed in Chinese sheep. Weak structuring was observed either among Chinese indigenous sheep populations or between Asian and European sheep and this can be attributable to long-term strong gene flow induced by historical human movements. The high levels of intra-population diversity in Chinese sheep and the weak phylogeographic structuring indicated three geographically independent domestication events have occurred and the domestication place was not only confined to the Near East, but also occurred in other regions.

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

    PubMed Central

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

    2015-01-01

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

  14. Some new aspects of the transient ionization layer of comet Siding Spring origin in the Martian upper atmosphere

    NASA Astrophysics Data System (ADS)

    Mohana Manasa, P.; Jayaraman, Achuthan; Rao Narukull, Venkateswara; Vijaya Bhaskara Rao, Sarangam

    2016-07-01

    On 19 October 2014, comet Siding Spring passed near to the Mars and deposited a large amount of dust on the Martian upper atmosphere. This resulted in the formation of a dense transient ionization layer on Mars at altitudes between 80 and 120 km. Gurnett et al., [2014] reported the detection of this layer with Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) instrument aboard Mars Express spacecraft. In this study, we re-analyzed the ionograms obtained by this instrument to get further insight on the recurrence of the layer. Data from three orbital passes of MARSIS that took place 5 h, 12 h, and 19 h after peak dust deposition are used in this analysis. We found that the transient ionization layer sustained at least for 19 hours on the nightside and 12 hours on the dayside. While the peak density of the layer on the nightside gradually decreases from orbit-to-orbit, it does not change much on the dayside. Some ionograms in all the three orbits show two transient ionization layers that are separated by several kilometers in apparent altitude. We propose two mechanisms to explain this double layer structure. The first one assumes a horizontal bifurcation of the layer in which specular reflections from the two horizontal parts result in a double layer structure in ionograms. In the second mechanism, we assume specular reflections from ionization bulges (formed in regions of vertical magnetic fields) at altitudes of transient ionization layer give rise to oblique echoes that form the bottom layer of the double layer structure.

  15. Single-layer honeycomb like structure of silica

    NASA Astrophysics Data System (ADS)

    Cahangirov, Seymur; Ozcelik, V. Ongun; Ciraci, Salim

    2014-03-01

    Silica or SiO2, the main constituent of earth's rocks has several 3D complex crystalline and amorphous phases, but it does not have a graphite like layered structure in 3D. Our theoretical analysis and numerical calculations from the first-principles predict that silica can have stable, suspended, single-layer honeycomb like allotrope, h α-silica (silicatene), which can be viewed to be derived from the oxidation of silicene and it has intriguing atomic structure with re-entrant angles in hexagons. It is a wide band gap semiconductor, which attains remarkable electromechanical properties showing geometrical changes under external electric field. In particular, it is an auxetic nanomaterial with negative Poisson's ratio and has high piezoelectric coefficient. Coverage of foreign adatoms can attribute new functionalities to h α-silica such that by oxidation it turns into to a wide band gap insulator like the parent quartz.

  16. Three-Dimensional Structure of Plane Mixing Layers.

    NASA Astrophysics Data System (ADS)

    Bell, James Horatio

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

  17. Four-layer nanocomposite structure as an effective optical waveguide switcher for near-IR regime

    NASA Astrophysics Data System (ADS)

    Panyaev, I. S.; Dadoenkova, N. N.; Dadoenkova, Yu S.; Rozhleys, I. A.; Krawczyk, M.; Lyubchanskii, I. L.; Sannikov, D. G.

    2016-11-01

    We present a theoretical study of the dispersion and energy properties of the eigenwaves (TE- and TM-modes) in a four-layer structure composed of a magneto-optical yttrium iron garnet guiding layer on a dielectric substrate covered by a planar nanocomposite guiding multilayer. The bigyrotropic properties of yttrium-iron garnet are taken into account for obtaining the dispersion equation and an original algorithm for the guided modes identification is proposed. We demonstrated the polarization switching of TE- and TM-modes dependent on the geometrical parameters of the guiding layers. The dispersion diagrams and field profiles are used to illustrate the change of propagation properties with variation of the multilayer thickness ratio of the nanocomposite’s layers. The energy flux distributions across the structure are calculated and the conditions of the optimal guiding regime are obtained. The power switching ratio in the waveguide layers of about 6 dB for the wavelength range of 100 nm is shown to be achieved.

  18. Thermal structure in the Venus middle cloud layer

    NASA Technical Reports Server (NTRS)

    Linkin, V. M.; Lipatov, A. N.; Shurupov, A. A.; Ignatova, S. P.; Frank, G. A.; Seiff, A.; Ragent, B.; Young, R. E.; Elson, L. S.; Preston, R. A.

    1986-01-01

    Thermal structure measurements obtained by the two Vega balloons show the Venus atmosphere in the middle cloud layer to be near-adiabatic, on the whole; but discrete air masses are present that differ slightly from one another in potential temperature and entropy. The Vega 1 temperatures are 6.5 K warmer than measured by Vega 2 at given pressures. Measurements taken by the Vega 2 lander on descent through these levels agree with the Vega 2 balloon data.

  19. Investigation of the Turbulence Producing Structures in the Boundary Layer

    DTIC Science & Technology

    1991-07-15

    34 . I, IS ieq/noni fCg of M na emE-t Ind Sudag". 0 8ew Or% Aodu tiOm Prole" (0704411), W.ash gon. OC 20SO3. ... RT DATE 3. REPORT TYPE AND DATE...Spalart, P.R., Spatial Character and Time Evolution of Coherent Structures in a Numerically Simulated Boundary Layer, AIAA 88-3577, 19884 ak Robinson

  20. Models for UT inspection of bolthole cracks in layered structures

    NASA Astrophysics Data System (ADS)

    Grandin, Robert; Gray, Tim; Roberts, Ron

    2017-02-01

    Due to the geometrical complexities of bolted, layered airframe structures, the application of Model Assisted Probability of Detection, or MAPOD, is an important tool for helping to assess the ultrasonic inspectability of those components. Of particular importance is the need to inspect for cracks on or near boltholes in those structures. This presentation describes the development and testing of analytical computer models of and their application to bolthole crack inspection. The modeling approach includes approximate, paraxial, bulk-wave models as well as more rigorous, analytical models that include both bulk and surface/plate modes. The simpler models have the flexibility and computational efficiency to handle complex geometries and structures. The more exact, rigorous models apply to simpler, canonical geometries for use in benchmarking and assessing the accuracy of the paraxial models. Previous model results for single layers will be reviewed and application of the models to multiple layers will be highlighted. Extensions of the models to more complex geometries and materials, computational challenges to future model development, and applications of the models to MAPOD, and will also be addressed.

  1. Facile preparation, optical and electrochemical properties of layer-by-layer V2O5 quadrate structures

    NASA Astrophysics Data System (ADS)

    Zhang, Yifu; Zheng, Jiqi; Wang, Qiushi; Hu, Tao; Tian, Fuping; Meng, Changgong

    2017-03-01

    Layer-by-layer V2O5 structures self-assembly by quadrate sheets like "multilayer cake" were successfully synthesized using NH4VO3 as the vanadium sources by a facile hydrothermal route and combination of the calcination. The structure and composition were characterized by field emission scanning electron microscopy, energy-dispersive X-ray spectrometer, X-ray powder diffraction, Raman and Fourier transform infrared spectroscopy. The optical properties of the as-obtained V2O5 layer-by-layer structures were investigated by the Ultraviolet-visible spectroscopy and photoluminescence spectrum. The electrochemical properties of the as-obtained V2O5 layer-by-layer structures as electrodes in supercapacitor device were measured by cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) both in the aqueous and organic electrolyte. The specific capacitance is 347 F g-1 at 1 A g-1 in organic electrolyte, which is improved by 46% compared with 238 F g-1 in aqueous electrolyte. During the cycle performance, the specific capacitances of V2O5 layer-by-layer structures after 100 cycles are 30% and 82% of the initial discharge capacity in the aqueous and organic electrolyte, respectively, indicating the cycle performance is significantly improved in organic electrolyte. Our results turn out that layer-by-layer V2O5 structures are an ideal material for supercapacitor electrode in the present work.

  2. Plasmon and exciton superconductivity mechanisms in layered structures

    NASA Technical Reports Server (NTRS)

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

    1977-01-01

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

  3. Structural origin of resistance drift in amorphous GeTe

    NASA Astrophysics Data System (ADS)

    Zipoli, Federico; Krebs, Daniel; Curioni, Alessandro

    2016-03-01

    We used atomistic simulations to study the origin of the change of resistance over time in the amorphous phase of GeTe, a prototypical phase-change material (PCM). Understanding the cause of resistance drift is one of the biggest challenges to improve multilevel storage technology. For this purpose, we generated amorphous structures via classical molecular-dynamics simulations under conditions as close as possible to the experimental operating ones of such memory devices. Moreover, we used the replica-exchange technique to generate structures comparable with those obtained in the experiment after long annealing that show an increase of resistance. This framework allowed us to overcome the main limitation of previous simulations, based on density-functional theory, that suffered from being computationally too expensive therefore limited to the nanosecond time scale. We found that resistance drift is caused by consumption of Ge atom clusters in which the coordination of at least one Ge atom differs from that of the crystalline phase and by removal of stretched bonds in the amorphous network, leading to a shift of the Fermi level towards the middle of the band gap. These results show that one route to design better memory devices based on current chalcogenide alloys is to reduce the resistance drift by increasing the rigidity of the amorphous network.

  4. The motor origins of human and avian song structure

    PubMed Central

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

    2011-01-01

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

  5. Origin of the large scale structures of the universe

    SciTech Connect

    Oaknin, David H.

    2004-11-15

    We revise the statistical properties of the primordial cosmological density anisotropies that, at the time of matter-radiation equality, seeded the gravitational development of large scale structures in the otherwise homogeneous and isotropic Friedmann-Robertson-Walker flat universe. Our analysis shows that random fluctuations of the density field at the same instant of equality and with comoving wavelength shorter than the causal horizon at that time can naturally account, when globally constrained to conserve the total mass (energy) of the system, for the observed scale invariance of the anisotropies over cosmologically large comoving volumes. Statistical systems with similar features are generically known as glasslike or latticelike. Obviously, these conclusions conflict with the widely accepted understanding of the primordial structures reported in the literature, which requires an epoch of inflationary cosmology to precede the standard expansion of the universe. The origin of the conflict must be found in the widespread, but unjustified, claim that scale invariant mass (energy) anisotropies at the instant of equality over comoving volumes of cosmological size, larger than the causal horizon at the time, must be generated by fluctuations in the density field with comparably large comoving wavelength.

  6. The motor origins of human and avian song structure.

    PubMed

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

    2011-09-13

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

  7. Nanoscale Structuring of Surfaces by Using Atomic Layer Deposition.

    PubMed

    Sobel, Nicolas; Hess, Christian

    2015-12-07

    Controlled structuring of surfaces is interesting for a wide variety of areas, including microelectronic device fabrication, optical devices, bio(sensing), (electro-, photo)catalysis, batteries, solar cells, fuel cells, and sorption. A unique feature of atomic layer deposition (ALD) is the possibility to form conformal uniform coatings on arbitrarily shaped materials with controlled atomic-scale thickness. In this Minireview, we discuss the potential of ALD for the nanoscale structuring of surfaces, highlighting its versatile application to structuring both planar substrates and powder materials. Recent progress in the application of ALD to porous substrates has even made the nanoscale structuring of high-surface-area materials now feasible, thereby enabling novel applications, such as those in the fields of catalysis and alternative energy.

  8. Phosphotyrosine phosphatase R3 receptors: Origin, evolution and structural diversification.

    PubMed

    Chicote, Javier U; DeSalle, Rob; García-España, Antonio

    2017-01-01

    Subtype R3 phosphotyrosine phosphatase receptors (R3 RPTPs) are single-spanning membrane proteins characterized by a unique modular composition of extracellular fibronectin repeats and a single cytoplasmatic protein tyrosine phosphatase (PTP) domain. Vertebrate R3 RPTPs consist of five members: PTPRB, PTPRJ, PTPRH and PTPRO, which dephosphorylate tyrosine residues, and PTPRQ, which dephosphorylates phophoinositides. R3 RPTPs are considered novel therapeutic targets in several pathologies such as ear diseases, nephrotic syndromes and cancer. R3 RPTP vertebrate receptors, as well as their known invertebrate counterparts from animal models: PTP52F, PTP10D and PTP4e from the fruitfly Drosophila melanogaster and F44G4.8/DEP-1 from the nematode Caenorhabditis elegans, participate in the regulation of cellular activities including cell growth and differentiation. Despite sharing structural and functional properties, the evolutionary relationships between vertebrate and invertebrate R3 RPTPs are not fully understood. Here we gathered R3 RPTPs from organisms covering a broad evolutionary distance, annotated their structure and analyzed their phylogenetic relationships. We show that R3 RPTPs (i) have probably originated in the common ancestor of animals (metazoans), (ii) are variants of a single ancestral gene in protostomes (arthropods, annelids and nematodes); (iii) a likely duplication of this ancestral gene in invertebrate deuterostomes (echinodermes, hemichordates and tunicates) generated the precursors of PTPRQ and PTPRB genes, and (iv) R3 RPTP groups are monophyletic in vertebrates and have specific conserved structural characteristics. These findings could have implications for the interpretation of past studies and provide a framework for future studies and functional analysis of this important family of proteins.

  9. Phosphotyrosine phosphatase R3 receptors: Origin, evolution and structural diversification

    PubMed Central

    Chicote, Javier U.; DeSalle, Rob; García-España, Antonio

    2017-01-01

    Subtype R3 phosphotyrosine phosphatase receptors (R3 RPTPs) are single-spanning membrane proteins characterized by a unique modular composition of extracellular fibronectin repeats and a single cytoplasmatic protein tyrosine phosphatase (PTP) domain. Vertebrate R3 RPTPs consist of five members: PTPRB, PTPRJ, PTPRH and PTPRO, which dephosphorylate tyrosine residues, and PTPRQ, which dephosphorylates phophoinositides. R3 RPTPs are considered novel therapeutic targets in several pathologies such as ear diseases, nephrotic syndromes and cancer. R3 RPTP vertebrate receptors, as well as their known invertebrate counterparts from animal models: PTP52F, PTP10D and PTP4e from the fruitfly Drosophila melanogaster and F44G4.8/DEP-1 from the nematode Caenorhabditis elegans, participate in the regulation of cellular activities including cell growth and differentiation. Despite sharing structural and functional properties, the evolutionary relationships between vertebrate and invertebrate R3 RPTPs are not fully understood. Here we gathered R3 RPTPs from organisms covering a broad evolutionary distance, annotated their structure and analyzed their phylogenetic relationships. We show that R3 RPTPs (i) have probably originated in the common ancestor of animals (metazoans), (ii) are variants of a single ancestral gene in protostomes (arthropods, annelids and nematodes); (iii) a likely duplication of this ancestral gene in invertebrate deuterostomes (echinodermes, hemichordates and tunicates) generated the precursors of PTPRQ and PTPRB genes, and (iv) R3 RPTP groups are monophyletic in vertebrates and have specific conserved structural characteristics. These findings could have implications for the interpretation of past studies and provide a framework for future studies and functional analysis of this important family of proteins. PMID:28257417

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

    NASA Astrophysics Data System (ADS)

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

    2017-01-01

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

  11. Dynamic rolling process of tires as layered structures

    NASA Astrophysics Data System (ADS)

    Böhm, F.

    1996-11-01

    Due to inner pressure the tire is a prestressed system of cord layers. The cord layers are covered by rubber layers. The whole structure is coated by a wear-resistive thread and a soft side wall coating. Serving as a boundary condition at the cord ends is a steel ring at both sides of the wheel rim. To stiffen the thread the structure has a steel cord belt with a ply angle of ±20° to the circumferential direction. The rolling system works like a spring with changing contact forces, and to compute the car dynamics it is necessary to take into account a high frequency and nonlinear varying contact. The forces between tire and road are limited by friction which gives rise to high frequency friction oscillations. Also the structural dynamics of the tire is nonconservative and self-excited, and an appropriate damping of cords and rubber is needed to stabilize the system dynamically. The computing static equilibrium and equations of motion of a continuum mechanics membrane model are treated, and the discretization to a multi-masspoint model is shown. The resulting nonlinear system of Newtonian equations is solved by using the predictor-corrector integration method in time. The time step of integration is due to the highest frequency of the system, and it is ten times shorter than the minimum of oscillation time in the system. All the nonlinearities, the hysteretic damping, and small bending moments of the rubber layers are taken into account to compute the nonstationary rolling with slip and spin on uneven roads or soft ground.

  12. 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 λ/10, where λ 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.

  13. Crystal structure of britvinite [Pb{sub 7}(OH){sub 3}F(BO{sub 3}){sub 2}(CO{sub 3})][Mg{sub 4.5}(OH){sub 3}(Si{sub 5}O{sub 14})]: A new layered silicate with an original type of silicon-oxygen networks

    SciTech Connect

    Yakubovich, O. V. Massa, W.; Chukanov, N. V.

    2008-03-15

    The crystal structure of a new mineral britvinite Pb{sub 7.1}Mg{sub 4.5}(Si{sub 4.8}Al{sub 0.2}O{sub 14})(BO{sub 3})(CO{sub 3})[(BO{sub 3}){sub 0.7}(SiO{sub 4}){sub 0.3}]= (OH, F){sub 6.7} from the Langban iron-manganese skarn deposit (Vaermland, Sweden) is determined at T = 173 K using X-ray diffraction (Stoe IPDS diffractometer, {lambda}MoK{alpha}, graphite monochromator, 2{theta}{sub max} = 58.43{sup o}, R = 0.052 for 6262 reflections). The main crystal data are as follows: a = 9.3409(8) A, b = 9.3579(7) A, c = 18.8333(14) A, {alpha} = 80.365(6) deg., {beta} = 75.816(6) deg., {gamma} = 59.870(5) deg., V = 1378.7(2) A{sup 3}, space group P1, Z = 2, and {rho}{sub calcd} = 5.42 g/cm{sup 3}. The idealized structural formula of the mineral is represented as [Pb{sub 7}(OH){sub 3}F(BO{sub 3}){sub 2}(CO{sub 3})][Mg{sub 4.5}(OH){sub 3}(Si{sub 5}O{sub 14})]. It is demonstrated that the mineral britvinite is a new representative of the group of mica-like layered silicates with structures in which three-layer (2: 1) 'sandwiches' composed of tetrahedra and octahedra alternate with blocks of other compositions, such as oxide, oxide-carbonate, oxide-carbonate-sulfate, and other blocks. The tetrahedral networks (Si{sub 5}O{sub 14}){sub {infinity}}{sub {infinity}} consisting of twelve-membered rings are fragments of the britvinite structure. Similar networks also form crystal structures of the mineral zeophyllite and the synthetic phase Rb{sub 6}Si{sub 10}O{sub 23}. In the crystal structures under consideration, the tetrahedral networks differ in the rotation of tetrahedra with respect to the layer plane.

  14. Crystal structure of britvinite [Pb{sub 7}(OH){sub 3}F(BO{sub 3}){sub 2}(CO{sub 3})][Mg{sub 4.5}(OH){sub 3}(Si{sub 5}O{sub 14})]: A new layered silicate with an original type of silicon-oxygen networks

    SciTech Connect

    Yakubovich, O. V.; Massa, W.; Chukanov, N. V.

    2008-03-15

    The crystal structure of a new mineral britvinite Pb{sub 7.1}Mg{sub 4.5}(Si{sub 4.8}Al{sub 0.2}O{sub 14})(BO{sub 3})(CO{sub 3})[(BO{sub 3}){sub 0.7}(SiO{sub 4}){sub 0.3}](OH, F){sub 6.7} from the Langban iron-manganese skarn deposit (Vaermland, Sweden) is determined at T = 173 K using X-ray diffraction (Stoe IPDS diffractometer, {lambda}MoK{alpha}, graphite monochromator, 2{theta}{sub max} = 58.43 Degree-Sign , R = 0.052 for 6262 reflections). The main crystal data are as follows: a = 9.3409(8) Angstrom-Sign , b = 9.3579(7) Angstrom-Sign , c = 18.8333(14) Angstrom-Sign , {alpha} = 80.365(6) Degree-Sign , {beta} = 75.816(6) Degree-Sign , {gamma} = 59.870(5) Degree-Sign , V = 1378.7(2) Angstrom-Sign {sup 3}, space group P1, Z = 2, and {rho}{sub calcd} = 5.42 g/cm{sup 3}. The idealized structural formula of the mineral is represented as [Pb{sub 7}(OH){sub 3}F(BO{sub 3}){sub 2}(CO{sub 3})][Mg{sub 4.5}(OH){sub 3}(Si{sub 5}O{sub 14})]. It is demonstrated that the mineral britvinite is a new representative of the group of mica-like layered silicates with structures in which three-layer (2: 1) 'sandwiches' composed of tetrahedra and octahedra alternate with blocks of other compositions, such as oxide, oxide-carbonate, oxide-carbonate-sulfate, and other blocks. The tetrahedral networks (Si{sub 5}O{sub 14}){sub {infinity}{infinity}} consisting of twelve-membered rings are fragments of the britvinite structure. Similar networks also form crystal structures of the mineral zeophyllite and the synthetic phase Rb{sub 6}Si{sub 10}O{sub 23}. In the crystal structures under consideration, the tetrahedral networks differ in the rotation of tetrahedra with respect to the layer plane.

  15. Evaluating Satiated Copepod Behavioral Responses to Thin Layer Flow Structure

    NASA Astrophysics Data System (ADS)

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

    2011-11-01

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

  16. Impact of structural heterogeneity in solar absorber layers (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Toney, Michael

    2016-09-01

    Impact of structural heterogeneity in solar absorber layers Michael F Toney SLAC National Accelerator Laboratory Structural and morphological heterogeneity is common in thin film and emerging solar cell absorber layers, including organic photovoltaic bulk heterojunctions (OPV BHJs), hybrid organic-inorganic perovskites (HOIP), and Cu2ZnSn(S,Se)4 (CZTSSe), and has a significant impact on the (opto)electronic heterogeneity and hence absorber properties. In this talk I will use X-ray based methods, including scattering and spectroscopies, to characterize and quantify the heterogeneity in OPV BHJs and HOIP absorber layers. The BHJ films are blends of the small molecule X2 and [6,6]-phenyl C71 butyric acid methyl ester (PC71BM) where it has been established that there are three distinct region of the films - pure PC71BM, pure X2 and intimately mixed X2:PC71BM. This talk will show how the absolute concentration of the mixed phase can be used to explain the large PC71BM:X2 composition range where good performance is observed [1]. The talk will also show that spin cast CH3NH3PbI3 films consistent of both crystalline and amorphous regions, which can explain previous heterogeneity in the PL imaging [2]. [1] Huang et al., Adv. Energy Mater. 4, 1301886 (2014). [2] deQuilettes et al., Science 348, 683 (2015).

  17. Two new barium sulfonates with pillared layered structures

    NASA Astrophysics Data System (ADS)

    Yang, Jin; Li, Li; Ma, Jian-Fang; Liu, Ying-Ying; Ma, Ji-Cheng

    2006-05-01

    The reactions of BaCl 2·2H 2O with NaHL a and K 3L b (H 2L a=4-hydroxybenzenesulfonic acid, H 3L b=4-hydroxy-5-nitro-1,3-benzenedisulfonic acid) gave two pillared layered coordination polymers: Ba(HL a)(Cl) 1 and KBaL b(H 2O) 32, respectively. The crystal structures were determined by X-ray diffraction method and refined by full-matrix least-squares methods to R=0.0509 and wR=0.1216 using 1455 reflections with I>2 σ( I) for 1; and R=0.0288 and wR=0.0727 using 2661 reflections with I>2 σ( I) for 2. The interesting feature of compound 1 is the coordination actions of chloride anions, which help to form the polymeric layers by bridging barium cations. In compound 2 the Lb3- anion acts as an unusual dodecadente ligand to form a coordination polymer with pillared layered structure.

  18. Two new barium sulfonates with pillared layered structures

    NASA Astrophysics Data System (ADS)

    Yang, Jin; Li, Li; Ma, Jian-Fang; Liu, Ying-Ying; Ma, Ji-Cheng

    2006-08-01

    The reactions of BaCl 2·2H 2O with NaHL a and K 3L b (H 2L a=4-hydroxybenzenesulfonic acid, H 3L b=4-hydroxy-5-nitro-1,3-benzenedisulfonic acid) gave two pillared layered coordination polymers: Ba(HL a)(Cl) 1 and KBaL b(H 2O) 32, respectively. The crystal structures were determined by X-ray diffraction method and refined by full-matrix least-squares methods to R=0.0509 and wR=0.1216 using 1455 reflections with I>2 σ( I) for 1; and R=0.0288 and wR=0.0727 using 2661 reflections with I>2 σ( I) for 2. The interesting feature of compound 1 is the coordination actions of chloride anions, which help to form the polymeric layers by bridging barium cations. In compound 2 the Lb3- anion acts as an unusual dodecadente ligand to form a coordination polymer with pillared layered structure.

  19. Origin and Significance of Magnetic Anisotropy in the Dufek Layered Intrusion

    NASA Astrophysics Data System (ADS)

    Gee, J. S.; Lusk, M. W.; Cheadle, M. J.; Grimes, C. B.; Meurer, W. P.

    2009-12-01

    Anisotropy of magnetic susceptibility (AMS) is commonly used as a rapid, precise and nondestructive measure of fabrics in igneous rocks. In mafic intrusions that lack cumulus magnetite, magnetic susceptibility is typically low and the anisotropy reflects the combined contribution from paramagnetic Fe-bearing silicates and trace amounts of silicate-hosted magnetite. The precise origin of the AMS signal may be difficult to ascertain and, consequently, inferences about magmatic processes may be limited. Here we illustrate that combined AMS, remanence anisotropy and silicate fabric data (from electron backscatter diffraction, EBSD) from large data sets allow the origin of the magnetic fabrics to be more clearly related to the silicate fabric. We collected approximately 800 cores (3600 specimens) from the lowermost 500m of the Jurassic Dufek layered intrusion in Antarctica. AMS for these specimens reveals moderate anisotropy (mean P' = 1.09) with dominantly oblate magnetic fabrics. We also determined anisotropy of thermoremanence (ATRM) for more than 500 specimens. Remanence anisotropy is much more pronounced, with an average anisotropy of P' = 2.1 (range 1.08-10.4) and dominantly prolate fabrics. AMS and ATRM reveal a consistent fabric, with subvertical minima approximating the pole to the magmatic foliation and subhorizontal maxima clustered in the northeast quadrant. EBSD results from 13 samples, spanning a range of magnetic fabric intensities and lithologies, indicate that statistically significant mineral lineations are absent in most samples. Because silicate-hosted magnetite is expected to be the dominant magnetic carrier in these cumulates (three quarters have susceptibility < 0.001 SI and no discrete magnetite grains are observed petrographically), the lack of detectable lineation in the silicates is apparently difficult to reconcile with the pronounced magnetic fabrics. However, when crystallographic data from all samples are combined, the substantial data set

  20. LiNiFe-based layered structure oxide and composite for advanced single layer fuel cells

    NASA Astrophysics Data System (ADS)

    Zhu, Bin; Fan, Liangdong; Deng, Hui; He, Yunjune; Afzal, Muhammad; Dong, Wenjing; Yaqub, Azra; Janjua, Naveed K.

    2016-06-01

    A layered structure metal oxide, LiNi0.1Fe0.90O2-δ (LNF), is explored for the advanced single layer fuel cells (SLFCs). The temperature dependent impedance profiles and concentration cells (hydrogen concentration, oxygen concentration, and H2/air atmospheres) tests prove LNF to be an intrinsically electronic conductor in air while mixed electronic and proton conductor in H2/air environment. SLFCs constructed by pure LNF materials show significant short circuiting reflected by a low device OCV and power output (175 mW cm-2 at 500 °C) due to high intrinsic electronic conduction. The power output is improved up to 640 and 760 mW cm-2, respectively at 500 and 550 °C by compositing LNF with ion conducting material, e.g., samarium doped ceria (SDC), to balance the electronic and ionic conductivity; both reached at 0.1 S cm-1 level. Such an SLFC gives super-performance and simplicity over the conventional 3-layer (anode, electrolyte and cathode) FCs, suggesting strong scientific and commercial impacts.

  1. Thermodynamic and radiative structure of stratocumulus-topped boundary layers*

    SciTech Connect

    Ghate, Virendra P.; Miller, Mark A.; Albrecht, Bruce A.; Fairall, Christopher W.

    2015-01-05

    Stratocumulus Topped Boundary Layers (STBL) observed in three different regions with distinctive environments are described in the context of their thermodynamic and radiative properties. Here, the primary data set consisted of 131 soundings from the South East Pacific (SEP), 90 soundings from the island of Graciosa (GRW) in the North Atlantic and 83 soundings from the US Southern Great Plains (SGP). A new technique that preserves the depths of the sub-layers within a STBL is proposed for averaging the profiles of thermodynamic and radiative variables. The STBL was deepest over SEP and had the strongest radiative cooling rates near cloud top among the three locations. Although the radiative cooling rates were comparable over GRW and SGP, the STBL was deeper over GRW compared to that over SGP. On average the STBL inversion was strongest over SEP (11.7 k and -5.43 g kg-1) and weakest over the SGP (6.89 k and -0.41 g kg-1). Significantly larger liquid water path, integrated water vapor, and variability in these two properties was found over GRW and evidence presented suggests that conditions at cloud top may play a lesser role in determining the resident cloud structure over GRW than over SEP. A modal analysis revealed ~26% of the STBL to be well-mixed, ~20% of STBL to be stable and ~30% STBL having a stable layer in-between a surface mixed layer and the cloud layer. Over all the three locations, the STBL was shallowest in well-mixed mode and deepest in the stable mode.

  2. Thermodynamic and radiative structure of stratocumulus-topped boundary layers*

    DOE PAGES

    Ghate, Virendra P.; Miller, Mark A.; Albrecht, Bruce A.; ...

    2015-01-05

    Stratocumulus Topped Boundary Layers (STBL) observed in three different regions with distinctive environments are described in the context of their thermodynamic and radiative properties. Here, the primary data set consisted of 131 soundings from the South East Pacific (SEP), 90 soundings from the island of Graciosa (GRW) in the North Atlantic and 83 soundings from the US Southern Great Plains (SGP). A new technique that preserves the depths of the sub-layers within a STBL is proposed for averaging the profiles of thermodynamic and radiative variables. The STBL was deepest over SEP and had the strongest radiative cooling rates near cloudmore » top among the three locations. Although the radiative cooling rates were comparable over GRW and SGP, the STBL was deeper over GRW compared to that over SGP. On average the STBL inversion was strongest over SEP (11.7 k and -5.43 g kg-1) and weakest over the SGP (6.89 k and -0.41 g kg-1). Significantly larger liquid water path, integrated water vapor, and variability in these two properties was found over GRW and evidence presented suggests that conditions at cloud top may play a lesser role in determining the resident cloud structure over GRW than over SEP. A modal analysis revealed ~26% of the STBL to be well-mixed, ~20% of STBL to be stable and ~30% STBL having a stable layer in-between a surface mixed layer and the cloud layer. Over all the three locations, the STBL was shallowest in well-mixed mode and deepest in the stable mode.« less

  3. Negative thermal expansion due to negative area compressibility in TlGaSe2 semiconductor with layered crystalline structure

    NASA Astrophysics Data System (ADS)

    Seyidov, MirHasan Yu.; Suleymanov, Rauf A.

    2010-09-01

    We conducted comparison of the original experimental data of the temperature dependences of thermal expansion in crystals with layered crystalline structure. It is shown that in most crystals with layered structure (graphite, boron nitride, GaSe, GaS, and InSe) the effect of negative thermal expansion can be explained by the specific character of the phonon spectra. It was shown, that in contrast to other crystals with layered structure, negative thermal expansion in the layers' plane of TlGaSe2 is the result of negative area compressibility. We demonstrate that the thermal expansion of TlGaSe2 crystals can be controlled by illumination, external electric field, and thermal annealing. The nature of observed effects and a special mechanism of the negative area compressibility in TlGaSe2 crystals are discussed.

  4. 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 α84 pigment and the first excited vibronic level of the β84 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

  5. 3D multi-layered fibrous cellulose structure using an electrohydrodynamic process for tissue engineering.

    PubMed

    Kim, Minseong; Kim, GeunHyung

    2015-11-01

    Micro/nanofibrous structures have been applied widely in various tissue-engineering applications because the topological structures are similar to the extracellular matrix (ECM), which encourages a high degree of cell adhesion and growth. However, it has been difficult to produce a three-dimensional (3D) fibrous structure using controllable macro-pores. Recently, cellulose has been considered a high-potential natural-origin biomaterial, but its use in 3D biomedical structures has been limited due to its narrow processing window. Here, we suggest a new 3D cellulose scaffold consisting of multi-layered struts made of submicron-sized entangled fibers that were fabricated using an electrohydrodynamic direct jet (EHDJ) process that is spin-printing. By optimizing processing conditions (electric field strength, cellulose feeding rate, and distance between nozzle and target), we can achieve a multi-layered cellulose structure consisting of the cylindrically entangled cellulose fibers. To compare the properties of the fabricated 3D cellulose structure, we used a PCL fibrous scaffold, which has a similar fibrous morphology and pore geometry, as a control. The physical and in vitro biocompatibilities of both fibrous scaffolds were assessed using human dermal fibroblasts, and the cellulose structure showed higher cell adhesion and metabolic activities compared with the control. These results suggest the EHDJ process to be an effective fabricating tool for tissue engineering and the cellulose scaffold has high potential as a tissue regenerative material.

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

    PubMed

    Scheurwater, Edie M; Burrows, Lori L

    2011-05-01

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

  7. 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.

  8. Platinum-induced structural collapse in layered oxide polycrystalline films

    SciTech Connect

    Wang, Jianlin; Liu, Changhui; Huang, Haoliang; Fu, Zhengping; Peng, Ranran E-mail: yllu@ustc.edu.cn; Zhai, Xiaofang; Lu, Yalin E-mail: yllu@ustc.edu.cn

    2015-03-30

    Effect of a platinum bottom electrode on the SrBi{sub 5}Fe{sub 1−x}Co{sub x}Ti{sub 4}O{sub 18} layered oxide polycrystalline films was systematically studied. The doped cobalt ions react with the platinum to form a secondary phase of PtCoO{sub 2}, which has a typical Delafossite structure with a weak antiferromagnetism and an exceptionally high in-plane electrical conductivity. Formation of PtCoO{sub 2} at the interface partially consumes the cobalt dopant and leads to the structural collapsing from 5 to 4 layers, which was confirmed by X-ray diffraction and high resolution transmission electron microscopy measurements. Considering the weak magnetic contribution from PtCoO{sub 2}, the observed ferromagnetism should be intrinsic of the Aurivillius compounds. Ferroelectric properties were also indicated by the piezoresponse force microscopy. In this work, the platinum induced secondary phase at the interface was observed, which has a strong impact on Aurivillius structural configuration and thus the ferromagnetic and ferroelectric properties.

  9. Characterization of structural response to hypersonic boundary-layer transition

    DOE PAGES

    Riley, Zachary B.; Deshmukh, Rohit; Miller, Brent A.; ...

    2016-05-24

    The inherent relationship between boundary-layer stability, aerodynamic heating, and surface conditions makes the potential for interaction between the structural response and boundary-layer transition an important and challenging area of study in high-speed flows. This paper phenomenologically explores this interaction using a fundamental two-dimensional aerothermoelastic model under the assumption of an aluminum panel with simple supports. Specifically, an existing model is extended to examine the impact of transition onset location, transition length, and transitional overshoot in heat flux and fluctuating pressure on the structural response of surface panels. Transitional flow conditions are found to yield significantly increased thermal gradients, and theymore » can result in higher maximum panel temperatures compared to turbulent flow. Results indicate that overshoot in heat flux and fluctuating pressure reduces the flutter onset time and increases the strain energy accumulated in the panel. Furthermore, overshoot occurring near the midchord can yield average temperatures and peak displacements exceeding those experienced by the panel subject to turbulent flow. Lastly, these results suggest that fully turbulent flow does not always conservatively predict the thermo-structural response of surface panels.« less

  10. Characterization of structural response to hypersonic boundary-layer transition

    SciTech Connect

    Riley, Zachary B.; Deshmukh, Rohit; Miller, Brent A.; McNamara, Jack J.; Casper, Katya M.

