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Sample records for alternating-phase fed single-layer

  1. Temperature distribution of single layer

    Science.gov (United States)

    Tang, Xuefei; Fan, Zhengxiu; Wang, ZhiJiang

    1993-03-01

    Temperature distributions of Ti02 single layer irradiated by iOns, 1. 06 m wavelength laser pulse were calculated with thermal transfer equation. Following conclusions were obtained: To improve thermal parameters of coating can reduce the peak temperature obviously; The thermal parameters of substrate have little effect on temperature response of coating; Temperature distribution of thin film depends on the electrical field distribution, The peak temperature of quarter -wavelength coatings is lower than that of half-wavelength coatings.

  2. FEDS

    DEFF Research Database (Denmark)

    Venable, John; Pries-Heje, Jan; Baskerville, Richard

    2016-01-01

    to enable Design Science Researchers to effectively design and incorporate evaluation activities into a DSR project that can achieve DSR goals and objectives. To address this research gap, this research paper develops, explicates, and provides evidence for the utility of a Framework for Evaluation in Design...... Science (FEDS) together with a process to guide design science researchers in developing a strategy for evaluating the artefacts they develop within a DSR project. A FEDS strategy considers why, when, how, and what to evaluate. FEDS includes a two-dimensional characterisation of DSR evaluation episodes...... on an actual DSR project....

  3. FEDS

    DEFF Research Database (Denmark)

    Pries-Heje, Jan; Venable, John; Baskerville, Richard

    2016-01-01

    Evaluation of design artefacts and design theories is a key activity in Design Science Research (DSR), as it provides feedback for further development and (if done correctly) assures the rigour of the research. However, the extant DSR literature provides insufficient guidance on evaluation...... to enable Design Science Researchers to effectively design and incorporate evaluation activities into a DSR project that can achieve DSR goals and objectives. To address this research gap, this research paper develops, explicates, and provides evidence for the utility of a Framework for Evaluation in Design...... Science (FEDS) together with a process to guide design science researchers in developing a strategy for evaluating the artefacts they develop within a DSR project. A FEDS strategy considers why, when, how, and what to evaluate. FEDS includes a two-dimensional characterisation of DSR evaluation episodes...

  4. First Principles Study on FeAs Single Layers

    Institute of Scientific and Technical Information of China (English)

    Jun Dai; Zhenyu Li; Jin-long Yang

    2009-01-01

    FeAs- single layer is tested as a simple model for LaFeAsO and BaFe2As2 based on firstprinciples calculations using generalized gradient approximation (GGA) and GGA+U. The calculated single-layer geometric and electronic structures are inconsistent with that of bulk materials. The bulk collinear antiferromagnetic ground state failed to be obtained in the FeAs- single layer. The monotonous behavior of the Fe-As distance in z direction upon electron or hole doping is also in contrast with bulk materials. The results indicate that,in LaFeAsO and BaFe2As2, interactions between FeAs layer and other layers beyond simple charge doping are important, and a single FeAs layer may not represent a good model for Fe based superconducting materials.

  5. Defect formation in single layer graphene under extreme ultraviolet irradiation

    NARCIS (Netherlands)

    Gao, An; Zoethout, E.; Zoethout, E.; Sturm, Jacobus Marinus; Lee, Christopher James; Bijkerk, Frederik

    2014-01-01

    We study extreme ultraviolet (EUV) radiation induced defects in single-layer graphene. Two mechanisms for inducing defects in graphene were separately investigated: photon induced chemical reactions between graphene and background residual gases, and breaking sp2 bonds, due to photon and/or photoele

  6. Breakwater stability with damaged single layer armour units

    NARCIS (Netherlands)

    De Rover, R.; Verhagen, H.J.; Van den Berge, A.; Reedijk, B.

    2008-01-01

    The effect of single layer interlocking armour unit breakage on the hydraulic armour layer stability and potential damage progression is addressed in this paper. A 2-dimensional scale model of a rubble mound breakwater with an armour layer consisting of Xbloc armour units was tested. The residual

  7. Electron tunneling in single layer graphene with an energy gap

    Institute of Scientific and Technical Information of China (English)

    Xu Xu-Guang; Zhang Chao; Xu Gong-Jie; Cao Jun-Cheng

    2011-01-01

    When a single layer graphene is epitaxially grown on silicon carbide, it will exhibit a finite energy gap like a conventional semiconductor, and its energy dispersion is no longer linear in momentum in the low energy regime. In this paper, we have investigated the tunneling characteristics through a two-dimensional barrier in a single layer graphene with an energy gap. It is found that when the electron is at a zero angle of incidence, the transmission probability as a function of incidence energy has a gap. Away from the gap the transmission coefficient oscillates with incidence energy which is analogous to that of a conventional semiconductor. The conductance under zero temperature has a gap. The properties of electron transmission may be useful for developing graphene-based nano-electronics.

  8. Stable single-layer structure of group-V elements

    Science.gov (United States)

    Ersan, F.; Aktürk, E.; Ciraci, S.

    2016-12-01

    In addition to stable single-layer buckled honeycomb and washboard structures of group-V elements (or pnictogens P, As, Sb, and Bi) we show that these elements can also form two-dimensional, single-layer structures consisting of buckled square and octagon rings. An extensive analysis comprising the calculation of mechanical properties, vibration frequencies, and finite-temperature ab initio molecular dynamics confirms that these structures are dynamically and thermally stable and suitable for applications at room temperature and above. All these structures are semiconductors with a fundamental band gap, which is wide for P but decreases with increasing row number. The effect of the spin-orbit coupling decreases the band gap and is found to be crucial for Sb and Bi. These results are obtained from first-principles calculations based on density functional theory.

  9. A microfluidic galvanic cell on a single layer of paper

    Science.gov (United States)

    Purohit, Krutarth H.; Emrani, Saina; Rodriguez, Sandra; Liaw, Shi-Shen; Pham, Linda; Galvan, Vicente; Domalaon, Kryls; Gomez, Frank A.; Haan, John L.

    2016-06-01

    Paper microfluidics is used to produce single layer galvanic and hybrid cells to produce energy that could power paper-based analytical sensors. When two aqueous streams are absorbed onto paper to establish co-laminar flow, the streams stay in contact with each other with limited mixing. The interface at which mixing occurs acts as a charge-transfer region, eliminating the need for a salt bridge. We designed a Cusbnd Zn galvanic cell that powers an LED when two are placed in series. We also used more powerful redox couples (formate and silver, formate and permanganate) to produce higher power density (18 and 3.1 mW mg-1 Pd). These power densities are greater than previously reported paper microfluidic fuel cells using formate or methanol. The single layer design is much more simplified than previous reports of multi-layer galvanic cells on paper.

  10. Bandgap tunability at single-layer molybdenum disulphide grain boundaries

    KAUST Repository

    Huang, Yu Li

    2015-02-17

    Two-dimensional transition metal dichalcogenides have emerged as a new class of semiconductor materials with novel electronic and optical properties of interest to future nanoelectronics technology. Single-layer molybdenum disulphide, which represents a prototype two-dimensional transition metal dichalcogenide, has an electronic bandgap that increases with decreasing layer thickness. Using high-resolution scanning tunnelling microscopy and spectroscopy, we measure the apparent quasiparticle energy gap to be 2.40±0.05 eV for single-layer, 2.10±0.05 eV for bilayer and 1.75±0.05 eV for trilayer molybdenum disulphide, which were directly grown on a graphite substrate by chemical vapour deposition method. More interestingly, we report an unexpected bandgap tunability (as large as 0.85±0.05 eV) with distance from the grain boundary in single-layer molybdenum disulphide, which also depends on the grain misorientation angle. This work opens up new possibilities for flexible electronic and optoelectronic devices with tunable bandgaps that utilize both the control of two-dimensional layer thickness and the grain boundary engineering.

  11. Thermoelectric properties of single-layered SnSe sheet.

    Science.gov (United States)

    Wang, Fancy Qian; Zhang, Shunhong; Yu, Jiabing; Wang, Qian

    2015-10-14

    Motivated by the recent study of inspiring thermoelectric properties in bulk SnSe [Zhao et al., Nature, 2014, 508, 373] and the experimental synthesis of SnSe sheets [Chen et al., J. Am. Chem. Soc., 2013, 135, 1213], we have carried out systematic calculations for a single-layered SnSe sheet focusing on its stability, electronic structure and thermoelectric properties by using density functional theory combined with Boltzmann transport theory. We have found that the sheet is dynamically and thermally stable with a band gap of 1.28 eV, and the figure of merit (ZT) reaches 3.27 (2.76) along the armchair (zigzag) direction with optimal n-type carrier concentration, which is enhanced nearly 7 times compared to its bulk counterpart at 700 K due to quantum confinement effect. Furthermore, we designed four types of thermoelectric couples by assembling single-layered SnSe sheets with different transport directions and doping types, and found that their efficiencies are all above 13%, which are higher than those of thermoelectric couples made of commercial bulk Bi2Te3 (7%-8%), suggesting the great potential of single-layered SnSe sheets for heat-electricity conversion.

  12. Organic photovoltaic devices with a single layer geometry (Conference Presentation)

    Science.gov (United States)

    Kolesov, Vladimir A.; Fuentes-Hernandez, Canek; Aizawa, Naoya; Larrain, Felipe A.; Chou, Wen-Fang; Perrotta, Alberto; Graham, Samuel; Kippelen, Bernard

    2016-09-01

    Organic photovoltaics (OPV) can lead to a low cost and short energy payback time alternative to existing photovoltaic technologies. However, to fulfill this promise, power conversion efficiencies must be improved and simultaneously the architecture of the devices and their processing steps need to be further simplified. In the most efficient devices to date, the functions of photocurrent generation, and hole/electron collection are achieved in different layers adding complexity to the device fabrication. In this talk, we present a novel approach that yields devices in which all these functions are combined in a single layer. Specifically, we report on bulk heterojunction devices in which amine-containing polymers are first mixed in the solution together with the donor and acceptor materials that form the active layer. A single-layer coating yields a self-forming bottom electron-collection layer comprised of the amine-containing polymer (e.g. PEIE). Hole-collection is achieved by subsequent immersion of this single layer in a solution of a polyoxometalate (e.g. phosphomolybdic acid (PMA)) leading to an electrically p-doped region formed by the diffusion of the dopant molecules into the bulk. The depth of this doped region can be controlled with values up to tens of nm by varying the immersion time. Devices with a single 500 nm-thick active layer of P3HT:ICBA processed using this method yield power conversion efficiency (PCE) values of 4.8 ± 0.3% at 1 sun and demonstrate a performance level superior to that of benchmark three-layer devices with separate layers of PEIE/P3HT:ICBA/MoOx (4.1 ± 0.4%). Devices remain stable after shelf lifetime experiments carried-out at 60 °C over 280 h.

  13. Single-layer graphene on silicon nitride micromembrane resonators

    DEFF Research Database (Denmark)

    Schmid, Silvan; Bagci, Tolga; Zeuthen, Emil

    2014-01-01

    for exciting new devices, such as optoelectromechanical transducers. Here, we add a single-layer graphene on SiN micromembranes and compare electromechanical coupling and mechanical properties to bare dielectric membranes and to membranes metallized with an aluminium layer. The electrostatic coupling...... of graphene covered membranes is found to be equal to a perfectly conductive membrane, without significantly adding mass, decreasing the superior mechanical quality factor or affecting the optical properties of pure SiN micromembranes. The concept of graphene-SiN resonators allows a broad range of new...... experiments both in applied physics and fundamental basic research, e.g., for the mechanical, electrical, or optical characterization of graphene....

  14. Electrical transport properties of single-layer WS2.

    Science.gov (United States)

    Ovchinnikov, Dmitry; Allain, Adrien; Huang, Ying-Sheng; Dumcenco, Dumitru; Kis, Andras

    2014-08-26

    We report on the fabrication of field-effect transistors based on single layers and bilayers of the semiconductor WS2 and the investigation of their electronic transport properties. We find that the doping level strongly depends on the device environment and that long in situ annealing drastically improves the contact transparency, allowing four-terminal measurements to be performed and the pristine properties of the material to be recovered. Our devices show n-type behavior with a high room-temperature on/off current ratio of ∼10(6). They show clear metallic behavior at high charge carrier densities and mobilities as high as ∼140 cm(2)/(V s) at low temperatures (above 300 cm(2)/(V s) in the case of bilayers). In the insulating regime, the devices exhibit variable-range hopping, with a localization length of about 2 nm that starts to increase as the Fermi level enters the conduction band. The promising electronic properties of WS2, comparable to those of single-layer MoS2 and WSe2, together with its strong spin-orbit coupling, make it interesting for future applications in electronic, optical, and valleytronic devices.

  15. Isolation of Leptospirillum ferriphilum by single-layered solid medium

    Institute of Scientific and Technical Information of China (English)

    LIU Jian-she; XIE Xue-hui; XIAO Sheng-mu; WANG Xiu-mei; ZHAO Wen-jie; TIAN Zhuo-li

    2007-01-01

    According to physiological and biochemical characteristics of Leptospirillum ferriphilum, a strain of object bacteria was isolated successfully. Bacteria were enriched by selective liquid medium and plated on designed single-layered agar solid medium.Colony was cultured and bacteria were collected. The morphologies of the object bacteria were observed using crystal violet staining,scanning electron microscope(SEM) and transmission electron microscope (TEM). The result of 16S rDNA identification shows that this bacterium belongs to Leptospirillum ferriphilum and it is named as Leptospirillum ferriphilum strain D1. These results indicate that this new single-layered agar solid medium is efficient and simple for isolation of Leptospirillum ferriphilum. Additionally,physiological-biochemical characteristics show that the optimum initial pH value and its growth temperature are 1.68 and 40 ℃,respectively. The culture of it is used to leach a complex concentrate chalcopyrite, the leaching efficiencies of copper and iron are 1.93% and 13.74%, respectively, and it is more effective than the A.ferrooxidans culture in the leaching of the complex concentrate chalcopyrite.

  16. Multiple charge beam dynamics in alternate phase focusing structure

    Directory of Open Access Journals (Sweden)

    S. Dechoudhury

    2014-07-01

    Full Text Available Asymmetrical alternate phase (A-APF focusing realized in a sequence of 36 superconducting quarter wave resonators (QWRs has been shown to accelerate almost 81% of input uranium beam before foil stripper to an energy of 6.2  MeV/u from 1.3  MeV/u. Ten charge states from 34+ to 43+ could be simultaneously accelerated with the phase of resonators tuned for 34+. The A-APF structure showed the unique nature of a large potential bucket for charge states higher than that of the tuned one. Steering inherent to QWRs can be mitigated by selecting appropriate phase variation of the APF periods and optimization of solenoid field strengths placed in each of the periods. This mitigation facilitates the multiple charge state acceleration scheme.

  17. Nanoscale imaging of freestanding nitrogen doped single layer graphene.

    Science.gov (United States)

    Iyer, Ganjigunte R S; Wang, Jian; Wells, Garth; Bradley, Michael P; Borondics, Ferenc

    2015-02-14

    Graphene can be p-type or n-type doped by introduction of specific species. Doping can modulate the electronic properties of graphene, but opening a sizable-well-tuned bandgap is essential for graphene-based tunable electronic devices. N-doped graphene is widely used for device applications and is mostly achieved by introducing ammonia into the synthesis gas during the chemical vapor deposition (CVD) process. Post synthesis treatment studies to fine-tune the electron hole doping in graphene are limited. In this work realization of N-doping in large area freestanding single layer graphene (LFG) is achieved by post treatment in nitrogen plasma. The changes in the chemical and electronic properties of graphene are followed with Raman microscopy and mapped via synchrotron based scanning transmission X-ray microscopy (STXM) at the nanoscale.

  18. Single-layer graphene on silicon nitride micromembrane resonators

    Energy Technology Data Exchange (ETDEWEB)

    Schmid, Silvan; Guillermo Villanueva, Luis; Amato, Bartolo; Boisen, Anja [Department of Micro- and Nanotechnology, Technical University of Denmark, DTU Nanotech, Building 345 East, 2800 Kongens Lyngby (Denmark); Bagci, Tolga; Zeuthen, Emil; Sørensen, Anders S.; Usami, Koji; Polzik, Eugene S. [QUANTOP, Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen (Denmark); Taylor, Jacob M. [Joint Quantum Institute/NIST, College Park, Maryland 20899 (United States); Herring, Patrick K.; Cassidy, Maja C. [School of Engineering and Applied Science, Harvard University, Cambridge, Massachusetts 02138 (United States); Marcus, Charles M. [Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen (Denmark); Cheol Shin, Yong; Kong, Jing [Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

    2014-02-07

    Due to their low mass, high quality factor, and good optical properties, silicon nitride (SiN) micromembrane resonators are widely used in force and mass sensing applications, particularly in optomechanics. The metallization of such membranes would enable an electronic integration with the prospect for exciting new devices, such as optoelectromechanical transducers. Here, we add a single-layer graphene on SiN micromembranes and compare electromechanical coupling and mechanical properties to bare dielectric membranes and to membranes metallized with an aluminium layer. The electrostatic coupling of graphene covered membranes is found to be equal to a perfectly conductive membrane, without significantly adding mass, decreasing the superior mechanical quality factor or affecting the optical properties of pure SiN micromembranes. The concept of graphene-SiN resonators allows a broad range of new experiments both in applied physics and fundamental basic research, e.g., for the mechanical, electrical, or optical characterization of graphene.

  19. Luminescent Efficiency in Single-layer Organic Electrophosphorescent Devices

    Institute of Scientific and Technical Information of China (English)

    OU Yang-jun; LI Hong-jian; DAI Xiao-yu

    2006-01-01

    Based on the charge injection and recombination processes and the triplet-triplet annihilation process, a model to calculate the electroluminescent(EL) efficiency is presented. The influences of the applied electric field on the injection efficiency, recombination efficiency and electroluminescent efficiency are discussed. It is found that: (1) The injection efficiency is increasing while the recombination efficiency is decreasing with the applied electric field increasing. (2) The EL efficiency is enhanced at low electric field slowly but is decreasing at high electric field with the increase of applied voltage. (3) The EL efficiency is decreasing with the increase of the host-guest molecular distance (R). So, it is concluded that the EL efficiency in single-layer organic electrophosphorescent devices is dominated by injection efficiency at lower electric field and recombination efficiency at higher electric field.

  20. Nanoscale imaging of freestanding nitrogen doped single layer graphene

    Science.gov (United States)

    Iyer, Ganjigunte R. S.; Wang, Jian; Wells, Garth; Bradley, Michael P.; Borondics, Ferenc

    2015-01-01

    Graphene can be p-type or n-type doped by introduction of specific species. Doping can modulate the electronic properties of graphene, but opening a sizable-well-tuned bandgap is essential for graphene-based tunable electronic devices. N-doped graphene is widely used for device applications and is mostly achieved by introducing ammonia into the synthesis gas during the chemical vapor deposition (CVD) process. Post synthesis treatment studies to fine-tune the electron hole doping in graphene are limited. In this work realization of N-doping in large area freestanding single layer graphene (LFG) is achieved by post treatment in nitrogen plasma. The changes in the chemical and electronic properties of graphene are followed with Raman microscopy and mapped via synchrotron based scanning transmission X-ray microscopy (STXM) at the nanoscale.Graphene can be p-type or n-type doped by introduction of specific species. Doping can modulate the electronic properties of graphene, but opening a sizable-well-tuned bandgap is essential for graphene-based tunable electronic devices. N-doped graphene is widely used for device applications and is mostly achieved by introducing ammonia into the synthesis gas during the chemical vapor deposition (CVD) process. Post synthesis treatment studies to fine-tune the electron hole doping in graphene are limited. In this work realization of N-doping in large area freestanding single layer graphene (LFG) is achieved by post treatment in nitrogen plasma. The changes in the chemical and electronic properties of graphene are followed with Raman microscopy and mapped via synchrotron based scanning transmission X-ray microscopy (STXM) at the nanoscale. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr05385k

  1. Alternating phase shift mask technology for 65nm logic applications

    Science.gov (United States)

    Chakravorty, Kishore K.; Henrichs, Sven; Qiu, Wei; Chavez, Joas L.; Liu, Yi-Ping; Ghadiali, Firoz; Yung, Karmen; Wilcox, Nathan; Silva, Mary; Ma, Jian; Qu, Ping; Irvine, Brian; Yun, Henry; Cheng, Wen-Hao; Farnsworth, Jeff

    2006-03-01

    Alternating Phase Shift Mask (APSM) Technology has been developed and successfully implemented for the poly gate of 65nm node Logic application at Intel. This paper discusses the optimization of the mask design rules and fabrication process in order to enable high volume manufacturability. Intel's APSM technology is based on a dual sided trenched architecture. To meet the stringent OPC requirements associated with patterning of narrow gates required for the 65nm node, Chrome width between the Zero and Pi aperture need to be minimized. Additionally, APSM lithography has an inherently low MEEF that furthermore, drives a narrower Chrome line as compared to the Binary approach. The double sided trenched structure with narrow Chrome lines are mechanically vulnerable and prone to damage when exposed to conventional mask processing steps. Therefore, new processing approaches were developed to minimize the damage to the patterned mask features. For example, cleaning processes were optimized to minimize Chrome & quartz damage while retaining the cleaning effectiveness. In addition, mask design rules were developed which ensured manufacturability. The narrow Chrome regions between the zero and Pi apertures severely restrict the tolerance for the placement of the second level resists edges with respect to the first level. UV Laser Writer based resist patterning capability, capable of providing the required Overlay tolerance, was developed, An AIMS based methodology was used to optimize the undercut and minimize the aerial image CD difference between the Zero and Pi apertures.

  2. Touch stimulated pulse generation in biomimetic single-layer graphene

    Science.gov (United States)

    Sul, Onejae; Chun, Hyunsuk; Choi, Eunseok; Choi, Jungbong; Cho, Kyeongwon; Jang, Dongpyo; Chun, Sungwoo; Park, Wanjun; Lee, Seung-Beck

    2016-02-01

    Detecting variation in contact pressure is a separate sensing mode in the human somatosensory system that differs from the detection of pressure magnitude. If pressure magnitude and variation sensing can be achieved simultaneously, an advanced biomimetic tactile system that better emulates human senses may be developed. We report on a novel single-layer graphene based artificial mechanoreceptor that generates a resistance pulse as the contact stimulus passes a specific threshold pressure, mimicking the generation of action potentials in a biological fast-adapting mechanoreceptor. The electric field from a flexible membrane gate electrode placed above a graphene channel raises the Fermi level from the valence band as pressure deflects the membrane. The threshold pressure is reached when the Fermi level crosses the Dirac point in the graphene energy band, which generates a sharp peak in the measured resistance. We found that by changing the gate potential it was possible to modulate the threshold pressure and using a series of graphene channels, a train of pulses were generated during a transient pressurizing stimulus demonstrating biomimetic behaviour.Detecting variation in contact pressure is a separate sensing mode in the human somatosensory system that differs from the detection of pressure magnitude. If pressure magnitude and variation sensing can be achieved simultaneously, an advanced biomimetic tactile system that better emulates human senses may be developed. We report on a novel single-layer graphene based artificial mechanoreceptor that generates a resistance pulse as the contact stimulus passes a specific threshold pressure, mimicking the generation of action potentials in a biological fast-adapting mechanoreceptor. The electric field from a flexible membrane gate electrode placed above a graphene channel raises the Fermi level from the valence band as pressure deflects the membrane. The threshold pressure is reached when the Fermi level crosses the Dirac

  3. Alternating-phase-focused IH-DTL for an injector of heavy-ion medical accelerators

    Science.gov (United States)

    Iwata, Y.; Yamada, S.; Murakami, T.; Fujimoto, T.; Fujisawa, T.; Ogawa, H.; Miyahara, N.; Yamamoto, K.; Hojo, S.; Sakamoto, Y.; Muramatsu, M.; Takeuchi, T.; Mitsumoto, T.; Tsutsui, H.; Watanabe, T.; Ueda, T.

    2006-12-01

    A compact Drift-Tube-Linac (DTL) using an Interdigital H-mode (IH) cavity was designed for an injector of medical accelerators. For beam focusing, the method of Alternating-Phase-Focusing (APF) was applied. The APF IH-DTL can accelerate heavy ions having a charge-to-mass ratio of q/m={1}/{3} up to 4.0 MeV/u. Having optimized an array of synchronous phases for cells, namely arranging drift tubes and gaps appropriately, both longitudinal and transverse focusing strengths were produced just with the rf acceleration field, and therefore no focusing element or cooling equipments had to be installed in the cavity. This allowed us to employ a rather high operating frequency, and hence to design a compact and cost-effective cavity. A further advantage of the APF linac can be found in its operation. Since the parameters to be adjusted are just the level and phase of the input rf, beam tuning can be made with ease. Consequently, the APF linac is suitable for an injector for medical accelerators. Tuning methods of the gap voltages and cavity frequency as well as the design of the cavity for APF IH-DTL have been developed. After constructing the cavity, measurements of the electric field and tuning of the gap voltages were performed. Finally, the rf power was fed into the cavity. In this paper, the design and results of the measurements are described.

  4. Controllable Curved Mirrors Made from Single-Layer EAP Films

    Science.gov (United States)

    Bao, Xiaoqi; Bar-Cohen, Yoseph; Sherrit, Stewart

    2004-01-01

    A document proposes that lightweight, deployable, large-aperture, controllable curved mirrors made of reflectively coated thin electroactive-polymer (EAP) films be developed for use in spaceborne microwave and optical systems. In these mirrors, the EAP films would serve as both structures and actuators. EAPs that are potentially suitable for such use include piezoelectric, electrostrictive, ferroelectric, and dielectric polymers. These materials exhibit strains proportional to the squares of applied electric fields. Utilizing this phenomenon, a curved mirror according to the proposal could be made from a flat film, upon which a nonuniform electrostatic potential (decreasing from the center toward the edge) would be imposed to obtain a required curvature. The effect would be analogous to that of an old-fashioned metalworking practice in which a flat metal sheet is made into a bowl by hammering it repeatedly, the frequency of hammer blows decreasing with distance from the center. In operation, the nonuniform electrostatic potential could be imposed by use of an electron gun. Calculations have shown that by use of a single- layer film made of a currently available EAP, it would be possible to control the focal length of a 2-m-diameter mirror from infinity to 1.25 m.

  5. Water desalination using nanoporous single-layer graphene.

    Science.gov (United States)

    Surwade, Sumedh P; Smirnov, Sergei N; Vlassiouk, Ivan V; Unocic, Raymond R; Veith, Gabriel M; Dai, Sheng; Mahurin, Shannon M

    2015-05-01

    By creating nanoscale pores in a layer of graphene, it could be used as an effective separation membrane due to its chemical and mechanical stability, its flexibility and, most importantly, its one-atom thickness. Theoretical studies have indicated that the performance of such membranes should be superior to state-of-the-art polymer-based filtration membranes, and experimental studies have recently begun to explore their potential. Here, we show that single-layer porous graphene can be used as a desalination membrane. Nanometre-sized pores are created in a graphene monolayer using an oxygen plasma etching process, which allows the size of the pores to be tuned. The resulting membranes exhibit a salt rejection rate of nearly 100% and rapid water transport. In particular, water fluxes of up to 10(6) g m(-2) s(-1) at 40 °C were measured using pressure difference as a driving force, while water fluxes measured using osmotic pressure as a driving force did not exceed 70 g m(-2) s(-1) atm(-1).

  6. Water desalination using nanoporous single-layer graphene

    Science.gov (United States)

    Surwade, Sumedh P.; Smirnov, Sergei N.; Vlassiouk, Ivan V.; Unocic, Raymond R.; Veith, Gabriel M.; Dai, Sheng; Mahurin, Shannon M.

    2015-05-01

    By creating nanoscale pores in a layer of graphene, it could be used as an effective separation membrane due to its chemical and mechanical stability, its flexibility and, most importantly, its one-atom thickness. Theoretical studies have indicated that the performance of such membranes should be superior to state-of-the-art polymer-based filtration membranes, and experimental studies have recently begun to explore their potential. Here, we show that single-layer porous graphene can be used as a desalination membrane. Nanometre-sized pores are created in a graphene monolayer using an oxygen plasma etching process, which allows the size of the pores to be tuned. The resulting membranes exhibit a salt rejection rate of nearly 100% and rapid water transport. In particular, water fluxes of up to 106 g m-2 s-1 at 40 °C were measured using pressure difference as a driving force, while water fluxes measured using osmotic pressure as a driving force did not exceed 70 g m-2 s-1 atm-1.

  7. Laser-assisted fabrication of single-layer flexible touch sensor

    OpenAIRE

    2016-01-01

    Single-layer flexible touch sensor that is designed for the indium-tin-oxide (ITO)-free, bendable, durable, multi-sensible, and single layer transparent touch sensor was developed via a low-cost and one-step laser-induced fabrication technology. To this end, an entirely novel approach involving material, device structure, and even fabrication method was adopted. Conventional metal oxides based multilayer touch structure was substituted by the single layer structure composed of integrated silv...

  8. Bending response of single layer MoS2.

    Science.gov (United States)

    Xiong, Si; Cao, Guoxin

    2016-03-11

    Using molecular mechanics (or dynamics) simulations, three different approaches, including the targeted molecular mechanics, four-point bending and nanotube methods, are employed to investigate the bending response of single layer MoS2 (SLMoS2), among which four-point bending is the most accurate approach to determine the bending stiffness according to the continuum theory. It is found that when the bending curvature radius is large enough (e.g. >4 nm), three approaches will give the same bending stiffness of SLMoS2 and the bending behavior is isotropic for SLMoS2, whereas the nanotube method with small tubes (e.g. bending stiffness. Compared with the reported result from the MoS2 nanotube calculated by density functional theory, the revised Stillinger-Weber (SW) and reactive empirical bond-order (REBO) potentials can give the reasonable bending stiffness of SLMoS2 (8.7-13.4 eV) as well as the effective deformed conformation. In addition, since the Mo-S bond deformation of SLMoS2 under bending is similar to that under in-plane tension/compression, the continuum bending theory can quite accurately predict the bending stiffness of SLMoS2 if a reasonable thickness of SLMoS2 is given. For SLMoS2, the reasonable thickness should be larger than the distance between its two S atomic planes and lower than the distance between two Mo atomic planes of bulk MoS2 crystal, e.g. 0.375-0.445 nm.

  9. Bending response of single layer MoS2

    Science.gov (United States)

    Xiong, Si; Cao, Guoxin

    2016-03-01

    Using molecular mechanics (or dynamics) simulations, three different approaches, including the targeted molecular mechanics, four-point bending and nanotube methods, are employed to investigate the bending response of single layer MoS2 (SLMoS2), among which four-point bending is the most accurate approach to determine the bending stiffness according to the continuum theory. It is found that when the bending curvature radius is large enough (e.g. >4 nm), three approaches will give the same bending stiffness of SLMoS2 and the bending behavior is isotropic for SLMoS2, whereas the nanotube method with small tubes (e.g. <4 nm) cannot give the correct bending stiffness. Compared with the reported result from the MoS2 nanotube calculated by density functional theory, the revised Stillinger-Weber (SW) and reactive empirical bond-order (REBO) potentials can give the reasonable bending stiffness of SLMoS2 (8.7-13.4 eV) as well as the effective deformed conformation. In addition, since the Mo-S bond deformation of SLMoS2 under bending is similar to that under in-plane tension/compression, the continuum bending theory can quite accurately predict the bending stiffness of SLMoS2 if a reasonable thickness of SLMoS2 is given. For SLMoS2, the reasonable thickness should be larger than the distance between its two S atomic planes and lower than the distance between two Mo atomic planes of bulk MoS2 crystal, e.g. 0.375-0.445 nm.

  10. Alternating phase-shifted mask for logic gate levels, design, and mask manufacturing

    Science.gov (United States)

    Liebmann, Lars W.; Graur, Ioana C.; Leipold, William C.; Oberschmidt, James M.; O'Grady, David S.; Regaill, Denis

    1999-07-01

    While the benefits of alternating phase shifted masks in improving lithographic process windows at increased resolution are well known throughout the lithography community, broad implementation of this potentially powerful technique has been slow due to the inherent complexity of the layout design and mask manufacturing process. This paper will review a project undertaken at IBM's Semiconductor Research and Development Center and Mask Manufacturing and Development facility to understand the technical and logistical issues associated with the application of alternating phase shifted mask technology to the gate level of a full microprocessor chip. The work presented here depicts an important milestone toward integration of alternating phase shifted masks into the manufacturing process by demonstrating an automated design solution and yielding a functional alternating phase shifted mask. The design conversion of the microprocessor gate level to a conjugate twin shifter alternating phase shift layout was accomplished with IBM's internal design system that automatically scaled the design, added required phase regions, and resolved phase conflicts. The subsequent fabrication of a nearly defect free phase shifted mask, as verified by SEM based die to die inspection, highlights the maturity of the alternating phase shifted mask manufacturing process in IBM's internal mask facility. Well defined and recognized challenges in mask inspection and repair remain and the layout of alternating phase shifted masks present a design and data preparation overhead, but the data presented here demonstrate the feasibility of designing and building manufacturing quality alternating phase shifted masks for the gate level of a microprocessor.

  11. Experimental research on the stability of armour and secondary layer in a single layered Tetrapod breakwater

    NARCIS (Netherlands)

    De Jong, W.; Verhagen, H.J.; Olthof, J.

    2004-01-01

    Physical model tests were done on an armour of Tetrapods, placed in a single layer. The objective of the investigations was to study the stability of the secondary layer, and to see if the material of this secondary layer could be washed out through the single layer of Tetrapods. It was concluded

  12. Synthesis of Layered Double Hydroxide Single-Layer Nanosheets in Formamide.

    Science.gov (United States)

    Yu, Jingfang; Liu, Jingjing; Clearfield, Abraham; Sims, Johnathan E; Speiegle, Michael T; Suib, Steven L; Sun, Luyi

    2016-11-21

    Layered double hydroxide (LDH) single-layer nanosheets were synthesized through a single-step process in the presence of formamide. This one-step process is simple, fast, and efficient and thus is potentially viable for large-scale production. Two key factors for the growth of LDH single-layer nanosheets, formamide concentration and LDH layer charge, were investigated thoroughly. A higher formamide concentration and a higher LDH layer charge are favorable for the growth of LDH single-layer nanosheets. The LDH single-layer nanosheets obtained at the premium formamide concentration and LDH layer charge were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and atomic force micrscopy (AFM). Poly(vinyl alcohol) (PVA)/LDH nanocomposite coatings were also prepared. The coated polyethylene terephthalate (PET) and poly(lactic acid) (PLA) films exhibited significantly improved oxygen gas barrier properties thanks to the well-dispersed and -aligned LDH single-layer nanosheets in the coating.

  13. Hydraulic Stability of Single-Layer Dolos and Accropode Armour Layers

    DEFF Research Database (Denmark)

    Christensen, M.; Burcharth, H. F.

    1995-01-01

    A new design for Dolos breakwater armour layers is presented: Dolos armour units are placed in a selected geometric pattern in a single layer. A series of model tests have been performed in order to determine the stability of such single-layer Dolos armour layers. The test results are presented...... and compared to the stability formula for the traditional double-layer, randomly placed Dolos armour layer design presented by Burcharth (1992). The results of a series of stability tests performed with Accropode® armour layers is presented and compared to the test results obtained with single-layer Dolos...

  14. Gap opening and tuning in single-layer graphene with combined electric and magnetic field modulation

    Institute of Scientific and Technical Information of China (English)

    Lin Xin; Wang Hai-Long; Pan Hui; Xu Huai-Zhe

    2011-01-01

    The energy band structure of single-layer graphene under one-dimensional electric and magnetic field modulation is theoretically investigated. The criterion for bandgap opening at the Dirac point is analytically derived with a two-fold degeneracy second-order perturbation method. It is shown that a direct or an indirect bandgap semiconductor could be realized in a single-layer graphene under some specific configurations of the electric and magnetic field arrangement. Due to the bandgap generated in the single-layer graphene, the Klein tunneling observed in pristine graphene is completely suppressed.

  15. Numerical study on short-circuit current of single layer organic solar cells with Schottkey contacts

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The influence of the cathode work function,carriers mobilities and temperature on the short-circuit current of single layer organic solar cells with Schottkey contacts was numerically studied,and the quantitative dependences of the short-circuit current on these quantities were obtained.The results provide the theoretical foundation for experimental study of single layer organic solar cells with Schottkey contacts.

  16. Electronic structure of 2H-NbSe2 single-layers in the CDW state

    Science.gov (United States)

    Ángel Silva-Guillén, José; Ordejón, Pablo; Guinea, Francisco; Canadell, Enric

    2016-09-01

    A density functional theory study of NbSe2 single-layers in the normal non-modulated and the 3 × 3 CDW states is reported. We show that, in the single layer, the CDW barely affects the Fermi surface of the system, thus ruling out a nesting mechanism as the driving force for the modulation. The CDW stabilizes levels lying around 1.35 eV below the Fermi level within the Se-based valence band but having a substantial Nb-Nb bonding character. The absence of interlayer interactions leads to the suppression of the pancake-like portion of the bulk Fermi surface in the single-layer. We perform scanning tunneling microscopy simulations and find that the images noticeably change with the sign and magnitude of the voltage bias. The atomic corrugation of the Se sublayer induced by the modulation plays a primary role in leading to these images, but the electronic reorganization also has an important contribution. The analysis of the variation of these images with the bias voltage does not support a Fermi surface nesting mechanism for the CDW. It is also shown that underlying graphene layers (present in some of the recent experimental work) do not modify the conduction band, but do affect the shape of the valence band of NbSe2 single-layers. The relevance of these results in understanding recent physical measurements for NbSe2 single-layers is discussed.

  17. Computational discovery of ferromagnetic semiconducting single-layer CrSnTe3

    Science.gov (United States)

    Zhuang, Houlong L.; Xie, Yu; Kent, P. R. C.; Ganesh, P.

    2015-07-01

    Despite many single-layer materials being reported in the past decade, few of them exhibit magnetism. Here we perform first-principles calculations using accurate hybrid density functional methods (HSE06) to predict that single-layer CrSnTe3 (CST) is a ferromagnetic semiconductor, with band gaps of 0.9 and 1.2 eV for the majority and minority spin channels, respectively. We determine the Curie temperature as 170 K, significantly higher than that of single-layer CrSiTe3 (90 K) and CrGeTe3 (130 K). This is due to the enhanced ionicity of the Sn-Te bond, which in turn increases the superexchange coupling between the magnetic Cr atoms. We further explore the mechanical and dynamical stability and strain response of this single-layer material for possible epitaxial growth. Our study provides an intuitive approach to understand and design single-layer magnetic semiconductors for a wide range of spintronics and energy applications.

  18. Morphology and atomic-scale structure of single-layer WS2 nanoclusters.

    Science.gov (United States)

    Füchtbauer, Henrik G; Tuxen, Anders K; Moses, Poul G; Topsøe, Henrik; Besenbacher, Flemming; Lauritsen, Jeppe V

    2013-10-14

    Two-dimensional sheets of transition metal (Mo and W) sulfides are attracting strong attention due to the unique electronic and optical properties associated with the material in its single-layer form. The single-layer MoS2 and WS2 are already in widespread commercial use in catalytic applications as both hydrotreating and hydrocracking catalysts. Consequently, characterization of the morphology and atomic structure of such particles is of utmost importance for the understanding of the catalytic active phase. However, in comparison with the related MoS2 system only little is known about the fundamental properties of single-layer WS2 (tungstenite). Here, we use an interplay of atom-resolved Scanning Tunneling Microscopy (STM) studies of Au(111)-supported WS2 nanoparticles and calculated edge structures using Density Functional Theory (DFT) to reveal the equilibrium morphology and prevalent edge structures of single-layer WS2. The STM results reveal that the single layer S-W-S sheets adopt a triangular equilibrium shape under the sulfiding conditions of the synthesis, with fully sulfided edges. The predominant edge structures are determined to be the (101[combining macron]0) W-edge, but for the smallest nanoclusters also the (1[combining macron]010) S-edges become important. DFT calculations are used to construct phase diagrams of the WS2 edges, and describe their sulfur and hydrogen coordination under different conditions, and in this way shed light on the catalytic role of WS2 edges.

  19. Solving Nonlinearly Separable Classifications in a Single-Layer Neural Network.

    Science.gov (United States)

    Conaway, Nolan; Kurtz, Kenneth J

    2017-03-01

    Since the work of Minsky and Papert ( 1969 ), it has been understood that single-layer neural networks cannot solve nonlinearly separable classifications (i.e., XOR). We describe and test a novel divergent autoassociative architecture capable of solving nonlinearly separable classifications with a single layer of weights. The proposed network consists of class-specific linear autoassociators. The power of the model comes from treating classification problems as within-class feature prediction rather than directly optimizing a discriminant function. We show unprecedented learning capabilities for a simple, single-layer network (i.e., solving XOR) and demonstrate that the famous limitation in acquiring nonlinearly separable problems is not just about the need for a hidden layer; it is about the choice between directly predicting classes or learning to classify indirectly by predicting features.

  20. Single layer of Ge quantum dots in HfO2 for floating gate memory capacitors.

    Science.gov (United States)

    Lepadatu, A M; Palade, C; Slav, A; Maraloiu, A V; Lazanu, S; Stoica, T; Logofatu, C; Teodorescu, V S; Ciurea, M L

    2017-04-28

    High performance trilayer memory capacitors with a floating gate of a single layer of Ge quantum dots (QDs) in HfO2 were fabricated using magnetron sputtering followed by rapid thermal annealing (RTA). The layer sequence of the capacitors is gate HfO 2/floating gate of single layer of Ge QDs in HfO 2/tunnel HfO 2/p-Si wafers. Both Ge and HfO2 are nanostructured by RTA at moderate temperatures of 600-700 °C. By nanostructuring at 600 °C, the formation of a single layer of well separated Ge QDs with diameters of 2-3 nm at a density of 4-5 × 10(15) m(-2) is achieved in the floating gate (intermediate layer). The Ge QDs inside the intermediate layer are arranged in a single layer and are separated from each other by HfO2 nanocrystals (NCs) about 8 nm in diameter with a tetragonal/orthorhombic structure. The Ge QDs in the single layer are located at the crossing of the HfO2 NCs boundaries. In the intermediate layer, besides Ge QDs, a part of the Ge atoms is segregated by RTA at the HfO2 NCs boundaries, while another part of the Ge atoms is present inside the HfO2 lattice stabilizing the tetragonal/orthorhombic structure. The fabricated capacitors show a memory window of 3.8 ± 0.5 V and a capacitance-time characteristic with 14% capacitance decay in the first 3000-4000 s followed by a very slow capacitance decrease extrapolated to 50% after 10 years. This high performance is mainly due to the floating gate of a single layer of well separated Ge QDs in HfO2, distanced from the Si substrate by the tunnel oxide layer with a precise thickness.

  1. Protecting nickel with graphene spin-filtering membranes: A single layer is enough

    Energy Technology Data Exchange (ETDEWEB)

    Martin, M.-B.; Dlubak, B.; Piquemal-Banci, M.; Collin, S.; Petroff, F.; Anane, A.; Fert, A.; Seneor, P. [Unité Mixte de Physique CNRS/Thales, 1 Avenue Augustin Fresnel, 91767 Palaiseau, France and Université Paris Sud, 91405 Orsay (France); Weatherup, R. S.; Hofmann, S.; Robertson, J. [Department of Engineering, University of Cambridge, Cambridge CB21PZ (United Kingdom); Yang, H. [IBS Center for Integrated Nanostructure Physics (CINAP), Institute for Basic Science, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of); Department of Energy Science, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of); Blume, R. [Helmholtz-Zentrum Berlin fur Materialien und Energie, 12489 Berlin (Germany); Schloegl, R. [Department of Inorganic Chemistry, Fritz Haber Institute of the Max Planck Society, Faradayweg 4-6, 14195 Berlin (Germany)

    2015-07-06

    We report on the demonstration of ferromagnetic spin injectors for spintronics which are protected against oxidation through passivation by a single layer of graphene. The graphene monolayer is directly grown by catalytic chemical vapor deposition on pre-patterned nickel electrodes. X-ray photoelectron spectroscopy reveals that even with its monoatomic thickness, monolayer graphene still efficiently protects spin sources against oxidation in ambient air. The resulting single layer passivated electrodes are integrated into spin valves and demonstrated to act as spin polarizers. Strikingly, the atom-thick graphene layer is shown to be sufficient to induce a characteristic spin filtering effect evidenced through the sign reversal of the measured magnetoresistance.

  2. Thermal conductivity of single-layer WSe2 by a Stillinger-Weber potential

    Science.gov (United States)

    Norouzzadeh, Payam; Singh, David J.

    2017-02-01

    In this study, we present the parameters of the Stillinger-Weber (SW) potential for single-layer WSe2 and calculate its in-plane thermal conductivity using a reverse non-equilibrium molecular dynamics simulation. The parameters are fitted to the phonon dispersion curves from literature density functional perturbation theory and experimental structural properties. The set reproduces the phonon dispersion well. The in-plane thermal conductivity of single-layer WSe2 and its dependency on sample length and temperature are calculated and the results are in good agreement with experimental values. Our developed SW-type potential facilitates further investigations on thermal, mechanical and other properties of WSe2.

  3. Damage mechanism of single-layer reticulated domes under severe earthquakes

    Institute of Scientific and Technical Information of China (English)

    YU Xiao-ye; FAN Feng; ZHI Xu-dong; SHEN Shi-zhao

    2009-01-01

    To study the damage mechanism of single-layer reticulated domes subject to severe earthquakes,three limit states of single-layer reticulated domes under earthquakes are defined firstly in this paper. Then, two failure modes are presented by analyzing damage behaviors, and their characteristics are pointed out respectively. Furthermore, the damage process is analyzed and the causes of structural damage in different levels are studied. Finally, by comparing deformation and vibration status of domes with different failure modes, the principles of different failures are revealed and an integrated frame of damage mechanism is set up.

  4. Single-layer skull approximations perform well in transcranial direct current stimulation modeling

    NARCIS (Netherlands)

    Rampersad, S.M.; Stegeman, D.F.; Oostendorp, T.F.

    2013-01-01

    In modeling the effect of transcranial direct current stimulation, the representation of the skull is an important factor. In a spherical model, we compared a realistic skull modeling approach, in which the skull consisted of three isotropic layers, to anisotropic and isotropic single-layer approxim

  5. Ultra-Short Optical Pulse Generation with Single-Layer Graphene

    CERN Document Server

    Lee, C -C; Bunch, J S; Schibli, T R

    2010-01-01

    Pulses as short as 260 fs have been generated in a diode-pumped low-gain Er:Yb:glass laser by exploiting the nonlinear optical response of single-layer graphene. The application of this novel material to solid-state bulk lasers opens up a way to compact and robust lasers with ultrahigh repetition rates.

  6. Experimental Study on a Single Layer Two-Way Grid Shell with Tension Members

    Institute of Scientific and Technical Information of China (English)

    Zhonghao Zhang; Masumi Fujimoto; Atsuo Takino; Katsuhiko Imai

    2015-01-01

    Single layer two⁃way grid shell with in⁃plane and out⁃of⁃plane tension members is a new type of single⁃layer latticed shell roofs. Compared with traditional single⁃layer latticed shells, this new type has a unique mesh form and excellent rigidity. In order to further understand the buckling behaviors of single layer two⁃way grid cylindrical shell roof with tension members, the buckling experiments have been undertaken to investigate the effect of tension members, in either out⁃of⁃plane or in⁃plane placement. A single layer two⁃way grid cylindrical shell roof with out⁃of⁃plane tension members has been tested under symmetric and asymmetric loading. The tension member placement, the introducing initial axial force to tension members and the load patterns are considered to investigate the buckling behavior. Experimental results indicate that four long out⁃of⁃plane tension members work well under symmetrical loading, but only two long out⁃of⁃plane tension members work under asymmetrical loading. It can be concluded that the PC bar members used as tension members for this study are useful in the construction of a single layer two⁃way grid cylindrical shell roof with structural members intersecting at small angles.

  7. The Complexity of Recognition in the Single-Layered PLN Network with Feedback Connections

    Institute of Scientific and Technical Information of China (English)

    1993-01-01

    Regarding a single-layered PLN network with feedback connections as an associative memory network,the complexity of recognitions is discussed.We have the main result:if the size of the network N is m,then the complexity of recognition is an exponential function of m.The necessary condition under which the complexity of recognition is polynomial is given.

  8. Characterization of grain sizes and roughness of HfOsub>2sub> single layers.

    Science.gov (United States)

    Zhang, Lei; Cheng, Xinbin; Zhang, Jinlong; Jiao, Hongfei; Bao, Ganghua; Ding, Tao; Wang, Zhanshan

    2017-02-01

    The grain sizes and their influence on the roughness of an HfOsub>2sub> single layer prepared with ion-assisted deposition were investigated. Three methods, x ray diffractometry, atomic force microscopy, and the k-correlated power spectral density function model, were used to obtain the grain sizes in two HfOsub>2sub> single layers with 16 and 20 nm thicknesses. X ray diffractometry showed that the grain sizes were about 7 and 9 nm, respectively, whereas the other two methods demonstrated that the grain sizes were about 14 and 16 nm. It was thought that x ray diffractometry underestimated the grain size due to micro strain or a shallow penetration depth. The grains in an HfOsub>2sub> single layer lead to a rough surface, which had a significant bulge at the middle-high frequency range in a power spectral density function curve. The coating intrinsic roughness of the HfOsub>2sub> single layer was separated from the substrate roughness.

  9. Atomically thick bismuth selenide freestanding single layers achieving enhanced thermoelectric energy harvesting.

    Science.gov (United States)

    Sun, Yongfu; Cheng, Hao; Gao, Shan; Liu, Qinghua; Sun, Zhihu; Xiao, Chong; Wu, Changzheng; Wei, Shiqiang; Xie, Yi

    2012-12-19

    Thermoelectric materials can realize significant energy savings by generating electricity from untapped waste heat. However, the coupling of the thermoelectric parameters unfortunately limits their efficiency and practical applications. Here, a single-layer-based (SLB) composite fabricated from atomically thick single layers was proposed to optimize the thermoelectric parameters fully. Freestanding five-atom-thick Bi(2)Se(3) single layers were first synthesized via a scalable interaction/exfoliation strategy. As revealed by X-ray absorption fine structure spectroscopy and first-principles calculations, surface distortion gives them excellent structural stability and a much increased density of states, resulting in a 2-fold higher electrical conductivity relative to the bulk material. Also, the surface disorder and numerous interfaces in the Bi(2)Se(3) SLB composite allow for effective phonon scattering and decreased thermal conductivity, while the 2D electron gas and energy filtering effect increase the Seebeck coefficient, resulting in an 8-fold higher figure of merit (ZT) relative to the bulk material. This work develops a facile strategy for synthesizing atomically thick single layers and demonstrates their superior ability to optimize the thermoelectric energy harvesting.

  10. Bioelectronic interfaces by spontaneously organized peptides on 2D atomic single layer materials

    Science.gov (United States)

    Hayamizu, Yuhei; So, Christopher R.; Dag, Sefa; Page, Tamon S.; Starkebaum, David; Sarikaya, Mehmet

    2016-09-01

    Self-assembly of biological molecules on solid materials is central to the “bottom-up” approach to directly integrate biology with electronics. Inspired by biology, exquisite biomolecular nanoarchitectures have been formed on solid surfaces. We demonstrate that a combinatorially-selected dodecapeptide and its variants self-assemble into peptide nanowires on two-dimensional nanosheets, single-layer graphene and MoS2. The abrupt boundaries of nanowires create electronic junctions via spatial biomolecular doping of graphene and manifest themselves as a self-assembled electronic network. Furthermore, designed peptides form nanowires on single-layer MoS2 modifying both its electric conductivity and photoluminescence. The biomolecular doping of nanosheets defined by peptide nanostructures may represent the crucial first step in integrating biology with nano-electronics towards realizing fully self-assembled bionanoelectronic devices.

  11. Electronic and magnetic properties of single-layer M P X3 metal phosphorous trichalcogenides

    Science.gov (United States)

    Chittari, Bheema Lingam; Park, Youngju; Lee, Dongkyu; Han, Moonsup; MacDonald, Allan H.; Hwang, Euyheon; Jung, Jeil

    2016-11-01

    We survey the electronic structure and magnetic properties of two-dimensional (2D) M P X3 (M =V,Cr,Mn,Fe,Co,Ni,Cu,Zn, and X =S,Se,Te ) transition-metal chalcogenophosphates to shed light on their potential role as single-layer van der Waals materials that possess magnetic order. Our ab initio calculations predict that most of these single-layer materials are antiferromagnetic semiconductors. The band gaps of the antiferromagnetic states decrease as the atomic number of the chalcogen atom increases (from S to Se to Te), leading in some cases to half-metallic ferromagnetic states or to nonmagnetic metallic states. We find that the competition between antiferromagnetic and ferromagnetic states can be substantially influenced by gating and by strain engineering. The sensitive interdependence we find between magnetic, structural, and electronic properties establishes the potential of this 2D materials class for applications in spintronics.

  12. Strong THz and Infrared Optical Forces on a Suspended Single-Layer Graphene Sheet

    CERN Document Server

    Mousavi, S Hossein; Wang, Zheng

    2014-01-01

    Single-layer graphene exhibits exceptional mechanical properties attractive for optomechanics: it combines low mass density, large tensile modulus, and low bending stiffness. However, at visible wavelengths, graphene absorbs weakly and reflects even less, thereby inadequate to generate large optical forces needed in optomechanics. Here, we numerically show that a single-layer graphene sheet is sufficient to produce strong optical forces under terahertz or infrared illumination. For a system as simple as graphene suspended atop a uniform substrate, high reflectivity from the substrate is crucial in creating a standing-wave pattern, leading to a strong optical force on graphene. This force is readily tunable in amplitude and direction by adjusting the suspension height. In particular, repellent optical forces can levitate graphene to a series of stable equilibrium heights above the substrate. One of the key parameters to maximize the optical force is the excitation frequency: peak forces are found near the scat...

  13. Evenly transferred single-layered graphene membrane assisted by strong substrate adhesion

    Science.gov (United States)

    Park, Seongjae; Kim, Hoijoon; Seol, Daehee; Park, Taejin; Leem, Mirine; Ha, Hyunwoo; An, Hyesung; You Kim, Hyun; Jeong, Seong-Jun; Park, Seongjun; Kim, Hyoungsub; Kim, Yunseok

    2017-04-01

    We explored the transfer of a single-layered graphene membrane assisted by substrate adhesion. A relatively larger adhesion force was measured on the SiO2 substrate compared with its van der Waals contribution, which is expected to result from the additional contribution of the chemical bonding force. Density functional theory calculations verified that the strong adhesion force was indeed accompanied by chemical bonding. The transfer of single-layered graphene and subsequent deposition of the dielectric layer were best performed on the SiO2 substrate exhibiting a larger adhesion force. This study suggests the selection and/or modification of the underlying substrate for proper transfer of graphene as well as other 2D materials similar to graphene.

  14. A novel and functional single-layer sheet of ZnSe.

    Science.gov (United States)

    Zhou, Jia; Sumpter, Bobby G; Kent, Paul R C; Huang, Jingsong

    2015-01-28

    The recently synthesized freestanding four-atom-thick double-layer sheet of ZnSe holds great promise as an ultraflexible and transparent photoelectrode material for solar water splitting. In this work, we report theoretical studies on a novel three-atom-thick single-layer sheet of ZnSe that demonstrates a strong quantum confinement effect by exhibiting a large enhancement of the band gap (2.0 eV) relative to the zinc blende (ZB) bulk phase. Theoretical optical absorbance shows that the largest absorption of this ultrathin single-layer sheet of ZnSe occurs at a wavelength similar to its four-atom-thick double-layer counterpart, suggesting a comparable behavior on incident photon-to-current conversion efficiency for solar water splitting, among a wealth of potential applications. The results presented herein for ZnSe may be generalized to other group II-VI analogues.

  15. The edge- and basal-plane-specific electrochemistry of a single-layer graphene sheet

    Science.gov (United States)

    Yuan, Wenjing; Zhou, Yu; Li, Yingru; Li, Chun; Peng, Hailin; Zhang, Jin; Liu, Zhongfan; Dai, Liming; Shi, Gaoquan

    2013-01-01

    Graphene has a unique atom-thick two-dimensional structure and excellent properties, making it attractive for a variety of electrochemical applications, including electrosynthesis, electrochemical sensors or electrocatalysis, and energy conversion and storage. However, the electrochemistry of single-layer graphene has not yet been well understood, possibly due to the technical difficulties in handling individual graphene sheet. Here, we report the electrochemical behavior at single-layer graphene-based electrodes, comparing the basal plane of graphene to its edge. The graphene edge showed 4 orders of magnitude higher specific capacitance, much faster electron transfer rate and stronger electrocatalytic activity than those of graphene basal plane. A convergent diffusion effect was observed at the sub-nanometer thick graphene edge-electrode to accelerate the electrochemical reactions. Coupling with the high conductivity of a high-quality graphene basal plane, graphene edge is an ideal electrode for electrocatalysis and for the storage of capacitive charges. PMID:23896697

  16. Edge structures and properties of triangular antidots in single-layer MoS2

    KAUST Repository

    Gan, Li Yong

    2016-08-30

    Density functional theory and experiments are employed to shed light on the edge structures of antidots in O etched single-layer MoS2. The equilibrium morphology is found to be the zigzag Mo edge with each Mo atom bonded to two O atoms, in a wide range of O chemical potentials. Scanning electron microscopy shows that the orientation of the created triangular antidots is opposite to the triangular shape of the single-layer MoS2 samples, in agreement with the theoretical predictions. Furthermore, edges induced by O etching turn out to be p-doped, suggesting an effective strategy to realize p-type MoS2 devices. Published by AIP Publishing.

  17. Free Energy Relationships in the Electrical Double Layer over Single-Layer Graphene

    Energy Technology Data Exchange (ETDEWEB)

    Achtyl, Jennifer L. [Northwestern University, Evanston; Vlassiouk, Ivan V [ORNL; Fulvio, Pasquale F [ORNL; Mahurin, Shannon Mark [ORNL; Dai, Sheng [ORNL; Geiger, Franz M. [Northwestern University, Evanston

    2013-01-01

    Fluid/solid interfaces containing singlelayer graphene are important in the areas of chemistry, physics, biology, and materials science, yet this environment is difficult to access with experimental methods, especially under flow conditions and in a label-free manner. Herein, we demonstrate the use of second harmonic generation to quantify the interfacial free energy at the fused silica/single-layer graphene/water interface at pH 7 and under conditions of flowing aqueous electrolyte solutions ranging in NaCl concentrations from 10 4 to 10 1 M. Our analysis reveals that single-layer graphene reduces the interfacial free energy density of the fused silica/water interface by a factor of up to 7, which is substantial given that many interfacial processes, including those that are electrochemical in nature, are exponentially sensitive to interfacial free energy density.

  18. Transparent actuators and robots based on single-layer superaligned carbon nanotube sheet and polymer composites

    Science.gov (United States)

    Chen, Luzhuo; Weng, Mingcen; Zhang, Wei; Zhou, Zhiwei; Zhou, Yi; Xia, Dan; Li, Jiaxin; Huang, Zhigao; Liu, Changhong; Fan, Shoushan

    2016-03-01

    Transparent actuators have been attracting emerging interest recently, as they demonstrate potential applications in the fields of invisible robots, tactical displays, variable-focus lenses, and flexible cellular phones. However, previous technologies did not simultaneously realize macroscopic transparent actuators with advantages of large-shape deformation, low-voltage-driven actuation and fast fabrication. Here, we develop a fast approach to fabricate a high-performance transparent actuator based on single-layer superaligned carbon nanotube sheet and polymer composites. Various advantages of single-layer nanotube sheets including high transparency, considerable conductivity, and ultra-thin dimensions together with selected polymer materials completely realize all the above required advantages. Also, this is the first time that a single-layer nanotube sheet has been used to fabricate actuators with high transparency, avoiding the structural damage to the single-layer nanotube sheet. The transparent actuator shows a transmittance of 72% at the wavelength of 550 nm and bends remarkably with a curvature of 0.41 cm-1 under a DC voltage for 5 s, demonstrating a significant advance in technological performances compared to previous conventional actuators. To illustrate their great potential usage, a transparent wiper and a humanoid robot ``hand'' were elaborately designed and fabricated, which initiate a new direction in the development of high-performance invisible robotics and other intelligent applications with transparency.Transparent actuators have been attracting emerging interest recently, as they demonstrate potential applications in the fields of invisible robots, tactical displays, variable-focus lenses, and flexible cellular phones. However, previous technologies did not simultaneously realize macroscopic transparent actuators with advantages of large-shape deformation, low-voltage-driven actuation and fast fabrication. Here, we develop a fast approach to

  19. Interactions between C and Cu atoms in single-layer graphene: direct observation and modelling.

    Science.gov (United States)

    Kano, Emi; Hashimoto, Ayako; Kaneko, Tomoaki; Tajima, Nobuo; Ohno, Takahisa; Takeguchi, Masaki

    2016-01-07

    Metal doping into the graphene lattice has been studied recently to develop novel nanoelectronic devices and to gain an understanding of the catalytic activities of metals in nanocarbon structures. Here we report the direct observation of interactions between Cu atoms and single-layer graphene by transmission electron microscopy. We document stable configurations of Cu atoms in the graphene sheet and unique transformations of graphene promoted by Cu atoms. First-principles calculations based on density functional theory reveal a reduction of energy barrier that caused rotation of C-C bonds near Cu atoms. We discuss two driving forces, electron irradiation and in situ heating, and conclude that the observed transformations were mainly promoted by electron irradiation. Our results suggest that individual Cu atoms can promote reconstruction of single-layer graphene.

  20. Biomass derived solvents for the scalable production of single layered graphene from graphite.

    Science.gov (United States)

    Sharma, Mukesh; Mondal, Dibyendu; Singh, Nripat; Prasad, Kamalesh

    2016-07-12

    Among four different biomass derived green and sustainable solvents namely levulinic acid (LA), ethyl lactate (EL), γ-valerolactone (GVL) and formic acid (FA) only LA was found to exfoliate graphite to single and few layered graphene sheets. During exfoliation, the formation of LA crystals embedded with single layered graphene sheets was observed. The process is scalable and the solvent can be recovered and reused in five subsequent cycles of exfoliation for the large scale production of graphene sheets.

  1. Adaptive control of chaotic systems based on a single layer neural network

    Energy Technology Data Exchange (ETDEWEB)

    Shen Liqun [Space Control and Inertia Technology Research Center, Harbin Institute of Technology, Harbin 150001 (China)], E-mail: liqunshen@gmail.com; Wang Mao [Space Control and Inertia Technology Research Center, Harbin Institute of Technology, Harbin 150001 (China)

    2007-08-27

    This Letter presents an adaptive neural network control method for the chaos control problem. Based on a single layer neural network, the dynamic about the unstable fixed period point of the chaotic system can be adaptively identified without detailed information about the chaotic system. And the controlled chaotic system can be stabilized on the unstable fixed period orbit. Simulation results of Henon map and Lorenz system verify the effectiveness of the proposed control method.

  2. Laser-assisted fabrication of single-layer flexible touch sensor

    Science.gov (United States)

    Son, Seokwoo; Park, Jong Eun; Lee, Joohyung; Yang, Minyang; Kang, Bongchul

    2016-01-01

    Single-layer flexible touch sensor that is designed for the indium-tin-oxide (ITO)-free, bendable, durable, multi-sensible, and single layer transparent touch sensor was developed via a low-cost and one-step laser-induced fabrication technology. To this end, an entirely novel approach involving material, device structure, and even fabrication method was adopted. Conventional metal oxides based multilayer touch structure was substituted by the single layer structure composed of integrated silver wire networks of sensors and bezel interconnections. This structure is concurrently fabricated on a glass substitutive plastic film via the laser-induced fabrication method using the low-cost organometallic/nanoparticle hybrid complex. In addition, this study addresses practical solutions to heterochromia and interference problem with a color display unit. As a result, a practical touch sensor is successfully demonstrated through resolving the heterochromia and interference problems with color display unit. This study could provide the breakthrough for early realization of wearable device. PMID:27703204

  3. Ionospheric correction for spaceborne single-frequency GPS based on single layer model

    Indian Academy of Sciences (India)

    Xia Yang; Jiancheng Li; Shoujian Zhang

    2014-06-01

    A modified ionospheric correction method and the corresponding approximate algorithm for spaceborne single-frequency Global Positioning System (GPS) users are proposed in this study. Single Layer Model (SLM) mapping function for spaceborne GPS was analyzed. SLM mapping functions at different altitudes were calculated. Ionospheric Pierce Point (IPP) trajectories of the dlft station (an IGS station located at the longitude of 4° 23′ 15.22′′E and the latitude of 51° 59′ 9.63′′N, in the TU Delft University, The Netherlands) and the GRACE satellite were computed with the corresponding single layer height of 350 and 500 km, respectively. The Klobuchar model was used to compute ionospheric delays for the dlft station, and modified Klobuchar model, together with scale factors, was used to compute the fractional ionospheric corrections above the GRACE altitudes. Calculation results were validated using dual-frequency observations. The study shows that the single layer height needs to be changed from 350 to 500 km according to the altitude of GRACE. Approximate forms of Earth angle and slant factor developed for modified Klobuchar model are applicable to GRACE, with accuracy adequate to preserve the essential elements required to compute ionospheric delays. Results show that the Klobuchar model is effective for ground GPS, and the modified Klobuchar model corrects more than 80% on average of the ionospheric delays for spaceborne single-frequency GPS.

  4. Ideal strength and phonon instability in single-layer MoS2

    Science.gov (United States)

    Li, Tianshu

    2012-06-01

    Ideal tensile stress strain relations for single-layer MoS2 are investigated based on first-principle calculation, for biaxial tension and uniaxial tension along zigzag and armchair directions. The predicted ideal tensile strengths and elastic moduli are in excellent agreement with the very recent experimental measurements of Bertolazzi [ACS Nano1936-085110.1021/nn203879f 5, 9703 (2011)] and Castellanos-Gomez [Adv. Mater.ADVMEW0935-964810.1002/adma.201103965 24, 772 (2012)]. It is identified that the tensile strength of single-layer MoS2 are dictated by out-of-plane soft-mode phonon instability under biaxial tension and uniaxial tension along the armchair direction. This failure mechanism, different from that of the truly two-dimensional material graphene, is attributed to the out-of-plane atomic relaxation upon tensile strain. Investigation of the electronic structures of single-layer MoS2 under tensile strain shows the material becomes an indirect semiconductor at small tensile strain (<2%) and turns into metallic before reaching the ideal tensile strength.

  5. Novel High-Gain Circularly Polarized Lens Antenna Using Single-Layer Transmissive Metasurface

    Science.gov (United States)

    Zhuang, Yaqiang; Wang, Guangming; Li, Haipeng; Guo, Wenlong

    2017-03-01

    A high-gain lens antenna employing single-layer focusing metasurface (MS) is proposed in this article. The single-layer element achieves a 360° transmission phase range with a transmission magnitude better than 0.9. And the focusing MS consists of 169 elements was designed by utilizing the technique of varying rotation angle to compensate the phase delay. Thus, a lens antenna is constructed by placing a circularly polarized (CP) patch antenna at the focal point of the MS. The fabricated lens antenna demonstrates a good performance of 4.6 % 3-dB axial ratio bandwidth and 6 % 1-dB gain bandwidth, respectively. Moreover, the maximum gain is 18.3 dBic at 15 GHz, which is enhanced by 11.4 dBic compared with the patch antenna. Due to the single-layer structure, this design has a low profile and easy fabrication process compared with the conventional designs, making it an attractive alternative to compact high-gain antenna.

  6. Derivation of single layer clothing penetration factors from the pesticide handlers exposure database.

    Science.gov (United States)

    Driver, Jeffrey; Ross, John; Mihlan, Gary; Lunchick, Curt; Landenberger, Bryce

    2007-11-01

    Quantitative characterization of the penetration of chemical residues through various types and configurations of clothing is an important underpinning of mitigation strategies to reduce dermal exposure to occupational cohorts. The objective of the evaluation presented herein is the development of pesticide clothing penetration (or conversely protection) factors for single layer clothing (i.e., long-sleeved shirt, long pants; gloves are not included) based on dermal exposure monitoring data (passive dosimetry) included in the Environmental Protection Agency's Pesticide Handlers Exposure Database (PHED). The analysis of penetration per replicate was conducted by comparison of the inside and outside (total deposition), expressed as mug/cm(2), for each replicate pair of dermal dosimeters. Clothing penetration was investigated as a function of job classification, dosimetry sampling method, body part, application method, and type of formulation. Grand mean single layer clothing penetration values for patch (n=2029) and whole-body (n=100) dosimeter samples from PHED were 12.12 (SE=0.33; SD=15.02) and 8.21 (SE=1.01; SD=10.14) percent, respectively. Linear regression was used to evaluate clothing penetration as a function of outer dosimeter loading. The regression analysis supports the hypothesis that single layer clothing penetration increases with decreasing outer dosimeter loading.

