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Sample records for thallium-transition metal contacts

  1. Two new examples of very short thallium-transition metal contacts

    DEFF Research Database (Denmark)

    Karanovic, Ljiljana; Poleti, Dejan; Balic Zunic, Tonci

    2008-01-01

    Two new sulphosalts Tl3Ag3Sb2S6, (1) and Tl(3)Ag(3)AS(2)S(6), (2) were prepared in reaction of synthetic binary sulfides: argentite (Ag2S), carlinite (Tl2S) and orpiment (As2O3) or stibnite (Sb2S3), and their crystal structures have been determined using single-crystal data. The compounds are iso....... It is also pointed out that if only valence shell electrons are considered (Tl-Ag)(2+) group is isoelectronic with the (Hg-Hg)(2+) ion, therefore new examples of short Tl-Ag contacts could be expected. (C) 2007 Elsevier B.V. All rights reserved....

  2. Metal semiconductor contacts and devices

    CERN Document Server

    Cohen, Simon S; Einspruch, Norman G

    1986-01-01

    VLSI Electronics Microstructure Science, Volume 13: Metal-Semiconductor Contacts and Devices presents the physics, technology, and applications of metal-semiconductor barriers in digital integrated circuits. The emphasis is placed on the interplay among the theory, processing, and characterization techniques in the development of practical metal-semiconductor contacts and devices.This volume contains chapters that are devoted to the discussion of the physics of metal-semiconductor interfaces and its basic phenomena; fabrication procedures; and interface characterization techniques, particularl

  3. Forces in Liquid Metal Contacts

    DEFF Research Database (Denmark)

    Duggen, Lars; Mátéfi-Tempfli, Stefan

    2014-01-01

    Using rather well known theory about capillary bridges between two electrodes we calculate the tensile force that can be applied to liquid metal contacts in the micrometer regime. Assuming circular symmetry, full wetting of the electrodes, and neglecting gravity, we present a brief review...... of the necessary theory and find numerically the forces to be in the 100μN range for liquid metals as mercury and liquid Gallium suspended between electrodes of 20μm radius....

  4. A Study on Graphene—Metal Contact

    Directory of Open Access Journals (Sweden)

    Hongyu Yu

    2013-03-01

    Full Text Available The contact resistance between graphene and metal electrodes is crucial for the achievement of high-performance graphene devices. In this study, we review our recent study on the graphene–metal contact characteristics from the following viewpoints: (1 metal preparation method; (2 asymmetric conductance; (3 annealing effect; (4 interfaces impact.

  5. Formation of Catalytic Metal-Molecule Contacts

    Science.gov (United States)

    Tulevski, George S.; Myers, Matt B.; Hybertsen, Mark S.; Steigerwald, Michael L.; Nuckolls, Colin

    2005-07-01

    We describe a new strategy for the in situ growth of molecular wires predicated on the synthesis of a trifunctional ``primed'' contact formed from metal-carbon multiple bonds. The ruthenium-carbon π bond provides structural stability to the molecular linkages under ambient conditions, and density functional calculations indicate the formation of an efficient conduit for charge carriers to pass between the metal and the molecule. Moreover, the metal-carbon π bond provides a chemically reactive site from which a conjugated molecular wire can be grown in situ through an olefin metathesis reaction.

  6. Contact material optimization and contact physics in metal-contact microelectromechanical systems (MEMS) switches

    Science.gov (United States)

    Yang, Zhenyin

    Metal-contact MEMS switches hold great promise for implementing agile radio frequency (RF) systems because of their small size, low fabrication cost, low power consumption, wide operational band, excellent isolation and exceptionally low signal insertion loss. Gold is often utilized as a contact material for metal-contact MEMS switches due to its excellent electrical conductivity and corrosion resistance. However contact wear and stiction are the two major failure modes for these switches due to its material softness and high surface adhesion energy. To strengthen the contact material, pure gold was alloyed with other metal elements. We designed and constructed a new micro-contacting test facility that closely mimic the typical MEMS operation and utilized this facility to efficiently evaluate optimized contact materials. Au-Ni binary alloy system as the candidate contact material for MEMS switches was systematically investigated. A correlation between contact material properties (etc. microstructure, micro-hardness, electrical resistivity, topology, surface structures and composition) and micro-contacting performance was established. It was demonstrated nano-scale graded two-phase Au-Ni film could possibly yield an improved device performance. Gold micro-contact degradation mechanisms were also systematically investigated by running the MEMS switching tests under a wide range of test conditions. According to our quantitative failure analysis, field evaporation could be the dominant failure mode for highfield (> critical threshold field) hot switching; transient thermal-assisted wear could be the dominant failure mode for low-field hot switching; on the other hand, pure mechanical wear and steady current heating (1 mA) caused much less contact degradation in cold switching tests. Results from low-force (50 muN/micro-contact), low current (0.1 mA) tests on real MEMS switches indicated that continuous adsorbed films from ambient air could degrade the switch contact

  7. Photoconductor-metal contact at higher densities.

    Science.gov (United States)

    Dussel, G. A.; Boer, K. W.; Stirn, R. J.

    1973-01-01

    The formation of space charge in the barrier region is discussed. This region extends to a distance, x-sub o, equal to 200 A plus twice the mean free path of majority carriers. The conventional transport equation can be used only for x greater than x-sub o, and the carrier density at x-sub o represents a boundary condition for the bulk. Its change as a function of applied voltage, temperature, and light intensity in photoconducting CdS is discussed. The time dependence of the space-charge formation in the region between 0 and x-sub o is analyzed. It is shown under which conditions the individuality of the metal contact is observable.

  8. Enhanced End-Contacts by Helium Ion Bombardment to Improve Graphene-Metal Contacts

    Directory of Open Access Journals (Sweden)

    Kunpeng Jia

    2016-08-01

    Full Text Available Low contact resistance between graphene and metals is of paramount importance to fabricate high performance graphene-based devices. In this paper, the impact of both defects induced by helium ion (He+ bombardment and annealing on the contact resistance between graphene and various metals (Ag, Pd, and Pt were systematically explored. It is found that the contact resistances between all metals and graphene are remarkably reduced after annealing, indicating that not only chemically adsorbed metal (Pd but also physically adsorbed metals (Ag and Pt readily form end-contacts at intrinsic defect locations in graphene. In order to further improve the contact properties between Ag, Pd, and Pt metals and graphene, a novel method in which self-aligned He+ bombardment to induce exotic defects in graphene and subsequent thermal annealing to form end-contacts was proposed. By using this method, the contact resistance is reduced significantly by 15.1% and 40.1% for Ag/graphene and Pd/graphene contacts with He+ bombardment compared to their counterparts without He+ bombardment. For the Pt/graphene contact, the contact resistance is, however, not reduced as anticipated with He+ bombardment and this might be ascribed to either inappropriate He+ bombardment dose, or inapplicable method of He+ bombardment in reducing contact resistance for Pt/graphene contact. The joint efforts of as-formed end-contacts and excess created defects in graphene are discussed as the cause responsible for the reduction of contact resistance.

  9. Direct measurement of graphene contact resistivity to pre-deposited metal in buried contact test structure

    KAUST Repository

    Qaisi, Ramy M.

    2013-08-01

    We demonstrate a buried contact based novel test structure for direct contact resistivity measurement of graphene-metal interfaces. We also observe excellent contact resistivity 1 μO-cm2 without any additional surface modification suggesting that the intrinsic Au-graphene contact is sufficient for achieving devices with low contact resistance. The chemical mechanical polishing less test structure and data described herein highlights an ideal methodology for systematic screening and engineering of graphene-metal contact resistivity to enable low power high speed carbon electronics. © 2013 IEEE.

  10. Organic modification of metal / semiconductor Schottky contacts

    Energy Technology Data Exchange (ETDEWEB)

    Mendez Pinzon, H.A.

    2006-07-10

    parallel conductance, with a significant contribution of the back contact. Additionally a non linear behaviour of the organic layer resistance probably due to the presence of traps was deduced. () ? ' R QTS measurements performed on the heterostructure showed the presence of two relaxations induced by deposition of the organic layer. The first one is attributed to the presence of a deep trap probably located at the metal / organic interface, while the second one has very small activation energy ({proportional_to} 20 meV) which are probably due to disorder at the organic film. Those processes with small activation energies proved to be determinant for fitting the I-V characteristics of DiMe-PTCDI organic modified diodes using the expressions of a trapped charge limited current regime TCLC. Such a model was the best analytical approach found for fitting the I-V response. Further improving probably will involve implementation of numerical calculations or additional considerations in the physics of the device. (orig.)

  11. Electronic transport across metal-graphene edge contact

    Science.gov (United States)

    Gong, Cheng; Zhang, Chenxi; Oh, Young Jun; Wang, Weichao; Lee, Geunsik; Shan, Bin; Wallace, Robert M.; Cho, Kyeongjae

    2017-06-01

    The electronic transport across metal-graphene edge-contact structures is studied by first principles methods. Unusual double-dip transmission as a function of Fermi level is found for a Pd electrode over varying grapheme lengths. Interface metal-carbon hybridization is shown to introduce random distribution of π-orbital local density of states at different carbon sites leading to transmission suppression. For a Ti electrode, two dips are merged into one with a ~0.2 eV transport gap opening. Our work sheds light on the origin of intrinsic contact resistance at metal-graphene edge contact.

  12. Contact resistance of carbon nanotubes and metals

    Science.gov (United States)

    Choi, Hyoung Joon; Ihm, Jisoon; Yoon, Young-Gui; Louie, Steven G.

    2000-03-01

    The quantum conductance of a metallic carbon nanotube with one end immersed in a jellium metal is studied. We find that the incident π-band electrons go through the tube without being scattered by the surrounding metal and contribute a quantum unit (2e^2/h) to the conductance. On the other hand, the incident π-band electrons experience strong resonant back-scattering because the low-angular-momentum states at the Fermi level have a dominantly metallic character in the nanotube-jellium metal coexistence region. These results provide a possible explanation for the experimentally observed conductance of one quantum unit instead of two for nanotubes with one end dipped into liquid metal such as mercury. The detailed form of the immersion-length dependence of the conductance, which is strongly related to the coherence of the electronic state in the immersed part of the tube, will also be discussed.

  13. Metal contacts to lowly doped Si and ultra thin SOI

    NARCIS (Netherlands)

    Rajasekharan, B.; Salm, Cora; Hueting, Raymond Josephus Engelbart; Wolters, Robertus A.M.; Schmitz, Jurriaan

    2009-01-01

    We present our investigations on the fabrication of ohmic and pchottky contacts of several metals on lowly doped bulk pi and plf wafers. qhrough this paper we evaluate the fabrication of rectifying devices in which no doping is intentionally introduced.

  14. Bias dependent specic contact resistance of phase change material to metal contacts

    NARCIS (Netherlands)

    Roy, Deepu; in 't Zandt, Micha; Wolters, Robertus A.M.

    2010-01-01

    Knowledge of contact resistance of phase change materials (PCM) to metal electrodes is important for scaling, device modeling and optimization of phase change random access memory (PCRAM) cells. In this article, we report the systematic determination of the speci_c contact resistance (_c) with

  15. Criterion for surface contact deformation of metals

    NARCIS (Netherlands)

    Jamari, Jamari; Schipper, Dirk J.

    2007-01-01

    In most engineering applications, bulk plastic deformation of the surface is avoided. There is, however, no criterion for determining whether or not bulk plastic deformation occurs during the contact between rough surfaces. This paper presents a criterion for predicting the deformation behaviour of

  16. Transmissive metallic contact for amorphous silicon solar cells

    Science.gov (United States)

    Madan, A.

    1984-11-29

    A transmissive metallic contact for amorphous silicon semiconductors includes a thin layer of metal, such as aluminum or other low work function metal, coated on the amorphous silicon with an antireflective layer coated on the metal. A transparent substrate, such as glass, is positioned on the light reflective layer. The metallic layer is preferably thin enough to transmit at least 50% of light incident thereon, yet thick enough to conduct electricity. The antireflection layer is preferably a transparent material that has a refractive index in the range of 1.8 to 2.2 and is approximately 550A to 600A thick.

  17. Band Structure and Contact Resistance of Carbon Nanotubes Deformed by a Metal Contact

    Science.gov (United States)

    Hafizi, Roohollah; Tersoff, Jerry; Perebeinos, Vasili

    2017-11-01

    Capillary and van der Waals forces cause nanotubes to deform or even collapse under metal contacts. Using ab initio band structure calculations, we find that these deformations reduce the band gap by as much as 30%, while fully collapsed nanotubes become metallic. Moreover, degeneracy lifting due to the broken axial symmetry, and wave functions mismatch between the fully collapsed and the round portions of a CNT, lead to a 3 times higher contact resistance. The latter we demonstrate by contact resistance calculations within the tight-binding approach.

  18. Detecting microwave radiation on metal-porous silicon contacts

    Science.gov (United States)

    Gradauskas, J.; Stupakova, J.; Sužiedėlis, A.; Samuolienė, N.

    2015-12-01

    We have studied the rise of electromotive force (emf) across ohmic and nonohmic metal-porous silicon contacts under the action of 10-GHz microwave radiation. It is established that emfs of opposite polarities with different growth (and decay) rates are generated across the contacts of different types. The emf growth across the potential barriers of contacts is explained using a model of the microwave-induced heating of charge carriers. It is shown that the use of a porous semiconductor layer is a promising way to increase the voltage-power responsivity of microwave detectors and eliminate the "point contact" effects.

  19. Back contact to film silicon on metal for photovoltaic cells

    Science.gov (United States)

    Branz, Howard M.; Teplin, Charles; Stradins, Pauls

    2013-06-18

    A crystal oriented metal back contact for solar cells is disclosed herein. In one embodiment, a photovoltaic device and methods for making the photovoltaic device are disclosed. The photovoltaic device includes a metal substrate with a crystalline orientation and a heteroepitaxial crystal silicon layer having the same crystal orientation of the metal substrate. A heteroepitaxial buffer layer having the crystal orientation of the metal substrate is positioned between the substrate and the crystal silicon layer to reduce diffusion of metal from the metal foil into the crystal silicon layer and provide chemical compatibility with the heteroepitaxial crystal silicon layer. Additionally, the buffer layer includes one or more electrically conductive pathways to electrically couple the crystal silicon layer and the metal substrate.

  20. Thermal conductivity and contact resistance of metal foams

    Energy Technology Data Exchange (ETDEWEB)

    Sadeghi, E [Department of Mechanical Engineering, University of Victoria, Victoria, BC, V8W 3P6 (Canada); Hsieh, S; Bahrami, M, E-mail: ehsans@uvic.ca [Mechatronic Systems Engineering, School of Engineering Science, Simon Fraser University, Surrey, BC, V3T 0A3 (Canada)

    2011-03-30

    Accurate information on heat transfer and temperature distribution in metal foams is necessary for design and modelling of thermal-hydraulic systems incorporating metal foams. The analysis of heat transfer requires determination of the effective thermal conductivity as well as the thermal contact resistance (TCR) associated with the interface between the metal foam and the adjacent surfaces/layers. In this study, a test bed that allows the separation of effective thermal conductivity and TCR in metal foams is described. Measurements are performed in a vacuum under varying compressive loads using ERG Duocel aluminium foam samples with different porosities and pore densities. Also, a graphical method associated with a computer code is developed to demonstrate the distribution of contact spots and estimate the real contact area at the interface. Our results show that the porosity and the effective thermal conductivity remain unchanged with the variation of compression in the range 0-2 MPa; but TCR decreases significantly with pressure due to an increase in the real contact area at the interface. Moreover, the ratio of real to nominal contact area varies between 0 and 0.013, depending upon the compressive force, porosity, pore density and surface characteristics.

  1. Computational Study of Metal Contacts to Monolayer Transition-Metal Dichalcogenide Semiconductors

    Directory of Open Access Journals (Sweden)

    Jiahao Kang

    2014-07-01

    Full Text Available Among various 2D materials, monolayer transition-metal dichalcogenide (mTMD semiconductors with intrinsic band gaps (1–2 eV are considered promising candidates for channel materials in next-generation transistors. Low-resistance metal contacts to mTMDs are crucial because currently they limit mTMD device performances. Hence, a comprehensive understanding of the atomistic nature of metal contacts to these 2D crystals is a fundamental challenge, which is not adequately addressed at present. In this paper, we report a systematic study of metal-mTMD contacts with different geometries (top contacts and edge contacts by ab initio density-functional theory calculations, integrated with Mulliken population analysis and a semiempirical van der Waals dispersion potential model (which is critical for 2D materials and not well treated before. Particularly, In, Ti, Au, and Pd, contacts to monolayer MoS_{2} and WSe_{2} as well as Mo-MoS_{2} and W-WSe_{2} contacts are evaluated and categorized, based on their tunnel barriers, Schottky barriers, and orbital overlaps. Moreover, going beyond Schottky theory, new physics in such contact interfaces is revealed, such as the metallization of mTMDs and abnormal Fermi level pinning. Among the top contacts to MoS_{2}, Ti and Mo show great potential to form favorable top contacts, which are both n-type contacts, while for top contacts to WSe_{2}, W or Pd exhibits the most advantages as an n- or p-type contact, respectively. Moreover, we find that edge contacts can be highly advantageous compared to top contacts in terms of electron injection efficiency. Our formalism and the results provide guidelines that would be invaluable for designing novel 2D semiconductor devices.

  2. Temperature dependence of contact resistance at metal/MWNT interface

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Sang-Eui; Moon, Kyoung-Seok; Sohn, Yoonchul, E-mail: yoonchul.son@samsung.com [Materials Research Center, Samsung Advanced Institute of Technology, Samsung Electronics, Suwon 443-803 (Korea, Republic of)

    2016-07-11

    Although contact resistance of carbon nanotube (CNT) is one of the most important factors for practical application of electronic devices, a study regarding temperature dependence on contact resistance of CNTs with metal electrodes has not been found. Here, we report an investigation of contact resistance at multiwalled nanotube (MWNT)/Ag interface as a function of temperature, using MWNT/polydimethylsiloxane (PDMS) composite. Electrical resistance of MWNT/PDMS composite revealed negative temperature coefficient (NTC). Excluding the contact resistance with Ag electrode, the NTC effect became less pronounced, showing lower intrinsic resistivity with the activation energy of 0.019 eV. Activation energy of the contact resistance of MWNT/Ag interface was determined to be 0.04 eV, two times larger than that of MWNT-MWNT network. The increase in the thermal fluctuation assisted electron tunneling is attributed to conductivity enhancement at both MWNT/MWNT and MWNT/Ag interfaces with increasing temperature.

  3. Reactive boundary layers in metallic rolling contacts

    Energy Technology Data Exchange (ETDEWEB)

    Burbank, John

    2016-05-01

    more thorough investigation into the effects of residual austenite on the properties of this material. The high-performance alternative steels, 36NiCrMoV1-5-7 (hot working steel) and 45SiCrMo6 (spring steel), were heat treated as recommended by their respective manufacturers, and were not case-hardened. The selection of materials with and materials without case-hardening allows for an investigation into whether or not case-hardening is even necessary to deliver acceptable friction behaviour and wear performance. Elemental analyses were conducted by multiple methods to ensure accurate results. Residual austenite contents of the steels and the depth profiles of residual stresses were determined by X-Ray diffraction (XRD), for 20MnCr5 ranging from approximately 6 - 14 vol.%, and under 2 vol.% for the alternative alloys. Hardness profiles were taken from the testing surfaces into the material core. The carburization of 20MnCr5 led to higher hardness and the greater concentration of carbon in the carburization zone more representative of a hardened SAE E52100, or 100Cr6/102Cr6, than of a non-case-hardened 20MnCr5. Residual stresses from machining and case-hardening were measured directly at the sample surface. The high-performance steels fulfilled manufacturer expectations in terms of elemental content, with hardness values between 50 - 55 HRC and strongly martensitic microstructure character. With characterization of the chosen materials complete, the materials could then be subjected to pre-conditioning. The first pre-conditioning method involved targeted generation of cold work hardening as induced boundary layers to protect the contact zone against wear. Work hardening was identified both by variations in residual stress profiles, i.e. the introduction of beneficial compressive residual stresses, and hardness increases in the contact zone, providing enhanced wear resistance. Parameters for work hardening were further optimized to reduce damage to the surface substrates

  4. Thermionic current in metal-superconducting semiconductor contact

    CERN Document Server

    Kuznetsov, G V

    2001-01-01

    The thermonuclear mechanism of the carriers transfer from the superconducting semiconductor into the metal is considered. The zonal energy diagram of the n-type metal-superconducting semiconductor is analyzed. The task on calculating the thermal electron current is reduced to determination of the above-the-barrier part of this current. The volt-ampere characteristics of the metal-superconducting semiconductor contact for various intervals of the applied external voltage are considered in detail. The changes in the volt-ampere characteristics are determined by the temperature and the parameter of the superconductor energy gap

  5. Electrical Properties of Antimony (Sb) Metal Contacts to Silicon (Si ...

    African Journals Online (AJOL)

    The study investigates the behaviour of the contacts formed by Antimony (Sb) metal to Silicon (Si) thin films for electric field values 10 – 100V/m. Measurements of I-v characteristics were obtained at temperatures 303, 313, 323, 333, 343 and 353K respectively. The results show linear I – V relationship over a specified range ...

  6. Mechanisms of Contact, Adhesion, and Failure of Metallic Nanoasperities in the Presence of Adsorbates: Toward Conductive Contact Design.

    Science.gov (United States)

    Yang, Fan; Carpick, Robert W; Srolovitz, David J

    2017-01-24

    The properties of contacting interfaces are strongly affected not only by the bulk and surface properties of contacting materials but also by the ubiquitous presence of adsorbed contaminants. Here, we focus on the properties of single asperity contacts in the presence of adsorbates within a molecular dynamics description of metallic asperity normal contact and a parametric description of adsorbate properties. A platinum-platinum asperity contact is modeled with adsorbed oligomers with variable properties. This system is particularly tailored to the context of nanoelectromechanical system (NEMS) contact switches, but the results are generally relevant to metal-metal asperity contacts in nonpristine conditions. Even though mechanical forces can displace adsorbate out of the contact region, increasing the adsorbate layer thickness and/or adsorbate/metal adhesion makes it more difficult for metal asperity/metal surface contact to occur, thereby lowering the electrical contact conductance. Contact separation is a competition between plastic necking in the asperity or decohesion at the asperity/substrate interface. The mechanism which operates at a lower tensile stress dominates. Necking dominates when the adsorbate/metal adhesion is strong and/or the adsorbate layer thickness is small. In broad terms, necking implies larger asperity deformation and mechanical work, as compared with decohesion. Optimal NEMS switch performance requires substantial contact conductance and minimal asperity deformation; these results indicate that these goals can be achieved by balancing the quantity of adsorbates and their adhesion to the metal surface.

  7. Z-Pinch Wire-Electrode Contact Resistance Studies Using Weighted and Soft Metal Gasket Contacts*

    Science.gov (United States)

    Gomez, M. R.; Zier, J. C.; Thurtell, A. F.; French, D. M.; Gilgenbach, R. M.; Tang, W.; Lau, Y. Y.

    2008-11-01

    The contact made between z-pinch wires and electrodes has a significant effect on both the energy deposited in the wires and the uniformity of the expansion profile of the wires. We have shown that using soft metal gaskets can improve wire-electrode contact significantly over typical weighted contacts. Images of wire expansion profile and wire plasma emission will be presented for single and double wire shots on a 16 kA, 100 kV 4-stage Marx bank with 150 ns risetime. Bench resistance measurements for aluminum, stainless steel, and tungsten wires with diameters ranging from 7.5 um to 30 um will be presented. These measurements utilized both soft metal gasket contacts (gaskets include: indium, silver, aluminum, tin, and lead) and double-ended wire weight contacts (weights ranged from 0.4 g to 1.9 g). *This research was supported by U. S. DoE through Sandia National Laboratories award document numbers 240985, 768225, 790791 and 805234 to the University of Michigan. MRG supported by NNSA Fellowship and JCZ supported by NPSC Fellowship sponsored by Sandia National Labs.

  8. Effects of metallic contacts on electron transport through graphene

    Science.gov (United States)

    Barraza-Lopez, Salvador; Vanevic, Mihajlo; Kindermann, Markus; Chou, Mei-Yin

    2010-03-01

    Despite their undoubted importance in eventual graphene electronics, theoretical studies of the specific features of electron transport through graphene between metal contacts are in their first stages. In order to bridge this gap we perform a first-principles based, non-equilibrium Green's functions study of the conductance through graphene junctions suspended between noncovalent aluminum contacts as a function of the distance L between metal leads and the width W (up to 100 nm) of the junction. Electron-hole asymmetry is obtained as a consequence of doping at the leads. Furthermore, the doping in graphene originated by charge transfer from metals at the leads results in two conductance minima at the energies of the crossing of the linear bands in suspended and clamped graphene, for sufficiently large L. We present a tight-binding model that accounts for the first-principles results and can be employed for larger lengths and widths of the junctions up to experimental accessible values and for arbitrary noncovalent-bonding metal leads.

  9. Metal contacts on ZnSe and GaN

    Energy Technology Data Exchange (ETDEWEB)

    Duxstad, Kristin Joy [Univ. of California, Berkeley, CA (United States). Materials Science and Mineral Engineering

    1997-05-01

    Recently, considerable interest has been focused on the development of blue light emitting materials and devices. The focus has been on GaN and ZnSe, direct band gap semiconductors with bands gaps of 3.4 and 2.6 eV, respectively. To have efficient, reliable devices it is necessary to have thermally and electrically stable Ohmic contacts. This requires knowledge of the metal-semiconductor reaction behavior. To date few studies have investigated this behavior. Much information has accumulated over the years on the behavior of metals on Si and GaAs. This thesis provides new knowledge for the more ionic wide band gap semiconductors. The initial reaction temperatures, first phases formed, and phase stability of Pt, Pd, and Ni on both semiconductors were investigated. The reactions of these metals on ZnSe and GaN are discussed in detail and correlated with predicted behavior. In addition, comparisons are made between these highly ionic semiconductors and Si and GaAs. The trends observed here should also be applicable to other II-VI and III-Nitride semiconductor systems, while the information on phase formation and stability should be useful in the development of contacts for ZnSe and GaN devices.

  10. Ohmic contact in monolayer InSe-metal interface

    Science.gov (United States)

    Jin, Hao; Li, Jianwei; Wan, Langhui; Dai, Ying; Wei, Yadong; Guo, Hong

    2017-06-01

    As conventional Si-based devices approach their scaling limit, it is of great significance to find new materials for future electronic logic devices. The emerging two-dimensional (2D) materials with atomic thickness have attracted intense interests for their exotic properties. However, the presence of the Schottky barrier limits their applications, which is difficult to control over due to the Fermi level pinning effect. Therefore, searching for low resistance metal contact to 2D semiconductors becomes one of the most important topics. Here, we report that Ohmic contact can be realized in a monolayer InSe-Cu system. Based on the density functional theory combined with the nonequilibrium Green’s functions, the geometry, overlapping states, tunneling barrier, Schottky barrier, and band alignment at the interface of group-IB (Cu, Ag, and Au) with InSe monolayer are discussed in details. Our results reveal that Cu, the most common electrode used in the industry, shows great potential to form favorable contact with single layer InSe due to the strong interaction and high orbital overlapping. The calculated drain-source current versus bias voltage (I  -  V) curve exhibits linear behavior, indicating good Ohmic contact between the Cu electrodes and InSe channel. Our work may pave the way for design of next-generation ultrathin and flexible devices.

  11. Metals Are Important Contact Sensitizers: An Experience from Lithuania

    Directory of Open Access Journals (Sweden)

    Kotryna Linauskienė

    2017-01-01

    Full Text Available Background. Metals are very frequent sensitizers causing contact allergy and allergic contact dermatitis worldwide; up-to-date data based on patch test results has proved useful for the identification of a problem. Objectives. In this retrospective study prevalence of contact allergy to metals (nickel, chromium, palladium, gold, cobalt, and titanium in Lithuania is analysed. Patients/Methods. Clinical and patch test data of 546 patients patch tested in 2014–2016, in Vilnius University Hospital Santariskiu Klinikos, was analysed and compared with previously published data. Results. Almost third of tested patients (29.56% were sensitized to nickel. Younger women were more often sensitized to nickel than older ones (36% versus 22.8%, p=0.0011. Women were significantly more often sensitized to nickel than men (33% versus 6.1%, p<0.0001. Younger patients were more often sensitized to cobalt (11.6% versus 5.7%, p=0.0183. Sensitization to cobalt was related to sensitization to nickel (p<0.0001. Face dermatitis and oral discomfort were related to gold allergy (28% versus 6.9% dermatitis of other parts, p<0.0001. Older patients were patch test positive to gold(I sodium thiosulfate statistically significantly more often than younger ones (44.44% versus 21.21%, p=0.0281. Conclusions. Nickel, gold, cobalt, and chromium are leading metal sensitizers in Lithuania. Cobalt sensitization is often accompanied by sensitization to nickel. Sensitivity rate to palladium and nickel indicates possible cross-reactivity. No sensitization to titanium was found.

  12. Epitaxial metal-gallium arsenide contacts via electrodeposition

    Science.gov (United States)

    Bao, Zhi Liang

    The fabrication of epitaxial metal-GaAs contacts via electrodeposition and the electrical properties of the Schottky diodes are reported in this dissertation. Epitaxial electrodeposition of copper, iron, cobalt, iron-nickel, and bismuth on GaAs was discovered to rely on three major factors: the preparation of the GaAs surface by (NH4)OH etching, the addition of (NH 4)2SO4 to the electrolytes, and the control of deposition current density. The surface preparation by (NH4)OH provides a hydrophilic surface likely due to passivation via a layer of hydroxide bonds. Ammonium sulphate inhibits oxidation of the metal cations and likely acts as a surfactant both on the metal and GaAs surfaces. Control of adatom flux, similar to vacuum deposition techniques such as molecular beam epitaxy, determined the crystallinity, varying from polycrystalline to epitaxial to dendritic for current densities from 0.01 to 1 mA/mm2. The effects of other electrodeposition conditions including pH and electrolyte temperature were also investigated. Neutral electrolytes are needed for copper, iron, nickel-iron alloy, and cobalt epitaxial deposition, while acidic solution works for bismuth deposition indicating that the control of hydrogen evolution may be important. Cobalt nanodisc formation was obtained for lower temperatures (2 - 22°C) while optimal copper, iron, and bismuth epitaxy required higher deposition temperatures, 53, 56, and 70°C, respectively. The growth is via island nucleation and coalescence. The iron films develop a small decrease in lattice constant with residual compressive stress, which is a function of temperature. This is likely due to an impurity such as oxygen. Copper and cobalt formed nanometer scale reacted interfaces with GaAs, while iron and bismuth/GaAs formed abrupt interfaces. The electrical properties of these Schottky diodes were, nevertheless, found to be close to ideal and comparable to vacuum deposited diodes. Fe and Co/GaAs diodes showed identical

  13. Nanoscale metal-InGaAs contacts with ultra-low specific contact resistivity: Improved interfacial quality and extraction methodology

    Science.gov (United States)

    Masudy-Panah, Saeid; Wu, Ying; Lei, Dian; Kumar, Annie; Yeo, Yee-Chia; Gong, Xiao

    2018-01-01

    To enable heterogeneous integration of InGaAs based transistors with Si complementary metal-oxide-semiconductor (CMOS) devices, metal contacts to n+-InGaAs need to have high thermal stability for CMOS process compatibility and ultra-low contact resistance to achieve good device performance. In this work, n+-InGaAs contacts with ultra-low contact resistivity ρc based on refractory metals such as molybdenum (Mo) were realized. Use of refractory metal contacts achieves good thermal stability. An improved process that eliminates oxide between the metal and n+-InGaAs by using an in situ Ar+-plasma treatment prior to metal deposition achieves ultra-low ρc. Furthermore, a nano-scale transmission line method (nano-TLM) structure with significantly reduced parasitic leakage was designed and fabricated to improve the ρc extraction accuracy. The improved test structure introduces a SiO2 isolation layer between Mo and InGaAs outside the active or mesa region to eliminate a parallel leakage path that is present in other nano-TLM structures reported in the literature.

  14. Speci﬿c contact resistance of phase change materials to metal electrode

    NARCIS (Netherlands)

    Roy, Deepu; in 't Zandt, Micha A.A.; Wolters, Robertus A.M.

    2010-01-01

    For phase change random access memory (PCRAM) cells, it is important to know the contact resistance of phase change materials (PCMs) to metal electrodes at the contacts. In this letter, we report the systematic determination of the speci﬿c contact resistance (Ͽc ) of doped Sb2Te and Ge2Sb2Te5 to TiW

  15. Metal contact properties of poly3-octylthiophene thin films

    Energy Technology Data Exchange (ETDEWEB)

    Salinas, Oscar H.; Lopez-Mata, C.; Hu, Hailin; Sanchez, Aaron [Centro de investigacion en Energia, UNAM, Av.Xochicalco S/N, Temixco, Morelos, 62580 (Mexico); Nicho, Ma. Elena [CIICAp-UAEM, Cuernavaca, Morelos (Mexico)

    2006-04-14

    Chemically synthesized undoped poly3-octylthiophene (P3OT) was deposited as thin films on conducting glass substrates by drop casting. Doping state of P3OT was obtained by adding FeCl{sub 3} into the original P3OT solution. A qualitative explanation of the electrical contact behavior of the P3OT films was given by a band diagram made from optical absorbance spectra and electrochemical current-voltage curves of the polymeric films. Gold contacts on both undoped and doped P3OT films give an ohmic contact. Silver/P3OT contact shows a rectifying behavior; the forward current is 500 times the reverse current at 0.5V. Aluminum also forms rectifying contact with the two types of P3OT films, although the experimental rectification ratio is lower than that of the silver. The I-V curves of rectifying contacts were analyzed with Schottky equation and different diode parameters were obtained. (author)

  16. Analysis of Contact Stresses in High Speed Sheet Metal Forming Processes

    OpenAIRE

    Bonnen, J.; Gillard, A.; Golovashchenko, S.; Ibrahim, R.; Mamutov, A.; SMITH, L.

    2012-01-01

    In high speed metal forming, determination of contact stresses applied to forming dies is necessary in order to identify the requirements to the die material. Contact stresses greatly control the die design due to their effects on die durability. Very high contact stresses and fracture under impulsive loading have been reported in literature on contact type of high speed forming. In pulsed forming operations using electro-hydraulic forming (EHF), a work piece is often accelerat...

  17. Opening Electrical Contacts: The Transition from the Molten Metal Bridge to the Electric Arc

    Science.gov (United States)

    Slade, Paul G.

    This paper presents a comprehensive explanation of the formation of the electric arc between opening contacts in a current carrying electric circuit. As the contacts begin to open a molten metal bridge forms between them. The rupture of this bridge and the initial formation of the electric arc are studied in both atmospheric air and vacuum using experiments to determine the direction of metal transfer between the contacts as a function of time after the rupture of the molten metal bridge. High speed streak photography is also used to show the rupture of the molten metal bridge and the initial formation of the electric arc. Analysis of these data show that a very high-pressure, high-temperature metal vapor zone exists between the contacts after the rupture of the molten metal bridge. Under this condition a pseudo-arc forms where current is carried by metal ions and an anomalous, high net transfer of metal to the cathodic contact occurs. The pressure in this region decreases rapidly and there is a transition to the usual electric arc, which still operates in the metal vapor. In this arc the current is now mostly carried by electrons. The data shows that there is still a net transfer of metal to the cathode, but now its volume is a function of the arcing time.

  18. THERMODYNAMIC ANALYSIS OF CHEMICAL REACTIONS IN CONTACT ZONE OF METAL-NONSTICK COVERING+

    Directory of Open Access Journals (Sweden)

    D. M. Kukuj

    2010-01-01

    Full Text Available An attempt to estimate by thermodynamic method the probability of chemical reactions flowing in contact zone of metal-casting mold at production of castings of iron-carbon alloys is undertaken.

  19. Influence of metal contacts on the electrical properties of a UV-MSM photodetector

    OpenAIRE

    Harzallah G.; Benmohammed Z.; Remram M.

    2013-01-01

    We have developed a two-dimensional theoretical model. This model allowed us to characterize the MSM photodetector based ZnO. It also allowed us to simulate the dark current and photocurrent of the device with different dimensions of the metal contact of structure. The simulation results were agreed with those of the experiment. We have identified the influence of geometry parameters of the metal contact on the dark current and also on the photocurrent. Calculating the ratio (photocurrent / d...

  20. Phase-coherent electron transport through metallic atomic-sized contacts and organic molecules

    Energy Technology Data Exchange (ETDEWEB)

    Pauly, F.

    2007-02-02

    This work is concerned with the theoretical description of systems at the nanoscale, in particular the electric current through atomic-sized metallic contacts and organic molecules. In the first part, the characteristic peak structure in conductance histograms of different metals is analyzed within a tight-binding model. In the second part, an ab-initio method for quantum transport is developed and applied to single-atom and single-molecule contacts. (orig.)

  1. Ambipolar field-effect transistors by few-layer InSe with asymmetry contact metals

    Science.gov (United States)

    Lin, Chang-Yu; Ulaganathan, Rajesh Kumar; Sankar, Raman; Chou, Fang-Cheng

    2017-07-01

    Group IIIA-VIA layered semiconductors (MX, where M = Ga and In, X = S, Se, and Te) have attracted tremendous interest for their anisotropic optical, electronic, and mechanical properties. In this study, we demonstrated that metal and InSe junctions can lead to carrier behaviors in few-layered InSe FETs. These results indicate that the polarity of few-layered InSe FETs can be determined by using metals with different work functions. We adopted FET S/D metal contacts with asymmetric work functions to reduce the Schottky barriers of electrons and holes, and discovered that few-layered InSe FETs with carefully selected metal contacts can achieve ambipolar behaviors. These results indicate that group IIIA-VIA layered semiconductor FETs with asymmetry contact metals have great potential for applications in photovoltaic devices, optical sensors, and CMOS inverter circuits.

  2. Ambipolar field-effect transistors by few-layer InSe with asymmetry contact metals

    Directory of Open Access Journals (Sweden)

    Chang-Yu Lin

    2017-07-01

    Full Text Available Group IIIA−VIA layered semiconductors (MX, where M = Ga and In, X = S, Se, and Te have attracted tremendous interest for their anisotropic optical, electronic, and mechanical properties. In this study, we demonstrated that metal and InSe junctions can lead to carrier behaviors in few-layered InSe FETs. These results indicate that the polarity of few-layered InSe FETs can be determined by using metals with different work functions. We adopted FET S/D metal contacts with asymmetric work functions to reduce the Schottky barriers of electrons and holes, and discovered that few-layered InSe FETs with carefully selected metal contacts can achieve ambipolar behaviors. These results indicate that group IIIA−VIA layered semiconductor FETs with asymmetry contact metals have great potential for applications in photovoltaic devices, optical sensors, and CMOS inverter circuits.

  3. Experimental Tooling for Contact Stress Measurement in Bulk Metal Forming Processes

    Science.gov (United States)

    Vilotić, Dragiša; Plančak, Miroslav

    2011-01-01

    Knowledge of contact stresses in metal forming operations is essential not only for optimal die design, but also for theoretical and numerical analysis of the metal forming processes. Determination of contact stresses can be performed theoretically and experimentally. This paper presents a tool construction with built-in pin-load cells for experimental determination of contact stresses and friction coefficient at upsetting of prismatic specimen with cylindrical dies. This construction allows measurement of contact stresses in any point of the contact surface of specimen, due to adjustable location of pin-load cells. The adjustments are performed by turning cylindrical dies around its own axis in combination with the change of axial position of the specimen. Experimental determination of contact stresses in upsetting of Ck35 prismatic specimens using cylindrical tools was performed at the Laboratory for technology of plasticity, FTN Novi Sad.

  4. Physical model of the contact resistivity of metal-graphene junctions

    Energy Technology Data Exchange (ETDEWEB)

    Chaves, Ferney A., E-mail: ferneyalveiro.chaves@uab.cat; Jiménez, David [Departament d' Enginyeria Electrònica, Escola d' Enginyeria, Universitat Autònoma de Barcelona, Campus UAB, 08193 Bellaterra, Barcelona (Spain); Cummings, Aron W. [ICN2–Institut Català de Nanociència i Nanotecnologia, Campus UAB, 08193 Bellaterra, Barcelona (Spain); Roche, Stephan [ICN2–Institut Català de Nanociència i Nanotecnologia, Campus UAB, 08193 Bellaterra, Barcelona (Spain); ICREA, Institució Catalana de Recerca i Estudis Avançats, 08070 Barcelona (Spain)

    2014-04-28

    While graphene-based technology shows great promise for a variety of electronic applications, including radio-frequency devices, the resistance of the metal-graphene contact is a technological bottleneck for the realization of viable graphene electronics. One of the most important factors in determining the resistance of a metal-graphene junction is the contact resistivity. Despite the large number of experimental works that exist in the literature measuring the contact resistivity, a simple model of it is still lacking. In this paper, we present a comprehensive physical model for the contact resistivity of these junctions, based on the Bardeen Transfer Hamiltonian method. This model unveils the role played by different electrical and physical parameters in determining the specific contact resistivity, such as the chemical potential of interaction, the work metal-graphene function difference, and the insulator thickness between the metal and graphene. In addition, our model reveals that the contact resistivity is strongly dependent on the bias voltage across the metal-graphene junction. This model is applicable to a wide variety of graphene-based electronic devices and thus is useful for understanding how to optimize the contact resistance in these systems.

  5. Passivation of a Metal Contact with a Tunneling Layer

    DEFF Research Database (Denmark)

    Loozen, X.; Larsen, J.B.; Dross, F.

    2011-01-01

    The potential of contact passivation for increasing cell performance is indicated by several results reported in the literature. However, scant characterization of the tunneling layers used for that purpose has been reported. In this paper, contact passivation is investigated by insertion...... of an ultra-thin AlOx layer between an n-type emitter and a Ti/Pd/Ag contact. By using a 1.5nm thick layer, an increase of the minority carrier lifetime by a factor of 2.7 is achieved. Since current-voltage measurements indicate that an ohmic behavior is conserved for AlOx layers as thick as 1.5nm, a 1.5nm Al...

  6. Impact of scaling on the performance and reliability degradation of metal-contacts in NEMS devices

    KAUST Repository

    Dadgour, Hamed F.

    2011-04-01

    Nano-electro-mechanical switches (NEMS) offer new possibilities for the design of ultra energy-efficient systems; however, thus far, all the fabricated NEMS devices require high supply voltages that limit their applicability for logic designs. Therefore, research is being conducted to lower the operating voltages by scaling down the physical dimensions of these devices. However, the impact of device scaling on the electrical and mechanical properties of metal contacts in NEMS devices has not been thoroughly investigated in the literature. Such a study is essential because metal contacts play a critical role in determining the overall performance and reliability of NEMS. Therefore, the comprehensive analytical study presented in this paper highlights the performance and reliability degradations of such metal contacts caused by scaling. The proposed modeling environment accurately takes into account the impact of roughness of contact surfaces, elastic/plastic deformation of contacting asperities, and various inter-molecular forces between mating surfaces (such as Van der Waals and capillary forces). The modeling results are validated and calibrated using available measurement data. This scaling analysis indicates that the key contact properties of gold contacts (resistance, stiction and wear-out) deteriorate "exponentially" with scaling. Simulation results demonstrate that reliable (stiction-free) operation of very small contact areas (≈ 6nm x 6nm) will be a daunting task due to the existence of strong surface forces. Hence, contact degradation is identified as a major problem to the scaling of NEMS transistors. © 2011 IEEE.

  7. Corrosion protection of aluminum alloys in contact with other metals

    Science.gov (United States)

    Kuster, C. A.

    1969-01-01

    Study establishes the quality of chemical and galvanized protection afforded by anodized and aldozided coatings applied to test panels of various aluminum alloys. The test panels, placed in firm contact with panels of titanium alloys, were subjected to salt spray tests and visually examined for corrosion effect.

  8. Study on Contact Between Double Metal Composite and Pipe Power Slip for Offshore Well

    Directory of Open Access Journals (Sweden)

    Yu Wang

    2017-08-01

    Full Text Available The whole process of clamping offshore well double metal composite pipe was established, Reviewing the problems that in the oil and gas wells the double metal composite pipes frequently get plastic damage or even fracture failure when the power slips hold fast to the double metal composite pipe, the effect Eq. of contact area to tooth plate and double metal composite pipe was deduced, and based on the elastoplastic contact analysis theory, the theoretical Eq. was verified. For the double metal composite pipe stress, displacement and stress of drill tooth plate, influence of slip teeth plate on the double metal composite pipe damage was analyzed, The plastic damage law of the double metal composite pipe was obtained with the influence factor of the contact surface and the influence factor of the tooth crown width. the analysis showed that, The double metal composite pipe can be clamped and the contact area value of the tooth plate with the minimum damage are fixed. Several sets of teeth were produced, and then used to carry out experiments, indoor and field experiments have fully proved the accuracy of the result, The research work provides a better theoretical basis for optimal design of slip tooth plate.

  9. Thermal Diffusion Processes in Metal-Tip-Surface Interactions: Contact Formation and Adatom Mobility

    DEFF Research Database (Denmark)

    Sørensen, Mads Reinholdt; Jacobsen, Karsten Wedel; Jonsson, Hannes

    1996-01-01

    We have carried out computer simulations to identify and characterize various thermally activated atomic scale processes that can play an important role in room temperature experiments where a metal tip is brought close to a metal surface. We find that contact formation between the tip and the su...

  10. Nickel Silicide Metallization for Passivated Tunneling Contacts for Silicon Solar Cells

    Energy Technology Data Exchange (ETDEWEB)

    Marshall, Alexander; Florent, Karine; Tapriya, Astha; Lee, Benjamin G.; Kurinec, Santosh K.; Young, David L.

    2016-11-21

    Passivated tunneling contacts offer promise for applications in Interdigitated Back Passivated Contact (IBPC) high efficiency silicon solar cells. Metallization of these contacts remains a key research topic. This paper investigates NiSi/poly-Si/SiO2/c-Si passivated contacts using photoluminescence and contact resistivity measurements. An amorphous Si interlayer between the NiSi and poly-Si is observed to improve passivation, decreasing recombination. The overall recombination loss has a linear trend with the NiSi thickness. Implied Voc values close to 700 mV and contact resistivities below 10 mohm-cm2 have been achieved in NiSi/poly-Si:P/SiO2/c-Si contacts.

  11. CdS-metal contact at higher current densities.

    Science.gov (United States)

    Stirn, R. J.; Boeer, K. W.; Dussel, G. A.

    1973-01-01

    An investigation is conducted concerning the mechanisms by which a steady flow of current proceeds through the contact when an external voltage is applied. The main characteristics of current mechanisms are examined, giving attention to photoemission from the cathode, thermionic emission, minority-carrier extraction, and the tunneling of electrons. A high-field domain analysis is conducted together with experimental studies. Particular attention is given to the range in which tunneling predominates.

  12. Revealing thermal effects in the electronic transport through irradiated atomic metal point contacts

    Directory of Open Access Journals (Sweden)

    Bastian Kopp

    2012-10-01

    Full Text Available We report on the electronic transport through nanoscopic metallic contacts under the influence of external light fields. Various processes can be of relevance here, whose underlying mechanisms can be studied by comparing different kinds of atomic contacts. For this purpose two kinds of contacts, which were established by electrochemical deposition, forming a gate-controlled quantum switch (GCQS, have been studied. We demonstrate that in these kinds of contacts thermal effects resulting from local heating due to the incident light, namely thermovoltage and the temperature dependences of the electrical resistivity and the electrochemical (Helmholtz double layer are the most prominent effects.

  13. Prediction of contact mechanics in metal-on-metal Total Hip Replacement for parametrically comprehensive designs and loads.

    Science.gov (United States)

    Donaldson, Finn E; Nyman, Edward; Coburn, James C

    2015-07-16

    Manufacturers and investigators of Total Hip Replacement (THR) bearings require tools to predict the contact mechanics resulting from diverse design and loading parameters. This study provides contact mechanics solutions for metal-on-metal (MoM) bearings that encompass the current design space and could aid pre-clinical design optimization and evaluation. Stochastic finite element (FE) simulation was used to calculate the head-on-cup contact mechanics for five thousand combinations of design and loading parameters. FE results were used to train a Random Forest (RF) surrogate model to rapidly predict the contact patch dimensions, contact area, pressures and plastic deformations for arbitrary designs and loading. In addition to widely observed polar and edge contact, FE results included ring-polar, asymmetric-polar, and transitional categories which have previously received limited attention. Combinations of design and load parameters associated with each contact category were identified. Polar contact pressures were predicted in the range of 0-200 MPa with no permanent deformation. Edge loading (with subluxation) was associated with pressures greater than 500 MPa and induced permanent deformation in 83% of cases. Transitional-edge contact (with little subluxation) was associated with intermediate pressures and permanent deformation in most cases, indicating that, even with ideal anatomical alignment, bearings may face extreme wear challenges. Surrogate models were able to accurately predict contact mechanics 18,000 times faster than FE analyses. The developed surrogate models enable rapid prediction of MoM bearing contact mechanics across the most comprehensive range of loading and designs to date, and may be useful to those performing bearing design optimization or evaluation. Published by Elsevier Ltd.

  14. Comparison of nickel silicide and aluminium ohmic contact metallizations for low-temperature quantum transport measurements

    Directory of Open Access Journals (Sweden)

    Polley Craig

    2011-01-01

    Full Text Available Abstract We examine nickel silicide as a viable ohmic contact metallization for low-temperature, low-magnetic-field transport measurements of atomic-scale devices in silicon. In particular, we compare a nickel silicide metallization with aluminium, a common ohmic contact for silicon devices. Nickel silicide can be formed at the low temperatures (<400°C required for maintaining atomic precision placement in donor-based devices, and it avoids the complications found with aluminium contacts which become superconducting at cryogenic measurement temperatures. Importantly, we show that the use of nickel silicide as an ohmic contact at low temperatures does not affect the thermal equilibration of carriers nor contribute to hysteresis in a magnetic field.

  15. Metal contact engineering and registration-free fabrication of complementary metal-oxide semiconductor integrated circuits using aligned carbon nanotubes.

