WorldWideScience

Sample records for surface work functions

  1. Work Functions for Models of Scandate Surfaces

    Science.gov (United States)

    Mueller, Wolfgang

    1997-01-01

    The electronic structure, surface dipole properties, and work functions of scandate surfaces have been investigated using the fully relativistic scattered-wave cluster approach. Three different types of model surfaces are considered: (1) a monolayer of Ba-Sc-O on W(100), (2) Ba or BaO adsorbed on Sc2O3 + W, and (3) BaO on SC2O3 + WO3. Changes in the work function due to Ba or BaO adsorption on the different surfaces are calculated by employing the depolarization model of interacting surface dipoles. The largest work function change and the lowest work function of 1.54 eV are obtained for Ba adsorbed on the Sc-O monolayer on W(100). The adsorption of Ba on Sc2O3 + W does not lead to a low work function, but the adsorption of BaO results in a work function of about 1.6-1.9 eV. BaO adsorbed on Sc2O3 + WO3, or scandium tungstates, may also lead to low work functions.

  2. Photoelectric scanner makes detailed work function maps of metal surface

    Science.gov (United States)

    Rasor, N. S.

    1966-01-01

    Photoelectric scanning device maps the work function of a metal surface by scanning it with a light spot and measuring the resulting photocurrent. The device is capable of use over a range of surface temperatures.

  3. Surface energy and work function of elemental metals

    DEFF Research Database (Denmark)

    Skriver, Hans Lomholt; Rosengaard, N. M.

    1992-01-01

    are in excellent agreement with a recent full-potential, all-electron, slab-supercell calculation of surface energies and work functions for the 4d metals. The present calculations explain the trend exhibited by the surface energies of the alkali, alkaline earth, divalent rare-earth, 3d, 4d, and 5d transition......We have performed an ab initio study of the surface energy and the work function for six close-packed surfaces of 40 elemental metals by means of a Green’s-function technique, based on the linear-muffin-tin-orbitals method within the tight-binding and atomic-sphere approximations. The results...... and noble metals, as derived from the surface tension of liquid metals. In addition, they give work functions which agree with the limited experimental data obtained from single crystals to within 15%, and explain the smooth behavior of the experimental work functions of polycrystalline samples...

  4. Low work function of the Ca2N surface

    NARCIS (Netherlands)

    Uijttewaal, M.A.; Wijs, G.A. de; 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 C

  5. Surface energy and work function of the light actinides

    DEFF Research Database (Denmark)

    Kollár, J.; Vitos, Levente; Skriver, Hans Lomholt

    1994-01-01

    We have calculated the surface energy and work function of the light actinides Fr, Ra, Ac, Th, Pa, U, Np, and Pu by means of a Green's-function technique based on the linear-muffin-tin-orbitals method within the tight-binding representation. In these calculations we apply an energy functional which...

  6. Thermionic scanner pinpoints work function of emitter surfaces

    Science.gov (United States)

    Rasor, N. S.

    1966-01-01

    In the electron tube testing, a thermionic scanner makes accurate spatial resolution measurements of the metallic surface work functions of emitters. The scanner determines the emitter function and its local departures from the mean value on a point-by-point basis for display on an oscilloscope.

  7. Recommended values of clean metal surface work functions

    Energy Technology Data Exchange (ETDEWEB)

    Derry, Gregory N., E-mail: gderry@loyola.edu; Kern, Megan E.; Worth, Eli H. [Department of Physics, Loyola University Maryland, 4501 N. Charles St., Baltimore, Maryland 21210 (United States)

    2015-11-15

    A critical review of the experimental literature for measurements of the work functions of clean metal surfaces of single-crystals is presented. The tables presented include all results found for low-index crystal faces except cases that were known to be contaminated surfaces. These results are used to construct a recommended value of the work function for each surface examined, along with an uncertainty estimate for that value. The uncertainties are based in part on the error distribution for all measured work functions in the literature, which is included here. The metals included in this review are silver (Ag), aluminum (Al), gold (Au), copper (Cu), iron (Fe), iridium (Ir), molybdenum (Mo), niobium (Nb), nickel (Ni), palladium (Pd), platinum (Pt), rhodium (Rh), ruthenium (Ru), tantalum (Ta), and tungsten (W)

  8. Work function modifications of graphite surface via oxygen plasma treatment

    Science.gov (United States)

    Duch, J.; Kubisiak, P.; Adolfsson, K. H.; Hakkarainen, M.; Golda-Cepa, M.; Kotarba, A.

    2017-10-01

    The surface modification of graphite by oxygen plasma was investigated experimentally (X-ray diffraction, nanoparticle tracking analysis, laser desorption ionization mass spectrometry, thermogravimetry, water contact angle) and by molecular modelling (Density Functional Theory). Generation of surface functional groups (mainly sbnd OHsurf) leads to substantial changes in electrodonor properties and wettability gauged by work function and water contact angle, respectively. The invoked modifications were analyzed in terms of Helmholtz model taking into account the theoretically determined surface dipole moment of graphite-OHsurf system (μ = 2.71 D) and experimentally measured work function increase (from 0.75 to 1.02 eV) to determine the sbnd OH surface coverage (from 0.70 to 1.03 × 1014 groups cm-2). Since the plasma treatment was confined to the surface, the high thermal stability of the graphite material was preserved as revealed by the thermogravimetric analysis. The obtained results provide a suitable quantitative background for tuning the key operating parameters of carbon electrodes: electronic properties, interaction with water and thermal stability.

  9. Ultralow effective work function surfaces using diamondoid monolayers.

    Science.gov (United States)

    Narasimha, Karthik Thimmavajjula; Ge, Chenhao; Fabbri, Jason D; Clay, William; Tkachenko, Boryslav A; Fokin, Andrey A; Schreiner, Peter R; Dahl, Jeremy E; Carlson, Robert M K; Shen, Z X; Melosh, Nicholas A

    2016-03-01

    Electron emission is critical for a host of modern fabrication and analysis applications including mass spectrometry, electron imaging and nanopatterning. Here, we report that monolayers of diamondoids effectively confer dramatically enhanced field emission properties to metal surfaces. We attribute the improved emission to a significant reduction of the work function rather than a geometric enhancement. This effect depends on the particular diamondoid isomer, with [121]tetramantane-2-thiol reducing gold's work function from ∼ 5.1 eV to 1.60 ± 0.3 eV, corresponding to an increase in current by a factor of over 13,000. This reduction in work function is the largest reported for any organic species and also the largest for any air-stable compound. This effect was not observed for sp(3)-hybridized alkanes, nor for smaller diamondoid molecules. The magnitude of the enhancement, molecule specificity and elimination of gold metal rearrangement precludes geometric factors as the dominant contribution. Instead, we attribute this effect to the stable radical cation of diamondoids. Our computed enhancement due to a positively charged radical cation was in agreement with the measured work functions to within ± 0.3 eV, suggesting a new paradigm for low-work-function coatings based on the design of nanoparticles with stable radical cations.

  10. Measuring Work Functions Of "Dirty" Surfaces With A Vibrating Capacitive Probe

    Science.gov (United States)

    Yost, William T.

    1995-01-01

    Apparatus measures work function of possibly contaminated surface of specimen of metal or other electrically conductive material. Measures work function of specimen indirectly, by vibrating capacitive measurement of contact potential. Work function of specimen affected by microstructure and by contamination.

  11. Error estimates for density-functional theory predictions of surface energy and work function

    Science.gov (United States)

    De Waele, Sam; Lejaeghere, Kurt; Sluydts, Michael; Cottenier, Stefaan

    2016-12-01

    Density-functional theory (DFT) predictions of materials properties are becoming ever more widespread. With increased use comes the demand for estimates of the accuracy of DFT results. In view of the importance of reliable surface properties, this work calculates surface energies and work functions for a large and diverse test set of crystalline solids. They are compared to experimental values by performing a linear regression, which results in a measure of the predictable and material-specific error of the theoretical result. Two of the most prevalent functionals, the local density approximation (LDA) and the Perdew-Burke-Ernzerhof parametrization of the generalized gradient approximation (PBE-GGA), are evaluated and compared. Both LDA and GGA-PBE are found to yield accurate work functions with error bars below 0.3 eV, rivaling the experimental precision. LDA also provides satisfactory estimates for the surface energy with error bars smaller than 10%, but GGA-PBE significantly underestimates the surface energy for materials with a large correlation energy.

  12. Low-work-function surfaces produced by cesium carbonate decomposition

    Science.gov (United States)

    Briere, T. R.; Sommer, A. H.

    1977-01-01

    Cesium carbonate (Cs2CO3) was heated to the decomposition temperature of approximately 600 C. The nonvolatile decomposition products were condensed on a nickel substrate while the carbon dioxide was removed by pumping. The deposited material is characterized by an effective work function of between 1.05 and 1.15 eV at 450 K and by photoemission in the visible and near-infrared region of the spectrum. It is suggested that the deposited material consists of Cs2O, possibly Cs2O2, and adsorbed cesium. Silver, evaporated from a heated silver bead, produced the typical photoemissive and thermionic properties of a silver-oxygen-cesium (S-1) photocathode. The material may be of interest for thermionic energy converters and for the formation of silver-oxygen-cesium photocathodes.

  13. Primary role of electron work function for evaluation of nanostructured titania implant surface against bacterial infection.

    Science.gov (United States)

    Golda-Cepa, M; Syrek, K; Brzychczy-Wloch, M; Sulka, G D; Kotarba, A

    2016-09-01

    The electron work function as an essential descriptor for the evaluation of metal implant surfaces against bacterial infection is identified for the first time. Its validity is demonstrated on Staphylococcus aureus adhesion to nanostructured titania surfaces. The established correlation: work function-bacteria adhesion is of general importance since it can be used for direct evaluation of any electrically conductive implant surfaces.

  14. Thermal stability of the work function of NEA type surfaces. [Negative Electron Affinity

    Science.gov (United States)

    Edwards, D., Jr.; Peria, W. T.

    1978-01-01

    The work-function stability of both Si(100) and Ge(100) surfaces activated with adsorptions of cesium and oxygen has been determined. In general, it has been found that the highest temperature to which the optimized Ge surface could be heated without an increase in its work function (1.06 eV) was about 200 C, whereas the optimized Si surface could be heated to approximately 250 C without a significant increase in the optimized work function (0.93 eV). Details are also presented on various characteristics of cesium and oxygen adsorption-desorption on these surfaces.

  15. Primary role of electron work function for evaluation of nanostructured titania implant surface against bacterial infection

    Energy Technology Data Exchange (ETDEWEB)

    Golda-Cepa, M., E-mail: golda@chemia.uj.edu.pl [Faculty of Chemistry, Jagiellonian University, Ingardena 3, 30-060 Krakow (Poland); Syrek, K. [Faculty of Chemistry, Jagiellonian University, Ingardena 3, 30-060 Krakow (Poland); Brzychczy-Wloch, M. [Department of Bacteriology, Microbial Ecology and Parasitology, Jagiellonian University Medical College, Czysta 18, 31-121 Krakow (Poland); Sulka, G.D. [Faculty of Chemistry, Jagiellonian University, Ingardena 3, 30-060 Krakow (Poland); Kotarba, A., E-mail: kotarba@chemia.uj.edu.pl [Faculty of Chemistry, Jagiellonian University, Ingardena 3, 30-060 Krakow (Poland)

    2016-09-01

    The electron work function as an essential descriptor for the evaluation of metal implant surfaces against bacterial infection is identified for the first time. Its validity is demonstrated on Staphylococcus aureus adhesion to nanostructured titania surfaces. The established correlation: work function–bacteria adhesion is of general importance since it can be used for direct evaluation of any electrically conductive implant surfaces. - Highlights: • The correlation between work function and bacteria adhesion was discovered. • The discovered correlation is rationalized in terms of electrostatic bacteria–surface repulsion. • The results provide basis for the simple evaluation of implant surfaces against infection.

  16. Surface Energy and Work Function Control of AlOx/Al Surfaces by Fluorinated Benzylphosphonic Acids.

    Science.gov (United States)

    Abraham, Ffion; Ford, William E; Scholz, Frank; Nelles, Gabriele; Sandford, Graham; von Wrochem, Florian

    2016-05-11

    The performance of organic electronic devices can be significantly improved by modifying metal electrodes with organic monolayers, which alter the physical and chemical nature of the interface between conductor and semiconductor. In this paper we examine a series of 12 phosphonic acid compounds deposited on the native oxide layer of aluminum (AlOx/Al), an electrode material with widespread applications in organic electronics. This series includes dodecylphosphonic acid as a reference and 11 benzylphosphonic acids, seven of which are fluorinated, including five newly synthesized derivatives. The monolayers are experimentally characterized by contact angle goniometry and by X-ray photoemission spectroscopy (XPS), and work function data obtained by low-intensity XPS are correlated with molecular dipoles obtained from DFT calculations. We find that monolayers are formed with molecular areas ranging from 17.7 to 42.9 Å(2)/molecule, and, by the choice of appropriate terminal groups, the surface energy can be tuned from 23.5 mJ/m(2) to 70.5 mJ/m(2). Depending on the number and position of fluorine substituents on the aromatic rings, a variation in the work function of AlOx/Al substrates over a range of 0.91 eV is achieved, and a renormalization procedure based on molecular density yields a surprising agreement of work function changes with interface dipoles as expected from Helmholtz' equation. The ability to adjust energetics and adhesion at organic semiconductor/AlOx interfaces has immediate applications in devices such as OLEDs, OTFTs, organic solar cells, and printed organic circuits.

  17. Detailed first-principles studies on surface energy and work function of hexagonal metals

    Science.gov (United States)

    Ji, De-Peng; Zhu, Quanxi; Wang, Shao-Qing

    2016-09-01

    The surface energies and work functions for ten kinds of Miller-indices surfaces of hexagonal metals, Be, Mg, Tc, Re, Ru, and Os are calculated by means of the density functional theory (DFT) method. The results show that the metals belonging to the same group have a very similar rule in work functions and surface energies. The work functions of (0001), (01 1 - 1)" separators=",, and (10 1 - 0)" separators=", surfaces are generally larger than the work functions of (11 2 - 1)" separators=",, (11 2 - 2)" separators=",, (11 2 - 3)" separators=",, and (31 4 - 0)" separators=", surfaces. In contrast to work functions, there is more regularity in the crystallographic orientation dependence of surface energies. However, for the metals belonging to different groups, there are always some differences in the exact order of orientation dependence. It is also shown that the work functions and surface energies of the main group metals decrease as they go from top to the bottom in the same group of periodic table, while for the transition metals, they do not always obey this rule.

  18. Effect of dielectric coating on the electron work function and the surface stress of a metal

    Science.gov (United States)

    Babich, A. V.; Pogosov, V. V.

    2009-08-01

    The electron work function, contact potential difference, and surface stress of the elastically deformed faces of the metal covered by a dielectric are calculated by using the Kohn-Sham method and stabilized jellium model. Our calculations demonstrate the opposite deformation dependencies of the work function and contact potential difference. Dielectric coating leads to a negative change in the work function and a positive change in the contact potential difference. It is shown that the measurements of the contact potential difference of a deformed face by the Kelvin method give only the change in the value of the one-electron effective potential in the plane of a virtual image behind the surface, rather than the value of the electron work function. The obtained values of the electron work function and surface stress for Al, Au, Cu, and Zn are in agreement with the results of experiments for polycrystals.

  19. Work function anisotropy and surface stability of half-metallic CrO(2)

    NARCIS (Netherlands)

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

    2008-01-01

    Insight in the interplay between work function and stability is important for many areas of physics. In this paper, we calculate the anisotropy in the work function and the surface stability of CrO(2), a prototype half-metal, and find an anisotropy of 3.8 eV. An earlier model for the relation betwee

  20. Work function anisotropy and surface stability of half-metallic CrO(2)

    NARCIS (Netherlands)

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

    Insight in the interplay between work function and stability is important for many areas of physics. In this paper, we calculate the anisotropy in the work function and the surface stability of CrO(2), a prototype half-metal, and find an anisotropy of 3.8 eV. An earlier model for the relation

  1. Theoretical studies of the work functions of Pd-based bimetallic surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Ding, Zhao-Bin; Wu, Feng; Wang, Yue-Chao; Jiang, Hong, E-mail: jianghchem@pku.edu.cn [Beijing National Laboratory of Molecular Sciences, State Key Laboratory of Rare Earth Materials Chemistry and Applications, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871 (China)

    2015-06-07

    Work functions of Pd-based bimetallic surfaces, including mainly M/Pd(111), Pd/M, and Pd/M/Pd(111) (M = 4d transition metals, Cu, Au, and Pt), are studied using density functional theory. We find that the work function of these bimetallic surfaces is significantly different from that of parent metals. Careful analysis based on Bader charges and electron density difference indicates that the variation of the work function in bimetallic surfaces can be mainly attributed to two factors: (1) charge transfer between the two different metals as a result of their different intrinsic electronegativity, and (2) the charge redistribution induced by chemical bonding between the top two layers. The first factor can be related to the contact potential, i.e., the work function difference between two metals in direct contact, and the second factor can be well characterized by the change in the charge spilling out into vacuum. We also find that the variation in the work functions of Pd/M/Pd(111) surfaces correlates very well with the variation of the d-band center of the surface Pd atom. The findings in this work can be used to provide general guidelines to design new bimetallic surfaces with desired electronic properties.

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

    Science.gov (United States)

    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.

  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. Ab initio and work function and surface energy anisotropy of LaB6

    NARCIS (Netherlands)

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

    2006-01-01

    Lanthanum hexaboride is one of the cathode materials most used in high-power electronics technology, but the many experimental results do not provide a consistent picture of the surface properties. Therefore, we report the first ab initio calculations of the work functions and surface energies of

  5. Interrelation of work function and surface stability : The case of BaAl4

    NARCIS (Netherlands)

    Uijttewaal, MA; de Wijs, GA; de Groot, RA; Coehoorn, R; van Elsbergen, [No Value; Weijtens, CHL

    2005-01-01

    The relationship between the work function (Phi) and the surface stability of compounds is, to our knowledge, unknown but very important for applications such as organic light-emitting diodes. This relation is studied using first-principles calculations on various surfaces of BaAl4. The most stable

  6. Ab initio and work function and surface energy anisotropy of LaB6

    NARCIS (Netherlands)

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

    2006-01-01

    Lanthanum hexaboride is one of the cathode materials most used in high-power electronics technology, but the many experimental results do not provide a consistent picture of the surface properties. Therefore, we report the first ab initio calculations of the work functions and surface energies of th

  7. Microscopic work function anisotropy and surface chemistry of 316L stainless steel using photoelectron emission microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Barrett, N., E-mail: nick.barrett@cea.fr [CEA, IRAMIS, SPEC, LENSIS, F-91191 Gif-sur-Yvette (France); Renault, O. [CEA, LETI, Minatec Campus, F-38054 Grenoble Cedex 09 (France); Lemaître, H. [Université de Cergy-Pontoise, Rue d’Eragny, Neuville sur Oise, 95 031 Cergy-Pontoise (France); Surface Dynamics Laboratory, Institut for Fysik og Astronomi Aarhus Universitet, Ny Munkegade 120, 8000 Aarhus C (Denmark); Bonnaillie, P. [CEA, DEN, DANS, DMN, SRMP, F-91191 Gif-sur-Yvette (France); Barcelo, F. [CEA, DEN, DANS, DMN, SRMA, LA2M, F-91191 Gif-sur-Yvette (France); Miserque, F. [CEA, DEN, DANS, DPC, SCCME, LECA, F-91191 Gif-sur-Yvette (France); Wang, M.; Corbel, C. [Laboratoire des Solides Irradis, Ecole Polytechnique, route de Saclay, F-91128 Palaiseau (France)

    2014-08-15

    Highlights: • PEEM and EBSD study of spatial variations in local work function of 316L steel. • Correlation between work function and crystal grain orientation at the surface of 316L steel. • Spatially resolved chemistry of residual oxide layer. - Abstract: We have studied the variation in the work function of the surface of sputtered cleaned 316L stainless steel with only a very thin residual oxide surface layer as a function of grain orientation using X-ray photoelectron emission microscopy (XPEEM) and Electron Backscattering Diffraction. The grains are mainly oriented [1 1 1] and [1 0 1]. Four distinct work function values spanning a 150 meV energy window are measured. Grains oriented [1 1 1] have a higher work function than those oriented [1 0 1]. From core level XPEEM we deduce that all grain surfaces are Cr enriched and Ni depleted whereas the Cr/Fe ratio is similar for all grains. The [1 1 1] oriented grains show evidence for a Cr{sub 2}O{sub 3} surface oxide and a higher concentration of defective oxygen sites.

  8. Field-Emission from Chemically Functionalized Diamond Surfaces: Does Electron Affinity Picture Work?

    Science.gov (United States)

    Miyamoto, Yoshiyuki; Miyazaki, Takehide; Takeuchi, Daisuke; Okushi, Hideyo; Yamasaki, Satoshi

    2014-03-01

    By means of the time-dependent density functional electron dynamics, we have revisited the field-emission efficiency of chemically functionalized diamond (100) surfaces. In order to achieve high efficiency and high (chemical) stability, proper chemical species are needed to terminate diamond surfaces. Hydrogen (H) termination is well known to achieve the negative electron affinity (NEA) of diamond surface which indeed enhances field emission performance than that of clean surface with positive electron affinity (PEA). Yet, the durability of H-terminated diamond surface was concerned for long-time operation of the field-emission. Meantime, oxidation, or hydroxyl (OH) termination was considered to achieve chemical stability of the surface but presence of oxygen (O) atom should reduce the emission efficiency. Recently, H- OH-co-terminated surface is reported as NEA and was expected to achieve both emission efficiency and chemical stability. However, our simulation showed that emission efficiency of the H- OH- co-terminated surface is much lower than clean surface with PEA, thus we note that the electron affinity cannot be a unique measure to determine the emission efficiency. In this talk, we introduce necessity of new concept to understand the emission efficiency which needs to know detailed potential profile from bulk to vacuum through surface, which is strongly dependent on the surface chemical functionalization. This work was supported by ALCA project conducted by Japan Science and Technology Agency.

  9. Investigation of a Solution-Processable, Nonspecific Surface Modifier for Low Cost, High Work Function Electrodes.

    Science.gov (United States)

    Hinckley, Allison C; Wang, Congcong; Pfattner, Raphael; Kong, Desheng; Zhou, Yan; Ecker, Ben; Gao, Yongli; Bao, Zhenan

    2016-08-03

    We demonstrate the ability of the highly fluorinated, chemically inert copolymer poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) to significantly increase the work function of a variety of common electrode materials. The work function change is hypothesized to occur via physisorption of the polymer layer and formation of a surface dipole at the polymer/conductor interface. When incorporated into organic solar cells, an interlayer of PVDF-HFP at an Ag anode increases the open circuit voltage by 0.4 eV and improves device power conversion efficiency by approximately an order of magnitude relative to Ag alone. Solution-processable in air, PVDF-HFP thin films provide one possible route toward achieving low cost, nonreactive, high work function electrodes.

  10. Surface Dipole Formation and Lowering of the Work Function by Cs Adsorption on InP(100) Surface

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Y.; Liu, Z.; Pianetta, P.

    2007-06-08

    The Cs adsorption on InP(100) surface is studied with Synchrotron Radiation Photoelectron Spectroscopy. The charge transfer from Cs to the InP substrate is observed from the Cs induced In4d and P2p components, and this charge transfer results in surface dipole formation and lowering of the work function. The Cs4d intensity saturates at coverage of one monolayer (ML). However, a break point is observed at 0.5 ML, which coincides with the achievement of the minimum work function. This break point is due to the different vertical placement of the first and the second half monolayer of Cs atoms. Based on this information, a simple bi-layer structure for the Cs layer is presented. This bi-layer structure is consistent with the behavior of the charge transfer from the Cs to the InP substrate at different Cs coverages. This, in turn, explains why the work function decreases to a minimum at 0.5 ML of Cs and remains almost constant beyond this coverage. The depolarization of the surface dipoles is attributed to the saturation of charge transfer to the surface In atoms and the polarization of the Cs atoms in the second half monolayer induced by the positively charged Cs atoms in the first half monolayer.

  11. Surface Dipole Formation and Lowering of the Work Function by Cs Adsorption on InP(100) Surface

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Y.; Liu, Z.; Pianetta, P.

    2007-06-08

    The Cs adsorption on InP(100) surface is studied with Synchrotron Radiation Photoelectron Spectroscopy. The charge transfer from Cs to the InP substrate is observed from the Cs induced In4d and P2p components, and this charge transfer results in surface dipole formation and lowering of the work function. The Cs4d intensity saturates at coverage of one monolayer (ML). However, a break point is observed at 0.5 ML, which coincides with the achievement of the minimum work function. This break point is due to the different vertical placement of the first and the second half monolayer of Cs atoms. Based on this information, a simple bi-layer structure for the Cs layer is presented. This bi-layer structure is consistent with the behavior of the charge transfer from the Cs to the InP substrate at different Cs coverages. This, in turn, explains why the work function decreases to a minimum at 0.5 ML of Cs and remains almost constant beyond this coverage. The depolarization of the surface dipoles is attributed to the saturation of charge transfer to the surface In atoms and the polarization of the Cs atoms in the second half monolayer induced by the positively charged Cs atoms in the first half monolayer.

  12. Polarization effects and work function differences for transition metal surfaces: A perturbation LCAO MO approach

    Science.gov (United States)

    Shustorovich, Evgeny

    1981-05-01

    An analytical LCAO MO perturbation model has been developed for treating the polarization p-d contributions to the internal surface dipole moments of transition metal surfaces. The results are applied for treating changes in work functions (Ø) under chemisorption. The main conclusions are as follows. (1) Chemisorption of electropositive A (such as alkali metals) will always decrease Ø on all surfaces. (2) Chemisorption of electronegative A (such as H or halogens) can result in either increase or decrease in Ø depending on the nature of A and M. The smallest differences in A vs. M electronegativity are most likely to produce the paradoxical change ΔØ<0. The results obtained agree with experiment.

  13. Correlation of H/sup -/ production and the work function of a surface in a hydrogen plasma

    Energy Technology Data Exchange (ETDEWEB)

    Wada, M.

    1983-03-01

    Surface-plasma negative hydrogen ion sources are being developed as possible parts for future neutral beam systems. In these ion sources, negative hydrogen ions (H/sup -/) are produced at low work function metal surfaces immersed in hydrogen plasmas. To investigate the correlation between the work function and the H/sup -/ 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.

  14. CONTROL OF METAL SURFACES MACHINED IN ACCORDANCE WITH THE DIAMOND NANOMACHINING TECHNOLOGY BASED ON THE ELECTRON WORK FUNCTION

    Directory of Open Access Journals (Sweden)

    G. V. Sharonov

    2015-01-01

    Full Text Available Dimensional machining technology is based on the use of integrated geometric parameters of machined surfaces. Technological impact of a pick results in oxidation processes and changes in physic-chemical parameters of surface. Control of only geometric parameters is insufficient to describe characteristics of machining and formation of ultra-smooth surfaces. The electron work function is therefore used. The aim of the work was to study electrophysical states of optic surfaces of non-ferrous metals and alloys in relation to geometric and physic-chemical parameters according to the distribution of the electron work function over the surface. We conducted the study on experimental metal samples made of copper and aluminum alloy, machined in accordance with the diamond nanomachining technology. The diamond nanomachining technology would be capable of ensuring the roughness of non-ferrous metals and alloys machined at the level of Ra ≤ 0,005 µm. Modernized Kelvin probe was used as the registration technique of the changes of the electron work function over the surface. Dependence between the electron work function value, as well as its alteration and the physicchemical and geometric parameters of a surface has been determined. It has been shown that the diamond nanomachining technology makes it possible to obtain electro-physically uniform optical surfaces on copper and aluminum alloy with the minimal range of the distribution of the electric potential over the surface

  15. The Work Function Associated with Ultra-relativistic Electron Emission from Strongly Magnetized Neutron Star Surface

    Indian Academy of Sciences (India)

    Arpita Ghosh; Somenath Chakrabarty

    2011-09-01

    Following an extremely interesting idea (Schieber 1984), published long ago, the work function associated with the emission of ultra-relativistic electrons from magnetically deformed metallic crystal (mainly iron) at the outer crust of a magnetar is obtained using relativistic version of Thomas–Fermi type model for electron distribution around the nuclei in this region. In the present scenario, surprisingly, the work function becomes anisotropic; the longitudinal part is an increasing function of magnetic field strength, whereas the transverse part diverges.

  16. Effect of surface chemical composition on the work function of silicon substrates modified by binary self-assembled monolayers.

    Science.gov (United States)

    Kuo, Che-Hung; Liu, Chi-Ping; Lee, Szu-Hsian; Chang, Hsun-Yun; Lin, Wei-Chun; You, Yun-Wen; Liao, Hua-Yang; Shyue, Jing-Jong

    2011-09-07

    It has been shown that the application of self-assembled monolayers (SAMs) to semiconductors or metals may enhance the efficiency of optoelectronic devices by changing the surface properties and tuning the work functions at their interfaces. In this work, binary SAMs with various ratios of 3-aminopropyltrimethoxysilane (APTMS) and 3-mercaptopropyltrimethoxysilane (MPTMS) were used to modify the surface of Si to fine-tune the work function of Si to an arbitrary energy level. As an electron-donor, amine SAM (from APTMS) produced outward dipole moments, which led to a lower work function. Conversely, electron-accepting thiol SAM (from MPTMS) increased the work function. It was found that the work function of Si changed linearly with the chemical composition and increased with the concentration of thiol SAMs. Because dipoles of opposite directions cancelled each other out, homogeneously mixing them leads to a net dipole moment (hence the additional surface potential) between the extremes defined by each dipole and changes linearly with the chemical composition. As a result, the work function changed linearly with the chemical composition. Furthermore, the amine SAM possessed a stronger dipole than the thiol SAM. Therefore, the SAMs modified with APTMS showed a greater work function shift than did the SAMs modified with MPTMS.

  17. Understanding charge transfer of Li+ and Na+ ions scattered from metal surfaces with high work function

    Science.gov (United States)

    Chen, Lin; Wu, Wen-Bin; Liu, Pin-Yang; Xiao, Yun-Qing; Li, Guo-Peng; Liu, Yi-Ran; Jiang, Hao-Yu; Guo, Yan-Ling; Chen, Xi-Meng

    2016-08-01

    For Li+ and Na+ ions scattered from high work function metal surfaces, efficient neutralization is observed, and it cannot be explained by the conventional free electron model. In order to explain these experimental data, we investigate the velocity-dependent neutral fraction with the modified Brako-Newns (BN) model. The calculated results are in agreement with the experimental data. We find that the parallel velocity effect plays an important role in neutralizing the Li+ and Na+ ions for large angle scattering. The nonmonotonic velocity behavior of neutral fraction is strongly related to the distance-dependent coupling strength between the atomic level and metal states. Project supported by the National Natural Science Foundation of China (Grant Nos. 11405078 and 11474140), the Fundamental Research Funds for the Central Universities, China (Grant Nos. lzujbky-2014-169 and lzujbky-2015-244), the Project sponsored by the Scientific Research Foundation for the Returned Overseas Chinese Scholars, the State Education Ministry, and the National Students’ Innovation and Entrepreneurship Training Program (Grant Nos. 201410730069 and 201510730078).

  18. Self-consistent many-electron theory of electron work functions and surface potential characteristics for selected metals

    Science.gov (United States)

    Smith, J. R.

    1969-01-01

    Electron work functions, surface potentials, and electron number density distributions and electric fields in the surface region of 26 metals were calculated from first principles within the free electron model. Calculation proceeded from an expression of the total energy as a functional of the electron number density, including exchange and correlation energies, as well as a first inhomogeneity term. The self-consistent solution was obtained via a variational procedure. Surface barriers were due principally to many-body effects; dipole barriers were small only for some alkali metals, becoming quite large for the transition metals. Surface energies were inadequately described by this model, which neglects atomistic effects. Reasonable results were obtained for electron work functions and surface potential characteristics, maximum electron densities varying by a factor of over 60.

  19. A surface work function measurement technique utilizing constant deflected grazing electron trajectories: oxygen uptake on Cu(001).

    Science.gov (United States)

    Ermakov, A V; Ciftlikli, E Z; Syssoev, S E; Shuttleworth, I G; Hinch, B J

    2010-10-01

    We report on the application of a novel nondestructive in-vacuum technique for relative work function measurements, employing a grazing incidence electron deflection above a sample with a planar surface. Two deflected electron beam detectors are used as a position sensitive detector to control feedback to the sample potential as the sample work function changes. With feedback the sample potential exactly follows the surface sample-size averaged work function variation, so that the deflected beam trajectory remains stable. We also discuss methods to optimize the initial electron trajectories for this method, so as to minimize unwanted effects such as from uncontrolled external magnetic fields. As the electron beam does not impinge on the surface in this new technique electron induced desorption, ionization, dissociation, and/or decomposition is not induced at the interface. Importantly also the technique allows for free access to the surfaces enabling simultaneous deposition/evaporation and/or application of other surface characterization methods. We demonstrate its application in concurrent measurements of helium atom reflectivity and work function changes taking place during molecular oxygen exposure of a Cu(001) surface. A work function measurement sensitivity and stability is demonstrated at ∼10 mV at a sampling rate of 1 Hz and after application of an ∼7 s smoothing routine. In comparison to the helium atom reflectivity measurements, the work function measurements are more sensitive to the initial O uptake, and less so to the final coverage variations and possible surface reordering at higher O coverages.

  20. Work function shifts of a zinc oxide surface upon deposition of self-assembled monolayers: a theoretical insight.

    Science.gov (United States)

    Cornil, D; Van Regemorter, T; Beljonne, D; Cornil, J

    2014-10-14

    We have investigated at the theoretical Density Functional Theory level the way the work function of zinc oxide layers is affected upon deposition of self-assembled monolayers (SAMs). 4-tert-Butylpyridine (4TBP) and various benzoic acids (BA) were adsorbed on the apolar (101[combining macron]0) ZnO and used as probe systems to assess the influence of several molecular parameters. For the benzoid acids, we have investigated the impact of changing the nature of the terminal group (H, CN, OCH3) and the binding mode of the carboxylic acid (monodentate versus bidentate) on the apolar (101[combining macron]0) surface. For each system, we have quantified the contribution from the molecular core and the anchoring group as well as of the degree of surface reconstruction on the work function shift. For the benzoic acids, the structural reorganization of the surface induces a negative shift of the work function by about 0.3 ± 0.15 eV depending on the nature of the binding mode, irrespective of the nature of the terminal function. The bond-dipole potential strongly contributes to the modification of the work function, with values in the range +1.2 to +2.0 eV. In the case of 4TBP, we further characterized the influence of the degree of coverage and of co-adsorbed species (H, OH, and water molecules) on the ZnO/SAM electronic properties as well as the influence of the ZnO surface polarity by considering several models of the polar (0001) ZnO surface. The introduction of water molecules in the (un)dissociated form at full coverage on the non-polar surface only reduces the work function by 0.3-0.4 eV compared to a reference system without co-adsorbed species. Regarding the polar surface, the work function is also significantly reduced upon deposition of a single 4BTP molecule (from -1.44 eV to -1.73 eV for our model structures), with a shift similar in direction and magnitude compared to the non-polar surfaces.

  1. Local changes of work function near rough features on Cu surfaces operated under high external electric field

    Energy Technology Data Exchange (ETDEWEB)

    Djurabekova, Flyura, E-mail: flyura.djurabekova@helsinki.fi; Ruzibaev, Avaz; Parviainen, Stefan [Helsinki Institute of Physics and Department of Physics, University of Helsinki, P.O. Box 43, FI-00014 Helsinki (Finland); Holmström, Eero [Department of Physics, University of Helsinki, P.O. Box 64, FIN-00014 Helsinki (Finland); Department of Earth Sciences, Faculty of Maths and Physical Sciences, UCL Earth Sciences, Gower Street, London WC1E 6BT (United Kingdom); Hakala, Mikko [Department of Physics, University of Helsinki, P.O. Box 64, FIN-00014 Helsinki (Finland)

    2013-12-28

    Metal surfaces operated under high electric fields produce sparks even if they are held in ultra high vacuum. In spite of extensive research on the topic of vacuum arcs, the mystery of vacuum arc origin still remains unresolved. The indications that the sparking rates depend on the material motivate the research on surface response to extremely high external electric fields. In this work by means of density-functional theory calculations we analyze the redistribution of electron density on (100) Cu surfaces due to self-adatoms and in presence of high electric fields from −1 V/nm up to −2 V/nm (−1 to −2 GV/m, respectively). We also calculate the partial charge induced by the external field on a single adatom and a cluster of two adatoms in order to obtain reliable information on charge redistribution on surface atoms, which can serve as a benchmarking quantity for the assessment of the electric field effects on metal surfaces by means of molecular dynamics simulations. Furthermore, we investigate the modifications of work function around rough surface features, such as step edges and self-adatoms.

  2. A new polarization model of changes in the work function for bare and covered transition metal surfaces

    Science.gov (United States)

    Shustorovich, E.; Baetzold, R. C.

    We suggest a new polarization mechanism for changes in the work function Δ φ for bare transition metal surfaces and those covered by electronegative adsorbates such as hydrogen or halogens. The mechanism, based on the p-d orbital rehybridization of the surface atoms, has been tested for the relevant metal slabs, within a Hückel-type LCAO MO approach, both analytically and computationally. We present the major results stressing the basic physics behind them. Some conceptual implications of the new model are discussed.

  3. Effect of contaminations and surface preparation on the work function of single layer MoS2.

    Science.gov (United States)

    Ochedowski, Oliver; Marinov, Kolyo; Scheuschner, Nils; Poloczek, Artur; Bussmann, Benedict Kleine; Maultzsch, Janina; Schleberger, Marika

    2014-01-01

    Thinning out MoS2 crystals to atomically thin layers results in the transition from an indirect to a direct bandgap material. This makes single layer MoS2 an exciting new material for electronic devices. In MoS2 devices it has been observed that the choice of materials, in particular for contact and gate, is crucial for their performance. This makes it very important to study the interaction between ultrathin MoS2 layers and materials employed in electronic devices in order to optimize their performance. In this work we used NC-AFM in combination with quantitative KPFM to study the influence of the substrate material and the processing on single layer MoS2 during device fabrication. We find a strong influence of contaminations caused by the processing on the surface potential of MoS2. It is shown that the charge transfer from the substrate is able to change the work function of MoS2 by about 40 meV. Our findings suggest two things. First, the necessity to properly clean devices after processing as contaminations have a great impact on the surface potential. Second, that by choosing appropriate materials the work function can be modified to reduce contact resistance.

  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. Electrochemical fabrication of surface chemical gradients in thiol self-assembled monolayers with tailored work-functions.

    Science.gov (United States)

    Fioravanti, Giulia; Lugli, Francesca; Gentili, Denis; Mucciante, Vittoria; Leonardi, Francesca; Pasquali, Luca; Liscio, Andrea; Murgia, Mauro; Zerbetto, Francesco; Cavallini, Massimiliano

    2014-10-01

    The studies on surface chemical gradients are constantly gaining interest both for fundamental studies and for technological implications in materials science, nanofluidics, dewetting, and biological systems. Here we report on a new approach that is very simple and very efficient, to fabricate surface chemical gradients of alkanethiols, which combines electrochemical desorption/partial readsorption, with the withdrawal of the surface from the solution. The gradient is then stabilized by adding a complementary thiol terminated with a hydroxyl group with a chain length comparable to desorbed thiols. This procedure allows us to fabricate a chemical gradient of the wetting properties and the substrate work-function along a few centimeters with a gradient slope higher than 5°/cm. Samples were characterized by cyclic voltammetry during desorption, static contact angle, XPS analysis, and Kelvin probe. Computer simulations based on the Dissipative Particle Dynamics methods were carried out considering a water droplet on a mixed SAM surface. The results help to rationalize the composition of the chemical gradient at different position on the Au surface.

  6. Electron work function and surface energy of body-centered and face-centered cubic modifications of 4 d- and 5 d-metals

    Science.gov (United States)

    Aref'eva, L. P.; Shebzukhova, I. G.

    2016-07-01

    A technique for the evaluation of the electron work function of metallic single crystals and the electron work function anisotropy has been developed in the framework of the electron-statistical method. The surface energy and the electron work function have been calculated for crystal faces of allotropic modifications of 4 d- and 5 d-metals. A change in the electron work function due to the allotropic transformations has been estimated, and the periodic dependence of the electron work function has been determined. It has been shown that the results obtained using the proposed technique correlate with the available experimental data for polycrystals.

  7. Study on the sweep gas effect on the surface of Li{sub 4}SiO{sub 4} by means of work function measurement

    Energy Technology Data Exchange (ETDEWEB)

    Suzuki, Atsushi; Yamaguchi, Kenji; Yamawaki, Michio [Tokyo Univ. (Japan)

    1998-03-01

    In the establishment of fuel cycle of tritium, it is important to make research on how the sweep gas composition affects the surface properties of breeder materials and the release of tritium from the surface of them. In this study, the change of contact potential difference (CPD) between Li{sub 4}SiO{sub 4} and Pt was measured in various gas compositions with a high temperature Kelvin probe. The work function change of Li{sub 4}SiO{sub 4} was obtained from the measured CPD and the work function change of Pt which was estimated from blank tests. From the results, the effect of oxygen deficient layer near the surface of Li{sub 4}SiO{sub 4} was observed, and the effect of OH{sup -} at the surface of Li{sub 4}SiO{sub 4} was considered. (author)

  8. High tunability of the work function of (001) surface of ReO{sub 3} with O-vacancies: First principles analysis

    Energy Technology Data Exchange (ETDEWEB)

    Suchitra [Chemistry and Physics of Materials Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore 560064 (India); Pan, Jaysree [Theoretical Sciences Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore 560064 (India); Waghmare, Umesh V., E-mail: waghmare@jncasr.ac.in [Theoretical Sciences Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore 560064 (India); Sheikh Saqr Laboratory, Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore 560064 (India)

    2014-07-21

    Physical and chemical properties of transition metal oxides are central to the emerging field of oxide electronics. However, they are greatly influenced by defects, particularly, oxygen vacancies, which are always present in oxides. Here, we show how the control of oxygen vacancies at (001) surface of ReO{sub 3} can be used to tune its work function from 7 to 3 eV, based on first-principles density functional theoretical calculations of its structure, electronic and magnetic properties. The work function is shown to correlate directly with the stability of surface and exhibit a linear dependence on surface energy. We further assess the stability of ReO{sub 3} surface by determining its phonon dispersion, and explain how the surface stresses effectively strengthen structural instability leading to size dependence of its pressure dependent structural phase transitions observed experimentally. Our results highlight how significantly oxygen vacancies alter the work function of a metallic oxide and has important consequences to development of electronic devices and catalysts based on oxide heterostructures.

  9. 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. Uijttewa

  10. 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.

  11. Functional properties of surface layers of X38CrMoV5-3 hot work tool steel alloyed with HPDL laser

    OpenAIRE

    L.A. Dobrzański; M. Piec; K. Labisz; M. Bonek; A. Klimpel

    2007-01-01

    Purpose: Improvement of functional properties alloyed of hot work tool steel surface layers is one of the goals of this paper.Design/methodology/approach: The material used for investigation was the hot work tool steel X38CrMoV5-3. Remelting and alloying of surface layers were made using the HPDL high power diode laser Rofin DL 020 in the laser power range of 1.2-2.3 kW. The carbide powders were applied on specimens prepared and degreased in this way; the powder was mixed with the sodium glas...

  12. Work Function Engineering of Graphene

    Directory of Open Access Journals (Sweden)

    Rajni Garg

    2014-04-01

    Full Text Available Graphene is a two dimensional one atom thick allotrope of carbon that displays unusual crystal structure, electronic characteristics, charge transport behavior, optical clarity, physical & mechanical properties, thermal conductivity and much more that is yet to be discovered. Consequently, it has generated unprecedented excitement in the scientific community; and is of great interest to wide ranging industries including semiconductor, optoelectronics and printed electronics. Graphene is considered to be a next-generation conducting material with a remarkable band-gap structure, and has the potential to replace traditional electrode materials in optoelectronic devices. It has also been identified as one of the most promising materials for post-silicon electronics. For many such applications, modulation of the electrical and optical properties, together with tuning the band gap and the resulting work function of zero band gap graphene are critical in achieving the desired properties and outcome. In understanding the importance, a number of strategies including various functionalization, doping and hybridization have recently been identified and explored to successfully alter the work function of graphene. In this review we primarily highlight the different ways of surface modification, which have been used to specifically modify the band gap of graphene and its work function. This article focuses on the most recent perspectives, current trends and gives some indication of future challenges and possibilities.

  13. Work Function Engineering of Graphene

    Science.gov (United States)

    Garg, Rajni; Dutta, Naba K.; Roy Choudhury, Namita

    2014-01-01

    Graphene is a two dimensional one atom thick allotrope of carbon that displays unusual crystal structure, electronic characteristics, charge transport behavior, optical clarity, physical & mechanical properties, thermal conductivity and much more that is yet to be discovered. Consequently, it has generated unprecedented excitement in the scientific community; and is of great interest to wide ranging industries including semiconductor, optoelectronics and printed electronics. Graphene is considered to be a next-generation conducting material with a remarkable band-gap structure, and has the potential to replace traditional electrode materials in optoelectronic devices. It has also been identified as one of the most promising materials for post-silicon electronics. For many such applications, modulation of the electrical and optical properties, together with tuning the band gap and the resulting work function of zero band gap graphene are critical in achieving the desired properties and outcome. In understanding the importance, a number of strategies including various functionalization, doping and hybridization have recently been identified and explored to successfully alter the work function of graphene. In this review we primarily highlight the different ways of surface modification, which have been used to specifically modify the band gap of graphene and its work function. This article focuses on the most recent perspectives, current trends and gives some indication of future challenges and possibilities. PMID:28344223

  14. Characterisation of Functional Surfaces

    DEFF Research Database (Denmark)

    Lonardo, P.M.; De Chiffre, Leonardo; Bruzzone, A.A.

    2004-01-01

    Characterisation of surfaces is of fundamental importance to control the manufacturing process and the functional performance of the part. Many applications concern contact and tribology problems, which include friction, wear and lubrication. This paper presents the techniques and instruments for...

  15. Model electrochemical interfaces in ultra-high vacuum: solvent-induced surface potential profiles on Pt(111) from work-function measurements and infrared Stark effects

    Science.gov (United States)

    Kizhakevariam, Naushad; Villegas, Ignacio; Weaver, Michael J.

    1995-08-01

    The influence of various solvents upon the interfacial-potential profile on Pt(111) has been investigated by means of work-function changes and infrared frequency Stark shifts attending sequential-molecular dosing in ultra-high vacuum (UHV) at a suitably low temperature (ca. 100 K) with the primary objective of assessing the role of surface solvation in related electrochemical systems. The solvents examined — dichloromethane, benzene, acetone, acetonitrile, methanol, and ammonia — span a range of polarity and other solvating properties. These species were dosed onto both clean and CO-saturated Pt(111), the Stark shifts being evaluated for the CO stretching mode of terminally co-ordinated carbon monoxide. Marked decreases (≥ 1 eV) in the work function, Φ, and hence in the surface potential, φ, are observed on the addition of most solvents onto clean Pt(111). Milder yet still substantial Φ decreases are also observed for solvent dosage upon CO-saturated Pt(111). These latter Φ changes correlate approximately with the observed vCO frequency downshifts, suggesting that the latter property is also sensitive to the solvent-induced electrostatic interfacial field. The functional form of both the Φ decreases and the corresponding vCO frequency downshifts induced by solvent dosage provide insight into the dosage-dependent potential profile and its relationship to both the monolayer and multilayer solvent structure. The present findings are also briefly compared with corresponding vtCO - Φ data obtained for potassium atom dosing, where the surface potential is altered instead by varying the surface electronic charge in the presence of a given solvent. The underlying factors responsible for the surprisingly large solvent-induced surface potential shifts are discussed in detail, and the likely importance of the surface electronic charge distribution as well as solvent dipole orientation and adsorbate-metal charge sharing is pointed out.

  16. Silver nanoparticles with tunable work functions

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Pangpang, E-mail: pangpang@molecular-device.kyushu-u.ac.jp [Education Center for Global Leaders in Molecular Systems for Devices, Kyushu University, Fukuoka 819-0395 (Japan); Tanaka, Daisuke [Department of Electrical and Electronic Engineering, National Institute of Technology, Oita College, Oita 870-0152 (Japan); Ryuzaki, Sou; Araki, Shohei; Okamoto, Koichi; Tamada, Kaoru [Institute for Materials Chemistry and Engineering, Kyushu University, Fukuoka 819-0395 (Japan)

    2015-10-12

    To improve the efficiencies of electronic devices, materials with variable work functions are required to decrease the energy level differences at the interfaces between working layers. Here, we report a method to obtain silver nanoparticles with tunable work functions, which have the same silver core of 5 nm in diameter and are capped by myristates and 1-octanethoilates self-assembled monolayers, respectively. The silver nanoparticles capped by organic molecules can form a uniform two-dimensional sheet at air-water interface, and the sheet can be transferred on various hydrophobic substrates. The surface potential of the two-dimensional nanoparticle sheet was measured in terms of Kelvin probe force microscopy, and the work function of the sheet was then calculated from the surface potential value by comparing with a reference material. The exchange of the capping molecules results in a work function change of approximately 150–250 meV without affecting their hydrophobicity. We systematically discussed the origin of the work function difference and found it should come mainly from the anchor groups of the ligand molecules. The organic molecule capped nanoparticles with tunable work functions have a potential for the applications in organic electronic devices.

  17. Ab initio work function of elemental metals

    DEFF Research Database (Denmark)

    Skriver, Hans Lomholt; Rosengaard, N. M.

    1992-01-01

    We have used a recently developed self-consistent Green’s-function technique based on tight-binding linear-muffin-tin-orbital theory to calculate the work function for the close-packed surfaces of 37 elemental metals. The results agree with the limited experimental data obtained from single...... crystals to within 15%, and they explain the smooth behavior of the polycrystalline data as a function of atomic number....

  18. Functional properties of surface layers of X38CrMoV5-3 hot work tool steel alloyed with HPDL laser

    Directory of Open Access Journals (Sweden)

    L.A. Dobrzański

    2007-10-01

    Full Text Available Purpose: Improvement of functional properties alloyed of hot work tool steel surface layers is one of the goals of this paper.Design/methodology/approach: The material used for investigation was the hot work tool steel X38CrMoV5-3. Remelting and alloying of surface layers were made using the HPDL high power diode laser Rofin DL 020 in the laser power range of 1.2-2.3 kW. The carbide powders were applied on specimens prepared and degreased in this way; the powder was mixed with the sodium glass as inorganic binder in proportion of 30% binder and 70% powder. Paste coating 0.5 mm thick was put down in each case.Findings: The hardness changes of the surface layers obtained by remelting and alloying with carbides using the high power diode laser are accompanied with the improved tribological properties compared to the conventionally heat treated steel. The highest abrasion wear resistance, more than 2.5 times higher than that of the base material, was revealed in case the steel alloyed with vanadium carbide.Research limitations/implications: These advantages are the result of features unique to the HPDL, such as: shorter wavelength (thus better beam absorption for most metallic materials, and smaller absorption length and better temporal beam stability (due to beam integration compared to Nd:YAG and CO2 lasers. HPDL materials processing is, therefore, expected to produce better quality and more consistent and repeatable results for applications requiring beam spot sizes larger than 0.5mm diameter. One of the issues of concern in the practical applications of the lasers in materials processing for mass production is the repeatability.Practical implications: The research results indicate to the feasibility and purposefulness of the practical use of remelting and alloying with the ceramic particles using the high power diode laser for manufacturing and regeneration of various tools from the X38CrMoV5-3 hot-work tool steel.Originality/value: The laser

  19. Low work function thermionic emission materials

    Energy Technology Data Exchange (ETDEWEB)

    Zavadil, K.R.; King, D.B.; Ruffner, J.A.

    1999-11-01

    Thermionic energy conversion in a microminiature format shows potential as a viable, high efficiency, on-chip power source. Microminiature thermionic converters (MTC) with inter-electrode spacings on the order of microns are currently being prototyped and evaluated at Sandia. The remaining enabling technology is the development of low work function materials and processes than can be integrated into these converters. In this report, the authors demonstrate a method of incorporating thin film emitters into converters using rf sputtering. They find that the resultant films possess a minimum work function of 1.2 eV. Practical energy conversion is hindered by surface work function non-uniformity. They postulate the source of this heterogeneity to be a result of limited bulk and surface transport of barium. Several methods are proposed for maximizing transport, including increased film porosity and the use of metal terminating layers. They demonstrate a novel method for incorporating film porosity based on metal interlayer coalescence.

  20. Work-Function and Surface Energy Tunable Cyanoacrylic Acid Small-Molecule Derivative Interlayer on Planar ZnO Nanorods for Improved Organic Photovoltaic Performance.

    Science.gov (United States)

    Ambade, Swapnil B; Ambade, Rohan B; Bagde, Sushil S; Lee, Soo-Hyoung

    2016-12-28

    The issue of work-function and surface energy is fundamental to "decode" the critical inorganic/organic interface in hybrid organic photovoltaics, which influences important photovoltaic events like exciton dissociation, charge transfer, photocurrent (Jsc), open-circuit voltage (Voc), etc. We demonstrate that by incorporating an interlayer of cyanoacrylic acid small molecular layer (SML) on solution-processed, spin-coated, planar ZnO nanorods (P-ZnO NRs), higher photovoltaic (PV) performances were achieved in both inverted organic photovoltaic (iOPV) and hybrid organic photovoltaic (HOPV) devices, where ZnO acts as an "electron-transporting layer" and as an "electron acceptor", respectively. For the tuned range of surface energy from 52.5 to 33 mN/m, the power conversion efficiency (PCE) in bulk heterojunction (BHJ) iOPVs based on poly(3-hexylthiophene) (P3HT) and phenyl-C60-butyric acid methyl ester (PC60BM) increases from 3.16% to 3.68%, and that based on poly[4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b;4,5b']dithiophene-2,6-diyl-alt-(4-(2-ethylhexyl)-3-fluorothieno[3,4-b]thiophene)-2-carboxylate-2-6-diyl)] (PTB7:Th):[6,6]-phenyl C71 butyric acid methyl ester (PC71BM) photoactive BHJ increases from 6.55% to 8.0%, respectively. The improved PV performance in iOPV devices is majorly attributed to enhanced photocurrents achieved as a result of reduced surface energy and greater electron affinity from the covalent attachment of the strong electron-withdrawing cyano moiety, while that in HOPV devices, where PCE increases from 0.21% to 0.79% for SML-modified devices, is ascribed to a large increase in Voc benefitted due to reduced work function effected from the presence of strong dipole moment in SML that points away from P-ZnO NRs.

  1. Wet Work and Barrier Function.

    Science.gov (United States)

    Fartasch, Manigé

    2016-01-01

    Wet work defined as unprotected exposure to humid environments/water; high frequencies of hand washing procedures or prolonged glove occlusion is believed to cause irritant contact dermatitis in a variety of occupations. This review considers the recent studies on wet-work exposure and focuses on its influence on barrier function. There are different methods to study the effect of wet work on barrier function. On the one hand, occupational cohorts at risk can be monitored prospectively by skin bioengineering technology and clinical visual scoring systems; on the other hand, experimental test procedures with defined application of water, occlusion and detergents are performed in healthy volunteers. Both epidemiological studies and the results of experimental procedures are compared and discussed. A variety of epidemiological studies analyze occupational cohorts at risk. The measurement of transepidermal water loss, an indicator of the integrity of the epidermal barrier, and clinical inspection of the skin have shown that especially the frequencies of hand washing and water contact/contact to aqueous mixtures seem to be the main factors for the occurrence of barrier alterations. On the other hand, in a single cross-sectional study, prolonged glove wearing (e.g. occlusion for 6 h per shift in clean-room workers) without exposure to additional hazardous substances seemed not to affect the skin negatively. But regarding the effect of occlusion, there is experimental evidence that previously occluded skin challenged with sodium lauryl sulfate leads to an increased susceptibility to the irritant with an aggravation of the irritant reaction. These findings might have relevance for the real-life situation in so far as after occupational glove wearing, the skin is more susceptible to potential hazards to the skin even during leisure hours.

  2. Electron work function: a novel probe for toughness.

    Science.gov (United States)

    Hua, Guomin; Li, Dongyang

    2016-02-14

    In this study, based on the calculation of surface properties, ideal strengths and responses of electron localization to the deformation, it was demonstrated that the fracture toughness of transition metals can be correlated to their electron work function. Within the range where the electron work function is smaller than 4.6 eV, the fracture toughness increases with the electron work function. However, if the electron work function exceeds 4.6 eV, then the fracture toughness decreases with an increase in electron work function. This evidence indicates that electron work function could be a sensitive parameter for material selection in order to control the fracture toughness.

  3. Characterisation of Functional Surfaces

    DEFF Research Database (Denmark)

    Lonardo, P.M.; De Chiffre, Leonardo; Bruzzone, A.A.

    2004-01-01

    for characterisation of surfaces, discussing their operating principles and metrological properties. A review of the conventional 2D and new 3D roughness parameters is given, considering both the current standards and new proposals for texture quantification, with a particular attention to the methods orientated...

  4. Surface computing and collaborative analysis work

    CERN Document Server

    Brown, Judith; Gossage, Stevenson; Hack, Chris

    2013-01-01

    Large surface computing devices (wall-mounted or tabletop) with touch interfaces and their application to collaborative data analysis, an increasingly important and prevalent activity, is the primary topic of this book. Our goals are to outline the fundamentals of surface computing (a still maturing technology), review relevant work on collaborative data analysis, describe frameworks for understanding collaborative processes, and provide a better understanding of the opportunities for research and development. We describe surfaces as display technologies with which people can interact directly, and emphasize how interaction design changes when designing for large surfaces. We review efforts to use large displays, surfaces or mixed display environments to enable collaborative analytic activity. Collaborative analysis is important in many domains, but to provide concrete examples and a specific focus, we frequently consider analysis work in the security domain, and in particular the challenges security personne...

  5. Quantify work load and muscle functional activation patterns in neck-shoulder muscles of female sewing machine operators using surface electromyogram.

    Science.gov (United States)

    Zhang, Fei-Ruo; He, Li-Hua; Wu, Shan-Shan; Li, Jing-Yun; Ye, Kang-Pin; Wang, Sheng

    2011-11-01

    Work-related musculoskeletal disorders (WMSDs) have high prevalence in sewing machine operators employed in the garment industry. Long work duration, sustained low level work and precise hand work are the main risk factors of neck-shoulder disorders for sewing machine operators. Surface electromyogram (sEMG) offers a valuable tool to determine muscle activity (internal exposure) and quantify muscular load (external exposure). During sustained and/or repetitive muscle contractions, typical changes of muscle fatigue in sEMG, as an increase in amplitude or a decrease as a shift in spectrum towards lower frequencies, can be observed. In this paper, we measured and quantified the muscle load and muscular activity patterns of neck-shoulder muscles in female sewing machine operators during sustained sewing machine operating tasks using sEMG. A total of 18 healthy women sewing machine operators volunteered to participate in this study. Before their daily sewing machine operating task, we measured the maximal voluntary contractions (MVC) and 20%MVC of bilateral cervical erector spinae (CES) and upper trapezius (UT) respectively, then the sEMG signals of bilateral UT and CES were monitored and recorded continuously during 200 minutes of sustained sewing machine operating simultaneously which equals to 20 time windows with 10 minutes as one time window. After 200 minutes' work, we retest 20%MVC of four neck-shoulder muscles and recorded the sEMG signals. Linear analysis, including amplitude probability distribution frequency (APDF), amplitude analysis parameters such as roof mean square (RMS) and spectrum analysis parameter as median frequency (MF), were used to calculate and indicate muscle load and muscular activity of bilateral CES and UT. During 200 minutes of sewing machine operating, the median load for the left cervical erector spinae (LCES), right cervical erector spinae (RCES), left upper trapezius (LUT) and right upper trapezius (RUT) were 6.78%MVE, 6.94%MVE, 6

  6. Quantify work load and muscle functional activation patterns in neck-shoulder muscles of female sewing machine operators using surface electromyogram

    Institute of Scientific and Technical Information of China (English)

    ZHANG Fei-ruo; HE Li-hua; WU Shan-shan; LI Jing-yun; YE Kang-pin; WANG Sheng

    2011-01-01

    Background Work-related musculoskeletal disorders (WMSDs) have high prevalence in sewing machine operators employed in the garment industry.Long work duration,sustained low level work and precise hand work are the main risk factors of neck-shoulder disorders for sewing machine operators.Surface electromyogram (sEMG) offers a valuable tool to determine muscle activity (internal exposure) and quantify muscular load (external exposure).During sustained and/or repetitive muscle contractions,typical changes of muscle fatigue in sEMG,as an increase in amplitude or a decrease as a shift in spectrum towards lower frequencies,can be observed.In this paper,we measured and quantified the muscle load and muscular activity patterns of neck-shoulder muscles in female sewing machine operators during sustained sewing machine operating tasks using sEMG.Methods A total of 18 healthy women sewing machine operators volunteered to participate in this study.Before their daily sewing machine operating task,we measured the maximal voluntary contractions (MVC) and 20%MVC of bilateral cervical erector spinae (CES) and upper trapezius (UT) respectively,then the sEMG signals of bilateral UT and CES were monitored and recorded continuously during 200 minutes of sustained sewing machine operating simultaneously which equals to 20 time windows with 10 minutes as one time window.After 200 minutes' work,we retest 20%MVC of four neck-shoulder muscles and recorded the sEMG signals.Linear analysis,including amplitude probability distribution frequency (APDF),amplitude analysis parameters such as roof mean square (RMS) and spectrum analysis parameter as median frequency (MF),were used to calculate and indicate muscle load and muscular activity of bilateral CES and UT.Results During 200 minutes of sewing machine operating,the median load for the left cervical erector spinae (LCES),right cervical erector spinae (RCES),left upper trapezius (LUT) and right upper trapezius (RUT) were 6.78%MVE,6.94

  7. Low work function silicon collector for thermionic converters

    Science.gov (United States)

    Chang, K. H.; Shimada, K.

    1976-01-01

    To improve the efficiency of present thermionic converters, single crystal silicon was investigated as a low work function collector material. The experiments were conducted in a test vehicle which resembled an actual thermionic converter. Work function as low as 1.0eV was obtained with an n-type silicon. The stabilities of the activated surfaces at elevated temperatures were tested by raising the collector temperature up to 829 K. By increasing the Cs arrival rate, it was possible to restore the originally activated low work function of the surface at elevated surface temperatures. These results, plotted in the form of Rasor-Warner curve, show a behavior similar to that of metal electrode except that the minimum work function was much lower with silicon than with metals.

  8. Surface modification and functionalization of nanostructured carbons

    Directory of Open Access Journals (Sweden)

    A. Stanishevsky

    2009-12-01

    -terminated NCD films, the role of specific type of surface groups present on carbon nanoparticles has yet to be determined.Practical implications: The development of optimal strategies to functionalize various nanocarbons will have strong impact on the design of efficient nanostructured surfaces and particles for a variety of biological and medical applications.Originality/value: This work adds new insights to the expanding research in biomedical applications of nanoscale carbon materials.

