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1

Structured luminescence conversion layer  

DOEpatents

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

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

2012-12-11

2

Bismuth oxyhalide nanomaterials: layered structures meet photocatalysis.  

PubMed

In recent years, layered bismuth oxyhalide nanomaterials have received more and more interest as promising photocatalysts because their unique layered structures endow them with fascinating physicochemical properties; thus, they have great potential photocatalytic applications for environment remediation and energy harvesting. In this article, we explore the synthesis strategies and growth mechanisms of layered bismuth oxyhalide nanomaterials, and propose design principles of tailoring a layered configuration to control the nanoarchitectures for high efficient photocatalysis. Subsequently, we focus on their layered structure dependent properties, including pH-related crystal facet exposure and phase transformation, facet-dependent photoactivity and molecular oxygen activation pathways, so as to clarify the origin of the layered structure dependent photoreactivity. Furthermore, we summarize various strategies for modulating the composition and arrangement of layered structures to enhance the photoactivity of nanostructured bismuth oxyhalides via internal electric field tuning, dehalogenation effect, surface functionalization, doping, plasmon modification, and heterojunction construction, which may offer efficient guidance for the design and construction of high-performance bismuth oxyhalide-based photocatalysis systems. Finally, we highlight some crucial issues in engineering the layered-structure mediated properties of bismuth oxyhalide photocatalysts and provide tentative suggestions for future research on increasing their photocatalytic performance. PMID:24975748

Li, Jie; Yu, Ying; Zhang, Lizhi

2014-08-01

3

Original article Tree canopy and herb layer transpiration in three Scots  

E-print Network

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

Paris-Sud XI, Université de

4

Origin and evolution of asthenospheric layers  

NASA Astrophysics Data System (ADS)

The global tectonics on terrestrial planets is determined mainly by interaction of lithosphere and lower mantle. The boundary between the lithosphere and the asthenosphere (LAB) is defined by a difference in response to stress: the lithosphere remains elastic or brittle, while the asthenosphere deforms viscously and accommodates strain through plastic deformation. The basic differences of lithosphere and asthenosphere properties could be explained as a result of the temperature/pressure and the stress tensor. We investigate simultaneously the processes of formation and evolution of low viscosity layers (‘asthenospheric layers’) resulting from both factors for large terrestrial planets. We find that the time scale of the changes of the low viscosity layer could be of the order of 30 Myr if existence of the layer is determined by the thermal conditions. The characteristic time of the low viscosity layer resulting from stress changes could be much shorter depending on the tectonic situation. Acknowledgments This work was partially supported by the National Science Centre (grant 2011/01/B/ST10/06653).

Czechowski, Leszek; Grad, Marek

5

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

SciTech Connect

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.

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

2011-12-31

6

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

E-print Network

ORIGINAL PAPER On the origin of mixed-layered clay minerals from the San Andreas Fault at 2.5­3 km coring at three key locations along the San Andreas Fault Observatory at depth (SAFOD) drill hole of the dominant authigenic clay species across the San Andreas Fault zone (sampled at 3,066 and 3,436 m measured

7

Origin of undesirable cracks during layer L. Ponsona)  

E-print Network

investigate the origin of undesirable transverse cracks often observed in thin films obtained by the layer ­ or equivalently the heating temperature ­ must be within the range -c thin film where and optics require the synthesis of high quality, defect-free single crystals on a substrate of a different

Paris-Sud XI, Université de

8

Tomographic reconstruction of layered tissue structures  

NASA Astrophysics Data System (ADS)

In recent years the interest in the determination of optical properties of layered tissue structure has resurfaced. Applications include, for example, studies on layered skin tissue and underlying muscles, imaging of the brain underneath layers of skin, skull, and meninges, and imaging of the fetal head in utero beneath the layered structures of the maternal abdomen. In this work we approach the problem of layered structures in the framework of model-based iterative image reconstruction schemes. These schemes are currently developed to determine the optical properties inside tissue from measurement on the surface. If applied to layered structure these techniques yield substantial improvements over currently available semi-analytical approaches.

Hielscher, Andreas H.; Azeez-Jan, Mohideen; Bartel, Sebastian

2001-11-01

9

Molecular origins of friction. The force on adsorbed layers  

SciTech Connect

Simulations and perturbation theory are used to study the molecular origins of an ideal model system, a layer of adsorbed molecules sliding over a substrate. These calculations reproduce several surprising features of experimental results. In most cases, the frictional force on a solid monolayer has a different form from that observed between macroscopic solids. No threshold force or static friction is needed to initiate sliding; instead, the velocity is proportional to the force. As in experiments, incommensurate solid layers actually slide more readily than fluid layers. A comparison of experiment, simulation, and analytic results shows that dissipation arises from anharmonic coupling between phonon modes and substrate-induced deformations in the adsorbate. 19 refs.

Cieplak, M.; Smith, E.D.; Robbins, M.O. [Johns Hopkins Univ, Baltimore, MD (United States)

1994-08-01

10

Coherent structure effects on shear layer optics  

Microsoft Academic Search

This experimental research investigated the effects of coherent structures and external perturbation on the optical propagation characteristics of shear layers. A low speed shear layer was generated using two parallel streams of gases (a helium\\/argon mixture and air) and a laser beam was passed perpendicularly through the shear layer. The optical quality of the laser beam was quantified by the

Larry Chew

1990-01-01

11

Anisotropic Layered Absorbers on Cylindrical Structures  

Microsoft Academic Search

A curved structure consisting of an imperfectly conducting circular cylinder coated by any number of coaxial thin anisotropic layers separated by isotroplc regions of different materials is considered. Each thin anisotroplc layer is represented by a sheet with an anisotropic Jump Impedance. Thus, the structure is a generalization to the anisotropic case of Jaumann absorbers on curved surfaces. For a

R. D. Graglia; P. L. E. Uslenghi

1987-01-01

12

Original Article Using Structured Decision Making to  

E-print Network

are increasing, posing signifi- cant threats to the health of wildlife, domestic animals, and human populationsOriginal Article Using Structured Decision Making to Manage Disease Risk for Montana Wildlife MICHAEL S. MITCHELL,1 United States Geological Survey, Montana Cooperative Wildlife Research Unit

Mitchell, Mike

13

Origin and Structure of Dynamic Cooperative Networks  

E-print Network

Origin and Structure of Dynamic Cooperative Networks Lucas Wardil & Christoph Hauert Department. 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

Hauert, Christoph

14

A Spreading Layer Origin for Dwarf Nova Oscillations  

E-print Network

Dwarf nova outbursts often show coherent ($Q\\sim10^4-10^6$) sinusoidal oscillations with the largest pulsed fraction in the extreme ultraviolet. Called dwarf nova oscillations (DNOs), they have periods of $P\\approx3-40 {\\rm s}$ and scale with luminosity as $P\\propto L^{-\\beta}$ with $\\beta\\approx0.1-0.2$. We propose that DNOs may be produced by nonradial oscillations in a thin hydrostatic layer of freshly accreted material, the ``spreading layer'' (SL), at the white dwarf (WD) equator. This would naturally explain a number of key properties of DNOs, including their frequency range, sinusoidal nature, sensitivity to accretion rate, and why they are only seen during outburst. In support of this hypothesis we construct a simple model that treats the SL as a cavity containing shallow surface waves, each with the same radial structure, but split into three different modes denoted by their azimuthal wavenumber, $m$. The $m=0$ latitudinally propagating mode best matches the periods and scalings associated with most DNOs, and DNOs with periods shorter than the WD Keplerian period are explained by the $m=-1$ prograde mode. We also predict a third set of oscillations, produced by the $m=1$ retrograde mode, and show its expected dependence on accretion rate.

Anthony L. Piro; Lars Bildsten

2004-10-19

15

Origin of the high conductivity layers in oceanic asthenosphere  

NASA Astrophysics Data System (ADS)

Origin of the high-conductivity layer (HCL) in oceanic asthenosphere is a key to understand mechanisms to allow smooth plate motion. Although it has been attributed to either partial melting or hydration, no definitive answer has been provided so far. We have compiled magnetotelluric studies in oceans to summarize the features of the oceanic HCL as follows. Firstly, HCL is observed about 80-100 km depth under juvenile plates, whereas no HCL is detected under mature plates. Secondly, the maximum conductivity of HCL is 3×10^(-2) S/m near normal ridges, whereas larger magnitudes of HCL are observed near ridges with higher volatiles. The first point suggests that the mechanism for HCL is related to high temperature, which declines the hydration hypothesis because of the small activation energy of proton conduction. Moreover, the magnitudes of HCL cannot be explained consistently with conductivity of asthenosphere under the matured plates in view of the proton conduction. The magnitudes of the HCL near the normal ridges are explained by 0.1 % of partial melting of the DMM induced by trace amounts of volatiles. Not hydration but partial melting is thus essential in oceanic asthenosphere.

Katsura, Tomoo; Yoshino, Takashi; Baba, Kiyoshi; Kogiso, Tetsu

2014-05-01

16

The kinematics of turbulent boundary layer structure  

NASA Technical Reports Server (NTRS)

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

Robinson, Stephen Kern

1991-01-01

17

DNS Study for the origin of the flow Randomization in Late Boundary Layer Transition  

E-print Network

This paper is devoted to the investigation of the origin and mechanism of randomization in late boundary layer transition over a flat plate without pressure gradient. The flow randomization is a crucial phase before flow transition to the turbulent state. According to existing literatures, the randomization was caused by the big background noises and non-periodic spanwise boundary conditions. It was assumed that the large ring structure is affected by background noises first, and then the change of large ring structure affects the small length scales quickly, which directly leads to randomization and formation of turbulence. However, by careful analysis of our high order DNS results, we believe that the internal instability of multiple ring cycles structure is the main reason. What we observed is that randomization begins when the third cycle overlaps the first and second cycles. A significant asymmetric phenomenon is originated from the second cycle in the middle of both streamwise and spanwise directions. More technically, a visible asymmetric phenomenon in the middle vortex ring cycle starts at time step t=16.25T and x=838.9{\\delta}in where the top and bottom level rings are still completely symmetric. The non-symmetric structure of middle level ring affects the small length scale in boundary layer bottom quickly. The randomization phenomenon spreads to top level through ejections. Finally, the whole flow domain becomes randomized. A hypothesis of C- and K-types shift is given as a possible mechanism of flow randomization.

Manoj Thapa; Ping Lu; Chaoqun Liu

2014-02-25

18

Shear deformation plate continua of large double layered space structures  

NASA Technical Reports Server (NTRS)

A simple method is presented to model large rigid-jointed lattice structures as continuous elastic media with couple stresses using energy equivalence. In the analysis, the transition from the discrete system to the continuous media is achieved by expanding the displacements and the rotations of the nodal points in a Taylor series about a suitable chosen origin. The strain energy of the continuous media with couple stresses is then specialized to obtain shear deformation plate continua. Equivalent continua for single layered grids, double layered grids, and three-dimensional lattices are then obtained.

Hefzy, Mohamed Samir; Nayfeh, Adnan H.

1986-01-01

19

Origins of serotonin innervation of forebrain structures  

NASA Technical Reports Server (NTRS)

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.

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

1977-01-01

20

Structural rearrangements in self-assembled surfactant layers at surfaces  

SciTech Connect

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

Sushko, Maria L.; Liu, Jun

2010-03-25

21

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

SciTech Connect

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

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

2011-10-01

22

The Origin of the Drosophila Subretinal Pigment Layer  

PubMed Central

Optical insulation plays a critical role in the fine visual acuity of the Drosophila compound eye. Screening pigments expressed by a number of cell types contribute to this phenomenon. They provide optical insulation that prevents extraneous light rays from inappropriately activating the photoreceptors. This optical insulation can be divided into two categories; the insulation of the individual ommatidia, and the insulation of the compound eye as a whole. The whole-eye insulation is provided by two sources. The sides of the eye are optically insulated by the pigment rim, a band of pigment cells that circumscribes the eye. The base of the eye is insulated by the subretinal pigment layer; a thick layer of pigment that lies directly underneath the retina. How this subretinal pigment layer is generated has not been clearly described. Here, experiments that manipulate pigment expression during eye development suggest that the subretinal pigment layer is directly derived from pigment cells in the overlying retina. PMID:22684937

Tomlinson, Andrew

2014-01-01

23

Origin and Maintenance of the Benthic Nepheloid Layer Primary Investigator: Nathan Hawley -NOAA GLERL  

E-print Network

Origin and Maintenance of the Benthic Nepheloid Layer Primary Investigator: Nathan Hawley - NOAA of chemical substances. In the Great Lakes the benthic nepheloid layer (bnl) may play a significant role transparency in the benthic nepheloid layer. The deployments will be made at a greater depth than the previous

24

Ion transport and structure of layer-by-layer assemblies  

E-print Network

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

Lutkenhaus, Jodie Lee

2007-01-01

25

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

NASA Astrophysics Data System (ADS)

The occurrence of charge-density waves in three selected layered transition-metal dichalcogenides—1T-TaS2, 2H-TaSe2 and 1T-TiSe2—is discussed from an experimentalist's point of view with a particular focus on the implications of recent angle-resolved photoelectron spectroscopy results. The basic models behind charge-density-wave formation in low-dimensional solids are recapitulated, the experimental and theoretical results for the three selected compounds are reviewed, and their band structures and spectral weight distributions in the commensurate charge-density-wave phases are calculated using an empirical tight-binding model. It is explored whether the origin of charge-density waves in the layered transition-metal dichalcogenides can be understood in a unified way on the basis of a few measured and calculated parameters characterizing the interacting electron-lattice system. It is found that the predictions of the standard mean-field model agree only semi-quantitatively with the experimental data and that there is not one generally dominant factor driving charge-density-wave formation in this family of layer compounds. The need for further experimental and theoretical scrutiny is emphasized.

Rossnagel, K.

2011-06-01

26

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

E-print Network

A sporadic layer in the Venus lower ionosphere of meteoric origin M. Pa¨tzold,1 S. Tellmann,1 B. Ha 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

Mendillo, Michael

27

Are there double layers in solar coronal transition region that accelerate ions originating solar wind?  

NASA Astrophysics Data System (ADS)

Drawing from the physics of laser plasma expansion, laboratory experiments, magnetospheric observations on double layers (DLs), theory and simulations, we suggest that solar coronal transition region may contain randomly distributed numerous patches of double layers, which accelerate the ions from the upper chromosphere into the low corona. We expect the DLs to be distributed in a vertically thin layer while horizontally they are distributed widely. Such DLs provide a novel mechanism for the origin of the solar wind. The DL-based mechanism is based on expansion of dense cold chromospheric plasma consisting of cold ions, cold electrons with temperature Tc and a minor hot electron population with temperature Teh. Such plasma expansion naturally involves electric double layers, which are thin structures with vertical widths L much less than, say, about 100 plasma Debye lengths d. We envision that such double layers form in the upper chromosphere where charged particles collisions with neutral particles become rare at heights h > 1500 km above the photosphere and where ion-electron collision mean-free-path length S > L~ 10d. Such DLs are likely to form in magnetic flux tubes (coronal funnels) undergoing magnetic reconnection with magnetic fields in the chromospheric magnetic networks. Such reconnections produce the prerequisite hot electron population in the flux tube. The apparent vertical width of the coronal transition region (CTR) of the order of a few hundred kilometers is the consequence of the DLs vertically displaced in the plasma volume where the condition S > L ~ 10d is met. Since the magnetic reconnection and the DLs are dynamically evolving events, the CTR must be a highly dynamic region giving the observed zigzag boundary. The existence of the DLs in the CTR can be inferred from the outflow of ions from the chromosphere as beams, consisting of heavy and light ions, having the same energy before they are affected by other plasma processes and the solar gravity. The CTR double layers are analogous to the terrestrial auroral double layers that form at the zigzag transition between the dense ionospheric cold plasma and the hot plasma in the auroral density cavities. In the latter case, the hot electrons in the ionosphere result from backscattered hot electrons mirroring in the Earth's magnetic field. The mirroring of hot coronal electrons penetrating into the chromosphere may provide an additional source of the minor hot electron population in the upper chromosphere, in addition to the reconnection.

Singh, N.

2013-12-01

28

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

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

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

29

4. SOUTH ELEVATION SHOWING PROJECTING STRUCTURAL GIRDERS FROM ORIGINAL CONSTRUCTION, ...  

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

4. SOUTH ELEVATION SHOWING PROJECTING STRUCTURAL GIRDERS FROM ORIGINAL CONSTRUCTION, VIEW EAST TO WEST - Terminal Tower Building, Cleveland Union Terminal, 50 Public Square, Cleveland, Cuyahoga County, OH

30

Effect Of Photoresist Composition On The Origin Of The Interfacial Layer In The Bilevel System.  

NASA Astrophysics Data System (ADS)

Although many attempts have been made to prevent the formation of the interfacial layer between the toplayer resist and the bottom layer resist PMMA, an interfacial layer always seems to be more or less present. After an extra treatment it is sometimes possible to re-move this thin layer. It would be an advantage if such an extra process step could be avoided by means of applying a toplayer photoresist which does not cause the formation of an interfacial layer. We therefore tried to gain a basic understanding of the parameters which have effect on the origin of the interfacial layer. From the investigation of the effects of the resin composition and its molecular weight (distribution), the solid content, the solvent composition and the prebake temperature on the interfacial layer formation it appeared that all these parameters are concerned in the origin of the interfacial layer. Prebake temperatures should be as low as possible, 450°C for novolak based resists (which results in bad resolution) and 480°C for a polyhydroxy-styrene based positive resist. The low and high molecular weight fraction of novolak are causing thicker interfacial layers than the medium molecular weight fraction. If cyclohexanone or ethylcellosolve were used as solvents and polyhydroxystyrene as the resin a positive near UV photoresist could be composed which can be used as the toplayer resist for the bilevel deep UV system in the capped mode with a negligible interfacial layer.

Wijdenes, J.; Geomini, M. J.

1985-04-01

31

Structured Water Layers Adjacent to Biological Membranes  

PubMed Central

Water amid the restricted space of crowded biological macromolecules and at membrane interfaces is essential for cell function, though the structure and function of this “biological water” itself remains poorly defined. The force required to remove strongly bound water is referred to as the hydration force and due to its widespread importance, it has been studied in numerous systems. Here, by using a highly sensitive dynamic atomic force microscope technique in conjunction with a carbon nanotube probe, we reveal a hydration force with an oscillatory profile that reflects the removal of up to five structured water layers from between the probe and biological membrane surface. Further, we find that the hydration force can be modified by changing the membrane fluidity. For 1,2-dipalmitoyl-sn-glycero-3-phosphocholine gel (L?) phase bilayers, each oscillation in the force profile indicates the force required to displace a single layer of water molecules from between the probe and bilayer. In contrast, 1,2-dipalmitoyl-sn-glycero-3-phosphocholine fluid (L?) phase bilayers at 60°C and 1,2-dioleoyl-sn-glycero-3-phosphocholine fluid (L?) phase bilayers at 24°C seriously disrupt the molecular ordering of the water and result predominantly in a monotonic force profile. PMID:16798815

Higgins, Michael J.; Polcik, Martin; Fukuma, Takeshi; Sader, John E.; Nakayama, Yoshikazu; Jarvis, Suzanne P.

2006-01-01

32

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

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

33

Characteristic Lifelength of Coherent Structure in the Turbulent Boundary Layer  

NASA Technical Reports Server (NTRS)

A characteristic lifelength is defined by which a Gaussian distribution is fit to data correlated over a 3 sensor array sampling streamwise sidewall pressure. The data were acquired at subsonic, transonic and supersonic speeds aboard a Tu-144. Lifelengths are estimated using the cross spectrum 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 distribution, thus providing a means to locate and study the nature of the coherent structure in the turbulent boundary layer. The lifelength data can be 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 coherent structure in the turbulent boundary layer.

Palumbo, Daniel L.

2006-01-01

34

Surfactant-induced layer-by-layer growth of Ag on Ag(111): Origins and side effects  

NASA Astrophysics Data System (ADS)

It has been shown that submonolayer deposits of Sb change the growth mode of Ag(111) from multilayer to layer-by-layer. Using scanning tunneling microscopy, we identify the two main origins of this behavior. (i) Sb lowers the mobility of Ag adatoms on terraces and growing islands. As a direct consequence, the additional edge barrier (barrier to descend a step minus surface diffusion barrier) is reduced. (ii) Sb lowers the mobility along step edges, inducing dendritic island shapes. Both effects favor smoother growth. Neither a lower Ag surface mobility nor heterogeneous nucleation is sufficient for smooth growth.

Vrijmoeth, J.; van der Vegt, H. A.; Meyer, J. A.; Vlieg, E.; Behm, R. J.

1994-06-01

35

A wind origin for Titan's haze structure  

E-print Network

.............................................................. A wind origin for Titan's haze K (ref. 1). A seasonally varying2 haze, which appears to be the main source of heating and cooling that drives atmospheric circulation3,4 , shrouds the moon. The haze has numerous features that have remained

Hourdin, Chez Frédéric

36

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

SciTech Connect

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

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

2000-01-27

37

ORIGINAL PAPER Population genetic structure of the European kestrel  

E-print Network

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

Paris-Sud XI, Université de

38

Origin and Structure of Dynamic Cooperative Networks  

NASA Astrophysics Data System (ADS)

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.

Wardil, Lucas; Hauert, Christoph

2014-07-01

39

Structural biology: Origins of chemical biodefence  

Microsoft Academic Search

The idea that complex biological systems can evolve through a series of simple, random events is not universally accepted. The structure of a vital immune protein shows how such evolution can occur at a molecular level.

Robert Liddington; Laurie Bankston

2005-01-01

40

Structural origins of gentamicin antibiotic action.  

PubMed Central

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

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

1998-01-01

41

Structural failure of two-density-layer cohesionless biaxial ellipsoids  

NASA Astrophysics Data System (ADS)

This paper quantitatively evaluates structural failure of biaxial cohesionless ellipsoids that have a two-density-layer distribution. The internal density layer is modeled as a sphere, while the external density layer is the rest of the part. The density is supposed to be constant in each layer. The present study derives averaged stresses over the whole volume of these bodies and uses limit analysis to determine their global failure. The upper bound of global failure is considered in terms of the size of the internal layer and the aspect ratio of the shape. The result shows that the two-density-layer causes the body to have different strength against structural failure.

Hirabayashi, Masatoshi

2014-07-01

42

Structural origins of morphing in plant tissues  

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

43

ORIGINAL ARTICLE The phylogenetic composition and structure of  

E-print Network

ORIGINAL ARTICLE The phylogenetic composition and structure of soil microbial communities shifts to comprehensively survey the richness, composition and structure of soil microbial communities in a grassland that the overall taxonomic structure of soil microbial communities was altered at eCO2. Mantel tests indicated

Minnesota, University of

44

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

SciTech Connect

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

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

2012-08-06

45

Stability of the parallel layer during alkane spreading and the domain structures of the standing-up layer.  

PubMed

The spreading of liquid alkanes over surfaces plays an important role in applications such as lubrication, painting, and printing. To make significant advances in these fields, it is essential to increase our understanding of the interactions between alkanes and surfaces. Long-chain alkanes form two typical adsorption structures on a surface--the parallel phase and the standing-up phase. The most thermodynamically stable structure is the parallel phase, in which the alkane molecules lie flat on the surface. If the temperature is slightly below the bulk melting point, then alkanes form a thermodynamically stable standing-up phase on top of an existing parallel layer. At lower temperatures, the standing-up phase becomes metastable. Using atomic force microscopy, we have found that the standing-up alkane layer consists of multiple domains, indicating that the standing-up layer forms through a multinucleation process during the liquid-solid transition on the surface. If, however, the temperature is above the melting point, then we have found that the standing-up layer shrinks to a droplet and leaves a residue on its original position. During the spreading of an alkane droplet, the parallel layer forms on the substrate surface surrounding the droplet by adsorption from the vapor, which precedes the arrival of the liquid. There has been uncertainty, however, as to whether the parallel layer moves with the liquid alkane or remains stationary during spreading. In this study, we used the residue left on the parallel layer as a landmark to monitor the movement of the parallel layer during the spreading of an alkane droplet. Using this landmark, we found that the parallel layer remained stationary on the substrate, indicating that the liquid alkane spreads on a stationary parallel layer surface. Therefore, this study reveals that the surface properties of the parallel layer--not the surface properties of the substrate--control the spreading and wetting of a liquid alkane. PMID:20297777

Lu, Lingbo; Zander, Kari J; Cai, Yuguang

2010-04-20

46

Boron-Based Layered Structures for Energy Storage  

SciTech Connect

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

Zhao, Y.; Wei, S. H.

2012-01-01

47

Do large structures control their own growth in a mixing layer? - An assessment  

NASA Technical Reports Server (NTRS)

Two different two-dimensional free shear layers, the T-layer developing in time from an initial tangential velocity discontinuity separating the two half-spaces, and the S-layer which develops downstream of the origin where two uniform streams of unequal velocity are brought into tangential contact, are compared. Calculations are performed in order to determine to what extent the perturbations induced upstream by large concentrations of vorticity found downstream hasten or retard the subharmonic instability that leads to the formations of these large structures. The results show that the elliptic influence, or the feedback, in a mixing layer is relatively small for small velocity ratios.

Kaul, Upender K.

1988-01-01

48

Evaluation of Techniques for Modeling of Layered Motion Structure  

Microsoft Academic Search

Motion information scalability is important for scalable bit- stream adaptation on low bit-rates, when motion rate occu- pies a significant portion of the total bit-rate. This type of scalability can be achieved by layered representation of mo- tion block partitioning and predictive coding of associated motion vectors across these layers. So far, several ap- proaches for creating layered motion structure

Marta Mrak; Nikola Sprljan; Ebroul Izquierdo

2006-01-01

49

Composite S-layer lipid structures  

PubMed Central

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

Schuster, Bernhard; Sleytr, Uwe B.

2010-01-01

50

Structural properties of replication origins in yeast DNA sequences  

NASA Astrophysics Data System (ADS)

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

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

2008-09-01

51

Deep subwavelength plasmonic waveguide switch in double graphene layer structure  

E-print Network

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

Fan, Shanhui

52

Multi-layer laminate structure and manufacturing method  

DOEpatents

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

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

2013-01-29

53

Multi-layer laminate structure and manufacturing method  

DOEpatents

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

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

2012-04-24

54

Lattice Vibrations and Superconductivity in Layered Structures  

E-print Network

of alternating films of heavy and light particles. An interface effectively lowers the vibrational frequencies of the heavy particles and raises those of the light particles. Interface effects are small compared to surface effects, how- ever. The decrease... in the frequencies for a three-layer film on a substrate (with respect to the bulk frequencies) is only 40?50% of the decrease for a free three-layer film. About two years ago, Strongin et a/. ' found large increases in superconducting transition tempera- tures...

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

1970-01-01

55

Structure of a Turbulent Reacting Mixing Layer  

Microsoft Academic Search

Results are presented of direct numerical simulations (DNS) of an unsteady, three-dimensional, temporally developing, compressible mixing layer under both non-reacting and reacting non-premixed conditions. In the reacting case, a simple chemistry model of the type A + rB -»(1 + r)Products is considered. Based on simulated results, it is shown that at sufficiently large Reynolds numbers the global and statistical

R. S. MILLER; C. K. MADNIA; P. GIVI

1994-01-01

56

Divergent fate and origin of neurosphere-like bodies from different layers of the gut.  

PubMed

Enteric neural stem cells (ENSCs) are a population of neural crest-derived multipotent stem cells present in postnatal gut that may play an important role in regeneration of the enteric nervous system. In most studies, these cells have been isolated from the layer of the gut containing the myenteric plexus. However, a recent report demonstrated that neurosphere-like bodies (NLBs) containing ENSCs could be isolated from mucosal biopsy specimens from children, suggesting that ENSCs are present in multiple layers of the gut. The aim of our study was to assess whether NLBs isolated from layers of gut containing either myenteric or submucosal plexus are equivalent. We divided the mouse small intestine into two layers, one containing myenteric plexus and the other submucosal plexus, and assessed for NLB formation. Differences in NLB density, proliferation, apoptosis, neural crest origin, and phenotype were investigated. NLBs isolated from the myenteric plexus layer were present at a higher density and demonstrated greater proliferation, lower apoptosis, and higher expression of nestin, p75, Sox10, and Ret than those from submucosal plexus. Additionally, they contained a higher percentage of neural crest-derived cells (99.4 ± 1.5 vs. 0.7 ± 1.19% of Wnt1-cre:tdTomato cells; P < 0.0001) and produced more neurons and glial cells than those from submucosal plexus. NLBs from the submucosal plexus layer expressed higher CD34 and produced more smooth muscle-like cells. NLBs from the myenteric plexus layer contain more neural crest-derived ENSCs while those from submucosal plexus appear more heterogeneous, likely containing a population of mesenchymal stem cells. PMID:22361728

Becker, Laren; Kulkarni, Subhash; Tiwari, Gunjan; Micci, Maria-Adelaide; Pasricha, Pankaj Jay

2012-05-01

57

Structural failure of two-density-layer cohesionless biaxial ellipsoids  

E-print Network

This paper quantitatively evaluates structural failure of biaxial cohesionless ellipsoids that have a two-density-layer distribution. The internal density layer is modeled as a sphere, while the external density layer is the rest of the part. The density is supposed to be constant in each layer. The present study derives averaged stresses over the whole volume of these bodies and uses limit analysis to determine their global failure. The upper bound condition of global failure is considered in terms of the size of the internal layer and the aspect ratio of the shape. The result shows that the two-density-layer causes the body to have different strength against structural failure.

