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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

    2015-01-01

    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

  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. 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.

  4. '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.

  5. 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.

  6. Structural Origin of Overcharge-Induced Thermal Instability of Ni-Containing Layered-Cathodes for High-Energy-Density Lithium Batteries

    SciTech Connect

    Wu, L.; Nam, K.-W.; Wang, X.; Zhou, Y.; Zheng, J.-C.; Yang, X.-Q.; Zhu, Y.

    2011-08-04

    Using a combination of time-resolved X-ray diffraction (XRD), in situ transmission electron microscopy (TEM), and first principles calculations, we explore the structural origin of the overcharge induced thermal instability of two cathode materials, LiNi{sub 0.8}Co{sub 0.15}Al{sub 0.05}O{sub 2} and LiNi{sub 1/3}Co{sub 1/3}Mn{sub 1/3}O{sub 2}, which exhibit significant difference in thermal stabilities. Detailed TEM analysis reveals, for the first time, a complex core-shell-surface structure of the particles in both materials that was not previously detected by XRD. Structural comparison indicates that the overcharged Li{sub x}Ni{sub 0.8}Co{sub 0.15}Al{sub 0.05}O{sub 2} (x < 0.15) particles consist of a rhombohedral core, a spinel shell, and a rock-salt structure at the surface, while the overcharged Li{sub x}Ni{sub 1/3}Co{sub 1/3}Mn{sub 1/3}O{sub 2} consists of a similar core-shell-surface structure but a very different CdI{sub 2}-type surface structure. The thermal instability of Li{sub x}Ni{sub 0.8}Co{sub 0.15}Al{sub 0.05}O{sub 2} can be attributed to the release of oxygen because of the rapid growth of the rock-salt-type structure on the surface during heating. In contrast, the CdI{sub 2}-type surface structure of the overcharged Li{sub x}Ni{sub 1/3}Co{sub 1/3}Mn{sub 1/3}O{sub 2} particles delays the oxygen-release reaction to a much higher temperature resulting in better stability. These results gave deep insight into the relationship between the local structural changes and the thermal stability of cathode materials, which is vital to the development of new cathode materials for the next generation of lithium-ion batteries.

  7. Structural Origin of Overcharge-induced Thermal Instability of Ni-containing Layered-cathodes for High-energy-density Lithium Batteries

    SciTech Connect

    L Wu; K Nam; X Wang; Y Zhou; J Zheng; X Yang; Y Zhu

    2011-12-31

    Using a combination of time-resolved X-ray diffraction (XRD), in situ transmission electron microscopy (TEM), and first principles calculations, we explore the structural origin of the overcharge induced thermal instability of two cathode materials, LiNi{sub 0.8}Co{sub 0.15}Al{sub 0.05}O{sub 2} and LiNi{sub 1/3}Co{sub 1/3}Mn{sub 1/3}O{sub 2}, which exhibit significant difference in thermal stabilities. Detailed TEM analysis reveals, for the first time, a complex core-shell-surface structure of the particles in both materials that was not previously detected by XRD. Structural comparison indicates that the overcharged Li{sub x}Ni{sub 0.8}Co{sub 0.15}Al{sub 0.05}O{sub 2} (x < 0.15) particles consist of a rhombohedral core, a spinel shell, and a rock-salt structure at the surface, while the overcharged LixNi{sub 1/3}Co{sub 1/3}Mn{sub 1/3}O{sub 2} consists of a similar core-shell-surface structure but a very different CdI{sub 2}-type surface structure. The thermal instability of LixNi{sub 0.8}Co{sub 0.15}Al{sub 0.05}O{sub 2} can be attributed to the release of oxygen because of the rapid growth of the rock-salt-type structure on the surface during heating. In contrast, the CdI{sub 2}-type surface structure of the overcharged LixNi{sub 1/3}Co{sub 1/3}Mn{sub 1/3}O{sub 2} particles delays the oxygen-release reaction to a much higher temperature resulting in better stability. These results gave deep insight into the relationship between the local structural changes and the thermal stability of cathode materials, which is vital to the development of new cathode materials for the next generation of lithium-ion batteries.

  8. Internal Structural Symmetry of Optimal Layered Structures

    NASA Astrophysics Data System (ADS)

    Gusev, E. L.

    2001-01-01

    Problems of the optimal synthesis of multilayer structures implementing the ultimate performance under the action of elastic waves are considered. It is required to design a multilayered structure by choosing the physical properties of materials, the thickness of the layers, their number, and the mutual arrangement of layers with different physical properties in a way such that the energy characteristics of an elastic wave be as close as possible to the desired characteristics. From an analysis of the necessary optimum conditions, it is inferred that the optimal solutions are characterized by a certain internal order in the structure parameters, i.e., by an internal symmetry. When known a priori, these qualitative relations considerably reduce the number of variants tested for the optimum and make it possible to efficiently design composite structures implementing the ultimate performance in terms of exhibiting the desired properties under the action of elastic waves.

  9. 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.

  10. 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.

  11. 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.

  12. Layered tektites - A multiple impact origin for the Australasian tektites

    NASA Astrophysics Data System (ADS)

    Wasson, J. T.

    1991-02-01

    The mechanisms proposed for the origin of tektites from the Australasian field are examined using neutron activation data for twenty layered tektites and six splash tektites of known and widely separated sites of a field greater than 1140 km in length. Evidence is presented indicating that the layered tektites formed as sheets or pools of melt. It is argued that their distribution across a field greater than 1140 km in length is inconsistent with their formation in a single crater, and that many impact craters are required to account for their distribution across such a large field.

  13. 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 ?= 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, ?-sheet content with increasing draw ratio measured by FTIR spectroscopy (C?? e2.5 ?), the concomitant increasing degree of orientation of ?-sheet crystals detected via WAXD (FWHM = 0.22° for ?= 2.7), and the improvement in silk piezoelectricity (d14? e2.4 ?). 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 ?-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, ?-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

  14. 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.

  15. 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.

  16. Simulation of Sintering of Layered Structures

    SciTech Connect

    OLEVSKY,EUGENE; TIKARE,VEENA; GARINO,TERRY J.; BRAGINSKY,MICHAEL V.

    2000-11-22

    An integrated approach, combining the continuum theory of sintering and Potts model based mesostructure evolution analysis, is used to solve the problem of bi-layered structure sintering. Two types of bi-layered structures are considered: layers of the same material with different initial porosity, and layers of two different materials. The effective sintering stress for the bi-layer powder sintering is derived, both at the meso- and the macroscopic levels. Macroscopic shape distortions and spatial distributions of porosity are determined as functions of the dimensionless specific time of sintering. The effect of the thickness of the layers on shrinkage, warpage, and pore-grain structure is studied. Ceramic ZnO powders are employed as a model experimental system to assess the model predictions.

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

    PubMed

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

    2015-06-17

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

  18. 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.

  19. Diffraction by glasses with a layer structure

    SciTech Connect

    Wright, A.C.; Price, D.L.; Clare, A.G.; Etherington, G.; Sinclair, R.N.

    1987-06-01

    An outline is presented of the expected form of the diffraction pattern and the real space correlation function for a glass with a layer structure. The diffraction evidence for and against the presence of layers in the structure of the vitreous arsenic and germanium chalcogenides is briefly reviewed with special reference to the outrigger raft model for vitreous GeSe/sub 2/. 14 refs., 5 figs.

  20. ORIGINAL PAPER Structural and dynamical

    E-print Network

    Singh, Jayant K.

    structure. Lithium in anti-depression medicines [2] is a life saver. The hygroscopic nature of LiCl and Li. The effect of DB18C6 has been visualized in terms of reduction in peak height and shift in peak positions . Interface . Li+ ion extraction . Molecular dynamics . Solvation effect Introduction Separation of metal ions

  1. PHYLOGENETIC ORIGINS OF ANTIBODY STRUCTURE

    PubMed Central

    Marchalonis, J.; Edelman, G. M.

    1965-01-01

    The elasmobranch Mustelus canis has been shown to produce antibodies to Limulus hemocyanin. The serum of both normal and immunized M. canis contains immunoglobulins having sedimentation coefficients of approximately 7S and 17S. Antibody activity was found in the 17S immunoglobulin which may be dissociated to 7S components with concomitant loss of activity. Both 17S and 7S serum, immunoglobulins were antigenically identical. They consisted of light and heavy chains present in amounts comparable to those of higher vertebrates. Peptide maps indicated that the light chains had an entirely different primary structure than the heavy chains, but that the corresponding chains of 7S and 17S dogfish serum immunoglobulins were similar in primary structure. The heavy chains appeared to resemble the n chains of immunoglobulins of higher vertebrates in their starch gel electrophoretic behavior. It is suggested that the elasmobranch M. canis may have only one major class of immunoglobulins resembling that of macroglobulins (?M-immunoglobulins) seen in higher vertebrates. The results indicate that the multichain structure of antibodies is an ancient evolutionary development. PMID:4158437

  2. Angiomatoid fibrous histiocytoma with cystic structures of sweat duct origin.

    PubMed

    Koletsa, Triantafyllia; Hytiroglou, Prodromos; Semoglou, Christos; Drevelegas, Antonios; Karkavelas, Georgios

    2007-08-01

    Angiomatoid fibrous histiocytoma is an unusual soft tissue tumor, mostly arising in the subcutaneous fibro-adipose tissue of children and young adults and measuring a few centimeters in greatest dimension. Reported herein is a unique case of angiomatoid fibrous histiocytoma containing epithelium-lined cystic structures. This large tumor (12 cm) was located in the subcutaneous tissue of the left leg of a 28-year-old woman. The cystic structures were variably sized and were lined by a double cell layer with areas of squamous metaplasia. Their overall histological features suggested a sweat duct origin. Immunohistochemical stains confirmed such origin, demonstrating an inner epithelial and an outer myoepithelial (smooth muscle actin and cytokeratin 17 positive) cell layer. The present case is illustrative of a mechanism of sweat duct dilatation that may occur during the growth of neoplasms involving the dermis and subcutis, resulting in formation of tumors with unusual histological features. PMID:17610476

  3. Origin and Structure of Dynamic Cooperative Networks

    E-print Network

    Hauert, Christoph

    Origin and Structure of Dynamic Cooperative Networks Lucas Wardil & Christoph Hauert Department of Mathematics, The University of British Columbia 1984 Mathematics Road, Vancouver B.C., Canada V6T 1Z2 the local structure of the social network. Here we propose a simple theoretical framework to model dynamic

  4. PHYLOGENETIC ORIGINS OF ANTIBODY STRUCTURE

    PubMed Central

    Marchalonis, J.; Edelman, G. M.

    1966-01-01

    The anuran amphibian, Rana catesbiana, has been found to possess at least two kinds of immunoglobulins corresponding to ?G- and ?M-classes. These classes have the same chain structures as those of their counterparts in higher animal species. Light chains of both immunoglobulins had molecular weights of 20,000. Heavy chains of the ?M-class had molecular weights of 72,100; those of the ?G-class had molecular weights of 53,600. The carbohydrate content of the ?G-immunoglobulin was 2.1%, and that of the ?M-protein was 10.8%. The amino acid compositions of the immunoglobulins were generally similar to those of mammalian immunoglobulins. After a single injection of phage antigen (f2), the order of appearance of phage-neutralizing activity in the frog immunoglobulin classes was (a) ?M-antibodies, and (b) ?G-antibodies. The results of this and previous studies suggest that the ?G-immunoglobulins emerged at some point in evolution between the elasmobranchs and the anuran amphibians. PMID:4162734

  5. 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.

  6. Multi-Layer Laminated Thin Films for Inflatable Structures

    NASA Technical Reports Server (NTRS)

    Yavrouian, Andre; Plett, Gary; Mannella, Jerami

    2005-01-01

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

  7. Electronic structure of bacterial surface protein layers

    SciTech Connect

    Maslyuk, Volodymyr V.; Mertig, Ingrid; Bredow, Thomas; Mertig, Michael; Vyalikh, Denis V.; Molodtsov, Serguei L.

    2008-01-15

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

  8. Electronic structure of bacterial surface protein layers

    NASA Astrophysics Data System (ADS)

    Maslyuk, Volodymyr V.; Mertig, Ingrid; Bredow, Thomas; Mertig, Michael; Vyalikh, Denis V.; Molodtsov, Serguei L.

    2008-01-01

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

  9. ORIGINAL ARTICLE Spatial structure and nutrients promote

    E-print Network

    Krone, Steve

    ORIGINAL ARTICLE Spatial structure and nutrients promote invasion of IncP-1 plasmids in bacterial In spite of the importance of plasmids in bacterial adaptation, we have a poor understanding of their dynamics. It is not known if or how plasmids persist in and spread through (invade) a bacterial population

  10. 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 ?-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.

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

    E-print Network

    Lutkenhaus, Jodie Lee

    2007-01-01

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

  12. Electronic Structure of Regular Bacterial Surface Layers

    NASA Astrophysics Data System (ADS)

    Vyalikh, Denis V.; Danzenbächer, Steffen; Mertig, Michael; Kirchner, Alexander; Pompe, Wolfgang; Dedkov, Yuriy S.; Molodtsov, Serguei L.

    2004-12-01

    We report photoemission and near-edge x-ray absorption fine structure measurements of the occupied and unoccupied valence electronic states of the regular surface layer of Bacillus sphaericus, which is widely used as the protein template for the fabrication of metallic nanostructures. The two-dimensional protein crystal shows a semiconductorlike behavior with a gap value of ˜3.0 eV and the Fermi energy close to the bottom of the lowest unoccupied molecular orbital. We anticipate that these results will open up new possibilities for the electric addressability of biotemplated low-dimensional hybrid structures.

  13. 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

  14. ORIGINAL PAPER Mechanical filtering by the boundary layer and fluidstructure

    E-print Network

    McHenry, Matt

    in larval zebrafish (Danio rerio). The model predicts that the boundary layer of flow over the body filters flow signals. Keywords Fish Á Mechanosensation Á Hair cells Á Biomechanics Á Zebrafish List cupula deflection ms cupula deflection by vibrating sphere qm density of cupular material qw density

  15. 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.

  16. 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.

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

    PubMed

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

    2015-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-02-01

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

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

    E-print Network

    Mendillo, Michael

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

  1. Structural Characterization of Layered Morphologies in Precise Copolymers

    NASA Astrophysics Data System (ADS)

    Trigg, Edward; Gaines, Taylor; Wagener, Kenneth; Winey, Karen

    2015-03-01

    Layered morphologies have been observed in precise polyethylene-based copolymers that contain acid, charged, or polar functional groups precisely spaced along a linear alkane chain. Sufficiently long alkane segments form structures resembling orthorhombic polyethylene crystals, while the functional groups form 2-D layers that disrupt the alkane crystal structure to varying degrees. Here, layered morphologies in precise copolymers containing acrylic acid, phosphonic acid, imidazolium bromide, and sulfone groups are studied via X-ray scattering. Specifically, the composition profiles of the layered structures are obtained by Fourier synthesis, and the coherence length is investigated using peak width analysis. This analysis indicates that the layers of functional groups are frequently bordered by two crystallites, which suggests different dynamics relative to layers bordered by one crystalline and one amorphous microdomain. Detailed understanding of the structure of the layered morphologies will allow for a systematic investigation of proton and ion conductivity mechanisms, which are expected to occur through the high-dielectric layers.

  2. Acoustic emissions from unsteady transitional boundary layer flow structures

    NASA Astrophysics Data System (ADS)

    Marboe, Richard Chostner

    The acoustic radiation contribution of boundary layer flow structures has long been the subject of debate. The research described critically examines the popular approaches to modeling the radiation mechanisms and attempts to bring some degree of closure to the physical and practical significance of noise and pseudo-noise originating in the laminar-to-turbulent transition zone within a natural boundary layer. This includes improving models to include recent computational and experimental statistics, evaluation of model sensitivities to input parameters, and applicability to situations of engineering relevance. Prior efforts to model wall pressure fluctuation statistics resulting from boundary layer transition zone flow structures allow further development of direct radiation prediction codes. Several refinements were made to theoretical models for directly radiated noise based upon the Liepmann analogy for fluctuating displacement thickness including the incorporation of a semi- empirically derived space-time correlation function for the intermittency indicator. A similar two-fluids model uses a Lighthill acoustic analogy. Radiation by vortex structures and direct numerical simulation methods are reviewed to help define their useful role in predicting sound radiation from transition. The role of pressure gradient in axisymmetric body flows, flat plate flows, and over hydrofoils is investigated. A quiet airflow facility was developed to measure the direct acoustic radiation from a naturally transitioning boundary layer. Real-time acoustic intensity measurement instrumentation was developed if measurements of isolated spots in otherwise laminar flow had been necessary. This technique uses a hot film signal from the transition structure to obtain the coherent output intensity (COI). Model predictions are compared to the measured acoustic radiation from a naturally transitioning boundary layer. Radiated noise measurements isolating the direct transition zone radiation demonstrated similar dependence with axial location within the transition zone as previous wall pressure measurements. The measurements suggest that radiation from transition flow structures is multipolar and has low radiation efficiency. Transition noise per unit area is greater than TBL noise per unit area. Thus, the contribution to overall directly radiated flow noise from the transition zone in typical engineering applications is negligible compared to the radiation from the much larger area of fully turbulent flow.

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

    NASA Astrophysics Data System (ADS)

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

    2015-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

  5. Magnetic dead layer in amorphous CoFeB layers with various top and bottom structures

    NASA Astrophysics Data System (ADS)

    Jang, Soo Young; Lim, S. H.; Lee, S. R.

    2010-05-01

    The magnetic dead layer (MDL) in amorphous CoFeB layers is investigated for four different unit structures. These structures are relevant to the synthetic ferrimagnetic (SyF) free layer structure in magnetic tunnel junctions used for high density magnetic random access memory (MRAM). The MDL results for these unit structures are then converted to those for the constituent interfaces of the SyF free layer structure. These MDL results are critically tested by fabricating the synthetic ferrimagnetic free layer structures with various thickness asymmetries. The observed switching properties of these tested structures are in good agreement with those expected from the effective thicknesses after the MDL correction, confirming the accuracy of the present results for the MDLs at the constituent interfaces.

  6. 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.

  7. 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 good agreement with that inferred from experimental measurements. Both the rotations (ACN only) and translations of interfacial ACN and ions are found to slow down as the electrode is electrified. We also observe an asymmetrical dependence of these motions on the sign of the electrode charge. The rotation/diffusion of ACN and the diffusion of ions in the region beyond the first ACN or ion layer differ only weakly from those in the bulk

  8. 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.

  9. THREE POSSIBLE ORIGINS FOR THE GAS LAYER ON GJ 1214b

    SciTech Connect

    Rogers, L. A.; Seager, S.

    2010-06-20

    We present an analysis of the bulk composition of the MEarth transiting super-Earth exoplanet GJ 1214b using planet interior structure models. We consider three possible origins for the gas layer on GJ 1214b: direct accretion of gas from the protoplanetary nebula, sublimation of ices, and outgassing from rocky material. Armed only with measurements of the planet mass (M{sub p} = 6.55 {+-} 0.98 M{sub +}), radius (R{sub p} = 2.678 {+-} 0.13 R{sub +}), and stellar irradiation level, our main conclusion is that we cannot infer a unique composition. A diverse range of planet interiors fits the measured planet properties. Nonetheless, GJ 1214b's relatively low average density ({rho}{sub p} = 1870 {+-} 400 kg m{sup -3}) means that it almost certainly has a significant gas component. Our second major conclusion is that under most conditions we consider GJ 1214b would not have liquid water. Even if the outer envelope is predominantly sublimated water ice, the envelope will likely consist of a super-fluid layer sandwiched between vapor above and plasma (electrically conductive fluid) below at greater depths. In our models, a low intrinsic planet luminosity ({approx_lt}2TW) is needed for a water envelope on GJ 1214b to pass through the liquid phase.

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

    E-print Network

    Rogers, Alan R.

    Population Structure and Modern Human Origins Alan R. Rogers 1997 Abstract This paper reviews population growth rather than selection, then the confidence regions reject the multiregional hypothesis hypothesis. Keywords coalescent, mitochondrial DNA, modern human origins, mismatch distribution, population

  11. Boundary-Layer Origin for Jets, and Non-Existence of the Boundary Layer in Young Jet-Producing Protostars

    NASA Astrophysics Data System (ADS)

    Williams, Peter T.

    2016-01-01

    Twenty-five years ago, Pringle suggested a boundary-layer origin for jets from YSOs. The jets were driven by a toroidal magnetic field generated by strong shear in the accretion boundary layer. Such a mechanism is clearly non-magnetocentrifugal in nature.Nearly fifteen years ago, we suggested a cartoon of the jet-launching mechanism in protostars in which shear, acting upon MHD turbulence generated by the magnetorotational instability (MRI), generated a tangled, toroidal magnetic field capable of driving a jet. This picture, which is also manifestly non-magnetocentrifugal in nature, relied upon a novel model for MRI-driven MHD turbulence based on a viscoelastic, rather than a viscous, prescription for the turbulent stress. Our hypothesis has some clear similarities to Pringle's mechanism, but it relied upon a large envelope surrounding the central star.An accretion boundary layer has long been recognized as a promising source for protostellar jets in good part because in a standard thin disk, matter loses circa half of all its accretion energy in this layer, but it is problematic to drive a well-collimated outflow from a boundary layer in a thin disk. In this presentation, we argue paradoxically that the "boundary layer" can drive jets when a true boundary layer, like the thin disk, does not exist. This changes the inner boundary condition for viscous angular momentum flux in the disk.The standard argument for a thin boundary layer is, we argue, circular. In high accretion-rate systems, or when the gas cannot cool efficiently, there is no reason to suspect the turbulent viscosity in this boundary layer to be small, and therefore neither is the boundary layer. When the boundary layer becomes larger than the central accretor itself, it is arguably no longer a boundary layer, but rather an envelope. It is still, however, a substantial source of power and toroidal MRI-driven magnetic fields.It is, again, only in relatively hot or high-accretion rate systems in which the boundary layer would be expected to inflate and so disappear. Not coincidentally, it is in such systems, such as Class 0 and Class I protostars, in which we have the strongest evidence for powerful, well-collimated jet outflows.

  12. 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.

  13. 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.

  14. Surface double-layer structure in (110) oriented BiFeO{sub 3} thin film

    SciTech Connect

    Yang, Tieying; Zhang, Xingmin; Gao, Xingyu; Li, Zhong; Li, Xiaolong; Wang, Can; Feng, Yu; Guo, Haizhong; Jin, Kuijuan

    2014-11-17

    Surface double-layer structure different from the interior was found in BiFeO{sub 3} thin film grown on SrRuO{sub 3} covered SrTiO{sub 3} (110) substrate by pulsed laser deposition. It was shown that BiFeO{sub 3} film exhibits epitaxial phase with single domain. X-ray reflectivity and X-ray photoelectron spectroscopy results revealed a skin layer of less than 1?nm with a reduced electron density and different surface state. Grazing incidence x-ray diffraction convinced a surface multi-domain structure of several nm beneath the surface skin layer. The double-layer near surface structure would be originated from the large depolarization field produced by the single-domain structure with strain.

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

    SciTech Connect

    Tasolamprou, Anna C.; Zhang, Lei; Kafesaki, Maria; Koschny, Thomas; Soukoulis, Costas M.

    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.

  16. 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.

  17. 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.

  18. Deep subwavelength plasmonic waveguide switch in double graphene layer structure

    E-print Network

    Fan, Shanhui

    Deep subwavelength plasmonic waveguide switch in double graphene layer structure Hideo Iizuka://apl.aip.org/features/most_downloaded Information for Authors: http://apl.aip.org/authors #12;Deep subwavelength plasmonic waveguide switch that in a deep subwavelength double graphene layer structure, graphene plasmons can be routed between two

  19. Electroluminescent apparatus having a structured luminescence conversion layer

    DOEpatents

    Krummacher, Benjamin Claus (Sunnyvale, CA)

    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.

  20. Origin of nonmonotonic Tc behavior in ferromagnet/superconductor structures

    NASA Astrophysics Data System (ADS)

    Khusainov, Mansur; Izyumov, Yurii A.; Proshin, Yurii N.

    2000-07-01

    The original theory of proximity effect in the layered ferromagnetic metal/superconductor (FM/S) structures taking into account a finite transparency of FM/S interface as well as a competition between 1D and 3D Larkin-Ovchinnikov-Fulde-Ferrell (LOFF) states is developed. It is shown that the oscillatory dependence of critical temperature Tc on the FM layer thickness df is due to oscillations of the Cooper pairs flux at the FM/S boundary. This effect is possible not only in the FM/S multilayers, but in the FM/S bilayers as well. The phenomena of reentrant and periodically reentrant superconductivity in the FM/S bilayers and superlattices are predicted. The competition between 1D and 3D LOFF states leads to significant smoothing of the Tc( df) dependence, so that in the most cases one maximum of this dependence is realized as this has been observed in Gd/Nb and Fe/Nb/Fe.

  1. Crystal Structure of the Eukaryotic Origin Recognition Complex

    PubMed Central

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

    2015-01-01

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

  2. Zipper layer method for linking two dissimilar structured meshes

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

  3. The Levantine Basin—crustal structure and origin

    NASA Astrophysics Data System (ADS)

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

    2006-06-01

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

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

    SciTech Connect

    Tynell, Tommi; Yamauchi, Hisao; Karppinen, Maarit

    2014-01-15

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

  5. Classification of structures in the stable boundary layer

    NASA Astrophysics Data System (ADS)

    Belusic, Danijel

    2015-04-01

    Ubiquitous but generally unknown flow structures populate the stable boundary layer at scales larger than turbulence. They introduce nonstationarity, affect the generation of turbulence and induce fluxes. Classification of the structures into clusters based on a similarity measure could reduce their apparent complexity and lead to better understanding of their characteristics and mechanisms. Here we explore different approaches to detect and classify structures, the usefulness of those approaches, and their potential to provide better understanding of the stable boundary layer.

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

    SciTech Connect

    Hsu, C. Y.

    2012-08-06

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

  7. 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) and strength (400--1400MPa): Y-TZP zirconia, InCeram alumina and Empress II glass-ceramic. Explicit relations for the critical loads P to produce these different damage modes in bilayer and trilayer structures are developed in terms of basic material properties (modulus E, strength, hardness H and toughness T) and geometrical variables (thickness d and contact sphere radius r). These experimentally validated relations are used to design of optimal material combinations for improved fracture resistance and to predict mechanical performance of current dental materials.

  8. Double-layer structure of OH dayglow in the mesosphere

    NASA Astrophysics Data System (ADS)

    Gao, Hong; Xu, Jiyao; Ward, William; Smith, Anne K.; Chen, Guang-Ming

    2015-07-01

    Observations by the Sounding of the Atmosphere using Broadband Emission Radiometry instrument on the Thermosphere-Ionosphere-Mesosphere Energetics and Dynamics satellite from January 2002 to June 2014 are used to study the vertical structure of OH dayglow. The results indicate for the first time that there is a double-layer structure in the distributions of 12 year averaged OH airglow emission, [O3], and [H] during the daytime. The upper layer of OH dayglow is located in the mesopause region (~88 km) at a similar altitude to that of the OH nightglow. The lower layer is situated in the range of 70-85 km. Both the peak emission and height of the lower layer increase with local time. The distance between the two layers decreases with local time. At the equator, the lower layer forms at ~09:00 LT and lasts for about 8 h; during this time the interlayer distance decreases from 13 km to 5 km. The double-layer structure is more obvious and longer-lived during the equinoxes and at lower latitudes. The double-layer structure of OH dayglow emission is a long-term stable structure and is mainly caused by photochemical processes involving [O3]. It is also modulated by background atmospheric temperature and [H].

  9. 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.

  10. A wind origin for Titan's haze structure

    E-print Network

    Hourdin, Chez Frédéric

    .............................................................. A wind origin for Titan's haze ............................................................................................................................................................................. Titan, the largest moon of Saturn, is the only satellite in the Solar System with a dense atmosphere that drives atmospheric circulation3,4 , shrouds the moon. The haze has numerous features that have remained

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

    E-print Network

    Gong, Xingao

    lower power consumption than classical transistors. Recently, few-layer black phosphorus crystals 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

  12. Origin of Indirect Optical Transitions in Few-Layer MoS2, WS2, and WSe2

    NASA Astrophysics Data System (ADS)

    Zhao, Weijie; Ribeiro, R. M.; Toh, Minglin; Carvalho, Alexandra; Kloc, Christian; Castro Neto, A. H.; Eda, Goki

    2013-11-01

    It has been well established that single layer MX2 (M=Mo,W and X=S,Se) are direct gap semiconductors with band edges coinciding at the K point in contrast to their indirect gap multilayer counterparts. In few-layer MX2, there are two valleys along the {\\Gamma}-K line with similar energy. There is little understanding on which of the two valleys forms the conduction band minimum (CBM) in this thickness regime. We investigate the conduction band valley structure in few-layer MX2 by examining the temperature-dependent shift of indirect exciton PL. Hihgly anisotropic thermal expansion of the lattice and corresponding evolution of the band structure result in distinct peak shift for indirect transitions involving the K and {\\Lambda} (midpoint along {\\Gamma}-K) valleys. We identify the origin of the indirect emission and concurrently determine the relative energy of these valleys. Our results show that the two valleys compete in energy in few-layer WSe2.

  13. Multiscale Structures in Tropical Cyclone Boundary Layers

    NASA Astrophysics Data System (ADS)

    Foster, Ralph

    2015-04-01

    We present recent advances in the development of the resonant triad interaction model of large scale roll vortices in the tropical cyclone boundary layer. The relatively shallow, high shear and strong surface buoyancy flux conditions that characterize the tropical cyclone boundary layer make it an ideal environment for the formation of mixed shear/convection roll vortices. The most commonly documented rolls tend to align close to the mean wind direction and have aspect ratios (wavelength/depth) of near 2.5 to 4. Some observations suggest much smaller scale rolls are nearly ubiquitous in the near surface layer. Recent analyses of synthetic aperture radar images of the sea surface under tropical cyclones find nearly ubiquitous signatures of very large aspect ratio rolls, with wavelengths of order 10 km or greater. These rolls apparently extend from the surface into the lower troposphere. Our studies hypothesize that nonlinear triad wave-wave interactions are a likely candidate to explain the formation and persistence of these large aspect ratio modes, the variability in detectability of "standard roll vortices and a possible reason why such large scale rolls are not formed in mesoscale numerical models.

  14. Surface Science Letters Structures of adsorbed water layers

    E-print Network

    Alavi, Ali

    Surface Science Letters Structures of adsorbed water layers on MgO: an ab initio study R.M. Lynden-55021 Mainz, Germany c University Chemical Laboratory, Lens®eld Road, Cambridge CB2 1EW, UK Received 15 of the lowest energy structure. We also found a structure with a similar energy with (2 Â 2) symmetry and half

  15. Electrochemical Double-Layer Capacitors Using Carbon Nanotube Electrode Structures

    E-print Network

    Schindall, Joel E.

    The structure and behavior of the electrical double-layer capacitor (EDLC) are described. The use of activated carbon electrodes is discussed and the limitations on voltage and accessible surface area are presented. Metrics ...

  16. Origin and phylogeographical structure of Chinese cattle.

    PubMed

    Lei, C Z; Chen, H; Zhang, H C; Cai, X; Liu, R Y; Luo, L Y; Wang, C F; Zhang, W; Ge, Q L; Zhang, R F; Lan, X Y; Sun, W B

    2006-12-01

    Complete mitochondrial D-loop sequences of 231 samples were used to explore the origin and genetic diversity of Chinese cattle. Phylogenetical analysis of these sequences revealed both Bos taurus and Bos indicus mitochondrial types in Chinese cattle. Four of the previously identified mitochondrial DNA lineages (T1-T4) were identified in the Bos taurus type, including lineage T1, which was found for the first time in Chinese cattle. Two lineages (I1 and I2) were identified in the Bos indicus type. Our results support the suggestion that the Yunnan-Guizhou Plateau is the domestication site of Chinese zebu. We also found evidence that Tibetan cattle originated from taurine and zebu cattle. The distribution pattern of Chinese cattle breeds was closely related to the geographical and climatic background. It was possible to divide Chinese cattle in this study into two major groups: northern and southern cattle. PMID:17121603

  17. Vertical columns originated in layers of depth hoar and near-surface faceted crystals

    NASA Astrophysics Data System (ADS)

    Kocianova, M.

    2009-04-01

    Vertical columns originated in layers of depth hoar and near-surface faceted crystals Milena Kocianova (1), Nils Åke Andersson (2), Josef Harcarik (1) (1) Krkonose National Park Administration, Dobrovskeho 3, 54301 Vrchlabi, Czech republic (2)Abisko Scientific Research Station, Abisko, Sweden Within the winter subpolar climatic conditions, the deep layers of depth hoar crystals/sugar snow are common. In course of study snow profiles between Abisko and Kiruna (Northern Sweden) in March/April 2008, we have observed complexes of vertical columns composed of chain of depth hoar crystals repeatably. The height of columns reaches to 20 cm and about 5 cm in diameter, columns were formed in distance from several centimetres to some tens of centimetres between them. The best developed columns were formed by ice body inside. Within deeper snow profile (to 1 m) the columns formed two layers one above another. Earlier, in May 2006, similar layers of columns we were discovered inside continuous snowpack near Riksgransen and inside rest of snow patches in Abisko as well. Columns were formed by harder firn grains. Their origin should correspond to International classification for seasonal snow (Collbeck at al.1990), subclass. No 8b „Ice column". (Ice column from refreezing of draining meltwater within flow fingers). However, based on our knowledges from 2008, there should exist another way of their origin, e.g. temperature metamorphosis of depth hoar columns. Consequently, analogous vertical columns were found within layers of near-surface faceted crystals in subalpine and mountain areas of the Krkonose Mountains (Central Europe). We suppose the influence of space design of all three types of harder columns (originated in depth hoar, near-surface faceted crystals, refreezing of meltwater) and adjacent soft interspace as on the flux of air (gases) inside snowpack as on its stability. Photodocumentation of all forms is enclosed.

  18. Dynamic characteristics of specialty composite structures with embedded damping layers

    NASA Technical Reports Server (NTRS)

    Saravanos, D. A.; Chamis, C. C.

    1993-01-01

    Damping mechanics for simulating the damped dynamic characteristics in specialty composite structures with compliant interlaminar damping layers are presented. Finite-element based mechanics incorporating a discrete layer (or layer-wise) laminate damping theory are utilized to represent general laminate configurations in terms of lay-up and fiber orientation angles, cross-sectional thickness, shape, and boundary conditions. Evaluations of the method with exact solutions and experimental data illustrate the accuracy of the method. Additional applications investigate the potential for significant damping enhancement in angle-ply composite laminates with cocured interlaminar damping layers.

  19. 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

  20. 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.

  1. The Origins of Eukaryotic Gene Structure Michael Lynch

    E-print Network

    Lynch, Michael

    The Origins of Eukaryotic Gene Structure Michael Lynch Department of Biology, Indiana University to the peculiar structure of the eukaryotic gene, which harbors numerous embellishments relative to the situation, a general hypothesis for the emergence of eukaryotic gene structure is provided here. Extensive information

  2. 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.

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

    DOEpatents

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

    1989-01-01

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

  4. A single metal layer MEMS self-assembling coplanar structure

    NASA Astrophysics Data System (ADS)

    Bagolini, A.; Giacomozzi, F.; Margesin, B.; Bellutti, P.

    2007-05-01

    Self-assembling perforated microplates modeled and fabricated on silicon wafers by means of surface micromachining are presented. The structures consist of a single Cr/Au metal layer and are set into position by the residual tensile in-plane stress of the material; the geometry is designed to obtain a lifted microplate coplanar to the surface of the wafer. The structures are modeled both analytically and by finite element simulation to correlate the displacement with the strain of the structural material. Samples are fabricated using IC technology on standard 4-inch silicon wafers by surface micromachining; a photoresist is used as a sacrificial layer and electroplated gold is used as a structural layer on a chromium-gold PVD seedlayer. The fabricated structures exhibit a vertical displacement of 38 µm. The resulting estimated strain is 0.001 66, which corresponds to a tensile stress of 173 MPa and is consistent with thermal residual strain.