    Science.gov (United States)

    Wang, Chuan; Ryu, Koungmin; Badmaev, Alexander; Zhang, Jialu; Zhou, Chongwu

    2011-02-22

    Complementary metal-oxide semiconductor (CMOS) operation is very desirable for logic circuit applications as it offers rail-to-rail swing, larger noise margin, and small static power consumption. However, it remains to be a challenging task for nanotube-based devices. Here in this paper, we report our progress on metal contact engineering for n-type nanotube transistors and CMOS integrated circuits using aligned carbon nanotubes. By using Pd as source/drain contacts for p-type transistors, small work function metal Gd as source/drain contacts for n-type transistors, and evaporated SiO(2) as a passivation layer, we have achieved n-type transistor, PN diode, and integrated CMOS inverter with an air-stable operation. Compared with other nanotube n-doping techniques, such as potassium doping, PEI doping, hydrazine doping, etc., using low work function metal contacts for n-type nanotube devices is not only air stable but also integrated circuit fabrication compatible. Moreover, our aligned nanotube platform for CMOS integrated circuits shows significant advantage over the previously reported individual nanotube platforms with respect to scalability and reproducibility and suggests a practical and realistic approach for nanotube-based CMOS integrated circuit applications.

  16. Experimental characterization of electrochemically polymerized polycarbazole film and study of its behavior with different metals contacts

    Science.gov (United States)

    Srivastava, Aditi; Chakrabarti, P.

    2017-12-01

    In this paper, we present the method of fabrication, experimental characterization, and comparison of electrical parameters of semiconducting polycarbazole film with different rectifying metals contacts. Electrochemical polymerization and deposition of organic semiconductor, i.e., polycarbazole on ITO-coated glass substrate, were performed using an electrochemical workstation. Experimental characterization of the prepared polymer film was done in respect of morphology, absorption, bandgap, and thickness. The stability and electro-activity of polycarbazole film were verified by the cyclic voltammetric method. Study of the behavior of prepared polycarbazole film with the different metals contacts such as Aluminum, Copper, Tungsten, and Tin has been done using semiconductor device analyzer. Various electrical parameters such as barrier height, ideality factor, and reverse saturation current have been extracted with different metal contacts, and the values were compared and contrasted. The nature of I- V characteristic of polycarbazole film in non-contact mode has also been analyzed using scanning tunneling microscope. The rectifying I- V characteristics obtained with different metals contacts have also been validated by the simulation on Deckbuild platform of the of ATLAS® software tool from Silvaco Inc.

  17. Activating "Invisible" Glue: Using Electron Beam for Enhancement of Interfacial Properties of Graphene-Metal Contact.

    Science.gov (United States)

    Kim, Songkil; Russell, Michael; Kulkarni, Dhaval D; Henry, Mathias; Kim, Steve; Naik, Rajesh R; Voevodin, Andrey A; Jang, Seung Soon; Tsukruk, Vladimir V; Fedorov, Andrei G

    2016-01-26

    Interfacial contact of two-dimensional graphene with three-dimensional metal electrodes is crucial to engineering high-performance graphene-based nanodevices with superior performance. Here, we report on the development of a rapid "nanowelding" method for enhancing properties of interface to graphene buried under metal electrodes using a focused electron beam induced deposition (FEBID). High energy electron irradiation activates two-dimensional graphene structure by generation of structural defects at the interface to metal contacts with subsequent strong bonding via FEBID of an atomically thin graphitic interlayer formed by low energy secondary electron-assisted dissociation of entrapped hydrocarbon contaminants. Comprehensive investigation is conducted to demonstrate formation of the FEBID graphitic interlayer and its impact on contact properties of graphene devices achieved via strong electromechanical coupling at graphene-metal interfaces. Reduction of the device electrical resistance by ∼50% at a Dirac point and by ∼30% at the gate voltage far from the Dirac point is obtained with concurrent improvement in thermomechanical reliability of the contact interface. Importantly, the process is rapid and has an excellent insertion potential into a conventional fabrication workflow of graphene-based nanodevices through single-step postprocessing modification of interfacial properties at the buried heterogeneous contact.

  18. Process for reducing series resistance of solar cell metal contact systems with a soldering flux etchant

    Science.gov (United States)

    Coyle, R. T.; Barrett, Joy M.

    1984-01-01

    Disclosed is a process for substantially reducing the series resistance of a solar cell having a thick film metal contact assembly thereon while simultaneously removing oxide coatings from the surface of the assembly prior to applying solder therewith. The process includes applying a flux to the contact assembly and heating the cell for a period of time sufficient to substantially remove the series resistance associated with the assembly by etching the assembly with the flux while simultaneously removing metal oxides from said surface of said assembly.

  19. Role of Metal Contacts in High-Performance Phototransistors Based on WSe 2 Monolayers

    KAUST Repository

    Zhang, Wenjing

    2014-08-26

    Phototransistors based on monolayer transition metal dichalcogenides (TMD) have high photosensitivity due to their direct band gap transition. However, there is a lack of understanding of the effect of metal contacts on the performance of atomically thin TMD phototransistors. Here, we fabricate phototransistors based on large-area chemical vapor deposition (CVD) tungsten diselenide (WSe2) monolayers contacted with the metals of different work function values. We found that the low Schottky-contact WSe2 phototransistors exhibit a very high photo gain (105) and specific detectivity (1014Jones), values higher than commercial Si- and InGaAs-based photodetectors; however, the response speed is longer than 5 s in ambient air. In contrast, the high Schottky-contact phototransistors display a fast response time shorter than 23 ms, but the photo gain and specific detectivity decrease by several orders of magnitude. Moreover, the fast response speed of the high Schottky-contact devices is maintained for a few months in ambient air. This study demonstrates that the contact plays an important role in TMD phototransistors, and barrier height tuning is critical for optimizing the photoresponse and photoresponsivity. © 2014 American Chemical Society.

  20. Defect Dominated Charge Transport and Fermi Level Pinning in MoS2/Metal Contacts.

    Science.gov (United States)

    Bampoulis, Pantelis; van Bremen, Rik; Yao, Qirong; Poelsema, Bene; Zandvliet, Harold J W; Sotthewes, Kai

    2017-06-07

    Understanding the electronic contact between molybdenum disulfide (MoS2) and metal electrodes is vital for the realization of future MoS2-based electronic devices. Natural MoS2 has the drawback of a high density of both metal and sulfur defects and impurities. We present evidence that subsurface metal-like defects with a density of ∼10(11) cm(-2) induce negative ionization of the outermost S atom complex. We investigate with high-spatial-resolution surface characterization techniques the effect of these defects on the local conductance of MoS2. Using metal nanocontacts (contact area MoS2 Schottky barrier height as compared to that in the pristine regions. The magnitude of this decrease depends on the contact metal. The decrease of the Schottky barrier height is attributed to strong Fermi level pinning at the defects. Indeed, this is demonstrated in the measured pinning factor, which is equal to ∼0.1 at defect locations and ∼0.3 at pristine regions. Our findings are in good agreement with the theoretically predicted values. These defects provide low-resistance conduction paths in MoS2-based nanodevices and will play a prominent role as the device junction contact area decreases in size.

  1. Powerful demolition techniques - plasma fusion cutting, contact arc metal cutting (CAMC), and contact arc metal grinding (CAMG); Leistungsfaehige Rueckbautechnologien - Plasmaschmelzschneiden, Kontakt-Lichtbogen-Metall-Schneiden (CAMC) und Kontakt-Lichtbogen-Metall-Trennschleifen (CAMG)

    Energy Technology Data Exchange (ETDEWEB)

    Bach, F.W.; Kremer, G.; Ruemenapp, T. [Leibniz Univ. Hannover, Inst. fuer Werkstoffkunde, Garbsen (Germany)

    2006-10-15

    One of the most complicated steps in the demolition of nuclear power plants is the disassembly of radiologically burdened large components. Most of this work must be performed remotely and under a cover of water. Moreover, dimensions, structures, and locations pose problems. Various techniques of disassembly are available which have specific pros and cons. Thermal cutting techniques, i.e. plasma fusion cutting, contact arc metal cutting (CAMC), and contact arc metal grinding (CAMG), can be used with comparatively simple handling systems even for large material thicknesses and complex geometries. These thermal cutting techniques have been advanced considerably at the Institute for Materials Technology of the University of Hanover in recent years. In plasma fusion cutting, the workpiece is molten, partly evaporated, and the melt is blown out of the kerf by the gas jet. CAMC and CAMG are based on the thermal abrasion of electrically conducting materials under water by means of repeated non-steady short-circuit high-current arcs resulting from contacts between the electrode and the workpiece. Unlike plasma or laser beam cutting, hollow structures and sandwich structures pose no problems. The performance capability of plasma fusion cutting and contact arc metal cutting has been demonstrated impressively in the disassembly of reactor internals of the Karlsruhe multi-purpose research reactor (MZFR). (orig.)

  2. The effect of metal-contacts on carbon nanotube for high frequency interconnects and devices

    Directory of Open Access Journals (Sweden)

    George Chimowa

    2014-08-01

    Full Text Available High frequency characterisation of platinum and tungsten contacts on individual multi-walled carbon nanotubes (MWNT is performed from 10 MHz to 50 GHz. By measuring the scattering parameters of aligned individual MWNTs, we show that metal contacts enhance an inductive response due to the improved MWNT-electrode coupling reducing the capacitive effect. This behaviour is pronounced in the frequency below 10 GHz and strong for tungsten contacts. We explain the inductive response as a result of the interaction of stimulus current with the localized (or defects states present at the contact region resulting in the current lagging behind the voltage. The results are further supported by direct current measurements that show tungsten to significantly increase carbon nanotube-electrode coupling. The immediate consequence is the reduction of the contact resistance, implying a reduction of electron tunnelling barrier from the electrode to the carbon nanotube.

  3. Comparison of properties of silver-metal oxide electrical contact materials

    Directory of Open Access Journals (Sweden)

    Ćosović V.

    2012-01-01

    Full Text Available Changes in physical properties such as density, porosity, hardness and electrical conductivity of the Ag-SnO2 and Ag-SnO2In2O3 electrical contact materials induced by introduction of metal oxide nanoparticles were investigated. Properties of the obtained silver-metal oxide nanoparticle composites are discussed and presented in comparison to their counterparts with the micro metal oxide particles as well as comparable Ag-SnO2WO3 and Ag-ZnO contact materials. Studied silvermetal oxide composites were produced by powder metallurgy method from very fine pure silver and micro- and nanoparticle metal oxide powders. Very uniform microstructures were obtained for all investigated composites and they exhibited physical properties that are comparable with relevant properties of equivalent commercial silver based electrical contact materials. Both Ag-SnO2 and Ag- SnO2In2O3 composites with metal oxide nanoparticles were found to have lower porosity, higher density and hardness than their respective counterparts which can be attributed to better dispersion hardening i.e. higher degree of dispersion of metal oxide in silver matrix.

  4. Thermal conductance of metallic atomic-size contacts: Phonon transport and Wiedemann-Franz law

    Science.gov (United States)

    Klöckner, J. C.; Matt, M.; Nielaba, P.; Pauly, F.; Cuevas, J. C.

    2017-11-01

    Motivated by recent experiments [Science 355, 1192 (2017), 10.1126/science.aam6622; Nat. Nanotechnol. 12, 430 (2017), 10.1038/nnano.2016.302], we present here an extensive theoretical analysis of the thermal conductance of atomic-size contacts made of three different metals, namely gold (Au), platinum (Pt), and aluminum (Al). The main goal of this work is to elucidate the role of phonons in the thermal transport through these atomic contacts as well as to study the validity of the Wiedemann-Franz law, which relates the electrical and the thermal conductance. For this purpose, we have employed two different custom-developed theoretical approaches. The first one is a transport method based on density functional theory (DFT) that allows one to accurately compute the contributions of both electrons and phonons to the thermal transport in few-atom-thick contacts. The second technique is based on a combination of classical molecular dynamics (MD) simulations and a tight-binding model that enables the efficient calculation of the electronic contribution to the thermal conductance of atomic contacts of larger size. Our DFT-based calculations show that the thermal conductance of few-atom contacts of Au and Pt is dominated by electrons, with phonons giving a contribution typically below 10% of the total thermal conductance, depending on the contact geometry. For these two metals we find that the small deviations from the Wiedemann-Franz law, reported experimentally, largely stem from phonons. In the case of Al contacts we predict that the phononic contribution can be considerably larger with up to 40% of the total thermal conductance. We show that these differences in the phononic contribution across metals originate mainly from their distinct Debye energies. On the other hand, our MD-based calculations demonstrate that the electronic contribution to the thermal conductance follows very closely the Wiedemann-Franz law, irrespective of the material and the contact size

  5. The friction and wear of ceramic/ceramic and ceramic/metal combinations in sliding contact

    Energy Technology Data Exchange (ETDEWEB)

    Sliney, H.E.; Dellacorte, C. (NASA Lewis Research Center, Cleveland, OH (United States))

    1994-07-01

    The tribological characteristics of ceramics sliding on ceramics are compared to those of ceramics sliding on a nickel-based turbine alloy. The friction and wear of oxide ceramics and silicon-based ceramics in air at temperatures from room ambient to 900 C (in a few cases to 1200 C) were measured for a hemispherically-tipped pin on a flat sliding contact geometry. In general, especially at high temperature, friction and wear were lower for ceramic/metal combinations than for ceramic/ceramic combinations. The better tribological performance for ceramic/metal combinations is attributed primarily to the lubricious nature of the oxidized surface of the metal.

  6. A new approach for the facile preparation of metal-organic framework composites directly contacting with metal nanoparticles through arc plasma deposition.

    Science.gov (United States)

    Sadakiyo, Masaaki; Yoshimaru, Shotaro; Kasai, Hidetaka; Kato, Kenichi; Takata, Masaki; Yamauchi, Miho

    2016-06-28

    The arc plasma deposition (APD) method is first applied to prepare metal-organic framework (MOF) composites loading metal nanoparticles having a direct contact with the MOF. We demonstrate the detailed growth mechanism of metal particles on the MOFs and the applicability of the APD for various combinations of metals and MOFs.

  7. Free surface modeling of contacting solid metal flows employing the ALE formulation

    NARCIS (Netherlands)

    van der Stelt, A.A.; Bor, Teunis Cornelis; Geijselaers, Hubertus J.M.; Akkerman, Remko; Huetink, Han; Merklein, M.; Hagenah, H.

    2012-01-01

    In this paper, a numerical problem with contacting solid metal flows is presented and solved with an arbitrary Lagrangian-Eulerian (ALE) finite element method. The problem consists of two domains which mechanically interact with each other. For this simulation a new free surface boundary condition

  8. Wrinkling criteria in sheet metal forming for single sided contact situation and its application

    NARCIS (Netherlands)

    Nagy, Geza T.; Valkering, Kasper; Huetink, Han

    2005-01-01

    The general wrinkling theory based on the rate formulation of the principle of virtual work has been applied in a number of studies on wrinkling during sheet metal forming. No contact with the die was allowed. In this study it is shown that with the right choice of wrinkling modes, the theory can

  9. Mechanical deformation of atomic-scale metallic contacts: Structure and mechanisms

    DEFF Research Database (Denmark)

    Sørensen, Mads Reinholdt; Brandbyge, Mads; Jacobsen, Karsten Wedel

    1998-01-01

    We have simulated the mechanical deformation of atomic-scale metallic contacts under tensile strain using molecular dynamics and effective medium theory potentials. The evolution of the structure of the contacts and the underlying deformation mechanisms are described along with the calculated...... electronic conductance. Various defects such as intersecting stacking faults, local disorder, and vacancies are created during the deformation. Disordered regions act as weak spots that reduce the strength of the contacts. The disorder tends to anneal out again during the subsequent atomic rearrangements......, but vacancies can be permanently present. The transition states and energies for slip mechanisms have been determined using the nudged elastic band method, and we find a size-dependent crossover from a dislocation-mediated slip to a homogeneous slip when the contact diameter becomes less than a few nm. We show...

  10. Characterization of metal contacts on and surfaces of cadmium zinc telluride

    CERN Document Server

    Bürger, A; Chattopadhyay, K; Shi, D; Morgan, S H; Collins, W E; James, R B

    1999-01-01

    In the past several years significant progress has been made in building a database of physical properties for detector quality Cd sub x Zn sub 1 sub - sub x Te (CZT) (x=0.1-0.2) crystal material. CZT's high efficiency combined with its room temperature operation make the material an excellent choice for imaging and spectroscopy in the 10-200 keV energy range. For detector grade material, superior crystallinity and high bulk resistivity are required. The surface preparation during the detector fabrication plays a vital role in determining the contact characteristics and the surface leakage current, which are often the dominant factors influencing its performance. This paper presents a surface and contact characterization study aimed at establishing the effects of the surface preparation steps prior to contacting (polishing and chemical etching), the choice of the metal and contact deposition technique, and the surface oxidation process. A photoconductivity mapping technique is used for studying the effects of...

  11. Review of test methods used to determine the corrosion rate of metals in contact with treated wood

    Science.gov (United States)

    Samuel L. Zelinka; Douglas R. Rammer

    2005-01-01

    The purpose of this literature review is to give an overview of test methods previously used to evaluate the corrosion of metals in contact with wood. This article reviews the test methods used to evaluate the corrosion of metals in contact with wood by breaking the experiments into three groups: exposure tests, accelerated exposure tests, and electrochemical tests....

  12. Impact of incomplete metal coverage on the electrical properties of metal-CNT contacts: A large-scale ab initio study

    Energy Technology Data Exchange (ETDEWEB)

    Fediai, Artem, E-mail: artem.fediai@nano.tu-dresden.de; Ryndyk, Dmitry A. [Institute for Materials Science and Max Bergman Center of Biomaterials, TU Dresden, 01062 Dresden (Germany); Center for Advancing Electronics Dresden, TU Dresden, 01062 Dresden (Germany); Seifert, Gotthard [Theoretical Chemistry, TU Dresden, 01062 Dresden (Germany); Center for Advancing Electronics Dresden, TU Dresden, 01062 Dresden (Germany); Dresden Center for Computational Materials Science, TU Dresden, 01062 Dresden (Germany); Mothes, Sven; Schroter, Michael; Claus, Martin [Chair for Electron Devices and Integrated Circuits, TU Dresden, 01062 Dresden (Germany); Center for Advancing Electronics Dresden, TU Dresden, 01062 Dresden (Germany); Cuniberti, Gianaurelio [Institute for Materials Science and Max Bergman Center of Biomaterials, TU Dresden, 01062 Dresden (Germany); Center for Advancing Electronics Dresden, TU Dresden, 01062 Dresden (Germany); Dresden Center for Computational Materials Science, TU Dresden, 01062 Dresden (Germany)

    2016-09-05

    Using a dedicated combination of the non-equilibrium Green function formalism and large-scale density functional theory calculations, we investigated how incomplete metal coverage influences two of the most important electrical properties of carbon nanotube (CNT)-based transistors: contact resistance and its scaling with contact length, and maximum current. These quantities have been derived from parameter-free simulations of atomic systems that are as close as possible to experimental geometries. Physical mechanisms that govern these dependences have been identified for various metals, representing different CNT-metal interaction strengths from chemisorption to physisorption. Our results pave the way for an application-oriented design of CNT-metal contacts.

  13. Copper-Metalized GaAs pHEMT with Cu/Ge Ohmic Contacts

    Directory of Open Access Journals (Sweden)

    E. V. Anichenko

    2012-01-01

    Full Text Available The fully Cu-metalized GaAs pHEMT using developed Cu/Ge-based ohmic contacts and T-gate Ti/Mo/Cu with length of the 150 nm has been successfully fabricated for the high-frequency applications. The fabricated Cu-metalized pHEMT has a maximum drain current of 360 mA/mm, an off-state gate-drain breakdown of 7 V, and a transconductance peak of 320 mS/mm at Vds=3 V. The maximum stable gain value was about 15 dB at frequency 10 GHz. The current gain cutoff frequency of the copper-metalized device is about 60 GHz at Vds=3 V, and maximum frequency of oscillations is beyond 100 GHz. This work investigated in detail the formation of Cu/Ge ohmic contacts to n-GaAs with an atomic hydrogen preannealing step. It was shown that after the first preliminary annealing is carried out in a flow of atomic hydrogen with a flow density of atoms of 1013/1016 at. cm2 s−1 a reduction in specific contact resistance by 2/2.5 times is observed. The reduction in specific contact resistance is apparently caused by the action of the hydrogen atoms which minimise the rate of the oxidizing reactions and activate solid phase reactions forming the ohmic contact during the thermal treatment process.

  14. A PROCESS FOR DEPOSITING METAL CONTACTS ON A BURIED GRID SOLAR CELL AND A SOLAR CELL OBTAINED BY THE PROCESS

    DEFF Research Database (Denmark)

    2002-01-01

    A buried grid solar cell is manufactured by a process for metallising one or more metal contacts of a buried grid solar cell having a body of doped semiconductor material, wherein the electrical contact(s) is/are provided by conducting material being arranged in a pattern of one or more grooves...... conducting contact forming material by electrolytic plating using a conventional electrolytic bath further comprising a levelling additive and a suppressing additive and using substantially constant cell voltage....

  15. High performance Ω-gated Ge nanowire MOSFET with quasi-metallic source/drain contacts.

    Science.gov (United States)

    Burchhart, T; Zeiner, C; Hyun, Y J; Lugstein, A; Hochleitner, G; Bertagnolli, E

    2010-10-29

    Ge nanowires (NWs) about 2 µm long and 35 nm in diameter are grown heteroepitaxially on Si(111) substrates in a hot wall low-pressure chemical vapor deposition (LP-CVD) system using Au as a catalyst and GeH(4) as precursor. Individual NWs are contacted to Cu pads via e-beam lithography, thermal evaporation and lift-off techniques. Self-aligned and atomically sharp quasi-metallic copper-germanide source/drain contacts are achieved by a thermal activated phase formation process. The Cu(3)Ge segments emerge from the Cu contact pads through axial diffusion of Cu which was controlled in situ by SEM, thus the active channel length of the MOSFET is adjusted without any restrictions from a lithographic process. Finally the conductivity of the channel is enhanced by Ga(+) implantation leading to a high performance Ω-gated Ge-NW MOSFET with saturation currents of a few microamperes.

  16. Decomposition of Imidazolium-Based Ionic Liquids in Contact with Lithium Metal.

    Science.gov (United States)

    Schmitz, Paulo; Jakelski, Rene; Pyschik, Marcelina; Jalkanen, Kirsi; Nowak, Sascha; Winter, Martin; Bieker, Peter

    2017-03-09

    Ionic liquids (ILs) are considered to be suitable electrolyte components for lithium-metal batteries. Imidazolium cation based ILs were previously found to be applicable for battery systems with a lithium-metal negative electrode. However, herein it is shown that, in contrast to the well-known IL N-butyl-N-methylpyrrolidinium bis[(trifluoromethyl)sulfonyl]imide ([Pyr14 ][TFSI]), 1-ethyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide ([C2MIm][TFSI]) and 1-butyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide ([C4MIm][TFSI]) are chemically unstable versus metallic lithium. A lithium-metal sheet was immersed in pure imidazolium-based IL samples and aged at 60 °C for 28 days. Afterwards, the aged IL samples were investigated to deduce possible decomposition products of the imidazolium cation. The chemical instability of the ILs in contact with lithium metal and a possible decomposition starting point are shown for the first time. Furthermore, the investigated imidazolium-based ILs can be utilized for lithium-metal batteries through the addition of the solid-electrolyte interphase (SEI) film-forming additive fluoroethylene carbonate. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Fundamentals and practice of metal contacts to wide band gap semiconductor devices

    Energy Technology Data Exchange (ETDEWEB)

    Borysiewicz, M.A.; Kaminska, E.; Mysliwiec, M.; Wzorek, M.; Piotrowska, A. [Institute of Electron Technology, Warsaw (Poland); Kuchuk, A. [Institute of Electron Technology, Warsaw (Poland); V.E. Lashkaryov Institute of Semiconductor Physics, Kyiv (Ukraine); Barcz, A.; Dynowska, E. [Institute of Electron Technology, Warsaw (Poland); Institute of Physic PAS, Warsaw (Poland); Di Forte-Poisson, M.A. [Alcatel-Thales III-V Lab, Marcoussis (France); Giesen, C. [AIXTRON SE, Herzogenrath (Germany)

    2012-03-15

    Presented are the theoretical and experimental fundamentals of the fabrication of ohmic contacts to n- and p-type wide band gap semiconductors such as SiC and GaN. In particular, the Ni-Si/n-SiC, Al-Ti/p-SiC, Ti-Al/n-GaN and Ni-Au/p-GaN systems are discussed with the focus on the thermally activated chemical reactions taking place at the metal-semiconductor interface, that lead to the appearance of ohmic behaviour in the contact. Examples of reactions at very intimate interfaces are shown, which are irresolvable using even such sophisticated characterisation methods as high-resolution transmission electron microscopy and can only be explained using modelling. The issue of thermal stability of the contacts is discussed and the introduction of specifically designed diffusion barriers (eg. Ta-Si-N) into the contact metallisation stack is presented as a solution improving drastically the thermal stability of the contacts without degrading their electrical properties. (copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  18. The challenge of screen printed Ag metallization on nano-scale poly-silicon passivated contacts for silicon solar cells

    Science.gov (United States)

    Jiang, Lin; Song, Lixin; Yan, Li; Becht, Gregory; Zhang, Yi; Hoerteis, Matthias

    2017-08-01

    Passivated contacts can be used to reduce metal-induced recombination for higher energy conversion efficiency for silicon solar cells, and are obtained increasing attentions by PV industries in recent years. The reported thicknesses of passivated contact layers are mostly within tens of nanometer range, and the corresponding metallization methods are realized mainly by plating/evaporation technology. This high cost metallization cannot compete with the screen printing technology, and may affect its market potential comparing with the presently dominant solar cell technology. Very few works have been reported on screen printing metallization on passivated contact solar cells. Hence, there is a rising demand to realize screen printing metallization technology on this topic. In this work, we investigate applying screen printing metallization pastes on poly-silicon passivated contacts. The critical challenge for us is to build low contact resistance that can be competitive to standard technology while restricting the paste penetrations within the thin nano-scale passivated contact layers. The contact resistivity of 1.1mohm-cm2 and the open circuit voltages > 660mV are achieved, and the most appropriate thickness range is estimated to be around 80 150nm.

  19. Mercaptopyridine and 4-aminothiophenol self-assembled layers in metal-molecule-metal contacts: a computational DFT study

    Energy Technology Data Exchange (ETDEWEB)

    Kucera, Jan; Gross, Axel [Institute fuer Theoretische Chemie, Universitaet Ulm (Germany)

    2008-07-01

    Recently it has become possible to deposit two-dimensional Pd layers on top of a 4-mercaptopyridine (Mpy) or a 4-aminothiophenol (4-ATP) self-assembled monolayer (SAM) on Au(111) leading to metal-molecule-metal contacts. We performed periodic density functional theory (DFT) calculations in order to contribute to the interpretation of the experimentally observed geometric and electronic structures. The calculations show that the adsorption structures of Mpy and 4-ATP on Au(111) are very similar. Both molecules prefer to bind to bridge-hollow sites at low as well as at high coverages. At low coverages, the molecules are significantly tilted from the Au(111) surface normal, whereas a denser packing leads to more upright configurations. The Pd/SAM interfaces correspond to metastable configurations in spite of the relatively strong Pd-Au interaction. The Pd-SAM contact is made through one-fold coordinated Pd-N bonds. In agreement with the experiment, the density of states (DOS) of Pd layer shows a significant reduction close to the Fermi level with respect to bulk Pd due to the Pd-N interaction. Also in agreement with experiment, the calculations confirm that 4-ATP is able to form bilayer structures connected through hydrogen bonds between the sulfur head group and up to to three hydrogen atoms of the amino group.

  20. An Investigation of Sliding Electrical Contact in Rail Guns and the Development of Grooved-Rail Liquid-Metal Interfaces

    National Research Council Canada - National Science Library

    Adamy, Mark

    2001-01-01

    ... the rails and yet provide sufficient electrical contact to sustain arc-free high-current flow is desirable, This thesis investigates the use of liquid metal as an interface material between the sliding...

  1. Ohmic contacts of Au and Ag metals to n-type GdN thin films

    Directory of Open Access Journals (Sweden)

    Felicia Ullstad

    2015-05-01

    Full Text Available The rare-earth nitrides appear as attractive alternatives to dilute ferromagnetic semiconductors for spintronics device applications. Most of them combine the properties of the ferromagnet and the semiconductor, an exceedingly rare combination. In this work we have grown n-type polycrystalline semiconducting GdN layers between pre-deposited contacts made of Cr/Au and Cr/Ag. The resistivity of the GdN layers ranges from 4.4×10-4 Ωcm to 3.1×10-2 Ωcm depending on the nitrogen pressure during the growth. The electrical properties of metal/n-type GdN/metal planar junctions are investigated as a function of the temperature. The current voltage characteristics of the junctions were linear for temperatures ranging from 300 K down to 5 K, suggesting an ohmic contact between the Au or Ag metal and the n-type GdN layer.

  2. Low Resistance Ohmic Contacts to Bi[sub 2]Te[sub 3] Using Ni and Co Metallization

    KAUST Repository

    Gupta, Rahul P.

    2010-04-27

    A detailed study of the impact of surface preparation and postdeposition annealing on contact resistivity for sputtered Ni and Co contacts to thin-film Bi2 Te3 is presented. The specific contact resistivity is obtained using the transfer length method. It is observed that in situ sputter cleaning using Ar bombardment before metal deposition gives a surface free of oxides and other contaminants. This surface treatment reduces the contact resistivity by more than 10 times for both Ni and Co contacts. Postdeposition annealing at 100°C on samples that were sputter-cleaned further reduces the contact resistivity to < 10-7 cm2 for both Ni and Co contacts to Bi2 Te3. Co as a suitable contact metal to Bi2 Te3 is reported. Co provided similar contact resistance values as Ni, but had better adhesion and less diffusion into the thermoelectric material, making it a suitable candidate for contact metallization to Bi2 Te3 based devices. © 2010 The Electrochemical Society.

  3. Role of metal/silicon semiconductor contact engineering for enhanced output current in micro-sized microbial fuel cells

    KAUST Repository

    Mink, Justine E.

    2013-11-25

    We show that contact engineering plays an important role to extract the maximum performance from energy harvesters like microbial fuel cells (MFCs). We experimented with Schottky and Ohmic methods of fabricating contact areas on silicon in an MFC contact material study. We utilized the industry standard contact material, aluminum, as well as a metal, whose silicide has recently been recognized for its improved performance in smallest scale integration requirements, cobalt. Our study shows that improvements in contact engineering are not only important for device engineering but also for microsystems. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Technology of Producing the Contact Connections of Superconductor Metal-Sheathed Cable

    Science.gov (United States)

    Jakubowski, Andrzej

    2017-06-01

    The technology of producing the current contact connections on the superconductor cable edges is presented. This lead cable is used as one of the major elements of the magnetic system in thermonuclear reactor construction, actuality for modern world energy. The technology is realized by the radial draft of metal thin-walled tube on the conductor's package. The filling of various profiles by round section wire is optimized. Geometrical characteristics of the dangerous crosssection (as a broken ring) of thin-walled tube injured by the sector cut-out are accounted. The comparative strength calculation of the solid and injured tubes at a longitudinal compression and lateral bending is acted. The radial draft mechanism of cylindrical thin-walled sheath with the wire packing is designed. The necessity to use the nonlinear theory for the sheaths calculate is set. The resilient co-operation of wires as the parallel located cylinders with the contact stripes of rectangular form is considered.

  5. Contact allergy to metals in adolescents: nickel release from metal accessories 7 years after the implementation of the EU Nickel Directive in Poland.

    Science.gov (United States)

    Krecisz, Beata; Chomiczewska, Dorota; Palczynski, Cezary; Kiec-Swierczynska, Marta

    2012-11-01

    Contact allergy among adolescents is an important issue. To assess the prevalence of contact allergy to metals in adolescents aged 15 years and nickel release from metal accessories that are in direct contact with the skin. Three hundred and nine females and 219 males, all 15 years old, from randomly selected secondary schools were examined and patch tested with nickel sulfate, cobalt chloride, palladium chloride, and potassium dichromate. Three hundred and ninety-nine metal accessories were tested with the dimethylglyoxime (DMG) test. 'Metal dermatitis' was reported by 19.4% of females and 0.5% of males. Positive patch test reactions were found in 8.5% of the adolescents (12.9% in females; 2.3% in males), namely to: nickel (12.3% of females; 1.4% of males); palladium (5.2% of females; 0.5% of males); cobalt (3.2% of females; 1.4% of males); and chromium (1.3% of females; 0.9% of males). Allergic contact dermatitis caused by metals was diagnosed in 9.7% of females and in 0.5% of males. Of the metal items, 26.1% gave positive DMG test results: 10.0% of earrings, 11.4% of snaps, and 56.2% of belt buckles. Despite the implementation of the Nickel Directive in Poland, nickel still remains an important causal factor for allergic contact dermatitis. Numerous metal accessories do not comply with the Directive. © 2012 John Wiley & Sons A/S.

  6. Photovoltaic Effect and Evidence of Carrier Multiplication in Graphene Vertical Homojunctions with Asymmetrical Metal Contacts.

    Science.gov (United States)

    Chen, Jing-Jing; Wang, Qinsheng; Meng, Jie; Ke, Xiaoxing; Van Tendeloo, Gustaaf; Bie, Ya-Qing; Liu, Junku; Liu, Kaihui; Liao, Zhi-Min; Sun, Dong; Yu, Dapeng

    2015-09-22

    Graphene exhibits exciting potentials for high-speed wideband photodetection and high quantum efficiency solar energy harvest because of its broad spectral absorption, fast photoelectric response, and potential carrier multiplication. Although photocurrent can be generated near a metal-graphene interface in lateral devices, the photoactive area is usually limited to a tiny one-dimensional line-like interface region. Here, we report photoelectric devices based on vertical graphene two-dimensional homojunction, which is fabricated via vertically stacking four graphene monolayers with asymmetric metal contacts. The devices show excellent photovoltaic output with excitation wavelength ranging from visible light to mid-infrared. The wavelength dependence of the internal quantum efficiency gives direct evidence of the carrier multiplication effect in graphene. The simple fabrication process, easy scale-up, large photoresponsive active area, and broadband response of the vertical graphene device are very promising for practical applications in optoelectronics and photovoltaics.

  7. Possible Immune Regulation of Natural Killer T Cells in a Murine Model of Metal Ion-Induced Allergic Contact Dermatitis

    Directory of Open Access Journals (Sweden)

    Kenichi Kumagai

    2016-01-01

    Full Text Available Metal often causes delayed-type hypersensitivity reactions, which are possibly mediated by accumulating T cells in the inflamed skin, called irritant or allergic contact dermatitis. However, accumulating T cells during development of a metal allergy are poorly characterized because a suitable animal model is unavailable. We have previously established novel murine models of metal allergy and found accumulation of both metal-specific T cells and natural killer (NK T cells in the inflamed skin. In our novel models of metal allergy, skin hypersensitivity responses were induced through repeated sensitizations by administration of metal chloride and lipopolysaccharide into the mouse groin followed by metal chloride challenge in the footpad. These models enabled us to investigate the precise mechanisms of the immune responses of metal allergy in the inflamed skin. In this review, we summarize the immune responses in several murine models of metal allergy and describe which antigen-specific responses occur in the inflamed skin during allergic contact dermatitis in terms of the T cell receptor. In addition, we consider the immune regulation of accumulated NK T cells in metal ion–induced allergic contact dermatitis.

  8. Contact Pressure and Sliding Velocity Maps of the Friction, Wear and Emission from a Low-Metallic/Cast-Iron Disc Brake Contact Pair

    Directory of Open Access Journals (Sweden)

    J. Wahlström

    2017-12-01

    Full Text Available Particulate matter with an aerodynamic diameter less than 10 µm (PM10 from car disc brakes contribute up to 50% of the total non-exhaust emissions from road transport in the EU. These emissions come from the wear of the pad and rotor contact surfaces. Yet few studies have reported contact pressures and offered sliding speed maps of the friction, wear, and particle emission performance of disc brake materials at a material level. Such maps are crucial to understanding material behaviour at different loads and can be used as input data to numerical simulations. A low-metallic pad and grey cast-iron rotor contact pair commonly used today in passenger car disc brakes was studied using a pin-on-disc tribometer at twelve contact pressure and sliding speed combinations. Maps of the coefficient of friction, specific wear rate, particle number, and mass rate are presented and discussed.

  9. Cytokine responses in metal-induced allergic contact dermatitis : Relationship to in vivo responses and implication for in vitro diagnosis

    OpenAIRE

    Minang, Jacob

    2005-01-01

    Transition metals such as nickel (Ni), cobalt (Co), palladium (Pd), chromium (Cr) and gold (Au) are widely used as alloys in jewelry and biomaterials such as orthodontic and orthopaedic appliances. These metals also cause cell-mediated allergic contact dermatitis (ACD) reactions in a significant proportion of the population upon prolonged direct exposure. The immune mechanisms underlying the response to these metals are not yet well defined. In the studies described in this thesis we therefor...

  10. Two-dimensional ferromagnet/semiconductor transition metal dichalcogenide contacts: p-type Schottky barrier and spin-injection control

    KAUST Repository

    Gan, Liyong

    2013-09-26

    We study the ferromagnet/semiconductor contacts formed by transition metal dichalcogenide monolayers, focusing on semiconducting MoS2 and WS2 and ferromagnetic VS2. We investigate the degree of p-type doping and demonstrate tuning of the Schottky barrier height by vertical compressive pressure. An analytical model is presented for the barrier heights that accurately describes the numerical findings and is expected to be of general validity for all transition metal dichalcogenide metal/semiconductor contacts. Furthermore, magnetic proximity effects induce a 100% spin polarization at the Fermi level in the semiconductor where the spin splitting increases up to 0.70 eV for increasing pressure.

  11. The Role of III-V Substrate Roughness and Deoxidation Induced by Digital Etch in Achieving Low Resistance Metal Contacts

    Directory of Open Access Journals (Sweden)

    Florent Ravaux

    2017-06-01

    Full Text Available To achieve low contact resistance between metal and III-V material, transmission-line-model (TLM structures of molybdenum (Mo were fabricated on indium phosphide (InP substrate on the top of an indium gallium arsenide (InGaAs layer grown by molecular beam epitaxy. The contact layer was prepared using a digital etch procedure before metal deposition. The contact resistivity was found to decrease significantly with the cleaning process. High Resolution Transmission & Scanning Electron Microscopy (HRTEM & HRSTEM investigations revealed that the surface roughness of treated samples was increased. Further analysis of the metal-semiconductor interface using Energy Electron Loss Spectroscopy (EELS showed that the amount of oxides (InxOy, GaxOy or AsxOy was significantly decreased for the etched samples. These results suggest that the low contact resistance obtained after digital etching is attributed to the combined effects of the induced surface roughness and oxides removal during the digital etch process.

  12. Role of Firing Temperature, Sheet Resistance, and Contact Area in Contact Formation on Screen-Printed Metal Contact of Silicon Solar Cell

    Science.gov (United States)

    Ahmad, Samir Mahmmod; Leong, Cheow Siu; Sopian, K.; Zaidi, Saleem H.

    2017-12-01

    Formation of an Ohmic contact requires a suitable firing temperature, appropriate doping profile, and contact dimensions within resolution limits of the screen-printing process. In this study, the role of the peak firing temperature in standard rapid thermal annealing (RTA) six-zone conveyor belt furnace (CBF) and two inexpensive alternate RTA systems [a custom-designed, three-zone, 5″-diameter quartz tube furnace (QTF) and a tabletop, 3″-diameter rapid thermal processing (RTP)] has been investigated. In addition, the role of sheet resistance and contact area in achieving low-resistance ohmic contacts has been examined. Electrical measurements of ohmic contacts between silver paste/n +-emitter layer with varying sheet resistances and aluminum paste/p-doped wafer were carried out in transmission line method configuration. Experimental measurements of the contact resistivity (ρ c) exhibited the lowest values for CBF at 0.14 mΩ cm2 for Ag and 100 mΩ cm2 for Al at a peak firing temperature of 870°C. For the QTF configuration, lowest measured contact resistivities were 3.1 mΩ cm2 for Ag and 74.1 mΩ cm2 for Al at a peak firing temperature of 925°C. Finally, for the RTP configuration, lowest measured contact resistivities were 1.2 mΩ cm2 for Ag and 68.5 mΩ cm2 for Al at a peak firing temperature of 780°C. The measured contact resistivity exhibits strong linear dependence on sheet resistance. The contact resistivity for Ag decreases with contact area, while for Al the opposite behavior is observed.

  13. Atomic resolution non-contact atomic force microscopy of clean metal oxide surfaces.

    Science.gov (United States)

    Lauritsen, J V; Reichling, M

    2010-07-07

    In the last two decades the atomic force microscope (AFM) has become the premier tool for topographical analysis of surface structures at the nanometre scale. In its ultimately sensitive implementation, namely dynamic scanning force microscopy (SFM) operated in the so-called non-contact mode (NC-AFM), this technique yields genuine atomic resolution and offers a unique tool for real space atomic-scale studies of surfaces, nanoparticles as well as thin films, single atoms and molecules on surfaces irrespective of the substrate being electrically conducting or non-conducting. Recent advances in NC-AFM have paved the way for groundbreaking atomic level insight into insulator surfaces, specifically in the most important field of metal oxides. NC-AFM imaging now strongly contributes to our understanding of the surface structure, chemical composition, defects, polarity and reactivity of metal oxide surfaces and related physical and chemical surface processes. Here we review the latest advancements in the field of NC-AFM applied to the fundamental atomic resolution studies of clean single crystal metal oxide surfaces with special focus on the representative materials Al(2)O(3)(0001), TiO(2)(110), ZnO(1000) and CeO(2)(111). © 2010 IOP Publishing Ltd

  14. Ion-selective electrodes with solid contact for heavy metals determination

    Directory of Open Access Journals (Sweden)

    Wardak C.

    2013-04-01

    Full Text Available Potentiometric properties of ion-selective electrodes with solid contact for lead, cadmium and zinc determination were investigated. The ionic liquids (ILs alkyl methyl imidazolium chlorides are used as lipophilic ionic additive to the membrane phase and as transducer media. The basic analytical parameters of the studied electrodes, such as the slope characteristic, the detection limit, response time, lifetime, selectivity coefficients against various inorganic cations as well as the dependence of the electrodes potential on pH were determined. The obtained electrode are characterized by good analytical parameters: theoretical characteristic slope, low detection limit, short response time and very long lifetime. The electrodes was successfully applied to the direct determination of lead, cadmium and zinc ions in waste water samples. The results obtained indicate that the electrodes provide a good alternative for the determination of these heavy metals in real samples.

  15. Contact Forces between Single Metal Oxide Nanoparticles in Gas-Phase Applications and Processes.

    Science.gov (United States)

    Salameh, Samir; van der Veen, Monique A; Kappl, Michael; van Ommen, J Ruud

    2017-03-14

    In this work we present a comprehensive experimental study to determine the contact forces between individual metal oxide nanoparticles in the gas-phase using atomic force microscopy. In addition, we determined the amount of physisorbed water for each type of particle surface. By comparing our results with mathematical models of the interaction forces, we could demonstrate that classical continuum models of van der Waals and capillary forces alone cannot sufficiently describe the experimental findings. Rather, the discrete nature of the molecules has to be considered, which leads to ordering at the interface and the occurrence of solvation forces. We demonstrate that inclusion of solvation forces in the model leads to quantitative agreement with experimental data and that tuning of the molecular order by addition of isopropanol vapor allows us to control the interaction forces between the nanoparticles.

  16. Low-temperature hydrogen absorption in metallic nanocontacts studied by point-contact spectroscopy measurements

    Science.gov (United States)

    Takata, H.; Islam, M. S.; Ienaga, K.; Inagaki, Y.; Hashizume, K.; Kawae, T.

    2017-09-01

    We report on hydrogen (H) and deuterium (D) atoms absorption below T = 20 K in metallic palladium (Pd) via quantum tunnelling (QT). When a small bias voltage is applied between Pd nanocontacts that are immersed in liquid H2 (D2), the differential conductance spectra measured by point-contact spectroscopy change enormously. The results indicate H (D) absorption in Pd nanocontacts at the temperature where H (D) absorption due to thermal hopping process is not expected, and can be explained by QT. The QT occurs when the energy level of the potential well trapping the H (D) atom coincides with those not trapping the H (D) atom, and is assisted by phonons induced by ballistic electrons.

  17. Contact-Free Support Structures for Part Overhangs in Powder-Bed Metal Additive Manufacturing

    Directory of Open Access Journals (Sweden)

    Kenneth Cooper

    2017-12-01

    Full Text Available This study investigates the feasibility of a novel concept, contact-free support structures, for part overhangs in powder-bed metal additive manufacturing. The intent is to develop alternative support designs that require no or little post-processing, and yet, maintain effectiveness in minimizing overhang distortions. The idea is to build, simultaneously during part fabrications, a heat sink (called “heat support”, underneath an overhang to alter adverse thermal behaviors. Thermomechanical modeling and simulations using finite element analysis were applied to numerically research the heat support effect on overhang distortions. Experimentally, a powder-bed electron beam additive manufacturing system was utilized to fabricate heat support designs and examine their functions. The results prove the concept and demonstrate the effectiveness of contact-free heat supports. Moreover, the method was tested with different heat support parameters and applied to various overhang geometries. It is concluded that the heat support proposed has the potential to be implemented in industrial applications.

  18. Hydrophobic/superhydrophobic oxidized metal surfaces showing negligible contact angle hysteresis.

    Science.gov (United States)

    Hozumi, Atsushi; Cheng, Dalton F; Yagihashi, Makoto

    2011-01-15

    Dynamic wettability of oxidized metal (aluminum and titanium) surfaces could be tuned by chemical vapor deposition (CVD) of 1,3,5,7-tetramethylcyclotetrasiloxane (D(4)(H)). This facile CVD method produces not only monomeric layers but also particulate films by changing the CVD temperature, resulting in a marked difference in the final wetting properties. In the samples prepared at 80°C for ~3 days, D(4)(H) layers with thicknesses of ~0.5 nm were formed on the surfaces without discernible change in surface morphology, as evidenced by X-ray photoelectron spectroscopy and atomic force microscopy. After this D(4)(H) monomeric layer formation, the hydrophilic oxidized aluminum and titanium surfaces became hydrophobic (advancing/receding water contact angles (θ(A)/θ(R))=102-104°/99-102°) showing essentially negligible contact angle hysteresis. Performing CVD of D(4)(H) at 180°C for ~1 day produced opaque film with particulate morphologies with diameters in the range of 500 nm to 4 μm observed on the surfaces. This geometric morphology enhanced the surface hydrophobicity (θ(A)/θ(R)=163°/160-161°). Droplets on these negligible-hysteresis surfaces moved very easily without "pinning". Copyright © 2010 Elsevier Inc. All rights reserved.

  19. The properties of metal contacts on TiO2 thin films produced by reactive magnetron sputtering

    Directory of Open Access Journals (Sweden)

    Brus V. V.

    2010-10-01

    Full Text Available The article deals with research on volt-ampere characteristics of metal contacts (Al, Cr, In, Mo, Ti on titanium dioxide thin films and influence of annealing in vacuum on their electric properties. Volt-ampere characteristics measurements were taken by three-probe method. There was established that indium contact on TiO2 thin films possessed sharply defined ohmic properties.

  20. Airborne irritant contact dermatitis from metal dust adhering to semisynthetic working suits.

    Science.gov (United States)

    Hafner, J; Rüegger, M; Kralicek, P; Elsner, P

    1995-05-01

    2 workers at an aircraft factory were employed in a plasma sparying unit. Soon after they were equipped with new semisynthetic working suits, they started to complain of pruritic eruptions after heavy exposure to metal dust. They noted that the dust was not as easily blown off the clothes by pressurized air as previously. Clinical findings consisted of discrete macular and papular lesions, partly follicular, on the ventral and medial thighs. Atopy score, IgE level and a standard series of prick tests ruled out atopic disposition. Patch tests revealed no reactions. A diagnosis of occupational airborne irritant contact dermatitis from metal dust was therefore made. To elucidate the role of the working suit, extensive physical investigations of the physical properties of the textile were performed. Microscopic pictures at low magnification showed more dust particles on the semisynthetic working suit, compared to the former pure cotton suit. This impression could not be confirmed by particle count because of too uneven particle distribution at higher magnification. Hairiness of the 2 textiles was low and ruled out irritation by the semisynthetic textile itself. No difference in electrostatic properties between the 2 working suits could be established either. Both textiles showed high static electrical propensity. When use of the semisynthetic overall was discontinued, the patients reported no recurrence.(ABSTRACT TRUNCATED AT 250 WORDS)

  1. Process for reducing series resistance of solar-cell metal-contact systems with a soldering-flux etchant

    Science.gov (United States)

    Coyle, R.T.; Barrett, J.M.

    1982-05-04

    Disclosed is a process for substantially reducing the series resistance of a solar cell having a thick film metal contact assembly thereon while simultaneously removing oxide coatings from the surface of the assembly prior to applying solder therewith. The process includes applying a flux to the contact assembly and heating the cell for a period of time sufficient to substantially remove the series resistance associated with the assembly by etching the assembly with the flux while simultaneously removing metal oxides from said surface of said assembly.

  2. Contacts realization by rapid thermal annealing in multicrystalline silicon solar cells with special emphasis on metal influence

    Energy Technology Data Exchange (ETDEWEB)

    El Omari, H.; Boyeaux, J.P.; Laugier, A. [Institut National des Sciences Appliquees de Lyon, Villeurbanne (France). Lab. de Physique de la Matiere

    1994-12-31

    To improve the quality of the screen printing contacts, the authors have previously shown the capability to sinter the screen printed contacts by Rapid Thermal Annealing (RTA) instead of commercial sintering; they have also noticed that the commonly used TiO{sub 2} coating deposited by spray enhances the quality of the contact either with classical annealing or RTA. The aim of the present work is to analyze the metal influence on either front or back contacts realization by RTA on Polix p type multicrystalline silicon subsequently phosphorus diffused. The screen printed contact was replaced by the chosen metal dot obtained by evaporation. The authors have studied: Al/TiO{sub 2}; Ag/Al/TiO{sub 2}; Cu/Al/TiO{sub 2}; Pt/Al/TiO{sub 2} and Cu/Cr/TiO{sub 2}. The RTA treatments were carried out at various temperatures and annealing time in an Ar ambience. The quality of the contacts are analyzed from I(V) characteristics, and possible diffusions of metallic species are characterized by SIMS experiments.