  7. Laser-assisted fabrication of single-layer flexible touch sensor

    Science.gov (United States)

    Son, Seokwoo; Park, Jong Eun; Lee, Joohyung; Yang, Minyang; Kang, Bongchul

    2016-10-01

    Single-layer flexible touch sensor that is designed for the indium-tin-oxide (ITO)-free, bendable, durable, multi-sensible, and single layer transparent touch sensor was developed via a low-cost and one-step laser-induced fabrication technology. To this end, an entirely novel approach involving material, device structure, and even fabrication method was adopted. Conventional metal oxides based multilayer touch structure was substituted by the single layer structure composed of integrated silver wire networks of sensors and bezel interconnections. This structure is concurrently fabricated on a glass substitutive plastic film via the laser-induced fabrication method using the low-cost organometallic/nanoparticle hybrid complex. In addition, this study addresses practical solutions to heterochromia and interference problem with a color display unit. As a result, a practical touch sensor is successfully demonstrated through resolving the heterochromia and interference problems with color display unit. This study could provide the breakthrough for early realization of wearable device.

  8. Application of single-layer mucosa-tomucosa pancreaticojejunal anastomosis in pancreaticoduodenectomy

    Institute of Scientific and Technical Information of China (English)

    Bing-Yang; Hu; Jian-Jun; Leng; Tao; Wan; Wen-Zhi; Zhang

    2015-01-01

    AIM: To investigate the simplicity, reliability, andsafety of the application of single-layer mucosa-tomucosa pancreaticojejunal anastomosis in pancreaticoduodenectomy. METHODS: A retrospective analysis was performed on the data of patients who received pancreaticoduodenectomy completed by the same surgical group between January 2011 and April 2014 in the General Hospital of the People’s Liberation Army. In total, 51 cases received single-layer mucosa-to-mucosa pancreaticojejunal anastomosis and 51 cases received double-layer pancreaticojejunal anastomosis. The diagnoses of pancreatic fistula and clinically relevant pancreatic fistula after pancreaticoduodenectomy were judged strictly by the International Study Group on pancreatic fistula definition. The preoperative and intraoperative data of these two groups were compared. χ2 test and Fisher’s exact test were used to analyze the incidences of pancreatic fistula, peritoneal catheterization, abdominal infection and overall complications between the single-layer anastomosis group and double-layer anastomosis group. Rank sum test were used to analyze the difference in operation time, pancreaticojejunal anastomosis time, postoperative hospitalization time, total hospitalization time and hospitalization expenses between the single-layer anastomosis group and double-layer anastomosis group.RESULTS: Patients with grade A pancreatic fistula accounted for 15.69%(8/51) vs 15.69%(8/51)(P = 1.0000), and patients with grades B and C pancreatic fistula accounted for 9.80%(5/51) vs 52.94%(27/51)(P = 0.0000) in the single-layer and double-layer anastomosis groups. Although there was no significant difference in the percentage of patients with grade A pancreatic fistula, there was a significant difference in the percentage of patients with grades B and C pancreatic fistula between the two groups. Theoperation time(220.059 ± 60.602 min vs 379.412 ± 90.761 min, P = 0.000), pancreaticojejunal anastomosis time(17.922 ± 5

  9. Interdigital H -mode drift-tube linac design with alternative phase focusing for muon linac

    Science.gov (United States)

    Otani, M.; Mibe, T.; Yoshida, M.; Hasegawa, K.; Kondo, Y.; Hayashizaki, N.; Iwashita, Y.; Iwata, Y.; Kitamura, R.; Saito, N.

    2016-04-01

    We have developed an interdigital H-mode (IH) drift-tube linac (DTL) design with an alternative phase focusing (APF) scheme for a muon linac, in order to measure the anomalous magnetic moment and electric dipole moment (EDM) of muons at the Japan Proton Accelerator Research Complex (J-PARC). The IH-DTL accelerates muons from β =v /c =0.08 to 0.28 at an operational frequency of 324 MHz. The output beam emittances are calculated as 0.315 π and 0.195 π mm mrad in the horizontal and vertical directions, respectively, which satisfies the experimental requirement.

  10. Effect of monolayer supports on the electronic structure of single-layer MoS2

    Science.gov (United States)

    Ramirez-Torres, Alfredo; Le, Duy; Rahman, Talat S.

    2015-03-01

    We present results of density functional theory based calculations of the electronic structure of a single-layer of MoS2, as modified by three different single-layer materials used as support: hexagonal boron nitride (h-BN), graphene, and silicene, using the local density approximation (LDA), on the one hand, and a functional that explicitly includes van der Waals interactions (optB88-vdW), on the other hand. Because the lattice mismatch between the primitive cell of MoS2 and those of the supports is large, calculations are performed with as large a supercell as computationally feasible, so as to reduce the incommensurability between lattices. Even though van der Waals interactions are expected to play an important role in the binding between MoS2, and h-BN and graphene, we find that the band structure and related conclusions obtained by optB88-vdW and LDA are quite similar for the three heterostructures considered here. Single-layer MoS2 interacts weakly with h-BN and graphene, while covalent bonds are formed with silicene. Detailed analysis of the electronic density of states also indicates little effect of h-BN and graphene, while silicene severely modifies it by introducing additional states within the band gap. Furthermore, adsorption on graphene brings the conduction bands of MoS2 down to the Fermi level of graphene as a result of charge transfer from graphene to MoS2, while adsorption on silicene shifts both valence and conduction bands towards the Fermi level, in addition to inducing a gap of ~50 meV in silicene itself.

  11. Spin effects in MoS{sub 2} and WS{sub 2} single layers

    Energy Technology Data Exchange (ETDEWEB)

    Kioseoglou, G. [Department of Materials Science and Technology, University of Crete, Heraklion (Greece); Institute of Electronic Structure and Laser (IESL), Foundation for Research and Technology Hellas (FORTH), Heraklion, Crete (Greece); Korkusinski, M. [Quantum Theory Group, Emerging Technologies Division, National Research Council, Ottawa, ON (Canada); Scrace, T. [University at Buffalo, SUNY, Buffalo, NY (United States); Hanbicki, A.T.; Currie, M.; Jonker, B.T.; Petrou, A. [Naval Research Laboratory, Washington, DC (United States); Hawrylak, P. [Quantum Theory Group, Emerging Technologies Division, National Research Council, Ottawa, ON (Canada); Department of Physics, University of Ottawa, ON (Canada)

    2016-01-15

    Replacing the two sublattices of carbon atoms in graphene with transition metal atoms and chalcogenide dimers results in single layers of transition metal dichalcogenides (TMDCs). TMDCs are promising new materials for light and energy harvesting, transistors, sensors and quantum information processing. One way to access the distinctive functionality of these materials is via their optical selection rules. In particular, light with positive or negative helicity is absorbed differently, therefore, understanding the interaction of circularly polarized light with various TMDCs should enable future applications. Using the examples of MoS{sub 2} and WS{sub 2} we summarize some recent results that illustrate the potential of these materials. First, when optically excited with circularly polarized light, single layers of MoS{sub 2} can emit light with an appreciable polarization. Depolarization mechanisms can be subsequently explored by monitoring the polarization of emitted photoluminescence as a function of the excess energy supplied to the system. As the energy of the pumping light increases further from the emission channel, the emission quickly becomes depolarized. The dominant relaxation mechanism is identified as phonon-assisted intervalley scattering. In single layers of WS{sub 2} containing electron gas, the main emission channel is from negatively charged excitons, or trions. In the presence of a two-dimensional electron gas this trion emission is circularly polarized at zero magnetic field, even when excited with linearly polarized light. This spontaneous circular polarization of the trion has a linear dependence on magnetic field and can be attributed to the existence of a valley polarized state of the two-dimensional electron gas. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  12. Optical implementation of a single-layer finite impulse response neural network

    Science.gov (United States)

    Silveira, Paulo E. X.; Pati, G. S.; Wagner, Kelvin H.

    2000-05-01

    This paper demonstrates a space integrating optical implementation of a single-layer FIRNN. A scrolling spatial light modulator is used for representing the spatio-temporal input plane, while the weights are implemented by the adaptive grating formation in a photorefractive crystal. Differential heterodyning is used for low-noise bipolar output detection and an active stabilization technique using a lock-in amplifier and a piezo-electric actuator is adopted for long term interferometric stability. Simulations and initial experimental results for adaptive sonar broadband beamforming are presented.

  13. Terahertz imaging and spectroscopy of large-area single-layer graphene

    OpenAIRE

    Tomaino, J. L.; Jameson, A. D.; Kevek, J. W.; Paul, M. J.; van der Zande, A. M.; Barton, R. A.; McEuen, P. L.; Minot, E. D.; Lee, Yun-Shik

    2011-01-01

    We demonstrate terahertz (THz) imaging and spectroscopy of a 15x15-mm^2 single-layer graphene film on Si using broadband THz pulses. The THz images clearly map out the THz carrier dynamics of the graphene-on-Si sample, allowing us to measure sheet conductivity with sub-mm resolution without fabricating electrodes. The THz carrier dynamics are dominated by intraband transitions and the THz-induced electron motion is characterized by a flat spectral response. A theoretical analysis based on the...

  14. Atomic-scale structure of single-layer MoS2 nanoclusters

    DEFF Research Database (Denmark)

    Helveg, S.; Lauritsen, J. V.; Lægsgaard, E.

    2000-01-01

    We have studied using scanning tunneling microscopy (STM) the atomic-scale realm of molybdenum disulfide (MoS2) nanoclusters, which are of interest as a model system in hydrodesulfurization catalysis. The STM gives the first real space images of the shape and edge structure of single-layer MoS2 n...... nanoparticles synthesized on Au(lll), and establishes a new picture of the active edge sires of the nanoclusters. The results demonstrate a way to get detailed atomic-scale information on catalysts in general....

  15. Design and analysis of frequency-independent reflectionless single-layer metafilms

    CERN Document Server

    Tamayama, Yasuhiro

    2016-01-01

    We develop a theory for realizing frequency-independent, reflectionless, single-layer metafilms based on the Brewster effect. A metafilm designed based on the theory is numerically analyzed using a finite-difference time-domain method. The numerical analysis demonstrates that the reflectance of the metafilm vanishes independent of the frequency and that the metafilm behaves like an all-pass filter (with finite loss). An analysis based on an electrical circuit model of the reflectionless metafilm reveals that the energy of the suppressed reflection wave is not stored in the metafilm but is radiated to the transmission direction.

  16. Electroluminescence in organic single-layer light-emitting diodes at high fields

    Institute of Scientific and Technical Information of China (English)

    杨盛谊; 徐征; 王振家; 侯延冰; 徐叙; 张希清

    2001-01-01

    By considering the interaction between Fowler-Nordheim tunneling injection theory and charge carriers transporting through the bulk, an electroluminescence model for organic single-layer diodes is presented. The expressions of the recombination current density, recombination efficiency and conductivity of the diodes are provided, which elucidate the controlling role of the electric field on mobility and recombination zone. The equilibrium of two opposite charge carriers injection and the central position of recombination zone are two important preconditions for reducing the leakage current. Space-charge-limited current occurs only over a certain high bias, meanwhile, the quantity of injection carriers increases over the transport capacity of the bulk.

  17. Valley polarization in magnetically doped single-layer transition-metal dichalcogenides

    KAUST Repository

    Cheng, Yingchun

    2014-04-28

    We demonstrate that valley polarization can be induced and controlled in semiconducting single-layer transition-metal dichalcogenides by magnetic doping, which is important for spintronics, valleytronics, and photonics devices. As an example, we investigate Mn-doped MoS2 by first-principles calculations. We study how the valley polarization depends on the strength of the spin orbit coupling and the exchange interaction and discuss how it can be controlled by magnetic doping. Valley polarization by magnetic doping is also expected for other honeycomb materials with strong spin orbit coupling and the absence of inversion symmetry.

  18. Adsorption and diffusion of Si adatom near single-layer steps on Si surface

    Institute of Scientific and Technical Information of China (English)

    Zhu Xiao-Yan; Huang Yan

    2005-01-01

    By use of the empirical tight-binding (ETB) method, the adsorption and diffusion behaviours of single silicon adatom on the reconstructed Si(100) surface with single-layer steps are simulated. The adsorption energies around the SA step, nonrebonded SB step, rebonded SB step, and rough SB step with a kink structure are specially mapped out in this paper, from which the favourable binding sites and several possible diffusion paths are achieved. Because of the rebonded and kink structures, the SB step is more suitable for the attachment of Si adatom than the SA step or defective surface.

  19. Large-Area Growth of Uniform Single-Layer MoS2 Thin Films by Chemical Vapor Deposition.

    Science.gov (United States)

    Baek, Seung Hyun; Choi, Yura; Choi, Woong

    2015-12-01

    We report the largest-size thin films of uniform single-layer MoS2 on sapphire substrates grown by chemical vapor deposition based on the reaction of gaseous MoO3 and S evaporated from solid sources. The as-grown thin films of single-layer MoS2 were continuous and uniform in thickness for more than 4 cm without the existence of triangular-shaped MoS2 clusters. Compared to mechanically exfoliated crystals, the as-grown single-layer MoS2 thin films possessed consistent chemical valence states and crystal structure along with strong photoluminescence emission and optical absorbance at high energy. These results demonstrate that it is possible to scale up the growth of uniform single-layer MoS2 thin films, providing potentially important implications on realizing high-performance MoS2 devices.

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

    Science.gov (United States)

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

    2012-07-03

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

  1. Wind-induced vibration of single-layer reticulated shell structures

    Institute of Scientific and Technical Information of China (English)

    ZHANG Jian-sheng; WU Yue; SHEN Shi-zhao

    2008-01-01

    Aiming at the dynamic response of reticulated shell structures under wind load, systematic parameter analyses on wind-induced responses of Kiewitt6-6 type single-layer spherical reticulated shell structures and three-way grid single-layer cylindrical reticulated shell structures were performed with the random simulation method in time domain, including geometric parameters, structural parameters and aerodynamic parameters. Moreover, a wind-induced vibration coefficient was obtained, which can be a reference to the wind-resistance design of reticulated shell structures. The results indicate that the geometric parameters are the most important factor influencing wind-induced responses of the reticulated shell structures; the wind-induced vibration coeffi-cient is 3.0 - 3.2 for the spherical reticulated shell structures and that is 2.8 - 3.0 for the cylindrical reticula-ted shell structures, which shows that the wind-induced vibration coefficients of these two kinds of space frames are well-proportioned.

  2. Single-layer graphene-TiO{sub 2} nanotubes array heterojunction for ultraviolet photodetector application

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Deng-Yue [School of Material Sciences and Engineering, Hefei University of Technology, Hefei, Anhui 230009 (China); Ge, Cai-Wang [School of Electronic Science and Applied Physics, Hefei University of Technology, Hefei, Anhui 230009 (China); Wang, Jiu-Zhen [School of Material Sciences and Engineering, Hefei University of Technology, Hefei, Anhui 230009 (China); Zhang, Teng-Fei [School of Electronic Science and Applied Physics, Hefei University of Technology, Hefei, Anhui 230009 (China); Wu, Yu-Cheng, E-mail: ycwu@hfut.edu.cn [School of Material Sciences and Engineering, Hefei University of Technology, Hefei, Anhui 230009 (China); Liang, Feng-Xia, E-mail: fxliang@hfut.edu.cn [School of Material Sciences and Engineering, Hefei University of Technology, Hefei, Anhui 230009 (China)

    2016-11-30

    Highlights: • Heterostructures comprised of a single-layer graphene and TiO{sub 2} nanotube arrays were constructed for ultraviolet detection. • The electrical properties of the fabricated heterostructures were dependent on the annealing atmospheres. • The effect of anodic TiO{sub 2} nanotube length on the performance of the photodetector were investigated. - Abstract: In this work, we reported on the fabrication of a single-layer graphene (SLG)-TiO{sub 2} nanotube arrays (NTs) heterostructures ultraviolet photodetector (UVPD) by transferring chemical vapor deposition derived MLG on the surface of anodic TiO{sub 2}NTs array. Through varying the annealing atmosphere and anodization time in the TiO{sub 2} synthesis procedure, the electronic and optoelectronic properties of the as-fabricated Schottky junction UVPD were studied. It was revealed that the anodic TiO{sub 2}NTs annealed in air showed a better rectifying behavior and was highly sensitive to UV light irradiation. Further investigation found that the device performance of the UVPD can be readily modulated by the anodization time, and the anodic TiO{sub 2}NTs with a medium tube length of 9.6 μm exhibits the highest device performance. These results demonstrated that the present SLG-TiO{sub 2}NTs array hetero-junction UVPD will be highly promising for fabricating high-performance optoelectronic device and system in the future.

  3. Suppressing Manganese Dissolution from Lithium Manganese Oxide Spinel Cathodes with Single-Layer Graphene

    Energy Technology Data Exchange (ETDEWEB)

    Jaber-Ansari, Laila; Puntambekar, Kanan P.; Kim, Soo; Aykol, Muratahan; Luo, Langli; Wu, Jinsong; Myers, Benjamin D.; Iddir, Hakim; Russell, John T.; Saldana, Spencer J.; Kumar, Rajan; Thackeray, Michael M.; Curtiss, Larry A.; Dravid, Vinayak P.; Wolverton, Christopher M.; Hersam, Mark C.

    2015-06-24

    Spinel-structured LiMn 2 O 4 (LMO) is a desirable cathode material for Li-ion batteries due to its low cost, abundance, and high power capability. However, LMO suffers from limited cycle life that is triggered by manganese dissolution into the electrolyte during electrochemical cycling. Here, it is shown that single-layer graphene coatings suppress manganese dissolution, thus enhancing the performance and lifetime of LMO cathodes. Relative to lithium cells with uncoated LMO cathodes, cells with graphene-coated LMO cathodes provide improved capacity retention with enhanced cycling stability. X-ray photoelectron spectroscopy reveals that graphene coatings inhibit manganese depletion from the LMO surface. Additionally, transmission electron microscopy demonstrates that a stable solid electrolyte interphase is formed on graphene, which screens the LMO from direct contact with the electrolyte. Density functional theory calculations provide two mechanisms for the role of graphene in the suppression of manganese dissolution. First, common defects in single-layer graphene are found to allow the transport of lithium while concurrently acting as barriers for manganese diffusion. Second, graphene can chemically interact with Mn 3+ at the LMO electrode surface, promoting an oxidation state change to Mn 4+ , which suppresses dissolution.

  4. A Coupled-Field Expansion Method for Single-Layer and Multilayer Planar Periodic Structures

    Directory of Open Access Journals (Sweden)

    Yading Li

    2012-01-01

    Full Text Available A new, rigorous, field-based, seminumerical analysis method is presented to obtain the reflection and transmission coefficients of 2D planar periodic structures with arbitrarily shaped metallization patterns for both normal and oblique incidence conditions. It is useful for the analysis, design, and optimization of many single-layer and multilayer planar structures, such as frequency-selective surfaces (FSSs, artificial magnetic conductor (AMC surfaces, electromagnetic bandgap (EBG structures, some metamaterials and high-impedance surfaces. In this coupled-field expansion method (CFEM, the x- and y-components of the vector magnetic potential in each homogeneous region in a unit cell are expanded in terms of Bloch-Floquet modes and the solution to the coupled-field problem is formulated. The unique, analytical formulation presented here leads to a linear system with reasonably simple matrix elements. By cascading the matrices representing each interface, multilayer periodic structures are analyzed in a very flexible way. Being field based, CFEM does not require substrate Green's functions to analyze surfaces printed on dielectric substrates. The method was validated by analyzing one single-layer periodic surface (a printed AMC on a dielectric substrate and one multilayer periodic surface (a circular polarizer and comparing CFEM results with HFSS results.

  5. Hydrogen-induced structural transition in single layer ReS2

    Science.gov (United States)

    Yagmurcukardes, M.; Bacaksiz, C.; Senger, R. T.; Sahin, H.

    2017-09-01

    By performing density functional theory-based calculations, we investigate how structural, electronic and mechanical properties of single layer ReS2 can be tuned upon hydrogenation of its surfaces. It is found that a stable, fully hydrogenated structure can be obtained by formation of strong S-H bonds. The optimized atomic structure of ReS2H2 is considerably different than that of the monolayer ReS2 which has a distorted-1T phase. By performing phonon dispersion calculations, we also predict that the Re2-dimerized 1T structure (called 1T {{}\\text{R{{\\text{e}}2}}} ) of the ReS2H2 is dynamically stable. Unlike the bare ReS2 the 1T {{}\\text{R{{\\text{e}}2}}} -ReS2H2 structure which is formed by breaking the Re4 clusters into separated Re2 dimers, is an indirect-gap semiconductor. Furthermore, mechanical properties of the 1T {{}\\text{R{{\\text{e}}2}}} phase in terms of elastic constants, in-plane stiffness (C) and Poisson ratio (ν) are investigated. It is found that full hydrogenation not only enhances the flexibility of the single layer ReS2 crystal but also increases anisotropy of the elastic constants.

  6. Stability of single-layer and multilayer arsenene and their mechanical and electronic properties

    Science.gov (United States)

    Kecik, D.; Durgun, E.; Ciraci, S.

    2016-11-01

    Using first-principles spin-polarized density functional theory, we carried out an analysis on the atomic structure, stability, energetics, and mechanical and electronic properties of single-layer structures of arsenene. These are buckled honeycomb, symmetric, and asymmetric washboard arsenene structures. Our analysis is extended to include layered three-dimensional crystalline phase of arsenic, as well as bilayer and trilayer structures to reveal dimensionality effects. The buckled honeycomb and symmetric washboard structures are shown to maintain their stability at high temperatures even when they are freestanding. As a manifestation of the confinement effect, the large fundamental band gap of single-layer phases decreases with increasing number of layers and eventually is closed. Concomitantly, lattice constants partially increase, while interlayer distances decrease. The effects of hybrid functional or self-energy corrections together with the spin-orbit coupling on the electronic structure of arsenene are crucial. The responses of direct and indirect band gaps to biaxial or uniaxial strain are rather complex and directional; while the fundamental band gap decreases and changes from indirect to direct with the biaxial strain applied to buckled arsenene, these effects are strongly directional for washboard arsenene. The width and the indirect/direct character of the band gap can be tuned by the number of layers, as well as by applied uniaxial/biaxial strain.

  7. Spin incommensurability varies linearly with hole content in single-layer Bi2201 cuprate

    Science.gov (United States)

    Tranquada, John; Enoki, M.; Fujita, M.; Nishizaki, T.; Yamada, K.; Iikubo, S.; Singh, D. K.; Chang, S.

    2013-03-01

    We have performed inelastic neutron scattering measurements on the single-layer cuprate Bi2+xSr2-xCuO6+y (Bi2201) with x = 0 . 2 , 0.3, 0.4 and 0.5, a doping range that spans the spin-glass (SG) to superconducting (SC) phase boundary. The doping evolution of low energy spin fluctuations (11 meV) was found to be characterized by a change of incommensurate modulation wave vector from the tetragonal [110] to [100]/[010] directions, while maintaining a linear relation between the incommensurability and the hole concentration, δ ~ p . In the SC regime, the spectral weight is strongly suppressed below ~ 4 meV. Similarities and differences in the spin correlations between Bi2201 and the prototypical single-layer system La2-xSrxCuO4 will be discussed. Work at BNL supported by Office of Basic Energy Sciences, US DOE, under Contract No. DE-AC02-98CH10886.

  8. Spatially resolved scanning tunneling spectroscopy of single-layer steps on Si(100) surfaces

    Science.gov (United States)

    Wang, Xiqiao; Namboodiri, Pradeep; Li, Kai; Deng, Xiao; Silver, Richard

    2016-09-01

    Single-layer steps at Si(100) surfaces/interfaces present significant challenges to the quantitative characterization of buried dopant devices as well as the accurate imaging and relocation of fabricated quantum structures. We demonstrate the detailed spatially resolved scanning tunneling spectroscopy study across monolayer step edges on Si(100) surfaces and quantitative determination of the local density of state distributions and behavior of the band gap at step edges. The influence on the local electrostatic environment due to step edge states has been quantified while accounting for the effects of scanning tunneling measurement conditions. The dangling bond states on Si(100) surfaces are utilized as a fingerprint to quantify the local band bending landscape and to make corrections to the experimentally observed surface state energy levels and band gap values at the step edge regions. We observe a significant band gap narrowing behavior along a rebonded single-layer type B step edge on a degenerately boron-doped p -type Si substrate.

  9. On-chip pressure sensor using single-layer concentric chambers.

    Science.gov (United States)

    Tsai, Chia-Hung Dylan; Kaneko, Makoto

    2016-03-01

    A vision-based on-chip sensor for sensing local pressure inside a microfluidic device is proposed and evaluated in this paper. The local pressure is determined from the change of color intensity in the sensing chamber which is pre-filled with colored fluid. The working principle of the sensor is based on polydimethylsiloxane deformation. The pressure at the point of interest is guided into a deformation chamber, where the structural stiffness is softened by chamber geometry, and thus, the chamber deforms as a result of pressure changes. Such deformation is transmitted to the sensing chamber, a same-layer concentric inside the deformation chamber. The deformation in the sensing chamber causes the colored fluid flowing in or out the chamber and leads to different color intensity from the top view through a microscope. Experimental evaluations on static and dynamic responses by regulated input pressures were conducted. The correlation in static response is 0.97 while the dynamic responses are successfully observed up to 16 Hz. The greatest advantage is that the local pressure can be directly seen without any additional hardware or electricity. The whole sensor is on a single-layer microfluidic design, so that the fabrication is simple, consistent, and low-cost. The single-layer design also provides the convenience of easy integration for existing microfluidic systems.

  10. Basics of quantum field theory of electromagnetic interaction processes in single-layer graphene

    Science.gov (United States)

    Hieu Nguyen, Van

    2016-09-01

    The content of this work is the study of electromagnetic interaction in single-layer graphene by means of the perturbation theory. The interaction of electromagnetic field with Dirac fermions in single-layer graphene has a peculiarity: Dirac fermions in graphene interact not only with the electromagnetic wave propagating within the graphene sheet, but also with electromagnetic field propagating from a location outside the graphene sheet and illuminating this sheet. The interaction Hamiltonian of the system comprising electromagnetic field and Dirac fermions fields contains the limits at graphene plane of electromagnetic field vector and scalar potentials which can be shortly called boundary electromagnetic field. The study of S-matrix requires knowing the limits at graphene plane of 2-point Green functions of electromagnetic field which also can be shortly called boundary 2-point Green functions of electromagnetic field. As the first example of the application of perturbation theory, the second order terms in the perturbative expansions of boundary 2-point Green functions of electromagnetic field as well as of 2-point Green functions of Dirac fermion fields are explicitly derived. Further extension of the application of perturbation theory is also discussed.

  11. Effect of flexural phonons on the hole states in single-layer black phosphorus

    Science.gov (United States)

    Brener, S.; Rudenko, A. N.; Katsnelson, M. I.

    2017-01-01

    Flexural thermal fluctuations in crystalline membranes affect the band structure of the carriers, which leads to an exponential density-of-states (DOS) tail beyond the unperturbed band edge. We present a theoretical description of this tail for a particular case of holes in single-layer black phosphorus, a material which exhibits an extremely anisotropic quasi-one-dimensional dispersion (my/mx≫1 ) and, as a result, an enhanced Van Hove singularity at the valence band top. The material parameters are determined by ab initio calculations and then are used for quantitative estimation of the effect of two-phonon (flexural) processes have on the charge carrier DOS. It is shown that unlike the isotropic case, the physics is determined by the phonons with wave vectors of the order of q*, where q* determines the crossover between harmonic and anharmonic behavior of the flexural phonons. The spectral density of the holes in single-layer black phosphorus at finite temperatures is calculated.

  12. Strong piezoelectricity in single-layer graphene deposited on SiO2 grating substrates.

    Science.gov (United States)

    da Cunha Rodrigues, Gonçalo; Zelenovskiy, Pavel; Romanyuk, Konstantin; Luchkin, Sergey; Kopelevich, Yakov; Kholkin, Andrei

    2015-06-25

    Electromechanical response of materials is a key property for various applications ranging from actuators to sophisticated nanoelectromechanical systems. Here electromechanical properties of the single-layer graphene transferred onto SiO2 calibration grating substrates is studied via piezoresponse force microscopy and confocal Raman spectroscopy. The correlation of mechanical strains in graphene layer with the substrate morphology is established via Raman mapping. Apparent vertical piezoresponse from the single-layer graphene supported by underlying SiO2 structure is observed by piezoresponse force microscopy. The calculated vertical piezocoefficient is about 1.4 nm V(-1), that is, much higher than that of the conventional piezoelectric materials such as lead zirconate titanate and comparable to that of relaxor single crystals. The observed piezoresponse and achieved strain in graphene are associated with the chemical interaction of graphene's carbon atoms with the oxygen from underlying SiO2. The results provide a basis for future applications of graphene layers for sensing, actuating and energy harvesting.

  13. Single-layer MoS2 nanopores as nanopower generators

    Science.gov (United States)

    Feng, Jiandong; Graf, Michael; Liu, Ke; Ovchinnikov, Dmitry; Dumcenco, Dumitru; Heiranian, Mohammad; Nandigana, Vishal; Aluru, Narayana R.; Kis, Andras; Radenovic, Aleksandra

    2016-08-01

    Making use of the osmotic pressure difference between fresh water and seawater is an attractive, renewable and clean way to generate power and is known as ‘blue energy’. Another electrokinetic phenomenon, called the streaming potential, occurs when an electrolyte is driven through narrow pores either by a pressure gradient or by an osmotic potential resulting from a salt concentration gradient. For this task, membranes made of two-dimensional materials are expected to be the most efficient, because water transport through a membrane scales inversely with membrane thickness. Here we demonstrate the use of single-layer molybdenum disulfide (MoS2) nanopores as osmotic nanopower generators. We observe a large, osmotically induced current produced from a salt gradient with an estimated power density of up to 106 watts per square metre—a current that can be attributed mainly to the atomically thin membrane of MoS2. Low power requirements for nanoelectronic and optoelectric devices can be provided by a neighbouring nanogenerator that harvests energy from the local environment—for example, a piezoelectric zinc oxide nanowire array or single-layer MoS2 (ref. 12). We use our MoS2 nanopore generator to power a MoS2 transistor, thus demonstrating a self-powered nanosystem.

  14. Single-Layer Graphene Enhances the Osteogenic Differentiation of Human Mesenchymal Stem Cells In Vitro and In Vivo.

    Science.gov (United States)

    Liu, Yunsong; Chen, Tong; Du, Feng; Gu, Ming; Zhang, Ping; Zhang, Xiao; Liu, Jianzhang; Lv, Longwei; Xiong, Chunyang; Zhou, Yongsheng

    2016-06-01

    In recent years, although several studies have demonstrated the potential of graphene-coated substrates in promoting attachment, proliferation and differentiation of osteoblasts and mesenchymal stem cells (MSCs), the effects of single-layer graphene on the osteogenic differentiation of human MSCs (hMSCs) remains unclear, especially in vivo. In this study, we transferred chemical vapor deposition (CVD) grown single-layer graphene to glass slides and observed its effects on adhesion, proliferation and osteogenic differentiation of human adipose-derived stem cells (hASCs) and human bone marrow mesenchymal stem cells (hBMMSCs) in vitro. Then, in vivo, we incubated hASCs and hBMMSCs on single-layer graphene-coated smooth titanium (Ti) disks before implanting them into the back subcutaneous area of nude mice. We found that single-layer graphene accelerated cell adhesion to the substrate without influencing cell proliferation of hMSCs. Moreover, we present the first study that explores the epigenetic role of single-layer graphene in determining stem cell fate. By utilizing epigenetic approaches, we reveal that single-layer graphene promotes osteogenic differentiation of hMSCs both in vitro and in vivo, potentially by upregulating methylation of H3K4 at the promoter regions of osteogenesis-associated genes. Overall, our results highlight the potential of this material in implants and injured tissues in clinical applications.

  15. Large theoretical thermoelectric power factor of suspended single-layer MoS{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Babaei, Hasan, E-mail: babaei@illinois.edu, E-mail: babaei@auburn.edu [Mechanical Science and Engineering Department, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801-2906 (United States); Mechanical Engineering Department, Auburn University, Auburn, Alabama 36849-5341 (United States); Khodadadi, J. M. [Mechanical Engineering Department, Auburn University, Auburn, Alabama 36849-5341 (United States); Sinha, Sanjiv [Mechanical Science and Engineering Department, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801-2906 (United States)

    2014-11-10

    We have calculated the semi-classical thermoelectric power factor of suspended single-layer (SL)- MoS{sub 2} utilizing electron relaxation times derived from ab initio calculations. Measurements of the thermoelectric power factor of SL-MoS{sub 2} on substrates reveal poor power factors. In contrast, we find the thermoelectric power factor of suspended SL-MoS{sub 2} to peak at ∼2.8 × 10{sup 4} μW/m K{sup 2} at 300 K, at an electron concentration of 10{sup 12} cm{sup −2}. This figure is higher than that in bulk Bi{sub 2}Te{sub 3}, for example. Given its relatively high thermal conductivity, suspended SL-MoS{sub 2} may hold promise for in-plane thin-film Peltier coolers, provided reasonable mobilities can be realized.

  16. Nanosecond spin relaxation times in single layer graphene spin valves with hexagonal boron nitride tunnel barriers

    Science.gov (United States)

    Singh, Simranjeet; Katoch, Jyoti; Xu, Jinsong; Tan, Cheng; Zhu, Tiancong; Amamou, Walid; Hone, James; Kawakami, Roland

    2016-09-01

    We present an experimental study of spin transport in single layer graphene using atomic sheets of hexagonal boron nitride (h-BN) as a tunnel barrier for spin injection. While h-BN is expected to be favorable for spin injection, previous experimental studies have been unable to achieve spin relaxation times in the nanosecond regime, suggesting potential problems originating from the contacts. Here, we investigate spin relaxation in graphene spin valves with h-BN barriers and observe room temperature spin lifetimes in excess of a nanosecond, which provides experimental confirmation that h-BN is indeed a good barrier material for spin injection into graphene. By carrying out measurements with different thicknesses of h-BN, we show that few layer h-BN is a better choice than monolayer for achieving high non-local spin signals and longer spin relaxation times in graphene.

  17. Probing Critical Point Energies of Transition Metal Dichalcogenides: Surprising Indirect Gap of Single Layer WSe 2

    KAUST Repository

    Zhang, Chendong

    2015-09-21

    By using a comprehensive form of scanning tunneling spectroscopy, we have revealed detailed quasi-particle electronic structures in transition metal dichalcogenides, including the quasi-particle gaps, critical point energy locations, and their origins in the Brillouin zones. We show that single layer WSe surprisingly has an indirect quasi-particle gap with the conduction band minimum located at the Q-point (instead of K), albeit the two states are nearly degenerate. We have further observed rich quasi-particle electronic structures of transition metal dichalcogenides as a function of atomic structures and spin-orbit couplings. Such a local probe for detailed electronic structures in conduction and valence bands will be ideal to investigate how electronic structures of transition metal dichalcogenides are influenced by variations of local environment.

  18. Edge states of graphene wrinkles in single-layer graphene grown on Ni(111)

    Science.gov (United States)

    Liu, Liwei; Xiao, Wende; Wang, Dongfei; Yang, Kai; Tao, Lei; Gao, Hong-Jun

    2016-10-01

    As quasi-one-dimensional (1D) structures with characteristic widths of nanometer scale, graphene wrinkles (GWs) have been widely observed in graphene grown by chemical vapor deposition. Similar to conventional 1D graphene-based nanostructures, e.g., carbon nanotubes and graphene nanoribbons, 1D electron confinement has been observed in the GWs. However, it remains an open question whether the GWs have effective edges and exhibit corresponding edge states. Here, we report on the edge states of the GWs in single-layer graphene grown on Ni(111) by means of low temperature scanning tunneling microscopy and spectroscopy. We show that the GWs are decoupled from the substrate, while the surrounding planar graphene are strongly coupled with the substrate. The different graphene-substrate coupling leads to effective edges and 1D character of the GWs. The chiral edges of the GWs give rise to pronounced edge states around the Fermi level in the density of states.

  19. Investigating change of properties in gallium ion irradiation patterned single-layer graphene

    Science.gov (United States)

    Wang, Quan; Dong, Jinyao; Bai, Bing; Xie, Guoxin

    2016-10-01

    Besides its excellent physical properties, graphene promises to play a significant role in electronics with superior properties, which requires patterning of graphene for device integration. Here, we presented the changes in properties of single-layer graphene before and after patterning using gallium ion beam. Combined with Raman spectra of graphene, the scanning capacitance microscopy (SCM) image confirmed that a metal-insulator transition occurred after large doses of gallium ion irradiation. The changes in work function and Raman spectra of graphene indicated that the defect density increased as increasing the dose and a structural transition occurred during gallium ion irradiation. The patterning width of graphene presented an increasing trend due to the scattering influence of the impurities and the substrate.

  20. Size-controllable synthesis and bandgap modulation of single-layered RF-sputtered bismuth nanoparticles

    Science.gov (United States)

    Wu, Bin-Kun; Chern, Ming-Yau; Lee, Hsin-Yen

    2014-05-01

    We here report a simple and efficient method to grow single-layer bismuth nanoparticles (BiNPs) with various sizes on glass substrates. Optimal conditions were found to be 200°C and 0.12 W/cm2 at a growth rate of 6 Å/s, with the deposition time around 40 s. Scanning electron microscope (SEM) images were used to calculate the particle size distribution statistics, and high-resolution X-ray diffraction (XRD) patterns were used to examine the chemical interactions between BiNPs and the substrates. By measuring the transmission spectra within the range of 300 to 1,000 nm, we found that the optical bandgap can be modulated from 0.45 to 2.63 eV by controlling the size of these BiNPs. These interesting discoveries offer an insight to explore the dynamic nature of nanoparticles.

  1. Circular Polarizer Realized by a Single Layer of Planar Chiral Metallic Nanostructure

    CERN Document Server

    Ye, Weimin; Guo, Chucai; Zhang, Jianfa; Yang, Biao; Liu, Ken; Zhu, Zhihong; Zeng, Chun

    2014-01-01

    As a basic optical element, circular polarizer plays significant roles in signal transmission, measurements and life science microscopy. Three-dimensional (3D) chiral structures have been thought to be necessary to realize circular polarizers. Here we demonstrate theoretically and experimentally for the first time that a high-efficiency circular polarizer could be realized by a single layer of planar 2D chiral structure. Our proposed circular polarizer is based on unidirectional polarization conversion instead of circular polarization stop bands. Since two-dimensional planar structures present obvious advantage for fabrication and integration on chip, the proposed circular polarizer is of great interest in integrated optics and microscopy. It provides a novel scheme to manipulate polarizations of light wave, as well as Terahertz wave and microwave.

  2. Crystal structure and electrical transport properties of single layered perovskite LaSrCoO4

    Science.gov (United States)

    Ahad, Abdul; Shukla, D. K.; Rahman, F.; Majid, S.; Tarachand; Okram, G. S.; Phase, D. M.

    2016-10-01

    We present here investigations on the influence of structure on electrical transport properties of polycrystalline LaSrCoO4 that is single layered perovskite with K2NiF4 type structure synthesized using solid state reaction route. Using Reitveld refinement of X-ray diffraction (XRD) data, it is found that the sample is in single phase with tetragonal structure (space group I4/mmm). Electrical resistivity performed in the temperature range 140-300K shows semiconducting character of the sample. Considerable contrasts in the Co-O bond length is associated with the intermediate spin (IS) state of Co ion that correlates the structural and transport properties. Detailed analysis indicates that the temperature dependent electrical resistivity follows the three-dimensional variable range hopping (VRH) model in low temperature region below 225K. The high temperature (225-300K) resistivity data has been found to follow the thermally activated behaviour.

  3. Holographic recording characteristics and applications of single-layer panchromatic dichromated gelatin material

    Science.gov (United States)

    Zhu, Jianhua; Xu, Min; Chen, Ligong; Guo, Yongkang; Guo, Lurong

    2005-09-01

    A high-quality single-layer panchromatic dichromated gelatin material is achieved successfully by employing new types of multi-color photosensitizers and photochemical promoters to conventional photo-crosslinking gelatin system. Its holographic recording characteristics such as spectral response, the photosensitivity of three primary colors, spectral selectivity of volume reflection hologram, angular and wavelength selectivity of volume transmission hologram, are studied in detail. Using red, green and blue lasers, namely three primary colors, the bright volume transmission and reflection holograms can be recorded on the panchromatic material at the exposure level of 30 mJ/cm2. Some preliminary results of space, angle and wavelength multiplexing holographic storage for storing multiple binary and grey-tone optical images, are also reported in this paper.

  4. Growth and electronic structure of single-layered transition metal dichalcogenides

    DEFF Research Database (Denmark)

    Dendzik, Maciej

    2016-01-01

    The discovery of graphene has opened a novel research direction focused on the properties of 2D materials. Transition metal dichalcogenides (TMDCs) were quickly identified as important materials due to the great variety of electronic properties that they manifest – properties that are markedly...... different from graphene’s. For example, semiconducting TMDCs undergo an indirectdirect band gap transition when thinned to a single layer (SL); this results in greatly enhanced photoluminescence, making those materials attractive for applications in optoelectronics. Furthermore, metallic TMDCs can host...... TMDCs is directly studied with angle-resolved photoemission spectroscopy (ARPES) and x-ray photoelectron spectroscopy (XPS) techniques. Experimental results are compared with density-functional theory calculations (DFT), both for a free-standing layer and for a layer adsorbed on a metallic substrate...

  5. Tunable multiple Fano resonances in magnetic single-layered core-shell particles

    CERN Document Server

    Arruda, Tiago Jose; Pinheiro, Felipe Arruda

    2015-01-01

    We investigate multiple Fano, comblike scattering resonances in single-layered, concentric core-shell nanoparticles composed of magnetic materials. Using the Lorenz-Mie theory, we derive, in the long-wavelength limit, an analytical condition for the occurrence of comblike resonances in the single scattering by coated spheres. This condition establishes that comblike scattering response uniquely depends on material parameters and thickness of the shell, provided that it is magnetic and thin compared to the scatterer radius. We also demonstrate that comblike scattering response shows up beyond the long-wavelength limit and it is robust against absorption. Since multiple Fano resonances are shown to depend explicitly on the magnetic permeability of the shell, we argue that both the position and profile of the comblike, morphology-dependent resonances could be externally tuned by exploiting the properties of engineered magnetic materials.

  6. Spin polarized surface resonance bands in single layer Bi on Ge(1 1 1)

    Science.gov (United States)

    Bottegoni, F.; Calloni, A.; Bussetti, G.; Camera, A.; Zucchetti, C.; Finazzi, M.; Duò, L.; Ciccacci, F.

    2016-05-01

    The spin features of surface resonance bands in single layer Bi on Ge(1 1 1) are studied by means of spin- and angle-resolved photoemission spectroscopy and inverse photoemission spectroscopy. We characterize the occupied and empty surface states of Ge(1 1 1) and show that the deposition of one monolayer of Bi on Ge(1 1 1) leads to the appearance of spin-polarized surface resonance bands. In particular, the C 3v symmetry, which Bi adatoms adopt on Ge(1 1 1), allows for the presence of Rashba-like occupied and unoccupied electronic states around the \\overline{\\text{M}} point of the Bi surface Brillouin zone with a giant spin-orbit constant |{α\\text{R}}| =≤ft(1.4+/- 0.1\\right) eV · Å.

  7. Density functional studies on edge-contacted single-layer MoS2 piezotronic transistors

    Science.gov (United States)

    Liu, Wei; Zhang, Aihua; Zhang, Yan; Wang, Zhong Lin

    2015-08-01

    The piezotronic effect uses strain-induced piezoelectric charges at interfaces and junctions to tune and/or control carrier transport in piezoelectric semiconductor devices. This effect has recently been observed in single-layer 2D MoS2 materials. However, previous work had found that metallic states are generated at the edge of a free-standing MoS2 flat sheet, and these states may screen the piezoelectric charges. Using density functional theory simulations, we found that the metal-MoS2 interface structure plays an important role in enhancing both the piezoelectric and piezotronic effects in MoS2 transistors by breaking the metallic state screening effect at the MoS2 edge. This study not only provides an understanding of the piezoelectric and piezotronic effects based on first principles calculations but also offers guidance for the design of two-dimensional piezotronic devices.

  8. Study of X-ray Kirkpatrick-Baez imaging with single layer

    Institute of Scientific and Technical Information of China (English)

    Baozhong Mu; Zhanshan Wang; Shengzhen Yi; Xin Wang; Shengling Huang; Jingtao Zhu; Chengchao Huang

    2009-01-01

    The X-ray Kirkpatrick-Baez(KB)imaging experiment with single layer is implemented.Based on the astigmatism aberration and residual geometric aberration of a single mirror.a KB system with 16x mean magnification and approxinlately 0.45° grazing incidence angle is designed.The mirrors are deposited with an Ir layer of 20-nm thickness.Au grids backlit by X-ray tube of 8 keV are imaged via the KB system on scintillator charge-coupled device(CCD).In the ±80 μm field,resolutions of less than 5 μm are measured.The result is in good agreenmnt with the simulated imaging.

  9. Double-dark-resonance-enhanced Kerr nonlinearity in a single layer of graphene nanostructure

    Science.gov (United States)

    Solookinejad, Gh.; Panahi, M.; Ahmadi Sangachin, E.; Hossein Asadpour, Seyyed

    2016-08-01

    In this paper, a novel scheme is proposed for the giant enhanced Kerr nonlinearity in a single layer of graphene nanostructure based on quantum optics and nonlinear optical sciences. The linear and the nonlinear susceptibility of the monolayer graphene system are presented in details by using the density matrix method and perturbation theory. After deriving the equations of motion in the steady-state regime, we analytically solve the linear and nonlinear susceptibility of the system. Our numerical results show that the giant enhanced Kerr nonlinearity can be obtained in the double-dark-resonance condition with zero linear and nonlinear absorption. Our results may have potential applications in quantum information science in infrared and terahertz regimes.

  10. Polarized dependence of nonlinear susceptibility in a single layer graphene system in infrared region

    Science.gov (United States)

    Solookinejad, G.

    2016-09-01

    In this study, the linear and nonlinear susceptibility of a single-layer graphene nanostructure driven by a weak probe light and an elliptical polarized coupling field is discussed theoretically. The Landau levels of graphene can be separated in infrared or terahertz regions under the strong magnetic field. Therefore, by using the density matrix formalism in quantum optic, the linear and nonlinear susceptibility of the medium can be derived. It is demonstrated that by adjusting the elliptical parameter, one can manipulate the linear and nonlinear absorption as well as Kerr nonlinearity of the medium. It is realized that the enhanced Kerr nonlinearity can be possible with zero linear absorption and nonlinear amplification at some values of elliptical parameter. Our results may be having potential applications in quantum information science based on Nano scales devices.

  11. Graphene-like single-layered covalent organic frameworks: synthesis strategies and application prospects.

    Science.gov (United States)

    Liu, Xuan-He; Guan, Cui-Zhong; Wang, Dong; Wan, Li-Jun

    2014-10-29

    Two-dimensional (2D) nanomaterials, such as graphene and transition metal chalcogenides, show many interesting dimension-related materials properties. Inspired by the development of 2D inorganic nanomaterials, single-layered covalent organic frameworks (sCOFs), featuring atom-thick sheets and crystalline extended organic structures with covalently bonded building blocks, have attracted great attention in recent years. With their unique graphene-like topological structure and the merit of structural diversity, sCOFs promise to possess novel and designable properties. However, the synthesis of sCOFs with well-defined structures remains a great challenge. Herein, the recent development of the bottom-up synthesis methods of 2D sCOFs, such as thermodynamic equilibrium control methods, growth-kinetics control methods, and surface-assisted covalent polymerization methods, are reviewed. Finally, some of the critical properties and application prospects of these materials are outlined.

  12. Water desalination with a single-layer MoS2 nanopore

    Science.gov (United States)

    Heiranian, Mohammad; Farimani, Amir Barati; Aluru, Narayana R.

    2015-10-01

    Efficient desalination of water continues to be a problem facing the society. Advances in nanotechnology have led to the development of a variety of nanoporous membranes for water purification. Here we show, by performing molecular dynamics simulations, that a nanopore in a single-layer molybdenum disulfide can effectively reject ions and allow transport of water at a high rate. More than 88% of ions are rejected by membranes having pore areas ranging from 20 to 60 Å2. Water flux is found to be two to five orders of magnitude greater than that of other known nanoporous membranes. Pore chemistry is shown to play a significant role in modulating the water flux. Pores with only molybdenum atoms on their edges lead to higher fluxes, which are ~70% greater than that of graphene nanopores. These observations are explained by permeation coefficients, energy barriers, water density and velocity distributions in the pores.

  13. Probing Critical Point Energies of Transition Metal Dichalcogenides: Surprising Indirect Gap of Single Layer WSe2.

    Science.gov (United States)

    Zhang, Chendong; Chen, Yuxuan; Johnson, Amber; Li, Ming-Yang; Li, Lain-Jong; Mende, Patrick C; Feenstra, Randall M; Shih, Chih-Kang

    2015-10-14

    By using a comprehensive form of scanning tunneling spectroscopy, we have revealed detailed quasi-particle electronic structures in transition metal dichalcogenides, including the quasi-particle gaps, critical point energy locations, and their origins in the Brillouin zones. We show that single layer WSe2 surprisingly has an indirect quasi-particle gap with the conduction band minimum located at the Q-point (instead of K), albeit the two states are nearly degenerate. We have further observed rich quasi-particle electronic structures of transition metal dichalcogenides as a function of atomic structures and spin-orbit couplings. Such a local probe for detailed electronic structures in conduction and valence bands will be ideal to investigate how electronic structures of transition metal dichalcogenides are influenced by variations of local environment.

  14. Dissipative optomechanics of a single-layer graphene in a microcavity

    CERN Document Server

    Xiao, Lin-Da; Liu, Yong-Chun; Yan, Meng-Yuan; Xiao, Yun-Feng

    2014-01-01

    We study the optomechanical coupling of a single-layer graphene with a high-Q Fabry-P?erot microcavity in the membrane-in-the-middle configuration. In ordinary dissipative coupling systems, mechanical oscillators modulate the loss associated with the input coupling of the cavity mode; while in our system, the graphene oscillator couples dissipatively with the cavity mode through modulating its absorption loss. By analyzing the effects of the interband transition of a graphene suspended near the node of the cavity field, we obtain strong and tunable dissipative coupling without excessively reducing the optical quality factor. Finally, it is found that the exural mode of the graphene could be cooled down to its ground state in the present coupling system. This study provides new insights for graphene optomechanics in the visible range.

  15. Polarized dependence of nonlinear susceptibility in a single layer graphene system in infrared region

    Energy Technology Data Exchange (ETDEWEB)

    Solookinejad, G., E-mail: ghsolooki@gmail.com

    2016-09-15

    In this study, the linear and nonlinear susceptibility of a single-layer graphene nanostructure driven by a weak probe light and an elliptical polarized coupling field is discussed theoretically. The Landau levels of graphene can be separated in infrared or terahertz regions under the strong magnetic field. Therefore, by using the density matrix formalism in quantum optic, the linear and nonlinear susceptibility of the medium can be derived. It is demonstrated that by adjusting the elliptical parameter, one can manipulate the linear and nonlinear absorption as well as Kerr nonlinearity of the medium. It is realized that the enhanced Kerr nonlinearity can be possible with zero linear absorption and nonlinear amplification at some values of elliptical parameter. Our results may be having potential applications in quantum information science based on Nano scales devices.

  16. Surface diffusion coefficient of Au atoms on single layer graphene grown on Cu

    Energy Technology Data Exchange (ETDEWEB)

    Ruffino, F., E-mail: francesco.ruffino@ct.infn.it; Cacciato, G.; Grimaldi, M. G. [Dipartimento di Fisica ed Astronomia-Universitá di Catania, via S. Sofia 64, 95123 Catania, Italy and MATIS IMM-CNR, via S. Sofia 64, 95123 Catania (Italy)

    2014-02-28

    A 5 nm thick Au film was deposited on single layer graphene sheets grown on Cu. By thermal processes, the dewetting phenomenon of the Au film on the graphene was induced so to form Au nanoparticles. The mean radius, surface-to-surface distance, and surface density evolution of the nanoparticles on the graphene sheets as a function of the annealing temperature were quantified by scanning electron microscopy analyses. These quantitative data were analyzed within the classical mean-field nucleation theory so to obtain the temperature-dependent Au atoms surface diffusion coefficient on graphene: D{sub S}(T)=[(8.2±0.6)×10{sup −8}]exp[−(0.31±0.02(eV)/(at) )/kT] cm{sup 2}/s.

  17. Temperature-dependent mechanical properties of single-layer molybdenum disulphide: Molecular dynamics nanoindentation simulations

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Junhua, E-mail: junhua.zhao@uni-weimar.de [Jiangsu Province Key Laboratory of Advanced Manufacturing Equipment and Technology of Food, Jiangnan University, 214122 Wuxi (China); Institute of Structural Mechanics, Bauhaus-University Weimar, 99423 Weimar (Germany); Jiang, Jin-Wu, E-mail: jwjiang5918@hotmail.com [Institute of Structural Mechanics, Bauhaus-University Weimar, 99423 Weimar (Germany); Rabczuk, Timon, E-mail: timon.rabczuk@uni-weimar.de [Institute of Structural Mechanics, Bauhaus-University Weimar, 99423 Weimar (Germany); School of Civil, Environmental and Architectural Engineering, Korea University, 136-701 Seoul (Korea, Republic of)

    2013-12-02

    The temperature-dependent mechanical properties of single-layer molybdenum disulphide (MoS{sub 2}) are obtained using molecular dynamics (MD) nanoindentation simulations. The Young's moduli, maximum load stress, and maximum loading strain decrease with increasing temperature from 4.2 K to 500 K. The obtained Young's moduli are in good agreement with those using our MD uniaxial tension simulations and the available experimental results. The tendency of maximum loading strain with different temperature is opposite with that of metal materials due to the short range Stillinger-Weber potentials in MoS{sub 2}. Furthermore, the indenter tip radius and fitting strain effect on the mechanical properties are also discussed.

  18. Single-layer versus two-layer stamps for reduced pressure thermal nanoimprint

    Science.gov (United States)

    Papenheim, Marc; Dhima, Khalid; Wang, Si; Steinberg, Christian; Scheer, Hella-Christin

    2015-11-01

    Low-pressure imprint is interesting to avoid stamp deformation, stamp failure as well as polymer recovery. When large-area stamps are prepared with a stepping procedure, low pressure is required to optimize the stitching. However, with low-pressure imprint, conformal contact between stamp and substrate is critical. Admittedly, the imprint pressure required for conformal contact depends on the stamp material and its thickness. To get an idea to which extent the imprint pressure can be reduced with a flexible stamp, we compared different stamp materials and stamp architectures, single-layer stamps and two-layer stamps. The two-layer stamps are replica stamps, where the structures were replicated in a thin layer of OrmoStamp, fixed by a backplane. On the background of plate theory, we deduce the pressure reduction compared to a Si stamp by calculating the respective pressure ratio, independent from geometries. In addition, temperature-induced issues are addressed which are of relevance for a thermal imprint process. These issues are related to the mismatch between the thermal expansion coefficients of the stamp and the substrate, and in case of a two-layer stamp, to the mismatch between the backplane material and the top layer. The latter results in temperature-induced stamp bending. On the basis of simple analytical calculations, the potential of single-layer stamps and two-layer stamps with respect to thermal imprint at reduced pressure is discussed and guidelines are provided to assess the imprint situation when replica stamps are used for imprint. The results demonstrate the attractiveness of two-layer stamps for reduced pressure nanoimprint, even in a temperature-based process.

  19. Fabrication of nanoelectrode ensembles by electrodepositon of Au nanoparticles on single-layer graphene oxide sheets

    Science.gov (United States)

    Wang, Zhijuan; Zhang, Juan; Yin, Zongyou; Wu, Shixin; Mandler, Daniel; Zhang, Hua

    2012-03-01

    Nanoelectrode ensembles (NEEs) have been fabricated by the electrodeposition of Au nanoparticles (AuNPs) on single-layer graphene oxide (GO) sheets coated on a glassy carbon electrode (GCE). The fabricated NEEs show a typical sigmoidal shaped voltammetric profile, arising from the low coverage density of AuNPs on GCE and large distance among them, which can be easily controlled by varying the electrodeposition time. As a proof of concept, after the probe HS-DNA is immobilized on the NEEs through the Au-S bonding, the target DNA is detected with the methylene blue intercalator. Our results show that the target DNA can be detected as low as 100 fM, i.e. 0.5 amol DNA in 5 μL solution.Nanoelectrode ensembles (NEEs) have been fabricated by the electrodeposition of Au nanoparticles (AuNPs) on single-layer graphene oxide (GO) sheets coated on a glassy carbon electrode (GCE). The fabricated NEEs show a typical sigmoidal shaped voltammetric profile, arising from the low coverage density of AuNPs on GCE and large distance among them, which can be easily controlled by varying the electrodeposition time. As a proof of concept, after the probe HS-DNA is immobilized on the NEEs through the Au-S bonding, the target DNA is detected with the methylene blue intercalator. Our results show that the target DNA can be detected as low as 100 fM, i.e. 0.5 amol DNA in 5 μL solution. Electronic supplementary information (ESI) available: The results of Raman, XPS, SEM and other electrochemical characterization are provided. See DOI: 10.1039/c2nr30142c

  20. Tuning the superconductivity in single-layer FeSe/oxides by interface engineering

    Science.gov (United States)

    Peng, Rui

    2015-03-01

    The discovery of high Tc in single-layer FeSe films has enormous implications for both searching new high Tc superconductors and exploring the important factors for high temperature superconductivity. In this talk, I will show our recent angle-resolved photoemission studies on various FeSe-based heterostructures grown by molecular beam epitaxy. We systematically studied the electronic structures and superconducting properties of FeSe with varied strain, different interfacial oxide materials and different thicknesses, and uncover that electronic correlations and superconducting gap-closing temperatures are tuned by interfacial effects. We exclude the direct relation between superconductivity and tensile strain, or the energy of an interfacial phonon mode, and demonstrate the crucial and non-trivial role of FeSe/oxide interface on the high pairing temperature. By tuning the interface, superconducting pairing temperature reaches up to 75K in FeSe/Nb:BaTiO3/KTaO3 with the in-plane lattice of 3.99 Å, which sets a new superconducting-gap-closing temperature record for iron-based superconductors, and may paves the way to more cost-effective applications of ultra-thin superconductors. Besides, in extremely tensile-strained single-layer FeSe films, we found that the Fermi surfaces consist of two elliptical electron pockets at the zone corner, without detectable hybridization. The lifting of degeneracy is clearly observed for the first time for the iron-based superconductors with only electron Fermi surfaces. Intriguingly, the superconducting gap distribution is anisotropic but nodeless around the electron pockets, with minima at the crossings of the two pockets. Our results provide important experimental foundations for understanding the interfacial superconductivity and the pairing symmetry puzzle of iron-based superconductors, and also provide clues for further enhancing Tc through interface engineering.

  1. Anomalous photoluminescence thermal quenching of sandwiched single layer MoS_2

    KAUST Repository

    Tangi, Malleswara

    2017-09-22

    We report an unusual thermal quenching of the micro-photoluminescence (µ-PL) intensity for a sandwiched single-layer (SL) MoS2. For this study, MoS2 layers were chemical vapor deposited on molecular beam epitaxial grown In0.15Al0.85N lattice matched templates. Later, to accomplish air-stable sandwiched SL-MoS2, a thin In0.15Al0.85N cap layer was deposited on the MoS2/In0.15Al0.85N heterostructure. We confirm that the sandwiched MoS2 is a single layer from optical and structural analyses using µ-Raman spectroscopy and scanning transmission electron microscopy, respectively. By using high-resolution X-ray photoelectron spectroscopy, no structural phase transition of MoS2 is noticed. The recombination processes of bound and free excitons were analyzed by the power-dependent µ-PL studies at 77 K and room temperature (RT). The temperature-dependent micro photoluminescence (TDPL) measurements were carried out in the temperature range of 77 – 400 K. As temperature increases, a significant red-shift is observed for the free-exciton PL peak, revealing the delocalization of carriers. Further, we observe unconventional negative thermal quenching behavior, the enhancement of the µ-PL intensity with increasing temperatures up to 300K, which is explained by carrier hopping transitions that take place between shallow localized states to the band-edges. Thus, this study renders a fundamental insight into understanding the anomalous thermal quenching of µ-PL intensity of sandwiched SL-MoS2.

  2. Alternating-Phase-Focused Linac with Interdigital H-Mode Structure for Medical Injectors

    CERN Document Server

    Iwata, Yoshiyuki; Fujimoto, Tetsuya; Fujisawa, Takashi; Furukawa, Takuji; Hojo, Satoru; Honma, T; Kanazawa, Mitsutaka; Kapin, Valery; Mitsumoto, Toshinori; Miyahara, Nobuyuki; Murakami, Takeshi; Muramatsu, Masayuki; Noda, Koji; Ogawa, Hirotsugu; Ogawa, Hiroyuki; Torikoshi, Masami; Tsutsui, Hiroshi; Yamada, Satoru; Yamamoto, Kazuo

    2005-01-01

    Tumor therapy using Heavy Ion Medical Accelerator in Chiba (HIMAC) has been performed at National Institute of Radiological Sciences (NIRS). With the successful clinical results over ten years, a project on developing compact accelerators has been started. To design these compact accelerators, a size of an injector as well as construction and operation costs plays an important role. To satisfy these requirements, we propose a compact injector consisting of a RFQ and Interdigital H-mode Drift-Tube-Linac (IH-DTL) having the resonant frequency of 200 MHz. The injector will accelerate carbon ion up to 4.0 AMeV. For the beam focusing of the IH-DTL, the method of Alternating-Phase-Focusing was employed. With the IH structure and rather high operating-frequency, the size of the cavities is compact; the radius is approximately 0.4 m, and the length of the RFQ and IH-DTL will be 2.5m and 3.5m respectively. The fabrication of the RFQ is in progress. For the IH-DTL, the full-scale model was fabricated. With the encourag...

  3. Phonon-limited mobility in n-type single-layer MoS2 from first principles

    DEFF Research Database (Denmark)

    Kaasbjerg, Kristen; Thygesen, Kristian S.; Jacobsen, Karsten W.

    2012-01-01

    to recent experimental findings for the mobility in single-layer MoS2 (similar to 200 cm(2)V(-1)s(-1)), our results indicate that mobilities close to the intrinsic phonon-limited mobility can be achieved in two-dimensional materials via dielectric engineering that effectively screens static Coulomb......We study the phonon-limited mobility in intrinsic n-type single-layer MoS2 for temperatures T > 100 K. The materials properties including the electron-phonon interaction are calculated from first principles and the deformation potentials and Frohlich interaction in single-layer MoS2 are established....... The calculated room-temperature mobility of similar to 410 cm(2)V(-1)s(-1) is found to be dominated by optical phonon scattering via intra and intervalley deformation potential couplings and the Frohlich interaction. The mobility is weakly dependent on the carrier density and follows a mu similar to T...

  4. Optical constants and dynamic conductivities of single layer MoS2, MoSe2, and WSe2

    Science.gov (United States)

    Morozov, Yurii V.; Kuno, Masaru

    2015-08-01

    The complex optical constants of single layer MoS2, MoSe2, and WSe2 transition metal dichalcogenides (TMDCs) have been measured using concerted frequency-dependent transmittance and reflectance measurements. Absolute absorptivities as well as complex refractive indices and dielectric permittivities have been extracted. Comparisons to associated bulk responses reveal differences due to increased electron-hole interactions in single layer TMDCs. In parallel, corresponding complex optical conductivities (σ) have been determined. For MoS2, extracted σ-values qualitatively agree with recent theoretical estimates. Significant differences exist, though, between experiment and theory regarding the imaginary part of σ. In all cases, the current approach distinguishes itself to other measurements of single layer TMDC optical constants in which it does not rely on Kramers-Kronig transformations of reflectance data.

  5. Thermo-Elastic Triangular Sandwich Element for the Complete Stress Field Based on a Single-Layer Theory

    Science.gov (United States)

    Das, M.; Barut, A.; Madenci, E.; Ambur, D. R.

    2004-01-01

    This study presents a new triangular finite element for modeling thick sandwich panels, subjected to thermo-mechanical loading, based on a {3,2}-order single-layer plate theory. A hybrid energy functional is employed in the derivation of the element because of a C interelement continuity requirement. The single-layer theory is based on five weighted-average field variables arising from the cubic and quadratic representations of the in-plane and transverse displacement fields, respectively. The variations of temperature and distributed loading acting on the top and bottom surfaces are non-uniform. The temperature varies linearly through the thickness.

  6. High-rate/high-temperature capability of a single-layer zicar-separator nickel-hydrogen cell

    Science.gov (United States)

    Wheeler, James R.

    1995-01-01

    A 50 Ampere-hour nickel-hydrogen cell with a single-layer Zircar separator stack design was fully charged and then discharged at a 2C current rate to an end voltage of 1 volt. This extreme test resulted in high temperatures which were recorded at three locations on the cell, i.e., the cell wall, the boss (barrel of the compression seal), and a terminal. The results provide new information about the high-temperature and high-discharge-rate capabilities of nickel-hydrogen cells. This information also adds to the growing data base for single-layer zirconium-oxide-cloth (Zircar) separator cell designs.

  7. Scanning Tunneling Spectroscopy Study of Single Layer Step Edges on Si (100) Surfaces

    Science.gov (United States)

    Wang, Xiqiao; Namboodiri, Pradeep; Li, Kai; Deng, Xiao; Silver, Richard

    Advanced Hydrogen lithography enables the fabrication of atomically precise donor-based quantum devices on Si(100) surfaces. Understanding the defect and step edge interaction with local electronic and geometric structures is needed to properly interpret device measurement results. Low temperature Si epitaxy, used to encapsulate devices, introduces island growth and step edges near/above buried donor nanostructures, presenting a real challenge in relocating and characterizing buried donor devices using Scanning Tunneling Microscopy/Spectroscopy (STM/STS). We present spatially resolved STS results across single layer steps on Si(100) surfaces. While the electronic properties across SA steps were found to be very similar to that on flat terraces, we observed an edge induced gap state on rebonded SB step edges, which was assigned to the unpaired dangling bond state at the lower edge atom of the rebonded SB steps. In addition, we used computational simulation within Bardeen's formalism to probe the influence of subsurface doping density profiles on the observed STS features over step edges and other defects. This study will help to elucidate the role played by surface step edges and subsurface doping densities in characterizing surface and subsurface nanostructures using STS/STM.

  8. Adhesion and migration of CHO cells on micropatterned single layer graphene

    Science.gov (United States)

    Keshavan, S.; Oropesa-Nuñez, R.; Diaspro, A.; Canale, C.; Dante, S.

    2017-06-01

    Cell patterning technology on single layer graphene (SLG) is a fairly new field that can find applications in tissue engineering and biomaterial/biosensors development. Recently, we have developed a simple and effective approach for the fabrication of patterned SLG substrates by laser micromachining, and we have successfully applied it for the obtainment of geometrically ordered neural networks. Here, we exploit the same approach to investigate the generalization of the cell response to the surface cues of the fabricated substrates and, contextually, to quantify cell adhesion on the different areas of the patterns. To attain this goal, we tested Chinese hamster ovary (CHO) cells on PDL-coated micropatterned SLG substrates and quantified the adhesion by using single cell force spectroscopy (SCFS). Our results indicate higher cell adhesion on PDL-SLG, and, consequently, an initial CHO cell accumulation on the graphene areas, confirming the neuronal behaviour observed previously; interestingly, at later time point in culture, cell migration was observed towards the adjacent SLG ablated regions, which resulted more favourable for cell proliferation. Therefore, our findings indicate that the mechanism of interaction with the surface cues offered by the micropatterned substrates is strictly cell-type dependent.

  9. Monolithic-Structured Single-Layered Textile-Based Dye-Sensitized Solar Cells

    Science.gov (United States)

    Yun, Min Ju; Cha, Seung I.; Kim, Han Seong; Seo, Seon Hee; Lee, Dong Y.

    2016-10-01

    Textile-structured solar cells are frequently discussed in the literature due to their prospective applications in wearable devices and in building integrated solar cells that utilize their flexibility, mechanical robustness, and aesthetic appearance, but the current approaches for textile-based solar cells—including the preparation of fibre-type solar cells woven into textiles—face several difficulties from high friction and tension during the weaving process. This study proposes a new structural concept and fabrication process for monolithic-structured textile-based dye-sensitized solar cells that are fabricated by a process similar to the cloth-making process, including the preparation of wires and yarns that are woven for use in textiles, printed, dyed, and packaged. The fabricated single-layered textile-based dye-sensitized solar cells successfully act as solar cells in our study, even under bending conditions. By controlling the inter-weft spacing and the number of Ti wires for the photoelectrode conductor, we have found that the performance of this type of dye-sensitized solar cell was notably affected by the spacing between photoelectrodes and counter-electrodes, the exposed areas of Ti wires to photoelectrodes, and photoelectrodes’ surface morphology. We believe that this study provides a process and concept for improved textile-based solar cells that can form the basis for further research.