    2016-05-24

    The inherent relationship between boundary-layer stability, aerodynamic heating, and surface conditions makes the potential for interaction between the structural response and boundary-layer transition an important and challenging area of study in high-speed flows. This paper phenomenologically explores this interaction using a fundamental two-dimensional aerothermoelastic model under the assumption of an aluminum panel with simple supports. Specifically, an existing model is extended to examine the impact of transition onset location, transition length, and transitional overshoot in heat flux and fluctuating pressure on the structural response of surface panels. Transitional flow conditions are found to yield significantly increased thermal gradients, and they can result in higher maximum panel temperatures compared to turbulent flow. Results indicate that overshoot in heat flux and fluctuating pressure reduces the flutter onset time and increases the strain energy accumulated in the panel. Furthermore, overshoot occurring near the midchord can yield average temperatures and peak displacements exceeding those experienced by the panel subject to turbulent flow. Lastly, these results suggest that fully turbulent flow does not always conservatively predict the thermo-structural response of surface panels.

  11. MOS structures based on epitaxial HgCdTe layers

    SciTech Connect

    Antonov, V.V.; Belashov, Y.G.; Kazak, E.P.; Mezentseva, M.P.; Voitsekhovskii, A.V.

    1985-08-01

    The authors present the results of a study of the dependence of the surface photoelectromotive force at wavelengths of 3.39 and 10.6 micrometers on the field electrode for MOS structures prepared from epitaxial Hg /SUB 1-x/ Cd /SUB x/ Te layers (x=0.20-0.25). They analyze the nature of the inhomogeneities in the region near the surface of semiconducting samples prepared under various heat treatment conditions and present their findings in a series of three charts.

  12. 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

  13. Vertical structure of aeolian turbulence in a boundary layer with sand transport

    NASA Astrophysics Data System (ADS)

    Lee, Zoe S.; Baas, Andreas C. W.

    2016-04-01

    Recently we have found that Reynolds shear stress shows a significant variability with measurement height (Lee and Baas, 2016), and so an alternative parameter for boundary layer turbulence may help to explain the relationship between wind forcing and sediment transport. We present data that were collected during a field study of boundary layer turbulence conducted on a North Atlantic beach. High-frequency (50 Hz) 3D wind velocity measurements were collected using ultrasonic anemometry at thirteen different measurement heights in a tight vertical array between 0.11 and 1.62 metres above the surface. Thanks to the high density installation of sensors a detailed analysis of the boundary layer flow can be conducted using methods more typically used in studies where data is only available from one or just a few measurement heights. We use quadrant analysis to explore the vertical structure of turbulence and track the changes in quadrant signatures with measurement elevation and over time. Results of quadrant analysis, at the 'raw' 50 Hz timescale, demonstrates the tendency for event clustering across all four quadrants, which implies that at-a-point quadrant events are part of larger-scale turbulent structures. Using an HSV colour model, applied to the quadrant analysis data and plotted in series, we create colour maps of turbulence, which can provide a clear visualisation of the clustering of event activity at each height and illustrate the shape of the larger coherent flow structures that are present within the boundary layer. By including a saturation component to the colour model, the most significant stress producing sections of the data are emphasised. This results in a 'banded' colour map, which relates to clustering of quadrant I (Outward Interaction) and quadrant IV (Sweep) activity, separate from clustering of quadrant II (Burst) and quadrant III (Inward Interaction). Both 'sweep-type' and 'burst-type' sequences are shown to have a diagonal structure

  14. On the Origin and Variability of CCN in the Remote Marine Boundary Layer

    NASA Astrophysics Data System (ADS)

    Clarke, A. D.; Freitag, S.; Hudson, J.; Howell, S. G.; Blot, R.; Kapustin, V. N.

    2012-12-01

    The role of CCN and their complex influence upon cloud albedo, cloudiness, radiative transfer and precipitation has emerged as a key research issue in the past decade due to the large and uncertain influence they may have on global climate. Aerosol that activate at low supersaturation in the marine boundary layer (MBL) (i.e. below about 0.4% S (CCN0.4) with sizes near 60 nm diameter) can influence clouds over a dominant fraction of the globe, including extensive regions of marine stratus. Hence, greater efforts have recently been directed at understanding the CCN cycle in this environment. Advection of continental aerosol in the MBL can often account for most CCN0.4 near coastal regions until precipitation scavenging reduces their concentrations to low values. Away from such influences, the dominant sources of new CCN0.4 are from the ocean surface via bubble bursting, from the free troposphere (FT) via entrainment and possibly from nucleation and growth of new particles in the MBL. As the latter process generally appears weak and uncommon, the former two sources appear to dominate most regions. Surface sources via bubble bursting were long presumed to be larger sea-salt with sizes above several hundred nanometers and with production rates driven by white cap coverage that increased with wind speed. More recently, production of sizes smaller than 20 nm has been observed and other constituents including organic aerosol and polysaccharides have become recognized contributors. Growth of smaller sizes into the CCN0.4 range is evident via uptake of sulfate originating from DMS. However, long range transport and entrainment of aerosol from the FT has been identified as another important source of MBL CCN0.4 that may be either natural (eg. sulfuric acid formed in cloud outflow) or continental (eg. biomass burning aerosol). Hence; regional wind speeds, entrainment rates, FT transport, oceanic bio-chemistry and removal rates via precipitation etc. can modulate the nature and

  15. 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. Supported by EU-Japan Project LEMSUPER, by a SNF Sinergia Project, and by the Slovak Research and Development Agency

  16. Synthesis and structural characterization of three-layer Aurivillius ceramics

    NASA Astrophysics Data System (ADS)

    Haluska, Michael Stephan

    2003-07-01

    The three layer Aurivillius crystal structure was investigated for use as an ionic conductor. Sample synthesis was investigated using high temperature x-ray diffraction (HTXRD) for a range of compounds, using solid state synthesis and the polymerized complex method. Isothermal Avrami type kinetics studies were performed on Bi4Ti3O12 using in situ HTXRD and quantitative analysis performed via Rietveld refinements using TOPAS. The kinetics analysis yielded Avrami exponents of approximately 0.54, which fell in the range of the diffusion controlled reaction mechanisms. The activation energy over a range of temperatures was calculated to be on the order of 140kJ/mol. Crystal structure refinements were performed on the Bi2Sr2-xAxNb2TiO12 (A = Ca,Ba, x = 0.5, 1) series using combined x-ray and neutron diffraction Rietveld refinements. Refinements indicated a static disorder between the Bi and A sites, and between the Nb and Ti sites. A-site lattice strain investigated via the bond valence method reveals a linear increase in strain with the size of the substituted alkaline earth cation. Furthermore, large isotropic thermal parameters for the O1 and O4 oxygen sites reveal possible oxygen vacancy formation as a result of unresolved strain between the A and Ti layers of the structure. Oxygen stoichiometry is found to decrease as the size of the a lattice parameter decreases. Synthesis of non-stoichiometric three-layer phases was accomplished by aliovalent substitution and via forced site-mixing. Neither method produced samples with conductivities greater than 10-3 Scm at 900°C. Non-stoichiometric compositions follow similar structural trends to those observed in the stoichiometric crystal structure refinements. Increased numbers of oxygen vacancies were recorded than anticipated from the dopants. The number of extra vacancies corresponds well with the amount shown in the stoichiometric compositions. Based on the conductivity and number of charge carriers, the mobilities of

  17. Local structures around the substituted elements in mixed layered oxides

    PubMed Central

    Akama, Shota; Kobayashi, Wataru; Amaha, Kaoru; Niwa, Hideharu; Nitani, Hiroaki; Moritomo, Yutaka

    2017-01-01

    The chemical substitution of a transition metal (M) is an effective method to improve the functionality of a material, such as its electrochemical, magnetic, and dielectric properties. The substitution, however, causes local lattice distortion because the difference in the ionic radius (r) modifies the local interatomic distances. Here, we systematically investigated the local structures in the pure (x = 0.0) and mixed (x = 0.05 or 0.1) layered oxides, Na(M1−xM′x)O2 (M and M′ are the majority and minority transition metals, respectively), by means of extended X-ray absorption fine structure (EXAFS) analysis. We found that the local interatomic distance (dM-O) around the minority element approaches that around the majority element to reduces the local lattice distortion. We further found that the valence of the minority Mn changes so that its ionic radius approaches that of the majority M. PMID:28252008

  18. Local structures around the substituted elements in mixed layered oxides

    NASA Astrophysics Data System (ADS)

    Akama, Shota; Kobayashi, Wataru; Amaha, Kaoru; Niwa, Hideharu; Nitani, Hiroaki; Moritomo, Yutaka

    2017-03-01

    The chemical substitution of a transition metal (M) is an effective method to improve the functionality of a material, such as its electrochemical, magnetic, and dielectric properties. The substitution, however, causes local lattice distortion because the difference in the ionic radius (r) modifies the local interatomic distances. Here, we systematically investigated the local structures in the pure (x = 0.0) and mixed (x = 0.05 or 0.1) layered oxides, Na(M1‑xM‧x)O2 (M and M‧ are the majority and minority transition metals, respectively), by means of extended X-ray absorption fine structure (EXAFS) analysis. We found that the local interatomic distance (dM-O) around the minority element approaches that around the majority element to reduces the local lattice distortion. We further found that the valence of the minority Mn changes so that its ionic radius approaches that of the majority M.

  19. Structure evolution in layers of polymer blend nanoparticles.

    PubMed

    Raczkowska, Joanna; Montenegro, Rivelino; Budkowski, Andrzej; Landfester, Katharina; Bernasik, Andrzej; Rysz, Jakub; Czuba, Paweł

    2007-06-19

    The early stages of phase evolution, not available for nanometer polymer blend films spin-cast from solutions of incompatible mixtures, have been examined for films prepared from nanoparticles of deuterated polystyrene/ poly(methyl methacrylate) blends (1:1 mass fraction of dPS/PMMA) with PS-PMMA diblock copolymer additives. The initial phase arrangement, confined to the size of nanoparticles, has provided the homogeneity of the initial film composition. The early stages of structure formation, promoted by annealing and traced with atomic and lateral force microscopy (AFM, LFM) as well as secondary ion mass spectroscopy (SIMS), resulted in bilayers, observed commonly for as-prepared solvent-cast blends. The initiated capillary instability of the upper dPS-rich layer depended on copolymer additives, which enhanced the lateral structures pinning the dewetting process.

  20. 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 β 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.

  1. Radial transmission line analysis of multi-layer structures

    SciTech Connect

    Hahn, H.; Hammons, L.

    2011-03-28

    The analysis of multi-layer beam tubes is a standard problem and involves axially propagating waves. This treatment is ill suited to a short multi-layer structure such as the present example of a ferrite covered ceramic break in the beam tube at the ERL photo-cathode electron gun. This paper demonstrates that such structure can better be treated by radial wave propagation. The theoretical method is presented and numerical results are compared with measured network analyser data and Microwave Studio generated simulations. The results confirm the concept of radial transmission lines as a valid analytical method. An Energy Recovery Linac (ERL) is being constructed at this laboratory for the purpose of research towards an envisioned Electron Ion Collider. One of the pertinent topics is damping of Higher Order Modes (HOM). In this ERL, the damping is provided by ferrite absorbers in the beam tube. A modified version thereof, a ceramic break surrounded by ferrite, is planed for the superconducting electron gun. The damper here is located at room temperature just outside of the gun. If used in a cavity chain, the ceramic break is in the vacuum tube at helium temperature whereas the ferrite is moved into the cryostat insulating vacuum allowing higher temperatures. The general properties of the ferrite HOM dampers have been published but are more detailed in this paper.

  2. Composite structure of plumes in stratus-topped boundary layers

    SciTech Connect

    Moeng, C.H. ); Schumann, U. )

    1991-10-15

    Knowledge of convective plumes within the clear convective boundary layer (CBL) is quite advanced owing to direct measurements, tank experiments, and large-eddy simulation studies. As a result, modeling of the CBL is relatively successful. Progress for the stratus-topped boundary layer (STBL), however, is slow. This study compares the plume structure of the surface-heated CBL with that of the cloud-top-cooled STBL in the hope of extending knowledge of the CBL to the STBL. A conditional sampling technique is applied to the STBL flow fields that are generated through large-eddy simulations, so that the structures of typical updrafts and downdrafts may be derived. For the purpose of comparing the surface-heated CBL and the cloud-top-cooled STBL, an idealized STBL, the compensating updrafts are nearly as strong as the top-cooling-generated downdrafts, and they contribute a significant amount to the heat, moisture, and momentum transports. This differs very much from the CBL, where the compensating downdrafts are much weaker than the surface-heating-generated updrafts and contribute much less to the transports. The mechanism that results in such an asymmetry between the CBL and STBL is examined, and suggestions on how the asymmetry affects the entrainment process are made. 25 refs., 26 figs.

  3. Electronic structure, tunneling magnetoresistance and spin polarization of amorphous ferromagnetic storage layer used in magnetic tunneling junction

    NASA Astrophysics Data System (ADS)

    Yang, See-Hun; Samant, Mahesh G.; Parkin, Stuart S. P.; Hughes, Brian; Guo, Jinghua; Augustsson, Andreas; Rotenberg, Eli

    2003-03-01

    Recently amorphous ferromagnetic materials such as boron doped Co-Fe alloys have received much attention because of their potential use as storage layers in magnetic tunnel junctions (MTJs) for non-volatile magnetic memory cells. The primary reason for this is that amorphous ferromagnetic alloys lack crystalline anisotropy and exhibit low coercivities. These properties significantly improve the magnetic switching characteristics of MTJ devices. We have demonstrated that MTJs with amorphous ferromagnetic storage layer have improved magneto-transport properties and superior thermal stabilities compared to similar structures with crystalline storage layers. To understand the origin of these improvements we have performed high energy resolution soft x-ray emission and resonant photoemission spectroscopy experiments on amorphous ferromagnet layers. We have observed that the tunneling magnetoresistance depends not only on the spin polarization of the ferromagnet but also depends critically on the detailed electronic structure in the valence band.

  4. Self-Healing Textile: Enzyme Encapsulated Layer-by-Layer Structural Proteins.

    PubMed

    Gaddes, David; Jung, Huihun; Pena-Francesch, Abdon; Dion, Genevieve; Tadigadapa, Srinivas; Dressick, Walter J; Demirel, Melik C

    2016-08-10

    Self-healing materials, which enable an autonomous repair response to damage, are highly desirable for the long-term reliability of woven or nonwoven textiles. Polyelectrolyte layer-by-layer (LbL) films are of considerable interest as self-healing coatings due to the mobility of the components comprising the film. In this work mechanically stable self-healing films were fabricated through construction of a polyelectrolyte LbL film containing squid ring teeth (SRT) proteins. SRTs are structural proteins with unique self-healing properties and high elastic modulus in both dry and wet conditions (>2 GPa) due to their semicrystalline architecture. We demonstrate LbL construction of multilayers containing native and recombinant SRT proteins capable of self-healing defects. Additionally, we show these films are capable of utilizing functional biomolecules by incorporating an enzyme into the SRT multilayer. Urease was chosen as a model enzyme of interest to test its activity via fluorescence assay. Successful construction of the SRT films demonstrates the use of mechanically stable self-healing coatings, which can incorporate biomolecules for more complex protective functionalities for advanced functional fabrics.

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

    NASA Astrophysics Data System (ADS)

    Ogawa, Tasuku; Ding, Bin; Sone, Yuji; Shiratori, Seimei

    2007-04-01

    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 the silver ragwort leaf fibre axis. The results showed that the FAS modification was the key process for increasing the surface hydrophobicity of the fibrous membranes. Additionally, the dependence of the hydrophobicity of the membrane surfaces upon the number of LBL coating bilayers was affected by the membrane surface roughness. Moreover, x-ray photoelectron spectroscopy (XPS) results further indicated that the surface of LBL film-coated fibres absorbed more fluoro groups than the fibre surface without the LBL coating. A (TiO2/PAA)10 film-coated cellulose acetate nanofibrous membrane with FAS surface modification showed the highest water contact angle of 162° and lowest water-roll angle of 2°.

  6. Giant interfacial perpendicular magnetic anisotropy in MgO/CoFe/capping layer structures

    NASA Astrophysics Data System (ADS)

    Peng, Shouzhong; Zhao, Weisheng; Qiao, Junfeng; Su, Li; Zhou, Jiaqi; Yang, Hongxin; Zhang, Qianfan; Zhang, Youguang; Grezes, Cecile; Amiri, Pedram Khalili; Wang, Kang L.

    2017-02-01

    Magnetic tunnel junction based on the CoFeB/MgO/CoFeB structures is of great interest due to its application in the spin-transfer-torque magnetic random access memory (STT-MRAM). Large interfacial perpendicular magnetic anisotropy (PMA) is required to achieve high thermal stability. Here, we use the first-principles calculations to investigate the magnetic anisotropy energy (MAE) of the MgO/CoFe/capping layer structures, where the capping materials include 5d metals Hf, Ta, Re, Os, Ir, Pt, and Au and 6p metals Tl, Pb, and Bi. We demonstrate that it is feasible to enhance PMA by using proper capping materials. Relatively large PMA is found in the structures with the capping materials of Hf, Ta, Os, Ir, and Pb. More importantly, the MgO/CoFe/Bi structure gives rise to giant PMA (6.09 mJ/m2), which is about three times larger than that of the MgO/CoFe/Ta structure. The origin of the MAE is elucidated by examining the contributions to MAE from each atomic layer and orbital. These findings provide a comprehensive understanding of the PMA and point towards the possibility to achieve the advanced-node STT-MRAM with high thermal stability.

  7. Graphene originated 3D structures grown on the assembled nickel particles

    NASA Astrophysics Data System (ADS)

    Paronyan, Tereza; Harutyunyan, Avetik; Honda Research Institute USA Inc. Team

    2013-03-01

    Recently, the fabrication of various morphologies of graphene originated structures became very important due to the perspective of wide range of new applications. Particularly, free standing 3D structured graphene foams could be imperative in energy related areas . Here, we present the new approach of the CVD growth of 3D graphene network by using primarily sintered Ni particle's (~40 μm size) assembles as a template-catalyst via decomposition of low rate of CH4 at 1100° C based on synthesis method described earlier. SEM and Raman spectra analysis revealed the formation of graphene structure containing a single up to few layers grown on the sintered metal particles served as a catalyst-template. After etching the metal frame without using any support polymer, 3D free-standing graphene microporous structure was formed demonstrating high BET surface area. Two probe measurements of frame resistance were ~2-8 Ω. Our approach allows controllable tune the pore size and thereby the surface area of 3D graphene network through the variation of the template-catalyst particles size.

  8. Origin of modal and rhythmic igneous layering by sedimentation in a convecting magma chamber

    NASA Astrophysics Data System (ADS)

    Sparks, R. Stephen; Huppert, Herbert E.; Koyaguchi, Takehiro; Hallworth, Mark A.

    1993-01-01

    EXPERIMENTAL investigations of convecting, particle-laden fluids show two regimes for convection driven by cooling from above1. In very dilute suspensions, convection will maintain a homogeneous distribution of particles throughout the convecting layer provided that particle fall velocities are small compared with turbulent fluid velocities. Above a critical concentration, convection is unable to keep the particles suspended, so the particles settle, leaving behind a layer of convecting fluid virtually free of particles. Here we apply these results to cooling magma chambers, in which crystallization leads to an increase in suspended crystal content with time. Discrete sedimentation events are predicted each time the concentration exceeds the critical value. For common igneous minerals, critical concentrations are very small (typically 0.002-0.03 wt%) and layers of the order of centimetres to a few metres thick will result. Because minerals of different density and size have different critical concentrations and settling velocities, complex fluctuations in sedimentation rate and mineral proportions can occur in a multi-component melt. This may lead to either regular repetitive cycles or more complex fluctuations. The process is confined to low-viscosity magmas, such as basalts, in which the crystals are able to separate from the active thermal boundary layer during convection.

  9. Propagation of longitudinal thermoplastic waves in layered structures

    NASA Astrophysics Data System (ADS)

    Li, Chen; Cetinkaya, Cetin

    2000-05-01

    The recent advances in photonics and laser instrumentation have been creating a favorable environment for thermal-based elastic wave generation techniques and their applications in various fields, such as nondestructive testing and smart structures. The main advantages of laser-based NDE include noncontact evaluation, freedom for complex surface geometry, high spatial and temporal resolution, easy access to cavities, and fast scanning. Two disadvantages are that the laser-based method requires a good physical understanding of thermoelastic wave propagation in solids, which is considerably more complicated than elastic wave propagation, and more complicated instrumentation needed for data collection. In an idealized solid, thermal energy is transported by two different mechanisms: by quantized electronic excitations, which are called free electrons, and the quanta of lattice vibrations, which are called phonons. These quanta undergo collisions of a dissipative nature, giving rise to thermal resistance in the medium. A relaxation time is associated with the average communication time between these collisions for the commencement of resistive flow. There are a number of optical methods available for elastic wave generation and detection. The most commonly utilized techniques include interferometric and noninterferometric techniques, optical heterodyning, differential interferometry, and time-delay interferometry. In the current work, a transfer matrix formulation including the second sound effect is developed for a thermoelastic layer. The second sound effect is included to eliminate the thermal wave travelling with infinite velocity as predicted by the diffusion heat transfer model, and, consequently, the immediate arrival of waves. Utilizing this formulation and the periodic systems framework, the attenuation and propagation properties of one-dimensional thermoelastic wave in both continuum and layered structures are studied. A perturbation analysis is carried out

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

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

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

  11. Structure of the nocturnal boundary layer over a complex terrain

    SciTech Connect

    Parker, M.J. ); Raman, S. . Dept. of Marine, Earth and Atmospheric Sciences)

    1992-01-01

    The complex nature of the nocturnal boundary layer (NBL) has been shown extensively in the literature Project STABLE was conducted in 1988 to study NBL turbulence and diffusion over the complex terrain of the Savannah River Site (SRS) near Augusta, Georgia. The third night of the study was particularly interesting because of the unusual phenomena observed in the structure of the NBL. Further analyses of microscale and mesoscale data from this night are presented using data from SRS network of eight 61 m towers over 900 km{sup 2}, from six launches of an instrumented tethersonde, from permanent SRL meteorological instrumentation at seven levels of the 304 m (1,000 ft) WJBF-TV tower near SRS, and additional data collected at 36 m (CC) by North Carolina State University (NCSU) including a one dimensional sonic anemometer, fine wire thermocouple, and a three dimensional propeller anemometer. Also, data from the nearby Plant Vogtle nuclear power plant observation tower and the National Weather Service at Augusta's Bush Field (AGS) are presented. The passage of a mesoscale phenomenon, defined as a microfront (with an explanation of the nomenclature used), and a vertical composite schematic of the NBL which shows dual low level wind maxima, dual inversions, and a persistent, elevated turbulent layer over a complex terrain are described.

  12. Structure of the nocturnal boundary layer over a complex terrain

    SciTech Connect

    Parker, M.J.; Raman, S.

    1992-08-01

    The complex nature of the nocturnal boundary layer (NBL) has been shown extensively in the literature Project STABLE was conducted in 1988 to study NBL turbulence and diffusion over the complex terrain of the Savannah River Site (SRS) near Augusta, Georgia. The third night of the study was particularly interesting because of the unusual phenomena observed in the structure of the NBL. Further analyses of microscale and mesoscale data from this night are presented using data from SRS network of eight 61 m towers over 900 km{sup 2}, from six launches of an instrumented tethersonde, from permanent SRL meteorological instrumentation at seven levels of the 304 m (1,000 ft) WJBF-TV tower near SRS, and additional data collected at 36 m (CC) by North Carolina State University (NCSU) including a one dimensional sonic anemometer, fine wire thermocouple, and a three dimensional propeller anemometer. Also, data from the nearby Plant Vogtle nuclear power plant observation tower and the National Weather Service at Augusta`s Bush Field (AGS) are presented. The passage of a mesoscale phenomenon, defined as a microfront (with an explanation of the nomenclature used), and a vertical composite schematic of the NBL which shows dual low level wind maxima, dual inversions, and a persistent, elevated turbulent layer over a complex terrain are described.

  13. Bose-Einstein condensation in low dimensional layered structures

    NASA Astrophysics Data System (ADS)

    Salas, Patricia; Solis, M. A.

    2008-03-01

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

  14. Modified silicas with different structure of grafted methylphenylsiloxane layer

    NASA Astrophysics Data System (ADS)

    Bolbukh, Yuliia; Terpiłowski, Konrad; Kozakevych, Roman; Sternik, Dariusz; Deryło-Marczewska, Anna; Tertykh, Valentin

    2016-06-01

    The method of a chemical assembly of the surface polymeric layer with high contents of the modifying agent was developed. Powders of nanodispersed silica with chemisorbed polymethylphenylsiloxane (PMPS) were synthesized by solvent-free chemical assembly technique with a dimethyl carbonate (DMC) as scission agent. Samples were characterized using FTIR spectroscopy, transmission electron microscopy (TEM), atomic force microscopy (AFM), and elemental analysis (CHN analysis). Coating microstructure, morphology, and hydrophilic-hydrophobic properties of nanoparticles were estimated. The results indicate a significant effect of the PMPS/DMC ratio at each modification stage on hydrophobic properties of modified silicas. Modification with a similar composition of the PMPS/DMC mixture, even with different polymer amount at each stage, provides the worst hydrophobicity. Results suggest that the highest hydrophobicity (contact angle θ = 135°-140°) is achieved in the case when silica modified with the PMPS/DMC mixture using multistage approach that providing a formation of the monomolecular layer of polysiloxane at the first modification step. The characteristics of surface structure were interpreted in terms of density of polymer-silica bonds at the interfaces that, usually, are reduced for modified surfaces, in a coupling with conformation model that accented the shape of chains (arch- and console-like) adsorbed on solid surfaces.

  15. The layered structure of the carbon arc discharge plasma

    NASA Astrophysics Data System (ADS)

    Vekselman, Vladislav; Stratton, Brentley; Raitses, Yevgeny; LaboratoryPlasma Nanosynthesis Team

    2016-10-01

    The arc discharge with a consumed anode is commonly used for synthesis of nanomaterials such as fullerenes, nanotubes and, more recently, graphene. The role of the arc plasma in nanosynthesis processes, including ablation of the graphite anode, nucleation and growth of nanostructures remains unclear. Our recent fast frame camera measurements revealed arc oscillations associated with the ablation processes at the anode. More sophisticated measurements using optical emission spectroscopy and spectrally resolved fast framing imaging revealed the complex, layered structure of plasma species distribution, which is dynamically changing. The results of this research include time- and space- resolved distributions of plasma species, plasma electron density and temperature. The obtained experimental data suggest a strong correlation between arc plasma parameters and nanosynthesis processes. This work was supported by US Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division.

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

    NASA Technical Reports Server (NTRS)

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

    1992-01-01

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

  17. The Origin of the Log Law Region for Wall-bounded Turbulent Boundary Layer Flows

    DTIC Science & Technology

    2011-02-25

    profile over a plate had a Gaussian-like appearance as illustrated in Fig. 1 ( 1µ will be defined shortly). The mathematical description of the...also as: “Mechanical Similitude and Turbulence”, Tech. Mem. NACA, no. 611, 1931). [3] L. Prandtl, “ Bemerkungen zur Theorie der freien Turbulenz...D. Weyburne, “A mathematical description of the fluid boundary layer,” Applied Mathematics and Computation, 175, 1675 (2006). Also D. Weyburne

  18. Origins of structural diversity within sequentially identical hexapeptides.

    PubMed Central

    Cohen, B. I.; Presnell, S. R.; Cohen, F. E.

    1993-01-01

    Efforts to predict protein secondary structure have been hampered by the apparent structural plasticity of local amino acid sequences. Kabsch and Sander (1984, Proc. Natl. Acad. Sci. USA 81, 1075-1078) articulated this problem by demonstrating that identical pentapeptide sequences can adopt distinct structures in different proteins. With the increased size of the protein structure database and the availability of new methods to characterize structural environments, we revisit this observation of structural plasticity. Within a set of proteins with less than 50% sequence identity, 59 pairs of identical hexapeptide sequences were identified. These local structures were compared and their surrounding structural environments examined. Within a protein structural class (alpha/alpha, beta/beta, alpha/beta, alpha + beta), the structural similarity of sequentially identical hexapeptides usually is preserved. This study finds eight pairs of identical hexapeptide sequences that adopt beta-strand structure in one protein and alpha-helical structure in the other. In none of the eight cases do the members of these sequences pairs come from proteins within the same folding class. These results have implications for class dependent secondary structure prediction algorithms. PMID:8298461

  19. Origin and reduction of impurities at GaAs epitaxial layer-substrate interfaces

    NASA Astrophysics Data System (ADS)

    Kanber, H.; Yang, H. T.; Zielinski, T.; Whelan, J. M.

    1988-09-01

    Surface cleaning techniques used for semi-insulating GaAs substrates prior to epitaxial growth can have an important and sometimes detrimental effect on the quality and characteristics of epitaxial layers that are grown on them. We observe that a HF rinse followed by a 5:1:1 H 2SO 4:H 2O 2:H 2O etch and H 2O rinse drastically reduced the maximum concentrations and total amount of both SIMS detected S and Si for MOCVD grown GaAs undoped epitaxial layers. Subsequent final HCl and H 2O reduced the S interfacial residues to the SIMS detection limit. Total amounts of residual Si are estimated to be equivalent to 10 -2 to 10 -3 monolayers. Residual S is less. Alternately the S residue can be comparable reduced by a HF rinse followed by a NH 4OH:H 2O 2:H 2O etch and H 2O rinse. Hot aqueous HCl removes S but not Si residues. The Si residue is not electrically active and most likely exists as islands of SiO 2. The relative significance of the impurity residues is most pronounced for halide VPE, smaller for MBE and least for MOCVD grown GaAs epitaxial layers.

  20. Origin of photogenerated carrier recombination at the metal-active layer interface in polymer solar cells.

    PubMed

    Kumar, Mukesh; Dubey, Ashish; Reza, Khan Mamun; Adhikari, Nirmal; Qiao, Qiquan; Bommisetty, Venkat

    2015-11-07

    The role of the metal-active layer interface in photogenerated recombination has been investigated using nanoscale current sensing atomic force microscopy (CS-AFM) and intensity modulated photocurrent spectroscopy (IMPS) in as-deposited, pre-annealed and post-annealed bulk heterojunction (BHJ) solar cells. Aluminum (Al) confined post-annealed BHJ solar cells exhibited a significantly improved device efficiency compared to pre-annealed BHJ solar cells having similar photocarrier harvesting ability in the active layer. The nanoscale topography and CS-AFM results indicate a uniform PCBM rich phase at the metal-active layer interface in the post-annealed cells, but PCBM segregation in the pre-annealed cells. These two different annealing processes showed different carrier dynamics revealed using IMPS under various light intensities. The IMPS results suggest reduced photo generated carrier recombination in uniform PCBM rich post-annealed BHJ solar cells. This study reveals the importance of the metal-bend interface in BHJ solar cells in order to obtain efficient charge carrier extraction for high efficiency.

  1. Neutrinos and the origin of fermion mass structure

    SciTech Connect

    Ross, Graham G.

    2007-11-20

    The pattern of neutrino masses and mixings is characteristically different from those observed in the quark sector. I discuss why this should be the case and what implications this has for the origin of quark and lepton masses, mixings and CP violation.

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

    NASA Astrophysics Data System (ADS)

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

    2013-10-01

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

  3. Structure Identification Within a Transitioning Swept-Wing Boundary Layer

    NASA Technical Reports Server (NTRS)

    Chapman, Keith; Glauser, Mark

    1996-01-01

    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

  4. 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: volkan@stanfordalumni.org; Volkan Demir, Hilmi E-mail: volkan@stanfordalumni.org

    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.

  5. High-Mobility Transport Anisotropy in Few-Layer MoO3 and Its Origin.

    PubMed

    Zhang, Wei-Bing; Qu, Qian; Lai, Kang

    2017-01-18

    The novel two-dimensional semiconductors with high carrier mobility and excellent stability are essential to the next-generation high-speed and low-power nanoelectronic devices. Because of the natural abundance, intrinsic gap, and chemical stability, metal oxides were also recently suggested as potential candidates for electronic materials. However, their carrier mobilities are typically on the order of tens of square centimeters per volt per second, much lower than that for commonly used silicon. By using first-principles calculations and deformation potential theory, we have predicted few-layer MoO3 as chemically stable wide-band-gap semiconductors with a considerably high acoustic-phonon-limited carrier mobility above 3000 cm(2) V(-1) s(-1), which makes them promising candidates for both electron- and hole-transport applications. Moreover, we also find a large in-plane anisotropy of the carrier mobility with a ratio of about 20-30 in this unusual system. Further analysis indicates that, because of the unique charge density distribution of whole valence electrons and the states near the band edge, both the elastic modulus and deformation potential are strongly directionally dependent. Also, the predicted high-mobility transport anisotropy of few-layer MoO3 can be attributed to the synergistic effect of the anisotropy of the elastic modulus and deformation potential. Our results not only give an insightful understanding for the high carrier mobility observed in few-layer MoO3 systems but also reveal the importance of the carrier-transport direction to the device performance.

  6. 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.

  7. Intercalation of cellulase enzyme into a hydrotalcite layer structure

    NASA Astrophysics Data System (ADS)

    Zou, N.; Plank, J.

    2015-01-01

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

  8. Unexpected strong magnetism of Cu doped single-layer MoS₂ and its origin.

    PubMed

    Yun, Won Seok; Lee, J D

    2014-05-21

    The magnetism of the 3d transition-metal (TM) doped single-layer (1L) MoS2, where the Mo atom is partially replaced by the 3d TM atom, is investigated using the first-principles density functional calculations. In a series of 3d TM doped 1L-MoS2's, the induced spin polarizations are negligible for Sc, Ti, and Cr dopings, while the induced spin polarizations are confirmed for V, Mn, Fe, Co, Ni, Cu, and Zn dopings and the systems become magnetic. Especially, the Cu doped system shows unexpectedly strong magnetism although Cu is nonmagnetic in its bulk state. The driving force is found to be a strong hybridization between Cu 3d states and 3p states of neighboring S, which results in an extreme unbalanced spin-population in the spin-split impurity bands near the Fermi level. Finally, we also discuss further issues of the Cu induced magnetism of 1L-MoS2 such as investigation of additional charge states, the Cu doping at the S site instead of the Mo site, and the Cu adatom on the layer (i.e., 1L-MoS2).

  9. Effect of magnetic structural processing on structure and texture of La2Zr2O7 buffer layers

    NASA Astrophysics Data System (ADS)

    Chibirova, F. Kh.; Kotina, G. V.; Bovina, E. A.; Tarasova, D. V.; Polisan, A. A.; Parkhomenko, Yu. N.

    2016-11-01

    Epitaxial CeO2 seed layer and La2Zr2O7 (LZO) buffer layers were deposited on biaxially-textured Ni-5 at.% W (NiW) tape substrate by liquid-phase polymer assisted nanoparticles deposition (PAND) method. LZO layers deposited by PAND have consistently shown tilting of the c-axis toward the direction of the sample’s surface normal. A new approach increasing the sharpening of the buffer texture by magnetic structural processing (MSP) of buffer layers was tested. The LZO layers, deposited on the seed and buffer layers after MSP, have dense and smooth surface structure, and more importantly, significantly improved out-of-plane texture, compared with the LZO layers that were deposited on a layer without MSP. Transmission electron microscopy study confirmed the c-axis tilting of CeO2 and LZO layers and revealed the absence of interfaces between LZO layers which have been grown on the layers after MSP. There are very small (2-4 nm) gated pores in the single-crystal structure of LZO layers that are not typical for structure of LZO layers obtained by liquid-phase methods. Thus the LZO buffer layers can serve as an effective metal-ion diffusion barrier.

  10. Evidence for diffusion and folding process based on the Mg# profile and the symmetrical layered structure in Horoman peridotite, Hokkaido, Japan

    NASA Astrophysics Data System (ADS)

    Nakano, T.; Toramaru, A.