  3. Investigation of a ceramic vane with a metal disk thermal and mechanical contact in a gas turbine impeller

    Directory of Open Access Journals (Sweden)

    Resnick S.V.

    2015-01-01

    Full Text Available Promising directions of a new generation gas turbine engines development include using in gas turbines ceramic materials blades with high strength, thermal and chemical stability. One of the serious problems in developing such motors is insufficient knowledge of contact phenomena occurring in ceramic and metal details connection nodes. This work presents the numerical modeling results of thermal processes on ceramic and metal details rough boundaries. The investigation results are used in conducting experimental researches in conditions reproducing operating.

  4. Preparation and investigation of burried metal/molecule contact interfaces with surface sensitive methods; Praeparation und Untersuchung verborgener Metall/Molekuel-Kontaktgrenzflaechen mit oberflaechensensitiven Methoden

    Energy Technology Data Exchange (ETDEWEB)

    Vrdoljak, Pavo

    2011-05-13

    The present thesis establishes an optimised concept of a delamination technique suitable for ultra high vacuum (UHV) with which model systems of buried interfaces were made accessible for surface sensitive methods which were applied to investigate their electronic and topographical properties. A primary focus of this work is on the question how buried interfaces could be accessed successfully for surface sensitive methods using buried metal/NTCDA and metal/PTCDA interfaces as model systems. Contacts of approximately 10 x 15 mm{sup 2} in size were accessed. The second focus of the thesis is on the investigation of the electronical and topographical properties of the buried interfaces, for which some similarities between delaminated metal (Au,Ag)/ PTCDA- and Ag/NTCDA interfaces were found: After the delamination of top-contacts there were inhomogeneous layers of molecules on the metal contacts. Whereas PTCDA covered metal contacts had thicker molecular layers (4-5 ML PTCDA on Ag), NTCDA covered contacts showed only one monolayer coverage over large areas of at least 2 mm in diameter. Regions with multilayer coverage showed smooth surfaces whereas metal surfaces showed a fissured, meander-like and rough surface. Both contact systems also had in common that the adhesive made PES investigations of valence states very difficult. Furthermore, it was possible to thin out the molecular layers thermally but afterwards no valence states could be measured. Investigating in-situ delaminated buried interfaces, the focus was on metal (Au,Ag)/PTCDA interfaces first. The molecular layers could be successfully desorbed thermally at 260 C to 1-3 monolayers so that valence states were investigated. The spectra of the in-situ delaminated and thermally desorbed Ag/PTCDA contact were noticeably broadened so that the positions of HOMO and FLUMO could only be estimated at 1.9 eV and 0.7 eV, respectively. Additionally, interfaces of Ag/NTCDA contacts were investigated. With UPS it was found

  5. Printed Nano Cu and NiSi Contacts and Metallization for Solar Cell Modules

    Energy Technology Data Exchange (ETDEWEB)

    Carmody, Michael John [Intrinsiq Materials Inc., Rochester, NY (United States)

    2017-10-11

    There has long been a desire to replace the front-side silver contacts in silicon solar cells. There are two driving forces to do this. First, silver is an expensive precious metal. Secondly, the process to use silver requires that it be formulated into screen print pastes that need a lead-containing glass frit, and the use of lead is forbidden in many parts of the world. Because of the difficulty in replacing these pastes and the attendant processes, lead exemptions have granted to solar cells. Copper has been the replacement metal of choice because it is significantly cheaper than silver and is very close to silver in electrical conductivity. Using processes which do not use lead, obviates it as an environmental contaminant. However, copper cannot be in contact with the silicon of the cell since it migrates through the silicon and causes defects which severely damage the efficiency of the cell. Hence, a conductive barrier must be placed between the copper and silicon and nickel, and especially nickel silicide, have been shown to be materials of choice. However, nickel must be sputtered and annealed to create the nickel silicide barrier, and copper has either been sputtered or plated. All of these processes require expensive, specialized equipment and plating uses environmentally unfriendly chemicals. Therefore, Intrinsiq proposed using printed nano nickel silicide ink (which we had previously invented) and printed nano copper ink to create these electrodes and barriers. We found that nano copper ink could be readily printed and sintered under a reducing atmosphere to give highly conductive grids. We further showed that nano nickel silicide ink could be readily jetted into grids on top of the silicon cell. It could then be annealed to create a barrier. However, it was found that the combination of printed NiSi and printed Cu did not give contact resistivity good enough to produce efficient cells. Only plated copper on top of the printed NiSi gave useful contact

  6. The monolithic transition metal oxide crossed nanosheets used for diesel soot combustion under gravitational contact mode

    Science.gov (United States)

    Cao, Chunmei; Xing, Lingli; Yang, Yuexi; Tian, Ye; Ding, Tong; Zhang, Jing; Hu, Tiandou; Zheng, Lirong; Li, Xingang

    2017-06-01

    Crossed nanosheets of transition metal oxide (TMO-NS: Co-NS, Mn-NS and Fe-NS) were synthesized by a facile hydrothermal method and employed for soot combustion in the NO/O2/N2 and O2/N2 atmosphere under gravitational contact mode (GCM). They show high catalytic activities for soot combustion due to the macroporous structure of the as-prepare catalysts increasing the soot-catalyst contact efficiency. The XRD and XPS results reveal that the active phases in the corresponding catalysts exist as Co3O4, Mn2O3 and Fe2O3, respectively. Among these catalysts, the Co-NS shows the best activity for soot combustion, especially in the presence of NO, whose catalytic activity of T50 (391 °C) and SCO2 (100%) is as good as that of the Pt/Al2O3 catalyst. The excellent performance of the Co-NS catalyst results from several factors: the highest intrinsic activity (TOF = 1.77 × 10-5 s-1); the highest redox property as revealed by H2-TPR and soot-TPR; the largest amount of active oxygen species as clarified by XPS; the highest ability of NO oxidation to NO2 supported by NO-TPO. In addition, the multiporous structure of Co3O4 nanosheets is facilitated for the mass transfer. In the O2 atmosphere, soot particulates are directly oxidized by the surface adsorbed oxygen. After introducing of NO, the soot particulates are readily oxidized by NO2 at the low temperature (< 330 °C); with the increase of the reaction temperature (330-450 °C), both the active oxygen species and NO2 involve in soot combustion.

  7. CONSIDERATION OF MECHANISMS OF FORMING THE SURFACE OF CASTING IN THE ZONE CONTACT METAL-MOLD CORE

    Directory of Open Access Journals (Sweden)

    I. B. Odarchenko

    2016-01-01

    Full Text Available Considered physico-mechanical, physico-chemical processes occurring in the zone contact metal-mold core at all stages of the formation of the casting. The degree of influence of these processes on the formation of internal surfaces of castings.

  8. Synchrotron based x-ray fluorescence microscopy confirms copper in the corrosion products of metals in contact with treated wood

    Science.gov (United States)

    Samuel L. Zelinka; Joseph E. Jakes; Grant T. Kirker; David Vine; Stefan Vogt

    2017-01-01

    Copper based waterborne wood preservatives are frequently used to extend the service life of wood products when subjected to frequent moisture exposure. While these copper based treatments protect the wood from fungal decay and insect attack, they increase the corrosion of metals embedded or in contact with the treated wood. Previous research has shown the most...

  9. An experimental and computational study of size-dependent contact-angle of dewetted metal nanodroplets below its melting temperature

    Science.gov (United States)

    Azeredo, Bruno P.; Yeratapally, Saikumar R.; Kacher, Josh; Ferreira, Placid M.; Sangid, Michael D.

    2016-11-01

    Decorating 1D nanostructures (e.g., wires and tubes) with metal nanoparticles serves as a hierarchical approach to integrate the functionalities of metal oxides, semiconductors, and metals. This paper examines a simple and low-temperature approach to self-assembling gold nanoparticles (Au-np)—a common catalytic material—onto silicon nanowires (SiNWs). A conformal ultra-thin film (i.e., temperature profile has a strong effect on the particle size. Additionally, the contact angle is found to be dependent on particle size and temperature even below the eutectic temperature of the Au-Si alloy. Molecular dynamics simulations were performed to investigate potential explanations for such experimental observation. In this temperature regime, the simulations reveal the formation of an amorphous phase at the interface between the catalyst and SiNW that is sensitive to temperature. This amorphous layer increases the adhesion energy at the interface and explains the contact angle dependence on temperature.

  10. Investigation of contact acoustic nonlinearities on metal and composite airframe structures via intensity based health monitoring.

    Science.gov (United States)

    Romano, P Q; Conlon, S C; Smith, E C

    2013-01-01

    Nonlinear structural intensity (NSI) and nonlinear structural surface intensity (NSSI) based damage detection techniques were improved and extended to metal and composite airframe structures. In this study, the measurement of NSI maps at sub-harmonic frequencies was completed to provide enhanced understanding of the energy flow characteristics associated with the damage induced contact acoustic nonlinearity mechanism. Important results include NSI source localization visualization at ultra-subharmonic (nf/2) frequencies, and damage detection results utilizing structural surface intensity in the nonlinear domain. A detection metric relying on modulated wave spectroscopy was developed and implemented using the NSSI feature. The data fusion of the intensity formulation provided a distinct advantage, as both the single interrogation frequency NSSI and its modulated wave extension (NSSI-MW) exhibited considerably higher sensitivities to damage than using single-sensor (strain or acceleration) nonlinear detection metrics. The active intensity based techniques were also extended to composite materials, and results show both NSSI and NSSI-MW can be used to detect damage in the bond line of an integrally stiffened composite plate structure with high sensitivity. Initial damage detection measurements made on an OH-58 tailboom (Penn State Applied Research Laboratory, State College, PA) indicate the techniques can be transitioned to complex airframe structures achieving high detection sensitivities with minimal sensors and actuators.

  11. Modelling of real area of contact between tool and workpiece in metal forming processes including the influence of subsurface deformation

    DEFF Research Database (Denmark)

    Nielsen, Chris Valentin; Martins, Paulo A. F.; Bay, Niels Oluf

    2016-01-01

    New equipment for testing asperity deformation at various normal loads and subsurface elongations is presented. Resulting real contact area ratios increase heavily with increasing subsurface expansion due to lowered yield pressure on the asperities when imposing subsurface normal stress parallel ...... for estimating friction in the numerical modelling of metal forming processes.......New equipment for testing asperity deformation at various normal loads and subsurface elongations is presented. Resulting real contact area ratios increase heavily with increasing subsurface expansion due to lowered yield pressure on the asperities when imposing subsurface normal stress parallel...... to the surface. Finite element modelling supports the presentation and contributes by extrapolation of results to complete the mapping of contact area as function of normal pressure and one-directional subsurface strain parallel to the surface. Improved modelling of the real contact area is the basis...

  12. Atomic Scale Understanding of Poly-Si/SiO2/c-Si Passivated Contacts: Passivation Degradation Due to Metallization

    Energy Technology Data Exchange (ETDEWEB)

    Aguiar, Jeffery A.; Young, David; Lee, Benjamin; Nemeth, William; Harvey, Steve; Aoki, Toshihiro; Al-Jassim, Mowafak; Stradins, Paul

    2016-11-21

    The key attributes for achieving high efficiency crystalline silicon solar cells include class leading developments in the ability to approach the theoretical limits of silicon solar technology (29.4% efficiency). The push for high efficiency devices is further compounded with the clear need for passivation to reduce recombination at the metal contacts. At the same time there is stringent requirement to retain the same material device quality, surface passivation, and performance characteristics following subsequent processing. The development of passivated silicon cell structures that retain active front and rear surface passivation and overall material cell quality is therefore a relevant and active area of development. To address the potential outcomes of metallization on passivated silicon stack, we report on some common microstructural features of degradation due to metallization for a series of silicon device stacks. A fundamental materials understanding of the metallization process on retaining high-efficiency passivated Si devices is therefore gained over these series of results.

  13. Characterization of the Resistance and Force of a Carbon Nanotube/Metal Side Contact by Nanomanipulation

    Science.gov (United States)

    Nakajima, Masahiro; Sun, Lining; Huang, Qiang; Fukuda, Toshio

    2017-01-01

    A high contact resistance restricts the application of carbon nanotubes (CNTs) in fabrication of field-effect transistors (FETs). Thus, it is important to decrease the contact resistance and investigate the critical influence factors such as the contact length and contact force. This study uses nanomanipulation to characterize both the resistance and the force at a CNT/Au side-contact interface inside a scanning electron microscopy (SEM). Two-terminal CNT manipulation methods, and models for calculating the resistance and force at contact area, are proposed to guide the measurement experiments of a total resistance and a cantilever's elastic deformation. The experimental results suggest that the contact resistance of CNT/Au interface is large (189.5 kΩ) when the van der Waals force (282.1 nN) dominates the contact force at the interface. Electron-beam-induced deposition (EBID) is then carried out to decrease the contact resistance. After depositing seven EBID points, the resistance is decreased to 7.5 kΩ, and the force increases to 1339.8 nN at least. The resistance and force at the contact area where CNT was fixed exhibit a negative exponential correlation before and after EBID. The good agreement of this correlation with previous reports validates the proposed robotic system and methods for characterizing the contact resistance and force. PMID:29109819

  14. Characterization of the Resistance and Force of a Carbon Nanotube/Metal Side Contact by Nanomanipulation

    Directory of Open Access Journals (Sweden)

    Ning Yu

    2017-01-01

    Full Text Available A high contact resistance restricts the application of carbon nanotubes (CNTs in fabrication of field-effect transistors (FETs. Thus, it is important to decrease the contact resistance and investigate the critical influence factors such as the contact length and contact force. This study uses nanomanipulation to characterize both the resistance and the force at a CNT/Au side-contact interface inside a scanning electron microscopy (SEM. Two-terminal CNT manipulation methods, and models for calculating the resistance and force at contact area, are proposed to guide the measurement experiments of a total resistance and a cantilever’s elastic deformation. The experimental results suggest that the contact resistance of CNT/Au interface is large (189.5 kΩ when the van der Waals force (282.1 nN dominates the contact force at the interface. Electron-beam-induced deposition (EBID is then carried out to decrease the contact resistance. After depositing seven EBID points, the resistance is decreased to 7.5 kΩ, and the force increases to 1339.8 nN at least. The resistance and force at the contact area where CNT was fixed exhibit a negative exponential correlation before and after EBID. The good agreement of this correlation with previous reports validates the proposed robotic system and methods for characterizing the contact resistance and force.

  15. Root Cause Analysis and Correction of Single Metal Contact Open-Induced Scan Chain Failure in 90nm node VLSI

    OpenAIRE

    Ting, Chao-Cheng; Liu, Ya-Chi; Chen, Hsuan-Hsien; Tsai, Chung-Ching; Shih, Liwen

    2018-01-01

    In this paper, the localization of open metal contact for 90nm node SOC is reported based on Electron Beam Absorbed Current (EBAC) technique and scan diagnosis for the first time. According to the detected excess carbon, silicon and oxygen signals obtained from X-ray energy dispersive spectroscopy (EDX), the failure was deemed to be caused by the incomplete removal of silicate photoresist polymer formed during the O2 plasma dry clean before copper plating. Based on this, we proposed to replac...

  16. Repeated exposures to cobalt or chromate on the hands of patients with hand eczema and contact allergy to that metal

    DEFF Research Database (Denmark)

    Nielsen, N H; Kristiansen, J; Borg, L

    2000-01-01

    The present study aimed at evaluating the effects of daily repeated exposures to low cobalt or chromate concentrations on the hands of patients with hand eczema and cobalt or chromate allergy. For 2 weeks, the patients immersed a finger for 10 min daily into the appropriate metal salt solution...... of providing evidence-based medicine in the area of allergic contact dermatitis in the future....

  17. Application Of Artificial Neural Networks In Modeling Of Manufactured Front Metallization Contact Resistance For Silicon Solar Cells

    Directory of Open Access Journals (Sweden)

    Musztyfaga-Staszuk M.

    2015-09-01

    Full Text Available This paper presents the application of artificial neural networks for prediction contact resistance of front metallization for silicon solar cells. The influence of the obtained front electrode features on electrical properties of solar cells was estimated. The front electrode of photovoltaic cells was deposited using screen printing (SP method and next to manufactured by two methods: convectional (1. co-fired in an infrared belt furnace and unconventional (2. Selective Laser Sintering. Resistance of front electrodes solar cells was investigated using Transmission Line Model (TLM. Artificial neural networks were obtained with the use of Statistica Neural Network by Statsoft. Created artificial neural networks makes possible the easy modelling of contact resistance of manufactured front metallization and allows the better selection of production parameters. The following technological recommendations for the screen printing connected with co-firing and selective laser sintering technology such as optimal paste composition, morphology of the silicon substrate, co-firing temperature and the power and scanning speed of the laser beam to manufacture the front electrode of silicon solar cells were experimentally selected in order to obtain uniformly melted structure well adhered to substrate, of a small front electrode substrate joint resistance value. The prediction possibility of contact resistance of manufactured front metallization is valuable for manufacturers and constructors. It allows preserving the customers’ quality requirements and bringing also measurable financial advantages.

  18. Transparent conducting oxide contacts and textured metal back reflectors for thin film silicon solar cells

    Science.gov (United States)

    Franken, R. H.-J.

    2006-09-01

    With the growing population and the increasing environmental problems of the 'common' fossil and nuclear energy production, the need for clean and sustainable energy sources is evident. Solar energy conversion, such as in photovoltaic (PV) systems, can play a major role in the urgently needed energy transition in electricity production. At the present time PV module production is dominated by the crystalline wafer technology. Thin film silicon technology is an alternative solar energy technology that operates at lower efficiencies, however, it has several significant advantages, such as the possibility of deposition on cheap (flexible) substrates and the much smaller silicon material consumption. Because of the small thickness of the solar cells, light trapping schemes are needed in order to obtain enough light absorption and current generation. This thesis describes the research on thin film silicon solar cells with the focus on the optimization of the transparent conducting oxide (TCO) layers and textured metal Ag substrate layers for the use as enhanced light scattering back reflectors in n-i-p type of solar cells. First we analyzed ZnO:Al (TCO) layers deposited in an radio frequent (rf) magnetron deposition system equipped with a 7 inch target. We have focused on the improvement of the electrical properties without sacrificing the optical properties by increasing the mobility and decreasing the grain boundary density. Furthermore, we described some of the effects on light trapping of ZnO:Al enhanced back reflectors. The described effects are able to explain the observed experimental data. Furthermore, we present a relation between the surface morphology of the Ag back contact and the current enhancement in microcrystalline (muc-Si:H) solar cells. We show the importance of the lateral feature sizes of the Ag surface on the light scattering and introduce a method to characterize the quality of the back reflector by combining the vertical and lateral feature sizes

  19. EXPANDED PERLITE, EXPANDED VERMICULITE AND MICROSPHERES AS FILLERS IN NEW GENERATION PAPER PULP MIXTURES USED FOR CONTACT WITH LIQUID METAL

    Directory of Open Access Journals (Sweden)

    Zbigniew Zawieja

    2015-05-01

    Full Text Available Liquid metal when filling sand casting mould while pouring it out from ladle at the first moment comes across the sprue/gate system of the mould the purpose of which is to transfer liquid metal and feed the mould recess. The materials presently used for the elements of the sprue/gate systems are based on ceramics or the mixtures based on paper pulp. In this study the use of alternative mineral additions such as expanded perlite, expanded vermiculite, and microspheres as the fillers to paper pulp acquired from waste-paper for the use for the elements of mould sprue/gate systems or also other applications for the contact with liquid metal are presented. Experimental mould tube shapes made on the basis of the paper pulp based mixture patented by the authors were poured over with liquid metal. For the comparison, ceramic shapes and commercially available cellulose shapes were investigated in the same way. In order to compare the crystallization processes, a measurement of the cooling off liquid metal was carried out for all the analysed tube samples. From the so obtained metal samples metallographic microsections were made to compare cast iron microstructures. The results obtained from the investigations carried out have shown that the patented paper pulp based mixture may well be applied as an alternative material used for the elements of the sprue/gate systems for disposable sand moulds.

  20. Efficient modeling of metallic interconnects for thermo-mechanical simulation of SOFC stacks: homogenized behaviors and effect of contact

    DEFF Research Database (Denmark)

    Tadesse Molla, Tesfaye; Kwok, Kawai; Frandsen, Henrik Lund

    2016-01-01

    Currently thermo-mechanical analysis of the entire solid oxide fuel cell (SOFC) stack at operational conditions is computationally challenging if the geometry of metallic interconnects is considered explicitly. This is particularly the case when creep deformations in the interconnect are considered...... model to calculate the homogenized mechanical response of corrugated metallic interconnects at high temperatures.Thereafter, a constitutive law for the homogenized structure (effective material law) is developed. In order to properly describe the mechanical behavior of the interconnect at high...... temperature, deformations involving the elastic, creep as well as effect of changes in the geometry due to contact should be accounted for. The constitutive law can be applied using 3D modeling, but for simple presentation of the theory, 2D plane strain formulation is used to model the corrugated metallic...

  1. Atlas of point contact spectra of electron-phonon interactions in metals

    CERN Document Server

    Khotkevich, A V

    1995-01-01

    The characteristics of electrical contacts have long attracted the attention of researchers since these contacts are used in every electrical and electronic device. Earlier studies generally considered electrical contacts of large dimensions, having regions of current concentration with diameters substantially larger than the characteristic dimensions of the material: the interatomic distance, the mean free path for electrons, the coherence length in the superconducting state, etc. [110]. The development of microelectronics presented to scientists and engineers the task of studying the characteristics of electrical contacts with ultra-small dimensions. Characteristics of point contacts such as mechanical stability under continuous current loads, the magnitudes of electrical fluctuations, inherent sensitivity in radio devices and nonlinear characteristics in connection with electromagnetic radiation can not be understood and altered in the required way without knowledge of the physical processes occurring in c...

  2. Effects of vacuum heat treatment on the photoelectric work function and surface morphology of multilayered silver–metal electrical contacts

    Energy Technology Data Exchange (ETDEWEB)

    Akbi, Mohamed, E-mail: akbi_mohamed@umbb.dz [Laboratoire “Arc Electrique et Plasmas Thermiques”, CNRS, UPRES-A 6069, 24, Avenue des Landais, F-63177 Aubière Cedex (France); Department of Physics, Faculty of Sciences, University of Boumerdes (UMBB), Independence Avenue, 35000 Boumerdes (Algeria); Bouchou, Aïssa [Faculty of Physics, University of Algiers (USTHB), B.P. 32, El-Alia, Bab-Ezzouar, 16111 Algiers (Algeria); Zouache, Noureddine [Laboratoire “Arc Electrique et Plasmas Thermiques”, CNRS, UPRES-A 6069, 24, Avenue des Landais, F-63177 Aubière Cedex (France)

    2014-06-01

    Contact materials used for electrical breakers are often made with silver alloys. Mechanical and thermodynamical properties as well as electron emission of such complicated alloys present a lack of reliable and accurate experimental data. This paper deals mainly with electron work function (EWF) measurements about silver–metal (Ag–Me) electrical contacts (Ag–Ni (60/40) and Ag–W (50/50)), before and after surface heat treatments at 513 K–873 K, under UHV conditions (residual gas pressure of 1.4 × 10{sup −7} mbar). The electron work function (EWF) of silver alloyed contacts was measured photoelectrically, using both Fowler's method of isothermal curves and linearized Fowler plots. An interesting fact brought to light by this investigation is that after vacuum heat treatments, the diffusion and/or evaporation phenomena, affecting the atomic composition of the alloy surface, somehow confine the EWF of the silver–nickel alloy, Φ(Ag–Ni), determined at room temperature in interval]Φ(Ag), Φ(Ni) [=] 4.26 eV, 4.51 eV[. Surface analysis of two specimens before and after heating showed a significant increase of tungsten atomic proportion on the contact surface for Ag–W contacts after VH treatments. A multilayer model, taking into account the strong intergranular and volume segregation gives a good interpretation of the obtained results.

  3. Metal contacts in nanocrystalline n-type GaN: Schottky diodes.

    Science.gov (United States)

    Das, S N; Sarangi, S; Sahu, S N; Pal, A K

    2009-04-01

    Contact properties in nanocrystalline n-GaN in thin film form were studied by depositing nanocrystalline films onto aluminium coated fused silica substrates by high pressure sputtering of Si (1 at%) doped GaN target. Schottky diodes were realized with Au, Ni and Pd as top contacts on the nanocrystalline n-GaN films to examine the contact properties of the diodes thus formed. Variation of current-voltage (I-V) and capacitance-voltage (C-V) characteristics of the Schottky diodes were recorded at different temperatures and analyzed in the light of the existing theories.

  4. Study of structure and surface morphology of two-layer contact Ti/Al metallization

    Directory of Open Access Journals (Sweden)

    Kirill D. Vanyukhin

    2016-06-01

    Full Text Available Ti/Al/Ni/Au metallization widely used in the technology of GaN base devices have a very important imperfection i.e. rough surface. There are different opinions about the causes of this imperfection: balling-up of molten aluminum or the appearance of intermetallic melt phases in the Au–Al system. To check the effect of the former cause, we have studied the formation of rough surface after annealing of Ti/Al metallization which is used as a basis of many metallization systems for GaN. The substrates were made from silicon wafers covered with Si3N4 films (0.15 μm. On these substrates we deposited the Ti(12 nm/Al(135 nm metallization system. After the deposition the substrates were annealed in nitrogen for 30 s at 850 °С. The as-annealed specimens were tested for metallization sheet resistivity, appearance and surface morphology. We have shown that during annealing of the Ti/Al metallization system, mutual diffusion of the metals and their active interaction with the formation of intermetallic phases occur. This makes the metallization system more resistant to subsequent annealing, oxidation and chemical etching. After annealing the surface of the Ti/Al metallization system becomes gently matted. However, large hemispherical convex areas (as in the Ti/Al/Ni/Au metallization system do not form. Thus, the hypothesis on the balling-up of molten aluminum on the surface of the Ti/Al metallization system has not been confirmed.

  5. Effect of contact metals on the piezoelectric properties of aluminum nitride thin films

    Energy Technology Data Exchange (ETDEWEB)

    Harman, J.; Kabulski, A.; Pagán, V. R.; Famouri, P.; Kasarla, K. R.; Rodak, L. E.; Peter Hensel, J.; Korakakis, D.

    2008-01-01

    The converse piezoelectric response of aluminum nitride evaluated using standard metal insulator semiconductor structures has been found to exhibit a linear dependence on the work function of the metal used as the top electrode. The apparent d33 of the 150–1100 nm films also depends on the dc bias applied to the samples.

  6. Effect of contact metals on the piezoelectric properties of aluminum nitride thin films

    Energy Technology Data Exchange (ETDEWEB)

    Harman, J.P.; Kabulski, A. (West Virginia U., Morgantown, WV); Pagan, V.R. (West Virginia U., Morgantown, WV); Famouri, K. (West Virginia U., Morgantown, WV); Kasarla, K.R.; Rodak, L.E. (West Virginia U., Morgantown, WV); Hensel, J.P.; Korakakis, D.

    2008-07-01

    The converse piezoelectric response of aluminum nitride evaluated using standard metal insulator semiconductor structures has been found to exhibit a linear dependence on the work function of the metal used as the top electrode. The apparent d33 of the 150–1100 nm films also depends on the dc bias applied to the samples.

  7. CIGS cells with metallized front contact: Longer cells and higher efficiency

    NARCIS (Netherlands)

    Deelen, J. van; Frijters, C.

    2017-01-01

    We have investigated the benefit of a patterned metallization on top of a transparent conductive oxide in CIGS thin-film solar panels. It was found that cells with a grid have a higher efficiency compared to cells with only a TCO. This was observed for all cell lengths used. Furthermore, metallic

  8. Detection of trace metallic elements in oral lichenoid contact lesions using SR-XRF, PIXE, and XAFS.

    Science.gov (United States)

    Sugiyama, Tomoko; Uo, Motohiro; Wada, Takahiro; Omagari, Daisuke; Komiyama, Kazuo; Miyazaki, Serika; Numako, Chiya; Noguchi, Tadahide; Jinbu, Yoshinori; Kusama, Mikio; Mori, Yoshiyuki

    2015-06-18

    Oral lichen planus (OLP) and oral lichenoid contact lesions (OLCL) are chronic inflammatory mucocutaneous reactions with a risk of malignant transformation that alter the epithelium. OLP and OLCL have similar clinical and histopathological features and it is difficult to distinguish one from the other. Metallic restorations are suspected to generate OLCLs. Trace metal analysis of OLCL specimens may facilitate the discrimination of symptoms and identification of causative metallic restorations. The purpose of this study was to assess OLCL tissue samples for the prevalence of metallic elements derived from dental restorations, and to discriminate OLCL from OLP by using synchrotron radiation-excited X-ray fluorescence analysis (SR-XRF), particle-induced X-ray emission (PIXE), and X-ray absorption fine structure (XAFS). Typical elements of dental materials were detected in the OLCL, whereas no obvious element accumulation was detected in OLP and negative control specimens. The origin of the detected metallic elements was presumed to be dental alloys through erosion. Therefore, our findings support the feasibility of providing supporting information to distinguish OLCL from OLP by using elemental analysis.

  9. A new non-contact approach for the measurement and uniformity evaluation of coating thickness for sheet metal.

    Science.gov (United States)

    Qiu, Zixue; Zheng, Tianchi; Wan, Liping; Lu, Guan; Shao, Jianxin; Yuan, Jiang

    2017-01-01

    To realize the automatic measurement and uniformity evaluation of the coating thickness for sheet metal, a new non-contact detection method for coating thickness was proposed based on a double laser probe and mechanical servo system. Non-contact measurement of coating thickness can be achieved by differential measurement principle of double laser probe, and the influences of sheet metal's Z position changes and platform's vibration on the measurement results can be removed by this method. A new coating thickness evaluation algorithm by integrating the least squares principle and cubic spline interpolation was given, which can fit the discrete thickness data into visual and accurate 3D graphics; and the measurement accuracy was evaluated based on grey theory, solving the problem of low accuracy by using limited measurement data to evaluate the thickness uniformity of an entire sheet metal. The stability and reliability of the system are verified by experiments, and the measurement results of the specimen show that the measurement uncertainty is 0.016 μm and the maximum range of the uniformity evaluation result is 1.4 μm.

  10. High-performance n-type black phosphorus transistors with type control via thickness and contact-metal engineering

    Science.gov (United States)

    Perello, David J.; Chae, Sang Hoon; Song, Seunghyun; Lee, Young Hee

    2015-01-01

    Recent work has demonstrated excellent p-type field-effect switching in exfoliated black phosphorus, but type control has remained elusive. Here, we report unipolar n-type black phosphorus transistors with switching polarity control via contact-metal engineering and flake thickness, combined with oxygen and moisture-free fabrication. With aluminium contacts to black phosphorus, a unipolar to ambipolar transition occurs as flake thickness increases from 3 to 13 nm. The 13-nm aluminium-contacted flake displays graphene-like symmetric hole and electron mobilities up to 950 cm2 V−1 s−1 at 300 K, while a 3 nm flake displays unipolar n-type switching with on/off ratios greater than 105 (107) and electron mobility of 275 (630) cm2 V−1 s−1 at 300 K (80 K). For palladium contacts, p-type behaviour dominates in thick flakes, while 2.5–7 nm flakes have symmetric ambipolar transport. These results demonstrate a leap in n-type performance and exemplify the logical switching capabilities of black phosphorus. PMID:26223778

  11. Theoretical study of the role of metallic contacts in probing transport features of pure and defected graphene nanoribbons

    Directory of Open Access Journals (Sweden)

    La Magna Antonino

    2011-01-01

    Full Text Available Abstract Understanding the roles of disorder and metal/graphene interface on the electronic and transport properties of graphene-based systems is crucial for a consistent analysis of the data deriving from experimental measurements. The present work is devoted to the detailed study of graphene nanoribbon systems by means of self-consistent quantum transport calculations. The computational formalism is based on a coupled Schrödinger/Poisson approach that respects both chemistry and electrostatics, applied to pure/defected graphene nanoribbons (ideally or end-contacted by various fcc metals. We theoretically characterize the formation of metal-graphene junctions as well as the effects of backscattering due to the presence of vacancies and impurities. Our results evidence that disorder can infer significant alterations on the conduction process, giving rise to mobility gaps in the conductance distribution. Moreover, we show the importance of metal-graphene coupling that gives rise to doping-related phenomena and a degradation of conductance quantization characteristics.

  12. Ohmic contact formation between metal and AlGaN/GaN heterostructure via graphene insertion

    Science.gov (United States)

    Sung Park, Pil; Reddy, Kongara M.; Nath, Digbijoy N.; Yang, Zhichao; Padture, Nitin P.; Rajan, Siddharth

    2013-04-01

    A simple method for the creation of Ohmic contact to 2D electron gas in AlGaN/GaN high electron-mobility transistors using Cr/graphene layer is demonstrated. A weak temperature dependence of this Ohmic contact observed in the range 77 to 300 K precludes thermionic emission or trap-assisted hopping as possible carrier-transport mechanisms. It is suggested that the Cr/graphene combination acts akin to a doped n-type semiconductor in contact with AlGaN/GaN heterostructure, and promotes carrier transport along percolating Al-lean paths through the AlGaN layer. This use of graphene offers a simple method for making Ohmic contacts to AlGaN/GaN heterostructures, circumventing complex additional processing steps involving high temperatures. These results could have important implications for the fabrication and manufacturing of AlGaN/GaN-based microelectronic and optoelectronic devices/sensors of the future.

  13. Friction and plasticity of micro- and nano-scale metal contacts

    NARCIS (Netherlands)

    Dikken, R.J.

    2017-01-01

    Sustainability has become an integral part of todays society. A thorough understanding of friction as a major cause of energy dissipation is therefore highly relevant. Friction of rough surfaces in contact is a physical phenomenon that involves multiple length- and time-scales, complicating a full

  14. Contact allergy and human biomonitoring--an overview with a focus on metals

    DEFF Research Database (Denmark)

    Thyssen, Jacob P; Roeske-Nielsen, Allan; Johansen, Jeanne D

    2011-01-01

    towards the use of human biomonitoring. A few studies have used human biomonitoring methodology to track contact allergens together with information on patch test reactivity. Hypothetically, the internal load of reactive chemicals might modify the immune response to haptens and the propensity to sensitize...

  15. Advances in corrosion testing of metals in contact with treated wood

    Science.gov (United States)

    Samuel Zelinka; D.S. Stone

    2010-01-01

    A January 2004 change in the regulation of wood preservatives used in the U.S.has increased the use of newer wood preservatives, such as alkaline copper quaternary (ACQ) and copper azole (CuAz). These preservatives contain high amounts of cupric ions, which may be reduced to copper metal at the expense of less noble steel and galvanized fasteners in the wood....

  16. [Contact allergic gastritis : Rare manifestation of a metal allergy].

    Science.gov (United States)

    Pföhler, C; Vogt, T; Müller, C S L

    2016-05-01

    Only a few cases of contact allergic gastritis in patients with nickel allergy have been reported in the literature. We report a case of probable contact-allergic gastritis in a 46-year-old woman. Clinical examination revealed lichenoid mucosal lesions of the gums adjacent to a bridge and crowns that had been implanted several weeks previously. Since implantation, the patient suffered from gastrointestinal complaints including stomach pain. Gastroscopy and histological investigation of stomach biopsies showed eosinophilic gastritis. Patch testing done under the diagnosis of contact allergic stomatitis showed positive reactions to gold sodium thiosulphate, manganese (II) chloride, nickel (II) sulphate, palladium chloride, vanadium (III) chloride, zirconium (IV) chloride, and fragrances. The crowns and the bridge contained gold, palladium, and zirconium, hence they were replaced by titan-based dentition. Shortly after replacing the artificial dentition, all gastrointestinal symptoms resolved spontaneously without further treatment. Delayed-type allergy to components in the artificial dentition seem to have caused the gastritis.

  17. On the nature of AFM tip metal-MoS2 contact; effect of single layer character and tip force

    Science.gov (United States)

    Kaushik, Vishakha; Varandani, Deepak; Das, Pintu; Mehta, Bodh R.

    2017-10-01

    In the present study, the nature of metal-MoS2 contacts has been investigated using conductive atomic force microscopy. The point I-V characteristics have been acquired as a function of loading force (53 nN-252 nN) for an interface formed between the atomic force microscopy (AFM) tip (Pt and Co coated) and MoS2 domains (single and multilayer). The metal-MoS2 junctions for both Co and Pt tips exhibit a rectifying nature with higher forward current for the Co tip as compared to the Pt tip for both single and multilayer samples. An interesting behavior of decreasing junction current and rectification ratio with increasing tip loading force is observed in the case of single layer MoS2. In comparison, negligible or very small change in the forward junction current is observed in the case of multilayer samples. The single layer MoS2 undergoes charge polarization in the presence of uniaxial strain exerted in the form of AFM tip loading force, resulting in current in a direction opposite to the forward current due to the migration of majority electron carriers away from the tip-MoS2 interface. Therefore, the net current which is a sum of the forward junction current and the force induced current reduces with loading force for single layer MoS2. This study emphasizes the influence of the single layer nature of MoS2 on the electrical properties of metal-MoS2 contacts, an understanding of which is important from the perspective of basic physics and its applications.

  18. Cyclic Hardening of Metallic Glasses under Hertzian Contacts: Experiments and STZ Dynamics Simulations

    OpenAIRE

    Packard, Corinne E.; Homer, Eric R.; Al-Aqeeli, N.; Schuh, Christopher A.

    2009-01-01

    A combined program of experiments and simulations is used to study the problem of cyclic indentation loading on metallic glasses. The experiments use a spherical nanoindenter tip to study shear band formation in three glasses (two based on Pd and one on Fe), after subjecting the glass to cycles of load in the nominal elastic range. In all three glasses, such elastic cycles lead to significant increases in the load required to subsequently trigger the first shear band. This cyclic hardening oc...

  19. [Test method for lead in metal utensils for food contact use].

    Science.gov (United States)

    Mutsuga, Motoh; Yotsuyanagi, Michiyo; Kawamura, Yoko

    2011-01-01

    We compared test methods for measurement of lead in metal utensils using flame-atomic absorption spectroscopy (AAS), graphite furnace-AAS (GFAA), inductively coupled plasma atomic emission spectrometry (ICP) and X-ray fluorescence analysis (XRF). The procedure for preparation of the test solution was improved. A 100 mg of sample was dissolved in 2.5 mL of HCl and HNO(3) (3 : 1) mixture (in the case of titanium sample, dissolved in HCl). Stock solution was prepared by diluting to 50 mL with water. The test solution was prepared by diluting with 0.1 mol/L HNO(3). The recoveries of lead added to various kinds of metal reagent at the level of 0.1% were 90-118%. When standard materials which contained lead at the level of 0.0098-0.11% were measured, the measured values were in close agreement with the standard values. These procedures are applicable to aluminum, iron, stainless steel, copper, tin and titanium products. The AAS method, GFAA method and ICP method were suitable as the lead test methods. Moreover, the XRF method was useful as a screening method or a simple determination method. The ICP method was used to determine the lead contents in 22 kinds of commercial metal utensils, and 0.011-0.040% of lead were detected in 6 samples.

  20. Effects of metal-soil contact time on the extraction of mercury from soils.

    Science.gov (United States)

    Ma, Lan; Zhong, Huan; Wu, Yong-Gui

    2015-03-01

    To investigate the mercury aging process in soils, soil samples were spiked with inorganic mercury (Hg(II)) or methylated mercury (MeHg) and incubated for 2, 7, 14 or 28 days in the laboratory. Potential availability of mercury, assessed by bovine serum albumin (BSA) or calcium chloride (CaCl2) extraction, decreased by 2-19 times for Hg(II) or 2-6 times for MeHg, when the contact time increased from 2 to 28 days. Decreased Hg(II) extraction could be explained by Hg(II) geochemical fractionation, i.e., Hg(II) migrated from more mobile fractions (water soluble and stomach acid soluble fractions) to refractory ones (organo-complexed, strongly complexed and residual fractions) over time, resulting in more stable association of Hg(II) with soils. In addition, decrease of mercury extraction was more evident in soils with lower organic content in most treatments, suggesting that organic matter may potentially play an important role in mercury aging process. In view of the significant decreased Hg(II) or MeHg extraction with prolonged contact time, mercury aging process should be taken into account when assessing risk of mercury in contaminated soils.

  1. Effect of Cl2 plasma treatment and annealing on vanadium based metal contacts to Si-doped Al0.75Ga0.25N

    Science.gov (United States)

    Lapeyrade, Mickael; Alamé, Sabine; Glaab, Johannes; Mogilatenko, Anna; Unger, Ralph-Stephan; Kuhn, Christian; Wernicke, Tim; Vogt, Patrick; Knauer, Arne; Zeimer, Ute; Einfeldt, Sven; Weyers, Markus; Kneissl, Michael

    2017-09-01

    In order to understand the electrical properties of V/Al/Ni/Au metal contacts to Si-doped Al0.75Ga0.25N layers, X-ray photoelectron spectroscopy analysis was performed on differently treated AlGaN:Si surfaces before metal deposition, and transmission electron microscopy was used to study the semiconductor-metal interface after contact annealing at 900 °C. Cl2 plasma etching of AlGaN increases the aluminum/nitrogen ratio at the surface, and Al oxide or oxynitride is always formed by any surface treatment applied after etching. After contact annealing, a complex interface structure including amorphous AlOx and different metal phases such as Al-Au-Ni, V-Al, and V2N were found. The electrical properties of the contacts were determined by thermionic emission and/or thermionic field emission in the low voltage regime. Nearly ohmic contacts on AlGaN surfaces exposed to a Cl2 plasma were only obtained by annealing the sample at a temperature of 815 °C under N2/NH3 prior to metallization. By this treatment, the oxygen contamination on the surface could be minimized, resulting in a larger semiconductor area to be in direct contact with metal phases such as Al-rich Al-Au-Ni or V-Al and leading to a contact resistivity of 2.5 × 10-2 Ω cm2. This treatment can be used to significantly reduce the operating voltage of current deep ultraviolet light emitting diodes which will increase their wall plug efficiency and lower the thermal stress during their operation.

  2. The method of contact angle measurements and estimation of work of adhesion in bioleaching of metals

    Directory of Open Access Journals (Sweden)

    Matlakowska Renata

    1999-01-01

    Full Text Available In this paper, we present our method for the measurement of contact angles on the surface of minerals during the bioleaching process because the standard deviation obtained in our measurements achieved unexpectedly low error. Construction of a goniometer connected with a specially prepared computer program allowed us to repeat measurements several times over a short time course, yielding excellent results. After defining points on the outline of the image of a drop and its baseline as well of the first approximation of the outline of the drop, an iterative process is initiated that is aimed at fitting the model of the drop and baseline. In turn, after defining the medium for which measurements were made, the work of adhesion is determined according to Young-Dupré equation. Calculations were made with the use of two methods named the L-M and L-Q methods.

  3. Partial Discharge Monitoring on Metal-Enclosed Switchgear with Distributed Non-Contact Sensors.

    Science.gov (United States)

    Zhang, Chongxing; Dong, Ming; Ren, Ming; Huang, Wenguang; Zhou, Jierui; Gao, Xuze; Albarracín, Ricardo

    2018-02-11

    Metal-enclosed switchgear, which are widely used in the distribution of electrical energy, play an important role in power distribution networks. Their safe operation is directly related to the reliability of power system as well as the power quality on the consumer side. Partial discharge detection is an effective way to identify potential faults and can be utilized for insulation diagnosis of metal-enclosed switchgear. The transient earth voltage method, an effective non-intrusive method, has substantial engineering application value for estimating the insulation condition of switchgear. However, the practical application effectiveness of TEV detection is not satisfactory because of the lack of a TEV detection application method, i.e., a method with sufficient technical cognition and analysis. This paper proposes an innovative online PD detection system and a corresponding application strategy based on an intelligent feedback distributed TEV wireless sensor network, consisting of sensing, communication, and diagnosis layers. In the proposed system, the TEV signal or status data are wirelessly transmitted to the terminal following low-energy signal preprocessing and acquisition by TEV sensors. Then, a central server analyzes the correlation of the uploaded data and gives a fault warning level according to the quantity, trend, parallel analysis, and phase resolved partial discharge pattern recognition. In this way, a TEV detection system and strategy with distributed acquisition, unitized fault warning, and centralized diagnosis is realized. The proposed system has positive significance for reducing the fault rate of medium voltage switchgear and improving its operation and maintenance level.

  4. Flexible high power-per-weight perovskite solar cells with chromium oxide-metal contacts for improved stability in air

    Science.gov (United States)

    Kaltenbrunner, Martin; Adam, Getachew; Głowacki, Eric Daniel; Drack, Michael; Schwödiauer, Reinhard; Leonat, Lucia; Apaydin, Dogukan Hazar; Groiss, Heiko; Scharber, Markus Clark; White, Matthew Schuette; Sariciftci, Niyazi Serdar; Bauer, Siegfried

    2015-10-01

    Photovoltaic technology requires light-absorbing materials that are highly efficient, lightweight, low cost and stable during operation. Organolead halide perovskites constitute a highly promising class of materials, but suffer limited stability under ambient conditions without heavy and costly encapsulation. Here, we report ultrathin (3 μm), highly flexible perovskite solar cells with stabilized 12% efficiency and a power-per-weight as high as 23 W g-1. To facilitate air-stable operation, we introduce a chromium oxide-chromium interlayer that effectively protects the metal top contacts from reactions with the perovskite. The use of a transparent polymer electrode treated with dimethylsulphoxide as the bottom layer allows the deposition--from solution at low temperature--of pinhole-free perovskite films at high yield on arbitrary substrates, including thin plastic foils. These ultra-lightweight solar cells are successfully used to power aviation models. Potential future applications include unmanned aerial vehicles--from airplanes to quadcopters and weather balloons--for environmental and industrial monitoring, rescue and emergency response, and tactical security applications.

  5. Spatial variation of permittivity of an electrolyte solution in contact with a charged metal surface: a mini review.

    Science.gov (United States)

    Gongadze, E; van Rienen, U; Kralj-Iglič, V; Iglič, A

    2013-01-01

    Contact between a charged metal surface and an electrolyte implies a particular ion distribution near the charged surface, i.e. the electrical double layer. In this mini review, different mean-field models of relative (effective) permittivity are described within a simple lattice model, where the orientational ordering of water dipoles in the saturation regime is taken into account. The Langevin-Poisson-Boltzmann (LPB) model of spatial variation of the relative permittivity for point-like ions is described and compared to a more general Langevin-Bikerman (LB) model of spatial variation of permittivity for finite-sized ions. The Bikerman model and the Poisson-Boltzmann model are derived as limiting cases. It is shown that near the charged surface, the relative permittivity decreases due to depletion of water molecules (volume-excluded effect) and orientational ordering of water dipoles (saturation effect). At the end, the LPB and LB models are generalised by also taking into account the cavity field.

  6. Flexible high power-per-weight perovskite solar cells with chromium oxide-metal contacts for improved stability in air.

    Science.gov (United States)

    Kaltenbrunner, Martin; Adam, Getachew; Głowacki, Eric Daniel; Drack, Michael; Schwödiauer, Reinhard; Leonat, Lucia; Apaydin, Dogukan Hazar; Groiss, Heiko; Scharber, Markus Clark; White, Matthew Schuette; Sariciftci, Niyazi Serdar; Bauer, Siegfried

    2015-10-01

    Photovoltaic technology requires light-absorbing materials that are highly efficient, lightweight, low cost and stable during operation. Organolead halide perovskites constitute a highly promising class of materials, but suffer limited stability under ambient conditions without heavy and costly encapsulation. Here, we report ultrathin (3 μm), highly flexible perovskite solar cells with stabilized 12% efficiency and a power-per-weight as high as 23 W g(-1). To facilitate air-stable operation, we introduce a chromium oxide-chromium interlayer that effectively protects the metal top contacts from reactions with the perovskite. The use of a transparent polymer electrode treated with dimethylsulphoxide as the bottom layer allows the deposition-from solution at low temperature-of pinhole-free perovskite films at high yield on arbitrary substrates, including thin plastic foils. These ultra-lightweight solar cells are successfully used to power aviation models. Potential future applications include unmanned aerial vehicles-from airplanes to quadcopters and weather balloons-for environmental and industrial monitoring, rescue and emergency response, and tactical security applications.

  7. Contact Metallization and Packaging Technology Development for SiC Bipolar Junction Transistors, PiN Diodes, and Schottky Diodes Designed for Long-Term Operations at 350degreeC

    Science.gov (United States)

    2006-05-01

    for high temperature contacts. A Bipolar Junction Transistor ( BJT ) in 4H-SiC can operate at higher temperatures (300oC) because its operation does not...AFRL-PR-WP-TR-2006-2181 CONTACT METALLIZATION AND PACKAGING TECHNOLOGY DEVELOPMENT FOR SiC BIPOLAR JUNCTION TRANSISTORS , PiN DIODES, AND...SUBTITLE CONTACT METALLIZATION AND PACKAGING TECHNOLOGY DEVELOPMENT FOR SiC BIPOLAR JUNCTION TRANSISTORS , PiN DIODES, AND SCHOTTKY DIODES DESIGNED

  8. The metal-tool contact friction at the ultrasonic vibration drawing of ball-bearing steel wires

    Directory of Open Access Journals (Sweden)

    Susan, Mihai

    1999-12-01

    Full Text Available The friction reversion mechanism during the ultrasonic vibration drawing (UVD of wires has been detailed for the case when the die is located at the oscillation maxima of the waves and actuated parallel to the friction force direction. The decrease of the drawing force for the UVD technology as compared to classical drawing has been explained by means of the intermittent contact in the metal-die forming area. A relationship has been derived for the UVD friction coefficient, μUS that allowed the analytical determination of the drawing force. In the case of the Romanian RUL 1V (AISI 52100 ball bearing steel wires, a good agreement has been found between the analytical and the experimental values of the drawing forces that have decreased, as compared to classical drawing, by more than 5 % for drawing rates lower than 0.66m/s.

