WorldWideScience

Sample records for stable low-work-function surfaces

  1. Generalised coexistence of a low work function and a stable surface : CaAl4 and BaAuIn3

    NARCIS (Netherlands)

    Uijttewaal, M. A.; de Wijs, G. A.; de Groot, R. A.

    2006-01-01

    Cathodes are used in many devices ranging from microwave ovens to organic light-emitting diodes (OLEDs). Crucial materials properties are a low work function (Phi) and a (relatively) stable surface. The relation between the two was not clear for more-complex metals. Our previous paper [M.A.

  2. Low work function of the Ca2N surface

    NARCIS (Netherlands)

    Uijttewaal, M.A.; de Wijs, G. A.; Groot, R.A. de

    2004-01-01

    Polymer diodes require cathodes that do not corrode the polymer but do have low work function to minimize the electron injection barrier. First-principles calculations demonstrate that the work function of the (1000) surface of the compound Ca2N is half an eV lower than that of the elemental metal

  3. Dithiocarbamate Self-Assembled Monolayers as Efficient Surface Modifiers for Low Work Function Noble Metals

    Energy Technology Data Exchange (ETDEWEB)

    Meyer, Dominik; Schäfer, Tobias; Schulz, Philip; Jung, Sebastian; Rittich, Julia; Mokros, Daniel; Segger, Ingolf; Maercks, Franziska; Effertz, Christian; Mazzarello, Riccardo; Wuttig, Matthias

    2016-09-06

    Tuning the work function of the electrode is one of the crucial steps to improve charge extraction in organic electronic devices. Here, we show that N,N-dialkyl dithiocarbamates (DTC) can be effectively employed to produce low work function noble metal electrodes. Work functions between 3.1 and 3.5 eV are observed for all metals investigated (Cu, Ag, and Au). Ultraviolet photoemission spectroscopy (UPS) reveals a maximum decrease in work function by 2.1 eV as compared to the bare metal surface. Electronic structure calculations elucidate how the complex interplay between intrinsic dipoles and dipoles induced by bond formation generates such large work function shifts. Subsequently, we quantify the improvement in contact resistance of organic thin film transistor devices with DTC coated source and drain electrodes. These findings demonstrate that DTC molecules can be employed as universal surface modifiers to produce stable electrodes for electron injection in high performance hybrid organic optoelectronics.

  4. Photoemission from Low Work Function Coated Metal Surfaces A Comparison of Theory to Experiment

    CERN Document Server

    Jensen, Kevin; Moody, Nathan A

    2005-01-01

    The development of rugged and/or self rejuvenating photocathodes with high quantum efficiency (QE) using the longest wavelength drive laser is of paramount importance for RF photo-injectors for high power FELs and accelerators. We report on our program to develop advanced photocathodes and to develop and validate models of photoemission from coated metals to analyze experimental data,* provide emission models usable by beam simulation codes,** and project performance. The model accounts for the effects of laser heating, thermal evolution, surface conditions, laser parameters, and material characteristics, and predicts current distribution and QE. The photoemission and QE from metals and dispenser photocathodes is evaluated: the later introduces complications such as coverage non-uniformity and field enhancement. The performance of the models is compared to our experimental results for dispenser photocathodes and cesiated surfaces (e.g., tungsten, silver, etc.) in which the time-dependent models are shown to a...

  5. Fabrication and Measurement of Low Work Function Cesiated Dispenser Photocathodes

    CERN Document Server

    Moody, Nathan A; Jensen, Kevin

    2005-01-01

    Photoinjector performance is a limiting factor in the continued development of high powered FELs and electron beam-based accelerators. Presently available photocathodes are plagued with limited efficiency and short lifetime in an RF-gun environment, due to contamination or evaporation of a photosensitive surface layer. An ideal photocathode should have high efficiency at long wavelengths, long lifetime in practical vacuum environments, and prompt emission. Cathodes with high efficiency typically have limited lifetime, and vice versa, and the needs of the photocathode are generally at odds with those of the drive laser. A potential solution is the low work function dispenser cathode, where lifetime issues are overcome by periodic in situ regeneration that restores the photosensitive surface layer, analogous to those used in the microwave power tube industry. This work reports on the fabrication techniques and performance of cesiated metal photocathodes and cesiated dispenser cathodes, with a focus on understan...

  6. Systems and methods for producing low work function electrodes

    Science.gov (United States)

    Kippelen, Bernard; Fuentes-Hernandez, Canek; Zhou, Yinhua; Kahn, Antoine; Meyer, Jens; Shim, Jae Won; Marder, Seth R.

    2015-07-07

    According to an exemplary embodiment of the invention, systems and methods are provided for producing low work function electrodes. According to an exemplary embodiment, a method is provided for reducing a work function of an electrode. The method includes applying, to at least a portion of the electrode, a solution comprising a Lewis basic oligomer or polymer; and based at least in part on applying the solution, forming an ultra-thin layer on a surface of the electrode, wherein the ultra-thin layer reduces the work function associated with the electrode by greater than 0.5 eV. According to another exemplary embodiment of the invention, a device is provided. The device includes a semiconductor; at least one electrode disposed adjacent to the semiconductor and configured to transport electrons in or out of the semiconductor.

  7. Study of Low Work Function Materials for Hot Cavity Resonance Ionization Laser Ion Sources

    CERN Document Server

    Catherall, R; Fedosseev, V; Marsh, B; Mattolat, C; Menna, Mariano; Österdahl, F; Raeder, S; Schwellnus, F; Stora, T; Wendt, K; CERN. Geneva. AB Department

    2008-01-01

    The selectivity of a hot cavity resonance ionization laser ion source (RILIS) is most often limited by contributions from competing surface ionization on the hot walls of the ionization cavity. In this article we present investigations on the properties of designated high-temperature, low-work function materials regarding their performance and suitability as cavity material for RILIS. Tungsten test cavities, impregnated with a mixture of barium oxide and strontium oxide (BaOSrO on W), or alternatively gadolinium hexaboride (GdB6) were studied in comparison to a standard tungsten RILIS cavity as being routinely used for hot cavity laser ionization at ISOLDE. Measurement campaigns took place at the off-line mass separators at ISOLDE / CERN, Geneva and RISIKO / University of Mainz.

  8. Study of low work function materials for hot cavity resonance ionization laser ion sources

    CERN Document Server

    Schwellnus, F; Crepieux, B; Fedosseev, V N; Marsh, B A; Mattolat, Ch; Menna, M; Österdahl, F K; Raeder, S; Stora, T; Wendta, K

    2009-01-01

    The selectivity of a hot cavity resonance ionization laser ion source (RILIS) is most often limited by contributions from competing surface ionization of the hot walls of the ionization cavity. In this article we present investigations on the properties of designated high temperature, low work function materials regarding their performance and suitability as cavity material for RILIS. Tungsten test cavities, impregnated with a mixture of barium oxide and strontium oxide (BaOSrO on W), or alternatively gadolinium hexaboride (GdB6) were studied in comparison to a standard tungsten RILIS cavity as being routinely used for hot cavity laser ionization at ISOLDE. Measurement campaigns took place at the off-line mass separators at ISOLDE/CERN, Geneva and RISIKO/University of Mainz.

  9. VLSI-compatible carbon nanotube doping technique with low work-function metal oxides.

    Science.gov (United States)

    Suriyasena Liyanage, Luckshitha; Xu, Xiaoqing; Pitner, Greg; Bao, Zhenan; Wong, H-S Philip

    2014-01-01

    Single-wall carbon nanotubes (SWCNTs) have great potential to become the channel material for future high-speed transistor technology. However, as-made carbon nanotube field effect transistors (CNFETs) are p-type in ambient, and a consistent and reproducible n-type carbon nanotube (CNT) doping technique has yet to be realized. In addition, for very large scale integration (VLSI) of CNT transistors, it is imperative to use a solid-state method that can be applied on the wafer scale. Herein we present a novel, VLSI-compatible doping technique to fabricate n-type CNT transistors using low work-function metal oxides as gate dielectrics. Using this technique we demonstrate wafer-scale, aligned CNT transistors with yttrium oxide (Y2Ox) gate dielectrics that exhibit n-type behavior with Ion/Ioff of 10(6) and inverse subthreshold slope of 95 mV/dec. Atomic force microscopy (AFM) and transmission electron microscopy (TEM) analyses confirm that slow (∼1 Å/s) evaporation of yttrium on the CNTs can form a smooth surface that provides excellent wetting to CNTs. Further analysis of the yttrium oxide gate dielectric using X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) techniques revealed that partially oxidized elemental yttrium content increases underneath the surface where it acts as a reducing agent on nanotubes by donating electrons that gives rise to n-type doping in CNTs. We further confirm the mechanism for this technique with other low work-function metals such as lanthanum (La), erbium (Er), and scandium (Sc) which also provide similar CNT NFET behavior after transistor fabrication. This study paves the way to exploiting a wide range of materials for an effective n-type carbon nanotube transistor for a complementary (p- and n-type) transistor technology.

  10. Are Vicinal Metal Surfaces Stable?

    DEFF Research Database (Denmark)

    Frenken, J. W. M.; Stoltze, Per

    1999-01-01

    We use effective medium theory to demonstrate that the energies of many metal surfaces are lowered when these surfaces are replaced by facets with lower-index orientations. This implies that the low-temperature equilibrium shapes of many metal crystals should be heavily faceted. The predicted...... instability of vicinal metal surfaces is at variance with the almost generally observed stability of these surfaces. We argue that the unstable orientations undergo a defaceting transition at relatively low temperatures, driven by the high vibrational entropy of steps....

  11. Tunable spin-tunnel contacts to silicon using low-work-function ferromagnets

    Science.gov (United States)

    Min, Byoung-Chul; Motohashi, Kazunari; Lodder, Cock; Jansen, Ron

    2006-10-01

    Magnetic tunnel junctions have become ubiquitous components appearing in magnetic random-access memory, read heads of magnetic disk drives and semiconductor-based spin devices. Inserting a tunnel barrier has been key to achieving spin injection from ferromagnetic (FM) metals into GaAs, but spin injection into Si has remained elusive. We show that Schottky barrier formation leads to a huge conductivity mismatch of the FM tunnel contact and Si, which cannot be solved by the well-known method of adjusting the tunnel barrier thickness. We present a radically different approach for spin-tunnelling resistance control using low-work-function ferromagnets, inserted at the FM/tunnel barrier interface. We demonstrate that in this way the resistance-area (RA) product of FM/Al2O3/Si contacts can be tuned over eight orders of magnitude, while simultaneously maintaining a reasonable tunnel spin polarization. This raises prospects for Si-based spintronics and presents a new category of ferromagnetic materials for spin-tunnel contacts in low-RA-product applications.

  12. Preparation of stable silica surfaces for surface forces measurement

    Science.gov (United States)

    Ren, Huai-Yin; Mizukami, Masashi; Kurihara, Kazue

    2017-09-01

    A surface forces apparatus (SFA) measures the forces between two surfaces as a function of the surface separation distance. It is regarded as an essential tool for studying the interactions between two surfaces. However, sample surfaces used for the conventional SFA measurements have been mostly limited to thin (ca. 2-3 μm) micas, which are coated with silver layers (ca. 50 nm) on their back, due to the requirement of the distance determination by transmission mode optical interferometry called FECO (fringes of equal chromatic order). The FECO method has the advantage of determining the absolute distance, so it should be important to increase the availability of samples other than mica, which is chemically nonreactive and also requires significant efforts for cleaving. Recently, silica sheets have been occasionally used in place of mica, which increases the possibility of surface modification. However, in this case, the silver layer side of the sheet is glued on a cylindrical quartz disc using epoxy resin, which is not stable in organic solvents and can be easily swollen or dissolved. The preparation of substrates more stable under severe conditions, such as in organic solvents, is necessary for extending application of the measurement. In this study, we report an easy method for preparing stable silica layers of ca. 2 μm in thickness deposited on gold layers (41 nm)/silica discs by sputtering, then annealed to enhance the stability. The obtained silica layers were stable and showed no swelling in organic solvents such as ethanol and toluene.

  13. Exploring Scintillometry in the Stable Atmospheric Surface Layer

    NARCIS (Netherlands)

    Hartogensis, O.K.

    2006-01-01

    The main objective of this thesis is to investigate observation methods of heat and momentum exchange and key variables that characterise turbulence in the atmospheric stable surface layer (SSL), a layer defined as the lower part of the stable boundary layer (SBL) where surface fluxes do not change

  14. Structure of stable degeneration of K3 surfaces into pairs of rational elliptic surfaces

    OpenAIRE

    Kimura, Yusuke

    2018-01-01

    F-theory/heterotic duality is formulated in the stable degeneration limit of a K3 fibration on the F-theory side. In this note, we analyze the structure of the stable degeneration limit. We discuss whether stable degeneration exists for pairs of rational elliptic surfaces. We demonstrate that, when two rational elliptic surfaces have an identical complex structure, stable degeneration always exists. We provide an equation that systematically describes the stable degeneration of a K3 surface i...

  15. Stable pair invariants of surfaces and Seiberg-Witten invariants

    NARCIS (Netherlands)

    Kool, M.

    2016-01-01

    The moduli space of stable pairs on a local surface X = KS is in general non-compact. The action of C ∗ on the fibres of X induces an action on the moduli space and the stable pair invariants of X are defined by the virtual localization formula. We study the contribution to these invariants of

  16. Highly stable superhydrophobic surfaces under flow conditions

    Science.gov (United States)

    Lee, Moonchan; Yim, Changyong; Jeon, Sangmin

    2015-01-01

    We synthesized hydrophobic anodic aluminum oxide nanostructures with pore diameters of 35, 50, 65, and 80 nm directly on quartz crystal microresonators, and the stability of the resulting superhydrophobicity was investigated under flow conditions by measuring changes in the resonance frequency and dissipation factor. When the quartz substrates were immersed in water, their hydrophobic surfaces did not wet due to the presence of an air interlayer. The air interlayer was gradually replaced by water over time, which caused decreases in the resonance frequency (i.e., increases in mass) and increases in the dissipation factor (i.e., increases in viscous damping). Although the water contact angles of the nanostructures increased with increasing pore size, the stability of their superhydrophobicity increased with decreasing pore size under both static conditions (without flow) and dynamic conditions (with flow); this increase can be attributed to an increase in the solid surface area that interacts with the air layer above the nanopores as the pore size decreases. Further, the effects of increasing the flow rate on the stability of the superhydrophobicity were quantitatively determined.

  17. The stable moduli space of Riemann surfaces: Mumford's conjecture

    DEFF Research Database (Denmark)

    Madsen, I.; Weiss, Michael

    2007-01-01

    , one may replace the stable moduli space of Riemann surfaces by $B\\Gamma_{\\infty}$, where $\\Gamma_\\infty$ is the group of isotopy classes of automorphisms of a smooth oriented connected surface of ``large'' genus. Tillmann's theorem that the plus construction makes $B\\Gamma_{\\infty}$ into an infinite...

  18. Long-term stable surface modification of DLC coatings

    Directory of Open Access Journals (Sweden)

    Gotzmann Gaby

    2017-09-01

    Full Text Available The use of coatings based on diamond like carbon (DLC for medical applications was established during the last years. Main advantages of these coatings are its high hardness, good wear and friction behavior and its biocompatibility. Using low-energy electron-beam treatment, we addressed the surface modification of DLC coatings. The aim was to generate new biofunctional surface characteristics that are long-term stable.

  19. Macromolecular surface design: photopatterning of functional stable nitrile oxides.

    Science.gov (United States)

    Altintas, Ozcan; Glassner, Mathias; Rodriguez-Emmenegger, Cesar; Welle, Alexander; Trouillet, Vanessa; Barner-Kowollik, Christopher

    2015-05-04

    The efficient trapping of photogenerated thioaldehydes with functional shelf-stable nitrile oxides in a 1,3-dipolar cycloaddition is a novel and versatile photochemical strategy for polymer end-group functionalization and surface modification under mild and equimolar conditions. The modular ligation in solution was followed in detail by electrospray ionization mass spectrometry (ESI-MS). X-ray photoelectron spectroscopy (XPS) was employed to analyze the functionalized surfaces, whereas time-of-flight secondary-ion mass spectrometry (ToF-SIMS) confirmed the spatial control of the surface functionalization using a micropatterned shadow mask. Polymer brushes were grown from the surface in a spatially confined regime by surface-initiated atom transfer radical polymerization (SI-ATRP) as confirmed by TOF-SIMS, XPS as well as ellipsometry. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Structure of stable degeneration of K3 surfaces into pairs of rational elliptic surfaces

    Science.gov (United States)

    Kimura, Yusuke

    2018-03-01

    F-theory/heterotic duality is formulated in the stable degeneration limit of a K3 fibration on the F-theory side. In this note, we analyze the structure of the stable degeneration limit. We discuss whether stable degeneration exists for pairs of rational elliptic surfaces. We demonstrate that, when two rational elliptic surfaces have an identical complex structure, stable degeneration always exists. We provide an equation that systematically describes the stable degeneration of a K3 surface into a pair of isomorphic rational elliptic surfaces. When two rational elliptic surfaces have different complex structures, whether their sum glued along a smooth fiber admits deformation to a K3 surface can be determined by studying the structure of the K3 lattice. We investigate the lattice theoretic condition to determine whether a deformation to a K3 surface exists for pairs of extremal rational elliptic surfaces. In addition, we discuss the configurations of singular fibers under stable degeneration. The sum of two isomorphic rational elliptic surfaces glued together admits a deformation to a K3 surface, the singular fibers of which are twice that of the rational elliptic surface. For special situations, singular fibers of the resulting K3 surface collide and they are enhanced to a fiber of another type. Some K3 surfaces become attractive in these situations. We determine the complex structures and the Weierstrass forms of these attractive K3 surfaces. We also deduce the gauge groups in F-theory compactifications on these attractive K3 surfaces times a K3. E 6, E 7, E 8, SU(5), and SO(10) gauge groups arise in these compactifications.

  1. Is bicarbonate stable in and on the calcite surface?

    Science.gov (United States)

    Andersson, M. P.; Rodriguez-Blanco, J. D.; Stipp, S. L. S.

    2016-03-01

    We have used density functional theory with the COSMO-RS implicit solvent model to predict the pKa for the deprotonation of bicarbonate to carbonate, i.e. HCO3- CO32- + H+, when HCO3- is included in, and adsorbed on, a calcite surface. We have used cluster models (80-100 atoms) to represent the flat {10.4} surface, acute steps, obtuse steps, two types of kinks on the acute step and two types of kinks on the obtuse steps. Based on the predicted pKa values, which range from -6.0 to 2.4 depending on the surface site, we conclude that bicarbonate deprotonates to carbonate when it is in calcite even when pH in solution is very low. This is true for all surface sites, even for solutions where 2.4 < pH < 6.35, where H2CO30 is the dominant dissolved species. When bicarbonate is adsorbed on calcite, the predicted pKa for deprotonation is 7.5, which is ∼3 pH units lower than in aqueous solution, 10.35. This means that adsorbed carbonate is stable even when the concentration of dissolved CO32- is several orders of magnitude lower. This has a significant effect on surface charge and thus the behaviour of the calcite surface. Our results help explain the potential determining behaviour of the carbonate species in calcite-water systems, particularly in the pH range where the bicarbonate species dominates in water and where the carbonate species dominates at the surface, i.e. when 7.5 < pH < 10.35. Our atomic scale data for the various calcite surface sites provide the needed input to improve and constrain surface complexation modelling and are especially useful for predicting behaviour in systems where experiments are difficult or impossible, such as at high temperature and pressure.

  2. In-induced stable ordering of stepped Si(553) surface

    Science.gov (United States)

    Chauhan, Amit Kumar Singh; Niazi, Asad; Nair, Lekha; Gupta, Govind

    2015-05-01

    The growth mechanism and adsorbate-induced surface morphology of metal atoms on semiconducting surfaces crucially determines the electronic and physicochemical properties of these metal/semiconductor systems. In this study, we investigate the kinetically controlled growth of indium (In) atoms on the high index stepped Si(553)-7 × 7 surface and the thermal stability of various novel In-induced superstructural phases formed during adsorption/desorption process. Auger electron spectroscopy analysis reveals that In adsorption at room temperature (RT) and at 350 °C, with a controlled incident flux of 0.0016 ML/s, proceeds in the Stranski-Krastanov growth mode where two dimensional (2D)/three dimensional (3D) islands are formed on top of two complete monolayers. At higher substrate temperature up to 450 °C, the growth of In atoms occurs in the form of islands on the bare Si(553) surface, and In coverage is limited to the sub-monolayer regime. During the thermal desorption of the RT grown In/Si(553) system, the In clusters rearrange themselves and an unusual "cluster to layer" transformation occurs on top of the stable monolayer. In situ low energy electron diffraction analysis during adsorption and desorption shows the development of various coverage and temperature dependent In-induced superstructural phases on Si(553) surface, such as: (8 × 2) after annealing at 520 °C with coverage 0.5 ML, (8 × 4) after annealing at 580 °C (∼1 ML coverage) and (553)-7 × 1 + (111)-√3 × √3-R30° at 0.3 ML (630 °C). These adsorbate-induced superstructural phases could potentially be utilized as templates for pattern assisted growth of various exotic 1D/2D structures for optoelectronics and photovoltaic applications.

  3. In-induced stable ordering of stepped Si(553) surface

    Energy Technology Data Exchange (ETDEWEB)

    Chauhan, Amit Kumar Singh [Physics of Energy Harvesting, (CSIR-NPL) , Dr. K.S. KrishnanRoad, New Delhi -110012 (India); Department of Physics, JMI, New Delhi 110025 (India); Niazi, Asad; Nair, Lekha [Department of Physics, JMI, New Delhi 110025 (India); Gupta, Govind, E-mail: govind@nplindia.org [Physics of Energy Harvesting, (CSIR-NPL) , Dr. K.S. KrishnanRoad, New Delhi -110012 (India)

    2015-05-15

    Highlights: • Control growth of In on step Si(553) & thermal stability of novel superstructure. • Influence of temperature on growth modes (SK,VB) under different growth conditions. • In-induced superstructure: (8 × 2), (8 × 4), mixed (553)-7 × 1 + (111)√3 × √3R30° phases. - Abstract: The growth mechanism and adsorbate-induced surface morphology of metal atoms on semiconducting surfaces crucially determines the electronic and physicochemical properties of these metal/semiconductor systems. In this study, we investigate the kinetically controlled growth of indium (In) atoms on the high index stepped Si(553)-7 × 7 surface and the thermal stability of various novel In-induced superstructural phases formed during adsorption/desorption process. Auger electron spectroscopy analysis reveals that In adsorption at room temperature (RT) and at 350 °C, with a controlled incident flux of 0.0016 ML/s, proceeds in the Stranski–Krastanov growth mode where two dimensional (2D)/three dimensional (3D) islands are formed on top of two complete monolayers. At higher substrate temperature up to 450 °C, the growth of In atoms occurs in the form of islands on the bare Si(553) surface, and In coverage is limited to the sub-monolayer regime. During the thermal desorption of the RT grown In/Si(553) system, the In clusters rearrange themselves and an unusual “cluster to layer” transformation occurs on top of the stable monolayer. In situ low energy electron diffraction analysis during adsorption and desorption shows the development of various coverage and temperature dependent In-induced superstructural phases on Si(553) surface, such as: (8 × 2) after annealing at 520 °C with coverage 0.5 ML, (8 × 4) after annealing at 580 °C (∼1 ML coverage) and (553)-7 × 1 + (111)-√3 × √3-R30° at 0.3 ML (630 °C). These adsorbate-induced superstructural phases could potentially be utilized as templates for pattern assisted growth of various exotic 1D/2D structures for

  4. Is bicarbonate stable in and on the calcite surface?

    DEFF Research Database (Denmark)

    Andersson, Martin Peter; Rodriguez Blanco, Juan Diego; Stipp, Susan Louise Svane

    2016-01-01

    We have used density functional theory with the COSMO-RS implicit solvent model to predict the pKa for the deprotonation of bicarbonate to carbonate, i.e. HCO3− CO32− + H+, when HCO3− is included in, and adsorbed on, a calcite surface. We have used cluster models (80–100 atoms) to represent...... the flat {10.4} surface, acute steps, obtuse steps, two types of kinks on the acute step and two types of kinks on the obtuse steps. Based on the predicted pKa values, which range from −6.0 to 2.4 depending on the surface site, we conclude that bicarbonate deprotonates to carbonate when it is in calcite...... even when pH in solution is very low. This is true for all surface sites, even for solutions where 2.4 bicarbonate is adsorbed on calcite, the predicted pKa for deprotonation is 7.5, which is ∼3 pH units lower than in aqueous solution...

  5. Thermodynamics of Minerals Stable Near the Earth's Surface

    International Nuclear Information System (INIS)

    Navrotsky, Alexandra

    2003-01-01

    OAK B262 Research and Education Activities We are working on developing calorimetric techniques for sulfide minerals. We have completed calorimetric studies of (Na, K, H3O) jarosites, of Na and K jarosite -alunite solid solutions, and of Cr6+ - containing jarosites. We are now working on phases containing As and Pb. These studies are important to issues of heavy metal pollution in the environment. A number of postdocs, graduate students, and undergrads have participated in the research. We have active collaboration with Dirk Baron, faculty at California State University, Bakersfield. In a collaboration with Peter Burns, Notre Dame University, we are working on thermochemistry of U6+ minerals. Navrotsky has participated in a number of national workshops that are helping to define the interfaces between nanotechnology and earth/environmental science. Major Findings Our first finding on uranyl minerals shows that studtite, a phase containing structural peroxide ion, is thermodynamically unstable in the absence of a source of aqueous peroxide ion but is thermodynamically stable in contact with a solution containing peroxide concentrations expected for the radiolysis of water in contact with spent nuclear fuel. This work is in press in Science. We have a consistent thermodynamic data set for the (Na, K, H3O) (Al, Fe) jarosite, alunite minerals and for Cr6+ substituting for S6+ in jarosite. The latter phases represent one of the few solid sinks for trapping toxic Cr6+ in groundwater. Contributions within Discipline Better understanding of thermodynamic driving for and constraints on geochemical and environmental processes

  6. Thermochemistry of minerals stable near the earth's surface

    International Nuclear Information System (INIS)

    1990-01-01

    The present proposal continues the evolution, of changing emphasis from silicate melts to glass and toward crystalline minerals stable in the shallow crustal environment, particularly amphiholes, micas, and related hydrous phases adding zeolites and carbonates to our areas of interest. This is made possible both by recent advances in our high-temperature calorimetric techniques and by an interest in extending our ideas about the systematics of ionic substitutions to more complex structures. The proposal presents the following: (a) a listing of papers, theses, and abstracts in the past 3 years supported by the present grant, (b) a summary of work on glasses containing highly charged cations and on some related crystalline phases, with proposed new directions, (c) a discussion of advances in calorimetric methods and what new possibilities they open, (d) completed and planned work on amphiboles, micas, and clays, (e) completed and proposed work on amorpous low temperature materials, (f) proposed work on zeolites, and (g) proposed work on carbonates and (h) a discussion of the energy relevance of the above projects. This is followed by the required forms, budget pages, and CV. 34 refs., 5 figs., 1 tab

  7. Stable isotope labeling of oligosaccharide cell surface antigens

    Energy Technology Data Exchange (ETDEWEB)

    Unkefer, C.J.; Silks, L.A. III; Martinez, R.A. [and others

    1998-12-31

    The overall goal of this Laboratory Directed Research and Development (LDRD) project was to develop new methods for synthesis of {sup 13}C-labeled oligosaccharides that are required for nuclear magnetic resonance (NMR) studies of their solution conformation. Oligosaccharides are components of the cell`s outer surface and are involved in important processes such as cell-cell recognition and adhesion. Recently, Danishefsky and coworkers at Slone-Kettering Cancer Center developed a method for the solid-phase chemical synthesis of oligosaccharides. The specific goal of this LDRD project was to prepare uniform {sup 13}C-labeled aldohexose precursors required for the solid-phase synthesis of the Lewis blood-group antigenic determinants. We report the synthesis of {sup 13}C-labeled D-glucal, D-galactal and Fucosyl precursors. We have been collaborating with the Danishefsky group on the synthesis of the Lewis oligosaccharides and the NMR analysis of their solution conformation.

  8. Systematic screening of different surface modifiers for the production of physically stable nanosuspensions.

    Science.gov (United States)

    Lestari, Maria L A D; Müller, Rainer H; Möschwitzer, Jan P

    2015-03-01

    The role of a surface modifier is important in the formation of stable nanosuspensions. In this study, a simple and systematic screening method for selecting optimum surface modifiers was performed by utilizing a low-energy wet ball milling method. Nine surface modifiers from different classes with different stabilization mechanisms were applied on six different models of active pharmaceutical ingredients (API). Particle size analysis showed that at concentration five times higher than the critical micelle concentration, SDS and sodium cholate (anionic surfactant) showed the highest percent success to produce stable nanosuspensions with particle size smaller than 250 nm. Similar findings were also shown by poloxamer 188 (nonionic surfactant) and hydroxypropylmethylcellulose E5 (polymeric stabilizer) at concentration 1% (w/v) and 0.8% (w/v), respectively. In addition, combinations of anionic surfactant and nonionic surfactant as well as combinations of anionic surfactant and polymeric stabilizer showed high percent success in the formation of stable nanosuspensions. In general, no correlation can be found between the physicochemical characteristics of the model API (molecular weight, melting point, log P, pKa, and crystallinity) with its feasibility to be nanosized. The concentration and the principle of stabilization of surface modifier determine the formation of stable nanosuspensions. © 2015 Wiley Periodicals, Inc. and the American Pharmacists Association.

  9. Covalent and stable CuAAC modification of silicon surfaces for control of cell adhesion

    DEFF Research Database (Denmark)

    Vutti, Surendra; Buch-Månson, Nina; Schoffelen, Sanne

    2015-01-01

    Stable primary functionalization of metal surfaces plays a significant role in reliable secondary attachment of complex functional molecules used for the interfacing of metal objects and nanomaterials with biological systems. In principle, this can be achieved through chemical reactions either in...

  10. Surface treatment of silica nanoparticles for stable and charge-controlled colloidal silica

    Science.gov (United States)

    Kim, Kyoung-Min; Kim, Hye Min; Lee, Won-Jae; Lee, Chang-Woo; Kim, Tae-il; Lee, Jong-Kwon; Jeong, Jayoung; Paek, Seung-Min; Oh, Jae-Min

    2014-01-01

    An attempt was made to control the surface charge of colloidal silica nanoparticles with 20 nm and 100 nm diameters. Untreated silica nanoparticles were determined to be highly negatively charged and have stable hydrodynamic sizes in a wide pH range. To change the surface to a positively charged form, various coating agents, such as amine containing molecules, multivalent metal cation, or amino acids, were used to treat the colloidal silica nanoparticles. Molecules with chelating amine sites were determined to have high affinity with the silica surface to make agglomerations or gel-like networks. Amino acid coatings resulted in relatively stable silica colloids with a modified surface charge. Three amino acid moiety coatings (L-serine, L-histidine, and L-arginine) exhibited surface charge modifying efficacy of L-histidine > L-arginine > L-serine and hydrodynamic size preservation efficacy of L-serine > L-arginine > L-histidine. The time dependent change in L-arginine coated colloidal silica was investigated by measuring the pattern of the backscattered light in a Turbiscan™. The results indicated that both the 20 nm and 100 nm L-arginine coated silica samples were fairly stable in terms of colloidal homogeneity, showing only slight coalescence and sedimentation. PMID:25565824

  11. TGP, an extremely stable, non-aggregating fluorescent protein created by structure-guided surface engineering

    OpenAIRE

    Close, Devin W.; Don Paul, Craig; Langan, Patricia S.; Wilce, Matthew C.J.; Traore, Daouda A.K.; Halfmann, Randal; Rocha, Reginaldo C.; Waldo, Geoffery S.; Payne, Riley J.; Rucker, Joseph B.; Prescott, Mark; Bradbury, Andrew R.M.

    2015-01-01

    In this paper we describe the engineering and X-ray crystal structure of Thermal Green Protein (TGP), an extremely stable, highly soluble, non-aggregating green fluorescent protein. TGP is a soluble variant of the fluorescent protein eCGP123, which despite being highly stable, has proven to be aggregation-prone. The X-ray crystal structure of eCGP123, also determined within the context of this paper, was used to carry out rational surface engineering to improve its solubility, leading to TGP....

  12. Stable water isotope and surface heat flux simulation using ISOLSM: Evaluation against in-situ measurements

    KAUST Repository

    Cai, Mick Y.

    2015-04-01

    The stable isotopes of water are useful tracers of water sources and hydrological processes. Stable water isotope-enabled land surface modeling is a relatively new approach for characterizing the hydrological cycle, providing spatial and temporal variability for a number of hydrological processes. At the land surface, the integration of stable water isotopes with other meteorological measurements can assist in constraining surface heat flux estimates and discriminate between evaporation (E) and transpiration (T). However, research in this area has traditionally been limited by a lack of continuous in-situ isotopic observations. Here, the National Centre for Atmospheric Research stable isotope-enabled Land Surface Model (ISOLSM) is used to simulate the water and energy fluxes and stable water isotope variations. The model was run for a period of one month with meteorological data collected from a coastal sub-tropical site near Sydney, Australia. The modeled energy fluxes (latent heat and sensible heat) agreed reasonably well with eddy covariance observations, indicating that ISOLSM has the capacity to reproduce observed flux behavior. Comparison of modeled isotopic compositions of evapotranspiration (ET) against in-situ Fourier Transform Infrared spectroscopy (FTIR) measured bulk water vapor isotopic data (10. m above the ground), however, showed differences in magnitude and temporal patterns. The disparity is due to a small contribution from local ET fluxes to atmospheric boundary layer water vapor (~1% based on calculations using ideal gas law) relative to that advected from the ocean for this particular site. Using ISOLSM simulation, the ET was partitioned into E and T with 70% being T. We also identified that soil water from different soil layers affected T and E differently based on the simulated soil isotopic patterns, which reflects the internal working of ISOLSM. These results highlighted the capacity of using the isotope-enabled models to discriminate

  13. Design and Fabrication of a Hybrid Superhydrophobic-Hydrophilic Surface That Exhibits Stable Dropwise Condensation.

    Science.gov (United States)

    Mondal, Bikash; Mac Giolla Eain, Marc; Xu, QianFeng; Egan, Vanessa M; Punch, Jeff; Lyons, Alan M

    2015-10-28

    Condensation of water vapor is an essential process in power generation, water collection, and thermal management. Dropwise condensation, where condensed droplets are removed from the surface before coalescing into a film, has been shown to increase the heat transfer efficiency and water collection ability of many surfaces. Numerous efforts have been made to create surfaces which can promote dropwise condensation, including superhydrophobic surfaces on which water droplets are highly mobile. However, the challenge with using such surfaces in condensing environments is that hydrophobic coatings can degrade and/or water droplets on superhydrophobic surfaces transition from the mobile Cassie to the wetted Wenzel state over time and condensation shifts to a less-effective filmwise mechanism. To meet the need for a heat-transfer surface that can maintain stable dropwise condensation, we designed and fabricated a hybrid superhydrophobic-hydrophilic surface. An array of hydrophilic needles, thermally connected to a heat sink, was forced through a robust superhydrophobic polymer film. Condensation occurs preferentially on the needle surface due to differences in wettability and temperature. As the droplet grows, the liquid drop on the needle remains in the Cassie state and does not wet the underlying superhydrophobic surface. The water collection rate on this surface was studied using different surface tilt angles, needle array pitch values, and needle heights. Water condensation rates on the hybrid surface were shown to be 4 times greater than for a planar copper surface and twice as large for silanized silicon or superhydrophobic surfaces without hydrophilic features. A convection-conduction heat transfer model was developed; predicted water condensation rates were in good agreement with experimental observations. This type of hybrid superhydrophobic-hydrophilic surface with a larger array of needles is low-cost, robust, and scalable and so could be used for heat

  14. Fabrication and characterization of stable superhydrophobic surface with good friction-reducing performance on Al foil

    Energy Technology Data Exchange (ETDEWEB)

    Li, Peipei [Key Laboratory of Ministry of Education for Special Functional Materials, Henan University, Kaifeng 475004 (China); Chen, Xinhua, E-mail: xuc0374@hotmail.com [College of Chemistry and Chemical Engineering, Xuchang University, Xuchang 461000 (China); Yang, Guangbin; Yu, Laigui [Key Laboratory of Ministry of Education for Special Functional Materials, Henan University, Kaifeng 475004 (China); Zhang, Pingyu, E-mail: pingyu@henu.edu.cn [Key Laboratory of Ministry of Education for Special Functional Materials, Henan University, Kaifeng 475004 (China)

    2014-05-01

    Graphical abstract: A lotus-leaf-like hierarchical structure was successfully created on Al foil by a facile three-step solution–immersion method. As-obtained etched-immersed Al/STA rough surface contains interconnected convex–concave micro-structure and uniformly distributed nano-sheets that endow the surface with excellent superhydrophobicity (WCA: 164.2°; WSA: below 5°). Besides, the as-prepared etched-immersed Al/STA superhydrophobic surface on Al foil exhibits good friction-reducing ability and stable superhydrophobicity. - Highlights: • A stable superhydrophobic surface was created on aluminum foil by a facile three-step solution–immersion method. • A lotus-leaf-like hierarchical structure consists of interconnected convex–concave micro-structure and uniformly distributed nano-sheets has been constructed on the aluminum surface. • The superhydrophobic surfaces on aluminum substrate showing effective friction-reducing performance and self-cleaning ability. - Abstract: A lotus-leaf-like hierarchical structure with superhydrophobicity was created on Al foil by a facile three-step solution–immersion method involving etching in hydrochloric acid solution and immersing in hot water as well as surface-modification by stearic acid (denoted as STA). As-prepared etched-immersed Al/STA rough surface was characterized by means of scanning electron microscopy and X-ray photoelectron spectroscopy. Moreover, the water contact angles and water sliding angles of as-prepared etched-immersed Al/STA rough surface were measured, and the friction-reducing performance and self-cleaning ability of the as-prepared surface were also evaluated. Results indicate that the etched-immersed Al/STA rough surface consists of interconnected convex–concave micro-structure and uniformly distributed nano-sheets. Besides, it exhibits stable superhydrophobicity and good friction-reducing ability. Namely, it has a contact angle of water as high as 164.2° and a water sliding

  15. Bioinspired self-repairing slippery surfaces with pressure-stable omniphobicity.

    Science.gov (United States)

    Wong, Tak-Sing; Kang, Sung Hoon; Tang, Sindy K Y; Smythe, Elizabeth J; Hatton, Benjamin D; Grinthal, Alison; Aizenberg, Joanna

    2011-09-21

    Creating a robust synthetic surface that repels various liquids would have broad technological implications for areas ranging from biomedical devices and fuel transport to architecture but has proved extremely challenging. Inspirations from natural nonwetting structures, particularly the leaves of the lotus, have led to the development of liquid-repellent microtextured surfaces that rely on the formation of a stable air-liquid interface. Despite over a decade of intense research, these surfaces are, however, still plagued with problems that restrict their practical applications: limited oleophobicity with high contact angle hysteresis, failure under pressure and upon physical damage, inability to self-heal and high production cost. To address these challenges, here we report a strategy to create self-healing, slippery liquid-infused porous surface(s) (SLIPS) with exceptional liquid- and ice-repellency, pressure stability and enhanced optical transparency. Our approach-inspired by Nepenthes pitcher plants-is conceptually different from the lotus effect, because we use nano/microstructured substrates to lock in place the infused lubricating fluid. We define the requirements for which the lubricant forms a stable, defect-free and inert 'slippery' interface. This surface outperforms its natural counterparts and state-of-the-art synthetic liquid-repellent surfaces in its capability to repel various simple and complex liquids (water, hydrocarbons, crude oil and blood), maintain low contact angle hysteresis (<2.5°), quickly restore liquid-repellency after physical damage (within 0.1-1 s), resist ice adhesion, and function at high pressures (up to about 680 atm). We show that these properties are insensitive to the precise geometry of the underlying substrate, making our approach applicable to various inexpensive, low-surface-energy structured materials (such as porous Teflon membrane). We envision that these slippery surfaces will be useful in fluid handling and

  16. Experimental and numerical investigations of stable crack growth of axial surface flaws in a pressure vessel

    International Nuclear Information System (INIS)

    Brocks, W.; Krafka, H.; Mueller, W.; Wobst, K.

    1988-01-01

    In connection with the problem of the transferability of parameters obtained experimentally with the help of fracture-mechanical test specimens and used for the initiation and the stable propagation of cracks in cases of pulsating stress and of the elasto-plastic behaviour of construction components, a pressure vessel with an inside diameter of 1500 mm, a cylindrical length of 3000 mm and a wall thickness of 40 mm was hydraulically loaded with the help of internal pressure in the first stage, to attain an average crack growth of 1 mm at Δ a ≅, the loading taking place at about 21deg C. This stress-free annealed vessel exhibited an axial semielliptical vibration-induced surface crack about 181 mm long and 20 mm deep, as a test defect, in a welded circular blank made of the steel 20MnMoNi 55. The fractographic analysis of the first stable crack revealed that its growth rate of Δa was highest in the area of transition from the weak to the strong bend of the crack front (55deg m /σ v (average principal stress: σ m , Mises' reference stress: σ v v). A comparison of the experimental with the numerical results from the first stable crack shows that the local stable crack growth Δa cannot be calculated solely with reference to J, because Δa appears to depend essentially on the quotient σ m /σ v . (orig./MM) [de

  17. Effect of surface texture and structure on the development of stable fluvial armors

    Science.gov (United States)

    Bertin, Stephane; Friedrich, Heide

    2018-04-01

    Stable fluvial armors are found in river systems under conditions of partial sediment transport and limited sediment supply, a common occurrence in nature. Stable armoring is also readily recreated in experimental flumes. Initially, this bed stabilizing phenomenon was examined for different flow discharges and solely related to surface coarsening and bedload transport reduction. The models developed suggest a specific armor composition (i.e., texture) dependent on the parent bed material and formative discharge. Following developments in topographic remote sensing, recent research suggests that armor structure is an important control on bed stability and roughness. In this paper, replicated flume runs during which digital elevation models (DEMs) were collected from both exposed and flooded gravel beds are used to interpret armoring manifestations and to assess their replicability. A range of methodologies was used for the analysis, providing information on (i) surface grain size and orientation, (ii) bed-elevation distributions, (iii) the spatial coherence of the elevations at the grain-scale, (iv) surface slope and aspect, (v) grain imbrication and (vi) the spatial variability in DEM properties. The bed-surface topography was found to be more responsive than bed-material size to changes in flow strength. Our experimental results also provide convincing evidence that gravel-beds' response to water-work during parallel degradation is unique (i.e., replicable) given the formative parameters. Based on this finding, relationships between the armors' properties and formative parameters are proposed, and are supported by adding extensive data from previous research.

  18. Abdominal muscle EMG-activity during bridge exercises on stable and unstable surfaces.

    Science.gov (United States)

    Czaprowski, Dariusz; Afeltowicz, Anna; Gębicka, Anna; Pawłowska, Paulina; Kędra, Agnieszka; Barrios, Carlos; Hadała, Michał

    2014-08-01

    To assess abdominal muscles (AM) activity during prone, side, and supine bridge on stable and unstable surfaces (BOSU, Swiss Ball). Prospective comparison study. Research laboratory. Thirty-three healthy volunteers from a university population. Surface electromyography of the rectus abdominis (RA), the external oblique (EO) and the internal oblique with the transversus abdominis (IO-TA). The AM exhibited the highest activity during prone bridge on a Swiss Ball (RA, EO, IO-TA 44.7 ± 19.2, 54.7 ± 22.9, 36.8 ± 18.6 in % of MVC, respectively). The lowest activity was observed during supine bridge on a stable surface and a BOSU (under 5.0). The lowest ratio analyzed on the basis of the relation of EO and IO-TA activity to RA was obtained during prone bridge on the Swiss Ball (1.4 ± 0.7 for EO, 0.9 ± 0.5 for IO-TA). The highest ratio was obtained during prone bridge on stable surface and supine bridges. The highest level of activity in the abdominal muscles is achieved during prone bridge on a Swiss Ball. However, this exercise provided the lowest activity of the EO and IO-TA in relation to RA. It is essential to conduct further studies verifying the usefulness of using Swiss Ball during core stability training. Copyright © 2013 Elsevier Ltd. All rights reserved.

  19. Stable Titania Nanostructures on Stainless Steel Coronary Stent Surface for Enhanced Corrosion Resistance and Endothelialization.

    Science.gov (United States)

    Mohan, Chandini C; Cherian, Aleena Mary; Kurup, Sujish; Joseph, John; Nair, Manitha B; Vijayakumar, Maniyal; Nair, Shantikumar V; Menon, Deepthy

    2017-06-01

    Stainless steel (SS) coronary stents continue to present risk of in-stent restenosis that impact its long term safety and efficacy. The present work focuses on developing a drug-free and polymer-less surface on coronary stents by utilizing a titania (TiO 2 ) nanotexturing approach through hydrothermal processing, that will offer improved stent performance in vivo. Mechanically stable and durable nanotextured coatings are obtained on SS stents that also offer good corrosion resistance. In vitro vascular cell (endothelial and smooth muscle cells) studies on surface modified SS show preferential rapid endothelialization with enhanced nitric oxide production and reduce smooth muscle cell proliferation, in comparison to unmodified SS. In vivo evaluation of the nanotextured stents after subcutaneous implantation in rabbits show reduced irritability and minimal localized inflammatory response. These beneficial effects suggest that the stable, easily scalable titania nanosurface modification strategy on coronary stent surfaces can be a much cheaper alternative to drug eluting stents in addressing in-stent restenosis. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Assessing the Impact of Sublimation on the Stable Water Isotope Signal of Surface Ice

    Science.gov (United States)

    Dennis, D. P.; Ehrenfeucht, S.; Marchant, D. R.

    2017-12-01

    Sublimation is often a significant, if not the dominant, mechanism for ablation in polar and high elevation glacial systems. Previous field studies on firn and ice have suggested that sublimation can enrich the stable water isotope (δD and δ18O) signatures of these exposed materials. Several additional studies have attempted to replicate this effect through laboratory experiments. However, neither the magnitude of alteration caused by sublimation nor the maximum depth at which ice is affected are well-constrained. The effect of sublimation-induced alteration on the original meteoric signal relative to other post-depositional processes is additionally unknown. Here, we present the results of an experimental study on the effect of sublimation on stable water isotope ratios in surface ice. Using high-resolution data, we attempt to assess the suitability of δD and δ18O in near-surface and exposed ice for use as paleoclimate proxies. This type of analysis is particularly useful for future studies of ice from hyper-arid polar regions like the Antarctic McMurdo Dry Valleys, and may be extended to icy planetary bodies, including surface ice on Mars.

  1. Surface oceanographic fronts influencing deep-sea biological activity: Using fish stable isotopes as ecological tracers

    Science.gov (United States)

    Louzao, Maite; Navarro, Joan; Delgado-Huertas, Antonio; de Sola, Luis Gil; Forero, Manuela G.

    2017-06-01

    Ecotones can be described as transition zones between neighbouring ecological systems that can be shaped by environmental gradients over a range of space and time scales. In the marine environment, the detection of ecotones is complex given the highly dynamic nature of marine systems and the paucity of empirical data over ocean-basin scales. One approach to overcome these limitations is to use stable isotopes from animal tissues since they can track spatial oceanographic variability across marine systems and, in turn, can be used as ecological tracers. Here, we analysed stable isotopes of deep-sea fishes to assess the presence of ecological discontinuities across the western Mediterranean. We were specifically interested in exploring the connection between deep-sea biological activity and particular oceanographic features (i.e., surface fronts) occurring in the pelagic domain. We collected samples for three different abundant deep-sea species in May 2004 from an experimental oceanographic trawling cruise (MEDITS): the Mictophydae jewel lanternfish Lampanyctus crocodilus and two species of the Gadidae family, the silvery pout Gadiculus argenteus and the blue whiting Micromesistius poutassou. The experimental survey occurred along the Iberian continental shelf and the upper and middle slopes, from the Strait of Gibraltar in the SW to the Cape Creus in the NE. The three deep-sea species were highly abundant throughout the study area and they showed geographic variation in their isotopic values, with decreasing values from north to south disrupted by an important change point around the Vera Gulf. Isotopic latitudinal gradients were explained by pelagic oceanographic conditions along the study area and confirm the existence of an ecotone at the Vera Gulf. This area could be considered as an oceanographic boundary where waters of Atlantic origin meet Mediterranean surface waters forming important frontal structures such as the Almeria-Oran front. In fact, our results

  2. Hydrophobic and Metallophobic Surfaces: Highly Stable Non-wetting Inorganic Surfaces Based on Lanthanum Phosphate Nanorods.

    Science.gov (United States)

    Sankar, Sasidharan; Nair, Balagopal N; Suzuki, Takehiro; Anilkumar, Gopinathan M; Padmanabhan, Moothetty; Hareesh, Unnikrishnan Nair S; Warrier, Krishna G

    2016-03-09

    Metal oxides, in general, are known to exhibit significant wettability towards water molecules because of the high feasibility of synergetic hydrogen-bonding interactions possible at the solid-water interface. Here we show that the nano sized phosphates of rare earth materials (Rare Earth Phosphates, REPs), LaPO4 in particular, exhibit without any chemical modification, unique combination of intrinsic properties including remarkable hydrophobicity that could be retained even after exposure to extreme temperatures and harsh hydrothermal conditions. Transparent nanocoatings of LaPO4 as well as mixture of other REPs on glass surfaces are shown to display notable hydrophobicity with water contact angle (WCA) value of 120° while sintered and polished monoliths manifested WCA greater than 105°. Significantly, these materials in the form of coatings and monoliths also exhibit complete non-wettability and inertness towards molten metals like Ag, Zn, and Al well above their melting points. These properties, coupled with their excellent chemical and thermal stability, ease of processing, machinability and their versatile photo-physical and emission properties, render LaPO4 and other REP ceramics utility in diverse applications.

  3. Polyaniline hybridized surface defective ZnO nanorods with long-term stable photoelectrochemical activity

    International Nuclear Information System (INIS)

    Bera, Susanta; Khan, Hasmat; Biswas, Indranil; Jana, Sunirmal

    2016-01-01

    Highlights: • Polyaniline (PANI) hybridized ZnO nanorods was synthesized by solution method. • Surface defects were found in the nanorods. • The hybrid material exhibited an enhancement in visible light absorption. • A long-term stable photoelectrochemical activity of the material was found. • Advancement in the properties would be PANI hybridization and surface defects. - Abstract: We report surfactant/template free precursor solution based synthesis of polyaniline (PANI) hybridized surface defective ZnO nanorods by a two-step process. Initially, ZnO nanorods have been prepared at 95 °C, followed by hybridization (coating) of PANI onto the ZnO via in situ polymerization of aniline monomer, forming ZnO-PANI nanohybrid (ZP). The structural properties of ZP have been analyzed by X-ray diffraction (XRD) and transmission electron microscopic (TEM) studies. The presence of surface defects especially the oxygen vacancies in ZnO has been characterized by photoluminescence emission, high resolution TEM, X-ray photoelectron spectroscopy (XPS) and micro-Raman spectral measurements. The chemical interaction of PANI with ZnO has been examined by Fourier transform infrared (FTIR) and XPS analyses. A significant enhancement in visible absorption of ZP sample is found as evidenced from UV–vis diffused reflectance spectral study. BET nitrogen adsorption-desorption isotherm shows an improved textural property (pore size, pore volume) of ZP. Moreover, a long-term stable photoelectrochemical activity (PEC) of ZP is found compare to pristine ZnO. The synergic effect of PANI hybridization and the presence of surface defects in ZnO NRs can enhance the PEC by prolonging the recombination rate of photogenerated charge carriers. The effect can also provide large number of active sites to make electrolyte diffusion and mass transportation easier in the nanohybrid. This simple synthesis strategy can be adopted for PANI hybridization with different metal oxide semiconductors

  4. Polyaniline hybridized surface defective ZnO nanorods with long-term stable photoelectrochemical activity

    Energy Technology Data Exchange (ETDEWEB)

    Bera, Susanta; Khan, Hasmat [Sol-Gel Division, CSIR-Central Glass and Ceramic Research Institute (CSIR-CGCRI), 196 Raja S.C. Mullick Road, P.O. Jadavpur University, Kolkata 700 032, West Bengal (India); Biswas, Indranil [Materials Characterization and Instrumentation Division, CSIR-Central Glass and Ceramic Research Institute (CSIR-CGCRI), 196 Raja S.C. Mullick Road, P.O. Jadavpur University, Kolkata 700 032, West Bengal (India); Jana, Sunirmal, E-mail: sjana@cgcri.res.in [Sol-Gel Division, CSIR-Central Glass and Ceramic Research Institute (CSIR-CGCRI), 196 Raja S.C. Mullick Road, P.O. Jadavpur University, Kolkata 700 032, West Bengal (India)

    2016-10-15

    Highlights: • Polyaniline (PANI) hybridized ZnO nanorods was synthesized by solution method. • Surface defects were found in the nanorods. • The hybrid material exhibited an enhancement in visible light absorption. • A long-term stable photoelectrochemical activity of the material was found. • Advancement in the properties would be PANI hybridization and surface defects. - Abstract: We report surfactant/template free precursor solution based synthesis of polyaniline (PANI) hybridized surface defective ZnO nanorods by a two-step process. Initially, ZnO nanorods have been prepared at 95 °C, followed by hybridization (coating) of PANI onto the ZnO via in situ polymerization of aniline monomer, forming ZnO-PANI nanohybrid (ZP). The structural properties of ZP have been analyzed by X-ray diffraction (XRD) and transmission electron microscopic (TEM) studies. The presence of surface defects especially the oxygen vacancies in ZnO has been characterized by photoluminescence emission, high resolution TEM, X-ray photoelectron spectroscopy (XPS) and micro-Raman spectral measurements. The chemical interaction of PANI with ZnO has been examined by Fourier transform infrared (FTIR) and XPS analyses. A significant enhancement in visible absorption of ZP sample is found as evidenced from UV–vis diffused reflectance spectral study. BET nitrogen adsorption-desorption isotherm shows an improved textural property (pore size, pore volume) of ZP. Moreover, a long-term stable photoelectrochemical activity (PEC) of ZP is found compare to pristine ZnO. The synergic effect of PANI hybridization and the presence of surface defects in ZnO NRs can enhance the PEC by prolonging the recombination rate of photogenerated charge carriers. The effect can also provide large number of active sites to make electrolyte diffusion and mass transportation easier in the nanohybrid. This simple synthesis strategy can be adopted for PANI hybridization with different metal oxide semiconductors

  5. High-performance heterogeneous catalysis with surface-exposed stable metal nanoparticles.

    Science.gov (United States)

    Huang, Ning; Xu, Yanhong; Jiang, Donglin

    2014-11-27

    Protection of metal nanoparticles from agglomeration is critical for their functions and applications. The conventional method for enhancing their stability is to cover them with passivation layers to prevent direct contact. However, the presence of a protective shell blocks exposure of the metal species to reactants, thereby significantly impeding the nanoparticles' utility as catalysts. Here, we report that metal nanoparticles can be prepared and used in a surface-exposed state that renders them inherently catalytically active. This strategy is realised by spatial confinement and electronic stabilisation with a dual-module mesoporous and microporous three-dimensional π-network in which surface-exposed nanoparticles are crystallised upon in situ reduction. The uncovered palladium nanoparticles serve as heterogeneous catalysts that are exceptionally active in water, catalyse unreactive aryl chlorides for straightforward carbon-carbon bond formation and are stable for repeated use in various types of cross couplings. Therefore, our results open new perspectives in developing practical heterogeneous catalysts.

  6. Electrostatic powder spraying process for the fabrication of stable superhydrophobic surfaces

    Science.gov (United States)

    Gu, Guotuan; Tian, Yuping; Li, Zhantie; Lu, Dongfang

    2011-03-01

    Nano-sized Al2O3 particles were modified by heptadecafluorodecyl trimethoxysilane and 2,3-epoxy propoxy propyl trimethoxysilicane to make it both hydrophobic and reactive. The reactive nano-particles were mixed with polyester resin containing curing agents and electrostatic sprayed on stainless steel substrates to obtain stable superhydrophobic coatings after curing. The water contact angle (WCA) on the hybrid coating is influenced by the content of Al2O3 particles in the coating. As the Al2O3 concentration in the coating was increased from 0% to 8%, WCA increased from 68° to 165°. Surface topography of the coatings was examined using scanning electron microscopy (SEM). Nano-particles covered on the coating surface formed continuous film with greatly enhanced roughness, which was found to be responsible for the superhydrophobicity. The method is simple and cost effective and can be used for preparing self-cleaning superhydrophobic coating on large areas.

  7. Geologic investigations of Australian earthquakes: Paleoseismicity and the recurrence of surface faulting in the stable regions of continents

    Science.gov (United States)

    Machette, Michael; Crone, Anthony

    1993-01-01

    Earthquakes that occur in the stable regions of continents are very rare compared to those that occur along plate margins, such as the San Andreas fault system of western California. Worldwide, only 11 historic earthquakes in stable continental regions are known to have produced surface ruptures. Five of these have occurred in Australia since 1968 (see map, next page).

  8. A stable isotope record of late Cenozoic surface uplift of southern Alaska

    Science.gov (United States)

    Bill, Nicholas S.; Mix, Hari T.; Clark, Peter U.; Reilly, Sean P.; Jensen, Britta J. L.; Benowitz, Jeffrey A.

    2018-01-01

    Although the timing of an acceleration in late-Cenozoic exhumation of southern Alaska is reasonably well constrained as beginning ∼5-∼6 Ma, the surface uplift history of this region remains poorly understood. To assess the extent of surface uplift relative to rapid exhumation, we developed a stable isotope record using the hydrogen isotope composition (δD) of paleo-meteoric water over the last ∼7 Ma from interior basins of Alaska and Yukon Territory. Our record, which is derived from authigenic clays (δDclay) in silicic tephras, documents a ∼50-60‰ increase in δD values from the late Miocene (∼6-∼7 Ma) through the Plio-Pleistocene transition (∼2-∼3 Ma), followed by near-constant values over at least the last ∼2 Ma. Although this enrichment trend is opposite that of a Rayleigh distillation model typically associated with surface uplift, we suggest that it is consistent with indirect effects of surface uplift on interior Alaska, including changes in aridity, moisture source, and seasonality of moisture. We conclude that the δDclay record documents the creation of a topographic barrier and the associated changes to the climate of interior Alaska and Yukon Territory.

  9. Stable water isotope simulation by current land-surface schemes:Results of IPILPS phase 1

    Energy Technology Data Exchange (ETDEWEB)

    Henderson-Sellers, A.; Fischer, M.; Aleinov, I.; McGuffie, K.; Riley, W.J.; Schmidt, G.A.; Sturm, K.; Yoshimura, K.; Irannejad, P.

    2005-10-31

    Phase 1 of isotopes in the Project for Intercomparison of Land-surface Parameterization Schemes (iPILPS) compares the simulation of two stable water isotopologues ({sup 1}H{sub 2} {sup 18}O and {sup 1}H{sup 2}H{sup 16}O) at the land-atmosphere interface. The simulations are off-line, with forcing from an isotopically enabled regional model for three locations selected to offer contrasting climates and ecotypes: an evergreen tropical forest, a sclerophyll eucalypt forest and a mixed deciduous wood. Here we report on the experimental framework, the quality control undertaken on the simulation results and the method of intercomparisons employed. The small number of available isotopically-enabled land-surface schemes (ILSSs) limits the drawing of strong conclusions but, despite this, there is shown to be benefit in undertaking this type of isotopic intercomparison. Although validation of isotopic simulations at the land surface must await more, and much more complete, observational campaigns, we find that the empirically-based Craig-Gordon parameterization (of isotopic fractionation during evaporation) gives adequately realistic isotopic simulations when incorporated in a wide range of land-surface codes. By introducing two new tools for understanding isotopic variability from the land surface, the Isotope Transfer Function and the iPILPS plot, we show that different hydrological parameterizations cause very different isotopic responses. We show that ILSS-simulated isotopic equilibrium is independent of the total water and energy budget (with respect to both equilibration time and state), but interestingly the partitioning of available energy and water is a function of the models' complexity.

  10. TGP, an extremely stable, non-aggregating fluorescent protein created by structure-guided surface engineering

    Science.gov (United States)

    Close, Devin W.; Don Paul, Craig; Langan, Patricia S.; Wilce, Matthew C.J.; Traore, Daouda A.K.; Halfmann, Randal; Rocha, Reginaldo C.; Waldo, Geoffery S.; Payne, Riley J.; Rucker, Joseph B.; Prescott, Mark; Bradbury, Andrew R.M.

    2014-01-01

    In this paper we describe the engineering and X-ray crystal structure of Thermal Green Protein (TGP), an extremely stable, highly soluble, non-aggregating green fluorescent protein. TGP is a soluble variant of the fluorescent protein eCGP123, which despite being highly stable, has proven to be aggregation-prone. The X-ray crystal structure of eCGP123, also determined within the context of this paper, was used to carry out rational surface engineering to improve its solubility, leading to TGP. The approach involved simultaneously eliminating crystal lattice contacts while increasing the overall negative charge of the protein. Despite intentional disruption of lattice contacts and introduction of high entropy glutamate side chains, TGP crystallized readily in a number of different conditions and the X-ray crystal structure of TGP was determined to 1.9 Å resolution. The structural reasons for the enhanced stability of TGP and eCGP123 are discussed. We demonstrate the utility of using TGP as a fusion partner in various assays and significantly, in amyloid assays in which the standard fluorescent protein, EGFP, is undesirable because of aberrant oligomerization. PMID:25287913

  11. Thermal green protein, an extremely stable, nonaggregating fluorescent protein created by structure-guided surface engineering.

    Science.gov (United States)

    Close, Devin W; Paul, Craig Don; Langan, Patricia S; Wilce, Matthew C J; Traore, Daouda A K; Halfmann, Randal; Rocha, Reginaldo C; Waldo, Geoffery S; Payne, Riley J; Rucker, Joseph B; Prescott, Mark; Bradbury, Andrew R M

    2015-07-01

    In this article, we describe the engineering and X-ray crystal structure of Thermal Green Protein (TGP), an extremely stable, highly soluble, non-aggregating green fluorescent protein. TGP is a soluble variant of the fluorescent protein eCGP123, which despite being highly stable, has proven to be aggregation-prone. The X-ray crystal structure of eCGP123, also determined within the context of this paper, was used to carry out rational surface engineering to improve its solubility, leading to TGP. The approach involved simultaneously eliminating crystal lattice contacts while increasing the overall negative charge of the protein. Despite intentional disruption of lattice contacts and introduction of high entropy glutamate side chains, TGP crystallized readily in a number of different conditions and the X-ray crystal structure of TGP was determined to 1.9 Å resolution. The structural reasons for the enhanced stability of TGP and eCGP123 are discussed. We demonstrate the utility of using TGP as a fusion partner in various assays and significantly, in amyloid assays in which the standard fluorescent protein, EGFP, is undesirable because of aberrant oligomerization. © 2014 Wiley Periodicals, Inc.

  12. Mapping Precipitation Patterns from the Stable Isotopic Composition of Surface Waters: Olympic Peninsula, Washington State

    Science.gov (United States)

    Anders, A. M.; Brandon, M. T.

    2008-12-01

    Available data indicate that large and persistent precipitation gradients are tied to topography at scales down to a few kilometers, but precipitation patterns in the majority of mountain ranges are poorly constrained at scales less than tens of kilometers. A lack of knowledge of precipitation patterns hampers efforts to understand the processes of orographic precipitation and identify the relationships between geomorphic evolution and climate. A new method for mapping precipitation using the stable isotopic composition of surface waters is tested in the Olympic Mountains of Washington State. Measured δD and δ18O of 97 samples of surface water are linearly related and nearly inseparable from the global meteoric water line. A linear orographic precipitation model extended to include in effects of isotopic fractionation via Rayleigh distillation predicts precipitation patterns and isotopic composition of surface water. Seven parameters relating to the climate and isotopic composition of source water are used. A constrained random search identifies the best-fitting parameter set. Confidence intervals for parameter values are defined and precipitation patterns are determined. Average errors for the best-fitting model are 4.8 permil in δD. The difference between the best fitting model and other models within the 95% confidence interval was less than 20%. An independent high-resolution precipitation climatology documents precipitation gradients similar in shape and magnitude to the model derived from surface water isotopic composition. This technique could be extended to other mountain ranges, providing an economical and fast assessment of precipitation patterns requiring minimal field work.