Hirabayashi, Masatoshi

2014-01-01

58

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

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

59

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

60

The Triple Layer Structure of a Transitional Wall-Jet  

Microsoft Academic Search

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

Sam Raben; Wing Ng; Pavlos Vlachos

2008-01-01

61

ORIGINAL ARTICLE Development of hierarchical structures for actions and motor  

E-print Network

sense, we know that human infants develop such skills by having rich sensory­motor interactionORIGINAL ARTICLE Development of hierarchical structures for actions and motor imagery that any rep- resentations which children might have should have developed through sensory­motor level

Tani, Jun

62

Turbulence Structure and Wall Signature in Hypersonic Turbulent Boundary Layer  

E-print Network

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

Martín, Pino

63

Layer selective control of the lattice structure in oxide superlattices.  

PubMed

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

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

2014-01-15

64

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

NASA Technical Reports Server (NTRS)

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

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

1982-01-01

65

Original size of the Vredefort structure, South Africa  

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

66

Electrochemical Double-Layer Capacitors Using Carbon Nanotube Electrode Structures  

E-print Network

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 ...

Schindall, Joel E.

67

Chasma Australe Mars: Structural Framework for a Catastrophic Outflow Origin  

NASA Technical Reports Server (NTRS)

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

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

1998-01-01

68

Impact origin of the Sudbury structure: Evolution of a theory  

NASA Technical Reports Server (NTRS)

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

Lowman, Paul D., Jr.

1992-01-01

69

Novel Nanoscroll Structures from Carbon Nitride Layers  

E-print Network

Nanoscrolls (papyrus-like nanostructures) are very attractive structures for a variety of applications, due to their tunable diameter values and large accessible surface area. They have been successfully synthesized from different materials. In this work we have investigated, through fully atomistic molecular dynamics simulations, the dynamics of scroll formation for a series of graphenelike carbon nitride (CN) twodimensional systems: gCN, triazinebased gC3N4, and heptazinebased gC3N4. Our results show that stable nanoscrolls can be formed for all of these structures. Possible synthetic routes to produce these nanostructures are also addressed.

Perim, Eric

2014-01-01

70

Structure of the outer layers of cool standard stars  

E-print Network

Context: Among late-type red giants, an interesting change occurs in the structure of the outer atmospheric layers as one moves to later spectral types in the Hertzsprung-Russell diagram: a chromosphere is always present, but the coronal emission diminishes and a cool massive wind steps in. Aims: Where most studies have focussed on short-wavelength observations, this article explores the influence of the chromosphere and the wind on long-wavelength photometric measurements. Methods: The observational spectral energy distributions are compared with the theoretical predictions of the MARCS atmosphere models for a sample of 9 K- and M-giants. The discrepancies found are explained using basic models for flux emission originating from a chromosphere or an ionized wind. Results: For 7 out of 9 sample stars, a clear flux excess is detected at (sub)millimeter and/or centimeter wavelengths. The precise start of the excess depends upon the star under consideration. The flux at wavelengths shorter than about 1 mm is mos...

Dehaes, S; Decin, L; Eriksson, K; Raskin, G; Butler, B; Dowell, C D; Ali, B; Blommaert, J A D L

2009-01-01

71

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

SciTech Connect

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

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

2010-07-15

72

Superconducting structure with layers of niobium nitride and aluminum nitride  

DOEpatents

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

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

1989-07-04

73

Superconducting structure with layers of niobium nitride and aluminum nitride  

DOEpatents

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

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

1989-01-01

74

Structural abnormality of the carburized layer  

Microsoft Academic Search

1.The tendency toward abnormality is characterized by the rate of decomposition of austentite into ferrite at definite temperatures.2.The horophilic elements (AI, V, W, Mn) increase the tendency toward abnormality; the horophobic substances (Mn, Cr, Ni) are conducive to the formation of a normal structure.3.By selecting the chemical composition it is possible in the process of melting to control the degree

B. S. Natapov

1962-01-01

75

Thalamic terminal morphology and distribution of single corticothalamic axons originating from layers 5 and 6 of the cat motor cortex.  

PubMed

We investigated the axonal morphology of single corticothalamic (CT) neurons of the motor cortex (Mx) in the cat thalamus, using a neuronal tracer, biotinylated dextran amine (BDA). After localized injection of BDA into the Mx, labeled CT axons were found ipsilaterally in the thalamic reticular nucleus (TRN), the ventroanterior-ventrolateral complex (VA-VL), the central lateral nucleus (CL), the central medial nucleus, and the centromedian nucleus, but with the primary focus in the VA-VL. The terminals in the VA-VL formed a large laminar cluster, which extended approximately in parallel with the internal medullary lamina. The laminar organization mirrored morphologic features of single CT axons. We reconstructed the trajectories of 25 single CT axons that arose from layer V (16 axons) or layer VI (9 axons) and terminated in the VA-VL. Terminals of single CT axons that originated from both layer V and layer VI were confined within a laminar structure about 700 microm thick, suggesting the existence of laminar input organization in the VA-VL. Otherwise, the two groups of the CT axons showed contrasting features. All of the CT axons derived from layer VI gave rise to a few short collaterals to the TRN and then formed extensive arborization with numerous small, drumstick-like terminals in the VA-VL. On the other hand, the CT axons arising from layer V gave rise to collaterals whose main axons descended into the cerebral peduncle. Each collateral projected to the VA-VL or CL without projection to the TRN and formed a few small clusters of giant terminals. The two groups of CT neurons in the same cortical column had convergent rather than segregated termination in the VA-VL. However, the terminals of layer VI CT neurons were distributed diffusely and widely in the VA-VL, whereas the terminals of layer V CT neurons were much more focused and surrounded by the terminals of the former group. These contrasting features of the two types of CT projections appear to represent their different functional roles in the generation of motor commands and control of movements in the Mx. PMID:11494250

Kakei, S; Na, J; Shinoda, Y

2001-08-20

76

Integrated characterization of multilayer periodic systems with nanosized layers as applied to Mo/Si structures  

NASA Astrophysics Data System (ADS)

The potential inherent in integrated characterization of multilayer periodic systems employed in development of extreme-ultraviolet mirrors was demonstrated using the example of Mo/Si structures grown by magnetron sputtering in different technological regimes. An integrated study provided mutually consistent data on the thicknesses and crystal structure of the layers, as well as on the quality of the interfaces. Measurements by atomic force microscopy permitted a comparison of surface roughness of the substrates and the multilayer systems grown on them. An analysis of the power spectral density functions revealed that low-frequency roughness is replicated from the substrate, whereas the high-frequency one can become smoothed out in the course of growth. X-ray diffractometry performed in the thin film mode showed that the Mo layers in the samples studied have different crystal structures, from the amorphous and polycrystalline to the [110]-textured one. An analysis of the transmission electron microscopy data confirmed that there is a difference in the degrees of crystallinity of Mo layers. The thicknesses of individual layers, the period, and the irreproducibility of the thicknesses and the period were determined using X-ray reflectometry. The root-mean-square roughness amplitude of the interfaces was estimated, and the existence of transition layers originating primarily from the Si layer was demonstrated. The study was used to formulate a proper strategy for the analysis of multilayer periodic systems with nanosized layers.

Valkovskiy, G. A.; Baidakova, M. V.; Brunkov, P. N.; Konnikov, S. G.; Sitnikova, A. A.; Yagovkina, M. A.; Zadiranov, Yu. M.

2013-03-01

77

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

NASA Astrophysics Data System (ADS)

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

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

2012-02-01

78

Structure and morphology of aluminium doped Zinc-oxide layers prepared by atomic layer deposition  

Microsoft Academic Search

The aim of this work is to study the effects of deposition temperature and aluminium incorporation on the crystalline properties, orientation and grain size of atomic layer deposited ZnO layers. X-ray diffraction analysis revealed a change in the dominant crystallite orientation with increasing substrate temperature. The most perfect crystal structure and largest grain size was found at 2at.% aluminium content.

Zs. Baji; Z. Lábadi; Z. E. Horváth; I. Bársony

79

Erosion calderas: origins, processes, structural and climatic control  

Microsoft Academic Search

The origin and development of erosion-modified, erosion-transformed, and erosion-induced depressions in volcanic terrains\\u000a are reviewed and systematized. A proposed classification, addressing terminology issues, considers structural, geomorphic,\\u000a and climatic factors that contribute to the topographic modification of summit or flank depressions on volcanoes. Breaching\\u000a of a closed crater or caldera generated by volcanic or non-volcanic processes results in an outlet valley.

Dávid Karátson; Jean-Claude Thouret; Ichio Moriya; Alejandro Lomoschitz

1999-01-01

80

A DNA Structure Is Required for Geminivirus Replication Origin Function  

Microsoft Academic Search

The genome of the geminivirus tomato golden mosaic virus (TGMV) consists of two single-stranded circular DNAs, A and B, that replicate through a rolling-circle mechanism in nuclei of infected plant cells. The TGMV originofreplicationislocatedinaconserved5*intergenicregionandincludesatleasttwofunctionalelements: the origin recognition site of the essential viral replication protein, AL1, and a sequence motif with the potential to form a hairpin or cruciform structure. To

B. M. OROZCO

1996-01-01

81

Development of dual layered dielectric-loaded accelerating structure  

Microsoft Academic Search

Due to the high magnetic field-induced surface currents on its conducting sleeve, a conventional single layer Dielectric-Loaded Accelerating (DLA) structure exhibits a relatively high RF loss. One possible way to solve this problem is to use multilayered DLA structures. In these devices, the RF power attenuation is reduced by making use of the Bragg Fiber concept: the EM fields are

C. Jing; A. Kanareykin; E. Techlabs; S. Kazakov

2007-01-01

82

GPR determination of physical parameters of railway structural layers  

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

83

Development of a dual layered dielectric-loaded accelerating structure.  

SciTech Connect

Due to the high magnetic field-induced surface currents on its conducting sleeve, a conventional single layer Dielectric-Loaded Accelerating (DLA) structure exhibits a relatively high RF loss. One possible way to solve this problem is to use multilayered DLA structures. In these devices, the RF power attenuation is reduced by making use of the Bragg Fiber concept: the EM fields are well confined by multiple reflections from multiple dielectric layers. This paper presents the design of an X-band dual layer DLA structure as well as the results of bench tests of the device. We will also present results on the design, numerical modeling, and fabrication of structures for coupling RF into multilayer DLAs such as a novel TM{sub 03} mode launcher and a TM{sub 01}-TM{sub 03} mode converter using dielectric-loaded corrugated waveguide.

Gai, W.; Liu, W.; Jing, C.; Kanareykin, A.; Antipov, S.; Nenasheva, E.; Schoessow, P.; High Energy Physics; Euclid Techlabs, LLC; Illinois Inst. of Tech.; KEK

2008-09-01

84

Structure formation and the origin of dark energy  

E-print Network

Cosmological constant a.k.a. dark energy problem is considered to be one major challenge in modern cosmology. Here we present a model where large scale structure formation causes spatially-flat FRW universe to fragment into numerous `FRW islands' surrounded by vacuum. We show that this mechanism can explain the origin of dark energy as well as the late time cosmic acceleration. This explanation of dark energy does not require any exotic matter source nor an extremely fine-tuned cosmological constant. This explanation is given within classical general relativity and relies on the fact that our universe has been undergoing structure formation since its recent past.

Golam Mortuza Hossain

2007-09-21

85

Prediction of silicon-based layered structures for optoelectronic applications.  

PubMed

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

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

2014-11-12

86

Fluid-structure Interaction within a Layered Aortic Arch Model  

Microsoft Academic Search

The response of wall stress to the elasticity of each layer in the aorta wall was investigated to understand the role of the\\u000a different elastic properties of layers in the aortic dissection. The complex mechanical interaction between blood flow and\\u000a wall dynamics in a three-dimensional arch model of an aorta was studied by means of computational coupled fluid-structure\\u000a interaction analysis.

Feng Gao; Zhihong Guo; Makoto Sakamoto; Teruo Matsuzawa

2006-01-01

87

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

NASA Astrophysics Data System (ADS)

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

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

2014-02-01

88

Electromagnetic normal modes and Casimir effects in layered structures  

E-print Network

We derive a general procedure for finding the electromagnetic normal modes in layered structures. We apply this procedure to planar, spherical and cylindrical structures. These normal modes are important in a variety of applications. They are the only input needed in calculations of Casimir interactions. We present explicit expression for the condition for modes and Casimir energy for a large number of specific geometries. The layers are allowed to be two-dimensional so graphene and graphene-like sheets as well as two-dimensional electron gases can be handled within the formalism. Also forces on atoms in layered structures are obtained. One side-result is the van der Waals and Casimir-Polder interaction between two atoms.

Sernelius, Bo E

2014-01-01

89

Electromagnetic normal modes and Casimir effects in layered structures  

E-print Network

We derive a general procedure for finding the electromagnetic normal modes in layered structures. We apply this procedure to planar, spherical and cylindrical structures. These normal modes are important in a variety of applications. They are the only input needed in calculations of Casimir interactions. We present explicit expression for the condition for modes and Casimir energy for a large number of specific geometries. The layers are allowed to be two-dimensional so graphene and graphene-like sheets as well as two-dimensional electron gases can be handled within the formalism. Also forces on atoms in layered structures are obtained. One side-result is the van der Waals and Casimir-Polder interaction between two atoms.

Bo E. Sernelius

2014-09-08

90

Electromagnetic cloaking by layered structure of homogeneous isotropic materials.  

PubMed

Electromagnetic invisibility cloak requires material with anisotropic distribution of the constitutive parameters as first proposed by Pendry et al. [Science 312, 1780 (2006)]. In this paper, we proposed an electromagnetic cloak structure that does not require metamaterials with subwavelength structured inclusions to realize the anisotropy or inhomogeneity of the material parameters. We constructed a concentric layered structure of alternating homogeneous isotropic materials that can be treated as an effective medium with the required radius-dependent anisotropy. With proper design of the permittivity or the thickness ratio of the alternating layers, we demonstrated the low-reflection and power-flow bending properties of the proposed cloaking structure through rigorous analysis of the scattered electromagnetic fields. The proposed cloaking structure could be possibly realized by normal materials, therefore may lead to a practical path to an experimental demonstration of electromagnetic cloaking, especially in the optical range. PMID:19547468

Huang, Ying; Feng, Yijun; Jiang, Tian

2007-09-01

91

Shock-like structures in the tropical cyclone boundary layer  

NASA Astrophysics Data System (ADS)

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).

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

2013-06-01

92

Original Size and Shape of the Sudbury Structure  

NASA Technical Reports Server (NTRS)

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

Lowman, P. D., Jr.

1997-01-01

93

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

PubMed

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. PMID:24730863

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

2014-03-01

94

Origin of weak layer contraction in de Vries smectic liquid crystals  

NASA Astrophysics Data System (ADS)

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.

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

2014-03-01

95

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

PubMed Central

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

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

2014-01-01

96

Lactobacillus helveticus MIMLh5-specific antibodies for detection of S-layer protein in Grana Padano protected-designation-of-origin cheese.  

PubMed

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

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

2014-01-01

97

Coherent structures in compressible free-shear-layer flows  

SciTech Connect

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

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

1997-08-01

98

Novel layer-by-layer structured nanofibrous mats coated by protein films for dermal regeneration.  

PubMed

Layer-by-layer coating technique is effective in modifying the surface of nanofibrous mats, but overmuch film-coating makes the mats less porous to hardly suit the condition for tissue engineering. We developed novel nanofibrous mats layer-by-layer coated by silk fibroin and lysozyme on the cellulose electrospun template via electrostatic interaction. The film-coating assembled on the mats was not excessive because the charge of the proteins varied in the coating process due to different pH value. In addition, pure nature materials made the mats nontoxic, biodegradable and low-cost. The morphology and composition variation during layer-by-layer coating process was investigated and the results showed that the structure and thickness of film-coatings could be well-controlled. The antibacterial assay and in vitro cell experiments indicated that the mats could actively inhibit bacteria and exhibit excellent biocompatibility. In vivo implant assay further verified the mats cultured with human epidermal cells could promote wound healing and avoid wound infection. Therefore, these mats showed promising prospects when performed for dermal reconstruction. PMID:24734533

Xin, Shangjing; Li, Xueyong; Wang, Qun; Huang, Rong; Xu, Xiaoli; Lei, Zhanjun; Deng, Hongbing

2014-05-01

99

Developmental origin and fate of middle ear structures.  

PubMed

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

Sienknecht, Ulrike J

2013-07-01

100

Love wave propagation in layered magnetoelectro-elastic structures  

NASA Astrophysics Data System (ADS)

An analytical approach was taken to investigate Love wave propagation in a layered magneto-electro-elastic structure, where a piezomagnetic (or piezoelectric) material thin layer was bonded to a semi-infinite piezoelectric (or piezomagnetic) substrate. Both piezoelectric and piezomagnetic ceramics were polarized in the anti-plane (z-axis) direction. The analytical solution of dispersion relations was obtained for magneto-electrically open and short boundary conditions. The phase velocity, group velocity, magneto-electromechanical coupling factor, electric potential, and magnetic potential were calculated and discussed in detail. The numerical results show that the piezomagnetic effects have remarkable effect on the propagation of Love waves in the layered piezomagnetic/piezoelectric structures.

Du, Jianke; Jin, Xiaoying; Wang, Ji

2008-06-01

101

Strained layer superlattice focal plane array having a planar structure  

DOEpatents

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

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

2012-10-23

102

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

PubMed

The recent discovery of high-temperature superconductivity in iron-based compounds has attracted much attention. How to further increase the superconducting transition temperature (T(c)) and how to understand the superconductivity mechanism are two prominent issues facing the current study of iron-based superconductors. The latest report of high-T(c) superconductivity in a single-layer FeSe is therefore both surprising and significant. Here we present investigations of the electronic structure and superconducting gap of the single-layer FeSe superconductor. Its Fermi surface is distinct from other iron-based superconductors, consisting only of electron-like pockets near the zone corner without indication of any Fermi surface around the zone centre. Nearly isotropic superconducting gap is observed in this strictly two-dimensional system. The temperature dependence of the superconducting gap gives a transition temperature T(c)~ 55 K. These results have established a clear case that such a simple electronic structure is compatible with high-T(c) superconductivity in iron-based superconductors. PMID:22760630

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

2012-01-01

103

Large-Scale Streamwise Turbulent Structures in Hypersonic Boundary Layers  

E-print Network

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...

English, Benjamin L.

2013-04-22

104

Layered Structure and Management in Internet of Things  

Microsoft Academic Search

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

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

2007-01-01

105

Surface Science Letters Structures of adsorbed water layers  

E-print Network

methods) the consecutive ad- sorption of water molecules and found that, as the coverage increasedSurface Science Letters Structures of adsorbed water layers on MgO: an ab initio study R.M. Lynden density-functional method has been carried out for energy minima for a monolayer of water on MgO. Minima

Alavi, Ali

106

Investigation of hydrogeologic processes in a dipping layer structure  

Microsoft Academic Search

Numerical simulation tools have been used to study the dominating processes during transport of aromatic hydrocarbons in the unsaturated soil zone. Simulations were based on field observations at an experimental site located on a glacial delta plain with pronounced layered sedimentary structures. A numerical model for transport in the unsaturated zone, SWMS-3D, has been extended to incorporate coupled multispecies transport,

E. Alfnes; G. D. Breedveld; W. Kinzelbach; P. Aagaard

2004-01-01

107

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

NASA Astrophysics Data System (ADS)

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

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

2014-01-01

108

Turbulent boundary-layer structure of flows over freshwater biofilms  

NASA Astrophysics Data System (ADS)

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.

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

2013-12-01

109

Stable Single-Layer Honeycomblike Structure of Silica  

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

110

Structural and electronic origin of the magnetic structures in hexagonal LuFeO3  

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

111

Multi-functional layered structure having structural and radiation shielding attributes  

NASA Technical Reports Server (NTRS)

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

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

2010-01-01

112

Structure of hydrated layers on silicate electrode glasses.  

PubMed

The structural changes of the silicate framework in hydrated layers of silicate electrode glasses compared with untreated glasses as well as the quality and quantity of water and its ionic species stored in the layer have been investigated by high-resolution solid-state nuclear magnetic resonance (NMR) techniques [29Si magic-angle spinning (MAS), 29Si cross-polarization (CP) MAS, 1H high-speed MAS, 1H CRAMPS and 1H Echo NMR]. To support the results, infrared (IR) spectroscopy, thermal analysis and sodium ion concentration analyses were used. It was found that at least two different water species exist in the hydrated layer: SiOH groups and not very mobile hydrogen-bonded molecular water. Concerning the framework modified, Q3 groups [(SiO)3SiOH] were formed in the hydrated glass. During the swelling process a condensation of silanol groups formed took place to a great extent. PMID:7827973

Herzog, K; Scholz, K; Thomas, B

1994-02-01

113

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)

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.

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

114

Terpenoid hydrocarbons in Hula peat: Structure and origins  

NASA Astrophysics Data System (ADS)

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

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

1986-06-01

115

Influence of Coulomb collisions on the structure of reconnection layers  

SciTech Connect

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

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

2009-07-15

116

Structure of cake layer in a submerged anaerobic membrane bioreactor  

Microsoft Academic Search

A laboratory-scale submerged anaerobic membrane bioreactor (SAnMBR) was used for thermomechanical pulping whitewater treatment. Sludge cake formation on membrane surfaces was identified as the dominant mechanism of membrane fouling. The spatial distribution of physical, chemical and microbiological structure of cake layers was characterized by various analytical techniques, including micro-tome slicing technique, confocal laser scanning microscopy (CLSM), conventional optical microscopy (COM),

W. J. Gao; H. J. Lin; K. T. Leung; H. Schraft; B. Q. Liao

2011-01-01

117

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

E-print Network

Constraints on the origin and evolution of the layered mound in Gale Crater, Mars using Mars Applied Physics Laboratory, 11100 John Hopkins Rd., Laurel, MD 20723, United States b University of Notre 106, Tucson, AZ 85719, United States d Jet Propulsion Laboratory, California Institute of Technology

Hutyra, Lucy R.

118

Redox Active Layer-by-Layer Structures containing MnO2 Nanoparticles  

SciTech Connect

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

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

2005-02-01

119

Band structures of phononic-crystal plates in the form of a sandwich-layered structure.  

PubMed

This study investigates the propagation of Lamb waves in phononic-crystal plates in the form of a sandwich-layered structure. The composite plates are composed of periodic layers bilaterally deposited on both sides of the homogeneous core layer. Using the analyses of the band structures and the transmission spectra, it is revealed that the core layer may induce significant modulations to the lower-order Lamb modes. The modulations are ascribed to the reshaped particle displacement fields of the eigenmodes. Prominently, the core layer made of soft material (rubber) combines the identical eigenmodes of the periodic layers into a pair of asymmetric and symmetric modes in which case the periodic layers vibrate independently. However, the core layer made of hard material (tungsten) or medium hardness material (silicon) couples the periodic layers tightly, in which case the composites vibrate as a whole. In addition, it is found that the phononic band gaps are very sensitive to the thickness of the core layer; this could be indispensable to practical applications such as bandgap tuning. PMID:22087902

Cheng, Y; Liu, X J; Wu, D J

2011-11-01

120

Removing the angular sensitivity of FSS structures using novel double-layer structures  

Microsoft Academic Search

A double-layered periodic structure composed of shorted rings is employed to reduce the angular sensitivity of the reflection coefficient of a frequency selective surface (FSS). The angular sensitivity appears to vanish altogether for certain separation of the two layers. The configuration of the proposed cell element makes it suitable for dual orthogonal or circular polarized applications

J. Shaker; L. Shafai

1995-01-01

121

The motor origins of human and avian song structure.  

PubMed

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

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

2011-09-13

122

The motor origins of human and avian song structure  

PubMed Central

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

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

2011-01-01

123

Photon-pair generation in random nonlinear layered structures  

E-print Network

Nonlinearity and sharp transmission spectra of random 1D nonlinear layered structures are combined together to produce photon pairs with extremely narrow spectral bandwidths. Indistinguishable photons in a pair are nearly unentangled. Also two-photon states with coincident frequencies can be conveniently generated in these structures if photon pairs generated into a certain range of emission angles are superposed. If two photons are emitted into two different resonant peaks, the ratio of their spectral bandwidths may differ considerably from one and two photons remain nearly unentangled.

Jan Perina Jr; Marco Centini; Concita Sibilia; Mario Bertolotti

2009-08-25

124

Plasmon and exciton superconductivity mechanisms in layered structures  

NASA Technical Reports Server (NTRS)

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

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

1977-01-01

125

Terminal morphology and distribution of corticothalamic fibers originating from layers 5 and 6 of cat primary auditory cortex.  

PubMed

Two types of terminations were observed on corticothalamic fibers arising from cells in different layers of cat auditory cortex. Injections of the anterograde tracers Phaseolus vulgaris leucoagglutinin (PHA-L) or biocytin were made into single cortical loci that included both superficial layer 5 (5a) and layer 6 in the primary auditory cortex (AI). These resulted in labeling of terminal fibers with small (approximately 1 micron) and large (approximately 2 microns) boutons in the medial geniculate complex (MG) and the lateral nucleus of the posterior complex. Large boutons were found in the deep and superficial dorsal nuclei, in the ventrolateral nucleus, and, less frequently, in the medial nucleus of the MG. They usually ended in grape-like clusters of boutons. By contrast, small boutons were found densely in the pars lateralis and pars ovoidea of the ventral nucleus, and to a lesser extent in the medial nucleus of MG. In the anterior third of the ventral nucleus, where the highest density of labeled fibers was observed, the small bouton terminations formed a plate-like plexus. In the inferior colliculus (IC), most terminal boutons on labeled corticotectal fibers were of large size. To reveal the cells of origin of the axons ending in the two different types of corticothalamic terminations, biocytin injections were localized in either layer 5 or layer 6 of AI or PHA-L injections were made into middle layers, including layer 5a but excluding layer 6. Virtually all labeled terminals found in the MG after layer 5 injections were of large size, while those found after layer 6 injections were of small size. The distribution of terminals of single-labeled axons was extensive and variable. For example, an axon recovered after a layer 5 injection of biocytin ended in at least seven patches of clusters of large boutons along much of the anteroposterior axis of MG. Our previous findings showed two neuronal populations situated in superficial layer 5 and in layer 6 of AI and projecting to the thalamus. The axons of these cells had different patterns of collateral distributions in the cortex. The present study shows that the extrinsically projecting axons of these two populations also have different terminal morphologies and distribution patterns in the MG. The findings suggest that the corticothalamic pathway in the cat auditory system consists of at least two feedback projections originating from different cortical layers that exert different influences on distinct thalamic neuronal populations. PMID:7703690

Ojima, H

1994-01-01

126

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

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

127

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

E-print Network

Turbulence structure of the surface layer Boun 2247-03D TURBULENCE STRUCTURE OF THE UNSTABLE presents a new model of the structure of turbulence in the unstable atmospheric surface layer, and of the structural transition between this and the outer layer. The archetypal element of wall-bounded shear

Moncrieff, John B.

128

Structural changes in individual retinal layers in diabetic macular edema.  

PubMed

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

Murakami, Tomoaki; Yoshimura, Nagahisa

2013-01-01

129

Structural Changes in Individual Retinal Layers in Diabetic Macular Edema  

PubMed Central

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

Yoshimura, Nagahisa

2013-01-01

130

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

NASA Astrophysics Data System (ADS)

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

Seyidov, MirHasan Yu.; Suleymanov, Rauf A.

2010-09-01

131

Dual termination modes of corticothalamic fibers originating from pyramids of layers 5 and 6 in cat visual cortical area 17.  

PubMed

Terminal morphology of corticothalamic fibers originating from cat area 17 was examined. Injections of an anterograde axonal tracer, phaseolus vulgaris leucoagglutinin (PHA-L), in area 17 resulted in labeling of small boutons in the dorsal lateral geniculate, perigeniculate, and thalamic reticular nuclei and in labeling of large boutons in the lateral nucleus of lateral posterior-pulvinar, ventral lateral geniculate, and pulvinar nuclei. Since it is well known that the dorsal geniculate nucleus is a major corticothalamic target for layer 6 pyramids and the lateral posterior-pulvinar complex is that for layer 5 pyramids, the findings indicate that layer 5 pyramids in cat area 17 project axons ending with large boutons, while layer 6 pyramids project those ending with small boutons. PMID:8731174

Ojima, H; Murakami, K; Kishi, K

1996-04-12

132

Origin of NMR temperature shift and electronic structure of vanadocene  

NASA Astrophysics Data System (ADS)

The 13C and 1H NMR spectra of vanodocene were measured in the temperature range 208-377 K and compared with theory. To this end, the 3d3 term scheme of vanodocene is evaluated by a Hamiltonian which involves the Coulomb repulsion of the d electrons, their interaction with the D5d -coordinated ligands, and spin-orbit coupling. The adjustable parameters are chosen to fit the experimental ESR data and the weak bands at the low-energy side of the absorption spectrum. The reduced NMR shifts T(?H/H) of 13C and 1H, as calculated from the fine structure of the electronic ground state, depend on the well-known spatial structure, the ESR parameters, and on the adjustable radial spin densities at the ligand nuclei. In both cases only a slight temperature dependence is to be expected due to the orbitally nondegenerate ground state. This is in contradiction with the observed temperature slope of the reduced carbon shift. Thus, two modifications of the original assumptions are discussed. In the first place, the ligand-centered dipolar contribution is investigated theoretically. Although this effect improves the fit of both sets of spectra, it seems probable that in addition the nuclear coordinates change about 1% within the observed temperature range. The radial spin densities of vanadocene, however, are independent of the details of the fit procedure, yielding u2F(C) =-0.124(3) Å-3 and u2F(H) =+0.0982(2) Å-3 for the carbons and protons, respectively.