  9. Tuning the work-function via strong coupling.

    Science.gov (United States)

    Hutchison, James A; Liscio, Andrea; Schwartz, Tal; Canaguier-Durand, Antoine; Genet, Cyriaque; Palermo, Vincenzo; Samorì, Paolo; Ebbesen, Thomas W

    2013-05-01

    The tuning of the molecular material work-function via strong coupling with vacuum electromagnetic fields is demonstrated. Kelvin probe microscopy extracts the surface potential (SP) changes of a photochromic molecular film on plasmonic hole arrays and inside Fabry-Perot cavities. Modulating the optical cavity resonance or the photochromic film effectively tunes the work-function, suggesting a new tool for tailoring material properties.

  10. Challenges and opportunities in chemical functionalization of semiconductor surfaces

    Science.gov (United States)

    Gao, Fei; Teplyakov, Andrew V.

    2017-03-01

    The field of chemical functionalization of semiconductor surfaces has developed tremendously over the last several decades. Since silicon occupied the main portion of the industrial applications of semiconductors, understanding its surface chemistry at a molecular level is very advanced. This particular field has also benefited from combining the work on well-defined clean silicon surfaces in vacuum, well-characterized chemically-passivated surfaces in ambient, and current and potential applications of the resulting interfaces. This article will use this work to build a generalized evaluation of the developments in surface chemical functionalization, specifically addressing organic functionalization of semiconductors, and consider the challenges and opportunities for further evolution of the field.

  11. The role of cesium suboxides in low-work-function surface layers studied by X-ray photoelectron spectroscopy - Ag-O-Cs

    Science.gov (United States)

    Yang, S.-J.; Bates, C. W., Jr.

    1980-01-01

    The oxidation of cesium on silver substrates has been studied using photoyield measurements and X-ray photoelectron spectroscopy. The occurrence of two O1s peaks in the core-level spectrum at 527.5 and 531.5-eV binding energy for cesium and oxygen exposures giving the optimum photoyield proves that two oxides of cesium exist in high-photoyield surfaces, and not Cs2O alone as previously thought. From the shape and position of the cesium peaks and the Auger parameter, the assignment of the O1s peaks at 527.5- and 531.5-eV binding energies to oxygen in Cs2O and Cs11O3, respectively, can be made. Hence the total cesium-oxygen layer is a mixed phase consisting of Cs2O + Cs11O3, approximately 20-40 A thick.

  12. Engineering Ultra-Low Work Function of Graphene.

    Science.gov (United States)

    Yuan, Hongyuan; Chang, Shuai; Bargatin, Igor; Wang, Ning C; Riley, Daniel C; Wang, Haotian; Schwede, Jared W; Provine, J; Pop, Eric; Shen, Zhi-Xun; Pianetta, Piero A; Melosh, Nicholas A; Howe, Roger T

    2015-10-14

    Low work function materials are critical for energy conversion and electron emission applications. Here, we demonstrate for the first time that an ultralow work function graphene is achieved by combining electrostatic gating with a Cs/O surface coating. A simple device is built from large-area monolayer graphene grown by chemical vapor deposition, transferred onto 20 nm HfO2 on Si, enabling high electric fields capacitive charge accumulation in the graphene. We first observed over 0.7 eV work function change due to electrostatic gating as measured by scanning Kelvin probe force microscopy and confirmed by conductivity measurements. The deposition of Cs/O further reduced the work function, as measured by photoemission in an ultrahigh vacuum environment, which reaches nearly 1 eV, the lowest reported to date for a conductive, nondiamond material.

  13. Tuning of metal work functions with self-assembled monolayers

    NARCIS (Netherlands)

    de Boer, B; Hadipour, A; Foekema, R; van Woudenbergh, T; Mandoc, MM; Mihailetchi, VD; Blom, PWM; Heremans, PL; Muccini, M; Hofstraat, H

    2004-01-01

    Tuning the work functions of metals was demonstrated by chemically modifying the metal surface through the formation of chemisorbed self-assembled monolayers (SAMs) derived from 1H,1H,2H,2H-perfluorinated alkanethiols and hexadecanethiol. The ordering inherent in the SAMs creates an effective, molec

  14. Silicon crystal as a low work function collector

    Science.gov (United States)

    Chang, K. H.; Shimada, K.

    1975-01-01

    A test vehicle with a low work function collector which can be incorporated in a thermionic converter was constructed from standard vacuum components including an ultrahigh vacuum ion pump. The collector assembly was fabricated by diffusion bonding a (100) oriented silicon single crystal to a molybdenum block. The silicon surface was treated with cesium and oxygen to produce an NEA-type condition and the results were tested by photoemission and work function measurements. An n-type silicon collector was successfully activated to a work function of 1.0 eV, which was verified by photoemission spectral yield measurements. The stability test of an activated surface at elevated temperatures was conducted in the range from room temperature to 619 K, which was slightly lower than the designed collector temperature of 700 K. The work function measurements clearly demonstrated that the behavior of cesium replenishment on the activated Si surface was similar in nature to that of a metallic surface; that is, the loss of cesium by thermal desorption could be compensated by maintaining an adequate vapor pressure of cesium.

  15. Work Function Calculation For Hafnium- Barium System

    Directory of Open Access Journals (Sweden)

    K.A. Tursunmetov

    2015-08-01

    Full Text Available The adsorption process of barium atoms on hafnium is considered. A structural model of the system is presented and on the basis of calculation of interaction between ions dipole system the dependence of the work function on the coating.

  16. Work of adhesion of dairy products on stainless steel surface

    Directory of Open Access Journals (Sweden)

    Patrícia Campos Bernardes

    2012-12-01

    Full Text Available The adhesion of the solids presents in food can difficult the process of surface cleaning and promotes the bacterial adhesion process and can trigger health problems. In our study, we used UHT whole milk, chocolate based milk and infant formula to evaluate the adhesion of Enterobacter sakazakii on stainless steel coupons, and we determine the work of adhesion by measuring the contact angle as well as measured the interfacial tension of the samples. Inaddition we evaluated the hydrophobicity of stainless steel after pre-conditioning with milk samples mentioned. E. sakazakii was able to adhere to stainless steel in large numbers in the presence of dairy products. The chocolate based milk obtained the lower contact angle with stainless steel surface, higher interfacial tension and consequently higher adhesion work. It was verified a tendency of decreasing the interfacial tension as a function of the increasing of protein content. The pre-conditioning of the stainless steel coupons with milk samples changed the hydrophobic characteristics of the surfaces and became them hydrophilic. Therefore, variations in the composition of the milk products affect parameters important that can influence the procedure of hygiene in surface used in food industry.

  17. 30 CFR 56.17001 - Illumination of surface working areas.

    Science.gov (United States)

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Illumination of surface working areas. 56.17001... NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH STANDARDS-SURFACE METAL AND NONMETAL MINES Illumination § 56.17001 Illumination of surface working areas. Illumination sufficient to provide safe...

  18. Theoretical determination of cesiated work functions

    Science.gov (United States)

    Szejn, R. M.

    1972-01-01

    A computer program based on the theoretical work of Gyftopoulos, Steiner, and Levine on bimetallic systems and using a modified version of Wilkins' SIMCON subroutine SURFAS was written for the Univac 1108. This program, WFGSL, accepts the operating conditions and the physical parameters pertinent to the substrate and adsorbate, and outputs the field-free work function, electron current (Richardson equation), ion current (Saha equation), and fractional substrate coverage by the adsorbate. A brief description of the theory is presented together with a program description and listing. An application of the program to a bimetallic system of cesium (adsorbate) and rhenium (substrate) is also described.

  19. 77 FR 50165 - Escape and Evacuation Plans for Surface Coal Mines, Surface Facilities and Surface Work Areas of...

    Science.gov (United States)

    2012-08-20

    ... Administration. Title: Escape and Evacuation Plans for Surface Coal Mines, Surface Facilities ] and Surface Work... Safety and Health Administration Escape and Evacuation Plans for Surface Coal Mines, Surface Facilities and Surface Work Areas of Underground Coal Mines AGENCY: Mine Safety and Health Administration,...

  20. Bioinspired Functional Surfaces for Technological Applications

    Science.gov (United States)

    Sharma, Vipul; Kumar, Suneel; Reddy, Kumbam Lingeshwar; Bahuguna, Ashish; Krishnan, Venkata

    2016-08-01

    Biological matters have been in continuous encounter with extreme environmental conditions leading to their evolution over millions of years. The fittest have survived through continuous evolution, an ongoing process. Biological surfaces are the important active interfaces between biological matters and the environment, and have been evolving over time to a higher state of intelligent functionality. Bioinspired surfaces with special functionalities have grabbed attention in materials research in the recent times. The microstructures and mechanisms behind these functional biological surfaces with interesting properties have inspired scientists to create artificial materials and surfaces which possess the properties equivalent to their counterparts. In this review, we have described the interplay between unique multiscale (micro- and nano-scale) structures of biological surfaces with intrinsic material properties which have inspired researchers to achieve the desired wettability and functionalities. Inspired by naturally occurring surfaces, researchers have designed and fabricated novel interfacial materials with versatile functionalities and wettability, such as superantiwetting surfaces (superhydrophobic and superoleophobic), omniphobic, switching wettability and water collecting surfaces. These strategies collectively enable functional surfaces to be utilized in different applications such as fog harvesting, surface-enhanced Raman spectroscopy (SERS), catalysis, sensing and biological applications. This paper delivers a critical review of such inspiring biological surfaces and artificial bioinspired surfaces utilized in different applications, where material science and engineering have merged by taking inspiration from the natural systems.

  1. Harvesting vibrational energy using material work functions.

    Science.gov (United States)

    Varpula, Aapo; Laakso, Sampo J; Havia, Tahvo; Kyynäräinen, Jukka; Prunnila, Mika

    2014-10-28

    Vibration energy harvesters scavenge energy from mechanical vibrations to energise low power electronic devices. In this work, we report on vibration energy harvesting scheme based on the charging phenomenon occurring naturally between two bodies with different work functions. Such work function energy harvester (WFEH) is similar to electrostatic energy harvester with the fundamental distinction that neither external power supplies nor electrets are needed. A theoretical model and description of different operation modes of WFEHs are presented. The WFEH concept is tested with macroscopic experiments, which agree well with the model. The feasibility of miniaturizing WFEHs is shown by simulating a realistic MEMS device. The WFEH can be operated as a charge pump that pushes charge and energy into an energy storage element. We show that such an operation mode is highly desirable for applications and that it can be realised with either a charge shuttle or with switches. The WFEH is shown to give equal or better output power in comparison to traditional electrostatic harvesters. Our findings indicate that WFEH has great potential in energy harvesting applications.

  2. Harvesting Vibrational Energy Using Material Work Functions

    Science.gov (United States)

    Varpula, Aapo; Laakso, Sampo J.; Havia, Tahvo; Kyynäräinen, Jukka; Prunnila, Mika

    2014-01-01

    Vibration energy harvesters scavenge energy from mechanical vibrations to energise low power electronic devices. In this work, we report on vibration energy harvesting scheme based on the charging phenomenon occurring naturally between two bodies with different work functions. Such work function energy harvester (WFEH) is similar to electrostatic energy harvester with the fundamental distinction that neither external power supplies nor electrets are needed. A theoretical model and description of different operation modes of WFEHs are presented. The WFEH concept is tested with macroscopic experiments, which agree well with the model. The feasibility of miniaturizing WFEHs is shown by simulating a realistic MEMS device. The WFEH can be operated as a charge pump that pushes charge and energy into an energy storage element. We show that such an operation mode is highly desirable for applications and that it can be realised with either a charge shuttle or with switches. The WFEH is shown to give equal or better output power in comparison to traditional electrostatic harvesters. Our findings indicate that WFEH has great potential in energy harvesting applications. PMID:25348004

  3. Curvature-Induced Anomalous Enhancement in the Work Function of Nanostructures.

    Science.gov (United States)

    Kaur, Jasmin; Kant, Rama

    2015-08-06

    An analytical theory to estimate the electronic work function in curved geometries is formulated under Thomas-Fermi approximation. The work function is framed as the work against the electrostatic self-capacitive energy. The contribution of surface curvature is characterized by mean and Gaussian curvature (through multiple scattering expansion). The variation in work function of metal and semimetal nanostructures is shown as the consequence of surface radius of curvature comparable to electronic screening length. For ellipsoidal particles, the maximum value of work function is observed at the equator and poles for oblate and prolate particles, respectively, whereas triaxial ellipsoid shows nonuniform distribution of the work function over the surface. Similarly, theory predicts manifold increase in the work function for a particle with atomic scale roughness. Finally, the theory is validated with experimental data, and it is concluded that the work function of a nanoparticle can be tailored through its shape.

  4. In-situ Remineralization of Dental Enamel Worked by Surface Functional Group%表面官能团作用下的牙釉质原位再矿化研究

    Institute of Scientific and Technical Information of China (English)

    李兰英; 薛博; 李红; 张渊明

    2011-01-01

    采用酸蚀后的牙釉质作为早期龋缺损模型,在缺损牙釉质表面修饰-SO3-功能基团,分别在人工唾液和含氟人工唾液中进行原位再矿化的研究.利用X-射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)、能谱仪(EDS)、选区电子衍射(SAED)研究原位再矿化晶体的组成和结构.结果表明,在人工唾液和含氟人工唾液中,表面修饰的官能团均可有效促进牙釉质再矿化.在含氟人工唾液中生成了沿c轴取向生长的具有较大长径比的棒状氟羟基磷灰石(FHA),这种FHA晶体具有类牙釉质的成分和结构,对修复早期龋有重要的意义.%An in-situ remineralization approach was applied on etched enamel surface as a superficial caries model. The model surface modified by -SO3~ function group and the remineralization experiment worked in artificial saliva with the presence and absence of fluoride respectively. The composition and structure of the obtained crystals were characterized by XRD, SEM, TEM, SAED and EDS. The results revealed that modified functional group improved the remineralization of dental enamel effectively. The crystals grown in the artificial saliva with the presence of fluoride were rod-like fluorapatite (FHA) with high aspect ratio aligning along the c-axis, which were quite analogous to the natural enamel in chemical components and microarchitectural structure. The study has significance for the repair of superficial caries.

  5. Quantifying Shannon's Work Function for Cryptanalytic Attacks

    CERN Document Server

    van Son, R J J H

    2010-01-01

    Attacks on cryptographic systems are limited by the available computational resources. A theoretical understanding of these resource limitations is needed to evaluate the security of cryptographic primitives and procedures. This study uses an Attacker versus Environment game formalism based on computability logic to quantify Shannon's work function and evaluate resource use in cryptanalysis. A simple cost function is defined which allows to quantify a wide range of theoretical and real computational resources. With this approach the use of custom hardware, e.g., FPGA boards, in cryptanalysis can be analyzed. Applied to real cryptanalytic problems, it raises, for instance, the expectation that the computer time needed to break some simple 90 bit strong cryptographic primitives might theoretically be less than two years.

  6. 30 CFR 57.17001 - Illumination of surface working areas.

    Science.gov (United States)

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Illumination of surface working areas. 57.17001 Section 57.17001 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND... Illumination § 57.17001 Illumination of surface working areas. Illumination sufficient to provide safe...

  7. Sensor for the working surface cleanliness definition in vacuum

    Science.gov (United States)

    Deulin, E. A.; Mashurov, S. S.; Gatsenko, A. A.

    2016-07-01

    Modern development of nanotechnology as one of the modern science priority directions is impossible to imagine without the use of vacuum systems and technologies. And the better the vacuum (lower the pressure), the “cleaner” we get a surface, which is very important for nanotechnology. Determination of the cleanliness of the surface or the amount of molecular layers of adsorbed gases on the working surface of the products especially in industry, where the cleanliness of the working surface is a key parameter of the technological process and has a significant influence on the output parameters of the final product is the main goal of this work.

  8. Toward Transfer Functions for Land Surface Phenologies

    Science.gov (United States)

    Henebry, G. M.

    2010-12-01

    A key problem in projecting future landscapes is simulating the associated land surface phenologies (or LSPs). A recent study of land surface models concluded that the representations of crop phenologies among the models diverged sufficiently to impede a useful intercomparison of simulation results from their associated climate models. Grassland phenologies are far more complicated than cropland phenologies due to multiple forcing factors, photosynthetic pathways (C3 vs C4), and spatial heterogeneities in both resource availabilities and land management practices. Furthermore, many tallgrass species (such as switchgrass) are widely distributed across temperature, but not moisture, gradients, resulting in significant ecotypic variation across the species' geographic range. Thus, how feasible is "transplanting" tallgrass LSPs across isotherms—but along isohyets—to simulate a shift in cultivation from maize-soy to switchgrass? Prior work has shown a quadratic model can provide a parsimonious link between a Normalized Difference Vegetation Index (or NDVI) time series and thermal time, measured in terms of accumulated growing degree-days (or AGDD). Moreover, the thermal time to peak NDVI (or TTP) is a simple function of the parameter coefficients of fitted model. I fitted quadratic models to MODIS NDVI and weather station data at multiple sites across the Northern Great Plains over ten growing seasons, 2000-2009. There is a strong latitudinal gradient in TTP that results in part from a quasi-linear gradient in accumulated daylight hours (or ADH) between 30 and 50 degrees north. However, AGDD improves upon ADH by providing sensitivity to the variability of growing season weather. In the quadratic parameter coefficients there is a geographic pattern apparent as a function of TTP, although it is more variable at shorter TTPs. Using these patterns, an LSP transfer function was implemented along a latitudinal transect to simulate switchgrass cultivation in areas now

  9. Functionals of finite Riemann surfaces

    CERN Document Server

    Schiffer, Menahem

    2014-01-01

    This advanced monograph on finite Riemann surfaces, based on the authors' 1949-50 lectures at Princeton University, remains a fundamental book for graduate students. The Bulletin of the American Mathematical Society hailed the self-contained treatment as the source of ""a plethora of ideas, each interesting in its own right,"" noting that ""the patient reader will be richly rewarded."" Suitable for graduate-level courses, the text begins with three chapters that offer a development of the classical theory along historical lines, examining geometrical and physical considerations, existence theo

  10. Work Criteria Function of Irreversible Heat Engines

    Directory of Open Access Journals (Sweden)

    Mahmoud Huleihil

    2014-01-01

    Full Text Available The irreversible heat engine is reconsidered with a general heat transfer law. Three criteria known in the literature—power, power density, and efficient power—are redefined in terms of the work criteria function (WCF, a concept introduced in this study. The formulation enabled the suggestion and analysis of a unique criterion—the efficient power density (which accounts for the efficiency and power density. Practically speaking, the efficient power and the efficient power density could be defined on any order based on the WCF. The applicability of the WCF is illustrated for the Newtonian heat transfer law (n=1 and for the radiative law (n=4. The importance of WCF is twofold: it gives an explicit design and educational tool to analyze and to display graphically the different criteria side by side and thus helps in design process. Finally, the criteria were compared and some conclusions were drawn.

  11. Structure and functions of fungal cell surfaces

    Science.gov (United States)

    Nozawa, Y.

    1984-01-01

    A review with 24 references on the biochemistry, molecular structure, and function of cell surfaces of fungi, especially dermatophytes: the chemistry and structure of the cell wall, the effect of polyene antibiotics on the morphology and function of cytoplasmic membranes, and the chemical structure and function of pigments produced by various fungi are discussed.

  12. Plasmon-mediated chemical surface functionalization at the nanoscale.

    Science.gov (United States)

    Nguyen, Mai; Lamouri, Aazdine; Salameh, Chrystelle; Lévi, Georges; Grand, Johan; Boubekeur-Lecaque, Leïla; Mangeney, Claire; Félidj, Nordin

    2016-04-28

    Controlling the surface grafting of species at the nanoscale remains a major challenge, likely to generate many opportunities in materials science. In this work, we propose an original strategy for chemical surface functionalization at the nanoscale, taking advantage of localized surface plasmon (LSP) excitation. The surface functionalization is demonstrated through aryl film grafting (derived from a diazonium salt), covalently bonded at the surface of gold lithographic nanostripes. The aryl film is specifically grafted in areas of maximum near field enhancement, as confirmed by numerical calculation based on the discrete dipole approximation method. The energy of the incident light and the LSP wavelength are shown to be crucial parameters to monitor the aryl film thickness of up to ∼30 nm. This robust and versatile strategy opens up exciting prospects for the nanoscale confinement of functional layers on surfaces, which should be particularly interesting for molecular sensing or nanooptics.

  13. 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...

  14. A short executive function training program improves preschoolers’ working memory

    Directory of Open Access Journals (Sweden)

    Emma eBlakey

    2015-11-01

    Full Text Available Cognitive training has been shown to improve executive functions in middle childhood and adulthood. However, fewer studies have targeted the preschool years – a time when executive functions undergo rapid development. The present study tested the effects of a short four session executive function training program in 54 four-year-olds. The training group significantly improved their working memory from pre-training relative to an active control group. Notably, this effect extended to a task sharing few surface features with the trained tasks, and continued to be apparent three months later. In addition, the benefits of training extended to a measure of mathematical reasoning three months later, indicating that training executive functions during the preschool years has the potential to convey benefits that are both long-lasting and wide-ranging.

  15. Functional Risk Modeling for Lunar Surface Systems

    Science.gov (United States)

    Thomson, Fraser; Mathias, Donovan; Go, Susie; Nejad, Hamed

    2010-01-01

    We introduce an approach to risk modeling that we call functional modeling , which we have developed to estimate the capabilities of a lunar base. The functional model tracks the availability of functions provided by systems, in addition to the operational state of those systems constituent strings. By tracking functions, we are able to identify cases where identical functions are provided by elements (rovers, habitats, etc.) that are connected together on the lunar surface. We credit functional diversity in those cases, and in doing so compute more realistic estimates of operational mode availabilities. The functional modeling approach yields more realistic estimates of the availability of the various operational modes provided to astronauts by the ensemble of surface elements included in a lunar base architecture. By tracking functional availability the effects of diverse backup, which often exists when two or more independent elements are connected together, is properly accounted for.

  16. Functionalization of Block Copolymer Vesicle Surfaces

    Directory of Open Access Journals (Sweden)

    Wolfgang Meier

    2011-01-01

    Full Text Available In dilute aqueous solutions certain amphiphilic block copolymers self-assemble into vesicles that enclose a small pool of water with a membrane. Such polymersomes have promising applications ranging from targeted drug-delivery devices, to biosensors, and nanoreactors. Interactions between block copolymer membranes and their surroundings are important factors that determine their potential biomedical applications. Such interactions are influenced predominantly by the membrane surface. We review methods to functionalize block copolymer vesicle surfaces by chemical means with ligands such as antibodies, adhesion moieties, enzymes, carbohydrates and fluorophores. Furthermore, surface-functionalization can be achieved by self-assembly of polymers that carry ligands at their chain ends or in their hydrophilic blocks. While this review focuses on the strategies to functionalize vesicle surfaces, the applications realized by, and envisioned for, such functional polymersomes are also highlighted.

  17. Engineering the work function of armchair graphene nanoribbons using strain and functional species: a first principles study.

    Science.gov (United States)

    Peng, Xihong; Tang, Fu; Copple, Andrew

    2012-02-22

    First principles density functional theory calculations were performed to study the effects of strain, edge passivation, and surface functional species on the structural and electronic properties of armchair graphene nanoribbons (AGNRs), with a particular focus on the work function. The work function was found to increase with uniaxial tensile strain and decrease with compression. The variation of the work function under strain is primarily due to the shift of the Fermi energy with strain. In addition, the relationship between the work function variation and the core level shift with strain is discussed. Distinct trends of the core level shift under tensile and compressive strain were discovered. For AGNRs with the edge carbon atoms passivated by oxygen, the work function is higher than for nanoribbons with the edge passivated by hydrogen under a moderate strain. The difference between the work functions in these two edge passivations is enlarged (reduced) under a sufficient tensile (compressive) strain. This has been correlated to a direct-indirect bandgap transition for tensile strains of about 4% and to a structural transformation for large compressive strains at about - 12%. Furthermore, the effect of the surface species decoration, such as H, F, or OH with different covering density, was investigated. It was found that the work function varies with the type and coverage of surface functional species. Decoration with F and OH increases the work function while H decreases it. The surface functional species were decorated on either one side or both sides of AGNRs. The difference in the work functions between one-sided and two-sided decorations was found to be relatively small, which may suggest an introduced surface dipole plays a minor role.

  18. Adsorption of Wine Constituents on Functionalized Surfaces.

    Science.gov (United States)

    Mierczynska-Vasilev, Agnieszka; Smith, Paul A

    2016-10-18

    The adsorption of macromolecules on solid surfaces is of great importance in the field of nanotechnology, biomaterials, biotechnological, and food processes. In the field of oenology adsorption of wine macromolecules such as polyphenols, polysaccharides, and proteins is much less desirable on membrane materials because of fouling and reduced filtering performance. On the other hand, adsorption of these molecules on processing aids is very beneficial for achieving wine clarity and stability. In this article, the effect of surface chemical functionalities on the adsorption of white, rosé, and red wine constituents was evaluated. Allylamine, acrylic acid, and ethanol were selected as precursors for plasma polymerization in order to generate coatings rich in amine, carboxyl, and hydroxyl chemical groups, respectively. The surface chemical functionalities were characterized by X-ray photoelectron spectroscopy (XPS) and the ability of different surface chemical functionalities to adsorb wine constituents were characterized by quartz crystal microbalance with dissipation (QCM-D) and atomic force microscopy (AFM). The results demonstrated that the amine and carboxyl modified surfaces encourage adsorption of constituents from white wine. The hydroxyl modified surfaces have the ability to preferentially adsorb rosé wine constituents, whereas red wine adsorbed to the highest extent on acrylic acid surface.

  19. Adsorption of Wine Constituents on Functionalized Surfaces

    Directory of Open Access Journals (Sweden)

    Agnieszka Mierczynska-Vasilev

    2016-10-01

    Full Text Available The adsorption of macromolecules on solid surfaces is of great importance in the field of nanotechnology, biomaterials, biotechnological, and food processes. In the field of oenology adsorption of wine macromolecules such as polyphenols, polysaccharides, and proteins is much less desirable on membrane materials because of fouling and reduced filtering performance. On the other hand, adsorption of these molecules on processing aids is very beneficial for achieving wine clarity and stability. In this article, the effect of surface chemical functionalities on the adsorption of white, rosé, and red wine constituents was evaluated. Allylamine, acrylic acid, and ethanol were selected as precursors for plasma polymerization in order to generate coatings rich in amine, carboxyl, and hydroxyl chemical groups, respectively. The surface chemical functionalities were characterized by X-ray photoelectron spectroscopy (XPS and the ability of different surface chemical functionalities to adsorb wine constituents were characterized by quartz crystal microbalance with dissipation (QCM-D and atomic force microscopy (AFM. The results demonstrated that the amine and carboxyl modified surfaces encourage adsorption of constituents from white wine. The hydroxyl modified surfaces have the ability to preferentially adsorb rosé wine constituents, whereas red wine adsorbed to the highest extent on acrylic acid surface.

  20. The dynamics of internal working surfaces in MHD jets

    CERN Document Server

    De Colle, Fabio; Esquivel, Alejandro

    2008-01-01

    The dynamical effects of magnetic fields in models of radiative, Herbig-Haro (HH) jets have been studied in a number of papers. For example, magnetized, radiative jets from variable sources have been studied with axisymmetric and 3D numerical simulations. In this paper, we present an analytic model describing the effect of a toroidal magnetic field on the internal working surfaces that result from a variability in the ejection velocity. We find that for parameters appropriate for HH jets the forces associated with the magnetic field dominate over the gas pressure force within the working surfaces. Depending on the ram pressure radial cross section of the jet, the magnetic field can produce a strong axial pinch, or, alternatively, a broadening of the internal working surfaces. We check the validity of the analytic model with axisymmetric numerical simulations of variable, magnetized jets.

  1. Periodic density-functional calculations on work-function change induced by adsorption of halogens on Cu(111).

    Science.gov (United States)

    Roman, Tanglaw; Groß, Axel

    2013-04-12

    Using periodic density-functional theory calculations, we address the work-function change induced by the adsorption of chlorine and iodine on Cu(111) which are shown to change the work function in opposite ways, contrary to what one may expect for these two electron acceptors. In contrast to previous studies, we demonstrate that substrate effects play only a minor role in work-function changes brought about by halogen adsorption on metals. Instead, polarization on the adsorbate not only explains the sign of the work-function change as a contributor to a positive surface dipole moment, but it is also the decisive factor in the dependence of adsorption-induced work-function changes on the coverage of halogens on metal surfaces.

  2. Ra and the average effective strain of surface asperities deformed in metal-working processes

    DEFF Research Database (Denmark)

    Bay, Niels; Wanheim, Tarras; Petersen, A. S

    1975-01-01

    Based upon a slip-line analysis of the plastic deformation of surface asperities, a theory is developed determining the Ra-value (c.l.a.) and the average effective strain in the surface layer when deforming asperities in metal-working processes. The ratio between Ra and Ra0, the Ra-value after...... and before deformation, is a function of the nominal normal pressure and the initial slope γ0 of the surface asperities. The last parameter does not influence Ra significantly. The average effective strain View the MathML sourcege in the deformed surface layer is a function of the nominal normal pressure...

  3. Work functioning measurement: tools for occupational mental health research

    NARCIS (Netherlands)

    K. Nieuwenhuijsen; R.L. Franche; F.J.H. van Dijk

    2010-01-01

    To review the status of work functioning research in workers with common mental disorders (CMDs) and also the work functioning measurement instruments. We distinguish between productivity, work role limitations, quality of work output, and extra effort required to remain productive. Two systematic l

  4. Work function engineering of graphene oxide via covalent functionalization for organic field-effect transistors

    Science.gov (United States)

    Ji, Seulki; Min, Bok Ki; Kim, Seong K.; Myung, Sung; Kang, Minseo; Shin, Hong-Suk; Song, Wooseok; Heo, Jungseok; Lim, Jongsun; An, Ki-Seok; Lee, Ill-Young; Lee, Sun Sook

    2017-10-01

    We report a simple method to produce work-function-tuned graphene nanosheets based on the nucleophilic substitution of the epoxy groups on graphene oxide. The electrical property of the graphene oxide is controlled dramatically, which results in the apparent work functions in a broad range between 3.73 eV and 5.1 eV, by attaching various functional groups on the graphene surface. As a proof of concept, we successfully demonstrated organic field effect transistors incorporating the functionalized graphene nanosheet interlayers. Here, when nanosheets were applied in an organic transistor as the interlayer material between electrodes and organic channel, the device performance was significantly improved. Our approach can be utilized to increase the performance and the flexibility of various advanced carbon-material-based hybrid electrical devices.

  5. Surface Functionalization for Enhanced Fluorescence Detection, Surface Plasmon Resonance Imaging and Microscopy

    OpenAIRE

    Fasoli, Jennifer Betsy

    2015-01-01

    This work presents several high throughput imaging and analysis techniques performed by fluorescence detection and surface plasmon resonance biosensing. The microarray fabrication methods introduced in this thesis, as well as the DNA functionalization on planar and nanoparticle surfaces, enable and facilitate the real-time study of adsorption events via DNA- DNA hybridization and protein-DNA interaction. Silica deposited on polyolefin film serves as the base for the development of DNA mic...

  6. Organic dipole layers for ultralow work function electrodes.

    Science.gov (United States)

    Ford, William E; Gao, Deqing; Knorr, Nikolaus; Wirtz, Rene; Scholz, Frank; Karipidou, Zoi; Ogasawara, Kodo; Rosselli, Silvia; Rodin, Vadim; Nelles, Gabriele; von Wrochem, Florian

    2014-09-23

    The alignment of the electrode Fermi level with the valence or conduction bands of organic semiconductors is a key parameter controlling the efficiency of organic light-emitting diodes, solar cells, and printed circuits. Here, we introduce a class of organic molecules that form highly robust dipole layers, capable of shifting the work function of noble metals (Au and Ag) down to 3.1 eV, that is, ∼1 eV lower than previously reported self-assembled monolayers. The physics behind the considerable interface dipole is elucidated by means of photoemission spectroscopy and density functional theory calculations, and a polymer diode exclusively based on the surface modification of a single electrode in a symmetric, two-terminal Au/poly(3-hexylthiophene)/Au junction is presented. The diode exhibits the remarkable rectification ratio of ∼2·10(3), showing high reproducibility, durability (>3 years), and excellent electrical stability. With this evidence, noble metal electrodes with work function values comparable to that of standard cathode materials used in optoelectronic applications are demonstrated.

  7. Functions of proteoglycans at the cell surface

    DEFF Research Database (Denmark)

    Höök, M; Woods, A; Johansson, S;

    1986-01-01

    Proteoglycans (primarily heparan sulphate proteoglycans) are found at the surface of most adherent eukaryotic cells. Earlier studies suggest that these molecules can be associated with the cell surface principally by two different mechanisms. Proteoglycans may occur as membrane......-intercalated glycoproteins, where the core protein of the proteoglycan is anchored in the lipid interior of the plasma membrane, or they may be bound via the polysaccharide components of the molecule to specific anchoring proteins present at the cell surface. A number of functions have been proposed for cell surface......-associated proteoglycans, including: regulation of cell-substrate adhesion; regulation of cell proliferation; participation in the binding and uptake of extracellular components; and participation in the regulation of extracellular matrix formation. Evidence is discussed suggesting that the cell-associated heparan...

  8. Working with the Functionally Illiterate Adult.

    Science.gov (United States)

    Grawe, Nancy E.

    Functionally illiterate adults differ in several ways from children in a learning setting: they have a broader range of experience, they are more rigid and resistant to change, they know what they want from education, they are free to drop out at any time, they may have a long history of failure, they want to see immediate and visible progress,…

  9. Work function mediated by deposition of ultrathin polar FeO on Pt(111)

    Science.gov (United States)

    Lu, Shuangzan; Qin, Zhihui; Guo, Qinmin; Cao, Gengyu

    2017-01-01

    Significant work function changes from bare Pt(111) surface to 1 monolayer and 2 monolayers of ultrathin iron oxide (FeO) films on it are investigated by means of scanning tunneling microscopy/spectroscopy (STM/STS). With FeO layer-by-layer growth, a continuous reduction of the work function along with the surface vacuum level (VL) shifting is observed. We found that the compression of the electron spill-out at the metal-oxide interface and the substantial reconstruction of 2 ML FeO film, respectively, make major contributions to the first and the second reductions of the work function. The rectifying effect in FeO films is also observed, which is attributed to the downward shift of band alignment imposed by the total change in surface dipole. Our work shows that the polar oxide films play an important role to adjust surface electronic structures for enhancing device functionality.

  10. SURFACE TEXTURE ANALYSIS FOR FUNCTIONALITY CONTROL

    DEFF Research Database (Denmark)

    De Chiffre, Leonardo; Andreasen, Jan Lasson; Tosello, Guido

    This document is used in connection with three exercises of 3 hours duration as a part of the course VISION ONLINE – One week course on Precision & Nanometrology. The exercises concern surface texture analysis for functionality control, in connection with three different case stories. This docume...... contains a short description of each case story, 3-D roughness parameters analysis and relation with the product’s functionality.......This document is used in connection with three exercises of 3 hours duration as a part of the course VISION ONLINE – One week course on Precision & Nanometrology. The exercises concern surface texture analysis for functionality control, in connection with three different case stories. This document...

  11. Diazo transfer for azido-functional surfaces

    Directory of Open Access Journals (Sweden)

    Laura Russo

    2011-04-01

    Full Text Available Preparation of azido-functionalized polymers is gaining increasing attention. We wish to report an innovative, novel strategy for azido functionalization of polymeric materials, coupling plasma technology and solution processed diazo transfer reactions. This novel approach allows the azido group to be introduced downstream of the material preparation, thus preserving its physicochemical and mechanical characteristics, which can be tailored a priori according to the desired application. The whole process involves the surface plasma functionalization of a material with primary amino groups, followed by a diazo transfer reaction, which converts the amino functionalities into azido groups that can be exploited for further chemoselective reactions. The diazo transfer reaction is performed in a heterogeneous phase, where the azido group donor is in solution. Chemical reactivity of the azido functionalities was verified by subsequent copper-catalyzed azide-alkyne cycloaddition.

  12. Napping and Human Functioning during Prolonged Work

    Science.gov (United States)

    1987-04-30

    alternative to napping is prolonged wakefulness. Polyphasic sleep , with frequent naps rather than a single sleep period per 24 hours, is natural for both the...very young and for the aged. It is not practiced by most adults, perhaps because of societal demands. Possibly a polyphasic sleep schedule could be...Functioning 1.2 Scope of this Chapter 2. REVIEW OF LITERATURE 2.1 Partial Sleep Deprivation Studies 2.2 Nap Studies: Four Nap Factors Affecting Performance

  13. Temperature dependence of the work function of caesiated materials under ion source conditions

    Science.gov (United States)

    Friedl, R.; Fantz, U.

    2015-04-01

    The key parameter for the performance of negative hydrogen ion sources based on surface conversion is the work function of the converter surface. In order to enhance the negative ion yield caesium is introduced into the source which lowers the converter work function upon adsorption. However, the Cs layer is subject to background pressures of 10-7-10-6 mbar and to H2 or D2 low-temperature plasmas which can have a major impact on the resultant work function. In order to determine the work function of caesiated surfaces under ion source relevant conditions and to identify influencing parameters, systematic investigations are performed at the laboratory experiment ACCesS. It is confirmed, that the work function of a sample surface in a vacuum of 10-6 mbar is decreased upon the evaporation and adsorption of caesium. However, the adsorbed layer is determined by the formation of Cs compounds with residual gases from the background pressure leading to an increased work function by about 0.6 eV compared to pure Cs layers. Elevated surface temperatures are beneficial for cleaning and against degradation in absence of Cs evaporation, but no further enhancement of the work function can be achieved by temperatures up to 260 °C if a Cs flux onto the surface is already present. Thus, the minimally achievable work function of a stainless steel surface in ion source relevant vacuum conditions is 2.75 eV. The influence of the substrate material and plasma surface interaction will be investigated next.

  14. METHODS FOR LOCAL CHANGES IN THE PLASTIC DEFORMATION DIAGNOSTICS ON THE WORK FUNCTION

    Directory of Open Access Journals (Sweden)

    K. V. Panteleyev

    2015-01-01

    Full Text Available The paper describes the electronic work function measurements by the contact potential difference technique, and experimental demonstration of the possibility of these methods application for the stress-strain state of the surface layer of the metals and alloys. The techniques end examples of their application of localization of plastic deformation studies using the Kelvin probe are developed and present. The study topology of work function the deformed surface possible to determine the type of deformation and dynamics of

  15. Gelatin Functionalization of Biomaterial Surfaces: Strategies for Immobilization and Visualization

    Directory of Open Access Journals (Sweden)

    Peter Dubruel

    2011-01-01

    Full Text Available In the present work, the immobilization of gelatin as biopolymer on two types of implantable biomaterials, polyimide and titanium, was compared. Both materials are known for their biocompatibility while lacking cell-interactive behavior. For both materials, a pre-functionalization step was required to enable gelatin immobilization. For the polyimide foils, a reactive succinimidyl ester was introduced first on the surface, followed by covalent grafting of gelatin. For the titanium material, methacrylate groups were first introduced on the Ti surface through a silanization reaction. The applied functionalities enabled the subsequent immobilization of methacrylamide modified gelatin. Both surface modified materials were characterized in depth using atomic force microscopy, static contact angle measurements, confocal fluorescence microscopy, attenuated total reflection infrared spectroscopy and X-ray photo-electron spectroscopy. The results indicated that the strategies elaborated for both material classes are suitable to apply stable gelatin coatings. Interestingly, depending on the material class studied, not all surface analysis techniques are applicable.

  16. Permanent isolation surface barrier: Functional performance

    Energy Technology Data Exchange (ETDEWEB)

    Wing, N.R.

    1993-10-01

    This document presents the functional performance parameters for permanent isolation surface barriers. Permanent isolation surface barriers have been proposed for use at the Hanford Site (and elsewhere) to isolate and dispose of certain types of waste in place. Much of the waste that would be disposed of using in-place isolation techniques is located in subsurface structures, such as solid waste burial grounds, tanks, vaults, and cribs. Unless protected in some way, the wastes could be transported to the accessible environment via transport pathways, such as water infiltration, biointrusion, wind and water erosion, human interference, and/or gaseous release.

  17. Surface functionalization of dopamine coated iron oxide nanoparticles for various surface functionalities

    Science.gov (United States)

    Sherwood, Jennifer; Xu, Yaolin; Lovas, Kira; Qin, Ying; Bao, Yuping

    2017-04-01

    We present effective conjugation of four small molecules (glutathione, cysteine, lysine, and Tris(hydroxymethyl)aminomethane) onto dopamine-coated iron oxide nanoparticles. Conjugation of these molecules could improve the surface functionality of nanoparticles for more neutral surface charge at physiological pH and potentially reduce non-specific adsorption of proteins to nanoparticles surfaces. The success of conjugation was evaluated with dynamic light scattering by measuring the surface charge changes and Fourier transform infrared spectroscopy for surface chemistry analysis. The stability of dopamine-coated nanoparticles and the ability of conjugated nanoparticles to reduce the formation of protein corona were evaluated by measuring the size and charge of the nanoparticles in biological medium. This facile conjugation method opens up possibilities for attaching various surface functionalities onto iron oxide nanoparticle surfaces for biomedical applications.

  18. Surface functionalization of polyamide fiber via dopamine polymerization

    Science.gov (United States)

    Kuang, Xiao-Hui; Guan, Jin-Ping; Tang, Ren-Cheng; Chen, Guo-Qiang

    2017-09-01

    The oxidative polymerization of dopamine for the functional surface modification of textile fibers has drawn great attention. In this work, the functionalization of polyamide fiber via dopamine polymerization was studied with the aim of the fabrication of hydrophilic and antistatic surface. The conditions of dopamine application were first discussed in the absence of specific oxidants in terms of the apparent color depth of polyamide fiber. Dopamine concentration, pH and time were found to exert great impact on color depth. The highest color depth was achieved at pH 8.5. In the process of modification, polydopamine was deposited onto the surface of polyamide fiber. The modified polyamide fiber displayed a yellowish brown color with excellent wash and light color fastness, and exhibited good hydrophilic, UV protection and antistatic effects. A disadvantage of the present approach was the slow rate of dopamine polymerization and functionalization.

  19. Green's functions potential fields on surfaces

    CERN Document Server

    Melnikov, Yuri A

    2017-01-01

    This book is comprehensive in its classical mathematical physics presentation, providing the reader with detailed instructions for obtaining Green's functions from scratch. Green's functions is an instrument easily accessible to practitioners who are engaged in design and exploitation of machines and structures in modern engineering practice. To date, there are no books available on the market that are devoted to the Green's function formalism for equations covered in this volume. The reader, with an undergraduate background in applied mathematics, can become an active user of the Green's function approach. For the first time, Green's functions are discussed for a specific class of problems dealing with potential fields induced in thin-wall structures and therefore, the reader will have first-hand access to a novel issue. This Work is accessible to researchers in applied mathematics, mechanics, and relevant disciplines such as engineering, as well as to upper level undergraduates and graduate students.

  20. Work function measurement of lanthanum-boron compounds

    Science.gov (United States)

    Jacobson, D. L.; Storms, E. K.

    1978-01-01

    The relationship between emission properties and sample composition is studied for lanthanum-boron compounds. Specifically, the La-B system is considered between 1400 and 2100 K and between LaB(4.24) and LaB(29.2) to determine the phase relationship, chemical activity of the compounds, vapor composition, and vaporization rate. The results indicate that: (1) a blue-colored phase near LaB(9) exists between a purple-colored LaB(6) and elemental boron, (2) vaporization is sufficiently more rapid than diffusion so that great compositional differences exist between the surface and the interior, (3) an activation energy lowers the boron vaporization rate from LaB(6), and (4) a steady-state surface composition between LaB(6.04) and LaB(6.07) exists for freely vaporizing materials as a function of interior composition, purity, and temperature. It is noted that the ultimate life of a thermionic diode is governed by electrode vaporization rate whereas efficiency is governed by the electrode work function.

  1. Functionalization and Polymerization on the CNT Surfaces

    KAUST Repository

    Albuerne, Julio

    2013-07-01

    In this review we focus on the current status of using carbon nanotube (CNT) as a filler for polymer nanocomposites. Starting with the historical background of CNT, its distinct properties and the surface functionalization of the nanotube, the three different surface polymerization techniques, namely grafting "from", "to" and "through/in between" were discussed. Wider focus has been given on "grafting from" surface initiated polymerizations, including atom transfer radical polymerization (ATRP), reversible addition fragmentation chain-transfer (RAFT) Polymerization, nitroxide mediated polymerization (NMP), ring opening polymerization (ROP) and other miscellaneous polymerization methods. The grafting "to" and "through / in between" also discussed and compared with grafting from polymerization. The merits and shortcomings of all three grafting methods were discussed and the bottleneck issue in grafting from method has been highlighted. Furthermore the current and potential future industrial applications were deliberated. Finally the toxicity issue of CNTs in the final product has been reviewed with the limited available literature knowledge. © 2013 Bentham Science Publishers.

  2. Equal variations of the Fermi level and work function in graphene at the nanoscale.

    Science.gov (United States)

    Samaddar, Sayanti; Coraux, Johann; Martin, Sylvain C; Grévin, Benjamin; Courtois, Hervé; Winkelmann, Clemens B

    2016-08-18

    If surface effects are neglected, any change of the Fermi level in a semiconductor is expected to result in an equal and opposite change of the work function. However, this is in general not observed in three-dimensional semiconductors, because of Fermi level pinning at the surface. By combining Kelvin probe force microscopy and scanning tunneling spectroscopy on single layer graphene, we measure both the local work function and the charge carrier density. The one-to-one equivalence of changes in the Fermi level and the work function is demonstrated to accurately hold in single layer graphene down to the nanometer scale.

  3. Molybdenum work function determined by electron emission microscopy.

    Science.gov (United States)

    Jacobson, D. L.; Campbell, A. E.

    1971-01-01

    A polycrystalline molybdenum sample was recrystallized and thermally stabilized. Quantitative measurements of the emission from each individual grain were obtained with an electron emission microscope. The effective work function for each grain was then calculated. The crystallographic orientation of each grain was determined by Laue back-reflection techniques. A polar plot of effective work function vs crystallographic orientation for the sample was constructed to provide a correlation between effective work function and crystallographic orientation.

  4. Surface Functionalization of Graphene-based Materials

    Science.gov (United States)

    Mathkar, Akshay

    Graphene-based materials have generated tremendous interest in the past decade. Manipulating their characteristics using wet-chemistry methods holds distinctive value, as it provides a means towards scaling up, while not being limited by yield. The majority of this thesis focuses on the surface functionalization of graphene oxide (GO), which has drawn tremendous attention as a tunable precursor due to its readily chemically manipulable surface and richly functionalized basal plane. Firstly, a room-temperature based method is presented to reduce GO stepwise, with each organic moiety being removed sequentially. Characterization confirms the carbonyl group to be reduced first, while the tertiary alcohol is reduced last, as the optical gap decrease from 3.5 eV down to 1 eV. This provides greater control over GO, which is an inhomogeneous system, and is the first study to elucidate the order of removal of each functional group. In addition to organically manipulating GO, this thesis also reports a chemical methodology to inorganically functionalize GO and tune its wetting characteristics. A chemical method to covalently attach fluorine atoms in the form of tertiary alkyl fluorides is reported, and confirmed by MAS 13C NMR, as two forms of fluorinated graphene oxide (FGO) with varying C/F and C/O ratios are synthesized. Introducing C-F bonds decreases the overall surface free energy, which drastically reduces GO's wetting behavior, especially in its highly fluorinated form. Ease of solution processing leads to development of sprayable inks that are deposited on a range of porous and nonporous surfaces to impart amphiphobicity. This is the first report that tunes the wetting characteristics of GO. Lastly as a part of a collaboration with ConocoPhillips, another class of carbon nanomaterials - carbon nanotubes (CNTs), have been inorganically functionalized to repel 30 wt% MEA, a critical solvent in CO 2 recovery. In addition to improving the solution processability of CNTs

  5. Neisserial surface lipoproteins: structure, function and biogenesis.

    Science.gov (United States)

    Hooda, Yogesh; Shin, Hyejin E; Bateman, Thomas J; Moraes, Trevor F

    2017-03-01

    The surface of many Gram-negative bacteria contains lipidated protein molecules referred to as surface lipoproteins or SLPs. SLPs play critical roles in host immune evasion, nutrient acquisition and regulation of the bacterial stress response. The focus of this review is on the SLPs present in Neisseria, a genus of bacteria that colonise the mucosal surfaces of animals. Neisseria contains two pathogens of medical interest, namely Neisseria meningitidis and N. gonorrhoeae. Several SLPs have been identified in Neisseria and their study has elucidated key strategies used by these pathogens to survive inside the human body. Herein, we focus on the identification, structure and function of SLPs that have been identified in Neisseria. We also survey the translocation pathways used by these SLPs to reach the cell surface. Specifically, we elaborate on the strategies used by neisserial SLPs to translocate across the outer membrane with an emphasis on Slam, a novel outer membrane protein that has been implicated in SLP biogenesis. Taken together, the study of SLPs in Neisseria illustrates the widespread roles played by this family of proteins in Gram-negative bacteria. © FEMS 2017. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  6. The work function of few-layer graphene

    Science.gov (United States)

    Leenaerts, O.; Partoens, B.; Peeters, F. M.; Volodin, A.; Van Haesendonck, C.

    2017-01-01

    A theoretical and experimental study of the work function of few-layer graphene is reported. The influence of the number of layers on the work function is investigated in the presence of a substrate, a molecular dipole layer, and combinations of the two. The work function of few-layer graphene is almost independent of the number of layers with only a difference between monolayer and multilayer graphene of about 60 meV. In the presence of a charge-donating substrate the charge distribution is found to decay exponentially away from the substrate and this is directly reflected in the work function of few-layer graphene. A dipole layer changes the work function only when placed in between the substrate and few-layer graphene through a change of the charge transfer between the two.

  7. Influence of H2 and D2 plasmas on the work function of caesiated materials

    Science.gov (United States)

    Friedl, R.; Fantz, U.

    2017-08-01

    Caesium-covered surfaces are used in negative hydrogen ion sources as a low work function converter for H-/D- surface production. The work function χ of the converter surface is one of the key parameters determining the performance of the ion source. Under idealized conditions, pure bulk Cs has 2.14 eV. However, residual gases at ion source background pressures of 10-7-10-6 mbar and the plasma surface interaction with the hydrogen discharge in front of the caesiated surface dynamically affect the actual surface work function. Necessary fundamental investigations on the resulting χ are performed at a dedicated laboratory experiment. Under the vacuum conditions of ion sources, the incorporation of impurities into the Cs layer leads to very stable Cs compounds. The result is a minimal work function of χvac ≈ 2.75 eV for Cs evaporation rates of up to 10 mg/h independent of substrate material and surface temperature (up to 260 °C). Moreover, a distinct degradation behavior can be observed in the absence of a Cs flux onto the surface leading to a deterioration of the work function by about 0.1 eV/h. However, in a hydrogen discharge with plasma parameters close to those of ion sources, fluxes of reactive hydrogen species and VUV photons impact on the surface which reduces the work function of the caesiated substrate down to about 2.6 eV even without Cs supply. Establishing a Cs flux onto the surface with ΓCs ≈ 1017 m-2 s-1 further enhances the work function obtaining values around 2.1 eV, which can be maintained stable for several hours of plasma exposure. Hence, Cs layers with work functions close to that of pure bulk Cs can be achieved for both H2 and D2 plasmas. Isotopic differences can be neglected within the measurement accuracy of about 0.1 eV due to comparable plasma parameters. Furthermore, after shutting down the Cs evaporation, continuing plasma exposure helps against degradation of the Cs layer resulting in a constant low work function for at least 1 h.

  8. Functional electrical stimulation with surface electrodes

    Directory of Open Access Journals (Sweden)

    Bajd Tadej

    2008-01-01

    Full Text Available The review investigates the objective evidences of benefits derived from surface functional electrical stimulation (FES of lower and upper extremities for people after incomplete spinal cord injury (SCI and stroke. FES can offer noticeable benefits in walking ability. It can be efficiently combined with treadmill and body weight support. Voluntary muscle strength and endurance gain can be achieved through FES assisted gait training together with increased gait velocity in absence of electrical stimulator. Cyclic FES, FES augmented by biofeedback, and FES used in various daily activities can result in substantial improvements of the voluntary control of upper extremities.

  9. Supersymmetric partition functions on Riemann surfaces

    CERN Document Server

    Benini, Francesco

    2016-01-01

    We present a compact formula for the supersymmetric partition function of 2d N=(2,2), 3d N=2 and 4d N=1 gauge theories on $\\Sigma_g \\times T^n$ with partial topological twist on $\\Sigma_g$, where $\\Sigma_g$ is a Riemann surface of arbitrary genus and $T^n$ is a torus with n=0,1,2, respectively. In 2d we also include certain local operator insertions, and in 3d we include Wilson line operator insertions along $S^1$. For genus g=1, the formula computes the Witten index. We present a few simple Abelian and non-Abelian examples, including new tests of non-perturbative dualities. We also show that the large N partition function of ABJM theory on $\\Sigma_g \\times S^1$ reproduces the Bekenstein-Hawking entropy of BPS black holes in AdS4 whose horizon has $\\Sigma_g$ topology.

  10. PREFACE Surface Modifications and Functionalization of Materials for Biomedical Applications

    Science.gov (United States)

    Endrino, Jose Luis; Puértolas, Jose A.; Albella, Jose M.

    2010-11-01

    Conference photograph This special issue contains selected papers which were presented as invited and contributed communications at the workshop entitled 'Surface modification and functionalization of materials for biomedical applications' (BIO-COAT 2010) which was held on 24 June 2010 in Zaragoza (Spain). The surface of a material plays a major role in its interaction with the biological medium. Processes related to the mechanical stability of articular devices in contact, osseointegration, thrombogenicity, corrosion and leaching, or the inflammatory response of rejection of a material, are clearly conditioned by the surface properties. Therefore, the modification or functionalization of surfaces can have an important impact on these issues. New techniques for functionalization by thin film deposition or surface treatments help to improve superficial properties, while understanding the interaction of the surface-biological medium is critical for their application in new devices. Jointly organized by the Spanish Materials Research Society, BIO-COAT 2010 provided an open forum to discuss the progress and latest developments in thin film processing and the engineering of biomaterials. Invited lectures were particularly aimed at providing overviews on scientific topics and were given by recognized world-class scientists. Two of them have contributed with a proceedings article to this selected collection (articles 012001 and 012008). The contributed communications were focused on particular cutting-edge aspects of thin film science and functionalization technologies for biomaterials, showing the major scientific push of Spanish research groups in the field. The 2010 BIO-COAT conference was organized along four main topics: (1) functionalization and texture on surfaces, (2) tribology and corrosion, (3) the surface modification of biomaterials, and (4) surface-biological environment interactions. The papers published in this volume were accepted for publication after

  11. Overweight, obesity and work functioning : The role of working-time arrangements

    NARCIS (Netherlands)

    Nigatu, Yeshambel T.; van de Ven, Hardy A.; van der Klink, Jac J. L.; Brouwer, Sandra; Reijneveld, Sijmen A.; Bultmann, Ute

    2016-01-01

    Background: Obesity is associated with productivity loss, but little is known about how obese workers function at work and also the role of working-time arrangements on this association is lacking. Therefore, the aim of this study was to examine the association of overweight and obesity with work fu

  12. Gaps to "Working" on the Surface of Small Bodies

    Science.gov (United States)

    Bellerose, J.

    2012-12-01

    Upcoming goals for human spaceflight include sending a crewed mission to a near-Earth asteroid (NEA) by 2025. As an alternative to this, a spacecraft could be sent to capture a small NEA, and return it to cislunar orbit where astronauts could take it apart (Brophy, 2012). In parallel, plans are also to take the next big step in resources utilization, and mine those NEAs (Lewicki, 2012). Although these exciting concepts are very different in scope, they share the same environment they will need to interact with. In this work, we discuss the required techniques for exploring and exploiting small bodies, and compare with the available tools and the current knowledge of small bodies. To support these types of missions, a number of in-situ data are required prior to start surface operations: the body shape and mass, the presence of volatiles and metals, the asteroid morphology, the internal structural properties, the surface and near-surface environments, the existence of hazards, and the time-evolution dynamics. Products obtained from remote sensing - maps, mosaics, shape models - are critical in selecting the locations to be investigated in more details, or the locations to be excavated. Composition measurements become especially important for mining, as it requires appropriate tools and techniques. Although spectrometers can be used in orbit and on the surface to determine elemental composition, the fine scale structure and mineralogical composition can only be done using surface probes or through a close-up camera. Those remote sensing images are also critical in planning the very close approaches by the spacecraft, as the small body environment is one of the most perturbed environments (Scheeres, 2000). Being able to recreate the small body dynamics is necessary to mitigate risks and to enable spacecraft docking. The navigation system, vision tools, and planning software become critical as the spacecraft will need to track features on the surface under different

  13. Tuning the work function in transition metal oxides and their heterostructures

    Science.gov (United States)

    Zhong, Z.; Hansmann, P.

    2016-06-01

    The development of novel functional materials in experimental labs combined with computer-based compound simulation brings the vision of materials design on a microscopic scale continuously closer to reality. For many applications interface and surface phenomena rather than bulk properties are key. One of the most fundamental qualities of a material-vacuum interface is the energy required to transfer an electron across this boundary, i.e., the work function. It is a crucial parameter for numerous applications, including organic electronics, field electron emitters, and thermionic energy converters. Being generally very resistant to degradation at high temperatures, transition metal oxides present a promising materials class for such devices. We have performed a systematic study for perovskite oxides that provides reference values and, equally important, reports on materials trends and the tunability of work functions. Our results identify and classify dependencies of the work function on several parameters including specific surface termination, surface reconstructions, oxygen vacancies, and heterostructuring.

  14. Work function measurement for Ag-TCNQ (TCNQ = tetracyanoquinodimethane) nanowires.

    Science.gov (United States)

    Ye, Chunnuan; Zheng, Kaibo; Chen, Guorong

    2012-08-01

    The Ag-TCNQ (TCNQ = tetracyanoquinodimethane) nanowires synthesized by a vapor transport reaction exhibit promising field emission properties. Their effective work function at high applied electric field was estimated to be about 1.70 eV according to the Fowler-Nordheim (F-N) theory. In this work, we directly measured the intrinsic work function of Ag-TCNQ nanowires via the ultraviolet photoemission spectroscopy (UPS). According to the threshold binding energy, the work function is obtained to be 5.45 eV, which shows a large discrepancy with the preivous estimation based on F-N theory. The reductive effecitive work function during the field emission is mainly attributed to the morphology-induced enhancement of the nanowire array.

  15. Strain engineering the work function in monolayer metal dichalcogenides.

    Science.gov (United States)

    Lanzillo, Nicholas A; Simbeck, Adam J; Nayak, Saroj K

    2015-05-08

    We use first-principles density functional theory to investigate the effect of both tensile and compressive strain on the work functions of various metal dichalcogenide monolayers. We find that for all six species considered, including MoS2, WS2, SnS2, VS2, MoSe2 and MoTe2, that compressive strain of up to 10% decreases the work function continuously by as much as 1.0 eV. Large enough tensile strain is also found to decrease the work function, although in some cases we observe an increase in the work function for intermediate values of tensile strain. This work function modulation is attributed to a weakening of the chalcogenide-metal bonds and an increase in total energy of each system as a function of strain. Values of strain which bring the metal atoms closer together lead to an increase in electrostatic potential energy, which in turn results in an increase in the vacuum potential level. The net effect on the work function can be explained in terms of the balance between the increases in the vacuum potential levels and Fermi energy.

  16. Image-potential states and work function of graphene.

    Science.gov (United States)

    Niesner, Daniel; Fauster, Thomas

    2014-10-01

    Image-potential states of graphene on various substrates have been investigated by two-photon photoemission and scanning tunneling spectroscopy. They are used as a probe for the graphene-substrate interaction and resulting changes in the (local) work function. The latter is driven by the work function difference between graphene and the substrate. This results in a charge transfer which also contributes to core-level shifts in x-ray photoemission. In this review article, we give an overview over the theoretical models and the experimental data for image-potential states and work function of graphene on various substrates.

  17. Surface Electromyographic Assessment of Swallowing Function

    Directory of Open Access Journals (Sweden)

    Marziyeh Poorjavad

    2017-03-01

    Full Text Available The reliability of surface electromyographic (sEMG variables during swallowing determines the potential usefulness of these measures in swallowing assessment and treatment. This study aimed to establish the reliability of the sEMG measures of the swallowing function of muscles during different swallowing conditions in healthy young and old volunteers. Two groups of volunteers (24 older adults, 10 younger adults participated in this cross-sectional study during 2014. The activity of masseter, submental, and infrahyoid groups were measured using sEMG during three repetitions of different swallowing tasks. Both the relative and absolute reliability (characterized respectively by ICC, SEM%, and SRD% were calculated for the sEMG indices of muscle activity during swallowing events. Statistical analyses were performed by the SPSS 19.0 and Microsoft Excel 2007 software packages. Statistical significance was set at P≤0.05. The relative reliability calculations showed significant agreements between repetitions for the mean and peak amplitude and the average of median frequency (MDF of the studied muscles function during most swallowing types in both groups. However, the duration and particularly the time to peak of muscle activity showed significant agreements during fewer swallowing conditions. Excluding MDF, we found high SEM% and SRD% for the studied measures (particularly timing measures of muscles function during most swallowing types in both groups. The reliability of sEMG measures was influenced by the age and swallowing types. Our findings suggest that the MDF of muscle function during almost all studied swallowing types can be a reliable measure for the sEMG assessment of swallowing function in both younger and older adults.

  18. Surface Electromyographic Assessment of Swallowing Function.

    Science.gov (United States)

    Poorjavad, Marziyeh; Talebian, Saeed; Ansari, Noureddin Nakhostin; Soleymani, Zahra

    2017-03-01

    The reliability of surface electromyographic (sEMG) variables during swallowing determines the potential usefulness of these measures in swallowing assessment and treatment. This study aimed to establish the reliability of the sEMG measures of the swallowing function of muscles during different swallowing conditions in healthy young and old volunteers. Two groups of volunteers (24 older adults, 10 younger adults) participated in this cross-sectional study during 2014. The activity of masseter, submental, and infrahyoid groups were measured using sEMG during three repetitions of different swallowing tasks. Both the relative and absolute reliability (characterized respectively by ICC, SEM%, and SRD%) were calculated for the sEMG indices of muscle activity during swallowing events. Statistical analyses were performed by the SPSS 19.0 and Microsoft Excel 2007 software packages. Statistical significance was set at P≤0.05. The relative reliability calculations showed significant agreements between repetitions for the mean and peak amplitude and the average of median frequency (MDF) of the studied muscles function during most swallowing types in both groups. However, the duration and particularly the time to peak of muscle activity showed significant agreements during fewer swallowing conditions. Excluding MDF, we found high SEM% and SRD% for the studied measures (particularly timing measures) of muscles function during most swallowing types in both groups. The reliability of sEMG measures was influenced by the age and swallowing types. Our findings suggest that the MDF of muscle function during almost all studied swallowing types can be a reliable measure for the sEMG assessment of swallowing function in both younger and older adults.