    2009-12-01

    The Horoman peridotite complex, Hokkaido, Japan exhibits a conspicuous parallel layered structure, which has a characteristic symmetry in the alignment of lithological layers at the northern ridge of Mt. Apoi peak, suggesting that the layering is formed by folding or streamline mixing in mantle. The symmetrical sequence of layers is mafic layer (3cm) -depleted peridotite (1cm) -mafic layer (6cm) -peridotite (4cm; center of symmetry) -mafic layer (5cm) -depleted peridotite (1cm) -mafic layer (2.5cm). In this study, we examine the chemical profile of minerals in the symmetrical layers of depleted peridotite (dunite-harzburgite), plagioclase-rich peridotite (olivine, opx, cpx) and mafic layer (plagioclase, olivine, cpx, opx, spinel and amphibole) and its origin. We carry out chemical analysis by SEM-EDS in order to determine the chemical compositions of the mafic minerals (olivine, opx, cpx) as functions of distance in peridotite and mafic layer. As a result, we find the different Mg# profiles of mafic minerals among different lithological layers, i.e.; peridotite and mafic layer. However, a pair of same lithological layers displaying symmetry has the nearly same Mg# profile, indicating that the lithological symmetry accompanies the chemical symmetry. The Mg# of mafic minerals in a mafic layer gradually decreases from the contact surface between peridotite and mafic layer to the center of the mafic layer. In addition, the Mg# takes wide range in mafic layer (82~89) whereas the Mg# of peridotite dose narrow range (89~91, 88, 84.5 in each layer). On the basis of this chemical signature and the spatially homogeneous mineral distribution in each layer, we propose that the key process of the cryptic layering in mineral chemistry results from a diffusion process between peridotite and mafic layer after the layers are contacted. The different chemical profile between peridotite and mafic layer can be explained by the different diffusivities due to the effect of the modal

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

    SciTech Connect

    Sutherland, Kevin Jerome

    2001-01-01

    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.

  12. Layered structure in the interaction of thin foil with two laser pulses

    SciTech Connect

    Yu, Yahong; Shen, Baifei E-mail: jill@siom.ac.cn; Yu, Wei; Wang, Wenpeng; Zhang, Xiaomei; Ji, Liangliang E-mail: jill@siom.ac.cn; Zhao, Xueyan; Wang, Xiaofeng; Yi, Longqing; Shi, Yin; Xu, Tongjun; Zhang, Lingang; Wen, Meng

    2014-02-15

    An interesting layered structure of multiple high density layers are formed when two counter-propagating circularly polarized laser pulses with the same polarization direction irradiate on an ultra-thin foil. This structure changes periodically. For light atoms most of which electrons may be fully ionized, this layered structure can keep for dozens of laser periods after the laser-foil interaction. This interesting structure may have potential applications.

  13. Layered Organization in the Coastal Ocean: 4-D Assessment of Thin Layer Structure, Dynamics and Impacts

    DTIC Science & Technology

    2009-09-30

    maintenance and dissipation of layers; (2) to understand the spatial coherence and spatial properties of thin layers in the coastal ocean (especially in...ORCAS profilers at K1 South and K2 had a Nortek ADV (Acoustic Doppler Velocity meter) for simultaneously measuring centimeter- scale currents and...year will be used to (1) detect the presence, intensity, thickness, temporal persistence, and spatial coherence of thin optical and acoustical layers

  14. 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 Γ 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.

  15. Reversible and irreversible structural transformations of nanocomponents of molecular layers by resonance photoexcitation or heating

    NASA Astrophysics Data System (ADS)

    Kaliteevskaya, Elena N.; Krutyakova, Valentina P.; Razumova, Tatyana K.; Starovoytov, Anton A.

    2010-09-01

    The reversible and irreversible structural transformations of monomolecular and associated nanocomponents of a polymethine dye layer by photoexcitation or heating are studied experimentally. The photo- and thermodestruction yields of the layers are investigated.

  16. On the origins of the mitotic shift in proliferating cell layers

    PubMed Central

    2014-01-01

    Background During plant and animal development, monolayer cell sheets display a stereotyped distribution of polygonal cell shapes. In interphase cells these shapes range from quadrilaterals to decagons, with a robust average of six sides per cell. In contrast, the subset of cells in mitosis exhibits a distinct distribution with an average of seven sides. It remains unclear whether this ‘mitotic shift’ reflects a causal relationship between increased polygonal sidedness and increased division likelihood, or alternatively, a passive effect of local proliferation on cell shape. Methods We use a combination of probabilistic analysis and mathematical modeling to predict the geometry of mitotic polygonal cells in a proliferating cell layer. To test these predictions experimentally, we use Flp-Out stochastic labeling in the Drosophila wing disc to induce single cell clones, and confocal imaging to quantify the polygonal topologies of these clones as a function of cellular age. For a more generic test in an idealized cell layer, we model epithelial sheet proliferation in a finite element framework, which yields a computationally robust, emergent prediction of the mitotic cell shape distribution. Results Using both mathematical and experimental approaches, we show that the mitotic shift derives primarily from passive, non-autonomous effects of mitoses in neighboring cells on each cell’s geometry over the course of the cell cycle. Computationally, we predict that interphase cells should passively gain sides over time, such that cells at more advanced stages of the cell cycle will tend to have a larger number of neighbors than those at earlier stages. Validating this prediction, experimental analysis of randomly labeled epithelial cells in the Drosophila wing disc demonstrates that labeled cells exhibit an age-dependent increase in polygonal sidedness. Reinforcing these data, finite element simulations of epithelial sheet proliferation demonstrate in a generic framework

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

    SciTech Connect

    Sutherland, Kevin Jerome

    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

  18. 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.

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

    DOEpatents

    Arendt, Paul N.; Foltyn, Stephen R.; Groves, James R.; Jia, Quanxi

    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.

  20. Electronic structure of the layered diboride dicarbide superconductor Y B2C2

    NASA Astrophysics Data System (ADS)

    Khmelevskyi, S.; Mohn, P.; Redinger, J.; Michor, H.

    2005-04-01

    The electronic structure of the layered diboride dicarbide superconductor Y B2C2 is calculated using the full potential LAPW method within the framework of ab initio density functional theory. Our results confirm that the crystal structure with P4/mbm symmetry is more stable than the originally claimed P\\overline {4}2c structure, which is in accordance with recent interpretations of the diffraction patterns of other related compounds of LaB2C2-type. It is found that the metallic conductivity in the stable P4/mbm structure is due to Y d-bands partially hybridized with pz-states from the B-C planes. Thus the structure of the conduction bands differs from those found in MgB2. However, a large portion of the Fermi surface of Y B2C2 exhibits distinctive two-dimensional features, which can make this compound interesting for experimental studies on superconductivity connected to effects of strong electronic structure anisotropy.

  1. Unusual ZFC and FC magnetic behavior in thin Co multi-layered structure

    NASA Astrophysics Data System (ADS)

    Ben-Dor, Oren; Yochelis, Shira; Felner, Israel; Paltiel, Yossi

    2017-04-01

    The observation of unusual magnetic phenomena in a Ni -based magnetic memory device ([4] O. Ben-Dor et al., 2013) encouraged us to conduct a systematic research on Co based multi-layered structure which contains a α-helix L polyalanine (AHPA-L) organic compound. The constant Co thickness is 7 nm and AHPA-L was also replaced by non-chiral 1-Decanethiol organic molecules. Both organic compounds were chemisorbed on gold by a thiol group. The dc magnetic field (H) was applied parallel and perpendicular to the surface layers. The perpendicular direction is the easy magnetization axis and along this orientation only, the zero-field-cooled (ZFC) plots exhibit a pronounced peak around 55-58 K. This peak is suppressed in the second ZFC and field-cooled (FC) runs performed shortly after the virgin ZFC one. Thus, around the peak position ZFC>FC a phenomenon seldom observed. This peak reappears after measuring the same material six months later. This behavior appears in layers with the non-chiral 1-Decanethiol and it is very similar to that obtained in sulfur doped amorphous carbon. The peak origin and the peculiar ZFC>FC case are qualitatively explained.

  2. 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

  3. A structural origin for the cantaloupe terrain of Triton

    NASA Technical Reports Server (NTRS)

    Boyce, Joseph M.

    1993-01-01

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

  4. Structure of Greyhound hemoglobin: origin of high oxygen affinity.

    PubMed

    Bhatt, Veer S; Zaldívar-López, Sara; Harris, David R; Couto, C Guillermo; Wang, Peng G; Palmer, Andre F

    2011-05-01

    This study presents the crystal structure of Greyhound hemoglobin (GrHb) determined to 1.9 Å resolution. GrHb was found to crystallize with an α₁β₁ dimer in the asymmetric unit and belongs to the R2 state. Oxygen-affinity measurements combined with the fact that GrHb crystallizes in the R2 state despite the high-salt conditions used for crystallization strongly indicate that GrHb can serve as a model high-oxygen-affinity hemoglobin (Hb) for higher mammals, especially humans. Structural analysis of GrHb and its comparison with the R2-state of human Hb revealed several regions that can potentially contribute to the high oxygen affinity of GrHb and serve to rationalize the additional stability of the R2-state of GrHb. A previously well studied hydrophobic cluster of bar-headed goose Hb near α119 was also incorporated in the comparison between GrHb and human Hb. Finally, a structural comparison with generic dog Hb and maned wolf Hb was conducted, revealing that in contrast to GrHb these structures belong to the R state of Hb and raising the intriguing possibility of an additional allosteric factor co-purifying with GrHb that can modulate its quaternary structure.

  5. Potassium under pressure: Electronic origin of complex structures

    NASA Astrophysics Data System (ADS)

    Degtyareva, V. F.

    2014-10-01

    Recent high-pressure X-ray diffraction studies of alkali metals revealed unusual complex structures that follow the body-centred and face-centred cubic structures on compression. The structural sequence of potassium under compression to 1 Mbar is as follows: bcc-fcc-h-g (tI19*), hP4-oP8-tI4-oC16. We consider configurations of Brillouin-Jones zones and the Fermi surface within a nearly-free-electron model in order to analyze the importance of these configurations for the crystal structure stability. Formation of Brillouin zone planes close to the Fermi surface is related to opening an energy gap at these planes and reduction of crystal energy. Under pressure, this mechanism becomes more important leading to appearance of complex low-symmetry structures. The stability of the post-fcc phases in K is attributed to the changes in the valence electron configuration under strong compression.

  6. A non-magnetic spacer layer effect on spin layers (7/2,3) in a bi-layer ferromagnetic dendrimer structure: Monte Carlo study

    NASA Astrophysics Data System (ADS)

    Jabar, A.; Tahiri, N.; Bahmad, L.; Benyoussef, A.

    2016-11-01

    A bi-layer system consisting of layers of spins (7/2, 3) in a ferromagnetic dendrimer structure, separated by a non-magnetic spacer, is studied by Monte Carlo simulations. The effect of the RKKY interactions is investigated and discussed for such system. It is shown that the magnetic properties in the two magnetic layers depend strongly on the thickness of the magnetic and non-magnetic layers. The total magnetizations and susceptibilities are studied as a function of the reduced temperature. The effect of the reduced exchange interactions as well as the reduced crystal field is outlined. On other hand, the critical temperature is discussed as a function of the magnetic layer values. To complete this study we presented and discussed the magnetic hysteresis cycles.

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

    PubMed

    Danilkin, I V; Simonov, Yu A

    2010-09-03

    The dynamical mechanism of channel coupling with the decay channels is applied to the case of coupled charmonium--DD* states with JPC=1++. A pole analysis is done and the DD* production cross section is calculated in qualitative agreement with experiment. The sharp peak at the D0D0* 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 23P1, QQ state. A similar analysis, applied to the n=2, 3P2, 1P1, 3P0, allows us to associate the first one with the observed Z(3930) J=2 and explains the destiny of 3P0.

  8. Structure and Response to Flow of the Glycocalyx Layer

    PubMed Central

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

    2014-01-01

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

  9. Structure and response to flow of the glycocalyx layer.

    PubMed

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

    2014-01-07

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

  10. Molecular analysis of neocortical layer structure in the ferret

    PubMed Central

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

    2010-01-01

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

  11. 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 α. 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 α, 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.

  12. 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 α . 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 α , 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.

  13. 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.

  14. The structural origin of anomalous properties of liquid water

    PubMed Central

    Nilsson, Anders; Pettersson, Lars G. M.

    2015-01-01

    Water is unique in its number of unusual, often called anomalous, properties. When hot it is a normal simple liquid; however, close to ambient temperatures properties, such as the compressibility, begin to deviate and do so increasingly on further cooling. Clearly, these emerging properties are connected to its ability to form up to four well-defined hydrogen bonds allowing for different local structural arrangements. A wealth of new data from various experiments and simulations has recently become available. When taken together they point to a heterogeneous picture with fluctuations between two classes of local structural environments developing on temperature-dependent length scales. PMID:26643439

  15. On the origin of photoluminescence in indium oxide octahedron structures

    SciTech Connect

    Kumar, Mukesh; Singh, V. N.; Mehta, B. R.; Singh, J. P.; Singh, F.; Lakshmi, K. V.

    2008-04-28

    A sixfold decrease in photoluminescence signal intensity at 590 nm with increase in deposition time from 3 to 12 h has been observed in single crystalline indium oxide octahedron structures grown by vapor-phase evaporation method. Electron paramagnetic resonance and energy dispersive x-ray analysis confirm that the concentration of oxygen vacancies increases with deposition time. These results are contrary to the previous reports where oxygen vacancies were shown to be responsible for photoluminescence in indium oxide structures. Our results indicate that indium interstitials and their associated complex defects other than oxygen vacancies are responsible for the photoluminescence in In{sub 2}O{sub 3} microstructures.

  16. Energy gap structure and tunneling characteristics of layered superconductors

    SciTech Connect

    Liu, S.H.; Klemm, R.A.

    1993-06-01

    The authors have analyzed the energy gaps and density-of-states (DOS) of layered superconductors with two inequivalent layers in a unit cell along the c-axis. In the physically interesting parameter range where the interlayer hopping strengths of the quasiparticles are comparable to the critical temperature, the peaks in the DOS curve do not correspond to the order parameters (OP`s) of each layer, but depend on the OP`s and the interlayer hopping strengths in a complex manner. In contrast to a BCS superconductor, the DOS of layered systems have logarithmic singularities. The simulated tunneling characteristics bear close resemblance to experimental results.

  17. Electronic origin of structural transition in 122 Fe based superconductors

    NASA Astrophysics Data System (ADS)

    Ghosh, Haranath; Sen, Smritijit; Ghosh, Abyay

    2017-03-01

    Direct quantitative correlations between the orbital order and orthorhombicity is achieved in a number of Fe-based superconductors of 122 family. The former (orbital order) is calculated from first principles simulations using experimentally determined doping and temperature dependent structural parameters while the latter (the orthorhombicity) is taken from already established experimental studies; when normalized, both the above quantities quantitatively corresponds to each other in terms of their doping as well as temperature variations. This proves that the structural transition in Fe-based materials is electronic in nature due to orbital ordering. An universal correlations among various structural parameters and electronic structure are also obtained. Most remarkable among them is the mapping of two Fe-Fe distances in the low temperature orthorhombic phase, with the band energies Edxz, Edyz of Fe at the high symmetry points of the Brillouin zone. The fractional co-ordinate zAs of As which essentially determines anion height is inversely (directly) proportional to Fe-As bond distances (with exceptions of K doped BaFe2As2) for hole (electron) doped materials as a function of doping. On the other hand, Fe-As bond-distance is found to be inversely (directly) proportional to the density of states at the Fermi level for hole (electron) doped systems. Implications of these results to current issues of Fe based superconductivity are discussed.

  18. Quantification of layered patterns with structural anisotropy: a comparison of biological and geological systems.

    PubMed

    Smolyar, I; Bromage, T; Wikelski, M

    2016-03-01

    Large-scale patterns evident from satellite images of aeolian landforms on Earth and other planets; those of intermediate scale in marine and terrestrial sand ripples and sediment profiles; and small-scale patterns such as lamellae in the bones of vertebrates and annuli in fish scales are each represented by layers of different thicknesses and lengths. Layered patterns are important because they form a record of the state of internal and external factors that regulate pattern formation in these geological and biological systems. It is therefore potentially possible to recognize trends, periodicities, and events in the history of the formation of these systems among the incremental sequences. Though the structures and sizes of these 2-D patterns are typically scale-free, they are also characteristically anisotropic; that is, the number of layers and their absolute thicknesses vary significantly during formation. The aim of the present work is to quantify the structure of layered patterns and to reveal similarities and differences in the processing and interpretation of layered landforms and biological systems. To reach this goal we used N-partite graph and Boolean functions to quantify the structure of layers and plot charts for "layer thickness vs. layer number" and "layer area vs. layer number". These charts serve as a source of information about events in the history of formation of layered systems. The concept of synchronization of layer formation across a 2-D plane is introduced to develop the procedure for plotting "layer thickness vs. layer number" and "layer area vs. layer number", which takes into account the structural anisotropy of layered patterns and increase signal-to-noise ratio in charts. Examples include landforms on Mars and Earth and incremental layers in human and iguana bones.

  19. The origin of the distortion product otoacoustic emission fine structure

    NASA Astrophysics Data System (ADS)

    Piskorski, Pawel

    Distortion-product otoacoustic emissions (DPOAEs) are sounds detected in the ear canal which are generated by the nonlinear processes in the inner ear (cochlea) in response to the external stimulation of two or more tones (primaries). Their generation region in the cochlea can be systematically changed by varying the primary frequencies, and they are currently being evaluated for possible clinical use in screening for hearing defects. The phase and amplitude of various orders of DPOAEs of frequencies, f/sb [dp]=f1-n(f2-f1),/ (n=1,2,/...), were measured in human subjects for two- tone stimuli of frequencies f1 and f2 (>f1). A number of experimental paradigms (fixed primary ratio f2/f1, fixed f1, fixed f2, and fixed f/sb [dp]) were used to investigate the nature of peaks and valleys (fine structure) of DPOAEs in their phase and amplitude dependence on the primary frequencies. This fine structure must be taken into account in any potential clinical applications of DPOAEs. The experimental results largely support a model in which the fine structure stems from interference at the base of the cochlea between distortion product (DP) components coming from the primary DPOAE source region (around the f2 tonotopic place) and components coming from the DP tonotopic place (via reflection of an apically moving DP wave). The spectral periodicity of the fine structures for several orders of apical DPOAEs corresponds to a tonotopic displacement of about 0.4 mm along the basilar membrane (BM) (0.4 bark). In agreement with the reaction model, this spectral spacing is also characteristic of synchronous evoked and spontaneous otoacoustic emission spectra as well as the microstructure of the hearing threshold. Approximate analytic expressions for the mechanisms which are responsible for the fine structure are used to interpret the data.

  20. Localised Ag(+) vibrations at the origin of ultralow thermal conductivity in layered thermoelectric AgCrSe2.

    PubMed

    Damay, F; Petit, S; Rols, S; Braendlein, M; Daou, R; Elkaïm, E; Fauth, F; Gascoin, F; Martin, C; Maignan, A

    2016-03-22

    In materials science, the substructure approach consists in imagining complex materials in which a particular property is associated with a distinct structural feature, so as to combine different chosen physical characteristics, which otherwise have little chance to coexist. Applied to thermoelectric materials, it has been used to achieve simultaneously phonon-glass and electron-crystal properties. Mostly studied for its superionic conductivity, AgCrSe2 is a naturally layered compound, which achieves very low thermal conductivity, ~0.4 W.K(-1).m(-1) at RT (room temperature), and is considered a promising thermoelectric. The Cr atoms of the [CrSe2]∞ layer bear a spin S = 3/2, which orders below TN = 55 K. Here we report low temperature inelastic neutron scattering experiments on AgCrSe2, alongside the magnetic field evolution of its thermal and electrical transport. We observe a very low frequency mode at 3 meV, ascribed to large anharmonic displacements of the Ag(+) ions in the [Ag]∞ layer, and 2D magnetic fluctuations up to 3 TN in the chromium layer. The low thermal conductivity of AgCrSe2 is attributed to acoustic phonon scattering by a regular lattice of Ag(+) oscillating in quasi-2D potential wells. These findings highlight a new way to achieve localised phonon modes in a perfectly crystalline solid.

  1. Localised Ag+ vibrations at the origin of ultralow thermal conductivity in layered thermoelectric AgCrSe2

    PubMed Central

    Damay, F.; Petit, S.; Rols, S.; Braendlein, M.; Daou, R.; Elkaïm, E.; Fauth, F.; Gascoin, F.; Martin, C.; Maignan, A.

    2016-01-01

    In materials science, the substructure approach consists in imagining complex materials in which a particular property is associated with a distinct structural feature, so as to combine different chosen physical characteristics, which otherwise have little chance to coexist. Applied to thermoelectric materials, it has been used to achieve simultaneously phonon-glass and electron-crystal properties. Mostly studied for its superionic conductivity, AgCrSe2 is a naturally layered compound, which achieves very low thermal conductivity, ~0.4 W.K−1.m−1 at RT (room temperature), and is considered a promising thermoelectric. The Cr atoms of the [CrSe2]∞ layer bear a spin S = 3/2, which orders below TN = 55 K. Here we report low temperature inelastic neutron scattering experiments on AgCrSe2, alongside the magnetic field evolution of its thermal and electrical transport. We observe a very low frequency mode at 3 meV, ascribed to large anharmonic displacements of the Ag+ ions in the [Ag]∞ layer, and 2D magnetic fluctuations up to 3 TN in the chromium layer. The low thermal conductivity of AgCrSe2 is attributed to acoustic phonon scattering by a regular lattice of Ag+ oscillating in quasi-2D potential wells. These findings highlight a new way to achieve localised phonon modes in a perfectly crystalline solid. PMID:27000414

  2. Structural origins of high-affinity biotin binding to streptavidin.

    PubMed

    Weber, P C; Ohlendorf, D H; Wendoloski, J J; Salemme, F R

    1989-01-06

    The high affinity of the noncovalent interaction between biotin and streptavidin forms the basis for many diagnostic assays that require the formation of an irreversible and specific linkage between biological macromolecules. Comparison of the refined crystal structures of apo and a streptavidin:biotin complex shows that the high affinity results from several factors. These factors include the formation of multiple hydrogen bonds and van der Waals interactions between biotin and the protein, together with the ordering of surface polypeptide loops that bury the biotin in the protein interior. Structural alterations at the biotin binding site produce quaternary changes in the streptavidin tetramer. These changes apparently propagate through cooperative deformations in the twisted beta sheets that link tetramer subunits.

  3. Origin and structure of polar domains in doped molecular crystals

    PubMed Central

    Meirzadeh, E.; Azuri, I.; Qi, Y.; Ehre, D.; Rappe, A. M.; Lahav, M.; Kronik, L.; Lubomirsky, I.

    2016-01-01

    Doping is a primary tool for the modification of the properties of materials. Occlusion of guest molecules in crystals generally reduces their symmetry by the creation of polar domains, which engender polarization and pyroelectricity in the doped crystals. Here we describe a molecular-level determination of the structure of such polar domains, as created by low dopant concentrations (<0.5%). The approach comprises crystal engineering and pyroelectric measurements, together with dispersion-corrected density functional theory and classical molecular dynamics calculations of the doped crystals, using neutron diffraction data of the host at different temperatures. This approach is illustrated using centrosymmetric α-glycine crystals doped with minute amounts of different L-amino acids. The experimentally determined pyroelectric coefficients are explained by the structure and polarization calculations, thus providing strong support for the local and global understanding of how different dopants influence the properties of molecular crystals. PMID:27824050

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

    NASA Astrophysics Data System (ADS)

    Yastrubchak, O.; Wosinski, T.; Gluba, L.; Andrearczyk, T.; Domagala, J. Z.; Żuk, J.; Sadowski, J.

    2014-01-01

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

  5. Origin and evolution of the deep thermochemical structure beneath Eurasia

    NASA Astrophysics Data System (ADS)

    Flament, N.; Williams, S.; Müller, R. D.; Gurnis, M.; Bower, D. J.

    2017-01-01

    A unique structure in the Earth's lowermost mantle, the Perm Anomaly, was recently identified beneath Eurasia. It seismologically resembles the large low-shear velocity provinces (LLSVPs) under Africa and the Pacific, but is much smaller. This challenges the current understanding of the evolution of the plate-mantle system in which plumes rise from the edges of the two LLSVPs, spatially fixed in time. New models of mantle flow over the last 230 million years reproduce the present-day structure of the lower mantle, and show a Perm-like anomaly. The anomaly formed in isolation within a closed subduction network ~22,000 km in circumference prior to 150 million years ago before migrating ~1,500 km westward at an average rate of 1 cm year-1, indicating a greater mobility of deep mantle structures than previously recognized. We hypothesize that the mobile Perm Anomaly could be linked to the Emeishan volcanics, in contrast to the previously proposed Siberian Traps.

  6. Origin and evolution of the deep thermochemical structure beneath Eurasia

    PubMed Central

    Flament, N.; Williams, S.; Müller, R. D.; Gurnis, M.; Bower, D. J.

    2017-01-01

    A unique structure in the Earth's lowermost mantle, the Perm Anomaly, was recently identified beneath Eurasia. It seismologically resembles the large low-shear velocity provinces (LLSVPs) under Africa and the Pacific, but is much smaller. This challenges the current understanding of the evolution of the plate–mantle system in which plumes rise from the edges of the two LLSVPs, spatially fixed in time. New models of mantle flow over the last 230 million years reproduce the present-day structure of the lower mantle, and show a Perm-like anomaly. The anomaly formed in isolation within a closed subduction network ∼22,000 km in circumference prior to 150 million years ago before migrating ∼1,500 km westward at an average rate of 1 cm year−1, indicating a greater mobility of deep mantle structures than previously recognized. We hypothesize that the mobile Perm Anomaly could be linked to the Emeishan volcanics, in contrast to the previously proposed Siberian Traps. PMID:28098137

  7. The Origins of Magnetic Structure in the Corona and Wind

    NASA Technical Reports Server (NTRS)

    Antiochos, Spiro K.

    2010-01-01

    One of the most important and most puzzling features of the coronal magnetic field is that it appears to have smooth magnetic structure with little evidence for non-potentiality except at two special locations: photospheric polarity inversions lines. (non-potentiality observed as a filament channel) and coronal hole boundaries, (observed as the slow solar wind). This characteristic feature of the closed-field corona is highly unexpected given that its magnetic field is continuously tangled by photospheric motions. Although reconnection can eliminate some of the injected structure, it cannot destroy the helicity, which should build up to produce observable complexity. I propose that an inverse cascade process transports the injected helicity from the interior of closed flux regions to their boundaries inversion lines and coronal holes, creating both filament channels and the slow wind. We describe how the helicity is injected and transported and calculate the relevant rates. I argue that one process, helicity transport, can explain both the observed lack and presence of structure in the coronal magnetic field. This work has been supported by the NASA HTP, SR&T, and LWS programs.

  8. Layered Organization in the Coastal Ocean: 4-D Assessment of Thin Layer Structure, Dynamics and Impacts

    DTIC Science & Technology

    2008-01-01

    oceans, and the processes responsible for the formation, maintenance and dissipation of layers; (2) to understand the spatial coherence and spatial...and K2 had a Nortek ADV (Acoustic Doppler Velocity meter) for simultaneously measuring centimeter- scale currents and turbulence. Our ORCAS profiler...detect the presence, intensity, thickness, temporal persistence, and spatial coherence of thin optical and acoustical layers, (2) quantify their optical

  9. Magnetic structure of the spin-1/2 layer compound NaNiO2

    NASA Astrophysics Data System (ADS)

    Darie, C.; Bordet, P.; de Brion, S.; Holzapfel, M.; Isnard, O.; Lecchi, A.; Lorenzo, J. E.; Suard, E.

    2005-01-01

    We have carried out high resolution neutron powder diffraction experiments aiming at a determination of the magnetic structure of the S=1/2 layer compound NaNiO2. The magnetic moments are ferromagnetically aligned in the NiO2 layers and antiparallel between layers. The direction of the magnetic moment has a small component along the a-direction.

  10. Active Structural Acoustic Control in an Original A400M Aircraft Structure

    NASA Astrophysics Data System (ADS)

    Koehne, C.; Sachau, D.; Renger, K.

    2016-09-01

    Low frequency noise has always been a challenge in propeller driven aircraft. At low frequencies passive noise treatments are not as efficient as active noise reduction systems. The Helmut-Schmidt-University has built up a full-scale test rig with an original A400M aircraft structure. This provides a good opportunity to develop and test active noise reduction systems in a realistic environment. The currently installed system consists of mechanical actuators and acoustical sensors. The actuators are called TVAs (Tuneable Vibration Absorber) and contain two spring-mass systems whose natural frequencies are adjusted to the BPFs (Blade Passage Frequency) of the propellers. The TVAs are mounted to the frames and the force direction is normal to the skin. The sensors are condenser microphones which are attached to the primary structure of the airframe. The TVAs are equipped with signal processing devices. These components carry out Fourier transforms and signal amplification for the sensor data and actuator signals. The communication between the TVAs and the central control unit is implemented by the CAN Bus protocol and mainly consists of complex coefficients for the sensor and actuator data. This paper describes the basic structure of the system, the hardware set-up and function tests of the controller.

  11. 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.

  12. Surface layer clamping as origin for size-dependent downshift of Curie temperature in PbTiO3 nanoparticles

    NASA Astrophysics Data System (ADS)

    Ma, Wenhui

    2013-07-01

    Size dependent Curie temperature in ferroelectric nanoparticles has been shown to originate from mechanical clamping of phase transition in particle core by a cubic surface layer. Based on a phenomenological model, the widely observed empirical relation between downshift of Curie point and particle size has been deduced by introducing an extra term of core-shell boundary energy into the free energy expression. Theoretical calculations of size dependent Curie temperature in PbTiO3 nanoparticles are in well agreement with the literature-reported experimental data. The positive boundary free energy of nano-sized PbTiO3 particles becomes increasingly large with size reduction, leading to a sharp drop of Curie temperature as compared to bulk single crystal.

  13. Structure of turbulence in three-dimensional boundary layers

    NASA Technical Reports Server (NTRS)

    Subramanian, Chelakara S.

    1993-01-01

    This report provides an overview of the three dimensional turbulent boundary layer concepts and of the currently available experimental information for their turbulence modeling. It is found that more reliable turbulence data, especially of the Reynolds stress transport terms, is needed to improve the existing modeling capabilities. An experiment is proposed to study the three dimensional boundary layer formed by a 'sink flow' in a fully developed two dimensional turbulent boundary layer. Also, the mean and turbulence field measurement procedure using a three component laser Doppler velocimeter is described.

  14. Structure of the zero-pressure-gradient turbulent boundary layer.

    PubMed

    Barenblatt, G I; Chorin, A J; Hald, O H; Prostokishin, V M

    1997-07-22

    A processing of recent experimental data by Nagib and Hites [Nagib, H. & Hites, M. (1995) AIAA paper 95-0786, Reno, NV) shows that the flow in a zero-pressure-gradient turbulent boundary layer, outside the viscous sublayer, consists of two self-similar regions, each described by a scaling law. The results concerning the Reynolds-number dependence of the coefficients of the wall-region scaling law are consistent with our previous results concerning pipe flow, if the proper definition of the boundary layer Reynolds number (or boundary layer thickness) is used.

  15. 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 μm) 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.

  16. 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.

  17. 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.

  18. Mirror instability and the origin of morningside auroral structure

    SciTech Connect

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

    1983-05-01

    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. We have constructed a theory of morningside auroras consistent with these features. The theory is based on modulation of the growth rates of electron cyclotron waves by the mirror instability, which is in turn driven by inward-convected ions that have become anisotropic. This modulation produces alternating bands of enhanced and reduced electron precipitation which approximate the observed multiple auroral bands and patches of the morning sector.

  19. Surface ozone-aerosol behaviour and atmospheric boundary layer structure in Saharan dusty scenario

    NASA Astrophysics Data System (ADS)

    Adame, Jose; Córdoba-Jabonero, Carmen; Sorrribas, Mar; Gil-Ojeda, Manuel; Toledo, Daniel; Yela, Margarita

    2016-04-01

    A research campaign was performed for the AMISOC (Atmospheric Minor Species relevant to the Ozone Chemistry) project at El Arenosillo observatory (southwest Spain) in May-June 2012. The campaign focused on the impact of Saharan dust intrusions at the Atmospheric Boundary Layer (ABL) and ozone-aerosol interactions. In-situ and remote-sensing techniques for gases and aerosols were used moreover to modelling analyses. Meteorology features, ABL structures and evolution, aerosol profiling distributions and aerosol-ozone interactions on the surface were analysed. Two four-day periods were selected according to non-dusty (clean conditions) and dusty (Saharan dust) situations. In both scenarios, sea-land breezes developed in the lower atmosphere, but differences were found in the upper levels. Results show that surface temperatures were greater than 3°C and humidity values were lower during dusty conditions than non-dusty conditions. Thermal structures on the surface layer (estimated using an instrument on a 100 m tower) show differences, mainly during nocturnal periods with less intense inversions under dusty conditions. The mixing layer during dusty days was 400-800 m thick, less than observed on non-dusty days. Dust also disturbed the typical daily ABL evolution. Stable conditions were observed during the early evening during intrusions. Aerosol extinction on dusty days was 2-3 times higher, and the dust was confined between 1500 and 5500 m. Back trajectory analyses confirmed that the dust had an African origin. On the surface, the particle concentration was approximately 3.5 times higher during dusty events, but the local ozone did not exhibit any change. The arrival of Saharan dust in the upper levels impacted the meteorological surface, inhibited the daily evolution of the ABL and caused an increase in aerosol loading on the surface and at higher altitudes; however, no dust influence was observed on surface ozone.

  20. The current structure of stratified tidal planetary boundary layer flow

    SciTech Connect

    Myrhaug, D.; Slaattelid, O.H.

    1995-12-31

    The paper presents the bottom shear stress and velocity profiles in stratified tidal planetary boundary layer flow by using similarity theory. For a given seabed roughness length, free stream current velocity components, frequency of tidal oscillation, Coriolis parameter and stratification parameter the maximum bottom shear stress is determined for flow conditions in the rough, smooth and transitional smooth-to-rough turbulent regime. Further, the direction of the bottom shear stress and the velocity profiles are given. Comparison is made with data from field measurements of time-independent as well as tidal planetary boundary layer flow for neutral conditions, and the agreement between the predictions and the data is generally good. Further, an example of application for stable stratification is given, and qualitatively the predictions show, as expected, that the bottom shear stress and the thickness of the boundary layer become smaller for stable than for neutral stratification. Other features of the tidal planetary boundary layer flow are also discussed.

  1. Cell lineage, axis formation, and the origin of germ layers in the amphipod crustacean Orchestia cavimana.

    PubMed

    Wolff, Carsten; Scholtz, Gerhard

    2002-10-01

    Embryos of the amphipod crustacean Orchestia cavimana are examined during cleavage, gastrulation, and segmentation by using in vivo labelling. Single blastomeres of the 8- and 16-cell stages were labelled with DiI to trace cell lineages. Early cleavage follows a distinct pattern and the a/p and d/v body axes are already determined at the 4- and 8-cell stages, respectively. In these stages, the germinal rudiment and the naupliar mesoderm can be traced back to a single blastomere each. In addition, the ectoderm and the postnaupliar mesoderm are separated into right and left components. At the16-cell stage, naupliar ectoderm is divided from the postnaupliar ectoderm, and extraembryonic lineages are separated from postnaupliar mesoderm and endoderm. From our investigation, it is evident that the cleavage pattern and cell lineage of Orchestia cavimana are not of the spiral type. Furthermore, the results of the labelling show many differences to cleavage patterns and cell lineages in other crustaceans, in particular, other Malacostraca. The cleavage and cell lineage patterns of the amphipod Orchestia are certainly derived within Malacostraca, whose ancestral cleavage mode was most likely of the superficial type. On the other hand, Orchestia exhibits a stereotyped cell division pattern during formation and differentiation of the germ band that is typical for malacostracans. Hence, a derived (apomorphic) early cleavage pattern is the ontogenetic basis for an evolutionarily older cell division pattern of advanced developmental stages. O. cavimana offers the possibility to trace the lineages and the fates of cells from early developmental stages up to the formation of segmental structures, including neurogenesis at a level of resolution that is not matched by any other arthropod system.