  5. A wind origin for Titan's haze structure.

    PubMed

    Rannou, P; Hourdin, F; McKay, C P

    2002-08-22

    Titan, the largest moon of Saturn, is the only satellite in the Solar System with a dense atmosphere. Titan's atmosphere is mainly nitrogen with a surface pressure of 1.5 atmospheres and a temperature of 95 K (ref. 1). A seasonally varying haze, which appears to be the main source of heating and cooling that drives atmospheric circulation, shrouds the moon. The haze has numerous features that have remained unexplained. There are several layers, including a 'polar hood', and a pronounced hemispheric asymmetry. The upper atmosphere rotates much faster than the surface of the moon, and there is a significant latitudinal temperature asymmetry at the equinoxes. Here we describe a numerical simulation of Titan's atmosphere, which appears to explain the observed features of the haze. The critical new factor in our model is the coupling of haze formation with atmospheric dynamics, which includes a component of strong positive feedback between the haze and the winds. PMID:12192403

  6. Endoscopic treatments for small gastric subepithelial tumors originating from muscularis propria layer

    PubMed Central

    Zhang, Yu; Ye, Li-Ping; Mao, Xin-Li

    2015-01-01

    Minimally invasive endoscopic resection has become an increasingly popular method for patients with small (less than 3.5 cm in diameter) gastric subepithelial tumors (SETs) originating from the muscularis propria (MP) layer. Currently, the main endoscopic therapies for patients with such tumors are endoscopic muscularis excavation, endoscopic full-thickness resection, and submucosal tunneling endoscopic resection. Although these endoscopic techniques can be used for complete resection of the tumor and provide an accurate pathological diagnosis, these techniques have been associated with several negative events, such as incomplete resection, perforation, and bleeding. This review provides detailed information on the technical details, likely treatment outcomes, and complications associated with each endoscopic method for treating/removing small gastric SETs that originate from the MP layer. PMID:26327758

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

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

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

  8. Structural origins of gentamicin antibiotic action.

    PubMed Central

    Yoshizawa, S; Fourmy, D; Puglisi, J D

    1998-01-01

    Aminoglycoside antibiotics that bind to the ribosomal A site cause misreading of the genetic code and inhibit translocation. The clinically important aminoglycoside, gentamicin C, is a mixture of three components. Binding of each gentamicin component to the ribosome and to a model RNA oligonucleotide was studied biochemically and the structure of the RNA complexed to gentamicin C1a was solved using magnetic resonance nuclear spectroscopy. Gentamicin C1a binds in the major groove of the RNA. Rings I and II of gentamicin direct specific RNA-drug interactions. Ring III of gentamicin, which distinguishes this subclass of aminoglycosides, also directs specific RNA interactions with conserved base pairs. The structure leads to a general model for specific ribosome recognition by aminoglycoside antibiotics and a possible mechanism for translational inhibition and miscoding. This study provides a structural rationale for chemical synthesis of novel aminoglycosides. PMID:9822590

  9. 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.

  10. Simple methods for determining the virtual origin of turbulent boundary layers in hypersonic flow on sharp-edged flat plates

    NASA Technical Reports Server (NTRS)

    Hopkins, E. J.

    1974-01-01

    Two methods for determining the virtual origin of turbulent boundary layers in hypersonic flow are evaluated. The results of the analyses are restricted to wind-tunnel models having sharp-edged surfaces with zero or small pressure gradients. Virtual origin and skin friction estimates from these two methods are compared with values from a base method for which the virtual origin is calculated from the measured momentum thickness at a station downstream of boundary layer transition.

  11. GPR determination of physical parameters of railway structural layers

    NASA Astrophysics Data System (ADS)

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

    2014-07-01

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

  12. Morphology Control of Layer-Structured Gallium Selenide Nanowires

    E-print Network

    Cui, Yi

    cells3 and solid-state batteries.4 Their one-dimensional nanowire (NW) structures may afford better for stable photocathodes and battery electrodes. We report the controlled synthesis and characterization of layer-structured GaSe nanowires via a catalyst-assisted vapor-liquid- solid (VLS) growth mechanism

  13. The simulation of coherent structures in a laminar boundary layer

    NASA Technical Reports Server (NTRS)

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

    1987-01-01

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

  14. Structural response of plates with piezoceramic layers

    NASA Astrophysics Data System (ADS)

    Shah, Dipen K.; Joshi, Shiv P.; Chan, Wen S.

    1993-09-01

    Smart structures can be developed using a variety of sensors and actuators such as piezoelectric, fiber-optic, acoustic, and pyroelectric materials, etc. A piezoelectric material produces electric charge when it is mechanically deformed and conversely, an electric potential causes mechanical deformation of the material. The main thrust of research in the area of smart structures has been in vibration control and geometric shape manipulation. Finite element analysis techniques have been introduced recently in vibration suppression and modal control. In the present study a finite element formulation is developed to analyze laminated plates with arbitrarily placed piezoceramic patches. The technique is applied to obtain static response and stress fields due to application of electric field to the piezoceramic patches.

  15. Love wave propagation in piezoelectric layered structure with dissipation.

    PubMed

    Du, Jianke; Xian, Kai; Wang, Ji; Yong, Yook-Kong

    2009-02-01

    We investigate analytically the effect of the viscous dissipation of piezoelectric material on the dispersive and attenuated characteristics of Love wave propagation in a layered structure, which involves a thin piezoelectric layer bonded perfectly to an unbounded elastic substrate. The effects of the viscous coefficient on the phase velocity of Love waves and attenuation are presented and discussed in detail. The analytical method and the results can be useful for the design of the resonators and sensors. PMID:19022465

  16. Origins of Structure in Planetary Systems

    NASA Astrophysics Data System (ADS)

    Murray-Clay, Ruth

    2016-01-01

    Observations confirm that planet formation is a ubiquitous process that produces a diversity of planetary systems. However, a class of solar system analogs has yet to be identified among the thousands of currently known planets and candidates, the overwhelming majority of which are more easily detectable than direct counterparts of the Sun's worlds. To understand whether our solar system's history was unusual and, more generally, to properly characterize the galactic population of extrasolar planets, we must identify how differences in formation environment translate into different planetary system architectures. In this talk, I will consider our solar system in the context of theoretical advances in planet formation driven by the study of extrasolar planets. Along the way, I will discuss several examples of physical processes operating at different stages of planet formation that imprint observable structures on the dynamical and compositional demographics of planetary systems.

  17. Origin and population structure of the Icelanders.

    PubMed

    Williams, J T

    1993-04-01

    The Norse and Celtic contributions to the founding population of Iceland have been estimated previously on a pan-Icelandic basis using gene frequency data for the entire island. Accounts of the settlement of Iceland, however, suggest that different regions received different proportions of Norse and Celtic settlers, indicating the need to incorporate geographic variation into Icelandic admixture studies. A formal likelihood ratio test rejects the null hypothesis of regional homogeneity in admixture proportions. Here, regional admixture estimates for Iceland are reported; they are in agreement with the settlement pattern inferred from historical accounts. The western, northern, and southern regions of Iceland exhibit a moderate Celtic component, consistent with historical indications that these regions were settled by Norse Vikings from the British Isles, accompanied by Celtic wives and slaves. Eastern Iceland, believed to have been settled chiefly by Vikings from Scandinavia, is characterized by a large Norse component of admixture. The northwestern peninsula is also found to be predominantly Norse. Regional genetic data are used to elucidate the contemporary population structure of Iceland. The observed structure correlates well with patterns of Icelandic geography, history, economy, marriage, urbanization, and internal migration. The northeastern region is strongly isolated, the urbanized areas of the north and southwest are representative of the overall population, and the remaining regions exhibit small-scale variation about the genetic central tendency. A high level of genetic homogeneity is indicated (RST = 0.0005), consistent with the high internal migration rate of the Icelanders. A regression of mean per-locus heterozygosity on distance from the gene frequency centroid reveals a greater than average external gene flow into the eastern region, whereas the northwestern peninsula has received less than average external gene flow. Iceland is compared with possible founding populations and was found to have diverged markedly from other northern European countries. PMID:8449480

  18. ORIGINAL ARTICLE Genetic diversity and population structure of the size-

    E-print Network

    Roy, Kaustuv

    ORIGINAL ARTICLE Genetic diversity and population structure of the size- selectively harvested owl such studies showing a change in genetic diversity or structure over time (Smith et al. 1991; Hauser et al species through changes in population genetic subdivision, genetic diversity and selective regimes. While

  19. 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.

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

    NASA Astrophysics Data System (ADS)

    Egorova, V.; Latypov, R.

    2012-04-01

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

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

    SciTech Connect

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

    1987-06-01

    Four hypotheses are discussed concerning the origin of the layered deposits in the Martian Valles Marineris, whose individual thicknesses range from about 70 to 300 m. The hypothesized processes are: (1) aeolian deposition; (2) deposition of remnants of the material constituting the canyon walls; (3) deposition of volcanic eruptions; and (4) deposition in standing bodies of water. The last process is chosen as most consistent with the rhythm and lateral continuity of the layers, as well as their great thickness and stratigraphic relationship with other units in the canyons. Attention is given to ways in which the sediments could have entered an ice-covered lake; several geologically feasible mechanisms are identified. 46 references.

  3. Air-mass origin in the tropical lower stratosphere: The influence of Asian boundary layer air

    NASA Astrophysics Data System (ADS)

    Orbe, Clara; Waugh, Darryn W.; Newman, Paul A.

    2015-05-01

    A climatology of air-mass origin in the tropical lower stratosphere is presented for the Goddard Earth Observing System Chemistry Climate Model. During late boreal summer and fall, air-mass fractions reveal that as much as 20% of the air in the tropical lower stratosphere last contacted the planetary boundary layer (PBL) over Asia; by comparison, the air-mass fractions corresponding to last PBL contact over North America and over Europe are negligible. Asian air reaches the extratropical tropopause within a few days of leaving the boundary layer and is quasi-horizontally transported into the tropical lower stratosphere, where it persists until January. The rapid injection of Asian air into the lower stratosphere—and its persistence in the deep tropics through late (boreal) winter—is important as industrial emissions over East Asia continue to increase. Hence, the Asian monsoon may play an increasingly important role in shaping stratospheric composition.

  4. Ternary metal-rich sulfide with a layered structure

    DOEpatents

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

    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.

  5. 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.

  6. 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.

  7. High {Tc} trilayer tunneling and Josephson junction structures made using atomic layer by layer growth

    SciTech Connect

    Eckstein, J.N.; Bozovic, I.; Virshup, G.F.

    1994-12-31

    Very precise artificial structuring of high {Tc} heterostructures is possible using atomic layer-by-layer molecular beam epitaxy (ALL-MBE). Cuprates are combined with other oxides, such as titanates, to make atomically precise heterostructures for studying transport and interfacial effects. Titanate slabs as thin as one unit cell thick can be grown without pinholes and provide tunneling barriers for c-axis transport. Single doped unit cells of BSCCO-2212 can also be used as barriers. These give SNS Josephson junctions at temperatures as high as 65 K. Since the crystallographic structure of the barrier is identical to the structure of the 2212 electrode material, it is easily possible to stack more than junction in close proximity. This results in phase-locked operation of two junctions together.

  8. 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)

  9. Adhesion of benzocyclobutene-passivated silicon in epoxy layered structures

    E-print Network

    Hutchinson, John W.

    Adhesion of benzocyclobutene-passivated silicon in epoxy layered structures Robert J. Hohlfelder; accepted 10 October 2000) Adhesion and subcritical debonding at interfaces between a silica-filled epoxy investigated. Adhesion was measured in terms of a critical value of the applied strain energy release rate, G

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

    E-print Network

    English, Benjamin L.

    2013-04-22

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

  11. Role of the Gelatinous Layer (G-Layer) on the Origin of the Physical Properties of the Tension Wood of Acer sieboldianum

    E-print Network

    Yamamoto, H; Arakawa, Y; Okuyama, T; Gril, J; Yamamoto, Hiroyuki; Abe, Kentaro; Arakawa, Yoshiharu; Okuyama, Takashi; Gril, Joseph

    2005-01-01

    The tension wood (TW) properties of a 70 year-old Acer sieboldianum Miq were analyzed by using the G-fiber model which was proposed in our previous paper. The roles of the G-layer on the origins of (1) a high large tensile growth stress, (2) a large longitudinal Young's modulus, and (3) a high longitudinal drying shrinkage in the tension wood xylem were discussed on the basis of the simulations using the G-fiber model. The results suggest that the G-layer generates a high tensile stress in the longitudinal direction during the xylem maturation; the longitudinal Young's modulus of the green G-layer becomes significantly higher than that of the lignified layer; furthermore, the G-layer tends to shrink extraordinarily higher than that of the lignified layer during the moisture desorption.

  12. Investigation Of Boundary Layers Fine Structure In Arid Regions

    NASA Astrophysics Data System (ADS)

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

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

  13. Origin of the F-Layer by ``Snowfall'' in the Earth's Core

    NASA Astrophysics Data System (ADS)

    Hernlund, J. W.; Li, J.; Armentrout, M. M.; Buono, A. S.; Chen, B.; Durand, S.; Gaeman, J.; Pigott, J. S.; Waszek, L.; Zheng, Z.

    2010-12-01

    Recent seismological observations of phases reflecting (PKiKP), diffracting (PKPdiff), or going through the inner core (PKIKP) called for modification of PREM at the top of the Inner Core Boundary (ICB). Both the AK135 and PREM2 models proposed a flattened P-wave velocity gradient relative to PREM in the ~200 km region above the ICB, often referred to as the F-layer. This reduced velocity gradient implies density stratification, which may reflect a gradient in the light element concentration decreasing from the top of the F-layer to the ICB. Here we propose a mechanism to generate a chemical stratification in the F-layer through crystallization of solid iron “snow” at the top of the F-layer, which then precipitates, partially dissolves, and eventually accumulates at the ICB to produce the F-layer and contribute to the growth of the inner core. The formation of iron “snow” in the outer core (OC) requires that the core geotherm intercepts the FeX liquidus, where X is an alloying light element, to create a region of stability for solid iron at the base of the OC. This study examines two potential scenarios in which iron “snowfall” might occur in the F-layer. The first scenario involves the FeX liquidus gradient decreasing or even changing sign such that a region of solid stability is created at the top of the F-layer. This behavior is observed in the Fe-S binary system at lower pressures and has been proposed to cause “snowing” in the interiors of Mercury and Ganymede. In the second case, the outer core temperature may increase relative to the FeX liquidus near the ICB due to viscomagnetic heating. Results based on mineral physics calculations of an iron-sulfur binary system show that an F-layer composition ranging from 7.2 wt% S at the top of the F-layer to 5.7 wt% S at the ICB is sufficient to explain the Vp structure of the F-layer in AK135. In these calculations, the density and bulk modulus as a function of depth were determined using the 3rd order Birch-Murnaghan equation of state. Temperature was accounted for using the Mie-Grüneisen-Debye equation of state. Published experimental values for Fe-FeS solid and liquid end-members were used and those of intermediate compositions were determined using ideal solution theory. The crystal fraction was assumed to be small enough to allow approximation of a pure liquid composition in the F-layer. Comparison of our F-layer model to PREM results in a better fit to the observed travel time data. Comparison of normal mode eigenfrequencies from the two models shows subtle differences; therefore normal modes have been determined to be insensitive to the small-scale structure of the relatively thin F-layer

  14. Turbulent boundary-layer structure of flows over freshwater biofilms

    NASA Astrophysics Data System (ADS)

    Walker, J. M.; Sargison, J. E.; Henderson, A. D.

    2013-12-01

    The structure of the turbulent boundary-layer for flows over freshwater biofilms dominated by the diatom Tabellaria flocculosa was investigated. Biofilms were grown on large test plates under flow conditions in an Australian hydropower canal for periods up to 12 months. Velocity-profile measurements were obtained using LDV in a recirculating water tunnel for biofouled, smooth and artificially sandgrain roughened surfaces over a momentum thickness Reynolds number range of 3,000-8,000. Significant increases in skin friction coefficient of up to 160 % were measured over smooth-wall values. The effective roughnesses of the biofilms, k s, were significantly higher than their physical roughness measured using novel photogrammetry techniques and consisted of the physical roughness and a component due to the vibration of the biofilm mat. The biofilms displayed a k-type roughness function, and a logarithmic relationship was found between the roughness function and roughness Reynolds number based on the maximum peak-to-valley height of the biofilm, R t. The structure of the boundary layer adhered to Townsend's wall-similarity hypothesis even though the scale separation between the effective roughness height and the boundary-layer thickness was small. The biofouled velocity-defect profiles collapsed with smooth and sandgrain profiles in the outer region of the boundary layer. The Reynolds stresses and quadrant analysis also collapsed in the outer region of the boundary layer.

  15. Love waves in layered piezoelectric/piezomagnetic structures

    NASA Astrophysics Data System (ADS)

    Liu, Jin-xi; Fang, Dai-Ning; Wei, Wei-Yi; Zhao, Xiao-Fang

    2008-08-01

    The propagation of Love waves in layered structures is investigated for two cases: a piezomagnetic (PM) layer on a piezoelectric (PE) half-space and the reverse configuration. The dispersion relations are obtained in explicit form. The numerical examples are provided to illustrate the variations of the phase and group velocities versus the wavenumber for the combinations of different materials. The results show that: (1) the phase and group velocities initiate at the bulk shear wave velocity of the half-space medium and approach the bulk shear wave velocity of the layer with increasing wavenumber; (2) the influence of the magnetic permeabilities of PE materials on the phase velocity can be neglected; (3) for the layered medium consisting of a PM layer and a PE half-space, the properties of PE materials have a great influence on the phase and group velocities at lower wavenumber for the lowest mode. These findings are useful for PE/PM composite media or structures in the microwave technology.

  16. In situ processing of silicon carbide layer structures

    SciTech Connect

    Padture, N.P.; Pender, D.C.; Wuttiphan, S.; Lawn, B.R.

    1995-11-01

    A novel route to low-cost processing of silicon carbide (SiC) layer structures is described. The processing involves pressureless liquid-phase cosintering of compacted powder layers of SiC, containing alumina (Al{sub 2}O{sub 3}) and yttria (Y{sub 2}O{sub 3}) sintering additives to yield a yttrium aluminum garnet (YAG) second phase. By adjusting the {beta}:{alpha} SiC phase ratios in the individual starting powders, alternate layers with distinctly different microstructures are produced: (i) homogeneous microstructures, with fine equiaxed SiC grains, designed for high strength; and (ii) heterogeneous microstructures with coarse and elongate SiC grains, designed for high toughness. By virtue of the common SiC and YAG phases, the interlayer interfaces are chemically compatible and strongly bonded. Exploratory Hertzian indentation tests across a bilayer interface confirm the capacity of the tough heterogeneous layer to inhibit potentially dangerous cracks propagating through the homogeneous layer. The potential for application of this novel processing approach to other layer architectures and other ceramic systems is considered.

  17. 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

  18. 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:E00d05 10.1029/2009je003343 (2009). [4] Mangold, N. et al. Spectral and geological study of the sulfate-rich region of West Candor Chasma, Mars. Icarus 194, 519-543, doi:10.1016/j.icarus.2007.10.021 (2008). [5] Le Deit, L. et al. Morphology, stratigraphy, and mineralogical composition of a layered formation covering the plateaus around Valles Marineris, Mars: Implications for its geological history. Icarus 208, 684-703, doi:10.1016/j.icarus.2010.03.012 (2010). [6] Gendrin, A. et al. Suffates in martian layered terrains: the OMEGA/Mars Express view. Science 307, 1587-1591, doi:10.1126/science.1109087 (2005). [7] Bibring, J.-P. et al. Coupled Ferric Oxides and Sulfates on the Martian Surface. Science 317, 1206-1210, doi:10.1126/science.1144174 (2007). [8] Roach, L. H., Mustard, J. F., Lane, M. D., Bishop, J. L. & Murchie, S. L. Diagenetic haematite and sulfate assemblages in Valles Marineris. Icarus 207, 659-674, doi:10.1016/j.icarus.2009.11.029 (2010). [9] Andrews-Hanna, J. C. & Lewis, K. W. Early Mars hydrology: 2. Hydrological evolution in the Noachian and Hesperian epochs. Journal of Geophysical Research-Planets 116, doi:E02007 10.1029/2010je003709 (2011).

  19. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-02-01

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

  1. 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, h? silica, which can be viewed to be derived from the oxidation of silicene and it has intriguing atomic structure with reentrant bond angles in hexagons. It is a wide band gap semiconductor, which attains remarkable electromechanical properties showing geometrical changes under an external electric field. In particular, it is an auxetic metamaterial with a negative Poisson's ratio and has a high piezoelectric coefficient. While it can form stable bilayer and multilayer structures, its nanoribbons can show metallic or semiconducting behavior depending on their chirality. Coverage of dangling Si orbitals by foreign adatoms can attribute new functionalities to h? silica. In particular, Si(2)O(5), where Si atoms are saturated by oxygen atoms from top and bottom sides alternatingly can undergo a structural transformation to make silicatene, another stable, single layer structure of silica. PMID:24996101

  2. Electromagnetic Response of Layered Dielectric Structures to Pulsed Acoustical Action

    NASA Astrophysics Data System (ADS)

    Bespal'ko, A. A.; Lyukshin, B. A.; Utsyn, G. E.; Yavorovich, L. V.

    2015-08-01

    The process of elastic wave propagation in the inhomogeneous sample with the known stress-strength properties is numerically modeled. The stress intensity distribution over the sample having a defect is calculated for different moments of time. The calculated stress intensities are compared with the experimentally measured parameters of electromagnetic signals arising in the model layered system under mechanoelectrical transformations accompanying the acoustic pulse propagation. The influence of the layered structure on the amplitude of the electromagnetic response is demonstrated experimentally for a serpentinite rock sample under deterministic action of the acoustic pulse.

  3. 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

  4. ORIGINAL PAPER Genetic diversity and population structure in cultivated sunflower

    E-print Network

    Burke, John M.

    ORIGINAL PAPER Genetic diversity and population structure in cultivated sunflower and a comparison of the primary gene pool of sunflower (Helianthus annuus L.) based on a broad sampling of 433 cultivated accessions from North America and Europe, as well as a range-wide collection of 24 wild sunflower populations

  5. ORIGINAL PAPER Fire frequency and tree canopy structure influence plant

    E-print Network

    Thomas, David D.

    vascular plant species and for three plant functional groups: grasses, forbs, and woody plants. UnderstoryORIGINAL PAPER Fire frequency and tree canopy structure influence plant species diversity Disturbances and environmental heterogeneity are two factors thought to influence plant species diversity

  6. ORIGINAL PAPER Pityopus californicus: structural characteristics of seed

    E-print Network

    Massicotte, Hugues

    ORIGINAL PAPER Pityopus californicus: structural characteristics of seed and seedling development of the USA. Young embryos of P. californicus developed mycorrhizal associa- tions in seed packets that had been buried for up to 681 days, suggesting that seeds of P. californicus may require the presence

  7. ORIGINAL PAPER Strong genetic structure among populations of the invasive

    E-print Network

    Hoddle, Mark S.

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

  8. 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.

  9. Structural analysis of interior layered deposits in Northern Coprates Chasma, Mars

    NASA Astrophysics Data System (ADS)

    Fueten, F.; Racher, H.; Stesky, R.; MacKinnon, P.; Hauber, E.; McGuire, P. C.; Zegers, T.; Gwinner, K.

    2010-06-01

    Interior layered deposits within an embayment on the northern wall of Coprates Chasma in the Valles Marineris, Mars, are studied using HRSC, CTX, HiRISE and CRISM data. The layered material outcrops in three separate locations. The largest layered deposit within the embayment, a free standing central mound, has an approximate stratigraphic thickness of 2 km. Dip directions change along the central axis of this mound, which is also a zone of deformation. The surface texture of layers within this mound displays polygonal structures at HiRISE scale. By contrast, the western layered deposit abuts directly against the chasm wall and appears to have a relatively uneroded depositional surface approximately 600 m below the current top elevation of the central mound. A basement ridge, exposed by a landslide scar near the eastern portion of the area, is covered with layered material and shows downward displacement. We suggest that the entire embayment originated as a small ancestral basin. The displaced basement ridge is evidence of the early basin collapse. The central mound was most likely deposited on a wall rock spur. Deposition did not fill the basin evenly. The detection of hydrated sulfates attests to alteration or deposition by liquid water. Following an erosion event, which coincided with or postdated Valles Marineris formation, thin mesa-forming materials covered most of the area.

  10. Multiple-scattering theory for clean superconducting layered structures

    NASA Astrophysics Data System (ADS)

    Koperdraad, R. T. W.; Otadoy, R. E. S.; Blaauboer, M.; Lodder, A.

    2001-09-01

    An exact expression is derived for the matrix Green's function of a clean superconducting layered structure with an arbitrary number of interfaces. A multiple-scattering approach is employed, in which the interfaces act as the scattering centres. Some initial applications of the theory to systems with transverse dimensions which vary from narrow to wide are given. The local density of states is calculated for an SNS and for an SNSNS junction ('S' standing for a superconducting layer and 'N' for a normal layer). For certain critical transverse widths the exact theory shows remarkable features not seen in the Andreev approximation. If the gap function for the systems is calculated self-consistently it turns out that for transverse dimensions smaller than twenty per cent of the superconducting coherence length, superconductivity is suppressed.

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

    NASA Astrophysics Data System (ADS)

    Wang, Rui; Wang, Zhen-Gang

    2013-09-01

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

  12. 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.

  13. 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.

  14. Polymer layered silicate nanocomposites: Structure, morphology, and properties

    NASA Astrophysics Data System (ADS)

    Nawani, Pranav

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

  15. Branched integumental structures in Sinornithosaurus and the origin of feathers.

    PubMed

    Xu, X; Zhou, Z; Prum, R O

    2001-03-01

    The evolutionary origin of feathers has long been obscured because no morphological antecedents were known to the earliest, structurally modern feathers of Archaeopteryx. It has been proposed that the filamentous integumental appendages on several theropod dinosaurs are primitive feathers; but the homology between these filamentous structures and feathers has been disputed, and two taxa with true feathers (Caudipteryx and Protarchaeopteryx) have been proposed to be flightless birds. Confirmation of the theropod origin of feathers requires documentation of unambiguously feather-like structures in a clearly non-avian theropod. Here we describe our observations of the filamentous integumental appendages of the basal dromaeosaurid dinosaur Sinornithosaurus millenii, which indicate that they are compound structures composed of multiple filaments. Furthermore, these appendages exhibit two types of branching structure that are unique to avian feathers: filaments joined in a basal tuft, and filaments joined at their bases in series along a central filament. Combined with the independent phylogenetic evidence supporting the theropod ancestry of birds, these observations strongly corroborate the hypothesis that the integumental appendages of Sinornithosaurus are homologous with avian feathers. The plesiomorphic feathers of Sinornithosaurus also conform to the predictions of an independent, developmental model of the evolutionary origin of feathers. PMID:11242078

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

    SciTech Connect

    Palchik, N. A. Grigorieva, T. N.; Moroz, T. N.

    2013-03-15

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

  17. Novel exact surface wave solutions for layered structures

    NASA Astrophysics Data System (ADS)

    Kiselev, Aleksei P.; Ducasse, Eric; Deschamps, Marc; Darinskii, Alexander

    2007-08-01

    Novel exact solutions describing surface acoustic waves on general layered structures have been found by the method of variable separation. First, solutions have been constructed with plane wavefronts and involving polynomial dependence on lateral variables. Second, their inhomogeneous plane-wave analogues have been found. At last, beam-like solutions highly localized at large lateral distances in a given sector have also been considered. To cite this article: A.P. Kiselev et al., C. R. Mecanique 335 (2007).

  18. Layered hafnium phosphates. Synthesis, characterization, crystalline structure and intercalation behaviour

    NASA Astrophysics Data System (ADS)

    Suárez, M.; Barcina, L. M.; Llavona, R.; Rodríguez, J.

    1998-10-01

    This review compiles the recent investigations on layered hafnium phosphates in the ? and ? varieties. Their preparation, properties and crystalline structures are described. The behaviour of both compounds during the intercalation of n-alkylamines ( n=1-6) and the cyclic amines aniline, benzylamine, cyclohexylamine, piperidine, pyridine, n-methylpiperidine and 4-methylpiperidine, in the vapour and liquid phases, is reported. The formula of the intercalates and the estimation of the guests arrangement in the interlayer space is discussed.

  19. Site-specific electronic structure of bacterial surface protein layers

    NASA Astrophysics Data System (ADS)

    Vyalikh, D. V.; Kummer, K.; Kade, A.; Blüher, A.; Katzschner, B.; Mertig, M.; Molodtsov, S. L.

    2009-03-01

    We applied resonant photoemission and X-ray absorption spectroscopy for a detailed characterization of the valence electronic structure of the regular two-dimensional bacterial surface protein layer of Bacillus sphaericus NCTC 9602. Using this approach, we detected valence electron emission from specific chemical sites. In particular, it was found that electrons from the ? clouds of aromatic systems make large contributions to the highest occupied molecular orbitals.

  20. 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.

  1. 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.

  2. 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. PMID:26164251

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

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

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

  4. The origin of Heinrich layers: evidence from H2 for European precursor events

    NASA Astrophysics Data System (ADS)

    Scourse, James D.; Hall, Ian R.; McCave, I. Nicholas; Young, Jeremy R.; Sugdon, Claire

    2000-10-01

    Recent well-dated isotopic (Sr-Nd) fingerprinting of Heinrich layer ice-rafted detritus (IRD) on the European margin indicates supply from European ice sheets as precursors to Laurentide Ice Sheet (LIS) supply [F.E. Grousset et al., Geology 28 (2000) 123-126, H. Snoeckx et al., Mar. Geol. 158 (1999) 197-208]. These precursor events lead LIS input by up to 1.5 ka [F.E. Grousset et al., Geology 28 (2000) 123-126] and have been interpreted to indicate LIS collapse during Heinrich events stimulated by events originating on the European side of the Atlantic [F.E. Grousset et al., Geology 28 (2000) 123-126]. Such phasing of IRD supply from different sources within Heinrich layers therefore has implications for the origin and mechanics of Heinrich events. We present evidence here that the IRD comprising Heinrich layer 2 (H2; ˜20-21 14C ka BP) on the European continental margin contains detrital Campanian Upper Chalk deriving from bedrock sources eroded on the Celtic shelf by the British Ice Sheet (BIS) in addition to lithic material sourced from the LIS. High-resolution radiocarbon chronology indicates chalk grain deposition as discrete pulses both before and coincident with supply of LIS-sourced detritus. The specificity of the chalk fingerprint to the BIS enables a 700-1000 yr lag between the BIS and LIS events to be identified. This phasing indicates a more rapid response of the outlet lobes draining the smaller BIS than those draining the LIS and implicates external climatic forcing of Heinrich events. It is unlikely that this precursor event represents IRD event 18, the recently identified 1-2 ka IRD cycle event which immediately precedes H2, because the lag between precursor and main event is here less than 1.5 ka and because such pervasive periodicity is not apparent in European continental margin IRD records. The later synchroneity between the BIS and LIS input in H2 identifies glacio-eustatic sea-level rise associated with LIS discharges as a possible feedback mechanism causing destabilisation of ice streams elsewhere during Heinrich events.

  5. The role of groundwater in the origin of the indurated layered deposits of Arabia Terra, Mars

    NASA Astrophysics Data System (ADS)

    Andrews-Hanna, J. C.; Wiseman, S. M.; Arvidson, R. E.

    2008-12-01

    Indurated layered deposits of likely sedimentary origin are widely distributed across the Arabia Terra region of Mars. In situ observations by the MER Opportunity rover of one such deposit in Meridiani Planum have been interpreted to represent grains composed of dirty evaporites that have been extensively reworked by fluvial and aeolian processes in a playa environment and diagenetically modified by a fluctuating water table. Stratigraphic relationships, morphological similarities, and spectral evidence suggest a related origin for the many layered deposits throughout Arabia Terra. Isolated intra-crater deposits, erosional outliers, and pedestal craters suggest that the Arabia Terra deposits were once thicker and more widespread than their current extent. We investigate the origin of these sedimentary deposits using global and regional hydrological models, in which groundwater flow is driven by evaporation where the water table intersects the surface and redistribution of that water as low-latitude precipitation. These models predict focused groundwater upwelling and evaporation in Arabia Terra during the Late Noachian to Early Hesperian, driven by its unique topography relative to the adjacent southern highlands and northern lowlands. This hydrological cycle would have brought a steady flux of groundwater to the surface, which upon evaporation, would concentrate any dissolved solutes as a cementing salt that would indurate aeolian material and allow buildup of thick sedimentary deposits. Groundwater upwelling would first be limited to the large craters in the region, resulting in rapid sedimentary infilling by a combination of evaporites and evaporite-cemented clastic material. As the craters were filled, groundwater upwelling would spread out over broad regions of Arabia Terra, producing widespread deposits covering much of the inter-crater plains. The observed distribution and thickness of the deposits agrees with the predictions from the hydrological models. This work suggests that the extensive sedimentary deposits of Arabia Terra preserve the record of a Late Noachian-Early Hesperian global hydrological system, and a climate in which surface temperatures in the low latitudes were largely above the freezing point of water, allowing liquid precipitation to infiltrate the surface to recharge aquifers and drive continued groundwater flow.

  6. 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

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

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

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

  8. 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 ?( I) for 1; and R=0.0288 and wR=0.0727 using 2661 reflections with I>2 ?( 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.

  9. 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 ?( I) for 1; and R=0.0288 and wR=0.0727 using 2661 reflections with I>2 ?( 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.

  10. Boundary layer structure during sea breeze conditions at Ahtopol, Bulgaria

    NASA Astrophysics Data System (ADS)

    Barantiev, D.; Batchvarova, E.; Novitzky, M. A.

    2012-04-01

    Continuous sodar (Scintec MFAS) and ultrasonic anemometer (Typhoon - Obninsk make) measurements were initiated in summer 2008 at the meteorological observatory of Ahtopol at the Black Sea coast (south-east Bulgaria) under a Bulgarian-Russian collaborative programme. These observations of high resolution form the basis for studies of the atmospheric boundary layer turbulence and vertical structure at a coastal site. This sodar is unique in Bulgaria and provides the first continuous high resolution data on the wind profile up to 400 - 500 m above the ground. In addition, the continuous turbulence parameters monitoring allows atmospheric boundary studies needed for different applications. The meteorological observatory at Ahtopol is under development as a background atmospheric composition station in coastal area and the wind data are essential for the studies of gases exchange under breeze conditions. The measurements revealed quite different sea breeze seasons during the years 2008 to 2011 and within the individual seasons, a number of different sea breeze types were identified depending on the interaction of local and larger-scale forcing. In this study we investigate the turbulence parameters and the vertical structure of the boundary layer related to only to sea breeze conditions. We also study the wind profile within the first 400 - 500 m above the ground. For the surface layer, we test the free convection theory against the sodar observations.

  11. Magnetic structure of Tb-Fe films with an artificially layered structure

    SciTech Connect

    Yamauchi, K.; Habu, K.; Sato, N.

    1988-11-15

    The magnetic structure of Tb-Fe films with an artificially layered structure has been investigated by measuring the temperature dependence of the magnetization of the films. Ferrimagnetic coupling between Tb and Fe through the interface was explicitly observed up to about 9-A Tb and 10-A Fe layers. Films with thinner Tb and Fe layers than these thicknesses are composed of only ferrimagnetically coupled Tb-Fe regions. Films with thicker layers of Tb and Fe are composed of ferrimagnetically coupled Tb-Fe, ferromagnetic Fe, ferromagnetic Tb, and/or magnetically compensated Tb regions. The Tb-Fe films exhibit various temperature dependencies of the magnetization corresponding to these magnetic structures.

  12. Thin polymer-layer decorated, structure adjustable crystals of nanoparticles.

    PubMed

    Cao, Xue-Zheng; Duan, Zhi-Guang; Wang, Jun-Shu; Cui, Wei; Liu, Yong-Song; Wu, Chen-Xu

    2015-09-21

    Flattened polymer chain decorated crystals of nanoparticles (NPs) are observed for polymer-NP mixtures confined between two parallel substrates. In order to minimize the entropy loss, polymer chains instead of NPs aggregate at the substrate surfaces when the number of NPs is high enough to have the conformation of chains significantly disturbed. Increasing NP concentration to be much higher than that of polymer chains leads to an ordered arrangement of NPs in the central region, which are sandwiched between two thin layers of polymer chains. A scaling model regarding polymer chains consisting of packed correlation blobs is provided to clarify the physics mechanism behind the formation of thin polymer layer and the crystallization of NPs. The order structure of the crystallized NPs is shown to be switchable through an adjustment of the bulk concentrations of polymer chains and NPs. PMID:26268892

  13. Hierarchical fractal structure of perfect single-layer grapheme

    NASA Astrophysics Data System (ADS)

    Zhang, T.; Ding, K.

    2013-12-01

    The atomic lattice structure of perfect singlelayer graphene that can actually be regarded as a kind of hierarchical fractal structure from the perspective of fractal geometry was studied for the first time. Three novel and special discoveries on hierarchical fractal structure and sets were unveiled upon examination of the regular crystal lattices of the single-layer graphene. The interior fractaltype structure was discovered to be the fifth space-filling curve from physical realm. Two efficient methods for calculating the fractal dimension of this fresh member was also provided. The outer boundary curve had a fractal dimension equal to one, and a multi-fractal structure from a naturally existing material was found for the first time. A series of strict self-similar hexagons comprised a rotating fractal set. These hexagons slewed at a constant counterclockwise angle ? of 19.1° when observed from one level to the next higher level. From the perspective of fractal geometry, these pioneering discoveries added three new members to the existing regular fractal structures and sets. A fundamental example of a multi-fractal structure was also presented.