Eicher, H.; Köhler, Frank H.; Cao, Ren-de

1987-02-01

133

Flexural strength and failure modes of layered ceramic structures  

PubMed Central

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

Borba, Marcia; de Araujo, Maico D.; de Lima, Erick; Yoshimura, Humberto N.; Cesar, Paulo F.; Griggs, Jason A.; Bona, Alvaro Della

2011-01-01

134

Modeling a Possible Volcanic Origin for Interior Layered Deposits on Mars  

NASA Astrophysics Data System (ADS)

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

Chapman, M. G.; Kneissl, T.

2011-12-01

135

Surface-plasmons lasing in double-graphene-layer structures  

NASA Astrophysics Data System (ADS)

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

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

2014-01-01

136

Intrinsic growth of layered structure GaS microtubes from banana-leaf like structures  

NASA Astrophysics Data System (ADS)

We report the growth of highly crystalline GaS tubular structures directly on Ga metal from banana-leaf like structures via a facile catalyst free physical vapor deposition process. GaS microtube arrays with 1.5-2 ?m length were synthesized by promoting the intrinsic layered crystal structure of GaS during thermal evaporation where the thermal stress and interlayer interactions are mostly dominant. We monitored the growth process systematically to build a proper understanding of the formed tubular structures in this layered material. Microstructural analyses indicate that the GaS microtubes start with the formation of ultra-long, uniform banana-leaf like morphology that eventually splits into thinner flakes and starts rolling in nanometer size diameters. Final realization of GaS microtubes happened by the expansion of these intermediate rolled-up layers in their outer diameter by minimizing the strain energy in the system in a self-catalytic growth process.

Datta, Anuja; Sinha, Godhuli; Panda, Subhendu K.

2013-04-01

137

3D spherical layer photonic band-gap structures in dichromate gelatin.  

E-print Network

??Three-dimensional spherical layer photonic band-gap structures were fabricated in dichromate gelatin (DCG) holographic emulsions by a holographic lithography technique. Five spherical layer structures with different… (more)

Hung, Jenny

2008-01-01

138

S4 : A free electromagnetic solver for layered periodic structures  

NASA Astrophysics Data System (ADS)

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

Liu, Victor; Fan, Shanhui

2012-10-01

139

Perpendicular magnetic anisotropy in FePt/AlN layered structure  

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

140

Layered manganites : magnetic structure at extreme doping levels.  

SciTech Connect

We report powder neutron diffraction results on the crystal and magnetic structures of the bilayer Ruddlesden-Popper phase Sr{sub 3}Mn{sub 2}O{sub 7{minus}{delta}} ({delta} = 0.0, 0.45) and correlate these structures with their magnetic and transport properties. The {delta} = 0.45 compound contains a large number of oxygen vacancies that are disordered in the MnO{sub 2} planes. As a result of this disordered vacancy structure, Sr{sub 3}Mn{sub 2}O{sub 6.55} is a nonmagnetic insulator. Sr{sub 3}Mn{sub 2}O{sub 7.0} ({delta} = 0) is an antiferromagnetic insulator whose magnetic structure is related to that of the SrMnO{sub 3} perovskite. Comparison of this end-member compound to its doped congeners in the La{sub 2{minus}2x}Sr{sub 1+2x}Mn{sub 2}O{sub 7} series highlights the extreme sensitivity of magnetic structure to dopant concentration in these layered materials.

Mitchell, J. F.

1998-09-11

141

Theoretical analysis on Love waves in a layered structure with a piezoelectric substrate and multiple elastic layers  

NASA Astrophysics Data System (ADS)

A method is developed to analyze the existence and behavior of piezoelectric Love waves in a multilayered structure consisting of a piezoelectric substrate and multiple elastic layers which are isotropic, nonpiezoelectric materials. The acoustic waves and electric fields in the substrate and the layers are investigated. A general dispersion equation is derived to describe the existence of Love surface waves with respect to phase velocity as a function of normalized layer thickness. An iteration formula for XN is introduced to describe the mechanical action between the layers and the substrate at the interface. Another formula for ?¯LN, the equivalent permittivity of the wave-guide layers, is produced to describe the electric fields in the layers. The dispersion equation including a mass loading on the surface of the top layer is deduced, and a formula for calculating the mass sensitivity of the phase velocity is presented. We also find the dispersion equation with an electric shorted interface and introduce a formula for calculating the electromechanical coupling coefficient K2. Numerical results illustrate the phase velocity, the mass sensitivity of the phase velocity and the electromechanical coupling coefficient as functions of the normalized layer thickness for the Love waves in a layered structure with a polymethylmethacrylate (PMMA) layer and a sputtered SiO2 layer on a 90° rotated ST-cut quartz (ST-quartz) substrate.

Liu, Jiansheng; He, Shitang

2010-04-01

142

Supersonic Boundary-Layer Control: Bleed-Induced Shock Structure  

NASA Astrophysics Data System (ADS)

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

Shih, Tom; Flores, Andrew

1999-11-01

143

Radial transmission line analysis of multi-layer structures  

SciTech Connect

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

Hahn, H.; Hammons, L.

2011-03-28

144

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

145

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

NASA Astrophysics Data System (ADS)

The role of CCN and their complex influence upon cloud albedo, cloudiness, radiative transfer and precipitation has emerged as a key research issue in the past decade due to the large and uncertain influence they may have on global climate. Aerosol that activate at low supersaturation in the marine boundary layer (MBL) (i.e. below about 0.4% S (CCN0.4) with sizes near 60 nm diameter) can influence clouds over a dominant fraction of the globe, including extensive regions of marine stratus. Hence, greater efforts have recently been directed at understanding the CCN cycle in this environment. Advection of continental aerosol in the MBL can often account for most CCN0.4 near coastal regions until precipitation scavenging reduces their concentrations to low values. Away from such influences, the dominant sources of new CCN0.4 are from the ocean surface via bubble bursting, from the free troposphere (FT) via entrainment and possibly from nucleation and growth of new particles in the MBL. As the latter process generally appears weak and uncommon, the former two sources appear to dominate most regions. Surface sources via bubble bursting were long presumed to be larger sea-salt with sizes above several hundred nanometers and with production rates driven by white cap coverage that increased with wind speed. More recently, production of sizes smaller than 20 nm has been observed and other constituents including organic aerosol and polysaccharides have become recognized contributors. Growth of smaller sizes into the CCN0.4 range is evident via uptake of sulfate originating from DMS. However, long range transport and entrainment of aerosol from the FT has been identified as another important source of MBL CCN0.4 that may be either natural (eg. sulfuric acid formed in cloud outflow) or continental (eg. biomass burning aerosol). Hence; regional wind speeds, entrainment rates, FT transport, oceanic bio-chemistry and removal rates via precipitation etc. can modulate the nature and variability of CCN in the remote MBL. This modulation also involves various size-dependent processes that influence the CCN growth and removal. The relative importance of these aerosol sources and removal to the CCN0.4 budget varies regionally and temporally in ways that are complex and uncertain. We focus here on recent observations in the equatorial and lower latitudes (<30 deg) of the South Pacific and highlight examples of transport and entrainment of FT aerosol as well as the production of sea spray aerosol (SSA) and the processes influencing their relative importance on MBL CCN0.4. Entrainment was found to be a dominant source of CCN0.4 in the MBL with concentrations in quasi equilibrium with overlying FT concentrations on a scale of several days. SSA was a weaker secondary source in these environments with winds below 14 m s-1. Entrainment of CCN0.4 appeared most active in cloudy (stratus) regions and SSA appeared rapidly depleted by drizzle in regions of higher winds and cloudiness in spite of increased production. Because the response time for a change in the MBL concentrations in these regions to a surface and FT source is on the order of a day(s), addressing CCN0.4 variability requires understanding processes active in the MBL and FT well beyond conditions at the point of measurement.

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

2012-12-01

146

Towards a model for the in situ origin of PGE reefs in layered intrusions: insights from chromitite seams of the Rum Eastern Layered Intrusion, Scotland  

NASA Astrophysics Data System (ADS)

The current debate on the origin of platinum-group element (PGE) reefs in layered intrusions centres mostly on gravity settling of sulphide liquid from overlying magma versus its introduction with interstitial melt/fluids migrating upward from the underlying cumulate pile. Here, we show that PGE-rich chromitite seams of the Rum Eastern Layered Intrusion provide evidence for an alternative origin of such deposits in layered intrusions. These laterally extensive 2-mm-thick chromitite seams occur at the bases of several cyclic mafic-ultramafic units and show lithological and textural relationships suggesting in situ growth directly at a crystal-liquid interface. This follows from chromitite development along the edges of steeply inclined culminations and depressions at unit boundaries, even where these are vertically oriented or overhanging. High concentrations of PGE (up to 2-3 ppm Pd + Pt) are controlled by fine-grained base-metal sulphides, which are closely associated with chromitite seams. The following sequence of events explains the origin of the PGE-rich chromitite seams: (a) emplacement of picritic magma that caused thermal and mechanical erosion of underlying cumulate, followed by in situ growth of chromite against the base, (b) precipitation of sulphide droplets on chromite grains acting as favourable substrate or catalyst for sulphide nucleation, (c) the scavenging of PGE by sulphide droplets from fresh magma continuously brought towards the base by convection. Since the rate of magma convection is 105-107 times higher than that of the solidification (km/year to km/day versus 0.5-1.0 cm/year), the in situ formed sulphide droplets can equilibrate with picritic magma of thousands to million times their own volume. As a result, the sulphide-bearing rocks are able to reach economic concentrations of PGE (several ppm). We tentatively suggest that the basic principles of our model may be used to explain the origin of PGE-rich chromitites and classical PGE reefs in other layered mafic-ultramafic intrusions.

Latypov, Rais; O'Driscoll, Brian; Lavrenchuk, Andrey

2013-07-01

147

Graphene originated 3D structures grown on the assembled nickel particles  

NASA Astrophysics Data System (ADS)

Recently, the fabrication of various morphologies of graphene originated structures became very important due to the perspective of wide range of new applications. Particularly, free standing 3D structured graphene foams could be imperative in energy related areas. Here, we present the new approach of the CVD growth of 3D graphene network by using primarily sintered Ni particle's (˜40?m size) assembles as a template-catalyst via decomposition of low rate of CH4 at 1100^o C based on synthesis method described earlier [1]. SEM and Raman spectra analysis revealed the formation of graphene structure containing a single up to few layers grown on the sintered metal particles served as a catalyst-template. After etching the metal frame without using any support polymer, 3D free-standing graphene microporous structure was formed demonstrating high BET surface area. Two probe measurements of frame resistance were ˜2-8?. Our approach allows controllable tune the pore size and thereby the surface area of 3D graphene network through the variation of the template-catalyst particles size. [4pt] [1]. T. M. Paronyan et al. ACS Nano, 5, p. 9619 (2011)

Paronyan, Tereza; Harutyunyan, Avetik

2013-03-01

148

Double-Layer ULVZ Shear Velocity Structure Imaged With Stacked ScS Data  

NASA Astrophysics Data System (ADS)

The ultra-low velocity zone (ULVZ) has been imaged as a thin (5-40 km thick) layer just above the core-mantle boundary (CMB), with P and S velocities reduced by up to 10 and 30%, respectively. Accurate characterization of the ULVZ is important, as it may relate to, for example, the role of the lowermost mantle in Earth's evolution, mantle and outer core convection, the geodynamo, and heat flux into the mantle. A direct measurement of S velocity in the ULVZ, independent of the P-wave velocity, is needed to better constrain ULVZ properties. We establish tangential component ScS data as a new probe of ULVZ shear velocity properties. Lowermost mantle structure beneath the central Pacific is studied using data from 38 deep focus Tonga-Fiji earthquakes, recorded by dense broadband seismic networks in western North America. Our data set consists of 442 instrument-deconvolved displacement seismograms, which are additionally deconvolved by average source-time functions (source wavelets) constructed for each event, in order to equalize the signals and to extend the signal bandwidth to high frequencies. The resulting traces are used in a double-beam stacking approach to enhance the signal-to-noise ratio of any coherent precursory reflections of the wide-angle transverse component ScS data, which should be detectable if ULVZ structure is present beneath our central Pacific study region. Our stacks reveal two distinct ScS precursors, which indicate a double layer ULVZ structure in this region. Both layers show strong lateral variations in shear velocity reduction (dVs) and thickness. The deeper ULVZ layer is well modeled by dVs drops varying from 3.3-7.4% (relative to PREM) with a thickness range of 24-30 km. The overlying layer has dVs reductions from 0.8-2.0% (relative to PREM), and 60-86 km thickness. Thus the imaged 2-layered ULVZ has dVs reductions far milder than previous studies (10-30%), which have argued for a partial melt origin to the ULVZ. Finer subdivisions of data will be examined and the variability across the study region of these ScS precursors will be investigated. Tradeoffs between layer thicknesses, shear velocity reductions, and density contrasts across the layer boundaries will also be explored, and results will be presented in the greater context of the entire D" region in this central Pacific study area.

Avants, M.; Lay, T.; Garnero, E.

2005-12-01

149

Nature and origin of layered deposits of the Martian polar regions  

NASA Technical Reports Server (NTRS)

Layered deposits in the Martian polar regions are interpreted as accumulations of dust derived from atmospheric suspensions. Depressed and eroded terrains of the equatorial region are considered to be the principal sources of dust. A depositional model based on polar precipitation of dust predicts the formation of a vast, dome-shaped, featureless plateau underlain by layered deposits and occupying most of the area of annual frost cover. The rates of accumulation of dust and water ice in the polar regions have been estimated on the basis of atmospheric conditions in the present era. The analysis indicates an accumulation time of about 500 x 1 million years for the layered deposits and the presence of significant quantities of water ice in the deposits beneath the perennial cap.

Cutts, J. A.

1973-01-01

150

Broadband metamaterial absorber based on a multi-layer structure  

NASA Astrophysics Data System (ADS)

In this paper, a broadband metamaterial absorber (MA) based on a multi-layer structure is presented. The advantages of this MA are the small periodic unit size, they are thin, have excellent polarization characteristics and are adaptive for wide angles of oblique incident electromagnetic waves. The unit cell of the broadband MA is composed of three dual-band sub-cells; each presents two resonant frequencies so as to form a wide absorptive spectrum when stacked. The sandwiched dual-band sub-cell is composed of one metallic annular patch and one metallic circular patch each etched on a lossy substrate. The radii of the metallic patches forming each sub-cell are different so as to appear to have different resonant frequencies. In the design of the unit cell there are metallic circular patches and an air layer at the bottom of each sub-cell to form magnetic coupling and avoid coupling between sub-cells. The broadband MA presents good absorptivity above 80% between 8.8 and 10.8 GHz, with a full width at half maximum (FWHM) absorption bandwidth of 2.3 GHz and a relative FWHM absorption bandwidth of 23%.

Wen, Ding-e.; Yang, Helin; Ye, Qiwei; Li, Minhua; Guo, Linyan; Zhang, Jianfeng

2013-07-01

151

Investigation of turbulent boundary layer structures using Tomographic PIV  

NASA Astrophysics Data System (ADS)

Tomographic particle image velocimetry (TPIV) data were acquired in the logarithmic region of a zero pressure gradient turbulent boundary layer flow at friction Reynolds number Re? = 1160. Experiments were conducted in a suction type wind tunnel seeded with olive oil particles of diameter ˜ 1?m. The volume of interest was illuminated by two Nd:YAG laser beams expanded with appropriate optics into sheets of 8mm thickness in the wall-normal direction (z). Images were acquired by four 2k x 2k pixel cameras, and correlation of reconstructed fields provided the full velocity gradient tensor in a volume of 0.7? x 0.7? x 0.07?, which resolved the region z^+ = 70-150 in the log layer. Various vortex identification techniques, such as Galilean decomposition and iso-surfaces of two- and three-dimensional swirl, were utilized to visualize and analyze the eddy structures present in instantaneous fields. The results of the present study will be compared to results from earlier experimental studies that relied on planar PIV data only to identify vortices and vortex packets as well as from a direct numerical simulation of fully developed channel flow at comparable Re?.

Saikrishnan, Neelakantan; Longmire, Ellen; Wieneke, Bernd

2008-11-01

152

Bose-Einstein condensation in low dimensional layered structures  

NASA Astrophysics Data System (ADS)

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

Salas, Patricia; Solis, M. A.

2008-03-01

153

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

Microsoft Academic Search

The circular Cloud Creek structure in central Wyoming, USA is buried beneath ~1200 m of Mesozoic sedimentary rocks and has a current diameter of ~7 km. The morphology\\/morphometry of the structure, as defined by borehole, seismic, and gravity data, is similar to that of other buried terrestrial complex impact structures in sedimentary target rocks, e.g., Red Wing Creek in North

D. S. Stone; A. M. Therriault

2003-01-01

154

Corrosion detection in multi-layered rotocraft structures  

SciTech Connect

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

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

2000-04-25

155

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

NASA Technical Reports Server (NTRS)

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

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

1992-01-01

156

Structural simplicity and complexity of compressed calcium: electronic origin.  

PubMed

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

Degtyareva, Valentina F

2014-06-01

157

The origin of current gain under illumination in amorphous silicon n-i-p-i-n structures  

NASA Astrophysics Data System (ADS)

Detailed computer modeling in conjunction with experiments has been used to explain the current gain sometimes observed in amorphous silicon n-i-p-i-n structures under illumination and to specify under what conditions such a gain is possible. Calculations reveal that the origin of the current gain at a given applied voltage, is excess injection of electrons from the contacts as a result of the lowering of the i-layer/n-layer barrier in the forward biased diode on account of photogenerated hole trapping. However to actually obtain this gain, the thickness and the density of states of the partitioning p layer must be small enough, so that all the excess injected electrons do not recombine in the p layer before being collected in the reverse biased diode. We also find that under conditions for which the gain varies linearly with voltage, it is almost independent of the incident light flux. On the other hand, when the barrier height at the p layer (Ec-EF0)max, where Ec is the conduction band edge and EF0 the thermodynamic equilibrium Fermi level, approaches its maximum value corresponding to a thick or highly doped p layer, there is no gain. This is the condition to be fulfilled for a color sensitive device.

Chatterjee, P.; Vanderhaghen, R.; Equer, B.

2000-02-01

158

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

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

159

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

NASA Astrophysics Data System (ADS)

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

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

2011-08-01

160

On the Origin of Irregular Structure in Saturn's Rings  

Microsoft Academic Search

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 ~105 dyn cm-2 is consistent with

Scott Tremaine

2003-01-01

161

Thermoacoustic effects on layered structures for the evaluation of structural parameters  

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

162

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

SciTech Connect

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

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

2013-08-15

163

Chirality in Liquid Crystals: from Microscopic Origins to Macroscopic Structure  

E-print Network

Molecular chirality leads to a wonderful variety of equilibrium structures, from the simple cholesteric phase to the twist-grain-boundary phases, and it is responsible for interesting and technologically important materials like ferroelectric liquid crystals. This paper will review some recent advances in our understanding of the connection between the chiral geometry of individual molecules and the important phenomenological parameters that determine macroscopic chiral structure. It will then consider chiral structure in columnar systems and propose a new equilibrium phase consisting of a regular lattice of twisted ropes.

T. C. Lubensky; A. B. Harris; Randall D. Kamien; Gu Yan

1997-10-31

164

Unexpected strong magnetism of Cu doped single-layer MoS? and its origin.  

PubMed

The magnetism of the 3d transition-metal (TM) doped single-layer (1L) MoS2, where the Mo atom is partially replaced by the 3d TM atom, is investigated using the first-principles density functional calculations. In a series of 3d TM doped 1L-MoS2's, the induced spin polarizations are negligible for Sc, Ti, and Cr dopings, while the induced spin polarizations are confirmed for V, Mn, Fe, Co, Ni, Cu, and Zn dopings and the systems become magnetic. Especially, the Cu doped system shows unexpectedly strong magnetism although Cu is nonmagnetic in its bulk state. The driving force is found to be a strong hybridization between Cu 3d states and 3p states of neighboring S, which results in an extreme unbalanced spin-population in the spin-split impurity bands near the Fermi level. Finally, we also discuss further issues of the Cu induced magnetism of 1L-MoS2 such as investigation of additional charge states, the Cu doping at the S site instead of the Mo site, and the Cu adatom on the layer (i.e., 1L-MoS2). PMID:24695769

Yun, Won Seok; Lee, J D

2014-05-21

165

9.14 Brain Structure and its Origins, Spring 2005  

E-print Network

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

Schneider, Gerald

166

On the origins of the mitotic shift in proliferating cell layers  

PubMed Central

Background During plant and animal development, monolayer cell sheets display a stereotyped distribution of polygonal cell shapes. In interphase cells these shapes range from quadrilaterals to decagons, with a robust average of six sides per cell. In contrast, the subset of cells in mitosis exhibits a distinct distribution with an average of seven sides. It remains unclear whether this ‘mitotic shift’ reflects a causal relationship between increased polygonal sidedness and increased division likelihood, or alternatively, a passive effect of local proliferation on cell shape. Methods We use a combination of probabilistic analysis and mathematical modeling to predict the geometry of mitotic polygonal cells in a proliferating cell layer. To test these predictions experimentally, we use Flp-Out stochastic labeling in the Drosophila wing disc to induce single cell clones, and confocal imaging to quantify the polygonal topologies of these clones as a function of cellular age. For a more generic test in an idealized cell layer, we model epithelial sheet proliferation in a finite element framework, which yields a computationally robust, emergent prediction of the mitotic cell shape distribution. Results Using both mathematical and experimental approaches, we show that the mitotic shift derives primarily from passive, non-autonomous effects of mitoses in neighboring cells on each cell’s geometry over the course of the cell cycle. Computationally, we predict that interphase cells should passively gain sides over time, such that cells at more advanced stages of the cell cycle will tend to have a larger number of neighbors than those at earlier stages. Validating this prediction, experimental analysis of randomly labeled epithelial cells in the Drosophila wing disc demonstrates that labeled cells exhibit an age-dependent increase in polygonal sidedness. Reinforcing these data, finite element simulations of epithelial sheet proliferation demonstrate in a generic framework that passive side-gaining is sufficient to generate a mitotic shift. Conclusions Taken together, our results strongly suggest that the mitotic shift reflects a time-dependent accumulation of shared cellular interfaces over the course of the cell cycle. These results uncover fundamental constraints on the relationship between cell shape and cell division that should be general in adherent, polarized cell layers. PMID:24886286

2014-01-01

167

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

PubMed

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

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

2014-07-01

168

Potassium under pressure: Electronic origin of complex structures  

NASA Astrophysics Data System (ADS)

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

Degtyareva, V. F.

2014-10-01

169

Structure and Dynamics of the Magnetopause and Its Boundary Layers  

NASA Astrophysics Data System (ADS)

The magnetopause is the key region in space for the transfer of solar wind mass, momentum, and energy into the magnetosphere. During the last decade, our understanding of the structure and dynamics of Earth's magnetopause and its boundary layers has advanced considerably, thanks largely to the advent of multi-spacecraft missions such as Cluster and THEMIS. Moreover, various types of physics-based techniques have been developed for visualizing two- or three-dimensional plasma and field structures from data taken by one or more spacecraft, providing a new approach to the analysis of the spatiotemporal properties of magnetopause processes, such as magnetic reconnection and the Kelvin-Helmholtz instability (KHI). Information on the size, shape, orientation, and evolution of magnetic flux ropes or flow vortices generated by those processes can be extracted from in situ measurements. Observations show that magnetopause reconnection can be globally continuous for both southward and northward interplanetary magnetic field (IMF) conditions, but even under such circumstances, more than one X-line may exist within a certain (low-latitude or high-latitude) portion on the magnetopause and some X-lines may retreat anti-sunward. The potential global effects of such behavior are discussed. An overview is also given of the identification, excitation, evolution, and possible consequences of the magnetopause KHI: there is evidence for nonlinear KHI growth and associated vortex-induced reconnection under northward IMF. Observation-based estimates indicate that reconnection tailward of both polar cusps can be the dominant mechanism for solar wind plasma entry into the dayside magnetosphere under northward IMF. However, the mechanism by which the transferred plasma is transported into the central portion of the magnetotail, and the role of magnetopause processes in this transport, remain unclear. Future prospects of magnetopause and other relevant studies are also discussed.

Hasegawa, H.

2012-08-01

170

Crustal Structure of Salton Trough using Deformable Layer Tomography  

NASA Astrophysics Data System (ADS)

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

Yuan, F.

2012-12-01

171

On the origin of irregular structure in Saturn's rings  

E-print Network

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

Scott Tremaine

2002-11-07

172

Visible range lasing in dye-doped doubly periodic layered structures in dichromate gelatin emulsions  

NASA Astrophysics Data System (ADS)

We have fabricated dye-doped doubly periodic layered structures exhibiting multiple bandgaps in the visible range in dichromate gelatin emulsions by a double-exposure holographic interference method. More importantly, optically pumped lasing with higher efficiency and lower threshold compared to that of singly periodic layered structures was observed in the dye-doped doubly periodic gelatin samples. This efficient lasing could be explained by the enhancement of the density of states at the overlapping bandgaps of two singly periodic layered structures.

Wang, Xia; Hin Kok, Mang; Lu, Weixin; Lee, Jeffrey Chi Wai; Tam, Wing Yim; Wong, George K. L.; Chan, C. T.

2012-01-01

173

Stromules: Origin, structure and functions in a plant cell  

Microsoft Academic Search

The review presents a critical analysis of experimental achievements concerning structure and peculiarities of stromules over\\u000a the last years. Stromules are dynamic thin protrusions of membrane envelope from plant cell plastids. The prospects of further\\u000a studies of the stromules are discussed.

G. A. Velikanov

2009-01-01

174

ORIGINAL PAPER Population genetic structure of the Daubenton's bat  

E-print Network

the potential for disease transmission. The genetic structure of the Daubenton's bat in western Europe and often associated with freshwater (Altringham 2003). It has a continuous transpalearctic distribution distribution, the Daubenton's bat has a poorly described spatial ecology. Bats are reservoirs and vectors

Paris-Sud XI, Université de

175

ORIGINAL PAPER Synthesis and Crystal Structure of the Azoxydichinyl Helicene,  

E-print Network

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

Gates, Kent. S.

176

ORIGINAL PAPER Genetic diversity and structure of western white pine  

E-print Network

of white pine blister rust) and reduced opportunities for regeneration. Amplified fragment length polymorphism (AFLP) markers were used to assess the genetic diversity and structure among populations at 15, regeneration ability, and occupancy of sites make WWP highly desirable throughout its range. Under optimal

177

Cosmology: The Origin and Evolution of Cosmic Structure  

Microsoft Academic Search

During recent years the subject of structure formation has attracted a considerable amount of attention. Increase in observational input and availability of powerful computers to do numerical simulations have allowed researchers to model the universe to far greater accuracy than was possible before. This increase in interest has also resulted in several new textbooks on this subject appearing in recent

T Padmanabhan

1996-01-01

178

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

NSDL National Science Digital Library

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

Computers &amp; Structures, Inc.

179

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

NASA Astrophysics Data System (ADS)

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

Hanley, Jacob; Adlakha, Erin

2013-04-01

180

Distribution, thickness and origin of Heinrich layer 3 in the Labrador Sea  

NASA Astrophysics Data System (ADS)

The presence of Heinrich layer 3 (HL-3) in the northwest Labrador Sea has been debated in the literature. Calypso giant piston core MD99-2233, five new standard piston cores, and re-interpretation of 34 cores from previous cruises confirm the presence of HL-3 in the Labrador Sea. It is identified by high total carbonate concentration (up to 45%), an increase in coarse fraction content, and lighter ? 18O values in polar species planktonic foraminifer Neogloboquadrina pachyderma (left-coiling) as low as 3.1‰. The age of HL-3 of ˜27 ka was bracketed in the various cores by about 50 14C-accelerator mass spectrometer dates. Where it is present in ice-proximal regions, it consists of nepheloid-flow deposits at the base and mud turbidites at the top. The thickness of HL-3 varies between 4.8 m (proximal to Hudson Strait) and 0.9 m (distal), decreasing rapidly seaward. On the upper continental slope, HL-3 was too deeply buried to be sampled. Elsewhere, HL-3 is absent in some cores, probably due to slumping or erosion associated with sandy turbidity currents or debris flows.

Rashid, Harunur; Hesse, Reinhard; Piper, David J. W.