  2. Porous Materials with Tunable Structure and Mechanical Properties via Templated Layer-by-Layer Assembly.

    PubMed

    Ziminska, Monika; Dunne, Nicholas; Hamilton, Andrew R

    2016-08-31

    The deposition of stiff and strong coatings onto porous templates offers a novel strategy for fabricating macroscale materials with controlled architectures at the micro- and nanoscale. Here, layer-by-layer assembly is utilized to fabricate nanocomposite-coated foams with highly customizable properties by depositing polymer-nanoclay coatings onto open-cell foam templates. The compressive mechanical behavior of these materials evolves in a predictable manner that is qualitatively captured by scaling laws for the mechanical properties of cellular materials. The observed and predicted properties span a remarkable range of density-stiffness space, extending from regions of very soft elastomer foams to very stiff, lightweight honeycomb and lattice materials.

  3. 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.

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

    SciTech Connect

    Chiar, J. E.; Ricca, A.; Tielens, A. G. G. M.; Adamson, A. J. E-mail: Alessandra.Ricca@1.nasa.gov E-mail: aadamson@gemini.edu

    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.

  5. [ICNP- International Classification of Nursing Practice: origin, structure and development].

    PubMed

    Marucci, Anna Rita; De Caro, Walter; Petrucci, Cristina; Lancia, Loreto; Sansoni, Julita

    2015-01-01

    ICNP is a standardized nursing terminology included within acknowledged terminologies by WHO, it is a relevant aspect of ICN programs and strategies. This paper aims to describe structure and characteristics of ICNP terminology as well as to highlight how this tool can be useful both in practice and in terms of nursing professional development. This version looks like a pyramid with seven axes describing different areas of nursing and related interventions, enriched by two special axes related to pre-coordinated Diagnosis / Outcomes (DC) and Operations (IC) which facilitate daily use in practice. In order to clarify how this tool can be actually be used in daily nursing practice some examples are provided, clarifying how adopting the current version of ICNP terminology (2015 release) Diagnosis/Outcomes and Interventions can be built. The ICNP Italian Centre is committed to introduce it to Italian nurses as a tool for sharing and disseminating terminology in our Country, having as main final aim to achieve even in Italy, professional visibility objectives promoted in different ways by the International Council of Nurses.

  6. 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.

  7. Morphology, Structure, and Origin of Island Paterae on Io

    NASA Astrophysics Data System (ADS)

    Howell, R. R.; Lopes, R. M.

    2011-12-01

    We are investigating both the small and large scale morphology of those paterae on Jupiter's moon Io which show central islands. At small scales a variety of features may be evidence of volatile transport processes. For example Loki Patera contains small bright spots colloquially known as sulfur bergs, which we suspect are fumarole deposits. They are near the limit of the best spatial resolution obtained in Voyager I images. Our preliminary results indicate their reflectance is consistent with sulfur (but not sulfur dioxide) as would be expected based on the temperatures seen in the infrared. At large scales we are beginning to model the stress patterns which could produce the overall morphology of island paterae. As discussed by Radebaugh (Ph.D. Dissertation, 2005) and Black (M.S. thesis, 2007), of 428 cataloged patera on Io, 35 contain bright islands. Most of these islands are irregularly shaped and may simply be regions not yet covered by lava. However several paterae, in particular Loki and Tupan, show more regular structure. Both patera have one straight edge, and in the case of Loki the most volcanically active part of the patera is located near that edge. As Turtle et al. (2001 JGR 106: 33175) and others have suggested, those straight edges may be faults which relieve the expected global compressive stresses and also act as magma conduits. Radebaugh (2005) has suggested that some of these large islands might be analogs of resurgent domes. We are investigating whether a hybrid stress model may be able to explain the overall morphology.

  8. 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

  9. Two-silicon-nanocrystal layer memory structure with improved retention characteristics.

    PubMed

    Nassiopoulou, A G; Salonidou, A

    2007-01-01

    It was demonstrated in the literature that the use of self-aligned doubly-stacked Si dots improves retention characteristics of a nanocrystal memory. In this paper, we show that a similar effect may be obtained by using two distinct layers of silicon nanocrystals within the gate dielectric of the MOS structure, if the nanocrystal density in each layer is high enough (above 10(12) dots/cm2) so as to get an average effect of at least one smaller dot underneath each larger one. The relative distance of the layers and their position from the silicon substrate and the gate metal are critical for optimum memory operation. Two different double-nanocrystal-layer structures were investigated. In the first structure the two nanocrystal layers were close together and they were composed of dots of different size (lower layer: 3 nm, upper layer: 5 nm), while in the second structure the dot layers were composed of dots of equal diameter (d = 3 nm) and their inter-distance was much larger. In both cases, the retention characteristics of the structure were improved compared with a single dot layer structure. In the second case this improvement was significantly larger than in the first case. Extrapolation of the data to ten years memory operation, showed that the charge loss after this time was only approximately 12%.

  10. Photodetectors Based on Two-Dimensional Layer-Structured Hybrid Lead Iodide Perovskite Semiconductors.

    PubMed

    Zhou, Jiachen; Chu, Yingli; Huang, Jia

    2016-10-05

    Hybrid lead iodide perovskite semiconductors have attracted intense research interests recently because of their easy fabrication processes and high power conversion efficiencies in photovoltaic applications. Layer-structured materials have interesting properties such as quantum confinement effect and tunable band gap due to the unique two-dimensional crystalline structures. ⟨100⟩-oriented layer-structured perovskite materials are inherited from three-dimensional ABX3 perovskite materials with a generalized formula of (RNH3)2(CH3NH3)n-1MnX3n+1, and adopt the Ruddlesden-Popper type crystalline structure. Here we report the synthesis and investigation of three layer-structured perovskite materials with different layer numbers: (C4H9NH3)2PbI4 (n = 1, one-layered perovskite), (C4H9NH3)2(CH3NH3)Pb2I7 (n = 2, two-layered perovskite) and (C4H9NH3)2(CH3NH3)2Pb3I10 (n = 3, three-layered perovskite). Their photoelectronic properties were investigated in related to their molecular structures. Photodetectors based on these two-dimensional (2D) layer-structured perovskite materials showed tunable photoresponse with short response time in milliseconds. The photodetectors based on three-layered perovskite showed better performances than those of the other two devices, in terms of output current, responsivity, Ilight/Idark ratio, and response time, because of its smaller optical band gap and more condensed microstructure comparing the other two materials. These results revealed the relationship between the molecular structures, film microstructures and the photoresponse properties of 2D layer-structured hybrid perovskites, and demonstrated their potentials as flexible, functional, and tunable semiconductors in optoelectronic applications, by taking advantage of their tunable quantum well molecular structure.

  11. Polarimetry of Pinctada fucata nacre indicates myostracal layer interrupts nacre structure

    PubMed Central

    Jones, Joshua A.; D'Addario, Anthony J.; Galvez, Enrique J.

    2017-01-01

    The inner layer of many bivalve and gastropod molluscs consists of iridescent nacre, a material that is structured like a brick wall with bricks consisting of crystalline aragonite and mortar of organic molecules. Myostracal layers formed during shell growth at the point of muscle attachment to the shell can be found interspersed within the nacre structure. Little has been done to examine the effect the myostracal layer has on subsequent nacre structure. Here we present data on the structure of the myostracal and nacre layers from a bivalve mollusc, Pinctada fucata. Scanning electron microscope imaging shows the myostracal layer consists of regular crystalline blocks. The nacre before the layer consists of tablets approximately 400 nm thick, while after the myostracal layer the tablets are approximately 500 nm thick. A new technique, imaging polarimetry, indicates that the aragonite crystals within the nacre following the myostracal layer have greater orientation uniformity than before the myostracal layer. The results presented here suggest a possible interaction between the myostracal layer and subsequent shell growth. PMID:28386442

  12. Fabrication of hierarchical hybrid structures using bio-enabled layer-by-layer self-assembly.

    PubMed

    Hnilova, Marketa; Karaca, Banu Taktak; Park, James; Jia, Carol; Wilson, Brandon R; Sarikaya, Mehmet; Tamerler, Candan

    2012-05-01

    Development of versatile and flexible assembly systems for fabrication of functional hybrid nanomaterials with well-defined hierarchical and spatial organization is of a significant importance in practical nanobiotechnology applications. Here we demonstrate a bio-enabled self-assembly technique for fabrication of multi-layered protein and nanometallic assemblies utilizing a modular gold-binding (AuBP1) fusion tag. To accomplish the bottom-up assembly we first genetically fused the AuBP1 peptide sequence to the C'-terminus of maltose-binding protein (MBP) using two different linkers to produce MBP-AuBP1 hetero-functional constructs. Using various spectroscopic techniques, surface plasmon resonance (SPR) and localized surface plasmon resonance (LSPR), we verified the exceptional binding and self-assembly characteristics of AuBP1 peptide. The AuBP1 peptide tag can direct the organization of recombinant MBP protein on various gold surfaces through an efficient control of the organic-inorganic interface at the molecular level. Furthermore using a combination of soft-lithography, self-assembly techniques and advanced AuBP1 peptide tag technology, we produced spatially and hierarchically controlled protein multi-layered assemblies on gold nanoparticle arrays with high molecular packing density and pattering efficiency in simple, reproducible steps. This model system offers layer-by-layer assembly capability based on specific AuBP1 peptide tag and constitutes novel biological routes for biofabrication of various protein arrays, plasmon-active nanometallic assemblies and devices with controlled organization, packing density and architecture.

  13. The secondary structure and the thermal unfolding parameters of the S-layer protein from Lactobacillus salivarius.

    PubMed

    Lighezan, Liliana; Georgieva, Ralitsa; Neagu, Adrian

    2016-09-01

    Surface layer (S-layer) proteins have been identified in the cell envelope of many organisms, such as bacteria and archaea. They self-assemble, forming monomolecular crystalline arrays. Isolated S-layer proteins are able to recrystallize into regular lattices, which proved useful in biotechnology. Here we investigate the structure and thermal unfolding of the S-layer protein isolated from Lactobacillus salivarius 16 strain of human origin. Using circular dichroism (CD) spectroscopy, and the software CDSSTR from DICHROWEB, CONTINLL from CDPro, as well as CDNN, we assess the fractions of the protein's secondary structural elements at temperatures ranging between 10 and 90 °C, and predict the tertiary class of the protein. To study the thermal unfolding of the protein, we analyze the temperature dependence of the CD signal in the far- and near-UV domains. Fitting the experimental data by two- and three-state models of thermal unfolding, we infer the midpoint temperatures, the temperature dependence of the changes in Gibbs free energy, enthalpy, and entropy of the unfolding transitions in standard conditions, and the temperature dependence of the equilibrium constant. We also estimate the changes in heat capacity at constant pressure in standard conditions. The results indicate that the thermal unfolding of the S-layer protein from L. salivarius is highly cooperative, since changes in the secondary and tertiary structures occur simultaneously. The thermodynamic analysis predicts a "cold" transition, at about -3 °C, of both the secondary and tertiary structures. Our findings may be important for the use of S-layer proteins in biotechnology and in biomedical applications.

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

    DOEpatents

    Campbell,; Christian X. , 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.

  15. 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

    2015-07-08

    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.

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

    SciTech Connect

    Prasoetsopha, Natkrita; Pinitsoontorn, Supree; Bootchanont, Atipong; Kidkhunthod, Pinit; Srepusharawoot, Pornjuk; Kamwanna, Teerasak; Amornkitbamrung, Vittaya; Kurosaki, Ken; Yamanaka, Shinsuke

    2013-08-15

    Polycrystalline Ca{sub 3}Co{sub 4−x}Fe{sub x}O{sub 9+δ} 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+δ} 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+δ}. • 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+δ} 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

  17. Wetting of mesoscopic soft cylinders: Structure and layering transitions

    NASA Astrophysics Data System (ADS)

    Ahrens, Heiko; Hugenberg, Norbert; Schmidt, Manfred; Helm, Christiane A.

    1999-10-01

    The wetting of soft mesoscopic long-chain particles is studied. As a model system, a cylindrical brush with poly(vinyl)pyridine side chains on the water surface is characterized by isotherms and x-ray reflectivity. The forces from the two planar interfaces and the intra- and interparticle interactions are all of comparable magnitude. Two layering transitions occur, one from the monolayer to the double layer, the next to a homogeneous multilayer. The hard wall from which layering starts is the smooth polymer/air interface. Indeed, they particles in the top layer of both the double- and the multilayer have their cylinder axis parallel to the surface and are laterally compressed. In contrast, the polymer/water interface is diffuse due to brush swelling. Generally, the long-chain particles adjacent to the respective interfaces do not maintain their circular diameters. The thickness of the monolayer can be varied by a factor 3.5, up to 53 Å. An additional phase transition occurs within the monolayer, which is attributed to a change of the side chains from a flattened to a compressed state at constant volume. Atmoic force microscope images of the monolayer transferred onto a solid indicate local cylinder alignment.

  18. Total absorption in ultra-thin lossy layer on transparent substrate using dielectric resonance structure

    NASA Astrophysics Data System (ADS)

    Matsui, T.; Iizuka, H.

    2017-03-01

    A resonant sub-wavelength structure made of a high-refractive-index dielectric material exhibits a resonator-like response and provides unity reflection. We show that near-unity absorption is obtained by using a sub-wavelength resonant structure, which consists of periodic high-refractive-index nano-blocks, when an ultra-thin absorption layer is attached to a transparent dielectric substrate. The resonant structure does not necessarily touch the absorption layer and, therefore, a coating film can be inserted between the absorption layer and the periodic structure. Our results significantly extend application scenarios of detectors and optoelectronic devices that can be implemented on transparent dielectric substrates.

  19. Optical and field emission properties of layer-structure GaN nanowires

    SciTech Connect

    Cui, Zhen; Li, Enling; Shi, Wei; Ma, Deming

    2014-08-15

    Highlights: • The layer-structure GaN nanowires with hexagonal-shaped cross-sections are produced via a process based on the CVD method. • The diameter of the layer-structure GaN nanowire gradually decreases from ∼500 nm to ∼200 nm along the wire axis. • The layer-structure GaN nanowire film possesses good field emission property. - Abstract: A layer-structure gallium nitride (GaN) nanowires, grown on Pt-coated n-type Si (1 1 1) substrate, have been synthesized using chemical vapor deposition (CVD). The results show: (1) SEM indicates that the geometry structure is layer-structure. HRTEM indicates that GaN nanowire’s preferential growth direction is along [0 0 1] direction. (2) The room temperature PL emission spectrum of the layer-structure GaN nanowires has a peak at 375 nm, which proves that GaN nanowires have potential application in light-emitting nano-devices. (3) Field-emission measurements show that the layer-structure GaN nanowires film has a low turn-on field of 4.39 V/μm (at room temperature), which is sufficient for electron emission devices, field emission displays and vacuum nano-electronic devices. The growth mechanism for GaN nanowires has also been discussed briefly.

  20. High-precision structure fabrication based on an etching resistance layer

    NASA Astrophysics Data System (ADS)

    Zhang, Man; Deng, Qiling; Shi, Lifang; Cao, Axiu; Pang, Hui; Liu, Xin; Wang, Jiazhou; Hu, Song

    2016-10-01

    The high-precision fabrication of micro-/nano-structure is a challenge. In this paper, we proposed a new fabrication method of high-precision structure based on an etching resistance layer. The high-precision features were fabricated by photolithography technique, followed by the etching process to transfer the features to the substrate. During this process, the etching uniformity and error lead to the feature distortion. We introduced an etching resistance layer between feature layer and substrate. The etching process will stop when arriving at the resistance layer. Due to the high precision of the plating film, the high-precision structure depth was achieved. In our experiment, we introduced aluminum trioxide as the etching resistance layer. The structures with low depth error of less than 5% were fabricated.

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

    SciTech Connect

    Yastrubchak, O.; Sadowski, J.; Domagala, J. Z.; Andrearczyk, T.; Wosinski, T.

    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.

  2. 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.

  3. Dichotomy of the electronic structure and superconductivity between single-layer and double-layer FeSe/SrTiO3 films.

    PubMed

    Liu, Xu; Liu, Defa; Zhang, Wenhao; He, Junfeng; Zhao, Lin; He, Shaolong; Mou, Daixiang; Li, Fangsen; Tang, Chenjia; Li, Zhi; Wang, Lili; Peng, Yingying; Liu, Yan; Chen, Chaoyu; Yu, Li; Liu, Guodong; Dong, Xiaoli; Zhang, Jun; Chen, Chuangtian; Xu, Zuyan; Chen, Xi; Ma, Xucun; Xue, Qikun; Zhou, X J

    2014-09-23

    The latest discovery of possible high-temperature superconductivity in the single-layer FeSe film grown on a SrTiO3 substrate has generated much attention. Initial work found that, while the single-layer FeSe/SrTiO3 film exhibits a clear signature of superconductivity, the double-layer film shows an insulating behaviour. Such a marked layer-dependent difference is surprising and the underlying origin remains unclear. Here we report a comparative angle-resolved photoemission study between the single-layer and double-layer FeSe/SrTiO3 films annealed in vacuum. We find that, different from the single-layer FeSe/SrTiO3 film, the double-layer FeSe/SrTiO3 film is hard to get doped and remains in the semiconducting/insulating state under an extensive annealing condition. Such a behaviour originates from the much reduced doping efficiency in the bottom FeSe layer of the double-layer FeSe/SrTiO3 film from the FeSe-SrTiO3 interface. These observations provide key insights in understanding the doping mechanism and the origin of superconductivity in the FeSe/SrTiO3 films.

  4. Spectral and total temperature-dependent emissivities of few-layer structures on a metallic substrate.

    PubMed

    Blandre, Etienne; Chapuis, Pierre-Olivier; Vaillon, Rodolphe

    2016-01-25

    We investigate the thermal radiative emission of few-layer structures deposited on a metallic substrate and its dependence on temperature with the Fluctuational Electrodynamics approach. We highlight the impact of the variations of the optical properties of metallic layers on their temperature-dependent emissivity. Fabry-Pérot spectral selection involving at most two transparent layers and one thin reflective layer leads to well-defined peaks and to the amplification of the substrate emission. For a single Fabry-Pérot layer on a reflective substrate, an optimal thickness that maximizes the emissivity of the structure can be determined at each temperature. A thin lossy layer deposited on the previous structure can enhance interference phenomena, and the analysis of the participation of each layer to the emission shows that the thin layer is the main source of emission. Eventually, we investigate a system with two Fabry-Pérot layers and a metallic thin layer, and we show that an optimal architecture can be found. The total hemispherical emissivity can be increased by one order of magnitude compared to the substrate emissivity.

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

    PubMed

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

    2012-06-01

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

  6. 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.

  7. Origin of the phase transition in IrTe2: structural modulation and local bonding instability

    SciTech Connect

    Cao, Huibo; Chakoumakos, Bryan C; Yan, Jiaqiang; Zhou, Haidong; Custelcean, Radu; Mandrus, D.; McGuire, Michael A; Singh, David J; Chen, Xin; Yang, Hui

    2013-01-01

    We used X-ray/neutron diffraction to determine the low temperature (LT) structure of IrTe2. A structural modulation was observed with a wavevector of k =(1/5, 0, 1/5) below Ts285 K, accompanied by a structural transition from a trigonal to a triclinic lattice. We also performed the first principles calculations for high temperature (HT) and LT structures, which elucidate the nature of the phase transition and the LT structure. A local bonding instability associated with the Te 5p states is likely the origin of the structural phase transition in IrTe2.

  8. Optical Detection Using Four-Layer Semiconductor Structures

    DTIC Science & Technology

    2005-06-01

    analog considers the thyristor, specifically in this case a Shockley diode, as two Bipolar Junction Transistors (BJTs), one npn and one pnp, con- 15...appropriate BJT layer: emitter (E), base (B) and collector (C). The subscript pnp or npn is used to distinguish between the two transistors . It must be...both transistors in the active mode. The holes gathering in the pnp collector (P2) and the electrons in npn collector (N1) have no external escape

  9. Key Role of Rutile Structure for Layered Magnetism in Chromium Compounds

    NASA Astrophysics Data System (ADS)

    Kondo, Yasuhiro; Hotta, Takashi

    CrCl2 and CrF2 with the distorted Rutile-type crystal structure are known to exhibit different antiferromagnetic (AF) structures at low temperatures. CrF2 has a simple N_eel structure in common with other uorides, whereas CrCl2 exhibits a characteristic layered AF structure. We provide a simple scenario to understand the emergence of such layered AF structure on the basis of an orbital degenerate double-exchange model on the Rutile-type structure lattice.

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

    PubMed

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

    2014-02-14

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

  11. Wet-chemical synthesis and applications of non-layer structured two-dimensional nanomaterials

    PubMed Central

    Tan, Chaoliang; Zhang, Hua

    2015-01-01

    Non-layer structured nanomaterials with single- or few-layer thickness have two-dimensional sheet-like structures and possess intriguing properties. Recent years have seen major advances in development of a host of non-layer structured ultrathin two-dimensional nanomaterials such as noble metals, metal oxides and metal chalcogenides. The wet-chemical synthesis has emerged as the most promising route towards high-yield and mass production of such nanomaterials. These nanomaterials are now finding increasing applications in a wide range of areas including catalysis, energy production and storage, sensor and nanotherapy, to name but a few. PMID:26303763

  12. Crystal structure, luminescence, and photoelectrochemistry of thin electroplated Cd-chalcogenide layers

    SciTech Connect

    Abramovich, M.; Brash, M.J.P.; Decker, F.; Moro, J.R.; Motisuke, P.; Muller-st., N.; Salvador, P.

    1985-08-01

    The relationship between crystal structure, photoluminescence spectrum and photoelectrochemical behavior of CdSe /SUB x/ Te /SUB 1-x/ alloy layers has been investigated. Layers having the hexagonal wurzite structure are strongly luminescent both in the red (at a photon energy corresponding to the direct bandgap of the alloy) and in the near infrared. Much weaker luminescence is shown by the layers with cubic zincblende structure. Annealing is responsible for recrystallization and cubic-to-hexagonal phase transformation (CdSe-rich alloys), being beneficial to the efficiency both of photoluminescence an of photoelectrochemical solar energy conversion.

  13. Structural Defects and the Origin of the Second Length Scale in SrTiO3

    NASA Astrophysics Data System (ADS)

    Wang, Renhui; Zhu, Yimei; Shapiro, S. M.

    1998-03-01

    To understand the origin of the second long-length scale in SrTiO 3, we studied structural defects in Verneuil-grown single crystals by transmission electron microscopy. The density of the dislocations was observed to decrease with increasing depth from the original cut surface of the crystals. The high density of dislocations in the skin region is most likely responsible for the second length scale.

  14. Structure of a Magnetic Flux Annihilation Layer Formed by the Collision of Supersonic, Magnetized Plasma Flows.

    PubMed

    Suttle, L G; Hare, J D; Lebedev, S V; Swadling, G F; Burdiak, G C; Ciardi, A; Chittenden, J P; Loureiro, N F; Niasse, N; Suzuki-Vidal, F; Wu, J; Yang, Q; Clayson, T; Frank, A; Robinson, T S; Smith, R A; Stuart, N

    2016-06-03

    We present experiments characterizing the detailed structure of a current layer, generated by the collision of two counterstreaming, supersonic and magnetized aluminum plasma flows. The antiparallel magnetic fields advected by the flows are found to be mutually annihilated inside the layer, giving rise to a bifurcated current structure-two narrow current sheets running along the outside surfaces of the layer. Measurements with Thomson scattering show a fast outflow of plasma along the layer and a high ion temperature (T_{i}∼Z[over ¯]T_{e}, with average ionization Z[over ¯]=7). Analysis of the spatially resolved plasma parameters indicates that the advection and subsequent annihilation of the inflowing magnetic flux determines the structure of the layer, while the ion heating could be due to the development of kinetic, current-driven instabilities.

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

    NASA Technical Reports Server (NTRS)

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

    1981-01-01

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

  16. Magnetic behavior of CoPt-AlN granular structure laminated with AlN layers

    NASA Astrophysics Data System (ADS)

    Yu, Youxing; Shi, Ji; Nakamura, Yoshio

    2011-04-01

    The magnetic behavior of CoPt-AlN granular structure laminated with AlN layers has been studied. Ultrathin multilayer structure, [CoPt0.5 nm/AlN0.5nm]4, is used as the precursor of the magnetic layers, which are separated by 5-nm-thick AlN layers. Upon thermal annealing, the ultrathin multilayer transforms into CoPt-AlN granular structure, and the thick AlN layers remain to be spacers. When the film was annealed at 400 °C, the out-of-plane direction becomes the easy axis of magnetization, although the coercivity remains small. TEM observation has proved that CoPt shows disklike shape at such an annealing temperature. When increasing the annealing temperature to 600 °C and above, the films show "isotropic" magnetic behavior due to the formation of equiaxial CoPt particles in the magnetic layers.

  17. Positively and negatively large Goos-Hänchen lateral displacements from a single negative layered structure.

    PubMed

    Talebzadeh, Robabeh; Namdar, Abdolrahman

    2012-09-20

    We study the electromagnetic beam reflection from layered structures that include the so-called ε-negative and the μ-negative materials, also called single negative materials. We predict that such structures can demonstrate a giant lateral Goos-Hänchen shift of the resonant excitation of surface waves at the interface between the conventional and single negative materials, as well as due to the excitation of leaky modes in the layered structures. Then we replace the conventional layer with a left-handed layer (a material with both ε<0 and μ<0). We show that the Goos-Hänchen shift can be positive and negative depending on the type of this layer (conventional or LH material), which can support TE or TM surface waves.

  18. 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.

  19. 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.

  20. Tunable magnetic resonance in double layered metallic structures.

    PubMed

    Zhou, L; Zhu, Y Y

    2011-12-01

    Double layered metallic gratings have been investigated both theoretically and experimentally. The authors have reported that tunable magnetic resonance (MR) can be achieved by modulating the vertical chirped width dh which could be controlled conveniently in the common electron and/or ion beam microfabrications. The linear relationship between MR wavelength and dh has been reported. By introducing the difference of electric and magnetic penetration depth, an analytic formula deduced from a modified LC model has shown good agreement with the simulation results, and an effective width for trapezoidal sandwiched microstructures has been presented. Our results may provide an alternative choice for tunable MR and broad bandwidth of magnetic metamaterials.

  1. Differential PIXE for investigating the layer structure of paintings

    NASA Astrophysics Data System (ADS)

    Mandò, P. A.; Fedi, M. E.; Grassi, N.; Migliori, A.

    2005-09-01

    This paper reports an example of how the differential PIXE technique can be successfully applied to the investigation of wood or canvas paintings. The work analysed is a famous wood painting by Leonardo da Vinci, the "Madonna dei fusi" (ex-Reford version, 1501), chosen for a pilot study in a wide international project aimed at analysing Leonardo's works of art by means of non-destructive techniques. While illustrating the results obtained concerning the identification of pigments and the discrimination of the stratigraphy of layers, the merits and limits of differential PIXE in general are pointed out.

  2. Impact of small-scale vegetation structure on tephra layer preservation.

    PubMed

    Cutler, Nick A; Shears, Olivia M; Streeter, Richard T; Dugmore, Andrew J

    2016-11-15

    The factors that influence tephra layer taphonomy are poorly understood, but vegetation cover is likely to play a role in the preservation of terrestrial tephra deposits. The impact of vegetation on tephra layer preservation is important because: 1) the morphology of tephra layers could record key characteristics of past land surfaces and 2) vegetation-driven variability in tephra thickness could affect attempts to infer eruption and dispersion parameters. We investigated small- (metre-) scale interactions between vegetation and a thin (<10 cm), recent tephra layer. We conducted surveys of vegetation structure and tephra thickness at two locations which received a similar tephra deposit, but had contrasting vegetation cover (moss vs shrub). The tephra layer was thicker and less variable under shrub cover. Vegetation structure and layer thickness were correlated on the moss site but not under shrub cover, where the canopy reduced the influence of understory vegetation on layer morphology. Our results show that vegetation structure can influence tephra layer thickness on both small and medium (site) scales. These findings suggest that some tephra layers may carry a signal of past vegetation cover. They also have implications for the sampling effort required to reliably estimate the parameters of initial deposits.

  3. Impact of small-scale vegetation structure on tephra layer preservation

    PubMed Central

    Cutler, Nick A.; Shears, Olivia M.; Streeter, Richard T.; Dugmore, Andrew J.

    2016-01-01

    The factors that influence tephra layer taphonomy are poorly understood, but vegetation cover is likely to play a role in the preservation of terrestrial tephra deposits. The impact of vegetation on tephra layer preservation is important because: 1) the morphology of tephra layers could record key characteristics of past land surfaces and 2) vegetation-driven variability in tephra thickness could affect attempts to infer eruption and dispersion parameters. We investigated small- (metre-) scale interactions between vegetation and a thin (<10 cm), recent tephra layer. We conducted surveys of vegetation structure and tephra thickness at two locations which received a similar tephra deposit, but had contrasting vegetation cover (moss vs shrub). The tephra layer was thicker and less variable under shrub cover. Vegetation structure and layer thickness were correlated on the moss site but not under shrub cover, where the canopy reduced the influence of understory vegetation on layer morphology. Our results show that vegetation structure can influence tephra layer thickness on both small and medium (site) scales. These findings suggest that some tephra layers may carry a signal of past vegetation cover. They also have implications for the sampling effort required to reliably estimate the parameters of initial deposits. PMID:27845415

  4. Impact of small-scale vegetation structure on tephra layer preservation

    NASA Astrophysics Data System (ADS)

    Cutler, Nick A.; Shears, Olivia M.; Streeter, Richard T.; Dugmore, Andrew J.

    2016-11-01

    The factors that influence tephra layer taphonomy are poorly understood, but vegetation cover is likely to play a role in the preservation of terrestrial tephra deposits. The impact of vegetation on tephra layer preservation is important because: 1) the morphology of tephra layers could record key characteristics of past land surfaces and 2) vegetation-driven variability in tephra thickness could affect attempts to infer eruption and dispersion parameters. We investigated small- (metre-) scale interactions between vegetation and a thin (<10 cm), recent tephra layer. We conducted surveys of vegetation structure and tephra thickness at two locations which received a similar tephra deposit, but had contrasting vegetation cover (moss vs shrub). The tephra layer was thicker and less variable under shrub cover. Vegetation structure and layer thickness were correlated on the moss site but not under shrub cover, where the canopy reduced the influence of understory vegetation on layer morphology. Our results show that vegetation structure can influence tephra layer thickness on both small and medium (site) scales. These findings suggest that some tephra layers may carry a signal of past vegetation cover. They also have implications for the sampling effort required to reliably estimate the parameters of initial deposits.

  5. On the period of the coherent structure in boundary layers at large Reynolds numbers

    NASA Technical Reports Server (NTRS)

    Narayanan, M. A. B.; Marvin, J. G.

    1978-01-01

    The period of the large coherent structure in a subsonic, compressible, turbulent boundary layer was determined using the autocorrelation of the velocity and pressure fluctuations for Reynolds numbers between 5,000 and 35,000. In low Reynolds number flows the overall correlation period scaled with the outer variables - namely, the free stream velocity and the boundary layer thickness.

  6. Electronic structure of the layered nitride LiMoN2

    NASA Astrophysics Data System (ADS)

    Singh, D. J.

    1992-10-01

    Electronic-structure calculations are reported for the layered ternary nitride LiMoN2. It is found that the material is best described as a three-dimensional metal consisting of strongly covalent MoN2 sheets and Li ions between them. Highly unusual strong direct bonding between N atoms in opposing layers is found.

  7. Structure determination of a partially ordered layered silicate material with an NMR crystallography approach.

    PubMed

    Brouwer, Darren Henry; Cadars, Sylvian; Hotke, Kathryn; Van Huizen, Jared; Van Huizen, Nicholas

    2017-03-01

    Structure determination of layered materials can present challenges for conventional diffraction methods due to the fact that such materials often lack full three-dimensional periodicity since adjacent layers may not stack in an orderly and regular fashion. In such cases, NMR crystallography strategies involving a combination of solid-state NMR spectroscopy, powder X-ray diffraction, and computational chemistry methods can often reveal structural details that cannot be acquired from diffraction alone. We present here the structure determination of a surfactant-templated layered silicate material that lacks full three-dimensional crystallinity using such an NMR crystallography approach. Through a combination of powder X-ray diffraction and advanced (29)Si solid-state NMR spectroscopy, it is revealed that the structure of the silicate layer of this layered silicate material templated with cetyltrimethylammonium surfactant cations is isostructural with the silicate layer of a previously reported material referred to as ilerite, octosilicate, or RUB-18. High-field (1)H NMR spectroscopy reveals differences between the materials in terms of the ordering of silanol groups on the surfaces of the layers, as well as the contents of the inter-layer space.

  8. Boundary layer structure over areas of heterogeneous heat fluxes

    SciTech Connect

    Doran, J.C. ); Barnes, F.J. ); Coulter, R.L. ); Crawford, T.L. . 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 within the grid area, and the larger the area the greater the likely variations. In balancing the benefits of higher resolution against increased computational time and expense, it is useful to consider what the consequences of such subgrid-scale variability may be. Moveover, in interpreting the results of a simulation, one must be able to define an appropriate average value over a grid. There are two aspects of this latter problem: (1) in observations, how does one take a set of discrete or volume-averaged measurements and relate these to properties of the entire domain, and (2) in computations, how can subgrid-scale features be accounted for in the model parameterizations To address these and related issues, two field campaigns were carried out near Boardman, Oregon, in June 1991 and 1992. These campaigns were designed to measure the surface fluxes of latent and sensible heat over adjacent areas with strongly contrasting surface types and to measure the response of the boundary layer to those fluxes. This paper discuses some initial findings from those campaigns.

  9. Boundary layer structure over areas of heterogeneous heat fluxes

    SciTech Connect

    Doran, J.C. ); Barnes, F.J. ); Coulter, R.L. ); Crawford, T.L. . 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.

  10. Boundary layer structure over areas of heterogeneous heat fluxes

    SciTech Connect

    Doran, J.C.; Barnes, F.J.; Coulter, R.L.; Crawford, T.L.

    1993-04-01

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

  11. Boundary layer structure over areas of heterogeneous heat fluxes

    SciTech Connect

    Doran, J.C.; Barnes, F.J.; Coulter, R.L.; Crawford, T.L.

    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. Origin of Degradation Phenomenon under Drain Bias Stress for Oxide Thin Film Transistors using IGZO and IGO Channel Layers

    PubMed Central

    Bak, Jun Yong; Kang, Youngho; Yang, Shinhyuk; Ryu, Ho-Jun; Hwang, Chi-Sun; Han, Seungwu; Yoon, Sung-Min

    2015-01-01

    Top-gate structured thin film transistors (TFTs) using In-Ga-Zn-O (IGZO) and In-Ga-O (IGO) channel compositions were investigated to reveal a feasible origin for degradation phenomenon under drain bias stress (DBS). DBS-driven instability in terms of VTH shift, deviation of the SS value, and increase in the on-state current were detected only for the IGZO-TFT, in contrast to the IGO-TFT, which did not demonstrate VTH shift. These behaviors were visually confirmed via nanoscale transmission electron microscopy and energy-dispersive x-ray spectroscopy observations. To understand the degradation mechanism, we performed ab initio molecular dynamic simulations on the liquid phases of IGZO and IGO. The diffusivities of Ga and In atoms were enhanced in IGZO, confirming the degradation mechanism to be increased atomic diffusion. PMID:25601183

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

    USGS Publications Warehouse

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

    2005-01-01

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

  14. Band structures and localization properties of aperiodic layered phononic crystals

    NASA Astrophysics Data System (ADS)

    Yan, Zhi-Zhong; Zhang, Chuanzeng

    2012-03-01

    The band structures and localization properties of in-plane elastic waves with coupling of longitudinal and transverse modes oblique propagating in aperiodic phononic crystals based on Thue-Morse and Rudin-Shapiro sequences are studied. Using transfer matrix method, the concept of the localization factor is introduced and the correctness is testified through the Rytov dispersion relation. For comparison, the perfect periodic structure and the quasi-periodic Fibonacci system are also considered. In addition, the influences of the random disorder, local resonance, translational and/or mirror symmetries on the band structures of the aperiodic phononic crystals are analyzed in this paper.

  15. 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.

  16. 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.

  17. Structure of a mushy layer at the inner core boundary

    NASA Astrophysics Data System (ADS)

    Deguen, R.; Huguet, L.; Bergman, M. I.; Labrosse, S.; Alboussiere, T.