  14. An experimental study on the preparation of tochilinite-originated intercalation compounds comprised of Fe 1-xS host layers and various kinds of guest layers

    NASA Astrophysics Data System (ADS)

    Peng, Yiya; Xi, Guangcheng; Zhong, Chang; Wang, Linping; Lu, Jun; Sun, Ximeng; Zhu, Lu; Han, Qikun; Chen, Lin; Shi, Lei; Sun, Mei; Li, Qianrong; Yu, Min; Yin, Mingwen

    2009-08-01

    Tochilinite represents a mineral group of ordered mixed-layer structures containing alternating Fe 1-xS layers with mackinawite-like structure and metal hydroxide layers with Mg(OH) 2-like structure. In this article, we report the preparation of a series of tochilinite-originated (or Fe 1-xS-based) intercalation compounds (ICs). According to their preparation procedures, these ICs can be divided into four kinds. The first kind of IC was sodium tochilinite (Na-tochilinite), which was prepared by the hydrothermal reaction of metallic Fe particles with concentrated Na 2S·9H 2O aqueous solutions. The hydroxide layer of the Na-tochilinite was a mixed hydroxide of Na + ions along with a certain amount of Fe 2+ ions. When the hydroxide layer of the Na-tochilinite completely dissolved in aqueous solutions, a Fe-deficient mackinawite-like phase Fe 1-xS was obtained, which was probably an electron-deficient p-type conductor. The second kind of ICs was prepared by 'low-temperature direct intercalation in aqueous solutions, using Na-tochilinite as a parental precursor. When the Na-tochilinite was ultrasonicated in aqueous solutions containing Lewis basic complexing agents (like NH 3, N 2H 4, 2,2'-bipyridine (bipy), and 1,10-phenanthroline (phen)), the Na + ions of the Na-tochilinite were removed and the Lewis basic complexing agents entered the hydroxide layer of the Na-tochilinite and became coordinated with the Fe 2+ ions, and the second kind of ICs was thus produced. The second kind of ICs includes NH 3 IC, N 2H 4 IC, N 2H 4-NH 3 IC, [Fe(bipy) 3] 2+-containing IC and [Fe(phen) 3] 2+-containing IC. The third kind of ICs, which includes NH 3 IC, N 2H 4-NH 3 IC and N 2H 4-LiOH (NaOH) IC, was prepared by the hydrothermal reaction of metallic Fe particles with (NH 4) 2S aqueous solution, S (elemental) + N 2H 4·H 2O aqueous solution, and S + N 2H 4·H 2O + LiOH (NaOH) aqueous solution, respectively. The third kind of ICs has a close relationship with the second kind of ICs both in composition and structure. The fourth kind of ICs was prepared by the oxidation and reduction of some of the N 2H 4-containing ICs mentioned above, which include N 2H 2 (diazene or diimide) IC, N 2 (dinitrogen) IC and NH 3 IC. The N 2H 2 IC was prepared by mild air oxidation of the N 2H 4-LiOH IC. The N 2 IC was prepared by strong air oxidation of the N 2H 4-LiOH IC, however, we have not been able to separate the pure phase N 2 IC. Hydrothermal reduction of the N 2H 4 IC made by the direct intercalation method in strong reducing environment by H 2S + Fe (metal) led to the production of the NH 3 IC of the fourth kind of ICs. The NH 3 ICs prepared by the three methods had similar compositions and structures. As almost all the ICs reported in this paper were extremely sensitive both to air and to the electron beam, they were mainly characterized by XRD. The properties and interrelationships (or mutual transformations) of the Fe 1-xS-based ICs revealed novel chemistry occurring in the sub-nanoscopic space between the micrometer- to nanometer-sized electron-deficient Fe 1-xS layers. An important finding of this novel chemistry was that the Fe 1-xS-based ICs tended to oxidize or reduce the intercalated species when the redox state of their environments varied. The results of our experiments potentially have many cosmochemical implications. The most important implication is that our experimental results, along with previous studies, strongly suggested that some of the ammonium salts, ammonia and carbonates existing in the matrix of the CM carbonaceous chondrites may have been formed by abiotic reactions employing molecular nitrogen as the nitrogen source and carbon monoxide as the carbon source and iron sulfide and/or iron hydroxide as catalysts.

  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. Analysis of the structure of original research papers: an aid to writing original papers for publication.

    PubMed Central

    Skelton, J

    1994-01-01

    BACKGROUND. An increasing number of people involved in medicine are under pressure to publish research, but there is little understanding of how to describe structured writing. AIM. This paper aims to describe the structure of original research papers published in the British Journal of General Practice with a view to providing insight into the nature of such analyses, and particularly to help researchers and trainers to write and teach writing more successfully. METHOD. A sample of 50 original papers published in the Journal between January 1989 and March 1993 were examined. The papers were subjected to a form of 'move structure analysis', a technique used in applied linguistics; move structure analysis assigns a tentative function to a piece of text, and identifies words/phrases associated with it. To be recognized, moves thus identified had to occur in the same section of the paper in 65% of the corpus, and/or appear in the same order relative to other moves in 50%. RESULTS. Fifteen moves were identified, four in the introduction, three in the method, and four each in the results and discussion. These moves functioned, for example in the discussion, to state limitations and defend successes; describe achievements; contextualize procedures and findings; and offer recommendations. Frequency scores ranged from 66% to 100%, and order stability scores from 50% to 80%, with three moves being unordered. CONCLUSION. It is possible to derive from this study a template for structuring academic medical writing. This template may be built up from the exemplary quotations in the text, to provide assistance to educators and less experienced writers. PMID:7748634

  17. 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.

  18. 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.

  19. 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.

  20. Hybrid compounds with chain and layered structures formed by ?-alanine

    NASA Astrophysics Data System (ADS)

    Ghosh, Anupama; Dan, Meenakshi; Rao, C. N. R.

    2008-08-01

    Inorganic-organic hybrid compounds of the amino acid alanine have been prepared and characterized for the first time. Thus by the reaction of ?-alanine with copper salts, one-dimensional hybrid chain compounds of the formulae [Cu(CO 2CH 2CH 2NH 3)Cl 2], I, and [Cu(H 2O) 2(NH 3CH 2CH 2CO 2)][SO 4]·H 2O, II, and a two-dimensional layered compound [NH 4] 0.33[Cu 0.5(CO 2CH 2CH 2NH 2)Cl 0.33]·H 2O, III, have been obtained and their structures established by X-ray crystallography and other techniques. Hybrid chain alaninates of lead and strontium of the formulae [Pb(CO 2CH 2CH 2NH 3) 2(NO 3) 2], IV and [Sr(CO 2CH 2CH 2NH 3) 2(NO 3) 2], V have also been obtained by the reaction of the corresponding metal salts with alanine. The linear chain compounds, I, II, IV and V contain extended metal-X-metal (X = Cl or O) bonds and have the I 1O 0 type inorganic (I) and organic (O) connectivities. The layered compound III also has metal-X-metal bonds with I 2O 0 type connectivity. Interestingly, the zero-dimensional copper alaninate dimer of the composition [Cu 2(CO 2CH 2CH 2NH 3) 4Cl 2]·2Cl·H 2O can be transformed to the linear chain structure I or the layered structure III under mild conditions.

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

    SciTech Connect

    Jitianu, Mihaela; Gunness, Darren C.; Aboagye, Doreen E.; Zaharescu, Maria; Jitianu, Andrei

    2013-05-15

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

  2. Surface-plasmons lasing in double-graphene-layer structures

    SciTech Connect

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

    2014-01-28

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

  3. Origin and deformation of intra-salt sulphate layers: an example from the Dutch Zechstein (Late Permian)

    NASA Astrophysics Data System (ADS)

    Biehl, B. C.; Reuning, L.; Strozyk, F.; Kukla, P. A.

    2014-04-01

    From salt mine galleries and well data it is known that thick rock salt layers can contain anhydrite and carbonate layers with thicknesses on the millimetre to tens of metre scale. The relatively thick Zechstein 3 anhydrite-carbonate layer in the northern Netherlands has been studied previously using 3-D seismic data. Observations from geophysical well logs in this study reveal the presence of thin sulphate layers on the sub-seismic scale imbedded in the Zechstein 2 (Z2) salt. Core samples, thin sections, seismic data and geochemical measurements were used to determine the mineralogy and origin of one of these Z2 sulphate layers. Bromine analyses show that they mark a freshening event in the Z2 salt, which can be correlated over large distances in the northern Netherlands. Their core-calibrated log signature indicates that the Z2 sulphate layers consist either of pure anhydrite or of anhydrite and polyhalite. The mineralogy and thickness of the sulphate layers are interpreted to vary between synsedimentary morphologic lows (thin anhydrite-polyhalite couplets) and highs (thicker anhydrite layers). Such a combination of core observations and well log analysis is a powerful tool to detect lateral trends in evaporite mineralogy and to reconstruct the environmental setting of their formation. Salt internal geometries can further be used to distinguish between different deformation mechanisms. In our study area, the distribution of sulphate layers within the Z2 salt indicates that subjacent salt dissolution was not the dominant process leading to salt-related deformation.

  4. Layers

    NASA Astrophysics Data System (ADS)

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

    2014-09-01

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

  5. Effect of image charges on double layer structure and forces

    NASA Astrophysics Data System (ADS)

    Wang, Rui; Wang, Zhen-Gang

    2014-03-01

    The study of the electrical double layer lies at the heart of colloid and interface sciences. Here, we examine the electrical double layer structure and forces between two neutral or like-charged plates by accounting for the image charge effects under weak-coupling conditions. By treating the fluctuation effect on the ion distribution and free energy self-consistently and nonperturbatively, we show that the image charge interaction appears as part of the self-energy in the Boltzmann factor: there is no limiting condition for which Poisson-Boltzmann (PB) theory is valid, contrary to the general consensus in the community that PB theory is the exact theory in the weak coupling limit. For electrolyte solutions between two neutral plates, we show that depletion of the salt ions by the image charge repulsion results in short-range attractive and long-range repulsive forces. If cations and anions are of different valency, the asymmetric depletion leads to the formation of an induced electrical double layer. In comparison to a 1:1 electrolyte solution, both the attractive and the repulsive parts of the interaction are stronger for the 2:1 electrolyte solution. For two charged plates, the competition between the surface charge and the image charge effect can give rise to like-charge attraction and charge inversion. These results are in stark contrast with predictions from the PB theory.

  6. Structure measurements in a synthetic turbulent boundary layer

    NASA Astrophysics Data System (ADS)

    Arakeri, Jaywant H.

    1987-09-01

    Extensive hot-wire measurements have been made to determine the structure of the large eddy in a synthejc turbulent boundary layer on a flat-plate model. The experiments were carried out in a wind tunnel at a nominal free-stream velocity of 12 m/s. The synthetic turbulent boundary layer had a hexagonal pattern of eddies and a ratio of streamwise scale to spanwise scale of 3.2:1. The measured celerity of the large eddy was 84.2 percent of the free-stream velocity. There was some loss of coherence, but very little distortion, as the eddies moved downstream. Several mean properties of the synthetic boundary layer were found to agree quite well with the mean properties of a natural turbulent boundary layer at the same Reynolds number. The large eddy is composed of a pair of primary counter-rotating vortices about five [...] long in the streamwise direction and about one [...] apart in the spanwise direction, where [...] is the mean boundary-layer thickness. The sense of the primary pair is such as to pump fluid away from the wall in the region between the vortices. A secondary pair of counter-rotating streamwise vortices, having a sense opposite to that of the primary pair, is observed outside of and slightly downstream from the primary vortices. Both pairs of vortices extend across the full thickness of the boundary layer and are inclined at a shallow angle to the surface of the flat plate. The data show that the mean vorticity vectors are not tangential to the large-eddy vortices. In fact, the streamwise and normal vorticity components that signal the presence of the eddy are of the same order of magnitude. Definite signatures are obtained in terms of the mean skin-friction coefficient and the mean wake parameter averaged at constant phase. Velocities induced by the vortices are partly responsible for entrainment of irrotational fluid, for transport of momentum, for generation of Reynolds stresses, and for maintenance of streamwise and normal vorticity in the outer flow. A stretching mechanism is important in matching spanwise vorticity close to the wall to variations in turbulent shearing stress. Regions where the stretching term is large coincide with regions of large wall shearing stress and large turbulence production.

  7. Original Size and Shape of the Sudbury Structure

    NASA Technical Reports Server (NTRS)

    Lowman, P. D., Jr.

    1997-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2007-07-01

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

  9. 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

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

    PubMed

    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

  11. Polymer Structure and Dynamics in Polymer / Layered-Silicate Nanocomposites

    NASA Astrophysics Data System (ADS)

    Anastasiadis, Spiros H.

    2014-03-01

    Polymer/layered silicate nanocomposites are of particular interest among different nanohybrids because of their anticipated superior properties. Mixing polymers with layered inorganic materials can lead to three different types of structure, depending on the interactions between the constituents: phase separated, intercalated and exfoliated. Intercalated hybrids, where the polymer is confined within the inorganic galleries, can serve as model systems for the study of the static and dynamic properties of macromolecules in nano-confinement. We describe our recent efforts to elucidate the effects of severe confinement utilizing hydrophilic nanohybrids of PEO or hyperbranched polymers mixed with Na+-MMT. Intercalated hybrids with mono-, bi- and tri-layers of chains are obtained for all compositions covering the complete range from pure polymer to pure clay. Severe confinement influences significantly the structure of the polymer: the PEO chains intercalated within the inorganic galleries as well as those in close proximity to the outside walls are purely amorphous; it is only when there is significant excess polymer outside the completely filled galleries that the bulk polymer crystallinity is abruptly recovered. In contrast, when the inorganic is incorporated as silica nanoparticles, the crystallinity varies smoothly with composition whereas a population with a lower melting temperature near the inorganic surfaces is observed under strong confinement. The dynamics of the polymers confined within the galleries is probed by quasi-elastic neutron scattering and dielectric spectroscopy. The very local dynamics of the confined chains show similarities with those in bulk, whereas the segmental dynamics depend very strongly on the polymer/inorganic interactions varying from much faster to much slower or even frozen dynamics as the strength of the interactions increases. Part of this research was sponsored by the European Union (POLYCAT; grant agreement CP-IP 246095-2).

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

    E-print Network

    Sparks, Donald L.

    MnOx and dependence of the crystal structure of BioMnOx on solution chemistry. Introduction Mn-oxidizing and -reducingCation Effects on the Layer Structure of Biogenic Mn-Oxides M E N G Q I A N G Z H U , * M A T T H E(BioMnOx)andmayserveasoneofthemajorformation pathways for layered Mn-oxides in soils and sediments. The structure of Mn octahedral layers in layered Mn

  13. The Electronic Structure of Single-Layer Graphene

    NASA Astrophysics Data System (ADS)

    Siegel, David Alan

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

  14. Thematic Questions about Planetary Interiors Planetary interiors tend to be layered structures

    E-print Network

    Polly, David

    Differentiation of Earth's Interior Mercury Venus Mars Moon Earth core mantle unsorted layered Fe,Ni primitive crust coreInterior Structures of Planets Layered · Core, mantle, crust · Lithosphere, asthenosphere G302 Development · Differentiated into core, mantle and crust from either unsorted or layered protoplanet · Resultant structure

  15. Large Anisotropy of Electrical Properties in Layer-Structured In2Se3

    E-print Network

    Cui, Yi

    Large Anisotropy of Electrical Properties in Layer-Structured In2Se3 Nanowires Hailin Peng, Chong Layer-structured indium selenide (In2Se3) nanowires (NWs) have large anisotropy in both shape and bonding. In2Se3 NWs show two types of growth directions: [11-20] along the layers and [0001] perpendicular

  16. Long Range Transmission and Preservation of Single Crystal Structural Information by Interfacial Polycrystalline Layers

    NASA Astrophysics Data System (ADS)

    Distler, G. I.; Obronov, V. G.

    1971-02-01

    IT has already been established in this laboratory that the mechanism accounting for the long range transmission and preservation of structural information by amorphous inter-facial layers prepared on top of crystals is the thermoelectret1 or photoelectret2 mechanism. The charged elements of the real structure of the surfaces of crystal substrates produce in these layers a certain electret structure which copies the electrical relief of the underlying substrate surface. This electret structure which is frozen in interfacial layers is so stable that it persists even after the layers are detached from the crystals; the interfacial layers turn out to be electrical copies of the surfaces of solids, in other words.

  17. 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.

  18. 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.

  19. Homogeneous optical cloak constructed with uniform layered structures.

    PubMed

    Zhang, Jingjing; Liu, Liu; Luo, Yu; Zhang, Shuang; Mortensen, Niels Asger

    2011-04-25

    The prospect of rendering objects invisible has intrigued researchers for centuries. Transformation optics based invisibility cloak design is now bringing this goal from science fictions to reality and has already been demonstrated experimentally in microwave and optical frequencies. However, the majority of the invisibility cloaks reported so far have a spatially varying refractive index which requires complicated design processes. Besides, the size of the hidden object is usually small relative to that of the cloak device. Here we report the experimental realization of a homogenous invisibility cloak with a uniform silicon grating structure. The design strategy eliminates the need for spatial variation of the material index, and in terms of size it allows for a very large obstacle/cloak ratio. A broadband invisibility behavior has been verified at near-infrared frequencies, opening up new opportunities for using uniform layered medium to realize invisibility at any frequency ranges, where high-quality dielectrics are available. PMID:21643114

  20. Aeroelectric structures and turbulence in the atmospheric boundary layer

    NASA Astrophysics Data System (ADS)

    Anisimov, S. V.; Mareev, E. A.; Shikhova, N. M.; Shatalina, M. V.; Galichenko, S. V.; Zilitinkevich, S. S.

    2013-10-01

    Complex electrical measurements with the use of sodar data show that electric field pulsation analysis is useful for electrodynamics/turbulence monitoring under different conditions. In particular, the number of aeroelectric structures (AES) generated per hour is a convenient measure of the turbulence intensity. During convectively unstable periods, as many as 5-10 AES form per hour. Under stable conditions, AES occasionally form as well, indicating the appearance of occasional mixing events reflected in the electric field perturbations. AES magnitudes under stable conditions are relatively small, except in special cases such as high humidity and fog. The analysis of electric field (EF) spectra gives additional useful information on the parameters of the atmospheric boundary layer and its turbulence. A rather sharp change in the spectrum slope takes place in the vicinity of 0.02 Hz under stable conditions. The characteristic slope of the spectrum and its change are reproduced in a simple model of EF formation.

  1. Structure function scaling in a Re? = 250 turbulent mixing layer

    NASA Astrophysics Data System (ADS)

    Attili, Antonio; Bisetti, Fabrizio

    2011-12-01

    A highly resolved Direct Numerical Simulation of a spatially developing turbulent mixing layer is presented. In the fully developed region, the flow achieves a turbulent Reynolds number Re? = 250, high enough for a clear separation between large and dissipative scales, so for the presence of an inertial range. Structure functions have been calculated in the self-similar region using velocity time series and Taylor's frozen turbulence hypothesis. The Extended Self-Similarity (ESS) concept has been employed to evaluate relative scaling exponents. A wide range of scales with scaling exponents and intermittency levels equal to homogeneous isotropic turbulence has been identified. Moreover an additional scaling range exists for larger scales; it is characterized by smaller exponents, similar to the values reported in the literature for flows with strong shear.

  2. Structure of spontaneous periodic deformations in hybrid aligned nematic layers.

    PubMed

    Krzyza?ski, D; Derfel, G

    2001-02-01

    Periodic deformations, arising spontaneously in hybrid nematic layers were investigated numerically. So called splay stripes, which appear when the surface anchoring energy of the planar alignment was greater than that of the homeotropic alignment, were considered. Conical degeneration of the anchoring is assumed. The role of the layer thickness d and the anchoring strength W was studied by means of the dimensionless control parameter gamma=Wd/k(11) defined for each boundary. The saddle-splay elastic constant k(24) was varied within the limits given by general Ericksen inequalities. The director distributions were calculated. Two structures with different properties were distinguished: one for k(24)<0 (mode 1) and the other for k(24)>0 (mode 2). For given nematic liquid crystal parameters, mode 1 existed when gamma exceeds some critical value. Below this critical gamma, the director distortion decayed and the spatial period simultaneously diverged to infinity. As a result mode 1 disappeared and the homogeneously planar orientation was realized. The width of the stripes also increased infinitely for high gamma. No upper limit of the gamma range in which mode 1 could exist was found. Mode 2 existed for gamma ranging from 0 to a certain critical value. Above this limit the periodic structure was replaced by the homogeneous hybrid alignment as a consequence of an infinite increase of the stripes' width. When k(24)>0 was sufficiently small, the gamma range was bounded from below, and a homogeneously planar orientation appeared for low gamma. The visibility of the stripes between crossed polarizers was estimated by calculations of light transmission. In general, the stripes for k(24)<0 turned out to be more distinct than that for k(24)>0. PMID:11308505

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

    SciTech Connect

    Kevin Jerome Sutherland

    2001-05-01

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

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

    SciTech Connect

    Kevin Jerome Sutherland

    2001-06-27

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

  5. 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 streamwise spatial POD solutions which isolate the growth of the primary and secondary instability mechanisms in the first and second modes, respectively. Temporal evolutions of dominant POD modes in all measured fields are calculated. These scalar POD coefficients contain the integrated characteristics of the entire field, greatly reducing the amount of data to characterize the instantaneous field. These modes may then be used to train future flow control algorithms based on neural networks.

  6. Corrosion detection in multi-layered rotocraft structures

    SciTech Connect

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

    2000-04-25

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

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

    DOEpatents

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

    2005-07-26

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

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

    SciTech Connect

    Pai, Chi-Feng; Nguyen, Minh-Hai; Vilela-Leão, Luis Henrique; Buhrman, R. A.; Belvin, Carina; Ralph, D. C.

    2014-02-24

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

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

    SciTech Connect

    Chumak, O. V.

    2013-08-15

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

  10. 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.

  11. Coupling effect between two adjacent chiral structure layers

    E-print Network

    Soukoulis, Costas

    Center, Department of Physics, and Department of Electrical and Electronics Engineering, Bilkent metallic cross-wires can produce giant optical activity. When this single chiral layer is stacked layer by layer in order to build a thick chiral metamaterial, strong coupling effects are found between the two

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

    NASA Astrophysics Data System (ADS)

    Chapman, M. G.; Kneissl, T.

    2011-12-01

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

  13. High Weissenberg number boundary layer structures for UCM J.D. Evans #

    E-print Network

    Bath, University of

    High Weissenberg number boundary layer structures for UCM fluids J.D. Evans # Department for the upper convected Maxwell (UCM) model. One is a single layer structure previously noted by Renardy [7 the main dominant balances that occur for the UCM equations near solid boundaries. For each structure

  14. 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

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

    SciTech Connect

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

    2014-01-07

    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.

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

    PubMed

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

    2015-07-01

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

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

    PubMed

    Katyal, Divya; Kant, Rama

    2015-04-01

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

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

    NASA Astrophysics Data System (ADS)

    Katyal, Divya; Kant, Rama

    2015-04-01

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

  19. Crustal Structure of Salton Trough using Deformable Layer Tomography

    NASA Astrophysics Data System (ADS)

    Yuan, F.

    2012-12-01

    Salton Trough is an important geologic structure to understand the active rift between Imperial Fault and San Andreas Fault. To determine the underground geometry of Salton Trough and its nearby faults, we analyzed seismic phase data recorded by Southern California Earthquake Data Center (SCEDC). Both 2-D and 3-D models have been made to refine the velocity model so as to determine the basin and moho geometry beneath Salton Trough region. Here three inline and five cross-line velocity profiles were built by using 2D Deformable Layer Tomography (DLT) method. From these 2D profiles, we can see that the velocity gradient is very small in the low velocity zone. The low velocity anomaly can be detected beneath the axis of the Salton Trough around the depth of 19-21 km, and the relatively high velocity can be seen beneath the San Andreas faults. Within 100*150*40 km3 model volume, 90,180 P-wave and S-wave first arrival picks from 27,663 local events (from 2001 to 2012), which were obtained from 44 stations, were used to build 3D seismic velocity model of the crust. During the iterations of velocity updating, full 3-D ray tracing is implemented. From these 3-D velocity models with different sizes of grids, low velocity anomalies are present under the southwest of Salton Sea, while high velocity zone is present across Southern San Andreas Fault throughout all the depths. Profiles from 2-D velocity models compared to 3-D velocity models show similar geometry. 3-D crustal structure, which is determined from 3-D DLT, helps to better understand the divergent boundary between the North American and the Pacific tectonic plates

  20. Effect of thin oxide layers incorporated in spin valve structures

    NASA Astrophysics Data System (ADS)

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

    2001-06-01

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

  1. Structure and dynamics of a layer of sedimented particles

    NASA Astrophysics Data System (ADS)

    Sonn-Segev, Adar; B?awzdziewicz, Jerzy; Wajnryb, Eligiusz; Ekiel-Je?ewska, Maria L.; Diamant, Haim; Roichman, Yael

    2015-08-01

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

  2. Structure and dynamics of a layer of sedimented particles.

    PubMed

    Sonn-Segev, Adar; B?awzdziewicz, Jerzy; Wajnryb, Eligiusz; Ekiel-Je?ewska, Maria L; Diamant, Haim; Roichman, Yael

    2015-08-21

    We investigate experimentally and theoretically thin layers of colloid particles held adjacent to a solid substrate by gravity. Epifluorescence, confocal, and holographic microscopy, combined with Monte Carlo and hydrodynamic simulations, are applied to infer the height distribution function of particles above the surface, and their diffusion coefficient parallel to it. As the particle area fraction is increased, the height distribution becomes bimodal, indicating the formation of a distinct second layer. In our theory, we treat the suspension as a series of weakly coupled quasi-two-dimensional layers in equilibrium with respect to particle exchange. We experimentally, numerically, and theoretically study the changing occupancies of the layers as the area fraction is increased. The decrease of the particle diffusion coefficient with concentration is found to be weakened by the layering. We demonstrate that particle polydispersity strongly affects the properties of the sedimented layer, because of particle size segregation due to gravity. PMID:26298145

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

    E-print Network

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

    2015-04-13

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

  4. 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

  5. Inverse scattering of two-dimensional photonic structures by layer stripping

    NASA Astrophysics Data System (ADS)

    Hatlo Andresen, Marte P.; Krogstad, Harald E.; Skaar, Johannes

    2011-04-01

    Design and reconstruction of 2d and 3d photonic structures are usually carried out by forward simulations combined with optimization or intuition. Reconstruction by means of layer-stripping has been applied in seismic processing as well as in design and characterization of 1d photonic structures such as fiber Bragg gratings. Layer-stripping is based on causality, where the earliest scattered light is used to recover the structure layer-by-layer. Our set-up is a 2d layered nonmagnetic structure probed by plane polarized harmonic waves entering normal to the layers. It is assumed that the dielectric permittivity in each layer only varies orthogonal to the polarization. Based on obtained reflectance data covering a suitable frequency interval, time-localized pulse data are synthesized and applied to reconstruct the refractive index profile in the leftmost layer by identifying the local, time-domain Fresnel reflection at each point. Once the first layer is known, its impact on the reflectance data is stripped off, and the procedure repeated for the next layer. Through numerical simulations it will be demonstrated that it is possible to reconstruct structures consisting of several layers. The impact of evanescent modes and limited bandwidth is discussed.

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

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

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

  7. Electron microscope studies of aerosol layers with likely Kuwaiti origins over Laramie, Wyoming during spring 1991

    NASA Astrophysics Data System (ADS)

    Sheridan, Patrick J.; Schnell, Russell C.; Hofmann, David J.; Harris, Joyce M.; Deshler, Terry

    1992-02-01

    Upper tropospheric aerosols observed in spring 1991 over Laramie, Wyoming, were sampled using balloon-borne cascade impactors. Three impactor samples were collected; two were in upper tropospheric aerosol layers and one was collected at the same altitude in cleaner, “background” upper tropospheric air. Optical particle counters measured concentrations of particles with radii ? 0.15 ?m in the layers which were increased 5-10 times over what is normally observed at these altitudes. Electron microscope analyses showed acidic and neutralized sulfate particles to be the dominant aerosol constituents in these layers, although carbonaceous soot aggregates and crustal dust particles were also found. The morphology and elemental composition of these particles closely resembled particles collected in the large mixed smoke plume of the Kuwaiti oil fires. Meteorological analyses showed favorable transport conditions from the Middle East to the continental U.S. when layers were present over Wyoming, and less than ideal conditions when the layers were absent. Based on these microanalytical results and the corroborating meteorological and air trajectory analyses, the most likely source of these aerosol layers is the oil fires in Kuwait.

  8. Long range transmission of structural information through disordered interfacial layers

    NASA Astrophysics Data System (ADS)

    Distler, G. I.

    1971-05-01

    Evidence is provided that epitaxial overgrowth of anthraquinone through interfacial polycrystalline ZnO layers on top of NaCl crystals persists up to ZnO film thicknesses of ?230 Å. Oriented crystallization of anthraquinone takes place on the contact side of ZnO films, stripped from NaCl crystals. The "memory" of the ZnO layers can be annihilated by exposure to light. Epitaxy on the surface of interfacial layers is explained in terms of the photoelectret mechanism, by which information is transmitted through interfacial layers.

  9. The Structure of Catalyst Layers and Cell Performance in Proton Exchange Membrane Fuel Cells

    NASA Astrophysics Data System (ADS)

    Inoue, Hiroyuki; Daiguji, Hirofumi; Hihara, Eiji

    A catalyst layer is one of the key elements in polymer electrolyte membrane fuel cells (PEMFC). Improvements in the performance of a membrane electrode assembly (MEA) for PEMFC are much influenced by an electrochemically active surface area in a catalyst layer. But the relation between the structure of a catalyst layer and the cell performance has not been clarified yet. In the present study, catalyst layers with different structure and composition were fabricated, and the structural properties of catalyst layers, such as thickness and roughness, and the polarization curves were measured. The experimental results suggested that there is an optimum mass ratio of electrolyte in a catalyst layer for the cell performance, and the thickness and roughness of a catalyst layer change significantly at the optimum mass ratio.

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

    NASA Astrophysics Data System (ADS)

    Day, J. M.; Pearson, D.

    2013-12-01

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

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

    SciTech Connect

    Akhtar, N.; Mahmood, S.

    2011-11-15

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

  12. POTTY ET AL. Simulation of Boundary Layer Structure over the Indian Summer Monsoon Trough

    E-print Network

    Raman, Sethu

    POTTY ET AL. Simulation of Boundary Layer Structure over the Indian Summer Monsoon Trough during The planetary boundary layer (PBL) structure over the Indian summer monsoon trough region has been simulated using a regional numerical model during the passage of a monsoon depression along the monsoon trough

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

    E-print Network

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

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

    E-print Network

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

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

    E-print Network

    Newman, David

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

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

    SciTech Connect

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

    2014-10-15

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

  17. 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.

  18. Stratigraphy, Structure, and Origin; A Geophysical Survey of the Mendeleev Ridge

    NASA Astrophysics Data System (ADS)

    Dove, D.; Coakley, B.; Hopper, J.

    2006-12-01

    The Mendeleev Ridge is a broad, aseismic ridge that extends from the Siberian Shelf into the central Arctic Ocean. While it is continuous with the Alpha Ridge and is inferred to be an oceanic plateau, it may have had a distinct and separate history. The origin of the Mendeleev ridge has only rarely been visited and, as a result, understanding the history of this region has largely been based on the presumption of a common origin for both features. In late summer 2005, a geophysical survey was conducted from USCGC Healy over the Mendeleev Ridge as part of a trans-arctic crossing. During this survey ~730 km of seismic reflection data was recovered over the ridge along with co-registered gravity and bathymetry data and seismic refraction profiles. The seismic source was two 250 cu in G-guns. The streamer length was limited by ice conditions to 300 meters. Wear and tear caused by towing the streamer through the ice pack eliminated hydrophones, so the number of active channels ranged from 24 to as few as 11. The seismic reflection data requires significant trace editing to eliminate random electrical noise and frequency-wave number filtering to eliminate low velocity noise caused by the streamer traveling through heavy ice. After trace editing the data are stacked and migrated with constant water velocity. Stacking velocities are used as input into initial ray tracing models. Derived boundary velocities from ray tracing models will be reapplied to the migration of reflection data and are converted through empirical relationships into densities, and used as input into gravity models. Brute stacked reflection images of the Mendeleev Ridge reveal pervasive extensional faulting of the basement and lower sediment layers, and a continuous, undeformed pelagic sediment layer mantling the ridge, indicative of recent tectonic inactivity. The age of the unconformity underlying this layer should date the end of significant deformation of the Alpha and Mendeleev Ridges. Consistency of modeled seismic velocities from the upper basement will provide some insight into the nature of the crustal material. Upper basement velocities estimated from the sonobuoy data range from 3.7-5.0 km/s, suggestive of a heterogeneous upper crust. Initial gravity models suggest that much of the amplitude variation over the Mendeleev Ridge is accommodated by invoking a single, continuous density layer for the crust. Future work will include: developing a structural map of the Mendeleev ridge as well as the refining of both the ray-tracing and gravity modeling in an attempt to better understand the crustal style of the ridge.

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

  20. 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.

  1. On the Impact Origin of the Anomalous "Blockhorizont" Layer in Eastern Switzerland

    NASA Astrophysics Data System (ADS)

    Alwmark, C.; Ferrière, L.; Hofmann, B. A.; Holm-Alwmark, S.; Meier, M. M. M.

    2015-09-01

    Here we confirm the presence of shocked quartz grains, by measurements and indexing of PDFs, in the so-called "Blockhorizont", a 10–15 cm thick anomalous layer situated in Miocene Upper Freshwater Molasse in the North Alpine foreland basin.

  2. Structure of the Es-layer during a solar eclipse.

    NASA Astrophysics Data System (ADS)

    Kardashev, Yu.; Gorbunova, T. A.

    1990-06-01

    The parameters of the Es-layer measured during an annular solar eclipse over Ashkhabad (38°N, 58°E) on April 29, 1976, are studied by spectral analysis. Additional maxima appear in the power spectra compared to a control period during the eclipse, while the spectral density levels are also strongly elevated. It is assumed that these spectral variations in the parameters of the Es-layer are caused by gravitational waves generated by the solar eclipse.

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

    SciTech Connect

    Campbell; Christian X. , Morrison; Jay A.

    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.

  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. Effect of thin oxide layers incorporated in spin valve structures

    SciTech Connect

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

    2001-06-01

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

  6. Origins.

    ERIC Educational Resources Information Center

    Online-Offline, 1999

    1999-01-01

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

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

    E-print Network

    Conway, Zana Kate

    2007-06-25

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

  8. 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

    2015-10-14

    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. PMID:26431263

  9. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2013-10-01

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

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

    NASA Astrophysics Data System (ADS)

    Hassan, J.; Bergman, J. P.

    2009-06-01

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

  12. The effect of adhesive layers on the fracture of laminated structures

    NASA Technical Reports Server (NTRS)

    Gecit, M. R.; Erdogan, F.

    1978-01-01

    The effect of the thickness and the elastic properties of the adhesive layers in laminated structures is considered. The structure is assumed to consist of two sets of periodically arranged dissimilar layers which may contain cracks perpendicular to the interfaces. The crack problem is solved under the assumption of plane strain or generalized plane stress and by using two different models for the adhesive layers. In the first model the adhesive layer is approximated by a combination of tensile and shear springs. In the second the adhesive layer is considered to be an elastic continuum, hence involving no approximating assumptions. The results regarding the stress intensity and stress concentration factors obtained from these two models and that found by ignoring the adhesive layers are presented and some comparisons are made.

  13. 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

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

    NASA Astrophysics Data System (ADS)

    Tan, Chaoliang; Zhang, Hua

    2015-08-01

    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.

  15. Direct Structure Determination of Multilayered Membrane-Type Systems Which Contain Fluid Layers

    PubMed Central

    Worthington, C. R.; King, G. I.; McIntosh, T. J.

    1973-01-01

    The theory of direct methods of structure analysis in the case of multilayered membrane-type systems which contain fluid layers is described. Diffraction formulas for this kind of analysis are derived. Deconvolution methods are used when the centrosymmetrical unit cells contain wide fluid layers. When the membrane systems contain narrow fluid layers, other direct methods are used. These direct methods involve computing either the Fourier series representations or the sampling theorem expressions. PMID:4704487

  16. ORIGINAL PAPER Analysis of subcellular surface structure, function

    E-print Network

    Bielefeld, Universität

    , the subcellular surface structure of living bacteria (Corynebacterium glutamicum) was investigated with atomic Single cell analysis at the subcellular level gives quantitative information from a structural mechanisms of specific interaction, binding kinetics and the interplay of genomic information and functional

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

    NASA Astrophysics Data System (ADS)

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

    2014-09-01

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

  18. 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.

  19. Vapor Solid Growth of One-Dimensional Layer-Structured Gallium

    E-print Network

    Zhou, Chongwu

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

  20. Microstructural characterisation of a prototype layer structure for a GaN-based photonic crystal cavity

    NASA Astrophysics Data System (ADS)

    El-Ella, H. W. A. R.; Sadler, T. C.; Kappers, M. J.; Oliver, R. A.