  10. Unexpected strong magnetism of Cu doped single-layer MoS₂ and its origin.

    Science.gov (United States)

    Yun, Won Seok; Lee, J D

    2014-05-21

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

  11. Statistical Mechanical Analysis of Online Learning with Weight Normalization in Single Layer Perceptron

    Science.gov (United States)

    Yoshida, Yuki; Karakida, Ryo; Okada, Masato; Amari, Shun-ichi

    2017-04-01

    Weight normalization, a newly proposed optimization method for neural networks by Salimans and Kingma (2016), decomposes the weight vector of a neural network into a radial length and a direction vector, and the decomposed parameters follow their steepest descent update. They reported that learning with the weight normalization achieves better converging speed in several tasks including image recognition and reinforcement learning than learning with the conventional parameterization. However, it remains theoretically uncovered how the weight normalization improves the converging speed. In this study, we applied a statistical mechanical technique to analyze on-line learning in single layer linear and nonlinear perceptrons with weight normalization. By deriving order parameters of the learning dynamics, we confirmed quantitatively that weight normalization realizes fast converging speed by automatically tuning the effective learning rate, regardless of the nonlinearity of the neural network. This property is realized when the initial value of the radial length is near the global minimum; therefore, our theory suggests that it is important to choose the initial value of the radial length appropriately when using weight normalization.

  12. A single-layer peptide nanofiber for enhancing the cytotoxicity of trastuzumab (anti-HER)

    Energy Technology Data Exchange (ETDEWEB)

    Malik, Ruchi; Wagh, Anil; Qian, Steven; Law, Benedict, E-mail: Shek.law@ndsu.edu [College of Pharmacy, Nursing, and Allied Sciences, North Dakota State University, Department of Pharmaceutical Sciences (United States)

    2013-06-15

    A multivalent system is often employed to enhance the effectiveness of a targeted therapy. In the present study, we report a single-layer peptide nanofiber (NFP) as a multivalent targeting platform to improve the cytotoxicity of trastuzumab (anti-HER), a monoclonal antibody targeting the human epidermal growth factor receptor 2 (HER-2) in approximately 20 % of breast cancer patients. The trastuzumab-conjugated nanofiber (anti-HER/NFP) was 100 Multiplication-Sign 4 nm in size and was assembled from multiple peptide units (mPEG-BK(FITC)SGASNRA-kldlkldlkldl-CONH{sub 2}). The optimized preparation was attached with approximately 10 antibodies at the surface. Because of an increase in the multivalency, anti-HER/NFP was able to truncate more cell surface HER-2 and, thus, showed an enhanced cytotoxicity toward HER-2 positive SKBr-3 human breast cancer as compared to the free anti-HER. Western blot analysis and fluorescence microscopic studies confirmed that there was a significant downregulation of the HER-2 level and also inhibition of the cell survival cell signaling pathways including the phosphatidylinositol 3-kinase (PI3K) and the mitogen activated protein kinase (MAPK) pathway. Our data suggested that NFP can be useful as a multivalent platform for immunotherapy, especially in combination with other chemotherapeutic agents in the future.

  13. Photocatalytic oxidation of aqueous ammonia using atomic single layer graphitic-C3N4.

    Science.gov (United States)

    Wang, Hua; Su, Yan; Zhao, Huanxin; Yu, Hongtao; Chen, Shuo; Zhang, Yaobin; Quan, Xie

    2014-10-21

    Direct utilization of solar energy for photocatalytic removal of ammonia from water is a topic of strong interest. However, most of the photocatalysts with effective performance are solely metal-based semiconductors. Here, we report for the first time that a new type of atomic single layer graphitic-C(3)N(4) (SL g-C(3)N(4)), a metal-free photocatalyst, has an excellent photocatalytic activity for total ammonia nitrogen (TAN) removal from water. The results demonstrated that over 80% of TAN (initial concentration 1.50 mg · L(-1)) could be removed in 6 h under Xe lamp irradiation (195 mW · cm(-2)). Furthermore, the SL g-C(3)N(4) exhibited a higher photocatalytic activity in alkaline solution than that in neutral or acidic solutions. The investigation suggested that both photogenerated holes and hydroxyl radicals were involved the TAN photocatalytic oxidation process and that the major oxidation product was NO3(-)-N. In addition, SL g-C(3)N(4) exhibited good photocatalytic stability in aqueous solution. This work highlights the appealing application of an inexpensive metal-free photocatalyst in aqueous ammonia treatment.

  14. A single-layer network unsupervised feature learning method for white matter hyperintensity segmentation

    Science.gov (United States)

    Vijverberg, Koen; Ghafoorian, Mohsen; van Uden, Inge W. M.; de Leeuw, Frank-Erik; Platel, Bram; Heskes, Tom

    2016-03-01

    Cerebral small vessel disease (SVD) is a disorder frequently found among the old people and is associated with deterioration in cognitive performance, parkinsonism, motor and mood impairments. White matter hyperintensities (WMH) as well as lacunes, microbleeds and subcortical brain atrophy are part of the spectrum of image findings, related to SVD. Accurate segmentation of WMHs is important for prognosis and diagnosis of multiple neurological disorders such as MS and SVD. Almost all of the published (semi-)automated WMH detection models employ multiple complex hand-crafted features, which require in-depth domain knowledge. In this paper we propose to apply a single-layer network unsupervised feature learning (USFL) method to avoid hand-crafted features, but rather to automatically learn a more efficient set of features. Experimental results show that a computer aided detection system with a USFL system outperforms a hand-crafted approach. Moreover, since the two feature sets have complementary properties, a hybrid system that makes use of both hand-crafted and unsupervised learned features, shows a significant performance boost compared to each system separately, getting close to the performance of an independent human expert.

  15. Highly efficient single-layer gas diffusion layers for the proton exchange membrane fuel cell

    Energy Technology Data Exchange (ETDEWEB)

    Hung, T.F.; Bai, S.H.; Lai, Y.J.; Chen-Yang, Y.W. [Department of Chemistry and Center for Nanotechnology, Chung Yuan Christian University, Chung-Li 32023 (China); Huang, J. [Yeu Ming Tai Chemical Industrial Co., Ltd., Taichung 40768 (China); Chuang, H.J. [Materials and Electro-Optics Research Division, Electric Energy Section, Chung Shan Institute of Science and Technology, Lung-Tan 32544 (China)

    2008-09-15

    In the present study, a series of highly efficient single-layer gas diffusion layers (SL-GDLs) was successfully prepared by the addition of a vapor grown carbon nanofiber (VGCF) in the carbon black/poly(tetrafluoroethylene) composite-based SL-GDL through a simple and inexpensive process. The scanning electron micrographs of the as-prepared VGCF-containing SL-GDLs (SL-GDL-CFs) showed that the GDLs had a microporous layer (MPL)-like structure, while the wire-like VGCFs were well dispersed and crossed among the carbon black particles in the SL-GDL matrix. Utilization of the SL-GDL-CFs for MEA fabrication was also done by direct coating with the catalyst layer. Due to the presence of VGCFs, the properties of the SL-GDL-CFs, including electronic resistivity, mechanical characteristic, gas permeability, and water repellency, varied with the VGCF content, with the overall effect beneficial to the performance of the proton exchange membrane fuel cell (PEMFC). The best performances obtained from the PEMFC with VGCFs at 15 wt.% was approximately 63% higher than those without VGCFs, and about 85% as efficient as ELAT GDL, a commercial dual-layer GDL, for both the H{sub 2}/O{sub 2} and H{sub 2}/air systems. (author)

  16. A theoretical study of pump–probe experiment in single-layer, bilayer and multilayer graphene

    Indian Academy of Sciences (India)

    Enamullah; Vipin Kumar; Upendra Kumar; Girish S Setlur

    2014-06-01

    The pump–probe experiment is typically used to study relaxation phenomena in nonlinear optical systems. Here we use it as a tool to study the phenomenon of anomalous Rabi oscillations in graphene that was predicted recently in single-layer graphene. Unlike conventional Rabi oscillations, anomalous Rabi oscillations are unique to graphene (and possibly to surface states of topological insulators (TIs)), attributable to the pseudospin (conventional spin for TI) degree of freedom and Dirac-fermion character of the graphene system. A pump pulse of a finite duration long enough to contain a large number of cycles induces a current density that oscillates with the frequency of the pump pulse. The amplitude associated with these fast oscillations is seen to exhibit much slower oscillations with a frequency given by $2^2_R/$–the anomalous Rabi frequency, where $_R$ is the conventional Rabi frequency and is the frequency of the external pump field. This effect is easily probed by a probe pulse subsequent to the pump, where it manifests itself as periodic oscillations of the probe susceptibility as a function of pump duration at each probe frequency. Alternatively, it is also seen as an oscillatory function of the pump–probe delay with other variables remaining fixed. This period corresponds to the anomalous Rabi frequency. An analysis of the previously reported experimental data confirms the presence of anomalous Rabi oscillations in graphene.

  17. Single layer graphene band hybridization with silver nanoplates: Interplay between doping and plasmonic enhancement

    Science.gov (United States)

    Syed, Salmaan R.; Lim, Guh-Hwan; Flanders, Stuart J.; Taylor, Adam B.; Lim, Byungkwon; Chon, James W. M.

    2016-09-01

    In this paper, we report single layer graphene (SLG) hybridized with silver nanoplates, in which nanoplates act as either a charge doping or a field enhancement source for the SLG Raman spectrum. Surprisingly, the stiffening of both G and 2D peaks of more than 10 cm-1 was observed with no plasmonic enhancement of peaks, indicating that p-doping from nanoplates on SLG is occurring. Such observation is explained in terms of the contact separation distance between the graphene and the silver nanoplates being enough (˜4 Å) to cause a Fermi level shift in graphene to allow p-doping. When nanoplates were modified in shape with laser irradiation by either photothermal plasmon printing or laser induced ablation, the charge doping was lifted and the strong plasmonic enhancement of Raman signals was observed, indicating that the separation distance is increased. Further, when the nanoplates are oxidized, the two effects on the Raman bands of SLG are turned off, returning the Raman signals back to the original SLG state.

  18. Monolithic-Structured Single-Layered Textile-Based Dye-Sensitized Solar Cells.

    Science.gov (United States)

    Yun, Min Ju; Cha, Seung I; Kim, Han Seong; Seo, Seon Hee; Lee, Dong Y

    2016-10-06

    Textile-structured solar cells are frequently discussed in the literature due to their prospective applications in wearable devices and in building integrated solar cells that utilize their flexibility, mechanical robustness, and aesthetic appearance, but the current approaches for textile-based solar cells-including the preparation of fibre-type solar cells woven into textiles-face several difficulties from high friction and tension during the weaving process. This study proposes a new structural concept and fabrication process for monolithic-structured textile-based dye-sensitized solar cells that are fabricated by a process similar to the cloth-making process, including the preparation of wires and yarns that are woven for use in textiles, printed, dyed, and packaged. The fabricated single-layered textile-based dye-sensitized solar cells successfully act as solar cells in our study, even under bending conditions. By controlling the inter-weft spacing and the number of Ti wires for the photoelectrode conductor, we have found that the performance of this type of dye-sensitized solar cell was notably affected by the spacing between photoelectrodes and counter-electrodes, the exposed areas of Ti wires to photoelectrodes, and photoelectrodes' surface morphology. We believe that this study provides a process and concept for improved textile-based solar cells that can form the basis for further research.

  19. Two single-layer porous gallium nitride nanosheets: A first-principles study

    Science.gov (United States)

    Zhang, Hui; Meng, Fan-Sun; Wu, Yan-Bin

    2017-01-01

    The gallium nitride (GaN) is a novel wide-gap semiconductor for photoelectric devices. In this paper, two 2D single-layer GaN crystal structures, called H-GaN and T-GaN, are discovered by the density functional theory calculations. The phase stability is confirmed by phonon dispersions. The sole-atom-thick crystals of H-GaN and T-GaN, has possess enlarged specific surface area than the graphene-like allotrope (g-GaN) due to the porous structures. In addition, they have indirect band gaps of 1.85-1.89 eV and the electronic structures can be further modulated by applied strains. For example, T-GaN transforms from an indirect semiconductor to a direct one due to compressed strains. Both the combination of high specific surface area and moderate band gaps make these 2D crystals potential high-efficiency photocatalysts. Our results will also stimulate the investigations on 2D GaN nano crystals with rich electronic structures for wide applications.

  20. Performance of finite-conductivity, vertically fractured wells in single-layer reservoirs

    Energy Technology Data Exchange (ETDEWEB)

    Bennett, C.O.; Reynolds, A.C.; Raghavan, R.; Elbel, J.L.

    1986-08-01

    Although even a perfunctory survey of the literature suggests that considerable information is available on the response of finite-conductivity fractures in single-layer systems, the influence of the settling of propping agents and the effect of fracture height on the well response need to be examined. These topics are examined in this paper. The authors suggest methods to analyze well performance when the fracture conductivity is a function of fracture height and fracture length. The performance of wells with fracture height greater than the formation thickness is documented. The consequences of being unable to contain the fracture within the pay zone are also examined. Although incidental to this study, the authors found that solutions presented by various authors are not in agreement for all time ranges. In this paper, they discuss a systematic procedure to obtain a grid (mesh) so that accurate results are obtained by a finite-difference model. This procedure can be used for both two-dimensional (2D) and three-dimensional (3D) problems.

  1. Selective ionic transport through tunable subnanometer pores in single-layer graphene membranes.

    Science.gov (United States)

    O'Hern, Sean C; Boutilier, Michael S H; Idrobo, Juan-Carlos; Song, Yi; Kong, Jing; Laoui, Tahar; Atieh, Muataz; Karnik, Rohit

    2014-03-12

    We report selective ionic transport through controlled, high-density, subnanometer diameter pores in macroscopic single-layer graphene membranes. Isolated, reactive defects were first introduced into the graphene lattice through ion bombardment and subsequently enlarged by oxidative etching into permeable pores with diameters of 0.40 ± 0.24 nm and densities exceeding 10(12) cm(-2), while retaining structural integrity of the graphene. Transport measurements across ion-irradiated graphene membranes subjected to in situ etching revealed that the created pores were cation-selective at short oxidation times, consistent with electrostatic repulsion from negatively charged functional groups terminating the pore edges. At longer oxidation times, the pores allowed transport of salt but prevented the transport of a larger organic molecule, indicative of steric size exclusion. The ability to tune the selectivity of graphene through controlled generation of subnanometer pores addresses a significant challenge in the development of advanced nanoporous graphene membranes for nanofiltration, desalination, gas separation, and other applications.

  2. Thermal vibration of a single-layered graphene with initial stress predicted by semiquantum molecular dynamics

    Science.gov (United States)

    Liu, Rumeng; Wang, Lifeng; Jiang, Jingnong

    2016-09-01

    Thermal vibration of a rectangular single-layered graphene sheet (RSLGS) with initial stress is investigated by a semiquantum molecular dynamics (SQMD) method on the basis of modified Langevin dynamics. The quantum effect in the thermal vibration of RSLGS is accounted by introducing a quantum thermal bath. The spectrum of the thermal vibration of RSLGSs is obtained both by SQMD and classical molecular dynamics (CMD). The RSLGS vibrates with the same frequencies via both the SQMD simulation and the CMD simulation. The root of mean squared (rms) amplitude obtained via the CMD is greater than that obtained via the SQMD. The energy in high order mode is frozen at very low temperature if quantum effect is taken into consideration. An elastic plate model with initial stress considering quantum effects is established to describe the thermal vibration of the RSLGS. The rms amplitude of RSLGS calculated by plate model with the law of energy equipartition and that obtained from the CMD coincide very well. The plate model considering the quantum effects provides accurate prediction of the rms amplitude of the RSLGS obtained from the SQMD. These results indicate that quantum effects cannot be neglected in the thermal vibration of the RSLGS at low temperature case.

  3. Thermal stability of a free nanotube from single-layer black phosphorus

    CERN Document Server

    Cai, Kun; Wei, Ning; Cai, Haifang; Qin, Qing-Hua

    2015-01-01

    Similar to the carbon nanotube fabricated from graphene sheet, a black phosphorus nanotube (BPNT) also can theoretically be produced by curling the rectangular single-layer black phosphorus (SLBP). In present study, the effect of thermal vibration of atoms on the failure of a BPNT is investigated using molecular dynamics simulations. Two types of double-shell BPNTs, which are obtained by curling the rectangular SLBP along its armchair/pucker direction and zigzag direction (in-plane normal) respectively, are involved in simulation. At finite temperature, a bond on the outer shell of tube is under tension due to both of curvature of tube and serious thermal vibration of atoms. As the length of a bond with such elongation approaches its critical value, i.e., 0.279 nm, or the smallest distance between two nonbonding phosphorus atoms is over 0.389nm caused by great variation of bond angle, the tube fails quickly. The critical stable states of either an armchair or a zigzag BPNT at finite temperature are calculated...

  4. Single-layer graphene-TiO2 nanotubes array heterojunction for ultraviolet photodetector application

    Science.gov (United States)

    Zhang, Deng-Yue; Ge, Cai-Wang; Wang, Jiu-Zhen; Zhang, Teng-Fei; Wu, Yu-Cheng; Liang, Feng-Xia

    2016-11-01

    In this work, we reported on the fabrication of a single-layer graphene (SLG)-TiO2 nanotube arrays (NTs) heterostructures ultraviolet photodetector (UVPD) by transferring chemical vapor deposition derived MLG on the surface of anodic TiO2NTs array. Through varying the annealing atmosphere and anodization time in the TiO2 synthesis procedure, the electronic and optoelectronic properties of the as-fabricated Schottky junction UVPD were studied. It was revealed that the anodic TiO2NTs annealed in air showed a better rectifying behavior and was highly sensitive to UV light irradiation. Further investigation found that the device performance of the UVPD can be readily modulated by the anodization time, and the anodic TiO2NTs with a medium tube length of 9.6 μm exhibits the highest device performance. These results demonstrated that the present SLG-TiO2NTs array hetero-junction UVPD will be highly promising for fabricating high-performance optoelectronic device and system in the future.

  5. Failure Process and Energy Transmission for Single-Layer Reticulated Domes Under Impact Loads

    Institute of Scientific and Technical Information of China (English)

    WANG Duozhi; ZHI Xudong; FAN Feng; SHEN Shizhao

    2008-01-01

    No failure,moderate failure,severe failure,and slight failure are the four failure modes generalized observed in the dynamic response of the single-layer reticulated dome under vertical impact load on apex.TE (the time that the end of impact force) and 7F (the time that members are broken) are two key times in the failure process.Characteristics of dynamic responses at the two key times are shown in order to make the failure mechanism clear.Then three steps of energy transfer are summarized,i.e.energy applying,energy loss and energy transfer,energy consumption.Based on the three steps,energy transfer process for the failure reticulated dome under once impact is introduced.Energy transmissibility and local loss ratio are put forward firstly to obtain ELF (the energy left in the main reticulated dome) from the initial kinetic energy of impactor.Moreover,the distribution of failure modes is decided by ELF which leads to the maximum dynamic response of the reticulated dome,but not by the initial impact kinetic energy of impaetor.

  6. Shape-responsive actuator from a single layer of a liquid-crystal polymer.

    Science.gov (United States)

    Kamal, Tahseen; Park, Soo-young

    2014-10-22

    Actuation of various shape changes, including bending, helical twisting, and reversible hinging, has been achieved from a single-layer sheet of poly(1,4-di(4-(3-acryloyloxypropyloxy)benzoyloxy)-2-methylbenzene) [poly(RM257)]. This actuator was developed through photopolymerization of a reactive liquid-crystal (LC) monomer (RM257) mixed with 4-pentyl-4'-cyanobiphenyl (5CB, nematic LC at room temperature) in a planar polyimide-coated LC cell. The UV beam perpendicular to one side of the LC cell produced an asymmetric phase separation between the poly(RM257) network and 5CB that resulted in an asymmetric porous structure along the thickness direction when the 5CB was extracted, in which the UV-exposed surface was pore-free and compact while the opposite surface was highly porous. As a result of this structure, the dry and curled poly(RM257) film exhibits actuation behavior when placed in acetone because of a difference in swelling between the two morphologically different sides, the film UV-exposed and nonexposed sides. The actuation of a three-dimensional tetrahedron (pyramidal) structure is also demonstrated for the first time by using a simple photopatterning technique to selectively control its asymmetric morphology at specific locations.

  7. Pregnancy rates after artificial insemination with cooled stallion spermatozoa either with or without single layer centrifugation.

    Science.gov (United States)

    Morrell, J M; Richter, J; Martinsson, G; Stuhtmann, G; Hoogewijs, M; Roels, K; Dalin, A-M

    2014-11-01

    A successful outcome after artificial insemination with cooled semen is dependent on many factors, the sperm quality of the ejaculate being one. Previous studies have shown that spermatozoa with good motility, normal morphology, and good chromatin integrity can be selected by means of colloid centrifugation, particularly single layer centrifugation (SLC) using species-specific colloids. The purpose of the present study was to conduct an insemination trial with spermatozoa from "normal" ejaculates, i.e., from stallions with no known fertility problem, to determine whether the improvements in sperm quality seen in SLC-selected sperm samples compared with uncentrifuged controls in laboratory tests are reflected in an increased pregnancy rate after artificial insemination. In a multicentre study, SLC-selected sperm samples and uncentrifuged controls from eight stallions were inseminated into approximately 10 mares per treatment per stallion. Ultrasound examination was carried out approximately 16 days after insemination to detect an embryonic vesicle. The pregnancy rates per cycle were 45% for controls and 69% for SLC-selected sperm samples, which is statistically significant (P < 0.0018). Thus, the improvement in sperm quality reported previously for SLC-selected sperm samples is associated with an increase in pregnancy rate, even for ejaculates from stallions with no known fertility problem.

  8. Effects of ultraviolet nanosecond laser irradiation on structural modification and optical transmission of single layer graphene

    Science.gov (United States)

    Li, Chunhong; Kang, Xiaoli; Zhu, Qihua; Zheng, Wanguo

    2017-03-01

    Structural modifications and optical transmission change of single layer graphene (SLG) on transparent SiO2 substrate induced by nanosecond 355 nm laser irradiation were systematically studied by scanning electron microscopy (SEM), laser-excited Raman, X-ray photon spectroscopy (XPS) and UV-vis transmission spectra. In this study, to avoid damage to graphene, the selected irradiation fluence was set to be smaller than the laser damage threshold of SLG. Laser-driven formation of nano-dots, carbon clusters and spherical carbon morphologies were clearly presented using SEM magnification images, and the formation mechanism of such structures were discussed. Raman spectra revealed formation of D' peak and the continuously increasing of ID/IG intensity ratio with the concurrent increase of laser fluence, indicating the increase in amount of structural defects and disordering in SLG. XPS results disclosed that the oxygen content in SLG increases with laser fluence. The formation and relative content increase of Cdbnd O, Csbnd Osbnd C and Osbnd Cdbnd O bonds in SLG induced by laser irradiation were also revealed by XPS. Laser-driven micro-structure modifications of crystalline graphene to nano-crystalline graphene and photo-chemical reactions between graphene and O2 and H2O in air environment were suggested to be responsible for the Raman and XPS revealed modifications in SLG. It is worthy to point out that the above mentioned structural modifications only caused a slight decrease (graphene aiming at modifying its structure and thus taiorling its properties.

  9. Relaxation Properties of Single Layer Graphene on SiO2 Substrate.

    Science.gov (United States)

    Wang, Weidong; Li, Shuai; Min, Jiaojiao; Shen, Cuili

    2015-04-01

    The relaxation properties of single layer graphene sheet on the SiO2 substrate are investigated through molecular dynamics simulation technique in this article. The graphene sheet models with different aspect ratios on SiO2 substrate are established and sufficiently relaxed at different thermodynamic temperatures. Subsequently, the morphology, equilibrium position and undulation of graphene on SiO2 substrate are discussed. It is observed that after sufficient relaxation processes, all the graphene sheets are adsorbed on SiO2 substrates and have some certain degree of undulations both on the edge and in the inner surface rather than perfect planar structures. Further observation from the simulation results shows that with different initial distances between the graphene sheet and SiO2 substrate, the graphene sheet would eventually stabilize to an identical equilibrium level at the same temperature. In addition, the final average distance between the graphene sheet and the substrate is a constant of 3.44 A at 0.01 K, in close proximity to the value of parameter r in Lennard-Jones potential function, and the higher the temperature is, the larger the final distance becomes. The results also indicate that for the same size of the graphene sheet, the increasing of temperature significantly aggravates the undulation of graphene sheet. With the increase of aspect ratios, the undulation of the graphene sheet is also aggravated, even the graphene sheet would crimp to a certain extent.

  10. Bioassisted multi-nanoparticle patterning using single-layer peptide templates

    Energy Technology Data Exchange (ETDEWEB)

    Nochomovitz, Ravit; Amit, Moran; Matmor, Maayan; Ashkenasy, Nurit, E-mail: nurita@bgu.ac.il [Department of Materials Engineering, Ben Gurion University of the Negev, PO Box 653, Beer-Sheva 84105 (Israel)

    2010-04-09

    Patterning of nanoparticles on solid substrates is one of the main challenges of current nanotechnology applications. The use of organic molecules as templates for the deposition of the nanoparticles makes it possible to utilize simple soft lithography techniques for patterning. Peptides appear to be powerful candidates for this job due to their versatility and design flexibility. In this work, we demonstrate the use of dual-affinity peptides, which bind both to the substrate and to the deposited nanoparticles, as single-layer linkers for the creation of multi-component nanoparticle patterns via microcontact printing processes. Controlled deposition and patterning of gold colloids or carbon nanotubes (CNTs) on silicon oxide surfaces and that of silicon oxide nanoparticles on gold surfaces have been achieved by the use of the corresponding dual-affinity peptides. Furthermore, patterning of both gold colloids and CNTs on a single substrate on predefined locations has been achieved. The suggested generic approach offers great flexibility by allowing binding of any material to a substrate of choice, provided that a peptide binding segment has been engineered for each of the inorganic components. Furthermore, the diversity of possible peptide sequences allows the formation of multi-component patterns, paving the way to fabricating complex functional structures based on peptide templates.

  11. Bioassisted multi-nanoparticle patterning using single-layer peptide templates

    Science.gov (United States)

    Nochomovitz, Ravit; Amit, Moran; Matmor, Maayan; Ashkenasy, Nurit

    2010-04-01

    Patterning of nanoparticles on solid substrates is one of the main challenges of current nanotechnology applications. The use of organic molecules as templates for the deposition of the nanoparticles makes it possible to utilize simple soft lithography techniques for patterning. Peptides appear to be powerful candidates for this job due to their versatility and design flexibility. In this work, we demonstrate the use of dual-affinity peptides, which bind both to the substrate and to the deposited nanoparticles, as single-layer linkers for the creation of multi-component nanoparticle patterns via microcontact printing processes. Controlled deposition and patterning of gold colloids or carbon nanotubes (CNTs) on silicon oxide surfaces and that of silicon oxide nanoparticles on gold surfaces have been achieved by the use of the corresponding dual-affinity peptides. Furthermore, patterning of both gold colloids and CNTs on a single substrate on predefined locations has been achieved. The suggested generic approach offers great flexibility by allowing binding of any material to a substrate of choice, provided that a peptide binding segment has been engineered for each of the inorganic components. Furthermore, the diversity of possible peptide sequences allows the formation of multi-component patterns, paving the way to fabricating complex functional structures based on peptide templates.

  12. Determination of band offsets at GaN/single-layer MoS2 heterojunction

    KAUST Repository

    Tangi, Malleswararao

    2016-07-25

    We report the band alignment parameters of the GaN/single-layer (SL) MoS2 heterostructure where the GaN thin layer is grown by molecular beam epitaxy on CVD deposited SL-MoS2/c-sapphire. We confirm that the MoS2 is an SL by measuring the separation and position of room temperature micro-Raman E1 2g and A1 g modes, absorbance, and micro-photoluminescence bandgap studies. This is in good agreement with HRTEM cross-sectional analysis. The determination of band offset parameters at the GaN/SL-MoS2 heterojunction is carried out by high-resolution X-ray photoelectron spectroscopy accompanying with electronic bandgap values of SL-MoS2 and GaN. The valence band and conduction band offset values are, respectively, measured to be 1.86 ± 0.08 and 0.56 ± 0.1 eV with type II band alignment. The determination of these unprecedented band offset parameters opens up a way to integrate 3D group III nitride materials with 2D transition metal dichalcogenide layers for designing and modeling of their heterojunction based electronic and photonic devices.

  13. Single-layer tungsten oxide as intelligent photo-responsive nanoagents for permanent male sterilization.

    Science.gov (United States)

    Liu, Zhen; Liu, Xianjun; Ran, Xiang; Ju, Enguo; Ren, Jinsong; Qu, Xiaogang

    2015-11-01

    Permanent male sterilization has been recognized as useful tools for the development of neuter experimental animals and fattening livestock, as well as efficient control of pet overpopulation. Traditional routes such as surgical ways, chemical injections, and anti-fertility vaccines have addressed these crucial problems with idea outcomes. However, these routes usually bring out serious pain and infection towards animals, as well as induce long-term adverse reaction and immune suppression. Thus, a convenient, but non-surgical strategy for male sterilization under a mild manner is highly desirable. Here, for the first time, we demonstrate a novel platform for male sterilization by using single-layer WO2.72 nanosheets as smart photo-responsive sterilants. Upon a 980 nm irradiation, these nanoagents can possess intrinsic NIR-induced hyperthermia and sensitize the formation of singlet oxygen due to the cooperation of photothermal and photodynamic effects. Mechanism of cellular injury can be attributed to the denaturation of protein and apoptosis-related death. Moreover, long-term toxicity and possible metabolism route after testicular injection are discussed, indicating the neglectable systemic toxicity and high bio-compatibility of our nanoagents. Overall, our strategy can extremely overcome the shortcomings in various routine routes and suggest the new biological application of nanomaterials.

  14. Band Alignment at GaN/Single-Layer WSe2 Interface

    KAUST Repository

    Tangi, Malleswara

    2017-02-21

    We study the band discontinuity at the GaN/single-layer (SL) WSe2 heterointerface. The GaN thin layer is epitaxially grown by molecular beam epitaxy on chemically vapor deposited SL-WSe2/c-sapphire. We confirm that the WSe2 was formed as an SL from structural and optical analyses using atomic force microscopy, scanning transmission electron microscopy, micro-Raman, absorbance, and microphotoluminescence spectra. The determination of band offset parameters at the GaN/SL-WSe2 heterojunction is obtained by high-resolution X-ray photoelectron spectroscopy, electron affinities, and the electronic bandgap values of SL-WSe2 and GaN. The valence band and conduction band offset values are determined to be 2.25 ± 0.15 and 0.80 ± 0.15 eV, respectively, with type II band alignment. The band alignment parameters determined here provide a route toward the integration of group III nitride semiconducting materials with transition metal dichalcogenides (TMDs) for designing and modeling of their heterojunction-based electronic and optoelectronic devices.

  15. The application of highly doped single-layer graphene as the top electrodes of semitransparent organic solar cells.

    Science.gov (United States)

    Liu, Zhike; Li, Jinhua; Sun, Zhen-Hua; Tai, Guoan; Lau, Shu-Ping; Yan, Feng

    2012-01-24

    A single-layer graphene film with high conductance and transparency was realized by effective chemical doping. The conductance of single-layer graphene was increased for more than 400% when it was doped with Au nanoparticles and poly(3,4-ethylenedioxythiophene): poly(styrene sulfonic acid). Then semitransparent organic solar cells based on poly(3-hexylthiophene) (P3HT) and phenyl-C61-butyric acid methyl ester (PCBM) were fabricated with single-layer graphene and indium tin oxide (ITO) as the top and bottom electrodes, respectively. The performance of the devices was optimized by tuning the active layer thickness and doping the single-layer graphene electrodes. The maximum efficiency of 2.7% was observed in the devices with the area of 20 mm(2) illuminated from graphene electrode under the AM1.5 solar simulator. It is notable that all of the devices showed higher efficiency from the graphene than ITO side, which was attributed to the better transmittance of the graphene electrodes. In addition, the influence of the active area of the organic solar cell on its photovoltaic performance was studied. We found that, when the active areas increased from 6 to 50 mm(2), the power conversion efficiencies decreased from 3% to 2.3% because of the increased series resistances and the decreased edge effect of the devices.

  16. The intrinsic defect structure of exfoliated MoS2 single layers revealed by Scanning Tunneling Microscopy

    Science.gov (United States)

    Vancsó, Péter; Magda, Gábor Zsolt; Pető, János; Noh, Ji-Young; Kim, Yong-Sung; Hwang, Chanyong; Biró, László P.; Tapasztó, Levente

    2016-01-01

    MoS2 single layers have recently emerged as strong competitors of graphene in electronic and optoelectronic device applications due to their intrinsic direct bandgap. However, transport measurements reveal the crucial role of defect-induced electronic states, pointing out the fundamental importance of characterizing their intrinsic defect structure. Transmission Electron Microscopy (TEM) is able to image atomic scale defects in MoS2 single layers, but the imaged defect structure is far from the one probed in the electronic devices, as the defect density and distribution are substantially altered during the TEM imaging. Here, we report that under special imaging conditions, STM measurements can fully resolve the native atomic scale defect structure of MoS2 single layers. Our STM investigations clearly resolve a high intrinsic concentration of individual sulfur atom vacancies, and experimentally identify the nature of the defect induced electronic mid-gap states, by combining topographic STM images with ab intio calculations. Experimental data on the intrinsic defect structure and the associated defect-bound electronic states that can be directly used for the interpretation of transport measurements are essential to fully understand the operation, reliability and performance limitations of realistic electronic devices based on MoS2 single layers. PMID:27445217

  17. Synergistic effect of temperature and point defect on the mechanical properties of single layer and bi-layer graphene

    Science.gov (United States)

    Debroy, Sanghamitra; Pavan Kumar, V.; Vijaya Sekhar, K.; Acharyya, Swati Ghosh; Acharyya, Amit

    2017-10-01

    The present study reports a comprehensive molecular dynamics simulation of the effect of a) temperature (300-1073 K at intervals of every 100 K) and b) point defect on the mechanical behaviour of single (armchair and zigzag direction) and bilayer layer graphene (AA and AB stacking). Adaptive intermolecular reactive bond order (AIREBO) potential function was used to describe the many-body short-range interatomic interactions for the single layer graphene sheet. Moreover, Lennard Jones model was considered for bilayer graphene to incorporate the van der Waals interactions among the interlayers of graphene. The effect of temperature on the strain energy of single layer and bilayer graphene was studied in order to understand the difference in mechanical behaviour of the two systems. The strength of the pristine single layer graphene was found to be higher as compared to bilayer AA stacked graphene at all temperatures. It was observed at 1073 K and in the presence of vacancy defect the strength for single layer armchair sheet falls by 30% and for bilayer armchair sheet by 33% as compared to the pristine sheets at 300 K. The AB stacked graphene sheet was found to have a two-step rupture process. The strength of pristine AB sheet was found to decrease by 22% on increase of temperature from 300 K to 1073 K.

  18. Estimation of rheological parameters from the geometry of a single-layer fold train

    Science.gov (United States)

    Adamuszek, Marta; Dabrowski, Marcin; Schmid, Daniel W.

    2013-04-01

    One of the focuses in the analysis of the geometry of buckle folds is their relation to the rheological parameters of the rocks and the amount of shortening. Even in the simple case of a single layer (where the effects of e.g., heterogeneity or anisotropy are neglected and the rock behaviour can be described as linear viscous material), such a relation is not determined in a satisfactory way. This is due to the dependence on the initial perturbation, whose influence on the fold shape is inaccurately quantified but known to be significant (e.g., Mancktelow, 2001). Thus, the aim of this work is to describe the fold shape as a function of the following parameters: viscosity ratio, shortening, and initial perturbation. We explore two approaches: 1) a range of possible fold geometries is constrained for a given set of parameters using forward simulations and 2) backward modelling. In the first approach, establishing the relations between the fold shape and the parameters requires an understanding of the influence of the analysed parameters on the final amplitude spectrum and then the correlation between the final amplitude spectrum and the fold geometry. The role of viscosity ratio, shortening, and initial perturbation can be quantitatively established using theoretical models. For this reason, we employ the Large Amplitude Folding model (Adamuszek et al., 2012), a mathematical model that satisfactorily predicts the evolution of fold geometry parameters up to large amplitudes. Using LAF, we calculate the final amplitude spectrum for selected initial amplitude spectra, viscosity ratio, and shortening. The characteristic features of the final spectrum are described and the influence of the input parameters is tested. Then, for given spectrum, we generate a fold interface by adding the waveforms from the spectrum (with determined wavelength and amplitude) and the phase shift is randomly chosen. The obtained fold train is analysed using the automated Fold Geometry Toolbox

  19. Seamless lamination of a concave-convex architecture with single-layer graphene

    Science.gov (United States)

    Park, Ji-Hoon; Lim, Taekyung; Baik, Jaeyoon; Seo, Keumyoung; Moon, Youngkwon; Park, Noejung; Shin, Hyun-Joon; Kyu Kwak, Sang; Ju, Sanghyun; Real Ahn, Joung

    2015-10-01

    Graphene has been used as an electrode and channel material in electronic devices because of its superior physical properties. Recently, electronic devices have changed from a planar to a complicated three-dimensional (3D) geometry to overcome the limitations of planar devices. The evolution of electronic devices requires that graphene be adaptable to a 3D substrate. Here, we demonstrate that chemical-vapor-deposited single-layer graphene can be transferred onto a silicon dioxide substrate with a 3D geometry, such as a concave-convex architecture. A variety of silicon dioxide concave-convex architectures were uniformly and seamlessly laminated with graphene using a thermal treatment. The planar graphene was stretched to cover the concave-convex architecture, and the resulting strain on the curved graphene was spatially resolved by confocal Raman spectroscopy; molecular dynamic simulations were also conducted and supported the observations. Changes in electrical resistivity caused by the spatially varying strain induced as the graphene-silicon dioxide laminate varies dimensionally from 2D to 3D were measured by using a four-point probe. The resistivity measurements suggest that the electrical resistivity can be systematically controlled by the 3D geometry of the graphene-silicon dioxide laminate. This 3D graphene-insulator laminate will broaden the range of graphene applications beyond planar structures to 3D materials.Graphene has been used as an electrode and channel material in electronic devices because of its superior physical properties. Recently, electronic devices have changed from a planar to a complicated three-dimensional (3D) geometry to overcome the limitations of planar devices. The evolution of electronic devices requires that graphene be adaptable to a 3D substrate. Here, we demonstrate that chemical-vapor-deposited single-layer graphene can be transferred onto a silicon dioxide substrate with a 3D geometry, such as a concave-convex architecture. A

  20. A Hybrid Constructive Algorithm for Single-Layer Feedforward Networks Learning.

    Science.gov (United States)

    Wu, Xing; Rózycki, Paweł; Wilamowski, Bogdan M

    2015-08-01

    Single-layer feedforward networks (SLFNs) have been proven to be a universal approximator when all the parameters are allowed to be adjustable. It is widely used in classification and regression problems. The SLFN learning involves two tasks: determining network size and training the parameters. Most current algorithms could not be satisfactory to both sides. Some algorithms focused on construction and only tuned part of the parameters, which may not be able to achieve a compact network. Other gradient-based optimization algorithms focused on parameters tuning while the network size has to be preset by the user. Therefore, trial-and-error approach has to be used to search the optimal network size. Because results of each trial cannot be reused in another trial, it costs much computation. In this paper, a hybrid constructive (HC)algorithm is proposed for SLFN learning, which can train all the parameters and determine the network size simultaneously. At first, by combining Levenberg-Marquardt algorithm and least-square method, a hybrid algorithm is presented for training SLFN with fixed network size. Then,with the hybrid algorithm, an incremental constructive scheme is proposed. A new randomly initialized neuron is added each time when the training entrapped into local minima. Because the training continued on previous results after adding new neurons, the proposed HC algorithm works efficiently. Several practical problems were given for comparison with other popular algorithms. The experimental results demonstrated that the HC algorithm worked more efficiently than those optimization methods with trial and error, and could achieve much more compact SLFN than those construction algorithms.

  1. Preliminary Investigation of Keyhole Phenomena during Single Layer Fabrication in Laser Additive Manufacturing of Stainless Steel

    Science.gov (United States)

    Matilainen, Ville-Pekka; Piili, Heidi; Salminen, Antti; Nyrhilä, Olli

    Laser additive manufacturing (LAM) is a fabrication technology that enables production of complex parts from metallic materials with mechanical properties comparable to conventionally manufactured parts. In the LAM process, parts are manufactured by melting metallic powder layer-by-layer with a laser beam. This manufacturing technology is nowadays called powder bed fusion (PBF) according to the ASTM F2792-12a standard. This strategy involves several different independent and dependent thermal cycles, all of which have an influence on the final properties of the manufactured part. The quality of PBF parts depends strongly on the characteristics of each single laser-melted track and each single layer. This study consequently concentrates on investigating the effects of process parameters such as laser power on single track and layer formation and laser-material interaction phenomena occurring during the PBF process. Experimental tests were done with two different machines: a modified research machine based on an EOS EOSINT M-series system and an EOS EOSINT M280 system. The material used was EOS stainless steel 17-4 PH. Process monitoring was done with an active illuminated high speed camera system. After microscopy analysis, it was concluded that a keyhole can form during laser additive manufacturing of stainless steel. It was noted that heat input has an important effect on the likelihood of keyhole formation. The threshold intensity value for keyhole formation of 106 W/cm2 was exceeded in all manufactured single tracks. Laser interaction time was found to have an effect on penetration depth and keyhole formation, since the penetration depth increased with increased laser interaction time. It was also concluded that active illuminated high speed camera systems are suitable for monitoring of the manufacturing process and facilitate process control.

  2. Fabricating Large-Area Sheets of Single-Layer Graphene by CVD

    Science.gov (United States)

    Bronikowski, Michael; Manohara, Harish

    2008-01-01

    This innovation consists of a set of methodologies for preparing large area (greater than 1 cm(exp 2)) domains of single-atomic-layer graphite, also called graphene, in single (two-dimensional) crystal form. To fabricate a single graphene layer using chemical vapor deposition (CVD), the process begins with an atomically flat surface of an appropriate substrate and an appropriate precursor molecule containing carbon atoms attached to substituent atoms or groups. These molecules will be brought into contact with the substrate surface by being flowed over, or sprayed onto, the substrate, under CVD conditions of low pressure and elevated temperature. Upon contact with the surface, the precursor molecules will decompose. The substituent groups detach from the carbon atoms and form gas-phase species, leaving the unfunctionalized carbon atoms attached to the substrate surface. These carbon atoms will diffuse upon this surface and encounter and bond to other carbon atoms. If conditions are chosen carefully, the surface carbon atoms will arrange to form the lowest energy single-layer structure available, which is the graphene lattice that is sought. Another method for creating the graphene lattice includes metal-catalyzed CVD, in which the decomposition of the precursor molecules is initiated by the catalytic action of a catalytic metal upon the substrate surface. Another type of metal-catalyzed CVD has the entire substrate composed of catalytic metal, or other material, either as a bulk crystal or as a think layer of catalyst deposited upon another surface. In this case, the precursor molecules decompose directly upon contact with the substrate, releasing their atoms and forming the graphene sheet. Atomic layer deposition (ALD) can also be used. In this method, a substrate surface at low temperature is covered with exactly one monolayer of precursor molecules (which may be of more than one type). This is heated up so that the precursor molecules decompose and form one

  3. Determination of the optimized single-layer ionospheric height for electron content measurements over China

    Science.gov (United States)

    Li, Min; Yuan, Yunbin; Zhang, Baocheng; Wang, Ningbo; Li, Zishen; Liu, Xifeng; Zhang, Xiao

    2017-08-01

    The ionosphere effective height (IEH) is a very important parameter in total electron content (TEC) measurements under the widely used single-layer model assumption. To overcome the requirement of a large amount of simultaneous vertical and slant ionospheric observations or dense "coinciding" pierce points data, a new approach comparing the converted vertical TEC (VTEC) value using mapping function based on a given IEH with the "ground truth" VTEC value provided by the combined International GNSS Service Global Ionospheric Maps is proposed for the determination of the optimal IEH. The optimal IEH in the Chinese region is determined using three different methods based on GNSS data. Based on the ionosonde data from three different locations in China, the altitude variation of the peak electron density (hmF2) is found to have clear diurnal, seasonal and latitudinal dependences, and the diurnal variation of hmF2 varies from approximately 210 to 520 km in Hainan. The determination of the optimal IEH employing the inverse method suggested by Birch et al. (Radio Sci 37, 2002. doi: 10.1029/2000rs002601) did not yield a consistent altitude in the Chinese region. Tests of the method minimizing the mapping function errors suggested by Nava et al. (Adv Space Res 39:1292-1297, 2007) indicate that the optimal IEH ranges from 400 to 600 km, and the height of 450 km is the most frequent IEH at both high and low solar activities. It is also confirmed that the IEH of 450-550 km is preferred for the Chinese region instead of the commonly adopted 350-450 km using the determination method of the optimal IEH proposed in this paper.

  4. Defect-Induced Optoelectronic Response in Single-layer Group-VI Transition-Metal Dichalcogenides

    Science.gov (United States)

    Chow, Philippe K.

    The ever-evolving symbiosis between mankind and nanoelectronics-driven technology pushes the limits of its constituent materials, largely due to the dominance of undesirable hetero-interfacial physiochemical behavior at the few-nanometer length scale, which dominates over bulk material characteristics. Driven by such instabilities, research into two-dimensional (2D) van der Waals-layered materials (e.g. graphene, transition metal dichalcogenides (TMDCs), boron nitride), which have characteristically inert surface chemistry, has virtually exploded over the past few years. The discovery of an indirect- to direct-gap conversion in semiconducting group-VI TMDCs (e.g. MoS2) upon thinning to a single atomic layer provided the critical link between metallic and insulating 2D materials. While proof-of-concept demonstrations of single-layer TMDC-based devices for visible-range photodetection, light-emission and solar energy conversion have showed promising results, the exciting qualities are downplayed by poorly-understood defectinduced photocarrier traps, limiting the best-achieved external quantum efficiencies to approximately ~1%. This thesis explores the behavior of defects in atomically-thin TMDC layers in response to optical stimuli using a combination of steady-state photoluminescence, reflectance and Raman spectroscopy at room-temperature. By systematically varying the defect density using plasma-irradiation techniques, an unprecedented room-temperature defect-induced monolayer PL feature was discovered. High-resolution transmission electron microscopy correlated the defect-induced PL with plasma-generation of sulfur vacancy defects while reflectance measurements indicate defect-induced sub-bandgap light absorption. Excitation intensity-dependent PL measurements and exciton rate modeling further help elucidate the origin of the defect-induced PL response and highlights the role of non-radiative recombination on exciton conversion processes. The results in this

  5. Nanoscale mapping of excitonic processes in single-layer MoS2 using tip-enhanced photoluminescence microscopy.

    Science.gov (United States)

    Su, Weitao; Kumar, Naresh; Mignuzzi, Sandro; Crain, Jason; Roy, Debdulal

    2016-05-19

    In two-dimensional (2D) semiconductors, photoluminescence originating from recombination processes involving neutral electron-hole pairs (excitons) and charged complexes (trions) is strongly affected by the localized charge transfer due to inhomogeneous interactions with the local environment and surface defects. Herein, we demonstrate the first nanoscale mapping of excitons and trions in single-layer MoS2 using the full spectral information obtained via tip-enhanced photoluminescence (TEPL) microscopy along with tip-enhanced Raman spectroscopy (TERS) imaging of a 2D flake. Finally, we show the mapping of the PL quenching centre in single-layer MoS2 with an unprecedented spatial resolution of 20 nm. In addition, our research shows that unlike in aperture-scanning near field microscopy, preferential exciton emission mapping at the nanoscale using TEPL and Raman mapping using TERS can be obtained simultaneously using this method that can be used to correlate the structural and excitonic properties.

  6. Mechanical and bending properties of a conductive thin single layer composite consisting of carbon nanofibers and polypyrrole

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Cheol [Kyungpook National University, Daegu (Korea, Republic of); Zhang, Shuai [Ningxia University, Yinchuan (China)

    2014-07-15

    A new conductive composite material with conductive polymer and carbon nanofibers (CNF) was developed to improve some problems such as a slow response and a low actuating force. The disadvantage has been improved in this study by means of using a single layer thin film of PPy (polypyrrole) and conductive composites consisting of CNF and PPy. The composite films were successfully fabricated by the electrophoretic and polymerization method newly developed. The tension tests results show that the strain of CNF/PPy decreases as CNF weight ratio increases. The bending actuation occurs for both pure PPy and CNF/PPy single layer films when an electric current was applied. The tip deflections of the films varied in the range 0.5mm to 2mm. Tension tests were performed with 0%, 3%, 5%, and 7% weight ratios of CNF's. Specimens with a higher CNF ratio showed larger moduli.

  7. Observing the morphology of single-layered embedded silicon nanocrystals by using temperature-stable TEM membranes

    Directory of Open Access Journals (Sweden)

    Sebastian Gutsch

    2015-04-01

    Full Text Available We use high-temperature-stable silicon nitride membranes to investigate single layers of silicon nanocrystal ensembles by energy filtered transmission electron microscopy. The silicon nanocrystals are prepared from the precipitation of a silicon-rich oxynitride layer sandwiched between two SiO2 diffusion barriers and subjected to a high-temperature annealing. We find that such single layers are very sensitive to the annealing parameters and may lead to a significant loss of excess silicon. In addition, these ultrathin layers suffer from significant electron beam damage that needs to be minimized in order to image the pristine sample morphology. Finally we demonstrate how the silicon nanocrystal size distribution develops from a broad to a narrow log-normal distribution, when the initial precipitation layer thickness and stoichiometry are below a critical value.

  8. A linear-to-circular polarization converter with half transmission and half reflection using a single-layered metamaterial

    CERN Document Server

    Tamayama, Yasuhiro; Nakanishi, Toshihiro; Kitano, Masao

    2014-01-01

    A linear-to-circular polarization converter with half transmission and half reflection using a single-layered metamaterial is theoretically and numerically demonstrated. The unit cell of the metamaterial consists of two coupled split-ring resonators with identical dimensions. A theoretical analysis based on an electrical circuit model of the coupled split-ring resonators indicates that the linear-to-circular polarization converter is achieved when the magnetic coupling between the split-ring resonators is set to a certain strength. A finite-difference time-domain simulation reveals that the single-layered metamaterial behaves as the linear-to-circular polarization converter and that the polarization converter has the combined characteristics of a half mirror and a quarter-wave plate.

  9. Resilience by Structural Entrenchment: Dynamics of Single-Layer and Multiplex Networks Following Sudden Changes to Tie Costs

    CERN Document Server

    Smaldino, Paul E; Maoz, Zeev

    2016-01-01

    We examine a model of network formation in single-layer and multiplex networks in which individuals have positive incentives for social ties, closed triangles, and spillover edges. In particular, we investigate the influence of shocks to the network in which the cost of social ties changes after an initial equilibrium. We highlight the emergence of structural entrenchment, a new concept we define as the persistence of structural features, such as closed triangles and spillover edges, which are formed under historically different conditions from those currently incentivizing the creation of new social ties or the destruction of existing ties. This work has broad implications for understanding path dependence in the structure and dynamics of single-layer and multiplex networks.

  10. Novel single-layer gas diffusion layer based on PTFE/carbon black composite for proton exchange membrane fuel cell

    Energy Technology Data Exchange (ETDEWEB)

    Chen-Yang, Y.W.; Hung, T.F.; Yang, F.L. [Department of Chemistry and Center for Nanotechnology, Chung Yuan Christian University, Chung-Li 32023 (China); Huang, J. [Yeu Ming Tai Chemical Industrial Co., Ltd, Taichung 40768 (China)

    2007-11-08

    A series of poly(tetrafluoroethylene)/carbon black composite-based single-layer gas diffusion layers (PTFE/CB-GDLs) for proton exchange membrane fuel cell (PEMFC) was successfully prepared from carbon black and un-sintered PTFE, which included powder resin and colloidal dispersion, by a simple inexpensive method. The scanning electron micrographs of PTFE/CB-GDLs indicated that the PTFE resins were homogeneously dispersed in the carbon black matrix and showed a microporous layer (MPL)-like structure. The as-prepared PTFE/CB-GDLs exhibited good mechanical property, high gas permeability, and sufficient water repellency. The best current density obtained from the PEMFC with the single-layer PTFE/CB-GDL was 1.27 and 0.42 A cm{sup -2} for H{sub 2}/O{sub 2} and H{sub 2}/air system, respectively. (author)

  11. Buckling of a single-layered graphene sheet on an initially strained InGaAs thin plate

    Energy Technology Data Exchange (ETDEWEB)

    Taziev, R M; Ya Prinz, V, E-mail: taziev@thermo.isp.nsc.ru [Institute of Semiconductor Physics, 630090, Novosibirsk (Russian Federation)

    2011-07-29

    The elastic buckling behavior of a defect-free single-layered graphene sheet deposited on a strained InGaAs substrate is investigated. Such a buckled sandwich structure can be formed by local etching of an initially strained InGaAs substrate. We numerically investigated the necessary buckling conditions for a single-layered graphene sheet of circular geometry on an initially strained InGaAs thin plate. A criterion for buckling for various axisymmetric buckling shapes was obtained. It is shown that for a thin circular InGaAs plate with a monolayer graphene sheet of radius 80 nm and thickness 4 nm three axisymmetric buckling shapes can be obtained. For an initial value of the elastic deformation of the plate of 3%, the in-plane strain in graphene can reach a value of 1%. This deformation is shown to be distributed inhomogeneously along the radius of the graphene monolayer.

  12. Spectral Monitoring CH/C2 Ratio of Methane Plasma for Growing Single-Layer Graphene on Cu

    Directory of Open Access Journals (Sweden)

    Shih-Hao Chan

    2015-01-01

    Full Text Available Single-layer graphene was grown on copper at a low temperature of 600°C by plasma-assisted thermal chemical vapor deposition. Its growth mechanism was discussed with reference to the emission spectra of the plasma. The methane plasma produces the active species (Hx, CHx, and Cx without the addition of flowing hydrogen, and the amounts of hydrogen-containing species can be controlled by varying the plasma power. The effective distance was found between the plasma initial stage and the deposition stage for the single-layer graphene synthesis. The results reveal that high-quality graphene can be synthesized using methane plasma at a suitable plasma power.

  13. Probing critical point energies of transition metal dichalcogenides: surprising indirect gap of single layer $SL-WSe_2$

    OpenAIRE

    Zhang, Chendong; CHEN, YUXUAN; Johnson, Amber; Li, Ming-Yang; Li, Lain-Jong; Mende, Patrick C.; Feenstra, Randall M.; Shih, Chih-Kang

    2014-01-01

    Understanding quasiparticle band structures of transition metal dichalcogenides (TMDs) is critical for technological advances of these materials for atomic layer electronics and photonics. Although theoretical calculations to date have shown qualitatively similar features, there exist subtle differences which can lead to important consequences in the device characteristics. For example, most calculations have shown that all single layer (SL) TMDs have direct band gaps, while some have shown t...

  14. Single-layer ZnS supported on Au(111): A combined XPS, LEED, STM and DFT study

    Science.gov (United States)

    Deng, Xingyi; Sorescu, Dan C.; Lee, Junseok

    2017-04-01

    Single-layer of ZnS, consisting of one atomic layer of ZnS(111) plane, has been grown on Au(111) and characterized using X-ray photoelectron spectroscopy (XPS), low energy electron diffraction (LEED) and scanning tunneling microscopy (STM). While the LEED measurement indicates a coincidence structure of ZnS-(3×3)/Au(111)-(4×4), high resolution STM images reveal hexagonal unit cells of 6.7×6.7 Å2 and 11.6×11.6 Å2, corresponding to √3 and 3 times the unit cell of the ideal zincblende ZnS-(1×1), respectively, depending on the tunneling conditions. Calculations based on density functional theory (DFT) indicate a significantly reconstructed non-planar structure of ZnS single-layer on Au(111) with 2/3 of the S anions being located nearly in the plane of the Zn cations and the rest 1/3 of the S anions protruding above the Zn plane. The calculated STM image shows similar characteristics to those of the experimental STM image. Additionally, the DFT calculations reveal the different bonding nature of the S anions in ZnS single-layer supported on Au(111).

  15. Effects of the dielectric environment on the electron transport properties of single-layer MoS2

    Science.gov (United States)

    Bertolazzi, Simone; Allain, Adrien; Lembke, Dominik; Kis, Andras

    2014-03-01

    Two-dimensional materials, such as graphene, boron nitride and transition metal dichalcogenides, offer a wide range of electronic, optical and mechanical properties that can be advantageous for several applications in nanotechnology. Among these materials, single-layer molybdenum disulfide (MoS2) shows great potential for scaling field-effect transistor devices, due to an optimal electrostatic control of the 2D semiconducting sheet, large energy bandgap and minimal leakage currents. However, to fully exploit the potential of this atomically thin semiconductor, additional experimental efforts need to be undertaken to boost the device performance and access the theoretical intrinsic electron mobilities. To pursue this objective, it is mandatory to reduce the density of charged impurities, both in the semiconducting sheet and in its surrounding environment, and to limit carrier scattering induced by polar optical phonons in the dielectric surface. Here we present the results of our recent experimental investigation of the electron transport properties of single-layer MoS2 mechanically exfoliated/transferred onto different substrates, with varying surface chemistry, surface roughness and dielectric permittivity. We will show temperature-dependent four-terminal measurements of the electrical conductivity of single-layer MoS2 in contact with various insulating materials, including 2D sheets of hexagonal boron nitride, organic polymers and metal oxides.

  16. Mechanical response of all-MoS2 single-layer heterostructures: a ReaxFF investigation.

    Science.gov (United States)

    Mortazavi, Bohayra; Ostadhossein, Alireza; Rabczuk, Timon; van Duin, Adri C T

    2016-09-14

    Molybdenum disulfide (MoS2) is a highly attractive 2D material due to its interesting electronic properties. Recent experimental advances confirm the possibility of further tuning the electronic properties of MoS2 through the fabrication of single-layer heterostructures consisting of semiconducting (2H) and metallic (1T) MoS2 phases. Nonetheless, despite significant technological and scientific interest, there is currently limited information concerning the mechanical properties of these heterostructure systems. This investigation aims at extending our understanding of the mechanical properties of all-MoS2 single-layer structures at room temperature. This goal was achieved by performing extensive classical molecular dynamics simulations using a recently developed ReaxFF force field. We first studied the direction dependent mechanical properties of defect-free 2H and 1T phases. Our modelling results for pristine 2H MoS2 were found to be in good agreement with the experimental tests and first-principles theoretical predictions. We also discuss the mechanical response of 2H/1T single layer heterostructures. Our reactive molecular dynamics results suggest all-MoS2 heterostructures as suitable candidates for providing a strong and flexible material with tuneable electronic properties.

  17. Tuning the electrical property via defect engineering of single layer MoS2 by oxygen plasma

    Science.gov (United States)

    Islam, Muhammad R.; Kang, Narae; Bhanu, Udai; Paudel, Hari P.; Erementchouk, Mikhail; Tetard, Laurene; Leuenberger, Michael N.; Khondaker, Saiful I.

    2014-08-01

    We have demonstrated that the electrical property of single-layer molybdenum disulfide (MoS2) can be significantly tuned from the semiconducting to the insulating regime via controlled exposure to oxygen plasma. The mobility, on-current and resistance of single-layer MoS2 devices were varied by up to four orders of magnitude by controlling the plasma exposure time. Raman spectroscopy, X-ray photoelectron spectroscopy and density functional theory studies suggest that the significant variation of electronic properties is caused by the creation of insulating MoO3-rich disordered domains in the MoS2 sheet upon oxygen plasma exposure, leading to an exponential variation of resistance and mobility as a function of plasma exposure time. The resistance variation calculated using an effective medium model is in excellent agreement with the measurements. The simple approach described here can be used for the fabrication of tunable two-dimensional nanodevices based on MoS2 and other transition metal dichalcogenides.We have demonstrated that the electrical property of single-layer molybdenum disulfide (MoS2) can be significantly tuned from the semiconducting to the insulating regime via controlled exposure to oxygen plasma. The mobility, on-current and resistance of single-layer MoS2 devices were varied by up to four orders of magnitude by controlling the plasma exposure time. Raman spectroscopy, X-ray photoelectron spectroscopy and density functional theory studies suggest that the significant variation of electronic properties is caused by the creation of insulating MoO3-rich disordered domains in the MoS2 sheet upon oxygen plasma exposure, leading to an exponential variation of resistance and mobility as a function of plasma exposure time. The resistance variation calculated using an effective medium model is in excellent agreement with the measurements. The simple approach described here can be used for the fabrication of tunable two-dimensional nanodevices based on MoS2

  18. Theory of substrate-directed heat dissipation for single-layer graphene and other two-dimensional crystals

    Science.gov (United States)

    Ong, Zhun-Yong; Cai, Yongqing; Zhang, Gang

    2016-10-01

    We present a theory of the phononic thermal (Kapitza) resistance at the interface between graphene or another single-layer two-dimensional (2D) crystal (e.g., MoS2) and a flat substrate, based on a modified version of the cross-plane heat transfer model by Persson, Volokitin, and Ueba [J. Phys.: Condens. Matter 23, 045009 (2011), 10.1088/0953-8984/23/4/045009]. We show how intrinsic flexural phonon damping is necessary for obtaining a finite Kapitza resistance and also generalize the theory to encased single-layer 2D crystals with a superstrate. We illustrate our model by computing the thermal boundary conductance (TBC) for bare and SiO2-encased single-layer graphene and MoS2 on a SiO2 substrate, using input parameters from first-principles calculation. The estimated room temperatures TBC for bare (encased) graphene and MoS2 on SiO2 are 34.6 (105) and 3.10 (5.07) MWK -1m-2 , respectively. The theory predicts the existence of a phonon frequency crossover point, below which the low-frequency flexural phonons in the bare 2D crystal do not dissipate energy efficiently to the substrate. We explain within the framework of our theory how the encasement of graphene with a top SiO2 layer introduces new low-frequency transmission channels, which significantly reduce the graphene-substrate Kapitza resistance. We emphasize that the distinction between bare and encased 2D crystals must be made in the analysis of cross-plane heat dissipation to the substrate.

  19. Self-assembly surface modified indium-tin oxide anodes for single-layer light-emitting diodes

    CERN Document Server

    Morgado, J; Charas, A; Matos, M; Alcacer, L; Cacialli, F

    2003-01-01

    We study the effect of indium-tin oxide surface modification by self assembling of highly polar molecules on the performance of single-layer light-emitting diodes (LEDs) fabricated with polyfluorene blends and aluminium cathodes. We find that the efficiency and light-output of such LEDs is comparable to, and sometimes better than, the values obtained for LEDs incorporating a hole injection layer of poly(3,4-ethylene dioxythiophene) doped with polystyrene sulphonic acid. This effect is attributed to the dipole-induced work function modification of indium-tin oxide.

  20. Defect-induced Raman spectroscopy in single-layer graphene with boron and nitrogen substitutional defects by theoretical investigation

    Science.gov (United States)

    Jiang, Jie; Pachter, Ruth; Islam, Ahmad E.; Maruyama, Benji; Boeckl, John J.

    2016-10-01

    Although advances in heteroatom incorporation into the single-layer graphene lattice resulted in films with large carrier densities, careful characterization by Raman spectroscopy is important for assessment of the material's quality. We investigated theoretically I(D)/I(D‧) Raman intensity ratios induced by B- and N- substitutional doping, demonstrated to be consistent with measurements. Calculated Fermi level shifts showed that for a moderate doping density results are comparable to electrolyte gating, while analytical analysis of the electron-defect scattering provided insight into changes of cross-sections. Effects of doping density on the D band intensity and broadening were quantified, and will assist in graphene characterization.

  1. Intrinsic carrier mobility of a single-layer graphene covalently bonded with single-walled carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Li, Dian; Shao, Zhi-Gang [Laboratory of Quantum Engineering and Quantum Materials, School of Physics and Telecommunication Engineering, South China Normal University, Guangzhou, Guangdong 510006 (China); Hao, Qing [Department of Aerospace and Mechanical Engineering, University of Arizona, Tucson, Arizona 85721 (United States); Zhao, Hongbo, E-mail: zhaohb@scnu.edu.cn [Laboratory of Quantum Engineering and Quantum Materials, School of Physics and Telecommunication Engineering, South China Normal University, Guangzhou, Guangdong 510006 (China); Department of Aerospace and Mechanical Engineering, University of Arizona, Tucson, Arizona 85721 (United States)

    2014-06-21

    We report intrinsic carrier mobility calculations of a two-dimensional nanostructure that consists of porous single layer graphene covalently bonded with single-walled carbon nanotubes on both sides. We used first-principles calculation and found that the deformation potential of such system is about 25% of that of graphene, and the carrier mobility is about 5 × 10{sup 4} cm{sup 2} V{sup −1} s{sup −1} for both electrons and holes, about one order of magnitude lower than that of graphene. This nanostructure and its three-dimensional stacking could serve as novel organic electronic materials.

  2. Femtosecond laser fabrication of micro and nano-disks in single layer graphene using vortex Bessel beams

    Energy Technology Data Exchange (ETDEWEB)

    Wetzel, Benjamin, E-mail: benjamin.wetzel@femto-st.fr; Xie, Chen; Lacourt, Pierre-Ambroise; Dudley, John M.; Courvoisier, Francois [Département d' Optique P.M. Duffieux, Institut FEMTO-ST, UMR–6174 CNRS, Université de Franche-Comté, 25030 Besançon (France)

    2013-12-09

    We report the fabrication of micro and nano-disks in single layer chemical vapor deposition graphene on glass substrate using femtosecond laser ablation with vortex Bessel beams. The fabricated graphene disks with diameters ranging from 650 nm to 4 μm were characterized by spatially resolved micro-Raman spectroscopy. The variation of ablation threshold was investigated as a function of the number of pulses showing an incubation effect. A very high degree of size control of the fabricated graphene disks is enabled using a sequence of femtosecond pulses with different vortex orders.

  3. Verification of electron doping in single-layer graphene due to H{sub 2} exposure with thermoelectric power

    Energy Technology Data Exchange (ETDEWEB)

    Hong, Sung Ju; Kang, Hojin; Soler-Delgado, David; Kim, Kyung Ho; Park, Yung Woo, E-mail: ywpark@phya.snu.ac.kr, E-mail: kbh37@incheon.ac.kr [Department of Physics and Astronomy, Seoul National University, Seoul 151-747 (Korea, Republic of); Park, Min [Department of Nano Science and Technology, Seoul National University, Seoul 151-747 (Korea, Republic of); Lee, Minwoo; Jeong, Dae Hong [Department of Chemistry Education, Seoul National University, Seoul 151-742 (Korea, Republic of); Shin, Dong Seok; Kim, Byung Hoon, E-mail: ywpark@phya.snu.ac.kr, E-mail: kbh37@incheon.ac.kr [Department of Physics, Incheon National University, Incheon 406-772 (Korea, Republic of); Kubatkin, Sergey [Department of Microtechnology and Nanoscience, Chalmers University of Technology, SE-412 96 Göteborg (Sweden)

    2015-04-06

    We report the electron doping of single-layer graphene (SLG) grown by chemical vapor deposition (CVD) by means of dissociative hydrogen adsorption. The transfer characteristic showed n-type doping behavior similar to that of mechanically exfoliated graphene. Furthermore, we studied the thermoelectric power (TEP) of CVD-grown SLG before and after exposure to high-pressure H{sub 2} molecules. From the TEP results, which indicate the intrinsic electrical properties, we observed that the CVD-grown SLG is n-type doped without degradation of the quality after hydrogen adsorption. Finally, the electron doping was also verified by Raman spectroscopy.

  4. Numerical Bifurcation Diagram for the Two-Dimensional Boundary-fed CDIMA System

    CERN Document Server

    Setayeshgar, S

    1999-01-01

    We present numerical solution of the chlorine dioxide-iodine-malonic acid reaction-diffusion system in two dimensions in a boundary-fed system using a realistic model. The bifurcation diagram for the transition from non-symmetry breaking structures along boundary feed gradients to transverse symmetry breaking patterns in a single layer is numerically determined. We find this transition to be discontinuous. We make connection with earlier results and discuss prospects for future work.

  5. Growing vertical ZnO nanorod arrays within graphite: efficient isolation of large size and high quality single-layer graphene.

    Science.gov (United States)

    Ding, Ling; E, Yifeng; Fan, Louzhen; Yang, Shihe

    2013-07-18

    We report a unique strategy for efficiently exfoliating large size and high quality single-layer graphene directly from graphite into DMF dispersions by growing ZnO nanorod arrays between the graphene layers in graphite.