  19. Solids and Their Surfaces: Division B / Commission 14 / Working Group Solids and Their Surfaces

    CERN Document Server

    Vidali, Gianfranco; Henning, Thomas

    2015-01-01

    Just a decade ago, only a handful of laboratories were engaged in the preparation and characterization of cosmic dust analogues and in the study of the formation of molecules on their surfaces. Now more than three dozen laboratories work on such topics. This report summarizes new publications in this field.

  20. Lung function changes in wildland firefighters working at prescribed burns.

    Energy Technology Data Exchange (ETDEWEB)

    Adetona, Olorunfemi; Hall, Daniel, B.; Naeher, L,P.

    2011-10-01

    Although decline in lung function across workshift has been observed in wildland firefighters, measurements have been restricted to days when they worked at fires. Consequently, such results could have been confounded by normal circadian variation associated with lung function. We investigated the across-shift changes in lung function of wildland firefighters, and the effect of cumulative exposure on lung function during the burn season.

  1. Modular surface functionalization of polyisobutylene-based biomaterials

    Science.gov (United States)

    Alvarez Albarran, Alejandra

    Polyisobutylene (PIB) has a unique combination of properties including chemical/oxidative resistance, low Tg (˜70 °C) and hydrophobicity. 1 PIB-based materials have also been found to have excellent biocompatibility and biostability: a PIB-based triblock copolymer thermoplastic elastomer (TPE) [poly(styrene-b-isobutylene-b-styrene)] (SIBS) is FDA-approved as a drug eluting coating for coronary stents.2 A new generation of PIB-based TPEs, with an arborescent or tree-like core (arbPIB) and plastic phases composed of blocks of polystyrene or poly(p-methyl styrene) (MS) has been developed in Professor Puskas group. These materials display unique TPE properties to make them very attractive for biomedical applications.3 The biocompatibility of these novel block copolymers has already been demonstrated in vitro and in vivo in rabbits.4. The Puskas group proposed to modify the surface properties of PIB-based TPEs using a modular approach. Using this approach it is possible to modify the surface chemistry and topology independently. The surface chemistry can be modified by "gluing" low molecular weight functionalized PIBs (PIB-X) to the surface of the TPEs. This "modular" approach will give unprecedented control over surface chemistry and topology and will contribute to new fundamental understanding of the effects of surface properties on the biocompatibility of polymeric materials. In this work PIB with a primary hydroxy head group (HO-PIB) was made in situ by living carbocationic polymerization using propylene oxide as initiator and titanium tetrachloride (TiCl4 ) as coinitiator. PIB functionalized with non-fouling moieties (PIB-X) was then synthesized from HO-PIB using Candida antarctica Lipase B (CALB) as enzymatic catalyst and spin coated onto the surface of the TPE. Protein adsorption studies using Surface Plasmon Resonance (SPR) demonstrated decreased fibrinogen (Fg) adsorption to the modified surface. XPS analyses provided clear evidence of the effectiveness of

  2. The work function of sub-monolayer cesium-covered gold: A photoelectronspectroscopy study

    Energy Technology Data Exchange (ETDEWEB)

    LaRue, J.L.; White, J.D.; Nahler, N.H.; Liu, Z.; Sun, Y.; Pianetta, P.A.; Auerbach, D.J.; Wodtke, A.M.; /SLAC, SSRL /UC, Santa Barbara, Chem. Dept.

    2008-06-13

    Using visible and X-ray photoelectron spectroscopy we measured the work function of a Au(111) surface at a well-defined sub-monolayer coverage of Cs. For a Cs coverage producing a photoemission maximum with a He-Ne laser, the work function is 1.61 {+-} 0.08 eV consistent with previous assumptions used to analyze vibrationally promoted electron emission. A discussion of possible Cs layer structures is also presented.

  3. Work function of elemental metals and its face dependence ...

    African Journals Online (AJOL)

    Journal of the Nigerian Association of Mathematical Physics. Journal Home ... Open Access DOWNLOAD FULL TEXT Subscription or Fee Access. Work function of elemental metals and its face dependence: Stabilized Jellium approach.

  4. Characteristic Work Function Variations of Graphene Line Defects.

    Science.gov (United States)

    Long, Fei; Yasaei, Poya; Sanoj, Raj; Yao, Wentao; Král, Petr; Salehi-Khojin, Amin; Shahbazian-Yassar, Reza

    2016-07-20

    Line defects, including grain boundaries and wrinkles, are commonly seen in graphene grown by chemical vapor deposition. These one-dimensional defects are believed to alter the electrical and mechanical properties of graphene. Unfortunately, it is very tedious to directly distinguish grain boundaries from wrinkles due to their similar morphologies. In this report, high-resolution Kelvin potential force microscopy (KPFM) is employed to measure the work function distribution of graphene line defects. The characteristic work function variations of grain boundaries, standing-collapsed wrinkles, and folded wrinkles could be clearly identified. Classical and quantum molecular dynamics simulations reveal that the unique work function distribution of each type of line defects is originated from the doping effect induced by the SiO2 substrate. Our results suggest that KPFM can be an easy-to-use and accurate method to detect graphene line defects, and also propose the possibility to tune the graphene work function by defect engineering.

  5. Change of the work function of platinum electrodes induced by halide adsorption.

    Science.gov (United States)

    Gossenberger, Florian; Roman, Tanglaw; Forster-Tonigold, Katrin; Groß, Axel

    2014-01-01

    The properties of a halogen-covered platinum(111) surface have been studied by using density functional theory (DFT), because halides are often present at electrochemical electrode/electrolyte interfaces. We focused in particular on the halogen-induced work function change as a function of the coverage of fluorine, chlorine, bromine and iodine. For electronegative adsorbates, an adsorption-induced increase of the work function is usually expected, yet we find a decrease of the work function for Cl, Br and I, which is most prominent at a coverage of approximately 0.25 ML. This coverage-dependent behavior can be explained by assuming a combination of charge transfer and polarization effects on the adsorbate layer. The results are contrasted to the adsorption of fluorine on calcium, a system in which a decrease in the work function is also observed despite a large charge transfer to the halogen adatom.

  6. Silver nanoprisms self-assembly on differently functionalized silica surface

    Science.gov (United States)

    Pilipavicius, J.; Chodosovskaja, A.; Beganskiene, A.; Kareiva, A.

    2015-03-01

    In this work colloidal silica/silver nanoprisms (NPRs) composite coatings were made. Firstly colloidal silica sols were synthesized by sol-gel method and produced coatings on glass by dip-coating technique. Next coatings were silanized by (3-Aminopropyl)triethoxysilane (APTES), N-[3-(Trimethoxysilyl)propyl]ethylenediamine (AEAPTMS), (3- Mercaptopropyl)trimethoxysilane (MPTMS). Silver NPRs where synthesized via seed-mediated method and high yield of 94±15 nm average edge length silver NPRs were obtained with surface plasmon resonance peak at 921 nm. Silica-Silver NPRs composite coatings obtained by selfassembly on silica coated-functionalized surface. In order to find the most appropriate silanization way for Silver NPRs self-assembly, the composite coatings were characterized by scanning electron microscopy (SEM), dynamic light scattering (DLS), water contact angle (CA) and surface free energy (SFE) methods. Results have showed that surface functionalization is necessary to achieve self-assembled Ag NPRs layer. MPTMS silanized coatings resulted sparse distribution of Ag NPRs. Most homogeneous, even distribution composite coatings obtained on APTES functionalized silica coatings, while AEAPTMS induced strong aggregation of Silver NPRs.

  7. Minimal models on Riemann surfaces: The partition functions

    Energy Technology Data Exchange (ETDEWEB)

    Foda, O. (Katholieke Univ. Nijmegen (Netherlands). Inst. voor Theoretische Fysica)

    1990-06-04

    The Coulomb gas representation of the A{sub n} series of c=1-6/(m(m+1)), m{ge}3, minimal models is extended to compact Riemann surfaces of genus g>1. An integral representation of the partition functions, for any m and g is obtained as the difference of two gaussian correlation functions of a background charge, (background charge on sphere) x (1-g), and screening charges integrated over the surface. The coupling constant x (compacitification radius){sup 2} of the gaussian expressions are, as on the torus, m(m+1), and m/(m+1). The partition functions obtained are modular invariant, have the correct conformal anomaly and - restricting the propagation of states to a single handle - one can verify explicitly the decoupling of the null states. On the other hand, they are given in terms of coupled surface integrals, and it remains to show how they degenerate consistently to those on lower-genus surfaces. In this work, this is clear only at the lattice level, where no screening charges appear. (orig.).

  8. The Analysis of F itzgerald’s Work by Functionality

    Institute of Scientific and Technical Information of China (English)

    谢倩

    2014-01-01

    Francis Scot Fitzgerald, who is the representative of the Jazz Age, was an American author of novels and short stories. In order to demonstrate the social influence of his works, this essay analyze the great author’s main novels from the perspective of functionality. By demonstrate the common features of those masterpieces, the real role of his works can be more clearer and the readers can have a beter understanding of the deeper meaning of functionality.

  9. Thermionic work function of /Cs/ZnO

    Science.gov (United States)

    Sommer, A. H.; Briere, T. R.

    1976-01-01

    The collector electrode of a thermionic converter requires a material having a low thermionic work function and chemical stability in a Cs atmosphere in the 800-K range. This letter reports that ZnO with an adsorbed Cs film meets these requirements. The work function is approximately 1.3 eV. Various methods of preparing the ZnO film are described as well as an experiment in which Cs was replaced by K.

  10. Workers with health problems : three perspectives on functioning at work

    NARCIS (Netherlands)

    Abma, Femke I.; Bultmann, Ute; Varekamp, Inge; van der Klink, Jac J. L.

    2013-01-01

    Purpose: Our aims were (i) to explore why it is that one worker with a health problem is able to stay at work while the other is not, (ii) to identify signals for decreased functioning at work, and (iii) to explore if and how this can be measured. Method: We conducted three focus groups: with worker

  11. The fragility of functional work systems in steel

    OpenAIRE

    Suzanne J. Konzelmann; Barnes, William

    1999-01-01

    The I/N case offers insight into the interrelationship between work systems, living standards and performance. It demonstrates that a high road approach and functional work systems positively impact stakeholders’ lives, improve production efficiency and benefit the local and macro-level economies and societies in which they are embedded. It also shows that such work systems can be implemented in contexts with a history of adversarial labor-management relations. However, broader external force...

  12. The Fragility of Functional Work Systems in American Steel

    OpenAIRE

    Barnes, W.; Sue Konzelmann

    1999-01-01

    The I/N case offers insight into the interrelationship between work systems, living standards and performance. It demonstrates that a high road approach and functional work systems positively impact stakeholders' lives, improve production efficiency and benefit the local and macro-level economies and societies in which they are embedded. It also shows that such work systems can be implemented in contexts with a history of adversarial labor-management relations. However, broader external force...

  13. Aluminum work function: Effect of oxidation, mechanical scraping and ion bombardment

    Science.gov (United States)

    Vinet, P.; Lemogne, T.; Montes, H.

    1985-01-01

    Surface studies have been performed on aluminum polycrystalline surfaces which have been mechanically scraped. Such studies were initiated in order to understand surface effects occurring in tribological processes which involve rubbing surfaces and the effects of adsorption of oxygen. To characterize the surfaces, the following three different experimental approaches have been used: (1) X.P.S. (X-ray photoelectron spectroscopy), in order to check the cleanliness of the surfaces and follow the adsorption and oxidation kinetics; (2) Analysis of the work function changes by following the energy spectra of secondary electrons emitted under low energy electron bombardment; and (3) Analysis of photoemission intensities under U.V. excitation. The reference state being chosen to be the surface cleaned by ion bombardment and exposures to oxygen atmospheres have been shown to lower the work function of clean polycrystalline aluminum by 1.2 eV. The oxygen pressure is found to affect only the kinetics of these experiments. Mechanical scraping has been shown to induce a decrease ( 0.3 eV) in the work function, which could sharply modify the kinetics of adsorption on the surface.

  14. Aryl Diazonium Chemistry for the Surface Functionalization of Glassy Biosensors.

    Science.gov (United States)

    Zheng, Wei; van den Hurk, Remko; Cao, Yong; Du, Rongbing; Sun, Xuejun; Wang, Yiyu; McDermott, Mark T; Evoy, Stephane

    2016-03-14

    Nanostring resonator and fiber-optics-based biosensors are of interest as they offer high sensitivity, real-time measurements and the ability to integrate with electronics. However, these devices are somewhat impaired by issues related to surface modification. Both nanostring resonators and photonic sensors employ glassy materials, which are incompatible with electrochemistry. A surface chemistry approach providing strong and stable adhesion to glassy surfaces is thus required. In this work, a diazonium salt induced aryl film grafting process is employed to modify a novel SiCN glassy material. Sandwich rabbit IgG binding assays are performed on the diazonium treated SiCN surfaces. Fluorescently labelled anti-rabbit IgG and anti-rabbit IgG conjugated gold nanoparticles were used as markers to demonstrate the absorption of anti-rabbit IgG and therefore verify the successful grafting of the aryl film. The results of the experiments support the effectiveness of diazonium chemistry for the surface functionalization of SiCN surfaces. This method is applicable to other types of glassy materials and potentially can be expanded to various nanomechanical and optical biosensors.

  15. Aryl Diazonium Chemistry for the Surface Functionalization of Glassy Biosensors

    Science.gov (United States)

    Zheng, Wei; van den Hurk, Remko; Cao, Yong; Du, Rongbing; Sun, Xuejun; Wang, Yiyu; McDermott, Mark T.; Evoy, Stephane

    2016-01-01

    Nanostring resonator and fiber-optics-based biosensors are of interest as they offer high sensitivity, real-time measurements and the ability to integrate with electronics. However, these devices are somewhat impaired by issues related to surface modification. Both nanostring resonators and photonic sensors employ glassy materials, which are incompatible with electrochemistry. A surface chemistry approach providing strong and stable adhesion to glassy surfaces is thus required. In this work, a diazonium salt induced aryl film grafting process is employed to modify a novel SiCN glassy material. Sandwich rabbit IgG binding assays are performed on the diazonium treated SiCN surfaces. Fluorescently labelled anti-rabbit IgG and anti-rabbit IgG conjugated gold nanoparticles were used as markers to demonstrate the absorption of anti-rabbit IgG and therefore verify the successful grafting of the aryl film. The results of the experiments support the effectiveness of diazonium chemistry for the surface functionalization of SiCN surfaces. This method is applicable to other types of glassy materials and potentially can be expanded to various nanomechanical and optical biosensors. PMID:26985910

  16. Contacting mode operation of work function energy harvester

    Science.gov (United States)

    Varpula, A.; Laakso, S. J.; Havia, T.; Kyynäräinen, J.; Prunnila, M.

    2014-11-01

    The work function energy harvester (WFEH) is a variable capacitance vibration energy harvester where the charging of the capacitor electrodes is driven by the work function difference of the electrode materials. In this work, we investigate operation modes of the WFEH by utilizing a macroscopic parallel plate capacitor with Cu and Al electrodes and varying plate distance. We show that by charging the electrodes of the WFEH by letting the electrode plates touch during the operation a significant output power enhancement can be achieved in comparison to the case where the electrodes are charged and discharged only through a load resistor.

  17. Skin and surface lead contamination, hygiene programs, and work practices of bridge surface preparation and painting contractors.

    Science.gov (United States)

    Virji, M Abbas; Woskie, Susan R; Pepper, Lewis D

    2009-02-01

    A 2005 regulatory review of the lead in construction standard by the Occupational Safety and Health Administration (OSHA) noted that alternative pathways of exposure can be as significant as inhalation exposure and that noncompliance with the standard pertaining to hygiene facilities and practices was the second most commonly violated section of the standard. Noncompliance with provisions of the standard and unhealthy work and hygiene practices likely increase the likelihood of take-home lead via contaminated clothing, automobiles, and skin, thus contributing to elevated blood lead levels (BLL) among construction workers and their family members. We performed a cross-sectional study of bridge painters working for small contractors in Massachusetts to investigate causes of persistent elevated BLLs and to assess lead exposures. Thirteen work sites were evaluated for a 2-week period during which surface and skin wipe samples were collected and qualitative information was obtained on personal hygiene practices, decontamination and hand wash facilities, and respiratory protection programs. Results showed lead contamination on workers' skin, respirators, personal automobiles, and the decontamination unit, indicating a significant potential for take-home lead exposure. Overall, the geometric mean (GM) skin lead levels ranged from 373 microg on workers' faces at end of shift to 814 microg on hands at break time. The overall GM lead level inside respirators was 143 microg before work and 286 microg after work. Lead contamination was also present inside workers' personal vehicles as well as on surfaces inside the clean side of the decontamination unit. Review of the respiratory protection programs, work site decontamination and hand wash facilities, and personal hygiene practices indicated that these factors had significant impact on skin and surface contamination levels and identified significant opportunities for improving work site facilities and personal practices

  18. Work function characterization of solution-processed cobalt silicide

    Science.gov (United States)

    Shihab Ullah, Syed; Robinson, Matt; Hoey, Justin; Sky Driver, M.; Caruso, A. N.; Schulz, Douglas L.

    2012-06-01

    Cobalt silicide thin films were prepared by spin-coating liquid cyclohexasilane-based inks onto silicon substrates followed by a thermal treatment. The work function of the solution-processed Co-Si was determined by both capacitance-voltage (C-V) measurements of metal-oxide-semiconductor (MOS) structures as well as by ultraviolet photoemission spectroscopy (UPS). Variable frequency C-V of MOS structures with silicon oxide layers of variable thickness showed that solution-processed metal silicide films exhibit a work function of 4.36 eV with one Co-Si film on Si giving a UPS-derived work function of 4.80 eV. Similar work function measurements were collected for vapor-deposited MOS capacitors where Al thin films were prepared according to standard class 100 cleanroom handling techniques. In both instances, the work function values established by the electrical measurements were lower than those measured by UPS and this difference appears to be a consequence of parasitic series resistance.

  19. Overweight, obesity and work functioning: the role of working-time arrangements.

    Science.gov (United States)

    Nigatu, Yeshambel T; van de Ven, Hardy A; van der Klink, Jac J L; Brouwer, Sandra; Reijneveld, Sijmen A; Bültmann, Ute

    2016-01-01

    Obesity is associated with productivity loss, but little is known about how obese workers function at work and also the role of working-time arrangements on this association is lacking. Therefore, the aim of this study was to examine the association of overweight and obesity with work functioning (WF), and to determine whether the associations differ between workers with different working-time arrangements. A cross-sectional study was conducted within the sampling frame of the 'Shift Your Work' study that examined the effect of irregular working-times in relation to health and functioning at work. We included N = 622 Dutch employees, of which N = 384 (62%) were shift-workers, N = 171 (27%) on-call workers and N = 67 (11%) day-workers. Overweight and obesity were defined as BMI 25-30 and ≥30, respectively. WF was assessed using the Work-Role Functioning Questionnaire. The prevalences of overweight and obesity were 48% and 10% in all workers, 49% and 11% in shift-workers, 45% and 10% in on-call workers, and 49% and 6% in day workers, respectively. In all workers, obesity was associated with lower WF scores for physical demands (adjusted estimate, aB = -5.5). In shift-workers, obesity was associated with lower WF scores for output and physical demands (aB = -8.8 and -6.8, respectively). In day and on-call workers, overweight and obesity were not associated with WF. Overweight and obesity are highly prevalent in the working population. Obesity might reduce the executive function performance beyond physical limitations, and limit the ability to accomplish tasks successfully, especially in shift workers. Copyright © 2015 Elsevier Ltd and The Ergonomics Society. All rights reserved.

  20. Plant Surfaces: Structures and Functions for Biomimetic Innovations

    Science.gov (United States)

    Barthlott, Wilhelm; Mail, Matthias; Bhushan, Bharat; Koch, Kerstin

    2017-04-01

    An overview of plant surface structures and their evolution is presented. It combines surface chemistry and architecture with their functions and refers to possible biomimetic applications. Within some 3.5 billion years biological species evolved highly complex multifunctional surfaces for interacting with their environments: some 10 million living prototypes (i.e., estimated number of existing plants and animals) for engineers. The complexity of the hierarchical structures and their functionality in biological organisms surpasses all abiotic natural surfaces: even superhydrophobicity is restricted in nature to living organisms and was probably a key evolutionary step with the invasion of terrestrial habitats some 350-450 million years ago in plants and insects. Special attention should be paid to the fact that global environmental change implies a dramatic loss of species and with it the biological role models. Plants, the dominating group of organisms on our planet, are sessile organisms with large multifunctional surfaces and thus exhibit particular intriguing features. Superhydrophilicity and superhydrophobicity are focal points in this work. We estimate that superhydrophobic plant leaves (e.g., grasses) comprise in total an area of around 250 million km2, which is about 50% of the total surface of our planet. A survey of structures and functions based on own examinations of almost 20,000 species is provided, for further references we refer to Barthlott et al. (Philos. Trans. R. Soc. A 374: 20160191, 1). A basic difference exists between aquatic non-vascular and land-living vascular plants; the latter exhibit a particular intriguing surface chemistry and architecture. The diversity of features is described in detail according to their hierarchical structural order. The first underlying and essential feature is the polymer cuticle superimposed by epicuticular wax and the curvature of single cells up to complex multicellular structures. A descriptive terminology

  1. [Comparison of Work Ability Index and cognitive function tests].

    Science.gov (United States)

    Suzuki, Hideki; Kumashiro, Masaharu; Kusanoi, Kayo; Shazuki, Shuichiro; Fuji, Atsunaru; Eto, Risa

    2004-05-01

    The purpose of this study was to evaluate the effect of aging with regard to scores for certain cognitive function tests and WAI (Work Ability Index), and to examine the relationship between cognitive function test scores and work ability as measured by WAI. The subjects were 139 male employees of a factory producing steel plate, and their average age was 48.1 yr (SD 16.4). The WAI and cognitive function tests were conducted and valid scores were obtained from 134 subjects as to WAI, and from 88 subjects as to cognitive function tests. The subjects were divided into two groups: young workers (under 45 yr) and middle-aged to elderly workers (45 yr and over). The WAI scores of the two groups were compared, but no significant differences were observed. Nevertheless, for two WAI items, WAI-2 and WAI-7, the scores of the middle-aged to elderly worker group were significantly higher than those of the young worker group. In contrast, the scores for WAI-3 of the middle-aged to elderly group were significantly lower than those of the young worker group. The cognitive function test scores for the two groups were also compared. The scores for Working Memory test, Tracking test, and Sentence-to-sentence Comparison test of the middle-aged to elderly worker group were significantly lower than those of the younger group. Moreover, for the middle-aged to elderly worker group, the average WAI-3 scores for those with good cognitive function test results and those with poor cognitive function test results were compared, but there were no significant differences. This result shows that deterioration of physical function caused by aging is not related to deterioration of cognitive function caused by aging in the subjects of this study. The reason for this may be that the subjects are blue-collar workers, and thus cognitive functions are less important for their work.

  2. Engineered microtopographies and surface chemistries direct cell attachment and function

    Science.gov (United States)

    Magin, Chelsea Marie

    Harrison, in 1914, first recognized that cells respond to physicochemical cues such as substratum topography when he observed that fibroblasts elongated while cultured on spider silk. Recently, techniques developed in the micro-electronics industry have been used to create molds for producing microscaled topographies with various shapes and spatial arrangements. Although these patterning techniques are well-established, very little is known about the mechanisms underlying cell sensing and response to microtopographies. In this work cellular micro-environments with varying surface topographies and chemistries were evaluated with marine organisms and mammalian cells to investigate cellular sensing and response. Biofouling---the accumulation of micro-organisms, plants, and animals on submerged surfaces---is an environmental and economic concern. Engineered topographies, replicated in polydimethylsiloxane elastomer (PDMSe) and functionalized poly(ethylene glycol)-dimethacrylate (PEGDMA) hydrogels, were evaluated for inhibition of marine fouling organism attachment. Microtopographies replicated in PDMSe inhibited attachment of the marine bacterium, Cobetia marina up to 99% versus smooth. The average normalized attachment densities of cells of C. marina and zoospores of the green algae Ulva on PDMSe topographies scaled inversely with the Engineered Roughness Index (ERIII), a representation of surface energy. Attachment densities of Ulva from four assays and C. marina from two growth phases to PDMSe surfaces scaled inversely with one equation: ERI II multiplied by the Reynolds number of the organism (Re) (R 2 = 0.77). The same microtopographies created in PDMSe reduced the initial attachment density and attachment strength of cells of the diatoms Navicula incerta and Seminavis robusta compared to smooth PDMSe. The average normalized attachment density of Navicula after exposure to shear stress (48 Pa) was correlated with the contact area between the diatom and a

  3. The work ability index and functional capacity among older workers

    Directory of Open Access Journals (Sweden)

    Rosimeire S. Padula

    2013-08-01

    Full Text Available BACKGROUND: Decreases in functional ability due to aging can impair work capacity and productivity among older workers. OBJECTIVE: This study compares the sociodemographics, health conditions, and physical functioning abilities of young and old workers as well as correlates of physical functioning capacity with the work ability index (WAI. METHOD: This exploratory, cross-sectional study examined employees of a higher education institution (HEI and those of a metallurgical industry. Older workers (50 years old or above were matched for gender and occupation type with younger workers (less than 50 years old. The following evaluations were applied: the multidimensional assessment questionnaire (which included sociodemographic, clinical, health perception, and physical health indices, the WAI, and a battery of physical functional tests. RESULTS: Diseases and regularly used medications were more common among the group of aging workers. The WAI did not differ between groups (p=0.237. Both groups showed similar physical functional capacity performances with regard to walking speed, muscle strength, and lower limb physical functioning. Aging workers showed a poorer performance on a test of right-leg support (p=0.004. The WAI was moderately correlated with the sit-to-stand test among older female workers (r=0.573, p=0.051. CONCLUSIONS: Unfavorable general health conditions did not affect the assessment of work ability or most of the tests of physical functional capacity in the aging group.

  4. High-Work-Function Transparent Conductive Oxides with Multilayer Films

    Science.gov (United States)

    Song, Chunyan; Chen, Hong; Fan, Yi; Luo, Jinsong; Guo, Xiaoyang; Liu, Xingyuan

    2012-04-01

    Transparent conductive oxide (TCO) films using WO3/Ag/WO3 (WAW) were fabricated under room temperature conditions. WAW has a low sheet resistance of 12 Ω/sq and a work function of 6.334 eV. This is one of the TCOs with the highest work function. These properties make it useful for application in electroluminescent devices and solar cells. Both theoretical calculation and experimental results show that the two WO3 layers strongly affect transparency, while the Ag layer determines transmittance and electrical performances. These rules can be applied in all dielectric/metal/dielectric structures.

  5. Change of Work Function of Pd, Ag, K on Al(001) as a Function of External Electric Field

    Institute of Scientific and Technical Information of China (English)

    侯柱峰; 黄美纯; 朱梓忠; 黄荣彬; 郑兰荪

    2001-01-01

    We present a local density functional calculation of the effect of an external electric field on the work function change of Pd and Ag adsorption on an Al(001) surface. The adsorption of K has also been considered for comparison. We found that the work functions for all the systems increased linearly when the strength of the external electric field was increased. Since the polarized electrons at the interstitial regions between the adsorbate and substrate for Pd/Al(001) and Ag/Al(001) react to the external electric field differently, the subtle differences between Pd/Al(001) and Ag/Al(001) bondings has been characterized through the comparison of the slopes of the work function change versus electric field.

  6. Reduced work function of graphene by metal adatoms

    Science.gov (United States)

    Legesse, Merid; Mellouhi, Fedwa El; Bentria, El Tayeb; Madjet, Mohamed E.; Fisher, Timothy S.; Kais, Sabre; Alharbi, Fahhad H.

    2017-02-01

    In this paper, the work function of graphene doped by different metal adatoms and at different concentrations is investigated. Density functional theory is used to maximize the reduction of the work function. In general, the work function drops significantly before reaching saturation. For example in the case of Cs doping, the work function saturates at 2.05 eV with a modest 8% doping. The adsorption of different concentrations on metal adatoms on graphene is also studied. Our calculations show that the adatoms prefer to relax at hollow sites. The transfer of electron from metallic dopants to the graphene for all the studied systems shifts the Fermi energy levels above the Dirac-point and the doped graphenes become metallic. The value of Fermi energy shifts depends on the type of metallic dopants and its concentrations. A detail analysis of the electronic structure in terms of band structure and density of states, absorption energy, and charge transfer for each adatom-graphene system is presented.

  7. Estimation of intrinsic work function of multilayer graphene by probing with electrostatic force microscopy

    Science.gov (United States)

    Singh, Anshika; Guha, Puspendu; Panwar, Amrish K.; Tyagi, Pawan K.

    2017-04-01

    In present study, electrostatic force microscopy (EFM) is used to estimate the intrinsic work function of few layer graphene (FLG) transferred on SiO2 (300 nm)/Si (500 μm) substrate. This FLG has been prepared by using the mechanical exfoliation technique. In exfoliated FLG, adhesive residues are always left from scotch tape on its surface. These residues as well as SiO2 substrate could modify the work function due to the formation of dipoles on the surface. Taking the effect of adhesive into account, FLG is pre-charged and then scanned with a tip biased with dc voltage. Intrinsic work function of FLG is determined and found to be 4.52 ± 0.1 eV.

  8. Conceptual modelling approach of mechanical products based on functional surface

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    A modelling framework based on functional surface is presented to support conceptual design of mechanical products. The framework organizes product information in an abstract and multilevel manner. It consists of two mapping processes: function decomposition process and form reconstitution process. The steady mapping relationship from function to form (function-functional surface-form) is realized by taking functional surface as the middle layer. It farthest reduces the possibilities of combinatorial explosion that can occur during function decomposition and form reconstitution. Finally, CAD tools are developed and an auto-bender machine is applied to demonstrate the proposed approach.

  9. Doping of graphite by an alkaline-earth metal to reduce the work function

    NARCIS (Netherlands)

    Baturin, AS; Nikolski, KN; Knyazev, AI; Tchesov, RG; Sheshin, EP

    2004-01-01

    A technique for reducing the work function of a field-emission graphite cathode by doping it by an alkaline-earth metal (barium) is suggested. A model of formation of a barium monolayer on the cathode surface is proposed. Field-emission tests show that the operating voltage of the doped cathode is l

  10. Evidence for the negative work function associated with positrons in gold.

    Science.gov (United States)

    Costello, D. G.; Groce, D. E.; Herring, D. F.; Mcgowan, J. W.

    1972-01-01

    Observation that positrons which have been thermalized in various moderators and coated with approximately 200-A gold leave the gold surface with an energy which peaks between 0.75 and 2.90 eV. This energy is thought to be associated with a positron or 'negative' work function of gold.

  11. Shape Error Analysis of Functional Surface Based on Isogeometrical Approach

    Science.gov (United States)

    YUAN, Pei; LIU, Zhenyu; TAN, Jianrong

    2017-05-01

    The construction of traditional finite element geometry (i.e., the meshing procedure) is time consuming and creates geometric errors. The drawbacks can be overcame by the Isogeometric Analysis (IGA), which integrates the computer aided design and structural analysis in a unified way. A new IGA beam element is developed by integrating the displacement field of the element, which is approximated by the NURBS basis, with the internal work formula of Euler-Bernoulli beam theory with the small deformation and elastic assumptions. Two cases of the strong coupling of IGA elements, "beam to beam" and "beam to shell", are also discussed. The maximum relative errors of the deformation in the three directions of cantilever beam benchmark problem between analytical solutions and IGA solutions are less than 0.1%, which illustrate the good performance of the developed IGA beam element. In addition, the application of the developed IGA beam element in the Root Mean Square (RMS) error analysis of reflector antenna surface, which is a kind of typical functional surface whose precision is closely related to the product's performance, indicates that no matter how coarse the discretization is, the IGA method is able to achieve the accurate solution with less degrees of freedom than standard Finite Element Analysis (FEA). The proposed research provides an effective alternative to standard FEA for shape error analysis of functional surface.

  12. Functional Requirements for an Electronic Work Package System

    Energy Technology Data Exchange (ETDEWEB)

    Oxstrand, Johanna H. [Idaho National Lab. (INL), Idaho Falls, ID (United States)

    2016-12-01

    This document provides a set of high level functional requirements for a generic electronic work package (eWP) system. The requirements have been identified by the U.S. nuclear industry as a part of the Nuclear Electronic Work Packages - Enterprise Requirements (NEWPER) initiative. The functional requirements are mainly applied to eWP system supporting Basic and Moderate types of smart documents, i.e., documents that have fields for recording input such as text, dates, numbers, and equipment status, and documents which incorporate additional functionalities such as form field data “type“ validation (e.g. date, text, number, and signature) of data entered and/or self-populate basic document information (usually from existing host application meta data) on the form when the user first opens it. All the requirements are categorized by the roles; Planner, Supervisor, Craft, Work Package Approval Reviewer, Operations, Scheduling/Work Control, and Supporting Functions. The categories Statistics, Records, Information Technology are also included used to group the requirements. All requirements are presented in Section 2 through Section 11. Examples of more detailed requirements are provided for the majority of high level requirements. These examples are meant as an inspiration to be used as each utility goes through the process of identifying their specific requirements. The report’s table of contents provides a summary of the high level requirements.

  13. Analysis of dynamic pulmonary functions in air conditioned work environment

    Directory of Open Access Journals (Sweden)

    Anu T. E.

    2016-07-01

    Conclusions: The results of the study indicate that the subjects working in AC environment for a long duration are prone to develop restrictive lung diseases. Hence, study concludes that periodic pulmonary function assessment should be made mandatory. Further, regular maintenance of ACs is also recommended. [Int J Res Med Sci 2016; 4(7.000: 2661-2664

  14. Functional Neuroanatomy of Spatial Working Memory in Children.

    Science.gov (United States)

    Nelson, Charles A.; Monk, Christopher S.; Lin, Joseph; Carver, Leslie J.; Thomas, Kathleen M.; Truwit, Charles L.

    2000-01-01

    Used functional magnetic resonance imaging (fMRI) to examine spatial working memory in 8- to 11-year-olds tested under 3 conditions. Found that subtracting activation of the motor condition from the memory condition revealed activity in dorsal aspects of the prefrontal cortex and in the posterior parietal and anterior cingulate cortex. Analysis of…

  15. A Density Functional Study of Atomic Carbon Adsorption on δ-Pu(111)Surface

    Institute of Scientific and Technical Information of China (English)

    WEI Hong-Yuan; XIONG Xiao-Ling; SONG Hong-Tao; LUO Shun-Zhong

    2010-01-01

    @@ Adsorption of atomic carbon on δ-Pu(111)surface is investigated systematically using density functional theory with RPBE functional.The adsorption energies,adsorption structures,Mulliken population,work functions,layer and projected density of states are calculated in wide ranges of coverage,which have never been studied before as far as we know.

  16. Plasma functionalization of titanium surface for repulsion of blood platelets

    OpenAIRE

    Cvelbar, Uros; Modic, Martina; Kovac, J.; Lazovic, S; Filipic, G; Vujosevic, D; Junkar, Ita; Elersic, Kristina; Brühl, S.P.; Canal Barnils, Cristina; Belmonte, Thierry; Mozetic, Miran

    2012-01-01

    Thrombosis and restenosis are the most common problems during insertion of biocompatible implants like titanium stents into human blood, due to aggregation of platelets on their surfaces. Because of this reason, we studied the response of blood platelets to a plasma treated titanium surface. The aim was to design a functionalized surface which would repel blood platelets or prevent their adhesion. Therefore, we functionalized surfaces with low-temperature inductively coupled oxygen plasma tre...

  17. Electroassisted Functionalization of Nitinol Surface, a Powerful Strategy for Polymer Coating through Controlled Radical Surface Initiation.

    Science.gov (United States)

    Arrotin, Bastien; Delhalle, Joseph; Dubois, Philippe; Mespouille, Laetitia; Mekhalif, Zineb

    2017-03-28

    Coating Nitinol (NiTi) surfaces with a polymer layer has become very appealing in the past few years owing to its increased attraction in the biomedical field. Although its intrinsic properties helped ensure its popularity, its extensive implementation is still hampered by its nickel inclusion, making it sensitive to pitting corrosion and therefore leading to the release of carcinogenic Ni(2+) ions. Among all recent ways to modify NiTi surfaces, elaboration of self-assembled monolayers is of great interest as their high order confers a reinforcement of the metal surface corrosion resistance and brings new functionalities to the metal for postmodification processes. In this work, we compare the electroassisted and thermally assisted self-assembling of 11-(2-bromoisobutyrate)-undecyl-1-phosphonic acid (BUPA) to the classical immersion process on NiTi surfaces initially submitted to a hydrothermal treatment. Among all tested conditions, the electroassisted grafting of BUPA at room temperature appears to be the most promising alternative, as it allows grafting in very short times (5-10 min), thus preventing its degradation. The thus-formed layer has been proven to be sufficient to enable the surface-initiated atom transfer radical polymerization (SI-ATRP) of 2-(dimethylamino)ethyl methacrylate.

  18. Career Development and Personal Functioning Differences between Work-Bound and Non-Work Bound Students

    Science.gov (United States)

    Creed, Peter A.; Patton, Wendy; Hood, Michelle

    2010-01-01

    We surveyed 506 Australian high school students on career development (exploration, planning, job-knowledge, decision-making, indecision), personal functioning (well-being, self-esteem, life satisfaction, school satisfaction) and control variables (parent education, school achievement), and tested differences among work-bound, college-bound and…

  19. Ellipsometry of functional organic surfaces and films

    CERN Document Server

    Hinrichs, Karsten

    2013-01-01

    Ellipsometry is the method of choice to determin the properties of surfaces and thin films. It provides comprehensive and sensitive characterization in a contactless and non-invasive measurements. This book gives a state-of-the-art survey of ellipsometric investigations of organic films and surfaces, from laboratory to synchrotron applications, with a special focus on in-situ use in processing environments and at solid-liquid interfaces.

  20. Interfacial adhesion between functionalized polyethylene surface and graphene via molecular dynamic simulation.

    Science.gov (United States)

    Nikkhah, S Javan; Moghbeli, M R; Hashemianzadeh, S M

    2015-05-01

    In this study, interfacial adhesion between functionalized polyethylene (PE) surfaces and graphene were examined using molecular simulation. Various functional groups including amino, carboxy, hydroxy, cyano, isocyanato, oxo, and ethylamino were used to cover the PE surface with surface densities of 0.48, 1.30, and 4.84 groups per nm(2). The interfacial adhesion between the modified PE surfaces and the graphene was quantified via calculation of work of separation (Wsep), the amount of the required work to separate two surfaces without occurring any relaxation and diffusion phenomena. Insertion of the functional groups on the PE surface decreased the amount of Wsep, except for the oxo, amino, and higher densities of the carboxy groups. Increasing the surface group density enhanced the adhesion due to decreasing the surface atomic roughness and increasing the atomic density at the interface. In addition, the effect of surface group rearrangement was investigated via calculation of the work of adhesion (Wadh) while sufficient time had been devoted to relax the interface. The surface reorganization during the relaxation process significantly enhanced adhesion due to eliminating the surface roughness and increasing the surface atomic density.

  1. Functional correlates of distractor suppression during spatial working memory encoding.

    Science.gov (United States)

    Toepper, M; Gebhardt, H; Beblo, T; Thomas, C; Driessen, M; Bischoff, M; Blecker, C R; Vaitl, D; Sammer, G

    2010-02-17

    Executive working memory operations are related to prefrontal regions in the healthy brain. Moreover, neuroimaging data provide evidence for a functional dissociation of ventrolateral and dorsolateral prefrontal cortex. Most authors either suggest a modality-specific or a function-specific prefrontal cortex organization. In the present study we particularly aimed at the identification of different prefrontal cerebral areas that are involved in executive inhibitory processes during spatial working memory encoding. In an fMRI study (functional magnetic resonance imaging) we examined the neural correlates of spatial working memory processing by varying the amount of executive demands of the task. Twenty healthy volunteers performed the Corsi Block-Tapping test (CBT) during fMRI. The CBT requires the storage and reproduction of spatial target sequences. In a second condition, we presented an adapted version of the Block-Suppression-Test (BST). The BST is based on the original CBT but additionally requires the active suppression of visual distraction within the target sequences. In comparison to the CBT performance, particularly the left dorsolateral prefrontal cortex (BA 9) showed more activity during the BST condition. Our results show that the left dorsolateral prefrontal cortex plays a crucial role for executive controlled inhibition of spatial distraction. Furthermore, our findings are in line with the processing model of a functional dorsolateral-ventrolateral prefrontal cortex organization.

  2. Work function reduction by a redox-active organometallic sandwich complex

    KAUST Repository

    Hyla, Alexander S.

    2016-07-14

    We have investigated, at the density functional theory level, the geometric and electronic structures of the pentamethyliridocene (IrCpCp*) monomer and dimer adsorbed on the Au(111) and indium tin oxide (ITO) (222) surfaces, as well as their impact on the work functions. Our calculations show that the adsorption of a monomer lowers the work function of ITO(222) by 1.2 eV and Au(111) by 1.2–1.3 eV. The main origin for this reduction is the formation of an interface dipole between the monomer and the substrate via charge transfer. Dimer adsorption as well as adsorption of possible byproducts formed from dimer bond-cleavage in solution, show a lesser ability to lower the work function. © 2016 Elsevier B.V.

  3. Surface Functionalization of Nanodiamonds Using the Biomacromolecule Chitosan (CS)

    Science.gov (United States)

    Lott, Lewis Q.

    NDs are highly promising drug delivery vehicles (DDVs) due to the materials low cytotoxicity and biocompatibility. The advantage of these materials lies within their tunable surface chemistry and inherent optical properties. Despite the numerous benefits, the use of NDs in biological systems is impeded by their high aggregation propensity in polar liquid medium, a caveat from its rich chemistry. ND particles typically aggregate into much larger groups >200 nm, which are too large for drug delivery applications. In this work, salt assisted attrition milling was utilized to decrease ND aggregates. After 5 hours of milling, dynamic light scattering (DLS) measurements revealed a maximum particle distribution at 127 nm, with significant reduction in the mass fraction of larger particle size distribution from 300-1000nm. The average size of the nanodiamond particles was also shown to increase with an increasing concentration of chitosan (0.25 w/v%; 142nm and 1 w/v%; 825nm). In the modification of nanodiamonds, FTIR was used to examine the chemical composition of the nanodiamonds, both before and after functionalization. FTIR results of the pristine nanodiamonds showed characteristic bands at 3400cm -1 (-OH) 1630 cm-1 (C=O) and 1080 (-C-O). Chitosan exhibited spectral regions of interest at 3350 cm-1 (-OH), 1665 cm-1 (NH2) and 1030 cm-1 (C-O). Successful functionalization of the nanodiamaond surface was confirmed by the appearance of the amide band I at 1664 cm-1 and presence of strong C-O stretching at 1197cm-1 from the chitosan backbone. This is indicative of the covalent binding of NH2 on chitosan with COOH on the ND surface. X-ray diffraction was performed to observe the structure and crystallinity of the NDs and showed crystalline characteristic peaks at 2theta 44° (111), 75° (220), and 91° (113) for the pristine ND. The appearance of an amorphous band at 2theta 22° in the analysis of ND-COOH-CS is indicative of the surface modification of the nanodiamond with

  4. Enhancing the accuracy of the Fowler method for monitoring non-constant work functions

    Science.gov (United States)

    Friedl, R.

    2016-04-01

    The Fowler method is a prominent non-invasive technique to determine the absolute work function of a surface based on the photoelectric effect. The evaluation procedure relies on the correlation of the photocurrent with the incident photon energy hν which is mainly dependent on the surface work function χ. Applying Fowler's theory of the photocurrent, the measurements can be fitted by the theoretical curve near the threshold hν⪆χ yielding the work function χ and a parameter A. The straightforward experimental implementation of the Fowler method is to use several particular photon energies, e.g. via interference filters. However, with a realization like that the restriction hν ≈ χ can easily be violated, especially when the work function of the material is decreasing during the measurements as, for instance, with coating or adsorption processes. This can lead to an overestimation of the evaluated work function value of typically some 0.1 eV, reaching up to more than 0.5 eV in an unfavorable case. A detailed analysis of the Fowler theory now reveals the background of that effect and shows that the fit-parameter A can be used to assess the accuracy of the determined value of χ conveniently during the measurements. Moreover, a scheme is introduced to quantify a potential overestimation and to perform a correction to χ to a certain extent. The issues are demonstrated exemplarily at the monitoring of the work function reduction of a stainless steel sample surface due to caesiation.

  5. The relationship between the electron work function and friction behavior of passive alloys under different conditions

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Shiyi [Department of Chemical and Materials Engineering, University of Alberta, Edmonton, Alberta T6G 2V4 (Canada); China Academy of Space Technology, 100094 Beijing (China); Lu, Hao [Department of Chemical and Materials Engineering, University of Alberta, Edmonton, Alberta T6G 2V4 (Canada); Li, D.Y., E-mail: dongyang.li@ualberta.ca [Department of Chemical and Materials Engineering, University of Alberta, Edmonton, Alberta T6G 2V4 (Canada)

    2015-10-01

    Highlights: • EWF and friction behavior of alloys in different conditions are investigated. • Damaged fresh active broken-bond on surface leads higher EWF and larger adhesion. • Inactive broken-bond covered with passive film leads higher EWF and lower adhesion. • Freshly polished surfaces and etched ones are consistent with above behaviors. - Abstract: Electron work function (EWF), adhesion and friction coefficient of three passive alloys were investigated. During dry sliding tests, surfaces having higher work functions showed larger coefficients of friction. While under oil-lubricated sliding condition, the trend was reversed. It appears that when the surface passive film was damaged, the surface broken atomic bonds became active, leading to larger friction. However, under the oil-lubricated sliding condition, the passive film was retained, resulting in a different trend. Surface adhesive forces of freshly polished surfaces and etched ones were measured using an atomic force microscope. Results of the adhesion measurement are consistent with the behaviors of the alloys observed during the friction tests.

  6. Psychometric properties of the Nurses Work Functioning Questionnaire (NWFQ.

    Directory of Open Access Journals (Sweden)

    Fania R Gärtner

    Full Text Available OBJECTIVES: The Nurses Work Functioning Questionnaire (NWFQ is a 50-item self-report questionnaire specifically developed for nurses and allied health professionals. Its seven subscales measure impairments in the work functioning due to common mental disorders. Aim of this study is to evaluate the psychometric properties of the NWFQ, by assessing reproducibility and construct validity. METHODS: The questionnaire was administered to 314 nurses and allied health professionals with a re-test in 112 subjects. Reproducibility was assessed by the intraclass correlations coefficients (ICC and the standard error of measurement (SEM. For construct validity, correlations were calculated with a general work functioning scale, the Endicott Work Productivity Scale (EWPS (convergent validity and with a physical functioning scale (divergent validity. For discriminative validity, a Mann Whitney U test was performed testing for significant differences between subjects with mental health complaints and without. RESULTS: All subscales showed good reliability (ICC: 0.72-0.86, except for one (ICC = 0.16. Convergent validity was good in six subscales, correlations ranged from 0.38-0.62. However, in one subscale the correlation with the EWPS was too low (0.22. Divergent validity was good in all subscales based on correlations ranged from (-0.06-(-0.23. Discriminative validity was good in all subscales, based on significant differences between subjects with and without mental health complaints (p<0.001-p = 0.003. CONCLUSION: The NWFQ demonstrates good psychometric properties, for six of the seven subscales. Subscale "impaired decision making" needs improvement before further use.

  7. Work function measurements by the field emission retarding potential method.

    Science.gov (United States)

    Strayer, R. W.; Mackie, W.; Swanson, L. W.

    1973-01-01

    Description of the theoretical foundation of the field electron retarding potential method, and review of its experimental application to the measurement of single crystal face work functions. The results obtained from several substrates are discussed. An interesting and useful fallout from the experimental approach described is the ability to accurately measure the elastic and inelastic reflection coefficient for impinging electrons to near zero-volt energy.

  8. Improving Assessment of Work Related Mental Health Function Using the Work Disability Functional Assessment Battery (WD-FAB).

    Science.gov (United States)

    Marfeo, Elizabeth E; Ni, Pengsheng; McDonough, Christine; Peterik, Kara; Marino, Molly; Meterko, Mark; Rasch, Elizabeth K; Chan, Leighton; Brandt, Diane; Jette, Alan M

    2017-05-05

    Purpose To improve the mental health component of the Work Disability Functional Assessment Battery (WD-FAB), developed for the US Social Security Administration's (SSA) disability determination process. Specifically our goal was to expand the WD-FAB scales of mood & emotions, resilience, social interactions, and behavioral control to improve the depth and breadth of the current scales and expand the content coverage to include aspects of cognition & communication function. Methods Data were collected from a random, stratified sample of 1695 claimants applying for the SSA work disability benefits, and a general population sample of 2025 working age adults. 169 new items were developed to replenish the WD-FAB scales and analyzed using factor analysis and item response theory (IRT) analysis to construct unidimensional scales. We conducted computer adaptive test (CAT) simulations to examine the psychometric properties of the WD-FAB. Results Analyses supported the inclusion of four mental health subdomains: Cognition & Communication (68 items), Self-Regulation (34 items), Resilience & Sociability (29 items) and Mood & Emotions (34 items). All scales yielded acceptable psychometric properties. Conclusions IRT methods were effective in expanding the WD-FAB to assess mental health function. The WD-FAB has the potential to enhance work disability assessment both within the context of the SSA disability programs as well as other clinical and vocational rehabilitation settings.

  9. Versatile Density Functionals for Computational Surface Science

    DEFF Research Database (Denmark)

    Wellendorff, Jess

    Density functional theory (DFT) emerged almost 50 years ago. Since then DFT has established itself as the central electronic structure methodology for simulating atomicscale systems from a few atoms to a few hundred atoms. This success of DFT is due to a very favorable accuracy-to-computational c......Density functional theory (DFT) emerged almost 50 years ago. Since then DFT has established itself as the central electronic structure methodology for simulating atomicscale systems from a few atoms to a few hundred atoms. This success of DFT is due to a very favorable accuracy...... resampling techniques, thereby systematically avoiding problems with overfitting. The first ever density functional presenting both reliable accuracy and convincing error estimation is generated. The methodology is general enough to be applied to more complex functional forms with higher-dimensional fitting...

  10. Surface functionalized hollow silica particles and composites

    KAUST Repository

    Rodionov, Valentin

    2017-05-26

    Composition comprising hollow spherical silica particles having outside particle walls and inside particle walls, wherein the particles have an average particle size of about 10 nm to about 500 nm and an average wall thickness of about 10 nm to about 50 nm; and wherein the particles are functionalized with at least one organic functional group on the outside particle wall, on the inside particle wall, or on both the outside and inside particle walls, wherein the organic functional group is in a reacted or unreacted form. The organic functional group can be epoxy. The particles can be mixed with polymer precursor or a polymer material such as epoxy to form a prepreg or a nanocomposite. Lightweight but strong materials can be formed. Low loadings of hollow particles can be used.

  11. Diamond surface functionalization with biomimicry – Amine surface tether and thiol moiety for electrochemical sensors

    Energy Technology Data Exchange (ETDEWEB)

    Sund, James B., E-mail: jim@jamessund.com [Department of Electrical and Computer Engineering, Duke University, Durham, NC (United States); Causey, Corey P. [Departments of Chemistry and Biochemistry, Duke University, Durham, NC (United States); Wolter, Scott D. [Department of Physics, Elon University, Elon, NC 27244 (United States); Parker, Charles B., E-mail: charles.parker@duke.edu [Department of Electrical and Computer Engineering, Duke University, Durham, NC (United States); Stoner, Brian R. [Department of Electrical and Computer Engineering, Duke University, Durham, NC (United States); Research Triangle Institute (RTI) International, Research Triangle Park, NC (United States); Toone, Eric J. [Departments of Chemistry and Biochemistry, Duke University, Durham, NC (United States); Glass, Jeffrey T. [Department of Electrical and Computer Engineering, Duke University, Durham, NC (United States)

    2014-05-01

    Highlights: • Diamond surfaces were functionalized with organic molecules using a novel approach. • Used biomimicry to select a molecule to bind NO, similar to the human body. • Molecular orbital theory predicted the molecule-analyte oxidation behavior. • A thiol moiety was attached to an amine surface tether on the diamond surface. • XPS analysis verified each surface functionalization step. - Abstract: The surface of conducting diamond was functionalized with a terminal thiol group that is capable of binding and detecting nitrogen–oxygen species. The functionalization process employed multiple steps starting with doped diamond films grown by plasma enhanced chemical vapor deposition followed by hydrogen termination and photochemical attachment of a chemically protected amine alkene. The surface tether was deprotected to reveal the amine functionality, which enabled the tether to be extended with surface chemistry to add a terminal thiol moiety for electrochemical sensing applications. Each step of the process was validated using X-ray photoelectron spectroscopy analysis.

  12. Bio-inspired functional surfaces for advanced applications

    DEFF Research Database (Denmark)

    Malshe, Ajay; Rajurkar, Kamlakar; Samant, Anoop

    2013-01-01

    surface strategies in order to learn clever surface architectures and implement those architectures to impart advanced functionalities into manufactured consumer products. This keynote paper delivers a critical review of such inspiring biological surfaces and their nonbiological product analogs, where...... manufacturing science and engineering have adopted such advanced functional surface architectures.......Over millions of years, biological subjects have been in continuous combat with extreme environmental conditions. The fittest have survived through continuous evolution, an ongoing process. In particular, biological surfaces, which are the active interfaces between subjects and the environment...

  13. Magnetic Iron Oxide Nanoparticles: Synthesis and Surface Functionalization Strategies

    Directory of Open Access Journals (Sweden)

    He Quanguo

    2008-01-01

    Full Text Available Abstract Surface functionalized magnetic iron oxide nanoparticles (NPs are a kind of novel functional materials, which have been widely used in the biotechnology and catalysis. This review focuses on the recent development and various strategies in preparation, structure, and magnetic properties of naked and surface functionalized iron oxide NPs and their corresponding application briefly. In order to implement the practical application, the particles must have combined properties of high magnetic saturation, stability, biocompatibility, and interactive functions at the surface. Moreover, the surface of iron oxide NPs could be modified by organic materials or inorganic materials, such as polymers, biomolecules, silica, metals, etc. The problems and major challenges, along with the directions for the synthesis and surface functionalization of iron oxide NPs, are considered. Finally, some future trends and prospective in these research areas are also discussed.

  14. Calculus on Surfaces with General Closest Point Functions

    KAUST Repository

    März, Thomas

    2012-01-01

    The closest point method for solving partial differential equations (PDEs) posed on surfaces was recently introduced by Ruuth and Merriman [J. Comput. Phys., 227 (2008), pp. 1943- 1961] and successfully applied to a variety of surface PDEs. In this paper we study the theoretical foundations of this method. The main idea is that surface differentials of a surface function can be replaced with Cartesian differentials of its closest point extension, i.e., its composition with a closest point function. We introduce a general class of these closest point functions (a subset of differentiable retractions), show that these are exactly the functions necessary to satisfy the above idea, and give a geometric characterization of this class. Finally, we construct some closest point functions and demonstrate their effectiveness numerically on surface PDEs. © 2012 Society for Industrial and Applied Mathematics.

  15. Calculus on Surfaces with General Closest Point Functions

    CERN Document Server

    März, Thomas

    2012-01-01

    The Closest Point Method for solving partial differential equations (PDEs) posed on surfaces was recently introduced by Ruuth and Merriman [J. Comput. Phys. 2008] and successfully applied to a variety of surface PDEs. In this paper we study the theoretical foundations of this method. The main idea is that surface differentials of a surface function can be replaced with Cartesian differentials of its closest point extension, i.e., its composition with a closest point function. We introduce a general class of these closest point functions (a subset of differentiable retractions), show that these are exactly the functions necessary to satisfy the above idea, and give a geometric characterization this class. Finally, we construct some closest point functions and demonstrate their effectiveness numerically on surface PDEs.

  16. Functionalized surfaces and nanostructures for nanotechnological applications

    Science.gov (United States)

    2003-01-01

    CMOS roadmap in sight at around 10 nm, combined with the uncertainly principal's limit of Von Neuman electronics at 2 nm, that merely making things smaller will not help us. Replacing CMOS transistors on a one for one basis with some type of nano device would have the effect of drastically increasing fabrication costs, while offering only a marginal improvement over current technologies. However, nanotechnology offers us a way out of this technological and financial cul-de-sac by building devices from the bottom up. Techniques such as self assembly, perhaps assisted by templates created by nano imprint lithography, a notable European success, combined with our understanding of the workings of polymers and molecules such as Rotoxane at the nanoscale open up a whole new host of possibilities. Whether it is avoiding Moore's second law by switching to plastic electronics, or using molecular electronics, our understanding of the behaviour of materials on the scale of small molecules allows a variety of alternative approaches, to produce smarter, cheaper devices. The new understandings will also allow us to design new architectures, with the end result that functionality will become a more valid measure of performance than transistor density or operations per second. 8. Nanotechnology is new It often comes as a surprise to learn that the Romans and Chinese were using nanoparticles thousands of years ago. Similarly, every time you light a match, fullerenes are produced. Degusssa have been producing carbon black, the substance that makes car tyres black and improves the wear resistance of the rubber, since the 1920s. Of course they were not aware that they were using nanotechnology, and as they had no control over particle size, or even any knowledge of the nanoscale they were not using nanotechnology as currently defined. What is new about nanotechnology is our ability to not only see, and manipulate matter on the nanoscale, but our understanding of atomic scale interactions

  17. Container Surface Evaluation by Function Estimation

    Energy Technology Data Exchange (ETDEWEB)

    Wendelberger, James G. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2017-08-03

    Container images are analyzed for specific surface features, such as, pits, cracks, and corrosion. The detection of these features is confounded with complicating features. These complication features include: shape/curvature, welds, edges, scratches, foreign objects among others. A method is provided to discriminate between the various features. The method consists of estimating the image background, determining a residual image and post processing to determine the features present. The methodology is not finalized but demonstrates the feasibility of a method to determine the kind and size of the features present.

  18. [Function of surface membrane structures in Thiobacillus thiooxidans].

    Science.gov (United States)

    Pivovarova, T A; Karavaĭko, G I

    1975-01-01

    The function of the surface membrane structures was studied with cytochemical techniques on ultrathin sections of Thiobacillus thiooxidans. The transport of elementary sulphur inside the cell involves the surface membrane structures, while oxidation of the sulphur to sulphuric acid takes place on the outer surface of the cytoplasmic membrane. The surface membrane structures are supposed also to participate in the primary dissolution of elementary sulphur at the site of contact of the cells with the mineral.

  19. On the impacts of working memory training on executive functioning

    Directory of Open Access Journals (Sweden)

    Tiina eSalminen

    2012-06-01

    Full Text Available Recent studies have reported improvements in a variety of cognitive functions following sole working memory (WM training. In spite of the emergence of several successful training paradigms, the scope of transfer effects has remained mixed. This is most likely due to the heterogeneity of cognitive functions that have been measured and tasks that have been applied. In the present study, we approached this issue systematically by investigating transfer effects from WM training to different aspects of executive functioning. Our training task was a demanding WM task that requires simultaneous performance of a visual and an auditory n-back task, while the transfer tasks tapped WM updating, coordination of the performance of multiple simultaneous tasks (i.e., dual-tasks and sequential tasks (i.e., task switching, and the temporal distribution of attentional processing. Additionally, we examined whether WM training improves reasoning abilities; a hypothesis that has so far gained mixed support. Following training, participants showed improvements in the trained task as well as in the transfer WM updating task. As for the other executive functions, trained participants improved in a task switching situation and in attentional processing. There was no transfer to the dual-task situation or to reasoning skills. These results therefore confirm previous findings that WM can be trained, and additionally, they show that the training effects can generalize to various other tasks tapping on executive functions.

  20. Laser grooving of surface cracks on hot work tool steel

    Directory of Open Access Journals (Sweden)

    D. Klobčar

    2011-10-01

    Full Text Available The paper presents the analysis of laser grooving of 1.2343 tool steel hardened to 46 HRC. The effect of laser power and grooving speed on groove shape (i.e. depth and width, the material removal rate and the purity of produced groove as a measure of groove quality was investigated and analyzed using response surface methodology. Optimal parameters of laser grooving were found, which enables pure grooves suitable for laser welding.

  1. Surface functionalized magnetic nanoparticles for cancer therapy applications

    Science.gov (United States)

    Wydra, Robert John

    Despite recent advances, cancer remains the second leading cause of deaths in the United States. Magnetic nanoparticles have found various applications in cancer research as drug delivery platforms, enhanced contrast agents for improved diagnostic imaging, and the delivery of thermal energy as standalone therapy. Iron oxide nanoparticles absorb the energy from an alternating magnetic field and convert it into heat through Brownian and Neel relaxations. To better utilize magnetic nanoparticles for cancer therapy, surface functionalization is essential for such factors as decreasing cytotoxicity of healthy tissue, extending circulation time, specific targeting of cancer cells, and manage the controlled delivery of therapeutics. In the first study, iron oxide nanoparticles were coated with a poly(ethylene glycol) (PEG) based polymer shell. The PEG coating was selected to prevent protein adsorption and thus improve circulation time and minimize host response to the nanoparticles. Thermal therapy application feasibility was demonstrated in vitro with a thermoablation study on lung carcinoma cells. Building on the thermal therapy demonstration with iron oxide nanoparticles, the second area of work focused on intracellular delivery. Nanoparticles can be appropriately tailored to enter the cell and deliver energy on the nanoscale eliminating individual cancer cells. The underlying mechanism of action is still under study, and we were interested in determining the role of reactive oxygen species (ROS) catalytically generated from the surface of iron oxide nanoparticles in this measured cytotoxicity. When exposed to an AMF, the nanoscale heating effects are capable of enhancing the Fenton-like generation of ROS determined through a methylene blue degradation assay. To deliver this enhanced ROS effect to cells, monosaccharide coated nanoparticles were developed and successfully internalized by colon cancer cell lines. Upon AMF exposure, there was a measured increase in

  2. 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.

  3. Surface defects and instanton partition functions

    Science.gov (United States)

    Gaiotto, Davide; Kim, Hee-Cheol

    2016-10-01

    We study the superconformal index of five-dimensional SCFTs and the sphere partition function of four-dimensional gauge theories with eight supercharges in the presence of co-dimension two half-BPS defects. We derive a prescription which is valid for defects which can be given a "vortex construction", i.e. can be defined by RG flow from vortex configurations in a larger theory. We test the prescription against known results and expected dualities. We employ our prescription to develop a general computational strategy for defects defined by coupling the bulk degrees of freedom to a Gauged Linear Sigma Model living in co-dimension two.