    2010-02-01

    A semiconductor multilayer consisting of an n-type GaN/sapphire pseudo-substrate with a double sacrificial layer (20 nm of InGaN and 20 nm of InAlN) and a GaN cavity structure on top incorporating an InGaN quantum dot active layer was grown. Atomic force microscopy (AFM) was used to measure the morphology of the upper surface of each layer of similar test structures and to assess the morphological evolution of the full structure during its growth. Transmission electron microscopy (TEM) was also used to assess defect incorporation into the structure. AFM showed that the incorporation of a double sacrificial layer was observed to have no detrimental affect on either the formation of the quantum dots, or the morphology of the top GaN capping layer. TEM highlighted the occurrence of threading dislocations propagating through the sacrificial layers into the capping GaN layer, but did not resolve the occurrence of defect generation in the sacrificial layers.

  1. Structural Transition in Layered As1-xPx Compounds: A Computational Study

    E-print Network

    Tománek, David

    of group V layered semiconductors, we propose to form in-layer 2D heterostructures of black phosphorus black phosphorus and pure gray arsenic monolayers differ in their equilibrium structure, we predict such as black phosphorus,12 with the designation A17 or -P, and gray arsenic,4 with the designation A7 or -As.13

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

    NASA Astrophysics Data System (ADS)

    Cruz, G. Gonzalez de la

    2015-07-01

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

  3. 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.

  4. 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%.

  5. 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.

  6. Radiation effects in strained-layer superlattice (SLS) structures

    SciTech Connect

    Barnes, C.E.; Samara, G.A.; Biefeld, R.M.; Zipperian, T.E.; Osbourn, G.C.

    1984-01-01

    The effects of gamma and neutron irradiation on GaP/GaAsP strained-layer superlattices (SLS's) have been studied and compared with results on similar non-SLS alloys. The carrier removal rate was significantly greater in the non-SLS samples for both types of radiation. Gamma irradiation resulted in layer-dependent removal rates which produced oscillations in the doping profile. Gamma-induced introduction rates of two prominent traps were the same in the various SLS samples, and in the non-SLS alloy. Thermal annealing was also similar in all the samples with the shallower (0.3 eV) trap recovering sharply in a stage at 175/sup 0/C. This was accompanied by a disappearance of the carrier removal oscillations at a somewhat higher annealing temperature. In contrast, the degree of recombination-enhanced annealing, and its variation with applied hydrostatic pressure, was strongly dependent on sample characteristics. This type of recovery was much stronger in the non-SLS samples, and was dependent on the layer thicknesses in the SLS samples. Hydrostatic pressure was found to enhance this process in the non-SLS samples, but had no significant effect on recombination-enhanced annealing in the SLS samples.

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

    E-print Network

    Sadoway, Donald Robert

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

  8. 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.

  9. Tunable THz surface plasmon polariton based on a topological insulator/layered superconductor hybrid structure

    E-print Network

    Li, Mingda

    We theoretically investigate the surface plasmon polariton (SPP) at the interface between a three-dimensional strong topological insulator (TI) and a layered superconductor/magnetic insulator structure, within the random ...

  10. Bias-dependent molecular-level structure of electrical double layer in ionic liquid on graphite

    SciTech Connect

    Black, Jennifer M; Walters, Deron; Labuda, Aleksander; Feng, Guang; Hillesheim, Patrick C; Dai, Sheng; Cummings, Peter T; Kalinin, Sergei V; Proksch, Roger; Balke, Nina

    2013-01-01

    Bias-dependent structure of electrochemical double layers at liquid-solid interfaces underpin a multitude of phenomena in virtually all areas of scientific enquiry ranging from energy storage and conversion systems, biology, to geophysics and geochemistry. Here we report the bias-evolution of the electric double layer structure of an ionic liquid on highly ordered pyrolytic graphite as a model system for carbon-based electrodes for electrochemical supercapacitors measured by atomic force microscopy. Matching the observed structures to molecular dynamics simulations allows us to resolve steric effects due to cation and anion layers. We observe reconfiguration under applied bias and the orientational transitions in the Stern layer. The synergy between molecular dynamics simulation and experiment provides a comprehensive picture of structural phenomena and long- and short range interactions. This insight will improve understanding of the mechanism of charge storage in electrochemical capacitors on a molecular level which can be used to enhance their electrochemical performance.

  11. Behavior of Turbulent Structures within a Mach 5 Mechanically Distorted Boundary Layer 

    E-print Network

    Peltier, Scott Jacob

    2013-08-05

    for the modified turbulent stresses present in mechanically distorted boundary layers. This is achieved by measuring the effects of the mechanical distortions upon the distribution, population, size, orientation, and energy content of the turbulent structures...

  12. Fluorescence enhancement by a photonic crystal with a nanorod-structured high index layer

    E-print Network

    Cunningham, Brian

    -dimensional photonic crystal slab incorporating a nanorod-structured TiO2 high index layer. The photonic crystal emission and the highly porous TiO2 film, not only increases the surface area of the device but more

  13. 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.

  14. Fabrication and properties of silicene and silicene-graphene layered structures on Ir (111)

    NASA Astrophysics Data System (ADS)

    Meng, Lei; Wang, Ye-Liang; Zhang, Li-Zhi; Du, Shi-Xuan; Gao, Hong-Jun

    2015-08-01

    Silicene, a two-dimensional (2D) honeycomb structure similar to graphene, has been successfully fabricated on various substrates. This work will mainly review the syntheses and the corresponding properties of silicene and silicene-graphene layered structures on Ir (111) substrates. For silicene on Ir (111), the buckled silicene/ Ir (111) configuration and its electronic structure are fully discussed. For silicene-graphene layered structures, silicene layer can be constructed underneath graphene layer by an intercalation method. These results indicate the possibility of integrating silicene with graphene and may link up with potential applications in nanoelectronics and related areas. Project supported by the National Basic Research Program of China (Grant Nos. 2013CBA01600 and 2011CB932700), the National Natural Science Foundation of China (Grant Nos. 61222112, 61390501, 51325204, 11334006, and 61306114), the Science Fund from Chinese Academy of Sciences (Grant Nos. 1731300500015 and XDB07030100), and the Fundamental Research Funds for the Central Universities, China.

  15. Exploring the origin of ultralow thermal conductivity in layered BiOCuSe

    NASA Astrophysics Data System (ADS)

    Saha, S. K.

    2015-07-01

    Using first-principles density functional theory calculations, a systematic study of the lattice dynamics and related (e.g., dielectric and anharmonic) properties of BiOCuSe (bismuth-copper oxyselenide), along with a comparison with its isostructural analog LaOCuSe, is performed to find the origin of the ultralow thermal conductivity ? in BiOCuSe. From the marked differences in some of these properties of the two materials, the reasons why BiOCuSe is a better thermal insulator than LaOCuSe are elucidated. For this class of oxychalcogenide thermoelectrics, phonon frequencies with symmetries, characters, spectroscopic activities, displacement patterns, and pressure coefficients of different zone-center modes, dielectric constants, dynamical charges, and phonon and Grüneisen dispersions are also determined.

  16. 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.

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

    PubMed

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

    2015-01-01

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

  18. 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.

  19. Inner plasma structure of the low-latitude reconnection layer Q.-H. Zhang,1

    E-print Network

    Lockwood, Mike

    Inner plasma structure of the low-latitude reconnection layer Q.-H. Zhang,1 M. W. Dunlop,2,3 M. Lockwood,2,4 B. Lavraud,5 Y. V. Bogdanova,6 H. Hasegawa,7 H.-G. Yang,1 R.-Y. Liu,1 H.-Q. Hu,1 B.-C. Zhang,1 electrons at the magnetopause current layer. Citation: Zhang, Q.-H., et al. (2012), Inner plasma structure

  20. Structural Origins of Aminoglycoside Specificity for Prokaryotic Ribosomes

    E-print Network

    Puglisi, Joseph

    paromomycin and gentamicin C1a were determined previously. Here, the structure of a eukaryotic decoding region., 1998), bound to paromomycin (Fourmy et al., 1996), and bound to gentamicin C1a (Yoshizawa et al., 1998, creates a pocket for ring I of par- omomycin (Figure 2) or gentamicin. The structures of the two RNA

  1. 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.

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

    PubMed

    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

  3. 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

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

    PubMed

    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

  5. 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

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

    NASA Astrophysics Data System (ADS)

    Karampudi, Naga Bhushana Rao; Bahadur, Ranjit Prasad

    2015-11-01

    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.

  7. Enhanced detectability of community structure in multilayer networks through layer aggregation

    E-print Network

    Dane Taylor; Saray Shai; Natalie Stanley; Peter J. Mucha

    2015-11-17

    Community detection is a central pursuit for understanding the structure and function of biological, social and technological networks, and it is important to understand the fundamental limitations on detectability. Many systems are naturally represented by a multilayer network in which edges exist in multiple layers that encode different--but potentially related--types of interactions. Using random matrix theory for stochastic block models, we analyze detectability limitations for multilayer networks and find that by aggregating together similar layers, it is possible to identify structure that is undetectable in a single layer. We explore this phenomenon for several aggregation methods including summation of the layers' adjacency matrices, for which detectability limit vanishes with increasing number of layers, L, decaying as O(L^{-1/2}). Interestingly, we find a similar scaling behavior when the summation is thresholded at an optimal value, supporting the common--but not well understood--practice of thresholding data matrices to obtain sparse network representations.

  8. Enhanced detectability of community structure in multilayer networks through layer aggregation

    E-print Network

    Taylor, Dane; Stanley, Natalie; Mucha, Peter J

    2015-01-01

    Community detection is a central pursuit for understanding the structure and function of biological, social and technological networks, and it is important to understand the fundamental limitations on detectability. Many systems are naturally represented by a multilayer network in which edges exist in multiple layers that encode different--but potentially related--types of interactions. Using random matrix theory for stochastic block models, we analyze detectability limitations for multilayer networks and find that by aggregating together similar layers, it is possible to identify structure that is undetectable in a single layer. We explore this phenomenon for several aggregation methods including summation of the layers' adjacency matrices, for which detectability limit vanishes with increasing number of layers, L, decaying as O(L^{-1/2}). Interestingly, we find a similar scaling behavior when the summation is thresholded at an optimal value, supporting the common--but not well understood--practice of thresh...

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

    SciTech Connect

    Ng, A.; Liu, X.; Sun, Y. C.; Djuriši?, 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.

  10. 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.

  11. Origin of the 2.45 eV luminescence band observed in ZnO epitaxial layers grown on c-plane sapphire by chemical vapour deposition

    NASA Astrophysics Data System (ADS)

    Saroj, R. K.; Dhar, S.

    2014-12-01

    Zinc oxide epitaxial layers have been grown on c-plane sapphire substrates by the chemical vapour deposition (CVD) technique. A structural study shows (0001)-oriented films with good crystalline quality. The temperature and excitation power dependence of the photoluminescence (PL) characteristics of these layers is studied as a function of various growth parameters, such as the growth temperature, oxygen flow rate and Zn flux, which suggest that the origin of the broad visible luminescence (VL), which peaks at 2.45 eV, is the transition between the conduction band and the Zn vacancy acceptor states. A bound excitonic transition observed at 3.32 eV in low temperature PL has been identified as an exciton bound to the neutral Zn vacancy. Our study also reveals the involvement of two activation processes in the dynamics of VL, which has been explained in terms of the fluctuation of the capture barrier height for the holes trapped in Zn vacancy acceptors. The fluctuation, which might be a result of the inhomogeneous distribution of Zn vacancies, is found to be associated with an average height of 7 and 90 meV, respectively, for the local and global maxima.

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

    PubMed

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

    2013-09-11

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

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. Origin of structure in the universe: quantum cosmology reconsidered

    NASA Astrophysics Data System (ADS)

    Anderson, Edward

    2015-09-01

    Based on a more careful canonical analysis, we motivate a reduced quantization—in the sense of superspace quantization—of slightly inhomogeneous cosmology in place of the Dirac quantization in the existing literature, and provide it in the vacuum case. This is attained through consideration of configuration space geometries at various levels of reduction. Some of these have the good fortunate of being flat. Geometrically natural coordinates for these are interpreted in terms of the original redundant formulation's well-known mode expansion coefficients.

  18. Preparation of superconducting nanometer structures by means of scanning tunneling microscopy and of layer-by-layer MBE

    SciTech Connect

    Buschmann, L.; Hoffschulz, H.; Dressen, J.

    1996-12-31

    Thin films of YBa{sub 2}Cu{sub 3}O{sub 7} (YBCO) were patterned down to the sub-{micro}m scale by means of electron-beam lithography (EBL). A resist system based on amorphous carbon layers was developed, which allows the production of uncovered high-{Tc} superconductor microstructures. With this method the authors generated microbridges with a width of minimum 200 nm and a length of up to 5 {micro}m. The layered structure of high {Tc} superconductors enables a further modification of the microbridges on the nm-scale into lateral weak-links by means of a scanning tunneling microscope (STM) using high tunneling currents in the range of nA and fast scanning modes (etching). This modification was carried out in N{sub 2}-atmosphere after the YBCO microstructures were sputtered in Ne-atmosphere. In UHV they did not observe any etching process. Using atomic layer-by-layer MBE they have prepared BiSrCaCuO thin films and vertical S-N-S junctions on SrTiO{sub 3} substrates at 720 C in 2 {center_dot} 10{sup {minus}5} mbar ozone pressure. 40 nm thick Bi-2212 films showed an inductively measured {Tc} of 84 K. Thinner films have {Tc} values of 64 K and 46 K for 15 nm and 10 nm thick films, respectively. They present in-situ-STM images of the surface topography and TEM investigations of the dependence of the substrate/film interface on the first deposited layer. The S-N-S junction was made with Bi-2201 as barrier material and showed quasiparticle tunneling dI/dU-U characteristic. They estimated 2{Delta}(0)/k{sub B}{Tc} to 3.5--4 with a non BCS-like linear temperature dependence.

  19. 9.14 Brain Structure and its Origins, Spring 2005

    E-print Network

    Schneider, Gerald

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

  20. Origins of Structural Hole Traps in Hydrogenated Amorphous Silicon

    E-print Network

    Johlin, Eric Carl

    The inherently disordered nature of hydrogenated amorphous silicon (a-Si:H) obscures the influence of atomic features on the trapping of holes. To address this, we have created a set of over two thousand ab initio structures ...

  1. Cap structures as diagnostic indicators of silcrete origin

    NASA Astrophysics Data System (ADS)

    Ullyott, J. Stewart; Nash, David J.; Huggett, Jennifer M.

    2015-07-01

    Cap structures within silcretes have long been used as a diagnostic indicator of pedogenic silicification. However, a growing number of studies of the micromorphology of non-pedogenic silcretes indicate that this may no longer be appropriate. This paper presents the first systematic investigation of the micro-fabric, geochemistry and mineralogy of cap structures in groundwater silcretes, through an analysis of conglomeratic varieties (puddingstones) from the southern UK. Our results suggest that cap structures in groundwater silcretes fall within a spectrum of types, related to the degree of sorting in the inter-gravel host sediment. At one end of this spectrum are well-defined caps within otherwise well-sorted, overgrowth-dominated silcretes. These caps exhibit a grain-supported fabric, are cemented by micro- and/or cryptocrystalline silica, and contain floating silt-sized quartz and Ti-oxide grains. We propose that these structures developed mainly as a result of in-washing of fine sediments that were subsequently silicified. At the other end of the spectrum are silcretes with caps defined by concentrations of Ti-oxide grains, as opposed to cement type and grain size. These formed mainly as a result of the remobilisation and precipitation of Ti during the silicification of gravels containing interstitial clay-rich sandy sediment. Between these end-members are silcretes with cap structures formed by a combination of in-washing and redistribution of fines plus some local remobilisation of Ti. Overall, the cap structures in this study exhibit a simple micromorphology, lacking the alternating Ti- and silica-rich lamellae typical of pedogenic silcrete. We conclude that the presence of cap structures alone should not be considered diagnostic of pedogenic silicification unless accompanied by other indicators such as a differentiated profile and abundant, complex, way-up structures within the micro-fabric.

  2. THE STRUCTURE AND ORIGIN OF SOLAR PLUMES: NETWORK PLUMES

    SciTech Connect

    Gabriel, A.; Tison, E.; Bely-Dubau, F.; Wilhelm, K.

    2009-07-20

    This study is based upon plumes seen close to the solar limb within coronal holes in the emission from ions formed in the temperature region of 1 MK, in particular, the band of Fe IX 171 A from EIT on the Solar and Heliospheric Observatory. It is shown, using geometric arguments, that two distinct classes of structure contribute to apparently similar plume observations. Quasi-cylindrical structures are anchored in discrete regions of the solar surface (beam plumes), and faint extended structures require integration along the line of sight (LOS) in order to reproduce the observed brightness. This second category, sometimes called 'curtains', are ubiquitous within the polar holes and are usually more abundant than the beam plumes, which depend more on the enhanced magnetic structures detected at their footpoints. It is here proposed that both phenomena are based on plasma structures in which emerging magnetic loops interact with ambient monopolar fields, involving reconnection. The important difference is in terms of physical scale. It is proposed that curtains are composed of a large number of microplumes, distributed along the LOS. The supergranule network provides the required spatial structure. It is shown by modeling that the observations can be reproduced if microplumes are concentrated within some 5 Mm of the cell boundaries. For this reason, we propose to call this second population 'network plumes'. The processes involved could represent a major contribution to the heating mechanism of the solar corona.

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

    NASA Astrophysics Data System (ADS)

    Münkel, Christoph; Roininen, Reijo

    2010-05-01

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

  4. Pigmented Structural Glass: Conserving Original Material Through Repair By Becky Walldroff

    E-print Network

    1 Pigmented Structural Glass: Conserving Original Material Through Repair By Becky Walldroff Advisor: Richard Pieper Pigmented structural glass is a form of opaque rolled plate glass manufactured with innovative marketing and governmental loan programs led to the installation of pigmented structural glass

  5. A multi-layered vascular scaffold with symmetrical structure by bi-directional gradient electrospinning.

    PubMed

    Wu, Tong; Huang, Chen; Li, Dawei; Yin, Anlin; Liu, Wei; Wang, Jing; Chen, Jianfeng; Ei-Hamshary, Hany; Al-Deyab, Salem S; Mo, Xiumei

    2015-09-01

    Multi-layered scaffolds are advantageous in vascular tissue engineering, in consideration of better combination of biomechanics, biocompatibility and biodegradability than the scaffolds with single structure. In this study, a bi-directional gradient electrospinning method was developed to fabricate poly(l-lactide-co-caprolactone) (P(LLA-CL)), collagen and chitosan based tubular scaffold with multi-layered symmetrical structure. The multi-layered composite scaffold showed improved mechanical property and biocompatibility, in comparison to the blended scaffold using the same proportion of raw materials. Endothelialization on the multi-layered scaffold was accelerated owing to the bioactive surface made of pure natural materials. hSMCs growth showed the similar results because of its better biocompatibility. Additionally, fibers morphology change, pH value balance and long term mechanical support results showed that the gradient structure effectively improved biodegradability. PMID:26101818

  6. 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.

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

    SciTech Connect

    Saini, L. K. Nayak, Mukesh G.

    2014-04-24

    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, S{sub ll}(q) and S{sub 12}(q), over a wide range of density parameter r{sub sl} and interlayer spacing d. In our present study, the sharp peak in S{sub 22}(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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  9. 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.

  10. Formation and Origin of Metabreccia from the Parkin Offset Dyke at the Sudbury Impact Structure

    NASA Astrophysics Data System (ADS)

    Anders, D.; Osinski, G. R.; Grieve, R. A. F.; Péntek, A.

    2015-09-01

    Metabreccia is an important litholgy of the Offset Dykes of the Sudbury impact structure, however, its formation and origin is still topic of discussion. Here we present evidence that Metabreccia is a metamorphosed Footwall Breccia.

  11. Origins of Aleuts and the Genetic Structure of Populations of the Archipelago: Molecular and Archaeological Perspectives

    E-print Network

    Crawford, Michael H.; Rubicz, Rohina C.; Zlojutro, Mark

    2010-01-01

    We summarize the results of a field and laboratory research program (1999–2006) in the Aleutian Islands on the origins of the inhabitants of the archipelago and the genetic structure of these populations. The Aleuts show closest genetic affinity...

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

    E-print Network

    Scott Tremaine

    2002-11-07

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

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

    E-print Network

    Diederik Aerts; Sandro Sozzo

    2015-03-10

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

  14. 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.

  15. Origin of non-spherical particles in the boundary layer over Beijing, China: based on balloon-borne observations.

    PubMed

    Chen, Bin; Yamada, Maromu; Iwasaka, Yasunobu; Zhang, Daizhou; Wang, Hong; Wang, Zhenzhu; Lei, Hengchi; Shi, Guangyu

    2015-10-01

    Vertical structures of aerosols from the ground to about 1,000 m altitude in Beijing were measured with a balloon-borne optical particle counter. The results showed that, in hazy days, there were inversions at approximately 500-600 m, below which the particulate matters were well mixed vertically, while the concentration of particles decreased sharply above the mixing layer. Electron microscopic observation of the particles collected with the balloon-borne impactor indicates that the composition of particles is different according to weather conditions in the boundary mixing layer of Beijing city and suggests that dust particles are always dominant in coarse-mode particles. Interestingly, sea-salt particles are frequently identified, suggesting the importance of marine air inflow to the Beijing area even in summer. The Ca-rich spherical particles are also frequently identified, suggesting chemical modification of dust particle by NOx or emission of CaO and others from local emission. Additionally, those types of particles showed higher concentration above the mixing layer under the relatively calm weather condition of summer, suggesting the importance of local-scale convection found in summer which rapidly transported anthropogenic particles above the mixing layer. Lidar extinction profiles qualitatively have good consistency with the balloon-borne measurements. Attenuation effects of laser pulse intensity are frequently observed due to high concentration of particulate matter in the Beijing atmosphere, and therefore quantitative agreement of lidar return and aerosol concentration can be hardly observed during dusty condition. Comparing the depolarization ratio obtained from the lidar measurements with the balloon-borne measurements, the contribution of the dry sea-salt particles, in addition to the dust particles, is suggested as an important factor causing depolarization ratio in the Beijing atmosphere. PMID:25537163

  16. The structural origin of anomalous properties of liquid water.

    PubMed

    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

  17. 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

  18. Structural and magnetic properties of Co films on highly textured and randomly oriented C60 layers

    NASA Astrophysics Data System (ADS)

    Kim, Dong-Ok; Choi, Jun Woo; Lee, Dong Ryeol

    2016-03-01

    The structural and magnetic properties of Co/C60/pentacene and Co/C60 thin film structures were investigated. Atomic force microscopy and x-ray reflectivity analysis show that the presence or absence of a pentacene buffer layer leads to a highly textured or randomly oriented C60 layer, respectively. A Co film deposited on a randomly oriented C60 layer penetrates into the C60 layer when it is deposited at a slow deposition rate. The Co penetration can be minimized, regardless of the Co deposition rate, by growth on a highly textured and nanostructured C60/pentacene layer. Vibrating sample magnetometry measurements show that the saturation magnetization of Co/C60/pentacene is significantly reduced compared to that of Co/C60. On the other hand, the Co penetration does not seem to have an effect on the magnetic properties, suggesting that the structural properties of the Co and C60 layer, rather than the Co penetration into the organic C60 layer, are critical to the magnetic properties of the Co/C60.

  19. Functional Nano-Structures Using Atomic Layer Deposition

    E-print Network

    Salgård Cunha, Pedro

    2014-05-27

    % and 170 % respectively since 1990, compared to 20 % and 7 % for the USA and the European Union over the same time period. The world’s energy usage is expected to continue to rise at an increasing rate to a predicted usage of 327 000 TW h by 2050. A... on the formation of gyroid-structured core- shell Cu/Cu2O/CuO solar cells via the post-deposition thermal oxidation of electro- deposited copper. Chapter 6 deals with the replication of gyroid-structured polystyrene templates using metal oxides deposited via ALD...

  20. Novel Be-intercalated Hexagonal Boron Layers Structure of BeB2

    NASA Astrophysics Data System (ADS)

    Ho, Kai-Ming; Nguyen, Manh Cuong; Zhao, Xin; Wang, Cai-Zhuang

    2014-03-01

    Using genetic algorithm method and first-principle calculations, we performed searches for low-energy crystal structures of BeB2. We found a new family of structures, where the B atoms form hexagonal layers intercalated by Be atoms. The lowest-energy structure has formation energy of -99.47 meV/atom with 4 formula units in the unit cell, which is much more stable than the models proposed before. The formation energies of structures in the new structure family can be well described by a Ising-like model with ``anti-ferromagnetic'' coupling between the displacements of Be atoms from the mid-plane between two B layers. We also performed phonon calculation as well as electronic band structure calculation to verify the stability and investigate the electronic properties of the newly found ground-state structure.

  1. 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.

  2. 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.

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

    E-print Network

    Cao, Wenwu

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

  4. Magnetoelectric interactions in ferromagnetic-piezoelectric layered structures: Phenomena and devices

    E-print Network

    Srinivasan, Gopalan

    /H and the piezoelectric charge generation P/l [1]. Here, in this paper, we are primarily interested in the dynamic MEMagnetoelectric interactions in ferromagnetic-piezoelectric layered structures: Phenomena magnetostrictive-piezoelectric structures are multifunctional due to their dual-responsiveness to mechanical

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

    NASA Astrophysics Data System (ADS)

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

    2013-06-01

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

  6. Electronic Structure and the Properties of Phosphorene and Few-Layer Black Phosphorus

    NASA Astrophysics Data System (ADS)

    Fukuoka, Shuhei; Taen, Toshihiro; Osada, Toshihito

    2015-12-01

    A single atomic layer of black phosphorus, phosphorene, was experimentally realized in 2014. It has a puckered honeycomb lattice structure and a semiconducting electronic structure. In the first part of this paper, we use a simple LCAO model, and qualitatively discuss the electronic structure of phosphorene systems under electric and magnetic fields, especially noting their midgap edge states. The next part is devoted to the review of the progress in research on phosphorene over the past one year since its realization in 2014. Phosphorene has been a typical material to study the semiconductor physics in atomic layers.

  7. Structural Transition in Layered As(1-x)P(x) Compounds: A Computational Study.

    PubMed

    Zhu, Zhen; Guan, Jie; Tománek, David

    2015-09-01

    As a way to further improve the electronic properties of group V layered semiconductors, we propose to form in-layer 2D heterostructures of black phosphorus and gray arsenic. We use ab initio density functional theory to optimize the geometry, determine the electronic structure, and identify the most stable allotropes as a function of composition. Because pure black phosphorus and pure gray arsenic monolayers differ in their equilibrium structure, we predict a structural transition and a change in frontier states, including a change from a direct-gap to an indirect-gap semiconductor, with changing composition. PMID:26295748

  8. Synthesis, structure and electrochemical properties of novel Li-Co-Mn-O epitaxial thin-film electrode using layer-by-layer deposition process

    NASA Astrophysics Data System (ADS)

    Lim, Jaemin; Lee, Soyeon; Suzuki, Kota; Kim, KyungSu; Kim, Sangryun; Taminato, Sou; Hirayama, Masaaki; Oshima, Yoshifumi; Takayanagi, Kunio; Kanno, Ryoji

    2015-04-01

    A novel epitaxial thin-film electrode for lithium batteries, with a composition of Li0.92Co0.65Mn1.35O4 and a cubic spinel structure, is fabricated on a SrTiO3(111) single-crystal substrate. Fabrication is carried out by layer-by-layer pulsed laser deposition of LiCoO2 with a layered rock-salt structure and LiMn2O4 with a spinel structure. The electrode is found to exhibit unique disordering of the lithium (8a) and transition-metal (16d) sites, leading to a higher rate capability and cycle retention ratio than those for a thin-film electrode with the same composition prepared by a conventional single-step deposition process. The proposed layer-by-layer deposition method allows an expanded range of compositional and structural variations for lithium battery electrode materials.

  9. 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.

  10. 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.

  11. 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.

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

    SciTech Connect

    Short, Andrew; Jewell, Leila; Bielecki, Anthony; Keiber, Trevor; Bridges, Frank; Carter, Sue; Alers, Glenn

    2014-01-15

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

  13. 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.

  14. Structural analysis of nitride layer formed on uranium metal by glow plasma surface nitriding

    NASA Astrophysics Data System (ADS)

    Liu, Kezhao; Bin, Ren; Xiao, Hong; Long, Zhong; Hong, Zhanglian; Yang, Hui; Wu, Sheng

    2013-01-01

    The nitride layer was formed on uranium metal by a glow plasma surface nitriding method. The structure and composition of the layer were investigated by X-ray diffraction and Auger electron spectroscopy. The nitride layer mainly consisted of ?-phase U2N3 nanocrystals with an average grain size about 10-20 nm. Four zones were identified in the layer, which were the oxide surface zone, the nitride mainstay zone, the oxide-existence interface zone, and the nitrogen-diffusion matrix zone. The gradual decrease of binding energies of uranium revealed the transition from oxide to nitride to metal states with the layer depth, while the chemical states of nitrogen and oxygen showed small variation.

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

    NASA Technical Reports Server (NTRS)

    Grabbe, C. L.

    1985-01-01

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

  16. 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.

  17. 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

  18. Scaling structure of the velocity statistics in atmospheric boundary layers

    NASA Astrophysics Data System (ADS)

    Kurien, Susan; L'vov, Victor S.; Procaccia, Itamar; Sreenivasan, K. R.

    2000-01-01

    The statistical objects characterizing turbulence in real turbulent flows differ from those of the ideal homogeneous isotropic model. They contain contributions from various two- and three-dimensional aspects, and from the superposition of inhomogeneous and anisotropic contributions. We employ the recently introduced decomposition of statistical tensor objects into irreducible representations of the SO(3) symmetry group (characterized by j and m indices, where j=0...?,-j<=m<=j) to disentangle some of these contributions, separating the universal and the asymptotic from the specific aspects of the flow. The different j contributions transform differently under rotations, and so form a complete basis in which to represent the tensor objects under study. The experimental data are recorded with hot-wire probes placed at various heights in the atmospheric surface layer. Time series data from single probes and from pairs of probes are analyzed to compute the amplitudes and exponents of different contributions to the second order statistical objects characterized by j=0, 1, and 2. The analysis shows the need to make a careful distinction between long-lived quasi-two-dimensional turbulent motions (close to the ground) and relatively short-lived three-dimensional motions. We demonstrate that the leading scaling exponents in the three leading sectors (j=0, 1, and 2) appear to be different but universal, independent of the positions of the probe, the tensorial component considered, and the large scale properties. The measured values of the scaling exponent are ?(j=0)2=0.68+/-0.01, ?(j=1)2=1.0+/-0.15, and ?(j=2)2=1.38+/-0.10. We present theoretical arguments for the values of these exponents using the Clebsch representation of the Euler equations; neglecting anomalous corrections, the values obtained are 2/3, 1, and 4/3, respectively. Some enigmas and questions for the future are sketched.

  19. Scaling structure of the velocity statistics in atmospheric boundary layers

    PubMed

    Kurien; L'vov; Procaccia; Sreenivasan

    2000-01-01

    The statistical objects characterizing turbulence in real turbulent flows differ from those of the ideal homogeneous isotropic model. They contain contributions from various two- and three-dimensional aspects, and from the superposition of inhomogeneous and anisotropic contributions. We employ the recently introduced decomposition of statistical tensor objects into irreducible representations of the SO(3) symmetry group (characterized by j and m indices, where j=0ellipsisinfinity,-jlayer. Time series data from single probes and from pairs of probes are analyzed to compute the amplitudes and exponents of different contributions to the second order statistical objects characterized by j=0, 1, and 2. The analysis shows the need to make a careful distinction between long-lived quasi-two-dimensional turbulent motions (close to the ground) and relatively short-lived three-dimensional motions. We demonstrate that the leading scaling exponents in the three leading sectors (j=0, 1, and 2) appear to be different but universal, independent of the positions of the probe, the tensorial component considered, and the large scale properties. The measured values of the scaling exponent are zeta((j=0))(2)=0.68+/-0.01, zeta((j=1))(2)=1.0+/-0.15, and zeta((j=2))(2)=1.38+/-0.10. We present theoretical arguments for the values of these exponents using the Clebsch representation of the Euler equations; neglecting anomalous corrections, the values obtained are 2/3, 1, and 4/3, respectively. Some enigmas and questions for the future are sketched. PMID:11046280

  20. Structure of Protein Layers in Polyelectrolyte Matrices Studied by Neutron Reflectivity

    SciTech Connect

    Kozlovskaya, Veronika; Ankner, John Francis; O'Neill, Hugh Michael; Zhang, Qiu; Kharlampieva, Eugenia

    2011-01-01

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

  1. 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.

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

    NASA Astrophysics Data System (ADS)

    He, Fupo; Ye, Jiandong

    2013-08-01

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

  3. The turbulent structure of the internal boundary layer near the shore

    NASA Astrophysics Data System (ADS)

    Ohara, Toshimasa; Ogawa, Yasushi

    1985-05-01

    The mean structure within the internal boundary layer (IBL) near the shore, which develop from the coast in the presence of a sea breeze, has been described in Part I of this study (Ogawa and Ohara, 1984). This paper presents the results of the similarity and energy budget analysis for the purpose of parameterization of the turbulent structure within the IBL. The analysis of the turbulent kinetic energy balance, turbulent intensities and spectra show that the wind is strongly affected by mechanical turbulence in comparison with the past results in a fully developed convective layer where thermal convection dominated. The standard deviations of the wind velocities normalized by the friction velocity u * (surface-layer scaling parameter) are functions only of the normalized height z/Z i within 160 m of the shoreline, where Z i is the IBL. On the other hand, the standard deviations of temperature normalized by ?* (mixing-layer scaling parameter) have less scatter with distance than those normalized by T * (surface-layer scaling parameter). The data showed that both u * (not a mixed-layer parameter), and Z i (not a surface-layer parameter) are necessary to describe the turbulent characteristics of the IBL near the shore.

  4. 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. PMID:26406729

  5. Formation Of Nano Layered Lamellar Structure In a Processed ?-TiAl Based Alloy

    NASA Astrophysics Data System (ADS)

    Heshmati-Manesh, S.; Shakoorian, H.; Armaki, H. Ghassemi; Ahmadabadi, M. Nili

    2009-06-01

    In this research, microstructures of an intermetallic alloy based on ?-TiAl has been investigated by optical and transmission electron microscopy. Samples of Ti-47Al-2Cr alloy were subjected to either a cyclic heat treatment or thermomechanical treatment with the aim of microstructural refinement. In both cases it was found that very fine lamellar structure with an interlamellar spacing in the nano scale is formed. Upon cyclic heat treatment, nano layers of ?2 and ? ordered intermetallic phases were either formed during rapid cooling cycle in competition with massive structure formation, or formed as secondary lamellar structure during final stages of cyclic heat treatment. Also, TEM observations in hot forged specimens with initial lamellar structure revealed that micro twins form during the deformation within lamellar structure with twinning plates parallel to lamellar interfaces. Concurrent dynamic recrystallisation results in a nano layered structure with an interlamellar spacing of less than 100 nm.

  6. Structural origins of intrinsic stress in amorphous silicon thin films

    NASA Astrophysics Data System (ADS)

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

    2012-02-01

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

  7. 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.

  8. Magnetic properties of iron oxalatophosphates with layer and framework structures

    NASA Astrophysics Data System (ADS)

    Lee, S. F.; Tsai, T. C.; Chang, G. S.; Sheu, C. Y.; Lii, K. H.

    2007-05-01

    The magnetic properties of two iron(III) oxalatophosphates, Cs2Fe(C2O4)0.5(HPO4)2 and CsFe(C2O4)0.5(H2PO4)(HPO4), were studied. The zero-field-cooled and field-cooled magnetizations versus temperature curves showed Curie-Weiss behavior from room temperature down to about 70K. Antiferromagnetic ordering and frustration behavior were observed in distinct temperature ranges at lower temperature. The frustration behavior can be attributed to the Dzyaloshinsky-Moriya interaction of the dimerlike magnetic structure, which causes spin canting states.

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

    DOEpatents

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

    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.

  10. 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

  11. 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.

  12. 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, understanding WF-ABL interactions and its effects is of significant scientific and societal importance.

  13. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2013-07-01

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

  15. Origin of the coloration and structure of azobenzene chromogen

    NASA Astrophysics Data System (ADS)

    Mikheev, Yu. A.; Guseva, L. N.; Ershov, Yu. A.

    2015-11-01

    Enhancement of the visible (VIS) absorption band intensity of trans-azobenzene ( t-AB) in solutions containing water and hydrogen ions is established. This contradicts the current belief that it is part of the n ? ?* transition. At the same time, it qualitatively reflects the properties of the ? ? ?* bands of protonated azobenzene (ABH+). It is concluded that t-AB molecules display an autopolarization property and exist in the form of two individual electronic (e) tautomers. One of these is nonpolar and has the canonical chemical structure; its content considerably exceeds that of the polar e-tautomer. The polar e-tautomer forms as a result of the reversible transfer of an electron from the nonbonding donor sp 2 orbital of nitrogen to the nonbonding acceptor Rydberg's 3 S orbital ( R 3 S ) of the local N=N chromophore within the molecule. The positively charged chromogen corresponding to it displays a ? ? ?* transition in the visible spectral region, and the ???* transition (not the traditionally postulated n ? ?* transition) is clearly responsible for the orange color of AB. A model of transient e-configurations with the participation of R 3 S and explaining the previous poorly understood experimental results from optical absorption, fluorescent, raman spectroscopic, and photoionization femtosecond kinetic studies is considered. It is shown that famous ideas about the violation of Kasha's rule in t-AB fluorescence and photoisomerization processes are incorrect. The reasons for the increased intensity of the VIS band of cis-azobenzene ( c-AB) are explained. It is concluded that there is an equilibrium between nonpolar and polarized e-tautomers in cis-azobenzene as well, but it is shifted more toward the polar tautomer in c-AB due to its structural features, making the VIS band more intense.