  13. No difference in 1RM strength and muscle activation during the barbell chest press on a stable and unstable surface.

    Science.gov (United States)

    Goodman, Craig A; Pearce, Alan J; Nicholes, Caleb J; Gatt, Brad M; Fairweather, Ian H

    2008-01-01

    Exercise or Swiss balls are increasingly being used with conventional resistance exercises. There is little evidence supporting the efficacy of this approach compared to traditional resistance training on a stable surface. Previous studies have shown that force output may be reduced with no change in muscle electromyography (EMG) activity while others have shown increased muscle EMG activity when performing resistance exercises on an unstable surface. This study compared 1RM strength, and upper body and trunk muscle EMG activity during the barbell chest press exercise on a stable (flat bench) and unstable surface (exercise ball). After familiarization, 13 subjects underwent testing for 1RM strength for the barbell chest press on both a stable bench and an exercise ball, each separated by at least 7 days. Surface EMG was recorded for 5 upper body muscles and one trunk muscle from which average root mean square of the muscle activity was calculated for the whole 1RM lift and the concentric and eccentric phases. Elbow angle during each lift was recorded to examine any range-of-motion differences between the two surfaces. The results show that there was no difference in 1RM strength or muscle EMG activity for the stable and unstable surfaces. In addition, there was no difference in elbow range-of-motion between the two surfaces. Taken together, these results indicate that there is no reduction in 1RM strength or any differences in muscle EMG activity for the barbell chest press exercise on an unstable exercise ball when compared to a stable flat surface. Moreover, these results do not support the notion that resistance exercises performed on an exercise ball are more efficacious than traditional stable exercises.

  14. Decontamination of radionuclide strontium polluted the analog instruments surface by high stable foam

    International Nuclear Information System (INIS)

    Zhu Gaolong; Chen Shuai; Lin Xiaoyan; Luo Xuegang

    2014-01-01

    Decontamination of the radionuclide strontium polluted the analog instruments surface radionuclide strontium by foam, where the high stable foam detergent was prepared by Sodium dodecylbenzene sulfonate (SDBS) as a foaming agent and hydroxyethyl cellulose (HEC) as a foam stabilizer. The effects of adding a foam stabilizer hydroxyethyl cellulose (HEC) on foam stability and the volume of drainage liquid were discussed and contact time, foaming agent concentration, temperature, humidity on foam decontamination efficiency of the analog instruments surface by radionuclide strontium were observed. The results show that there has been a significant increase of foam stability with the increase of HEC addition, the volume of drainage liquid was decrease from 7.8 g to 0 g and the half decay time of foam was extended from 305 seconds to 1050 seconds after the HEC addition increase from 0 % to 3%. The half decay time increase with the continue to increase of HEC addition but decrease of the foamability. The foam drainage speed up with the increase of temperture, the foam will burst rapidly when the temperture is higer than 600 ℃. The high table foam has a effective decontamination efficiency between 88%∼95%. contact time, foaming agent concentration, humidity do not much affect on the foam decontamination. In order to reduce the affect of volume of drainage liquid on the precision instrument, the contact time should control in 3 min. (authors)

  15. Stable water isotopes in the coupled atmosphere–land surface model ECHAM5-JSBACH

    Directory of Open Access Journals (Sweden)

    B. Haese

    2013-09-01

    Full Text Available In this study we present first results of a new model development, ECHAM5-JSBACH-wiso, where we have incorporated the stable water isotopes H218O and HDO as tracers in the hydrological cycle of the coupled atmosphere–land surface model ECHAM5-JSBACH. The ECHAM5-JSBACH-wiso model was run under present-day climate conditions at two different resolutions (T31L19, T63L31. A comparison between ECHAM5-JSBACH-wiso and ECHAM5-wiso shows that the coupling has a strong impact on the simulated temperature and soil wetness. Caused by these changes of temperature and the hydrological cycle, the δ18O in precipitation also shows variations from −4‰ up to 4‰. One of the strongest anomalies is shown over northeast Asia where, due to an increase of temperature, the δ18O in precipitation increases as well. In order to analyze the sensitivity of the fractionation processes over land, we compare a set of simulations with various implementations of these processes over the land surface. The simulations allow us to distinguish between no fractionation, fractionation included in the evaporation flux (from bare soil and also fractionation included in both evaporation and transpiration (from water transport through plants fluxes. While the isotopic composition of the soil water may change for δ18O by up to +8&permil:, the simulated δ18O in precipitation shows only slight differences on the order of ±1‰. The simulated isotopic composition of precipitation fits well with the available observations from the GNIP (Global Network of Isotopes in Precipitation database.

  16. Variance Method to Determine Turbulent Fluxes of Momentum And Sensible Heat in The Stable Atmospheric Surface Layer

    NARCIS (Netherlands)

    Debruin, H.A.R.; Hartogensis, O.K.

    2005-01-01

    Evidence is presented that in the stable atmospheric surface layer turbulent fluxes of heat and momentum can be determined from the standard deviations of longitudinal wind velocity and temperature, ¿u and ¿T respectively, measured at a single level. An attractive aspect of this method is that it

  17. Interactions between surface waters in King George Island, Antarctica - a stable isotope perspective

    Science.gov (United States)

    Perşoiu, Aurel; Bădăluşă, Carmen

    2017-04-01

    In this paper we present a first study of the isotopic composition of surface waters in the southern peninsulas (Barton, Fildes, Weaver and Potter) of King George Island, Antarctica. We have collected > 200 samples of snow and snowmelt, water (lake, river and spring), ice (glacier ice and permafrost) from the four peninsulas in February 2016 and analyzed them for their oxygen and hydrogen stable isotopic composition. Samples from lake water (50+) indicate a clear west-east depletion trend, suggesting a rain-out process as air masses are moving westward (and are progressively depleted in heavy isotopes) from their origin in the Drake Passage. In both Fildes and Barton Peninsulas, permafrost samples have the heaviest isotopic composition, most probably due to preferential incorporation of heavy isotopes in the ice during freezing (and no fractionation during melting). As permafrost melts, the resulting water mixes with isotopically lighter infiltrated snowmelt, and thus the groundwater has a lower isotopic composition. Further, lake and river (the later fed by lakes) water has the lightest isotopic composition, being derived mostly from the melting of light snow and glacier ice. It seems feasible to separate isotopically water in lakes/rivers (largely fed by melting multi-year glaciers and snow) and water from melting of snow/ground ice This preliminary study suggests that it is possible to separate various water sources in the southern peninsulas of King George Island, and this separation could be used to study permafrost degradation, as well as feeding and migration patterns in the bird fauna, with implications for protection purposes. Acknowledgments. The National Institute of Research and Development for Biological Sciences (Bucharest, Romania) and the Korean polar institute financially supported fieldwork in King George Island. We thank the personal at King Sejong (South Korea), Belingshaussen (Russia) and Carlini (Argentina) stations in King George Island for

  18. Calculation of the vibration properties of the Pd/Au (111 ordered surface alloy in its stable domain

    Directory of Open Access Journals (Sweden)

    Tigrine R.

    2012-06-01

    Full Text Available In the present paper, a calculation is presented for the vibration properties of the ordered surface alloy alloy Au(111 − (√3×√3R30° − Pd, which is a stable system in the temperature range of 500K to 600K. This surface alloy is formed by depositing Pd atoms onto the Au(111surface, and annealing at higher temperatures. The matching theory is applied to calculate the surface phonons and local vibration densities of states (LDOS for the clean Au (111 surface, and for the Au(111 − (√3×√3R30° − Pd surface alloy. Our theoretical results for the surface phonon branches of the clean Au (111 surface compare favorably with previous ab initio results and experimental data. In contrast, there are no previous results for the vibrational LDOS for the atomic Au site in a clean Au (111 surface, or results for the surface phonons and vibration spectra for the surface alloy. The surface phonons are calculated for the clean Au (111 surface and the ordered surface alloy along three directions of high symmetry, namely, ΓΜ¯, MML:MK¯ $overline {Gamma {m M}} ,{m{ }}overline {{m{MK}}} $ , and KΓ¯ $overline {KGamma } $ . The phonon branches are strongly modified from the Au (111 surface to the surface alloy. In particular a remarkable change takes place for the LDOS between the clean Au (111 surface and the surface alloy, which may find its origin in the charge transfer from Au atoms to Pd atoms.

  19. A stable high-order perturbation of surfaces method for numerical simulation of diffraction problems in triply layered media

    Energy Technology Data Exchange (ETDEWEB)

    Hong, Youngjoon, E-mail: hongy@uic.edu; Nicholls, David P., E-mail: davidn@uic.edu

    2017-02-01

    The accurate numerical simulation of linear waves interacting with periodic layered media is a crucial capability in engineering applications. In this contribution we study the stable and high-order accurate numerical simulation of the interaction of linear, time-harmonic waves with a periodic, triply layered medium with irregular interfaces. In contrast with volumetric approaches, High-Order Perturbation of Surfaces (HOPS) algorithms are inexpensive interfacial methods which rapidly and recursively estimate scattering returns by perturbation of the interface shape. In comparison with Boundary Integral/Element Methods, the stable HOPS algorithm we describe here does not require specialized quadrature rules, periodization strategies, or the solution of dense non-symmetric positive definite linear systems. In addition, the algorithm is provably stable as opposed to other classical HOPS approaches. With numerical experiments we show the remarkable efficiency, fidelity, and accuracy one can achieve with an implementation of this algorithm.

  20. Athletes trained using stable compared to unstable surfaces exhibit distinct postural control profiles when assessed by traditional and nonlinear measures.

    Science.gov (United States)

    Powell, Douglas W; Williams, D S Blaise

    2015-12-01

    Athletes are assumed to exhibit better balance than non-athletes; however, few studies have examined the role of different types of sports on balance measures. Two athlete groups that experience divergent sport-specific balance training are stable- (i.e. basketball) and unstable-surface athletes (i.e. surfers). The purpose of this study was to quantify the effect of stable- compared to unstable-surface sports on postural stability. Eight non-athletes (NON), eight stable-surface athletes (SSA) and eight unstable-surface athletes (USA) performed five 20-s quiet standing trials while ground reaction forces were recorded. Approximate entropy (ApEn), total excursion and root mean square distances (RMS) of the center of pressure position were calculated. Univariate ANOVAs with post hoc tests were conducted for each variable. ApEn values were lower in SSA compared to NON in the ML direction (p=0.012) and USA had lower ApEn values compared to SSA in the AP direction (p=0.036). The USA had smaller AP RMS compared to SSA (p=0.002) while the USA had greater ML RMS (p=0.008) and resultant RMS values compared to SSA (p=0.025). These data suggest that USA and SSA may exhibit direction-specific differences in balance strategy due to feedback paradigm. Copyright © 2015 Elsevier B.V. All rights reserved.

  1. Production of stable superhydrophilic surfaces on 316L steel by simultaneous laser texturing and SiO2 deposition

    Science.gov (United States)

    Rajab, Fatema H.; Liu, Zhu; Li, Lin

    2018-01-01

    Superhydrophilic surfaces with liquid contact angles of less than 5 ° have attracted much interest in practical applications including self-cleaning, cell manipulation, adhesion enhancement, anti-fogging, fluid flow control and evaporative cooling. Standard laser metal texturing method often result in unstable wetting characteristics, i.e. changing from super hydrophilic to hydrophobic in a few days or weeks. In this paper, a simple one step method is reported for fabricating a stable superhydrophilic metallic surface that lasted for at least 6 months. Here, 316L stainless steel substrates were textured using a nanosecond laser with in-situ SiO2 deposition. Morphology and chemistry of laser-textured surfaces were characterised using SEM, XRD, XPS and an optical 3D profiler. Static wettability analysis was carried out over a period of 6 months after the laser treatment. The effect of surface roughness on wettability was also studied. Results showed that the wettability of the textured surfaces could be controlled by changing the scanning speed of laser beam and number of passes. The main reason for the realisation of the stable superhydrophilic surface is the combination of the melted glass particles mainly Si and O with that of stainless steel in the micro-textured patterns. This study presents a useful method

  2. Facile Fabrication and Characterization of a PDMS-Derived Candle Soot Coated Stable Biocompatible Superhydrophobic and Superhemophobic Surface.

    Science.gov (United States)

    Iqbal, R; Majhy, B; Sen, A K

    2017-09-13

    We report a simple, inexpensive, rapid, and one-step method for the fabrication of a stable and biocompatible superhydrophobic and superhemophobic surface. The proposed surface comprises candle soot particles embedded in a mixture of PDMS+n-hexane serving as the base material. The mechanism responsible for the superhydrophobic behavior of the surface is explained, and the surface is characterized based on its morphology and elemental composition, wetting properties, mechanical and chemical stability, and biocompatibility. The effect of %n-hexane in PDMS, the thickness of the PDMS+n-hexane layer (in terms of spin coating speed) and sooting time on the wetting property of the surface is studied. The proposed surface exhibits nanoscale surface asperities (average roughness of 187 nm), chemical compositions of soot particles, very high water and blood repellency along with excellent mechanical and chemical stability and excellent biocompatibility against blood sample and biological cells. The water contact angle and roll-off angle is measured as 160° ± 1° and 2°, respectively, and the blood contact angle is found to be 154° ± 1°, which indicates that the surface is superhydrophobic and superhemophobic. The proposed superhydrophobic and superhemophobic surface offers significantly improved (>40%) cell viability as compared to glass and PDMS surfaces.

  3. Stable, metastable and unstable solutions of a spin-1 Ising system based on the free energy surfaces

    Science.gov (United States)

    Keskİin, Mustafa; Özgan, Şükrü

    1990-04-01

    Stable, metastable and unstable solutions of a spin-1 Ising model with bilinear and biquadratic interactions are found by using the free energy surfaces. The free energy expression is obtained in the lowest approximation of the cluster variation method. All these solutions are shown in the two-dimensional phase space, especially the unstable solutions which in some cases are difficult to illustrate in the two-dimensional phase space, found by Keskin et al. recently.

  4. Long-Term Stable Surface Treatments on CdTe and CdZnTe Radiation Detectors

    Science.gov (United States)

    Pekarek, Jakub; Belas, Eduard; Zazvorka, Jakub

    2017-04-01

    The spectral resolution and charge collection efficiency (CCE) of cadmium telluride (CdTe) and cadmium zinc telluride (CZT) room-temperature x-ray and gamma-ray detectors are often limited by high surface leakage current due to conducting surface species created during detector fabrication. Surface treatments play a major role in reduction of this surface leakage current. The effect of various types of surface etching and passivation on the leakage current and thereby the spectral energy resolution, CCE, and internal electric field profile of CdTe/CZT detectors has been studied. The main aim of this work is preparation of long-term stable detectors with strongly reduced leakage current. The time stability of the current-voltage characteristic and spectral resolution was investigated during 21 days and 1 year, respectively, after performing surface treatments. Our results suggest that the optimal detector preparation method is chemomechanical polishing in bromine-ethylene glycol solution followed by chemical etching in bromine-methanol solution then surface passivation in potassium hydroxide or ammonium fluoride (NH4F/H2O2). Detectors prepared using this optimal treatment exhibited low leakage current, high spectral resolution, and long-term stability compared with those subjected to other surface preparation methods.

  5. Stable Isotopes of Ice on the Surface of Taylor Glacier, Antarctica, Version 1

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set contains Oxygen and Deuterium isotope ratios for approximately 980 sites on the surface of the ablation zone of Taylor Glacier, Antarctica. The data...

  6. Highly stable surface modification of hypercrosslinked monolithic capillary columns and their application in hydrophilic interaction chromatography.

    Science.gov (United States)

    Škeříková, Veronika; Urban, Jiří

    2013-09-01

    A two-step surface modification of poly(styrene-co-vinylbenzyl chloride-co-divinylbenzene) monolithic stationary phases, including hypercrosslinking and thermally initiated surface grafting of [2-(methacryloyloxy)ethyl]dimethyl(3-sulfopropyl)ammonium hydroxide, has been used to prepare capillary columns for the isocratic separation of small polar compounds in hydrophilic interaction chromatography (HILIC). The prepared monolithic columns provided a dual retention mechanism, combining RP and hydrophilic interaction chromatography, controlled by the composition of the mobile phase. By the optimization of the surface grafting reaction using response surface methodology, we have found that the grafting time is the main synergistic effect controlling the retention of polar compounds in HILIC. The prepared monolithic columns achieved long column lifetimes and did not lose their separation power following >10,000 injections. Finally, hypercrosslinked columns have been used in the 1- and 2D LC of phenolic compounds. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Fabrication of Water Jet Resistant and Thermally Stable Superhydrophobic Surfaces by Spray Coating of Candle Soot Dispersion.

    Science.gov (United States)

    Qahtan, Talal F; Gondal, Mohammed A; Alade, Ibrahim O; Dastageer, Mohammed A

    2017-08-08

    A facile synthesis method for highly stable carbon nanoparticle (CNP) dispersion in acetone by incomplete combustion of paraffin candle flame is presented. The synthesized CNP dispersion is the mixture of graphitic and amorphous carbon nanoparticles of the size range of 20-50 nm and manifested the mesoporosity with an average pore size of 7 nm and a BET surface area of 366 m 2 g -1 . As an application of this material, the carbon nanoparticle dispersion was spray coated (spray-based coating) on a glass surface to fabricate superhydrophobic (water contact angle > 150° and sliding angle fabricated from direct candle flame soot deposition (candle-based coating). This study proved that water jet resistant and thermally stable superhydrophobic surfaces can be easily fabricated by simple spray coating of CNP dispersion gathered from incomplete combustion of paraffin candle flame and this technique can be used for different applications with the potential for the large scale fabrication.

  8. Comparison of weak-wind characteristics across different Surface Types in stable stratification

    Science.gov (United States)

    Freundorfer, Anita; Rehberg, Ingo; Thomas, Christoph

    2017-04-01

    Atmospheric transport in weak winds and very stable conditions is often characterized by phenomena collectively referred to as submeso motions since their time and spatial scales exceed those of turbulence, but are smaller than synoptic motions. Evidence is mounting that submeso motions invalidate models for turbulent dispersion and diffusion since their physics are not captured by current similarity theories. Typical phenomena in the weak-wind stable boundary layer include meandering motions, quasi two-dimensional pancake-vortices or wavelike motions. These motions may be subject to non-local forcing and sensitive to small topographic undulations. The invalidity of Taylor's hypothesis of frozen turbulence for submeso motions requires the use of sensor networks to provide observations in both time and space domains simultaneously. We present the results from the series of Advanced Resolution Canopy Flow Observations (ARCFLO) experiments using a sensor network consisting of 12 sonic anemometers and 12 thermohygrometers. The objective of ARCFLO was to observe the flow and the turbulent and submeso transport at a high spatial and temporal resolution at 4 different sites in the Pacific Northwest, USA. These sites represented a variable degree of terrain complexity (flat to mountainous) and vegetation architecture (grass to forest, open to dense). In our study, a distinct weak-wind regime was identified for each site using the threshold velocity at which the friction velocity becomes dependent upon the mean horizontal wind speed. Here we used the scalar mean of the wind speed because the friction velocity showed a clearer dependence on the scalar mean compared to the vector mean of the wind velocity. It was found that the critical speed for the weak wind regime is higher in denser vegetation. For an open agricultural area (Botany and Plant Pathology Farm) we found a critical wind speed of v_crit= (0.24±0.05) ms-1 while for a very dense forest (Mary's River Douglas Fir

  9. Fabrication of stable and durable superhydrophobic surface on copper substrates for oil-water separation and ice-over delay.

    Science.gov (United States)

    Guo, Jie; Yang, Fuchao; Guo, Zhiguang

    2016-03-15

    We report a simple and rapid method to fabricate superhydrophobic films on copper substrates via Fe(3+) etching and octadecanethiol (ODT) modification. The etching process can be as short as 5 min and the ODT treatment only takes several seconds. In addition, the whole process is quite flexible in reaction time. The superhydrophobicity of as-prepared surfaces is mechanically durable and chemically stable, which have great performance in oil-water separation and ice-over resistance. Copyright © 2015 Elsevier Inc. All rights reserved.

  10. Ion beam induced surface pattern formation and stable travelling wave solutions.

    Science.gov (United States)

    Numazawa, Satoshi; Smith, Roger

    2013-03-06

    The formation of ripple structures on ion bombarded semiconductor surfaces is examined theoretically. Previous models are discussed and a new nonlinear model is formulated, based on the infinitesimal local atomic relocation induced by elastic nuclear collisions in the early stages of collision cascades and an associated density change in the near surface region. Within this framework ripple structures are shown to form without the necessity to invoke surface diffusion or large sputtering as important mechanisms. The model can also be extended to the case where sputtering is important, and it is shown that in this case certain 'magic' angles can occur at which the ripple patterns are most clearly defined. The results are in very good agreement with experimental observations.

  11. Preparation of Stable Superhydrophobic Coatings on Wood Substrate Surfaces via Mussel-Inspired Polydopamine and Electroless Deposition Methods

    Directory of Open Access Journals (Sweden)

    Kaili Wang

    2017-06-01

    Full Text Available Mussel-inspired polydopamine (PDA chemistry and electroless deposition approaches were used to prepare stable superhydrophobic coatings on wood surfaces. The as-formed PDA coating on a wood surface exhibited a hierarchical micro/nano roughness structure, and functioned as an “adhesive layer” between the substrate and a metallic film by the metal chelating ability of the catechol moieties on PDA, allowing for the formation of a well-developed micro/nanostructure hierarchical roughness. Additionally, the coating acted as a stable bridge between the substrate and hydrophobic groups. The morphology and chemical components of the prepared superhydrophobic wood surfaces were characterized by scanning electron microscopy (SEM, Fourier transform infrared (FT-IR spectroscopy, and X-ray photoelectron spectroscopy (XPS. The PDA and octadecylamine (OA modified surface showed excellent superhydrophobicity with a water contact angle (CA of about 153° and a rolling angle (RA of about 9°. The CA further increased to about 157° and RA reduced to about 5° with the Cu metallization. The superhydrophobic material exhibited outstanding stability in harsh conditions including ultraviolet aging, ultrasonic washing, strong acid-base and organic solvent immersion, and high-temperature water boiling. The results suggested that the PDA/OA layers were good enough to confer robust, degradation-resistant superhydrophobicity on wood substrates. The Cu metallization was likely unnecessary to provide significant improvements in superhydrophobic property. However, due to the amazing adhesive capacity of PDA, the electroless deposition technique may allow for a wide range of potential applications in biomimetic materials.

  12. A stable fused bicyclic disilene as a model for silicon surface.

    Science.gov (United States)

    Kobayashi, Hideki; Iwamoto, Takeaki; Kira, Mitsuo

    2005-11-09

    We synthesized the first fused bicyclic disilene 1 representing topologically a partial structure of the Si(001) surface up to the third layer. In the solid state, the five-membered rings adopt the envelope conformation, and the Si=Si double bond in 1 exists in the slightly cis-bent form (bent angle theta is 3.6 degrees ) compared to that of the highly cis-bent dimer on the Si(001) surface. Highly symmetric 1H NMR spectral pattern of 1 remains even at -80 degrees C, indicating the facile ring flipping of the bicyclic skeleton in solution. While syn-adduct was obtained in the reaction of 1 with water, anti-addition of chlorine atoms across the Si=Si double bond in 1 was observed in the reaction with carbon tetrachloride. The structural characteristics of the 9,10-phenanthrenequinone adduct 7 are in good accord with those of the proposed structure of the 9,10-phenanthrenequinone molecule adsorbed on the Si(001) surface.

  13. Surface Stress with Non-stationary Weak Winds and Stable Stratification

    Science.gov (United States)

    Mahrt, L.; Thomas, Christoph K.

    2016-04-01

    The behaviour of turbulent transport in the weak-wind, stably-stratified, boundary layer over land is examined in terms of the non-stationarity of the wind field using measurements from three field programs. These field programs include towers ranging from 12 to 20 m in height and an extensive horizontal network of sonic anemometers. The relationship of the friction velocity to the stratification and non-stationary submeso motions is investigated from several points of view and nominally quantified. The relationship of the turbulence to the stratification is less systematic than expected partly due to enhancement of the turbulence by submeso motions. Cause and effect relationships are difficult to isolate because the non-stationary momentum flux significantly modifies the profile of the non-stationary mean flow. The link between the turbulence and accelerations at the surface is examined in terms of the changing vertical structure of the wind profile and sudden increases in the downward transport of momentum.

  14. A novel metamaterial filter with stable passband performance based on frequency selective surface

    Directory of Open Access Journals (Sweden)

    C. Y. Fang

    2014-07-01

    Full Text Available In this paper, a novel metamaterial filter based on frequency selective surface (FSS is proposed. Using the mode matching method, we theoretically studied the transmission performance of the structure. Results show that, by rotating its neighboring elements 90 degree, the novel filter has a better stability to angle of incidence than traditional structures for TE and TM polarization. As the incident angles vary from 0 to 50 degrees, the metamaterial filter exhibits a transmittance higher than 0.98 and the center frequency slightly shifts downward (from 10 GHz to 0.96 GHz for TE polarization. For TM polarization, a transmittance of 0.98 is achieved and the center frequency retains 0.96 GHz with the varying of the incident angles. Furthermore, an experimental prototype fabricated was tested in a microwave chamber, and the measured results show good agreement with the simulated ones.

  15. Observation of Stable Low Surface Resistance in Large-Grain Niobium SRF Cavities

    Energy Technology Data Exchange (ETDEWEB)

    Geng, Rongli [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Huang, Shichun [Institute of Modern Physics (IMP)/Chinese Academy of Sciences (CAS), Lanzhou (China)

    2016-05-01

    Low surface resistance, or high unloaded quality factor (Q0), superconducting radio frequency (SRF) cavities are being pursued actively nowadays as their application in large-scale CW SRF accelerators can save capital and operational cost in cryogenics. There are different options in realization of such cavities. One of them is the large-grain (LG) niobium cavity. In this contribution, we present new experimental results in evaluation of LG niobium cavities cooled down in the presence of an external magnetic field. High Q0 values are achieved even with an ambient magnetic field of up to 100 mG. More over, it is observed that these high Q0 values are super-robust against repeated quench, literally not affected at all after the cavity being deliberately quenched for hundreds of times in the presence of an ambient magnetic field of up to 200 mG.

  16. Chemically immobilised carbon nanotubes on silicon: Stable surfaces for aqueous electrochemistry

    International Nuclear Information System (INIS)

    Flavel, Benjamin S.; Garrett, David J.; Lehr, Joshua; Shapter, Joseph G.; Downard, Alison J.

    2010-01-01

    Diazonium ion chemistry has been used to electrochemically graft aminophenyl layers onto p-type silicon (1 0 0) substrates. A condensation reaction was used to immobilise single-walled carbon nanotubes with high carboxylic acid functionality directly to this layer. Electrochemical monitoring of the aminophenyl groups confirmed the formation of an amide linkage between the single-walled carbon nanotubes and the aminophenyl layer. The carbon nanotube electrode showed high stability and good electrochemical performance in aqueous solution. At moderate scan rates the Ru(NH 3 ) 6 +3/+2 couple exhibited quasi-reversible electron transfer kinetics with a standard heterogenous rate constant of 1.2 x 10 -3 cm s -1 at the covalently-linked carbon nanotube surface. The electrode thus combines the advantages of a silicon substrate for easy integration into sophisticated electrical and electronic devices, carbon nanotubes for desirable electrochemical properties, and stability in aqueous medium for future applications in environmental sensing.

  17. Surface transport and stable trapping of particles and cells by an optical waveguide loop.

    Science.gov (United States)

    Hellesø, Olav Gaute; Løvhaugen, Pål; Subramanian, Ananth Z; Wilkinson, James S; Ahluwalia, Balpreet Singh

    2012-09-21

    Waveguide trapping has emerged as a useful technique for parallel and planar transport of particles and biological cells and can be integrated with lab-on-a-chip applications. However, particles trapped on waveguides are continuously propelled forward along the surface of the waveguide. This limits the practical usability of the waveguide trapping technique with other functions (e.g. analysis, imaging) that require particles to be stationary during diagnosis. In this paper, an optical waveguide loop with an intentional gap at the centre is proposed to hold propelled particles and cells. The waveguide acts as a conveyor belt to transport and deliver the particles/cells towards the gap. At the gap, the diverging light fields hold the particles at a fixed position. The proposed waveguide design is numerically studied and experimentally implemented. The optical forces on the particle at the gap are calculated using the finite element method. Experimentally, the method is used to transport and trap micro-particles and red blood cells at the gap with varying separations. The waveguides are only 180 nm thick and thus could be integrated with other functions on the chip, e.g. microfluidics or optical detection, to make an on-chip system for single cell analysis and to study the interaction between cells.

  18. CONDITIONS FOR STABLE CHIP BREAKING AND PROVISION OF MACHINED SURFACE QUALITY WHILE TURNING WITH ASYMMETRIC TOOL VIBRATIONS

    Directory of Open Access Journals (Sweden)

    V. K. Sheleh

    2015-01-01

    Full Text Available The paper considers a process of turning structural steel with asymmetric tool vibrations directed along feeding. Asymmetric vibrations characterized by asymmetry coefficient of vibration cycle, their frequency and amplitude are additionally transferred to the tool in the turning process with the purpose to crush chips. Conditions of stable chip breaking and obtaining optimum dimensions of chip elements have been determined in the paper. In order to reduce a negative impact of the vibration amplitude on a cutting process and quality of the machined surfaces machining must be carried out with its minimum value. In this case certain ratio of the tool vibration frequency to the work-piece rotation speed has been ensured in the paper. A formula has been obtained for calculation of this ratio with due account of the expected length of chip elements and coefficient of vibration cycle asymmetry.Influence of the asymmetric coefficient of the tool vibration cycle on roughness of the machined surfaces and cutting tool wear has been determined in the paper. According to the results pertaining to machining of work-pieces made of 45 and ШХ15 steel the paper presents mathematical relationships of machined surface roughness with cutting modes and asymmetry coefficient of tool vibration cycle. Tool feeding being one of the cutting modes exerts the most significant impact on the roughness value and increase of the tool feeding entails increase in roughness. Reduction in coefficient of vibration cycle asymmetry contributes to surface roughness reduction. However, the cutting tool wear occurs more intensive. Coefficient of the vibration cycle asymmetry must be increased in order to reduce wear rate. Therefore, the choice of the coefficient of the vibration cycle asymmetry is based on the parameters of surface roughness which must be obtained after machining and intensity of tool wear rate.The paper considers a process of turning structural steel with asymmetric

  19. The Impact of Wind Speed Changes on the Surface Stress in the Weak-wind Stable Boundary Layer

    Science.gov (United States)

    Thomas, C. K.

    2015-12-01

    The behaviour of turbulent transport in the weak-wind stably stratified boundary layer is examined in terms of the non-stationarity of the wind field based upon field observations. Extensive sonic anemometer measurements from horizontal networks and vertical towers ranging from 12 to 20 m height were collected from three field programs in moderately sloped terrain with a varying degree of surface heterogeneity, namely the Shallow Cold Pool (SCP) and the Flow Over Snow Surfaces (FLOSS) II experiments in Colorado (USA), and the Advanced Canopy Resolution Experiment (ARCFLO) in Oregon (USA). The relationship of the friction velocity to the stratification and small non-stationary submeso motions is studied from several points of view and nominally quantified. The relationship of the turbulence to the stratification is less systematic than expected due to the important submeso-scale motions. Consequently, the roles of the wind speed and stratification are not adequately accommodated by a single non-dimensional combination, such as the bulk Richardson number. Howver, cause and effect relationships are difficult to isolate because the non-stationary momentum flux significantly modifies the profile of the non-stationary mean flow. The link between the turbulence and accelerations at the surface is examined in terms of the changing vertical structure of the wind profile and sudden increases of downward transport of momentum. The latter may be significant in explaining the small-scale weak turbulence during stable stratification and deviations from conventional flux-profile relationships.

  20. Fabricating a Homogeneously Alloyed AuAg Shell on Au Nanorods to Achieve Strong, Stable, and Tunable Surface Plasmon Resonances

    KAUST Repository

    Huang, Jianfeng

    2015-08-13

    Colloidal metal nanocrystals with strong, stable, and tunable localized surface plasmon resonances (SPRs) can be useful in a corrosive environment for many applications including field-enhanced spectroscopies, plasmon-mediated catalysis, etc. Here, a new synthetic strategy is reported that enables the epitaxial growth of a homogeneously alloyed AuAg shell on Au nanorod seeds, circumventing the phase segregation of Au and Ag encountered in conventional synthesis. The resulting core–shell structured bimetallic nanorods (AuNR@AuAg) have well-mixed Au and Ag atoms in their shell without discernible domains. This degree of mixing allows AuNR@AuAg to combine the high stability of Au with the superior plasmonic activity of Ag, thus outperforming seemingly similar nanostructures with monometallic shells (e.g., Ag-coated Au NRs (AuNR@Ag) and Au-coated Au NRs (AuNR@Au)). AuNR@AuAg is comparable to AuNR@Ag in plasmonic activity, but that it is markedly more stable toward oxidative treatment. Specifically, AuNR@AuAg and AuNR@Ag exhibit similarly strong signals in surface-enhanced Raman spectroscopy that are some 30-fold higher than that of AuNR@Au. When incubated with a H2O2 solution (0.5 m), the plasmonic activity of AuNR@Ag immediately and severely decayed, whereas AuNR@AuAg retained its activity intact. Moreover, the longitudinal SPR frequency of AuNR@AuAg can be tuned throughout the red wavelengths (≈620–690 nm) by controlling the thickness of the AuAg alloy shell. The synthetic strategy is versatile to fabricate AuAg alloyed shells on different shaped Au, with prospects for new possibilities in the synthesis and application of plasmonic nanocrystals.

  1. The impact of non-stationary flows on the surface stress in the weak-wind stable boundary layer

    Science.gov (United States)

    Thomas, Christoph; Mahrt, Larry

    2016-04-01

    The behaviour of turbulent transport in the weak-wind stably stratified boundary layer is examined in terms of the non-stationarity of the wind field based upon field observations. Extensive sonic anemometer measurements from horizontal networks and vertical towers ranging from 12 to 20 m height and innovative fiber-optic distributed temperature sensing observations were collected from three field programs in moderately sloped terrain with a varying degree of surface heterogeneity, namely the Shallow Cold Pool (SCP) and the Flow Over Snow Surfaces (FLOSS) II experiments in Colorado (USA), and the Advanced Canopy Resolution Experiment (ARCFLO) in Oregon (USA). The relationship of the friction velocity to the stratification and small non-stationary submeso motions is studied from several points of view and nominally quantified. The relationship of the turbulence to the stratification is less systematic than expected due to the important submeso-scale motions. Consequently, the roles of the wind speed and stratification are not adequately accommodated by a single non-dimensional combination, such as the bulk Richardson number. However, cause and effect relationships are difficult to isolate because the non-stationary momentum flux significantly modifies the profile of the non-stationary mean flow. The link between the turbulence and accelerations at the surface is examined in terms of the changing vertical structure of the wind profile and sudden increases of downward transport of momentum. The latter may be significant in explaining the small-scale weak turbulence during stable stratification and deviations from conventional flux-profile relationships. Contrary to expectations, the vertical coherence was strongest for weakest winds and declined fast with increasing velocities, which suggests that submeso-scale motions are much deeper than previously thought.

  2. Marinobacter sp. from marine sediments produce highly stable surface-active agents for combatting marine oil spills.

    Science.gov (United States)

    Raddadi, Noura; Giacomucci, Lucia; Totaro, Grazia; Fava, Fabio

    2017-11-02

    The application of chemical dispersants as a response to marine oil spills is raising concerns related to their potential toxicity also towards microbes involved in oil biodegradation. Hence, oil spills occurring under marine environments necessitate the application of biodispersants that are highly active, stable and effective under marine environment context. Biosurfactants from marine bacteria could be good candidates for the development of biodispersant formulations effective in marine environment. This study aimed at establishing a collection of marine bacteria able to produce surface-active compounds and evaluating the activity and stability of the produced compounds under conditions mimicking those found under marine environment context. A total of 43 different isolates were obtained from harbor sediments. Twenty-six of them produced mainly bioemulsifiers when glucose was used as carbon source and 16 were biosurfactant/bioemulsifiers producers after growth in the presence of soybean oil. Sequencing of 16S rRNA gene classified most isolates into the genus Marinobacter. The produced emulsions were shown to be stable up to 30 months monitoring period, in the presence of 300 g/l NaCl, at 4 °C and after high temperature treatment (120 °C for 20 min). The partially purified compounds obtained after growth on soybean oil-based media exhibited low toxicity towards V. fischeri and high capability to disperse crude oil on synthetic marine water. To the best of our knowledge, stability characterization of bioemulsifiers/biosurfactants from the non-pathogenic marine bacterium Marinobacter has not been previously reported. The produced compounds were shown to have potential for different applications including the environmental sector. Indeed, their high stability in the presence of high salt concentration and low temperature, conditions characterizing the marine environment, the capability to disperse crude oil and the low ecotoxicity makes them interesting for

  3. Effects of core strength training using stable versus unstable surfaces on physical fitness in adolescents: a randomized controlled trial.

    Science.gov (United States)

    Granacher, Urs; Schellbach, Jörg; Klein, Katja; Prieske, Olaf; Baeyens, Jean-Pierre; Muehlbauer, Thomas

    2014-01-01

    It has been demonstrated that core strength training is an effective means to enhance trunk muscle strength (TMS) and proxies of physical fitness in youth. Of note, cross-sectional studies revealed that the inclusion of unstable elements in core strengthening exercises produced increases in trunk muscle activity and thus provide potential extra training stimuli for performance enhancement. Thus, utilizing unstable surfaces during core strength training may even produce larger performance gains. However, the effects of core strength training using unstable surfaces are unresolved in youth. This randomized controlled study specifically investigated the effects of core strength training performed on stable surfaces (CSTS) compared to unstable surfaces (CSTU) on physical fitness in school-aged children. Twenty-seven (14 girls, 13 boys) healthy subjects (mean age: 14 ± 1 years, age range: 13-15 years) were randomly assigned to a CSTS (n = 13) or a CSTU (n = 14) group. Both training programs lasted 6 weeks (2 sessions/week) and included frontal, dorsal, and lateral core exercises. During CSTU, these exercises were conducted on unstable surfaces (e.g., TOGU© DYNAIR CUSSIONS, THERA-BAND© STABILITY TRAINER). Significant main effects of Time (pre vs. post) were observed for the TMS tests (8-22%, f = 0.47-0.76), the jumping sideways test (4-5%, f = 1.07), and the Y balance test (2-3%, f = 0.46-0.49). Trends towards significance were found for the standing long jump test (1-3%, f = 0.39) and the stand-and-reach test (0-2%, f = 0.39). We could not detect any significant main effects of Group. Significant Time x Group interactions were detected for the stand-and-reach test in favour of the CSTU group (2%, f = 0.54). Core strength training resulted in significant increases in proxies of physical fitness in adolescents. However, CSTU as compared to CSTS had only limited additional effects (i.e., stand-and-reach test). Consequently, if the

  4. Comparison of hamstring and quadriceps femoris electromyographic activity between men and women during a single-limb squat on both a stable and labile surface.

    Science.gov (United States)

    Youdas, James W; Hollman, John H; Hitchcock, James R; Hoyme, Gregory J; Johnsen, Jeremiah J

    2007-02-01

    The purpose of this study was to determine if women are quadriceps dominant and men are hamstring dominant during the performance of a partial single-leg squat (SLS) on both a stable and labile ground surface against body weight resistance. Thirty healthy participants (15 men and 15 women) performed an SLS on both a stable surface and a 6.4-cm-thick vinyl pad. Surface electromyographic (EMG) recordings were obtained from the quadriceps femoris and hamstring muscles during the extension phase of the SLS. Statistical analysis revealed that women produced 14% more EMG activity (p = 0.04) in their quadriceps than the men during the SLS on a stable surface, whereas the men generated 18% more EMG activity (p = 0.04) in their hamstrings than the women during the SLS on a labile surface. Additionally, we found a statistically significant sex effect (p = 0.048) for the hamstring/quadriceps (H/Q) EMG ratio, which was 2.25 and 0.62, respectively, for men and women on the stable surface and 2.52 and 0.71, respectively, on the labile surface. We concluded that women are quadriceps dominant and men are hamstring dominant during the performance of SLS against body weight resistance on either a stable or labile surface condition. During an SLS, men showed an H/Q ratio approximately 3.5 times larger than their female counterparts, suggesting that men activate their hamstrings more effectively than women during an SLS. According to our data, the SLS may not be an ideal exercise for activating the hamstring muscles in women without additional neuromuscular training techniques, because women are quadriceps dominant during the SLS.

  5. Effect of Built-Up Edge Formation during Stable State of Wear in AISI 304 Stainless Steel on Machining Performance and Surface Integrity of the Machined Part.

    Science.gov (United States)

    Ahmed, Yassmin Seid; Fox-Rabinovich, German; Paiva, Jose Mario; Wagg, Terry; Veldhuis, Stephen Clarence

    2017-10-25

    During machining of stainless steels at low cutting -speeds, workpiece material tends to adhere to the cutting tool at the tool-chip interface, forming built-up edge (BUE). BUE has a great importance in machining processes; it can significantly modify the phenomenon in the cutting zone, directly affecting the workpiece surface integrity, cutting tool forces, and chip formation. The American Iron and Steel Institute (AISI) 304 stainless steel has a high tendency to form an unstable BUE, leading to deterioration of the surface quality. Therefore, it is necessary to understand the nature of the surface integrity induced during machining operations. Although many reports have been published on the effect of tool wear during machining of AISI 304 stainless steel on surface integrity, studies on the influence of the BUE phenomenon in the stable state of wear have not been investigated so far. The main goal of the present work is to investigate the close link between the BUE formation, surface integrity and cutting forces in the stable sate of wear for uncoated cutting tool during the cutting tests of AISI 304 stainless steel. The cutting parameters were chosen to induce BUE formation during machining. X-ray diffraction (XRD) method was used for measuring superficial residual stresses of the machined surface through the stable state of wear in the cutting and feed directions. In addition, surface roughness of the machined surface was investigated using the Alicona microscope and Scanning Electron Microscopy (SEM) was used to reveal the surface distortions created during the cutting process, combined with chip undersurface analyses. The investigated BUE formation during the stable state of wear showed that the BUE can cause a significant improvement in the surface integrity and cutting forces. Moreover, it can be used to compensate for tool wear through changing the tool geometry, leading to the protection of the cutting tool from wear.

  6. Effect of Built-Up Edge Formation during Stable State of Wear in AISI 304 Stainless Steel on Machining Performance and Surface Integrity of the Machined Part

    Science.gov (United States)

    Fox-Rabinovich, German; Wagg, Terry

    2017-01-01

    During machining of stainless steels at low cutting -speeds, workpiece material tends to adhere to the cutting tool at the tool–chip interface, forming built-up edge (BUE). BUE has a great importance in machining processes; it can significantly modify the phenomenon in the cutting zone, directly affecting the workpiece surface integrity, cutting tool forces, and chip formation. The American Iron and Steel Institute (AISI) 304 stainless steel has a high tendency to form an unstable BUE, leading to deterioration of the surface quality. Therefore, it is necessary to understand the nature of the surface integrity induced during machining operations. Although many reports have been published on the effect of tool wear during machining of AISI 304 stainless steel on surface integrity, studies on the influence of the BUE phenomenon in the stable state of wear have not been investigated so far. The main goal of the present work is to investigate the close link between the BUE formation, surface integrity and cutting forces in the stable sate of wear for uncoated cutting tool during the cutting tests of AISI 304 stainless steel. The cutting parameters were chosen to induce BUE formation during machining. X-ray diffraction (XRD) method was used for measuring superficial residual stresses of the machined surface through the stable state of wear in the cutting and feed directions. In addition, surface roughness of the machined surface was investigated using the Alicona microscope and Scanning Electron Microscopy (SEM) was used to reveal the surface distortions created during the cutting process, combined with chip undersurface analyses. The investigated BUE formation during the stable state of wear showed that the BUE can cause a significant improvement in the surface integrity and cutting forces. Moreover, it can be used to compensate for tool wear through changing the tool geometry, leading to the protection of the cutting tool from wear. PMID:29068405

  7. Effect of Built-Up Edge Formation during Stable State of Wear in AISI 304 Stainless Steel on Machining Performance and Surface Integrity of the Machined Part

    Directory of Open Access Journals (Sweden)

    Yassmin Seid Ahmed

    2017-10-01

    Full Text Available During machining of stainless steels at low cutting -speeds, workpiece material tends to adhere to the cutting tool at the tool–chip interface, forming built-up edge (BUE. BUE has a great importance in machining processes; it can significantly modify the phenomenon in the cutting zone, directly affecting the workpiece surface integrity, cutting tool forces, and chip formation. The American Iron and Steel Institute (AISI 304 stainless steel has a high tendency to form an unstable BUE, leading to deterioration of the surface quality. Therefore, it is necessary to understand the nature of the surface integrity induced during machining operations. Although many reports have been published on the effect of tool wear during machining of AISI 304 stainless steel on surface integrity, studies on the influence of the BUE phenomenon in the stable state of wear have not been investigated so far. The main goal of the present work is to investigate the close link between the BUE formation, surface integrity and cutting forces in the stable sate of wear for uncoated cutting tool during the cutting tests of AISI 304 stainless steel. The cutting parameters were chosen to induce BUE formation during machining. X-ray diffraction (XRD method was used for measuring superficial residual stresses of the machined surface through the stable state of wear in the cutting and feed directions. In addition, surface roughness of the machined surface was investigated using the Alicona microscope and Scanning Electron Microscopy (SEM was used to reveal the surface distortions created during the cutting process, combined with chip undersurface analyses. The investigated BUE formation during the stable state of wear showed that the BUE can cause a significant improvement in the surface integrity and cutting forces. Moreover, it can be used to compensate for tool wear through changing the tool geometry, leading to the protection of the cutting tool from wear.

  8. The O and H stable isotope composition of freshwaters in the British Isles. 2. Surface waters and groundwater

    Directory of Open Access Journals (Sweden)

    W. G. Darling

    2003-01-01

    Full Text Available The utility of stable isotopes as tracers of the water molecule has a long pedigree. The study reported here is part of an attempt to establish a comprehensive isotopic 'baseline' for the British Isles as background data for a range of applications. Part 1 of this study (Darling and Talbot, 2003 considered the isotopic composition of rainfall in Britain and Ireland. The present paper is concerned with the composition of surface waters and groundwater. In isotopic terms, surface waters (other than some upland streams are poorly characterised in the British Isles; their potential variability has yet to be widely used as an aid in hydrological research. In what may be the first study of a major British river, a monthly isotopic record of the upper River Thames during 1998 was obtained. This shows high damping of the isotopic variation compared to that in rainfall over most of the year, though significant fluctuations were seen for the autumn months. Smaller rivers such as the Stour and Darent show a more subdued response to the balance between runoff and baseflow. The relationship between the isotopic composition of rainfall and groundwater is also considered. From a limited database, it appears that whereas Chalk groundwater is a representative mixture of weighted average annual rainfall, for Triassic sandstone groundwater there is a seasonal selection of rainfall biased towards isotopically-depleted winter recharge. This may be primarily the result of physical differences between the infiltration characteristics of rock types, though other factors (vegetation, glacial history could be involved. In the main, however, groundwaters appear to be representative of bulk rainfall within an error band of 0.5‰ δ18O. Contour maps of the δ18O and δ2H content of recent groundwaters in the British Isles show a fundamental SW-NE depletion effect modified by topography. The range of measured values, while much smaller than those for rainfall, still covers

  9. Chemically stable Au nanorods as probes for sensitive surface enhanced scattering (SERS) analysis of blue BIC ballpoint pens

    Science.gov (United States)

    Alyami, Abeer; Saviello, Daniela; McAuliffe, Micheal A. P.; Cucciniello, Raffaele; Mirabile, Antonio; Proto, Antonio; Lewis, Liam; Iacopino, Daniela

    2017-08-01

    Au nanorods were used as an alternative to commonly used Ag nanoparticles as Surface Enhanced Raman Scattering (SERS) probes for identification of dye composition of blue BIC ballpoint pens. When used in combination with Thin Layer Chromatography (TLC), Au nanorod colloids allowed identification of the major dye components of the BIC pen ink, otherwise not identifiable by normal Raman spectroscopy. Thanks to their enhanced chemical stability compared to Ag colloids, Au nanorods provided stable and reproducible SERS signals and allowed easy identification of phthalocyanine and triarylene dyes in the pen ink mixture. These findings were supported by FTIR and MALDI analyses, also performed on the pen ink. Furthermore, the self-assembly of Au nanorods into large area ordered superstructures allowed identification of BIC pen traces. SERS spectra of good intensity and high reproducibility were obtained using Au nanorod vertical arrays, due to the high density of hot spots and morphological reproducibility of these superstructures. These results open the way to the employment of SERS for fast screening analysis and for quantitative analysis of pens and faded pens which are relevant for the fields of forensic and art conservation sciences.

  10. Stable phase CdS nanoparticles for optoelectronics: a study on surface morphology, structural and optical characterization

    Directory of Open Access Journals (Sweden)

    Kumar Suresh

    2016-06-01

    Full Text Available This work presents a study on the surface morphology, structure and optical behavior of stable phase cadmium sulphide (CdS nanoparticles synthesized via co-precipitation technique. Scanning electron microscopy (SEM analysis has been employed to study a cluster formation in the aggregated nanoparticles. An image analysis approach using ImageJ has been used to measure the size of nanoparticles from the SEM micrographs. Fourier transform infrared spectroscopic (FT-IR analysis identified absorption peaks of Cd–S stretching along with moisture content. X-ray diffraction (XRD analysis showed that CdS nanoparticles crystallized in wurtzite structure with a preferential orientation along (0 0 2 plane. The particle size, microstrain and lattice constants have been evaluated using XRD data. The lattice parameters of these nanoparticles were found to be shorter than the bulk value which led to lattice contraction. The optical absorption study showed a blue shift in the fundamental absorption edge indicating a quantum size effect.

  11. Quantification of Gaseous Elemental Mercury Dry Deposition to Environmental Surfaces using Mercury Stable Isotopes in a Controlled Environment

    Science.gov (United States)

    Rutter, A. P.; Schauer, J. J.; Shafer, M. M.; Olson, M.; Robinson, M.; Vanderveer, P.; Creswell, J. E.; Parman, A.; Mallek, J.; Gorski, P.

    2009-12-01

    atmospheric turbulence and wind speed. GEM enriched in stable isotope 198 (GEM-198) was released into the room from source at elevated but environmentally relevant concentrations of GEM-198 for several days. Uptake of GEM-198 from deciduous and conifer trees, grass turf, 3 types of soil, sand, concrete, asphalt, and adsorbent coated deposition coupons were quantified over several days. Exposures were conducted between 10oC and 30oC, in dark and light conditions. Mercury was recovered from the samples using acidic digestions and surface leaches, and then analyzed for the content of GEM-198 by high resolution ICPMS. Experimental results demonstrated that uptake by White Ash, White Spruce, and Kentucky bluegrass were significantly higher than uptakes measured for two Wisconsin soils, peat, sand, concrete and asphalt at all of the conditions studied. Deposition resistances for surface transfer processes for were calculated for each of the substrates across the conditions studied for use in atmospheric model simulations.

  12. A stable metal-organic framework with suitable pore sizes and rich uncoordinated nitrogen atoms on the internal surface of micropores for highly efficient CO2 capture

    NARCIS (Netherlands)

    Bao, S.J.; Krishna, R.; He, Y.B.; Qin, J.S.; Su, Z.M.; Li, S.L.; Xie, W.; Du, D.Y.; He, W.W.; Zhang, S.R.; Lan, Y.Q.

    2015-01-01

    An air-stable tetrazolate-containing framework, [ZN(2)L(2)]center dot 2DMF (NENU-520, H2L = 4-(1H-tetrazole-5-yl) biphenyl-4-carboxylic acid), with uncoordinated N atoms on its internal surface was solvothermally synthesized and structurally characterized. This metal-organic framework (MOF)

  13. The role of snow-surface coupling, radiation, and turbulent mixing in modeling a stable boundary layer over Arctic sea ice

    NARCIS (Netherlands)

    Sterk, H.A.M.; Steeneveld, G.J.; Holtslag, A.A.M.

    2013-01-01

    To enhance the understanding of the impact of small-scale processes in the polar climate, this study focuses on the relative role of snow-surface coupling, radiation and turbulent mixing in an Arctic stable boundary layer. We extend the GABLS1 (GEWEX Atmospheric Boundary-Layer Study 1) model

  14. Quantification of long-term wastewater fluxes at the surface water/groundwater-interface: an integrative model perspective using stable isotopes and acesulfame.

    Science.gov (United States)

    Engelhardt, I; Barth, J A C; Bol, R; Schulz, M; Ternes, T A; Schüth, C; van Geldern, R

    2014-01-01

    The suitability of acesulfame to trace wastewater-related surface water fluxes from streams into the hyporheic and riparian zones over long-term periods was investigated. The transport behavior of acesulfame was compared with the transport of water stable isotopes (δ(18)O or δ(2)H). A calibrated model based on a joint inversion of temperature, acesulfame, and piezometric pressure heads was employed in a model validation using data sets of acesulfame and water stable isotopes collected over 5months in a stream and groundwater. The spatial distribution of fresh water within the groundwater resulting from surface water infiltration was estimated by computing groundwater ages and compared with the predicted acesulfame plume obtained after 153day simulation time. Both, surface water ratios calculated with a mixing equation from water stable isotopes and simulated acesulfame mass fluxes, were investigated for their ability to estimate the contribution of wastewater-related surface water inflow within groundwater. The results of this study point to limitations for the application of acesulfame to trace surface water-groundwater interactions properly. Acesulfame completely missed the wastewater-related surface water volumes that still remained in the hyporheic zone under stream-gaining conditions. In contrast, under stream-losing conditions, which developed after periods of stagnating hydraulic exchange, acesulfame based predictions lead to an overestimation of the surface water volume of up to 25% in the riparian zone. If slow seepage velocities prevail a proportion of acesulfame might be stored in smaller pores, while when released under fast flowing water conditions it will travel further downstream with the groundwater flow direction. Therefore, under such conditions acesulfame can be a less-ideal tracer in the hyporheic and riparian zones and additional monitoring with other environmental tracers such as water stable isotopes is highly recommended. © 2013 Elsevier

  15. Hydrogeochemistry and stable isotopes of ground and surface waters from two adjacent closed basins, Atacama Desert, northern Chile

    Science.gov (United States)

    Alpers, Charles N.; Whittemore, D.O.

    1990-01-01

    The geochemistry and stable isotopes of groundwaters, surface waters, and precipitation indicate different sources of some dissolved constituents, but a common source of recharge and other constituents in two adjacent closed basins in the Atacama Desert region of northern Chile (24??15???-24??45???S). Waters from artesian wells, trenches, and ephemeral streams in the Punta Negra Basin are characterized by concentrations of Na>Ca>Mg and Cl ???SO4, with TDS Mg ??? Ca and SO4 > Cl, with TDS also Mg ??? Ca and SO4 > Cl, but with TDS up to 40 g/l. The deep mine waters have pH between 3.2 and 3.9, and are high in dissolved CO2 (??13 C = -4.8%PDB), indicating probable interaction with oxidizing sulfides. The deep mine waters have ??18O values of ???-1.8%.compared with values < -3.5??? for other Hamburgo Basin waters; thus the mine waters may represent a mixture of meteoric waters with deeper "metamorphic" waters, which had interacted with rocks and exchanged oxygen isotopes at elevated temperatures. Alternatively, the deep mine waters may represent fossil meteoric waters which evolved isotopically along an evaporative trend starting from values quite depleted in ??18O and ??Dd relative to either precipitation or shallow groundwaters. High I/Br ratios in the Hamburgo Basin waters and La Escondida mine waters are consistent with regionally high I in surficial deposits in the Atacama Desert region and may represent dissolution of a wind-blown evaporite component. Rain and snow collected during June 1984, indicate systematic ??18O and ??D fractionation with increasing elevation between 3150 and 4180 m a.s.l. (-0.21??.??18O and -1.7??.??D per 100 m). Excluding the deep mine waters from La Escondida, the waters from the Hamburgo and Punta Negra Basins have similar ??D and ??18O values and together show a distinct evaporative trend (??D = 5.0 ??18O - 20.2). Snowmelt from the central Andes Cordillera to the east is the most likely source of recharge to both basins. Some of the

  16. Stable Boundary Layer Issues

    NARCIS (Netherlands)

    Steeneveld, G.J.

    2012-01-01

    Understanding and prediction of the stable atmospheric boundary layer is a challenging task. Many physical processes are relevant in the stable boundary layer, i.e. turbulence, radiation, land surface coupling, orographic turbulent and gravity wave drag, and land surface heterogeneity. The

  17. Conditions for Stable Chip Breaking and Provision of Machined Surface Quality While Turning with Asymmetric Tool Vibrations

    OpenAIRE

    Шелег, В. К.; Молочко, В. И.; Данильчик, С. С.

    2015-01-01

    The paper considers a process of turning structural steel with asymmetric tool vibrations directed along feeding. Asymmetric vibrations characterized by asymmetry coefficient of vibration cycle, their frequency and amplitude are additionally transferred to the tool in the turning process with the purpose to crush chips. Conditions of stable chip breaking and obtaining optimum dimensions of chip elements have been determined in the paper. In order to reduce a negative impact of the vibration a...

  18. Water stable isotope shifts of surface waters as proxies to quantify evaporation, transpiration and carbon uptake on catchment scales

    Science.gov (United States)

    Barth, Johannes; van Geldern, Robert; Veizer, Jan; Karim, Ajaz; Freitag, Heiko; Fowlwer, Hayley

    2017-04-01

    Comparison of water stable isotopes of rivers to those of precipitation enables separation of evaporation from transpiration on the catchment scale. The method exploits isotope ratio changes that are caused exclusively by evaporation over longer time periods of at least one hydrological year. When interception is quantified by mapping plant types in catchments, the amount of water lost by transpiration can be determined. When in turn pairing transpiration with the water use efficiency (WUE i.e. water loss by transpiration per uptake of CO2) and subtracting heterotrophic soil respiration fluxes (Rh), catchment-wide carbon balances can be established. This method was applied to several regions including the Great Lakes and the Clyde River Catchments ...(Barth, et al., 2007, Karim, et al., 2008). In these studies evaporation loss was 24 % and 1.3 % and transpiration loss was 47 % and 22 % when compared to incoming precipitation for the Great Lakes and the Clyde Catchment, respectively. Applying WUE values for typical plant covers and using area-typical Rh values led to estimates of CO2 uptake of 251 g C m-2 a-1 for the Great Lakes Catchment and CO2 loss of 21 g C m2 a-1 for the Clyde Catchment. These discrepancies are most likely due to different vegetation covers. The method applies to scales of several thousand km2 and has good potential for improvement via calibration on smaller scales. This can for instance be achieved by separate treatment of sub-catchments with more detailed mapping of interception as a major unknown. These previous studies have shown that better uncertainty analyses are necessary in order to estimate errors in water and carbon balances. The stable isotope method is also a good basis for comparison to other landscape carbon balances for instance by eddy covariance techniques. This independent method and its up-scaling combined with the stable isotope and area-integrating methods can provide cross validation of large-scale carbon budgets

  19. A Simple Nanocellulose Coating for Self-Cleaning upon Water Action: Molecular Design of Stable Surface Hydrophilicity.

    Science.gov (United States)

    Huang, Shu; Wang, Dayang

    2017-07-24

    Coating solid surfaces with cellulose nanofibril (CNF) monolayers via physical deposition was found to keep the surfaces free of a variety of oils, ranging from viscous engine oil to polar n-butanol, upon water action. The self-cleaning function was well correlated with the unique molecular structure of the CNF, in which abundant surface carboxyl and hydroxy groups are uniformly, densely, and symmetrically arranged to form a polar corona on a crystalline nanocellulose strand. This isotropic core-corona configuration offers new and easily adoptable guidance to design self-cleaning surfaces at the molecular level. Thanks to its excellent self-cleaning behavior, the CNF coating converted conventional meshes into highly effective membranes for oil-water separation with no prior surface treatment required. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Study, using stable isotopes, of flow distribution, surface-groundwater relations and evapotranspiration in the Okavango Swamp, Botswana

    International Nuclear Information System (INIS)

    Dincer, T.; Hutton, L.G.; Kupee, B.B.J.

    1979-01-01

    Stable isotope data collected in the Okavango Delta have confirmed that the central distributary system is more active at present than the peripheral systems. The data also show that there is no groundwater outflow at the western and southern margins of the delta. A salinity-isotope model of the deltaic swamp has been developed to study the relation between the salinity and isotopic composition of the swamp waters. An attempt has been made to separate the atmospheric losses from the swamp into its evapotranspiration components. The results indicate that in winter, when high water levels prevail, these losses are almost entirely due to evaporation whilst in summer, when the water levels are low, evaporation and transpiration contribute almost equally to the total atmospheric losses. (author)

  1. On a free-surface problem with moving contact line: From variational principles to stable numerical approximations

    Science.gov (United States)

    Fumagalli, Ivan; Parolini, Nicola; Verani, Marco

    2018-02-01

    We analyze a free-surface problem described by time-dependent Navier-Stokes equations. Surface tension, capillary effects and wall friction are taken into account in the evolution of the system, influencing the motion of the contact line - where the free surface hits the wall - and of the dynamics of the contact angle. The differential equations governing the phenomenon are first derived from the variational principle of minimum reduced dissipation, and then discretized by means of the ALE approach. The numerical properties of the resulting scheme are investigated, drawing a parallel with the physical properties holding at the continuous level. Some instability issues are addressed in detail, in the case of an explicit treatment of the geometry, and novel additional terms are introduced in the discrete formulation in order to damp the instabilities. Numerical tests assess the suitability of the approach, the influence of the parameters, and the effectiveness of the new stabilizing terms.

  2. Sn surface-enriched Pt-Sn bimetallic nanoparticles as a selective and stable catalyst for propane dehydrogenation

    KAUST Repository

    Zhu, Haibo

    2014-12-01

    A new one pot, surfactant-free, synthetic route based on the surface organometallic chemistry (SOMC) concept has been developed for the synthesis of Sn surface-enriched Pt-Sn nanoparticles. Bu3SnH selectively reacts with [Pt]-H formed in situ at the surface of Pt nanoparticles, Pt NPs, obtained by reduction of K2PtCl4 by LiB(C2H5)3H. Chemical analysis, 1H MAS and 13C CP/MAS solid-state NMR as well as two-dimensional double-quantum (DQ) and triple-quantum (TQ) experiments show that organo-tin moieties Sn(n-C4H9) are chemically linked to the surface of Pt NPs to produce, in fine, after removal of most of the n-butyl fragment, bimetallic Pt-Sn nanoparticles. The Sn(n-CH2CH2CH2CH3) groups remaining at the surface are believed to stabilize the as-synthesized Pt-Sn NPs, enabling the bimetallic NPs to be well dispersed in THF. Additionally, the Pt-Sn nanoparticles can be supported on MgAl2O4 during the synthesis of the nanoparticles. Some of the Pt-Sn/MgAl2O4 catalyst thus prepared exhibits high activity in PROX of CO and an extremely high selectivity and stability in propane dehydrogenation to propylene. The enhanced activity in propane dehydrogenation is associated with the high concentration of inactive Sn at the surface of Pt nanoparticles which ”isolates” the active Pt atoms. This conclusion is confirmed by XRD, NMR, TEM, and XPS analysis.

  3. Properties of the surface snow in Princess Elizabeth Land, East Antarctica - climate and non-climate dependent variability of the surface mass balance and stable water isotopic composition

    Science.gov (United States)

    Vladimirova, D.; Ekaykin, A.; Lipenkov, V.; Popov, S. V.; Petit, J. R.; Masson-Delmotte, V.

    2017-12-01

    Glaciological and meteorological observations conducted during the past four decades in Princess Elizabeth Land, East Antarctica, are compiled. The database is used to investigate spatial patterns of surface snow isotopic composition and surface mass balance, including detailed information near subglacial lake Vostok. We show diverse relationships between snow isotopic composition and surface temperature. In the most inland part (elevation 3200-3400 m a.s.l.), surface snow isotopic composition varies independently from surface temperature, and is closely related to the distance to the open water source (with a slope of 0.98±0.17 ‰ per 100 km). Surface mass balance values are higher along the ice sheet slope, and relatively evenly distributed inland. The minimum values of snow isotopic composition and surface mass balance are identified in an area XX km southwestward from Vostok station. The spatial distribution of deuterium excess delineates regions influenced by the Indian Ocean and Pacific Ocean air masses, with Vostok area being situated close to their boundary. Anomalously high deuterium excess values are observed near Dome A, suggesting high kinetic fractionation for its moisture source, or specifically high post-deposition artifacts. The dataset is available for further studies such as the assessment of skills of general circulation or regional atmospheric models, and the search for the oldest ice.