  6. Strain-induced magnetic transitions in half-fluorinated single layers of BN, GaN and graphene

    Science.gov (United States)

    Ma, Yandong; Dai, Ying; Guo, Meng; Niu, Chengwang; Yu, Lin; Huang, Baibiao

    2011-05-01

    Recently, extensive experimental and theoretical studies on single layers of BN, GaN and graphene have stimulated enormous interest in exploring the properties of these sheets by decorating their surfaces. In the present work we discuss half-fluorinated single layers of BN, GaN and graphene, in the context of intercoupling between strain and magnetic property. First-principles calculations reveal that the energy difference between ferromagnetic and antiferromagnetic couplings increases significantly with strain increasing for half-fluorinated BN, GaN and graphene sheets. More surprisingly, the half-fluorinated BN and GaN sheets exhibit intriguing magnetic transitions between ferromagnetism and antiferromagnetism by applying strain, even giving rise to half-metal when the sheets are under compression of 6%. It is found that the magnetic coupling as well as the strain-dependent magnetic transition behavior arise from the combined effects of both through-bond and p-p direct interactions. Our work offers a new avenue to facilitate the design of controllable and tunable spin devices.

  7. First-principles study of thermal expansion and thermomechanics of single-layer black and blue phosphorus

    Science.gov (United States)

    Sun, Hongyi; Liu, Gang; Li, Qingfang; Wan, X. G.

    2016-05-01

    The linear thermal expansion coefficients (LTEC) and thermomechanics of single-layer black and blue phosphorus are systematically studied using first-principles based on quasiharmonic approximation. We find the thermal expansion of black phosphorus is very anisotropic. The LTEC along zigzag direction has a turning from negative to positive at around 138 K, while the LTEC along armchair direction is positive (except below 8 K) and about 2.5 times larger than that along zigzag direction at 300 K. For blue phosphorus, the LTEC is negative in the temperature range from 0 to 350 K. In addition, we find that the Young's modulus and Poisson's ratio of black phosphorus along zigzag direction are 4 to 5 times larger than those along armchair direction within considered temperature range, showing a remarkable anisotropic in-plane thermomechanics property. The mechanisms of these peculiar thermal properties are also explored. This work provides a theoretical understanding of the thermal expansion and thermomechanics of this single layer phosphorus family, which will be useful in nanodevices.

  8. Mutual Photoluminescence Quenching and Photovoltaic Effect in Large-Area Single-Layer MoS2-Polymer Heterojunctions.

    Science.gov (United States)

    Shastry, Tejas A; Balla, Itamar; Bergeron, Hadallia; Amsterdam, Samuel H; Marks, Tobin J; Hersam, Mark C

    2016-11-22

    Two-dimensional transition metal dichalcogenides (TMDCs) have recently attracted attention due to their superlative optical and electronic properties. In particular, their extraordinary optical absorption and semiconducting band gap have enabled demonstrations of photovoltaic response from heterostructures composed of TMDCs and other organic or inorganic materials. However, these early studies were limited to devices at the micrometer scale and/or failed to exploit the unique optical absorption properties of single-layer TMDCs. Here we present an experimental realization of a large-area type-II photovoltaic heterojunction using single-layer molybdenum disulfide (MoS2) as the primary absorber, by coupling it to the organic π-donor polymer PTB7. This TMDC-polymer heterojunction exhibits photoluminescence intensity that is tunable as a function of the thickness of the polymer layer, ultimately enabling complete quenching of the TMDC photoluminescence. The strong optical absorption in the TMDC-polymer heterojunction produces an internal quantum efficiency exceeding 40% for an overall cell thickness of less than 20 nm, resulting in exceptional current density per absorbing thickness in comparison to other organic and inorganic solar cells. Furthermore, this work provides insight into the recombination processes in type-II TMDC-polymer heterojunctions and thus provides quantitative guidance to ongoing efforts to realize efficient TMDC-based solar cells.

  9. Ultrahigh energy density realized by a single-layer β-Co(OH)2 all-solid-state asymmetric supercapacitor.

    Science.gov (United States)

    Gao, Shan; Sun, Yongfu; Lei, Fengcai; Liang, Liang; Liu, Jiawei; Bi, Wentuan; Pan, Bicai; Xie, Yi

    2014-11-17

    A conceptually new all-solid-state asymmetric supercapacitor based on atomically thin sheets is presented which offers the opportunity to optimize supercapacitor properties on an atomic level. As a prototype, β-Co(OH)2 single layers with five-atoms layer thickness were synthesized through an oriented-attachment strategy. The increased density-of-states and 100 % exposed hydrogen atoms endow the β-Co(OH)2 single-layers-based electrode with a large capacitance of 2028 F g(-1) . The corresponding all-solid-state asymmetric supercapacitor achieves a high cell voltage of 1.8 V and an exceptional energy density of 98.9 Wh kg(-1) at an ultrahigh power density of 17 981 W kg(-1) . Also, this integrated nanodevice exhibits excellent cyclability with 93.2 % capacitance retention after 10 000 cycles, holding great promise for constructing high-energy storage nanodevices.

  10. Tuning the electrical property via defect engineering of single layer MoS2 by oxygen plasma.

    Science.gov (United States)

    Islam, Muhammad R; Kang, Narae; Bhanu, Udai; Paudel, Hari P; Erementchouk, Mikhail; Tetard, Laurene; Leuenberger, Michael N; Khondaker, Saiful I

    2014-09-07

    We have demonstrated that the electrical property of single-layer molybdenum disulfide (MoS2) can be significantly tuned from the semiconducting to the insulating regime via controlled exposure to oxygen plasma. The mobility, on-current and resistance of single-layer MoS2 devices were varied by up to four orders of magnitude by controlling the plasma exposure time. Raman spectroscopy, X-ray photoelectron spectroscopy and density functional theory studies suggest that the significant variation of electronic properties is caused by the creation of insulating MoO3-rich disordered domains in the MoS2 sheet upon oxygen plasma exposure, leading to an exponential variation of resistance and mobility as a function of plasma exposure time. The resistance variation calculated using an effective medium model is in excellent agreement with the measurements. The simple approach described here can be used for the fabrication of tunable two-dimensional nanodevices based on MoS2 and other transition metal dichalcogenides.

  11. Structure and Electronic Properties of In Situ Synthesized Single-Layer MoS2 on a Gold Surface

    DEFF Research Database (Denmark)

    Sørensen, Signe Grønborg; Füchtbauer, Henrik Gøbel; Tuxen, Anders Kyrme

    2014-01-01

    with scanning tunneling microscopy and X-ray photoelectron spectroscopy characterization of two-dimensional single-layer islands of MoS2 synthesized directly on a gold single crystal substrate. Thanks to a periodic modulation of the atom stacking induced by the lattice mismatch, we observe a structural buckling...... of the MoS2 layer resulting in a characteristic moiré pattern. X-ray photoelectron spectroscopy indicates that the system develops the characteristics of n-doped MoS2 due to electron donation. Scanning tunneling spectroscopy furthermore reflects a convolution of MoS2 and Au donor states where the MoS2 band......When transition metal sulfides such as MoS2 are present in the single-layer form, the electronic properties change in fundamental ways, enabling them to be used, e.g., in two-dimensional semiconductor electronics, optoelectronics, and light harvesting. The change is related to a subtle modification...

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

    Science.gov (United States)

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

    2014-01-01

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

  13. Corrugated single layer templates for molecules: From $h$-BN Nanomesh to Graphene based Quantum dot arrays

    CERN Document Server

    Ma, Haifeng; Schmidlin, Jeanette; Roth, Silvan; Morscher, Martin; Greber, Thomas

    2010-01-01

    Functional nano-templates enable self-assembly of otherwise impossible arrangements of molecules. A particular class of such templates is that of sp2 hybridized single layers of hexagonal boron nitride or carbon (graphene) on metal supports. If the substrate and the single layer have a lattice mismatch, superstructures are formed. On substrates like rhodium or ruthenium these superstructures have unit cells with ~3 nm lattice constant. They are corrugated and contain sub-units, which behave like traps for molecules or quantum dots, which are small enough to become operational at room temperature. For graphene on Rh(111) we emphasize a new structural element of small extra hills within the corrugation landscape. For the case of molecules like water it is shown that new phases assemble on such templates, and that they can be used as "nano-laboratories" where many individual processes are studied in parallel. Furthermore, it is shown that the h-BN/Rh(111) nanomesh displays a strong scanning tunneling microscopy ...

  14. Infiltrating a thin or single layer opal with an atomic vapour: sub-doppler signals and crystal optics

    CERN Document Server

    Moufarej, Elias; Zabkov, Ilya; Laliotis, Athanasios; Ballin, Philippe; Klimov, Vasily; Bloch, Daniel

    2014-01-01

    Artificial thin glass opals can be infiltrated with a resonant alkali-metal vapour, providing novel types of hybrid systems. The reflection at the interface between the substrate and the opal yields a resonant signal, which exhibits sub-Doppler structures in linear spectroscopy for a range of oblique incidences. This result is suspected to originate in an effect of the three-dimensional confinement of the vapour in the opal interstices. It is here extended to a situation where the opal is limited to a few or even a single layer opal film, which is a kind of bidimensional grating. We have developed a flexible one-dimensional layered optical model, well suited for a Langmuir-Blodgett opal. Once extended to the case of a resonant infiltration, the model reproduces quick variations of the lineshape with incidence angle or polarization. Alternately, for an opal limited to a single layer of identical spheres, a three-dimensional numerical calculation was developed. It predicts crystalline anisotropy, which is demon...

  15. Ab-initio study of gold nanoparticles supported on defect-laden single-layer MoS2

    Science.gov (United States)

    Rawal, Takat B.; Le, Duy; Rahman, Talat S.

    We have investigated the geometry, electronic structure, and catalytic properties of gold nanoparticles on defect-laden single-layer MoS2 using density functional theory (DFT) based calculations with semi-empirical van der Waals interaction (DFT-D3). Our results show that the two-dimensional planar structure, the most favorable one for unsupported Au13 nanoparticle, transforms into a distorted three-dimensional (3D) structure when supported on single-layer MoS2 with single S-vacancy which is more favorable than the icosahedral, decahedron and cuboctahedron forms. The MoS2 support substantially alters the electronic structure of Au13 nanoparticle near the Fermi level, owing to the strong interaction of MoS2 support with Au13 in the presence of an S-vacancy. The modified electronic structure remarkably affects the catalytic activity of the MoS2-supported Au13, offering enhanced activity towards methanol synthesis reaction via CO hydrogenation reaction - a contrast from that of titania-supported Au13 nanoparticlewhich promotes methanol decomposition. This work is supported in part by U.S. Department of Energy (DOE DE-FG02-07ER15842).

  16. Design of an alternating phase focusing Interdigital H-mode Drift-Tube-Linac with low injection energy

    Science.gov (United States)

    Zhao, L.; Pang, J.; He, X.; Ying, Z.; Shi, J.

    2016-01-01

    An Inter-digital H-mode (IH) Drift Tube Linac (DTL) was designed to accelerate a proton beam in the low energy region with high RF efficiency and high gradient. The IH DTL is 1.078 m long and operates at 200 MHz. Protons could be accelerated from 0.04 MeV to 2.4 MeV (the β range is from 0.0092 to 0.0714). The method of alternating phase focusing (APF) was applied for beam focusing. The simulation results show that the transmission is 38% and the longitudinal acceptance is approximately 140°. The shunt impedance of the entire cavity is 365 MΩ/m. Adjustments of the electric-field were performed, and the beam dynamics design was described. The beam loss and voltage sensitivity were calculated.

  17. Three-dimensional combined finite-discrete element approach for simulation of single layer powder compaction process

    Institute of Scientific and Technical Information of China (English)

    陈普庆; 夏伟; 周照耀; 朱权利; 李元元

    2004-01-01

    The application of a combined finite-discrete element modeling approach to simulate the three-dimensional microscopic compaction behavior of single-layer metal powder system was described. The process was treated as a static problem, with kinematical component being neglected. Due to ill condition, Cholesky's method failed to solve the system equations, while conjugate gradient method was tried and yielded good results. Deformation of the particles was examined and compared with the results of physical modeling experiments. In both cases, the inner particles were deformed from sphere to polygonal column, with the edges turning from arc to straight line. The edge number of a particle was equal to the number of particles surrounding it. And the experiments show that the ductile metal particles can be densified only by their plastic deformation without the occurrence of rearrangement phenomenon.

  18. p-wave triggered superconductivity in single-layer graphene on an electron-doped oxide superconductor

    Science.gov (United States)

    di Bernardo, A.; Millo, O.; Barbone, M.; Alpern, H.; Kalcheim, Y.; Sassi, U.; Ott, A. K.; de Fazio, D.; Yoon, D.; Amado, M.; Ferrari, A. C.; Linder, J.; Robinson, J. W. A.

    2017-01-01

    Electron pairing in the vast majority of superconductors follows the Bardeen-Cooper-Schrieffer theory of superconductivity, which describes the condensation of electrons into pairs with antiparallel spins in a singlet state with an s-wave symmetry. Unconventional superconductivity was predicted in single-layer graphene (SLG), with the electrons pairing with a p-wave or chiral d-wave symmetry, depending on the position of the Fermi energy with respect to the Dirac point. By placing SLG on an electron-doped (non-chiral) d-wave superconductor and performing local scanning tunnelling microscopy and spectroscopy, here we show evidence for a p-wave triggered superconducting density of states in SLG. The realization of unconventional superconductivity in SLG offers an exciting new route for the development of p-wave superconductivity using two-dimensional materials with transition temperatures above 4.2 K.

  19. Colloid single-layer centrifugation improves post-thaw donkey (Equus asinus) sperm quality and is related to ejaculate freezability.

    Science.gov (United States)

    Ortiz, I; Dorado, J; Acha, D; Gálvez, M J; Urbano, M; Hidalgo, M

    2015-01-01

    The aim of this study was to determine whether colloid single-layer centrifugation (SLC) improves post-thaw donkey sperm quality and if this potential enhancement is related to ejaculate freezability. Semen from Andalusian donkeys was frozen following a standard protocol. SLC was performed on frozen-thawed semen and post-thaw sperm parameters were compared with uncentrifuged samples. Sperm quality was estimated by integrating in a single value sperm motility (assessed by computer-assisted sperm analysis), morphology and viability (evaluated under brightfield or fluorescence microscopy). Sperm freezability was calculated as the relationship between sperm quality obtained before freezing and after thawing. Ejaculates were classified into low, medium and high freezability groups using the 25th and 75th percentiles as thresholds. All sperm parameters were significantly (Pdonkey semen, in particular for those ejaculates with low freezability.

  20. Acrylated poly(3,4-propylenedioxythiophene) for enhancement of lifetime and optical properties for single-layer electrochromic devices.

    Science.gov (United States)

    Otley, Michael T; Alamer, Fahad Alhashmi; Zhu, Yumin; Singhaviranon, Ashwin; Zhang, Xiaozheng; Li, Mengfang; Kumar, Amrita; Sotzing, Gregory A

    2014-02-12

    We utilized our in situ method for the one-step assembly of single-layer electrochromic devices (ECDs) with a 3,4-propylenedioxythiophene (ProDOT) acrylate derivative, and long-term stability was achieved. By coupling the electroactive monomer to the cross-linkable polymer matrix, preparation of the electrochromic ProDOT polymer can occur followed by UV cross-linking. Thus, we achieve immobilization of the unreacted monomer, which prevents any degradative processes from occurring at the counter electrode. This approach eliminated spot formation in the device and increased stability to over 10 000 cycles when compared to 500 cycles with conventional ProDOT devices wherein the monomer is not immobilized. The acrylated electrochromic polymer exhibits similar electrochromic properties as conventional ProDOT devices, such as photopic contrast (48% compared to 46%) and switch speed (both 2 s). This method can be applied to any one-layer electrochromic system where improved stability is desired.

  1. p-wave triggered superconductivity in single-layer graphene on an electron-doped oxide superconductor.

    Science.gov (United States)

    Di Bernardo, A; Millo, O; Barbone, M; Alpern, H; Kalcheim, Y; Sassi, U; Ott, A K; De Fazio, D; Yoon, D; Amado, M; Ferrari, A C; Linder, J; Robinson, J W A

    2017-01-19

    Electron pairing in the vast majority of superconductors follows the Bardeen-Cooper-Schrieffer theory of superconductivity, which describes the condensation of electrons into pairs with antiparallel spins in a singlet state with an s-wave symmetry. Unconventional superconductivity was predicted in single-layer graphene (SLG), with the electrons pairing with a p-wave or chiral d-wave symmetry, depending on the position of the Fermi energy with respect to the Dirac point. By placing SLG on an electron-doped (non-chiral) d-wave superconductor and performing local scanning tunnelling microscopy and spectroscopy, here we show evidence for a p-wave triggered superconducting density of states in SLG. The realization of unconventional superconductivity in SLG offers an exciting new route for the development of p-wave superconductivity using two-dimensional materials with transition temperatures above 4.2 K.

  2. Charge density wave order in 1D mirror twin boundaries of single-layer MoSe2

    Science.gov (United States)

    Barja, Sara; Wickenburg, Sebastian; Liu, Zhen-Fei; Zhang, Yi; Ryu, Hyejin; Ugeda, Miguel M.; Hussain, Zahid; Shen, Zhi-Xun; Mo, Sung-Kwan; Wong, Ed; Salmeron, Miquel B.; Wang, Feng; Crommie, Michael F.; Ogletree, D. Frank; Neaton, Jeffrey B.; Weber-Bargioni, Alexander

    2016-08-01

    We provide direct evidence for the existence of isolated, one-dimensional charge density waves at mirror twin boundaries (MTBs) of single-layer semiconducting MoSe2. Such MTBs have been previously observed by transmission electron microscopy and have been predicted to be metallic in MoSe2 and MoS2. Our low-temperature scanning tunnelling microscopy/spectroscopy measurements revealed a substantial bandgap of 100 meV opening at the Fermi energy in the otherwise metallic one-dimensional structures. We found a periodic modulation in the density of states along the MTB, with a wavelength of approximately three lattice constants. In addition to mapping the energy-dependent density of states, we determined the atomic structure and bonding of the MTB through simultaneous high-resolution non-contact atomic force microscopy. Density functional theory calculations based on the observed structure reproduced both the gap opening and the spatially resolved density of states.

  3. Controlling the formation of wrinkles in a single layer graphene sheet subjected to in-plane shear

    KAUST Repository

    Duan, Wen Hui

    2011-08-01

    The initiation and development of wrinkles in a single layer graphene sheet subjected to in-plane shear displacements are investigated. The dependence of the wavelength and amplitude of wrinkles on the applied shear displacements is explicitly obtained with molecular mechanics simulations. A continuum model is developed for the characteristics of the wrinkles which show that the wrinkle wavelength decreases with an increase in shear loading, while the amplitude of the wrinkles is found to initially increase and then become stable. The propagation and growth process of the wrinkles in the sheet is elucidated. It is expected that the research could promote applications of graphenes in the transportation of biological systems, separation science, and the development of the fluidic electronics. © 2011 Elsevier Ltd. All rights reserved.

  4. Single-layer MoS{sub 2} roughness and sliding friction quenching by interaction with atomically flat substrates

    Energy Technology Data Exchange (ETDEWEB)

    Quereda, J. [Departamento de Física de la Materia Condensada, Universidad Autónoma de Madrid, Madrid E-28049 (Spain); Castellanos-Gomez, A. [Kavli Institute of Nanoscience, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft (Netherlands); Agraït, N. [Departamento de Física de la Materia Condensada, Universidad Autónoma de Madrid, Madrid E-28049 (Spain); Instituto Madrileño de Estudios Avanzados en Nanociencia, IMDEA-Nanociencia, E-28049 Madrid (Spain); Instituto de Ciencia de Materiales Nicolás Cabrera, Campus de Cantoblanco, E-28049 Madrid (Spain); Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid, E-28049 Madrid (Spain); Rubio-Bollinger, G., E-mail: gabino.rubio@uam.es [Departamento de Física de la Materia Condensada, Universidad Autónoma de Madrid, Madrid E-28049 (Spain); Instituto de Ciencia de Materiales Nicolás Cabrera, Campus de Cantoblanco, E-28049 Madrid (Spain); Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid, E-28049 Madrid (Spain)

    2014-08-04

    We experimentally study the surface roughness and the lateral friction force in single-layer MoS{sub 2} crystals deposited on different substrates: SiO{sub 2}, mica, and hexagonal boron nitride (h-BN). Roughness and sliding friction measurements are performed by atomic force microscopy. We find a strong dependence of the MoS{sub 2} roughness on the underlying substrate material, being h-BN the substrate which better preserves the flatness of the MoS{sub 2} crystal. The lateral friction also lowers as the roughness decreases, and attains its lowest value for MoS{sub 2} flakes on h-BN substrates. However, it is still higher than for the surface of a bulk MoS{sub 2} crystal, which we attribute to the deformation of the flake due to competing tip-to-flake and flake-to-substrate interactions.

  5. Ab-initio quantum transport simulation of self-heating in single-layer 2-D materials

    Science.gov (United States)

    Stieger, Christian; Szabo, Aron; Bunjaku, Teutë; Luisier, Mathieu

    2017-07-01

    Through advanced quantum mechanical simulations combining electron transport and phonon transport from first-principles, self-heating effects are investigated in n-type transistors with single-layer MoS2, WS2, and black phosphorus as channel materials. The selected 2-D crystals all exhibit different phonon-limited mobility values, as well as electron and phonon properties, which have a direct influence on the increase in their lattice temperature and on the power dissipated inside their channel as a function of the applied gate voltage and electrical current magnitude. This computational study reveals (i) that self-heating plays a much more important role in 2-D materials than in Si nanowires, (ii) that it could severely limit the performance of 2-D devices at high current densities, and (iii) that black phosphorus appears less sensitive to this phenomenon than transition metal dichalcogenides.

  6. Phase Conjugated and Transparent Wavelength Conversions of Nyquist 16-QAM Signals Employing a Single-Layer Graphene Coated Fiber Device.

    Science.gov (United States)

    Hu, Xiao; Zeng, Mengqi; Long, Yun; Liu, Jun; Zhu, Yixiao; Zou, Kaiheng; Zhang, Fan; Fu, Lei; Wang, Jian

    2016-03-02

    We fabricate a nonlinear optical device based on a fiber pigtail cross-section coated with a single-layer graphene grown by chemical vapor deposition (CVD) method. Using the fabricated graphene-assisted nonlinear optical device and employing Nyquist 16-ary quadrature amplitude modulation (16-QAM) signal, we experimentally demonstrate phase conjugated wavelength conversion by degenerate four-wave mixing (FWM) and transparent wavelength conversion by non-degenerate FWM in graphene. We study the conversion efficiency as functions of the pump power and pump wavelength and evaluate the bit-error rate (BER) performance. We also compare the time-varying symbol sequence for graphene-assisted phase conjugated and transparent wavelength conversions of Nyquist 16-QAM signal.

  7. Photo-Induced Bandgap Renormalization Governs the Ultrafast Response of Single-Layer MoS2.

    Science.gov (United States)

    Pogna, Eva A A; Marsili, Margherita; De Fazio, Domenico; Dal Conte, Stefano; Manzoni, Cristian; Sangalli, Davide; Yoon, Duhee; Lombardo, Antonio; Ferrari, Andrea C; Marini, Andrea; Cerullo, Giulio; Prezzi, Deborah

    2016-01-26

    Transition metal dichalcogenides (TMDs) are emerging as promising two-dimensional (2D) semiconductors for optoelectronic and flexible devices. However, a microscopic explanation of their photophysics, of pivotal importance for the understanding and optimization of device operation, is still lacking. Here, we use femtosecond transient absorption spectroscopy, with pump pulse tunability and broadband probing, to monitor the relaxation dynamics of single-layer MoS2 over the entire visible range, upon photoexcitation of different excitonic transitions. We find that, irrespective of excitation photon energy, the transient absorption spectrum shows the simultaneous bleaching of all excitonic transitions and corresponding red-shifted photoinduced absorption bands. First-principle modeling of the ultrafast optical response reveals that a transient bandgap renormalization, caused by the presence of photoexcited carriers, is primarily responsible for the observed features. Our results demonstrate the strong impact of many-body effects in the transient optical response of TMDs even in the low-excitation-density regime.

  8. Single-layered light-emitting diodes possessing methoxy-modified pyrazoloquinoline dyes in poly-N-vinylcarbazole matrix

    Energy Technology Data Exchange (ETDEWEB)

    Gondek, E. [Institute of Physics, Technical University of Cracow, Podhorazych 1, Cracow (Poland); Danel, A. [Department of Chemistry, Agricultural University of Cracow, ul. Balicka 122, 31-149, Krakow (Poland); Kityk, I.V. [Institute of Physics, J.Dlugosz University Czestochowa, Al.Armii Krajowej13/15, Czestochowa (Poland)], E-mail: i.kityk@ajd.czest.pl

    2008-03-15

    A principal opportunity to operate by current-voltage and electroluminescent-current dependences for the single-layered light-emitting diodes (LED) on the basis of the polyvinylcarbazole (PVK) polymers doped by methoxy-substituted pyrazoloquinoline (PQ) emitting dye chromphore is demonstrated. The principal light-emitting parameters in the architecture ITO/PQ: PVK/Ca (Al) were investigated. The maximally achieved quantum efficiency of the investigated LED was equal to about 0.87% and corresponded to the brightness about the 44 Cd/m{sup 2}. The absence of blue shift for the electroluminescence (EL) compared to PL may indicate on an absence of near-the-surface exciton diffusion for the methoxy-PQ contrary to the phenyl-methyl-substituted PQ. The quantum chemical calculations have shown principal role of the dye chromophore state dipole moments in the observed carrier kinetics determining the EL.

  9. Evidence for strain-induced local conductance modulations in single-layer graphene on SiO2.

    Science.gov (United States)

    Teague, M L; Lai, A P; Velasco, J; Hughes, C R; Beyer, A D; Bockrath, M W; Lau, C N; Yeh, N-C

    2009-07-01

    Graphene has emerged as an electronic material that is promising for device applications and for studying two-dimensional electron gases with relativistic dispersion near two Dirac points. Nonetheless, deviations from Dirac-like spectroscopy have been widely reported with varying interpretations. Here we show evidence for strain-induced spatial modulations in the local conductance of single-layer graphene on SiO(2) substrates from scanning tunneling microscopic (STM) studies. We find that strained graphene exhibits parabolic, U-shaped conductance vs bias voltage spectra rather than the V-shaped spectra expected for Dirac fermions, whereas V-shaped spectra are recovered in regions of relaxed graphene. Strain maps derived from the STM studies further reveal direct correlation with the local tunneling conductance. These results are attributed to a strain-induced frequency increase in the out-of-plane phonon mode that mediates the low-energy inelastic charge tunneling into graphene.

  10. Optical and Electrical Characteristics of Graphene Double Layer Formed by a Double Transfer of Graphene Single Layers.

    Science.gov (United States)

    Kim, Young Jun; Bae, Gi Yoon; Chun, Sungwoo; Park, Wanjun

    2016-03-01

    We demonstrate formation of double layer graphene by means of a double transfer using two single graphene layers grown by a chemical vapor deposition method. It is observed that shiftiness and broadness in the double-resonance of Raman scattering are much weaker than those of bilayer graphene formed naturally. Transport characteristics examined from transmission line measurements and field effect transistors show the similar behavior with those of single layer graphene. It indicates that interlayer separation, in electrical view, is large enough to avoid correlation between layers for the double layer structure. It is also observed from a transistor with the double layer graphene that molecules adsorpted on two inner graphene surfaces in the double layered structure are isolated and conserved from ambient environment.

  11. Effect of Kenaf Parts on the Performance of Single-Layer and Three-Layer Particleboard Made from Kenaf and Rubberwood

    Directory of Open Access Journals (Sweden)

    Juliana Abdul Halip

    2014-01-01

    Full Text Available This study investigated the effect of kenaf parts (kenaf whole stem, kenaf core, and kenaf bast on the mechanical and physical properties of single-layer and three-layer particleboards made from kenaf (Hibiscus cannabinus L. and rubberwood (Hevea brasiliensis. The findings showed that the use of kenaf whole stem, which consists of both core and bast, had a positive effect on the modulus of rupture (MOR, modulus of elasticity (MOE, internal bond (IB, permeability, thickness swelling (TS, and water absorption (WA values of single-layer and three-layer panels. Single-layer admixture panels made from a combination of 70% rubberwood and 30% kenaf had greater strength and stability than single-layer homogeneous panels. The presence of rubberwood particles on surface layers significantly improved the elastic properties of three-layer panels. Panels with kenaf whole stem in the middle layer had better performance than panels with kenaf core. The MOE values of 35RW-30KWS-35RW panels were 56% and 79%, which were higher than those comprising single layers of 100% KWS and 100% KC, respectively. This study suggests that kenaf whole stem is the preferred material to be used in particleboard manufacture incorporated with rubberwood as an admixture for three-layer panels.

  12. Optical DC overlay measurement in the 2nd level process of 65 nm alternating phase shift mask

    Science.gov (United States)

    Ma, Jian; Han, Ke; Lee, Kyung; Korobko, Yulia; Silva, Mary; Chavez, Joas; Irvine, Brian; Henrichs, Sven; Chakravorty, Kishore; Olshausen, Robert; Chandramouli, Mahesh; Mammen, Bobby; Padmanaban, Ramaswamy

    2005-11-01

    Alternating phase shift mask (APSM) techniques help bridge the significant gap between the lithography wavelength and the patterning of minimum features, specifically, the poly line of 35 nm gate length (1x) in Intel's 65 nm technology. One of key steps in making APSM mask is to pattern to within the design tolerances the 2nd level resist so that the zero-phase apertures will be protected by the resist and the pi-phase apertures will be wide open for quartz etch. The ability to align the 2nd level to the 1st level binary pattern, i.e. the 2nd level overlay capability is very important, so is the capability of measuring the overlay accurately. Poor overlay could cause so-called the encroachment after quartz etch, producing undesired quartz bumps in the pi-apertures or quartz pits in the zero-apertures. In this paper, a simple, low-cost optical setup for the 2nd level DC (develop check) overlay measurements in the high volume manufacturing (HVM) of APSM masks is presented. By removing systematic errors in overlay associated with TIS and MIS (tool-induced shift and Mask-process induced shift), it is shown that this setup is capable of supporting the measurement of DC overlay with a tolerance as small as +/- 25 nm. The outstanding issues, such as DC overlay error component analysis, DC - FC (final check) overlay correlation and the overlay linearity (periphery vs. indie), are discussed.

  13. Optical constants and dynamic conductivities of single layer MoS{sub 2}, MoSe{sub 2}, and WSe{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Morozov, Yurii V. [Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556 (United States); Department of Physics, Taras Shevchenko National University, Kiev (Ukraine); Kuno, Masaru [Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556 (United States)

    2015-08-24

    The complex optical constants of single layer MoS{sub 2}, MoSe{sub 2}, and WSe{sub 2} transition metal dichalcogenides (TMDCs) have been measured using concerted frequency-dependent transmittance and reflectance measurements. Absolute absorptivities as well as complex refractive indices and dielectric permittivities have been extracted. Comparisons to associated bulk responses reveal differences due to increased electron-hole interactions in single layer TMDCs. In parallel, corresponding complex optical conductivities (σ) have been determined. For MoS{sub 2}, extracted σ-values qualitatively agree with recent theoretical estimates. Significant differences exist, though, between experiment and theory regarding the imaginary part of σ. In all cases, the current approach distinguishes itself to other measurements of single layer TMDC optical constants in which it does not rely on Kramers-Kronig transformations of reflectance data.

  14. Structural and optical properties of silicon nanocrystals embedded in silicon carbide: Comparison of single layers and multilayer structures

    Energy Technology Data Exchange (ETDEWEB)

    Weiss, Charlotte, E-mail: charlotte.weiss@ise.fraunhofer.de; Schnabel, Manuel; Reichert, Andreas; Löper, Philipp; Janz, Stefan

    2015-10-01

    Highlights: • Si nanocrystal size control in a SiC matrix achieved by Si content variation. • We proved sublayer intermixing in Si{sub x}C{sub 1−x}/SiC multilayer during annealing. • Excess Si in SiC hinders SiC crystallization. • We performed a comparison between Si{sub x}C{sub 1−x}/SiC multilayers and Si{sub x}C{sub 1−x} single layers. • Si nanocrystal size correlates with the E{sub 04} bandgap. - Abstract: The outstanding demonstration of quantum confinement in Si nanocrystals (Si NC) in a SiC matrix requires the fabrication of Si NC with a narrow size distribution. It is understood without controversy that this fabrication is a difficult exercise and that a multilayer (ML) structure is suitable for such fabrication only in a narrow parameter range. This parameter range is sought by varying both the stoichiometric SiC barrier thickness and the Si-rich SiC well thickness between 3 and 9 nm and comparing them to single layers (SL). The samples processed for this investigation were deposited by plasma-enhanced chemical vapor deposition (PECVD) and subsequently subjected to thermal annealing at 1000–1100 °C for crystal formation. Bulk information about the entire sample area and depth were obtained by structural and optical characterization methods: information about the mean Si NC size was determined from grazing incidence X-ray diffraction (GIXRD) measurements. Fourier-transform infrared spectroscopy (FTIR) was applied to gain insight into the structure of the Si–C network, and spectrophotometry measurements were performed to investigate the absorption coefficient and to estimate the bandgap E{sub 04}. All measurements showed that the influence of the ML structure on the Si NC size, on the Si–C network and on the absorption properties is subordinate to the influence of the overall Si content in the samples, which we identified as the key parameter for the structural and optical properties. We attribute this behavior to interdiffusion of the

  15. EFFECT OF THICKNESS ON MICROSTRUCTURE, DIELECTRIC AND OPTICAL PROPERTIES OF SINGLE LAYER Ba0.6Sr0.4TiO3 THIN FILM

    OpenAIRE

    VELUCHAMY ESWARAMOORTHI; RAYAR VICTOR WILLIAMS

    2014-01-01

    Single layered Ba0.6Sr0.4TiO3 (BST) thin films were prepared on stainless steel (304) and quartz substrates by solution method. The microstructure, grain size, surface morphology and thickness of the films were reported on the basis of X-ray diffraction (XRD), atomic force microscopy (AFM), field emission scanning electron microscopy (FESEM) and UV-visible spectrometer. Variation in thickness influences the microstructure of the films. The single layered thin film had uniform crack-free surfa...

  16. EFFECT OF THICKNESS ON MICROSTRUCTURE, DIELECTRIC AND OPTICAL PROPERTIES OF SINGLE LAYER Ba0.6Sr0.4TiO3 THIN FILM

    OpenAIRE

    VELUCHAMY ESWARAMOORTHI; RAYAR VICTOR WILLIAMS

    2014-01-01

    Single layered Ba0.6Sr0.4TiO3 (BST) thin films were prepared on stainless steel (304) and quartz substrates by solution method. The microstructure, grain size, surface morphology and thickness of the films were reported on the basis of X-ray diffraction (XRD), atomic force microscopy (AFM), field emission scanning electron microscopy (FESEM) and UV-visible spectrometer. Variation in thickness influences the microstructure of the films. The single layered thin film had uniform crack-free surfa...

  17. Comparative studies on single-layer reduced graphene oxide films obtained by electrochemical reduction and hydrazine vapor reduction

    Science.gov (United States)

    Wang, Zhijuan; Wu, Shixin; Zhang, Juan; Chen, Peng; Yang, Guocheng; Zhou, Xiaozhu; Zhang, Qichun; Yan, Qingyu; Zhang, Hua

    2012-02-01

    The comparison between two kinds of single-layer reduced graphene oxide (rGO) sheets, obtained by reduction of graphene oxide (GO) with the electrochemical method and hydrazine vapor reduction, referred to as E-rGO and C-rGO, respectively, is systematically studied. Although there is no morphology difference between the E-rGO and C-rGO films adsorbed on solid substrates observed by AFM, the reduction process to obtain the E-rGO and C-rGO films is quite different. In the hydrazine vapor reduction, the nitrogen element is incorporated into the obtained C-rGO film, while no additional element is introduced to the E-rGO film during the electrochemical reduction. Moreover, Raman spectra show that the electrochemical method is more effective than the hydrazine vapor reduction method to reduce the GO films. In addition, E-rGO shows better electrocatalysis towards dopamine than does C-rGO. This study is helpful for researchers to understand these two different reduction methods and choose a suitable one to reduce GO based on their experimental requirements.

  18. Development and characterization of light-emitting diodes (LEDs) based on ruthenium complex single layer for transparent displays

    Energy Technology Data Exchange (ETDEWEB)

    Santos, G.; Fonseca, F.; Andrade, A.M. [Laboratorio de Microelectronica, Departamento de Engenharia de Sistemas Electronicos, Escola Politecnica da Universidade de Sao Paulo (Brazil); Patrocinio, A.O.T.; Mizoguchi, S.K.; Murakami Iha, N.Y. [Laboratorio de Fotoquimica Inorganica e Conversao de Energia, Instituto de Quimica da Universidade de Sao Paulo (Brazil); Peres, M.; Monteiro, T.; Pereira, L. [Departamento de Fisica e I3N, Universidade de Aveiro (Portugal)

    2008-08-15

    In this work, two ruthenium complexes,[Ru(bpy){sub 3}](PF{sub 6}){sub 2} and[Ru(ph2phen){sub 3}](PF{sub 6}){sub 2} in poly(methylmethacrylate) matrix were employed to build single-layer light-emitting electrochemical cells by spin coating on indium tin oxide substrate. In both cases the electroluminescence spectra exhibit a relatively broad band with maxima near to 625 nm and CIE (x,y) color coordinates of (0.64,0.36), which are comparable with the photoluminescence data in the same medium. The best result was obtained with the[Ru(bpy){sub 3}](PF{sub 6}){sub 2} device where the optical output power approaches 10{mu}W at the band maximum with a wall-plug efficiency higher than 0.03%. The lowest driving voltage is about 4 V for an electrical current of 20 mA. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  19. Electronic evidence of an insulator-superconductor crossover in single-layer FeSe/SrTiO3 films.

    Science.gov (United States)

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

    2014-12-30

    In high-temperature cuprate superconductors, it is now generally agreed that superconductivity is realized by doping an antiferromagnetic Mott (charge transfer) insulator. The doping-induced insulator-to-superconductor transition has been widely observed in cuprates, which provides important information for understanding the superconductivity mechanism. In the iron-based superconductors, however, the parent compound is mostly antiferromagnetic bad metal, raising a debate on whether an appropriate starting point should go with an itinerant picture or a localized picture. No evidence of doping-induced insulator-superconductor transition (or crossover) has been reported in the iron-based compounds so far. Here, we report an electronic evidence of an insulator-superconductor crossover observed in the single-layer FeSe film grown on a SrTiO3 substrate. By taking angle-resolved photoemission measurements on the electronic structure and energy gap, we have identified a clear evolution of an insulator to a superconductor with increasing carrier concentration. In particular, the insulator-superconductor crossover in FeSe/SrTiO3 film exhibits similar behaviors to that observed in the cuprate superconductors. Our results suggest that the observed insulator-superconductor crossover may be associated with the two-dimensionality that enhances electron localization or correlation. The reduced dimensionality and the interfacial effect provide a new pathway in searching for new phenomena and novel superconductors with a high transition temperature.

  20. Single-layer MnO2 nanosheets for sensitive and selective detection of glutathione by a colorimetric method

    Science.gov (United States)

    Di, Weihua; Zhang, Xiang; Qin, Weiping

    2017-04-01

    The rapid, sensitive and selective detection of glutathione (GSH) is of great importance in the biological systems. In this work, a template-free and one-step method was used to synthesize the single-layer MnO2 nanosheets via a redox reaction. The resulting product was characterized by XRD, TEM, FTIR, XPS and UV-vis absorption. The addition of GSH results in the change of solution color depth owing to the occurrence of a redox reaction between MnO2 and GSH, enabling colorimetric detection of GSH. At a pH of 3.6, the proposed sensor gives a linear calibration over a GSH concentration range of 10-100 μM, with a rapid response of less than 2 min and a low detection limit of 0.5 μM. The relative standard deviation for seven repeated determinations of GSH is lower than 5.6%. Furthermore, the chemical response of the synthesized MnO2 nanosheets toward GSH is selective. Owing to the advantages with good water solubility, rapid response, high sensitivity, good biocompatibility and operation simplicity, this two-dimensional MnO2-based sensing material might be potential for detecting GSH in biological applications.

  1. Efficient organic photovoltaic cells on a single layer graphene transparent conductive electrode using MoOx as an interfacial layer.

    Science.gov (United States)

    Du, J H; Jin, H; Zhang, Z K; Zhang, D D; Jia, S; Ma, L P; Ren, W C; Cheng, H M; Burn, P L

    2017-01-07

    The large surface roughness, low work function and high cost of transparent electrodes using multilayer graphene films can limit their application in organic photovoltaic (OPV) cells. Here, we develop single layer graphene (SLG) films as transparent anodes for OPV cells that contain light-absorbing layers comprised of the evaporable molecular organic semiconductor materials, zinc phthalocyanine (ZnPc)/fullerene (C60), as well as a molybdenum oxide (MoOx) interfacial layer. In addition to an increase in the optical transmittance, the SLG anodes had a significant decrease in surface roughness compared to two and four layer graphene (TLG and FLG) anodes fabricated by multiple transfer and stacking of SLGs. Importantly, the introduction of a MoOx interfacial layer not only reduced the energy barrier between the graphene anode and the active layer, but also decreased the resistance of the SLG by nearly ten times. The OPV cells with the structure of polyethylene terephthalate/SLG/MoOx/CuI/ZnPc/C60/bathocuproine/Al were flexible, and had a power conversion efficiency of up to 0.84%, which was only 17.6% lower than the devices with an equivalent structure but prepared on commercial indium tin oxide anodes. Furthermore, the devices with the SLG anode were 50% and 86.7% higher in efficiency than the cells with the TLG and FLG anodes. These results show the potential of SLG electrodes for flexible and wearable OPV cells as well as other organic optoelectronic devices.

  2. Kinetics of low-pressure, low-temperature graphene growth: toward single-layer, single-crystalline structure.

    Science.gov (United States)

    Mehdipour, Hamid; Ostrikov, Kostya Ken

    2012-11-27

    Graphene grown on metal catalysts with low carbon solubility is a highly competitive alternative to exfoliated and other forms of graphene, yet a single-layer, single-crystal structure remains a challenge because of the large number of randomly oriented nuclei that form grain boundaries when stitched together. A kinetic model of graphene nucleation and growth is developed to elucidate the effective controls of the graphene island density and surface coverage from the onset of nucleation to the full monolayer formation in low-pressure, low-temperature CVD. The model unprecedentedly involves the complete cycle of the elementary gas-phase and surface processes and shows a precise quantitative agreement with the recent low-energy electron diffraction measurements and also explains numerous parameter trends from a host of experimental reports. These agreements are demonstrated for a broad pressure range as well as different combinations of precursor gases and supporting catalysts. The critical role of hydrogen in controlling the graphene nucleation and monolayer formation is revealed and quantified. The model is generic and can be extended to even broader ranges of catalysts and precursor gases/pressures to enable the as yet elusive effective control of the crystalline structure and number of layers of graphene using the minimum amounts of matter and energy.

  3. Improved multicrystalline silicon ingot quality using single layer silicon beads coated with silicon nitride as seed layer

    Science.gov (United States)

    babu, G. Anandha; Takahashi, Isao; Matsushima, Satoru; Usami, Noritaka

    2016-05-01

    We propose to utilize single layer silicon beads (SLSB) coated with silicon nitride as cost-effective seed layer to grow high-quality multicrystalline silicon (mc-Si) ingot. The texture structure of silicon nitride provides a large number of nucleation sites for the fine grain formation at the bottom of the crucible. No special care is needed to prevent seed melting, which would lead to decrease of red zone owing to decrease of feedstock melting time. As we expected, mc-Si ingot seeded with SLSB was found to consist of small, different grain orientations, more uniform grain distribution, high percentage of random grain boundaries, less twin boundaries, and low density of dislocation clusters compared with conventional mc-Si ingot grown under identical growth conditions. These results show that the SLSB seeded mc-Si ingot has enhanced ingot quality. The correlation between grain boundary structure and defect structure as well as the reason responsible for dislocation clusters reduction in SLSB seeded mc-Si wafer are also discussed.

  4. Magnetism and magnetocrystalline anisotropy in single-layer PtSe{sub 2}: Interplay between strain and vacancy

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Wei, E-mail: zhangw@nfpc.edu.cn; Tao, Qiu Chen; Song, Xiao Jiao; Li, Hao [Physicochemical Group of Department of Criminal Science and Technology, Nanjing Forest Police College, Nanjing 210023 (China); Guo, Hai Tao; Jiang, Jing [Physicochemical Group of Department of Criminal Science and Technology, Nanjing Forest Police College, Nanjing 210023 (China); National Judicial Authentication Center of Public Security Bureau of State Forestry Bureau, Nanjing Forest Police College, Nanjing 210023 (China); Huang, Jie [Department of Physics and Institute of Theoretical Physics, Nanjing Normal University, Nanjing 210023 (China)

    2016-07-07

    The electronic and magnetic properties of the newly synthesized single-layer (1 L) transition-metal dichalcogenide (TMD) PtSe{sub 2} are studied by first-principles calculations. We find the strain or selenium vacancy (V{sub Se}) alone cannot induce the magnetism. However, an interplay between strain and V{sub Se} leads to the magnetism due to the breaking of Pt-Pt metallic bonds. Different from the case of 1 L-MoS{sub 2} with V{sub S}, the defective 1 L-PtSe{sub 2} has the spatially extended spin density, which is responsible for the obtained long range ferromagnetic coupling. Moreover, the 1 L-PtSe{sub 2} with V{sub Se} undergoes a spin reorientation transition from out-of-plane to in-plane magnetization, accompanying a maximum magnetocrystalline anisotropy energy of ∼9–10.6 meV/V{sub Se}. These results indicate the strain not only can effectively tune the magnetism but also can manipulate the magnetization direction of 1 L-TMDs.

  5. Quantitative annular dark-field imaging of single-layer graphene-II: atomic-resolution image contrast.

    Science.gov (United States)

    Yamashita, Shunsuke; Koshiya, Shogo; Nagai, Takuro; Kikkawa, Jun; Ishizuka, Kazuo; Kimoto, Koji

    2015-12-01

    We have investigated how accurately atomic-resolution annular dark-field (ADF) images match between experiments and simulations to conduct more reliable crystal structure analyses. Quantitative ADF imaging, in which the ADF intensity at each pixel represents the fraction of the incident probe current, allows us to perform direct comparisons with simulations without the use of fitting parameters. Although the conventional comparison suffers from experimental uncertainties such as an amorphous surface layer and specimen thickness, in this study we eliminated such uncertainties by using a single-layer graphene as a specimen. Furthermore, to reduce image distortion and shot noises in experimental images, multiple acquisitions with drift correction were performed, and the atomic ADF contrast was quantitatively acquired. To reproduce the experimental ADF contrast, we used three distribution functions as the effective source distribution in simulations. The optimum distribution function and its full-width at half-maximum were evaluated by measuring the residuals between the experimental and simulated images. It was found that the experimental images could be explained well by a linear combination of a Gaussian function and a Lorentzian function with a longer tail than the Gaussian function.

  6. Structure and Electronic Properties of In Situ Synthesized Single-Layer MoS2 on a Gold Surface

    DEFF Research Database (Denmark)

    Sørensen, Signe Grønborg; Füchtbauer, Henrik Gøbel; Tuxen, Anders Kyrme;

    2014-01-01

    When transition metal sulfides such as MoS2 are present in the single-layer form, the electronic properties change in fundamental ways, enabling them to be used, e.g., in two-dimensional semiconductor electronics, optoelectronics, and light harvesting. The change is related to a subtle modification...... of the MoS2 layer resulting in a characteristic moiré pattern. X-ray photoelectron spectroscopy indicates that the system develops the characteristics of n-doped MoS2 due to electron donation. Scanning tunneling spectroscopy furthermore reflects a convolution of MoS2 and Au donor states where the MoS2 band...... structure appears modified at the band gap edges. This electronic effect is further modulated by the moiré periodicity and leads to small substrate-induced electronic perturbations near the conduction band minimum in the band gap of MoS2. The results may be highly relevant in the context of nanopatterned...

  7. Theoretical study on the top- and enclosed-contacted single-layer MoS2 piezotronic transistors

    Science.gov (United States)

    Liu, Wei; Zhou, Yongli; Zhang, Aihua; Zhang, Yan; Wang, Zhong Lin

    2016-05-01

    Recently, the piezotronic effect has been observed in two-dimensional single-layer MoS2 materials, which have potential applications in force and pressure triggered or controlled electronic devices, sensors, and human-machine interfaces. However, classical theory faces the difficulty in explaining the mechanism of the piezotronic effect for the top- and enclosed-contacted MoS2 transistors, since the piezoelectric charges are assumed to exist only at the edge of the MoS2 flake that is far from the electronic transport pathway. In the present study, we identify the piezoelectric charges at the MoS2/metal-MoS2 interface by employing both the density functional theory and finite element method simulations. This interface is on the transport pathway of both top- and enclosed-contacted MoS2 transistors, thus it is capable of controlling their transport properties. This study deepens the understanding of piezotronic effect and provides guidance for the design of two-dimensional piezotronic devices.

  8. Morphological effects of single-layer graphene oxide in the formation of covalently bonded polypyrrole composites using intermediate diisocyanate chemistry

    Science.gov (United States)

    Whitby, Raymond L. D.; Korobeinyk, Alina; Mikhalovsky, Sergey V.; Fukuda, Takahiro; Maekawa, Toru

    2011-10-01

    Single-layer graphene oxide (SLGO) possesses carboxylic and hydroxyl groups suitable for reactions with aliphatic or aromatic diisocyanate molecules. TEM analysis reveals that aliphatic diisocyanate molecules caused SLGO to scroll into star-like formations, whereas aromatic diisocyanate molecules retained SGLO in a flat-sheet morphology. TGA confirms the stabilisation of the formed urea and urethane groups on SLGO, but the onset of sheet pyrolysis occurs at a lower temperature due to isocyanate reactions with anhydride and epoxide groups embedded in the sheet. Pendant isocyanate groups act as bridging units to facilitate the attachment of pyrrole molecules, which are then used as anchor sites for the covalent polymerisation of pyrrole to polypyrrole (PPy). The use of FeCl3 as the polymerisation catalyst generated both covalent and free PPy, but also iron hydroxide nanoparticles were observed decorating the SLGO surface. When using ammonium persulfate as a catalyst and dodecylbenzenesulfonate as a dopant, free PPy could be removed under treatment with solvents to leave a purely covalent system. Discrete regions of SLGO were observed decorated with nanoparticles of PPy along the edge or across the surface of individual sheets. It was found that the flexibility of the SLGO sheet and the type of diisocyanate used directly affected the electrical resistance of the final composite.

  9. The effect of the hole injection layer on the performance of single layer organic light-emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Wenjin, Zeng; Ran, Bi; Hongmei, Zhang, E-mail: iamhmzhang@njupt.edu.cn, E-mail: iamwhuang@njupt.edu.cn [Key Laboratory for Organic Electronics and Information Displays (KLOEID), Nanjing University of Posts and Telecommunications (NUPT), Nanjing 210023 (China); Institute of Advanced Materials (IAM), Nanjing University of Posts and Telecommunications (NUPT), Nanjing 210023 (China); Wei, Huang, E-mail: iamhmzhang@njupt.edu.cn, E-mail: iamwhuang@njupt.edu.cn [Key Laboratory for Organic Electronics and Information Displays (KLOEID), Nanjing University of Posts and Telecommunications (NUPT), Nanjing 210023 (China)

    2014-12-14

    Efficient single-layer organic light-emitting diodes (OLEDs) were reported based on a green fluorescent dye 10-(2-benzothiazolyl)-2,3,6,7-tetrahydro-1,1,7,7–tetramethyl-1H,5H,11H-(1) benzopyropyrano (6,7-8-I,j)quinolizin-11-one (C545T). Herein, poly(3,4-ethylenedioxy thiophene) poly(styrene sulfonate) were, respectively, applied as the injection layer for comparison. The hole transport properties of the emission layer with different hole injection materials are well investigated via current-voltage measurement. It was clearly found that the hole injection layers (HILs) play an important role in the adjustment of the electron/hole injection to attain transport balance of charge carriers in the single emission layer of OLEDs with electron-transporting host. The layer of tris-(8-hydroxyquinoline) aluminum played a dual role of host and electron-transporting materials within the emission layer. Therefore, appropriate selection of hole injection layer is a key factor to achieve high efficiency OLEDs with single emission layer.

  10. Highly sensitive UVA and violet photodetector based on single-layer graphene-TiOsub>2sub> heterojunction.

    Science.gov (United States)

    Liang, Feng-Xia; Zhang, Deng-Yue; Wang, Jiu-Zhen; Kong, Wei-Yu; Zhang, Zhi-Xiang; Wang, Yi; Luo, Lin-Bao

    2016-11-14

    A highly sensitive ultraviolet A (UVA) and violet photodetector based on p-type single-layer graphene (SLG)-TiOsub>2sub> heterostructure was fabricated by transferring chemical vapor deposition derived SLG on the surface of commercial single-crystal TiOsub>2sub> wafer. Optoelectronic analysis reveals the as-fabricated Schottky junction PD was highly sensitive to light illumination in UVA and violet range, with peak sensitivity at 410 nm and excellent stability and reproducibility, but virtually blind to illumination with wavelength less than 350 nm or more than 460 nm. The on/off ratio of the device was calculated to be 6.8 × 104, which is better than the majority of previously reported TiOsub>2sub> based PDs. What is more, the rise/fall time were estimated to be 0.74/1.18 ms, much faster than other TiOsub>2sub> based counterparts. The totality of the above result signifies that the present SLG-TiOsub>2sub> Schottky junction photodetector may have promising application in future high-speed, high-sensitivity optoelectronic nanodevices and systems.

  11. First-principles study of hydrogen adsorption on titanium-decorated single-layer and bilayer graphenes

    Institute of Scientific and Technical Information of China (English)

    Pan Hong-Zhe; Wang Yong-Long; He Kai-Hua; Wei Ming-Zhen; Ouyang Yu; Chen Li

    2013-01-01

    The adsorption of hydrogen molecules on titanium-decorated (Ti-decorated) single-layer and bilayer graphenes is studied using density functional theory (DFT) with the relativistic effect.Both the local density approximation (LDA) and the generalized gradient approximation (GGA) are used for obtaining the region of the adsorption energy of H2 molecules on Ti-decorated graphene.We find that a graphene layer with titanium (Ti) atoms adsorbed on both sides can store hydrogen up to 9.51 wt% with average adsorption energy in a range from-0.170 eV to-0.518 eV.Based on the adsorption energy criterion,we find that chemisorption is predominant for H2 molecules when the concentration of H2 molecules absorbed is low while physisorption is predominant when the concentration is high.The computation results for the bilayer graphene decorated with Ti atoms show that the lower carbon layer makes no contribution to hydrogen adsorption.

  12. Single-layer nano-carbon film, diamond film, and diamond/nano-carbon composite film field emission performance comparison

    Science.gov (United States)

    Wang, Xiaoping; Wang, Jinye; Wang, Lijun

    2016-05-01

    A series of single-layer nano-carbon (SNC) films, diamond films, and diamond/nano-carbon (D/NC) composite films have been prepared on the highly doped silicon substrate by using microwave plasma chemical vapor deposition techniques. The films were characterised by scanning electron microscopy, Raman spectroscopy, and field emission I-V measurements. The experimental results indicated that the field emission maximum current density of D/NC composite films is 11.8-17.8 times that of diamond films. And the field emission current density of D/NC composite films is 2.9-5 times that of SNC films at an electric field of 3.0 V/μm. At the same time, the D/NC composite film exhibits the advantage of improved reproducibility and long term stability (both of the nano-carbon film within the D/NC composite cathode and the SNC cathode were prepared under the same experimental conditions). And for the D/NC composite sample, a high current density of 10 mA/cm2 at an electric field of 3.0 V/μm was obtained. Diamond layer can effectively improve the field emission characteristics of nano-carbon film. The reason may be due to the diamond film acts as the electron acceleration layer.

  13. Effect of non-sperm cells removal with single-layer colloidal centrifugation on myeloperoxidase concentration in post-thaw equine semen.

    Science.gov (United States)

    Ponthier, Jérôme; Teague, Sheila R; Franck, Thierry Y; de la Rebière, Geoffroy; Serteyn, Didier D; Brinsko, Steven P; Love, Charles C; Blanchard, Terry L; Varner, Dickson D; Deleuze, Stéfan C

    2013-12-01

    Myeloperoxidase (MPO) is a pro-oxidant enzyme contained in and released by neutrophils during degranulation or after lysis. Post-thaw semen contains MPO and its concentration is associated with decreased sperm motility. Recently, MPO concentration in post-thaw semen was shown to be associated with the presence of non-sperm cells (NSC). The objective of this study was to evaluate the effect of a single-layer colloidal centrifugation before cryopreservation on NSC and MPO concentrations in equine semen. The experimental design consisted of freezing semen with or without previous centrifugation through two concentrations of single-layer colloid media. Non-sperm cells and MPO concentrations were assessed in pellet and upper layer at each step of the procedure and MPO was detected in cells by immunocytochemistry. Single-layer colloid centrifugation decreased NSC and MPO concentrations in post-thaw semen. The MPO concentration was correlated with concentration of NSC in the upper layer of the supernatant. In post-thaw semen, with or without previous single-layer colloid centrifugation, MPO concentration was correlated with concentration of NSC. Overall, neutrophils were rarely observed and NSC were mainly epithelial cells or cellular debris, as demonstrated by MPO immunocytochemistry. At all steps of the semen processing and cryopreservation, MPO immunostaining was clearly identified only on NSC. In conclusion, our study shows that NSC present in fresh semen release MPO during freezing.

  14. Aromatic structure degradation of single layer graphene on an amorphous silicon substrate in the presence of water, hydrogen and Extreme Ultraviolet light

    NARCIS (Netherlands)

    Mund, Baibhav Kumar; Sturm, J.M.; Lee, Christopher James; Bijkerk, Frederik

    2018-01-01

    In this paper we study the reaction of water and graphene under Extreme Ultraviolet (EUV) irradiation and in the presence of hydrogen. In this work, single layer graphene (SLG) on amorphous Si as an underlying substrate was dosed with water (0.75 ML) and exposed to EUV (λ = 13.5 nm, 92 eV) with

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

    Science.gov (United States)

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

    2014-09-23

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

  16. Suitability and effectiveness of single layer centrifugation using Androcoll-P in the cryopreservation protocol for boar spermatozoa.

    Science.gov (United States)

    Martinez-Alborcia, Maria J; Morrell, Jane M; Gil, Maria A; Barranco, Isabel; Maside, Carolina; Alkmin, Diego V; Parrilla, Inmaculada; Martinez, Emilio A; Roca, Jordi

    2013-08-01

    The goal of the present experiment was to evaluate the suitability and effectiveness of single layer centrifugation (SLC), using the pig-specific colloid Androcoll-P, as a routine procedure for selecting boar spermatozoa for cryopreservation. The study focuses special attention on the effectiveness of SLC for processing a whole sperm rich ejaculate fraction and the fertilizing ability of frozen-thawed (FT) sperm selected using SLC prior to freezing. Thirteen sperm rich ejaculate fractions (one per boar) were split into three aliquots. Two aliquots of 15 and 150mL were SLC-processed (500×g for 20min) using 15 and 150mL (v/v) of Androcoll-P-Large and Androcoll-P-XL, respectively. The third aliquot remained un-processed as a control. The percentages of spermatozoa that were morphologically normal and showed rapid and progressive motility (assessed by CASA) spermatozoa were higher (Psperm chromatin dispersion test) were lower (Psperm motility (both total motility and rapid progressive motility), viability and intact nuclear DNA were higher (Psperm (679 in vitro matured oocytes inseminated with a viable sperm:oocyte ratio of 300:1 and coincubated for 6h), measured as the percentage of penetrated oocytes and the mean number of swollen sperm heads and/or male pronuclei in penetrated oocytes. However, there was no effect of SLC-processing on the in vitro ability of putative zygotes to develop to blastocysts. Overall these results indicate that SLC-processing of boar ejaculates using Androcoll-P improves the quality and fertilizing ability of cryosurvival boar sperm. However, efforts should be made to ensure continued high recovery yields before considering the inclusion of SLC as a routine procedure in the cryopreservation protocol of boar ejaculates.

  17. Predicting Single-Layer Technetium Dichalcogenides (TcX₂, X = S, Se) with Promising Applications in Photovoltaics and Photocatalysis.

    Science.gov (United States)

    Jiao, Yalong; Zhou, Liujiang; Ma, Fengxian; Gao, Guoping; Kou, Liangzhi; Bell, John; Sanvito, Stefano; Du, Aijun

    2016-03-01

    One of the least known compounds among transition metal dichalcogenides (TMDCs) is the layered triclinic technetium dichalcogenides (TcX2, X = S, Se). In this work, we systematically study the structural, mechanical, electronic, and optical properties of TcS2 and TcSe2 monolayers based on density functional theory (DFT). We find that TcS2 and TcSe2 can be easily exfoliated in a monolayer form because their formation and cleavage energy are analogous to those of other experimentally realized TMDCs monolayer. By using a hybrid DFT functional, the TcS2 and TcSe2 monolayers are calculated to be indirect semiconductors with band gaps of 1.91 and 1.69 eV, respectively. However, bilayer TcS2 exhibits direct-bandgap character, and both TcS2 and TcSe2 monolayers can be tuned from semiconductor to metal under effective tensile/compressive strains. Calculations of visible light absorption indicate that 2D TcS2 and TcSe2 generally possess better capability of harvesting sunlight compared to single-layer MoS2 and ReSe2, implying their potential as excellent light-absorbers. Most interestingly, we have discovered that the TcSe2 monolayer is an excellent photocatalyst for splitting water into hydrogen due to the perfect fit of band edge positions with respect to the water reduction and oxidation potentials. Our predictions expand the two-dimensional (2D) family of TMDCs, and the remarkable electronic/optical properties of monolayer TcS2 and TcSe2 will place them among the most promising 2D TMDCs for renewable energy application in the future.

  18. GaN: From three- to two-dimensional single-layer crystal and its multilayer van der Waals solids

    Science.gov (United States)

    Onen, A.; Kecik, D.; Durgun, E.; Ciraci, S.

    2016-02-01

    Three-dimensional (3D) GaN is a III-V compound semiconductor with potential optoelectronic applications. In this paper, starting from 3D GaN in wurtzite and zinc-blende structures, we investigated the mechanical, electronic, and optical properties of the 2D single-layer honeycomb structure of GaN (g -GaN ) and its bilayer, trilayer, and multilayer van der Waals solids using density-functional theory. Based on high-temperature ab initio molecular-dynamics calculations, we first showed that g -GaN can remain stable at high temperature. Then we performed a comparative study to reveal how the physical properties vary with dimensionality. While 3D GaN is a direct-band-gap semiconductor, g -GaN in two dimensions has a relatively wider indirect band gap. Moreover, 2D g -GaN displays a higher Poisson ratio and slightly less charge transfer from cation to anion. In two dimensions, the optical-absorption spectra of 3D crystalline phases are modified dramatically, and their absorption onset energy is blueshifted. We also showed that the physical properties predicted for freestanding g -GaN are preserved when g -GaN is grown on metallic as well as semiconducting substrates. In particular, 3D layered blue phosphorus, being nearly lattice-matched to g -GaN , is found to be an excellent substrate for growing g -GaN . Bilayer, trilayer, and van der Waals crystals can be constructed by a special stacking sequence of g -GaN , and they can display electronic and optical properties that can be controlled by the number of g -GaN layers. In particular, their fundamental band gap decreases and changes from indirect to direct with an increasing number of g -GaN layers.

  19. Stress evolution during 3D single-layer visco-elastic buckle folding: Implications for the initiation of fractures

    Science.gov (United States)

    Liu, Xiaolong; Eckert, Andreas; Connolly, Peter

    2016-06-01

    Buckle folds of sedimentary strata commonly feature a variety of different fracture sets. Some fracture sets including outer arc tensile fractures and inner arc shear fractures at the fold hinge zones are well understood by the extensional and compressional strain/stress pattern. However, other commonly observed fracture sets, including tensile fractures parallel to the fold axis, tensile fractures cutting through the limb, extensional faults at the fold hinge, and other shear fractures of various orientations in the fold limb, fail to be intuitively explained by the strain/stress regimes during the buckling process. To obtain a better understanding of the conditions for the initiation of the various fractures sets associated with single-layer cylindrical buckle folds, a 3D finite element modeling approach using a Maxwell visco-elastic rheology is utilized. The influences of three model parameters with significant influence on fracture initiation are considered: burial depth, viscosity, and permeability. It is concluded that these parameters are critical for the initiation of major fracture sets at the hinge zone with varying degrees. The numerical simulation results further show that the buckling process fails to explain most of the fracture sets occurring in the limb unless the process of erosional unloading as a post-fold phenomenon is considered. For fracture sets that only develop under unrealistic boundary conditions, the results demonstrate that their development is realistic for a perclinal fold geometry. In summary, a more thorough understanding of fractures sets associated with buckle folds is obtained based on the simulation of in-situ stress conditions during the structural development of buckle folds.

  20. Newtype single-layer magnetic semiconductor in transition-metal dichalcogenides VX2 (X = S, Se and Te)

    Science.gov (United States)

    Fuh, Huei-Ru; Chang, Ching-Ray; Wang, Yin-Kuo; Evans, Richard F. L.; Chantrell, Roy W.; Jeng, Horng-Tay

    2016-01-01

    We present a newtype 2-dimensional (2D) magnetic semiconductor based on transition-metal dichalcogenides VX2 (X = S, Se and Te) via first-principles calculations. The obtained indirect band gaps of monolayer VS2, VSe2, and VTe2 given from the generalized gradient approximation (GGA) are respectively 0.05, 0.22, and 0.20 eV, all with integer magnetic moments of 1.0 μB. The GGA plus on-site Coulomb interaction U (GGA + U) enhances the exchange splittings and raises the energy gap up to 0.38~0.65 eV. By adopting the GW approximation, we obtain converged G0W0 gaps of 1.3, 1.2, and 0.7 eV for VS2, VSe2, and VTe2 monolayers, respectively. They agree very well with our calculated HSE gaps of 1.1, 1.2, and 0.6 eV, respectively. The gap sizes as well as the metal-insulator transitions are tunable by applying the in-plane strain and/or changing the number of stacking layers. The Monte Carlo simulations illustrate very high Curie-temperatures of 292, 472, and 553 K for VS2, VSe2, and VTe2 monolayers, respectively. They are nearly or well beyond the room temperature. Combining the semiconducting energy gap, the 100% spin polarized valence and conduction bands, the room temperature TC, and the in-plane magnetic anisotropy together in a single layer VX2, this newtype 2D magnetic semiconductor shows great potential in future spintronics. PMID:27601195

  1. The implementation of biofiltration systems, rainwater tanks and urban irrigation in a single-layer urban canopy model

    Science.gov (United States)

    Demuzere, Matthias; Coutts, Andrew; Goehler, Maren; Broadbent, Ashley; Wouters, Hendrik; van Lipzig, Nicole; Gebert, Luke

    2015-04-01

    Urban vegetation is generally considered as a key tool to modify the urban energy balance through enhanced evapotranspiration (ET). Given that vegetation is most effective when it is healthy, stormwater harvesting and retention strategies (such as water sensitive urban design) could be used to support vegetation and promote ET. This study presents the implementation of a vegetated lined bio-filtration system (BFS) combined with a rainwater tank (RWT) and urban irrigation system in the single-layer urban canopy model Community Land Model-Urban. Runoff from roof and impervious road surface fractions is harvested and used to support an adequate soil moisture level for vegetation in the BFS. In a first stage, modelled soil moisture dynamics are evaluated and found reliable compared to observed soil moisture levels from biofiltration pits in Smith Street, Melbourne (Australia). Secondly, the impact of BFS, RWT and urban irrigation on ET is illustrated for a two-month period in 2012 using varying characteristics for all components. Results indicate that (i) a large amount of stormwater is potentially available for indoor and outdoor water demands, including irrigation of urban vegetation, (ii) ET from the BFS is an order of magnitude larger compared to the contributions from the impervious surfaces, even though the former only covers 10% of the surface fraction and (iii) attention should be paid to the cover fraction and soil texture of the BFS, size of the RWT and the surface fractions contributing to the collection of water in the RWT. Overall, this study reveals that this model development can effectuate future research with state-of-the-art urban climate models to further explore the benefits of vegetated biofiltration systems as a water sensitive urban design tool optimised with an urban irrigation system to maintain healthy vegetation.

  2. The magnetisation profiles and ac magnetisation losses in a single layer YBCO thin film caused by travelling magnetic field waves

    Science.gov (United States)

    Wang, Wei; Coombs, Timothy

    2015-05-01

    This paper studies the magnetisation and ac magnetisation losses caused by a travelling magnetic wave on a single-layer YBCO thin film. This work provides thorough investigations on how the critical magnetic field gradient has been changed by the application of a travelling wave. Several conditions were studied such as zero-field cooling (ZFC), field cooling (FC) and a delta-shaped trapped field. It was found that the travelling wave tends to attenuate the existing critical magnetic field gradients in all these conditions. This interesting magnetic behaviour can be well predicted by the finite element (FEM) software with the E-J power law and Maxwell’s equations. The numerical simulations show that the existing critical current density has been compromised after applying the travelling wave. The magnetisation profile caused by the travelling wave is very different from the standing wave, while the magnetisation based on the standing wave can be interpreted by the Bean model and constant current density assumption. Based on the numerical method, which has reliability that has been solidly proven in the study, we have extended the study to the ac magnetisation losses. Comparisons were made between the travelling wave and the standing wave for this specific YBCO sample. It was found that by applying the magnetic wave of the same amplitude, the ac magnetisation loss caused by the travelling wave is about 1/3 of that caused by the standing wave. These results are helpful in understanding the general magnetism problems and ac magnetisation loss in the travelling magnetic wave conditions such as inside a high temperature superconducting (HTS) rotating machine, etc.