    Se hace un análisis pormenorizado del mecanismo de reversión de la fricción al estirado por vibraciones ultrasonoras (EVU de los alambres, para el caso en que la trefiladora está ubicada en los máximos de oscilación de las ondas y activada paralelamente a la dirección de estirado. La disminución de la fuerza de estirado para la tecnología EVU en comparación con el estirado clásico, se ha explicado a través del contacto intermitente en el área de deformación metal-herramienta. Se halló una relación para el coeficiente de fricción EVU, μUS que permitió la determinación analítica de la fuerza de estirado. En el caso de los alambres de acero rumano de rodamientos RUL 1V (AISI 52100 se encontró una justa concordancia entre los valores analítico y experimental de la fuerza de estirado que, en comparación con los de estirado clásico, se encontraron disminuidos en más de un 5 % para velocidades de estirado menores de 0,66m/s.

  9. Transmission electron microscopy studies of regrown GaN Ohmic contacts on patterned substrates for metal oxide semiconductor field effect transistor applications

    Science.gov (United States)

    Saripalli, Y. N.; Pei, L.; Biggerstaff, T.; Ramachandran, S.; Duscher, G. J.; Johnson, M. A. L.; Zeng, C.; Dandu, K.; Jin, Y.; Barlage, D. W.

    2007-05-01

    Contact selected area regrowth of GaN was performed by metal organic chemical vapor deposition using a silicon nitride dielectric hard mask to define plasma etched recesses and to define source-drain regions. A low temperature regrowth process at 750-850°C was adopted to limit lateral overgrowth. High resolution electron microscopy images and selected area diffraction confirmed the regrowth selectivity and revealed that the low temperature regrown GaN is epitaxial and has a wurtzite crystal structure. I-V characteristics of the fabricated metal oxidesemiconductor field effect transistor show enhancement mode operation.

  10. Stable MoS2 Field-Effect Transistors Using TiO2 Interfacial Layer at Metal/MoS2 Contact

    KAUST Repository

    Park, Woojin

    2017-09-07

    Molybdenum disulphide (MoS2) is an emerging 2-dimensional (2D) semiconductor for electronic devices. However, unstable and low performance of MoS2 FETs is an important concern. In this study, inserting an atomic layer deposition (ALD) titanium dioxide (TiO2) interfacial layer between contact metal and MoS2 channel is suggested to achieve more stable performances. The reduced threshold voltage (VTH) shift and reduced series resistance (RSD) were simultaneously achieved.

  11. Low Contact Resistivity with Low Silicide/p+-Silicon Schottky Barrier for High-Performance p-Channel Metal-Oxide-Silicon Field Effect Transistors

    Science.gov (United States)

    Tanaka, Hiroaki; Isogai, Tatsunori; Goto, Tetsuya; Teramoto, Akinobu; Sugawa, Shigetoshi; Ohmi, Tadahiro

    2010-04-01

    A current drivability improvement of p-channel metal-oxide-silicon field effect transistors (MOSFETs) is necessary for the performance enhancement of complementary metal-oxide-semiconductor (CMOS) circuits. In this paper, we present the key technology for fabricating indispensable CMOS circuits with a small Schottky barrier height and a low contact resistance for p-type silicon using Pd2Si. We fabricated a Pd2Si gate Schottky barrier diode and a Kelvin pattern on silicon. The measured Schottky barrier height is 0.29 eV for p-type silicon. We also realized a very low contact resistivity of 3.7 ×10-9 Ω cm2 for the p+ region of silicon. The p-channel MOSFET with Pd2Si source/drain contacts realized a good characteristic, that is, a small off current. The technology developed in this work involves silicide formation for source/drain contacts of p-channel MOSFETs, which is expected to realize the performance enhancement of MOSFETs.

  12. Uptake of nickel from 316L stainless steel into contacting osteoblastic cells and metal ion interference with BMP-2-induced alkaline phosphatase.

    Science.gov (United States)

    Mölders, Martina; Felix, Joachim; Bingmann, Dieter; Hirner, Alfred; Wiemann, Martin

    2007-11-01

    Bone cells contacting nickel (Ni)-containing implant materials may be affected by Ni species via disturbed signaling pathways involved in bone cell development. Here we analyze effects of the Ni-containing steel 316L and major metal constituents thereof on bone morphogenetic protein-2 (BMP-2)-induced alkaline phosphatase (ALP) of MC3T3-E1 cells. While cells grew normally on 316L, cellular Ni content increased 10-fold vs. control within 4 days. With respect to the major components of 316L, Ni2+ (3-50 microM) was most inhibitory to BMP-2-induced ALP, whereas even 50 microM Fe3+, Cr3+, Mo5+, or Mn2+ had no such effect. In line with this, BMP-2-induced ALP was significantly reduced in cells on 316L. This effect was not prevented by the metal ion chelator diethylenetriaminepentaacetic acid (DTPA). Instead, DTPA abolished the stimulatory effect of BMP-2 on ALP, pointing to chelatable metal ions involved. Zn2+, as one possible candidate, antagonized the Ni2+ inhibition of BMP-2-induced ALP in both MC3T3-E1 and human bone marrow stromal cells. Results show that cells contacting 316L steel are exposed to increased concentrations of Ni which suffice to impair BMP-2-induced ALP activity. Zn2+, as a competitor of this inhibition, may help to restore normal osteoblastic function and bone development under these conditions. Copyright (c) 2007 Wiley Periodicals, Inc.

  13. Effects of sputtering power Schottky metal layers on rectifying performance of Mo-SiC Schottky contacts

    Science.gov (United States)

    Lee, Seula; Lee, Jinseon; You, Sslimsearom; Kyoung, Sinsu; Kim, Kyung Hwan

    2016-01-01

    In this study, Schottky barrier diodes based on silicon carbide with various levels of Schottky metal layer input power were prepared and characterized. In this structure, molybdenum and aluminum were employed as the Schottky metal and top electrode, respectively. Schottky metal layers were deposited with input power ranging from 30 to 210 W. Schottky metal layers and top electrodes were deposited with a thickness of 3000 Å. The Schottky barrier heights, series resistances, and ideality factor were calculated from current-voltage (I-V) curves obtained using the Cheung-Cheung and Norde methods. All deposition processes were conducted using a facing targets sputtering system. Turn on voltage was minimized when the input power was 90 W, at which point electrical characteristics were observed to have properties superior to those at other levels of input power.

  14. Theoretical Analysis of Unit Friction Force Working on the Metal Contact Surface with the Roll Change during Feedstock with Non-Uniform Temperature Distribution Rolling Process

    Directory of Open Access Journals (Sweden)

    Sygut P.

    2016-06-01

    Full Text Available The paper presents the results of theoretical studies influence of non-uniform temperature distribution along the feedstock length to the unit friction force working on the metal contact surface with the roll change during the round bars 70 mm in diameter continuous rolling process. This value is one of the major factors affecting the grooves wear during the rolling process. The studies were carried out based on the actual engineering data for 160 × 160 mm square cross-section feedstock of steel S355J0. Numerical modelling of the rolling process was performed using Forge2008®, a finite-element based computer program.

  15. Friction and wear of selected metals and alloys in sliding contact with AISI 440 C stainless steel in liquid methane and in liquid natural gas

    Science.gov (United States)

    Wisander, D. W.

    1978-01-01

    Aluminum, titanium, beryllium, nickel, iron, copper, and several copper alloys were run in sliding contact with AISI 440C in liquid methane and natural gas. All of the metals run except copper and the copper alloys of tin and tin-lead showed severely galled wear scars. Friction coefficients varied from 0.2 to 1.0, the lowest being for copper, copper-17 wt. % tin, and copper-8 wt. % tin-22 wt. % lead. The wear rate for copper was two orders of magnitude lower than that of the other metals run. An additional order of magnitude of wear reduction was achieved by the addition of tin and/or lead to copper.

  16. Annealing behaviors of vacancy-type defects near interfaces between metal contacts and GaN probed using a monoenergetic positron beam

    Energy Technology Data Exchange (ETDEWEB)

    Uedono, Akira, E-mail: uedono.akira.gb@u.tsukuba.ac.jp; Yoshihara, Nakaaki [Division of Applied Physics, Faculty of Pure and Applied Science, University of Tsukuba, Tsukuba, Ibaraki 305-8573 (Japan); Fujishima, Tatsuya; Piedra, Daniel; Palacios, Tomás [Microsystems Technology Laboratories, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139-4307 (United States); Ishibashi, Shoji [Nanosystem Research Institute “RICS,” National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki 305-8568 (Japan); Sumiya, Masatomo [Wide Bandgap Material Group, National Institute for Materials Science, Tsukuba 305-0044 (Japan); Laboutin, Oleg; Johnson, Wayne [IQE, 200 John Hancock Road, Taunton, Massachusetts 01581 (United States)

    2014-08-04

    Vacancy-type defects near interfaces between metal contacts and GaN grown on Si substrates by metal organic chemical vapor deposition have been studied using a monoenergetic positron beam. Measurements of Doppler broadening spectra of the annihilation radiation for Ti-deposited GaN showed that optically active vacancy-type defects were introduced below the Ti/GaN interface after annealing at 800 °C. Charge transition of those defects due to electron capture was observed and was found to correlate with a yellow band in the photoluminescence spectrum. The major defect species was identified as vacancy clusters such as three to five Ga-vacancies coupled with multiple nitrogen-vacancies. The annealing behaviors of vacancy-type defects in Ti-, Ni-, and Pt-deposited GaN were also examined.

  17. Systems and Methods for Designing and Fabricating Contact-Free Support Structures for Overhang Geometries of Parts in Powder-Bed Metal Additive Manufacturing

    Science.gov (United States)

    Chou, Yuag-Shan (Inventor); Cooper, Kenneth (Inventor)

    2017-01-01

    Systems and methods are provided for designing and fabricating contact-free support structures for overhang geometries of parts fabricated using electron beam additive manufacturing. One or more layers of un-melted metallic powder are disposed in an elongate gap between an upper horizontal surface of the support structure and a lower surface of the overhang geometry. The powder conducts heat from the overhang geometry to the support structure. The support structure acts as a heat sink to enhance heat transfer and reduce the temperature and severe thermal gradients due to poor thermal conductivity of metallic powders underneath the overhang. Because the support structure is not connected to the part, the support structure can be removed freely without any post-processing step.

  18. Assessment of nickel and cobalt release from 200 unused hand-held work tools for sale in Denmark — Sources of occupational metal contact dermatitis?

    DEFF Research Database (Denmark)

    Thyssen, Jacob P.; Jensen, Peter; Lidén, Carola

    2011-01-01

    IntroductionNickel and cobalt allergy remain frequent in dermatitis patients. It is important to determine possible nickel and cobalt exposures at work as these may offer important information to regulators and physicians who perform patch testing. Clinical relevance of metal exposure is usually...... assessed by the treating physician via the medical history and by presentation of allergic contact dermatitis. ObjectivesTo screen unused non-powered hand-held work tools for nickel and cobalt release by using colorimetric spot tests. Materials & methodsA random selection of 200 non-powered hand-held work...... tools for sale in 2 retailers of home improvement and construction products were analyzed qualitatively for metal release using the colorimetric nickel and cobalt spot tests. ResultsNickel release was identified from 5% of 200 work tools using the dimethylglyoxime (DMG) test. In 8 of 10, positive...

  19. Impact of semiconductor/metal interfaces on contact resistance and operating speed of organic thin film transistors

    KAUST Repository

    Wondmagegn, Wudyalew T.

    2010-09-24

    The contact resistance of field effect transistors based on pentacene and parylene has been investigated by experimental and numerical analysis. The device simulation was performed using finite element two-dimensional drift-diffusion simulation taking into account field-dependent mobility, interface/bulk trap states and fixed charge density at the organic/insulator interface. The width-normalized contact resistance extracted from simulation which included an interface dipole layer between the gold source/drain electrodes and pentacene was 91 kΩcm. However, contact resistance extracted from the simulation, without consideration of interface dipole was 52.4 kΩcm, which is about half of the experimentally extracted 108 kΩcm. This indicates that interface dipoles are critical effects which degrade performances of organic field effect transistors by increasing the contact resistance. Using numerical calculations and circuit simulations, we have predicted a 1 MHz switching frequency for a 1 μm channel length transistor without dipole interface between gold and pentacene. The transistor with dipole interface is predicted, via the same methods, to exhibit an operating frequency of less than 0.5 MHz. © 2010 Springer Science+Business Media LLC.

  20. A Novel Sub-20 V Contact Gate Metal Oxide Semiconductor Field Effect Transistor with Fully Complementary Metal Oxide Semiconductor Compatible Process

    Science.gov (United States)

    Lee, Te Liang; Tsang Tsai, Ming; King, Ya Chin; Lin, Chrong Jung

    2013-04-01

    In this paper, a novel sub-20 V device which is called contact gate MOSFET (CGMOS) with fully CMOS logic compatible process is proposed and demonstrated. Comparing with lateral double diffusion MOSFET (LDMOS), CGMOS uses P substrate instead of N minus layer as drift region in logic process, and a contact on resistance protection oxide (RPO) layers to form an extra gate on the drain side of the channel region to provide a better gate control and reduce the surface field. This new device significantly rises up the breakdown voltage to 18 V with specific on-resistance 8.8 mΩ.mm2 in a small high voltage (HV) MOSFET area. Since there is no extra mask for creating the drift region or additional step for the wire bonding, CGMOS makes the integration of high voltage and logic circuits much simpler and area-saving.

  1. Contact toxicity of metals in sewage sludge: Evaluation of alternatives to sodium chloride in the Microtox[reg sign] assay

    Energy Technology Data Exchange (ETDEWEB)

    Carlson-Ekvall, C.E.A.; Morrison, G.M. (Chalmers Univ. of Technology, Goeteborg (Sweden). Dept. of Sanitary Engineering)

    1995-01-01

    The presence of chloride ions in the Microtox[reg sign] test can cause problems when testing metal toxicity, both due to extraction of metals from solid samples and formation of chloro complexes of metals in the liquid phase. To investigate alternatives to NaCl in the Microtox test, the toxicity of Cu, Cd, Pb, and Zn to Photobacterium phosphoreum was tested in 28 osmotic surrogates for NaCl. It was found that Na[sup +] must be present to keep the blank luminescence stable for 30 min. The results point to NaClO[sub 4] as the most satisfactory surrogate solution as it has an inert behavior and does not form complexes with any metal of environmental interest. Raw, digested, and reference sewage sludges were tested in the osmotic surrogates. The EC50 values for sludges were lower in solutions of NaNO[sub 3], Na[sub 2]SO[sub 4], and NaClO[sub 4], and higher in sucrose, mannitol, and KCl, compared to NaCl. NaClO[sub 4] can be recommended as an osmotic surrogate for sewage sludge testing. Another problem with the Microtox assay is the lack of pH control in the cuvette. Copper toxicity tests were carried out in Tris buffer and KH[sub 2]PO[sub 4] at two different concentrations and at pH 7 and 8. The results show that 1 mM phosphate buffer, pH 7.0, can be recommended for solid samples. However, owing to formation of KClO[sub 4] a buffer containing potassium is not recommended in combination with NaClO[sub 4].

  2. Establishing contact between cell-laden hydrogels and metallic implants with a biomimetic adhesive for cell therapy supported implants.

    Science.gov (United States)

    Barthes, Julien; Mutschler, Angela; Dollinger, Camille; Gaudinat, Guillaume; Lavalle, Philippe; Le Houerou, Vincent; Brian McGuinness, Garrett; Engin Vrana, Nihal

    2017-12-15

    For in-dwelling implants, controlling the biological interface is a crucial parameter to promote tissue integration and prevent implant failure. For this purpose, one possibility is to facilitate the establishment of the interface with cell-laden hydrogels fixed to the implant. However, for proper functioning, the stability of the hydrogel on the implant should be ensured. Modification of implant surfaces with an adhesive represents a promising strategy to promote the adhesion of a cell-laden hydrogel on an implant. Herein, we developed a peptidic adhesive based on mussel foot protein (L-DOPA-L-lysine)2-L-DOPA that can be applied directly on the surface of an implant. At physiological pH, unoxidized (L-DOPA-L-lysine)2-L-DOPA was supposed to strongly adhere to metallic surfaces but it only formed a very thin coating (less than 1 nm). Once oxidized at physiological pH, (L-DOPA-L-lysine)2-L-DOPA forms an adhesive coating about 20 nm thick. In oxidized conditions, L-lysine can adhere to metallic substrates via electrostatic interaction. Oxidized L-DOPA allows the formation of a coating through self-polymerization and can react with amines so that this adhesive can be used to fix extra-cellular matrix based materials on implant surfaces through the reaction of quinones with amino groups. Hence, a stable interface between a soft gelatin hydrogel and metallic surfaces was achieved and the strength of adhesion was investigated. We have shown that the adhesive is non-cytotoxic to encapsulated cells and enabled the adhesion of gelatin soft hydrogels for 21 days on metallic substrates in liquid conditions. The adhesion properties of this anchoring peptide was quantified by a 180° peeling test with a more than 60% increase in peel strength in the presence of the adhesive. We demonstrated that by using a biomimetic adhesive, for the application of cell-laden hydrogels to metallic implant surfaces, the hydrogel/implant interface can be ensured without relying on the properties

  3. CAB-DWTM for 5 μm trace-width deposition of solar cell metallization top-contacts

    Energy Technology Data Exchange (ETDEWEB)

    Justin Hoey; Drew Thompson; Matt Robinson; Zakaria Mahmud; Orven F. Swenson; Iskander S. Akhatov; Douglas L. Schulz

    2009-06-08

    This paper reviews methods for creating solar cell grid contacts and explores how cell efficiency can be increased using CAB-DW{trademark}. Specifically, the efficiency of p-i-n structure solar cells built in-house with 90 {micro}m sputtered lines and 5 {micro}m CAB-DW lines were compared. Preliminary results of the comparison show a marked improvement in solar cell efficiency using CAB-DW. In addition to this, a theoretical and experimental analysis of the dynamics of particle impaction on a substrate (i.e. whether particle stick or bounce) will be discussed including how this analysis may lead to further improvement of CAB-DW.

  4. The Effect of Metal-Semiconductor Contact on the Transient Photovoltaic Characteristic of HgCdTe PV Detector

    Directory of Open Access Journals (Sweden)

    Haoyang Cui

    2013-01-01

    Full Text Available The transient photovoltaic (PV characteristic of HgCdTe PV array is studied using an ultrafast laser. The photoresponse shows an apparent negative valley first, then it evolves into a positive peak. By employing a combined theoretical model of pn junction and Schottky potential, this photo-response polarity changing curves can be interpreted well. An obvious decreasing of ratio of negative valley to positive peak can be realized by limiting the illumination area of the array electrode. This shows that the photoelectric effect of Schottky barrier at metal-semiconductor (M/S interface is suppressed, which will verify the correctness of the model. The characteristic parameters of transient photo-response induced from p-n junction and Schottky potential are extracted by fitting the response curve utilizing this model. It shows that the negative PV response induced by the Schottky barrier decreases the positive photovoltage generated by the pn junction.

  5. Electrical contacts principles and applications

    CERN Document Server

    Slade, Paul G

    2013-01-01

    Covering the theory, application, and testing of contact materials, Electrical Contacts: Principles and Applications, Second Edition introduces a thorough discussion on making electric contact and contact interface conduction; presents a general outline of, and measurement techniques for, important corrosion mechanisms; considers the results of contact wear when plug-in connections are made and broken; investigates the effect of thin noble metal plating on electronic connections; and relates crucial considerations for making high- and low-power contact joints. It examines contact use in switch

  6. Particles, sweat, and tears: a comparative study on bioaccessibility of ferrochromium alloy and stainless steel particles, the pure metals and their metal oxides, in simulated skin and eye contact.

    Science.gov (United States)

    Hedberg, Yolanda; Midander, Klara; Wallinder, Inger Odnevall

    2010-07-01

    Ferrochromium alloys are manufactured in large quantities and placed on the global market for use as master alloys (secondary raw materials), primarily for stainless steel production. Any potential human exposure to ferrochromium alloy particles is related to occupational activities during production and use, with 2 main exposure routes, dermal contact and inhalation and subsequent digestion. Alloy and reference particles exposed in vitro in synthetic biological fluids relevant for these main exposure routes have been investigated in a large research effort combining bioaccessibility; chemical speciation; and material, surface, and particle characteristics. In this paper, data for the dermal exposure route, including skin and eye contact, will be presented and discussed. Bioaccessibility data have been generated for particles of a ferrochromium alloy, stainless steel grade AISI 316L, pure Fe, pure Cr, iron(II,III)oxide, and chromium(III)oxide, upon immersion in artificial sweat (pH 6.5) and artificial tear (pH 8.0) fluids for various time periods. Measured released amounts of Fe, Cr, and Ni are presented in terms of average Fe and Cr release rates and amounts released per amount of particles loaded. The results are discussed in relation to bulk and surface composition of the particles. Additional information, essential to assess the bioavailability of Cr released, was generated by determining its chemical speciation and by providing information on its complexation and oxidation states in both media investigated. The effect of differences in experimental temperature, 30 degrees C and 37 degrees C, on the extent of metal release in artificial sweat is demonstrated. Iron was the preferentially released element in all test media and for all time periods and iron-containing particles investigated. The extent of metal release was highly pH dependent and was also dependent on the medium composition. Released amounts of Cr and Fe were very low (close to the limit of

  7. Initial stages of indoor atmospheric corrosion of electronics contact metals in humid tropical climate: tin and nickel

    Directory of Open Access Journals (Sweden)

    Veleva, L.

    2007-04-01

    Full Text Available Samples of electrolytic tin and nickel have been exposed for 1 to 12 m in indoor environment, inside a box (rain sheltered cabinet, placed in tropical humid marine-urban climate, as a part of Gulf of Mexico. The corrosion aggressiveness of box has been classified as a very high corrosive, based on the monitored chlorides and SO2 deposition rates, and the Temperature/Relative Humidity air daily complex. The annual mass increasing of nickel is approximately twice higher than its values of mass loss (C. The relation between nickel mass loss or increasing and time of wetness (t of metal surface is linear and does not obey the power equation C = A tn, which has be found for tin. The SEM images reveal a localized corrosion on nickel and tin surfaces. XRD detects the formation of SnCl2.H2O as a corrosion product. Within the time on the tin surface appear black spots, considered as organic material.

    Muestras de estaño y níquel electrolíticos han sido expuestas de 1 a 12 m en ambiente interno (indoor, en una caseta (gabinete protegido de lluvia, colocada en clima tropical húmedo marino-urbano del Golfo de México. La agresividad de la caseta ha sido clasificada como muy altamente corrosiva, basada al registro de la velocidad de deposición de cloruros y SO2, y en el complejo diario de temperatura/humedad relativa del aire. El incremento de masa anual de níquel es, aproximadamente, dos veces mayor que del valor de su pérdida de masa (C. La relación entre la pérdida de masa de Ni o su incremento, y el tiempo de humectación (t de la superficie metálica y lineal y no obedece la ley de potencia C = A tn , que ha sido encontrada para el estaño. Las imágenes del SEM revelan una corrosión localizada en las superficie de níquel y estaño. El análisis de rayos-X detecta la formación de SnCl2.H2O como producto de corrosión. Con el tiempo

  8. Contact arc metal cutting (CAMC), a young cutting technique has matured. Successful use under water in the demolition of the Karlsruhe multipurpose research reactor (MFZR); Contact-Arc-Metal-Cutting (CAMC) - Eine junge Schneidtechnologie ist den Kinderschuhen entwachsen. Erfolgreicher Einsatz unter Wasser beim Rueckbau des Mehrzweckforschungsreaktors Karlsruhe (MZFR)

    Energy Technology Data Exchange (ETDEWEB)

    Stanke, D.; Bienia, H.; Loeb, A.; Thoma, M. [RWE NUKEM GmbH, Alzenau (Germany); Eisenmann, B.; Prechtl, E. [Forschungszentrum Karlsruhe GmbH, Eggenstein-Leopoldshafen (Germany); Suessdorf, W. [Studsvik-IFM, Stutensee-Blankenloch (Germany); Kremer, G.; Ruemenapp, T. [Hannover Univ. (Germany). Inst. fuer Werkstoffkunde

    2006-03-15

    Dismantling radiologically burdened large components is among the most complex and difficult jobs in the demolition of nuclear installations. The technologies used and their safe operation play a key role in demolition. Dismantling highly activated components as a rule requires shielding by water. As a consequence, the techniques employed must be designed for use under water. A variety of technologies are available for these applications. One established mechanical cutting method is water abrasive suspension jet cutting (WASS). Because of the small cutting nozzle employed, this highly flexible cutting technique can be used nearly anywhere together with different guiding systems. In the course of disassembly under water of the MZFR, plasma cutting has been found to be a reliable and efficient technique for remote operation. Contact arc metal cutting is a thermal cutting technique allowing all electrically conducting materials, including those with claddings, to be cut nearly irrespective of their component geometries. The methods, technology, possible uses, and practical operation of contact arc metal cutting in the demolition of the MZFR are covered in this article. (orig.)

  9. Electroless deposition of NiWB alloy on p-type Si(1 0 0) for NiSi contact metallization

    Energy Technology Data Exchange (ETDEWEB)

    Duhin, A. [Department of Physical Electronics, Engineer Faculty, Tel-Aviv University, Ramat-Aviv 69978 (Israel)], E-mail: alla.douhin@gmail.com; Sverdlov, Y. [Department of Physical Electronics, Engineer Faculty, Tel-Aviv University, Ramat-Aviv 69978 (Israel); Feldman, Y. [Department of Materials and Interfaces, Weizmann Institute of Science, Rehovot 76100 (Israel); Shacham-Diamand, Y. [Department of Physical Electronics, Engineer Faculty, Tel-Aviv University, Ramat-Aviv 69978 (Israel)

    2009-10-30

    Recently, we have proposed a novel method to form NiSi contacts using electroless plating of Ni-alloys (NiP, NiWP, NiWB) on p-type Si(1 0 0) modified by aminopropyltriethoxysilane (APTS) activated with Pd-citrate [A. Duhin, Y. Sverdlov, Yishay Feldman, Y. Shacham-Diamand, Microelectron. Eng. 84 (2007) 2506]. In this work we focus on NiWB thin films that were formed by this method. Alkali metal free electroless plating was developed using dimethylamine-borane (DMAB) and tungstatic acid (H{sub 2}WO{sub 4}) as a reducing agent and a source of tungsten ions, respectively. Using this method we succeeded to receive relatively high tungsten concentration (maximum value of 19-21 at%) in the electroless deposited NiWB films with good adhesion to the Si-substrate. In this paper, the advantages of using the APTS activated with Pd-citrate for NiWB alloy deposition on the Si substrate is discussed. The chemically deposited NiWB samples were annealed for 1-2 h in vacuum (<10{sup -6} Torr) forming the silicide layer. The annealing temperatures were 650 deg. C for NiWB alloys. X-ray diffraction (XRD) measurement confirmed the presence of NiSi phase after annealing. In addition the WSi{sub 2} phase was formed. The results are reported and summarized.

  10. Fully tensile strained partial silicon-on-insulator n-type lateral-double-diffused metal-oxide-semiconductor field effect transistor using localized contact etching stop layers

    Science.gov (United States)

    Wang, Xiangzhan; Tan, Changgui; Zou, Xi; Zhang, Yi; Pan, Jianhua; Liu, Yang

    2017-05-01

    The use of contact etching stop layer (CESL) stressors is a popular technique for introducing stress into a transistor channel. However, when tensile stress is applied to an n-type lateral double-diffused metal-oxide-semiconductor (LDMOS) by covering the whole device with a CESL, the drift region adjacent to the channel will be compressively strained, which is detrimental to device performance. The current work presents a strained partial silicon-on-insulator LDMOS in which tensile stress was introduced in both the channel and drift region via a CESL to reduce the device's on-resistance and improve its frequency performance. An n-type LDMOS device with a top-layer Si thickness that was varied between 300 and 20 nm was simulated to investigate the effect of CESLs on device performance. Devices in which the channel and drift region were fully strained had larger carrier mobilities, and their cut-off frequencies were increased by 25% compared with a normal unstrained partial silicon-on-insulator LDMOS field effect transistor. Meanwhile stress was shown to have little impact on the breakdown voltage of the two types of LDMOS field effect transistor studied here.

  11. Reducing contact resistance in graphene devices through contact area patterning.

    Science.gov (United States)

    Smith, Joshua T; Franklin, Aaron D; Farmer, Damon B; Dimitrakopoulos, Christos D

    2013-04-23

    Performance of graphene electronics is limited by contact resistance associated with the metal-graphene (M-G) interface, where unique transport challenges arise as carriers are injected from a 3D metal into a 2D-graphene sheet. In this work, enhanced carrier injection is experimentally achieved in graphene devices by forming cuts in the graphene within the contact regions. These cuts are oriented normal to the channel and facilitate bonding between the contact metal and carbon atoms at the graphene cut edges, reproducibly maximizing "edge-contacted" injection. Despite the reduction in M-G contact area caused by these cuts, we find that a 32% reduction in contact resistance results in Cu-contacted, two-terminal devices, while a 22% reduction is achieved for top-gated graphene transistors with Pd contacts as compared to conventionally fabricated devices. The crucial role of contact annealing to facilitate this improvement is also elucidated. This simple approach provides a reliable and reproducible means of lowering contact resistance in graphene devices to bolster performance. Importantly, this enhancement requires no additional processing steps.

  12. Prevalence of contact allergy in the general population: Sensitization to metals with a focus on nickel sulfate, the EDEN Fragrance Study Group

    NARCIS (Netherlands)

    Schuttelaar, M.-L.; Ofenloch, R.; Bruze, M.; Cazzaniga, S.; Elsner, P.; Gonçalo, M.; Naldi, L.; Svensson, Å.; Diepgen, T.

    2016-01-01

    Sensitization to metals is assessed mostly in clinical populations. Studies in the general population are scarce. Our objective was to determine the prevalence of metal sensitization in the general population and to determine risk factors for nickel sensitization. In five European countries (the

  13. In-Situ Fabrication of a Self-Aligned Selective Emitter Silicon Solar Cell Using the Gold Top Contacts To Facilitate the Synthesis of a Nanostructured Black Silicon Antireflective Layer Instead of an External Metal Nanoparticle Catalyst.

    Science.gov (United States)

    Lu, Yen-Tien; Barron, Andrew R

    2015-06-10

    Silicon solar cells with nanopore-type black silicon (b-Si) antireflection (AR) layers and self-aligned selective emitter (SE) are reported in which the b-Si structure is prepared without the traditional addition of a nanoparticle (NP) catalyst. The contact-assisted chemical etching (CACE) method is reported here for the first time, in which the metal top contacts on silicon solar cell surfaces function as the catalysts for b-Si fabrication and the whole etching process can be done in minutes at room temperature. The CACE method is based on the metal-assisted chemical etching (MACE) solution but without or metal precursor in the Si etchant (HF:H2O2:H2O), and the Au top contacts, or catalysts, are not removed from the solar cell surface after the etching. The effects of etching time, HF and H2O2 concentration, and the HF:H2O2 ratio on the b-Si morphology, surface reflectivity, and solar cell efficiency have been investigated. Higher [HF] and [H2O2] with longer etching time cause collapse of the b-Si nanoporous structure and penetration of the p-n junctions, which are detrimental to the solar cell efficiency. The b-Si solar cell fabricated with the HF:H2O2:H2O volume ratio of 3:3:20 and a 3 min etch time shows the highest efficiency 8.99% along with a decrease of reflectivity from 36.1% to 12.6% compared to that of the nonetched Si solar cell.

  14. Polar Metal Oxide Surfaces of MgAl2O4 and ZnO Studied with Non-Contact Atomic Force Microscopy

    DEFF Research Database (Denmark)

    Rasmussen, Morten Karstoft

    2011-01-01

    large and complicated surface reconstructions. However, by utilizing the non-contact atomic force microscope together with complimentary experimental techniques and theoretical calculations, the work presented in this thesis introduces a new general route for resolving the atomic structure of a polar...

  15. Current-voltage curves of atomic-sized transition metal contacts: An explanation of why Au is ohmic and Pt is not

    DEFF Research Database (Denmark)

    Nielsen, S.K.; Brandbyge, Mads; Hansen, K.

    2002-01-01

    We present an experimental study of current-voltage (I-V) curves on atomic-sized Au and Pt contacts formed under cryogenic vacuum (4.2 K). Whereas I-V curves for Au are almost Ohmic, the conductance G=I/V for Pt decreases with increasing voltage, resulting in distinct nonlinear I-V behavior...

  16. Self-aligned two-layer metallization with low series resistance for litho-less contacting of large-area photodiodes

    NARCIS (Netherlands)

    Mok, K.R.C.; Qi, L.; Vlooswijk, A.H.G.; Nanver, Lis Karen

    2015-01-01

    In this work, a double-layer Al metallization scheme for large-area photodiodes is presented. This scheme combines a self-alignment of two separate layers of sputtered Al with an anodic Al2O3 as the intermediate insulating layer. One initial patterning step, that could be performed litho-less by for

  17. Assessment of nickel and cobalt release from 200 unused hand-held work tools for sale in Denmark - Sources of occupational metal contact dermatitis?

    DEFF Research Database (Denmark)

    Thyssen, Jacob P; Jensen, Peter; Lidén, Carola

    2011-01-01

    Nickel and cobalt allergy remain frequent in dermatitis patients. It is important to determine possible nickel and cobalt exposures at work as these may offer important information to regulators and physicians who perform patch testing. Clinical relevance of metal exposure is usually assessed...

  18. Uneven damage on head and liner contact surfaces of a retrieved Co–Cr-based metal-on-metal hip joint bearing: An important reason for the high failure rate

    Energy Technology Data Exchange (ETDEWEB)

    Koizumi, Yuichiro, E-mail: koizumi@imr.tohoku.ac.jp [Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577 (Japan); Chen, Yan; Li, Yunping; Yamanaka, Kenta; Chiba, Akihiko [Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577 (Japan); Tanaka, Shun-Ichiro [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai 980-8577 (Japan); Hagiwara, Yoshihiro [Tohoku University School of Medicine, 2-1 Seiryo-machi, Aoba-ku, Sendai, Miyagi 980-8575 (Japan)

    2016-05-01

    Detailed metallurgical investigations have been performed on a used Co–Cr-based metal-on-metal (MoM) hip joint bearing containing a type of liner that is commonly used in such joints. The damage on the metal-liner sliding surface was considerably more severe than that on the metal head counterpart, in terms of wear-scar density and width and microcrack frequency. Cross-sectional transmission electron microscopy revealed that a thick (> 3 μm) nanocrystalline layer formed on the sliding surface of the head, whereas the liner had coarse carbides embedded in it and nanocrystals were formed in a very limited region no deeper than 1 μm. Comparative investigation of an unused head and a liner of identical type showed that although the chemical compositions of the liner and head were nearly identical, their microstructures were significantly different. Specifically, the grain size in the liner was larger than that in the head on average, and the grain boundaries of the liner were decorated with coarse carbides. Moreover, X-ray diffraction analysis revealed a large tensile residual stress only in the liner. These differences are possibly responsible for the wear damage on the liner being more serious than that on the head. - Highlights: • Microstructures in a used metal-on-metal (MoM) hip joint have been investigated in detail. • The damage on the liner sliding surface was considerably more severe than that on the head. • Relatively coarse microstructures are probably responsible for the severe damage on the liner.

  19. Prioritized Contact Transport Stream

    Science.gov (United States)

    Hunt, Walter Lee, Jr. (Inventor)

    2015-01-01

    A detection process, contact recognition process, classification process, and identification process are applied to raw sensor data to produce an identified contact record set containing one or more identified contact records. A prioritization process is applied to the identified contact record set to assign a contact priority to each contact record in the identified contact record set. Data are removed from the contact records in the identified contact record set based on the contact priorities assigned to those contact records. A first contact stream is produced from the resulting contact records. The first contact stream is streamed in a contact transport stream. The contact transport stream may include and stream additional contact streams. The contact transport stream may be varied dynamically over time based on parameters such as available bandwidth, contact priority, presence/absence of contacts, system state, and configuration parameters.

  20. ADSORPTION TO CHITIN – A VIABLE AND ORGANISM-PROTECTING METHOD FOR BIOMONITORING METALS PRESENT IN DIFFERENT ENVIRONMENTAL COMPARTMENTS GETTING CONTACTED WITH ARTHROPODS

    Directory of Open Access Journals (Sweden)

    S. Fränzle

    2015-04-01

    Full Text Available Among the various biopolymers which cover outer interfaces of organisms, chitin is the most abundant: each year several billion metric tons (possibly even much more are produced by arthropods and processed in soil and litter, wet sediment  (especially in moist soils while otherwise chitin samples can persist virtually unchanged for geological periods of time. Moreover, arthropods, among which Coleoptera are represented by some 400,000 species alone, inhabit almost all ecosystems, way beyond the ecological range of, say, mosses. Given that adsorption of metalliferous analytes (ions, volatile compounds, complexes of whatever net charge to chitin obtained from arthropods can be demonstrated (and it partly was already, it is feasible to obtain data on environmental element contents in all water, soil and gas phase (atmosphere by dissolving, analyzing outermost (part of exocuticle chitin layers. Data on relative uptake contributions/environmental burdens of either compartment can be obtained by both interspecies-comparisons and sampling of different parts of some larger arthropod (abdomen-, outer- and inner wing surfaces of sizable beetles. As just a very thin chitin layer (< 2 µm is ablated from the animal´s outer surface by dissolution using little toxic components, sampling will not cause harm to them, enabling a repeated sampling of the same specimen (e.g. for taking t = 0 starting values and b use of rare or/and protected species. Applications are with both biomonitoring and a better understanding of metal ion transport in ecosystems, e.g. concerning interfacial Mn+ binding to dying zooplankton then sinking below the chemokline of euxinic water bodies. An indirect metal levels monitoring of woody plants and underneath soils also appears feasible.

  1. Ultra-low temperature radio-frequency performance of partially depleted silicon-on-insulator n-type metal-oxide-semiconductor field-effect transistors with tunnel diode body contact structures

    Science.gov (United States)

    Lu, Kai; Chen, Jing; Huang, Yuping; Liu, Jun; Luo, Jiexin; Wang, Xi

    2016-11-01

    Radio-frequency (RF) characteristics under ultra-low temperature of multi-finger partially depleted silicon-on-insulator (PD SOI) n-type metal-oxide-semiconductor field-effect transistors (nMOSFETs) with tunnel diode body-contact (TDBC) structure and T-gate body-contact (TB) structure are investigated in this paper. When operating at 77 K, TDBC device suppresses floating-body effect (FBE) as well as the TB device. For TB device and TDBC device, cut-off frequency (f T) improves as the temperature decreases to liquid-helium temperature (77 K) while that of the maximum oscillation frequency (f MAX) is opposite due to the decrease of the unilateral power gain. While operating under 77 K, f T and f MAX of TDBC device reach to 125 GHz and 77 GHz, representing 8% and 15% improvements compared with those of TB device, respectively, which is mainly due to the lower parasitic resistances and capacitances. The results indicate that TDBC SOI MOSFETs could be considered as promising candidates for analog and RF applications over a wide range of temperatures and there is immense potential for the development of RF CMOS integrated circuits for cryogenic applications.

  2. First-principles analysis of MoS2/Ti2C and MoS2/Ti2CY2 (Y=F and OH) all-2D semiconductor/metal contacts

    KAUST Repository

    Gan, Liyong

    2013-06-13

    First-principles calculations are used to explore the geometry, bonding, and electronic properties of MoS2/Ti2C and MoS2/Ti2CY2 (Y = F and OH) semiconductor/metal contacts. The structure of the interfaces is determined. Strong chemical bonds formed at the MoS2/Ti2C interface result in additional states next to the Fermi level, which extend over the three atomic layers of MoS2 and induce a metallic character. The interaction in MoS2/Ti2CY2, on the other hand, is weak and not sensitive to the specific geometry, and the semiconducting nature thus is preserved. The energy level alignment implies weak and strong n-type doping of MoS2 in MoS2/Ti2CF2 and MoS2/Ti2C(OH)2, respectively. The corresponding n-type Schottky barrier heights are 0.85 and 0.26 eV. We show that the MoS2/Ti2CF2 interface is close to the Schottky limit. At the MoS2/Ti2C(OH)2 interface, we find that a strong dipole due to charge rearrangement induces the Schottky barrier. The present interfaces are well suited for application in all-two-dimensional devices.

  3. Front contact solar cell with formed emitter

    Science.gov (United States)

    Cousins, Peter John [Menlo Park, CA

    2012-07-17

    A bipolar solar cell includes a backside junction formed by an N-type silicon substrate and a P-type polysilicon emitter formed on the backside of the solar cell. An antireflection layer may be formed on a textured front surface of the silicon substrate. A negative polarity metal contact on the front side of the solar cell makes an electrical connection to the substrate, while a positive polarity metal contact on the backside of the solar cell makes an electrical connection to the polysilicon emitter. An external electrical circuit may be connected to the negative and positive metal contacts to be powered by the solar cell. The positive polarity metal contact may form an infrared reflecting layer with an underlying dielectric layer for increased solar radiation collection.

  4. Fingertip contact influences human postural control

    Science.gov (United States)

    Jeka, J. J.; Lackner, J. R.

    1994-01-01

    Touch and pressure stimulation of the body surface can strongly influence apparent body orientation, as well as the maintenance of upright posture during quiet stance. In the present study, we investigated the relationship between postural sway and contact forces at the fingertip while subjects touched a rigid metal bar. Subjects were tested in the tandem Romberg stance with eyes open or closed under three conditions of fingertip contact: no contact, touch contact (postural sway when compared to the no contact, eyes closed condition. Body sway and fingertip forces were essentially in phase with force contact, suggesting that fingertip contact forces are physically counteracting body sway. Time delays between body sway and fingertip forces were much larger with light touch contact, suggesting that the fingertip is providing information that allows anticipatory innervation of musculature to reduce body sway. The results are related to observations on precision grip as well as the somatosensory, proprioceptive, and motor mechanisms involved in the reduction of body sway.

  5. Contact Allergy To Hard Contact Lens

    Directory of Open Access Journals (Sweden)

    J S Pasricha

    1985-01-01

    Full Text Available Three patients developed recurrent irritation, redness and watery discharge from their eyes after using hard contact lens. Patch tests were positive with the material of the hard contact lens and negative with teepol, sodium lauryl sulphate and material of the soft contact lens. All the three patients became alright after they stopped,using hard contact lens.

  6. Lipstick Induced Contact Leucoderma

    Directory of Open Access Journals (Sweden)

    Gupta Lalit Kumar

    2001-01-01

    Full Text Available Lipstick is a commonly used cosmetic. Its use may sometimes lead to contact dermatitis. Contact leucoderma to lipsticks however, is not common. We report a patient developing contact leucoderma to lipstick in association with contact dermatitis.

  7. Lipstick Induced Contact Leucoderma

    OpenAIRE

    Gupta Lalit Kumar; Jain Suresh Kumar; Khare Ashok Kumar

    2001-01-01

    Lipstick is a commonly used cosmetic. Its use may sometimes lead to contact dermatitis. Contact leucoderma to lipsticks however, is not common. We report a patient developing contact leucoderma to lipstick in association with contact dermatitis.

  8. EDITORIAL: Close contact Close contact

    Science.gov (United States)

    Demming, Anna

    2010-07-01

    The development of scanning probe techniques, such as scanning tunnelling microscopy [1], has often been touted as the catalyst for the surge in activity and progress in nanoscale science and technology. Images of nanoscale structural detail have served as an invaluable investigative resource and continue to fascinate with the fantastical reality of an intricate nether world existing all around us, but hidden from view of the naked eye by a disparity in scale. As is so often the case, the invention of the scanning tunnelling microscope heralded far more than just a useful new apparatus, it demonstrated the scope for exploiting the subtleties of electronic contact. The shrinking of electronic devices has been a driving force for research into molecular electronics, in which an understanding of the nature of electronic contact at junctions is crucial. In response, the number of experimental techniques in molecular electronics has increased rapidly in recent years. Scanning tunnelling microscopes have been used to study electron transfer through molecular films on a conducting substrate, and the need to monitor the contact force of scanning tunnelling electrodes led to the use of atomic force microscopy probes coated in a conducting layer as studied by Cui and colleagues in Arizona [2]. In this issue a collaboration of researchers at Delft University and Leiden University in the Netherlands report a new device architecture for the independent mechanical and electrostatic tuning of nanoscale charge transport, which will enable thorough studies of molecular transport in the future [3]. Scanning probes can also be used to pattern surfaces, such as through spatially-localized Suzuki and Heck reactions in chemical scanning probe lithography. Mechanistic aspects of spatially confined Suzuki and Heck chemistry are also reported in this issue by researchers in Oxford [4]. All these developments in molecular electronics fabrication and characterization provide alternative

  9. Organic semiconductors. Fundamental aspects of metal contacts, highly ordered films and the application in field effect transistors; Organische Halbleiter. Fundamentale Aspekte von Metallkontakten, hochgeordneten Schichten und deren Anwendung in Feldeffekttransistoren

    Energy Technology Data Exchange (ETDEWEB)

    Sachs, Soenke

    2010-05-31

    In this thesis, fundamental aspects of organic semiconductor devices are investigated and incorporated into the construction and optimization of an organic semiconductor field effect transistor (OFET). In order to approach the ''high end'' of OFETs, elaborate steps to optimize the devices are taken, despite the fact that they might not be feasible in a direct application. Well-characterized model systems are selected to study fundamental properties of devices, in particular the electronic structure at molecule/metal contacts and in the organic semiconductor bulk, as well as the growth of organic semiconductor molecules on single crystalline insulator substrates. The realization of a high performance OFET is pursued by a comprehensive approach in order to optimize particularly the interfaces of the device. Considerable progress is made towards a working OFET with best possible properties. A primary focus of this work, the investigation of the electronic structure at molecule/metal contacts and in the molecular bulk of the model system PTCDA/Ag(111) is performed using two photon photoelectron spectroscopy (2PPE). Of special interest is the excitation of the lowest unoccupied molecular orbital (LUMO) that shows different energetic relaxation mechanisms, depending on the origin of excitation. In addition to the importance of the molecule/metal contacts, the performance of OFETs is determined to a large extend by the quality of the organic semiconductor/gate insulator interface where the charge carrier channel is established. The morphology and structure of a molecular layer are investigated for diindenoperylene (DIP) molecules, adsorbed on a single crystalline Al{sub 2}O{sub 3} substrate, by atomic force microscopy and optical microscopy. Dependent on the substrate temperature during growth, the morphology shows grains with lateral dimensions of about 200 nm at 350 K which increase up to 700 nm at 450 K. This change in morphology is accompanied by

  10. Contact metallurgy optimization for ohmic contacts to InP

    DEFF Research Database (Denmark)

    Clausen, Thomas; Pedersen, Arne Skyggebjerg; Leistiko, Otto

    1991-01-01

    AuGeNi and AuZnNi metallizations to n- and p-InP were studied as a function of the annealing temperature in a Rapid Thermal Annealing (RTA) system. For n-InP (S:8×1018cm-3) a broad minimum existed from 385°C to 500°C, in which the specific contact resistance, rc, was about 10-7 ¿cm2. The lowe...

  11. Systemic contact dermatitis

    Directory of Open Access Journals (Sweden)

    Daria Nowak

    2016-02-01

    Full Text Available Systemic contact dermatitis (SCD is a skin inflammation occurring in a patient after systemic administration of a hapten, which previously caused an allergic contact skin reaction in the same person. Most frequently, hypersensitivity reactions typical for SCD occur after absorption of haptens with food or inhalation. Haptens occur mainly in the forms of metals and compounds present in natural resins, preservatives, food thickeners, flavorings and medicines. For many years, several studies have been conducted on understanding the pathogenesis of SCD in which both delayed type hypersensitivity (type IV and immediate type I are observed. Components of the complement system are also suspected to attend there. Helper T cells (Th (Th1 and Th2, cytotoxic T lymphocytes (Tc, and NK cells play a crucial role in the pathogenesis of SCD. They secrete a number of pro-inflammatory cytokines. In addition, regulatory T cells (Tregs have an important role. They control and inhibit activity of the immune system during inflammation. Tregs release suppressor cytokines and interact directly with a target cell through presentation of immunosuppressive particles at the cell surface. Diagnostic methods are generally the patch test, oral provocation test, elimination diet and lymphocyte stimulation test. There are many kinds of inflammatory skin reactions caused by systemic haptens’ distribution. They are manifested in a variety of clinical phenotypes of the disease.

  12. All-graphene edge contacts

    DEFF Research Database (Denmark)

    Jacobsen, Kåre Wedel; Falkenberg, Jesper Toft; Papior, Nick Rübner

    2016-01-01

    Using ab-initio methods we investigate the possibility of three-terminalgraphene "T-junction" devices and show that these all-graphene edge contactsare energetically feasible when the 1D interface itself is free from foreignatoms. We examine the energetics of various junction structures as a func......Using ab-initio methods we investigate the possibility of three-terminalgraphene "T-junction" devices and show that these all-graphene edge contactsare energetically feasible when the 1D interface itself is free from foreignatoms. We examine the energetics of various junction structures...... to be in therange of 1-10 kΩμm which is comparable to the best contact resistance reportedfor edge-contacted graphene-metal contacts. We conclude that conductingall-carbon T-junctions should be feasible....

  13. Colored Contact Lens Dangers

    Medline Plus

    Full Text Available ... with Colored Contact Lenses Julian: Teenager Blinded In One Eye By Non-Prescription Contact Lens Laura: Vision ... Robyn: Blurry Vision and Daily Eye Drops After One Use Facts About Colored Contacts and Halloween Safety ...

  14. Colored Contact Lens Dangers

    Medline Plus

    Full Text Available ... People, Real Problems with Colored Contact Lenses Julian: Teenager Blinded In One Eye By Non-Prescription Contact ... colored contact lenses , from the U.S. Food and Drug Administration (FDA). Are the colored lenses you are ...

  15. Colored Contact Lens Dangers

    Medline Plus

    Full Text Available ... Purchase the colored contact lenses from an eye product retailer who asks for a prescription. Follow the contact lens care directions for cleaning, disinfecting, and wearing the lenses. Never share contact ...

  16. Colored Contact Lens Dangers

    Medline Plus

    Full Text Available ... One Use Facts About Colored Contacts and Halloween Safety Colored Contact Lens Facts Over-the-Counter Costume ... use of colored contact lenses , from the U.S. Food and Drug Administration (FDA). Are the colored lenses ...