  4. Efficient, Hysteresis-Free, and Stable Perovskite Solar Cells with ZnO as Electron-Transport Layer: Effect of Surface Passivation.

    Science.gov (United States)

    Cao, Jing; Wu, Binghui; Chen, Ruihao; Wu, Youyunqi; Hui, Yong; Mao, Bing-Wei; Zheng, Nanfeng

    2018-01-19

    The power conversion efficiency of perovskite solar cells (PSCs) has ascended from 3.8% to 22.1% in recent years. ZnO has been well-documented as an excellent electron-transport material. However, the poor chemical compatibility between ZnO and organo-metal halide perovskite makes it highly challenging to obtain highly efficient and stable PSCs using ZnO as the electron-transport layer. It is demonstrated in this work that the surface passivation of ZnO by a thin layer of MgO and protonated ethanolamine (EA) readily makes ZnO as a very promising electron-transporting material for creating hysteresis-free, efficient, and stable PSCs. Systematic studies in this work reveal several important roles of the modification: (i) MgO inhibits the interfacial charge recombination, and thus enhances cell performance and stability; (ii) the protonated EA promotes the effective electron transport from perovskite to ZnO, further fully eliminating PSCs hysteresis; (iii) the modification makes ZnO compatible with perovskite, nicely resolving the instability of ZnO/perovskite interface. With all these findings, PSCs with the best efficiency up to 21.1% and no hysteresis are successfully fabricated. PSCs stable in air for more than 300 h are achieved when graphene is used to further encapsulate the cells. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Evolution of subpolar North Atlantic surface circulation since the early Holocene inferred from planktic foraminifera faunal and stable isotope records

    DEFF Research Database (Denmark)

    Staines-Urias, Francisca; Kuijpers, Antoon; Korte, Christoph

    2013-01-01

    of the Faroe Islands, are located in the transitional area where surface waters of subpolar and subtropical origin mix before entering the Arctic Mediterranean. In these areas, large-amplitude millennial variability in the characteristics of the upper-water column appears modulated by changes in the intensity...

  6. Stable isotope biogeochemistry of the sulfur cycle in modern marine sediments: I. Seasonal dynamics in a temperate intertidal sandy surface sediment.

    Science.gov (United States)

    Böttcher, Michael; Hespenheide, Britta; Brumsack, Hans-Jürgen; Bosselmann, Katja

    2004-12-01

    A biogeochemical and stable isotope geochemical study was carried out in surface sediments of an organic-matter poor temperate intertidal sandy surface sediment (German Wadden Sea of the North Sea) to investigate the activity of sulfate-reducing bacteria and the dynamics of the vertical partitioning of sedimentary sulfur, iron, and manganese species in relation to the availability of total organic carbon (TOC) and mud contents. The contents and stable isotopic compositions ((34)S/(32)S) of total reduced inorganic sulfur species (TRIS) and dissolved sulfate were measured. Maximum oxygen penetration depths were estimated from the onset of a blackening of the sediments due to FeS accumulation and ranged from 5 to 10 mm below surface (mmbsf). A zone of relatively moderate relative organic-matter enrichment was found between 5 and 20 mmbsf leading to enhanced activities of sulfate-reducing bacteria with sulfate-reduction rates (SRR) up to 350 nmol cm(-3) d(-1). Below this zone, microbial SRR dropped significantly. Depth integrated SRR seem to depend not only on temperature but also on the availability of reactive organic matter. The sulfur-isotopic composition of TRIS was depleted in (34)S by 33-40 per thousand with respect to coexisting dissolved sulfate (constant at about +21 per thousand vs. Vienna-Canyon Diablo Troilite (V-CDT)). Since sulfate reduction is not limited by dissolved sulfate (open system), depth variations of the isotopic composition of TRIS reflect changes in overall isotope effect due to superimposed microbial and abiotic reactions. Most of the solid-phase iron and manganese was bonded to (non-reactive) heavy minerals. However, a layer of reactive Fe(III) and Mn(IV) oxi(hydroxi)des was found in the uppermost sediment section due to re-oxidation of dissolved Fe(II) and Mn(II) species at the sediment-water interface. Metal cycling below the surface is at least partially coupled to intense sulfur cycling.

  7. Intracellular surface-enhanced Raman scattering (SERS) with thermally stable gold nanoflowers grown from Pt and Pd seeds

    KAUST Repository

    Song, Hyon Min

    2013-01-01

    SERS provides great sensitivity at low concentrations of analytes. SERS combined with near infrared (NIR)-resonant gold nanomaterials are important candidates for theranostic agents due to their combined extinction properties and sensing abilities stemming from the deep penetration of laser light in the NIR region. Here, highly branched gold nanoflowers (GNFs) grown from Pd and Pt seeds are prepared and their SERS properties are studied. The growth was performed at 80°C without stirring, and this high temperature growth method is assumed to provide great shape stability of sharp tips in GNFs. We found that seed size must be large enough (>30 nm in diameter) to induce the growth of those SERS-active and thermally stable GNFs. We also found that the addition of silver nitrate (AgNO3) is important to induce sharp tip growth and shape stability. Incubation with Hela cells indicates that GNFs are taken up and reside in the cytoplasm. SERS was observed in those cells incubated with 1,10-phenanthroline (Phen)-loaded GNFs. This journal is © 2013 The Royal Society of Chemistry.

  8. Searching for stable Si(n)C(n) clusters: combination of stochastic potential surface search and pseudopotential plane-wave Car-Parinello simulated annealing simulations.

    Science.gov (United States)

    Duan, Xiaofeng F; Burggraf, Larry W; Huang, Lingyu

    2013-07-22

    To find low energy Si(n)C(n) structures out of hundreds to thousands of isomers we have developed a general method to search for stable isomeric structures that combines Stochastic Potential Surface Search and Pseudopotential Plane-Wave Density Functional Theory Car-Parinello Molecular Dynamics simulated annealing (PSPW-CPMD-SA). We enhanced the Sunders stochastic search method to generate random cluster structures used as seed structures for PSPW-CPMD-SA simulations. This method ensures that each SA simulation samples a different potential surface region to find the regional minimum structure. By iterations of this automated, parallel process on a high performance computer we located hundreds to more than a thousand stable isomers for each Si(n)C(n) cluster. Among these, five to 10 of the lowest energy isomers were further optimized using B3LYP/cc-pVTZ method. We applied this method to Si(n)C(n) (n = 4-12) clusters and found the lowest energy structures, most not previously reported. By analyzing the bonding patterns of low energy structures of each Si(n)C(n) cluster, we observed that carbon segregations tend to form condensed conjugated rings while Si connects to unsaturated bonds at the periphery of the carbon segregation as single atoms or clusters when n is small and when n is large a silicon network spans over the carbon segregation region.

  9. Searching for Stable SinCn Clusters: Combination of Stochastic Potential Surface Search and Pseudopotential Plane-Wave Car-Parinello Simulated Annealing Simulations

    Directory of Open Access Journals (Sweden)

    Larry W. Burggraf

    2013-07-01

    Full Text Available To find low energy SinCn structures out of hundreds to thousands of isomers we have developed a general method to search for stable isomeric structures that combines Stochastic Potential Surface Search and Pseudopotential Plane-Wave Density Functional Theory Car-Parinello Molecular Dynamics simulated annealing (PSPW-CPMD-SA. We enhanced the Sunders stochastic search method to generate random cluster structures used as seed structures for PSPW-CPMD-SA simulations. This method ensures that each SA simulation samples a different potential surface region to find the regional minimum structure. By iterations of this automated, parallel process on a high performance computer we located hundreds to more than a thousand stable isomers for each SinCn cluster. Among these, five to 10 of the lowest energy isomers were further optimized using B3LYP/cc-pVTZ method. We applied this method to SinCn (n = 4–12 clusters and found the lowest energy structures, most not previously reported. By analyzing the bonding patterns of low energy structures of each SinCn cluster, we observed that carbon segregations tend to form condensed conjugated rings while Si connects to unsaturated bonds at the periphery of the carbon segregation as single atoms or clusters when n is small and when n is large a silicon network spans over the carbon segregation region.

  10. Characterization of Dissolved Organic Matter in Surface, Soil, and Ground Waters of a Small (10 ha) Catchment Using Stable Isotopes (C, N, S) and Chemical Methods

    Science.gov (United States)

    Frentress, J.; Lajtha, K.; Jones, J.; Kendall, C.

    2007-12-01

    In order to better understand sources of dissolved organic matter (DOM) in streams at the small watershed scale, we initiated a one-year investigation of the chemical and isotopic characteristics of DOM at the HJ Andrews Research Forest in Blue River, OR. These data will be used to test two mechanistic hypotheses to explain observed hysteresis patterns where dissolved organic carbon (DOC) concentrations in surface flow are greatest during the ascending limb of the hydrograph during storms and over the water year, with decreased DOC concentrations in surface flow during the descending limb of the hydrograph: Hypothesis 1) A flushing effect with no change in dominant flowpaths; Stream DOC concentrations directly reflect the DOC concentrations in the soil that are initially high and decrease during the event and throughout the water year due to the flushing of DOC. Hypothesis 2) A change in dominance from near-surface to subsurface hydrologic flowpaths during the event, with high-DOC sources in near-surface flowpaths dominating early and low-DOC sources in groundwater dominating later in the event. In order to address this ambiguity, the characterization of DOM using stable isotopes and other fingerprinting techniques (e.g. SUVA, C:N) was used to identify sources of organic matter to streams throughout an individual storm event and through the water year. If the first hypothesis (flushing effect) is correct, DOM in surface water should carry a similar fingerprint to the DOM in soil waters throughout the rain event and water year. If the second hypothesis (change in flowpaths) is correct, the fingerprint of DOM in the surface water should closely resemble that of soil water early in the event and change to reflect a mix of the two fingerprinted DOM sources - groundwater and soil water - later in the event. In addition to established chemical characterization methods like SUVA and C:N, a new technique of DOM isolation via solid-phase extraction using C-18 resin was used

  11. Stable isotopes

    International Nuclear Information System (INIS)

    Evans, D.K.

    1986-01-01

    Seventy-five percent of the world's stable isotope supply comes from one producer, Oak Ridge Nuclear Laboratory (ORNL) in the US. Canadian concern is that foreign needs will be met only after domestic needs, thus creating a shortage of stable isotopes in Canada. This article describes the present situation in Canada (availability and cost) of stable isotopes, the isotope enrichment techniques, and related research programs at Chalk River Nuclear Laboratories (CRNL)

  12. Atomic structure of a stable high-index Ge surface: G2(103)-(4x1)

    DEFF Research Database (Denmark)

    Seehofer, L.; Bunk, O.; Falkenberg, G.

    1997-01-01

    Based on scanning tunneling microscopy and surface X-ray diffraction, we propose a complex structural model for the Ge(103)-(4 x 1) reconstruction. Each unit cell contains two (103) double steps, which gives rise to the formation of stripes of Ge atoms oriented in the [] direction....... The stripes and the spaces between them are covered with threefold-coordinated Ge adatoms. Charge is transferred from the bulk-like edge atoms of the double steps to the adatoms. The formation of the reconstruction can be explained in terms of stress relief, charge transfer, and minimization of the dangling...

  13. Ultra-stable Molecule-Surface Architectures at Metal Oxides: Structure, Bonding, and Electron-transfer Processes

    Energy Technology Data Exchange (ETDEWEB)

    Hamers, Robert John

    2013-12-07

    Research funded by this project focused on the development of improved strategies for functionalization of metal oxides to enhance charge-transfer processes relevant to solar energy conversion. Initial studies included Fe2O3, WO3, TiO2, SnO2, and ZnO as model oxide systems; these systems were chosen due to differences in metal oxidation state and chemical bonding types in these oxides. Later studies focused largely on SnO2 and ZnO, as these materials show particularly promising surface chemistry, have high electron mobility, and can be readily grown in both spherical nanoparticles and as elongated nanorods. New molecules were synthesized that allowed the direct chemical assembly of novel nanoparticle ?dyadic? structures in which two different oxide materials are chemically joined, leading to an interface that enhances the separation of of charge upon illumination. We demonstrated that such junctions enhance photocatalytic efficiency using model organic compounds. A separate effort focused on novel approaches to linking dye molecules to SnO2 and ZnO as a way to enhance solar conversion efficiency. A novel type of surface binding through

  14. Tracing the origin of Pb using stable Pb isotopes in surface sediments along the Korean Yellow Sea coast

    Science.gov (United States)

    Park, Jong-Kyu; Choi, Man-Sik; Song, Yunho; Lim, Dhong-Il

    2017-06-01

    To investigate the factors controlling lead (Pb) concentration and identify the sources of Pb in Yellow Sea sediments along the Korean coast, the concentration of Pb and Pb isotopes in 87 surface and 6 core sediment samples were analyzed. The 1 M HCl leached Pb concentrations had a similar geographic distribution to those of fine-grained sediments, while the distribution of residual Pb concentrations resembled that of coarse-grained sediments. Leached Pb was presumed to be associated with manganese (Mn) oxide and iron (Fe) oxy/hydroxide, while residual Pb was associated with potassium (K)-feldspar, based on good linear relationships between the leached Pb and the Fe/Mn concentrations, and the residual Pb and K concentrations. Based on a ratio-ratio plot with three isotopes (207Pb/206Pb and 208Pb/206Pb) and the geographic location of each sediment, sediments were categorized into two groups of samples as group1 and group2. Group 1 sediments, which were distributed in Gyeonggi Bay and offshore (north of 36.5°N), were determined to be a mixture of anthropogenic and natural Pb originating from the Han River, based on a 208Pb/206Pb against a Cs/Pbleached mixing plot of core and surface sediments. Group 2 sediments, which were distributed in the south of 36.5°N, also showed a two endmembers mixing relationship between materials from the Geum River and offshore materials, which had very different Pb concentrations and isotope ratios. Based on the isotopes and their concentrations in core and surface sediments, this mixing relationship was interpreted as materials from two geographically different origins being mixed, rather than anthropogenic or natural mixing of materials with the same origin. Therefore, the relative percentage of materials supplied from the Geum River was calculated using a two endmembers mixing model and estimated to be as much as about 50% at 35°N. The spatial distribution of materials derived from the Geum River represented that of fine

  15. A ternary functional Ag@GO@Au sandwiched hybrid as an ultrasensitive and stable surface enhanced Raman scattering platform

    Science.gov (United States)

    Zhang, Cong-yun; Hao, Rui; Zhao, Bin; Hao, Yao-wu; Liu, Ya-qing

    2017-07-01

    The graphene-mediated surface enhanced Raman scattering (SERS) substrates by virtues of plasmonic metal nanostructures and graphene or its derivatives have attracted tremendous interests which are expected to make up the deficiency of traditional plasmonic metal substrates. Herein, we designed and fabricated a novel ternary Ag@GO@Au sandwich hybrid wherein the ultrathin graphene oxide (GO) films were seamlessly wrapped around the hierarchical flower-like Ag particle core and meanwhile provided two-dimensional anchoring scaffold for the coating of Au nanoparticles (NPs). The surface coverage density of loading Au NPs could be readily controlled by tuning the dosage amount of Au particle solutions. These features endowed the sandwiched structures high enrichment capability for analytes such as aromatic molecules and astonishing SERS performance. The Raman signals were enormously enhanced with an ultrasensitive detection limit of rhodamine-6G (R6G) as low as 10-13 M based on the chemical enhancement from GO and multi-dimensional plasmonic coupling between the metal nanoparticles. In addition, the GO interlayer as an isolating shell could effectively prevent the metal-molecule direct interaction and suppress the oxidation of Ag after exposure at ambient condition which enabled the substrates excellent reproducibility with less than 6% signal variations and prolonged life-time. To evaluate the feasibility and the practical application for SERS detection in real-world samples based on GO sandwiched hybrid as SERS-active substrate, three different prohibited colorants with a series of concentrations were measured with a minimum detected concentration down to 10-9 M. Furthermore, the prepared GO sandwiched nanostructures can be used to identify different types of colorants existing in red wine, implying the great potential applications for single-particle SERS sensing of biotechnology and on-site monitoring in food security.

  16. Analysis of pushing exercises: muscle activity and spine load while contrasting techniques on stable surfaces with a labile suspension strap training system.

    Science.gov (United States)

    McGill, Stuart M; Cannon, Jordan; Andersen, Jordan T

    2014-01-01

    Labile surfaces in the form of suspension straps are increasingly being used as a tool in resistance training programs. Pushing is a common functional activity of daily living and inherently part of a well-rounded training program. This study examined pushing exercises performed on stable surfaces and unstable suspension straps, specifically muscle activation levels and spine loads were quantified together with the influence of employing technique coaching. There were several main questions that this study sought to answer: Which exercises challenged particular muscles? What was the magnitude of the resulting spine load? How did stable and unstable surfaces differ? Did coaching influence the results? Fourteen men were recruited as part of a convenience sample (mean age, 21.1 ± 2.0 years; height, 1.77 ± 0.06 m; mean weight, 74.6 ± 7.8 kg). Data were processed and input to a sophisticated and anatomically detailed 3D model that used muscle activity and body segment kinematics to estimate muscle force-in this way, the model was sensitive to the individuals choice of motor control for each task; muscle forces and linked segment joint loads were used to calculate spine loads. Exercises were performed using stable surfaces for hand/feet contact and repeated where possible with labile suspension straps. Speed of movement was standardized across participants with the use of a metronome for each exercise. There were gradations of muscle activity and spine load characteristics to every task. In general, the instability associated with the labile exercises required greater torso muscle activity than when performed on stable surfaces. Throughout the duration of an exercise, there was a range of compression; the TRX push-up ranged from 1,653 to 2,128.14 N, whereas the standard push-up had a range from 1,233.75 to 1,530.06 N. There was no significant effect of exercise on spine compression (F(4,60) = 0.86, p = 0.495). Interestingly, a standard push-up showed significantly

  17. Adsorbed carbon nanomaterials for surface and interface-engineered stable rubidium multi-cation perovskite solar cells.

    Science.gov (United States)

    Mahmud, Md Arafat; Elumalai, Naveen Kumar; Upama, Mushfika Baishakhi; Wang, Dian; Zarei, Leila; Gonçales, Vinicius R; Wright, Matthew; Xu, Cheng; Haque, Faiazul; Uddin, Ashraf

    2018-01-03

    The current work reports the simultaneous enhancement in efficiency and stability of low-temperature, solution-processed triple cation based MA 0.57 FA 0.38 Rb 0.05 PbI 3 (MA: methyl ammonium, FA: formamidinium, Rb: rubidium) perovskite solar cells (PSCs) by means of adsorbed carbon nanomaterials at the perovskite/electron transporting layer interface. The quantity and quality of the adsorbents are precisely controlled to electronically modify the ETL surface and lower the energy barrier across the interface. Carbon derivatives namely fullerene (C 60 ) and PC 71 BM ([6,6]-phenyl C71 butyric acid methyl ester) are employed as adsorbents in conjunction with ZnO and together serve as a bilayer electron transporting layer (ETL). The adsorbed fullerene (C 60 -ZnO, abbreviated as C-ZnO) passivates the interstitial trap-sites of ZnO with interstitial intercalation of oxygen atoms in the ZnO lattice structure. C-ZnO ETL based PSCs demonstrate about a 19% higher average PCE compared to conventional ZnO ETL based devices and a nearly 9% higher average PCE than PC 71 BM adsorbed-ZnO (P-ZnO) ETL based PSCs. In addition, the interstitial trap-state passivation with a C-ZnO film upshifts the Fermi-level position of the C-ZnO ETL by 130 meV, with reference to the ZnO ETL, which contributes to an enhanced n-type conductivity. The photocurrent hysteresis phenomenon in C-ZnO PSCs is also substantially reduced due to mitigated charge trapping phenomena and concomitant reduction in an electrode polarization process. Another major highlight of this work is that, C-ZnO PSCs demonstrate a superior device stability retaining about 94% of its initial PCE in the course of a month-long, systematic degradation study conducted in our work. The enhanced device stability with C-ZnO PSCs is attributed to their high resistance to aging-induced recombination phenomena and a water-induced perovskite degradation process, due to a lower content of oxygen-related chemisorbed species on the C-ZnO ETL

  18. Carboxymethylated lignins with low surface tension toward low viscosity and highly stable emulsions of crude bitumen and refined oils.

    Science.gov (United States)

    Li, Shuai; Ogunkoya, Dolanimi; Fang, Tiegang; Willoughby, Julie; Rojas, Orlando J

    2016-11-15

    Kraft and organosolv lignins were subjected to carboxymethylation to produce fractions that were soluble in water, displayed a minimum surface tension as low as 34mN/m (25°C) and a critical aggregation concentration of ∼1.5wt%. The carboxymethylated lignins (CML), which were characterized in terms of their degree of substitution ((31)P NMR), elemental composition, and molecular weight (GPC), were found suitable in the formulation of emulsions with bitumens of ultra-high viscosity, such as those from the Canadian oil sands. Remarkably, the interfacial features of the CML enabled fuel emulsions that were synthesized in a very broad range of internal phase content (30-70%). Cryo-replica transmission electron microscopy, which was used here the first time to assess the morphology of the lignin-based emulsions, revealed the droplets of the emulsion stabilized with the modified lignin. The observed drop size (diametersoil) that enabled operation of a fuel engine. A significant finding is that under certain conditions and compared to the respective pure fuel, combustion of the O/W emulsions stabilized by CML presented lower NOx and CO emissions and maintained a relatively high combustion efficiency. The results highlight the possibilities in high volume application for lignin biomacromolecules. Copyright © 2016 Elsevier Inc. All rights reserved.

  19. Stable structures and potential energy surface of the metallic clusters: Ni, Cu, Ag, Au, Pd, and Pt

    Science.gov (United States)

    Wu, Xia; Sun, Yan

    2017-06-01

    Metallic clusters have been widely studied due to their special electrical, optical, and catalytic properties. The many-body Gupta potential is applied to describe the interatomic interaction of Ni, Cu, Ag, Au, Pd, and Pt clusters, and their global minimal structures within 100 atoms are optimized using dynamic lattice searching (DLS) method. The configurational distribution of global minima is analyzed, and the geometrical difference among these clusters is demonstrated. Results show that the dominant motif of Ni and Cu clusters is the icosahedron, and in Ag and Au clusters the number of decahedra is slightly larger than that of the icosahedra. However, more face-centered cubic (fcc), stacking fault fcc, and amorphous structures are formed in Au clusters than in Ag clusters. Furthermore, the main motif of Pd and Pt clusters is the decahedron. In particular, Ni98 adopts a Leary tetrahedral motif, and Pt54 is a central vacant icosahedron. The difference related to the potential parameters of these metallic clusters is further investigated by energy analysis. Moreover, the potential energy surfaces (PES) of 38-atom metallic clusters is characterized in terms of conformational analysis. It was found that the sequence of the number of local minima on the PES from large to low is Ni, Cu, Ag, Pt, Pd, and Au.

  20. Stable isotopes of hydrogen and oxygen in surface water and ground water at selected sites on or near the Idaho National Engineering Laboratory, Idaho

    International Nuclear Information System (INIS)

    Ott, D.S.; Cecil, L.D.; Knobel, L.L.

    1994-01-01

    Relative stable isotopic ratios for hydrogen and oxygen compared to standard mean ocean water are presented for water from 4 surface-water sites and 38 ground-water sites on or near the Idaho National Engineering Laboratory (INEL). The surface-water samples were collected monthly from March 1991 through April 1992 and after a storm event on June 18, 1992. The ground-water samples either were collected during 1991 or 1992. These data were collected as part of the US Geological Survey's continuing hydrogeological investigations at the INEL. The relative isotopic ratios of hydrogen and oxygen are reported as delta 2 H (δ 2 H) and as delta 18 O (δ 18 O), respectively. The values of δ 2 H and δ 18 O in water from the four surface-water sites ranged from -143.0 to -122 and from -18.75 to -15.55, respectively. The values of δ 2 H and δ 18 O in water from the 38 ground-water sites ranged from -141.0 to -120.0 and from -18.55 to -14.95, respectively

  1. An inexpensive and simple method for thermally stable immobilization of DNA on an unmodified glass surface: UV linking of poly(T)10-poly(C)10-tagged DNA probes

    DEFF Research Database (Denmark)

    Guðnason, Haukur; Dufva, Hans Martin; Bang, Dang Duong

    2008-01-01

    the hybridization performance of the immobilized probes on the amino-silane surface, indicating a general benefit of adding a TC tag to DNA probes. In conclusion, our results show that using TC-tagged DNA probes immobilized on an unmodified glass surface is a robust, heat-stable, very simple, and inexpensive method...

  2. Hydrogeochemistry and quality of surface water and groundwater in the vicinity of Lake Monoun, West Cameroon: approach from multivariate statistical analysis and stable isotopic characterization.

    Science.gov (United States)

    Kamtchueng, Brice T; Fantong, Wilson Y; Wirmvem, Mengnjo J; Tiodjio, Rosine E; Takounjou, Alain F; Ndam Ngoupayou, Jules R; Kusakabe, Minoru; Zhang, Jing; Ohba, Takeshi; Tanyileke, Gregory; Hell, Joseph V; Ueda, Akira

    2016-09-01

    With the use of conventional hydrogeochemical techniques, multivariate statistical analysis, and stable isotope approaches, this paper investigates for the first time surface water and groundwater from the surrounding areas of Lake Monoun (LM), West Cameroon. The results reveal that waters are generally slightly acidic to neutral. The relative abundance of major dissolved species are Ca(2+) > Mg(2+) > Na(+) > K(+) for cations and HCO3 (-) ≫ NO3 (-) > Cl(-) > SO4 (2-) for anions. The main water type is Ca-Mg-HCO3. Observed salinity is related to water-rock interaction, ion exchange process, and anthropogenic activities. Nitrate and chloride have been identified as the most common pollutants. These pollutants are attributed to the chlorination of wells and leaching from pit latrines and refuse dumps. The stable isotopic compositions in the investigated water sources suggest evidence of evaporation before recharge. Four major groups of waters were identified by salinity and NO3 concentrations using the Q-mode hierarchical cluster analysis (HCA). Consistent with the isotopic results, group 1 represents fresh unpolluted water occurring near the recharge zone in the general flow regime; groups 2 and 3 are mixed water whose composition is controlled by both weathering of rock-forming minerals and anthropogenic activities; group 4 represents water under high vulnerability of anthropogenic pollution. Moreover, the isotopic results and the HCA showed that the CO2-rich bottom water of LM belongs to an isolated hydrological system within the Foumbot plain. Except for some springs, groundwater water in the area is inappropriate for drinking and domestic purposes but good to excellent for irrigation.

  3. Stable isotope oxygen-18 and deuterium analysis in surface and groundwater of the Jequitibá Creek Basin, Sete Lagoas, MG

    Energy Technology Data Exchange (ETDEWEB)

    Linhares, Giovanna Maria Gardini; Moreira, Rubens Martins; Pimenta, Rafael Colombo; Scarpelli, Raquel Pazzini; Santos, Elizangela Augusta dos, E-mail: giovannagardini@gmail.com, E-mail: rubens@cdtn.br, E-mail: colombopimenta@gmail.com, E-mail: raquelscarpelli@gmail.com, E-mail: elizangela.augusta@gmail.com [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN/CNEN-MG), Belo Horizonte, MG (Brazil)

    2017-07-01

    Groundwater is an important source of public and industrial supplies, and inadequate exploitation of water reflects negatively on its quality and production of wells, especially when located in karstic aquifers. The study area includes the Maize and Sorghum National Research / Embrapa, located in the karst region of Sete Lagoas, within of the Jequitibá creek sub-basin, an affluent of the Velhas River. The evaluation of the content of stable isotopes of hydrogen ({sup 2}H), or deuterium, and oxygen ({sup 18}O) of surface waters (lagoons) and groundwater (production and monitoring wells) collected from the study area allowed to know directly the origin of these waters, active climatic processes and interactions between different aquifers and surface bodies, as possible mixtures of water from different sources. The collected samples were analyzed by isotopic ratio mass spectrometry, IRMS Advantege - Thermo Science, from the Center for the Development of Nuclear Technology (CDTN). The mean values found for δ{sup 18}O and δ{sup 2}H in the waters of the monitoring wells were -6.40‰ and -43.21‰, respectively. For the production wells, mean values for δ{sup 18}O and δ{sup 2}H of -5.87 ‰ and -40.09‰, respectively, were obtained. When compared to GMWL, the collected groundwater originates attributed to the precipitations. The lagoon waters had mean values for δ{sup 18}O and δ{sup 2}H of -3.73‰ and -30.08‰. The water collected in the crystalline fissured aquifer presented mean values δ{sup 18}O and δ{sup 2}H of -6.91‰ and -40.26 ‰ respectively, in its rockier portion, and -6.09‰ and -43.05‰. (author)

  4. Stable isotope oxygen-18 and deuterium analysis in surface and groundwater of the Jequitibá Creek Basin, Sete Lagoas, MG

    International Nuclear Information System (INIS)

    Linhares, Giovanna Maria Gardini; Moreira, Rubens Martins; Pimenta, Rafael Colombo; Scarpelli, Raquel Pazzini; Santos, Elizangela Augusta dos

    2017-01-01

    Groundwater is an important source of public and industrial supplies, and inadequate exploitation of water reflects negatively on its quality and production of wells, especially when located in karstic aquifers. The study area includes the Maize and Sorghum National Research / Embrapa, located in the karst region of Sete Lagoas, within of the Jequitibá creek sub-basin, an affluent of the Velhas River. The evaluation of the content of stable isotopes of hydrogen ( 2 H), or deuterium, and oxygen ( 18 O) of surface waters (lagoons) and groundwater (production and monitoring wells) collected from the study area allowed to know directly the origin of these waters, active climatic processes and interactions between different aquifers and surface bodies, as possible mixtures of water from different sources. The collected samples were analyzed by isotopic ratio mass spectrometry, IRMS Advantege - Thermo Science, from the Center for the Development of Nuclear Technology (CDTN). The mean values found for δ 18 O and δ 2 H in the waters of the monitoring wells were -6.40‰ and -43.21‰, respectively. For the production wells, mean values for δ 18 O and δ 2 H of -5.87 ‰ and -40.09‰, respectively, were obtained. When compared to GMWL, the collected groundwater originates attributed to the precipitations. The lagoon waters had mean values for δ 18 O and δ 2 H of -3.73‰ and -30.08‰. The water collected in the crystalline fissured aquifer presented mean values δ 18 O and δ 2 H of -6.91‰ and -40.26 ‰ respectively, in its rockier portion, and -6.09‰ and -43.05‰. (author)

  5. Stable particles

    International Nuclear Information System (INIS)

    Samios, N.P.

    1994-01-01

    I have been asked to review the subject of stable particles, essentially the particles that eventually comprised the meson and baryon octets, with a few more additions - with an emphasis on the contributions made by experiments utilizing the bubble chamber technique. In this activity, much work had been done by the photographic emulsion technique and cloud chambers - exposed to cosmic rays as well as accelerator based beams. In fact, many if not most of the stable particles were found by these latter two techniques, however, the foree of the bubble chamber (coupled with the newer and more powerful accelerators) was to verify, and reinforce with large statistics, the existence of these states, to find some of the more difficult ones, mainly neutrals and further to elucidate their properties, i.e., spin, parity, lifetimes, decay parameters, etc. (orig.)

  6. Stable particles

    International Nuclear Information System (INIS)

    Samios, N.P.

    1993-01-01

    I have been asked to review the subject of stable particles, essentially the particles that eventually comprised the meson and baryon octets. with a few more additions -- with an emphasis on the contributions made by experiments utilizing the bubble chamber technique. In this activity, much work had been done by the photographic emulsion technique and cloud chambers-exposed to cosmic rays as well as accelerator based beams. In fact, many if not most of the stable particles were found by these latter two techniques, however, the forte of the bubble chamber (coupled with the newer and more powerful accelerators) was to verify, and reinforce with large statistics, the existence of these states, to find some of the more difficult ones, mainly neutrals and further to elucidate their properties, i.e., spin, parity, lifetimes, decay parameters, etc

  7. Stable beams

    CERN Multimedia

    2015-01-01

    Stable beams: two simple words that carry so much meaning at CERN. When LHC page one switched from "squeeze" to "stable beams" at 10.40 a.m. on Wednesday, 3 June, it triggered scenes of jubilation in control rooms around the CERN sites, as the LHC experiments started to record physics data for the first time in 27 months. This is what CERN is here for, and it’s great to be back in business after such a long period of preparation for the next stage in the LHC adventure.   I’ve said it before, but I’ll say it again. This was a great achievement, and testimony to the hard and dedicated work of so many people in the global CERN community. I could start to list the teams that have contributed, but that would be a mistake. Instead, I’d simply like to say that an achievement as impressive as running the LHC – a machine of superlatives in every respect – takes the combined effort and enthusiasm of everyone ...

  8. Calcium stable isotope geochemistry

    Energy Technology Data Exchange (ETDEWEB)

    Gausonne, Nikolaus [Muenster Univ. (Germany). Inst. fuer Mineralogie; Schmitt, Anne-Desiree [Strasbourg Univ. (France). LHyGeS/EOST; Heuser, Alexander [Bonn Univ. (Germany). Steinmann-Inst. fuer Geologie, Mineralogie und Palaeontologie; Wombacher, Frank [Koeln Univ. (Germany). Inst. fuer Geologie und Mineralogie; Dietzel, Martin [Technische Univ. Graz (Austria). Inst. fuer Angewandte Geowissenschaften; Tipper, Edward [Cambridge Univ. (United Kingdom). Dept. of Earth Sciences; Schiller, Martin [Copenhagen Univ. (Denmark). Natural History Museum of Denmark

    2016-08-01

    This book provides an overview of the fundamentals and reference values for Ca stable isotope research, as well as current analytical methodologies including detailed instructions for sample preparation and isotope analysis. As such, it introduces readers to the different fields of application, including low-temperature mineral precipitation and biomineralisation, Earth surface processes and global cycling, high-temperature processes and cosmochemistry, and lastly human studies and biomedical applications. The current state of the art in these major areas is discussed, and open questions and possible future directions are identified. In terms of its depth and coverage, the current work extends and complements the previous reviews of Ca stable isotope geochemistry, addressing the needs of graduate students and advanced researchers who want to familiarize themselves with Ca stable isotope research.

  9. Glacial-interglacial changes in the surface water characteristics of the Andaman Sea: Evidence from stable isotopic ratios of planktonic foraminifera

    Digital Repository Service at National Institute of Oceanography (India)

    Ahmad, S.M.; Patil, D.J.; Rao, P.S.; Nath, B.N.; Rao, B.R.; Rajagopalan, G.

    Stable carbon and oxygen isotopic analyses of the planktonic foraminifera (Globigerinoides ruber) from a deep sea sediment core (GC-1) in the Andaman Sea show high glacial-to-Holocene d18O amplitude of 2.1% which is consistent...

  10. Stability of the Encoding Plasmids and Surface Expression of CS6 Differs in Enterotoxigenic Escherichia coli (ETEC) Encoding Different Heat-Stable (ST) Enterotoxins (STh and STp).

    Science.gov (United States)

    Tobias, Joshua; Von Mentzer, Astrid; Loayza Frykberg, Patricia; Aslett, Martin; Page, Andrew J; Sjöling, Åsa; Svennerholm, Ann-Mari

    2016-01-01

    Enterotoxigenic Escherichia coli (ETEC), one of the most common reasons of diarrhea among infants and children in developing countries, causes disease by expression of either or both of the enterotoxins heat-labile (LT) and heat-stable (ST; divided into human-type [STh] and porcine-type [STp] variants), and colonization factors (CFs) among which CS6 is one of the most prevalent ETEC CFs. In this study we show that ETEC isolates expressing CS6+STh have higher copy numbers of the cssABCD operon encoding CS6 than those expressing CS6+STp. Long term cultivation of up to ten over-night passages of ETEC isolates harboring CS6+STh (n = 10) or CS6+STp (n = 15) showed instability of phenotypic expression of CS6 in a majority of the CS6+STp isolates, whereas most of the CS6+STh isolates retained CS6 expression. The observed instability was a correlated with loss of genes cssA and cssD as examined by PCR. Mobilization of the CS6 plasmid from an unstable CS6+STp isolate into a laboratory E. coli strain resulted in loss of the plasmid after a single over-night passage whereas the plasmid from an CS6+STh strain was retained in the laboratory strain during 10 passages. A sequence comparison between the CS6 plasmids from a stable and an unstable ETEC isolate revealed that genes necessary for plasmid stabilization, for example pemI, pemK, stbA, stbB and parM, were not present in the unstable ETEC isolate. Our results indicate that stable retention of CS6 may in part be affected by the stability of the plasmid on which both CS6 and STp or STh are located.

  11. Stability of the Encoding Plasmids and Surface Expression of CS6 Differs in Enterotoxigenic Escherichia coli (ETEC Encoding Different Heat-Stable (ST Enterotoxins (STh and STp.

    Directory of Open Access Journals (Sweden)

    Joshua Tobias

    Full Text Available Enterotoxigenic Escherichia coli (ETEC, one of the most common reasons of diarrhea among infants and children in developing countries, causes disease by expression of either or both of the enterotoxins heat-labile (LT and heat-stable (ST; divided into human-type [STh] and porcine-type [STp] variants, and colonization factors (CFs among which CS6 is one of the most prevalent ETEC CFs. In this study we show that ETEC isolates expressing CS6+STh have higher copy numbers of the cssABCD operon encoding CS6 than those expressing CS6+STp. Long term cultivation of up to ten over-night passages of ETEC isolates harboring CS6+STh (n = 10 or CS6+STp (n = 15 showed instability of phenotypic expression of CS6 in a majority of the CS6+STp isolates, whereas most of the CS6+STh isolates retained CS6 expression. The observed instability was a correlated with loss of genes cssA and cssD as examined by PCR. Mobilization of the CS6 plasmid from an unstable CS6+STp isolate into a laboratory E. coli strain resulted in loss of the plasmid after a single over-night passage whereas the plasmid from an CS6+STh strain was retained in the laboratory strain during 10 passages. A sequence comparison between the CS6 plasmids from a stable and an unstable ETEC isolate revealed that genes necessary for plasmid stabilization, for example pemI, pemK, stbA, stbB and parM, were not present in the unstable ETEC isolate. Our results indicate that stable retention of CS6 may in part be affected by the stability of the plasmid on which both CS6 and STp or STh are located.

  12. Oxygen and silicon stable isotopes of diatom silica. Reconstructing changes in surface water hydrography and silicic acid utilization in the late Pleistocene subarctic Pacific

    International Nuclear Information System (INIS)

    Maier, Edith

    2014-01-01

    Deglacial variations in upper ocean nutrient dynamics and stratification in high latitudes, as well as associated changes in thermohaline overturning circulation, are thought to have played a key role in changing atmospheric CO 2 concentrations. This thesis examines the relationship between past changes in subarctic Pacific upper ocean stratification and nutrient (silicic acid) utilization, using oxygen and silicon stable isotopes of diatom silica, for the first time at millennial-scale resolution and analyzed with a new and efficient instrumentation set-up. The isotopic data, presented in three manuscripts, show a consistent picture of millennial-scale variability in upper ocean stratification and silicic acid utilization during the last ∝50 ka BP, e.g. indicating that the subarctic Pacific was a source region for atmospheric CO 2 during the last deglaciation (late Heinrich Stadial 1 and the Boelling/Alleroed). The presented results demonstrate the high potential of combined diatom oxygen and silicon stable isotope analysis especially for, but not restricted to, marine regions characterized by a low biogenic carbonate content like the subarctic Pacific and the Southern Ocean.

  13. Oxygen and silicon stable isotopes of diatom silica. Reconstructing changes in surface water hydrography and silicic acid utilization in the late Pleistocene subarctic Pacific

    Energy Technology Data Exchange (ETDEWEB)

    Maier, Edith

    2014-03-05

    Deglacial variations in upper ocean nutrient dynamics and stratification in high latitudes, as well as associated changes in thermohaline overturning circulation, are thought to have played a key role in changing atmospheric CO{sub 2} concentrations. This thesis examines the relationship between past changes in subarctic Pacific upper ocean stratification and nutrient (silicic acid) utilization, using oxygen and silicon stable isotopes of diatom silica, for the first time at millennial-scale resolution and analyzed with a new and efficient instrumentation set-up. The isotopic data, presented in three manuscripts, show a consistent picture of millennial-scale variability in upper ocean stratification and silicic acid utilization during the last ∝50 ka BP, e.g. indicating that the subarctic Pacific was a source region for atmospheric CO{sub 2} during the last deglaciation (late Heinrich Stadial 1 and the Boelling/Alleroed). The presented results demonstrate the high potential of combined diatom oxygen and silicon stable isotope analysis especially for, but not restricted to, marine regions characterized by a low biogenic carbonate content like the subarctic Pacific and the Southern Ocean.

  14. A flexible and stable surface-enhanced Raman scattering (SERS) substrate based on Au nanoparticles/Graphene oxide/Cicada wing array

    Science.gov (United States)

    Shi, Guochao; Wang, Mingli; Zhu, Yanying; Shen, Lin; Wang, Yuhong; Ma, Wanli; Chen, Yuee; Li, Ruifeng

    2018-04-01

    In this work, we presented an eco-friendly and low-cost method to fabricate a kind of flexible and stable Au nanoparticles/graphene oxide/cicada wing (AuNPs/GO/CW) substrate. By controlling the ratio of reactants, the optimum SERS substrate with average AuNPs size of 65 nm was obtained. The Raman enhancement factor for rhodamine 6G (R6G) was 1.08 ×106 and the limit of detection (LOD) was as low as 10-8 M. After calibrating the Raman peak intensities of R6G, it could be quantitatively detected. In order to better understand the experimental results, the 3D finite-different time-domain simulation was used to simulate the AuNPs/GO/CW-1 (the diameter of the AuNPs was 65 nm) to further investigate the SERS enhancement effect. More importantly, the AuNPs/GO/CW-1 substrates not only can provide strong enhancement factors but also can be stable and reproducible. This SERS substrates owned a good stability for the SERS intensity which was reduced only by 25% after the aging time of 60 days and the relative standard deviation was lower than 20%, revealing excellent uniformity and reproducibility. Our positive findings can pave a new way to optimize the application of SERS substrate as well as provide more SERS platforms for quantitative detection of organic contaminants vestige, which makes it very promising in the trace detection of biological molecules.

  15. Formation of ZnO-Cd(OH){sub 2} core-shell nanoparticles by sol-gel method: An approach to modify surface chemistry for stable and enhanced green emission

    Energy Technology Data Exchange (ETDEWEB)

    Mishra, Rupali, E-mail: rupalimishra@rediffmail.co [Department of Physics, University of Allahabad, Allahabad-211002 (India); Nanophosphor Application Centre, University of Allahabad, Allahabad-211002 (India); Yadav, Raghvendra S.; Pandey, Avinash C. [Department of Physics, University of Allahabad, Allahabad-211002 (India); Nanophosphor Application Centre, University of Allahabad, Allahabad-211002 (India); Sanjay, Sharda. S. [Department of Chemistry, Ewing Christian College, Allahabad (India); Dar, Chitra [Department of Physics, University of Allahabad, Allahabad-211002 (India)

    2010-03-15

    We report the formation of highly stable and luminescent ZnO-Cd(OH){sub 2} core-shell nanoparticles by simple introduction of cadmium salt in the initial precursor solution, used to synthesize ZnO nanoparticles by sol-gel route. The cadmium to zinc salt concentration ratio has been also varied to control the growth of ZnO nanoparticles at the smaller particle size. Formation of ZnO-Cd(OH){sub 2} core-shell nanostructure has been confirmed by X-ray diffraction (XRD), energy dispersive analysis of X-rays (EDAX) and X-ray photoelectron spectroscopy (XPS). UV-vis absorption spectroscopy exhibits blue-shift in absorption edge on increasing cadmium concentrations. The photoluminescence emission spectra showed the remarkably stable and enhanced visible (green) emission from suspended ZnO-Cd(OH){sub 2} nanoparticles in comparison to bare ZnO nanoparticles. It is postulated that Cd(OH){sub 2} layer at the surface of ZnO nanoparticles prevents the agglomeration of nanoparticles and efficiently assists the trapping of hole at the surface site, a first step necessary for visible emission. The Fourier transform infrared spectroscopy (FTIR) also supports our assumption about surface chemistry.

  16. Stable Isotope Data

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Tissue samples (skin, bone, blood, muscle) are analyzed for stable carbon, stable nitrogen, and stable sulfur analysis. Many samples are used in their entirety for...

  17. Surface enrichment of Pt in stable Pt-Ir nano-alloy particles on MgAl 2 O 4 spinel in oxidizing atmosphere

    Energy Technology Data Exchange (ETDEWEB)

    Li, Weizhen; Nie, Lei; Chen, Ying; Kovarik, Libor; Liu, Jun; Wang, Yong

    2017-04-01

    With the capability of MgAl2O4 spinel {111} nano-facets in stabilizing small Rh, Ir and Pt particles, bimetallic Ir-Pt catalysts on the same support were investigated, aiming at further lowering the catalyst cost by substituting expensive Pt with cheaper Ir in the bulk. Small Pt-Ir nano-alloy particles (< 2nm) were successfully stabilized on the spinel {111} nano-facets as expected. Interestingly, methanol oxidative dehydrogenation (ODH) rate on the surface Pt atoms increases with oxidizing aging but decreases upon reducing treatment, where Ir is almost inactive under the same reaction conditions. Up to three times enhancement in Pt exposure was achieved when the sample was oxidized at 800 °C in air for 1 week and subsequently reduced by H2 for 2 h, demonstrating successful surface enrichment of Pt on Pt-Ir nano-alloy particles. A dynamic stabilization mechanism involving wetting\

  18. New insight in the structural features of haloadaptation in α-amylases from halophilic Archaea following homology modeling strategy: folded and stable conformation maintained through low hydrophobicity and highly negative charged surface

    Science.gov (United States)

    Zorgani, Mohamed Amine; Patron, Kevin; Desvaux, Mickaël

    2014-07-01

    Proteins from halophilic archaea, which live in extreme saline conditions, have evolved to remain folded, active and stable at very high ionic strengths. Understanding the mechanism of haloadaptation is the first step toward engineering of halostable biomolecules. Amylases are one of the main enzymes used in industry. Yet, no three-dimensional structure has been experimentally resolved for α-amylases from halophilic archaea. In this study, homology structure modeling of α-amylases from the halophilic archaea Haloarcula marismortui, Haloarcula hispanica, and Halalkalicoccus jeotgali were performed. The resulting models were subjected to energy minimization, evaluation, and structural analysis. Calculations of the amino acid composition, salt bridges and hydrophobic interactions were also performed and compared to a set of non-halophilic counterparts. It clearly appeared that haloarchaeal α-amylases exhibited lower propensities for helix formation and higher propensities for coil-forming regions. Furthermore, they could maintain a folded and stable conformation in high salt concentration through highly negative charged surface with over representation of acidic residues, especially Asp, and low hydrophobicity with increase of salt bridges and decrease in hydrophobic interactions on the protein surface. This study sheds some light on the stability of α-amylases from halophilic archaea and provides strong basis not only to understand haloadaptation mechanisms of proteins in microorganisms from hypersalines environments but also for biotechnological applications.

  19. Use of stable isotopes of carbon, nitrogen, and sulfer to identify sources of nitrogen in surface waters in the Lower Susquehanna River basin, Pennsylvania

    Science.gov (United States)

    Cravotta, C.A.

    1995-01-01

    Stable isotopes of carbon (C), nitrogen (N), and sulfur (S) in nitrogen sources and nearby samples of topsoil, subsoil, runoff water, and stream water were measured to evaluate the feasibility of using isotopic data to identify nitrogen sources in stream water from forested, agricultural, or suburban land-use areas. Chemical and isotopic compositions were measured for six N-source types consisting of rain water, forest-leaf litter, synthetic fertilizer, farm-animal manure, municipal-sewage effluent and sludge, and septic-tank effluent and sludge. Compositions of topsoil, subsoil, runoff water, and stream water were measured to evaluate changes in compositions of transported N-containing materials near the N source. Animal manure, human waste (sewage plus septic), and forest-leaf litter can be distinguished on the basis of C; however, most N-sources can not be distinguished on the basis of N and S, owing to wide ranges of compositions and overlap among different N-source types. Although values of N for soil and runoff-water samples are qualitatively similar to those of the applied N source, values of C and S for runoff-water and stream-water samples appear to reflect the compositions of relatively large reservoirs of the elements in soil organic matter and minerals, respectively, and not the composition of the applied N source. Because of incomplete chemical transfor- mations, the ratio of organic carbon to total nitrogen for particulates in runoff or stream waters generally is lower than that for associated, nearby soils, and isotopic compositions commonly differ between particulate and dissolved fractions in the water.

  20. Targeted disruption of a ring-infected erythrocyte surface antigen (RESA)-like export protein gene in Plasmodium falciparum confers stable chondroitin 4-sulfate cytoadherence capacity

    DEFF Research Database (Denmark)

    Goel, Suchi; Muthusamy, Arivalagan; Miao, Jun

    2014-01-01

    . In this study, microarray transcriptome analysis showed that the absence of a gene cluster, comprising kahrp, pfemp3, and four other genes, results in the loss of parasitized erythrocytes adhering to chondroitin 4-sulfate (C4S). The role of one of these genes, PF3D7_0201600/PFB0080c, which encodes PHISTb...... (Plasmodium helical interspersed subtelomeric b) domain-containing RESA-like protein 1 expressed on the infected erythrocyte surface, was investigated. Disruption of PFB0080c resulted in increased var2csa transcription and VAR2CSA surface expression, leading to higher C4S-binding capacity of infected...... erythrocytes. Further, PFB0080c-knock-out parasites stably maintained the C4S adherence through many generations of growth. Although the majority of PFB0080c-knock-out parasites bound to C4S even after culturing for 6 months, a minor population bound to both C4S and CD36. These results strongly suggest...

  1. Stable convergence and stable limit theorems

    CERN Document Server

    Häusler, Erich

    2015-01-01

    The authors present a concise but complete exposition of the mathematical theory of stable convergence and give various applications in different areas of probability theory and mathematical statistics to illustrate the usefulness of this concept. Stable convergence holds in many limit theorems of probability theory and statistics – such as the classical central limit theorem – which are usually formulated in terms of convergence in distribution. Originated by Alfred Rényi, the notion of stable convergence is stronger than the classical weak convergence of probability measures. A variety of methods is described which can be used to establish this stronger stable convergence in many limit theorems which were originally formulated only in terms of weak convergence. Naturally, these stronger limit theorems have new and stronger consequences which should not be missed by neglecting the notion of stable convergence. The presentation will be accessible to researchers and advanced students at the master's level...

  2. Ni- and Mn-Promoted Mesoporous Co3O4: A Stable Bifunctional Catalyst with Surface-Structure-Dependent Activity for Oxygen Reduction Reaction and Oxygen Evolution Reaction.

    Science.gov (United States)

    Song, Wenqiao; Ren, Zheng; Chen, Sheng-Yu; Meng, Yongtao; Biswas, Sourav; Nandi, Partha; Elsen, Heather A; Gao, Pu-Xian; Suib, Steven L

    2016-08-17

    Efficient bifunctional catalysts for electrochemical oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are highly desirable due to their wide applications in fuel cells and rechargeable metal air batteries. However, the development of nonprecious metal catalysts with comparable activities to noble metals is still challenging. Here we report a one-step wet-chemical synthesis of Ni-/Mn-promoted mesoporous cobalt oxides through an inverse micelle process. Various characterization techniques including powder X-ray diffraction (PXRD), N2 sorption, transmission electron microscopy (TEM), and scanning electron microscopy (SEM) confirm the successful incorporation of Ni and Mn leading to the formation of Co-Ni(Mn)-O solid solutions with retained mesoporosity. Among these catalysts, cobalt oxide with 5% Ni doping demonstrates promising activities for both ORR and OER, with an overpotential of 399 mV for ORR (at -3 mA/cm(2)) and 381 mV (at 10 mA/cm(2)) for OER. Furthermore, it shows better durability than precious metals featuring little activity decay throughout 24 h continuous operation. Analyses of cyclic voltammetry (CV), X-ray photoelectron spectroscopy (XPS), Raman, and O2-temperature-programmed desorption (O2-TPD) reveal that redox activity of Co(3+) to Co(4+) is crucial for OER performance, while the population of surface oxygen vacancies and surface area determine ORR activities. The comprehensive investigation of the intrinsic active sites for ORR and OER by correlating different physicochemical properties to the electrochemical activities is believed to provide important insight toward the rational design of high-performance electrocatalysts for ORR and OER reactions.

  3. stableGP

    Data.gov (United States)

    National Aeronautics and Space Administration — The code in the stableGP package implements Gaussian process calculations using efficient and numerically stable algorithms. Description of the algorithms is in the...

  4. Modelling stable atmospheric boundary layers over snow

    NARCIS (Netherlands)

    Sterk, H.A.M.

    2015-01-01

    Thesis entitled:

    Modelling Stable Atmospheric Boundary Layers over Snow

    H.A.M. Sterk

    Wageningen, 29th of April, 2015

    Summary

    The emphasis of this thesis is on the understanding and forecasting of the Stable Boundary Layer (SBL) over snow-covered surfaces. SBLs

  5. Modelling stable atmospheric boundary layers over snow

    NARCIS (Netherlands)

    Sterk, H.A.M.

    2015-01-01

    Thesis entitled: Modelling Stable Atmospheric Boundary Layers over Snow H.A.M. Sterk Wageningen, 29th of April, 2015 Summary The emphasis of this thesis is on the understanding and forecasting of the Stable Boundary Layer (SBL) over snow-covered surfaces. SBLs typically form at night and in polar

  6. Surface generation of negative hydrogen ion beams

    International Nuclear Information System (INIS)

    Bommel, P.J.M. van.

    1984-01-01

    This thesis describes investigations on negative hydrogen ion sources at the ampere level. Formation of H - ions occurs when positive hydrogen ions capture two electrons at metal surfaces. The negative ionization probability of hydrogen at metal surfaces increases strongly with decreasing work function of the surface. The converters used in this study are covered with cesium. Usually there are 'surface plasma sources' in which the hydrogen source plasma interacts with a converter. In this thesis the author concentrates upon investigating a new concept that has converters outside the plasma. In this approach a positive hydrogen ion beam is extracted from the plasma and is subsequently reflected from a low work function converter surface. (Auth.)

  7. Air-Stable Field-Enhanced III-Nitride Photocathodes

    Science.gov (United States)

    Strittmatter, Robert; Blacksberg, Jordana; Nikzad, Shouleh; Dabiran, Amir; Wowchak, Andrew; Chow, Peter

    2005-03-01

    We report on recent investigations of Si delta-doping by molecular beam epitaxy (MBE) near the surface of p-type GaN films to attain high efficiency photocathodes for use in intensified ultraviolet imagers. These delta-layers are prepared to achieve effective negative electron affinity (NEA) without the use of low work function metal coatings, such as cesium, which are suitable only in ultra-high vacuum environments. Hall measurements, secondary ion mass spectrometry (SIMS), and capacitance-voltage (C-V) depth profiling reveal highly confined delta-layers with activated carrier densities in excess of 10^14 cm-2 as close as 2 nm from the semiconductor surface. When the delta-layer is biased relative to the bulk, a large field-enhancement of the photoelectron yield is observed. In addition to UV spectroscopic quantum efficiency data, we will present total electron yield measurements for these photocathodes under electron-beam bombardment at various incident energies.

  8. Appendix to Health and Safety Laboratory environmental quarterly report. [Fallout radionuclides deposited and in surface air at various world sites; /sup 137/Cs and /sup 90/Sr in milk and drinking water in New York City; and stable Pb in surface air

    Energy Technology Data Exchange (ETDEWEB)

    Hardy, E.P. Jr.

    1977-07-01

    Tabulated data are presented on the deposition of fallout /sup 89/Sr and /sup 90/Sr at various world land sites through 1976; the ..gamma.. spectra and content of /sup 7/Be, /sup 95/Zr, /sup 137/Cs, /sup 144/Ce, /sup 90/Sr, /sup 210/Pb, /sup 238/Pu, /sup 239/Pu, and stable Pb in samples of surface air collected during 1966 at various world sites; and the content of fallout /sup 137/Cs and /sup 90/Sr in samples of drinking water and milk collected in New York City through 1976. (CH)

  9. Stable isotopes labelled compounds

    International Nuclear Information System (INIS)

    1982-09-01

    The catalogue on stable isotopes labelled compounds offers deuterium, nitrogen-15, and multiply labelled compounds. It includes: (1) conditions of sale and delivery, (2) the application of stable isotopes, (3) technical information, (4) product specifications, and (5) the complete delivery programme

  10. Evolutionary Stable Strategy

    Indian Academy of Sciences (India)

    IAS Admin

    After Maynard-Smith and Price [1] mathematically derived why a given behaviour or strategy was adopted by a certain proportion of the population at a given time, it was shown that a strategy which is currently stable in a population need not be stable in evolutionary time (across generations). Additionally it was sug-.

  11. Normal modified stable processes

    DEFF Research Database (Denmark)

    Barndorff-Nielsen, Ole Eiler; Shephard, N.

    2002-01-01

    This paper discusses two classes of distributions, and stochastic processes derived from them: modified stable (MS) laws and normal modified stable (NMS) laws. This extends corresponding results for the generalised inverse Gaussian (GIG) and generalised hyperbolic (GH) or normal generalised inverse...... Gaussian (NGIG) laws. The wider framework thus established provides, in particular, for added flexibility in the modelling of the dynamics of financial time series, of importance especially as regards OU based stochastic volatility models for equities. In the special case of the tempered stable OU process...

  12. Applications of stable isotopes

    International Nuclear Information System (INIS)

    Letolle, R.; Mariotti, A.; Bariac, T.

    1991-06-01

    This report reviews the historical background and the properties of stable isotopes, the methods used for their measurement (mass spectrometry and others), the present technics for isotope enrichment and separation, and at last the various present and foreseeable application (in nuclear energy, physical and chemical research, materials industry and research; tracing in industrial, medical and agronomical tests; the use of natural isotope variations for environmental studies, agronomy, natural resources appraising: water, minerals, energy). Some new possibilities in the use of stable isotope are offered. A last chapter gives the present state and forecast development of stable isotope uses in France and Europe

  13. Analysing Stable Time Series

    National Research Council Canada - National Science Library

    Adler, Robert

    1997-01-01

    We describe how to take a stable, ARMA, time series through the various stages of model identification, parameter estimation, and diagnostic checking, and accompany the discussion with a goodly number...

  14. Evolutionary Stable Strategy

    Indian Academy of Sciences (India)

    2016-08-26

    Aug 26, 2016 ... Home; Journals; Resonance – Journal of Science Education; Volume 21; Issue 9. Evolutionary Stable Strategy: Application of Nash Equilibrium in Biology. General ... Using some examples of classical games, we show how evolutionary game theory can help understand behavioural decisions of animals.

  15. The Stable Concordance Genus

    OpenAIRE

    Kearney, M. Kate

    2013-01-01

    The concordance genus of a knot is the least genus of any knot in its concordance class. Although difficult to compute, it is a useful invariant that highlights the distinction between the three-genus and four-genus. In this paper we define and discuss the stable concordance genus of a knot, which describes the behavior of the concordance genus under connected sum.

  16. Manifolds admitting stable forms

    Czech Academy of Sciences Publication Activity Database

    Le, Hong-Van; Panák, Martin; Vanžura, Jiří

    2008-01-01

    Roč. 49, č. 1 (2008), s. 101-11 ISSN 0010-2628 R&D Projects: GA ČR(CZ) GP201/05/P088 Institutional research plan: CEZ:AV0Z10190503 Keywords : stable forms * automorphism groups Subject RIV: BA - General Mathematics

  17. Stable isotope studies

    International Nuclear Information System (INIS)

    Ishida, T.

    1992-01-01

    The research has been in four general areas: (1) correlation of isotope effects with molecular forces and molecular structures, (2) correlation of zero-point energy and its isotope effects with molecular structure and molecular forces, (3) vapor pressure isotope effects, and (4) fractionation of stable isotopes. 73 refs, 38 figs, 29 tabs

  18. Interactive Stable Ray Tracing

    DEFF Research Database (Denmark)

    Dal Corso, Alessandro; Salvi, Marco; Kolb, Craig

    2017-01-01

    Interactive ray tracing applications running on commodity hardware can suffer from objectionable temporal artifacts due to a low sample count. We introduce stable ray tracing, a technique that improves temporal stability without the over-blurring and ghosting artifacts typical of temporal post-pr...

  19. The stable subgroup graph

    Directory of Open Access Journals (Sweden)

    Behnaz Tolue

    2018-07-01

    Full Text Available In this paper we introduce stable subgroup graph associated to the group $G$. It is a graph with vertex set all subgroups of $G$ and two distinct subgroups $H_1$ and $H_2$ are adjacent if $St_{G}(H_1\\cap H_2\

  20. Stable isotope analysis

    International Nuclear Information System (INIS)

    Tibari, Elghali; Taous, Fouad; Marah, Hamid

    2014-01-01

    This report presents results related to stable isotopes analysis carried out at the CNESTEN DASTE in Rabat (Morocco), on behalf of Senegal. These analyzes cover 127 samples. These results demonstrate that Oxygen-18 and Deuterium in water analysis were performed by infrared Laser spectroscopy using a LGR / DLT-100 with Autosampler. Also, the results are expressed in δ values (‰) relative to V-SMOW to ± 0.3 ‰ for oxygen-18 and ± 1 ‰ for deuterium.

  1. Forensic Stable Isotope Biogeochemistry

    Science.gov (United States)

    Cerling, Thure E.; Barnette, Janet E.; Bowen, Gabriel J.; Chesson, Lesley A.; Ehleringer, James R.; Remien, Christopher H.; Shea, Patrick; Tipple, Brett J.; West, Jason B.

    2016-06-01

    Stable isotopes are being used for forensic science studies, with applications to both natural and manufactured products. In this review we discuss how scientific evidence can be used in the legal context and where the scientific progress of hypothesis revisions can be in tension with the legal expectations of widely used methods for measurements. Although this review is written in the context of US law, many of the considerations of scientific reproducibility and acceptance of relevant scientific data span other legal systems that might apply different legal principles and therefore reach different conclusions. Stable isotopes are used in legal situations for comparing samples for authenticity or evidentiary considerations, in understanding trade patterns of illegal materials, and in understanding the origins of unknown decedents. Isotope evidence is particularly useful when considered in the broad framework of physiochemical processes and in recognizing regional to global patterns found in many materials, including foods and food products, drugs, and humans. Stable isotopes considered in the larger spatial context add an important dimension to forensic science.

  2. Marginally Stable Nuclear Burning

    Science.gov (United States)

    Strohmayer, Tod E.; Altamirano, D.

    2012-01-01

    Thermonuclear X-ray bursts result from unstable nuclear burning of the material accreted on neutron stars in some low mass X-ray binaries (LMXBs). Theory predicts that close to the boundary of stability oscillatory burning can occur. This marginally stable regime has so far been identified in only a small number of sources. We present Rossi X-ray Timing Explorer (RXTE) observations of the bursting, high- inclination LMXB 4U 1323-619 that reveal for the first time in this source the signature of marginally stable burning. The source was observed during two successive RXTE orbits for approximately 5 ksec beginning at 10:14:01 UTC on March 28, 2011. Significant mHz quasi- periodic oscillations (QPO) at a frequency of 8.1 mHz are detected for approximately 1600 s from the beginning of the observation until the occurrence of a thermonuclear X-ray burst at 10:42:22 UTC. The mHz oscillations are not detected following the X-ray burst. The average fractional rms amplitude of the mHz QPOs is 6.4% (3 - 20 keV), and the amplitude increases to about 8% below 10 keV.This phenomenology is strikingly similar to that seen in the LMXB 4U 1636-53. Indeed, the frequency of the mHz QPOs in 4U 1323-619 prior to the X-ray burst is very similar to the transition frequency between mHz QPO and bursts found in 4U 1636-53 by Altamirano et al. (2008). These results strongly suggest that the observed QPOs in 4U 1323-619 are, like those in 4U 1636-53, due to marginally stable nuclear burning. We also explore the dependence of the energy spectrum on the oscillation phase, and we place the present observations within the context of the spectral evolution of the accretion-powered flux from the source.

  3. Stability of Picard Bundle Over Moduli Space of Stable Vector ...

    Indian Academy of Sciences (India)

    Abstract. Answering a question of [BV] it is proved that the Picard bundle on the moduli space of stable vector bundles of rank two, on a Riemann surface of genus at least three, with fixed determinant of odd degree is stable.