  3. Multi-layer model vs. single-layer model for N and P doped poly layers in etch bias modeling

    Science.gov (United States)

    Li, Jianliang; Vidal-Russell, Ezequiel; Beale, Daniel; Wang, Chunqing; Melvin, Lawrence S., III

    2010-09-01

    In modern photolithography, ever smaller critical dimension (CD) budgets require tighter control over the entire process, demanding more accurate practice of optical proximity correction (OPC). In last decade, the model based OPC (MBOPC) has outpaced the rule based OPC (RBOPC) and become widely adopted in semiconductor industry. During the MBOPC process, the physical models are called to compute the signal values at the evaluation points and the design patterns are perturbed such that the final model contours are as close to the targets as possible. It has been demonstrated that in addition to simulating the optics and resist effects, the physical models must accommodate the pattern distortion due to etch process as well. While the etch process may be lumped with optics and resist processes into one model for the 65nm and above nodes, it can no longer be treated as small perturbations on photolithographic effects for more advanced nodes and it is highly desired to build a physics-based etch model formulations that differ from the conventional convolution-based process models used to simulate the optical and resist effect. Our previous studies proposed a novel non-linear etch modeling object in combination with conventional convolution kernels, which simulates the non-optics and non-resist proximity effect successfully. This study examines further the non-linear etch modeling method by checking the different behaviors of N and p doped layers which physically have different etching rates and should be represented differently in etch modeling. The experimental results indicate that the fitting accuracy is significantly improved when the data points are split into N and P groups and calibrated separately. The N and P layer etch models are used in staged MBOPCs and the results are compared with single-layer model as well.

  4. Ultraviolet laser damage and optical properties of high-refractive-index single layers, multiple layers, and high/low index multilayer stacks

    Science.gov (United States)

    McInnes, Hazel A.; Andrew, James E.; Bazin, Nicholas J.; Morris, A. J.; Porter, K. J.

    1998-04-01

    Laser induced damage thresholds, measured using N-on-1 and R-on-1 testing, of single layer high index zirconia and hafnia coatings, derived from nitric or acetic acid stabilized sol-gel processing, are reported. Single layer acetic acid, nitric acid and base catalyzed silica sol-gel coatings have also been tested. The sol-gels were dip coated onto fused silica substrates at a rate of 3mm/s. The refractive index of the materials were measured using transmission spectra of multiple pairs of high and low refractive index materials. Absorption in the UV region was similarly measured with multiple layers of the same material and fitting to a Beer's law behavior. The high index materials used were zirconia or hafnia, the low index material was silica. The compatibility of the various combinations of high and low index materials for physical stacking without cracking, achieving high reflectivity and high damage thresholds are discussed and compared.

  5. Spin-Stripe Density Varies Linearly With the Hole Content in Single-Layer Bi2+xSr2-xCuO6+y Cuprate Superconductors

    Science.gov (United States)

    Enoki, M.; Fujita, M.; Nishizaki, T.; Iikubo, S.; Singh, D. K.; Chang, S.; Tranquada, J. M.; Yamada, K.

    2013-01-01

    We have performed inelastic neutron scattering measurements on the single-layer cuprate Bi2+xSr2-xCuO6+y (Bi2201) with x=0.2, 0.3, 0.4, and 0.5, a doping range that spans the spin-glass to superconducting phase boundary. The doping evolution of low energy spin fluctuations (≲11meV) was found to be characterized by a change in the incommensurate modulation wave vector from the tetragonal [110] to [100]/[010] directions, while maintaining a linear relation between the incommensurability and the hole concentration, δ≈p. In the superconducting regime, the spectral weight is strongly suppressed below ˜4meV. Similarities and differences in the spin correlations between Bi2201 and the prototypical single-layer system La2-xSrxCuO4 are discussed.

  6. Ionization potentials of transparent conductive indium tin oxide films covered with a single layer of fluorine-doped tin oxide nanoparticles grown by spray pyrolysis deposition

    OpenAIRE

    2005-01-01

    Indium tin oxide (ITO) films deposited with single layers of monodispersive fluorine-doped tin oxide (FTO) nanoparticles of several nanometers in size were grown on glass substrates by intermittent spray pyrolysis deposition using conventional atomizers. These films have significantly higher ionization potentials than the bare ITO and FTO films grown using the same technique. The ITO films covered with FTO particles of 7 nm in average size show an ionization potential of 5.01 eV, as compared ...

  7. Single-layer electroluminescent devices based on fluorene-1H-pyrazolo[3,4-b]quinoxaline co-polymers

    Science.gov (United States)

    Pokladko-Kowar, Monika; Danel, Andrzej; Chacaga, Łukasz

    2013-11-01

    A fluorene based copolymer was synthesized for electroluminescent application. To the main chain of polymer the nitrogen heterocyclic, 1H-pyrazolo[3,4-b]quinoxaline, unit was introduced. The incorporation of this derivative tuned the emission from the blue to yellow-green one. A simple, single layered device was fabricated with the configuration ITO/PEDOT/co-poly-FLU-PQX/Ca/Mg.

  8. Self-Assembly of Single-Layer CoAl-Layered Double Hydroxide Nanosheets on 3D Graphene Network Used as Highly Efficient Electrocatalyst for Oxygen Evolution Reaction.

    Science.gov (United States)

    Ping, Jianfeng; Wang, Yixian; Lu, Qipeng; Chen, Bo; Chen, Junze; Huang, Ying; Ma, Qinglang; Tan, Chaoliang; Yang, Jian; Cao, Xiehong; Wang, Zhijuan; Wu, Jian; Ying, Yibin; Zhang, Hua

    2016-09-01

    A non-noble metal based 3D porous electrocatalyst is prepared by self-assembly of the liquid-exfoliated single-layer CoAl-layered double hydroxide nanosheets (CoAl-NSs) onto 3D graphene network, which exhibits higher catalytic activity and better stability for electrochemical oxygen evolution reaction compared to the commercial IrO2 nanoparticle-based 3D porous electrocatalyst.

  9. Surface nanopatterning of Al/Ti multilayer thin films and Al single layer by a low-fluence UV femtosecond laser beam

    Energy Technology Data Exchange (ETDEWEB)

    Kovačević, Aleksander G., E-mail: Aleksander.Kovacevic@ipb.ac.rs [Institute of Physics, University of Belgrade, Pregrevica 118, 11080 Beograd (Serbia); Petrović, Suzana [Institute of Nuclear Sciences “Vinča”, University of Belgrade, PO Box 522, 11001 Belgrade (Serbia); Bokić, Bojana [Institute of Physics, University of Belgrade, Pregrevica 118, 11080 Beograd (Serbia); Gaković, Biljana [Institute of Nuclear Sciences “Vinča”, University of Belgrade, PO Box 522, 11001 Belgrade (Serbia); Bokorov, Miloš T. [Center for Electron Microscopy, University of Novi Sad, Trg Dositeja Obradovića 2, 21000 Novi Sad (Serbia); Vasić, Borislav; Gajić, Radoš [Institute of Physics, University of Belgrade, Pregrevica 118, 11080 Beograd (Serbia); Trtica, Milan [Institute of Nuclear Sciences “Vinča”, University of Belgrade, PO Box 522, 11001 Belgrade (Serbia); Jelenković, Branislav M. [Institute of Physics, University of Belgrade, Pregrevica 118, 11080 Beograd (Serbia)

    2015-01-30

    Highlights: • Femtosecond laser beam was applied to multilayer Al/Ti and single layer Al thin film. • The evolution of laser induced periodic surface structures and its causes is explained. • The structures remained stable after great number of pulses. • The different outcomes of the two cases (single and multilayer) have been explained in the light of the presence of the Ti underlayer. - Abstract: The effects of UV femtosecond laser beam with 76 MHz repetition rate on two types of thin films on Si substrate – the Al single layer thin film, and the multilayered thin film consisted of five Al/Ti bilayers (total thickness 130 nm) – were studied. The surface modification of the target was done by low fluences and different irradiation times, not exceeding ∼300 s. Nanopatterns in the form of femtosecond-laser induced periodic surface structures (fs-LIPSS) with periodicity of <315 nm and height of ∼45 nm were registered upon irradiation of the thin films. It was shown that: (i) the fs-LIPSS evolve from ruffles similar to high spatial frequency LIPSS (HSFL) into a low spatial frequency LIPSS (LSFL) if a certain threshold of the fluence is met, (ii) the number of LSFL increases with the exposition time and (iii) the LSFL remain stable even after long exposure times. We achieved high-quality highly-controllable fabrication of periodic structures on the surface of nanosized multilayer films with high-repetition-rate low-fluence femtosecond laser pulses. Compared to the Al single layer, the presence of the Ti underlayer in the Al/Ti multilayer thin film enabled more efficient heat transmittance through the Al/Ti interface away from the interaction zone which caused the reduction of the ablation effects leading to the formation of more regular LIPSS. The different outcomes of interactions with multi and single layer thin films lead to the conclusion that the behavior of the LIPSS is due to thin film structure.

  10. Near Room-Temperature Memory Devices Based on Hybrid Spin-Crossover@SiO2 Nanoparticles Coupled to Single-Layer Graphene Nanoelectrodes.

    Science.gov (United States)

    Holovchenko, Anastasia; Dugay, Julien; Giménez-Marqués, Mónica; Torres-Cavanillas, Ramón; Coronado, Eugenio; van der Zant, Herre S J

    2016-09-01

    The charge transport properties of SCO [Fe(Htrz)2 (trz)](BF4 ) NPs covered with a silica shell placed in between single-layer graphene electrodes are reported. A reproducible thermal hysteresis loop in the conductance above room-temperature is evidenced. This bistability combined with the versatility of graphene represents a promising scenario for a variety of technological applications but also for future sophisticated fundamental studies.

  11. A platform for large-scale graphene electronics--CVD growth of single-layer graphene on CVD-grown hexagonal boron nitride.

    Science.gov (United States)

    Wang, Min; Jang, Sung Kyu; Jang, Won-Jun; Kim, Minwoo; Park, Seong-Yong; Kim, Sang-Woo; Kahng, Se-Jong; Choi, Jae-Young; Ruoff, Rodney S; Song, Young Jae; Lee, Sungjoo

    2013-05-21

    Direct chemical vapor deposition (CVD) growth of single-layer graphene on CVD-grown hexagonal boron nitride (h-BN) film can suggest a large-scale and high-quality graphene/h-BN film hybrid structure with a defect-free interface. This sequentially grown graphene/h-BN film shows better electronic properties than that of graphene/SiO2 or graphene transferred on h-BN film, and suggests a new promising template for graphene device fabrication.

  12. High-Density Single-Layer Coating of Gold Nanoparticles onto Multiple Substrates by Using an Intrinsically Disordered Protein of α-Synuclein for Nanoapplications.

    Science.gov (United States)

    Bhak, Ghibom; Lee, Junghee; Kim, Chang-Hyun; Chung, Dong Young; Kang, Jin Hyoun; Oh, Soojung; Lee, Jungsup; Kang, Jin Soo; Yoo, Ji Mun; Yang, Jee Eun; Rhoo, Kun Yil; Park, Sunghak; Lee, Somin; Nam, Ki Tae; Jeon, Noo Li; Jang, Jyongsik; Hong, Byung Hee; Sung, Yung-Eun; Yoon, Myung-Han; Paik, Seung R

    2017-03-15

    Functional graffiti of nanoparticles onto target surface is an important issue in the development of nanodevices. A general strategy has been introduced here to decorate chemically diverse substrates with gold nanoparticles (AuNPs) in the form of a close-packed single layer by using an omni-adhesive protein of α-synuclein (αS) as conjugated with the particles. Since the adsorption was highly sensitive to pH, the amino acid sequence of αS exposed from the conjugates and its conformationally disordered state capable of exhibiting structural plasticity are considered to be responsible for the single-layer coating over diverse surfaces. Merited by the simple solution-based adsorption procedure, the particles have been imprinted to various geometric shapes in 2-D and physically inaccessible surfaces of 3-D objects. The αS-encapsulated AuNPs to form a high-density single-layer coat has been employed in the development of nonvolatile memory, fule-cell, solar-cell, and cell-culture platform, where the outlying αS has played versatile roles such as a dielectric layer for charge retention, a sacrificial layer to expose AuNPs for chemical catalysis, a reaction center for silicification, and biointerface for cell attachment, respectively. Multiple utilizations of the αS-based hybrid NPs, therefore, could offer great versatility to fabricate a variety of NP-integrated advanced materials which would serve as an indispensable component for widespread applications of high-performance nanodevices.

  13. Effect of Particle Size and Geometry on the Performance of Single-layer and Three-layer Particleboard Made from Sunflower Seed Husks

    Directory of Open Access Journals (Sweden)

    Camelia N. Cosereanu

    2014-12-01

    Full Text Available The effects of particle size and geometry on the physical (density, water absorption, and thickness swelling, thermal, and mechanical (modulus of elasticity, bending strength, internal bond strength, and screw holding strength properties of single-layer and three-layer particleboards made from sunflower seed husks were investigated. Panels manufactured from particles with various sizes using a urea-formaldehyde adhesive had densities ranging from 535 to 682 kg/m3. The adhesive ratio was at a level of 16% for the single-layer mat configuration; for the three-layer structure, levels of 14% for the core and 16% for the faces were used, based on the weight of particles. The best results occurred in single-layer particleboard made from fine particles, which nearly met the general purpose requirements of the EN 312 Standard. Determination of the thermal conductivity coefficient demonstrated good insulation properties of all panels and their potential use for different structural configurations which are not subjected to strong stresses, suitable for interior design.

  14. Surface nanopatterning of Al/Ti multilayer thin films and Al single layer by a low-fluence UV femtosecond laser beam

    Science.gov (United States)

    Kovačević, Aleksander G.; Petrović, Suzana; Bokić, Bojana; Gaković, Biljana; Bokorov, Miloš T.; Vasić, Borislav; Gajić, Radoš; Trtica, Milan; Jelenković, Branislav M.

    2015-01-01

    The effects of UV femtosecond laser beam with 76 MHz repetition rate on two types of thin films on Si substrate - the Al single layer thin film, and the multilayered thin film consisted of five Al/Ti bilayers (total thickness 130 nm) - were studied. The surface modification of the target was done by low fluences and different irradiation times, not exceeding ∼300 s. Nanopatterns in the form of femtosecond-laser induced periodic surface structures (fs-LIPSS) with periodicity of LIPSS evolve from ruffles similar to high spatial frequency LIPSS (HSFL) into a low spatial frequency LIPSS (LSFL) if a certain threshold of the fluence is met, (ii) the number of LSFL increases with the exposition time and (iii) the LSFL remain stable even after long exposure times. We achieved high-quality highly-controllable fabrication of periodic structures on the surface of nanosized multilayer films with high-repetition-rate low-fluence femtosecond laser pulses. Compared to the Al single layer, the presence of the Ti underlayer in the Al/Ti multilayer thin film enabled more efficient heat transmittance through the Al/Ti interface away from the interaction zone which caused the reduction of the ablation effects leading to the formation of more regular LIPSS. The different outcomes of interactions with multi and single layer thin films lead to the conclusion that the behavior of the LIPSS is due to thin film structure.

  15. Common electronic origin of superconductivity in (Li,Fe)OHFeSe bulk superconductor and single-layer FeSe/SrTiO3 films.

    Science.gov (United States)

    Zhao, Lin; Liang, Aiji; Yuan, Dongna; Hu, Yong; Liu, Defa; Huang, Jianwei; He, Shaolong; Shen, Bing; Xu, Yu; Liu, Xu; Yu, Li; Liu, Guodong; Zhou, Huaxue; Huang, Yulong; Dong, Xiaoli; Zhou, Fang; Liu, Kai; Lu, Zhongyi; Zhao, Zhongxian; Chen, Chuangtian; Xu, Zuyan; Zhou, X J

    2016-02-08

    The mechanism of high-temperature superconductivity in the iron-based superconductors remains an outstanding issue in condensed matter physics. The electronic structure plays an essential role in dictating superconductivity. Recent revelation of distinct electronic structure and high-temperature superconductivity in the single-layer FeSe/SrTiO3 films provides key information on the role of Fermi surface topology and interface in inducing or enhancing superconductivity. Here we report high-resolution angle-resolved photoemission measurements on the electronic structure and superconducting gap of an FeSe-based superconductor, (Li0.84Fe0.16)OHFe0.98Se, with a Tc at 41 K. We find that this single-phase bulk superconductor shows remarkably similar electronic behaviours to that of the superconducting single-layer FeSe/SrTiO3 films in terms of Fermi surface topology, band structure and the gap symmetry. These observations provide new insights in understanding high-temperature superconductivity in the single-layer FeSe/SrTiO3 films and the mechanism of superconductivity in the bulk iron-based superconductors.

  16. Synthesis, characterization, and transport properties of single-layer pure and molybdenum-doped vanadium oxide thin films on metallic conductive substrates

    Energy Technology Data Exchange (ETDEWEB)

    Karthikeyan, Muthukkumaran; Um, Sukkee, E-mail: sukkeeum@hanyang.ac.kr

    2016-05-01

    Single-layer undoped and 10 mol% molybdenum (Mo)-doped vanadium oxide (V{sub 2}O{sub 3}) thin films with thicknesses of approximately 342 nm are fabricated by an aqueous sol–gel method and then deposited onto 316L stainless steel conductive substrates. The influence of various annealing temperatures (in a nitrogen atmosphere) on the structural and electrical properties of undoped and Mo-doped vanadium oxide thin films is investigated. Through a controlled annealing process, the electrical resistances of the single-layer thin films are optimized to attain the required amount of Joule heating for cold-start fuel cell applications within an ambient temperature range (273.15 to 253.15 K). The films show a negative temperature coefficient (NTC) behavior and a transition from a metal to an insulator at sub-zero temperatures. The highest electrical resistivities are measured to be 0.032 Ω·cm and 0.071 Ω·cm for undoped and Mo-doped vanadium oxide films, respectively, after annealing under 20 sccm N{sub 2} at 673.15 K. Consequently, the equilibrium surface temperature of the single-layer Mo-doped vanadium oxide thin film increases from 253.15 K to 299.46 K upon induced Joule heating at a current density of 0.1 A·cm{sup −2}. Thus, it is concluded that single-layer NTC Mo-doped vanadium oxides can be effectively used for cold-start fuel cell applications. - Highlights: • Single-layer undoped and 10 mol% Mo-doped vanadium oxide films were fabricated. • Mo-doped V{sub 2}O{sub 3} thin films showed am enhanced NTC behavior through annealing. • Mo-doped V{sub 2}O{sub 3} thin films revealed the high resistivity of 0.071 Ω·cm at 253.15 K. • Remarkable temperature rise of a Mo-doped V{sub 2}O{sub 3} film was achieved by Joule heating. • Mo-doped V{sub 2}O{sub 3} films can be effectively used for cold-start fuel cell applications.

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

    Energy Technology Data Exchange (ETDEWEB)

    Ovchinnikov, Stanislav, E-mail: ovm@spti.tsu.ru; Pinzhin, Yurii, E-mail: pinzhin@phys.tsu.ru [Institute of Strength Physics and Materials Science SB RAS, Tomsk, 634055 (Russian Federation); National Research Tomsk State University, Tomsk, 634050 (Russian Federation)

    2015-10-27

    Using the method of microprobe analysis and transmission electron microscopy, the influence of obtaining conditions upon particular elemental composition and growth structure coatings of Ti–Al–Si–Mo–S–N system was studied. The possibility of formation and characteristics of the structural and elastic-stress state single-layer coatings with nanoscale columnar or equiaxed grains and gradient-layered, combining two types of selected structure, was defined. On the basis of hardness, tribological properties and coating hardness, a conclusion was made about the relative prospects of its use as wear-resistant coatings with a nanocrystalline structure.

  18. The synthesis of single layers of Ag nanocrystals by ultra-low-energy ion implantation for large-scale plasmonic structures

    Energy Technology Data Exchange (ETDEWEB)

    Carles, R; Farcau, C; Bonafos, C; Benassayag, G; Pecassou, B; Zwick, A, E-mail: robert.carles@cemes.f [Groupe Nanomat-CEMES-CNRS-Universite de Toulouse, 29 rue Jeanne Marvig, BP 94347, F-31055 Toulouse Cedex 4 (France)

    2009-09-02

    Single layers of silver (Ag) nanoparticles embedded in silica (SiO{sub 2}) have been fabricated by ultra-low-energy ion implantation. The distance between the Ag particles and the free SiO{sub 2} surface is controlled with nanometer precision. Raman scattering and reflectivity measurements strongly correlate to transmission electron microscopy analyses, allowing the use of these non-invasive techniques to monitor structural and dynamical properties. These results open up new opportunities to manipulate electromagnetic near-field interactions on wafer-scale plasmonic devices.

  19. Bond polarons and high-Tc superconductivity in single layer La_(2-x)Sr_xCuO_4: normal state currents and pairing

    CERN Document Server

    Georgiev, Mladen

    2011-01-01

    We use the term "bond polaron" for a phonon coupled entity which makes the link between neighboring conductive CuO_2 layers in high-Tc superconductive materials. The link is essential for the superconductivity which requires a long range phase coherence in addition to pairing of carriers. The linkage features studied point to a process which is less dependent on the doped hole density implanted as x in the solid solution. The analysis applies to single layered materials mostly but may help understand multilayer ones as well.

  20. Reaching state-of-the art requirements for MIM capacitors with a single-layer anodic Al2O3 dielectric and imprinted electrodes

    Science.gov (United States)

    Hourdakis, Emmanouel; Nassiopoulou, Androula G.

    2017-07-01

    Metal-Insulator-Metal (MIM) capacitors with a high capacitance density and low non-linearity coefficient using a single-layer dielectric of barrier-type anodic alumina (Al2O3) and an imprinted bottom Al electrode are presented. Imprinting of the bottom electrode aimed at increasing the capacitor effective surface area by creating a three-dimensional MIM capacitor architecture. The bottom Al electrode was only partly nanopatterned so as to ensure low series resistance of the MIM capacitor. With a 3 nm thick anodic Al2O3 dielectric, the capacitor with the imprinted electrode showed a 280% increase in capacitance density compared to the flat electrode capacitor, reaching a value of 20.5 fF/μm2. On the other hand, with a 30 nm thick anodic Al2O3 layer, the capacitance density was 7.9 fF/μm2 and the non-linearity coefficient was as low as 196 ppm/V2. These values are very close to reaching all requirements of the last International Technology Roadmap for Semiconductors for MIM capacitors [ITRS, http://www.itrs2.net/2013-itrs.html for ITRS Roadmap (2013)], and they are achieved by a single-layer dielectric instead of the complicated dielectric stacks of the literature. The obtained results constitute a real progress compared to previously reported results by our group for MIM capacitors using imprinted electrodes.

  1. Comparison of Single-Layer and Double-Layer Anti-Reflection Coatings Using Laser-Induced Damage Threshold and Photothermal Common-Path Interferometry

    Directory of Open Access Journals (Sweden)

    Caspar Clark

    2016-05-01

    Full Text Available The dielectric thin-film coating on high-power optical components is often the weakest region and will fail at elevated optical fluences. A comparison of single-layer coatings of ZrO2, LiF, Ta2O5, SiN, and SiO2 along with anti-reflection (AR coatings optimized at 1064 nm comprised of ZrO2 and Ta2O5 was made, and the results of photothermal common-path interferometry (PCI and a laser-induced damage threshold (LIDT are presented here. The coatings were grown by radio frequency (RF sputtering, pulsed direct-current (DC sputtering, ion-assisted electron beam evaporation (IAD, and thermal evaporation. Test regimes for LIDT used pulse durations of 9.6 ns at 100 Hz for 1000-on-1 and 1-on-1 regimes at 1064 nm for single-layer and AR coatings, and 20 ns at 20 Hz for a 200-on-1 regime to compare the //ZrO2/SiO2 AR coating.

  2. Investigation of single-layer/multilayer self-assembled InAs quantum dots on GaAs1-xSbx/GaAs composite substrates

    Science.gov (United States)

    Tang, Dinghao; Kim, Yeongho; Faleev, Nikolai; Honsberg, Christiana B.; Smith, David J.

    2015-09-01

    The structure-performance properties of single-layered and multi-layered InAs/GaAs1-xSbx quantum dot (QD) system, grown by molecular beam epitaxy on GaAs (001) substrates, have been investigated as a function of Sb concentration. Electron microscopy observations showed no significant crystalline defects for the single-layered InAs QDs (Sb 20%). X-ray diffraction analysis revealed that the increase of Sb concentration from 7.3% to 10.2% for the multi-layered QDs increased the strain relaxation from 0% to ˜23% and the dislocation density of GaAsSb layers went up to 3.6 × 109 cm-2. The peak energy of QD luminescence was red-shifted with increasing Sb concentration due to reduced strain inside QDs. Moreover, the carrier lifetime of the QDs was highly improved from 1.7 to 36.7 ns due to weak hole confinement as the Sb concentration was increased from 7.3% to 10.2%. These structures should be highly promising as the basis for photovoltaic solar-cell applications. Finally, the increased Sb concentration increased the thermal activation energy of electrons confined in the QDs from 163.7 to 206.8 meV, which was indicative of the improved thermal stability with Sb concentration.

  3. Minimizing Unintentional Strain and Doping of Single-Layer Graphene on SiO2 in Aqueous Environments by Acid Treatments.

    Science.gov (United States)

    Masuda, Katsuya; Sano, Masahito

    2015-05-05

    The effects of treating SiO2/Si with either acidic or alkaline solutions on single-layer graphene were investigated using Raman microscopy. It is well-known that in air graphene on SiO2 is unintentionally strained and hole-doped to different degrees, varying widely by sample. It is also known that various amine compounds act as electron donors to graphitic materials. In this study, a SiO2/Si substrate was simply dipped in either a concentrated HCl solution or pH 9.0 NaOH solution and then rinsed, prior to transferring graphene on it. The G and 2D peaks were followed at a fixed position on a single-layer graphene flake in water and various concentrations of pH 7.4 tris(hydroxymethyl)aminomethane (Tris) buffer. The results demonstrate that these treatments reduce the sample variation, improve the stability against Tris, and even bring some graphene samples close to a freestanding state. The Raman analysis reveals that the main effect of dipping is to relieve strain. The undoping effect on some samples is explained by the HCl solution becoming trapped between the graphene and SiO2 surface.

  4. Copper-vapor-assisted chemical vapor deposition for high-quality and metal-free single-layer graphene on amorphous SiO2 substrate.

    Science.gov (United States)

    Kim, Hyungki; Song, Intek; Park, Chibeom; Son, Minhyeok; Hong, Misun; Kim, Youngwook; Kim, Jun Sung; Shin, Hyun-Joon; Baik, Jaeyoon; Choi, Hee Cheul

    2013-08-27

    We report that high-quality single-layer graphene (SLG) has been successfully synthesized directly on various dielectric substrates including amorphous SiO2/Si by a Cu-vapor-assisted chemical vapor deposition (CVD) process. The Cu vapors produced by the sublimation of Cu foil that is suspended above target substrates without physical contact catalyze the pyrolysis of methane gas and assist nucleation of graphene on the substrates. Raman spectra and mapping images reveal that the graphene formed on a SiO2/Si substrate is almost defect-free and homogeneous single layer. The overall quality of graphene grown by Cu-vapor-assisted CVD is comparable to that of the graphene grown by regular metal-catalyzed CVD on a Cu foil. While Cu vapor induces the nucleation and growth of SLG on an amorphous substrate, the resulting SLG is confirmed to be Cu-free by synchrotron X-ray photoelectron spectroscopy. The SLG grown by Cu-vapor-assisted CVD is fabricated into field effect transistor devices without transfer steps that are generally required when SLG is grown by regular CVD process on metal catalyst substrates. This method has overcome two important hurdles previously present when the catalyst-free CVD process is used for the growth of SLG on fused quartz and hexagonal boron nitride substrates, that is, high degree of structural defects and limited size of resulting graphene, respectively.

  5. Phase diagram and electronic indication of high-temperature superconductivity at 65 K in single-layer FeSe films.

    Science.gov (United States)

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

    2013-07-01

    The recent discovery of possible high-temperature superconductivity in single-layer FeSe films has generated significant experimental and theoretical interest. In both the cuprate and the iron-based high-temperature superconductors, superconductivity is induced by doping charge carriers into the parent compound to suppress the antiferromagnetic state. It is therefore important to establish whether the superconductivity observed in the single-layer sheets of FeSe--the essential building blocks of the Fe-based superconductors--is realized by undergoing a similar transition. Here we report the phase diagram for an FeSe monolayer grown on a SrTiO3 substrate, by tuning the charge carrier concentration over a wide range through an extensive annealing procedure. We identify two distinct phases that compete during the annealing process: the electronic structure of the phase at low doping (N phase) bears a clear resemblance to the antiferromagnetic parent compound of the Fe-based superconductors, whereas the superconducting phase (S phase) emerges with the increase in doping and the suppression of the N phase. By optimizing the carrier concentration, we observe strong indications of superconductivity with a transition temperature of 65±5 K. The wide tunability of the system across different phases makes the FeSe monolayer ideal for investigating not only the physics of superconductivity, but also for studying novel quantum phenomena more generally.

  6. The Fed's Year of Transition

    Science.gov (United States)

    Schug, Mark C.; Niederjohn, Scott

    2006-01-01

    The purpose of this article is to: (1) Examine the historical development of the Federal Reserve System; (2) Provide background on Ben Bernanke, the new Fed chairman; (3) Explain the basic tools of monetary policy used by the Fed; (4) Examine the causes of the Great Depression, a topic of special interest to Bernanke; and (5) Provide some key…

  7. Effects of voltage errors caused by gap-voltage and automatic-frequency tuning in an alternating-phase-focused linac

    Science.gov (United States)

    Iwata, Y.; Yamada, S.; Murakami, T.; Fujimoto, T.; Fujisawa, T.; Ogawa, H.; Miyahara, N.; Yamamoto, K.; Hojo, S.; Sakamoto, Y.; Muramatsu, M.; Takeuchi, T.; Mitsumoto, T.; Tsutsui, H.; Watanabe, T.; Ueda, T.

    2008-05-01

    A compact injector for a heavy-ion medical-accelerator complex was developed. It consists of an electron-cyclotron-resonance ion-source (ECRIS) and two linacs, which are a radio-frequency-quadrupole (RFQ) linac and an Interdigital H-mode drift-tube-linac (IH-DTL). Beam acceleration tests of the compact injector were performed, and the designed beam quality was verified by the measured results, as reported earlier. Because the method of alternating-phase-focusing (APF) was used for beam focusing of the IH-DTL, the motion of beam ions would be sensitive to gap-voltage errors, caused during tuning of the gap-voltage distribution and by automatic-frequency tuning in actual operation. To study the effects of voltage errors to beam quality, further measurements were performed during acceleration tests. In this report, the effects of voltage errors for the APF IH-DTL are discussed.

  8. Single-layer homographic cloud computing scheme based on LWE%基于LWE的单层同态云计算方案

    Institute of Scientific and Technical Information of China (English)

    王旭阳; 胡爱群; 方昊

    2016-01-01

    为了实现安全的远程操作,通过分析研究一次或单层的同态运算,构造了一个基于错误学习(LWE)的单层同态云计算方案(sLHCC)。首先,根据解密者是否知道LWE问题中所使用的随机向量,构造了2个不同的单层同态加密方案sLHE1和sLHE2,并得到了相应的sLHCC 方案。该方案在保持LWE问题困难性的基础上,实现了云端单次的同态加和乘运算。根据合理的操作约定和同态结果,用户可以在不泄露操作需求(密文)的情况下,执行远程操作和控制。结果表明,与其他同态加密方案相比,sLHCC的公钥尺寸从传统的矩阵降为向量,从而减小了密文尺寸和云端的存储需求。%To achieve safe remote operation,a single-layer homographic cloud computing scheme (sLHCC)based on learning with errors(LWE)is constructed by analyzing one-time-layer or single-layer homomorphic operation.First,according to whether the decryption accesses the random vector in LWE problem or not,two different single-layer homographic encryption schemes,named sLHE1 and sLHE2,are proposed,and the corresponding sLHCC schemes are put forward.The sLHCC schemes can realize one-time homomorphic addition and one-time homomorphic multiplication in cloud with maintaining the difficulty of LWE problem.According to the reasonable operation agree-ment and homomorphism results,users can execute the remote operation and control without leaking operation requirements (ciphertexts).The results show that compared with other homomorphic en-cryption schemes,the size of the public key of the sLHCC schemes reduces from matrix to vector, inducing the decrease of the ciphertext size and the demands of the cloud storage.

  9. NMR studies of Borrelia burgdorferi OspA, a 28 kDa protein containing a single-layer {beta}-sheet

    Energy Technology Data Exchange (ETDEWEB)

    Pham, Thuy-Nga; Koide, Shohei

    1998-05-15

    The crystal structure of outer surface protein A (OspA) from Borrelia burgdorferi contains a single-layer {beta}-sheet connecting the N- and C-terminal globular domains. The central {beta}-sheet consists largely of polar amino acids and it is solvent-exposed on both faces, which so far appears to be unique among known protein structures. We have accomplished nearly complete backbone H, C and N and C{sup ;}/H{sup {beta}} assignments of OspA (28 kDa) using standard triple resonance techniques without perdeuteration. This was made possible by recording spectra at a high temperature (45 {sup o}C ). The chemical shift index and {sup 15}N T{sub 1}/T{sub 2} ratios show that both the secondary structure and the global conformation of OspA in solution are similar to the crystal structure, suggesting that the unique central {beta}-sheet is fairly rigid.

  10. Mathematical modelling of a single-line flow-injection analysis systems with single-layer enzyme electrode detection. Pt. 3; Experimental verification of the model

    Energy Technology Data Exchange (ETDEWEB)

    Kolev, S.D. (Sofia Univ. (Bulgaria). Khimicheski Fakultet); Nagy, Geza; Pungor, Ernoe (Budapesti Mueszaki Egyetem, Budapest (Hungary). Altalanos es Analitikai Kemia Tanszek)

    1991-11-20

    Glucose and urea electrodes, prepared by two different enzyme immobilization techniques and used as detectors in a single-line flow-injection manifold, were experimentally investigated for elucidating the influence of their most important parameters, i.e., the initial substrate concentration in the sample, the enzyme concentration in the reaction layer and its thickness and the buffer concentration, on the output signal. The results obtained were compared with the theoretical predictions based on simulations of the model for single-line flow-injection systems with single-layer enzyme electrode detection. The good qualitative agreement which was observed is a convincing experimental verification of this model and the guidelines for the production of flow-through biocatalytic electrodes with optimum design based upon it. (author). 12 refs.; 6 figs.

  11. Current induced annealing and electrical characterization of single layer graphene grown by chemical vapor deposition for future interconnects in VLSI circuits

    Science.gov (United States)

    Prasad, Neetu; Kumari, Anita; Bhatnagar, P. K.; Mathur, P. C.; Bhatia, C. S.

    2014-09-01

    Single layer graphene (SLG) grown by chemical vapor deposition (CVD) has been investigated for its prospective application as horizontal interconnects in very large scale integrated circuits. However, the major bottleneck for its successful application is its degraded electronic transport properties due to the resist residual trapped in the grain boundaries and on the surface of the polycrystalline CVD graphene during multi-step lithographic processes, leading to increase in its sheet resistance up to 5 MΩ/sq. To overcome this problem, current induced annealing has been employed, which helps to bring down the sheet resistance to 10 kΩ/sq (of the order of its initial value). Moreover, the maximum current density of ˜1.2 × 107 A/cm2 has been obtained for SLG (1 × 2.5 μm2) on SiO2/Si substrate, which is about an order higher than that of conventionally used copper interconnects.

  12. Phonon transport in single-layer M o1 -xWxS2 alloy embedded with W S2 nanodomains

    Science.gov (United States)

    Gu, Xiaokun; Yang, Ronggui

    2016-08-01

    Two-dimensional (2D) transition metal dichalcogenides have shown numerous interesting physical and chemical properties, making them promising materials for electronic, optoelectronic, and energy applications. Tuning thermal conductivity of 2D materials could expand their applicability in many of these fields. In this paper, we propose a strategy of using alloying and nanodomains to suppress the thermal conductivity of 2D materials. To predict the thermal conductivity of a 2D alloy embedded with nanodomains, we employ the Green's function approach to assess the phonon scattering strength due to alloying and nanodomain embedding. Our first-principles-driven phonon Boltzmann transport equation calculations show that the thermal conductivity of single-layer Mo S2 can be reduced to less than one-tenth of its intrinsic thermal conductivity after alloying with W and introducing nanodomains due to the strong scattering for both high- and low-frequency phonons. Strategies to further reduce thermal conductivity are also discussed.

  13. Effect of single layer centrifugation using Androcoll-E-Large on the sperm quality parameters of cooled-stored donkey semen doses.

    Science.gov (United States)

    Ortiz, I; Dorado, J; Ramírez, L; Morrell, J M; Acha, D; Urbano, M; Gálvez, M J; Carrasco, J J; Gómez-Arrones, V; Calero-Carretero, R; Hidalgo, M

    2014-02-01

    The aim of this study was to determine the effect of single layer centrifugation (SLC) using Androcoll-E-Large on donkey sperm quality parameters after 24 h of cool-storage. Ejaculates were collected from Andalusian donkeys and then cooled at 5°C. SLC was carried out after 24 h of cool-storage using Androcoll-E-Large. In the first experiment, all sperm parameters assessed (total and progressive sperm motility, viability, sperm morphology and sperm kinematics VCL, VSL, VAP, LIN, STR, WOB, ALH and BCF) were statistically compared between semen samples processed or not with Androcoll-E-Large. Significant differences (Pdonkeys, increasing the sperm quality of cooled-stored donkey semen doses after 24 h of cool storage.

  14. R&D for a single-layer $Nb_{3}Sn$ common coil dipole using the react-and-wind fabrication technique

    CERN Document Server

    Ambrosio, G; Barzi, E; Bauer, P; Chichili, D R; Ewald, K D; Fehér, S; Imbasciati, L; Kashikhin, V V; Limon, P J; Litvinenko, L; Novitski, I; Rey, J M; Scanlan, R M; Yadav, S; Yamada, R; Zlobin, A V

    2002-01-01

    A dipole magnet based on the common coil design, using prereacted Nb /sub 3/Sn superconductor, is under development at Fermilab, for a future Very Large Hadron Collider. This magnet has some innovative design and technological features such as single layer coils, a 22 mm wide 60-strand Rutherford type cable and stainless steel collars reinforced by horizontal bridges inserted between coil blocks. Both left and right coils are wound simultaneously into the collar structure and then impregnated with epoxy. In order to optimize the design and fabrication techniques an R&D program is underway. The production of cables with the required characteristics was shown possible. Collar laminations were produced, assembled and tested in order to check the effectiveness of the bridges and the validity of the mechanical design. A mechanical model consisting in a 165 mm long section of the magnet straight section was assembled and tested. This paper summarizes the status of the program, and reports the results of fabrica...

  15. Electro-optical response of polymer-dispersed liquid crystal single layers of large nematic droplets oriented by rubbed teflon nanolayers

    Science.gov (United States)

    Marinov, Y. G.; Hadjichristov, G. B.; Petrov, A. G.; Marino, S.; Versace, C.; Scaramuzza, N.

    2013-02-01

    The surface orienting effect of rubbed teflon nanolayers on the morphology and electro-optical (EO) response of polymer-dispersed liquid crystal (PDLC) single layers of large nematic droplets was studied experimentally. In PDLC composites of the nematic liquid crystal (LC) E7 and NOA65 polymer, single droplets of LC with diameters as larger as 10 μm were confined in layers with a thickness of 10 μm, and the nematic director field was efficiently modified by nanostructuring teflon rubbing of the glass plates of the PDLC cell. For layered PDLCs arranged and oriented in this way, the modulated EO response by the dielectric oscillations of the nematic director exhibits a selective amplitude-frequency modulation controllable by both temperature and voltage applied, and is simply related to the LC droplet size. That may be of practical interest for PDLC-based modulators operating in the infrasound frequency range.

  16. Lowering the Operational Voltage of Single-Layer Polymer Electroluminescent Devices by Using CuOx Modifying Indium-Tin Oxide Electrode

    Institute of Scientific and Technical Information of China (English)

    ZHOU Xin-ran; ZHAO Xin-wen; HU Wen-ping

    2007-01-01

    In this study it is demonstrated that oxygen-plasma-generated CuOx can enhance the holes injection from ITO anode into polymer layer in single-layer polymer EL devices. The possible reason for this enhancement is because the ITO anode modified with CuOx possesses much higher work function than pure ITO anode, which reduces the barrier for hole-injection and further lowers the operational voltage of the polymer EL devices. The work function shift is probable due to the oxygen-plasma-generated CuOx can store more releasable oxygen, and the releasable oxygen in turn changes the oxygen concentration just near ITO surface, which will shift the work function of ITO anode.

  17. Effects of plasmonic coupling and electrical current on persistent photoconductivity of single-layer graphene on pristine and silver-nanoparticle-coated SiO2/Si.

    Science.gov (United States)

    Liu, Chih-Yi; Liang, Kengchih; Chang, Chun-Cheng; Tzeng, Yonhua

    2012-09-24

    Effects and mechanisms of conductivity variation of chemically vapor deposited single-layer graphene covering silver nanoparticles on SiO(2)/Si are reported based on blue-light (405 nm) induced plasmonic coupling and electrical current induced annealing and desorption of surface adsorbates. With 1V applied voltage, photoconductivity is positive except a brief negative period when the graphene is first illuminated by light. At 10 mV applied voltage, negative photoconductivity persists for hours. In comparison, negative photoconductivity of graphene on pristine SiO(2)/Si persists for tens of hours. When the applied voltage is increased to 1V, it takes tens of hours of light illumination to change to positive photoconductivity.

  18. Aqueous oxidation reaction enabled layer-by-layer corrosion of semiconductor nanoplates into single-crystalline 2D nanocrystals with single layer accuracy and ionic surface capping.

    Science.gov (United States)

    Ji, Muwei; Xu, Meng; Zhang, Jun; Liu, Jiajia; Zhang, Jiatao

    2016-02-25

    A controllable aqueous oxidation reaction enabled layer-by-layer corrosion has been proposed to prepare high-quality two-dimensional (2D) semiconductor nanocrystals with single layer accuracy and well-retained hexagonal shapes. The appropriate oxidizing agent, such as H2O2, Fe(NO3)3, and HNO3, could not only corrode the layered-crystalline-structured Bi2Te3 nanoplates layer-by-layer to be a single quintuple layer, but also replace the organic barriers to be ionic ligands on the surface synergistically. AFM analysis was used to confirm the layer-by-layer exfoliation from the side to the center. Together with precise XRD, LRTEM and HRTEM characterizations, the controllable oxidation reaction enabled aqueous layer-by-layer corrosion mechanism has been studied.

  19. Relaxation along a fictitious field (RAFF and Z-spectroscopy using alternating-phase irradiation (ZAPI in permanent focal cerebral ischemia in rat.

    Directory of Open Access Journals (Sweden)

    Kimmo T Jokivarsi

    Full Text Available Cerebral ischemia alters the molecular dynamics and content of water in brain tissue, which is reflected in NMR relaxation, diffusion and magnetization transfer (MT parameters. In this study, the behavior of two new MRI contrasts, Relaxation Along a Fictitious Field (RAFF and Z-spectroscopy using Alternating-Phase Irradiation (ZAPI, were quantified together with conventional relaxation parameters (T1, T2 and T1ρ and MT ratios in acute cerebral ischemia in rat. The right middle cerebral artery was permanently occluded and quantitative MRI data was acquired sequentially for the above parameters for up to 6 hours. The following conclusions were drawn: 1 Time-dependent changes in RAFF and T1ρ relaxation are not coupled to those in MT. 2 RAFF relaxation evolves more like transverse, rather than longitudinal relaxation. 3 MT measured with ZAPI is less sensitive to ischemia than conventional MT. 4 ZAPI data suggest alterations in the T2 distribution of macromolecules in acute cerebral ischemia. It was shown that both RAFF and ZAPI provide complementary MRI information from acute ischemic brain tissue. The presented multiparametric MRI data may aid in the assessment of brain tissue status early in ischemic stroke.

  20. Single-Layer Wire Routing.

    Science.gov (United States)

    1987-08-01

    is an epimorphism (onto). Let /3 be a loop at 04 Section 2B Covering Spaces x0 ; we prove that [/#]p is in the image of i. by applying the deformation... epimorphism 0: 7r𔃻(Y, y) --- HI(Y). The kernel of this homomorphism is the commutator subgroup of 7r,(Y, y), which vanishes if 7r1 (Y, y) is abelian. Let y... regenerate the layout. This completes the proof that the compaction algorithm is correct. Optimizations of Algorithm C Both the time and space performance

  1. Circularly Polarized Antenna Array Fed by Air-Bridge Free CPW-Slotline Network

    Directory of Open Access Journals (Sweden)

    Yilin Liu

    2017-01-01

    Full Text Available A novel design of 1×2 and 2×2 circularly polarized (CP microstrip patch antenna arrays is presented in this paper. The two CP antenna arrays are fed by sequentially rotated coplanar waveguide (CPW to slotline networks and are processed on 1 mm thick single-layer FR4 substrates. Both of the two arrays are low-profile and lightweight. An air-bridge free CPW-slotline power splitter is appropriately designed to form the feeding networks and realize the two CP antenna arrays. The mechanism of circular polarization in this design is explained. The simulated and measured impedance bandwidths as well as the 3 dB axial ratio bandwidths and the radiation patterns of the two proposed antenna arrays are presented. This proposed design can be easily extended to form a larger plane array with good performance owing to its simple structure.

  2. Single-Layer Halide Perovskite Light-Emitting Diodes with Sub-Band Gap Turn-On Voltage and High Brightness.

    Science.gov (United States)

    Li, Junqiang; Shan, Xin; Bade, Sri Ganesh R; Geske, Thomas; Jiang, Qinglong; Yang, Xin; Yu, Zhibin

    2016-10-03

    Charge-carrier injection into an emissive semiconductor thin film can result in electroluminescence and is generally achieved by using a multilayer device structure, which requires an electron-injection layer (EIL) between the cathode and the emissive layer and a hole-injection layer (HIL) between the anode and the emissive layer. The recent advancement of halide perovskite semiconductors opens up a new path to electroluminescent devices with a greatly simplified device structure. We report cesium lead tribromide light-emitting diodes (LEDs) without the aid of an EIL or HIL. These so-called single-layer LEDs have exhibited a sub-band gap turn-on voltage. The devices obtained a brightness of 591 197 cd m(-2) at 4.8 V, with an external quantum efficiency of 5.7% and a power efficiency of 14.1 lm W(-1). Such an advancement demonstrates that very high efficiency of electron and hole injection can be obtained in perovskite LEDs even without using an EIL or HIL.

  3. Thermo-mechanical vibration of a single-layer graphene sheet and a single-walled carbon nanotube on a substrate

    Science.gov (United States)

    Ding, Dongqing; Yang, Zhaoyao; Dong, Shuhong; Yu, Peishi; Zhao, Junhua

    2017-03-01

    The thermo-mechanical vibration of a single-layer graphene sheet (SLGP) and a single-walled carbon nanotube (SWCNT) on a substrate is studied by using a nonlocal elastic plate model and two nonlocal elastic beam models (including Timoshenko-beam model and Euler-beam model) with quantum effects, respectively. The effect of the van der Waals (vdW) interactions between the SLGP (or the SWCNT) and the substrate on the vibration is obtained. Checking against our molecular dynamics simulations shows that the present models are reasonable. In particular, the radial vibration of the SWCNT on the substrate with quantum effects is further derived through the continuum shell model due to the different vdW forces on each point of the SWCNT circumference. The present models show that the normalized transverse frequency decreases and the normalized radial frequency increases with increasing SWCNT radius, respectively. The radial amplitude of the SWCNT (or the amplitude of the SLGP) nonlinearly increases and the transverse amplitude of the SWCNT linearly increases with increasing temperature for a given distance, respectively. The obtained analytical solution should be of great importance for understanding the thermo-mechanical vibration of nanoelectronic devices on a substrate.

  4. Effect of single-layer centrifugation or washing on frozen-thawed donkey semen quality: Do they have the same effect regardless of the quality of the sample?

    Science.gov (United States)

    Ortiz, I; Dorado, J; Morrell, J M; Crespo, F; Gosálvez, J; Gálvez, M J; Acha, D; Hidalgo, M

    2015-07-15

    The aims of this study were to determine the sperm quality of frozen-thawed donkey sperm samples after single-layer centrifugation (SLC) using Androcoll-E in comparison to sperm washing or no centrifugation and to determine if the effect on the sperm quality after SLC or sperm washing depends on the quality of the sample. Frozen-thawed sperm samples from Andalusian donkeys were divided into three aliquots, and they were processed using three different techniques after thawing: uncentrifuged diluted control (UDC), sperm washing (SW), and SLC. Afterward, sperm quality index was estimated by integrating all parameters (total and progressive sperm motility, membrane integrity, and DNA fragmentation) in a single value. The relationship between the sperm quality of thawed UDC samples and the effect on sperm parameters in SW and SLC-selected samples was assessed. Sperm quality index was significantly higher (P donkey spermatozoa using Androcoll-E-Small can be a suitable procedure for selecting frozen-thawed donkey sperm with better quality, in particular in those samples where an improvement in motility is needed.

  5. Highly-flexible, ultra-thin, and transparent single-layer graphene/silver composite electrodes for organic light emitting diodes

    Science.gov (United States)

    Li, Kun; Wang, Hu; Li, Huiying; Li, Ye; Jin, Guangyong; Gao, Lanlan; Marco, Mazzeo; Duan, Yu

    2017-08-01

    Transparent conductive electrode (TCE) platforms are required in many optoelectronic devices, including organic light emitting diodes (OLEDs). To date, indium tin oxide based electrodes are widely used in TCEs but they still have few limitations in term of achieving flexible OLEDs and display techniques. In this paper, highly-flexible and ultra-thin TCEs were fabricated for use in OLEDs by combining single-layer graphene (SLG) with thin silver layers of only several nanometers in thickness. The as-prepared SLG + Ag (8 nm) composite electrodes showed low sheet resistances of 8.5 Ω/□, high stability over 500 bending cycles, and 74% transmittance at 550 nm wavelength. Furthermore, SLG + Ag composite electrodes employed as anodes in OLEDs delivered turn-on voltages of 2.4 V, with luminance exceeding 1300 cd m-2 at only 5 V, and maximum luminance reaching up 40 000 cd m-2 at 9 V. Also, the devices could work normally under less than the 1 cm bending radius.

  6. Ultra-thin single-layer transparent geometrical phase gradient metasurface and its application to high-gain circularly-polarized lens antenna

    Science.gov (United States)

    Li, Tang-Jing; Liang, Jian-Gang; Li, Hai-Peng; Liu, Ya-Qiao

    2016-09-01

    A new method to design an ultra-thin high-gain circularly-polarized antenna system with high efficiency is proposed based on the geometrical phase gradient metasurface (GPGM). With an accuracy control of the transmission phase and also the high transmission amplitude, the GPGM is capable of manipulating an electromagnetic wave arbitrarily. A focusing transmission lens working at Ku band is well optimized with the F/D of 0.32. A good focusing effect is demonstrated clearly by theoretical calculation and electromagnetic simulation. For further application, an ultra-thin single-layer transmissive lens antenna based on the proposed focusing metasurface operating at 13 GHz is implemented and launched by an original patch antenna from the perspective of high integration, simple structure, and low cost. Numerical and experimental results coincide well, indicating the advantages of the antenna system, such as a high gain of 17.6 dB, the axis ratio better than 2 dB, a high aperture efficiency of 41%, and also a simple fabrication process based on the convenient print circuit board technology. The good performance of the proposed antenna indicates promising applications in portable communication systems. Project supported by the National Natural Science Foundation of China (Grant No. 61372034).

  7. Atomic Layer Deposition of Titanium Oxide on Single-Layer Graphene: An Atomic-Scale Study toward Understanding Nucleation and Growth

    Science.gov (United States)

    2017-01-01

    Controlled synthesis of a hybrid nanomaterial based on titanium oxide and single-layer graphene (SLG) using atomic layer deposition (ALD) is reported here. The morphology and crystallinity of the oxide layer on SLG can be tuned mainly with the deposition temperature, achieving either a uniform amorphous layer at 60 °C or ∼2 nm individual nanocrystals on the SLG at 200 °C after only 20 ALD cycles. A continuous and uniform amorphous layer formed on the SLG after 180 cycles at 60 °C can be converted to a polycrystalline layer containing domains of anatase TiO2 after a postdeposition annealing at 400 °C under vacuum. Using aberration-corrected transmission electron microscopy (AC-TEM), characterization of the structure and chemistry was performed on an atomic scale and provided insight into understanding the nucleation and growth. AC-TEM imaging and electron energy loss spectroscopy revealed that rocksalt TiO nanocrystals were occasionally formed at the early stage of nucleation after only 20 ALD cycles. Understanding and controlling nucleation and growth of the hybrid nanomaterial are crucial to achieving novel properties and enhanced performance for a wide range of applications that exploit the synergetic functionalities of the ensemble.

  8. A Complete Reporting of MCNP6 Validation Results for Electron Energy Deposition in Single-Layer Extended Media for Source Energies <= 1-MeV

    Energy Technology Data Exchange (ETDEWEB)

    Dixon, David A. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Hughes, Henry Grady [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-05-04

    In this paper, we expand on previous validation work by Dixon and Hughes. That is, we present a more complete suite of validation results with respect to to the well-known Lockwood energy deposition experiment. Lockwood et al. measured energy deposition in materials including beryllium, carbon, aluminum, iron, copper, molybdenum, tantalum, and uranium, for both single- and multi-layer 1-D geometries. Source configurations included mono-energetic, mono-directional electron beams with energies of 0.05-MeV, 0.1-MeV, 0.3- MeV, 0.5-MeV, and 1-MeV, in both normal and off-normal angles of incidence. These experiments are particularly valuable for validating electron transport codes, because they are closely represented by simulating pencil beams incident on 1-D semi-infinite slabs with and without material interfaces. Herein, we include total energy deposition and energy deposition profiles for the single-layer experiments reported by Lockwood et al. (a more complete multi-layer validation will follow in another report).

  9. Structural stability of single-layered LaNi4.25Al0.75 film and its electrochemical hydrogen-storage properties

    Institute of Scientific and Technical Information of China (English)

    WANG Zhongmin; Chi Ying Vanessa Li; ZHOU Huaiying; Sammy Lap Ip Chan; SHI Liu

    2006-01-01

    AB5-based hydrogen storage thin films (LaNi4.25Al0.75), deposited on Cu substrate by dc magnetron sputtering were investigated in this study. X-ray diffraction (XRD) revealed that the microstructure of the layer was in crystal form. SEM and AFM analyses proved that the film appeared to be rather rough with numerous randomly sized pores of approximately 15-40 in nm diameter. Structural stability of the film was examined by the combined analyses of DSC, XRD, and SEM, which indicated that this film maintained its structural stability below 500 K or so, and a network structure was ob served on the film after being heated at 700 K for 30 min. Electrochemical hydrogen-storage properties of the films were investigated by simulated battery tests. It was found that single-layered LaNi4.25Al0.75 film exhibited electrochemical hydrogen-storage properties similar to typical AB5 alloys in bulk, and the maximum discharge capacity of the film was about 220 mAh/g. After 20 charge/discharge cycles, small needle-shaped aluminium oxide was formed on some fractions of the film surface.

  10. Structure and Properties of Vacuum Arc Single-Layer and Multiperiod Two-Layer Nitride Coatings Based on Ti(Al:Si Layers

    Directory of Open Access Journals (Sweden)

    V.M. Beresnev

    2017-02-01

    Full Text Available The paper provides an analysis of impact of deposition conditions on structural and phase state and thermal stability of vacuum arc coatings based on Ti(Al:Si layers. We studied single-phase single-layer coatings, and multiperiod bilayer coatings with second phase nitride interlayers of one of the following three metals: Mo, Cr or Zr. It was established that hexagonal and cubic lattices may form in the coatings when transition to the cubic lattice occurs with Al content of about 25 at. %. Presence of second nanoscale (7-8 nm layers in bilayer multiperiod compositions, which consist of one nitride from CrNx, MoNx or ZrNx group, does not change the type of lattice in [Ti(Al:Si]Nx layers. Also, an fcc lattice with a strong or weak texture [111] forms in CrNx and ZrNx layers, while crystallites with hexagonal lattice form in MoNx layers. High-temperature annealing at 700 °С during 40 minutes leads to a significant (by 23 % or up to Н  47.56 GPa increase in microhardness of coating of the [Ti(Al]Nx/ZrNy system due to formation of a nano-size structure with an average size of crystallites of 3.6 nm in [Ti(Al]Nx layers, and 6.3 nm in ZrNx layers.

  11. Large scale atomistic simulation of single-layer graphene growth on Ni(111) surface: molecular dynamics simulation based on a new generation of carbon-metal potential.

    Science.gov (United States)

    Xu, Ziwei; Yan, Tianying; Liu, Guiwu; Qiao, Guanjun; Ding, Feng

    2016-01-14

    To explore the mechanism of graphene chemical vapor deposition (CVD) growth on a catalyst surface, a molecular dynamics (MD) simulation of carbon atom self-assembly on a Ni(111) surface based on a well-designed empirical reactive bond order potential was performed. We simulated single layer graphene with recorded size (up to 300 atoms per super-cell) and reasonably good quality by MD trajectories up to 15 ns. Detailed processes of graphene CVD growth, such as carbon atom dissolution and precipitation, formation of carbon chains of various lengths, polygons and small graphene domains were observed during the initial process of the MD simulation. The atomistic processes of typical defect healing, such as the transformation from a pentagon into a hexagon and from a pentagon-heptagon pair (5|7) to two adjacent hexagons (6|6), were revealed as well. The study also showed that higher temperature and longer annealing time are essential to form high quality graphene layers, which is in agreement with experimental reports and previous theoretical results.

  12. Photodiodes based in La0.7Sr0.3MnO3/single layer MoS2 hybrid vertical heterostructures

    Science.gov (United States)

    Niu, Yue; Frisenda, Riccardo; Svatek, Simon A.; Orfila, Gloria; Gallego, Fernando; Gant, Patricia; Agraït, Nicolás; Leon, Carlos; Rivera-Calzada, Alberto; Pérez De Lara, David; Santamaria, Jacobo; Castellanos-Gomez, Andres

    2017-09-01

    The fabrication of artificial materials by stacking of individual two-dimensional (2D) materials is amongst one of the most promising research avenues in the field of 2D materials. Moreover, this strategy to fabricate new man-made materials can be further extended by fabricating hybrid stacks between 2D materials and other functional materials with different dimensionality making the potential number of combinations almost infinite. Among all these possible combinations, mixing 2D materials with transition metal oxides can result especially useful because of the large amount of interesting physical phenomena displayed separately by these two material families. We present a hybrid device based on the stacking of a single layer MoS2 onto a lanthanum strontium manganite (La0.7Sr0.3MnO3) thin film, creating an atomically thin device. It shows a rectifying electrical transport with a ratio of 103, and a photovoltaic effect with V oc up to 0.4 V. The photodiode behaviour arises as a consequence of the different doping character of these two materials. This result paves the way towards combining the efforts of these two large materials science communities.

  13. Electronic properties of single-layer antimony: Tight-binding model, spin-orbit coupling, and the strength of effective Coulomb interactions

    Science.gov (United States)

    Rudenko, A. N.; Katsnelson, M. I.; Roldán, R.

    2017-02-01

    The electronic properties of single-layer antimony are studied by a combination of first-principles and tight-binding methods. The band structure obtained from relativistic density functional theory is used to derive an analytic tight-binding model that offers an efficient and accurate description of single-particle electronic states in a wide spectral region up to the mid-UV. The strong (λ =0.34 eV) intra-atomic spin-orbit interaction plays a fundamental role in the band structure, leading to splitting of the valence band edge and to a significant reduction of the effective mass of the hole carriers. To obtain an effective many-body model of two-dimensional Sb we calculate the screened Coulomb interaction and provide numerical values for the on-site V¯00 (Hubbard) and intersite V¯i j interactions. We find that the screening effects originate predominantly from the 5 p states, and are thus fully captured within the proposed tight-binding model. The leading kinetic and Coulomb energies are shown to be comparable in magnitude, | t01|/ (V¯00-V¯01) ˜1.6 , which suggests a strongly correlated character of 5 p electrons in Sb. The results presented here provide an essential step toward the understanding and rational description of a variety of electronic properties of this two-dimensional material.

  14. Current induced annealing and electrical characterization of single layer graphene grown by chemical vapor deposition for future interconnects in VLSI circuits

    Energy Technology Data Exchange (ETDEWEB)

    Prasad, Neetu, E-mail: neetu.prasad@south.du.ac.in, E-mail: neetu23686@gmail.com; Kumari, Anita; Bhatnagar, P. K.; Mathur, P. C. [Department of Electronic Science, University of Delhi South Campus, Benito Juarez Road, New Delhi 110021 (India); Bhatia, C. S. [Department of Electrical and Computer Engineering, National University of Singapore, Singapore 117576 (Singapore)

    2014-09-15

    Single layer graphene (SLG) grown by chemical vapor deposition (CVD) has been investigated for its prospective application as horizontal interconnects in very large scale integrated circuits. However, the major bottleneck for its successful application is its degraded electronic transport properties due to the resist residual trapped in the grain boundaries and on the surface of the polycrystalline CVD graphene during multi-step lithographic processes, leading to increase in its sheet resistance up to 5 MΩ/sq. To overcome this problem, current induced annealing has been employed, which helps to bring down the sheet resistance to 10 kΩ/sq (of the order of its initial value). Moreover, the maximum current density of ∼1.2 × 10{sup 7 }A/cm{sup 2} has been obtained for SLG (1 × 2.5 μm{sup 2}) on SiO{sub 2}/Si substrate, which is about an order higher than that of conventionally used copper interconnects.

  15. Angle-resolved photoemission spectroscopy on high-temperature superconductors. Studies of Bi2212 and single-layer FeSe film grown on SrTiO{sub 3} substrate

    Energy Technology Data Exchange (ETDEWEB)

    He, Junfeng [Chinese Academy of Sciences, Beijing (China). Inst. of Physics

    2016-07-01

    This book mainly focuses on the study of the high-temperature superconductor Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+δ} (Bi2212) and single-layer FeSe film grown on SrTiO{sub 3} (STO) substrate by means of angle-resolved photoemission spectroscopy (ARPES). It provides the first electronic evidence for the origin of the anomalous high-temperature superconductivity in single-layer FeSe grown on SrTiO{sub 3} substrate. Two coexisted sharp-mode couplings have been identified in superconducting Bi2212. The first ARPES study on single-layer FeSe/STO films has provided key insights into the electronic origin of superconductivity in this system. A phase diagram and electronic indication of high T{sub c} and insulator to superconductor crossover have been established in the single-layer FeSe/STO films. Readers will find essential information on the techniques used and interesting physical phenomena observed by ARPES.

  16. Improved Gate Dielectric Deposition and Enhanced Electrical Stability for Single-Layer MoS2 MOSFET with an AlN Interfacial Layer.

    Science.gov (United States)

    Qian, Qingkai; Li, Baikui; Hua, Mengyuan; Zhang, Zhaofu; Lan, Feifei; Xu, Yongkuan; Yan, Ruyue; Chen, Kevin J

    2016-01-01

    Transistors based on MoS2 and other TMDs have been widely studied. The dangling-bond free surface of MoS2 has made the deposition of high-quality high-k dielectrics on MoS2 a challenge. The resulted transistors often suffer from the threshold voltage instability induced by the high density traps near MoS2/dielectric interface or inside the gate dielectric, which is detrimental for the practical applications of MoS2 metal-oxide-semiconductor field-effect transistor (MOSFET). In this work, by using AlN deposited by plasma enhanced atomic layer deposition (PEALD) as an interfacial layer, top-gate dielectrics as thin as 6 nm for single-layer MoS2 transistors are demonstrated. The AlN interfacial layer not only promotes the conformal deposition of high-quality Al2O3 on the dangling-bond free MoS2, but also greatly enhances the electrical stability of the MoS2 transistors. Very small hysteresis (ΔVth) is observed even at large gate biases and high temperatures. The transistor also exhibits a low level of flicker noise, which clearly originates from the Hooge mobility fluctuation instead of the carrier number fluctuation. The observed superior electrical stability of MoS2 transistor is attributed to the low border trap density of the AlN interfacial layer, as well as the small gate leakage and high dielectric strength of AlN/Al2O3 dielectric stack.

  17. Amorphous Si{sub x}C{sub 1-x}:H single layers before and after thermal annealing: Correlating optical and structural properties

    Energy Technology Data Exchange (ETDEWEB)

    Hartel, Andreas M. [IMTEK, Faculty of Engineering, Albert-Ludwigs-University Freiburg, Georges-Koehler-Allee 103, 79110 Freiburg (Germany); Kuenle, M.; Loeper, P.; Janz, S.; Bett, A.W. [Fraunhofer Institute for Solar Energy Systems, Heidenhofstr. 2, 79110 Freiburg (Germany)

    2010-11-15

    Amorphous Si{sub x}C{sub 1-x}:H single layers with varying stoichiometry were prepared using plasma enhanced chemical vapour deposition (PECVD). The as-deposited layers were annealed at different temperatures (T{sub a}) from 500 to 1100 C. The influence of annealing on layers with varying composition x was investigated by a variety of analytical techniques including photoluminescence (PL) spectroscopy, reflectance and transmittance measurements, grazing incidence X-ray diffraction (GIXRD) and Fourier transform infrared spectrometry (FTIR). Before annealing, PL measurements show a shift of the spectra to higher energies with increase in carbon content. Calculations of the optical bandgap by other groups confirm this trend. The FTIR investigations show in addition to the expected Si-C bonds also the formation of oxygen and hydrogen related bonds within the layers. After annealing, solely a broad PL signal appears at energies around 2.0 eV. This might be due to luminescence of defects, created by the incorporated amount of carbon and the evolution of crystalline phases in the layers. GIXRD measurements confirmed the formation of both Si NCs after 700 C and SiC NCs after annealing at 1000 C. The FTIR spectra exhibit a shift of the SiC absorption band and an increase in the Si-C bond density due to the crystallization of SiC. After annealing a hydrogen passivation was performed, which leads to a strong decrease in the PL intensity. However, annealed Si-rich films show a peak around 1.2 eV after H-passivation, which might originate from quantum confinement effects in Si NCs. (author)

  18. Online, efficient and precision laser profiling of bronze-bonded diamond grinding wheels based on a single-layer deep-cutting intermittent feeding method

    Science.gov (United States)

    Deng, Hui; Chen, Genyu; He, Jie; Zhou, Cong; Du, Han; Wang, Yanyi

    2016-06-01

    In this study, an online, efficient and precision laser profiling approach that is based on a single-layer deep-cutting intermittent feeding method is described. The effects of the laser cutting depth and the track-overlap ratio of the laser cutting on the efficiency, precision and quality of laser profiling were investigated. Experiments on the online profiling of bronze-bonded diamond grinding wheels were performed using a pulsed fiber laser. The results demonstrate that an increase in the laser cutting depth caused an increase in the material removal efficiency during the laser profiling process. However, the maximum laser profiling efficiency was only achieved when the laser cutting depth was equivalent to the initial surface contour error of the grinding wheel. In addition, the selection of relatively high track-overlap ratios of laser cutting for the profiling of grinding wheels was beneficial with respect to the increase in the precision of laser profiling, whereas the efficiency and quality of the laser profiling were not affected by the change in the track-overlap ratio. After optimized process parameters were employed for online laser profiling, the circular run-out error and the parallelism error of the grinding wheel surface decreased from 83.1 μm and 324.6 μm to 11.3 μm and 3.5 μm, respectively. The surface contour precision of the grinding wheel significantly improved. The highest surface contour precision for grinding wheels of the same type that can be theoretically achieved after laser profiling is completely dependent on the peak power density of the laser. The higher the laser peak power density is, the higher the surface contour precision of the grinding wheel after profiling.

  19. Testování Fed modelu

    OpenAIRE

    Hříbalová, Pavlína

    2010-01-01

    Diploma Thesis focuses on Fed Model testing and its credibility on market data. The research is based on Gordon Model and Capital Asset Pricing Model (CAPM), it explains, what the basic features of the Fed Model are and describes its derivation from Gordon Model. The Thesis shows possible Fed Model limitation. It uses the US market, Great Britain and Germany 1979 -- 2011 data to demonstrate validity of the model. Eventually possible reasons of Fed Model development in period 2002 -- 2011 are ...