  17. Colored Contact Lens Dangers

    Medline Plus

    Full Text Available ... One Use Facts About Colored Contacts and Halloween Safety Colored Contact Lens Facts Over-the-Counter Costume ... Costume Contact Lenses Can Ruin Vision Eye Makeup Safety In fact, it is illegal to sell colored ...

  18. Colored Contact Lens Dangers

    Medline Plus

    Full Text Available ... Vision and Daily Eye Drops After One Use Facts About Colored Contacts and Halloween Safety Colored Contact Lens Facts Over-the-Counter Costume Contacts May Contain Chemicals ...

  19. Electrical contacts to individual SWCNTs: A review

    Directory of Open Access Journals (Sweden)

    Wei Liu

    2014-11-01

    Full Text Available Owing to their superior electrical characteristics, nanometer dimensions and definable lengths, single-walled carbon nanotubes (SWCNTs are considered as one of the most promising materials for various types of nanodevices. Additionally, they can be used as either passive or active elements. To be integrated into circuitry or devices, they are typically connected with metal leads to provide electrical contacts. The properties and quality of these electrical contacts are important for the function and performance of SWCNT-based devices. Since carbon nanotubes are quasi-one-dimensional structures, contacts to them are different from those for bulk semiconductors. Additionally, some techniques used in Si-based technology are not compatible with SWCNT-based device fabrication, such as the contact area cleaning technique. In this review, an overview of the investigations of metal–SWCNT contacts is presented, including the principle of charge carrier injection through the metal–SWCNT contacts and experimental achievements. The methods for characterizing the electrical contacts are discussed as well. The parameters which influence the contact properties are summarized, mainly focusing on the contact geometry, metal type and the cleanliness of the SWCNT surface affected by the fabrication processes. Moreover, the challenges for widespread application of CNFETs are additionally discussed.

  20. Contact effects in graphene nanoribbon transistors.

    Science.gov (United States)

    Liang, Gengchiau; Neophytou, Neophytos; Lundstrom, Mark S; Nikonov, Dmitri E

    2008-07-01

    The effects of the various contact types and shapes on the performance of Schottky barrier graphene nanoribbon field-effect-transistors (GNRFETs) have been investigated using a real-space quantum transport simulator based on the NEGF approach self-consistently coupled to a three-dimensional Poisson solver for treating the electrostatics. The device channel considered is a double gate semiconducting armchair nanoribbon. The types of contacts considered are (a) a semi-infinite normal metal, (b) a semi-infinite graphene sheet, (c) finite size rectangular shape armchair graphene contacts, (d) finite size wedge shape graphene contacts, and (e) zigzag graphene nanoribbon contacts. Among these different contact types, the semi-infinite graphene sheet contacts show the worst performance because of their very low density of states around the Dirac point resulting in low transmission possibility through the Schottky barrier, both at ON and OFF states. Although all other types of contacts can have significant enhancement in I ON to I OFF ratio, the zigzag GNR contacts show promising and size invariant performance due to the metallic properties.

  1. EFFECTS OF SURFACE MORPHOLOGY ON THERMAL CONTACT RESISTANCE

    Directory of Open Access Journals (Sweden)

    Haiming Huang

    2011-01-01

    Full Text Available The thermal contact resistance is common in aerospace industry, nuclear reactors and electronic equipments. The work addresses a new scheme for determining the thermal contact resistance between a smooth surface of a film and a rough surface of a metal specimen. The finite element method was used as a tool to explore the surface morphology effect on the thermal contact resistance while the temperature of the contact surface was determined by a regression method. According to the results developed, the temperature on the contact surfaces linearly drops with the increasing average height of surface roughness and nonlinearly drops with the increasing ratio between non-contact area and nominal contact area. On the other hand, the thermal contact resistance increases linearly with increases in the average height of the surface roughness. What's more, the thermal contact resistance increases in a non-linear manner as the ratio of the non-contact area to the nominal contact area is increasing.

  2. Scientific Challenges in the Risk Assessment of Food Contact Materials

    DEFF Research Database (Denmark)

    Muncke, Jane; Backhaus, Thomas; Geueke, Birgit

    2017-01-01

    Food contact articles (FCAs) are manufactured from food contact materials (FCMs) that include plastics, paper, metal, glass, and printing inks. Chemicals can migrate from FCAs into food during storage, processing, and transportation. Food contact materials' safety is evaluated using chemical risk...

  3. Ohmic contacts to InN-based materials

    Directory of Open Access Journals (Sweden)

    Sai P. O.

    2016-10-01

    Full Text Available The key aspects of ohmic contact formation to InN-based materials were investigated. Detailed analysis of studies conducted over the past three decades, allows determining the basic principles of such contacts. The contact structure properties and optimal conditions for them are presented. Different types of metallization are considered, the advantages and disadvantages of each are determined, including the basic requirements that such contact must meet. There is emphasis on the using multilayer metallization with the barrier layers. In the case of the InAlN/GaN systems, the general approaches of forming ohmic contacts were considered.

  4. The contact conductance on a molecular wire

    Science.gov (United States)

    Stojkovic, S.; Joachim, C.; Grill, L.; Moresco, F.

    2005-06-01

    On a metal-molecule-metal nanojunction, the scanning tunneling microscope (STM) scans at the precise location of the electronic metal-molecule interaction permit a measurement of the contact conductance G0. The conversion curve between the change in the STM contrast Δ h due to this interaction and G0 is presented for a series of conjugated molecular wires. At chemisorption distances, the two-valued character of the G0(Δ h) function is discussed, indicating experimental ways to evaluate G0 as a function of Δ h for different metal-molecule interaction ranges.

  5. Contact lenses following keratoplasty.

    Science.gov (United States)

    Beekhuis, W H; van Rij, G; Eggink, F A; Vreugdenhil, W; Schoevaart, C E

    1991-01-01

    Bandage contact lenses can be used following keratoplasty to protect the ocular surface and promote epithelial healing. Rigid gas permeable contact lenses are indicated to correct irregular astigmatism and anisometropia. The Rotterdam Eye Hospital fit 77 keratoplasty patients with contact lenses following their surgery. The methods of fitting contact lenses over the irregular or highly astigmatic surface of a graft are discussed.

  6. Superconductor-normal-superconductor with distributed Sharvin point contacts

    Science.gov (United States)

    Holcomb, Matthew J.; Little, William A.

    1994-01-01

    A non-linear superconducting junction device comprising a layer of high transient temperature superconducting material which is superconducting at an operating temperature, a layer of metal in contact with the layer of high temperature superconducting material and which remains non-superconducting at the operating temperature, and a metal material which is superconducting at the operating temperature and which forms distributed Sharvin point contacts with the metal layer.

  7. [Correct contact lens hygiene].

    Science.gov (United States)

    Blümle, S; Kaercher, T; Khaireddin, R

    2013-06-01

    Although contact lenses have long been established in ophthalmology, practical aspects of handling contact lenses is becoming increasingly less important in the clinical training as specialist for ophthalmology. Simultaneously, for many reasons injuries due to wearing contact lenses are increasing. In order to correct this discrepancy, information on contact lenses and practical experience with them must be substantially increased from a medical perspective. This review article deals with the most important aspects for prevention of complications, i.e. contact lens hygiene.

  8. Method for preparing metal powder, device for preparing metal powder, method for processing spent nuclear fuel

    Science.gov (United States)

    Park, Jong-Hee [Clarendon Hills, IL

    2011-11-29

    A method for producing metal powder is provided the comprising supplying a molten bath containing a reducing agent, contacting a metal oxide with the molten bath for a time and at a temperature sufficient to reduce the metal in the metal oxide to elemental metal and produce free oxygen; and isolating the elemental metal from the molten bath.

  9. PRODUCTION OF HAFNIUM METAL

    Science.gov (United States)

    Elger, G.W.; Boubel, R.W.

    1963-01-01

    This patent deals with a process of producing pure Hf metal from oxygen- contaminated gaseous Hf chloride. The oxygen compounds in the chioride gas are halogenated by contacting the gas at elevated temperature with Cl/sub 2/ in the presence of C. The Hf chloride, still in gaseous form, is contacted with molten Mg whereby Hf metal is formed and condensed on the Mg. (AEC)

  10. Sensing with Superconducting Point Contacts

    Directory of Open Access Journals (Sweden)

    Argo Nurbawono

    2012-05-01

    Full Text Available Superconducting point contacts have been used for measuring magnetic polarizations, identifying magnetic impurities, electronic structures, and even the vibrational modes of small molecules. Due to intrinsically small energy scale in the subgap structures of the supercurrent determined by the size of the superconducting energy gap, superconductors provide ultrahigh sensitivities for high resolution spectroscopies. The so-called Andreev reflection process between normal metal and superconductor carries complex and rich information which can be utilized as powerful sensor when fully exploited. In this review, we would discuss recent experimental and theoretical developments in the supercurrent transport through superconducting point contacts and their relevance to sensing applications, and we would highlight their current issues and potentials. A true utilization of the method based on Andreev reflection analysis opens up possibilities for a new class of ultrasensitive sensors.

  11. Colored Contact Lens Dangers

    Medline Plus

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    Full Text Available ... glow-in-the-dark lizard lenses, costume contacts can certainly add a spooky, eye-popping touch. But ... consideration as a standard contact lens because they can be purchased over-the-counter or on the ...

  13. Contact Us about Asbestos

    Science.gov (United States)

    How to contact EPA for more information on asbestos, including state and regional contacts, EPA’s Asbestos Abatement/Management Ombudsman and the Toxic Substances Control Act (TSCA) Assistance Information Service (TSCA Hotline).

  14. Colored Contact Lens Dangers

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    Full Text Available ... popping touch. But colored contact lenses are popular year-round, not just at Halloween. But few know ... contact lenses for Halloween or any time of year, follow these guidelines: Get an eye exam from ...

  17. Corporate Consumer Contact API

    Data.gov (United States)

    General Services Administration — The data in the Corporate Consumer Contact API is based on the content you can find in the Corporate Consumer Contact listing in the Consumer Action Handbook (PDF)....

  18. Colored Contact Lens Dangers

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  20. Colored Contact Lens Dangers

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    Full Text Available ... Contact Lens Facts Over-the-Counter Costume Contacts May Contain Chemicals Harmful to Eyes Four Ways Over- ... without a prescription are breaking the law, and may be fined $11,000 per violation. "Many of ...

  1. Colored Contact Lens Dangers

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    Full Text Available ... contact lenses , from the U.S. Food and Drug Administration (FDA). Are the colored lenses you are considering buying approved by the FDA? Check the FDA's database of approved contact lenses . Related Stories Gene Therapy ...

  2. Colored Contact Lens Dangers

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  5. Colored Contact Lens Dangers

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  6. Colored Contact Lens Dangers

    Medline Plus

    Full Text Available ... contact lenses, remove the lenses and seek immediate medical attention from an ophthalmologist. Related resources: Learn how to properly care for contact lenses . Learn about the members of ...

  7. Contact Angle Goniometer

    Data.gov (United States)

    Federal Laboratory Consortium — Description:The FTA32 goniometer provides video-based contact angle and surface tension measurement. Contact angles are measured by fitting a mathematical expression...

  8. Ultra-thin ohmic contacts for p-type nitride light emitting devices

    Science.gov (United States)

    Raffetto, Mark [Raleigh, NC; Bharathan, Jayesh [Cary, NC; Haberern, Kevin [Cary, NC; Bergmann, Michael [Chapel Hill, NC; Emerson, David [Chapel Hill, NC; Ibbetson, James [Santa Barbara, CA; Li, Ting [Ventura, CA

    2012-01-03

    A semiconductor based Light Emitting Device (LED) can include a p-type nitride layer and a metal ohmic contact, on the p-type nitride layer. The metal ohmic contact can have an average thickness of less than about 25 .ANG. and a specific contact resistivity less than about 10.sup.-3 ohm-cm.sup.2.

  9. Contact Lenses - A Review

    OpenAIRE

    Dada V; Sharma Rajiv

    1987-01-01

    A review of recent literature on contact lenses shows increasingly more studies on soft contact lenses than PMMA hard lenses The articles on contact lens wear and ulcerative keratitis have highlighted the increased risk of microbial keratitis in contact lens wearers compared to the general population, higher virulence of pathogens isolated and special association of fungi with EWSCL This high risk is due to multiple factors, organism survival in moist lens cases and cleaning solutions, microt...

  10. Contact lens in keratoconus

    OpenAIRE

    Rathi, Varsha M; Preeji S Mandathara; Srikanth Dumpati

    2013-01-01

    Contact lenses are required for the visual improvement in patients with keratoconus. Various contact lens options, such as rigid gas permeable (RGP) lenses, soft and soft toric lenses, piggy back contact lenses (PBCL), hybrid lenses and scleral lenses are availble. This article discusses about selection of a lens depending on the type of keratoconus and the fitting philosophies of various contact lenses including the starting trial lens. A Medline search was carried out for articles in the En...

  11. Colored Contact Lens Dangers

    Medline Plus

    Full Text Available ... an Ophthalmologist Patient Stories Español Eye Health / News Halloween Hazard: The Hidden Dangers of Buying Decorative Contact ... After One Use Facts About Colored Contacts and Halloween Safety Colored Contact Lens Facts Over-the-Counter ...

  12. New Cosmetic Contact Allergens

    Directory of Open Access Journals (Sweden)

    An Goossens

    2015-02-01

    Full Text Available Allergic and photo-allergic contact dermatitis, and immunologic contact urticaria are potential immune-mediated adverse effects from cosmetics. Fragrance components and preservatives are certainly the most frequently observed allergens; however, all ingredients must be considered when investigating for contact allergy.

  13. Colored Contact Lens Dangers

    Medline Plus

    Full Text Available ... Costume Contact Lenses Can Ruin Vision Eye Makeup Safety In fact, it is illegal to sell colored contact lenses without a prescription in the United States. All contact lenses are medical devices that require a prescription and proper fitting by ...

  14. Ohmic contacts to Gallium Nitride materials

    Energy Technology Data Exchange (ETDEWEB)

    Greco, Giuseppe [Consiglio Nazionale delle Ricerche—Istituto per la Microelettronica e Microsistemi (CNR-IMM), Strada VIII, n. 5 - Zona Industriale, 95121 Catania (Italy); Iucolano, Ferdinando [STMicroelectronics, Stradale Primosole 50, 95121 Catania (Italy); Roccaforte, Fabrizio, E-mail: fabrizio.roccaforte@imm.cnr.it [Consiglio Nazionale delle Ricerche—Istituto per la Microelettronica e Microsistemi (CNR-IMM), Strada VIII, n. 5 - Zona Industriale, 95121 Catania (Italy)

    2016-10-15

    Highlights: • Ohmic contacts are a crucial issue for wide band gap semiconductors devices. • This paper reviews the mechanisms of Ohmic contact formation on GaN-based materials. • Ti/Al-based contacts and multilayers (Ti/Al/X/Au) are used for n-type GaN. • Ni/Au-based bilayers are used for Ohmic contacts to p-type GaN. • Several parameters affect Ohmic contact formation to AlGaN/GaN heterostructures . • Au-free contacts are important for the integration of GaN technology on Si-fabs. - Abstract: In this review article, a comprehensive study of the mechanisms of Ohmic contact formation on GaN-based materials is presented. After a brief introduction on the physics of Ohmic contacts, a resume of the most important results obtained in literature is reported for each of the systems taken in consideration (n-type GaN, p-type GaN and AlGaN/GaN heterostructures). The optimal metallization schemes and processing conditions to obtain low resistance Ohmic contacts are presented, discussing the role of the single metals composing the stack and the modification induced by the thermal annealing, either on the metal layers or at the interface with GaN. Physical insights on the mechanism of Ohmic contact formation have been gained by correlating the temperature dependence of the electrical parameters with a morphological/structural analysis of the interface. In the case of the AlGaN/GaN systems, the influence of the heterostructure parameters on the Ohmic contacts has been taken into account adapting the classical thermionic field emission model to the presence of the two dimensional electron gas (2DEG). Finally, the state of the art of “Au-free” metallization to AlGaN/GaN heterostructures is also presented, being this latter a relevant topic for the integration of GaN technology on large scale Silicon devices fabs.

  15. Contact lens in keratoconus

    Directory of Open Access Journals (Sweden)

    Varsha M Rathi

    2013-01-01

    Full Text Available Contact lenses are required for the visual improvement in patients with keratoconus. Various contact lens options, such as rigid gas permeable (RGP lenses, soft and soft toric lenses, piggy back contact lenses (PBCL, hybrid lenses and scleral lenses are availble. This article discusses about selection of a lens depending on the type of keratoconus and the fitting philosophies of various contact lenses including the starting trial lens. A Medline search was carried out for articles in the English language with the keywords keratoconus and various contact lenses such as Rose k lens, RGP lens, hybrid lens, scleral lens and PBCL.

  16. Experimental consideration of contact resistance related to modified configuration of line contact; Sen sessyokusi no sessyoku keitai ni tomonau sessyoku teiko no jikkenteki kosatsu

    Energy Technology Data Exchange (ETDEWEB)

    Aichi, H. [Daido Institute of Technology, Aichi (Japan); Miyachi, I. [Aichi Institute of Technology, Aichi (Japan)

    1997-06-20

    The contact form of electric contact which is used on a switchgear is roughly divided to a point, a line and a plane contact. Among them, a point contact is considered as the foundation of contact form and according to the contact structures such as spherical surface vs. spherical surface and spherical surface vs. plane and so on, one of the minute circular contacts, so called a point contact, is formed. On the most of the connectors and the circuit-breakers, the line or the plane contact member is applied. Authors have been developed an unique contact model be able to measure the contact resistance of any form. In this model, it is available to select the size, the member and the configuration of contact spots by macroscopic arrangement of some metal electrodes immersed in electrolyte solution of dilute sulfuric acid. In this paper, the contact resistance of a case that changes from line to plane contact and that of several line contacts in parallel are studied. The experimental results obtained clarify that the characteristics of contact resistance changed form line to plane contact are equivalent to those of a point contact, the contact resistance of line contacts in parallel has the same characteristics as that of a long line contact and so forth. 9 refs., 8 figs.

  17. Introduction to contact mechanics

    CERN Document Server

    Fischer-Cripps, Anthony C

    2000-01-01

    Contact mechanics deals with the elastic or plastic contact between two solid objects, and is thus intimately connected with such topics as fracture, hardness, and elasticity.This text, intended for advanced undergraduates, begins with an introduction to the mechanical properties of materials, general fracture mechanics, and fractures in brittle solids.This is followed by a detailed discussion of stresses and the nature of elastic and elastic-plastic contact.

  18. Composition and doping control for metal-organic chemical vapor deposition of InP-based double heterojunction bipolar transistor with hybrid base structure consisting of GaAsSb contact and InGaAsSb graded layers

    Science.gov (United States)

    Hoshi, Takuya; Kashio, Norihide; Sugiyama, Hiroki; Yokoyama, Haruki; Kurishima, Kenji; Ida, Minoru; Matsuzaki, Hideaki

    2017-07-01

    We report on a method for composition and doping control for metalorganic chemical vapor deposition of a double heterojunction bipolar transistor (DHBT) with a hybrid base structure consisting of a compositionally graded InGaAsSb for boosting an average electron velocity and a heavily doped thin GaAsSb for lowering the base contact resistivity. The GaAsSb contact layer can be formed by simply turning off the supply of In precursor tetramethylindium (TMIn) after the growth of the composition and doping graded InGaAsSb base. Consequently, the solid composition and hole concentration of hybrid base can be properly controlled by just modulating the supply of only TMIn and carbon tetrabromide. Secondary ion mass spectroscopy for the DHBT wafer reveals that the contents of In, Ga, and C inside the base are actually modulated from the collector side to the emitter side as expected. Transmission-line-model measurements were performed for the compositionally graded-InGaAsSb/GaAsSb hybrid base. The contact resistivity is estimated to be 5.3 Ω µm2, which is lower than half the value of a compositionally graded InGaAsSb base without the GaAsSb contact layer. The results indicate that the compositionally-graded-InGaAsSb/GaAsSb-contact hybrid base structure grown by this simple method is very advantageous for obtaining DHBTs with a very high maximum oscillation frequency.

  19. Contact Quality in Participation

    DEFF Research Database (Denmark)

    Simonsen, Jesper; Jensen, Olav Storm

    2016-01-01

    We investigate the concept of participation from the perspective of quality of the contact in the communicative interactions between participants. We argue for the need for an academic-personal competence that qualifies the human contact central in all Participatory Design (PD) activities as a way...... to contribute to “an era of participation.” We describe a contact perspective in PD developed through a collaboration with body-oriented psychotherapeutic research that have specialized experiences in investigating open-minded contact and authentic meetings as body-related experiences....

  20. Contact lenses for children.

    Science.gov (United States)

    Jurkus, J M

    1996-01-01

    Contact lenses for children are used to correct a variety of conditions. This paper reviews fitting of soft, silicone elastimer, and rigid gas-permeable contact lenses for therapeutic treatment of aphakia, anisometropia, myopia, hyperopia, esotropia, irregular astigmatism, and nystagmus. Cosmetic custom designs are described for the treatment of aniridia, albinism, amblyopia, and corneal disfigurement. Working with children and gaining their trust requires inventiveness and patience. Prescribing contact lenses for them requires developing good cooperation between the child, the parents, and the practitioner. The rewards of contact lenses wear for the appropriate pediatric patients include improving not only their vision but also their quality of life.

  1. Rigid Bodies in Contact

    DEFF Research Database (Denmark)

    Niebe, Sarah Maria

    The topic of this thesis is the numerics of rigid body simulation, with focus on the contact force problem. Three contact force models are presented, followed by three contact point determination methods. To solve the contact force problem, six different numerical methods are presented, each......-Seidel (PGS), although computationally more expensive. The NNCG method has been implemented in the physics library Bullet, as of revision r2709, as an alternative to the PGS method. A subspace minimization method is developed to improve convergence of the PGS method, improving the results of large mass ratio...

  2. Allergic Contact Dermatitis

    Directory of Open Access Journals (Sweden)

    Meltem Önder

    2009-03-01

    Full Text Available Allergic contact dermatitis is the delayed type hypersensitivity reaction to exogenous agents. Allergic contact dermatitis may clinically present acutely after allergen exposure and initial sensitization in a previously sensitized individual. Acute phase is characterized by erythematous, scaly plaques. In severe cases vesiculation and bullae in exposed areas are very characteristic. Repeated or continuous exposure of sensitized individual with allergen result in chronic dermatitis. Lichenification, erythematous plaques, hyperkeratosis and fissuring may develop in chronic patients. Allergic contact dermatitis is very common dermatologic problem in dermatology daily practice. A diagnosis of contact dermatitis requires the careful consideration of patient history, physical examination and patch testing. The knowledge of the clinical features of the skin reactions to various contactans is important to make a correct diagnosis of contact dermatitis. It can be seen in every age, in children textile product, accessories and touch products are common allergens, while in adults allergic contact dermatitis may be related with topical medicaments. The contact pattern of contact dermatitis depends on fashion and local traditions as well. The localization of allergic reaction should be evaluated and patients’ occupation and hobbies should be asked. The purpose of this review is to introduce to our collaques up dated allergic contact dermatitis literatures both in Turkey and in the World.

  3. Skin contact with gold and gold alloys.

    Science.gov (United States)

    Rapson, W S

    1985-08-01

    3 types of reaction to gold merit discussion. First, there is the effect known as black dermographism, in which stroking with certain metals immediately produces well-defined black lines on the skin. Some gold alloys are amongst such metals. The evidence indicates that the effect is the result of impregnation of the skin with black metallic particles generated by mechanical abrasion of the metal by contaminants of the skin. There is no positive and unequivocal evidence of the ability of metals to mark uncontaminated skin so rapidly that it is possible to write upon it. Secondly there are the 2 related phenomena of the wear of gold jewelry, and the susceptibility to certain individuals to blackening of the skin where it is in contact with such jewelry. The occurrence of smudge, as it is often called, is not very common, but is brought to the attention of most jewelers from time to time. In extreme cases it may make it embarrassing for the person concerned to wear metallic jewelry. It would appear as if gold smudge also results mainly from mechanical abrasion of jewelry, though this may be aided and/or supplemented in some instances by corrosion of gold or gold alloy induced by certain components of the sweat. Finally, there is the question of true allergic responses to contact of the skin with gold and its alloys. Judging from the very few cases which have been recorded, such responses are extremely rare. Some recent observations on the reactions of metallic gold with amino acids and of reaction to contact of the skin with gold on the part of rheumatoid arthritis patients undergoing gold therapy, are, however, relevant in this connection.

  4. The epidemiology of contact allergy. Allergen exposure and recent trends

    DEFF Research Database (Denmark)

    Thyssen, J P

    2009-01-01

    Contact allergy is frequent among dermatitis patients and subjects in the general population. This review aims to update the reader on the epidemiology of contact allergy epidemics. It presents recent epidemiological data on metals, fragrances, hair dyes, preservatives and thiurams. It concludes ...

  5. Colored Contact Lens Dangers

    Medline Plus

    Full Text Available ... People, Real Problems with Colored Contact Lenses Julian: Teenager Blinded In One Eye By Non-Prescription Contact ... the United States. Gene Therapy May Be a Game-Changer for People With ... Professionals Link your website to EyeSmart Embed EyeSmart videos on your website Promotional materials for eye health ...

  6. Colored Contact Lens Dangers

    Science.gov (United States)

    ... People, Real Problems with Colored Contact Lenses Julian: Teenager Blinded In One Eye By Non-Prescription Contact ... the United States. Gene Therapy May Be a Game-Changer for People With ... Professionals Link your website to EyeSmart Embed EyeSmart videos on your website Promotional materials for eye health ...

  7. Contact Hamiltonian mechanics

    Energy Technology Data Exchange (ETDEWEB)

    Bravetti, Alessandro, E-mail: alessandro.bravetti@iimas.unam.mx [Instituto de Investigaciones en Matemáticas Aplicadas y en Sistemas, Universidad Nacional Autónoma de México, A. P. 70543, México, DF 04510 (Mexico); Cruz, Hans, E-mail: hans@ciencias.unam.mx [Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, A. P. 70543, México, DF 04510 (Mexico); Tapias, Diego, E-mail: diego.tapias@nucleares.unam.mx [Facultad de Ciencias, Universidad Nacional Autónoma de México, A.P. 70543, México, DF 04510 (Mexico)

    2017-01-15

    In this work we introduce contact Hamiltonian mechanics, an extension of symplectic Hamiltonian mechanics, and show that it is a natural candidate for a geometric description of non-dissipative and dissipative systems. For this purpose we review in detail the major features of standard symplectic Hamiltonian dynamics and show that all of them can be generalized to the contact case.

  8. Colored Contact Lens Dangers

    Medline Plus

    Full Text Available ... in Cleveland. "This is far from the truth." Real People, Real Problems with Colored Contact Lenses Julian: Teenager Blinded ... use of colored contact lenses , from the U.S. Food and Drug Administration (FDA). Are the colored lenses ...

  9. Colored Contact Lens Dangers

    Medline Plus

    Full Text Available ... level of care or consideration as a standard contact lens because they can be purchased over-the-counter ... Teenager Blinded In One Eye By Non-Prescription Contact Lens Laura: Vision Loss After Just 10 Hours Robyn: ...

  10. African Zoology: Contact

    African Journals Online (AJOL)

    Principal Contact. Lester Isaacs Phone: +27466229698. Fax: +2746 622 9550. Email: lester@nisc.co.za. Support Contact. NISC office. Email: info@nisc.co.za. ISSN: 2224-073X. AJOL African Journals Online. HOW TO USE AJOL... for Researchers · for Librarians · for Authors · FAQ's · More about AJOL · AJOL's Partners ...

  11. Colored Contact Lens Dangers

    Medline Plus

    Full Text Available ... Global Ophthalmology Guide Eye Health Find an Ophthalmologist Academy Store Eye Health A-Z Symptoms Glasses & Contacts Tips & Prevention News ... videos on your website Promotional materials for eye health observances EyeSmart resources are also available in Spanish . Follow The ... Public & Patients: Contact ...

  12. Animal Research International: Contact

    African Journals Online (AJOL)

    Principal Contact. Dr. J. E. Eyo Dr. Department of Zoology, University of Nig Department of Zoology, POBox 3146, University of Nigeria, Nsukka, Enugu State, Nigeria. Phone: 234 42 308030. Email: joseph.eyo@unn.edu.ng. Support Contact. N. S. Oluah Phone: +234-83732127. Email: ndubusioluah@yahoo.com.

  13. Colored Contact Lens Dangers

    Medline Plus

    Full Text Available ... medical attention from an ophthalmologist. Related resources: Learn how to properly care for contact lenses . Learn about the ... FDA's database of approved contact lenses . Related Stories How long does it take the eye to go back to its original shape after wearing ...

  14. Zimbabwe Science News: Contact

    African Journals Online (AJOL)

    Principal Contact. Prof. S Feresu Editor P.O. Box CY 124 Causeway, Harare, Zimbabwe Email: feresu@ies.uz.ac.zw. Support Contact. Prof. S Feresu Email: feresu@ies.uz.ac.zw. ISSN: 1016-1503. AJOL African Journals Online. HOW TO USE AJOL... for Researchers · for Librarians · for Authors · FAQ's · More about AJOL ...

  15. Glasses and Contact Lenses

    Science.gov (United States)

    ... really fun part of new glasses or contact lenses is how well you can see. They can make your whole world look better! Reviewed by: Jonathan H. Salvin, ... Abrasions Why Do Eyes Water? What It's Like to Be Color Blind Contact ...

  16. Contact Lens Risks

    Science.gov (United States)

    ... any lens solution. Do not expose your contact lenses to any water: tap, bottled, distilled, lake or ocean water. Never ... resistant to treatment and cure. Remove your contact lenses before swimming. ... in swimming pool water, hot tubs, lakes and the ocean Replace your ...

  17. Nigerian Food Journal: Contact

    African Journals Online (AJOL)

    Nigerian Food Journal. ... Nigerian Food Journal: Contact. Journal Home > About the Journal > Nigerian Food Journal: Contact. Log in or Register to get access to full text downloads. ... Mailing Address. Department of Food Science and Technology University of Agriculture, Makurdi, Nigeria ...

  18. Contact Hamiltonian Mechanics

    OpenAIRE

    Bravetti, Alessandro; Cruz, Hans; Tapias, Diego

    2016-01-01

    In this work we introduce contact Hamiltonian mechanics, an extension of symplectic Hamiltonian mechanics, and show that it is a natural candidate for a geometric description of non-dissipative and dissipative systems. For this purpose we review in detail the major features of standard symplectic Hamiltonian dynamics and show that all of them can be generalized to the contact case.

  19. Sciences & Nature: Contact

    African Journals Online (AJOL)

    Principal Contact. Ehouan Etienne Ehile Professor University of Abobo-Adjamé 02 BP 801 Abidjan 02. Phone: (+225) 2030 4201. Fax: (+225) 2030 4203. Email: eh_ehile@yahoo.fr. Support Contact. Irie Zoro Bi Email: banhiakalou@yahoo.fr. ISSN: 1812-0741. AJOL African Journals Online. HOW TO USE AJOL.

  20. LBS Management Review: Contact

    African Journals Online (AJOL)

    Principal Contact. Dr Obinna Muogboh Managing Editor Lagos Business School Pan African University 2 Ahmed Onibudo Street, P.O. Box 73688, Victoria Island, Lagos, NIGERIA Email: omuogboh@lbs.edu.ng. Support Contact. Editor Email: omuogboh@lbs.edu.ng. ISSN: 1118-3713. AJOL African Journals Online.

  1. Africa Insight: Contact

    African Journals Online (AJOL)

    Principal Contact. Mmakwena Chipu Assistant Editor: Publications Africa Institute of South Africa. Human Sciences Research Council. Private Bag X41. Pretoria. 0001. South Africa. Phone: +27 12 316 9762. Email: mchipu@hsrc.ac.za. Support Contact. Rosemary Lepule Phone: +27 12 316 9743. Email: rlepule@hsrc.ac.za.

  2. Colored Contact Lens Dangers

    Medline Plus

    Full Text Available ... Halloween Hazard: The Hidden Dangers of Buying Decorative Contact Lenses Without a Prescription Leer en Español: Peligros asociados ... the truth." Real People, Real Problems with Colored Contact Lenses Julian: Teenager Blinded In One Eye By Non- ...

  3. African Health Sciences: Contact

    African Journals Online (AJOL)

    Principal Contact. Dr James Tumwine Editor-in-Chief. Makerere University Medical School P. O. Box 7072 Kampala Uganda. Phone: 256-41-530020/1. Email: kabaleimc@gmail.com. Support Contact. Pauline Salamula Email: paulinesalamula@gmail.com. ISSN: 1680-6905. AJOL African Journals Online. HOW TO USE ...

  4. Factor XII Contact Activation.

    Science.gov (United States)

    Naudin, Clément; Burillo, Elena; Blankenberg, Stefan; Butler, Lynn; Renné, Thomas

    2017-11-01

    Contact activation is the surface-induced conversion of factor XII (FXII) zymogen to the serine protease FXIIa. Blood-circulating FXII binds to negatively charged surfaces and this contact to surfaces triggers a conformational change in the zymogen inducing autoactivation. Several surfaces that have the capacity for initiating FXII contact activation have been identified, including misfolded protein aggregates, collagen, nucleic acids, and platelet and microbial polyphosphate. Activated FXII initiates the proinflammatory kallikrein-kinin system and the intrinsic coagulation pathway, leading to formation of bradykinin and thrombin, respectively. FXII contact activation is well characterized in vitro and provides the mechanistic basis for the diagnostic clotting assay, activated partial thromboplastin time. However, only in the past decade has the critical role of FXII contact activation in pathological thrombosis been appreciated. While defective FXII contact activation provides thromboprotection, excess activation underlies the swelling disorder hereditary angioedema type III. This review provides an overview of the molecular basis of FXII contact activation and FXII contact activation-associated disease states. Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.

  5. Colored Contact Lens Dangers

    Medline Plus

    Full Text Available ... from the truth." Real People, Real Problems with Colored Contact Lenses Julian: Teenager Blinded In One Eye By Non- ... Safety In fact, it is illegal to sell colored contact lenses without a prescription in the United States. All ...

  6. Contact Lenses - A Review

    Directory of Open Access Journals (Sweden)

    Dada V

    1987-01-01

    Full Text Available A review of recent literature on contact lenses shows increasingly more studies on soft contact lenses than PMMA hard lenses The articles on contact lens wear and ulcerative keratitis have highlighted the increased risk of microbial keratitis in contact lens wearers compared to the general population, higher virulence of pathogens isolated and special association of fungi with EWSCL This high risk is due to multiple factors, organism survival in moist lens cases and cleaning solutions, microtrauma to the corneal epithelium by repeated insertion and removal, corneal hypoxia and lens deposits in soft lenses Special problems of tonometry in eyes with bandage soft lenses and contact lens sterilization have been studied and useful suggestions have come forth from the authors

  7. Contact materials for nanoelectronics

    KAUST Repository

    Alshareef, Husam N.

    2011-02-01

    In this article, we review current research activities in contact material development for electronic and nanoelectronic devices. A fundamental issue in contact materials research is to understand and control interfacial reactions and phenomena that modify the expected device performance. These reactions have become more challenging and more difficult to control as new materials have been introduced and as device sizes have entered the deep nanoscale. To provide an overview of this field of inquiry, this issue of MRS Bulletin includes articles on gate and contact materials for Si-based devices, junction contact materials for Si-based devices, and contact materials for alternate channel substrates (Ge and III-V), nanodevices. © 2011 Materials Research Society.

  8. Intergroup contact theory.

    Science.gov (United States)

    Pettigrew, T F

    1998-01-01

    Allport specified four conditions for optimal intergroup contact: equal group status within the situation, common goals, intergroup cooperation and authority support. Varied research supports the hypothesis, but four problems remain. 1. A selection bias limits cross-sectional studies, since prejudiced people avoid intergroup contact. Yet research finds that the positive effects of cross-group friendship are larger than those of the bias. 2. Writers overburden the hypothesis with facilitating, but not essential, conditions. 3. The hypothesis fails to address process. The chapter proposes four processes: learning about the outgroup, changed behavior, affective ties, and ingroup reappraisal. 4. The hypothesis does not specify how the effects generalize to other situations, the outgroup or uninvolved outgroups. Acting sequentially, three strategies enhance generalization-decategorization, salient categorization, and recategorization. Finally, both individual differences and societal norms shape intergroup contact effects. The chapter outlines a longitudinal intergroup contact theory. It distinguishes between essential and facilitating factors, and emphasizes different outcomes for different stages of contact.

  9. Development of economical improved thick film solar cell contact

    Science.gov (United States)

    Ross, B.

    1979-01-01

    Metal screened electrodes were investigated with base metal pastes and silver systems being focused upon. Contact resistance measurements were refined. A facility allowing fixing in hydrogen and other atmospheres was acquired. Several experiments were made applying screenable pastes to solar cells. Doping investigations emphasized eutectic alloys reduced to powders. Metal systems were reviewed and base metal experiments were done with nickel and copper using lead and tin as the frit metals. Severe adhesion problems were experienced with hydrogen atmospheres in all metal systems. A two step firing schedule was devised. Aluminum-silicon and aluminum-germanium eutectic doping additions to copper pastes were tried on 2 1/4 in diameter solar cell back contacts, both with good results.

  10. Telescopic vision contact lens

    Science.gov (United States)

    Tremblay, Eric J.; Beer, R. Dirk; Arianpour, Ashkan; Ford, Joseph E.

    2011-03-01

    We present the concept, optical design, and first proof of principle experimental results for a telescopic contact lens intended to become a visual aid for age-related macular degeneration (AMD), providing magnification to the user without surgery or external head-mounted optics. Our contact lens optical system can provide a combination of telescopic and non-magnified vision through two independent optical paths through the contact lens. The magnified optical path incorporates a telescopic arrangement of positive and negative annular concentric reflectors to achieve 2.8x - 3x magnification on the eye, while light passing through a central clear aperture provides unmagnified vision.

  11. Electroplated contacts and porous silicon for silicon based solar cells applications

    Energy Technology Data Exchange (ETDEWEB)

    Kholostov, Konstantin, E-mail: kholostov@diet.uniroma1.it [Department of information engineering, electronics and telecommunications, University of Rome “La Sapienza”, Via Eudossiana 18, 00184 Rome (Italy); Serenelli, Luca; Izzi, Massimo; Tucci, Mario [Enea Casaccia Research Centre Rome, via Anguillarese 301, 00123 Rome (Italy); Balucani, Marco [Department of information engineering, electronics and telecommunications, University of Rome “La Sapienza”, Via Eudossiana 18, 00184 Rome (Italy); Rise Technology S.r.l., Lungomare Paolo Toscanelli 170, 00121 Rome (Italy)

    2015-04-15

    Highlights: • Uniformity of the Ni–Si interface is crucial for performance of Cu–Ni contacts on Si. • Uniformly filled PS is the key to obtain the best performance of Cu–Ni contacts on Si. • Optimization of anodization and electroplating allows complete filling of PS layer. • Highly adhesive and low contact resistance Cu–Ni contacts are obtained on Si. - Abstract: In this paper, a two-layer metallization for silicon based solar cells is presented. The metallization consists of thin nickel barrier and thick copper conductive layers, both obtained by electrodeposition technique suitable for phosphorus-doped 70–90 Ω/sq solar cell emitter formed on p-type silicon substrate. To ensure the adhesion between metal contact and emitter a very thin layer of mesoporous silicon is introduced on the emitter surface before metal deposition. This approach allows metal anchoring inside pores and improves silicon–nickel interface uniformity. Optimization of metal contact parameters is achieved varying the anodization and electrodeposition conditions. Characterization of contacts between metal and emitter is carried out by scanning electron microscopy, specific contact resistance and current–voltage measurements. Mechanical strength of nickel–copper contacts is evaluated by the peel test. Adhesion strength of more than 4.5 N/mm and contact resistance of 350 μΩ cm{sup 2} on 80 Ω/sq emitter are achieved.

  12. Experimental consideration on the contact resistance caused by the distribution of contact spots with the contact model using electrolyte bath; Denkai yokuso wo mochiita sesshoku model ni yoru sesshokuten no bunpu to sesshoku teiko tokusei ni kansuru jikkenteki kosatsu

    Energy Technology Data Exchange (ETDEWEB)

    Aichi, H. [Daido Institute of Technology, Aichi (Japan); Miyachi, I. [Aichi Institute of Technology, Aichi (Japan)

    1996-09-20

    Electric contact members are classified by the form such as a point, a line, and a plane. Particularly, the point contact member which makes a small circular contact spot is basis of the contact form. Also, the plane contact member will make many contact spots which are different in size and distributing over the contacting portion. Authors have been developing the contact model to measure the contact resistance. In this model, it is available to select the size, the number, and the arrangement of contact spots by the macroscopical contact spots which are formed with some metal electrodes arranged in electrolyte solution of dilute sulfuric acid. In this paper, the fundamental characteristics of the contact resistance caused by the construction of current are investigated with 1 to 3 contact spot models. Then the relations between the contact resistance and the distribution of the contact spots are examined with 2 to 9 multi-contact spot models. As the results, it is cleared that the proposed contact model presents the successful experimental method for the analysis of the contact resistance. 9 refs., 8 tabs.

  13. Colored Contact Lens Dangers

    Medline Plus

    Full Text Available ... Hidden Dangers of Buying Decorative Contact Lenses Without a Prescription Leer en Español: Peligros asociados con los ... 2013 It started as an impulsive buy from a souvenir shop, but 10 hours after she first ...

  14. Colored Contact Lens Dangers

    Medline Plus

    Full Text Available ... FDA's database of approved contact lenses . Related Stories Gene Therapy May Be a Game-Changer for People ... Eyes Aug 16, 2016 More Eye Health News Gene Therapy May Be a Game-Changer for People ...

  15. Colored Contact Lens Dangers

    Medline Plus

    Full Text Available ... sell contacts without a prescription are breaking the law, and may be fined $11,000 per violation. " ... American Academy of Ophthalmology 2017 Our Sites EyeWiki International Society of Refractive Surgery * Required * First Name: * Last ...

  16. Colored Contact Lens Dangers

    Medline Plus

    Full Text Available ... she said. "I now live with a corneal scar, vision damage and a drooping eyelid." To safely ... database of approved contact lenses . Related Stories Gene Therapy May Be a Game-Changer for People With ...

  17. Colored Contact Lens Dangers

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    Full Text Available ... Multimedia Public & Patients: Contact Us About the Academy Jobs at the Academy Financial Relationships with Industry Medical Disclaimer Privacy Policy Terms of Service For Advertisers For Media Ophthalmology ...

  18. Colored Contact Lens Dangers

    Medline Plus

    Full Text Available ... use of colored contact lenses , from the U.S. Food and Drug Administration (FDA). Are the colored lenses ... and Your Eyes Aug 16, 2016 More Eye Health News Gene Therapy May Be a Game-Changer ...

  19. Colored Contact Lens Dangers

    Medline Plus

    Full Text Available ... about the members of the eye-care team . Consumer warning about the improper use of colored contact ... Eyes SEP 20, 2017 By Dan Gudgel A report published in a medical journal reinforces what that ...

  20. Colored Contact Lens Dangers

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    Full Text Available ... New Dry Eye Treatment is a Tear-Jerker JUL 21, 2017 By Susanne Medeiros Patients suffering from ... ointments. 27 Contact Lenses Found in Woman’s Eye JUL 17, 2017 By Susanne Medeiros and Beatrice Shelton ...

  1. Colored Contact Lens Dangers

    Medline Plus

    Full Text Available ... medical attention from an ophthalmologist. Related resources: Learn how to properly care for contact lenses . Learn about ... People With Inherited Retinal Disease Oct 30, 2017 How long does it take the eye to go ...

  2. Colored Contact Lens Dangers

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    Full Text Available ... Ophthalmology Guide Eye Health Find an Ophthalmologist Academy Store Eye Health A-Z Symptoms Glasses & Contacts Tips & ... salons, novelty shops or in pop-up Halloween stores are not FDA-approved and are being sold ...

  3. Colored Contact Lens Dangers

    Medline Plus

    Full Text Available ... lentes de contacto de color Sep. 26, 2013 It started as an impulsive buy from a souvenir ... Can Ruin Vision Eye Makeup Safety In fact, it is illegal to sell colored contact lenses without ...

  4. Journal of Humanities: Contact

    African Journals Online (AJOL)

    Principal Contact. Dr. Japhet Bakuwa Copy and Production Editor Chancellor College Publications Journal of Humanities Chancellor College Publications PO Box 280 Zomba Malawi Email: jbakuwa@cc.ac.mw ...

  5. Colored Contact Lens Dangers

    Medline Plus

    Full Text Available ... Patient Stories Español Eye Health / News Halloween Hazard: The Hidden Dangers of Buying Decorative Contact Lenses Without a Prescription Leer en Español: Peligros asociados con los ...

  6. Colored Contact Lens Dangers

    Medline Plus

    Full Text Available ... in beauty salons, novelty shops or in pop-up Halloween stores are not FDA-approved and are ... share contact lenses with another person. Get follow up exams with your eye care provider. If you ...

  7. Colored Contact Lens Dangers

    Medline Plus

    Full Text Available ... use of colored contact lenses , from the U.S. Food and Drug Administration (FDA). Are the colored lenses you are ... With Inherited Retinal Disease Oct 30, 2017 How long does it take ...

  8. Colored Contact Lens Dangers

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    Full Text Available ... Contact Lens-Related Eye Infections Mar 01, 2017 New Technology Helps the Legally Blind Be More Independent ... tech and from super cool to super gross. New treatment possibilities were a feel-good favorite. But ...

  9. Colored Contact Lens Dangers

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    Full Text Available ... Eye By Non-Prescription Contact Lens Laura: Vision Loss After Just 10 Hours Robyn: Blurry Vision and ... Therapy Approved to Treat Rare Cause of Vision Loss DEC 21, 2017 By Dan Gudgel The U.S. ...

  10. Tomato contact dermatitis

    DEFF Research Database (Denmark)

    Paulsen, Evy; Christensen, Lars P; Andersen, Klaus Ejner

    2012-01-01

    The tomato plant (Solanum lycopersicum) is an important crop worldwide. Whereas immediate-type reactions to tomato fruits are well known, contact dermatitis caused by tomatoes or tomato plants is rarely reported. The aims of this study were to present new data on contact sensitization to tomato...... plants and review the literature on contact dermatitis caused by both plants and fruits. An ether extract of tomato plants made as the original oleoresin plant extracts, was used in aimed patch testing, and between 2005 and 2011. 8 of 93 patients (9%) tested positive to the oleoresin extracts....... This prevalence is in accordance with the older literature that reports tomato plants as occasional sensitizers. The same applies to tomato fruits, which, in addition, may cause protein contact dermatitis. The allergens of the plant are unknown, but both heat-stable and heat-labile constituents seem...

  11. Colored Contact Lens Dangers

    Medline Plus

    Full Text Available ... lens. In Butler's case, the lenses caused an infection and left her with a corneal abrasion. "I ... lenses? Sep 13, 2017 Contact Lens-Related Eye Infections Mar 01, 2017 New Technology Helps the Legally ...

  12. Colored Contact Lens Dangers

    Medline Plus

    Full Text Available ... sell contacts without a prescription are breaking the law, and may be fined $11,000 per violation. " ... Academy of Ophthalmology 2017 Our Sites EyeWiki International Society of Refractive Surgery * Required * First Name: * Last Name: ...

  13. Colored Contact Lens Dangers

    Medline Plus

    Full Text Available ... had not been properly fitted by an eye care professional, the lenses stuck to my eye like ... lenses do not require the same level of care or consideration as a standard contact lens because ...

  14. Colored Contact Lens Dangers

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    Full Text Available ... for people to use colored contact lenses to enhance their costumes. From blood-drenched vampire eyes to ... Ophthalmologist Browse Answers Free Newsletter Get ophthalmologist-reviewed tips and information about eye health and preserving your ...

  15. Colored Contact Lens Dangers

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    Full Text Available ... The Academy Professionals: Education Guidelines News Multimedia Public & Patients: Contact Us About the Academy Jobs at the Academy Financial Relationships with Industry Medical Disclaimer Privacy Policy Terms of ...

  16. Colored Contact Lens Dangers

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    Full Text Available ... impulsive buy from a souvenir shop, but 10 hours after she first put in a pair of ... Contact Lens Laura: Vision Loss After Just 10 Hours Robyn: Blurry Vision and Daily Eye Drops After ...

  17. Colored Contact Lens Dangers

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    Full Text Available ... MD, professor of ophthalmology at Case Western Reserve University in Cleveland. "This is far from the truth." ... Multimedia Public & Patients: Contact Us About the Academy Jobs at the Academy Financial Relationships with Industry Medical ...

  18. Colored Contact Lens Dangers

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    Full Text Available ... Hidden Dangers of Buying Decorative Contact Lenses Without a Prescription Leer en Español: Peligros asociados con los ... contacto de color Sep. 26, 2013 It started as an impulsive buy from a souvenir shop, but ...

  19. Colored Contact Lens Dangers

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    Full Text Available ... Contact Lens-Related Eye Infections Mar 01, 2017 New Technology Helps the Legally Blind Be More Independent ... at bedtime, can significantly slow the progression o… New Dry Eye Treatment is a Tear-Jerker JUL ...

  20. Colored Contact Lens Dangers

    Medline Plus

    Full Text Available ... contact lenses for Halloween or any time of year, follow these guidelines: Get an eye exam from a licensed eye care professional such as an ophthalmologist — an eye medical ...

  1. Colored Contact Lens Dangers

    Medline Plus

    Full Text Available ... colored contact lenses to enhance their costumes. From blood-drenched vampire eyes to glow-in-the-dark ... properly fitted may scratch the eye or cause blood vessels to grow into the cornea. Even if ...

  2. Colored Contact Lens Dangers

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    Full Text Available ... Health A-Z Symptoms Glasses & Contacts Tips & Prevention News Ask an Ophthalmologist Patient Stories Español Eye Health / News Halloween Hazard: The Hidden Dangers of Buying Decorative ...

  3. Colored Contact Lens Dangers

    Medline Plus

    Full Text Available ... be purchased over-the-counter or on the Internet," says Thomas Steinemann, MD, professor of ophthalmology at ... ask for a prescription. There is no such thing as a "one size fits all" contact lens. ...

  4. Ergonomics SA: Contact

    African Journals Online (AJOL)

    Principal Contact. Mrs June McDougall. Rhodes University. Department of Human Kinetics and Ergonomics. P.O. Box 94. Rhodes University. Grahamstown. 6140. Phone: +27 46 6038471. Email: j.mcdougall@ru.ac.za ...