2003-01-01

181

Adularia in epithermal veins, Queensland: morphology, structural state and origin  

Microsoft Academic Search

Four types of adularia (i.e. sub-rhombic, rhombic, tabular and pseudo-acicular) are recognised from examination of samples from ten epithermal vein deposits and prospects in Queensland, based on morphology of the individual crystals. Further investigation of the structural state of adularia reveals that each group has some specific features in terms of the degree of Al\\/Si disordering, which can be related

G. Dong; G. W. Morrison

1995-01-01

182

Observing the Origins of Galaxy Structure in the Illustris Simulation  

NASA Astrophysics Data System (ADS)

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

Snyder, Greg

2014-10-01

183

Impact of vertical transport processes on the tropospheric ozone layering above Europe. Part I: Study of air mass origin using multivariate analysis, clustering and trajectories  

Microsoft Academic Search

A new method is proposed to classify ozone-rich layers observed in tropospheric profiles in terms of their origin using multivariate analysis. We combine principal component and discriminant analyses to quantify the respective ability of 21 measured physical parameters to describe the layers. Agglomerative hierarchical clustering shows the existence of clusters of air masses with specific physical characteristics. Quadratic discriminant analysis

Augustin Colette; Gérard Ancellet; François Borchi

2005-01-01

184

Numerical simulations of the structure of supersonic shear layers  

Microsoft Academic Search

Time-dependent two-dimensional numerical calculations were performed to study the mixing characteristics of unforced, planar, confined shear layers formed by two parallel streams of air that come into contact after passing over a splitter plate. The evolution of the shear layer was examined by systematically varying the velocities, densities, and the static pressures of the two streams that come into contact

B. Farouk; E. S. Oran; K. Kailasanath

1991-01-01

185

Structured Analysis of a Layered Manufacturing Decision Support System  

Microsoft Academic Search

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

M. M. Ghazy; K. W. Dalgarno

186

Elastic and structural properties of supported porous silicon layers  

NASA Astrophysics Data System (ADS)

Brillouin spectroscopy has been used to investigate the elastic properties of (111)-oriented pi - Si samples formed from p - and p+ type c - Si substrates. In the frequency regime studied, Brillouin spectra of low porosity (28%--40%) p+ samples consist of a single set of inelastic peaks due to the surface acoustic wave. These surface waves were found to have velocities which are significantly lower than the corresponding c - Si velocity, and, for samples of a given set, decreased with increasing porosity, xi. Removal of the thin native oxide film present on low porosity p + type samples by an HF dip, results in a 3%--6% decrease in surface acoustic wave velocity compared to pre-dip values. Adsorbed water on the porous silicon surface appears to have no measurable effect on the surface acoustic wave velocity. Complete sets of elastic constants for several low porosity layers formed from p+ type substrates were determined from the directional dependence of the surface acoustic wave velocity in the (111) plane. The elastic constants Cij, were found to be much smaller than those for c - Si and, for a given set, decreased with increasing porosity. Empirical fitting of expressions of the form Cp-Siij=Cp-Si ij1-xm ij to the experimental data leads to the following relations for the porosity dependence of the elastic constants: Cp-Si11 =168.51-x 3.00 Cp-Si12=6.26 1-x6.23 0.1 Cp-Si44=79.0 1-x2.30 The exponents m11, m 12 and m44 differ from those of porous samples formed from p- type substrates. This is attributed to microstructural differences between porous layers formed from p- and p + type substrates. In addition, Young's modulus values were calculated from the elastic constants and compared with those determined in other experiments. In contrast to other studies, elastic anisotropy is taken into account. A limited number of Brillouin spectra was also obtained from intermediate porosity (50% and 60%) samples fabricated from p- type substrates. These spectra exhibited multiple broad Brillouin peaks at relatively low frequency shifts (<15 GHz) and are qualitatively similar to those collected by Beghi et al. from samples with similar porosity formed from p- type substrates. The structural and light-emitting properties of pi - Si prepared from p- and p+ type (111)-oriented c - Si substrates have been studied using Raman scattering. A detailed analysis of the Raman lineshapes was performed using a phonon confinement model with realistic longitudinal and transverse optic phonon dispersion curves. This model basically explains the reduced Raman shifts and asymmetric broadening of the Raman peaks in the porous silicon samples of the present work. Characteristic nanocrystallite sizes and shapes were determined for samples with porosities in the range 35% to 80%. The highly porous samples consist of fine Si spheres, while those of lower porosity are primarily wire-like. The photoluminescence spectra are less size-sensitive than the Raman spectra and no clear correlation between the Raman scattering structural information and the photoluminescence spectra has been observed.

Andrews, Gordon Todd

187

Synthesis of the originally proposed structures of elatenyne and an enyne from Laurencia majuscula.  

PubMed

A bidirectional synthesis of the originally proposed structures for the natural products elatenyne and a chloroenyne from Laurencia majuscula is described along with a reassessment of the structures of the halogenated enynes based upon a 13C NMR chemical shift/structure correlation. PMID:19109668

Sheldrake, Helen M; Jamieson, Craig; Pascu, Sofia I; Burton, Jonathan W

2009-01-21

188

Charge carrier transport properties in layer structured hexagonal boron nitride  

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

189

Raman Spectroscopy Study of Rotated Double-Layer Graphene: Misorientation-Angle Dependence of Electronic Structure  

E-print Network

Raman Spectroscopy Study of Rotated Double-Layer Graphene: Misorientation-Angle Dependence of unconventionally stacked double-layer graphene, and find that the spectrum strongly depends on the relative structure of rotated double-layer graphene, and leads to a practical way to identify and analyze rotation

Zettl, Alex

190

Instability of myelin tubes under dehydration: Deswelling of layered cylindrical structures C.-M. Chen,1  

E-print Network

Instability of myelin tubes under dehydration: Deswelling of layered cylindrical structures C stress swelling or dehydration , we find a stable, deformed state in which the layer deformation is given, and h is the repeat distance of layers. Also, above a finite threshold of dehydration or osmotic stress

Chen, Chi-Ming

191

A Turbulent Origin for Flocculent Spiral Structure in Galaxies  

E-print Network

The flocculent structure of star formation in 7 galaxies has a Fourier transform power spectrum for azimuthal intensity scans with a power law slope that increases systematically from -1 at large scales to -1.7 at small scales. This is the same pattern as in the power spectra for azimuthal scans of HI emission in the Large Magellanic Clouds and for flocculent dust clouds in galactic nuclei. The steep part also corresponds to the slope of -3 for two-dimensional power spectra that have been observed in atomic and molecular gas surveys of the Milky Way and the Large and Small Magellanic Clouds. The same power law structure for star formation arises in both flocculent and grand design galaxies, which implies that the star formation process is the same in each. Fractal Brownian motion models that include discrete stars and an underlying continuum of starlight match the observations if all of the emission is organized into a global fractal pattern with an intrinsic 1D power spectrum having a slope between 1.3 and 1...

Elmegreen, B G; Leitner, S N; Elmegreen, Bruce G.; Elmegreen, Debra Meloy; Leitner, Samuel N.

2003-01-01

192

A Turbulent Origin for Flocculent Spiral Structure in Galaxies  

E-print Network

The flocculent structure of star formation in 7 galaxies has a Fourier transform power spectrum for azimuthal intensity scans with a power law slope that increases systematically from -1 at large scales to -1.7 at small scales. This is the same pattern as in the power spectra for azimuthal scans of HI emission in the Large Magellanic Clouds and for flocculent dust clouds in galactic nuclei. The steep part also corresponds to the slope of -3 for two-dimensional power spectra that have been observed in atomic and molecular gas surveys of the Milky Way and the Large and Small Magellanic Clouds. The same power law structure for star formation arises in both flocculent and grand design galaxies, which implies that the star formation process is the same in each. Fractal Brownian motion models that include discrete stars and an underlying continuum of starlight match the observations if all of the emission is organized into a global fractal pattern with an intrinsic 1D power spectrum having a slope between 1.3 and 1.8. We suggest that the power spectrum of optical light in galaxies is the result of turbulence, and that large-scale turbulent motions are generated by sheared gravitational instabilities which make flocculent spiral arms first and then cascade to form clouds and clusters on smaller scales.

Bruce G. Elmegreen; Debra Meloy Elmegreen; Samuel N. Leitner

2003-05-04

193

The Omeonga Structure, Democratic Republic of Congo: Geological and Petrographical Results, and Implications for its Origin  

NASA Astrophysics Data System (ADS)

For the first time, the origin of the ~38-km-diameter Omeonga structure, located in the Democratic Republic of Congo, is discussed using geological field observations and petrographic investigations on samples from our July 2011 field campaign.

Ferrière, L.; Kaseti, P. K.; Lubala, F. R. T.; Koeberl, C.

2012-03-01

194

Mirror instability and origin of morningside auroral structure  

NASA Technical Reports Server (NTRS)

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

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

1983-01-01

195

Coherent structures in a boundary layer and shear layer of a turbulent backward-facing step flow  

NASA Technical Reports Server (NTRS)

A wind tunnel experiment has been carried out at the NASA Ames Research Center to analyze the evolution of coherent structures from a boundary layer to a shear layer in a turbulent, backward-facing, step flow. A miniature X-wire/cold-wire probe has been used in conjunction with two arrays of cold wires, one aligned in the plane of main shear and the other in the spanwise direction of the flow, to detect and characterize delta-scale organized structures in the outer regions of the flow and to provide detailed information concerning these structures. Kinematic features of the events associated with the large scale structures were analyzed and topological pictures of the evolving flow, as well as the contributions to the Reynolds shear stress components are presented.

Jovic, Srba; Browne, L. W. B.

1989-01-01

196

Origin of Permeability and Structure of Flows in Fractured Media  

NASA Astrophysics Data System (ADS)

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.

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

2013-12-01

197

Structure of surface reaction layer of poly-Si etched by fluorocarbon plasma  

SciTech Connect

A structure of surface reaction layer of poly-Si substrate during fluorocarbon plasma etching was studied by using a plasma beam irradiation apparatus and a quasi-in situ x-ray photoelectron spectroscopy. A fluorinated silicon (SiF) layer was formed under a fluorocarbon (CF) layer. It was found that the thickness of the SiF layer linearly increased with the etch yield of poly-Si regardless of the change of the CF layer thickness. The average ratio of the number of Si to that of F in the SiF layer did not strongly depend on the etch yield. The carbon-rich region of the CF layer was formed just above the SiF layer due to the consumption of fluorine for the formation of SiF layer.

Kurihara, Kazuaki; Egami, Akihiko; Nakamura, Moritaka [Corporate Research and Development Center, Toshiba Corporation, 8 Shinsugita-cho, Isogo-ku, Yokohama 235-8522 (Japan); Environmentally Benign Etching Technology Laboratory, Association of Super-Advanced Electronics Technologies (ASET), 3-1 Morinosato Wakamiya, Atsugi-shi, Kanagawa 243-0198 (Japan)

2006-03-15

198

Resonant transparency of a two-layer plasma structure in a magnetic field.  

PubMed

Transparency of a two-layer plasma structure in an external steady-state magnetic field, perpendicular to the wave incidence plane, is studied. The case of the p-polarized electromagnetic wave is considered. The electromagnetic wave is obliquely incident on the two-layer structure and is evanescent in both layers. The conditions for total transparency of the two-layer structure are found. The parametric dependencies of the transparency coefficient on the plasma slab widths, the magnitude of the wave number component, as well on the magnetic field magnitude are obtained. PMID:21867322

Ivko, S; Smolyakov, A; Denysenko, I; Azarenkov, N A

2011-07-01

199

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

SciTech Connect

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

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

2011-11-15

200

THE STRUCTURE, ORIGIN, AND EVOLUTION OF INTERSTELLAR HYDROCARBON GRAINS  

SciTech Connect

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.

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

2013-06-10

201

Dynamic response research of multi-layered protective structure under explosive loadings  

Microsoft Academic Search

Based on the theoy of transmisson and reflection of stress wave, several multi-layered structures with foam-concrete in civil engineering were proposed to decrease the strength of stress wave and hence, to raise the protective performance of underground structures. The propagation of stress wave in the mulit-layered structures was simulated and the dynamic response and damage development of the structures were

Zhao Kai; Luo Wen-chao; Wang Xiao-jun; Gao Guang-fa; Liu Fei

2011-01-01

202

Structure and phase transitions into ionic adsorption layers on liquid interfaces  

E-print Network

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

R. Tsekov

2014-03-02

203

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

E-print Network

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

Arnold, Frances H.

204

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

E-print Network

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

Raman, Sethu

205

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

E-print Network

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

Newman, David

206

Observations of the layering structure in the Martian Polar Layered Deposits with the MARSIS instrument  

Microsoft Academic Search

One of the many goals of Martian exploration is to uncover the history of Mars through analysis of the polar layered deposits (PLD). Martian polar ice caps contain most of the exposed water ice on the surface on Mars and yet their history and physical processes involved in their formation are unclear. This work will concentrate on analysis of the

A. Ivanov; A. Safaeinili; J. Plaut; S. Milkovich; G. Picardi

2006-01-01

207

Vertical anisotropy of hydraulic conductivity in the fissured layer of hard-rock aquifers due to the geological structure of weathering profiles  

E-print Network

to the geological structure of weathering profiles J.C. Maréchala,* , R.Wynsb , P. Lachassagnec , K. Subrahmanyamd observations, the fissured layer of the weathered granite profile showing the existence of many sub to the weathering process over that one of fissures with a tectonic origin. Keywords: weathering, hard

Paris-Sud XI, Université de

208

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)

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.

Saroj, R. K.; Dhar, S.

2014-12-01

209

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

DOEpatents

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

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

2011-12-20

210

Complete photonic bandgaps in the visible range from spherical layer structures in dichromate gelatin emulsions  

NASA Astrophysics Data System (ADS)

We have fabricated spherical layer structures that exhibit complete photonic bandgaps in the visible range in dichromate gelatin emulsions by holographic interference. The complete bandgap was not a result of the high dielectric contrast but was due to the fact that the spherical layer structure was isotropic with equal spacing in all accessible directions. Angular dependence spectral measurements of the spherical layer structures were in good agreement with the expected results from an ideal structure of dielectric concentric spherical shells with equal spacing. Our fabrication technique and results could pave the way for new applications using complete bandgap photonic crystals.

Hung, Jenny; Kok, Mang Hin; Tam, Wing Yim

2009-01-01

211

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

E-print Network

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

Blouin-Demers, Gabriel

212

ORIGINAL PAPER Influence of the Metal Oxide Substrate Structure on Vanadium  

E-print Network

ORIGINAL PAPER Influence of the Metal Oxide Substrate Structure on Vanadium Oxide Monomer Formation 2013 � Springer Science+Business Media New York 2013 Abstract Vanadium oxide (VOx) molecular species. This study demonstrates that the atomic structure of the support can strongly influence the molec- ular

Marks, Laurence D.

213

ORIGINAL ARTICLE Development of a mobile welding robot for double-hull structures  

E-print Network

ORIGINAL ARTICLE Development of a mobile welding robot for double-hull structures in shipbuilding describes the development of a self- driving mobile welding robot. The robot is used to weld U platform. Keywords Self-driving mobile welding robot Á Double-hull ship structure Á Industrial automation 1

Kim, Jongwon

214

Laser-Gyro Mirrors Of Differing Layer Structure  

NASA Astrophysics Data System (ADS)

High reflectance low-scatter mirrors have been developed for laser-gyro applications. Different types of multilayer systems: Ti02/Si02, Ag/Ti02/Si02, and Ta205/Si02 combinations were investigated. In the first system TiO2 was rf-sputtered while Si02 was electron-gun evaporated. The best results were achieved for these materials with 21 alternating ? /4 layers. In the second system a thin silver film was rf-sputtered as a first layer on the substrate. Ten additional dielectric layers on the silver base were deposited to reach the same reflectivity as with pure dielectric mirrors. In the third system both Ta205 and Si02 were electron-gun evaporated. The best quality was achieved with 29 alternating layers. The mirrors of Ti02/Si02 and Ag/Ti02/Si02 exhibited no shift of the center wave length after exposition to air, while the mirrors of Ta205 /Si02 showed a shift of 30 nm. The mirrors were investigated in terms of reflectivity and scattering using an ultraprecise measurement equipment. Scattering was measured in an Ulbricht integrating sphere; resolution: 0.2-10-6 . Reflectivity measurements were carried out in a special developed reflectometer; resolution: 10.10-6.

Schmitt, Dirk-Roger

1989-02-01

215

Transverse surface waves in a layered structure with a functionally graded piezoelectric substrate and a hard dielectric layer.  

PubMed

As to an ideally layered structure with a functionally graded piezoelectric substrate (material parameters change continuously along the thickness direction) and a hard dielectric layer, the existence and propagation behavior of transverse surface waves is studied by analytical technique. The dispersion equations for the existence of the transverse surface waves with respect to phase velocity are obtained for electrically open and short circuit conditions, respectively. A detailed investigation of the effect of gradient coefficient on dispersion relation, electromechanical coupling factor and penetration depth is carried out. It is found by numerical examples that adjusting gradient coefficient makes the electromechanical coupling factor of the transverse surface waves achieve quite high values at some appropriate ratio values of the layer thickness to the wavelength, and at the same time, the penetration depth can be reduced to the same order as the wavelength. PMID:19036395

Qian, Zheng-Hua; Jin, Feng; Lu, Tianjian; Kishimoto, Kikuo

2009-03-01

216

Transmission of electromagnetic waves through a two-layer plasma structure with spatially nonuniform electron density.  

PubMed

Transmission of a p-polarized electromagnetic wave through a two-layer plasma structure with spatially nonuniform distributions of electron density in the layers is studied. The case, when the electromagnetic wave is obliquely incident on the structure and is evanescent in both plasma layers, is considered. The conditions for total transparency of the two-layer structure are found for the thin slab case and when the plasma inhomogeneity is weak. It is shown that the transmission coefficient of the p-polarized wave can be about unity, even if the plasma inhomogeneity is large. The effects of plasma inhomogeneity on transparency of the structure are more important if the slabs are thick, comparing with the case of thin layers. PMID:23214891

Denysenko, I B; Ivko, S; Smolyakov, A; Azarenkov, N A

2012-11-01

217

Performance improvement of InGaN-based laser diodes by epitaxial layer structure design  

NASA Astrophysics Data System (ADS)

Blue laser diode (LD) structures with GaN waveguide layers and with In0.03Ga0.97N waveguide layers were grown. A comparison study showed In0.03Ga0.97N waveguide layers significantly enhance the LD performance. The mechanism behind this was investigated using reciprocal space mapping of X-ray diffraction and time-resolved cathodoluminescence measurements. Room-temperature lasing of laser diodes at 454.6 nm was realized for LD structure with In0.03Ga0.97N waveguide layers.

Liu, Jianping; Zhang, Yun; Lochner, Zachary; Kim, Seong-soo; Kim, Hyunsoo; Ryou, Jae-Hyun; Shen, Shyh-Chiang; Yoder, P. Doug; Dupuis, Russell D.; Wei, Qiyuan; Sun, Kewei; Fischer, Alec; Ponce, Fernando

2010-03-01

218

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

PubMed

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

Huang, Ping-jie; Wu, Zhao-tong

2004-01-01

219

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

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

220

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

PubMed

The latest discovery of possible high-temperature superconductivity in the single-layer FeSe film grown on a SrTiO3 substrate has generated much attention. Initial work found that, while the single-layer FeSe/SrTiO3 film exhibits a clear signature of superconductivity, the double-layer film shows an insulating behaviour. Such a marked layer-dependent difference is surprising and the underlying origin remains unclear. Here we report a comparative angle-resolved photoemission study between the single-layer and double-layer FeSe/SrTiO3 films annealed in vacuum. We find that, different from the single-layer FeSe/SrTiO3 film, the double-layer FeSe/SrTiO3 film is hard to get doped and remains in the semiconducting/insulating state under an extensive annealing condition. Such a behaviour originates from the much reduced doping efficiency in the bottom FeSe layer of the double-layer FeSe/SrTiO3 film from the FeSe-SrTiO3 interface. These observations provide key insights in understanding the doping mechanism and the origin of superconductivity in the FeSe/SrTiO3 films. PMID:25248072

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

2014-01-01

221

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

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

222

Targeted structure modulation of "pillar-layered" metal-organic frameworks for CO? capture.  

PubMed

Two new zinc MOFs with similar "pillar-layered" framework structures based on 1,1'-biphenyl-2,2',6,6'-tetracarboxylic acid (H4bpta) and two different bipyridine pillar ligands, namely {[Zn4(bpta)2(4-pna)2(H2O)2]·4DMF·3H2O}n (1) and {[Zn2(bpta)(bpy-ea)(H2O)]·2DMF·H2O}n (2) (4-pna = N-(4-pyridyl)isonicotinamide and bpy-ea = 1,2-bis(4-pyridyl)ethane), have been synthesized and investigated with their CO2 adsorption properties. By analysis of the structure properties and the CO2 adsorption performances of these two MOFs, it was found that the introduction of polar acylamide groups via 4-pna resulted in 1 with enhanced CO2 capacity and CO2/CH4 selectivity at low pressure. In contrast, the framework of 2 shows flexible properties originating from the flexibility of the ethanediylidene group in the bpy-ea ligand, which benefits the sieve effect of pores to give higher CO2/CH4 selectivity at a relatively high pressure range. PMID:25127434

Xuan, Zhi-Hong; Zhang, Da-Shuai; Chang, Ze; Hu, Tong-Liang; Bu, Xian-He

2014-09-01

223

On the origin of mixed-layered clay minerals from the San Andreas Fault at 2.5-3 km vertical depth (SAFOD drillhole at Parkfield, California)  

NASA Astrophysics Data System (ADS)

A detailed mineralogical study is presented of the matrix of mudrocks sampled from spot coring at three key locations along the San Andreas Fault Observatory at depth (SAFOD) drill hole. The characteristics of authigenic illite-smectite (I-S) and chlorite-smectite (C-S) mixed-layer mineral clays indicate a deep diagenetic origin. A randomly ordered I-S mineral with ca. 20-25% smectite layers is one of the dominant authigenic clay species across the San Andreas Fault zone (sampled at 3,066 and 3,436 m measured depths/MD), whereas an authigenic illite with ca. 2-5% smectite layers is the dominant phase beneath the fault (sampled at 3,992 m MD). The most smectite-rich mixed-layered assemblage with the highest water content occurs in the actively deforming creep zone at ca. 3,300-3,353 m (true vertical depth of ca. 2.7 km), with I-S (70:30) and C-S (50:50). The matrix of all mudrock samples show extensive quartz and feldspar (both plagioclase and K-feldspar) dissolution associated with the crystallization of pore-filling clay minerals. However, the effect of rock deformation in the matrix appears only minor, with weak flattening fabrics defined largely by kinked and fractured mica grains. Adopting available kinetic models for the crystallization of I-S in burial sedimentary environments and the current borehole depths and thermal structure, the conditions and timing of I-S growth can be evaluated. Assuming a typical K+ concentration of 100-200 ppm for sedimentary brines, a present-day geothermal gradient of 35°C/km and a borehole temperature of ca. 112°C for the sampled depths, most of the I-S minerals can be predicted to have formed over the last 4-11 Ma and are probably still in equilibrium with circulating fluids. The exception to this simple burial pattern is the occurrence of the mixed layered phases with higher smectite content than predicted by the burial model. These minerals, which characterize the actively creeping section of the fault and local thin film clay coating on polished brittle slip surfaces, can be explained by the influence of either cooler fluids circulating along this segment of the fault or the flow of K+-depleted brines.

Schleicher, A. M.; Warr, L. N.; van der Pluijm, B. A.

2009-02-01

224

Dynamics of coherent structures in a plane mixing layer  

NASA Technical Reports Server (NTRS)

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.

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

1988-01-01

225

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

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

226

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

NASA Technical Reports Server (NTRS)

In recent years, many geoscientists have come to believe that the Sudbury event was exogenic rather than endogenic. Critical to a recent exogenic hypothesis is the impact melt origin of the Sudbury Igneous Complex (SIC). Such origin implies that the SIC was emplaced before deposition of the Whitewater Group, in contrast to origins in which the SIC postdates the lithification of the Onaping Formation. Structural and sedimentological evidence is summarized herein that supports an intrusion of the SIC after lithification of all Whitewater Group strata, and conflicts with the hypothesis advanced by other researchers.

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

1992-01-01

227

Improved structural/morphological durability for organic solar cells based on poly(3-hexylthiophene) fibers photoactive layers  

NASA Astrophysics Data System (ADS)

Organic photovoltaic (OPV) materials must meet some stringent technological requirements, to bear continuous operation under variable temperature conditions. Here, an original approach to control the degradation pathway associated to the active material morphological instability is proposed. We demonstrate, for the first time, that polymer-fullerene nanostructured films incorporating poly(3-hexylthiophene) nanofibers, obtained from concentrated solutions at room-temperature, are characterized by superior structural durability. This is obtained monitoring in situ the active layer bulk/interface morphological properties by joint energy dispersive X-ray and atomic force microscopy time-resolved techniques: the preservation of the nanoscale morphology of the pristine films is very promising for flexible OPV applications.

Paci, B.; Generosi, A.; Albertini, V. Rossi; de Bettignes, R.

2013-11-01

228

``Sedimentary'' Structures in a Layered Granodiorite: A Window Into Physical Conditions Present During the Development of the Tuolumne Intrusive Suite, Sierra Nevada California  

NASA Astrophysics Data System (ADS)

The presence of sedimentary-type features exposed in layered Tuolumne Intrusive Suite (TIS) outcrops provides a unique opportunity to assess fluid dynamic processes associated with both pluton assembly and magma chamber processes. Previous analyses of layered mafic intrusions, experimental and mathematical modeling of igneous layering, analogs in sedimentary rocks, and layering in granitic intrusions, have not defined a set of physical conditions that exist during intermediate granitic pluton development. Using constraints provided by field, petrographic, and geochemical relations among the layered outcrops in the TIS field area, both the dynamic conditions and rheological state necessary to form these "sedimentary" structures can be identified. Similar layer orientations at many different outcrops and sharp upper and lower layer/host rock contacts suggest that the layers occupy shallowly dipping, near-planar, "slot-like" openings in the outer members of the TIS. The TIS layers appear to originate by a combination of flow sorting and crystal settling due to the modal grading of the cm-scale layers, cumulate mineral textures, and mafic glomercrysts. Groups of layers with similar features demonstrate the repetition of this process. Examination of reoriented hornblende crystals along fault surfaces shows that slumps form due to the addition of overlying layers when the melt fraction is between 20 and 50%. Given the presence of (1) dikes full of K-feldspar megacrysts that cross-cut the layers but not the host rock, (2) resorbed crystal edges, (3) zoned hornblende crystals with pyroxene cores and (4) adjacent groups of layers that have features different from one another; the layering conditions such as magmatic temperature, water content, and direction of layer deposition must change periodically.

Loetterle, J.; Bergantz, G.

2004-12-01

229

Structure, properties and corrosion resistivity of polymeric nanocomposite coatings based on layered silicates  

Microsoft Academic Search

This paper reviews the recent research and development of polymeric nanocomposite coatings based on layered silicates. In\\u000a the past few decades, extensive research activities have been conducted on clay minerals due to their unique layered structure,\\u000a rich intercalation chemistry and availability at low cost, environmental stability, and good processability. One of the most\\u000a important categories of layered silicates is nanoclays.

Davood Zaarei; Ali Asghar Sarabi; Farhad Sharif; Seid Mahmood Kassiriha

2008-01-01

230

Utilization and Modification of Perovskite-Type Layered Structures as Inorganic-Organic Hybrid Materials  

Microsoft Academic Search

The aromatic ammonium-based layered halide compounds were obtained of bis(4-nitroanilinium)tetrachlorocadmate and bis(2-methyl-4-nitroanilinium) tetrachlorocadmate, aiming at a new type of inorganic-organic hybrid layered material. X-ray diffraction analyses of the single crystals revealed that both of the crystals take an alternate layered structure of the organic bilayer and the inorganic sheet. Cadmium ion and chloride anions form six-coordinated octahedra whose corner anions

Reiko Azumi; Kazumasa Honda; Midori Goto; Junji Akimoto; Yoshinao Oosawa; Hiroaki Tachibana; Motoo Tanaka; Mutsuyoshi Matsumoto

1996-01-01

231

Theoretical Consideration of High-Sensitive Biosensor Using Shear Horizontal Acoustic Waves in Layered Structures  

NASA Astrophysics Data System (ADS)

Realization of high sensitive biosensors is required. As an acoustic wave based biosensor can detect immunoreactions, it is expected for applying the biosensor. In this paper, a shear horizontal (SH) acoustic wave in layered structures, namely Love wave, is discussed on the basis of numerical calculations. For generating the Love wave, a 36YX-LiTaO3 is chosen as a piezoelectric substrate. Also, SiO2, polymer, and gold are chosen as guiding layer materials. First, phase velocity and propagation loss are calculated as a function of layer thickness. Then, an additional mass layer is loaded on the guiding layer for simulating bio-layer deposition. The simulated results indicate that high sensitive biosensor is realized by using gold guiding layer.