  4. Effects of Mars Regolith Analogs, UVC radiation, Temperature, Pressure, and pH on the Growth and Survivability of Methanogenic Archaea and Stable Carbon Isotope Fractionation: Implications for Surface and Subsurface Life on Mars

    Science.gov (United States)

    Sinha, Navita

    Mars is one of the suitable bodies in our solar system that can accommodate extraterrestrial life. The detection of plumes of methane in the Martian atmosphere, geochemical evidence, indication of flow of intermittent liquid water on the Martian surface, and geomorphologies of Mars have bolstered the plausibility of finding extant or evidence of extinct life on its surface and/or subsurface. However, contemporary Mars has been considered as an inhospitable planet for several reasons, such as low atmospheric surface pressure, low surface temperature, and intense DNA damaging radiation. Despite the hostile conditions of Mars, a few strains of methanogenic archaea have shown survivability in limited surface and subsurface conditions of Mars. Methanogens, which are chemolithoautotrophic non-photosynthetic anaerobic archaea, have been considered ideal models for possible Martian life forms for a long time. The search for biosignatures in the Martian atmosphere and possibility of life on the Martian surface under UVC radiation and deep subsurface under high pressure, temperature, and various pHs are the motivations of this research. Analogous to Earth, Martian atmospheric methane could be biological in origin. Chapter 1 provides relevant information about Mars' habitability, methane on Mars, and different strains of methanogens used in this study. Chapter 2 describes the interpretation of the carbon isotopic data of biogenic methane produced by methanogens grown on various Mars analogs and the results provide clues to determine ambiguous sources of methane on Mars. Chapter 3 illustrates the sensitivity of hydrated and desiccated cultures of halophilic and non-halophilic methanogens to DNA-damaging ultraviolet radiations, and the results imply that UVC radiation may not be an enormous constraint for methanogenic life forms on the surface of Mars. Chapters 4, 5, and 6 discuss the data for the survivability, growth, and morphology of methanogens in presumed deep subsurface

  5. Dynamical attraction to stable processes

    OpenAIRE

    Fisher, Albert M.; Talet, Marina

    2012-01-01

    We apply dynamical ideas within probability theory, proving an almost-sure invariance principle in log density for stable processes. The familiar scaling property (self-similarity) of the stable process has a stronger expression, that the scaling flow on Skorokhod path space is a Bernoulli flow. We prove that typical paths of a random walk with i.i.d. increments in the domain of attraction of a stable law can be paired with paths of a stable process so that, after applying a non-random regula...

  6. Identifying nitrate sources and transformations in surface water by combining dual isotopes of nitrate and stable isotope mixing model in a watershed with different land uses and multi-tributaries

    Science.gov (United States)

    Wang, Meng; Lu, Baohong

    2017-04-01

    Nitrate is essential for the growth and survival of plants, animals and humans. However, excess nitrate in drinking water is regarded as a health hazard as it is linked to infant methemoglobinemia and esophageal cancer. Revealing nitrate characteristics and identifying its sources are fundamental for making effective water management strategies, but nitrate sources in multi-tributaries and mixed land covered watersheds remain unclear. It is difficult to determine the predominant NO3- sources using conventional water quality monitoring techniques. In our study, based on 20 surface water sampling sites for more than two years' monitoring from April 2012 to December 2014, water chemical and dual isotopic approaches (δ15N-NO3- and δ18O-NO3-) were integrated for the first time to evaluate nitrate characteristics and sources in the Huashan watershed, Jianghuai hilly region, East China. The results demonstrated that nitrate content in surface water was relatively low in the downstream (qualitatively analyze nitrate sources and transformations as well as quantitatively estimate the contributions of potential nitrate sources in surface water. With the assessment of nitrate sources and characteristics, effective management strategies can be implemented to reduce N export and improve water quality in this region.

  7. High and stable photoelectrochemical activity of ZnO/ZnSe/CdSe/Cu(x)S core-shell nanowire arrays: nanoporous surface with Cu(x)S as a hole mediator.

    Science.gov (United States)

    Ouyang, Wei-Xin; Yu, Yu-Xiang; Zhang, Wei-De

    2015-06-14

    Advanced materials for electrocatalytic and photoelectrochemical water splitting are key for taking advantage of renewable energy. In this study, ZnO/ZnSe/CdSe/Cu(x)S core-shell nanowire arrays with a nanoporous surface were fabricated via ion exchange and successive ionic layer adsorption and reaction (SILAR) processes. The ZnO/ZnSe/CdSe/Cu(x)S sample displays a high photocurrent density of 12.0 mA cm(-2) under AM 1.5G illumination, achieves the highest IPCE value of 89.5% at 500 nm at a bias potential of 0.2 V versus Ag/AgCl, and exhibits greatly improved photostability. The functions of the ZnSe, CdSe, and Cu(x)S layers in the ZnO/ZnSe/CdSe/Cu(x)S heterostructure were clarified. ZnSe is used as a passivation layer to reduce the trapping and recombination of charge carriers at the interfaces of the semiconductors. CdSe functions as a highly efficient visible light absorber and builds heterojunctions with the other components to improve the separation and transportation of the photoinduced electrons and holes. Cu(x)S serves as a passivation layer and an effective p-type hole mediator, which passivates the defects and surface states of the semiconductors and forms p-n junctions with CdSe to promote the hole transportation at the semiconductor-electrolyte interface. The nanoporous surface of the ZnO/ZnSe/CdSe/Cu(x)S core-shell nanowire arrays, together with the tunnel transportation of the charge carriers in the thin films of ZnSe and CdSe, also facilitates the kinetics of photoelectrochemical reactions and improves the optical absorption as well.

  8. Generation of H-, H2(v double-prime), and H atoms by H2+ and H3+ ions incident upon barium surfaces

    International Nuclear Information System (INIS)

    Hiskes, J.R.; Karo, A.M.

    1989-01-01

    The generation of vibrationally excited molecules by electron excitation collisions and the subsequent generation of negative ions by dissociative attachment to these molecules has become a standard model for volume source operation. These processes have been supplemented recently by the demonstration of atom-surface recombination to form vibrationally excited molecules, and enhanced negative ion formation by protons incident upon barium electrodes. In this paper we consider the additional processes of molecular vibrational excitation generated by recombination of molecular ions on the electrode surfaces, and negative ion formation by vibrationally excited molecules rebounding from low work-function electrodes. 10 refs., 4 figs

  9. Shelf-Stable Food Safety

    Science.gov (United States)

    ... is an MRE? Is an MRE shelf stable? What foods are packaged in retort packages? What is aseptic ... type of package is used for aseptic processing? What foods are packaged in aseptic packages? Can I microwave ...

  10. Pharmaceuticals labelled with stable isotopes

    International Nuclear Information System (INIS)

    Krumbiegel, P.

    1986-11-01

    The relatively new field of pharmaceuticals labelled with stable isotopes is reviewed. Scientific, juridical, and ethical questions are discussed concerning the application of these pharmaceuticals in human medicine. 13 C, 15 N, and 2 H are the stable isotopes mainly utilized in metabolic function tests. Methodical contributions are given to the application of 2 H, 13 C, and 15 N pharmaceuticals showing new aspects and different states of development in the field under discussion. (author)

  11. Stable isotope research pool inventory

    International Nuclear Information System (INIS)

    1984-03-01

    This report contains a listing of electromagnetically separated stable isotopes which are available at the Oak Ridge National Laboratory for distribution for nondestructive research use on a loan basis. This inventory includes all samples of stable isotopes in the Research Materials Collection and does not designate whether a sample is out on loan or is in reprocessing. For some of the high abundance naturally occurring isotopes, larger amounts can be made available; for example, Ca-40 and Fe-56

  12. In situ controllable synthesis of novel surface plasmon resonance-enhanced Ag{sub 2}WO{sub 4}/Ag/Bi{sub 2}MoO{sub 6} composite for enhanced and stable visible light photocatalyst

    Energy Technology Data Exchange (ETDEWEB)

    Lv, Jiali [College of Physics and Electronic Information, Huaibei Normal University, Huaibei 235000 (China); Dai, Kai, E-mail: daikai940@chnu.edu.cn [College of Physics and Electronic Information, Huaibei Normal University, Huaibei 235000 (China); Zhang, Jinfeng [College of Physics and Electronic Information, Huaibei Normal University, Huaibei 235000 (China); Lu, Luhua, E-mail: lhlu@cug.edu.cn [Engineering Research Center of Nano-Geomaterials of Ministry of Education, China University of Geosciences, Wuhan 430074 (China); Liang, Changhao, E-mail: chliang@issp.ac.cn [College of Physics and Electronic Information, Huaibei Normal University, Huaibei 235000 (China); Key Laboratory of Materials Physics and Anhui Key Laboratory of Nanomaterials and Nanotechnology, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 23003 (China); Geng, Lei; Wang, Zhongliao; Yuan, Guangyu; Zhu, Guangping [College of Physics and Electronic Information, Huaibei Normal University, Huaibei 235000 (China)

    2017-01-01

    Highlights: • Novel Ag{sub 2}WO{sub 4}/Ag/Bi{sub 2}MoO{sub 6} ternary photocatalyst was prepared. • Ag{sub 2}WO{sub 4}/Ag/Bi{sub 2}MoO{sub 6} showed enhanced catalytic activity. • Ag{sub 2}WO{sub 4}/Ag/Bi{sub 2}MoO{sub 6} showed long reusable life. - Abstract: A novel hierarchical Ag{sub 2}WO{sub 4}/Ag/Bi{sub 2}MoO{sub 6} ternary visible-light-driven photocatalyst was successfully synthesized by in situ doping Ag{sub 2}WO{sub 4} with Bi{sub 2}MoO{sub 6} nanosheets through a facile hydrothermal and photochemical process. The morphology, structure, optical performance and crystallinity of the products were measured by field emission scanning electron microscope (FESEM), energy dispersive spectrometer (EDS), UV–vis diffuse reflectance spectroscopy (DRS) and X-ray diffraction (XRD). The results showed that Ag{sub 2}WO{sub 4}/Ag was uniformly dispersed on the surface of Bi{sub 2}MoO{sub 6} nanosheets. The photocatalytic performance of Ag{sub 2}WO{sub 4}/Ag/Bi{sub 2}MoO{sub 6} heterostructures was evaluated by the degradation of methylene blue (MB) under 410 nm LED arrays. The ternary Ag{sub 2}WO{sub 4}/Ag/Bi{sub 2}MoO{sub 6} nanocomposite exhibits higher photocatalytic activity than Bi{sub 2}MoO{sub 6} and Ag{sub 2}WO{sub 4}. The synergistic effect of Ag{sub 2}WO{sub 4} and Bi{sub 2}MoO{sub 6} could generated more heterojunctions which promoted photoelectrons transfer from Ag{sub 2}WO{sub 4} to Bi{sub 2}MoO{sub 6}, leading to the improvement of photocatalytic performance by photoelectrons-holes recombination suppression. At the same time, the surface plasmon resonance of Ag{sub 2}WO{sub 4}/Ag/Bi{sub 2}MoO{sub 6} is another crucial reason for the high photocatalytic performance of organic pollutants degradation. And the 20 wt% Ag{sub 2}WO{sub 4}-loaded Bi{sub 2}MoO{sub 6} shows the optimal photocatalytic performance in the degradation of MB. In addition, the ternary composites can be easily reclaimed by precipitation and exhibits high stability of photocatalytic

  13. Stable Boundary Layer Education (STABLE) Final Campaign Summary

    Energy Technology Data Exchange (ETDEWEB)

    Turner, David D. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2016-03-01

    The properties of, and the processes that occur in, the nocturnal stable boundary layer are not well understood, making it difficult to represent adequately in numerical models. The nocturnal boundary layer often is characterized by a temperature inversion and, in the Southern Great Plains region, a low-level jet. To advance our understanding of the nocturnal stable boundary layer, high temporal and vertical resolution data on the temperature and wind properties are needed, along with both large-eddy simulation and cloud-resolving modeling.

  14. Ice Surfaces

    Science.gov (United States)

    Shultz, Mary Jane

    2017-05-01

    Ice is a fundamental solid with important environmental, biological, geological, and extraterrestrial impact. The stable form of ice at atmospheric pressure is hexagonal ice, Ih. Despite its prevalence, Ih remains an enigmatic solid, in part due to challenges in preparing samples for fundamental studies. Surfaces of ice present even greater challenges. Recently developed methods for preparation of large single-crystal samples make it possible to reproducibly prepare any chosen face to address numerous fundamental questions. This review describes preparation methods along with results that firmly establish the connection between the macroscopic structure (observed in snowflakes, microcrystallites, or etch pits) and the molecular-level configuration (detected with X-ray or electron scattering techniques). Selected results of probing interactions at the ice surface, including growth from the melt, surface vibrations, and characterization of the quasi-liquid layer, are discussed.

  15. Radiation-stable polyolefin compositions

    International Nuclear Information System (INIS)

    Rekers, J.W.

    1986-01-01

    This invention relates to compositions of olefinic polymers suitable for high energy radiation treatment. In particular, the invention relates to olefinic polymer compositions that are stable to sterilizing dosages of high energy radiation such as a gamma radiation. Stabilizers are described that include benzhydrol and benzhydrol derivatives; these stabilizers may be used alone or in combination with secondary antioxidants or synergists

  16. Monitoring of stable glaucoma patients

    NARCIS (Netherlands)

    K.M. Holtzer-Goor (Kim); N.S. Klazinga (Niek); M.A. Koopmanschap (Marc); H.G. Lemij (Hans); T. Plochg; E. van Sprundel (Esther)

    2010-01-01

    textabstractA high workload for ophthalmologists and long waiting lists for patients challenge the organization of ophthalmic care. Tasks that require less specialized skills, like the monitoring of stable (well controlled) glaucoma patients could be substituted from ophthalmologists to other

  17. Analysis of Stable Isotope Contents of Surface and Underground ...

    African Journals Online (AJOL)

    Sam Eshun

    Upper West regions, the to east by the Republic of Togo, south by the Volta and Brong Ahafo regions and west by the La Côte d'Ivoire. Climate. The climate of the study area is tropical and semi-arid. Annual precipitation averages just over. 1050 mm, while potential evapotranspiration is about 1770 mm (Pelig-Ba, 2000).

  18. Macromolecular surface design: photopatterning of functional stable nitrile oxides

    Czech Academy of Sciences Publication Activity Database

    Altintas, O.; Glassner, M.; Rodriguez-Emmenegger, Cesar; Welle, A.; Trouillet, V.; Barner-Kowollik, C.

    2015-01-01

    Roč. 54, č. 19 (2015), s. 5777-5783 ISSN 1433-7851 R&D Projects: GA ČR(CZ) GBP205/12/G118 Institutional support: RVO:61389013 Keywords : modular ligation * nitrogen heterocycles * polymerization Subject RIV: BO - Biophysics Impact factor: 11.709, year: 2015

  19. Toward Practical Secure Stable Matching

    Directory of Open Access Journals (Sweden)

    Riazi M. Sadegh

    2017-01-01

    Full Text Available The Stable Matching (SM algorithm has been deployed in many real-world scenarios including the National Residency Matching Program (NRMP and financial applications such as matching of suppliers and consumers in capital markets. Since these applications typically involve highly sensitive information such as the underlying preference lists, their current implementations rely on trusted third parties. This paper introduces the first provably secure and scalable implementation of SM based on Yao’s garbled circuit protocol and Oblivious RAM (ORAM. Our scheme can securely compute a stable match for 8k pairs four orders of magnitude faster than the previously best known method. We achieve this by introducing a compact and efficient sub-linear size circuit. We even further decrease the computation cost by three orders of magnitude by proposing a novel technique to avoid unnecessary iterations in the SM algorithm. We evaluate our implementation for several problem sizes and plan to publish it as open-source.

  20. Towards stable acceleration in LINACS

    CERN Document Server

    Dubrovskiy, A D

    2014-01-01

    Ultra-stable and -reproducible high-energy particle beams with short bunches are needed in novel linear accelerators and, in particular, in the Compact Linear Collider CLIC. A passive beam phase stabilization system based on a bunch compression with a negative transfer matrix element R56 and acceleration at a positive off-crest phase is proposed. The motivation and expected advantages of the proposed scheme are outlined.

  1. Air stable organic-inorganic nanoparticles hybrid solar cells

    Science.gov (United States)

    Qian, Lei; Yang, Jihua; Xue, Jiangeng; Holloway, Paul H.

    2015-09-29

    A solar cell includes a low work function cathode, an active layer of an organic-inorganic nanoparticle composite, a ZnO nanoparticle layer situated between and physically contacting the cathode and active layers; and a transparent high work function anode that is a bilayer electrode. The inclusion of the ZnO nanoparticle layer results in a solar cell displaying a conversion efficiency increase and reduces the device degradation rate. Embodiments of the invention are directed to novel ZnO nanoparticles that are advantageous for use as the ZnO nanoparticle layers of the novel solar cells and a method to prepare the ZnO nanoparticles.

  2. Temperature and CO/sub 2/ changes in tropical surface waters of the Philippines during the past 120 years: Record in the stable isotopes of hermatypic corals. Temperatur- und CO/sub 2/-Aenderungen im tropischen Oberflaechenwasser der Philippinen waehrend der letzten 120 Jahre: Speicherung in stabilen Isotopen hermatyper Korallen

    Energy Technology Data Exchange (ETDEWEB)

    Paetzold, J.

    1986-01-01

    The massive coral Porites lobata has seasonal growth bands of varying skeletal density which enables dating as well as selective sampling for the purpose of isotope analyses. High-density bands are formed in summer and low-density bands in winter. The stable oxygen isotope ratios reflect the seasonal temperature variations of the surface water. The mean values show decreasing temperatures in the late 19th century, with minimum values around 1900. Since 1900, the delta/sup 18/O values have been decreasing continuously, which may indicate a heat-up by about 1,5/sup 0/C. Seasonal lighting can be reconstructed via the carbon isotope distribution which is influenced by the symbiotic algae. /sup 13/C is accumulated in periods of high light intensity and low precipitation. In contrast, /sup 12/C is accumulated at low light intensities and high precipitation. The seasonal variations of delta/sup 13/C are superposed by a general trend towards /sup 12/C accumulation, which is assumed to be due to an increased CO/sub 2/ concentration in the atmosphere.

  3. Stable Hemiaminals: 2-Aminopyrimidine Derivatives

    Directory of Open Access Journals (Sweden)

    Anna Kwiecień

    2015-08-01

    Full Text Available Stable hemiaminals can be obtained in the one-pot reaction between 2-aminopyrimidine and nitrobenzaldehyde derivatives. Ten new hemiaminals have been obtained, six of them in crystal state. The molecular stability of these intermediates results from the presence of both electron-withdrawing nitro groups as substituents on the phenyl ring and pyrimidine ring, so no further stabilisation by intramolecular interaction is required. Hemiaminal molecules possess a tetrahedral carbon atom constituting a stereogenic centre. As the result of crystallisation in centrosymmetric space groups both enantiomers are present in the crystal structure.

  4. Organic synthesis with stable isotopes

    International Nuclear Information System (INIS)

    Daub, G.H.; Kerr, V.N.; Williams, D.L.; Whaley, T.W.

    1978-01-01

    Some general considerations concerning organic synthesis with stable isotopes are presented. Illustrative examples are described and discussed. The examples include DL-2-amino-3-methyl- 13 C-butanoic-3,4- 13 C 2 acid (DL-valine- 13 C 3 ); methyl oleate-1- 13 C; thymine-2,6- 13 C 2 ; 2-aminoethanesulfonic- 13 C acid (taurine- 13 C); D-glucose-6- 13 C; DL-2-amino-3-methylpentanoic-3,4- 13 C 2 acid (DL-isoleucine- 13 C 2 ); benzidine- 15 N 2 ; and 4-ethylsulfonyl-1-naphthalene-sulfonamide- 15 N

  5. Stable agents for imaging investigations

    International Nuclear Information System (INIS)

    Tofe, A.J.

    1976-01-01

    This invention concerns highly stable compounds useful in preparing technetium 99m based scintiscanning exploration agents. The compounds of this invention include a pertechnetate reducing agent or a solution of oxidized pertechnetate and an efficient proportion, sufficient to stabilize the compounds in the presence of oxygen and of radiolysis products, of ascorbic acid or a pharmaceutically acceptable salt or ester of this acid. The invention also concerns a perfected process for preparing a technetium based exploration agent, consisting in codissolving the ascorbic acid or a pharmaceutically acceptable salt or ester of such an acid and a pertechnetate reducing agent in a solution of oxidized pertechnetate [fr

  6. Stable cosmology in chameleon bigravity

    Science.gov (United States)

    De Felice, Antonio; Mukohyama, Shinji; Oliosi, Michele; Watanabe, Yota

    2018-02-01

    The recently proposed chameleonic extension of bigravity theory, by including a scalar field dependence in the graviton potential, avoids several fine-tunings found to be necessary in usual massive bigravity. In particular it ensures that the Higuchi bound is satisfied at all scales, that no Vainshtein mechanism is needed to satisfy Solar System experiments, and that the strong coupling scale is always above the scale of cosmological interest all the way up to the early Universe. This paper extends the previous work by presenting a stable example of cosmology in the chameleon bigravity model. We find a set of initial conditions and parameters such that the derived stability conditions on general flat Friedmann background are satisfied at all times. The evolution goes through radiation-dominated, matter-dominated, and de Sitter eras. We argue that the parameter space allowing for such a stable evolution may be large enough to encompass an observationally viable evolution. We also argue that our model satisfies all known constraints due to gravitational wave observations so far and thus can be considered as a unique testing ground of gravitational wave phenomenologies in bimetric theories of gravity.

  7. Design of partially optically stable reflector systems and prisms

    Science.gov (United States)

    Tsai, Chuang-Yu

    2010-09-01

    The characteristics and design method of the total optically stable (TOS) reflector systems/prisms were introduced in an early paper (Tsai and Lin in Appl. Opt. 47:4158-4163, 2008), where only two types of TOS reflector system exist, namely preservation or retroreflection. In this paper, we introduce the partially optically stable (POS) reflector system, which is only optically stable about a specific directional vector; nevertheless, the exiting light ray is not restricted to preservation or retroreflection. The proposed paper also presents an analytic method for the design of POS reflector systems comprised of multiple reflectors. Furthermore, it is shown that a POS prism can be obtained by adding two refracting flat boundary surfaces with specific conditions at the entrance and exit positions of the light ray in an optical system with multiple reflectors.

  8. Stable isotope mass spectrometry in petroleum exploration

    International Nuclear Information System (INIS)

    Mathur, Manju

    1997-01-01

    The stable isotope mass spectrometry plays an important role to evaluate the stable isotopic composition of hydrocarbons. The isotopic ratios of certain elements in petroleum samples reflect certain characteristics which are useful for petroleum exploration

  9. Stability of Picard bundle over moduli space of stable vector bundles ...

    Indian Academy of Sciences (India)

    Springer Verlag Heidelberg #4 2048 1996 Dec 15 10:16:45

    E-mail: indranil@math.tifr.res.in; tomas@math.tifr.res.in. MS received 14 September 2000. Abstract. Answering a question of [BV] it is proved that the Picard bundle on the moduli space of stable vector bundles of rank two, on a Riemann surface of genus at least three, with fixed determinant of odd degree is stable. Keywords ...

  10. Stable rotating dipole solitons in nonlocal media

    DEFF Research Database (Denmark)

    Lopez-Aguayo, Servando; Skupin, Stefan; Desyatnikov, Anton S.

    2006-01-01

    We present the first example of stable rotating two-soliton bound states in nonlinear optical media with nonlocal response. We show that, in contrast to media with local response, nonlocality opens possibilities to generate stable azimuthons.......We present the first example of stable rotating two-soliton bound states in nonlinear optical media with nonlocal response. We show that, in contrast to media with local response, nonlocality opens possibilities to generate stable azimuthons....

  11. Stable colloids in molten inorganic salts

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Hao; Dasbiswas, Kinjal; Ludwig, Nicholas B.; Han, Gang; Lee, Byeongdu; Vaikuntanathan, Suri; Talapin, Dmitri V.

    2017-02-15

    A colloidal solution is a homogeneous dispersion of particles or droplets of one phase (solute) in a second, typically liquid, phase (solvent). Colloids are ubiquitous in biological, chemical and technological processes1, 2, homogenizing highly dissimilar constituents. To stabilize a colloidal system against coalescence and aggregation, the surface of each solute particle is engineered to impose repulsive forces strong enough to overpower van der Waals attraction and keep the particles separated from each other2. Electrostatic stabilization3, 4 of charged solutes works well in solvents with high dielectric constants, such as water (dielectric constant of 80). In contrast, colloidal stabilization in solvents with low polarity, such as hexane (dielectric constant of about 2), can be achieved by decorating the surface of each particle of the solute with molecules (surfactants) containing flexible, brush-like chains2, 5. Here we report a class of colloidal systems in which solute particles (including metals, semiconductors and magnetic materials) form stable colloids in various molten inorganic salts. The stability of such colloids cannot be explained by traditional electrostatic and steric mechanisms. Screening of many solute–solvent combinations shows that colloidal stability can be traced to the strength of chemical bonding at the solute–solvent interface. Theoretical analysis and molecular dynamics modelling suggest that a layer of surface-bound solvent ions produces long-ranged charge-density oscillations in the molten salt around solute particles, preventing their aggregation. Colloids composed of inorganic particles in inorganic melts offer opportunities for introducing colloidal techniques to solid-state science and engineering applications.

  12. Uses of stable isotopes in fish ecology

    Science.gov (United States)

    Analyses of fish tissues (other than otoliths) for stable isotope ratios can provide substantial information on fish ecology, including physiological ecology. Stable isotopes of nitrogen and carbon frequently are used to determine the mix of diet sources for consumers. Stable i...

  13. Periodicity of the stable isotopes

    CERN Document Server

    Boeyens, J C A

    2003-01-01

    It is demonstrated that all stable (non-radioactive) isotopes are formally interrelated as the products of systematically adding alpha particles to four elementary units. The region of stability against radioactive decay is shown to obey a general trend based on number theory and contains the periodic law of the elements as a special case. This general law restricts the number of what may be considered as natural elements to 100 and is based on a proton:neutron ratio that matches the golden ratio, characteristic of biological and crystal growth structures. Different forms of the periodic table inferred at other proton:neutron ratios indicate that the electronic configuration of atoms is variable and may be a function of environmental pressure. Cosmic consequences of this postulate are examined. (author)

  14. Stable States of Biological Organisms

    Science.gov (United States)

    Yukalov, V. I.; Sornette, D.; Yukalova, E. P.; Henry, J.-Y.; Cobb, J. P.

    2009-04-01

    A novel model of biological organisms is advanced, treating an organism as a self-consistent system subject to a pathogen flux. The principal novelty of the model is that it describes not some parts, but a biological organism as a whole. The organism is modeled by a five-dimensional dynamical system. The organism homeostasis is described by the evolution equations for five interacting components: healthy cells, ill cells, innate immune cells, specific immune cells, and pathogens. The stability analysis demonstrates that, in a wide domain of the parameter space, the system exhibits robust structural stability. There always exist four stable stationary solutions characterizing four qualitatively differing states of the organism: alive state, boundary state, critical state, and dead state.

  15. Theory of stable allocations II

    Directory of Open Access Journals (Sweden)

    Pantelić Svetlana

    2015-01-01

    Full Text Available The Swedish Royal Academy awarded the 2012 Nobel Prize in Economics to Lloyd Shapley and Alvin Roth, for the theory of stable allocations and the practice of market design. These two American researchers worked independently from each other, combining basic theory and empirical investigations. Through their experiments and practical design they generated a flourishing field of research and improved the performance of many markets. Shapley provided the fundamental theoretical contribution to this field of research, whereas Roth, a professor at the Harvard University in Boston, developed and upgraded these theoretical investigations by applying them to the American market of medical doctors. Namely, their research helps explain the market processes at work, for instance, when doctors are assigned to hospitals, students to schools and human organs for transplant to recipients.

  16. Stable massive particles at colliders

    Energy Technology Data Exchange (ETDEWEB)

    Fairbairn, M.; /Stockholm U.; Kraan, A.C.; /Pennsylvania U.; Milstead, D.A.; /Stockholm U.; Sjostrand, T.; /Lund U.; Skands, P.; /Fermilab; Sloan, T.; /Lancaster U.

    2006-11-01

    We review the theoretical motivations and experimental status of searches for stable massive particles (SMPs) which could be sufficiently long-lived as to be directly detected at collider experiments. The discovery of such particles would address a number of important questions in modern physics including the origin and composition of dark matter in the universe and the unification of the fundamental forces. This review describes the techniques used in SMP-searches at collider experiments and the limits so far obtained on the production of SMPs which possess various colour, electric and magnetic charge quantum numbers. We also describe theoretical scenarios which predict SMPs, the phenomenology needed to model their production at colliders and interactions with matter. In addition, the interplay between collider searches and open questions in cosmology such as dark matter composition are addressed.

  17. [Angle-stable fixation of intramedullary nails using the Angular Stable Locking System® (ASLS)].

    Science.gov (United States)

    Höntzsch, D; Blauth, M; Attal, R

    2011-12-01

    Greater stability in intramedullary osteosynthesis using angle-stable fixation with intramedullary nails and proximal locking screws. A novel screw-and-sleeve system (ASLS®, Synthes GmbH, Oberdorf, Switzerland) is applied using normal cannulated nails. Decisions can be made intraoperatively. This technology widens the range of indications for intramedullary nailing: The smaller and less stable the fragment requiring fixation, the greater the indication for angular stable fixation of the proximal and/or distal fragment. Femoral, tibial and humeral fractures, intramedullary osteosynthesis in osteoporotic bone and ante- and retrograde nailing. Particularly in the case of retrograde nailing, sustained prevention of nail toggling is achieved. None. Drill with the first drill bit, which has the same core diameter as the screw shaft. Drill the cortex to the external diameter of the sleeve. Place the sleeve on the tip of the screw. The screw-sleeve combination is then advanced through the larger near hole until the sleeve-covered screw tip sits in the locking hole of the intramedullary fixation nail. Advance the screw. As the screw diameter becomes larger, the sleeve expands resulting in an angular stable locking effect. The screw is then advanced until the head of the screw sits on the exposed surface of the cortex. The hole is filled with the expanded part of the screw shaft beneath the screw head. The necessary 1-3 turns are cut by the self-tapping flute on the screw. According to experience to date, this form of angle-stable fixation enables earlier and/or greater partial mobilization or earlier full mobilization. In all other respects, the guidelines for aftercare in intramedullary nailing apply. A multi-center pilot study has shown the technique to be reproducible and simple. There have been no complications using this technique to date. Biomechanical laboratory studies have demonstrated that stability with respect to axial and torsional loading is statically and

  18. Use of Spacecraft Data to Drive Regions on Mars where Liquid Water would be Stable

    Science.gov (United States)

    Lobitz, Brad; Wood, Byron L.; Averner, Maurice M.; McKay, Christopher P.; MacElroy, Robert D.

    2001-01-01

    Combining Viking pressure and temperature data with Mars Orbital Laser Altimeter (MOLA) topography data we have computed the fraction of the martian year during which pressure and temperature allow for liquid water to be stable on the martian surface. We find that liquid water would be stable within the Hellas and Argyre basin and over the northern lowlands equatorward of about 40 degrees. The location with the maximum period of stable conditions for liquid water is in the southeastern portion of Utopia Planitia where 34% of the year liquid water would be stable if it was present. Locations of stability appear to correlate with the distribution of valley networks.

  19. Stable Treemaps via Local Moves.

    Science.gov (United States)

    Sondag, Max; Speckmann, Bettina; Verbeek, Kevin

    2018-01-01

    Treemaps are a popular tool to visualize hierarchical data: items are represented by nested rectangles and the area of each rectangle corresponds to the data being visualized for this item. The visual quality of a treemap is commonly measured via the aspect ratio of the rectangles. If the data changes, then a second important quality criterion is the stability of the treemap: how much does the treemap change as the data changes. We present a novel stable treemapping algorithm that has very high visual quality. Whereas existing treemapping algorithms generally recompute the treemap every time the input changes, our algorithm changes the layout of the treemap using only local modifications. This approach not only gives us direct control over stability, but it also allows us to use a larger set of possible layouts, thus provably resulting in treemaps of higher visual quality compared to existing algorithms. We further prove that we can reach all possible treemap layouts using only our local modifications. Furthermore, we introduce a new measure for stability that better captures the relative positions of rectangles. We finally show via experiments on real-world data that our algorithm outperforms existing treemapping algorithms also in practice on either visual quality and/or stability. Our algorithm scores high on stability regardless of whether we use an existing stability measure or our new measure.

  20. Stable isotope paleoaltimetry of the Mount Everest region

    Science.gov (United States)

    Gebelin, A.; Mulch, A.; Teyssier, C.; Jessup, M. J.; Law, R. D.; Brunel, M.

    2012-12-01

    Long-term climatic evolution and atmospheric circulation patterns are influenced to a first order by the topography of the largest mountain ranges. Reconstructing the Neogene elevation history of the Mount Everest region is of particular interest for understanding the tectonic history of the Himalaya-Tibet orogen as well as global scale atmospheric circulation and biotic changes through time. Stable isotope paleoaltimetry uses the isotopic lapse rate of precipitations preserved in the near-surface record. In the absence of surface deposits such as paleosols, volcanic ashes, or lacustrine limestone that record the stable isotopic composition of early to mid-Miocene water preserved in the highly erosive Himalayan range, we conduct stable-isotope paleoaltimetry based on the hydrogen isotopic composition (δD) of hydrous minerals that crystallized in the South Tibetan detachment (STD) shear zone at ~17 Ma. For paleoaltimetry reconstruction we compare stable isotope records from the STD mylonitic footwall to age-equivalent oxygen isotope ratios (δ18O) measured within pedogenic carbonate from Siwalik foreland paleosols that developed near Miocene sea level. The relative differences between meteoric water compositions in the foreland basin and the δ18Owater calculated from the hydrogen isotope composition of syntectonic minerals suggest that by ~17 Ma the central Himalaya was at an elevation similar to what it is today, and that a rain shadow likely existed at that time. Our results demonstrate the power of shear-zone based paleoaltimetry in eroded mountain belts, call for caution in interpreting basin-based stable isotope paleoaltimetry in the rain shadow of the mid-Miocene Himalayan range and suggest that strengthening of the South Asian monsoon may have occurred in early to mid-Miocene, earlier than previously thought.

  1. Advanced thermally stable jet fuels

    Energy Technology Data Exchange (ETDEWEB)

    Schobert, H.H.

    1999-01-31

    The Pennsylvania State University program in advanced thermally stable coal-based jet fuels has five broad objectives: (1) Development of mechanisms of degradation and solids formation; (2) Quantitative measurement of growth of sub-micrometer and micrometer-sized particles suspended in fuels during thermal stressing; (3) Characterization of carbonaceous deposits by various instrumental and microscopic methods; (4) Elucidation of the role of additives in retarding the formation of carbonaceous solids; (5) Assessment of the potential of production of high yields of cycloalkanes by direct liquefaction of coal. Future high-Mach aircraft will place severe thermal demands on jet fuels, requiring the development of novel, hybrid fuel mixtures capable of withstanding temperatures in the range of 400--500 C. In the new aircraft, jet fuel will serve as both an energy source and a heat sink for cooling the airframe, engine, and system components. The ultimate development of such advanced fuels requires a thorough understanding of the thermal decomposition behavior of jet fuels under supercritical conditions. Considering that jet fuels consist of hundreds of compounds, this task must begin with a study of the thermal degradation behavior of select model compounds under supercritical conditions. The research performed by The Pennsylvania State University was focused on five major tasks that reflect the objectives stated above: Task 1: Investigation of the Quantitative Degradation of Fuels; Task 2: Investigation of Incipient Deposition; Task 3: Characterization of Solid Gums, Sediments, and Carbonaceous Deposits; Task 4: Coal-Based Fuel Stabilization Studies; and Task 5: Exploratory Studies on the Direct Conversion of Coal to High Quality Jet Fuels. The major findings of each of these tasks are presented in this executive summary. A description of the sub-tasks performed under each of these tasks and the findings of those studies are provided in the remainder of this volume

  2. Population Games, Stable Games, and Passivity

    Directory of Open Access Journals (Sweden)

    Michael J. Fox

    2013-10-01

    Full Text Available The class of “stable games”, introduced by Hofbauer and Sandholm in 2009, has the attractive property of admitting global convergence to equilibria under many evolutionary dynamics. We show that stable games can be identified as a special case of the feedback-system-theoretic notion of a “passive” dynamical system. Motivated by this observation, we develop a notion of passivity for evolutionary dynamics that complements the definition of the class of stable games. Since interconnections of passive dynamical systems exhibit stable behavior, we can make conclusions about passive evolutionary dynamics coupled with stable games. We show how established evolutionary dynamics qualify as passive dynamical systems. Moreover, we exploit the flexibility of the definition of passive dynamical systems to analyze generalizations of stable games and evolutionary dynamics that include forecasting heuristics as well as certain games with memory.

  3. Tungsten Stable Isotope Compositions of Ferromanganese Crusts

    Science.gov (United States)

    Abraham, K.; Barling, J.; Hein, J. R.; Schauble, E. A.; Halliday, A. N.

    2014-12-01

    We report the first accurate and precise data for mass-dependent fractionation of tungsten (W) stable isotopes, using a double spike technique and MC-ICPMS. Results are expressed relative to the NIST 3136 W isotope standard as per mil deviations in 186W/184W (δ186W). Although heavy element mass-dependent fractionations are expected to be small, Tl and U both display significant low temperature isotopic fractionations. Theoretical calculations indicate that W nuclear volume isotopic effects should be smaller than mass-dependent fractionations at low temperatures. Hydrogenetic ferromanganese (Fe-Mn) crusts precipitate directly from seawater and have been used as paleoceanographic recorders of temporal changes in seawater chemistry. Crusts are strongly enriched in W and other metals, and are a promising medium for exploring W isotopic variability. Tungsten has a relatively long residence time in seawater of ~61,000 years, mainly as the tungstate ion (WO42-). Water depth profiles show conservative behaviour. During adsorption on Fe-Mn crusts, W species form inner-sphere complexes in the hexavalent (W6+) state. The major host phase is thought to be Mn oxides and the lighter W isotope is expected to be absorbed preferentially. Surface scrapings of 13 globally distributed hydrogenetic Fe-Mn crusts display δ186W from -0.08 to -0.22‰ (±0.03‰, 2sd). A trend toward lighter W isotope composition exists with increasing water depth (~1500 to ~5200m) and W concentration. One hydrothermal Mn-oxide sample is anomalously light and Mn nodules are both heavy and light relative to Fe-Mn crusts. Tungsten speciation depends on concentration, pH, and time in solution and is not well understood because of the extremely slow kinetics of the reactions. In addition, speciation of aqueous and/or adsorbed species might be sensitive to pressure, showing similar thermodynamic stability but different effective volumes. Thus, W stable isotopes might be used as a water-depth barometer in

  4. [Stable Isotopes Characters of Soil Water Movement in Shijiazhuang City].

    Science.gov (United States)

    Chen, Tong-tong; Chen, Hui; Han, Lu; Xing, Xing; Fu, Yang-yang

    2015-10-01

    In this study, we analyzed the stable hydrogen and oxygen isotope values of precipitation, soil water, irrigation water that collected in Shijiazhuang City from April 2013 to May 2014 to investigate the changing rule of the stable isotopes in different soil profiles and the process of soil water movement according to using the isotope tracer technique. The results showed that the mean excess deuterium of the local precipitation was -6.188 5 per thousand. Those reflected that the precipitation in Shijiazhuang City mainly brought by the monsoon from the ocean surface moisture, and also to some extent by the local evaporation. Precipitation was the main source of the soil water and the irrigation water played the supplementary role. In the rainy season, precipitation was enough to supply the soil water. The stable oxygen isotopes at 10-100 cm depth decreased with the increase of depth, the maximum depth of evaporation in the rainy season reached 40 cm. The peak of stable oxygen isotopes of soil water pushed down along the profile, which was infected by the interaction of the precipitation infiltration, evaporation and the mixing water.

  5. Gas phase thermal diffusion of stable isotopes

    International Nuclear Information System (INIS)

    Eck, C.F.

    1979-01-01

    The separation of stable isotopes at Mound Facility is reviewed from a historical perspective. The historical development of thermal diffusion from a laboratory process to a separation facility that handles all the noble gases is described. In addition, elementary thermal diffusion theory and elementary cascade theory are presented along with a brief review of the uses of stable isotopes

  6. physico-chemical and stable isotopes

    African Journals Online (AJOL)

    This paper details the mineralogical, chemical and stable isotope abundances of calcrete in the Letlhakeng fossil valley. The stable isotope abundances (O and C) of calcretes yielded some values which were tested against the nature of the calcretes – pedogenic or groundwater type. The Kgalagadi (Kalahari) is a vast ...

  7. Stable isotopes and biomarkers in microbial ecology

    NARCIS (Netherlands)

    Boschker, H.T.S.; Middelburg, J.J.

    2002-01-01

    The use of biomarkers in combination with stable isotope analysis is a new approach in microbial ecology and a number of papers on a variety of subjects have appeared. We will first discuss the techniques for analysing stable isotopes in biomarkers, primarily gas chromatography-combustion-isotope

  8. Stable Agrobacterium -mediated transformation of the halophytic ...

    African Journals Online (AJOL)

    Stable Agrobacterium-mediated transformation of the halophytic Leymus chinensis (Trin.) Yan-Lin Sun, Soon-Kwan Hong. Abstract. In this study, an efficient procedure for stable Agrobacterium-mediated transformation of Leymus chinensis (Trin.) was established. Agrobacterium tumefaciens strain EHA105, harboring a ...

  9. Structure of acid-stable carmine.

    Science.gov (United States)

    Sugimoto, Naoki; Kawasaki, Yoko; Sato, Kyoko; Aoki, Hiromitsu; Ichi, Takahito; Koda, Takatoshi; Yamazaki, Takeshi; Maitani, Tamio

    2002-02-01

    Acid-stable carmine has recently been distributed in the U.S. market because of its good acid stability, but it is not permitted in Japan. We analyzed and determined the structure of the major pigment in acid-stable carmine, in order to establish an analytical method for it. Carminic acid was transformed into a different type of pigment, named acid-stable carmine, through amination when heated in ammonia solution. The features of the structure were clarified using a model compound, purpurin, in which the orientation of hydroxyl groups on the A ring of the anthraquinone skeleton is the same as that of carminic acid. By spectroscopic means and the synthesis of acid-stable carmine and purpurin derivatives, the structure of the major pigment in acid-stable carmine was established as 4-aminocarminic acid, a novel compound.

  10. Stable Fly, (L., Dispersal and Governing Factors

    Directory of Open Access Journals (Sweden)

    Allan T. Showler

    2015-01-01

    Full Text Available Although the movement of stable fly, Stomoxys calcitrans (L., has been studied, its extent and significance has been uncertain. On a local scale (13 km is mainly wind-driven by weather fronts that carry stable flies from inland farm areas for up to 225 km to beaches of northwestern Florida and Lake Superior. Stable flies can reproduce for a short time each year in washed-up sea grass, but the beaches are not conducive to establishment. Such movement is passive and does not appear to be advantageous to stable fly's survival. On a regional scale, stable flies exhibit little genetic differentiation, and on the global scale, while there might be more than one “lineage”, the species is nevertheless considered to be panmictic. Population expansion across much of the globe likely occurred from the late Pleistocene to the early Holocene in association with the spread of domesticated nomad livestock and particularly with more sedentary, penned livestock.

  11. Modelling of the flow of stable air over a complex region

    CSIR Research Space (South Africa)

    Scholtz, MT

    1976-01-01

    Full Text Available The flow of stable air over a general region of complex topography and non-uniform surface temperature has been investigated. In order to gain further understanding of the motion of surface air, it was necessary to study the vertical structure...

  12. Stable configurations of graphene on silicon

    Energy Technology Data Exchange (ETDEWEB)

    Javvaji, Brahmanandam; Shenoy, Bhamy Maithry [Department of Aerospace Engineering, Indian Institute of Science, Bangalore 560012 (India); Mahapatra, D. Roy, E-mail: droymahapatra@aero.iisc.ernet.in [Department of Aerospace Engineering, Indian Institute of Science, Bangalore 560012 (India); Ravikumar, Abhilash [Department of Metallurgical and Materials Engineering, National Institute of Technology Karnataka, Surathkal 575025 (India); Hegde, G.M. [Center for Nano Science and Engineering, Indian Institute of Science, Bangalore 560012 (India); Rizwan, M.R. [Department of Metallurgical and Materials Engineering, National Institute of Technology Karnataka, Surathkal 575025 (India)

    2017-08-31

    Highlights: • Simulations of epitaxial growth process for silicon–graphene system is performed. • Identified the most favourable orientation of graphene sheet on silicon substrate. • Atomic local strain due to the silicon–carbon bond formation is analyzed. - Abstract: Integration of graphene on silicon-based nanostructures is crucial in advancing graphene based nanoelectronic device technologies. The present paper provides a new insight on the combined effect of graphene structure and silicon (001) substrate on their two-dimensional anisotropic interface. Molecular dynamics simulations involving the sub-nanoscale interface reveal a most favourable set of temperature independent orientations of the monolayer graphene sheet with an angle of ∽15° between its armchair direction and [010] axis of the silicon substrate. While computing the favorable stable orientations, both the translation and the rotational vibrations of graphene are included. The possible interactions between the graphene atoms and the silicon atoms are identified from their coordination. Graphene sheet shows maximum bonding density with bond length 0.195 nm and minimum bond energy when interfaced with silicon substrate at 15° orientation. Local deformation analysis reveals probability distribution with maximum strain levels of 0.134, 0.047 and 0.029 for 900 K, 300 K and 100 K, respectively in silicon surface for 15° oriented graphene whereas the maximum probable strain in graphene is about 0.041 irrespective of temperature. Silicon–silicon dimer formation is changed due to silicon–carbon bonding. These results may help further in band structure engineering of silicon–graphene lattice.

  13. Dewatered sewage biosolids provide a productive larval habitat for stable flies and house flies (Diptera: Muscidae).

    Science.gov (United States)

    Doud, C W; Taylor, D B; Zurek, L

    2012-03-01

    Species diversity and seasonal abundance of muscoid flies (Diptera: Muscidae) developing in biosolid cake (dewatered biosolids) stored at a wastewater treatment facility in northeastern Kansas were evaluated. Emergence traps were deployed 19 May through 20 October 2009 (22 wk) and 27 May through 18 November 2010 (25 wk). In total, 11,349 muscoid flies were collected emerging from the biosolid cake. Stable flies (Stomoxys calcitrans (L.)) and house flies (Musca domestica (L.)), represented 80 and 18% of the muscoid flies, respectively. An estimated 550 stable flies and 220 house flies per square-meter of surface area developed in the biosolid cake annually producing 450,000 stable flies and 175,000 house flies. Stable fly emergence was seasonally bimodal with a primary peak in mid-July and a secondary peak in late August. House fly emergence peaked with the first stable fly emergence peak and then declined gradually for the remainder of the year. House flies tended to emerge from the biosolid cake sooner after its deposition than did stable flies. In addition, house fly emergence was concentrated around midsummer whereas stable fly emergence began earlier in the spring and continued later into the fall. Biosolid age and temperature were the most important parameters affecting emergence for house flies and stable flies, whereas precipitation was not important for either species. This study highlights the importance of biosolid cake as a larval developmental habitat for stable flies and house flies.

  14. Stable Organic Neutral Diradical via Reversible Coordination.

    Science.gov (United States)

    Lu, Zhenpin; Quanz, Henrik; Burghaus, Olaf; Hofmann, Jonas; Logemann, Christian; Beeck, Sebastian; Schreiner, Peter R; Wegner, Hermann A

    2017-12-27

    We report the formation of a stable neutral diboron diradical simply by coordination of an aromatic dinitrogen compound to an ortho-phenyldiborane. This process is reversible upon addition of pyridine. The diradical species is stable above 200 °C. Computations are consistent with an open-shell triplet diradical with a very small open-shell singlet-triplet energy gap that is indicative of the electronic disjointness of the two radical sites. This opens a new way of generating stable radicals with fascinating electronic properties useful for a large variety of applications.

  15. Stable lithium electrodeposition in liquid and nanoporous solid electrolytes

    KAUST Repository

    Lu, Yingying

    2014-08-10

    Rechargeable lithium, sodium and aluminium metal-based batteries are among the most versatile platforms for high-energy, cost-effective electrochemical energy storage. Non-uniform metal deposition and dendrite formation on the negative electrode during repeated cycles of charge and discharge are major hurdles to commercialization of energy-storage devices based on each of these chemistries. A long-held view is that unstable electrodeposition is a consequence of inherent characteristics of these metals and their inability to form uniform electrodeposits on surfaces with inevitable defects. We report on electrodeposition of lithium in simple liquid electrolytes and in nanoporous solids infused with liquid electrolytes. We find that simple liquid electrolytes reinforced with halogenated salt blends exhibit stable long-term cycling at room temperature, often with no signs of deposition instabilities over hundreds of cycles of charge and discharge and thousands of operating hours. We rationalize these observations with the help of surface energy data for the electrolyte/lithium interface and impedance analysis of the interface during different stages of cell operation. Our findings provide support for an important recent theoretical prediction that the surface mobility of lithium is significantly enhanced in the presence of lithium halide salts. Our results also show that a high electrolyte modulus is unnecessary for stable electrodeposition of lithium.

  16. Stable Isotope Group 1983 progress report

    International Nuclear Information System (INIS)

    Stewart, M.K.

    1984-06-01

    The work of the Stable Isotope Group of the Institute of Nuclear Sciences in the fields of isotope geology, isotope hydrology, geochronology, isotope biology and related fields, and mass spectrometer instrumentation, during 1983, is described

  17. Stable Isotope Group 1982 progress report

    International Nuclear Information System (INIS)

    Stewart, M.K.

    1983-06-01

    The work of the Stable Isotope Group of the Institute of Nuclear Sciences during 1982, in the fields of isotope geology, isotope hydrology, geochronology, isotope biology and mass spectrometer instrumentation, is described

  18. Bartolome Island, Galapagos Stable Oxygen Calibration Data

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Galapagos Coral Stable Oxygen Calibration Data. Sites: Bartolome Island: 0 deg, 17'S, 90 deg 33' W. Champion Island: 1 deg, 15'S, 90 deg, 05' W. Urvina Bay (Isabela...

  19. Allan Hills Stable Water Isotopes, Version 1

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set includes stable water isotope values at 10 m resolution along an approximately 5 km transect through the main icefield of the Allan Hills Blue Ice...

  20. Applications of stable isotopes in clinical pharmacology

    Science.gov (United States)

    Schellekens, Reinout C A; Stellaard, Frans; Woerdenbag, Herman J; Frijlink, Henderik W; Kosterink, Jos G W

    2011-01-01

    This review aims to present an overview of the application of stable isotope technology in clinical pharmacology. Three main categories of stable isotope technology can be distinguished in clinical pharmacology. Firstly, it is applied in the assessment of drug pharmacology to determine the pharmacokinetic profile or mode of action of a drug substance. Secondly, stable isotopes may be used for the assessment of drug products or drug delivery systems by determination of parameters such as the bioavailability or the release profile. Thirdly, patients may be assessed in relation to patient-specific drug treatment; this concept is often called personalized medicine. In this article, the application of stable isotope technology in the aforementioned three areas is reviewed, with emphasis on developments over the past 25 years. The applications are illustrated with examples from clinical studies in humans. PMID:21801197

  1. Tannaka duality and stable infinity-categories

    OpenAIRE

    Iwanari, Isamu

    2014-01-01

    We introduce the notion of fine tannakian infinity-categories and prove Tannaka duality results for symmetric monoidal stable infinity-categories over a field of characteristic zero. We also discuss several examples.

  2. On Stable Marriages and Greedy Matchings

    Energy Technology Data Exchange (ETDEWEB)

    Manne, Fredrik; Naim, Md; Lerring, Hakon; Halappanavar, Mahantesh

    2016-12-11

    Research on stable marriage problems has a long and mathematically rigorous history, while that of exploiting greedy matchings in combinatorial scientific computing is a younger and less developed research field. In this paper we consider the relationships between these two areas. In particular we show that several problems related to computing greedy matchings can be formulated as stable marriage problems and as a consequence several recently proposed algorithms for computing greedy matchings are in fact special cases of well known algorithms for the stable marriage problem. However, in terms of implementations and practical scalable solutions on modern hardware, the greedy matching community has made considerable progress. We show that due to the strong relationship between these two fields many of these results are also applicable for solving stable marriage problems.

  3. Highly Photoluminescent and Stable Aqueous ZnS Quantum Dots

    OpenAIRE

    Li, Hui; Shih, Wan Y.; Shih, Wei-Heng

    2010-01-01

    We report an all-aqueous synthesis of highly photoluminescent and stable ZnS quantum dots (QDs) with water as the medium, i.e. first synthesizing ZnS QDs with 3-mercaptopropionic acid (MPA) as the capping molecule, followed by replacing some of MPA with (3-mercaptopropyl) trimethoxysilane (MPS). The resultant MPS-replaced ZnS QDs were about 5 nm in size with a cubic zinc blende crystalline structure, and had both MPA and MPS on the surface as confirmed by the Fourier Transform Infrared (FTIR)...

  4. Electropolishing of Stainless Steel Implants for Stable Functional Osteosynthesis

    Directory of Open Access Journals (Sweden)

    Omel’chuk, A.О.

    2016-01-01

    Full Text Available A new method for the electropolishing stainless steel for stable functional osteosynthesis has been developed. The polishing of implants was carried out in solutions, based on the ternary system H2SO4—H3PO4—H2O with stepwise decreasing the current density and increasing the orthophosphoric acid concentration. The optimal polishing conditions (current density, solution composition, temperature and duration have been determined. The developed method improves the quality and mechanical properties of the surface.

  5. The motion control of a statically stable biped robot on an uneven floor.

    Science.gov (United States)

    Shih, C L; Chiou, C J

    1998-01-01

    This work studies the motion control of a statically stable biped robot having seven degrees of freedom. Statically stable walking of the biped robot is realized by maintaining the center-of-gravity inside the convex region of the supporting foot and/or feet during both single-support and double-support phases. The main points of this work are framing the stability in an easy and correct way, the design of a bipedal statically stable walker, and walking on sloping surfaces and stairs.

  6. The Reactivity of Stable Metallacyclobutenes and Vinylcarbenes

    OpenAIRE

    Holland, Ryan Lynn

    2016-01-01

    Chapter 1. Historical Development of Stable Metallacyclobutenes Fred Tebbe and co-workers synthesized the first stable metallacyclobutene complexes in the late 1970’s by treatment of an intermediate titanium methylene species – later popularized as the “Tebbe reagent” – with acetylenes. Robert Grubbs at Caltech further studied this system, using it to detail a degenerate metathesis reaction and to isolate a metallacyclobutane complex – which was implicated in the emerging field of alkene meta...

  7. Stable atomic hydrogen: Polarized atomic beam source

    International Nuclear Information System (INIS)

    Niinikoski, T.O.; Penttilae, S.; Rieubland, J.M.; Rijllart, A.

    1984-01-01

    We have carried out experiments with stable atomic hydrogen with a view to possible applications in polarized targets or polarized atomic beam sources. Recent results from the stabilization apparatus are described. The first stable atomic hydrogen beam source based on the microwave extraction method (which is being tested ) is presented. The effect of the stabilized hydrogen gas density on the properties of the source is discussed. (orig.)

  8. Air-stable n-type colloidal quantum dot solids

    KAUST Repository

    Ning, Zhijun

    2014-06-08

    Colloidal quantum dots (CQDs) offer promise in flexible electronics, light sensing and energy conversion. These applications rely on rectifying junctions that require the creation of high-quality CQD solids that are controllably n-type (electron-rich) or p-type (hole-rich). Unfortunately, n-type semiconductors made using soft matter are notoriously prone to oxidation within minutes of air exposure. Here we report high-performance, air-stable n-type CQD solids. Using density functional theory we identify inorganic passivants that bind strongly to the CQD surface and repel oxidative attack. A materials processing strategy that wards off strong protic attack by polar solvents enabled the synthesis of an air-stable n-type PbS CQD solid. This material was used to build an air-processed inverted quantum junction device, which shows the highest current density from any CQD solar cell and a solar power conversion efficiency as high as 8%. We also feature the n-type CQD solid in the rapid, sensitive, and specific detection of atmospheric NO2. This work paves the way for new families of electronic devices that leverage air-stable quantum-tuned materials. © 2014 Macmillan Publishers Limited. All rights reserved.

  9. Local Search Approaches in Stable Matching Problems

    Directory of Open Access Journals (Sweden)

    Toby Walsh

    2013-10-01

    Full Text Available The stable marriage (SM problem has a wide variety of practical applications, ranging from matching resident doctors to hospitals, to matching students to schools or, more generally, to any two-sided market. In the classical formulation, n men and n women express their preferences (via a strict total order over the members of the other sex. Solving an SM problem means finding a stable marriage where stability is an envy-free notion: no man and woman who are not married to each other would both prefer each other to their partners or to being single. We consider both the classical stable marriage problem and one of its useful variations (denoted SMTI (Stable Marriage with Ties and Incomplete lists where the men and women express their preferences in the form of an incomplete preference list with ties over a subset of the members of the other sex. Matchings are permitted only with people who appear in these preference lists, and we try to find a stable matching that marries as many people as possible. Whilst the SM problem is polynomial to solve, the SMTI problem is NP-hard. We propose to tackle both problems via a local search approach, which exploits properties of the problems to reduce the size of the neighborhood and to make local moves efficiently. We empirically evaluate our algorithm for SM problems by measuring its runtime behavior and its ability to sample the lattice of all possible stable marriages. We evaluate our algorithm for SMTI problems in terms of both its runtime behavior and its ability to find a maximum cardinality stable marriage. Experimental results suggest that for SM problems, the number of steps of our algorithm grows only as O(n log(n, and that it samples very well the set of all stable marriages. It is thus a fair and efficient approach to generate stable marriages. Furthermore, our approach for SMTI problems is able to solve large problems, quickly returning stable matchings of large and often optimal size, despite the

  10. Surface chemical analysis and ab initio investigations of CsI coated C fiber cathodes for high power microwave sources

    Science.gov (United States)

    Vlahos, Vasilios; Morgan, Dane; LaCour, Matthew; Golby, Ken; Shiffler, Don; Booske, John H.

    2010-02-01

    CsI coated C fiber cathodes are promising electron emitters utilized in field emission applications. Ab initio calculations, in conjunction with experimental investigations on CsI-spray coated C fiber cathodes, were performed in order to better understand the origin of the low turn-on E-field obtained, as compared to uncoated C fibers. One possible mechanism for lowering the turn-on E-field is surface dipole layers reducing the work function. Ab initio modeling revealed that surface monolayers of Cs, CsI, Cs2O, and CsO are all capable of producing low work function C fiber cathodes (1 eVcoabsorption of Cs and I into the fiber interior and Cs and O on the fiber surface, with no surface I. It is therefore proposed that a cesium oxide (CsxOy) surface coating is responsible, at least in part, for the low turn E-field and superior emission characteristics of this type of fiber cathode. This CsxOy layer could be formed during preconditioning heating. CsxOy surface layers cannot only lower the fiber work function by the formation of surface dipoles (if they are thin enough) but may also enhance surface emission through their ability to emit secondary electrons due to a process of grazing electron impact. These multiple electron emission processes may explain the reported 10-100 fold reduction in the turn-on E-field of coated C fibers.

  11. Stable superhydrophilic coating on superhydrophobic porous media by functionalized nanoparticles

    Science.gov (United States)

    Khazaei, Masoud; Taghi Sadeghi, Mohammad; Sadat Hosseini, Marzieh

    2018-01-01

    In this study, the hydrophilicity property of TiO2 nano-coating was improved by zinc acetate-assisted sol-gel method. The stable superhydrophilic coating was fabricated on a superhydrophobic mineral rock surface. The wettability of surface before and after coating was characterized by contact angle measurements. The n-heptane and water droplet contact angle was 0° and 168° respectively, so the untreated rock was superhydrophobic. After nano-treatment, the n-heptane and water contact angle changed to 172° and 0° respectively, so the superhydrophilic coating was formed on the superhydrophobic surface. The thermal, mechanical and salinity stability of the fabricated coatings was investigated. The coatings had high thermal and salinity stability; they also had moderate mechanical stability that was evaluated by abrasion test. The morphology and composition of synthesized nanoparticles were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy and x-ray diffraction (XRD) analyses. Characterization of the coated surfaces was conducted by SEM and XRD analyses. Applications of these nano-coatings include surfaces where cleanliness is paramount such as in hospitals as well as the protection of public monuments and building facades from weathering. Novel industrial application includes wettability alteration of oil wet carbonate rock for enhanced oil recovery.

  12. Correlation of H- production and the work function of a surface in a hydrogen plasma

    International Nuclear Information System (INIS)

    Wada, M.

    1983-01-01

    Surface-plasma negative hydrogen ion sources are being developed as possible parts for future netural beam systems. In these ion sources, negative hydrogen ions (H - ) are produced at low work function metal surfaces immersed in hydrogen plasmas. To investigate the correlation between the work function and the H-production at the surface with a condition similar to the one in the actual plasma ion source, these two parameters were simultaneously measured in the hydrogen plasma environment. The photoelectron emission currents from Mo and Cu surfaces in a cesiated hydrogen discharge were measured in the photon energy range from 1.45 to 4.14 eV, to determine the work function based on Fowler's theory. A small magnetic line cusp plasma container was specially designed to minimize the plasma noise and to realize the efficient collection of incident light onto the target. The photelectron current was detected phase sensitively and could be measured with reasonable accuracy up to about 5 x 10 11 cm -3 of the plasma electron density. As Cs density was increased in the hydrogen discharge, the work function decreased until it reached a minimum value. This value of the lowest work function was approximately 1.4 eV for both Mo and Cu surfaces, and the detected total H - current was a maximum at this condition

  13. Properties of stable nonstoichiometric nanoceria produced by thermal plasma

    Science.gov (United States)

    Lan, Yuan-Pei; Sohn, Hong Yong; Mohassab, Yousef; Liu, Qingcai; Xu, Baoqiang

    2017-08-01

    Thermally stable blue nonstoichiometric nanoceria was produced by feeding nanoceria with an average size of 50 nm into a DC thermal plasma reactor. The effects of different plasma power levels and atmospheres were investigated. XRD results showed the ceria lattice parameter increased with plasma power. SEM and TEM results showed that the shape of nanoparticles changed after plasma treatment; the blue nonstoichiometric nanoceria had highly regular shapes such as triangular pyramids and polyhedral in contrast to the irregular shape of the raw nanoceria. Significant downshift was found in the Raman spectra of the plasma products, with a 7.9-cm-1 shift compared with raw nanoceria, which was explained by the reduction of Ce4+. X-ray photoelectron spectroscopy results showed that the Ce3+ fraction increased from 14% in the raw nanoceria to 38-39% for the product CeO2- x , indicating the high reduction state on the ceria surface. It was determined that this blue nonstoichiometric nanoceria was stable up to 400 °C in air, but the color changed to pale yellow after 4 h at 500 °C in air indicating oxidation to CeO2. Additionally, this novel stable nano-CeO2- x caused a red shift in the UV-visible absorption results; a 48-nm red shift occurred for the nonstoichiometric nanoceria produced at 15 kW compared with the raw nanoceria. The band gap was calculated to be 2.5 eV while it was 3.2 eV for the raw nanoceria, indicating that this novel stable blue nonstoichiometric nanoceria should be a promising material for optical application.

  14. The Healing Potential of Stable Juvenile Osteochondritis Dissecans Knee Lesions

    Science.gov (United States)

    Wall, Eric J.; Vourazeris, Jason; Myer, Gregory D.; Emery, Kathleen H.; Divine, Jon G.; Nick, Todd G.; Hewett, Timothy E.