    2015-12-01

    We present experimental results on the solidification of ammonium chloride from an aqueous solution, yielding a mushy zone, under hyper-gravity. A commercial centrifuge has been equipped with a slip-ring so that electric power, temperature and ultrasonic signals could be transmitted between the experimental setup and the laboratory. A Peltier element provides cooling at the bottom of the cell. Probes monitor the temperature along the height of the cell. Ultrasound measurements (2 to 6 MHz) is used to detect the position of the front of the mushy zone and to determine attenuation in the mush. A significant increase of solid fraction (or decrease of mushy layer thickness) and attenuation in the mush is observed as gravity is increased. Kinetic undercooling is significant in our experiments and has been included in a macroscopic mush model. The other ingredients of the model are conservation of energy and chemical species, along with heat/species transfer between the mush and the liquid phase: boundary-layer exchanges at the top of the mush and bulk convection within the mush (formation of chimneys). The outputs of the model compare well with our experiments. We have then run the model in a range of parameters suitable for the Earth's inner core, which has shown the role of bulk mush convection for the inner core and the reason why a solid fraction very close to unity should be expected. We have also run melting experiments: after crystallization of a mush, the liquid has been heated from above until the mush started to melt, while the bottom cold temperature was maintained. These melting experiments were motivated by the possible local melting at the inner core boundary that has been invoked to explain the formation of the anomalously slow F-layer at the bottom of the outer core or inner core hemispherical asymmetry. Oddly, the consequences of melting are an increase in solid fraction and a decrease in attenuation. It is hence possible that surface seismic velocity

  18. Photovoltaic structures having a light scattering interface layer and methods of making the same

    DOEpatents

    Liu, Xiangxin; Compaan, Alvin D.; Paudel, Naba Raj

    2015-10-13

    Photovoltaic (PV) cell structures having an integral light scattering interface layer configured to diffuse or scatter light prior to entering a semiconductor material and methods of making the same are described.

  19. Controllable synthesis of layered Co-Ni hydroxide hierarchical structures for high-performance hybrid supercapacitors

    NASA Astrophysics Data System (ADS)

    Yuan, Peng; Zhang, Ning; Zhang, Dan; Liu, Tao; Chen, Limiao; Ma, Renzhi; Qiu, Guanzhou; Liu, Xiaohe

    2016-01-01

    A facile solvothermal method is developed for synthesizing layered Co-Ni hydroxide hierarchical structures by using hexamethylenetetramine (HMT) as alkaline reagent. The electrochemical measurements reveal that the specific capacitances of layered bimetallic (Co-Ni) hydroxides are generally superior to those of layered monometallic (Co, Ni) hydroxides. The as-prepared Co0.5Ni0.5 hydroxide hierarchical structures possesses the highest specific capacitance of 1767 F g-1 at a galvanic current density of 1 A g-1 and an outstanding specific capacitance retention of 87% after 1000 cycles. In comparison with the dispersed nanosheets of Co-Ni hydroxide, layered hydroxide hierarchical structures show much superior electrochemical performance. This study provides a promising method to construct hierarchical structures with controllable transition-metal compositions for enhancing the electrochemical performance in hybrid supercapacitors.

  20. Construction of layered structures on valve metal alloys by microplasma oxidation

    NASA Astrophysics Data System (ADS)

    Baranova, T. A.; Chubenko, A. K.; Mamaev, A. I.; Mamaeva, V. A.; Kovalskaya, Ya B.

    2016-11-01

    Process of layered structure materials creation based on aluminum alloys is presented. Microplasma texturing method, microplasma oxidation method and chemical metallization method were used to create these structures. Non-conductive nonmetallic inorganic coatings were produced by microplasma oxidation method. Obtained structures showed high durability under thermal stress loads due to substrate metal - non-conductive nonmetallic inorganic coating phase boundary texturing.

  1. 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.

  2. A Long-Lived Tracer Perspective on the Origin of Air in the Tropical Tropopause Layer during ATTREX

    NASA Astrophysics Data System (ADS)

    Hintsa, E. J.; Moore, F.; Dutton, G. S.; Hall, B. D.; Nance, J. D.; Elkins, J. W.; Gao, R.; Rollins, D. W.; Thornberry, T. D.; Watts, L.; Fahey, D. W.; Daube, B. C.; Pittman, J. V.; Wofsy, S. C.; Atlas, E. L.; Navarro, M. A.; Dessler, A. E.; Mahoney, M.

    2013-12-01

    The origin of air in the tropical tropopause layer (TTL) and the subsequent transport pathways of these air masses play a critical role in the delivery of trace gases, including ozone depleting substances and water vapor, to the stratosphere. The Airborne Tropical Tropopause Experiment (ATTREX) is designed to study this transport and processing in the TTL over the Pacific Ocean, including how dehydration occurs in this region and how trace gases involved in ozone depletion and climate reach the tropical lower stratosphere. For this mission, the NASA Global Hawk aircraft is carrying a suite of in situ and remote sensing instruments for trace gases, aerosols, radiation, and meteorology. Two deployments have occurred from NASA/Dryden Flight Research Center, with flights to the eastern and central tropical Pacific. Two more deployments, targeting the western equatorial Pacific, are planned for 2014 from Guam and one other location. Over 100 vertical profiles from about 14 to 18 km have now been obtained from the tropics to midlatitudes, as well as long sections at nearly constant altitude. Results are shown here from the UAS Chromatograph for Atmospheric Trace Species (UCATS) instrument and other sensors. UCATS was configured to measure the long-lived tracers N2O, SF6, H2, and CH4, as well as water vapor, CO, and ozone. Results thus far have shown a mix of midlatitude and tropical air in the tropical and subtropical lower stratosphere, particularly for flights in November 2011. Recent results from February 2013 indicate much more homogeneous air masses in the TTL during this period. This homogeneity may be related to fact that these flights occurred in the middle of (northern) winter rather than fall, or to the 'sudden stratospheric warming' in January 2013, with sinking motion in the Arctic polar region and a corresponding rising motion and cooling in the tropics. Data will be presented in the context of trajectory model calculations of the origin and fate of the air

  3. Structural, morphology and electrical properties of layered copper selenide thin film

    NASA Astrophysics Data System (ADS)

    Ying Chyi Liew, J.; Talib, Zainal; Mahmood, W.; Yunus, M.; Zainal, Zulkarnain; Halim, Shaari; Moksin, Mohd; Yusoff, Wan; Pah Lim, K.

    2009-06-01

    Thin films of copper selenide (CuSe) were physically deposited layer-by-layer up to 5 layers using thermal evaporation technique onto a glass substrate. Various film properties, including the thickness, structure, morphology, surface roughness, average grain size and electrical conductivity are studied and discussed. These properties are characterized by X-ray diffraction (XRD), atomic force microscopy (AFM), ellipsometer and 4 point probe at room temperature. The dependence of electrical conductivity, surface roughness, and average grain size on number of layers deposited is discussed.

  4. The elasticity of lawsonite at high pressure and the origin of low velocity layers in subduction zones

    NASA Astrophysics Data System (ADS)

    Chantel, Julien; Mookherjee, Mainak; Frost, Daniel J.

    2012-10-01

    Subduction zones exhibit faster seismic wave velocities compared to the surrounding mantle due to the recycling of relatively cold oceanic lithosphere. In certain subduction zones, however, a 5-10 km thick low velocity layer (LVL) has been inferred to exist along the top surface of the subducting slab at depths of up to 250 km. Shear-wave velocities, in particular, within these layers have been estimated as up to 10% slower than the surrounding mantle. We have conducted high-pressure ultrasonic interferometric measurements to gain insight into the elastic properties of lawsonite [CaAl2(Si2O7)(OH)2·H2O], a hydrous mineral phase stabilized under cold subduction zone conditions. In addition, we have computed the full elastic constant tensor at elevated pressures and temperature, using static electronic structure calculations and molecular dynamics simulations. The bulk and shear modulus obtained from theory and experiments are in good agreement. We find that lawsonite has an unusually low shear modulus at high pressure and its formation in subducted oceanic crust can explain some seismic evidence for LVL at depths exceeding 100 km. To approach estimated LVL velocities requires lawsonite to form in the subducting crust as a result of a fluid influx due to the breakdown of other hydrous minerals such as serpentine. The formation of lawsonite additionally lowers seismic velocities because it forms at the expense of garnet, a mineral with relatively fast seismic velocities. LVL observations may therefore be used to place constraints on the amount of H2O subducted into the deep mantle.

  5. Fabrication of multi-layered absorption structure for high quantum efficiency photon detectors

    SciTech Connect

    Fujii, Go; Fukuda, Daiji; Numata, Takayuki; Yoshizawa, Akio; Tsuchida, Hidemi; Fujino, Hidetoshi; Ishii, Hiroyuki; Itatani, Taro; Zama, Tatsuya; Inoue, Shuichiro

    2009-12-16

    We report on some efforts to improve a quantum efficiency of titanium-based optical superconducting transition edge sensors using the multi-layered absorption structure for maximizing photon absorption in the Ti layer. Using complex refractive index values of each film measured by a Spectroscopic Ellipsometry, we designed and optimized by a simulation code. An absorption measurement of fabricated structure was in good agreement with the design and was higher than 99% at optimized wavelength of 1550 nm.

  6. Radiation efficiency and the gain of a source inside a two-layered grounded dielectric structure

    NASA Astrophysics Data System (ADS)

    Bhattacharyya, Arun K.

    1992-08-01

    The integral-transformation technique is used to derive the space- and surface-wave radiation fields generated by a source contained in a two-layered grounded dielectric structure. It is established that (1) surface wave loss leads to a substantial difference between the overall and the directive gain, (2) directivity and radiation efficiency are maximized at distinctive thicknesses of the dielectric layers, and (3) bandwidth decreases with increasing gain of the structure.

  7. Cooperation in group-structured populations with two layers of interactions

    PubMed Central

    Zhang, Yanling; Fu, Feng; Chen, Xiaojie; Xie, Guangming; Wang, Long

    2015-01-01

    Recently there has been a growing interest in studying multiplex networks where individuals are structured in multiple network layers. Previous agent-based simulations of games on multiplex networks reveal rich dynamics arising from interdependency of interactions along each network layer, yet there is little known about analytical conditions for cooperation to evolve thereof. Here we aim to tackle this issue by calculating the evolutionary dynamics of cooperation in group-structured populations with two layers of interactions. In our model, an individual is engaged in two layers of group interactions simultaneously and uses unrelated strategies across layers. Evolutionary competition of individuals is determined by the total payoffs accrued from two layers of interactions. We also consider migration which allows individuals to move to a new group within each layer. An approach combining the coalescence theory with the theory of random walks is established to overcome the analytical difficulty upon local migration. We obtain the exact results for all “isotropic” migration patterns, particularly for migration tuned with varying ranges. When the two layers use one game, the optimal migration ranges are proved identical across layers and become smaller as the migration probability grows. PMID:26632251

  8. Evolution of structural properties of Si(001) subsurface layer containing He bubbles by low temperature annealing

    NASA Astrophysics Data System (ADS)

    Lomov, Andrey A.; Shcherbachev, Kirill D.; Chesnokov, Yury M.; Kiselev, Dmitrii A.; Miakonkikh, Andrew V.

    2016-12-01

    Transformation of microstructure of the buried He bubbles of silicon surface layer after He+ low energy plasma immersion ion implantation and subsequent low-thermal annealing were studied by high resolution X-ray diffraction and reflectivity, Rutherford backscattering spectroscopy, transmission electron and atomic force microscopy methods. The ion energies varied in the range 2 - 5 keV at constant exposure ion doses 5×·1017 cm-2. Formation of a three-layer structure (amorphous a-SiOx layer at the surface, amorphous a-Si layer with helium bubbles and buried helium bubbles heavy damaged tensile strained crystalline c-Si layer) that is retained after annealing was observed. Helium-filled bubbles are observed in an as-implanted sample. Evolution of the multilayer structure and the bubbles due to annealing are revealed and comparing with the structural parameters of an as-implanted sample was done. The bubbles are shown to trend into two-model distribution after annealing. The characteristic bubble size is determined to be in a range of 2-20 nm. Large size helium-filled bubbles are located in the amorphous a-Si layer. Small size bubbles are revealed inside the damaged crystalline Si layer. These bubbles are a major source of tensile strain in c-Si layer.

  9. A perspective on coherent structures and conceptual models for turbulent boundary layer physics

    NASA Technical Reports Server (NTRS)

    Robinson, Stephen K.

    1990-01-01

    Direct numerical simulations of turbulent boundary layers have been analyzed to develop a unified conceptual model for the kinematics of coherent motions in low Reynolds number canonical turbulent boundary layers. All classes of coherent motions are considered in the model, including low-speed streaks, ejections and sweeps, vortical structures, near-wall and outer-region shear layers, sublayer pockets, and large-scale outer-region eddies. The model reflects the conclusions from the study of the simulated boundary layer that vortical structures are directly associated with the production of turbulent shear stresses, entrainment, dissipation of turbulence kinetic energy, and the fluctuating pressure field. These results, when viewed from the perspective of the large body of published work on the subject of coherent motions, confirm that vortical structures may be considered the central dynamic element in the maintenance of turbulence in the canonical boundary layer. Vortical structures serve as a framework on which to construct a unified picture of boundary layer structure, providing a means to relate the many known structural elements in a consistent way.

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

    NASA Technical Reports Server (NTRS)

    Maestrello, L.

    2004-01-01

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

  11. Ordered mixed-layer structures in the Mighei carbonaceous chondrite matrix

    NASA Technical Reports Server (NTRS)

    Mackinnon, I. D. R.

    1982-01-01

    High resolution transmission electron microscopy of the Mighei carbonaceous chondrite matrix has revealed the presence of a new mixed layer structure material. This mixed-layer material consists of an ordered arrangement of serpentine-type (S) and brucite-type (B) layers in the sequence SBBSBB. Electron diffraction and imaging techniques show that the basal periodicity is approximately 17 A. Discrete crystals of SBB-type material are typically curved, of small size (less than 1 micron) and show structural variations similar to the serpentine group minerals. Mixed-layer material also occurs in association with planar serpentine. Characteristics of SBB-type material are not consistent with known terrestrial mixed-layer clay minerals. Evidence for formation by a condensation event or by subsequent alteration of pre-existing material is not yet apparent.

  12. Structure of a magnetic flux annihilation layer formed by the collision of supersonic, magnetized plasma flows

    SciTech Connect

    Suttle, L. G.; Hare, J. D.; Lebedev, S. V.; Swadling, G. F.; Burdiak, G. C.; Ciardi, A.; Chittenden, J. P.; Loureiro, N. F.; Niasse, N.; Suzuki-Vidal, F.; Wu, J.; Yang, Q.; Clayson, T.; Frank, A.; Robinson, T. S.; Smith, R. A.; Stuart, N.

    2016-05-31

    We present experiments characterizing the detailed structure of a current layer, generated by the collision of two counter-streaming, supersonic and magnetized aluminum plasma flows. The anti parallel magnetic fields advected by the flows are found to be mutually annihilated inside the layer, giving rise to a bifurcated current structure—two narrow current sheets running along the outside surfaces of the layer. Measurements with Thomson scattering show a fast outflow of plasma along the layer and a high ion temperature (Ti~¯ZTe, with average ionization ¯Z=7). Lastly, analysis of the spatially resolved plasma parameters indicates that the advection and subsequent annihilation of the in-flowing magnetic flux determines the structure of the layer, while the ion heating could be due to the development of kinetic, current-driven instabilities.

  13. Structure of a magnetic flux annihilation layer formed by the collision of supersonic, magnetized plasma flows

    DOE PAGES

    Suttle, L. G.; Hare, J. D.; Lebedev, S. V.; ...

    2016-05-31

    We present experiments characterizing the detailed structure of a current layer, generated by the collision of two counter-streaming, supersonic and magnetized aluminum plasma flows. The anti parallel magnetic fields advected by the flows are found to be mutually annihilated inside the layer, giving rise to a bifurcated current structure—two narrow current sheets running along the outside surfaces of the layer. Measurements with Thomson scattering show a fast outflow of plasma along the layer and a high ion temperature (Ti~¯ZTe, with average ionization ¯Z=7). Lastly, analysis of the spatially resolved plasma parameters indicates that the advection and subsequent annihilation of themore » in-flowing magnetic flux determines the structure of the layer, while the ion heating could be due to the development of kinetic, current-driven instabilities.« less

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

    SciTech Connect

    Ng, A.; Liu, X.; Sun, Y. C.; Djurišić, A. B.; Ng, A. M. C.; Chan, W. K.

    2013-12-04

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

  15. Direct observation of the layer-dependent electronic structure in phosphorene

    NASA Astrophysics Data System (ADS)

    Li, Likai; Kim, Jonghwan; Jin, Chenhao; Ye, Guo Jun; Qiu, Diana Y.; da Jornada, Felipe H.; Shi, Zhiwen; Chen, Long; Zhang, Zuocheng; Yang, Fangyuan; Watanabe, Kenji; Taniguchi, Takashi; Ren, Wencai; Louie, Steven G.; Chen, Xian Hui; Zhang, Yuanbo; Wang, Feng

    2017-01-01

    Phosphorene, a single atomic layer of black phosphorus, has recently emerged as a new two-dimensional (2D) material that holds promise for electronic and photonic technologies. Here we experimentally demonstrate that the electronic structure of few-layer phosphorene varies significantly with the number of layers, in good agreement with theoretical predictions. The interband optical transitions cover a wide, technologically important spectral range from the visible to the mid-infrared. In addition, we observe strong photoluminescence in few-layer phosphorene at energies that closely match the absorption edge, indicating that they are direct bandgap semiconductors. The strongly layer-dependent electronic structure of phosphorene, in combination with its high electrical mobility, gives it distinct advantages over other 2D materials in electronic and opto-electronic applications.

  16. Comparison of different structures of niobium oxide blocking layer for dye-sensitized solar cells.

    PubMed

    Chun, Jae Hwan; Kim, Jong Sung

    2014-08-01

    In this study, four different types of Nb2O5 thin layers were prepared using sol-gel process to improve energy conversion efficiency of dye sensitized solar cells (DSSCs). Nb2O5 layer was prepared on the fluorine-doped tin oxide (FTO) layer, TiO2 electrode layer, and inside of TiO2 layer, respectively. The Nb2O5 layer was used to reduce the recombination of photo induced electrons and holes. The DSSCs were assembled with platinum (Pt) coated counter electrode, ruthenium dye, and iodine based electrolyte. The photocurrent-voltage (I-V) characteristics of DSSCs with different types of Nb2O5 were studied. The efficiency depends not only on the structure of DSSCs but also on the initial compositions for the preparation of Nb2O5.

  17. Polarization-dependent plasmonic coupling in dual-layer metallic structures at terahertz frequencies.

    PubMed

    Zhang, Zhong Xiang; Chan, Kam Tai

    2011-01-31

    Dual-layer metallic wire-hole structures were fabricated and their terahertz transmission properties were measured. They exhibit polarization-dependent transmittance with large extinction ratios. Simulation and experimental results on structures with different wire-to-hole orientations provide strong evidence that the resonance peaks are caused by plasmonic coupling between the two metallic layers. A simplified LC-circuit model is proposed to explain the coupling mechanism and to estimate the peak frequencies. Our results suggest that specific electromagnetic response can be achieved by appropriate design of the geometrical patterns on the two metallic layers and a suitable polarization of the incident wave.

  18. 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%.

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

    NASA Astrophysics Data System (ADS)

    Sing, M.; Meyer, J.; Hoinkis, M.; Glawion, S.; Blaha, P.; Gavrila, G.; Jacobsen, C. S.; Claessen, R.

    2007-12-01

    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.

  20. Asymmetric transmission of acoustic waves in a layer thickness distribution gradient structure using metamaterials

    NASA Astrophysics Data System (ADS)

    Chen, Jung-San; Chang, I.-Ling; Huang, Wan-Ting; Chen, Lien-Wen; Huang, Guan-Hua

    2016-09-01

    This research presents an innovative asymmetric transmission design using alternate layers of water and metamaterial with complex mass density. The directional transmission behavior of acoustic waves is observed numerically inside the composite structure with gradient layer thickness distribution and the rectifying performance of the present design is evaluated. The layer thickness distributions with arithmetic and geometric gradients are considered and the effect of gradient thickness on asymmetric wave propagation is systematically investigated using finite element simulation. The numerical results indicate that the maximum pressure density and transmission through the proposed structure are significantly influenced by the wave propagation direction over a wide range of audible frequencies. Tailoring the thickness of the layered structure enables the manipulation of asymmetric wave propagation within the desired frequency range. In conclusion, the proposed design offers a new possibility for developing directional-dependent acoustic devices.

  1. A review of quasi-coherent structures in a numerically simulated turbulent boundary layer

    NASA Technical Reports Server (NTRS)

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

    1989-01-01

    Preliminary results of a comprehensive study of the structural aspects of a numerically simulated number turbulent boundary layer are presented. A direct Navier-Stokes simulation of a flat-plate, zero pressure gradient boundary layer at Re0 = 670 was used. Most of the known nonrandom, coherent features of turbulent boundary layers are confirmed in the simulation, and several new aspects of their spatial character are reported. The spatial relationships between many of the various structures are described, forming the basis for a more complete kinematical picture of boundary layer physics than has been previously known. In particular, the importance of vortex structures of various forms to the generation of Reynolds shear stress is investigated.

  2. Unequal density effect on static structure factor of coupled electron layers

    NASA Astrophysics Data System (ADS)

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

    2014-04-01

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

  3. Structure A, steel shelving. Drawing no. H3300. Original drawing by ...

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

    Structure A, steel shelving. Drawing no. H3-300. Original drawing by Black & Veatch, Consulting Engineers, Kansas City, Missouri, prepared for the U.S. Department of the Army, Office of Engineers, Military Construction Division, Washington D.C. dated November 5, 1951. - Travis Air Force Base, Building No. 925, W Street, Fairfield, Solano County, CA

  4. Structure A, reinforcing details. Drawing No. H2302, as built, Original ...

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

    Structure A, reinforcing details. Drawing No. H2-302, as built, Original drawing by Black & Veatch, Consulting Engineers, Kansas City, Missouri, prepared for the U.S. Department of the Army, Office of Engineers, Military Construction Division, Washington, D.C. dated October 1, 1951. - Travis Air Force Base, Building No. 925, W Street, Fairfield, Solano County, CA

  5. 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.

  6. Origin and Control of the Flow Structure on Unmanned Combat Air Vehicle

    DTIC Science & Technology

    2007-12-01

    Prescrtbed by ANSI Ski Z3S.18 AFOSR Final Repot 013108 ORIGIN AND CONTROL OF THE FLOW STRUCTURE ON UNMANNED COMBAT AIR VEHICLES AFOSR GRANT #FA9550-05...1991) described low-dimensional models for flows past a grooved channel and circular cylinders. By employing a Galerkin method, a governing partial

  7. Complex Adaptive Systems and the Origins of Adaptive Structure: What Experiments Can Tell Us

    ERIC Educational Resources Information Center

    Cornish, Hannah; Tamariz, Monica; Kirby, Simon

    2009-01-01

    Language is a product of both biological and cultural evolution. Clues to the origins of key structural properties of language can be found in the process of cultural transmission between learners. Recent experiments have shown that iterated learning by human participants in the laboratory transforms an initially unstructured artificial language…

  8. Electronic structure of tetraphenylporphyrin layers on Ag(100)

    NASA Astrophysics Data System (ADS)

    Classen, Andrej; Pöschel, Rebecca; Di Filippo, Gianluca; Fauster, Thomas; Malcıoǧlu, Osman Barış; Bockstedte, Michel

    2017-03-01

    The electronic structure of Mg and free-base tetraphenylporphyrin films on Ag(100) is investigated by one- and two-photon photoemission in combination with electronic structure calculations using density functional theory and the self-consistent G W0 method. We determine the two highest occupied and the nearly degenerate lowest unoccupied molecular orbitals. Higher unoccupied states are seen in an enhanced emission as a final-state effect. For photon energies close to the prominent absorption of the Soret band we observe a strong electron emission attributed to the break up of the bound electron-hole pairs in the S2 excited state. The experimental results on the occupied and unoccupied energy levels for the molecular films on Ag(100) nicely agree with calculated quasiparticle energies and experiments of the molecules in the gas phase.

  9. Structure and friction-reducing property of the sulfide layer produced by ion sulfuration

    SciTech Connect

    Ning, Z.; Da-Ming, Z.; Yan-Hua, W.; Jia-Jun, L.; Xiao-Dong, F.; Ming-Xi, G.

    2000-04-01

    Sulfide layers with a certain thickness were made on the surface of 1045 and 52100 steels by means of the low-temperature ion sulfuration technique. Metallography, scanning electron microscope (SEM) + energy-dispersive x-ray analysis (EDX), and x-ray diffraction (XRD) were adopted to analyze the structure of sulfide layers; the tribological properties of the layers lubricated by paraffin oil were also investigated on a reciprocating tester. The results showed that sulfide layer is porous, and its structure is mainly composed of FeS, FeS{sub 2}, and substrate phases. The sulfide layer possessed a remarkable friction-reducing effect; its friction coefficient was lower on average, by about 50%, than that of the surface without layer. With the increase of layer thickness, its friction coefficient was unchanged, and under low load conditions, its operational period was prolonged. Under the same experimental conditions, the operational period of sulfide layer on 52100 steel was longer than that on 1045 steel, and its friction coefficient was lower as well.

  10. Double-layer structure in polar mesospheric clouds observed from SOFIE/AIM

    NASA Astrophysics Data System (ADS)

    Gao, Haiyang; Shepherd, Gordon G.; Tang, Yuanhe; Bu, Lingbing; Wang, Zhen

    2017-02-01

    Double-layer structures in polar mesospheric clouds (PMCs) are observed by using Solar Occultation for Ice Experiment (SOFIE) data between 2007 and 2014. We find 816 and 301 events of double-layer structure with percentages of 10.32 and 7.25 % compared to total PMC events, and the mean distances between two peaks are 3.06 and 2.73 km for the Northern Hemisphere (NH) and Southern Hemisphere (SH) respectively. Double-layer PMCs almost always have less mean ice water content (IWC) than daily IWC during the core of the season, but they are close to each other at the beginning and the end. The result by averaging over all events shows that the particle concentration has obvious double peaks, while the particle radius exhibits an unexpected monotonic increase with decreasing altitude. By further analysis of the background temperature and water vapour residual profiles, we conclude that the lower layer is a reproduced one formed at the bottom of the upper layer. 56.00 and 47.51 % of all double-layer events for the NH and SH respectively have temperature enhancements larger than 2 K locating between their double peaks. The longitudinal anti-correlation between the gravity waves' (GWs') potential energies and occurrence frequencies of double-layer PMCs suggests that the double-layer PMCs tend to form in an environment where the GWs have weaker intensities.

  11. Turbulent Structures and Coherence in the Atmospheric Surface Layer

    NASA Astrophysics Data System (ADS)

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

    2015-01-01

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

  12. Layers: A molecular surface peeling algorithm and its applications to analyze protein structures

    PubMed Central

    Karampudi, Naga Bhushana Rao; Bahadur, Ranjit Prasad

    2015-01-01

    We present an algorithm ‘Layers’ to peel the atoms of proteins as layers. Using Layers we show an efficient way to transform protein structures into 2D pattern, named residue transition pattern (RTP), which is independent of molecular orientations. RTP explains the folding patterns of proteins and hence identification of similarity between proteins is simple and reliable using RTP than with the standard sequence or structure based methods. Moreover, Layers generates a fine-tunable coarse model for the molecular surface by using non-random sampling. The coarse model can be used for shape comparison, protein recognition and ligand design. Additionally, Layers can be used to develop biased initial configuration of molecules for protein folding simulations. We have developed a random forest classifier to predict the RTP of a given polypeptide sequence. Layers is a standalone application; however, it can be merged with other applications to reduce the computational load when working with large datasets of protein structures. Layers is available freely at http://www.csb.iitkgp.ernet.in/applications/mol_layers/main. PMID:26553411

  13. Crystal Orientation Control of Bismuth Layer-Structured Dielectric Films Using Interface Layers of Perovskite-Type Oxides

    NASA Astrophysics Data System (ADS)

    Kondoh, Yohta; Sasajima, Keiichi; Hayashi, Mari; Kimura, Junichi; Takuwa, Itaru; Ehara, Yoshitaka; Funakubo, Hiroshi; Uchida, Hiroshi

    2011-09-01

    Thin films of SrBi4Ti4O15, a kind of bismuth layer-structured dielectrics (BLSDs), were prepared on platinized silicon wafers buffered by perovskite-type oxide interface layers, (100)LaNiO3/(111)Pt/TiO2/(100)Si and (001)Ca2Nb3O10-nanosheets/(111)Pt/TiO2/(100)Si, by chemical solution deposition (CSD). The Ca2Nb3O10 nanosheets were supported on a (111)Pt/TiO2/(100)Si substrate by dip coating using an aqueous dispersion, while (100)LaNiO3 was prepared by CSD. The (00l) planes of BLSD crystal were preferentially oriented on the surface of both substrates, which is caused by suitable lattice matching between the a-(b-)axis of BLSD and perovskite-type oxide layers. The film deposition on (001)Ca2Nb3O10 nanosheets yielded (001)-oriented BLSD films with higher crystallinity and smaller fluctuation in the tilting angle of the (001)BLSD plane than those on the (100)LaNiO3 interface layer. The dielectric constant (ɛr) of (001)-oriented SrBi4Ti4O15 film on (001)Ca2Nb3O10-nanosheets/(111)Pt/TiO2/(100)Si substrate was approximately 190, which was significantly stable against the change of frequency and bias voltage compared with that of the randomly-oriented SrBi4Ti4O15 film.

  14. Spatiotemporal structure of wind farm-atmospheric boundary layer interactions

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

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

  15. 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.

  16. Confined Water in Layered Silicates: The Origin of Anomalous Thermal Expansion Behavior in Calcium-Silicate-Hydrates.

    PubMed

    Krishnan, N M Anoop; Wang, Bu; Falzone, Gabriel; Le Pape, Yann; Neithalath, Narayanan; Pilon, Laurent; Bauchy, Mathieu; Sant, Gaurav

    2016-12-28

    Water, under conditions of nanoscale confinement, exhibits anomalous dynamics, and enhanced thermal deformations, which may be further enhanced when such water is in contact with hydrophilic surfaces. Such heightened thermal deformations of water could control the volume stability of hydrated materials containing nanoconfined structural water. Understanding and predicting the thermal deformation coefficient (TDC, often referred to as the CTE, coefficient of thermal expansion), which represents volume changes induced in materials under conditions of changing temperature, is of critical importance for hydrated solids including: hydrogels, biological tissues, and calcium silicate hydrates, as changes in their volume can result in stress development, and cracking. By pioneering atomistic simulations, we examine the physical origin of thermal expansion in calcium-silicate-hydrates (C-S-H), the binding agent in concrete that is formed by the reaction of cement with water. We report that the TDC of C-S-H shows a sudden increase when the CaO/SiO2 (molar ratio; abbreviated as Ca/Si) exceeds 1.5. This anomalous behavior arises from a notable increase in the confinement of water contained in the C-S-H's nanostructure. We identify that confinement is dictated by the topology of the C-S-H's atomic network. Taken together, the results suggest that thermal deformations of hydrated silicates can be altered by inducing compositional changes, which in turn alter the atomic topology and the resultant volume stability of the solids.

  17. The origin of endothelial cells in novel structures, Bonghan ducts and Bonghan corpuscles determined using immunofluorescence.

    PubMed

    Yi, Sun-Shin; Hwang, In-Koo; Kim, Min-Su; Soh, Kwang-Sup; Yoon, Yeo-Sung

    2009-09-01

    Bonghan ducts (BHDs), and their associated Bonghan corpuscles (BHCs), which are novel threadlike structures, were recently observed in rats and rabbits by using various methods. As further support for the putative circulatory function of the novel threadlike structures (NTS), we investigated the presence and the origin of the endothelial cells within these structures. We immunostained the NTS with anti-CD146, an endothelial cell marker, and with anti-podoplanin, a lymphatic cell marker. Positive expression of CD146 in the BHDs was obtained, and the distribution of endothelial cells showed that the inner boundaries of the channels in the subducts branched from the BHDs and curled around, in a complicated manner, inside a BHCs. The negative expression of podoplanin implies that the endothelial cells in the BHDs are likely to be of vascular and not of lymphatic origin.

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

    NASA Astrophysics Data System (ADS)

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

    A comparison of the determination of boundary-layer structures by a SODAR, by a RASS, and by a ceilometer is presented. One important structure is the mixing-layer height (MLH). The comparison is focused on 3 days with an evolution of a convective boundary layer over a larger city in Germany. The three instruments give information that partly agree and partly complement each other. By this, a picture of the diurnal evolution of the vertical structure of this urban boundary layer is presented. The ceilometer gives information on the aerosol content of the air and the RASS provides a direct measurement of the vertical temperature distribution in the boundary layer. The RASS and the ceilometer add information on the moisture structure of the boundary layer that is not detected by the SODAR. On the other hand this comparison validates known techniques by which the MLH is derived from SODAR data. Especially the temperature information from the RASS agrees well with lifted inversions derived from the analysis of the SODAR data. The ceilometer, being the smallest instrument, has a potential to be used in future MLH studies.

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

    SciTech Connect

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

    2015-05-07

    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 Fe{sub 0.5}Ir{sub 0.5} interfacial alloy supported on the Ir(111) substrate. The competition between the negative formation heat of Fe{sub 0.5}Ir{sub 0.5} 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 Fe{sub 0.5}Ir{sub 0.5}/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 Fe{sub 0.5}Ir{sub 0.5}/Ir(111). These results emphasize the importance of the substrate induced strain and layered structure of Fe/Fe{sub 0.5}Ir{sub 0.5}/Ir(111) on the magnetic properties and provide valuable information for future applications.

  20. 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.

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

    NASA Astrophysics Data System (ADS)

    Schoofs, Stan; Trompert, Ron A.; Hansen, Ulrich

    2000-03-01

    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 φ 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 solute through the liquid by the factor φ, while diffusion of heat through the bulk porous medium is larger by the factor φ-1 times the ratio between the thermal and chemical diffusivities. By performing numerical experiments in which a rigid low-porosity medium is heated from below, we have studied the formation and evolution of layers in an initially stably stratified liquid. Growth of a convective layer through convective entrainment, the formation of a stable density interface on top of the layer and destabilization of the next layer are intimately linked. By monitoring the heat (solute) fluxes, it is observed that the transport of heat (solute) across the interface changes from convective entrainment towards a regime in which transfer is purely diffusive (dispersive). Because this transition occurs before the stage at which the lower layer arrives at the thermal equilibrium, we conclude that the layer growth stops when the density interface on top has grown sufficiently strong to keep the ascending plumes in the lower layer from convectively entraining more fluid from above. A simple balance between the most important forces, exerted on a fluid parcel in the lower layer, is proposed to determine this transition. This force balance also indicates whether a density interface keeps intact, migrates upwards or breaks down during the further evolution of the layered sequence. Finally, mechanical dispersion tends to increase transport of chemically dissolved elements across the density interface. Since this reduces the density difference between

  2. 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.

  3. 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

  4. 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 λ = 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.

  5. 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.

  6. On the structural origins of ferroelectricity in HfO2 thin films

    NASA Astrophysics Data System (ADS)

    Sang, Xiahan; Grimley, Everett D.; Schenk, Tony; Schroeder, Uwe; LeBeau, James M.

    2015-04-01

    Here, we present a structural study on the origin of ferroelectricity in Gd doped HfO2 thin films. We apply aberration corrected high-angle annular dark-field scanning transmission electron microscopy to directly determine the underlying lattice type using projected atom positions and measured lattice parameters. Furthermore, we apply nanoscale electron diffraction methods to visualize the crystal symmetry elements. Combined, the experimental results provide unambiguous evidence for the existence of a non-centrosymmetric orthorhombic phase that can support spontaneous polarization, resolving the origin of ferroelectricity in HfO2 thin films.

  7. On the structural origins of ferroelectricity in HfO{sub 2} thin films

    SciTech Connect

    Sang, Xiahan; Grimley, Everett D.; LeBeau, James M.; Schenk, Tony; Schroeder, Uwe

    2015-04-20

    Here, we present a structural study on the origin of ferroelectricity in Gd doped HfO{sub 2} thin films. We apply aberration corrected high-angle annular dark-field scanning transmission electron microscopy to directly determine the underlying lattice type using projected atom positions and measured lattice parameters. Furthermore, we apply nanoscale electron diffraction methods to visualize the crystal symmetry elements. Combined, the experimental results provide unambiguous evidence for the existence of a non-centrosymmetric orthorhombic phase that can support spontaneous polarization, resolving the origin of ferroelectricity in HfO{sub 2} thin films.