  20. An analytical solution for the estimation of the critical available soil water fraction for a single layer water balance model under growing crops

    Directory of Open Access Journals (Sweden)

    N. Brisson

    1998-01-01

    . The atmospheric demand together with the rooting depth appear as the most important factors. However, when assuming predictable climatic and crop evolution, compensation occurs between those two effects leading to a relative stability of F when the crop is fully developed. Though relying on well-known physical laws, the present approach remains in the framework of single layer models with the same limitations.

  1. Prototype pre-clinical PET scanner with depth-of-interaction measurements using single-layer crystal array and single-ended readout

    Science.gov (United States)

    Lee, Min Sun; Kim, Kyeong Yun; Ko, Guen Bae; Lee, Jae Sung

    2017-05-01

    In this study, we developed a proof-of-concept prototype PET system using a pair of depth-of-interaction (DOI) PET detectors based on the proposed DOI-encoding method and digital silicon photomultiplier (dSiPM). Our novel cost-effective DOI measurement method is based on a triangular-shaped reflector that requires only a single-layer pixelated crystal and single-ended signal readout. The DOI detector consisted of an 18  ×  18 array of unpolished LYSO crystal (1.47  ×  1.47  ×  15 mm3) wrapped with triangular-shaped reflectors. The DOI information was encoded by depth-dependent light distribution tailored by the reflector geometry and DOI correction was performed using four-step depth calibration data and maximum-likelihood (ML) estimation. The detector pair and the object were placed on two motorized rotation stages to demonstrate 12-block ring PET geometry with 11.15 cm diameter. Spatial resolution was measured and phantom and animal imaging studies were performed to investigate imaging performance. All images were reconstructed with and without the DOI correction to examine the impact of our DOI measurement. The pair of dSiPM-based DOI PET detectors showed good physical performances respectively: 2.82 and 3.09 peak-to-valley ratios, 14.30% and 18.95% energy resolution, and 4.28 and 4.24 mm DOI resolution averaged over all crystals and all depths. A sub-millimeter spatial resolution was achieved at the center of the field of view (FOV). After applying ML-based DOI correction, maximum 36.92% improvement was achieved in the radial spatial resolution and a uniform resolution was observed within 5 cm of transverse PET FOV. We successfully acquired phantom and animal images with improved spatial resolution and contrast by using the DOI measurement. The proposed DOI-encoding method was successfully demonstrated in the system level and exhibited good performance, showing its feasibility for animal PET applications with high spatial

  2. Strong visible and near infrared photoluminescence from ZnO nanorods/nanowires grown on single layer graphene studied using sub-band gap excitation

    Science.gov (United States)

    Biroju, Ravi K.; Giri, P. K.

    2017-07-01

    Fabrication and optoelectronic applications of graphene based hybrid 2D-1D semiconductor nanostructures have gained tremendous research interest in recent times. Herein, we present a systematic study on the origin and evolution of strong broad band visible and near infrared (NIR) photoluminescence (PL) from vertical ZnO nanorods (NRs) and nanowires (NWs) grown on single layer graphene using both above band gap and sub-band gap optical excitations. High resolution field emission scanning electron microscopy and X-ray diffraction studies are carried out to reveal the morphology and crystalline quality of as-grown and annealed ZnO NRs/NWs on graphene. Room temperature PL studies reveal that besides the UV and visible PL bands, a new near-infrared (NIR) PL emission band appears in the range between 815 nm and 886 nm (1.40-1.52 eV). X-ray photoelectron spectroscopy studies revealed excess oxygen content and unreacted metallic Zn in the as-grown ZnO nanostructures, owing to the low temperature growth by a physical vapor deposition method. Post-growth annealing at 700 °C in the Ar gas ambient results in the enhanced intensity of both visible and NIR PL bands. On the other hand, subsequent high vacuum annealing at 700 °C results in a drastic reduction in the visible PL band and complete suppression of the NIR PL band. PL decay dynamics of green emission in Ar annealed samples show tri-exponential decay on the nanosecond timescale including a very slow decay component (time constant ˜604.5 ns). Based on these results, the NIR PL band comprising two peaks centered at ˜820 nm and ˜860 nm is tentatively assigned to neutral and negatively charged oxygen interstitial (Oi) defects in ZnO, detected experimentally for the first time. The evidence for oxygen induced trap states on the ZnO NW surface is further substantiated by the slow photocurrent response of graphene-ZnO NRs/NWs. These results are important for tunable light emission, photodetection, and other cutting edge

  3. Corrosion Resistance Behavior of Single-Layer Cathodic Arc PVD Nitride-Base Coatings in 1M HCl and 3.5 pct NaCl Solutions

    Science.gov (United States)

    Adesina, Akeem Yusuf; Gasem, Zuhair M.; Madhan Kumar, Arumugam

    2017-04-01

    The electrochemical behavior of single-layer TiN, CrN, CrAlN, and TiAlN coatings on 304 stainless steel substrate, deposited using state-of-the-art and industrial size cathodic arc PVD machine, were evaluated in 1M HCl and 3.5 pct NaCl solutions. The corrosion behavior of the blank and coated substrates was analyzed by electrochemical impedance spectroscopy (EIS), linear polarization resistance, and potentiodynamic polarization. Bond-coat layers of pure-Ti, pure-Cr, alloyed-CrAl, and alloyed-TiAl for TiN, CrN, CrAlN, and TiAlN coatings were, respectively, first deposited for improved coating adhesion before the actual coating. The average coating thickness was about 1.80 µm. Results showed that the corrosion potentials ( E corr) of the coated substrates were shifted to more noble values which indicated improvement of the coated substrate resistance to corrosion susceptibility. The corrosion current densities were lower for all coated substrates as compared to the blank substrate. Similarly, EIS parameters showed that these coatings possessed improved resistance to defects and pores in similar solution compared to the same nitride coatings developed by magnetron sputtering. The charge transfer resistance ( R ct) can be ranked in the following order: TiAlN > CrN > TiN > CrAlN in both media except in NaCl solution where R ct of TiN is lowest. While the pore resistance ( R po) followed the order: CrAlN > CrN > TiAlN > TiN in HCl solution and TiAlN > CrN > CrAlN > TiN in NaCl solution. It is found that TiAlN coating has the highest protective efficiencies of 79 and 99 pct in 1M HCl and 3.5 pct NaCl, respectively. SEM analysis of the corroded substrates in both media was also presented.

  4. H{sup −} ion implantation induced ten-fold increase of photoluminescence efficiency in single layer InAs/GaAs quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Sreekumar, R.; Mandal, A. [Centre for Nanoelectronics, Department of Electrical Engineering, Indian Institute of Technology Bombay, Mumbai 400076, Maharashtra (India); Chakrabarti, S., E-mail: subho@ee.iitb.ac.in [Centre for Nanoelectronics, Department of Electrical Engineering, Indian Institute of Technology Bombay, Mumbai 400076, Maharashtra (India); Gupta, S.K. [Nuclear Physics Division, Bhabha Atomic Research Centre, Mumbai 400085, Maharashtra (India)

    2014-09-15

    We demonstrate a ten-fold increase in photoluminescence (PL) efficiency from 50 keV H{sup −} ion-implanted InAs/GaAs quantum dots (QDs) at a temperature of 8 K and/or 145 K. Enhancement occurred without post-annealing treatment. PL efficiency increased with increasing implantation fluence from 6×10{sup 12} ions/cm{sup 2} up to an optimum value of 2.4×10{sup 13} ions/cm{sup 2}, beyond which PL efficiency decreased drastically (up to a fluence of 2.4×10{sup 15} ions/cm{sup 2}). Passivation of non-radiative recombination centres (due to direct interaction of H{sup −} ions with lattice defects) and de-excitation of photo-generated carriers to QDs through quantum mechanical tunnelling via H{sup −} ion-induced defects (e-traps) that are created near the QD–cap layer interface, resulted in PL efficiency enhancement. Shallow e-traps with activation energy ∼90 meV and 30 meV created near the conduction band of GaAs cap layer for the samples implanted with H{sup −} of fluence 6×10{sup 12} and 2.4×10{sup 13} ions/cm{sup 2} respectively are identified using low temperature PL study. Contribution of de-trapped electrons from the e-traps to the QDs enhanced the PL efficiency at 145 K. Cross-section transmission electron microscopy and X-ray diffraction study revealed that the structural damage created by H{sup −} ions at the high fluence level of 2.4×10{sup 15} ions/cm{sup 2}, caused the degradation in PL efficiency. - Highlights: • Self-assembled single layer InAs/GaAs quantum dots. • Low energy hydrogen ion implantation. • PL efficiency enhancement for implanted samples. • Eradication of defects from dots and capping layers.

  5. Corrosion Resistance Behavior of Single-Layer Cathodic Arc PVD Nitride-Base Coatings in 1M HCl and 3.5 pct NaCl Solutions

    Science.gov (United States)

    Adesina, Akeem Yusuf; Gasem, Zuhair M.; Madhan Kumar, Arumugam

    2017-01-01

    The electrochemical behavior of single-layer TiN, CrN, CrAlN, and TiAlN coatings on 304 stainless steel substrate, deposited using state-of-the-art and industrial size cathodic arc PVD machine, were evaluated in 1M HCl and 3.5 pct NaCl solutions. The corrosion behavior of the blank and coated substrates was analyzed by electrochemical impedance spectroscopy (EIS), linear polarization resistance, and potentiodynamic polarization. Bond-coat layers of pure-Ti, pure-Cr, alloyed-CrAl, and alloyed-TiAl for TiN, CrN, CrAlN, and TiAlN coatings were, respectively, first deposited for improved coating adhesion before the actual coating. The average coating thickness was about 1.80 µm. Results showed that the corrosion potentials (E corr) of the coated substrates were shifted to more noble values which indicated improvement of the coated substrate resistance to corrosion susceptibility. The corrosion current densities were lower for all coated substrates as compared to the blank substrate. Similarly, EIS parameters showed that these coatings possessed improved resistance to defects and pores in similar solution compared to the same nitride coatings developed by magnetron sputtering. The charge transfer resistance (R ct) can be ranked in the following order: TiAlN > CrN > TiN > CrAlN in both media except in NaCl solution where R ct of TiN is lowest. While the pore resistance (R po) followed the order: CrAlN > CrN > TiAlN > TiN in HCl solution and TiAlN > CrN > CrAlN > TiN in NaCl solution. It is found that TiAlN coating has the highest protective efficiencies of 79 and 99 pct in 1M HCl and 3.5 pct NaCl, respectively. SEM analysis of the corroded substrates in both media was also presented.

  6. FED baseline engineering studies report

    Energy Technology Data Exchange (ETDEWEB)

    Sager, P.H.

    1983-04-01

    Studies were carried out on the FED Baseline to improve design definition, establish feasibility, and reduce cost. Emphasis was placed on cost reduction, but significant feasibility concerns existed in several areas, and better design definition was required to establish feasibility and provide a better basis for cost estimates. Design definition and feasibility studies included the development of a labyrinth shield ring concept to prevent radiation streaming between the torus spool and the TF coil cryostat. The labyrinth shield concept which was developed reduced radiation streaming sufficiently to permit contact maintenance of the inboard EF coils. Various concepts of preventing arcing between adjacent shield sectors were also explored. It was concluded that installation of copper straps with molybdenum thermal radiation shields would provide the most reliable means of preventing arcing. Other design studies included torus spool electrical/structural concepts, test module shielding, torus seismic response, poloidal conditions in the magnets, disruption characteristics, and eddy current effects. These additional studies had no significant impact on cost but did confirm the feasibility of the basic FED Baseline concept.

  7. Seismic parameters of single-layer buckling-restrained braced frame%单层屈曲约束支撑框架的抗震参数

    Institute of Scientific and Technical Information of China (English)

    冯玉龙; 吴京; 孟少平; 付康

    2015-01-01

    To provide the design reference for the frame structure with buckling-restrained brace ( BRB) , the seismic parameters of the single-layer buckling-restrained braced frame ( BRBF) struc-ture are studied.By lateral displacement analysis, three key parameters characterizing the structural force and deformation, the BRB-to-frame stiffness ratio, the BRB-to-frame yield strength ratio and the beam-to-column line stiffness ratio, are derived.By taking the maximum displacement and the residual displacement under the specific ground motion as the evaluation indexes, parametric analyses are carried out.The analysis results show that when the BRB-to-frame stiffness ratio and the beam-to-column line stiffness ratio are small, both kinds of displacements decrease with the increase of the ratios.The BRB-to-frame yield strength ratio influences greatly on the structural yield displacement and mechanism.The reasonable values of the BRB-to-frame stiffness ratio, the BRB-to-frame yield strength ratio and the beam-to-column line stiffness ratio are 2, 0.7 and 0.45~5.00, respectively. Base on these reasonable values, two examples are designed and the corresponding seismic perform-ance is analyzed.The results show that the BRB-beam-column yield mechanism is formed in the structures.After the BRB yields, the ratio of the shear forces of the frame increases gradually.The layout principle of BRB has almost no obvious influence on the roof displacement response, but af-fects significantly the axial force of the adjacent columns.%为了给屈曲约束支撑框架设计提供参考,对单层屈曲约束支撑框架的抗震参数进行了研究.通过结构侧移分析,推导出表征该结构体系受力和变形特性的3个关键参数:支撑框架刚度比、支撑框架屈服强度比和梁柱线刚度比.以特定地震动下结构最大位移和残余位移作为评价指标,对结构进行了参数化分析.分析结果表明:当支撑框架刚度比和梁柱线刚

  8. 考虑地震损伤的单层球面网壳结构静力稳定性%Static Stability of Single-layer Latticed Shells Considering Damage Due to Earthquake

    Institute of Scientific and Technical Information of China (English)

    李永梅; 胡琨; 张微敬; 李运运

    2015-01-01

    To study the effect on the static performance of single-layer latticed shells under earthquake damage, based on the material constructive relationship considering damage cumulative effect, the dynamic stable analysis is first carried out for a K8 type and single-layer latticed shell through the incremental dynamic analysis ( IDA) method, in which B-R kinetic criterion in combination with plastic strain energy density is put forward as the criterion for judging dynamic instability of single-layer latticed shells, from which the dynamic critical load value can be derived. Then, nonlinear buckling analysis by the arc-length method combined with Newton-Raphson method is done to the damaged structure due to earthquake, from which the static critical load value can be derived. Results show that the reduction to the structural static stable ability will be obvious after considering damage accumulation effect for single-layer latticed shells, which can be a reference for the structural seismic design, performance assessment, and engineering repair or reinforcement after earthquake.%为了研究地震损伤对单层网壳结构静力稳定性能的影响,基于考虑材料损伤累积效应的本构模型,对一K8型单层球面网壳结构,首先利用动态增量( incremental dynamic analysis,IDA)方法对单层网壳结构进行动力稳定分析,提出将B-R准则与塑性应变能曲线相结合作为结构动力失稳破坏的判断准则,得到结构动力失稳临界值;然后采用弧长法和Newton-Raphson法相结合的增量迭代法对损伤后的结构进行非线性屈曲分析,得到震后结构的静力稳定临界荷载。结果表明:考虑地震损伤累积效应的结构静力稳定性能显著降低,为该类结构抗震设计、性能评估和震后修复、加固提供参考。

  9. A Comparative Study on the Optical Properties of Multilayer CdSe / CdTe Thin Film with Single Layer CdTe and CdSe Films

    Directory of Open Access Journals (Sweden)

    M. Melvin David Kumar

    2013-07-01

    Full Text Available CdTe and CdSe single layer thin films and CdSe / CdTe multilayer (ML thin film were prepared by using physical vapour deposition method. Optical properties of CdSe / CdTe multilayer thin film shows different behavior due to type II band structure alignment. Energy band gap value of CdSe / CdTe ML thin film is shifted to higher value than that of single layer CdTe film. This is due to decrease in crystallite size to dimension smaller than the Bohr exciton radius of CdTe (14 nm. Crystallite size of the multilayer sample was calculated with the predictions of the effective mass approximation model (i.e., Brus model. It is observed that the photoluminescence peak of CdSe / CdTe ML thin film is red shifted compared to the peaks corresponding to individual CdSe and CdTe thin films. This may be due to the presence of type II quantum dot formation in the CdSe / CdTe heterostructure multilayer thin film.

  10. End-on extramucosal single layer suture with double anchoring in the submucosa on rabbits SUTURA EM PLANO ÚNICO EXTRAMUCOSO COM ANCORAMENTO DUPLO DE SUBMUCOSA EM COELHOS

    Directory of Open Access Journals (Sweden)

    Luiz Roberto do Nascimento

    1999-04-01

    Full Text Available The techniques of gastrointestinal surgical sutures have been frequently focused in controversial publications. These ones concern not only anastomosis’ types but also about thread types and how to apply them. The values of the submucosa as layer of greatest resistence of the digestive tube was already known since the past century. The aim of this study is to avaluate the suture in an extramucosal single-layer suture with double anchoring of the submucosa, a technical detail not found in the searched literature. This experiment was carried out using 36 white,male adults New Zealand, rabbits divided into three groups which differed only regarding day of re-operation and euthanasia, as followed: group I ( 4 days, group II (7 days and group III ( 15 days. Two transversal and parallel gastrotomies were perfomed in the same animal, one distal and other proximal, of with 4 cm extension each. In these gastrotomies two types of sutures were alternated : 1- End-on extramucosal single-layer suture and 2- End-on extramucosal single-layer suture, with double anchoring in the submucosa. Macroscopic and microscopic studies were perfomed on the suture line in both gastrotomies and in each period of euthanasia. Except for the serosa item whose results were similar for both sutures, statiscally, the extramucosal single-layer suture, with double anchoring of submucosa layer showed better macro and microscopic results than the extramucosal single-layer suture in group I (4 days. In the others periods of euthanasia (groups II and III, the statistical results were similar.As técnicas de sutura gastrointestinais sempre foram motivo de estudos e controvérsias na literatura. As divergências dizem respeito não só aos tipos de anastomose, mas também aos tipos de fios e ao modo de aplicá-los. Desde o século passado o valor da submucosa como camada de maior resistência das túnicas do tubo digestivo já era conhecida. O propósito desse trabalho é avaliar a

  11. 不同肠管吻合方式对吻合口愈合的影响%Comparison of single-layer anastomosis and double-layer anastomosis of small intestine in dogs

    Institute of Scientific and Technical Information of China (English)

    沈凯; 周刚; 叶颖江; 梁斌

    2012-01-01

    目的 观察不同吻合方法对犬小肠手术后吻合口愈合的影响,探讨其有效性及安全性.方法 成年犬12条,根据吻合部位不同随机分为A、B2组,A组距离屈式韧带100 cm小肠采用双层吻合,距离屈式韧带200 cm小肠采用单层吻合;B组反之.术中记录2种吻合方式的操作时间.术后7d再次手术,找到吻合口并评价吻合口周围粘连分级,测量吻合破裂压(ABP)、小肠浆肌层破裂压.结果 单层吻合与双层吻合后局部粘连分级末见明显差异;单层吻合与双层吻合的ABP分别为(325.83±88.03)和(331.25±70.33) cmH2O(1 cm H2O=0.098 kPa,P>0.05);单层吻合与双层吻合的浆肌层破裂压分别为(185.42±40.87)和(182.08±20.72) cm H2O(P>0.05);单层吻合和双层吻合时间分别为(17.08±3.20)和(23.50±2.50) min(P <0.01).结论 单层吻合法是一种安全、有效的小肠吻合方法.%Objective To evaluate the effectiveness and safety of single-layer anastomosis and double-layer anastomosis of small intestine.Methods Twelve dogs were divided into two groups:group A ( single-layer anastomosis at small intestine 100 cm after Treitz ligament and double-layer anastomosis at small intestine 200 cm after Treitz ligament,n =6) ; group B (double-layer anastomosis at small intestine 100 cm after Treitz ligament and single-layer anastomosis at small intestine 200 cm after Treitz ligament,n =6).The time used for each anastomosis were recorded.The second operations were performed on postoperative day 7 on all the dogs to determine in situ anastomostic bursting pressures (ABP) and the pressures while the serosa layer was tom.Results No anastomosis leak was found in twenty-four stoma of the twelve dogs.There was no significant difference between the stoma created by single-layer anastomosis and double-layer anastomosis on intraperitoneal adhesions.The averaged ABP in the single-layer anastomosis group and the double-layer anastomosis group was (325.83 ± 88

  12. 某钢筋混凝土粮食平房仓抗震设计中的问题及处理建议%Seismic Design Questions and Treatment Suggestion of A Reinforced Concrete Single-layer Grain Storehouses

    Institute of Scientific and Technical Information of China (English)

    张敬书; 司伟龙; 冯立平; 金德保; 姚远

    2012-01-01

    “200亿斤国家粮食储备库平房仓通用施工图-24m跨预应力钢筋混凝土折线形屋架平房仓”存在山墙承重、砌体围护墙嵌砌在排架柱间、未设柱间支撑等对结构抗震不利的问题.本文从抗震概念设计的原理出发,将该平房仓与传统单层排架厂房进行了对比,分析了粮食荷载对上部结构、地基基础设计的影响,指出了该平房仓存在的抗震问题.最后有针对性的提出了改变储粮方式和围护墙的位置、采用钢筋混凝土墙板和钢结构门式刚架体系等实用设计建议.%There are several problems in "the standard drawing of the 100 - billion-kilogram national grain reserve warehouse-the single-layer grain storehouse adopting 24 meter span prestressed concrete broken-line roof truss" , e. g. gable borne, the enclosure wall masonryed in the middle of bent frame column, no column bracings set etc. These problems may have negative effect on seismic of grain storehouse. In the paper, trational single-layer bent factory buildings and single-layer grain storehouses are compared, the effect of grain load on the design of structure and foundation is analyzed, seismic problems existing in storehouse are pointed out according to the seismic conceptual design theory. At last, several design suggestions are presented, e. g. changing the position of enclosure wall and the grain storage way of grain, adopting reinforce concrete enclosure wallboard and steel portal frame etc.

  13. Transcriptomic profiling of spleen in grass-fed and grain-fed Angus cattle

    Science.gov (United States)

    The grass-fed cattle obtain nutrients directly from pastures containing limited assimilable energy but abundant amount of fiber; by contrast, grain-fed steers receive a diet that is comprised mainly of grains and serves as an efficient source of high-digestible energy. Besides energy, these two type...

  14. Relationship of Breast-fed and Bottle-fed First Grade Students and I.Q.

    Science.gov (United States)

    Humphrey, Danette

    Previous studies have indicated some support for the hypothesis that breast feeding has a positive effect on intelligence and attainment among young children. This study examined the effects of breast-feeding versus bottle-feeding on the intelligence quotients (IQs) of first graders. A total of 26 breast-fed and 26 bottle-fed first graders from an…

  15. Dynamic stability of single-layer reticulated shell structures subjected to impact loads%冲击荷载作用下单层网壳结构动力稳定性研究

    Institute of Scientific and Technical Information of China (English)

    马肖彤; 王秀丽

    2015-01-01

    针对冲击荷载不同于地震作用,而常规动力稳定性判定准则不适用问题,阐述求解冲击问题的基本理论及冲击荷载取值;据冲击荷载特性提出适合冲击碰撞问题的单层网壳结构动力稳定性判定准则;选 K6型单层网壳结构模型,利用非线性有限元软件 ANSYS /LS -DYNA 进行结构冲击作用下动力稳定性分析,通过大量算例,分析其在不同冲击物质量比及速度作用下全过程动力响应,结合动力响应模式获得冲击荷载作用下单层网壳动力失稳的临界能量区域,并从矢跨比、跨度、杆件截面三方面对结构进行参数分析。结果表明,基于网壳动力响应模式与冲击能量相结合方法对单层网壳进行动力稳定性判定合理;结构刚度越小,冲击作用下动力稳定性越差;加大主肋利于提高结构动力稳定性。%Unlike for the case of seismic action,the conventional dynamic stability criteria are no longer applicable for the case of impact load.The basic theory of solving the impact problem and the problem of how to take resonably the value of impact load were expounded.According to the impact load characteristics,the dynamic stability criterion suitable for impact collision problem of single-layer reticulated shell structure was proposed.Taking a K6 single-layer reticulated shell model as an object,the dynamic stability analysis under impact was carried out by using the nonlinear finite element software ANSYS /LS-DYNA.The whole process of dynamic response under the action of different quality and speed of impact loads was analyzed.The critical energy region of dynamic instability of the single-layer reticulated shell under impact loads was obtained based on the dynamic response model.The dynamic stability under earthquake was also analysed in order to get the instability critical load which was then compared with that under impact action.From the aspects of rise-span ratio

  16. X-ray study of the charge-density-wave transition in single-layer TiSe2

    Energy Technology Data Exchange (ETDEWEB)

    Fang, Xin-Yue; Hong, Hawoong; Chen, Peng; Chiang, T. -C.

    2017-05-01

    Synchrotron x-ray studies of single-layer TiSe2 reveal displacements of the Ti and Se atoms as a function of temperature. The measurements, with a high sensitivity of 0.001 Å, show a (2x2) charge density wave (CDW) structure at temperatures below a critical temperature of TC1 = 233 K. The temperature dependence follows a BCS-like second-order mean-field behavior. A fivelayer TiSe2 film also exhibits a CDW transition of the same character but at a lower transition temperature of TC5 = 204 K, which is the same as that for bulk TiSe2. The results demonstrate that lattice distortion is an integral part of the CDW transition that must also involve renormalization of the electronic structure.

  17. Dynamic instability of a single-layer cylindrical reticulated shell under wind loads%风荷载下单层柱面网壳的动力稳定

    Institute of Scientific and Technical Information of China (English)

    黄友钦; 顾明

    2011-01-01

    A single-layer cylindrical reticulated shell was taken as an example to study the dynamic instability of spatial structures with Budiansky-Roth criterion. Budiansky-Roth criterion was explained, and the wind tunnel test of the single-layer cylindrical reticulated shell was conducted to obtain fluctuating wind loads on it. Then, its dynamic instability under fluctuating wind loads was studied, the influences of initial geometrical imperfections, wind direction anagles and wind pressure coefficients were discussed, comparisons among the stability analysis results and those using the Chinese standard and the gust response factor (GRF) method were made. The results showed that studying on the dynamic instability of spatial structures under fluctuating wind loads is necessary.%以一单层柱面网壳为例,利用Budiansky-Roth准则研究空间结构在风荷载下的动力稳定性.介绍了Budiansky-Roth准则,通过风洞试验获得单层柱面网壳上的风荷载并研究其动力稳定性,讨论了初始几何缺陷、风向角和风压系数的影响,并将动力失稳分析结果与我国规范和阵风响应因子法(GRF法)计算动力响应导致结构破坏的方法作了比较.研究结果表明,空间结构进行风荷载下的稳定性设计时有必要研究其在风荷载下的动力稳定性.

  18. Proceedings of FED remote maintenance equipment workshop

    Energy Technology Data Exchange (ETDEWEB)

    Sager, P.; Garin, J.; Hager, E.R.; Spampinato, P.T.; Tobias, D.; Young, N.

    1981-11-01

    A workshop was convened in two sessions in January and March 1981, on the remote maintenance equipment for the Fusion Engineering Device (FED). The objectives of the first session were to familiarize the participants with the status of the design of the FED and to develop a remote maintenance equipment list for the FED. The objective of the second session was to have the participants present design concepts for the equipment which had been identified in the first session. The equipment list was developed for general purpose and special purpose equipment. The general purpose equipment was categorized as manipulators and other, while the special purpose equipment was subdivided according to the reactor subsystem it serviced: electrical, magnetic, and nuclear. Both mobile and fixed base manipulators were identified. Handling machines were identified as the major requirement for special purpose equipment.

  19. FedEX Sponsors China's Badminton Team

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The reigning world champion team joins hands with the express delivery service to greet the coming Olympics Starting this year, Olympic badminton champion Zhang Ning and world badminton champion Lin Dan will be wearing clothing with the FedEx logo on it.

  20. Wideband electromagnetically coupled coaxial probe fed slot ...

    African Journals Online (AJOL)

    user

    ... and low gain that limits its application in practice (Bahl et al, 1980 and Balanis, ... distribution in upper and lower patches at both the resonance frequencies is .... The equivalent circuit of rectangular patch stacked with U-slot loaded fed patch ...

  1. Supervision of Fed-Batch Fermentations

    DEFF Research Database (Denmark)

    Gregersen, Lars; Jørgensen, Sten Bay

    1999-01-01

    Process faults may be detected on-line using existing measurements based upon modelling that is entirely data driven. A multivariate statistical model is developed and used for fault diagnosis of an industrial fed-batch fermentation process. Data from several (25) batches are used to develop a mo...

  2. Transverse abdominal incision sutured by single layer extraperitoneal suture for purulent appendicitis during gestational period%横切口腹膜外单层缝合用于妊娠期化脓性阑尾炎治疗

    Institute of Scientific and Technical Information of China (English)

    薛玉珍; 吕会增; 陈图锋; 郑宗珩; 周如建

    2011-01-01

    目的 探讨横切口腹膜外单层缝合法应用于妊娠期化脓性阑尾炎的临床效果.方法 2006年1月至2010年11月3所大学附属医院收治129例妊娠期化脓阑尾炎患者,分为2组,观察组68例采用横切口腹膜外单层缝合法行阑尾切除术,对照组61例常规麦氏切口(或横切口)分层缝合法行阑尾切除术,对2组患者的手术时间、术后疼痛程度、术后流产或早产率、术后切口感染率、术后住院时间等指标进行观察比较.结果 观察组与对照组术后流产或早产率比较差别无统计学意义(P>0.05).观察组可明显减少手术时间(P<0.01),降低患者术后切口疼痛、切口感染率及术后住院时间(P<0.01).2组患者在住院治疗期间均未发生切口出血、切口疝、肠粘连、肠梗阻等并发症.结论 横切口腹膜外单层缝合法在妊娠期化脓性阑尾炎切除术中具有操作简单、安全、并发症少等优点,值得推广.%Objective To investigate the clinical effect of transverse abdominal incision sutured by single layer extrap eritoneal suture for purulent appendicitis during gestational period. Methods During January 2006 to November 2010 , 129 pa tients with suppurative appendicitis from three universities ' affiliated hospital were divided into observation group and control group. Sixty-eight patients in observation group were taken transverse incision sutured by single layer extraperitoneal suture af ter appendectomy. Sixty-one patients in control group were taken McBumeys' incision ( or transverse incision) sutured by multi-layer extraperitoneal suture for the appendectomy. The operating time, the degree of postoperative pain, the abortion or premature birth rate, the incision infection rate and the length of hospitalization of patients between observation group and con trol group were compared. Results There were no statisitic significance of the abortion or premature birth rate between obser vatioin group and control

  3. Dynamic Responses of Single-Layer Spherical Steel Reticulated Shell Under Internal Explosions%单层球面钢网壳结构在内爆炸作用下的动力响应

    Institute of Scientific and Technical Information of China (English)

    高轩能; 李超; 江媛

    2015-01-01

    采用LS-DYNA程序建立了单层球面钢网壳的内爆炸数值模拟计算模型。应用所建模型,对单层球面钢网壳在内爆炸作用下的动力响应进行了数值模拟计算,分析讨论了炸药 TNT 量、矢跨比和爆炸点位置等参数变化对结构动力响应的影响。结果表明,在内爆炸作用下,单层球壳结构的最大位移和最大应力响应随 TNT 量的增加而增大,最大应力响应的增幅小于最大位移;最大位移和最大应力响应随矢跨比的增大呈非线性减小,矢跨比大、跨度小的结构防(抗)爆炸波的能力较强。数值结果还揭示,邻近结构支座1/4跨度范围内的偏心爆炸对结构最为不利,进行防爆和抗爆设计时,应按偏心爆炸效应选取设计控制参数。%A numerical calculation model for simulating the internal explosions in the single-layer spherical steel re-ticulated shell was established by using LS-DYNA. Based on the model,the numerical simulation and calculation of dynamic responses of the single-layer spherical steel reticulated shell were carried out under internal explosions,and the influences of the TNT equivalence of dynamite,the rise-to-span ratio and the position of explosions on the dy-namic responses of the spherical steel reticulated shell wereanalyzed and discussed. The results showed that the maximum displacement and stress responses of the single-layer spherical steel reticulated shell under the internal ex-plosions increase with increasing TNT equivalence of dynamite,but the increasing rate of the maximum stress re-sponse is less than that of the maximum displacement response. The maximum displacement and stress responses of the shell decrease nonlinearly with the increase of the rise-to-span ratio,and the bigger the rise-to-span ratio and the smaller the span of the shell,the stronger the capacity of resistance to(anti-)explosive shock waves. The numerical results also revealed that the eccentric

  4. Higher lipid accumulation in broilers fed on saturated fats than in those fed on unsaturated fats.

    Science.gov (United States)

    Sanz, M; Flores, A; De Ayala, P P; Lopez-Bote, C J

    1999-03-01

    1. Two experiments were conducted to assess the effect of fat sources differing in degree of saturation on the performance of and fat deposition in broiler chickens fed on isocaloric and isonitrogenous diets. 2. There were no differences in initial body weight between sexes but female broilers had lower daily gains (Psaturation. Broilers fed on diets containing an animal fat blend or tallow had higher abdominal fat pad weight (Psaturation affects fat accumulation in broiler chickens.

  5. Sutura intestinal monoplano extramucosa, discontinua, a bordes invertidos: Su aplicación en 22 años Discontinuos extramucosal single layer intestinal suture on reversed edges: Application of this technique for 22 years

    Directory of Open Access Journals (Sweden)

    José Miguel Pérez Morales

    2007-06-01

    Full Text Available Durante el período de enero de 1982 a diciembre del 2004 se aplicó la sutura intestinal monoplano extramucosa, discontinua y a bordes invertidos (SIMEDI en 580 pacientes con 25 enfermedades del tubo digestivo. El estudio fue prospectivo, analítico y descriptivo. La técnica se aplicó 703 veces porque hubo pacientes con más de una sutura y se empleó solamente en segmentos intestinales con serosa. Se realizaron 463 anastomosis, 171 enterorrafias y 69 cierres de un extremo intestinal. Se operaron 373 pacientes de forma programada y 207 pacientes, de urgencia. Hubo 85 pacientes que presentaron complicaciones, 13 de las cuales eran dependientes de la técnica y 72, no dependientes de ella. Las complicaciones dependientes fueron 12 dehiscencias de suturas y 1 estenosis. La combinación anastomótica término-lateral más latero-lateral y cierre de un extremo intestinal fue la que más complicaciones presentó. La neoplasia maligna gástrica y de colon derecho fueron las enfermedades con más complicaciones dependientes. Se ahorró material de sutura. La SIMEDI constituye una buena opción en la cirugía del tubo digestivosummary In the period from January 1982 to December 2004, discontinuos extramucosal single layer intestinal suture on reversed edges was performed in 580 patients who had presented with 25 diseases of the digestive tract. A prospective, analytical and descriptive study was conducted. The technique was applied 703 times because there were patients with more than one suture and it was used only in intestinal segments with serose. Four hundred and sixty three anastomoses, 171 enterorrhaphies and 69 closures of an intestinal end were performed. Three hundred and seventy three patients were scheduled to be operated on whereas 207 patients were operated on due to emergency situation. There were 85 patients who developed complications, 13 had surgical technique-depending complications and 72 did not. Depending complications covered 12

  6. Performance of broiler fed pure glycerine

    Directory of Open Access Journals (Sweden)

    Dássia Daiane Oliveira

    2014-02-01

    Full Text Available Two experiments evaluated the pure glycerin in broiler chicken diets. Experiment 1 was a metabolism test using total feces sampling method with 96 male chickens aging from 17 to 25 d when animals were fed on two treatments: diet1 = no glycerin and diet2 = 60g/kg of glycerin. The apparent metabolized energy measured 4015 kcal/kg and the apparent metabolized corrected for nitrogen balance was 3911 kcal/kg. Experiment 2 evaluated weight gains, feed intake and feed conversion in 480 chicks at 6, 20 and 34 d old fed on diets with 0, 40, 80 and 120 g/kg of glycerin. The results indicate that pure glycerin in chicken diets, as a source of energy must take into consideration the age of the animals and it may be added up to 120 g/kg, from 20 to 41 d of age.

  7. A Study of End-Fed Arrays

    CERN Document Server

    Kondylis, Konstantinos; Zimourtopoulos, Petros

    2010-01-01

    This paper presents a general analysis of end-fed space arrays with application to self-standing linear arrays of parallel dipoles. A number of test array models were simulated, constructed and their radiation pattern was then measured. The experimental and computational results were found to be in good agreement. The developed software applications are available through the Internet as FLOSS Free Libre Open Source Software.

  8. Harmonic analysis of Doubly Fed Induction Generators

    DEFF Research Database (Denmark)

    Lindholm, Morten; Rasmussen, Tonny Wederberg

    2003-01-01

    This paper gives an overview of the frequency spectrum of the stator and rotor currents in a doubly fed induction generator (DFIG) used in wind power applications. The paper also presents a method to eliminate higher harmonics and interharmonics in the DFIG stator current. The method is implemented...... on a 40 kW laboratory model connected to the utility-grid, where the DFIG is supplied by a back-to-back 3-level NPC-converter....

  9. Stallion spermatozoa selected by single layer centrifugation are capable of fertilization after storage for up to 96 h at 6°C prior to artificial insemination

    Directory of Open Access Journals (Sweden)

    Lindahl Johanna

    2012-07-01

    Full Text Available Abstract Background One of the challenges faced by equine breeders is ensuring delivery of good quality semen doses for artificial insemination when the mare is due to ovulate. Single Layer Centrifugation (SLC has been shown to select morphologically normal spermatozoa with intact chromatin and good progressive motility from the rest of the ejaculate, and to prolong the life of these selected spermatozoa in vitro. The objective of the present study was a proof of concept, to determine whether fertilizing ability was retained in SLC-selected spermatozoa during prolonged storage. Findings Sixteen mares were inseminated with SLC-selected sperm doses that had been cooled and stored at 6°C for 48 h, 72 h or 96 h. Embryos were identified in 11 mares by ultrasound examination 16–18 days after presumed ovulation. Conclusion SLC-selected stallion spermatozoa stored for up to 96 h are capable of fertilization.

  10. Growth of Cu2ZnSnSe4 thin films by selenization of sputtered single-layered Cu-Zn-Sn metallic precursors from a Cu-Zn-Sn alloy target

    Science.gov (United States)

    Kim, Kyoo-Ho; Amal, Ikhlasul

    2011-09-01

    Cu2ZnSnSe4 (CZTSe) thin films were prepared by the simple process of selenization of single-layered metallic Cu-Zn-Sn precursors. These metallic precursors were deposited by radio frequency magnetron sputtering of a ternary Cu-Zn-Sn alloy target. Successive selenization was performed at various temperatures between 250°C and 500°C for 30 min. X-ray diffraction and Raman analysis showed that a single phase of the CZTSe compound can be obtained by selenization at 400°C, while increasing the selenization temperature to 500°C improves the grain size and crystal quality. The direct optical band gap of CZTSe films was calculated to be 1.06 eV to 1.09 eV with a high absorption coefficient on the order of 104 cm-1 for samples selenized at 400°C to 500°C. The obtained films are p-type semiconductors with bulk carrier concentrations of 2.41 to 7.96 × 1018 cm3, mobilities of 1.30 cm2 V-1 s-1 to 9.27 cm2 V-1 s-1, and resistivities of 0.20 Ωcm to 1.95 Ωcm.

  11. Analysis of laser energy deposition leading to damage and ablation of HfO{sub 2} and Nb{sub 2}O{sub 5} single layers submitted to 500 fs pulses at 1030 and 343 nm

    Energy Technology Data Exchange (ETDEWEB)

    Douti, Dam-Be; Begou, Thomas; Lemarchand, Fabien; Lumeau, Julien; Commandre, Mireille; Gallais, Laurent [Aix-Marseille Universite, CNRS, Centrale Marseille, Institut Fresnel UMR 7249, Marseille (France)

    2016-07-15

    Laser- induced damage thresholds and morphologies of laser ablated sites on dielectric thin films are studied based on experiments and simulations. The films are single layers of hafnia and niobia deposited on fused silica substrates with a magnetron sputtering technique. Laser experiments are conducted with 500 fs pulses at 1030 and 343 nm, and the irradiated sites are characterized with optical profilometry and scanning electron microscopy. The results, i.e., LIDT and damage morphologies, are compared to simulations of energy deposition in the films based on the single rate equation for electron excitation, taking into account transient optical properties of the films during the pulse. The results suggest that a critical absorbed energy as a damage criterion gives consistent results both with the measured LIDT and the observed damage morphologies at fluences close to the damage threshold. Based on the numerical and experimental results, the determined LIDT evolution with the wavelength is described as nearly constant in the near-infrared region, and as rapidly decreasing with laser wavelength in the visible and near-ultraviolet regions. (orig.)

  12. Faecal Excretion of Glycosphingolipids of Breast-fed and Formula-fed Infants

    OpenAIRE

    Larson, G.; Falk, P; Hynsjö, L.; Midtvedt, A. -C.; Midtvedt, T

    2011-01-01

    Faecal samples of six healthy breast-fed, or formula-fed, infants were collected at intervals up to 9 mth of age and analysed for their contents of sphingolipids. Comparisons were made with faecal samples of one older child and one adult. The mean faccal content of sphingolipids during the first 9 mth of life (8.2 μmol sphingosine/g dry stool) was significantly less than that of meconium samples (23.3 μmol/gj but higher than that of adult stools (1.2 μmol/g). Sphingomyelin excretion ...

  13. 电镀单层CBN薄片砂轮磨粒分布的实验研究%Experimental Study on Abrasive Distribution of Electroplating Single-layer CBN Thin-grinding-wheel

    Institute of Scientific and Technical Information of China (English)

    梁国星; 吕明; 刘圣晨; 李文斌; 马麟

    2012-01-01

    A new method for evaluating the density and uniformity on electroplating single layer CBN thin-grinding-wheel was mentioned herein.The maximum area-percentage-concentration of CBN abrasive was derived by means of establishing mathematical model under the condition of single layer distribution.Combining the experimental results,the relationships among the space-factor,planting-grit time and grinding-wheel density and among the space-factor,planting-grit time and uniformity were analyzed.Then the changing regular of grinding-wheel density and uniformity were obtained at the different space-factor and planting time.It is shown in the experimental results that the nonuniformity of the grit distribution mainly presents the specific surface difference of crowded grit and the amount difference of non-crowded grit in each observation area when the average current density value is 0.6A/dm2 and the duty factor is from 0.4 to 0.6.When the average cathode current density value is 0.2A/dm2,and the duty factor is from 0.1 to 0.3,the nonuniformity of the grit distribution mainly presents the amount difference of non-crowded grit in each observation area.In addition,extending plant-grind-time can increase the density of grinding wheel effectively when the average value electric current is a constant,but the abrasive distribution level of uniformity will be reduced obviously.%提出一种电镀单层CBN砂轮磨粒浓度和分布均匀性的评价计算方法,通过建立数学模型推导出磨粒在单层分布状态下的面积百分比浓度最大值。结合实验分析了脉冲占空比和植砂时间与砂轮浓度及分布均匀性之间的关系,得出不同的占空比和植砂时间下砂轮磨粒浓度及分布均匀性的变化规律。实验结果表明:当阴极均值电流密度取0.6A/dm2,且占空比为0.4~0.6时,磨粒分布的不均匀性主要表现形式为堆挤磨粒比面积在各观测区域的差异和未堆积磨粒在各观测区域数量上的差

  14. Research and Design of High Voltage LDMOS with Single Layer Floating Field Plate Structure%具有单层浮空场板的高压LDMOS器件研究

    Institute of Scientific and Technical Information of China (English)

    文帅; 乔明

    2015-01-01

    In the paper, the high voltage RESURF-LDMOS with single layer floating field plate has been researched andoptimized through simulation tool Silvaco.The simulation results show that: for the high voltage device with RESURF structure, field plates have a significant effect for the optimization of device surface electric field, the number and the length of field plates have great influence on the BV of device, and field plates can reduce the peak of electric field. Also, field plates can increase the tolerance range of the P-top dose of the double RESURF-LDMOS, and this lead to the change of the on resistance of device.%通过器件仿真软件Silvaco对带单层浮空场板的高压LDMOS(Lateral Double-diffused MOSFET)器件进行了设计与优化。仿真结果表明:对于击穿电压为600 V的RESURF(reduced surface field)LDMOS器件,场板能够有效地优化器件表面电势分布,降低电场峰值,提高器件的击穿电压。其中场板的数量、长度等参数对高压RESURF-LDMOS器件的耐压有较大影响。并且场板结构增加了double RESURF器件P-top剂量的容差范围,影响了器件的导通电阻。

  15. Single-layer graphene-assembled 3D porous carbon composites with PVA and Fe₃O₄ nano-fillers: an interface-mediated superior dielectric and EMI shielding performance.

    Science.gov (United States)

    Rao, B V Bhaskara; Yadav, Prasad; Aepuru, Radhamanohar; Panda, H S; Ogale, Satishchandra; Kale, S N

    2015-07-28

    In this study, a novel composite of Fe3O4 nanofiller-decorated single-layer graphene-assembled porous carbon (SLGAPC) with polyvinyl alcohol (PVA) having flexibility and a density of 0.75 g cm(-3) is explored for its dielectric and electromagnetic interference (EMI) response properties. The composite is prepared by the solution casting method and its constituents are optimized as 15 wt% SLGAPC and 20 wt% Fe3O4 through a novel solvent relaxation nuclear magnetic resonance experiment. The PVA-SLGAPC-Fe3O4 composite shows high dielectric permittivity in the range of 1 Hz-10 MHz, enhanced by a factor of 4 as compared to that of the PVA-SLGAPC composite, with a reduced loss by a factor of 2. The temperature dependent dielectric properties reveal the activation energy behaviour with reference to the glass transition temperature (80 °C) of PVA. The dielectric hysteresis with the temperature cycle reveals a remnant polarization. The enhanced dielectric properties are suggested to be the result of improvement in the localized polarization of the integrated interface system (Maxwell-Wagner-Sillars (MWS) polarization) formed by the uniform adsorption of Fe3O4 on the surface of SLGAPC conjugated with PVA. The EMI shielding property of the composite with a low thickness of 0.3 mm in the X-band (8.2-12.4 GHz) shows a very impressive shielding efficiency of ∼15 dB and a specific shielding effectiveness of 20 dB (g cm(-3))(-1), indicating the promising character of this material for flexible EMI shielding applications.

  16. Exocrine pancreatic secretion is stimulated in piglets fed Fish oil compared with those fed Coconut Oil or Lard

    DEFF Research Database (Denmark)

    Hedemann, Mette Skou; Pedersen, Asger Roer; Engberg, Ricarda M.

    2001-01-01

    An experiment was conducted to study the effect of feeding diets containing fat sources with different fatty acid composition (fish oil, coconut oil or lard, 10 g/100 g diet) on exocrine pancreatic secretion in piglets after weaning. A total of 16 barrows were weaned at 4 wk of age; 3 d later...... the coconut oil or lard diets. The output [U/(h. kg(0.75))] of lipase was higher in piglets fed fish oil than in piglets fed lard or coconut oil. The output of colipase was greater in piglets fed fish oil and coconut oil than in those fed lard. The dietary treatments did not affect the output of carboxylester...... hydrolase. The output of trypsin was significantly lower in piglets fed lard than in piglets fed fish oil or coconut oil diets and the output of carboxypeptidase B was greater in those fed the fish oil diet. Protein, chymotrypsin, carboxypeptidase A, elastase and amylase outputs did not differ among...

  17. Converter fed sub sea motor drives

    Energy Technology Data Exchange (ETDEWEB)

    Raad, R.O.

    1995-09-01

    Minor offshore gas and oil resources located 20-50 km from existing installations may often be commercially exploited only by use of complete sub sea solutions. This thesis deals with analyses of a sub sea adjustable speed electric motor which is fed by a frequency converter via a long cable (up to 50 km) between the converter and the motor. The author develops a general model for analysing such motor drive systems with the objective of verifying the feasibility of specific applications and of specifying the requirements on the system components. The simulation model is used to identify the critical frequency ranges in which the converter must not generate significant harmonics, to verify the start-up strategy chosen, and to verify the stability with potential disturbances applied to the system. Simulation models are developed for both transient and steady state analyses. They are accurate up to 5 kHz and can incorporate the frequency dependency of the motor and cable parameters. Ideal thyristors and diodes are used. The models are implemented in existing simulation tools. Most of the results relate to a base case with a 670 kW squirrel cage motor fed from a 30 km long cable, but cases with 3 MW rating or with 50 km cable have also been analyzed and found to be feasible. Each specific application must be separately studied. Results of simulation calculations are presented and conclusions given. 53 refs., 124 figs., 23 tabs.

  18. Coupling Between Waveguide-Fed Slot Arrays

    Science.gov (United States)

    Rengarajan, Sembiam

    2011-01-01

    Coupling between two waveguide-fed planar slot arrays has been investigated using full-wave analysis. The analysis employs the method-of-moments solution to the pertinent coupled integral equations for the aperture electric field of all slots. In order to compute coupling between two arrays, the input port of the first array is excited with a TE(sub 10) mode wave while the second one is match-terminated. After solving the moment method matrix equations, the aperture fields of all slots are obtained and thereby the TE(sub 10) mode wave received at the input port of the second array is determined. Coupling between two arrays is the ratio of the wave amplitude arriving in the second array port to the incident wave amplitude at the first array port. The coupling mechanism has been studied as a function of spacing between arrays in different directions, e.g. the electric field plane, the magnetic field plane, and the diagonal plane. Computed coupling values are presented for different array geometries. This work is novel since it provides a good understanding of coupling between waveguide-fed slot arrays as a function of spacing and orientation for different aperture distributions and array architectures. This serves as a useful tool for antenna design engineers and system engineers.

  19. Exocrine pancreatic secretion is stimulated in piglets fed fish oil compared with those fed coconut oil or lard.

    Science.gov (United States)

    Hedemann, M S; Pedersen, A R; Engberg, R M

    2001-12-01

    An experiment was conducted to study the effect of feeding diets containing fat sources with different fatty acid composition (fish oil, coconut oil or lard, 10 g/100 g diet) on exocrine pancreatic secretion in piglets after weaning. A total of 16 barrows were weaned at 4 wk of age; 3 d later, they were surgically fitted with a catheter in the pancreatic duct for continuous collection of pancreatic juice. Collections of pancreatic juice were made every other day starting 4 d postsurgically. Piglets fed the fish oil diet secreted a significantly greater volume of pancreatic juice than piglets fed the coconut oil or lard diets. The output [U/(h. kg(0.75))] of lipase was higher in piglets fed fish oil than in piglets fed lard or coconut oil. The output of colipase was greater in piglets fed fish oil and coconut oil than in those fed lard. The dietary treatments did not affect the output of carboxylester hydrolase. The output of trypsin was significantly lower in piglets fed lard than in piglets fed fish oil or coconut oil diets and the output of carboxypeptidase B was greater in those fed the fish oil diet. Protein, chymotrypsin, carboxypeptidase A, elastase and amylase outputs did not differ among the dietary treatment groups. The apparent digestibilities of nutrients and energy were measured in feces and did not differ among groups. Thus, the greater output of lipase in fish oil-fed piglets did not result in a greater digestibility of fat in this diet.

  20. L-strip proximity fed ga

    Directory of Open Access Journals (Sweden)

    Ashish Singh

    2014-03-01

    Full Text Available In this article, the analysis of dualband L-strip fed compact semi-circular disk microstrip patch antenna has been presented using circuit theory concept. The antenna parameters such as return loss, VSWR and radiation pattern are calculated. The effect of geometric dimensions of the proposed antenna such as length of vertical and horizontal portion of L-strip is investigated. It is found that antenna resonate at two distinct modes i.e. 1.3 GHz and 6.13 GHz for lower and upper resonance frequencies respectively. The bandwidth of the proposed antenna at lower resonance frequency is 6.61% (simulated and 10.64% (theoretical whereas at upper resonance frequency, it is 6.02% (simulated and 9.06 % (theoretical. The theoretical results are compared with IE3D simulation results as well as experimental results and they are in close agreement.

  1. Development of an Acetate-Fed or Sugar-Fed Microbial Power Generator for Military Bases

    Science.gov (United States)

    2011-01-01

    Sucrose • Acetate Propionate • Hydrogen gas • Lactate • Formate • !so-butyrate Unknown fbiomass -’-soluble products ) KM. 80 60 I" 20 DavO...lactate and acetate as fermentation products and is ready for test in the MFC modules. 1. Anode materials We compared the performances of acetate-fed...microbial electrolysis cells (MECs) with graphite rods and stainless steel meshes as anodes to select the optimum material for use in MFC modules to

  2. Growth indices and economic implications of weaned rabbits fed ...

    African Journals Online (AJOL)

    Growth indices and economic implications of weaned rabbits fed Leucaena ... the 13.47g weight gain on rabbits fed the control diet but statistically (P<0.05) lower ... economic efficiency of 0.35 and 194.44%, respectively indicated the optimal ...

  3. Digital Implementation of Two Inductor Boost Converter Fed DC Drive

    Directory of Open Access Journals (Sweden)

    G. Kishor

    2011-01-01

    Full Text Available The study deals w ith simulation and implementation of two inductor boost converter fed DC drive. The two inductor boost converter fed DC drive is simulated and implemented. The circuit has advantages like higher output voltage and improved power factor. The laboratory model is implemented and the experimental results are obtained. The experimental results were compared w ith the simulation results.

  4. Manure total nitrogen flux from condensed tannin fed beef cattle

    Science.gov (United States)

    A study was conducted to determine the effects of three levels of condensed tannins fed to 27 beef feedyard steers on total nitrogen (N) flux from manure. Condensed tannins were fed at rates of 0, 0.5, and 1 percent of the daily ration on a dry matter basis. Manure and urine were collected over two ...

  5. K8型单层球面网壳基于AUTODYN的外爆响应分析%RESPONSES OF SINGLE-LAYER RETICULATED DOMES SUBJECTED TO EXTERNAL BLAST LOADING USING AUTODYN

    Institute of Scientific and Technical Information of China (English)

    杨帆; 支旭东; 范峰

    2015-01-01

    The dynamic responses of single-layer reticulated domes are analyzed through the explicit dynamic finite element software AUTODYN.The load is applied using the FSI method,and the material is adopted using a multi-segment linear model for steel.First,the accuracy is verified by analyzing near-field and far-field explosions.Then the responses of a 20m span reticulated dome are obtained under external blast loading,including the loading spread,change in maximum nodal displacement,and development of plastic members.The laws governing structural response are researched,accounting for the mass of TNT,explosion distance,and explosion height.The results of numerical simulations indicate that AUTODYN can be used to analyze near-field and far-field explosions;the reticulated dome experiences two main shock wave loadings under external blast loading and the maximum nodal displacement occurs at the first shock wave loading;the plasticity development of structural members ends at 0.05 seconds;the structural responses strengthen with the increase of TNT mass and the explosion height,but weaken with the increase of explosion distance.%该文采用显式动力有限元软件AUTODYN对K8型单层球面网壳在外爆荷载下的动态响应进行了研究.数值模拟中采用流固耦合方法施加荷载,钢材采用多段线性模型,首先验证了AUTODYN进行近场爆炸分析和远场爆炸分析的准确性;考察了跨度为20 m的网壳结构在外爆荷载下的荷载传播规律、最大节点位移变化规律以及塑性杆件发展规律,考察了跨度为40 m网壳结构在TNT质量、炸点距离以及炸点高度参数变化下的结构响应规律.数值分析的结果表明:AUTODYN具备准确进行近场爆炸和远场爆炸分析的能力;单层球面网壳在外爆荷载下主要经历两次冲击波荷载,最大节点位移出现在第一次冲击荷载作用时,结构杆件的塑性发展在0.05 s后基本结束;网壳结构的响应随TNT质量增加和

  6. Formation mechanism of karst soil-void in single-layer soil structure condition%单层土体结构岩溶土洞的形成机理

    Institute of Scientific and Technical Information of China (English)

    蒋小珍; 雷明堂; 管振德

    2012-01-01

    Subsurface soil-voids are main potential geologic hazards being faced in engineering construction in karst regions. In order to analyze the formation mechanism of soil-voids, laboratory tests including physics model experiment and slaking test have been taken based on site investigation. For the regions with single-layer clay or silty clay, the authors divide the process of soil-void development into three phases corresponding to the void's position and its relationship with groundwater table. In the first phase, the initial soil-void forms usually along the weak zones of soil such as fractures and bedrock surface, and seepage deformation induced by karst water flow plays an important part in this process. In the second phase, the soil-void exists in the belt of phreatic fluctuation, and the soil disintegration for repeat soak is the key reason in the formation of soil-void. In the last phase, the soil-void is generally within the unsaturated zone and closes to ground, so the rainfall and surface water leakage along the soil fracture will influence the stability of the soil-void greatly.%岩溶土洞是岩溶区工程路基施工中的主要地质灾害.本文首先对广西桂林阳朔高速公路雁山段、西气东输二线工程广西贵港段两个典型工程路基单层土体结构的岩溶土洞进行详细剖析,然后通过室内模型试验、崩解试验的验证,研究岩溶土洞的形成机理.结果表明:单层主体结构的岩溶土洞发育是先从基岩面逐渐往地面发展,在发展过程中,对于较厚的土层,岩溶土洞的发育与扩展分为3个阶段:(1)基岩面附近的土洞形成与地下水位的承压状态和地下水位初始下降速度密切相关,土洞的形态主要以缝(洞)的形式出现,规模较小,多形成于土体中的裂隙面或非均质部位;(2)在地下水包气带(季节变动带)土洞的扩展以崩解为主,规模较大;(3)近地表(垂直渗入带)土洞扩展机制以上部降雨入渗、洞

  7. Iron status in breast-fed infants

    Directory of Open Access Journals (Sweden)

    I Gusti Ayu Asih Ratnadi

    2001-08-01

    Full Text Available Ninety infants were selected stratified proportionally random sampling and they met the inclusion criteria. Iron status was determined by the serum ferritin level concentration. The nutritional status was determined by the body weight to age based on the standard criteria of WHO NCHS. The quality of food was defined by asking the parents to keep a diary of consumed in the last 7 days minimally for three days. Out of the 90 infants, 50.4 % of them were males and 45.6 % of them were females. Most of them (93.7% had normal nourished and 8.3 % had undernourished. The prevalence status of low iron was 18.9%. The low iron status began to occur at the age of 4 – 6 months old (6% and the highest at the age of 9 – 12 months old (65%. Statistically significant differences were found between the iron status and the quality of food supplements over age group. The low quality of food is a risk factor influence the status of low iron. It is suggested that the iron supplements be given to breast-fed infant at the age of 4 – 6 months old.

  8. Plasma polychlorinated biphenyl levels in Dutch preschool children either breast-fed or formula-fed during infancy

    NARCIS (Netherlands)

    Patandin, S; WeisglasKuperus, N; deRidder, MAJ; KoopmanEsseboom, C; vanStaveren, WA; vanderPaauw, CG; Sauer, PJJ

    1997-01-01

    Objectives. This study examined the influence of lactational and in utero exposure to polychlorinated biphenyls (PCBs) on plasma PCB levels in children. Methods. Plasma PCB levels were measured in 173 children at 3.5 years, of whom 91 were breast-fed and 82 were formula-fed in infancy. Results. Medi

  9. Dietary CLA-induced lipolysis is delayed in soy oil-fed mice compared to coconut oil-fed mice.

    Science.gov (United States)

    Ippagunta, S; Angius, Z; Sanda, M; Barnes, K M

    2013-11-01

    Conjugated linoleic acid (CLA) has been shown to cause a reduction in obesity in several species. CLA-induced body fat loss is enhanced when mice are fed coconut oil (CO) and involves increased lipolysis. The objective of this paper was to determine if the CLA-induced lipolysis in mice fed with different oil sources was time-dependent. Mice were fed 7 % soybean oil (SO) or CO diets for 6 week and then supplemented with 0 or 0.5 % CLA for 3, 7, 10 or 14 days. Body fat and ex-vivo lipolysis was determined. Body fat was reduced by CO on day 7 (P Lipolysis was increased by CLA in CO-fed mice (P lipolysis in both CO- and SO-fed mice (P lipolysis and lipogenesis was determined by western blotting and real-time PCR, respectively. No significant differences were detected in protein expression. CO-fed mice had greater fatty acid synthase and stearyl CoA desaturase 1 mRNA expression and less acetyl CoA carboxylase mRNA expression (P lipolysis occurs more rapidly in CO vs SO-fed mice and lipogenesis is decreased in CO-fed mice with CLA supplementation.

  10. MODEL STUDY OF THE DOUBLE FED MACHINE WITH CURRENT CONTROL

    Directory of Open Access Journals (Sweden)

    A. S. Lyapin

    2016-07-01

    Full Text Available The paper deals with modeling results of the double fed induction machine with current control in the rotor circuit. We show the most promising applications of electric drives on the basis of the double fed induction machine and their advantages. We present and consider functional scheme of the electric drive on the basis of the double fed induction machine with current control. Equations are obtained for creation of such machine mathematical model. Expressions for vector projections of rotor current are given. According to the obtained results, the change of the vector projections of rotor current ensures operation of the double fed induction machine with the specified values of active and reactive stator power throughout the variation range of sliding motion. We consider static characteristics of double fed machine with current control. Energy processes proceeding in the machine are analyzed. We confirm the operationpossibility of double fed induction machine with current controlin the rotor circuit with given values of active and reactive stator power. The presented results can be used for creation of mathematical models and static characteristics of double fed machines with current control of various capacities.

  11. A review of fatty acid profiles and antioxidant content in grass-fed and grain-fed beef

    Directory of Open Access Journals (Sweden)

    Nader Glenn A

    2010-03-01

    Full Text Available Abstract Growing consumer interest in grass-fed beef products has raised a number of questions with regard to the perceived differences in nutritional quality between grass-fed and grain-fed cattle. Research spanning three decades suggests that grass-based diets can significantly improve the fatty acid (FA composition and antioxidant content of beef, albeit with variable impacts on overall palatability. Grass-based diets have been shown to enhance total conjugated linoleic acid (CLA (C18:2 isomers, trans vaccenic acid (TVA (C18:1 t11, a precursor to CLA, and omega-3 (n-3 FAs on a g/g fat basis. While the overall concentration of total SFAs is not different between feeding regimens, grass-finished beef tends toward a higher proportion of cholesterol neutral stearic FA (C18:0, and less cholesterol-elevating SFAs such as myristic (C14:0 and palmitic (C16:0 FAs. Several studies suggest that grass-based diets elevate precursors for Vitamin A and E, as well as cancer fighting antioxidants such as glutathione (GT and superoxide dismutase (SOD activity as compared to grain-fed contemporaries. Fat conscious consumers will also prefer the overall lower fat content of a grass-fed beef product. However, consumers should be aware that the differences in FA content will also give grass-fed beef a distinct grass flavor and unique cooking qualities that should be considered when making the transition from grain-fed beef. In addition, the fat from grass-finished beef may have a yellowish appearance from the elevated carotenoid content (precursor to Vitamin A. It is also noted that grain-fed beef consumers may achieve similar intakes of both n-3 and CLA through the consumption of higher fat grain-fed portions.

  12. SWFSC FED Mid Water Trawl Juvenile Rockfish Survey, Surface Data

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — SWFSC FED Mid Water Trawl Juvenile Rockfish Survey: Station Information and Surface Data. Surveys have been conducted along the central California coast in May/June...

  13. SWFSC FED Mid Water Trawl Juvenile Rockfish Survey, CTD Data

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — SWFSC FED Mid Water Trawl Juvenile Rockfish Survey: CTD Data. Surveys have been conducted along the central California coast in May/June every year since 1983. In...

  14. Intake and rumen degradation in cattle fed napier grass ...

    African Journals Online (AJOL)

    ... fed napier grass ( Pennisetum purpureum ) supplemented with various levels of ... increasing inclusion level of desmodium (74-90 g/kg 0.75) and sweet potato ... Supplementation improved DM degradation but did not change rumen pH.

  15. Testicular Morphometry and Sperm Quality of Rabbit Bucks Fed ...

    African Journals Online (AJOL)

    Testicular Morphometry and Sperm Quality of Rabbit Bucks Fed Graded Levels ... for their nutritional and medicinal values and are rich in minerals and vitamins. ... used to evaluate the effect of Moringa oleifera leaf meal (MOLM) on testicular ...

  16. Performance of growing Yankasa rams Fed graded levels of ...

    African Journals Online (AJOL)

    SH

    The results revealed that animals fed 0% inclusion level (Control diet) had higher DMI, EEI and ... conducted using T. indica leaves to ascertain the nutritive value and its suitability as feedstuff for small ..... Research Project, submitted to the.

  17. Optimal control of a fed-batch fermentation

    Energy Technology Data Exchange (ETDEWEB)

    Dekkers, R.M.

    1984-01-01

    The common cultivation of bakers' yeast is an aerobic fed-batch fermentation under sugar-limited growth. The ultimate objective of on-line computer control is to optimize the process through maximizing the productivity of biomass formation while minimizing the consumption of raw materials for the product. Results obtained on the optimal control of a fed-batch fermentation are given. The aspects to be considered are instrumentation, state estimation, optimization and process control.

  18. Performance and Carcass Characteristics of Rabbits Fed Oil Supplemented Diets

    Directory of Open Access Journals (Sweden)

    Jamal Abo OMAR

    2016-02-01

    Full Text Available The objective of this study is to investigate the effects of feeding different dietary fat supplements in the finisher rations of Baladi rabbits, including sesame oil (SO, olive oil sediments (OOS, and poultry grease (PG, in comparison to the traditional oil supplement, the soybean soap stock oil (SS, on growth performance, blood lipid profile, dressing percentage and carcass cut, and meat quality: water holding capacity (WHC and cell forming unit (CFU. A total of 48 Baladi rabbits were used, with individual body weights (BW of 519 ± 22 g at the beginning of the experiment. Rabbits were randomly divided into 4 groups of 12, and those in each group were individually fed cereal grain-soybean meal (SBM with a fixed amount (i.e. 30 g/kg dry matter (DM of oil, being either soybean oil (SOY, olive oil sediments (OOS, recycled restaurant oil (RRO, or poultry grease (PG. All rations were isonitrogenous and contained iso-metabolizable energy (ME. At the end of the 44 day feeding trial, all animals were slaughtered. Rabbits fed a SOY supplemented diet consumed more (P < 0.05 feed than those fed the OOS, RRO, or PG supplemented diets. However, rabbits fed the SOY had a better (P < 0.05 feed conversion ratio than rabbits fed the OOS, PG, or RRO diets. Oil source had no effect on carcass components weights. Liver was heavier (P < 0.05 in rabbits fed the SOY supplemented diet. However, the RRO fed rabbits had heavier (P < 0.05 small intestine, large intestine and cecum. In conclusion, the positive effects of the tested oil supplements (i.e. RRO, OOS, PG on the studied performance and carcass traits is encouraging, but more investigation is needed to identify the optimal levels for these supplements in various diets of local rabbits.

  19. Growth and Reproduction of Artificially Fed Cnaphalocrocis medinalis

    Institute of Scientific and Technical Information of China (English)

    XU Jian; LI Chuan-ming; YANG Ya-jun; QI Jian-hang; ZHENG Xu-song; Hu Rong-li; LU Zhong-xian; LIU Qin

    2012-01-01

    The growth and reproduction of rice leaffolder,Cnaphalocrocis medinalis,fed on an artificial diet were studied.The results showed that the larvae were able to grow and pupate on the artificial diet.The durations of larvae and pupas of C.medinalis on the artificial diet were 28.1 d and 10.1 d,postponed 4.9 d and 1.7 d respectively,compared with those reared with rice leaves.The number of ovipositions was 41.6 per female,26.2% higher than that fed on rice leaves.Survival rate curve of larvae was a descent function of mortality-age,with no significant differences from the curve of larvae fed on rice leaves.The net reproductive rate (Ro),intrinsic rate of increase (rm) and finite rate of increase (λ) of the population fed on diet were 17.6928,0.0884 and 1.0924,respectively,and the mean generation time (T) and double time (td) were prolonged 4.9 d and 1.3 d in comparison with the treatment of rice leaves.Population trend index (Ⅰ) was 3.26,indicating a growing number of the population of C.medinalis fed on artificial diet.

  20. Performance optimization for doubly fed wind power generation systems

    Energy Technology Data Exchange (ETDEWEB)

    Bhowmik, S.; Spee, R.; Enslin, J.H.R.

    1999-08-01

    Significant variation of the resource kinetic energy, in the form of wind speed, results in substantially reduced energy capture in a fixed-speed wind turbine. In order to increase the wind energy capture in the turbine, variable-speed generation (VSG) strategies have been proposed and implemented. However, that requires an expensive ac/ac power converter, which increases the capital investment significantly. Consequently, doubly fed systems have been proposed to reduce the size of the power converter and, thereby, the associated cost. Additionally, in doubly fed systems, as a fixed operating point (power and speed), power flow can be regulated between the two winding systems on the machine. This feature can by utilized to essentially minimize losses in the machine associated with the given operating point or achieve other desired performance enhancements. In this paper, a brushless doubly fed machine (BDFM) is utilized to develop a VSG wind power generator. The VSG controller employs a wind-speed-estimation-based maximum power point tracker and a heuristic-model-based maximum efficiency point tracker to optimize the power output of the system. The controller has been verified for efficacy on a 1.5-kW laboratory VSG wind generator. The strategy is applicable to all doubly fed configurations, including conventional wound-rotor induction machines, Scherbius cascades, BDFM's and doubly fed reluctance machines.