  16. ORIGINAL PAPER Influence of the Metal Oxide Substrate Structure on Vanadium

    E-print Network

    Marks, Laurence D.

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

  17. ORIGINAL PAPER Structure of genetic diversity in the two major gene pools

    E-print Network

    Gepts, Paul

    ORIGINAL PAPER Structure of genetic diversity in the two major gene pools of common bean (Phaseolus modified the structure and level of genetic diversity in common bean. Specifically, we analyzed the genome by distance. Domesticated common bean populations possessed lower genetic diversity, higher FST, and generally

  18. Investigation of Oxide Layer Structure on Niobium Surfaces using a Secondary Ion Mass Spectrometer

    SciTech Connect

    Andy T. Wu

    2005-07-10

    Oxide layer structure on the surfaces of niobium (Nb) can be studied by continuously monitoring peaks of the secondary ions of Nb and its relevant oxides as a function of time during depth profiling measurements employing a secondary ion mass spectrometer (SIMS). This is based on the fact that different oxides have different cracking patterns. This new approach is much simpler and easier for studying oxide layer structure on Nb surfaces than the conventional approach through deconvolution of oxide peaks obtained from an x-ray photoemission spectrometer. Eventually it can be developed into an in-situ tool for monitoring the oxide layer structure on Nb surfaces prepared by various procedures. Preliminary results of SIMS measurements on the surfaces of Nb samples treated by buffered electropolishing and buffered chemical polishing will be reported.

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

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

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

  20. 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.

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

    NASA Astrophysics Data System (ADS)

    Nettelmann, Nadine; Püstow, Robert; Redmer, Ronald

    2013-07-01

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

  2. 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.

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

    NASA Astrophysics Data System (ADS)

    Shepherd, Micah R.

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

  5. 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(?-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

  6. 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.

  7. The Nature and Origin of Time-asymmetric Spacetime Structures

    E-print Network

    H. D. Zeh

    2013-09-05

    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.

  8. On the Origin of the Inner Structure of Halos

    E-print Network

    Alberto Manrique; Andreu Raig; Eduard Salvador-Sole; Teresa Sanchis; Jose M. Solanes

    2003-05-16

    We calculate by means of the Press-Schechter formalism the density profile developed by dark-matter halos during accretion, i.e., the continuous aggregation of small clumps. We find that the shape of the predicted profile is similar to that shown by halos in high-resolution cosmological simulations. Furthermore, the mass-concentration relation is correctly reproduced at any redshift in all the hierarchical cosmologies analyzed, except for very large halo masses. The role of major mergers, which can cause the rearrangement of the halo structure through violent relaxation, is also investigated. We show that, as a result of the boundary conditions imposed by the matter continuously infalling into the halo during the violent relaxation process, the shape of the density profile emerging from major mergers is essentially identical to the shape the halo would have developed through pure accretion. This result explains why, according to high-resolution cosmological simulations, relaxed halos of a given mass have the same density profile regardless of whether they have had a recent merger or not, and why both spherical infall and hierarchical assembly lead to very similar density profiles. Finally, we demonstrate that the density profile of relaxed halos is not affected either by the capture of clumps of intermediate mass.

  9. Catfish gonadotrophins: cellular origin, structural properties and physiology.

    PubMed

    Chaube, R; Joy, K P; Acharjee, A

    2015-06-01

    Gonadotrophins (GTHs) play a central role in the regulation of gametogenesis and spawning. The structural duality of the GTHs [luteinising hormone (LH) and follicle-stimulating hormone (FSH)] is established in fishes with the exception of ancestral vertebrates. Most studies indicate that, in teleosts, the GTHs are secreted in separate cells. Phylogenetic analysis shows that the common ?-subunit of the GTHs (and also of thyroid-stimulating hormone) and LH? are highly conserved in fishes, as in tetrapods. However, FSH? shows considerable divergence in teleosts. There may be 12 or 13 cysteine residues, with an additional one near the N-terminus. There may be one or two N-linked glycolsyation sites. In catfishes, there are 13 cysteine residues and one N-linked glycosylation site. In an extreme situation, a potential glycosylation site is lacking in some fishes. Both FSH and LH receptors are characterised in teleosts. The FSH receptor is promiscuous and can be cross-activated by LH. By contrast, the LH receptor is highly selective, being activated by its natural ligand or by heterologous ligands (e.g. human chorionic gonadotrophin). Consequently, teleosts show different patterns of LH and FSH secretion. In catfishes, in the absence of native FSH protein, LH controls all aspects of reproduction, from early gametogenesis to spawning. PMID:25879854

  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. PMID:24211511

  11. 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.

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

    PubMed

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

    2015-04-01

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

  13. Band structure and broadband compensation of absorption by amplification in layered optical metamaterials

    SciTech Connect

    Rozanov, N. N. Fedorov, S. V.; Savel'ev, R. S.; Sukhorukov, A. A.; Kivshar, Yu. S.

    2012-05-15

    The frequency dependence of the gain required to compensate for absorption is determined for a layered structure consisting of alternating absorbing and amplifying layers. It is shown that the fulfillment of the same conditions is required for the existence of a band structure consisting of alternating bands allowed and forbidden for optical radiation propagation in the frequency-wave vector parametric region. Conditions are found under which the gain required for compensation is smaller than thresholds for absolute (parasitic lasing) and convective (waveguide amplification of radiation) instabilities.

  14. The inviscid secondary instability of fully nonlinear longitudinal vortex structures in growing boundary layers

    NASA Technical Reports Server (NTRS)

    Hall, Philip; Horseman, Nicola J.

    1990-01-01

    The inviscid instability of a longitudinal vortex structure within a steady boundary layer is investigated. The instability has a wavelength comparable with the boundary layer thickness so that a quasi-parallel approach to the instability problem can be justified. The generalization of the Rayleigh equation to such a flow is obtained and solved for the case when the vortex structure is induced by curvature. Two distinct modes of instability are found; these modes correspond with experimental observations on the breakdown process for Goertler vortices.

  15. Electronic structure of the ferroelectric layered perovskite SrBi{sub 2}Ta{sub 2}O{sub 9}

    SciTech Connect

    Robertson, J.; Chen, C.W.; Warren, W.L.; Gutleben, C.D.

    1996-09-01

    The band structure of the layered perovskite SrBi{sub 2}Ta{sub 2}O{sub 9} (SBT) was calculated by tight binding and the valence band density of states was measured by x-ray photoemission spectroscopy. We find both the valence and conduction band edges to consist of states primarily derived from the Bi{endash}O layer rather than the perovskite Sr{endash}Ta{endash}O blocks. The valence band maximum arises from O {ital p} and some Bi {ital s} states, while the conduction band minimum consists of Bi {ital p} states, with a wide band gap of 5.1 eV. It is argued that the Bi{endash}O layers largely control the electronic response whereas the ferroelectric response originates mainly from the perovskite Sr{endash}Ta{endash}O block. Bi and Ta centered traps are calculated to be shallow, which may account in part for its excellent fatigue properties. {copyright} {ital 1996 American Institute of Physics.}

  16. Tuning the magnetic anisotropy in single-layer crystal structures

    NASA Astrophysics Data System (ADS)

    Torun, E.; Sahin, H.; Bacaksiz, C.; Senger, R. T.; Peeters, F. M.

    2015-09-01

    The effect of an applied electric field and the effect of charging are investigated on the magnetic anisotropy (MA) of various stable two-dimensional (2D) crystals such as graphene, FeCl2, graphone, fluorographene, and MoTe2 using first-principles calculations. We found that the magnetocrystalline anisotropy energy of Co-on-graphene and Os-doped-MoTe2 systems change linearly with electric field, opening the possibility of electric field tuning MA of these compounds. In addition, charging can rotate the easy-axis direction of Co-on-graphene and Os-doped-MoTe2 systems from the out-of-plane (in-plane) to in-plane (out-of-plane) direction. The tunable MA of the studied materials is crucial for nanoscale electronic technologies such as data storage and spintronics devices. Our results show that controlling the MA of the mentioned 2D crystal structures can be realized in various ways, and this can lead to the emergence of a wide range of potential applications where the tuning and switching of magnetic functionalities are important.

  17. 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.

  18. The internal structure of Jupiter family cometary nuclei from Deep Impact observations: The “talps” or “layered pile” model

    NASA Astrophysics Data System (ADS)

    Belton, Michael J. S.; Thomas, Peter; Veverka, J.; Schultz, Peter; A'Hearn, Michael F.; Feaga, Lori; Farnham, Tony; Groussin, Olivier; Li, Jian-Yang; Lisse, Casey; McFadden, Lucy; Sunshine, Jessica; Meech, Karen J.; Delamere, W. Alan; Kissel, Jochen

    2007-03-01

    We consider the hypothesis that the layering observed on the surface of Comet 9P/Tempel 1 from the Deep Impact spacecraft and identified on other comet nuclei imaged by spacecraft (i.e., 19P/Borrelly and 81P/Wild 2) is ubiquitous on Jupiter family cometary nuclei and is an essential element of their internal structure. The observational characteristics of the layers on 9P/Tempel 1 are detailed and considered in the context of current theories of the accumulation and dynamical evolution of cometary nuclei. The works of Donn [Donn, B.D., 1990. Astron. Astrophys. 235, 441-446], Sirono and Greenberg [Sirono, S.-I., Greenberg, J.M., 2000. Icarus 145, 230-238] and the experiments of Wurm et al. [Wurm, G., Paraskov, G., Krauss, O., 2005. Icarus 178, 253-263] on the collision physics of porous aggregate bodies are used as basis for a conceptual model of the formation of layers. Our hypothesis is found to have implications for the place of origin of the JFCs and their subsequent dynamical history. Models of fragmentation and rubble pile building in the Kuiper belt in a period of collisional activity (e.g., [Kenyon, S.J., Luu, J.X., 1998. Astron. J. 115, 2136-2160; 1999a. Astron. J. 118, 1101-1119; 1999b. Astrophys. J. 526, 465-470; Farinella, P., Davis, D.R., Stern, S.A., 2000. In: Mannings, V., Boss, A.P., Russell, S.S. (Eds.), Protostars and Planets IV. Univ. of Arizona Press, Tucson, pp. 1255-1282; Durda, D.D., Stern, S.J., 2000. Icarus 145, 220-229]) following the formation of Neptune appear to be in conflict with the observed properties of the layers and irreconcilable with the hypothesis. Long-term residence in the scattered disk [Duncan, M.J., Levison, H.F., 1997. Science 276, 1670-1672; Duncan, M., Levison, H., Dones, L., 2004. In: Festou, M., Keller, H.U., Weaver, H.A. (Eds.), Comets II. Univ. of Arizona Press, Tucson, pp. 193-204] and/or a change in fragmentation outcome modeling may explain the long-term persistence of primordial layers. In any event, the existence of layers places constraints on the environment seen by the population of objects from which the Jupiter family comets originated. If correct, our hypothesis implies that the nuclei of Jupiter family comets are primordial remnants of the early agglomeration phase and that the physical structure of their interiors, except for the possible effects of compositional phase changes, is largely as it was when they were formed. We propose a new model for the interiors of Jupiter family cometary nuclei, called the talps or "layered pile" model, in which the interior consists of a core overlain by a pile of randomly stacked layers. We discuss how several cometary characteristics—layers, surface texture, indications of flow, compositional inhomogeneity, low bulk density low strength, propensity to split, etc., might be explained in terms of this model. Finally, we make some observational predictions and suggest goals for future space observations of these objects.

  19. The internal structure of Jupiter family cometary nuclei from Deep Impact observations: The “talps” or “layered pile” model

    NASA Astrophysics Data System (ADS)

    Belton, Michael J. S.; Thomas, Peter; Veverka, J.; Schultz, Peter; A'Hearn, Michael F.; Feaga, Lori; Farnham, Tony; Groussin, Olivier; Li, Jian-Yang; Lisse, Casey; McFadden, Lucy; Sunshine, Jessica; Meech, Karen J.; Delamere, W. Alan; Kissel, Jochen

    We consider the hypothesis that the layering observed on the surface of Comet 9P/Tempel 1 from the Deep Impact spacecraft and identified on other comet nuclei imaged by spacecraft (i.e., 19P/Borrelly and 81P/Wild 2) is ubiquitous on Jupiter family cometary nuclei and is an essential element of their internal structure. The observational characteristics of the layers on 9P/Tempel 1 are detailed and considered in the context of current theories of the accumulation and dynamical evolution of cometary nuclei. The works of Donn [Donn, B.D., 1990. Astron. Astrophys. 235, 441 446], Sirono and Greenberg [Sirono, S.-I., Greenberg, J.M., 2000. Icarus 145, 230 238] and the experiments of Wurm et al. [Wurm, G., Paraskov, G., Krauss, O., 2005. Icarus 178, 253 263] on the collision physics of porous aggregate bodies are used as basis for a conceptual model of the formation of layers. Our hypothesis is found to have implications for the place of origin of the JFCs and their subsequent dynamical history. Models of fragmentation and rubble pile building in the Kuiper belt in a period of collisional activity (e.g., [Kenyon, S.J., Luu, J.X., 1998. Astron. J. 115, 2136 2160; 1999a. Astron. J. 118, 1101 1119; 1999b. Astrophys. J. 526, 465 470; Farinella, P., Davis, D.R., Stern, S.A., 2000. In: Mannings, V., Boss, A.P., Russell, S.S. (Eds.), Protostars and Planets IV. Univ. of Arizona Press, Tucson, pp. 1255 1282; Durda, D.D., Stern, S.J., 2000. Icarus 145, 220 229]) following the formation of Neptune appear to be in conflict with the observed properties of the layers and irreconcilable with the hypothesis. Long-term residence in the scattered disk [Duncan, M.J., Levison, H.F., 1997. Science 276, 1670 1672; Duncan, M., Levison, H., Dones, L., 2004. In: Festou, M., Keller, H.U., Weaver, H.A. (Eds.), Comets II. Univ. of Arizona Press, Tucson, pp. 193 204] and/or a change in fragmentation outcome modeling may explain the long-term persistence of primordial layers. In any event, the existence of layers places constraints on the environment seen by the population of objects from which the Jupiter family comets originated. If correct, our hypothesis implies that the nuclei of Jupiter family comets are primordial remnants of the early agglomeration phase and that the physical structure of their interiors, except for the possible effects of compositional phase changes, is largely as it was when they were formed. We propose a new model for the interiors of Jupiter family cometary nuclei, called the talps or “layered pile” model, in which the interior consists of a core overlain by a pile of randomly stacked layers. We discuss how several cometary characteristics—layers, surface texture, indications of flow, compositional inhomogeneity, low bulk density low strength, propensity to split, etc., might be explained in terms of this model. Finally, we make some observational predictions and suggest goals for future space observations of these objects.

  20. 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.

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

    DOEpatents

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

    1998-03-10

    The semiconductor structure comprises a plurality of semiconductor layers formed on a substrate including at least one layer of a III-V compound semiconductor alloy comprising aluminum (Al) and antimony (Sb), with at least a part of the AlSb-alloy layer being chemically converted by an oxidation process to form superposed electrically insulating and electrically conducting portions. The electrically insulating portion formed from the AlSb-alloy layer comprises an oxide of aluminum (e.g., Al{sub 2}O{sub 3}), while the electrically conducting portion comprises Sb. A lateral oxidation process allows formation of the superposed insulating and conducting portions below monocrystalline semiconductor layers for forming many different types of semiconductor structures having particular utility for optoelectronic devices such as light-emitting diodes, edge-emitting lasers, vertical-cavity surface-emitting lasers, photodetectors and optical modulators (waveguide and surface normal), and for electronic devices such as heterojunction bipolar transistors, field-effect transistors and quantum-effect devices. The invention is expected to be particularly useful for forming light-emitting devices for use in the 1.3--1.6 {mu}m wavelength range, with the AlSb-alloy layer acting to define an active region of the device and to effectively channel an electrical current therein for efficient light generation. 10 figs.

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

    NASA Astrophysics Data System (ADS)

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

    2015-01-01

    In this work, we study the thermal transport properties of platelike composite two-layer samples made of polyester resin and magnetite inclusions. By means of photoacoustic spectroscopy and thermal relaxation, their effective thermal diffusivity and conductivity were experimentally measured. The composite layers were prepared under the action of a static magnetic field, resulting in anisotropic (fractal) inclusion structures with the formation of chain-like magnetite aggregates parallel to the faces of the layers. In one kind of the bilayers, a composite layer was formed on top of a resin layer while their relative thickness was varied. These samples can be described by known models. In contrast, bilayers with the same concentration of inclusions and the same thickness on both sides, where only the angle between their inclusion structures was systematically varied, show a nontrivial behaviour of their thermal conductivity as a function of this angle. Through a multifractal and lacunarity analysis, we explain the observed thermal response in terms of the complexity of the interface between the layers.

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

    NASA Astrophysics Data System (ADS)

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

    2015-09-01

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

  4. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

  6. Ultra-fine structural characterization and bioactivity evaluation of TiO2 nanotube layers.

    PubMed

    Jang, JaeMyung; Kwon, TaeYub; Kim, KyoHan

    2008-10-01

    For an application as biomedical materials of high performance with a good biocompatibility, the TiO2 nanotube-type oxide film on Ti substrate has been fabricated by electrochemical method, and the effects of surface characteristics of TiO2 naotube layer have been investigated. The surface morphology of TiO2 nanotube layer depends on factors such as anodizing time, current density, and electrolyte temperature. Moreover, the cell and pore size gradually were increased with the passage of anodizing time. X-ray diffraction (XRD) results indicated that the TiO2 nanotube layer formed in acidic electrolytes was mainly composed of anatase structure containing rutile. From the analysis of chemical states of TiO2 nanotube layer using X-ray photoelectron spectroscopy (XPS), Ti2p, P2p and O1s were observed in the nanotubes layer, which were penetrated from the electrolyte into the oxide layer during anodic process. The incorporated phosphate species were found mostly in the forms of HPO4-, PO4-, and PO3-. From the result of biological evaluation in simulated body fluid (SBF) the TiO2 nanotube layer was effective for bioactive property. PMID:19198362

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

    E-print Network

    Zanin, Massimiliano

    2015-01-01

    Functional networks, i.e. networks representing dynamic relationships between the components of a complex system, have been instrumental for our understanding of, among others, the human brain. Due to limited data availability, the multi-layer nature of numerous functional networks has hitherto been neglected, and nodes are endowed with a single type of links even when multiple relationships coexist at different physical levels. A relevant problem is the assessment of the benefits yielded by studying a multi-layer functional network, against the simplicity guaranteed by the reconstruction and use of the corresponding single layer projection. Here, I tackle this issue by using as a test case, the functional network representing the dynamics of delay propagation through European airports. Neglecting the multi-layer structure of a functional network has dramatic consequences on our understanding of the underlying system, a fact to be taken into account when a projection is the only available information.

  8. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-02-01

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

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

    NASA Astrophysics Data System (ADS)

    Zanin, Massimiliano

    2015-07-01

    Functional networks, i.e. networks representing dynamic relationships between the components of a complex system, have been instrumental for our understanding of, among others, the human brain. Due to limited data availability, the multi-layer nature of numerous functional networks has hitherto been neglected, and nodes are endowed with a single type of links even when multiple relationships coexist at different physical levels. A relevant problem is the assessment of the benefits yielded by studying a multi-layer functional network, against the simplicity guaranteed by the reconstruction and use of the corresponding single layer projection. Here, I tackle this issue by using as a test case, the functional network representing the dynamics of delay propagation through European airports. Neglecting the multi-layer structure of a functional network has dramatic consequences on our understanding of the underlying system, a fact to be taken into account when a projection is the only available information.

  11. Optical properties of thin semiconductor device structures with reflective back-surface layers

    SciTech Connect

    Clevenger, M.B.; Murray, C.S.; Ringel, S.A.; Sachs, R.N.; Qin, L.; Charache, G.W.; Depoy, D.M.

    1998-11-01

    Ultrathin semiconductor device structures incorporating reflective internal or back surface layers have been investigated recently as a means of improving photon recuperation, eliminating losses associated with free carrier absorption in conductive substrates and increasing the above bandgap optical thickness of thermophotovoltaic device structures. However, optical losses in the form of resonance absorptions in these ultrathin devices have been observed. This behavior in cells incorporating epitaxially grown FeAl layers and in devices that lack a substrate but have a back-surface reflector (BSR) at the rear of the active layers has been studied experimentally and modeled effectively. For thermophotovoltaic devices, these resonances represent a significant loss mechanism since the wavelengths at which they occur are defined by the active TPV cell thickness of {approximately} 2--5 microns and are in a spectral range of significant energy content for thermal radiators. This study demonstrates that ultrathin semiconductor structures that are clad by such highly reflective layers or by films with largely different indices of refraction display resonance absorptions that can only be overcome through the implementation of some external spectral control strategy. Effective broadband, below-bandgap spectral control using a back-surface reflector is only achievable using a large separation between the TPV active layers and the back-surface reflector.

  12. Optical properties of thin semiconductor device structures with reflective back-surface layers

    SciTech Connect

    Clevenger, M.B.; Murray, C.S.; Sacks, R.N.; Qin, L.; Depoy, D.M.

    1999-03-01

    Ultrathin semiconductor device structures incorporating reflective internal or back surface layers have been investigated recently as a means of improving photon recuperation eliminating losses associated with free carrier absorption in conductive substrates and increasing the above bandgap optical thickness of thermophotovoltaic device structures. However, optical losses in the form of resonance absorptions in these ultrathin devices have been observed. This behavior in cells incorporating epitaxially grown FeAl layers and in devices that lack a substrate but have a back-surface reflector (BSR) at the rear of the active layers has been studied experimentally and modeled effectively. For thermophotovoltaic devices, these resonances represent a significant loss mechanism since the wavelengths at which they occur are defined by the active TPV cell thickness of {approximately}2{endash}5 microns and are in a spectral range of significant energy content for thermal radiators. This study demonstrates that ultrathin semiconductor structures that are clad by such highly reflective layers or by films with largely different indices of refraction display resonance absorptions that can only be overcome through the implementation of some external spectral control strategy. Effective broadband below-bandgap spectral control using a back-surface reflector is only achievable using a large separation between the TPV active layers and the back-surface reflector. {copyright} {ital 1999 American Institute of Physics.}

  13. Batch fabrication of a double-layer metamaterial resonator using scalloping structures

    NASA Astrophysics Data System (ADS)

    Isozaki, Akihiro; Kan, Tetsuo; Takano, Keisuke; Hangyo, Masanori; Matsumoto, Kiyoshi; Shimoyama, Isao

    2013-08-01

    We propose a batch fabrication method for a double-layer microscale metamaterial resonator operating in the terahertz (THz) region. The proposed method takes advantage of scalloping structures formed by a general deep etching process. The scalloping structures function as a shadow mask. The shadow mask structure allows for the simultaneous fabrication of multiple metal layers with only a one-time evaporation step. The evaporated metal layers are electrically isolated from each other. In this paper, we fabricated a double-layer split-ring resonator (SRR) on a silicon substrate. The typical length of an arm of the SRRs was 40 µm, and the interlayer distance was 4 µm. Using energy-dispersive x-ray analysis, we confirmed that there was a nonevaporation area between the two SRR layers. We also confirmed that the fabricated sample functioned as a metamaterial in the THz region by transmittance measurements and simulation. These results prove that our method could lead to the realization of multilayer metamaterials.

  14. 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.

  15. 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

  16. 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.

  17. Three-Layered Atmospheric Structure in Accretion Disks Around Stellar-Mass Black Holes

    E-print Network

    S. N. Zhang; Wei Cui; Wan Chen; Yangsen Yao; Xiaoling Zhang; Xuejun Sun; Xue-Bing Wu; Haiguang Xu

    2000-02-24

    Modeling of the x-ray spectra of the Galactic superluminal jet sources GRS 1915+105 and GRO J1655-40 reveal a three-layered atmospheric structure in the inner region of their accretion disks. Above the cold and optically thick disk of a temperature 0.2-0.5 keV, there is a warm layer with a temperature of 1.0-1.5 keV and an optical depth around 10. Sometimes there is also a much hotter, optically thin corona above the warm layer, with a temperature of 100 keV or higher and an optical depth around unity. The structural similarity between the accretion disks and the solar atmosphere suggest that similar physical processes may be operating in these different systems.

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

    NASA Astrophysics Data System (ADS)

    Avanov, L. A.; Chandler, M. O.

    2008-12-01

    We have begun an investigation of the formation of the dayside low latitude boundary layer under different solar wind conditions using data from the THEMIS spacecraft. We present two cases of magnetopause/LLBL interface crossings made by the five spacecraft; one under long lasting northward IMF and a second for a period of southward IMF. All spacecraft during these observations traversed the day side magnetosphere in a string-of-pearls configuration with the farthest distance between spacecraft less than ~2 RE. The sequence of observations from spacecraft, as they crossed the magnetopause, shows the development of a highly structured boundary layer regardless of the polarity of the IMF. We discuss possible scenarios for the development of such structured boundary layers, including low latitude reconnection under northward IMF as well as double reconnection in opposite hemispheres.

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

    2010-07-13

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

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

    E-print Network

    Peixoto, Tiago P

    2015-01-01

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

  2. The structure and properties of single-layer and gradient-layered coatings of the Ti-Al-Si-Cr-Mo-S-N system

    NASA Astrophysics Data System (ADS)

    Ovchinnikov, Stanislav; Pinzhin, Yurii

    2015-10-01

    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.

  3. Ovarian carcinoma patient derived xenografts reproduce their tumor of origin and preserve an oligoclonal structure.

    PubMed

    Colombo, Pierre-Emmanuel; du Manoir, Stanislas; Orsett, Béatrice; Bras-Gonçalves, Rui; Lambros, Mario B; MacKay, Alan; Nguyen, Tien-Tuan; Boissière, Florence; Pourquier, Didier; Bibeau, Frédéric; Reis-Filho, Jorge S; Theillet, Charles

    2015-09-29

    Advanced Epithelial Ovarian Cancer (EOC) patients frequently relapse by 24 months and develop resistant disease. Research on EOC therapies relies on cancer cell lines established decades ago making Patient Derived Xenografts (PDX) attractive models, because they are faithful representations of the original tumor. We established 35 ovarian cancer PDXs resulting from the original graft of 77 EOC samples onto immuno-compromised mice. PDXs covered the diversity of EOC histotypes and graft take was correlated with early patient death. Fourteen PDXs were characterized at the genetic and histological levels. PDXs reproduced phenotypic features of the ovarian tumors of origin and conserved the principal characteristics of the original copy number change (CNC) profiles over several passages. However, CNC fluctuations in specific subregions comparing the original tumor and the PDXs indicated the oligoclonal nature of the original tumors. Detailed analysis by CGH, FISH and exome sequencing of one case, for which several tumor nodules were sampled and grafted, revealed that PDXs globally maintained an oligoclonal structure. No overgrowth of a particular subclone present in the original tumor was observed in the PDXs. This suggested that xenotransplantation of ovarian tumors and growth as PDX preserved at least in part the clonal diversity of the original tumor. We believe our data reinforce the potential of PDX as exquisite tools in pre-clinical assays. PMID:26334103

  4. The Acoustic Performance of Plane Laggings and Similar Multi-Layer Acoustic Structures.

    NASA Astrophysics Data System (ADS)

    Au, Chak Kuen

    Acoustic laggings are used to inhibit the transmission of the sound radiated from the vibrating surfaces of machines, ducts, pipes, etc. They are formed of layers of porous materials such as fibreglass or mineral wool, layers of impervious materials such as metal cladding sheets and sometimes airspaces. A novel procedure for estimating the diffuse field 1/3 octave band insertion loss which a plane acoustic lagging produces when applied to a plane structure is developed. This novel procedure, which constitutes the major contribution of the work described in the thesis to new knowledge, is based on sets of formulae which describe how obliquely incident plane sound waves interact with the different basic layers, such as the porous layers and the impervious layers which form the lagging. The validity of the procedure is demonstrated by comparing the results it produces with measured results. The procedure is then used to undertake a parametric study to assess the effect of the properties of the various types of layers. Often the cladding sheet of a lagging is fastened to the base structure which is being lagged and an approximate analysis to consider the effect of such fastening is presented. The influence of corrugated cladding sheets is also considered. The principles used to predict the performance of plane acoustic laggings can be adapted to predict other acoustic properties such as the acoustic absorption of plane acoustic structures and this is done in the final part of the thesis. A comparison is made between the predicted and the measured performances of various types of acoustic structures.

  5. 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.

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

    PubMed Central

    2014-01-01

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

  7. GMR sensing array technique validation study for the inspection of multi-layer metallic structures

    NASA Astrophysics Data System (ADS)

    Motes, Doyle; Aldrin, John C.; Keiser, Mark; Steffes, Gary; Forsyth, David S.

    2013-01-01

    Giant Magnetoresistive (GMR) sensing arrays have been developed to detect fatigue cracks in thick, multi-layered metallic structures. As part of a program conducted by the U.S. Air Force Research Laboratory, fatigue crack specimens were fabricated to provide inspection targets for a GMR array. These specimens were mounted to simulate a wing structure and inspected using a Boeing Mobile Automated Scanner (MAUS). Probability of Detection (POD) from inspections and the results of capability studies are presented.

  8. Numerical Simulation of Boundary Layer Structure and Cross-Equatorial Flow in the Eastern Pacific*

    E-print Network

    Xie, Shang-Ping

    * R. JUSTIN SMALL International Pacific Research Center, School of Ocean and Earth Science Pacific Research Center Contribution Number 299 and School of Ocean and Earth Science and Technology ConNumerical Simulation of Boundary Layer Structure and Cross-Equatorial Flow in the Eastern Pacific

  9. Investigation of the Turbulent Structure of a Cloud-Capped Mixed Layer Using Doppler Radar

    E-print Network

    Mark, Pinsky

    Investigation of the Turbulent Structure of a Cloud-Capped Mixed Layer Using Doppler Radar M. A vertically pointed Doppler radar is an efficient tool for investigating cloud microphysical parameters by a vertically pointed Doppler radar, namely, the radar reflectivity Z(h, t) and the mean ver- tical velocity V

  10. Matrix Backpropagation for Deep Networks with Structured Layers Catalin Ionescu2,3

    E-print Network

    Sminchisescu, Cristian

    widely used architecture is the con- volutional network (ConvNet) [26, 25], a deep processing model based and learning. While ConvNets are sufficiently expressive for classification tasks, a comprehensive, deep mathematical contributions. The first shows how to operate with structured layers when learning a deep net

  11. 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.

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

    DOE PAGESBeta

    Zhao, Zhao; Zhang, Haijun; Yuan, Hongtao; Wang, Shibing; Lin, Yu; Zeng, Qiaoshi; Xu, Gang; Liu, Zhenxian; Solanki, G. K.; Patel, K. D.; et al

    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

  13. High-frequency permeability in double-layered structure of amorphous Co-Ta-Zr films

    SciTech Connect

    Ochiai, Y.; Hayakawa, M.; Hayashi, K.; Aso, K.

    1988-06-01

    The high-frequency permeability of amorphous Co-Ta-Zr films was studied and the frequency dependence was described in terms of the eddy-current-loss formula. For the double-layered structure intervened with SiO/sub 2/ film, the degradation of the permeability became apparent with the decrease of SiO/sub 2/ thickness.

  14. Structure formation in the oceanic subsurface bubble layer by an internal wave field

    E-print Network

    Structure formation in the oceanic subsurface bubble layer by an internal wave field R of Sciences, 71 Prospect Oktyabrya, Ufa 450054, Russia Abstract We model the effects of an internal wave of surface waves with an internal wave. We find that the effects are twofold; bubbles are driven

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

    PubMed Central

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

    2015-01-01

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

  16. Characteristics of the behavior of the small-scale turbulence structure in the boundary layer

    SciTech Connect

    Dobrocheev, O.V.; Wojciechowski, J.

    1995-12-01

    Results of theoretical and experimental studies of the structure of turbulence in the boundary layer are presented. It is shown that the spectral density of turbulence energy deviates systematically from Kolmogorov-Obukhov`s law and a theoretical explanation of this deviation is given.

  17. 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 ?COO - 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 ?-sheet structures and to reduce the amount of ?-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.

  18. Growth and surface structure analysis of a new SiON single layer on SiC(0001)

    NASA Astrophysics Data System (ADS)

    Kohmatsu, Ryo; Nakagawa, Takeshi; Mizuno, Seigi

    2014-10-01

    A new silicon oxynitride layer was formed on a 6H-SiC(0001) surface by a nitrogen oxide treatment. The atomic structure of this single layer on the SiC(0001) substrate was determined by means of low-energy electron diffraction (LEED) analysis. The surface layer has a (?{3}×?{3}) R30° periodicity. Its LEED I(E) spectra are different from those of the previously reported silicon oxynitride layer which has a Si4O5N3 composition [Phys. Rev. Lett. 98 (2007) 136105]. The best-fit structure has a single layer of Si2ON3 composition terminated by O bridges. The Si-N layer of the determined structure has the same structure as that in the Si4O5N3 surface. The obtained Si2O3 structure would be useful for preparing an ideal SiC-insulator interfaces with a low interfacial density of states.

  19. The Research Magazine of the University of Potsdam Layers give structure and repetition. They are based on each

    E-print Network

    Potsdam, Universität

    within the Earth up to the surface, perhaps during the process of moun- tain building. Thin layers of ashThe Research Magazine of the University of Potsdam One 2013 #12;Layers give structure hierarchies, periods of growth and much more. A photo depicting layers allows for various associations about

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-01-01

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

  2. 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)( ?3-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 ?3-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.

  3. Optical and structural characterization of AlInN layers for optoelectronic applications

    NASA Astrophysics Data System (ADS)

    Aschenbrenner, T.; Dartsch, H.; Kruse, C.; Anastasescu, M.; Stoica, M.; Gartner, M.; Pretorius, A.; Rosenauer, A.; Wagner, Thomas; Hommel, D.

    2010-09-01

    Al1-xInxN layers with an indium content between x =10.5% and x =24% were grown by metal-organic vapor-phase epitaxy and characterized concerning their optical, structural and morphological properties with regard to the realization of optoelectronic devices. The indium content and the strain of these layers were measured by high resolution x-ray diffraction. Ellipsometric measurements were used to determine the optical constants [refractive index n(? ) and extinction coefficient ?(? )] in dependence of wavelength and indium content. The values determined for the electronic bandgaps are in good agreement with theoretical predictions and previous publications on this topic but are more focused on AlInN layers which are pseudomorphically grown on GaN. A bowing parameter of b =10.3±0.1 was determined for fully strained layers with an indium content between 13% and 24%. In order to investigate the suitability of these layers for use in distributed Bragg reflectors, the surface morphology is characterized with respect to the indium content. Furthermore, the influence of an annealing step which often is necessary during device growth, was studied. The influence of this annealing step on the roughness was analyzed by atomic force microscopy, while structural features are monitored by high resolution secondary electron microscopy images. Based on these results distributed Bragg reflectors for the green spectral region with up to 40 pairs and a peak reflectivity of 97% have been realized. Transmission electron microscopic analysis of the layer interfaces are in good agreement with the atomic force and secondary electron microscopy images of the single layer surfaces.

  4. Paleocene and Early Eocene volcanic ash layers in the Schlieren Flysch, Switzerland: U-Pb dating and Hf-isotopes of zircons, pumice geochemistry and origin

    NASA Astrophysics Data System (ADS)

    Koch, Simone; Winkler, Wilfried; Von Quadt, Albrecht; Ulmer, Peter

    2015-11-01

    Thin mm to cm thick bentonite layers of Paleocene to Early Eocene age in the Tonsteinschichten of the Schlieren Flysch represent volcanic ash layers. Heavy mineral analysis of the layers indicates basic to acidic volcanic sources. U/Pb dating of single zircon crystals of a Paleocene layer (WW1948) by LA-ICP-MS points to an eruption at 59.87 ± 0.41 Ma, whereas ID-TIMS shows an eruption age of 60.96 ± 0.07 Ma. Taking into account the external precision of LA-ICP-MS analyses of 1-2% both ages are overlapping and indicate an apparent minimal durations of zircon crystallization of 350 ka. Hf-isotope analysis of the same zircon crystals reveals the hybrid character of the source magma. The geochemical composition of the pumice grains of all bentonite layers is strongly affected by alteration. Nevertheless, the original character of the volcanic source can be evaluated. The Paleocene ashes (Lower Tonsteinschichten, LT) show a more fractionated multi-element pattern than the ashes of Early Eocene (Upper Tonsteinschichten, UT). The LT ash series are of rhyodacite to dacite character whereas the UT ashes fall in the field of alkali basalts. Both ash series seem to originate from a within-plate volcanic setting according to their trace element concentrations. Geochemical and temporary counterparts can be found in ash layers from Anthering (Austria) and the Danish Basin. As proposed for those ashes, volcanism connected to the opening of the North Atlantic might be the source as well for the ashes in the Schlieren Flysch. By comparison of the composition of rocks from the British Paleogene Igneous Province BPIP and the Schlieren Flysch ashes many correlations can be drawn which supports the suggestion of a North Atlantic origin of the Alpine ashes.