Kondoh, Jun

232

Corrosion detection in multi-layered rotocraft structures  

Microsoft Academic Search

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

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

2000-01-01

233

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

NASA Technical Reports Server (NTRS)

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

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

1981-01-01

234

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

NASA Technical Reports Server (NTRS)

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

Palumbo, Dan

2008-01-01

235

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

PubMed

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

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

2014-02-14

236

A stochastic sea: The source of plasma sheet boundary layer ion structures observed by Cluster  

NASA Astrophysics Data System (ADS)

On 14 February 2001 the Cluster Ion Spectrometry (CIS) experiment onboard three of the Cluster spacecraft observed velocity-dispersed ion structures (VDIS) as the spacecraft passed from the tail lobes into the plasma sheet boundary layer. These are the first multiple spacecraft observations of the VDIS phenomenon. The Cluster 1 spacecraft (SC1) observed a dispersed ion signature with beamlets and a second structure like that expected to be produced by an echo, while Cluster 3 (SC3) observed much less pronounced structuring a few minutes later. During this same event and over an extended interval the ACE spacecraft observed an interplanetary magnetic field that was directed southward. We have inferred the sources and acceleration mechanisms of the ions in these VDIS observations by following millions of ion trajectories backward and forward in time through time-dependent electric and magnetic fields obtained from a global MHD simulation. ACE data were used as input for the MHD model. We found that almost all of the particles comprising the first (A1) and second (A2) beamlets observed by SC1 had been nonadiabatic earlier in their history, while particles in the A3 beamlet exhibited a combination of adiabatic and nonadiabatic behavior. Beamlet A4 particles were always adiabatic. Moreover, for all of the beamlets the current sheet crossing that took place prior to their detection occurred between x = -13 RE and x = -16 RE in the tail, well earthward of the permanent stochastic "sea" from which all of the beamlets originated. Our model does not favor the multiple source scenario suggested by A. Keiling et al. Instead, it indicates that the source regions of the structures are spatially correlated. We have carried out a similar analysis of the SC3 observations. In general, SC3 beamlets have higher ? values, partly because of the depolarization of the field lines during these observations. In time forward calculations only a small fraction of ions from SC1 A structures returned to the spacecraft location. "Echoes" were more pronounced on SC3. In addition, in our calculations, some particles from SC1 A structures interacted with the current sheet and returned to the SC3 location, at the time when SC3 observed the A structures. When Cluster observations were organized by latitude instead of time, we found that all three Cluster spacecraft seemed to observe the same primary structure that persisted throughout the interval of observation.

Ashour-Abdalla, M.; Bosqued, J. M.; El-Alaoui, M.; Peroomian, V.; Zelenyi, L. M.; Walker, R. J.; Wright, J.

2005-12-01

237

Structure characterization of adsorbed poly (ethylene oxide) layers on solid substrate  

NASA Astrophysics Data System (ADS)

In recent years, irreversibly adsorbed polymer layers formed on solid substrates have been received considerable interest since they can modify various properties of polymeric materials confined at the nanometer scale. In this thesis, I investigate the annealing time dependence of the poly (ethylene oxide) (PEO) adsorbed layer formed at the substrate interface. The detailed structures of the PEO adsorbed layer prepared were characterized by ellipsometry, atomic force microscopy (AFM), and x-ray reflectivity techniques. The total thickness of the PEO adsorbed layer is generally around 3 nm. Different from PS, the annealing time dependence of the PEO adsorbed layer simple show minor increase when annealing 2hr, then stay the same. ScCO2 and toluene rinse cycle can further reduce the thickness of PS adsorbed layer. For PEO, only toluene rinse is enough to obtain the final adsorbed layer. We discuss the model of the structure of the adsorbed layer, and estimate that there is no crystal structure formed in the PEO adsorbed layer.

Chen, Fen

238

SH surface acoustic wave propagation in a cylindrically layered piezomagnetic/piezoelectric structure  

E-print Network

SH surface acoustic wave propagation in a cylindrically layered piezomagnetic Accepted 30 July 2008 Available online 22 August 2008 Keywords: SH surface acoustic waves Cylindrically layered structure Piezoelectric Piezomagnetic Dispersive relation a b s t r a c t SH surface acoustic wave

Wang, Ji

239

A model of the excitation of orderly structures in a shear layer  

NASA Technical Reports Server (NTRS)

The artificial excitation of shear layers is investigated theoretically and experimentally. The present paper describes quantitatively the coupling between exciting sound field and shear layer fluctuations. The mathematical model is restricted to low Strouhal numbers at which large scale structures are occurring. The theory does not contain any empirical constants and it is confirmed by the experiments in the expected validity range.

Bechert, D. W.

1984-01-01

240

Effect of free surface heat transfer on thermocapillary flow in double-layer fluid structures  

NASA Astrophysics Data System (ADS)

In this paper, we examine the effect of heat transfer at the free encapsulant-air surface on thermocapillary flow in a rectangular melt-encapsulant double-layer fluid structure. We show that increased heat transfer to the double-layer system through the free surface weakens thermocapillary convection in the encapsulant phase and enhances the convection in the melt phase.

Gupta, N. R.; Haj-Hariri, H.; Borhan, A.

2014-03-01

241

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

NASA Technical Reports Server (NTRS)

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

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

1978-01-01

242

Love waves propagation in a piezoelectric layered structure with initial stresses  

Microsoft Academic Search

Summary. The propagation behavior of Love waves in a piezoelectric layered structure with inhomogeneous initial stress is studied. Solutions of the mechanical displacement and electrical potential function are obtained for the isotropic elastic layer and transversely isotropic piezoelectric substrate, respectively, by solving the coupled electromechanical field equations. Firstly, effects of the inhomogeneous initial stress on the dispersion relations and phase

Z. Qian; F. Jin; Z. Wang; K. Kishimoto

2004-01-01

243

Boundary layer structure over areas of heterogeneous heat fluxes  

SciTech Connect

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

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

1993-01-01

244

Boundary layer structure over areas of heterogeneous heat fluxes  

SciTech Connect

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

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

1993-01-01

245

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

E-print Network

Acoustic Performance Analysis of Bionic Coupling Multi-layer Structure Yonghua Wang1,2,a Laboratory of Bionic Engineering (Ministry of Education), Jilin University, Changchun 130022, P. R. China 2 bionic method to develop a new sound absorption structure. Inspired by the coupling absorption structure

Boyer, Edmond

246

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

SciTech Connect

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.

Black, Jennifer M [ORNL] [ORNL; Walters, Deron [Asylum Research, Santa Barbara, CA] [Asylum Research, Santa Barbara, CA; Labuda, Aleksander [Asylum Research, Santa Barbara, CA] [Asylum Research, Santa Barbara, CA; Feng, Guang [ORNL] [ORNL; Hillesheim, Patrick C [ORNL] [ORNL; Dai, Sheng [ORNL] [ORNL; Cummings, Peter T [ORNL] [ORNL; Kalinin, Sergei V [ORNL] [ORNL; Proksch, Roger [Asylum Research, Santa Barbara, CA] [Asylum Research, Santa Barbara, CA; Balke, Nina [ORNL] [ORNL

2013-01-01

247

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

E-print Network

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 ...

Li, Mingda

248

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

USGS Publications Warehouse

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

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

2005-01-01

249

Surface-enhanced Raman scattering on dual-layer metallic grating structures  

Microsoft Academic Search

Dual-layer Metallic grating (DMG) structures as surface-enhanced Raman scattering (SERS) substrates are studied using benzenethiol\\u000a as the probe analyte. The DMG structure consists of a SiO2 grating and 100-nm-thick gold coating layers. An enhancement factor of 105 is achieved by optimizing the SiO2 grating height within the range from 165 to 550 nm. The enhancement factor dependence on the SiO2

ZhiQiang Guan; Ulf Håkanson; Nicklas Anttu; Hong Wei; HongQi Xu; Lars Montelius; HongXing Xu

2010-01-01

250

Guided-wave characteristics of waveguide based periodic structures loaded with various FSS strip layers  

Microsoft Academic Search

In this paper, frequency-dependent guided-wave characteristics of waveguide based periodic structures loaded with transversal strip layers of frequency selective surfaces (FSS) are extensively studied in terms of per-unit-length transmission parameters, i.e., complex propagation constant and complex wave impedance. Such a periodic structure with various FSS strip layers are in theory characterized using the hybrid method of moments (MoM)-immittance approach so

Rakhesh S. Kshetrimayum; Lei Zhu

2005-01-01

251

Modeling and system identification of three-layer structure electrostatic film motors for a robotic fish  

Microsoft Academic Search

We have developed an underwater fish-like robot using two-four-phase three-layer structure electrostatic film motors. In the robotic fish, the novel motors actuated the flexible caudal fin to propel itself via an elaborate power transmission system. In this paper, we first theoretically analyze the dynamic properties of the three-layer structure electrostatic film motors by modeling it as a 10-terminal capacitance network,

Zu Guang Zhang; Norio Yamashita; Akio Yamamoto; Masahiko Gondo; Toshiro Higuchi

2009-01-01

252

Thermal balance and photon-number quantization in layered structures  

E-print Network

The quantization of the electromagnetic field in lossy and dispersive dielectric media has been widely studied during the last few decades. However, several aspects of energy transfer and its relation to consistently defining position-dependent ladder operators for the electromagnetic field in nonequilibrium conditions have partly escaped the attention. In this work we define the position-dependent ladder operators and an effective local photon-number operator that are consistent with the canonical commutation relations and use these concepts to describe the energy transfer and thermal balance in layered geometries. This approach results in a position-dependent photon-number concept that is simple and consistent with classical energy conservation arguments. The operators are formed by first calculating the vector potential operator using Green's function formalism and Langevin noise source operators related to the medium and its temperature, and then defining the corresponding position-dependent annihilation ...

Partanen, Mikko; Oksanen, Jani; Tulkki, Jukka

2014-01-01

253

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

NASA Technical Reports Server (NTRS)

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

Maestrello, L.

2004-01-01

254

Thermal balance and photon-number quantization in layered structures  

E-print Network

The quantization of the electromagnetic field in lossy and dispersive dielectric media has been widely studied during the last few decades. However, several aspects of energy transfer and its relation to consistently defining position-dependent ladder operators for the electromagnetic field in nonequilibrium conditions have partly escaped the attention. In this work we define the position-dependent ladder operators and an effective local photon-number operator that are consistent with the canonical commutation relations and use these concepts to describe the energy transfer and thermal balance in layered geometries. This approach results in a position-dependent photon-number concept that is simple and consistent with classical energy conservation arguments. The operators are formed by first calculating the vector potential operator using Green's function formalism and Langevin noise source operators related to the medium and its temperature, and then defining the corresponding position-dependent annihilation operator that is required to satisfy the canonical commutation relations in arbitrary geometry. Our results suggest that the effective photon number associated with the electric field is generally position dependent and enables a straightforward method to calculate the energy transfer rate between the field and the local medium. In particular, our results predict that the effective photon number in a vacuum cavity formed between two lossy material layers can oscillate as a function of the position suggesting that also the local field temperature oscillates. These oscillations are expected to be directly observable using relatively straightforward experimental setups in which the field-matter interaction is dominated by the coupling to the electric field.

Mikko Partanen; Teppo Häyrynen; Jani Oksanen; Jukka Tulkki

2014-03-17

255

Thermal balance and photon-number quantization in layered structures  

NASA Astrophysics Data System (ADS)

The quantization of the electromagnetic field in lossy and dispersive dielectric media has been widely studied during the last few decades. However, several aspects of energy transfer and its relation to consistently defining position-dependent ladder operators for the electromagnetic field in nonequilibrium conditions have partly escaped the attention. In this work we define the position-dependent ladder operators and an effective local photon-number operator that are consistent with the canonical commutation relations and use these concepts to describe the energy transfer and thermal balance in layered geometries. This approach results in a position-dependent photon-number concept that is simple and consistent with classical energy conservation arguments. The operators are formed by first calculating the vector potential operator using Green's function formalism and Langevin noise source operators related to the medium and its temperature, and then defining the corresponding position-dependent annihilation operator that is required to satisfy the canonical commutation relations in arbitrary geometry. Our results suggest that the effective photon number associated with the electric field is generally position dependent and enables a straightforward method to calculate the energy transfer rate between the field and the local medium. In particular, our results predict that the effective photon number in a vacuum cavity formed between two lossy material layers can oscillate as a function of the position suggesting that also the local field temperature oscillates. These oscillations are expected to be directly observable using relatively straightforward experimental setups in which the field-matter interaction is dominated by the coupling to the electric field. The approach also gives further insight on separating the photon ladder operators into the conventional right and left propagating parts and on the anomalies reported for the commutation relations of the corresponding operators within optical cavities.

Partanen, Mikko; Häyrynen, Teppo; Oksanen, Jani; Tulkki, Jukka

2014-03-01

256

Instantaneous wavenumber estimation for damage quantification in layered plate structures  

NASA Astrophysics Data System (ADS)

Guided wavefield detection is at the basis of a number of promising techniques for the identification and the characterization of damage in plate structures. Among the processing techniques proposed, the estimation of instantaneous and local wavenumbers can lead to effective metrics that quantify the extent of delaminations in composite plates. This paper illustrates the application of instantaneous and local wavenumber damage quantification techniques for high frequency guided wave interrogation. The proposed methodologies can be considered as first steps towards a hybrid structural health monitoring/ nondestructive evaluation approach for damage assessment in composites.

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

2014-03-01

257

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

NASA Technical Reports Server (NTRS)

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

Pitz, R. W.

1981-01-01

258

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

259

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

SciTech Connect

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

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

2013-12-04

260

Effects of the amorphous layer on laser-induced subwavelength structures on carbon allotropes.  

PubMed

By micro-Raman spectroscopy, we show that the structured surfaces of highly oriented pyrolytic graphite and diamond induced by 800 nm, 125 fs or 532 nm, 30 ps laser pulses are capped by thin amorphous carbon layers. Based on the results, we propose that for multiphoton ablation the thin amorphous layer with a reduced bandgap can facilitate surface ionization, raise free electron density, bring on plasmonic effects, and thus promote the growth of subwavelength structures. Therefore, concerning multipulse laser ablation of wide bandgap materials, we should take into account the effects of the superficial amorphous layer produced by preceding pulses instead of the intrinsic surface. PMID:22344145

Huang, Min; Zhao, Fuli; Cheng, Ya; Xu, Zhizhan

2012-02-15

261

Nonlinear layered lattice model and generalized solitary waves in imperfectly bonded structures  

NASA Astrophysics Data System (ADS)

We study nonlinear waves in a two-layered imperfectly bonded structure using a nonlinear lattice model. The key element of the model is an anharmonic chain of oscillating dipoles, which can be viewed as a basic lattice analog of a one-dimensional macroscopic waveguide. Long nonlinear longitudinal waves in a layered lattice with a soft middle (or bonding) layer are governed by a system of coupled Boussinesq-type equations. For this system we find conservation laws and show that pure solitary waves, which exist in a single equation and can exist in the coupled system in the symmetric case, are structurally unstable and are replaced with generalized solitary waves.

Khusnutdinova, Karima R.; Samsonov, Alexander M.; Zakharov, Alexey S.

2009-05-01

262

Crustal structure and origin of the Cape Verde Rise , C. Peirce b,  

E-print Network

Crustal structure and origin of the Cape Verde Rise J. Pim a , C. Peirce b, , A.B. Watts a , I (Te) and the age of oceanic lithosphere at the time of loading (Watts, 1978). As the oceanic loads (e.g. Hawaii -- Watts and ten Brink, 1989; Marquesas -- Caress et al.,1995; Tenerife -- Watts et

Watts, A. B. "Tony"

263

The origin and structure of wooded permafrost mounds at the arctic treeline in eastern Canada  

Microsoft Academic Search

Background: Permafrost mounds covered by open or dense forests (or krummholz – stunted trees) correspond to the category of wooded palsas and wooded peat plateaux extensively distributed in wetlands of North America. Very few data exist on the origin and development of wooded palsas, in particular their inception during the Holocene and the structure and dynamics of their forest\\/krummholz cover

S. Cyr; S. Payette

2010-01-01

264

ORIGINAL PAPER Evolution of growth but not structural or chemical defense  

E-print Network

ORIGINAL PAPER Evolution of growth but not structural or chemical defense in Verbascum thapsus with increased growth in introduced Verbascum thapsus populations. Intro- duced populations had significantly growth in V. thapsus is not fueled by decreased allocation to defense, and that selection on defense may

Hufbauer, Ruth A.

265

ORIGINAL PAPER Evolution of growth but not structural or chemical defense  

E-print Network

ORIGINAL PAPER Evolution of growth but not structural or chemical defense in Verbascum thapsus in a single defense) is associated with increased growth in introduced Verbascum thapsus populations. Intro that evolution of increased growth in V. thapsus is not fueled by decreased allocation to defense

Hufbauer, Ruth A.

266

Population structure and possible origin of Amylostereum areolatum in South Africa  

E-print Network

Population structure and possible origin of Amylostereum areolatum in South Africa B. Slippers*², M, University of Pretoria, Pretoria, South Africa 0002 The woodwasp, Sirex noctilio, and its symbiotic fungus was first reported from South Africa in 1994. In this study, the population diversity of A. areolatum

267

ORIGINAL PAPER Small-scale gold mining erodes fish assemblage structure  

E-print Network

ORIGINAL PAPER Small-scale gold mining erodes fish assemblage structure in small neotropical- turbing freshwater ecosystems. Indeed, streams act as receptors for the water that drains gold mining sites and that contain a high load of sediment and toxicants. We here investigated how gold mining

Grenouillet, Gael

268

Population structure and origins of Purple Sandpipers Calidris maritima in north Norway during winter  

Microsoft Academic Search

Wintering Purple Sandpipers Calidris maritima were captured at Varangerfjorden, Finnmark, in March 1992, and compared with samples from Troms county in November 1988 to describe the population structure in north Norway in terms of age and sex classes, and to determine the origins of these wintering birds. The overall percentage of first?year birds was 35% at Varangerfjorden, higher than that

Ron W. Summers; Rab Rae

2006-01-01

269

Origin, taxonomy and population structure of the allopolyploid peat moss Sphagnum majus  

Microsoft Academic Search

The polyploid peat mossSphagnum majus shows considerable phenotypic plasticity along ecological gradients in mires. It is considered taxonomically heterogeneous, and two subspecies have been described. Isozyme analyses were carried out on populations ofS. majus from Central Norway and from eastern coast of North America in order to assess the origin, taxonomy and population structure of this species. High levels of

S. M. Såstad; K. I. Flatberg; L. Hanssen

2000-01-01

270

Protein folding, protein structure and the origin of life: Theoretical methods and solutions of dynamical problems  

NASA Technical Reports Server (NTRS)

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.

Weaver, D. L.

1982-01-01

271

Sequential observations of the local neutral wind field structure associated with E region plasma layers  

NASA Astrophysics Data System (ADS)

The first sequential rocket experiment to study intermediate layers in over 30 years was launched from Wallops Island, Virginia on the night of 29-30 June 2003. Using an onsite digisonde to determine the presence of sporadic E and conditions indicating the possible presence of an intermediate layer, four rockets were launched over a 4-hour period. Three of the rockets launched with at least an hour separation; they each contained chemical release experiments and plasma impedance probes. All four payloads encountered two plasma layers on both the ascent and descent of the flights. The lower-altitude layer, located at approximately 100 km, is clearly a sporadic E layer. The higher-altitude layer, located between 120 and 130 km, displays many characteristics of an intermediate layer, but it exhibits little downward motion over time. The neutral wind profiles resulting from the chemical tracer experiment are presented here along with the vertical drift velocities derived from the wind measurements. These are compared with the electron density profiles. They show a good agreement between the convergent regions in the velocity profiles and the location of the sporadic E layers. However, agreement between the center of the convergent vertical drift regions and the location of the higher-altitude layer is poor. The inclusion in the drift calculation of electric field data from the instrumented rocket significantly improves the overall agreement between the convergent vertical drift region center and the intermediate layer center. The convergent region is within 4 km of the intermediate layer. Further, the density depletions surrounding the layers coincide with the regions of divergent drift. The relatively large discrepancy observed between the shear in the vertical drift and the location of the intermediate layer implies that other factors such as horizontal motion structure variations may be important. Thus intermediate layer formation theory and subsequent evolution is still not fully understood.

Bishop, R. L.; Earle, G. D.; Larsen, M. F.; Swenson, C. M.; Carlson, C. G.; Roddy, P. A.; Fish, C.; Bullett, T. W.

2005-04-01

272

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

NASA Astrophysics Data System (ADS)

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

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

2007-12-01

273

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

NASA Astrophysics Data System (ADS)

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

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

2012-10-01

274

Layered CMR manganites: Structure, properties, and unconventional magnetism  

SciTech Connect

Neutron powder diffraction studies of the layered compounds R{sub 1.2}Sr{sub 1.8}Mn{sub 2}O{sub 7}, (R = La, Pr, Nd), RSr{sub 2}Mn{sub 2}O{sub 7} (R = Pr, Nd), and La{sub 1.4}Sr{sub 1.6}Mn{sub 2}O{sub 7} show that the degree of distortion of the MnO{sub 6} octahedra do not correlate with the appearance of a metal-insulator (MI) transition in these compounds. Instead, the in-plane Mn-O bond length appears to be a better indicator of the electronic behavior. Detailed bulk magnetization studies on single crystal La{sub 1.2}Sr{sub 1.8}Mn{sub 2}O{sub 7} show that there are three magnetic regimes as a function of temperature: paramagnetic insulator, short-range ordered (SRO) ferromagnet, and long-range ordered (LRO) ferromagnet. Scaling analysis indicates that a 2D finite-size XY model is an appropriate description of the magnetic state in the SRO regime.

Mitchell, J.F.; Argyriou, D.N.; Potter, C.D.; Jorgensen, J.D.; Hinks, D.G.; Bader, S.D. [Argonne National Lab., IL (United States). Materials Science Div.

1996-12-31

275

4E-2 Theoretical and Experimental Study of the Differential Thermal Expansion Effect on the TCD of Layered SAW Temperature Sensors Application to Aluminum Nitride Based Layered Structures  

Microsoft Academic Search

In this paper, we show that the stress and strain fields induced in a layered SAW structure by the thermal expansion of the different layers must be taken into account to compute the global structure temperature coefficient of delay (TCD). Experimental and numerical results are provided. The numerical model is described. It is based at the same time on the

P. Nicolay; O. Elmazria; B. Assouar; F. Sarry; L. Lebrizoual

2007-01-01

276

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

NASA Technical Reports Server (NTRS)

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.

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

1989-01-01

277

Functional Nano-Structures Using Atomic Layer Deposition  

E-print Network

with the help of numerous people, and thanks to the finanical support provided by the UK Engineering and Physical Sciences Research Council and Trinity College. I would like to start by thanking my supervisor Prof. Dr. Ullrich Steiner for giving me... are not well- adapted for the fabrication of complicated, for example three-dimensional, structures. Recently bottom-up fabrication protocols have been developed which overcome the problems outline above. In general these protocols rely on self-assembly, which...

Salgård Cunha, Pedro

2014-05-27

278

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

NASA Astrophysics Data System (ADS)

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

Münkel, Christoph; Roininen, Reijo

2010-05-01

279

Observation of double-layer-like structures at rocket altitudes  

NASA Technical Reports Server (NTRS)

Two hundred and thirty large amplitude electric field pulses in a rocket flight to an apogee of 585 km over an aurora have been observed. While the limitations of the instrumentation only allow limits to be set on the characteristics of these pulses, the limits are nevertheless significant. A typical lower limit on the potential jump of the pulses is about .4 volts. Many of the pulses show structure at a frequency very close (less than 2 percent) to the proton-cyclotron frequency.

Kellogg, P. J.; Monson, S. J.; Whalen, B. A.

1984-01-01

280

Direct imaging of fluorescent structures behind turbid layers.  

PubMed

We present a method to directly image fluorescent structures inside turbid media. This is based on wave-front shaping to optimize the scattered light onto a single fluorescent particle, as the optical memory effect for a scanning image of the surroundings of this particle. We show that iterating the optimization leads to the focusing on a single particle whose surroundings are subsequently scanned. In combination with a parabolic phase pattern, this method can be extended to a three dimensional imaging method inside turbid media. PMID:24515207

Ghielmetti, Giulia; Aegerter, Christof M

2014-01-27

281

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

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

282

Instantaneous Wavenumber Estimation for Damage Quantification in Layered Plate Structures  

NASA Technical Reports Server (NTRS)

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

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

2014-01-01

283

Resonance near-field optical response of metal nanoparticle structures in a layer environment  

NASA Astrophysics Data System (ADS)

The near-field response of optically excited nanoparticle structure buried within thin dielectric layer is theoretically and numerically studied. Nanostructure is modeled as a finite-size periodic array of dipole-like gold nanoparticles, the size of the structure is assumed to be much smaller than the wavelength of the external electromagnetic wave. The layer with the particles is located on a dielectric substrate which is irradiated by an external monochromatic optical wave under condition of total internal reflection. For the determination of the field in the system we make use of the Green's function formalism and the dipole approximation. The dyadic Green's function of a three layer system is used in the unretarded approximation. In order to investigate plasmon resonance response of the nanoparticle structure we calculated the average dipole moment magnitude of the particles as a function of light wavelength for different parameters characterizing the layer environment and the structure. It has been found that the dielectric constant of layer containing the particle structure can strongly effect the resonance shifts in the system. This influence is depended on the external field polarization and inter-particle distances in the structure.

Evlyukhin, A. B.; Leksin, A. Yu.; Gerke, M. N.; Evlyukhina, E. V.

2007-06-01

284

Mechanical characteristics of solid-freeform-fabricated porous calcium polyphosphate structures with oriented stacked layers  

Microsoft Academic Search

This study addresses the mechanical properties of calcium polyphosphate (CPP) structures formed by stacked layers using a powder-based solid freeform fabrication (SFF) technique. The mechanical properties of the 35% porous structures were characterized by uniaxial compression testing for compressive strength determination and diametral compression testing to determine tensile strength. Fracture cleavage surfaces were analyzed using scanning electron microscopy. The effects

Yaser Shanjani; Youxin Hu; Robert M. Pilliar; Ehsan Toyserkani

2011-01-01

285

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

E-print Network

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

Cao, Wenwu

286

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

NASA Technical Reports Server (NTRS)

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

Albrecht, Bruce A.

1993-01-01

287

Analysis of mixed-layer clay mineral structures  

USGS Publications Warehouse

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

Bradley, W. F.

1953-01-01

288

Saturn layered structure and homogeneous evolution models with different EOSs  

NASA Astrophysics Data System (ADS)

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.

Nettelmann, Nadine; Püstow, Robert; Redmer, Ronald

2013-07-01

289

The structure of nanoscale polaron correlations in the layered manganites  

NASA Astrophysics Data System (ADS)

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.

Campbell, Branton

2002-03-01

290

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

NASA Astrophysics Data System (ADS)

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

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

2006-12-01

291

Anatomy and origin of carbonate structures in a Miocene cold-seep field  

NASA Astrophysics Data System (ADS)

Miocene calcite concretions resembling modern carbonate structures that form at cold seeps are present in fractured opal- CT porcelanites that are interbedded with mudstones in coastal cliffs at Santa Cruz, California. The morphologies of the carbonate structures differ markedly from conventional concretions and are spatially aligned with orthogonal joints in the porcelanites. The structures contain tubular holes that are identical to fluid and gas conduits in modern carbonate seep structures; the orientations of these tubes suggest that fluid and gas flow was both vertical and horizontal, the latter along extensional joints that formed preferentially in the brittle, silica-rich layers that had enhanced bedding- parallel permeability. Petrographic and isotopic characteristics of the carbonate structures indicate that calcite precipitation occurred in a shallow, subseafloor environment in either the zone of microbial sulfate reduction or of methanogenesis, prior to or possibly simultaneously with the silica phase transformation of opal- A in diatom shells to opal-CT.

Aiello, Ivano W.; Garrison, Robert E.; Moore, J. Casey; Kastner, Miriam; Stakes, Debra S.

2001-12-01

292

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

NASA Technical Reports Server (NTRS)

A microporous structure with layered interstitial surface treatments, and 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.

Koontz, Steven L. (inventor)

1994-01-01

293

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

NASA Technical Reports Server (NTRS)

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

Koontz, Steven L. (inventor)

1992-01-01

294

Structural origin of apparent Fermi surface pockets in angle-resolved photoemission of Bi?Sr(2-x)La(x)CuO(6+?).  

PubMed

We observe apparent hole pockets in the Fermi surfaces of single-layer Bi-based cuprate superconductors from angle-resolved photoemission. From detailed low-energy electron diffraction measurements and an analysis of the angle-resolved photoemission polarization dependence, we show that these pockets are not intrinsic but arise from multiple overlapping superstructure replicas of the main and shadow bands. We further demonstrate that the hole pockets reported recently from angle-resolved photoemission [Meng et al., Nature (London) 462, 335 (2009)] have a similar structural origin and are inconsistent with an intrinsic hole pocket associated with the electronic structure of a doped CuO? plane. PMID:21517346

King, P D C; Rosen, J A; Meevasana, W; Tamai, A; Rozbicki, E; Comin, R; Levy, G; Fournier, D; Yoshida, Y; Eisaki, H; Shen, K M; Ingle, N J C; Damascelli, A; Baumberger, F

2011-03-25

295

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

NASA Astrophysics Data System (ADS)

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.

Shepherd, Micah R.

296

proteinsSTRUCTURE O FUNCTION O BIOINFORMATICS Structural origins of pH-dependent chemical  

E-print Network

chemical shifts remain too complex for detailed structural analysis, changes in chemical shifts can provide and can often be meaningfully interpreted.7,8 We have there- fore focused on changes in chemical shift and their relationship to structure. pH-dependent changes in chemical shift can provide a lot of informa- tion

Williamson, Mike P.

297

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)

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.

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

2013-12-01

298

Saturn layered structure and homogeneous evolution models with different EOSs  

E-print Network

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

Nettelmann, N; Redmer, R

2013-01-01

299

Magnetic resonance imaging of structure and convection in solidifying mushy layers  

NASA Astrophysics Data System (ADS)

We have used magnetic resonance imaging to study the structure of and convection within a solidifying mushy layer formed from an aqueous sucrose solution cooled from above. We focus on the situation in which dissolution channels, known as chimneys, are created by the action of buoyancy-driven convection. We have obtained high-resolution images of the microstructure formed by individual ice platelets and coarser-grained images that average over the platelets to show the geometry of the dissolution channels. We observe that the chimneys are branched and occur only in the lower part of the mushy layer. By acquiring low-resolution images rapidly, we have made detailed measurements of the thickness of the mushy layer, its porosity distribution and the number and total area of the chimneys. The mushy layer is seen to grow in a self-similar manner until internal convection begins, whereafter the solid fraction increases in the lower part of the layer.