    2008-01-01

    Background: The purpose of the present study was to determine if patient age, lesion size, lesion location, presenting knee symptoms, and sex predict the healing status after six months of a standard protocol of nonoperative treatment for stable juvenile osteochondritis dissecans of the knee. Methods: Forty-two skeletally immature patients (forty-seven knees) who presented with a stable osteochondritis dissecans lesion were included in the present study. All patients were managed with temporary immobilization followed by knee bracing and activity restriction. The primary outcome measure of progressive lesion reossification was determined from serial radiographs every six weeks, for up to six months of nonoperative treatment. A multivariable logistic regression model was used to determine potential predictors of healing status from the listed independent variables. Results: After six months of nonoperative treatment, sixteen (34%) of forty-seven stable lesions had failed to progress toward healing. The mean surface area (and standard deviation) of the lesions that showed progression toward healing (208.7 ± 135.4 mm2) was significantly smaller than that of the lesions that failed to show progression toward healing (288.0 ± 102.6 mm2) (p = 0.05). A logistic regression model that included patient age, normalized lesion size (relative to the femoral condyle), and presenting symptoms (giving-way, swelling, locking, or clicking) was predictive of healing status. Age was not a significant contributor to the predictive model (p = 0.25). Conclusions: In two-thirds of immature patients, six months of nonoperative treatment that includes activity modification and immobilization results in progressive healing of stable osteochondritis dissecans lesions. Lesions with an increased size and associated swelling and/or mechanical symptoms at presentation are less likely to heal. Level of Evidence: Prognostic Level II. See Instructions to Authors for a complete description of

  15. Stable chaos in fluctuation driven neural circuits

    International Nuclear Information System (INIS)

    Angulo-Garcia, David; Torcini, Alessandro

    2014-01-01

    Highlights: • Nonlinear instabilities in fluctuation driven (balanced) neural circuits are studied. • Balanced networks display chaos and stable phases at different post-synaptic widths. • Linear instabilities coexists with nonlinear ones in the chaotic regime. • Erratic motion appears also in linearly stable phase due to stable chaos. - Abstract: We study the dynamical stability of pulse coupled networks of leaky integrate-and-fire neurons against infinitesimal and finite perturbations. In particular, we compare mean versus fluctuations driven networks, the former (latter) is realized by considering purely excitatory (inhibitory) sparse neural circuits. In the excitatory case the instabilities of the system can be completely captured by an usual linear stability (Lyapunov) analysis, whereas the inhibitory networks can display the coexistence of linear and nonlinear instabilities. The nonlinear effects are associated to finite amplitude instabilities, which have been characterized in terms of suitable indicators. For inhibitory coupling one observes a transition from chaotic to non chaotic dynamics by decreasing the pulse-width. For sufficiently fast synapses the system, despite showing an erratic evolution, is linearly stable, thus representing a prototypical example of stable chaos

  16. Metabolic studies in man using stable isotopes

    International Nuclear Information System (INIS)

    Faust, H.; Jung, K.; Krumbiegel, P.

    1993-01-01

    In this project, stable isotope compounds and stable isotope pharmaceuticals were used (with emphasis on the application of 15 N) to study several aspects of nitrogen metabolism in man. Of the many methods available, the 15 N stable isotope tracer technique holds a special position because the methodology for application and nitrogen isotope analysis is proven and reliable. Valid routine methods using 15 N analysis by emission spectrometry have been demonstrated. Several methods for the preparation of biological material were developed during our participation in the Coordinated Research Programme. In these studies, direct procedures (i.e. use of diluted urine as a samples without chemical preparation) or rapid isolation methods were favoured. Within the scope of the Analytical Quality Control Service (AQCS) enriched stable isotope reference materials for medical and biological studies were prepared and are now available through the International Atomic Energy Agency. The materials are of special importance as the increasing application of stable isotopes as tracers in medical, biological and agricultural studies has focused interest on reliable measurements of biological material of different origin. 24 refs

  17. Patterns in Stable Isotope Values of Nitrogen and Carbon in ...

    Science.gov (United States)

    Stable isotope measurements of nitrogen and carbon (15N, 13ddC) are often used to characterize estuarine, nearshore, and open ocean ecosystems. Reliable information about the spatial distribution of base-level stable isotope values, often represented by primary producers, is critical to interpreting values in these ecosystems. While base-level isotope data are generally readily available for estuaries, nearshore coastal waters, and the open ocean, the continental shelf is less studied. To address this, and as a first step toward developing a surrogate for base-level isotopic signature in this region, we collected surface and deep water samples from the United States’ eastern continental shelf in the Western Atlantic Ocean, from the Gulf of Maine to Cape Hatteras, periodically between 2000 and 2013. During the study, particulate matter 15dN values ranged from 0.8 to 17.4‰, and 13dC values from −26.4 to −15.6‰over the region. We used spatial autocorrelation analysis and random forest modeling to examine the spatial trends and potential environmental drivers of the stable isotope values. We observed general trends toward lower values for both nitrogen and carbon isotopes at the seaward edge of the shelf. Conversely, higher 15dN and 13dC values were observed on the landward edge of the shelf, in particular in the southern portion of the sampling area. Across all sites, the magnitude of the difference between the 15dN of subsurface and surface particulate m

  18. Marginally stable resonant modes of the polytropic hydrodynamic vortex

    Science.gov (United States)

    Hod, Shahar

    2017-11-01

    The polytropic hydrodynamic vortex describes an effective (2 + 1)-dimensional acoustic spacetime with an inner reflecting boundary at r =rc. This physical system, like the spinning Kerr black hole, possesses an ergoregion of radius re and an inner non-pointlike curvature singularity of radius rs. Interestingly, the fundamental ratio re /rs which characterizes the effective geometry is determined solely by the dimensionless polytropic index Np of the circulating fluid. It has recently been proved that, in the Np = 0 case, the effective acoustic spacetime is characterized by an infinite countable set of reflecting surface radii, {rc (Np ; n) }n=1n=∞, that can support static (marginally-stable) sound modes. In the present paper we use analytical techniques in order to explore the physical properties of the polytropic hydrodynamic vortex in the Np > 0 regime. In particular, we prove that in this physical regime, the effective acoustic spacetime is characterized by a finite discrete set of reflecting surface radii, {rc (Np , m ; n) }n=1n=Nmax, that can support the marginally-stable static sound modes (here m is the azimuthal harmonic index of the acoustic perturbation field). Interestingly, it is proved analytically that the dimensionless outermost supporting radius rcmax /re, which marks the onset of superradiant instabilities in the polytropic hydrodynamic vortex, increases monotonically with increasing values of the integer harmonic index m and decreasing values of the dimensionless polytropic index Np.

  19. STICS: surface-tethered iterative carbohydrate synthesis.

    Science.gov (United States)

    Pornsuriyasak, Papapida; Ranade, Sneha C; Li, Aixiao; Parlato, M Cristina; Sims, Charles R; Shulga, Olga V; Stine, Keith J; Demchenko, Alexei V

    2009-04-14

    A new surface-tethered iterative carbohydrate synthesis (STICS) technology is presented in which a surface functionalized 'stick' made of chemically stable high surface area porous gold allows one to perform cost efficient and simple synthesis of oligosaccharide chains; at the end of the synthesis, the oligosaccharide can be cleaved off and the stick reused for subsequent syntheses.

  20. Stable isotope paleoaltimetry and the evolution of landscapes and life

    Science.gov (United States)

    Mulch, Andreas

    2016-01-01

    Reconstructing topography of our planet not only advances our knowledge of the geodynamic processes that shape the Earth's surface; equally important it adds a key element towards understanding long-term continental moisture transport, atmospheric circulation and the distribution of biomes and biodiversity. Stable isotope paleoaltimetry exploits systematic decreases in the oxygen (δ18O) or hydrogen (δD) isotopic composition of precipitation along a mountain front when the interaction of topography and advected moist air masses induces orographic precipitation. These changes in δ18O or δD can be recovered from the geologic record and recent geochemical and modeling advances allow a broad range of proxy materials to be evaluated. Over the last 10 yr stable isotope paleoaltimetry has witnessed rapidly expanding research activities and has produced a broad array of fascinating tectonic and geomorphologic studies many of which have concentrated on determining the elevation history of continental plateau regions. These single-site studies have greatly expanded what used to be very sparse global paleoaltimetric data. The challenge now lies in disentangling the surface uplift component from the impact of climate change on δ18O and δD in precipitation. The robustness of stable isotope paleoaltimetry can be enhanced when high-elevation δ18O or δD data are referenced against low-elevation sites that track climate-modulated sea level δ18O or δD of precipitation through time (' δ- δ approach'). Analysis of central Andean paleosols documents that differences in δ18O of soil carbonate between the Subandean foreland and the Bolivian Altiplano are small between 11 and 7 Ma but rise rapidly to ca. 2.9‰ after 7 Ma, corroborating the magnitude of late Miocene change in δ18O on the Altiplano. Future advances in stable isotope paleoaltimetry will greatly benefit from addressing four key challenges: (1) Identifying topographically-induced changes in atmospheric

  1. Temperature and Humidity Control in Livestock Stables

    DEFF Research Database (Denmark)

    Hansen, Michael; Andersen, Palle; Nielsen, Kirsten M.

    2010-01-01

    The paper describes temperature and humidity control of a livestock stable. It is important to have a correct air flow pattern in the livestock stable in order to achieve proper temperature and humidity control as well as to avoid draught. In the investigated livestock stable the air flow...... is controlled using wall mounted ventilation flaps. In the paper an algorithm for air flow control is presented meeting the needs for temperature and humidity while taking the air flow pattern in consideration. To obtain simple and realisable controllers a model based control design method is applied....... In the design dynamic models for temperature and humidity are very important elements and effort is put into deriving and testing the models. It turns out that non-linearities are dominating in both models making feedback linearization the natural design method. The air controller as well as the temperature...

  2. On some topological properties of stable measures

    DEFF Research Database (Denmark)

    Nielsen, Carsten Krabbe

    1996-01-01

    Summary The paper shows that the set of stable probability measures and the set of Rational Beliefs relative to a given stationary measure are closed in the strong topology, but not closed in the topology of weak convergence. However, subsets of the set of stable probability measures which...... are characterized by uniformity of convergence of the empirical distribution are closed in the topology of weak convergence. It is demonstrated that such subsets exist. In particular, there is an increasing sequence of sets of SIDS measures who's union is the set of all SIDS measures generated by a particular...... system and such that each subset consists of stable measures. The uniformity requirement has a natural interpretation in terms of plausibility of Rational Beliefs...

  3. Concentration of stable elements in food products

    Energy Technology Data Exchange (ETDEWEB)

    Montford, M.A.; Shank, K.E.; Hendricks, C.; Oakes, T.W.

    1980-01-01

    Food samples were taken from commercial markets and analyzed for stable element content. The concentrations of most stable elements (Ag, Al, As, Au, Ba, Br, Ca, Ce, Cl, Co, Cr, Cs, Cu, Fe, Hf, I, K, La, Mg, Mn, Mo, Na, Rb, Sb, Sc, Se, Sr, Ta, Th, Ti, V, Zn, Zr) were determined using multiple-element neutron activation analysis, while the concentrations of other elements (Cd, Hg, Ni, Pb) were determined using atomic absorption. The relevance of the concentrations found are noted in relation to other literature values. An earlier study was extended to include the determination of the concentration of stable elements in home-grown products in the vicinity of the Oak Ridge National Laboratory. Comparisons between the commercial and local food-stuff values are discussed.

  4. Faster and Simpler Approximation of Stable Matchings

    Directory of Open Access Journals (Sweden)

    Katarzyna Paluch

    2014-04-01

    Full Text Available We give a 3 2 -approximation algorithm for finding stable matchings that runs in O(m time. The previous most well-known algorithm, by McDermid, has the same approximation ratio but runs in O(n3/2m time, where n denotes the number of people andm is the total length of the preference lists in a given instance. In addition, the algorithm and the analysis are much simpler. We also give the extension of the algorithm for computing stable many-to-many matchings.

  5. Stable isotopes in Lithuanian bioarcheological material

    Science.gov (United States)

    Skipityte, Raminta; Jankauskas, Rimantas; Remeikis, Vidmantas

    2015-04-01

    Investigation of bioarcheological material of ancient human populations allows us to understand the subsistence behavior associated with various adaptations to the environment. Feeding habits are essential to the survival and growth of ancient populations. Stable isotope analysis is accepted tool in paleodiet (Schutkowski et al, 1999) and paleoenvironmental (Zernitskaya et al, 2014) studies. However, stable isotopes can be useful not only in investigating human feeding habits but also in describing social and cultural structure of the past populations (Le Huray and Schutkowski, 2005). Only few stable isotope investigations have been performed before in Lithuanian region suggesting a quite uniform diet between males and females and protein intake from freshwater fish and animal protein. Previously, stable isotope analysis has only been used to study a Stone Age population however, more recently studies have been conducted on Iron Age and Late medieval samples (Jacobs et al, 2009). Anyway, there was a need for more precise examination. Stable isotope analysis were performed on human bone collagen and apatite samples in this study. Data represented various ages (from 5-7th cent. to 18th cent.). Stable carbon and nitrogen isotope analysis on medieval populations indicated that individuals in studied sites in Lithuania were almost exclusively consuming C3 plants, C3 fed terrestrial animals, and some freshwater resources. Current investigation demonstrated social differences between elites and country people and is promising in paleodietary and daily life reconstruction. Acknowledgement I thank prof. dr. G. Grupe, Director of the Anthropological and Palaeoanatomical State Collection in Munich for providing the opportunity to work in her laboratory. The part of this work was funded by DAAD. Antanaitis-Jacobs, Indre, et al. "Diet in early Lithuanian prehistory and the new stable isotope evidence." Archaeologia Baltica 12 (2009): 12-30. Le Huray, Jonathan D., and Holger

  6. Bordism, stable homotopy and adams spectral sequences

    CERN Document Server

    Kochman, Stanley O

    1996-01-01

    This book is a compilation of lecture notes that were prepared for the graduate course "Adams Spectral Sequences and Stable Homotopy Theory" given at The Fields Institute during the fall of 1995. The aim of this volume is to prepare students with a knowledge of elementary algebraic topology to study recent developments in stable homotopy theory, such as the nilpotence and periodicity theorems. Suitable as a text for an intermediate course in algebraic topology, this book provides a direct exposition of the basic concepts of bordism, characteristic classes, Adams spectral sequences, Brown-Peter

  7. Modelling stable water isotopes: Status and perspectives

    Directory of Open Access Journals (Sweden)

    Werner M.

    2010-12-01

    Full Text Available Modelling of stable water isotopes H2 18O and HDO within various parts of the Earth’s hydrological cycle has clearly improved our understanding of the interplay between climatic variations and related isotope fractionation processes. In this article key principles and major research results of stable water isotope modelling studies are described. Emphasis is put on research work using explicit isotope diagnostics within general circulation models as this highly complex model setup bears many resemblances with studies using simpler isotope modelling approaches.

  8. Evidence for Sticky-Trap Avoidance by Stable Fly, Stomoxys calcitrans (Diptera: Muscidae), in Response to Trapped Flies.

    Science.gov (United States)

    Beresford, D V; Sutcliffe, J F

    2017-09-01

    Populations of stable flies, Stomoxys calcitrans, and other filth flies are often sampled using sticky traps. We wanted to know whether flies already caught on sticky traps might inhibit to some extent subsequent flies from being caught. To test this, we recorded the number of stable flies landing on white plastic corrugated panels (Coroplast®), which were prepared according to 4 treatments: 12 live stable flies glued to the surface, 12 live house flies (Musca domestica) glued to the surface, 12 black dots, and no treatment. From 160 observations, we found that fewer stable flies landed on panels with either attached stable flies (129) or house flies (133) compared with the number landing on panels with black dots (259) and/or with no treatment (210). This apparent inhibitory effect of trapped flies may explain published trap-catch patterns from field studies.

  9. CO oxidation on PdO surfaces

    DEFF Research Database (Denmark)

    Hirvi, Janne T.; Kinnunen, Toni-Jani J.; Suvanto, Mika

    2010-01-01

    Density functional calculations were performed in order to investigate CO oxidation on two of the most stable bulk PdO surfaces. The most stable PdO(100) surface, with oxygen excess, is inert against CO adsorption, whereas strong adsorption on the stoichiometric PdO(101) surface leads to favorable...... oxidation via the Langmuir–Hinshelwood mechanism. The reaction with a surface oxygen atom has an activation energy of 0.66 eV, which is comparable to the lowest activation energies observed on metallic surfaces. However, the reaction rate may be limited by the coverage of molecular oxygen. Actually...... adsorption, following the Eley–Rideal mechanism and taking advantage of the reaction tunnel provided by the adjacent palladium atom, has an activation energy of only 0.24 eV. The reaction mechanism and activation energy for the palladium activated CO oxidation on the most stable PdO(100)–O surface...

  10. Comparative biogeochemical behaviors of iron-55 and stable iron in the marine environment

    International Nuclear Information System (INIS)

    Weimer, W.C.; Langford, J.C.; Jenkins, C.E.

    1978-01-01

    Studies of atmospheric aerosols have demonstrated that much of the 55 Fe associated with the aerosol input to the oceans is present as either an amorphous or hydrous iron oxide or as very small particulate species attached to the surfaces of the large aerosol particles. By comparison, nearly all of the stable iron is bound in the mineral phase of aerosol particles. This difference in the chemical and physical forms of the radioactive and stable iron isotopes results in the 55 Fe being more biologically available than is the stable iron. This difference in availability is responsible for the transfer of a much higher specific activity 55 Fe to certain ocean organisms and man relative to the specific activity of the total aerosol or of sea water. This differential biological uptake of the radioactive element and its stable element counterpart points out that natural levels of stable elements in the marine environment may not effectively dilute radioelements or other stable elements of anthropogenic sources. The effectiveness of dilution by natural sources depends on the chemical and physical forms of the materials in both the source terms and the receiving environments. The large difference in specific activities of 55 Fe in aerosols and sea water relative to ocean organisms reflects the independent behaviors of 55 Fe and stable iron

  11. Stable isotope analysis of dynamic lipidomics.

    Science.gov (United States)

    Brandsma, Joost; Bailey, Andrew P; Koster, Grielof; Gould, Alex P; Postle, Anthony D

    2017-08-01

    Metabolic pathway flux is a fundamental element of biological activity, which can be quantified using a variety of mass spectrometric techniques to monitor incorporation of stable isotope-labelled substrates into metabolic products. This article contrasts developments in electrospray ionisation mass spectrometry (ESI-MS) for the measurement of lipid metabolism with more established gas chromatography mass spectrometry and isotope ratio mass spectrometry methodologies. ESI-MS combined with diagnostic tandem MS/MS scans permits the sensitive and specific analysis of stable isotope-labelled substrates into intact lipid molecular species without the requirement for lipid hydrolysis and derivatisation. Such dynamic lipidomic methodologies using non-toxic stable isotopes can be readily applied to quantify lipid metabolic fluxes in clinical and metabolic studies in vivo. However, a significant current limitation is the absence of appropriate software to generate kinetic models of substrate incorporation into multiple products in the time domain. Finally, we discuss the future potential of stable isotope-mass spectrometry imaging to quantify the location as well as the extent of lipid synthesis. This article is part of a Special Issue entitled: BBALIP_Lipidomics Opinion Articles edited by Sepp Kohlwein. Copyright © 2017 Elsevier B.V. All rights reserved.

  12. Petrography, compositional characteristics and stable isotope ...

    African Journals Online (AJOL)

    Petrography, compositional characteristics and stable isotope geochemistry of the Ewekoro formation from Ibese Corehole, eastern Dahomey basin, southwestern Nigeria. ME Nton, MO ... Preserved pore types such as; intercrystaline, moldic and vuggy pores were observed as predominant conduits for fluids. The major ...

  13. petrography, compositional characteristics and stable isotope ...

    African Journals Online (AJOL)

    PROF EKWUEME

    Subsurface samples of the predominantly carbonate Ewekoro Formation, obtained from Ibese core hole within the Dahomey basin were used in this study. Investigations entail petrographic, elemental composition as well as stable isotopes (carbon and oxygen) geochemistry in order to deduce the different microfacies and ...

  14. Substitution of stable isotopes in Chlorella

    Science.gov (United States)

    Flaumenhaft, E.; Katz, J. J.; Uphaus, R. A.

    1969-01-01

    Replacement of biologically important isotopes in the alga Chlorella by corresponding heavier stable isotopes produces increasingly greater deviations from the normal cell size and changes the quality and distribution of certain cellular components. The usefulness of isotopically altered organisms increases interest in the study of such permuted organisms.

  15. Champion Island, Galapagos Stable Oxygen Calibration Data

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Galapagos Coral Stable Oxygen Calibration Data. Sites: Bartolome Island: 0 deg, 17 min S, 90 deg 33 min W. Champion Island: 1 deg, 15 min S, 90 deg, 05 min W. Urvina...

  16. Stable propagation of 'selfish'genetic elements

    Indian Academy of Sciences (India)

    Unknown

    viruses such as the Epstein-Barr virus (Harris et al 1985;. Kanda et al 2001) and bovine papilloma virus (Lehman and Botchan 1998; Ilves et al 1999), which exist pre- dominantly as extrachromosomal episomes, have been shown to utilize chromosome tethering as a means for stable segregation. The tethering mechanism ...

  17. Unconditionally stable perfectly matched layer boundary conditions

    NARCIS (Netherlands)

    De Raedt, H.; Michielsen, K.

    2007-01-01

    A brief review is given of a systematic, product-formula based approach to construct unconditionally stable algorithms for solving the time-dependent Maxwell equations. The fundamental difficulties that arise when we want to incorporate uniaxial perfectly matched layer boundary conditions into this

  18. Facies, dissolution seams and stable isotope compositions

    Indian Academy of Sciences (India)

    Stable isotope analysis of the limestone shows that 13C and 18O values are compatible with the early Mesoproterozoic open seawater composition. The ribbon limestone facies in the Rohtas Limestone is characterized by micritic beds, each decoupled in a lower band enriched and an upper band depleted in dissolution ...

  19. Connected domination stable graphs upon edge addition ...

    African Journals Online (AJOL)

    A set S of vertices in a graph G is a connected dominating set of G if S dominates G and the subgraph induced by S is connected. We study the graphs for which adding any edge does not change the connected domination number. Keywords: Connected domination, connected domination stable, edge addition ...

  20. Stable magnetic remanence in antiferromagnetic goethite.

    Science.gov (United States)

    Strangway, D W; McMahon, B E; Honea, R M

    1967-11-10

    Goethite, known to be antiferromagnetic, acquires thermoremanent magnetization at its Neel temperature of 120 degrees C. This remanence, extremely stable, is due to the presence of unbalanced spins in the antiferromagnetic structure; the spins may result from grain size, imperfections, or impurities.

  1. Properties of lanthanum hexaboride a compilation

    CERN Document Server

    Fisher, D J

    2013-01-01

    Lanthanum hexaboride is useful because it possesses a high melting point (2210C), a low work function, one of the highest known electron emissivities, and is stable in vacuum. This volume summarises the extant data on the properties of this material, including the: bulk modulus, conductivity, crystal structure, Debye temperature, defect structure, elastic constants, electronic structure, emissivity, Fermi surface, hardness, heat capacity, magnetoresistance, reflectivity, resistivity, specific heat, surface structure, thermal conductivity, thermoelectric power, toughness and work function. The

  2. Strontium stable isotope behaviour accompanying basalt weathering

    Science.gov (United States)

    Burton, K. W.; Parkinson, I. J.; Gíslason, S. G. R.

    2016-12-01

    The strontium (Sr) stable isotope composition of rivers is strongly controlled by the balance of carbonate to silicate weathering (Krabbenhöft et al. 2010; Pearce et al. 2015). However, rivers draining silicate catchments possess distinctly heavier Sr stable isotope values than their bedrock compositions, pointing to significant fractionation during weathering. Some have argued for preferential release of heavy Sr from primary phases during chemical weathering, others for the formation of secondary weathering minerals that incorporate light isotopes. This study presents high-precision double-spike Sr stable isotope data for soils, rivers, ground waters and estuarine waters from Iceland, reflecting both natural weathering and societal impacts on those environments. The bedrock in Iceland is dominantly basaltic, d88/86Sr ≈ +0.27, extending to lighter values for rhyolites. Geothermal waters range from basaltic Sr stable compositions to those akin to seawater. Soil pore waters reflect a balance of input from primary mineral weathering, precipitation and litter recycling and removal into secondary phases and vegetation. Rivers and ground waters possess a wide range of d88/86Sr compositions from +0.101 to +0.858. Elemental and isotope data indicate that this fractionation primarily results from the formation or dissolution of secondary zeolite (d88/86Sr ≈ +0.10), but also carbonate (d88/86Sr ≈ +0.22) and sometimes anhydrite (d88/86Sr ≈ -0.73), driving the residual waters to heavier or lighter values, respectively. Estuarine waters largely reflect mixing with seawater, but are also be affected by adsorption onto particulates, again driving water to heavy values. Overall, these data indicate that the stability and nature of secondary weathering phases, exerts a strong control on the Sr stable isotope composition of silicate rivers. [1] Krabbenhöft et al. (2010) Geochim. Cosmochim. Acta 74, 4097-4109. [2] Pearce et al. (2015) Geochim. Cosmochim. Acta 157, 125-146.

  3. Activated carbon derived from waste coffee grounds for stable methane storage.

    Science.gov (United States)

    Kemp, K Christian; Baek, Seung Bin; Lee, Wang-Geun; Meyyappan, M; Kim, Kwang S

    2015-09-25

    An activated carbon material derived from waste coffee grounds is shown to be an effective and stable medium for methane storage. The sample activated at 900 °C displays a surface area of 1040.3 m(2) g(-1) and a micropore volume of 0.574 cm(3) g(-1) and exhibits a stable CH4 adsorption capacity of ∼4.2 mmol g(-1) at 3.0 MPa and a temperature range of 298 ± 10 K. The same material exhibits an impressive hydrogen storage capacity of 1.75 wt% as well at 77 K and 100 kPa. Here, we also propose a mechanism for the formation of activated carbon from spent coffee grounds. At low temperatures, the material has two distinct types with low and high surface areas; however, activation at elevated temperatures drives off the low surface area carbon, leaving behind the porous high surface area activated carbon.

  4. Activated carbon derived from waste coffee grounds for stable methane storage

    Science.gov (United States)

    Kemp, K. Christian; Baek, Seung Bin; Lee, Wang-Geun; Meyyappan, M.; Kim, Kwang S.

    2015-09-01

    An activated carbon material derived from waste coffee grounds is shown to be an effective and stable medium for methane storage. The sample activated at 900 °C displays a surface area of 1040.3 m2 g-1 and a micropore volume of 0.574 cm3 g-1 and exhibits a stable CH4 adsorption capacity of ˜4.2 mmol g-1 at 3.0 MPa and a temperature range of 298 ± 10 K. The same material exhibits an impressive hydrogen storage capacity of 1.75 wt% as well at 77 K and 100 kPa. Here, we also propose a mechanism for the formation of activated carbon from spent coffee grounds. At low temperatures, the material has two distinct types with low and high surface areas; however, activation at elevated temperatures drives off the low surface area carbon, leaving behind the porous high surface area activated carbon.

  5. Development of a Safety Management Web Tool for Horse Stables.

    Science.gov (United States)

    Leppälä, Jarkko; Kolstrup, Christina Lunner; Pinzke, Stefan; Rautiainen, Risto; Saastamoinen, Markku; Särkijärvi, Susanna

    2015-11-12

    Managing a horse stable involves risks, which can have serious consequences for the stable, employees, clients, visitors and horses. Existing industrial or farm production risk management tools are not directly applicable to horse stables and they need to be adapted for use by managers of different types of stables. As a part of the InnoEquine project, an innovative web tool, InnoHorse, was developed to support horse stable managers in business, safety, pasture and manure management. A literature review, empirical horse stable case studies, expert panel workshops and stakeholder interviews were carried out to support the design. The InnoHorse web tool includes a safety section containing a horse stable safety map, stable safety checklists, and examples of good practices in stable safety, horse handling and rescue planning. This new horse stable safety management tool can also help in organizing work processes in horse stables in general.

  6. Stable Free-Standing Lipid Bilayer Membranes in Norland Optical Adhesive 81 Microchannels

    NARCIS (Netherlands)

    Marin, Victor; Kieffer, R.Y.; Padmos, Raymond; Aubin-Tam, M.E.

    2016-01-01

    We report a simple, cost-effective, and reproducible method to form free-standing lipid bilayer membranes in microdevices made with Norland Optical Adhesive 81 (NOA81). Surface treatment with either alkylsilane or fluoroalkylsilane enables the self-assembly of stable

  7. Harder–Narasimhan filtration for rank 2 tensors and stable coverings

    Indian Academy of Sciences (India)

    Hence, this filtration is unique and we define the Harder--Narasimhan filtration for rank 2 tensors as this unique filtration coming from GIT. Symmetric rank 2 tensors over smooth projective complex curves define curve coverings lying on a ruled surface, hence we can translate the stability condition to define stable coverings ...

  8. The determinant bundle on the moduli space of stable triples over a ...

    Indian Academy of Sciences (India)

    R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

    Abstract. We construct a holomorphic Hermitian line bundle over the moduli space of stable triples of the form (E1,E2,φ), where E1 and E2 are holomorphic vector bundles over a fixed compact Riemann surface X, and φ : E2 −→ E1 is a holomorphic vector bundle homomorphism. The curvature of the Chern connection of ...

  9. Stable carbon isotope fractionation in the UV photolysis of CFC-11 and CFC-12

    NARCIS (Netherlands)

    Zuiderweg, A.T.; Kaiser, J.; Laube, J.C.; Röckmann, T.; Holzinger, R.

    2012-01-01

    The chlorofluorocarbons CFC-11 (CFCl3) and CFC-12 (CF2Cl2) are stable atmospheric compounds that are produced at the earth’s surface, but removed only at high altitudes in the stratosphere by photolytic reactions. Their removal liberates atomic chlorine that then catalytically destroys stratospheric

  10. Stable nocturnal spectral characteristics over a vineyard (Conference Presentation)

    Science.gov (United States)

    Prueger, John H.; Alfieri, joesph G.; Hipps, Lawrence E.; Kustas, William P.; Neale, Christopher M.

    2016-10-01

    Vineyards are agricultural surfaces that present a unique structural perturbation to the mean wind flow. As part of the Grape Remote Sensing Atmospheric Profiling and Evapotranspiration Experiment (GRAPEX) a 10-m profile tower of three sonic anemometers at 2, 3.75 and 8 m above ground level in in a mature vineyard having was deployed to measure high frequency diurnal variations of 3-dimensional velocity components (u, v, w) and temperature (T) throughout the growing season. Previous work has been published involving eddy covariance measurements in vineyards but these mostly represented convective daytime unstable conditions. Significantly less has been published about turbulence in vineyards during stable nocturnal periods. Hence, in this study we focused on the nocturnal stable periods under clear skies and relatively light winds typical of the northern portion of California's Central Valley. Our objective was to characterize and evaluate turbulent exchange processes in the layer near the top of a vine canopy during nocturnal periods which are often characterized by weak and intermittent turbulence. Spectra, cospectra and coherence plots were evaluated for nocturnal periods. The spectra suggest there are periods of intermittent turbulence with features indicative of local and regional scale processes. Additionally the impact of the vine structure and spacing on slow meandering flows enhance the decomposition of organized turbulent eddies resulting in intricate mechanical turbulence generated by intermittent eddies that are rapidly decomposed as eddies interact with the vine structure and spacing. Preliminary results will be discussed that provide insight into turbulence characteristics at several heights above a canopy vineyard as affected by vine structure and spacing, wind speed, direction and stable conditions.

  11. Preparation and characterization of stable aqueous higher-order fullerenes

    International Nuclear Information System (INIS)

    Aich, Nirupam; Flora, Joseph R V; Saleh, Navid B

    2012-01-01

    Stable aqueous suspensions of nC 60 and individual higher fullerenes, i.e. C 70 , C 76 and C 84 , are prepared by a calorimetric modification of a commonly used liquid–liquid extraction technique. The energy requirement for synthesis of higher fullerenes has been guided by molecular-scale interaction energy calculations. Solubilized fullerenes show crystalline behavior by exhibiting lattice fringes in high resolution transmission electron microscopy images. The fullerene colloidal suspensions thus prepared are stable with a narrow distribution of cluster radii (42.7 ± 0.8 nm, 46.0 ± 14.0 nm, 60 ± 3.2 nm and 56.3 ± 1.1 nm for nC 60 , nC 70 , nC 76 and nC 84 , respectively) as measured by time-resolved dynamic light scattering. The ζ-potential values for all fullerene samples showed negative surface potentials with similar magnitude ( − 38.6 ± 5.8 mV, − 39.1 ± 4.2 mV, − 38.9 ± 5.8 mV and − 41.7 ± 5.1 mV for nC 60 , nC 70 , nC 76 and nC 84 , respectively), which provide electrostatic stability to the colloidal clusters. This energy-based modified solubilization technique to produce stable aqueous fullerenes will likely aid in future studies focusing on better applicability, determination of colloidal properties, and understanding of environmental fate, transport and toxicity of higher-order fullerenes. (paper)

  12. On The Roman Domination Stable Graphs

    Directory of Open Access Journals (Sweden)

    Hajian Majid

    2017-11-01

    Full Text Available A Roman dominating function (or just RDF on a graph G = (V,E is a function f : V → {0, 1, 2} satisfying the condition that every vertex u for which f(u = 0 is adjacent to at least one vertex v for which f(v = 2. The weight of an RDF f is the value f(V (G = Pu2V (G f(u. The Roman domination number of a graph G, denoted by R(G, is the minimum weight of a Roman dominating function on G. A graph G is Roman domination stable if the Roman domination number of G remains unchanged under removal of any vertex. In this paper we present upper bounds for the Roman domination number in the class of Roman domination stable graphs, improving bounds posed in [V. Samodivkin, Roman domination in graphs: the class RUV R, Discrete Math. Algorithms Appl. 8 (2016 1650049].

  13. Design of optically stable image reflector system.

    Science.gov (United States)

    Tsai, Chung-Yu

    2013-08-01

    The design of a partially optically stable (POS) reflector system, in which the exit ray direction and image pose are unchanged as the reflector system rotates about a specific directional vector, was presented in an earlier study by the current group [Appl. Phys. B100, 883-890 (2010)]. The present study further proposes an optically stable image (OSI) reflector system, in which not only is the optical stability property of the POS system retained, but the image position and total ray path length are also fixed. An analytical method is proposed for the design of OSI reflector systems comprising multiple reflectors. The validity of the proposed approach is demonstrated by means of two illustrative examples.

  14. Stable microfluidic flow focusing using hydrostatics.

    Science.gov (United States)

    Gnyawali, Vaskar; Saremi, Mohammadali; Kolios, Michael C; Tsai, Scott S H

    2017-05-01

    We present a simple technique to generate stable hydrodynamically focused flows by driving the flow with hydrostatic pressure from liquid columns connected to the inlets of a microfluidic device. Importantly, we compare the focused flows generated by hydrostatic pressure and classical syringe pump driven flows and find that the stability of the hydrostatic pressure driven technique is significantly better than the stability achieved via syringe pumps, providing fluctuation-free focused flows that are suitable for sensitive microfluidic flow cytometry applications. We show that the degree of flow focusing with the hydrostatic method can be accurately controlled by the simple tuning of the liquid column heights. We anticipate that this approach to stable flow focusing will find many applications in microfluidic cytometry technologies.

  15. Utilization of stable isotopes in medicine

    International Nuclear Information System (INIS)

    1980-11-01

    The ten lectures given at this round table are presented together with a discussion. Five lectures, relating to studies in which deuterium oxide was employed as a tracer of body water, dealt with pulmonary water measurements in man and animals, the total water pool in adipose subjects, and liquid compartments in children undergoing hemodyalisis. The heavy water is analysed by infrared spectrometry and a new double spectrodoser is described. Two studies using 13 C as tracer, described the diagnosis of liver troubles and diabetes respectively. A general review of the perspectives of the application of stable isotopes in clinical medicine is followed by a comparison of the use of stable and radioactive isotopes in France [fr

  16. Turbulent heat flux measurements in thermally stable boundary layers

    Science.gov (United States)

    Williams, Owen J.; van Buren, Tyler; Smits, Alexander J.

    2014-11-01

    Thermally stable turbulent boundary layers are prevalent in the polar regions and nocturnal atmospheric surface layer but heat and momentum flux measurements in such flow are often difficult. Here, a new method is employed using a nanoscale cold-wire (T-NSTAP) adjacent to a 2D PIV light sheet to measure these fluxes within rough-wall turbulent boundary layer. This method combines the advantages of fast thermal frequency response with measurement of the spatial variation of the velocity field. Resolution is limited solely by the separation of the probe and the light sheet. The new technique is used to examine the applicability of Monin-Obukhov similarity over a range of Richardson numbers from weak to strongly stable. In addition, the velocity fields are conditionally averaged subject to strong deviations of temperature above and below the local average in an effort to determine the relationship between the coherent turbulent motions and the fluctuating temperature field. This work was supported by the Princeton University Cooperative Institute for Climate Science.

  17. Highly Photoluminescent and Stable Aqueous ZnS Quantum Dots.

    Science.gov (United States)

    Li, Hui; Shih, Wan Y; Shih, Wei-Heng

    2010-01-01

    We report an all-aqueous synthesis of highly photoluminescent and stable ZnS quantum dots (QDs) with water as the medium, i.e. first synthesizing ZnS QDs with 3-mercaptopropionic acid (MPA) as the capping molecule, followed by replacing some of MPA with (3-mercaptopropyl) trimethoxysilane (MPS). The resultant MPS-replaced ZnS QDs were about 5 nm in size with a cubic zinc blende crystalline structure, and had both MPA and MPS on the surface as confirmed by the Fourier Transform Infrared (FTIR) spectroscopy. They exhibited blue trap-state emissions around 415 nm and a quantum yield (QY) of 75% with Rhodamine 101 as the reference, and remained stable for more than 60 days under the ambient conditions. Through the capping molecule replacement procedure, the MPS-replaced ZnS QDs avoided the shortcomings of both the MPA-ZnS QDs and the MPS-ZnS QDs, and acquired the advantages of strong photoluminescence and good stability, which are important to the QDs' applications especially for bioimaging.

  18. Stable Nafion-functionalized graphene dispersions for transparent conducting films

    International Nuclear Information System (INIS)

    Liu Yangqiao; Gao Lian; Sun Jing; Wang Yan; Zhang Jing

    2009-01-01

    Nafion was used for the first time to aid in preparing stable graphene dispersions in mixed water/ethanol (1:1) solvents via the reduction of graphite oxide using hydrazine. The dispersion was characterized by ultraviolet-visible (UV-vis) spectra, transmission electron microscopy, zeta potential analysis, etc. It was found that for Nafion-to-graphene ratios higher than 5:1, graphene solutions with concentrations up to 1 mg ml -1 and stabilities of over three months were obtained. It was proposed that the Nafion adsorbed onto the graphene by the hydrophobic interaction of its fluoro-backbones with the graphene layer and imparted stability by an electrosteric mechanism. Furthermore, transparent and conductive films were prepared using these highly stable Nafion-stabilized graphene dispersions. The prepared Nafion-graphene films possess smooth and homogeneous surfaces and the sheet resistance was as low as 30 kΩ/sq for a transmittance of 80% at 550 nm, which was much lower than for other graphene films obtained by chemical reduction. X-ray photoelectron spectroscopy and Raman spectroscopy confirmed the p-doping of the graphene by Nafion. It was expected that this p-doping effect, as well as the high dispersing ability of Nafion for graphene and the connection of the sp 2 domains by residual Nafion combined to produce good properties of the Nafion-graphene films.

  19. Thermally Stable, Latent Olefin Metathesis Catalysts

    OpenAIRE

    Thomas, Renee M.; Fedorov, Alexey; Keitz, Benjamin K.; Grubbs, Robert H.

    2011-01-01

    Highly thermally stable N-aryl,N-alkyl N-heterocyclic carbene (NHC) ruthenium catalysts were designed and synthesized for latent olefin metathesis. These catalysts showed excellent latent behavior toward metathesis reactions, whereby the complexes were inactive at ambient temperature and initiated at elevated temperatures, a challenging property to achieve with second generation catalysts. A sterically hindered N-tert-butyl substituent on the NHC ligand of the ruthenium complex was found to i...

  20. The nature of stable insomnia phenotypes.

    Science.gov (United States)

    Pillai, Vivek; Roth, Thomas; Drake, Christopher L

    2015-01-01

    We examined the 1-y stability of four insomnia symptom profiles: sleep onset insomnia; sleep maintenance insomnia; combined onset and maintenance insomnia; and neither criterion (i.e., insomnia cases that do not meet quantitative thresholds for onset or maintenance problems). Insomnia cases that exhibited the same symptom profile over a 1-y period were considered to be phenotypes, and were compared in terms of clinical and demographic characteristics. Longitudinal. Urban, community-based. Nine hundred fifty-four adults with Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition based current insomnia (46.6 ± 12.6 y; 69.4% female). None. At baseline, participants were divided into four symptom profile groups based on quantitative criteria. Follow-up assessment 1 y later revealed that approximately 60% of participants retained the same symptom profile, and were hence judged to be phenotypes. Stability varied significantly by phenotype, such that sleep onset insomnia (SOI) was the least stable (42%), whereas combined insomnia (CI) was the most stable (69%). Baseline symptom groups (cross-sectionally defined) differed significantly across various clinical indices, including daytime impairment, depression, and anxiety. Importantly, however, a comparison of stable phenotypes (longitudinally defined) did not reveal any differences in impairment or comorbid psychopathology. Another interesting finding was that whereas all other insomnia phenotypes showed evidence of an elevated wake drive both at night and during the day, the 'neither criterion' phenotype did not; this latter phenotype exhibited significantly higher daytime sleepiness despite subthreshold onset and maintenance difficulties. By adopting a stringent, stability-based definition, this study offers timely and important data on the longitudinal trajectory of specific insomnia phenotypes. With the exception of daytime sleepiness, few clinical differences are apparent across stable phenotypes.

  1. A belief-based evolutionarily stable strategy

    OpenAIRE

    Deng, Xinyang; Wang, Zhen; Liu, Qi; Deng, Yong; Mahadevan, Sankaran

    2014-01-01

    As an equilibrium refinement of the Nash equilibrium, evolutionarily stable strategy (ESS) is a key concept in evolutionary game theory and has attracted growing interest. An ESS can be either a pure strategy or a mixed strategy. Even though the randomness is allowed in mixed strategy, the selection probability of pure strategy in a mixed strategy may fluctuate due to the impact of many factors. The fluctuation can lead to more uncertainty. In this paper, such uncertainty involved in mixed st...

  2. Stable iodine prophylaxis. Recommendations of the 2nd UK Working Group on Stable Iodine Prophylaxis

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2001-07-01

    The Working Group reviewed the revised Who guidance and the information published since 1991 on the risks of thyroid cancer in children from radioiodine and the risks of side effects from stable iodine. In particular, it reviewed data compiled on the incidence of thyroid cancers in children following the accident at the Chernobyl nuclear power plant in 1986. It considered whether the NRPB Earls were still appropriate, in the light of the new data. It also reviewed a range of other recommendations given by the 1st Working Group, concerning the chemical form of stable iodine tablets and practical issues concerning implementation of stable iodine prophylaxis. Finally, it reviewed the Patient Information Leaflet that is required, by law, to be included in each box of tablets and provided suggestions for information to be included in a separate information leaflet to be handed out to the public when stable iodine tablets are distributed.

  3. Detonation of Meta-stable Clusters

    Energy Technology Data Exchange (ETDEWEB)

    Kuhl, Allen; Kuhl, Allen L.; Fried, Laurence E.; Howard, W. Michael; Seizew, Michael R.; Bell, John B.; Beckner, Vincent; Grcar, Joseph F.

    2008-05-31

    We consider the energy accumulation in meta-stable clusters. This energy can be much larger than the typical chemical bond energy (~;;1 ev/atom). For example, polymeric nitrogen can accumulate 4 ev/atom in the N8 (fcc) structure, while helium can accumulate 9 ev/atom in the excited triplet state He2* . They release their energy by cluster fission: N8 -> 4N2 and He2* -> 2He. We study the locus of states in thermodynamic state space for the detonation of such meta-stable clusters. In particular, the equilibrium isentrope, starting at the Chapman-Jouguet state, and expanding down to 1 atmosphere was calculated with the Cheetah code. Large detonation pressures (3 and 16 Mbar), temperatures (12 and 34 kilo-K) and velocities (20 and 43 km/s) are a consequence of the large heats of detonation (6.6 and 50 kilo-cal/g) for nitrogen and helium clusters respectively. If such meta-stable clusters could be synthesized, they offer the potential for large increases in the energy density of materials.

  4. Cryogenic surface ion traps

    International Nuclear Information System (INIS)

    Niedermayr, M.

    2015-01-01

    Microfabricated surface traps are a promising architecture to realize a scalable quantum computer based on trapped ions. In principle, hundreds or thousands of surface traps can be located on a single substrate in order to provide large arrays of interacting ions. To this end, trap designs and fabrication methods are required that provide scalable, stable and reproducible ion traps. This work presents a novel surface-trap design developed for cryogenic applications. Intrinsic silicon is used as the substrate material of the traps. The well-developed microfabrication and structuring methods of silicon are utilized to create simple and reproducible traps. The traps were tested and characterized in a cryogenic setup. Ions could be trapped and their life time and motional heating were investigated. Long ion lifetimes of several hours were observed and the measured heating rates were reproducibly low at around 1 phonon per second at a trap frequency of 1 MHz. (author) [de

  5. Ultrathin and stable Nickel films as transparent conductive electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Grilli, M.L., E-mail: marialuisa.grilli@enea.it [ENEA, Materials Technology Unit, Via Anguillarese 301, 00123 Rome (Italy); Di Sarcina, I. [ENEA, Materials Technology Unit, Via Anguillarese 301, 00123 Rome (Italy); Bossi, S. [ENEA, Robotics Laboratory, Via Anguillarese 301, 00123 Rome (Italy); The Biorobotics Institute, Scuola Superiore Sant' Anna, Viale Rinaldo Piaggio 34, 56025 Pontedera, Pisa (Italy); Rinaldi, A.; Pilloni, L.; Piegari, A. [ENEA, Materials Technology Unit, Via Anguillarese 301, 00123 Rome (Italy)

    2015-11-02

    Ultrathin stable transparent conductive nickel films were deposited on quartz substrates by radio frequency sputtering at room temperature. Such films showed visible transmittance up to 80% and conductivity up to 1.8 × 10{sup 4} S/cm, further increased to 2,3 × 10{sup 5} S/cm by incorporation of a micrometric silver grid. Atomic force microscopy and scanning electron microscopy revealed quite compact, smooth and low surface roughness films. Excellent film stability, ease, fast and low cost process fabrication make these films highly competitive compared to indium tin oxide alternative transparent conductors. Films were characterized regarding their morphological, optical and electrical properties. - Highlights: • Indium-free transparent conductors are proposed. • Ultrathin Ni films are fabricated with a very fast process at room temperature. • Films have conductivity values up to 1.8 × 10{sup 4} S/cm. • Ni ultrathin films are good candidates for UV and NIR optoelectronic applications.

  6. Two stable steady states in the Hodgkin-Huxley axons

    OpenAIRE

    Aihara, K.; Matsumoto, G.

    1983-01-01

    Two stable steady states were found in the numerical solution of the Hodgkin-Huxley equations for the intact squid axon bathed in potassium-rich sea water with an externally applied inward current. Under the conditions the two stable steady-states exist, the Hodgkin-Huxley equations have a complex bifurcation structure including, in addition to the two stable steady-states, a stable limit cycle, two unstable equilibrium points, and one asymptotically stable equilibrium point. It was also conc...

  7. Unconditionally energy stable numerical schemes for phase-field vesicle membrane model

    Science.gov (United States)

    Guillén-González, F.; Tierra, G.

    2018-02-01

    Numerical schemes to simulate the deformation of vesicles membranes via minimizing the bending energy have been widely studied in recent times due to its connection with many biological motivated problems. In this work we propose a new unconditionally energy stable numerical scheme for a vesicle membrane model that satisfies exactly the conservation of volume constraint and penalizes the surface area constraint. Moreover, we extend these ideas to present an unconditionally energy stable splitting scheme decoupling the interaction of the vesicle with a surrounding fluid. Finally, the well behavior of the proposed schemes are illustrated through several computational experiments.

  8. Microbiological characterization of stable resuspended dust

    Directory of Open Access Journals (Sweden)

    Nora Kováts

    2016-06-01

    Full Text Available Objectives: Air quality in the stables is characterized by elevated level of dust and aeroallergens which are supposed to directly cause or exacerbate several respiratory disorders. The most often recognized problem is recurrent airway obstruction (RAO, previously known as chronic obstructive pulmonary disease (COPD. There is some indication that aeroallergens (among them endotoxins may also cause inflammation in human airways and may exceed safe levels in stables. Monitoring studies have covered mainly the determination of the concentration of respirable particles and of culturable fungi and their toxins. However, these particles do not only directly affect the respiratory system, but might act as a carrier conveying toxic contaminants and biological agents such as bacteria. In a typical, 20-horse Hungarian stable, microbial community of respirable fraction of resuspended dust has been characterized to reveal if these particles convey hazardous pathogenic bacteria, posing risk to either horses or staff. Material and Methods: Resuspended dust was sampled using a mobile instrument. The instrument contains a PARTISOL-FRM model 2000 sampler that was operated at a flow rate of 16.7 l/min and a cyclone separator which collected the particulate matter with an aerodynamic size between 1 μm and 10 μm (PM1–10 fraction. Microbial taxa were identified by culture-independent next generation sequencing (NGS of variable 16S ribosomal ribonucleic acid (rRNA gene regions. Results: In total, 1491 different taxa were identified, of them 384 were identified to species level, 961 to genus level. The sample was dominated by common ubiquitous soil and organic material-dwelling taxa. Conclusions: Pathogens occurred at low abundance, and were represented by mostly facultative human pathogens, with the prevalence of Staphylococcus species.

  9. Stable channel of reclaimed tidal lowland

    Science.gov (United States)

    Syarifudin, Achmad; Imanuddin, Momon S.; Moerwanto, Arie S.; Suryadi, F. X.

    2017-11-01

    This study aimed to develop models of the Operation and Maintenance in the reclaimed tidal marsh area to get a stable channel. The research location is reclaimed tidal delta area Telang I Primary 8 representing land typology A/B and a survey conducted in 13 South Secondary Schemes following existing tertiary Telang I. MIKE - 11 computer models used used to analyze the movement of sediment in the channel in both the Primary channel 8, SPD, SDU and tertiary channels in block 13 South. Calibration model with multiple channels in the field of physical parameters has been performed to obtain results close to the results of measurement modeling sediment movement in the channel. The integration models of MIKE - 11 models with various scenarios are used to model the operation and maintenance of the channel in the tidal marsh area to get a stable channel. According to the scheme P8 - 13S, OM models obtained 75 percent, in which the secondary channel (SPD/SDU) and built flap gate in tertiary channel, get a well prototype model of the stable channel (equilibriums), where the average erosion on P8 at a distance of 3,200 m in the amount of 4,472,049 m3 and the mean sedimentation in the SPD of 963,836 m3 and mean of sedimentation in the tertiary channel of 3,508,213 m3. Similarly, on average erosion P8 by 4,135,649 m3 and the mean sedimentation in the SDU of 681,304 m3 and the mean sedimentation in the tertiary channel of 3,454,345 m3.

  10. Aggressive Fibromatosis: Evidence for a Stable Phase

    Directory of Open Access Journals (Sweden)

    Gillian Mitchell

    1998-01-01

    Full Text Available Purpose. Aggressive fibromatosis (AF is an uncommon locally infiltrating benign disease of soft tissue for which treatment comprises complete surgical resection. Radiotherapy can be given postoperatively if the margin is incompletely resected. If the tumour is inoperable radiotherapy provides an alternative treatment. Hormone therapy and cytotoxic chemotherapy have also been used for unresectable or recurrent disease. All treatment modalities carry an associated morbidity. We believe that the natural history of aggressive fibromatosis may include a period of stable disease without progression, during which time, treatment is not always necessary.

  11. Stable isogeometric analysis of trimmed geometries

    Science.gov (United States)

    Marussig, Benjamin; Zechner, Jürgen; Beer, Gernot; Fries, Thomas-Peter

    2017-04-01

    We explore extended B-splines as a stable basis for isogeometric analysis with trimmed parameter spaces. The stabilization is accomplished by an appropriate substitution of B-splines that may lead to ill-conditioned system matrices. The construction for non-uniform knot vectors is presented. The properties of extended B-splines are examined in the context of interpolation, potential, and linear elasticity problems and excellent results are attained. The analysis is performed by an isogeometric boundary element formulation using collocation. It is argued that extended B-splines provide a flexible and simple stabilization scheme which ideally suits the isogeometric paradigm.

  12. Remarks on stable and quasi-stable k-strings at large N

    International Nuclear Information System (INIS)

    Armoni, A.; Shifman, M.

    2003-01-01

    We discuss k-strings in the large-N Yang-Mills theory and its supersymmetric extension. Whereas the tension of the bona fide (stable) QCD string is expected to depend only on the N-ality of the representation, tensions that depend on specific representation R are often reported in the lattice literature. In particular, adjoint strings are discussed and found in certain simulations. We clarify this issue by systematically exploiting the notion of the quasi-stable strings which becomes well-defined at large N. The quasi-stable strings with representation-dependent tensions decay, but the decay rate (per unit length per unit time) is suppressed as Λ 2 F(N) where F(N) falls off as a function of N. It can be determined on the case-by-case basis. The quasi-stable strings eventually decay into stable strings whose tension indeed depends only on the N-ality. We also briefly review large-N arguments showing why the Casimir formula for the string tension cannot be correct, and present additional arguments in favor of the sine formula. Finally, we comment on the relevance of our estimates to Euclidean lattice measurements

  13. Multivariate Max-Stable Spatial Processes

    KAUST Repository

    Genton, Marc G.

    2014-01-06

    Analysis of spatial extremes is currently based on univariate processes. Max-stable processes allow the spatial dependence of extremes to be modelled and explicitly quantified, they are therefore widely adopted in applications. For a better understanding of extreme events of real processes, such as environmental phenomena, it may be useful to study several spatial variables simultaneously. To this end, we extend some theoretical results and applications of max-stable processes to the multivariate setting to analyze extreme events of several variables observed across space. In particular, we study the maxima of independent replicates of multivariate processes, both in the Gaussian and Student-t cases. Then, we define a Poisson process construction in the multivariate setting and introduce multivariate versions of the Smith Gaussian extremevalue, the Schlather extremal-Gaussian and extremal-t, and the BrownResnick models. Inferential aspects of those models based on composite likelihoods are developed. We present results of various Monte Carlo simulations and of an application to a dataset of summer daily temperature maxima and minima in Oklahoma, U.S.A., highlighting the utility of working with multivariate models in contrast to the univariate case. Based on joint work with Simone Padoan and Huiyan Sang.

  14. Application of stable isotope to breath test

    International Nuclear Information System (INIS)

    Sasaki, Yasuto

    1988-01-01

    Needles to say, radioisotopes have good characteristics as a tracer for examining biological functions. In fact, scyntigraphy is widely used over Japan. It is true, however, that there are some difficulties in applying radioisotopes to humans. Thus, greater attention began to be attracted to stable isotopes in the late 1960s, because these substances can be used for infants and pregnant women. They can be stored for a long period of time since they do not suffer damping as in the case of radioisotopes. In addition to serving as a tracer, stable isotopes can provide structural-chemical information including the position of isotope labels, and the mass and atomic composition of fragment ions. Such techniques as NMR spectroscopy is employed for this purpose. The method is currently used to perform examinations of congenital metabolic disorders. The carbon isotopes of 13 C and 14 C are used for breath test. Compounds labeled with these isotopes are administered and their ratio to the total CO 2 in breath is measured to diagnose diseases. In the early 1970s, 13 C has come into use for breath test. Similar breath test is applied to diagnosis of the bacterial overgrowth syndrome and ileal dysfunction syndrome. (Nogami, K.)

  15. Stable states in a strong IR field

    Science.gov (United States)

    Zhong, Changchun; Robicheaux, Francis

    2015-05-01

    It is found that 10% of atoms stay in the quasi-stable states after being exposed to intense laser or microwave (MW) pulses, even though the pulses' intensity is much stronger than that needed for static fields ionization. The reason why atoms survive those strong pulses has attracted growing attentions. A. Arakelyan et al. have observed the optical spectra of the surviving Lithium atoms after interaction with intense 38-GHz MW fields for more than 1000 cycles, and the spectra exhibit a periodic train of peaks 38 GHz apart. It suggests that those weakly bound Rydberg electrons seldom go back to the ionic core, where the cycle average energy exchange happens. In this study, we are interested in the electron behavior in the presence of intense infrared fields with a much shorter wavelength (1000 nm). By solving the full 3D time dependent Schrodinger equation, we calculate the spectra of the surviving atoms under intense IR fields. Our numerical calculations show atoms survive the intense field in quasi-stable states for a long time, and the optical spectra are obviously modulated by the IR frequency. Through tuning the ponderomotive energy, we see how field parameters affect the behavior of electrons. Different atoms, such as Hydrogen, Helium, Lithium, and Sodium, are tested to see how atom's energy structures influence the results.

  16. Color stable manganese-doped phosphors

    Science.gov (United States)

    Lyons, Robert Joseph [Burnt Hills, NY; Setlur, Anant Achyut [Niskayuna, NY; Deshpande, Anirudha Rajendra [Twinsburg, OH; Grigorov, Ljudmil Slavchev [Sofia, BG

    2012-08-28

    A process for preparing color stable Mn.sup.+4 doped phosphors includes providing a phosphor of formula I; A.sub.x[MF.sub.y]:Mn.sup.+4 I and contacting the phosphor in particulate form with a saturated solution of a composition of formula II in aqueous hydrofluoric acid; A.sub.x[MF.sub.y]; II wherein A is Li, Na, K, Rb, Cs, NR.sub.4 or a combination thereof; M is Si, Ge, Sn, Ti, Zr, Al, Ga, In, Sc, Y, La, Nb, Ta, Bi, Gd, or a combination thereof; R is H, lower alkyl, or a combination thereof; x is the absolute value of the charge of the [MF.sub.y] ion; and y is 5, 6 or 7. In particular embodiments, M is Si, Ge, Sn, Ti, Zr, or a combination thereof. A lighting apparatus capable of emitting white light includes a semiconductor light source; and a phosphor composition radiationally coupled to the light source, and which includes a color stable Mn.sup.+4 doped phosphor.

  17. Stable isotope studies: Progress report, March 1985--August 1987

    International Nuclear Information System (INIS)

    Ishida, Takanobu.

    1987-01-01

    Studies have been carried out in the following areas: Stable Isotope Fractionation (1) Effects of chemical poisons and surface modifiers on polycrystalline platinum electrode surfaces have been investigated with a goal to develop a new form of heterogeneous catalyst for the hydrogen isotope exchange between dihydrogen and water. (2) A new nitrogen-15 fractionation process has been developed, based on the isotope exchange between liquid N 2 O 3 -N 2 O 4 mixture and their vapor phase at a subambient temperature and a raised pressure. (3) A closed chemical recycle process has been developed for use in connection with the refluxer in the Nitrox-type nitrogen-15 plant. Isotope Effects (1) The vapor pressure isotope effect (VPIE) study of liquid fluoromethanes have been completed. (2) The VPIE study of solid and liquid ammonia has been completed. (3) A theoretical foundation of the additivity for the vibrational zero-point energy (ZPE) has been developed. Studies of Liquid Ammonia. With an aim to study intermolecular interaction (and the inversion phenomenon, in particular) in liquid ammonia, and to further investigate various ammonia solutions, a molecular dynamics (MD) study has been initiated. An MD program has been completed, and force field functions have been developed for an ensemble of non-rigid ammonia molecules. 107 refs., 41 figs., 10 tabs

  18. A stable boundary layer perspective on global temperature trends

    International Nuclear Information System (INIS)

    McNider, R T; Christy, J R; Biazar, A

    2010-01-01

    One of the most significant signals in the thermometer-observed temperature record since 1900 is the decrease in the diurnal temperature range over land, largely due to warming of the minimum temperatures. While some data sets have indicated this asymmetrical warming has been reduced since 1979, regional analyses (e.g. East Africa) indicate that the nocturnal warming continues at a pace greater than daytime temperatures. The cause for this night time warming in the observed temperatures has been attributed to a variety of causes. Climate models have in general not replicated the change in diurnal temperature range well. Here we would like to try to distinguish between warming in the nocturnal boundary layer due to a redistribution of heat and warming due to the accumulation of heat. The temperature at night at shelter height is a result of competition between thermal stability and mechanical shear. If stability wins then turbulence is suppressed and the cooling surface becomes cut-off from the warmer air aloft, which leads to sharp decay in surface air temperature. If shear wins, then turbulence is maintained and warmer air from aloft is continually mixed to the surface, which leads to significantly lower cooling rates and warmer temperatures. This warming occurs due to a redistribution of heat. As will be shown by techniques of nonlinear analysis the winner of the stability and shear contest can be very sensitive to changes in greenhouse gas forcing, surface roughness, cloudiness, and surface heat capacity (including soil moisture). Further, the minimum temperatures measured in the nocturnal boundary layer represent only a very shallow layer of the atmosphere which is usually only a few hundred meters thick. It is likely that the observed warming in minimum temperature, whether caused by additional greenhouse forcing or land use changes or other land surface dynamics, is reflecting a redistribution of heat by turbulence-not an accumulation of heat. Because minimum

  19. Surface heterogeneity and ionization of Cs promoter in carbon-based ruthenium catalyst for ammonia synthesis

    International Nuclear Information System (INIS)

    Kotarba, Andrzej; Dmytrzyk, Jaromir; Rarog-Pilecka, Wioletta; Kowalczyk, Zbigniew

    2003-01-01

    Second-generation ammonia synthesis cesium-doped ruthenium catalyst supported on turbostratic carbon was investigated by the species resolved thermal alkali desorption method (SR-TAD). Energetic barriers for cesium ions (2.86 eV), ground state (1.96 eV) and electronically excited atoms (5.76 eV) desorbing from the Cs-Ru/C catalyst were determined. In the case of ruthenium-free Cs/C system, cesium desorbs as ground state atoms only, with an energy barrier of 2.87 eV. The work functions determined by the thermionic emission of electrons from Cs/C and Cs-Ru/C were of the same value (2.9 eV). It was concluded that ruthenium induces heterogeneous distribution of cesium on the catalyst surface. The promoter stability is reduced on low work function areas and its surface ionization on high work function areas opens the ionic desorption channel. The Cs desorption from the catalyst is discussed in terms of the literature data for the cesium/graphite system

  20. Minimal surfaces

    CERN Document Server

    Dierkes, Ulrich; Sauvigny, Friedrich; Jakob, Ruben; Kuster, Albrecht

    2010-01-01

    Minimal Surfaces is the first volume of a three volume treatise on minimal surfaces (Grundlehren Nr. 339-341). Each volume can be read and studied independently of the others. The central theme is boundary value problems for minimal surfaces. The treatise is a substantially revised and extended version of the monograph Minimal Surfaces I, II (Grundlehren Nr. 295 & 296). The first volume begins with an exposition of basic ideas of the theory of surfaces in three-dimensional Euclidean space, followed by an introduction of minimal surfaces as stationary points of area, or equivalently

  1. Stable, streamlined and helical cavity formation by the impact of Leidenfrost spheres

    Science.gov (United States)

    Mansoor, Mohammad; Vakarelski, Ivan; Marston, Jeremy; Truscott, Tadd; Thoroddsen, Sigurdur

    2016-11-01

    This work reports results from an experimental study on the formation of stable-streamlined and helical cavity wakes following the free-surface impact of Leidenfrost spheres. The Leidenfrost effect encapsulates the sphere by a vapor layer to prevent any physical contact with the surrounding liquid. This phenomenon is essential for the pacification of acoustic rippling along the cavity interface to result in a stable-streamlined cavity wake. Such a streamlined configuration experiences drag coefficients an order of magnitude lower than those acting on room temperature spheres. A striking observation is the formation of helical cavities which occur for impact Reynolds numbers Re0 >= 1 . 4 ×105 and are characterized by multiple interfacial ridges, stemming from and rotating synchronously about an evident contact line around the sphere equator. This helical configuration has 40 - 55 % smaller overall force coefficients than those obtained in the formation of stable cavity wakes.

  2. From Coordination Cages to a Stable Crystalline Porous Hydrogen-Bonded Framework

    Energy Technology Data Exchange (ETDEWEB)

    Ju, Zhanfeng [State Key Lab of Structure Chemistry, Fujian Institute of Research on the Structure of Matter, CAS, Fuzhou 350002 P. R. China; Liu, Guoliang [State Key Lab of Structure Chemistry, Fujian Institute of Research on the Structure of Matter, CAS, Fuzhou 350002 P. R. China; Chen, Yu-Sheng [ChemMatCARS, Center for Advanced Radiation Sources, The University of Chicago, Argonne Illinois 60439 USA; Yuan, Daqiang [State Key Lab of Structure Chemistry, Fujian Institute of Research on the Structure of Matter, CAS, Fuzhou 350002 P. R. China; Chen, Banglin [Department of Chemistry, University of Texas at San Antonio, San Antonio Texas 78249-0698 USA

    2017-03-20

    A stable framework has been constructed through multiple charge-assisted H-bonds between cationic coordination cages and chloride ions. The framework maintained its original structure upon desolvation, which has been established by single-crystal structure analysis. This is the first fully characterized stable porous framework based on coordination cages after desolvation, with a moderately high Brunauer–Emmett–Teller (BET) surface area of 1201 m2 g-1. This work will not only give a light to construct stable porous frameworks based on coordination cages and thus broaden their applications, but will also provide a new avenue to the assembly of other porous materials such as porous organic cages and hydrogen-bonded organic frameworks (HOFs) through non covalent bonds.