  1. From Fed-batch to Continuous Enzymatic Biodiesel Production

    DEFF Research Database (Denmark)

    2015-01-01

    In this this paper, we use mechanistic modelling to guide the development of acontinuous enzymatic process that is performed as a fed-batch operation. In this workwe use the enzymatic biodiesel process as a case study. A mechanistic model developedin our previous work was used to determine...... measured components (triglycerides, diglycerides, monoglycerides, free fatty acid and fatty acid methyl esters(biodiesel)) much better than using fed-batch data alone given the smaller residuals. We also observe a reduction in the correlation between the parameters.The model was then used to predict that 5...... reactors are required (with a combined residence time of 30 hours) to reach a final biodiesel concentration within 2 % of the95.6 mass % achieved in a fed-batch operation, for 24 hours....

  2. Behavior of mallard ducklings from parents fed 3 ppm DDE

    Science.gov (United States)

    Heinz, G.H.

    1976-01-01

    Mallard ducks fed a diet containing 3 ppm DDE (equal to about 0.6 ppm in a natural succulent diet) laid eggs that contained an average of 5.8 ppm DDE; ducklings that hatched from these eggs differed from controls in behavioral tests designed to measure responses to a maternal call and to a frightening stimulus. In response to the maternal call, ducklings from parents fed DDE were hyper-responsive; compared to controls, a greater percentage approached the call and a greater percentage of those that approached remained near the call for the remainder of the test. In a test of avoidance behavior, ducklings whose parents were fed DDE traveled shorter distances from the firghtening stimulus than did controls.

  3. The Photonic TIGER: a multicore fiber-fed spectrograph

    CERN Document Server

    Leon-Saval, Sergio G; Bland-Hawthorn, Joss

    2012-01-01

    We present a proof of concept compact diffraction limited high-resolution fiber-fed spectrograph by using a 2D multicore array input. This high resolution spectrograph is fed by a 2D pseudo-slit, the Photonic TIGER, a hexagonal array of near-diffraction limited single-mode cores. We study the feasibility of this new platform related to the core array separation and rotation with respect to the dispersion axis. A 7 core compact Photonic TIGER fiber-fed spectrograph with a resolving power of around R~31000 and 8 nm bandwidth in the IR centered on 1550 nm is demonstrated. We also describe possible architectures based on this concept for building small scale compact diffraction limited Integral Field Spectrographs (IFS).

  4. FEDS : A Framework for Evaluation in Design Science Research

    DEFF Research Database (Denmark)

    Venable, John; Pries-Heje, Jan; Baskerville, Richard

    2015-01-01

    Evaluation of design artefacts and design theories is a key activity in Design Science Research (DSR), as it provides feedback for further development and (if done correctly) assures the rigour of the research. However, the extant DSR literature provides insufficient guidance on evaluation...... to enable Design Science Researchers to effectively design and incorporate evaluation activities into a DSR project that can achieve DSR goals and objectives. To address this research gap, this research paper develops, explicates, and provides evidence for the utility of a Framework for Evaluation in Design...... Science (FEDS) together with a process to guide design science researchers in developing a strategy for evaluating the artefacts they develop within a DSR project. A FEDS strategy considers why, when, how, and what to evaluate. FEDS includes a two-dimensional characterisation of DSR evaluation episodes...

  5. Methane emissions from feedlot cattle fed barley or corn diets.

    Science.gov (United States)

    Beauchemin, K A; McGinn, S M

    2005-03-01

    Methane emitted from the livestock sector contributes to greenhouse gas emissions worldwide. Understanding the variability in enteric methane production related to diet is essential to decreasing uncertainty in greenhouse gas emission inventories and to identifying viable greenhouse gas reduction strategies. Our study focused on measuring methane in growing beef cattle fed corn- or barley-based diets typical of those fed to cattle in North American feedlots. The experiment was designed as a randomized complete block (group) design with two treatments, barley and corn. Angus heifer calves (initial BW = 328 kg) were allocated to two groups (eight per group), with four cattle in each group fed a corn or barley diet. The experiment was conducted over a 42-d backgrounding phase, a 35-d transition phase and a 32-d finishing phase. Backgrounding diets consisted of 70% barley silage or corn silage and 30% concentrate containing steam-rolled barley or dry-rolled corn (DM basis). Finishing diets consisted of 9% barley silage and 91% concentrate containing barley or corn (DM basis). All diets contained monensin (33 mg/kg of DM). Cattle were placed into four large environmental chambers (two heifers per chamber) during each phase to measure enteric methane production for 3 d. During the backgrounding phase, DMI was greater by cattle fed corn than for those fed barley (10.2 vs. 7.6 kg/d, P cattle were in the chambers; thus, methane emissions (g/d) reported may underestimate those of the feedlot industry. Methane emissions per kilogram of DMI and as a percentage of GE intake were not affected by grain source during the backgrounding phase (24.6 g/kg of DMI; 7.42% of GE), but were less (P methane emissions of cattle fed high-forage backgrounding diets and barley-based finishing diets. Mitigating methane losses from cattle will have long-term environmental benefits by decreasing agriculture's contribution to greenhouse gas emissions.

  6. FED-R: a fusion engineering device utilizing resistive magnets

    Energy Technology Data Exchange (ETDEWEB)

    Jassby, D.L.; Kalsi, S.S. (eds.)

    1983-04-01

    The principal purpose of the FED-R tokamak facility is to provide a substantial quasi-steady flux of fusion neutrons irradiating a large test area in order to carry out thermal, neutronic, and radiation effects testing of experimental blanket assemblies having a variety of configurations, compositions, and purposes. The design of the FED-R device also suggests potential for an upgrade that could be employed as a full-scale demonstration reactor for some specific fusion-neutron application when required.

  7. Analysis of Capacitive Parasitism in PWM Inverter-Fed Motor

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The effects of parasitic capacitance in induction motor system are unnoticed when it is fed from the AC line. but they are obvious when supplied directly from a PWM inverter. Consequently. many parasitic problems occur, such as motor-to-earth leakage current, bearing current, incoming line current distortion and uneven distribution of electrical stresses along the winding. On the ba sis of the uniform transmission line principle, a complete equivalent circuit of the PWM inverter-fed motor system is presented, based on which all the capacitive parasitic problems mentioned above are analyzed and simulated by means of PSPICE. All the results are consistent with the existing ones.

  8. Performance of broiler chicken fed varied nutrient density diets supplemented with direct fed microbial

    Directory of Open Access Journals (Sweden)

    Katoch S.

    2013-01-01

    Full Text Available Comparative dietary response of different isolated strains (Direct fed microbial- DFM of lactobacilli, streptococci and yeast isolated from leopard feces (Panthera leo was studied as probiotic in poultry broiler birds reared as per varied mineral densities viz. calcium and phosphorus. Various treatments consisted of T0 (Control, culture medium, T1 (Lactobacillus casei + Streptococcus fecalis + Saccharomyces cerevisiae offered standard formulated diet D1, T2 - Control (Culture medium offered ten percent lower calcium and phosphorus diet D2, T3 (Lactobacillus casei + Streptococcus fecalis + Saccharomyces cerevisiae offered ten percent lower calcium and phosphorus diet D2. Growth results obtained during the starter phase (1st to 3rd week exhibited higher gain in live body weight and lower feed conversion ratio, both by DFM supplemented treatment T1 offered standard formulated diet D1 and treatment T3 offered experimentally formulated mineral (Ca and P deficient (10% diet D2 compared to respective control T0 and T2. The obtained results revealed a significantly higher growth performance in treatment T1 compared to its control T0 where a higher growth in treatment T3 offered experimentally formulated mineral (Ca and P deficient (10% diet D2 supplemented with isolated DFM compared to its control T2 was exhibited. Treatment groups T1 and T3 supplemented with isolated DFM exhibited a better intestinal micro flora balance, effective colonization and higher count in the intestinal tract with higher calcium and phosphorus retention in the digestibility studies. Thus, it was found that supplementation of isolated DFM has the potential to improve biological growth performance of poultry broiler birds offered both standard formulated diet D1, as well as mineral deficient diet D2. [Projekat Ministarstva nauke Republike Srbije, br. III 46002

  9. Performance of lambs fed alternative protein sources to soybean meal

    Directory of Open Access Journals (Sweden)

    Felipe José Lins Alves

    2016-04-01

    Full Text Available ABSTRACT The objective of this study was to evaluate the effect of alternative protein sources (castor bean cake, sunflower cake, and sunflower seed to soybean meal on the intake and performance of 40 lambs, initially weighing 19.8±1.84 kg, fed diets based on Tifton grass hay. The experimental design was completely randomized blocks. There were no differences in the nutrient intake of castor bean diets compared with soybean meal. The intake of nutrients in the sunflower cake and sunflower seed diets was decreased compared with soybean meal. The apparent digestibility coefficients of dry matter, organic matter, crude protein, and neutral detergent fiber of sunflower cake and sunflower seed diets were decreased compared with soybean meal. The average daily weight gain of animals fed the castor bean diet (0.190 kg was not different from that of the animals fed the soybean meal diet (0.217 kg. The sunflower cake and sunflower seed diets provided less weight gain (0.171 and 0.135 kg d-1, respectively than soybean meal due to the lower nutrient intake. The hot carcass yield and true yield were not affected by the protein sources. The neck, ribs, and ham weights were similar in lambs fed soybean meal and castor bean cake diets. It is recommended to use castor bean as an alternative protein source in the diet of lambs.

  10. Optimal parametric sensitivity control for a fed-batch reactor

    NARCIS (Netherlands)

    Stigter, J.D.; Keesman, K.J.

    2001-01-01

    The paper presents a method to derive an optimal parametric sensitivity controller for optimal estimation of a set of parameters in an experiment. The method is demonstrated for a fed batch bio-reactor case study for optimal estimation of the saturation constant Ks and, albeit intuitively, the param

  11. Optimal parametric sensitivity control of a fed-batch reactor

    NARCIS (Netherlands)

    Stigter, J.D.; Keesman, K.J.

    2004-01-01

    The paper presents an optimal parametric sensitivity controller for estimation of a set of parameters in an experiment. The method is demonstrated for a fed-batch bioreactor case study for optimal estimation of the half-saturation constant KS and the parameter combination µmaxX/Y in which µmax is th

  12. A Current-Fed Isolated Bidirectional DC-DC Converter

    DEFF Research Database (Denmark)

    Sun, Xiaofeng; Wu, Xiaoying; Shen, Yanfeng;

    2017-01-01

    This paper proposes a current-fed isolated bidirectional DC-DC converter (CF-IBDC) which has the advantages of wide input voltage range, low input current ripple, low conduction losses, and soft switching over the full operating range. Compared with conventional CF-IBDCs, the voltage spikes of th...

  13. Using glycerin as a supplement for forage-fed ruminants.

    Science.gov (United States)

    The utility of crude glycerin as a feed additive for forage–fed ruminants depends largely on how well the animals are able to utilize the glycerol and other dietary components when crude glycerin is added to the diet. Several studies have demonstrated that ruminal fermentation of pure glycerol resul...

  14. Discrimination learning in adult bobwhite quail fed paraquat

    Science.gov (United States)

    Bunck, C.M.; Bunck, T.J.; Sileo, L.

    1986-01-01

    Adult male bobwhite quail (Colinus virginianus) were fed a diet containing 0, 25 or 100 ppm paraquat dichloride. After 60 d on treated diets, discrimination learning was evaluated with acquisition and reversal tests. The three groups performed similarly on these tests. Dose-related histopathological lesions were not found in liver, kidney or lung tissues

  15. Tandem fluid queues fed by homogeneous on-off sources

    NARCIS (Netherlands)

    Scheinhardt, Willem R.W.; Aalto, Samuli

    2000-01-01

    We consider a tandem fluid model with multiple consecutive buffers. The input of buffer j+1 is the output from buffer j, while the first buffer is fed by a, possibly infinite, number of independent homogeneous on–off sources. The sources have exponentially distributed silent periods and generally di

  16. Comparative Performance Of Broiler Chicks fed Diets Containing ...

    African Journals Online (AJOL)

    Comparative Performance Of Broiler Chicks fed Diets Containing Differently Processed ... A 28-day feeding trial was conducted to determine the effects of dietary inclusion of ... The first batch was soaked in 3% Ca(OH)2 for 48 hours. ... performance of the birds in terms of feed intake, growth rate and feed conversion ratio.

  17. Growth and carcass characteristics of broiler chickens fed water ...

    African Journals Online (AJOL)

    Growth and carcass characteristics of broiler chickens fed water soaked and cooked velvet ... A 56-day feeding trial was conducted to determine the effects of dietary raw and ... The second batch was soaked for 24 h, subdivided into four parts and ... of the birds in terms of feed intake, growth rate and feed conversion ratio.

  18. Fate and transport of arsenic from organoarsenicals fed to poultry

    Science.gov (United States)

    Little is known about the fate of arsenic (As) in land-applied litter from chickens that have been fed roxarsone, an organic feed additive containing As. This chapter seeks to review the likelyhood of the biodegradation of roxarsone and the subsequent transport of As in runoff from a case study cond...

  19. Light attenuation characteristics of glacially-fed lakes

    Science.gov (United States)

    Rose, Kevin C.; Hamilton, David P.; Williamson, Craig E.; McBride, Chris G.; Fischer, Janet M.; Olson, Mark H.; Saros, Jasmine E.; Allan, Mathew G.; Cabrol, Nathalie

    2014-07-01

    Transparency is a fundamental characteristic of aquatic ecosystems and is highly responsive to changes in climate and land use. The transparency of glacially-fed lakes may be a particularly sensitive sentinel characteristic of these changes. However, little is known about the relative contributions of glacial flour versus other factors affecting light attenuation in these lakes. We sampled 18 glacially-fed lakes in Chile, New Zealand, and the U.S. and Canadian Rocky Mountains to characterize how dissolved absorption, algal biomass (approximated by chlorophyll a), water, and glacial flour contributed to attenuation of ultraviolet radiation (UVR) and photosynthetically active radiation (PAR, 400-700 nm). Variation in attenuation across lakes was related to turbidity, which we used as a proxy for the concentration of glacial flour. Turbidity-specific diffuse attenuation coefficients increased with decreasing wavelength and distance from glaciers. Regional differences in turbidity-specific diffuse attenuation coefficients were observed in short UVR wavelengths (305 and 320 nm) but not at longer UVR wavelengths (380 nm) or PAR. Dissolved absorption coefficients, which are closely correlated with diffuse attenuation coefficients in most non-glacially-fed lakes, represented only about one quarter of diffuse attenuation coefficients in study lakes here, whereas glacial flour contributed about two thirds across UVR and PAR. Understanding the optical characteristics of substances that regulate light attenuation in glacially-fed lakes will help elucidate the signals that these systems provide of broader environmental changes and forecast the effects of climate change on these aquatic ecosystems.

  20. Centralised control of wind farm with doubly fed induction generators

    DEFF Research Database (Denmark)

    Hansen, Anca-Daniela; Sorensen, Poul; Iov, Florin;

    2005-01-01

    This paper describes the development of an advanced wind farm controller for a wind farm made-up exclusively of doubly-fed generators. The overall aim of such controller is to enable the wind farms to behave as active controllable components in the power system. The attention is mainly drawn to t...

  1. Doubly-Fed Induction Generator Control Under Voltage Sags

    DEFF Research Database (Denmark)

    Teodorescu, Remus; Blaabjerg, Frede; Lima, K.;

    2008-01-01

    This paper proposes a new control technique to improve the fault-ride through capability of doubly fed induction generators (DFIG). In such generators the appearance of severe voltage sags at the coupling point make rise to high over currents at the rotor/stator windings, something that makes...

  2. Weaning Preparation for Children Fed by G-Tube

    Science.gov (United States)

    ... of the child’s problem and his or her development, the child may need to be tube fed for several ... game playing. Do not try to wean a child from a G-tube single-handedly. Most children and their parents/caregivers gain success as they work together with ...

  3. Nutritive value and biochemical changes in broiler chickens fed ...

    African Journals Online (AJOL)

    Mr Akande

    2012-02-09

    Feb 9, 2012 ... chickens fed detoxified castor kernel cake based diets. Akande, T. O.* ... There was downward trend in serum protein while an upward trend was observed for urea and creatinine ... the neem kernel as good protein supplement compared ... Ten diets were formulated comprising 9 diets containing varying.

  4. Linear Parameter Varying Control of Doubly Fed Induction Machines

    NARCIS (Netherlands)

    Tien, H. Nguyen; Scherer, Carsten W.; Scherpen, Jacquelien M.A.; Müller, Volkmar

    2016-01-01

    This paper is concerned with the design of a self-scheduled current controller for doubly fed induction machines. The design is based on the framework of linear parameter-varying systems where the mechanical angular speed is considered to be a measurable time-varying parameter. The objective is to o

  5. Performance and cost implication of finisher turkeys fed varying ...

    African Journals Online (AJOL)

    Performance and cost implication of finisher turkeys fed varying levels of rice millingwaste. ... Log in or Register to get access to full text downloads. ... 50% rice milling waste produced enhanced performance that was next to the control in terms ...

  6. fed a low or a medium protein diet

    African Journals Online (AJOL)

    Department of Physiology, Veterinary Science, University of Pretoria, Private Bag X4, .... Group 1 were fed a low nitrogen diet (LN) based on milled oats {Avena sativa) hay, with a metabolizable energy .... Halving the intake of drinking water halved the output of urine ..... Book, Prentice-Hall, Englewood Cliffs, New Jersey, pp.

  7. Triglyceride kinetics in fasted and fed E. coli septic rats

    Energy Technology Data Exchange (ETDEWEB)

    Lanza-Jacoby, S.; Tabares, A. (Jefferson Medical Coll., Philadelphia, PA (United States))

    1990-02-26

    The mechanism for the development of hypertriglyceridemia during gram-negative sepsis was studies by examining the liver production and clearance of very-low-density lipoprotein (VLDL) triglyceride (TG). To assess the liver output and peripheral clearance the kinetics of VLDL-TG were determined by a constant intravenous infusion of (2-{sup 3}H) glycerol-labeled VLDL in fasted control, fasted E. coli-treated, fed control, and fed E.coli-treated rats. Lewis inbred rats, 275-300 g, were made septic with 8 {times} 10{sup 7} live E.coli colonies per 100 g body weight. Twenty-four hours following E.coli injection serum TG of fasted E.coli-treated rats was elevated by 170% which was attributed to a 67% decrease in the clearance rate of VLDL-TG in fasted E.coli-treated rats compared with their fasted controls. The secretion of VLDL-TG declined by 31% in the livers of the fasted E.coli-treated rats which was accompanied by a 2-fold increase in the composition of liver TG. In a second series of experiments control and E.coli-treated rats were fed intragastrically (IG) a balanced solution containing glucose plus fat as the sources of nonprotein calories. Serum TG were 26% lower in the fed E.coli-treated rats because the clearance rate increased by 86%. The secretion of TG in the fed septic rats increased by 40% but this difference was not significant. In the septic rat the ability to clear triglycerides from the plasma depends upon the nutritional state.

  8. 应变对单层二硫化钼能带影响的第一性原理研究%The effect of strain on band structure of single-layer MoS2: an ab initio study

    Institute of Scientific and Technical Information of China (English)

    吴木生; 徐波; 刘刚; 欧阳楚英

    2012-01-01

    We study the electronic properties of single-layer MoS2 with biaxial tensile strain by using an ab initio method of plane wave potential technique based on the density function theory. Our results show that a smalL tensile strain (0.5%) will result in the transition from direct to indirect gap for ingle-layer MoS2. With the increase of strain, the feature of the indirect gap can be preserved but the gap decreases linearly. Based on the further analysis of the density of states and the projected charge density for single-layer MoS2, the reason of the change of band structure is revealed.%采用密度泛函理论框架下的第一性原理平面波赝势方法,研究了双轴拉应变下单层二硫化钼晶体的电子结构性质.本文的计算结果表明对单层二硫化钼晶体施加一个很小的应变(0.5%)时,其能带结构由直接带隙转变为间接带隙.随着应变的增加,能带仍然保持间接带隙的特征,且禁带宽度呈现线性下降的趋势.通过对单层二硫化钼晶体态密度和投影电荷密度的进一步分析,揭示了单层二硫化钼晶体能带变化的原因.

  9. Dietary conjugated linoleic acid induces lipolysis in adipose tissue of coconut oil-fed mice but not soy oil-fed mice.

    Science.gov (United States)

    Ippagunta, S; Hadenfeldt, T J; Miner, J L; Hargrave-Barnes, K M

    2011-09-01

    Mice fed diets containing conjugated linoleic acid (CLA) are leaner than mice not fed CLA. This anti-obesity effect is amplified in mice fed coconut oil-containing or fat free diets, compared to soy oil diets. The present objective was to determine if CLA alters lipolysis in mice fed different base oils. Mice were fed diets containing soy oil (SO), coconut oil (CO), or fat free (FF) for 6 weeks, followed by 10 or 12 days of CLA or no CLA supplementation. Body fat, tissue weights, and ex vivo lipolysis were determined. Relative protein abundance and activation of perilipin, hormone sensitive lipase (HSL), adipose triglyceride lipase (ATGL), and adipose differentiation related protein (ADRP) were determined by western blotting. CLA feeding caused mice to have less (P oil source, P oil source interaction on lipolysis as CO + CLA and FF + CLA-fed mice had increased (P < 0.05) rates of lipolysis but SO + CLA-fed mice did not. However, after 12 days of CLA consumption, activated perilipin was increased (P < 0.05) only in SO + CLA-fed mice and total HSL and ATGL were decreased (P < 0.05) in CO + CLA-fed mice. Therefore, the enhanced CLA-induced body fat loss in CO and FF-fed mice appears to involve increased lipolysis but this effect may be decreasing by 12 days of CLA consumption.

  10. Cross Federal Workgroup on Telehealth (FedTel) Inventory of Activities

    Data.gov (United States)

    U.S. Department of Health & Human Services — This dataset is a collection of the submitted activities and projects from member of the Cross Federal Workgroup on Telehealth (FedTel). The FedTel's membership...

  11. Doubly Fed Drives for Variable Speed Wind Turbines

    DEFF Research Database (Denmark)

    Lindholm, Morten

    2004-01-01

    This thesis deals with the use of variable speed wind turbines. Different wind turbine generator topologies are described. In particular, the reduced variable speed turbine, which uses a doubly fed induction generator, is covered. An overview of the power electronic inverters of interest...... in the machine is nearly constant. This means that changes of either the flux or torque producing current in the rotor circuit is limited by the transient time constant of the machine. A 40 kW laboratory model with a doubly fed induction generator and a 3-level neutral point clamped back to back power converter...... is constructed. Adaptive active flters are used to reduce harmonics and slip harmonics in the stator current. The flters are implemented in both inverters. The active flters reduce the stator harmonics by 20-30 dB. The flters can reduce the slip harmonics at variable speed....

  12. SIMULATION OF CYCLOCONVERTER FED SPLIT PHASE INDUCTION MOTOR

    Directory of Open Access Journals (Sweden)

    Abhishek Pratap Singh

    2012-01-01

    Full Text Available Single-phase induction motors are widely used in many applications. Improvements in its performance mean a great saving in electrical energy consumption. A cycloconverter fed variable frequency motor is a typical example of such improvement. In this regard, the paper presents an analysis of the performance and speed control of the split phase induction motor when it is fed with cycloconverter. Dynamic models and analysis of the motor behavior during transient and steady state phases are presented. A speed controller based oncycloconverter is proposed. The controlled motor exhibited better performance at staring state. A cycloconverter is a device that converts AC, power at one frequency into AC power of an adjustable but lower frequency without any direct current, or DC, stage in between. It can also be considered as a static frequency changer andtypically contains silicon-controlled rectifiers.

  13. Impulse Testing of Corporate-Fed Patch Array Antennas

    Science.gov (United States)

    Chamberlain, Neil F.

    2011-01-01

    This paper discusses a novel method for detecting faults in antenna arrays. The method, termed Impulse Testing, was developed for corporate-fed patch arrays where the element is fed by a probe and is shorted at its center. Impulse Testing was devised to supplement conventional microwave measurements in order to quickly verify antenna integrity. The technique relies on exciting each antenna element in turn with a fast pulse (or impulse) that propagates through the feed network to the output port of the antenna. The resulting impulse response is characteristic of the path through the feed network. Using an oscilloscope, a simple amplitude measurement can be made to detect faults. A circuit model of the antenna elements and feed network was constructed to assess various fault scenarios and determine fault-detection thresholds. The experimental setup and impulse measurements for two patch array antennas are presented. Advantages and limitations of the technique are discussed along with applications to other antenna array topologies

  14. Voltage Control in Wind Power Plants with Doubly Fed Generators

    DEFF Research Database (Denmark)

    Garcia, Jorge Martinez

    In this work, the process of designing a wind power plant composed of; doubly fed induction generators, a static compensator unit, mechanically switched capacitors and on-load tap changer, for voltage control is shown. The selected control structure is based on a decentralized system, since...... supplied by the doubly fed induction generator wind turbines is overcome by installing a reactive power compensator, i.e. a static compensator unit, which is coordinated with the plant control by a specific dispatcher. This dispatcher is set according to the result of the wind power plant load flow....... To release the operation of the converters during steady-state disturbances, mechanically switched capacitors are installed in the wind power plant, which due to their characteristics, they are appropriate for permanent disturbances compensation. The mechanically switched capacitors are controlled to allow...

  15. Accurate Sky Continuum Subtraction with Fibre-fed Spectrographs

    CERN Document Server

    Yang, Yanbin; Puech, Mathieu; Flores, Hector; Royer, Frederic; Disseau, Karen; Gonçalves, Thiago; Hammer, François; Cirasuolo, Michele; Evans, Chris; Causi, Gianluca Li; Maiolino, Roberto; Melo, Claudio

    2013-01-01

    Fibre-fed spectrographs now have throughputs equivalent to slit spectrographs. However, the sky subtraction accuracy that can be reached has often been pinpointed as one of the major issues associated with the use of fibres. Using technical time observations with FLAMES-GIRAFFE, two observing techniques, namely dual staring and cross beam-switching, were tested and the resulting sky subtraction accuracy reached in both cases was quantified. Results indicate that an accuracy of 0.6% on sky subtraction can be reached, provided that the cross beam-switching mode is used. This is very encouraging with regard to the detection of very faint sources with future fibre-fed spectrographs, such as VLT/MOONS or E-ELT/MOSAIC.

  16. Ultra-Wideband Coplanar-Fed Monopoles: A Comparative Study

    Directory of Open Access Journals (Sweden)

    J. Jilkova

    2008-04-01

    Full Text Available The paper provides an experimental comparison of four types of ultra-wideband coplanar-fed planar monopole antennas. Parameters of the open stub completed by an L-shaped monopole and the cross monopole were adopted from the literature. The forked monopole and the coplanar monopole were fabricated and measured. Monopoles were compared from the viewpoint of the impedance bandwidth, gain, directivity patterns and dimensions.

  17. Six-Phase Matrix Converter Fed Double Star Induction Motor

    OpenAIRE

    Bendiabdellah Azeddine; Bachir Ghalem

    2010-01-01

    two different control strategies applied to a direct AC-AC six-phase matrixconverter are investigated in the present paper. The first strategy is derived from theVenturini method, and the second approach is practically an extension of the scalarstrategy control. Both strategies were originally applied to the three-phase matrixconverter.The current investigation deals with a comparative performance study of a double starinduction motor fed from a six-phase matrix converter using the two above ...

  18. Spermatogenesis in bald eagles experimentally fed a diet containing DDT

    Science.gov (United States)

    Locke, L.N.; Chura, N.J.; Stewart, P.A.

    1966-01-01

    When Bald Eagles were fed DDT in the diet at the level of 10 ppm (dry weight basis) for periods of 60 and 120 days, there was no interference with spermatogenic activity. Degenerative testicular changes were produced only by levels of DDT that produced abnormal neurological signs and usually resulted in death. Histological examination of these testes indicates that Bald Eagles have a seasonal testicular cycle similar to that reported for many other birds of the Northern Hemisphere.

  19. Anticholesteremic property of Lactobacillus acidophilus yogurt fed to mature boars.

    Science.gov (United States)

    Danielson, A D; Peo, E R; Shahani, K M; Lewis, A J; Whalen, P J; Amer, M A

    1989-04-01

    Three strains of Lactobacilus acidophilus (LA) were isolated from the feces of mature boars that were not being fed antibiotics from the Nebraska Gene Pool (NGP). All three LA isolates were screened in vitro for anticholesteremic and antimicrobial activities. One strain, LA16, caused the greatest reduction in cholesterol and inhibited both Bacillus subtilis and Escherichia coli the most. LA16 was used to produce 16, 18.9-liter quantities of acidophilus yogurt (AY), over a period of 8 wk, for use as a feed ingredient in diets for the NGP boars. Colony forming units (cfu), pH, protein, energy, Ca and P were consistent across all 16 batches of yogurt. All of the 18 boars were fed a high-cholesterol diet for a period of 56 d at a rate of 2.268 kg/(hd.d) to furnish 6.661 g/(hd.d) of cholesterol. Nine of the boars then were fed 1.81 kg/(hd.d) of a second diet that was supplemented with .454 kg/(hd.d) of AY. The other nine boars were fed the original diet. Cholesterol intake was the same for the two dietary treatments. Blood samples were collected weekly from the brachial-jugular region and the sera were analyzed for lipids. Acidophilus yogurt reduced serum cholesterol (P less than .01) and low density lipoproteins (P less than .08), but it had no effect on serum triglycerides (P greater than .23) or on high density lipoproteins (P greater than .11).

  20. Demographic responses of Daphnia magna fed transgenic Bt-maize

    OpenAIRE

    2009-01-01

    The food/feed quality of a variety of genetically modified (GM) maize expressing Cry1Ab Bt-toxin was tested over the life-cycle of Daphnia magna, an arthropod commonly used as model organism in ecotoxicological studies. Demographic responses were compared between animals fed GM or unmodified (UM) near isogenic maize, with and without the addition of predator smell. Age-specific data on survival and birth rates were integrated and analysed using life tables and Leslie matrices. Survival, fecun...

  1. Organochlorine compounds in breast-fed vs. bottle-fed infants: preliminary results at six weeks of age

    Energy Technology Data Exchange (ETDEWEB)

    Lackmann, G.-M.; Schaller, K.-H.; Angerer, J

    2004-08-15

    Background: Polychlorinated biphenyls (PCBs), hexachlorobenzene (HCB), and 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (DDT) are ubiquitous compounds with carcinogenic and teratogenic properties. They are chemically very stable and lipophilic and, therefore, accumulate in our food-chain. They are prenatally transmitted from mother to foetus, and mother's milk due to its high lipid content is an elimination pathway of special importance. Therefore, breast-feeding has been held responsible for elevated concentrations of these organochlorine compounds as well as for harmful effects in children later in life. Methods: Blood samples (2.5 ml) were taken from each 10 breast-fed and bottle-fed infants at 6 weeks of age. Blood specimens were immediately centrifuged, and serum was stored in glass tubes at -20 degree sign C until analysis. Three higher chlorinated PCB congeners (IUPAC nos. 138, 153 and 180), HCB, and the organic metabolite of DDT, p,p<<-DDE, were analysed with capillary gas chromatography with electron capture detection. Reliability was tested with gas chromatography-mass spectrometry. Results: There were no differences between the study groups of breast-fed and bottle-fed infants with regard to sex distribution, gestational age, birth-weight, age of the mothers, and smoking behaviour of the parents. In contrast, serum concentrations of all organochlorine compounds were significantly higher (P<0.0001) in breast-fed than in bottle-fed infants (mean): PCB 138, 0.38 vs. 0.10 {mu}g/l; PCB 153, 0.49 vs. 0.1 {mu}g/l; PCB 180, 0.31 vs. 0.04 {mu}g/l; {sigma}PCB, 1.19 vs. 0.29 {mu}g/l; HCB, 0.13 vs. 0.04 {mu}g/l; p,p<<-DDE, 1.05 vs. 0.18 {mu}g/l. Conclusions: Breast-feeding significantly increases the pollution of our infants with different organochlorine compounds as early as at 6 weeks of age. The progress of the present study will show whether this pollution will further increase with longer duration of breast-feeding, and whether breast-feeding bears any

  2. Continuous Cellulosic Bioethanol Fermentation by Cyclic Fed-Batch Cocultivation

    Science.gov (United States)

    Jiang, He-Long; He, Qiang; He, Zhili; Hemme, Christopher L.; Wu, Liyou

    2013-01-01

    Cocultivation of cellulolytic and saccharolytic microbial populations is a promising strategy to improve bioethanol production from the fermentation of recalcitrant cellulosic materials. Earlier studies have demonstrated the effectiveness of cocultivation in enhancing ethanolic fermentation of cellulose in batch fermentation. To further enhance process efficiency, a semicontinuous cyclic fed-batch fermentor configuration was evaluated for its potential in enhancing the efficiency of cellulose fermentation using cocultivation. Cocultures of cellulolytic Clostridium thermocellum LQRI and saccharolytic Thermoanaerobacter pseudethanolicus strain X514 were tested in the semicontinuous fermentor as a model system. Initial cellulose concentration and pH were identified as the key process parameters controlling cellulose fermentation performance in the fixed-volume cyclic fed-batch coculture system. At an initial cellulose concentration of 40 g liter−1, the concentration of ethanol produced with pH control was 4.5-fold higher than that without pH control. It was also found that efficient cellulosic bioethanol production by cocultivation was sustained in the semicontinuous configuration, with bioethanol production reaching 474 mM in 96 h with an initial cellulose concentration of 80 g liter−1 and pH controlled at 6.5 to 6.8. These results suggested the advantages of the cyclic fed-batch process for cellulosic bioethanol fermentation by the cocultures. PMID:23275517

  3. Survival and reproductive success of black ducks fed methyl mercury

    Science.gov (United States)

    Finley, M.T.; Stendell, R.C.

    1978-01-01

    A diet containing 3 ppm mercury was fed to black ducks (Anas rubripes) for periods of 28 weeks during two consecutive breeding seasons. Clutch size, egg production, number of eggs incubated, hatchability and survival of ducklings were lower during both years in hens fed mercury. Reduced hatchability and poor duckling survival were the most harmful effects. During 2 years, 13 pairs of breeders fed mercury produced only 16 ducklings that survived 1 week compared with 73 ducklings from 13 pairs of controls. Mercury residues in eggs, embryos and ducklings averaged about 30% lower during the second breeding season compared with first year results. Third eggs laid by treated hens contained a mean of 6?14 and 3?86 ppm mercury during the first and second years. Whole embryos that failed to hatch contained means of 9?62 and 6?08 ppm mercury during the first and second years. Brains of dead ducklings contained between 3?25 and 6?98 ppm mercury and exhibited lesions characteristic of mercury poisoning. Relative tissue mercury levels for treated adult breeders were: feathers > liver > kidney > breast muscle > brain. Mercury levels in males and females did not differ.

  4. Control aspects of the brushless doubly-fed machine

    Science.gov (United States)

    Lauw, H. K.; Krishnan, S.

    1990-09-01

    This report covers the investigations into the control aspects of a variable-speed generation (VSG) system using a brushless double-fed generator excited by a series-resonant converter. The brushless double-fed machine comprises two sets of stator 3-phase systems which are designed with common windings. The rotor is a cage rotor resembling the low-cost and robust squirrel cage of a conventional induction machine. The system was actually designed and set up in the Energy Laboratory of the Department of Electrical and Computer Engineering at Oregon State University. The series-resonant converter designed to achieve effective control for variable-speed generation with the brushless doubly-fed generator was adequate in terms of required time response and regulation as well as in providing for adequate power quality. The three elements of the VSG controller, i.e., voltage or reactive power controller, the efficiency maximizer and the stabilizer, could be designed using conventional microprocessor elements with a processing time well within the time period required for sampling the variables involved with executing the control tasks. The report treats in detail the stability problem encountered in running the machine at certain speed regions, even if requirements for steady-state stability are satisfied. In this unstable region, shut down of the VSG system is necessary unless proper stabilization controls are provided for. The associated measures to be taken are presented.

  5. Crowbar system in doubly fed induction wind generators

    Energy Technology Data Exchange (ETDEWEB)

    Salles, M. B. C.; Cardoso, J. R. [Laboratory of Applied Electromagnetism-LMAG, University of Sao Paulo (Brazil); Hameyer, K. [Institute of Electrical Machines-IEM, RWTH Aachen University (Germany); Grilo, A. P. [Engineering, Modeling and Applied Social Science Center-Federal University of ABC, Santo Andre (Brazil); Rahmann, C. [Institute of Power Systems and Power Economics-IAEW, RWTH Aachen University (Germany)

    2010-07-01

    In the last 15 years, the use of doubly fed induction machines in modern variable-speed wind turbines has increased rapidly. This development has been driven by the cost reduction as well as the low-loss generation of Insulated Gate Bipolar Transistors (IGBT). According to new grid code requirements, wind turbines must remain connected to the grid during grid disturbances. Moreover, they must also contribute to voltage support during and after grid faults. The crowbar system is essential to avoid the disconnection of the doubly fed induction wind generators from the network during faults. The insertion of the crowbar in the rotor circuits for a short period of time enables a more efficient terminal voltage control. As a general rule, the activation and the deactivation of the crowbar system is based only on the DC-link voltage level of the back-to-back converters. In this context, the authors discuss the critical rotor speed to analyze the instability of doubly fed induction generators during grid faults. (author)

  6. Evaluation of DCS III Transmission Alternatives, Phase II, Task 1.

    Science.gov (United States)

    1981-08-31

    Virtual circuits vs. "real" circuits. Particularly those digital services based on advanced concentration and multiple access schemes may not meet the...amplifiers, filters, modems, and line interface circuits; these devices are necessary for the realization of fully integrated digital services (e.g

  7. Evaluation of DCS III Transmission Alternatives. Phase 1A Report.

    Science.gov (United States)

    1980-05-26

    Waves . . . . ... . 3-13 3.4 EHF Satellite Communicatins ... 3-15 *3.5 Optical Fibers . . . . . . . . . . . . . . . . . . . . . . 3-17 3.5.1 Optical Fiber...Defense and Space Systems Group, TRW Inc. and by TRW’s subcontractor, Page Communications Engineers, Inc., Northrop Corporation . 1.1 Purpose of the DCS III...tactical and long haul communicatins systems study have been sponsored by the U.S. Army, and the U.S. Navy also is working on submarine fiber optics

  8. Performance and carcass traits of finishing heifers fed crude glycerin.

    Science.gov (United States)

    Parsons, G L; Shelor, M K; Drouillard, J S

    2009-02-01

    Crossbred heifers (n = 373; 421.6 kg +/- 28.9) were fed finishing diets containing 0, 2, 4, 8, 12, or 16% crude glycerin (DM basis). Diets consisted of steam-flaked corn with 6% alfalfa hay and 1.2% urea and provided 300 mg of monensin, 90 mg of tylosin, and 0.5 mg of melengestrol acetate per animal daily. Cattle were stratified by BW and allocated randomly, within strata, to concrete-surfaced feedlot pens each containing 6 to 7 heifers, with 9 pens per dietary treatment. Cattle were transitioned from the control diet to diets containing increasing proportions of glycerin over a period of 10 d. Cattle had ad libitum access to feed, and diets were delivered once daily throughout the 85-d trial period. As the concentration of glycerin increased, DMI decreased linearly (P glycerin had ADG of 1.19, 1.34, 1.29, 1.25, 1.17, and 1.03 kg, respectively (linear, P = 0.013; quadratic, P = 0.010). Feeding glycerin had a quadratic effect on G:F, and G:F was optimal when glycerin was fed at 2% of the diet (quadratic, P = 0.046). Glycerin increased the final BW by 12.7, 8.1, and 5.3 kg when fed at 2, 4, and 8% of the diet, respectively, but reduced the final BW by 1.9 and 14.3 kg when included at 12 and 16% of the diet (linear, P = 0.009; quadratic, P = 0.006). Similarly, HCW increased by 8.1, 5.1, and 3.3 kg when glycerin was fed at 2, 4, and 8% of the diet, respectively, but were 1.2 and 9.1 kg less than controls when glycerin was fed at 12 and 16%, respectively (linear, P = 0.009; quadratic, P = 0.006). Longissimus muscle area decreased linearly as glycerin concentrations increased (P glycerin resulted in linear decreases in subcutaneous fat over the 12th rib and marbling scores (P = 0.045). Glycerin tended to decrease the percentage of cattle grading USDA Choice (P = 0.084) and increase the percentage of cattle grading USDA Select. Adding glycerin to cattle-finishing diets improved BW gain and feed efficiency, particularly when added at concentrations of 8% or less on a DM

  9. Incidence of nosocomial rotavirus infections, symptomatic and asymptomatic, in breast-fed and non-breast-fed infants.

    Science.gov (United States)

    Gianino, P; Mastretta, E; Longo, P; Laccisaglia, A; Sartore, M; Russo, R; Mazzaccara, A

    2002-01-01

    Rotavirus is one of the most important aetiological agents of nosocomial infections in childhood. We studied the incidence of nosocomial rotavirus infections in 420 patients (age range 1-18 months) consecutively admitted from 1 December 1999 to 31 May 2000 to the infant ward of the Department of Paediatrics, University of Turin. We also evaluated the protective effect of breast feeding. Faecal specimens were collected from every child (whether developing diarrhoeic symptoms or not) and tested for rotavirus during hospitalization and 72 h after discharge. The incidence of rotavirus nosocomial infections was 27.7%. The incidence of symptomatic nosocomial infections was 16.8%, and the incidence of asymptomatic infections was 10.9%. The attack rate of the infections that occurred during hospitalization was 11.8%, while for those occurring after discharge, it was 15.9%. Rotavirus infection, on average, prolonged hospital stay from 5.2 to 6.4 days. 10.6% of breast-fed infants and 32.4% of non-breast-fed infants contracted rotavirus infection (P<0.005). None of the breast-fed infants who contracted rotavirus infection developed diarrhoeic symptoms.

  10. 肋环型单层曲板网壳结构的风振响应及等效静风荷载%Wind-induced response and equivalent static wind load of single-layer Geiger lattice shell with curved plate

    Institute of Scientific and Technical Information of China (English)

    冯若强; 丁静鹄; 李庆祥; 叶继红

    2012-01-01

    The wind pressure and the wind-induced vibration of a single-layer Geiger lattice shell with curved plate are analyzed. Different methods are used to calculate the equivalent static wind load, and the calculation accuracy are compared. The results of the wind tunnel experiment show that the wind pressure is mostly negative on the single-layer Geiger lattice shell with curved plate. But under the 90° wind direction, because of the flow obstruction of the front building, the positive pressure appears on some area of the roof s edge. The wind-induced response analysis results show that many modes make contribution to the structural wind-induced response, and the higher modes should be considered. Subjected to the fluctuating wind load, the mode coupling should be considered in order to obtain a good accuracy of the wind-induced response for all the structural nodes. If only the accuracy of the larger displacement is needed, the square root sum of square(SRSS) method which ignores the mode coupling can be also used. It is found that both the load-response correlation (LRC) with inertia force method and the modified LRC method for calculating the equivalent static wind load of the single-layer Geiger lattice shell with curved plate can ensure the equivalence of the largest displacements rather than all the nodal displacements.%分析了肋环型单层曲板网壳结构的风荷载和风振响应,并对采用不同方法计算结构等效静风荷载的精度进行了比较.风洞试验结果表明:肋环型单层曲板网壳结构屋面主要受负风压作用;但在90°风向角下,由于体育馆受前方入口建筑的影响,屋盖边缘局部出现正风压.风振响应分析结果表明:有多阶振型参与结构的风致振动,高阶模态影响不可忽略;为保证结构表面所有节点位移准确,结构的模态耦合项不能忽略.但如果只保证较大位移处的准确性,忽略模态耦合项的SRSS方法也是可取的.利用LRC惯性力法和

  11. Spin Transport in Single Layer Transition Metal Dichalcogenides

    Science.gov (United States)

    Phillips, Michael; Aji, Vivek

    Inversion symmetry breaking and strong spin orbit coupling in two dimensional transition metal dichalcogenides leads to interesting new phenomena such as the valley hall and spin hall effects. The nontrivial Berry curvature of the bands yields transverse spin currents in applied field. In this talk we characterize the spin transport in hole-doped systems. Due to the large spin-splitting, time-reversal invariance, and the large separation of hole pockets in momentum space, spin flip scattering involves inter-valley processes with large momentum. As such, one expects large spin life times and a large spin hall angle. We analyze the robustness of the phenomena to various scattering processes and explore the viability of transition metal dichalcogenides for spintronic applications. We acknowledge the support of the NSF via Grant NSF DMR-1506707.

  12. Thermal transport across graphene and single layer hexagonal boron nitride

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Jingchao, E-mail: zhang@unl.edu, E-mail: yyue@whu.edu.cn [Holland Computing Center, University of Nebraska-Lincoln, Lincoln, Nebraska 68588 (United States); Hong, Yang [Department of Chemistry, University of Nebraska-Lincoln, Lincoln, Nebraska 68588 (United States); Yue, Yanan, E-mail: zhang@unl.edu, E-mail: yyue@whu.edu.cn [School of Power and Mechanical Engineering, Wuhan University, Wuhan, Hubei 430072 (China)

    2015-04-07

    As the dimensions of nanocircuits and nanoelectronics shrink, thermal energies are being generated in more confined spaces, making it extremely important and urgent to explore for efficient heat dissipation pathways. In this work, the phonon energy transport across graphene and hexagonal boron-nitride (h-BN) interface is studied using classic molecular dynamics simulations. Effects of temperature, interatomic bond strength, heat flux direction, and functionalization on interfacial thermal transport are investigated. It is found out that by hydrogenating graphene in the hybrid structure, the interfacial thermal resistance (R) between graphene and h-BN can be reduced by 76.3%, indicating an effective approach to manipulate the interfacial thermal transport. Improved in-plane/out-of-plane phonon couplings and broadened phonon channels are observed in the hydrogenated graphene system by analyzing its phonon power spectra. The reported R results monotonically decrease with temperature and interatomic bond strengths. No thermal rectification phenomenon is observed in this interfacial thermal transport. Results reported in this work give the fundamental knowledge on graphene and h-BN thermal transport and provide rational guidelines for next generation thermal interface material designs.

  13. Phonon transport in single-layer boron nanoribbons

    Science.gov (United States)

    Zhang, Zhongwei; Xie, Yuee; Peng, Qing; Chen, Yuanping

    2016-11-01

    Inspired by the successful synthesis of three two-dimensional (2D) allotropes, the boron sheet has recently been one of the hottest 2D materials around. However, to date, phonon transport properties of these new materials are still unknown. By using the non-equilibrium Green’s function (NEGF) combined with the first principles method, we study ballistic phonon transport in three types of boron sheets; two of them correspond to the structures reported in the experiments, while the third one is a stable structure that has not been synthesized yet. At room temperature, the highest thermal conductance of the boron nanoribbons is comparable with that of graphene, while the lowest thermal conductance is less than half of graphene’s. Compared with graphene, the three boron sheets exhibit diverse anisotropic transport characteristics. With an analysis of phonon dispersion, bonding charge density, and simplified models of atomic chains, the mechanisms of the diverse phonon properties are discussed. Moreover, we find that many hybrid patterns based on the boron allotropes can be constructed naturally without doping, adsorption, and defects. This provides abundant nanostructures for thermal management and thermoelectric applications.

  14. Ultrafast Non-Thermal Electron Dynamics in Single Layer Graphene

    Directory of Open Access Journals (Sweden)

    Novoselov K.S.

    2013-03-01

    Full Text Available We study the ultrafast dynamics of non-thermal electron relaxation in graphene upon impulsive excitation. The 10-fs resolution two color pump-probe allows us to unveil the non-equilibrium electron gas decay at early times.

  15. Phonon transport in single-layer Boron nanoribbons

    CERN Document Server

    Zhang, Zhongwei; Peng, Qing; Chen, Yuanping

    2016-01-01

    Inspired by the successful synthesis of several allotropes, boron sheets have been one of the hottest spot areas of focus in various fields. Here, we study phonon transport in three types of boron nanoribbons with zigzag and armchair edges by using a non-equilibrium Green's function combined with first principles methods. Diverse transport properties are found in the nanoribbons. At the room temperature, their highest thermal conductance can be comparable with that of graphene, while the lowest thermal conductance is less than half of graphene's. The three boron sheets exhibit different anisotropic transport characteristics. Two of these sheets have stronger phonon transport abilities along the zigzag edges than the armchair edges, while in the case of the third, the results are reversed. With the analysis of phonon dispersion, bonding charge density, and simplified models of atomic chains, the mechanisms of the diverse phonon properties are discussed. Because all boron allotropes consists of hexagonal and tr...

  16. Droplet Measurement below Single-Layer Grid Fill

    Directory of Open Access Journals (Sweden)

    Vitkovic Pavol

    2016-01-01

    Full Text Available The main part of the heat transfer in a cooling tower is in a fill zone. This one is consist of a cooling fill. For the cooling tower is used a film fill or grid fill or splash fill in the generally. The grid fill has lower heat transfer performance like film fill usually. But their advantage is high resistance to blockage of the fill. The grid fill is consisted with independent layers made from plastic usually. The layers consist of several bars connected to the different shapes. For experiment was used the rhombus shape. The drops diameter was measured above and below the Grid fill.

  17. Interlayer tunnelling mechanism : experimental test of single layer compounds

    NARCIS (Netherlands)

    Tsvetkov, AA; van der Marel, D; Dulic, D; Molegraaf, HJ; Kolesnikov, NN; Willemsen, B; Ren, ZF; Bozovic,; Pavuna, D

    1998-01-01

    The c-axis optical properties of cuprate superconductors have been studied by grazing angle reflectivity technique. We tested the interlayer tunnelling (ILT) model of high temperature superconductivity and showed that the basic relation between the condensation energy of the superconducting state

  18. Heterogeneous fluorescence intermittency in single layer reduced graphene oxide

    Science.gov (United States)

    Si, Jixin; Volkan-Kacso, Sandor; Eltom, Ahmed; Morozov, Yurii; McDonald, Matthew P.; Ruth, Anthony; Kuno, Masaru; Janko, Boldizsar

    Fluorescence intermittency, or blinking, has been observed in a wide range of systems, including quantum dots, nanorods, and nanowires. Striking similarities have been documented in the optical response of these nanoscale emitters. However, the mechanism behind blinking still remains elusive. For the first time, blinking has been observed in a two-dimensional system in recent experiments on reduced graphene oxide (rGO). Here we reveal the power spectral density (PSD) of the blinking in rGO shares the same 1/f-like behavior of previously known blinking systems; meanwhile, the heterogeneous dynamic evolution and spatial correlation make rGO a unique blinking system. To investigate the origin of blinking, we self-consistently explain the evolution of rGO blinking using the phenomenological multiple recombination center (MRC) model that captures common features of nanoscale blinking. Furthermore, tight binding method and ab-initio method calculations of carbon nanodots are utilized to look for the microscopic structure corresponding to the RCs in the MRC model. M. K. thanks the American Chemical Society Petroleum Research Fund, the Army Research Office (W911NF-12-1-0578) for support. B.J. was supported in part by the U. S. DOE, Office of Science, Office of Basic Energy Sciences, under Contract W-31-109-Eng-38.

  19. Interlayer tunnelling mechanism : experimental test of single layer compounds

    NARCIS (Netherlands)

    Tsvetkov, AA; van der Marel, D; Dulic, D; Molegraaf, HJ; Kolesnikov, NN; Willemsen, B; Ren, ZF; Bozovic,; Pavuna, D

    1998-01-01

    The c-axis optical properties of cuprate superconductors have been studied by grazing angle reflectivity technique. We tested the interlayer tunnelling (ILT) model of high temperature superconductivity and showed that the basic relation between the condensation energy of the superconducting state an

  20. Charge-carrier screening in single-layer graphene.

    Science.gov (United States)

    Siegel, David A; Regan, William; Fedorov, Alexei V; Zettl, A; Lanzara, Alessandra

    2013-04-05

    The effect of charge-carrier screening on the transport properties of a neutral graphene sheet is studied by directly probing its electronic structure. We find that the Fermi velocity, Dirac point velocity, and overall distortion of the Dirac cone are renormalized due to the screening of the electron-electron interaction in an unusual way. We also observe an increase of the electron mean free path due to the screening of charged impurities. These observations help us to understand the basis for the transport properties of graphene, as well as the fundamental physics of these interesting electron-electron interactions at the Dirac point crossing.

  1. Optical extinction in a single layer of nanorods

    CERN Document Server

    Ghenuche, Petru; Laroche, Marine; Bardou, Nathalie; Haïdar, Riad; Pelouard, Jean-Luc; Collin, Stéphane

    2012-01-01

    We demonstrate that almost 100 % of incident photons can interact with a monolayer of scatterers in a symmetrical environment. Nearly-perfect optical extinction through free-standing transparent nanorod arrays has been measured. The sharp spectral opacity window, in the form of a characteristic Fano resonance, arises from the coherent multiple scattering in the array. In addition, we show that nanorods made of absorbing material exhibit a 25-fold absorption enhancement per unit volume compared to unstructured thin film. These results open new perspectives for light management in high-Q, low volume dielectric nanostructures, with potential applications in optical systems, spectroscopy, and optomechanics.

  2. Ultra-thin, single-layer polarization rotator

    Energy Technology Data Exchange (ETDEWEB)

    Son, T. V.; Truong, V. V., E-mail: Truong.Vo-Van@Concordia.Ca [Department of Physics, Concordia University, Montreal, Quebec, H4B 1R6 (Canada); Do, P. A.; Haché, A. [Département de Physique et d’Astronomie, Université de Moncton, Moncton, New Brunswick, E1A 3E9 (Canada)

    2016-08-15

    We demonstrate light polarization control over a broad spectral range by a uniform layer of vanadium dioxide as it undergoes a phase transition from insulator to metal. Changes in refractive indices create unequal phase shifts on s- and p-polarization components of incident light, and rotation of linear polarization shows intensity modulation by a factor of 10{sup 3} when transmitted through polarizers. This makes possible polarization rotation devices as thin as 50 nm that would be activated thermally, optically or electrically.

  3. 基于双粒子耦合的单层介质柱阵列对电磁波的调控∗%Rectifying electromagnetic waves by a single-layer dielectric particle array based on dual-particle coupling

    Institute of Scientific and Technical Information of China (English)

    郑红霞; 周鑫; 韩影; 俞昕宁; 刘士阳

    2015-01-01

    Metamaterials, composed of subwavelength building blocks with artificial electric/magnetic response, have attracted the intensive interest due to the unprecedented controllability of electromagnetic (EM) waves and the potential applica-tions. Nonetheless, the resonance of the metallic building block induces a strong loss, severely limiting the performance. Dielectric particle based subwavelength structures provide an alternative choice for the manipulation of EM waves, meanwhile, circumventing the loss problem inevitable for metallic metamaterials, in particular, in optical regime. It is shown that this kind of metamaterial can be used to guide the surface wave with the dielectric particle chain, which is similar to the surface plasmon mediated wave guiding. The structure is also shown to be capable of implementing negative refraction with negligible loss theoretically and experimentally. In addition, the single-layer dielectric rod array can be used to achieve omnidirectional total reflection at subwavelength scale. To further extend the functionality of dielectric based metamaterials and make them more appropriate for integrated optics, a variety of experimentally feasible configurations should be designed. In this work, based on the Mie scattering theory and the multiple scattering theory, we investigate the manipulation of EM waves through a single-layer subwavelength dielectric rod array (SDRA) and particle coupled system. Our results show that by removing the central dielectric rod in the SDRA and at the beam focus, like a vacancy defect, a normal incident transverse electric polarized Gaussian beam is weakly transmitted with an efficiency of less than 12 percent. By further introducing a dielectric rod with optimized parameters on the incident side of the vacancy defect, an enhanced transmitted EM wave with an efficiency of 36 percent is exhibited, nearly triple that with a solely vacancy defect. By adding another identical dielectric rod symmetrically on

  4. Glucose Metabolism in Sheep Fed Grass Supplemented with Gliricidia Sepium

    Directory of Open Access Journals (Sweden)

    Y. Widiawati

    2014-12-01

    Full Text Available The limiting factor on improving ruminant production for most of the available feed in developing countries are low in quality. Therefore high fibre diet must be supplemented by high nutritivefeed such as leguminous trees that much available in those regions. Gliricidia sepium was one of very potential candidates. Glucose as a major energy source in fed animals required precursor in form of propionat and amino acids from diet. Those precursors might be supplied by these legume leaves. The aim of this research was to investigate the glucose metabolism in the sheep fed grass supplemented by Gliricidia sepium. Fifteen sheeps (18 months old were used in the experiment. Theseare were divided into three groups that fed by experimental diet of Mitchell grass (MG group, Gliricidia(GS group, and MG supplemented with GS (MGGS group. D-[U-14C]glucoseinfusate was infused continuously through the left jugular venous catheter of each animal to measure glucose metabolism in those sheeps. The measurements were done on feed utilisation and glucose metabolism. The results indicated that there was an improvement in efficiency of feed utilisation in the MGGS group as reflected by lower feed conversion ratio by the group. Plasma glucose concentration profile per unit of OM intake were similar for GS and MGGS groups, but higher than that in the MG group (P<0.01. Glucose entry rate (GER increased in MG group through GS to the MGGS group, while N retention accordingly was increased. It can be concluded that theutilization of GS by the ruminant animal could be improved by feeding it with a low quality feed at a ratio of 40:60 (GS:Low quality feed to achieve an NI:DOMI ratio of 0.03 - 0.04. This improvement would be manifested in increasing DOMI, with subsequent increase in GER or net protein deposition as might be expressed in positive N retention.

  5. Urotensin II promotes atherosclerosis in cholesterol-fed rabbits.

    Directory of Open Access Journals (Sweden)

    Yafeng Li

    Full Text Available Urotensin II (UII is a vasoactive peptide composed of 11 amino acids that has been implicated to contribute to the development of cardiovascular disease. The purpose of this study was to investigate whether UII affects the development of atherosclerosis in cholesterol-fed rabbits. UII was infused for 16 weeks through an osmotic mini-pump into male Japanese White rabbits fed on a high-cholesterol diet. Plasma lipids and body weight were measured every 4 weeks. Aortic atherosclerotic lesions along with cellular components, collagen fibers, matrix metalloproteinase-1 and -9 were examined. Moreover, vulnerability index of atherosclerotic plaques was evaluated. UII infusion significantly increased atherosclerotic lesions within the entire aorta by 21% over the control (P = 0.013. Atherosclerotic lesions were increased by 24% in the aortic arch (P = 0.005, 11% in the thoracic aorta (P = 0.054 and 18% in the abdominal aorta (P = 0.035. These increases occurred without changes in plasma levels of total cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, triglycerides or body weight. Immunohistochemical staining revealed that macrophages and matrix metalloproteinase-9 were significantly enhanced by 2.2-fold and 1.6-fold in UII group. In vitro studies demonstrated that UII up-regulated the expression of vascular cell adhesion protein-1 and intercellular adhesion molecule-1 in human umbilical vein endothelial cells, which was inhibited by the UII receptor antagonist urantide. In conclusion, our results showed that UII promotes the development of atherosclerotic lesions and destabilizes atherosclerotic plaques in cholesterol-fed rabbits.

  6. Stator insulation systems for medium voltage PWM drives fed motors

    Energy Technology Data Exchange (ETDEWEB)

    Gao, G.; Chen, W. [TECO-Westinghouse Motor Co., Round Rock, TX (United States)

    2005-07-01

    Adjustable speed drives (ASD) are commonly used in power electronics and control systems. It is estimated that more than 15 per cent of medium voltage motors are currently fed by such drives worldwide. A research project was conducted to examine the influence of medium voltage pulse width modulated (PWM) ASD on motor stator insulation systems. The findings, based on accelerated laboratory tests, have helped designers to improve the capabilities of the insulation system used for ASD-fed motors. Repetitive, high magnitude voltage spikes with fast rise time create significant stress on insulation systems. Gradual deterioration and premature failure of the motor insulation can result from surge voltages which generate surface discharges between phase windings/end windings, or partial discharges between stator turns. However, there is no industrial standard to evaluate motor insulation life under ASD-cable-motor conditions. Several material manufacturers have developed their own version of corona resistant material. However, the insulation life of ASD-fed motors does not depend solely on the raw materials. Rather, it depends on the complete insulation system, including the stator manufacturing process. In order to address this problem, TECO-Westinghouse Motor Company has developed special design criteria and manufacturing practices in order to reduce winding insulation temperature and to compensate for the additional heat generated by high frequency contents in the PWM voltage waveform. A patent pending new cooling system should reduce winding temperature by 15 to 20 degrees C. This paper presented design considerations for turn insulation, groundwall insulation, and a voltage stress grading system. A new thermal class H insulation system was also described. 6 refs., 2 tabs., 5 figs.

  7. Energy intake of rats fed a cafeteria diet.

    Science.gov (United States)

    Prats, E; Monfar, M; Castellà, J; Iglesias, R; Alemany, M

    1989-02-01

    The proportion of lipid, carbohydrate and protein energy self-selected by male and female rats from a cafeteria diet has been studied for a 48-day period (36-day in female rats). The diet consisted in 12 different items and was offered daily, in excess and under otherwise standard conditions, to rats--caged in groups of three--from weaning to adulthood. Groups of control animals were studied in parallel and compared with the cafeteria groups. Cafeteria diet fed groups of rats ingested more energy and lowered their metabolic efficiency with age. Male rats ate more than females and increased their body weight even after female practically stopped growing. There was a wide variation in the aliments consumed each day by the cafeteria-fed rats. However, the proportion of lipid, protein and carbohydrate the rats ate remained constant. Male rats ingested more lipid than females. Carbohydrate consumption was constant in control and cafeteria fed groups of rats independently of sex. Protein consumption was higher in cafeteria rats than in controls, but the differences were not so important as with liquid. Fiber content of the cafeteria diet was lower than that of the control diet. The cafeteria diet selected by the rats was, thus, hypercaloric and hyperlipidic, with practically the same amount of carbohydrate than the control diet, slightly hyperproteic and, nevertheless, remarkably constant in its composition with respect to time. Cafeteria rats had a higher water intake than controls. All these trends were maintained despite the observed changes in the animals' tastes and their differential consumption of the ailments of the diet.

  8. Modeling of wind turbines with doubly fed generator system

    CERN Document Server

    Fortmann, Jens

    2014-01-01

    Jens Fortmann describes the deduction of models for the grid integration of variable speed wind turbines and the reactive power control design of wind plants. The modeling part is intended as background to understand the theory, capabilities and limitations of the generic doubly fed generator and full converter wind turbine models described in the IEC 61400-27-1 and as 2nd generation WECC models that are used as standard library models of wind turbines for grid simulation software. Focus of the reactive power control part is a deduction of the origin and theory behind the reactive current requ

  9. Electric Vehicle IM Controller Based on Voltage-Fed Inverter

    Institute of Scientific and Technical Information of China (English)

    宋建国; 张承宁; 袁学; 谭建

    2004-01-01

    A novel electric vehicle (EV) induction motor (IM) controller based on voltage-fed inverter is presented. It is shown that the proposed adaptive control algorithm effectively both simplifies the structure and expands the capacity of controller. The relationship between stator's voltage and that of current under rotor's flux-oriented-coordinates is first introduced, and then the structure of vector control is analyzed, in which voltage compensation is inducted as the core feedback procedure. Experiments prove that, together with a facility for realization, a smooth transition, a prompt torque response and small concussion are gained. Extensive research conducted by varying parameters that result in practical ripple is proposed in conclusion.

  10. Estimation of optimal feeding strategies for fed-batch bioprocesses.

    Science.gov (United States)

    Franco-Lara, Ezequiel; Weuster-Botz, Dirk

    2005-07-01

    A generic methodology for feeding strategy optimization is presented. This approach uses a genetic algorithm to search for optimal feeding profiles represented by means of artificial neural networks (ANN). Exemplified on a fed-batch hybridoma cell cultivation, the approach has proven to be able to cope with complex optimization tasks handling intricate constraints and objective functions. Furthermore, the performance of the method is compared with other previously reported standard techniques like: (1) optimal control theory, (2) first order conjugate gradient, (3) dynamical programming, (4) extended evolutionary strategies. The methodology presents no restrictions concerning the number or complexity of the state variables and therefore constitutes a remarkable alternative for process development and optimization.

  11. Antimicrobial resistance in enterococci isolated from Turkey flocks fed virginiamycin.

    Science.gov (United States)

    Welton, L A; Thal, L A; Perri, M B; Donabedian, S; McMahon, J; Chow, J W; Zervos, M J

    1998-03-01

    From 125 separate cloacal cultures from three turkey flocks fed virginiamycin, 104 Enterococcus faecium and 186 Enterococcus faecalis isolates were obtained. As the turkeys aged, there was a higher percentage of quinupristin-dalfopristin-resistant E. faecium isolates, with isolates from the oldest flock being 100% resistant. There were no vancomycin-resistant enterococci. Results of pulsed-field gel electrophoresis (PFGE) indicated there were 11 PFGE types of E. faecalis and 7 PFGE types of E. faecium that were in more than one group of flock cultures.

  12. Fed-Batch Feeding Strategies for Enzymatic Biodiesel Production

    DEFF Research Database (Denmark)

    Price, Jason Anthony; Nordblad, Mathias; Woodley, John

    2014-01-01

    of the differences in the interfacial and bulk concentrations of the enzyme. The model is then used to evaluate various feeding strategies to improve the enzymatic biodiesel production. The feeding strategies investigated, gave insight into how the methanol should be fed to potentially mitigate enzyme deactivation...... while improving the biodiesel yield. The best experimental results gave a yield of 703 .76 g FAME L-1 and a reactor productivity of 28.12 g FAME L-1 h-1. In comparison, to reach the same yield, the optimised two step feeding strategy took 6.25 hours less, which equates to an increase the reactor...

  13. Exploring New Clustering Algorithms for the CMS Tracker FED

    CERN Document Server

    Gamboa Alvarado, Jose Leandro

    2013-01-01

    In the current Front End (FE) firmware clusters of hits within the APV frames are found using a simple threshold comparison (which is made between the data and a 3 or 5 sigma strip noise cut) on reordered pedestal and Common Mode (CM) noise subtracted data. In addition the CM noise subtraction requires the baseline of each APV frame to be approximately uniform. Therefore, the current algorithm will fail if the APV baseline exhibits large-scale non-uniform behavior. Under very high luminosity conditions the assumption of a uniform APV baseline breaks down and the FED is unable to maintain a high efficiency of cluster finding. \

  14. Wind Generator Stabilization with Doubly-Fed Asynchronous Machine

    Institute of Scientific and Technical Information of China (English)

    WU Li; WANG Zhi-xin

    2007-01-01

    This paper investigates the function of doubly-fed asynchronous machine(DASM) with emphasis placed on its ability to the stabilization of the power system including wind generators. P(active power) and Q(reactive power) compensation from DASM can be regulated independently through secondary-excitation controlling. Simulation results by power system computer aided design(PSCAD) show that DASM can restore the wind-generator system to a normal operating condition rapidly even following severe transmission-line failures. Comparison studies have also been performed between wind turbine pitch control and proposed method.

  15. NUTRIENT UTILIZATION IN BUFFALO BULLS FED CROP RESIDUE BASED RATIONS

    OpenAIRE

    Venkateswarlu, S.; D Srinivas Kumar; D. NARENDRANATH

    2013-01-01

    In 4 x 4 LSD, four graded Murrah buffalo bulls (6 yrs; 353 ± 8.26 kg) were fed four iso-nitrogenous complete rations comprising of jowar stover (CR1), maize stover (CR2), red gram straw (CR3) and black gram straw (CR4) as roughage source and concentrate mixture in 60:40 proportion, to study the effect of feeding complete rations on nutrient utilization. The DM intake (kg/d) was similar in all the groups. The digestibility coefficients of DM, OM, CP, EE, CF, NDF, ADF, Cellulose and Hemi-cellul...

  16. Power balance considerations for brushless doubly-fed machines

    Energy Technology Data Exchange (ETDEWEB)

    Gorti, B.V.; Alexander, G.C.; Spee, R. [Oregon State Univ., Corvalis, OR (United States). Dept. of Electrical and Computer Engineering

    1996-12-01

    This paper discusses the power balances in a Brushless Doubly-Fed Machine (BDFM). Equations of power in the two stator windings and the rotor circuit, showing the distribution of electrical and mechanical powers in the air-gap, are obtained in two different speed ranges of BDFM synchronous mode operation. Comparisons vis-a-vis power distribution are made between the Wound-Rotor Induction machine (WRIM) and the BDFM. A brief analysis of the power balances, along with experimental data points obtained using a laboratory prototype machine, are given.