  5. Occupational Contact Dermatitis

    Directory of Open Access Journals (Sweden)

    Sasseville Denis

    2008-06-01

    Full Text Available Occupational contact dermatitis accounts for 90% of all cases of work-related cutaneous disorders. It can be divided into irritant contact dermatitis, which occurs in 80% of cases, and allergic contact dermatitis. In most cases, both types will present as eczematous lesions on exposed parts of the body, notably the hands. Accurate diagnosis relies on meticulous history taking, thorough physical examination, careful reading of Material Safety Data Sheets to distinguish between irritants and allergens, and comprehensive patch testing to confirm or rule out allergic sensitization. This article reviews the pathogenesis and clinical manifestations of occupational contact dermatitis and provides diagnostic guidelines and a rational approach to management of these often frustrating cases.

  6. Colored Contact Lens Dangers

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    Full Text Available ... by an eye care professional, the lenses stuck to my eye like a suction cup." Halloween is a popular time for people to use colored contact lenses to enhance their costumes. ...

  7. Colored Contact Lens Dangers

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    Full Text Available ... Patient Stories Español Eye Health / News Halloween Hazard: The Hidden Dangers of Buying Decorative Contact Lenses Without ... been properly fitted by an eye care professional, the lenses stuck to my eye like a suction ...

  8. Colored Contact Lens Dangers

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    Full Text Available ... videos on your website Promotional materials for eye health observances EyeSmart resources are also available in Spanish . Follow The Academy Professionals: Education Guidelines News Multimedia Public & Patients: Contact Us About the Academy Jobs at ...

  9. Colored Contact Lens Dangers

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    Full Text Available ... colored contact lenses , from the U.S. Food and Drug Administration (FDA). Are the colored lenses you are ... from dry eye now have a completely new, drug-free alternative to lubricating eye drops and topical ...

  10. The impact of contact

    Science.gov (United States)

    Finney, B.

    1986-10-01

    Scenarios of the impact on human society of radio contact with an extraterrestrial civilization are presented. Some believe that contact with advanced extraterrestrials would quickly devastate the human spirit, while others believe that these super-intelligent beings would show the inhabitants of the earth how to live in peace. It is proposed that the possible existence of extraterrestrial civilizations and the development of means of studying and communicating with them need to be considered.

  11. Contact Lens Compliance

    OpenAIRE

    Jinabhai, A.

    2013-01-01

    Although contact lens-related complications are rare, and most are managed without any lasting side-effects, several reports have identified a variety of risk factors associated with lens wear complications. Among these risk factors, some are unalterable, such as age or gender. Others, however, are modifiable, for example, poor lens case hygiene or hand-washing and, therefore, can be targeted to maximise successful lens wear. This article reviews different aspects of contact lens non-compliance

  12. PREFACE: Non-contact AFM Non-contact AFM

    Science.gov (United States)

    Giessibl, Franz J.; Morita, Seizo

    2012-02-01

    Kelvin probe force microscopy for Si surfaces by taking account of chemical forces Masaru Tsukada, Akira Masago and Mamoru Shimizu Reversal of atomic contrast in scanning probe microscopy on (111) metal surfaces M Ondrácek, C González and P Jelínek Mechanical properties of H2Pc self-assembled monolayers at the single molecule level by noncontact atomic force microscopy Han-Qing Mao, Na Li, Xi Chen and Qi-Kun Xue High-resolution imaging of C60 molecules using tuning-fork-based non-contact atomic force microscopy R Pawlak, S Kawai, S Fremy, T Glatzel and E Meyer NC-AFM contrast formation on the calcite (101¯4) surface Philipp Rahe, Jens Schütte and Angelika Kühnle Imaging and manipulation of adatoms on an alumina surface by noncontact atomic force microscopy G H Simon, M Heyde and H-J Freund Three-dimensional scanning force/tunneling spectroscopy at room temperature Yoshiaki Sugimoto, Keiichi Ueda, Masayuki Abe and Seizo Morita Imaging and manipulation of the Si(100) surface by small-amplitude NC-AFM at zero and very low applied biasA Sweetman, R Danza, S Gangopadhyay and P Moriarty Manipulation of individual water molecules on CeO2(111) S Torbrügge, O Custance, S Morita and M Reichling FM-AFM imaging of a commercial polyethylene film immersed in n-dodecaneTakumi Hiasa, Tomoki Sugihara, Kenjiro Kimura and Hiroshi Onishi

  13. Black phosphorus transistors with van der Waals-type electrical contacts.

    Science.gov (United States)

    Quhe, Ruge; Wang, Yangyang; Ye, Meng; Zhang, Qiaoxuan; Yang, Jie; Lu, Pengfei; Lei, Ming; Lu, Jing

    2017-09-28

    Contact engineering is a possible solution to decrease the pervasive Schottky barrier in a two dimensional (2D) material transistor with bulk metal electrodes. In this paper, two kinds of typical van der Waals (vdW)-type electrical contacts (a 2D metal contact and a 2D material/bulk metal hybrid contact) in monolayer (ML) black phosphorus (BP) transistors are investigated by ab initio energy band calculations and quantum transport simulations. Compared with the traditional bulk metal Ni contact, the gate electrostatic control is significantly improved by using both 2D graphene and borophene electrodes featuring a decrease of 30-50% in the subthreshold swing and an increase by a factor of 4-7 in the on-state current due to the depressed metal induced gap states and reduced screening of the 2D metal electrodes to the gate. In contrast, graphene insertion between the Ni electrode and ML BP shows only a slight improvement in the gate electrostatic control ability and BN insertion shows almost no improvement. The higher efficiency using the 2D metal contact than the 2D material/bulk metal hybrid contact in improving the ML BP FET device performance also provides helpful guidance in the selection of vdW-type electrical contacts of other 2D transistors.

  14. Laryngeal contact granuloma.

    Science.gov (United States)

    Wani, M K; Woodson, G E

    1999-10-01

    To report outcomes of treatment for laryngeal contact granuloma. Prospective treatment of 21 patients with laryngeal contact granulomas using proton-pump inhibitor (PPI) medication. Patients were diagnosed and followed by office endoscopy and patient interview. Three patients did not tolerate PPI medication and were managed by treatment with type 2 histamine (H2) blockers. The lesion completely resolved in 14 of the 18 patients maintained on PPI medication, and significantly regressed in the other 4. Residual granulomas were surgically excised in one patient. Lesions resolved in two patients following injection of botulinum toxin into one thyroarytenoid muscle. One patient had a residual lesion, but symptoms were controlled by medication, and he declined treatment with botulinum toxin. Of the three patients treated with H2-blocker medication, the lesion resolved in only one. PPI medication is effective in the treatment of laryngeal contact granuloma, even in the absence of identifiable symptoms of gastroesophageal reflux.

  15. Rough Surface Contact

    Directory of Open Access Journals (Sweden)

    T Nguyen

    2017-06-01

    Full Text Available This paper studies the contact of general rough curved surfaces having nearly identical geometries, assuming the contact at each differential area obeys the model proposed by Greenwood and Williamson. In order to account for the most general gross geometry, principles of differential geometry of surface are applied. This method while requires more rigorous mathematical manipulations, the fact that it preserves the original surface geometries thus makes the modeling procedure much more intuitive. For subsequent use, differential geometry of axis-symmetric surface is considered instead of general surface (although this “general case” can be done as well in Chapter 3.1. The final formulas for contact area, load, and frictional torque are derived in Chapter 3.2.

  16. ALLERGIC CONTACT DERMATITIS

    Directory of Open Access Journals (Sweden)

    Trisna Yuliharti Tersinanda

    2013-07-01

    Full Text Available Normal 0 false false false EN-US X-NONE X-NONE Allergic contact dermatitis is an immunologic reaction that tends to involve the surrounding skin and may even spread beyond affected sites. This skin disease is one of the more frequent, and costly dermatologic problems. Recent data from United Kingdom and United States suggest that the percentage of occupational contact dermatitis due to allergy may be much higher, thus raising the economic impact of occupational allergic contact dermatitis. There is not enough data about the epidemiology of allergic contact dermatitis in Indonesia, however based on research that include beautician in Denpasar, about 27,6 percent had side effect of cosmetics, which is 25,4 percent of it manifested as allergic contact dermatitis. Diagnosis of allergic contact dermatitis is based on anamnesis, physical examination, patch test, and this disease should be distinguished from other eczematous skin disease. The management is prevention of allergen exposure, symptomatic treatment, and physicochemical barrier /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin-top:0in; mso-para-margin-right:0in; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0in; line-height:115%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;}

  17. Psoriasis and Contact Sensitivitiy

    Directory of Open Access Journals (Sweden)

    Deniz Arlı

    2013-03-01

    Full Text Available Objective: The aim of this study was to investigate the frequency of contact sensitivity in patients with psoriasis, whether there was an association between clinical types and contact sensitivity, whether patch test is a factor that causes Koebner reaction and frequency of contact sensitivity against commonly used topical corticosteroids. Methods: Fifty patients with psoriasis and 50 healthy volunteers were included in this study and ‘European standard series' and test units of active ingredients of some corticosteroids were performed on their upper back. The patches were read on hours 24, 48 and on day 7 in order to detect delayed allergic reactions and also Koebner reaction. The results of both groups were compared by using chi-square test. Results: At the end of the patch test allergic reaction was observed in 7 of 50 (14% patients with psoriasis and 12 of 50 (24% healthy volunteers. There was no statistically significant difference between allergic reaction of study group and healthy volunteers. There was no statistically significant difference between the clinical types of psoriasis and allergic contact sensitivity. The frequency of reaction increased in individuals having a positive sensitivity history to any substance in both patient and control groups. Reaction to topical steroids was not seen in any patients. Koebner phenomenon due to patch test was also not seen in any patients. Conclusion: We did not show any association between psoriasis and contact sensitivity in this study. We believe that contact allergens should be determined by using patch test in psoriatic patients with a positive history to any substance.

  18. Spa contact dermatitis.

    Science.gov (United States)

    Yankura, Jessica A; Marks, James G; Anderson, Bryan E; Adams, David R

    2008-01-01

    Potassium monopersulfate (MPS) is widely used in spa and pool "shock" treatments, yet contact dermatitis associated with MPS has been rarely reported. A patient presented with a generalized scattered dermatitis from the neck down that worsened after spa use. Patch testing elicited a ++ reaction to ammonium persulfate. Contact with ammonium persulfate was ruled out; however, MPS, which can cross-react with ammonium persulfate, was found to be the active ingredient in the patient's spa shock treatments. The dermatitis cleared after the patient switched to a hydrogen peroxide-based shock treatment.

  19. Instability of Contact Resistance in MEMS and NEMS DC Switches under Low Force: the Role of Alien Films on the Contact Surface

    Directory of Open Access Journals (Sweden)

    Haodong Qiu

    2013-11-01

    Full Text Available The metal contact is one of the most crucial parts in ohmic-contact microelectromechanical (MEMS switches, as it determines the device performance and reliability. It has been observed that there is contact instability when the contact force is below a threshold value (minimum contact force. However, there has been very limited knowledge so far about the unstable electrical contact behavior under low contact force. In this work, the instability of Au-Au micro/nano-contact behavior during the initial stage of contact formation is comprehensively investigated for the first time. It has been found that the alien film on the contact surface plays a critical role in determining the contact behavior at the initial contact stage under low contact force. A strong correlation between contact resistance fluctuation at the initial contact stage and the presence of a hydrocarbon alien film on the contact surface is revealed. The enhancement of contact instability due to the alien film can be explained within a framework of trap-assisted tunneling.

  20. Contact sensitivity in palmar hyperkeratotic dermatitis

    Directory of Open Access Journals (Sweden)

    Minocha Y

    1993-01-01

    Full Text Available 230 patients presenting with palmar hyperkeratotic dermatitis were investigated by patch tests against various antigens depending upon occupation of the patients. Contact sensitivity was detected in 130 patients comprising of housewives (55, businessmen (20, farmers (15, teachers / clerks / students (13, doctors and nurses (9, factory workers and labourers (8, massons (7 and motor mechanics (3. Vegetables were found to be the most common agents followed by detergents and metals predominantly affecting housewives. Among the vegetables, garlic and onion were the most potent sensitizers whereas nickel was a common sensitizer among metals. Occupational factors were seen to have some influence in relation to the causative agents as indicated by higher positivity of vegetables in housewives; detergents, metals, rubber, leather, plastics in businessmen, teachers, clerks and students; fertilizers or animal foods in farmers; drugs in doctors and nurses and chromium and cobalt in massons.

  1. Pile on the metal

    Science.gov (United States)

    Lee, Dung-Hai

    2008-09-01

    Discovering superconductivity above room temperature is a dream for modern science and technology. Now, theorists propose that for certain types of superconductors, contact with a metal layer could greatly increase the transition temperatures of these materials—in some cases by as much as an order of magnitude.

  2. Contact engineering for nano-scale CMOS

    KAUST Repository

    Hussain, Muhammad Mustafa

    2012-09-10

    High performance computation with longer battery lifetime is an essential component in our today\\'s digital electronics oriented life. To achieve these goals, field effect transistors based complementary metal oxide semiconductor play the key role. One of the critical requirements of transistor structure and fabrication is efficient contact engineering. To catch up with high performance information processing, transistors are going through continuous scaling process. However, it also imposes new challenges to integrate good contact materials in a small area. This can be counterproductive as smaller area results in higher contact resistance thus reduced performance for the transistor itself. At the same time, discovery of new one or two-dimensional materials like nanowire, nanotube, or atomic crystal structure materials, introduces new set of challenges and opportunities. In this paper, we are reviewing them in a synchronized fashion: fundamentals of contact engineering, evolution into non-planar field effect transistors, opportunities and challenges with one and two-dimensional materials and a new opportunity of contact engineering from device architecture perspective. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Allergic contact granuloma: an uncommon reaction to pierced earrings in a child.

    Science.gov (United States)

    Capriotti, Kara; Lee, Jason B; Hyde, Patrice

    2009-01-01

    Allergic contact dermatitis associated with pierced earrings typically presents as erythematous patches and plaques, with prominent spongiosis histologically. The most common inciting metal is nickel. Allergic contact granulomatous reactions to pierced earrings are rare, and are often more nodular in appearance and associated with metals other than nickel. We hereby report the first case of allergic contact granulomas associated with pierced earrings in a child.

  4. Disproportionate Minority Contact.

    Science.gov (United States)

    Fix, Rebecca L; Cyperski, Melissa A; Burkhart, Barry R

    2017-04-01

    The overrepresentation of racial/ethnic minorities within the criminal justice system relative to their population percentage, a phenomenon termed disproportionate minority contact, has been examined within general adult and adolescent offender populations; yet few studies have tested whether this phenomenon extends to juvenile sexual offenders (JSOs). In addition, few studies have examined whether offender race/ethnicity influences registration and notification requirements, which JSOs are subject to in some U.S. states. The present study assessed for disproportionate minority contact among general delinquent offenders and JSOs, meaning it aimed to test whether the criminal justice system treats those accused of sexual and non-sexual offenses differently by racial/ethnic group. Furthermore, racial/ethnic group differences in risk, legal classification, and sexual offending were examined for JSOs. Results indicated disproportionate minority contact was present among juveniles with non-sexual offenses and JSOs in Alabama. In addition, offense category and risk scores differed between African American and European American JSOs. Finally, registration classifications were predicted by offending characteristics, but not race/ethnicity. Implications and future directions regarding disproportionate minority contact among JSOs and social and legal policy affecting JSOs are discussed.

  5. Mathematics Connection: Contact

    African Journals Online (AJOL)

    Principal Contact. Dr. Kofi Mereku Executive Editor Department of Mathematics Education, UCE Mathematical Association of Ghana, C/o Department of Mathematics Education University College of Education of Winneba P. O. Box 25, Winneba, Ghana Phone: +233244961318. Email: dkmereku@uew.edu.gh ...

  6. Zoologist (The): Contact

    African Journals Online (AJOL)

    Principal Contact. Prof. A.B. Odaibo Editor-in-Chief University of Ibadan, Ibadan. Nigeria. Hydrobiology & Fisheries Unit, Department of Zoology, University of Ibadan, Ibadan. Oyo State. Nigeria. West Africa. Alternative Email Address: adebakar19@yahoo.com. Phone: +234-(0)- 803-049-74. Fax: +234-02-8103043

  7. Have Confidence in Contact

    Science.gov (United States)

    Crisp, Richard J.; Turner, Rhiannon N.

    2010-01-01

    In an article in the May-June 2009 "American Psychologist," we discussed a new approach to reducing prejudice and encouraging more positive intergroup relations (Crisp & Turner, 2009). We named the approach imagined intergroup contact and defined it as "the mental simulation of a social interaction with a member or members of an outgroup category"…

  8. Colored Contact Lens Dangers

    Medline Plus

    Full Text Available ... Lens-Related Eye Infections Mar 01, 2017 New Technology Helps the Legally Blind Be More Independent Oct 31, 2016 What You Should Know About Swimming and Your Eyes Aug 16, 2016 5 Steps to Healthy Contact Lens Use May 31, 2016 More Eye Health News Eyeglasses May One Day Treat Glaucoma JAN 18, ...

  9. Ebonyi Medical Journal: Contact

    African Journals Online (AJOL)

    Principal Contact. OUJ Umeora Dr. Ebonyi State Uni. Teaching Hospital. P.O. Box 980 Abakaliki – Ebonyi State Nigeria. Postal code: 480001. Alternative email address: ebsuthemj@yahoo.com. Phone: +234 8039558074. Fax: +234 43 221856, +234. Email: oujair@yahoo.com ...

  10. Nigeria Agricultural Journal: Contact

    African Journals Online (AJOL)

    Principal Contact. Prof. J.A. Mbanasor Editor in Chief Head of Department, Agribusiness and Management College of Agribusiness and Financial Management Michael Okpara University of Agriculture Office of the Head of Department. Agribusiness and Management. College of Agribusiness and Financial Management.

  11. Ghana Mining Journal: Contact

    African Journals Online (AJOL)

    Principal Contact. Professor Daniel Mireku-Gyimah Editor-in-Chief University of Mines & Technology Ghana Mining Journal University of Mines & Technology P. O. BOX 237 Tarkwa Ghana Phone: +233 362 20280/20324. Fax: +233 362 20306. Email: dm.gyimah@umat.edu.gh ...

  12. Contact allergy to spices

    NARCIS (Netherlands)

    W. Van den Akker Th. (W.); I.D. Roesyanto-Mahadi (I.); A.W. van Toorenenbergen (Albert); Th. van Joost (Theo)

    1990-01-01

    textabstractA group of 103 patients suspected of contact allergy was tested with the European standard series, wood tars and spices; paprika, cinnamon, laurel, celery seed, nutmeg, curry, black pepper, cloves, while pepper, coriander, cacao and garlic. 32 patients (Group I) were selected on the

  13. Colored Contact Lens Dangers

    Medline Plus

    Full Text Available ... Tips & Prevention News Ask an Ophthalmologist Patient Stories Español Eye Health / News Halloween Hazard: The Hidden Dangers ... Decorative Contact Lenses Without a Prescription Leer en Español: Peligros asociados con los lentes de contacto de ...

  14. Genital contact allergy.

    Science.gov (United States)

    Ljubojević, Suzana; Lipozencić, Jasna; Celić, Diana; Turcić, Petra

    2009-01-01

    Irritant and allergic contact dermatitis is commonly seen in patients complaining of itching, burning and irritation in the genital area. The aim of this retrospective study was to establish the prevalence of allergic contact dermatitis patients with genital complaints. We followed 33 patients with persistent or recurrent genital redness, itching and burning sensation. Diagnosis was made by history, clinical examination and patch testing. Patch tests were carried out according to the International Contact Dermatitis Research Group with a standard series of allergens. We also tested topical pharmaceutical products that individual patients used for treating genital symptoms and patients self intimate hygiene products. There were 11 male and 22 female patients, mean age 38 years. Thirteen (39%) patients had one or more positive allergic reactions, mainly to nickel-sulfate, thimerosal, balsam of Peru, formaldehyde and neomycin sulfate. In seven of 13 patients with positive patch test results, these reactions were considered to be relevant to their clinical condition. Three patients had positive patch test reactions to their intimate hygiene products. One patient had positive patch test reaction to latex condom. Patients with genital symptoms are at a risk of developing contact sensitivity. Patch testing is useful in the management of these patients and many can be helped by allergen avoidance.

  15. Open Veterinary Journal: Contact

    African Journals Online (AJOL)

    Principal Contact. Dr. Ibrahim Eldaghayes Faculty of Veterinary Medicine, University of Tripoli Faculty of Veterinary Medicine, University of Tripoli, P. O. Box 13662, Tripoli, Libya Phone: +218 21 462 8422. Fax: +218 21 462 8421. Email: ibrahim.eldaghayes@vetmed.edu.ly ...

  16. Colored Contact Lens Dangers

    Medline Plus

    Full Text Available ... be purchased over-the-counter or on the Internet," says Thomas Steinemann, MD, professor of ophthalmology at Case Western Reserve University in Cleveland. "This is far from the truth." Real People, Real Problems with Colored Contact Lenses Julian: ...

  17. Lettuce contact allergy

    DEFF Research Database (Denmark)

    Paulsen, Evy; Andersen, Klaus E

    2016-01-01

    Lettuce (Lactuca sativa L.) and its varieties are important vegetable crops worldwide. They are also well-known, rarely reported, causes of contact allergy. As lettuce allergens and extracts are not commercially available, the allergy may be underdiagnosed. The aims of this article are to present...

  18. Colored Contact Lens Dangers

    Medline Plus

    Full Text Available ... contact lenses , from the U.S. Food and Drug Administration (FDA). Are the colored lenses you are considering ... By Dan Gudgel The U.S. Food and Drug Administration has approved sales of a gene therapy treatment ...

  19. Colored Contact Lens Dangers

    Medline Plus

    Full Text Available ... in the United States. All contact lenses are medical devices that require a prescription and proper fitting by an eye-care professional. ... care professional such as an ophthalmologist — an eye medical doctor — who will ... a valid prescription that includes the brand name, lens measurements, and ...

  20. Colored Contact Lens Dangers

    Medline Plus

    Full Text Available ... Professionals Link your website to EyeSmart Embed EyeSmart videos on your website Promotional materials for eye health observances EyeSmart resources are also available in Spanish . Follow The Academy Professionals: Education Guidelines News Multimedia Public & Patients: Contact Us About ...

  1. Quantum contact interactions

    Indian Academy of Sciences (India)

    This is the transfer matrix representation [3], which has been treated as the standard form of generalized point .... the two-body interaction has no effect on identical bosons, but does have an effect on the fermions. ... We now go back to the generalU(2) representation of contact interactions, and look at the structure of the ...

  2. Colored Contact Lens Dangers

    Medline Plus

    Full Text Available ... colored contact lenses , from the U.S. Food and Drug Administration (FDA). Are the colored lenses you are ... 2017 By Dan Gudgel The U.S. Food and Drug Administration has approved sales of a gene therapy ...

  3. Colored Contact Lens Dangers

    Medline Plus

    Full Text Available ... eye health observances EyeSmart resources are also available in Spanish . Follow The Academy Professionals: Education Guidelines News Multimedia Public & Patients: Contact Us About the Academy Jobs at the Academy Financial Relationships with Industry Medical Disclaimer Privacy Policy Terms ...

  4. Oromia Law Journal: Contact

    African Journals Online (AJOL)

    com. ISSN: 2304-8239. AJOL African Journals Online. HOW TO USE AJOL... for Researchers · for Librarians · for Authors · FAQ's · More about AJOL · AJOL's Partners · Terms and Conditions of Use · Contact AJOL · News. OTHER RESOURCES.

  5. Colored Contact Lens Dangers

    Medline Plus

    Full Text Available ... Retailers that sell contacts without a prescription are breaking the law, and may be fined $11,000 per violation. "Many of the lenses found online or in beauty salons, novelty shops or in pop-up Halloween stores are not FDA-approved and are ...

  6. Language Contact and Bilingualism

    NARCIS (Netherlands)

    Appel, René; Muysken, Pieter

    2006-01-01

    What happens - sociologically, linguistically, educationally, politically - when more than one language is in regular use in a community? How do speakers handle these languages simultaneously, and what influence does this language contact have on the languages involved? Although most people in the

  7. Contact: Releasing the news

    Science.gov (United States)

    Pinotti, Roberto

    The problem of mass behavior after man's future contacts with other intelligences in the universe is not only a challenge for social scientists and political leaders all over the world, but also a cultural time bomb as well. In fact, since the impact of CETI (Contact with Extraterrestrial Intelligence) on human civilization, with its different cultures, might cause a serious socio-anthropological shock, a common and predetermined worldwide strategy is necessary in releasing the news after the contact, in order to keep possible manifestations of fear, panic and hysteria under control. An analysis of past studies in this field and of parallel historical situations as analogs suggests a definite "authority crisis" in the public as a direct consequence of an unexpected release of the news, involving a devastating "chain reaction" process (from both the psychological and sociological viewpoints) of anomie and maybe the collapse of today's society. The only way to prevent all this is to prepare the world's public opinion concerning contact before releasing the news, and to develop a long-term strategy through the combined efforts of scientists, political leaders, intelligence agencies and the mass media, in order to create the cultural conditions in which a confrontation with ETI won't affect mankind in a traumatic way. Definite roles and tasks in this multi-level model are suggested.

  8. Colored Contact Lens Dangers

    Medline Plus

    Full Text Available ... Facts Over-the-Counter Costume Contacts May Contain Chemicals Harmful to Eyes Four Ways Over-the-Counter ... vision. Privacy Policy Free EyeSmart Resources for Professionals Link your website to EyeSmart Embed EyeSmart videos on ...

  9. Colored Contact Lens Dangers

    Medline Plus

    Full Text Available ... Lens-Related Eye Infections Mar 01, 2017 New Technology Helps the Legally Blind Be More Independent Oct 31, 2016 What You Should Know About Swimming and Your Eyes Aug 16, 2016 5 Steps to Healthy Contact Lens Use May 31, 2016 More Eye Health News Top ...

  10. Colored Contact Lens Dangers

    Medline Plus

    Full Text Available ... use of colored contact lenses , from the U.S. Food and Drug Administration (FDA). Are the colored lenses ... DEC 21, 2017 By Dan Gudgel The U.S. Food and Drug Administration has approved sales of a ...

  11. Colored Contact Lens Dangers

    Medline Plus

    Full Text Available ... FDA's database of approved contact lenses . Related Stories Gene Therapy May Be a Game-Changer for People With ... Eyes Aug 16, 2016 More Eye Health News Gene Therapy May Be a Game-Changer for People With ...

  12. Colored Contact Lens Dangers

    Medline Plus

    Full Text Available ... seek immediate medical attention from an ophthalmologist. Related resources: Learn how to properly care for contact lenses . ... and preserving your vision. Privacy Policy Free EyeSmart Resources for Professionals Link your website to EyeSmart Embed ...

  13. Duality based contact shape optimization

    DEFF Research Database (Denmark)

    Vondrák, Vít; Dostal, Zdenek; Rasmussen, John

    2001-01-01

    An implementation of semi-analytic method for the sensitivity analysis in contact shape optimization without friction is described. This method is then applied to the contact shape optimization.......An implementation of semi-analytic method for the sensitivity analysis in contact shape optimization without friction is described. This method is then applied to the contact shape optimization....

  14. Total Internal Reflection for Effectively Transparent Solar Cell Contacts

    CERN Document Server

    Jahelka, Phillip; Atwater, Harry

    2016-01-01

    A new strategy for eliminating photocurrent losses due to the metal contacts on the front of a solar cell was proposed, simulated, and tested. By placing triangular cross-section lines of low refractive index on top of the contacts, total-internal reflection at the interface of the low-index triangles and the surrounding material can direct light away from the metal and into the photoactive absorber. Simulations indicated that losses can be eliminated for any incident angle, and that yearly energy production improvements commensurate with the metallized area are possible. Proof of principle experiments were carried out to eliminate the reflective losses of a commercial solar cell's busbar contact. Spatially resolved laser beam induced current measurements demonstrated that reflection losses due to the busbar were reduced by voids with triangular cross-section.

  15. Contact Graph Routing

    Science.gov (United States)

    Burleigh, Scott C.

    2011-01-01

    Contact Graph Routing (CGR) is a dynamic routing system that computes routes through a time-varying topology of scheduled communication contacts in a network based on the DTN (Delay-Tolerant Networking) architecture. It is designed to enable dynamic selection of data transmission routes in a space network based on DTN. This dynamic responsiveness in route computation should be significantly more effective and less expensive than static routing, increasing total data return while at the same time reducing mission operations cost and risk. The basic strategy of CGR is to take advantage of the fact that, since flight mission communication operations are planned in detail, the communication routes between any pair of bundle agents in a population of nodes that have all been informed of one another's plans can be inferred from those plans rather than discovered via dialogue (which is impractical over long one-way-light-time space links). Messages that convey this planning information are used to construct contact graphs (time-varying models of network connectivity) from which CGR automatically computes efficient routes for bundles. Automatic route selection increases the flexibility and resilience of the space network, simplifying cross-support and reducing mission management costs. Note that there are no routing tables in Contact Graph Routing. The best route for a bundle destined for a given node may routinely be different from the best route for a different bundle destined for the same node, depending on bundle priority, bundle expiration time, and changes in the current lengths of transmission queues for neighboring nodes; routes must be computed individually for each bundle, from the Bundle Protocol agent's current network connectivity model for the bundle s destination node (the contact graph). Clearly this places a premium on optimizing the implementation of the route computation algorithm. The scalability of CGR to very large networks remains a research topic

  16. Supersensitive, Fast-Response Nanowire Sensors by Using Schottky Contacts

    KAUST Repository

    Hu, Youfan

    2010-05-31

    A Schottky barrier can be formed at the interface between a metal electrode and a semiconductor. The current passing through the metal-semiconductor contact is mainly controlled by the barrier height and barrier width. In conventional nanodevices, Schottky contacts are usually avoided in order to enhance the contribution made by the nanowires or nanotubes to the detected signal. We present a key idea of using the Schottky contact to achieve supersensitive and fast response nanowire-based nanosensors. We have illustrated this idea on several platforms: UV sensors, biosensors, and gas sensors. The gigantic enhancement in sensitivity of up to 5 orders of magnitude shows that an effective usage of the Schottky contact can be very beneficial to the sensitivity of nanosensors. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Block copolymer directed nanoporous metal thin films.

    NARCIS (Netherlands)

    Arora, H.; Li, Z.H.; Sai, H.; Kamperman, M.M.G.; Warren, S.C.; Wiesner, U.

    2010-01-01

    Porous metal thin films have high potential for use in applications such as catalysis, electrical contacts, plasmonics, as well as energy storage and conversion. Structuring metal thin films on the nanoscale to generate high surface areas poses an interesting challenge as metals have high surface

  18. Contact allergy to cosmetics

    DEFF Research Database (Denmark)

    Held, E; Johansen, J D; Agner, T

    1999-01-01

    In a 2-year period, 1527 patients with contact dermatitis were investigated in the patch-test clinic. In 531 patients, allergy to cosmetics was suspected from the history and they were tested with their own cosmetic products. 40 (7.5%) (of the 531 patients) had 1 or more positive reactions, 82 (15.......4%) had doubtfully positive reaction(s) and 31 (5.8%) had irritant reaction(s). Skin-care products were tested most frequently and were also found to cause most positive, doubtfully positive and irritant reactions, 80% of the patients with positive reactions to their own products had no history of contact...... of common cosmetic ingredients. Fragrance mix and formaldehyde were found to be the ingredients most often responsible and were significantly more frequent in patients with positive reactions to their own products, compared to a control group of eczema patients also seen in the patch-test clinic....

  19. Contact allergy to lanolin

    DEFF Research Database (Denmark)

    Fransen, Marloes; Overgaard, Line E K; Johansen, Jeanne D

    2018-01-01

    BACKGROUND: Lanolin has been tested as lanolin alcohols (30% pet.) in baseline patch test series since 1969, and this has shown clinically relevant allergic contact dermatitis cases. OBJECTIVES: To investigate the temporal development of lanolin allergy (i.e. positive reaction to lanolin alcohols...... and/or Amerchol™ L-101), and the association between contact allergy to lanolin and patient characteristics from the MOAHLFA index. METHODS: A retrospective observational study of consecutively patch tested dermatitis patients (n = 9577) between 1 January 2004 and 31 December 2015 with lanolin...... alcohols 30% pet. and Amerchol™ L-101 50% pet. was performed. RESULTS: The prevalence of lanolin allergy increased from 0.45% in 2004 to 1.81% in 2015. In age-adjusted and sex-adjusted analyses, weak, significant associations were found between atopic dermatitis and lanolin and lanolin alcohols allergy...

  20. Critical Points of Contact

    DEFF Research Database (Denmark)

    Jensen, Ole B.; Morelli, Nicola

    2011-01-01

    In contemporary urban societies multiple networks and systems interact, overlap, exist in parallel, converge, conflict etc. creating unforeseen complexity and less transparency. By exploring how layered networks of physical movement, service information, goods delivery, commercial communication etc....... are connected (and disconnected) we get a much better understanding of how to design and intervene regardless if we are thinking about public spaces in the city or new systems of service design. The many networks orchestrating and facilitating contemporary everyday life are dependent on the strategic sites...... where the networks meet and establish contact. Thus we argue for the usefulness of the notion of Critical Point of Contact (CPC) to deepen our understanding of the actual life within networks. En route to this notion we draw upon theories within as diverse realms such as interaction design, service...

  1. Particles, contacts, bulk behavior

    NARCIS (Netherlands)

    Luding, Stefan; Tomas, J.

    2014-01-01

    Granular matter consists of discrete “particles”. These can be separate sand-grains, agglomerates (made of many primary particles), or solid materials like rock, composites, or metal-alloys—all with particulate inhomogeneous, possibly anisotropic micro-structure. Particles can be as small as

  2. Contact stress sensor

    Science.gov (United States)

    Kotovsky, Jack

    2014-02-11

    A method for producing a contact stress sensor that includes one or more MEMS fabricated sensor elements, where each sensor element of includes a thin non-recessed portion, a recessed portion and a pressure sensitive element adjacent to the recessed portion. An electric circuit is connected to the pressure sensitive element. The circuit includes a pressure signal circuit element configured to provide a signal upon movement of the pressure sensitive element.

  3. Contact stress sensor

    Science.gov (United States)

    Kotovsky, Jack [Oakland, CA

    2012-02-07

    A contact stress sensor includes one or more MEMS fabricated sensor elements, where each sensor element of includes a thin non-recessed portion, a recessed portion and a pressure sensitive element adjacent to the recessed portion. An electric circuit is connected to the pressure sensitive element. The circuit includes a thermal compensator and a pressure signal circuit element configured to provide a signal upon movement of the pressure sensitive element.

  4. Paraben Contact Hypersensitivity

    Directory of Open Access Journals (Sweden)

    A K Bajaj

    1985-01-01

    Full Text Available One hundred patients suspected to be having contact hypersensitivity to topical medicaments were patch tested with methly and propyl parabens along with commercially available topical medicaments. Six patients showed positive reactions to parabens. Two patients each were positive to methyl paraben and propyl paraben and two showed positive reactions to both of these. Three patients each showed positive reactions to soframycin, econazole and nitrofurazone also.

  5. Contact allergy to spices

    OpenAIRE

    Van den Akker Th., W.; Roesyanto-Mahadi, I.; Toorenenbergen, Albert van; Joost, Theo

    1990-01-01

    textabstractA group of 103 patients suspected of contact allergy was tested with the European standard series, wood tars and spices; paprika, cinnamon, laurel, celery seed, nutmeg, curry, black pepper, cloves, while pepper, coriander, cacao and garlic. 32 patients (Group I) were selected on the basis of positive tests to one or more of possible indicators for allergy to spices: colophony, balsam of Peru, fragrance‐mix and/or wood tars. 71 patients (Group II) showed no response to these indica...

  6. Cryotrons based on a simultaneously distributed Josephson contact

    Energy Technology Data Exchange (ETDEWEB)

    Bakhtin, P.A.; Lapir, G.M.; Makhov, V.I.; Samus, A.N.; Semenov, V.K.; Tyablikov, A.V.

    1982-01-01

    The features of the construction of cryotrons based on an evenly distributed Josephson contact are examined. The possibility is demonstrated of producing cryotrons with an assigned form of the controlling characteristic through the spatial isolation of the transport and controlling streams. The theoretical and experimental controlling characteristics of cryotrons based on bridges of variable thickness with connectors of normal metal are cited. The proposed principles of cryotron production are also suitable for other types of Josephson contacts.

  7. Pediatric contact dermatitis

    Directory of Open Access Journals (Sweden)

    Sharma Vinod

    2010-01-01

    Full Text Available Allergic contact dermatitis (ACD in children, until recently, was considered rare. ACD was considered as a disorder of the adult population and children were thought to be spared due to a lack of exposure to potential allergens and an immature immune system. Prevalence of ACD to even the most common allergens in children, like poison ivy and parthenium, is relatively rare as compared to adults. However, there is now growing evidence of contact sensitization of the pediatric population, and it begins right from early childhood, including 1-week-old neonates. Vaccinations, piercing, topical medicaments and cosmetics in younger patients are potential exposures for sensitization. Nickel is the most common sensitizer in almost all studies pertaining to pediatric contact dermatitis. Other common allergens reported are cobalt, fragrance mix, rubber, lanolin, thiomersol, neomycin, gold, mercapto mix, balsum of Peru and colophony. Different factors like age, sex, atopy, social and cultural practices, habit of parents and caregivers and geographic changes affect the patterns of ACD and their variable clinical presentation. Patch testing should be considered not only in children with lesions of a morphology suggestive of ACD, but in any child with dermatitis that is difficult to control.

  8. Temperature dependences of the contact resistivity in ohmic contacts to n{sup +}-InN

    Energy Technology Data Exchange (ETDEWEB)

    Sachenko, A. V.; Belyaev, A. E. [National Academy of Sciences, Lashkaryov Institute of Semiconductor Physics (Ukraine); Boltovets, N. S. [“Orion” Research Institute (Ukraine); Brunkov, P. N.; Jmerik, V. N.; Ivanov, S. V. [Russian Academy of Sciences, Ioffe Physical-Technical Institute (Russian Federation); Kapitanchuk, L. M. [National Academy of Sciences of Ukraine, Paton Electric Welding Institute (Ukraine); Konakova, R. V., E-mail: konakova@isp.kiev.ua; Klad’ko, V. P.; Romanets, P. N.; Saja, P. O.; Safryuk, N. V.; Sheremet, V. N. [National Academy of Sciences, Lashkaryov Institute of Semiconductor Physics (Ukraine)

    2015-04-15

    The temperature dependences of the contact resistivity (ρ{sub c}) of ohmic contacts based on the Au-Ti-Pd-InN system are measured at an InN doping level of 2 × 10{sup 18} cm{sup −3} in the temperature range of 4.2–300 K. At temperatures T > 150 K, linearly increasing dependences ρ{sub c}(T) are obtained. The dependences are explained within the mechanism of thermionic current flow through metal shunts associated with dislocations. Good agreement between theoretical and experimental dependences is achieved assuming that the flowing current is limited by the total resistance of the metal shunts, and the density of conductive dislocations is ∼5 × 10{sup 9} cm{sup −2}. Using the X-ray diffraction method, the density of screw and edge dislocations in the structure under study is measured: their total density exceeds 10{sup 10} cm{sup −2}.

  9. Metal-metal-hofteproteser

    DEFF Research Database (Denmark)

    Ulrich, Michael; Overgaard, Søren; Penny, Jeannette

    2014-01-01

    In Denmark 4,456 metal-on-metal (MoM) hip prostheses have been implanted. Evidence demonstrates that some patients develope adverse biological reactions causing failures of MoM hip arthroplasty. Some reactions might be systemic. Failure rates are associated with the type and the design of the Mo...

  10. Distance Dependence of the Electronic Contact of a Molecular Wire

    Science.gov (United States)

    Grill, L.; Moresco, F.; Jiang, P.; Stojkovic, S.; Gourdon, A.; Joachim, C.; Rieder, K.-H.

    2005-09-01

    The central molecular wire of a so-called Reactive Lander molecule is brought in electronic contact with an atomic scale metallic nanostructure by manipulation with the STM tip. Several stable conformations are obtained in a controlled way, in accordance with calculations. An additional contribution to the tunneling current is observed at the end of the molecular board, reflecting the electronic interaction between the molecular wire and the nanostructure. The characteristic intensity of this electronic contact for different conformations is discussed by means of the vertical interatomic distance between the molecular wire and the metal atoms.

  11. Prolonging contact lens wear and making contact lens wear safer.

    Science.gov (United States)

    Foulks, Gary N

    2006-02-01

    To summarize the present status of safety and efficacy of contact lens wear. Literature review. Ovid Medline searches were performed on records from 1966 through 2005 using keywords: keratitis, contact lens complications, extended-wear contact lenses, and silicone-hydrogel contact lenses. Patients desire comfort, clarity of vision, and prolonged contact lens wear when contact lenses are used to correct refractive error. Practitioners desire patient satisfaction but also require maintenance of the integrity of the eye and no complications that jeopardize vision or health of the eye. Improvements in the oxygen permeability of the contact lens materials, design of the contact lens and its surface, and solutions for the maintenance of the lens have reduced but not eliminated the risks of infection, inflammation, and conjunctival papillary reaction associated with contact lens wear. The lessons of past and recent history suggest that patient education and practitioner participation in the management of contact lens wear continue to be critical factors for patient satisfaction and safety in the extended wear of contact lenses. The availability of highly oxygen permeable contact lenses has increased the tolerance and safety of extended contact lens wear, but patient instruction and education in proper use and care of lenses is required and caution is advised.

  12. Mechanical Contact Experiments and Simulations

    DEFF Research Database (Denmark)

    Nielsen, Chris Valentin; Martins, P; Zhang, W.

    2011-01-01

    Mechanical contact is studied under dynamic development by means of a combined numerical and experimental investigation. The experiments are designed to allow dynamical development of non-planar contact areas with significant expansion in all three directions as the load is increased. Different....... The overall investigation serves for testing and validating the numerical implementation of the mechanical contact, which is one of the main contributions to a system intended for 3D simulation of resistance welding. Correct modelling of contact between parts to be welded, as well as contact with electrodes......, is crucial for satisfactory modelling of the resistance welding process. The resistance heating at the contact interfaces depends on both contact area and pressure, and as the contact areas develop dynamically, the presented tests are relevant for assessing the validity and accuracy of the mechanical contact...

  13. Metallated metal-organic frameworks

    Energy Technology Data Exchange (ETDEWEB)

    Bury, Wojciech; Farha, Omar K.; Hupp, Joseph T.; Mondloch, Joseph E.

    2017-08-22

    Porous metal-organic frameworks (MOFs) and metallated porous MOFs are provided. Also provided are methods of metallating porous MOFs using atomic layer deposition and methods of using the metallated MOFs as catalysts and in remediation applications.

  14. Metallated metal-organic frameworks

    Science.gov (United States)

    Bury, Wojciech; Farha, Omar K.; Hupp, Joseph T.; Mondloch, Joseph E.

    2017-02-07

    Porous metal-organic frameworks (MOFs) and metallated porous MOFs are provided. Also provided are methods of metallating porous MOFs using atomic layer deposition and methods of using the metallated MOFs as catalysts and in remediation applications.

  15. Interdigitated back contact solar cells with polycrystalline silicon on oxide passivating contacts for both polarities

    Science.gov (United States)

    Haase, Felix; Kiefer, Fabian; Schäfer, Sören; Kruse, Christian; Krügener, Jan; Brendel, Rolf; Peibst, Robby

    2017-08-01

    We demonstrate an independently confirmed 25.0%-efficient interdigitated back contact silicon solar cell with passivating polycrystalline silicon (poly-Si) on oxide (POLO) contacts that enable a high open circuit voltage of 723 mV. We use n-type POLO contacts with a measured saturation current density of J 0n = 4 fA cm-2 and p-type POLO contacts with J 0p = 10 fA cm-2. The textured front side and the gaps between the POLO contacts on the rear are passivated by aluminum oxide (AlO x ) with J 0AlO x = 6 fA cm-2 as measured after deposition. We analyze the recombination characteristics of our solar cells at different process steps using spatially resolved injection-dependent carrier lifetimes measured by infrared lifetime mapping. The implied pseudo-efficiency of the unmasked cell, i.e., cell and perimeter region are illuminated during measurement, is 26.2% before contact opening, 26.0% after contact opening and 25.7% for the finished cell. This reduction is due to an increase in the saturation current density of the AlO x passivation during chemical etching of the contact openings and of the rear side metallization. The difference between the implied pseudo-efficiency and the actual efficiency of 25.0% as determined by designated-area light current-voltage (I-V) measurements is due to series resistance and diffusion of excess carriers into the non-illuminated perimeter region.

  16. Deriving site-specific clean-up criteria to protect ecological receptors (plants and soil invertebrates) exposed to metal or metalloid soil contaminants via the direct contact exposure pathway

    Science.gov (United States)

    Checkai, Ron; Van Genderen, Eric; Sousa, José Paulo; Stephenson, Gladys; Smolders, Erik

    2014-01-01

    Soil contaminant concentration limits for the protection of terrestrial plants and soil invertebrates are commonly based on thresholds derived using data from laboratory ecotoxicity tests. A comprehensive assessment has been made for the derivation of ecological soil screening levels (Eco-SSL) in the United States; however, these limits are conservative because of their focus on high bioavailability scenarios. Here, we explain and evaluate approaches to soil limit derivation taken by 4 jurisdictions, 2 of which allow for correction of data for factors affecting bioavailability among soils, and between spiked and field-contaminated soils (Registration Evaluation Authorisation and Restriction of Chemicals [REACH] Regulation, European Union [EU], and the National Environment Protection Council [NEPC], Australia). Scientifically advanced features from these methods have been integrated into a newly developed method for deriving soil clean-up values (SCVs) within the context of site-specific baseline ecological risk assessment. Resulting site-specific SCVs that account for bioavailability may permit a greater residual concentration in soil when compared to generic screening limit concentrations (e.g., Eco-SSL), while still affording acceptable protection. Two choices for selecting the level of protection are compared (i.e., allowing higher effect levels per species, or allowing a higher percentile of species that are potentially unprotected). Implementation of this new method is presented for the jurisdiction of the United States, with a focus on metal and metalloid contaminants; however, the new method can be used in any jurisdiction. A case study for molybdate shows the large effect of bioavailability corrections and smaller effects of protection level choices when deriving SCVs. Integr Environ Assess Manag 2014;10:346–357. PMID:24470189

  17. Contact mechanics of reverse engineered distal humeral hemiarthroplasty implants.

    Science.gov (United States)

    Willing, Ryan; King, Graham J W; Johnson, James A

    2015-11-26

    Erosion of articular cartilage is a concern following distal humeral hemiarthroplasty, because native cartilage surfaces are placed in contact with stiff metallic implant components, which causes decreases in contact area and increases in contact stresses. Recently, reverse engineered implants have been proposed which are intended to promote more natural contact mechanics by reproducing the native bone or cartilage shape. In this study, finite element modeling is used in order to calculate changes in cartilage contact areas and stresses following distal humeral hemiarthroplasty with commercially available and reverse engineered implant designs. At the ulna, decreases in contact area were -34±3% (p=0.002), -27±1% (pengineered and cartilage reverse engineered designs, respectively. Peak contact stresses increased by 461±57% (p=0.008), 387±127% (p=0.229) and 165±16% (p=0.003). At the radius, decreases in contact area were -21±3% (p=0.013), -13±2% (p0.999), 241±32% (p=0.010) and 61±10% (p=0.021). Between the three different implant designs, the cartilage reverse engineered design yielded the largest contact areas and lowest contact stresses, but was still unable to reproduce the contact mechanics of the native joint. These findings align with a growing body of evidence indicating that although reverse engineered hemiarthroplasty implants can provide small improvements in contact mechanics when compared with commercially available designs, further optimization of shape and material properties is required in order reproduce native joint contact mechanics. Copyright © 2015 Elsevier Ltd. All rights reserved.

  18. Metal Matrix Composite Solar Cell Metallization

    Directory of Open Access Journals (Sweden)

    Wilt David M.

    2017-01-01

    Full Text Available Advanced solar cells are moving to ever thinner formats in order to save mass and in some cases improve performance. As cells are thinned, the possibility that they may fracture or cleave due to mechanical stresses is increased. Fractures of the cell can degrade the overall device performance if the fracture propagates through the contact metallization, which frequently occurs. To address this problem, a novel semiconductor metallization system based on multi-walled carbon nanotube (CNT reinforcement, termed metal matrix composite (MMC metallization is under investigation. Electro-mechanical characterization of MMC films demonstrate their ability to provide electrical conductivity over >40 micron wide cracks in the underlying semiconductor, with the carbon nanotubes bridging the gap. In addition, these materials show a “self-healing” behaviour, electrically reconnecting at ~30 microns when strained past failure. Triple junction (TJ space cells with MMC metallization demonstrated no loss in Jsc after intentional fracture, whereas TJ cells with conventional metallization suffer up to 50% Jsc loss.

  19. Rethinking contact lens aftercare.

    Science.gov (United States)

    Efron, Nathan; Morgan, Philip B

    2017-09-01

    The evolution of contact lens technology and clinical practice over the past three decades has been remarkable, with dramatic improvements in material biocompatibility, better lens designs and care systems, and more flexible and convenient modalities of wear. However, our approach to the aftercare examination has remained conservative, with the general modus operandi having not fully evolved from the difficult, early years of fitting non-regular replacement rigid and low water content hydrogel lenses. In this paper, we review current aftercare practice and in particular, the preferred frequency that lens wearers should return for routine visits and the appropriateness of regulations governing contact lens prescription expiry. Four key clinical reasons for conducting a routine aftercare visit are identified: preserving ocular health, maintaining good vision, optimising comfort and ensuring satisfactory lens fitting performance. Commercial reasons for conducting aftercare visits are also considered. A decision matrix is presented to help practitioners decide on an appropriate time interval between routine aftercare visits. The first aftercare visit should always take place within one to two weeks of lens dispensing. After this, the following time intervals between routine aftercare visits are advised as a general guideline: soft daily disposable, 24 months; soft daily reusable and rigid daily wear, 12 months; soft and rigid extended wear, six months. These aftercare visit frequencies may need to be adjusted when rapid rates of refractive change are anticipated, such as every six months during child/teenager myopic progression and every 12 months during the advancement of presbyopia. Numerous clinical caveats for varying these recommended aftercare frequencies are also discussed. Those new to lens wear should be seen within the first two months of lens dispensing. Regulatory authorities charged with the responsibility of stipulating the validity of a contact

  20. Thermal contact conductance

    CERN Document Server

    Madhusudana, Chakravarti V

    2013-01-01

    The work covers both theoretical and practical aspects of thermal contact conductance. The theoretical discussion focuses on heat transfer through spots, joints, and surfaces, as well as the role of interstitial materials (both planned and inadvertent). The practical discussion includes formulae and data that can be used in designing heat-transfer equipment for a variety of joints, including special geometries and configurations. All of the material has been updated to reflect the latest advances in the field.