Aussillous, Pascale; Sederman, Andrew J.; Gladden, Lynn F.; Huppert, Herbert E.; Grae Worster, M.

2006-04-01

300

Magneto-Optical Enhancement in Cavity Structure Consisted of Perpendicular Antiferromagnetically Coupled CoPt Layers  

NASA Astrophysics Data System (ADS)

Magneto-optical properties of a stacked-layer structure with perpendicular antiferromagnetically coupled CoPt layers have been investigated under the polar Kerr measurement condition. The stacked layer included an optical cavity that was basically composed of a [CoPt/ZnO/CoPt] trilayer inside the film. It also acted as a magneto-optical cavity under the residual magnetization condition. The enhancement of the residual Kerr rotation was observed by the antiparallel magnetization alignment of the CoPt layers. The enhanced residual rotation angle in the AF sample was greater than the saturation angle of a 5-nm-thick CoPt single film. Moreover, by the finite-difference time-domain simulation, in this system, we demonstrated that a large enhancement of the magneto-optical effect can be anticipated by adopting a two-dimensional photonic crystal structure.

Yamane, Haruki

2012-09-01

301

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

PubMed

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

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

2014-12-21

302

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

PubMed

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

Buskila, Y; Crowe, S E; Ellis-Davies, G C R

2013-12-19

303

Preparation of thermoelectric Si:B/SiGe multilayer structures on quartz glasses by RF-magnetron sputtering with layer-by-layer annealing methods  

NASA Astrophysics Data System (ADS)

We prepared boron-doped Si/Si0.8Ge0.2 (Si:B/SiGe) multilayers sputter-deposited on quartz glass substrates, and investigated their structural and thermoelectric properties. These samples were processed by using conventional whole-layer annealing and layer-by-layer annealing methods. Si:B/SiGe multilayer samples annealed layer-by-layer showed good periodicity with well-defined interfaces as compared with conventionally annealed samples (whole-layer annealing). However, Ge diffusion was observed at the interfaces near substrates since the SiGe layer near the substrates suffered a longer integrated annealing time during the layer-by-layer annealing process. It was found that the Si:B/SiGe multilayer annealed layer-by-layer showed thermally stable thermoelectric properties in a wide temperature range from 50 to 800 °C. The present experiment proved that the layer-by-layer-annealing method is an effective way of achieving stable and reliable thermoelectric properties in Si:B/SiGe multilayer micro-thermoelectric devices.

Ookura, Takuya; Toyota, Hideyuki; Takeda, Masatoshi; Kambayashi, Toshio; Uchitomi, Naotaka

2014-08-01

304

The ancient history of the structure of ribonuclease P and the early origins of Archaea  

PubMed Central

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

2010-01-01

305

Influences of complex loading and margin geometry: failure of curved brittle layer structures  

Microsoft Academic Search

This study investigates the influences of off-axis loading and of margin geometry on “margins failure” observed in loaded\\u000a curved bi-layer structures, away from the contact loading point. Specimens of hemispherical bi-layer model consist of glass\\u000a shells with varying margins geometry, and filled with epoxy resin substrate are prepared. These specimens are loaded with\\u000a compliant PTFE Teflon cylindrical indenters, with a

Tarek Qasim

2007-01-01

306

Structure of Protein Layers in Polyelectrolyte Matrices Studied by Neutron Reflectivity  

SciTech Connect

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

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

2011-01-01

307

Use of heat treatment to modify the structure of a hard-faced layer  

NASA Astrophysics Data System (ADS)

The methods of metal physics and x-ray diffraction analysis are used to study the effect of heat treatments (quenching, tempering, high-temperature tempering) on the structure and properties (hardness, wear resistance) of a layer composed of an electroslag hard-facing alloyed with boron carbide and chromium. It is shown that the most effective heat treatment for increasing the hardness and wear resistance of the layer is one which includes high-temperature tempering, quenching, and low-temperature tempering.

Borisov, M. D.; Kraev, G. V.; Poletika, I. M.

1992-02-01

308

Voltage-controlled surface plasmon-polaritons in double graphene layer structures  

NASA Astrophysics Data System (ADS)

The spectra and damping of surface plasmon-polaritons (SPPs) in double graphene layer structures are studied. It is proved that SPPs in those structures exhibit an outstanding voltage tunability of velocity and damping, inherent to gated graphene, and a pronounced low-frequency coupling with photons inherent to non-gated structures. It is also shown that the spatial dispersion of conductivity significantly augments the free path and cutoff frequency of SPPs, which is of great importance for practical applications.

Svintsov, D.; Vyurkov, V.; Ryzhii, V.; Otsuji, T.

2013-02-01

309

Structures of two different surface layers found in six Bacteroides strains.  

PubMed Central

The structures of crystalline layers from six Bacteroides strains were studied by electron microscopy. Two different hexagonal crystalline surface layers were found, one with a unit cell spacing of 21.5 nm and another with a spacing of 7.7 nm. A three-dimensional structure of the 21.5-nm layer and a two-dimensional projection of the 7.7-nm layer were determined to 3.0- and 3.8-nm resolution, respectively, by computerized image processing of electron micrographs. Both of these two crystalline layers were found in all six strains studied: B. pentosaceus NP333T and WPH61, B. capillus ATCC 33690T and ATCC 33691, and B. buccae ATCC 33574T and ES57. This further supports the identity of B. pentosaceus, B. capillus, and B. buccae as suggested by M. Haapasalo, K. Lounatmaa, H. Ranta, H. Shah, and K. Ranta (Int. J. Syst. Bacteriol. 35:65-72, 1985). The surface layer with 21.5-nm spacing is an intricate network with two classes of pores through the layer. Images PMID:4066614

Sjögren, A; Hovmöller, S; Farrants, G; Ranta, H; Haapasalo, M; Ranta, K; Lounatmaa, K

1985-01-01

310

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

NASA Astrophysics Data System (ADS)

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.

He, Fupo; Ye, Jiandong

2013-08-01

311

Effect of layer stacking on the electronic structure of graphene nanoribbons.  

PubMed

The evolution of electronic structure of graphene nanoribbons (GNRs) as a function of the number of layers stacked together is investigated using ab initio density functional theory (DFT), including interlayer van der Waals interactions. Multilayer armchair GNRs (AGNRs), similar to single-layer AGNRs, exhibit three classes of band gaps depending on their width. In zigzag GNRs (ZGNRs), the geometry relaxation resulting from interlayer interactions plays a crucial role in determining the magnetic polarization and the band structure. The antiferromagnetic (AF) interlayer coupling is more stable compared to the ferromagnetic (FM) interlayer coupling. ZGNRs with the AF in-layer and AF interlayer coupling have a finite band gap, while ZGNRs with the FM in-layer and AF interlayer coupling do not have a band gap. The ground state of the bilayer ZGNR is nonmagnetic with a small but finite band gap. The magnetic ordering is less stable in multilayer ZGNRs compared to that in single-layer ZGNRs. The quasiparticle GW corrections are smaller for bilayer GNRs compared to single-layer GNRs because of the reduced Coulomb effects in bilayer GNRs compared to single-layer GNRs. PMID:21766785

Kharche, Neerav; Zhou, Yu; O'Brien, Kevin P; Kar, Swastik; Nayak, Saroj K

2011-08-23

312

Titan: Predicted Bulk Chemical Composition and Interior Structure for a Capture Origin  

NASA Astrophysics Data System (ADS)

I report a predicted bulk chemical composition and internal structure for Titan based on the idea that this body is a captured satellite of Saturn which originally condensed within the gas ring shed by the proto-Solar cloud (PSC) at Saturn's initial helio-centric distance ˜ 8.1 AU . The case for capture rests on the large disparity (by a factor of ˜ 58) between the masses of Titan and Rhea. Rhea's mass (2.3 × 1024 g) is consistent with the mass mcond = 9.3 × 1024 of rock, H2O, and NH3 ices expected for a native moon of Saturn, had Rhea condensed from a gas ring shed by the proto-Saturnian cloud (Prentice, \\textit{JPL Pub.} 80-80 1980; \\textit{Proc. Astron. Soc. Australia} 4 164 1981; \\textit{Earth, Moon Planets} 30 209 1984). Here I assume an efficiency of 25% in the process of satellite accretion and adopt the proto-solar elemental abundances of Lodders (\\textit{Astrophys.J} 591 1220 2003). Titan's mass exceeds mcond by a factor of ˜ 14, so speaking against a native origin (http://www.aas.org/publications/baas/v36n2/aas204/887.htm). Previously it has been supposed that the process of shedding discrete gas rings by the parent gas cloud comes about solely through the action of large turbulent stresses arising from powerful convective motions (Prentice, \\textit{Moon & Planets} 19 341 1978, \\textit{Earth, Moon & Planets} 87 11 2001, http://www.lpi.usra.edu/meetings/mercury01/pdf/8061.pdf). This has necessitated convective speeds vt up to ˜ 5 times the local adiabatic sound speed vs, which is unacceptable. An exact numerical simulation of supersonic turbulent convection in a model atmosphere which represents the outer layers of the PSC shows, however, that the upper layers are strongly super-adiabatic (Prentice & Dyt, \\textit{MNRAS} 341 644 2003). This results in a natural density inversion at the top boundary . Gas ring shedding can now be achieved for speeds vt ? 3vs, which is OK. A new model for PSC has thus been constructed to include the influence of very strong super-adiabaticity. The controlling paramters are chosen so that the mean density of the condensate at the orbit of Mercury matches the inferred uncompressed value ? unc = 5.3 g/cm3 and that the fraction of water vapour in the gas ring at Jupiter's orbit which condenses is ? {H{2 O}} = 0.665. This later accounts for the densities of Ganymede and Callisto, following condensation from the gas rings shed by proto-Jovian cloud (Prentice 2001). At Saturn's initial orbit, where the gas ring temperature is Tn= 94 K and the mean orbit pressure pn= 4.7 × 10-7 bar, the bulk chemical constituents of the condensate are anhydrous rock (mass fraction 0.494), water ice (0.474) and graphite (0.032). The mean density is 1.52 g/cm3. Structural models for a present-day Titan based on this composition yield mean densities of 2.10 g/cm3 (homogeneous case) and 1.93 g/cm3 (differentiated 2-zone case). For the latter, C/MR2 = 0.32. Titan is thus most likely fully differentiated between its rock, graphite and water ice constituents. It is predicted that Titan has no internal ocean or induced magnetic field but it may possess a small magnetic dipole moment of magnitude ˜ 2× 1011 T m3. This was acquired through thermoremanence at ˜ 1.5 × 109 yr after satellite formation. Capture of Titan was achieved by gas drag within the proto-Saturnian envelope whose initial size was ˜ 60 RSat. Titan's surface should thus look much like that of Triton. I thank John D. Anderson [NASA/JPL] for much support, and Nicole Rappaport and Bob Jacobson for helpful discussions.

Prentice, A. J.

2004-12-01

313

Elementary solutions for streaky structures in boundary layers with and without suction  

NASA Astrophysics Data System (ADS)

The temporal evolutions of small, streamwise elongated disturbances in the asymptotic suction boundary layer (ASBL) and the Blasius boundary layer (BBL) are compared. In particular, initial perturbations localized ( ?-functions) in the wall-normal direction are studied, corresponding to an axi-symmetric jet coming out of a plane parallel to the flat plate. Analytical solutions are presented for the wall-normal and streamwise velocities in the ASBL case whereas both analytical and numerical methods are used for the BBL case. The initial position of the perturbation and its spanwise wave number are varied in a parameter study. We present results of maximum amplitudes obtained, the time to reach them, their position and optimal spanwise scales. Free-stream disturbances are shown to migrate towards the wall and reach their (negative) optimum inside the boundary layer. The migration is faster for the ASBL case and a larger amplitude is reached than for the BBL. For perturbations originating inside the boundary layer the amplitudes are overall larger and show the phenomenon of overshoot, i.e. positive amplitudes moving out of the boundary layer. The overall largest amplitudes are obtained for the BBL case, as in other studies, but it is shown that for free-stream disturbances initiated somewhere downstream the leading edge streak growth may be amplified due to suction since in the BBL the disturbance mainly advects above the boundary layer.

Davidsson, E. Niklas; Gustavsson, L. HÅkan

2008-03-01

314

Fabrication and mechanical evaluation of anatomically-inspired quasilaminate hydrogel structures with layer-specific formulations.  

PubMed

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

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

2013-02-01

315

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

PubMed

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. PMID:25226541

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

2014-10-01

316

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

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

317

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

NASA Astrophysics Data System (ADS)

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

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

1997-03-01

318

Structure and catalytic property of coherent spinel surface layers on hexaaluminate microcrystals  

SciTech Connect

Formation of coherent surface layers of Mn{sub 3}O{sub 4} on hexaaluminate microcrystals has been studied as a structural modification to enhance the catalytic activity for methane combustion. The spinel oxide surface layer was successfully produced on planar microcrystals of hexaaluminate by employing the air oxidation of an aqueous Mn(II) solution. As evident from TEM, XPS, and CO{sub 2} chemisorption measurements, as-prepared surface layers completely covered the basal plane of planar microcrystals. This characteristic structure appears to be a result of liquid phase epitaxy at the structurally coherent interface between hexaaluminate and spinel. A completely different structure was observed for the samples from the conventional impregnation method, which contain insular Mn{sub 3}O{sub 4} particles dispersed on hexaaluminate. The catalytic activity for methane combustion was evaluated as a function of the Mn{sub 3}O{sub 4} loading and the metal composition of the spinel surface layer. It was revealed that the higher specific activity was observed over air-oxidation-derived samples than over the impregnated samples. Partial substitution of Fe for Mn on the surface layer was effective in enhancing the combustion activity as a result of promoting the reduction/oxidation property. 20 refs., 9 figs.

Machida, Masato; Sato, Akihiro; Murakami, Manabu [Miyazaki Univ. (Japan)] [and others] [Miyazaki Univ. (Japan); and others

1995-12-01

319

A five-dimensional structural investigation of the misfit layer compound  

PubMed

The structure of the misfit layer compound [Bi0.87SrO2]2[CoO2]1.82, bismuth strontium cobaltite, was determined by single-crystal X-ray diffraction using the five-dimensional superspace-group formalism. This composite crystal, of monoclinic symmetry, is composed of two subsystems exhibiting incommensurate periodicities along b, the binary axis direction. The first composite part [Bi0.87SrO2] displays an intrinsic modulation of planar monoclinic type characterized by the wavevector q* = 0.293a* + 0.915c*. The second composite part [CoO2] shows two different centered lattice variants. The structure of the misfit layer crystal can be described as an alternation along c of distorted rock-salt-type slabs, formed from [BiO] and [SrO] layers (first subsystem), and of [CoO2] layers (second subsystem) displaying a distorted CdI2-type structure. Two main structural results are obtained. First, as a consequence of the intrinsic modulation, disordered zones, characterized by Bi vacancies, are regularly distributed in the [BiO] layers. Second, strong chemical bonds are implied between the strontium atoms of the first subsystem and the oxygen atoms of the second one. PMID:10794269

Leligny; Grebille; Perez; Masset; Hervieu; Raveau

2000-04-01

320

Structural Layers of Ex Vivo Rat Hippocampus at 7T MRI  

PubMed Central

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

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

2013-01-01

321

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

NASA Astrophysics Data System (ADS)

The family of bulk metal phosphorus trichalcogenides (APX3, A = MII, M_{0.5}^IM_{0.5}^{III}; X = S, Se; MI, MII, and MIII 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 APX3 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 ZnPSe3, CdPSe3, Ag0.5Sc0.5PSe3, and Ag0.5In0.5PX3 (X = S and Se) have both suitable band gaps for visible-light driving and sufficient over-potentials for water splitting. More fascinatingly, single-layer Ag0.5Sc0.5PSe3 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.

Liu, Jian; Li, Xi-Bo; Wang, Da; Lau, Woon-Ming; Peng, Ping; Liu, Li-Min

2014-02-01

322

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

SciTech Connect

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.

Rozanov, N. N., E-mail: nrosanov@yahoo.com; Fedorov, S. V.; Savel'ev, R. S.; Sukhorukov, A. A.; Kivshar, Yu. S. [St. Petersburg State University of Information Technologies, Mechanics and Optics (Russian Federation)

2012-05-15

323

Frequency separation of surface acoustic waves in layered structures with acoustic metamaterials  

NASA Astrophysics Data System (ADS)

We show theoretically that in elastic layered structures containing an upper layer of smoothly varied thickness and a substrate of a highly dispersive metametarial it is possible to significantly enhance spatial frequency separation of surface acoustic waves. Theory of Love surface acoustic waves propagation in waveguides with varied thickness, taking into account mutual modes coupling, is built. Appropriate structure of metamatererial with resonant frequency dependence of material parameters, making frequency separation effective, is provided. Efficiency of spatial frequency separation and modes coupling is calculated for various metamaterial parameters and wave frequencies.

Kalyabin, D.; Lisenkov, I.; Lee, Y. P.; Nikitov, S.

2014-06-01

324

Monitoring thickness deviations in planar multi-layer elastic structures using impedance signatures.  

PubMed

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 mum. 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. PMID:18646950

Fisher, Karl A

2008-07-01

325

Optimization of active layer structures to minimize leakage current for an AlGaInP laser diode  

Microsoft Academic Search

Theoretical analysis for different active layer structures under the same waveguide confinement is conducted to minimize the electron overflow from the active layer to the p-cladding layer for the AlGaInP laser diode. An active layer with five quantum wells and a (AlxGa1-x)InP barrier with an x composition of 0.5 has found to be the optimal structure for the AlGaInP laser

M.-F. Huang; M.-L. Tsai; J.-Y. Shin; Y.-L. Sun; R.-M. Yang; Y.-K. Kuo

2005-01-01

326

Highly reducing conditions during core formation on Mercury: Implications for internal structure and the origin of a magnetic field  

NASA Astrophysics Data System (ADS)

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.

Malavergne, Valérie; Toplis, Michael J.; Berthet, Sophie; Jones, John

2010-03-01

327

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

PubMed

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

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

2011-01-01

328

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

NASA Astrophysics Data System (ADS)

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.

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

2013-12-01

329

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

NASA Astrophysics Data System (ADS)

Aerospace structures contain multi-layered components connected by fasteners, where fatigue cracks and disbonds or localized lack of sealant can develop due to cyclic loading conditions and stress concentration. High frequency guided waves propagating along such a structure allow for the efficient non-destructive testing of large components, such as aircraft wings. The type of multi-layered model structure investigated in this contribution consists of two aluminium plates adhesively bonded with an epoxy based sealant layer. Using commercially available transducer equipment, specific high frequency guided ultrasonic wave modes that penetrate through the complete thickness of the structure were excited. The wave propagation along the structure was measured experimentally using a laser interferometer. Two types of hidden damage were considered: a localized lack of sealant and small surface defects in the metallic layer facing the sealant. The detection sensitivity using standard pulse-echo measurement equipment has been quantified and the detection of small hidden defects from significant stand-off distances has been shown. Fatigue experiments were carried out and the potential of high frequency guided waves for the monitoring of fatigue crack growth at a fastener hole during cyclic loading was discussed.

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

2011-04-01

330

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

DOEpatents

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

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

1998-03-10

331

The boundary layer structure in Rayleigh-B'enard convection in a cylindrical cell  

NASA Astrophysics Data System (ADS)

We report first results of our studies of the boundary layer structure in turbulent Rayleigh-B'enard convection in a cylindrical cell of aspect ratio one. They are based on three-dimensional direct numerical simulations (DNS) of the Boussinesq equations at Ra=3x10^9 and Pr=0.7. The study is motivated by two recent experiments: LDA measurements of the velocity boundary layer structure in the cylindrical Barrel of Ilmenau by du Puits et al. and PIV measurements in a slender rectangular convection cell by Xia et al. Both experiments detected deviations from the classical Blasius solution for time-averaged flow profiles. A rescaling by the instantaneous boundary layer thickness resulted however in a much better agreement with the Blasius profile in case of the rectangular cell. The DNS allow us to combine the analysis methods of both experiments. We confirm the significant deviation for the time-averaged profiles. Closer agreement with the Blasius solution is also reproduced for the fit with the instantaneous thickness. Our analysis is extended to the Pohlhausen solution in case of the thermal boundary layer. The flow profiles are also taken at different positions in the boundary layers. Further statistical properties in both boundary layers are reported.

Shi, Nan; Schumacher, Joerg

2010-11-01

332

A study of the band structures of elastic wave propagating in piezoelectric\\/piezomagnetic layered periodic structures  

Microsoft Academic Search

This paper is concerned with wave propagation and localization in piezoelectric (PE) and piezomagnetic (PM) layered periodic structures. Both normal and oblique propagation of waves are considered. The materials are assumed to be transversely isotropic. Wave behaviors are analyzed by calculating the dispersion curves, localization factors and response spectra using the transfer matrix and\\/or the stiffness matrix methods. The results

Yu Pang; Yue-Sheng Wang; Jin-Xi Liu; Dai-Ning Fang

2010-01-01

333

Structural origin of the nonlinear optical properties of lead niobium germanate film glasses  

SciTech Connect

The structural origin of the nonlinear optical susceptibility (/{chi}{sup (3)}/) of lead-niobium-germanate film glasses with large Nb{sub 2}O{sub 5} contents has been investigated. /{chi}{sup (3)}/ shows a strong enhancement with the Nb content in the films with /{chi}{sup (3)}/ values close to 2 x 10{sup -11} esu at 800 nm for a Nb content as high as 0.71. Boling-Glass-Owyoung and Lines' semiempirical models predict accurately the values of /{chi}{sup (3)}/ for transparent bulk glasses but not for film glasses. This discrepancy is related to the remarkable structural differences between them. Raman spectroscopy suggests the formation of a three-dimensional (3D) structure of [NbO{sub 6}] octahedra in the case of film glasses having large Nb contents, while X-ray photoelectron spectroscopy shows that a significant fraction of these units contain Nb{sup 4+} ions. The combination of a 3D structure of [NbO{sub 6}] with the presence of Nb{sup 4+} polarons and their migration through electron intervalence transfer is proposed as the origin of the observed enhancement of /{chi}{sup (3)}/ in the film glasses.

Munoz-Martin, D.; Ruiz de La Cruz, A.; Fernandez-Navarro, J. M.; Solis, J.; Gonzalo, J. [Laser Processing Group, Instituto de Optica (CSIC), Serrano 121, 28006 Madrid (Spain); Domingo, C. [Instituto de Estructura de la Materia (CSIC), Serrano 121, 28006 Madrid (Spain)

2011-07-15

334

Plant Biomechanics Conference Cayenne, November 16 21, 2009 Origins of abnormal behaviors of gelatinous layer in tension wood  

E-print Network

6th Plant Biomechanics Conference ­ Cayenne, November 16 ­ 21, 2009 Origins of abnormal behaviors, published in "6th Plant Biomechanics Conference, French Guiana (2009)" #12;6th Plant Biomechanics Conference

Paris-Sud XI, Université de

335

Nonlinear instability research of longitudinal structure generated by roughness in unswept wing boundary layer  

NASA Astrophysics Data System (ADS)

The results of experimental study of a nonlinear varicose instability of the streaky structure generated by roughness element in unswept-wing boundary layer are presented. Features of the varicose breakdown of longitudinal steady streaky structure such as modulation of structure in transverse and streamwise directions by secondary disturbance, occurrence of the new streaky structures and A-structures downstream are shown. Spatio-temporal pictures of the hot-wire visualization of flow during spatial evolution of the streaky structures under influence of secondary high-frequency disturbance are discussed. Features of the adverse pressure gradient influence upon processes of the nonlinear varicose instability evolution and flow structure are revealed. Essential influence of the adverse pressure gradient on evolution of disturbances in shown. Comparison of varicose instability of the streaky structures generated in two different ways (the roughness element as in the given work, and continuous air blowing as in the earlier published work) is the carried out.

Chernorai, V. G.; Litvinenko, Yu. A.; Kozlov, V. V.; Grek, G. R.

2007-09-01

336

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

NASA Astrophysics Data System (ADS)

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

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

337

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

NASA Astrophysics Data System (ADS)

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

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

2007-03-01

338

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

SciTech Connect

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

Clevenger, M.B.; Murray, C.S. [Westinghouse Electric Co., West Mifflin, PA (United States); Ringel, S.A.; Sachs, R.N.; Qin, L. [Ohio State Univ., Columbus, OH (United States). Dept. of Electrical Engineering; Charache, G.W.; Depoy, D.M. [Lockheed Martin, Inc., Schenectady, NY (United States)

1998-11-01

339

Shrinkage anisotropy characteristics from soil structure and initial sample/layer size  

E-print Network

The objective of this work is a physical prediction of such soil shrinkage anisotropy characteristics as variation with drying of (i) different sample/layer sizes and (ii) the shrinkage geometry factor. With that, a new presentation of the shrinkage anisotropy concept is suggested through the sample/layer size ratios. The work objective is reached in two steps. First, the relations are derived between the indicated soil shrinkage anisotropy characteristics and three different shrinkage curves of a soil relating to: small samples (without cracking at shrinkage), sufficiently large samples (with internal cracking), and layers of similar thickness. Then, the results of a recent work with respect to the physical prediction of the three shrinkage curves are used. These results connect the shrinkage curves with the initial sample size/layer thickness as well as characteristics of soil texture and structure (both inter- and intra-aggregate) as physical parameters. The parameters determining the reference shrinkage c...

Chertkov, V Y

2014-01-01

340

Structure of local pressure-driven three-dimensional transient boundary-layer separation  

NASA Astrophysics Data System (ADS)

The separation of a flat-plate, laminar boundary layer under the influence of a suddenly imposed three-dimensional external adverse pressure gradient was studied computationally by time-accurate numerical solution of the incompressible Navier-Stokes equations. The separation decay was then investigated by impulsively removing the pressure gradient. The development and decay of the separation structure were compared with experimental results reported by other investigators for the same geometry. The periodic vortex shedding of the three-dimensional separation was described in terms of a Strouhal number based on the freestream velocity and Blasius boundary-layer momentum thickness at the location where separation occurs. The characteristic Strouhal number of 0.0136 during the separation development from the computation compared favorably with 0.0134 from the experiment. When the adverse pressure gradient was impulsively removed, the boundary layer returned to an attached boundary layer much faster than the time required for the separation development.

Pauley, Laura L.

1994-05-01

341

Controlled gentamicin release from multi-layered electrospun nanofibrous structures of various thicknesses.  

PubMed

Polyvinyl alcohol nanofibers incorporating the wide spectrum antibiotic gentamicin were prepared by Nanospider™ needleless technology. A polyvinyl alcohol layer, serving as a drug reservoir, was covered from both sides by polyurethane layers of various thicknesses. The multilayered structure of the nanofibers was observed using scanning electron microscopy, the porosity was characterized by mercury porosimetry, and nitrogen adsorption/desorption measurements were used to determine specific surface areas. The stability of the gentamicin released from the electrospun layers was proved by high-performance liquid chromatography (HPLC) and inhibition of bacterial growth. Drug release was investigated using in vitro experiments with HPLC/MS quantification, while the antimicrobial efficacy was evaluated on Gram-positive Staphylococcus aureus and Gram-negative Pseudomonas aeruginosa. Both experiments proved that the released gentamicin retained its activity and showed that the retention of the drug in the nanofibers was prolonged with the increasing thickness of the covering layers. PMID:23071393

Sirc, Jakub; Kubinova, Sarka; Hobzova, Radka; Stranska, Denisa; Kozlik, Petr; Bosakova, Zuzana; Marekova, Dana; Holan, Vladimir; Sykova, Eva; Michalek, Jiri

2012-01-01

342

A randomly nano-structured scattering layer for transparent organic light emitting diodes.  