  8. Enhanced Magnetoelectric Coupling in Layered Structure of Piezoelectric Bimorph and Metallic Alloy

    NASA Astrophysics Data System (ADS)

    Petrov, V. M.; Bichurin, M. I.; Lavrentyeva, K. V.; Leontiev, V. S.

    2016-08-01

    We have investigated the enhanced magnetoelectric (ME) coupling in a layered structure of piezoelectric bimorph and magnetostrictive metallic alloy. The observed ME coefficient in the piezoelectric bimorph-based structure was found to be two times higher than in the traditional piezoelectric/magnetostrictive bilayer. The observed enhancement in ME coupling strength is related to equal signs of induced voltage in both lead zirconate titanate layers with opposite poling directions due to the flexural deformations. The piezoelectric bimorph-based structure has promising potential for sensor and technological applications.

  9. Single-hole borehole radar detection of layered structures orthogonal to the borehole

    NASA Astrophysics Data System (ADS)

    Murray, W.; Williams, C.; Lewis, C.; Josh, M.

    2000-04-01

    A vertical borehole may pass through natural layered structures which are orthogonal or near-orthogonal to the borehole. Such structures, particularly if they are layers with a smooth surface, can be very difficult to detect with a borehole radar which has the required long range and low center frequency for remote structure detection. Methods of supplementing the radar data are discussed and include the use of an additional radar with a much higher center frequency, the use of a dielectric probe and the use of a look-ahead radar.

  10. Effects of precipitation on the thermodynamic structure of the trade wind boundary layer

    NASA Technical Reports Server (NTRS)

    Albrecht, Bruce A.

    1993-01-01

    A model of the thermodynamic structure of the trade wind boundary layer is formulated to include the parameterization of precipitation in relatively shallow clouds. Although the area-averaged simulated precipitation rates are relatively small (less than 1 mm/day), the inclusion of precipitation has an appreciable effect on the predicted thermodynamic structure. The cloud layer structure simulated with precipitation is warmer, drier, and more stable than that simulated without precipitation. The simulated inversion height is lowered by as much as 60 mbar when precipitation is included.

  11. Secondary ion emission from ultra-thin oxide layers bombarded by energetic (MeV) heavy ions: depth of origin and layer homogeneity

    NASA Astrophysics Data System (ADS)

    Allali, H.; Cabaud, B.; Fuchs, G.; Hoareau, A.; Nsouli, B.; Thomas, J.-P.; Treilleux, M.; Danel, J.-S.

    1994-02-01

    The escape depth of the secondary ions resulting from electronic sputtering of fast heavy ions in inorganic thin films has been investigated. Chromium layers deposited onto SiO 2 substrate as well as SiO x layers deposited onto chromium substrate have been characterised by secondary ion emission mass spectrometry (SIMS) in combination with time-of-flight (TOF) mass analysis (also referred to as HSF-SIMS [B.U.R. Sundqvist, in: Sputtering by Particle Bombardment III, eds. R. Behrisch and K. Wittmaack (Springer, Berlin, Heidelberg, 1991) p. 257]). These crossed experiments lead to a value around 1 nm for SiO x layers and 0.5 nm for Cr layers. On the other hand, HSF-SIMS can be used to correlate the intensity of the secondary ion emission to the film coverage rate (Θ) and (or) the morphology of particular films like those produced by low energy cluster beam deposition (LECBD). Using Sb deposits, the non-linear relationship between ion emission and Θ is interpreted in terms of sputtering enhancement in the individual supported clusters.

  12. The study of origin of interfacial perpendicular magnetic anisotropy in ultra-thin CoFeB layer on the top of MgO based magnetic tunnel junction

    NASA Astrophysics Data System (ADS)

    Li, Zhi-Peng; Li, Shaoping; Zheng, Yuankai; Fang, Jason; Chen, Lifan; Hong, Liang; Wang, Haifeng

    2016-10-01

    A comprehensive microstructure study has been conducted experimentally for identifying the origin or mechanism of perpendicular magnetic anisotropy (PMA) in the ultra-thin (10 Å) CoFeB layer on the top of magnetic tunnel junction (MTJ). The high resolution transmission electron microscopy reveals that the feature of crystal structure in 10 Å-CoFeB layer is localized in nature at the CoFeB-MgO interface. On the other hand, the strain-relaxed crystalline structure is observed in the thick CoFeB (20 Å) layer at the CoFeB-MgO interface, associated with a series of dislocation formations. The electron energy loss spectroscopy further suggests that the local chemical stoichiometry of the ultra-thin 10 Å-CoFeB layer is notably changed at the CoFeB-MgO interface, compared with an atomic stoichiometry in a thick 20 Å-CoFeB layer. The origin of PMA mechanism is therefore identified experimentally as an interface effect, which can be attributed to a change of local atom bonding or lattice constant of the transition metal at the CoFeB-MgO based MTJ interface. Furthermore, such a local interfacial atom bonding change is seemly induced by the localized anisotropic strain and consistent with previous theoretical speculations and calculations. The observed experimental findings provide some perspective on microstructure and chemistry on PMA in ultra-thin CoFeB film at the MTJ interface, then deepening our understanding of the mechanism of PMA within MTJ stack and thus facilitating advancement for emerging spintronics technology.

  13. 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.

  14. Structure and physical properties for a new layered pnictide-oxide: BaTi₂As₂O.

    PubMed

    Wang, X F; Yan, Y J; Ying, J J; Li, Q J; Zhang, M; Xu, N; Chen, X H

    2010-02-24

    We have successfully synthesized a new layered pnictide-oxide: BaTi(2)As(2)O. It shares similar characteristics with Na(2)Ti(2)Sb(2)O. The crystal has a layered structure with a tetragonal P4/nmm group (a = 4.047(3) Å, c = 7.275(4) Å). The resistivity shows an anomaly at 200 K, which should be ascribed to an SDW or structural transition. The SDW or structural transition is confirmed by magnetic susceptibility and heat capacity measurements. These behaviors are very similar to those observed in parent compounds of high-T(c) iron-based pnictide superconductors, in which the superconductivity shows up when the anomaly due to the SDW or structural transition is suppressed. Therefore, the new layered pnictide-oxide, BaTi(2)As(2)O, could be a potential parent compound for superconductivity. It is found that Li( + ) doping significantly suppresses the anomaly, but no superconductivity emerges so far.

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

    NASA Astrophysics Data System (ADS)

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

    2011-06-01

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

  16. 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.

  17. Strengthening of polymer ordered porous materials based on a layered nanocomposite internal structure

    NASA Astrophysics Data System (ADS)

    Heng, Liping; Guo, Xieyou; Guo, Tianqi; Wang, Bin; Jiang, Lei

    2016-07-01

    Ordered porous polymeric films attract more and more attention because they have many advantages and broad application prospects in many fields. But because of their large flexibility and poor mechanical properties, some of the scope for application is greatly limited. Inspired by the ordered pore structure of the honeycomb and the layered structure of natural nacre, we prepared an ordered porous polymer film with a layered structure in the pore wall by the solvent-evaporation-restriction assisted hard template method. Compared with other samples, this kind of film with the layered structure showed both excellent mechanical properties and good stability. This kind of film with high mechanical strength, is considered to have wide applications in the areas of separation, biomedicine, precision instruments, aerospace, environmental protection and so on.Ordered porous polymeric films attract more and more attention because they have many advantages and broad application prospects in many fields. But because of their large flexibility and poor mechanical properties, some of the scope for application is greatly limited. Inspired by the ordered pore structure of the honeycomb and the layered structure of natural nacre, we prepared an ordered porous polymer film with a layered structure in the pore wall by the solvent-evaporation-restriction assisted hard template method. Compared with other samples, this kind of film with the layered structure showed both excellent mechanical properties and good stability. This kind of film with high mechanical strength, is considered to have wide applications in the areas of separation, biomedicine, precision instruments, aerospace, environmental protection and so on. Electronic supplementary information (ESI) available: SEM image of hexagonal silicon pillar templates, AFM images of clay platelets on a silicon substrate, photographs of free-standing gels, X-ray diffraction profiles for dried materials, FTIR and TGA of the samples, and

  18. Multi-layered population structure in Island Southeast Asians

    PubMed Central

    Ricaut, Francois-Xavier; Yngvadottir, Bryndis; Harney, Eadaoin; Castillo, Cristina; Hoogervorst, Tom; Antao, Tiago; Kusuma, Pradiptajati; Razafindrazaka, Harilanto; Cardona, Alexia; Pierron, Denis; Letellier, Thierry; Wee, Joseph; Abdullah, Syafiq; Metspalu, Mait; Kivisild, Toomas

    2016-01-01

    The history of human settlement in Southeast Asia has been complex and involved several distinct dispersal events. Here we report the analyses of 1825 individuals from Southeast Asia including new genome-wide genotype data for 146 individuals from three Mainland Southeast Asian (Burmese, Malay and Vietnamese) and four Island Southeast Asian (Dusun, Filipino, Kankanaey and Murut) populations. While confirming the presence of previously recognized major ancestry components in the Southeast Asian population structure, we highlight the Kankanaey Igorots from the highlands of the Philippine Mountain Province as likely the closest living representatives of the source population that may have given rise to the Austronesian expansion. This conclusion rests on independent evidence from various analyses of autosomal data and uniparental markers. Given the extensive presence of trade goods, cultural and linguistic evidence of Indian influence in Southeast Asia starting from 2.5kya we also detect traces of a South Asian signature in different populations in the region dating to the last couple of thousand years. PMID:27302840

  19. Multi-layered population structure in Island Southeast Asians.

    PubMed

    Mörseburg, Alexander; Pagani, Luca; Ricaut, Francois-Xavier; Yngvadottir, Bryndis; Harney, Eadaoin; Castillo, Cristina; Hoogervorst, Tom; Antao, Tiago; Kusuma, Pradiptajati; Brucato, Nicolas; Cardona, Alexia; Pierron, Denis; Letellier, Thierry; Wee, Joseph; Abdullah, Syafiq; Metspalu, Mait; Kivisild, Toomas

    2016-11-01

    The history of human settlement in Southeast Asia has been complex and involved several distinct dispersal events. Here, we report the analyses of 1825 individuals from Southeast Asia including new genome-wide genotype data for 146 individuals from three Mainland Southeast Asian (Burmese, Malay and Vietnamese) and four Island Southeast Asian (Dusun, Filipino, Kankanaey and Murut) populations. While confirming the presence of previously recognised major ancestry components in the Southeast Asian population structure, we highlight the Kankanaey Igorots from the highlands of the Philippine Mountain Province as likely the closest living representatives of the source population that may have given rise to the Austronesian expansion. This conclusion rests on independent evidence from various analyses of autosomal data and uniparental markers. Given the extensive presence of trade goods, cultural and linguistic evidence of Indian influence in Southeast Asia starting from 2.5 kya, we also detect traces of a South Asian signature in different populations in the region dating to the last couple of thousand years.

  20. Creating new layered structures at high pressures: SiS2

    PubMed Central

    Plašienka, Dušan; Martoňák, Roman; Tosatti, Erio

    2016-01-01

    Old and novel layered structures are attracting increasing attention for their physical, electronic, and frictional properties. SiS2, isoelectronic to SiO2, CO2 and CS2, is a material whose phases known experimentally up to 6 GPa exhibit 1D chain-like, 2D layered and 3D tetrahedral structures. We present highly predictive ab initio calculations combined with evolutionary structure search and molecular dynamics simulations of the structural and electronic evolution of SiS2 up to 100 GPa. A highly stable CdI2-type layered structure, which is octahedrally coordinated with space group surprisingly appears between 4 and up to at least 100 GPa. The tetrahedral-octahedral switch is naturally expected upon compression, unlike the layered character realized here by edge-sharing SiS6 octahedral units connecting within but not among sheets. The predicted phase is semiconducting with an indirect band gap of about 2 eV at 10 GPa, decreasing under pressure until metallization around 40 GPa. The robustness of the layered phase suggests possible recovery at ambient pressure, where calculated phonon spectra indicate dynamical stability. Even a single monolayer is found to be dynamically stable in isolation, suggesting that it could possibly be sheared or exfoliated from bulk -SiS2. PMID:27886243

  1. Creating new layered structures at high pressures: SiS2

    NASA Astrophysics Data System (ADS)

    Plašienka, Dušan; Martoňák, Roman; Tosatti, Erio

    2016-11-01

    Old and novel layered structures are attracting increasing attention for their physical, electronic, and frictional properties. SiS2, isoelectronic to SiO2, CO2 and CS2, is a material whose phases known experimentally up to 6 GPa exhibit 1D chain-like, 2D layered and 3D tetrahedral structures. We present highly predictive ab initio calculations combined with evolutionary structure search and molecular dynamics simulations of the structural and electronic evolution of SiS2 up to 100 GPa. A highly stable CdI2-type layered structure, which is octahedrally coordinated with space group surprisingly appears between 4 and up to at least 100 GPa. The tetrahedral-octahedral switch is naturally expected upon compression, unlike the layered character realized here by edge-sharing SiS6 octahedral units connecting within but not among sheets. The predicted phase is semiconducting with an indirect band gap of about 2 eV at 10 GPa, decreasing under pressure until metallization around 40 GPa. The robustness of the layered phase suggests possible recovery at ambient pressure, where calculated phonon spectra indicate dynamical stability. Even a single monolayer is found to be dynamically stable in isolation, suggesting that it could possibly be sheared or exfoliated from bulk -SiS2.

  2. Graphene Substrate for van der Waals Epitaxy of Layer-Structured Bismuth Antimony Telluride Thermoelectric Film.

    PubMed

    Kim, Eun Sung; Hwang, Jae-Yeol; Lee, Kyu Hyoung; Ohta, Hiromichi; Lee, Young Hee; Kim, Sung Wng

    2017-02-01

    Graphene as a substrate for the van der Waals epitaxy of 2D layered materials is utilized for the epitaxial growth of a layer-structured thermoelectric film. Van der Waals epitaxial Bi0.5 Sb1.5 Te3 film on graphene synthesized via a simple and scalable fabrication method exhibits good crystallinity and high thermoelectric transport properties comparable to single crystals.

  3. Vortical and turbulent structure of planar and lobed mixer free-shear layers

    NASA Astrophysics Data System (ADS)

    McCormick, Duane Clark

    A comprehensive experimental investigation of the free-shear layer vortical and turbulent structure downstream of a lobed mixer has been conducted. Pulsed-laser flow visualization with smoke and three-dimensional velocity measurements with triple-sensor hot film anemometry were obtained for two lobed mixer configurations (symmetric and unsymmetric waveforms) and a baseline, planar configuration. Both laminar and turbulent initial boundary layer conditions were documented for each of the three configurations. The main result of this investigation is that a new vortex structure was found to exist for the lobed mixers in addition to the well-known streamwise vortex array. The normal vortex (due to the Kelvin-Helmholtz instability) sheds periodically from the convoluted trailing edge of the lobed mixer and plays a major part in the enhanced mixing process in combination with the streamwise vorticity. The streamwise vorticity deforms the normal vortex into a pinched-off structure that creates intense turbulence and mixing. The scale of the normal vortex was approximately one fourth that of the planar case, thereby introducing a small-scale turbulence over a large cross-stream area of the flow that dominates the near-field Reynolds shear stress distribution. Thus, the lobed mixer free-shear layer provides enhanced mixing down to the molecular scale. The shear layer growth rate for the first 5-6 lobe heights was substantially greater than the planar free-shear layer due to the normal and streamwise vortex interaction. Downstream of six lobe heights, the growth rate slowed considerably to a rate below that of the planar configuration due to the reduced turbulent kinetic energy of a double-layered shear layer structure. The streamwise and normal vorticity were completely dissipated by 5-6 lobe heights. Also, the lobe mixer development was found to be surprisingly insensitive to initial laminar and turbulent boundary layer conditions (unlike the planar case).

  4. Vortical and Turbulent Structure of Planar and Lobed Mixer Free-Shear Layers

    NASA Astrophysics Data System (ADS)

    McCormick, Duane Clark

    A comprehensive experimental investigation of the free-shear layer vortical and turbulent structure downstream of a lobed mixer has been conducted. Pulsed-laser flow visualization with smoke and three-dimensional velocity measurements with triple-sensor hot film anemometry were obtained for two lobed mixer configurations (symmetric and unsymmetric waveforms) and a baseline, planar configuration. Both laminar and turbulent initial boundary layer conditions were documented for each of the three configurations. The main result of this investigation is that a new vortex structure was found to exist for the lobed mixers in addition to the well-known streamwise vortex array. The normal vortex (due to the Kelvin-Helmholtz instability) sheds periodically from the convoluted trailing edge of the lobed mixer and plays a major part in the enhanced mixing process in combination with the streamwise vorticity. The streamwise vorticity deforms the normal vortex into a pinched -off structure that creates intense turbulence and mixing. The scale of the normal vortex was approximately one fourth that of the planar case, thereby introducing a small-scale turbulence over a large cross-stream area of the flow that dominates the near-field Reynolds shear stress distribution. Thus, the lobed mixer free-shear layer provides enhanced mixing down to the molecular scale. The shear layer growth rate for the first 5-6 lobe heights was substantially greater than the planar free-shear layer due to the normal and streamwise vortex interaction. Downstream of six lobe heights, the growth rate slowed considerably to a rate below that of the planar configuration due to the reduced turbulent kinetic energy of a double-layered shear layer structure. The streamwise and normal vorticity were completely dissipated by 5-6 lobe heights. Also, the lobed mixer development was found to be surprisingly insensitive to initial laminar and turbulent boundary layer conditions (unlike the planar case).

  5. Angular and positional dependence of Purcell effect for layered metal-dielectric structures

    NASA Astrophysics Data System (ADS)

    Gubaydullin, A. R.; Mazlin, V. A.; Ivanov, K. A.; Kaliteevski, M. A.; Balocco, C.

    2016-04-01

    We study the angular dependence of the spontaneous emission enhancement of a dipole source inserted into a layered metal-dielectric metamaterial. We analyse the dependence of Purcell effect from the position of the dipole in the layered hyperbolic media. We analyse the impact of the complex structure of eigenmodes of the system operating in hyperbolic regime. We have shown that the spontaneous emission rate of the dipole emitter depends on its position, which mainly affect the interaction with Langmuir modes.

  6. Fine-scale radar observations of boundary layer structures in landfalling hurricanes

    NASA Astrophysics Data System (ADS)

    Kosiba, K.; Wurman, J.; Robinson, P.

    2012-04-01

    The hurricane boundary layer is comprised of coherent structures that are potentially responsible for significant transport of turbulent fluxes throughout the hurricane boundary layer as well as regions of enhanced damage at the surface. These coherent structures are not well understood and consequently their effects are poorly represented in numerical models. Consequently, an understanding of the flow modulating processes in the hurricane boundary layer is necessary to improve hurricane intensity forecasts. Further, enhanced regions of turbulent momentum transport are hypothesized to cause areas of enhanced damage at the surface. In order to characterize these turbulent processed and quantify their effects, the Doppler on Wheels radars (DOWs) have deployed in several hurricanes, obtaining both dual-Doppler and rapid single-Doppler observations in the boundary layer of landfalling hurricanes. Results will be presented from Hurricanes Frances (2004), Gustav (2008), and Ike (2008). During Hurricane Frances, high-resolution, dual-Doppler radar observations of the lowest hundred meters of the boundary layer allowed for the four-dimensional (time and space) analysis of the boundary layer velocity structure and for the quantification of the turbulent fluxes as Frances transitioned from ocean to land. These results will be discussed in the context of current turbulent parameterization schemes used in numerical models. In Hurricanes Gustav and Ike, rapid, single-Doppler observations were obtained of the boundary layers. This allowed for the two-dimensional quantification rapidly evolving of boundary layer structures. Further an array of surface based instruments were deployed in Hurricanes Gustav and Ike in order to correlate observations at radar level with surface observations. Through turbulent considerations, a reduction factor was derived for the radar winds, which allowed for the comparison between radar level winds and winds observed at 1, 2, and 10 m. These results

  7. Geographic population structure analysis of worldwide human populations infers their biogeographical origins.

    PubMed

    Elhaik, Eran; Tatarinova, Tatiana; Chebotarev, Dmitri; Piras, Ignazio S; Maria Calò, Carla; De Montis, Antonella; Atzori, Manuela; Marini, Monica; Tofanelli, Sergio; Francalacci, Paolo; Pagani, Luca; Tyler-Smith, Chris; Xue, Yali; Cucca, Francesco; Schurr, Theodore G; Gaieski, Jill B; Melendez, Carlalynne; Vilar, Miguel G; Owings, Amanda C; Gómez, Rocío; Fujita, Ricardo; Santos, Fabrício R; Comas, David; Balanovsky, Oleg; Balanovska, Elena; Zalloua, Pierre; Soodyall, Himla; Pitchappan, Ramasamy; Ganeshprasad, Arunkumar; Hammer, Michael; Matisoo-Smith, Lisa; Wells, R Spencer

    2014-04-29

    The search for a method that utilizes biological information to predict humans' place of origin has occupied scientists for millennia. Over the past four decades, scientists have employed genetic data in an effort to achieve this goal but with limited success. While biogeographical algorithms using next-generation sequencing data have achieved an accuracy of 700 km in Europe, they were inaccurate elsewhere. Here we describe the Geographic Population Structure (GPS) algorithm and demonstrate its accuracy with three data sets using 40,000-130,000 SNPs. GPS placed 83% of worldwide individuals in their country of origin. Applied to over 200 Sardinians villagers, GPS placed a quarter of them in their villages and most of the rest within 50 km of their villages. GPS's accuracy and power to infer the biogeography of worldwide individuals down to their country or, in some cases, village, of origin, underscores the promise of admixture-based methods for biogeography and has ramifications for genetic ancestry testing.

  8. Crystal structure of the simian virus 40 large T-antigen origin-binding domain.

    PubMed

    Meinke, Gretchen; Bullock, Peter A; Bohm, Andrew

    2006-05-01

    The origins of replication of DNA tumor viruses have a highly conserved feature, namely, multiple binding sites for their respective initiator proteins arranged as inverted repeats. In the 1.45-angstroms crystal structure of the simian virus 40 large T-antigen (T-ag) origin-binding domain (obd) reported herein, T-ag obd monomers form a left-handed spiral with an inner channel of 30 angstroms having six monomers per turn. The inner surface of the spiral is positively charged and includes residues known to bind DNA. Residues implicated in hexamerization of full-length T-ag are located at the interface between adjacent T-ag obd monomers. These data provide a high-resolution model of the hexamer of origin-binding domains observed in electron microscopy studies and allow the obd's to be oriented relative to the hexamer of T-ag helicase domains to which they are connected.

  9. Crystal Structure of the Simian Virus 40 Large T-Antigen Origin-Binding Domain

    SciTech Connect

    Meinke,G.; Bullock, P.; Bohm, A.

    2006-01-01

    The origins of replication of DNA tumor viruses have a highly conserved feature, namely, multiple binding sites for their respective initiator proteins arranged as inverted repeats. In the 1.45- Angstroms crystal structure of the simian virus 40 large T-antigen (T-ag) origin-binding domain (obd) reported herein, T-ag obd monomers form a left-handed spiral with an inner channel of 30 Angstroms having six monomers per turn. The inner surface of the spiral is positively charged and includes residues known to bind DNA. Residues implicated in hexamerization of full-length T-ag are located at the interface between adjacent T-ag obd monomers. These data provide a high-resolution model of the hexamer of origin-binding domains observed in electron microscopy studies and allow the obd's to be oriented relative to the hexamer of T-ag helicase domains to which they are connected.

  10. 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.

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

    PubMed Central

    He, Fupo; Ye, Jiandong

    2013-01-01

    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. PMID:27877603

  12. Three-Dimensional Mapping of Atmospheric Boundary Layer Structure and Winds with a High Performance Lidar

    DTIC Science & Technology

    1991-04-01

    layer (usually less than half the boundary layer height) for each of the shots in a PPI scan using 12 Si 12--F1 S ( 1 ) 2- 1 1 = 11 where Sil is the natural...between 1 and 1024), and ( 11 to 12) is the range segment located well within the boundary layer. Within this range interval, the aerosol contribution...the CBL, mean CBL wind, surface wind, and the wind at a height of 1 . 1 Zi. The orientation of the aerosol structures is also shown. Figure 11 . The

  13. Enhanced structural color generation in aluminum metamaterials coated with a thin polymer layer.

    PubMed

    Cheng, Fei; Yang, Xiaodong; Rosenmann, Daniel; Stan, Liliana; Czaplewski, David; Gao, Jie

    2015-09-21

    A high-resolution and angle-insensitive structural color generation platform is demonstrated based on triple-layer aluminum-silica-aluminum metamaterials supporting surface plasmon resonances tunable across the entire visible spectrum. The color performances of the fabricated aluminum metamaterials can be strongly enhanced by coating a thin transparent polymer layer on top. The results show that the presence of the polymer layer induces a better impedance matching for the plasmonic resonances to the free space so that strong light absorption can be obtained, leading to the generation of pure colors in cyan, magenta, yellow and black (CMYK) with high color saturation.

  14. Al{sub 2}O{sub 3} multi-density layer structure as a moisture permeation barrier deposited by radio frequency remote plasma atomic layer deposition

    SciTech Connect

    Jung, Hyunsoo; Jeon, Heeyoung; Choi, Hagyoung; Ham, Giyul; Shin, Seokyoon; Jeon, Hyeongtag

    2014-02-21

    Al{sub 2}O{sub 3} films deposited by remote plasma atomic layer deposition have been used for thin film encapsulation of organic light emitting diode. In this study, a multi-density layer structure consisting of two Al{sub 2}O{sub 3} layers with different densities are deposited with different deposition conditions of O{sub 2} plasma reactant time. This structure improves moisture permeation barrier characteristics, as confirmed by a water vapor transmission rate (WVTR) test. The lowest WVTR of the multi-density layer structure was 4.7 × 10{sup −5} gm{sup −2} day{sup −1}, which is one order of magnitude less than WVTR for the reference single-density Al{sub 2}O{sub 3} layer. This improvement is attributed to the location mismatch of paths for atmospheric gases, such as O{sub 2} and H{sub 2}O, in the film due to different densities in the layers. This mechanism is analyzed by high resolution transmission electron microscopy, elastic recoil detection, and angle resolved X-ray photoelectron spectroscopy. These results confirmed that the multi-density layer structure exhibits very good characteristics as an encapsulation layer via location mismatch of paths for H{sub 2}O and O{sub 2} between the two layers.

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

    PubMed

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

    2012-12-14

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

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

    PubMed

    Dijckmans, A; Vermeir, G; Lauriks, W

    2010-12-01

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

  17. The Evolutionary Origin of Man Can Be Traced in the Layers of Defunct Ancestral Alpha Satellites Flanking the Active Centromeres of Human Chromosomes

    PubMed Central

    Shepelev, Valery A.; Alexandrov, Alexander A.; Yurov, Yuri B.; Alexandrov, Ivan A.

    2009-01-01

    Alpha satellite domains that currently function as centromeres of human chromosomes are flanked by layers of older alpha satellite, thought to contain dead centromeres of primate progenitors, which lost their function and the ability to homogenize satellite repeats, upon appearance of a new centromere. Using cladistic analysis of alpha satellite monomers, we elucidated complete layer patterns on chromosomes 8, 17, and X and related them to each other and to primate alpha satellites. We show that discrete and chronologically ordered alpha satellite layers are partially symmetrical around an active centromere and their succession is partially shared in non-homologous chromosomes. The layer structure forms a visual representation of the human evolutionary lineage with layers corresponding to ancestors of living primates and to entirely fossil taxa. Surprisingly, phylogenetic comparisons suggest that alpha satellite arrays went through periods of unusual hypermutability after they became “dead” centromeres. The layer structure supports a model of centromere evolution where new variants of a satellite repeat expanded periodically in the genome by rounds of inter-chromosomal transfer/amplification. Each wave of expansion covered all or many chromosomes and corresponded to a new primate taxon. Complete elucidation of the alpha satellite phylogenetic record would give a unique opportunity to number and locate the positions of major extinct taxa in relation to human ancestors shared with extant primates. If applicable to other satellites in non-primate taxa, analysis of centromeric layers could become an invaluable tool for phylogenetic studies. PMID:19749981

  18. 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

  19. Strain compensation in a semiconducting device structure using an intentionally mismatched uniform buffer layer

    NASA Astrophysics Data System (ADS)

    Kujofsa, Tedi; Ayers, John E.

    2016-12-01

    The extent of strain relaxation in semiconducting device heterostructures has important implications in the design of high electron mobility transistors, light-emitting diodes, and laser diodes, in which the residual strain affects the device characteristics. In this work, we develop the theoretical framework for understanding strain compensation in a semiconductor device layer using a uniform buffer layer which can be intentionally mismatched to the material above. Specifically, we determined the critical condition for complete strain compensation in the device layer by intentionally introducing a compositional mismatch at the device-buffer interface. We present minimum energy calculations and show that for a given device layer with fixed mismatch and layer thickness, the buffer layer may be designed with the appropriate combination of thickness and mismatch such that the device layer will have zero residual strain in equilibrium. Such a structure can be referred to as a completely strain-compensated design. In the more general case, there may be partial strain compensation, and we give a simple physics-based Gaussian-type function describing the residual strain in the device layer. We have applied this general framework to In x Ga1-x As/GaAs (001) heterostructures for the purpose of illustration, but the work is applicable to any diamond or zinc blende (001) heteroepitaxial material system.

  20. Normal and lateral forces between lipid covered solids in solution: correlation with layer packing and structure.

    PubMed Central

    Grant, L M; Tiberg, F

    2002-01-01

    We report on the normal and lateral forces between controlled-density mono- and bilayers of phospholipid co-adsorbed onto hydrophobic and hydrophilic solid supports, respectively. Interactions between 1,2-dioleoyl-sn-glycero-3-phosphocholine layers were measured using an atomic force microscope. Notable features of the normal force curves (barrier heights and widths) were found to correlate with the thickness and density of the supported lipid layers. The friction and normal force curves were also found interrelated. Thus, very low friction values were measured as long as the supported layer(s) resisted the normal pressure of the tip. However, as the applied load exceeded the critical value needed for puncturing the layers, the friction jumped to values close to those recorded between bare surfaces. The lipid layers were self-healing between measurements, but a significant hysteresis was observed in the force curves measured on approach and retraction, respectively. The study shows the potential of using atomic force microscopy for lipid layer characterization both with respect to structure and interactions. It further shows the strong lubricating effect of adsorbed lipid layers and how this varies with surface density of lipids. The findings may have important implications for the issue of joint lubrication. PMID:11867453

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

    DOEpatents

    Spahn, Olga B.; Lear, Kevin L.

    1998-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2001-02-01

    Self-organizing layered perovskite compounds like (formula available in paper) 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 of about 10 nm has been reported. As the organic-inorganic layered structure has promising properties for EL-devices, we investigated two- and three layer structures using this perovskite as emitter material in combination with additional hole and electron injection layers. To get more insight into electrical properties and electroluminescence- mechanisms of this material, temperature dependent current- voltage-luminance characteristics have been measured, showing an increasing onset-voltage for current flow from 2.6 V at room temperature to about 8.8 V at 80 K. Electroluminescence is detected at temperatures below 150 K with onset voltages of about 13 V. At liquid nitrogen temperature efficiencies of (formula available in paper) are obtained.

  3. First-principles study of the structure of water layers on flat and stepped Pb electrodes

    PubMed Central

    Lin, Xiaohang; Evers, Ferdinand

    2016-01-01

    Summary On the basis of perodic density functional theory (DFT) calculations, we have addressed the geometric structures and electronic properties of water layers on flat and stepped Pb surfaces. In contrast to late d-band metals, on Pb(111) the energy minimum structure does not correspond to an ice-like hexagonal arrangement at a coverage of 2/3, but rather to a distorted structure at a coverage of 1 due to the larger lattice constant of Pb. At stepped Pb surfaces, the water layers are pinned at the step edge and form a complex network consisting of rectangles, pentagons and hexagons. The thermal stability of the water layers has been studied by using ab initio molecular dynamics simulations (AIMD) at a temperature of 140 K. Whereas the water layer on Pb(111) is already unstable at this temperature, the water layers on Pb(100), Pb(311), Pb(511) and Pb(711) exhibit a higher stability because of stronger water–water interactions. The vibrational spectra of the water layers at the stepped surfaces show a characteristic splitting into three modes in the O–H stretch region. PMID:27335744

  4. The ancient history of the structure of ribonuclease P and the early origins of Archaea

    PubMed Central

    2010-01-01

    Background Ribonuclease P is an ancient endonuclease that cleaves precursor tRNA and generally consists of a catalytic RNA subunit (RPR) and one or more proteins (RPPs). It represents an important macromolecular complex and model system that is universally distributed in life. Its putative origins have inspired fundamental hypotheses, including the proposal of an ancient RNA world. Results To study the evolution of this complex, we constructed rooted phylogenetic trees of RPR molecules and substructures and estimated RPP age using a cladistic method that embeds structure directly into phylogenetic analysis. The general approach was used previously to study the evolution of tRNA, SINE RNA and 5S rRNA, the origins of metabolism, and the evolution and complexity of the protein world, and revealed here remarkable evolutionary patterns. Trees of molecules uncovered the tripartite nature of life and the early origin of archaeal RPRs. Trees of substructures showed molecules originated in stem P12 and were accessorized with a catalytic P1-P4 core structure before the first substructure was lost in Archaea. This core currently interacts with RPPs and ancient segments of the tRNA molecule. Finally, a census of protein domain structure in hundreds of genomes established RPPs appeared after the rise of metabolic enzymes at the onset of the protein world. Conclusions The study provides a detailed account of the history and early diversification of a fundamental ribonucleoprotein and offers further evidence in support of the existence of a tripartite organismal world that originated by the segregation of archaeal lineages from an ancient community of primordial organisms. PMID:20334683

  5. Layer selective magnetometry in ultrathin magnetic structures by polarised neutron reflection

    NASA Astrophysics Data System (ADS)

    Bland, J. A. C.; Lee, J.; Hope, S.; Lauhoff, G.; Penfold, J.; Bucknall, D.

    1997-06-01

    We discuss the application of polarised neutron reflection to layer selective vector magnetometry measurements in thin magnetic films. To illustrate the application of PNR, we review recent measurements of the absolute moment in X/Fe/Ag(001) structures with X = Pd, Ag, Au and Cu and compare the results with the predictions based on theoretical calculations which take into account the measured interface roughness. For the case of strained fct Ni/Cu(001) structures we illustrate the use of PNR as a self-calibrating magnetometric technique in determining both the magnetic layer thickness and total sample moment for which a reduced moment per Ni atom is observed. Finally we present measurements of the layer dependent moments in FeNi/Cu/Co spin valve structures. We show that by comparing the PNR measurements with SQUID magnetometry measurements of the total sample moment we are able to determine the interface moments on an atomic scale.

  6. Layer selective magnetometry in ultrathin magnetic structures by polarised neutron reflection

    NASA Astrophysics Data System (ADS)

    Bland, J. A. C.; Lee, J.; Hope, S.; Lauhoff, G.; Penfold, J.; Bucknall, D.

    1997-01-01

    We discuss the application of polarised neutron reflection to layer selective vector magnetometry measurements in thin magnetic films. To illustrate the application of PNR, we review recent measurements of the absolute moment in X/Fe/Ag(001) structures with X = Pd, Ag, Au and Cu and compare the results with the predictions based on theoretical calculations which take into account the measured interface roughness. For the case of strained fct Ni/Cu(001) structures we illustrate the use of PNR as a self-calibrating magnetometric technique in determining both the magnetic layer thickness and total sample moment for which a reduced moment per Ni atom is observed. Finally we present measurements of the layer dependent moments in FeNi/Cu/Co spin valve structures. We show that by comparing the PNR measurements with SQUID magnetometry measurements of the total sample moment we are able to determine the interface moments on an atomic scale.