  5. On the origin of filamentary structure in sunspot penumbrae: linear instabilities

    NASA Astrophysics Data System (ADS)

    Tildesley, M. J.

    2003-01-01

    The fine structure present in sunspot penumbrae first appears when filamentary convection sets in at the outer edge of large pores, coinciding with an increase in magnetic field inclination to the vertical. The formation of this filamentary structure is investigated in a highly idealized Boussinesq model. A two-dimensional equilibrium is constructed with the magnetic field at the bottom of the layer concentrated towards one side of the box, but fanning out towards the top of the layer, mimicking a sunspot. This two-dimensional steady state is then perturbed in the third direction, to seek filamentary instabilities leading to a filamentary structure. The two-dimensional model is found to be highly unstable for a range of transverse wavenumbers. The form of the instability is such that an alternating pattern of bright and dark filaments develops at the upper surface. This is the first numerical evidence of filamentary instabilities driven by external convection.

  6. Features of oxide layer formation in high-aspect slot structures by means of MOCVD

    NASA Astrophysics Data System (ADS)

    Shevtsov, Yuri V.; Kuchumov, Boris ?.; Kruchinin, Vladimir N.; Spesivtsev, Evgeni V.; Golovnev, Igor F.; Igumenov, Igor ?.

    2015-03-01

    Processes were studied concerning the deposition of Hf and Mg oxide layers in the slot structures with the aspect ratio values from 30 to 500 by means of a pulsed MOCVD technique with a discrete components dosing. For assembling the slot structures, different combinations of materials have been used such as Si/Si, Si/glass, glass/chromium patterned glass, and Si/chromium patterned glass. The layers were characterized by means of XRD, XPS, and SEM methods. The thickness profiles of deposited films were measured using a high spatial resolution laser ellipsometry. It has been demonstrated that the radial distribution profiles of the thickness are determined by the process temperature, the aspect ratio value and the type of precursor. In contrast to HfO2 the layers of MgO with decreasing process temperature demonstrate change in the shape of layer profile distribution from a bowl-like shape to a dome-like one, with an increase of the film thickness at the center of the substrate. An image transfer process in the slot structure wherein one of the glass substrates is chromium-patterned has been studied within a wide range of experimental parameters. In order to describe these effects there has been a hybrid model proposed involving a combination of molecular dynamics and Monte Carlo methods. All the results obtained are discussed in detail.

  7. Buried amorphous layers by electronic excitation in ion-beam irradiated lithium niobate: Structure and kinetics

    NASA Astrophysics Data System (ADS)

    Olivares, J.; García-Navarro, A.; García, G.; Agulló-López, F.; Agulló-Rueda, F.; García-Cabañes, A.; Carrascosa, M.

    2007-02-01

    The formation of buried heavily damaged and amorphous layers by a variety of swift-ion irradiations (F at 22MeV, O at 20MeV, and Mg at 28MeV) on congruent LiNbO3 has been investigated. These irradiations assure that the electronic stopping power Se(z ) is dominant over the nuclear stopping Sn(z) and reaches a maximum value inside the crystal. The structural profile of the irradiated layers has been characterized in detail by a variety of spectroscopic techniques including dark-mode propagation, micro-Raman scattering, second-harmonic generation, and Rutherford backscattering spectroscopy/channeling. The growth of the damage on increasing irradiation fluence presents two differentiated stages with an abrupt structural transition between them. The heavily damaged layer reached as a final stage is optically isotropic (refractive index n =2.10, independent of bombarding ion) and has an amorphous structure. Moreover, it has sharp profiles and its thickness progressively increases with irradiation fluence. The dynamics under irradiation of the amorphous-crystalline boundaries has been associated with a reduction of the effective amorphization threshold due to the defects created by prior irradiation (cumulative damage). The kinetics of the two boundaries of the buried layer is quite different, suggesting that other mechanisms aside from the electronic stopping power should play a role on ion-beam damage.

  8. Buried amorphous layers by electronic excitation in ion-beam irradiated lithium niobate: Structure and kinetics

    SciTech Connect

    Olivares, J.; Garcia-Navarro, A.; Garcia, G.; Agullo-Lopez, F.; Agullo-Rueda, F.; Garcia-Cabanes, A.; Carrascosa, M.

    2007-02-01

    The formation of buried heavily damaged and amorphous layers by a variety of swift-ion irradiations (F at 22 MeV, O at 20 MeV, and Mg at 28 MeV) on congruent LiNbO{sub 3} has been investigated. These irradiations assure that the electronic stopping power S{sub e}(z) is dominant over the nuclear stopping S{sub n}(z) and reaches a maximum value inside the crystal. The structural profile of the irradiated layers has been characterized in detail by a variety of spectroscopic techniques including dark-mode propagation, micro-Raman scattering, second-harmonic generation, and Rutherford backscattering spectroscopy/channeling. The growth of the damage on increasing irradiation fluence presents two differentiated stages with an abrupt structural transition between them. The heavily damaged layer reached as a final stage is optically isotropic (refractive index n=2.10, independent of bombarding ion) and has an amorphous structure. Moreover, it has sharp profiles and its thickness progressively increases with irradiation fluence. The dynamics under irradiation of the amorphous-crystalline boundaries has been associated with a reduction of the effective amorphization threshold due to the defects created by prior irradiation (cumulative damage). The kinetics of the two boundaries of the buried layer is quite different, suggesting that other mechanisms aside from the electronic stopping power should play a role on ion-beam damage.

  9. Electronic Structure of Epitaxial Single-Layer MoS2

    NASA Astrophysics Data System (ADS)

    Miwa, Jill A.; Ulstrup, Søren; Sørensen, Signe G.; Dendzik, Maciej; ?abo, Antonija Grubiši?; Bianchi, Marco; Lauritsen, Jeppe Vang; Hofmann, Philip

    2015-01-01

    The electronic structure of epitaxial single-layer MoS2 on Au(111) is investigated by angle-resolved photoemission spectroscopy. Pristine and potassium-doped layers are studied in order to gain access to the conduction band. The potassium-doped layer is found to have a (1.39 ±0.05 ) eV direct band gap at K ¯ with the valence band top at ? ¯ having a significantly higher binding energy than at K ¯. The moiré superstructure of the epitaxial system does not lead to the presence of observable replica bands or minigaps. The degeneracy of the upper valence band at K ¯ is found to be lifted by the spin-orbit interaction, leading to a splitting of (145 ±4 ) meV . This splitting is anisotropic and in excellent agreement with recent calculations. Finally, it is shown that the potassium doping does not only give rise to a rigid shift of the band structure but also to a distortion, leading to the possibility of band structure engineering in single-layers of transition metal dichalcogenides.

  10. Structural characterization of nano-oxide layers in PtMn based specular spin valves

    SciTech Connect

    Zhou Min; Chen Lifan; Diao Zhitao; Park, C.-M.; Huai Yiming

    2005-05-15

    A systematic structure characterization of nano-oxide layers (NOLs) and specular spin valves using x-ray diffraction and high-resolution transmission electron microscopy (HRTEM) has been studied. High-angle x-ray diffraction data show almost identical fcc textures for both natural and plasma NOL spin-valves. Low-angle x-ray reflectivity spectrum shows more deteriorated Kiessig fringes at high incident angles for natural oxide sample, indicating rougher interfaces in natural oxidation than in plasma oxidation. Oxygen exposure plays an important role in NOLs process. Fabricating NOLs without any crystal structure degradation is critical to obtain high MR ratio. HRTEM reveals that oxide clusters mixing with insufficiently oxidized CoFe layers prevailed in natural NOL, and the natural oxidation was inhomogeneous. In contrast, plasma NOL has a thinner, more homogeneously oxidized CoFe layers with sharp interfaces. In plasma NOLs, the structures still maintain CoFe crystal structure. The structures and magnetic correlation of the NOL specular spin valves are discussed.

  11. Structural characterization of nano-oxide layers in PtMn based specular spin valves

    NASA Astrophysics Data System (ADS)

    Zhou, Min; Chen, Lifan; Diao, Zhitao; Park, Chang-Man; Huai, Yiming

    2005-05-01

    A systematic structure characterization of nano-oxide layers (NOLs) and specular spin valves using x-ray diffraction and high-resolution transmission electron microscopy (HRTEM) has been studied. High-angle x-ray diffraction data show almost identical fcc textures for both natural and plasma NOL spin-valves. Low-angle x-ray reflectivity spectrum shows more deteriorated Kiessig fringes at high incident angles for natural oxide sample, indicating rougher interfaces in natural oxidation than in plasma oxidation. Oxygen exposure plays an important role in NOLs process. Fabricating NOLs without any crystal structure degradation is critical to obtain high MR ratio. HRTEM reveals that oxide clusters mixing with insufficiently oxidized CoFe layers prevailed in natural NOL, and the natural oxidation was inhomogeneous. In contrast, plasma NOL has a thinner, more homogeneously oxidized CoFe layers with sharp interfaces. In plasma NOLs, the structures still maintain CoFe crystal structure. The structures and magnetic correlation of the NOL specular spin valves are discussed.

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

    NASA Astrophysics Data System (ADS)

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

    2012-11-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-06-01

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

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

    NASA Astrophysics Data System (ADS)

    Peixoto, Tiago P.

    2015-10-01

    Many network systems are composed of interdependent but distinct types of interactions, which cannot be fully understood in isolation. These different types of interactions are often represented as layers, attributes on the edges, or as a time dependence of the network structure. Although they are crucial for a more comprehensive scientific understanding, these representations offer substantial challenges. Namely, it is an open problem how to precisely characterize the large or mesoscale structure of network systems in relation to these additional aspects. Furthermore, the direct incorporation of these features invariably increases the effective dimension of the network description, and hence aggravates the problem of overfitting, i.e., the use of overly complex characterizations that mistake purely random fluctuations for actual structure. In this work, we propose a robust and principled method to tackle these problems, by constructing generative models of modular network structure, incorporating layered, attributed and time-varying properties, as well as a nonparametric Bayesian methodology to infer the parameters from data and select the most appropriate model according to statistical evidence. We show that the method is capable of revealing hidden structure in layered, edge-valued, and time-varying networks, and that the most appropriate level of granularity with respect to the additional dimensions can be reliably identified. We illustrate our approach on a variety of empirical systems, including a social network of physicians, the voting correlations of deputies in the Brazilian national congress, the global airport network, and a proximity network of high-school students.

  15. Self-assembly Columnar Structure in Active Layer of Bulk Heterojunction Solar Cell

    NASA Astrophysics Data System (ADS)

    Pan, Cheng; Segui, Jennifer; Yu, Yingjie; Li, Hongfei; Akgun, Bulent; Satijia, Sushil. K.; Gersappe, Dilip; Nam, Chang-Yong; Rafailovich, Miriam

    2012-02-01

    Bulk Heterojunction (BHJ) polymer solar cells are an area of intense interest due to their flexibility and relatively low cost. However, due to the disordered inner structure in active layer, the power conversion efficiency of BHJ solar cell is relatively low. Our research provides the method to produce ordered self-assembly columnar structure within active layer of bulk heterojunction (BHJ) solar cell by introducing polystyrene (PS) into the active layer. The blend thin film of polystyrene, poly (3-hexylthiophene-2,5-diyl) (P3HT) and [6,6]-phenyl C61 butyric acid methyl ester (PCBM) at different ratio are spin coated on substrate and annealed in vacuum oven for certain time. Atomic force microscopy (AFM) images show uniform phase segregation on the surface of polymer blend thin film and highly ordered columnar structure is then proven by etching the film with ion sputtering. TEM cross-section technology is also used to investigate the column structure. Neutron reflectometry was taken to establish the confinement of PCBM at the interface of PS and P3HT. The different morphological structures formed via phase segregation will be correlated with the performance of the PEV cells to be fabricated at the BNL-CFN.

  16. Mass Conservation in Modeling Moisture Diffusion in Multi-Layer Carbon Composite Structures

    NASA Technical Reports Server (NTRS)

    Nurge, Mark A.; Youngquist, Robert C.; Starr, Stanley O.

    2009-01-01

    Moisture diffusion in multi-layer carbon composite structures is difficult to model using finite difference methods due to the discontinuity in concentrations between adjacent layers of differing materials. Applying a mass conserving approach at these boundaries proved to be effective at accurately predicting moisture uptake for a sample exposed to a fixed temperature and relative humidity. Details of the model developed are presented and compared with actual moisture uptake data gathered over 130 days from a graphite epoxy composite sandwich coupon with a Rohacell foam core.

  17. Layer-dependent electronic structure of an atomically heavy two-dimensional dichalcogenide

    NASA Astrophysics Data System (ADS)

    Yeh, Po-Chun; Jin, Wencan; Zaki, Nader; Zhang, Datong; Liou, Jonathan T.; Sadowski, Jerzy T.; Al-Mahboob, Abdullah; Dadap, Jerry I.; Herman, Irving P.; Sutter, Peter; Osgood, Richard M.

    2015-01-01

    We report angle-resolved photoemission spectroscopic measurements of the evolution of the thickness-dependent electronic band structure of the atomically heavy two-dimensional layered dichalcogenide, tungsten diselenide (WS e2 ). Our data, taken on mechanically exfoliated WS e2 single crystals, provide direct evidence for shifting of the valence-band maximum from ? ¯ (multilayer WS e2 ) to K ¯ (single-layer WS e2 ). Further, our measurements also set a lower bound on the energy of the direct band gap and provide direct measurement of the hole effective mass.

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

    NASA Astrophysics Data System (ADS)

    Chan, Henry; Fromme, Paul

    2015-03-01

    Varying loading conditions of aircraft structures result in stress concentration at fastener holes, where multi-layered components are connected, possibly leading to the development of fatigue cracks. High frequency guided waves propagating along the structure allow for the non-destructive testing of such components, e.g., aircraft wings. However, the sensitivity for the detection of small, potentially hidden, fatigue cracks has to be ascertained. The type of multi-layered model structure investigated consists of two adhesively bonded aluminium plate-strips. Fatigue experiments were carried out. The sensitivity of the high frequency guided wave modes to monitor fatigue crack growth at a fastener hole during cyclic loading was investigated, using both standard pulse-echo equipment and laser interferometry. The sensitivity and repeatability of the measurements were ascertained, having the potential for fatigue crack growth monitoring at critical and difficult to access fastener locations from a stand-off distance.

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

    PubMed

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

    2015-02-01

    In this study, we investigate the influence of surface structure on the fouling propensity of thin-film composite (TFC) forward osmosis (FO) membranes. Specifically, we compare membranes fabricated through identical procedures except for the use of different solvents (dimethylformamide, DMF and N-methyl-2-pyrrolidinone, NMP) during phase separation. FO fouling experiments were carried out with a feed solution containing a model organic foulant. The TFC membranes fabricated using NMP (NMP-TFC) had significantly less flux decline (7.47 ± 0.15%) when compared to the membranes fabricated using DMF (DMF-TFC, 12.70 ± 2.62% flux decline). Water flux was also more easily recovered through physical cleaning for the NMP-TFC membrane. To determine the fundamental cause of these differences in fouling propensity, the active and support layers of the membranes were extensively characterized for physical and chemical characteristics relevant to fouling behavior. Polyamide surface roughness was found to dominate all other investigated factors in determining the fouling propensities of our membranes relative to each other. The high roughness polyamide surface of the DMF-TFC membrane was also rich in larger leaf-like structures, whereas the lower roughness NMP-TFC membrane polyamide layer contained more nodular and smaller features. The support layers of the two membrane types were also characterized for their morphological properties, and the relation between support layer surface structure and polyamide active layer formation was discussed. Taken together, our findings indicate that support layer structure has a significant impact on the fouling propensity of the active layer, and this impact should be considered in the design of support layer structures for TFC membranes. PMID:25564877

  20. Adaptive nonlinear polynomial neural networks for control of boundary layer/structural interaction

    NASA Technical Reports Server (NTRS)

    Parker, B. Eugene, Jr.; Cellucci, Richard L.; Abbott, Dean W.; Barron, Roger L.; Jordan, Paul R., III; Poor, H. Vincent

    1993-01-01

    The acoustic pressures developed in a boundary layer can interact with an aircraft panel to induce significant vibration in the panel. Such vibration is undesirable due to the aerodynamic drag and structure-borne cabin noises that result. The overall objective of this work is to develop effective and practical feedback control strategies for actively reducing this flow-induced structural vibration. This report describes the results of initial evaluations using polynomial, neural network-based, feedback control to reduce flow induced vibration in aircraft panels due to turbulent boundary layer/structural interaction. Computer simulations are used to develop and analyze feedback control strategies to reduce vibration in a beam as a first step. The key differences between this work and that going on elsewhere are as follows: that turbulent and transitional boundary layers represent broadband excitation and thus present a more complex stochastic control scenario than that of narrow band (e.g., laminar boundary layer) excitation; and secondly, that the proposed controller structures are adaptive nonlinear infinite impulse response (IIR) polynomial neural network, as opposed to the traditional adaptive linear finite impulse response (FIR) filters used in most studies to date. The controllers implemented in this study achieved vibration attenuation of 27 to 60 dB depending on the type of boundary layer established by laminar, turbulent, and intermittent laminar-to-turbulent transitional flows. Application of multi-input, multi-output, adaptive, nonlinear feedback control of vibration in aircraft panels based on polynomial neural networks appears to be feasible today. Plans are outlined for Phase 2 of this study, which will include extending the theoretical investigation conducted in Phase 2 and verifying the results in a series of laboratory experiments involving both bum and plate models.

  1. Some aspects of the double layer structure in magnetized electronegative plasmas with q-nonextensive electrons

    NASA Astrophysics Data System (ADS)

    Mehdipoor, M.; Mohsenpour, T.

    2015-11-01

    In this paper, the double layer (DL) structure in a magnetized electronegative plasma consisting of ions and nonextensive electrons is studied by using the reductive perturbation method. The basic set of fluid equations is reduced to the extended Korteweg-de Vries equation. It is shown that around the critical density, DL structures coexist. The effects of negative to positive ion density ratio ( ?), nonextensive index ( q ), the angle between the directions of the wave propagation vector and the external magnetic field ( lz ), and positive (negative) ion gyrofrequency ( ?± ) and positive to negative ion mass ratio ( Q ) on DL structure are discussed.

  2. COMMUNITY ECOLOGY -ORIGINAL RESEARCH Geographic variation in salt marsh structure and function

    E-print Network

    Pennings, Steven C.

    COMMUNITY ECOLOGY - ORIGINAL RESEARCH Geographic variation in salt marsh structure and function and function of salt marsh communities along the Atlantic and Gulf coasts of the United States. Focusing on the arthropod community in the dominant salt marsh plant Spartina alterniflora, we tested two hypotheses: first

  3. ORIGINAL ARTICLE Structural basis for the altered drug sensitivities of non-small cell lung

    E-print Network

    Zhijie, Liu

    ORIGINAL ARTICLE Structural basis for the altered drug sensitivities of non-small cell lung cancer and subsequent activation of its intracellular tyrosine kinase (TK) domain. The non-small cell lung cancer (NSCLC transduction pathways im- plicated in cancers (Wakeling et al., 2002). Tumors from non-small cell lung cancer

  4. 11. 22'X34' original blueprint, VariableAngle Launcher, 'CONTROL STATION STRUCTURAL DETAILS' ...

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

    11. 22'X34' original blueprint, Variable-Angle Launcher, 'CONTROL STATION STRUCTURAL DETAILS' drawn at 1 1/2'=1'-0'. (BUORD Sketch # 208401). - Variable Angle Launcher Complex, Control Station, CA State Highway 39 at Morris Reservior, Azusa, Los Angeles County, CA

  5. 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…

  6. 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.

  7. Deep structure and origin of the Baikal rift zone Dapeng Zhao a,, Jianshe Lei a

    E-print Network

    Gao, Stephen Shangxing

    -east. Lake Baikal occupies only about a third of the rift zone. It is the deepest lake (1620m) in the worldDeep structure and origin of the Baikal rift zone Dapeng Zhao a,, Jianshe Lei a , Tomofumi Inoue: S. King Abstract P-wave velocity images are determined under the Baikal rift zone in Siberia

  8. A planetary system as the origin of structure in Fomalhaut's dust belt

    E-print Network

    Kalas, Paul G.

    A planetary system as the origin of structure in Fomalhaut's dust belt Paul Kalas1 , James R resolution of 0.5 AU. The dust is distributed in a belt 25 AU wide, with a very sharp inner edge at a radial distance of 133 AU, and we measure an offset of 15 AU between the belt's geometric centre and Fomalhaut

  9. A Parametric Study of Cathode Catalyst Layer Structural Parameters on the Performance of a PEM Fuel Cell

    E-print Network

    Stockie, John

    A Parametric Study of Cathode Catalyst Layer Structural Parameters on the Performance of a PEM Fuel exchange membrane fuel cell (PEMFC) and how changes in its structural parameters affect performance. These results give useful guidelines for manufactures of PEMFC catalyst layers. Keywords: PEM fuel cell

  10. Highly Insulating Glazing Systems using Non-Structural Center Glazing Layers

    SciTech Connect

    Kohler, Christian; Arasteh, Dariush; Goudey, Howdy; Kohler, Christian

    2008-04-09

    Three layer insulating glass units with two low-e coatings and an effective gas fill are known to be highly insulating, with center-of-glass U-factors as low as 0.57 W/m{sup 2}-K (0.10 Btu/h-ft{sup 2}- F). Such units have historically been built with center layers of glass or plastic which extend all the way through the spacer system. This paper shows that triple glazing systems with non-structural center layers which do not create a hermetic seal at the edge have the potential to be as thermally efficient as standard designs, while potentially removing some of the production and product integration issues that have discouraged the use of triples.

  11. Hairpin Structures in a Turbulent Boundary Layer under Stalled-Airfoil-Type Flow Conditions

    NASA Astrophysics Data System (ADS)

    Maciel, Y.; Mayam, M. H. Shafiei

    Hairpin structures in the outer region of a turbulent boundary layer subjected to a strong adverse pressure gradient have been studied using PIV. The external flow conditions are similar to those found on the suction side of airfoils in trailing-edge post-stall conditions. Even if the flow is very different from zeropressure- gradient turbulent boundary layers, the gross features of the hairpin vortices and hairpin packets remain similar, even as separation is approached. The hairpin vortices are however slightly more inclined with respect to the wall, and their streamwise separation is smaller when scaled with the boundary layer thickness. The upward growth of the hairpin packets in the streamwise direction is also more important. The variations of these properties are consistent with the variations of the mean strain rates, in particular rates of streamwise contraction and wall-normal extension.

  12. Possibility of periodically reentrant superconductivity in ferromagnet/superconductor layered structures

    NASA Astrophysics Data System (ADS)

    Khusainov, M. G.; Proshin, Yu. N.

    1997-12-01

    We develop the theory of the proximity effect in layered ferromagnetic metal/superconductor (F/S) structures taking into account finite transparency of the F/S interface as well as depression of the Cooper pairing and diffusionlike motion of conduction electrons by a strong exchange field of the ferromagnet. It is shown that the oscillatory dependence of the critical temperature on the F-layer thickness is due to a periodic modulation of the F/S boundary transparency by the oscillations of pair amplitude within the F layer. It is possible not only in the F/S multilayers, but in the F/S bilayers as well. The phenomena of reentrant and periodically reentrant superconductivity in the F/S contacts and superlattices are predicted. The competition between the ``0'' phase and ``?'' phase types of superconductivity in the F/S multilayers is also discussed.

  13. Partial dark-field microscopy for investigating domain structures of double-layer microsphere film

    PubMed Central

    Heon Kim, Joon; Su Park, Jung

    2015-01-01

    A lateral dislocation in a double-layer microsphere film is very difficult to identify because the constituent domains have the same two-dimensional crystalline orientation. Orientation-sensitive optical techniques cannot resolve this issue. Here, we demonstrate that partial dark-field (pDF) optical microscopy can be very effective in identifying this type of domain boundary and dislocation of a close-packed microsphere double-layer. Using the hexagonal symmetry of the close-packed microsphere film and the light-focusing property of microspheres, the partially blocked dark-field condenser can provide much higher contrast than other optical microscopy modes can in identifying the laterally dislocated domains. The former can also distinguish domains with different crystalline orientation by rotating the pDF stop. The simplicity of the pDF mode will make it an ideal tool for the structural study of close-packed double-layer microsphere films. PMID:25959375

  14. Diverse and tunable electronic structures of single-layer metal phosphorus trichalcogenides for photocatalytic water splitting

    SciTech Connect

    Liu, Jian; Beijing Computational Science Research Center, Beijing 100084; College of Electrical and Information Engineering, Hunan Institute of Engineering, Xiangtan 411105, Hunan ; Li, Xi-Bo; Wang, Da; Liu, Li-Min E-mail: limin.liu@csrc.ac.cn; Lau, Woon-Ming; Chengdu Green Energy and Green Manufacturing Technology R and D Center, Chengdu, Sichuan 610207 ; Peng, Ping E-mail: limin.liu@csrc.ac.cn

    2014-02-07

    The family of bulk metal phosphorus trichalcogenides (APX{sub 3}, A = M{sup II}, M{sub 0.5}{sup I}M{sub 0.5}{sup III}; X = S, Se; M{sup I}, M{sup II}, and M{sup III} represent Group-I, Group-II, and Group-III metals, respectively) has attracted great attentions because such materials not only own magnetic and ferroelectric properties, but also exhibit excellent properties in hydrogen storage and lithium battery because of the layered structures. Many layered materials have been exfoliated into two-dimensional (2D) materials, and they show distinct electronic properties compared with their bulks. Here we present a systematical study of single-layer metal phosphorus trichalcogenides by density functional theory calculations. The results show that the single layer metal phosphorus trichalcogenides have very low formation energies, which indicates that the exfoliation of single layer APX{sub 3} should not be difficult. The family of single layer metal phosphorus trichalcogenides exhibits a large range of band gaps from 1.77 to 3.94 eV, and the electronic structures are greatly affected by the metal or the chalcogenide atoms. The calculated band edges of metal phosphorus trichalcogenides further reveal that single-layer ZnPSe{sub 3}, CdPSe{sub 3}, Ag{sub 0.5}Sc{sub 0.5}PSe{sub 3}, and Ag{sub 0.5}In{sub 0.5}PX{sub 3} (X = S and Se) have both suitable band gaps for visible-light driving and sufficient over-potentials for water splitting. More fascinatingly, single-layer Ag{sub 0.5}Sc{sub 0.5}PSe{sub 3} is a direct band gap semiconductor, and the calculated optical absorption further convinces that such materials own outstanding properties for light absorption. Such results demonstrate that the single layer metal phosphorus trichalcogenides own high stability, versatile electronic properties, and high optical absorption, thus such materials have great chances to be high efficient photocatalysts for water-splitting.

  15. Annealing effects on the magnetic dead layer and saturation magnetization in unit structures relevant to a synthetic ferrimagnetic free structure

    NASA Astrophysics Data System (ADS)

    Jang, Soo Young; You, Chun-Yeol; Lim, S. H.; Lee, S. R.

    2011-01-01

    The changes in the magnetic dead layer (MDL) and saturation magnetization of the CoFeB layers are investigated as a function of the annealing temperature for four different unit structures, that are relevant to the synthetic ferrimagnetic free structure in MgO-based magnetic tunnel junctions. The MDL results for these unit structures are then converted into those for the constituent interfaces of the free structure. Most of the changes in the MDL thickness occur during annealing at a low temperature of 150 °C while those in the saturation magnetization occur at a high annealing temperature of 350 °C. These results for the MDL and saturation magnetization are critically tested by using the synthetic ferrimagnetic free structures with various thickness asymmetries. The observed switching properties of these tested structures are in good agreement with those expected from the results for the MDL and saturation magnetization, confirming the accuracy of the present results. The accuracy of the saturation magnetization is further confirmed by ferromagnetic resonance experiments.

  16. 3D printing of layered brain-like structures using peptide modified gellan gum substrates.

    PubMed

    Lozano, Rodrigo; Stevens, Leo; Thompson, Brianna C; Gilmore, Kerry J; Gorkin, Robert; Stewart, Elise M; in het Panhuis, Marc; Romero-Ortega, Mario; Wallace, Gordon G

    2015-10-01

    The brain is an enormously complex organ structured into various regions of layered tissue. Researchers have attempted to study the brain by modeling the architecture using two dimensional (2D) in vitro cell culturing methods. While those platforms attempt to mimic the in vivo environment, they do not truly resemble the three dimensional (3D) microstructure of neuronal tissues. Development of an accurate in vitro model of the brain remains a significant obstacle to our understanding of the functioning of the brain at the tissue or organ level. To address these obstacles, we demonstrate a new method to bioprint 3D brain-like structures consisting of discrete layers of primary neural cells encapsulated in hydrogels. Brain-like structures were constructed using a bio-ink consisting of a novel peptide-modified biopolymer, gellan gum-RGD (RGD-GG), combined with primary cortical neurons. The ink was optimized for a modified reactive printing process and developed for use in traditional cell culturing facilities without the need for extensive bioprinting equipment. Furthermore the peptide modification of the gellan gum hydrogel was found to have a profound positive effect on primary cell proliferation and network formation. The neural cell viability combined with the support of neural network formation demonstrated the cell supportive nature of the matrix. The facile ability to form discrete cell-containing layers validates the application of this novel printing technique to form complex, layered and viable 3D cell structures. These brain-like structures offer the opportunity to reproduce more accurate 3D in vitro microstructures with applications ranging from cell behavior studies to improving our understanding of brain injuries and neurodegenerative diseases. PMID:26231917

  17. Structural and Chemical Evolution of Li- and Mn-rich Layered Cathode Material

    SciTech Connect

    Zheng, Jianming; Xu, Pinghong; Gu, Meng; Xiao, Jie; Browning, Nigel D.; Yan, Pengfei; Wang, Chong M.; Zhang, Jiguang

    2015-02-24

    Lithium (Li)- and manganese-rich (LMR) layered-structure materials are very promising cathodes for high energy density lithium-ion batteries. However, their voltage fading mechanism and its relationships with fundamental structural changes are far from being sufficiently understood. Here we report the detailed phase transformation pathway in the LMR cathode (Li[Li0.2Ni0.2Mn0.6]O2) during cycling for the samples prepared by hydro-thermal assistant method. It is found the transformation pathway of LMR cathode is closely correlated to its initial structure and preparation conditions. The results reveal that LMR cathode prepared by HA approach experiences a phase transformation from the layered structure to a LT-LiCoO2 type defect spinel-like structure (Fd-3m space group) and then to a disordered rock-salt structure (Fm-3m space group). The voltage fade can be well correlated with the Li ion insertion into octahedral sites, rather than tetrahedral sites, in both defect spinel-like structure and disordered rock-salt structure. The reversible Li insertion/removal into/from the disordered rock-salt structure is ascribed to the Li excess environment that can satisfy the Li percolating in the disordered rock-salt structure despite the increased kinetic barrier. Meanwhile, because of the presence of a great amount of oxygen vacancies, a significant decrease of Mn valence is detected in the cycled particle, which is below that anticipated for a potentially damaging Jahn-Teller distortion (+3.5). Clarification of the phase transformation pathway, cation redistribution, oxygen vacancy and Mn valence change undoubtedly provides insights into a profound understanding on the voltage fade, and capacity degradation of LMR cathode. The results also inspire us to further enhance the reversibility of LMR cathode via improving its surface structural stability.

  18. Active structural acoustic control using active constrained layer damping system and secondary acoustic controller

    NASA Astrophysics Data System (ADS)

    Lee, Joshua Taekyoung

    The active structural acoustic control of a beam with classical boundary conditions using an active constrained layer damping and a secondary acoustic controller is investigated. The beam is placed on an infinite rigid baffle. It is excited by a plane wave acoustic load and radiates sound into an anechoic acoustic medium. The primary goal of the control mechanisms is to reduce the radiated sound in a wide frequency range. The active constrained layer damping is used to dissipate the vibration energy of the beam. Although a damping device is usually more effective in mid- to high frequency ranges than in low frequency range, this research has developed a methodology that makes the active constrained layer damping effective in controlling resonant responses in the low frequency range. The secondary acoustic controller complements the active constrained layer damping by minimizing the subsequent radiated sound power. This acoustic controller is highly effective in reducing the overall noise in the low to mid-frequency ranges. In conclusion, it is found that, for a tonal excitation, the combined application of the active constrained layer damping and the secondary acoustic controller is an effective means to control acoustic response of a vibrating beam. By using them together, an efficient control of radiating sound power of vibrating beams is achieved in a wide frequency range.

  19. Structure and properties of titanium surface layers after electron beam alloying with powder mixtures containing carbon

    NASA Astrophysics Data System (ADS)

    Lenivtseva, O. G.; Bataev, I. A.; Golkovskii, M. G.; Bataev, A. A.; Samoilenko, V. V.; Plotnikova, N. V.

    2015-11-01

    The structure and tribological properties of commercially pure titanium (cp-Ti) samples after non-vacuum electron beam surface alloying with carbon were studied. Two types of powders were used to introduce carbon in surface layer of cp-Ti: titanium carbide (TiC) and mixture of pure titanium and graphite ("Ti + C"). Single layer and multilayer coatings were studied. Application of electron beam for alloying provided cladding rate of 4.5 m2/h. The thickness of the clad coatings was 1.6-2.0 mm. The main phases received after "Ti + C" powder cladding were ?-titanium, TiC, and retained graphite. In the samples obtained by cladding of TiC, graphite was not observed. A factor determining the microhardness and tribological properties of the cladded layer was the volume fraction of TiC. Maximum coating microhardness of 8 GPa was obtained by cladding of single layer of TiC powder or two layers of the "Ti + C" mixture. Two types of tests were carried out to evaluate the wear resistance of the samples. In friction tests against loose abrasive particles, the wear rate of the best samples was 9.3 times lower than that of cp-Ti. In wear tests using fixed abrasive particles, the relative wear resistance of the best samples was 2.3 times higher than that of cp-Ti.

  20. Picosecond laser structuring of thin film platinum layers covered with tantalum pentoxide isolation

    SciTech Connect

    Heise, Gerhard; Huber, Heinz; Trappendreher, Daniel; Ilchmann, Florian; Weiss, Robin S.; Wolf, Bernhard

    2012-07-01

    A thin film layer system consisting of platinum (Pt) as conductive layer on a glass substrate and tantalum pentoxide as isolating layer on top of the platinum is attractive for designing biocompatible conductor paths and contact pads for bio sensor chips. For the flexible and rapid patterning of the conductive and the isolating layers, both, the complete removal and the selective ablation of the individual thin films were investigated using ultra-short laser pulses with about 10 ps pulse duration and 1064 nm wavelength at low laser fluences. A platinum film covered with tantalum pentoxide shows a significantly lower ablation threshold than a single Pt film on glass alone when illuminated from the front side. Furthermore, we explored that the tantalum pentoxide film can be removed by glass side illumination from the Pt film, without affecting the Pt film and leaving the Pt film on the glass substrate intact. Those ablation phenomena occur at laser fluences of about 0.2 J/cm{sup 2}, far below the evaporation limit of platinum. We present a detailed ablation threshold value examination for the structuring of these layer systems by front side and glass side irradiation for different film thicknesses. Furthermore, we discuss the possible underlying physical mechanisms of these ablation phenomena.

  1. Effects of Complex Structured Anodic Oxide Dielectric Layer Grown in Pore Matrix for Aluminum Capacitor.

    PubMed

    Shin, Jin-Ha; Yun, Sook Young; Lee, Chang Hyoung; Park, Hwa-Sun; Suh, Su-Jeong

    2015-11-01

    Anodization of aluminum is generally divided up into two types of anodic aluminum oxide structures depending on electrolyte type. In this study, an anodization process was carried out in two steps to obtain high dielectric strength and break down voltage. In the first step, evaporated high purity Al on Si wafer was anodized in oxalic acidic aqueous solution at various times at a constant temperature of 5 degrees C. In the second step, citric acidic aqueous solution was used to obtain a thickly grown sub-barrier layer. During the second anodization process, the anodizing potential of various ranges was applied at room temperature. An increased thickness of the sub-barrier layer in the porous matrix was obtained according to the increment of the applied anodizing potential. The microstructures and the growth of the sub-barrier layer were then observed with an increasing anodizing potential of 40 to 300 V by using a scanning electron microscope (SEM). An impedance analyzer was used to observe the change of electrical properties, including the capacitance, dissipation factor, impedance, and equivalent series resistance (ESR) depending on the thickness increase of the sub-barrier layer. In addition, the breakdown voltage was measured. The results revealed that dielectric strength was improved with the increase of sub-barrier layer thickness. PMID:26726615

  2. Preparation and crystal structure of U3Fe2C5: An original uranium-iron carbide

    NASA Astrophysics Data System (ADS)

    Henriques, M. S.; Paixão, J. A.; Henriques, M. S. C.; Gonçalves, A. P.