PubMed

A random scattering layer (RSL) consisting of a random nano-structure (RNS) and a high refractive index planarization layer (HRI PL) is suggested and demonstrated as an efficient internal light-extracting layer for transparent organic light emitting diodes (TOLEDs). By introducing the RSL, a remarkable enhancement of 40% and 46% in external quantum efficiency (EQE) and luminous efficacy (LE) was achieved without causing deterioration in the transmittance. Additionally, with the use of the RSL, the viewing angle dependency of EL spectra was reduced to a marginal degree. The results were interpreted as the stronger influence of the scattering effect over the microcavity. The RSL can be applied widely in TOLEDs as an effective light-extracting layer for extracting the waveguide mode of confined light at the indium tin oxide (ITO)/OLED stack without introducing spectral changes in TOLEDs. PMID:25099663

Huh, Jin Woo; Shin, Jin-Wook; Cho, Doo-Hee; Moon, Jaehyun; Joo, Chul Woong; Park, Seung Koo; Hwang, Joohyun; Cho, Nam Sung; Lee, Jonghee; Han, Jun-Han; Chu, Hye Yong; Lee, Jeong-Ik

2014-09-21

343

A randomly nano-structured scattering layer for transparent organic light emitting diodes  

NASA Astrophysics Data System (ADS)

A random scattering layer (RSL) consisting of a random nano-structure (RNS) and a high refractive index planarization layer (HRI PL) is suggested and demonstrated as an efficient internal light-extracting layer for transparent organic light emitting diodes (TOLEDs). By introducing the RSL, a remarkable enhancement of 40% and 46% in external quantum efficiency (EQE) and luminous efficacy (LE) was achieved without causing deterioration in the transmittance. Additionally, with the use of the RSL, the viewing angle dependency of EL spectra was reduced to a marginal degree. The results were interpreted as the stronger influence of the scattering effect over the microcavity. The RSL can be applied widely in TOLEDs as an effective light-extracting layer for extracting the waveguide mode of confined light at the indium tin oxide (ITO)/OLED stack without introducing spectral changes in TOLEDs.A random scattering layer (RSL) consisting of a random nano-structure (RNS) and a high refractive index planarization layer (HRI PL) is suggested and demonstrated as an efficient internal light-extracting layer for transparent organic light emitting diodes (TOLEDs). By introducing the RSL, a remarkable enhancement of 40% and 46% in external quantum efficiency (EQE) and luminous efficacy (LE) was achieved without causing deterioration in the transmittance. Additionally, with the use of the RSL, the viewing angle dependency of EL spectra was reduced to a marginal degree. The results were interpreted as the stronger influence of the scattering effect over the microcavity. The RSL can be applied widely in TOLEDs as an effective light-extracting layer for extracting the waveguide mode of confined light at the indium tin oxide (ITO)/OLED stack without introducing spectral changes in TOLEDs. Electronic supplementary information (ESI) available: Simulation results of total (bottom and top) radiance of TOLEDs with the RSL depending on HTL and ETL thicknesses. See DOI: 10.1039/c4nr01520g

Huh, Jin Woo; Shin, Jin-Wook; Cho, Doo-Hee; Moon, Jaehyun; Joo, Chul Woong; Park, Seung Koo; Hwang, Joohyun; Cho, Nam Sung; Lee, Jonghee; Han, Jun-Han; Chu, Hye Yong; Lee, Jeong-Ik

2014-08-01

344

YBCO/manganite layered structures on NdGaO3 substrates  

NASA Astrophysics Data System (ADS)

Results of deposition of YBa2Cu3O7-x/CeO2/(La0.7Ca0.3MnO3 or La0.7Sr0.3MnO3) structures on the standard oriented and tilted ( = 8°) NdGaO3 substrates and results of investigation of electrical parameters of YBa2Cu3O7-x (YBCO) films in such structures are presented. The YBCO component of the structure exhibits lower value of the critical parameters in comparison with those of single YBCO films. The contribution of the magnetic layer to the microwave losses of the YBCO film in the layered structure is evaluated.

Nurgaliev, T.; Blagoev, B.; Donchev, T.; Miteva, S.; Mozhaev, P. B.; Mozhaeva, J. E.; Ovsyannikov, G. A.; Kotelyanskii, I. M.; Jacobsen, C.

2006-06-01

345

Investigation of interface states in single-negative metamaterial layered structures based on the phase properties.  

PubMed

The physical mechanism of the interface states in layered structures consisting of single-negative metamaterials is investigated using a simple resonant cavity model. We found that the interface states and their corresponding tunneling transmission modes appeared when the resonant condition is satisfied. Such resonant condition depends on the phase changes inside the resonant cavity. Based on these results, we proposed an efficient method to precisely predict the frequencies of the tunneling interface states inside the single-negative metamaterial layers. Our method is effective for interface states corresponding to perfect or imperfect tunneling transmission. Composite right/left-handed transmission lines were used to realize the pair and sandwich metamaterial layered structures in the microwave region. Electromagnetic tunneling interface states were observed in the measurements, which agreed well with the theory. Our study offers a way for effectively designing metamaterial devices with novel electromagnetic tunneling properties. PMID:23938526

Zheng, Jian; Chen, Yihang; Chen, Zefeng; Wang, Xinggang; Han, Peng; Yong, Zehui; Wang, Yu; Leung, Chi Wah; Soukoulis, Costas M

2013-07-15

346

EXAFS Signatures of Structural Zn at Trace Levels in Layered Minerals  

SciTech Connect

Many in situ XAFS studies have shown that zinc incorporated in layered minerals is a major form of zinc in Zn-contaminated soils. Quantitative information on the local structural environment(s) and ordering of Zn in these minerals is required to better understand its behavior in soils. In this study, EXAFS spectroscopy was used to assess the structural environment of zinc incorporated at trace levels (40 ppm to 4,000 ppm) within the octahedral sheets of various natural and synthetic layered minerals. Results indicate that EXAFS data analyzed using ab initio FEFF calculations (FEFF 8.10) can unambiguously distinguish between zinc incorporation within the octahedral sheet of dioctahedral versus trioctahedral layered minerals and can determine the distribution (random or ordered) of zinc cations within the octahedral sheets of these minerals.

Juillot, Farid; Morin, Guillaume; Calas, Georges [Institut de Mineralogie et de Physique des Milieux Condenses (IMPMC), UMR CNRS 7590, Universites Paris 6/7-IPGP, (France); Hazemann, Jean-Louis; Proux, Olivier [European Synchrotron Radiation Facility (ESRF), Grenoble, (France); Belin, Stephanie; Briois, Valerie [Synchrotron SOLEIL, Saint Aubin, (France); Brown, Gordon E. Jr. [Department of Geological and Environmental Sciences, Stanford University, Stanford, CA (United States); Stanford Synchrotron Radiation Laboratory, Menlo Park, CA (United States)

2007-02-02

347

Plasmonic Light Trapping in an Ultrathin Photovoltaic Layer with Film-Coupled Metamaterial Structures  

E-print Network

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 in the film-coupled metamaterial structure, resulting in significant enhancement on the short-circuit current density by three times over a free-standing GaAs layer at the same thickness. The results would facilitate the development of next-generation ultrathin solar cells with lower cost and higher efficiency.

Wang, Hao

2014-01-01

348

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

NASA Technical Reports Server (NTRS)

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

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

2000-01-01

349

The Performance of RAMS in Representing the Convective Boundary Layer Structure in a Very Steep Valley  

SciTech Connect

Data from a comprehensive field study in the Riviera Valley of Southern Switzerland are used to investigate convective boundary layer structure in a steep valley and to evaluate wind and temperature fields, convective boundary layer height, and surface sensible heat fluxes as predicted by the mesoscale model RAMS. Current parameterizations of surface and boundary layer processes in RAMS, as well as in other mesoscale models, are based on scaling laws strictly valid only for flat topography and uniform land cover. Model evaluation is required to investigate whether this limits the applicability of RAMS in steep, inhomogeneous terrain. One clear-sky day with light synoptic winds is selected from the field study. Observed temperature structure across and along the valley is nearly homogeneous while wind structure is complex with a wind speed maximum on one side of the valley. Upvalley flows are not purely thermally driven and mechanical effects near the valley entrance also affect the wind structure. RAMS captured many of the observed boundary layer characteristics within the steep valley. The wind field, temperature structure, and convective boundary layer height in the valley are qualitatively simulated by RAMS, but the horizontal temperature structure across and along the valley is less homogeneous in the model than in the observations. The model reproduced the observed net radiation, except around sunset and sunrise when RAMS does not take into account the shadows cast by the surrounding topography. The observed sensible heat fluxes fall within the range of simulated values at grid points surrounding the measurement sites. Some of the scatter between observed and simulated turbulent sensible heat fluxes are due to sub-grid scale effects related to local topography.

De Wekker, Stephan; Steyn, D. G.; Fast, Jerome D.; Rotach, Mathias W.; Zhong, Shiyuan

2005-04-01

350

A Phobos geodesy experiment to constrain its bulk interior structure and origin  

NASA Astrophysics Data System (ADS)

The origin of the Martian moons is still an open question [1]. The ill-fated Phobos Soil mission was an ambitious mission devoted to find out an answer to this open issue. Among the suite of instruments dedicated to the interior of Phobos, the radio-science experiment [2] (as well as the libration experiment [3]) were wellsuited to provide constraints on the bulk interior structure of Phobos. As such information is one of the key pieces still required to understand the origin of this small body [1], we present here the scientific rationale and the goals of a geodesy experiment, which could easily composed the payload of future missions toward the Martian moon system.

Rosenblatt, P.; Le Maistre, S.; Lainey, V.; Rivoldini, A.; Mocquet, A.; Verhoeven, O.; Rambaux, N.; Le Poncin-Laffite, C.; Gurvits, L.; Marty, J. C.; Zakharov, A.; Castillo-Rogez, J.; Dehant, V.

2012-09-01

351

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

PubMed Central

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

2014-01-01

352

Evolution of three-dimensional coherent structures in a flat-plate boundary layer  

Microsoft Academic Search

Using a data base generated by a numerical simulation, the three-dimensional coherent structures of a transitional, spatially evolving boundary layer are determined and their spatio-temporal behavior is investigated in detail. The coherent structures are calculated by the proper orthogonal decomposition method (POD), which leads to an expansion of the flow field variables into Karhunen-Loeve eigenfunctions. It is shown that the

Dietmar Rempfer; Hermann F. Fasel

1994-01-01

353

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

NASA Astrophysics Data System (ADS)

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.

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

2013-01-01

354

Three-Dimensional Buoyancy and Shear-Induced Local Structure of the Atmospheric Boundary Layer  

Microsoft Academic Search

Three-dimensional visualization together with statistical measures are used to describe the instantaneous local structure of the atmospheric boundary layer (ABL) under various stability states using large-eddy simulation (LES) data. To explore the relative roles of buoyancy and shear in ABL structure, a wide range of zi\\/L ABL states, from 0.44 to 730, is analyzed. It is known that buoyancy-induced updrafts

Samir Khanna; James G. Brasseur

1998-01-01

355

Terahertz and infrared surface plasmon-polaritons in double-graphene layer structures  

NASA Astrophysics Data System (ADS)

Spectra and damping of surface plasmon-polaritons (SPPs) in double graphene layer structures are studied theoretically. The SPPs in those structures exhibit a remarkable voltage tunability of velocity and damping, inherent to gated graphene. The spatial dispersion of conductivity significantly augments the free path and cutoff frequency of SPPs. It is also pointed out to the effect of photon-assisted interlayer tunneling, which leads to a substantial decrease in SPP damping.

Svintsov, Dmitry; Vyurkov, Vladimir; Ryzhii, Victor; Otsuji, Taiichi

2014-03-01

356

Hybrid electromagnetic-spin oscillations in layered structures with uniaxial hexaferrites  

NASA Astrophysics Data System (ADS)

Spectra of magnetostatic oscillations in layered dielectric-ferrite-metal structures are studied theoretically and experimentally. Hybridization of the magnetostatic oscillations and dielectric resonant modes is experimentally investigated both under saturation and in the domain region in the presence of a cylindrical magnetic domain. The experiments are performed on the platelets of magnetoplumbite, as well as barium and strontium hexaferrites. In composite structures, quartz platelets of various thicknesses are used as dielectrics.

Kostenko, V. I.; Sorochak, A. M.; Chamor, T. G.; Chevnyuk, L. V.

2011-05-01

357

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

SciTech Connect

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.

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

2013-02-15

358

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

NASA Astrophysics Data System (ADS)

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.

Au, Chak Kuen

359

The Propagation of Rayleigh Waves in Layered Piezoelectric Structures with Viscosity  

E-print Network

, the usual structure of surface wave resonators with discrete electrodes (IDTs) will result in more mechanism and energy loss mechanism of acoustic wave resonators, we have been able to formulate the wave, the dominant energy loss, or the viscosity, is from the bonding process of layers which brought contamination

Wang, Ji

360

Pseudoepitaxial transrotational structures in 14 nm-thick NiSi layers on [001] silicon.  

PubMed

In a system consisting of two different lattices, structural stability is ensured when an epitaxial relationship occurs between them and allows the system to retain the stress whilst avoiding the formation of a polycrystalline film. The phenomenon occurs if the film thickness does not exceed a critical value. Here we show that in spite of its orthorhombic structure, a 14 nm-thick NiSi layer can three-dimensionally adapt to the cubic Si lattice by forming transrotational domains. Each domain arises by the continuous bending of the NiSi lattice, maintaining a close relationship with the substrate structure. The presence of transrotational domains does not cause a roughening of the layer, but instead it improves the structural and electrical stability of the silicide in comparison with a 24 nm-thick layer formed using the same annealing process. These results have relevant implications for the thickness scaling of NiSi layers which are currently used as metallizations of electronic devices. PMID:16186648

Alberti, Alessandra; Bongiorno, Corrado; Cafra, Brunella; Mannino, Giovanni; Rimini, Emanuele; Metzger, Till; Mocuta, Cristian; Kammler, Thorsten; Feudel, Thomas

2005-10-01

361

SH-SAW PROPAGATION IN A PIEZOELECTRIC STRUCTURE WITH VISCOELASTIC LAYER  

E-print Network

93 SH-SAW PROPAGATION IN A PIEZOELECTRIC STRUCTURE WITH VISCOELASTIC LAYER Jing CUI, Jian-ke DU on the properties of the SH-SAW are figured and presented. Keywords: Shear horizontal waves; Piezoelectric to the electronic industry. In 1911, Love [2] analyzed the shear horizontal surface acoustic waves (SH

Wang, Ji

362

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

PubMed

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

Xia, Hong; Hirai, Toshihiro

2010-08-26

363

Energy predictions of turbulent boundary layer induced mid-high frequency structural vibrations  

Microsoft Academic Search

This paper addresses the study of vibrations induced by turbulent boundary layers (TBLs) flowing over plate-like structures. The aim is here to propose a predictive method in order to evaluate the vibroacoustical behaviour of a plate excited by TBL pressure fluctuations. The ultimate goal is to develop tools for predicting internal cabin noise in an aircraft during flight. Hence TBL

M. N. Ichchou; O. Bareille; Y. Jacques

2009-01-01

364

Magnetic resonance imaging of structure and convection in solidifying mushy layers  

Microsoft Academic Search

(Received 25 April 2005 and in revised form 21 September 2005) We have used magnetic resonance imaging to study the structure of and convection within a solidifying mushy layer formed from an aqueous sucrose solution cooled from above. We focus on the situation in which dissolution channels, known as chimneys, are created by the action of buoyancy-driven convection. We have

P ASCALE A USSILLOUS; J. S EDERMAN; LYNN F. G LADDEN; H ERBERT E. H UPPERT; M. G RAE

2006-01-01

365

On simulating the transmission through structures of noise from turbulent boundary layer pressure fluctuations  

Microsoft Academic Search

An experimental study of the transmission of noise through structures subjected to turbulent boundary layer flow is suggested as a prerequisite to the formulation of the simplifying assumptions necessary to theoretical analysis of the problem. Since, for flight vehicles at least, full scale testing is a prohibitively expensive and time consuming process, a simulative approach using suitable scaled models is

F. J. Fahy

1966-01-01

366

Structural considerations of layered and spinel lithiated oxides for lithium ion batteries  

Microsoft Academic Search

Rechargeable lithium batteries that can be assembled in the discharged state with lithiated metal oxide cathodes and carbon anodes are being developed to minimize the safety hazards associated with batteries that use pure metallic lithium anodes. This paper reviews crystallographic aspects of insertion electrodes with layered (LiMO) and spinel (LiMO) structures (M = Co, Ni, Mn, V). The use of

M. M. Thackeray

1995-01-01

367

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

Microsoft Academic Search

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

Stan Schoofs; Ron A. Trompert; Ulrich Hansen

2000-01-01

368

ALPS: The Age-Layered Population Structure for Reducing the Problem of Premature Convergence  

E-print Network

ALPS: The Age-Layered Population Structure for Reducing the Problem of Premature Convergence Algorithms, Design, Performance, Reliability Keywords Age, Computer-Automated Design, Premature Convergence Center Moffett Field, CA hornby@email.arc.nasa.gov ABSTRACT To reduce the problem of premature

Fernandez, Thomas

369

Seasonal benthic nepheloid layer in the Gulf of Riga, Baltic Sea: Sources, structure and geochemical interactions  

Microsoft Academic Search

The sources of particles, as well as the geochemical structure and interfacial exchange were studied for the summer benthic nepheloid layer of the shallow (50m) Gulf of Riga. The material was sampled at nine stations during three cruises of August 2001–2003 with a main focus on the deep waters. Suspended particulate matter (SPM) and its major (N, Si, P, Al,

Aivars Yurkovskis

2005-01-01

370

A flat panel antenna with two-layer structure for satellite broadcasting reception  

Microsoft Academic Search

Technical aspects of flat-panel antennas for DBS reception, namely increasing the bandwidth and decreasing the feeder loss, are studied. In particular, the feeder loss related to substrate thickness is calculated, and it is shown that there is an optimum substrate thickness for which the sum of the conductor loss and the radiation loss is a minimum. A two-layer structure is

Takao Murata; Kenji Ohmaru

1989-01-01

371

FTIR spectroscopy structural analysis of the interaction between Lactobacillus kefir S-layers and metal ions  

NASA Astrophysics Data System (ADS)

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.

Gerbino, E.; Mobili, P.; Tymczyszyn, E.; Fausto, R.; Gómez-Zavaglia, A.

2011-02-01

372

Influences of the spacer layer growth temperature on multilayer InAs\\/GaAs quantum dot structures  

Microsoft Academic Search

The growth temperature of spacer layers (SPLs) is investigated as a means to obtain identical layers for multilayer quantum dot (QD) structures. A 5-layer 1.3-mum InAs\\/GaAs QD structure with 50-nm GaAs SPLs served as a model system. It is found that the growth temperature of the GaAs SPLs has pronounced effects on both the structural and optical properties of the

H. Y. Liu; I. R. Sellers; M. Gutiérrez; K. M. Groom; W. M. Soong; M. Hopkinson; J. P. R. David; R. Beanland; T. J. Badcock; D. J. Mowbray; M. S. Skolnick

2004-01-01

373

a Monte Carlo Study of Carbon Monoxide Layers Adsorbed on Ionic Substrates:. Structures and Phase Transitions  

NASA Astrophysics Data System (ADS)

We have studied the order-disorder phase transitions of carbon monoxide layers adsorbed on sodium chloride and lithium flouride substrates using the Metropolis Monte Carlo method. The simulations have been performed in the temperature range from 5 K to 60 K. At low temperature and monolayer coverage, both of these systems form ordered phases which disorder as the temperature is increased. The transition temperature (Tc) is between 30 K and 35 K for CO/NaCl, and from 40 K to 45 K for CO/LiF. Below Tc, both systems have an ordered p(2 × 1) type structure due to correlated azimuthal orientations. Above Tc, both systems undergo a phase transition to an azimuthally disordered p(1 × 1) structure, i.e. one with no preferred orientation in the surface plane. The heat capacity shows a characteristic divergence at the transition temperature. Coverages of less than a monolayer of the CO/NaCl system have also been studied. The CO molecules are found to aggregate and form islands with an ordered structure in the middle of the islands. These islands also undergo an order-disorder transition but at lower temperatures. Multilayer systems were found to destabilize the p(2 × 1) structure of the bottommost layer in favor of a p(1 × 1) structure with the upper layers adopting the bulk structure.

Vu, Ngoc-Thanh; Jack, David B.

374

Study on Marine Boundary Layer Structure and Clouds over Southern Oceans with Satellite Observations  

NASA Astrophysics Data System (ADS)

Marine boundary layer (MBL) clouds contribute significantly to the energy and moisture budgets of the earth due to their high occurrence and albedo. However, in current weather and climate models, the cloud cover and MBL structure are still poorly represented, especially in regions of persistent marine stratocumulus and Southern oceans. Due to complex interactions of MBL clouds with the vertical structure and turbulence of the MBL, the representation of convective and boundary layer processes are critical to successful simulations of climate. However, these interactions are poorly understood due to the lack of observations over ocean. In this study, 4-year A-train satellite observations over Southern Oceans were used to study the MBL structure, aerosol and cloud. With vertical structure of aerosols from CALIPSO lidar measurements, reliable methods are developed to determine MBL height and the mixing layer height. The characteristics of MBL decoupling structure were further analyzed and its controlling factors were examined. Results showed that the surface wind speed has the major influence on MBL decoupling structure in terms of aerosol loading. And the cloud-aerosol interaction especially the effects of biological aerosol on MBL mixed-phase clouds were also explored. These results highlighted that satellite multi-sensor observations offer an effective way to understand the MBL processes and clouds over the Southern Oceans.

Luo, T.; Wang, Z.

2013-12-01

375

Population Genetic Structure and Origins of Native Hawaiians in the Multiethnic Cohort Study  

PubMed Central

The population genetic structure of Native Hawaiians has yet to be comprehensively studied, and the ancestral origins of Polynesians remain in question. In this study, we utilized high-resolution genome-wide SNP data and mitochondrial genomes of 148 and 160 Native Hawaiians, respectively, to characterize their population structure of the nuclear and mitochondrial genomes, ancestral origins, and population expansion. Native Hawaiians, who self-reported full Native Hawaiian heritage, demonstrated 78% Native Hawaiian, 11.5% European, and 7.8% Asian ancestry with 99% belonging to the B4 mitochondrial haplogroup. The estimated proportions of Native Hawaiian ancestry for those who reported mixed ancestry (i.e. 75% and 50% Native Hawaiian heritage) were found to be consistent with their self-reported heritage. A significant proportion of Melanesian ancestry (mean?=?32%) was estimated in 100% self-reported Native Hawaiians in an ADMIXTURE analysis of Asian, Melanesian, and Native Hawaiian populations of K?=?2, where K denotes the number of ancestral populations. This notable proportion of Melanesian admixture supports the “Slow-Boat” model of migration of ancestral Polynesian populations from East Asia to the Pacific Islands. In addition, approximately 1,300 years ago a single, strong expansion of the Native Hawaiian population was estimated. By providing important insight into the underlying population structure of Native Hawaiians, this study lays the foundation for future genetic association studies of this U.S. minority population. PMID:23144833

Kim, Sung K.; Gignoux, Christopher R.; Wall, Jeffrey D.; Lum-Jones, Annette; Wang, Hansong; Haiman, Christopher A.; Chen, Gary K.; Henderson, Brian E.; Kolonel, Laurence N.; Le Marchand, Loic; Stram, Daniel O.; Saxena, Richa; Cheng, Iona

2012-01-01

376

Endogenous and nonimpact origin of the Arkenu circular structures (al-Kufrah basin—SE Libya)  

NASA Astrophysics Data System (ADS)

The twin Arkenu circular structures (ACS), located in the al-Kufrah basin in southeastern Libya, were previously considered as double impact craters (the "Arkenu craters"). The ACS consist of a NE (Arkenu 1) and a SW structure (Arkenu 2), with approximate diameters of about 10 km. They are characterized by two shallow depressions surrounded by concentric circular ridges and silica-impregnated sedimentary dikes cut by local faults. Our field, petrographic, and textural observations exclude that the ACS have an impact origin. In fact, we did not observe any evidence of shock metamorphism, such as planar deformation features in the quartz grains of the collected samples, and the previously reported "shatter cones" are wind-erosion features in sandstones (ventifacts). Conversely, the ACS should be regarded as a "paired" intrusion of porphyritic stocks of syenitic composition that inject the Nubia Formation and form a rather simple and eroded ring dike complex. Stock emplacement was followed by hydrothermal activity that involved the deposition of massive magnetite-hematite horizons (typical of iron oxide copper-gold deposits). Their origin was nearly coeval with the development of silicified dikes in the surroundings. Plugs of tephritic-phonolitic rocks and lamprophyres (monchiquites) inject the Nubian sandstone along conjugate fracture zones, trending NNW-SSE and NE-SW, that crosscut the structural axis of the basin.

Cigolini, Corrado; di Martino, Mario; Laiolo, Marco; Coppola, Diego; Rossetti, Piergiorgio; Morelli, Marco

2012-11-01

377

Remarkable transition from rocksalt/perovskite layered structure to fluorite/rocksalt layered structure in rapidly cooled Ln2CuO4  

PubMed Central

Lanthanide cuprates of formula Ln2CuO4 exist in two principal forms, T and T? which are renowned for their exhibition at low temperatures of hole and electronic types of superconductivity, respectively. These structures differ primarily in the arrangement of oxygen between the perovskite layers and also in nature of the copper oxygen planes. The Cu-O distance in the T structure (~1.90 Å) is much shorter than the T? (1.97Å), reflecting a transition between partial Cu+ and partial Cu3+ character. In seeking to find compositions that bridge these two structure/electron carrier types, we observed the transition from a T structure to a T? type structure, resulting in the metastable form T? with slightly larger volume but similar character to T?. This transition from T to T? is associated with 5% increase in a and a 5% decrease in c parameters of the tetragonal unit cells, which results in disintegration of ceramic bodies. PMID:23514849

Patabendige, Chami N. K.; Azad, Abul K.; Connor, Paul A.; Rolle, Aurelie; Irvine, John T. S.

2013-01-01

378

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

NASA Astrophysics Data System (ADS)

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.

Kohmatsu, Ryo; Nakagawa, Takeshi; Mizuno, Seigi

2014-10-01

379

Structural properties of ZnO layers deposited on glass substrates by PECVD  

NASA Astrophysics Data System (ADS)

Thin ZnO layers were grown by metal-organic plasma-enhanced CVD (RF - 13.56 MHz) on glass substrates without and with ZnO seed film. The properties of the ZnO layers obtained were studied in dependence of the partial oxygen pressure by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results obtained show that by controlling the partial oxygen pressure during the layer growth one can control the crystallinity and texture of the layers obtained on pure glass substrates. It was found that ZnO layers deposited at low O2 pressure have well-developed grain structures with a predominant c-axis phase and better crystalline quality than that of the samples obtained at high partial oxygen pressure. In the presence of ZnO seed films, the formation of c-axis phase and its quality are less dependent on partial PO2. Nanorods with good alignment and orientated vertically with respect to the substrate surface can be observed in the layers deposited on glass substrates with ZnO seeds and substrate temperature of 400 °C at low content of O2 in the plasma. This behavior is interpreted in the framework of the so-called preferential nucleation and preferential grain growth.

Kitova, S.; Kazakov, R.; Danev, G.

2012-03-01

380

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

NASA Astrophysics Data System (ADS)

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.

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

2014-06-01

381

Structure analysis of 1×1 Cu layer formed on Mo(1 1 0) surface  

NASA Astrophysics Data System (ADS)

The surface structure, epitaxial orientation relationship, and adsorption site for Cu deposited on Mo(1 1 0) surface were studied by reflection high-energy electron diffraction (RHEED) and Li + impact collision ion scattering spectroscopy (Li +-ICISS). The Cu layer less than 1 monolayer thick shows 1×1 structure in RHEED pattern, and the Li +-ICISS measurements indicate that Cu grows by forming a pseudomorphic structure the same as Mo(1 1 0) atomic arrangement. The adsorption site of the Cu atom is a long bridge site, and space between the Cu layer and the Mo(1 1 0) surface is 0.21 nm, which is consistent with that the value expected from the radius of hard sphere model of Cu and Mo atoms.

Kawanowa, H.; Suzuki, J.; Mahara, Y.; Gotoh, Y.; Souda, R.

2005-02-01

382

STRUCTURAL MODELS RELATED TO TRANSPORT PROPERTIES FOR THE DRIED LAYER OF FOOD MATERIALS UNDERGOING FREEZE-DRYING  

Microsoft Academic Search

The values of thermal conductivity and permeability have been presented for the dried layer of raw beef, coffee solutions and sliced as well as mashed apples. A structural model for beef, coffee solution and mashed apple was developed for predicting the permeability of water-vapor flowing through the dried layer. In modeling the porous dried layer was assumed to be a

Yasuyuki Sagara

2001-01-01

383

Geographic population structure analysis of worldwide human populations infers their biogeographical origins.  