  7. A novel intermediate layer for Au/CdZnTe/FTO photoconductive structure

    NASA Astrophysics Data System (ADS)

    Zhang, Yuelu; Wang, Linjun; Xu, Run; Huang, Jian; Tao, Jun; Meng, Hua; Zhang, Jijun; Min, Jiahua

    2016-12-01

    In this work, graphene is tried to use to improve the performance of polycrystalline CdZnTe high-energy radiation and photon detectors. A graphene intermediate layer is prepared by spin-coating process on the surface of polycrystalline CdZnTe film, which forms a photoconductive Au/graphene/CdZnTe/FTO structure. XRD, Raman, photoelectric response and other characterisation methods are adopted to investigate the effect of graphene layer on the electrical characteristics and UV photo-response performance of CdZnTe photoconductive structure. It is demonstrated that graphene layer can significantly improve the contact property of Au/CdZnTe structure, and obviously enhance its UV photo-response and the UV sensitivity increased with one order of magnitude.

  8. Resistance of three-layered structures to static and cyclic bending

    NASA Astrophysics Data System (ADS)

    Bareishis, I. P.; Mikul'skas, A. V.; Paulauskas, V. V.

    1987-09-01

    The above studies of two types of three-layer structural elements showed that the types have different resistances to static deformation in bending. Regardless of the materials, the use of structures which are symmetrical in regard to stiffness makes it possible to obtain a stiffness and strength for the structure which are 10-15% lower than the stiffness and strength of the external plates if the thickness of the latter does not account for more than 25% of the thickness of the structure. This finding, in turn, permits a substantial reduction in the weight of the structure by the use of a lower-density material for the internal layer. Resistance to static bending is determined mainly by the resistance of the structure to shear stresses. The mechanism of fatigue fracture differs appreciably from the fracture mechanism in static deformation. Regardless of the thickness of the structural elements, fatigue fracture for both types of structure occurs as a result of the acting normal compressive stresses. The endurance limit of the hybrid structure is determined by the fatigue resistance of the external layers, and its value is nearly equal to the resistance of the "pure" materials.

  9. Polyoxometalate-based layered structures for charge transport control in molecular devices.

    PubMed

    Douvas, Antonios M; Makarona, Eleni; Glezos, Nikos; Argitis, Panagiotis; Mielczarski, Jerzy A; Mielczarski, Ela

    2008-04-01

    Hybrid organic-inorganic films consisted of molecular layers of a Keggin-structure polyoxometalate (POM: 12-tungstophosphoric acid, H(3)PW(12)O(40)) and 1,12-diaminododecane (DD) on 3-aminopropyl triethoxysilane (APTES)-modified silicon surface, fabricated via the layer-by-layer (LBL) self-assembly method are evaluated as molecular materials for electronic devices. The effect of the fabrication process parameters, including primarily compositions of deposition solutions, on the structural characteristics of the POM-based multilayers was studied extensively with a combination of spectroscopic methods (UV, FTIR, and XPS). Well-characterized POM-based films (both single-layers and multilayers) in a controlled and reproducible way were obtained. The conduction mechanisms in single-layered and multilayered structures were elucidated by the electrical characterization of the produced films supported by the appropriate theoretical analysis. Fowler-Nordheim (FN) tunneling and percolation mechanisms were encountered in good correlation with the structural characteristics of the films encouraging further investigation on the use of these materials in electronic and, in particular, in memory devices.

  10. 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.

  11. Computing the origin and evolution of the ribosome from its structure — Uncovering processes of macromolecular accretion benefiting synthetic biology

    PubMed Central

    Caetano-Anollés, Gustavo; Caetano-Anollés, Derek

    2015-01-01

    Accretion occurs pervasively in nature at widely different timeframes. The process also manifests in the evolution of macromolecules. Here we review recent computational and structural biology studies of evolutionary accretion that make use of the ideographic (historical, retrodictive) and nomothetic (universal, predictive) scientific frameworks. Computational studies uncover explicit timelines of accretion of structural parts in molecular repertoires and molecules. Phylogenetic trees of protein structural domains and proteomes and their molecular functions were built from a genomic census of millions of encoded proteins and associated terminal Gene Ontology terms. Trees reveal a ‘metabolic-first’ origin of proteins, the late development of translation, and a patchwork distribution of proteins in biological networks mediated by molecular recruitment. Similarly, the natural history of ancient RNA molecules inferred from trees of molecular substructures built from a census of molecular features shows patchwork-like accretion patterns. Ideographic analyses of ribosomal history uncover the early appearance of structures supporting mRNA decoding and tRNA translocation, the coevolution of ribosomal proteins and RNA, and a first evolutionary transition that brings ribosomal subunits together into a processive protein biosynthetic complex. Nomothetic structural biology studies of tertiary interactions and ancient insertions in rRNA complement these findings, once concentric layering assumptions are removed. Patterns of coaxial helical stacking reveal a frustrated dynamics of outward and inward ribosomal growth possibly mediated by structural grafting. The early rise of the ribosomal ‘turnstile’ suggests an evolutionary transition in natural biological computation. Results make explicit the need to understand processes of molecular growth and information transfer of macromolecules. PMID:27096056

  12. Origin and structure of the fossil resin from an Indonesian Miocene coal

    NASA Astrophysics Data System (ADS)

    Brackman, W.; Spaargaren, K.; van Dongen, J. P. C. M.; Couperus, P. A.; Bakker, F.

    1984-12-01

    The structure of a fossil resin from Miocene coal outcrops of the Bukit Asam region (Sumatra) has been studied. The fossil material has been formed from sesqui- and tri-terpenes from trees of the Dipterocarp family. The original terpenes have lost virtually all oxygen-containing functions and the resulting mono- and di-olefins have polymerized to a mainly non-crosslinked resin whose components have molecular weights of up to 300,000.

  13. 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).

  14. Engineering meniscus structure and function via multi-layered mesenchymal stem cell-seeded nanofibrous scaffolds.

    PubMed

    Fisher, Matthew B; Henning, Elizabeth A; Söegaard, Nicole; Bostrom, Marc; Esterhai, John L; Mauck, Robert L

    2015-06-01

    Despite advances in tissue engineering for the knee meniscus, it remains a challenge to match the complex macroscopic and microscopic structural features of native tissue, including the circumferentially and radially aligned collagen bundles essential for mechanical function. To mimic this structural hierarchy, this study developed multi-lamellar mesenchymal stem cell (MSC)-seeded nanofibrous constructs. Bovine MSCs were seeded onto nanofibrous scaffolds comprised of poly(ε-caprolactone) with fibers aligned in a single direction (0° or 90° to the scaffold long axis) or circumferentially aligned (C). Multi-layer groups (0°/0°/0°, 90°/90°/90°, 0°/90°/0°, 90°/0°/90°, and C/C/C) were created and cultured for a total of 6 weeks under conditions favoring fibrocartilaginous tissue formation. Tensile testing showed that 0° and C single layer constructs had stiffness values several fold higher than 90° constructs. For multi-layer groups, the stiffness of 0°/0°/0° constructs was higher than all other groups, while 90°/90°/90° constructs had the lowest values. Data for collagen content showed a general positive interactive effect for multi-layers relative to single layer constructs, while a positive interaction for stiffness was found only for the C/C/C group. Collagen content and cell infiltration occurred independent of scaffold alignment, and newly formed collagenous matrix followed the scaffold fiber direction. Structural hierarchies within multi-lamellar constructs dictated biomechanical properties, and only the C/C/C constructs with non-orthogonal alignment within layers featured positive mechanical reinforcement as a consequence of the layered construction. These multi-layer constructs may serve as functional substitutes for the meniscus as well as test beds to understand the complex mechanical principles that enable meniscus function.

  15. Engineering Meniscus Structure and Function via Multi-layered Mesenchymal Stem Cell-seeded Nanofibrous Scaffolds

    PubMed Central

    Fisher, Matthew B.; Henning, Elizabeth A.; Söegaard, Nicole; Bostrom, Marc; Esterhai, John L.; Mauck, Robert L.

    2015-01-01

    Despite advances in tissue engineering for the knee meniscus, it remains a challenge to match the complex macroscopic and microscopic structural features of native tissue, including the circumferentially and radially aligned collagen bundles essential for mechanical function. To mimic this structural hierarchy, this study developed multi-lamellar mesenchymal stem cell (MSC)-seeded nanofibrous constructs. Bovine MSCs were seeded onto nanofibrous scaffolds comprised of poly(ε-caprolactone) with fibers aligned in a single direction (0° or 90° to the scaffold long axis) or circumferentially aligned (C). Multi-layer groups (0°/0°/0°, 90°/90°/90°, 0°/90°/0°, 90°/0°/90°, and C/C/C) were created and cultured for a total of 6 weeks under conditions favoring fibrocartilaginous tissue formation. Tensile testing showed that 0° and C single layer constructs had stiffness values several fold higher than 90° constructs. For multi-layer groups, the stiffness of 0°/0°/0° constructs was higher than all other groups, while 90°/90°/90° constructs had the lowest values. Data for collagen content showed a general positive interactive effect for multi-layers relative to single layer constructs, while a positive interaction for stiffness was found only for the C/C/C group. Collagen content and cell infiltration occurred independent of scaffold alignment, and newly formed collagenous matrix followed the scaffold fiber direction. Structural hierarchies within multi-lamellar constructs dictated biomechanical properties, and only the C/C/C constructs with non-orthogonal alignment within layers featured positive mechanical reinforcement as a consequence of the layered construction. These multi-layer constructs may serve as functional substitutes for the meniscus as well as test beds to understand the complex mechanical principles that enable meniscus function. PMID:25817333

  16. 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.

  17. Layer-by-layer structured films of TiO2 nanoparticles and poly(acrylic acid) on electrospun nanofibres

    NASA Astrophysics Data System (ADS)

    Ding, Bin; Kim, Jinho; Kimura, Eiji; Shiratori, Seimei

    2004-08-01

    We report a new approach for fabricating layer-by-layer (LBL) structured ultrathin hybrid films on electrospun nanofibres. Oppositely charged anatase TiO2 nanoparticles and poly(acrylic acid) (PAA) were alternately deposited on the surface of negatively charged cellulose acetate (CA) nanofibres using the electrostatic LBL self-assembly technique. The fibrous mats were characterized by wide-angle x-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy and Brunauer-Emmett-Teller (BET) surface area techniques. The crystalline phase of anatase TiO2 remained unchanged in the resultant TiO2/PAA films coated on CA fibrous mats. Moreover, the TiO2/PAA film coated fibres showed rough surfaces with grains due to the deposition of aggregated TiO2 particles. The average diameter of the fibres increased from 344 to 584 nm and the BET surface area of the fibrous mats increased from 2.5 to 6.0 m2 g-1 after coating with five bilayers of TiO2/PAA films.

  18. Formation of the seed layers for layer-transfer process silicon solar cells by zone-heating recrystallization of porous silicon structures

    NASA Astrophysics Data System (ADS)

    Lukianov, A.; Murakami, K.; Takazawa, C.; Ihara, M.

    2016-05-01

    Thin-film crystalline silicon is promising for photovoltaic application to reduce the cost of photovoltaic energy. Porous silicon structures have been intensively studied as a seed layer for epitaxial growth of thin Si film and layer-transfer process (LTP). In this article, another approach for LTP has been proposed. The seed layers for epitaxial silicon growth have been formed by zone-heating recrystallization of double-layer por-Si structures. The influence of annealing parameters on porous silicon structures was studied. The transformation of por-Si layer to crystalline Si was observed with the formation of smooth continuous surface with the roughness 0.3 nm, peak-to-valley distance around 3.5 nm, and reduced density of pores. The mechanism of the transformation of por-Si surface due to the action of hydrogen in the passivated pores with preventing surface oxidation was proposed.

  19. Local structures surrounding Zr in nanostructurally stabilized cubic zirconia: Structural origin of phase stability

    SciTech Connect

    Soo, Y. L.; Chen, P. J.; Huang, S. H.; Shiu, T. J.; Tsai, T. Y.; Chow, Y. H.; Lin, Y. C.; Weng, S. C.; Chang, S. L.; Wang, G.; Cheung, C. L.; Sabirianov, R. F.; Mei, W. N.; Namavar, F.; Haider, H.; Garvin, K. L.; Lee, J. F.; Lee, H. Y.; Chu, P. P.

    2008-12-01

    Local environment surrounding Zr atoms in the thin films of nanocrystalline zirconia (ZrO{sub 2}) has been investigated by using the extended x-ray absorption fine structure (EXAFS) technique. These films prepared by the ion beam assisted deposition exhibit long-range structural order of cubic phase and high hardness at room temperature without chemical stabilizers. The local structure around Zr probed by EXAFS indicates a cubic Zr sublattice with O atoms located on the nearest tetragonal sites with respect to the Zr central atoms, as well as highly disordered locations. Similar Zr local structure was also found in a ZrO{sub 2} nanocrystal sample prepared by a sol-gel method. Variations in local structures due to thermal annealing were observed and analyzed. Most importantly, our x-ray results provide direct experimental evidence for the existence of oxygen vacancies arising from local disorder and distortion of the oxygen sublattice in nanocrystalline ZrO{sub 2}. These oxygen vacancies are regarded as the essential stabilizing factor for the nanostructurally stabilized cubic zirconia.

  20. The separation of TM and TE wave in multi-layer metamaterial structure

    NASA Astrophysics Data System (ADS)

    Xia, Lijuan; Yu, Guanxia; Wang, Qian

    2014-02-01

    A mixed-structure form of one-dimensional metamaterial structure composed of single negative permittivity material and anisotropic metamaterial has been investigated in this paper. Such a multi-layer metamaterial structure constitutes special resonant structures, which can be used to control wave propagation and realize the complete separation of TM and TE wave by choosing specific parameters. Theoretical analysis and numerical calculations have been performed to confirm the above results. Specifically, augments in incident angles of TM and TE waves make complete transmission frequencies right shift, and the thicknesses of this resonant structure determine propagation modes and propagation frequencies.

  1. On the origin of a band gap in compounds of diamond-like structures.

    PubMed

    Köhler, Jürgen; Deng, Shuiquan; Lee, Changhoon; Whangbo, Myung-Hwan

    2007-03-19

    Electronic structure calculations were performed to examine the origin of a band gap present in most 18-electron half-Heusler compounds and its absence in NaTl. In these compounds of diamond-like structures, the presence or absence of a band gap is controlled by the sigma antibonding between the valence s orbitals, and the bonding characteristics of the late-main-group elements depend on the extent of their ns/np hybridization. Implications of these observations on the formal oxidation state and the covalent bonding of the transition-metal atoms in 18-electron half-Heusler and related compounds were discussed.

  2. Evaluating forensic DNA mixtures with contributors of different structured ethnic origins: a computer software.

    PubMed

    Hu, Yue-Qing; Fung, Wing K

    2003-08-01

    The effect of a structured population on the likelihood ratio of a DNA mixture has been studied by the current authors and others. In practice, contributors of a DNA mixture may belong to different ethnic/racial origins, a situation especially common in multi-racial countries such as the USA and Singapore. We have developed a computer software which is available on the web for evaluating DNA mixtures in multi-structured populations. The software can deal with various DNA mixture problems that cannot be handled by the methods given in a recent article of Fung and Hu.

  3. 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.

  4. Mointoring Thickness Deviations in Planar Multi-Layered Elastic Structures Using Impedance Signatures

    SciTech Connect

    Fisher, K A

    2007-01-26

    In this letter, a low frequency ultrasonic resonance technique that operates in the (20 - 80 kHz) regime is presented that demonstrates detection of thickness changes on the order of +/- 10{micro}m. This measurement capability is a result of the direct correlation between the electrical impedance of an electro-acoustic transducer and the mechanical loading it experiences when placed in contact with a layered elastic structure. The relative frequency shifts of the resonances peaks can be estimated through a simple one-dimensional transmission model. Separate experimental measurements confirm this technique to be sensitive to subtle changes in the underlying layered elastic structure.

  5. Method for remote diagnostics of the internal structure of layered media

    SciTech Connect

    Lychagov, V V; Kal'yanov, A L; Ryabukho, V P; Lyakin, D V

    2008-06-30

    The method of autocorrelation low coherence interferometry is proposed for diagnostics of inhomogeneities and the internal structure of layered technical and biological samples. In this method the low coherence optical field reflected from the layered sample is analysed by using a Michelson interferometer. Because the object is outside the interferometer, the distance between the interferometer and the object under study is not limited and thus the object can move during the measurements. Theoretical substantiation of the autocorrelation method for media with discrete and continuous optical structure modifications is presented. (special issue devoted to application of laser technologies in biophotonics and biomedical studies)

  6. Magnetic layering transitions in a polyamidoamine (PAMAM) dendrimer nano-structure: Monte Carlo study

    NASA Astrophysics Data System (ADS)

    Ziti, S.; Aouini, S.; Labrim, H.; Bahmad, L.

    2017-02-01

    We study the magnetic layering transitions in a polyamidoamine (PAMAM) dendrimer nano-structure, under the effect of an external magnetic field. We examine the magnetic properties, of this model of the spin S=1 Ising ferromagnetic in real nanostructure used in several scientific domains. For T=0, we give and discuss the ground state phase diagrams. At non null temperatures, we applied the Monte Carlo simulations giving important results summarized in the form of the phase diagrams. We also analyzed the effect of varying the external magnetic field, and found the layering transitions in the polyamidoamine (PAMAM) dendrimer nano-structure.

  7. Internal deformation in layered Zechstein-III K-Mg salts. Structures formed by complex deformation and high contrasts in viscosity observed in drill cores.

    NASA Astrophysics Data System (ADS)

    Raith, Alexander; Urai, Janos L.

    2016-04-01

    During the evaporation of a massive salt body, alternations of interrupted and full evaporation sequences can form a complex layering of different lithologies. Viscosity contrasts of up to five orders of magnitude between these different lithologies are possible in this environment. During the late stage of an evaporation cycle potassium and magnesium (K-Mg) salts are precipitated. These K-Mg salts are of economic interest but also a known drilling hazard due to their very low viscosity. How up to 200m thick layers of these evaporites affect salt deformation at different scales is not well known. A better understanding of salt tectonics with extreme mechanical stratification is needed for better exploration and production of potassium-magnesium salts and to predict the internal structure of potential nuclear waste repositories in salt. To gain a better understanding of the internal deformation of these layers we analyzed K-Mg salt rich drill cores out of the Zechstein III-1b subunit from the Veendam Pillow 10 km southeast of Groningen, near the city Veendam in the NE Netherlands. The study area has a complex geological history with multiple tectonic phases of extension and compression forming internal deformation in the pillow but also conserving most of the original layering. Beside halite the most common minerals in the ZIII-1b are carnallite, kieserite, anhydrite and bischofite alternating in thin layers of simple composition. Seismic interpretation revealed that the internal structure of the Veendam Pillow shows areas, in which the K-Mg salt rich ZIII 1b layer is much thicker than elsewhere, as a result of salt deformation. The internal structure of the ZIII-1b on the other hand, remains unknown. The core analysis shows a strong strain concentration in the weaker Bischofite (MgCl2*6H20) and Carnallite (KMgCl3*6H20) rich layers producing tectonic breccias and highly strained layers completely overprinting the original layering. Layers formed by alternating beds

  8. The Accretion Flow and Boundary Layer Structure in the Dwarf Nova SS Aur

    NASA Astrophysics Data System (ADS)

    Nabizadeh, Armin; Balman, Solen; Godon, Patrick; Sion, Edward; Hertfelder, Marius

    2016-07-01

    We present X-ray analysis of dwarf novae SS Aur (51 ksec) using XMM-Newton Observatory archival data obtained in quiescence for a better understanding of the accretion flow structure. We find X-ray orbital modulations. We report power spectral analysis for EPIC (X-ray) and OM (UV) light curves suggesting high levels of red noise with no significant QPO or periodicities. We simultaneously fitted EPIC pn, MOS1 and MOS2 data using a model for interstellar medium absorption (tbabs) and a multi-temperature plasma emission model (cevmkl) as expected from low accretion rate quiescent dwarf novae. However, the composite model fit yields unacceptable reduced χ ^{2} values due to the existence of soft excess. The soft excess is well modeled using a blackbody model (kT˜˜24 eV) giving a better reduced χ ^{2} value over 3σ significance level. This may indicate the existence of optically thick boundary layer emission. We will discuss the origin of this excess. The best fitting model is a combination of a blackbody, a cevmkl and a power law with an interstellar absorption which yields a reduced χ ^{2} of 1.05. The fit also shows some oxygen and iron over abundances. SS Aur has a maximum thermal plasma temperature of ˜22 keV. The X-ray luminosity in the 0.1 to 50.0 keV energy band is ˜2.0×10 ^{33} ergs ^{-1}. Finally, we discuss these characteristics in the light of standard disk models and accretion flows and geometry in nonmagnetic cataclysmic variables.

  9. Vertical structure of boundary layer convection during cold-air outbreaks at Barrow, Alaska

    NASA Astrophysics Data System (ADS)

    Wang, Yonggang; Geerts, Bart; Chen, Yaosheng

    2016-01-01

    Boundary layer convection (BLC) is common over high-latitude oceans and adjacent coastal regions when a cold airmass becomes exposed to a sufficient fetch of open water. The vertical structure of mixed-phase BLC clouds and precipitation is examined using the Atmospheric Radiation Measurement Program data set collected at the North Slope of Alaska (NSA) site at Barrow, Alaska. BLC may occur at this location in autumn, when cold air masses originating at higher latitudes advect southward over the still ice-free coastal waters north of Alaska. This study identifies such BLC and documents its occurrence and characteristics. Instruments used for this study include profiling Ka band radars, a depolarization backscatter profiling lidar, a scanning X band radar, a microwave radiometer, a ceilometer, surface meteorological probes, and radiosondes. Six criteria are applied to objectively identify the BLC events, using data collected between 2004 and 2013. BLC episodes are relatively common at the NSA site, but almost exclusively in the month of October, and most episodes are relatively short, less than 10 h in duration. Liquid water is commonly found in these mixed-phase BLC clouds, with a typical liquid water path of 150 g/m2, and snowfall rates average ~3 mm h-1 (water equivalent), in some cases over 10 mm h-1, notwithstanding the low cloud echo tops (~1.0-1.5 km). In one rather weak but persistent episode fall speed estimates derived from the profiling Ka band radar indicates the presence of rimed particles, confirming the convective nature of this precipitation.

  10. Columnar structured FePt films epitaxially grown on large lattice mismatched intermediate layer.

    PubMed

    Dong, K F; Deng, J Y; Peng, Y G; Ju, G; Chow, G M; Chen, J S

    2016-09-30

    The microstructure and magnetic properties of the FePt films grown on large mismatched ZrN (15.7%) intermediate layer were investigated. With using ZrN intermediate layer, FePt 10 nm films exhibited (001) texture except for some weaker FePt (110) texture. Good epitaxial relationships of FePt (001) <100>//ZrN (001) <100>//TiN (001) <100> among FePt and ZrN/TiN were revealed from the transmission electron microscopy (TEM) results. As compared with TiN intermediate layer, although FePt-SiO2-C films grown on ZrN/TiN intermediate layer showed isotropic magnetic properties, the large interfacial energy and lattice mismatch between FePt and ZrN would lead to form columnar structural FePt films with smaller grain size and improved isolation. By doping ZrN into the TiN layer, solid solution of ZrTiN was formed and the lattice constant is increased comparing with TiN and decreased comparing with ZrN. Moreover, FePt-SiO2-C films grown on TiN 2 nm-20 vol.% ZrN/TiN 3 nm intermediate layer showed an improved perpendicular magnetic anisotropy. Simultaneously, columnar structure with smaller grain size retained.

  11. Hydrodynamic structure of the boundary layers in a rotating cylindrical cavity with radial inflow

    NASA Astrophysics Data System (ADS)

    Herrmann-Priesnitz, Benjamín; Calderón-Muñoz, Williams R.; Salas, Eduardo A.; Vargas-Uscategui, Alejandro; Duarte-Mermoud, Manuel A.; Torres, Diego A.

    2016-03-01

    A flow model is formulated to investigate the hydrodynamic structure of the boundary layers of incompressible fluid in a rotating cylindrical cavity with steady radial inflow. The model considers mass and momentum transfer coupled between boundary layers and an inviscid core region. Dimensionless equations of motion are solved using integral methods and a space-marching technique. As the fluid moves radially inward, entraining boundary layers develop which can either meet or become non-entraining. Pressure and wall shear stress distributions, as well as velocity profiles predicted by the model, are compared to numerical simulations using the software OpenFOAM. Hydrodynamic structure of the boundary layers is governed by a Reynolds number, Re, a Rossby number, Ro, and the dimensionless radial velocity component at the periphery of the cavity, Uo. Results show that boundary layers merge for Re < < 10 and Ro > > 0.1, and boundary layers become predominantly non-entraining for low Ro, low Re, and high Uo. Results may contribute to improve the design of technology, such as heat exchange devices, and turbomachinery.

  12. Columnar structured FePt films epitaxially grown on large lattice mismatched intermediate layer

    PubMed Central

    Dong, K. F.; Deng, J. Y.; Peng, Y. G.; Ju, G.; Chow, G. M.; Chen, J. S.

    2016-01-01

    The microstructure and magnetic properties of the FePt films grown on large mismatched ZrN (15.7%) intermediate layer were investigated. With using ZrN intermediate layer, FePt 10 nm films exhibited (001) texture except for some weaker FePt (110) texture. Good epitaxial relationships of FePt (001) <100>//ZrN (001) <100>//TiN (001) <100> among FePt and ZrN/TiN were revealed from the transmission electron microscopy (TEM) results. As compared with TiN intermediate layer, although FePt-SiO2-C films grown on ZrN/TiN intermediate layer showed isotropic magnetic properties, the large interfacial energy and lattice mismatch between FePt and ZrN would lead to form columnar structural FePt films with smaller grain size and improved isolation. By doping ZrN into the TiN layer, solid solution of ZrTiN was formed and the lattice constant is increased comparing with TiN and decreased comparing with ZrN. Moreover, FePt-SiO2-C films grown on TiN 2 nm-20 vol.% ZrN/TiN 3 nm intermediate layer showed an improved perpendicular magnetic anisotropy. Simultaneously, columnar structure with smaller grain size retained. PMID:27686046

  13. The azimuthally averaged boundary layer structure of a numerically simulated major hurricane

    NASA Astrophysics Data System (ADS)

    Abarca, Sergio F.; Montgomery, Michael T.; McWilliams, James C.

    2015-09-01

    This work examines the azimuthally averaged boundary layer structure of a numerically simulated hurricane. We nominally define the hurricane boundary layer as the layer in which the effects of surface friction are associated with significant departures from gradient wind balance. The boundary layer in the intensifying primary and forming secondary eyewalls is found to be nonlinear. At large radii, exterior to the eyewalls, Ekman-like balance as traditionally defined, is found to hold true. Where significant departures from Ekman-like balance are found, the departures are characterized by large vertical advection of horizontal velocity through the depth of the boundary layer. Shock-like structures are not found to be prominent in the azimuthally averaged view of the vortex boundary layer, with the largest azimuthally averaged radial gradients of the radial and tangential velocities being on the order of only a few meters per second per kilometer. Also, in the radial regions of the eyewalls, at the height where the averaged tangential wind is a maximum, the radial advection of radial velocity is an order of magnitude smaller than the agradient force per unit mass. Some physical implications of these findings are discussed.

  14. Printed PEDOT layers as transparent emitter electrodes for application in flexible inorganic photovoltaic structures

    NASA Astrophysics Data System (ADS)

    Znajdek, Katarzyna; Sibiński, Maciej; Przymecki, Krzysztof; Wróblewski, Grzegorz; Lisik, Zbigniew

    2016-12-01

    The purpose of the work is to find an appropriate flexible material to replace commonly used transparent conductive oxides (TCO) in photovoltaic (PV) emitter electrode applications. Authors show the alternative, potential possibility of using PEDOT conductive polymer as transparent emitter contacts for thin-film, flexible photovoltaic structures. The vast majority of contacts made of TCO layers, dominantly indium tin oxide ITO, are electrically unstable under the influence of mechanical stresses [1,2,3]. This drawback inhibits their usage in flexible devices, such as solar cells. The need of the development in the field of flexible PV structures induces searching for new materials. Investigated transparent conductive layers (TCL) were made of organic compositions based on PEDOT polymer and their parameters were compared with equally measured parameters of carbon nanotube (CNT) layers, commercial ITO and AgHT ultra-thin silver layers. Transparent conductive layers based on PEDOT:PSS compound were deposited on flexible substrates by screen printing technique. The analysis of achieved results shows the broad spectrum of application possibilities for PEDOT layers.

  15. Characterization of cake layer structure on the microfiltration membrane permeability by iron pre-coagulation.

    PubMed

    Wang, Jin; Pan, Siru; Luo, Dongping

    2013-02-01

    A cake layer is formed by coagulation aggregates under certain transmembrane pressure in the coagulation-microfiltration (MF) process. The characteristics of humic acid aggregates coagulated by different iron-based coagulants, such as charge, size, fractal dimension and compressibility, have an effect on the cake layer structure. At the optimum iron dose of 0.6 to 0.8 mmol/L for ferric chloride (FC) and polymer ferric sulfate (PFS) pre-coagulation, at the point of charge neutralization for near zero zeta potential, the aggregate particles produced possess the greatest size and highest fractal dimension, which contributes to the cake layer being most loose with high porosity and low compressibility. Thus the membrane filterability is better. At a low or high iron dose of FC and PFS, a high negative or positive zeta potential with high charge repulsion results in so many small aggregate particles and low fractal dimension that the cake layer is compact with low porosity and high compressibility. Therefore the membrane fouling is accelerated and MF permeability becomes worse. The variation of cake layer structure as measured by scanning electric microscopy corresponds with the fact that the smaller the coagulation flocs size and fractal dimension are, the lower the porosity and the tighter the cake layer conformation. This also explains the MF membrane flux variation visually and accurately.

  16. Columnar structured FePt films epitaxially grown on large lattice mismatched intermediate layer

    NASA Astrophysics Data System (ADS)

    Dong, K. F.; Deng, J. Y.; Peng, Y. G.; Ju, G.; Chow, G. M.; Chen, J. S.

    2016-09-01

    The microstructure and magnetic properties of the FePt films grown on large mismatched ZrN (15.7%) intermediate layer were investigated. With using ZrN intermediate layer, FePt 10 nm films exhibited (001) texture except for some weaker FePt (110) texture. Good epitaxial relationships of FePt (001) <100>//ZrN (001) <100>//TiN (001) <100> among FePt and ZrN/TiN were revealed from the transmission electron microscopy (TEM) results. As compared with TiN intermediate layer, although FePt-SiO2-C films grown on ZrN/TiN intermediate layer showed isotropic magnetic properties, the large interfacial energy and lattice mismatch between FePt and ZrN would lead to form columnar structural FePt films with smaller grain size and improved isolation. By doping ZrN into the TiN layer, solid solution of ZrTiN was formed and the lattice constant is increased comparing with TiN and decreased comparing with ZrN. Moreover, FePt-SiO2-C films grown on TiN 2 nm-20 vol.% ZrN/TiN 3 nm intermediate layer showed an improved perpendicular magnetic anisotropy. Simultaneously, columnar structure with smaller grain size retained.

  17. 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.

  18. Characteristics of Spontaneous Emission of Polarized Atoms in Metal Dielectric Multiple Layer Structures

    NASA Astrophysics Data System (ADS)

    Zhao, Li-Ming; Gu, Ben-Yuan; Zhou, Yun-Song

    2007-11-01

    The spontaneous emission (SE) progress of polarized atoms in a stratified structure of air-dielectric(D0)-metal(M)-dielectric(D1)-air can be controlled effectively by changing the thickness of the D1 layer and rotating the polarized direction of atoms. It is found that the normalized SE rate of atoms located inside the D0 layer crucially depends on the atomic position and the thickness of the D1 layer. When the atom is located near the D0-M interface, the normalized atomic SE rate as a function of the atomic position is abruptly onset for the thin D1 layer. However, with the increasing thickness of the D1 layer, the corresponding curve profile exhibits plateau and stays nearly unchanged. The substantial change of the SE rate stems from the excitation of the surface plasmon polaritons in metal-dielectric interface, and the feature crucially depends on the thickness of D1 layer. If atoms are positioned near the D0-air interface, the substantial variation of the normalized SE rate appears when rotating the polarized direction of atoms. These findings manifest that the atomic SE processes can be flexibly controlled by altering the thickness of the dielectric layer D1 or rotating the orientation of the polarization of atoms.

  19. 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.

  20. Development of a dual-layered dielectric-loaded accelerating structure

    NASA Astrophysics Data System (ADS)

    Jing, Chunguang; Kanareykin, Alexei; Kazakov, Sergey; Liu, Wanming; Nenasheva, Elizaveta; Schoessow, Paul; Gai, Wei

    2008-09-01

    rf Power attenuation is a critical problem in the development of dielectric-loaded structures for particle acceleration. In a previous paper [C. Jing, W. Liu, W. Gai, J. Power, T. Wong, Nucl. Instr. Meth. A 539 (2005) 445] we suggested the use of a Multilayer Dielectric-Loaded Accelerating Structure (MDLA) as a possible approach for reducing the rf losses in a single layer device. The MDLA is based on the principle of Bragg reflection familiar from optics that is used to partially confine the fields inside the dielectric layers and reduce the wall current losses at the outer boundary. We report here on the design, construction and testing of a prototype X-band double-layer structure (2DLA). The measurements show an rf power attenuation for the 2DLA more than ten times smaller than that of a comparable single-layer structure, in good agreement with the analytic results. Testing and operation of MDLAs also requires efficient power coupling from test equipment or rf power systems to the device. We describe the design and construction of two novel structures: a TM 03 mode launcher for cold testing and a power coupler for planned high-gradient experiments.

  1. DNS study of large-scale structures in a separated turbulent boundary layer

    NASA Astrophysics Data System (ADS)

    Abe, Hiroyuki; Mizobuchi, Yasuhiro; Matsuo, Yuichi

    2011-11-01

    Direct numerical simulations (DNSs) of a separated flat-plate turbulent boundary layer have been carried out. The inlet data are prescribed by DNSs of a zero-pressure-gradient turbulent boundary layer with the rescaling-recycling method; blowing and suction are imposed at the upper boundary for producing a separation bubble. The Reynolds numbers at the inlet are set to be Reθ =300, 600 and 900, where Reθ is the Reynolds number based on the freestream velocity and the momentum thickness. Particular attention is given to large- scale structures existing in a separated region. Results indicate that large-scale organized structures of the streamwise velocity fluctuation appear in a detached shear layer when a large separated region is formed. The latter structures consist of positive and negative regions alternating in the spanwise direction with a spacing of about 2 ~ 3δ99 (δ99 denotes the 99% boundary layer thickness at the inlet), which become more apparent with increasing Reynolds number. They are most likely associated with large-scale spanwise meandering of the separation line. There is also close relationship between the large-scale structures and vortical structures, the latter tending to form vortex clusters where hairpin-like vortices are also observed.

  2. Relating instantaneous structures and mean flow characteristics of turbulent boundary layers

    NASA Astrophysics Data System (ADS)

    de Silva, Charitha; Philip, Jimmy; Hutchins, Nicholas; Marusic, Ivan

    2016-11-01

    Recent works have highlighted the presence of thin interfacial layers of high shear that demarcate regions of relatively uniform streamwise momentum in turbulent boundary layers. Here, we aim to further our understanding of how such a zonal-like structural arrangement manifests in the averaged flow statistics. To this end, we start by identifying high shear interfaces in turbulent boundary layers employing particle image velocimetry databases that span more than an order of magnitude of friction Reynolds number (Reτ =103 -104). Inspection of these recurrent features reveal that their geometry is highly contorted and exhibits self-similarity across a wide range of scales. The Reynolds number dependence of these features is also investigated, together with their associated scaling. Based on these findings and the persistent presence of sharp changes in momentum in turbulent boundary layers, a simple model is presented towards reconstructing the mean velocity profile.

  3. A review of vortex structures and associated coherent motions in turbulent boundary layers

    NASA Technical Reports Server (NTRS)

    Robinson, Stephen K.

    1990-01-01

    The experimental and computational evidence for the existence and role of vortices in turbulent boundary layers is briefly reviewed. Quasi-streamwise and transverse vortices are considered, and various published conceptual models for horseshoe-like vortical structures are compared. The causes for upright and inverted horseshoe-shaped vorticity lines are discussed, and the distinction between vorticity lines and vortices is demonsrated. Finally, results from a numerically-simulated turbulent boundary layer are used to compute distributions of diameter, height, and strength for quasi-streamwise and spanwise vortices. These results confirm that quasi-streamwise vortices are clustered near the wall, while spanwise vortices are distributed throughout the layer. The variation of spanwise vortex core diameter with distance from the wall is found to be consistent with the mixing-length distribution for a boundary layer.