    2015-09-01

    The U3Fe2C5 compound was prepared from the elements by arc-melting, followed by an heat-treatment in an induction furnace, at 1250 °C for 1 h and 1300 °C for 2 h. The crystal structure of this phase was determined by direct methods from single crystal X-ray diffraction data. U3Fe2C5 crystallizes in an original tetragonal crystal structure, with space group I4/mmm, a = 3.4980(3) Å and c = 19.8380(15) Å as lattice constants and two formula units per cell. This new type structure is characterized by the simultaneous presence of isolated and pairs of carbon atoms, the interatomic distances in the pairs being similar to a typical carbon-carbon double bond length found in a molecule. U3Fe2C5 is closely related to UC and UFeC2, and can be seen as build from two (distorted) UFeC2 unit cells and a UC layer.

  3. The Evolution of Electronic Structure in Few-layer Graphene Revealed by Optical Spectroscopy

    SciTech Connect

    Mak, K.; Sfeir, M; Misewich, J; Heinz, T

    2010-01-01

    The massless Dirac spectrum of electrons in single-layer graphene has been thoroughly studied both theoretically and experimentally. Although a subject of considerable theoretical interest, experimental investigations of the richer electronic structure of few-layer graphene (FLG) have been limited. Here we examine FLG graphene crystals with Bernal stacking of layer thicknesses N = 1,2,3,...8 prepared using the mechanical exfoliation technique. For each layer thickness N, infrared conductivity measurements over the spectral range of 0.2-1.0 eV have been performed and reveal a distinctive band structure, with different conductivity peaks present below 0.5 eV and a relatively flat spectrum at higher photon energies. The principal transitions exhibit a systematic energy-scaling behavior with N. These observations are explained within a unified zone-folding scheme that generates the electronic states for all FLG materials from that of the bulk 3D graphite crystal through imposition of appropriate boundary conditions. Using the Kubo formula, we find that the complete infrared conductivity spectra for the different FLG crystals can be reproduced reasonably well within the framework a tight-binding model.

  4. The Evolution of Electronic Structure in Few-layerGraphene Revealed by Optical Spectroscopy

    SciTech Connect

    Mak, K.F.; Sfeir, M.; Misewich, J.A.; Heinz, T.F.

    2010-08-24

    The massless Dirac spectrum of electrons in single-layer graphene has been thoroughly studied both theoretically and experimentally. Although a subject of considerable theoretical interest, experimental investigations of the richer electronic structure of few-layer graphene (FLG) have been limited. Here we examine FLG graphene crystals with Bernal stacking of layer thicknesses N = 1,2,3,...8 prepared using the mechanical exfoliation technique. For each layer thickness N, infrared conductivity measurements over the spectral range of 0.2-1.0 eV have been performed and reveal a distinctive band structure, with different conductivity peaks present below 0.5 eV and a relatively flat spectrum at higher photon energies. The principal transitions exhibit a systematic energy-scaling behavior with N. These observations are explained within a unified zone-folding scheme that generates the electronic states for all FLG materials from that of the bulk 3D graphite crystal through imposition of appropriate boundary conditions. Using the Kubo formula, we find that the complete infrared conductivity spectra for the different FLG crystals can be reproduced reasonably well within the framework a tight-binding model.

  5. Organic and inorganic–organic thin film structures by molecular layer deposition: A review

    PubMed Central

    Sundberg, Pia

    2014-01-01

    Summary The possibility to deposit purely organic and hybrid inorganic–organic materials in a way parallel to the state-of-the-art gas-phase deposition method of inorganic thin films, i.e., atomic layer deposition (ALD), is currently experiencing a strongly growing interest. Like ALD in case of the inorganics, the emerging molecular layer deposition (MLD) technique for organic constituents can be employed to fabricate high-quality thin films and coatings with thickness and composition control on the molecular scale, even on complex three-dimensional structures. Moreover, by combining the two techniques, ALD and MLD, fundamentally new types of inorganic–organic hybrid materials can be produced. In this review article, we first describe the basic concepts regarding the MLD and ALD/MLD processes, followed by a comprehensive review of the various precursors and precursor pairs so far employed in these processes. Finally, we discuss the first proof-of-concept experiments in which the newly developed MLD and ALD/MLD processes are exploited to fabricate novel multilayer and nanostructure architectures by combining different inorganic, organic and hybrid material layers into on-demand designed mixtures, superlattices and nanolaminates, and employing new innovative nanotemplates or post-deposition treatments to, e.g., selectively decompose parts of the structure. Such layer-engineered and/or nanostructured hybrid materials with exciting combinations of functional properties hold great promise for high-end technological applications. PMID:25161845

  6. Structural and optical properties of layers of pentacene formed by PLD method

    NASA Astrophysics Data System (ADS)

    Potera, Piotr; Sagan, Piotr; Virt, Ihor; Kuzma, Marian; Wisz, Grzegorz; Rudyj, Ihor; Frugynski, Marian

    2008-12-01

    Organic films fabrication offers the possibility of producing electronic devices of low weight, mechanical flexibility and low cost. One suitable material for organic film fabrigation which is the subject of the great interest is pentacene, because it is characterized by the large carrier mobility (˜1 cm2/Vs). In this work, the growth of pentacene layers using pulse laser deposition (PLD) on different substrates (glass/ITO, Si) is described and various processing parameters are investigated. Two pulsed YAG:Nd3+ laser wavelengths were used for the ablation of the PLD target: the first harmonic at 1064 nm aGn:dNdth3+e second at 532 nm. The structure of the layers formed was examined using SEM and RHEED methods. The results were compared with results of optical spectroscopy studies. It will be shown that layers deposed using second harmonics have a higher quality than those for first harmonic. The other PLD parametersalso have a strong influence on the structure quality of layers.

  7. Interrelated structures of the transport shock and collisional relaxation layer in a multitemperature, multilevel ionized gas

    NASA Technical Reports Server (NTRS)

    Vinolo, A. R.; Clarke, J. H.

    1973-01-01

    The gas dynamic structures of the transport shock and the downstream collisional relaxation layer are evaluated for partially ionized monatomic gases. Elastic and inelastic collisional nonequilibrium effects are taken into consideration. In the microscopic model of the atom, three electronic levels are accounted for. By using an asymptotic technique, the shock morphology is found on a continuum flow basis. This procedure gives two distinct layers in which the nonequilibrium effects to be considered are different. A transport shock appears as the inner solution to an outer collisional relaxation layer. The results show four main interesting points: (1) on structuring the transport shock, ionization and excitation rates must be included in the formulation, since the flow is not frozen with respect to the population of the different electronic levels; (2) an electron temperature precursor appears at the beginning of the transport shock; (3) the collisional layer is rationally reduced to quadrature for special initial conditions, which (4) are obtained from new Rankine-Hugoniot relations for the inner shock.

  8. Characterization of the planetary boundary layer height and structure by Raman lidar: comparison of different approaches

    NASA Astrophysics Data System (ADS)

    Summa, D.; Di Girolamo, P.; Stelitano, D.; Cacciani, M.

    2013-06-01

    The Planetary Boundary Layer (PBL) includes the portion of the atmosphere which is directly influenced by the presence of the Earth's surface. Aerosol particles trapped within the PBL can be used as tracers to study the boundary-layer vertical structure and time variability. As a result of this, elastic backscatter signals collected by lidar systems can be used to determine the height and the internal structure of the PBL. The present analysis considers three different methods to estimate the PBL height. A first method is based on the determination of the first order derivative of the logarithm of the range-corrected elastic lidar signals. Estimates of the PBL height for specific case studies obtained from this approach are compared with simultaneous estimates from the potential temperature profiles measured by radiosondes launched simultaneously to lidar operation. Additional estimates of the boundary layer height are based on the determination of the first order derivative of the range-corrected rotational Raman lidar signals. This latter approach results to be successfully applicable also in the afternoon-evening decaying phase of the PBL, when the effectiveness of the approach based on the elastic lidar signals may be compromised or altered by the presence of the residual layer. Results from these different approaches are compared and discussed in the paper, with a specific focus on selected case studies collected by the University of Basilicata Raman lidar system BASIL during the Convective and Orographically-induced Precipitation Study (COPS).

  9. Characterization of the planetary boundary layer height and structure by Raman lidar: comparison of different approaches

    NASA Astrophysics Data System (ADS)

    Summa, D.; Di Girolamo, P.; Stelitano, D.; Cacciani, M.

    2013-12-01

    The planetary boundary layer (PBL) includes the portion of the atmosphere which is directly influenced by the presence of the earth's surface. Aerosol particles trapped within the PBL can be used as tracers to study the boundary-layer vertical structure and time variability. As a result of this, elastic backscatter signals collected by lidar systems can be used to determine the height and the internal structure of the PBL. The present analysis considers three different methods to estimate the PBL height. The first method is based on the determination of the first-order derivative of the logarithm of the range-corrected elastic lidar signals. Estimates of the PBL height for specific case studies obtained through this approach are compared with simultaneous estimates from the potential temperature profiles measured by radiosondes launched simultaneously to lidar operation. Additional estimates of the boundary layer height are based on the determination of the first-order derivative of the range-corrected rotational Raman lidar signals. This latter approach results to be successfully applicable also in the afternoon-evening decaying phase of the PBL, when the effectiveness of the approach based on the elastic lidar signals may be compromised or altered by the presence of the residual layer. Results from these different approaches are compared and discussed in the paper, with a specific focus on selected case studies collected by the University of Basilicata Raman lidar system BASIL during the Convective and Orographically-induced Precipitation Study (COPS).

  10. Study on the multi-layer structure and the formation mechanism of the interface layer between WN_x/Si(100)

    NASA Astrophysics Data System (ADS)

    Choi, Ilsang; Park, Jucheol; Choi, Jintae; Kim, Hojoung; Lee, Sounyoung

    2001-03-01

    A poly-metal gate composed of W/WN_x/poly-Si or denuded-WN_x/poly-Si gate is the most promising candidate for a low resistive gate in the deep submicron ULSI^1,2. In these cases, it has been reported there exists the interface layer between WN_x/poly-Si and its thickness increase as the annealing temperature does. It has been known that the interface layer plays a role as a barrier against silicidation up to 1000^oC. But the layered structure of the interface and the mechanism of the barrier formation are not clear yet. By using XRD, HRTEM, EELS, and ARXPS, we could uncover the chemical bonding states and the formation mechanism of interface layers between WN_x/Si(100) with the help of chemical wet etching. We observed that the multi-layer structure of the interface is W/(Si,W)-oxide/SiON/WSi_x/Si(100). The thickness and the layered structure of the barrier are varied as the annealing temperature increases up to 1000^oC. The formation mechanism of the barrier will be discussed in this presentation. 1 Y.Akasaka, etc, IEEE Trans. Electron Devices 43, 1864 (1996) 2 B.H.Lee, etc, Appl. Phys. Lett. 76, 2538 (2000)

  11. Investigating the performance of catalyst layer micro-structures with different platinum loadings

    SciTech Connect

    Khakaz-Baboli, Moben; Harvey, David; Pharoah, Jon

    2012-07-01

    In this study a four-phase micro-structure of a PEFC catalyst layer was reconstructed by randomly placing overlapping spheres for each solid catalyst phase. The micro-structure was mirrored to make a micro-structure. A body-fit computational mesh was produced for the reconstructed micro-structure in OpenFOAM. Associated conservation equations were solved within all the phases with electrochemical reaction as the boundary condition at the interface between ionomer and platinum phases. The study is focused on the platinum loading of CL. The polarization curves of the micro-structure performance have been compared for different platinum loadings. This paper gives increased insight into the relatively greater losses at decreased platinum loadings.

  12. 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.

  13. Finite Element Analysis of Layered Fiber Composite Structures Accounting for the Material's Microstructure and Delamination

    NASA Astrophysics Data System (ADS)

    Stier, Bertram; Simon, Jaan-Willem; Reese, Stefanie

    2015-04-01

    The present paper focuses on composite structures which consist of several layers of carbon fiber reinforced plastics (CFRP). For such layered composite structures, delamination constitutes one of the major failure modes. Predicting its initiation is essential for the design of these composites. Evaluating stress-strength relation based onset criteria requires an accurate representation of the through-the-thickness stress distribution, which can be particularly delicate in the case of shell-like structures. Thus, in this paper, a solid-shell finite element formulation is utilized which allows to incorporate a fully three-dimensional material model while still being suitable for applications involving thin structures. Moreover, locking phenomena are cured by using both the EAS and the ANS concept, and numerical efficiency is ensured through reduced integration. The proposed anisotropic material model accounts for the material's micro-structure by using the concept of structural tensors. It is validated by comparison to experimental data as well as by application to numerical examples.

  14. Magnetic field tunable acoustic resonator with ferromagnetic-ferroelectric layered structure

    NASA Astrophysics Data System (ADS)

    Polzikova, Natalia; Alekseev, Sergey; Kotelyanskii, Iosif; Raevskiy, Alexander; Fetisov, Yuri

    2013-05-01

    High overtone acoustic resonator with yttrium iron garnet/zinc oxide layered structure was theoretically considered, fabricated, and experimentally investigated. The theory of the resonator, containing an arbitrary number of magnetic and nonmagnetic dielectric/ferroelectric layers, placed in a transverse magnetic field is presented. The simulation shows the possibility to tune the resonant frequency in the range of ±1 MHz by magnetic field. This tuning is due to the resonance magnetoelastic interaction in the saturated ferrite film and the total phase shift of acoustic wave in the structure. The experiment proves the magnetic field influence on resonance frequencies and attenuation of transverse wave with polarization vector quasicollinear with the field direction. The tuning about 0.25 MHz near the acoustic resonant frequency 2 GHz was obtained in the field 260 Oe. This frequency is close to the ferromagnetic resonance frequency in ferrite film, corresponding to the field applied.

  15. Uranium nitride chloride UNCl: 30 K-class ferromagnet with layered structure

    NASA Astrophysics Data System (ADS)

    Nakamura, Akio; Akabori, Mitsuo; Ogawa, Toru; Huntelaar, M.

    2005-04-01

    Uranium nitride chloride (UNCl) has an unique tetragonal crystal structure, in which the U/N/U trilayer is sandwiched by the chlorine (Cl) double layers. This structure is homologous to Hf(Zr)NCl, for which high- TC superconductivity ( T=25.5 K) has been recently discovered to result from the lithium (Li) intercalation. Recent specific heat measurements on this compound have revealed the existence of a lambda-type phase transition around 32 K. In the present study, this anomaly was confirmed to be correspondent for a ferromagnetic transition in the uranium ions having a localized 4f 2(U 4+) character: Its saturation moment ( ?B(sat)) attains a value of ?1.56 ?B at 2 K. Among varieties of actinide (An) compounds, UNCl and related systems, AnNX (X=halogens (Cl, Br, I)) may represent a novel class of layer mixed compounds with intriguing magnetic, electronic and chemical-bonding properties.

  16. Swept shock/boundary-layer interactions: Scaling laws, flowfield structure, and experimental methods

    NASA Technical Reports Server (NTRS)

    Settles, Gary S.

    1993-01-01

    A general review is given of several decades of research on the scaling laws and flowfield structures of swept shock wave/turbulent boundary layer interactions. Attention is further restricted to the experimental study and physical understanding of the steady-state aspects of these flows. The interaction produced by a sharp, upright fin mounted on a flat plate is taken as an archetype. An overall framework of quasiconical symmetry describing such interactions is first developed. Boundary-layer separation, the interaction footprint, Mach number scaling, and Reynolds number scaling are then considered, followed by a discussion of the quasiconical similarity of interactions produced by geometrically-dissimilar shock generators. The detailed structure of these interaction flowfields is next reviewed, and is illustrated by both qualitative visualizations and quantitative flow images in the quasiconical framework. Finally, the experimental techniques used to investigate such flows are reviewed, with emphasis on modern non-intrusive optical flow diagnostics.

  17. Observation of Exchange Anisotropy in Single-Phase Layer-Structured Oxides with Long Periods

    PubMed Central

    Huang, Yan; Wang, Guopeng; Sun, Shujie; Wang, Jianlin; Peng, Ranran; Lin, Yue; Zhai, Xiaofang; Fu, Zhengping; Lu, Yalin

    2015-01-01

    A remarkable exchange bias effect arising from the temperature-dependent interaction among the ferromagnetic-like cluster glasses and antiferromagnetic regions was observed in a newly developed single-phase multiferroic compound of Bi10Fe6Ti3O30 which has a nine-layer Aurivillius structure. Inhomogeneous distribution of magnetic Fe ions inside this long-period layered structure was experimentally identified via the atomic level imaging. The results confirmed the presence of the short-range magnetic ordering (the cluster glassy state) and the canted antiferromagnetism, and then the direct interaction among them was further confirmed. Finding of this new single-phase material accompanying this remarkable exchange bias effect would be beneficial to both basic physics understanding and the potential device development. PMID:26487509

  18. Electronic Structure of Few-Layer Graphene: Experimental Demonstration of Strong Dependence on Stacking Sequence

    NASA Astrophysics Data System (ADS)

    Mak, Kin Fai; Shan, Jie; Heinz, Tony F.

    2010-04-01

    The electronic structure of few-layer graphene (FLG) samples with crystalline order was investigated experimentally by infrared absorption spectroscopy for photon energies ranging from 0.2-1 eV. Distinct optical conductivity spectra were observed for different samples having precisely the same number of layers. The different spectra arise from the existence of two stable polytypes of FLG, namely, Bernal (AB) stacking and rhombohedral (ABC) stacking. The observed absorption features, reflecting the underlying symmetry of the two polytypes and the nature of the associated van Hone singularities, were reproduced by explicit calculations within a tight-binding model. The findings demonstrate the pronounced effect of stacking order on the electronic structure of FLG.

  19. Observation of Exchange Anisotropy in Single-Phase Layer-Structured Oxides with Long Periods.

    PubMed

    Huang, Yan; Wang, Guopeng; Sun, Shujie; Wang, Jianlin; Peng, Ranran; Lin, Yue; Zhai, Xiaofang; Fu, Zhengping; Lu, Yalin

    2015-01-01

    A remarkable exchange bias effect arising from the temperature-dependent interaction among the ferromagnetic-like cluster glasses and antiferromagnetic regions was observed in a newly developed single-phase multiferroic compound of Bi10Fe6Ti3O30 which has a nine-layer Aurivillius structure. Inhomogeneous distribution of magnetic Fe ions inside this long-period layered structure was experimentally identified via the atomic level imaging. The results confirmed the presence of the short-range magnetic ordering (the cluster glassy state) and the canted antiferromagnetism, and then the direct interaction among them was further confirmed. Finding of this new single-phase material accompanying this remarkable exchange bias effect would be beneficial to both basic physics understanding and the potential device development. PMID:26487509

  20. Hydrogen storage in a chemical bond stabilized Co9S8-graphene layered structure.

    PubMed

    Qin, Wei; Han, Lu; Bi, Hai; Jian, Jiahuang; Wu, Xiaohong; Gao, Peng

    2015-12-21

    With the high energy ball milling method, a Co9S8-decorated reduced graphene oxide (RGO) composite, which shows excellent hydrogen storage capacity, has been successfully fabricated with a well-organized layered structure. Moreover, the stabilized mechanism of the well-organized layered structure is investigated and attributed to the strong interactions between Co9S8 and defective RGO. The C-S bond interaction is identified and the hydrogen storage process is also studied with different analysis methods. Finally, an optimized Co9S8 to RGO weight ratio of 6?:?1 shows excellent electrochemical performances in terms of the excellent cycling stability and competitive hydrogen storage capacity of 4.86 wt%. PMID:26572221

  1. Confinement Effects on the Structure and Dynamics in Intercalated Polymer / Layered Silicates Nanohybrids

    SciTech Connect

    Chrissopoulou, K.; Afratis, A.; Fotiadou, S.; Frick, B.; Anastasiadis, S. H.

    2010-06-02

    The structure and dynamics of PEO/Na{sup +} MMT nanocomposites are investigated by XRD, DSC, and quasielastic neutron scattering (QENS). For concentrations up to 20 wt% the PEO chains within the galleries form either a single- or a double-layered structure of intercalated chains; at higher PEO content only double layers of intercalated PEO chains are formed within the 0.9 nm galleries. Moreover, it is only for polymer content above 70 wt% that peaks corresponding to crystalline PEO and DSC melting transition are observed, indicating that the confined chains remain liquid-like and only the excess polymer outside the completely full galleries can crystallize. QENS investigated the dynamics of PEO in bulk and in confinement. A jump of the bulk PEO dynamics at T{sub m} is observed whereas the dynamics of confined PEO shows only weak wavevector and temperature dependence and goes smoothly through the bulk T{sub m}.

  2. Structure-phase states of silumin surface layer after electron beam and high cycle fatigue

    NASA Astrophysics Data System (ADS)

    Konovalov, S. V.; Alsaraeva, K. V.; Gromov, V. E.; Ivanov, Yu F.

    2015-11-01

    Modification of eutectic silumin surface has been implemented by high-intensity pulsed electron beam. The irradiation mode has been revealed; it allows increasing silumin fatigue life in more than 3.5 times. It has been established that the main reason of this fact is the formation of a multiphase submicro- and nanosized structure. It has been elicited that the most danger stress concentrators are large silicon plates situated on the surface and near-surface layers.

  3. Complex layered materials and periodic electromagnetic band-gap structures: Concepts, characterizations, and applications

    NASA Astrophysics Data System (ADS)

    Mosallaei, Hossein

    The main objective of this dissertation is to characterize and create insight into the electromagnetic performances of two classes of composite structures, namely, complex multi-layered media and periodic Electromagnetic Band-Gap (EBG) structures. The advanced and diversified computational techniques are applied to obtain their unique propagation characteristics and integrate the results into some novel applications. In the first part of this dissertation, the vector wave solution of Maxwell's equations is integrated with the Genetic Algorithm (GA) optimization method to provide a powerful technique for characterizing multi-layered materials, and obtaining their optimal designs. The developed method is successfully applied to determine the optimal composite coatings for Radar Cross Section (RCS) reduction of canonical structures. Both monostatic and bistatic scatterings are explored. A GA with hybrid planar/curved surface implementation is also introduced to efficiently obtain the optimal absorbing materials for curved structures. Furthermore, design optimization of the non-uniform Luneburg and 2-shell spherical lens antennas utilizing modal solution/GA-adaptive-cost function is presented. The lens antennas are effectively optimized for both high gain and suppressed grating lobes. The second part demonstrates the development of an advanced computational engine, which accurately computes the broadband characteristics of challenging periodic electromagnetic band-gap structures. This method utilizes the Finite Difference Time Domain (FDTD) technique with Periodic Boundary Condition/Perfectly Matched Layer (PBC/PML), which is efficiently integrated with the Prony scheme. The computational technique is successfully applied to characterize and present the unique propagation performances of different classes of periodic structures such as Frequency Selective Surfaces (FSS), Photonic Band-Gap (PBG) materials, and Left-Handed (LH) composite media. The results are incorporated into some novel applications such as high Q nanocavity lasers, guiding the electromagnetic waves at sharp bends, and miniaturized microstrip patch antennas.

  4. Layered Structure and Swelling Behavior of a Multiple Hydrate-Forming Pharmaceutical Compound

    SciTech Connect

    Kiang, Y.; Xu, W; Stephens, P; Ball, R; Yasuda, N

    2009-01-01

    Investigation of one anhydrous and four hydrated forms of a pharmaceutical compound (1) using both single-crystal and high-resolution powder X-ray diffraction methods revealed a two-dimensional framework which, upon exposure to moisture, absorbed water between the layers, causing the lattice to expand by as much as 20% of the axial length along a. The single-crystal structure was solved and refined for the pentahydrate form in space group C2 with unit cell parameters a = 36.961(5) Angstroms, b = 7.458(2) Angstroms, c = 20.691(4) Angstroms, e = 99.461(1), and V = 5626(4) Angstroms3. In the single-crystal structure the water layers were parallel to the bc plane and sandwiched by the crystalline compound 1 framework. Upon a change of relative humidity, water goes in and out of the interlayer space with the retention of the layer structure of the development compound. Starting from the anhydrous form, each additional water of hydration increased the interlayer spacing of the pharmaceutical solid by 1.3 Angstroms, half the size of a water molecule. In an exploratory formulation, this expansion of interlayer spacing caused tablets to crack upon storage at high relative humidity.

  5. Superheating suppresses structural disorder in layered BiI3 semiconductors grown by the Bridgman method

    NASA Astrophysics Data System (ADS)

    Johns, Paul M.; Sulekar, Soumitra; Yeo, Shinyoung; Baciak, J. E.; Bliss, Mary; Nino, Juan C.

    2016-01-01

    The susceptibility of layered structures to stacking faults is a problem in some of the more attractive semiconductor materials for ambient-temperature radiation detectors. In this work, Bridgman-grown BiI3 layered single crystals are investigated to understand and eliminate structural disorder, which reduces radiation detector performance. The use of superheating gradients has been shown by others to improve crystal quality in non-layered semiconductor crystals (Rudolph et al., 1996) [26]; thus the technique was explored to improve the growth of BiI3. When investigating the homogeneity of non-superheated crystals, highly geometric void defects were found to populate the bulk of the crystals. Applying a superheating gradient to the melt prior to crystal growth improved structural quality and decreased defect density from the order of 4600 voids per cm3 to 300 voids per cm3. Corresponding moderate improvements to electronic properties also resulted from the superheat gradient method of crystal growth. Comparative measurements through infrared microscopy, etch-pit density, X-ray rocking curves, and sheet resistivity readings show that superheat gradients in BiI3 growth led to higher quality crystals.

  6. Capacity of graphite's layered structure to suppress the sputtering yield: A molecular dynamics study

    NASA Astrophysics Data System (ADS)

    Tian, Jiting; Zheng, Tao; Yang, Jiangyan; Kong, Shuyan; Xue, Jianming; Wang, Yugang; Nordlund, Kai

    2015-05-01

    20-120 keV C60 bombardment on graphite and 20 keV C60 impact on diamond are studied by classical molecular dynamics (MD) simulations. The number of atoms ejected from graphite after a 20 keV C60 impact is found to be much smaller than that from diamond. By analyzing the microscopic sputtering process, we find this difference is due to the combined effects of graphite's low number density and layered structure. These two features of graphite make the pressure waves during the spike stage much weaker and the crater rim much more stable, compared to the case of diamond. While the role of atomic density on sputtering has been discussed in previous studies, effect of layered structure has not gained much attention yet. To affirm this effect and exclude the influence of density, we have also simulated C60 impact on an amorphous carbon (a-C) target whose density is very close to that of graphite. The yield of a-C is higher than that of graphite, certifying the capacity of graphite's layered structure to suppress the sputtering yield.

  7. Structural system identification of buildings by a wave method based on a layered Timoshenko beam model

    NASA Astrophysics Data System (ADS)

    Ebrahimian, Mahdi; Todorovska, Maria I.

    2014-03-01

    A layered Timoshenko beam (TB) model of a high-rise building is presented and applied to system identification of a full-scale building from recorded seismic response. This model is a new development in a wave method for earthquake damage detection and structural health monitoring being developed by the authors' research group. The method is based on monitoring changes in the wave properties of the structure, such as the velocity of wave propagation vertically through the structure. This model is an improvement over the previously used layered shear beam (SB) model because it accounts for wave dispersion caused by flexural deformation present in addition to shear. It also accounts for the rotatory inertia and the variation of the building properties with height. The case study is a 54-story steel frame building located in downtown Los Angeles. Recorded accelerations during the Northridge earthquake of 1994 are used for system identification of the NS response. The model parameters are identified by matching, in the least squares sense, the model and observed impulse response functions at all levels where motion was recorded. The model is then used to compute the building vertical phase and group velocities. Impulse responses computed by deconvolution of the recorded motions with the roof response are used, which represent the building response to a virtual source at the roof. The better match of transfer-function amplitudes of the fitted TB model than of previously fitted SB model indicates that the layered TB model is a better physical model for this building.

  8. Plasmonic light trapping in an ultrathin photovoltaic layer with film-coupled metamaterial structures

    NASA Astrophysics Data System (ADS)

    Wang, Hao; Wang, Liping

    2015-02-01

    A film-coupled metamaterial structure is numerically investigated for enhancing the light absorption in an ultrathin photovoltaic layer of crystalline gallium arsenide (GaAs). The top subwavelength concave grating and the bottom metallic film could not only effectively trap light with the help of wave interference and magnetic resonance effects excited above the bandgap, but also practically serve as electrical contacts for photon-generated charge collection. The energy absorbed by the active layer is greatly enhanced with the help of the film-coupled metamaterial structure, resulting in significant improvement on the short-circuit current density by three times over a free-standing GaAs layer at the same thickness. The performance of the proposed light trapping structure is demonstrated to be little affected by the grating ridge width considering the geometric tolerance during fabrication. The optical absorption at oblique incidences also shows direction-insensitive behavior, which is highly desired for efficiently converting off-normal sunlight to electricity. The results would facilitate the development of next-generation ultrathin solar cells with lower cost and higher efficiency.

  9. Born energy, acid-base equilibrium, structure and interactions of end-grafted weak polyelectrolyte layers

    NASA Astrophysics Data System (ADS)

    Nap, R. J.; Tagliazucchi, M.; Szleifer, I.

    2014-01-01

    This work addresses the effect of the Born self-energy contribution in the modeling of the structural and thermodynamical properties of weak polyelectrolytes confined to planar and curved surfaces. The theoretical framework is based on a theory that explicitly includes the conformations, size, shape, and charge distribution of all molecular species and considers the acid-base equilibrium of the weak polyelectrolyte. Namely, the degree of charge in the polymers is not imposed but it is a local varying property that results from the minimization of the total free energy. Inclusion of the dielectric properties of the polyelectrolyte is important as the environment of a polymer layer is very different from that in the adjacent aqueous solution. The main effect of the Born energy contribution on the molecular organization of an end-grafted weak polyacid layer is uncharging the weak acid (or basic) groups and consequently decreasing the concentration of mobile ions within the layer. The magnitude of the effect increases with polymer density and, in the case of the average degree of charge, it is qualitatively equivalent to a small shift in the equilibrium constant for the acid-base equilibrium of the weak polyelectrolyte monomers. The degree of charge is established by the competition between electrostatic interactions, the polymer conformational entropy, the excluded volume interactions, the translational entropy of the counterions and the acid-base chemical equilibrium. Consideration of the Born energy introduces an additional energetic penalty to the presence of charged groups in the polyelectrolyte layer, whose effect is mitigated by down-regulating the amount of charge, i.e., by shifting the local-acid base equilibrium towards its uncharged state. Shifting of the local acid-base equilibrium and its effect on the properties of the polyelectrolyte layer, without considering the Born energy, have been theoretically predicted previously. Account of the Born energy leads to systematic, but in general small, corrections to earlier theoretical predictions describing the behavior of weak polyelectrolyte layers. However, polyelectrolyte uncharging results in a decrease in the concentration of counterions and inclusion of the Born Energy can result in a substantial decrease of the counterion concentration. The effect of considering the Born energy contribution is explored for end-grafted weak polyelectrolyte layers by calculating experimental observables which are known to depend on the presence of charges within the polyelectrolyte layer: inclusion of the Born energy contribution leads to a decrease in the capacitance of polyelectrolyte-modified electrodes, a decrease of conductivity of polyelectrolyte-modified nanopores and an increase in the repulsion exerted by a planar polyelectrolyte layer confined by an opposing wall.

  10. Born energy, acid-base equilibrium, structure and interactions of end-grafted weak polyelectrolyte layers.

    PubMed

    Nap, R J; Tagliazucchi, M; Szleifer, I

    2014-01-14

    This work addresses the effect of the Born self-energy contribution in the modeling of the structural and thermodynamical properties of weak polyelectrolytes confined to planar and curved surfaces. The theoretical framework is based on a theory that explicitly includes the conformations, size, shape, and charge distribution of all molecular species and considers the acid-base equilibrium of the weak polyelectrolyte. Namely, the degree of charge in the polymers is not imposed but it is a local varying property that results from the minimization of the total free energy. Inclusion of the dielectric properties of the polyelectrolyte is important as the environment of a polymer layer is very different from that in the adjacent aqueous solution. The main effect of the Born energy contribution on the molecular organization of an end-grafted weak polyacid layer is uncharging the weak acid (or basic) groups and consequently decreasing the concentration of mobile ions within the layer. The magnitude of the effect increases with polymer density and, in the case of the average degree of charge, it is qualitatively equivalent to a small shift in the equilibrium constant for the acid-base equilibrium of the weak polyelectrolyte monomers. The degree of charge is established by the competition between electrostatic interactions, the polymer conformational entropy, the excluded volume interactions, the translational entropy of the counterions and the acid-base chemical equilibrium. Consideration of the Born energy introduces an additional energetic penalty to the presence of charged groups in the polyelectrolyte layer, whose effect is mitigated by down-regulating the amount of charge, i.e., by shifting the local-acid base equilibrium towards its uncharged state. Shifting of the local acid-base equilibrium and its effect on the properties of the polyelectrolyte layer, without considering the Born energy, have been theoretically predicted previously. Account of the Born energy leads to systematic, but in general small, corrections to earlier theoretical predictions describing the behavior of weak polyelectrolyte layers. However, polyelectrolyte uncharging results in a decrease in the concentration of counterions and inclusion of the Born Energy can result in a substantial decrease of the counterion concentration. The effect of considering the Born energy contribution is explored for end-grafted weak polyelectrolyte layers by calculating experimental observables which are known to depend on the presence of charges within the polyelectrolyte layer: inclusion of the Born energy contribution leads to a decrease in the capacitance of polyelectrolyte-modified electrodes, a decrease of conductivity of polyelectrolyte-modified nanopores and an increase in the repulsion exerted by a planar polyelectrolyte layer confined by an opposing wall. PMID:24437914

  11. Born energy, acid-base equilibrium, structure and interactions of end-grafted weak polyelectrolyte layers

    SciTech Connect

    Nap, R. J.; Tagliazucchi, M.; Szleifer, I.

    2014-01-14

    This work addresses the effect of the Born self-energy contribution in the modeling of the structural and thermodynamical properties of weak polyelectrolytes confined to planar and curved surfaces. The theoretical framework is based on a theory that explicitly includes the conformations, size, shape, and charge distribution of all molecular species and considers the acid-base equilibrium of the weak polyelectrolyte. Namely, the degree of charge in the polymers is not imposed but it is a local varying property that results from the minimization of the total free energy. Inclusion of the dielectric properties of the polyelectrolyte is important as the environment of a polymer layer is very different from that in the adjacent aqueous solution. The main effect of the Born energy contribution on the molecular organization of an end-grafted weak polyacid layer is uncharging the weak acid (or basic) groups and consequently decreasing the concentration of mobile ions within the layer. The magnitude of the effect increases with polymer density and, in the case of the average degree of charge, it is qualitatively equivalent to a small shift in the equilibrium constant for the acid-base equilibrium of the weak polyelectrolyte monomers. The degree of charge is established by the competition between electrostatic interactions, the polymer conformational entropy, the excluded volume interactions, the translational entropy of the counterions and the acid-base chemical equilibrium. Consideration of the Born energy introduces an additional energetic penalty to the presence of charged groups in the polyelectrolyte layer, whose effect is mitigated by down-regulating the amount of charge, i.e., by shifting the local-acid base equilibrium towards its uncharged state. Shifting of the local acid-base equilibrium and its effect on the properties of the polyelectrolyte layer, without considering the Born energy, have been theoretically predicted previously. Account of the Born energy leads to systematic, but in general small, corrections to earlier theoretical predictions describing the behavior of weak polyelectrolyte layers. However, polyelectrolyte uncharging results in a decrease in the concentration of counterions and inclusion of the Born Energy can result in a substantial decrease of the counterion concentration. The effect of considering the Born energy contribution is explored for end-grafted weak polyelectrolyte layers by calculating experimental observables which are known to depend on the presence of charges within the polyelectrolyte layer: inclusion of the Born energy contribution leads to a decrease in the capacitance of polyelectrolyte-modified electrodes, a decrease of conductivity of polyelectrolyte-modified nanopores and an increase in the repulsion exerted by a planar polyelectrolyte layer confined by an opposing wall.