  4. A Kind of Nanofluid Consisting of Surface-Functionalized Nanoparticles

    Directory of Open Access Journals (Sweden)

    Yang Xuefei

    2010-01-01

    Full Text Available Abstract A method of surface functionalization of silica nanoparticles was used to prepare a kind of stable nanofluid. The functionalization was achieved by grafting silanes directly to the surface of silica nanoparticles in silica solutions (both a commercial solution and a self-made silica solution were used. The functionalized nanoparticles were used to make nanofluids, in which well-dispersed nanoparticles can keep good stability. One of the unique characteristics of the nanofluids is that no deposition layer forms on the heated surface after a pool boiling process. The nanofluids have applicable prospect in thermal engineering fields with the phase-change heat transfer.

  5. Triboelectric Hydrogen Gas Sensor with Pd Functionalized Surface

    Directory of Open Access Journals (Sweden)

    Sung-Ho Shin

    2016-10-01

    Full Text Available Palladium (Pd-based hydrogen (H2 gas sensors have been widely investigated thanks to its fast reaction and high sensitivity to hydrogen. Various sensing mechanisms have been adopted for H2 gas sensors; however, all the sensors must be powered through an external battery. We report here an H2 gas sensor that can detect H2 by measuring the output voltages generated during contact electrification between two friction surfaces. When the H2 sensor, composed of Pd-coated ITO (indium tin oxide and PET (polyethylene Terephthalate film, is exposed to H2, its output voltage is varied in proportion to H2 concentration because the work function (WF of Pd-coated surface changes, altering triboelectric charging behavior. Specifically, the output voltage of the sensor is gradually increased as exposing H2 concentration increases. Reproducible and sensitive sensor response was observed up 1% H2 exposure. The approach introduced here can easily be adopted to development of triboelectric gas sensors detecting other gas species.

  6. Molecular dynamics simulation of functionalized graphene surface for high efficient loading of doxorubicin

    Science.gov (United States)

    Mirhosseini, Mohammad Masoud; Rahmati, Mahmoud; Zargarian, Seyed Shahrooz; Khordad, Reza

    2017-08-01

    Molecular dynamics simulations are performed to study the design and optimization of nanocarriers with high drug loading capacity. Functionalized graphene is considered as the nominated high capacity drug carrier and Dox as the drug model. The graphene surface functionalized with hydroxyl (- OH), carboxyl (- COOH), methyl (- CH3) and amine (- NH2) groups and their associated properties are investigated. The simulation results are illustrated that G - COOH surface absorbs Dox more effectively in comparison to other functionalized graphene surfaces due to the higher binding energy of carboxylic groups and the model drug. The effect of hydrogen bonding, temperature and surface porosity are also evaluated. The results show that binding energy and the solubility parameter are temperature-dependent. The simulation results in this present work reveal the underlying mechanisms of Dox loading on neat and functionalized graphene surfaces may be employed to design better graphene-based nanocarriers for the Dox delivery applications.

  7. Transparent Conducting Oxides for Photovoltaics: Manipulation of Fermi Level, Work Function and Energy Band Alignment

    Directory of Open Access Journals (Sweden)

    Diana E. Proffit

    2010-11-01

    Full Text Available Doping limits, band gaps, work functions and energy band alignments of undoped and donor-doped transparent conducting oxides Zn0, In2O3, and SnO2 as accessed by X-ray and ultraviolet photoelectron spectroscopy (XPS/UPS are summarized and compared. The presented collection provides an extensive data set of technologically relevant electronic properties of photovoltaic transparent electrode materials and illustrates how these relate to the underlying defect chemistry, the dependence of surface dipoles on crystallographic orientation and/or surface termination, and Fermi level pinning.

  8. Direct work function measurement by gas phase photoelectron spectroscopy and its application on PbS nanoparticles.

    Science.gov (United States)

    Axnanda, Stephanus; Scheele, Marcus; Crumlin, Ethan; Mao, Baohua; Chang, Rui; Rani, Sana; Faiz, Mohamed; Wang, Suidong; Alivisatos, A Paul; Liu, Zhi

    2013-01-01

    Work function is a fundamental property of a material's surface. It is playing an ever more important role in engineering new energy materials and efficient energy devices, especially in the field of photovoltaic devices, catalysis, semiconductor heterojunctions, nanotechnology, and electrochemistry. Using ambient pressure X-ray photoelectron spectroscopy (APXPS), we have measured the binding energies of core level photoelectrons of Ar gas in the vicinity of several reference materials with known work functions (Au(111), Pt(111), graphite) and PbS nanoparticles. We demonstrate an unambiguously negative correlation between the work functions of reference samples and the binding energies of Ar 2p core level photoelectrons detected from the Ar gas near the sample surface region. Using this experimentally determined linear relationship between the surface work function and Ar gas core level photoelectron binding energy, we can measure the surface work function of different materials under different gas environments. To demonstrate the potential applications of this ambient pressure XPS technique in nanotechnology and solar energy research, we investigate the work functions of PbS nanoparticles with various capping ligands: methoxide, mercaptopropionic acid, and ethanedithiol. Significant Fermi level position changes are observed for PbS nanoparticles when the nanoparticle size and capping ligands are varied. The corresponding changes in the valence band maximum illustrate that an efficient quantum dot solar cell design has to take into account the electrochemical effect of the capping ligand as well.

  9. Functional oxide structures on a surface of metals and alloys

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    @@ The investigations of the plasma electrolytic processes in our laboratory are aimed to the development of conditions of formation of oxide layers with determined composition, structure and functional properties on the surface of valve metals (Al, Ti) and their alloys.

  10. Quantitative Evaluation of Bioorthogonal Chemistries for Surface Functionalization of Nanoparticles

    DEFF Research Database (Denmark)

    Feldborg, Lise Nørkjær; Jølck, Rasmus Irming; Andresen, Thomas Lars

    2012-01-01

    We present here a highly efficient and chemoselective liposome functionalization method based on oxime bond formation between a hydroxylamine and an aldehyde-modified lipid component. We have conducted a systematic and quantitative comparison of this new approach with other state-of-the-art...... affinity between the peptide and the liposome surface. These studies demonstrate the importance of hoosing the correct chemistry in order to obtain a quantitative surface functionalization of liposomes....

  11. In-situ investigation of graphene oxide under UV irradiation: Evolution of work function

    Directory of Open Access Journals (Sweden)

    Jun Li

    2015-06-01

    Full Text Available Using in-situ Kelvin probe force microscopy (KPFM to measure surface potential, we investigated the time-dependent work function evolution of solution-processed graphene oxide (GO under ultraviolet (UV irradiation. We found that the work function of GO exposed in UV shows a notable decrease with increasing irradiation time, which is proposed to be attributed to the gradual disappearance of oxygen-containing functional groups in GO during the UV-induced reduction reaction process. Fourier transform infrared spectrum and Raman spectrum were used to confirm the reduction of GO under UV irradiation. Our study would give an insight into understanding the transformation of GO’s electronic structures during the reduction process.

  12. Detection of a periodic structure embedded in surface roughness, for various correlation functions

    Indian Academy of Sciences (India)

    V C Vani; S Chatterjee

    2011-10-01

    This paper deals with surface profilometry, where we try to detect a periodic structure, hidden in randomness using the matched filter method of analysing the intensity of light, scattered from the surface. From the direct problem of light scattering from a composite rough surface of the above type, we find that the detectability of the periodic structure can be hindered by the randomness, being dependent on the correlation function of the random part. In our earlier works, we had concentrated mainly on the Cauchy-type correlation function for the rough part. In the present work, we show that this technique can determine the periodic structure of different kinds of correlation functions of the roughness, including Cauchy, Gaussian etc. We study the detection by the matched filter method as the nature of the correlation function is varied.

  13. Surface plasma functionalization influences macrophage behavior on carbon nanowalls

    Energy Technology Data Exchange (ETDEWEB)

    Ion, Raluca [University of Bucharest, Department of Biochemistry and Molecular Biology, 91-95 Spl. Independentei, 050095 Bucharest (Romania); Vizireanu, Sorin [National Institute for Laser, Plasma and Radiation Physics, 409 Atomistilor, PO Box MG-36, 077125, Magurele, Bucharest (Romania); Stancu, Claudia Elena [National Institute for Laser, Plasma and Radiation Physics, 409 Atomistilor, PO Box MG-36, 077125, Magurele, Bucharest (Romania); Leibniz Institute for Plasma Science and Technology (INP Greifswald), Felix-Hausdorff-Str. 2, 17489 Greifswald (Germany); Luculescu, Catalin [National Institute for Laser, Plasma and Radiation Physics, 409 Atomistilor, PO Box MG-36, 077125, Magurele, Bucharest (Romania); Cimpean, Anisoara, E-mail: anisoara.cimpean@bio.unibuc.ro [University of Bucharest, Department of Biochemistry and Molecular Biology, 91-95 Spl. Independentei, 050095 Bucharest (Romania); Dinescu, Gheorghe [National Institute for Laser, Plasma and Radiation Physics, 409 Atomistilor, PO Box MG-36, 077125, Magurele, Bucharest (Romania)

    2015-03-01

    The surfaces of carbon nanowall samples as scaffolds for tissue engineering applications were treated with oxygen or nitrogen plasma to improve their wettability and to functionalize their surfaces with different functional groups. X-ray photoelectron spectroscopy and water contact angle results illustrated the effective conversion of the carbon nanowall surfaces from hydrophobic to hydrophilic and the incorporation of various amounts of carbon, oxygen and nitrogen functional groups during the treatments. The early inflammatory responses elicited by un-treated and modified carbon nanowall surfaces were investigated by quantifying tumor necrosis factor-alpha and macrophage inflammatory protein-1 alpha released by attached RAW 264.7 macrophage cells. Scanning electron microscopy and fluorescence studies were employed to investigate the changes in macrophage morphology and adhesive properties, while MTT assay was used to quantify cell proliferation. All samples sustained macrophage adhesion and growth. In addition, nitrogen plasma treatment was more beneficial for cell adhesion in comparison with un-modified carbon nanowall surfaces. Instead, oxygen plasma functionalization led to increased macrophage adhesion and spreading suggesting a more activated phenotype, confirmed by elevated cytokine release. Thus, our findings showed that the chemical surface alterations which occur as a result of plasma treatment, independent of surface wettability, affect macrophage response in vitro. - Highlights: • N{sub 2} and O{sub 2} plasma treatments alter the CNW surface chemistry and wettability. • Cells seeded on CNW scaffolds are viable and metabolically active. • Surface functional groups, independent of surface wettability, affect cell response. • O{sub 2} plasma treatment of CNW leads to a more activated macrophage phenotype.

  14. Algorithms and software for areal surface texture function parameters

    Science.gov (United States)

    Smith, I. M.; Harris, P. M.; Todhunter, L. D.; Giusca, C.; Jiang, X.; Scott, P.; Leach, R. K.

    2017-10-01

    Software for the evaluation of areal surface texture function parameters is described. Definitions of the parameters, expressed in terms of the inverse areal material ratio function, are provided along with details of the numerical algorithms employed in the software to implement calculations to evaluate approximations to the parameters according to those definitions. Results obtained using the software to process a number of data sets representing different surfaces are compared with those returned by proprietary software for surface texture measurement. Differences in the results, arising from different choices being made when implementing the steps in the parameter evaluation process, are discussed.

  15. Measuring skew in average surface roughness as a function of surface preparation

    Science.gov (United States)

    Stahl, Mark T.

    2015-08-01

    Characterizing surface roughness is important for predicting optical performance. Better measurement of surface roughness reduces polishing time, saves money and allows the science requirements to be better defined. This study characterized statistics of average surface roughness as a function of polishing time. Average surface roughness was measured at 81 locations using a Zygo® white light interferometer at regular intervals during the polishing process. Each data set was fit to a normal and Largest Extreme Value (LEV) distribution; then tested for goodness of fit. We show that the skew in the average data changes as a function of polishing time.

  16. Strain effects on the work function of an organic semiconductor

    KAUST Repository

    Wu, Yanfei

    2016-02-01

    Establishing fundamental relationships between strain and work function (WF) in organic semiconductors is important not only for understanding electrical properties of organic thin films, which are subject to both intrinsic and extrinsic strains, but also for developing flexible electronic devices. Here we investigate tensile and compressive strain effects on the WF of rubrene single crystals. Mechanical strain induced by thermal expansion mismatch between the substrate and rubrene is quantified by X-ray diffraction. The corresponding WF change is measured by scanning Kelvin probe microscopy. The WF of rubrene increases (decreases) significantly with in-plane tensile (compressive) strain, which agrees qualitatively with density functional theory calculations. An elastic-to-plastic transition, characterized by a steep rise of the WF, occurs at ~0.05% tensile strain along the rubrene π-stacking direction. The results provide the first concrete link between mechanical strain and WF of an organic semiconductor and have important implications for understanding the connection between structural and electronic disorder in soft organic electronic materials.

  17. Cross Functional Working and Concurrent Engineering – a UK Study

    Directory of Open Access Journals (Sweden)

    H. Williams

    2000-01-01

    Full Text Available This paper reports on the preliminary results of an investigative study into the implementation of concurrent engineering applied to new product development. Concurrent (or Simultaneous engineering is the term commonly given to creating new products using multi-disciplined teams of marketing, design, manufacturing and support functions together with supplier and customers. Such techniques have produced robust, low cost quality products in short concept to market times compared to traditional ones. The research investigated design management practice and performance in a number of organisations across a range of industrial sectors in the UK by means of a questionnaire survey. The results identify the current use of a variety of design practices and methodologies such as different organisational structures, the extent of cross-functional working, the use of design and phase reviews and the use of different technologies. They indicate that companies implementing CE are more successful in time to market performance than those who don’t implement CE. Factors most influencing the successful adoption of CE are design and phase reviews, and, to a lesser extent, the use of multifunctional teams and supplier partnerships.

  18. Curves and surfaces represented by polynomial support functions

    DEFF Research Database (Denmark)

    Sir, Z.; Gravesen, Jens; Juttler, B.

    2008-01-01

    This paper studies shapes (curves and surfaces) which can be described by (piecewise) polynomial support functions. The class of these shapes is closed under convolutions, offsetting, rotations and translations. We give a geometric discussion of these shapes and present methods for the approximat......This paper studies shapes (curves and surfaces) which can be described by (piecewise) polynomial support functions. The class of these shapes is closed under convolutions, offsetting, rotations and translations. We give a geometric discussion of these shapes and present methods...... for the approximation of general curves and surfaces by them. Based on the rich theory of spherical spline functions, this leads to computational techniques for rational curves and surfaces with rational offsets, which can deal with shapes without inflections/parabolic points....

  19. Kabat's Surface Terms in the $\\zeta$-Function approach

    CERN Document Server

    Iellici, D; Iellici, Devis; Moretti, Valter

    1997-01-01

    The thermal partition functions of photons in any covariant gauge and gravitons in the harmonic gauge, propagating in a Rindler wedge, are computed using a local zeta-function approach. The relation with the surface terms previously obtained by D. Kabat is studied. The results are discussed in relation to the quantum corrections to the black hole entropy.

  20. Kabat's Surface Terms in the Zeta-Function Approach

    Science.gov (United States)

    Iellici, D.; Moretti, V.

    The thermal partition functions of photons in any covariant gauge and gravitons in the harmonic gauge, propagating in a Rindler wedge, are computed using a local zeta-function approach. The relation with the surface terms previously obtained by D. Kabat is studied. The results are discussed in relation to the quantum corrections to the black hole entropy.

  1. Kinetic-energy functionals studied by surface calculations

    DEFF Research Database (Denmark)

    Vitos, Levente; Skriver, Hans Lomholt; Kollár, J.

    1998-01-01

    The self-consistent jellium model of metal surfaces is used to study the accuracy of a number of semilocal kinetic-energy functionals for independent particles. It is shown that the poor accuracy exhibited by the gradient expansion approximation and most of the semiempirical functionals in the low...

  2. Diamond surface functionalization with biomimicry - Amine surface tether and thiol moiety for electrochemical sensors

    Science.gov (United States)

    Sund, James B.; Causey, Corey P.; Wolter, Scott D.; Parker, Charles B.; Stoner, Brian R.; Toone, Eric J.; Glass, Jeffrey T.

    2014-05-01

    The surface of conducting diamond was functionalized with a terminal thiol group that is capable of binding and detecting nitrogen-oxygen species. The functionalization process employed multiple steps starting with doped diamond films grown by plasma enhanced chemical vapor deposition followed by hydrogen termination and photochemical attachment of a chemically protected amine alkene. The surface tether was deprotected to reveal the amine functionality, which enabled the tether to be extended with surface chemistry to add a terminal thiol moiety for electrochemical sensing applications. Each step of the process was validated using X-ray photoelectron spectroscopy analysis.

  3. Semilocal density functional theory with correct surface asymptotics

    Science.gov (United States)

    Constantin, Lucian A.; Fabiano, Eduardo; Pitarke, J. M.; Della Sala, Fabio

    2016-03-01

    Semilocal density functional theory is the most used computational method for electronic structure calculations in theoretical solid-state physics and quantum chemistry of large systems, providing good accuracy with a very attractive computational cost. Nevertheless, because of the nonlocality of the exchange-correlation hole outside a metal surface, it was always considered inappropriate to describe the correct surface asymptotics. Here, we derive, within the semilocal density functional theory formalism, an exact condition for the imagelike surface asymptotics of both the exchange-correlation energy per particle and potential. We show that this condition can be easily incorporated into a practical computational tool, at the simple meta-generalized-gradient approximation level of theory. Using this tool, we also show that the Airy-gas model exhibits asymptotic properties that are closely related to those at metal surfaces. This result highlights the relevance of the linear effective potential model to the metal surface asymptotics.

  4. Superhydrophobic surfaces: from natural to biomimetic to functional.

    Science.gov (United States)

    Guo, Zhiguang; Liu, Weimin; Su, Bao-Lian

    2011-01-15

    Nature is the creation of aesthetic functional systems, in which many natural materials have vagarious structures. Inspired from nature, such as lotus leaf, butterfly' wings, showing excellent superhydrophobicity, scientists have recently fabricated a lot of biomimetic superhydrophobic surfaces by virtue of various smart and easy routes. Whilst, many examples, such as lotus effect, clearly tell us that biomimicry is dissimilar to a simple copying or duplicating of biological structures. In this feature article, we review the recent studies in both natural superhydrophobic surfaces and biomimetic superhydrophobic surfaces, and highlight some of the recent advances in the last four years, including the various smart routes to construct rough surfaces, and a lot of chemical modifications which lead to superhydrophobicity. We also review their functions and applications to date. Finally, the promising routes from biomimetic superhydrophobic surfaces in the next are proposed.

  5. On the optimal choice of wavelet function for multiscale honed surface characterization

    Energy Technology Data Exchange (ETDEWEB)

    Mezghani, S; Mansori, M El [Arts and Metiers ParisTech, LMPF, rue St Dominique - BP 508, 51006 Chalons-en-Champagne (France); Sabri, L [RENAULT S.A.S., Direction de la Mecanique/Direction de l' Ingenierie Process, Rueil Malmaison, Paris (France); Zahouani, H, E-mail: sabeur.mezghani@ensam.eu [Ecole Centrale de Lyon, LTDS UMR CNRS 5513, 36 avenue Guy de Collongue, 69131 Ecully Cedex (France)

    2011-08-19

    Multiscale surface topography characterization is mostly suited than standard approaches because it is more adapted to the multi-stage process generation. Wavelet transform represents a power tool to perform the multiscale decomposition of the surface topography in a wide range of wavelength. However, characterization results depend closely on the topography data acquisition instrument (resolution, height accuracy, sensitivity...) and also on the wavelet analysis method (discrete or continuous transform). In particular, the choice of wavelet function can have significant effect on the analysis results. In this paper, we present experimental work on a number of popular wavelets functions with the aim of finding wavelets that exhibit optimal description of honed surface features when continuous wavelet transform is used. We demonstrate that the regularity property of wavelet function has a significant influence on the characterization performances. This comparative study shows also that the Morlet wavelet is the more adapted wavelet basis function for multiscale characterization of honed surfaces using continuous wavelet transform.

  6. Use of anodes with tunable work function for improving organic light-emitting diode performance

    Science.gov (United States)

    Li, Meng-Chi; Lo, Yen-Ming; Liao, Shih-Fang; Chen, Hsi-Chao; Chang, Hsin-Hua; Lee, Cheng-Chung; Kuo, Chien-Cheng

    2015-12-01

    The effect of reactive gases-oxygen and hydrogen-on the tunable work function of Al-doped ZnO (AZO) films was studied. An increase in the work function with an increase in the oxygen flow rate was mainly interpreted as reflecting a decrease in the carrier concentration, which was attributed to the filling of oxygen vacancies. However, a decrease in the carrier concentration would result in the resistivity increasing sharply. This article presents a new concept for improving the performance of organic light-emitting diodes (OLEDs) through easy and effective hole injection from a multilayer AZO anode to the organic layer. A bilayer AZO film prepared using a tunable work function technique was used to modify the surface of AZO anodes and to ensure that the anodes had low resistivity. The AZO anode stacked with high-work-function AZO films, similar to hole transport buffer layers, had a low turn-on voltage of 2.89 V, and its luminance efficiency and power efficiency were 5.01% and 6.1% greater than those of tin-doped indium oxide anodes used in OLEDs.

  7. Work function engineering of SnO single crystal microplates with thermal annealing.

    Science.gov (United States)

    Doh, Won Hui; Jeong, Wooseok; Lee, Hyunsoo; Park, Jonghyurk; Park, Jeong Young

    2016-08-19

    We synthesized black SnO single-crystal microplates via a sonochemical process and engineered the work function of the SnO microplates using thermal treatments. The as-synthesized SnO microplates have a wide (001) plane, as is clearly evident from TEM images and diffraction patterns. Surface potential measurements on the SnO microplates show that the work function changes as the annealing temperature increases. The TEM and XAS results after thermal treatments imply that the micro-sized SnO(001) single-crystals are stable up to about 400 °C in air, after which the surface starts to become locally oxidized. Consequently, the long-range ordering and lattice parameter of the SnO(001) single crystals started to change to make polycrystalline SnO2 at about 600 °C. These results demonstrate the ability to tune the work function of the microplates and suggest an intriguing way to engineer the electrical properties of nanostructures.

  8. Surface Functionalization of Thin-Film Composite Membranes with Copper Nanoparticles for Antimicrobial Surface Properties

    KAUST Repository

    Ben-Sasson, Moshe

    2014-01-07

    Biofouling is a major operational challenge in reverse osmosis (RO) desalination, motivating a search for improved biofouling control strategies. Copper, long known for its antibacterial activity and relatively low cost, is an attractive potential biocidal agent. In this paper, we present a method for loading copper nanoparticles (Cu-NPs) on the surface of a thin-film composite (TFC) polyamide RO membrane. Cu-NPs were synthesized using polyethyleneimine (PEI) as a capping agent, resulting in particles with an average radius of 34 nm and a copper content between 39 and 49 wt.%. The positive charge of the Cu-NPs imparted by the PEI allowed a simple electrostatic functionalization of the negatively charged RO membrane. We confirmed functionalization and irreversible binding of the Cu-NPs to the membrane surface with SEM and XPS after exposing the membrane to bath sonication. We also demonstrated that Cu-NP functionalization can be repeated after the Cu-NPs dissolve from the membrane surface. The Cu-NP functionalization had minimal impact on the intrinsic membrane transport parameters. Surface hydrophilicity and surface roughness were also maintained, and the membrane surface charge became positive after functionalization. The functionalized membrane exhibited significant antibacterial activity, leading to an 80-95% reduction in the number of attached live bacteria for three different model bacterial strains. Challenges associated with this functionalization method and its implementation in RO desalination are discussed. © 2013 American Chemical Society.

  9. Microarray of DNA probes on carboxylate functional beads surface

    Institute of Scientific and Technical Information of China (English)

    黄承志; 李原芳; 黄新华; 范美坤

    2000-01-01

    The microarray of DNA probes with 5’ -NH2 and 5’ -Tex/3’ -NH2 modified terminus on 10 um carboxylate functional beads surface in the presence of 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC) is characterized in the preseni paper. it was found that the microarray capacity of DNA probes on the beads surface depends on the pH of the aqueous solution, the concentra-tion of DNA probe and the total surface area of the beads. On optimal conditions, the minimum distance of 20 mer single-stranded DNA probe microarrayed on beads surface is about 14 nm, while that of 20 mer double-stranded DNA probes is about 27 nm. If the probe length increases from 20 mer to 35 mer, its microarray density decreases correspondingly. Mechanism study shows that the binding mode of DNA probes on the beads surface is nearly parallel to the beads surface.

  10. Microarray of DNA probes on carboxylate functional beads surface

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The microarray of DNA probes with 5′-NH2 and 5′-Tex/3′-NH2 modified terminus on 10 m m carboxylate functional beads surface in the presence of 1-ethyl-3-(3-dimethylaminopropyl)- carbodiimide (EDC) is characterized in the present paper. It was found that the microarray capacity of DNA probes on the beads surface depends on the pH of the aqueous solution, the concentration of DNA probe and the total surface area of the beads. On optimal conditions, the minimum distance of 20 mer single-stranded DNA probe microarrayed on beads surface is about 14 nm, while that of 20 mer double-stranded DNA probes is about 27 nm. If the probe length increases from 20 mer to 35 mer, its microarray density decreases correspondingly. Mechanism study shows that the binding mode of DNA probes on the beads surface is nearly parallel to the beads surface.

  11. Electrochemical characterization of organosilane-functionalized nanostructured ITO surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Pruna, R., E-mail: rpruna@el.ub.edu; Palacio, F.; López, M. [SIC, Departament d' Enginyeries: Electrònica, Universitat de Barcelona, C/ Martí i Franquès 1, E-08028 Barcelona (Spain); Pérez, J. [Nanobioengineering Group, Institute for Bioengineering of Catalonia (IBEC), Baldiri Reixac 15-21, E-08028 Barcelona (Spain); Mir, M. [Nanobioengineering Group, Institute for Bioengineering of Catalonia (IBEC), Baldiri Reixac 15-21, E-08028 Barcelona (Spain); Centro de Investigación Biomédica en Red en Bioingeniería, Biomateriales y Nanomedicina (CIBER-BBN), Monforte de Lemos 3-5 Pabellón 11, E-28029 Madrid (Spain); Blázquez, O.; Hernández, S.; Garrido, B. [MIND-IN" 2UB, Departament d' Enginyeries: Electrònica, Universitat de Barcelona, C/ Martí i Franquès 1, E-08028 Barcelona (Spain)

    2016-08-08

    The electroactivity of nanostructured indium tin oxide (ITO) has been investigated for its further use in applications such as sensing biological compounds by the analysis of redox active molecules. ITO films were fabricated by using electron beam evaporation at different substrate temperatures and subsequently annealed for promoting their crystallization. The morphology of the deposited material was monitored by scanning electron microscopy, confirming the deposition of either thin films or nanowires, depending on the substrate temperature. Electrochemical surface characterization revealed a 45 % increase in the electroactive surface area of nanostructured ITO with respect to thin films, one third lower than the geometrical surface area variation determined by atomic force microscopy. ITO surfaces were functionalized with a model organic molecule known as 6-(ferrocenyl)hexanethiol. The chemical attachment was done by means of a glycidoxy compound containing a reactive epoxy group, the so-called 3-glycidoxypropyltrimethoxy-silane. ITO functionalization was useful for determining the benefits of nanostructuration on the surface coverage of active molecules. Compared to ITO thin films, an increase in the total peak height of 140 % was observed for as-deposited nanostructured electrodes, whereas the same measurement for annealed electrodes resulted in an increase of more than 400 %. These preliminary results demonstrate the ability of nanostructured ITO to increase the surface-to-volume ratio, conductivity and surface area functionalization, features that highly benefit the performance of biosensors.

  12. Stable functionalization of germanium surface and its application in biomolecules immobilization

    Energy Technology Data Exchange (ETDEWEB)

    Cai, Qi [State Key Laboratory of Transducer Technology, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, No.865, Changning Road, Shanghai 200050 (China); University of Chinese Academy of Sciences, No.19A, Yuquan Road, Beijing 100049 (China); Xu, Baojian [State Key Laboratory of Transducer Technology, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, No.865, Changning Road, Shanghai 200050 (China); Ye, Lin [Sate Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, No.865, Changning Road, Shanghai 200050 (China); University of Chinese Academy of Sciences, No.19A, Yuquan Road, Beijing 100049 (China); Tang, Teng; Huang, Shanluo; Du, Xiaowei [State Key Laboratory of Transducer Technology, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, No.865, Changning Road, Shanghai 200050 (China); University of Chinese Academy of Sciences, No.19A, Yuquan Road, Beijing 100049 (China); Bian, Xiaojun; Zhang, Jishen [State Key Laboratory of Transducer Technology, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, No.865, Changning Road, Shanghai 200050 (China); Di, Zengfeng, E-mail: zfdi@mail.sim.ac.cn [Sate Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, No.865, Changning Road, Shanghai 200050 (China); Jin, Qinghui [State Key Laboratory of Transducer Technology, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, No.865, Changning Road, Shanghai 200050 (China); Zhao, Jianlong, E-mail: jlzhao@mail.sim.ac.cn [State Key Laboratory of Transducer Technology, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, No.865, Changning Road, Shanghai 200050 (China)

    2014-10-15

    Highlights: • An effective method to immobilize biomolecules on the functionalized Ge surface. • The surface of Ge was functionalized with 11-Mercaptoundecanoic acid (11-MUA). • Stable and uniform SAMs was obtained on Ge surface after 11-MUA treatment. • The functionalized Ge was employed as substrate for protein immobilization. • Paving the way of Ge for further applications in bioelectronics field. - Abstract: As a typical semiconductor material, germanium (Ge) has the potential to be utilized in microelectronics and bioelectronics. Herein, we present a simple and effective method to immobilize biomolecules on the surface of functionalized Ge. The surface oxide of Ge was removed with the pretreatment of hydrochloric acid and the Cl-terminated Ge reacted with 11-Mercaptoundecanoic acid (11-MUA). The surface of Ge was coated with 11-MUA self-assembled monolayers (SAMs) due to the bonding reaction between the sulfhydryl group of 11-MUA and Cl-terminated Ge. Furthermore, typical biomolecule, a green fluorescent protein was chosen to be immobilized on the surface of the functionalized Ge. Contact angle analysis, atomic force microscopy and X-ray photoelectron spectroscopy were used to study the characteristics including wettability, stability, roughness and component of the functionalized Ge, respectively. Fluorescence microscopy was utilized to indicate the efficiency of protein immobilization on the surface of the functionalized Ge. With these studies, stable and uniform functionalized monolayer was obtained on the surface of Ge after 11-MUA treatment and the functionalized Ge was effectively applied in protein immobilization. Furthermore, this study may pave the way for further applications such as the integration of bioelectronics and biosensors with the attractive semiconductor material-Ge in future work.

  13. Functional brain activation associated with working memory training and transfer.

    Science.gov (United States)

    Clark, Cameron M; Lawlor-Savage, Linette; Goghari, Vina M

    2017-09-15

    While behavioural trials of working memory (WM) training have received much attention in recent years, a lesser explored parallel approach is functional neuroimaging. A small literature has suggested a complex time course for functional activation pattern changes following WM training (i.e. not simply increasing or decreasing due to training); however, no study to date has examined such neuroplastic effects in both the training task (dual n-back) and the fluid intelligence transfer task to which the training is purported to transfer (Raven's Matrices). This study investigated neural correlates of WM training in healthy young adults randomized to six weeks of WM training, or an active control condition (processing speed training) with a pre- and post-training fMRI design. Results indicated significant reductions in activation for the WM trained group in key WM-task related areas for trained WM tasks after training compared to the processing speed active control group. The same pattern of training related decreases in activation for the WM trained group was not observed for the transfer task, which is consistent with null results for all cognitive outcomes of the present trial. The observed pattern of results suggests that repetitive practice with a complex task does indeed lead to neuroplastic processes that very likely represent the reduced demand for attentional control while sub-components of the task become more routinized with practice. We suggest that future research investigate neural correlates of WM training in populations for which WM itself is impaired and/or behavioural trials of WM training have returned more promising results. Copyright © 2017 Elsevier B.V. All rights reserved.

  14. THERMAL FRACTURE OF FUNCTIONALLY GRADED PLATE WITH PARALLEL SURFACE CRACKS

    Institute of Scientific and Technical Information of China (English)

    Yuezhong Feng; Zhihe Jin

    2009-01-01

    This work examines the fracture behavior of a functionally graded material (FGM) plate containing parallel surface cracks with alternating lengths subjected to a thermal shock. The thermal stress intensity factors (TSIFs) at the tips of long and short cracks are calculated using a singular integral equation technique. The critical thermal shock △T_c that causes crack initiation is calculated using a stress intensity factor criterion. Numerical examples of TSIFs and △T_c for an Al_2O_3/Si_3N_4 FGM plate are presented to illustrate the effects of thermal property gradation, crack spacing and crack length ratio on the TSIFs and △T_c. It is found that for a given crack length ratio, the TSIFs at the tips of both long and short cracks can be reduced significantly and △T_c can be enhanced by introducing appropriate material gradation. The TSIFs also decrease dramatically with a decrease in crack spacing. The TSIF at the tips of short cracks may be higher than that for the long cracks under certain crack geometry conditions. Hence, the short cracks instead of long cracks may first start to grow under the thermal shock loading.

  15. Extremely environment-hard and low work function transfer-mold field emitter arrays

    Energy Technology Data Exchange (ETDEWEB)

    Nakamoto, Masayuki, E-mail: m-nakamoto@rie.shizuoka.ac.jp [Research Institute of Electronics, Shizuoka University, 3-5-1 Johoku, Naka-ku, Hamamatsu, Shizuoka 432-8011 (Japan); Moon, Jonghyun [Research Institute of Electronics, Shizuoka University, 3-5-1 Johoku, Naka-ku, Hamamatsu, Shizuoka 432-8011 (Japan)

    2013-06-15

    Extremely environment-hard and low work function field-emitter arrays (FEAs) were fabricated by a transfer-mold emitter fabrication method to produce highly reliable vacuum nanoelectronic devices able to operate stably at low voltage in highly oxidizing atmospheres. Amorphous carbon (a-C) having a work function of 3.6 eV and sp{sup 3} fraction of 85.6% prepared by plasma-enhanced chemical vapor deposition was used as the emitter material. The field-emission characteristics of the obtained transfer-mold FEAs strongly depended on their work function and morphology. The environment-hard characteristics of the transfer-mold a-C FEAs were compared with those of the transfer-mold titanium nitride FEAs and nickel FEAs. X-ray photoelectron spectroscopy was used to confirm the stable chemical states of the FEAs after oxygen radical treatment. The small amount of material oxidized (6.3%) at the surface of the a-C FEAs compared with 11.8% for the TiN-FEAs and 39.0% for Ni FEAs after oxygen radical treatment explained their almost constant work function in oxidizing atmospheres. The emission fluctuation rates of transfer-mold a-C FEAs without resistive layers under in situ radical treatment were as low as ±5.0%, compared with 5–100% for conventional FEAs with resistive layers not under highly oxidizing atmospheres. Therefore, the present environment-hard and low work function transfer-mold a-C FEAs are expected to be useful for reliable vacuum nanoelectronic devices.

  16. Surface functionalization of aluminosilicate nanotubes with organic molecules

    Directory of Open Access Journals (Sweden)

    Wei Ma

    2012-02-01

    Full Text Available The surface functionalization of inorganic nanostructures is an effective approach for enriching the potential applications of existing nanomaterials. Inorganic nanotubes attract great research interest due to their one-dimensional structure and reactive surfaces. In this review paper, recent developments in surface functionalization of an aluminosilicate nanotube, “imogolite”, are introduced. The functionalization processes are based on the robust affinity between phosphate groups of organic molecules and the aluminol (AlOH surface of imogolite nanotubes. An aqueous modification process employing a water soluble ammonium salt of alkyl phosphate led to chemisorption of molecules on imogolite at the nanotube level. Polymer-chain-grafted imogolite nanotubes were prepared through surface-initiated polymerization. In addition, the assembly of conjugated molecules, 2-(5’’-hexyl-2,2’:5’,2’’-terthiophen-5-ylethylphosphonic acid (HT3P and 2-(5’’-hexyl-2,2’:5’,2’’-terthiophen-5-ylethylphosphonic acid 1,1-dioxide (HT3OP, on the imogolite nanotube surface was achieved by introducing a phosphonic acid group to the corresponding molecules. The optical and photophysical properties of these conjugated-molecule-decorated imogolite nanotubes were characterized. Moreover, poly(3-hexylthiophene (P3HT chains were further hybridized with HT3P modified imogolite to form a nanofiber hybrid.

  17. Erosion resistance of bionic functional surfaces inspired from desert scorpions.

    Science.gov (United States)

    Zhiwu, Han; Junqiu, Zhang; Chao, Ge; Li, Wen; Ren, Luquan

    2012-02-01

    In this paper, a bionic method is presented to improve the erosion resistance of machine components. Desert scorpion (Androctonus australis) is a typical animal living in sandy deserts, and may face erosive action of blowing sand at a high speed. Based on the idea of bionics and biologic experimental techniques, the mechanisms of the sand erosion resistance of desert scorpion were investigated. Results showed that the desert scorpions used special microtextures such as bumps and grooves to construct the functional surfaces to achieve the erosion resistance. In order to understand the erosion resistance mechanisms of such functional surfaces, the combination of computational and experimental research were carried out in this paper. The Computational Fluid Dynamics (CFD) method was applied to predict the erosion performance of the bionic functional surfaces. The result demonstrated that the microtextured surfaces exhibited better erosion resistance than the smooth surfaces. The further erosion tests indicated that the groove surfaces exhibited better erosion performance at 30° injection angle. In order to determine the effect of the groove dimensions on the erosion resistance, regression analysis of orthogonal multinomials was also performed under a certain erosion condition, and the regression equation between the erosion rate and groove distance, width, and height was established.

  18. Mindfulness, Authentic Functioning, and Work Engagement: A Growth Modeling Approach

    Science.gov (United States)

    Leroy, Hannes; Anseel, Frederik; Dimitrova, Nicoletta G.; Sels, Luc

    2013-01-01

    Previous research has demonstrated that mindfulness helps reduce symptoms of work stress but research has yet to clarify "whether" and "how" mindfulness is linked to work engagement. Using self-determination theory we hypothesize that mindfulness is positively related to work engagement and that this relationship can be better understood through…

  19. Mindfulness, Authentic Functioning, and Work Engagement: A Growth Modeling Approach

    Science.gov (United States)

    Leroy, Hannes; Anseel, Frederik; Dimitrova, Nicoletta G.; Sels, Luc

    2013-01-01

    Previous research has demonstrated that mindfulness helps reduce symptoms of work stress but research has yet to clarify "whether" and "how" mindfulness is linked to work engagement. Using self-determination theory we hypothesize that mindfulness is positively related to work engagement and that this relationship can be better understood through…

  20. Oxygen adsorption on pyrite (100) surface by density functional theory

    Institute of Scientific and Technical Information of China (English)

    孙伟; 胡岳华; 邱冠周; 覃文庆

    2004-01-01

    Pyrite (FeS2) bulk and (100) surface properties and the oxygen adsorption on the surface were studied by using density functional theory methods. The results show that in the formation of FeS2 (100) surface, there exists a process of electron transfer from Fe dangling bond to S dangling bond. In this situation, surface Fe and S atoms have more ionic properties. Both Fe2+ and S2- have high electrochemistry reduction activity, which is the base for oxygen adsorption. From the viewpoint of adsorption energy, the parallel form oxygen adsorption is in preference.The result also shows that the state of oxygen absorbed on FeS2 surface acts as peroxides rather than O2.

  1. Self-consistent Green’s-function technique for surfaces and interfaces

    DEFF Research Database (Denmark)

    Skriver, Hans Lomholt; Rosengaard, N. M.

    1991-01-01

    We have implemented an efficient self-consistent Green’s-function technique for calculating ground-state properties of surfaces and interfaces, based on the linear-muffin-tin-orbitals method within the tight-binding representation. In this approach the interlayer interaction is extremely short ra...... surface energies in close agreement with values derived from surface tensions of the liquid metals, and work functions that deviate less than 10% from the experimental values.......We have implemented an efficient self-consistent Green’s-function technique for calculating ground-state properties of surfaces and interfaces, based on the linear-muffin-tin-orbitals method within the tight-binding representation. In this approach the interlayer interaction is extremely short...... ranged, and only a few layers close to the interface need be treated self-consistently via a Dyson equation. For semi-infinite jellium, the technique gives work functions and surface energies that are in excellent agreement with earlier calculations. For the bcc(110) surface of the alkali metals, we find...

  2. A Frame Work for Frequent Pattern Mining Using Dynamic Function

    Directory of Open Access Journals (Sweden)

    Sunil Joshi

    2011-05-01

    Full Text Available Discovering frequent objects (item sets, sequential patterns is one of the most vital fields in data mining. It is well understood that it require running time and memory for defining candidates and this is the motivation for developing large number of algorithm. Frequent patterns mining is the paying attention research issue in association rules analysis. Apriori algorithm is a standard algorithm of association rules mining. Plenty of algorithms for mining association rules and their mutations are projected on the foundation of Apriori Algorithm. Most of the earlier studies adopted Apriori-like algorithms which are based on generate-and-test candidates theme and improving algorithm approach and formation but no one give attention to the structure of database. Several modifications on apriori algorithms are focused on algorithm Strategy but no one-algorithm emphasis on least transaction and more attribute representation of database. We presented a new research trend on frequent pattern mining in which generate Transaction pair to lighten current methods from the traditional blockage, providing scalability to massive data sets and improving response time. In order to mine patterns in database with more columns than rows, we proposed a complete framework for the frequent pattern mining. A simple approach is if we generate pair of transaction instead of item id where attributes are much larger then transaction so result is very fast. Newly, different works anticipated a new way to mine patterns in transposed databases where there is a database with thousands of attributes but merely tens of stuff. We suggest a novel dynamic algorithm for frequent pattern mining in which generate transaction pair and for generating frequent pattern we find out by longest common subsequence using dynamic function. Our solutions give result more rapidly. A quantitative investigation of these tradeoffs is conducted through a wide investigational study on artificial and

  3. Direct quantification of negatively charged functional groups on membrane surfaces

    KAUST Repository

    Tiraferri, Alberto

    2012-02-01

    Surface charge plays an important role in membrane-based separations of particulates, macromolecules, and dissolved ionic species. In this study, we present two experimental methods to determine the concentration of negatively charged functional groups at the surface of dense polymeric membranes. Both techniques consist of associating the membrane surface moieties with chemical probes, followed by quantification of the bound probes. Uranyl acetate and toluidine blue O dye, which interact with the membrane functional groups via complexation and electrostatic interaction, respectively, were used as probes. The amount of associated probes was quantified using liquid scintillation counting for uranium atoms and visible light spectroscopy for the toluidine blue dye. The techniques were validated using self-assembled monolayers of alkanethiols with known amounts of charged moieties. The surface density of negatively charged functional groups of hand-cast thin-film composite polyamide membranes, as well as commercial cellulose triacetate and polyamide membranes, was quantified under various conditions. Using both techniques, we measured a negatively charged functional group density of 20-30nm -2 for the hand-cast thin-film composite membranes. The ionization behavior of the membrane functional groups, determined from measurements with toluidine blue at varying pH, was consistent with published data for thin-film composite polyamide membranes. Similarly, the measured charge densities on commercial membranes were in general agreement with previous investigations. The relative simplicity of the two methods makes them a useful tool for quantifying the surface charge concentration of a variety of surfaces, including separation membranes. © 2011 Elsevier B.V.

  4. Study on Dielectric Function Models for Surface Plasmon Resonance Structure

    Directory of Open Access Journals (Sweden)

    Peyman Jahanshahi

    2014-01-01

    Full Text Available The most common permittivity function models are compared and identifying the best model for further studies is desired. For this study, simulations using several different models and an analytical analysis on a practical surface Plasmon structure were done with an accuracy of ∼94.4% with respect to experimental data. Finite element method, combined with dielectric properties extracted from the Brendel-Bormann function model, was utilized, the latter being chosen from a comparative study on four available models.

  5. Surface analysis of gold nanoparticles functionalized with thiol-modified glucose SAMs for biosensor applications.

    Directory of Open Access Journals (Sweden)

    Valentina eSpampinato

    2016-02-01

    Full Text Available In this work, Time of Flight Secondary Ion Mass Spectrometry (ToF-SIMS, Principal Component Analysis (PCA and X-ray Photoelectron Spectroscopy (XPS have been used to characterize the surface chemistry of gold substrates before and after functionalization with thiol-modified glucose self-assembled monolayers and subsequent biochemical specific recognition of maltose binding protein (MBP.The results indicate that the surface functionalization is achieved both on flat and nanoparticles gold substrates thus showing the potential of the developed system as biodetection platform. Moreover, the method presented here has been found to be a sound and valid approach to characterize the surface chemistry of nanoparticles functionalized with large molecules.Both techniques were proved to be very useful tools for monitoring all the functionalization steps, including the investigation of the biological behaviour of the glucose-modified particles in presence of the maltose binding protein.

  6. Functional surfaces for tribological applications: inspiration and design

    Science.gov (United States)

    Abdel-Aal, Hisham A.

    2016-12-01

    Surface texturing has been recognized as a method for enhancing the tribological properties of surfaces for many years. Adding a controlled texture to one of two faces in relative motion can have many positive effects, such as reduction of friction and wear and increase in load capacity. To date, the true potential of texturing has not been realized not because of the lack of enabling texturing technologies but because of the severe lack of detailed information about the mechanistic functional details of texturing in a tribological situation. Experimental as well as theoretical analysis of textured surfaces define important metrics for performance evaluation. These metrics represent the interaction between geometry of the texturing element and surface topology. To date, there is no agreement on the optimal values that should be implemented given a particular surface. More importantly, a well-defined methodology for the generation of deterministic textures of optimized designs virtually does not exist. Nature, on the other hand, offers many examples of efficient texturing strategies (geometries and topologies) specifically applied to mitigate frictional effects in a variety of situations. Studying these examples may advance the technology of surface engineering. This paper therefore, provides a comparative review of surface texturing that manifest viable synergy between tribology and biology. We attempt to provide successful emerging examples where borrowing from nature has inspired viable surface solutions that address difficult tribological problems both in dry and lubricated contact situations.

  7. Density functional theory in surface science and heterogeneous catalysis

    DEFF Research Database (Denmark)

    Nørskov, Jens Kehlet; Scheffler, M.; Toulhoat, H.

    2006-01-01

    amount of experimental data gathered during the last decades. This article shows how density functional theory can be used to describe the state of the surface during reactions and the rate of catalytic reactions. It will also show how we are beginning to understand the variation in catalytic activity...

  8. Synthesis, Characterization, and Surface Initiated Polymerization of Carbazole Functionalized Isocyanides

    NARCIS (Netherlands)

    Schwartz, Erik; Lim, Eunhee; Gowda, Chandrakala M.; Liscio, Andrea; Fenwick, Oliver; Tu, Guoli; Palermo, Vincenzo; Gelder, de Rene; Cornelissen, Jeroen J.L.M.; Eck, van Ernst R.H.; Kentgens, Arno P.M.; Cacialli, Franco; Nolte, Roeland J.M.; Samori, Paolo; Huck, Wilhelm T.S.; Rowan, Alan E.

    2010-01-01

    We describe the design and synthesis of carbazole functionalized isocyanides and the detailed investigation of their properties. Characterization by solid state NMR, CD, and IR spectroscopic techniques reveals that the polymer has a well-defined helical architecture. Surface-initiated polymerization

  9. Functional oxide structures on a surface of metals and alloys

    Institute of Scientific and Technical Information of China (English)

    Rudnev; V.; S.; Yarovaya; T.; P.; Boguta; D.; L.; Lukiyanchuk; I.; V.; Tyrina; L.; M.; Morozova; V.; P.; Nedozorov; P.; M.; Vasilyeva; M.; S.; Kondrikov; N.; B.

    2005-01-01

    The investigations of the plasma electrolytic processes in our laboratory are aimed to the development of conditions of formation of oxide layers with determined composition, structure and functional properties on the surface of valve metals (Al, Ti) and their alloys.……

  10. Tailor-made functionalization of silicon nitride surfaces

    NARCIS (Netherlands)

    Arafat, A.; Schroën, C.G.P.H.; Smet, de L.C.P.M.; Sudhölter, E.J.R.; Zuilhof, H.

    2004-01-01

    This communication presents the first functionalization of a hydrogen-terminated silicon-rich silicon nitride (Si3Nx) surface with a well-defined, covalently attached organic monolayer. Properties of the resulting monolayers are monitored by measurement of the static water contact angle, X-ray photo

  11. Plasma polymerized epoxide functional surfaces for DNA probe immobilization.

    Science.gov (United States)

    Chu, Li-Qiang; Knoll, Wolfgang; Förch, Renate

    2008-09-15

    The development of functional surfaces for the immobilization of DNA probe is crucial for a successful design of a DNA sensor. In this report, epoxide functional thin films were achieved simply by pulsed plasma polymerization (PP) of glycidyl methacrylate (GMA) at low duty cycle. The presence of epoxide groups in the resulting ppGMA films was confirmed by Fourier transform infrared spectroscopy. The ppGMA coatings were found to be resistant to the non-specific adsorption of DNA strands, while the epoxide groups obtained could react with amine-modified DNA probes in a mild basic environment without any activation steps. A DNA sensor was made, and was successfully employed to distinguish different DNA sequences with one base pair mismatch as seen by surface plasmon enhanced fluorescence spectroscopy (SPFS). The regeneration of the present DNA sensor was also discussed. This result suggests that surface modification with ppGMA films is very promising for the fabrication of various DNA sensors.

  12. FUNCTIONALIZED LATERAL SURFACE COATED LASERS FOR CHEM-BIO DETECTION

    Energy Technology Data Exchange (ETDEWEB)

    Goddard, L L; Bond, T C; Cole, G D; Behymer, E M

    2007-07-05

    We present a class of compact, monolithic, photonic sensors consisting of multiple section edge emitting lasers with functionalized lateral surface coatings for low level detection of chemical or biological agents. Specifically, we discuss 8 {micro}m x 250 {micro}m Pd-coated H{sub 2} sensors and configurations to reduce the minimum detection limit from 138ppm for passive sensors to 1ppm for active sensors. Compared with conventional optical H{sub 2} sensors that use fiber gratings, surface plasmon resonances, or surface reflectance, our sensors offer the advantages of smaller size, wider dynamic range, monolithic integration of laser source and detector, and 2-D scalability to arrays of sensors that are functionalized to detect different agents.

  13. Selective surface functionalization of silicon nanowires via nanoscale joule heating.

    Science.gov (United States)

    Park, Inkyu; Li, Zhiyong; Pisano, Albert P; Williams, R Stanley

    2007-10-01

    In this letter, we report a novel approach to selectively functionalize the surface of silicon nanowires located on silicon-based substrates. This method is based upon highly localized nanoscale Joule heating along silicon nanowires under an applied electrical bias. Numerical simulation shows that a high-temperature (>800 K) with a large thermal gradient can be achieved by applying an appropriate electrical bias across silicon nanowires. This localized heating effect can be utilized to selectively ablate a protective polymer layer from a region of the chosen silicon nanowire. The exposed surface, with proper postprocessing, becomes available for surface functionalization with chemical linker molecules, such as 3-mercaptopropyltrimethoxysilanes, while the surrounding area is still protected by the chemically inert polymer layer. This approach is successfully demonstrated on silicon nanowire arrays fabricated on SOI wafers and visualized by selective attachment of gold nanoparticles.

  14. Solvation of complex surfaces via molecular density functional theory

    CERN Document Server

    Levesque, Maximilien; Rotenberg, Benjamin; Jeanmairet, Guillaume; Vuilleumier, Rodolphe; Borgis, Daniel

    2012-01-01

    We show that classical molecular density functional theory (MDFT), here in the homogeneous reference fluid approximation in which the functional is inferred from the properties of the bulk solvent, is a powerful new tool to study, at a fully molecular level, the solvation of complex surfaces and interfaces by polar solvents. This implicit solvent method allows for the determination of structural, orientational and energetic solvation properties that are on a par with all-atom molecular simulations performed for the same system, while reducing the computer time by two orders of magnitude. This is illustrated by the study of an atomistically-resolved clay surface composed of over a thousand atoms wetted by a molecular dipolar solvent. The high numerical efficiency of the method is exploited to carry a systematic analysis of the electrostatic and non-electrostatic components of the surface-solvent interaction within the popular CLAYFF force field. Solvent energetics and structure are found to depend weakly upon ...

  15. Atomic Resolution Imaging and Quantification of Chemical Functionality of Surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Schwarz, Udo D. [Yale Univ., New Haven, CT (United States). Dept. of Mechanical Engineering and Materials Science; Altman, Eric I. [Yale Univ., New Haven, CT (United States). Dept. of Chemical and Environmental Engineering

    2014-12-10

    The work carried out from 2006-2014 under DoE support was targeted at developing new approaches to the atomic-scale characterization of surfaces that include species-selective imaging and an ability to quantify chemical surface interactions with site-specific accuracy. The newly established methods were subsequently applied to gain insight into the local chemical interactions that govern the catalytic properties of model catalysts of interest to DoE. The foundation of our work was the development of three-dimensional atomic force microscopy (3DAFM), a new measurement mode that allows the mapping of the complete surface force and energy fields with picometer resolution in space (x, y, and z) and piconewton/millielectron volts in force/energy. From this experimental platform, we further expanded by adding the simultaneous recording of tunneling current (3D-AFM/STM) using chemically well-defined tips. Through comparison with simulations, we were able to achieve precise quantification and assignment of local chemical interactions to exact positions within the lattice. During the course of the project, the novel techniques were applied to surface-oxidized copper, titanium dioxide, and silicon oxide. On these materials, defect-induced changes to the chemical surface reactivity and electronic charge density were characterized with site-specific accuracy.

  16. Atomic Resolution Imaging and Quantification of Chemical Functionality of Surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Schwarz, Udo [Yale University

    2014-12-10

    The work carried out from 2006-2014 under DoE support was targeted at developing new approaches to the atomic-scale characterization of surfaces that include species-selective imaging and an ability to quantify chemical surface interactions with site-specific accuracy. The newly established methods were subsequently applied to gain insight into the local chemical interactions that govern the catalytic properties of model catalysts of interest to DoE. The foundation of our work was the development of three-dimensional atomic force microscopy (3D-AFM), a new measurement mode that allows the mapping of the complete surface force and energy fields with picometer resolution in space (x, y, and z) and piconewton/millielectron volts in force/energy. From this experimental platform, we further expanded by adding the simultaneous recording of tunneling current (3D-AFM/STM) using chemically well-defined tips. Through comparison with simulations, we were able to achieve precise quantification and assignment of local chemical interactions to exact positions within the lattice. During the course of the project, the novel techniques were applied to surface-oxidized copper, titanium dioxide, and silicon oxide. On these materials, defect-induced changes to the chemical surface reactivity and electronic charge density were characterized with site-specific accuracy.

  17. Multifunctional surfaces with discrete functionalized regions for biological applications.

    Science.gov (United States)

    Ghosh, Moniraj; Alves, Christina; Tong, Ziqiu; Tettey, Kwadwo; Konstantopoulos, Konstantinos; Stebe, Kathleen J

    2008-08-05

    In this paper we describe a method for creating multifunctional glass surfaces presenting discrete patches of different proteins on an inert PEG-functionalized background. Microcontact printing is used to stamp the substrate with octadecyltrichlorosilane to define the active regions. The substrate is then back-filled with PEG-silane {[[2-methoxypoly(ethyleneoxy)]propyl]trimethoxysilane} to define passive regions. A microfluidics device is subsequently affixed to the substrate to deliver proteins to the active regions, with as many channels as there are proteins to be patterned. Examples of trifunctional surfaces are given which present three terminating functional groups, i.e., protein 1, protein 2, and PEG. These surfaces should be broadly useful in biological studies, as patch size is well established to influence cell viability, growth, and differentiation. Three examples of cellular interactions with the surfaces are demonstrated, including the capture of cells from a single cell suspension, the selective sorting of cells from a mixed suspension, and the adhesion of cells to ligand micropatches at critical shear stresses. Within these examples, we demonstrate that the patterned immobilized proteins are active, as they retain their ability to interact with either antibodies in solution or receptors presented by cells. When appropriate (e.g., for E-selectin), proteins are patterned in their physiological orientations using a sandwich immobilization technique, which is readily accommodated within our method. The protein surface densities are highly reproducible in the patches, as supported by fluorescence intensity measurements. Potential applications include biosensors based on the interaction of cells or of marker proteins with protein patches, fundamental studies of cell adhesion as a function of patch size and shear stress, and studies of cell differentiation as a function of surface cues.

  18. Surface functionalization of metal organic frameworks for mixed matrix membranes

    Energy Technology Data Exchange (ETDEWEB)

    Albenze, Erik; Lartey, Michael; Li, Tao; Luebke, David R.; Nulwala, Hunaid B.; Rosi, Nathaniel L.; Venna, Surendar R.

    2017-03-21

    Mixed Matrix Membrane (MMM) are composite membranes for gas separation and comprising a quantity of inorganic filler particles, in particular metal organic framework (MOF), dispersed throughout a polymer matrix comprising one or more polymers. This disclosure is directed to MOF functionalized through addition of a pendant functional group to the MOF, in order to improve interaction with a surrounding polymer matrix in a MMM. The improved interaction aids in avoiding defects in the MMM due to incompatible interfaces between the polymer matrix and the MOF particle, in turn increasing the mechanical and gas separation properties of the MMM. The disclosure is also directed to a MMM incorporating the surface functionalized MOF.

  19. Density functional theory calculations of the stress of oxidised (110) silicon surfaces

    CERN Document Server

    Melis, C; Colombo, L; Mana, G

    2016-01-01

    The measurement of the lattice-parameter of silicon by x-ray interferometry assumes the use of strain-free crystals. This might not be the case because surface relaxation, reconstruction, and oxidation cause strains without the application of any external force. In a previous work, this intrinsic strain was estimated by a finite element analysis, where the surface stress was modeled by an elastic membrane having a 1 N/m tensile strength. The present paper quantities the surface stress by a density functional theory calculation. We found a value exceeding the nominal value used, which potentially affects the measurement accuracy.

  20. Large work function reduction by adsorption of a molecule with a negative electron affinity: pyridine on ZnO(1010).

    Science.gov (United States)

    Hofmann, Oliver T; Deinert, Jan-Christoph; Xu, Yong; Rinke, Patrick; Stähler, Julia; Wolf, Martin; Scheffler, Matthias

    2013-11-07

    Using thermal desorption and photoelectron spectroscopy to study the adsorption of pyridine on ZnO(1010), we find that the work function is significantly reduced from 4.5 eV for the bare ZnO surface to 1.6 eV for one monolayer of adsorbed pyridine. Further insight into the interface morphology and binding mechanism is obtained using density functional theory. Although semilocal density functional theory provides unsatisfactory total work functions, excellent agreement of the work function changes is achieved for all coverages. In a closed monolayer, pyridine is found to bind to every second surface Zn atom. The strong polarity of the Zn-pyridine bond and the molecular dipole moment act cooperatively, leading to the observed strong work function reduction. Based on simple alignment considerations, we illustrate that even larger work function modifications should be achievable using molecules with negative electron affinity. We expect the application of such molecules to significantly reduce the electron injection barriers at ZnO/organic heterostructures.

  1. Photofabrication of surface relief gratings using post functionalized azo polymers

    Energy Technology Data Exchange (ETDEWEB)

    Tripathy, S.K.; Kumar, J.; Kim, D.Y.; Jiang, X.; Wang, X.; Li, L.; Sukwattanasinitt, M.; Sandman, D.J.

    1998-07-01

    A series of azobenzene funtionalized polymers has been synthesized by post polymerization azo coupling reaction. Photo-fabrication of surface relief gratings were studied on the polymer films. Epoxy based azo polymers were prepared by post azo coupling reaction to form polymers containing donor-acceptor type azo chromophores. The azo chromophores were designed to contain ionizable groups to impart self-assembling and photoprocessing capabilities to the polymers. The polymers containing 4-(4-(carboxylic acid)phenylazo)aniline chromophores can be directly photofabricated to form surface relief gratings with large surface modulations. Charge interactions had a strong influence on the details of the writing process. A new soluble polydiacetylene, post-functionalized with azobenzene groups was also prepared. Large amplitude surface gratings could be fabricated on this polydiacetylene film as well.

  2. Revisiting the Fermi Surface in Density Functional Theory

    Science.gov (United States)

    Das, Mukunda P.; Green, Frederick

    2016-06-01

    The Fermi surface is an abstract object in the reciprocal space of a crystal lattice, enclosing the set of all those electronic band states that are filled according to the Pauli principle. Its topology is dictated by the underlying lattice structure and its volume is the carrier density in the material. The Fermi surface is central to predictions of thermal, electrical, magnetic, optical and superconducting properties in metallic systems. Density functional theory is a first-principles method used to estimate the occupied-band energies and, in particular, the isoenergetic Fermi surface. In this review we survey several key facts about Fermi surfaces in complex systems, where a proper theoretical understanding is still lacking. We address some critical difficulties.

  3. The role of surface functionalization of silica nanoparticles for bioimaging

    Directory of Open Access Journals (Sweden)

    Maria C. Gomes

    2016-07-01

    Full Text Available Among the several types of inorganic nanoparticles available, silica nanoparticles (SNP have earned their relevance in biological applications namely, as bioimaging agents. In fact, fluorescent SNP (FSNP have been explored in this field as protective nanocarriers, overcoming some limitations presented by conventional organic dyes such as high photobleaching rates. A crucial aspect on the use of fluorescent SNP relates to their surface properties, since it determines the extent of interaction between nanoparticles and biological systems, namely in terms of colloidal stability in water, cellular recognition and internalization, tracking, biodistribution and specificity, among others. Therefore, it is imperative to understand the mechanisms underlying the interaction between biosystems and the SNP surfaces, making surface functionalization a relevant step in order to take full advantage of particle properties. The versatility of the surface chemistry on silica platforms, together with the intrinsic hydrophilicity and biocompatibility, make these systems suitable for bioimaging applications, such as those mentioned in this review.

  4. Surface structure of polymer Gels and emerging functions

    CERN Document Server

    Kobiki, Y

    1999-01-01

    We report the surface structure of polymer gels on a submicrometer scale during the volume phase transition. Sponge-like domains with a mesoscopic scale were directly observed in water by using at atomic force microscope (AFM). The surface structure characterized by the domains is discussed in terms of the root-mean-square roughness and the auto-correlation function, which were calculated from the AFM images. In order to demonstrate the role of surface structure in determining the macroscopic properties of film-like poly (N-isopropylacrylamide: NIPA) gels. It was found that the temperature dependence, as well as the absolute values of the static contact angle, were strongly dependent on the bulk network inhomogeneities. The relation between the mesoscopic structure and the macroscopic properties is qualitatively discussed in terms of not only the changes in the chemical, but also in the physical, surface properties of the NIPA gels in response to a temperature change.