  3. Estimation of Time-Varying Autoregressive Symmetric Alpha Stable

    Data.gov (United States)

    National Aeronautics and Space Administration — In the last decade alpha-stable distributions have become a standard model for impulsive data. Especially the linear symmetric alpha-stable processes have found...

  4. Lowering coefficient of friction in Cu alloys with stable gradient nanostructures.

    Science.gov (United States)

    Chen, Xiang; Han, Zhong; Li, Xiuyan; Lu, K

    2016-12-01

    The coefficient of friction (COF) of metals is usually high, primarily because frictional contacts induce plastic deformation underneath the wear surface, resulting in surface roughening and formation of delaminating tribolayers. Lowering the COF of metals is crucial for improving the reliability and efficiency of metal contacts in engineering applications but is technically challenging. Refining the metals' grains to nanoscale cannot reduce dry-sliding COFs, although their hardness may be elevated many times. We report that a submillimeter-thick stable gradient nanograined surface layer enables a significant reduction in the COF of a Cu alloy under high-load dry sliding, from 0.64 (coarse-grained samples) to 0.29, which is smaller than the COFs of many ceramics. The unprecedented stable low COF stems from effective suppression of sliding-induced surface roughening and formation of delaminating tribolayer, owing to the stable gradient nanostructures that can accommodate large plastic strains under repeated sliding for more than 30,000 cycles.

  5. Stable electroluminescence from passivated nano-crystalline porous silicon using undecylenic acid

    Science.gov (United States)

    Gelloz, B.; Sano, H.; Boukherroub, R.; Wayner, D. D. M.; Lockwood, D. J.; Koshida, N.

    2005-06-01

    Stabilization of electroluminescence from nanocrystalline porous silicon diodes has been achieved by replacing silicon-hydrogen bonds terminating the surface of nanocrystalline silicon with more stable silicon-carbon (Si-C) bonds. Hydrosilylation of the surface of partially and anodically oxidized porous silicon samples was thermally induced at about 90 °C using various different organic molecules. Devices whose surface have been modified with stable covalent bonds shows no degradation in the EL efficiency and EL output intensity under DC operation for several hours. The enhanced stability can be attributed to the high chemical resistance of Si-C bonds against current-induced surface oxidation associated with the generation of nonradiative defects. Although devices treated with 1-decene exhibit reduced EL efficiency and brightness compared to untreatred devices, other molecules, such as ethyl-undecylenate and particularly undecylenic acid provide stable and more efficient visible electroluminescence at room temperature. Undecylenic acid provides EL brightness as high as that of an untreated device.

  6. Stable electroluminescence from passivated nano-crystalline porous silicon using undecylenic acid

    Energy Technology Data Exchange (ETDEWEB)

    Gelloz, B.; Sano, H.; Koshida, N. [Dept. Elec. and Elec. Eng., Tokyo Univ. of A and T, Koganei, Tokyo 184-8588 (Japan); Boukherroub, R. [Laboratoire de Physique de la Matiere Condensee, Ecole Polytechnique, Route de Saclay, 91128 Palaiseau (France); Wayner, D.D.M.; Lockwood, D.J. [National Research Council, Ottawa (Canada)

    2005-06-01

    Stabilization of electroluminescence from nanocrystalline porous silicon diodes has been achieved by replacing silicon-hydrogen bonds terminating the surface of nanocrystalline silicon with more stable silicon-carbon (Si-C) bonds. Hydrosilylation of the surface of partially and anodically oxidized porous silicon samples was thermally induced at about 90 C using various different organic molecules. Devices whose surface have been modified with stable covalent bonds shows no degradation in the EL efficiency and EL output intensity under DC operation for several hours. The enhanced stability can be attributed to the high chemical resistance of Si-C bonds against current-induced surface oxidation associated with the generation of nonradiative defects. Although devices treated with 1-decene exhibit reduced EL efficiency and brightness compared to untreated devices, other molecules, such as ethyl-undecylenate and particularly undecylenic acid provide stable and more efficient visible electroluminescence at room temperature. Undecylenic acid provides EL brightness as high as that of an untreated device. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  7. Stable CSR in Storage Rings: A Model

    International Nuclear Information System (INIS)

    Sannibale, F.

    2005-01-01

    A comprehensive historical view of the work done on coherent synchrotron radiation (CSR) in storage rings is given in reference [1]. Here we want just to point out that even if the issue of CSR in storage rings was already discussed over 50 years ago, it is only recently that a considerable number of observations have been reported. In fact, intense bursts of coherent synchrotron radiation with a stochastic character were measured in the terahertz frequency range, at several synchrotron light source storage rings [2-8]. It has been shown [8-11], that this bursting emission of CSR is associated with a single bunch instability, usually referred as microbunching instability (MBI), driven by the fields of the synchrotron radiation emitted by the bunch itself. Of remarkably different characteristics was the CSR emission observed at BESSY II in Berlin, when the storage ring was tuned into a special low momentum compaction mode [12, 13]. In fact, the emitted radiation was not the quasi-random bursting observed in the other machines, but a powerful and stable flux of broadband CSR in the terahertz range. This was an important result, because it experimentally demonstrated the concrete possibility of constructing a stable broadband source with extremely high power in the terahertz region. Since the publication of the first successful experiment using the ring as a CSR source [14], BESSY II has regular scheduled user's shifts dedicated to CSR experiments. At the present time, several other laboratories are investigating the possibility of a CSR mode of operation [15-17] and a design for a new ring optimized for CSR is at an advanced stage [18]. In what follows, we describe a model that first accounts for the BESSY II observations and then indicates that the special case of BESSY II is actually quite general and typical when relativistic electron storage rings are tuned for short bunches. The model provides a scheme for predicting and optimizing the performance of ring

  8. Stable CSR in storage rings: A model

    International Nuclear Information System (INIS)

    Sannibale, Fernando; Byrd, John M.; Loftsdottir, Agusta; Venturini, Marco; Abo-Bakr, Michael; Feikes, Jorge; Holldack, Karsten; Kuske, Peter; Wustefeld, Godehart; Hubers, Heinz-Willerm; Warnock, Robert

    2005-01-01

    A comprehensive historical view of the work done on coherent synchrotron radiation (CSR) in storage rings is given in reference [1]. Here we want just to point out that even if the issue of CSR in storage rings was already discussed over 50 years ago, it is only recently that a considerable number of observations have been reported. In fact, intense bursts of coherent synchrotron radiation with a stochastic character were measured in the terahertz frequency range, at several synchrotron light source storage rings [2-8]. It has been shown [8-11], that this bursting emission of CSR is associated with a single bunch instability, usually referred as microbunching instability (MBI), driven by the fields of the synchrotron radiation emitted by the bunch itself. Of remarkably different characteristics was the CSR emission observed at BESSY II in Berlin, when the storage ring was tuned into a special low momentum compaction mode [12, 13]. In fact, the emitted radiation was not the quasi-random bursting observed in the other machines, but a powerful and stable flux of broadband CSR in the terahertz range. This was an important result, because it experimentally demonstrated the concrete possibility of constructing a stable broadband source with extremely high power in the terahertz region. Since the publication of the first successful experiment using the ring as a CSR source [14], BESSY II has regular scheduled user s shifts dedicated to CSR experiments. At the present time, several other laboratories are investigating the possibility of a CSR mode of operation [15-17] and a design for a new ring optimized for CSR is at an advanced stage [18]. In what follows, we describe a model that first accounts for the BESSY II observations and then indicates that the special case of BESSY II is actually quite general and typical when relativistic electron storage rings are tuned for short bunches. The model provides a scheme for predicting and optimizing the performance of ring

  9. Chance and stability stable distributions and their applications

    CERN Document Server

    Uchaikin, Vladimir V

    1999-01-01

    An introduction to the theory of stable distributions and their applications. It contains a modern outlook on the mathematical aspects of the theory. The authors explain numerous peculiarities of stable distributions and describe the principle concept of probability theory and function analysis. A significant part of the book is devoted to applications of stable distributions. Another notable feature is the material on the interconnection of stable laws with fractals, chaos and anomalous transport processes.

  10. Rumble surfaces

    CSIR Research Space (South Africa)

    National Institute for Transport and Road

    1977-01-01

    Full Text Available Rumble surfaces are intermittent short lengths of coarse-textured road surfacings on which vehicle tyres produce a rumbling sound. used in conjunction with appropriate roadsigns and markings, they can reduce accidents on rural roads by alerting...

  11. Surface thermodynamics

    International Nuclear Information System (INIS)

    Garcia-Moliner, F.

    1975-01-01

    Basic thermodynamics of a system consisting of two bulk phases with an interface. Solid surfaces: general. Discussion of experimental data on surface tension and related concepts. Adsorption thermodynamics in the Gibbsian scheme. Adsorption on inert solid adsorbents. Systems with electrical charges: chemistry and thermodynamics of imperfect crystals. Thermodynamics of charged surfaces. Simple models of charge transfer chemisorption. Adsorption heat and related concepts. Surface phase transitions

  12. Thermodynamically stable emulsions using Janus dumbbells as colloid surfactants.

    Science.gov (United States)

    Tu, Fuquan; Park, Bum Jun; Lee, Daeyeon

    2013-10-15

    One of the most important properties of emulsions is their stability. Most emulsions stabilized with molecular surfactants tend to lose their stability over time via different mechanisms. Although the stability of emulsions stabilized with homogeneous particles have been shown to be superior to that of surfactant-stabilized emulsions, these Pickering emulsions nevertheless are only kinetically stable and thus can undergo destabilization. Janus particles that have two opposite wetting surfaces have shown promise in imparting emulsions with long-term stability because of their strong attachment to the oil-water interface. In this theoretical study, we consider thermodynamics of emulsion stabilization using amphiphilic Janus dumbbells, which are nonspherical particles made of two partially fused spherical particles of opposite wettability. These amphiphilic dumbbells are attractive candidates as colloid surfactants for emulsion stabilization because highly uniform Janus dumbbells can be synthesized in large quantities; thus, their application in emulsion stabilization can become practical. Our theoretical calculation demonstrates that Janus dumbbells can indeed generate thermodynamically stable Pickering emulsions. In addition, we also find that there exists a total oil-water interfacial area that results in the lowest energy state in the system, which occurs when Janus dumbbells available in the system are completely consumed to fully cover the droplet interfaces. We show that the geometry of dumbbells as well as the composition of the emulsion mixtures has significant influences on the average size of dumbbell-stabilized emulsions. We also investigate the effect of asymmetry of Janus dumbbells on the average droplet radius. Our results clearly show that amphiphilic Janus dumbbells provide unique opportunities in stabilizing emulsions for various applications.

  13. A Note on Interpolation of Stable Processes | Nassiuma | Journal of ...

    African Journals Online (AJOL)

    Interpolation procedures tailored for gaussian processes may not be applied to infinite variance stable processes. Alternative techniques suitable for a limited set of stable case with index α∈(1,2] were initially studied by Pourahmadi (1984) for harmonizable processes. This was later extended to the ARMA stable process ...

  14. Respiratory depression by stable xenon in goats

    International Nuclear Information System (INIS)

    Winkler, S.S.

    1986-01-01

    Regional cerebral blood flow (rCBF) studies with stable xenon have recently become practical. Xenon pharmacology is thus a more than academic interest. The authors studied the respiratory response of three trained goats to a mixture of 70% xenon, 30% oxygen. The relatively high xenon concentration was used because of the animals' resistance to anesthetic effects. Two other goats were treated with equivalent anesthetic concentration of nitrous oxide and halothane. The xenon-treated animals showed respiratory depression, in contrast to the stimulating effects observed with halothane and nitrous oxide. Elevation of PaCO/sub 2/ was significant and would substantially increase cRBF. Their findings emphasize the need to monitor ventilation and respond appropriately if necessary

  15. The production of stable isotopes in Spain

    Energy Technology Data Exchange (ETDEWEB)

    Urgel, M.; Iglesias, J.; Casas, J.; Saviron, J. M.; Quintanilla, M.

    1965-07-01

    The activities developed in the field of the production of stable isotopes by means of ion-exchange chromatography and thermal diffusion techniques are reported. The first method was used to study the separation of the nitrogen and boron isotopes, whereby the separation factor was determined by the break through method. Values ranging from 1,028 to 1,022 were obtained for the separation factor of nitrogen by using ammonium hydroxide solutions while the corresponding values as obtained for boron amounted to 1,035-1,027 using boric acid solutions. Using ammonium chloride or acetate and sodium borate, respectively, resulted in the obtention of values for the separation factor approaching unity. The isotopic separation has been carried out according to the method of development by displacement. The separation of the isotopes of the noble gases, oxygen, nitrogen and carbon has been accomplished resorting to the method of thermal diffusion. (Author) 16 refs.

  16. The uniqueness of stable crack growth data

    International Nuclear Information System (INIS)

    Smith, E.

    1981-01-01

    The paper addresses the uniqueness of the stable crack growth relation, with particular reference to creep crack growth and stress corrosion crack growth, where it is the pattern to use laboratory data which relates the stress intensity K to the crack growth rate dc/dt. Simple models are used to define the conditions under which the K versus dc/dt data is unique. Extensive use is made of the Dugdale-Bilby-Cottrell-Swinden (DBCS) model, in which the yield accompanying crack growth is assumed to be confined to an infinitesimal thin strip coplanar with the growing crack. The DBCS model can be modified to give an incremental growth criterion, which is in the form of a differential equation relating the stress intensity to crack length. The conditions under which this equation gives a unique relation between stress intensity and crack length are then investigated. (orig./HP)

  17. The production of stable isotopes in Spain

    International Nuclear Information System (INIS)

    Urgel, M.; Iglesias, J.; Casas, J.; Saviron, J. M.; Quintanilla, M.

    1965-01-01

    The activities developed in the field of the production of stable isotopes by means of ion-exchange chromatography and thermal diffusion techniques are reported. The first method was used to study the separation of the nitrogen and boron isotopes, whereby the separation factor was determined by the break through method. Values ranging from 1,028 to 1,022 were obtained for the separation factor of nitrogen by using ammonium hydroxide solutions while the corresponding values as obtained for boron amounted to 1,035-1,027 using boric acid solutions. Using ammonium chloride or acetate and sodium borate, respectively, resulted in the obtention of values for the separation factor approaching unity. The isotopic separation has been carried out according to the method of development by displacement. The separation of the isotopes of the noble gases, oxygen, nitrogen and carbon has been accomplished resorting to the method of thermal diffusion. (Author) 16 refs

  18. The Search for Stable, Massive, Elementary Particles

    International Nuclear Information System (INIS)

    Kim, Peter C.

    2001-01-01

    In this paper we review the experimental and observational searches for stable, massive, elementary particles other than the electron and proton. The particles may be neutral, may have unit charge or may have fractional charge. They may interact through the strong, electromagnetic, weak or gravitational forces or through some unknown force. The purpose of this review is to provide a guide for future searches--what is known, what is not known, and what appear to be the most fruitful areas for new searches. A variety of experimental and observational methods such as accelerator experiments, cosmic ray studies, searches for exotic particles in bulk matter and searches using astrophysical observations is included in this review

  19. Multivariate max-stable spatial processes

    KAUST Repository

    Genton, Marc G.

    2015-02-11

    Max-stable processes allow the spatial dependence of extremes to be modelled and quantified, so they are widely adopted in applications. For a better understanding of extremes, it may be useful to study several variables simultaneously. To this end, we study the maxima of independent replicates of multivariate processes, both in the Gaussian and Student-t cases. We define a Poisson process construction and introduce multivariate versions of the Smith Gaussian extreme-value, the Schlather extremal-Gaussian and extremal-t, and the Brown–Resnick models. We develop inference for the models based on composite likelihoods. We present results of Monte Carlo simulations and an application to daily maximum wind speed and wind gust.

  20. Stable computation of generalized singular values

    Energy Technology Data Exchange (ETDEWEB)

    Drmac, Z.; Jessup, E.R. [Univ. of Colorado, Boulder, CO (United States)

    1996-12-31

    We study floating-point computation of the generalized singular value decomposition (GSVD) of a general matrix pair (A, B), where A and B are real matrices with the same numbers of columns. The GSVD is a powerful analytical and computational tool. For instance, the GSVD is an implicit way to solve the generalized symmetric eigenvalue problem Kx = {lambda}Mx, where K = A{sup {tau}}A and M = B{sup {tau}}B. Our goal is to develop stable numerical algorithms for the GSVD that are capable of computing the singular value approximations with the high relative accuracy that the perturbation theory says is possible. We assume that the singular values are well-determined by the data, i.e., that small relative perturbations {delta}A and {delta}B (pointwise rounding errors, for example) cause in each singular value {sigma} of (A, B) only a small relative perturbation {vert_bar}{delta}{sigma}{vert_bar}/{sigma}.

  1. Stable Oxygen-18 and Deuterium Isotopes

    DEFF Research Database (Denmark)

    Müller, Sascha

    The application of stable Oxygen-18 (18O) and Deuterium (2H) isotopes, as a tracer for fluxes between different compartments of the water cycle was subject of the present PhD-thesis. During a three year period, temporal data from a wide range of water cycle constituents was collected from...... the Skjern River catchment, Denmark. The presented applications focused on studying the isotopic 'input signal' to the hydrosphere in the form of precipitation, the isotopic 'output signal' with its related dynamic processes at a coastal saltwater-freshwater interface (groundwater isotopes) and the temporal...... development within a given lowland headwater catchment (stream water isotopes). Based on our investigations on the precipitation isotopic composition a local meteoric water line (LMWL) was constructed and expressed as: δ2H=7.4 δ18O + 5.36‰. Moreover, we showed that under maritime temperature climate influence...

  2. A belief-based evolutionarily stable strategy.

    Science.gov (United States)

    Deng, Xinyang; Wang, Zhen; Liu, Qi; Deng, Yong; Mahadevan, Sankaran

    2014-11-21

    As an equilibrium refinement of the Nash equilibrium, evolutionarily stable strategy (ESS) is a key concept in evolutionary game theory and has attracted growing interest. An ESS can be either a pure strategy or a mixed strategy. Even though the randomness is allowed in mixed strategy, the selection probability of pure strategy in a mixed strategy may fluctuate due to the impact of many factors. The fluctuation can lead to more uncertainty. In this paper, such uncertainty involved in mixed strategy has been further taken into consideration: a belief strategy is proposed in terms of Dempster-Shafer evidence theory. Furthermore, based on the proposed belief strategy, a belief-based ESS has been developed. The belief strategy and belief-based ESS can reduce to the mixed strategy and mixed ESS, which provide more realistic and powerful tools to describe interactions among agents. Copyright © 2014 Elsevier Ltd. All rights reserved.

  3. Stable orbits for lunar landing assistance

    Science.gov (United States)

    Condoleo, Ennio; Cinelli, Marco; Ortore, Emiliano; Circi, Christian

    2017-10-01

    To improve lunar landing performances in terms of mission costs, trajectory determination and visibility the use of a single probe located over an assistance orbit around the Moon has been taken into consideration. To this end, the properties of two quasi-circular orbits characterised by a stable behaviour of semi-major axis, eccentricity and inclination have been investigated. The analysis has demonstrated the possibility of using an assistance probe, located over one of these orbits, as a relay satellite between lander and Earth, even in the case of landings on the far side of the Moon. A comparison about the accuracy in retrieving the lander's state with respect to the use of a probe located in the Lagrangian point L2 of the Earth-Moon system has also been carried out.

  4. Stable glomerular filtration rate in normotensive IDDM patients with stable microalbuminuria. A 5-year prospective study

    DEFF Research Database (Denmark)

    Mathiesen, E R; Feldt-Rasmussen, B; Hommel, E

    1997-01-01

    OBJECTIVE: To investigate the long-term course of glomerular filtration rate (GFR) in IDDM patients with microalbuminuria in order to identify patients with stable or declining kidney function over a 5-year study. RESEARCH DESIGN AND METHODS: Forty normotensive (129 +/- 11/80 +/- 8 mmHg) IDDM...

  5. Radioactive and Stable Cesium Distributions in Fukushima Forests

    Science.gov (United States)

    Ioshchenko, V.; Kivva, S.; Konoplev, A.; Nanba, K.; Onda, Y.; Takase, T.; Zheleznyak, M.

    2015-12-01

    Fukushima Dai-ichi NPP accident has resulted in release into the environment of large amounts of 134Cs and 137Cs and in radioactive contamination of terrestrial and aquatic ecosystems. In Fukushima prefecture up to 2/3 of the most contaminated territory is covered with forests, and understanding of its further fate in the forest ecosystems is essential for elaboration of the long-term forestry strategy. At the early stage, radiocesium was intercepted by the trees' canopies. Numerous studies reported redistribution of the initial fallout in Fukushima forests in the followed period due to litterfall and leaching of radiocesium from the foliage with precipitations. By now these processes have transported the major part of deposited radiocesium to litter and soil compartments. Future levels of radiocesium activities in the aboveground biomass will depend on relative efficiencies of the radiocesium root uptake and its return to the soil surface with litterfall and precipitations. Radiocesium soil-to-plant transfer factors for typical tree species, soil types and landscape conditions of Fukushima prefecture have not been studied well; moreover, they may change in time with approaching to the equilibrium between radioactive and stable cesium isotopes in the ecosystem. The present paper reports the results of several ongoing projects carried out by Institute of Environmental Radioactivity of Fukushima University at the experimental sites in Fukushima prefecture. For typical Japanese cedar (Cryptomeria japonica) forest, we determined distributions of radiocesium in the ecosystem and in the aboveground biomass compartments by the end of 2014; available results for 2015 are presented, too, as well as the results of test application of D-shuttle dosimeters for characterization of seasonal variations of radiocesium activity in wood. Based on the radiocesium activities in biomass we derived the upper estimates of its incorporation and root uptake fluxes, 0.7% and 3% of the total

  6. Stable carbides in transition metal alloys

    International Nuclear Information System (INIS)

    Piotrkowski, R.

    1991-01-01

    In the present work different techniques were employed for the identification of stable carbides in two sets of transition metal alloys of wide technological application: a set of three high alloy M2 type steels in which W and/or Mo were total or partially replaced by Nb, and a Zr-2.5 Nb alloy. The M2 steel is a high speed steel worldwide used and the Zr-2.5 Nb alloy is the base material for the pressure tubes in the CANDU type nuclear reactors. The stability of carbide was studied in the frame of Goldschmidt's theory of interstitial alloys. The identification of stable carbides in steels was performed by determining their metallic composition with an energy analyzer attached to the scanning electron microscope (SEM). By these means typical carbides of the M2 steel, MC and M 6 C, were found. Moreover, the spatial and size distribution of carbide particles were determined after different heat treatments, and both microstructure and microhardness were correlated with the appearance of the secondary hardening phenomenon. In the Zr-Nb alloy a study of the α and β phases present after different heat treatments was performed with optical and SEM metallographic techniques, with the guide of Abriata and Bolcich phase diagram. The α-β interphase boundaries were characterized as short circuits for diffusion with radiotracer techniques and applying Fisher-Bondy-Martin model. The precipitation of carbides was promoted by heat treatments that produced first the C diffusion into the samples at high temperatures (β phase), and then the precipitation of carbide particles at lower temperature (α phase or (α+β)) two phase field. The precipitated carbides were identified as (Zr, Nb)C 1-x with SEM, electron microprobe and X-ray diffraction techniques. (Author) [es

  7. Stable isotopes as tracers for radionuclides

    International Nuclear Information System (INIS)

    Giussani, A.; Bartolo, D. de; Cantone, M.C.; Zilker, T.; Greim, H.; Roth, P.; Werner, E.

    2000-01-01

    The assessment of internal dose after incorporation of radionuclides requires as input data the knowledge of the uptake into the systemic circulation, the distribution and retention in selected organs, the excretion pathways. Realistic biokinetic models are needed for reliable estimates, correct interpretation of bioassay measurements, appropriate decision-making in radiological emergencies. For many radionuclides, however, the biokinetic models currently recommended are often generic, with very few specific parameters, due to the lack of experimental human data. The use of stable isotopes as tracers enables to determine important biokinetic parameters such as the fractional uptake, the clearance from the transfer compartment, the excretion patterns under experimentally controlled conditions. The subjects investigated are not exposed to any radiation risk, so this technique enables to obtain biokinetic information also for sensitive groups of the population, such as children or pregnant women, and to determine age- and gender-specific model parameters. Sophisticated analytical method, able to discriminate and quantitate different isotopes of the same element in complex matrices such as biological fluids, have to be purposely developed and optimized. Activation analysis and mass spectrometry are the most proper techniques of choice. Experiments were conducted with molybdenum, tellurium, ruthenium and zirconium. Activation analysis with protons, thermal ionization mass spectrometry and inductively coupled mass spectrometry were employed for the determination of stable isotopes of these elements in blood plasma and urine samples. Several deviations from the predictions of the ICRP models were observed. For example, modifications to the current model for molybdenum have been suggested on the basis of these results. The dose coefficients to the target regions calculated with this proposed model are even of one order of magnitude different than the ICRP estimates

  8. Superhydrophobic surfaces fabricated by surface modification of alumina particles

    Science.gov (United States)

    Richard, Edna; Aruna, S. T.; Basu, Bharathibai J.

    2012-10-01

    The fabrication of superhydrophobic surfaces has attracted intense interest because of their widespread potential applications in various industrial fields. Recently, some attempts have been carried out to prepare superhydrophobic surfaces using metal oxide nanoparticles. In the present work, superhydrophobic surfaces were fabricated with low surface energy material on alumina particles with different sizes. It was found that particle size of alumina is an important factor in achieving stable superhydrophobic surface. It was possible to obtain alumina surface with water contact angle (WCA) of 156° and a sliding angle of Superhydrophobicity of the modified alumina is attributed to the combined effect of the micro-nanostructure and low surface energy of fatty acid on the surface. The surface morphology of the alumina powder and coatings was determined by FESEM. The stability of the coatings was assessed by conducting water immersion test. Effect of heat treatment on WCA of the coating was also studied. The transition of alumina from hydrophilic to superhydrophobic state was explained using Wenzel and Cassie models. The method is shown to have potential application for creating superhydrophobic surface on cotton fabrics.

  9. Stability properties of nonlinear dynamical systems and evolutionary stable states

    Energy Technology Data Exchange (ETDEWEB)

    Gleria, Iram, E-mail: iram@fis.ufal.br [Instituto de Física, Universidade Federal de Alagoas, 57072-970 Maceió-AL (Brazil); Brenig, Leon [Faculté des Sciences, Université Libre de Bruxelles, 1050 Brussels (Belgium); Rocha Filho, Tarcísio M.; Figueiredo, Annibal [Instituto de Física and International Center for Condensed Matter Physics, Universidade de Brasília, 70919-970 Brasília-DF (Brazil)

    2017-03-18

    Highlights: • We address the problem of equilibrium stability in a general class of non-linear systems. • We link Evolutionary Stable States (ESS) to stable fixed points of square quasi-polynomial (QP) systems. • We show that an interior ES point may be related to stable interior fixed points of QP systems. - Abstract: In this paper we address the problem of stability in a general class of non-linear systems. We establish a link between the concepts of asymptotic stable interior fixed points of square Quasi-Polynomial systems and evolutionary stable states, a property of some payoff matrices arising from evolutionary games.

  10. Influence of horse stable environment on human airways

    Directory of Open Access Journals (Sweden)

    Pringle John

    2009-05-01

    Full Text Available Abstract Background Many people spend considerable amount of time each day in equine stable environments either as employees in the care and training of horses or in leisure activity. However, there are few studies available on how the stable environment affects human airways. This study examined in one horse stable qualitative differences in indoor air during winter and late summer conditions and assessed whether air quality was associated with clinically detectable respiratory signs or alterations to selected biomarkers of inflammation and lung function in stable personnel. Methods The horse stable environment and stable-workers (n = 13 in one stable were investigated three times; first in the winter, second in the interjacent late summer and the third time in the following winter stabling period. The stable measurements included levels of ammonia, hydrogen sulphide, total and respirable dust, airborne horse allergen, microorganisms, endotoxin and glucan. The stable-workers completed a questionnaire on respiratory symptoms, underwent nasal lavage with subsequent analysis of inflammation markers, and performed repeated measurements of pulmonary function. Results Measurements in the horse stable showed low organic dust levels and high horse allergen levels. Increased viable level of fungi in the air indicated a growing source in the stable. Air particle load as well as 1,3-β-glucan was higher at the two winter time-points, whereas endotoxin levels were higher at the summer time-point. Two stable-workers showed signs of bronchial obstruction with increased PEF-variability, increased inflammation biomarkers relating to reported allergy, cold or smoking and reported partly work-related symptoms. Furthermore, two other stable-workers reported work-related airway symptoms, of which one had doctor's diagnosed asthma which was well treated. Conclusion Biomarkers involved in the development of airway diseases have been studied in relation to

  11. Stable water isotopes as tracers in studies of lacustrine groundwater discharge

    Science.gov (United States)

    Lewandowski, Jörg; Pöschke, Franziska; Meinikmann, Karin; Rudnick, Sebastian; Périllon, Cécile; Elmarami, Hatem; Massmann, Gudrun; Stumpp, Christine

    2015-04-01

    Different tracers are used in ecohydrology to study transport processes across groundwater-surface water interfaces. The stable water isotopes oxygen-18 and deuterium as parts of the water molecule are close to perfect tracers since their behavior in aquifers is quite conservative. Isotopic signatures of groundwater and surface water differ due to the impact of evaporation on lake water. Stable isotope measurements are nowadays orders of magnitude cheaper, faster, and easier due to the recent development of cavity ring-down spectroscopy. Based on that analytical progress, we suggest a much broader use and highlight a number of promising ecohydrological applications in studies of lacustrine groundwater discharge. For example, they might be used to clearly distinguish between in- and exfiltration zones of lakes, to identify temporal fluctuations of in- and exfiltration, but also to identify sampling artifacts due to short circuits during sampling with lakebed piezometers.

  12. Surface Relaxations, Surface Energies and Electronic Structures of BaSnO3 (001) Surfaces: Ab Initio Calculations

    Science.gov (United States)

    Slassi, A.; Hammi, M.; El Rhazouani, O.

    2017-07-01

    The surface relaxations, surface energies and electronic structures of BaO- and SnO2-terminated BaSnO3 (001) surfaces have been studied by employing the first-principles density functional theory. For both terminations, we find that the upper-layer Ba and Sn atoms move inward, whereas upper-layer O atoms move outward from the surface. Moreover, the largest relaxations are occurred on the first-layer atoms of both terminations. The surface rumpling of BaO-terminated BaSnO3 (001) is slightly less than that of the SnO2-terminated BaSnO3 (001) surface. The surface energies show that both terminated surfaces are energetically stable and favorable. Finally, the surface band gap is slightly decreased for the BaO termination, while it is dramatically decreased for the SnO2 termination.

  13. Stable isotope analysis in primatology: a critical review.

    Science.gov (United States)

    Sandberg, Paul A; Loudon, James E; Sponheimer, Matt

    2012-11-01

    Stable isotope analysis has become an important tool in ecology over the last 25 years. A wealth of ecological information is stored in animal tissues in the relative abundances of the stable isotopes of several elements, particularly carbon and nitrogen, because these isotopes navigate through ecological processes in predictable ways. Stable carbon and nitrogen isotopes have been measured in most primate taxonomic groups and have yielded information about dietary content, dietary variability, and habitat use. Stable isotopes have recently proven useful for addressing more fine-grained questions about niche dynamics and anthropogenic effects on feeding ecology. Here, we discuss stable carbon and nitrogen isotope systematics and critically review the published stable carbon and nitrogen isotope data for modern primates with a focus on the problems and prospects for future stable isotope applications in primatology. © 2012 Wiley Periodicals, Inc.

  14. Increased energy in stable dry-band arcs due to length compression

    OpenAIRE

    Zhang, X.; Rowland, S. M.; Terzija, V.

    2010-01-01

    The occurrence of dry-band arcs on outdoor composite insulators can degrade the polymeric materials' surface and ultimately may lead to insulator failure. The degradation processes are generally considered as aging effects occurring over long periods of time, from years to decades. In this paper, it is shown that if a stable dryband arc is physically compressed in length by external forces, such as electrolyte deformation due to wind or gravity, the arcing activities will become more severe. ...

  15. Stable atmospheric methane in the 2000s: key-role of emissions from natural wetlands

    OpenAIRE

    I. Pison; B. Ringeval; P. Bousquet; C. Prigent; F. Papa

    2013-01-01

    Two atmospheric inversions (one fine-resolved and one process-discriminating) and a process-based model for land surface exchanges are brought together to analyze the variations of methane emissions from 1990 to 2009. A focus is put on the role of natural wetlands and on the years 2000–2006, a period of stable atmospheric concentrations. From 1990 to 2000, the two inversions agree on the time-phasing of global emission anomalies. The process-discriminating inversion further indicates...

  16. Highly stable lipid-encapsulation of fluorescent nanodiamonds for bioimaging applications.

    Science.gov (United States)

    Sotoma, Shingo; Hsieh, Feng-Jen; Chen, Yen-Wei; Tsai, Pei-Chang; Chang, Huan-Cheng

    2018-01-23

    Highly stable lipid-encapsulated fluorescent nanodiamonds (FNDs) are produced by photo-crosslinking of diacetylene-containing lipids physically attached to the FND surface. Not only is this coating method simple and fast, but also it gives the FND-lipid hybrids favorable properties for bioapplications. The hybrids are useful as fluorescent biolabels as well as fiducial markers for correlative light and electron microscopy.

  17. Stable nuclear transformation of Eudorina elegans

    Directory of Open Access Journals (Sweden)

    Lerche Kai

    2013-02-01

    Full Text Available Abstract Background A fundamental step in evolution was the transition from unicellular to differentiated, multicellular organisms. Volvocine algae have been used for several decades as a model lineage to investigate the evolutionary aspects of multicellularity and cellular differentiation. There are two well-studied volvocine species, a unicellular alga (Chlamydomonas reinhardtii and a multicellular alga with differentiated cell types (Volvox carteri. Species with intermediate characteristics also exist, which blur the boundaries between unicellularity and differentiated multicellularity. These species include the globular alga Eudorina elegans, which is composed of 16–32 cells. However, detailed molecular analyses of E. elegans require genetic manipulation. Unfortunately, genetic engineering has not yet been established for Eudorina, and only limited DNA and/or protein sequence information is available. Results Here, we describe the stable nuclear transformation of E. elegans by particle bombardment using both a chimeric selectable marker and reporter genes from different heterologous sources. Transgenic algae resistant to paromomycin were achieved using the aminoglycoside 3′-phosphotransferase VIII (aphVIII gene of Streptomyces rimosus, an actinobacterium, under the control of an artificial promoter consisting of two V. carteri promoters in tandem. Transformants exhibited an increase in resistance to paromomycin by up to 333-fold. Co-transformation with non-selectable plasmids was achieved with a rate of 50 - 100%. The luciferase (gluc gene from the marine copepod Gaussia princeps, which previously was engineered to match the codon usage of C. reinhardtii, was used as a reporter gene. The expression of gluc was mediated by promoters from C. reinhardtii and V. carteri. Heterologous heat shock promoters induced an increase in luciferase activity (up to 600-fold at elevated temperatures. Long-term stability and both constitutive and

  18. Nacre-inspired design of mechanical stable coating with underwater superoleophobicity.

    Science.gov (United States)

    Xu, Li-Ping; Peng, Jitao; Liu, Yibiao; Wen, Yongqiang; Zhang, Xueji; Jiang, Lei; Wang, Shutao

    2013-06-25

    Because of the frequent oil spill accidents in marine environment, stable superoleophobic coatings under seawater are highly desired. Current underwater superoleophobic surfaces often suffer from mechanical damages and lose their superoleophobicity gradually. It remains a challenge to fabricate a stable and robust underwater superoleophobic film which can endure harsh conditions in practical application. Nacre is one of most extensively studied rigid biological materials. Inspired by the outstanding mechanical property of seashell nacre and those underwater superoleophobic surfaces from nature, we fabricated a polyelectrolyte/clay hybrid film via typical layer-by-layer (LBL) method based on building blocks with high surface energy. 'Bricks-and-mortar' structure of seashell nacre was conceptually replicated into the prepared film, which endows the obtained film with excellent mechanical property and great abrasion resistance. In addtion, the prepared film also exhibits stable underwater superoleophobicity, low oil adhesion, and outstanding environment durability in artificial seawater. We anticipate that this work will provide a new method to design underwater low-oil-adhesion film with excellent mechanical property and improved stability, which may advance the practical applications in marine antifouling and microfluidic devices.

  19. Introducing Stable Radicals into Molecular Machines.

    Science.gov (United States)

    Wang, Yuping; Frasconi, Marco; Stoddart, J Fraser

    2017-09-27

    Ever since their discovery, stable organic radicals have received considerable attention from chemists because of their unique optical, electronic, and magnetic properties. Currently, one of the most appealing challenges for the chemical community is to develop sophisticated artificial molecular machines that can do work by consuming external energy, after the manner of motor proteins. In this context, radical-pairing interactions are important in addressing the challenge: they not only provide supramolecular assistance in the synthesis of molecular machines but also open the door to developing multifunctional systems relying on the various properties of the radical species. In this Outlook, by taking the radical cationic state of 1,1'-dialkyl-4,4'-bipyridinium (BIPY •+ ) as an example, we highlight our research on the art and science of introducing radical-pairing interactions into functional systems, from prototypical molecular switches to complex molecular machines, followed by a discussion of the (i) limitations of the current systems and (ii) future research directions for designing BIPY •+ -based molecular machines with useful functions.

  20. Canonical, stable, general mapping using context schemes.

    Science.gov (United States)

    Novak, Adam M; Rosen, Yohei; Haussler, David; Paten, Benedict

    2015-11-15

    Sequence mapping is the cornerstone of modern genomics. However, most existing sequence mapping algorithms are insufficiently general. We introduce context schemes: a method that allows the unambiguous recognition of a reference base in a query sequence by testing the query for substrings from an algorithmically defined set. Context schemes only map when there is a unique best mapping, and define this criterion uniformly for all reference bases. Mappings under context schemes can also be made stable, so that extension of the query string (e.g. by increasing read length) will not alter the mapping of previously mapped positions. Context schemes are general in several senses. They natively support the detection of arbitrary complex, novel rearrangements relative to the reference. They can scale over orders of magnitude in query sequence length. Finally, they are trivially extensible to more complex reference structures, such as graphs, that incorporate additional variation. We demonstrate empirically the existence of high-performance context schemes, and present efficient context scheme mapping algorithms. The software test framework created for this study is available from https://registry.hub.docker.com/u/adamnovak/sequence-graphs/. anovak@soe.ucsc.edu Supplementary data are available at Bioinformatics online. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

  1. Chemically Stable Lipids for Membrane Protein Crystallization

    Energy Technology Data Exchange (ETDEWEB)

    Ishchenko, Andrii; Peng, Lingling; Zinovev, Egor; Vlasov, Alexey; Lee, Sung Chang; Kuklin, Alexander; Mishin, Alexey; Borshchevskiy, Valentin; Zhang, Qinghai; Cherezov, Vadim (MIPT); (USC); (Scripps)

    2017-05-01

    The lipidic cubic phase (LCP) has been widely recognized as a promising membrane-mimicking matrix for biophysical studies of membrane proteins and their crystallization in a lipidic environment. Application of this material to a wide variety of membrane proteins, however, is hindered due to a limited number of available host lipids, mostly monoacylglycerols (MAGs). Here, we designed, synthesized, and characterized a series of chemically stable lipids resistant to hydrolysis, with properties complementary to the widely used MAGs. In order to assess their potential to serve as host lipids for crystallization, we characterized the phase properties and lattice parameters of mesophases made of two most promising lipids at a variety of different conditions by polarized light microscopy and small-angle X-ray scattering. Both lipids showed remarkable chemical stability and an extended LCP region in the phase diagram covering a wide range of temperatures down to 4 °C. One of these lipids has been used for crystallization and structure determination of a prototypical membrane protein bacteriorhodopsin at 4 and 20 °C.

  2. 26 S proteasomes function as stable entities

    DEFF Research Database (Denmark)

    Hendil, Klavs B; Hartmann-Petersen, Rasmus; Tanaka, Keiji

    2002-01-01

    , shuttles between a free state and the 26-S proteasome, bringing substrate to the complex. However, S5a was not found in the free state in HeLa cells. Besides, all subunits in PA700, including S5a, exchanged at similar low rates. It therefore seems that 26-S proteasomes function as stable entities during...... dissociate and reassemble during initiation of protein degradation in a ternary complex with the substrate, as in the dissociation-reassembly cycles found for ribosomes and the chaperonin GroEL/GroES. Here we followed disassembly and assembly of 26-S proteasomes in cell extracts as the exchange of PA700...... subunits between mouse and human 26-S proteasomes. Compared to the rate of proteolysis in the same extract, the disassembly-reassembly cycle was much too slow to present an obligatory step in a degradation cycle. It has been suggested that subunit S5a (Mcb1, Rpn10), which binds poly-ubiquitin substrates...

  3. Migration, fertility, and aging in stable populations.

    Science.gov (United States)

    Alho, Juha M

    2008-08-01

    Fertility is below replacement level in all European countries, and population growth is expected to decline in the coming decades. Increasing life expectancy will accentuate concomitant aging of the population. Migration has been seen as a possible means to decelerate aging. In this article, I introduce a stable, open-population model in which cohort net migration is proportional to births. In this case, the migration-fertility trade-off can be studied with particular ease. I show that although migration can increase the growth rate, which tends to make the age distribution younger, it also has an opposite effect because of its typical age pattern. I capture the effect of the age pattern of net migration in a migration-survivor function. The effect of net migration on growth is quantified with data from 17 European countries. I show that some countries already have a level of migration that will lead to stationarity. For other countries with asymptotically declining population, migration still provides opportunities for slowing down aging of the population as a whole.

  4. Shelf-stable foods through irradiation processing

    International Nuclear Information System (INIS)

    1995-11-01

    This survey has been produced from a database on analytical reference materials of biological and environmental origin, which is maintained at the International Atomic Energy Agency. It is an updated version of earlier reports, the last published in 1990. The information presented refers mostly to reference materials for trace element constituents; however, information is also included on a number of other selected measurands of relevance to IAEA programmes, i.e. radionuclides, stable isotopes, anions, cations, organometallic compounds and organic contaminants. The database presently contains over 10,000 analyte values for 455 measurands in 650 reference materials produced by 30 different suppliers. Additional information on the cost of the materials, the unit size supplied, and recommended minimum weight of material for analysis is also provided, if this information is available to the authors. It is expected that this survey will help analysts to select reference materials for quality assurance purposes that match as closely as possible, with respect to matrix type and concentrations of the measurands of interest, their samples to be analyzed. 22 refs, 2 tabs

  5. STABLE ISOTOPE GEOCHEMISTRY OF MASSIVE ICE

    Directory of Open Access Journals (Sweden)

    Yurij K. Vasil’chuk

    2016-01-01

    Full Text Available The paper summarises stable-isotope research on massive ice in the Russian and North American Arctic, and includes the latest understanding of massive-ice formation. A new classification of massive-ice complexes is proposed, encompassing the range and variabilityof massive ice. It distinguishes two new categories of massive-ice complexes: homogeneousmassive-ice complexes have a similar structure, properties and genesis throughout, whereasheterogeneous massive-ice complexes vary spatially (in their structure and properties andgenetically within a locality and consist of two or more homogeneous massive-ice bodies.Analysis of pollen and spores in massive ice from Subarctic regions and from ice and snow cover of Arctic ice caps assists with interpretation of the origin of massive ice. Radiocarbon ages of massive ice and host sediments are considered together with isotope values of heavy oxygen and deuterium from massive ice plotted at a uniform scale in order to assist interpretation and correlation of the ice.

  6. LHC Report: Towards stable beams and collisions

    CERN Multimedia

    CERN Bulletin

    2011-01-01

    Over the past two weeks, the LHC re-commissioning with beam has continued at a brisk pace. The first collisions of 2011 were produced on 2 March, with stable beams and collisions for physics planned for the coming days. Low intensity beams with just a few bunches of particles were used to test the energy ramp to 3.5 TeV and the squeeze. The results were successful and, as a by-product, the first collisions of 2011 were recorded 2 March. One of the main activities carried out by the operation teams has been the careful set-up of the collimation system, and the injection and beam dump protection devices. The collimation system provides essential beam cleaning, preventing stray particles from impacting other elements of the machine, particularly the superconducting magnets. In addition to the collimation system, also the injection and beam dump protection devices perform a vital machine protection role, as they detect any beam that might be mis-directed during rare, but not totally unavoidable, hardware hiccups...

  7. Stable Isotope Group 1984 progress report

    International Nuclear Information System (INIS)

    Lyon, G.L.

    1985-04-01

    The work of the group in 1984 is described and includes studies in isotope geology, isotope hydrology, geochronology, isotope biology and mass spectrometer instrumentation. Geothermal studies have decreased compared to other years, but major data summaries were made for Wairakei and Ngawha. The hydrology of Whakarewarewa and Rotorua is being elucidated using water isotopes. Models of the subsurface flows at Kawerau and Ngawha are being made to relate fluid to mineral isotope compositions. A study of the δ 13 C and δ 34 S compositions of New Zealand oils has been started. Groups of oils of related origin are being defined, and compositions will be compared with those of potential source rocks. A method was developed for isotope analysis of sulphur in rocks. The isotopic composition of water is being used to identify and characterise groundwater aquifers in the Wairarapa and at Poverty Bay. Stable carbon isotopes have been used to identify food sources for invertebrates, and to show biochemical pathways in lactation by cows. The geochronology group is involved in major studies in Antarctica, using U-Pb, Rb-Sr and K-Ar methods. Rocks from North Victoria Land, Marie Byrd Land and the USARP mountains are being compared with possible correlatives in New Zealand and Argentina. Strontium isotope data is being applied to the origin of magmas in several regions of New Zealand. The K-Ar data is being stored on computer files. Fission track measurements are being applied to unravel uplift histories in Westland and Taranaki

  8. Stable curves and screens on fatgraphs

    DEFF Research Database (Denmark)

    Penner, Robert; McShane, Greg

    The mapping class group invariant ideal cell decomposition of the Teichmueller space of a punctured surface times an open simplex has been used in a number of computations. This paper answers a question about the asymptotics of this decomposition, namely, in a given cell of the decomposition, whi...... curves can be short? Screens are a new combinatorial structure which provide an answer to this question. The heart of the calculation here involves Ptolemy transformations and the triangle inequalities on lambda lengths....

  9. Embryotoxicity of stable isotopes and use of stable isotopes in studies of teratogenetic mechanisms

    International Nuclear Information System (INIS)

    Spielmann, H.; Nau, H.

    1986-01-01

    Experiments on teratogenic effects of stable isotopes from our own and other laboratories are evaluated. In the first series of investigations, the enrichment of the stable isotope 13 C derived from U- 13 C-glucose was studied in mouse embryos at various stages of development, including limb buds in organ culture. Preimplantation mouse embryos incubated in vitro in 13 C-enriched medium for 48 hours showed normal development during subsequent differentiation in vitro and also in vivo after embryo transfer to faster mothers. These embryos were 15% to 20% enriched in 13 C. Administration of U-13-C-glucose to pregnant mice during organogenesis led to an increase of the absolute 13 C content of the embryo for several days after the end of isotope administration, whereas the enrichment in maternal tissue decreased. No alterations of embryonic development were detected due to stable isotope enrichment. Development of cultured mouse limb buds was unaffected by incubation with 82 mol% U- 13 C-glucose as judged from morphologic and biochemical criteria. The second part of the article describes the value of deuterium-labeled drugs as probes into the mechanism of activation of teratogenic metabolites. A comparison of the pharmacokinetics as well as the teratogenicity between cyclophosphamide and some specific deuterium-labeled analogues showed that the isotope effect observed can be related to a particular metabolic pathway crucial for teratogenic activation by this drug

  10. Stable hovering of a jellyfish-like flying machine.

    Science.gov (United States)

    Ristroph, Leif; Childress, Stephen

    2014-03-06

    Ornithopters, or flapping-wing aircraft, offer an alternative to helicopters in achieving manoeuvrability at small scales, although stabilizing such aerial vehicles remains a key challenge. Here, we present a hovering machine that achieves self-righting flight using flapping wings alone, without relying on additional aerodynamic surfaces and without feedback control. We design, construct and test-fly a prototype that opens and closes four wings, resembling the motions of swimming jellyfish more so than any insect or bird. Measurements of lift show the benefits of wing flexing and the importance of selecting a wing size appropriate to the motor. Furthermore, we use high-speed video and motion tracking to show that the body orientation is stable during ascending, forward and hovering flight modes. Our experimental measurements are used to inform an aerodynamic model of stability that reveals the importance of centre-of-mass location and the coupling of body translation and rotation. These results show the promise of flapping-flight strategies beyond those that directly mimic the wing motions of flying animals.

  11. Toward highly stable electrocatalysts via nanoparticle pore confinement.

    Science.gov (United States)

    Galeano, Carolina; Meier, Josef C; Peinecke, Volker; Bongard, Hans; Katsounaros, Ioannis; Topalov, Angel A; Lu, Anhui; Mayrhofer, Karl J J; Schüth, Ferdi

    2012-12-19

    The durability of electrode materials is a limiting parameter for many electrochemical energy conversion systems. In particular, electrocatalysts for the essential oxygen reduction reaction (ORR) present some of the most challenging instability issues shortening their practical lifetime. Here, we report a mesostructured graphitic carbon support, Hollow Graphitic Spheres (HGS) with a specific surface area exceeding 1000 m(2) g(-1) and precisely controlled pore structure, that was specifically developed to overcome the long-term catalyst degradation, while still sustaining high activity. The synthetic pathway leads to platinum nanoparticles of approximately 3 to 4 nm size encapsulated in the HGS pore structure that are stable at 850 °C and, more importantly, during simulated accelerated electrochemical aging. Moreover, the high stability of the cathode electrocatalyst is also retained in a fully assembled polymer electrolyte membrane fuel cell (PEMFC). Identical location scanning and scanning transmission electron microscopy (IL-SEM and IL-STEM) conclusively proved that during electrochemical cycling the encapsulation significantly suppresses detachment and agglomeration of Pt nanoparticles, two of the major degradation mechanisms in fuel cell catalysts of this particle size. Thus, beyond providing an improved electrocatalyst, this study describes the blueprint for targeted improvement of fuel cell catalysts by design of the carbon support.

  12. Polyelectrolyte brushes: a novel stable lubrication system in aqueous conditions.

    Science.gov (United States)

    Kobayashi, Motoyasu; Terada, Masami; Takahara, Atsushi

    2012-01-01

    Surface-initiated controlled radical copolymerizations of 2-dimethylaminoethyl methacrylate (DMAEMA), 2-(methacryloyloxy)ethyl phosphorylcholine (MPC), 2-(methacryloyloxy)ethyltrimethylammonium chloride) (MTAC), and 3-sulfopropyl methacrylate potassium salt (SPMK) were carried out on a silicon wafer and glass ball to prepare polyelectrolyte brushes with excellent water wettability. The frictional coefficient of the polymer brushes was recorded on a ball-on-plate type tribometer by linear reciprocating motion of the brush specimen at a selected velocity of 1.5 x 10(-3) m s-1 under a normal load of 0.49 N applied to the stationary glass ball (d = 10 mm) at 298 K. The poly(DMAEMA-co-MPC) brush partially cross-linked by bis(2-iodoethoxy)ethane maintained a relatively low friction coefficient around 0.13 under humid air (RH > 75%) even after 200 friction cycles. The poly(SPMK) brush revealed an extremely low friction coefficient around 0.01 even after 450 friction cycles. We supposed that the abrasion of the brush was prevented owing to the good affinity of the poly(SPMK) brush for water forming a water lubrication layer, and electrostatic repulsive interactions among the brushes bearing sulfonic acid groups. Furthermore, the poly(SPMK-co-MTAC) brush with a chemically cross-linked structure showed a stable low friction coefficient in water even after 1400 friction cycles under a normal load of 139 MPa, indicating that the cross-linking structure improved the wear resistance of the brush layer.

  13. Stable organic-inorganic hybrid multilayered photoelectrochemical cells

    Science.gov (United States)

    Park, Sun-Young; Kim, Min-gyeong; Jung, Jaehoon; Heo, Jinhee; Hong, Eun Mi; Choi, Sung Mook; Lee, Joo-Yul; Cho, Shinuk; Hong, Kihyon; Lim, Dong Chan

    2017-02-01

    The production of hydrogen from water via solar energy conversion has attracted immense attention as a potential solution for addressing energy supply issues. We demonstrated a stable and efficient organic-inorganic hybrid photoelectrochemical (H-PEC) cell. Modifying the surface energy and structure of the organic photoactive layer using multi-functional nanomaterials including -OH-modified NiO nanoparticles and reduced graphene oxide (RGO) led to a 2.8-fold enhancement of the water splitting performance in a single junction H-PEC cell. The enhanced performance was attributed to the i) improved water-wettability, ii) enhanced charge extraction property by band-edge alignment, and iii) the catalytic effect of the introduced NiO-OH nanoparticles. In addition, because of the effects of the RGO layer preventing water penetration and photo-corrosion during the oxidation of water, a distinguishable long-term stability was achieved from the H-PEC cell with an RGO capping layer. The best performance was obtained from the organic-inorganic hybrid multi-junction PEC cells consisting of the WO3 photo-anode (activated under UV irradiation) and the H-PEC cell (activated under visible light irradiation). The H-PEC cell with a WO3 photo-anode exhibited significantly enhanced stability and performance by a factor of 11.6 higher than photocurrent of the single H-PEC cell.

  14. Using stable isotopes to examine watershed connectivity to ...

    Science.gov (United States)

    Water bodies within the USA are protected by the US Clean Water Act when they have a significant nexus to downstream navigable waters. As a research scientist with the US Environmental Protection Agency, I have used water stable isotopes to examine hydrologic connectivity dynamics. I will share two case studies. In the first case, we used the isotopic evaporation signal in water to examine wetland-stream hydrologic connectivity within the Pipestem Creek watershed, North Dakota, a watershed dominated by prairie-pothole wetlands. Prairie-Pothole wetlands are a special case of wetlands whose protection needs to be determined under the Clean Water Rule. Pipestem Creek exhibited an evaporated-water signal that had approximately half the isotopic-enrichment signal found in most evaporatively enriched prairie-pothole wetlands. Groundwater measured at the water table adjacent to Pipestem Creek had isotopic values that indicated recharge from winter precipitation and had no significant evaporative enrichment. Using isotopic theory and discharge data, we estimated the area of surface water necessary to generate the evaporation signal found within Pipestem Creek over two years. Our results indicated that prairie-pothole wetlands were important sources of stream flow in Pipestem Creek throughout the summer, as well as during snowmelt. They also demonstrated that at the lowest flows, the stream itself became disconnected from headwater stream reaches. In the second ca

  15. Potential uses of stable isotope ratios of Sr, Nd, and Pb in geological materials for environmental studies.

    Science.gov (United States)

    Nakano, Takanori

    2016-01-01

    The ratios of stable isotopes of certain elements in rocks and minerals have strong regional characteristics that are reflected in atmospheric components, in water, and in the living organisms that form Earth's surface environment as well as in agricultural and fishery products. Geologically derived stable isotope ratios can be used as a tracer for the source of many kinds of substances, with current geochemical techniques allowing the precise determination of numerous stable isotope ratios in both natural and manmade objects. This review presents examples of the use of stable isotopes as tracers within diverse dynamic ecosystems, focusing on Sr isotopes but also including examples of Nd and Pb isotopic analysis, and reviewing the potential of this technique for a wide range of environmental research, including determining the geographic origin of food and archeological materials.

  16. Potential uses of stable isotope ratios of Sr, Nd, and Pb in geological materials for environmental studies

    Science.gov (United States)

    NAKANO, Takanori

    2016-01-01

    The ratios of stable isotopes of certain elements in rocks and minerals have strong regional characteristics that are reflected in atmospheric components, in water, and in the living organisms that form Earth’s surface environment as well as in agricultural and fishery products. Geologically derived stable isotope ratios can be used as a tracer for the source of many kinds of substances, with current geochemical techniques allowing the precise determination of numerous stable isotope ratios in both natural and manmade objects. This review presents examples of the use of stable isotopes as tracers within diverse dynamic ecosystems, focusing on Sr isotopes but also including examples of Nd and Pb isotopic analysis, and reviewing the potential of this technique for a wide range of environmental research, including determining the geographic origin of food and archeological materials. PMID:27302069

  17. Unit of stable isotopic N15 analysis

    International Nuclear Information System (INIS)

    Cabrera de Bisbal, Evelin; Paredes U, Maria

    1997-01-01

    The continuous and growing demand of crops and cattle for the domestic inhabitants, forces the search of technical solutions in agriculture. One of the solutions able to be covered in a near future it is the escalation of agricultural production in lands already being cultivated, either by means of an intensification of cultivation and / or increasing the unitary yields. In the intensive cropping systems, the crops extract substantial quantities of nutriments that is recovered by means of the application of fertilizers. Due to the lack of resources and to the increase of commercial inputs prices, it has been necessary to pay attention to the analysis and improvement of low inputs cropping systems and to the effective use of resources. Everything has made to establish a concept of plant nutrition focused system, which integrate the sources of nutriments for plants and the production factors of crops in a productive cropping system, to improve the fertility of soils, the agricultural productivity and profitability. This system includes the biggest efficiency of chemical fertilizers as the maximum profit of alternative sources of nutriments, such as organic fertilizers, citrate-phosphate rocks and biological nitrogen fixation. By means of field experiments under different environmental conditions (soils and climate) it can be determined the best combination of fertilizers practice (dose, placement, opportunity and source) for selected cropping systems. The experimentation with fertilizer, marked with stable and radioactive isotopes, provides a direct and express method to obtain conclusive answers to the questions: where, when and how should be applied. The fertilizers marked with N 1 5 have been used to understand the application of marked fertilizer to the cultivations, and the determination of the proportion of crops nutritious element derived from fertilizer. The isotopic techniques offer a fast and reliable mean to obtain information about the distribution of

  18. Superhydrophobic surfaces

    Science.gov (United States)

    Wang, Evelyn N; McCarthy, Matthew; Enright, Ryan; Culver, James N; Gerasopoulos, Konstantinos; Ghodssi, Reza

    2015-03-24

    Surfaces having a hierarchical structure--having features of both microscale and nanoscale dimensions--can exhibit superhydrophobic properties and advantageous condensation and heat transfer properties. The hierarchical surfaces can be fabricated using biological nanostructures, such as viruses as a self-assembled nanoscale template.

  19. Spherical Surfaces

    DEFF Research Database (Denmark)

    Brander, David

    2016-01-01

    We study surfaces of constant positive Gauss curvature in Euclidean 3-space via the harmonicity of the Gauss map. Using the loop group representation, we solve the regular and the singular geometric Cauchy problems for these surfaces, and use these solutions to compute several new examples. We give...

  20. How structurally stable are global socioeconomic systems?

    Science.gov (United States)

    Saavedra, Serguei; Rohr, Rudolf P; Gilarranz, Luis J; Bascompte, Jordi

    2014-11-06

    The stability analysis of socioeconomic systems has been centred on answering whether small perturbations when a system is in a given quantitative state will push the system permanently to a different quantitative state. However, typically the quantitative state of socioeconomic systems is subject to constant change. Therefore, a key stability question that has been under-investigated is how strongly the conditions of a system itself can change before the system moves to a qualitatively different behaviour, i.e. how structurally stable the systems is. Here, we introduce a framework to investigate the structural stability of socioeconomic systems formed by a network of interactions among agents competing for resources. We measure the structural stability of the system as the range of conditions in the distribution and availability of resources compatible with the qualitative behaviour in which all the constituent agents can be self-sustained across time. To illustrate our framework, we study an empirical representation of the global socioeconomic system formed by countries sharing and competing for multinational companies used as proxy for resources. We demonstrate that the structural stability of the system is inversely associated with the level of competition and the level of heterogeneity in the distribution of resources. Importantly, we show that the qualitative behaviour of the observed global socioeconomic system is highly sensitive to changes in the distribution of resources. We believe that this work provides a methodological basis to develop sustainable strategies for socioeconomic systems subject to constantly changing conditions. © 2014 The Author(s) Published by the Royal Society. All rights reserved.

  1. Stable gastric pentadecapeptide BPC 157 and bupivacaine.

    Science.gov (United States)

    Zivanovic-Posilovic, Gordana; Balenovic, Diana; Barisic, Ivan; Strinic, Dean; Stambolija, Vasilije; Udovicic, Mario; Uzun, Sandra; Drmic, Domagoj; Vlainic, Josipa; Bencic, Martina Lovric; Sindic, Aleksandra; Seiwerth, Sven; Sikiric, Predrag

    2016-12-15

    Bupivacaine toxicity following accidental overdose still lacks therapeutic solution. However, there are major arguments for testing BPC 157 against bupivacaine toxicity in vivo in rats, in particular, and then finally, in vitro. These are: the lack of any known BPC 157 toxicity, a lifesaving effect via the mitigation of arrhythmias in rats underwent hyperkalemia or digitalis toxicity, the elimination of hyperkalemia and arrhythmias in rats underwent succinylcholine toxicity and finally, the reduction of potassium-induced depolarization in vitro (in HEK293 cells) in severe hyperkalemia. Most importantly, BPC 157 successfully prevents and counteracts bupivacaine cardiotoxicity; BPC 157 is effective even against the worst outcomes such as a severely prolonged QRS complex. Here, rats injected with bupivacaine (100mg/kg IP) exhibited bradycardia, AV-block, ventricular ectopies, ventricular tachycardia, T-wave elevation and asystole. All of the fatalities had developed T-wave elevation, high-degree AV-block, respiratory arrest and asystole. These were largely counteracted by BPC 157 administration (50µg/kg, 10µg/kg, 10ng/kg, or 10pg/kg IP) given 30min before or 1min after the bupivacaine injection. When BPC 157 was given 6min after bupivacaine administration, and after the development of prolonged QRS intervals (20ms), the fatal outcome was markedly postponed. Additionally, the effect of bupivacaine on cell membrane depolarization was explored by measuring membrane voltages (Vm) in HEK293 cells. Bupivacaine (1mM) alone caused depolarization of the cells, while in combination with BPC 157 (1µm), the bupivacaine-induced depolarization was inhibited. Together, these findings suggest that the stable gastric pentadecapeptide BPC 157 should be a potential antidote for bupivacaine cardiotoxicity. Copyright © 2016 Elsevier B.V. All rights reserved.

  2. Stable Continental Region Earthquakes in South China

    Science.gov (United States)

    Liu, L.

    This paper reviews some remarkable characteristics of earthquakes in a Stable Continental Region (SCR) of the South China Block (SCB). The kernel of the SCB is the Yangtze platform solidified in late Proterozoic time, with continental growth to the southeast by a series of fold belts in Paleozoic time. The facts that the deviatoric stress is low, the orientations of the major tectonic features in the SCB are substantially normal to the maximum horizontal principal stress, and a relatively uniform crust, seem to be the major reasons for lack of significant seismicity in most regions of the SCB. Earthquakes in this region are mainly associated with three seismic zones: (1) the Southeast China Coast seismic zone related to Guangdong-Fujian coastal folding belt (associated with Eurasia-Philippine Sea plate collision); (2) the Southern Yellow Sea seismic zone associated with continental shelf rifts and basins; and (3) the Downstream Yangtze River seismic zone spatially coinciding with Tertiary rifts and basin development. All three seismic zones are close to one or two major economic and population centers in the SCB so that they pose significant seismic hazards. Earthquake focal mechanisms in the SCB are consistent with strike-slip to normal faulting stress regimes. Because of the global and national economic significance of the SCB and its dense population, the seismic hazard of the region is of outstanding importance. Comparing the SCB with another less developed region, a pending earthquake with the same size and tectonic setting would cause substantially more severe social and economic losses in the SCB. This paper also compiles an inventory of historic moderate to great earthquakes in the SCB; most of the data are not widely available in English literature.

  3. Tempered stable distributions stochastic models for multiscale processes

    CERN Document Server

    Grabchak, Michael

    2015-01-01

    This brief is concerned with tempered stable distributions and their associated Levy processes. It is a good text for researchers interested in learning about tempered stable distributions.  A tempered stable distribution is one which takes a stable distribution and modifies its tails to make them lighter. The motivation for this class comes from the fact that infinite variance stable distributions appear to provide a good fit to data in a variety of situations, but the extremely heavy tails of these models are not realistic for most real world applications. The idea of using distributions that modify the tails of stable models to make them lighter seems to have originated in the influential paper of Mantegna and Stanley (1994). Since then, these distributions have been extended and generalized in a variety of ways. They have been applied to a wide variety of areas including mathematical finance, biostatistics,computer science, and physics.