  12. Highly reducing conditions during core formation on Mercury: Implications for internal structure and the origin of a magnetic field

    NASA Astrophysics Data System (ADS)

    Malavergne, Valérie; Toplis, Michael J.; Berthet, Sophie; Jones, John

    2010-03-01

    The high average density and low surface FeO content of the planet Mercury are shown to be consistent with very low oxygen fugacity during core segregation, in the range 3-6 log units below the iron-wüstite buffer. These low oxygen fugacities, and associated high metal content, are characteristic of high-iron enstatite (EH) and Bencubbinite (CB) chondrites, raising the possibility that such materials may have been important building blocks for this planet. With this idea in mind we have explored the internal structure of a Mercury sized planet of EH or CB bulk composition. Phase equilibria in the silicate mantle have been modeled using the thermodynamic calculator p-MELTS, and these simulations suggest that orthopyroxene will be the dominant mantle phase for both EH and CB compositions, with crystalline SiO 2 being an important minor phase at all pressures. Simulations for both compositions predict a plagioclase-bearing "crust" at low pressure, significant clinopyroxene also being calculated for the CB bulk composition. Concerning the core, comparison with recent high pressure and high temperature experiments relevant to the formation of enstatite meteorites, suggest that the core of Mercury may contain several wt.% silicon, in addition to sulfur. In light of the pressure of the core-mantle boundary on Mercury (˜7 GPa) and the pressure at which the immiscibility gap in the system Fe-S-Si closes (˜15 GPa) we suggest that Mercury's core may have a complex shell structure comprising: (i) an outer layer of Fe-S liquid, poor in Si; (ii) a middle layer of Fe-Si liquid, poor in S; and (iii) an inner core of solid metal. The distribution of heat-producing elements between mantle and core, and within a layered core have been quantified. Available data for Th and K suggest that these elements will not enter the core in significant amounts. On the other hand, for the case of U both recently published metal/silicate partitioning data, as well as observations of U distribution in enstatite chondrites, suggest that this element behaves as a chalcophile element at low oxygen fugacity. Using these new data we predict that U will be concentrated in the outer layer of the mercurian core. Heat from the decay of U could thus act to maintain this part of Mercury's core molten, potentially contributing to the origin of Mercury's magnetic field. This result contrasts with the Earth where the radioactive decay of U represents a negligible contribution to core heating.

  13. Structural changes in the nano-oxide layer with annealing in specular spin valves

    NASA Astrophysics Data System (ADS)

    Jang, S. H.; Kim, Y. W.; Kang, T.; Kim, H. J.; Kim, K. Y.

    2003-05-01

    We investigated microstructural changes in a nano-oxide layer (NOL) with annealing in specular spin valves (SVs) by cross-sectional transmission electron microscopy and x-ray photoelectron spectroscopy analysis. In the SV annealed at high temperature of 400 °C, an increase in thickness and a local breakdown of the NOL were observed. This local coarsening of the NOL is closely related to the formation of Mn oxides in the oxide-rich part of the NOL through Mn diffusion. Thus, the chemical structure of the NOL changes to the structure with Mn oxide-rich content after annealing.

  14. Defect mode suppression in a photonic crystal structure with a resonance nanocomposite layer

    SciTech Connect

    Moiseev, Sergey G; Ostatochnikov, Vladimir A; Sementsov, Dmitrii I

    2012-06-30

    This paper examines the key features of the transmission and reflection spectra of a one-dimensional photonic crystal structure in which a nanocomposite layer is sandwiched between dielectric Bragg mirrors. Two orthogonal polarisations of an incident wave correspond to different plasmon resonance frequencies of the nanocomposite. If one of the plasmon frequencies coincides with the defect mode frequency in one of the photonic bandgaps, complete suppression of the defect mode in the transmission spectrum is possible, which makes the spectra of such structures polarisation-sensitive.

  15. Anti-plane transverse waves propagation in nanoscale periodic layered piezoelectric structures.

    PubMed

    Chen, A-Li; Yan, Dong-Jia; Wang, Yue-Sheng; Zhang, Chuanzeng

    2016-02-01

    In this paper, anti-plane transverse wave propagation in nanoscale periodic layered piezoelectric structures is studied. The localization factor is introduced to characterize the wave propagation behavior. The transfer matrix method based on the nonlocal piezoelectricity continuum theory is used to calculate the localization factor. Additionally, the stiffness matrix method is applied to compute the wave transmission spectra. A cut-off frequency is found, beyond which the elastic waves cannot propagate through the periodic structure. The size effect or the influence of the ratio of the internal to external characteristic lengths on the cut-off frequency and the wave propagation behavior are investigated and discussed. PMID:26518526

  16. Determining crustal structure beneath seismic stations overlying a low-velocity sedimentary layer using receiver functions

    NASA Astrophysics Data System (ADS)

    Yu, Youqiang; Song, Jianguo; Liu, Kelly H.; Gao, Stephen S.

    2015-05-01

    The receiver function (RF) technique has been widely applied to investigate crustal and mantle layered structures using P-to-S converted (Ps) phases from velocity discontinuities. However, the presence of low-velocity (relative to that of the bedrock) sediments can give rise to strong reverberations in the resulting RFs, frequently masking the Ps phases from crustal and mantle boundaries. Such reverberations are caused by P-to-S conversions and their multiples associated with the strong impedance contrast across the bottom of the low-velocity sedimentary layer. Here we propose and test an approach to effectively remove the near-surface reverberations and decipher the Ps phases associated with the Moho discontinuity. Autocorrelation is first applied on the observed RFs to determine the strength and two-way traveltime of the reverberations, which are then used to construct a resonance removal filter in the frequency domain to remove or significantly reduce the reverberations. The filtered RFs are time corrected to eliminate the delay effects of the sedimentary layer and applied to estimate the subsediment crustal thickness and VP/VSusing a H-k stacking procedure. The resulting subsediment crustal parameters (thickness and VP/VS) are subsequently used to determine the thickness and VP/VS of the sedimentary layer, using a revised version of the H-k stacking procedure. Testing using both synthetic and real data suggests that this computationally inexpensive technique is efficient in resolving subsediment crustal properties beneath stations sitting on a low-velocity sedimentary layer and can also satisfactorily determine the thickness and VP/VS of the sedimentary layer.

  17. Topology optimization of damping layers for minimizing sound radiation of shell structures

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaopeng; Kang, Zhan

    2013-05-01

    This paper deals with the sensitivity analysis of structural acoustic performance in presence of non-proportional damping and optimal layout design of the damping layer of vibrating shell structures under harmonic excitations. The structural system with a partially-covered damping layer has a non-proportional global damping matrix. Therefore, the method of complex mode superposition in the state space is employed in the dynamic response analysis. The sound pressure is calculated with the structural response solution by using the boundary element method. In this context, an adjoint variable scheme for the design sensitivity analysis of sound pressure is developed. In the optimal design problem, the design objective is to minimize the structural vibration-induced sound pressure at a specified point in the acoustic medium by distributing a given amount of damping material. An artificial damping material model that has a similar form as in the SIMP approach is employed, and the relative densities of the damping material are considered as design variables. Numerical examples are given to illustrate the validity and efficiency of this approach. The influences of the excitation frequency, the damping coefficients and the locations of the reference point on the optimal topologies are also discussed.

  18. High-frequency guided ultrasonic waves for hidden defect detection in multi-layered aircraft structures.

    PubMed

    Masserey, Bernard; Raemy, Christian; Fromme, Paul

    2014-09-01

    Aerospace structures often contain multi-layered metallic components where hidden defects such as fatigue cracks and localized disbonds can develop, necessitating non-destructive testing. Employing standard wedge transducers, high frequency guided ultrasonic waves that penetrate through the complete thickness were generated in a model structure consisting of two adhesively bonded aluminium plates. Interference occurs between the wave modes during propagation along the structure, resulting in a frequency dependent variation of the energy through the thickness with distance. The wave propagation along the specimen was measured experimentally using a laser interferometer. Good agreement with theoretical predictions and two-dimensional finite element simulations was found. Significant propagation distance with a strong, non-dispersive main wave pulse was achieved. The interaction of the high frequency guided ultrasonic waves with small notches in the aluminium layer facing the sealant and on the bottom surface of the multilayer structure was investigated. Standard pulse-echo measurements were conducted to verify the detection sensitivity and the influence of the stand-off distance predicted from the finite element simulations. The results demonstrated the potential of high frequency guided waves for hidden defect detection at critical and difficult to access locations in aerospace structures from a stand-off distance. PMID:24856653

  19. Tuning structures and electronic spectra of graphene layers with tilt grain boundaries

    NASA Astrophysics Data System (ADS)

    Yin, Long-Jing; Qiao, Jia-Bin; Wang, Wen-Xiao; Chu, Zhao-Dong; Zhang, Kai Fen; Dou, Rui-Fen; Gao, Chun Lei; Jia, Jin-Feng; Nie, Jia-Cai; He, Lin

    2014-05-01

    Despite the fact that structures and properties of tilt grain boundaries of graphite surface and graphene have been extensively studied, their effect on the structures and electronic spectra of graphene layers has not been fully addressed. Here we study effects of one-dimensional tilt grain boundaries on structures and electronic spectra of graphene multilayers by scanning tunneling microscopy and spectroscopy. A tilt grain boundary of a top graphene sheet in graphene multilayers leads to a twist between consecutive layers and generates superstructures (Moiré patterns) on one side of the boundary. Our results demonstrate that the twisting changes the electronic spectra of Bernal graphene bilayer and graphene trilayers dramatically. We also study quantum-confined twisted graphene bilayer generated between two adjacent tilt grain boundaries and find that the band structure of such a system is still valid even when the number of superstructures is reduced to two in one direction. It implies that the electronic structure of this system is driven by the physics of a single Moiré spot.

  20. 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

  1. Structural characterization of graphene layers in various Indian coals by X-Ray Diffraction technique

    NASA Astrophysics Data System (ADS)

    Manoj, B.; Kunjomana, A. G.

    2015-02-01

    The results of the structural investigation of three Indian coals showed that, the structural parameters like fa & Lc increased where as interlayer spacing d002 decreased with increase in carbon content, aromaticity and coal rank. These structural parameters change just opposite with increase in volatile matter content. Considering the 'turbostratic' structure for coals, the minimum separation between aromatic lamellae was found to vary between 3.34 to 3.61 A° for these coals. As the aromaticity increased, the interlayer spacing decreased an indication of more graphitization of the sample. Volatile matter and carbon content had a strong influence on the aromaticity, interlayer spacing and stacking height on the sample. The average number of carbon atoms per aromatic lamellae and number of layers in the lamellae was found to be 16-21 and 7-8 for all the samples.

  2. Effect of Diffusion Control Layer on Reverse Al-Induced Layer Exchange Process for High-Quality Ge/Al/Glass Structure

    NASA Astrophysics Data System (ADS)

    Nakazawa, K.; Toko, K.; Suemasu, T.

    2015-05-01

    Fabricating large-grained polycrystalline Ge (poly-Ge) thin films on conducting-layer coated glass is a promising approach to lower the manufacturing cost of high-efficiency III-V tandem solar cells. We investigated the self-organizing formation of poly-Ge/Al/glass structures by using Al-induced layer exchange. The layer exchange between amorphous Ge and Al layers was completed at a low temperature of 350°C. Forming the interlayer between Ge and Al, i.e., limiting the diffusion of Ge to Al lowered the Ge nucleation rate and then enlarged the grain size of the resulting poly-Ge layer. The natively oxidized Al interlayer, formed by exposing a thin Al membrane (2-nm thickness) to air for 180 min, led to the poly-Ge with grains 46 ?m in size. Moreover, the Ge layer was highly (111)-oriented. This Ge/Al/glass structure appears promising for use in the bottom cell of the III-V semiconductor based tandem solar cells, as well as in the epitaxial templates for aligned nanowires and other advanced materials.

  3. Convection and correlation of coherent structure in turbulent boundary layer using tomographic particle image velocimetry

    NASA Astrophysics Data System (ADS)

    Wang, Wei; Guan, Xin-Lei; Jiang, Nan

    2014-10-01

    The present experimental work focuses on a new model for space—time correlation and the scale-dependencies of convection velocity and sweep velocity in turbulent boundary layer over a flat wall. A turbulent boundary layer flow at Re? = 2460 is measured by tomographic particle image velocimetry (tomographic PIV). It is demonstrated that arch, cane, and hairpin vortices are dominant in the logarithmic layer. Hairpins and hairpin packets are responsible for the elongated low-momentum zones observed in the instantaneous flow field. The conditionally-averaged coherent structures systemically illustrate the key roles of hairpin vortice in the turbulence dynamic events, such as ejection and sweep events and energy transport. The space—time correlations of instantaneous streamwise fluctuation velocity are calculated and confirm the new elliptic model for the space—time correlation instead of Taylor hypothesis. The convection velocities derived from the space—time correlation and conditionally-averaged method both suggest the scaling with the local mean velocity in the logarithmic layer. Convection velocity result based on Fourier decomposition (FD) shows stronger scale- dependency in the spanwise direction than in streamwise direction. Compared with FD, the proper orthogonal decomposition (POD) has a distinct distribution of convection velocity for the large- and small-scales which are separated in light of their contributions of turbulent kinetic energy.

  4. On atomic structure of Ge huts growing on the Ge/Si(001) wetting layer

    SciTech Connect

    Arapkina, Larisa V.; Yuryev, Vladimir A.

    2013-09-14

    Structural models of growing Ge hut clusters—pyramids and wedges—are proposed on the basis of data of recent STM investigations of nucleation and growth of Ge huts on the Si(001) surface in the process of molecular beam epitaxy. It is shown that extension of a hut base along <110> directions goes non-uniformly during the cluster growth regardless of its shape. Growing pyramids, starting from the second monolayer, pass through cyclic formation of slightly asymmetrical and symmetrical clusters, with symmetrical ones appearing after addition of every fourth monolayer. We suppose that pyramids of symmetrical configurations composed by 2, 6, 10, etc., monolayers over the wetting layer are more stable than asymmetrical ones. This might explain less stability of pyramids in comparison with wedges in dense arrays forming at low temperatures of Ge deposition. Possible nucleation processes of pyramids and wedges on wetting layer patches from identical embryos composed by 8 dimers through formation of 1 monolayer high 16-dimer nuclei different only in their symmetry is discussed. Schematics of these processes are presented. It is concluded from precise STM measurements that top layers of wetting layer patches are relaxed when huts nucleate on them.

  5. Structure of the turbulent/non-turbulent interface of turbulent boundary layers - DNS results

    NASA Astrophysics Data System (ADS)

    Ishihara, Takashi; Ogasawara, Hiroki; Hunt, Julian C. R.

    2013-11-01

    Direct numerical simulations (DNS) of turbulent boundary layers (TBL) along a flat plate are used to study the properties of turbulent/non-turbulent (T/NT) interface of the TBL. The values of the momentum-thickness-based Reynolds numbers, Re? , used for this study, are 500 - 2200 . Analysis of the conditional statistics near the interface of the TBL shows that there is a small peak in the span-wise vorticity, and an associated small jump in stream-wise velocity. It is shown that the interfacial layer has a double structure which consists of a turbulent sub-layer with thickness of the order of the Taylor micro scale and its outer boundary (super layer) with thickness of the order of the Kolmogorov length scale. An approximate profile of the conditional average of span-wise vorticity near the interface fits well to the DNS data. The velocity jump near the T/NT interface of the TBL is of the order of the rms value of velocity fluctuations near the interface. Conditional cross correlations of the stream-wise or the wall-normal velocity fluctuations change sharply across the interface, which are consistent with the blocking mechanism of the interface (Hunt and Durbin 1999).

  6. Simulation and Implementation of Moth-eye Structures as a Broadband Anti-Reflective Layer

    NASA Astrophysics Data System (ADS)

    Deshpande, Ketan S.

    Conventional single layer thin anti-reflective coatings (ARCs) are only suitable for narrowband applications. A multilayer film stack is often employed for broadband applications. A coating of multiple layers with alternating low and high refractive index materials increases the overall cost of the system. This makes multilayer ARCs unsuitable for low-cost broadband applications. Since the discovery of moth-eye corneal nipple patterns and their potential applicability in the field of broadband ARCs, many studies have been carried out to fabricate these bio-inspired nanostructures with available manufacturing processes. Plasma etching processes used in microelectronic manufacturing are applied for creating these nanostructures at the Rochester Institute of Technology's Semiconductor & Microsystems Fabrication Laboratory (SMFL). Atomic Force Microscope (AFM) scanned surfaces of the nanostructure layer are simulated and characterized for their optical properties using a Finite-Difference Time Domain (FDTD) simulator from Lumerical Solutions, Inc. known as FDTD Solutions. Simulation results show that the layer is anti-reflective over 50 to 350 nm broadband of wavelengths at 0° angle of incidence. These simulation results were supported by ellipsometer reflection measurements off the actual samples at multiple angles of light incidence, which show a 10% to 15% decrease in reflection for 240 to 400 nm wavelengths. Further improvements in the optical efficiency of these structures can be achieved through simulation-fabrication-characterization cycles performed for this project. The optimized nanostructures can then serve the purpose of low-cost anti-reflective coatings for solar cells and similar applications.

  7. The peculiarities of the Bleustein-Gulyaev wave propagation in structures containing conductive layer.

    PubMed

    Kuznetsova, I ?; Zaitsev, B D

    2015-05-01

    As known, anomalous resisto-acoustic effect is a fundamental property for weakly inhomogeneous piezoactive waves (Bleustein-Gulyaev, Love, and some leaky waves). It consists in that the velocity of aforementioned waves first increases, achieves its maximum, and only then decreases with increasing conductance of a layer placed at the surface of piezoelectric half-space. In this paper we continue to study the peculiarities of the effect appearance and the influence of different electrical boundary conditions on its characteristics. Conditions have been found under which the said effect appears and, respectively, disappears. The magnitude of positive change in velocity with increasing layer conductance is demonstrated to be reduced up to zero as a layer with arbitrary conductance has been moved away from the piezoelectric surface. The positive change in velocity increases when an perfectly conductive screen moves away from the "piezoelectric half-space - conductive layer" structure. The obtained results are useful for a more deep understanding the physical basis of propagation of weakly inhomogeneous piezoactive acoustic waves (Bleustein-Gulyaev, Love, and some leaky waves). PMID:25670410

  8. The structure of variable property, compressible mixing layers in binary gas mixtures

    NASA Technical Reports Server (NTRS)

    Kozusko, F.; Grosch, C. E.; Jackson, T. L.; Kennedy, Christipher A.; Gatski, Thomas B.

    1996-01-01

    We present the results of a study of the structure of a parallel compressible mixing layer in a binary mixture of gases. The gases included in this study are hydrogen (H2), helium (He), nitrogen (N2), oxygen (02), neon (Ne) and argon (Ar). Profiles of the variation of the Lewis and Prandtl numbers across the mixing layer for all thirty combinations of gases are given. It is shown that the Lewis number can vary by as much as a factor of eight and the Prandtl number by a factor of two across the mixing layer. Thus assuming constant values for the Lewis and Prandtl numbers of a binary gas mixture in the shear layer, as is done in many theoretical studies, is a poor approximation. We also present profiles of the velocity, mass fraction, temperature and density for representative binary gas mixtures at zero and supersonic Mach numbers. We show that the shape of these profiles is strongly dependent on which gases are in the mixture as well as on whether the denser gas is in the fast stream or the slow stream.

  9. The first layer of water on Rh(111): Microscopic structure and desorption kinetics

    SciTech Connect

    Beniya, Atsushi; Yamamoto, Susumu; Mukai, Kozo; Yamashita, Yoshiyuki; Yoshinobu, Jun

    2006-08-07

    The adsorption states and growth process of the first water (D{sub 2}O) layer on Rh(111) were investigated using infrared reflection absorption spectroscopy, temperature programed desorption, and spot-profile-analysis low energy electron diffraction. Water molecules wet the Rh(111) surface intact. At the early stage of first layer growth, a ({radical}3x{radical}3)R30 deg. commensurate water layer grows where 'up' and 'down' species coexist; the up and down species represent water molecules which have free OD, pointing to a vacuum and the substrate, respectively. The up domain was a flatter structure than an icelike bilayer. Water desorption from Rh(111) was a half-order process. The activation energy and the preexponential factor of desorption are estimated to be 60 kJ/mol and 4.8x10{sup 16} ML{sup 1/}2/s at submonolayer coverage, respectively. With an increase in water coverage, the flat up domain becomes a zigzag layer, like an ice bilayer. At the saturation coverage, the amount of down species is 1.3 times larger than that of the up species. In addition, the activation energy and the preexponential factor of desorption decrease to 51 kJ/mol and 1.3x10{sup 14} ML{sup 1/2}/s, respectively.

  10. Layered zirconium phosphonate with inorganic-organic hybrid structure: Preparation and its assembly with DNA

    NASA Astrophysics Data System (ADS)

    Liu, Li-Min; Lu, Guo-Yuan; Jiang, Li-Ping; Zhu, Jun-Jie

    2014-07-01

    An aminoethoxy-functionalized zirconium phosphonate (Zr(O3POCH2CH2NH2)2·3H2O), abbreviated as ZrRP (R=OCH2CH2NH2), with layered structure has been synthesized. This layered compound possesses the characteristic of inorganic-organic hybrid, due to the covalently linked aminoethoxy in the host layer. The anion exchanged property of this zirconium phosphonate is suitable for the direct intercalation of negatively charged DNA, which is different from these reported zirconium phosphates or zirconium phosphonates. As a precursor, this prepared zirconium phosphonate was utilized to fabricate a novel DNA/ZrRP binary hybrid via a delamination-reassembly procedure. The release behavior of DNA from the DNA/ZrRP composite was investigated at different medium pH, because the combination between zirconium phosphonate sheets and DNA was pH-dependent sensitively. Moreover, the helical conformation of DNA was almost retained after the intercalation and release process. These properties of the DNA/ZrRP composite suggested the potential application of layered zirconium phosphonate as a non-viral vector in gene delivery.

  11. Turbulence vertical structure of the boundary layer during the afternoon transition

    NASA Astrophysics Data System (ADS)

    Darbieu, Clara; Lohou, Fabienne; Lothon, Marie; Vilà-Guerau de Arellano, Jordi; Couvreux, Fleur; Durand, Pierre; Pino, David; Patton, Ned; Nilsson, Erik; Blay-Carreras, Estel; Gioli, Beniamino

    2015-04-01

    The transition from a well-mixed convective boundary layer to a residual layer overlying a stabilized nocturnal layer raises several issues, which remain difficult to address from both modeling and observational perspectives. The well mixed convective boundary layer is mainly forced by buoyancy, with fully developed turbulence. The daily decrease of the surface buoyancy flux leads to the decay of the turbulence kinetic energy (TKE), and a possible change of the structure of the turbulence before it reaches the stable regime, with more anisotropy and intermittency. It is important to better understand these processes, as they can impact on the dispersion of tracers in the atmosphere, and on the development of the nocturnal and daytime boundary layers of the following days. The presented work is based on both observations from the BLLAST (Boundary Layer Later Afternoon and Sunset Turbulence) experiment and Large-Eddy Simulation (NCAR LES code). The field campaign took place in summer 2011 in France, on the northern side of the Pyrenean foothills. A well-documented cloud-free weak wind day is considered here to analyze in details the evolution of the turbulence along the day, from midday to sunset. The case study combines observations of the mean structure and of the turbulence. It is the base of a complementary idealized numerical study with a large eddy simulation. From both observations and numerical simulations, the turbulence is described, according to time and height, with the characteristics of the spectral energy density, especially the typical turbulence lengthscales and the sharpness of the transition from energy-containing eddies to the inertial subrange. An analytical model proposed by Kristensen and Lenschow (1988) for homogeneous nonisotropic turbulence is used to approximate the observed and LES-modeled spectra and estimate their characteristics. The study points out the LES ability to reproduce th­e turbulence evolution throughout the afternoon. Two periods have been defined and caracterized: the "Early Afternoon", quasi-stationary, during which the TKE decays with a slow rate, with no significant change in the turbulence characteristics, and the "Late Afternoon", characterized by a larger TKE decay rate and a change of its spectral characteristics (increase of vertical velocity lengthscale, and change of the inertial spectral range slope). We also point out that the turbulent changes occur first in the upper part of the ABL. We have extended the analysis to several other days of aircraft observation, and to a LES sensitivity analysis with a TKE budget analysis, in order to confirm our findings and propose an explanation of these results with the role of the wind shear, entrainment, and by considering the effect of turbulent structures and anisotropy.

  12. Subsurface Structure in the Martian Polar Layered Deposits: The Deep Space 2 Impact Accelerometry Experiment

    NASA Technical Reports Server (NTRS)

    Moersch, J. E.; Lorenz, R. D.

    1998-01-01

    While primarily a technology demonstration mission, the New Millenium Mars Microprobes (also known as Deep Space 2, or simply DS2)will also provide the first in situ science measurements of the martian subsurface. The DS2 impact accelerometry experiment will provide both engineering data about the depth of probe emplacement and science data about the physical nature of the subsurface at the probes' landing sites. Little is known about the detailed physical properties or small-scale vertical structure of the subsurface at the DS2 landing site in the southern martian polar layered deposits. Imaging data from the Viking Orbiters and Mars Global Surveyor reveal alternating bands of light and dark material in this region with thicknesses at least as small as the limit of resolution, about 10 m. The overall composition of these layers is poorly constrained, but generally thought to be a mixture of dust and ice with the layers being caused by variations in the dust/ice ratio, or perhaps by dust deposits of different densities. Low thermal inertias in the region suggest that the top few centimeters of the surface are composed of a mantling of fine-grained dust. However, 3.5-cm radar returns indicate that the maximum depth of this dust is not greater than a few tens of centimeters. Thermal models generally agree that, while the layered deposits do provide a potential near-surface reservoir for ice, the uppermost few centimeters to meters in these regions are likely to be ice-free because of sublimation losses. Finally, while it is generally agreed that the layered deposits are the product of variations in the martian climate, no direct correlation has been made between band sequences and specific climate changes. Our intention is to shed light on some of these questions about the martian polar layered deposits by using the DS2 accelerometry experiment to determine the physical nature of the layered deposits, and to detect the presence of any subsurface layering of dust, ice, and/or rock. In the process, we will also determine the final resting depth of the two microprobes, an important parameter in the interpretation of other DS2 experiments.

  13. Defects of crystal structure of Hg 1- xCd xTe thin layers growing by pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Virt, I. S.; Rudyj, I. O.; Frugynskiji, M. S.; Kurilo, I. V.; Sagan, P.; Zawislak, J.; Kuzma, M.

    2003-03-01

    Hg 1- xCd xTe layers have been obtained by pulsed laser deposition method using two types of lasers: YAG:Nd 3+ ( ?=250 ?s or 40 ns) and excimer ( ?=25 ns). The crystal structures of layers were investigated by the electron diffraction method. The dependence of the laser beam parameters on the layer structure was determined. Layers obtained were of various crystallography qualities (polycrystalline, monocrystalline). The layers with texture were more representative. Their diffraction patterns exhibit a rich symmetry, which points on a various orientation of nucleus of crystallisation. The proposed model of twins growing during deposition is under consideration. The influence of layer growing conditions on the size of the macroscopic defects was discussed too.

  14. Influence of layer thickness on the structure and the magnetic properties of Co/Pd epitaxial multilayer films

    NASA Astrophysics Data System (ADS)

    Tobari, Kousuke; Ohtake, Mitsuru; Nagano, Katsumasa; Futamoto, Masaaki

    2012-03-01

    Co/Pd epitaxial multilayer films were prepared on Pd(111)fcc underlayers hetero-epitaxially grown on MgO(111)B1 single-crystal substrates at room temperature by ultra-high vacuum RF magnetron sputtering. In-situ reflection high energy electron diffraction shows that the in-plane lattice spacing of Co on Pd layer gradually decreases with increasing the Co layer thickness, whereas that of Pd on Co layer remains unchanged during the Pd layer formation. The CoPd alloy phase formation is observed around the Co/Pd interface. The atomic mixing is enhanced for thinner Co and Pd layers in multilayer structure. With decreasing the Co and the Pd layer thicknesses and increasing the repetition number of Co/Pd multilayer film, stronger perpendicular magnetic anisotropy is observed. The relationships between the film structure and the magnetic properties are discussed.

  15. PREFACE: Ultrathin layers of graphene, h-BN and other honeycomb structures Ultrathin layers of graphene, h-BN and other honeycomb structures

    NASA Astrophysics Data System (ADS)

    Geber, Thomas; Oshima, Chuhei

    2012-08-01

    Since ancient times, pure carbon materials have been familiar in human society—not only diamonds in jewellery and graphite in pencils, but also charcoal and coal which have been used for centuries as fuel for living and industry. Carbon fibers are stronger, tougher and lighter than steel and increase material efficiency because of their lower weight. Today, carbon fibers and related composite materials are used to make the frames of bicycles, cars and even airplane parts. The two-dimensional allotrope, now called graphene, is just a single layer of carbon atoms, locked together in a strongly bonded honeycomb lattice. In plane, graphene is stiffer than diamond, but out-of-plane it is soft, like rubber. It is virtually invisible, may conduct electricity (heat) better than copper and weighs next to nothing. Carbon compounds with two carbon atoms as a base, such as graphene, graphite or diamond, have isoelectronic sister compounds made of boron-nitrogen pairs: hexagonal and cubic boron nitride, with almost the same lattice constant. Although the two 2D sisters, graphene and h-BN, have the same number of valence electrons, their electronic properties are very different: freestanding h-BN is an insulator, while charge carriers in graphene are highly mobile. The past ten years have seen a great expansion in studies of single-layer and few-layer graphene. This activity has been concerned with the ? electron transport in graphene, in electric and magnetic fields. More than 30 years ago, however, single-layer graphene and h-BN on solid surfaces were widely investigated. It was noted that they drastically changed the chemical reactivity of surfaces, and they were known to 'poison' heterogeneous catalysts, to passivate surfaces, to prevent oxidation of surfaces and to act as surfactants. Also, it was realized that the controlled growth of h-BN and graphene on substrates yields the formation of mismatch driven superstructures with peculiar template functionality on the nanometer scale. This special section contains interesting papers on graphene, h-BN and related 'honeycomb' compounds on solid surfaces, which are currently in development. Interfacial interaction strongly modifies the electronic and atomic structures of these overlayer systems and substrate surfaces. In addition, one can recognize a variety of growth phenomena by changing the surface and growth conditions, which are promising as regards fabricating those noble nanosystems. We have great pleasure in acknowledging the enthusiastic response and participation of our invited authors and their diligent preparation of the manuscripts. Ultrathin layers of graphene, h-BN and other honeycomb structures contents Ultrathin layers of graphene, h-BN and other honeycomb structuresThomas Geber and Chuhei Oshima Templating of arrays of Ru nanoclusters by monolayer graphene/Ru Moirés with different periodicitiesEli Sutter, Bin Wang, Peter Albrecht, Jayeeta Lahiri, Marie-Laure Bocquet and Peter Sutter Controllable p-doping of graphene on Ir(111) by chlorination with FeCl3N A Vinogradov, K A Simonov, A V Generalov, A S Vinogradov, D V Vyalikh, C Laubschat, N Mårtensson and A B Preobrajenski Optimizing long-range order, band gap, and group velocities for graphene on close-packed metal surfacesF D Natterer, S Rusponi, M Papagno, C Carbone and H Brune Epitaxial growth of graphene on transition metal surfaces: chemical vapor deposition versus liquid phase depositionSamuel Grandthyll, Stefan Gsell, Michael Weinl, Matthias Schreck, Stefan Hüfner and Frank Müller High-yield boron nitride nanosheets from 'chemical blowing': towards practical applications in polymer compositesXuebin Wang, Amir Pakdel, Chunyi Zhi, Kentaro Watanabe, Takashi Sekiguchi, Dmitri Golberg and Yoshio Bando BCx layers with honeycomb lattices on an NbB2(0001) surfaceChuhei Oshima Epitaxial growth of boron-doped graphene by thermal decomposition of B4CWataru Norimatsu, Koichiro Hirata, Yuta Yamamoto, Shigeo Arai and Michiko Kusunoki Mechanical exfoliation of epitaxial graphene on Ir(111) enabled by Br2 intercalationCh

  16. Low-frequency noise in AlGaN/GaN HEMT structures with AlN thin film layer

    NASA Astrophysics Data System (ADS)

    Vitusevich, S. A.; Antoniuk, O. A.; Petrychuk, M. V.; Danylyuk, S. V.; Kurakin, A. M.; Belyaev, A. E.; Klein, N.

    2006-06-01

    Low-frequency noise in AlGaN/GaN high electron mobility transistor (HEMT) heterostructures with additional AlN thin barrier layer is investigated. Transmission line model structures with different lengths of the conducting channel formed by polarization effects at the heterointerface of undoped AlGaN/AlN/GaN layers are studied. The measured noise demonstrates an unusual broadening of the generation-recombination components of the spectra. To explain the noise behaviour of the structure we consider a model taking into account peculiarities of the band structure of the interface with inserted AlN high molar fraction barrier layer.

  17. Nonequilibrium structural condition in the medical TiNi-based alloy surface layer treated by electron beam

    SciTech Connect

    Neiman, Aleksei A. Lotkov, Aleksandr I.; Meisner, Ludmila L. Semin, Viktor O.; Koval, Nikolai N.; Teresov, Anton D.

    2014-11-14

    The research is devoted to study the structural condition and their evolution from the surface to the depth of TiNi specimens treated by low-energy high-current electron beams with surface melting at a beam energy density E = 10 J/cm{sup 2}, number of pulses N = 10, and pulse duration ? = 50 ?s. Determined thickness of the remelted layer, found that it has a layered structure in which each layer differs in phase composition and structural phase state. Refinement B2 phase lattice parameters in local areas showed the presence of strong inhomogeneous lattice strain.

  18. Recrystallized S-layer protein of a probiotic Propionibacterium: structural and nanomechanical changes upon temperature or pH shifts probed by solid-state NMR and AFM.

    PubMed

    de sa Peixoto, Paulo; Roiland, Claire; Thomas, Daniel; Briard-Bion, Valérie; Le Guellec, Rozenn; Parayre, Sandrine; Deutsch, Stéphanie-Marie; Jan, Gwénaël; Guyomarc'h, Fanny

    2015-01-13

    Surface protein layers (S layers) are common constituents of the bacterial cell wall and originate from the assembly of strain-dependent surface layer proteins (Slps). These proteins are thought to play important roles in the bacteria's biology and to have very promising technological applications as biomaterials or as part of cell-host cross-talk in probiotic mechanism. The SlpA from Propionibacterium freudenreichii PFCIRM 118 strain was isolated and recrystallized to investigate organization and assembly of the protein using atomic force microscopy and solid-state (1)H and (13)C-nuclear magnetic resonance. SlpA was found to form hexagonal p1 monolayer lattices where the protein exhibited high proportions of disordered regions and of bound water. The lattice structure was maintained, but softened, upon mild heating or acidification, probably in relation with the increasing mobilities of the disordered protein regions. These results gave structural insights on the mobile protein regions exposed by S layer films, upon physiologically relevant changes of their environmental conditions. PMID:25479375

  19. Comparison of the layer structure of vapor phase and leached SRL glass by use of AEM

    SciTech Connect

    Biwer, B.M.; Bates, J.K.; Abrajano, T.A. Jr.; Bradley, J.P.

    1990-12-31

    Test samples of 131 type glass that have been reacted for extended time periods in water vapor atmospheres of different relative humidities and in static leaching solution have been examined to characterize the reaction products. Analytical electron microscopy (AEM) was used to characterize the leached samples, and a complicated layer structure was revealed, consisting of phases that precipitate from solution and also form within the residual glass layer. The precipitated phases include birnes-site, saponite, and an iron species, while the intralayer phases include the U-Ti containing phase brannerite distributed within a matrix consisting of bands of an Fe rich montmorillonite clay. Comparison is made between samples leached at 40C for 4 years with those leached at 90C for 3-1/2 years. The samples reacted in water vapor were examined with scanning electron microscopy and show increasing reaction as both the relative humidity and time of reaction increases. These samples also contain a layered structure with reaction products on the glass surface.

  20. Crystal chemistry of layered structures formed by linear rigid silyl-capped molecules.

    PubMed

    Lumpi, Daniel; Kautny, Paul; Stöger, Berthold; Fröhlich, Johannes

    2015-09-01

    The crystallization behavior of methylthio- or methylsulfonyl-containing spacer extended Z,Z-bis-ene-yne molecules capped with trimethylsilyl groups obtained by (tandem) thiophene ring fragmentation and of two non-spacer extended analogs were investigated. The rigid and linear molecules generally crystallized in layers whereby the flexibility of the layer interfaces formed by the silyl groups leads to a remarkably rich crystal chemistry. The molecules with benzene and thiophene spacers both crystallized with C2/c symmetry and can be considered as merotypes. Increasing the steric bulk of the core by introduction of ethylenedioxythiophene (EDOT) gave a structure incommensurately modulated in the [010] direction. Further increase of steric demand in the case of a dimethoxythiophene restored periodicity along [010] but resulted in a doubling of the c vector. Two different polytypes were observed, which feature geometrically different layer interfaces (non-OD, order-disorder, polytypes), one with a high stacking fault probability. Oxidation of the methylthio groups of the benzene-based molecule to methylsulfonyl groups led to three polymorphs (two temperature-dependent), which were analyzed by Hirshfeld surface d e/d i fingerprint plots. The analogously oxidized EDOT-based molecule crystallized as systematic twins owing to its OD polytypism. Shortening of the backbone by removal of the aryl core resulted in an enantiomorphic structure and a further shortening by removal of a methylthio-ene fragment again in a systematically twinned OD polytype. PMID:26306200