  5. Orbital nodal surfaces: Topological challenges for density functionals

    Science.gov (United States)

    Aschebrock, Thilo; Armiento, Rickard; Kümmel, Stephan

    2017-06-01

    Nodal surfaces of orbitals, in particular of the highest occupied one, play a special role in Kohn-Sham density-functional theory. The exact Kohn-Sham exchange potential, for example, shows a protruding ridge along such nodal surfaces, leading to the counterintuitive feature of a potential that goes to different asymptotic limits in different directions. We show here that nodal surfaces can heavily affect the potential of semilocal density-functional approximations. For the functional derivatives of the Armiento-Kümmel (AK13) [Phys. Rev. Lett. 111, 036402 (2013), 10.1103/PhysRevLett.111.036402] and Becke88 [Phys. Rev. A 38, 3098 (1988), 10.1103/PhysRevA.38.3098] energy functionals, i.e., the corresponding semilocal exchange potentials, as well as the Becke-Johnson [J. Chem. Phys. 124, 221101 (2006), 10.1063/1.2213970] and van Leeuwen-Baerends (LB94) [Phys. Rev. A 49, 2421 (1994), 10.1103/PhysRevA.49.2421] model potentials, we explicitly demonstrate exponential divergences in the vicinity of nodal surfaces. We further point out that many other semilocal potentials have similar features. Such divergences pose a challenge for the convergence of numerical solutions of the Kohn-Sham equations. We prove that for exchange functionals of the generalized gradient approximation (GGA) form, enforcing correct asymptotic behavior of the potential or energy density necessarily leads to irregular behavior on or near orbital nodal surfaces. We formulate constraints on the GGA exchange enhancement factor for avoiding such divergences.

  6. Momentary Work Happiness as a Function of Enduring Burnout and Work Engagement.

    Science.gov (United States)

    Bakker, Arnold B; Oerlemans, Wido G M

    2016-08-17

    The present study (N = 136) combined global measures with specific, experience-based measures to investigate how enduring job burnout and engagement influence the impact of daily work activities on momentary need satisfaction and happiness. We used the day reconstruction method (DRM) to ask employees from various occupations to reconstruct their working days. On the basis of employee work engagement and self-determination theories, we hypothesized that time spent on (a) core work tasks; (b) administrative work tasks; (c) client interactions; (d) interactions with colleagues; and (e) meetings would be negatively related to need satisfaction on the task level for employees high (vs. low) in enduring burnout; and positively related to need satisfaction on the task level for employees high (vs. low) in enduring work engagement. In addition, we predicted that psychological need satisfaction would mediate the relationships between time spent on work tasks and happiness during the tasks. The results of multilevel analyses largely supported these hypotheses. Our findings contribute to the literature by showing how those with high levels of burnout do not manage to satisfy their basic needs through their work, whereas those with high levels of work engagement satisfy their daily needs and stay happy.

  7. Evolution of the transfer function characterization of surface scatter phenomena

    Science.gov (United States)

    Harvey, James E.; Pfisterer, Richard N.

    2016-09-01

    Based upon the empirical observation that BRDF measurements of smooth optical surfaces exhibited shift-invariant behavior when plotted versus    o , the original Harvey-Shack (OHS) surface scatter theory was developed as a scalar linear systems formulation in which scattered light behavior was characterized by a surface transfer function (STF) reminiscent of the optical transfer function (OTF) of modern image formation theory (1976). This shift-invariant behavior combined with the inverse power law behavior when plotting log BRDF versus log   o was quickly incorporated into several optical analysis software packages. Although there was no explicit smooth-surface approximation in the OHS theory, there was a limitation on both the incident and scattering angles. In 1988 the modified Harvey-Shack (MHS) theory removed the limitation on the angle of incidence; however, a moderate-angle scattering limitation remained. Clearly for large incident angles the BRDF was no longer shift-invariant as a different STF was now required for each incident angle. In 2011 the generalized Harvey-Shack (GHS) surface scatter theory, characterized by a two-parameter family of STFs, evolved into a practical modeling tool to calculate BRDFs from optical surface metrology data for situations that violate the smooth surface approximation inherent in the Rayleigh-Rice theory and/or the moderate-angle limitation of the Beckmann-Kirchhoff theory. And finally, the STF can be multiplied by the classical OTF to provide a complete linear systems formulation of image quality as degraded by diffraction, geometrical aberrations and surface scatter effects from residual optical fabrication errors.

  8. APPROXIMATE FUNCTION FOR UNSTEADY AERODYNAMIC KERNEL FUNCTION OF AEROELASTIC LIFTING SURFACES

    Directory of Open Access Journals (Sweden)

    Erwin Sulaeman

    2014-05-01

    Full Text Available Normal 0 false false false EN-US X-NONE X-NONE ABSTRACT: Prediction of unsteady aerodynamic loads is still the most challenging task in flutter aeroelastic analysis. Generally the numerical estimation of steady and unsteady aerodynamic of thin lifting surface is conducted based on an integral equation relating aerodynamic pressure and normal wash velocity. The present work attempts to increase the accuracy of the prediction by using an approximate approach to evaluate kernel function occurring in the integral equation in the form of cylindrical function.  Following previous approximation approach by other researchers to solve the cylindrical function for planar lifting surfaces, in the present work such approach is extended to non planar lifting surfaces.  To increase the accuracy of the method, the integration region of the kernel function is divided into two parts namely near and far regions, where a nonlinear regression curve fitting technique is adapted to approximate the denominator part of the cylindrical function of each region.ABSTRAK: Penelahan daya aerodinamik tidak stabil merupakan satu tugas yang mencabar dalam menganalisis getaran aeroanjalan. Umumnya, anggaran berangka untuk daya aerodinamik stabil dan tidak stabil pada permukaan mengangkat yang nipis, adalah berdasarkan kepada persamaan kamiran di antara tekanan aerodinamik dan halaju aliran udara pada garis normal yang terhasil di bawah sayap pesawat. Kajian ini adalah bertujuan untuk menghasilkan penelahan daya aerodinamik yang lebih tepat dengan menggunakan pendekatan kira hampir untuk menilai fungsi Kernel yang terdapat dalam persamaan kamiran dalam bentuk fungsi silinder. Dengan menggunakan pendekatan kira hampir yang digunakan oleh penyelidik sebelumnya untuk menyelesaikan fungsi silinder pada permukaan mengangkat satah, kajian ini mengembangkan pendekatan tersebut kepada permukaan mengangkat tak sesatah. Untuk meningkatkan lagi ketepatan penelahan, kawasan pengamiran

  9. Working activity hygiene, central nervous system and attention function parameters of the working females at knitting enterprises of Uzbekistan

    Directory of Open Access Journals (Sweden)

    Aziz Iskandarov

    2013-04-01

    Full Text Available Last years in Uzbekistan the knitted manufactures have developed intensively, supplied with the new equipment and modern technologies which result in change of working conditions at the knitted-goods enterprises, in increase of intensity, strained nervous-emotional state and intellectuality of working processes. The purpose was to reveal influence of working conditions of the working women of knitted manufactures on dynamics of working activity, on the central nervous system and functions of attention. The healthy working women of the Tashkent knitted manufactures making a knitted cloth and wears (knitters, seamstresses, ironers at the age from 20 till 40 years with the operational experience from 2 till 20 years were enrolled in this study. It was established that of all unfavourable factors that effect on the reduction of the working activity the air dust contamination accounts for 13.6%, noise 13.6% and light exposure of workplace 32.4%. For decrease of a functional strain of the central nervous system and function of attention of the working women it is necessary to introduce the rational mode of work and rest as well as measures for improvement of working conditions.

  10. Work function determination of promising material for thermionic converters

    Science.gov (United States)

    Jacobs, M. H.; Jacobson, D.

    1980-01-01

    The work done to fabricate Marchuk plasma discharge tubes for measurement of the cesiated emission of lanthanum hexaboride and thoriated tungsten electrodes is described. A photon counting pyrometer was completed and is to be calibrated with a gold standard.

  11. On the Additive Constant of the k-server Work Function Algorithm

    CERN Document Server

    Emek, Yuval; Korman, Amos; Rosen, Adi

    2009-01-01

    We consider the Work Function Algorithm for the k-server problem. We show that if the Work Function Algorithm is c-competitive, then it is also strictly (2c)-competitive. As a consequence of [Koutsoupias and Papadimitriou, JACM 1995] this also shows that the Work Function Algorithm is strictly (4k-2)-competitive.

  12. Surface Appendages of Archaea: Structure, Function, Genetics and Assembly

    Directory of Open Access Journals (Sweden)

    Sarah Siu

    2013-01-01

    Full Text Available Organisms representing diverse subgroupings of the Domain Archaea are known to possess unusual surface structures. These can include ones unique to Archaea such as cannulae and hami as well as archaella (archaeal flagella and various types of pili that superficially resemble their namesakes in Bacteria, although with significant differences. Major advances have occurred particularly in the study of archaella and pili using model organisms with recently developed advanced genetic tools. There is common use of a type IV pili-model of assembly for several archaeal surface structures including archaella, certain pili and sugar binding structures termed bindosomes. In addition, there are widespread posttranslational modifications of archaellins and pilins with N-linked glycans, with some containing novel sugars. Archaeal surface structures are involved in such diverse functions as swimming, attachment to surfaces, cell to cell contact resulting in genetic transfer, biofilm formation, and possible intercellular communication. Sometimes functions are co-dependent on other surface structures. These structures and the regulation of their assembly are important features that allow various Archaea, including thermoacidophilic, hyperthermophilic, halophilic, and anaerobic ones, to survive and thrive in the extreme environments that are commonly inhabited by members of this domain.

  13. Changes in Work Function and Electrical Resistance of Pt Thin Films in the Presence of Hydrogen Gas

    Science.gov (United States)

    Tsukada, Keiji; Inoue, Hirotsugu; Katayama, Fumiya; Sakai, Kenji; Kiwa, Toshihiko

    2012-01-01

    The changes in the electrical properties, such as work function and resistance, of Pt thin films in the presence of hydrogen gas were studied. They were simultaneously measured with a flow-through cell at different concentrations of hydrogen gas in atmosphere containing gaseous nitrogen and that containing air. The resistance was measured by a four-terminal sensing method and the relative work function changes were measured using a field effect transistor. In both atmospheres, the resistance decreased as the concentration of hydrogen gas increased. This result was repeatable only in air because of the differences in the dynamic mechanism of increased density of electrical carriers inside the Pt film as a result of diffused H atoms. In the nitrogen atmosphere, the diffused H atoms were not easily released because of the surface barrier. On the other hand, oxygen gas reacted with H atoms at the surface and this reaction accelerated atom release into air. The work function showed repeatable responses in both atmospheres, but the response characteristics were different. The equilibrium reaction between the adsorption and desorption of hydrogen occurred at the surface in the nitrogen atmosphere, whereas the equilibrium reaction of hydrogen and oxygen to form water molecules occurred in air. The changes in work function and resistance in the presence of hydrogen were due to changes in dissociated hydrogen intensity in the bulk, as well as to the surface reactions.

  14. Dry-Surface Simulation Method for the Determination of the Work of Adhesion of Solid-Liquid Interfaces.

    Science.gov (United States)

    Leroy, Frédéric; Müller-Plathe, Florian

    2015-08-01

    We introduce a methodology, referred to as the dry-surface method, to calculate the work of adhesion of heterogeneous solid-liquid interfaces by molecular simulation. This method employs a straightforward thermodynamic integration approach to calculate the work of adhesion as the reversible work to turn off the attractive part of the actual solid-liquid interaction potential. It is formulated in such a way that it may be used either to evaluate the ability of force fields to reproduce reference values of the work of adhesion or to optimize force-field parameters with reference values of the work of adhesion as target quantities. The methodology is tested in the case of water on a generic model of nonpolar substrates with the structure of gold. It is validated through a quantitative comparison to phantom-wall calculations and against a previous characterization of the thermodynamics of the gold-water interface. It is found that the work of adhesion of water on nonpolar substrates is a nonlinear function of the microscopic solid-liquid interaction energy parameter. We also comment on the ability of mean-field approaches to predict the work of adhesion of water on nonpolar substrates. In addition, we discuss in detail the information on the solid-liquid interfacial thermodynamics delivered by the phantom-wall approach. We show that phantom-wall calculations yield the solid-liquid interfacial tension relative to the solid surface tension rather than the absolute solid-liquid interfacial tension as previously believed.

  15. Self-consistent density functional calculation of the image potential at a metal surface

    Energy Technology Data Exchange (ETDEWEB)

    Jung, J [Departamento de Fisica Fundamental, Universidad Nacional de Educacion a Distancia, Apartado 60141, 28080 Madrid (Spain); Alvarellos, J E [Departamento de Fisica Fundamental, Universidad Nacional de Educacion a Distancia, Apartado 60141, 28080 Madrid (Spain); Chacon, E [Instituto de Ciencias de Materiales de Madrid, Consejo Superior de Investigaciones CientIficas, E-28049 Madrid (Spain); GarcIa-Gonzalez, P [Departamento de Fisica Fundamental, Universidad Nacional de Educacion a Distancia, Apartado 60141, 28080 Madrid (Spain)

    2007-07-04

    It is well known that the exchange-correlation (XC) potential at a metal surface has an image-like asymptotic behaviour given by -1/4(z-z{sub 0}), where z is the coordinate perpendicular to the surface. Using a suitable fully non-local functional prescription, we evaluate self-consistently the XC potential with the correct image behaviour for simple jellium surfaces in the range of metallic densities. This allows a proper comparison between the corresponding image-plane position, z{sub 0}, and other related quantities such as the centroid of an induced charge by an external perturbation. As a by-product, we assess the routinely used local density approximation when evaluating electron density profiles, work functions, and surface energies by focusing on the XC effects included in the fully non-local description.

  16. Engineering the work function of buckled boron α-sheet by lithium adsorption: a first-principles investigation.

    Science.gov (United States)

    Zheng, Bing; Yu, Hai-tao; Xie, Ying; Lian, Yong-fu

    2014-11-26

    First-principles density functional theory calculations were performed to study the effect of Li adsorption on the structural and electronic properties, particularly the work function, of boron α-sheet. The calculated binding energies indicated that boron α-sheet could be well stabilized by the adsorption of Li atoms. Furthermore, the work functions of Li-adsorbed boron α-sheets were observed to decrease drastically with increasing Li coverage. The work functions are lower than that of Mg and even, for some of them, lower than that of Ca, indicating a considerable potential application of Li-adsorbed boron α-sheets as field-emission and electrode materials. Based on the calculated geometric and electronic structures, we discuss in details some possible aspects affecting the work function. The Li coverage dependence of the work functions of Li-adsorbed boron α-sheets was further confirmed by electrostatic potential analyses. The relationship between the work function variation and the Fermi and vacuum energy level shifts was also discussed, and we observed that the variation of the work function is primarily associated with the shift of the Fermi energy level. It is the surface dipole formed by the interaction between adatoms and substrate that should be responsible for the observed variation of the work function, whereas the increasing negative charge and rumpling for boron α-sheet only play minor roles. Additionally, the effect of Li adatoms on the work function of boron α-sheet was confirmed to be much stronger than that of graphene or a graphene double layer.

  17. Tuning the work function of ultrathin oxide films on metals by adsorption of alkali atoms.

    Science.gov (United States)

    Martinez, Umberto; Giordano, Livia; Pacchioni, Gianfranco

    2008-04-28

    We report a theoretical investigation of the adsorption of alkali metal atoms deposited on ultrathin oxide films. The properties of Li, Na, and K atoms adsorbed on SiO(2)/Mo(112) and of K on MgO / Ag(100) and TiO(2)/Pt(111) have been analyzed with particular attention to the induced changes in the work function of the system, Phi. On the nonreducible SiO(2) and MgO oxide films there is a net transfer of the outer ns electron of the alkali atom to the metal substrate conduction band; the resulting surface dipole substantially lowers Phi. The change in Phi depends (a) on the adsorption site (above the oxide film or at the interface) and (b) on the alkali metal coverage. Deposition of K on reducible TiO(2) oxide films results in adsorbed K(+) ions and in the formation of Ti(3+) ions. No charge transfer to the metal substrate is observed but also in this case the surface dipole resulting from the K-TiO(2) charge transfer has the effect to considerably reduce the work function of the system.

  18. Usage of analytical diagnostics when evaluating functional surface material defects

    Directory of Open Access Journals (Sweden)

    R. Frischer

    2015-10-01

    Full Text Available There are occurring defects due to defects mechanisms on parts of production devices surfaces. Outer defects pronouncement is changing throw the time with unequal speed. This variability of defect’s mechanism development cause that is impossible to evaluate technical state of the device in any moment, without the necessary underlying information. Proposed model is based on analytical diagnostics basis. Stochastic model with usage of Weibull probability distribution can assign probability of function surface defect occurrence on the operational information in any moment basis. The knowledge of defect range limiting moment, then enable when and in what range will be necessary to make renewal.

  19. Properties of distance functions on convex surfaces and Alexandrov spaces

    CERN Document Server

    Rataj, Jan

    2009-01-01

    If $X$ is a convex surface in a Euclidean space, then the squared (intrinsic) distance function $\\dist^2(x,y)$ is d.c. (DC, delta-convex) on $X\\times X$ in the only natural extrinsic sense. For the proof we use semiconcavity (in an intrinsic sense) of $\\dist^2(x,y)$ on $X \\times X$ if $X$ is an Alexandrov space with nonnegative curvature. Applications concerning $r$-boundaries (distance spheres) and the ambiguous locus (exoskeleton) of a closed subset of a convex surface are given.

  20. SURFACE SYMMETRY ENERGY OF NUCLEAR ENERGY DENSITY FUNCTIONALS

    Energy Technology Data Exchange (ETDEWEB)

    Nikolov, N; Schunck, N; Nazarewicz, W; Bender, M; Pei, J

    2010-12-20

    We study the bulk deformation properties of the Skyrme nuclear energy density functionals. Following simple arguments based on the leptodermous expansion and liquid drop model, we apply the nuclear density functional theory to assess the role of the surface symmetry energy in nuclei. To this end, we validate the commonly used functional parametrizations against the data on excitation energies of superdeformed band-heads in Hg and Pb isotopes, and fission isomers in actinide nuclei. After subtracting shell effects, the results of our self-consistent calculations are consistent with macroscopic arguments and indicate that experimental data on strongly deformed configurations in neutron-rich nuclei are essential for optimizing future nuclear energy density functionals. The resulting survey provides a useful benchmark for further theoretical improvements. Unlike in nuclei close to the stability valley, whose macroscopic deformability hangs on the balance of surface and Coulomb terms, the deformability of neutron-rich nuclei strongly depends on the surface-symmetry energy; hence, its proper determination is crucial for the stability of deformed phases of the neutron-rich matter and description of fission rates for r-process nucleosynthesis.

  1. Effect of surface texture and working gap on the braking performance of the magnetorheological fluid brake

    Science.gov (United States)

    Wang, Na; Li, Dong Heng; Li Song, Wan; Chao Xiu, Shi; Zhi Meng, Xiang

    2016-10-01

    In this paper, the effect of the surface textures of braking disc on the braking performance is experimentally investigated under the conditions of different working gaps and applied currents. For this purpose, a new configuration of magnetorheological fluid brake (MRB) with adjustable working gap is developed to improve the manufacturing accuracy and cost, and to reduce the problem of replacing the braking disc. In addition, the braking discs with three types of surface texture are designed and machined. Based on the test bed developed for the proposed MRB, a series of experiments are carried out on the manufactured prototype and the results are presented to obtain the relationship among the surface texture of the braking disc, applied current, working gap and the braking performance. The results show that the braking torque is significantly influenced by the working gap and surface texture of the braking disc, and the maximum braking torque is obtained on the conditions of 0.25 mm working gap and the braking disc with square surface texture.

  2. Toward spatial control of gold nanorod surface functionalization

    Science.gov (United States)

    Eller, Jonathan R.

    Gold nanorods (GNRs) show much promise for applications in biological, optoelectronic and energy applications. The resonant generation of a localized surface plasmon resonance (LSPR) at the GNR surface results in interesting optical properties and unique interactions with molecules. Combined with their biocompatibility, ease of synthesis and facile surface functionalization, these anisotropic metal particles are excellent scaffolds for the study of the interactions between nanoscale surfaces and their chemical/biological environments. Regardless of the application, however, GNR utility will not be fully realized until the chemical nature of the surface is understood and controlled. GNRs can enhance various photophysical properties of molecules. In the case of two-photon absorption (TPA), cross-section enhancements have been shown to increase with strong distance-dependence. Here, a dual approach for the conjugation of a TPA chromophore to GNRs is presented, relying on layer-by- layer (LbL) polymer wrapping and direct thiol coating of the same parent chromophore structure. Together, these approaches allow for estimated chromophore-particle distances from nanomaterials. Surface-initiated Atom transfer radical polymerization (SI-ATRP) is a popular method for grafting polymers from a surface. We demonstrate our ability to grow poly(N-isopropylacrylamide) (PNIPAM) shells on the GNR surface, toward a "smart" thermoresponsive polymer shell. The role of ligand choice, molar ratio of monomer to initiator and polymerization on presence and control of shell thickness are investigated. The introduction of a tetradentate (vs. the commonly-used tridentate) ATRP ligand was necessary for the growth of PNIPAM shells in our studies, and consideration of the molar ratio of monomer and initiator and reaction time allowed control of shell thickness and extent of aggregation.

  3. Functionalization of nylon membranes via surface-initiated atom-transfer radical polymerization.

    Science.gov (United States)

    Xu, F J; Zhao, J P; Kang, E T; Neoh, K G; Li, J

    2007-07-31

    The ability to manipulate and control the surface properties of nylons is of crucial importance to their widespread applications. In this work, surface-initiated atom-transfer radical polymerization (ATRP) is employed to tailor the functionality of the nylon membrane and pore surfaces in a well-controlled manner. A simple two-step method, involving the activation of surface amide groups with formaldehyde and the reaction of the resulting N-methylol polyamide with 2-bromoisobutyryl bromide, was first developed for the covalent immobilization of ATRP initiators on the nylon membrane and its pore surfaces. Functional polymer brushes of 2-hydroxyethyl methacrylate (HEMA) and poly(ethylene glycol)monomethacrylate (PEGMA) were prepared via surface-initiated ATRP from the nylon membranes. A kinetics study revealed that the chain growth from the membranes was consistent with a "controlled" process. The dormant chain ends of the grafted HEMA polymer (P(HEMA)) and PEGMA polymer (P(PEGMA)) on the nylon membranes could be reactivated for the consecutive surface-initiated ATRP to produce the corresponding nylon membranes functionalized by P(HEMA)-b-P(PEGMA) and P(PEGMA)-b-P(HEMA) diblock copolymer brushes. In addition, membranes with grafted P(HEMA) and P(PEGMA) brushes exhibited good resistance to protein adsorption and fouling under continuous-flow conditions.

  4. Beyond Conflict: Functional Facets of the Work-Family Interplay

    Science.gov (United States)

    Wiese, Bettina S.; Seiger, Christine P.; Schmid, Christian M.; Freund, Alexandra M.

    2010-01-01

    The present paper deals with three positive facets of the work-family interplay, i.e., transfer of competencies, transfer of positive mood, and cross-domain compensation. The latter refers to the experience that engagement in one domain helps dealing with failures in the other domain. In two correlational studies (N[subscript 1] = 107 working…

  5. Microscopic view of osseointegration and functional mechanisms of implant surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Han, Guang; Shen, Zhijian, E-mail: shen@mmk.su.se

    2015-11-01

    Argon ion beam polishing technique was applied to prepare the cross sections of implants feasible for high resolution scanning electron microscope investigation. The interfacial microstructure between newly formed bone and implants with three modified surfaces retrieved after in vivo test using three different animal models was characterized. By this approach it has become possible to directly observe early bone formation, the increase of bone density, and the evolution of bone structure. The two bone growth mechanisms, distant osteogenesis and contact osteogenesis, can also be distinguished. These direct observations give, at microscopic level, a better view of osseointegration and expound the functional mechanisms of various implant surfaces for osseointegration. - Highlights: • Argon ion beam polishing was used for cross sections of interface. • The interfaces between new bone and implants can be distinguished. • Two bone growth mechanisms were verified. • The functional mechanisms of three modified implants were expounded.

  6. Biomimetic micro∕nanostructured functional surfaces for microfluidic and tissue engineering applications.

    Science.gov (United States)

    Stratakis, E; Ranella, A; Fotakis, C

    2011-03-30

    This paper reviews our work on the application of ultrafast pulsed laser micro∕nanoprocessing for the three-dimensional (3D) biomimetic modification of materials surfaces. It is shown that the artificial surfaces obtained by femtosecond-laser processing of Si in reactive gas atmosphere exhibit roughness at both micro- and nanoscales that mimics the hierarchical morphology of natural surfaces. Along with the spatial control of the topology, defining surface chemistry provides materials exhibiting notable wetting characteristics which are potentially useful for open microfluidic applications. Depending on the functional coating deposited on the laser patterned 3D structures, we can achieve artificial surfaces that are (a) of extremely low surface energy, thus water-repellent and self-cleaned, and (b) responsive, i.e., showing the ability to change their surface energy in response to different external stimuli such as light, electric field, and pH. Moreover, the behavior of different kinds of cells cultured on laser engineered substrates of various wettabilities was investigated. Experiments showed that it is possible to preferentially tune cell adhesion and growth through choosing proper combinations of surface topography and chemistry. It is concluded that the laser textured 3D micro∕nano-Si surfaces with controllability of roughness ratio and surface chemistry can advantageously serve as a novel means to elucidate the 3D cell-scaffold interactions for tissue engineering applications.

  7. "Click-functional" block copolymers provide precise surface functionality via spin coating.

    Science.gov (United States)

    Rengifo, Hernán R; Chen, Lu; Grigoras, Cristian; Ju, Jingyue; Koberstein, Jeffrey T

    2008-07-15

    There are few existing methods for the quantitative functionalization of surfaces, especially for polymeric substrates. We demonstrate that alkyne end-functional diblock copolymers can be used to provide precise areal densities of reactive functionality on both hard (e.g., glass and silicon oxide) and soft (i.e., polymeric) substrates. Alkyne functionality is extremely versatile because the resultant functional surfaces are reactive toward azide functional molecules by Sharpless click chemistry. Spin-coated films of alpha-alkyne-omega-Br-poly( tert-butylacrylate- b-methylmethacrylate) (poly( tBA-MMA)) spontaneously self-assemble on the aforementioned substrates to present a surface monolayer of PtBA with a thickness in the range of 1 to 9 nm. The PMMA block physisorbs to provide multivalent anchoring onto hard substrates and is fixed onto polymer surfaces by interpenetration with the substrate polymer. The areal density of alkyne functional groups is precisely controlled by adjusting the thickness of the block copolymer monolayer, which is accomplished by changing either the spin coating conditions (i.e., rotational speed and solution concentration) or the copolymer molecular weight. The reactivity of surface-bound alkynes, in 1,3-dipolar cycloaddition reactions or by so-called "click chemistry", is demonstrated by covalent surface immobilization of fluorescently labeled azides. The modificed surfaces are characterized by atomic force microscopy (AFM), contact angle, ellipsometry, fluorescent imaging and angle-dependent X-ray photoelectron spectroscopy (ADXPS) measurements. Microarrays of covalently bound fluorescent molecules are created to demonstrate the approach and their performance is evaluated by determining their fluorescence signal-to-noise ratios.

  8. Interaction between Palladium Nanoparticles and Surface-Modified Carbon Nanotubes: Role of Surface Functionalities

    DEFF Research Database (Denmark)

    Zhang, Bingsen; Shao, Lidong; Zhang, Wei;

    2014-01-01

    It is crucial to accurately describe the interaction between the surface functionality and the supported metal catalyst because it directly determines the activity and selectivity of a catalytic reaction. It is, however, challenging with a metal-carbon catalytic system owing to the ultrafine feat...

  9. Cobalt-silica magnetic nanoparticles with functional surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Vadala, Michael L. [Department of Chemistry and the Macromolecules and Interfaces Institute, Virginia Polytechnic Institute and State University, Mail Code 0212, Blacksburg, VA 24061-0344 (United States); Zalich, Michael A. [School of Physics, The University of Western Australia, Crawley, WA 6009 (Australia); Fulks, David B. [Department of Chemistry and the Macromolecules and Interfaces Institute, Virginia Polytechnic Institute and State University, Mail Code 0212, Blacksburg, VA 24061-0344 (United States); St Pierre, Tim G. [School of Physics, The University of Western Australia, Crawley, WA 6009 (Australia); Dailey, James P. [Department of Ophthalmology, Case Western Reserve University, Cleveland, OH (United States); Riffle, Judy S. [Department of Chemistry and the Macromolecules and Interfaces Institute, Virginia Polytechnic Institute and State University, Mail Code 0212, Blacksburg, VA 24061-0344 (United States)]. E-mail: judyriffle@aol.com

    2005-05-15

    Cobalt nanoparticles encased in polysiloxane block copolymers have been heated at 600-700 deg C to form protective shells around the particles, which contain crosslinked Si-O structures, and to anneal the cobalt. Methods to functionalize and modify the surfaces of the pyrolyzed/annealed silica-cobalt complexes with amines, isocyanates, poly(ethylene oxide), poly(L-lactide) and polydimethylsiloxane (PDMS) are presented.

  10. Solvation of complex surfaces via molecular density functional theory.

    Science.gov (United States)

    Levesque, Maximilien; Marry, Virginie; Rotenberg, Benjamin; Jeanmairet, Guillaume; Vuilleumier, Rodolphe; Borgis, Daniel

    2012-12-14

    We show that classical molecular density functional theory, here in the homogeneous reference fluid approximation in which the functional is inferred from the properties of the bulk solvent, is a powerful new tool to study, at a fully molecular level, the solvation of complex surfaces and interfaces by polar solvents. This implicit solvent method allows for the determination of structural, orientational, and energetic solvation properties that are on a par with all-atom molecular simulations performed for the same system, while reducing the computer time by two orders of magnitude. This is illustrated by the study of an atomistically-resolved clay surface composed of over a thousand atoms wetted by a molecular dipolar solvent. The high numerical efficiency of the method is exploited to carry a systematic analysis of the electrostatic and non-electrostatic components of the surface-solvent interaction within the popular Clay Force Field (CLAYFF). Solvent energetics and structure are found to depend weakly upon the atomic charges distribution of the clay surface, even for a rather polar solvent. We conclude on the consequences of such findings for force-field development.

  11. Surface functionalization with strontium-containing nanocomposite coatings via EPD.

    Science.gov (United States)

    Ma, Kena; Huang, Dan; Cai, Jing; Cai, Xinjie; Gong, Lingling; Huang, Pin; Wang, Yining; Jiang, Tao

    2016-10-01

    Metal orthopedic implants still face challenges in some compromised conditions, partly due to bio-inertness. The present study aimed to functionalize metallic implants with organic-inorganic nanocomposite (strontium-containing chitosan/gelatin) coatings through a simple single-step electrophoretic deposition under mild conditions. The surface characterization and in vitro cellular response were studied and compared with chitosan/gelatin (CS/G) coatings. SEM images suggested the inorganic nanoparticles may be encapsulated within or mixed with organic polymers. The XRD patterns showed that strontium carbonate was generated in the coatings. The TEM images revealed strontium-containing nanoparticles were released from the coatings in PBS. The continuous release after the initial burst release ensured the enduring effects of the functionalized surface. The tensile bond strength of the coatings to the substrates increased after the addition of strontium. In vitro cellular study confirmed that strontium-containing coatings supported the proliferation of MC3T3-E1 cells and exhibited excellent ability to enhance the differentiation of such pre-osteoblasts. Therefore, such organic-inorganic nanocomposite coatings are a promising candidate to functionalize orthopedic implant surfaces.

  12. High temperature oxidation behavior of AISI 304L stainless steel-Effect of surface working operations

    Science.gov (United States)

    Ghosh, Swati; Kumar, M. Kiran; Kain, Vivekanand

    2013-01-01

    The oxidation behavior of grade 304L stainless steel (SS) subjected to different surface finishing (machining and grinding) operations was followed in situ by contact electric resistance (CER) and electrochemical impedance spectroscopy (EIS) measurements using controlled distance electrochemistry (CDE) technique in high purity water (conductivity electrochemical properties and distinct morphological features of the oxide layer as a result of surface working were attributed to the prevalence of heavily fragmented grain structure and presence of martensite.

  13. Applying Cognitive Work Analysis to Time Critical Targeting Functionality

    Science.gov (United States)

    2004-10-01

    Target List/Dynamic Target Queue (DTL/ DTQ ) in the same place. Figure 4-27 shows the task steps involved in achieving Goal 7. 4- 30 Figure 4-27...GUI WG to brainstorm the order of columns in the DTL/ DTQ Table, a critical component of the TCTF CUI, with successful results, which were...Cognitive Work Analysis DTD Display Task Description DTL/ DTQ Dynamic Target List/Dynamic Target Queue FDO Fighter Duty Officer FEBA Forward Edge

  14. Filtering Non-Linear Transfer Functions on Surfaces.

    Science.gov (United States)

    Heitz, Eric; Nowrouzezahrai, Derek; Poulin, Pierre; Neyret, Fabrice

    2014-07-01

    Applying non-linear transfer functions and look-up tables to procedural functions (such as noise), surface attributes, or even surface geometry are common strategies used to enhance visual detail. Their simplicity and ability to mimic a wide range of realistic appearances have led to their adoption in many rendering problems. As with any textured or geometric detail, proper filtering is needed to reduce aliasing when viewed across a range of distances, but accurate and efficient transfer function filtering remains an open problem for several reasons: transfer functions are complex and non-linear, especially when mapped through procedural noise and/or geometry-dependent functions, and the effects of perspective and masking further complicate the filtering over a pixel's footprint. We accurately solve this problem by computing and sampling from specialized filtering distributions on the fly, yielding very fast performance. We investigate the case where the transfer function to filter is a color map applied to (macroscale) surface textures (like noise), as well as color maps applied according to (microscale) geometric details. We introduce a novel representation of a (potentially modulated) color map's distribution over pixel footprints using Gaussian statistics and, in the more complex case of high-resolution color mapped microsurface details, our filtering is view- and light-dependent, and capable of correctly handling masking and occlusion effects. Our approach can be generalized to filter other physical-based rendering quantities. We propose an application to shading with irradiance environment maps over large terrains. Our framework is also compatible with the case of transfer functions used to warp surface geometry, as long as the transformations can be represented with Gaussian statistics, leading to proper view- and light-dependent filtering results. Our results match ground truth and our solution is well suited to real-time applications, requires only a few

  15. Brain injury impairs working memory and prefrontal circuit function

    Directory of Open Access Journals (Sweden)

    Colin James Smith

    2015-11-01

    Full Text Available More than 2.5 million Americans suffer a traumatic brain injury (TBI each year. Even mild to moderate traumatic brain injury causes long-lasting neurological effects. Despite its prevalence, no therapy currently exists to treat the underlying cause of cognitive impairment suffered by TBI patients. Following lateral fluid percussion injury (LFPI, the most widely used experimental model of TBI, we investigated alterations in working memory and excitatory/inhibitory synaptic balance in the prefrontal cortex. LFPI impaired working memory as assessed with a T-maze behavioral task. Field excitatory postsynaptic potentials recorded in the prefrontal cortex were reduced in slices derived from brain-injured mice. Spontaneous and miniature excitatory postsynaptic currents onto layer 2/3 neurons were more frequent in slices derived from LFPI mice while inhibitory currents onto layer 2/3 neurons were smaller after LFPI. Additionally, an increase in action potential threshold and concomitant decrease in firing rate was observed in layer 2/3 neurons in slices from injured animals. Conversely, no differences in excitatory or inhibitory synaptic transmission onto layer 5 neurons were observed; however, layer 5 neurons demonstrated a decrease in input resistance and action potential duration after LFPI. These results demonstrate synaptic and intrinsic alterations in prefrontal circuitry that may underlie working memory impairment caused by TBI.

  16. Facile Doping and Work-Function Modification of Few-Layer Graphene Using Molecular Oxidants and Reductants

    KAUST Repository

    Mansour, Ahmed

    2017-01-03

    Doping of graphene is a viable route toward enhancing its electrical conductivity and modulating its work function for a wide range of technological applications. In this work, the authors demonstrate facile, solution-based, noncovalent surface doping of few-layer graphene (FLG) using a series of molecular metal-organic and organic species of varying n- and p-type doping strengths. In doing so, the authors tune the electronic, optical, and transport properties of FLG. The authors modulate the work function of graphene over a range of 2.4 eV (from 2.9 to 5.3 eV)-unprecedented for solution-based doping-via surface electron transfer. A substantial improvement of the conductivity of FLG is attributed to increasing carrier density, slightly offset by a minor reduction of mobility via Coulomb scattering. The mobility of single layer graphene has been reported to decrease significantly more via similar surface doping than FLG, which has the ability to screen buried layers. The dopant dosage influences the properties of FLG and reveals an optimal window of dopant coverage for the best transport properties, wherein dopant molecules aggregate into small and isolated clusters on the surface of FLG. This study shows how soluble molecular dopants can easily and effectively tune the work function and improve the optoelectronic properties of graphene.

  17. Work function measurements during plasma exposition at conditions relevant in negative ion sources for the ITER neutral beam injection.

    Science.gov (United States)

    Gutser, R; Wimmer, C; Fantz, U

    2011-02-01

    Cesium seeded sources for surface generated negative hydrogen ions are major components of neutral beam injection systems in future large-scale fusion experiments such as ITER. The stability and delivered current density depend highly on the work function during vacuum and plasma phases of the ion source. One of the most important quantities that affect the source performance is the work function. A modified photocurrent method was developed to measure the temporal behavior of the work function during and after cesium evaporation. The investigation of cesium exposed Mo and MoLa samples under ITER negative hydrogen ion based neutral beam injection relevant surface and plasma conditions showed the influence of impurities which result in a fast degradation when the plasma exposure or the cesium flux onto the sample is stopped. A minimum work function close to that of bulk cesium was obtained under the influence of the plasma exposition, while a significantly higher work function was observed under ITER-like vacuum conditions.

  18. Momentary Work Happiness as a Function of Enduring Burnout and Work Engagement

    NARCIS (Netherlands)

    A.B. Bakker (Arnold); W.G.M. Oerlemans (Wido)

    2016-01-01

    textabstractThe present study (N = 136) combined global measures with specific, experience-based measures to investigate how enduring job burnout and engagement influence the impact of daily work activities on momentary need satisfaction and happiness. We used the day reconstruction method (DRM) to

  19. Work.

    Science.gov (United States)

    Haines, Annette M.

    2003-01-01

    Draws upon Maria Montessori's writings to examine work as a universal human tendency throughout life. Discusses the work of adaptation of the infant, work of "psycho-muscular organism" for the preschooler, work of the imagination for the elementary child, community work of the adolescent, and work of the adult. Asserts that…

  20. Surface reactivity of Ge[111] for organic functionalization by means of a radical-initiated reaction: A DFT study

    Science.gov (United States)

    Rubio-Pereda, Pamela; Takeuchi, Noboru

    2016-08-01

    The study of interfacial chemistry at semiconductor surfaces has become an important area of research. Functionalities such as molecular recognition, biocompatibility of surfaces, and molecular computing, could be achieved by the combinations of organic chemistry with the semiconductor technology. One way to accomplish this goal is by means of organic functionalization of semiconductor surfaces such as the bulk-terminated germanium surfaces, more specifically the Ge[111]. In this work, we theoretically study, by applying density functional theory, the surface reactivity of the bulk-terminated Ge[111] surface for organic functionalization by means of a radical-initiated reaction of unsaturated molecules such as acetylene, ethylene and styrene with a hydrogen vacancy on a previously hydrogen-terminated Ge[111] surface. Results derived from this work are compared with those obtained in our previous calculations on the germanene surface, following the same chemical route. Our calculations show an accumulation of electronic charge at the H-vacancy having as a result electron pairing due to strong lattice-electron coupling and therefore a diminished surface reactivity. Calculation of the transition states for acetylene and ethylene indicates that the surface reactivity of the hydrogen-terminated Ge[111] surface is less promising than its two-dimensional analogue, the hydrogen-terminated germanene.

  1. Influence of Conditioned Surface Textures on Plain Journal Bearing Performance Working on HL Conditions

    OpenAIRE

    Vélez-Restrepo J.M.; Toro-Botero F.M.; Suárez-Bustamante F.A.

    2012-01-01

    As an answer to the need for reducing friction losses on bearings, dynamic seals, piston rings, cutting tools and others, a lot of work has been dedicated to mechanical systems study whose surfaces have been textured in a controlled way. Theoretical models and experimental results have shown improvements on the tribological performance of these systems regarding untextured systems, working under the same conditions. This paper presents a numerical model for getting relationships among the ope...

  2. Analysis III analytic and differential functions, manifolds and Riemann surfaces

    CERN Document Server

    Godement, Roger

    2015-01-01

    Volume III sets out classical Cauchy theory. It is much more geared towards its innumerable applications than towards a more or less complete theory of analytic functions. Cauchy-type curvilinear integrals are then shown to generalize to any number of real variables (differential forms, Stokes-type formulas). The fundamentals of the theory of manifolds are then presented, mainly to provide the reader with a "canonical'' language and with some important theorems (change of variables in integration, differential equations). A final chapter shows how these theorems can be used to construct the compact Riemann surface of an algebraic function, a subject that is rarely addressed in the general literature though it only requires elementary techniques. Besides the Lebesgue integral, Volume IV will set out a piece of specialized mathematics towards which the entire content of the previous volumes will converge: Jacobi, Riemann, Dedekind series and infinite products, elliptic functions, classical theory of modular fun...

  3. Surface nanobubbles as a function of gas type

    CERN Document Server

    van Limbeek, Michiel; 10.1021/la2005387

    2011-01-01

    We experimentally investigate the nucleation of surface nanobubbles on PFDTS-coated silicon as a function of the specific gas dissolved in the water. In each case we restrict ourselves to equilibrium conditions ($c=100%$, $T_{liquid} = T_{substrate}$). Not only is nanobubble nucleation a strong function of gas type, but there also exists an optimal system temperature of $\\sim 35-40\\mathrm{^oC}$ where nucleation is maximized, which is weakly dependent on gas type. We also find that contact angle is a function of nanobubble radius of curvature for all gas types investigated. Fitting this data allows us to describe a line tension which is dependent on the type of gas, indicating that the nanobubbles are sat on top of adsorbed gas molecules. The average line tension was $\\tau \\sim -0.8 \\mathrm{nN}$.

  4. Artificial Molecular Machine Immobilized Surfaces: A New Platform To Construct Functional Materials.

    Science.gov (United States)

    Zhang, Qi; Qu, Da-Hui

    2016-06-17

    Artificial molecular machines have received significant attention from chemists because of their unique ability to mimic the behaviors of biological systems. Artificial molecular machines can be easily modified with functional groups to construct new types of functional molecular switches. However, practical applications of artificial molecular machines are still challenging, because the working platform of artificial molecular machines is mostly in solution. Artificial molecular machine immobilized surfaces (AMMISs) are considered a promising platform to construct functional materials. Herein, we provide a minireview of some recent advances of functional AMMISs. The functions of AMMISs are highlighted and strategies for their construction are also discussed. Furthermore, a brief perspective of the development of artificial molecular machines towards functional materials is given.

  5. Bone-like apatite coating on functionalized poly(etheretherketone) surface via tailored silanization layers technique.

    Science.gov (United States)

    Zheng, Yanyan; Xiong, Chengdong; Zhang, Shenglan; Li, Xiaoyu; Zhang, Lifang

    2015-10-01

    Poly(etheretherketone) (PEEK) is a rigid semi-crystalline polymer with outstanding mechanical properties, bone-like stiffness and suitable biocompatibility that has attracted much interest as a biomaterial for orthopedic and dental implants. However, the bio-inert surface of PEEK limits its biomedical applications when direct osteointegration between the implants and the host tissue is desired. In this work, -PO4H2, -COOH and -OH groups were introduced on the PEEK surface by further chemical treatments of the vinyl-terminated silanization layers formed on the hydroxylation-pretreated PEEK surface. Both the surface-functionalized and pristine specimens were characterized by X-ray photoelectron spectroscopy (XPS), attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy and water contact angle measurements. When placed in 1.5 strength simulated body fluid (SBF) solution, apatite was observed to form uniformly on the functionalized PEEK surface and firmly attach to the substrate. The characterized results demonstrated that the coating was constituted by poorly crystallized bone-like apatite and the effect of surface functional groups on coating formation was also discussed in detail. In addition, in vitro biocompatibility of PEEK, in terms of pre-osteoblast cell (MC3T3-E1) attachment, spreading and proliferation, was remarkably enhanced by the bone-like apatite coating. Thus, this study provides a method to enhance the bioactivity of PEEK and expand its applications in orthopedic and dental implants.

  6. Light-induced reversible modification of the work function of a new perfluorinated biphenyl azobenzene chemisorbed on Au (111)

    Science.gov (United States)

    Masillamani, Appan Merari; Osella, Silvio; Liscio, Andrea; Fenwick, Oliver; Reinders, Federica; Mayor, Marcel; Palermo, Vincenzo; Cornil, Jérôme; Samorì, Paolo

    2014-07-01

    We describe the synthesis of a novel biphenyl azobenzene derivative exhibiting: (i) a protected thiol anchoring group in the α-position to readily form self-assembled monolayers (SAMs) on Au surfaces; and (ii) a terminal perfluorinated benzene ring in the ω-position to modify the surface properties. The design of this molecule ensured both an efficient in situ photoswitching between the trans and cis isomers when chemisorbed on Au(111), due to the presence of a biphenyl bridge between the thiol protected anchoring group and the azo dye, and a significant variation of the work function of the SAM in the two isomeric states, induced by the perfluorinated phenyl head group. By exploiting the light responsive nature of the chemisorbed molecules, it is possible to dynamically modify in situ the work function of the SAM-covered electrode, as demonstrated both experimentally and by quantum-chemical calculations, revealing changes in work function up to 220 meV. These findings are relevant for tuning the work function of metallic electrodes, and hence to dynamically modulate charge injection at metal-semiconductor interfaces for organic opto-electronic applications.We describe the synthesis of a novel biphenyl azobenzene derivative exhibiting: (i) a protected thiol anchoring group in the α-position to readily form self-assembled monolayers (SAMs) on Au surfaces; and (ii) a terminal perfluorinated benzene ring in the ω-position to modify the surface properties. The design of this molecule ensured both an efficient in situ photoswitching between the trans and cis isomers when chemisorbed on Au(111), due to the presence of a biphenyl bridge between the thiol protected anchoring group and the azo dye, and a significant variation of the work function of the SAM in the two isomeric states, induced by the perfluorinated phenyl head group. By exploiting the light responsive nature of the chemisorbed molecules, it is possible to dynamically modify in situ the work function of

  7. Determination of work functions near melting points of refractory metals by using a direct-current arc

    Science.gov (United States)

    Gordon, W. A.; Chapman, G. B., II

    1972-01-01

    Effective work functions of refractory metals at temperatures near their melting points were determined by using a direct-current arc. A metal wire connected as the cathode was melted by striking an arc discharge in an argon atmosphere. A melted sphere was formed with a definite emitting area which was calculated from the sphere diameter measured after terminating the arc. Effective work functions were calculated from the Richardson-Dushman equation by using this emission area. The procedure is experimentally advantageous because surface cleanliness of the specimen is not critical, high vacuum is not required, and the anode-cathode spacing is not critical.

  8. Predictors of impaired work functioning in employees with major depression in remission

    NARCIS (Netherlands)

    Vries, G. de; Koeter, M.W.; Nieuwenhuijsen, K.; Hees, H.L.; Schene, A.H.

    2015-01-01

    OBJECTIVES: This study aims to (i) assess work functioning in employees returning to work with a major depression in remission, (ii) study the predictors of impaired work functioning. METHODS: Participants diagnosed with major depressive disorder (MDD), on long term sick leave (mean 27 weeks) and

  9. Predictors of impaired work functioning in employees with major depression in remission

    NARCIS (Netherlands)

    Vries, G. de; Koeter, M.W.; Nieuwenhuijsen, K.; Hees, H.L.; Schene, A.H.

    2015-01-01

    OBJECTIVES: This study aims to (i) assess work functioning in employees returning to work with a major depression in remission, (ii) study the predictors of impaired work functioning. METHODS: Participants diagnosed with major depressive disorder (MDD), on long term sick leave (mean 27 weeks) and tr

  10. Work functioning in persons with depressive and anxiety disorders : The role of specific psychopathological characteristics

    NARCIS (Netherlands)

    Plaisier, I.; Beekman, A.T.F.; de Graaf, R.; Smit, J. H.; van Dyck, R.; Penninx, Brenda

    Background: Depressive and anxiety disorders affect work functioning and cause high labour costs. Aims: To examine and compare psychopathological characteristics of depressive and anxiety disorders in their effect on work functioning. Method: In 1876 working participants of the Netherlands Study of

  11. Work functioning in persons with depressive and anxiety disorders : The role of specific psychopathological characteristics

    NARCIS (Netherlands)

    Plaisier, I.; Beekman, A.T.F.; de Graaf, R.; Smit, J. H.; van Dyck, R.; Penninx, Brenda

    2010-01-01

    Background: Depressive and anxiety disorders affect work functioning and cause high labour costs. Aims: To examine and compare psychopathological characteristics of depressive and anxiety disorders in their effect on work functioning. Method: In 1876 working participants of the Netherlands Study of

  12. Functionalization of silicon nanowire surfaces with metal-organic frameworks

    KAUST Repository

    Liu, Nian

    2011-12-28

    Metal-organic frameworks (MOFs) and silicon nanowires (SiNWs) have been extensively studied due to their unique properties; MOFs have high porosity and specific surface area with well-defined nanoporous structure, while SiNWs have valuable one-dimensional electronic properties. Integration of the two materials into one composite could synergistically combine the advantages of both materials and lead to new applications. We report the first example of a MOF synthesized on surface-modified SiNWs. The synthesis of polycrystalline MOF-199 (also known as HKUST-1) on SiNWs was performed at room temperature using a step-by-step (SBS) approach, and X-ray photoelectron spectroscopy, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and energy dispersive spectroscopy elemental mapping were used to characterize the material. Matching of the SiNW surface functional groups with the MOF organic linker coordinating groups was found to be critical for the growth. Additionally, the MOF morphology can by tuned by changing the soaking time, synthesis temperature and precursor solution concentration. This SiNW/MOF hybrid structure opens new avenues for rational design of materials with novel functionalities. © 2011 Tsinghua University Press and Springer-Verlag Berlin Heidelberg.

  13. Molecular Approaches to Functionalization of Dental Implant Surfaces

    Directory of Open Access Journals (Sweden)

    Angelina O. Zekiy

    2015-12-01

    Full Text Available The present review examines several approaches to improve properties of dental implants by modifying their bioactive surfaces (functionalization using the techniques of molecular transplantation. The first group of functional ligands is designed to enhance osseointegration of implants, it includes growth factors, promoting the formation and bone remodeling: bone morphogenetic proteins (BMPs, platelet-derived growth factor (PDGF, fibroblast growth factor (FGF and their combinations with each other, and several other ones. The second group of bioactive molecules does not directly stimulate bone formation, but it promotes osteoblast seeding on the implant surface due to the adhesive properties, thus accelerating osseointegration. Finally, the third group of substances used to increase the antibacterial properties of coatings, thereby reducing the formation of bacterial film on the implant surface and the risk of inflammatory rejection of the implant. Key issues of using biofunctional coatings, despite their obvious promise today still are relatively high cost, difficulties of controlling properties and its storage between the fabrication and installation of implants in the bone of the recipient.

  14. Electrochemically polymerized conjugated polymer films: Stability improvement and surface functionalization

    Science.gov (United States)

    Wei, Bin

    Conjugated polymers have been widely used in various applications including organic solar cells, electrochromic devices, chemical sensors, and biomedical devices. Poly(3,4-ethylenedioxythiophene) (PEDOT) and its derivatives have received considerable interest because of their low oxidation potential, relatively high chemical stability, and high conductivity. Electrochemical deposition is a convenient method for precisely fabricating conjugated polymer thin films. Here, we report the stability improvement and surface functionalization of electrochemically polymerized PEDOT films. The long-term performance of PEDOT coatings is limited by their relatively poor stability on various inorganic substrates. Two different methods were used to improve the stability of PEDOT coatings, one involved using carboxylic acid functionalized EDOT (EDOT-acid) as adhesion promoter. EDOT-acid molecules were chemically bonded onto activated metal oxide substrates via chemisorption. PEDOT was then polymerized onto the EDOT-acid modified substrates, forming covalently bonded coatings. An aggressive ultrasonication test confirmed the significantly improved adhesion of the PEDOT films on electrodes with EDOT-acid treatment over those without treatment. The other method was to use an octa-ProDOT-functionalized POSS derivative (POSSProDOT) as cross-linker. PEDOT copolymer films were electrochemically deposited with various concentrations of POSS-ProDOT. The optical, morphological and electrochemical properties of the copolymer films could be systematically tuned with the incorporation of POSS-ProDOT. Significantly enhanced electrochemical and mechanical stability of the copolymers were observed at intermediate levels of POSS-ProDOT content (3.1 wt%) via chronic stimulation tests. Surface functionalization of conducting polymer films provides a potential means for systematically tailoring their chemical and physical properties. We have synthesized, polymerized and characterized a dialkene-functionalized

  15. Work function determination of promising electrode materials for thermionic converters

    Science.gov (United States)

    Jacobson, D.

    1977-01-01

    Work performed on this contract was primarily for the evaluation of selected electrode materials for thermionic energy converters. The original objective was to characterize selected nickel based superalloys up to temperatures of 1400 K. It was found that an early selection, Inconel 800 produced a high vapor pressure which interfered with the vacuum emission measurements. The program then shifted to two other areas. The first area was to obtain emission from the superalloys in a cesiated atmosphere. The cesium plasma helps to suppress the vaporization interference. The second area involved characterization of the Lanthanum-Boron series as thermionic emitters. These final two areas resulted in three journal publications which are attached to this report.

  16. A comparative study of atomic oxygen adsorption at Pd surfaces from Density Functional Theory

    Science.gov (United States)

    Bukas, Vanessa J.; Reuter, Karsten

    2017-04-01

    Based on density functional theory, we present a detailed investigation into the on-surface adsorption of atomic oxygen at all three low-index Pd facets in the low-coverage regime. Relying on one consistent computational framework allows for a systematic comparison with respect to surface symmetry, while discerning trends in the adsorption geometries, energies, work functions, and electron densities. We overall find a persisting degree of O-Pd hybridization that is accompanied by minimal charge transfer from the substrate to the adsorbate, thereby resulting in comparable binding energies and diffusion barriers at the three surfaces. Small differences in reactivity are nevertheless reflected in subtle variations of the underlying electronic structure which do not, however, follow the expected order according to atom packing density.

  17. Surface electromyographic amplitude-to-work ratios during isokinetic and isotonic muscle actions.

    Science.gov (United States)

    Purkayastha, Sushmita; Cramer, Joel T; Trowbridge, Cynthia A; Fincher, A Louise; Marek, Sarah M

    2006-01-01

    Isokinetic and isotonic resistance training exercises are commonly used to increase strength during musculoskeletal rehabilitation programs. Our study was designed to examine the efficacy of isokinetic and isotonic muscle actions using surface electromyographic (EMG) amplitude-to-work ratios (EMG/WK) and to extend previous findings to include a range of isokinetic velocities and isotonic loads. To examine work (WK), surface EMG amplitude, and EMG/WK during concentric-only maximal isokinetic muscle actions at 60, 120, 180, 240, and 300 degrees /s and isotonic muscle actions at 10%, 20%, 30%, 40%, and 50% of the maximal voluntary isometric contraction (MVIC) torque during leg extension exercises. A randomized, counterbalanced, cross-sectional, repeated-measures design. A university-based human muscle physiology research laboratory. Ten women (mean age = 22.0 +/- 2.6 years) and 10 men (mean age = 20.8 +/- 1.7 years) who were apparently healthy and recreationally active. Using the dominant leg, each participant performed 5 maximal voluntary concentric isokinetic leg extension exercises at randomly ordered angular velocities of 60, 120, 180, 240, and 300 degrees /s and 5 concentric isotonic leg extension exercises at randomly ordered loads of 10%, 20%, 30%, 40%, and 50% of the isometric MVIC. Work was recorded by a Biodex System 3 dynamometer, and surface EMG was recorded from the superficial quadriceps femoris muscles (vastus lateralis, rectus femoris, and vastus medialis) during the testing and was normalized to the MVIC. The EMG/WK ratios were calculated as the quotient of EMG amplitude (muVrms) and WK (J) during the concentric phase of each exercise. Isotonic EMG/WK remained unchanged ( P > .05) from 10% to 50% MVIC, but isokinetic EMG/WK increased ( P Isotonic EMG/WK was greater ( P .05) between 20% MVIC versus 240 degrees /s or 10% MVIC versus 300 degrees /s. An 18% decrease in active range of motion was seen for the isotonic muscle actions, from 10% to 50% MVIC

  18. Influence of the work of adhesion on the dynamic wetting of chemically heterogeneous surfaces.

    Science.gov (United States)

    Ray, Santanu; Sedev, Rossen; Priest, Craig; Ralston, John

    2008-11-18

    The velocity dependence of the dynamic contact angle for a glycerol-water mixture wetting two different chemically heterogeneous surfaces (mixed thiols on gold and partially methylated titania, 16 samples in all) was studied. The molecular kinetic theory (MKT) of wetting was used to interpret the dynamic contact angle data. The equilibrium displacement frequency ( K 0) was predominantly determined by the viscous contribution from the bulk liquid, with a minor contribution from the surface. The mean distance between surface sites (lambda) decreased with increasing work of adhesion. The contact line friction coefficient zeta 0 was found to vary exponentially with the work of adhesion, enabling the unit flow volume of the liquid to be obtained.

  19. Surface functional groups and redox property of modified activated carbons

    Institute of Scientific and Technical Information of China (English)

    Zhang Xianglan; Deng Shengfu; Liu Qiong; Zhang Yan; Cheng Lei

    2011-01-01

    A series of activated carbons (ACs) were prepared using HNO3, H2O2 and steam as activation agents with the aim to introduce functional groups to carbon surface in the ACs preparation process. The effects of concentration of activation agent, activation time on the surface functional groups and redox property of ACs were characterized by Temperature Program Desorption (TPD) and Cyclic Voitammetry (CV). Results showed that lactone groups of ACs activated by HNO3 increase with activation time, and the carboxyl groups increase with the concentration of HNO3. Carbonyl/quinine groups of ACs activated by H2O2 increase with the activation time and the concentration of H2O2, although the acidic groups decrease with the concentration of H2O2. The redox property reflected by CV at 0 and 0.5 V is different with any kinds of oxygen functional groups characterized by TPD, but it is consistent with the SO2 catalytic oxidization/oxidation properties indicated by TPR.

  20. Orbifold Riemann surfaces: Teichmueller spaces and algebras of geodesic functions

    Energy Technology Data Exchange (ETDEWEB)

    Mazzocco, Marta [Loughborough University, Loughborough (United Kingdom); Chekhov, Leonid O [Institute for Theoretical and Experimental Physics (Russian Federation State Scientific Center), Moscow (Russian Federation)

    2009-12-31

    A fat graph description is given for Teichmueller spaces of Riemann surfaces with holes and with Z{sub 2}- and Z{sub 3}-orbifold points (conical singularities) in the Poincare uniformization. The corresponding mapping class group transformations are presented, geodesic functions are constructed, and the Poisson structure is introduced. The resulting Poisson algebras are then quantized. In the particular cases of surfaces with n Z{sub 2}-orbifold points and with one and two holes, the respective algebras A{sub n} and D{sub n} of geodesic functions (classical and quantum) are obtained. The infinite-dimensional Poisson algebra D{sub n}, which is the semiclassical limit of the twisted q-Yangian algebra Y'{sub q}(o{sub n}) for the orthogonal Lie algebra o{sub n}, is associated with the algebra of geodesic functions on an annulus with n Z{sub 2}-orbifold points, and the braid group action on this algebra is found. From this result the braid group actions are constructed on the finite-dimensional reductions of this algebra: the p-level reduction and the algebra D{sub n}. The central elements for these reductions are found. Also, the algebra D{sub n} is interpreted as the Poisson algebra of monodromy data of a Frobenius manifold in the vicinity of a non-semisimple point. Bibliography: 36 titles.

  1. Polymer Brushes as Functional, Patterned Surfaces for Nanobiotechnology.

    Science.gov (United States)

    Welch, M Elizabeth; Xu, Youyong; Chen, Hongjun; Smith, Norah; Tague, Michele E; Abruña, Héctor D; Baird, Barbara; Ober, Christopher K

    2013-01-01

    Polymer brushes have many desirable characteristics such as the ability to tether molecules to a substrate or change the properties of a surface. Patterning of polymer films has been an area of great interest due to the broad range of applications including bio-related and medicinal research. Consequently, we have investigated patterning techniques for polymer brushes which allow for two different functionalities on the same surface. This method has been applied to a biosensor device which requires both polymer brushes and a photosensitizer to be polymerized on a patterned gold substrate. Additionally, the nature of patterned polymer brushes as removable thin films was explored. An etching process has enabled us to lift off very thin membranes for further characterization with the potential of using them as Janus membranes for biological applications.

  2. Plasma functionalized surface of commodity polymers for dopamine detection

    Science.gov (United States)

    Fabregat, Georgina; Osorio, Joaquin; Castedo, Alejandra; Armelin, Elaine; Buendía, Jorge J.; Llorca, Jordi; Alemán, Carlos

    2017-03-01

    We have fabricated potentially generalizable sensors based on polymeric-modified electrodes for the electrochemical detection of dopamine. Sensitive and selective sensors have been successfully obtained by applying a cold-plasma treatment during 1-2 min not only to conducting polymers but also to electrochemically inert polymers, such as polyethylene, polypropylene, polyvinylpyrrolidone, polycaprolactone and polystyrene. The effects of the plasma in the electrode surface activation, which is an essential requirement for the dopamine detection when inert polymers are used, have been investigated using X-ray photoelectron spectroscopy. Results indicate that exposure of polymer-modified electrodes to cold-plasma produces the formation of a large variety of reactive species adsorbed on the electrode surface, which catalyse the dopamine oxidation. With this technology, which is based on the application of a very simple physical functionalization, we have defined a paradox-based paradigm for the fabrication of electrochemical sensors by using inert and cheap plastics.

  3. Bionanohybrid based on bioplastic and surface-functionalized carbon nanotubes.

    Science.gov (United States)

    Singh, Ravina; Ray, Suprakas Sinha

    2010-12-01

    A bionanohybrid consisting of biodegradable/biocompatible poly(butylene succinate) (PBS) and surface-oxidized carbon nanotubes (o-CNTs) was prepared via melt-mixing method. The inherent properties of PBS were concurrently improved by the incorporation of a small amount of o-CNTs. For example, at room temperature, elongation at break increased from approximately 21.2% for pure PBS to approximately 55.1% for the nanohybrid and an increase of about approximately 150% in the value of toughness with moderate improvement in tensile modulus and strength. The dynamic mechanical properties of PBS also increased significantly after nanocomposite formation with o-CNTs. Electron microscopy and Raman spectroscopy were used to investigate the mechanical properties and improvement mechanism of surface-functionalized o-CNTs containing PBS nanohybrid.