  4. Synthetic magnetic field effects on neutral bosonic condensates in quasi-three-dimensional anisotropic layered structures

    SciTech Connect

    Zaleski, T. A.; Polak, T. P.

    2011-02-15

    We discuss a system of dilute Bose gas confined in a layered structure of stacked square lattices (slab geometry). A derived phase diagram reveals a nonmonotonic dependence of the ratio of tunneling to on-site repulsion on the artificial magnetic field applied to the system. The effect is reduced when more layers are added, which mimics a two- to quasi-three-dimensional geometry crossover. Furthermore, we establish a correspondence between anisotropic infinite (quasi-three-dimensional) and isotropic finite (slab geometry) systems that share exactly the same critical values, which can be an important clue for choosing experimental setups that are less demanding, but still leading to the identical results. Finally, we show that the properties of the ideal Bose gas in a three-dimensional optical lattice can be closely mimicked by finite (slab) systems when the number of two-dimensional layers is larger than 10 for isotropic interactions, or even less when the layers are weakly coupled.

  5. Terahertz time-gated spectral imaging for content extraction through layered structures

    PubMed Central

    Redo-Sanchez, Albert; Heshmat, Barmak; Aghasi, Alireza; Naqvi, Salman; Zhang, Mingjie; Romberg, Justin; Raskar, Ramesh

    2016-01-01

    Spatial resolution, spectral contrast and occlusion are three major bottlenecks for non-invasive inspection of complex samples with current imaging technologies. We exploit the sub-picosecond time resolution along with spectral resolution provided by terahertz time-domain spectroscopy to computationally extract occluding content from layers whose thicknesses are wavelength comparable. The method uses the statistics of the reflected terahertz electric field at subwavelength gaps to lock into each layer position and then uses a time-gated spectral kurtosis to tune to highest spectral contrast of the content on that specific layer. To demonstrate, occluding textual content was successfully extracted from a packed stack of paper pages down to nine pages without human supervision. The method provides over an order of magnitude enhancement in the signal contrast and can impact inspection of structural defects in wooden objects, plastic components, composites, drugs and especially cultural artefacts with subwavelength or wavelength comparable layers. PMID:27610926

  6. A computer controlled chemical bevel etching apparatus: applications to Auger analysis of multi-layered structures

    NASA Astrophysics Data System (ADS)

    El-Gomati, M.; Gelsthorpe, A.; Srnanek, R.; Liday, J.; Vogrincic, P.; Kovac, J.

    1999-04-01

    Analysis of thin layer structures can be achieved by chemically etching a bevel and subsequently analysing the surface. However non-linear bevels often result due to differing etch rates of the materials leading to incorrect analysis results. We report on a computer controlled stepper motor reactor whereby the specimen is lowered into the etchant at a rate which compensates for the different etch rates of the various layers constituting the sample. The apparatus is used to produce linear bevels of various magnifications on GaAs/AlGaAs heterostructures. The etchant of H 3PO 4/H 2O 2/H 2O is used for bevel preparation capped by a water layer to suppress the meniscus. Application of the technique to Multi Quantum Wells (MQW) and Bragg diffraction layers is shown. The depth resolution of the bevelled samples are analysed by AES and a comparison is made to conventional ion sputtering techniques.

  7. Terahertz time-gated spectral imaging for content extraction through layered structures

    NASA Astrophysics Data System (ADS)

    Redo-Sanchez, Albert; Heshmat, Barmak; Aghasi, Alireza; Naqvi, Salman; Zhang, Mingjie; Romberg, Justin; Raskar, Ramesh

    2016-09-01

    Spatial resolution, spectral contrast and occlusion are three major bottlenecks for non-invasive inspection of complex samples with current imaging technologies. We exploit the sub-picosecond time resolution along with spectral resolution provided by terahertz time-domain spectroscopy to computationally extract occluding content from layers whose thicknesses are wavelength comparable. The method uses the statistics of the reflected terahertz electric field at subwavelength gaps to lock into each layer position and then uses a time-gated spectral kurtosis to tune to highest spectral contrast of the content on that specific layer. To demonstrate, occluding textual content was successfully extracted from a packed stack of paper pages down to nine pages without human supervision. The method provides over an order of magnitude enhancement in the signal contrast and can impact inspection of structural defects in wooden objects, plastic components, composites, drugs and especially cultural artefacts with subwavelength or wavelength comparable layers.

  8. Nanometric Cutting of Silicon with an Amorphous-Crystalline Layered Structure: A Molecular Dynamics Study

    NASA Astrophysics Data System (ADS)

    Wang, Jinshi; Fang, Fengzhou; Zhang, Xiaodong

    2017-01-01

    Materials with specific nanometric layers are of great value in both theoretical and applied research. The nanometric layer could have a significant influence on the response to the mechanical loading. In this paper, the nanometric cutting on the layered systems of silicon has been studied by molecular dynamics. This kind of composite structure with amorphous layer and crystalline substrate is important for nanomachining. Material deformation, stress status, and chip formation, which are the key issues in nano-cutting, are analyzed. A new chip formation mechanism, i.e., the mixture of extrusion and shear, has been observed. In addition, from the perspective of engineering, some specific composite models show the desired properties due to the low subsurface damage or large material removal rate. The results enrich the cutting theory and provide guidance on nanometric machining.

  9. Polarized GaN-based LED with an integrated multi-layer subwavelength structure.

    PubMed

    Zhang, Guiju; Wang, Chinhua; Cao, Bing; Huang, Zengli; Wang, Jianfeng; Zhang, Baoshun; Xu, Ke

    2010-03-29

    A novel type of GaN-based LED with a highly polarized output using an integrated multi-layer subwavelength grating structure is proposed. Characteristics of both optical transmission and polarization extinction ratio of the polarized GaN-based LED with three different multi-layer subwavelength structures are investigated. It is found that both TM transmission (T(TM)) and the extinction ratio(ER) of the LED output can be effectively enhanced by incorporating a dielectric transition layer between the metal grating and GaN substrate with a lower refractive index than that of the GaN substrate. Flat sensitivity of the T(TM) on the period, duty cycle of the metallic grating, and the wide range of operating wavelength have been achieved in contrast to the conventional sensitive behavior in single-layer metallic grating. Up to 0.75 high duty cycle of the metallic grating can be employed to achieve >60dB ER while T(TM) maintains higher than ~90%, which breaks the conventional limit of T(TM) and ER being always a pair of trade-off parameters. Typical optimized multilayer structures in terms of material, thickness, grating periods and duty cycle using MgF(2) and ZnS, respectively, as the transition layers are obtained. The results provide guidance in designing, optimizing and fabricating the novel integrated GaN-based and polarized photonic devices.

  10. Structure and Properties of Some Layered U2O5 Phases: A Density Functional Theory Study.

    PubMed

    Molinari, Marco; Brincat, Nicholas A; Allen, Geoffrey C; Parker, Stephen C

    2017-04-05

    U2O5 is the boundary composition between the fluorite and the layered structures of the UO2→3 system and the least studied oxide in the group. δ-U2O5 is the only layered structure proposed so far experimentally, although evidence of fluorite-based phases has also been reported. Our DFT work explores possible structures of U2O5 stoichiometry by starting from existing M2O5 structures (where M is an actinide or transition metal) and replacing the M ions with uranium ions. For all structures, we predicted structural and electronic properties including bulk moduli and band gaps. The majority of structures were found to be less stable than δ-U2O5. U2O5 in the R-Nb2O5 structure was found to be a competitive structure in terms of stability, whereas U2O5 in the Np2O5 structure was found to be the most stable overall. Indeed, by including the vibrational contribution to the free energy using the frequencies obtained from the optimized unit cells we predict that Np2O5 structured U2O5 is the most thermodynamically stable under ambient conditions. δ-U2O5 only becomes more stable at high temperatures and/or pressures. This suggests that a low-temperature synthesis route should be tested and so potentially opens a new avenue of research for pentavalent uranium oxides.

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

    NASA Astrophysics Data System (ADS)

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

    2016-08-01

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

  12. Structural and electronic properties of the transition layer at the SiO{sub 2}/4H-SiC interface

    SciTech Connect

    Li, Wenbo; Wang, Dejun; Zhao, Jijun

    2015-01-15

    Using first-principles methods, we generate an amorphous SiO{sub 2}/4H-SiC interface with a transition layer. Based this interface model, we investigate the structural and electronic properties of the interfacial transition layer. The calculated Si 2p core-level shifts for this interface are comparable to the experimental data, indicating that various SiC{sub x}O{sub y} species should be present in this interface transition layer. The analysis of the electronic structures reveals that the tetrahedral SiC{sub x}O{sub y} structures cannot introduce any of the defect states at the interface. Interestingly, our transition layer also includes a C-C=C trimer and SiO{sub 5} configurations, which lead to the generation of interface states. The accurate positions of Kohn-Sham energy levels associated with these defects are further calculated within the hybrid functional scheme. The Kohn-Sham energy levels of the carbon trimer and SiO{sub 5} configurations are located near the conduction and valence band of bulk 4H-SiC, respectively. The result indicates that the carbon trimer occurred in the transition layer may be a possible origin of near interface traps. These findings provide novel insight into the structural and electronic properties of the realistic SiO{sub 2}/SiC interface.

  13. A randomly nano-structured scattering layer for transparent organic light emitting diodes

    NASA Astrophysics Data System (ADS)

    Huh, Jin Woo; Shin, Jin-Wook; Cho, Doo-Hee; Moon, Jaehyun; Joo, Chul Woong; Park, Seung Koo; Hwang, Joohyun; Cho, Nam Sung; Lee, Jonghee; Han, Jun-Han; Chu, Hye Yong; Lee, Jeong-Ik

    2014-08-01

    A random scattering layer (RSL) consisting of a random nano-structure (RNS) and a high refractive index planarization layer (HRI PL) is suggested and demonstrated as an efficient internal light-extracting layer for transparent organic light emitting diodes (TOLEDs). By introducing the RSL, a remarkable enhancement of 40% and 46% in external quantum efficiency (EQE) and luminous efficacy (LE) was achieved without causing deterioration in the transmittance. Additionally, with the use of the RSL, the viewing angle dependency of EL spectra was reduced to a marginal degree. The results were interpreted as the stronger influence of the scattering effect over the microcavity. The RSL can be applied widely in TOLEDs as an effective light-extracting layer for extracting the waveguide mode of confined light at the indium tin oxide (ITO)/OLED stack without introducing spectral changes in TOLEDs.A random scattering layer (RSL) consisting of a random nano-structure (RNS) and a high refractive index planarization layer (HRI PL) is suggested and demonstrated as an efficient internal light-extracting layer for transparent organic light emitting diodes (TOLEDs). By introducing the RSL, a remarkable enhancement of 40% and 46% in external quantum efficiency (EQE) and luminous efficacy (LE) was achieved without causing deterioration in the transmittance. Additionally, with the use of the RSL, the viewing angle dependency of EL spectra was reduced to a marginal degree. The results were interpreted as the stronger influence of the scattering effect over the microcavity. The RSL can be applied widely in TOLEDs as an effective light-extracting layer for extracting the waveguide mode of confined light at the indium tin oxide (ITO)/OLED stack without introducing spectral changes in TOLEDs. Electronic supplementary information (ESI) available: Simulation results of total (bottom and top) radiance of TOLEDs with the RSL depending on HTL and ETL thicknesses. See DOI: 10.1039/c4nr01520g

  14. The vertical turbulence structure of the coastal marine atmospheric boundary layer

    SciTech Connect

    Tjernstroem, M.; Smedman, A.S. )

    1993-03-15

    The vertical turbulence structure in the marine atmosphere along a shoreline has been investigated using data from tower and aircraft measurements performed along the Baltic coast in the southeast of Sweden. Two properties make the Baltic Sea particularly interesting. It is surrounded by land in all directions within moderate advection distances, and it features a significant annual lag in sea surface temperature as compared with inland surface temperature. The present data were collected mostly during spring or early summer, when the water is cool, i.e., with a stably or neutrally stratified marine boundary layer usually capped by an inversion. Substantial daytime heating over the land area results in a considerable horizontal thermal contrast. Measurements were made on a small island, on a tower with a good sea fetch, and with an airborne instrument package. The profile data from the aircraft is from 25 slant soundings performed in connection to low level boundary layer flights. The results from the profiles are extracted through filtering techniques on individual time (space) series (individual profiles), applying different normalization and finally averaging over all or over groups of profiles. The land-based data are from a low tower situated on the shoreline of a small island with a wide sector of unobstructed sea fetch. Several factors are found that add to the apparent complexity of the coastal marine environment: the state of the sea appears to have a major impact on the turbulence structure of the surface layer, jet-shaped wind speed profiles were very common at the top of the boundary layer (in about 50% of the cases) and distinct layers with increased turbulence were frequently found well above the boundary layer (in about 80% of the cases). The present paper will concentrate on a description of the experiment, the analysis methods, and a general description of the boundary layer turbulence structure over the Baltic Sea. 40 refs., 16 figs., 2 tabs.

  15. Structural origin of the nonlinear optical properties of lead niobium germanate film glasses

    SciTech Connect

    Munoz-Martin, D.; Ruiz de La Cruz, A.; Fernandez-Navarro, J. M.; Solis, J.; Gonzalo, J.; Domingo, C.

    2011-07-15

    The structural origin of the nonlinear optical susceptibility (/{chi}{sup (3)}/) of lead-niobium-germanate film glasses with large Nb{sub 2}O{sub 5} contents has been investigated. /{chi}{sup (3)}/ shows a strong enhancement with the Nb content in the films with /{chi}{sup (3)}/ values close to 2 x 10{sup -11} esu at 800 nm for a Nb content as high as 0.71. Boling-Glass-Owyoung and Lines' semiempirical models predict accurately the values of /{chi}{sup (3)}/ for transparent bulk glasses but not for film glasses. This discrepancy is related to the remarkable structural differences between them. Raman spectroscopy suggests the formation of a three-dimensional (3D) structure of [NbO{sub 6}] octahedra in the case of film glasses having large Nb contents, while X-ray photoelectron spectroscopy shows that a significant fraction of these units contain Nb{sup 4+} ions. The combination of a 3D structure of [NbO{sub 6}] with the presence of Nb{sup 4+} polarons and their migration through electron intervalence transfer is proposed as the origin of the observed enhancement of /{chi}{sup (3)}/ in the film glasses.

  16. Carbonaceous structures in the Tissint Martian Meteorite: evidence of a biogenetic origin

    NASA Astrophysics Data System (ADS)

    Wallis, Jamie; Wickramasinghe, N. C.; Wallis, Daryl H.; Miyake, Nori; Wallis, M. K.; Hoover, Richard B.

    2015-09-01

    We report for the first time in situ observations of 5-50μm spherical carbonaceous structures in the Tissint Martian meteorite comprising of pyrite (FeS2) cores and carbonaceous outer coatings. The structures are characterized as smooth immiscible spheres with curved boundaries occasionally following the contours of the pyrite inclusion. The structures bear striking resemblance to similar-sized immiscible carbonaceous spheres found in hydrothermal calcite vein deposits in the Mullaghwornia Quarry in central Ireland. Similar structures have been reported in Proterozoic and Ordovician sandstones from Canada as well as in a variety of astronomical sources including carbonaceous chondrites, chondritic IDPs and primitive chondritic meteorites. SEM and X-Ray elemental mapping confirmed the presence of organic carbon filling the crack and cleavage space in the pyroxene substrate, with further evidence of pyrite acting as an attractive substrate for the collection of organic matter. The detection of precipitated carbon collecting around pyrite grains is at variance with an igneous origin as proposed for the reduced organic component in Tissint, and is more consistent with a biogenetic origin.

  17. Structural origin of the nonlinear optical properties of lead niobium germanate film glasses

    NASA Astrophysics Data System (ADS)

    Munoz-Martin, D.; de La Cruz, A. Ruiz; Fernandez-Navarro, J. M.; Domingo, C.; Solis, J.; Gonzalo, J.

    2011-07-01

    The structural origin of the nonlinear optical susceptibility (/χ(3)/) of lead-niobium-germanate film glasses with large Nb2O5 contents has been investigated. /χ(3)/ shows a strong enhancement with the Nb content in the films with /χ(3)/ values close to 2 × 10-11 esu at 800 nm for a Nb content as high as 0.71. Boling-Glass-Owyoung and Lines' semiempirical models predict accurately the values of /χ(3)/ for transparent bulk glasses but not for film glasses. This discrepancy is related to the remarkable structural differences between them. Raman spectroscopy suggests the formation of a three-dimensional (3D) structure of [NbO6] octahedra in the case of film glasses having large Nb contents, while X-ray photoelectron spectroscopy shows that a significant fraction of these units contain Nb4+ ions. The combination of a 3D structure of [NbO6] with the presence of Nb4+ polarons and their migration through electron intervalence transfer is proposed as the origin of the observed enhancement of /χ(3)/ in the film glasses.

  18. EXAFS Signatures of Structural Zn at Trace Levels in Layered Minerals

    SciTech Connect

    Juillot, Farid; Morin, Guillaume; Hazemann, Jean-Louis; Proux, Olivier; Belin, Stephanie; Briois, Valerie; Brown, Gordon E., Jr.; Calas, Georges; /Paris U., VI-VII, LMCP

    2006-12-13

    Many in situ XAFS studies have shown that zinc incorporated in layered minerals is a major form of zinc in Zn-contaminated soils. Quantitative information on the local structural environment(s) and ordering of Zn in these minerals is required to better understand its behavior in soils. In this study, EXAFS spectroscopy was used to assess the structural environment of zinc incorporated at trace levels (40 ppm to 4,000 ppm) within the octahedral sheets of various natural and synthetic layered minerals. Results indicate that EXAFS data analyzed using ab initio FEFF calculations (FEFF 8.10) can unambiguously distinguish between zinc incorporation within the octahedral sheet of dioctahedral versus trioctahedral layered minerals and can determine the distribution (random or ordered) of zinc cations within the octahedral sheets of these minerals.

  19. The second-harmonic generation in a dissipative and dispersion layered structure

    NASA Astrophysics Data System (ADS)

    Soltanmohammadi, Jamshid; Jamshidi-Ghaleh, Kazem; Arghand-Hesar, Afshin; Lotfi, Erik S.; Masalehdan, Hossein

    2015-10-01

    Conversion efficiency of second-harmonic generation (SHG) in a multicrystal structure arrangement, under linearly absorption of interacting waves was analytically investigated. Different linear absorption and nonlinear interaction coefficients were considered for both of the fundamental and the second harmonic waves in cascade layers. The intensity-constant approximation on fundamental wave radiation was applied in calculations. Behavior of conversion efficiency with interaction coherence length of fundamental wave, phase miss-matching and ratio of linear absorption coefficients were graphically illustrated. The results are shown that in multicrystal structure scheme, the conversion efficiency can be tuned by the interaction coherent length and it is possible to compensate the phase differences induced in the previous layers. The phase compensation between the layers is the physical reason of efficiency improvement. Contribution to the topical issue "Advanced Electromagnetics Symposium (AES 2014) - Elected submissions", edited by Adel Razek

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

    DOEpatents

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

    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.

  1. Improvement of luminescence properties of GaN buffer layer for fast nitride scintillator structures

    NASA Astrophysics Data System (ADS)

    Hubáček, T.; Hospodková, A.; Oswald, J.; Kuldová, K.; Pangrác, J.

    2017-04-01

    We have optimized technology of GaN buffer layer growth with respect to the application in fast scintillation structures. The deep defect luminescence so called yellow band (YB) with decay time up to tens of microseconds is undesired for these applications and should be suppressed or at least the ratio of intensities of excitonic to YB maximum has to be considerably increased. The required photoluminescence properties were achieved by optimization of growth parameters of nucleation and coalescence layer on sapphire substrate. We have shown that decrease of NH3 flow, decrease of coalescence temperature, increase of nucleation time and nucleation pressure lead to improvement of the structure and luminescence properties of the buffer layer. Results indicate a significant increased ratio of excitonic/YB luminescence intensity.

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

    PubMed

    Emly, Alexandra; Van der Ven, Anton

    2015-05-04

    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 Mg(x)TiS2 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.

  3. Population structure of Cynara cardunculus complex and the origin of the conspecific crops artichoke and cardoon

    PubMed Central

    Gatto, Angela; De Paola, Domenico; Bagnoli, Francesca; Vendramin, Giovanni Giuseppe; Sonnante, Gabriella

    2013-01-01

    Background and Aims Globe artichoke and leafy cardoon, two crops within the same species Cynara cardunculus, are traditionally cultivated in the Mediterranean region and play a significant role in the agricultural economy of this area. The two cultigens have different reproductive systems: artichoke is generally vegetatively propagated, while leafy cardoon is seed propagated. The domestication events underlying the origin of both artichoke and cultivated cardoon from their wild relative and the area of occurrence are not yet fully understood. The aim of this study was to investigate population structure in wild cardoon, globe artichoke and leafy cardoon material and infer domestication events. Methods Thirty-five microsatellite (simple sequence repeat) markers, distributed in the C. cardunculus genome, and a large geographical and numerical sampling in southern Europe and North Africa were used to assess population structure and diversity. Key Results The results suggest the presence of two distinct domestication events for artichoke and leafy cardoon, and also suggest a new possible scenario, with western wild cardoon having originated from cultivated cardoon escaped from cultivation. Evidence was found for a demographic bottleneck in the past history of globe artichoke. Conclusions The results shed new light on the relationships between the three taxa of C. cardunculus and highlight relevant aspects on the evolution of domestication of two crops with a different reproductive system within the same species. It is proposed that the probable centre of origin of artichoke is located in southern Italy, probably Sicily. PMID:23877076

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

    SciTech Connect

    Kalo, Hussein; Milius, Wolfgang; Braeu, Michael; Breu, Josef

    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.

  5. Surface modification induced phase transformation and structure variation on the rapidly solidified recast layer of titanium

    SciTech Connect

    Tsai, Ming-Hung; Haung, Chiung-Fang; Shyu, Shih-Shiun; Chou, Yen-Ru; Lin, Ming-Hong; Peng, Pei-Wen; and others

    2015-08-15

    In this study, neodymium-doped yttrium orthovanadate (Nd:YVO{sub 4}) as a laser source with different scanning speeds was used on biomedical Ti surface. The microstructural and biological properties of laser-modified samples were investigated by means of optical microscope, electron microscope, X-ray diffraction, surface roughness instrument, contact angle and cell cytotoxicity assay. After laser modification, the rough volcano-like recast layer with micro-/nanoporous structure and wave-like recast layer with nanoporous structure were generated on the surfaces of laser-modified samples, respectively. It was also found out that, an α → (α + rutile-TiO{sub 2}) phase transition occurred on the recast layers of laser-modified samples. The Ti surface becomes hydrophilic at a high speed laser scanning. Moreover, the cell cytotoxicity assay demonstrated that laser-modified samples did not influence the cell adhesion and proliferation behaviors of osteoblast (MG-63) cell. The laser with 50 mm/s scanning speed induced formation of rough volcano-like recast layer accompanied with micro-/nanoporous structure, which can promote cell adhesion and proliferation of MG-63 cell on Ti surface. The results indicated that the laser treatment was a potential technology to enhance the biocompatibility for titanium. - Highlights: • Laser induced the formation of recast layer with micro-/nanoporous structure on Ti. • An α → (α + rutile-TiO{sub 2}) phase transition was observed within the recast layer. • The Ti surface becomes hydrophilic at a high speed laser scanning. • Laser-modified samples exhibit good biocompatibility to osteoblast (MG-63) cell.

  6. Chemical and structural composition of organic carbonaceous structures in Tissint: evidence for a biogenetic origin

    NASA Astrophysics Data System (ADS)

    Wallis, Jamie; Wickramasinghe, N. C.; Wallis, Daryl H.; Miyake, Nori; Wallis, M. K.; Hoover, Richard B.

    2015-09-01

    Earlier studies of the Tissint Martian meteorite identified the presence of a number of 5-50μm carbonaceous spherical structures. SEM and EDS elemental spectra for 11 selected structures confirmed that they comprise of a carbonaceous outer coating with a inner core of FeS2 (pyrite) and are characterised as immiscible globules with curved boundaries. Here we report on the results of Raman spectroscopic studies that unambiguously confirm the mantle as comprising of `disordered carbonaceous material'. R1 = ID/IG against ΓD (cm-1) band parameter plots of the carbonaceous coatings imply a complex precursor carbon inventory comparable to the precursor carbon component of materials of known biotic source (plants, algae, fungi, crustaceans, prokaryotes). Correlation between peak metamorphic temperatures and Raman D-band (ΓD) parameters further indicate the carbonaceous component was subjected to a peak temperature of ~250 OC suggesting a possible link with the hydrothermal precipitation processes responsible for the formation of similar globules observed in hydrothermal calcite veins in central Ireland. Ω G (cm-1), ΓG (cm-1), Ω D (cm-1) and ΓD (cm-1) parameters further imply a level of crystallinity and disorder of the carbon component consistent with carbonaceous material recovered from a variety of non-terrestrial sources. Cl, N, O and S to C elemental ratios are typical of high volatility bituminous coals and distinctly higher than equivalent graphite standards.

  7. (±)-2,2-Dimethyl-5-oxotetrahydrofuran-3-carboxylic acid (terebic acid): a racemic layered structure.

    PubMed

    Santos, L M; Legendre, A O; Villis, P C M; Viegas, C; Doriguetto, A C

    2012-08-01

    A racemic crystalline form of terebic acid, C(7)H(10)O(4), which is an important industrial chemical compound, is reported for the first time. The crystal structure is stabilized by O-H···O and C-H···O hydrogen bonds which form racemic double layers parallel to (001).

  8. Form and structure factors for impedance and reflection from periodic layers.

    PubMed

    Pan, Janet L

    2007-01-20

    In an exact treatment of the Maxwell equations, we derive form and structure factors for reflection from periodic layers, and we show that these factors are significantly different from their analogs in kinematic x-ray diffraction. Quite generally, we show that reflection and impedance can be written precisely as the sum of an additive form factor and the product of a structure factor and a second form factor. This additive form factor does not have an analog in kinematic x-ray diffraction. It is demonstrated that the form factors are found by analytic continuation to an arbitrary wavelength of expressions for the impedance both at long wavelengths and at quarter wavelengths. A correction to the Bragg law relating fringe spacing to the total structure thickness is derived. We go beyond previous numerical work by deriving simple analytic exact expressions for reflection and impedance of periodic layers for all frequencies within the reflection passband, and for an arbitrary number of periods in the structure, an arbitrary index profile within each period, arbitrary layer thicknesses (not just quarter-wave layers), and for arbitrary sizes of the refractive index differences.

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

    SciTech Connect

    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.

    2015-06-19

    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.

  10. Pseudoepitaxial transrotational structures in 14 nm-thick NiSi layers on [001] silicon.

    PubMed

    Alberti, Alessandra; Bongiorno, Corrado; Cafra, Brunella; Mannino, Giovanni; Rimini, Emanuele; Metzger, Till; Mocuta, Cristian; Kammler, Thorsten; Feudel, Thomas

    2005-10-01

    In a system consisting of two different lattices, structural stability is ensured when an epitaxial relationship occurs between them and allows the system to retain the stress whilst avoiding the formation of a polycrystalline film. The phenomenon occurs if the film thickness does not exceed a critical value. Here we show that in spite of its orthorhombic structure, a 14 nm-thick NiSi layer can three-dimensionally adapt to the cubic Si lattice by forming transrotational domains. Each domain arises by the continuous bending of the NiSi lattice, maintaining a close relationship with the substrate structure. The presence of transrotational domains does not cause a roughening of the layer, but instead it improves the structural and electrical stability of the silicide in comparison with a 24 nm-thick layer formed using the same annealing process. These results have relevant implications for the thickness scaling of NiSi layers which are currently used as metallizations of electronic devices.

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

    DOE PAGES

    Zhao, Zhao; Zhang, Haijun; Yuan, Hongtao; ...

    2015-06-19

    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 tunablemore » 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.« less

  12. FTIR spectroscopy structural analysis of the interaction between Lactobacillus kefir S-layers and metal ions

    NASA Astrophysics Data System (ADS)

    Gerbino, E.; Mobili, P.; Tymczyszyn, E.; Fausto, R.; Gómez-Zavaglia, A.

    2011-02-01

    FTIR spectroscopy was used to structurally characterize the interaction of S-layer proteins extracted from two strains of Lactobacillus kefir (the aggregating CIDCA 8348 and the non-aggregating JCM 5818) with metal ions (Cd +2, Zn +2, Pb +2 and Ni +2). The infrared spectra indicate that the metal/protein interaction occurs mainly through the carboxylate groups of the side chains of Asp and Glut residues, with some contribution of the NH groups belonging to the peptide backbone. The frequency separation between the νCOO - anti-symmetric and symmetric stretching vibrations in the spectra of the S-layers in presence of the metal ions was found to be ca. 190 cm -1 for S-layer CIDCA 8348 and ca. 170 cm -1 for JCM 5818, denoting an unidentate coordination in both cases. Changes in the secondary structures of the S-layers induced by the interaction with the metal ions were also noticed: a general trend to increase the amount of β-sheet structures and to reduce the amount of α-helices was observed. These changes allow the proteins to adjust their structure to the presence of the metal ions at minimum energy expense, and accordingly, these adjustments were found to be more important for the bigger ions.

  13. Graphene oxide. Origin of acidity, its instability in water, and a new dynamic structural model.

    PubMed

    Dimiev, Ayrat M; Alemany, Lawrence B; Tour, James M

    2013-01-22

    The existing structural models of graphene oxide (GO) contradict each other and cannot adequately explain the acidity of its aqueous solutions. Inadequate understanding of chemical structure can lead to a misinterpretation of observed experimental phenomena. Understanding the chemistry and structure of GO should enable new functionalization protocols while explaining GO's limitations due to its water instability. Here we propose an unconventional view of GO chemistry and develop the corresponding "dynamic structural model" (DSM). In contrast to previously proposed models, the DSM considers GO as a system, constantly changing its chemical structure due to interaction with water. Using potentiometric titration, (13)C NMR, FTIR, UV-vis, X-ray photoelectron microscopy, thermogravimetric analysis, and scanning electron microscopy we show that GO does not contain any significant quantity of preexisting acidic functional groups, but gradually generates them through interaction with water. The reaction with water results in C-C bond cleavage, formation of vinylogous carboxylic acids, and the generation of protons. An electrical double layer formed at the GO interface in aqueous solutions plays an important role in the observed GO chemistry. Prolonged exposure to water gradually degrades GO flakes converting them into humic acid-like structures. The proposed DSM provides an explanation for the acidity of GO aqueous solutions and accounts for most of the known spectroscopic and experimental data.

  14. Structural origins of Johari-Goldstein relaxation in a metallic glass

    NASA Astrophysics Data System (ADS)

    Liu, Y. H.; Fujita, T.; Aji, D. P. B.; Matsuura, M.; Chen, M. W.

    2014-02-01

    Johari-Goldstein or β relaxation, persisting down to glassy state from a supercooled liquid, is a universal phenomenon of glassy dynamics. Nevertheless, the underlying micromechanisms leading to the relaxation are still in debate despite great efforts devoted to this problem for decades. Here we report experimental evidence on the structural origins of Johari-Goldstein relaxation in an ultra-quenched metallic glass. The measured activation energy of the relaxation (~26 times of the product of gas constant and glass transition temperature) is consistent with the dynamic characteristics of Johari-Goldstein relaxation. Synchrotron X-ray investigations demonstrate that the relaxation originates from short-range collective rearrangements of large solvent atoms, which can be realized by local cooperative bonding switch. Our observations provide experimental insights into the atomic mechanisms of Johari-Goldstein relaxation and will be helpful in understanding the low-temperature dynamics and properties of metallic glasses.

  15. Structural origins of Johari-Goldstein relaxation in a metallic glass.

    PubMed

    Liu, Y H; Fujita, T; Aji, D P B; Matsuura, M; Chen, M W

    2014-01-01

    Johari-Goldstein or β relaxation, persisting down to glassy state from a supercooled liquid, is a universal phenomenon of glassy dynamics. Nevertheless, the underlying micromechanisms leading to the relaxation are still in debate despite great efforts devoted to this problem for decades. Here we report experimental evidence on the structural origins of Johari-Goldstein relaxation in an ultra-quenched metallic glass. The measured activation energy of the relaxation (~26 times of the product of gas constant and glass transition temperature) is consistent with the dynamic characteristics of Johari-Goldstein relaxation. Synchrotron X-ray investigations demonstrate that the relaxation originates from short-range collective rearrangements of large solvent atoms, which can be realized by local cooperative bonding switch. Our observations provide experimental insights into the atomic mechanisms of Johari-Goldstein relaxation and will be helpful in understanding the low-temperature dynamics and properties of metallic glasses.

  16. Syntheses, characterizations and crystal structures of two new lead(II) amino and carboxylate-sulfonates with a layered and a pillared layered structure

    NASA Astrophysics Data System (ADS)

    Yuan, Yan-Ping; Mao, Jiang-Gao; Song, Jun-Ling

    2004-03-01

    Reactions of lead(II) acetate with m-aminobenzenesulfonic acid (H L1) and 5-sulfoisophthalic acid (H 3L2) afforded two new lead(II) sulfonates, Pb( L1) 21 and Pb 2( L2)( μ3-OH)(H 2O) 2. In compound 1, the lead(II) ion is eight-coordinated by two sulfonate groups bidentately, two sulfonate groups unidentately and two amino groups from six ligands. Each L1 ligand is tetradentate and bridges with three Pb(II) ions. The interconnection of the Pb(II) ions via bridging sulfonate ligands resulted in <100> and <200> layers. In compound 2, one Pb(II) ion is six-coordinated by a carboxylate group bidentately, by two carboxylate groups unidentately, by a sulfonate oxygen atom and by an OH anion, whereas the other one is six-coordinated by a bidentate chelating carboxylate group, two μ3-OH anions, a sulfonate oxygen atom and an aqua ligand. The interconnection of irregular PbO 6 polyhedra via carboxylate-sulfonate ligands resulted in the formation of a pillared layered structure with the 2D layer being formed; the lead(II) ions, hydroxyl groups, carboxylate and sulfonate groups and the benzene ring as the pillar agent.

  17. The structure and properties of single-layer and gradient-layered coatings of the Ti–Al–Si–Cr–Mo–S–N system

    SciTech Connect

    Ovchinnikov, Stanislav Pinzhin, Yurii

    2015-10-27

    Using the method of microprobe analysis and transmission electron microscopy, the influence of obtaining conditions upon particular elemental composition and growth structure coatings of Ti–Al–Si–Mo–S–N system was studied. The possibility of formation and characteristics of the structural and elastic-stress state single-layer coatings with nanoscale columnar or equiaxed grains and gradient-layered, combining two types of selected structure, was defined. On the basis of hardness, tribological properties and coating hardness, a conclusion was made about the relative prospects of its use as wear-resistant coatings with a nanocrystalline structure.

  18. Alkali-assisted mild aqueous exfoliation for single-layered and structure-preserved graphitic carbon nitride nanosheets.

    PubMed

    Li, Gengnan; Li, Liang; Yuan, Haiyang; Wang, Haifeng; Zeng, Huarong; Shi, Jianlin

    2017-06-01

    Single-layered g-C3N4 nanosheets have been fabricated by delaminating directly its bulk counterpart in an alkaline solution. According to the theoretical modeling, the interaction of OH(-) with terminal NH2 or bridged NH group of the triazine units within bulk g-C3N4 crystal structure could result in decreased bonding energy between layers and promote the total delamination. The resulting g-C3N4 nanosheets colloid has a relatively high concentration (12g/L) compared with the traditional ultrasonic assistant exfoliation method. The delaminated nanosheets are revealed by atomic force microscopy to show a lateral size of a hundred nanometers and a thickness of about 0.4nm, which provides a direct evidence for the total exfoliation of g-C3N4 crystals into their single sheets. More importantly, the X-ray diffraction measurement confirms that the g-C3N4 nanosheets could be re-assembled with well-preserved original crystal structure. The exfoliation mechanism was also c