  17. Control of a Doubly-Fed Induction Generator

    Directory of Open Access Journals (Sweden)

    Makhlouf Laakam

    2014-11-01

    Full Text Available In this paper, a grid connected wind power generation scheme using a doubly fed induction generator (DFIG is studied. The aims of this paper are: The modelling and simulation of the operating in two quadrants (torque-speed of a DFIG, the analysis employs a stator flux vector control algorithm to control rotor current using the PI regulator. The simulation calculations were achieved using MATLAB®-SIMULINK® package. The obtained results are presented, illustrating the good control performances of the system

  18. Band-notched reconfigurable CPW-fed UWB antenna

    Science.gov (United States)

    Majid, H. A.; Rahim, M. K. A.; Hamid, M. R.; Murad, N. A.; Samsuri, N. A.; Yusof, M. F. M.; Kamarudin, M. R.

    2016-04-01

    A reconfigurable band-notched CPW-fed UWB antenna using electromagnetic bandgap (EBG) structure is proposed. Two structures are positioned adjacent to the transmission line of the UWB antenna. The band-notched characteristic can be disabled by switching the state of switch place at the strip line. The EBG structure produces reconfigurable band notched at 4.0 GHz, which covers C-band satellite communication (3.625-4.2 GHz) systems. The proposed antenna is suitable for UWB systems, which requires reconfigurable band reject function.

  19. Energy utilization and growth in breast-fed and formula-fed infants measured prospectively during the first year of life

    NARCIS (Netherlands)

    N.C. de Bruin (Niels); H.J. Degenhart (Herman); S. Gal; K.R. Westerterp (Klaas); Th. Stijnen (Theo); H.K.A. Visser (Henk)

    1998-01-01

    textabstractThis study is the first to report approximations of energy requirements for male and female breast-fed and formula-fed infants based on individual estimates of total daily energy expenditure (TDEE) and energy deposition derived from total body fat (TBF) and

  20. Analysis of intestinal flora development in breast-fed and formula-fed infants by using molecular identification and detection methods

    NARCIS (Netherlands)

    Harmsen, HJM; Wildeboer-Veloo, ACM; Raangs, GC; Wagendorp, AA; Klijn, N; Bindels, JG; Welling, GW

    2000-01-01

    Background: An obvious difference between breast-fed and formula-fed newborn infants is the development of the intestinal flora, considered to be of importance for protection against harmful micro-organisms and for the maturation of the intestinal immune system. In this study, novel molecular identi

  1. Energy utilization and growth in breast-fed and formula-fed infants measured prospectively during the first year of life

    NARCIS (Netherlands)

    N.C. de Bruin (Niels); H.J. Degenhart (Herman); S. Gal; K.R. Westerterp (Klaas); Th. Stijnen (Theo); H.K.A. Visser (Henk)

    1998-01-01

    textabstractThis study is the first to report approximations of energy requirements for male and female breast-fed and formula-fed infants based on individual estimates of total daily energy expenditure (TDEE) and energy deposition derived from total body fat (TBF) and

  2. Novel Design of A Compact Proximity Coupled Fed Antenna

    Directory of Open Access Journals (Sweden)

    Mahdi Ali

    2012-01-01

    Full Text Available Certain applications such as RFID, on body sensors network, microwave systems usually require good matching impedance, high gain and large bandwidth for their antennas. The aperture coupled antenna is one candidate that can provide high gain large bandwidth and little packaging. Thus, it would be of interest to enhance the characteristics of a singly-fed aperture antenna used for Zigbee application. In this paper, we are presenting a new design of aperture coupled rectangular patch antenna operating at 2.45 GHz ISM-band frequency. The objective of this design is not limited to the improvement of the impedance bandwidth but also to better the coupling involved. The cross-polarisation (X-pol, the backward radiation and the half-power beam width in two orthogonal planes are also examined. The proposed design is based on a new aperture coupling technique in which two slots are fed by a microstrip line and coupled to a parasitic patch radiator etched on the opposite side from the slots. The matching impedance for a conventional aperture coupled microstrip antenna is obtained by the adjustment of the dimension of the slot and the feeding line. Here, the distance separating the slots is employed to control the coupling and modifying the input impedance of the antenna. Therefore, accurate matching impedance is reached with a good radiation pattern.

  3. Dental pathology in conventionally fed and pasture managed dairy cattle.

    Science.gov (United States)

    Fadden, A N; Poulsen, K P; Vanegas, J; Mecham, J; Bildfell, R; Stieger-Vanegas, S M

    2016-01-02

    Healthy teeth are important in the first stages of digestion for dairy cattle, yet little is known about bovine dental disease. This study aimed to investigate dental pathology of dairy cattle in two parts. First dairy cattle cadaver heads (n=11) were examined at the time of culling. Second, the authors performed oral exams in cattle fed a total mixed ration (TMR) (n=200) and pasture-based (n=71) grazing cattle. Cadaver heads were imaged using radiography and computed tomography before gross dissection to study dental anatomy and pathology. The most prevalent dental abnormalities were excessive transverse ridging of the occlusal surface, the presence of diastemas and third molar dental overgrowths (M3DO) in cadaver heads. Average thickness of subocclusal dentine ranged from 3.5 mm to 5.8 mm in cheek teeth but was >10 mm in maxillary teeth with M3DO. Radiographic findings were compared with oral examinations in live cattle. Prevalence of M3DO upon oral examination was 19 per cent and 28 per cent in herds of cattle fed a TMR diet and 0 per cent in a herd of grazing cattle. Dental abnormalities are prevalent in dairy cattle but due to thin subocclusal dentine in the cheek teeth, established equine dental treatment methodology is not appropriate for bovine cheek teeth with the exception of those that have developed M3DO.

  4. Reproduction and residue accumulation in black ducks fed toxaphene

    Science.gov (United States)

    Haseltine, S.D.; Finley, M.T.; Cromartie, E.

    1980-01-01

    Three sets of 15 pairs of black ducks (Anas rubripes) were given 0, 10, or 50 ppm toxaphene in a dry mash diet for a period of 19 months, which included two breeding seasons. Survival of adults was not affected, but the weights of treated males were depressed during the summer months. Egg production, fertility, hatchability, eggshell thickness, growth, and survival of young did not vary with toxaphene ingestion in either breeding season. However, the mean number of days required to complete a clutch was lower in birds fed toxaphene than in birds on the control diet. Clutches of hens fed 50 ppm toxaphene showed improved hatching success in the second year of the study. Carcass wet-weight (70% moisture) residues in adults and the young birds averaged from 50 to 100% of the dietary concentration (7% moisture); egg residues showed a similar trend. Carcass residues did not reflect those found in the livers or brains of the adults, which seldom exceeded 0.5 ppm. Toxaphene residues were found in the brain of only one 10 ppm bird, but were present in nearly all of the 50 ppm birds. Toxaphene residues were present in the liver of all birds ingesting toxaphene.

  5. The effects of phentolamine on fructose-fed rats.

    Science.gov (United States)

    Zhou, Kangbin; Kumar, Ujendra; Yuen, Violet G; McNeill, John H

    2012-08-01

    Metabolic syndrome (MS) is a combination of medical disorders that increase the risk of developing cardiovascular disease and diabetes. MS is associated with obesity, increased blood pressure, hyperlipidemia, and hyperglycemia. This study was designed to investigate the pharmacological profile of phentolamine, a nonselective α adrenergic receptor antagonist, in the prevention of increased blood pressure in fructose-fed rats. Phentolamine prevented the fructose-induced increase in systolic blood pressure without affecting insulin sensitivity and major metabolic parameters. The levels of plasma noradrenaline and angiotensin II, 2 proposed contributors to the development of fructose-induced elevated blood pressure, were examined. Neither noradrenaline nor angiotensin II levels were affected by phentolamine treatment. Since overproduction of nitric oxide has been shown to lead to an elevation in peroxynitrite, the role of oxidative stress, a proposed mechanism of fructose-induced elevated blood pressure and insulin resistance, was examined by measuring plasma levels of total nitrate/nitrite. Plasma nitrate/nitrite was significantly elevated in all fructose-fed animals, regardless of treatment with phentolamine. Another proposed contributor toward fructose-induced MS is an elevation in uric acid levels. In this experiment, plasma levels of uric acid were found to be increased by dietary fructose and were unaffected by phentolamine treatment.

  6. Fed-batch production of tetanus toxin by Clostridium tetani.

    Science.gov (United States)

    Fratelli, Fernando; Siquini, Tatiana Joly; de Abreu, Marcelo Estima; Higashi, Hisako Gondo; Converti, Attilio; de Carvalho, João Carlos Monteiro

    2010-01-01

    This study deals with the effects of the initial nitrogen source (NZ Case TT) level and the protocol of glucose addition during the fed-batch production of tetanus toxin by Clostridium tetani. An increase in the initial concentration of NZ Case TT (NZ(0)) accelerated cell growth, increased the consumption of the nitrogen source as well as the final yield of tetanus toxin, which achieved the highest values (50-60 L(f)/mL) for NZ(0) > or = 50 g/L. The addition of glucose at fixed times (16, 56, and 88 h) ensured a toxin yield ( approximately 60 L(f)/mL) about 33% higher than those of fed-batch runs with addition at fixed concentration ( approximately 45 L(f)/mL) and about 300% higher than those obtained in reference batch runs nowadays used at industrial scale. The results of this work promise to substantially improve the present production of tetanus toxin and may be adopted for human vaccine production after detoxification and purification.

  7. Are breast-fed infants vitamin K deficient?

    Science.gov (United States)

    Greer, F R

    2001-01-01

    Hemorrhagic disease of the newborn is a disease of breast-fed infants. We have followed 119 exclusively breast-fed infants for up to 6 months of age, who received 1 mg of vitamin K, intramuscularly at birth. As vitamin K is undetectable in cord blood, the only other source in breast-fed infants is human milk. We found persistently low vitamin K1 plasma concentrations in these infants by 4 weeks, and vitamin K concentrations at 2, 4, 6, 8, 12, and 26 weeks averaged 1.18+/-0.99, 0.50+/-0.70, 0.16 +/-0.07, 0.20+/-0.20, 0.25+/-0.34, and 0.24+/-0.23 ng/mL, respectively (lower limit of adult normal = 0.5ng/mL). Vitamin K, in breast milk at 2, 6, 12, and 26 weeks was also very low, averaging 1.17+/-0.70, 0.95+/-0.50, 1.15+/-0.62, and 0.87+/-0.50 mg/mL, respectively. This may be secondary to low maternal vitamin K1 intakes or inability of vitamin K1 to penetrate human milk. We had previously reported a relatively high mean vitamin K intake of 316+/-548 microg in 20 lactating women during the first 6 months of lactation (mean of 60, 3-day dietary recalls) which greatly exceeded the recommended daily allowance of 1 microg/kg/day. The vitamin K content of foods was recently revised downward utilizing newer analytical methods (Booth et al. 1995). Recalculating maternal vitamin K intakes in this original cohort resulted in a dramatic decrease in intake to 74+/-57 microg/day, an amount closely approximating 1 microg/kg/day. We have completed 69 new dietary recalls in 23 lactating women and, combining these data with the previous study, determined a maternal vitamin K1 mean intake of 65+/-48 microg/day (0.8-1.3 microg/kg/day). Other than plasma vitamin K1 concentrations, PIVKA (undercarboxylated prothrombin produced in the absence of vitamin K) is a marker of vitamin K deficiency. We measured PIVKA in 156 cord bloods of full-term infants. Seventy-five (48%) had a significantly elevated PIVKA (> or =0.1 absorption units per milliliter). Seventy-seven of these infants who were

  8. Growth, behavior, and economics of group-fed dairy calves fed once or twice daily in an organic production system.

    Science.gov (United States)

    Kienitz, M J; Heins, B J; Chester-Jones, H

    2017-04-01

    Heifer calves (n = 102) were used to evaluate the effect of once- or twice-daily feeding on growth, behavior, and economics of calves in an organic group management system. Calves were assigned to replicate feeding groups of 10 in superhutches by birth order, during 2 seasons from September to December 2013 and March to May 2014 at the University of Minnesota West Central Research and Outreach Center, Morris. Calves in groups were the experimental unit. Breed groups of calves were Holsteins (n = 26), crossbreds (n = 45) including combinations Holsteins, Montbéliarde, and Viking Red (selected for high production), and crossbreds (n = 31) including combinations of Holsteins, Jersey, Normande, and Viking Red (selected for robustness). Treatment groups were once-daily feeding (1×) or twice-daily feeding (2×). Calves in both groups were fed 6 L per calf/daily of organic milk with 13% total solids and then weaned at 60 d when the group consumption averaged 0.91 kg/d of starter per calf. Body weight and hip height were recorded at birth, once a week, at weaning, and at 90 and 120 d of age. Hobo Pendant G loggers (Onset Computer Corp., Bourne, MA) were applied to the right rear leg of calves to measure total lying and standing time. Data were analyzed using PROC MIXED of SAS (SAS Institute Inc., Cary, NC). Independent variables for analyses were the fixed effects of birth weight (co-variable), season of birth, and treatment group, along with replicate as a random effect. No significant differences were found between feeding groups for body weight, weight gain, average daily gain, hip height, or heart girth. For calves in 1× and 2× groups, respectively, weaning group performance was as follows: gain per day was 0.79 and 0.81 kg, weaning weight was 92.7 and 93.3 kg, and weaning hip height was 95.2 and 95.3 cm. Daily gain to 90 d was 0.85 and 0.85 kg, and daily gain to 120 d was 0.85 and 0.83 kg for 1× and 2× calves, respectively. For lying time, calves in groups 1

  9. Reproduction, growth, and tissue residues of deer fed dieldrin

    Science.gov (United States)

    Murphy, D.A.; Korschgen, L.J.

    1970-01-01

    Feeding tests were conducted from January, 1966, to January, 1969, to ascertain the effects of daily ingestions of sublethal amounts of dieldrin on white-tailed deer (Odocoileus virginianus). Groups of deer on 0 ppm dieldrin (controls), 5 ppm, and 25 ppm dieldrin were maintained at these respective levels, as were their progeny. Treated food was readily accepted. Dieldrin intoxication was not observed, and 9 of 10 animals of each group survived 3 years of treatment. No differences in conception or in utero mortality were found between groups. Fawns from dieldrin-fed does were smaller at birth and greater post-partum mortality occurred. Fertility of male progeny was not affected. Growth was slower and remained reduced in dieldrin-treated females which were immature when the study began. Hematologic values and serum protein concentrations were not significantly (P > 0.05) related to treatment. Liver/body weight ratios were significantly (P < 0.05) larger for the 25-ppm-dieldrin group. Pituitary glands were smaller and thyroids were larger in dieldrin-fed deer. Weight gains of fawns were significantly (P < 0.05) reduced 2 of 3 years in dieldrin-treated groups. Placental transfer of dieldrin occurred. Whole milk from does fed 25 ppm dieldrin contained residues of 17 ppm. Residue levels in brain, liver, and thigh muscle tissues showed no evidence of increasing with length of treatment, but showed definite relationships to levels of dieldrin in daily diets. Nursing fawns had higher residues in brain tissues than did older deer on 5 ppm a d 25 ppm dieldrin. Highest brain residues (12.60 and 12.10 ppm, wet weight) occurred in fawns only a few days of age at death. Equilibrium between ingestion and storage or excretion of dieldrin occurred prior to 200 days and continued until nearly 1,100 days. There was no evidence of a sharp decline in residues after a long period of continued dosage. Daily ingestion of 100 and 200 ppm of dieldrin proved fatal to yearling male deer at 27

  10. Staphylococcus epidermidis: A differential trait of the fecal microbiota of breast-fed infants

    Directory of Open Access Journals (Sweden)

    Fernández Leonides

    2008-09-01

    Full Text Available Abstract Background Breast milk is an important source of staphylococci and other bacterial groups to the infant gut. The objective of this work was to analyse the bacterial diversity in feces of breast-fed infants and to compare it with that of formula-fed ones. A total of 23 women and their respective infants (16 breast-fed and 7 formula-fed participated in the study. The 16 women and their infants provided a sample of breast milk and feces, respectively, at days 7, 14, and 35. The samples were plated onto different culture media. Staphylococcal and enterococcal isolates were submitted to genetic profiling and to a characterization scheme, including detection of potential virulence traits and sensitivity to antibiotics. Results The feeding practice had a significant effect on bacterial counts. A total of 1,210 isolates (489 from milk, 531 from breast-fed and 190 from formula-fed infants were identified. Staphylococcus epidermidis was the predominant species in milk and feces of breast-fed infants while it was less prevalent in those of formula fed-infants. Enterococcus faecalis was the second predominant bacterial species among the fecal samples provided by the breast-fed infants but it was also present in all the samples from the formula-fed ones. The biofilm-related icaD gene and the mecA gene were only detected in a low number of the S. epidermidis strains. Several enterococcal isolates were also characterized and none of them contained the cylA or the vanABDEG antibiotic-resistance genes. All were sensitive to vancomycin. Conclusion The presence of S. epidermidis is a differential trait of the fecal microbiota of breast-fed infants. Globally, the staphyloccal isolates obtained from milk and feces of breast-fed infants contain a low number of virulence determinants and are sensitive to most of the antibiotics tested.

  11. Antigenic specificity of serum antibodies in mice fed soy protein

    DEFF Research Database (Denmark)

    Christensen, Hanne Risager; Bruun, S.W.; Frøkiær, Hanne

    2003-01-01

    ingesting soy protein. Methods: Blood from mice fed a soy-containing diet was analyzed using ELISA and immunoblot for antibody reactivity towards various soy protein fractions and pure soy proteins/subunits. Mice bred on a soy-free diet were used as controls. Results: The detectable antigenic specificity...... of the serum antibodies of soy-consuming mice comprised glycinin and beta-conglycinin. Immunoblots with soy protein extract demonstrated antibody reactivity towards both the basic and the acidic chains of glycinin and the beta-conglycinin subunits with an individual response pattern among mice. Moreover......Background: Soybean protein is used in a number of food products but unfortunately is also a common cause of food allergy. Upon ingestion of soy protein, healthy mice like other animals and humans generate a soy-specific antibody response in the absence of signs of illness. Not much is known about...

  12. Analysis of Variable Speed PFC Chopper Fed BLDC Motor Drive

    Directory of Open Access Journals (Sweden)

    A Jeya Selvan Renius

    2015-02-01

    Full Text Available This paper provides the detailed analysis of the DC-DC chopper fed Brushless DC motor drive used for low-power applications. The various methods used to improve the power quality at the ac mains with lesser number of components are discussed. The most effective method of power quality improvement is also simulated using MATLAB Simulink. Improved method of speed control by controlling the dc link voltage of Voltage Source Inverter is also discussed with reduced switching losses. The continuous and discontinuous modes of operation of the converters are also discussed based on the improvement in power quality. The performance of the most effective solution is simulated in MATLAB Simulink environment and the obtained results are presented.

  13. Wireless Sensor Networking for Rain-fed Farming Decision Support

    CERN Document Server

    Panchard, J; Sheshshayee, M S; Papadimitratos, P; Kumar, S; Hubaux, J-P

    2009-01-01

    Wireless sensor networks (WSNs) can be a valuable decision-support tool for farmers. This motivated our deployment of a WSN system to support rain-fed agriculture in India. We defined promising use cases and resolved technical challenges throughout a two-year deployment of our COMMON-Sense Net system, which provided farmers with environment data. However, the direct use of this technology in the field did not foster the expected participation of the population. This made it difficult to develop the intended decision-support system. Based on this experience, we take the following position in this paper: currently, the deployment of WSN technology in developing regions is more likely to be effective if it targets scientists and technical personnel as users, rather than the farmers themselves. We base this claim on the lessons learned from the COMMON-Sense system deployment and the results of an extensive user experiment with agriculture scientists, which we describe in this paper.

  14. Neural network based PWM AC chopper fed induction motor drive

    Directory of Open Access Journals (Sweden)

    Venkatesan Jamuna

    2009-01-01

    Full Text Available In this paper, a new Simulink model for a neural network controlled PWM AC chopper fed single phase induction motor is proposed. Closed loop speed control is achieved using a neural network controller. To maintain a constant fluid flow with a variation in pressure head, drives like fan and pump are operated with closed loop speed control. The need to improve the quality and reliability of the drive circuit has increased because of the growing demand for improving the performance of motor drives. With the increased availability of MOSFET's and IGBT's, PWM converters can be used efficiently in low and medium power applications. From the simulation studies, it is seen that the PWM AC chopper has a better harmonic spectrum and lesser copper loss than the Phase controlled AC chopper. It is observed that the drive system with the proposed model produces better dynamic performance, reduced overshoot and fast transient response. .

  15. Meat quality of lambs fed diets with peanut cake.

    Science.gov (United States)

    Bezerra, L S; Barbosa, A M; Carvalho, G G P; Simionato, J I; Freitas, J E; Araújo, M L G M L; Pereira, L; Silva, R R; Lacerda, E C Q; Carvalho, B M A

    2016-11-01

    Replacement of soybean meal by peanut cake was evaluated on the meat quality of 45 Dorper × Santa Inês crossbred lambs. Animals were distributed in a completely randomized design, with five treatments and nine repetitions, and fed Tifton-85 hay and a concentrate mixed with 0.0%, 25.0%, 50.0%, 75.0% or 100.0% peanut cake based on the dry mass of the complete diet. The longissimus lumborum muscle was used to determine the proximate composition, physical-chemical characteristics and fatty acid profile. Significant differences (P0.05) by the diets. The fatty acid profile was affected by peanut cake supplementation for myristic, myristoleic, palmitoleic, linolenic and arachidonic fatty acids. Peanut cake can be added in the diet of lambs no effect on physical-chemical characteristics. However, the total replacement of the soybean meal altered the proximate composition and fatty acid profile of the meat.

  16. Pump Fed Propulsion for Mars Ascent and Other Challenging Maneuvers

    Energy Technology Data Exchange (ETDEWEB)

    Whitehead, J C

    2007-05-09

    Returning Mars geology samples to Earth within science mission budgets requires a miniature launch vehicle (100-200 kg) for ascending from Mars to an orbital rendezvous. A Mars Ascent Vehicle must deliver a velocity change exceeding 4 km/s within minutes, entirely outside the capabilities of satellite propulsion. A possible solution is to scale down liquid launch vehicle principles to achieve stage propellant mass fractions near 90 percent. Feeding a high-pressure engine from thin-walled low pressure tanks permits stage hardware to be sufficiently lightweight and compact, if very high performance pumps can be made available. NASA's Mars Technology Program has funded refinement and testing of a miniature piston pump, powered by reacted propellant. A pump-fed bipropellant rocket stage remains to be developed. The technology could also benefit other future lunar and planetary science programs.

  17. Robust Adaptive Reactive Power Control for Doubly Fed Induction Generator

    Directory of Open Access Journals (Sweden)

    Huabin Wen

    2014-01-01

    Full Text Available The problem of reactive power control for mains-side inverter (MSI in doubly fed induction generator (DFIG is studied in this paper. To accommodate the modelling nonlinearities and inherent uncertainties, a novel robust adaptive control algorithm for MSI is proposed by utilizing Lyapunov theory that ensures asymptotic stability of the system under unpredictable external disturbances and significant parametric uncertainties. The distinguishing benefit of the aforementioned scheme consists in its capabilities to maintain satisfactory performance under varying operation conditions without the need for manually redesigning or reprogramming the control gains in contrast to the commonly used PI/PID control. Simulations are also built to confirm the correctness and benefits of the control scheme.

  18. Six-Phase Matrix Converter Fed Double Star Induction Motor

    Directory of Open Access Journals (Sweden)

    Bendiabdellah Azeddine

    2010-10-01

    Full Text Available two different control strategies applied to a direct AC-AC six-phase matrixconverter are investigated in the present paper. The first strategy is derived from theVenturini method, and the second approach is practically an extension of the scalarstrategy control. Both strategies were originally applied to the three-phase matrixconverter.The current investigation deals with a comparative performance study of a double starinduction motor fed from a six-phase matrix converter using the two above controlstrategies.After a theoretical introduction of the six-phase matrix converter, a detailed description ofthe strategies implementation is presented followed by a discussion of results obtained fromsimulation results.

  19. Vertical-Strip-Fed Broadband Circularly Polarized Dielectric Resonator Antenna.

    Science.gov (United States)

    Altaf, Amir; Jung, Jin-Woo; Yang, Youngoo; Lee, Kang-Yoon; Hwang, Keum Cheol

    2017-08-18

    A vertical-strip-fed dielectric resonator antenna exhibiting broadband circular polarization characteristics is presented. A broad 3 dB axial ratio bandwidth (ARBW) is achieved by combining multiple orthogonal modes due to the use of a special-shaped dielectric resonator. The proposed antenna is fabricated to evaluate its actual performance capabilities. The antenna exhibits a measured 3 dB ARBW of 44.2% (3.35-5.25 GHz), lying within a -10 dB reflection bandwidth of 82.7% (2.44-5.88 GHz). The measured peak gain within 3 dB ARBW is found to be 5.66 dBic at 4.8 GHz. The measured results are in good agreement with the simulated results.

  20. A New Asymmetrical Current-fed Converter with Voltage Lifting

    Directory of Open Access Journals (Sweden)

    DELSHAD, M.

    2011-05-01

    Full Text Available This paper presents a new zero voltage switching current-fed DC-DC converter with high voltage gain. In this converter all switches (main and auxiliary turn on under zero voltage switching and turn off under almost zero voltage switching due to snubber capacitor. Furthermore, the voltage spike across the main switch due to leakage inductance of forward transformer is absorbed. The flyback transformer which is connected to the output in series causes to high voltage gain and less voltage stress on the power devices. Considering high efficiency and voltage gain of this converter, it is suitable for green generated systems such as fuel cells or photovoltaic systems. The presented experimental results verify the integrity of the proposed converter.

  1. Growth, food consumption, and energy status of juvenile pallid sturgeon fed natural or artificial diets

    Science.gov (United States)

    Meyer, Hilary A.; Chipps, Steven R.; Graeb, Brian D. S.; Klumb, Robert A.

    2016-01-01

    Stocking of hatchery-raised fish is an important part of the pallid sturgeon Scaphirhynchus albus recovery program. In the wild, juvenile pallid sturgeon consume primarily aquatic insects, although little is known about specific dietary needs. In hatchery settings, pallid sturgeon are fed commercial diets that are formulated for salmonids. To compare food consumption, growth, and energy status of pallid sturgeon fed artificial or natural diets, we conducted a laboratory study using 24 juvenile pallid sturgeon (initial fork length 153–236 mm). Pallid sturgeon were fed a daily ration of either commercial pellets (1 mm, slow sinking; 45% protein, 19% fat) or chironomid larvae for 5 wk. Natural-fed pallid sturgeon exhibited a greater specific growth rate (2.12% d−1) than pellet-fed fish (0.06% d−1). Similarly, relative condition was greater for natural-fed sturgeon (Kn = 1.11) than that observed for pellet-fed fish (Kn = 0.87). In contrast, the hepatosomatic index was significantly higher in pellet-fed fish (2.5%), indicating a high lipid diet compared with natural-fed sturgeon (1.4%). Given the importance of natural diets to fish digestion and growth, it is suggested that a more holistic approach be applied in the development of a practical diet for pallid sturgeon that incorporates attributes of natural prey.

  2. Alpha-mannosidase activity in goats fed with Sida carpinifolia.

    Science.gov (United States)

    Bedin, Marisete; Moleta Colodel, Edson; Viapiana, Marli; Matte, Ursula; Driemeier, David; Giugliani, Roberto

    2010-03-01

    Human alpha-mannosidosis results from alpha-mannosidase deficiency and progressive accumulation of mannose-rich oligosaccharides in lysosomes. Two days before Saanen goats were fed with Sida carpinifolia, alpha-mannosidase activity in leukocytes was 128+/-28 nmoles4-MU/h/mgprotein (first trial) and 104+/-6 nmoles4-MU/h/mgprotein (second trial). At day 5, after the introduction of S. carpinifolia diet, the alpha-mannosidase activity in leukocytes was significantly increased, both in the first (288+/-13 nmoles4-MU/h/mgprotein) and in the second trial (303+/-45 nmoles4-MU/h/mgprotein), and it returned to normal levels 2 days after the withdrawal of the plant from the diet (114+/-7 nmoles4-MU/h/mgprotein in first trial, and 108+/-25 nmoles4-MU/h/mgprotein in the second one). Plasma alpha-mannosidase activity decreased significantly 4 days after animal exposure to the S. carpinifolia diet (769+/-167 nmoles4-MU/h/ml) and returned to normal values 10 days after the withdrawal of the plant from the diet (1289+/-163 nmoles4-MU/h/ml). Thin-layer chromatography showed an abnormal excretion of oligosaccharides in urine as of day 2 after diet exposure, which persisted until one day after the withdrawal of the plant. Animals presented neurological clinical signs beginning at day 37 (in the first trial) and at day 25 (in the second trial) after being fed with the plant. The results obtained herein suggest that oligosaccharides observed in urine are a result of a decrease in alpha-mannosidase activity in plasma. S. carpinifolia seems to have other compounds that act on alpha-mannosidase enzyme in leukocytes in a competitive manner with swainsonine. The increase in alpha-mannosidase enzyme in leukocytes could be attributed to one of these compounds present in S. carpinifolia. Copyright 2009 Elsevier GmbH. All rights reserved.

  3. Performance of layers fed diets containing different oils

    Directory of Open Access Journals (Sweden)

    GR Lelis

    2009-12-01

    Full Text Available A trial was carried out at the Animal Science Department of the Federal University of Viçosa to evaluate the performance of heavy and light layers. During four periods of twenty-eight days, 432 layers in the second production cycle, being 216 Hy Line W36 (light birds and 216 Hy Line Brown (heavy birds, were used. A completely randomized experimental design with a 1+(4x2x2 factorial arrangement (one control treatment, four oil sources, two inclusion levels, and two genetic lines with four replicates of six birds per experimental unit, was applied. The treatments consisted of diets containing 16.5% crude protein, formulated to supply the nutritional requirements, and the inclusion of each oil source at 2 or 4%. Soybean, canola, linseed and fish oils were used. The control diet did not contain any oil. The studied parameters were: feed intake (g/hen/day, egg production (%, egg weight (g, egg mass (g/hen/day, feed conversion ratio (kg feed /dozen of eggs and per kg eggs. Oil levels and sources did not influence egg mass, feed conversion ratio (per kg eggs and dozen eggs, or egg production. During the first three periods, independently of oil source or genetics, eggs from layers fed 4% oil were the heaviest, except for those of light birds fed soybean oil during the third period, which egg weight was similar for the 2 and 4% levels. Light layers presented lower feed intake and better feed conversion ratio (per kg eggs and dozen eggs as compared to heavy layers, and there was no influence of the evaluated oil sources on feed intake.

  4. 纵边落地支承单层柱面网壳强震倒塌机理及参数分析%Collapse mechanism and parameter analysis of single-layer cylindrical latticed shell with longitudinal edge supports on ground under severe earthquake

    Institute of Scientific and Technical Information of China (English)

    杨大彬; 张毅刚; 吴金志

    2011-01-01

    采用基于荷载域的全过程分析方法对纵边落地支承单层柱面网壳的强震倒塌机理进行了研究.结果表明,该类型网壳呈现明显的沿跨度方向的单向受力特征,长宽比对其受力几乎没有影响;其强震倒塌具有很强的规律性,破坏类型均为动力强度破坏;矢跨比对能引起其倒塌的PGA有很大影响,但对其发展趋势并无固定的影响规律;屋面质量的增大及初始几何缺陷均会降低该类型柱面网壳的倒塌PGA,其降低程度因柱壳而异.%The collapse mechanism of single-layer cylindrical latticed shell under severe earthquakes is analyzed with full-range responses method based on load domain. Results show that this kind of shell takes on a very distinct one-way mechanical characteristic along the span direction, and its length to span ratio has little influence on its mechanical performance. There is a strong regularity in its collapse behaviour, and all the collapse patterns belong to the dynamic strength failure mode. Its rise to span ratio has a tremendous influence on the collapse PGA, but the influence has no fixed regularity. The collapse PGA will decrease when the roof mass increases or there is initial geometrical imperfection, but the decreased magnitude depends on the shells.

  5. Variation of terpenes in milk and cultured cream from Norwegian alpine rangeland-fed and in-door fed cows.

    Science.gov (United States)

    Borge, Grethe Iren A; Sandberg, Ellen; Øyaas, Jorun; Abrahamsen, Roger K

    2016-05-15

    The terpene content of milk and cream made from milk obtained from cows fed indoors, and by early or late grazing, in alpine rangeland farms in Norway, were analysed for three consecutive years. The main terpenes identified and semi-quantified were the monoterpenes β-pinene, α-pinene, α-thujene, camphene, sabinene, δ-3-carene, d-limonene, γ-terpinene, camphor, β-citronellene, and the sesquiterpene β-caryophyllene. The average total terpene content increased five times during the alpine rangeland feeding period. The terpenes α-thujene, sabinene, γ-terpinene and β-citronellene were only detected in milk and cultured cream from the alpine rangeland feeding period and not in samples from the indoors feeding period. These four terpenes could be used, as indicators, to show that milk and cultured cream originate from the alpine rangeland feeding period. The terpenes did not influence the sensorial quality of the milk or the cultured cream.

  6. Global transcriptional dynamics of diapause induction in non-blood-fed and blood-fed Aedes albopictus.

    Directory of Open Access Journals (Sweden)

    Xin Huang

    2015-04-01

    Full Text Available Aedes albopictus is a vector of increasing public health concern due to its rapid global range expansion and ability to transmit Dengue virus, Chikungunya virus and a wide range of additional arboviruses. Traditional vector control strategies have been largely ineffective against Ae. albopictus and novel approaches are urgently needed. Photoperiodic diapause is a crucial ecological adaptation in a wide range of temperate insects. Therefore, targeting the molecular regulation of photoperiodic diapause or diapause-associated physiological processes could provide the basis of novel approaches to vector control.We investigated the global transcriptional profiles of diapause induction in Ae. albopictus by performing paired-end RNA-Seq of biologically replicated libraries. We sequenced RNA from whole bodies of adult females reared under diapause-inducing and non-diapause-inducing photoperiods either with or without a blood meal. We constructed a comprehensive transcriptome assembly that incorporated previous assemblies and represents over 14,000 annotated dipteran gene models. Mapping of sequence reads to the transcriptome identified differential expression of 2,251 genes in response to diapause-inducing short-day photoperiods. In non-blood-fed females, potential regulatory elements of diapause induction were transcriptionally up-regulated, including two of the canonical circadian clock genes, timeless and cryptochrome 1. In blood-fed females, genes in metabolic pathways related to energy production and offspring provisioning were differentially expressed under diapause-inducing conditions, including the oxidative phosphorylation pathway and lipid metabolism genes.This study is the first to utilize powerful RNA-Seq technologies to elucidate the transcriptional basis of diapause induction in any insect. We identified candidate genes and pathways regulating diapause induction, including a conserved set of genes that are differentially expressed as part

  7. Implementation of Sliding Mode Controller with Boundary Layer for Saccharomyces cerevisiae Fed-batch Cultivation

    Directory of Open Access Journals (Sweden)

    Stoyan Tzonkov

    2005-04-01

    Full Text Available An implementation of sliding mode control for yeast fed-batch cultivation is presented in this paper. Developed controller has been implemented on two real fed-batch cultivations of Saccharomyces cerevisiae. The controller successfully stabilizes the process and shows a very good performance at high input disturbances.

  8. Passage of Salmonella through the crop and gizzard of broiler chickens fed with fermented liquid feed.

    NARCIS (Netherlands)

    Heres, L.; Wagenaar, J.A.; Knapen, van F.; Urlings, B.A.P.

    2003-01-01

    In vivo experiments were conducted in order to investigate the passage and bacterial reduction of Salmonella in the crop and gizzard of chickens when fed two different feeds. The chickens were fed dry conventional feed and fermented liquid feed. The fermented feed contains a relatively high concentr

  9. Investigation of transient models and performances for a doubly fed wind turbine under a grid fault

    DEFF Research Database (Denmark)

    Wang, M.; Zhao, B.; Li, H.

    2011-01-01

    fed induction generator (DFIG), the assessments of the impact on the electrical transient performances were investigated for the doubly fed wind turbine with different representations of wind turbine drive-train dynamics models, different initial operational conditions and different active crowbar...

  10. A novel LTCC differentially Fed UWB antenna for the 60 GHz band

    NARCIS (Netherlands)

    Yang, B.; Yarovoy, A.G.; Valavan, A.S.E.; Buisman, K.; Shoykhetbrod, O.

    2011-01-01

    In this paper a novel differentially fed Ultra-Wide Band (UWB) antenna in low-temperature co-fired ceramics (LTCC) technology to be used in the 60 GHz band for integrated RF front-ends is presented. The antenna is based on the aperture stacked patch fed via H-shaped aperture to achieve more than 10

  11. Manure ammonia and greenhouse gas emissions from beef cattle fed condensed tannins

    Science.gov (United States)

    A study was conducted to determine the effects of three levels of condensed tannins fed to 27 beef feed yard steers on ammonia and GHG emissions from manure. Condensed tannins were fed at rates of 0, 0.5 and 1.0 percent on a dry matter basis. Manure and urine were collected from two periods over 6 d...

  12. Nitrogen dynamics of spring-fed wetland ecosystems of the Sierra Nevada foothills oak woodland

    Science.gov (United States)

    Randall D. Jackson; Barbara Allen-Diaz

    2002-01-01

    Spring-fed wetlands are small, highly productive, patchy ecosystems nested within the oak woodland/annual grassland matrix of the Sierra Nevada foothills. In an effort to place these wetlands in a landscape context, we described seasonal variation (1999-2000 growing season) in nitrogen cycling parameters at 6 spring-fed wetland sites of the Sierra Nevada foothill oak...

  13. Fatty acids in beef from grain- and grass-fed cattle: the unique South ...

    African Journals Online (AJOL)

    2015-09-10

    Sep 10, 2015 ... Keywords: grain fed, grass fed, cattle, fatty acids, red meat. Fatty acids in beef ... of high-fat, low-carbohydrate diets.5. When dietary ..... fat-soluble vitamins. They also play ..... of South African dairy and beef cattle. SAJAS. 2013 ...

  14. Similar calcium status is present in infants fed formula with and without prebiotics

    Science.gov (United States)

    Prebiotic oligosaccharides can increase calcium absorption in adolescents and adults. Whether they affect calcium absorption in infants has not been assessed. Few data are available to compare the calcium status of infants fed modern infant formulas to that of breast fed infants. To evaluate calcium...

  15. A novel LTCC differentially Fed UWB antenna for the 60 GHz band

    NARCIS (Netherlands)

    Yang, B.; Yarovoy, A.G.; Valavan, A.S.E.; Buisman, K.; Shoykhetbrod, O.

    2011-01-01

    In this paper a novel differentially fed Ultra-Wide Band (UWB) antenna in low-temperature co-fired ceramics (LTCC) technology to be used in the 60 GHz band for integrated RF front-ends is presented. The antenna is based on the aperture stacked patch fed via H-shaped aperture to achieve more than 10

  16. Model and performance of current sensor observers for a doubly fed induction generator

    DEFF Research Database (Denmark)

    Li, Hui; Yang, Chao; Hu, Yaogang

    2014-01-01

    a MATLAB/Simulink software platform under the conditions of active power change of doubly fed induction generators and grid voltage dip fault. Furthermore, the robustness of the proposed current observer is investigated when the doubly fed induction generator rotor resistance is changed. Results show...

  17. MASS PRODUCTION OF THE BENEFICIAL NEMATODE STEINERNEMA CARPOCAPSAE UTILIZING A FED-BATCH CULTURING PROCESS

    Directory of Open Access Journals (Sweden)

    Leonard D. Holmes

    2013-04-01

    Full Text Available The present study deals with the batch and fed-batch mass production of Steinernema carpocapsae. S. carpocapsae is an entomoparasitic nematode that is used as a biological control agent of soil-borne crop insect pests. The ability and efficiency of fed-batch culture process was successful through the utilization of the nematode’s bacterial symbiont Xenorhabdus nematophila. Results from the fed-batch process were compared to those obtain from the standard batch process. The fed-batch process successively improved the mass production process of S. carpocapsae employing liquid medium technology. Within the first week of the fed-batch process (day six, the nematode density obtained was 202,000 nematodes mL−1; whereas on day six, batch culture mode resulted in a nematode density of 23,000 nematodes mL−1. The fed-batch process was superior to that of batch production with a yield approximately 8.8-fold higher. In fed-batch process, the nematode yield was improved 88.6 % higher within a short amount of time compared to the batch process. Fed-batch seems to make the process more efficient and possibly economically viable.

  18. Performance optimization for doubly-fed generation systems

    Science.gov (United States)

    Bhowmik, Shibashis

    A variable speed generation (VSG) system converts energy from a variable resource such as wind or water flow into variable rotational mechanical energy of a turbine or a similar device that converts translational kinetic energy into rotational mechanical energy. The mechanical energy is then converted into electrical energy by an electrical generator. Presently available and proposed generators include systems based mainly on dc machines, synchronous and induction machine technology as well as reluctance machines. While extracting more energy from the resource, most proposed VSG systems suffer a cost disadvantage due to the required rating of the power electronic interface. This cost penalty may eventually render the additional energy capture meaningless. Thus, reducing the cost of the power electronic hardware is essential for VSG systems to achieve viable and competitive $/kWh ratios when compared to fossil fuel-based generating systems. A variable speed constant frequency (VSCF) system and controller are proposed that utilize a doubly-fed machine (DFM) as the energy conversion device. The system includes a power converter that provides the current excitation for the control winding of the DFM. Both the magnitude and frequency of the excitation is determined by an adaptive model-based controller which maximizes the power flow from the mechanical turbine to the electrical grid and reduces the generator losses by maintaining the maximum efficiency point throughout the mechanical input power range. The proposed strategy has been experimentally verified in controlled laboratory conditions for a proof-of-concept brushless doubly-fed machine (BDFM) system of 1500 Watts power rating. Issues relating to power converter development and its incorporation in the system have been investigated. The controller and circuit design of a four quadrant, AC/AC power converter is presented and a novel sensorless current controller for the active rectifier stage is presented in detail

  19. Development of a Gas-Fed Pulse Detonation Research Engine

    Science.gov (United States)

    Litchford, Ron J.; Hutt, John (Technical Monitor)

    2001-01-01

    In response to the growing need for empirical data on pulse detonation engine performance and operation, NASA Marshall Space Flight Center has developed and placed into operation a low-cost gas-fed pulse detonation research engine. The guiding design strategy was to achieve a simple and flexible research apparatus, which was inexpensive to build and operate. As such, the engine was designed to operate as a heat sink device, and testing was limited to burst-mode operation with run durations of a few seconds. Wherever possible, maximum use was made of standard off-the-shelf industrial or automotive components. The 5-cm diameter primary tube is about 90-cm long and has been outfitted with a multitude of sensor and optical ports. The primary tube is fed by a coaxial injector through an initiator tube, which is inserted directly into the injector head face. Four auxiliary coaxial injectors are also integrated into the injector head assembly. All propellant flow is controlled with industrial solenoid valves. An automotive electronic ignition system was adapted for use, and spark plugs are mounted in both tubes so that a variety of ignition schemes can be examined. A microprocessor-based fiber-optic engine control system was developed to provide precise control over valve and ignition timing. Initial shakedown testing with hydrogen/oxygen mixtures verified the need for Schelkin spirals in both the initiator and primary tubes to ensure rapid development of the detonation wave. Measured pressure wave time-of-flight indicated detonation velocities of 2.4 km/sec and 2.2 km/sec in the initiator and primary tubes, respectively. These values implied a fuel-lean mixture corresponding to an H2 volume fraction near 0.5. The axial distribution for the detonation velocity was found to be essentially constant along the primary tube. Time-resolved thrust profiles were also acquired for both underfilled and overfilled tube conditions. These profiles are consistent with previous time

  20. Feeding behavior of steers fed a complete mixed ration.

    Science.gov (United States)

    Chase, L E; Wangsness, P J; Baumgardt, B R

    1976-11-01

    Feeding behavior of five Holstein steers fed a complete mixed ration was studied by use of individual, electronically controlled feeding behavior units. Both individual meal and daily behavioral parameters were measured. Number of meals, size of each individual meal, time spent eating, and intervals between meals were measured. Eating rates were then calculated. Diurnal feeding patterns were observed with 60.9% of the meals occurring between 0600 and 1800 h. For individual meals, body weight accounted for less than 30% of the variation in meal size. Average meal size was 414.5 g. Respective means for overall meal duration, actual meal duration, overall eating rate, and actual eating rate were 20.3 min, 13.7 min, 23.1 g/min, and 30.0 g/min. Meal size per body weight (g/kg or g/kg.75) was relatively constant during observation. Both increased eating rate and increased meal length were associated with larger meals. However, eating rate tended to plateau while meal length continued to increase with larger meals. Steers consumed 10.01 meals per day while total daily overall meal duration and actual meal duration were 220.9 and 156.4 min.

  1. Feeding behavior of lambs fed diets containing peach palm meal

    Directory of Open Access Journals (Sweden)

    Alana Batista dos Santos

    2016-06-01

    Full Text Available The aim of this study was to evaluate the feeding behavior of lambs fed diets containing peach palm meal replacing maize (0, 10, 40, 60, and 85% DM. Thirty Santa Inês sheep with an average initial body weight of 21.6 ± 0.87 kg were distributed in a completely randomized design with five diets and six replicates. Feeding time in min kg–1 DM and min kg–1 NDFap increased by 34 min and 99.6 min, respectively, with each level of substitution of maize for the peach palm meal. Rumination and chewing times, in min kg–1 DM and min kg–1 NDF, also increased in response to the substitution of maize for peach palm meal. When expressed in min day–1, rumination and chewing activities decreased by 12.4 and 14.6 min, respectively, as the amount of peach palm meal in the concentrate was increased. The time spent idle increased linearly (P < 0.05, by 14.6 min day–1, with the replacement levels, compared with the control diet. Peach palm meal in the composition of sheep diets reduces the intakes of dry matter and fiber and decreases the feed and rumination efficiencies. Replacing maize by peach palm meal increases the feeding time and rumination and chewing activities of feedlot lambs.

  2. The hemolymph proteome of fed and starved Drosophila larvae.

    Directory of Open Access Journals (Sweden)

    Björn Handke

    Full Text Available The co-operation of specialized organ systems in complex multicellular organisms depends on effective chemical communication. Thus, body fluids (like blood, lymph or intraspinal fluid contain myriads of signaling mediators apart from metabolites. Moreover, these fluids are also of crucial importance for immune and wound responses. Compositional analyses of human body fluids are therefore of paramount diagnostic importance. Further improving their comprehensiveness should increase our understanding of inter-organ communication. In arthropods, which have trachea for gas exchange and an open circulatory system, the single dominating interstitial fluid is the hemolymph. Accordingly, a detailed analysis of hemolymph composition should provide an especially comprehensive picture of chemical communication and defense in animals. Therefore we used an extensive protein fractionation workflow in combination with a discovery-driven proteomic approach to map out the detectable protein composition of hemolymph isolated from Drosophila larvae. Combined mass spectrometric analysis revealed more than 700 proteins extending far beyond the previously known Drosophila hemolymph proteome. Moreover, by comparing hemolymph isolated from either fed or starved larvae, we provide initial provisional insights concerning compositional changes in response to nutritional state. Storage proteins in particular were observed to be strongly reduced by starvation. Our hemolymph proteome catalog provides a rich basis for data mining, as exemplified by our identification of potential novel cytokines, as well as for future quantitative analyses by targeted proteomics.

  3. Forced accretion in stochastically fed AGN and quasars

    CERN Document Server

    Nayakshin, Sergei

    2007-01-01

    Steady state accretion discs larger than ~ 0.01-0.1 pc are known to be gravitationally unstable for the accretion rates needed to explain super-massive black hole (SMBH) activity. We propose that SMBH are fed by a succession of mass deposition events with randomly directed angular momenta. Because of incomplete angular momentum cancellation a warped accretion disc forms in the inner few parsec. The orientation of the disc performs a random walk. Deposition of new material promotes SMBH accretion at rates much faster than viscous. Observational implications of this picture include: (i) lighter accretion discs that can fuel AGN and quasars and yet avoid star formation at R >> 0.1 pc; (ii) star formation inside the disc is not a function of mass accretion rate only. It can take place at high or low accretion rates, e.g., when too few clouds arrive in the inner region. An example of this might be the central parsec of our Galaxy. (iii) The discs can form Compton-thick obscuring structures of ~ parsec size as requ...

  4. Review: Drinking water for liquid-fed pigs.

    Science.gov (United States)

    Meunier-Salaün, M-C; Chiron, J; Etore, F; Fabre, A; Laval, A; Pol, F; Prunier, A; Ramonet, Y; Nielsen, B L

    2016-11-07

    Liquid feeding has the potential to provide pigs with sufficient water to remain hydrated and prevent prolonged thirst. However, lack of permanent access to fresh water prevents animals from drinking when they are thirsty. Moreover, individual differences between pigs in a pen may result in uneven distribution of the water provided by the liquid feed, leading to some pigs being unable to meet their water requirements. In this review, we look at the need for and provision of water for liquid-fed pigs in terms of their production performance, behaviour, health and welfare. We highlight factors which may lead to water ingestion above or below requirements. Increases in the need for water may be caused by numerous factors such as morbidity, ambient temperature or competition within the social group, emphasising the necessity of permanent access to water as also prescribed in EU legislation. The drinkers can be the target of redirected behaviour in response to feed restriction or in the absence of rooting materials, thereby generating water losses. The method of water provision and drinker design is critical to ensure easy access to water regardless of the pig's physiological state, and to limit the amount of water used, which does not benefit the pig.

  5. Sheep fed with banana leaf hay reduce ruminal protozoa population.

    Science.gov (United States)

    Freitas, Cláudio Eduardo Silva; Duarte, Eduardo Robson; Alves, Dorismar David; Martinele, Isabel; D'Agosto, Marta; Cedrola, Franciane; de Moura Freitas, Angélica Alves; Dos Santos Soares, Franklin Delano; Beltran, Makenzi

    2017-04-01

    A ciliate protozoa suppression can reduce methane production increasing the energy efficiency utilization by ruminants. The physicochemical characteristics of rumen fluid and the profile of the rumen protozoa populations were evaluated for sheep fed banana leaf hay in replacement of the Cynodon dactylon cv. vaqueiro hay. A total of 30 male sheep were raised in intensive system during 15 days of adaptation and 63 days of experimental period. The animals were distributed in a completely randomized design that included six replicates of five treatments with replacement levels (0, 25, 50, 75, and 100%) of the grass vaquero for the banana leaf hay. Samples of fluid were collected directly from the rumen with sterile catheters. Color, odor, viscosity, and the methylene blue reduction potential (MBRP) were evaluated and pH estimated using a digital potentiometer. After decimal dilutions, counts of genus protozoa were performed in Sedgewick Rafter chambers. The averages of pH, MBRP, color, odor, and viscosity were not influenced by the inclusion of the banana leaf hay. However, the total number of protozoa and Entodinium spp. population significantly decreased at 75 and 100% inclusions of banana leaf hay as roughage.

  6. Photovoltaic Cell Fed 3-Phase Induction Motor Using MPPT Technique

    Directory of Open Access Journals (Sweden)

    Gudimetla Ramesh

    2014-10-01

    Full Text Available This Paper emphasizes on proposing a cost effective photovoltaic (PV fed 3 phase Induction motor drive which serves for rural pumping applications. Generally in a standalone system, the PV unit will charge the battery and the battery set up in turn will serve as a source for the inverter. A new single stage battery less power conversion is employed by designing a maximum power point tracker (MPPT embedded boost converter which makes the overall cost of the setup to go down considerably. The realized as a prototype consisting PV array of 500watts, MPPT aided boost converter, three phase inverter and a three phase squirrel cage induction drive of 300 watts. An efficient and low cost micro controller dspic4011 is used a platform to code and implement the prominent perturb and observe MPPT technique .Sinusoidal pulse width modulation (SPWM is the  control technique employed for  the three phase  inverter. To validate the experimental results simulation of the whole set up is carried out in matlab /simulink environment. Simulation and hardware results reveal that the system is versatile.

  7. Mitochondrial myopathy in Senna occidentalis-seed-fed chicken.

    Science.gov (United States)

    Cavaliere, M J; Calore, E E; Haraguchi, M; Górniak, S L; Dagli, M L; Raspantini, P C; Calore, N M; Weg, R

    1997-07-01

    Plants of the genus Senna (formerly Cassia) have been recognized as the cause of a natural and experimental syndrome of muscle degeneration frequently leading to death in animals. Histologically, it demonstrated skeletal and cardiac muscle necrosis, with floccular degeneration and proliferation of sarcolemmal nuclei. Recently, it was described as an experimental model of mitochondrial myopathy in hens chronically treated with Senna occidentalis. Currently, skeletal muscles of chicks intoxicated with seeds of the poisonous plant S. occidentalis were studied by histochemistry and electron microscopy. Since birth, the birds were fed ground dried seeds of this plant with a regular chicken ration at a dose of 4% for 11 days. Microscopic examination revealed, besides muscle-fiber atrophy, lipid storage in most fibers and a moderate amount of cytochrome oxidase-negative fibers. By electron microscopy, enlarged mitochondria with disrupted or excessively branched cristae were seen. This picture was characteristic of mitochondrial myopathy. These findings have hitherto remained unnoticed in skeletal muscle of young birds treated with S. occidentalis.

  8. dc power control for a liquid-fed resistojet

    Science.gov (United States)

    Gruber, Robert P.

    1988-01-01

    A simple breadboard power controller was designed and demonstrated for a new liquid-fed water resistojet. The 1-piece laboratory model thruster has an integrated vaporizer/superheater using a single heating element. Heater temperature was maintained at or near a preset reference value with the closed loop controller providing pulse width modulated (PWM) dc power into the thruster heater. A combined thruster, temperature readout, PWM transfer function was experimentally determined. This transfer function was used to design a proportional plus integral controller that demonstrated zero steady state error, conservative stability margins and adequate transient response to step changes in propellant flow rate, input voltage and temperature reference. Initial turn-on temperature overshoot from room temperature to a 650 C setpoint was 80 C. In addition, EMI was alleviated by reducing heater dI/dt and dV/dt using a simple diode-inductor-capacitor network. Based on limited initial tests, thruster preheat with no propellant flow was necessary to achieve stable system operation during startup. Breadboard power efficiency was 99 percent at 1 kW, and component mass was 0.4 kg excluding the power loss and mass of an input filter required for spacecraft integration.

  9. The dc power control for a liquid-fed resistojet

    Science.gov (United States)

    Gruber, Robert P.

    1988-01-01

    A simple breadboard power controller was designed and demonstrated for a new liquid-fed water resistojet. The 1-piece laboratory model thruster has an integrated vaporizer/superheater using a single heating element. Heater temperature was maintained at or near a preset reference value with the closed loop controller providing pulse width modulated (PWM) dc power into the thruster heater. A combined thruster, temperature readout, PWM transfer function was experimentally determined. This transfer function was used to design a proportional plus integral controller that demonstrated zero steady state error, conservative stability margins and adequate transient response to step changes in propellant flow rate, input voltage and temperature reference. Initial turn-on temperature overshoot from room temperature to a 650 C setpoint was 80 C. In addition, EMI was alleviated by reducing heater dI/dt and dV/dt using a simple diode-inductor-capacitor network. Based on limited initial tests, thruster preheat with no propellant flow was necessary to achieve stable system operation during startup. Breadboard power efficiency was 99 percent at 1 kW, and component mass was 0.4 kg excluding the power loss and mass of an input filter required for spacecraft integration.

  10. Absorption line systems in simulated galaxies fed by cold streams

    CERN Document Server

    Fumagalli, Michele; Kasen, Daniel; Dekel, Avishai; Ceverino, Daniel; Primack, Joel R

    2011-01-01

    Hydro cosmological simulations reveal that massive galaxies at high redshift are fed by long narrow streams of merging galaxies and a smoother component of cold gas. We post-process seven high-resolution simulated galaxies with radiative transfer to study the absorption characteristics of the gas in galaxies and streams, in comparison with the statistics of observed absorption-line systems. We find that much of the stream gas is ionized by UV radiation from background and local stellar sources, but still optically thick (N_HI > 10^17 cm^2) so that the streams appear as Lyman-limit systems (LLSs). At z>3, the fraction of neutral gas in streams becomes non-negligible, giving rise to damped Lyman-alpha (DLA) absorbers as well. The gas in the central and incoming galaxies remains mostly neutral, responsible for DLAs. Within one (two) virial radii, the covering factor of optically thick gas is 30% of the observed absorbers in the foreground of quasars, the rest possibly arising from smaller galaxies or the interga...

  11. Spectrophotometry with Hectospec, the MMT's Fiber-Fed Spectrograph

    CERN Document Server

    Fabricant, Daniel G; Geller, Margaret J; Caldwell, Nelson; Woods, Deborah

    2008-01-01

    We describe techniques for photometric calibration of optical spectra obtained with the MMT's fiber-fed spectrograph, Hectospec. The atmospheric dispersion compensation prisms built into the MMT's f/5 wide field corrector effectively eliminate errors due to differential refraction, and simplify the calibration procedure. The procedures that we describe here are applicable to all 220,000+ spectra obtained to date with Hectospec because the instrument response is stable. We estimate the internal error in the Hectospec measurements by comparing duplicate measurements of $\\sim$1500 galaxies. For a sample of 400 galaxies in the Smithsonian Hectospec Lensing Survey (SHELS) with a median z=0.10, we compare line and continuum fluxes measured by Hectospec through a 1.5 arcsec diameter optical fiber with those measured by the Sloan Digital Sky Survey (SDSS) through a 3 arcsec diameter optical fiber. Agreement of the [OII] and H alpha SHELS and SDSS line fluxes, after scaling by the R band flux in the different aperture...

  12. DESIGN OF SEQUENTIALLY FED BALANCED AMPLIFYING ANTENNA FOR CIRCULAR POLARIZATION

    Directory of Open Access Journals (Sweden)

    S. K. Behera

    2010-12-01

    Full Text Available This paper presents a sequentially fed balanced amplifying antenna that exhibits circularly polarized radiation. The inherent benefits of good isolation between input and output ports as well as improved matching capabilities of balanced amplifiers provide overall system gain of 8 dBi at frequency 2.36GHz. The planar arrangement of the patch antenna elements are considered to form an array. The phase of the feeding in the array increases progressively from 00 to 2700.Each element in the array is linearly polarized. Here four elements were considered and 2arranged at the four corners of a square domain. This arrangement shows that each antenna sees its adjacent ones to be radiating from an edge orthogonal to its edge of radiation. Circular polarization is achieved due to this sequential feeding. This array is designed with operating frequency 2.4 GHz. A good axial ratio of 2.4 is obtained at 2.37 GHz frequency. The noise figure is considerably reduced and which is around -19dB.

  13. Brain glucose content in fetuses of ethanol-fed rats

    Energy Technology Data Exchange (ETDEWEB)

    Pullen, G.; Singh, S.P.; Snyder, A.K.; Hoffen, B.

    1986-03-01

    The authors have previously demonstrated impaired placental glucose transfer and fetal hypoglycemia in association with ethanol ingestion by pregnant rats. The present study examines the relationship between glucose availability and fetal brain growth under the same conditions. Rats (EF) were fed ethanol (30% of caloric intake) in liquid diet throughout gestation. Controls received isocaloric diet without ethanol by pair-feeding (PF) or ad libitum (AF). On the 22nd day of gestation fetuses were obtained by cesarean section. Fetal brains were removed and freeze-clamped. Brain weight was significantly reduced (p < 0.001) by maternal ethanol ingestion (206 +/- 2, 212 +/- 4 and 194 +/- 2 mg in AF, FP and EF fetuses respectively). Similarly, fetal brain glucose content was lower (p < 0.05) in the EF group (14.3 +/- 0.9 mmoles/g dry weight) than in the PF (18.6 +/- 1.0) or the AF (16.2 +/- 0.9) groups. The protein: DNA ratio, an indicator of cell size, correlated positively (r = 0.371, p < 0.005) with brain glucose content. In conclusion, maternal ethanol ingestion resulted in lower brain weight and reduced brain glucose content. Glucose availability may be a significant factor in the determination of cell size in the fetal rat brain.

  14. THE PERFORMANCE OF LAYING HENS FED DIFFERENT CALCIUM SOURCE

    Directory of Open Access Journals (Sweden)

    S. Kismiati

    2014-10-01

    Full Text Available The research was aimed to evaluate the performance of laying hens fed different calcium sources.Two hundreds of Isa Brown laying hens were used in this study. The hens were raised in individualbattery cages units for 12 weeks. Four calcium source (limestone as a control, 5% limestone + 2.5%eggshells waste, 2.5% limestone + 5% eggshells waste and 7.5% eggshell waste were used in feedexperiment. A completely randomized design was applied, with 4 treatments and 5 replications. Eachexperimental unit consisted of 10 laying hens. The parameters measured were feed intake, proteinintake, calcium intake, phosphorus intake, egg production, egg weight and feed conversion ratio. Resultsof the research showed that the calcium source had significantly effect on performance productions. Theuse of eggshell waste 7.5% significantly increased the feed intake, calcium intake, phosphorus intake,egg production and egg weight except for feed conversion ratio. The conclusion of this research was thatthe use of eggshell waste as calcium source of feed resulted in better performance than using limestoneor mixed limestone with eggshell waste.

  15. XAS Studies of Se Speciation in Selenite-Fed Rats

    Science.gov (United States)

    Weekley, Claire M.; Aitken, Jade B.; Witting, Paul K.; Harris, Hugh H.

    2014-01-01

    The biological activity of selenium is dependent on its chemical form. Therefore, knowledge of Se chemistry in vivo is required for efficacious use of selenium compounds in disease prevention and treatment. Using X-ray absorption spectroscopy, Se speciation in the kidney, liver, heart, spleen, testis and red blood cells of rats fed control (~0.3 ppm Se) or selenite-supplemented (1 ppm or 5 ppm Se) diets for 3 or 6 weeks, was investigated. X-ray absorption spectroscopy revealed the presence of Se–Se and Se–C species in the kidney and liver, and Se–S species in the kidney, but not the liver. X-ray absorption near edge structure (XANES) spectra showed that there was variation in speciation in the liver and kidneys, but Se speciation was much more uniform in the remaining organs. Using principal component analysis (PCA) to interpret the Se K-edge X-ray absorption spectra, we were able to directly compare the speciation of Se in two different models of selenite metabolism – human lung cancer cells and rat tissues. The effects of Se dose, tissue type and duration of diet on selenium speciation in rat tissues were investigated, and a relationship between the duration of the diet (3 weeks versus 6 weeks) and selenium speciation was observed. PMID:25363824

  16. Nitrogen excretion and ammonia emissions from pigs fed modified diets.

    Science.gov (United States)

    Panetta, D M; Powers, W J; Xin, H; Kerr, B J; Stalder, K J

    2006-01-01

    Two swine feeding trials were conducted (initial body weight = 47 +/- 2 and 41 +/- 3 kg for Trials 1 and 2, respectively) to evaluate reduced crude protein (CP) and yucca (Yucca schidigera Roezl ex Ortgies) extract-supplemented diets on NH3 emissions. In Trial 1, nine pigs were offered a corn-soybean meal diet (C, 174 g kg(-1) CP), a Lys-supplemented diet (L, 170 g kg(-1) CP), or a 145 g kg(-1) CP diet supplemented with Lys, Met, Thr, and Trp (LMTT). In Trial 2, nine pigs were fed diet L supplemented with 0, 62.5, or 125 mg of yucca extract per kg diet. Each feeding period consisted of a 4-d dietary adjustment followed by 72 h of continuous NH3 measurement. Urine and fecal samples were collected each period. Feeding the LMTT diet reduced (P Yucca had no effect on feed intake, ADG, or G:F. Ammonium and N concentrations of manure and NH3 emission rates did not differ with yucca content. Caution must be executed to maintain animal performance when strategies are implemented to reduce NH3 emissions.

  17. Design and construction of CPW fed circular microstrip patch antennas

    Science.gov (United States)

    Vyas, Kirti; Singhal, P. K.; Sharma, A. K.; Pal, Manisha

    2013-01-01

    In this paper, we present feeding approaches of coplanar waveguide fed (CPW) circular microstrip patch antennas, with and without defected ground structure (DGS)`. The antenna feeding impedance is proposed as 50 ohms, built over FR4, a high dielectric constant substrate to obtain broad impedance bandwidth along with stability of the radiation patterns. The antenna with defected ground structure is designed to have band-notched characteristics at 3.5 GHz (for Wi-MAX band-3.3 to 3.7 GHz), at 8.2 GHz (for ITU band-8.025 GHz to 8.4 GHz) so as to avoid interference from these. The FR4 is used as dielectric with value of dielectric loss tangent constant as 0.002 and relative permittivity with 4.4. After applying DGS in ground of the proposed antenna there were improvements concerning bandwidth, and also a small increase in gain was noticed. These antennas are of small sizes with dimensions; 30 mm X 43 mm X 1.6 mm, cheap, compact and easy to fabricate, and achieve good radiation characteristics with higher return loss. This first antenna can have wide application in a great variety of wireless communication and second can operate well as UWB antenna with band notched characteristics. The performance of two antennas is compared in respect to gain, VSWR, return loss and impedance matching.

  18. Photosensitization in sheep fed Ammi majus (Bishop's weed) seed.

    Science.gov (United States)

    Witzel, D A; Dollahite, J W; Jones, L P

    1978-02-01

    Ammi majus (bishop's weed) grows on the coastal region of southern United States and in other parts of the world. This plant causes severe photosensitization in livestock and probably contributes to the severe photosensitization outbreaks seen in Texas. Sheep were fed finely ground seed of A majus via stomach tube at dose rates of 1, 2, 4, and 8 g/kg of body weight and exposed to sunlight. The single dose of 8 g/kg produced severe clinical signs (in 24 to 48 hours): cloudy cornea, conjunctivokeratitis, photophobia, and edema of the muzzle, ears, and vulva. Daily dosing at 2 and 4 g/kg produced (in 72 to 96 hours) similar signs, whereas the smallest dose (1 g/kg) produced mild irritation of the muzzle. Pathologic changes included (1) corneal edema and marked neutrophilic infiltration of the cornea and corneal/ciliary process, (2) subacute ulcerative and exudative dermatitis of the skin of ears, muzzle, and vulva, and (3) mild focal tubular degeneration (vacuolar type) of the kidney.

  19. The Radial Velocity Precision of Fiber-fed Spectrographs

    CERN Document Server

    Walker, G A H; Bohlender, D A; Yang, S; Walker, Gordon A.H.; Shkolnik, Evgenya; Bohlender, David A.; Yang, Stephenson

    2003-01-01

    We have measured the radial velocities of five 51 Peg-type stars and one star with constant velocity. Our measurements, on 20 \\AA centered at 3947 \\AA, were conventional using Th/Ar comparison spectra taken every 20 or 40 minutes between the stellar exposures. Existing IRAF routines were used for the reduction. We find $\\sigma_{RV}$ $\\leq$ 20 m s$^{-1}$, provided 4 measurements (out of 72) with residuals $>5\\sigma_{RV}$ are neglected. The observations were made with the CFHT Gecko spectrograph, fiber-fed with the CAFE system (R$\\sim$110,000). $\\sigma_{RV}$ $\\leq$10 m s$^{-1}$ seems possible with additional care. This study was incidental to the main program and so not exhaustive but the small value of $\\sigma_{RV}$ implies that the fiber feed/image slicer system on Gecko + CAFE, essentially eliminates the long standing problem of guiding errors in radial velocity measurements. We are not suggesting this conventional approach for serious Doppler planet searches (especially with Gecko which has such a small mul...

  20. Mortality of adult Stomoxys calcitrans fed isolates of Bacillus thuringiensis.

    Science.gov (United States)

    Lysyk, T J; Kalischuk-Tymensen, L D; Selinger, L B

    2012-10-01

    We examined the ability of five isolates of Bacillus thuringiensis Berliner to cause mortality in adult stable flies, Stomoxys calcitrans (L.). Isolates Bacillus thuringiensis tolworthi 4L3 (serotype 9), Bacillus thuringiensis darmstadiensis 4M1 (serotype 10a10b), Bacillus thuringiensis thompsoni 401 (serotype 12), Bacillus thuringiensis thuringiensis HD2 (serotype 1), and Bacillus thuringiensis kurstaki HD945 (serotype 3a3b3c) were administered to adult flies in diets containing blood only, sugar only, and both sugar and blood combined. B. t. tolworthi 4L3 had no effect on adult mortality regardless of the feeding substrate. The remaining isolates tended to cause the greatest mortality when administered in blood alone. B. t. thompsoni 401 was the only isolate that consistently caused adult mortality when fed in blood at concentrations ranging from 0.21 to 50.0 microg of protein per ml of blood. This isolate also caused mortality when applied topically. The time to 50% mortality declined with dose and reached a lower asymptote at approximately equal to 1.3 d at an oral dose of 8.75 microg/ml and at a topical dose of 0.14 microg per fly.