  4. Absolute Continuity of Stable Foliations for Mappings of Banach Spaces

    Science.gov (United States)

    Blumenthal, Alex; Young, Lai-Sang

    2017-09-01

    We prove the absolute continuity of stable foliations for mappings of Banach spaces satisfying conditions consistent with time- t maps of certain classes of dissipative PDEs. This property is crucial for passing information from submanifolds transversal to the stable foliation to the rest of the phase space; it is also used in proofs of ergodicity. Absolute continuity of stable foliations is well known in finite dimensional hyperbolic theory. On Banach spaces, the absence of nice geometric properties poses some additional difficulties.

  5. Tukey max-stable processes for spatial extremes

    KAUST Repository

    Xu, Ganggang

    2016-09-21

    We propose a new type of max-stable process that we call the Tukey max-stable process for spatial extremes. It brings additional flexibility to modeling dependence structures among spatial extremes. The statistical properties of the Tukey max-stable process are demonstrated theoretically and numerically. Simulation studies and an application to Swiss rainfall data indicate the effectiveness of the proposed process. © 2016 Elsevier B.V.

  6. Stable SU(5) monopoles with higher magnetic charge

    International Nuclear Information System (INIS)

    Miyamoto, S.; Sato, H.; Tomohiro, S.

    1985-01-01

    Taking into account the electroweak breaking effects, some multiply charged monopoles were shown to be stable by Gardner and Harvey. We give the explicit Ansa$uml: tze for finite-energy, nonsingular solutions of these stable higher-strength monopoles with eg = 1,(3/2),3. We also give the general stability conditions and the detailed behavior of the interaction potentials between two monopoles which produce the stable higher-strength monopoles

  7. Sense of Humor, Stable Affect, and Psychological Well-Being

    Directory of Open Access Journals (Sweden)

    Arnie Cann

    2014-08-01

    Full Text Available A good sense of humor has been implicated as a quality that could contribute to psychological well-being. The mechanisms through which sense of humor might operate include helping to reappraise threats, serving as a character strength, or facilitating happiness. The current research attempts to integrate these possibilities by examining whether a good sense of humor might operate globally by helping to maintain a more stable positive affect. Stable positive affect has been shown to facilitate more effective problem solving and to build resilience. However, not all humor is adaptive humor, so we also examine the roles that different styles of humor use might play. Individual differences in humor styles were used to predict stable levels of affect. Then, in a longitudinal design, humor styles and stable affect were used to predict subsequent resilience and psychological health. The results indicated that stable affect was related to resilience and psychological well-being, and that a sense of humor that involves self-enhancing humor, humor based on maintaining a humorous perspective about one’s experiences, was positively related to stable positive affect, negatively related to stable negative affect, and was mediated through stable affect in influencing resilience, well-being and distress. Thus, while a good sense of humor can lead to greater resilience and better psychological health, the current results, focusing on stable affect, find only self-enhancing humor provides reliable benefits.

  8. Iron oxide surfaces

    Science.gov (United States)

    Parkinson, Gareth S.

    2016-03-01

    known with a high degree of precision and the major defects and properties are well characterised. A major factor in this is that a termination at the Feoct-O plane can be reproducibly prepared by a variety of methods, as long as the surface is annealed in 10-7-10-5 mbar O2 in the final stage of preparation. Such straightforward preparation of a monophase termination is generally not the case for iron oxide surfaces. All available evidence suggests the oft-studied (√2×√2)R45° reconstruction results from a rearrangement of the cation lattice in the outermost unit cell in which two octahedral cations are replaced by one tetrahedral interstitial, a motif conceptually similar to well-known Koch-Cohen defects in Fe1-xO. The cation deficiency results in Fe11O16 stoichiometry, which is in line with the chemical potential in ultra-high vacuum (UHV), which is close to the border between the Fe3O4 and Fe2O3 phases. The Fe3O4(111) surface is also much studied, but two different surface terminations exist close in energy and can coexist, which makes sample preparation and data interpretation somewhat tricky. Both the Fe3O4(100) and Fe3O4(111) surfaces exhibit Fe-rich terminations as the sample selvedge becomes reduced. The Fe3O4(110) surface forms a one-dimensional (1×3) reconstruction linked to nanofaceting, which exposes the more stable Fe3O4(111) surface. α-Fe2O3(0001) is the most studied haematite surface, but difficulties preparing stoichiometric surfaces under UHV conditions have hampered a definitive determination of the structure. There is evidence for at least three terminations: a bulk-like termination at the oxygen plane, a termination with half of the cation layer, and a termination with ferryl groups. When the surface is reduced the so-called "bi-phase" structure is formed, which eventually transforms to a Fe3O4(111)-like termination. The structure of the bi-phase surface is controversial; a largely accepted model of coexisting Fe1-xO and α-Fe2O3(0001) islands

  9. A temperature-stable cryo-system for high-temperature superconducting MR in-vivo imaging.

    Directory of Open Access Journals (Sweden)

    In-Tsang Lin

    Full Text Available To perform a rat experiment using a high-temperature superconducting (HTS surface resonator, a cryostat is essential to maintain the rat's temperature. In this work, a compact temperature-stable HTS cryo-system, keeping animal rectal temperature at 37.4°C for more than 3 hours, was successfully developed. With this HTS cryo-system, a 40-mm-diameter Bi2Sr2Ca2Cu3Ox (Bi-2223 surface resonator at 77 K was demonstrated in a 3-Tesla MRI system. The proton resonant frequency (PRF method was employed to monitor the rat's temperature. Moreover, the capacity of MR thermometry in the HTS experiments was evaluated by correlating with data from independent fiber-optic sensor temperature measurements. The PRF thermal coefficient was derived as 0.03 rad/°C and the temperature-monitoring architecture can be implemented to upgrade the quality and safety in HTS experiments. The signal-to-noise ratio (SNR of the HTS surface resonator at 77 K was higher than that of a professionally made copper surface resonator at 300 K, which has the same geometry, by a 3.79-fold SNR gain. Furthermore, the temperature-stable HTS cryo-system we developed can obtain stable SNR gain in every scan. A temperature-stable HTS cryo-system with an external air-blowing circulation system is demonstrated.

  10. Stable glomerular filtration rate in normotensive IDDM patients with stable microalbuminuria. A 5-year prospective study

    DEFF Research Database (Denmark)

    Mathiesen, E R; Feldt-Rasmussen, B; Hommel, E

    1997-01-01

    . Out of 40 patients, 14 progressed to diabetic nephropathy (UAE > 300 mg/24 h). These patients had a significant reduction in GFR (mean -2.2 +/- 3.8 ml x min-1 x year-1; P = 0.05), while GFR remained stable in the remaining 26 patients with nonprogressive microalbuminuria (change in GFR 0.5 +/- 2.1 ml...... x min-1 x year-1; NS). The difference in the rate of decline of GFR was significant (mean 2.7 ml x min-1 x year-1; P

  11. Stable and Continuous Long-term Enzymatic Reaction using an Enzyme-Nanofiber Composite

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Jin Hyung; Hwang, Ee Taek; Kim, Byoung Chan; Lee, Sun Mi; Sang, Byoung-In; Choi, Yong Su; Kim, Jungbae; Gu, Man Bock

    2007-07-01

    This study shows the preparation and application of enzyme-nanofiber composites for long-term stable operation. The enzyme-nanofiber composite was prepared by coating an enzyme-aggregate, the esterase from Rhizopus oryzae, on the surface of the nanofibers. The activity and stability of the esterase-nanofiber composite was evaluated by measuring the production of p-nitrophenol from the hydrolysis of p-nitrophenyl butyrate. It was found that enzyme-nanofiber was very stable, even when the fibers were shaken in glasses, preserving 80 % of the initial activity for 100 days. In addition, the enzyme nanofiber composite was repeatedly used in 30 cycles of substrate hydrolysis and still remained active. Consequently, the esterase-nanofiber composite was finally employed to find its feasibility of long-term and stable continuous substrate hydrolysis reaction. In the sample reactor, the production of p-nitrophenol was consistent for 400 hr. Additionally, it was found that the production of p-nitrophenol proportionally decreased as the dilution rate was increased, showing the relationship between the efficiency of hydrolysis and the retention time within the reactor. This study demonstrates that the enzyme-nanofiber composite can be used in both repeated-batch and continuous modes for long-term stable operation.

  12. Surface boxplots

    KAUST Repository

    Genton, Marc G.

    2014-01-22

    In this paper, we introduce a surface boxplot as a tool for visualization and exploratory analysis of samples of images. First, we use the notion of volume depth to order the images viewed as surfaces. In particular, we define the median image. We use an exact and fast algorithm for the ranking of the images. This allows us to detect potential outlying images that often contain interesting features not present in most of the images. Second, we build a graphical tool to visualize the surface boxplot and its various characteristics. A graph and histogram of the volume depth values allow us to identify images of interest. The code is available in the supporting information of this paper. We apply our surface boxplot to a sample of brain images and to a sample of climate model outputs.

  13. Convex surfaces

    CERN Document Server

    Busemann, Herbert

    2008-01-01

    This exploration of convex surfaces focuses on extrinsic geometry and applications of the Brunn-Minkowski theory. It also examines intrinsic geometry and the realization of intrinsic metrics. 1958 edition.

  14. The Stable Trajectory Tracking Control of a Skid-Steered Mobile Platform with Dynamic Uncertainties

    Directory of Open Access Journals (Sweden)

    Seungwoo Jeon

    2015-09-01

    Full Text Available In order to clean the surfaces of air ducts in underground facilities, recent research has been conducted on driving the control and development of an autonomous mobile duct-cleaning platform. The duct-cleaning robots removes contaminants that are inside a duct using the friction between a rotating cleaning brush and the duct surface. For the effective removal of the contaminants and stable steering control of the autonomous mobile platform, the interaction force between the brush and the duct surface needs to be measured. However, it is not possible to achieve an accurate measurement of the contact force for the duct surface and brush, which has a nonlinear deformation characteristic. Therefore, in this study, a simple and robust controller has been proposed. This controller integrates the backstepping method with an I-PD controller for the robust platform control against irregular external forces on the cleaning brush. In addition, various trajectory tracking simulations have been conducted and the results present stable trajectory tracking of the mobile platform in air duct cleaning.

  15. Partitioning of Evapotranspiration Using a Stable Water Isotope Technique in a High Temperature Agricultural Production System

    Science.gov (United States)

    Lu, X.; Liang, L.; Wang, L.; Jenerette, D.; Grantz, D. A.

    2015-12-01

    Agricultural production in the hot and arid low desert systems of southern California relies heavily on irrigation. A better understanding of how much and to what extent the irrigation water is transpired by crops relative to being lost through evaporation will contribute to better management of increasingly limited agricultural water resources. In this study, we examined the evapotranspiration (ET) partitioning over a field of forage sorghum (S. bicolor) during a growing season with several irrigation cycles. In several field campaigns we used continuous measurements of near-surface variations in the stable isotopic composition of water vapor (δ2H). We employed custom built transparent chambers coupled with a laser-based isotope analyzer and used Keeling plot and mass balance methods for surface flux partitioning. The preliminary results show that δT is more enriched than δE in the early growing season, and becomes less enriched than δE later in the season as canopy cover increases. There is an increase in the contribution of transpiration to ET as (1) leaf area index increases, and (2) as soil surface moisture declines. These results are consistent with theory, and extend these measurements to an environment that experiences extreme soil surface temperatures. The data further support the use of chamber based methods with stable isotopic analysis for characterization of ET partitioning in challenging field environments.

  16. Surface decontamination

    International Nuclear Information System (INIS)

    Silva, S. da; Teixeira, M.V.

    1986-06-01

    The general methods of surface decontamination used in laboratory and others nuclear installations areas, as well as the procedures for handling radioactive materials and surfaces of work are presented. Some methods for decontamination of body external parts are mentioned. The medical supervision and assistance are required for internal or external contamination involving or not lesion in persons. From this medical radiation protection decontamination procedures are determined. (M.C.K.) [pt

  17. Transport-Statistics and Energetics in Stable-Continuous Turbulence

    Science.gov (United States)

    Bergmann, Juan Carlos

    2010-05-01

    Continuous turbulence (CT) is the basic condition for relatively simple quantifications in stable stratification, e.g., Monin-Obukhov (MO) theory. From a statistical point of view, CT guarantees spatial and temporal randomness of variables, which is an important basis for quantitative considerations. Also, the entire concept of an exchange (diffusion) coefficient can only be applied under randomness conditions. Thus, there is equivalence of diffusion and random walk (RW), as demonstrated by Einstein in his annum mirabilis 1905. In stable stratification, the limitation of vertical displacements by surface-distance is supplemented by buoyancy-effects. The latter can be quantified by the energy balance of vertical displacements: Vertical turbulent kinetic energy (VTKE) is transformed to potential energy (PE). This transformation happens in combination with deflection of vertical motion by the random interactions of fluid parcels that also happen in neutrality. By application of the RW-definition of the diffusion coefficient it is possible to implement the buoyancy-related limitations (energy balance) to the determination of the exchange coefficient, most simply in the stable limit z >> L. Determination of the exchange coefficient in its turn automatically yields the profile-constant. Depending on a dimensionless turbulence parameter (ratio of average-square vertical velocity to squared friction velocity), the most probable approximate value of the profile-constant is 2.9. This value is within the traditional experimental range (2.0 to 12) but clearly below the ‘community's' favourite range of 5 to 6. Due to an involved approximation, the value of 2.9 is systematically over-estimated, so that the RW result is not compatible with larger values. The applied energy-balance formulation necessarily has to reflect the energetic processes. In the usual concept of energetics, shear-produced TKE is absorbed by the buoyancy flux (BF) and -BF acts as source of turbulent

  18. Stable isotope composition of atmospheric carbon monoxide. A modelling study

    International Nuclear Information System (INIS)

    Gromov, Sergey S.

    2014-01-01

    This study aims at an improved understanding of the stable carbon and oxygen isotope composition of the carbon monoxide (CO) in the global atmosphere by means of numerical simulations. At first, a new kinetic chemistry tagging technique for the most complete parameterisation of isotope effects has been introduced into the Modular Earth Submodel System (MESSy) framework. Incorporated into the ECHAM/MESSy Atmospheric Chemistry (EMAC) general circulation model, an explicit treatment of the isotope effects on the global scale is now possible. The expanded model system has been applied to simulate the chemical system containing up to five isotopologues of all carbon- and oxygen-bearing species, which ultimately determine the δ 13 C, δ 18 O and Δ 17 O isotopic signatures of atmospheric CO. As model input, a new stable isotope-inclusive emission inventory for the relevant trace gases has been compiled. The uncertainties of the emission estimates and of the resulting simulated mixing and isotope ratios have been analysed. The simulated CO mixing and stable isotope ratios have been compared to in-situ measurements from ground-based observatories and from the civil-aircraft-mounted CARIBIC-1 measurement platform. The systematically underestimated 13 CO/ 12 CO ratios of earlier, simplified modelling studies can now be partly explained. The EMAC simulations do not support the inferences of those studies, which suggest for CO a reduced input of the highly depleted in 13 C methane oxidation source. In particular, a high average yield of 0.94 CO per reacted methane (CH 4 ) molecule is simulated in the troposphere, to a large extent due to the competition between the deposition and convective transport processes affecting the CH 4 to CO reaction chain intermediates. None of the other factors, assumed or disregarded in previous studies, however hypothesised to have the potential in enriching tropospheric CO in 13 C, were found significant when explicitly simulated. The

  19. Surface phonons

    CERN Document Server

    Wette, Frederik

    1991-01-01

    In recent years substantial progress has been made in the detection of surface phonons owing to considerable improvements in inelastic rare gas scattering tech­ niques and electron energy loss spectroscopy. With these methods it has become possible to measure surface vibrations in a wide energy range for all wave vectors in the two-dimensional Brillouin zone and thus to deduce the complete surface phonon dispersion curves. Inelastic atomic beam scattering and electron energy loss spectroscopy have started to play a role in the study of surface phonons similar to the one played by inelastic neutron scattering in the investigation of bulk phonons in the last thirty years. Detailed comparison between experimen­ tal results and theoretical studies of inelastic surface scattering and of surface phonons has now become feasible. It is therefore possible to test and to improve the details of interaction models which have been worked out theoretically in the last few decades. At this point we felt that a concise, co...

  20. Stable isotope methodology and its application to nutrition and gastroenterology

    International Nuclear Information System (INIS)

    Klein, P.D.; Hachey, D.L.; Wong, W.W.; Abrams, S.A.

    1993-01-01

    This report describes the activities of the Stable Isotope Laboratory in its function as a core resource facility for stable isotope applications in human nutrition research. Three aspects are covered: Training of visitors, assessment of new instrumentation, and development of new methodology. The research achievements of the laboratory are indicated in the publications that appeared during this period. (author). 23 refs

  1. Visual and olfactory enhancement of stable fly trapping.

    Science.gov (United States)

    Zhu, Junwei J; Zhang, Qing-He; Taylor, David B; Friesen, Kristina A

    2016-09-01

    Stable flies are considered to be one of the major blood-feeding pests in the US livestock industry, causing losses running into billions of dollars annually. Adult stable flies are highly attracted to Alsynite traps; however, Alsynite is becoming increasingly difficult to obtain and is expensive. Here, we report on the development of a less expensive and more efficacious trap based upon a white panel with the option to add visual and olfactory stimuli for enhanced stable fly trapping. White panel traps caught twice as many stable flies than Alsynite traps. Baiting the traps with synthetic manure volatiles increased catches 2-3-fold. Electroretinographic recordings of stable flies showed strong peaks of visual sensitivities occurring at 330-360 nm, 460-525 nm and 605-635 nm. A laboratory study indicated that young stable flies are more responsive to white, whereas gravid females prefer blue; in the field, white traps caught more stable flies than patterned or blue-black traps. Stable fly control can be enhanced by developing more efficient trapping systems with added visual and olfactory stimuli. Published 2015. This article is a U.S. Government work and is in the public domain in the USA. Published 2015. This article is a U.S. Government work and is in the public domain in the USA.

  2. Stable isotope geochemistry. 3. rev. and enl. ed.

    International Nuclear Information System (INIS)

    Hoefs, J.

    1987-01-01

    Stable Isotope Geochemistry is an authoritative book comprising theoretical and experimental principles; surveying important fractionation mechanisms affecting the most important elements; discussing the natural variations of geologically important reservoirs. This updated 3rd edition, with a completely rewritten and extended main part, contains two new chapters on stable isotope composition of mantle material and on changes of the ocean during the geological past. (orig.)

  3. DFT computations of the lattice constant, stable atomic structure and ...

    African Journals Online (AJOL)

    This paper presents the most stable atomic structure and lattice constant of Fullerenes (C60). FHI-aims DFT code was used to predict the stable structure and the computational lattice constant of C60. These were compared with known experimental structures and lattice constants of C60. The results obtained showed that ...

  4. Saturate hydraulic conductivity, water stable aggregates and soil ...

    African Journals Online (AJOL)

    Saturate hydraulic conductivity, water stable aggregates and soil organic matter in a sandy-loam soil in Ikwuano lga of Abia state. ... carbon content of the soil. . Keywords: Toposequence, Water stable aggregates, Saturated hydraulic conductivity, Organic carbon, Slope position. Agro-Science Vol. 4 (1) 2005: pp. 34-37.

  5. Optimization for getting stable plasma initiation in JT-60

    International Nuclear Information System (INIS)

    Yoshino, Ryuji; Neyatani, Yuzuru; Abe, T.

    1988-06-01

    This paper analyses the plasma current build-up just after the breakdown, and investigates the method for obtaining more stable plasma initiation with reduced Volt-second consumption. Control of the amount of particles contained in the wall is necessary for getting the optimum plasma density just after the breakdown, and is essential for obtaining the stable current build-up. (author)

  6. Improved Atmospheric Stable Boundary Layer Formulations for Navy Seasonal Forecasting

    Science.gov (United States)

    2012-09-30

    Long-term goals are to develop methods, descriptions and parameterizations that will alleviate long-standing problems in basically all large-scale numerical atmospheric models in dealing with statically stable and/or very stable conditions, and to implement these for Navy extended forecasting

  7. Fitted-Stable Finite Difference Method for Singularly Perturbed Two ...

    African Journals Online (AJOL)

    A fitted-stable central difference method is presented for solving singularly perturbed two point boundary value problems with the boundary layer at one end (left or right) of the interval. A fitting factor is introduced in second order stable central difference scheme (SCD Method) and its value is obtained using the theory of ...

  8. Stable isotope methods in biological and ecological studies of arthropods

    NARCIS (Netherlands)

    Hood-Nowotny, R.C.; Knols, B.G.J.

    2007-01-01

    This is an eclectic review and analysis of contemporary and promising stable isotope methodologies to study the biology and ecology of arthropods. It is augmented with literature from other disciplines, indicative of the potential for knowledge transfer. It is demonstrated that stable isotopes can

  9. Formulation of stable protein powders by supercritical fluid drying

    NARCIS (Netherlands)

    Jovanović, N.

    2007-01-01

    Protein pharmaceuticals are potent drugs for the treatment of several chronic and life-threatening diseases. However, the complex and sensitive nature of protein molecules requires special attention in the development of stable dosage forms. Developing stable aqueous protein formulations is often a

  10. Enhanced trapping of stable flies via olfactory and visual cues

    Science.gov (United States)

    Adult stable flies are highly attracted to the so-called Alsynite cylinder trap; however this trap is expensive. Here we report the development of a cheaper and better white panel trap with options of adding visual and olfactory stimuli for enhanced stable fly trapping. The white panel trap attracte...

  11. Unraveling of permafrost hydrological variabilities on Central Qinghai-Tibet Plateau using stable isotopic technique.

    Science.gov (United States)

    Yang, Yuzhong; Wu, Qingbai; Hou, Yandong; Zhang, Zhongqiong; Zhan, Jing; Gao, Siru; Jin, Huijun

    2017-12-15

    Permafrost degradation on the Qinghai-Tibet Plateau (QTP) will substantially alter the surface runoff discharge and generation, which changes the recharge processes and influences the hydrological cycle on the QTP. Hydrological connections between different water bodies and the influence of thawing permafrost (ground ice) are not well understood on the QTP. This study applied water stable isotopic method to investigate the permafrost hydrological variabilities in Beiluhe Basin (BLB) on Central QTP. Isotopic variations of precipitation, river flow, thermokarst lake, and near-surface ground ice were identified to figure out the moisture source of them, and to elaborate the hydrological connections in permafrost region. Results suggested that isotopic seasonalities in precipitation is evident, it is showing more positive values in summer seasons, and negative values in winter seasons. Stable isotopes of river flow are mainly distributed in the range of precipitation which is indicative of important replenishment from precipitation. δ 18 O, δD of thermokarst lakes are more positive than precipitation, indicating of basin-scale evaporation of lake water. Comparison of δ I values in different water bodies shows that hydrology of thermokarst lakes was related to thawing of permafrost (ground ice) and precipitation. Near-surface ground ice in BLB exhibits different isotopic characteristics, and generates a special δD-δ 18 O relationship (freezing line): δD=5.81δ 18 O-23.02, which reflects typical freezing of liquid water. From isotopic analysis, it is inferred that near-surface ground ice was mainly recharged by precipitation and active layer water. Stable isotopic and conceptual model is suggestive of striking hydrological connections between precipitation, river flow, thermokarst lake, and ground ice under degrading permafrost. This research provides fundamental comprehensions into the hydrological processes in permafrost regions on QTP, which should be considered

  12. Surface Pourbaix diagrams and oxygen reduction activity of Pt, Ag and Ni(111) surfaces studied by DFT

    DEFF Research Database (Denmark)

    Hansen, Heine Anton; Rossmeisl, Jan; Nørskov, Jens Kehlet

    2008-01-01

    The electrochemical most stable surface structures is investigated as function of pH and potential for Pt, Ag and Ni based on DFT calculations and constructed surface Pourbaix diagrams. It is also explained why metals such as Ag and Ni may be used successfully in alkaline fuel cells but not in ac......The electrochemical most stable surface structures is investigated as function of pH and potential for Pt, Ag and Ni based on DFT calculations and constructed surface Pourbaix diagrams. It is also explained why metals such as Ag and Ni may be used successfully in alkaline fuel cells...

  13. STUDY OF STABLE NITROGEN FORMS IN NATURAL SURFACE WATERS IN THE PRESENCE OF MINERAL SUBSTRATES

    Directory of Open Access Journals (Sweden)

    Petru Spataru

    2015-12-01

    Full Text Available The influence of substrates on the oxidation of reduced toxic forms of nitrogen in river water was investigated by laboratory modelling. Granite and expended clay accelerate the oxidation of ammonium and nitrite ions from 2 to 4 times. The presence of calcium carbonate in water hinders the oxidation of nitrogen in the polluted water.

  14. Surface-Initiated Polymerization by Means of Novel, Stable, Non-Ester-Based Radical Initiator

    Czech Academy of Sciences Publication Activity Database

    Bain, E. D.; Dawes, K.; Ozcam, A. E.; Hu, X.; Gorman, C. B.; Šrogl, Jiří; Genzer, J.

    2012-01-01

    Roč. 45, č. 9 (2012), s. 3802-3815 ISSN 0024-9297 Institutional support: RVO:61388963 Keywords : self -assembled monolayers * poly(acrylic acid) brushes * thermoresponsive polymer Subject RIV: CC - Organic Chemistry Impact factor: 5.521, year: 2012

  15. Colloidally stable surface-modified iron oxide nanoparticles: preparation, characterization and anti-tumor activity

    Czech Academy of Sciences Publication Activity Database

    Macková, Hana; Horák, Daniel; Donchenko, G. V.; Andriyaka, V. I.; Palyvoda, O. M.; Chernishov, V. I.; Chekhun, V. F.; Todor, I. N.; Kuzmenko, O. I.

    2015-01-01

    Roč. 380, 15 April (2015), s. 125-131 ISSN 0304-8853. [International Conference on the Scientific and Clinical Applications of Magnetic Carriers /10./. Dresden, 10.06.2014-14.06.2014] R&D Projects: GA MŠk 7E12054; GA MŠk(CZ) LH14318; GA MŠk(CZ) ED1.1.00/02.0109 EU Projects: European Commission(XE) 259796 - DIATOOLS Institutional support: RVO:61389013 Keywords : iron oxide nanoparticle * poly(N,N-dimethylacrylamide-co-acrylic acid) * protein oxidation Subject RIV: CD - Macromolecular Chemistry Impact factor: 2.357, year: 2015

  16. Experimental Study of Stable Surfaces for Anti-Slug Control in Multi-phase Flow

    DEFF Research Database (Denmark)

    Pedersen, Simon; Løhndorf, Petar Durdevic; Yang, Zhenyu

    2014-01-01

    -phase flow dynamics, the slug can be avoided or eliminated by proper facility design and control of operational conditions. Based on a testing facility which can emulate a pipeline-riser or a gas-lifted production well in a scaled-down manner, this paper experimentally studies the correlations of key...

  17. Experimental Study of Stable Surfaces for Anti-Slug Control in Multi-phase Flow

    DEFF Research Database (Denmark)

    Pedersen, Simon; Løhndorf, Petar Durdevic; Stampe, Kasper

    2016-01-01

    , the slug can be avoided or eliminated by proper facility design or control of operational conditions. Based on a testing facility which can emulate a pipeline-riser or a gas-lifted production well in a scaled-down manner, this paper experimentally studies the correlations of key operational parameters...

  18. Space Environmentally Stable Polyimides and Copolyimides

    Science.gov (United States)

    Watson, Kent A.; Connell, John W.

    2000-01-01

    Polyimides with a unique combination of properties including low color in thin films, atomic oxygen (AO), ultra-violet (UV) radiation resistance, solubility in organic solvents in the imide form, high glass transition (T(sub g)) temperatures and high thermal stability have been prepared and characterized. The polymers were prepared by reacting a novel aromatic diamine with aromatic dianhydrides in a polar aprotic solvent. The solubility of the polymers in the imide form as well as the color density of thin films were dependent upon the chemical structure of the dianhydride. Several thin films (25-50 mm thick) prepared by solution casting of amide acid or imide solutions exhibited very low color and high optical transparency (approximately 90%) as determined by UV/visible spectroscopy. The polymers exhibited T(sub g)s >200 C depending upon the structure of the dianhydride and temperatures of 5% weight loss approximately 500C in air as determined by dynamic thermogravimetric analysis. Thin films coated with silver/inconel were exposed to a high fluence of AO and 1000 equivalent solar hours of UV radiation. The effects of these exposures on optical properties were minor. These space environmentally durable polymers are potentially useful in a variety of applications on spacecraft such as thin film membranes on antennas, second-surface mirrors, thermal/optical coatings and multi-layer thermal insulation (MLI) blanket materials. The chemistry, physical and mechanical properties of the polymers as well as their responses to AO and UV exposure will be discussed.

  19. Palladium - silicon nanocomposites as a stable electrocatalyst for hydrogen evolution reaction.

    Science.gov (United States)

    Yin, Kui; Cheng, Yafei; Jiang, Binbin; Liao, Fan; Shao, Mingwang

    2018-07-15

    Pd nanoparticles grown in-situ on the surface of silicon nanowires (Pd-SiNW nanocomposites) were employed as electrocatalysts in hydrogen evolution reaction and exhibited satisfactory catalytic performance. Here, SiNWs served as the carrier with vast surface area. It is interesting to note that Pd-SiNW nanocomposites were more stable for hydrogen evolution reaction than the commercial Pt/C catalysts, which might be attributed to the three-dimensional crisscrossing structure of the composites and the strong interaction between Pd and Si. The strong interaction is due to the low lattice mismatch in the epitaxial growth of Pd particles on the surface of Si. Such special structure and interaction help to tightly hold Pd nanoparticles, which could avoid the loss of catalysts and keep the catalyst from being agglomerated and growing large. Copyright © 2018 Elsevier Inc. All rights reserved.

  20. Stable dispersion of nanodiamonds in oil and their tribological properties as lubricant additives

    Science.gov (United States)

    Lee, Gyoung-Ja; Park, Jin-Ju; Lee, Min-Ku; Rhee, Chang Kyu

    2017-09-01

    Nanodiamonds (NDs) are innovative additives when a combination of mechanical, thermal, tribological, and dielectric properties are required. In this study, a surface modification with oleic acid (OA) is developed for the deaggregation and prolonged dispersion of NDs in oil, and the effect of the NDs as lubricant additives on the tribological properties of a steel substrate is investigated. The OA renders the ND surface hydrophobic and decreases the average particle size from 268.6 to 20.1 nm. The OA-treated NDs exhibit very stable dispersion in oil even after more than 10 days, compared with the untreated NDs. From the analyses of the friction coefficient, wear loss, and worn surfaces using a ball-on-disk wear test, it is concluded that a 0.05 wt% addition of OA-treated NDs in oil lubricant provides excellent friction and anti-wear properties with the friction coefficient being reduced by 23%.

  1. Relative intensity noise of temperature-stable, energy-efficient 980 nm VCSELs

    Directory of Open Access Journals (Sweden)

    Hui Li

    2017-02-01

    Full Text Available The relative intensity noise (RIN of temperature-stable, energy-efficient oxide confined vertical-cavity surface-emitting lasers (VCSELs have been investigated. Low energy consumption data transmission is achieved by using small oxide-aperture diameter VCSELs biased at small currents. We demonstrate that energy efficiency is not in conflict with our VCSELs’ RIN characteristics. The experimental results indicate that small oxide-aperture diameter VCSELs, which are most suitable for energy-efficient, temperature-stable operation, exhibit lower laser RIN due to less mode competition inside the smaller optical cavity volume. Our energy-efficient VCSELs fulfill the RIN requirements of the 32G Fibre Channel standard.

  2. Stable Covalent Organic Frameworks for Exceptional Mercury Removal from Aqueous Solutions.

    Science.gov (United States)

    Huang, Ning; Zhai, Lipeng; Xu, Hong; Jiang, Donglin

    2017-02-15

    The pre-designable porous structures found in covalent organic frameworks (COFs) render them attractive as a molecular platform for addressing environmental issues such as removal of toxic heavy metal ions from water. However, a rational structural design of COFs in this aspect has not been explored. Here we report the rational design of stable COFs for Hg(II) removal through elaborate structural design and control over skeleton, pore size, and pore walls. The resulting framework is stable under strong acid and base conditions, possesses high surface area, has large mesopores, and contains dense sulfide functional termini on the pore walls. These structural features work together in removing Hg(II) from water and achieve a benchmark system that combines capacity, efficiency, effectivity, applicability, selectivity, and reusability. These results suggest that COFs offer a powerful platform for tailor-made structural design to cope with various types of pollution.

  3. The evolution of stable magnetic fields in stars: an analytical approach

    Science.gov (United States)

    Mestel, Leon; Moss, David

    2010-07-01

    The absence of a rigorous proof of the existence of dynamically stable, large-scale magnetic fields in radiative stars has been for many years a missing element in the fossil field theory for the magnetic Ap/Bp stars. Recent numerical simulations, by Braithwaite & Spruit and Braithwaite & Nordlund, have largely filled this gap, demonstrating convincingly that coherent global scale fields can survive for times of the order of the main-sequence lifetimes of A stars. These dynamically stable configurations take the form of magnetic tori, with linked poloidal and toroidal fields, that slowly rise towards the stellar surface. This paper studies a simple analytical model of such a torus, designed to elucidate the physical processes that govern its evolution. It is found that one-dimensional numerical calculations reproduce some key features of the numerical simulations, with radiative heat transfer, Archimedes' principle, Lorentz force and Ohmic decay all playing significant roles.

  4. Preparation and thermal properties of form stable paraffin phase change material encapsulation

    International Nuclear Information System (INIS)

    Liu Xing; Liu Hongyan; Wang Shujun; Zhang Lu; Cheng Hua

    2006-01-01

    Paraffin waxes are cheap and have moderate thermal energy storage density but low thermal conductivity and, hence, require large surface area to be used in energy storage. Form stable paraffin phase change materials (PCM) in which paraffin serves as a latent heat storage material and polyolefins act as a supporting material, because of paraffin leakage, are required to be improved. The form stable paraffin PCM in the present paper was encapsulated in an inorganic silica gel polymer successfully by in situ polymerization. The differential scanning calorimeter (DSC) was used to measure its thermal properties. At the same time, the Washburn equation, which measures the wetting properties of powder materials, was used to test the hydrophilic-lipophilic properties of the PCMs. The result indicated that the enthalpy of the microencapsulated PCMs was reduced little, while their hydrophilic properties were enhanced largely

  5. Importance of surface structure on dissolution of fluorite: Implications for surface dynamics and dissolution rates

    Science.gov (United States)

    Godinho, J. R. A.; Piazolo, S.; Balic-Zunic, T.

    2014-02-01

    Dissolution rates are usually calculated as a function of surface area, which is assumed to remain constant ignoring the changes occurring on the surface during dissolution. Here we present a study of how topography of natural fluorite surfaces with different orientation changes during up to 3200 h of dissolution. Results are analyzed in terms of changes in surface area, surface reactivity and dissolution rates. All surfaces studied present fast changes in topography during the initial 200 h of dissolution. The controlling factors that cause the development of topography are the stability of the step edges forming the initial surface and its inclination to the closest stable planes, which are specific for each surface orientation. During an initial dissolution regime dissolution rates decrease significantly, even though the total surface area increases. During a second dissolution regime, some surfaces continue to present significant changes in topography, while for others the topography tends to remain approximately constant. The observed variation of dissolution rates are attributed to a decrease of the density of step edges on the surface and the continuous increase in exposure of more stable surfaces. Calculations of dissolution rates, which assume that dissolution rates are directly proportional to surface area, are not valid for the type of surfaces studied. Instead, to develop accurate kinetic dissolution models and more realistic stochastic dissolution simulations the surface reactivity, determined by the relative stability of the planes and type of edges that constitute a surface needs to be considered. Significant differences between dissolution rates calculated based on surface area alone, and based on surface reactivity are expected for materials with the fluorite structure.

  6. The unusual properties of beryllium surfaces

    International Nuclear Information System (INIS)

    Stumpf, R.; Hannon, J.B.

    1994-01-01

    Be is a ''marginal metal.'' The stable phase, hcp-Be, has a low Fermi-level density of states and very anisotropic structural and elastic properties, similar to a semiconductor's. At the Be(0001) surface, surface states drastically increase the Fermi-level density of states. The different nature of bonding in bulk-Be and at the Be(0001) surface explains the large outward relaxation. The presence of surface states causes large surface core-level shifts by inducing a higher electrostatic potential in the surface layers and by improving the screening at the surface. The authors experimental and theoretical investigations of atomic vibrations at the Be(0001) surface demonstrate clearly that Be screening of atomic motion by the surface states makes the surface phonon dispersion fundamentally different from that of the bulk. Properties of Be(0001) are so different from those of the bulk that the surface can be considered a new ''phase'' of beryllium with unique electronic and structural characteristics. For comparison they also study Be(11 bar 20), a very open surface without important surface states. Be(11 bar 20) is the only clean s-p metal surface known to reconstruct (1 x 3 missing row reconstruction)

  7. Stable isotopes for improving human nutrition

    International Nuclear Information System (INIS)

    Uauy, Ricardo

    2001-01-01

    recent FAO review of nutrition programs in 19 Latin American countries found that over 20 percent of the population - approximately 83 million people out of an estimated 414 million in the study countries - receives some level of benefits in nutrition-related programs. The allocation of limited national and international assistance resources for these activities in the region is on the order of several billion dollars annually. Undoubtedly these programs are influencing child growth. Significant reductions in underweight and wasting have occurred; but stunting has been more resistant to change. In this setting providing food supplements may be beneficial for some while it may be detrimental for others. The definition of who should benefit from the programs and what is the right combination of nutrients/foods, education, and lifestyle interventions that is required to optimise nutrition and health at each stage of the life cycle is a truly complex problem. This demands the use of the best scientific tools to define who should benefit, what should done and measured as an outcome, how programs should be evaluated, when programs should be expanded, and when they should be stopped. Isotopic and nuclear techniques are tools, not solutions. This presentation will serve to demonstrate how isotopes can contribute to refining nutrition interventions and their impact on public health. Isotopic methods can shorten the time needed to evaluate impact, because they provide sensitive measurements of biological effects. They are faster than traditional methods such as anthropometry for detecting changes in growth and body composition. Micronutrient malnutrition, and especially the bioavailability of vitamins and minerals from traditional foods, are not well evaluated using routine biochemical methods. Radioisotopes have been used successfully in the past. But recent developments in stable isotope techniques offer unique advantages for the design and evaluation of programmes that address

  8. Chromium Stable Isotope Fractionation - An Indicator of Hexavalent Chromium Reduction.

    Science.gov (United States)

    Ellis, A.; Johnson, T. M.; Bullen, T. D.

    2001-12-01

    Chromium is a common anthropogenic contaminant in surface water and ground water, and is also of interest in oceanography. It is redox-active; the two common valences in natural waters are Cr(VI), which is highly soluble and toxic, and Cr(III), which is relatively insoluble. Redox reactions thus control Cr mobility in aqueous solutions, and reduction of Cr(VI) to Cr(III) is the most important reaction controlling attenuation of Cr in groundwater. Our results show that Cr(VI) reduction favors the lighter isotopes and leads to enrichment of heavier isotopes in the remaining Cr(VI). Cr isotope measurements thus show great promise as indicators of Cr(VI) reduction. We report here the first measurements of the magnitude of Cr isotope fractionation during Cr(VI) reduction and variations in δ 53Cr values obtained from three contaminated sites. Experiments were conducted to measure Cr isotope fractionation during Cr(VI) reduction by suspensions of magnetite and unamended sediments from a local pond, Urbana, IL and San Francisco Estuary near Martinez, CA. Suspensions were incubated anaerobically with constant shaking, and complete Cr(VI) reduction occurred within a few days. Cr(VI) from intermediate time points in the experiments was purified via ion exchange and 53Cr/52Cr ratios were measured via TIMS with a double isotope spike. The instantaneous per mil fractionation, ɛ , was calculated assuming a Rayleigh fractionation model. The ɛ for Cr(VI) reduction on magnetite surfaces yielded a fractionation of -3.5 ‰ . The ɛ values for the pond and estuary sediments were -3.5 ‰ and -3.3 ‰ respectively. The size of this Cr isotope fractionation is encouraging, as current precision is 0.2 \\permil. δ 53Cr values in dissolved Cr(VI) from three contaminated sites range from 1.1 ‰ to 5.8 ‰ , suggesting that Cr(VI) reduction has occurred and has induced isotopic fractionation in these settings. δ 53Cr values measured from Cr(VI) in plating baths show little or no

  9. Surface microhardening by ion implantation

    International Nuclear Information System (INIS)

    Singh, Amarjit

    1986-01-01

    The paper discusses the process and the underlying mechanism of surface microhardening by implanting suitable energetic ions in materials like 4145 steel, 304 stainless steel, aluminium and its 2024-T351 alloy. It has been observed that boron and nitrogen implantation in materials like 4145 steel and 304 stainless steel can produce a significant increase in surface hardness. Moreover the increase can be further enhanced with suitable overlay coatings such as aluminium (Al), Titanium (Ti) and carbon (C). The surface hardening due to implantation is attributed to precipitation hardening or the formation of stable/metastable phase or both. The effect of lithium implantation in aluminium and its alloy on microhardness with increasing ion dose and ion beam energy is also discussed. (author)

  10. Assessing anthropogenic pressures on groundwater using stable OH isotopes: perspectives and issues

    Science.gov (United States)

    Negrel, Philippe; Ollivier, Patrick; Flehoc, Christine; Hube, Daniel

    2015-04-01

    Large developments of isotope hydrogeology were done and well-established techniques mainly applying stable isotopes of the water molecule (hydrogen and oxygen) are now used largely to trace water provenance but also recharge processes. New methods allow the use of non-traditional isotopes (metals, compound specific stable isotope analysis CSIA...) to trace anthropogenic pressures in surface- and groundwater. Groundwater contamination in large industrial sites may come from several origins such as leakage from tanks during the production process of chemical products, liquid storage tanks, solid end product or past accumulated product in soil which is released over the time. The understanding of the origin and the further evolution of the chemical contamination in groundwater in an industrial site issued from past or current industrial activities is essential for the industrial companies regarding their environmental policies. The objective of this study was to use with an innovative way the stable isotopes of the water molecule as a low cost tool to trace pollutant plumes in groundwater and help to a better management of contaminated industrial sites. We present data on stable isotopes O and H in an European region where electrochemistry plants occur. For confidentiality purposes, the sites remain anonymous. Present day industrial activities have a direct impact on the groundwater over the site and migration of the contaminant(s) plume out of the site is supposed. We first characterize the natural groundwater background through the O-H characterization of surface water, lakes, thermal waters and regional shallow aquifers. High and low altitude recharge can be demonstrated in the area. Secondly, we used the stable isotope of the water molecule to trace over the site the impact of the Cl-rich liquor manufacturing process. Large deuterium enrichment was evidenced in the groundwater and the high values can be related to a direct contamination of the groundwater through

  11. Stable carbon isotope analysis of fluvial sediment fluxes over two contrasting C(4) -C(3) semi-arid vegetation transitions.

    Science.gov (United States)

    Puttock, Alan; Dungait, Jennifer A J; Bol, Roland; Dixon, Elizabeth R; Macleod, Christopher J A; Brazier, Richard E

    2012-10-30

    Globally, many drylands are experiencing the encroachment of woody vegetation into grasslands. These changes in ecosystem structure and processes can result in increased sediment and nutrient fluxes due to fluvial erosion. As these changes are often accompanied by a shift from C(4) to C(3) vegetation with characteristic δ(13) C values, stable isotope analysis provides a promising mechanism for tracing these fluxes. Input vegetation, surface sediment and fluvially eroded sediment samples were collected across two contrasting C(4) -C(3) dryland vegetation transitions in New Mexico, USA. Isotope ratio mass spectrometric analyses were performed using a Carlo Erba NA2000 analyser interfaced to a SerCon 20-22 isotope ratio mass spectrometer to determine bulk δ(13) C values. Stable isotope analyses of contemporary input vegetation and surface sediments over the monitored transitions showed significant differences (p fluvially eroded sediment from each of the sites, with no significant variation between surface sediment and eroded sediment values. The significant differences in bulk δ(13) C values between sites were dependent on vegetation input. Importantly, these values were robustly expressed in fluvially eroded sediments, suggesting that stable isotope analysis is suitable for tracing sediment fluxes. Due to the prevalent nature of these dryland vegetation transitions in the USA and globally, further development of stable isotope ratio mass spectrometry has provided a valuable tool for enhanced understanding of functional changes in these ecosystems. Copyright © 2012 John Wiley & Sons, Ltd.

  12. The use of stable isotopes in drug metabolism studies.

    Science.gov (United States)

    Abramson, F P

    2001-06-01

    Although there is a long history of stable isotopes use in drug metabolism research, it is appropriate to evaluate them in pregnancy drug studies in which safety takes highest priority. It is well established through a number of human and animal experiments that stable isotopes themselves rarely generate additional toxicities beyond the molecules to which they are attached. For the analysis of stable isotopes involved in metabolism studies, mass spectrometry plays the predominant role. Several mass spectrometry-based techniques now exist that enable the selective quantitative detection of stable isotopes with better sensitivity and better retention of chromatographic resolution than do in-line radioactivity monitors for 14C. Even mass balance studies can be performed by using stable isotopes, a type of experiment that still predominantly uses radioisotopes. Some of the newest developments in the use of stable isotopes involve biopolymers, in which fully isotope-labeled species can be generated from cells grown in isotopically labeled growth media. Having shown safety, sensitivity, specificity, and versatility, stable isotopes should play an important role in drug metabolism studies in pregnancy.

  13. Surfacing Moves

    DEFF Research Database (Denmark)

    Lutz, Peter

    2013-01-01

    such as schedules, machines, and aging bodies. To this end, the article also experiments with ‘surfacing’ as an ethnographic heuristic for figuring these different ‘spatial-timings’. The article concludes that surfacing matters not only in senior home care but also in the field-desks of ethnographic analysis....

  14. Attack surfaces

    DEFF Research Database (Denmark)

    Gruschka, Nils; Jensen, Meiko

    2010-01-01

    The new paradigm of cloud computing poses severe security risks to its adopters. In order to cope with these risks, appropriate taxonomies and classification criteria for attacks on cloud computing are required. In this work-in-progress paper we present one such taxonomy based on the notion...... of attack surfaces of the cloud computing scenario participants....

  15. A Model Describing Stable Coherent Synchrotron Radiation in Storage Rings

    International Nuclear Information System (INIS)

    Sannibale, F.

    2004-01-01

    We present a model describing high power stable broadband coherent synchrotron radiation (CSR) in the terahertz frequency region in an electron storage ring. The model includes distortion of bunch shape from the synchrotron radiation (SR), which enhances higher frequency coherent emission, and limits to stable emission due to an instability excited by the SR wakefield. It gives a quantitative explanation of several features of the recent observations of CSR at the BESSY II storage ring. We also use this model to optimize the performance of a source for stable CSR emission

  16. A model describing stable coherent synchrotron radiation in storage rings

    International Nuclear Information System (INIS)

    Sannibale, F.; Byrd, J.M.; Loftsdottir, A.; Venturini, M.; Abo-Bakr, M.; Feikes, J.; Holldack, K.; Kuske, P.; Wuestefeld, G.; Huebers, H.-W.; Warnock, R.

    2004-01-01

    We present a model describing high power stable broadband coherent synchrotron radiation (CSR) in the terahertz frequency region in an electron storage ring. The model includes distortion of bunch shape from the synchrotron radiation (SR), which enhances higher frequency coherent emission, and limits to stable emission due to an instability excited by the SR wakefield. It gives a quantitative explanation of several features of the recent observations of CSR at the BESSY II storage ring. We also use this model to optimize the performance of a source for stable CSR emission

  17. Stable black phosphorus quantum dots for alkali PH sensor

    Science.gov (United States)

    Guo, Weilan; Song, Haizeng; Yan, Shancheng

    2018-01-01

    Black phosphorus, as a new two-dimensional material has been widely used in sensors, photovoltaic devices, etc. However, thin layered black phosphorus chemically degrades rapidly under ambient and aqueous conditions, which hinders the application of it in the chemical sensors. In this work, stable black phosphorus quantum dots (BPQDs) in solution are successfully synthesized by functionalization with 4-nitrobenzene-diazonium (4-NBD). The stable BPQDs are investigated by TEM, AFM, Raman, and UV-absorption. As a potential application, the stable BPQDs are used as sensors in alkali solution, which exhibit outstanding performance. Our work paves the way towards a new application with BPQDs in solution.

  18. Use of stable isotopes in human nutrition in Senegal

    International Nuclear Information System (INIS)

    2016-01-01

    In Senegal, the Laboratory of Nutrition of the Department of Animal Biology of the Faculty of Science and Technology of UCAD has been using stable isotopic techniques for nearly twenty years. Stable isotopes were applied to different target populations to measure milk production, exclusive breastfeeding, body composition, micronutrient bioavailability and total energy expenditure.The application of stable isotopic techniques in nutrition has contributed to advocacy for exclusive breastfeeding for up to 6 months in Senegal. It enabled government decision-makers to obtain essential information on the quality of foods needed for optimal effect during pregnancy and for infant growth and the results were reflected in the national policy on micronutrient supplementation.

  19. High-Order Entropy Stable Formulations for Computational Fluid Dynamics

    Science.gov (United States)

    Carpenter, Mark H.; Fisher, Travis C.

    2013-01-01

    A systematic approach is presented for developing entropy stable (SS) formulations of any order for the Navier-Stokes equations. These SS formulations discretely conserve mass, momentum, energy and satisfy a mathematical entropy inequality. They are valid for smooth as well as discontinuous flows provided sufficient dissipation is added at shocks and discontinuities. Entropy stable formulations exist for all diagonal norm, summation-by-parts (SBP) operators, including all centered finite-difference operators, Legendre collocation finite-element operators, and certain finite-volume operators. Examples are presented using various entropy stable formulations that demonstrate the current state-of-the-art of these schemes.

  20. Stable emulsions in extraction systems containing zirconium and silicic acid

    International Nuclear Information System (INIS)

    Sinegribova, O.A.; Chizhevskaya, S.V.; Kotenko, A.A.

    1989-01-01

    The effect of zirconium nitrate compound nature and silicic acid on the rate of emulsions stratification in extraction systems depending on the components concentration, solution acidity, its past history, is studied. It is stated that stable multinuclear zirconium compounds have an influence on formation of stable emulsions in systems containing silicic acid. On the basis of results of chemical analysis and properties of interphase precipitates, being part of stable emulsion, suppositions on mechanism of interaction of zirconium nitrate compounds with silicic acid β-form are made

  1. What can Fe stable isotopes tell us about magmas?

    DEFF Research Database (Denmark)

    Stausberg, Niklas

    The majority of the Earth’s crust is formed by magmas, and understanding their production and differentiation is important to interpret the geologic rock record. A powerful tool to investigate magmatic processes is the distribution of the stable isotopes of the major redox-sensitive element...... the differentiation of magmas from the perspective of Fe stable isotopes, integrated with petrology, by studying igneous rocks and their constituent phases (minerals and glasses) from the Bushveld Complex, South Africa, Thingmuli, Iceland, Pantelleria, Italy, and the Bishop Tuff, USA. The findings are interpreted...... and for more quantitative model of the magmatic processes producing enigmatic stable isotope compositions of rhyolitic and granite magmas....

  2. Total vertical sediment flux and PM10 emissions from disturbed Chihuahuan Desert Surfaces

    Science.gov (United States)

    Desert surfaces are typically stable and represent some of the oldest landforms on Earth. For surfaces without vegetation, the evolution of a desert pavements of gravel protects the surface from erosive forces and vegetation further protects the surface in arid and semi-arid rangelands. The suscep...

  3. Enhancement of plasmid-mediated stable gene expression by ...

    African Journals Online (AJOL)

    WPRE) is a possible enhancer of gene expression in mammalian cells that promotes efficient export of unspliced (RNA) into the cytoplasm, as has been proved in transient transfection. In this study, WPRE was evaluated for enhancing stable ...

  4. Stable isotope labeling strategy based on coding theory

    International Nuclear Information System (INIS)

    Kasai, Takuma; Koshiba, Seizo; Yokoyama, Jun; Kigawa, Takanori

    2015-01-01

    We describe a strategy for stable isotope-aided protein nuclear magnetic resonance (NMR) analysis, called stable isotope encoding. The basic idea of this strategy is that amino-acid selective labeling can be considered as “encoding and decoding” processes, in which the information of amino acid type is encoded by the stable isotope labeling ratio of the corresponding residue and it is decoded by analyzing NMR spectra. According to the idea, the strategy can diminish the required number of labelled samples by increasing information content per sample, enabling discrimination of 19 kinds of non-proline amino acids with only three labeled samples. The idea also enables this strategy to combine with information technologies, such as error detection by check digit, to improve the robustness of analyses with low quality data. Stable isotope encoding will facilitate NMR analyses of proteins under non-ideal conditions, such as those in large complex systems, with low-solubility, and in living cells

  5. Estimation of Time Varying Autoregressive Symmetric Alpha Stable

    Data.gov (United States)

    National Aeronautics and Space Administration — In this work, we present a novel method for modeling time-varying autoregressive impulsive signals driven by symmetric alpha stable distributions. The proposed...

  6. Quantification of stable isotope label in metabolites via mass spectrometry.

    Science.gov (United States)

    Huege, Jan; Goetze, Jan; Dethloff, Frederik; Junker, Bjoern; Kopka, Joachim

    2014-01-01

    Isotope labelling experiments with stable or radioactive isotopes have long been an integral part of biological and medical research. Labelling experiments led to the discovery of new metabolic pathways and made it possible to calculate the fluxes responsible for a metabolic phenotype, i.e., the qualitative and quantitative composition of metabolites in a biological system. Prerequisite for efficient isotope labelling experiments is a reliable and precise method to analyze the redistribution of isotope label in a metabolic network. Here we describe the use of the CORRECTOR program, which utilizes matrix calculations to correct mass spectral data from stable isotope labelling experiments for the distorting effect of naturally occurring stable isotopes (NOIs). CORRECTOR facilitates and speeds up the routine quantification of experimentally introduced isotope label from multiple mass spectral readouts, which are generated by routine metabolite profiling when combined with stable isotope labelling experiments.

  7. On the classification of complex vector bundles of stable rank

    Indian Academy of Sciences (India)

    , the tuples of cohomology classes on a compact, complex manifold, corresponding to the Chern classes of a complex vector bundle of stable rank. This classification becomes more effective on generalized flag manifolds, where the Lie ...

  8. Comparing Fr\\'echet and positive stable laws

    OpenAIRE

    Simon, Thomas

    2013-01-01

    Let ${\\bf L}$ be the unit exponential random variable and ${\\bf Z}_\\alpha$ the standard positive $\\alpha$-stable random variable. We prove that $\\{(1-\\alpha) \\alpha^{\\gamma_\\alpha} {\\bf Z}_\\alpha^{-\\gamma_\\alpha}, 0< \\alpha

  9. Thermally-Stable High Strain Deployable Structures, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — The proposed innovation is for the development of a thermally-stable composite made of carbon fibers and elastomeric resin. This combination of materials will allow...

  10. Using stable isotopes to determine seabird trophic relationships

    Science.gov (United States)

    Hobson, Keith A.; Piatt, John F.; Pitocchelli, Jay

    1994-01-01

    1. The stable isotopes of nitrogen (δ15N) and carbon (δ13C) were analysed in 22 species of marine birds from coastal waters of the northeast Pacific Ocean. Analyses confirm that stable nitrogen isotopes can predict seabird trophic positions.2. Based on δ15N analyses, seabird trophic-level inferences generally agree with those of conventional dietary studies, but suggest that lower trophic-level organisms are more important to several seabirds than was recognized previously.3. Stable-carbon isotope analysis may be a good indicator of inshore vs. offshore feeding preference.4. In general, stable-isotope analysis to determine trophic level offers many advantages over conventional dietary approaches since trophic inferences are based on time-integrated estimates of assimilated and not just ingested foods, and isotopic abundance represents a continuous variable that is amenable to statistical analysis.

  11. STABLE ISOTOPES IN ECOLOGICAL STUDIES: NEW DEVELOPMENTS IN MIXING MODELS

    Science.gov (United States)

    Stable isotopes are increasingly being used as tracers in ecological studies. One application uses isotopic ratios to quantify the proportional contributions of multiple sources to a mixture. Examples include food sources for animals, water sources for plants, pollution sources...

  12. Stable isotope views on ecosystem function: challenging or challenged?

    Science.gov (United States)

    Resco, Víctor; Querejeta, José I.; Ogle, Kiona; Voltas, Jordi; Sebastià, Maria-Teresa; Serrano-Ortiz, Penélope; Linares, Juan C.; Moreno-Gutiérrez, Cristina; Herrero, Asier; Carreira, José A.; Torres-Cañabate, Patricia; Valladares, Fernando

    2010-01-01

    Stable isotopes and their potential for detecting various and complex ecosystem processes are attracting an increasing number of scientists. Progress is challenging, particularly under global change scenarios, but some established views have been challenged. The IX meeting of the Spanish Association of Terrestrial Ecology (AAET, Úbeda, 18–22 October 2009) hosted a symposium on the ecology of stable isotopes where the linear mixing model approach of partitioning sinks and sources of carbon and water fluxes within an ecosystem was challenged, and new applications of stable isotopes for the study of plant interactions were evaluated. Discussion was also centred on the need for networks that monitor ecological processes using stable isotopes and key ideas for fostering future research with isotopes. PMID:20015858

  13. US ITASE Stable Isotope Data, Antarctica, Version 1

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set includes stable isotope measurements from snow pits, firn, and ice cores collected by the the US component of the International Trans-Antarctic...

  14. A stable isotopic study of the diet of Potamonautes sidneyi ...

    African Journals Online (AJOL)

    Natal, South Africa. Recent flood events in the iSimangaliso Wetland Park have allowed a substantial range expansion of this species, including previously hypersaline and desiccated areas. A stable isotope study was conducted to examine ...

  15. Stable isotopes: essential tools in biological and medical research

    Energy Technology Data Exchange (ETDEWEB)

    Klein, P. D.; Hachey, D. L.; Kreek, M. J.; Schoeller, D. A.

    1977-01-01

    Recent developments in the use of the stable isotopes, /sup 13/C, /sup 15/N, /sup 17/O, and /sup 18/O, as tracers in research studies in the fields of biology, medicine, pharmacology, and agriculture are briefly reviewed. (CH)

  16. Stable field emission from arrays of vertically aligned free-standing metallic nanowires

    DEFF Research Database (Denmark)

    Xavier, S.; Mátéfi-Tempfli, Stefan; Ferain, E.

    2008-01-01

    the nanowire surface is developed to explain this particular field emission behaviour. Finally, we present an in situ cleaning procedure by ion bombardment that collectively removes this oxide layer, leading to a stable and reproducible emission behaviour. After treatment, the emission current density is ∼1 m......We present a fully elaborated process to grow arrays of metallic nanowires with controlled geometry and density, based on electrochemical filling of nanopores in track-etched templates. Nanowire growth is performed at room temperature, atmospheric pressure and is compatible with low cost...

  17. Photoluminescence properties of thermally stable highly crystalline CdS nanoparticles

    Directory of Open Access Journals (Sweden)

    Sanjay R. Dhage

    2013-04-01

    Full Text Available Thermally stable and highly crystalline CdS nanoparticles were obtained via chemical bath method. The optical properties of CdS nanocrystals were characterized by ultraviolet-vis and photoluminescence spectroscopy. Improvement in the photoluminescence properties of the synthesized CdS nanocrystals was observed. This improvement is believed to be due to highly crystalline CdS nanoparticles which may reduce the local surface-trap states. The CdS nanoparticles were characterized by x-ray powder diffraction (XRD, thermo gravimetric analysis (TGA/DTA and transmission electron microscopy (TEM.

  18. Fabrication of stable, transparent and superhydrophobic nanocomposite films with polystyrene functionalized carbon nanotubes

    International Nuclear Information System (INIS)

    Yang Jin; Zhang Zhaozhu; Men Xuehu; Xu Xianghui

    2009-01-01

    Stable, transparent and superhydrophobic carbon nanotube (CNT) nanocomposite films were fabricated by one-step spray casting process using the polystyrene functionalized CNTs, which were prepared by 'living' free-radical polymerization and analyzed by means of infrared spectroscopy and thermal gravimetric analysis. The CNT film has a high water contact angle of 160 o and a sliding angle of less than 3 deg. The surface topography of the fabricated film was characterized by field emission scanning electron microscopy. The transparency of the CNT film was investigated by UV-vis spectroscopy. The result shows that the CNT film has light transmittance of about 78% in the visible light region.

  19. [Fractionation of hydrogen stable isotopes in the human body].

    Science.gov (United States)

    Siniak, Iu E; Grigor'ev, A I; Skuratov, V M; Ivanova, S M; Pokrovskiĭ, B G

    2006-01-01

    Fractionation of hydrogen stable isotopes was studied in 9 human subjects in a chamber with normal air pressure imitating a space cabin. Mass-spectrometry of isotopes in blood, urine, saliva, and potable water evidenced increases in the contents of heavy H isotope (deuterium) in the body liquids as compared with water. These results support one of the theories according to which the human organism eliminates heavy stable isotopes of biogenous chemical elements.

  20. Stable isotopes in pharmacology studies: present and future

    International Nuclear Information System (INIS)

    Browne, T.R.

    1986-01-01

    Stable-isotope techniques offer advantages over older methods in safety, sensitivity, specificity, and reduction in numbers of subjects required and analytic determinations for some types of pharmacology studies. In addition to their use as internal standards in gas chromatography-mass spectrometry analytic methods, stable isotopes have been successfully employed in studies of absorption, bioavailability, distribution, biotransformation, excretion, metabolite identification, time-dependent and dose-dependent pharmacokinetic changes, drug interactions, pharmacologic changes during pregnancy, mutagenicity, and teratogenicity. 32 references

  1. Elastic Stable Intramedullary Nailing for Treatment of Pediatric Tibial Fractures

    OpenAIRE

    Sandeep Gurung; Dipendra KC; Roshni Khatri

    2016-01-01

    Introduction: Tibia fractures in the skeletally immature patient can usually be treated with above knee cast or patellar tendon bearing cast. The purpose of our study was to evaluate epidemiology and outcome of Elastic stable intramedullary nailing fixation of pediatric tibial shaft fractures treated at our institution. Methods: Over a period of one year, fifty pediatric patients of tibial shaft fractures, with average age of 9.68 yr (SD=2.37), were treated with elastic stable intramedul...

  2. The stable stiffness triangle - drained sand during deformation cycles

    DEFF Research Database (Denmark)

    Sabaliauskas, Tomas; Ibsen, Lars Bo

    2017-01-01

    Cyclic, drained sand stiffness was observed using the Danish triaxial appa- ratus. New, deformation dependant soil property (the stable stiffness triangle) was detected. Using the the stable stiffness triangle, secant stiffness of drained sand was plausible to predict (and control) even during ir...... findings can find application in off-shore, seismic and other engi- neering practice, or inspire new branches of research and modelling wherever dynamic, cyclic or transient loaded sand is encountered....

  3. Risk following hospitalization in stable chronic systolic heart failure

    DEFF Research Database (Denmark)

    Abrahamsson, Putte; Swedberg, Karl; Borer, Jeffrey S

    2013-01-01

    We explored the impact of being hospitalized due to worsening heart failure (WHF) or a myocardial infarction (MI) on subsequent mortality in a large contemporary data set of patients with stable chronic systolic heart failure (HF).......We explored the impact of being hospitalized due to worsening heart failure (WHF) or a myocardial infarction (MI) on subsequent mortality in a large contemporary data set of patients with stable chronic systolic heart failure (HF)....

  4. A parallel approach to the stable marriage problem

    DEFF Research Database (Denmark)

    Larsen, Jesper

    1997-01-01

    This paper describes two parallel algorithms for the stable marriage problem implemented on a MIMD parallel computer. The algorithms are tested against sequential algorithms on randomly generated and worst-case instances. The results clearly show that the combination fo a very simple problem...... and a commercial MIMD system results in parallel algorithms which are not competitive with sequential algorithms wrt. practical performance. 1 Introduction In 1962 the Stable Marriage Problem was....