  4. Influence of Conditioned Surface Textures on Plain Journal Bearing Performance Working on HL Conditions

    Directory of Open Access Journals (Sweden)

    Vélez-Restrepo J.M.

    2012-07-01

    Full Text Available As an answer to the need for reducing friction losses on bearings, dynamic seals, piston rings, cutting tools and others, a lot of work has been dedicated to mechanical systems study whose surfaces have been textured in a controlled way. Theoretical models and experimental results have shown improvements on the tribological performance of these systems regarding untextured systems, working under the same conditions. This paper presents a numerical model for getting relationships among the operational conditions (load, speed, and dynamic viscosity, the minimum lubricate film thickness, the friction coefficient and the conditioned micro-topography of a plain sliding bearing working under a hydrodynamic regime. Moreover, regarding other similar works the constructed model allows studying the combined effect of the micro-wedges that work as micro-bearings, and the typical convergent macro-wedge of these study elements.

  5. Swarm formation control utilizing elliptical surfaces and limiting functions.

    Science.gov (United States)

    Barnes, Laura E; Fields, Mary Anne; Valavanis, Kimon P

    2009-12-01

    In this paper, we present a strategy for organizing swarms of unmanned vehicles into a formation by utilizing artificial potential fields that were generated from normal and sigmoid functions. These functions construct the surface on which swarm members travel, controlling the overall swarm geometry and the individual member spacing. Nonlinear limiting functions are defined to provide tighter swarm control by modifying and adjusting a set of control variables that force the swarm to behave according to set constraints, formation, and member spacing. The artificial potential functions and limiting functions are combined to control swarm formation, orientation, and swarm movement as a whole. Parameters are chosen based on desired formation and user-defined constraints. This approach is computationally efficient and scales well to different swarm sizes, to heterogeneous systems, and to both centralized and decentralized swarm models. Simulation results are presented for a swarm of 10 and 40 robots that follow circle, ellipse, and wedge formations. Experimental results are included to demonstrate the applicability of the approach on a swarm of four custom-built unmanned ground vehicles (UGVs).

  6. Protein function annotation by local binding site surface similarity.

    Science.gov (United States)

    Spitzer, Russell; Cleves, Ann E; Varela, Rocco; Jain, Ajay N

    2014-04-01

    Hundreds of protein crystal structures exist for proteins whose function cannot be confidently determined from sequence similarity. Surflex-PSIM, a previously reported surface-based protein similarity algorithm, provides an alternative method for hypothesizing function for such proteins. The method now supports fully automatic binding site detection and is fast enough to screen comprehensive databases of protein binding sites. The binding site detection methodology was validated on apo/holo cognate protein pairs, correctly identifying 91% of ligand binding sites in holo structures and 88% in apo structures where corresponding sites existed. For correctly detected apo binding sites, the cognate holo site was the most similar binding site 87% of the time. PSIM was used to screen a set of proteins that had poorly characterized functions at the time of crystallization, but were later biochemically annotated. Using a fully automated protocol, this set of 8 proteins was screened against ∼60,000 ligand binding sites from the PDB. PSIM correctly identified functional matches that predated query protein biochemical annotation for five out of the eight query proteins. A panel of 12 currently unannotated proteins was also screened, resulting in a large number of statistically significant binding site matches, some of which suggest likely functions for the poorly characterized proteins.

  7. Functional MRI in Awake Dogs Predicts Suitability for Assistance Work

    Science.gov (United States)

    Berns, Gregory S.; Brooks, Andrew M.; Spivak, Mark; Levy, Kerinne

    2017-03-01

    The overall goal of this work was to measure the efficacy of fMRI for predicting whether a dog would be a successful service dog. The training and imaging were performed in 49 dogs entering service training at 17–21 months of age. 33 dogs completed service training and were matched with a person, while 10 were released for behavioral reasons (4 were selected as breeders and 2 were released for medical reasons.) After 2 months of training, fMRI responses were measured while each dog observed hand signals indicating either reward or no reward and given by both a familiar handler and a stranger. Using anatomically defined ROIs in the caudate, amygdala, and visual cortex, we developed a classifier based on the dogs’ subsequent training outcomes. The classifier had a positive predictive value of 94% and a negative predictive value of 67%. The area under the ROC curve was 0.91 (0.80 with 4-fold cross-validation, P = 0.01), indicating a significant predictive capability. The magnitude of response in the caudate was positively correlated with a successful outcome, while the response in the amygdala depended on the interaction with the visual cortex during the stranger condition and was negatively correlated with outcome (higher being associated with failure). These results suggest that, as indexed by caudate activity, successful service dogs generalize associations to hand signals regardless who gives them but without excessive arousal as measured in the amygdala.

  8. Functional MRI in Awake Dogs Predicts Suitability for Assistance Work

    Science.gov (United States)

    Berns, Gregory S.; Brooks, Andrew M.; Spivak, Mark; Levy, Kerinne

    2017-01-01

    The overall goal of this work was to measure the efficacy of fMRI for predicting whether a dog would be a successful service dog. The training and imaging were performed in 49 dogs entering service training at 17–21 months of age. 33 dogs completed service training and were matched with a person, while 10 were released for behavioral reasons (4 were selected as breeders and 2 were released for medical reasons.) After 2 months of training, fMRI responses were measured while each dog observed hand signals indicating either reward or no reward and given by both a familiar handler and a stranger. Using anatomically defined ROIs in the caudate, amygdala, and visual cortex, we developed a classifier based on the dogs’ subsequent training outcomes. The classifier had a positive predictive value of 94% and a negative predictive value of 67%. The area under the ROC curve was 0.91 (0.80 with 4-fold cross-validation, P = 0.01), indicating a significant predictive capability. The magnitude of response in the caudate was positively correlated with a successful outcome, while the response in the amygdala depended on the interaction with the visual cortex during the stranger condition and was negatively correlated with outcome (higher being associated with failure). These results suggest that, as indexed by caudate activity, successful service dogs generalize associations to hand signals regardless who gives them but without excessive arousal as measured in the amygdala. PMID:28266550

  9. Matching physical work demands with functional capacity in healthy workers : Can it be more efficient?

    NARCIS (Netherlands)

    Soer, Remko; Hollak, Niek; Deijs, Marieke; van der Woude, Lucas H.; Reneman, Michiel F.

    2014-01-01

    Objectives: To determine if functional capacity (FC) and physical work demands can be matched and to determine the validity of normative values for FC related to physical work demands as a screening instrument for work ability. Methods: Forty healthy working subjects were included in this study. Sub

  10. Electron work function-a promising guiding parameter for material design.

    Science.gov (United States)

    Lu, Hao; Liu, Ziran; Yan, Xianguo; Li, Dongyang; Parent, Leo; Tian, Harry

    2016-04-14

    Using nickel added X70 steel as a sample material, we demonstrate that electron work function (EWF), which largely reflects the electron behavior of materials, could be used as a guide parameter for material modification or design. Adding Ni having a higher electron work function to X70 steel brings more "free" electrons to the steel, leading to increased overall work function, accompanied with enhanced e(-)-nuclei interactions or higher atomic bond strength. Young's modulus and hardness increase correspondingly. However, the free electron density and work function decrease as the Ni content is continuously increased, accompanied with the formation of a second phase, FeNi3, which is softer with a lower work function. The decrease in the overall work function corresponds to deterioration of the mechanical strength of the steel. It is expected that EWF, a simple but fundamental parameter, may lead to new methodologies or supplementary approaches for metallic materials design or tailoring on a feasible electronic base.

  11. Bacteria-mimicking nanoparticle surface functionalization with targeting motifs

    Science.gov (United States)

    Lai, Mei-Hsiu; Clay, Nicholas E.; Kim, Dong Hyun; Kong, Hyunjoon

    2015-04-01

    In recent years, surface modification of nanocarriers with targeting motifs has been explored to modulate delivery of various diagnostic, sensing and therapeutic molecular cargo to desired sites of interest in in vitro bioengineering platforms and in vivo pathologic tissue. However, most surface functionalization approaches are often plagued by complex chemical modifications and effortful purifications. To resolve such challenges, this study demonstrates a unique method to immobilize antibodies that can act as targeting motifs on the surfaces of nanocarriers, inspired by a process that bacteria use for immobilization of the host's antibodies. We hypothesized that alkylated Staphylococcus aureus protein A (SpA) would self-assemble with micelles and subsequently induce stable coupling of antibodies to the micelles. We examined this hypothesis by using poly(2-hydroxyethyl-co-octadecyl aspartamide) (PHEA-g-C18) as a model polymer to form micelles. The self-assembly between the micelles and alkylated SpA became more thermodynamically favorable by increasing the degree of substitution of octadecyl chains to PHEA-g-C18, due to a positive entropy change. Lastly, the mixing of SpA-PA-coupled micelles with antibodies resulted in the coating of micelles with antibodies, as confirmed with a fluorescence resonance energy transfer (FRET) assay. The micelles coated with antibodies to VCAM-1 or integrin αv displayed a higher binding affinity to substrates coated with VCAM-1 and integrin αvβ3, respectively, than other controls, as evaluated with surface plasmon resonance (SPR) spectroscopy and a circulation-simulating flow chamber. We envisage that this bacteria-inspired protein immobilization approach will be useful to improve the quality of targeted delivery of nanoparticles, and can be extended to modify the surface of a wide array of nanocarriers.In recent years, surface modification of nanocarriers with targeting motifs has been explored to modulate delivery of various

  12. Holographic partition functions and phases for higher genus Riemann surfaces

    Science.gov (United States)

    Maxfield, Henry; Ross, Simon F.; Way, Benson

    2016-06-01

    We describe a numerical method to compute the action of Euclidean saddle points for the partition function of a two-dimensional holographic CFT on a Riemann surface of arbitrary genus, with constant curvature metric. We explicitly evaluate the action for the saddles for genus two and map out the phase structure of dominant bulk saddles in a two-dimensional subspace of the moduli space. We discuss spontaneous breaking of discrete symmetries, and show that the handlebody bulk saddles always dominate over certain non-handlebody solutions.

  13. Lp Estimates of Rough Maximal Functions Along Surfaces with Applications

    Institute of Scientific and Technical Information of China (English)

    Ahmad AL-SALMAN; Abdulla M. JARRAH

    2016-01-01

    In this paper, we study the Lp mapping properties of certain class of maximal oscillatory singular integral operators. We prove a general theorem for a class of maximal functions along surfaces. As a consequence of such theorem, we establish the Lp boundedness of various maximal oscillatory singular integrals provided that their kernels belong to the natural space L log L(Sn−1). Moreover, we highlight some additional results concerning operators with kernels in certain block spaces. The results in this paper substantially improve previously known results.

  14. Enzymes go big: surface hydrolysis and functionalization of synthetic polymers.

    Science.gov (United States)

    Guebitz, Georg M; Cavaco-Paulo, Artur

    2008-01-01

    Enzyme technology has progressed from the biotransformation of small substrates to biotransformation of synthetic polymers. Important breakthroughs have been the isolation and design of novel enzymes with enhanced activity on synthetic polymer substrates. These were made possible by efficient screening procedures and genetic engineering approaches based on an in-depth understanding of the mechanisms of enzymes on synthetic polymers. Enhancement of the hydrophilicity of synthetic polymers is a key requirement for many applications, ranging from electronics to functional textile production. This review focuses on enzymes that hydrolyse polyalkyleneterephthalates, polyamides or polyacrylonitriles, specifically on the polymer surface thereby replacing harsh chemical processes currently used for hydrophilisation.

  15. Holographic partition functions and phases for higher genus Riemann surfaces

    CERN Document Server

    Maxfield, Henry; Way, Benson

    2016-01-01

    We describe a numerical method to compute the action of Euclidean saddlepoints for the partition function of a two-dimensional holographic CFT on a Riemann surface of arbitrary genus, with constant curvature metric. We explicitly evaluate the action for the saddles for genus two and map out the phase structure of dominant bulk saddles in a two-dimensional subspace of the moduli space. We discuss spontaneous breaking of discrete symmetries, and show that the handlebody bulk saddles always dominate over certain non-handlebody solutions.

  16. Slippery versus slip resistant work surfaces: The background for a regulatory definition

    Science.gov (United States)

    Miller, J. M.

    1983-02-01

    There has been over fifty years of scattered research into the areas of walking/working surface slipperiness and coefficient of friction (COF) measurement. In spite of this research, numerous standards address slip/fail type accidents only in terms of requiring surfaces to be qualitatively useful in providing guidelines for establishing quantitative criteria for "slippery' vs. "slip resistant' combinations of surface, shoe, task, and contaminant conditions. Recommendations applicable to standards making organizations are made. Among them are: (1) changing legally inappropriate descriptor terms such as "nonslip' to "slip resistant'; and (2) defining "slippery' vs. "slip resistant' in terms of quantitative COF values (i.e., for persons walking unloaded on level surfaces a COF of 0.5 would be a reasonable standard).

  17. 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.

  18. 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.

  19. Fabrication of Bioactive Surfaces by Functionalization of Electroactive and Surface-Active Block Copolymers

    Directory of Open Access Journals (Sweden)

    Omotunde Olubi

    2014-08-01

    Full Text Available Biofunctional block copolymers are becoming increasingly attractive materials as active components in biosensors and other nanoscale electronic devices. We have described two different classes of block copolymers with biofuctional properties. Biofunctionality for block copolymers is achieved through functionalization with appropriate biospecific ligands. We have synthesized block copolymers of electroactive poly(3-decylthiophene and 2-hydroxyethyl methacrylate by atom transfer radical polymerization. The block copolymers were functionalized with the dinitrophenyl (DNP groups, which are capable of binding to Immunoglobulin E (IgE on cell surfaces. The block copolymers were shown to be redox active. Additionally, the triblock copolymer of α, ω-bi-biotin (poly(ethylene oxide-b-poly (styrene-b-poly(ethylene oxide was also synthesized to study their capacity to bind fluorescently tagged avidin. The surface-active property of the poly(ethylene oxide block improved the availability of the biotin functional groups on the polymer surfaces. Fluorescence microscopy observations confirm the specific binding of biotin with avidin.

  20. In Situ Measurement of Surface Functional Groups on Silica Nanoparticles Using Solvent Relaxation Nuclear Magnetic Resonance.

    Science.gov (United States)

    Yuan, Li; Chen, Lan; Chen, Xiaohong; Liu, Renxiao; Ge, Guanglu

    2017-09-05

    In situ analysis and study on the surface of nanoparticles (NPs) is a key to obtain their important physicochemical properties for the subsequent applications. Of them, most works focus on the qualitative characterization whereas quantitative analysis and measurement on the NPs under their storage and usage conditions is still a challenge. In order to cope with this challenge, solvation relaxation-based nuclear magnetic resonance (NMR) technology has been applied to measure the wet specific surface area and, therefore, determine the number of the bound water molecules on the surface of silica NPs in solution and the hydrophilic groups of various types grafted on the surface of the NPs. By changing the surface functional group on silica particles, the fine distinction for the solvent-particle interaction with different surface group can be quantitatively differentiated by measuring the number of water molecules absorbed on the surface. The results show that the number of the surface hydroxyl, amine, and carboxyl group per nm(2) is 4.0, 3.7, and 2.3, respectively, for the silica particles with a diameter of 203 nm. The method reported here is the first attempt to determine in situ the number of bound solvent molecules and any solvophilic groups grafted on nanoparticles.

  1. Work function of bulk-insulating topological insulator Bi2-xSbxTe3-ySey

    Science.gov (United States)

    Takane, Daichi; Souma, Seigo; Sato, Takafumi; Takahashi, Takashi; Segawa, Kouji; Ando, Yoichi

    2016-08-01

    Recent discovery of bulk insulating topological insulator (TI) Bi2-xSbxTe3-ySey paved a pathway toward practical device application of TIs. For realizing TI-based devices, it is necessary to contact TIs with a metal. Since the band-bending at the interface dominates the character of devices, knowledge of TIs' work function is of essential importance. We have determined the compositional dependence of the work function in Bi2-xSbxTe3-ySey by high-resolution photoemission spectroscopy. The obtained work-function values (4.95-5.20 eV) track the energy shift of the surface chemical potential seen by angle-resolved photoemission spectroscopy. The present result serves as a useful guide for developing TI-based electronic devices.

  2. 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.

  3. In Situ Characterization of the Local Work Function along Individual Free Standing Nanowire by Electrostatic Deflection.

    Science.gov (United States)

    Chen, Yicong; Zhao, Chengchun; Huang, Feng; Zhan, Runze; Deng, Shaozhi; Xu, Ningsheng; Chen, Jun

    2016-02-17

    In situ characterization of the work function of quasi one dimensional nanomaterials is essential for exploring their applications. Here we proposed to use the electrostatic deflection induced by work function difference between nanoprobe and nanowire for in situ measuring the local work function along a free standing nanowire. The physical mechanism for the measurement was discussed in details and a parabolic relationship between the deflection and the potential difference was derived. As a demonstration, measurement of the local work functions on the tip and the sidewall of a ZnO nanowire with Au catalyst at its end and a LaB6 nanowire have been achieved with good accuracy.

  4. Surface reactivity of Ge[111] for organic functionalization by means of a radical-initiated reaction: A DFT study

    Energy Technology Data Exchange (ETDEWEB)

    Rubio-Pereda, Pamela, E-mail: rubio.pereda@gmail.com [Centro de Investigación Científica y de Educación Superior de Ensenada 3918, Código Postal 22860, Ensenada, Baja California (Mexico); Takeuchi, Noboru, E-mail: takeuchi@cnyn.unam.mx [Centro de Nanociencias y Nanotecnología, Universidad Nacional Autónoma de México, Apartado Postal 14, Código Postal 22800, Ensenada, Baja California (Mexico)

    2016-08-30

    Highlights: • The surface reactivity of the Ge [111] surface is studied with DFT for the attachment of organic molecules by means of a radical-initiated reaction. • A hydrogen vacancy in the hydrogen terminated Ge [111] surface exhibits an accumulation of charge and electron pairing. • These characteristics make the hydrogen vacancy less reactive for the attachment of unsaturated organic molecules. • The adsorption of acetylene is probable to occur while the adsorption of ethylene and styrene is substantially less probable to occur. • The hydrogen terminated Ge [111] surface is found to be less reactive than its two-dimensional analogue, the hydrogen-terminated germanene. - Abstract: The study of interfacial chemistry at semiconductor surfaces has become an important area of research. Functionalities such as molecular recognition, biocompatibility of surfaces, and molecular computing, could be achieved by the combinations of organic chemistry with the semiconductor technology. One way to accomplish this goal is by means of organic functionalization of semiconductor surfaces such as the bulk-terminated germanium surfaces, more specifically the Ge[111]. In this work, we theoretically study, by applying density functional theory, the surface reactivity of the bulk-terminated Ge[111] surface for organic functionalization by means of a radical-initiated reaction of unsaturated molecules such as acetylene, ethylene and styrene with a hydrogen vacancy on a previously hydrogen-terminated Ge[111] surface. Results derived from this work are compared with those obtained in our previous calculations on the germanene surface, following the same chemical route. Our calculations show an accumulation of electronic charge at the H-vacancy having as a result electron pairing due to strong lattice-electron coupling and therefore a diminished surface reactivity. Calculation of the transition states for acetylene and ethylene indicates that the surface reactivity of the

  5. Evaluation of working practices and surface contamination with antineoplastic drugs in outpatient oncology health care settings.

    Science.gov (United States)

    Kopp, Bettina; Schierl, Rudolf; Nowak, Dennis

    2013-01-01

    Many antineoplastic drugs are classified as carcinogenic, mutagenic and teratogenic for humans. Therefore, minimization of exposure is required to reduce health risks to employees. The aim of this study was to evaluate working practices and safety measures during drug administration and to assess workplace contamination in outpatient oncology health care settings. Questionnaires about working procedures were sent to 137 day hospitals and private practices. Workplace contamination with 5-fluorouracil, platinum, gemcitabine, cyclophosphamide, ifosfamide, methotrexate, docetaxel and paclitaxel was assessed using wipe samples. Forty institutions participated in the study, and in 28 departments, wipe samples were taken. Depending on the kind of activity, working procedures often (5-80%) were not confirmed with recommendations for safe handling of antineoplastic drugs. Altogether, 60.9% of the sampling results were above the limit of detection (LOD). Most frequent loads were detected with 5-FU (93.5%) and platinum (88.4%). Contamination was detected on all surfaces and the results ranged between drugs handled and the extent of surface contamination. However, specific working practices resulting in a lower number of positive wipe samples could be identified (e.g., use of closed infusion systems). Workplace contamination with antineoplastic drugs is still present. As patients have to be considered as a potential source of contamination, surface contamination is difficult to avoid. However, our study revealed that it is possible to administer a large number of preparations without causing high workplace contamination.

  6. Work of Adhesion of a Sessile Drop to a Clean Surface.

    Science.gov (United States)

    Schroder

    1999-05-15

    According to the Young-Dupré equation, as interpreted by Bangham and Razouk, the work of adhesion of a sessile drop to a smooth solid surface is given by WS(V)L = gammaL (1 + cos θ), where θ is the equilibrium contact angle measured at equilibrium of the system with the saturated vapor of the liquid, and WS(V)L is the work of adhesion of that drop to the solid surface which is in equilibrium with that vapor and may contain an adlayer of the vapor. For calculation of WSL, the work of adhesion of a sessile drop to a clean solid surface, the equation WSL = gammaL (1 + cos θ) + Pie is generally used (although Bangham and Razouk never proposed it). Pie is the negative of the free energy of formation of the adlayer, sometimes called the spreading pressure. In the present work it is shown that the latter equation cannot be accurate. Copyright 1999 Academic Press.

  7. Introducing trimming and function ranking to Solid Works based on function analysis

    NARCIS (Netherlands)

    Chechurin, Leonid S.; Wits, Wessel W.; Bakker, Hans M.; Vaneker, Tom H.J.; Cascini, G.; Vaneker, T.H.J.

    2011-01-01

    TRIZ based Function Analysis models existing products based on functional interactions between product parts. Such a function model description is the ideal starting point for product innovation. Design engineers can apply (TRIZ) methods such as trimming and function ranking to this function model t

  8. Introducing Trimming and Function Ranking to SolidWorks based on Function Analysis

    NARCIS (Netherlands)

    Chechurin, L.S.; Wits, W.W.; Bakker, H.M.; Vaneker, T.H.J.

    2015-01-01

    TRIZ based Function Analysis models existing products based on functional interactions between product parts. Such a function model description is the ideal starting point for product innovation. Design engineers can apply (TRIZ) methods such as trimming and function ranking to this function model t

  9. Introducing Trimming and Function Ranking to SolidWorks based on Function Analysis

    NARCIS (Netherlands)

    Chechurin, L.S.; Wits, Wessel Willems; Bakker, Hans M.; Vaneker, Thomas H.J.

    2015-01-01

    TRIZ based Function Analysis models existing products based on functional interactions between product parts. Such a function model description is the ideal starting point for product innovation. Design engineers can apply (TRIZ) methods such as trimming and function ranking to this function model

  10. ADSORPTION OF ASSOCIATING FLUIDS AT ACTIVE SURFACES: A DENSITY FUNCTIONAL THEORY

    Directory of Open Access Journals (Sweden)

    S.Tripathi

    2003-01-01

    Full Text Available We present a density functional theory (DFT to describe adsorption in systems where molecules of associating fluids can bond (or associate with discrete, localized functional groups attached to the surfaces, in addition to other fluid molecules. For such systems as water adsorbing on activated carbon, silica, clay minerals etc. this is a realistic model to account for surface heterogeneity rather than using a continuous smeared surface-fluid potential employed in most of the theoretical works on adsorption on heterogeneous surfaces. Association is modelled within the framework of first order thermodynamic perturbation theory (TPT1. The new theory accurately predicts the distribution of bonded and non-bonded species and adsorption behavior under various conditions of bulk pressure, surface-fluid and fluid-fluid association strengths. Competition between the surface-fluid and fluid-fluid association is analyzed for fluids with multiple association sites and its impact on adsorption is discussed. The theory, supported by simulations demonstrates that the extent and the nature of adsorption (e.g. monolayer vary with the number of association sites on the fluid molecules.

  11. Highly Hydrophilic Thin-Film Composite Forward Osmosis Membranes Functionalized with Surface-Tailored Nanoparticles

    KAUST Repository

    Tiraferri, Alberto

    2012-09-26

    Thin-film composite polyamide membranes are state-of-the-art materials for membrane-based water purification and desalination processes, which require both high rejection of contaminants and high water permeabilities. However, these membranes are prone to fouling when processing natural waters and wastewaters, because of the inherent surface physicochemical properties of polyamides. The present work demonstrates the fabrication of forward osmosis polyamide membranes with optimized surface properties via facile and scalable functionalization with fine-tuned nanoparticles. Silica nanoparticles are coated with superhydrophilic ligands possessing functional groups that impart stability to the nanoparticles and bind irreversibly to the native carboxyl moieties on the membrane selective layer. The tightly tethered layer of nanoparticles tailors the surface chemistry of the novel composite membrane without altering the morphology or water/solute permeabilities of the membrane selective layer. Surface characterization and interfacial energy analysis confirm that highly hydrophilic and wettable membrane surfaces are successfully attained. Lower intermolecular adhesion forces are measured between the new membrane materials and model organic foulants, indicating the presence of a bound hydration layer at the polyamide membrane surface that creates a barrier for foulant adhesion. © 2012 American Chemical Society.

  12. Antibacterial surfaces through dopamine functionalization and silver nanoparticle immobilization

    Energy Technology Data Exchange (ETDEWEB)

    Liao Yuan [Key Laboratory of Carbon Fiber and Functional Polymers, Ministry of Education, Beijing University of Chemical Technology, Beijing 100029 (China); Key Laboratory of Beijing City on Preparation and Processing of Novel Polymer Materials, Beijing University of Chemical Technology, Beijing 100029 (China); Wang Yaqin; Feng Xiaoxia [College of Life Science and Technology, Beijing University of Chemical Technology, Beijing 100029 (China); Wang Wencai, E-mail: wangw@mail.buct.edu.cn [Key Laboratory of Carbon Fiber and Functional Polymers, Ministry of Education, Beijing University of Chemical Technology, Beijing 100029 (China); Key Laboratory of Beijing City on Preparation and Processing of Novel Polymer Materials, Beijing University of Chemical Technology, Beijing 100029 (China); Xu Fujian; Zhang Liqun [Key Laboratory of Carbon Fiber and Functional Polymers, Ministry of Education, Beijing University of Chemical Technology, Beijing 100029 (China); Key Laboratory of Beijing City on Preparation and Processing of Novel Polymer Materials, Beijing University of Chemical Technology, Beijing 100029 (China)

    2010-06-01

    Immobilization of silver nanoparticles on the dopamine functionalized polyimide (PI) films was carried out by photo-induced silver ion-reduction under atmosphere conditions. The dopamine has been successfully deposited on the PI surface in mild aqueous environments. The effects of pH, dopamine concentration and reaction time on the dopamine polymerization were investigated. The water contact angles of the poly(dopamine) functionalized PI films reduced remarkably in comparison with that of the pristine PI film. The chemical composition and structure of the UV-induced deposited-silver on the modified PI films were characterized by X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). The topography of the modified PI films was investigated by scanning electron microscope (SEM). The deposited poly(dopamine) layer acted as binding sites for the silver ions. The silver-plated PI films showed good antibacterial activity due to that biofilm formation was inhibited on the polymeric surfaces in contact with bacteria.

  13. Studying surface movements in working bed Sloistiy-II at the Anadyrskaya mine

    Energy Technology Data Exchange (ETDEWEB)

    Rozenbaum, M.A.; Gromov, Yu.V.; Shatrov, V.F.

    1983-01-01

    Results are presented of observations of surface movement during working of the bed SloistiyII in the field of the Anadyrskaya mine by mechanized complex KM-81 E. It is shown that simultaneously with collapse of the main roofing, the entire rock mass subsides to the earth's surface with the formation on it of cave-ins and rupture fractures. For the first time for conditions of permafrost, values are defined for the initial parameters and angles of advance which should be used in solving different types of geochemical problems.

  14. Tuning the ITO work function by capacitively coupled plasma and its application in inverted organic solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Fang, Ming [Laboratory of Plasma Physics and Materials, Beijing Institute of Graphic Communication, Beijing (China); Zhang, Chunmei, E-mail: zhangchunmei@bigc.edu.cn [Laboratory of Plasma Physics and Materials, Beijing Institute of Graphic Communication, Beijing (China); Chen, Qiang [Laboratory of Plasma Physics and Materials, Beijing Institute of Graphic Communication, Beijing (China); State Key Laboratory of Electrical Insulation and Power Equipment, Xi’an Jiaotong University, Xi’an (China)

    2016-11-01

    Highlights: • The work function of ITO was reduced by plasma treatment. • The reduction of the work function was attributed to the variation in chemical component of ITO surface. • The inverted solar cell without electron transport layer was fabricated using plasma-treated ITO. • Optimal power conversion efficiency of 3.22% was achieved. - Abstract: In this paper, we investigated the performance of inverted organic solar cells (OSCs) with plasma-treated indium tin oxide (ITO) as the cathode for omitting an electron transport layer. The Ar plasma was produced by capcitively coupled plasma setup under 20 Pa chamber pressure. For the device with the structure of plasma-treated ITO/P3HT:PCBM/MoO{sub 3}/Ag, a power conversion efficiency (PCE) of 3.22% was achieved, whereas PCE of 1.13% was recorded from the device fabricated with the pristine ITO. The photovoltaic performance was found to be dependent on the applied power of plasma. After analyzing by atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS), we concluded that the chemical component variation of ITOs surface resulted in the decrease of ITO work function, which meant that the ITO Fermi level became shallow relative to the vacuum level. The low work function of ITO should be responsible for the improvement of inverted OSCs because of the better energy level alignment between ITO and the photoactive layer.

  15. THE BAND STRUCTURE AND WORK FUNCTION OF TRANSPARENT CONDUCTING ALUMINUM AND MANGANESE CO-DOPED ZINC OXIDE FILMS

    Institute of Scientific and Technical Information of China (English)

    H.T. Cao; Z.L. Pei; X.B. Zhang; J. Gong; C. Sun; L.S. Wen

    2005-01-01

    Al and Mn co-doped-ZnO films have been prepared at room temperature by DC reactive magnetron sputtering technique. The optical absorption coefficient, apparent and fundamental band gap, and work function of the films have been investigated using optical spectroscopy, band structure analyses and ultraviolet photoelectron spectroscopy (UPS). ZnO films have direct allowed transition band structure, which has been confirmed by the character of the optical absorption coefficient. The apparent band gap has been found directly proportional to N2/3, showing that the effect of Burstein-Moss shift on the band gap variations dominates over the many-body effect. With only standard cleaning protocols, the work function of ZnO: (Al, Mn) and ZnO: Al films have been measured to be 4.26 and 4.21eV, respectively. The incorporation of Mn element into the matrix of ZnO, as a relatively deep donor, can remove some electrons from the conduction band and deplete the density of occupied states at the Fermi energy, which causes a loss in measured photoemission intensity and an increase in the surface work function. Based on the band gap and work function results, the energy band diagram of the ZnO: (Al, Mn)film near its surface is also given.

  16. Light-induced reversible modification of the work function of a new perfluorinated biphenyl azobenzene chemisorbed on Au (111).

    Science.gov (United States)

    Masillamani, Appan Merari; Osella, Silvio; Liscio, Andrea; Fenwick, Oliver; Reinders, Federica; Mayor, Marcel; Palermo, Vincenzo; Cornil, Jérôme; Samorì, Paolo

    2014-08-07

    We describe the synthesis of a novel biphenyl azobenzene derivative exhibiting: (i) a protected thiol anchoring group in the α-position to readily form self-assembled monolayers (SAMs) on Au surfaces; and (ii) a terminal perfluorinated benzene ring in the ω-position to modify the surface properties. The design of this molecule ensured both an efficient in situ photoswitching between the trans and cis isomers when chemisorbed on Au(111), due to the presence of a biphenyl bridge between the thiol protected anchoring group and the azo dye, and a significant variation of the work function of the SAM in the two isomeric states, induced by the perfluorinated phenyl head group. By exploiting the light responsive nature of the chemisorbed molecules, it is possible to dynamically modify in situ the work function of the SAM-covered electrode, as demonstrated both experimentally and by quantum-chemical calculations, revealing changes in work function up to 220 meV. These findings are relevant for tuning the work function of metallic electrodes, and hence to dynamically modulate charge injection at metal-semiconductor interfaces for organic opto-electronic applications.

  17. Surface Functionalization of Orthopedic Titanium Implants with Bone Sialoprotein.

    Directory of Open Access Journals (Sweden)

    Andreas Baranowski

    Full Text Available Orthopedic implant failure due to aseptic loosening and mechanical instability remains a major problem in total joint replacement. Improving osseointegration at the bone-implant interface may reduce micromotion and loosening. Bone sialoprotein (BSP has been shown to enhance bone formation when coated onto titanium femoral implants and in rat calvarial defect models. However, the most appropriate method of BSP coating, the necessary level of BSP coating, and the effect of BSP coating on cell behavior remain largely unknown. In this study, BSP was covalently coupled to titanium surfaces via an aminosilane linker (APTES, and its properties were compared to BSP applied to titanium via physisorption and untreated titanium. Cell functions were examined using primary human osteoblasts (hOBs and L929 mouse fibroblasts. Gene expression of specific bone turnover markers at the RNA level was detected at different intervals. Cell adhesion to titanium surfaces treated with BSP via physisorption was not significantly different from that of untreated titanium at any time point, whereas BSP application via covalent coupling caused reduced cell adhesion during the first few hours in culture. Cell migration was increased on titanium disks that were treated with higher concentrations of BSP solution, independent of the coating method. During the early phases of hOB proliferation, a suppressive effect of BSP was observed independent of its concentration, particularly when BSP was applied to the titanium surface via physisorption. Although alkaline phosphatase activity was reduced in the BSP-coated titanium groups after 4 days in culture, increased calcium deposition was observed after 21 days. In particular, the gene expression level of RUNX2 was upregulated by BSP. The increase in calcium deposition and the stimulation of cell differentiation induced by BSP highlight its potential as a surface modifier that could enhance the osseointegration of orthopedic implants

  18. Multiply Surface-Functionalized Nanoporous Carbon for Vehicular Hydrogen Storage

    Energy Technology Data Exchange (ETDEWEB)

    Pfeifer, Peter [Univ. of Missouri, Columbia, MO (United States). Dept. of Physics; Gillespie, Andrew [Univ. of Missouri, Columbia, MO (United States). Dept. of Physics; Stalla, David [Univ. of Missouri, Columbia, MO (United States). Dept. of Physics; Dohnke, Elmar [Univ. of Missouri, Columbia, MO (United States). Dept. of Physics

    2017-02-20

    The purpose of the project “Multiply Surface-Functionalized Nanoporous Carbon for Vehicular Hydrogen Storage” is the development of materials that store hydrogen (H2) by adsorption in quantities and at conditions that outperform current compressed-gas H2 storage systems for electric power generation from hydrogen fuel cells (HFCs). Prominent areas of interest for HFCs are light-duty vehicles (“hydrogen cars”) and replacement of batteries with HFC systems in a wide spectrum of applications, ranging from forklifts to unmanned areal vehicles to portable power sources. State-of-the-art compressed H2 tanks operate at pressures between 350 and 700 bar at ambient temperature and store 3-4 percent of H2 by weight (wt%) and less than 25 grams of H2 per liter (g/L) of tank volume. Thus, the purpose of the project is to engineer adsorbents that achieve storage capacities better than compressed H2 at pressures less than 350 bar. Adsorption holds H2 molecules as a high-density film on the surface of a solid at low pressure, by virtue of attractive surface-gas interactions. At a given pressure, the density of the adsorbed film is the higher the stronger the binding of the molecules to the surface is (high binding energies). Thus, critical for high storage capacities are high surface areas, high binding energies, and low void fractions (high void fractions, such as in interstitial space between adsorbent particles, “waste” storage volume by holding hydrogen as non-adsorbed gas). Coexistence of high surface area and low void fraction makes the ideal adsorbent a nanoporous monolith, with pores wide enough to hold high-density hydrogen films, narrow enough to minimize storage as non-adsorbed gas, and thin walls between pores to minimize the volume occupied by solid instead of hydrogen. A monolith can be machined to fit into a rectangular tank (low pressure, conformable tank), cylindrical tank

  19. Ocular surface area and human eye blink frequency during VDU work

    DEFF Research Database (Denmark)

    Nielsen, Pernille Kofoed; Søgaard, Karen; Skotte, Jørgen

    2008-01-01

    The purpose of this study was to investigate how the ocular surface area (OSA) and the eye blink frequency (BF) are affected by a high versus a low-monitor position during visual display unit (VDU) work with varying cognitive demands. In a balanced randomized (2 x 2) design ten healthy subjects....... The low BF during the active task was succeded by a burst with high BF after cessation of the active task, indicating a compensatory blinking process. This stresses that interchange of work tasks with different cognitive load is as important as the monitor position in the prevention of visual...

  20. Adjustment of surface chemical and physical properties with functionalized polymers to control cell adhesion

    Science.gov (United States)

    Zhou, Zhaoli

    Cell-surface interaction is crucial in many cellular functions such as movement, growth, differentiation, proliferation and survival. In the present work, we have developed several strategies to design and prepare synthetic polymeric materials with selected cues to control cell attachment. To promote neuronal cell adhesion on the surfaces, biocompatible, non-adhesive PEG-based materials were modified with neurotransmitter acetylcholine functionalities to produce hydrogels with a range of porous structures, swollen states, and mechanical strengths. Mice hippocampal cells cultured on the hydrogels showed differences in number, length of processes and exhibited different survival rates, thereby highlighting the importance of chemical composition and structure in biomaterials. Similar strategies were used to prepare polymer brushes to assess how topographical cues influence neuronal cell behaviors. The brushes were prepared using the "grown from" method through surface-initiated atom transfer radical polymerization (SI-ATRP) reactions and further patterned via UV photolithography. Protein absorption tests and hippocampal neuronal cell culture of the brush patterns showed that both protein and neuronal cells can adhere to the patterns and therefore can be guided by the patterns at certain length scales. We also prepared functional polymers to discourage attachment of undesirable cells on the surfaces. For example, we synthesized PEG-perfluorinated alkyl amphiphilic surfactants to modify polystyrene-block-poly(ethylene-ran-butylene)- block-polyisoprene (SEBI or K3) triblock copolymers for marine antifouling/fouling release surface coatings. Initial results showed that the polymer coated surfaces can facilitate removal of Ulva sporelings on the surfaces. In addition, we prepared both bioactive and dual functional biopassive/bioactive antimicrobial coatings based on SEBI polymers. Incubating the polymer coated surfaces with gram-positive bacteria (S. aureus), gram

  1. Highly sensitive BTX detection using surface functionalized QCM sensor

    Energy Technology Data Exchange (ETDEWEB)

    Bozkurt, Asuman Aşıkoğlu; Özdemir, Okan; Altındal, Ahmet, E-mail: altindal@yildiz.edu.tr [Department of Physics, Yildiz Technical University, Davutpasa, 34210 Istanbul (Turkey)

    2016-03-25

    A novel organic compound was designed and successfully synthesized for the fabrication of QCM based sensors to detect the low concentrations of BTX gases in indoor air. The effect of the long-range electron orbital delocalization on the BTX vapour sensing properties of azo-bridged Pcs based chemiresistor-type sensors have also been investigated in this work. The sensing behaviour of the film for the online detection of volatile organic solvent vapors was investigated by utilizing an AT-cut quartz crystal resonator. It was observed that the adsorption of the target molecules on the coating surface cause a reversible negative frequency shift of the resonator. Thus, a variety of solvent vapors can be detected by using the phthalocyanine film as sensitive coating, with sensitivity in the ppm range and response times in the order of several seconds depending on the molecular structure of the organic solvent.

  2. Large work function shift of gold induced by a novel perfluorinated azobenzene-based self-assembled monolayer.

    Science.gov (United States)

    Crivillers, Núria; Osella, Silvio; Van Dyck, Colin; Lazzerini, Giovanni M; Cornil, David; Liscio, Andrea; Di Stasio, Francesco; Mian, Shabbir; Fenwick, Oliver; Reinders, Federica; Neuburger, Markus; Treossi, Emanuele; Mayor, Marcel; Palermo, Vincenzo; Cacialli, Franco; Cornil, Jérôme; Samorì, Paolo

    2013-01-18

    Tune it with light! Self-assembled monolayers on gold based on a chemisorbed novel azobenzene derivative with a perfluorinated terminal phenyl ring are prepared. The modified substrate shows a significant work function increase compared to the bare metal. The photo-conversion between trans and cis isomers chemisorbed on the surface shows great perspectives for being an accessible route to tune the gold properties by means of light.

  3. INVESTIGATION OF HIGH-CURRENT INTERRUPTING CONTACTS WORKING SURFACES MECHANICAL INTERACTION NATURE

    Directory of Open Access Journals (Sweden)

    O.G. Volkova

    2016-03-01

    Full Text Available Introduction. The nature of the interaction of high-working surfaces of the electrical contact uniquely affects their performance. By the failure of the contacts in the main drive processes resulting from complex destructive factors affecting their performance. However, not all processes are studied in detail and give in modeling. The purpose of the paper is to show the possibility of using the method of holographic interferometry to estimate the plastic deformation in the zone of contact interaction. One of the significant factors affecting the work of the contact pair is the compressive force of the contact surfaces. Compression discontinuous contact is directly connected with the processes of elastic and plastic deformation of the contact material, which is particularly evident in the contact details of the powder or composite materials. The paper focuses on the plastic deformation of the surface layers of discontinuous contact in circuit, it is believed that it is directly related to the mechanism of conductivity of contacts. As shown, a significant effect on the deformation of the contact surfaces and renders the working environment, in particular transformer oil. Methodology. Assessing the impact of compression forces on the deformation of the contact surface was conducted experimentally using the method of holographic interferometry. Results. Experimental studies, which indicated that the compact and powder materials plastic deformation in and around the area microcontacts simplistically stated that requires experimental verification. A method for evaluating the state of stress, which affects the formation and destruction of the local contact spots. Practical value. Using the experimental method of determining the movement of the contact region allows you to optimize discontinuous contacts from composite and powder materials.

  4. Reliability and Validity of the Work Role Functioning Questionnaire (Spanish Version)

    NARCIS (Netherlands)

    Ramada, Jose M.; Serra, Consol; Amick, Benjamin C.; Abma, Femke I.; Castano, Juan R.; Pidemunt, Gemma; Bultmann, Ute; Delclos, George L.

    2014-01-01

    Purpose Recently, the cross-cultural adaptation of the Work Role Functioning Questionnaire to Spanish was carried out, achieving satisfactory psychometric properties. Now we examined the reliability and validity of the adapted [Work role functioning questionnaire-Spanish version (WRFQ-SpV)] in a gen

  5. Zinc surface complexes on birnessite: A density functional theory study

    Energy Technology Data Exchange (ETDEWEB)

    Kwon, Kideok D.; Refson, Keith; Sposito, Garrison

    2009-01-05

    Biogeochemical cycling of zinc is strongly influenced by sorption on birnessite minerals (layer-type MnO2), which are found in diverse terrestrial and aquatic environments. Zinc has been observed to form both tetrahedral (Zn{sup IV}) and octahedral (Zn{sup VI}) triple-corner-sharing surface complexes (TCS) at Mn(IV) vacancy sites in hexagonal birnessite. The octahedral complex is expected to be similar to that of Zn in the Mn oxide mineral, chalcophanite (ZnMn{sub 3}O{sub 7} {center_dot} 3H{sub 2}O), but the reason for the occurrence of the four-coordinate Zn surface species remains unclear. We address this issue computationally using spin-polarized Density Functional Theory (DFT) to examine the Zn{sub IV}-TCS and Zn{sup VI}-TCS species. Structural parameters obtained by DFT geometry optimization were in excellent agreement with available experimental data on Zn-birnessites. Total energy, magnetic moments, and electron-overlap populations obtained by DFT for isolated Zn{sup IV}-TCS revealed that this species is stable in birnessite without a need for Mn(III) substitution in the octahedral sheet and that it is more effective in reducing undersaturation of surface O at a Mn vacancy than is Zn{sub VI}-TCS. Comparison between geometry-optimized ZnMn{sub 3}O{sub 7} {center_dot} 3H{sub 2}O (chalcophanite) and the hypothetical monohydrate mineral, ZnMn{sub 3}O{sub 7} {center_dot} H{sub 2}O, which contains only tetrahedral Zn, showed that the hydration state of Zn significantly affects birnessite structural stability. Finally, our study also revealed that, relative to their positions in an ideal vacancy-free MnO{sub 2}, Mn nearest to Zn in a TCS surface complex move toward the vacancy by 0.08-0.11 {angstrom}, while surface O bordering the vacancy move away from it by 0.16-0.21 {angstrom}, in agreement with recent X-ray absorption spectroscopic analyses.

  6. Characterization of Sea Lettuce Surface Functional Groups by Potentiometric Titrations

    Science.gov (United States)

    Ebling, A. M.; Schijf, J.

    2008-12-01

    In pursuit of our ultimate goal to better understand the prodigious capacity of the marine macroalga Ulva lactuca (sea lettuce) for adsorbing a broad range of dissolved trace metals from seawater, we performed an initial characterization of its surface functional groups. Specifically, the number of distinct functional groups as well as their individual bulk concentrations and acid dissociation constants (pKas) were determined by potentiometric titrations in NaCl solutions of various ionic strengths (I = 0.01-5.0 M), under inert nitrogen atmosphere at 25°C. Depending on the ionic strength, Ulva samples were manually titrated down to pH 2 or 3 with 1 N HCl and then up to pH 10 with 1 N NaOH in steps of 0.1-0.2 units, continuously monitoring pH with a glass combination electrode. Titrations of a dehydrated Ulva standard reference material (BCR-279) were compared with fresh Ulva tissue cultured in our laboratory. A titration in filtered natural seawater was also compared with one in an NaCl solution of equal ionic strength. Equilibrium constants for the ionization of water in NaCl solutions as a function of ionic strength were obtained from the literature. Fits to the titration data ([H]T vs. pH) were performed with the FITEQL4.0 computer code using non-electrostatic 3-, 4-, and 5-site models, either by fixing ionic strength at its experimental value or by allowing it to be extrapolated to zero, while considering all functional group pKas and bulk concentrations as adjustable parameters. Since pKas and bulk concentrations were found to be strongly correlated, the latter were also fixed in some cases to further constrain the pKas. Whereas these calculations are currently ongoing, preliminary results point to three, possibly four, functional groups with pKas of about 4.1, 6.3, and 9.5 at I = 0. Bulk concentrations of the three groups are very similar, about 5-6×10-4 mol/g based on dry weight, which suggests that all are homogeneously distributed over the surface and

  7. Working Memory Functioning in Children with Learning Disorders and Specific Language Impairment

    Science.gov (United States)

    Schuchardt, Kirsten; Bockmann, Ann-Katrin; Bornemann, Galina; Maehler, Claudia

    2013-01-01

    Purpose: On the basis of Baddeley's working memory model (1986), we examined working memory functioning in children with learning disorders with and without specific language impairment (SLI). We pursued the question whether children with learning disorders exhibit similar working memory deficits as children with additional SLI. Method: In…

  8. Stress dependence of the suspended graphene work function: Vacuum Kelvin probe force microscopy and density functional theory

    Science.gov (United States)

    Volodin, A.; Van Haesendonck, C.; Leenaerts, O.; Partoens, B.; Peeters, F. M.

    2017-05-01

    We report on work function measurements on graphene, which is exfoliated over a predefined array of wells in silicon oxide, by Kelvin probe force microscopy operating in a vacuum. The obtained graphene sealed microchambers can support large pressure differences, providing controllable stretching of the nearly impermeable graphene membranes. These measurements allow detecting variations of the work function induced by the mechanical stresses in the suspended graphene where the work function varies linearly with the strain and changes by 62 ± 2 meV for 1 percent of strain. Our related ab initio calculations result in a work function variation that is a factor of 1.4 larger than the experimental value. The limited discrepancy between the theory and the experiment can be accounted for by a charge transfer from the unstrained to the strained graphene regions.

  9. Surface morphology evolution of Si(110) by ion sputtering as a function of sample temperature

    Institute of Scientific and Technical Information of China (English)

    Qi Le-Jun; Ling Li; Li Wei-Qing; Yang Xin-Ju; Gu Chang-Xin; Lu Ming

    2005-01-01

    Si(110) surface morphology evolution under normal-incident Ar+ ion sputtering has been studied as a function of Si temperature with the ion energy of 1.5keV and the ion flux 20μA/cm2. During temperature rising from room temperature to 800℃, Si(110) surface morphology changes from a dim dot/hole pattern to a distinct dot one, meanwhile the surface roughness increases steadily. The usually-accepted Bradley-Harper model fails to explain these data. By taking into account the Ehrlich-Schwoebel effect in the nanostructuring process, a simulation work was conducted based on a continuum dynamic model, which reproduces the experimental results.

  10. Prediction of the adhesive behavior of bio-inspired functionally graded materials against rough surfaces

    Directory of Open Access Journals (Sweden)

    Chen Peijian

    2014-06-01

    Full Text Available Roughness effect and adhesion properties are important characteristics to be accessed in the development of functionally graded materials for biological and biomimetic applications, particularly for the hierarchical composition in biomimetic gecko robot. A multi-asperities adhesion model to predict the adhesive forces is presented in this work. The effect of surface roughness and graded material properties, which significantly alter the adhesive strength between contact bodies, can be simultaneously considered in the generalized model. It is found that proper interfacial strength can be controlled by adjusting surface roughness σ / R, graded exponent k and material parameter E*R / Δγ. The results should be helpful in the design of new biomimetic materials and useful in application of micro functional instruments.

  11. Solubility studies of inorganic–organic hybrid nanoparticle photoresists with different surface functional groups

    KAUST Repository

    Li, Li

    2016-01-01

    © 2016 The Royal Society of Chemistry. The solubility behavior of Hf and Zr based hybrid nanoparticles with different surface ligands in different concentrations of photoacid generator as potential EUV photoresists was investigated in detail. The nanoparticles regardless of core or ligand chemistry have a hydrodynamic diameter of 2-3 nm and a very narrow size distribution in organic solvents. The Hansen solubility parameters for nanoparticles functionalized with IBA and 2MBA have the highest contribution from the dispersion interaction than those with tDMA and MAA, which show more polar character. The nanoparticles functionalized with unsaturated surface ligands showed more apparent solubility changes after exposure to DUV than those with saturated ones. The solubility differences after exposure are more pronounced for films containing a higher amount of photoacid generator. The work reported here provides material selection criteria and processing strategies for the design of high performance EUV photoresists.

  12. Self-chemisorption of azurin on functionalized oxide surfaces for the implementation of biomolecular devices

    Energy Technology Data Exchange (ETDEWEB)

    Biasco, A.; Maruccio, G.; Visconti, P.; Bramanti, A.; Calogiuri, P.; Cingolani, R.; Rinaldi, R

    2004-06-01

    In this work, we investigate the formation of redox protein Azurin (Az) monolayers on functionalized oxygen exposing surfaces. These metallo-proteins mediate electron transfer in the denitrifying chain of Pseudomonas bacteria and exhibit self-assembly properties, therefore they are good candidates for bio-electronic applications. Azurin monolayers are self-assembled onto silane functionalized surfaces and characterized by atomic force microscopy (AFM). We show also that a biomolecular field effect transistor (FET) in the solid state can be implemented by interconnecting an Azurin monolayer immobilized on SiO{sub 2} with two gold nanoelectrodes. Transport experiments, carried out at room temperature and ambient pressure, show FET behavior with conduction modulated by the gate potential.

  13. Implicit solvation model for density-functional study of nanocrystal surfaces and reaction pathways

    Science.gov (United States)

    Mathew, Kiran; Sundararaman, Ravishankar; Letchworth-Weaver, Kendra; Arias, T. A.; Hennig, Richard G.

    2014-02-01

    Solid-liquid interfaces are at the heart of many modern-day technologies and provide a challenge to many materials simulation methods. A realistic first-principles computational study of such systems entails the inclusion of solvent effects. In this work, we implement an implicit solvation model that has a firm theoretical foundation into the widely used density-functional code Vienna ab initio Software Package. The implicit solvation model follows the framework of joint density functional theory. We describe the framework, our algorithm and implementation, and benchmarks for small molecular systems. We apply the solvation model to study the surface energies of different facets of semiconducting and metallic nanocrystals and the SN2 reaction pathway. We find that solvation reduces the surface energies of the nanocrystals, especially for the semiconducting ones and increases the energy barrier of the SN2 reaction.

  14. Polarized reflectance and transmittance distribution functions of the ocean surface.

    Science.gov (United States)

    Hieronymi, Martin

    2016-07-11

    Two aspects of ocean modelling are treated: representation of ocean waves considering all size-classes of waves and tracing of light-interactions at the wavy sea surface. Nonlinear wave profiles are realized accounting for a wide range of climatologically relevant sea states and wind speeds. Polarized ray tracing is used to investigate air-incident and whitecap-free reflectance and transmittance distributions with high angular resolution subject to sea-characterizing parameters, such as significant wave height, peak wave period, wind speed, and surface roughness. Wave-shadowing effects of incident and multiple reflected rays are fully considered. Their influence mostly starts with incidence angles greater than 60°, i.e., when the sun is near the horizon, and is especially pronounced for steep sea states. The net effect of multiple reflections is a redistribution of reflectance and transmittance fractions in their respective hemispheres and a slight increase of the net transmission of light into the sea. Revised reflectance and transmittance distribution functions, RDF and TDF, are provided depending on surface roughness in terms of the mean-square slope; reference is made to other sea state parameters. In comparison with the slope statistics approach, uncertainties related to sun near the horizon are reduced and on average this study yields somewhat higher reflectance values with some variability related to the sea state. By means of provided data, irradiance and radiance reflectances can be computed using desired sky radiance distributions, e.g., clear sky, overcast or partly cloudy sky, as well as wind or sea state information including wave propagation direction.

  15. Fluids of the ocular surface: concepts, functions and physics.

    Science.gov (United States)

    Cher, Ivan

    2012-08-01

    General adoption of the ocular surface (OS) concept has advanced the therapy of the external eye. Fresh physical findings have prompted new concepts; examples taken from each section of the text are: (i) ever-present lipid sealant bridges the palpebral fissure capping the three-dimensional 'OS' sac. The muco-aqueous pool (MAP) is thus enclosed, secluded from atmosphere, evaporation mitigated. Hence, the OS is conceptually, a compartment. The term 'dacruon' (otherwise 'tear film') has been coined for the combined fluids of the OS, viz. lipid film and MAP. (ii) Investigative techniques of physics yield data on (say) surface tension and viscosity, and on functions such as anchorage of dacruon base to the varied mucosae of the OS, lubrication, renovation of intermarginal fluid layers as the eye opens after each blink, and refinement of optics and vision by the fluids attached to the cornea. (iii) Physical events in the opening eye produce the unique 'black line' phenomenon in which capillary force induces subsurface flows into thirsty menisci, bringing about parameniscal dark grooves, pupil-ward of each meniscus. Attenuation of fluorescein in the shallowed fluid gaps behind each groove makes the dye appear unilluminated ('black lines') relative to adjacent full-thickness MAP fluid glowing under cobalt-blue illumination. Isolated from cornea by grooves and gaps, the meniscal fluid cannot pass freely over the cornea. It therefore streams through the menisci to nasolacrimal outflow.

  16. Structures and Functions of Pestivirus Glycoproteins: Not Simply Surface Matters

    Directory of Open Access Journals (Sweden)

    Fun-In Wang

    2015-06-01

    Full Text Available Pestiviruses, which include economically important animal pathogens such as bovine viral diarrhea virus and classical swine fever virus, possess three envelope glycoproteins, namely Erns, E1, and E2. This article discusses the structures and functions of these glycoproteins and their effects on viral pathogenicity in cells in culture and in animal hosts. E2 is the most important structural protein as it interacts with cell surface receptors that determine cell tropism and induces neutralizing antibody and cytotoxic T-lymphocyte responses. All three glycoproteins are involved in virus attachment and entry into target cells. E1-E2 heterodimers are essential for viral entry and infectivity. Erns is unique because it possesses intrinsic ribonuclease (RNase activity that can inhibit the production of type I interferons and assist in the development of persistent infections. These glycoproteins are localized to the virion surface; however, variations in amino acids and antigenic structures, disulfide bond formation, glycosylation, and RNase activity can ultimately affect the virulence of pestiviruses in animals. Along with mutations that are driven by selection pressure, antigenic differences in glycoproteins influence the efficacy of vaccines and determine the appropriateness of the vaccines that are currently being used in the field.

  17. Functionalization of ceramic tile surface by sol-gel technique.

    Science.gov (United States)

    Bondioli, F; Taurino, R; Ferrari, A M

    2009-06-15

    The aim of this investigation was the surface functionalization of industrial ceramic tiles by sol-gel technique to improve at the same time the cleanability of unglazed surfaces. This objective was pursued through the design and preparation of nanostructured coating that was deposited on polished unglazed tiles by air-brushing. In particular TiO(2)-SiO(2) binary film with 1, 2 or 5wt% of titania were prepared by using tetraethoxysilane and titania nanoparticles as precursors. The obtained films were characterized by scratch tests to verify the adhesion of the coatings to the polished tiles. To mainly evaluate the effect of the thermal treatment (temperature range 100-600 degrees C) on the photocatalicity of the coatings, the films were studied under UV exposure by contact angle measurements and cleanability test. Particular attention has been paid to preserve the aesthetical aspect of the final product and the obtained hue variation was evaluated by means of UV-visible spectroscopy and colorimetric analysis.

  18. Functional Design and Qualification of Surface Tension Propellant Tanks

    Science.gov (United States)

    Figus, C.; Haddad, D.; Ounougha, L.; Autric, J.

    2004-10-01

    During two decades, EADS Astrium has designed and qualified the surface tension device used in the propellant tanks equipping the Eurostar telecommunication satellites platforms. Recent re- orbiting phases of Eurostar E2000 satellites, have allowed to validate those designs and to graveyard the spacecraft with less than 1 kg of propellant left per tank. Moreover, with the emergence of new powerful satellites with full chemical or mixed chemical-plasma propulsion subsystems, EADS Astrium has designed a new larger and improved surface tension propellant tank. Such challenging performances require analyses, and tests in order to assess and confirm the predicted performances. The present article shows the recent development of a new enlarged Eurostar E3000 propellant tanks for Eurostar 3000 satellites and presents the main functional analyses and neutral buoyancy tests results obtained for this new propellant tank These last two years, have contributed to improve this background with the successful graveyard of the first Eurostar spacecraft with less than 1 kg of liquid propellant per tank at the end of the manoeuvre. Moreover, a new enlarged E3000 propellant tank has been designed and qualified in order to cope with the future 12 kW telecom spacecraft applications. This tank designed by EADS-ASTRIUM, is manufactured by EADS-Space transportation. This paper presents the performances and tests results obtained on this new propellant tank.

  19. Surface functionalization of 3D glass-ceramic porous scaffolds for enhanced mineralization in vitro

    Science.gov (United States)

    Ferraris, Sara; Vitale-Brovarone, Chiara; Bretcanu, Oana; Cassinelli, Clara; Vernè, Enrica

    2013-04-01

    Bone reconstruction after tissue loosening due to traumatic, pathological or surgical causes is in increasing demand. 3D scaffolds are a widely studied solution for supporting new bone growth. Bioactive glass-ceramic porous materials can offer a three-dimensional structure that is able to chemically bond to bone. The ability to surface modify these devices by grafting biologically active molecules represents a challenge, with the aim of stimulating physiological bone regeneration with both inorganic and organic signals. In this research work glass ceramic scaffolds with very high mechanical properties and moderate bioactivity have been functionalized with the enzyme alkaline phosphatase (ALP). The material surface was activated in order to expose hydroxyl groups. The activated surface was further grafted with ALP both via silanization and also via direct grafting to the surface active hydroxyl groups. Enzymatic activity of grafted samples were measured by means of UV-vis spectroscopy before and after ultrasonic washing in TRIS-HCl buffer solution. In vitro inorganic bioactivity was investigated by soaking the scaffolds after the different steps of functionalization in a simulated body fluid (SBF). SEM observations allowed the monitoring of the scaffold morphology and surface chemical composition after soaking in SBF. The presence of ALP enhanced the in vitro inorganic bioactivity of the tested material.

  20. Technical work plan for Surface Impoundments Operable Unit engineering support studies

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1995-11-01

    This document provides a comprehensive work plan which, when utilized as a data collection guide for field activities, will provide the necessary information required to complete a report on geotechnical properties of the sediments contained in the Surface Impoundments Operable Unit at Oak Ridge National Laboratory in Oak Ridge, Tennessee. Detailed guidance is provided for the following activities: collection of samples from the impoundments; compressive strength testing of the raw sediments; compressive strength testing of the structurally modified (lime and cement additives) sediments; testing for sediment physical properties and settling rates; testing for sediment dewatering characteristics; testing for radiation activity during the field work; testing for polymer additions that may enhance settling. The work plan additionally provides guidance and examples for the preparation of documents necessary to establish readiness for safe and satisfactory performance of the field activities. An outline for the format requested for a report of these data is also provided.

  1. Determination of work function of graphene under a metal electrode and its role in contact resistance.

    Science.gov (United States)

    Song, Seung Min; Park, Jong Kyung; Sul, One Jae; Cho, Byung Jin

    2012-08-08

    Although the work function of graphene under a given metal electrode is critical information for the realization of high-performance graphene-based electronic devices, relatively little relevant research has been carried out to date. In this work, the work function values of graphene under various metals are accurately measured for the first time through a detailed analysis of the capacitance-voltage (C-V) characteristics of a metal-graphene-oxide-semiconductor (MGOS) capacitor structure. In contrast to the high work function of exposed graphene of 4.89-5.16 eV, the work function of graphene under a metal electrode varies depending on the metal species. With a Cr/Au or Ni contact, the work function of graphene is pinned to that of the contacted metal, whereas with a Pd or Au contact the work function assumes a value of ∼4.62 eV regardless of the work function of the contact metal. A study of the gate voltage dependence on the contact resistance shows that the latter case provides lower contact resistance.

  2. Solubility studies of inorganic-organic hybrid nanoparticle photoresists with different surface functional groups

    Science.gov (United States)

    Li, Li; Chakrabarty, Souvik; Jiang, Jing; Zhang, Ben; Ober, Christopher; Giannelis, Emmanuel P.