  1. Contact dermatitis to methylisothiazolinone*

    Science.gov (United States)

    Scherrer, Maria Antonieta Rios; Rocha, Vanessa Barreto; Andrade, Ana Regina Coelho

    2015-01-01

    Methylisothiazolinone (MI) is a preservative found in cosmetic and industrial products. Contact dermatitis caused by either methylchloroisothiazolinone/methylisothiazolinone (MCI/MI or Kathon CG) or MI has shown increasing frequency. The latter is preferably detected through epicutaneous testing with aqueous MI 2000 ppm, which is not included in the Brazilian standard tray. We describe a series of 23 patients tested using it and our standard tray. A case with negative reaction to MCI/MI and positive to MI is emphasized. PMID:26734880

  2. Contact Control, Version 1

    Energy Technology Data Exchange (ETDEWEB)

    2016-07-21

    The contact control code is a generalized force control scheme meant to interface with a robotic arm being controlled using the Robot Operating System (ROS). The code allows the user to specify a control scheme for each control dimension in a way that many different control task controllers could be built from the same generalized controller. The input to the code includes maximum velocity, maximum force, maximum displacement, and a control law assigned to each direction and the output is a 6 degree of freedom velocity command that is sent to the robot controller.

  3. Fragrance contact allergy

    DEFF Research Database (Denmark)

    Johansen, Jeanne D

    2003-01-01

    typically have a history of rash to a fine fragrance or scented deodorants. Chemical analysis has revealed that well known allergens from the fragrance mix are present in 15-100% of cosmetic products, including deodorants and fine fragrances, and most often in combinations of three to four allergens...... fragrance ingredients are currently used in the composition of perfumes and at least 100 of these are known contact allergens. Therefore, it is advisable to supplement standard patch testing with the patient's own stay-on cosmetic products, as well as the fragrance chemical hydroxyisohexyl-3-cyclohexane...

  4. A single-pixel wireless contact lens display

    Science.gov (United States)

    Lingley, A. R.; Ali, M.; Liao, Y.; Mirjalili, R.; Klonner, M.; Sopanen, M.; Suihkonen, S.; Shen, T.; Otis, B. P.; Lipsanen, H.; Parviz, B. A.

    2011-12-01

    We present the design, construction and in vivo rabbit testing of a wirelessly powered contact lens display. The display consists of an antenna, a 500 × 500 µm2 silicon power harvesting and radio integrated circuit, metal interconnects, insulation layers and a 750 × 750 µm2 transparent sapphire chip containing a custom-designed micro-light emitting diode with peak emission at 475 nm, all integrated onto a contact lens. The display can be powered wirelessly from ~1 m in free space and ~2 cm in vivo on a rabbit. The display was tested on live, anesthetized rabbits with no observed adverse effect. In order to extend display capabilities, design and fabrication of micro-Fresnel lenses on a contact lens are presented to move toward a multipixel display that can be worn in the form of a contact lens. Contact lenses with integrated micro-Fresnel lenses were also tested on live rabbits and showed no adverse effect.

  5. Impact of environmental conditions on the contact physics of gold contact RF microelectromechanical systems (MEMS) switches

    Science.gov (United States)

    Brown, Christopher John

    RF MEMS switch technology is poised to create a new generation of devices capable of vastly outperforming current mechanical and semiconductor switching technology. Despite the efforts of top industrial, academic, and government labs, commercialization of RF MEMS switches has lagged expectations. This dissertation focuses on issues associated with switch contact physics. Understanding the failure mechanisms for metal contact switches is a complex challenge. There is strong interplay between variables such as mechanical creep, deformation, contact heating, contact asperity size, real contact area, and current flow leading to the eventual failure of the switch. Stiction failures moreover are highly sensitive to ambient conditions and absorbed film layers at the switch contact. The experiments in this thesis seek to isolate individual failure mechanisms and tie them to the physics driving that behavior through correlation of experimental data and theoretical modeling. Four experiments in controlled environments were performed: (1) the impact of cryogenic temperatures on RF MEMS contacts, (2) a correlation between experimental data and theoretical modeling for gold asperity creep at room and cryogenic temperatures, (3) a power law relationship between contact resistance and time dependent creep, and (4) the pressure dependence of switch closure. Cryogenic temperatures were used to isolate contaminant film effects. Contaminant films were found to have less mobility at 77 K, and contact resistance measurements showed that the film could be reduced on the contact surface through mechanical cycling and high temperatures at the gold asperities. It was also noted at cryogenic temperatures that the choice of atmosphere was important. A nitrogen atmosphere at liquid nitrogen temperature produced variable contact resistance as the condensed liquid boiled off the switch contacts. Data was correlated with a single asperity creep model to show that change in contact resistance as

  6. Optimal contact definition for reconstruction of Contact Maps

    Directory of Open Access Journals (Sweden)

    Stehr Henning

    2010-05-01

    Full Text Available Abstract Background Contact maps have been extensively used as a simplified representation of protein structures. They capture most important features of a protein's fold, being preferred by a number of researchers for the description and study of protein structures. Inspired by the model's simplicity many groups have dedicated a considerable amount of effort towards contact prediction as a proxy for protein structure prediction. However a contact map's biological interest is subject to the availability of reliable methods for the 3-dimensional reconstruction of the structure. Results We use an implementation of the well-known distance geometry protocol to build realistic protein 3-dimensional models from contact maps, performing an extensive exploration of many of the parameters involved in the reconstruction process. We try to address the questions: a to what accuracy does a contact map represent its corresponding 3D structure, b what is the best contact map representation with regard to reconstructability and c what is the effect of partial or inaccurate contact information on the 3D structure recovery. Our results suggest that contact maps derived from the application of a distance cutoff of 9 to 11Å around the Cβ atoms constitute the most accurate representation of the 3D structure. The reconstruction process does not provide a single solution to the problem but rather an ensemble of conformations that are within 2Å RMSD of the crystal structure and with lower values for the pairwise average ensemble RMSD. Interestingly it is still possible to recover a structure with partial contact information, although wrong contacts can lead to dramatic loss in reconstruction fidelity. Conclusions Thus contact maps represent a valid approximation to the structures with an accuracy comparable to that of experimental methods. The optimal contact definitions constitute key guidelines for methods based on contact maps such as structure prediction through

  7. A Prototype Antifungal Contact Lens

    OpenAIRE

    Ciolino, Joseph B; Hudson, Sarah P.; Mobbs, Ashley N.; Hoare, Todd R.; Iwata, Naomi G.; Fink, Gerald R.; Kohane, Daniel S.

    2011-01-01

    Econazole-eluting contact lenses with a novel design provided extended antifungal activity against the Candida albicans fungus. This drug-eluting contact lens could be used to treat and prevent fungal ocular infections.

  8. Contact Center Manager Administration (CCMA)

    Data.gov (United States)

    Social Security Administration — CCMA is the server that provides a browser-based tool for contact center administrators and supervisors. It is used to manage and configure contact center resources...

  9. Contact Lenses in the Laboratory.

    Science.gov (United States)

    Kingston, David W.

    1981-01-01

    Summarizes results of a three-item questionnaire returned by 43 Michigan institutions expressing views on wearing contact lenses in chemical laboratories. Questions focused on eye protection, type of protection, and use of contact lenses. (SK)

  10. Contact allergy to spices.

    Science.gov (United States)

    van den Akker, T W; Roesyanto-Mahadi, I D; van Toorenenbergen, A W; van Joost, T

    1990-05-01

    A group of 103 patients suspected of contact allergy was tested with the European standard series, wood tars and spices: paprika, cinnamon, laurel, celery seed, nutmeg, curry, black pepper, cloves, white pepper, coriander, cacao and garlic. 32 patients (Group I) were selected on the basis of positive tests to one or more of possible indicators for allergy to spices: colophony, balsam of Peru, fragrance-mix and/or wood tars. 71 patients (Group II) showed no response to these indicators. In Group I (n = 32) a statistically significantly higher % of patients (47%) showed positive reactions to 1 or more spices, compared with 15% in Group II (N = 71). Among the spices, the highest numbers of reactions were found to nutmeg (28%), paprika (19%) and cloves (12%) in the indicator-positive Group I. Fragrance-mix turned out to be a particularly important indicator allergen, especially for paprika, nutmeg and cloves. The contact allergy in 11 out of 32 (Group I) and 7 out of 25 patch-tested patients (recruited from Group II) appeared to be directed mainly against the ether-extractable volatile fractions of the spices.

  11. Fatigue and material response in rolling contact

    Energy Technology Data Exchange (ETDEWEB)

    Voskamp, A.P. [SKF Engineering & Research Centre, Nieuwegein (Netherlands)

    1998-12-31

    Metal softening, induced during the so-called third stage of material response to rolling contact loading, increases the probability of spalling fatigue failure. Metal softening in the most heavily loaded subsurface region leads to micro-plastic deformation noticeable from the occurrence of microstructural change. The probability of crack initiation increases with the growth of the plastically deformed subsurface region. Subsequent crack growth in that region is stimulated by the induced residual stress and texture. Fatigue failure in modern clean bearing steel develops only when the material has reached the third stage. The threshold to the third stage can be determined, and thus fatigue life can be assessed from observations of microstructural change. Examples are discussed of observed reduction of the ferrite (211) diffraction-line width in relation to observed endurance.

  12. [Contact lenses: indications and limits].

    Science.gov (United States)

    Neuhann, T

    1979-10-04

    Contact lens wear may be indicated for cosmetic, professional, optical or therapeutic reasons. For each of these indications the arguments are given, why and when contact lenses are better than spectacle correction and which possibilities there are. Contact lens wear is contraindicated in certain eye diseases and in the case of problems of handling and hygiene. The author's preferences concerning the different contact lens materials are summarized briefly.

  13. Incidental discovery of circle contact lens by MRI: you can't scan my poker face, circle contact lens as a potential MRI hazard.

    Science.gov (United States)

    Tokue, Hiroyuki; Taketomi-Takahashi, Ayako; Tokue, Azusa; Tsushima, Yoshito

    2013-03-25

    Circle contact lenses, also known as color contact lenses and big eye contact lenses, are a type of cosmetic contact lens. It is not generally known that a circle contact lens usually contains iron oxide and other metals, which means their use during magnetic resonance imaging (MRI) is a potential hazard. We present a rare case of incidental discovery of circle contact lenses by MRI and MRI images of circle lenses in vitro. Circle contact lenses usually contain iron oxide, which is a known source of susceptibility artifact on MRI. Not only radiologists and radiographers but also referring physicians should be familiar with the imaging findings and potential risk of scanning circle contact lenses by MRI.

  14. Incidental discovery of circle contact lens by MRI: you can’t scan my poker face, circle contact lens as a potential MRI hazard

    Science.gov (United States)

    2013-01-01

    Background Circle contact lenses, also known as color contact lenses and big eye contact lenses, are a type of cosmetic contact lens. It is not generally known that a circle contact lens usually contains iron oxide and other metals, which means their use during magnetic resonance imaging (MRI) is a potential hazard. Case presentation We present a rare case of incidental discovery of circle contact lenses by MRI and MRI images of circle lenses in vitro. Conclusions Circle contact lenses usually contain iron oxide, which is a known source of susceptibility artifact on MRI. Not only radiologists and radiographers but also referring physicians should be familiar with the imaging findings and potential risk of scanning circle contact lenses by MRI. PMID:23530981

  15. The importance of contact quality

    DEFF Research Database (Denmark)

    van Bakel, Marian; Gerritsen, Marinel; van Oudenhoven, Jan Pieter

    . Expatriates in the Netherlands were randomly divided into an experimental group (n = 33) of which 21 developed high-quality contact with their host, and a control group (n = 32) without host. The results show that contact quality plays an important role and suggest that the higher the quality of the contact...

  16. [The adaptation to contact lenses].

    Science.gov (United States)

    Koos, D; Koos, M J

    1992-01-01

    The indications of contact lens adaptation in optical purpose are widely large, starting, with refractive errors [correction of vices], unilateral and bilateral aphakia, myopia, anisometropia and astigmatism, together with the use of contact lens in esthetic purpose. We have been presented the adaptation techniques, the supervise, and maintenance of contact lens.

  17. Polyurethane toilet seat contact dermatitis.

    Science.gov (United States)

    Turan, Hakan; Saricaoğlu, Hayriye; Turan, Ayşegül; Tunali, Sükran

    2011-01-01

    Polyurethane chemicals are produced by the reaction of isocyanates and they may cause allergic contact dermatitis or precipitate asthma attacks. Contact dermatitis to polyurethane toilet seat has not been reported before. Herein we present a case of allergic contact dermatitis to polyurethane toilet seat. © 2011 Wiley Periodicals, Inc.

  18. Aluminum–Titanium Alloy Back Contact Reducing Production Cost of Silicon Thin-Film Solar Cells

    Directory of Open Access Journals (Sweden)

    Hsin-Yu Wu

    2016-11-01

    Full Text Available In this study, metal films are fabricated by using an in-line reactive direct current magnetron sputtering system. The aluminum–titanium (AlTi back contacts are prepared by changing the pressure from 10 mTorr to 25 mTorr. The optical, electrical and structural properties of the metal back contacts are investigated. The solar cells with the AlTi had lower contact resistance than those with the silver (Ag back contact, resulting in a higher fill factor. The AlTi contact can achieve a solar cell conversion efficiency as high as that obtained from the Ag contact. These findings encourage the potential adoption of AlTi films as an alternative back contact to silver for silicon thin-film solar cells.

  19. Semiconductor structural damage attendant to contact formation in III-V solar cells

    Science.gov (United States)

    Fatemi, Navid S.; Weizer, Victor G.

    1991-01-01

    In order to keep the resistive losses in solar cells to a minimum, it is often necessary for the ohmic contacts to be heat treated to lower the metal-semiconductor contact resistivity to acceptable values. Sintering of the contacts, however can result in extensive mechanical damage of the semiconductor surface under the metallization. An investigation of the detailed mechanisms involved in the process of contact formation during heat treatment may control the structural damage incurred by the semiconductor surface to acceptable levels, while achieving the desired values of contact resistivity for the ohmic contacts. The reaction kinetics of sintered gold contacts to InP were determined. It was found that the Au-InP interaction involves three consecutive stages marked by distinct color changes observed on the surface of the Au, and that each stage is governed by a different mechanism. A detailed description of these mechanisms and options to control them are presented.

  20. Method of producing microporous joints in metal bodies

    Science.gov (United States)

    Danko, Joseph C.

    1982-01-01

    Tungsten is placed in contact with either molybdenum, tantalum, niobium, vanadium, rhenium, or other metal of atoms having a different diffusion coefficient than tungsten. The metals are heated so that the atoms having the higher diffusion coefficient migrate to the metal having the lower diffusion rate, leaving voids in the higher diffusion coefficient metal. Heating is continued until the voids are interconnected.

  1. Influence of Thermal Contact Resistance of Aluminum Foams in Forced Convection: Experimental Analysis.

    Science.gov (United States)

    Guarino, Stefano; Di Ilio, Giovanni; Venettacci, Simone

    2017-08-05

    In this paper, the heat transfer performances of aluminum metal foams, placed on horizontal plane surface, was evaluated in forced convection conditions. Three different types of contacts between the sample and the heated base plate have been investigated: simple contact, brazed contact and grease paste contact. First, in order to perform the study, an ad hoc experimental set-up was built. Second, the value of thermal contact resistance was estimated. The results show that both the use of a conductive paste and the brazing contact, realized by means of a copper electro-deposition, allows a great reduction of the global thermal resistance, increasing de facto the global heat transfer coefficient of almost 80%, compared to the simple contact case. Finally, it was shown that, while the contribution of thermal resistance is negligible for the cases of brazed and grease paste contact, it is significantly high for the case of simple contact.

  2. Influence of Thermal Contact Resistance of Aluminum Foams in Forced Convection: Experimental Analysis

    Directory of Open Access Journals (Sweden)

    Stefano Guarino

    2017-08-01

    Full Text Available In this paper, the heat transfer performances of aluminum metal foams, placed on horizontal plane surface, was evaluated in forced convection conditions. Three different types of contacts between the sample and the heated base plate have been investigated: simple contact, brazed contact and grease paste contact. First, in order to perform the study, an ad hoc experimental set-up was built. Second, the value of thermal contact resistance was estimated. The results show that both the use of a conductive paste and the brazing contact, realized by means of a copper electro-deposition, allows a great reduction of the global thermal resistance, increasing de facto the global heat transfer coefficient of almost 80%, compared to the simple contact case. Finally, it was shown that, while the contribution of thermal resistance is negligible for the cases of brazed and grease paste contact, it is significantly high for the case of simple contact.

  3. Dissimilar metals joint evaluation

    Science.gov (United States)

    Wakefield, M. E.; Apodaca, L. E.

    1974-01-01

    Dissimilar metals tubular joints between 2219-T851 aluminum alloy and 304L stainless steel were fabricated and tested to evaluate bonding processes. Joints were fabricated by four processes: (1) inertia (friction) weldings, where the metals are spun and forced together to create the weld; (2) explosive welding, where the metals are impacted together at high velocity; (3) co-extrusion, where the metals are extruded in contact at high temperature to promote diffusion; and (4) swaging, where residual stresses in the metals after a stretching operation maintain forced contact in mutual shear areas. Fifteen joints of each type were prepared and evaluated in a 6.35 cm (2.50 in.) O.D. size, with 0.32 cm (0.13 in.) wall thickness, and 7.6 cm (3.0 in) total length. The joints were tested to evaluate their ability to withstand pressure cycle, thermal cycle, galvanic corrosion and burst tests. Leakage tests and other non-destructive test techniques were used to evaluate the behavior of the joints, and the microstructure of the bond areas was analyzed.

  4. Acrylates in contact dermatitis.

    Science.gov (United States)

    Sasseville, Denis

    2012-01-01

    Acrylates are plastic materials that are formed by the polymerization of monomers derived from acrylic or methacrylic acid. They have found numerous applications in paints, varnishes and adhesives, in the printing industry, in the medical and dental professions, and in artificial nails. Beginning in the 1950s, many reports of occupational and nonoccupational allergic contact dermatitis to (meth)acrylate monomers have been published. These molecules are strong irritants, and patch testing can induce active sensitization. When patch tested, acrylate-allergic patients often display multiple positive tests. These reactions may represent cross-reactions, or concomitant reactions due to the presence, in the products responsible for sensitization, of impurities not disclosed in material safety data sheets. (Meth)acrylates are volatile and unstable chemicals, as demonstrated by their rapid disappearance from commercially available patch test allergens when exposed to air for more than a few hours.

  5. Fragrance contact allergy

    DEFF Research Database (Denmark)

    Johansen, Jeanne D

    2003-01-01

    in the same products. This means that it is difficult to avoid exposure, as products labelled as 'fragrance free' have also been shown to contain fragrance ingredients, either because of the use of fragrance ingredients as preservatives or masking perfumes, or the use of botanicals. About 2500 different...... fragrance ingredients are currently used in the composition of perfumes and at least 100 of these are known contact allergens. Therefore, it is advisable to supplement standard patch testing with the patient's own stay-on cosmetic products, as well as the fragrance chemical hydroxyisohexyl-3-cyclohexane...... carboxaldehyde, which on its own gives responses in 1-3% of tested patients. The focus in recent years on the ingredients of the fragrance mix will probably result in the fragrance industry changing the composition of perfumes, and thus make the current diagnostic test less useful. New diagnostic tests are under...

  6. Hair dye contact allergy

    DEFF Research Database (Denmark)

    Søsted, Heidi; Rastogi, Suresh Chandra; Andersen, Klaus Ejner

    2004-01-01

    Colouring of hair can cause severe allergic contact dermatitis. The most frequently reported hair dye allergens are p-phenylenediamine (PPD) and toluene-2,5-diamine, which are included in, respectively, the patch test standard series and the hairdressers series. The aim of the present study...... was to identify dye precursors and couplers in hair dyeing products causing clinical hair dye dermatitis and to compare the data with the contents of these compounds in a randomly selected set of similar products. The patient material comprised 9 cases of characteristic clinical allergic hair dye reaction, where...... exposure history and patch testing had identified a specific hair dye product as the cause of the reaction. The 9 products used by the patients were subjected to chemical analysis. 8 hair dye products contained toluene-2,5-diamine (0.18 to 0.98%). PPD (0.27%) was found in 1 product, and m-aminophenol (0...

  7. [Mercury contact dermatitis].

    Science.gov (United States)

    Camarasa, J G; Huguet, J; Alomar, A; Calderon, P G

    1983-01-01

    Eight female patients with contact allergy to Mercury were studied with the L. T. T. and the Histamine degranulation test of basophiles. In the eight cases the L. T. T. was specific. P. H. A. (an inspecific lymphocyte stimulator lectin) and the Histamine degranulation basophile test, were used as controls. Thirty subjects were used as controls. All of them were negative to the patch test with mercury at 0,5% in petrolatum. No atopic antecedents were among them and their families. No once case of lymphocyte activity to mercury was observed. Mercury acetate solutions at: 12,5 ng/ml. 25 ng/ml and 5 ng/ml were employed. This salt was the unique useful for the L. T. T. practice. Extremely difficulties for the solubilization of mercury bichloride, mercury oxide, phenyl mercury and ammoniated mercury, impaired the L. T. T. with these salts.

  8. Cosmetic Contact Allergens

    Directory of Open Access Journals (Sweden)

    An Goossens

    2016-02-01

    Full Text Available This article presents trends in the frequency of cosmetics as causal factors of allergic contact dermatitis during a 26-year period in 14,911 patients patch-tested between 1990 and 2014, and discusses the cosmetic allergens identified during the last six years (2010–2015 in 603 patients out of 3105 tested. The data were retrieved from, and evaluated with, a patient database developed in-house. The results show the increasing importance of cosmetic allergies, up to 25% of the patients tested during the last five-year period. As expected, fragrance materials, preservatives, and hair dyes were the most frequent culprits, but a great variety of other allergenic ingredients were involved as well. This underlines the need of additional and extensive patch testing with the patient’s products used and their ingredients.

  9. Mechanoluminescent Contact Type Sensor

    Directory of Open Access Journals (Sweden)

    A. K. Yefremov

    2017-01-01

    Full Text Available Mechanoluminescent sensing elements convert mechanical stress into optical radiation. Advantages of such sensors are the ability to generate an optical signal, solid-state, simple structure, and resistance to electromagnetic interference. Mechanoluminescent sensor implementations can possess the concentrated and distributed sensitivity, thereby allowing us to detect the field of mechanical stresses distributed across the area and in volume. Most modern semiconductor photo-detectors can detect mechanoluminescent radiation, so there are no difficulties to provide its detection when designing the mechanoluminescent sensing devices. Mechanoluminescent substances have especial sensitivity to shock loads, and this effect can be used to create a fuse the structure of which includes a target contact type sensor with a photosensitive actuator. The paper briefly describes the theoretical basics of mechanoluminiscence: a light signal emerges from the interaction of crystalline phosphor luminescence centers with electrically charged dislocations, moving due to the deformation of the crystal. A mathematical model of the mechanoluminescent conversion is represented as a functional interaction between parameters of the mechanical shock excitation and the sensor light emission. Examples of computing the optical mechanoluminescent output signal depending on the duration and peak level of impulse load are given. It is shown that the luminous flux, generated by mechanoluminescent sensing element when there is an ammunition-target collision causes the current emerging in photo-detector (photodiode that is sufficient for a typical actuator of the fuse train to operate. The potential possibility to create a contact target type sensor based on the light-sensitive mechanoluminescent sensor was proved by the calculation and simulation results.

  10. Management of contact dermatitis due to nickel allergy: an update

    Directory of Open Access Journals (Sweden)

    Fernanda Torres1

    2009-04-01

    Full Text Available Fernanda Torres1, Maria das Graças Mota Melo2, Antonella Tosti31Department of Dermatology, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil; 2Occupational Dermatology Sector, Center for the Study of Worker Health and Human Ecology, National School of Public Health, FIOCRUZ, Rio de Janeiro, Brazil; 3Department of Dermatology, University of Bologna, Bologna, ItalyAbstract: Nickel is the major cause of allergic contact dermatitis in the general population, both among children and adults, as well as in large occupational groups. This metal is used in numerous industrial and consumer products, including stainless steel, magnets, metal plating, coinage, and special alloys, and is therefore almost impossible to completely avoid in daily life. Nickel contact dermatitis can represent an important morbidity, particularly in patients with chronic hand eczema, which can lead to inability to work, a decrease in quality of life and significant healthcare expenses. Therefore, its management is of great importance. This article reviews diagnostic, preventive and therapeutic strategies in this field.Keywords: allergic contact dermatitis, metals, contact hypersensitivity, occupational exposure, children, contact dermatitis

  11. Tribology of flat contacts and its application in deep drawing

    NARCIS (Netherlands)

    Emmens, W.C.

    1997-01-01

    The difference between steel and aluminium in sheet metal forming operations, and the influence of roughness in these operations, have been studied by making deep draw and friction experiments. The friction tests have been carried out with flat contacts to simulate the conditions in the blankholder.

  12. Migration of compounds from food contact materials and articles

    DEFF Research Database (Denmark)

    Petersen, Jens Højslev

    2003-01-01

    This chapter presents the different types of food contact/packaging materials (plastics, paper and cardboard, metals, glass, rubbers, lacquers and coatings) and discusses the EU legislation concerning the safety of using these materials. Case studies on the migration of lead, bisphenol A, bisphen...

  13. Blocking contacts for N-type cadmium zinc telluride

    Science.gov (United States)

    Stahle, Carl M. (Inventor); Parker, Bradford H. (Inventor); Babu, Sachidananda R. (Inventor)

    2012-01-01

    A process for applying blocking contacts on an n-type CdZnTe specimen includes cleaning the CdZnTe specimen; etching the CdZnTe specimen; chemically surface treating the CdZnTe specimen; and depositing blocking metal on at least one of a cathode surface and an anode surface of the CdZnTe specimen.

  14. Contact and Non-contact Measurements of Grinding Pins

    Directory of Open Access Journals (Sweden)

    Magdziak Marek

    2015-01-01

    Full Text Available The paper presents the results of contact and non-contact measurements of external profiles of selected grinding pins. The measurements were conducted in order to choose the appropriate measuring technique in the case of the considered measurement task. In the case of contact measurements the coordinate measuring machine ACCURA II was applied. The used coordinate measuring machine was equipped with the contact scanning probe VAST XT and the Calypso inspection software. Contact coordinate measurements were performed by using of different measurement strategies. The applied strategies included different scanning velocities and distances between measured points. Non-contact measurements were conducted by means of the tool presetter produced by the Mahr company. On the basis of gained results the guidelines concerning measurements of grinding pins were formulated. The measurements of analyzed grinding pins performed by means of the non-contact measuring system are characterized by higher reproducibility than the contact measurements. The low reproducibility of contact measurements may be connected with the inaccuracy of the selected coordinate measuring machine and the measuring probe, the measurement parameters and environmental conditions in the laboratory where the coordinate measuring machine is located. Moreover, the paper presents the possible application of results of conducted investigations. The results of non-contact measurements can be used in the simulation studies of grinding processes. The simulations may reduce the costs of machining processes.

  15. Contact lens care in keratoconus.

    Science.gov (United States)

    Zhou, Alana J; Kitamura, Keiko; Weissman, Barry A

    2003-12-01

    To quantify the complexity involved in fitting contact lenses on the eyes of patients with keratoconus. The contact lens care of one randomly selected eye each of 38 keratoconus patients was retrospectively analyzed and compared to that of 38 gender and age matched controls. We evaluated the number of diagnostic contact lenses used to establish the initial contact lens order, number of ordered rigid gas permeable (RGP) contact lenses needed to complete the fit, number of office visits during the initial 4 months of care, best spectacle and RGP contact lenses corrected Log MAR visual acuities, complications encountered, and whether or not the patient was successful in contact lens wear. Keratoconic eyes statistically used more diagnostic lenses, more ordered lenses, and more office visits than did normal eyes. Visual acuities improved from an average of 20/40 with spectacles to an average of 20/20 by use of RGP contact lenses in keratoconic eyes. Visions were corrected to 20/20 with both spectacles and contact lenses in control eyes. Sixty nine percent (69%) of keratoconic eyes and 95% of controls were successful in contact lens wear. Contact lens care of keratoconic eyes is more challenging than care of normal eyes because of the need for more diagnostic and ordered contact lenses and the use of more professional time. Keratoconic eyes may suffer more complications than normals during contact lens care, but this does not affect the success rates, and such patients benefit from enhanced visual acuity with RGP contact lenses compared to that achieved with spectacles.

  16. Contact sensitivity in patients with recalcitrant atopic dermatitis.

    Science.gov (United States)

    Tamagawa-Mineoka, Risa; Masuda, Koji; Ueda, Sachiko; Nakamura, Naomi; Hotta, Eri; Hattori, Junko; Minamiyama, Rina; Yamazaki, Akiko; Katoh, Norito

    2015-07-01

    Patients with atopic dermatitis are usually responsive to conventional treatment such as topical steroids; however, they are sometimes refractory to the treatment. The influence of contact sensitivities on the course of patients with recalcitrant atopic dermatitis is not known. The aim of this study was to investigate whether contact sensitivities affect the course of patients with recalcitrant atopic dermatitis. We evaluated 45 patients with atopic dermatitis who had failed conventional therapy. Patch testing was performed with the Japanese standard series, metal series and/or suspected items. A total of 15 patients had a positive patch test reaction to at least one allergen. The most common allergens were nickel, topical drugs and rubber accelerators. Avoidance of products or food containing allergic substances greatly or partially improved skin symptoms in nine patients. These results suggest that contact allergens and metals may be critical factors causing eczematous lesions in patients with recalcitrant atopic dermatitis. © 2015 Japanese Dermatological Association.

  17. Contact dermatitis to cobalt chloride with an unusual mechanism.

    Science.gov (United States)

    Arslan, Sevket; Aksan, Serkan; Ucar, Ramazan; Caliskaner, Ahmet Zafer

    2015-10-01

    Contact dermatitis is a frequent inflammatory skin disease. A suspected diagnosis is based on clinical symptoms, a plausible contact to allergens and a suitable history of dermatitis. Therefore, careful diagnosis by patch testing is of great importance because the patch testing is important to find out which allergen/material causes the complaints. Metallic allergens such as cobalt are among the most common causes of allergic contact dermatitis, but frequencies of contact dermatitis to these allergens may vary in different skin areas. Here, we report an unusual case of cobalt allergy on the skin contact with the prosthetic leg of a 30-year-old female patient. The patient developed maculopapular and vesicular lesions on her contact region of residual limb to prosthetic leg. She underwent standard patch testing, which resulted in a strong positive reaction to cobalt chloride. This case report may serve to remind doctors to be aware of potential allergic reactions to prostheses and to enable them to recognize a metal allergy if it appears. Prosthetists should also be reminded of potential allergic reactions. Cobalt can be used as an accelerator in making a prosthetic socket. Several cases have been reported concerning allergies to components of the prosthetic socket. This is the first report of sensitization to cobalt which is used in making a prosthetic leg. © The International Society for Prosthetics and Orthotics 2014.

  18. Toward barrier free contact to molybdenum disulfide using graphene electrodes.

    Science.gov (United States)

    Liu, Yuan; Wu, Hao; Cheng, Hung-Chieh; Yang, Sen; Zhu, Enbo; He, Qiyuan; Ding, Mengning; Li, Dehui; Guo, Jian; Weiss, Nathan O; Huang, Yu; Duan, Xiangfeng

    2015-05-13

    Two-dimensional layered semiconductors such as molybdenum disulfide (MoS2) have attracted tremendous interest as a new class of electronic materials. However, there are considerable challenges in making reliable contacts to these atomically thin materials. Here we present a new strategy by using graphene as the back electrodes to achieve ohmic contact to MoS2. With a finite density of states, the Fermi level of graphene can be readily tuned by a gate potential to enable a nearly perfect band alignment with MoS2. We demonstrate for the first time a transparent contact to MoS2 with zero contact barrier and linear output behavior at cryogenic temperatures (down to 1.9 K) for both monolayer and multilayer MoS2. Benefiting from the barrier-free transparent contacts, we show that a metal-insulator transition can be observed in a two-terminal MoS2 device, a phenomenon that could be easily masked by Schottky barriers found in conventional metal-contacted MoS2 devices. With further passivation by boron nitride (BN) encapsulation, we demonstrate a record-high extrinsic (two-terminal) field effect mobility up to 1300 cm(2)/(V s) in MoS2 at low temperature.

  19. Occupational contact dermatitis from a grease.

    Science.gov (United States)

    Svedman, Cecilia; Isaksson, Marléne; Zimerson, Erik; Bruze, Magnus

    2004-03-01

    Contact allergy to grease is rare and often not even suspected. We investigated such a case in which the detected allergen was the stabilizer in the grease, which is rarely found as an allergen. Thin-layer chromatography (TLC) was used in a novel way and helped detect the allergen. Patch testing with our standard series, a metal-working series, the different substances individually, the grease in serial dilution and extracts of personal objects, the TLC plate. Gas chromatography-mass spectrometry was also used. Test results indicated contact allergy to grease containing N-phenyl-1-naphthylamine and contact allergy to Disperse Orange 1, N-cyclohexyl-N'-phenyl-4-phenylenediamine, N-isopropyl-N'-phenyl-4-phenylenediamine, and N,N'-diphenyl-4-phenylenediamine. N-phenyl-1-naphthylamine was the main cause of the patient's dermatitis. This case report underlines the importance of testing the patient's own products and also underlines the benefit of using TLC strips for patch testing and of visiting the workplace to get correct information about exposure conditions.

  20. A Low Resistance Calcium/Reduced Titania Passivated Contact for High Efficiency Crystalline Silicon Solar Cells

    KAUST Repository

    Allen, Thomas G.

    2017-02-04

    Recent advances in the efficiency of crystalline silicon (c-Si) solar cells have come through the implementation of passivated contacts that simultaneously reduce recombination and resistive losses within the contact structure. In this contribution, low resistivity passivated contacts are demonstrated based on reduced titania (TiOx) contacted with the low work function metal, calcium (Ca). By using Ca as the overlying metal in the contact structure we are able to achieve a reduction in the contact resistivity of TiOx passivated contacts of up to two orders of magnitude compared to previously reported data on Al/TiOx contacts, allowing for the application of the Ca/TiOx contact to n-type c-Si solar cells with partial rear contacts. Implementing this contact structure on the cell level results in a power conversion efficiency of 21.8% where the Ca/TiOx contact comprises only ≈6% of the rear surface of the solar cell, an increase of 1.5% absolute compared to a similar device fabricated without the TiOx interlayer.

  1. AMC 2015 – Advanced Metallization Conference

    OpenAIRE

    2016-01-01

    Since its inception as the Tungsten Workshop in 1984, AMC has served as the leading conference for the interconnect and contact metallization communities, and has remained at the leading edge of the development of tungsten, aluminum, and copper/low-K interconnects. As the semiconductor industry evolves, exciting new challenges in metallization are emerging, particularly in the areas of contacts to advanced devices, local interconnect solutions for highly-scaled devices, advanced memory device...

  2. Pinguecula and contact lenses.

    Science.gov (United States)

    Mimura, T; Usui, T; Mori, M; Yamamoto, H; Obata, H; Yamagami, S; Funatsu, H; Noma, H; Honda, N; Amano, S

    2010-11-01

    To assess the relationship between age and the incidence and severity (determined by a grading system) of pinguecula in contact lens (CL) wearers, and to compare the grade of pinguecula between CL wearers and non-wearers. A total of 600 CL wearers (94 wore hard CLs (HCLs) and 506 wore soft CLs (SCLs)) aged 11-60 years and 579 non-wearers aged 10-60 years were enrolled. The age, gender, medical history, ocular history, and grade of pinguecula at two locations (nasal and temporal) were determined in all subjects. There was an age-related increase in the grade of pinguecula among both CL wearers and non-wearers. The grade of pinguecula at the temporal conjunctiva was higher in CL wearers than in non-wearers (P=0.01907), whereas it was higher in HCL wearers than SCL wearers at both the nasal and temporal conjunctiva (P<0.00001 and P<0.00001). This was the first assessment of the severity of pinguecula in a large consecutive series of CL wearers. Our results suggest that the use of CLs is an important risk factor for pinguecula.

  3. Conjunctivochalasis and contact lenses.

    Science.gov (United States)

    Mimura, Tatsuya; Usui, Tomohiko; Yamamoto, Hiroki; Yamagami, Satoru; Funatsu, Hideharu; Noma, Hidetaka; Honda, Norihiko; Fukuoka, Shima; Amano, Shiro

    2009-07-01

    To assess the relationship between age and the incidence and severity of conjunctivochalasis in contact lens (CL) wearers by grading of conjunctivochalasis, and to compare the severity of conjunctivochalasis between CL wearers and nonwearers. Prospective, nonrandomized consecutive case study. A total of 600 CL wearers (94 hard CLs [HCL] and 506 soft CLs [SCL]) aged 11 to 60 years and 579 nonwearers aged 10 to 60 years were enrolled. The age, gender, medical history, ocular history, and the grade and other parameters of conjunctivochalasis at 3 locations (nasal, middle, and temporal areas) were determined in all subjects. The prevalence of conjunctivochalasis increased dramatically with age in all groups. The mean grade of conjunctivochalasis was higher in CL wearers than in nonwearers (nasal area, P < .00001; temporal area, P < .00001) and was higher in HCL wearers than in SCL wearers (nasal area, P < .00001; temporal area, P = .00003). Parameters such as the downward gaze-dependent or digital pressure-dependent changes of conjunctivochalasis and the presence of superficial punctate keratitis all increased with age in both CL wearers and nonwearers. The gaze-dependent and pressure-dependent changes of conjunctivochalasis showed an increase with age and the duration of CL wear in both SCL and HCL wearers. This was the first assessment of the severity of conjunctivochalasis in a large series of consecutive CL wearers. Our results strongly suggest that wearing CLs is an important risk factor for conjunctivochalasis.

  4. [Vital contact with reality].

    Science.gov (United States)

    Ravagnan, L M

    1976-12-01

    From the standpoint of existential phenomenology, the contact with reality lies in the very phocus of theory, being closely related to another basic conception: that of being-in-the-world. In order to ratify those conceptions, the author reviews some concepts imported from Kurt Lewin's Field Theory, among which: a) vital psychological space, embedding the subject and in close interchange with him; b) intrapsychic regions, having, to a certain extent, autonomous functions, but being related to each other and integrated into the higher unity of the subject. As both systems are interdependent, any modification of the equilibrium of one of them reverberates into the other's, and changes the general conditions of both of them. Reviewing, at the same time, Minkowski's views on schizophrenia, the author sets forth the production of an inner world that becomes autonomous and possesses a degree of reality that overwhelms the true outer world. There is not only the splitting from reality, but the creation of a whole fantastic field, in which the individual participates with all his vital availability. Both views lead to a similar contention: that in some pathological states, the primal link man-real world, is replaced by a new inner correspondence, focused on the imaginary and having effects similar to those of the real world.

  5. Contact sport and osteoarthritis.

    LENUS (Irish Health Repository)

    Molloy, Michael G

    2011-04-01

    Osteoarthritis (OA) is the most common joint disease in the world and the single largest cause of disability for those over 18 years. It affects more than twice as many people as does cardiac disease, and increases in incidence and prevalence with age. Animal and human studies have shown no evidence of increased risk of hip or knee OA with moderate exercise and in the absence of traumatic injury, sporting activity has a protective effect. One age-matched case control study found recreational runners who ran 12-14 miles per week for up to 40 years had no increase in radiological or symptomatic hip or knee OA. However, higher rates of hip OA occur in contact sports than in age-matched controls, with the highest rate in professional players. Soccer players with torn anterior cruciate ligaments (ACL) are more likely to develop knee OA than those with intact ACL. Early ACL repair reduces the risk of knee OA, but does not prevent it. Established injury prevention programmes have been refined to prevent injuries such as ACL rupture.

  6. Metallization of Large Silicon Wafers

    Science.gov (United States)

    Pryor, R. A.

    1978-01-01

    A metallization scheme was developed which allows selective plating of silicon solar cell surfaces. The system is comprised of three layers. Palladium, through the formation of palladium silicide at 300 C in nitrogen, makes ohmic contact to the silicon surface. Nickel, plated on top of the palladium silicide layer, forms a solderable interface. Lead-tin solder on the nickel provides conductivity and allows a convenient means for interconnection of cells. To apply this metallization, three chemical plating baths are employed.

  7. Patients with multiple contact allergies

    DEFF Research Database (Denmark)

    Carlsen, Berit Christina; Andersen, Klaus Ejner; Menné, Torkil

    2008-01-01

    Patients with multiple contact allergies, also referred to as polysensitized, are more frequent than predicted from prevalence of single sensitivities. The understanding of why some people develop multiple contact allergies, and characterization of patients with multiple contact allergies...... is limited. This review presents the current knowledge on the topic and discusses the evidence and characteristics of an increased susceptibility factor, possible causes to and genetic markers for the increased susceptibility, composition of the patient group and identification of patients at risk...... of developing multiple contact allergies. Evidence of allergen clusters among polysensitized individuals is also reviewed. The literature supports the idea that patients with multiple contact allergies constitute a special entity within the field of contact allergy. There is no generally accepted definition...

  8. Fabricating customized hydrogel contact lens

    OpenAIRE

    Andre Childs; Hao Li; Daniella M. Lewittes; Biqin Dong; Wenzhong Liu; Xiao Shu; Cheng Sun; Zhang, Hao F.

    2016-01-01

    Contact lenses are increasingly used in laboratories for in vivo animal retinal imaging and pre-clinical studies. The lens shapes often need modification to optimally fit corneas of individual test subjects. However, the choices from commercially available contact lenses are rather limited. Here, we report a flexible method to fabricate customized hydrogel contact lenses. We showed that the fabricated hydrogel is highly transparent, with refractive indices ranging from 1.42 to 1.45 in the spe...

  9. Influence of contact surface quality and contact material on the contact resistances of high current connections

    Energy Technology Data Exchange (ETDEWEB)

    Lange, Christian, E-mail: c.lange@kit.edu [Karlsruhe Institute of Technology (KIT), Institute for Technical Physics, Karlsruhe (Germany); Fietz, Walter H.; Gröner, Frank [Karlsruhe Institute of Technology (KIT), Institute for Technical Physics, Karlsruhe (Germany)

    2013-10-15

    Highlights: ► Contact resistance at a connection between high current Cu–Cu and Cu–Al busbars at room temperature. ► Influence of the surface finish to contact resistance at a connection between high current busbars. ► Influence of gold plating to contact resistance at high current copper busbars. -- Abstract: At the connection between high current room temperature busbars, e.g. feeders for fusion machines, the contact resistance has to be low to avoid high electrical losses. Otherwise an excessive cooling is needed to prevent the busbar from local overheating caused by these losses. In order to determine the parameters, which are relevant to ensure a reproducible and reliable low contact resistance, detailed tests at room temperature with different high current connection types were performed. The contact resistance of aluminum–copper and copper–copper connection was measured for contact areas with different surfaces as e.g. polished, oxidized and gold plated contact area. In addition the change of the contact resistance during a long time operation and at different current densities was determined. Furthermore the effect of humidity, e.g. condensed water and over temperature, e.g. at an overload or a breakdown of the cooling system, on the contact resistance quality were analyzed.

  10. African Journal of Psychiatry: Contact

    African Journals Online (AJOL)

    Principal Contact. Andrew Thomas Division of Psychiatry, Department of Neurosciences, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, SOUTH AFRICA Email: inhouse@iafrica.com ...

  11. Contact lens correction of presbyopia.

    Science.gov (United States)

    Morgan, Philip B; Efron, Nathan

    2009-08-01

    The ageing population highlights the need to provide effective optical solutions for presbyopic contact lens wearers. However, data gathered from annual contact lens fitting surveys demonstrate that fewer than 40% of contact lens wearers over 45 years of age (virtually all of whom can be presumed to suffer a partial or complete loss of accommodation) are prescribed a presbyopic correction. Furthermore, monovision is prescribed as frequently as multifocal lenses. These observations suggest that an optimal solution to the contact lens correction of presbyopia remains elusive.

  12. Contextualizing Intergroup Contact: Do Political Party Cues Enhance Contact Effects?

    DEFF Research Database (Denmark)

    Sønderskov, Kim Mannemar; Thomsen, Jens Peter Frølund

    2015-01-01

    This article examines intergroup contact effects in different political contexts. We expand on previous efforts of social psychologists by incorporating the messages of political parties as a contextual trigger of group membership awareness in contact situations. We argue that the focus among pol...

  13. Multi-Material Front Contact for 19% Thin Film Solar Cells

    Directory of Open Access Journals (Sweden)

    Joop van Deelen

    2016-02-01

    Full Text Available The trade-off between transmittance and conductivity of the front contact material poses a bottleneck for thin film solar panels. Normally, the front contact material is a metal oxide and the optimal cell configuration and panel efficiency were determined for various band gap materials, representing Cu(In,GaSe2 (CIGS, CdTe and high band gap perovskites. Supplementing the metal oxide with a metallic copper grid improves the performance of the front contact and aims to increase the efficiency. Various front contact designs with and without a metallic finger grid were calculated with a variation of the transparent conductive oxide (TCO sheet resistance, scribing area, cell length, and finger dimensions. In addition, the contact resistance and illumination power were also assessed and the optimal thin film solar panel design was determined. Adding a metallic finger grid on a TCO gives a higher solar cell efficiency and this also enables longer cell lengths. However, contact resistance between the metal and the TCO material can reduce the efficiency benefit somewhat.

  14. Nanocrystalline Metal Oxides for Methane Sensors: Role of Noble Metals

    Directory of Open Access Journals (Sweden)

    S. Basu

    2009-01-01

    Full Text Available Methane is an important gas for domestic and industrial applications and its source is mainly coalmines. Since methane is extremely inflammable in the coalmine atmosphere, it is essential to develop a reliable and relatively inexpensive chemical gas sensor to detect this inflammable gas below its explosion amount in air. The metal oxides have been proved to be potential materials for the development of commercial gas sensors. The functional properties of the metal oxide-based gas sensors can be improved not only by tailoring the crystal size of metal oxides but also by incorporating the noble metal catalyst on nanocrystalline metal oxide matrix. It was observed that the surface modification of nanocrystalline metal oxide thin films by noble metal sensitizers and the use of a noble metal catalytic contact as electrode reduce the operating temperatures appreciably and improve the sensing properties. This review article concentrates on the nanocrystalline metal oxide methane sensors and the role of noble metals on the sensing properties.

  15. Multi-Material Front Contact for 19% Thin Film Solar Cells

    NARCIS (Netherlands)

    Deelen, J. van; Tezsevin, Y.; Barink, M.

    2016-01-01

    The trade-off between transmittance and conductivity of the front contact material poses abottleneck for thin film solar panels. Normally, the front contact material is a metal oxide and the optimal cell configuration and panel efficiency were determined for various band gap materials, representing

  16. Alternative current source based Schottky contact with additional electric field

    Science.gov (United States)

    Mamedov, R. K.; Aslanova, A. R.

    2017-07-01

    Additional electric field (AEF) in the Schottky contacts (SC) that covered the peripheral contact region wide and the complete contact region narrow (as TMBS diode) SC. Under the influence of AEF is a redistribution of free electrons produced at certain temperatures of the semiconductor, and is formed the space charge region (SCR). As a result of the superposition of the electric fields SCR and AEF occurs the resulting electric field (REF). The REF is distributed along a straight line perpendicular to the contact surface, so that its intensity (and potential) has a minimum value on the metal surface and the maximum value at a great distance from the metal surface deep into the SCR. Under the influence of AEF as a sided force the metal becomes negative pole and semiconductor - positive pole, therefore, SC with AEF becomes an alternative current source (ACS). The Ni-nSi SC with different diameters (20-1000 μm) under the influence of the AEF as sided force have become ACS with electromotive force in the order of 0.1-1.0 mV, which are generated the electric current in the range of 10-9-10-7 A, flowing through the external resistance 1000 Ohm.

  17. Negative-resistance voltage-current characteristics of superconductor contact junctions for macro-scale applications

    CERN Document Server

    Takayasu, M; Minervini, J V; 10.1109/TASC.2003.812854

    2003-01-01

    Voltage-current characteristics of mechanical pressure contact junctions between superconducting wires are investigated using a voltage-driving method. It is found that the switching regions at low voltages result from negative resistance of the contact junction. The current transport of the contact junctions is discussed from the perspective of two existing models: the multiple Andreev reflections at the two SN interfaces of a SNS (Superconductor/Normal metal /Superconductor) junction and the inhomogeneous multiple Josephson weak-link array. (13 refs).

  18. Investigation into Contact Resistance And Damage of Metal Contacts Used in RF-MEMS Switches

    Science.gov (United States)

    2009-09-01

    thickness of 0.762 mm (0.030”) was used, which required beveling of the cantilever mounting edge to reduce the edge thickness and avoid interference with...Analytic, Finite Element, and Experimental Results,” Sensors and Actuators A, 2(A115):252–258, 21 September 2004. 45. Coutu, Ronald A., James R. Reid...Material, 48:4531–4541, 2000. 49. DelRio, Frank W., Maarten P. de Boer, James A. Knapp, Jr. E. David Reedy, Peggy J. Clews, and Martin L. Dunn. “The role of

  19. Nigerian School Library Journal: Contact

    African Journals Online (AJOL)

    Principal Contact. Prof. DF Elaturoti Editor-in-Chief Abadina Media Resource Centre, University of Ibadan, Nigeria Abadina Media Resource Centre, University of Ibadan, Nigeria Phone: +2348033893853. Email: davidelaturoti@yahoo.com. Support Contact. KA Aramide Email: kolaakinjide@gmail.com. ISSN: 0331-8214.