PubMed

The search for a method that utilizes biological information to predict humans' place of origin has occupied scientists for millennia. Over the past four decades, scientists have employed genetic data in an effort to achieve this goal but with limited success. While biogeographical algorithms using next-generation sequencing data have achieved an accuracy of 700 km in Europe, they were inaccurate elsewhere. Here we describe the Geographic Population Structure (GPS) algorithm and demonstrate its accuracy with three data sets using 40,000-130,000 SNPs. GPS placed 83% of worldwide individuals in their country of origin. Applied to over 200 Sardinians villagers, GPS placed a quarter of them in their villages and most of the rest within 50 km of their villages. GPS's accuracy and power to infer the biogeography of worldwide individuals down to their country or, in some cases, village, of origin, underscores the promise of admixture-based methods for biogeography and has ramifications for genetic ancestry testing. PMID:24781250

Elhaik, Eran; Tatarinova, Tatiana; Chebotarev, Dmitri; Piras, Ignazio S; Maria Calò, Carla; De Montis, Antonella; Atzori, Manuela; Marini, Monica; Tofanelli, Sergio; Francalacci, Paolo; Pagani, Luca; Tyler-Smith, Chris; Xue, Yali; Cucca, Francesco; Schurr, Theodore G; Gaieski, Jill B; Melendez, Carlalynne; Vilar, Miguel G; Owings, Amanda C; Gómez, Rocío; Fujita, Ricardo; Santos, Fabrício R; Comas, David; Balanovsky, Oleg; Balanovska, Elena; Zalloua, Pierre; Soodyall, Himla; Pitchappan, Ramasamy; Ganeshprasad, Arunkumar; Hammer, Michael; Matisoo-Smith, Lisa; Wells, R Spencer

2014-01-01

384

Geographic population structure analysis of worldwide human populations infers their biogeographical origins  

PubMed Central

The search for a method that utilizes biological information to predict humans’ place of origin has occupied scientists for millennia. Over the past four decades, scientists have employed genetic data in an effort to achieve this goal but with limited success. While biogeographical algorithms using next-generation sequencing data have achieved an accuracy of 700?km in Europe, they were inaccurate elsewhere. Here we describe the Geographic Population Structure (GPS) algorithm and demonstrate its accuracy with three data sets using 40,000–130,000 SNPs. GPS placed 83% of worldwide individuals in their country of origin. Applied to over 200 Sardinians villagers, GPS placed a quarter of them in their villages and most of the rest within 50?km of their villages. GPS’s accuracy and power to infer the biogeography of worldwide individuals down to their country or, in some cases, village, of origin, underscores the promise of admixture-based methods for biogeography and has ramifications for genetic ancestry testing. PMID:24781250

Elhaik, Eran; Tatarinova, Tatiana; Chebotarev, Dmitri; Piras, Ignazio S.; Maria Calo, Carla; De Montis, Antonella; Atzori, Manuela; Marini, Monica; Tofanelli, Sergio; Francalacci, Paolo; Pagani, Luca; Tyler-Smith, Chris; Xue, Yali; Cucca, Francesco; Schurr, Theodore G.; Gaieski, Jill B.; Melendez, Carlalynne; Vilar, Miguel G.; Owings, Amanda C.; Gomez, Rocio; Fujita, Ricardo; Santos, Fabricio R.; Comas, David; Balanovsky, Oleg; Balanovska, Elena; Zalloua, Pierre; Soodyall, Himla; Pitchappan, Ramasamy; GaneshPrasad, ArunKumar; Hammer, Michael; Matisoo-Smith, Lisa; Wells, R. Spencer; Acosta, Oscar; Adhikarla, Syama; Adler, Christina J.; Bertranpetit, Jaume; Clarke, Andrew C.; Cooper, Alan; Der Sarkissian, Clio S. I.; Haak, Wolfgang; Haber, Marc; Jin, Li; Kaplan, Matthew E.; Li, Hui; Li, Shilin; Martínez-Cruz, Begoña; Merchant, Nirav C.; Mitchell, John R.; Parida, Laxmi; Platt, Daniel E.; Quintana-Murci, Lluis; Renfrew, Colin; Lacerda, Daniela R.; Royyuru, Ajay K.; Sandoval, Jose Raul; Santhakumari, Arun Varatharajan; Soria Hernanz, David F.; Swamikrishnan, Pandikumar; Ziegle, Janet S.

2014-01-01

385

Studies of the boundary layer structure in turbulent Rayleigh-B'enard convection  

NASA Astrophysics Data System (ADS)

The structure of the laminar boundary layer in turbulent Rayleigh-B'enard convection is studied by three-dimensional direct numerical simulations. We consider convection in a cylindrical cell at an aspect ratio of one for Rayleigh numbers of 3x10^9 and 3x10^10 and at a Prandtl number of Pr=0.7. The laminar boundary layers of the velocity and temperature fields are found to deviate from the classical prediction of the Prandtl-Blasius-Pohlhausen theory, even when a dynamical rescaling of the data with an instantaneously defined thickness scale is performed in a plane that is aligned with the instantaneous orientation of the large-scale wind. We show on the basis of the existing numerical data that none of the assumptions that enter this classical solution are satisfied. Three-dimensional structures are present and important, the large-scale wind changes direction and amplitude and the pressure gradients are found to fluctuate significantly. The local boundary layer structure is compared with perturbative expansions of the boundary layer equations of forced and natural convection.

Schumacher, Joerg; Shi, Nan; Emran, Mohammad

2011-11-01

386

Self-assembled structurally complex double-layers of 3-HPLN on Cu(111)  

NASA Astrophysics Data System (ADS)

The self-assembly of 3-Hydroxyphenalenone (3-HPLN) on metal surface has been studied with scanning tunneling microscopy and first principles theory. 3-HPLN belongs to the group of topological ferroelectric organics, where the electric polarization is related to the hydrogen bonds between the molecules. It is observed that the structure of the self-assembled 2D networks is strongly dependent of the substrate material and the preparation conditions. Of particular interest in this presentation is the chiral Kagome lattices of 3-HPLN observed after annealing on Cu(111). A unique feature of the molecular network is the CH-pi bond formation between flat-lying molecules and molecules attached perpendicular to the surface. It will be demonstrated that the addition of a second layer on the first monolayer of 3-HPLN triggers a structural reorganization in the first layer, to form a complex double layer structure that is not merely the addition of two single layers. The chiral pores in the film can serve as a host or a template for metal nanoparticles, such as Fe. The so-obtained hybrid nanostructures might be a useful milestone towards self-asembled metal-organics multiferroics.

Beniwal, Sumit; Kunkel, Donna; Hooper, James; Simpson, Scott; Zurek, Eva; Enders, Axel

2013-03-01

387

Upper layer structure and variability of the Antarctic Circumpolar Current in the Drake Passage  

NASA Astrophysics Data System (ADS)

The spatiotemporal variability of the Antarctic Circumpolar Current (ACC) structure in the upper 100-800 m layer is analyzed at two sections in the Drake Passage. The existence of the Subantarctic and Polar Current superjets, formed due to the confluence of a few jets together, is confirmed. Peak eddy activity at the periphery of all the ACC jets is revealed, which demonstates intensive meridional eddy exchange of properties across the Passage. The ACC jets are strongly coherent in the vertical direction. The ACC upper layer transport intensifies over bottom relief rises because of jet acceleration during their crossing.

Gladyshev, S. V.

2014-07-01

388

Origin of the energy level alignment at organic/organic interfaces: The role of structural defects  

NASA Astrophysics Data System (ADS)

In this paper, the electronic properties of as-deposited and N2-exposedCuPc/F16CuPc interface, a prototype system for organic photovoltaic applications, are investigated by using ultralow background, high-sensitivity photoemission spectroscopy. It is found that (i) N2 exposure significantly modifies the energy level alignment (ELA) at the interface between CuPc and F16CuPc layer and (ii) the direction of the N2-induced energy level shift of the CuPc depends on the position of the Fermi level (EF) in the CuPc highest occupied molecular orbital-lowest unoccupied molecular orbital gap of the as-deposited film. These observations are related to the changes in the density of gap states (DOGS) produced by structural imperfections in the molecular packing geometry, as introduced by the N2 penetration into the CuPc layer. This result demonstrates the key role of structure-induced DOGS in controlling the ELA at organic/organic interfaces.

Bussolotti, Fabio; Yang, Jinpeng; Hinderhofer, Alexander; Huang, Yuli; Chen, Wei; Kera, Satoshi; Wee, Andrew T. S.; Ueno, Nobuo

2014-03-01

389

Red Wing Creek structure, North Dakota: Petrographical and geochemical studies, and confirmation of impact origin  

NASA Astrophysics Data System (ADS)

The 9 km diameter Red Wing Creek structure, North Dakota, is located within the oil-rich Williston Basin at 47°36'N and 103°33'W. Earlier geophysical studies indicated that this subsurface structure has a central uplift, surrounded by an annular crater moat, and a raised rim. Breccias were encountered during drilling between ˜2000 and 2800 m depth in the central uplift area, and the presence of shatter cone fragments in drill core samples was suggested to indicate an impact origin of the Red Wing Creek structure. We studied the petrographic and geochemical characteristics of samples of well cuttings from two boreholes at the center of the structure: the True Oil 22-27 Burlington Northern and True Oil 11-27 Burlington Northern wells. We found planar deformation features (PDFs) in quartz with up to three sets of different crystallographic orientations in sandstone- and siltstone-dominated samples from the True Oil 11-27 borehole. U-stage measurements of the crystallographic orientations of the PDFs showed the occurrence of the shock-characteristic (0001), ? and ? orientations, with a dominance of (0001) and ? orientations. The relative frequencies of the orientations indicate a shock pressure of at least 12-20 GPa. These results provide unambiguous evidence for shock metamorphism at Red Wing Creek and confirm that the structure was formed by impact.

Koeberl, Christian; Reimold, Wolf Uwe; Brandi, Dion

1996-05-01

390

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

NASA Astrophysics Data System (ADS)

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.

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

1993-12-01

391

Origin of fine structure of the giant dipole resonance in sd-shell nuclei  

E-print Network

A set of high resolution zero-degree inelastic proton scattering data on 24Mg, 28Si, 32S, and 40Ca provides new insight into the long-standing puzzle of the origin of fragmentation of the Giant Dipole Resonance (GDR) in sd-shell nuclei. Understanding is provided by state-of-the-art theoretical Random Phase Approximation (RPA) calculatios for deformed nuclei using for the first time a realistic nucleon-nucleon interaction derived from the Argonne V18 potential with the unitary correlation operator method and supplemented by a phenomenological three-nucleon contact interaction. A wavelet analysis allows to extract significant scales both in the data and calculations characterizing the fine structure of the GDR. The fair agreement supports that the fine structure arises from ground-state deformation driven by alpha clustering.

R. W. Fearick; B. Erler; H. Matsubara; P. von Neumann-Cosel; A. Richter; R. Roth; A. Tamii

2014-09-03

392

Towards precise defect control in layered oxide structures by using oxide molecular beam epitaxy  

PubMed Central

Summary In this paper we present the atomic-layer-by-layer oxide molecular beam epitaxy (ALL-oxide MBE) which has been recently installed in the Max-Planck Institute for Solid State Research and we report on its present status, providing some examples that demonstrate its successful application in the synthesis of different layered oxides, with particular reference to superconducting La2CuO4 and insulator-to-metal La2? xSrxNiO4. We briefly review the ALL-oxide MBE technique and its unique capabilities in the deposition of atomically smooth single-crystal thin films of various complex oxides, artificial compounds and heterostructures, introducing our goal of pursuing a deep investigation of such systems with particular emphasis on structural defects, with the aim of tailoring their functional properties by precise defects control. PMID:24995148

Baiutti, Federico; Christiani, Georg

2014-01-01

393

Instability of Myelin Tubes under Dehydration: deswelling of layered cylindrical structures  

E-print Network

We report experimental observations of an undulational instability of myelin figures. Motivated by this, we examine theoretically the deformation and possible instability of concentric, cylindrical, multi-lamellar membrane structures. Under conditions of osmotic stress (swelling or dehydration), we find a stable, deformed state in which the layer deformation is given by \\delta R ~ r^{\\sqrt{B_A/(hB)}}, where B_A is the area compression modulus, B is the inter-layer compression modulus, and h is the repeat distance of layers. Also, above a finite threshold of dehydration (or osmotic stress), we find that the system becomes unstable to undulations, first with a characteristic wavelength of order \\sqrt{xi d_0}, where xi is the standard smectic penetration depth and d_0 is the thickness of dehydrated region.

C. -M. Chen; C. F. Schmidt; P. D. Olmsted; F. C. MacKintosh

2001-08-27

394

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

NASA Technical Reports Server (NTRS)

The gas dynamic structures of the transport shock and the downstream collisional relaxation layer are evaluated for partially ionized monatomic gases. Elastic and inelastic collisional nonequilibrium effects are taken into consideration. Three electronic levels are accounted for in the microscopic model of the atom. Nonequilibrium processes with respect to population of levels and species plus temperature are considered. By using an asymptotic technique the shock morphology is found on a continuum flow basis. The asymptotic procedure gives two distinct layers in which the nonequilibrium effects to be considered are different. A transport shock appears as the inner solution to an outer collisional relaxation layer in which the gas reaches local equilibrium. A family of numerical examples is displayed for different flow regimes. Argon and helium models are used in these examples.

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

1972-01-01

395

Highly Insulating Glazing Systems using Non-Structural Center Glazing Layers  

SciTech Connect

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.

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

2008-04-09

396

Stacking Sequence and Layer-Type Changes in Topologically Close-Packed Structures.  

NASA Astrophysics Data System (ADS)

Crystal structure changes in several A _3B-type quasi-binary alloy series, involving Fe, Co, Ni, Cu, Pd and Pt as the A-component elements and Ti, V, Zr and Nb as the B-component elements, have been explored experimentally using X-ray and electron diffraction. The aim of this work was to discover various stacking sequence and ordered layer-type changes in close-packed structures. Our experimental data further confirm that the hexagonality of the stacking always increases in these alloy series as either the electron concentration (e/a) of a given alloy, or the size ratio (R_{rm B} /R_{rm A}) between two types of atoms is increased. This trend is consistent with the results observed by earlier workers in similar alloy systems. Interestingly, we also note that these observed trends are independent of the component, either the A- or B-, and of the type of stacking layers, either the triangularly-ordered (T-type) or the rectangularly -ordered (R-type), involved in the substitutional change. In addition, two new paths of stacking sequence changes have been established through our experimental work, namely, 3 to 3 to 2 and 1 to 5 to 2. An Ising model has been explored to discover if the observed stacking sequence changes can be interpreted in terms of interactions between a few adjacent layers. Using these interactions as phenomenological parameters, a stacking stability map was constructed showing the arrangement of predicted ground state phases on a two-dimensional parameter -plane. Comparing this map with the known experimental data, it was found that the position and the extent of phase regions in the derived map are rather similar to several real composition phase diagrams. Therefore, such a map can provide useful information about the stacking sequence changes (e.g., allowed or excluded stacking arrangements for the neighboring phases) to be expected in an actual alloy phase diagrams. In a different approach, a total energy calculation utilizing the linearized muffin-tin orbitals (LMTO) method has been carried out in order to study the relative stabilities between close-packed structures involving differently-ordered stacking layers. Two binary compounds were selected for this investigation. They are Co_3Ti and Ni_3V, and they involve, respectively, the T-type and R-type layers. Correct structures and lattice parameters were obtained for both alloys. The derived structural preferences were further analyzed in terms of the calculation of density of states. This suggests that structures built up from the R-type layers tend to exist in a relatively higher e/a region.

Pei, Shiyou

1988-12-01

397

Physical origins of the high structural stability of CLN025 with only ten residues  

NASA Astrophysics Data System (ADS)

CLN025, a peptide with only 10 residues, folds into a specific ?-hairpin structure (this is referred to as "native structure"). Here we investigate the stabilization mechanism for CLN025 using our free-energy function F. F comprises two components, the hydration entropy and the component related to the energetic dehydration effect. The former component is calculated using the hybrid of the angle-dependent integral equation theory (ADIET) and our recently developed morphometric approach. The ADIET is a statistical-mechanical theory applied to a molecular model for water. The latter component is calculated in a simple but judicious manner accounting for physically the most important factors: the break of polypeptide-water hydrogen bonds and formation of polypeptide intramolecular hydrogen bonds upon structural change to a more compact one. We consider the native structure, compact nonnative structures newly generated, and a set of random coils mimicking the unfolded state. F and its components are calculated for all the structures considered. The loss of the polypeptide conformational entropy upon structural transition from the unfolded state to a compact structure is also estimated using a simple but physically reasonable manner. We find that the key factor is the water-entropy gain upon folding originating primarily from an increase in the total volume available to the translational displacement of water molecules in the system, which is followed by the reduction of water crowding. The amino-acid sequence of CLN025 enables it not only to closely pack the backbone and side chains including those with large aromatic groups but also to assure the intramolecular hydrogen bonding upon burial of a donor and an acceptor when the backbone forms the native structure. The assurance leads to essentially no enthalpy increase upon folding. The close packing brings a water-entropy gain which is large enough to surpass the conformational-entropy loss. By contrast, it is not possible for the design template of CLN025, GPM12, to realize the same type of structure formation. There are significantly many compact structures which are equally stable in terms of F, and due to the conformational-entropy effect, the unfolded state is favorably stabilized.

Yasuda, Satoshi; Hayashi, Tomohiko; Kinoshita, Masahiro

2014-09-01

398

Geology of coronae and domal structures on Venus and models of their origin  

SciTech Connect

Coronae (160 to 670 km across) and domal structures (greater than 1000 km across) are complex topographic highs on Venus that were affected by volcanic and topographic processes. The geology of coronae and a major domal structure, Beta Regio, are documented using Pioneer Venus, Arecibo, and Venera 15/16 data. The evolution and possible models of origin of these features are also investigated. Beta Regio is a 2000 x 2300 km topographic high located in the equatorial region of Venus that rises over 5 km above the surrounding region. Within Beta Regio lie two large volcanic shields, Theia and Rhea Mons. Coronae are circular to elongate structures on Venus, characterized by an annulus of concentric compressional ridges and relatively raised topography surrounded by a peripheral trough. Volcanic domes, flows and edifices, as well as tectonic lineaments characterize the interiors of coronae. Thirty one coronae were detected on Venus. Two analytical models were developed that are consistent with the general characteristics and evolution of coronae: hotspot or rising mantle diapir model and sinking mantle diapir model. Coronae appear to be part of a continuum of thermally produced features on Venus, along with volcanic complexes and domal structures such as Beta Regio.

Stofan, E.R.

1989-01-01

399

Can magnetism-assisted quasiperiodic structures in Russell-FeS `bubbles' offer a quantum coherent origin of life?  

E-print Network

This paper seeks to expand the scope of the alkaline seepage site hydrothermal mound scenario of Russell et al, by appealing to its wider canvas for hypothesizing self-assembly of gregite clusters via interplay of forces within the gel phase of FeS membranes: directed heat transport a la Rayleigh-Benard convection for dissociation, vs oriented attachment (small clusters) and magnetic forces (large clusters) for association, the latter assisted by magnetic mound constituents. The directed movement of tiny clusters through cluster layers are reminiscent of processes like budding, molecular motors, pre-RNA world on the lines of Cairns-Smith's hypothesis, and optical polarity. Higher rate of (soft) multinucleate formation vs growth rate of (rigid) microcrystals, correlates with icosahedral (forbidden crystallographically!) framboidal morphology. This pattern indicates a link to phylotaxis, thus reinforcing the quasi-periodicity connection which can provide a natural access to features like surface limit, anomalous transport and low thermal conductivity, while facilitating diffusion through clusters. And magnetism offers a hierarchy of features: primordial multicellularity; phase correlations of assembled molecules; overcoming thermal decoherence. These dynamical nested structures offer possibilities for iterative computations, adaptive learning, and coherent quantum searches. The link between enzymatic FeS clusters and the Hadean ocean floor is seen as part of a larger conceptual framework uncovering a role for Magnetism and the Origin of Life.

Gargi Mitra--Delmotte; A. N. Mitra

2007-10-01

400

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

SciTech Connect

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.

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

2012-07-01

401

Local orderings in long-range-disordered bismuth-layered intergrowth structure  

NASA Astrophysics Data System (ADS)

A series of intergrowth bismuth-layered (Bi3TiNbO9)2(Bi4Ti3O12) (223) ceramics were prepared by conventional solid-state reaction to study the characteristics of the local orderings in long-range-disordered intergrowth structures. High-resolution high-angle annular dark-field (HAADF) imaging reveals the intergrowth structure composed of mixtures of -23-, -223-, -2223- and -22- sequences, while the -223- structure is the thermodynamic stable state of this intergrowth system. It was confirmed by the crystals of recurrent -223- structure prepared by self-flux method and the nature of the local ordering was discussed from their differences in repeating units. The statistics show that when repeating units reach 4 or higher, the independent -223- intergrowth ordering emerges clearly among the competing associated orderings. We infer it is the kinetic factor that induces local compositional variance to result in long-range disordered intergrowth structures.

Zhang, Faqiang; Li, Yongxiang; Gu, Hui; Gao, Xiang

2014-04-01

402

Atmospheric boundary-layer structure observed during a haze event due to forest-fire smoke  

NASA Astrophysics Data System (ADS)

During a haze event in Baltimore, U.S.A. from July 6 to 8, 2002, smoke from forest fires in the Québec region (Canada), degraded air quality and impacted upon local climate, decreasing solar radiation and air temperature. The smoke particles in and above the atmospheric boundary layer (ABL) served as a tracer and provided a unique opportunity to investigate the ABL structure, especially entrainment. Elastic backscatter lidar measurements taken during the haze event distinctly reveal the downward sweeps (or wisps) of smoke-laden air from the free atmosphere into the ABL. Visualisations of mechanisms such as dry convection, the entrainment process, detrainment, coherent entrainment structures, and mixing inside the ABL, are presented. Thermals overshooting at the ABL top are shown to create disturbances in the form of gravity waves in the free atmosphere aloft, as evidenced by a corresponding ripple structure at the bottom of the smoke layer. Lidar data, aerosol ground-based measurements and supporting meteorological data are used to link free atmosphere, mixed-layer and ground-level aerosols. During the peak period of the haze event (July 7, 2002), the correlation between time series of elastic backscatter lidar data within the mixed layer and the scattering coefficient from a nephelometer at ground level was found to be high (R=0.96 for z =324 m, and R=0.89 for z=504 m). Ground-level aerosol concentration was at a maximum about 2 h after the smoke layer intersected with the growing ABL, confirming that the wisps do not initially reach the ground.

Pahlow, Markus; Kleissl, Jan; Parlange, Marc B.

403

Comparison of Structural Models of Mixed-Layer Illite\\/Smectite and Reaction Mechanisms of Smectite Illitization  

Microsoft Academic Search

This paper compares mechanisms of the reaction of smectite to illite, in light of structural models for interstratified illite\\/smectite (US). The crystal structure of US has been described previously by a nonpolar and polar 2:1 layer model. In a nonpolar model, individual 2:1 layers are chemically homogeneous, whereas a polar model assumes a 2: l layer can have a smectite

Stephen P. Altaner; ROBERT E YLAGAN

1997-01-01

404

Dynamical robustness of the conductivity of ultracold bosons confined in layered structures  

NASA Astrophysics Data System (ADS)

We study dynamical conductivity of strongly correlated bosons loaded in an optical lattice with restricted geometry in which gauge fields are present. We show that dynamics influenced by the uniform synthetic magnetic field combined with layered lattice structures changes into rich insulator-metallic behavior in the strongly correlated regime. Especially, the amplitude of optical conductivity for a given frequency is a nonmonotonous function of the number of layers L. In particular, conductivity for frequency corresponding to on-site interaction energy can abruptly vanish for a special number of applied layers. Moreover, such an insulating behavior is stable in the whole range of parameters in the Mott phase. This robustness arises from the complex gaplike behavior or from Dirac-like physics reflected in the quasiparticle energy spectra. Furthermore we show that a large interlayer tunneling anisotropy destabilizes the absence of conducting state. We also investigate the critical conductivity on the Mott-insulator-superfluid phase boundary and show the correspondence between the number of Hofstadter subbands and the number of layers. The obtained results also reveal that the value of critical conductivity gradually goes to zero when a three-dimensional system is approached. The experimental setup for generation of layered optical lattices is also proposed.

Sajna, A. S.; Polak, T. P.

2014-10-01

405

SH surface acoustic wave propagation in a cylindrically layered piezomagnetic/piezoelectric structure.  

PubMed

SH surface acoustic wave (SH-SAW) propagation in a cylindrically layered magneto-electro-elastic structure is investigated analytically, where a piezomagnetic (or piezoelectric) material layer is bonded to a piezoelectric (or piezomagnetic) substrate. By means of transformation, the governing equations of the coupled waves are reduced to Bessel equation and Laplace equation. The boundary conditions imply that the displacements, shear stresses, electric potential, and electric displacements are continuous across the interface between the layer and the substrate together with the traction free at the surface of the layer. The magneto-electrically open and shorted conditions at cylindrical surface are taken to solve the problem. The phase velocity is numerically calculated for different thickness of the layer and wavenumber for piezomagnetic ceramics CoFe(2)O(4) and piezoelectric ceramics BaTiO(3). The effects of magnetic permeability on propagation properties of SH-SAW are discussed in detail. The distributions of displacement, magnetic potential and magneto-electromechanical coupling factor are also figured and discussed. PMID:18922557

Du, Jianke; Xian, Kai; Wang, Ji

2009-01-01

406

Electrostatic soliton and double layer structures in unmagnetized degenerate pair plasmas  

SciTech Connect

The acoustic solitons and double layers are studied in unmagnetized quantum electron-positron plasmas in the presence of stationary ions. The quantum hydrodynamic model is employed and reductive perturbation method is used to derive the Korteweg-de Vries (KdV) and extended KdV equations for solitons and double layers, respectively. It is found that in the linear limit both slow acoustic and fast Langmuir waves can propagate in such type of quantum plasmas like in classical pair-ion or pair plasmas. The amplitude and width of the electrostatic solitons are found to be decreasing with the increase in concentration of positrons (or decrease in the concentration of ions) in degenerate electron-positron-ion plasmas. It is found that only rarefactive double layer can exist in such plasmas which depend on various parameters. The dependence of double layer structure on ion concentration and quantum diffraction effects of electrons and positrons are also discussed. The results are also elaborated graphically by considering dense plasma parameters in the outer layers of astrophysical objects such as white dwarfs and neutron stars.

Mahmood, S. [Theoretical Plasma Physics Division (TPPD), PINSTECH, P.O. Nilore, Islamabad 44000 (Pakistan); National Centre for Physics, Quaid-i-Azam University Campus, Shahdra Valley Road, Islamabad 44000 (Pakistan); Department of Physics and Applied Mathematics (DPAM), PIEAS, P.O. Nilore, Islamabad 44000 (Pakistan); Khan, S. A. [National Centre for Physics, Quaid-i-Azam University Campus, Shahdra Valley Road, Islamabad 44000 (Pakistan); Department of Physics, COMSATS Institute of Information Technology (CIIT), Islamabad 44000 (Pakistan); Ur-Rehman, H. [Theoretical Plasma Physics Division (TPPD), PINSTECH, P.O. Nilore, Islamabad 44000 (Pakistan); Department of Physics and Applied Mathematics (DPAM), PIEAS, P.O. Nilore, Islamabad 44000 (Pakistan)

2010-11-15

407

Interface structure and flux laws in a natural double-diffusive layering  

NASA Astrophysics Data System (ADS)

The diffusive regime of double-diffusive convection generates staircases consisting of thin high-gradient interfaces sandwiched between convectively mixed layers. Simultaneous microstructure measurements of both temperature and conductivity from the staircases in Lake Kivu are used to test flux laws and theoretical models for double diffusion. Density ratios in Lake Kivu are between one and ten and mixed layer thicknesses on average 0.7 m. The larger interface thickness of temperature (average 9 cm) compared to dissolved substances (6 cm) confirms the boundary-layer structure of the interface. Our observations suggest that the boundary-layer break-off cannot be characterized by a single critical boundary-layer Rayleigh number, but occurs within a range of O(102) to O(104). Heat flux parameterizations which assume that the Nusselt number follows a power law increase with the Rayleigh number Ra are tested for their exponent ?. In contrast to the standard estimate ? = 1/3, we found ? = 0.20 ± 0.03 for density ratios between two and six. Therefore, we suggest a correction of heat flux estimates which are based on ? = 1/3. The magnitude of the correction depends on Ra in the system of interest. For Lake Kivu (average heat flux 0.10 W m-2) with Ra = O(108), corrections are marginal. In the Arctic Ocean with Ra = O(108) to O(1012), however, heat fluxes can be overestimated by a factor of four.

Sommer, Tobias; Carpenter, Jeffrey R.; Schmid, Martin; Lueck, Rolf G.; Schurter, Michael; Wüest, Alfred

2013-11-01

408

Analysis of cloud layer structure in Shouxian, China using RS92 radiosonde aided by 95 GHz cloud radar  

E-print Network

Analysis of cloud layer structure in Shouxian, China using RS92 radiosonde aided by 95 GHz cloud to analyze cloud vertical structure over this area by taking advantage of the first direct measurements of cloud vertical layers from the 95 GHz radar. Singlelayer, twolayer, and threelayer clouds account for 28

Li, Zhanqing

409

Water ice permafrost on Mars: Layering structure and subsurface distribution according to HEND/Odyssey and MOLA/MGS data  

E-print Network

Water ice permafrost on Mars: Layering structure and subsurface distribution according to HEND. [1] To elucidate the nature of permafrost in the shallow subsurface of Mars, we analyze jointly: Mitrofanov, I. G., et al. (2007), Water ice permafrost on Mars: Layering structure and subsurface

Zuber, Maria

410

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

PubMed

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

Sundberg, Pia; Karppinen, Maarit

2014-01-01

411

The evolution of electronic structure in few-layer graphene revealed by optical spectroscopy  

PubMed Central

The massless Dirac spectrum of electrons in single-layer graphene has been thoroughly studied both theoretically and experimentally. Although a subject of considerable theoretical interest, experimental investigations of the richer electronic structure of few-layer graphene (FLG) have been limited. Here we examine FLG graphene crystals with Bernal stacking of layer thicknesses N = 1,2,3,…8 prepared using the mechanical exfoliation technique. For each layer thickness N, infrared conductivity measurements over the spectral range of 0.2–1.0 eV have been performed and reveal a distinctive band structure, with different conductivity peaks present below 0.5 eV and a relatively flat spectrum at higher photon energies. The principal transitions exhibit a systematic energy-scaling behavior with N. These observations are explained within a unified zone-folding scheme that generates the electronic states for all FLG materials from that of the bulk 3D graphite crystal through imposition of appropriate boundary conditions. Using the Kubo formula, we find that the complete infrared conductivity spectra for the different FLG crystals can be reproduced reasonably well within the framework a tight-binding model. PMID:20696939

Mak, Kin Fai; Sfeir, Matthew Y.; Misewich, James A.; Heinz, Tony F.

2010-01-01

412