    2016-01-01

    The solubility behavior of Hf and Zr based hybrid nanoparticles with different surface ligands in different concentrations of photoacid generator as potential EUV photoresists was investigated in detail. The nanoparticles regardless of core or ligand chemistry have a hydrodynamic diameter of 2-3 nm and a very narrow size distribution in organic solvents. The Hansen solubility parameters for nanoparticles functionalized with IBA and 2MBA have the highest contribution from the dispersion interaction than those with tDMA and MAA, which show more polar character. The nanoparticles functionalized with unsaturated surface ligands showed more apparent solubility changes after exposure to DUV than those with saturated ones. The solubility differences after exposure are more pronounced for films containing a higher amount of photoacid generator. The work reported here provides material selection criteria and processing strategies for the design of high performance EUV photoresists.The solubility behavior of Hf and Zr based hybrid nanoparticles with different surface ligands in different concentrations of photoacid generator as potential EUV photoresists was investigated in detail. The nanoparticles regardless of core or ligand chemistry have a hydrodynamic diameter of 2-3 nm and a very narrow size distribution in organic solvents. The Hansen solubility parameters for nanoparticles functionalized with IBA and 2MBA have the highest contribution from the dispersion interaction than those with tDMA and MAA, which show more polar character. The nanoparticles functionalized with unsaturated surface ligands showed more apparent solubility changes after exposure to DUV than those with saturated ones. The solubility differences after exposure are more pronounced for films containing a higher amount of photoacid generator. The work reported here provides material selection criteria and processing strategies for the design of high performance EUV photoresists. Electronic supplementary

  3. DESIGN AND FEM STATIC ANALYSIS OF AN INSTRUMENT FOR SURFACE PLASTIC DEFORMATION OF NON-PLANAR FUNCTIONAL SURFACES OF MACHINE PARTS

    Directory of Open Access Journals (Sweden)

    STOYAN SLAVOV

    2015-12-01

    Full Text Available The paper presents the design of a specialized instrument for formation different types of regular microshape roughness on functional surfaces of parts with non-planar macroshape by using the process, called “surface plastic deformation”. The elements of which it is constructed are explained and the results from carried out strength and deformation analysis, obtained by Finite Element Method, conducted using the Simulation module of the SolidWorks are also represented. On this basis some advantages and limitations of some of the surface plastic deformation process technological parameters are identified and recommendations for its implementation are given.

  4. A Green's function method for surface acoustic waves in functionally graded materials.

    Science.gov (United States)

    Matsuda, Osamu; Glorieux, Christ

    2007-06-01

    Acoustic wave propagation in anisotropic media with one-dimensional inhomogeneity is discussed. Using a Green's function approach, the wave equation with inhomogeneous variation of elastic property and mass density is transformed into an integral equation, which is then solved numerically. The method is applied to find the dispersion relation of surface acoustic waves for a medium with continuously or discontinuously varying elastic property and mass density profiles.

  5. Factors predicting work outcome in Japanese patients with schizophrenia: role of multiple functioning levels

    Directory of Open Access Journals (Sweden)

    Chika Sumiyoshi

    2015-09-01

    Full Text Available Functional outcomes in individuals with schizophrenia suggest recovery of cognitive, everyday, and social functioning. Specifically improvement of work status is considered to be most important for their independent living and self-efficacy. The main purposes of the present study were 1 to identify which outcome factors predict occupational functioning, quantified as work hours, and 2 to provide cut-offs on the scales for those factors to attain better work status. Forty-five Japanese patients with schizophrenia and 111 healthy controls entered the study. Cognition, capacity for everyday activities, and social functioning were assessed by the Japanese versions of the MATRICS Cognitive Consensus Battery (MCCB, the UCSD Performance-based Skills Assessment-Brief (UPSA-B, and the Social Functioning Scale Individuals’ version modified for the MATRICS-PASS (Modified SFS for PASS, respectively. Potential factors for work outcome were estimated by multiple linear regression analyses (predicting work hours directly and a multiple logistic regression analyses (predicting dichotomized work status based on work hours. ROC curve analyses were performed to determine cut-off points for differentiating between the better- and poor work status. The results showed that a cognitive component, comprising visual/verbal learning and emotional management, and a social functioning component, comprising independent living and vocational functioning, were potential factors for predicting work hours/status. Cut-off points obtained in ROC analyses indicated that 60–70% achievements on the measures of those factors were expected to maintain the better work status. Our findings suggest that improvement on specific aspects of cognitive and social functioning are important for work outcome in patients with schizophrenia.

  6. Synthesis of S-Layer Conjugates and Evaluation of Their Modifiability as a Tool for the Functionalization and Patterning of Technical Surfaces

    OpenAIRE

    Ulrike Weinert; Katrin Pollmann; Astrid Barkleit; Manja Vogel; Tobias Günther; Johannes Raff

    2015-01-01

    Chemical functional groups of surface layer (S-layer) proteins were chemically modified in order to evaluate the potential of S-layer proteins for the introduction of functional molecules. S-layer proteins are structure proteins that self-assemble into regular arrays on surfaces. One general feature of S-layer proteins is their high amount of carboxylic and amino groups. These groups are potential targets for linking functional molecules, thus producing reactive surfaces. In this work, these ...

  7. Estimating the surface relaxivity as a function of pore size from NMR T2 distributions and micro-tomographic images

    Science.gov (United States)

    Benavides, Francisco; Leiderman, Ricardo; Souza, Andre; Carneiro, Giovanna; Bagueira, Rodrigo

    2017-09-01

    In the present work, we formulate and solve an inverse problem to recover the surface relaxivity as a function of pore size. The input data for our technique are the T2 distribution measurement and the micro-tomographic image of the rock sample under investigation. We simulate the NMR relaxation signal for a given surface relaxivity function using the random walk method and rank different surface relaxivity functions according to the correlation of the resulting simulated T2 distributions with the measured T2 distribution. The optimization is performed using genetic algorithms and determines the surface relaxivity function whose corresponding simulated T2 distribution best matches the measured T2 distribution. In the proposed methodology, pore size is associated with a number of collisions in the random walk simulations. We illustrate the application of the proposed method by performing inversions from synthetic and laboratory input data and compare the obtained results with those obtained using the uniform relaxivity assumption.

  8. Basis for a functional capacity evaluation methodology for patients with work-related neck disorders

    NARCIS (Netherlands)

    Reesink, David D.; Jorritsma, Wim; Reneman, Michiel F.

    2007-01-01

    Neck pain is a common musculoskeletal complaint and a relationship with reduced work-related functional capacity is assumed. A validated instrument to test functional capacity of patients with neck pain is unavailable. The objective of this study was to develop a Functional Capacity Evaluation (FCE)

  9. AFM imaging and analysis of local mechanical properties for detection of surface pattern of functional groups

    Energy Technology Data Exchange (ETDEWEB)

    Knotek, Petr, E-mail: petr.knotek@upce.cz [University of Pardubice, Faculty of Chemical Technology, Joint Laboratory of Solid State Chemistry of IMC ASCR and University of Pardubice, Studentska 573, 532 10 Pardubice (Czech Republic); Chanova, Eliska; Rypacek, Frantisek [Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Heyrovskeho sq. 2, 162 06 Prague (Czech Republic)

    2013-05-01

    In this work we evaluate the applicability of different atomic force microscopy (AFM) modes, such as Phase Shift Imaging, Atomic Force Acoustic Microscopy (AFAM) and Force Spectroscopy, for mapping of the distribution pattern of low-molecular-weight biomimetic groups on polymer biomaterial surfaces. Patterns with either random or clustered spatial distribution of bioactive peptide group derived from fibronectin were prepared by surface deposition of functional block copolymer nano-colloids and grafted with RGDS peptide containing the sequence of amino acids arginine–glycine–aspartic acid–serine (conventionally labeled as RGDS) and carrying biotin as a tag. The biotin-tagged peptides were labeled with 40 nm streptavidin-modified Au nanospheres. The peptide molecules were localized through the detection of bound Au nanospheres by AFM, and thus, the surface distribution of peptides was revealed. AFM techniques capable of monitoring local mechanical properties of the surface were proved to be the most efficient for identification of Au nano-markers. The efficiency was successfully demonstrated on two different patterns, i.e. random and clustered distribution of RGDS peptides on structured surface of the polymer biomaterial. Highlights: ► Bioactive peptides for cell adhesion on PLA-b-PEO biomimetic surface were visualized. ► The biotin-tagged RGDS peptides were labeled with streptavidin-Au nanospheres. ► The RGDS pattern was detected using different atomic force microscopy (AFM) modes. ► Phase Shift Image was proved to be suitable method for studying peptide distribution.

  10. Functionality of porous silicon particles: Surface modification for biomedical applications

    Energy Technology Data Exchange (ETDEWEB)

    Gallach, D.; Recio Sanchez, G.; Munoz Noval, A. [Departamento de Fisica Aplicada y Departamento de Biologia Molecular, Facultad de Ciencias, Cantoblanco, 28049 Madrid (Spain); Centro de Investigaciones Biomedicas en Red, Biomateriales, Bioingenieria y Nanomedicina (CIBERbbn) (Spain); Manso Silvan, M., E-mail: miguel.manso@uam.es [Departamento de Fisica Aplicada y Departamento de Biologia Molecular, Facultad de Ciencias, Cantoblanco, 28049 Madrid (Spain); Centro de Investigaciones Biomedicas en Red, Biomateriales, Bioingenieria y Nanomedicina (CIBERbbn) (Spain); Ceccone, G. [Institute for Health and Consumer Protection, European Commission, 21020 Ispra (Italy); Martin Palma, R.J.; Torres Costa, V.; Martinez Duart, J.M. [Departamento de Fisica Aplicada y Departamento de Biologia Molecular, Facultad de Ciencias, Cantoblanco, 28049 Madrid (Spain); Centro de Investigaciones Biomedicas en Red, Biomateriales, Bioingenieria y Nanomedicina (CIBERbbn) (Spain)

    2010-05-25

    Porous silicon-based particles (PSps) with tailored physical and biological properties have recently attracted great attention given their biomedical potential. Within this context, the objective of the present work is to optimize the experimental parameters for the formation of biofunctional mesoporous PSps. Their functionality has been studied on the one hand by analyzing the fluorescence characteristics, such as tunable narrow band emission and fluorescence aging for PSps with different molecular capping. With regard to the biofunctional characteristics, two different molecular end-capping processes have been assayed: antifouling polyethylene glycol (PEG) and polar binding amino silanes (APTS), which were evaluated by X-ray photoelectron spectroscopy (XPS). Both PEG and APTS binding to the particles could be confirmed from the analysis of Si 2p and C 1s XPS core level spectra. The finding that these PSp-molecule conjugates allow the reduction of fluorescence degradation with time in solution is of interest for the development of cellular or tissue markers. From the morphological point of view, PEG termination is of special interest allowing the PSps after an ultrasonic treatment to get spherical shapes in the micron scale. The functionality as solid state dyes is preliminarily evaluated by direct fluorescence imaging.

  11. Adsorption and destruction of PCDD/Fs using surface-functionalized activated carbons.

    Science.gov (United States)

    Atkinson, J D; Hung, P C; Zhang, Z; Chang, M B; Yan, Z; Rood, M J

    2015-01-01

    Activated carbon adsorbs polychlorinated dibenzo-p-dioxins and -furans (PCDD/Fs) from gas streams but can simultaneously generate PCDD/Fs via de novo synthesis, increasing an already serious disposal problem for the spent sorbent. To increase activated carbon's PCDD/F sorption capacity and lifetime while reducing the impact of hazardous waste, it is beneficial to develop carbon-based sorbents that simultaneously destroy PCDD/Fs while adsorbing the toxic chemicals from gas streams. In this work, hydrogen-treated and surface-functionalized (i.e., oxygen, bromine, nitrogen, and sulfur) activated carbons are tested in a bench-scale reactor as adsorbents for PCDD/Fs. All tested carbons adsorb PCDD/F efficiently, with international toxic equivalent removal efficiencies exceeding 99% and mass removal efficiencies exceeding 98% for all but one tested material. Hydrogen-treated materials caused negligible destruction and possible generation of PCDD/Fs, with total mass balances between 100% and 107%. All tested surface-functionalized carbons, regardless of functionality, destroyed PCDD/Fs, with total mass balances between 73% and 96%. Free radicals on the carbon surface provided by different functional groups may contribute to PCDD/F destruction, as has been hypothesized in the literature. Surface-functionalized materials preferentially destroyed higher-order (more chlorine) congeners, supporting a dechlorination mechanism as opposed to oxidation. Carbons impregnated with sulfur are particularly effective at destroying PCDD/Fs, with destruction efficiency improving with increasing sulfur content to as high as 27%. This is relevant because sulfur-treated carbons are used for mercury adsorption, increasing the possibility of multi-pollutant control.

  12. Method for producing functionally graded nanocrystalline layer on metal surface

    Science.gov (United States)

    Ajayi, Oyelayo O.; Hershberger, Jeffrey G.

    2010-03-23

    An improved process for the creation or formation of nanocrystalline layers on substrates' surfaces is provided. The process involves "prescuffing" the surface of a substrate such as a metal by allowing friction to occur on the surface by a load-bearing entity making rubbing contact and moving along and on the substrate's surface. The "prescuffing" action is terminated when the coefficient of friction between the surface and the noise is rising significantly. Often, the significant rise in the coefficient of friction is signaled by a change in pitch of the scuffing action sound emanating from the buffeted surface. The "prescuffing" gives rise to a harder and smoother surface which withstands better any inadequate lubrication that may take place when the "prescuffed" surface is contacted by other surfaces.

  13. Non-covalent functionalization of high-surface area nanomaterials: a new class of sorbent materials

    Energy Technology Data Exchange (ETDEWEB)

    Nell, Kara M.; Fontenot, Sean A.; Carter, Timothy G.; Warner, Marvin G.; Warner, Cynthia L.; Addleman, R. Shane; Johnson, Darren W.

    2015-10-27

    non-covalent approach to functionalizing nanostructured materials with high-specificity ligands is described. In this work a variety of thiol ligands were non-covalently attached to self-assembled phenyl monolayers on nanostructured materials by taking advantage of favorable aromatic interactions. The resulting sorbent materials, both mesoporous silica and magnetic nanoparticles, were found to be very effective at scavenging soft heavy metal cations, Cd(II), Hg(II), Pb(II) and Ag(I), from aqueous matrices, performing better than commercial sorbents and comparably to the best covalently functionalized thiol sorbents available. This approach can be extended to a variety of surface chemistries and has application to chemical functionalization of a broad range of support structures used for chemical separations and processing.

  14. The orthogonal gradients method: A radial basis functions method for solving partial differential equations on arbitrary surfaces

    KAUST Repository

    Piret, Cécile

    2012-05-01

    Much work has been done on reconstructing arbitrary surfaces using the radial basis function (RBF) method, but one can hardly find any work done on the use of RBFs to solve partial differential equations (PDEs) on arbitrary surfaces. In this paper, we investigate methods to solve PDEs on arbitrary stationary surfaces embedded in . R3 using the RBF method. We present three RBF-based methods that easily discretize surface differential operators. We take advantage of the meshfree character of RBFs, which give us a high accuracy and the flexibility to represent the most complex geometries in any dimension. Two out of the three methods, which we call the orthogonal gradients (OGr) methods are the result of our work and are hereby presented for the first time. © 2012 Elsevier Inc.

  15. Cytotoxicity of surface-functionalized silicon and germanium nanoparticles: the dominant role of surface charges

    Science.gov (United States)

    Bhattacharjee, Sourav; Rietjens, Ivonne M. C. M.; Singh, Mani P.; Atkins, Tonya M.; Purkait, Tapas K.; Xu, Zejing; Regli, Sarah; Shukaliak, Amber; Clark, Rhett J.; Mitchell, Brian S.; Alink, Gerrit M.; Marcelis, Antonius T. M.; Fink, Mark J.; Veinot, Jonathan G. C.; Kauzlarich, Susan M.; Zuilhof, Han

    2013-05-01

    Although it is frequently hypothesized that surface (like surface charge) and physical characteristics (like particle size) play important roles in cellular interactions of nanoparticles (NPs), a systematic study probing this issue is missing. Hence, a comparative cytotoxicity study, quantifying nine different cellular endpoints, was performed with a broad series of monodisperse, well characterized silicon (Si) and germanium (Ge) NPs with various surface functionalizations. Human colonic adenocarcinoma Caco-2 and rat alveolar macrophage NR8383 cells were used to clarify the toxicity of this series of NPs. The surface coatings on the NPs appeared to dominate the cytotoxicity: the cationic NPs exhibited cytotoxicity, whereas the carboxylic acid-terminated and hydrophilic PEG- or dextran-terminated NPs did not. Within the cationic Si NPs, smaller Si NPs were more toxic than bigger ones. Manganese-doped (1% Mn) Si NPs did not show any added toxicity, which favors their further development for bioimaging. Iron-doped (1% Fe) Si NPs showed some added toxicity, which may be due to the leaching of Fe3+ ions from the core. A silica coating seemed to impart toxicity, in line with the reported toxicity of silica. Intracellular mitochondria seem to be the target for the toxic NPs since a dose-, surface charge- and size-dependent imbalance of the mitochondrial membrane potential was observed. Such an imbalance led to a series of other cellular events for cationic NPs, like decreased mitochondrial membrane potential (ΔΨm) and ATP production, induction of ROS generation, increased cytoplasmic Ca2+ content, production of TNF-α and enhanced caspase-3 activity. Taken together, the results explain the toxicity of Si NPs/Ge NPs largely by their surface characteristics, provide insight into the mode of action underlying the observed cytotoxicity, and give directions on synthesizing biocompatible Si and Ge NPs, as this is crucial for bioimaging and other applications in for example

  16. The role of cold work and applied stress on surface oxidation of 304 stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Lozano-Perez, Sergio, E-mail: sergio.lozano-perez@materials.ox.ac.uk [Department of Materials, University of Oxford, Parks Rd., Oxford OX1 3PH (United Kingdom); Kruska, Karen [Department of Materials, University of Oxford, Parks Rd., Oxford OX1 3PH (United Kingdom); Iyengar, Ilya [Winchester College, College Street, Winchester SO23 9LX (United Kingdom); Terachi, Takumi; Yamada, Takuyo [Institute of Nuclear Safety System (INSS), 64 Sata, Mihama-cho, Mikata-gun, Fukui 919-1205 (Japan)

    2012-03-15

    Highlights: Black-Right-Pointing-Pointer FIB 3D sequential sectioning is an ideal technique to characterize surface oxidation. Black-Right-Pointing-Pointer 3D models of the oxide can be produced with nanometre resolution. Black-Right-Pointing-Pointer The effects of stress and cold work in grain boundary oxidation have been analysed. Black-Right-Pointing-Pointer At least three different oxidation modes are observed when stress is applied. - Abstract: FIB 3-dimensional (3D) sequential sectioning has been used to characterize environmental degradation of 304 stainless steels in pressurized water reactor (PWR) simulated primary water. In particular, the effects of cold work and applied stress on oxidation have been studied in detail. It was found that a description of the oxidation behaviour of this alloy is only complete if it is treated statistically, since it can suffer from high variability depending on the feature described.

  17. Cognitive functioning, aging, and work: A review and recommendations for research and practice.

    Science.gov (United States)

    Fisher, Gwenith G; Chaffee, Dorey S; Tetrick, Lois E; Davalos, Deana B; Potter, Guy G

    2017-07-01

    There is a larger proportion and number of older adults in the labor force than ever before. Furthermore, older adults in the workforce are working until later ages. Although a great deal of research has examined physical health and well-being of working older adults, less research has focused on cognitive functioning. The purpose of this article is to provide a broad contemporary and multidisciplinary review of the intersection between cognitive functioning, aging, and work as a follow-up to a paper previously written by Fisher et al. (2014). We begin by providing definitions and background about cognitive functioning and how it changes over the life span. Next we discuss theories relevant to the intersection of cognitive functioning and work, including the use-it-or-lose-it hypothesis, the cognitive reserve hypothesis, hypotheses regarding environmental influences on intellectual functioning, and the job-demands-resources model. Then we summarize recent research about the effects of work on cognitive functioning, as well as ways that cognitive functioning may influence work motivation, learning, development, training, and safety. We conclude by emphasizing the importance of person-environment fit, suggesting avenues for future research, and discussing practical implications for the field of occupational health psychology. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

  18. Surface Functionalization of Plasma Treated Ultrananocrystalline Diamond/Amorphous Carbon Composite Films

    Science.gov (United States)

    Koch, Hermann; Popov, Cyril; Kulisch, Wilhelm; Spassov, G.; Reithmaier, Johann Peter

    Diamond possesses a number of outstanding properties which make it a perspective material as platform for preparation of biosensors. The diamond surface needs to be activated before the chemical attachment of crosslinkers with which biomolecules can interact. In the current work we have investigated the modification of ultrananocrystalline diamond/amorphous carbon (UNCD/a-C) films by oxygen and ammonia plasmas. Afterwards the layers were functionalized in a further step to obtain thiol-active maleimide groups on the surface. We studied the possibility for direct binding of maleimide to terminal OH-groups on the UNCD surface and for silanization with 3-aminopropyltriethoxysilane (APTES) to obtain NH2-groups for the following attachment of sulfosuccinimidyl 4-(N-maleimidomethyl)-cyclohexane-1-carboxylate (SSMCC). The thiol-bearing fluorescein-related dye 5-((2-(and-3)-S-(acetylmercapto) succinoyl) amino) fluorescein (SAMSA) was immobilized as an model biomolecule to evaluate the achieved thiol-activity by fluorescence microscopy. The results of the above mentioned surface modification and functionalization steps were investigated by Auger electron spectroscopy (AES) and contact angle measurements.

  19. Specific Features of Chip Making and Work-piece Surface Layer Formation in Machining Thermal Coatings

    Directory of Open Access Journals (Sweden)

    V. M. Yaroslavtsev

    2016-01-01

    of chip element formation are cycled. Fluctuations of the cutting force components completely repeat all the stages of local destruction and formation of individual chip elements. Studies have shown that with increased thickness of the cut-off layer the main crack develops below the cut-off line thus significantly affecting the quality of the machined surface: emerging cracks, cavities, chips, and other defects that significantly reduce the product performance.In machining the plasma-sprayed coatings, their high tendency to strengthening and rehardening because of the cutting action has a great impact on the surface quality. This is evident as a loss of the elastic equilibrium state stability and as a destruction of the work-piece surface layer (chipping, peeling, flaking. With increasing curvature of the machined surface (e.g., decreasing radius of cylindrical billet the surface layer is increasingly prone to destruction.Specific problems are cutting fluids used in grinding the plasma-sprayed coatings. Machining in this case comes with saturated liquid vapours formed in the surface layer of a billet under high pressure. With a pressure drop on the tool-side in cutting there is such an intensity of vaporization that micro- and macro-fractures of the machined work-piece surface can be initiated.

  20. A Conceptual Foundation for Measures of Physical Function and Behavioral Health Function for Social Security Work Disability Evaluation

    Science.gov (United States)

    Marfeo, Elizabeth E.; Haley, Stephen M.; Jette, Alan M.; Eisen, Susan V.; Ni, Pengsheng; Bogusz, Kara; Meterko, Mark; McDonough, Christine M.; Chan, Leighton; Brandt, Diane E.; Rasch, Elizabeth K.

    2014-01-01

    Physical and mental impairments represent the two largest health condition categories for which workers receive Social Security disability benefits. Comprehensive assessment of physical and mental impairments should include aspects beyond medical conditions such as a person’s underlying capabilities as well as activity demands relevant to the context of work. The objective of this paper is to describe the initial conceptual stages of developing new measurement instruments of behavioral health and physical functioning relevant for Social Security work disability evaluation purposes. To outline a clear conceptualization of the constructs to be measured, two content models were developed using structured and informal qualitative approaches. We performed a structured literature review focusing on work disability and incorporating aspects of the International Classification of Functioning, Disability, and Health (ICF) as a unifying taxonomy for framework development. Expert interviews provided advice and consultation to enhance face validity of the resulting content models. The content model for work-related behavioral health function identifies five major domains (1) Behavior Control, (2) Basic Interactions, (3) Temperament and Personality, (4) Adaptability, and (5) Workplace Behaviors. The content model describing physical functioning includes three domains (1) Changing and Maintaining Body Position, (2) Whole Body Mobility, and (3) Carrying, Moving and Handling Objects. These content models informed subsequent measurement properties including item development, measurement scale construction, and provided conceptual coherence guiding future empirical inquiry. The proposed measurement approaches show promise to comprehensively and systematically assess physical and behavioral health functioning relevant to work. PMID:23548543

  1. Testing of newly developed functional surfaces under pure sliding conditions

    DEFF Research Database (Denmark)

    Godi, Alessandro; Mohaghegh, Kamran; Grønbæk, J.;

    2013-01-01

    The employment of surface texturing for improved tribological contacts has spread over the years. The possibilities of designing and manufacturing textured surfaces with predetermined geometries have multiplied as well as the need of performing experimental laboratory tests before applying...

  2. A work-loop method for characterizing leg function during sagittal plane movements.

    Science.gov (United States)

    Maykranz, Daniel; Grimmer, Sten; Seyfarth, Andre

    2013-10-01

    The work-loop method is frequently used to determine the mechanical work performed by a system, for instance, when analyzing muscles or describing the work balance at the joint level. While for these examples usually only one-dimensional movements are investigated, for two- or three-dimensional movements, such as leg function during walking and running, the work-loop has to be adapted. In this paper, we present an analytical derivation that extends the work-loop method to two-dimensional sagittal plane movements. Three effects contribute to the mechanical work of the leg: (1) forces directed along the leg axis, (2) forces acting perpendicular to the leg axis, and (3) a shift of the center of pressure (COP) during stance. These three contributors to the mechanical work performed can be interpreted as three general tasks of the leg. To demonstrate the new work-loop method, we analyzed experimental data on hopping, running and walking. The results indicate that the proposed new generalized work-loop concept is suitable for describing the overall mechanical work performed on the COM during stance with energy consistent net work balances. Depending on the type of gait, specific contributions of each work term were found that characterize leg function during locomotion.

  3. Characterization of Bimetallic Castings with an Austenitic Working Surface Layer and an Unalloyed Cast Steel Base

    Science.gov (United States)

    Wróbel, Tomasz

    2014-05-01

    The paper presents the technology of bimetallic castings based on the founding method of layer coating directly in the cast process of the so-called method of mold cavity preparation. The prepared castings consist of two fundamental parts, i.e., the base and the working surface layer. The base part of the bimetallic casting is typical foundry material, i.e., unalloyed cast steel, whereas the working layer is a plate of austenitic alloy steel sort X2CrNi 18-9. The quality of the joint between the base part and the working layer was evaluated on the basis of ultrasonic non-destructive testing and structure examinations containing metallographic macro- and microscopic studies with the use of a light microscope (LOM) with microhardness measurements and a scanning electron microscope (SEM) with microanalysis of the chemical composition (energy dispersive spectroscopy—EDS). On the basis of the obtained results it was confirmed that the decisive phenomena needed to create a permanent joint between the two components of the bimetallic casting are carbon and heat transport in the direction from the high-carbon and hot base material which was poured into the mold in the form of liquid metal to the low-carbon and cold material of the working layer which was placed in the mold cavity in the form of a monolithic insert.

  4. Formation of Triboelectric Series via Atomic-Level Surface Functionalization for Triboelectric Energy Harvesting.

    Science.gov (United States)

    Shin, Sung-Ho; Bae, Young Eun; Moon, Hyun Kyung; Kim, Jungkil; Choi, Suk-Ho; Kim, Yongho; Yoon, Hyo Jae; Lee, Min Hyung; Nah, Junghyo

    2017-06-27

    Triboelectric charging involves frictional contact of two different materials, and their contact electrification usually relies on polarity difference in the triboelectric series. This limits the choices of materials for triboelectric contact pairs, hindering research and development of energy harvest devices utilizing triboelectric effect. A progressive approach to resolve this issue involves modification of chemical structures of materials for effectively engineering their triboelectric properties. Here, we describe a facile method to change triboelectric property of a polymeric surface via atomic-level chemical functionalizations using a series of halogens and amines, which allows a wide spectrum of triboelectric series over single material. Using this method, tunable triboelectric output power density is demonstrated in triboelectric generators. Furthermore, molecular-scale calculation using density functional theory unveils that electrons transferred through electrification are occupying the PET group rather than the surface functional group. The work introduced here would open the ability to tune triboelectric property of materials by chemical modification of surface and facilitate the development of energy harvesting devices and sensors exploiting triboelectric effect.

  5. Bone-like apatite coating on functionalized poly(etheretherketone) surface via tailored silanization layers technique

    Energy Technology Data Exchange (ETDEWEB)

    Zheng, Yanyan [Chengdu Institute of Organic Chemistry, Chinese Academy of Sciences, Chengdu 610041 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Xiong, Chengdong; Zhang, Shenglan [Chengdu Institute of Organic Chemistry, Chinese Academy of Sciences, Chengdu 610041 (China); Li, Xiaoyu [State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu 610041 (China); Zhang, Lifang, E-mail: zhanglfcioc@163.com [Chengdu Institute of Organic Chemistry, Chinese Academy of Sciences, Chengdu 610041 (China)

    2015-10-01

    Poly(etheretherketone) (PEEK) is a rigid semi-crystalline polymer with outstanding mechanical properties, bone-like stiffness and suitable biocompatibility that has attracted much interest as a biomaterial for orthopedic and dental implants. However, the bio-inert surface of PEEK limits its biomedical applications when direct osteointegration between the implants and the host tissue is desired. In this work, –PO{sub 4}H{sub 2}, –COOH and –OH groups were introduced on the PEEK surface by further chemical treatments of the vinyl-terminated silanization layers formed on the hydroxylation-pretreated PEEK surface. Both the surface-functionalized and pristine specimens were characterized by X-ray photoelectron spectroscopy (XPS), attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy and water contact angle measurements. When placed in 1.5 strength simulated body fluid (SBF) solution, apatite was observed to form uniformly on the functionalized PEEK surface and firmly attach to the substrate. The characterized results demonstrated that the coating was constituted by poorly crystallized bone-like apatite and the effect of surface functional groups on coating formation was also discussed in detail. In addition, in vitro biocompatibility of PEEK, in terms of pre-osteoblast cell (MC3T3-E1) attachment, spreading and proliferation, was remarkably enhanced by the bone-like apatite coating. Thus, this study provides a method to enhance the bioactivity of PEEK and expand its applications in orthopedic and dental implants. - Highlights: • –PO{sub 4}H{sub 2}, –COOH and –OH groups were successfully introduced onto PEEK surface via tailored silanization layer technique. • Bone-like apatite formed uniformly on surface-functionalized PEEK after immersion in SBF, and tightly adhered to the PEEK. • SEM, EDS, FTIR, XPS and XRD results showed that apatite layer is composed of low-crystalline bone-like apatite. • Bone-like apatite coating

  6. Emissivity as a Function of Surface Roughness: A Computer Model.

    Science.gov (United States)

    1986-08-29

    dependance on surface roughness sheds some light on ship wake measurements (8] , and corrects some of the analysis of spatial sea surface temperature...variation recently reported in (6) . The wind wave spectral dependance of surface emissivity also indicates that shorter wavelengths, such as...definition, a power spectrum contains no phase dependance . Therefore, in order to create a reasonable model of the surface elevation, we assume that the

  7. Bending energy penalty enhances the adhesive strength of functional amyloid curli to surfaces.

    Science.gov (United States)

    Zhang, Yao; Wang, Ao; DeBenedictis, Elizabeth P; Keten, Sinan

    2017-09-27

    The functional amyloid curli fiber, a major proteinaceous component of biofilm extracellular matrices, plays an important role in biofilm formation and enterobacteriaceae adhesion. Curli nanofibers exhibit exceptional underwater adhesion to various surfaces, have high rigidity and strong tensile mechanical properties, and thus hold great promise in biomaterials. The mechanisms of how curli fibers strongly attach to surfaces and detach under force remain elusive. To investigate curli fiber adhesion to surfaces, we developed a coarse-grained curli fiber model, in which the protein subunit CsgA (curli specific gene A) self-assembles into the fiber. The coarse-grained model yields physiologically relevant and tunable bending rigidity and persistence length. The force-induced desorption of a single curli fiber is examined using coarse-grained modeling and theoretical analysis. We find that the bending energy penalty arising from high persistence length enhances the resistance of the curli fiber against desorption and thus strengthens the adhesion of the curli fiber to surfaces. The CsgA-surface adhesion energy and the curli fiber bending rigidity both play crucial roles in the resistance of curli fiber against desorption from surfaces. To enable the desorption process, the applied peeling force must overcome both the interfacial adhesion energy and the energy barrier for bending the curli fiber at the peeling front. We show that the energy barrier to desorption increases with the interfacial adhesion energy, however, the bending induced failure of a single curli fiber limits the work of adhesion if the proportion of the CsgA-surface adhesion energy to the CsgA-CsgA cohesive energy becomes large. These results illustrate that the optimal adhesion performance of nanofibers is dictated by the interplay between bending, surface energy and cohesive energy. Our model provides timely insight into enterobacteriaceae adhesion mechanisms as well as future designs of engineered

  8. Theory of Metallic Work Functions Between Metals and Layers of Exclusion Zone Ordered Water

    CERN Document Server

    Widom, A; Srivastava, Y N

    2016-01-01

    The magnitude of the work function to bring an electron from a metal into the exclusion zone water layer making hydrophilic contact with the metallic interface is theoretically computed. The agreement with recent experimental measurements is satisfactory.

  9. Synthesis and characterization of low work function alkali oxide thin films for unconventional thermionic energy converters

    Science.gov (United States)

    Giorgis, V.; Morini, F.; Zhu, T.; Robillard, J.-F.; Wallart, X.; Codron, J.-L.; Dubois, E.

    2016-11-01

    In this work, we present the synthesis and the characterization of low work function thin films for Micro Thermionic Converters (MTC). The objective is producing a device operating at relatively low temperature (caesium oxides. Our choice to exploit those materials relies on their low work function and their abundance. For both materials, we present the results on the synthesis of the oxides under high vacuum and controlled temperature. The oxide thin films were characterized by X-ray photoelectron spectroscopy, photoemission, and thermionic emission measurements. By exploiting the latter technique, a quantitative evaluation of the current density, emitted by the heated oxides, is obtained as a function of temperature. Our results demonstrate that it is possible to decrease the silicon work function by almost 3 eV, enabling significant thermionic currents despite relatively low temperatures (below 850 K).

  10. Understanding effects of TCO work function on the performance of organic solar cells by numerical simulation

    CERN Document Server

    Chen, Aqing; Shao, Qingyi; Ji, Zhenguo

    2016-01-01

    The influences of work function of transparent conducting oxides (TCO) on the per-formance of organic solar cells, including open circuit voltage, conversion efficiency and fill factor, has been simulated. It is obtained that for non-Ohmic contact the open circuit voltage and conversion efficiency increase monotonically with the TCO work function but keep constant for Ohmic contact. Fill factor decreases and increases with the electrode work function when the electrode work function is below and above a critical value (4.2 eV for TCO and 4.5 eV for back-contact), respectively. The results of this simulation are significant in the choice of TCO contacts to optimize organic planar heterojunction solar cells.

  11. Dendritic surface functionalization of nanomaterials: controlling properties and functions for biomedical applications

    Directory of Open Access Journals (Sweden)

    Ali Nazemi

    2013-01-01

    Full Text Available A wide variety of nanomaterials have demonstrated promise in medical applications such as drug delivery and imaging. In these applications, the surface chemistry of the materials is critical as it plays an important role in determining the toxicity and biodistribution behavior of the material. We review here the functionalization of nanomaterials with dendrons as an efficient method to alter the surface chemistry of the materials, introducing new properties and functions. Described here is the functionalization of superparamagnetic iron oxide nanoparticles (SPIO with dendritic guanidines to enhance their transport into cells for magnetic resonance imaging applications. The introduction of dendrons bearing peripheral hydroxyls, amines, guanidines, carbohydrates and Gd(III chelates to polymer vesicles (polymersomes is also described. These dendritic moieties allow for modulation of toxicity, cell uptake, protein binding, and contrast agent efficiency, while at the same time allowing the stabilities of the polymersomes to be maintained. Thus, this approach holds promise for the development of a wide range of multifunctional materials for pharmaceutical applications.

  12. Mixed time-dependent density-functional theory/classical trajectory surface hopping study of oxirane photochemistry

    NARCIS (Netherlands)

    Tapavicza, Enrico; Tavernelli, Ivano; Rothlisberger, Ursula; Filippi, Claudia; Casida, Mark E.

    2008-01-01

    We present a mixed time-dependent density-functional theory (TDDFT)/classical trajectory surface hopping (SH) study of the photochemical ring opening in oxirane. Previous preparatory work limited to the symmetric CC ring-opening pathways of oxirane concluded that the Tamm-Dancoff approximation (TDA)

  13. The Effect of Surface Functionalization on the Immobilization of Gold Nanoparticles on Graphene Sheets

    Directory of Open Access Journals (Sweden)

    Min Song

    2012-01-01

    Full Text Available In our study, graphene oxide is synthesized by Hummers method. And then, carboxylic acid functionalized graphene (graphene-COOH, thiol-functionalized graphene (graphene-SH, and highly dispersive graphene are prepared by chemical modification of respective groups on the graphene surface. Furthermore, we explore a solution-based approach to prepare three differently functionalized graphene-gold composites by one-step chemical reduction of AuCl4 - ions in respective functionalized graphene suspensions, where the gold nanoparticles are deposited on the functionalized graphene surface during their synthesis process. In addition, we compare the influence of surface functionalization on the growth of gold nanoparticles on graphene surface. Transmission electron morphology (TEM and ultraviolet-visible (UV-Vis spectroscopy are employed to study the effect of surface functionalities on AuNPs distribution onto the graphene surface and demonstrate the successful immobilization of AuNPs on graphene surface.

  14. Binary Pseudo-Random Gratings and Arrays for Calibration of Modulation Transfer Functions of Surface Profilometers

    Energy Technology Data Exchange (ETDEWEB)

    Barber, Samuel K.; Anderson, Erik D.; Cambie, Rossana; McKinney, Wayne R.; Takacs, Peter Z.; Stover, John C.; Voronov, Dmitriy L.; Yashchuk, Valeriy V.

    2009-09-11

    A technique for precise measurement of the modulation transfer function (MTF), suitable for characterization of a broad class of surface profilometers, is investigated in detail. The technique suggested in [Proc. SPIE 7077-7, (2007), Opt. Eng. 47(7), 073602-1-5 (2008)]is based on use of binary pseudo-random (BPR) gratings and arrays as standard MTF test surfaces. Unlike most conventional test surfaces, BPR gratings and arrays possess white-noise-like inherent power spectral densities (PSD), allowing the direct determination of the one- and two-dimensional MTF, respectively, with a sensitivity uniform over the entire spatial frequency range of a profiler. In the cited work, a one dimensional realization of the suggested method based on use of BPR gratings has been demonstrated. Here, a high-confidence of the MTF calibration technique is demonstrated via cross comparison measurements of a number of two dimensional BPR arrays using two different interferometric microscopes and a scatterometer. We also present the results of application of the experimentally determined MTF correction to the measurement taken with the MicromapTM-570 interferometric microscope of the surface roughness of a super-polished test mirror. In this particular case, without accounting for the instrumental MTF, the surface rms roughness over half of the instrumental spatial frequency bandwidth would be underestimated by a factor of approximately 1.4.

  15. Surface functionalization of fluorine-doped tin oxide samples through electrochemical grafting.

    Science.gov (United States)

    Lamberti, F; Agnoli, S; Brigo, L; Granozzi, G; Giomo, M; Elvassore, N

    2013-12-26

    Transparent conductive oxides are emerging materials in several fields, such as photovoltaics, photoelectrochemistry, and optical biosensing. Their high chemical inertia, which ensured long-term stability on one side, makes challenging the surface modification of transparent conductive oxides; long-term robust modification, high yields, and selective surface modifications are essential prerequisite for any further developments. In this work, we aim at inducing chemical functionality on fluorine-doped tin oxide surfaces (one of the most inexpensive transparent conductive oxide) by means of electrochemical grafting of aryl diazonium cations. The grafted layers are fully characterized by photoemission spectroscopy, cyclic voltammetry, and atomic force microscopy showing linear correlation between surface coverage and degree of modification. The electrochemical barrier effect of modified surfaces was studied at different pH to characterize the chemical nature of the coating. We showed immuno recognition of biotin complex built onto grafted fluorine-doped tin oxides, which opens the perspective of integrating FTO samples with biological-based devices.

  16. Surface Functionalized Nanostructured Ceramic Sorbents for the Effective Collection and Recovery of Uranium from Seawater

    Energy Technology Data Exchange (ETDEWEB)

    Chouyyok, Wilaiwan; Pittman, Jonathan W.; Warner, Marvin G.; Nell, Kara M.; Clubb, Donald C.; Gill, Gary A.; Addleman, Raymond S.

    2016-05-02

    The ability to collect uranium from seawater offers the potential for a nearly limitless fuel supply for nuclear energy. We evaluated the use of functionalized nanostructured sorbents for the collection and recovery of uranium from seawater. Extraction of trace minerals from seawater and brines is challenging due to the high ionic strength of seawater, low mineral concentrations, and fouling of surfaces over time. We demonstrate that rationally assembled sorbent materials that integrate high affinity surface chemistry and high surface area nanostructures into an application relevant micro/macro structure enables collection performance that far exceeds typical sorbent materials. High surface area nanostructured silica with surface chemistries composed of phosphonic acid, phosphonates, 3,4 hydroxypyridinone, and EDTA showed superior performance for uranium collection. A few phosphorous-based commercial resins, specifically Diphonix and Ln Resin, also performed well. We demonstrate an effective and environmentally benign method of stripping the uranium from the high affinity sorbents using inexpensive nontoxic carbonate solutions. The cyclic use of preferred sorbents and acidic reconditioning of materials was shown to improve performance. Composite thin films composed of the nanostructured sorbents and a porous polymer binder are shown to have excellent kinetics and good capacity while providing an effective processing configuration for trace mineral recovery from solutions. Initial work using the composite thin films shows significant improvements in processing capacity over the previously reported sorbent materials.

  17. The assessment of functional work capacity in the South African mining industry.

    Science.gov (United States)

    Hofmann, Tia-Mari; Kielblock, Johan

    2007-01-01

    Overall physical work fitness is a prerequisite in numerous industries. Apart from improved productivity, it remains fundamental with regards to the maintenance of good health and safety. To address worker fitness in the mining industry, AngloGold Ashanti and Anglo Platinum Mining Houses developed a Functional Work Capacity (FWC) test battery. The FWC test battery consists of 19 work simulations representing the required functional work capacity to cope with all types of physical work tasks and work environments in the mining industry. This assessment tool is not only used to evaluate injured or medically affected workers for alternative placement but also to ensure that the new employee is placed in a job matching his physical capacity. This paper reviews the design process and application of the FWC test battery in the mining industry.

  18. Variations in erosive wear of metallic materials with temperature via the electron work function

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Xiaochen; Yu, Bin [Department of Chemical and Materials Engineering, University of Alberta, Edmonton, Alberta, T6G 2V4 (Canada); Yan, X.G. [School of Mechanical Engineering, Taiyuan University of Science and Technology, Taiyuan, Shanxi (China); Li, D.Y., E-mail: dongyang.li@ualberta.ca [Department of Chemical and Materials Engineering, University of Alberta, Edmonton, Alberta, T6G 2V4 (Canada); School of Mechanical Engineering, Taiyuan University of Science and Technology, Taiyuan, Shanxi (China)

    2016-04-01

    Mechanical properties of metals are intrinsically determined by their electron behavior, which is largely reflected by the electron work function (EWF or φ). Since the work function varies with temperature, the dependence of material properties on temperature could be predicted via variations in work function with temperature. Combining a hardness – φ relationship and the dependence of work function on temperature, a temperature-dependent model for predicting solid-particle erosion is proposed. Erosive wear losses of copper, nickel, and carbon steel as sample materials were measured at different temperatures. Results of the tests are consistent with the theoretical prediction. This study demonstrates a promising parameter, electron work function, for looking into fundamental aspects of wear phenomena, which would also help develop alternative methodologies for material design. - Highlights: • Metallic materials' wear resistance is influenced by temperature. • Electron work function (EWF) intrinsically determines materials' wear resistance. • An EWF-based temperature-dependent solid-particle erosion model is proposed.

  19. Effects of marital status and shift work on family function among registered nurses.

    Science.gov (United States)

    Tai, Shu-Yu; Lin, Pei-Chen; Chen, Yao-Mei; Hung, Hsin-Chia; Pan, Chih-Hong; Pan, Shung-Mei; Lee, Chung-Yin; Huang, Chia-Tsuan; Wu, Ming-Tsang

    2014-01-01

    This study aims to assess the interactive effect of marital status and shift work on family function. A population-based sample of 1,438 nurses between the ages of 20-45 yr was recruited from Taiwan during the period from July 2005 to April 2006 using a mailed questionnaire. The self-administered questionnaire contained information about demographic data, work status, shift work schedule, and the Family APGAR (Adaptation, Partnership, Growth, Affection, and Resolve) Scale, to evaluate family function. Compared to day shift nurses, non-night and rotation shift nurses had 1.53- and 1.38-fold (95% CI=1.09-2.14 and 1.01-1.88) risk to have poor family function after adjusting for other covariates. Married nurses, by contrast, had a 0.44-fold (95% CI=0.29-0.66) risk to have poor family function compared to single nurses. In addition, married nurses who worked non-night or rotation shifts had a significantly higher percent of poor family function than those married nurses working day shifts; however, similar results were not replicated in single nurses. We concluded that shift work and marital status could influence family function.

  20. Unemployment and Work Interruption among African American Single Mothers: Effects on Parenting and Adolescent Socioemotional Functioning.

    Science.gov (United States)

    McLoyd, Vonnie C.; And Others

    1994-01-01

    Using interview data from 241 single African American mothers and their seventh- and eighth-grade children, this study tested a model of how 2 economic stressors, maternal unemployment and work interruption, influenced adolescent socioemotional functioning. Found that current unemployment, but not past work interruption, contributed to depressive…

  1. Unemployment and Work Interruption among African American Single Mothers: Effects on Parenting and Adolescent Socioemotional Functioning.

    Science.gov (United States)

    McLoyd, Vonnie C.; And Others

    1994-01-01

    Using interview data from 241 single African American mothers and their seventh- and eighth-grade children, this study tested a model of how 2 economic stressors, maternal unemployment and work interruption, influenced adolescent socioemotional functioning. Found that current unemployment, but not past work interruption, contributed to depressive…

  2. Working memory performance and executive function behaviors in young children with SLI

    NARCIS (Netherlands)

    Vugs, B.A.M.; Hendriks, M.P.H.; Cuperus, J.M.; Verhoeven, L.T.W.

    2014-01-01

    The present study compared the performances of young children with specific language impairment (SLI) to that of typically developing (TD) children on cognitive measures of working memory (WM) and behavioral ratings of executive functions (EF). The Automated Working Memory Assessment was administere

  3. Age-experience changes of functional stress and work capability of miners with physical labor

    Energy Technology Data Exchange (ETDEWEB)

    Soldakm, I.I.

    1987-06-01

    Examines relation of functional stress and work capability to age and period of service of miners. Through time and motion studies work stress was measured by frequency of pulse, and work capability by work produced in a period of time. Four groups of workers were studied: 2 groups aged 23-28 with 2-5 years experience and 2 groups aged 30-42 with 7-15 years experience. The first 2 members of each group were employed at mechanized tasks directing mining machines and mechanisms; the second members of the 2 groups performed manual and partly mechanical and manual tasks. Results of time and motion study measurements demonstrate that degree of functional stress of miners increases and work capability diminishes with age, length of service and heaviness of physical work. Mathematical models relating functional stress and work capability were developed having the form of a nonlinear regression based on a function that enables prediction of work capability depending on age, experience and physical workload. 13 refs.

  4. Working memory network plasticity after anterior temporal lobe resection: a longitudinal functional magnetic resonance imaging study

    OpenAIRE

    Stretton, Jason; Sidhu, Meneka K; Winston, Gavin P.; Bartlett, Philippa; McEvoy, Andrew W; Symms, Mark R.; Koepp, Matthias J; Thompson, Pamela J; Duncan, John S.

    2014-01-01

    Working memory is a crucial cognitive function that is disrupted in temporal lobe epilepsy. It is unclear whether this impairment is a consequence of temporal lobe involvement in working memory processes or due to seizure spread to extratemporal eloquent cortex. Anterior temporal lobe resection controls seizures in 50–80% of patients with drug-resistant temporal lobe epilepsy and the effect of surgery on working memory are poorly understood both at a behavioural and neural level. We investiga...

  5. Surface functionalization of two-dimensional metal chalcogenides by Lewis acid-base chemistry

    Science.gov (United States)

    Lei, Sidong; Wang, Xifan; Li, Bo; Kang, Jiahao; He, Yongmin; George, Antony; Ge, Liehui; Gong, Yongji; Dong, Pei; Jin, Zehua; Brunetto, Gustavo; Chen, Weibing; Lin, Zuan-Tao; Baines, Robert; Galvão, Douglas S.; Lou, Jun; Barrera, Enrique; Banerjee, Kaustav; Vajtai, Robert; Ajayan, Pulickel

    2016-05-01

    Precise control of the electronic surface states of two-dimensional (2D) materials could improve their versatility and widen their applicability in electronics and sensing. To this end, chemical surface functionalization has been used to adjust the electronic properties of 2D materials. So far, however, chemical functionalization has relied on lattice defects and physisorption methods that inevitably modify the topological characteristics of the atomic layers. Here we make use of the lone pair electrons found in most of 2D metal chalcogenides and report a functionalization method via a Lewis acid-base reaction that does not alter the host structure. Atomic layers of n-type InSe react with Ti4+ to form planar p-type [Ti4+n(InSe)] coordination complexes. Using this strategy, we fabricate planar p-n junctions on 2D InSe with improved rectification and photovoltaic properties, without requiring heterostructure growth procedures or device fabrication processes. We also show that this functionalization approach works with other Lewis acids (such as B3+, Al3+ and Sn4+) and can be applied to other 2D materials (for example MoS2, MoSe2). Finally, we show that it is possible to use Lewis acid-base chemistry as a bridge to connect molecules to 2D atomic layers and fabricate a proof-of-principle dye-sensitized photosensing device.

  6. Prediction of the Functional Performance of Machined Components Based on Surface Topography: State of the Art

    Science.gov (United States)

    Grzesik, Wit

    2016-10-01

    This survey overviews the functional performance of manufactured components produced by typical finishing machining operations in terms of their topographical characteristics. Surface topographies were characterized using both profile (2D) and 3D (areal) surface roughness parameters. The prediction of typical functional properties such as fatigue, friction, wear, bonding and corrosion is discussed based on appropriate surface roughness parameters. Some examples of real 3D surface topographies produced with desired functional characteristics are provided. This survey highlights technological possibilities of producing surfaces with enhanced functional properties by machining processes.

  7. Modulation of the effective work function of TiN metal gate for PMOS application

    Institute of Scientific and Technical Information of China (English)

    Han Kai; Ma Xueli; Yang Hong; Wang Wenwu

    2013-01-01

    It is important to find a way to modulate the work function of TiN metal gate towards the valence band edge of Si,which can meet the lower threshold voltage requirement of p-type metal-oxide-semiconductor (MOS) transistor.In this work,effects of TiN thickness,post-deposition annealing (PDA),oxygen incorporation and N concentration variation on the work function of TiN metal gate in MOS structures are systematically investigated.It can be found that the work function positively shifts at the initial stage as the thickness of the TiN layer increases and stabilizes at such a thickness.PDA at N2 ambience with a trace of O2 can also cause a positive shift in the work function of TiN metal gate.The same tendency can be observed when oxygen is incorporated into TiN.Finally,increasing the N concentration in TiN can also positively shift the work function.All these measures are effective in modulating the TiN metal gate so that it is more suitable for PMOS application.

  8. Configurational study of amino-functionalized silica surfaces: A density functional theory modeling.

    Science.gov (United States)

    Hozhabr Araghi, Samira; Entezari, Mohammad H; Sadeghi Googheri, Mohammad Sadegh

    2015-06-01

    Despite extensive studies of the amino-functionalized silica surfaces, a comprehensive investigation of the effects of configuration and hydrolysis of 3-aminopropyltriethoxysilan (APTES) molecules attached on silica has not been studied yet. Therefore, the methods of quantum mechanics were used for the study of configuration and hydrolysis forms of APTES molecules attached on the surface. For this purpose, five different categories based on the number of hydrolyzed ethoxy groups including 16 configurations were designed and analyzed by the density functional theory (DFT) method. The steric hindrance as an effective factor on the stability order was extracted from structural analysis. Other impressive parameters such as the effects of hydrogen bond and electron delocalization energy were obtained by using the atoms in molecules (AIM) and natural bond orbitals (NBO) theories. Consequently, it was found that the stability of configurations was attributed to steric effects, hydrogen bond numbers and electron delocalization energy. The maximum stability was achieved when at least two of these parameters cooperate with each other.

  9. Psychological, academic, and work functioning in college students with childhood-onset asthma.

    Science.gov (United States)

    Carpentier, Melissa Y; Mullins, Larry L; Van Pelt, Jill C

    2007-03-01

    This study investigated differences in psychological, academic, and work functioning between college students with and without asthma and identified predictors of functioning. Both participants with asthma (n = 121) and age-and gender-matched healthy control subjects (n = 121) completed measures of psychological distress, provided information on missed school and work days, and consented to have their grade point averages released from the registrar. College students with asthma also completed measures of illness uncertainty and illness intrusiveness. Participants with asthma reported greater anxiety, general psychological distress, and more missed school and work days compared to healthy control subjects. Within the asthma group, both illness uncertainty and illness intrusiveness independently predicted anxious and depressive symptoms and general psychological distress; illness intrusiveness also predicted missed school days. Although enrollment in college implies resilient functioning, college students with asthma remain at risk for problems with psychological and academic functioning.

  10. Effects of surface functionalization on the surface phage coverage and the subsequent performance of phage-immobilized magnetoelastic biosensors.

    Science.gov (United States)

    Horikawa, Shin; Bedi, Deepa; Li, Suiqiong; Shen, Wen; Huang, Shichu; Chen, I-Hsuan; Chai, Yating; Auad, Maria L; Bozack, Michael J; Barbaree, James M; Petrenko, Valery A; Chin, Bryan A

    2011-01-15

    One of the important applications for which phage-immobilized magnetoelastic (ME) biosensors are being developed is the wireless, on-site detection of pathogenic bacteria for food safety and bio-security. Until now, such biosensors have been constructed by immobilizing a landscape phage probe on gold-coated ME resonators via physical adsorption. Although the physical adsorption method is simple, the immobilization stability and surface coverage of phage probes on differently functionalized sensor surfaces need to be evaluated as a potential way to enhance the detection capabilities of the biosensors. As a model study, a filamentous fd-tet phage that specifically binds streptavidin was adsorbed on either bare or surface-functionalized gold-coated ME resonators. The surface functionalization was performed through the formation of three self-assembled monolayers with a different terminator, based on the sulfur-gold chemistry: AC (activated carboxy-terminated), ALD (aldehyde-terminated), and MT (methyl-terminated). The results, obtained by atomic force microscopy, showed that surface functionalization has a large effect on the surface phage coverage (46.8%, 49.4%, 4.2%, and 5.2% for bare, AC-, ALD-, and MT-functionalized resonators, respectively). In addition, a direct correlation of the observed surface phage coverage with the quantity of subsequently captured streptavidin-coated microbeads was found by scanning electron microscopy and by resonance frequency measurements of the biosensors. The differences in surface phage coverage on the differently functionalized surfaces may then be used to pattern the phage probe layer onto desired parts of the sensor surface to enhance the detection capabilities of ME biosensors.

  11. Surface nitrogen functionality for the enhanced field emission of free-standing few-layer graphene nanowalls

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, C.X. [State Key Laboratory of Optoelectronic Materials and Technologies, Guangdong Province Key Laboratory of Display Material and Technology, and School of Electronics and Information Technology, Sun Yat-sen University, Guangzhou 510275 (China); Guangzhou Key Laboratory of Vacuum Coating Technologies and New Energy Materials, Department of Physics, Jinan University, Guangzhou 510632 (China); Zhang, Yu; Deng, S.Z.; Xu, N.S. [State Key Laboratory of Optoelectronic Materials and Technologies, Guangdong Province Key Laboratory of Display Material and Technology, and School of Electronics and Information Technology, Sun Yat-sen University, Guangzhou 510275 (China); Chen, Jun, E-mail: stscjun@mail.sysu.edu.cn [State Key Laboratory of Optoelectronic Materials and Technologies, Guangdong Province Key Laboratory of Display Material and Technology, and School of Electronics and Information Technology, Sun Yat-sen University, Guangzhou 510275 (China)

    2016-07-05

    The effects of nitrogen functionalization on the field emission properties of vertically aligned few-layer graphene (FLG) nanowall thin films are investigated. Lowered work function and enhanced electron emission property are observed after ammonia plasma treatment. The turn-on field (defined at 10 μAcm{sup −2}) is found to be decreased from 6.5 to 4.6 Vμm{sup −1}. Additionally, more stable emission with fluctuation less than 5% is obtained after surface N-functionalization. The electron configuration of nitrogen in FLG edge is proposed to be amine (C–NH{sub 2}) terminal configuration. Nitrogen doping could significantly increases the π density states near the Fermi level. The maximum upward shift of E{sub F} is determined to be ∼0.23 eV by low-energy XPS measurements, which mainly accounts for the lower turn-on electric field. Meanwhile, nitrogen functionalization would minimize surface desorption and accounts for more uniform work function distribution. Finally, the nonlinear characteristics of Fowler–Nordheim plots could be understood by thermionic-field emission process. - Highlights: • Enhanced field emission was found in nitrogen functionalization of FLG nanowalls. • Work function shows remarkable reduce of 0.23 eV after nitrogen functionalization. • Nitrogen in FLG edge is proposed to be amine terminal configuration. • The underlying mechanism about the nonlinear F–N plots was proposed.

  12. Forming of a functional biofilm on wood surfaces

    NARCIS (Netherlands)

    Sailer, M.F.; Nieuwenhuijzen, E.J. van; Knol, W.

    2010-01-01

    The protecting and staining properties of biofilms grown on oil-treated surfaces of Pinus sylvestris L. sapwood were investigated with respect to their potential to create homogeneous coloured surfaces. Linseed oil pressure-treated blocks of P. sylvestris L. were evaluated after 36 months of outdoor

  13. Interactions between acid- and base-functionalized surfaces

    NARCIS (Netherlands)

    Giesbers, M.; Kleijn, J.M.; Cohen Stuart, M.A.

    2002-01-01

    In this paper we present an AFM force study on interactions between chemically modified surfaces. Surfaces with terminal groups of either NH2 or COOH were obtained by chemisorption of a silane-based compound (3-amino-propyltriethoxysilane) on silica or a thiol compound (11-mercapto undecanoic acid)

  14. Investigation of Tooling for Anisotropic Optical Functional Surfaces

    DEFF Research Database (Denmark)

    Li, Dongya; Regi, Francesco; Zhang, Yang

    is assessed by processing the images obtained from a digital microscope Hirox RH-2000 [1]. Figure 1 illustrates the studied surface structure and the microscope. The optical axis of microscope can be tilted within 90 degrees from the horizontal level, which simulates the viewing angle; the analysed surface...

  15. Developing Research on Performance-Based Functional Work Assessment : Report on the First International Functional Capacity Evaluation Research Meeting

    NARCIS (Netherlands)

    Reneman, M. F.; Soer, R.; Gross, D. P.

    2013-01-01

    Introduction Research on Performance-Based Work Assessment, also known as Functional Capacity Evaluation (FCE), has evolved substantially over the past decades. Although this field of research has developed, the use of FCE has been an object of discussion and debate internationally. Unfortunately, t

  16. Structurally Integrated, Damage Tolerant Thermal Spray Coatings: Processing Effects on Surface and System Functionalities

    Science.gov (United States)

    Vackel, Andrew

    Thermal Spray (TS) coatings have seen extensive application as protective surfaces to enhance the service life of substrates prone to damage in their operating environment (wear, corrosion, heat etc.). With the advent of high velocity TS processes, the ability to deposit highly dense (>99%) metallic and cermet coatings has further enhanced the protective ability of these coatings. In addition to surface functionality, the influence of the coating application on the mechanical performance of a coated component is of great concern when such a component will experience either static or cyclic loading during service. Using a process mapping methodology, the processing-property interplay between coating materials meant to provide damage tolerant surface or for structural restoration are explored in terms of relevant mechanical properties. Most importantly, the residual stresses inherent in TS deposited coatings are shown to play a significant role in the integrated mechanical performance of these coatings. Unique to high velocity TS processes is the ability to produce compressive stresses within the deposit from the cold working induced by the high kinetic energy particles upon impact. The extent of these formation stresses are explored with different coating materials, as well as processing influence. The ability of dense TS coatings to carry significant structural load and synergistically strengthen coated tensile specimens is demonstrated as a function of coating material, processing, and thickness. The sharing of load between the substrate and otherwise brittle coating enables higher loads before yield for the bi-material specimens, offering a methodology to improve the tensile performance of coated components for structural repair or multi-functionality (surface and structure). The concern of cyclic fatigue damage in coated components is explored, since the majority of service application are designed for loading to be well below the yield point. The role of

  17. Automatic monitoring of ecosystem structure and functions using integrated low-cost near surface sensors

    Science.gov (United States)

    Kim, J.; Ryu, Y.; Jiang, C.; Hwang, Y.

    2016-12-01

    Near surface sensors are able to acquire more reliable and detailed information with higher temporal resolution than satellite observations. Conventional near surface sensors usually work individually, and thus they require considerable manpower from data collection through information extraction and sharing. Recent advances of Internet of Things (IoT) provides unprecedented opportunities to integrate various low-cost sensors as an intelligent near surface observation system for monitoring ecosystem structure and functions. In this study, we developed a Smart Surface Sensing System (4S), which can automatically collect, transfer, process and analyze data, and then publish time series results on public-available website. The system is composed of micro-computer Raspberry pi, micro-controller Arduino, multi-spectral spectrometers made from Light Emitting Diode (LED), visible and near infrared cameras, and Internet module. All components are connected with each other and Raspberry pi intelligently controls the automatic data production chain. We did intensive tests and calibrations in-lab. Then, we conducted in-situ observations at a rice paddy field and a deciduous broadleaf forest. During the whole growth season, 4S obtained landscape images, spectral reflectance in red, green, blue, and near infrared, normalized difference vegetation index (NDVI), fraction of photosynthetically active radiation (fPAR), and leaf area index (LAI) continuously. Also We compared 4S data with other independent measurements. NDVI obtained from 4S agreed well with Jaz hyperspectrometer at both diurnal and seasonal scales (R2 = 0.92, RMSE = 0.059), and 4S derived fPAR and LAI were comparable to LAI-2200 and destructive measurements in both magnitude and seasonal trajectory. We believe that the integrated low-cost near surface sensor could help research community monitoring ecosystem structure and functions closer and easier through a network system.