  20. African Crop Science Journal: Contact

    African Journals Online (AJOL)

    Principal Contact. Dr. J.S. Tenywa Editor-in-Chief Faculty of Agriculture. Makerere University PO Box 7062 Kampala Uganda. Alternative email address: acsj@caes.mak.ac.ug. Email: acss@caes.mak.ac.ug. Support Contact. Editor Email: johntenywa@gmail.com. ISSN: 2072-6589. AJOL African Journals Online. HOW TO ...

  1. Contact Allergy to Neem Oil.

    Science.gov (United States)

    de Groot, Anton; Jagtman, Berend A; Woutersen, Marjolijn

    A case of allergic contact dermatitis from neem oil is presented. Neem oil (synonyms: Melia azadirachta seed oil [INCI name], nim oil, margosa oil) is a vegetable (fixed) oil obtained from the seed of the neem tree Azadirachta indica by cold pressing. Contact allergy to neem oil has been described previously in only 3 patients. The allergen(s) is/are unknown.

  2. Emotional Satisfaction of Customer Contacts

    NARCIS (Netherlands)

    Güngör, Hüseyin

    2007-01-01

    For marketing and customer services researchers and professionals who are interested in customer contacts, customer satisfaction and loyalty issues. Contact centers are playing a pivotal role in customer services of the 21st century. Nevertheless, despite their growing importance and presence,

  3. Aluminum break-point contacts

    NARCIS (Netherlands)

    Heinemann, Martina; Groot, R.A. de

    1997-01-01

    Ab initio molecular dynamics is used to study the contribution of a single Al atom to an aluminum breakpoint contact during the final stages of breaking and the initial stages of the formation of such a contact. A hysteresis effect is found in excellent agreement with experiment and the form of the

  4. Drops, contact lines, and electrowetting

    NARCIS (Netherlands)

    't Mannetje, Dieter

    2013-01-01

    In this work, we study the behaviour of drops and contact lines under the influence of electric fields, and how these can answer fundamental and industrial questions. Our focus is on studying the varying balance of the electric field, hysteresis forces and inertia as the speed of a contact line

  5. Focusing on Contact Lens Safety

    Science.gov (United States)

    ... these solutions require special care. Always remove contact lenses before swimming. Never reuse any lens solution. Always discard all of the used solution after each use, and add fresh solution to your lens case. Do not expose your contacts to any water (which includes lake, pond, and ocean water as ...

  6. Fabricating customized hydrogel contact lens

    Science.gov (United States)

    Childs, Andre; Li, Hao; Lewittes, Daniella M.; Dong, Biqin; Liu, Wenzhong; Shu, Xiao; Sun, Cheng; Zhang, Hao F.

    2016-10-01

    Contact lenses are increasingly used in laboratories for in vivo animal retinal imaging and pre-clinical studies. The lens shapes often need modification to optimally fit corneas of individual test subjects. However, the choices from commercially available contact lenses are rather limited. Here, we report a flexible method to fabricate customized hydrogel contact lenses. We showed that the fabricated hydrogel is highly transparent, with refractive indices ranging from 1.42 to 1.45 in the spectra range from 400 nm to 800 nm. The Young’s modulus (1.47 MPa) and hydrophobicity (with a sessile drop contact angle of 40.5°) have also been characterized experimentally. Retinal imaging using optical coherence tomography in rats wearing our customized contact lenses has the quality comparable to the control case without the contact lens. Our method could significantly reduce the cost and the lead time for fabricating soft contact lenses with customized shapes, and benefit the laboratorial-used contact lenses in pre-clinical studies.

  7. Contact modeling for robotics applications

    Energy Technology Data Exchange (ETDEWEB)

    Lafarge, R.A.; Lewis, C.

    1998-08-01

    At Sandia National Laboratories (SNL), the authors are developing the ability to accurately predict motions for arbitrary numbers of bodies of arbitrary shapes experiencing multiple applied forces and intermittent contacts. In particular, the authors are concerned with the simulation of systems such as part feeders or mobile robots operating in realistic environments. Preliminary investigation of commercial dynamics software packages led them to the conclusion that they could use commercial software to provide everything they needed except for the contact model. They found that ADAMS best fit their needs for a simulation package. To simulate intermittent contacts, they need collision detection software that can efficiently compute the distances between non-convex objects and return the associated witness features. They also require a computationally efficient contact model for rapid simulation of impact, sustained contact under load, and transition to and from contact conditions. This paper provides a technical review of a custom hierarchical distance computation engine developed at Sandia, called the C-Space Toolkit (CSTk). In addition, they describe an efficient contact model using a non-linear damping term developed by SNL and Ohio State. Both the CSTk and the non-linear damper have been incorporated in a simplified two-body testbed code, which is used to investigate how to correctly model the contact using these two utilities. They have incorporated this model into the ADAMS software using the callable function interface. An example that illustrates the capabilities of the 9.02 release of ADAMS with their extensions is provided.

  8. Pan African Medical Journal: Contact

    African Journals Online (AJOL)

    Principal Contact. Dr Raoul Kamadjeu Editor-in-Chief The Pan African Medical Journal Phone: +254 714 606 223. Email: raoul.kamadjeu@gmail.com. Support Contact. Editor Email: editor@panafrican-med-journal.com. ISSN: 1937-8688. AJOL African Journals Online. HOW TO USE AJOL... for Researchers · for Librarians ...

  9. Body contact and body language

    DEFF Research Database (Denmark)

    Winther, Helle

    2008-01-01

    Body contact and body language are unique and existential and, although culturally dependent and socially embodied, they are also universal communication forms. For small children all over the world, warm, close and nourishing body contact is fundamental to their embodied experi­ence of themselves...... and the boundaries between self and world. In western societies, the modern premises for contact are in some ways developing from close contact to virtual communication. With this breadth of perspective in mind, the ques­tion is whether conscious and experimental work with body contact and body language in move......­ment psychology and education provide potential for intense personal develop­ment as well as for social and cultural learning processes. This performative research project originates from the research project entitled, Movement Psy­chol­ogy: The Language of the Body and the Psy­chol­ogy of Movement based...

  10. Photo-induced currents in the sandwich metal-ferroelectric-metal structure

    Science.gov (United States)

    Ivanov, V.; Karpets, Yu; Perkov, Yu

    2017-01-01

    It was described the photoelectric effect in thin sandwich metal-ferroelectric-metal system. The effect was observed in doped lithium niobate crystals with two electrodes of different metals. The effect is observed only in doped lithium niobate crystals and has a maximum for concentrations of impurities of iron around 0.3 % weight. This paper proposed thermal model of the investigated phenomena resulting from field contact potential difference on the borders of section of metal-ferroelectric material. The results obtained can be used to develop radiation receivers, as well as in the interpretation of experimental results on studying the properties of sandwiched metal-ferroelectric-metal structure.

  11. Radioactive Material in Scrap Metal | RadTown USA | US EPA

    Science.gov (United States)

    2017-08-07

    Sometimes radioactive materials are disposed of improperly and end up in scrap metal yards. You will probably never come into contact with contaminated scrap metal. If you think you have found contaminated scrap metal, do not touch it. Immediately contact your state radiation control office.

  12. Advanced source/drain and contact design for nanoscale CMOS

    Science.gov (United States)

    Vega, Reinaldo

    The development of nanoscale MOSFETs has given rise to increased attention paid to the role of parasitic source/drain and contact resistance as a performance-limiting factor. Dopant-segregated Schottky (DSS) source/drain MOSFETs have become popular in recent years to address this series resistance issue, since DSS source/drain regions comprise primarily of metal or metal silicide. The small source/drain extension (SDE) regions extending from the metallic contact regions are an important design parameter in DSS MOSFETs, since their size and concentration affect contact resistance, series resistance, band-to-band tunneling (BTBT), SDE tunneling, and direct source-to-drain tunneling (DSDT) leakage. This work investigates key design issues surrounding DSS MOSFETs from both a modeling and experimental perspective, including the effect of SDE design on ambipolar leakage, the effect of random dopant fluctuation (RDF) on specific contact resistivity, 3D FinFET source/drain and contact design optimization, and experimental methods to achieve tuning of the SDE region. It is found that DSS MOSFETs are appropriate for thin body high performance (HP) and low operating power (LOP) MOSFETs, but not low standby power (LSTP) MOSFETs, due to a trade-off between ambipolar leakage and contact resistance. It is also found that DSDT will not limit DSS MOSFET scalability, nor will RDF limit contact resistance scaling, at the end of the CMOS roadmap. Furthermore, it is found that SDE tunability in DSS MOSFETs is achievable in the real-world, for an implant-to-silicide (ITS) process, by employing fluorine implant prior to metal deposition and silicidation. This is found to open up the DSS process design space for the trade-off between SDE junction depth and contact resistance. Si1-xGex process technology is also explored, and Ge melt processing is found to be a promising low-cost alternative to epitaxial Si1-xGex growth for forming crystalline Si1-xGe x films. Finally, a new device

  13. Contact resistance and stability study for Au, Ti, Hf and Ni contacts on thin-film Mg2Si

    KAUST Repository

    Zhang, Bo

    2016-12-28

    We present a detailed study of post-deposition annealing effects on contact resistance of Au, Ti, Hf and Ni electrodes on Mg2Si thin films. Thin-film Mg2Si and metal contacts were deposited using magnetron sputtering. Various post-annealing temperatures were studied to determine the thermal stability of each contact metal. The specific contact resistivity (SCR) was determined using the Cross Bridge Kelvin Resistor (CBKR) method. Ni contacts exhibits the best thermal stability, maintaining stability up to 400 °C, with a SCR of approximately 10−2 Ω-cm2 after annealing. The increased SCR after high temperature annealing is correlated with the formation of a Mg-Si-Ni mixture identified by cross-sectional scanning transmission electron microscopy (STEM) characterization, X-ray diffraction characterization (XRD) and other elemental analyses. The formation of this Mg-Si-Ni mixture is attributed to Ni diffusion and its reaction with the Mg2Si film.

  14. Two cases of occupational allergic contact dermatitis from a cycloaliphatic epoxy resin in a neat oil: Case Report

    Science.gov (United States)

    Jensen, Charlotte D; Andersen, Klaus E

    2003-01-01

    Background Metal-working fluids contain complex mixtures of chemicals and metal workers constitute a potential risk group for the development of allergic contact dermatitis. Case presentation Two metal workers developed allergic contact dermatitis on the hands and lower arms from exposure to a neat oil used in metal processing. Patch testing revealed that the relevant contact allergen was a cycloaliphatic epoxy resin, 1,2-cyclohexanedicarboxylic acid, bis(oxiranylmethyl) ester, added to the oil as a stabilizer. None of the patients had positive reactions to the bisphenol A-based epoxy resin in the standard series. Conclusions These cases emphasize that well-known contact allergens may show up from unexpected sources of exposure. Further, it can be a long-lasting, laborious process to detect an occupational contact allergen and cooperation from the patient and the manufacturer of the sensitizing product is essential. PMID:12685935

  15. Single closed contact for 0.18-micron photolithography process

    Science.gov (United States)

    Cheung, Cristina; Phan, Khoi A.; Chiu, Robert J.

    2000-06-01

    With the rapid advances of deep submicron semiconductor technology, identifying defects is converted into a challenge for different modules in the fabrication of chips. Yield engineers often do bitmap on a memory circuit array (SRAM) to identify the failure bits. This is followed by a wafer stripback to look for visual defects at each deprocessed layer for feedback to the Fab. However, to identify the root cause of a problem, Fab engineers must be able to detect similar defects either on the product wafers in process or some short loop test wafers. In the photolithography process, we recognize that the detection of defects is becoming as important as satisfying the critical dimension (CD) of the device. For a multi-level metallization chemically mechanical polish backend process, it is very difficult to detect missing contacts or via at the masking steps due to metal grain roughness, film color variation and/or previous layer defects. Often, photolithography engineer must depend on Photo Cell Monitor (PCM) and short loop experiments for controlling baseline defects and improvement. In this paper, we discuss the findings on the Poly mask PCM and the Contact mask PCM. We present the comparison between the Poly mask and the Contact mask of the I-line Phase Shifted Via mask and DUV mask process for a 0.18 micron process technology. The correlation and the different type of defects between the Contact PCM and the Poly Mask are discussed. The Contact PCM was found to be more sensitive and correlated to contact failure at sort yield better. We also dedicate to study the root cause of a single closed contact hole in the Contact mask short loop experiment for a 0.18 micron process technology. A single closed contact defect was often caused by the developer process, such as bubbles in the line, resist residue left behind, and the rinse mechanism. We also found surfactant solution helps to improve the surface tension of the wafer for the developer process and this prevents

  16. Incidence of allergic contact sensitization in Danish adults between 1990 and 1998; the Copenhagen Allergy Study, Denmark

    DEFF Research Database (Denmark)

    Nielsen, N H; Linneberg, A; Menné, T

    2002-01-01

    BACKGROUND: Studies of incidence of contact allergy in a general population have not been reported. Data from incidence studies may support and direct strategies for prevention of contact allergy and allergic contact dermatitis. OBJECTIVE: To study the incidence of contact allergy and evaluate risk...... contact allergy to one or more haptens other than nickel were found. The data indicate that female sex, young age and ear piercing (before 1990) were risk factors for developing nickel allergy. Between 1990 and 1998 metal contact dermatitis was reported in seven women with incident nickel allergy. Six...

  17. Liquid metal cooled nuclear reactor plant system

    Science.gov (United States)

    Hunsbedt, Anstein; Boardman, Charles E.

    1993-01-01

    A liquid metal cooled nuclear reactor having a passive cooling system for removing residual heat resulting for fuel decay during reactor shutdown, or heat produced during a mishap. The reactor system is enhanced with sealing means for excluding external air from contact with the liquid metal coolant leaking from the reactor vessel during an accident. The invention also includes a silo structure which resists attack by leaking liquid metal coolant, and an added unique cooling means.

  18. Speciation in Metal Toxicity and Metal-Based Therapeutics

    Directory of Open Access Journals (Sweden)

    Douglas M. Templeton

    2015-04-01

    Full Text Available Metallic elements, ions and compounds produce varying degrees of toxicity in organisms with which they come into contact. Metal speciation is critical to understanding these adverse effects; the adjectives “heavy” and “toxic” are not helpful in describing the biological properties of individual elements, but detailed chemical structures are. As a broad generalization, the metallic form of an element is inert, and the ionic salts are the species that show more significant bioavailability. Yet the salts and other chelates of a metal ion can give rise to quite different toxicities, as exemplified by a range of carcinogenic potential for various nickel species. Another important distinction comes when a metallic element is organified, increasing its lipophilicity and hence its ability to penetrate the blood brain barrier, as is seen, for example, with organic mercury and tin species. Some metallic elements, such as gold and platinum, are themselves useful therapeutic agents in some forms, while other species of the same element can be toxic, thus focusing attention on species interconversions in evaluating metal-based drugs. The therapeutic use of metal-chelating agents introduces new species of the target metal in vivo, and this can affect not only its desired detoxification, but also introduce a potential for further mechanisms of toxicity. Examples of therapeutic iron chelator species are discussed in this context, as well as the more recent aspects of development of chelation therapy for uranium exposure.

  19. Multifocal contact lens myopia control.

    Science.gov (United States)

    Walline, Jeffrey J; Greiner, Katie L; McVey, M Elizabeth; Jones-Jordan, Lisa A

    2013-11-01

    Previous studies on soft multifocal contact lens myopia control published in the peer-reviewed literature reported findings of noncommercial contact lenses worn for 1 year or less. This study sought to determine the progression of myopia and axial elongation of children fitted with commercially available distance center soft multifocal contact lenses for 2 years. Eight- to eleven-year-old children with -1.00 D to -6.00 D spherical component and less than 1.00 D astigmatism were fitted with soft multifocal contact lenses with a +2.00 D add (Proclear Multifocal "D"; CooperVision, Fairport, NY). They were age- and gender-matched to participants from a previous study who were fitted with single-vision contact lenses (1 Day Acuvue; Vistakon, Jacksonville, FL). A-scan ultrasound and cycloplegic autorefraction were performed at baseline, after 1 year, and after 2 years. Multilevel modeling was used to compare the rate of change of myopia and axial length between single-vision and soft multifocal contact lens wearers. Forty participants were fitted with soft multifocal contact lenses, and 13 did not contribute complete data (5 contributed 1 year of data). The adjusted mean ± standard error spherical equivalent progression of myopia at 2 years was -1.03 ± 0.06 D for the single-vision contact lens wearers and -0.51 ± 0.06 for the soft multifocal contact lens wearers (p < 0.0001). The adjusted mean axial elongation was 0.41 ± 0.03 and 0.29 ± 0.03 for the single-vision and soft multifocal contact lens wearers, respectively (p < 0.0016). Soft multifocal contact lens wear resulted in a 50% reduction in the progression of myopia and a 29% reduction in axial elongation during the 2-year treatment period compared to a historical control group. Results from this and other investigations indicate a need for a long-term randomized clinical trial to investigate the potential for soft multifocal contact lens myopia control.

  20. Metallization failures

    Science.gov (United States)

    Beatty, R.

    1971-01-01

    Metallization-related failure mechanisms were shown to be a major cause of integrated circuit failures under accelerated stress conditions, as well as in actual use under field operation. The integrated circuit industry is aware of the problem and is attempting to solve it in one of two ways: (1) better understanding of the aluminum system, which is the most widely used metallization material for silicon integrated circuits both as a single level and multilevel metallization, or (2) evaluating alternative metal systems. Aluminum metallization offers many advantages, but also has limitations particularly at elevated temperatures and high current densities. As an alternative, multilayer systems of the general form, silicon device-metal-inorganic insulator-metal, are being considered to produce large scale integrated arrays. The merits and restrictions of metallization systems in current usage and systems under development are defined.

  1. Electrical properties of aluminum contacts deposited by DC sputtering method for photovoltaic applications

    Directory of Open Access Journals (Sweden)

    Krawczak Ewelina

    2017-01-01

    Full Text Available The use of aluminum contacts is common in the process of silicon solar cells production because of low contact resistivity. It has also a great importance in thin film technology for photovoltaics, especially in copper-indium-gallium-diselenide (CIGS devices. The final stage of CIGS cell production is the top contact deposition of high conductivity layer for lateral current collection. Such material has to be highly optically transparent as well. In order to make a contact, metal is deposited onto TCO layer with minimum shadowing to allow as much light as possible into device. The metal grid contact is being made by deposition of few microns of aluminum. The resistivity of the deposited material as well as resistance between the metal grid and TCO layer plays a great role in high quality solar cell production. This paper presents the results of four point probe conductivity analysis of Al thin films deposited by direct current (DC magnetron sputtering method. Influence of technological parameters of the Al deposition process on sheet resistance of deposited layers has been showed. In order to obtain the lowest resistivity of the thin contact layer, optimal set of sputtering parameters, i.e. power applied, deposition time and deposition pressure was found. The resistivity of the contact between two adjacent Al metal fingers deposited onto transparent conductive Al-doped zinc oxide film has been also examined.

  2. Electrical properties of aluminum contacts deposited by DC sputtering method for photovoltaic applications

    Science.gov (United States)

    Krawczak, Ewelina; Gułkowski, Sławomir

    2017-10-01

    The use of aluminum contacts is common in the process of silicon solar cells production because of low contact resistivity. It has also a great importance in thin film technology for photovoltaics, especially in copper-indium-gallium-diselenide (CIGS) devices. The final stage of CIGS cell production is the top contact deposition of high conductivity layer for lateral current collection. Such material has to be highly optically transparent as well. In order to make a contact, metal is deposited onto TCO layer with minimum shadowing to allow as much light as possible into device. The metal grid contact is being made by deposition of few microns of aluminum. The resistivity of the deposited material as well as resistance between the metal grid and TCO layer plays a great role in high quality solar cell production. This paper presents the results of four point probe conductivity analysis of Al thin films deposited by direct current (DC) magnetron sputtering method. Influence of technological parameters of the Al deposition process on sheet resistance of deposited layers has been showed. In order to obtain the lowest resistivity of the thin contact layer, optimal set of sputtering parameters, i.e. power applied, deposition time and deposition pressure was found. The resistivity of the contact between two adjacent Al metal fingers deposited onto transparent conductive Al-doped zinc oxide film has been also examined.

  3. Nordic project food contact materials

    DEFF Research Database (Denmark)

    Li, Ågot; Tesdal Håland, Julie; Petersen, Jens Højslev

    Denmark, Finland, Faroe Islands, Iceland, Norway and Sweden have in 2013––2015 conducted a Nordic project on food contact materials. Food contact materials are used in all stages of food production and can be a general source of contamination. The food safety authorities in most of the Nordic...... countries have had a limited focus on the FCM area with the exception of Denmark and Finland. The aim of the project was therefore to control establishments producing, importing or using plastic food contact materials as well as to increase the knowledge of the inspectors performing these controls....... The focus of the inspections was to control the declaration of compliance (DoC) for plastic food contact materials. The requirement for a Doc is mandatory in order to ensure that the FCM complies with the legislation. In addition some products were analyzed for phthalates....

  4. [Contact granuloma of the larynx].

    Science.gov (United States)

    Vasilenko, Iu S; Kittel, G

    2006-01-01

    The authors analyse the results of clinical examination of patients with contact granuloma of the larynx treated in Moscow and Erlangen (Germany) clinics. Etiology, pathogenesis of this disease and treatment policy are discussed.

  5. Ghana Journal of Geography: Contact

    African Journals Online (AJOL)

    Principal Contact. Joseph A. Yaro Professor University of Ghana, Legon. Department of Geography and Resource Development. P. O. Box LG 59. Legon. Ghana. Alternative email address: jayaro@ug.edu.gh. Phone: +233244038915. Email: jayaro@ug.edu.gh ...

  6. Occupational contact dermatitis in hairdressers

    DEFF Research Database (Denmark)

    Schwensen, Jakob F; Johansen, Jeanne D; Veien, Niels K

    2014-01-01

    BACKGROUND: Occupational contact dermatitis among hairdressers is frequent, owing to daily exposure to irritants and allergens. OBJECTIVES: To identify sensitization to the most common allergens associated with the occupation of hairdressing. METHODS: Patch test results of 399 hairdressers and 19...

  7. Journal of Business Research: Contact

    African Journals Online (AJOL)

    Principal Contact. Goski Alabi Mrs Institute of Professional Studies (IPS) P. 0 Box 149 Institute Of Professional Studies (IPS) Legon, Accra Ghana Phone: +233 24 64 52798. Fax: +233 21 513539. Email: goskia@yahoo.com ...

  8. Scalable algorithms for contact problems

    CERN Document Server

    Dostál, Zdeněk; Sadowská, Marie; Vondrák, Vít

    2016-01-01

    This book presents a comprehensive and self-contained treatment of the authors’ newly developed scalable algorithms for the solutions of multibody contact problems of linear elasticity. The brand new feature of these algorithms is theoretically supported numerical scalability and parallel scalability demonstrated on problems discretized by billions of degrees of freedom. The theory supports solving multibody frictionless contact problems, contact problems with possibly orthotropic Tresca’s friction, and transient contact problems. It covers BEM discretization, jumping coefficients, floating bodies, mortar non-penetration conditions, etc. The exposition is divided into four parts, the first of which reviews appropriate facets of linear algebra, optimization, and analysis. The most important algorithms and optimality results are presented in the third part of the volume. The presentation is complete, including continuous formulation, discretization, decomposition, optimality results, and numerical experimen...

  9. [Contact lens-related keratitis].

    Science.gov (United States)

    Steiber, Zita; Berta, András; Módis, László

    2013-11-10

    Nowadays, keratitis, corneal infection due to wearing contact lens means an increasingly serious problem. Neglected cases may lead to corneal damage that can cause blindness in cases of otherwise healthy eyes. Early diagnosis based on the clinical picture and the typical patient history is an important way of prevention. Prophylaxis is substantial to avoid bacterial and viral infection that is highly essential in this group of diseases. Teaching contact lens wearers the proper contact lens care, storage, sterility, and hygiene regulations is of great importance. In case of corneal inflammation early accurate diagnosis supported by microbiological culture from contact lenses, storage boxes or cornea is very useful. Thereafter, targeted drug therapy or in therapy-resistant cases surgical treatment may even be necessary in order to sustain suitable visual acuity.

  10. Contact vitiligo: etiology and treatment

    Directory of Open Access Journals (Sweden)

    Singh P

    2003-01-01

    Full Text Available Fifty patients of contact vitiligo were studied. EtiologicaI agents of contact vitiligo were identified by clinical history, distribution of lesions and patch testing with suspected material. All patients were advised to avoid the suspected agent and treated with PUVASOL and topical steroid. Out of 50 patients (Male 8%, Female 92% age 14-60 years., etiological agent of contact vitiligo was found to be sticking bindi alone in 24 (48%, while bindi along with other etiological agents were found to be purse, foot wear, plastic watch strap, lipstick and tooth paste in 14 ( 28% cases. 14 (28% patients also had disseminated lesions of vitiligo along with contact vitiligo. Positive reaction with patch testing was observed in 18 (36% while depigmentation was seen in 4 ( 8% cases. We observed that response of treatment was better in patients with shorter duration of disease while poor response was seen in patients with longer duration of disease.

  11. Highland Medical Research Journal: Contact

    African Journals Online (AJOL)

    Principal Contact. Professor Emmanuel I Agaba Editor-in-Chief Department of Medicine. Department of Medicine. Jos University Teaching Hospital. PMB 2076. Jos, Nigeria. Phone: +2348037001392. Fax: +243 073454172. Email: highmedresj@gmail.com ...

  12. Animal Production Research Advances: Contact

    African Journals Online (AJOL)

    Principal Contact. Dr I Charles Okoli Editor-in-Chief Federal University of Technology Department of Animal Science and Technology PMB 1526 Owerri Nigeria Phone: +2348056647100. Email: dr_charleso@yahoo.com ...

  13. Liquid Metal Machine Triggered Violin-Like Wire Oscillator.

    Science.gov (United States)

    Yuan, Bin; Wang, Lei; Yang, Xiaohu; Ding, Yujie; Tan, Sicong; Yi, Liting; He, Zhizhu; Liu, Jing

    2016-10-01

    The first ever oscillation phenomenon of a copper wire embraced inside a self-powered liquid metal machine is discovered. When contacting a copper wire to liquid metal machine, it would be swallowed inside and then reciprocally moves back and forth, just like a violin bow. Such oscillation could be easily regulated by touching a steel needle on the liquid metal surface.

  14. Waste printing paper as analogous adsorbents for heavy metals in ...

    African Journals Online (AJOL)

    H2O), 0.1M nitric acid, (HNO3), and ethylenediaminetetracetic acid (EDTA) was evaluated for possible recovery of Pb2+. The results showed WPP has adsorption efficacy of >90.0% and metal uptake of ≤ 25 mg/g for the assessed metal ions. There was high effect of metal dosage and contact time on WPP adsorption ...

  15. Coupling of Armchair and Zigzag Tubes to a Free Electron Metal

    Science.gov (United States)

    Anantram, M. P.; Biegel, Bryan (Technical Monitor)

    2001-01-01

    The effect of nanotube chirality is of prime importance in determining its electronic properties. We address the issue of how chirality affects the coupling of a nanotube to metal contacts. We model coupling of armchair and zigzag nanotubes to metal contacts, in both the side- and end-contacted geometries. In the side-contacted geometry, the coupling of armchair and metallic-zigzag nanotubes to a free electron metal are significantly different. Namely, it is possible to drive a larger current through a metallic-zigzag nanotube. The predicted difference holds good when both (a) the entire circumference and (b) only a finite sector of the nanotube makes contact to the metal electrode. It might be possible to observe the predicted difference between armchair and zigzag nanotubes using gold contacts.

  16. Embodied Archives as Contact Zones

    OpenAIRE

    Judit Vidiella

    2015-01-01

    This article proposes a reflection about affective politics from locating some theoretical and conceptual genealogies like «emotion», «affection», «zones of contact»…, that understand them as action and force fields. These contributions allow us to rethink the relation of affects with politics and strategies of archive linked to performance, and understood as zones of friction, collision, circulation and contact: performative writing, repertoire, memes…

  17. Embodied Archives as Contact Zones

    Directory of Open Access Journals (Sweden)

    Judit Vidiella

    2015-02-01

    Full Text Available This article proposes a reflection about affective politics from locating some theoretical and conceptual genealogies like «emotion», «affection», «zones of contact»…, that understand them as action and force fields. These contributions allow us to rethink the relation of affects with politics and strategies of archive linked to performance, and understood as zones of friction, collision, circulation and contact: performative writing, repertoire, memes…

  18. Contact dermatitis to botanical extracts.

    Science.gov (United States)

    Kiken, David A; Cohen, David E

    2002-09-01

    A review of the literature of reported cases of contact dermatitis to a variety of natural herbal extracts is Presented. Natural extracts are commonly used ingredients in many cosmetic preparations and homeopathic remedies. Although the term natural botanical extracts inherently purports to have beneficial and benign properties, these extracts can cause adverse reactions in individuals. As such, dermatologists should be cognizant of these agents as possible sources of allergenicity in patients presenting with contact dermatitis. Copyright 2002, Elsevier Science (USA). All rights reserved.

  19. Study on the deterioration origin of thermomechanical contact fatigue

    Science.gov (United States)

    Tudose-Sandu-Ville, O. F.

    2016-08-01

    Thermomechanical wear is a complex phenomenon present in a number of industrial domains, such as rolling bearings, gears, friction wheels, rolling mill rollers. In this type of surface tribological deterioration, both fundamental and some peculiar wears are combined (abrasive, adhesive, corrosive wear and contact fatigue), with mechanical ant thermal causes. The present paper takes into account the contact fatigue type of deterioration, with both causes in mechanical variable load and the thermal tide action on the contact surface. There are some theories synthetically presented regarding the location of critical stresses in rolling contact fatigue. The Jacq thermal effect is briefly presented with some considerations concerning the temperature gradient in the metallic wall. The connection between the Jacq thermal anomaly and the thermomechanical contact fatigue is considered to be a new approach. Also, the same location for both mechanical and thermal critical stresses gives a strong support for the thermomechanical contact fatigue primary deterioration, according to the results obtained during the author's PhD research.

  20. [Contact lens care and maintenance].

    Science.gov (United States)

    Bloise, L

    2017-04-01

    All contact lenses with replacement schedules longer than daily must be maintained. At each step of their use, the lenses may be contaminated. Contact lens solutions perform the essential functions of cleaning, decontaminating and preserving the lenses to prevent infectious problems and improve wearing comfort. Contact lens contamination essentially comes from hands, cleaning solutions, cases, water and the environment. The pathogenic microorganisms are mainly Gram-negative bacteria, fungi and amoebae. Contact lens deposits may or may not have an organic origin. Their presence increases the risk of infection because they serve as a nutrient matrix for microbes, and they are responsible for wearing discomfort. Contact lens solutions differ in their composition, their mechanism of action and the concentration of the various agents. To prescribe the best lens care system to each wearer and for each material, it is necessary to be very familiar with them. Maintenance is the main cause of discomfort with contact lenses, either through improper use, solution-material incompatibility, or a reaction of the wearer to the components. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

  1. [Contact allergy to henna tattoos].

    Science.gov (United States)

    Steinkjer, Bjarte; Stangeland, Katarina Zak; Mikkelsen, Carsten Sauer

    2011-03-18

    Tattoos with henna colours have become very popular and the prevalence of contact allergy seems to increase. This is a short review article based on our own clinical experience and literature identified through a search in PubMed with the words "henna", "paraphenylendiamin" and "allergic contact dermatitis." A case report is included. It is well documented that many experience skin reactions after henna tattoos. The cause is almost always contact allergy to the azo compound paraphenylendiamin, which is added to speed up the process and make the colour darker. Most people, including children, get henna tattoos during vacations in Asia or the Mediterranean. Established contact allergy is permanent. Many hair-colour products contain paraphenylendiamin, and persons with contact allergy against the product may develop a very strong contact allergic eczema by use of such substances. Acute reactions are treated with local cortisone products, or with systemic steroids. Cross reaction to substances with a similar chemical structure may occur. Tattoos with paraphenylendiamin-containing henna colours should be avoided.

  2. Contact printed masks for 3D microfabrication in negative resists

    DEFF Research Database (Denmark)

    Häfliger, Daniel; Boisen, Anja

    2005-01-01

    We present a process based on contact printed shadow masks for three dimensional microfabrication of soft and sensitive overhanging membranes in SU-8. A metal mask is transferred onto unexposed SU-8 from an elastomer stamp made of polydimethylsiloxane. This mask is subsequently embedded into the ......We present a process based on contact printed shadow masks for three dimensional microfabrication of soft and sensitive overhanging membranes in SU-8. A metal mask is transferred onto unexposed SU-8 from an elastomer stamp made of polydimethylsiloxane. This mask is subsequently embedded...... into the negative resist to protect buried material from UV-exposure. Unlike direct evaporation-deposition of a mask onto the SU-8, printing avoids high stress and radiation, thus preventing resist wrinkling and prepolymerization. We demonstrate effective monolithic fabrication of soft, 4-μm thick and 100-μm long...

  3. Strong paramagnon scattering in single atom Pd contacts

    Science.gov (United States)

    Schendel, V.; Barreteau, C.; Brandbyge, M.; Borca, B.; Pentegov, I.; Schlickum, U.; Ternes, M.; Wahl, P.; Kern, K.

    2017-07-01

    Among all transition metals, palladium (Pd) has the highest density of states at the Fermi energy at low temperatures yet does not fulfill the Stoner criterion for ferromagnetism. However, close proximity to magnetism renders it a nearly ferromagnetic metal, which hosts paramagnons, strongly damped spin fluctuations. Here we compare the total and the differential conductance of monoatomic contacts consisting of single Pd and cobalt (Co) atoms between Pd electrodes. Transport measurements reveal a conductance for Co of 1 G0 , while for Pd we obtain 2 G0 . The differential conductance of monoatomic Pd contacts shows a reduction with increasing bias, which gives rise to a peculiar Λ -shaped spectrum. Supported by theoretical calculations, we correlate this finding with the lifetime of hot quasiparticles in Pd, which is strongly influenced by paramagnon scattering. In contrast to this, Co adatoms locally induce magnetic order, and transport through single cobalt atoms remains unaffected by paramagnon scattering, consistent with theory.

  4. Implementation of Tunneling Passivated Contacts into Industrially Relevant n-Cz Si Solar Cells

    Energy Technology Data Exchange (ETDEWEB)

    Nemeth, William; LaSalvia, Vincenzo; Page, Matthew R.; Warren, Emily L.; Dameron, Arrelaine; Norman, Andrew G.; Lee, Benjamin G.; Young, David L.; Stradins, Paul

    2015-06-14

    We identify bottlenecks, and propose solutions, to implement a B-diffused front emitter and a backside pc-Si/SiO2 pasivated tunneling contact into high efficiency n-Cz Si cells in an industrially relevant way. We apply an O-precipitate dissolution treatment to make n-Cz wafers immune to bulk lifetime process degradation, enabling robust, passivated B front emitters with J0 <; 20fA/cm2. Adding ultralow recombination n+ pc-Si/SiO2 back contacts enables pre-metallized cells with iVoc=720 mV and J0=8.6 fA/cm2. However, metallization significantly degrades performance of these contacts due to pinholes and possibly, grain boundary diffusion of primary metal and source contaminates such as Cu. An intermediate, doped a-Si:H capping layer is found to significantly block the harmful metal penetration into pc-Si.

  5. Crane-Load Contact Sensor

    Science.gov (United States)

    Youngquist, Robert; Mata, Carlos; Cox, Robert

    2005-01-01

    An electronic instrument has been developed as a prototype of a portable crane-load contact sensor. Such a sensor could be helpful in an application in which the load rests on a base in a horizontal position determined by vertical alignment pins (see Figure 1). If the crane is not positioned to lift the load precisely vertically, then the load can be expected to swing once it has been lifted clear of the pins. If the load is especially heavy, large, and/or fragile, it could hurt workers and/or damage itself and nearby objects. By indicating whether the load remains in contact with the pins when it has been lifted a fraction of the length of the pins, the crane-load contact sensor helps the crane operator determine whether it is safe to lift the load clear of the pins: If there is contact, then the load is resting against the sides of the pins and, hence, it may not be safe to lift; if contact is occasionally broken, then the load is probably not resting against the pins, so it should be safe to lift. It is assumed that the load and base, or at least the pins and the surfaces of the alignment holes in the load, are electrically conductive, so the instrument can use electrical contact to indicate mechanical contact. However, DC resistance cannot be used as an indicator of contact for the following reasons: The load and the base are both electrically grounded through cables (the load is grounded through the lifting cable of the crane) to prevent discharge of static electricity. In other words, the DC resistance between the load and the pins is always low, as though they were always in direct contact. Therefore, instead of DC resistance, the instrument utilizes the AC electrical impedance between the pins and the load. The signal frequency used in the measurement is high enough (.1 MHz) that the impedance contributed by the cables and the electrical ground network of the building in which the crane and the base are situated is significantly greater than the contact

  6. Proposed ICDRG Classification of the Clinical Presentation of Contact Allergy

    DEFF Research Database (Denmark)

    Pongpairoj, Korbkarn; Ale, Iris; Andersen, Klaus Ejner

    2016-01-01

    eczema, multifactorial dermatitis including allergic contact dermatitis, by proxy, mimicking angioedema, airborne contact dermatitis, photo-induced contact dermatitis, systemic contact dermatitis, noneczematous contact dermatitis, contact urticaria, protein contact dermatitis, respiratory...

  7. Comparison between frictional behavior of the soft and brittle materials at different contact pressures

    Directory of Open Access Journals (Sweden)

    Mehdi Eskandarzade

    2017-06-01

    Full Text Available Miavaghi, A. Kangarlou, H. and Eskandarzade, M. 2017. Comparison between frictional behavior of the soft and brittle materials at different contact pressures. Lebanese Science Journal. 18(1: 98-105. Coefficient of friction changed significantly by the change in contact pressure. Experimental measurement of the coefficient of friction in different contact pressures can be useful in numerical and analytical analysis of many engineering problems, such as metal forming process. This study dedicated to investigate the sensitivity of the friction coefficient to changes in contact pressures. To aim this goal the special tribometer device has been fabricated and the coefficient of friction of the soft and brittle metals when sliding with a low speed on a rigid body are measured for different contact pressures. The friction sensitivity of the soft (copper and aluminum and brittle (steel samples to changes in contact pressure are compared and discussed. The results showed that both brittle and soft metals are highly sensitive for change in contact pressure but their behaviour is slightly different. While the coefficient of friction of the steel sample when sliding on a steel substrate is reduced sharply by a little increase in contact pressure; the coefficient of friction of the soft material when sliding on a steel substrate is reduced slowly depending on the magnetude of the applied normal load.

  8. Optimization of Contact Force and Pull-in Voltage for Series based MEMS Switch

    Directory of Open Access Journals (Sweden)

    Abhijeet KSHIRSAGAR

    2010-04-01

    Full Text Available Cantilever based metal-to-metal contact type MEMS series switch has many applications namely in RF MEMS, Power MEMS etc. A typical MEMS switch consists of a cantilever as actuating element to make the contact between the two metal terminals of the switch. The cantilever is pulled down by applying a pull-in voltage to the control electrode that is located below the middle portion of the cantilever while only the tip portion of the cantilever makes contact between the two terminals. Detailed analysis of bending of the cantilever for different pull-in voltages reveals some interesting facts. At low pull-in voltage the cantilever tip barely touches the two terminals, thus resulting in very less contact area. To increase contact area a very high pull-in voltage is applied, but it lifts the tip from the free end due to concave curving of the cantilever in the middle region of the cantilever where the electrode is located. Again it results in less contact area. Furthermore, the high pull-in voltage produces large stress at the base of the cantilever close to the anchor. Therefore, an optimum, pull-in voltage must exist at which the concave curving is eliminated and contact area is maximum. In this paper authors report the finding of optimum contact force and pull-in voltage.

  9. Ferromagnetic tunnel contacts to graphene: Contact resistance and spin signal

    Energy Technology Data Exchange (ETDEWEB)

    Cubukcu, M.; Laczkowski, P.; Vergnaud, C.; Marty, A.; Attané, J.-P.; Notin, L.; Vila, L., E-mail: laurent.vila@cea.fr; Jamet, M. [University Grenoble Alpes, CEA, INAC-SP2M, F-38054 Grenoble (France); Martin, M.-B.; Seneor, P.; Anane, A.; Deranlot, C.; Fert, A. [Unité Mixte de Physique CNRS-Thales, F-91767 Palaiseau (France); Auffret, S. [University Grenoble Alpes, CNRS, CEA, INAC-SPINTEC, Grenoble F-38054 (France); Ducruet, C. [Crocus Technology, 4 place Robert Schuman, 38000 Grenoble (France)

    2015-02-28

    We report spin transport in CVD graphene-based lateral spin valves using different magnetic contacts. We compared the spin signal amplitude measured on devices where the cobalt layer is directly in contact with the graphene to the one obtained using tunnel contacts. Although a sizeable spin signal (up to ∼2 Ω) is obtained with direct contacts, the signal is strongly enhanced (∼400 Ω) by inserting a tunnel barrier. In addition, we studied the resistance-area product (R.A) of a variety of contacts on CVD graphene. In particular, we compared the R.A products of alumina and magnesium oxide tunnel barriers grown by sputtering deposition of aluminum or magnesium and subsequent natural oxidation under pure oxygen atmosphere or by plasma. When using an alumina tunnel barrier on CVD graphene, the R.A product is high and exhibits a large dispersion. This dispersion can be highly reduced by using a magnesium oxide tunnel barrier, as for the R.A value. This study gives insight in the material quest for reproducible and efficient spin injection in CVD graphene.

  10. Contact printed masks for 3D microfabrication in negative resists

    OpenAIRE

    Häfliger, Daniel; Boisen, Anja

    2005-01-01

    We present a process based on contact printed shadow masks for three dimensional microfabrication of soft and sensitive overhanging membranes in SU-8. A metal mask is transferred onto unexposed SU-8 from an elastomer stamp made of polydimethylsiloxane. This mask is subsequently embedded into the negative resist to protect buried material from UV-exposure. Unlike direct evaporation-deposition of a mask onto the SU-8, printing avoids high stress and radiation, thus preventing resist wrinkling a...

  11. Solar cell with back side contacts

    Science.gov (United States)

    Nielson, Gregory N; Okandan, Murat; Cruz-Campa, Jose Luis; Resnick, Paul J; Wanlass, Mark Woodbury; Clews, Peggy J

    2013-12-24

    A III-V solar cell is described herein that includes all back side contacts. Additionally, the positive and negative electrical contacts contact compoud semiconductor layers of the solar cell other than the absorbing layer of the solar cell. That is, the positive and negative electrical contacts contact passivating layers of the solar cell.

  12. Measuring The Contact Resistances Of Photovoltaic Cells

    Science.gov (United States)

    Burger, D. R.

    1985-01-01

    Simple method devised to measure contact resistances of photovoltaic solar cells. Method uses readily available equipment and applicable at any time during life of cell. Enables evaluation of cell contact resistance, contact-end resistance, contact resistivity, sheet resistivity, and sheet resistivity under contact.

  13. Skin barrier and contact allergy: Genetic risk factor analyses

    DEFF Research Database (Denmark)

    Ross-Hansen, Katrine

    2013-01-01

    Background Contact allergy is frequent in the general population and arises from prolonged or repeated skin contact with chemical substances. The environmental risk factor is obvious, yet some studies report on associations between genetic variance and an increased risk of developing contact......) in particular. Methods Epidemiological genetic association studies were performed on a general Danish population. Participants were patch tested, answered a questionnaire on general health and were genotyped for GST, CLDN1 and FLG polymorphisms. Filaggrin’s nickel binding potential was evaluated biochemically...... by extracting epidermal proteins from human surgical waste samples and stratum corneum scrapings followed by binding studies using immobilized metal affinity chromatography. Results As suggested by Kaplan-Meier event history analyses, FLG null mutations lowered the age of onset of nickel dermatitis, when ear...

  14. Contact resistance and adhesion characteristics of oxidized tantalum nitride mirors

    Energy Technology Data Exchange (ETDEWEB)

    Kramer, D.K.

    1975-11-01

    Oxidation of tantalum nitride resistor films used in hybrid microcircuits is an unavoidable phenomenon known to affect interfacial properties between resistor and conductor layers. At room temperature, oxide thickness increases with time at an unknown rate; therefore, a three-day limitation between Ta/sub 2/N and Cr/Au conductor deposition is presently specified for hybrid microcircuits. The effects of Ta/sub 2/N aging on resistor-conductor contact resistance and conductor bondability were evaluated. Accelerated aging produced oxide layers of various thicknesses which were then correlated to contact resistance. Analytical data and calculations indicate that a 25 percent increase in contact resistance would occur by exposing the Ta/sub 2/N to air for approximately three years at room temperature and pressure prior to metallization. However, little or no change in bondability would be expected.

  15. Testing and Modeling of Contact Problems in Resistance Welding

    DEFF Research Database (Denmark)

    Song, Quanfeng

    together two or three cylindrical parts as well as disc-ring pairs of dissimilar metals. The tests have demonstrated the effectiveness of the model. A theoretical and experimental study is performed on the contact resistance aiming at a more reliable model for numerical simulation of resistance welding...... is validated in some projection welding experiments. The program is also applied to solve some resistance welding operations involving contact problems, showing that numerical simulation facilitates better understand of resistance welding.......As a part of the efforts towards a professional and reliable numerical tool for resistance welding engineers, this Ph.D. project is dedicated to refining the numerical models related to the interface behavior. An FE algorithm for the contact problems in resistance welding has been developed...

  16. Photovoltaic effect in individual asymmetrically contacted lead sulfide nanosheets.

    Science.gov (United States)

    Dogan, Sedat; Bielewicz, Thomas; Lebedeva, Vera; Klinke, Christian

    2015-03-21

    Solution-processable, two-dimensional semiconductors are promising optoelectronic materials which could find application in low-cost solar cells. Lead sulfide nanocrystals raised attention since the effective band gap can be adapted over a wide range by electronic confinement and observed multi-exciton generation promises higher efficiencies. We report on the influence of the contact metal work function on the properties of transistors based on individual two-dimensional lead sulfide nanosheets. Using palladium we observed mobilities of up to 31 cm(2) V(-1) s(-1). Furthermore, we demonstrate that asymmetrically contacted nanosheets show photovoltaic effect and that the nanosheets' height has a decisive impact on the device performance. Nanosheets with a thickness of 5.4 nm contacted with platinum and titanium show a power conversion efficiency of up to 0.94% (EQE 75.70%). The results underline the high hopes put on such materials.

  17. Lateral spreading of Au contacts on InP

    Science.gov (United States)

    Fatemi, Navid S.; Weizer, Victor G.

    1990-01-01

    The contact spreading phenomenon observed when small area Au contacts on InP are annealed at temperatures above about 400 C was investigated. It was found that the rapid lateral expansion of the contact metallization which consumes large quantities of InP during growth is closely related to the third stage in the series of solid state reactions that occur between InP and Au, i.e., to the Au3In-to-Au9In4 transition. Detailed descriptions are presented of both the spreading process and the Au3In-to-Au9In4 transition along with arguments that the two processes are manifestations of the same basic phenomenon.

  18. Novel Way to Characterize Metal-Insulator-Metal Devices via Nanoindentation: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Periasamy, P.; Packard, C. E.; O?Hayre, R. P.; Berry, J. J.; Parilla, P. A.; Ginley, D. S.

    2011-07-01

    Metal-Insulator-Metal (MIM) devices are crucial components for applications ranging from optical rectennas for harvesting sunlight to infrared detectors. To date, the relationship between materials properties and device performance in MIM devices is not fully understood, partly due to the difficulty in making and reproducing reliable devices. One configuration that is popular due to its simplicity and ease of fabrication is the point-contact diode where a metal tip serves as one of the metals in the MIM device. The intrinsic advantage of the point-contact configuration is that it is possible to achieve very small contact areas for the device thereby allowing very high-frequency operation. In this study, precise control over the contact area and penetration depth of an electrically conductive tip into a metal/insulator combination is achieved using a nanoindenter with in-situ electrical contact resistance measurement capabilities. A diamond probe tip, doped (degeneratively) with boron for conductivity, serves as the point contact and second 'metal' (b-Diamond) of the MIM diode. The base layer consists of Nb/Nb2O5 thin films on Si substrates and serves as the first metal /insulator combination of the MIM structure. The current-voltage response of the diodes is measured under a range of conditions to assess the validity and repeatability of the technique. Additionally, we compare the results of this technique to those acquired using a bent-wire approach and find that Nb/Nb2O5/b-Diamond MIM devices show an excellent asymmetry (60-300) and nonlinearity values (~6-9). This technique shows great promise for screening metal-insulator combinations for performance without the uncertainty that stems from a typical bent-wire point-contact.

  19. Population Genomics of Secondary Contact

    Directory of Open Access Journals (Sweden)

    Anthony Geneva

    2010-06-01

    Full Text Available One common form of reticulate evolution arises as a consequence of secondary contact between previously allopatric populations. Using extensive coalescent simulations, we describe the conditions for, and extent of, the introgression of genetic material into the genome of a colonizing population from an endemic population. The simulated coalescent histories are sampled from models that describe the evolution of entire chromosomes, thereby allowing the expected length of introgressed haplotypes to be estimated. The results indicate that our ability to identify reticulate evolution from genetic data is highly variable and depends critically upon the duration of the period of allopatry, the timing of the secondary contact event, as well as the sizes of the populations at the time of contact. One particularly interesting result arises when secondary contact occurs close to the time of a severe founder event, in this case, genetic introgression can be substantially more difficult to detect. However, if secondary contact occurs after such a founding event, when the range of the colonizing population increases, introgression is more readily detectable across the genome. This result may have important implications for our ability to detect introgression between ancestrally bottlenecked modern human populations and archaic hominin species, such as Neanderthals.

  20. Young Children's Contact with the Elderly

    Science.gov (United States)

    Sheehan, Robert

    1978-01-01

    This research investigates frequency and type of contact young children have had with elderly persons. It also examines the relationship between this contact and children's frequency of contact with elderly persons and their ability to identify the elderly. (Author)