  5. Metastability in plyometric training on unstable surfaces: a pilot study

    Science.gov (United States)

    2014-01-01

    Background In the past, plyometric training (PT) has been predominantly performed on stable surfaces. The purpose of this pilot study was to examine effects of a 7-week lower body PT on stable vs. unstable surfaces. This type of exercise condition may be denoted as metastable equilibrium. Methods Thirty-three physically active male sport science students (age: 24.1 ± 3.8 years) were randomly assigned to a PT group (n = 13) exercising on stable (STAB) and a PT group (n = 20) on unstable surfaces (INST). Both groups trained countermovement jumps, drop jumps, and practiced a hurdle jump course. In addition, high bar squats were performed. Physical fitness tests on stable surfaces (hexagonal obstacle test, countermovement jump, hurdle drop jump, left-right hop, dynamic and static balance tests, and leg extension strength) were used to examine the training effects. Results Significant main effects of time (ANOVA) were found for the countermovement jump, hurdle drop jump, hexagonal test, dynamic balance, and leg extension strength. A significant interaction of time and training mode was detected for the countermovement jump in favor of the INST group. No significant improvements were evident for either group in the left-right hop and in the static balance test. Conclusions These results show that lower body PT on unstable surfaces is a safe and efficient way to improve physical performance on stable surfaces. PMID:25089202

  6. On stability of Kummer surfaces' tangent bundle

    International Nuclear Information System (INIS)

    Bozhkov, Y.D.

    1988-10-01

    In this paper we propose an explicit approximation of the Kaehler-Einstein-Calabi-Yau metric on the Kummer surfaces, which are manifolds of type K3. It is constructed by gluing 16 pieces of the Eguchi-Hanson metric and 16 pieces of the Euclidean metric. Two estimates on its curvature are proved. Then we prove an estimate on the first eigenvalue of a covariant differential operator of second order. This enables us to apply Taubes' iteration procedure to obtain that there exists an anti-self-dual connection on the considered Kummer surface. In fact, it is a Hermitian-Einstein connection from which we conclude that Kummer surfaces' co-tangent bundle is stable and therefore their tangent bundle is stable too. (author). 40 refs

  7. Wideband quin-stable energy harvesting via combined nonlinearity

    Directory of Open Access Journals (Sweden)

    Chen Wang

    2017-04-01

    Full Text Available In this work, we propose a wideband quintuple-well potential piezoelectric-based vibration energy harvester using a combined nonlinearity: the magnetic nonlinearity induced by magnetic force and the piecewise-linearity produced by mechanical impact. With extra stable states compared to other multi-stable harvesters, the quin-stable harvester can distribute its potential energy more uniformly, which provides shallower potential wells and results in lower excitation threshold for interwell motion. The mathematical model of this quin-stable harvester is derived and its equivalent piecewise-nonlinear restoring force is measured in the experiment and identified as piecewise polynomials. Numerical simulations and experimental verifications are performed in different levels of sinusoid excitation ranging from 1 to 25 Hz. The results demonstrate that, with lower potential barriers compared with tri-stable counterpart, the quin-stable arrangement can escape potential wells more easily for doing high-energy interwell motion over a wider band of frequencies. Moreover, by utilizing the mechanical stoppers, this harvester can produce significant output voltage under small tip deflections, which results in a high power density and is especially suitable for a compact MEMS approach.

  8. Medieval horse stable; the results of multi proxy interdisciplinary research.

    Science.gov (United States)

    Dejmal, Miroslav; Lisá, Lenka; Fišáková Nývltová, Miriam; Bajer, Aleš; Petr, Libor; Kočár, Petr; Kočárová, Romana; Nejman, Ladislav; Rybníček, Michal; Sůvová, Zdenka; Culp, Randy; Vavrčík, Hanuš

    2014-01-01

    A multi proxy approach was applied in the reconstruction of the architecture of Medieval horse stable architecture, the maintenance practices associated with that structure as well as horse alimentation at the beginning of 13th century in Central Europe. Finally, an interpretation of the local vegetation structure along Morava River, Czech Republic is presented. The investigated stable experienced two construction phases. The infill was well preserved and its composition reflects maintenance practices. The uppermost part of the infill was composed of fresh stabling, which accumulated within a few months at the end of summer. Horses from different backgrounds were kept in the stable and this is reflected in the results of isotope analyses. Horses were fed meadow grasses as well as woody vegetation, millet, oat, and less commonly hemp, wheat and rye. Three possible explanations of stable usage are suggested. The stable was probably used on a temporary basis for horses of workers employed at the castle, courier horses and horses used in battle.

  9. Medieval Horse Stable; The Results of Multi Proxy Interdisciplinary Research

    Science.gov (United States)

    Dejmal, Miroslav; Lisá, Lenka; Fišáková Nývltová, Miriam; Bajer, Aleš; Petr, Libor; Kočár, Petr; Kočárová, Romana; Nejman, Ladislav; Rybníček, Michal; Sůvová, Zdenka; Culp, Randy; Vavrčík, Hanuš

    2014-01-01

    A multi proxy approach was applied in the reconstruction of the architecture of Medieval horse stable architecture, the maintenance practices associated with that structure as well as horse alimentation at the beginning of 13th century in Central Europe. Finally, an interpretation of the local vegetation structure along Morava River, Czech Republic is presented. The investigated stable experienced two construction phases. The infill was well preserved and its composition reflects maintenance practices. The uppermost part of the infill was composed of fresh stabling, which accumulated within a few months at the end of summer. Horses from different backgrounds were kept in the stable and this is reflected in the results of isotope analyses. Horses were fed meadow grasses as well as woody vegetation, millet, oat, and less commonly hemp, wheat and rye. Three possible explanations of stable usage are suggested. The stable was probably used on a temporary basis for horses of workers employed at the castle, courier horses and horses used in battle. PMID:24670874

  10. Stable Fly, Stomoxys calcitrans (L.), Dispersal and Governing Factors.

    Science.gov (United States)

    Showler, Allan T; Osbrink, Weste L A

    2015-01-01

    Although the movement of stable fly, Stomoxys calcitrans (L.), has been studied, its extent and significance has been uncertain. On a local scale (fly movement occurs between host animals and resting sites to feed and mate, mainly at on-farm locations where herbivorous livestock regularly congregate. Small numbers emigrate from livestock congregation sites in search of other hosts and oviposition substrate, mostly within stable flies are active year-round in warm latitudes, cold winters in temperate areas result in substantial population and activity declines, limiting movement of any sort to warmer seasons. Long-distance dispersal (>13 km) is mainly wind-driven by weather fronts that carry stable flies from inland farm areas for up to 225 km to beaches of northwestern Florida and Lake Superior. Stable flies can reproduce for a short time each year in washed-up sea grass, but the beaches are not conducive to establishment. Such movement is passive and does not appear to be advantageous to stable fly's survival. On a regional scale, stable flies exhibit little genetic differentiation, and on the global scale, while there might be more than one "lineage", the species is nevertheless considered to be panmictic. Population expansion across much of the globe likely occurred from the late Pleistocene to the early Holocene in association with the spread of domesticated nomad livestock and particularly with more sedentary, penned livestock.

  11. Metal stable isotope signatures as tracers in environmental geochemistry.

    Science.gov (United States)

    Wiederhold, Jan G

    2015-03-03

    The biogeochemical cycling of metals in natural systems is often accompanied by stable isotope fractionation which can now be measured due to recent analytical advances. In consequence, a new research field has emerged over the last two decades, complementing the traditional stable isotope systems (H, C, O, N, S) with many more elements across the periodic table (Li, B, Mg, Si, Cl, Ca, Ti, V, Cr, Fe, Ni, Cu, Zn, Ge, Se, Br, Sr, Mo, Ag, Cd, Sn, Sb, Te, Ba, W, Pt, Hg, Tl, U) which are being explored and potentially applicable as novel geochemical tracers. This review presents the application of metal stable isotopes as source and process tracers in environmental studies, in particular by using mixing and Rayleigh model approaches. The most important concepts of mass-dependent and mass-independent metal stable isotope fractionation are introduced, and the extent of natural isotopic variations for different elements is compared. A particular focus lies on a discussion of processes (redox transformations, complexation, sorption, precipitation, dissolution, evaporation, diffusion, biological cycling) which are able to induce metal stable isotope fractionation in environmental systems. Additionally, the usefulness and limitations of metal stable isotope signatures as tracers in environmental geochemistry are discussed and future perspectives presented.

  12. Medieval horse stable; the results of multi proxy interdisciplinary research.

    Directory of Open Access Journals (Sweden)

    Miroslav Dejmal

    Full Text Available A multi proxy approach was applied in the reconstruction of the architecture of Medieval horse stable architecture, the maintenance practices associated with that structure as well as horse alimentation at the beginning of 13th century in Central Europe. Finally, an interpretation of the local vegetation structure along Morava River, Czech Republic is presented. The investigated stable experienced two construction phases. The infill was well preserved and its composition reflects maintenance practices. The uppermost part of the infill was composed of fresh stabling, which accumulated within a few months at the end of summer. Horses from different backgrounds were kept in the stable and this is reflected in the results of isotope analyses. Horses were fed meadow grasses as well as woody vegetation, millet, oat, and less commonly hemp, wheat and rye. Three possible explanations of stable usage are suggested. The stable was probably used on a temporary basis for horses of workers employed at the castle, courier horses and horses used in battle.

  13. Stable and sporadic symbiotic communities of coral and algal holobionts

    Science.gov (United States)

    Hester, Eric R; Barott, Katie L; Nulton, Jim; Vermeij, Mark JA; Rohwer, Forest L

    2016-01-01

    Coral and algal holobionts are assemblages of macroorganisms and microorganisms, including viruses, Bacteria, Archaea, protists and fungi. Despite a decade of research, it remains unclear whether these associations are spatial–temporally stable or species-specific. We hypothesized that conflicting interpretations of the data arise from high noise associated with sporadic microbial symbionts overwhelming signatures of stable holobiont members. To test this hypothesis, the bacterial communities associated with three coral species (Acropora rosaria, Acropora hyacinthus and Porites lutea) and two algal guilds (crustose coralline algae and turf algae) from 131 samples were analyzed using a novel statistical approach termed the Abundance-Ubiquity (AU) test. The AU test determines whether a given bacterial species would be present given additional sampling effort (that is, stable) versus those species that are sporadically associated with a sample. Using the AU test, we show that coral and algal holobionts have a high-diversity group of stable symbionts. Stable symbionts are not exclusive to one species of coral or algae. No single bacterial species was ubiquitously associated with one host, showing that there is not strict heredity of the microbiome. In addition to the stable symbionts, there was a low-diversity community of sporadic symbionts whose abundance varied widely across individual holobionts of the same species. Identification of these two symbiont communities supports the holobiont model and calls into question the hologenome theory of evolution. PMID:26555246

  14. Surface-Controlled Metal Oxide Resistive Memory

    KAUST Repository

    Ke, Jr-Jian

    2015-10-28

    To explore the surface effect on resistive random-access memory (ReRAM), the impact of surface roughness on the characteristics of ZnO ReRAM were studied. The thickness-independent resistance and the higher switching probability of ZnO ReRAM with rough surfaces indicate the importance of surface oxygen chemisorption on the switching process. Furthermore, the improvements in switching probability, switching voltage and resistance distribution observed for ReRAM with rough surfaces can be attributed to the stable oxygen adatoms under various ambience conditions. The findings validate the surface-controlled stability and uniformity of ReRAM and can serve as the guideline for developing practical device applications.

  15. Stable fly (Stomoxys calcitrans: Diptera, Muscidae) trap response to changes in effective trap height caused by growing vegetation.

    Science.gov (United States)

    Beresford, D V; Sutcliffe, J F

    2008-06-01

    Stable flies (Stomoxys calcitrans L.) are blood-feeding pests of cattle, whose populations are often monitored using sticky traps. Trap responses at different heights were compared with: 1) a choice and no-choice test, with sticky cards set at 30 and 121 cm heights (above ground), and 2) tall (120 cm) traps placed in short (3 cm) and tall (40 cm) grass to assess how vegetation height affects trap catches. In the first experiment, the percentage of upper to lower trap catches were similar at choice (16%) and no-choice traps (15%). In the vegetation study, stable fly catch height data were fitted to gamma distributions to determine the most productive trap heights; 20 cm above short grass and 24 cm above tall grass (from lower edge of trap). The results indicate that traps used to monitor stable fly populations should be maintained at a constant distance above surrounding vegetation rather than ground surface, otherwise trap data can be misleading.

  16. Fractional surface termination of diamond by electrochemical oxidation.

    Science.gov (United States)

    Hoffmann, René; Obloh, Harald; Tokuda, Norio; Yang, Nianjun; Nebel, Christoph E

    2012-01-10

    The crystalline form of sp(3)-hybridized carbon, diamond, offers various electrolyte-stable surface terminations. The H-termination-selective attachment of nitrophenyl diazonium, imaged by AFM, shows that electrochemical oxidation can control the fractional hydrogen/oxygen surface termination of diamond on the nanometer scale. This is of particular interest for all applications relying on interfacial electrochemistry, especially for biointerfaces.

  17. Surface Modification of PDMS and Plastics with Zwitterionic Polymers.

    Science.gov (United States)

    Tanaka, Mutsuo; Kurosawa, Shigeru

    2017-07-01

    Surface modification of PDMS, polycarbonate, and acrylic resin was examined using various methacryl polymers bearing sulfobetaine, phosphoryl choline, and oligoethylene glycol units. We have found that zwitterionic polymers are adsorbed on the PDMS surface treated with plasma. The surface of PDMS is stable to keep high hydrophilicity after a month of the modification. On the other hand, one of sulfobetaine polymers showed distinguished adsorption behavior in the case of polycarbonate surface treated with plasma. Suppression effect for nonspecific adsorption of BSA was evaluated using polycarbonate and acrylic resin modified with the polymers. The modified surfaces showed suppression effect for nonspecific adsorption of BSA compared with the surface only treated with plasma.

  18. Continuous control of asymmetric forebody vortices in a bi-stable state

    Science.gov (United States)

    Wang, Qi-te; Cheng, Ke-ming; Gu, Yun-song; Li, Zhuo-qi

    2018-02-01

    Aiming at the problem of continuous control of asymmetric forebody vortices at a high angle of attack in a bi-stable regime, a dual synthetic jet actuator embedded in an ogive forebody was designed. Alternating unsteady disturbance with varying degree asymmetrical flow fields near the nozzles is generated by adjusting the duty cycle of the drive signal of the actuator, specifically embodying the asymmetric time-averaged pattern of jet velocity, vorticity, and turbulent kinetic energy. Experimental results show that within the range of relatively high angles of attack, including the angle-of-attack region in a bi-stable state, the lateral force of the ogive forebody is continuously controlled by adjusting the duty cycle of the drive signal; the position of the forebody vortices in space, the vorticity magnitude, the total pressure coefficient near the vortex core, and the vortex breakdown location are continuously changed with the duty cycle increased observed from the time-averaged flow field. Instantaneous flow field results indicate that although the forebody vortices are in an unsteady oscillation state, a continuous change in the forebody vortices' oscillation balance position as the duty cycle increases leads to a continuous change in the model's surface pressure distribution and time-averaged lateral force. Different from the traditional control principle, in this study, other different degree asymmetrical states of the forebody vortices except the bi-stable state are obtained using the dual synthetic jet control technology.

  19. A novel Lagrangian approach for the stable numerical simulation of fault and fracture mechanics

    Energy Technology Data Exchange (ETDEWEB)

    Franceschini, Andrea; Ferronato, Massimiliano, E-mail: massimiliano.ferronato@unipd.it; Janna, Carlo; Teatini, Pietro

    2016-06-01

    The simulation of the mechanics of geological faults and fractures is of paramount importance in several applications, such as ensuring the safety of the underground storage of wastes and hydrocarbons or predicting the possible seismicity triggered by the production and injection of subsurface fluids. However, the stable numerical modeling of ground ruptures is still an open issue. The present work introduces a novel formulation based on the use of the Lagrange multipliers to prescribe the constraints on the contact surfaces. The variational formulation is modified in order to take into account the frictional work along the activated fault portion according to the principle of maximum plastic dissipation. The numerical model, developed in the framework of the Finite Element method, provides stable solutions with a fast convergence of the non-linear problem. The stabilizing properties of the proposed model are emphasized with the aid of a realistic numerical example dealing with the generation of ground fractures due to groundwater withdrawal in arid regions. - Highlights: • A numerical model is developed for the simulation of fault and fracture mechanics. • The model is implemented in the framework of the Finite Element method and with the aid of Lagrange multipliers. • The proposed formulation introduces a new contribution due to the frictional work on the portion of activated fault. • The resulting algorithm is highly non-linear as the portion of activated fault is itself unknown. • The numerical solution is validated against analytical results and proves to be stable also in realistic applications.

  20. Areal-averaged trace gas emission rates from long-range open-path measurements in stable boundary layer conditions

    Directory of Open Access Journals (Sweden)

    K. Schäfer

    2012-07-01

    Full Text Available Measurements of land-surface emission rates of greenhouse and other gases at large spatial scales (10 000 m2 are needed to assess the spatial distribution of emissions. This can be readily done using spatial-integrating micro-meteorological methods like flux-gradient methods which were evaluated for determining land-surface emission rates of trace gases under stable boundary layers. Non-intrusive path-integrating measurements are utilized. Successful application of a flux-gradient method requires confidence in the gradients of trace gas concentration and wind, and in the applicability of boundary-layer turbulence theory; consequently the procedures to qualify measurements that can be used to determine the flux is critical. While there is relatively high confidence in flux measurements made under unstable atmospheres with mean winds greater than 1 m s−1, there is greater uncertainty in flux measurements made under free convective or stable conditions. The study of N2O emissions of flat grassland and NH3 emissions from a cattle lagoon involves quality-assured determinations of fluxes under low wind, stable or night-time atmospheric conditions when the continuous "steady-state" turbulence of the surface boundary layer breaks down and the layer has intermittent turbulence. Results indicate that following the Monin-Obukhov similarity theory (MOST flux-gradient methods that assume a log-linear profile of the wind speed and concentration gradient incorrectly determine vertical profiles and thus flux in the stable boundary layer. An alternative approach is considered on the basis of turbulent diffusivity, i.e. the measured friction velocity as well as height gradients of horizontal wind speeds and concentrations without MOST correction for stability. It is shown that this is the most accurate of the flux-gradient methods under stable conditions.

  1. Multi-stable perception balances stability and sensitivity

    Directory of Open Access Journals (Sweden)

    Alexander ePastukhov

    2013-03-01

    Full Text Available We report that multi-stable perception operates in a consistent, dynamical regime, balancing the conflicting goals of stability and sensitivity. When a multi-stable visual display is viewed continuously, its phenomenal appearance reverses spontaneously at irregular intervals. We characterized the perceptual dynamics of individual observers in terms of four statistical measures: the distribution of dominance times (mean and variance and the novel, subtle dependence on prior history (correlation and time-constant.The dynamics of multi-stable perception is known to reflect several stabilizing and destabilizing factors. Phenomenologically, its main aspects are captured by a simplistic computational model with competition, adaptation, and noise. We identified small parameter volumes (~3% of the possible volume in which the model reproduced both dominance distribution and history-dependence of each observer. For 21 of 24 data sets, the identified volumes clustered tightly (~15% of the possible volume, revealing a consistent `operating regime' of multi-stable perception. The `operating regime' turned out to be marginally stable or, equivalently, near the brink of an oscillatory instability. The chance probability of the observed clustering was <0.02.To understand the functional significance of this empirical `operating regime', we compared it to the theoretical `sweet spot' of the model. We computed this `sweet spot' as the intersection of the parameter volumes in which the model produced stable perceptual outcomes and in which it was sensitive to input modulations. Remarkably, the empirical `operating regime' proved to be largely coextensive with the theoretical `sweet spot'. This demonstrated that perceptual dynamics was not merely consistent but also functionally optimized (in that it balances stability with sensitivity. Our results imply that multi-stable perception is not a laboratory curiosity, but reflects a functional optimization of perceptual

  2. Introducing fecal stable isotope analysis in primate weaning studies.

    Science.gov (United States)

    Reitsema, Laurie J

    2012-10-01

    This research investigates the potential of a new, noninvasive method for determining age of weaning among primates using stable carbon and nitrogen isotope ratios in feces. Analysis of stable isotope ratios in body tissues is a well-established method in archeology and ecology for reconstructing diet. This is the first study to investigate weaning in primates using fecal stable isotope ratios. Diets of a single François' langur (Trachypithecus francoisi) mother-infant pair at the Toledo Zoo are reconstructed using this technique to track changes in infant suckling behavior over the weaning period. Stable isotope ratios in feces are sampled instead of more traditional samples such as bone or hair to enable daily, noninvasive snapshots of weaning status. Isotopic assessments of weaning status are compared to visual assessments to identify any discordance between the two. Three measurements documented the transition from breast milk to solid foods: stable carbon isotope ratios (δ(13)C), stable nitrogen isotope ratios (δ(15)N), and nitrogen content of feces (%N). It appears that solid foods were introduced at approximately 2 months of infant age, but that nursing continued into the 12th month, when sample collection ceased. Stable isotope data exposed a much longer weaning period than what was expected based on previously published data for captive langurs, and clarified visual estimates of weaning status. This reflects the method's sensitivity to suckling at night and ability to distinguish actual nursing from comfort nursing. After testing this method with zoo animals, it can readily be applied among wild populations. An isotopic approach to weaning provides a new, accurate, and biologically meaningful assessment of interbirth intervals, and facilitates a better understanding of mother-infant interactions. Both of these outcomes are critical for developing successful conservation strategies for captive and wild primates. © 2012 Wiley Periodicals, Inc.

  3. Thermally stable single-atom platinum-on-ceria catalysts via atom trapping

    Energy Technology Data Exchange (ETDEWEB)

    Jones, John; Xiong, Haifeng; DelaRiva, Andrew; Peterson, Eric J.; Pham, Hien; Challa, Sivakumar R.; Qi, Gongshin; Oh, Se H.; Wiebenga, Michelle H.; Pereira Hernandez, Xavier I.; Wang, Yong; Datye, Abhaya K.

    2016-07-08

    Catalysts based on single atoms of scarce precious metals can lead to more efficient use through enhanced reactivity and selectivity. However, single atoms on catalyst supports can be mobile and aggregate into nanoparticles when heated at elevated temperatures. High temperatures are detrimental to catalyst performance unless these mobile atoms can be trapped. We used ceria powders having similar surface areas but different exposed surface facets. When mixed with a platinum/ aluminum oxide catalyst and aged in air at 800°C, the platinum transferred to the ceria and was trapped. Polyhedral ceria and nanorods were more effective than ceria cubes at anchoring the platinum. Performing synthesis at high temperatures ensures that only the most stable binding sites are occupied, yielding a sinter-resistant, atomically dispersed catalyst.

  4. Application of carbon and oxygen stable isotopes to the study of Brazilian precambrian

    International Nuclear Information System (INIS)

    Torquato, J.R.F.

    1980-01-01

    Samples of carbonated rocks of precambrian age are studied. The stable carbon and oxygen isotopes are applied to the study of terrestrial materials considering the variations of some element isotopic composition in function of the environment of sedimentation. The isotopic analysis was done using mass spectrometers. The analytical results and the description of region geology of the site of each sample are presented. The isotopic data are interpreted aiming to the environment of sedimentation. New techniques for better improvement of carbon and oxygen ratios, are proposed, such as: to use the analysis of surface trend and the isotopic logging in mapping of surface and subsurface. A new method for approximated determination of the ages of precambrian carbonated rocks, considering the limitations of their new technique, is also presented. (M.C.K.) [pt

  5. Multisample conversion of water to hydrogen by zinc for stable isotope determination

    Science.gov (United States)

    Kendall, C.; Coplen, T.B.

    1985-01-01

    Two techniques for the conversion of water to hydrogen for stable isotope ratio determination have been developed that are especially suited for automated multisample analysis. Both procedures involve reaction of zinc shot with a water sample at 450 ??C. in one method designed for water samples in bottles, the water is put in capillaries and is reduced by zinc in reaction vessels; overall savings in sample preparation labor of 75% have been realized over the standard uranium reduction technique. The second technique is for waters evolved under vacuum and is a sealed-tube method employing 9 mm o.d. quartz tubing. Problems inherent with zinc reduction include surface inhomogeneity of the zinc and exchange of hydrogen both with the zinc and with the glass walls of the vessels. For best results, water/zinc and water/glass surface area ratios of vessels should be kept as large as possible.

  6. Stable Aqueous Suspension and Self-Assembly of Graphite Nanoplatelets Coated with Various Polyelectrolytes

    Directory of Open Access Journals (Sweden)

    Jue Lu

    2010-01-01

    Full Text Available Exfoliated graphite nanoplatelets (xGnPs with an average thickness of 1–10 nm present an inexpensive alternative to carbon nanotubes in many applications. In this paper, stable aqueous suspension of xGnP was achieved by noncovalent functionalization of xGnP with polyelectrolytes. The surfactants and polyelectrolytes were compared with respect to their ability to suspend graphite nanoplatelets. The surface charge of the nanoplatelets was characterized with zeta potential measurements, and the bonding strength of the polymer chains to the surface of xGnP was characterized with Raman spectroscopy. This robust method opens up the possibility of using this inexpensive nanomaterial in many applications, including electrochemical devices, and leads to simple processing techniques such as layer-by-layer deposition. Therefore, the formation of xGnP conductive coatings using layer-by-layer deposition was also demonstrated.

  7. Development of stable low-electroosmotic mobility coatings. [for use in electrophoresis systems in space

    Science.gov (United States)

    Vanderhoff, J. W.; Micale, F. J.

    1979-01-01

    Long-time rinsings of the Z6040-methlycellulose coating used successfully on the ASTP MA=011 experiment indicate the permanency of this coating is inadequate for continuous flowing systems. Two approaches are described for developing coatings which are stable under continuous fluid movement and which exhibit finite and predictable electroosmotic mobility values while being effective on different types of surfaces, such as glass, plastics, and ceramic alumina, such as is currently used as the electrophoresis channel in the GE-SPAR-CPE apparatus. The surface charge modification of polystyrene latex, especially by protein absorption, to be used as model materials for ground-based electrophoresis experiments, and the preliminary work directed towards the seeded polymerization of large-particle-size monodisperse latexes in a microgravity environment are discussed.

  8. Water stable isotopes: application to the water cycle and climate variations study

    International Nuclear Information System (INIS)

    Risi, C.

    2009-12-01

    The stable isotopic composition of water (H 2 16 , HDO, H 2 18 , H 2 17 ) is a promising tracer of the present day water cycle and past climates. While the isotopic composition recorded in polar ice core have long been used to reconstruct past temperatures, however, what controls the isotopic composition of the tropical precipitation is more complex. The goal of this thesis is thus to better understand the processes that affect the isotopic composition of tropical precipitation and atmospheric water, more particularly in the tropics. Since most of the tropical precipitation arises from atmospheric convection, and most isotopic archives are on land, we focus more particularly on the impact of convective and land surface processes. In turn, what can be learned about convection and land surface processes using isotopic measurements? Can they help constrain their representation in models? At the inter-annual to climate change scale, what information about the tropical climate variability is recorded in isotopic signals observed in archives? First, we investigate the influence of convection on water stable isotopes. We use both (1) numerical modeling, with a hierarchy of models (single column model, two-dimensional model of squall lines, general circulation model) and (2) data analysis, using isotopic data from rain collected in the Sahel during the African Monsoon Multidisciplinary Analysis campaign, at the event and intra-event scales. These studies highlight the strong impact of convection on the precipitation composition, and stress the importance of rain evaporation and convective or meso-scale subsidence in controlling the rain isotopic composition. Convection also plays an important role on isotopic profiles in the upper troposphere-lower stratosphere. Second, we study what information about climatic variability is recorded by water stable isotopes in precipitation. We analyze simulations of present day and past climates with LMDZ, and evaluate to what extent

  9. The stable isotopes of site wide waters at an oil sands mine in northern Alberta, Canada

    Science.gov (United States)

    Baer, Thomas; Barbour, S. Lee; Gibson, John J.

    2016-10-01

    Oil sands mines have large disturbance footprints and contain a range of new landforms constructed from mine waste such as shale overburden and the byproducts of bitumen extraction such as sand and fluid fine tailings. Each of these landforms are a potential source of water and chemical release to adjacent surface and groundwater, and consequently, the development of methods to track water migration through these landforms is of importance. The stable isotopes of water (i.e. 2H and 18O) have been widely used in hydrology and hydrogeology to characterize surface water/groundwater interactions but have not been extensively applied in mining applications, or specifically to oil sands mining in northern Alberta. A prerequisite for applying these techniques is the establishment of a Local Meteoric Water Line (LMWL) to characterize precipitation at the mine sites as well as the development of a 'catalogue' of the stable water isotope signatures of various mine site waters. This study was undertaken at the Mildred Lake Mine Site, owned and operated by Syncrude Canada Ltd. The LMWL developed from 2 years (2009/2012) of sample collection is shown to be consistent with other LMWLs in western Canada. The results of the study highlight the unique stable water isotope signatures associated with hydraulically placed tailings (sand or fluid fine tailings) and overburden shale dumps relative to natural surface water and groundwater. The signature associated with the snow melt water on reclaimed landscapes was found to be similar to ground water recharge in the region. The isotopic composition of the shale overburden deposits are also distinct and consistent with observations made by other researchers in western Canada on undisturbed shales. The process water associated with the fine and coarse tailings streams has highly enriched 2H and 18O signatures. These signatures are developed through the non-equilibrium fractionation of imported fresh river water during evaporation from

  10. Highly stable, protein capped gold nanoparticles as effective drug delivery vehicles for amino-glycosidic antibiotics

    International Nuclear Information System (INIS)

    Rastogi, Lori; Kora, Aruna Jyothi; Arunachalam, J.

    2012-01-01

    A method for the production of highly stable gold nanoparticles (Au NP) was optimized using sodium borohydride as reducing agent and bovine serum albumin as capping agent. The synthesized nanoparticles were characterized using UV–visible spectroscopy, transmission electron microscopy, X‐ray diffraction (XRD) and dynamic light scattering techniques. The formation of gold nanoparticles was confirmed from the appearance of pink colour and an absorption maximum at 532 nm. These protein capped nanoparticles exhibited excellent stability towards pH modification and electrolyte addition. The produced nanoparticles were found to be spherical in shape, nearly monodispersed and with an average particle size of 7.8 ± 1.7 nm. Crystalline nature of the nanoparticles in face centered cubic structure is confirmed from the selected‐area electron diffraction and XRD patterns. The nanoparticles were functionalized with various amino-glycosidic antibiotics for utilizing them as drug delivery vehicles. Using Fourier transform infrared spectroscopy, the possible functional groups of antibiotics bound to the nanoparticle surface have been examined. These drug loaded nanoparticle solutions were tested for their antibacterial activity against Gram-negative and Gram-positive bacterial strains, by well diffusion assay. The antibiotic conjugated Au NP exhibited enhanced antibacterial activity, compared to pure antibiotic at the same concentration. Being protein capped and highly stable, these gold nanoparticles can act as effective carriers for drugs and might have considerable applications in the field of infection prevention and therapeutics. - Highlights: ► Method for NaBH 4 reduced and BSA capped gold nanoparticle was standardized. ► Nanoparticles were spherical and nearly monodispersed with a size of 7.8 nm. ► Nanoparticles are extremely stable towards pH modification and electrolyte addition. ► Antibiotic conjugated nanoparticles exhibited enhanced antibacterial activity

  11. Highly stable, protein capped gold nanoparticles as effective drug delivery vehicles for amino-glycosidic antibiotics

    Energy Technology Data Exchange (ETDEWEB)

    Rastogi, Lori; Kora, Aruna Jyothi; Arunachalam, J., E-mail: aruncccm@gmail.com

    2012-08-01

    A method for the production of highly stable gold nanoparticles (Au NP) was optimized using sodium borohydride as reducing agent and bovine serum albumin as capping agent. The synthesized nanoparticles were characterized using UV-visible spectroscopy, transmission electron microscopy, X-ray diffraction (XRD) and dynamic light scattering techniques. The formation of gold nanoparticles was confirmed from the appearance of pink colour and an absorption maximum at 532 nm. These protein capped nanoparticles exhibited excellent stability towards pH modification and electrolyte addition. The produced nanoparticles were found to be spherical in shape, nearly monodispersed and with an average particle size of 7.8 {+-} 1.7 nm. Crystalline nature of the nanoparticles in face centered cubic structure is confirmed from the selected-area electron diffraction and XRD patterns. The nanoparticles were functionalized with various amino-glycosidic antibiotics for utilizing them as drug delivery vehicles. Using Fourier transform infrared spectroscopy, the possible functional groups of antibiotics bound to the nanoparticle surface have been examined. These drug loaded nanoparticle solutions were tested for their antibacterial activity against Gram-negative and Gram-positive bacterial strains, by well diffusion assay. The antibiotic conjugated Au NP exhibited enhanced antibacterial activity, compared to pure antibiotic at the same concentration. Being protein capped and highly stable, these gold nanoparticles can act as effective carriers for drugs and might have considerable applications in the field of infection prevention and therapeutics. - Highlights: Black-Right-Pointing-Pointer Method for NaBH{sub 4} reduced and BSA capped gold nanoparticle was standardized. Black-Right-Pointing-Pointer Nanoparticles were spherical and nearly monodispersed with a size of 7.8 nm. Black-Right-Pointing-Pointer Nanoparticles are extremely stable towards pH modification and electrolyte addition. Black

  12. Seasonal and ENSO Influences on the Stable Isotopic Composition of Galápagos Precipitation

    Science.gov (United States)

    Martin, N. J.; Conroy, J. L.; Noone, D.; Cobb, K. M.; Konecky, B. L.; Rea, S.

    2018-01-01

    The origin of stable isotopic variability in precipitation over time and space is critical to the interpretation of stable isotope-based paleoclimate proxies. In the eastern equatorial Pacific, modern stable isotope measurements in precipitation (δ18Op and δDp) are sparse and largely unevaluated in the literature, although insights from such analyses would benefit the interpretations of several regional isotope-based paleoclimate records. Here we present a new 3.5 year record of daily-resolved δ18Op and δDp from Santa Cruz, Galápagos. With a prior 13 year record of monthly δ18Op and δDp from the island, these new data reveal controls on the stable isotopic composition of regional precipitation on event to interannual time scales. Overall, we find Galápagos δ18Op is significantly correlated with precipitation amount on daily and monthly time scales. The majority of Galápagos rain events are drizzle, or garúa, derived from local marine boundary layer vapor, with corresponding high δ18Op values due to the local source and increased evaporation and equilibration of smaller drops with boundary layer vapor. On monthly time scales, only precipitation in very strong, warm season El Niño months has substantially lower δ18Op values, as the sea surface temperature threshold for deep convection (28°C) is only surpassed at these times. The 2015/2016 El Niño event did not produce strong precipitation or δ18Op anomalies due to the short period of warm SST anomalies, which did not extend into the peak of the warm season. Eastern Pacific proxy isotope records may be biased toward periods of high rainfall during strong to very strong El Niño events.

  13. Efficiency of Cs-free materials for negative ion production in H2 and D2 plasmas

    Science.gov (United States)

    Friedl, R.; Kurutz, U.; Fantz, U.

    2017-08-01

    High power negative ion sources use caesium to reduce the work function of the converter surface which significantly increases the negative ion yield. Caesium, however, is a very reactive alkali-metal and shows complex redistribution dynamics in consequence of plasma-surface-interaction. Thus, maintaining a stable and homogenous low work function surface is a demanding task, which is not easily compatible with the RAMI issues (reliability, availability, maintainability, inspectability) for a future DEMO fusion reactor. Hence, Cs-free alternative materials for efficient negative ion formation are desirable. At the laboratory experiment HOMER materials which are referred to as promising are investigated under identical and ion source relevant parameters: the refractory metals Ta and W, non-doped and boron-doped diamond as well as materials with inherent low work function (lanthanum-doped molybdenum, MoLa and lanthanum hexaboride, LaB6). The results are compared to the effect of in-situ caesiation, which at HOMER leads to a maximal increase of the negative ion density by a factor of 2.5. Among the examined samples low work function materials are most efficient. In particular, MoLa leads to an increase of almost 50 % compared to pure volume formation. The difference to a caesiated surface can be attributed to the still higher work function of MoLa, which is expected to be slightly below 3 eV. Using deuterium instead of hydrogen leads to increased atomic and positive ion densities, while comparable negative ion densities are achieved. In contrast to the low work function materials, bulk samples of the refractory metals as well as carbon based materials have no enhancing effect on H-, where the latter materials furthermore show severe erosion due to the hydrogen plasma.

  14. Enhanced TOF-SIMS imaging of a micropatterned protein by stable isotope protein labeling.

    Science.gov (United States)

    Belu, A M; Yang, Z; Aslami, R; Chilkoti, A

    2001-01-15

    Patterning of biomolecules on surfaces is an increasingly important technological goal. Because the fabrication of biomolecule arrays often involves stepwise, spatially resolved derivatization of surfaces, spectroscopic imaging of these arrays is important in their fabrication and optimization. Although imaging time-of-flight secondary ion mass spectrometry (TOF-SIMS) is a powerful method for spatially resolved surface analysis, TOF-SIMS images of micropatterned proteins on organic substrates can be difficult to acquire, because of the lack of high intensity, protein-specific molecular ions that are essential for imaging under static conditions. In contrast, low-mass ions are of suitable intensity for imaging, but can originate from different chemical species on the surface. A potential solution to this problem is to utilize stable isotope labeled proteins, an approach that has heretofore not been explored in TOF-SIMS imaging of micropatterned proteins and peptides. To investigate the feasibility of stable isotope enhanced TOF-SIMS imaging of proteins, we synthesized 15N-labeled streptavidin by labeling of the protein during expression from a recombinant gene. The spatial distribution of streptavidin bound to biotin micropatterns, fabricated on a polymer and on a self-assembled monolayer on gold, was imaged by TOF-SIMS. Imaging of high-intensity, low-m/z secondary ions (e.g., C15N-) unique to streptavidin enabled unambiguous spatial mapping of the micropatterned protein with a lateral resolution of a few micrometers. TOF-SIMS imaging of micropatterned 15N-labeled streptavidin also illustrated the exquisite sensitivity of TOF-SIMS to low fractional coverage of protein (5 A effective thickness) in the background regions of the protein micropattern.

  15. Dynamics and control of twisting bi-stable structures

    Science.gov (United States)

    Arrieta, Andres F.; van Gemmeren, Valentin; Anderson, Aaron J.; Weaver, Paul M.

    2018-02-01

    Compliance-based morphing structures have the potential to offer large shape adaptation, high stiffness and low weight, while reducing complexity, friction, and scalability problems of mechanism based systems. A promising class of structure that enables these characteristics are multi-stable structures given their ability to exhibit large deflections and rotations without the expensive need for continuous actuation, with the latter only required intermittently. Furthermore, multi-stable structures exhibit inherently fast response due to the snap-through instability governing changes between stable states, enabling rapid configuration switching between the discrete number of programmed shapes of the structure. In this paper, the design and utilisation of the inherent nonlinear dynamics of bi-stable twisting I-beam structures for actuation with low strain piezoelectric materials is presented. The I-beam structure consists of three compliant components assembled into a monolithic single element, free of moving parts, and showing large deflections between two stable states. Finite element analysis is utilised to uncover the distribution of strain across the width of the flange, guiding the choice of positioning for piezoelectric actuators. In addition, the actuation authority is maximised by calculating the generalised coupling coefficient for different positions of the piezoelectric actuators. The results obtained are employed to tailor and test I-beam designs exhibiting desired large deflection between stable states, while still enabling the activation of snap-through with the low strain piezoelectric actuators. To this end, the dynamic response of the I-beams to piezoelectric excitation is investigated, revealing that resonant excitations are insufficient to dynamically trigger snap-through. A novel bang-bang control strategy, which exploits the nonlinear dynamics of the structure successfully triggers both single and constant snap-through between the stable states

  16. Book review: Use of Stable Iodine in Nuclear Emergencies

    Directory of Open Access Journals (Sweden)

    Iraj Nabipour

    2011-11-01

    Full Text Available Following a radiological or nuclear event, radioactive iodine may be get into the body through respiratory or gastrointestinal systems. In the contaminated cases with radioactive iodine, the radioactive iodine absorbed by the thyroid can injure the gland. Because of the carcinogenic effects of its radiation, there is a significant public health risk in the event of exposure to radioactive iodine. On other hand, due to stable (non-radioactive iodine acts to block radioactive iodine from being taken into the thyroid gland, it can help protect this gland from injury and following side effects. In this query, potassium iodide (also called KI is a salt of stable iodine in a medicine form which is recommended to use sine many years ago. With effective planning and the use of stable iodine prophylaxis, accompanied with other protective implementations, this risk is mostly avoidable. This book contains information such as iodine and physiology kinetic , exposure risk to radioactive iodine, how to use stable iodine in this events , complications attributed to stable(non-radioactive iodine and also at last chapter the final recommendation published by WHO is included.

  17. Development of a stable cation modified graphene oxide membrane for water treatment

    Science.gov (United States)

    Yu, Wenzheng; (Yet Yu, Tong; Graham, Nigel

    2017-12-01

    Membranes prepared from layers of graphene oxide (GO) offer substantial advantages over conventional materials for water treatment (e.g. greater flux), but the stability of GO membranes in water has not been achieved until now. In this study the behavior of GO membranes prepared with different quantities and species of cations has been investigated to establish the feasibility of their application in water treatment. A range of cation-modified GO membranes were prepared and exposed to aqueous solutions containing specific chemical constituents. In pure water, unmodified and Na-modified GO membranes were highly unstable, while GO membranes modified with multivalent cations were stable provided there were sufficient quantities of cations present; their relative capability to achieve GO stability was as follows: Al3+  >  Ca2+  >  Mg2+  >  Na+. It is believed that the mechanism of cross-linking, and membrane stability, is via metal-carboxylate chelates and cation-graphite surface interactions (cation-π interaction), and that the latter appears to increase with increasing cation valency. The instability of cation (Ca or Al)-modified GO membranes by NaCl solutions during permeation occurred as Na+ exchanged with the incorporated multivalent cations, but a high content of Al3+ in the GO membrane impeded Al3+/Na+ exchange and thus retained membrane stability. In solutions containing biopolymers representative of surface waters or seawater (protein and polysaccharide solutions), Ca-GO membranes (even with high Ca2+ content) were not stable, while Al-GO membranes were stable if the Al3+ content was sufficiently high; Al-formed membranes also had a greater flux than Ca-GO membranes.

  18. Evaporation and abstraction determined from stable isotopes during normal flow on the Gariep River, South Africa

    Science.gov (United States)

    Diamond, Roger E.; Jack, Sam

    2018-04-01

    Changes in the stable isotope composition of water can, with the aid of climatic parameters, be used to calculate the quantity of evaporation from a water body. Previous workers have mostly focused on small, research catchments, with abundant data, but of limited scope. This study aimed to expand such work to a regional or sub-continental scale. The first full length isotope survey of the Gariep River quantifies evaporation on the river and the man-made reservoirs for the first time, and proposes a technique to calculate abstraction from the river. The theoretically determined final isotope composition for an evaporating water body in the given climate lies on the empirically determined local evaporation line, validating the assumptions and inputs to the Craig-Gordon evaporation model that was used. Evaporation from the Gariep River amounts to around 20% of flow, or 40 m3/s, of which about half is due to evaporation from the surface of the Gariep and Vanderkloof Reservoirs, showing the wastefulness of large surface water impoundments. This compares well with previous estimates based on evapotranspiration calculations, and equates to around 1300 GL/a of water, or about the annual water consumption of Johannesburg and Pretoria, where over 10 million people reside. Using similar evaporation calculations and applying existing transpiration estimates to a gauged length of river, the remaining quantity can be attributed to abstraction, amounting to 175 L/s/km in the lower middle reaches of the river. Given that high water demand and climate change are global problems, and with the challenges of maintaining water monitoring networks, stable isotopes are shown to be applicable over regional to national scales for modelling hydrological flows. Stable isotopes provide a complementary method to conventional flow gauging for understanding hydrology and management of large water resources, particularly in arid areas subject to significant evaporation.

  19. Structural insights into methanol-stable variants of lipase T6 from Geobacillus stearothermophilus.

    Science.gov (United States)

    Dror, Adi; Kanteev, Margarita; Kagan, Irit; Gihaz, Shalev; Shahar, Anat; Fishman, Ayelet

    2015-11-01

    Enzymatic production of biodiesel by transesterification of triglycerides and alcohol, catalyzed by lipases, offers an environmentally friendly and efficient alternative to the chemically catalyzed process while using low-grade feedstocks. Methanol is utilized frequently as the alcohol in the reaction due to its reactivity and low cost. However, one of the major drawbacks of the enzymatic system is the presence of high methanol concentrations which leads to methanol-induced unfolding and inactivation of the biocatalyst. Therefore, a methanol-stable lipase is of great interest for the biodiesel industry. In this study, protein engineering was applied to substitute charged surface residues with hydrophobic ones to enhance the stability in methanol of a lipase from Geobacillus stearothermophilus T6. We identified a methanol-stable variant, R374W, and combined it with a variant found previously, H86Y/A269T. The triple mutant, H86Y/A269T/R374W, had a half-life value at 70 % methanol of 324 min which reflects an 87-fold enhanced stability compared to the wild type together with elevated thermostability in buffer and in 50 % methanol. This variant also exhibited an improved biodiesel yield from waste chicken oil compared to commercial Lipolase 100L® and Novozyme® CALB. Crystal structures of the wild type and the methanol-stable variants provided insights regarding structure-stability correlations. The most prominent features were the extensive formation of new hydrogen bonds between surface residues directly or mediated by structural water molecules and the stabilization of Zn and Ca binding sites. Mutation sites were also characterized by lower B-factor values calculated from the X-ray structures indicating improved rigidity.

  20. Stable Myoelectric Control of a Hand Prosthesis using Non-Linear Incremental Learning

    Directory of Open Access Journals (Sweden)

    Arjan eGijsberts

    2014-02-01

    Full Text Available Stable myoelectric control of hand prostheses remains an open problem. The only successful human-machine interface is surface electromyography, typically allowing control of a few degrees of freedom. Machine learning techniques may have the potential to remove these limitations, but their performance is thus far inadequate: myoelectric signals change over time under the influence of various factors, deteriorating control performance. It is therefore necessary, in the standard approach, to regularly retrain a new model from scratch.We hereby propose a non-linear incremental learning method in which occasional updates with a modest amount of novel training data allow continual adaptation to the changes in the signals. In particular, Incremental Ridge Regression and an approximation of the Gaussian Kernel known as Random Fourier Features are combined to predict finger forces from myoelectric signals, both finger-by-finger and grouped in grasping patterns.We show that the approach is effective and practically applicable to this problem by first analyzing its performance while predicting single-finger forces. Surface electromyography and finger forces were collected from 10 intact subjects during four sessions spread over two different days; the results of the analysis show that small incremental updates are indeed effective to maintain a stable level of performance.Subsequently, we employed the same method on-line to teleoperate a humanoid robotic arm equipped with a state-of-the-art commercial prosthetic hand. The subject could reliably grasp, carry and release everyday-life objects, enforcing stable grasping irrespective of the signal changes, hand/arm movements and wrist pronation and supination.

  1. Air-stable n-type doping of graphene from overlying Si3N4 film

    International Nuclear Information System (INIS)

    Wang, Zegao; Li, Pingjian; Chen, Yuanfu; Liu, Jingbo; Qi, Fei; Tian, Hongjun; Zheng, Binjie; Zhou, Jinhao

    2014-01-01

    In this study, we report a facile method to obtain air-stable n-type graphene by plasma-enhanced chemical vapor depositing Si 3 N 4 film on the surface of graphene. We have demonstrated that the overlying Si 3 N 4 film can not only act as the penetration-barrier against H 2 O and O 2 adsorbed on the graphene surface, but also cause an effective n-type doping due to the amine groups at the interface of graphene/Si 3 N 4 . Furthermore, the studies reveal that the Dirac point of graphene can be modulated by the thickness of Si 3 N 4 film, which is due to competing effects of Si 3 N 4 -induced doping (n-type) and penetrating H 2 O (O 2 )-induced doping (p-type). We expect this method to be used for obtaining stable n-type graphene field-effect transistors in air, which will be widely used in graphene electronic devices.

  2. Highly stable noble-metal nanoparticles in tetraalkylphosphonium ionic liquids for in situ catalysis.

    Science.gov (United States)

    Banerjee, Abhinandan; Theron, Robin; Scott, Robert W J

    2012-01-09

    Gold and palladium nanoparticles were prepared by lithium borohydride reduction of the metal salt precursors in tetraalkylphosphonium halide ionic liquids in the absence of any organic solvents or external nanoparticle stabilizers. These colloidal suspensions remained stable and showed no nanoparticle agglomeration over many months. A combination of electrostatic interactions between the coordinatively unsaturated metal nanoparticle surface and the ionic-liquid anions, bolstered by steric protection offered by the bulky alkylated phosphonium cations, is likely to be the reason behind such stabilization. The halide anion strongly absorbs to the nanoparticle surface, leading to exceptional nanoparticle stability in halide ionic liquids; other tetraalkylphosphonium ionic liquids with non-coordinating anions, such as tosylate and hexafluorophosphate, show considerably lower affinities towards the stabilization of nanoparticles. Palladium nanoparticles stabilized in the tetraalkylphosphonium halide ionic liquid were stable, efficient, and recyclable catalysts for a variety of hydrogenation reactions at ambient pressures with sustained activity. Aerial oxidation of the metal nanoparticles occurred over time and was readily reversed by re-reduction of oxidized metal salts. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Silanization of quartz, silicon and mica surfaces with light-driven molecular motors : construction of surface-bound photo-active nanolayers

    NARCIS (Netherlands)

    London, Gabor; Carroll, Gregory T.; Feringa, Ben L.

    2013-01-01

    The attachment of molecular rotary motors containing triethoxysilane functional groups to quartz, silicon and mica surfaces is described. Motors containing silane coupling agents in their structure form stable molecular layers on quartz and silicon surfaces. Motors attached to these surfaces were

  4. Stable Isotope Ratios as Biomarkers of Diet for Health Research.

    Science.gov (United States)

    O'Brien, Diane M

    2015-01-01

    Diet is a leading modifiable risk factor for chronic disease, but it remains difficult to measure accurately due to the error and bias inherent in self-reported methods of diet assessment. Consequently, there is a pressing need for more objective biomarkers of diet for use in health research. The stable isotope ratios of light elements are a promising set of candidate biomarkers because they vary naturally and reproducibly among foods, and those variations are captured in molecules and tissues with high fidelity. Recent studies have identified valid isotopic measures of short- and long-term sugar intake, meat intake, and fish intake in specific populations. These studies provide a strong foundation for validating stable isotopic biomarkers in the general US population. Approaches to improve specificity for specific foods are needed; for example, by modeling intake using multiple stable isotope ratios or by isolating and measuring specific molecules linked to foods of interest.

  5. Picosecond pulse generated supercontinuum as a stable seed for OPCPA.

    Science.gov (United States)

    Indra, Lukáš; Batysta, František; Hříbek, Petr; Novák, Jakub; Hubka, Zbyněk; Green, Jonathan T; Antipenkov, Roman; Boge, Robert; Naylon, Jack A; Bakule, Pavel; Rus, Bedřich

    2017-02-15

    We present a stable supercontinuum (SC) generated in a bulk YAG crystal, pumped by 3 ps chirped pulses at 1030 nm. The SC is generated in a loose focus geometry in a 13 cm long YAG crystal, allowing for stable and robust single-filament generation. The SC energy stability exceeds that of the pump laser by almost a factor of 3. Additionally, we show that the SC spectrum has long-term stability and that the SC is coherent and compressible by compressing the portions of SC spectra close to the corresponding Fourier limit. This makes the picosecond-pulse-driven SC a suitable stable seed for OPCPA amplifiers.

  6. Self-similar anomalous diffusion and Levy-stable laws

    International Nuclear Information System (INIS)

    Uchaikin, Vladimir V

    2003-01-01

    Stochastic principles for constructing the process of anomalous diffusion are considered, and corresponding models of random processes are reviewed. The self-similarity and the independent-increments principles are used to extend the notion of diffusion process to the class of Levy-stable processes. Replacing the independent-increments principle with the renewal principle allows us to take the next step in generalizing the notion of diffusion, which results in fractional-order partial space-time differential equations of diffusion. Fundamental solutions to these equations are represented in terms of stable laws, and their relationship to the fractality and memory of the medium is discussed. A new class of distributions, called fractional stable distributions, is introduced. (reviews of topical problems)

  7. Stable solitons of quadratic ginzburg-landau equations

    Science.gov (United States)

    Crasovan; Malomed; Mihalache; Mazilu; Lederer

    2000-07-01

    We present a physical model based on coupled Ginzburg-Landau equations that supports stable temporal solitary-wave pulses. The system consists of two parallel-coupled cores, one having a quadratic nonlinearity, the other one being effectively linear. The former core is active, with bandwidth-limited amplification built into it, while the latter core has only losses. Parameters of the model can be easily selected so that the zero background is stable. The model has nongeneric exact analytical solutions in the form of solitary pulses ("dissipative solitons"). Direct numerical simulations, using these exact solutions as initial configurations, show that they are unstable; however, the evolution initiated by the exact unstable solitons ends up with nontrivial stable localized pulses, which are very robust attractors. Direct simulations also demonstrate that the presence of group-velocity mismatch (walkoff) between the two harmonics in the active core makes the pulses move at a constant velocity, but does not destabilize them.

  8. Do planetary seasons play a role in attaining stable climates?

    Science.gov (United States)

    Olsen, Kasper Wibeck; Bohr, Jakob

    2018-02-01

    A simple phenomenological account for planetary climate instabilities is presented. The description is based on the standard model where the balance of incoming stellar radiation and outward thermal radiation is described by the effective planet temperature. Often, it is found to have three different points, or temperatures, where the influx of radiation is balanced with the out-flux, even with conserved boundary conditions. Two of these points are relatively long-term stable, namely the point corresponding to a cold climate and the point corresponding to a hot climate. In a classical sense these points are equilibrium balance points. The hypothesis promoted in this paper is the possibility that the intermediate third point can become long-term stable by being driven dynamically. The initially unstable point is made relatively stable over a long period by the presence of seasonal climate variations.

  9. Embedded Controller Design for Pig Stable Ventilation Systems

    DEFF Research Database (Denmark)

    Jessen, Jan Jacob

    present an early result for performing system identification for zone based climate dynamics, based on an idea of guaranteed internal flow directions. Paper 6 presents a verified stable distributed temperature controller for pig stables divided into zones. Paper 7 is an expanded journal version of paper 6......This thesis focuses on zone based climate control in pig stables and how to implement climate controllers in a new range of products. The presented controllers are based on simple models of climate dynamics and simple models of actuators. The implementation uses graphical point and click features...... from the Mathworks' range of products and automatic code generation. It is furthermore shown how to build new climate control systems based on cheap and readily available hardware and software. An early result for performing system identification for zone based climate dynamics is also presented...

  10. Ranking stability and super-stable nodes in complex networks.

    Science.gov (United States)

    Ghoshal, Gourab; Barabási, Albert-László

    2011-07-19

    Pagerank, a network-based diffusion algorithm, has emerged as the leading method to rank web content, ecological species and even scientists. Despite its wide use, it remains unknown how the structure of the network on which it operates affects its performance. Here we show that for random networks the ranking provided by pagerank is sensitive to perturbations in the network topology, making it unreliable for incomplete or noisy systems. In contrast, in scale-free networks we predict analytically the emergence of super-stable nodes whose ranking is exceptionally stable to perturbations. We calculate the dependence of the number of super-stable nodes on network characteristics and demonstrate their presence in real networks, in agreement with the analytical predictions. These results not only deepen our understanding of the interplay between network topology and dynamical processes but also have implications in all areas where ranking has a role, from science to marketing.

  11. Source Partitioning Using Stable Isotopes: Coping with Too Much Variation

    Science.gov (United States)

    Parnell, Andrew C.; Inger, Richard; Bearhop, Stuart; Jackson, Andrew L.

    2010-01-01

    Background Stable isotope analysis is increasingly being utilised across broad areas of ecology and biology. Key to much of this work is the use of mixing models to estimate the proportion of sources contributing to a mixture such as in diet estimation. Methodology By accurately reflecting natural variation and uncertainty to generate robust probability estimates of source proportions, the application of Bayesian methods to stable isotope mixing models promises to enable researchers to address an array of new questions, and approach current questions with greater insight and honesty. Conclusions We outline a framework that builds on recently published Bayesian isotopic mixing models and present a new open source R package, SIAR. The formulation in R will allow for continued and rapid development of this core model into an all-encompassing single analysis suite for stable isotope research. PMID:20300637

  12. Stable Isotope Ratios as Biomarkers of Diet for Health Research

    Science.gov (United States)

    O’Brien, Diane M.

    2016-01-01

    Diet is a leading modifiable risk factor for chronic disease, but it remains difficult to measure accurately due to the error and bias inherent in self-reported methods of diet assessment. Consequently there is a pressing need for more objective biomarkers of diet for use in health research. The stable isotope ratios of light elements are a promising set of candidate biomarkers because they vary naturally and reproducibly among foods, and those variations are captured in molecules and tissues with high fidelity. Recent studies have identified valid isotopic measures of short and long-term sugar intake, meat intake, and fish intake in specific populations. These studies provide a strong foundation for validating stable isotopic biomarkers in the general United States population. Approaches to improve specificity for specific foods are needed, for example, by modeling intake using multiple stable isotope ratios, or by isolating and measuring specific molecules linked to foods of interest. PMID:26048703

  13. Application of enriched stable isotopes as tracers in biological systems

    DEFF Research Database (Denmark)

    Stürup, Stefan; Hansen, Helle Rüsz; Gammelgaard, Bente

    2008-01-01

    The application of enriched stable isotopes of minerals and trace elements as tracers in biological systems is a rapidly growing research field that benefits from the many new developments in inorganic mass spectrometric instrumentation, primarily within inductively coupled plasma mass spectrometry...... (ICP-MS) instrumentation, such as reaction/collision cell ICP-MS and multicollector ICP-MS with improved isotope ratio measurement and interference removal capabilities. Adaptation and refinement of radioisotope tracer experiment methodologies for enriched stable isotope experiments......, and the development of new methodologies coupled with more advanced compartmental and mathematical models for the distribution of elements in living organisms has enabled a broader use of enriched stable isotope experiments in the biological sciences. This review discusses the current and future uses of enriched...

  14. Leaf water stable isotopes and water transport outside the xylem.

    Science.gov (United States)

    Barbour, M M; Farquhar, G D; Buckley, T N

    2017-06-01

    How water moves through leaves, and where the phase change from liquid to vapour occurs within leaves, remain largely mysterious. Some time ago, we suggested that the stable isotope composition of leaf water may contain information on transport pathways beyond the xylem, through differences in the development of gradients in enrichment within the various pathways. Subsequent testing of this suggestion provided ambiguous results and even questioned the existence of gradients in enrichment within the mesophyll. In this review, we bring together recent theoretical developments in understanding leaf water transport pathways and stable isotope theory to map a path for future work into understanding pathways of water transport and leaf water stable isotope composition. We emphasize the need for a spatially, anatomically and isotopically explicit model of leaf water transport. © 2016 John Wiley & Sons Ltd.

  15. High precision and stable structures for particle detectors

    CERN Document Server

    Da Mota Silva, S; Hauviller, Claude

    1999-01-01

    The central detectors used in High Energy Physics Experiments require the use of light and stable structures capable of supporting delicate and precise radiation detection elements. These structures need to be highly stable under environmental conditions where external vibrations, high radiation levels, temperature and humidity gradients should be taken into account. Their main design drivers are high dimension and dynamic stability, high stiffness to mass ratio and large radiation length. For most applications, these constraints lead us to choose Carbon Fiber Reinforced Plastics ( CFRP) as structural element. The construction of light and stable structures with CFRP for these applications can be achieved by careful design engineering and further confirmation at the prototyping phase. However, the experimental environment can influence their characteristics and behavior. In this case, theuse of adaptive structures could become a solution for this problem. We are studying structures in CFRP with bonded piezoel...

  16. Topological Surface States in Dense Solid Hydrogen.

    Science.gov (United States)

    Naumov, Ivan I; Hemley, Russell J

    2016-11-11

    Metallization of dense hydrogen and associated possible high-temperature superconductivity represents one of the key problems of physics. Recent theoretical studies indicate that before becoming a good metal, compressed solid hydrogen passes through a semimetallic stage. We show that such semimetallic phases predicted to be the most stable at multimegabar (∼300  GPa) pressures are not conventional semimetals: they exhibit topological metallic surface states inside the bulk "direct" gap in the two-dimensional surface Brillouin zone; that is, metallic surfaces may appear even when the bulk of the material remains insulating. Examples include hydrogen in the Cmca-12 and Cmca-4 structures; Pbcn hydrogen also has metallic surface states but they are of a nontopological nature. The results provide predictions for future measurements, including probes of possible surface superconductivity in dense hydrogen.

  17. Stable isotope tracers and exercise physiology: past, present and future.

    Science.gov (United States)

    Wilkinson, Daniel J; Brook, Matthew S; Smith, Kenneth; Atherton, Philip J

    2017-05-01

    Stable isotope tracers have been invaluable assets in physiological research for over 80 years. The application of substrate-specific stable isotope tracers has permitted exquisite insight into amino acid, fatty-acid and carbohydrate metabolic regulation (i.e. incorporation, flux, and oxidation, in a tissue-specific and whole-body fashion) in health, disease and response to acute and chronic exercise. Yet, despite many breakthroughs, there are limitations to 'substrate-specific' stable isotope tracers, which limit physiological insight, e.g. the need for intravenous infusions and restriction to short-term studies (hours) in controlled laboratory settings. In recent years significant interest has developed in alternative stable isotope tracer techniques that overcome these limitations, in particular deuterium oxide (D 2 O or heavy water). The unique properties of this tracer mean that through oral administration, the turnover and flux through a number of different substrates (muscle proteins, lipids, glucose, DNA (satellite cells)) can be monitored simultaneously and flexibly (hours/weeks/months) without the need for restrictive experimental control. This makes it uniquely suited for the study of 'real world' human exercise physiology (amongst many other applications). Moreover, using D 2 O permits evaluation of turnover of plasma and muscle proteins (e.g. dynamic proteomics) in addition to metabolomics (e.g. fluxomics) to seek molecular underpinnings, e.g. of exercise adaptation. Here, we provide insight into the role of stable isotope tracers, from substrate-specific to novel D 2 O approaches, in facilitating our understanding of metabolism. Further novel potential applications of stable isotope tracers are also discussed in the context of integration with the snowballing field of 'omic' technologies. © 2016 The Authors. The Journal of Physiology © 2016 The Physiological Society.

  18. Target-like pigmentation after minipunch grafting in stable vitiligo

    Directory of Open Access Journals (Sweden)

    Nelee Bisen

    2014-01-01

    Full Text Available Surgical treatment for vitiligo has been ever evolving. Each surgical modality has its own benefits and limitations. Miniature punch grafting is the most extensively performed surgery, which gives good results in stable vitiligo. Herein we report an unusual type of repigmentation observed after minipunch grafting in a patient of stable vitiligo, which resembled target-like lesions with a "perigraft halo" surrounding individual grafts. Such pigment spread occurred despite the use of 0.5 mm larger graft from the donor site.

  19. Stable isotope geochemistry : definitions, terminology, measurement and some applications

    International Nuclear Information System (INIS)

    Faure, K.

    2005-01-01

    In 1936, Alfred Nier produced the first precise measurement of isotope abundance ratios and his design still remains the basis of stable isotope mass spectrometry. With this gift from the physicists for routine measurement of isotope ratios, earth scientists began to explore the natural variations of isotopes. Thus began a new era in geoscience research with the hydrological cycle and marine palaeoclimatic research being the first topics to be investigated. Stable isotope measurements have been applied to many fundamental problems in geochemistry, petrology and paleoclimatology, as well as related fields in archaeology, anthropology, physical chemistry, biology and forensic sciences. (author). 52 refs., 11 figs., 2 tabs

  20. Coexistence of collapse and stable spatiotemporal solitons in multimode fibers

    Science.gov (United States)

    Shtyrina, Olga V.; Fedoruk, Mikhail P.; Kivshar, Yuri S.; Turitsyn, Sergei K.

    2018-01-01

    We analyze spatiotemporal solitons in multimode optical fibers and demonstrate the existence of stable solitons, in a sharp contrast to earlier predictions of collapse of multidimensional solitons in three-dimensional media. We discuss the coexistence of blow-up solutions and collapse stabilization by a low-dimensional external potential in graded-index media, and also predict the existence of stable higher-order nonlinear waves such as dipole-mode spatiotemporal solitons. To support the main conclusions of our numerical studies we employ a variational approach and derive analytically the stability criterion for input powers for the collapse stabilization.