  18. Density Functional Study on Adsorption of NO on AuSe (010) Surface

    Institute of Scientific and Technical Information of China (English)

    XU,Xiang-Lan; CHEN,Wen-Kai; WANG,Xia; SUN,Bao-Zhen; LI,Yi; LU,Chun-Hai

    2008-01-01

    NO molecule adsorption on (010) surface of gold selenide (AuSe) has been studied with a periodic slab model by means of the GGA-PW91 exchange-correlation functional within the framework of density functional theory (DFT). Four different on-top adsorption sites Au(1), Au(2), Se(1) and Se(2) were considered for α-AuSe and three on-top adsorption sites Au(1), Au(2) and Se(1) for β-AuSe. N-end and O-end adsorptions of NO were investigated for the above sites. The results show that N-end adsorptions are preferred for α- and β-AuSe and O-end adsorptions are not feasible and thought as physisorption with the weak adsorption energies from 6.0 to 10.8 kJ/mol. For the N-end adsorptions on α-and β-AuSe (010) surfaces, Au(2) sites are most favorable with the adsorption energies 89.0 and 78.0 kJ/mol for α-and β-AuSe, respectively. However, the adsorptions at Au1 sites are very weak with the adsorption energies of 27.8 and 7.5 kJ/mol, respectively. In case of the adsorption of N-down orientations of NO at Se sites for α-and β-AuSe (010) surfaces, the adsorption activities of Se(1) and Se(2) sites on the α-AuSe (010) surface and Se(1) site on the β-AuSe (010) surface are almost the same with the adsorption energies 51.2, 52.7 and 49.2 kJ/mol. The geometric optimizations for adsorption configurations were calculated along with accounting for stretching frequency and density of states in our work.

  19. Cytotoxicity of surface-functionalized silicon and germanium nanoparticles: the dominant role of surface charges

    NARCIS (Netherlands)

    Bhattacharjee, S.; Rietjens, I.M.C.M.; Singh, M.P.; Atkins, T.M.; Purkait, T.K.; Xu, Z.; Regli, S.; Shukaliak, A.; Clark, R.J.; Mitchell, B.S.; Alink, G.M.; Marcelis, A.T.M.; Fink, M.J.; Veinot, J.G.C.; Kauzlarich, S.M.; Zuilhof, H.

    2013-01-01

    Although it is frequently hypothesized that surface (like surface charge) and physical characteristics (like particle size) play important roles in cellular interactions of nanoparticles (NPs), a systematic study probing this issue is missing. Hence, a comparative cytotoxicity study, quantifying

  20. Cytotoxicity of surface-functionalized silicon and germanium nanoparticles: the dominant role of surface charges

    NARCIS (Netherlands)

    Bhattacharjee, S.; Rietjens, I.M.C.M.; Singh, M.P.; Atkins, T.M.; Purkait, T.K.; Xu, Z.; Regli, S.; Shukaliak, A.; Clark, R.J.; Mitchell, B.S.; Alink, G.M.; Marcelis, A.T.M.; Fink, M.J.; Veinot, J.G.C.; Kauzlarich, S.M.; Zuilhof, H.

    2013-01-01

    Although it is frequently hypothesized that surface (like surface charge) and physical characteristics (like particle size) play important roles in cellular interactions of nanoparticles (NPs), a systematic study probing this issue is missing. Hence, a comparative cytotoxicity study, quantifying nin

  1. A microfluidic surface enhanced Raman spectroscopic biosensor using aptamer functionalized nanopillars

    DEFF Research Database (Denmark)

    Yang, J.; Palla, M.; Bosco, F. G.

    2013-01-01

    This paper presents a microchip incorporating an aptamer-functionalized nanopillar substrate, enabling the specific detection of low-abundance biomolecules using surface enhanced Raman spectroscopy (SERS). In a temperature controlled microchamber, aptamers immobilized on the nanostructure surface...

  2. Suppressed primary osteoblast functions on nanoporous titania surface.

    Science.gov (United States)

    Zhao, Lingzhou; Mei, Shenglin; Wang, Wei; Chu, Paul K; Zhang, Yumei; Wu, Zhifen

    2011-01-01

    Titiania nanotubes have large potential in medical implant applications but their tissue compatibility is still controversial. Considering that the biological behavior of primary osteoblasts is closer to the in vivo situation than other common cell lines, we investigate the response of primary osteoblasts on anodized nanotextured titania surfaces. Two nanotextured surface morphologies, namely the 5 V anodized surface with a pore diameter of 25 nm and the 20 V anodized surface with a tube diameter of 80 nm are chosen for this study. Initial cell adhesion is not obviously affected by the anodized surfaces. With the exception of slightly higher intracellular alkaline phosphatase activity and more extracellular matrix deposition, cell growth, and cell differentiation represented by the expressions of osteogenesis-related genes are impaired on both anodized surfaces. This may be attributed to the compromised focal contact formation on the anodized surfaces. The difference in the phenotypes of the primary osteoblasts and the osteoblastic cell lines may partly account for the controversy in osteoblast cytocompatibility on titania nanotubes.

  3. Conceptual foundation for measures of physical function and behavioral health function for Social Security work disability evaluation.

    Science.gov (United States)

    Marfeo, Elizabeth E; Haley, Stephen M; Jette, Alan M; Eisen, Susan V; Ni, Pengsheng; Bogusz, Kara; Meterko, Mark; McDonough, Christine M; Chan, Leighton; Brandt, Diane E; Rasch, Elizabeth K

    2013-09-01

    Physical and mental impairments represent the 2 largest health condition categories for which workers receive Social Security disability benefits. Comprehensive assessment of physical and mental impairments should include aspects beyond medical conditions such as a person's underlying capabilities as well as activity demands relevant to the context of work. The objective of this article is to describe the initial conceptual stages of developing new measurement instruments of behavioral health and physical functioning relevant for Social Security work disability evaluation purposes. To outline a clear conceptualization of the constructs to be measured, 2 content models were developed using structured and informal qualitative approaches. We performed a structured literature review focusing on work disability and incorporating aspects of the International Classification of Functioning, Disability and Health as a unifying taxonomy for framework development. Expert interviews provided advice and consultation to enhance face validity of the resulting content models. The content model for work-related behavioral health function identifies 5 major domains: (1) behavior control, (2) basic interactions, (3) temperament and personality, (4) adaptability, and (5) workplace behaviors. The content model describing physical functioning includes 3 domains: (1) changing and maintaining body position, (2) whole-body mobility, and (3) carrying, moving, and handling objects. These content models informed subsequent measurement properties including item development and measurement scale construction, and provided conceptual coherence guiding future empirical inquiry. The proposed measurement approaches show promise to comprehensively and systematically assess physical and behavioral health functioning relevant to work. Copyright © 2013 American Congress of Rehabilitation Medicine. Published by Elsevier Inc. All rights reserved.

  4. Assessing the temporal stability of surface functional groups introduced by plasma treatments on the outer shells of carbon nanotubes

    Science.gov (United States)

    Merenda, Andrea; Ligneris, Elise Des; Sears, Kallista; Chaffraix, Thomas; Magniez, Kevin; Cornu, David; Schütz, Jürg A.; Dumée, Ludovic F.

    2016-08-01

    Plasma treatments are emerging as superior efficiency treatment for high surface to volume ratio materials to tune functional group densities and alter crystallinity due to their ability to interact with matter at the nanoscale. The purpose of this study is to assess for the first time the long term stability of surface functional groups introduced across the surface of carbon nanotube materials for a series of oxidative, reductive and neutral plasma treatment conditions. Both plasma duration dose matrix based exposures and time decay experiments, whereby the surface energy of the materials was evaluated periodically over a one-month period, were carried out. Although only few morphological changes across the graphitic planes of the carbon nanotubes were found under the uniform plasma treatment conditions, the time dependence of pertinent work functions, supported by Raman analysis, suggested that the density of polar groups decreased non-linearly over time prior to reaching saturation from 7 days post treatment. This work provides critical considerations on the understanding of the stability of functional groups introduced across high specific surface area nano-materials used for the design of nano-composites, adsorptive or separation systems, or sensing materials and where interfacial interactions are key to the final materials performance.

  5. Influence of Surface Position along the Working Range of Conoscopic Holography Sensors on Dimensional Verification of AISI 316 Wire EDM Machined Surfaces

    Directory of Open Access Journals (Sweden)

    Pedro Fernández

    2014-03-01

    Full Text Available Conoscopic holography (CH is a non-contact interferometric technique used for surface digitization which presents several advantages over other optical techniques such as laser triangulation. Among others, the ability for the reconstruction of high-sloped surfaces stands out, and so does its lower dependence on surface optical properties. Nevertheless, similarly to other optical systems, adjustment of CH sensors requires an adequate selection of configuration parameters for ensuring a high quality surface digitizing. This should be done on a surface located as close as possible to the stand-off distance by tuning frequency (F and power (P until the quality indicators Signal-to-Noise Ratio (SNR and signal envelope (Total meet proper values. However, not all the points of an actual surface are located at the stand-off distance, but they could be located throughout the whole working range (WR. Thus, the quality of a digitized surface may not be uniform. The present work analyses how the quality of a reconstructed surface is affected by its relative position within the WR under different combinations of the parameters F and P. Experiments have been conducted on AISI 316 wire EDM machined flat surfaces. The number of high-quality points digitized as well as distance measurements between different surfaces throughout the WR allowed for comparing the metrological behaviour of the CH sensor with respect to a touch probe (TP on a CMM.

  6. Surface functionalization of SPR chip for specific molecular interaction analysis under flow condition

    OpenAIRE

    Tao Ma; Xiaoxia Chen; Qing Peng; Pengfei Zhang; Yonghong He

    2017-01-01

    Surface functionalization of sensor chip for probe immobilization is crucial for the biosensing applications of surface plasmon resonance (SPR) sensors. In this paper, we report a method circulating the dopamine aqueous solution to coat polydopamine film on sensing surface for surface functionalization of SPR chip. The polydopamine film with available thickness can be easily prepared by controlling the circulation time and the biorecognition elements can be immobilized on the polydopamine fil...

  7. Robust self-cleaning surfaces that function when exposed to either air or oil

    OpenAIRE

    Lu, Y.

    2015-01-01

    Superhydrophobic self-cleaning surfaces are based on the surface micro/nanomorphologies; however, such surfaces are mechanically weak and stop functioning when exposed to oil. We have created an ethanolic suspension of perfluorosilane-coated titanium dioxide nanoparticles that forms a paint that can be sprayed, dipped, or extruded onto both hard and soft materials to create a self-cleaning surface that functions even upon emersion in oil. Commercial adhesives were used to bond the paint to va...

  8. Methodologies to analyze surface bonding properties using parametric and density functional methods

    Science.gov (United States)

    Ruette, Fernando; Sánchez, Morella; Castellano, Olga; Soscún, Humberto

    This work presents two general methodologies to calculate bond adsorption energy (BAE) between surface and adsorbate using parametric quantum (PQM) and density functional (DFM) methods. The first one corresponds to the bond partition energy technique that is directly applied to PQMs by using energy partition approach and considering diatomic and monoatomic energy changes. The second methodology to evaluate BAE, as well as for PQMs and DFMs, is by means of the following equation: {BAE} = E_{ads} - Delta E_{s} - Delta E_{a'} where Eads is the adsorption energy and ΔEs and ΔEa correspond to energy changes in the surface and substrate due to adsorption, respectively. Applications to radical adsorption: H°, CH2°, and CH3° is performed on a grafitic grain model, using a polyaromatic hydrocarbon (PAH), such as coronene. The methods employed are a PQM (CATIVIC program) and DFMs (GAUSSIAN and DMol software packages). Results show that Eads is completely different of BAE, because of distortion of surface and adsorbate. There is a strong destabilization in the region adjacent to the adsorption site and stabilization in the rest of the surface. Two terms for BAE are reported: one that corresponds to direct bonding interaction (BAEb) and other to long range ones, due to electrostatic interaction (BAEe). Owing to the important effects of bond strength adsorbate-surface interaction, results suggest that BAE is fundamental for understanding bond activation in adsorbate and surface, cooperative effects, diffusion, reaction, and desorption process. In general, similar results were found for both CATIVIC and DFMs, by using the second methodology.

  9. Anisotropic surface functionalization of Au nanorods driven by molecular architecture and curvature effects.

    Science.gov (United States)

    Solveyra, Estefania Gonzalez; Tagliazucchi, Mario; Szleifer, Igal

    2016-10-06

    This work suggests a novel strategy to coat the caps and body of Au-nanorods (Au-NRs) with end-grafted polymer layers of different compositions by taking advantage of the different curvature of these two regions. A molecular theory was used to theoretically investigate the effect of local curvature and molecular architecture (intramolecular connectivity of the monomers) on the adsorption of polymer mixtures on cylindrical (Au-NR body) and spherical (Au-NR caps) surfaces. The adsorption process was systematically studied as a function of the backbone length, number and position of branches, quality of the solvent and total number of monomers of the polymer molecules in the mixture. The balance between repulsive forces and polymer-surface and polymer-polymer attractions governs the amount and composition of the adsorbed layer. This balance is in turn modulated by the architecture of the polymers, the curvature of the surface and the competition between the different polymers in the mixture for the available area. As a result, the equilibrium composition of the polymer layer on spheres and cylinders of the same radius differs, and in turn departs from that of the bulk solution. Curvature plays a major role: the available volume at a given distance from the surface is larger for spherical surfaces than for cylindrical ones, therefore the surface density of the bulkier (more branched) polymer in the mixture is larger on the Au-NR caps than on the Au-NR body. These results suggest that the combination of curvature at the nanoscale and tailored molecular architecture can confer anisotropic nanoparticles with spatially enriched domains and, therefore, lead to nanoconstructs with directional chemical interactions.

  10. BASIC SURFACE MARKERS OF FUNCTIONAL ACTIVITY T-LYMPHOCYTES

    Directory of Open Access Journals (Sweden)

    L. S. Litvinova

    2014-01-01

    Full Text Available In present review article, an effort is undertaken to consolidate current opinions on the most significant surface antigens of immunocompetent cells, and to evaluate their relative roles in regulation of cellular homeostasis and development of pathological conditions.

  11. Microwave assisted organic modification and surface functionalization of Phyllosilicates

    CSIR Research Space (South Africa)

    Kesavan Pillai, Sreejarani

    2012-11-01

    Full Text Available Organically modified phyllosilicates (montmorillonite and palygorskite) using Arquad 2HT-75 surfactant were effectively synthesized utilizing a microwave irradiation technique. The microwave method was successfully used also for the surface...

  12. Optimization of metal working fluids treatment using calcium chloride by response surface methodology

    Directory of Open Access Journals (Sweden)

    HA. Jamali

    2016-11-01

    Full Text Available Background: Extensive use of metal working fluids degrades their chemical composition. They should be treated using a safe method. Chemical coagulation-flocculation process is one the treatment methods. Objective: The aim of this study was to optimize the coagulation-flocculation process using calcium chloride in metal working fluids treatment. Methods: This laboratory based study was performed in School of Health affiliated to Qazvin University of Medical Sciences in 2014. Using calcium chloride and a six-compartment jar, the efficiency of coagulation-flocculation process was assessed for removal of chemical oxygen demand (COD and turbidity and amount of released oil. Central composite design (CCD and response surface methodology (RSM were applied to optimize the treatment operation parameters (pH and dosage of coagulant. Quadratic models were developed for calculation of the three responses (COD, turbidity, and released oil. Findings: The optimum condition for coagulation-flocculation process was seen after treatment with 4.2 g/L calcium chloride at pH 3.71 in which COD and turbidity removal efficiency were 93% and 96.9%, respectively and the amount of released oil was 31.8 ml. The level of desirability was 91.2%. The values of laboratory study were in good agreement with the values predicted by the model. Conclusion: Metal working fluids treatment with calcium chloride was efficient in the removal of pollution parameters. Dosage of calcium chloride was similar to the conventional coagulants such as Alum, but its efficiency was higher.

  13. Is Work-related Rumination Associated with deficits in Executive Functioning?

    Directory of Open Access Journals (Sweden)

    Mark Cropley

    2016-09-01

    Full Text Available AbstractWork-related rumination, that is, perseverative thinking about work during leisure time, has been associated with a range of negative health and wellbeing issues. The present paper examined the association between work-related rumination and cognitive processes centred around the theoretical construct of executive functioning. Executive functioning is an umbrella term for high level cognitive processes such as planning, working memory, inhibition, mental flexibility; and it underlies how people manage and regulate their goal directed behaviour. Three studies are reported. Study I, reports the results of a cross-sectional study of 240 employees, and demonstrates significant correlations between work-related rumination and three proxy measures of executive functioning: cognitive failures (.33, cognitive flexibility (-.24 and situational awareness at work (-.28. Study II (n = 939, expands on the findings from study 1 and demonstrates that workers reporting medium and high work-related rumination were 2.8 and 5 times, respectively, more likely to report cognitive failures relative to low ruminators. High ruminators also demonstrated greater difficulties with ‘lapses of attention’ (OR = 4.8, ‘lack of focus of attention’ (OR = 3.4, and ‘absent mindedness’ (OR = 4.3. The final study, examined the association between work-related rumination and executive functioning using interview data from 2460 full time workers. Workers were divided into tertiles low, medium and high. The findings showed that high work-related rumination was associated with deficits in starting (OR = 2.3 and finishing projects (OR = 2.4, fidgeting (OR = 1.9, memory (OR = 2.2, pursuing tasks in order (OR = 1.8, and feeling compelled to do things (OR = 2.0. It was argued that work-related rumination may not be related to work demands per se, but appears to be an executive functioning/control issue. Such findings are important for the design and delivery of

  14. Is Work-Related Rumination Associated with Deficits in Executive Functioning?

    Science.gov (United States)

    Cropley, Mark; Zijlstra, Fred R. H.; Querstret, Dawn; Beck, Sarah

    2016-01-01

    Work-related rumination, that is, perseverative thinking about work during leisure time, has been associated with a range of negative health and wellbeing issues. The present paper examined the association between work-related rumination and cognitive processes centerd around the theoretical construct of executive functioning. Executive functioning is an umbrella term for high level cognitive processes such as planning, working memory, inhibition, mental flexibility; and it underlies how people manage and regulate their goal directed behavior. Three studies are reported. Study I, reports the results of a cross-sectional study of 240 employees, and demonstrates significant correlations between work-related rumination and three proxy measures of executive functioning: cognitive failures (0.33), cognitive flexibility (-0.24), and situational awareness at work (-0.28). Study II (n = 939), expands on the findings from study 1 and demonstrates that workers reporting medium and high work-related rumination were 2.8 and 5 times, respectively, more likely to report cognitive failures relative to low ruminators. High ruminators also demonstrated greater difficulties with ‘lapses of attention’ (OR = 4.8), ‘lack of focus of attention’ (OR = 3.4), and ‘absent mindedness’ (OR = 4.3). The final study, examined the association between work-related rumination and executive functioning using interview data from 2460 full time workers. Workers were divided into tertiles low, medium, and high. The findings showed that high work-related rumination was associated with deficits in starting (OR = 2.3) and finishing projects (OR = 2.4), fidgeting (OR = 1.9), memory (OR = 2.2), pursuing tasks in order (OR = 1.8), and feeling compelled to do things (OR = 2.0). It was argued that work-related rumination may not be related to work demands per se, but appears to be an executive functioning/control issue. Such findings are important for the design and delivery of intervention

  15. Work function increase of Al-doped ZnO thin films by B+ ion implantation.

    Science.gov (United States)

    Hong, Sang-Jin; Heo, Gi-Seok; Park, Jong-Woon; Lee, In-Hwan; Choi, Bum-Ho; Lee, Jong-Ho; Park, Se-Yeon; Shin, Dong-Chan

    2007-11-01

    The work function of an Al-doped ZnO (AZO) thin film can be increased via B+ ion implantation from 3.92 eV up to 4.22 eV. The ion implantation has been carried out with the ion dose of 1 x 10(16) cm(-2) and ion energy of 5 keV. The resistance of the B+ implanted AZO films has been a bit raised, while their transmittance is slightly lowered, compared to those of un-implanted AZO films. These behaviors can be explained by the doping profile and the resultant band diagram. It is concluded that the coupling between the B+ ions and oxygen vacancies would be the main reason for an increase in the work function and a change in the other properties. We also address that the work function is more effectively alterable if the defect density of the top transparent conducting oxide layer can be controlled.

  16. Low-Work-Function, ITO-Free Transparent Cathodes for Inverted Polymer Solar Cells.

    Science.gov (United States)

    Xue, Zhichao; Liu, Xingyuan; Lv, Ying; Zhang, Nan; Guo, Xiaoyang

    2015-09-16

    A low-work-function, indium tin oxide (ITO)-free transparent cathode having a tin oxide (SnOX)/Ag/SnOX/bismuth oxide (Bi2O3) (SASB) structure is developed without using annealing treatment. This represents the first time that Bi2O3 has been introduced to lower the work function of transparent electrodes. The SASB transparent cathode exhibits excellent photoelectric properties with a maximum transmittance of ∼88%, a low sheet resistance of ∼9.0 Ω·sq(-1), and a suitable work function of 4.22 eV that matches the lowest unoccupied molecular orbital level of the acceptor for exacting electrons efficiently. The power conversion efficiency of the polymer solar cell with the SASB electrode is 6.21%, which is comparable to that of ITO-based devices. The results indicate that SASB is a good alternative to ITO as transparent cathodes in optoelectronic devices.

  17. Controlling the work function of molybdenum disulfide by in situ metal deposition.

    Science.gov (United States)

    Zhou, Peng; Song, Xiongfei; Yan, Xiao; Liu, Chunsen; Chen, Lin; Sun, Qingqing; Zhang, David Wei

    2016-08-26

    Control of the work function of molybdenum disulfide (MoS2) under ultrathin metal was investigated using in situ metal deposition and direct ultraviolet photoelectron spectroscopy measurement in an ultra-high vacuum system. When the metal thickness turned from two dimensional into bulk, the work function was also raised up at the nickel-MoS2 interface, barely changed at the titanium-MoS2 interface and lowered at the hafnium-MoS2 interface. Meanwhile, the mechanisms of charge transfer and band alignment with metal deposition were also discussed. The Schottky barrier at metal-MoS2 interfaces could be tailored by both types and thicknesses of deposited metal. The low work function metal was a good indicator for MoS2 contact electrodes. It paved the way towards future high performance MoS2 device applications.

  18. Quantitative secondary electron imaging for work function extraction at atomic level and layer identification of graphene.

    Science.gov (United States)

    Zhou, Yangbo; Fox, Daniel S; Maguire, Pierce; O'Connell, Robert; Masters, Robert; Rodenburg, Cornelia; Wu, Hanchun; Dapor, Maurizio; Chen, Ying; Zhang, Hongzhou

    2016-02-16

    Two-dimensional (2D) materials usually have a layer-dependent work function, which require fast and accurate detection for the evaluation of their device performance. A detection technique with high throughput and high spatial resolution has not yet been explored. Using a scanning electron microscope, we have developed and implemented a quantitative analytical technique which allows effective extraction of the work function of graphene. This technique uses the secondary electron contrast and has nanometre-resolved layer information. The measurement of few-layer graphene flakes shows the variation of work function between graphene layers with a precision of less than 10 meV. It is expected that this technique will prove extremely useful for researchers in a broad range of fields due to its revolutionary throughput and accuracy.

  19. Investigation of electrostatic performance for a conical surrounding gate MOSFET with linearly modulated work-function

    Science.gov (United States)

    Ramkrishna, B. S.; Jena, B.; Dash, S.; Mishra, G. P.

    2017-01-01

    In this paper, for the first time a continuous variation of work-function based gate metal has been introduced in conical surrounding gate MOSFET. Here, a comparative study of the electrostatic as well as RF characteristics for basic conical surrounding gate MOSFET and the work-function modulated conical MOSFET is carried out using TCAD device simulator. These simulated results reveal that the work-function modulated conical model provides better electrostatic and RF performance in terms of drain current, transconductance, transconductance generation factor, unity gain cut-off frequency and intrinsic delay. An overall performance investigation has been presented for both the aforementioned models and verified using TCAD device simulator from Synopsys.

  20. Accuracy assessment of reverse surface on SolidWorks%面向 SolidWorks 反求曲面的精度评价

    Institute of Scientific and Technical Information of China (English)

    蒋洪平; 宋浩

    2014-01-01

    The characteristics of reverse modeling on SolidWorks were analyzed .The method of the accuracy assessment of reverse surface on SolidWorks was put forward .The main factors of the reverse surface accuracy on SolidWorks was sure .With electric bi-cycle seat surface accuracy assessment as an example ,the process of accuracy assessment was introduced ,the surface reverse so-lution accord with engineering practice need was obtained based on the analysis of the evaluation results .%分析采用SolidWorks软件反求建模的特点,提出针对SolidWorks 反求曲面进行精度评价的方法,确定影响Solid-Works反求曲面精度的主要因素。以电动自行车坐垫曲面精度评价为例,详细介绍精度评价的过程,通过对评价结果的分析获得符合工程实践需要的曲面反求方案。

  1. A COGNITIVE-BEHAVIOURAL GROUP TREATMENT IMPROVED WORK ABILITY IN PATIENTS WITH SEVERE FUNCTIONAL SOMATIC SYNDROMES

    DEFF Research Database (Denmark)

    Schröder, Andreas; Ørnbøl, Eva; Jensen, Jens Søndergaard

    2014-01-01

    Objective: Functional somatic syndromes (FSS) such as fibromyalgia, irritable bowel and chronic fatigue syndrome often disrupt employment and may lead to long-term dependence on social benefits and permanently reduced work ability. Cognitive-behavioural treatments (CBT) relief symptoms and improve...... functioning in FSS, but their effect on work ability is unclear. The aim of this study was to estimate the long-term effect of group CBT on work ability in patients with severe FSS. Methods: 120 Patients from a recently published randomised controlled trial comparing group CBT with enhanced usual care (EUC...... before to 3 years after treatment by means of random effects modelling allowing individual levels and slopes. Results: Compared with the general population, FSS patients showed a continuous decline in self-support, leading to markedly reduced work ability at trial entry. In the following years, EUC...

  2. Intensive Working Memory Training Produces Functional Changes in Large-scale Frontoparietal Networks.

    Science.gov (United States)

    Thompson, Todd W; Waskom, Michael L; Gabrieli, John D E

    2016-04-01

    Working memory is central to human cognition, and intensive cognitive training has been shown to expand working memory capacity in a given domain. It remains unknown, however, how the neural systems that support working memory are altered through intensive training to enable the expansion of working memory capacity. We used fMRI to measure plasticity in activations associated with complex working memory before and after 20 days of training. Healthy young adults were randomly assigned to train on either a dual n-back working memory task or a demanding visuospatial attention task. Training resulted in substantial and task-specific expansion of dual n-back abilities accompanied by changes in the relationship between working memory load and activation. Training differentially affected activations in two large-scale frontoparietal networks thought to underlie working memory: the executive control network and the dorsal attention network. Activations in both networks linearly scaled with working memory load before training, but training dissociated the role of the two networks and eliminated this relationship in the executive control network. Load-dependent functional connectivity both within and between these two networks increased following training, and the magnitudes of increased connectivity were positively correlated with improvements in task performance. These results provide insight into the adaptive neural systems that underlie large gains in working memory capacity through training.

  3. The effect of Bond number on pool boiling for mini-fin surfaces and different working fluids

    Science.gov (United States)

    Strąk, Ewelina; Pastuszko, Robert

    2016-03-01

    Experimental nucleate pool boiling data were collected for structures in the form of extended surfaces sintered with perforated foil. The article describes experimental investigations for two kinds of surfaces: smooth and mini-fins with sintered perforated foil (MFP). The MFP surfaces were manufactured out of perforated copper foil (pore diameters: 0.05 - 0.3 mm) sintered with the mini-fins, uniformly spaced on the base surface. The experiments were carried out at atmospheric pressure for four kinds of the fluids: water, ethanol, FC-72 and Novec 649. The results for these working fluids were compared in terms of the Bond number and other dimensionless parameters. For all working fluids, the heat transfer coefficients obtained for the MFP surfaces were from 2 to 5 times higher than those for the smooth surface. Using a regression analysis with reference to selected physical properties and several characteristic dimensions, it was possible to develop a correlation for the Nusselt number.

  4. Influence of substituents and functional groups on the surface composition of ionic liquids.

    Science.gov (United States)

    Kolbeck, Claudia; Niedermaier, Inga; Deyko, Alexey; Lovelock, Kevin R J; Taccardi, Nicola; Wei, Wei; Wasserscheid, Peter; Maier, Florian; Steinrück, Hans-Peter

    2014-04-01

    We have performed a systematic study addressing the surface behavior of a variety of functionalized and non-functionalized ionic liquids (ILs). From angle-resolved X-ray photoelectron spectroscopy, detailed conclusions on the surface enrichment of the functional groups and the molecular orientation of the cations and anions is derived. The systems include imidazolium-based ILs methylated at the C2 position, a phenyl-functionalized IL, an alkoxysilane-functionalized IL, halo-functionalized ILs, thioether-functionalized ILs, and amine-functionalized ILs. The results are compared with the results for corresponding non-functionalized ILs where available. Generally, enrichment of the functional group at the surface is only observed for systems that have very weak interaction between the functional group and the ionic head groups.

  5. Functional brain network modularity captures inter- and intra-individual variation in working memory capacity.

    Directory of Open Access Journals (Sweden)

    Alexander A Stevens

    Full Text Available BACKGROUND: Cognitive abilities, such as working memory, differ among people; however, individuals also vary in their own day-to-day cognitive performance. One potential source of cognitive variability may be fluctuations in the functional organization of neural systems. The degree to which the organization of these functional networks is optimized may relate to the effective cognitive functioning of the individual. Here we specifically examine how changes in the organization of large-scale networks measured via resting state functional connectivity MRI and graph theory track changes in working memory capacity. METHODOLOGY/PRINCIPAL FINDINGS: Twenty-two participants performed a test of working memory capacity and then underwent resting-state fMRI. Seventeen subjects repeated the protocol three weeks later. We applied graph theoretic techniques to measure network organization on 34 brain regions of interest (ROI. Network modularity, which measures the level of integration and segregation across sub-networks, and small-worldness, which measures global network connection efficiency, both predicted individual differences in memory capacity; however, only modularity predicted intra-individual variation across the two sessions. Partial correlations controlling for the component of working memory that was stable across sessions revealed that modularity was almost entirely associated with the variability of working memory at each session. Analyses of specific sub-networks and individual circuits were unable to consistently account for working memory capacity variability. CONCLUSIONS/SIGNIFICANCE: The results suggest that the intrinsic functional organization of an a priori defined cognitive control network measured at rest provides substantial information about actual cognitive performance. The association of network modularity to the variability in an individual's working memory capacity suggests that the organization of this network into high

  6. Variation in the thermionic work function of semiconductor powders exposed to electromagnetic radiation

    Science.gov (United States)

    Bourasseau, S.; Martin, J. R.; Juillet, F.; Teichner, S. J.

    1977-01-01

    The study of the variation of thermoelectronic work function potential of TiO2 in the presence of isobutane shows that this gas is not adsorbed on this solid, in either the presence or the absence of ultraviolet radiation. These results, as well as those obtained in a previous work, lead to the mechanism of the photo-oxidation of isobutane at room temperature, in which excited atomic oxygen is the active species.

  7. Tuning the work functions of graphene quantum dot-modified electrodes for polymer solar cell applications.

    Science.gov (United States)

    Zhang, L; Ding, Z C; Tong, T; Liu, J

    2017-03-09

    The graphene quantum dot (GQD) is a new kind of anode/cathode interlayer material for polymer solar cells (PSCs). The key requirement for a cathode interlayer (CIL) is a low work function. In this article, aiming at application as a CIL for PSCs, we report a general approach to tune the work function of GQD-modified electrodes using alkali metal cations, e.g. Li(+), Na(+), K(+), Rb(+) and Cs(+). For ITO electrodes modified with these GQDs containing alkali metal cations, the work function can be finely tuned within the range of 4.0-4.5 eV. Owing to their low work function, GQDs containing K(+), Rb(+) and Cs(+) can be used as CILs for PSCs. Their device performance is fairly comparable to that of the state-of-the-art CIL material ZnO. This work provides a rational approach to tune the properties of GQD and to design solution-processable electrode interlayer materials for organic electronic devices.

  8. Doped polymer semiconductors with ultrahigh and ultralow work functions for ohmic contacts.

    Science.gov (United States)

    Tang, Cindy G; Ang, Mervin C Y; Choo, Kim-Kian; Keerthi, Venu; Tan, Jun-Kai; Syafiqah, Mazlan Nur; Kugler, Thomas; Burroughes, Jeremy H; Png, Rui-Qi; Chua, Lay-Lay; Ho, Peter K H

    2016-11-24

    To make high-performance semiconductor devices, a good ohmic contact between the electrode and the semiconductor layer is required to inject the maximum current density across the contact. Achieving ohmic contacts requires electrodes with high and low work functions to inject holes and electrons respectively, where the work function is the minimum energy required to remove an electron from the Fermi level of the electrode to the vacuum level. However, it is challenging to produce electrically conducting films with sufficiently high or low work functions, especially for solution-processed semiconductor devices. Hole-doped polymer organic semiconductors are available in a limited work-function range, but hole-doped materials with ultrahigh work functions and, especially, electron-doped materials with low to ultralow work functions are not yet available. The key challenges are stabilizing the thin films against de-doping and suppressing dopant migration. Here we report a general strategy to overcome these limitations and achieve solution-processed doped films over a wide range of work functions (3.0-5.8 electronvolts), by charge-doping of conjugated polyelectrolytes and then internal ion-exchange to give self-compensated heavily doped polymers. Mobile carriers on the polymer backbone in these materials are compensated by covalently bonded counter-ions. Although our self-compensated doped polymers superficially resemble self-doped polymers, they are generated by separate charge-carrier doping and compensation steps, which enables the use of strong dopants to access extreme work functions. We demonstrate solution-processed ohmic contacts for high-performance organic light-emitting diodes, solar cells, photodiodes and transistors, including ohmic injection of both carrier types into polyfluorene-the benchmark wide-bandgap blue-light-emitting polymer organic semiconductor. We also show that metal electrodes can be transformed into highly efficient hole- and electron

  9. Determinants of work outcome in schizophrenia and schizoaffective disorder: role of cognitive function.

    Science.gov (United States)

    Kaneda, Yasuhiro; Jayathilak, Karuna; Meltzer, Herbert Y

    2009-09-30

    Cognitive impairment has been reported to be more important than clinical symptomatology as a determinant of work and social function in schizophrenia. In a retrospective analysis of a group of 152 patients with chronic schizophrenia or schizoaffective disorder, performance on a battery of neuropsychological tests was contrasted in employed (32, 21.1%) versus unemployed subgroups. As predicted, neurocognitive performance was more important than clinical symptoms in predicting employment status. Among neurocognitive functions, verbal working memory (as reflected by the Consonant Trigram Test) was the strongest predictor of employment status.

  10. Work function of few layer graphene covered nickel thin films measured with Kelvin probe force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Eren, B. [Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel (Switzerland); Material Sciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720 (United States); Gysin, U.; Marot, L., E-mail: Laurent.marot@unibas.ch; Glatzel, Th.; Steiner, R.; Meyer, E. [Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel (Switzerland)

    2016-01-25

    Few layer graphene and graphite are simultaneously grown on a ∼100 nm thick polycrystalline nickel film. The work function of few layer graphene/Ni is found to be 4.15 eV with a variation of 50 meV by local measurements with Kelvin probe force microscopy. This value is lower than the work function of free standing graphene due to peculiar electronic structure resulting from metal 3d-carbon 2p(π) hybridization.

  11. Functional connectivity among spike trains in neural assemblies during rat working memory task.

    Science.gov (United States)

    Xie, Jiacun; Bai, Wenwen; Liu, Tiaotiao; Tian, Xin

    2014-11-01

    Working memory refers to a brain system that provides temporary storage to manipulate information for complex cognitive tasks. As the brain is a more complex, dynamic and interwoven network of connections and interactions, the questions raised here: how to investigate the mechanism of working memory from the view of functional connectivity in brain network? How to present most characteristic features of functional connectivity in a low-dimensional network? To address these questions, we recorded the spike trains in prefrontal cortex with multi-electrodes when rats performed a working memory task in Y-maze. The functional connectivity matrix among spike trains was calculated via maximum likelihood estimation (MLE). The average connectivity value Cc, mean of the matrix, was calculated and used to describe connectivity strength quantitatively. The spike network was constructed by the functional connectivity matrix. The information transfer efficiency Eglob was calculated and used to present the features of the network. In order to establish a low-dimensional spike network, the active neurons with higher firing rates than average rate were selected based on sparse coding. The results show that the connectivity Cc and the network transfer efficiency Eglob vaired with time during the task. The maximum values of Cc and Eglob were prior to the working memory behavior reference point. Comparing with the results in the original network, the feature network could present more characteristic features of functional connectivity.

  12. Fast optical work-function tuning at an organic/metal interface

    Science.gov (United States)

    Bronsch, Wibke; Przyrembel, Daniel; Boie, Larissa; Gahl, Cornelius; Weinelt, Martin

    2017-08-01

    In a two-color experiment, we demonstrate how light can be used as an external control to continuously tune the work function of a gold substrate functionalized with a dilute azobenzene-based self-assembled monolayer (SAM). The work function is measured by two-photon photoelectron spectroscopy. While in the ground state the azobenzene moiety adopts the trans configuration, illumination with pulsed laser light at a wavelength of 368 nm results in a photostationary state (PSS) mainly comprising cis isomers. An additional 450 nm continuous-wave laser with tunable intensity serves to shift the PSS back towards the ground state. This way the work function is freely adjustable in real time over a range of ˜240 meV between the two PSS extrema. We furthermore relate the change in work function to the average change in dipole moment per azobenzene chromophore. Quantum-chemical calculations that take into account available structural data of the molecules in the SAM must consider at least two different trans and four different cis orientations. The computed respective perpendicular trans-cis dipole-moment changes indicate that in experiment the cis molecules adopt different orientations along with a very high cis azobenzene yield in the UV PSS.

  13. The dopamine agonist bromocriptine differentially affects fronto-striatal functional connectivity during working memory.

    Directory of Open Access Journals (Sweden)

    Deanna L. Wallace

    2011-03-01

    Full Text Available We investigated the effect of bromocriptine, a dopamine agonist, on individual differences in behavior as well as frontal-striatal connectivity during a working memory task. After dopaminergic augmentation, frontal-striatal connectivity in low working memory capacity individuals increases, corresponding with behavioral improvement whereas decreases in connectivity in high working memory capacity individuals are associated with poorer behavioral performance. These findings corroborate an inverted U-shape response of dopamine function in behavioral performance and provide insight on the corresponding neural mechanisms.

  14. Dynamic response of AFM cantilevers to dissimilar functionalized silica surfaces in aqueous electrolyte solutions.

    Science.gov (United States)

    Wu, Yan; Misra, Sambit; Karacor, M Basar; Prakash, Shaurya; Shannon, Mark A

    2010-11-16

    The dynamic response of an oscillating microcantilever with a gold-coated tip interacting with dissimilar functionalized silica surfaces was studied in electrolyte solutions with pH ranging from 4 to 9. Silica surfaces were chemically modified, yielding dissimilar surfaces with -Br, -NH(2), and -CH(3) functional group terminations. The relative hydrophobicity of the surfaces was characterized by contact angle measurements. The surface charge of the functionalized surfaces was first probed with commonly used static AFM measurements and serves as a reference to the dynamic response data. The amplitude and phase of the cantilever oscillation were monitored and used to calculate the effective interaction stiffness and damping coefficient, which relate to the electrical double layer interactions and also to distance-dependent hydrodynamic damping at the solid/water interface. The data for the dynamic response of the AFM over silica surfaces as a function of chemical functionalization and electrolyte pH show that the effective stiffness has a distinctive dependence on the surface charge of functionalized silica surfaces. The hydrodynamic damping also correlates strongly with the relative hydrophobicity of the surface. The data reported here indicate that interfacial properties can be strongly affected by changing the chemical composition of surfaces.

  15. Radial Basis Function Based Quadrature over Smooth Surfaces

    Science.gov (United States)

    2016-03-24

    Function Interpolation . . . . . . . . . . . . . . . . . . . . . . . . . 17 2.3 Weight calculations...methods: product Gaussian quadrature and finite element integration. The product Gaussian quadrature uses Gauss-Legendre nodes and quadrature weights ...with Gaussian Radial Basis Functions ,” SIAM J. Sci. Comput., vol. 33, pp. 869–892, 2011. 10. B. Fornberg and J. Zuev, “The Runge Phenomenon and

  16. Social anhedonia and work and social functioning in the acute and recovered phases of eating disorders.

    Science.gov (United States)

    Harrison, Amy; Mountford, Victoria A; Tchanturia, Kate

    2014-08-15

    Interpersonal difficulties are proposed to maintain eating disorders (EDs). This study explored whether social anhedonia (SA) was an additional social emotional maintenance factor which might also explain work/social problems in EDs. Additionally, the study explored SA and work and social adjustment in recovered participants. Women with anorexia nervosa (AN; n=105), bulimia nervosa (BN; n=46), recovered from AN (RAN; n=30) and non-ED controls (n=136) completed the Work and Social Adjustment Scale (WSAS) and the Revised Social Anhedonia Scale. ED participants reported greater SA and WSAS scores than non-ED controls; the RAN group reported an intermediate profile. AN participants had poorer work/social adjustment than BN participants. SA was associated with longer illness duration. SA, current severity (BMI) and lifetime severity (lowest adult BMI) significantly predicted work/social difficulties. Recovered participants scoring in the clinical range for SA experienced significantly greater work/social difficulties than recovered participants scoring outside the clinical range for SA. EDs are associated with clinical levels of SA and poor work/social functioning which reduce in recovery. SA may maintain the interpersonal functioning difficulties.

  17. Vitamin D, surface electromyography and physical function in uraemic patients

    DEFF Research Database (Denmark)

    Heaf, J.G.; Mølsted, Stig; Harrison, Adrian Paul

    2010-01-01

    Background: Muscle function is impaired in uraemic patients and several causes have been proposed. Deficiency of 25-hydroxyvitamin D (25-OHD), which affects muscle function in non-uraemic patients, may very well also be associated with the myopathy found in these patients. The aim of this study...... was to investigate the association between 25-OHD and muscle function as well as physical function in chronic kidney disease (CKD) and peritoneal dialysis (PD) patients. Methods: In this cross-sectional study, 21 adult patients with CKD stage 3-5 and 21 patients treated with PD were included. Standard biochemistry......% of patients with CKD and in 71% of the patients on PD. Severe deficiency (CKD and PD patients in terms of sEMG results. 25-OHD was not correlated to any results from the tests of sEMG or physical function...

  18. Surface functionalization of porous glass networks: effects on bovine serum albumin and porcine insulin immobilization.

    Science.gov (United States)

    Mansur, H S; Lobato, Z P; Oréfice, R L; Vasconcelos, W L; Oliveira, C; Machado, L J

    2000-01-01

    Biomolecules can be immobolized in many different ways. They can also be entrapped or tightly adsorbed within porous gels, clays, membranes, resins, and several other materials, but it is crucial that they retain their active conformation after the incorporation procedure. Porous gel matrixes with functionalized surfaces offer unlimited possibilities to control the protein-substrate interaction behavior. In the present work, we have studied the adsorption and the relative stability of bovine serum albumin (BSA) and porcine insulin(PI) incorporated in gels of SiO2 glass matrixes. The porous gel matrixes were obtained using tetramethoxysilane (TMOS)/metanol and functionalized with (3-mercaptopropyl) trimethoxysilane and (3-aminopropyl) triethoxysilane. The relative adsorption kinetics and stability of BSA and PI incorporated in glass networks were evaluated by immersion in phosphate buffer saline (PBS) and alkaline elution media for different periods of time. The kinetics of protein release from the gel matrix was monitored by UV-visible spectroscopy. A significantly larger PI release was observed compared to BSA in PBS solutions. We believe this is mainly associated with the difference on protein interactions with the modified surface, according to the characterization results of porosity, surface area, and contact angle of different functionalized gel matrixes. We could not observe any evidence of denaturation with either proteins after their desorption from gel matrixes using the ultraviolet spectroscopy technique. These results have also been confirmed with the strong bioactivity response from "in vivo" test conducted in rats, where porous gels with PI incorporated were implanted, showing that released proteins retained their native conformation.

  19. Factors influencing work functioning after cancer diagnosis : a focus group study with cancer survivors and occupational health professionals

    NARCIS (Netherlands)

    Dorland, H. F.; Abma, F. I.; Roelen, C. A. M.; Smink, J. G.; Ranchor, A. V.; Bultmann, U.

    2016-01-01

    Cancer survivors (CSs) frequently return to work, but little is known about work functioning after return to work (RTW). We aimed to identify barriers and facilitators of work functioning among CSs. Three focus groups were conducted with CSs (n = 6, n = 8 and n = 8) and one focus group with occupati

  20. Working memory network plasticity after anterior temporal lobe resection: a longitudinal functional magnetic resonance imaging study

    Science.gov (United States)

    Stretton, Jason; Sidhu, Meneka K.; Winston, Gavin P.; Bartlett, Philippa; McEvoy, Andrew W.; Symms, Mark R.; Koepp, Matthias J.; Thompson, Pamela J.

    2014-01-01

    Working memory is a crucial cognitive function that is disrupted in temporal lobe epilepsy. It is unclear whether this impairment is a consequence of temporal lobe involvement in working memory processes or due to seizure spread to extratemporal eloquent cortex. Anterior temporal lobe resection controls seizures in 50–80% of patients with drug-resistant temporal lobe epilepsy and the effect of surgery on working memory are poorly understood both at a behavioural and neural level. We investigated the impact of temporal lobe resection on the efficiency and functional anatomy of working memory networks. We studied 33 patients with unilateral medial temporal lobe epilepsy (16 left) before, 3 and 12 months after anterior temporal lobe resection. Fifteen healthy control subjects were also assessed in parallel. All subjects had neuropsychological testing and performed a visuospatial working memory functional magnetic resonance imaging paradigm on these three separate occasions. Changes in activation and deactivation patterns were modelled individually and compared between groups. Changes in task performance were included as regressors of interest to assess the efficiency of changes in the networks. Left and right temporal lobe epilepsy patients were impaired on preoperative measures of working memory compared to controls. Working memory performance did not decline following left or right temporal lobe resection, but improved at 3 and 12 months following left and, to a lesser extent, following right anterior temporal lobe resection. After left anterior temporal lobe resection, improved performance correlated with greater deactivation of the left hippocampal remnant and the contralateral right hippocampus. There was a failure of increased deactivation of the left hippocampal remnant at 3 months after left temporal lobe resection compared to control subjects, which had normalized 12 months after surgery. Following right anterior temporal lobe resection there was a

  1. Optical excitation and electron relaxation dynamics at semiconductor surfaces: a combined approach of density functional and density matrix theory applied to the silicon (001) surface

    Energy Technology Data Exchange (ETDEWEB)

    Buecking, N.

    2007-11-05

    In this work a new theoretical formalism is introduced in order to simulate the phononinduced relaxation of a non-equilibrium distribution to equilibrium at a semiconductor surface numerically. The non-equilibrium distribution is effected by an optical excitation. The approach in this thesis is to link two conventional, but approved methods to a new, more global description: while semiconductor surfaces can be investigated accurately by density-functional theory, the dynamical processes in semiconductor heterostructures are successfully described by density matrix theory. In this work, the parameters for density-matrix theory are determined from the results of density-functional calculations. This work is organized in two parts. In Part I, the general fundamentals of the theory are elaborated, covering the fundamentals of canonical quantizations as well as the theory of density-functional and density-matrix theory in 2{sup nd} order Born approximation. While the formalism of density functional theory for structure investigation has been established for a long time and many different codes exist, the requirements for density matrix formalism concerning the geometry and the number of implemented bands exceed the usual possibilities of the existing code in this field. A special attention is therefore attributed to the development of extensions to existing formulations of this theory, where geometrical and fundamental symmetries of the structure and the equations are used. In Part II, the newly developed formalism is applied to a silicon (001)surface in a 2 x 1 reconstruction. As first step, density-functional calculations using the LDA functional are completed, from which the Kohn-Sham-wave functions and eigenvalues are used to calculate interaction matrix elements for the electron-phonon-coupling an the optical excitation. These matrix elements are determined for the optical transitions from valence to conduction bands and for electron-phonon processes inside the

  2. Superparamagnetic bead interactions with functionalized surfaces characterized by an immunomicroarray

    DEFF Research Database (Denmark)

    Skottrup, Peter Durand; Hansen, Mikkel Fougt; Moresco, Jacob Lange;

    2010-01-01

    SiO2 performed better than polyethylene glycol-modified surfaces Two beads, Masterbeads and M-280 beads, were found to give superior results compared with other bead types. Antibody/ antigen interactions, Illustrated by C-reactive protein, were best performed with Masterbeads The results provide...

  3. Density Functional Theory in Surface Chemistry and Catalysis

    Energy Technology Data Exchange (ETDEWEB)

    Norskov, Jens

    2011-05-19

    Recent advances in the understanding of reactivity trends for chemistry at transition metal surfaces have enabled in silico design of heterogeneous catalysts in a few cases. Current status of the field is discussed with an emphasis on the role of coupling between theory and experiment and future challenges.

  4. Density functional theory in surface chemistry and catalysis

    DEFF Research Database (Denmark)

    Nørskov, Jens Kehlet; Abild-Pedersen, Frank; Studt, Felix

    2011-01-01

    Recent advances in the understanding of reactivity trends for chemistry at transition-metal surfaces have enabled in silico design of heterogeneous catalysts in a few cases. The current status of the field is discussed with an emphasis on the role of coupling theory and experiment and future...

  5. Frequency Selective Surfaces for extended Bandwidth backing reflector functions

    NARCIS (Netherlands)

    Pasian, M.; Neto, A.; Monni, S.; Ettorre, M.; Gerini, G.

    2008-01-01

    This paper deals with the use of Frequency Selective Surfaces (FSS) to increase the Efficiency × Bandwidth product in Ultra-Wide Band (UWB) antenna arrays whose efficiency is limited by the front-to-back ratio. If the backing reflector is realized in one metal plane solution its location will be sui

  6. Work-function oscillations during the surfactant induced layer-by-layer growth of copper on oxygen precovered Ru(0001)

    Science.gov (United States)

    Schmidt, M.; Wolter, H.; Wandelt, K.

    1994-04-01

    In the present work the Cu-film growth on a clean and an oxygen precovered Ru(0001) surface, as monitored with dynamical work function measurements (ΔΦ measurements) during the Cu evaporation using a special Kelvin-probe is compared. For Cu adsorption on the clean surface the observed temperature dependence of the ΔΦ measurements is understood in terms of a change of the growth structure of the Cu films from layer-by-layer growth up to ~ 3 ML at ~ 600 K to a 3D-growth mode at ~ 400 K. In turn, as recently reported, in the case of Cu adsorption on the oxygen-precovered surface at ~ 400 K remarkable ΔΦ oscillations are observed, which could be resolved over many periods clearly indicating a layer-wise growth of high quality at this temperature. Furthermore, in the present paper we report on new and detailed results about the dependence of the ΔΦ oscillations on the oxygen precoverage as well as the Cu deposition rate.

  7. Ocular Surface and Tear Film Changes in Older Women Working with Computers.

    Science.gov (United States)

    Ribelles, Alfredo; Galbis-Estrada, Carmen; Parras, Maria A; Vivar-Llopis, Bárbara; Marco-Ramírez, Carla; Diaz-Llopis, Manuel

    2015-01-01

    The aim of this work is to investigate changes in the ocular surface (OS) and tear film (TF) by means of questionnaire-based subjective symptoms, TF break-up time, Schirmer test, and TF analysis in women working with computers and to analyze the effects of the oral supplementation with antioxidants/omega 3 fatty acids (A/ω3) in the OS outcomes. Women aged 40-65 years (n = 148) were recruited at the Administrative Offices of Valencia (Spain) and distributed into two age groups, 40-52 years (AGE1; n = 87) and 53-65 years (AGE2; n = 61), and then subdivided according to being (or not) computer users (CUG; NCUG) during the workday. Homogeneous subgroups were randomly assigned (or not) to the daily intake of three pills of A/ω3 for three months. At baseline and at the end of follow-up, personalized interviews and ocular examination were done. Reflex tear samples were collected from the inferior meniscus and processed for a multiplexed particle-based flow cytometry assay to measure proinflammatory molecules. Statistics were performed using the SPSS 15.0 program. The OS pathology was clinically evident in the AGE1-CUG (33%) versus the AGE2-CUG (64%) of women. Significantly higher interleukins-1β and -6 tear levels were found in the AGE1 versus the AGE2 women employees (P = 0.006 and P = 0.001, resp.), as well as in the CUG versus the NCUG (P = 0.001 and P = 0.000, resp.). Supplementation with A/ω3 positively influenced the OS pathology as manifested by the amelioration of the clinical signs/symptoms related to computer uses. Strategies involving a safe environment and oral micronutrient supplements may be managed within eye-care standards in older women.

  8. Improving the technology of surfacing heterogeneous working layer on hot rolling bulky rolls

    Directory of Open Access Journals (Sweden)

    Віталій Петрович Iванов

    2016-07-01

    Full Text Available Ways to increase efficiency of rolls by enhancing resistance to the formation and development of cracks due to the anisotropy of the working layer properties were explored. The destruction mechanisms of such materials were considered. The possibility of cracks deceleration, due to the layer ruptures or abrupt change of its properties has been marked. It has been shown that the optimum combination of the means braking dislocations provides for a rational metal alloying. The analysis of the rolls of rolling mills service conditions as well as the analysis of types of wear and destruction of products made it possible to formulate requirements on the surface layer of the rolls properties. However increase in strength decreases ductility and toughness of the steel. The solution of the problem of the strength and plasticity increase necessitates either methods of metal deep cleaning of contaminants development or significant grain refinement. The part played by structural formations, such as non-metallic inclusions, carbide particles, grain boundaries, etc.in the kinetics of crack propagation has been studied. Since sharp contrast of the properties at the grain boundaries is inconsistent with the requirements of welding technology, the determining factor for making up the working layer is the service conditions. The durability of the roll is determined by allowable wear out of the layer between resharpenings. The correct choice of optimum parameters for the twq adjacent layers - operating and the layer to be maintained is the reserve to improve performance of the roll. The paper has proposed welding-up compositions making it possible to extend the durability due to the optimum ratio of the mechanical and thermal properties of adjacent layers. This approach can improve the durability of the deposited products both at the stage of nucleation and at the stage of thermal fatigue cracks growth

  9. Ocular Surface and Tear Film Changes in Older Women Working with Computers

    Directory of Open Access Journals (Sweden)

    Alfredo Ribelles

    2015-01-01

    Full Text Available The aim of this work is to investigate changes in the ocular surface (OS and tear film (TF by means of questionnaire-based subjective symptoms, TF break-up time, Schirmer test, and TF analysis in women working with computers and to analyze the effects of the oral supplementation with antioxidants/omega 3 fatty acids (A/ω3 in the OS outcomes. Women aged 40–65 years (n=148 were recruited at the Administrative Offices of Valencia (Spain and distributed into two age groups, 40–52 years (AGE1; n=87 and 53–65 years (AGE2; n=61, and then subdivided according to being (or not computer users (CUG; NCUG during the workday. Homogeneous subgroups were randomly assigned (or not to the daily intake of three pills of A/ω3 for three months. At baseline and at the end of follow-up, personalized interviews and ocular examination were done. Reflex tear samples were collected from the inferior meniscus and processed for a multiplexed particle-based flow cytometry assay to measure proinflammatory molecules. Statistics were performed using the SPSS 15.0 program. The OS pathology was clinically evident in the AGE1-CUG (33% versus the AGE2-CUG (64% of women. Significantly higher interleukins-1β and -6 tear levels were found in the AGE1 versus the AGE2 women employees (P=0.006 and P=0.001, resp., as well as in the CUG versus the NCUG (P=0.001 and P=0.000, resp.. Supplementation with A/ω3 positively influenced the OS pathology as manifested by the amelioration of the clinical signs/symptoms related to computer uses. Strategies involving a safe environment and oral micronutrient supplements may be managed within eye-care standards in older women.

  10. Bio-Inspired Functional Surfaces Based on Laser-Induced Periodic Surface Structures

    Directory of Open Access Journals (Sweden)

    Frank A. Müller

    2016-06-01

    Full Text Available Nature developed numerous solutions to solve various technical problems related to material surfaces by combining the physico-chemical properties of a material with periodically aligned micro/nanostructures in a sophisticated manner. The utilization of ultra-short pulsed lasers allows mimicking numerous of these features by generating laser-induced periodic surface structures (LIPSS. In this review paper, we describe the physical background of LIPSS generation as well as the physical principles of surface related phenomena like wettability, reflectivity, and friction. Then we introduce several biological examples including e.g., lotus leafs, springtails, dessert beetles, moth eyes, butterfly wings, weevils, sharks, pangolins, and snakes to illustrate how nature solves technical problems, and we give a comprehensive overview of recent achievements related to the utilization of LIPSS to generate superhydrophobic, anti-reflective, colored, and drag resistant surfaces. Finally, we conclude with some future developments and perspectives related to forthcoming applications of LIPSS-based surfaces.

  11. Recovery to Preinterventional Functioning, Return-to-Work, and Life Satisfaction After Treatment of Unruptured Aneurysms

    NARCIS (Netherlands)

    Backes, Daan; Rinkel, Gabriel J. E.; van der Schaaf, Irene C.; Bijvank, Jenny A. Nij; Verweij, Bon H.; Visser-Meily, Johanna M. A.; Post, Marcel W.; Algra, Ale; Vergouwen, Mervyn D. I.

    2015-01-01

    Background and Purpose-The eventual goal of preventive treatment of unruptured intracranial aneurysms is to increase the number of life years with high life satisfaction. Insight in the time with reduced functioning, working capacity, and life satisfaction after aneurysm treatment is pivotal to bala

  12. Functional specialization of the left ventral parietal cortex in working memory

    Directory of Open Access Journals (Sweden)

    Jennifer Lou Langel

    2014-06-01

    Full Text Available The function of the ventral parietal cortex (VPC is subject to much debate. Many studies suggest a lateralization of function in the VPC, with the left hemisphere facilitating verbal working memory and the right subserving stimulus-driven attention. However, many attentional tasks elicit activity in the VPC bilaterally. To elucidate the potential divides across the VPC in function, we assessed the pattern of activity in the VPC bilaterally across two tasks that require different demands, an oddball attentional task with low working memory demands and a working memory task. An anterior region of the VPC was bilaterally active during novel targets in the oddball task and during retrieval in WM, while more posterior regions of the VPC displayed dissociable functions in the left and right hemisphere, with the left being active during the encoding and retrieval of WM, but not during the oddball task and the right showing the reverse pattern. These results suggest that bilateral regions of the anterior VPC subserve non-mnemonic processes, such as stimulus-driven attention during WM retrieval and oddball detection. The left posterior VPC may be important for speech-related processing important for both working memory and perception, while the right hemisphere is more lateralized for attention.

  13. Does work-related training reduce the discrepancy between function requirements and competencies?

    NARCIS (Netherlands)

    E.R. Kappe; G.E. Bijwaard (Govert)

    2005-01-01

    textabstractThe issue of lifelong learning is high on the political agenda. However, despite this political interest and the large economic literature on human capital, the impact of work-related training on the discrepancy between function requirements and the skills of the employee has been ignore

  14. Magnetic tunnel contacts to silicon with low-work-function ytterbium nanolayers

    NARCIS (Netherlands)

    Patel, R.S.; Dash, S.P.; de Jong, Machiel Pieter; Jansen, R.

    2009-01-01

    Unambiguous proof of spin transport in semiconductor spintronic devices requires a control experiment to exclude spurious signals that arise from the presence of the ferromagnetic contacts. It is shown here that insertion of a low-work-function Yb nanolayer in ferromagnetic tunnel contacts to

  15. Can Functional Capacity Tests Predict Future Work Capacity in Patients With Whiplash-Associated Disorders?

    NARCIS (Netherlands)

    Trippolini, Maurizio A.; Dijkstra, Pieter U.; Cote, Pierre; Scholz-Odermatt, Stefan M.; Geertzen, J.H.B.; Reneman, Michiel F.

    2014-01-01

    Objective: To determine whether functional capacity evaluation (FCE) tests predict future work capacity (WC) of patients with whiplash-associated disorders (WADs) grades I and II who did not regain full WC 6 to 12 weeks after injury. Design: Prospective cohort study. Setting: Rehabilitation center.

  16. Utility of the International Classification of Functioning, Disability and Health (ICF) for Educational Psychologists' Work

    Science.gov (United States)

    Aljunied, Mariam; Frederickson, Norah

    2014-01-01

    Despite embracing a bio-psycho-social perspective, the World Health Organization's International Classification of Functioning, Disability and Health (ICF) assessment framework has had limited application to date with children who have special educational needs (SEN). This study examines its utility for educational psychologists' work with…

  17. High work function transparent middle electrode for organic tandem solar cells

    NARCIS (Netherlands)

    Moet, D. J. D.; de Bruyn, P.; Blom, P. W. M.

    2010-01-01

    The use of poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS) in combination with ZnO as middle electrode in solution-processed organic tandem solar cells requires a pH modification of the PEDOT:PSS dispersion. We demonstrate that this neutralization leads to a reduced work function

  18. Large Work Function Modulation of Monolayer MoS2 by Ambient Gases.

    Science.gov (United States)

    Lee, Si Young; Kim, Un Jeong; Chung, JaeGwan; Nam, Honggi; Jeong, Hye Yun; Han, Gang Hee; Kim, Hyun; Oh, Hye Min; Lee, Hyangsook; Kim, Hyochul; Roh, Young-Geun; Kim, Jineun; Hwang, Sung Woo; Park, Yeonsang; Lee, Young Hee

    2016-06-28

    Although two-dimensional monolayer transition-metal dichalcogenides reveal numerous unique features that are inaccessible in bulk materials, their intrinsic properties are often obscured by environmental effects. Among them, work function, which is the energy required to extract an electron from a material to vacuum, is one critical parameter in electronic/optoelectronic devices. Here, we report a large work function modulation in MoS2 via ambient gases. The work function was measured by an in situ Kelvin probe technique and further confirmed by ultraviolet photoemission spectroscopy and theoretical calculations. A measured work function of 4.04 eV in vacuum was converted to 4.47 eV with O2 exposure, which is comparable with a large variation in graphene. The homojunction diode by partially passivating a transistor reveals an ideal junction with an ideality factor of almost one and perfect electrical reversibility. The estimated depletion width obtained from photocurrent mapping was ∼200 nm, which is much narrower than bulk semiconductors.

  19. The dependence of polymer conductivity on the work function of metallic electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Dunaevskii, M.S. [A. F. Ioffe Physico-Technical Institute, 194021 St. Petersburg (Russian Federation); Nikolaeva, M.N. [Institute of Macromolecular Compounds of the Russian Academy of Sciences, Bolshoi Pr. 31, 199004 St. Petersburg (Russian Federation); Rentzsch, R. [Institut fuer Experimentalphysik, Freie Universitaet Berlin, 14195 Berlin (Germany); Ionov, A.N.

    2009-12-15

    It is shown that the occurrence of metallic conductivity in polymers is due to their electrification. In particular, the current density depends on the electron work function of metallic electrodes which are in contact with the polymer. (Abstract Copyright [2009], Wiley Periodicals, Inc.)

  20. Self-Regulation, Executive Function, Working Memory, and Academic Achievement of Female High School Students

    Science.gov (United States)

    Halloran, Roberta Kathryn

    2011-01-01

    Self-regulation, executive function and working memory are areas of cognitive processing that have been studied extensively. Although many studies have examined the constructs, there is limited empirical support suggesting a formal link between the three cognitive processes and their prediction of academic achievement. Thus, the present study…